JP5168226B2 - Magnetic proximity sensor - Google Patents

Description

  In the present invention, when the magnetic field generation unit made of a magnet and the detection unit made of a magnetic sensor move relatively, the approach between the magnetic field generation unit and the detection unit is detected based on a change in magnetic flux density detected by the magnetic sensor. The present invention relates to a magnetic proximity sensor.

A magnetic proximity sensor is known to be applied when detecting the arrival of a work on a belt conveyor at a predetermined position in a factory or when the elevator reaches the floor. . The position detection accuracy varies depending on the distance between the detection target and the sensor, but is generally several mm to several cm.

As shown in FIG. 1 of Patent Document 1, the conventional magnetic proximity sensor includes a moving body provided with a magnet and a fixed body provided with a Hall element, and the magnet of the moving body that is a detection target is a detection unit. When passing just above the Hall element, the polarity of the magnetic flux density sensed by the Hall element is reversed. The detection signal corresponding to the magnetic flux density sensed by the Hall element is compared with the reference signal, and the approach between the detection target and the detection unit is detected by detecting the position where both are equal.

JP 2003-329405 A (page 3, FIG. 1)

However, in the magnetic proximity sensor of the type in which the detection target and the detection unit are arranged so as to face each other as described above, if the gap between the detection target and the detection unit becomes wide, the magnetic field strength received by the detection unit decreases, so noise As a result, the position detection error at the time of approach detection occurs, and the detection position accuracy is lowered.
The magnetic proximity detector of Patent Document 1 detects the magnetic flux density in the normal direction of the magnetization direction of the magnet, compares the detection voltage corresponding to the magnetic flux density at the position where the polarity of the magnetic field is reversed, with a reference signal, Is detected. However, due to the nature of the magnet, a strong magnetic field is generated in the magnetization direction. However, since the magnetic field in the magnetization direction and the normal direction is weak, the magnetic field strength decreases as the gap between the detection target and the detection unit increases. As a result, the output voltage of the Hall element becomes low, and if noise is superimposed, the detection voltage fluctuates, which causes a problem that an error occurs in position detection.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to improve the detection position accuracy of a magnetic proximity sensor that detects that a detection target has entered a certain detection range. It is another object of the present invention to ensure high accuracy even when the distance between the detection target and the detection unit is long, or when the gap between the detection target and the detection unit varies.

The magnetic proximity sensor according to the present invention detects the magnetic field generation unit and the magnetic field detection unit based on a change in magnetic flux density detected by the magnetic sensor when the magnetic field generation unit including the magnet and the detection unit including the magnetic sensor move relatively. In the magnetic proximity sensor having a determination unit for detecting the approach to the magnetic field generator, the magnetic field generators are arranged side by side in a direction in which the magnetic field generator and the detector are relatively moved, and their magnetization directions are substantially parallel to each other. The magnetic sensor is composed of a pair of magnets arranged so as to face in opposite directions, passes through each of the pair of magnets, and generates a magnetic field that forms a pair of magnetic field reversal surfaces in which the direction of the magnetic field detected by the magnetic sensor is reversed. When the magnetic field generation unit and the detection unit move relatively, at least one of the magnetic field inversion surfaces is crossed, and the determination unit generates a detection signal of the magnetic sensor and a reference signal for detecting the magnetic field inversion surface. Comparison , It is characterized in that it comprises a comparator for outputting a predetermined level proximity detection signal indicating that between the magnetic sensor of the magnetic field reversal surface when the output level is higher than the level of the reference signal of the detection signal.

  The present invention provides a magnetic proximity sensor including a determination unit that detects an approach between a magnetic field generation unit and a detection unit, wherein the magnetic field generation unit is arranged in parallel in a direction in which the magnetic field generation unit and the detection unit move relatively, It consists of a pair of magnets that are arranged so that their magnetization directions are substantially parallel and facing each other, and pass through each of the pair of magnets to form a pair of magnetic field reversal surfaces that reverse the direction of the magnetic field detected by the magnetic sensor The magnetic sensor crosses at least one of the magnetic field inversion surfaces when the magnetic field generation unit and the detection unit relatively move, and the determination unit is configured to detect the detection signal of the magnetic sensor and the magnetic field inversion surface. A comparator that outputs a proximity detection signal at a predetermined level indicating that the magnetic sensor is between the magnetic field reversal surfaces when the output level of the detection signal is greater than the level of the reference signal. Since a strong magnetic field can be obtained even in a region where the gap between the magnetic field generation unit and the detection unit is wide, the signal strength can be increased and the stability of the signal against noise can be improved. it can. Thereby, even when the gap between the magnetic field generation unit and the detection unit becomes wide, it is possible to reduce the position detection error at the time of approach detection. In addition, since the location where the direction of the magnetic field is reversed corresponds to the detection position, even if the gap between the magnetic field generation unit and the detection unit changes, the detection signal level is higher than before and the detection signal zero point is set. Since the detection method can be adopted, the position detection error at the time of approach detection can be made extremely small.

