JP2021071350A - Position detector - Google Patents

Abstract

To provide a position detector that reduces errors arising from a noise magnetic field without causing large restraints on the installation of a magnetism sensor.SOLUTION: A position detector 1 comprises a magnetic scale 2 and a magnetic sensor 3. The magnetic sensor 3 includes detection units 11, 12, 21, 22 and a computation circuit. The detection units 11, 12 are arranged so as to detect a first composite magnetic field which is the composite magnetic field of a detection target magnetic field of first strength and a noise magnetic field. The detection units 21, 22 are arranged so as to detect a second composite magnetic field which is the composite magnetic field of a detection target magnetic field of second strength and a noise magnetic field. The computation circuit generates a detection value on the basis of a signal after computation that corresponds to a difference between the detection signals generated by the detection units 11, 21 and a signal after computation that corresponds to a difference between the detection signals generated by the detection units 12, 22.SELECTED DRAWING: Figure 1

Description

The present invention relates to a magnetic position detector equipped with a magnetic scale and a magnetic sensor.

A magnetic position detector equipped with a magnetic scale and a magnetic sensor is used, for example, to detect the position of a movable object whose position changes in a linear direction or a rotational direction. The position detection device used for detecting the position of a movable object is configured so that the relative position of the magnetic scale with respect to the magnetic sensor changes within a predetermined range in response to the change in the position of the movable object. ..

The magnetic scale includes, for example, a plurality of magnets arranged along a linear or rotational direction. When the relative position of the magnetic scale with respect to the magnetic sensor changes, the direction of the magnetic field to be detected generated by the magnetic scale and applied to the magnetic sensor rotates. The magnetic sensor, for example, detects components in two different directions of the magnetic field to be detected and generates two detection signals corresponding to the intensities of the components in the two directions. Then, the magnetic sensor generates a detection value having a correspondence relationship with the relative position of the magnetic scale with respect to the magnetic sensor based on the two detection signals.

Patent Document 1 includes a magnetic sensing element and a plurality of magnetic members whose magnetic pole surfaces are linearly arranged facing the magnetic sensing element, and position detection for detecting the position of the magnetic sensing element with respect to the plurality of magnetic members. The device is described. Patent Document 2 describes two magnetic encoders that detect the rotation angle of a magnetic drum, which are arranged at positions facing the multi-pole magnetizing layer formed on the outer peripheral surface of the magnetic drum and at a position facing about 180 °. A magnetic encoder equipped with a magnetic sensor of is described.

Patent Document 3 describes a magnetic encoder that detects the rotational position of a rotation axis to be detected, and includes first and second magnetic detection elements and third and fourth magnetic detection elements arranged along the circular outer peripheral surface of a multi-pole magnet. Described is a magnetic encoder in which a magnetic detection element is arranged at an angle position 180 ° away from the mechanical angle along the circumferential direction of a multi-pole magnet. In this magnetic encoder, the sum signal or difference signal of the output signal of the first detection signal and the output signal of the third magnetic detection element, the output signal of the second detection signal, and the output signal of the fourth magnetic detection element A signal representing the rotation position of the rotation axis is generated based on the sum signal or the difference signal of.

Patent Document 4 describes a magnetic detection device including two Hall elements arranged side by side on the rotation axis of the detection magnet and a differential output circuit for differentially outputting detection signals from the two Hall elements. ing. In this magnetic detector, the offset voltage caused by the disturbance magnetic field is canceled by taking the differential between the two Hall voltages, and a voltage having an output waveform substantially equal to that when the disturbance magnetic field is not applied is output.

Japanese Unexamined Patent Publication No. 2011-137996 Japanese Unexamined Patent Publication No. 2001-12967 International Publication No. 2008/136054 Japanese Unexamined Patent Publication No. 2006-250580

In the magnetic position detection device, a noise magnetic field other than the detection target magnetic field may be applied to the magnetic sensor in addition to the detection target magnetic field. Examples of the noise magnetic field include geomagnetism and leakage magnetic field from a motor. When the noise magnetic field is applied to the magnetic sensor in this way, the magnetic sensor detects the combined magnetic field of the detection target magnetic field and the noise magnetic field. Therefore, when the direction of the magnetic field to be detected and the direction of the noise magnetic field are different, an error occurs in the detected value.

The noise magnetic field is not considered in the position detection device described in Patent Document 1 and the magnetic encoder described in Patent Document 2. On the other hand, in the magnetic encoder described in Patent Document 3 and the magnetic detector described in Patent Document 4, the error caused by the noise magnetic field can be reduced, but the position of the magnetic sensor is restricted.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a position detecting device capable of reducing an error caused by a noise magnetic field without causing a great restriction on the installation of a magnetic sensor. It is in.

The position detection device of the present invention is a magnet that detects a magnetic scale that generates an external magnetic field having a spatial distribution in intensity and direction, a magnetic field to be detected that is a part of the external magnetic field, and a noise magnetic field other than the magnetic field to be detected. It is a position detection device equipped with a sensor. The position of the magnetic scale can be changed relative to the magnetic sensor within a predetermined range along a moving direction which is a linear direction or a rotational direction. The direction of the magnetic field to be detected at an arbitrary position rotates around the arbitrary position as the relative position changes. The intensity of the magnetic field to be detected changes according to the distance from the magnetic scale.

The magnetic sensor includes a first detection unit, a second detection unit, and a first detection unit arranged so as to detect a first combined magnetic field which is a combined magnetic field of a first intensity detection target magnetic field and a noise magnetic field. It includes a third detection unit and a fourth detection unit arranged to detect a second combined magnetic field, which is a combined magnetic field of a magnetic field to be detected having a second intensity different from the intensity and a noise magnetic field. .. The first detection unit generates a first detection signal corresponding to the intensity of the component in the first direction of the first synthetic magnetic field. The second detection unit generates a second detection signal corresponding to the intensity of the component in the second direction different from the first direction of the first synthetic magnetic field. The third detection unit generates a third detection signal corresponding to the intensity of the component in the third direction of the second synthetic magnetic field. The fourth detection unit generates a fourth detection signal corresponding to the intensity of the component in the fourth direction different from the third direction of the second synthetic magnetic field.

The magnetic sensor further includes a first arithmetic circuit that generates a first post-calculation signal corresponding to the difference between the first detection signal and the third detection signal, and a second detection signal and a fourth detection signal. A second calculation circuit that generates a second post-calculation signal corresponding to the difference between the two, and a third that generates a detection value having a correspondence relationship with the relative position based on the first and second post-calculation signals. Includes an arithmetic circuit.

In the position detection device of the present invention, the angle formed by the direction of the detection target magnetic field detected by the first detection unit with respect to the first direction, which is assumed when the direction of the detection target magnetic field changes ideally, is the first. When the angle is 1, and the angle formed by the direction of the detection target magnetic field detected by the third detection unit with respect to the third direction is the third angle, the first detection unit and the third detection unit are , The first angle and the third angle may be arranged so as to be equal to each other. Further, the angle formed by the direction of the detection target magnetic field detected by the second detection unit with respect to the second direction, which is assumed when the direction of the detection target magnetic field changes ideally, is defined as the second angle. When the angle formed by the direction of the detection target magnetic field detected by the detection unit 4 with respect to the fourth direction is the fourth angle, the second detection unit and the fourth detection unit have the second angle. The fourth angles may be arranged so as to be equal to each other. The difference between the first angle and the second angle may be 90 °, and the difference between the third angle and the fourth angle may be 90 °.

Further, in the position detecting device of the present invention, the third direction may be the same as the first direction, and the fourth direction may be the same as the second direction.

Further, in the position detecting device of the present invention, the moving direction may be a linear direction. In this case, the first combined magnetic field may be the combined magnetic field of the detection target magnetic field and the noise magnetic field at the first detection position on the virtual straight line intersecting the magnetic scale and orthogonal to the moving direction. Further, the second combined magnetic field may be a combined magnetic field of the detection target magnetic field and the noise magnetic field at the second detection position different from the first detection position on the virtual straight line.

Further, in the position detecting device of the present invention, the moving direction may be a rotation direction centered on a predetermined central axis. In this case, the first combined magnetic field detected by the first detection unit is the combined magnetic field of the detection target magnetic field and the noise magnetic field at the first detection position on the first virtual straight line intersecting the central axis. May be good. Further, the first synthetic magnetic field detected by the second detection unit intersects the central axis and is the magnetic field to be detected at the second detection position on the second virtual straight line different from the first virtual straight line. It may be a combined magnetic field with a noise magnetic field. Further, the second combined magnetic field detected by the third detection unit is the combined magnetic field of the detection target magnetic field and the noise magnetic field at the third detection position different from the first detection position on the first virtual straight line. There may be. Further, the second combined magnetic field detected by the fourth detection unit is a combined magnetic field of the detection target magnetic field and the noise magnetic field at the fourth detection position different from the second detection position on the second virtual straight line. There may be.

Further, the position detecting device of the present invention may include a plurality of magnets arranged along the moving direction. The external magnetic field is a combination of magnetic fields generated by each of a plurality of magnets. The plurality of magnets may be arranged at intervals from each other. In this case, the magnetic scale may further be made of a magnetic material and include a yoke that magnetically connects the plurality of magnets.

Further, in the position detection device of the present invention, each of the first to fourth detection units may include at least one magnetoresistive sensor. Alternatively, each of the first to fourth detection units may include at least one Hall element.

The position detection device of the present invention corresponds to the difference between the first post-calculation signal corresponding to the difference between the first detection signal and the third detection signal, and the difference between the second detection signal and the fourth detection signal. Based on the second post-calculation signal, a detection value having a correspondence with the relative position is generated. In the present invention, there is a requirement that the first and second detection units are arranged at positions where the detection target magnetic field whose intensity is the first intensity can be detected, and the detection whose intensity is the second intensity. It is necessary to satisfy the requirement of arranging the third and fourth detection units at positions where the target magnetic field can be detected, but these requirements greatly limit the installation of the first to fourth detection units. It does not cause it. Therefore, according to the present invention, there is an effect that the error caused by the noise magnetic field can be reduced without causing a big restriction on the installation of the magnetic sensor.

It is a perspective view which shows the schematic structure of the position detection apparatus which concerns on 1st Embodiment of this invention. It is a front view which shows the schematic structure of the position detection apparatus which concerns on 1st Embodiment of this invention. It is explanatory drawing which shows the reference direction and the 1st to 4th directions in 1st Embodiment of this invention. It is a block diagram which shows the structure of the magnetic sensor in 1st Embodiment of this invention. It is a circuit diagram which shows an example of the structure of the 1st detection part in the 1st example of the magnetic sensor in 1st Embodiment of this invention. It is a circuit diagram which shows an example of the structure of the 2nd detection part in the 1st example of the magnetic sensor in 1st Embodiment of this invention. 5 is a perspective view showing a part of one magnetoresistive sensor in FIGS. 5 and 6. It is a perspective view which shows the main part of the electronic component in the 2nd example of the magnetic sensor in 1st Embodiment of this invention. It is a circuit diagram which shows an example of the structure of the 1st detection part in the 2nd example of the magnetic sensor in 1st Embodiment of this invention. It is a circuit diagram which shows an example of the structure of the 2nd detection part in the 2nd example of the magnetic sensor in 1st Embodiment of this invention. It is a waveform diagram which shows the waveform of the 1st and 2nd detection signals in the 1st simulation. It is a waveform diagram which shows the waveform of the 3rd and 4th detection signals in the 1st simulation. It is a waveform diagram which shows the waveform of the 1st and 2nd post-calculation signals in a 1st simulation. It is a characteristic diagram which shows the detected value of the comparative example in the 1st simulation. It is a characteristic figure which shows the error of the comparative example in the 1st simulation. It is a characteristic diagram which shows the detected value of the Example in the 1st simulation. It is a characteristic figure which shows the error of the Example in the 1st simulation. It is a perspective view which shows the modification of the magnetic scale in 1st Embodiment of this invention. It is a top view which shows the schematic structure of the position detection apparatus which concerns on 2nd Embodiment of this invention. It is a characteristic diagram which shows the volatility obtained by the 2nd simulation. It is a characteristic diagram which shows the fluctuation width obtained by the 2nd simulation. It is a characteristic diagram which shows the volatility obtained by the 3rd simulation. It is a top view which shows the modification of the magnetic scale in the 2nd Embodiment of this invention.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, a schematic configuration of the position detecting device according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. The position detecting device 1 according to the present embodiment includes a magnetic scale 2 and a magnetic sensor 3. The magnetic scale 2 generates an external magnetic field MF having a spatial distribution of intensity and direction. The magnetic sensor 3 detects a detection target magnetic field that is a part of the external magnetic field MF and a noise magnetic field Mex other than the detection target magnetic field.

