JP2015175762A - Encoder, electromechanical device, robot, and railway vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform position detection accurately using an encoder.SOLUTION: An encoder comprises a first magnet body of M1 poles (M1 is an even number of 4 or more), a second magnet body of M2 poles (M2 is an even number of two or more), a first biaxial magnetic sensor circuit, a second biaxial magnetic sensor circuit, and a position signal generation unit. Individual small magnets constituting each magnet body are magnetized in a direction crossing a magnetic sensitive surface of the biaxial magnetic sensor circuit.

Description

  The present invention relates to an encoder using a magnetic sensor and various devices using the encoder.

  As an encoder using a magnetic sensor, a rotary encoder described in Patent Document 1 is known. The rotary body of the rotary encoder is provided with a first magnet at the center and a plurality of annular second magnets on the outer peripheral side. Further, the fixed body facing the rotating body is provided with a first magnetosensitive element for detecting the magnetic field of the first magnet and a second magnetosensitive element for detecting the magnetic field of the second magnet. Each of the first magnetosensitive element and the second magnetosensitive element is composed of two magnetoresistive patterns provided in directions orthogonal to each other. In order to appropriately detect the magnetic field with the magnetoresistive pattern, the first magnet and the second magnet are magnetized along the direction toward the magnetosensitive element (that is, the direction parallel to the rotation axis), and the magnetized surface thereof. (A surface orthogonal to the magnetization direction) is arranged to face the magnetosensitive element. However, an absolute rotation angle cannot be detected with these first and second magnetosensitive elements. Therefore, in order to detect an absolute rotation angle, two Hall elements arranged at an angle of 90 degrees are provided on the fixed body.

JP 2012-112707 A

  However, in the conventional encoder described above, since the magnetic field is detected using the magnetoresistive pattern, the detection accuracy of the rotation angle is limited by the accuracy of the resistance of the magnetoresistive pattern. In general, it is difficult to increase the accuracy of the resistance of the magnetoresistive pattern. Therefore, a technique capable of detecting the rotation angle with higher accuracy has been desired. Further, not only the rotation angle but generally an encoder capable of detecting a position with high accuracy has been desired. Furthermore, regarding an electromechanical device, a technique that enables highly accurate position detection using an encoder has been desired.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.

(1) According to one form of this invention, the encoder which measures the position of the 2nd member which moves along a predetermined | prescribed movement direction with respect to a 1st member is provided. The encoder includes a first magnet body having an M1 pole (M1 is an even number of 4 or more) including a plurality of first small magnets provided on the second member; and a plurality of second small magnets provided on the second member. A second magnet body having an M2 pole (M2 is an even number of 2 or more) including a magnet; a first biaxial magnet disposed on the first member with a certain gap from the surface of the first magnet body A sensor circuit; a second biaxial magnetic sensor circuit disposed on the first member with a certain gap from a surface of the second magnet body; the first biaxial magnetic sensor circuit and the first And a position signal generation unit that processes output signals of the two 2-axis magnetic sensor circuits. The first two-axis magnetic sensor circuit and the second two-axis magnetic sensor circuit each have two magnetosensitive axis directions. The individual first small magnets constituting the first magnet body are magnetized in a direction intersecting the magnetic sensitive surface of the first two-axis magnetic sensor circuit, and the individual first small magnets constituting the second magnet body are magnetized. The two small magnets are magnetized in a direction crossing the magnetic sensitive surface of the second two-axis magnetic sensor circuit. The position signal generator is configured to output the first member with respect to the first member according to a first magnetic angle output of the first two-axis magnetic sensor circuit and a second magnetic angle output of the second two-axis magnetic sensor circuit. A position signal indicating the position of the second member is generated.
According to this encoder, since a biaxial magnetic sensor circuit is used, position detection can be performed with high accuracy. The position signal generation unit generates a position signal according to the first magnetic angle output of the first two-axis magnetic sensor circuit and the second magnetic angle output of the second two-axis magnetic sensor circuit. Position detection can be performed with higher accuracy than in the case of using a biaxial magnetic sensor circuit. Furthermore, since the individual small magnets constituting each magnet body are magnetized in the direction intersecting the magnetic sensitive surface of the biaxial magnetic sensor circuit, the strong magnetic field of the small magnet can be detected by the biaxial magnetic sensor circuit. As a result, highly accurate position detection is possible.

(2) In the encoder, each of the first two-axis magnetic sensor circuit and the second two-axis magnetic sensor circuit measures a magnetic field along the X axis of the X axis and the Y axis orthogonal to each other. A plurality of X-axis sensor elements for measuring, and a plurality of Y-axis sensor elements for measuring a magnetic field along the Y-axis.
According to this configuration, it is possible to obtain a sine wave-like output with less magnetostriction as the output of a plurality of Hall elements of the two-axis magnetic sensor circuit, and accurately detect the position based on these sine wave-like outputs with little magnetostriction. Can be done.

(3) In the encoder, the integers M1 and M2 are integers in which M1 / 2 and M2 / 2 are prime, and the position signal generation unit is configured to output a first magnetic angle of the first biaxial magnetic sensor. The position signal may be generated from an output and a second magnetic angle output of the second two-axis magnetic sensor.
According to this configuration, the position of the second member relative to the first member can be detected with high accuracy from the first magnetic angle output of the first two-axis magnetic sensor and the second magnetic angle output of the second two-axis magnetic sensor. It is.

(4) In the encoder, the integer M1 is equal to 2 ^{Q + 1} (Q is an integer of 1 or more), the integer M2 is equal to 2, and the first magnetic angle of the first two-axis magnetic sensor circuit The output is a digital signal of N1 bits (N1 is an integer of 2 or more) indicating the relative position of the second member with respect to the first member, and the second magnetic angle output of the second biaxial magnetic sensor circuit is: The digital signal of N2 bits (N2 is an integer of 2 or more) indicating the relative position of the second member with respect to the first member, and the position signal generation unit outputs the most significant Q bit of the second magnetic angle output It is also possible to generate a (N1 + Q) -bit signal as the position signal in which the N1 bit of the first magnetic angle output is arranged below the most significant Q bit of the second magnetic angle output. .
According to this configuration, since the number of bits of the position signal can be increased by combining the most significant Q bit of the second magnetic angle output and the N1 bit of the first magnetic angle output, position detection with high accuracy (high resolution) Is possible.

(5) In the encoder, the position signal generation unit includes the first magnetic angle output of the first two-axis magnetic sensor circuit and the second two-axis magnetic sensor circuit according to the movement of the second member. When the first magnetic angle output of the second magnetic angle output increases, the timing at which the first magnetic angle output returns from the maximum value of the first magnetic angle output to the minimum value, and the highest Q of the second magnetic angle output. The most significant Q bit of the second magnetic angle output is corrected in accordance with the first magnetic angle output so that the timing at which the bit is incremented, and the highest magnetic bit output of the second magnetic angle output after the correction is corrected. The position signal of the (N1 + Q) bits may be generated using the upper Q bits.
According to this configuration, even when there is a non-negligible error in the second magnetic angle output, the combination of the most significant Q bit of the second magnetic angle output and the N1 bit of the first magnetic angle output is correct. A position signal can be obtained.

(6) In the encoder, the second member is a rotating body, and the first magnet body includes a plurality of pairs of small magnets configured by two first small magnets magnetized in opposite directions to each other. The plurality of small magnet pairs may be arranged along a circular orbit around the rotation axis of the rotating body.
According to this configuration, the position detection accuracy of the encoder can be further increased.

(7) In the encoder, each first small magnet has a rectangular parallelepiped shape, and each small magnet pair covers two first small magnets and at least a part of the periphery of the two first small magnets. By doing so, it is good also as what has the coating | coated member which makes the whole shape of the said small magnet pair the equilateral trapezoid column shape.
According to this configuration, an encoder with high position detection accuracy using a plurality of small magnet pairs can be easily created.

(8) In the encoder, at least one of the first small magnet and the second small magnet may be formed of a ferromagnetic thin film.
According to this configuration, since a small and powerful small magnet can be used, the entire encoder can be made compact while improving the position detection accuracy.

(9) According to another aspect of the invention, an electromechanical device is provided. The electromechanical device includes an encoder connected to a rotor of the electromechanical device, and a control unit that controls the operation of the electromechanical device.
According to this electromechanical device, the position of the rotor of the electromechanical device can be detected with high accuracy.

