JP2011095034A - Electrostatic rotary encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a substrate size and hence the entire size of an encoder by composing a track for disposing an electrode for generating a magnetic pole position signal by one track. <P>SOLUTION: A plurality of induction electrodes E2 are disposed at a prescribed pitch on an optional rotary track TK2 in a rotating substrate 3; sections with and without motor magnetic pole signal electrodes UVW are disposed alternately with the same sectional length on a separate rotary track TK5; a plurality of detection electrodes E2' are disposed at a pitch equal to or less than the prescribed pitch divided by N (N is an integer of two or more) on a fixed track TK2' opposing the optional rotary track TK2 in a fixed substrate 4; and at least respective electrodes U, V, W of U, V, W phases having electrode width of 1/3 or smaller than the section having an electrode are disposed on the fixed track TK5' opposing the separate rotary track TK5. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention has a fixed substrate and a rotating substrate provided with electrodes on opposite surfaces, and due to the electrostatic induction action between the electrodes provided on the opposite surfaces with the relative rotation of both substrates, The present invention relates to an electrostatic encoder that detects a rotation amount, a rotation speed, and the like of a rotation detection object.

  The electrostatic encoder, for example, obtains an electrical signal indicating the mechanical displacement of rotation due to a change in electrostatic induction action between the electrodes on the opposite surfaces of the two substrates due to relative rotation between the fixed substrate and the rotating substrate. The signal can be processed to detect the rotation amount and rotation speed of the rotation shaft.

  When such an electrostatic encoder is used for rotation control of an AC servo motor, for example, electrodes for generating A-phase and B-phase signals as rotation information are provided on the opposite surfaces of the rotating substrate and the fixed substrate. (See Patent Documents 1 and 2).

Japanese Patent No. 40385558 JP 2005-221472 A

  In such an electrostatic encoder, when electrodes for generating U-phase, V-phase, and W-phase signals representing magnetic pole positions for controlling the magnetic poles of the motor rotor are provided, the electrodes are formed in the radial direction of each of the rotating substrate and the fixed substrate. Therefore, a large number of tracks are required, and as a result, the size of the electrostatic encoder is increased along with the increase in size of both substrates.

  Therefore, according to the present invention, even if the number of electrodes for generating the magnetic pole position signal is increased, the number of tracks on which the magnetic pole position signal is arranged can be reduced to one track so that the substrate size can be reduced and the encoder size can be reduced. It is a thing.

  An electrostatic encoder according to the present invention has a fixed substrate and a rotating substrate having at least electrodes for generating A-phase and B-phase signals on tracks on opposite surfaces, and both electrodes according to relative rotation of the two substrates. Electrostatic rotary encoder capable of generating the above signal based on the electrostatic induction action between the motors, and the motor magnetic pole signal electrodes are provided on the arbitrary one of the tracks on the rotating substrate at intervals corresponding to the number of motor magnetic poles. The section and the non-section are alternately formed as a rotating electrode pattern, and the electrode width is one third or less of the section with the motor magnetic pole signal on one track on the fixed substrate facing the one arbitrary track on the rotating substrate. Therefore, the magnetic pole position detection electrodes of each phase are arranged as fixed electrode patterns at predetermined intervals.

  In the present invention, the U phase indicating the magnetic pole position by the electrostatic induction action between the non-existing and non-existing sections of the motor magnetic pole signal electrode on one track of the rotating substrate and the detection electrodes of each phase on one track of the fixed substrate. V-phase and W-phase signals can be generated. In the present invention, since the track on which the electrode indicating the magnetic pole position is arranged is one track on both the rotating substrate and the fixed substrate, the number of tracks can be greatly reduced, the substrate size can be reduced, and the encoder The overall size can be reduced. For example, even if the magnetic pole position signals are 6 magnetic pole position signals of U, V, W, -U, -V, and -W, both the rotation and the fixed substrate need only one track, and even if the magnetic pole position signal increases, the substrate There is no such thing as an increase in size.

  Preferably, the rotary substrate is provided with a continuous belt-shaped secondary induction electrode on the outer diameter side and inner diameter side tracks on the entire circumference in the circumferential direction, and a predetermined circumferential direction is provided on the track between the outer diameter side and the inner diameter side. A plurality of excitation electrodes are provided at a pitch, and each excitation electrode is connected to the secondary induction electrode on the outer diameter side and the inner diameter side alternately in the circumferential direction. By providing a continuous belt-shaped primary induction electrode on the entire circumference in the direction and providing a plurality of detection electrodes at a pitch equal to or less than a plurality of pitches in the circumferential direction of the track between the outer diameter side and the inner diameter side. The electrode is an electrode for generating A phase and B phase signals.