The position of the magnetic scale 2 relative to the magnetic sensor 3 can be changed within a predetermined range along a moving direction which is a linear direction or a rotational direction. Further, the magnetic scale 2 includes a plurality of magnets arranged along the moving direction. The plurality of magnets may be arranged at intervals from each other. In particular, in the present embodiment, the magnetic scale 2 includes three magnets 4, 5 and 6 arranged at intervals from each other as a plurality of magnets. The external magnetic field MF is a combination of magnetic fields generated by each of the three magnets 4, 5 and 6.

In particular, in the present embodiment, the magnetic scale 2 is a linear scale. The magnets 4, 5 and 6 are arranged in this order in one direction. The distance between the magnet 4 and the magnet 5 and the distance between the magnet 5 and the magnet 6 are equal to each other. The magnetic scale 2 further includes a yoke 7 made of a magnetic material such as NiFe. The yoke 7 magnetically connects the magnets 4, 5 and 6 and is used as a substrate for supporting the magnets 4, 5 and 6. The yoke 7 has a plate shape that is long in one direction. Further, the yoke 7 has an upper surface 7a and a lower surface 7b. The magnets 4, 5 and 6 are arranged on the upper surface 7a of the yoke 7. The magnetic sensor 3 is arranged so as to face the upper surface 7a of the yoke 7.

The magnetic scale 2 is further made of a non-magnetic material such as resin, and includes magnets 4, 5 and 6 and a protective portion 8 that covers a part of the yoke 7. In FIG. 2, the protection unit 8 is omitted.

Here, as shown in FIGS. 1 and 2, the X direction, the Y direction, and the Z direction are defined. In the present embodiment, the direction from the lower surface 7b to the upper surface 7a perpendicular to the upper surface 7a of the yoke 7 is the Z direction. Further, the two directions perpendicular to the Z direction and orthogonal to each other are defined as the X direction and the Y direction. In FIG. 2, the Y direction is represented as the direction from the front to the back in FIG. Further, the direction opposite to the X direction is defined as the −X direction, the direction opposite to the Y direction is defined as the −Y direction, and the direction opposite to the Z direction is defined as the −Z direction.

The three magnets 4, 5 and 6 are arranged in this order in the X direction. Further, each of the three magnets 4, 5 and 6 has an N pole and an S pole. In the magnets 4 and 6, the north pole and the south pole are arranged in this order in the −Z direction. In the magnet 5, the north pole and the south pole are arranged in this order in the Z direction. The yoke 7 magnetically connects the end face of the magnet 4 on the south pole side, the end face of the magnet 5 on the north pole side, and the end face of the magnet 6 on the south pole side. The yoke 7 controls the flow of magnetic flux so that the magnetic flux generated from the end face on the north pole side of the magnet 5 efficiently flows into the end face on the south pole side of the magnet 4 and the end face on the south pole side of the magnet 6. Has the function of magnetizing.

The moving direction is a linear direction and is a direction parallel to the X direction. Hereinafter, the moving direction is represented by the symbol X1. The position of the magnetic scale 2 relative to the magnetic sensor 3 can be changed within a predetermined range along the moving direction X1. Hereinafter, the relative position of the magnetic scale 2 with respect to the magnetic sensor 3 is simply referred to as a relative position. In the present embodiment, one of the magnetic scale 2 and the magnetic sensor 3 moves linearly in the X direction or the −X direction in conjunction with a movable object (not shown). As a result, the relative position changes in the X direction or the −X direction. The direction of the magnetic field to be detected at an arbitrary position rotates around the arbitrary position as the relative position changes.

The position detection device 1 is a device for detecting a relative position. The magnetic sensor 3 generates a detection value having a correspondence relationship with the relative position. In particular, in the present embodiment, the magnetic sensor 3 generates, as a detection value, a value θs representing an angle formed by the direction of the detection target magnetic field at the reference position with respect to the reference direction DR in the reference plane. Hereinafter, the detected value is also referred to as a detected value θs. The detected value θs has a correspondence relationship with the relative position.

In the present embodiment, the range of the detected value θs may be a range in which the relative position can be uniquely specified. The range of such detected values θs is a range in which the detected values θs do not become the same value at a plurality of relative positions. This is, for example, a range narrower than 0 ° to 360 °. In order to make the range of the detected value θs narrower than 0 ° to 360 °, the predetermined range in which the relative position can be changed (hereinafter referred to as the movable range) is set to 0 ° to 360 ° of the detected value θs. Although the corresponding range is set, the range of the detected value θs actually generated by the magnetic sensor 3 is limited to a range narrower than 0 ° to 360 °, and the relative position corresponding to the limited range of the detected value θs Only the range may be the range of detectable relative positions. Alternatively, the movable range may be narrower than the range in which the detected value θs is 0 ° to 360 °. As a result, the relative position can be uniquely specified by the detected value θs.

The magnetic sensor 3 includes two electronic components 10 and 20. Further, the magnetic sensor 3 includes a first detection unit 11, a second detection unit 12, a third detection unit 21, and a fourth detection unit 22. The first detection unit 11 and the second detection unit 12 are included in the electronic component 10. The third detection unit 21 and the fourth detection unit 22 are included in the electronic component 20. The electronic components 10 and 20 are located apart from the magnetic scale 2 in the Z direction.

Here, as shown in FIG. 2, a virtual straight line L that intersects the magnetic scale 2 and is orthogonal to the moving direction X1 is assumed. The electronic components 10 and 20 are arranged at different positions on the virtual straight line L. The electronic component 20 is arranged at a position farther from the magnetic scale 2 than the electronic component 10.

The strength of the magnetic field to be detected changes according to the distance from the magnetic scale 2. The first and second detection units 11 and 12 are arranged so as to detect the first combined magnetic field MF1, which is the combined magnetic field of the detection target magnetic field of the first intensity and the noise magnetic field Mex. The third and fourth detection units 21 and 22 are arranged so as to detect the second combined magnetic field MF2, which is the combined magnetic field of the detection target magnetic field of the second intensity different from the first intensity and the noise magnetic field Mex. Has been done.

In this embodiment, in particular, the first combined magnetic field MF1 is a combined magnetic field of the detection target magnetic field and the noise magnetic field Mex at the first detection position P1 on the virtual straight line L. The electronic component 10 is arranged at the first detection position P1. As a result, the first and second detection units 11 and 12 can detect the first synthetic magnetic field MF1. Similarly, the second combined magnetic field MF2 is a combined magnetic field of the detection target magnetic field and the noise magnetic field Mex at the second detection position P2 different from the first detection position P1 on the virtual straight line L. The electronic component 20 is arranged at the second detection position P2. As a result, the third and fourth detection units 21 and 22 can detect the second synthetic magnetic field MF2.

As shown in FIG. 2, in the present embodiment, the second detection position P2 is set to a position farther from the magnetic scale 2 than the first detection position P1.

The direction and intensity of the noise magnetic field Mex at the second detection position P2 are equal to the direction and intensity of the noise magnetic field Mex at the first detection position P1, respectively. The noise magnetic field Mex may be a magnetic field whose direction and intensity are constant in time, a magnetic field whose direction and intensity change periodically in time, and the direction and intensity are time. It may be a magnetic field that changes randomly.

Hereinafter, the magnetic field to be detected at the first detection position P1 is referred to as a first partial magnetic field MFa, and the magnetic field to be detected at the second detection position P2 is referred to as a second partial magnetic field MFb. The strength of the first partial magnetic field MFa is the first strength, and the strength of the second partial magnetic field MFb is the second strength. The directions of the first and second partial magnetic fields MFa and MFb change according to the change in the relative position.

Here, it is assumed that the direction of the magnetic field to be detected changes ideally. When the direction of the magnetic field to be detected changes ideally, the relationship between the change in the relative position and the change in the angle between the direction of the magnetic field to be detected at an arbitrary position with respect to a predetermined direction satisfies the linearity. If there is a relationship. Hereinafter, the case where the direction of the magnetic field to be detected changes ideally is referred to as an ideal state. The direction of the first partial magnetic field MFa and the direction of the second partial magnetic field MFb, which are assumed in the ideal state, coincide with each other.

The first combined magnetic field MF1 is a combined magnetic field of the first partial magnetic field MFa and the noise magnetic field Mex. The first detection unit 11 detects the first synthetic magnetic field MF1 and generates a first detection signal S1 corresponding to the intensity of the component in the first direction D1 of the first synthetic magnetic field MF1. The second detection unit 12 detects the first synthetic magnetic field MF1 and has a second detection corresponding to the intensity of the component in the second direction D2 different from the first direction D1 of the first synthetic magnetic field MF1. Generate signal S2. The first direction D1 is a direction that serves as a reference for the first detection unit 11 to generate the first detection signal S1. The second direction D2 is a direction that serves as a reference for the second detection unit 12 to generate the second detection signal S2.

The second combined magnetic field MF2 is a combined magnetic field of the second partial magnetic field MFb and the noise magnetic field Mex. The third detection unit 21 detects the second synthetic magnetic field MF2 and generates a third detection signal S3 corresponding to the intensity of the component in the third direction D3 of the second synthetic magnetic field MF2. The fourth detection unit 22 detects the second synthetic magnetic field MF2, and the fourth detection corresponding to the intensity of the component in the fourth direction D4 different from the third direction D3 of the second synthetic magnetic field MF2. Generate signal S4. The third direction D3 is a direction that serves as a reference for the third detection unit 21 to generate the third detection signal S3. The fourth direction D4 is a direction that serves as a reference for the fourth detection unit 22 to generate the fourth detection signal S4.

Here, the angle formed by the direction of the first partial magnetic field MFa detected by the first detection unit 11 with respect to the first direction D1, which is assumed in the ideal state, is called the first angle and is represented by the symbol θ1. .. Further, the angle formed by the direction of the first partial magnetic field MFa detected by the second detection unit 12 with respect to the second direction D2, which is assumed in the ideal state, is referred to as a second angle and is represented by the symbol θ2. Further, the angle formed by the direction of the second partial magnetic field MFb detected by the third detection unit 21 with respect to the third direction D3, which is assumed in the ideal state, is referred to as a third angle and is represented by the symbol θ3. Further, the angle formed by the direction of the second partial magnetic field MFb detected by the fourth detection unit 22 with respect to the fourth direction D4, which is assumed in the ideal state, is referred to as a fourth angle and is represented by the symbol θ4. The first detection unit 11 and the third detection unit 21 are arranged so that the first angle θ1 and the third angle θ3 are equal to each other. The second detection unit 12 and the fourth detection unit 22 are arranged so that the second angle θ2 and the fourth angle θ4 are equal to each other.