It is a block diagram of the magnetic proximity sensor by Embodiment 1 of this invention. It is a schematic diagram of the magnetic force line at the time of the magnetic proximity sensor operation | movement by Embodiment 1 of this invention. It is a schematic diagram of the magnetic force line at the time of the magnetic proximity sensor operation | movement by Embodiment 1 of this invention. It is a schematic diagram of the magnetic force line at the time of the magnetic proximity sensor operation | movement by Embodiment 1 of this invention. It is a figure which shows the magnetic flux density which penetrates the magnetic sensor at the time of the magnetic proximity sensor operation | movement by Embodiment 1 of this invention, and a comparator output. It is a figure which shows the magnetic flux density which penetrates the magnetic sensor at the time of the magnetic proximity sensor operation | movement by Embodiment 1 of this invention. It is a schematic diagram of the magnetic force line at the time of the magnetic proximity sensor operation | movement by Embodiment 1 of this invention. It is a schematic diagram of the magnetic force line at the time of the magnetic proximity sensor operation | movement by Embodiment 1 of this invention. It is a block diagram of the magnetic proximity sensor by Embodiment 2 of this invention. It is a figure which shows the magnetic flux density which penetrates the magnetic sensor at the time of the magnetic proximity sensor operation | movement by Embodiment 2 of this invention, a comparator output, and an amplifier output. It is a block diagram of the magnetic proximity sensor by Embodiment 3 of this invention. It is a figure which shows the magnetic flux density which penetrates the magnetic sensor at the time of magnetic proximity sensor operation | movement by Embodiment 3 of this invention, a comparator output, an amplifier output, and an AND operation circuit output. It is a figure which shows the magnetic flux density which penetrates the magnetic sensor at the time of magnetic proximity sensor operation | movement by Embodiment 3 of this invention, a comparator output, an amplifier output, and an AND operation circuit output. It is a block diagram of the magnetic proximity sensor by Embodiment 4 of this invention. It is a figure which shows the magnetic flux density which penetrates the magnetic sensor at the time of the magnetic proximity sensor operation | movement by Embodiment 4 of this invention, a comparator output, and an amplifier output. It is a block diagram of the magnetic proximity sensor by Embodiment 5 of this invention. It is a block diagram of the magnetic proximity sensor by Embodiment 6 of this invention.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a magnetic proximity sensor according to Embodiment 1 of the present invention. The magnetic proximity sensor according to the present invention includes a detection unit 1, a magnetic field generation unit 2, and a determination unit 3. The detection unit 1 is composed of a magnetic sensor 101 such as a Hall element, and soft magnetic bodies 102a and 102b such as iron in the form of two rods or plates disposed on both sides of the magnetic sensor 101. FIG. 1 shows an example of a rod-like material as the soft magnetic bodies 102a and 102b. The magnetic sensing direction of the magnetic sensor 101 is the direction indicated by the arrow 104 in FIG. The soft magnetic bodies 102 a and 102 b are arranged such that the longitudinal direction thereof is along the magnetic sensing direction 104 of the magnetic sensor 101. The same applies to the case of a plate-like soft magnetic body, and the thickness direction of the plate-like soft magnetic body is arranged so as to be orthogonal to the magnetic sensing direction 104 in FIG. The magnetic field generator 2 is composed of two magnets 201a and 201b. The detector 1 and the magnetic field generator 2 move relatively, and the direction of this relative movement is indicated by the direction of the arrow 105 in FIG.

In addition, for convenience of explanation, the following embodiments including this embodiment will mainly describe the case where the detection unit 1 moves. However, in the present invention, the detection unit 1 and the magnetic field generation unit 2 include The detection unit 1 or the magnetic field generation unit 2 may be moved, or both may be moved together.

The magnetization directions of the magnets 201a and 201b in the magnetic field generation unit 2 are the directions indicated by the white arrows 202a and 202b in FIG. 1, the magnetic sensing direction of the magnetic sensor 101 (both directions indicated by the arrow 104), the detection unit 1 and the magnetic field. The direction of magnetization of the two magnets 201a and 201b is opposite to each other, both perpendicular to the direction in which the generator 2 moves relatively (the direction of the arrow 105). Further, planes that pass through the centers of the two magnets 201a and 201b and are parallel to the magnetization direction and perpendicular to the paper surface are denoted by 203a and 203b, respectively. FIG. 1 shows a case where the magnetic sensing direction 104 of the magnetic sensor 101 is perpendicular to the planes 203a and 203b.
The determination unit 3 includes a comparator 301 that receives the output of the magnetic sensor 101 and a reference voltage as input signals.

Next, the operation will be described.
First, an operation when the detection unit 1 slides in the direction indicated by the arrow 105 in FIG. 1 will be described. 2 illustrates only the components of the magnetic sensor 101, the soft magnetic bodies 102a and 102b, and the magnets 201a and 201b among the components illustrated in FIG. 1, and other components are omitted. FIG. 2 shows a case where the position of the magnetic sensor 101 is on the left side of the plane 203a. FIG. 2 also shows the state of the lines of magnetic force generated at this time, and a leftward magnetic field is applied to the magnetic sensor 101 on the paper surface.

Next, FIG. 3 shows the state of the lines of magnetic force when the detection unit 1 moves to the right from the state of FIG. 2 and the magnetic sensor 101 is located between the planes 203a and 203b. As shown in FIG. 3, a rightward magnetic field is applied to the magnetic sensor 101. FIG. 4 shows a case where the detector 1 further moves to the right from the state of FIG. 3 and the magnetic sensor 101 moves to the right from the plane 203b. From the state of the lines of magnetic force at this time, a magnetic field leftward in the drawing is applied to the magnetic sensor 101. When the detection unit 1 moves in the direction of the arrow 105 in FIG. 1, the magnetic flux density penetrating the magnetic sensor 101, that is, the magnetic flux density component in the direction of the arrow 105 is as shown in FIG. . Here, the horizontal axis of FIG. 5 (a) is the position of the magnetic sensor 101, and the vertical axis is the magnetic flux density penetrating the magnetic sensor 101 (the component in the normal direction of the plane 203a or 203b of the magnetic flux density). The rightward direction in FIGS. 1 to 4 is positive.