  According to the present invention, even if the number of magnetic pole position signal generating electrodes is increased, only one track is required for arranging these electrodes. Therefore, it is possible to reduce the substrate size and thus the overall size of the encoder.

FIG. 1 is a diagram illustrating a servo motor and an electrostatic encoder according to an embodiment of the present invention. FIG. 2 is a view showing a state where an electrostatic encoder is attached to an encoder attachment shaft of a servo motor. FIG. 3 is a diagram showing a rotating substrate and a fixed substrate of the electrostatic encoder with respect to the shaft from the side. FIG. 4 is a diagram showing an external configuration of the rotary substrate and the fixed substrate of the electrostatic encoder with respect to the shaft. FIG. 5 is a diagram showing circuit blocks of the servo motor, electrostatic encoder, and servo controller, and input / output relationships of signals related to them. FIG. 6 is a developed view of the rotating substrate of the electrostatic encoder. FIG. 7 is an unfolded view of the fixed substrate of the electrostatic encoder. FIG. 8A is a diagram showing an example of a processing circuit that processes the output of the electrostatic encoder, and FIG. 8B is a diagram showing another example of the processing circuit that processes the output of the electrostatic encoder. 9 (a-1) to 9 (a-8) are diagrams showing operation timing charts by the processing circuit of FIG. 8 (a), and FIGS. 9 (b-1) to 9 (b-8) are diagrams of FIG. 8 (b). It is a figure which shows the operation | movement timing chart by a processing circuit. FIG. 10 is a diagram showing a timing chart of the rotating electrode pattern, the fixed electrode pattern, and the U-phase, V-phase, and W-phase signals. FIG. 11 is a diagram showing another timing chart for the rotating electrode pattern, the fixed electrode pattern, and the U-phase, V-phase, and W-phase signals.

  Hereinafter, an electrostatic encoder according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  Referring to FIG. 1, reference numeral 1 denotes a servo motor, and 2 denotes an encoder. The servo motor 1 has a drive shaft 1b at the front end of the motor body 1a and an encoder mounting shaft 1c at the rear end. The encoder 2 has a rotating substrate 3 and a fixed substrate 4. After the encoder 2 is attached to the encoder mounting shaft 1c as shown by an arrow in FIG. 1, the rear side of the motor body 1a is covered with a motor cover 1d as shown in FIG. As shown in FIGS. 3 and 4, the encoder 2 is fixed so that the rotary substrate 3 can rotate integrally with the circular encoder mounting shaft 1 c, and the fixed substrate 4 is axially opposed to the rotary substrate 3. It is fixed non-rotating by this mechanism.

  As shown in FIG. 5, in the encoder 2, electrodes (not shown in FIG. 5) are formed on opposite surfaces of the rotating substrate 3 and the fixed substrate 4, and these electrodes are capacitively coupled to each other on the fixed substrate 4. A signal corresponding to the rotation of the rotary substrate 3 is generated by electrostatic induction on the electrodes. This signal outputs A-phase and B-phase signals that are position signals and Z-phase signals that are origin signals, and also outputs U-phase, V-phase, and W-phase magnetic pole position signals.

  The position signal and the origin signal are input to a detection device above the encoder 2, such as a counter or a programmable controller.

  U-phase, V-phase, and W-phase magnetic pole position signals are input to the servo driver 5. The servo driver 5 determines the approximate position of the magnetic pole of the motor from the UVW signal from the encoder 2 when the power is turned on, generates a current command having the same phase as the voltage for exciting the motor, and rotates the servo motor 1. Therefore, the servo driver 5 applies excitation voltages Eu, Ev, and Ew for driving the magnetic poles of the servo motor 1 to the U-phase, V-phase, and W-phase input terminals of the servo motor 1 based on the UVW signal from the encoder 2, respectively. The servo motor 1 is driven and controlled by application.

  Such a servo motor 1 has been downsized in recent years, and accordingly, the encoder 2 is also required to be downsized. For this reason, the reduction of the number of tracks related to the generation of the U-phase, V-phase, and W-phase magnetic pole position signals is an important technique for promoting the downsizing of the encoder 2. Therefore, in this embodiment, the number of tracks related to the magnetic pole position signal generation is set to one track on the rotating substrate 3 and the fixed substrate 4. This will be described below.

   FIG. 6 shows a partial development of the rotating substrate 3. The rotary substrate 3 is a substrate having the first to sixth tracks TK1 to TK6 from the outer diameter side to the inner diameter side.

  The first track TK1 is provided with a continuous inductive secondary induction electrode E1 on the entire circumference in the circumferential direction.