FIG. 3 is an explanatory diagram showing the reference direction DR and the first to fourth directions D1 to D4 in the present embodiment. The reference direction DR is located in the reference plane P. In this embodiment, the Z direction is the reference direction DR. The reference plane P is an XZ plane that intersects the magnetic scale 2. In this reference plane P, the first partial magnetic field MFa rotates around the first detection position P1, and the second partial magnetic field MFb rotates around the second detection position P2. In the following description, the directions of the first and second partial magnetic fields MFa and MFb refer to the directions located in the reference plane P.

FIG. 3 shows the first and second partial magnetic fields MFa and MFb assumed in the ideal state, and the first to fourth angles θ1 to θ4. In FIG. 3, the length of the arrow with MFa schematically represents the intensity of the first partial magnetic field MFa, that is, the first intensity. Further, the length of the arrow with MFb schematically represents the strength of the second partial magnetic field MFb, that is, the second strength. As shown in FIG. 3, the second intensity is smaller than the first intensity.

The angle formed by the direction of the first partial magnetic field MFa with respect to the reference direction DR and the angle formed by the direction of the second partial magnetic field MFb with respect to the reference direction DR, which are assumed in the ideal state, are equal to each other. Hereinafter, these angles are represented by the symbol θ. The angle θ is represented by a positive value when viewed in the clockwise direction from the reference direction DR, and is represented by a negative value when viewed in the counterclockwise direction from the reference direction DR.

The reference position is located in the reference plane P. In the following description, it is assumed that the directions of the first and second partial magnetic fields MFa and MFb assumed in the ideal state coincide with the directions of the magnetic field to be detected at the reference position assumed in the ideal state. As long as this requirement is satisfied, the reference position may coincide with the first detection position P1, may coincide with the second detection position P2, or may be at any position different from these positions. There may be. The angle formed by the direction of the magnetic field to be detected at the reference position assumed in the ideal state with respect to the reference direction DR is equal to the angle θ.

In the present embodiment, the first direction D1 and the third direction D3 are the X direction, and the second direction D2 and the fourth direction D4 are the Z direction. That is, in the present embodiment, the third direction D3 is the same direction as the first direction D1, and the fourth direction D4 is the same direction as the second direction D2.

As described above, the first angle θ1 and the third angle θ3 are equal to each other, and the second angle θ2 and the fourth angle θ4 are equal to each other. The difference between the first angle θ1 and the second angle θ2 is 90 °, and the difference between the third angle θ3 and the fourth angle θ4 is 90 °. The positive and negative definitions of the first to fourth angles θ1 to θ4 are the same as those of the angles θ. As shown in FIG. 3, the second and fourth angles θ2 and θ4 are equal to the angles θ.

Next, the configuration of the magnetic sensor 3 will be described in detail with reference to FIG. FIG. 4 is a block diagram showing the configuration of the magnetic sensor 3. As described above, the magnetic sensor 3 includes the first to fourth detection units 11, 12, 21, 22. The magnetic sensor 3 further includes analog-to-digital converters (hereinafter referred to as A / D converters) 31, 32, 33, 34. The A / D converter 31 converts the first detection signal S1 into a digital signal. The A / D converter 32 converts the second detection signal S2 into a digital signal. The A / D converter 33 converts the third detection signal S3 into a digital signal. The A / D converter 34 converts the fourth detection signal S4 into a digital signal.

The magnetic sensor 3 further includes a first arithmetic circuit 35, a second arithmetic circuit 36, and a third arithmetic circuit 37. The first to third arithmetic circuits 35 to 37 can be realized by, for example, an application specific integrated circuit (ASIC) or a microcomputer. The first to third arithmetic circuits 35 to 37 may be functional blocks or may be physically separate circuits.

The first arithmetic circuit 35 includes a first detection signal S1 converted into a digital signal by the A / D converter 31 and a third detection signal S3 converted into a digital signal by the A / D converter 33. The first post-calculation signal Sa corresponding to the difference S1-S3 is generated. The first post-calculation signal Sa may be the difference S1-S3 itself, or may be the difference S1-S3 with predetermined corrections such as gain adjustment and offset adjustment.

The second arithmetic circuit 36 includes a second detection signal S2 converted into a digital signal by the A / D converter 32 and a fourth detection signal S4 converted into a digital signal by the A / D converter 34. A second post-calculation signal Sb corresponding to the difference S2-S4 is generated. The second post-calculation signal Sb may be the difference S2-S4 itself, or may be the difference S2-S4 with predetermined corrections such as gain adjustment and offset adjustment.

The third arithmetic circuit 37 generates the detected value θs based on the first and second post-calculation signals Sa and Sb. Specifically, the third arithmetic circuit 37 calculates θs by, for example, the following equation (1). In addition, "atan" represents an arctangent.

θs = atan (Sa / Sb)… (1)

Within the range of θs of 0 ° or more and less than 360 °, the solution of θs in the equation (1) has two values different by 180 °. However, it is possible to determine which of the two solutions of θs in the equation (1) is the true value of θs by the combination of positive and negative of Sa and Sb. The third arithmetic circuit 37 obtains θs within a range of 0 ° or more and less than 360 ° by determining the combination of the positive and negative of the equation (1) and Sa and Sb.

Next, the first and second examples of the magnetic sensor 3 will be described. First, a first example of the magnetic sensor 3 will be described. In the first example, each of the first to fourth detection units 11, 12, 21, 22 includes at least one magnetoresistive sensor. Hereinafter, the magnetoresistive element will be referred to as an MR element.

FIG. 5 shows an example of a specific configuration of the first detection unit 11 in the first example. In this example, the first detection unit 11 includes two MR elements R11 and R12, a power supply port V11, a ground port G11, and an output port E11. One end of the MR element R11 is connected to the power supply port V11. The other end of the MR element R11 is connected to one end of the MR element R12 and the output port E11. The other end of the MR element R12 is connected to the ground port G11. A power supply voltage of a predetermined magnitude is applied to the power supply port V11. The grand port G11 is connected to the ground. The output port E11 outputs a signal corresponding to the potential at the connection point of the MR elements R11 and R12.

In the first example, the configuration of the third detection unit 21 is the same as the configuration of the first detection unit 11. Therefore, in the following description, the same reference numerals as those of the first detection unit 11 are used for the components of the third detection unit 21.

FIG. 6 shows an example of a specific configuration of the second detection unit 12 in the first example. In this example, the second detection unit 12 includes two MR elements R21 and R22, a power supply port V12, a ground port G12, and an output port E12. One end of the MR element R21 is connected to the power supply port V12. The other end of the MR element R21 is connected to one end of the MR element R22 and the output port E12. The other end of the MR element R22 is connected to the ground port G12. A power supply voltage of a predetermined magnitude is applied to the power supply port V12. The grand port G12 is connected to the ground. The output port E12 outputs a signal corresponding to the potential at the connection point of the MR elements R21 and R22.

In the first example, the configuration of the fourth detection unit 22 is the same as the configuration of the second detection unit 12. Therefore, in the following description, the same reference numerals as those of the second detection unit 12 are used for the components of the fourth detection unit 22.

The MR element is, for example, a spin valve type MR element. The spin valve type MR element has a magnetization fixed layer in which the magnetization direction is fixed, a free layer which is a magnetic layer in which the magnetization direction changes according to the direction of the magnetic field to be detected, and a magnetization fixed layer and the free layer. It has an arranged non-magnetic layer. The spin valve type MR element may be a TMR element or a GMR element. In the TMR element, the non-magnetic layer is a tunnel barrier layer. In the GMR element, the non-magnetic layer is a non-magnetic conductive layer. In a spin valve type MR element, the resistance value changes according to the angle formed by the magnetization direction of the free layer with respect to the magnetization direction of the magnetization fixed layer, and when this angle is 0 °, the resistance value becomes the minimum value. , The resistance value becomes the maximum value when the angle is 180 °. The arrows drawn on the MR elements R11, R12, R21, and R22 in FIGS. 5 and 6 indicate the direction of magnetization of the magnetization-fixed layer contained therein, respectively.

In the first detection unit 11, the magnetization direction of the magnetization fixed layer of the MR element R11 is the first direction D1 (X direction), and the magnetization direction of the magnetization fixed layer of the MR element R12 is the first direction D1. Is in the opposite direction. In this case, the potential at the connection point of the MR elements R11 and R12 changes according to the intensity of the component in the first direction D1 of the first synthetic magnetic field MF1. Therefore, the first detection unit 11 detects the component in the first direction D1 of the first synthetic magnetic field MF1 and outputs a signal corresponding to the intensity as the first detection signal S1.

In the second detection unit 12, the magnetization direction of the magnetization fixed layer of the MR element R21 is the second direction D2 (Z direction), and the magnetization direction of the magnetization fixed layer of the MR element R22 is the second direction D2. Is in the opposite direction. In this case, the potential at the connection point of the MR elements R21 and R22 changes according to the intensity of the component in the second direction D2 of the first synthetic magnetic field MF1. Therefore, the second detection unit 12 detects the component in the second direction D2 of the first synthetic magnetic field MF1 and outputs a signal corresponding to the intensity as the second detection signal S2.

In the third detection unit 21, the magnetization direction of the magnetization fixed layer of the MR element R11 is the third direction D3 (X direction), and the magnetization direction of the magnetization fixed layer of the MR element R12 is the third direction D3. Is in the opposite direction. In this case, the potential at the connection point of the MR elements R11 and R12 changes according to the intensity of the component in the third direction D3 of the second synthetic magnetic field MF2. Therefore, the third detection unit 21 detects the component in the third direction D3 of the second synthetic magnetic field MF2 and outputs a signal corresponding to the intensity as the third detection signal S3.

In the fourth detection unit 22, the magnetization direction of the magnetization fixed layer of the MR element R21 is the fourth direction D4 (Z direction), and the magnetization direction of the magnetization fixed layer of the MR element R22 is the fourth direction D4. Is in the opposite direction. In this case, the potential at the connection point of the MR elements R21 and R22 changes according to the intensity of the component in the fourth direction D4 of the second synthetic magnetic field MF2. Therefore, the fourth detection unit 22 detects the component of the second synthetic magnetic field MF2 in the fourth direction D4, and outputs a signal corresponding to the intensity as the fourth detection signal S4.

The direction of magnetization of the magnetization fixed layer in the plurality of MR elements in the detection units 11, 12, 21 and 22, may be slightly deviated from the above-mentioned direction from the viewpoint of the accuracy of manufacturing the MR element and the like.

As described above, in order for the first to fourth detection signals S1 to S4 to represent the intensity of the component in one direction of the magnetic field to be detected, the resistance values of the MR elements are set to the first and second. The relationship between the fact that the combined magnetic fields MF1 and MF2 are not saturated within the intensity range of MF1 and MF2, and the change in the strength of the unidirectional component of the magnetic field to be detected and the change in the resistance value of the MR element satisfy the linearity relationship. is required. In order to satisfy the above requirements, as the MR elements R11, R12, R21, and R22, MR elements of a type that detects the intensity of a component in one direction of the magnetic field may be used. In this type of MR element, for example, by making the planar shape of the MR element substantially rectangular, the direction of magnetization of the free layer of the MR element is substantially constant with respect to a change in the intensity of a component in one direction of the magnetic field. It is configured to change with speed.