As can be seen from FIG. 5A, the direction of the magnetic flux passing through the magnetic sensor 101 is reversed before and after the magnetic sensor 101 passes through the planes 203a and 203b. That is, when the magnetic sensor 101 is between the flat surface 203a and the flat surface 203b, and when the magnetic sensor 101 is at a position other than that, the directions of the magnetic flux passing through the magnetic sensor are opposite to each other. As described above, since the magnetic field generated by the magnetic field generating unit 2 is reversed in the direction of the magnetic field at the positions of the planes 203a and 203b, the planes 203a and 203b are hereinafter referred to as magnetic field reversal surfaces.

As the magnetic sensor 101, a device that converts the magnitude and direction of a magnetic field into an electric signal, such as a Hall element, is used. For example, in the Hall element, a voltage output proportional to the magnetic flux density penetrating the Hall element can be obtained.
The comparator 301 in the determination unit 3 is connected to the output of the magnetic sensor 101. The output of the magnetic sensor 101 and the reference voltage V0 serving as a reference signal at the position of the magnetic field reversal surface 203a or 203b, that is, the position where the magnetic flux density is zero. Compare with. That is, the value of the reference voltage V0 is the same value as the magnetic sensor output when the magnetic field is zero. As shown in FIG. 5B, the output of the comparator 301 is switched between Hi (high) and Lo (low) when the magnetic field is zero. Since the comparator output is Hi, the approach between the detector 1 and the magnetic field generator 2 can be detected. In the present invention, when the magnetic sensor 101 is located between the two magnetic field reversal surfaces 203a and 203b or at the position of the magnetic field reversal surface 203a or 203b, it is detected as the proximity of the detection unit 1 and the magnetic field generation unit 2. Thus, the approach between the detection target and the detection unit can be detected.

On the magnetic field reversal surface 203a or 203b, since the magnetic flux density becomes zero as described above, the output of the magnetic sensor 101 is compared with the reference voltage V0, and when both become equal, the magnetic sensor 101 becomes the reference. It is also possible to detect the position of the magnetic field reversal surface 203a or 203b and to detect that the detection target is approaching.
Further, as described above, the direction of the magnetic flux density detected by the magnetic sensor 101 is positive in the right direction in FIGS. 1 to 4, and the rise and fall of the output of the comparator 301 shown in FIG. 5B is determined. The direction in which the detection unit 1 and the magnetic field generation unit 2 move relatively can be determined.

  With this configuration, since the magnetization direction 202a of the magnet 201a of the magnetic field generation unit 2 and the magnetization direction 202b of the magnet 201b are both perpendicular to the direction in which the detection unit 1 and the magnetic field generation unit 2 move relatively, Even if the gap between the detection unit 1 and the magnetic field generation unit 2 is widened, the magnetic field intensity received by the detection unit 1 is kept strong, and the output voltage of the magnetic sensor 101 becomes high. For this reason, the output change of the magnetic sensor is large in the vicinity where the magnetic field direction is reversed, and the voltage waveform that is the output of the magnetic sensor shows a steep rise or fall. As a result, the detection signal level is higher than the conventional method and the detection signal zero point can be detected, so that the accuracy of position detection at the time of proximity detection can be improved and the error can be extremely reduced. Can do.

  FIG. 6 shows the magnetic flux density penetrating the magnetic sensor 101 when the gap between the detector 1 and the magnetic field generator 2 is small (in the case of a short distance) and large (in the case of a long distance). From FIG. 6, even if the gap between the magnetic field generation unit and the detection unit changes, the position of the magnetic field zero does not change. Thus, since the position where the output of the comparator 301 switches between Hi and Lo corresponds to the position where the magnetic field direction is reversed, if the gap between the detection unit 1 and the magnetic field generation unit 2 changes, the magnetic field direction changes. Although there is a change in the absolute value of the magnetic flux density detected near the inversion position (the position of the magnetic field inversion surface 203a or 203b in FIG. 6), the position of the magnetic field zero does not change. As a result, since the detection signal level is higher than in the prior art and the zero point of the detection signal can be detected, even if the gap between the detection unit 1 and the magnetic field generation unit 2 changes, the detection position error Can be made extremely small.

With the configuration described above, even when the magnetic characteristics of the magnetic sensor and the magnet vary or when the ambient temperature changes, the absolute value of the magnetic flux density varies, but the position of the magnetic field zero hardly changes. Therefore, it is only necessary to correct the output fluctuation (offset fluctuation) of the magnetic sensor 101 with zero magnetic field, and the detection position fluctuation can be suppressed to be extremely small. For example, the change rate of the Hall element sensitivity with respect to the temperature is about 0.01% / ° C. to about 10% / ° C. depending on the type of the Hall element, but in this embodiment, the point where the magnetic flux density is zero is measured. Since it is not necessary to consider the temperature variation with respect to the sensitivity of the Hall element, the temperature drift can be made almost zero.
Further, in the configuration of the present embodiment, since the magnetic sensor 101 is sandwiched between the soft magnetic bodies 102a and 102b, magnetic flux concentrates on the magnetic sensor, so that the magnetic sensitivity of the magnetic sensor 101 is increased and the signal-to-noise ratio is increased. As a result, the detection signal level is higher than in the prior art and the zero point of the detection signal can be detected, so that the detection error can be reduced.

