JP2006138738A - Magnetic type encoder device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic type encoder device that prevents the occurrence of an eddy current due to a rotating magnetic field and can perform angle detection with high precision with wide-range rotation speed of from a low speed rotation to a high speed rotation. <P>SOLUTION: The magnetic type encoder device comprises a magnetic type encoder 10 having a permanent magnet 12 fixed to a rotator 11 and a magnetic field detection element 14 that faces the permanent magnet 12 via a clearance and is attached to a fixed body 13, and a signal processing circuit (not shown) for processing a signal from the magnetic field detection element 14. The fixed body 13 is constituted by a magnetic substance wire. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetic encoder that detects the rotational position of a rotating body, and more particularly to a magnetic encoder device that can maintain high accuracy from low speed rotation to high speed rotation.

Conventionally, in order to detect the rotation angle of a rotating body such as a motor shaft, a disk-shaped permanent magnet magnetized with two poles is fixed to the rotating body, and the magnetic field from the disk-shaped permanent magnet is fixed to the fixed body. A magnetic encoder device that is detected by a magnetic field detection element and detects the absolute position of a rotating body is disclosed (for example, see Patent Document 1).
FIG. 7 is a perspective view of a conventional magnetic encoder.
In FIG. 7, 11 is a rotating body (shaft), 12 is a disk-shaped permanent magnet fixed to the rotating body 11 so that the rotation axis is the same, and is in one direction parallel to the axis of the rotating body 11 in a direction perpendicular to the axis. Is magnetized. Reference numeral 13 denotes a ring-shaped fixed body provided on the outer peripheral side of the permanent magnet 12 and is made of a magnetic block material. Four magnetic field detection elements 14 are attached to the fixed body 13 at intervals of 90 degrees in the circumferential direction. The four magnetic field detection elements are opposed to the outer peripheral surface of the permanent magnet 12 via a gap and have a mechanical angle of 90 degrees with respect to each other. They are staggered.
Next, the operation will be described.
When the rotating body 11 rotates, the magnetic field detection element 14 detects a sinusoidal magnetic flux density with respect to the rotation angle. The rotation angle of the rotating body 11 is detected by processing the output signal from each magnetic field detection element 14.
WO99 / 013296 (pages 4-5, FIG. 1)

The rotating body and permanent magnet of the magnetic encoder are coupled to a rotor of a servo motor, for example, and rotate at the rotational speed of the rotor. When the rotating magnetic field generated by the permanent magnet flows into the fixed body, an eddy current is generated on the surface of the fixed body in a direction that reduces the flowing magnetic field. Conventionally, a magnetic field generated by this eddy current is applied to a magnetic field detecting element arranged on a fixed body, and there is a problem that encoder accuracy deteriorates. In particular, the higher the rotation speed, the larger the generated eddy current and the greater the deterioration of the encoder accuracy.
The present invention has been made in view of such problems, and an object thereof is to provide a magnetic encoder device capable of detecting a rotation angle with high accuracy regardless of the rotation speed.

In order to solve the above problems, the present invention is configured as follows.
The invention according to claim 1 is a magnetic encoder comprising a permanent magnet fixed to a rotating body, and a magnetic field detecting element attached to the fixed body so as to face the permanent magnet through a gap, and the magnetic field detecting element And a signal processing circuit for processing a signal from the magnetic encoder device, wherein the fixed body is made of a magnetic wire.
The invention according to claim 2 is characterized in that the magnetic wire is made of an Fe-based or Co-based amorphous wire, and the surface of the amorphous wire is insulation-coated.

  According to the present invention, since the fixed body is made of a soft magnetic wire, an eddy current generated in the fixed body is suppressed, and a magnetic encoder device capable of detecting a rotation angle with high accuracy from low speed rotation to high speed rotation is provided. realizable.