(10) The electromechanical device is an AC brushless motor having a two-phase electromagnetic coil, and the control unit is configured to output the sine wave signal and the cosine output from the first two-axis magnetic sensor circuit of the encoder. A drive signal generation unit that generates a drive signal for the two-phase electromagnetic coil from a wave signal may be provided.
According to this configuration, since the two-phase drive signal is generated from the sine wave signal and the cosine wave signal output from one two-axis magnetic sensor circuit, the phase shift of the drive signal due to the position shift of the magnetic sensor or the like. Can be prevented.

  The present invention can be realized in various forms other than the apparatus. For example, an encoder, a rotary encoder, a position detection method, a rotational position detection method, an electromechanical device equipped with an encoder, a robot, a railway vehicle, a computer program for realizing the function of the method or device, and the computer program recorded It can be realized in the form of a non-transitory storage medium.

Explanatory drawing which shows the structure and operation | movement of the rotary encoder of 1st Embodiment. The graph which shows the various detection signals obtained with a biaxial magnetic sensor circuit. Explanatory drawing which shows the magnetic sensing direction of several Hall element in a biaxial magnetic sensor circuit. Explanatory drawing which shows the circuit structure and operation | movement of a biaxial magnetic sensor circuit. Explanatory drawing which shows the output level of the biaxial magnetic sensor circuit according to arrangement | positioning of the biaxial magnetic sensor circuit with respect to a small magnet. Explanatory drawing which shows the magnetic angle output output from two 2-axis magnetic sensor circuits. Explanatory drawing which shows the position signal production | generation part which determines the absolute position (absolute angle) of a rotary body using the output of two biaxial magnetic sensor circuits. Explanatory drawing which shows the correction | amendment object range of the short period interval value Px. The flowchart which shows the algorithm of correction | amendment of the short period interval value Px. Explanatory drawing which shows the number of bits of an absolute position output at the time of changing the pole number of a 1st magnet body. Explanatory drawing which shows the structure of the rotary encoder of 2nd Embodiment. Explanatory drawing which shows the structure of the rotary encoder of 3rd Embodiment. Explanatory drawing which shows the structure of the rotary encoder of 4th Embodiment. Explanatory drawing which shows the structure of the rotary encoder of 5th Embodiment. Explanatory drawing which shows the structure of the rotary coder of 6th Embodiment. The block diagram which shows the electric constitution of an electric machine apparatus provided with the encoder of embodiment. The block diagram which shows the internal structure of a main control circuit. Explanatory drawing which shows the internal structure and operation | movement of a rotation speed calculation part. Explanatory drawing which shows the robot using the electromechanical device of embodiment. Explanatory drawing which shows the rail vehicle using the electric machine apparatus of embodiment.

A. First embodiment (rotary encoder)
FIG. 1 is an explanatory diagram showing the configuration and operation of a rotary encoder 100A as the first embodiment. As shown in FIGS. 1A and 1B, the encoder 100 </ b> A includes an annular first magnet body 110 and a second magnet body 210 disposed inside the first magnet body 110. . Further, the first two-axis magnetic sensor circuit 130 provided with a certain gap from the surface of the first magnet body 110 along the outer periphery of the first magnet body 110, and the second magnet body 210 And a second biaxial magnetic sensor circuit 230 provided with a certain gap from the surface. The two magnet bodies 110 and 210 are provided on a substantially disk-shaped rotating body 400 (FIG. 1B) including the support member 150, and the two two-axis magnetic sensor circuits 130 and 230 are provided on the substrate 140 ( It is provided in FIG. The biaxial magnetic sensor circuits 130 and 230 are drawn in the shape of an IC package. Further, FIG. 1B depicts a state in which the second magnet body 210 can be seen through the second two-axis magnetic sensor circuit 230. The substrate 140 constitutes a fixed body (also referred to as “first member”) that does not rotate, and the rotating body 400 constitutes a rotating body (also referred to as “second member”) that rotates around the rotation axis C. The support member 150 of the rotator 400 is preferably formed of a lightweight and rigid non-magnetic material with a small moment of inertia, and is preferably formed of aluminum, magnesium, duralumin, resin, composite resin, or the like. An annular first yoke member 120 is provided on the inner peripheral side of the first magnet body 110, and a disc-shaped second yoke member 220 is provided on the back side of the second magnet body 210. It has been. Further, a magnetic shielding member 160 is provided at a position between the two magnet bodies 110 and 210. These members 120, 220, and 160 are for reducing leakage of unnecessary magnetic flux, and are preferably formed of a soft magnetic material. However, some or all of these members 120, 220, and 160 may be omitted. This encoder 100A can be applied to position detection of an arbitrary rotating body, and is connected to the rotating shaft 530 of the motor 500 in the example of FIG.

  The first magnet body 110 is a 64-pole magnet body composed of 64 small magnet pairs 111 ps provided over the entire outer periphery of the rotating body 400. One small magnet pair 111 ps constitutes one magnetic pole of the first magnet body 110. Each small magnet pair 111ps is composed of two small magnets 111s (FIG. 1A) arranged side by side along a direction parallel to the rotation axis C of the rotating body 400. FIG. 1C shows an enlarged part of a cross section when one small magnet pair 111ps is viewed from the front direction as in FIG. 1B, and FIG. As in FIG. 1A, a part of a cross section when one small magnet pair 111ps is viewed from the side surface is shown enlarged. One small magnet pair 111ps is composed of two small magnets 111s having a rectangular parallelepiped shape and a covering member 112, and has an isosceles trapezoidal column shape as a whole. That is, it has an isosceles trapezoidal shape when viewed from the front (FIG. 1C), and has a rectangular shape when viewed from the side (FIG. 1D). The isosceles trapezoidal shape in plan view has a height H and an outer width WD. Further, the rectangular shape in side view has a depth DP and a height H. The outer peripheral width WD is determined according to the size of the diameter of the first magnet body 110 and the number of poles M1 of the first magnet body 110. For example, when the diameter of the first magnet body 110 is 30 mm, the number of poles M1 is 64, and the height H of the small magnet pair 111ps is 5 mm, WD = 1.47 mm, and the small magnet pair 111ps The size is extremely small. If it is going to manufacture the whole of such a small isosceles trapezoidal column shape with a magnet, the taper process for it is difficult. Therefore, in the present embodiment, the small magnet pair 111ps having the isosceles trapezoidal column shape as a whole is formed by covering the two small rectangular magnets 111s with the covering member 112. The covering member 112 is a member provided to cover at least a part of the periphery of two rectangular parallelepiped small magnets 111s and to make the entire shape of the small magnet pair 111ps an isosceles trapezoidal shape. As the material of the covering member 112, it is possible to use a non-magnetic material such as an aluminum material or a resin in consideration of ease of processing and durability.

  As shown in an enlarged view in FIG. 1D, the individual small magnets 111s are magnetized in parallel along a direction parallel to a direction (that is, a radial direction) passing from the rotation axis C through the center of each small magnet 111s. ing. Further, the two small magnets 111s constituting each small magnet pair 111ps are magnetized in opposite directions. As shown in FIG. 1E, by arranging a large number of small magnet pairs 111ps on the outer periphery of the rotating body 400, the multipolar first magnet body 110 can be easily created. For example, a 64-pole first magnet body 110 can be configured by arranging 64 small magnet pairs 111 ps in an annular shape. In this configuration, it can be understood that the small magnet pair 111ps is arranged along a circular path around the rotation axis C of the rotating body 400. As shown in FIG. 1A, the center of the first two-axis magnetic sensor circuit 130 is a straight line passing through the middle of the two small magnets 111s constituting each small magnet pair 111ps (that is, the two small magnets 111s). It is preferable to be arranged on a trajectory followed by the boundary.

  The second magnet body 210 is formed of two semicircular disk-shaped small magnets 211s arranged around the rotation axis C of the encoder 100A inside the first magnet body 110, and is circular as a whole. This is a two-pole magnet body having a plate shape. The magnetization direction of the individual small magnets 211s of the second magnet body 210 is a direction parallel to the rotation axis C, and the two small magnets 211s are magnetized in opposite directions. The center of the second magnet body 210 is preferably disposed at a position on the rotation axis C of the rotating body 400. The center of the second two-axis magnetic sensor circuit 230 is arranged at a position on the rotation axis C of the rotating body 400.