  The second track TK2 is provided with a plurality of induction electrodes E2 with a predetermined circumferential pitch P. The induction electrode E2 is alternately connected to the secondary induction electrode E1 of the first track TK1 and the secondary induction electrode E6 of the sixth track TK6 described later, one by one in the circumferential direction.

  The third track TK3 is provided with a Z-phase electrode E3 at one place in the circumferential direction. This Z-phase electrode E3 is connected to the secondary induction electrode E1 of the first track TK1.

  The fourth track TK4 is provided with a −Z phase electrode E4 in a band shape in a region where the Z phase electrode E3 does not exist in the radial direction in the circumferential direction. The -Z phase electrode E4 is connected to a secondary induction electrode E6 of a sixth track TK6 described later.

  In the fifth track TK5, a plurality of sections having the same section length L are provided for the sections having no motor magnetic pole signal electrode and the sections having the motor pole signal electrode alternately in the circumferential direction. A UVW phase electrode for generating a motor magnetic pole signal is provided in the section with electrodes. This UVW phase electrode is connected to a secondary induction electrode E6 of the sixth track TK6 described later. In the servo motor 1, the number of magnetic poles (the number of poles) is the total number of N poles and S poles formed in the field of the servo motor 1. For example, if there are two poles (one pair), the electrode UVW is 90. If there are 6 (3 pairs) poles, the UVW phase electrodes are provided by 60 °, and if 8 (4 pairs) poles, the UVW phase electrodes are provided by 45 °.

  The sixth track TK6 is provided with a continuous belt-shaped secondary induction electrode E6 on the entire circumference in the circumferential direction.

  FIG. 7 shows a partial development of the fixed substrate 4. The fixed substrate 4 is configured as a substrate having first to sixth tracks TK1 ′ to TK6 ′ facing the first to sixth tracks TK1 to TK6 of the rotating substrate 3 from the outer diameter side to the inner diameter side. The fixed substrate 4 faces the rotating substrate 3 in the embodiment, but may be arranged on both sides of the rotating substrate 3.

  In the first track TK1 ′, a primary induction electrode E1 ′ is provided in a belt shape continuously in the circumferential direction. An input signal 1 (Asin ωt or pulse wave) is applied to the primary induction electrode E1 ′ of the first track TK1 ′. The frequency of the input signal 1 is determined to be, for example, 50 MHz in consideration of the maximum rotation speed, maximum resolution, necessary detection accuracy, and the like of the encoder 2. The same applies to the frequency of the input signal 2 (-Asin ωt or pulse wave) in the sixth track TK6 ′ described later.

  The second track TK2 ′ is provided with a plurality of rectangular detection (induction) electrodes E2 ′ in plan view with a predetermined electrode width in the circumferential direction at a pitch (P / 4) at equal intervals in the circumferential direction. This detection electrode E2 'is a set of four electrodes that are continuously adjacent in the circumferential direction to form one set. The first to fourth electrodes in each set (the first electrode in each set is hatched in the figure for convenience of illustration). The first electrode of each set, the second electrode, the third electrode, and the fourth electrode are connected in common, and signals (for A-phase and B-phase signal generation) from signal lines on the substrate Signal). The number of electrode sets is not limited to the number shown in FIG. 7, and can be determined as appropriate according to the level of the signal to be extracted. The arrangement pitch of the plurality of induction electrodes E2 on the second track TK2 of the rotating substrate 3 is P, and the input signals 1 and 2 are alternately applied to the induction electrode E2, while the second track of the fixed substrate 4 is applied. Since the arrangement pitch of the detection electrodes E2 ′ of TK2 ′ is P / 4, a signal having a phase difference of 90 degrees is applied to the detection electrodes E2 ′ by electrostatic induction as the rotating substrate 3 rotates. It can be taken out. Then, A-phase and B-phase signals can be generated from this signal.

  The third track TK3 ′ is provided with a Z-phase electrode E3 ′ at one place in the circumferential direction. The Z-phase signal generated at the Z-phase electrode E3 ′ is extracted from the signal line on the substrate.

 The fourth track TK4 ′ is provided with a −Z phase electrode E4 ′ in a region facing the Z phase electrode E3 ′ in the circumferential direction in the radial direction. The -Z phase signal generated on the -Z phase electrode E4 'is extracted from the signal line on the substrate.