  Hereinafter, specific examples of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing the structure of a magnetic encoder device of the present invention.
In FIG. 1, 11 is a rotating body (shaft), 12 is a disk-like permanent magnet fixed to the rotating body 11 so that the rotation axis is the same, and is in one direction parallel to the axis of the rotating body 11 in a direction perpendicular to the axis. Is magnetized. Reference numeral 13 denotes a ring-shaped fixed body that is provided on the outer peripheral side of the permanent magnet 12 and is composed of soft magnetic wires 131. Four magnetic field detection elements 14 are attached to the fixed body 13 at intervals of 90 degrees in the circumferential direction. The A1 phase detection element 141 and the B1 phase detection element 142 are provided so as to face the outer peripheral surface of the permanent magnet 12 with a gap and are shifted from each other by 90 degrees in mechanical angle. On the other hand, the A2 phase detection element 143 is provided by shifting the phase by 180 degrees by the mechanical angle, and the B2 phase detection element 144 is provided by shifting the phase by 180 degrees by the mechanical angle with respect to the B1 phase detection element 142.
The difference between the present embodiment and the prior art is that the magnetic block material is used for the fixed body 13 in the prior art. However, in this embodiment, the fixed body 13 is formed by using a magnetic wire 131 and winding it in a coil shape. In other respects, the other configurations are the same as those of the prior art. The magnetic wire 131 is an Fe-Si-B amorphous wire having an insulating coating on the surface.

Next, the operation of the magnetic encoder device of the present invention will be described.
When the rotating body 11 rotates, the permanent magnet 12 also rotates. Due to the change in the magnetic field of the permanent magnet 12, a single-cycle sinusoidal signal is output from the magnetic field detection element 14 for one rotation of the rotating body 11.
FIG. 2 is a block diagram of the signal processing circuit, which processes a signal from the magnetic field detection element 14 and converts it into an angle signal θ. In FIG. 2, 151 and 152 are differential amplifiers, and 153 is an angle calculation circuit. The respective detection signals Va1 and Va2 from the A1 phase detection element 141 and the A2 phase detection element 143 arranged at positions opposed to each other by 180 degrees are input to the differential amplifier 151, and the A phase signal Va which is a differential signal of both signals. Is obtained. Similarly, the respective detection signals Vb1 and Vb2 from the B1 phase detection element 142 and the B2 phase detection element 144 arranged at positions opposite to each other by 180 degrees are input to the differential amplifier 152, and B is a differential signal of both signals. A phase signal Vb is obtained.
FIG. 3 is an explanatory diagram showing the output of the magnetic field detection element, and shows waveform diagrams of the A-phase signal Va and the B-phase signal Vb which are differential signals of the magnetic field detection element. The A-phase signal Va and the B-phase signal Vb are signals that are 90 degrees out of phase from the corresponding arrangement of detection elements.
The A phase signal Va and the B phase signal Vb are input to the angle calculation circuit 153. FIG. 4 is a graph showing the output of the signal processing circuit, and shows the output of the angle calculation circuit 153 when the rotating body 11 rotates. An angle signal θ that linearly changes with respect to the rotation angle is obtained by the arithmetic processing of arctan (Va / Vb).
As described above, since the magnetic wire is used for the fixed body in this embodiment, an eddy current generated in the fixed body is suppressed, and a magnetic encoder device capable of detecting the rotation angle with high accuracy from low speed rotation to high speed rotation is realized. it can.
In this embodiment, an Fe-Si-B amorphous wire is used for the fixed body, but other Fe-based amorphous wires or Co-based amorphous wires may be used.

FIG. 5 is a sectional view of a magnetic encoder device showing a second embodiment of the present invention.
In FIG. 5, 11 is a ring-shaped rotating body made of a magnetic material, 12 is a permanent magnet formed in a ring shape inscribed and fixed on the inner peripheral side of the rotating body 11, and is perpendicular to the central axis of the rotating body 11. Magnetized in one direction. Reference numeral 13 denotes a fixed body having a circular outer periphery having a hollow portion. Similarly to the first embodiment, the fixed body 13 is configured by using a magnetic wire and winding it in a coil shape. Reference numeral 14 denotes a magnetic field detection element which is fixed to the outer peripheral side of the fixed body 13 so as to face the inner peripheral side of the permanent magnet 12 via a gap. With this configuration, the central portion of the fixed body 13, that is, the central portion of the magnetic encoder device can be made hollow.
An example of a specific configuration is as follows.
The rotating body 11 is a magnetic body (SS41) having an outer diameter of 50 mm and a hollow diameter of 20 mm. The permanent magnet 12 is an SmCo-based ring magnet having a linear anisotropy of 40 mm in outer diameter. The fixed body 13 is a Co—Si—B amorphous wire having a diameter of several hundred μm. The magnetic field detection element 14 is a Hall element.
Since the angle detection operation is the same as that in the first embodiment, the description thereof is omitted.