1 to 4 show a case where the magnetic sensing directions of the soft magnetic bodies 102a and 102b and the magnetic sensor 101 are parallel, the present invention is not limited to this. For example, even if the longitudinal direction of the soft magnetic body 102a or 102b is inclined with respect to the magnetic sensing direction 104, the effect of concentrating the magnetic flux on the magnetic sensor 101 is lower than that in the case of being parallel. There is an effect of increasing the sensitivity. However, the smaller one of the angle of intersection between the magnetic sensitive direction 104 and the longitudinal direction of the soft magnetic body 102a or 102b is preferably within 5 degrees, more preferably within 3 degrees, and even more preferably within 1 degree. The proximity position can be detected with high accuracy. This applies not only to the present embodiment but also to other embodiments of the present invention.

  Further, the positions of the magnetic field reversal surfaces 203a and 203b are such that the magnetization strengths of the magnets 201a and 201b are uniform along the relative moving direction 105 of the detection unit 1 and the magnetic field generation unit 2 in FIG. It is the approximate center of each magnet. In the case where the intensity of magnetization is not uniform along the moving direction 105 described above, for example, it may be stronger on the right side than the center position of the magnet in FIG. Also in this case, the position of the magnetic field reversal surface 203a is located anywhere on the magnet 201a, and the magnetic field reversal surface 203a is a flat surface. Therefore, by detecting the position where the magnetic flux density is zero, the approach between the detection unit 1 and the magnetic field generation unit 2 can be detected with the magnetic field reversal surface 203a as the reference position (one of them).

In the present embodiment, the case where the detection unit 1 and the magnetic field generation unit 2 slide relative to each other, that is, the case where the detection unit 1 and the magnetic field generation unit 2 face each other at a predetermined interval and move in parallel is described as an example. The relative movement is not limited to this example. For example, when the detection unit 1 rotates, even when the detection unit 1 crosses one of the magnetic field reversal surfaces 203a and 203b, the approach of the detection unit 1 and the magnetic field generation unit 2 can be detected by the above-described procedure.

1 to 4 show the case where the relative movement direction (the direction of the arrow 105) is perpendicular to the magnetic field reversal surfaces 203a and 203b, the present invention is not limited to this. As shown in FIG. 7, the magnetic field reversal surface 203a or 203b may be crossed obliquely (in the direction of the arrow 106). In this case as well, the magnetic flux density detected by the magnetic sensor 101 is the magnetic field reversal surface 203a or 203b. In this case, the approach between the detection unit 1 and the magnetic field generation unit 2 can be detected from the output of the comparator 301 by the above-described method.

Further, even when the detection unit 1 or the magnetic field generation unit 2 rotates, when the magnetic sensor 101 crosses either the magnetic field reversal surface 203a or 203b, the tangential direction of the rotational motion is perpendicular to the magnetic field reversal surface 203a or 203b. It may not be the case. Even in this case, the normal direction component of the magnetic field reversal surface 203a or 203b is used as the input of the comparator 301 in the magnetic flux density detected by the magnetic sensor 101 as in the case where the detector 1 crosses obliquely as shown in FIG. Thus, it is possible to detect the approach between the detection unit 1 and the magnetic field generation unit 2.
In short, when the detector 1 and the magnetic field generator 2 move relatively, the magnetic sensor 101 crosses either or both of the magnetic field reversal surfaces 203a and 203b, and the magnetic flux density detected by the magnetic sensor 101 at that time If the normal direction component of the magnetic field reversal surface 203a or 203b is acquired and used as the input of the comparator 301, the proximity of the detection unit 1 and the magnetic field generation unit 2 can be detected.

1 to 4, the magnets 201a and 201b in the magnetic field generator 2 are described as being parallel to the magnetization directions 202a and 202b. However, the present invention is not limited to this. For example, the present embodiment can be used even when the magnetization direction 202b is inclined with respect to the magnetization direction 202a. However, the inclination angle (the smaller of the crossing angles formed by the extended lines of 202a and 202b) is preferably within 3 degrees, more preferably within 1 degree, and even more preferably within 0.5 degrees, a more accurate proximity position. Can be detected. This applies not only to the present embodiment but also to the following embodiments of the present invention.

1 to 4, the magnets 201a and 201b in the magnetic field generating unit 2 have the same height on the paper surface (that is, for example, the distance between the magnets 201a and 201b and the magnetic sensor 101 is the same in FIG. 1). Although demonstrated, the structure of the magnetic field generation | occurrence | production part 2 is not restricted to this. For example, as shown in FIG. 8, when the interval between the magnet 201a and the magnetic sensor 101 is different from the interval between the magnet 201b and the magnetic sensor 101 (FIG. 8 shows a case where the magnet 201a is closer to the magnetic sensor 101). However, since the magnetic field generator 2 generates a magnetic field having a pair of magnetic field reversal surfaces 203a and 203b, proximity detection using the pair of magnetic field reversal surfaces as a reference position is possible. In short, it is only necessary that the magnetization directions of the two magnets are parallel or substantially parallel and the magnetization directions thereof are opposite to each other, and a magnetic field is generated.

Embodiment 2. FIG.
FIG. 9 is a block diagram showing a magnetic proximity sensor according to the second embodiment of the present invention. The differences from the first embodiment are as follows. First, the detection unit 1 is composed of two types of magnetic sensors, and one is a first magnetic sensor 111 that converts the magnitude and direction of a magnetic field into an electrical signal, similar to the magnetic sensor 101 in the first embodiment. A Hall element or the like is used. The other of the magnetic sensors is a second magnetic sensor 112 that outputs a signal on a pulse when the direction of the magnetic field to be detected is reversed. For example, a large Barkhausen effect application element is used. Further, as a difference from the first embodiment, the determination unit 3 includes a comparator 302 that receives the output of the first magnetic sensor 111 and the reference signal V0 for detecting the position of the magnetic field reversal surface 203a or 203b, and It comprises an amplifier 303 that amplifies the output of the second magnetic sensor 112.