  In the fifth track TK5 ′, six detection electrodes E5 ′ in the circumferential direction are provided adjacently in this order: U electrode, −W electrode, V electrode, −U electrode, W electrode, and −V electrode. The electrode width of the detection electrode E5 ′ is equal to or less than one third of the section length of the motor magnetic pole signal electrode in the fifth track TK5 of the rotating substrate 3. Signals generated on these U electrode, -W electrode, V electrode, -U electrode, W electrode, and -V electrode are extracted from signal lines on the substrate.

  The sixth track TK6 ′ is provided with a primary induction electrode E6 ′ in a strip shape continuously around the entire circumference. An input signal 2 (−Asinωt or pulse wave) is applied to the primary induction electrode E6 ′ of the sixth track TK6 ′.

  FIG. 8A shows a processing circuit example including the electrodes E1 ′ to E6 ′ of the fixed substrate 4, and FIG. 8B shows another processing circuit example. Further, FIGS. 9A-1 to 9A-8 show operation timing charts by the processing circuit of FIG. 8A, and FIGS. 9B-1 to 9B-8 show the processing of FIG. The operation | movement timing chart by a circuit is shown. The processing circuit shown in FIG. 8A includes the fixed detection electrode unit 5a, the amplification unit 6a, the demodulation unit 7a, the waveform shaping unit 8a, and the oscillation unit 9a. The processing circuit shown in FIG. 8B includes fixed detection electrode unit 5b, amplification unit 6b, waveform shaping unit 7b, latch unit 8b, and oscillation unit 9b.

  First, referring to FIG. 8 (a) and FIGS. 9 (a-1) to (a-8), the primary induction electrodes E1 ′ and E6 ′ in the fixed detection electrode portion 5a of the fixed substrate 4 include the oscillation portion 9a. Input signals (Asin ωt, -Asin ωt) 1 and 2 are applied as carrier signals (a-1, a-2). The carrier signal may be a pulse wave.

  The input signals 1 and 2 applied to the primary induction electrodes E1 ′ and E6 ′ of the first and sixth tracks TK1 ′ and TK6 ′ of the fixed substrate 4 are respectively corresponding to the first corresponding to the rotary substrate 3 by electrostatic induction. , Are guided to the secondary induction electrodes E1 and E6 of the sixth tracks TK1 and TK6, respectively. The input signals 1 and 2 induced by the secondary induction electrodes E1 and E6 are applied to the induction electrode E2 on the second track TK2 of the rotating substrate 3. Then, the induction electrode E2 on the second track TK2 of the rotating substrate 3 is guided to the detection electrode E2 ′ on the second track TK2 ′ of the fixed substrate 4. In this case, since the rotating substrate 3 rotates, the input signals 1 and 2 are modulated into two modulation signals 1 and 2 in a sine wave shape corresponding to the rotational position of the rotating substrate 3 (a-3, a-4). ). The modulated signals 1 and 2 are amplified by the amplifying unit 6a, demodulated by the demodulating unit 7a and converted into position signals 1 and 2 having a phase difference of 90 degrees (a-5, a-6), and then by the waveform shaping unit 8a. Waveform shaping is performed, and the shaped waveforms 1 and 2 become an A-phase signal and a B-phase signal (a-7, a-8).

  Next, referring to FIG. 8 (b) and FIGS. 9 (b-1) to (b-8), the primary induction electrodes E1 ′ and E6 ′ in the fixed detection electrode unit 5b are supplied with input signals (from the oscillation unit 9b). Asinωt) 1 and 2 are applied as carrier signals (b-1, b-2). The carrier signal may be a pulse wave.

  The input signals 1 and 2 applied to the primary induction electrodes E1 ′ and E6 ′ of the first and sixth tracks TK1 ′ and TK6 ′ of the fixed substrate 4 are respectively corresponding to the first corresponding to the rotary substrate 3 by electrostatic induction. , Are guided to the secondary induction electrodes E1 and E6 of the sixth tracks TK1 and TK6, respectively. The input signals 1 and 2 induced by the secondary induction electrodes E1 and E6 are applied to the induction electrode E2 on the second track TK2 of the rotating substrate 3. Then, the induction electrode E2 on the second track TK2 of the rotating substrate 3 is guided to the detection electrode E2 ′ on the second track TK2 ′ of the fixed substrate 4. In this case, since the rotating substrate 3 rotates, the input signals 1 and 2 are modulated into two modulation signals 1 and 2 in a sine wave form corresponding to the rotational position of the rotating substrate 3 (b-3, b-4). ). The modulated signals 1 and 2 are amplified by the amplifying unit 6b, the waveform shaping unit 7b shapes the waveform of the modulated signals 1 and 2 after amplification using the reference voltage Verf (b-5, b-6), and the latch unit. By latching at 8b, an A-phase signal and a B-phase signal are obtained (b-7, b-8).