Here, a description will be given of a phenomenon in which an eddy current is generated by a rotating magnetic field generated by a permanent magnet and an influence of the eddy current on a detection signal when the magnetic block material shown in the related art is used for the fixed body.
FIG. 6 is a schematic diagram for explaining generation of eddy current.
As shown in FIG. 6, the rotating magnetic field generated by the permanent magnet 12 passes through the fixed body 13 constituting the magnetic circuit. When the permanent magnet 12 fixed to the rotating body 11 rotates, an eddy current is generated in the vicinity of the surface of the fixed body in a direction to cancel the magnetic flux change in the fixed body 13. The magnitude of the eddy current is proportional to the product of the magnetic flux flowing into the stationary body, the radius of the stationary body, the rotational speed, and the electrical conductivity of the stationary body. In addition, whether the rotation is forward or reverse, the phase of the eddy current is delayed from the rotating magnetic field, reducing the magnetic flux flowing into the fixed body and degrading the encoder accuracy.
That is, when a magnetic block material such as a mechanical structure material (S45C) is used for the fixed body 13, the rotating magnetic field is affected by the eddy current, the phase of the detection signal is changed, and the output voltage is lowered. It can also be seen that the effect increases with the rotational speed.

In this embodiment, a magnetic wire is used as the fixed body and is wound in a coil shape. The magnetic wires are electrically insulated from each other, and the amorphous wire used as the magnetic wire has a thin diameter of several hundreds of micrometers, so that the eddy current that affects the encoder accuracy is extremely small. The angular error due to the eddy current was measured up to 5000 min ⁻¹ using the rotational speed as a parameter, but no increase in error due to the rotational speed was observed.

Thus, in this embodiment, since the fixed body of the magnetic encoder having the hollow portion is formed of the magnetic wire, the eddy current generated in the fixed body is suppressed, and the rotation angle of the actuator having the hollow portion is changed from low speed to high speed. A magnetic encoder device capable of detecting with high accuracy up to rotation can be realized.
In this embodiment, the Co—Si—B amorphous wire is used as the fixed body, but other Co-based amorphous wires or Fe-based amorphous wires may be used.

  The magnetic encoder device of the present invention can be applied as a magnetic encoder device that detects the rotation angle of an actuator used in a robot or the like.

It is a perspective view which shows the structure of the magnetic encoder of this invention. It is a block diagram of a signal processing circuit. It is explanatory drawing which shows the output of a magnetic field detection element. It is a graph which shows the output of a signal processing circuit. It is sectional drawing which shows the structure of the magnetic encoder apparatus of 2nd Example of this invention. It is a schematic diagram explaining generation | occurrence | production of an eddy current. It is a perspective view of the conventional magnetic encoder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Magnetic encoder 11 Rotating body 12 Permanent magnet 13 Fixed body 14 Magnetic field detection element 141 A1 phase detection element 142 B1 phase detection element 143 A2 phase detection element 144 B2 phase detection element 15 Signal processing circuit 151, 152 Differential amplifier 153 Angle calculation circuit

Claims (2)

A magnetic encoder comprising a permanent magnet fixed to a rotating body and a magnetic field detecting element attached to the fixed body facing the permanent magnet through a gap, and a signal processing circuit for processing a signal from the magnetic field detecting element In a magnetic encoder device comprising:
The magnetic encoder device, wherein the fixed body is made of a magnetic wire.   2. The magnetic encoder device according to claim 1, wherein the magnetic wire is composed of an Fe-based or Co-based amorphous wire, and the surface of the amorphous wire is insulation-coated.

Images