Next, the operation will be described.
The first magnetic sensor 111 and the second magnetic sensor 112 are arranged so that the magnetic sensing direction is the direction of the arrow 104 in FIG. Thereby, among the magnetic flux densities applied to the first magnetic sensor 111 and the second magnetic sensor 112, the magnetic flux density components in the normal direction of the magnetic field reversal surfaces 203a and 203b are magnets 201a and 201b and soft magnetic bodies 102a and 102b. Since the positional relationship of the magnetic material is the same as that of the first embodiment, it is the same as that shown in FIG. With respect to the positions of the first magnetic sensor 111 and the second magnetic sensor 112, the transverse component of the magnetic flux density penetrating these elements (that is, the magnetic flux density component in the normal direction of the magnetic field reversal surfaces 203a and 203b), the comparator 302 10 and the output of the amplifier 303 are shown in FIGS. 10 (a), (b) and (c), respectively.

For example, when a large Barkhausen effect application element is used as the second magnetic sensor 112, this includes a wire having a large Barkhausen effect and a coil winding wound around the wire, and only when the direction of the magnetic field is reversed. A pulse-like output is generated, and the polarity of the pulse is opposite to that in the direction in which the magnetic field changes. Therefore, the output of the second magnetic sensor 112 generates a pulse when the direction of the magnetic field is reversed, that is, when the second magnetic sensor 112 passes through the magnetic field reversal surfaces 203a and 203b of FIG. The polarities are opposite to each other when passing through the magnetic field reversal surfaces 203a and 203b. By using such a second magnetic sensor 112, even if the gap between the detection unit 1 and the magnetic field generation unit 2 fluctuates, the position of the magnetic field reversal surface does not change, so that the detection signal level is higher than before and Since the zero point of the detection signal can be detected, the accuracy of position detection at the time of approach detection can be increased, and the error can be extremely reduced.

  Here, the output of the comparator 302 that compares the output from the first magnetic sensor 111 with the reference voltage V0 serves as “zone detection” indicating that the detection target is within a certain range. Further, the output of the second magnetic sensor 112, that is, the output of the amplifier 303, plays a role of "position detection" for accurately measuring that the detection target has passed a predetermined position. Therefore, the configuration in this embodiment has both “zone detection” and “position detection” outputs, so the position detection accuracy at the time of approach detection is not questioned, but the output of the comparator 302 is adopted when detecting a zone. However, when the position is detected with high accuracy, it is possible to use the output of the amplifier 303.

The polarity of the output of the amplifier 303, that is, the output of the second magnetic sensor 112 changes depending on the direction of the magnetic field change. From this, by determining the polarity of the output of the amplifier 303, it is also possible to determine the direction in which the detection unit 1 and the magnetic field generation unit 2 move relatively.

Embodiment 3 FIG.
FIG. 11 is a block diagram showing a magnetic proximity sensor according to the third embodiment of the present invention. The differences from the first embodiment are as follows. The magnetic sensor in the detection unit 1 is composed of two types, and one is the first magnetic sensor 111 that converts the magnitude and direction of the magnetic field into an electric signal, like the magnetic sensor 101 in the first embodiment. Etc. are used. The other of the magnetic sensors is a second magnetic sensor 112 that outputs a signal on a pulse when the direction of the magnetic field to be detected is reversed. For example, a large Barkhausen effect application element is used. In FIG. 11, a soft magnetic body 102c is disposed on the right side of the first magnetic sensor 111, a soft magnetic body 102b is disposed between the first magnetic sensor 111 and the second magnetic sensor 112, and a second second A soft magnetic body 102 a is arranged on the left side of the magnetic sensor 112.

In addition, the comparator 302a that receives the output of the first magnetic sensor 111 and the reference voltage V1, the comparator 302b that receives the output of the first magnetic sensor 111 and the reference voltage V0, and the second magnetic sensor 112. And an AND circuit 304a having the amplifier 303 and the comparator 302b as inputs, and an AND circuit 304b having the amplifier 303 and the comparator 302b as inputs.

  Next, the operation will be described. Both the first magnetic sensor 111 and the second magnetic sensor 112 are arranged such that the direction of magnetic sensitivity is the direction of the arrow 104 in the drawing. Of the magnetic flux density detected by the first magnetic sensor 111 or the second magnetic sensor 112 when the detection unit 1 moves in the direction of the arrow 105, the component in the normal direction of the magnetic field reversal surface 203a is the first embodiment. This is almost the same as FIG. The reason is that in this embodiment, the number of components of the soft magnetic material is 3, and the soft magnetic material 102b is also arranged between the first magnetic sensor and the second magnetic sensor. However, since the distance between the soft magnetic material and the soft magnetic material is only about the thickness of the first magnetic sensor (for example, a Hall element) and is very small, the first embodiment and the present embodiment are substantially the same. This is because there is no big difference in the magnetic circuit of the form, and it can be regarded as almost equivalent.