Here, an example of the configuration of the MR element will be described with reference to FIG. 7. FIG. 7 is a perspective view showing a part of one MR element in the detection units 11 and 12 shown in FIGS. 5 and 6. In this example, one magnetic detection element has a plurality of lower electrodes 62, a plurality of MR films 50, and a plurality of upper electrodes 63. The plurality of lower electrodes 62 are arranged on a substrate (not shown). The individual lower electrodes 62 have an elongated shape. A gap is formed between the two lower electrodes 62 adjacent to each other in the longitudinal direction of the lower electrode 62. As shown in FIG. 7, MR films 50 are arranged on the upper surface of the lower electrode 62 in the vicinity of both ends in the longitudinal direction. The MR film 50 includes a free layer 51, a non-magnetic layer 52, a magnetization fixing layer 53, and an antiferromagnetic layer 54 that are laminated in order from the lower electrode 62 side. The free layer 51 is electrically connected to the lower electrode 62. The antiferromagnetic layer 54 is made of an antiferromagnetic material and forms an exchange bond with the magnetization fixing layer 53 to fix the magnetization direction of the magnetization fixing layer 53. The plurality of upper electrodes 63 are arranged on the plurality of MR films 50. The individual upper electrodes 63 have an elongated shape and are arranged on two lower electrodes 62 adjacent to each other in the longitudinal direction of the lower electrodes 62 to electrically connect the antiferromagnetic layers 54 of the two adjacent MR films 50 to each other. To do. With such a configuration, the MR element shown in FIG. 7 has a plurality of MR films 50 connected in series by a plurality of lower electrodes 62 and a plurality of upper electrodes 63. The arrangement of the layers 51 to 54 on the MR film 50 may be upside down from the arrangement shown in FIG.

Next, a second example of the magnetic sensor 3 will be described. In the second example, each of the first to fourth detection units 11, 12, 21, 22 includes at least one Hall element.

FIG. 8 is a perspective view showing a main part of the electronic component 10 in the second example. In the second example, the first detection unit 11 includes the first Hall element H1 and the third Hall element H3, and the second detection unit includes the second Hall element H2 and the fourth Hall element. Includes H4. The electronic component 10 further includes a substrate 41 made of a non-magnetic material and having an upper surface 41a, and a yoke 42 made of a magnetic material. The upper surface 41a is parallel to the XZ plane.

The first to fourth Hall elements H1 to H4 are embedded in the substrate 41 in a posture in which the magnetically sensitive surface is parallel to the upper surface 41a in the vicinity of the upper surface 41a. The first and third Hall elements H1 and H3 are arranged so as to be arranged in the X direction. The second and fourth Hall elements H2 and H4 are arranged so as to be arranged in the Z direction.

The yoke 42 has a disc shape. The yoke 42 is arranged on the upper surface 41a of the substrate 41 so as to straddle each part of the first to fourth Hall elements H1 to H4. The first Hall element H1 is located near the end of the yoke 42 in the −X direction. The second Hall element H2 is located near the end of the yoke 42 in the −Z direction. The third Hall element H3 is located near the end of the yoke 42 in the X direction. The fourth Hall element H4 is located near the end of the yoke 42 in the Z direction.

FIG. 9 shows an example of a specific configuration of the first detection unit 11 in the second example. FIG. 10 shows an example of a specific configuration of the second detection unit 12 in the second example. As shown in FIG. 9, the first detection unit 11 further includes a power supply port V21, a grand port G21, two output ports E21 and E22, and a difference detector 13. As shown in FIG. 10, the second detection unit 12 further includes a power supply port V22, a grand port G22, two output ports E23 and E24, and a difference detector 23. As shown in FIGS. 9 and 10, each of the first to fourth Hall elements H1 to H4 has a power supply terminal Ha, a ground terminal Hc, and two output terminals Hb and Hd.

In the first detection unit 11, the power supply terminals Ha of the first and third Hall elements H1 and H3 are connected to the power supply port V21. The ground terminals Hc of the first and third Hall elements H1 and H3 and the output terminals Hd of the first and third Hall elements H1 and H3 are connected to the ground port G21. The output terminal Hb of the first Hall element H1 is connected to the output port E21. The output terminal Hb of the third Hall element H3 is connected to the output port E22. A power supply voltage of a predetermined magnitude is applied to the power supply port V21. The grand port G21 is connected to the ground.

In the second detection unit 12, the power supply terminals Ha of the second and fourth Hall elements H2 and H4 are connected to the power supply port V22. The ground terminals Hc of the second and fourth Hall elements H2 and H4 and the output terminals Hd of the second and fourth Hall elements H2 and H4 are connected to the ground port G22. The output terminal Hb of the second Hall element H2 is connected to the output port E23. The output terminal Hb of the fourth Hall element H4 is connected to the output port E24. A power supply voltage of a predetermined magnitude is applied to the power supply port V22. The grand port G22 is connected to the ground.

In the electronic component 10, the yoke 42 receives the first combined magnetic field MF1 to generate an output magnetic field. The output magnetic field is an output magnetic field component in a direction parallel to the Y direction, and includes an output magnetic field component that changes according to the first combined magnetic field MF1. Specifically, when the yoke 42 receives the component in the X direction of the first synthetic magnetic field MF1, the yoke 42 generates an output magnetic field component in the −Y direction in the vicinity of the first Hall element H1, and the third An output magnetic field component in the Y direction is generated in the vicinity of the Hall element H3. When the yoke 42 receives a component in the −X direction of the first synthetic magnetic field MF1, the direction of the output magnetic field component is opposite to that when the yoke 42 receives a component in the X direction of the first synthetic magnetic field MF1. become.

In the first detection unit 11, the first and third Hall elements H1 and H3 detect the output magnetic field components in the Y direction or −Y direction generated in the vicinity of the first and third Hall elements H1 and H3. Thereby, the component in the X direction or the −X direction of the first synthetic magnetic field MF1 is detected. The potential difference between the output ports E21 and E22 changes according to the intensity of the components in the X direction, that is, the first direction D1 of the first synthetic magnetic field MF1. The difference detector 13 detects a signal corresponding to the potential difference between the output ports E21 and E22, that is, a signal corresponding to the intensity of a component in the first direction D1 (X direction) of the first synthetic magnetic field MF1 as a first detection signal. Output as S1.

Further, in the electronic component 10, when the yoke 42 receives a component in the Z direction of the applied magnetic field, it generates an output magnetic field component in the −Y direction in the vicinity of the second Hall element H2, and the fourth Hall element. An output magnetic field component in the Y direction is generated in the vicinity of H4. When the yoke 42 receives a component in the −Z direction of the applied magnetic field, the direction of the output magnetic field component is opposite to that when the yoke 42 receives a component in the Z direction of the applied magnetic field.

In the second detection unit 12, the second and fourth Hall elements H2 and H4 detect the output magnetic field components in the Y direction or −Y direction generated in the vicinity of the second and fourth Hall elements H2 and H4. Thereby, the Z-direction or −Z-direction component of the first synthetic magnetic field MF1 is detected. The potential difference between the output ports E23 and E24 changes according to the intensity of the components in the Z direction of the first synthetic magnetic field MF1, that is, the second direction D2. The difference detector 23 uses a second detection signal for a signal corresponding to the potential difference between the output ports E23 and E24, that is, a signal corresponding to the intensity of the component in the second direction D2 (Z direction) of the first synthetic magnetic field MF1. Output as S2.

The configurations of the electronic component 20 and the third and fourth detection units 21 and 22 in the second example are the same as the configurations of the electronic component 10 and the first and second detection units 11 and 12 shown in FIGS. 8 to 10. It is the same. Therefore, in the following description, the same reference numerals as those of the electronic component 10 and the components of the first and second detection units 11 and 12 are used for the components of the electronic component 20 and the third and fourth detection units 21 and 22. ..

In the electronic component 20, the yoke 42 receives the second combined magnetic field MF2 to generate an output magnetic field. The output magnetic field is an output magnetic field component in a direction parallel to the Y direction, and includes an output magnetic field component that changes according to the second combined magnetic field MF2. Specifically, when the yoke 42 receives the component in the X direction of the second combined magnetic field MF2, the yoke 42 generates an output magnetic field component in the −Y direction in the vicinity of the first Hall element H1, and the third An output magnetic field component in the Y direction is generated in the vicinity of the Hall element H3. When the yoke 42 receives a component in the −X direction of the second synthetic magnetic field MF2, the direction of the output magnetic field component is opposite to that when the yoke 42 receives a component in the X direction of the second synthetic magnetic field MF2. become.

In the third detection unit 21, the first and third Hall elements H1 and H3 detect the output magnetic field components in the Y direction or −Y direction generated in the vicinity of the first and third Hall elements H1 and H3. Thereby, the component in the X direction or the −X direction of the second synthetic magnetic field MF2 is detected. The potential difference between the output ports E21 and E22 changes according to the intensity of the components in the X direction, that is, the third direction D3 of the second synthetic magnetic field MF2. The difference detector 13 detects a signal corresponding to the potential difference between the output ports E21 and E22, that is, a signal corresponding to the intensity of a component in the third direction D3 (X direction) of the second synthetic magnetic field MF2, as a third detection signal. Output as S3.

Further, in the electronic component 20, when the yoke 42 receives a component in the Z direction of the applied magnetic field, it generates an output magnetic field component in the −Y direction in the vicinity of the second Hall element H2, and the fourth Hall element. An output magnetic field component in the Y direction is generated in the vicinity of H4. When the yoke 42 receives a component in the −Z direction of the applied magnetic field, the direction of the output magnetic field component is opposite to that when the yoke 42 receives a component in the Z direction of the applied magnetic field.

In the fourth detection unit 22, the second and fourth Hall elements H2 and H4 detect the output magnetic field components in the Y direction or −Y direction generated in the vicinity of the second and fourth Hall elements H2 and H4. Thereby, the Z-direction or −Z-direction component of the second synthetic magnetic field MF2 is detected. The potential difference between the output ports E23 and E24 changes according to the intensity of the components in the Z direction of the second synthetic magnetic field MF2, that is, the fourth direction D4. The difference detector 23 uses a second detection signal for a signal corresponding to the potential difference between the output ports E23 and E24, that is, a signal corresponding to the intensity of the component in the fourth direction D4 (Z direction) of the second synthetic magnetic field MF2. Output as S2.

Next, the operation and effect of the position detection device 1 according to the present embodiment will be described. In the present embodiment, the first detection unit 11 generates the first detection signal S1 corresponding to the intensity of the component in the first direction D1 of the first synthetic magnetic field MF1, that is, the X direction, and the second detection. The unit 12 generates a second detection signal S2 corresponding to the intensity of the component in the second direction D2, that is, the Z direction of the first synthetic magnetic field MF1, and the third detection unit 21 generates the second synthetic magnetic field MF2. A third detection signal S3 corresponding to the intensity of the component in the third direction D3, that is, the X direction is generated, and the fourth detection unit 22 is in the fourth direction D4, that is, in the Z direction of the second synthetic magnetic field MF2. A fourth detection signal S4 corresponding to the intensity of the component is generated. Then, the first post-calculation signal Sa corresponding to the difference between the first detection signal S1 and the third detection signal S3 is generated, and the difference between the second detection signal S2 and the fourth detection signal S4 is supported. The second post-calculation signal Sb is generated, and the detected value θs is generated based on the first and second post-calculation signals Sa and Sb.