  The small magnet 111s may be simply referred to as “magnet 111s”, the small magnet pair 111ps may be referred to as “magnet pair 111ps”, and the magnet body 110 may be referred to as “magnet assembly 110”. The same applies to the small magnet 211s, the small magnet pair 211ps, and the magnet body 210.

  FIG. 2 is a graph showing various detection signals sin θm, cos θm, D1 obtained by the biaxial magnetic sensor circuit 130. Since the configuration and operation of the two two-axis magnetic sensor circuits 130 and 230 are the same, the following description will be given mainly for the first two-axis magnetic sensor circuit 130. The horizontal axis of the graph of FIG. 2 is the rotation angle θr of the encoder 100A (that is, the rotating body). This rotation angle θr is also called “mechanical angle”. The magnetic field along the circumferential direction of the first magnet body 110 shows a sinusoidal change with two adjacent small magnet pairs 111 ps as one cycle. The position of each period of the magnetic field is represented by a magnetic angle θm. Signals sin θm and cos θm shown in the upper part of FIG. 2 are a sine wave signal and a cosine wave signal corresponding to the magnetic angle θm. However, FIG. 2 shows an example in which the first magnet body 110 has eight poles for convenience of illustration. A signal D1 shown at the bottom of FIG. 2 is a signal that linearly changes from 0 to the maximum value in each period of the magnetic angle θm, and is a magnetic angle output D1 output from the biaxial magnetic sensor circuit 130 to an external circuit. is there. The magnetic angle output D1 can be generated, for example, by decoding the sine wave signal sin θm and the cosine wave signal cos θm.

  FIG. 3 is an explanatory diagram showing an example of arrangement of a plurality of Hall elements included in the biaxial magnetic sensor circuit 130 and their magnetic sensitive directions. Here, as directions parallel to the surface of the biaxial magnetic sensor circuit 130, an X-axis direction and a Y-axis direction perpendicular to each other are drawn. The Z-axis direction is orthogonal to the X-axis direction and the Y-axis direction, and is a direction parallel to the magnetization direction of the small magnet 111s (or 211s). In addition, the direction from the south pole to the north pole is indicated by an arrow as the magnetic sensing direction of the hall element (direction of detecting the lines of magnetic force). A white circle including a black circle inside indicates that the direction from the back side to the front side of the paper surface is the magnetosensitive direction. A white circle including “X” in the inside indicates that the direction from the front side to the back side of the paper surface is the magnetosensitive direction.

  The two-axis magnetic sensor circuit 130 shown in FIG. 3A includes two X-axis Hall elements X1 and X2 whose X-axis direction is a magnetic sensitive direction, and two Y-axis Hall elements Y1 whose Y-axis direction is a magnetic sensitive direction. , Y2. The number of X-axis Hall elements is preferably a plurality, and is not limited to two and may be three or more. The same applies to the Y-axis Hall element. As will be described later, a first magnetic angle signal sin θm is generated from the plurality of X-axis Hall elements X1 and X2, and a second magnetic angle signal cos θm is generated from the plurality of Y-axis Hall elements Y1 and Y2. This point will be further described later.

  The biaxial magnetic sensor circuit 130 of FIG. 3B has a first set of hall elements YX1 and YX2 and a second set of hall elements XY1 and XY2. In these two sets of Hall elements, a direction that is inclined by 45 degrees with respect to the X-axis direction and the Y-axis direction is defined as a magnetosensitive direction. The two-axis magnetic sensor circuit 130 in FIG. 3C has two Y-axis Hall elements Y1 and Y2 and two X-axis Hall elements X1 and X2. The circuit of FIG. 3C is different from the circuit of FIG. 3A in that the magnetosensitive directions of the two Y-axis Hall elements Y1 and Y2 and the two X-axis Hall elements X1 and X2 face each other. Yes. The two-axis magnetic sensor circuit 130 in FIG. 3D has four Y-axis Hall elements Y1a, Y1b, Y2a, Y2b and four Z-axis Hall elements Z1a, Z1b, Z2a, Z2b. When using the two-axis magnetic sensor circuit 130 of FIG. 3D, the outputs of the upper two Y-axis Hall elements Y1a and Y1b are added, and the lower two Y-axis Hall elements Y2a and Y2b are added. It is possible to obtain an output equivalent to the outputs of the two Y-axis Hall elements Y1 and Y2 in FIG. The same applies to the Z-axis Hall elements Z1a, Z1b, Z2a, Z2b. Regardless of which of the two-axis magnetic sensor circuits 130 shown in FIGS. 3B to 3D, the magnetic angle signals sinθm and cosθm can be generated by combining the outputs of the plurality of Hall elements. is there. As can be understood from these examples, the biaxial magnetic sensor circuit 130 is a circuit capable of detecting a magnetic field along two orthogonal directions. Further, in the two-axis magnetic sensor circuit 130, a plurality of X-axis sensor elements are arranged at locations separated from each other along the X-axis by a first set of X-axis Hall elements and a second set of X-axis Hall elements. Similarly, the plurality of Y-axis sensor elements include a first set of Y-axis Hall elements and a second set of Y-axis Hall elements arranged at locations separated from each other along the Y-axis. It is possible to configure. The center of the two-axis magnetic sensor circuit 130 coincides with the center position between the plurality of Hall elements.

  FIG. 4 is an explanatory diagram showing the circuit configuration and operation of the biaxial magnetic sensor circuit 130. Here, the configuration of the Hall element shown in FIG. 3A is used. The biaxial magnetic sensor circuit 130 includes amplification circuits 131 and 132, AD conversion circuits 133 and 134, and a signal processing circuit 135 in addition to the X axis Hall elements X1 and X2 and the Y axis Hall elements Y1 and Y2. ing. The outputs of the two X-axis Hall elements X1 and X2 are input to the first amplifier circuit 131, and the outputs of the two Y-axis Hall elements Y1 and Y2 are input to the second amplifier circuit 132. As shown in FIG. 4B, the outputs of the two X-axis Hall elements X1 and X2 are each a first sinusoidal signal. The outputs of the two Y-axis Hall elements Y1 and Y2 are second sine wave (cosine wave) signals that are 90 degrees out of phase with the first sine wave. The first amplifier circuit 131 is configured as a differential amplifier that takes a difference (X1-X2) between outputs of the two X-axis Hall elements X1 and X2. This is because the circuits and wirings of the Hall elements X1 and X2 are configured so that the signs of the outputs of the two X-axis Hall elements X1 and X2 input to the first amplifier circuit 131 are reversed. Because. In the example of FIG. 4B, the outputs of the two X-axis Hall elements X1 and X2 are drawn as signals having opposite signs and equal absolute values. However, depending on the installation position of the two-axis magnetic sensor circuit 130 and the magnetic pole position due to the magnetic flux distortion of the magnet, the absolute values of the outputs of these two X-axis Hall elements X1 and X2 may be different from each other. However, also in this case, the difference between the outputs of the two X-axis Hall elements X1 and X2 (X1-X2) is obtained by the first amplifier circuit 131, so that the installation position of the two-axis magnetic sensor circuit 130 and the magnetic flux of the magnet are obtained. Regardless of the displacement of the magnetic pole position due to distortion, it is possible to obtain a correct sine wave output corresponding to the magnetic angle θm. The same applies to the Y-axis Hall elements Y1 and Y2 and the second amplifier circuit 132. Thus, a sine wave signal (X1-X2) is generated by taking the difference between the output signals of the plurality of X-axis Hall elements, and a sine wave signal ( A cosine wave signal (Y1-Y2) that is 90 degrees out of phase with X1-X2) can be generated. Further, based on the sine wave signal (X1-X2) and the cosine wave signal (Y1-Y2), the magnetic angle output D1 indicating the position (rotation position) of the rotating body can be generated.

  Note that the outputs of the two X-axis Hall elements X1 and X2 input to the first amplifier circuit 131 may be signals having the same sign. In this case, the first amplifier circuit 131 is configured as a summing amplifier. However, if the first amplifier circuit 131 is configured as a differential amplifier, even when the two output signals X1 and X2 include common noise (for example, high-frequency noise accompanying PWM control of the electromagnetic coil) It is preferable in that noise can be reduced by taking the difference (X−X2). These points are also the same for the second amplifier circuit 132.