In FIG. 12A, the horizontal component of the magnetic flux density penetrating the first magnetic sensor 111 and the second magnetic sensor 112 when the horizontal axis is the position of the first magnetic sensor 111 (that is, the magnetic field reversal surface). (B), the output of the comparator 302a is shown, the output of the second magnetic sensor is amplified by the amplifier 303, and the output of the second magnetic sensor is further shown in FIG. Shows the output of the AND operation circuit 304a. Here, the distance P between the first magnetic sensor 111 and the second magnetic sensor 112 is the distance between the position where the magnetic flux density component perpendicular to the magnetization direction of the magnet 201a is maximized and the center position of the magnet 201a. (That is, approximately the same as P shown in FIG. 3C). With this configuration, since the distance between the first magnetic sensor 111 and the second magnetic sensor 112 is separated by P, the magnetic flux density applied to the first magnetic sensor as shown in FIG. The magnetic flux density applied to the second magnetic sensor is shifted by the interval P.

  Here, when the reference voltage V1 of the comparator is set to an appropriate negative value as shown in FIG. 12A, the output of the comparator 302a is only a distance P from the magnetic field reversal surface 203a as shown in FIG. 12B. Hi is displayed near the left position. On the other hand, since the output of the second magnetic sensor 112 is on the left side by the distance P when the first magnetic sensor 111 passes through the magnetic field reversal surface 203a, as shown in FIG. In other words, the output of the second magnetic sensor 112 outputs a pulse at a distance P to the left of the magnetic field reversal surface 203a.

When the logical product operation circuit 304a calculates the logical product of the output of the comparator 302a and the output of the amplifier 303, and the first magnetic sensor 111 passes the position separated by the distance P to the left from the magnetic field reversal surface 203a. Only the output signal can be extracted. In this way, a gate signal can be obtained from the output of the first magnetic sensor 111 as the output of the AND operation circuit 304a. Since it is possible to detect that the magnetic sensor 111 is located at a predetermined distance (offset) P on the left side from the magnetic field reversal surface 203a based on the gate signal, it is possible to improve the reliability of proximity detection. The offset P can be set to various values by adjusting the value of the reference voltage V1.

  On the other hand, the position of another magnetic field reversal surface 203b can be detected by the following method. Since the reference voltage V0 of the comparator 302b is a value corresponding to zero magnetic flux density as described in the first embodiment, the output of the comparator 302b is as shown in FIG. The output becomes Hi in between. This section includes a position separated to the left by a distance P from the magnetic field reversal surface 203b. Since the output of the second magnetic sensor 112 is on the left side by the distance P when the first magnetic sensor 111 passes through the magnetic field reversal surface 203b, as shown in FIG. The second magnetic sensor 112 outputs a pulse at a distance P to the left of the magnetic field reversal surface 203b.

Then, the logical product operation circuit 304b calculates the logical product of the output of the comparator 302b and the output of the amplifier 303, so that only when the first magnetic sensor 111 passes the position left by the distance P from the magnetic field reversal surface 203b. Can be extracted. In this way, the output of the first magnetic sensor 111 can also be used as a gate signal for the magnetic field reversal surface 203b. Since it is possible to detect that the magnetic sensor 111 is located at a predetermined distance (offset) P on the right side from the magnetic field reversal surface 203b based on the gate signal, it is possible to improve the reliability of proximity detection.

In the present embodiment, as shown in FIG. 13, the case where the set value of the offset P is smaller than the distance between the magnetic field reversal surfaces 203a and 203b has been shown, but when the offset value needs to be set larger, For example, the value of the offset P can be increased by increasing the distance between the magnets 201a and 201b in the magnetic field generator 2. Further, by setting the reference voltage to be compared by the comparator 302b to a value lower than the value of V0, which is the same value as the magnetic field zero, the section in which the comparator 302b outputs Hi can be widened, and the set value of the offset P is increased. be able to.
Note that the polarity of the output of the amplifier 303 (that is, the output of the second magnetic sensor 112) changes depending on the direction of the magnetic field change. That is, the moving direction can be determined by determining the polarity of the output of the amplifier 303.
In the first embodiment of the present invention, when the magnetic sensor 101 is located between the two magnetic field reversal surfaces 203a and 203b or at the position of the magnetic field reversal surface 203a or 203b, the detection unit 1 and the magnetic field generation unit 2 are approached. In the present embodiment, the detection unit 1 and the magnetic field generation unit 2 are approached by a predetermined distance P from the magnetic field reversal surface 203a or 203b, in addition to using the two magnetic field reversal surfaces 203a and 203b as a reference. It is also possible to use a remote position as a reference. Which position is used as a reference to detect the approach of the detection unit 1 and the magnetic field generation unit 2 may be appropriately selected according to the application.

Embodiment 4 FIG.
FIG. 14 is a block diagram showing a magnetic proximity sensor according to the fourth embodiment of the present invention. The differences from the first embodiment are as follows. The detection unit 1 includes two magnetic sensors 101a and 101b that convert the magnitude and direction of a magnetic field into electric signals. For example, Hall elements are used as the magnetic sensors 101a and 101b.
In FIG. 14, a soft magnetic body 102a is disposed on the left side of the magnetic sensor 101a, a soft magnetic body 102b is disposed between the magnetic sensors 101a and 101b, and a soft magnetic body 102c is disposed on the right side of the magnetic sensor 101. The determination unit 3 compares and compares the comparator 301a that receives the output of the magnetic sensor 101a and the reference voltage V0, the comparator 301b that receives the output of the magnetic sensor 101b and the reference voltage V0, and the outputs of the comparators 301a and 301b. The circuit 305 is configured.