According to the present embodiment, the first post-calculation signal Sa corresponding to the difference between the first detection signal S1 and the third detection signal S3 is generated, and the second detection signal S2 and the fourth detection signal are generated. By generating the second post-calculation signal Sb corresponding to the difference from S4, the error caused by the noise magnetic field Mix can be reduced. The reason will be described in detail below.

The strength of the first synthetic magnetic field MF1 is B1, the strength of the second synthetic magnetic field MF2 is B2, the strength of the first partial magnetic field MFa is Ba, the strength of the second partial magnetic field MFb is Bb, and the noise magnetic field. Let Bex be the intensity of Mex, and the angle formed by the direction of the noise magnetic field Mex at the first detection position P1 with respect to the reference direction DR (the angle formed by the direction of the noise magnetic field Mex at the second detection position P2 with respect to the reference direction DR). (Same as) is the symbol θex. The intensity B1 of the component in the first direction D1 of the first synthetic magnetic field MF1 and the intensity B2 of the component in the second direction D2 of the first synthetic magnetic field MF1 assumed in the ideal state use an angle θ. , Can be expressed by the following equations (2) and (3), respectively.

B1 = Ba · sinθ + Bex · sinθex… (2)
B2 = Ba · cosθ + Bex · cosθex… (3)

In the formula (2), Bex · sinθex represents the intensity of the component of the noise magnetic field Mex in the X direction. Further, in the equation (3), Bex · cosθex represents the intensity of the component of the noise magnetic field Mex in the Z direction.

Similarly, the intensity B3 of the component in the third direction D3 of the second synthetic magnetic field MF2 and the intensity B4 of the component in the fourth direction D4 of the second synthetic magnetic field MF2, which are assumed in the ideal state, are at an angle θ. Can be expressed by the following equations (4) and (5), respectively.

B3 = Bb · sinθ + Bex · sinθex… (4)
B4 = Bb · cosθ + Bex · cosθex… (5)

Hereinafter, the first detection signal S1 is a product A / B1 of the intensity B1 and an arbitrary constant A, the second detection signal S2 is a product A / B2 of the intensity B2 and the constant A, and the third detection signal S3. Is the product A and B3 of the intensity B3 and the constant A, and the fourth detection signal S4 is the product A and B4 of the intensity B4 and the constant A. Assuming that the first post-calculation signal Sa is the difference S1-S3 itself between the first detection signal S1 and the third detection signal S3, the first post-calculation signal Sa is represented by the following equation (6). To.

Sa = A ・ B1-A ・ B3
= A (Ba · sinθ + Bex · sinθex)
−A (Bb ・ sinθ + Bex ・ sinθex)
= A (Ba-Bb) sinθ ... (6)

Further, assuming that the second post-calculation signal Sb is the difference S2-S4 itself between the second detection signal S2 and the fourth detection signal S4, the second post-calculation signal Sb is calculated by the following equation (7). expressed.

Sb = A ・ B2-A ・ B4
= A (Ba · cos θ + Bex · cos θex)
−A (Bb ・ cosθ + Bex ・ cosθex)
= A (Ba-Bb) cosθ ... (7)

As shown in the equation (6), when the difference between the first detection signal S1 and the third detection signal S3 is obtained, Bex · sinθex are canceled and a signal independent of the noise magnetic field Mex is obtained. Further, as shown in the equation (7), when the difference between the second detection signal S2 and the fourth detection signal S4 is obtained, Bex · cosθex is canceled and a signal independent of the noise magnetic field Mex is obtained. .. By substituting the equations (6) and (7) into the equation (1), the following equation (8) is obtained.

θs = atan (Sa / Sb)
= Atan ((A (Ba-Bb) sinθ) / (A (Ba-Bb) cosθ))
= Atan (sinθ / cosθ)
= Θ… (8)

As shown in the equation (8), the detected value θs is theoretically equal to the angle θ, that is, the angle formed by the direction of the magnetic field to be detected at the reference position with respect to the reference direction DR, which is assumed in the ideal state. As can be understood from the equations (6) to (8), according to the present embodiment, the first post-calculation signal Sa corresponding to the difference between the first detection signal S1 and the third detection signal S3 is obtained. By generating and generating the second post-calculation signal Sb corresponding to the difference between the second detection signal S2 and the fourth detection signal S4, the error caused by the noise magnetic field Mix of the detection value θs is reduced. Can be done.

In addition, in order to reduce the error caused by the noise magnetic field Mex as described above, the detection target magnetic field at the position where the intensity becomes the first intensity, that is, the position where the first partial magnetic field MFa can be detected is set. The first requirement of arranging the first and second detection units 11 and 12 and the position where the detection target magnetic field, that is, the second partial magnetic field MFb can be detected at the position where the intensity becomes the second intensity. , It is necessary to satisfy the second requirement that the third and fourth detection units 21 and 22 are arranged. In other words, the first to fourth detection units 11, 12, 21, 22 can be arranged at arbitrary positions as long as the first and second requirements are satisfied. For example, in the present embodiment, the electronic component 20 including the third and fourth detection units 21 and 22 is moved from the magnetic scale 2 more than the electronic component 10 including the first and second detection units 11 and 12. It is located farther away. As long as the first and second requirements are satisfied, the electronic component 10 and the electronic component 20 may be arranged at the same position in the Y direction or may be arranged at different positions in the Y direction.

Further, as long as the first and second requirements are satisfied, the electronic component 10 and the electronic component 20 may be arranged at the same position in the X direction or may be arranged at different positions in the X direction. In the latter case, at least one of the first detection signal S1 and the third detection signal S3 may be corrected so that the phase difference between the first detection signal S1 and the third detection signal S3 becomes zero. At least one of the second detection signal S2 and the fourth detection signal S4 may be corrected so that the phase difference between the second detection signal S2 and the fourth detection signal S4 becomes zero. Further, in the latter case, particularly when each of the first to fourth detection units 11, 12, 21, 22 includes at least one MR element, the first detection signals S1 and the third detection signal S1 and the third The direction of magnetization of the magnetization fixed layer of the MR element included in the first detection unit 11 and the magnetization of the magnetization fixed layer of the MR element included in the third detection unit 21 so that the phase difference of the detection signal S3 becomes 0. At least one of the directions may be shifted from the direction shown in FIG. 5, and is included in the second detection unit 12 so that the phase difference between the second detection signal S2 and the fourth detection signal S4 becomes zero. At least one of the magnetization direction of the magnetization fixed layer of the MR element and the magnetization direction of the magnetization fixed layer of the MR element included in the fourth detection unit 22 may be deviated from the direction shown in FIG.

Further, the first detection unit 11 and the second detection unit 12 may be included in two physically separated electronic components instead of the electronic component 10. In this case, the electronic component including the first detection unit 11 and the electronic component including the second detection unit 12 may be arranged at the same position in the X direction or at different positions in the X direction. You may be. In the latter case, at least one of the first detection signal S1 and the second detection signal S2 may be corrected so that the phase difference between the first detection signal S1 and the second detection signal S2 is 90 °. .. Further, in the latter case, particularly when each of the first and second detection units 11 and 12 includes at least one MR element, the first detection signal S1 and the second detection signal S2 The direction of magnetization of the magnetization-fixed layer of the MR element included in the first detection unit 11 and the direction of magnetization of the magnetization-fixed layer of the MR element included in the second detection unit 12 so that the phase difference is 90 °. At least one may be offset from the directions shown in FIGS. 5 and 6.

Similarly, the third detection unit 21 and the fourth detection unit 22 may be contained in two physically separated electronic components instead of the electronic component 20. In this case, the electronic component including the third detection unit 21 and the electronic component including the fourth detection unit 22 may be arranged at the same position in the X direction, or may be arranged at different positions in the X direction. You may be. In the latter case, at least one of the third detection signal S3 and the fourth detection signal S4 may be corrected so that the phase difference between the third detection signal S3 and the fourth detection signal S4 is 90 °. .. Further, in the latter case, particularly when each of the third and fourth detection units 21 and 22 includes at least one MR element, the third detection signal S3 and the fourth detection signal S4 The direction of magnetization of the magnetization-fixed layer of the MR element included in the third detection unit 21 and the direction of magnetization of the magnetization-fixed layer of the MR element included in the fourth detection unit 22 so that the phase difference is 90 °. At least one may be offset from the directions shown in FIGS. 5 and 6.

As described above, in the present embodiment, the first to fourth detection units 11, 12, 21, and 22 can be arranged at arbitrary positions as long as the first and second requirements are satisfied. Therefore, according to the present embodiment, it is possible to reduce the error caused by the noise magnetic field Mix without causing a large restriction on the installation of the first to fourth detection units 11, 12, 21, and 22.

Up to this point, the effects of the present embodiment have been described assuming an ideal state. Actually, at relative positions other than the relative positions where the angles θ are 0 °, 90 °, 180 ° and 270 °, when the distance from the magnetic scale 2 changes, the direction of the magnetic field to be detected at an arbitrary position is ideal. It deviates from the direction in the state. As a result, an error due to the magnetic scale 2 may occur in the detected value θs. Therefore, conventionally, it has been necessary to arrange the detection unit of the magnetic sensor so that the direction of the magnetic field to be detected does not deviate. On the other hand, in the present embodiment, the deviation in the direction of the magnetic field to be detected is allowed. Instead, in the present embodiment, the first to fourth detection units 11, 12, 21, 22 are arranged so as to satisfy the first and second requirements, and the error caused by the noise magnetic field Mex is reduced. doing. The error caused by the magnetic scale 2 is, for example, gain adjustment, offset adjustment, etc. so that the waveform of the change of the first and second post-calculation signals Sa and Sb due to the change of the relative position approaches a sine wave. Therefore, it can be reduced by correcting the first and second post-calculation signals Sa and Sb.

Hereinafter, the effect of the present embodiment will be described with reference to the result of the first simulation. In the first simulation, the error of the detected value θs when the detected value θs was generated in the presence of the noise magnetic field Mex having a constant direction and intensity was obtained. In the first simulation, the magnitude of the intensity Bex of the noise magnetic field Mex is determined by the intensity Ba of the first partial magnetic field MFa detected by the first and second detection units 11 and 12, that is, 30 of the magnitude of the first intensity. %, And the angle θex formed by the direction of the noise magnetic field Mex at the first detection position P1 with respect to the reference direction DR was set to 60 °.

In the first simulation, a model corresponding to the position detection device 1 was used. Here, the positions of the magnets 4, 5 and 6 in the X direction are defined as follows. First, a straight line located on the upper surface 7a of the yoke 7 and extending in the X direction and in contact with the magnets 4, 5 and 6 is defined as a position reference line. Then, the position of the midpoint of the line segment overlapping each of the magnets 4, 5 and 6 in the position reference line is set as the position of the magnets 4, 5 and 6 in the X direction. In the model used in the first simulation, the distance between the position of the magnet 4 in the X direction and the position of the magnet 5 in the X direction and the distance between the position of the magnet 5 in the X direction and the position of the magnet 6 in the X direction are set. Both were set to 12 mm.

Further, in the model used in the first simulation, the relative position is defined with the state where the magnet 5 and the electronic components 10 and 20 are at the same position in the X direction as the origin. That is, in the model of the embodiment, the relative position of the magnet 5 and the electronic components 10 and 20 at the same position in the X direction is 0 mm, and the magnet 4 and the electronic components 10 and 20 are at the same position in the X direction. The relative position was set to -12 mm, and the relative position when the magnet 6 and the electronic components 10 and 20 were at the same position in the X direction was set to 12 mm.