  The outputs (X1-X2) and (Y1-Y2) of the amplifier circuits 131 and 132 are converted into digital signals by the AD conversion circuits 133 and 134, respectively, and become magnetic angle signals sin θm and cos θm. The signal processing circuit 135 generates a magnetic angle output D1 shown in FIG. 2 by performing a decoding operation based on these magnetic angle signals sin θm and cos θm. The signal processing circuit 135 further generates the two-phase pulse signals Pa and Pb and the periodic signal Z shown in FIG. 4C by using the magnetic angle output D1.

The two-phase pulse signals Pa and Pb and the periodic signal Z are generated as follows, for example. The magnetic angle output D1 is a signal representing the magnetic angle θm by a plurality of bits. For example, when the magnetic angle output D1 is configured as a 12-bit signal, the value of the magnetic angle output D1 is 0 to 4095 (= 2 ¹² −1) while the magnetic angle θm changes from 0 to 2π. It changes linearly. The two-phase pulse signals Pa and Pb are signals whose phases are shifted from each other by 90 degrees, and are signals corresponding to an A-phase output and a B-phase output of an optical incremental encoder. The periodic signal Z is a signal that generates one pulse every time the magnetic angle θm changes by 2π, and is a signal that corresponds to the Z-phase signal of the optical incremental encoder. For example, the A-phase pulse signal Pa is generated as a signal indicating a change in the second least significant bit of the magnetic angle output D1. The B-phase pulse signal Pb is generated as a signal obtained by taking an exclusive OR (XOR) of the least significant 2 bits of the angle signal D1. The periodic signal Z is generated as a signal obtained by taking a negative logical sum (NOR) of all bits of the angle signal D1. When the angle signal D1 is a 12-bit signal, 1024 pulses of the two-phase pulse signals Pa and Pb are generated while the magnetic angle θm changes by 2π.

  The signal processing circuit 135 can output the angle signal D1, the sine wave signal sin θm, the cosine wave signal cos θm, the two-phase pulse signals Pa and Pb, and the periodic signal Z to the outside. A device using the rotary encoder 100A can perform position control and speed control using some of these signals.

  By the way, as described in FIG. 1, the individual small magnets 111 s of the first magnet body 110 are magnetized in a direction parallel to the direction passing through the center of the individual small magnet 111 s from the rotation axis C. The two-axis magnetic sensor circuit 130 is arranged so that its Z-axis (FIG. 3) is parallel to the magnetization direction of the small magnet 111s. The individual small magnets 211s of the second magnet body 210 are magnetized in a direction parallel to the rotation axis C, and the second biaxial magnetic sensor circuit 230 has a Z-axis magnetization direction of the small magnets 211s. Are arranged in parallel with each other. The reason why such an arrangement is adopted is based on the experimental results described below.

  FIG. 5 is an explanatory diagram showing the output level of the biaxial magnetic sensor circuit according to the arrangement of the biaxial magnetic sensor circuit with respect to the small magnet. As shown in FIG. 5A, here, a large number of small magnets 111 s are provided on the outer periphery of a disk-shaped support member 150. However, FIG. 5A shows only a portion corresponding to 1/8 of the whole (portion having a central angle of 45 degrees) for convenience of illustration, and eight small magnets 111s are provided. FIG. 5B is a cross-sectional view of FIG. 5A, and shows a cross section of one small magnet 111s. The magnetization direction of each small magnet 111s is parallel to the direction from the rotation axis C toward the center of each small magnet 111s (that is, the radial direction). In this experiment, the biaxial magnetic sensor circuit 130 was arranged at the first measurement position SP1 and the second measurement position SP2, and the magnetic fields were measured at the respective positions SP1 and SP2. The first measurement position SP1 is a position 0.5 mm upward from the surface of the plurality of small magnets 111s, and the two magnetosensitive axis directions of the two-axis magnetic sensor circuit 130 (X and Y axis directions in FIG. 4). The biaxial magnetic sensor circuit 130 is installed so that the plane defined by is parallel to the magnetization direction of the small magnet 111s. The “surface defined by the two magnetosensitive axis directions” corresponds to the magnetosensitive surface of the biaxial magnetic sensor circuit 130. The magnetic sensitive surface of the biaxial magnetic sensor circuit 130 can be defined as a plane parallel to the surface of the magnetic body provided in the biaxial magnetic sensor circuit 130. The second measurement position SP2 is a position 0.5 mm away from the outer periphery of the plurality of small magnets 111s, and is 2 so that the magnetic sensitive surface of the biaxial magnetic sensor circuit 130 is orthogonal to the magnetization direction of the small magnets 111s. An axial magnetic sensor circuit 130 was installed. FIG. 5C shows the output level of the biaxial magnetic sensor circuit 130 at these two measurement positions SP1 and SP2. As can be understood from this, the intensity of the magnetic field detected at the second measurement position SP2 is extremely higher than the intensity of the magnetic field detected at the first measurement position SP1. Therefore, the biaxial magnetic sensor circuit 130 is preferably installed so that its magnetic sensitive surface is orthogonal to the magnetization direction of the small magnet 111s. In other words, the small magnet 111 s is preferably magnetized in a direction orthogonal to the magnetic sensitive surface of the biaxial magnetic sensor circuit 130. By doing so, the signal level of the two-axis magnetic sensor 130 becomes higher, and the measurement accuracy of the encoder can be further increased. Note that the magnetization direction of the small magnet 111s does not have to be orthogonal to the magnetic sensitive surface of the biaxial magnetic sensor circuit 130, but is preferably a direction that intersects the magnetic sensitive surface of the biaxial magnetic sensor circuit 130. Most preferably, the direction is perpendicular to the plane.

  FIG. 6 shows an example of the first magnetic angle output D1 output from the first two-axis magnetic sensor circuit 130 and the second magnetic angle output D2 output from the second two-axis magnetic sensor circuit 230. It is explanatory drawing. The horizontal axis of FIG. 6 is the mechanical angle θr, and the vertical axis is the magnetic angle outputs D1 and D2 of the two biaxial magnetic sensor circuits 130 and 230. However, FIG. 6 shows an example in which the first magnet body 110 has eight poles for convenience of illustration. When the first magnet body 110 has eight poles, four short-period sections of the first magnet body 110 are generated during one rotation (360 degrees in mechanical angle) of the support member 150 of the encoder 100A. Here, the “small cycle section” means a section in which the magnetic angle θm of the first magnet body 110 changes by 360 degrees (2π). The short cycle interval value Px shown in FIG. 6A is a value for distinguishing these four short cycle intervals, and takes four values from 0 to 3. As will be described later, the short period interval value Px is generated from the magnetic angle output of the second biaxial magnetic sensor circuit 230. When the first magnet body 110 has 64 poles, 32 short-period sections of the first magnet body 110 are generated during one rotation of the support member 150 of the encoder 100A. However, in FIG. 6, if a diagram in which 32 small-cycle sections of the first magnet body 110 are generated during one rotation of the support member 150 of the encoder 100 </ b> A is drawn, it becomes an excessively fine figure. For convenience, a simplified diagram is used.

  In the example of FIG. 6, the magnetic angle outputs D1 and D2 of the biaxial magnetic sensor circuits 130 and 230 are each composed of 12 bits, and the magnetic angle outputs D1 and D2 take values between 0 and 4095. However, in general, the first magnetic angle output D1 of the first two-axis magnetic sensor circuit 130 is a digital signal of N1 bits (N1 is an integer of 2 or more), and the second magnetic field of the second two-axis magnetic sensor circuit 230 is set. The square output D2 can be a digital signal of N2 bits (N2 is an integer of 2 or more). Here, the bit numbers N1 and N2 may be the same value or different values.

  The first magnetic angle output D1 shown in FIG. 6B shows the change of the magnetic angle accompanying the rotation of the first magnet body 110, and the change from 0 to 4095 while the mechanical angle θr changes 360 degrees. A sawtooth change in which the value is repeated four times is shown. That is, the first magnetic angle output D1 shows a linear change that increases from 0 to 4095 during each short period. On the other hand, the second magnetic angle output D2 shown in FIG. 6A shows the change of the magnetic angle accompanying the rotation of the second magnet body 210, and from 0 to 4095 while the mechanical angle θr changes 360 degrees. Indicates a linear change that occurs only once. The most significant 2 bits of the second magnetic angle output D2 can be used as the short period interval value Px shown in FIG.