  Next, the operation will be described. The magnetic sensors 101a and 101b are arranged so that the magnetic sensing direction is the direction 104 in the figure. Of the magnetic flux density applied to the magnetic sensor 101a or 101b when the detector 1 moves in the direction of the arrow 105, the magnetic flux density component in the normal direction of the magnetic field reversal surface 203a is almost the same as that shown in FIG. Be the same. The reason is that the number of parts of the soft magnetic material is 3 in the present embodiment, which is different from the first embodiment, but the interval between the soft magnetic material and the soft magnetic material is the magnetic sensor 101a (for example, a Hall element). This is because there is substantially no difference between the magnetic circuit of the first embodiment and the present embodiment, and it can be regarded as almost equivalent.

  FIG. 15A shows the lateral component of the magnetic flux density penetrating the magnetic sensors 101a and 101b when the horizontal axis is the position of the magnetic sensor 101a (that is, the component in the normal direction of the magnetic field reversal surface 203a). Here, the magnetic sensors 101a and 101b are separated by a predetermined distance Q. Therefore, as shown in FIG. 15A, the magnetic flux densities detected by the magnetic sensors 101a and 101b are out of phase by the interval Q.

Here, when the reference voltage V0 of the comparator is set to a value when the magnetic sensor indicates zero magnetic field, the outputs of the comparators 301a and 301b are shifted from each other by the interval Q as shown in FIGS. 15B and 15C. become. When the detection unit 1 moves in the direction of the arrow 105 or in the opposite direction, the output of the comparator 301a and the output of 301b always become Hi (or Lo) after one becomes Hi (or Lo). That is, the movement direction can be determined by comparing the outputs of the comparators 301a and 301b and determining the order of Hi (or Lo).

In addition, when the predetermined interval Q is set smaller than the interval between the two magnetic field reversal surfaces 203a and 203b, when the detection unit 1 passes near the magnetic field generation unit 2 and there is no failure point, the comparators 301a and 301b Between the time when one of the outputs becomes Hi and the time when it becomes Lo, the output of the other comparator always becomes Hi. If one comparator output does not become Hi at all between the time when one comparator output becomes Hi and then becomes Lo, it can be determined that there is some failure. In this way, by detecting changes in the two comparator outputs, it is possible to perform a self-diagnosis as to whether or not there is a failure in the detection unit.

Embodiment 5 FIG.
FIG. 16 is a block diagram showing a magnetic proximity sensor according to Embodiment 5 of the present invention. In FIG. 16, the detection unit 1 and the determination unit 3 are shown. The difference between this embodiment and this embodiment is as follows. The shapes of the soft magnetic bodies 102a and 102b are plate-like, and the magnetic sensor 101 is disposed between the end of one soft magnetic body and the end of the other soft magnetic body. The magnetic sensing direction of the magnetic sensor 101 is the direction indicated by the arrow 104 in the figure.

  As shown in FIG. 16, most of the magnetic flux passes through the narrowest gap between the two soft magnetic bodies as indicated by the broken line arrow 107, so the direction of the magnetic flux passing through the magnetic sensor 101 is the direction of the arrow 104. Become. With this configuration, since magnetic flux concentrates on the magnetic sensor 101, the magnetic sensitivity of the magnetic sensor 101 can be increased, and the signal-to-noise ratio can be increased. As a result, the detection error can be reduced. . In order to ensure magnetic sensitivity, the cross-sectional area in the direction perpendicular to the magnetic flux direction of the soft magnetic material may be increased. In order to obtain the same cross-sectional area as the rod-shaped soft magnetic material (that is, magnetic sensitivity). Since the plate-like soft magnetic body can be formed thinner than the rod-like soft magnetic body, the detection unit can be made thinner and smaller.

Embodiment 6 FIG.
FIG. 17 is a block diagram showing a magnetic proximity sensor according to Embodiment 6 of the present invention. In FIG. 17, only the magnetic field generator 2 is shown. The difference between this embodiment and this embodiment is as follows. The magnetic field generation unit 2 includes two magnets 201a and 202b and a soft magnetic material 204 such as iron connected to the two magnets.

With this arrangement, most of the magnetic fields generated from the magnets 201a and 201b that pass downward in the figure pass through the soft magnetic body 204, and the outside of the soft magnetic body 204 (shown in the figure). In the lower part, almost no magnetic field leaks. Moreover, even if there is something that disturbs the magnetic field such as iron, magnet, current line, etc. outside the soft magnetic body 204 (lower side in FIG. 15), it is shielded by the soft magnetic body 204. Thus, even when there is a disturbance magnetic field, the influence can be reduced, and the detection performance can be ensured.
Of the magnetic fields generated from the magnets 201a and 201b, a magnetic field is applied to the side (upper part of the drawing) through which the detection unit 1 passes, as in the first embodiment. Therefore, as in the first to fifth embodiments. The proximity detection of the detection target can be performed with high accuracy.

DESCRIPTION OF SYMBOLS 1 Detection part, 101, 101a, 101b Magnetic sensor, 102a, 102b, 102c Soft magnetic body, 104 Magnetosensitive direction of magnetic sensor, 105, 106 Movement direction of detection part, 107 Direction of magnetic flux, 111 1st magnetic sensor, 112 Second magnetic sensor, 2 magnetic field generator, 201a, 201b magnet, 202a, 202b magnet magnetization direction, 203a, 203b magnetic field reversal surface, 204 soft magnetic material, 3 determination unit, 301, 301a, 301b, 302 comparator, 303 Amplifier, 304a, 304b AND Operation Circuit, 305 Comparison Operation Circuit

Claims (11)