Further, in the model used in the first simulation, the strength Bb of the second partial magnetic field MFb detected by the third and fourth detection units 21 and 22, that is, the magnitude of the second strength is the first and second. The first to fourth detection units 11, 12, 21, 22 are set so that the intensity Ba of the first partial magnetic field MF detected by the detection units 11, 12 of the above, that is, 20% of the magnitude of the first intensity. Placed.

In the first simulation, the difference S1-S3 between the first detection signal S1 and the third detection signal S3 is set as the first post-calculation signal Sa, and the second detection signal S2 and the fourth detection signal S4 The difference S2-S4 was used as the second post-calculation signal Sb. Then, the detected values θs were obtained by substituting the respective values of the first and second post-calculation signals Sa and Sb into the equation (1). Hereinafter, this detected value θs is referred to as the detected value θs of the embodiment.

Further, in the first simulation, a comparative example is obtained by substituting the value of the first detection signal S1 for Sa in the equation (1) and substituting the value of the second detection signal S2 for Sb in the equation (1). The detected value θs of was obtained.

Further, in the first simulation, the error of the detected value θs of the example (hereinafter referred to as the error E1 of the example) and the error of the detected value θs of the comparative example (hereinafter referred to as the error E2 of the comparative example) are obtained. I asked. In the first simulation, the difference between the detected value θs of the example and the angle θ was defined as the error E1 of the example, and the difference between the detected value θs of the comparative example and the angle θ was defined as the error E2 of the comparative example.

FIG. 11 is a waveform diagram showing the waveforms of the first and second detection signals S1 and S2 in the first simulation. FIG. 12 is a waveform diagram showing waveforms of the third and fourth detection signals S3 and S4 in the first simulation. FIG. 13 is a waveform diagram showing the waveforms of the first and second post-calculation signals Sa and Sb in the first simulation. The horizontal axis in FIGS. 11 to 13 indicates a relative position. The vertical axis in FIG. 11 indicates the magnitudes of the first and second detection signals S1 and S2. The vertical axis in FIG. 12 indicates the magnitudes of the third and fourth detection signals S3 and S4. The vertical axis in FIG. 13 indicates the magnitudes of the first and second post-calculation signals Sa and Sb. In FIG. 11, the curve with reference numeral 71 shows the waveform of the first detection signal S1, and the curve with reference numeral 72 shows the waveform of the second detection signal S2. In FIG. 12, the curve with reference numeral 73 indicates the waveform of the third detection signal S3, and the curve with reference numeral 74 indicates the waveform of the fourth detection signal S4. In FIG. 13, the curve with reference numeral 75 shows the waveform of the first post-calculation signal Sa, and the curve with reference numeral 76 shows the waveform of the second post-calculation signal Sb. In the first simulation, the first to fourth detection signals S1 to S4 are standardized so that the amplitudes of the first and second detection signals S1 and S2 in the absence of the noise magnetic field Mex are 1. ing.

FIG. 14 is a characteristic diagram showing the detected value θs of the comparative example. FIG. 15 is a characteristic diagram showing an error E2 of the comparative example. FIG. 16 is a characteristic diagram showing the detected value θs of the embodiment. FIG. 17 is a characteristic diagram showing an error E1 of the embodiment. The horizontal axis in FIGS. 14 to 17 indicates a relative position. The vertical axis in FIG. 14 indicates the magnitude of the detected value θs in the comparative example. The vertical axis in FIG. 15 indicates the magnitude of the error E2 in the comparative example. The vertical axis in FIG. 16 indicates the magnitude of the detected value θs of the embodiment. The vertical axis in FIG. 17 indicates the magnitude of the error E1 of the embodiment. As shown in FIGS. 15 and 17, the error E1 of the embodiment is smaller than the error E2 of the comparative example, and is theoretically 0. The error E1 of the embodiment is an error when the detection value θs is generated based only on the first and second detection signals S1 and S2. Therefore, according to the present embodiment, the error of the detected value θs can be reduced as compared with the case where the detected value θs is generated only based on the first and second detection signals S1 and S2.

[Modification example]
Next, a modified example of the magnetic scale 2 will be described with reference to FIG. FIG. 18 is a perspective view showing a modified example of the magnetic scale 2. The configuration of the modified example of the magnetic scale 2 is different from the configuration of the magnetic scale 2 shown in FIGS. 1 and 2 in the following points. In the modified example, the magnet 6 is not provided. That is, in the modified example, the magnetic scale 2 includes two magnets 4 and 5 as a plurality of magnets. In the modified example, the range of the detected value θs is limited to a range wider than 0 ° to 180 ° to some extent.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 19 is a plan view showing a schematic configuration of the position detection device according to the present embodiment. The position detecting device 1 according to the present embodiment includes a magnetic scale 102 that generates an external magnetic field having a spatial distribution in intensity and direction instead of the magnetic scale 2 in the first embodiment. The magnetic scale 102 includes a plurality of magnets 104. The plurality of magnets 104 are arranged at intervals from each other. The external magnetic field generated by the magnetic scale 102 is a combination of the magnetic fields generated by each of the plurality of magnets 104.

The magnetic scale 102 is further made of a non-magnetic material such as resin or aluminum and includes a substrate 105 that supports a plurality of magnets 104. The substrate 105 has a disk shape whose center is located on a predetermined central axis C. Further, the substrate 105 has an upper surface 105a and a lower surface. The plurality of magnets 104 are arranged on the upper surface 105a of the substrate 105.

The magnetic scale 102 is interlocked with a movable object (not shown) that rotates, and rotates in the rotation direction R about the central axis C. As a result, the position of the magnetic scale 102 with respect to the magnetic sensor 3 changes within a predetermined range along the rotation direction R. Hereinafter, the relative position of the magnetic scale 102 with respect to the magnetic sensor 3 is simply referred to as a relative position. The rotation direction R includes a clockwise direction in FIG. 19 and a counterclockwise direction in FIG. The rotation direction R corresponds to the movement direction in the present invention.

The plurality of magnets 104 are arranged along the rotation direction R (movement direction). Each of the plurality of magnets 104 has a first end face closest to the central axis C and a second end face farthest from the center of rotation. The distance from the central axis C to the first end face of each of the plurality of magnets 104 is equal to each other, and the distance from the central axis C to the second end face of each of the plurality of magnets 104 is equal to each other.

Further, each of the plurality of magnets 104 has an north pole and an south pole. Here, attention is paid to any two magnets 104 adjacent to the rotation direction R among the plurality of magnets 104. In one of the two magnets 104, the north and south poles are arranged in this order in the direction away from the central axis C. On the other side of the two magnets 104, the north and south poles are arranged in this order in the direction closer to the central axis C.

Although not shown, in the present embodiment, the magnetic sensor 3 detects a detection target magnetic field which is a part of an external magnetic field generated by the magnetic scale 102 and a noise magnetic field Mex other than the detection target magnetic field. The first to fourth detection units 11, 12, 21, and 22 of the magnetic sensor 3 are arranged so as to face the outer peripheral portion of the substrate 105 on the outer side in the radial direction of the substrate 105. The direction of the magnetic field to be detected at an arbitrary position rotates around the arbitrary position as the relative position changes. In the example shown in FIG. 19, in particular, when the magnetic scale 102 makes one rotation, the direction of the magnetic field to be detected at an arbitrary position makes four rotations.

Here, as shown in FIG. 19, a first virtual straight line L1 intersecting the central axis C and a second virtual straight line L2 intersecting the central axis C and different from the first virtual straight line L1. Is assumed. In this embodiment, in particular, the first and second virtual straight lines L1 and L2 are orthogonal to the central axis C. Further, the first and second virtual straight lines L1 and L2 are both on a virtual plane intersecting the magnetic scale 102 and perpendicular to the central axis C. Hereinafter, this virtual plane is referred to as a reference plane. Further, any one position on the reference plane where the magnetic field to be detected has the first intensity is defined as the first detection position P11. The first virtual straight line L1 passes through the first detection position P11. A second position on the reference plane where the magnetic field to be detected has the first intensity and is deviated from the first detection position P11 by an angle corresponding to 90 ° of the electric angle in the rotation direction R. The detection position is P12. The second virtual straight line L2 passes through the second detection position P12. In particular, in the example shown in FIG. 19, the second detection position P12 is located at a position deviated by 22.5 ° in the rotation direction R from the first detection position P11.

As described in the first embodiment, the first and second detection units 11 and 12 detect the first synthetic magnetic field, which is the composite magnetic field of the detection target magnetic field of the first intensity and the noise magnetic field Mix. It is arranged to do. In the present embodiment, the first detection unit 11 is arranged at the first detection position P11, and as the first combined magnetic field, the combined magnetic field of the detection target magnetic field and the noise magnetic field Mex at the first detection position P11 is used. To detect. The second detection unit 12 is arranged at the second detection position P12, and detects the combined magnetic field of the detection target magnetic field and the noise magnetic field Mex at the second detection position P12 as the first combined magnetic field.

Further, a position different from the first detection position P11 on the first virtual straight line L1 and the position on the first virtual straight line L1 where the detection target magnetic field has the second intensity is detected by the third. The position is P21. Further, a fourth detection is performed at a position different from the second detection position P12 on the second virtual straight line L2 and where the detection target magnetic field has the second intensity on the second virtual straight line L2. The position is P22. In the example shown in FIG. 19, the third detection position P21 is a position separated from the first detection position P11 by a predetermined distance in the direction away from the central axis C, and the fourth detection position P22 is the second. It is a position separated by a predetermined distance from the detection position P12 in the direction away from the central axis C.

As described in the first embodiment, the third and fourth detection units 21 and 22 detect the second synthetic magnetic field, which is the composite magnetic field of the detection target magnetic field of the second intensity and the noise magnetic field Mix. It is arranged to do. In the present embodiment, the third detection unit 21 is arranged at the third detection position P21, and as the second combined magnetic field, the combined magnetic field of the detection target magnetic field and the noise magnetic field Mex at the third detection position P21 is used. To detect. The fourth detection unit 22 is arranged at the fourth detection position P22, and detects the combined magnetic field of the detection target magnetic field and the noise magnetic field Mex at the fourth detection position P22 as the second combined magnetic field.

In the present embodiment, the first direction D1, which is a reference for the first detection unit 11 to generate the first detection signal S1, is one direction orthogonal to the first virtual straight line L1 (on the right side in FIG. 19). The direction to go). Further, the second direction D2, which is a reference for the second detection unit 12 to generate the second detection signal S2, is one direction orthogonal to the second virtual straight line L2 (direction toward the upper right side in FIG. 19). Is. The third direction D3, which is a reference for the third detection unit 21 to generate the third detection signal S3, is the same direction as the first direction D1. The fourth direction D4, which is a reference for the fourth detection unit 22 to generate the fourth detection signal S4, is the same direction as the second direction D2.

The first angle θ1 that the direction of the detection target magnetic field detected by the first detection unit 11 is assumed in the ideal state with respect to the first direction D1 and the detection target magnetic field detected by the third detection unit 21. The third angle θ3 formed by the directions with respect to the third direction D3 is equal to each other. Further, the second angle θ2 that the direction of the detection target magnetic field detected by the second detection unit 12 is assumed in the ideal state with respect to the second direction D2, and the detection detected by the fourth detection unit 22. The fourth angle θ4 formed by the direction of the target magnetic field with respect to the fourth direction D4 is equal to each other. The difference between the first angle θ1 and the second angle θ2 is 90 °, and the difference between the third angle θ3 and the fourth angle θ4 is 90 °.