  The short period interval value Px is used to determine the absolute position of the mechanical angle θr with high accuracy. The mechanical angle θr can be detected with an accuracy of 12 bits only from the second magnetic angle output D2. However, if both the short period interval value Px and the first magnetic angle output D1 are used, the absolute position of the mechanical angle θr can be determined with higher accuracy (high resolution). Specifically, in the example of FIG. 6, since the short period interval value Px is 2 bits and the first magnetic angle output D1 is 12 bits, both of these are used to obtain a mechanical angle with a precision (resolution) of 14 bits. θr can be detected.

  FIG. 7 is an explanatory diagram showing a position signal generator 300 that determines the absolute position (absolute angle) of the rotating body using the outputs of the two two-axis magnetic sensor circuits 130 and 230. The position signal generation unit 300 combines the magnetic angle outputs D1 and D2 of the two two-axis magnetic sensor circuits 130 and 230 to generate an absolute position output Dabs. FIG. 7B shows the processing contents of the position signal generation unit 300. In this example, the first magnetic angle output D1 is a 12-bit signal from the least significant bit M0 to the most significant bit M11, and the second magnetic angle output D2 is also 12 from the least significant bit S0 to the most significant bit S11. It is a bit signal. The most significant 2 bits S11 and S10 of the second magnetic angle output D2 are used as the short period interval value Px. In the absolute position output Dabs, the most significant 2 bits are the short period interval value Px, and the lower 12 bits are the first magnetic angle output D1. This absolute position output Dabs is a signal representing the value of the mechanical angle θr with an accuracy of 14 bits.

  In the present embodiment, each of the biaxial magnetic sensor circuits 130 and 230 uses a plurality of Hall elements (see the example of FIG. 3). Therefore, when the power of the biaxial magnetic sensor circuits 130 and 230 is turned on, the magnetic angle outputs D1 and D2 shown in FIG. 6 are obtained according to the absolute position (mechanical angle θr) of the rotating body at that time. The absolute position (mechanical angle θr) of the rotating body can be determined according to the magnetic angle outputs D1 and D2. Therefore, when the power of the biaxial magnetic sensor circuits 130 and 230 is turned off, it is not necessary to store the absolute position (the value of the mechanical angle θr) of the rotating body at that time, and two magnetic angle outputs D1 obtained when the power is turned on. , D2 alone, there is an advantage that the absolute position of the rotating body when the power is off can be known.

  Incidentally, in the example of FIG. 6, the boundary of the short period interval of the first magnetic angle output D1 and the change position of the value of the short period interval value Px obtained from the second magnetic angle output D2 coincide. However, in an actual circuit, there is a possibility that a problem in which the two differ due to some error. In order to prevent such inconvenience, the position signal generation unit 300 detects the timing at which the first magnetic angle output D1 returns from the maximum value D1max to the minimum value 0 in accordance with the increase in the mechanical angle θr, and the small cycle interval value Px ( That is, it is preferable to correct the short period interval value Px so that the timing at which the most significant 2 bits of the second magnetic angle output D2) are incremented.

  FIG. 8 is an explanatory diagram illustrating a correction target range of the short cycle interval value Px performed by the position signal generation unit 300. In the lower part of the figure, a sawtooth change of the first magnetic angle output D1 is shown, and in the upper part, the error width (vertical width) of the second magnetic angle output D2 is shown by hatching. . The first magnetic angle output D1 changes in the range from the minimum value 0 to the maximum value D1max, and returns to the minimum value 0 after reaching the maximum value D1max. If the timing at which the first magnetic angle output D1 returns from the maximum value D1max to the minimum value 0 coincides with the timing at which the most significant 2 bits of the second magnetic angle output D2 are incremented, the result is shown in FIG. As described above, the most significant 2 bits of the second magnetic angle output D2 can be used as they are as the short period interval value Px. On the other hand, when the timings of both are shifted, the short period interval value Px is corrected. The short period interval value Px needs to be corrected in the range R1 immediately after the timing when the first magnetic angle output D1 returns from the maximum value D1max to the minimum value 0 and the range R3 immediately before that timing. In the middle range R2 between these two ranges R1 and R3, the value of the most significant 2 bits of the second magnetic angle output D2 shows a correct value as the short period interval value Px, so there is no need for correction.

FIG. 9 is a flowchart illustrating an example of an algorithm for correcting the short cycle interval value Px. This correction is performed by the position signal generator 300 (FIG. 7). In step S100, the bit number N1 of the first magnetic angle output D1, the bit number N2 of the second magnetic angle output D2, and the bit number Nx of the short period interval value Px are set. Parameters Nss (= N2−Nx) and D1max (= 2 ^N1 −1) are also set. In this embodiment, N1 = N2 = 12, Nx = 2, Nss = 10, and D1max = 4095.

  In step S110, the position signal generator 300 receives the magnetic angle outputs D1 and D2 from the two two-axis magnetic sensor circuits 130 and 230 (FIG. 7). In step S120, it is determined which one of the three ranges R1, R2, and R3 shown in FIG. 8 is in the first magnetic angle output D1. In the example of FIG. 9, the first range R1 is set to 0 ≦ D1 ≦ (D1max / 4), the second range R2 is set to (D1max / 4) <D1 <(D1max * 3/4), and the third range is set. R3 is set to (D1max * 3/4) ≦ D1 ≦ D1max. In the first range R1 and the third range R3, the second magnetic angle output D2 is corrected in order to correct the short period interval value Px.

Steps S130 to S150, which are correction execution steps, are performed based on the following idea.
(1) When the first magnetic angle output D1 is in the first range R1, the short period interval value Px represented by the upper 2 bits of the second magnetic angle output D2 is erroneously reduced by one. There is a possibility. Therefore, in order to eliminate this possibility, a value half of the maximum value (= 2 ^Nss ) represented by the lower Nss bits of the second magnetic angle output D2 is added to the second magnetic angle output D2, and its upper Nx bits are used as the short cycle interval value Px (steps S130 and S150).
(2) When the first magnetic angle output D1 is in the second range R2, the most significant 2 bits of the second magnetic angle output D2 are used as they are as the short period interval value Px (step S150).
(3) When the first magnetic angle output D1 is in the third range R3, the short period interval value Px represented by the upper 2 bits of the second magnetic angle output D2 is erroneously increased by one. There is a possibility. Therefore, in order to eliminate this possibility, a value half of the maximum value (= 2 ^Nss ) represented by the lower Nss bits of the second magnetic angle output D2 is subtracted from the second magnetic angle output D2, and its upper Nx The bit is used as the short cycle interval value Px (steps S140 and S150).

By performing such correction, it is possible to determine the short cycle interval value Px so that the boundary of the short cycle interval of the first magnetic angle output D1 always coincides with the change point of the short cycle interval value Px. It is. According to the inventor's calculation, if the magnetic angle error of the second magnetic angle output D2 is ± 2 ^N1−Nx−2 or less, it is possible to obtain a correct small period interval value Px by the above correction. For example, if N1 = 12, Nx = 2, the tolerance is ± 2 ⁸ = ± 256. Since this allowable error is quite large, it can be understood that the tolerance to the error is very large and that the correction is extremely effective in practice. However, if the error of the magnetic angle outputs D1 and D2 is negligible, the correction of the short period interval value Px is not necessary.

  Note that the minimum widths of the ranges R1 and R3 that require correction vary depending on the magnitude of the error in the magnetic angle outputs D1 and D2. Therefore, these three ranges R1 to R3 can be set to predetermined ranges different from those described above. However, each of the three ranges R1 to R3 is preferably set to a range in which the width is not zero. Moreover, it is preferable that the ranges R1 and R3 on both sides of the boundary of the short cycle section have the same width.