When the magnetic field generation unit made of a magnet and the detection unit made of a magnetic sensor move relatively, the approach between the magnetic field generation unit and the detection unit is detected based on a change in magnetic flux density detected by the magnetic sensor. In the magnetic proximity sensor including the determination unit, the magnetic field generation unit is arranged in parallel in a direction in which the magnetic field generation unit and the detection unit relatively move, and the magnetization directions of the magnetic field generation units are substantially parallel to each other. The magnetic sensor generates a magnetic field that passes through each of the pair of magnets and forms a pair of magnetic field reversal surfaces in which the direction of the magnetic field detected by the magnetic sensor is reversed. When the magnetic field generation unit and the detection unit move relatively, they cross at least one of the magnetic field reversal surfaces, and the determination unit detects the detection signal of the magnetic sensor and the magnetic field reversal surface. A comparator that compares a reference signal and outputs a proximity detection signal at a predetermined level indicating that the magnetic sensor is between the magnetic field reversal surfaces when the output level of the detection signal is greater than the level of the reference signal; Magnetic proximity sensor characterized by that. The determination unit compares the detection signal of the magnetic sensor with the reference signal, and changes the output level of the proximity detection signal when both output levels become equal, thereby causing the magnetic sensor to invert the magnetic field. The magnetic proximity sensor according to claim 1, further comprising a comparator indicating that it is on the surface. The detection unit includes first and second magnetic sensors, and is arranged such that a distance measured along the normal direction of the magnetic field reversal surface of the first and second magnetic sensors is a positive value. The determination unit compares the detection signal of the first magnetic sensor with the reference signal, and changes the output level of the first proximity detection signal when both output levels become equal. A comparator and a second comparator that compares the detection signal of the second magnetic sensor with the reference signal and changes the output level of the second proximity detection signal when both output levels are equal to each other. 3. The direction in which the magnetic field generation unit and the detection unit move relative to each other is determined based on the order in which the output levels of the first and second proximity detection signals are changed. A magnetic proximity sensor according to 1. The detection unit includes first and second magnetic sensors, and a distance measured along the normal direction of the magnetic field reversal surface between the first and second magnetic sensors is between the magnetic field reversal surfaces. The determination unit compares the detection signal of the first magnetic sensor with the reference signal, and the first proximity detection signal is output when both output levels are equal. The first comparator for changing the output level of the second magnetic sensor, the detection signal of the second magnetic sensor and the reference signal are compared, and when the output levels of both are equal, the output level of the second proximity detection signal is determined. When the output level of the second proximity signal is not changed between the time when the output level of the first proximity detection signal is changed and the time when the output level is changed again. In the above detection unit Other magnetic proximity sensor according to claim 2, characterized in that determining that there is a failure in the determination unit. The detection unit outputs a first magnetic sensor that outputs a detection signal corresponding to the value of the magnetic flux density, and a first magnetic sensor that outputs a pulsed magnetic field direction reversal signal when the direction of the magnetic field is reversed based on the value of the magnetic flux density. The determination unit compares the detection signal of the first magnetic sensor with the reference signal, and when the level of the detection signal is greater than the level of the reference signal, A comparator that outputs a proximity detection signal at a predetermined level indicating that the magnetic sensor is between the magnetic field reversal surfaces, and the second magnetic sensor is configured to detect the pair of magnetic field reversal surfaces based on the magnetic field direction reversal signal. 2. The magnetic proximity sensor according to claim 1, wherein a reference surface position detection signal indicating that it is on any one of the surfaces is output. The distance measured along the normal direction of the pair of magnetic field reversal surfaces between the first and second magnetic sensors is the position of one surface of the pair of magnetic field reversal surfaces, and the first and second magnetic sensors. The magnetic field component of the second magnetic sensor is arranged so as to be approximately equal to the distance from the position where the magnetic flux component is maximized, and the determination unit calculates the logical product of the proximity detection signal and the magnetic field direction inversion signal. On the basis of the result, the first magnetic sensor outputs a proximity detection signal at a predetermined level indicating that the first magnetic sensor is located at a predetermined distance from one surface of the pair of magnetic field reversal surfaces. The magnetic proximity sensor according to claim 5. When the magnetic flux density detected by the second magnetic sensor changes from a negative value to a positive value, a magnetic field inversion signal having a positive output level is output, and the magnetic flux density changes from a positive value to a negative value. A magnetic field inversion signal having a negative output level is sometimes output, and the determination unit is configured to move the magnetic field generation unit and the detection unit relative to each other based on an output polarity of the magnetic field inversion signal. The magnetic proximity sensor according to claim 5 or 6, wherein the magnetic proximity sensor is determined. 8. The detection unit according to claim 1, further comprising: a bar-shaped or plate-shaped soft magnetic body disposed on both outer sides of the magnetic sensor and substantially parallel to the magnetic sensing direction of the magnetic sensor. A magnetic proximity sensor according to claim 1. The detection unit includes first and second magnetic sensors arranged substantially parallel to a direction in which the magnetic field generation unit and the detection unit relatively move, and the first and second magnetic sensors The rod-shaped or plate-shaped soft magnetic material disposed between and on both sides and substantially parallel to the magnetic sensing direction of the magnetic sensor is provided. Magnetic proximity sensor. The said detection part is provided with two plate-shaped soft magnetic bodies which are arrange | positioned on both sides of a magnetic sensor, and are arrange | positioned in the mutually opposite direction substantially perpendicular | vertical to the magnetic sensing direction of the said magnetic sensor. The magnetic proximity sensor according to 2, 4, 4 or 5. 11. The magnetic proximity sensor according to claim 1, wherein a soft magnetic material is connected to the pair of magnets of the magnetic field generation unit.

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