Although not shown, the reference direction DR is located in the above-mentioned reference plane. The reference position may be the same as any of the first to fourth detection positions P11, P12, P21, and P22, or a position different from the first to fourth detection positions P11, P12, P21, and P22. It may be. In one example, the reference position is the same position as the first detection position P11, and the reference direction DR is the direction from the first detection position P11 toward the central axis C.

Similar to the first example of the magnetic sensor 3 in the first embodiment, each of the first to fourth detection units 11, 12, 21, 22 may include at least one MR element. The relationship between the magnetization direction of the magnetization fixed layer of the MR element included in the first detection unit 11 and the first direction D1 is the same as that of the first embodiment. Similarly, the relationship between the magnetization direction of the magnetization fixed layer of the MR element included in the second detection unit 12 and the second direction D2 is the same as that of the first embodiment. Similarly, the relationship between the magnetization direction of the magnetization fixed layer of the MR element included in the third detection unit 21 and the third direction D3 is the same as that of the first embodiment. Similarly, the relationship between the magnetization direction of the magnetization fixed layer of the MR element included in the fourth detection unit 22 and the fourth direction D4 is the same as that of the first embodiment.

Alternatively, as in the second example of the magnetic sensor 3 in the first embodiment, each of the first to fourth detection units 11, 12, 21, 22 may include at least one Hall element. Good. In particular, in the present embodiment, each of the first to fourth detection units 11, 12, 21, 22 may be included in separate electronic components. This electronic component includes a substrate made of a non-magnetic material and a yoke made of a magnetic material, similarly to the electronic components 10 and 20 of the second example of the magnetic sensor 3 in the first embodiment. The substrate has an upper surface parallel to the above-mentioned reference plane. At least one Hall element is embedded in the substrate.

The electronic components including the first detection unit 11 include the Hall element and the yoke so that the Hall element included in the first detection unit 11 can detect the component in the first direction D1 of the first synthetic magnetic field. Is configured. The electronic component including the second detection unit 12 includes the Hall element and the yoke so that the Hall element included in the second detection unit 12 can detect the component in the second direction D2 of the first synthetic magnetic field. Is configured. The electronic components including the third detection unit 21 include the Hall element and the yoke so that the Hall element included in the third detection unit 21 can detect the component in the third direction D3 of the second synthetic magnetic field. Is configured. The electronic components including the fourth detection unit 22 include the Hall element and the yoke so that the Hall element included in the fourth detection unit 22 can detect the component in the fourth direction D4 of the second synthetic magnetic field. Is configured.

Up to this point, the first detection position P11 and the third detection position P21 are on the first virtual straight line L1, and the second detection position P12 and the second detection position P12 are on the second virtual straight line L2. An example in which the detection position P22 of 4 is present has been described. However, the positions of the first to fourth detection positions P11, P12, P21, and P22 in the present embodiment are not limited to the example shown in FIG. For example, the third detection position P21 may be a position deviated from the third detection position P21 shown in FIG. 19 in the rotation direction R by an angle corresponding to 360 ° of the electric angle, that is, 90 °. Similarly, the fourth detection position P22 may be a position deviated from the fourth detection position P22 shown in FIG. 19 in the rotation direction R by an angle corresponding to 360 ° of the electric angle, that is, 90 °. ..

Next, the results of the second and third simulations in which the shapes and arrangements of the plurality of magnets 104 of the magnetic scale 102 are investigated will be described. Ideally, the intensity of the magnetic field to be detected at an arbitrary detection position is constant regardless of the change in the relative position of the magnetic scale 102 with respect to the magnetic sensor 3. However, in reality, the intensity of the magnetic field to be detected at an arbitrary detection position is a change in the relative position of the magnetic scale 102 with respect to the magnetic sensor 3, specifically, a change in the relative position of the plurality of magnets 104 with respect to the arbitrary detection position. It can fluctuate with.

By the way, in order to reduce the influence of the noise magnetic field Mex, it is conceivable to move the detection position closer to the magnetic scale 102 so that the strength of the noise magnetic field Mex is relatively small with respect to the strength of the detection target magnetic field. As a result, it is possible to reduce the influence of the noise magnetic field Mix and increase the strength of the detection target magnetic field itself to improve the quality of the first to fourth detection signals S1 to S4. However, if the detection position is too close to the plurality of magnets 104, the intensity of the magnetic field to be detected fluctuates remarkably due to the change in the relative position. In this embodiment, in particular, the second detection position P12 is located at a position deviated from the first detection position P11 in the rotation direction R, and the fourth detection position P22 is in the rotation direction R from the third detection position P21. It is in a position shifted to. Therefore, if the intensity of the magnetic field to be detected fluctuates, the first detection unit 11 and the second detection unit 12 cannot detect the magnetic field to be detected with the same intensity at the same timing, and the third detection unit 21 and the third detection unit 21 cannot detect the magnetic field. The fourth detection unit 22 cannot detect the magnetic field to be detected with the same intensity at the same timing. As a result, the detected value θs cannot be generated accurately. Therefore, it is preferable that the first to fourth detection positions P11, P12, P21, and P22 are located so that the fluctuation of the intensity of the detection target magnetic field due to the change of the relative position becomes small.

In the second simulation, the position where the change in the intensity of the magnetic field to be detected becomes small due to the change in the relative position was investigated. Specifically, a plurality of points having different distances from the magnetic scale 102 are assumed. Then, the intensities of the magnetic field to be detected at these plurality of points were obtained.

In the second simulation, the model of the magnetic scale 102 shown in FIG. 19 was used. However, in the second simulation, the distance between the two magnets 104 adjacent to the rotation direction R is set to 0. Further, the maximum dimension of the magnet 104 in the rotation direction R when viewed from one direction parallel to the central axis C is 6 mm, and the magnet 104 in the radial direction of the substrate 105 when viewed from one direction parallel to the central axis C. The size of was set to 3 mm.

Here, among the plurality of magnets 104, the three magnets 104 arranged in the rotation direction R are referred to as a first magnet, a second magnet, and a third magnet. Further, it is a point on a virtual straight line passing through the boundary between the first magnet and the second magnet and the central axis C in the reference plane, and is at a position separated from the magnetic scale 102 by a predetermined interval and is the first. The point closest to the magnet is the first point. Further, it is a point on a virtual straight line passing through the center and the central axis C in the rotation direction R of the third magnet in the reference plane, and is located at a position separated from the magnetic scale 102 by the predetermined interval and is the third. The point closest to the magnet is defined as the tenth point.

Further, a virtual curve that passes through the first and tenth points in the reference plane and is located at a position separated from the magnetic scale 102 by the predetermined interval, and the first and tenth points on the virtual curve. Assume eight points in between. These eight points are designated as the second to ninth points in the order of proximity to the first point. The first to tenth points are arranged at equal intervals. The first to tenth points are different from each other in the positional relationship with the first to third magnets. The fourth point is a point on a virtual straight line passing through the center and the central axis C in the rotation direction R of the second magnet in the reference plane, and is located at a position separated from the magnetic scale 102 by the predetermined interval. It is the closest point to the second magnet. The seventh point is a point on a virtual straight line passing through the boundary between the second magnet and the third magnet and the central axis C in the reference plane, and is a position separated from the magnetic scale 102 by the predetermined distance. And is the closest point to the second magnet.

Hereinafter, the distance between the virtual curve and the magnetic scale 102 is represented by the symbol WD. In the second simulation, the interval WD is changed by 0.5 mm in the range of 1 mm to 3.5 mm, and the first point or the first point on the virtual curve is set for each of a plurality of virtual curves having different interval WDs. The average value of the intensity of the magnetic field to be detected at each of the tenth points and the intensity of the magnetic field to be detected at all the points on the virtual curve was obtained. Then, for each point, the difference between the intensity of the magnetic field to be detected at that point and the average value of the magnetic field to be detected at all points on the virtual curve passing through that point is obtained, and the average value of this difference is obtained. Was calculated. Hereinafter, this ratio is referred to as a volatility.

The fluctuation of the intensity of the magnetic field to be detected at each of the first to tenth points on any one virtual curve is on the virtual curve as the relative position of the magnetic scale 102 with respect to the magnetic sensor 3 changes. It represents the fluctuation of the intensity of the magnetic field to be detected at an arbitrary detection position. The difference between the maximum value and the minimum value of the volatility of all the points on any one virtual curve represents the fluctuation range of the intensity of the magnetic field to be detected at any detection position on the virtual curve. In the second simulation, the difference between the maximum value and the minimum value of the volatility was obtained for each of a plurality of virtual curves. Hereinafter, this difference is referred to as a fluctuation range.

FIG. 20 is a characteristic diagram showing the volatility obtained by the second simulation. In FIG. 20, the horizontal axis indicates a position on a virtual curve. In FIG. 20, the first to tenth points are shown as positions on the virtual curve. In FIG. 20, the first to tenth points are represented by numbers from 1 to 10, respectively. Further, in FIG. 20, the vertical axis indicates the volatility. Further, in FIG. 20, the curve with reference numeral 81 indicates the volatility of each point on the virtual curve having an interval WD of 1 mm. The curve with reference numeral 82 indicates the volatility of each point on the virtual curve having an interval WD of 1.5 mm. The curve with reference numeral 83 shows the volatility of each point on the virtual curve having an interval WD of 2.0 mm. The curve with reference numeral 84 shows the volatility of each point on the virtual curve having an interval WD of 2.5 mm. The curve with reference numeral 85 indicates the volatility of each point on the virtual curve having an interval WD of 3.0 mm. The curve with reference numeral 86 shows the volatility of each point on the virtual curve having an interval WD of 3.5 mm. From FIG. 20, it can be seen that the volatility of any point on the virtual curve changes depending on the positional relationship with the first to third magnets. From this result, it can be seen that the intensity of the magnetic field to be detected at an arbitrary detection position fluctuates with the change of the relative position.

FIG. 21 is a characteristic diagram showing the fluctuation range obtained by the second simulation. In FIG. 21, the horizontal axis represents the interval WD and the vertical axis represents the fluctuation range. From FIG. 21, it can be seen that the volatility of the virtual curve having an interval WD of 2.5 mm is minimized. From this result, it can be seen that when the distance between the detection position and the magnetic scale 102 is 2.5 mm, the fluctuation range of the intensity of the detection target magnetic field due to the change in the relative position is minimized.

As described above, in order to improve the quality of the first to fourth detection signals S1 to S4, it is preferable to bring the detection position closer to the magnetic scale 102, that is, to reduce the interval WD. From FIG. 21, it can be seen that when the interval WD is smaller than 2.5 mm, the fluctuation range increases as the interval WD decreases. From this result, when the distance between the detection position and the magnetic scale 102 is smaller than 2.5 mm, the fluctuation range of the intensity of the magnetic field to be detected becomes larger as the distance between the detection position and the magnetic scale 102 becomes smaller. It turns out that it becomes.

By the way, the volatility can also change depending on the distance between two magnets 104 adjacent to each other in the rotation direction R. By changing the distance between the two magnets 104, the intensity of the magnetic field to be detected at each of the first to tenth points on one virtual curve was obtained. Then, as in the second simulation, the volatility was obtained for each point.