  As described above, the position signal generation unit 300 corresponds to the first magnetic angle output D1 of the first two-axis magnetic sensor circuit 130 and the second magnetic angle output D2 of the second two-axis magnetic sensor circuit 230. A position signal (absolute position output Dabs) indicating the absolute position (mechanical angle θr) of the rotating body is generated. If this position signal Dabs is used, the position can be determined with higher accuracy (higher resolution) than that of one two-axis magnetic sensor circuit 130 (or 230). Further, as described above, in this embodiment, since the biaxial magnetic sensor circuits 130 and 230 use a plurality of Hall elements, two magnetic angle outputs obtained when the biaxial magnetic sensor circuits 130 and 230 are powered on. From only D1 and D2, the absolute position of the rotating body when the power is turned off can be directly read.

  In addition, when the number of poles of the first magnet body 110 is M1, and the number of poles of the second magnet body 210 is M2, it is preferable that M1 and M2 are each even numbers, and in particular, M1 is 4 or more. It is preferable that the number is even and M2 is an even number of 2 or more. In this way, position detection can be performed with higher accuracy than when one magnet body is used.

The number of poles M1 of the first magnet body 110 and the number of poles M2 of the second magnet body 210 are preferably integers in which M1 / 2 and M2 / 2 are relatively prime. Here, two integers being “relative to each other” means that they do not have a common divisor other than 1. If M1 / 2 and M2 / 2 are integers that are prime to each other, the boundary of the section of the magnetic angle 2π of the first magnet body 110 (the short period section of FIG. 6) and the magnetic angle of the second magnet body 210 Since the position where the boundary of the 2π section coincides is only the position of the mechanical angle θr = 0, the absolute value of the mechanical angle θr can be determined from the two magnetic angle outputs D1 and D2. In the examples of FIGS. 6 and 7, M1 = 8 = 2 ³ and M2 = 2. In the encoder 100A shown in FIG. 1, M1 = 64 = 2 ⁶ and M2 = 2.

Generally, in order to use the most significant bits of the second magnetic angle output D2 as the short period interval value Px, the number of poles M1 of the first magnet body 110 is set to 2 ^{Q + 1} (Q is an integer of 1 or more). It is preferable to set the number of poles M2 of the second magnet body 210 to 2. At this time, the position signal generation unit 300 arranges the most significant Q bits of the second magnetic angle output D2 at the most significant position, and arranges all the bits (N1 bits) of the first magnetic angle output D1 below ( It is preferable to generate a signal of N1 + Q) bits as the absolute position output Dabs. For example, in the example of FIGS. 6 and 7, since N1 = 12, Q = 2, the absolute position output Dabs is a 14-bit signal.

  FIG. 10 is an explanatory diagram showing the number of bits of the absolute position output Dabs when the number of poles M1 of the first magnet body 110 is changed. In this example, the number of bits of the two magnetic angle outputs D1 and D2 is assumed to be 12 bits. If the number of poles M1 of the first magnet body 110 changes, the number of small period sections per rotation of the rotating body 400 of the encoder 100A changes accordingly, so the bit number Q of the small period section value Px is also changed. It changes accordingly. As described above, the number of bits of the absolute position output Dabs is a value (N1 + Q) obtained by adding the number of bits N1 of the first magnetic angle output D1 and the number of bits Q of the short period interval value Px.

  Thus, in the rotary encoder 100A of the first embodiment, each small magnet 111s included in the first magnet body 110 is magnetized in a direction intersecting the magnetic sensitive surface of the biaxial magnetic sensor circuit 130. The biaxial magnetic sensor circuit 130 can detect a strong magnetic field, and as a result, a magnetic angle output D1 with high resolution can be obtained. The biaxial magnetic sensor circuit 130 has a plurality of X-axis Hall elements X1 and X2 and a plurality of Y-axis Hall elements Y1 and Y2, and a magnetic angle output D1 according to the output signals of those Hall elements. Therefore, even when the installation position of the two-axis magnetic sensor circuit 130 is slightly deviated from the first magnet body 110, it is possible to obtain an accurate magnetic angle output D1. These feature points are the same for the second magnet body 210 and the second two-axis magnetic sensor circuit 230.

  Furthermore, in the first embodiment, the position signal generation unit 300 outputs the first magnetic angle output D1 of the first two-axis magnetic sensor circuit 130 and the second magnetic angle output D2 of the second two-axis magnetic sensor circuit 230. Accordingly, since the position signal Dabs is generated, position detection can be performed with higher accuracy than when only one two-axis magnetic sensor circuit is used.

B. Second to sixth embodiments (rotary encoder)
FIG. 11 is an explanatory diagram showing a configuration of a rotary encoder 100B as the second embodiment. This rotary encoder 100B is different from the rotary encoder 100A of the first embodiment (FIG. 1) in that the first magnet body 110 is provided not on the outer periphery of the rotating body 400 but on the surface of the rotating body 400, and The arrangement of the first two-axis magnetic sensor circuit 130 is changed in accordance with the position of the first magnet body 110. That is, in the encoder 100B of the second embodiment, the two small magnets 111s constituting the small magnet pair 111ps of the first magnet body 110 are arranged along the radial direction of the rotating body 400. Each small magnet 111 s is magnetized in a direction parallel to the rotation axis C of the rotating body 400. The first two-axis magnetic sensor circuit 130 is arranged so that the Z-axis direction thereof coincides with the magnetization direction of these small magnets 111s. Note that the second embodiment is common to the first embodiment in that a plurality of small magnet pairs 111 ps are arranged along a circular path around the rotation axis C of the rotating body 400. Understandable. The first implementation is also in that the center of the first two-axis magnetic sensor circuit 130 is arranged on a trajectory followed by a straight line passing between the two small magnets 111s constituting each small magnet pair 111ps. Common with form. The arrangement of the second magnet body 210 and the second biaxial magnetic sensor circuit 230 is the same as that in the first embodiment. In the rotary encoder 100B of the second embodiment, since the two biaxial magnetic sensor circuits 130 and 230 can be arranged side by side on the same plane, the installation of the biaxial magnetic sensor circuits 130 and 230 and the routing of the wiring are the same as in the first embodiment. It is easy compared.

  FIG. 12 is an explanatory diagram showing a configuration of a rotary encoder 100C as the third embodiment. This rotary encoder 100C is different from the rotary encoder 100B (FIG. 11) of the second embodiment only in that the second magnet body 210 is not a disc shape but a rectangular parallelepiped shape. The other configuration of the rotating body 400 including the same is the same as that of the second embodiment. In the rotary encoder 100C of the third embodiment, since the second magnet body 210 has a rectangular parallelepiped shape, there is an advantage that its manufacture is easier.

  FIG. 13 is an explanatory diagram showing a configuration of a rotary encoder 100D as the fourth embodiment. This rotary encoder 100D is different from the rotary encoder 100B (FIG. 11) of the second embodiment in that the two small magnets 111s constituting the small magnet pair 111ps of the first magnet body 110 are in close contact (or contact) with each other. It is only the point which is not spaced, and the other structure of the rotary body 400 containing the 2nd magnet body 210 is the same as 2nd Embodiment. In the rotary encoder 100D of the fourth embodiment, the first biaxial magnetism is adjusted by adjusting at least one of the distance between the two small magnets 111s and the material of the member provided between the two small magnets 111s. It is possible to adjust the shapes of the detection signals sinθm and cosθm (FIG. 2) of the sensor circuit 130 to be closer to a sine wave.

  FIG. 14 is an explanatory diagram showing a configuration of a rotary encoder 100E as the fifth embodiment. This rotary encoder 100E is different from the rotary encoder 100B (FIG. 11) of the second embodiment only in that the second magnet body 210 is composed of two small magnet pairs 211ps. Other configurations of the rotating body 400 including the magnet body 110 are the same as those in the second embodiment. The entire second magnet body 210 has a hollow cylindrical shape, and each small magnet pair 211ps has a semicylindrical shape. The two small magnets 211s constituting the small magnet pair 211ps are also semicylindrical. The magnetization direction of each small magnet 211s is a direction parallel to the rotation axis C of the rotating body 400, and the two small magnets 211s are magnetized in opposite directions. The number of poles of the second magnet body 210 is two. However, if the angle of the arc of the small magnet pair 211ps is made smaller and the number of small magnet pairs 211ps constituting the hollow cylindrical second magnet body 210 is increased, the number of poles of the second magnet body 210 is increased. It is possible to change arbitrarily.

  FIG. 15 is an explanatory diagram showing a configuration of a rotary encoder 100F as the sixth embodiment. The rotary encoder 100F has a configuration in which two annular magnet bodies 110 and 210 having the same diameter are arranged in parallel around a hollow cylindrical support member 150 along a direction parallel to the rotation axis C. ing. Yoke members 120 and 220 are provided on the inner circumferences of the two magnet bodies 110 and 210, respectively. Further, a magnetic shielding member 160 is provided between the two magnet bodies 110 and 210. Biaxial magnetic sensor circuits 130 and 230 are provided on the substrate 140 at positions with a predetermined gap with respect to the outer peripheral surfaces of the two magnet bodies 110 and 210.

  The first magnet body 110 is composed of eight small magnet pairs 111 ps, and its pole number M1 is eight. The second magnet body 210 is composed of two small magnet pairs 211ps, and the number of poles M2 thereof is two. However, these pole numbers M1 and M2 can be set to various integers as described in FIG. The magnetization directions of the individual small magnets 111s and 211s of the two magnet bodies 110 and 210 are parallel to the direction (radial direction) passing from the rotation axis C through the centers of the small magnets 111s and 211s. This magnetization direction is parallel to the Z-axis direction of the biaxial magnetic sensor circuits 130 and 230. Other configurations and operations are the same as those described in the first to fifth embodiments.

  The rotary encoders 100B to 100F of the second to sixth embodiments also have the same effect as that of the first embodiment. The two magnet bodies 110 and 210 provided on the disk-shaped rotating body 400 are used as in the first to fifth embodiments, or the cylindrical rotating body (support member) as in the sixth embodiment. Whether to use two magnet bodies 110 and 210 of the same diameter provided in 150) can be selected as appropriate according to the application of the encoder and spatial constraints. For example, when it is desired to arrange the encoder in a space having a smaller outer diameter, the sixth embodiment is more advantageous than the first to fifth embodiments.

C. Seventh embodiment (electromechanical device including an encoder)
FIG. 16 is a block diagram showing an electrical configuration of an electric motor 500 including a rotary encoder as an embodiment of the present invention. As a motor portion of the electric motor 500, a rotor 510 and electromagnetic coils 522A and 522B for two phases are drawn. The electromagnetic coils 522A and 522B are provided on a stator (not shown). A rotary encoder 100 including two biaxial magnetic sensor circuits 130 and 230 is connected to the rotation shaft 530 of the electric motor 500. As the rotary encoder 100, the encoders of the first to sixth embodiments described above can be used. The control unit 600 includes a main control circuit 610, two-phase drive signal generation units 620A and 620B, and two-phase drive circuits 630A and 630B. The main control circuit 610 is supplied with output signals D1, Pa, Pb, Z (see FIG. 4) of the first two-axis magnetic sensor circuit 130 and an output signal D2 of the second two-axis magnetic sensor circuit 230. Based on these signals, position control and speed control are executed. The internal configuration of the main control circuit 610 will be described later. The drive signal generators 620A and 620B for two phases receive digital signals sin θm and cos θm indicating sine waves and cosine waves from one two-axis magnetic sensor circuit 130, and perform PWM control based on these digital signals sin θm and cos θm. By executing this, a drive signal for two phases is generated. These drive signals are supplied to drive circuits 630A and 630B, respectively. The drive circuits 630A and 630B are so-called bridge driver circuits. For a method of generating drive signals for two phases by PWM control based on sinusoidal digital signals sin θm and cos θm, and a circuit configuration thereof, for example, FIG. 10 of Japanese Patent Application Laid-Open No. 2008-17678 disclosed by the present applicant. It is possible to use the circuit (excluding the AD converter) shown in FIG. In the present embodiment, the drive signal for two phases is generated using the sine wave signal sinθm and the cosine wave signal cosθm output from one two-axis magnetic sensor circuit 130, and therefore, when two magnetic sensors are used. Compared to the above, it is preferable in that a phase shift of the drive signal due to a shift between the two sensor positions does not occur. As a result, it is possible to increase the efficiency of the motor.

  FIG. 17 is a block diagram showing the internal configuration of the main control circuit 610. The communication interface 710 of the main control circuit 610 receives the first magnetic angle output D1 from the first two-axis magnetic sensor circuit 130 and receives the second magnetic angle output D2 from the second two-axis magnetic sensor circuit 230. The received magnetic angle outputs D1 and D2 are supplied to the position signal generation unit 730 through the data reception unit 720. The position signal generation unit 730 has the same function as the position signal generation unit 300 described with reference to FIGS. The absolute position output Dabs obtained by the position signal generation unit 730 is supplied to the angular velocity calculation unit 740, and the angular velocity (rotational speed) of the rotor 510 is calculated. The angular velocity is supplied to the angular acceleration calculation unit 750, and the angular acceleration of the rotor 510 is calculated. Output signals Pa, Pb, Z (FIG. 4) of the first two-axis magnetic sensor circuit 130 are supplied to the rotation speed calculation unit 760.

  FIG. 18 is an explanatory diagram showing the internal configuration and operation of the rotation speed calculation unit 760. The B-phase pulse signal Pb is supplied to the data input terminal of the D flip-flop 761, and the A-phase pulse signal Pa is supplied to the clock terminal. The up / down signal Ua / Da that is the output of the D flip-flop 761 is supplied to the input terminal of the up / down counter 762. The high level of the up / down signal Ua / Da indicates that the rotation direction of the rotor 510 is the forward direction (forward direction), and the low level indicates that it is the reverse direction. The periodic signal Z is supplied to the clock terminal of the up / down counter 762, and the count value is changed according to the rising edge of the periodic signal. That is, when the up / down signal Ua / Da is at a high level, the count value is incremented by one, and when the up / down signal Ua / Da is at a low level, the count value is decremented by one. The count value of the up / down counter 762 is supplied to the latch 763. The periodic signal Z is supplied to the clock terminal of the latch 763, and the count value Dn is held in the latch 763 in accordance with the falling edge of the periodic signal Z. The output of the latch 763 is output to the outside as the rotational speed Nr of the rotor 510. The rotation speed Nr indicates the rotation speed of the electric motor 500 from a predetermined reference position with respect to a member (for example, a robot joint) driven by the electric motor 500. The rotational speed Nr is supplied to and stored in the rotational speed storage unit 770 (FIG. 17).

  The main control circuit 610 of FIG. 17 further includes an input / output interface 780, a register 790, and an MPU 795. The input / output interface 780 is connected to the above-described circuits 730, 740, 750, 760, 790, and 795, and supplies outputs from these circuits to the outside as necessary. The register 790 temporarily stores data such as the number of poles of the first magnet body 110 and the absolute position (mechanical angle θr) of the rotor 510. The rotational speed storage unit 770 and the register 790 are preferably backed up by the battery 800 in order to retain the stored contents when the control unit 600 is powered off. In this way, for example, when the electric motor is used as a drive source for the joint of the robot, the position of the joint when the power of the robot is turned off is determined based on the stored contents in the rotation speed storage unit 770 and the register 790. When the power is turned on, the position of the joint can be correctly recognized and controlled. An MPU (Micro Processing Unit) 795 executes various controls (for example, servo control) regarding the electric motor 500. Note that the control process executed by the MPU 795 is realized by the MPU 795 executing a computer program stored in a memory (not shown). As described above, when the electromechanical device is configured using the encoder of the above-described embodiment, it is possible to control the electromechanical device while performing position detection with high accuracy.

  The encoder is applicable not only to an electromechanical device that generates a driving force but also to an electromechanical device that generates power (that is, performs regeneration) and an electromechanical device that can perform both driving and regeneration. is there. Examples of such electromechanical devices include various motors such as a two-phase AC brushless motor, a three-phase AC brushless motor, and a three-phase synchronous motor, a generator, and a motor / generator. Various encoders described in the first to sixth embodiments can be used as encoders used in these electromechanical devices. Also in the electromechanical apparatus using these various encoders, it is preferable to use the driving or regenerating magnet body in the electromechanical apparatus as the first magnet body of the encoder. However, an encoder may be connected to the outside of the electromechanical device without sharing the magnet body.