In the third simulation, the model of the magnetic scale 102 shown in FIG. 19 was used as in the second simulation. However, in the third simulation, the rotation direction R is changed by changing the maximum dimension of the magnet 104 in the rotation direction R when viewed from one direction parallel to the central axis C to 6 mm, 5 mm, 4.35 mm, and 4 mm. The distance between the two magnets 104 adjacent to the magnet 104 was changed to 0 mm, 1 mm, 1.65 mm, and 2 mm. Further, in the third simulation, it is assumed that the detection position is brought closer to the magnetic scale 102 in order to improve the quality of the first to fourth detection signals S1 to S4, and the distance WD between the virtual curve and the magnetic scale 102 is set. , 1.5 mm, which is smaller than 2.5 mm, which minimizes the fluctuation width.

FIG. 22 is a characteristic diagram showing the volatility obtained by the third simulation. In FIG. 22, the horizontal axis shows the position on the virtual curve, and the vertical axis shows the volatility. The representation of the position on the virtual curve in FIG. 22 is the same as that in FIG. Further, in FIG. 22, the curve with reference numeral 91 indicates the volatility of each point when the distance between the two magnets 104 is 0 mm. The curve with reference numeral 92 shows the volatility of each point when the distance between the two magnets 104 is 1 mm. The curve with reference numeral 93 shows the volatility of each point when the distance between the two magnets 104 is 1.65 mm. The curve with reference numeral 94 shows the volatility of each point when the distance between the two magnets 104 is 2 mm. From FIG. 22, when the distance between the two magnets 104 is 0 mm (reference numeral 91), the difference between the maximum value and the minimum value of the volatility, that is, the fluctuation width is maximized, and the distance between the two magnets 104 is other than 0 mm. Sometimes, the fluctuation width is smaller than when the distance between the two magnets 104 is 0 mm, and when the distance between the two magnets 104 is 1.65 mm (reference numeral 93), the fluctuation width is minimized. I understand. From the result of the third simulation, it can be seen that the fluctuation range of the intensity of the magnetic field to be detected due to the change in the relative position can be reduced by providing the unmagnetized portion between the two magnets 104.

The distance WD between the virtual curve and the magnetic scale 102 is a reference for determining the positions of the first to fourth detection positions P11, P12, P21, and P22. From the result of the third simulation, when the interval WD is 1.5 mm, the maximum dimension of the magnet 104 in the rotation direction R when viewed from one direction parallel to the central axis C is 4.35 mm, and the rotation direction R is set. The distance between the two magnets 104 adjacent to the magnet 104 is 1.65 mm, the distance between the first and second detection positions P11 and P12 and the magnetic scale 102 is slightly smaller than 1.5 mm, and the third and fourth detection positions are set to 1.65 mm. By making the distance between the detection positions P21 and P22 and the magnetic scale 102 slightly larger than 1.5 mm, the intensity of the magnetic field to be detected fluctuates at all of the first to fourth detection positions P11, P12, P21, and P22. The width can be reduced.

As can be understood from the results of the second and third simulations, the distance between the first to fourth detection positions P11, P12, P21, P22 and the magnetic scale 102 is adjusted, and the distance between the two magnets 104 is adjusted. By adjusting, the fluctuation range of the intensity of the magnetic field to be detected at each of the first to fourth detection positions P11, P12, P21, and P22 can be reduced. Therefore, as a study for reducing the fluctuation range of the intensity of the magnetic field to be detected, it is possible to determine the first to fourth detection positions P11, P12, P21, and P22 after examining the adjustment of these intervals. preferable.

The results of the second and third simulations also apply to the position detecting device 1 according to the first embodiment. That is, by adjusting the distance between the first and second detection positions P1 and P2 and the magnetic scale 2, and adjusting the distance between the magnets 4 and 5 and the distance between the magnets 5 and 6, the first and second detection positions P1 and P2 are adjusted. The fluctuation range of the intensities of the partial magnetic fields MFa and MFb can be reduced. Therefore, as a study for reducing the fluctuation range of the intensity of the magnetic field to be detected, it is preferable to determine the first and second detection positions P1 and P2 after examining the adjustment of these intervals.

[Modification example]
Next, a modified example of the magnetic scale 102 will be described with reference to FIG. 23. FIG. 23 is a plan view showing a modified example of the magnetic scale 102. In the modified example, the magnetic scale 102 includes, in addition to the plurality of magnets 104 and the substrate 105, a plurality of non-magnetic materials 106 made of a non-magnetic material such as resin or aluminum, and a yoke 107 made of a magnetic material such as NiFe. I'm out. The plurality of non-magnetic materials 106 and the yoke 107 are arranged on the upper surface 105a of the substrate 105. Each of the plurality of non-magnetic materials 106 is arranged between two adjacent magnets 104.

The yoke 107 magnetically connects a plurality of magnets 104. In the example shown in FIG. 23, the yoke 107 has an annular shape whose center is located on the central axis C. The yoke 107 magnetically connects the first end faces of each of the plurality of magnets 104, which are closest to the central axis C. Here, attention is paid to any two magnets 104 adjacent to the rotation direction R among the plurality of magnets 104. Of these two magnets 104, the magnet 104 whose first end face is the end face on the N pole side is called the first magnet 104, and the magnet 104 whose first end face is the end face on the S pole side is the second magnet. It is called 104. The yoke 107 has a function of controlling the flow of magnetic flux so that the magnetic flux generated from the first end face of the first magnet 104 efficiently flows into the first end face of the second magnet 104. ing.

Other configurations, actions and effects in this embodiment are similar to those in the first embodiment.

The present invention is not limited to each of the above embodiments, and various modifications can be made. For example, as long as the requirements of the claims are satisfied, the arrangement of the first to fourth detection units 11, 12, 21, 22 is not limited to the examples shown in the respective embodiments, and is arbitrary.

Further, the number, shape, and positions of the north pole and the south pole of the plurality of magnets of the magnetic scale 2 or 102 are not limited to the examples shown in the respective embodiments, and are arbitrary. Further, in the first embodiment, the magnetic scale 2 may include a linear multi-pole magnetizing magnet instead of the magnets 4, 5 and 6. Further, in the second embodiment, the magnetic scale 102 may include an annular multi-pole magnetizing magnet instead of the plurality of magnets 104.

1 ... position detector, 2 ... magnetic scale, 3 ... magnetic sensor, 4-6 ... magnet, 7 ... yoke, 8 ... protection unit, 10, 20 ... electronic component, 11 ... first detector, 12 ... second Detection unit, 21 ... 3rd detection unit, 22 ... 4th detection unit, 31-34 ... A / D converter, 35 ... 1st arithmetic circuit, 36 ... 2nd arithmetic circuit, 37 ... 3rd Calculation circuit, 41 ... board, 42 ... yoke, 85,86 ... difference detector, 87 ... angle calculation unit, H1 to H4 ... Hall element, R11, R12, R21, R22 ... MR element.

Claims (11)

A position provided with a magnetic scale that generates an external magnetic field having a spatial distribution of intensity and direction, and a magnetic sensor that detects a detection target magnetic field that is a part of the external magnetic field and a noise magnetic field other than the detection target magnetic field. It ’s a detector,
The position of the magnetic scale can be changed relative to the magnetic sensor within a predetermined range along a moving direction which is a linear direction or a rotational direction.
The direction of the magnetic field to be detected at an arbitrary position rotates around the arbitrary position as the relative position changes.
The intensity of the magnetic field to be detected changes according to the distance from the magnetic scale.
The magnetic sensor is
A first detection unit and a second detection unit arranged so as to detect a first combined magnetic field which is a combined magnetic field of the detection target magnetic field and the noise magnetic field of the first intensity,
A third detection unit and a fourth detection arranged so as to detect a second combined magnetic field which is a combined magnetic field of the detection target magnetic field and the noise magnetic field having a second intensity different from the first intensity. Including part
The first detection unit generates a first detection signal corresponding to the intensity of the component in the first direction of the first synthetic magnetic field.
The second detection unit generates a second detection signal corresponding to the intensity of the component in the second direction different from the first direction of the first synthetic magnetic field.
The third detection unit generates a third detection signal corresponding to the intensity of the component in the third direction of the second synthetic magnetic field.
The fourth detection unit generates a fourth detection signal corresponding to the intensity of the component in the fourth direction different from the third direction of the second synthetic magnetic field.
The magnetic sensor further
A first arithmetic circuit that generates a first post-calculation signal corresponding to the difference between the first detection signal and the third detection signal, and a first arithmetic circuit.
A second calculation circuit that generates a second post-calculation signal corresponding to the difference between the second detection signal and the fourth detection signal, and a second calculation circuit.
A position detection device including a third calculation circuit that generates a detection value having a correspondence relationship with the relative position based on the first and second post-calculation signals. The angle formed by the direction of the detection target magnetic field detected by the first detection unit with respect to the first direction, which is assumed when the direction of the detection target magnetic field changes ideally, is defined as the first angle. When the angle formed by the direction of the detection target magnetic field detected by the third detection unit with respect to the third direction is set to the third angle, the first detection unit and the third detection unit Are arranged so that the first angle and the third angle are equal to each other.
The angle formed by the direction of the detection target magnetic field detected by the second detection unit with respect to the second direction, which is assumed when the direction of the detection target magnetic field changes ideally, is defined as the second angle. When the angle formed by the direction of the detection target magnetic field detected by the fourth detection unit with respect to the fourth direction is set to the fourth angle, the second detection unit and the fourth detection unit The position detecting device according to claim 1, wherein the second angle and the fourth angle are arranged so as to be equal to each other. The difference between the first angle and the second angle is 90 °.
The position detecting device according to claim 2, wherein the difference between the third angle and the fourth angle is 90 °. The third direction is the same direction as the first direction.
The position detecting device according to any one of claims 1 to 3, wherein the fourth direction is the same direction as the second direction. The moving direction is a linear direction,
The first combined magnetic field is a combined magnetic field of the detection target magnetic field and the noise magnetic field at the first detection position on a virtual straight line intersecting the magnetic scale and orthogonal to the moving direction.
The claim is characterized in that the second combined magnetic field is a combined magnetic field of the detection target magnetic field and the noise magnetic field at a second detection position different from the first detection position on the virtual straight line. The position detecting device according to any one of 1 to 4. The moving direction is a rotation direction centered on a predetermined central axis.
The first synthetic magnetic field detected by the first detection unit is the combined magnetic field of the detection target magnetic field and the noise magnetic field at the first detection position on the first virtual straight line intersecting the central axis. Yes,
The first synthetic magnetic field detected by the second detection unit intersects the central axis, and the detection at a second detection position on a second virtual straight line different from the first virtual straight line. It is a combined magnetic field of the target magnetic field and the noise magnetic field.
The second synthetic magnetic field detected by the third detection unit includes the detection target magnetic field and the noise magnetic field at a third detection position different from the first detection position on the first virtual straight line. Is the combined magnetic field of
The second synthetic magnetic field detected by the fourth detection unit includes the detection target magnetic field and the noise magnetic field at a fourth detection position different from the second detection position on the second virtual straight line. The position detection device according to any one of claims 1 to 4, wherein the position detection device is a composite magnetic field of the above. The magnetic scale includes a plurality of magnets arranged along the moving direction.
The position detecting device according to any one of claims 1 to 6, wherein the external magnetic field is a combination of magnetic fields generated by each of the plurality of magnets. The position detecting device according to claim 7, wherein the plurality of magnets are arranged at intervals from each other. The position detecting device according to claim 8, wherein the magnetic scale is further made of a magnetic material and includes a yoke for magnetically connecting the plurality of magnets. The position detection device according to any one of claims 1 to 8, wherein each of the first to fourth detection units includes at least one magnetoresistive sensor. The position detection device according to any one of claims 1 to 8, wherein each of the first to fourth detection units includes at least one Hall element.

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