D. Various devices Figure utilizing an electromechanical device comprising an encoder 19 is an explanatory diagram showing an example of a double-arm seven-axis robot using an electromechanical device of the above embodiment. The double-arm 7-axis robot 3450 includes a joint motor 3460, a gripper motor 3470, an arm 3480, and a gripper 3490. The joint motor 3460 is disposed at a position corresponding to each joint portion such as a shoulder, an elbow, and a wrist. The joint motor 3460 includes two motors for each joint in order to move the arm 3480 and the grip portion 3490 in a three-dimensional manner. In addition, the gripper motor 3470 opens and closes the gripper 3490 and causes the gripper 3490 to grip an object. In the double-arm 7-axis robot 3450, the above-described electromechanical device with an encoder may be used as the joint motor 3460 or the gripper motor 3470.

  FIG. 20 is an explanatory diagram showing a railway vehicle using the electric machine device of the embodiment. The railway vehicle 3500 includes a transmission-equipped motor 3510 and wheels 3520. The transmission-equipped motor 3510 drives the wheel 3520. Further, the transmission-equipped motor 3510 is used as a generator when the railway vehicle 3500 is braked to regenerate electric power. As the transmission-equipped motor 3510, the above-described electromechanical device with an encoder may be used.

  As can be understood from the examples of FIGS. 19 and 20, the electromechanical device having the encoder of the embodiment can be used for various devices including a moving body such as a robot and a vehicle.

E. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

・ Modification 1:
In the various embodiments described above, the encoder is provided with the two magnet bodies of the first magnet body and the second magnet body. However, only one of the magnet bodies may be provided. When only one magnet body is provided in the encoder, the number M of poles of the magnet body is preferably an even number (a multiple of 2). However, it is more preferable that two magnet bodies are provided in that the absolute position of the rotary body of the encoder can be detected.

Modification 2
In the various embodiments described above, the rectangular parallelepiped small magnets 111s and 211s are used, but instead, at least one of the small magnets 111s and 211s may be formed using a ferromagnetic thin film. That is, it is possible to form a thin and strong magnet by magnetizing the ferromagnetic thin film to its thickness. If a ferromagnetic thin film is used, the size of the encoder can be made more compact.

・ Modification 3:
The present invention can be applied not only to a rotary encoder but also to a linear encoder.

DESCRIPTION OF SYMBOLS 100A-100F ... Rotary encoder 110 ... 1st magnet body 111s ... Small magnet 111ps ... Small magnet pair 112 ... Cover member 120 ... 1st yoke member 130 ... 1st biaxial magnetic sensor circuit 131,132 ... Amplifying circuit 135 ... Signal processing circuit 140 ... Substrate 150 ... Support member 160 ... Magnetic shielding member 210 ... Second magnet body 220 ... Second yoke member 230 ... Second biaxial magnetic sensor circuit 300 ... Position signal generator 400 ... Rotating body DESCRIPTION OF SYMBOLS 500 ... Electric motor 522A, 522B ... Electromagnetic coil 530 ... Rotating shaft 600 ... Control part 610 ... Main control circuit 620A, 620B ... Drive signal generation part 630A, 630B ... Drive circuit 710 ... Communication interface 720 ... Data receiving part 730 ... Position signal Generation unit 740 ... angular velocity calculation unit 750 ... angular acceleration calculation Unit 760... Rotation speed calculation unit 762. Up / down counter 763... Latch 770.
800 ... Battery 3460 ... Joint motor 3470 ... Grip motor 3480 ... Arm 3490 ... Grip 3500 ... Railway vehicle 3510 ... Transmission motor 3520 ... Wheel

Claims (12)

An encoder that measures the position of a second member that moves along a predetermined direction of movement with respect to the first member,
A first magnet body having an M1 pole (M1 is an even number of 4 or more) including a plurality of first small magnets provided on the second member;
A second magnet body having M2 poles (M2 is an even number of 2 or more) including a plurality of second small magnets provided on the second member;
A first two-axis magnetic sensor circuit disposed on the first member with a certain gap from the surface of the first magnet body;
A second biaxial magnetic sensor circuit disposed on the first member with a certain gap from the surface of the second magnet body;
A position signal generator for processing output signals of the first two-axis magnetic sensor circuit and the second two-axis magnetic sensor circuit;
With
The first two-axis magnetic sensor circuit and the second two-axis magnetic sensor circuit each have two magnetosensitive axis directions,
Each of the first small magnets constituting the first magnet body is magnetized in a direction crossing the magnetic sensitive surface of the first two-axis magnetic sensor circuit,
Each of the second small magnets constituting the second magnet body is magnetized in a direction crossing the magnetic sensitive surface of the second biaxial magnetic sensor circuit,
The position signal generator is configured to output the first member with respect to the first member according to a first magnetic angle output of the first two-axis magnetic sensor circuit and a second magnetic angle output of the second two-axis magnetic sensor circuit. An encoder that generates a position signal indicating the position of the second member. The encoder according to claim 1,
Each of the first two-axis magnetic sensor circuit and the second two-axis magnetic sensor circuit includes a plurality of Xs for measuring a magnetic field along the X axis of the X axis and the Y axis orthogonal to each other. An encoder comprising an axis sensor element and a plurality of Y axis sensor elements for measuring a magnetic field along the Y axis. The encoder according to claim 1 or 2,
The integers M1 and M2 are integers in which M1 / 2 and M2 / 2 are relatively prime,
The position signal generation unit is an encoder that generates the position signal from a first magnetic angle output of the first two-axis magnetic sensor and a second magnetic angle output of the second two-axis magnetic sensor. The encoder according to claim 3, wherein
The integer M1 is equal to 2 ^{Q + 1} (Q is an integer of 1 or more),
The integer M2 is equal to 2,
The first magnetic angle output of the first two-axis magnetic sensor circuit is a digital signal of N1 bits (N1 is an integer of 2 or more) indicating a relative position of the second member with respect to the first member.
The second magnetic angle output of the second two-axis magnetic sensor circuit is a digital signal of N2 bits (N2 is an integer of 2 or more) indicating the relative position of the second member with respect to the first member,
The position signal generation unit arranges the most significant Q bit of the second magnetic angle output at the most significant position, and sets the N1 bit of the first magnetic angle output below the most significant Q bit of the second magnetic angle output. An encoder that generates a signal of (N1 + Q) bits arranged in the position signal as the position signal. The encoder according to claim 4, wherein
The position signal generator is
When the first magnetic angle output of the first two-axis magnetic sensor circuit and the second magnetic angle output of the second two-axis magnetic sensor circuit both increase in accordance with the movement of the second member. The timing at which the first magnetic angle output returns from the maximum value of the first magnetic angle output to the minimum value coincides with the timing at which the most significant Q bit of the second magnetic angle output is incremented. Correcting the most significant Q bit of the second magnetic angle output according to one magnetic angle output;
Generating the position signal of the (N1 + Q) bits using the most significant Q bits of the corrected second magnetic angle output;
encoder. The encoder according to any one of claims 1 to 5,
The second member is a rotating body,
The first magnet body includes a plurality of small magnet pairs configured by two first small magnets magnetized in opposite directions to each other,
The plurality of small magnet pairs are arranged along a circular orbit around a rotation axis of the rotating body. The encoder according to claim 6, wherein
Each first small magnet has a rectangular parallelepiped shape,
Each small magnet pair includes two first small magnets and a covering member that covers at least a part of the periphery of the two first small magnets so that the entire shape of the small magnet pair is an isosceles trapezoidal columnar shape. , Having an encoder. The encoder according to any one of claims 1 to 6,
An encoder in which at least one of the first small magnet and the second small magnet is formed of a ferromagnetic thin film. An electromechanical device,
The encoder according to any one of claims 1 to 7, connected to a rotor of the electromechanical device;
A control unit for controlling the operation of the electromechanical device;
An electromechanical device comprising: An electromechanical device according to claim 9,
The electromechanical device is a two-phase AC brushless motor having a two-phase electromagnetic coil;
The control unit includes a drive signal generation unit that generates a drive signal for the two-phase electromagnetic coil from the sine wave signal and the cosine wave signal output from the first two-axis magnetic sensor circuit of the encoder. , Electromechanical devices.   A robot comprising the electromechanical device according to claim 9.   A railway vehicle comprising the electromechanical device according to claim 9 or 10.

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