  As described above, both the processing circuit of FIG. 8A and the processing circuit of FIG. 8B output the A phase signal and the B phase signal from the encoder 2 by the rotation of the rotating substrate 3. A description of the Z-phase and -Z-phase signals that are origin signals is omitted.

  Next, referring to FIG. 10, the rotating electrode pattern (UVW phase electrode arrangement pattern) on the fifth track TK5 of the rotating substrate 3 and the fifth track TK5 ′ of the fixed substrate 4 at one rotation (360 °) of the rotating substrate. Upper fixed electrode pattern (U electrode, -W electrode, V electrode, -U electrode, W electrode, -V electrode arrangement pattern), U phase, -W phase, V phase, -U phase, W in each electrode The output waveform of the phase and -V phase will be described. In the rotating electrode pattern, the rotation direction is indicated by an arrow.

  The arrangement of each of the U electrode, -W electrode, V electrode, -U electrode, W electrode, and -V electrode constituting the fixed electrode pattern is defined by the following equations (1) to (6). N indicates the number of U-phase, V-phase, and W-phase output pulses or the number of motor magnetic pole pairs in one rotation of the motor.

In FIG. 10, in the fixed electrode pattern,
The U electrode has a mechanical angle θu = 0 ° (1)
The V electrode has a mechanical angle θv = 360 ° / 3 × N (2)
The W electrode has a mechanical angle θw = 2 × 360 ° / 3 × N (3)
-U electrode has mechanical angle θ-u = 360 ° / 2 × N (4)
The -V electrode has a mechanical angle θ−v = 5 × 360 ° / 6 × N (5)
The -W electrode has a mechanical angle θ−w = 360 ° / 6 × N (6)
The electrode width α of each electrode of the fixed electrode pattern is obtained by the following formula (7).

Electrode width α ≦ 360 ° / 6 × N (7)
The electrode width t of the rotating electrode pattern is obtained by the following equation (8).

Electrode width t = 360 ° / 2 × N (8)
In FIG. 10, the UVW-phase fixed electrode has a differential detection arrangement. Therefore, the differential output between the U electrode and the -U electrode is a U-phase signal output, the differential output between the V electrode and the -V electrode is a V-phase signal output, and the differential output between the W electrode and the -W electrode is W phase signal output.

  In the fixed electrode pattern shown in FIG. 10, the electrodes are differentially detected, but the fixed electrode can also be realized by a single element of the U electrode, the V electrode, and the W electrode. As an example, FIG. 11 shows a fixed electrode pattern in an 8-pole (4-pair) servo motor. In the rotating electrode pattern, the motor magnetic pole signal electrode non-existing section and the existing section are 45 °. Further, the arrangement positions of the U electrode, the V electrode, and the W electrode in the fixed electrode pattern can be calculated by the above formulas (1) to (3). In the calculation, the mechanical angle θu of the U electrode is 0 °, the mechanical angle θv of the V electrode is 30 °, and the mechanical angle θw of the W electrode is 60 °. Moreover, the electrode width α of each of the U electrode, the V electrode, and the W electrode is obtained by the equation (7), and α is 15 ° or less.

  In the case of non-differential detection, signal processing with the circuit of FIG. 8B is convenient.

  As described above, in this embodiment, the track on which the electrode for generating the magnetic pole position signal is arranged is one track of the fifth tracks TK5 and TK5 ′ in both the rotating substrate 3 and the fixed substrate 4. As a result, the number of tracks can be greatly reduced, and the size of the substrate can be reduced, and thus the overall size of the encoder can be reduced. For example, even if the magnetic pole position signals are 6 magnetic pole position signals of U, V, W, -U, -V, and -W, both the rotation and fixed substrates 3 and 4 need only one track, and the magnetic pole position signal increases. However, the substrate size does not increase.

1 Servo motor 2 Encoder 3 Rotating board 4 Fixed board

Claims (2)

Based on the electrostatic induction effect between the two electrodes due to relative rotation of the two substrates, having a fixed substrate and a rotating substrate having at least electrodes for generating the A-phase and B-phase signals on the tracks on the opposite surfaces. An electrostatic rotary encoder capable of generating the signal,
On the rotating substrate, the section with and without the motor magnetic pole signal electrode is alternately formed as a rotating electrode pattern at an interval corresponding to the number of motor magnetic poles on the arbitrary one track.
On the fixed substrate, the magnetic pole position detection electrodes of each phase are fixed at predetermined intervals with an electrode width of one third or less of the section with the motor magnetic pole signal on one track facing the one arbitrary track on the rotating substrate. An electrostatic rotary encoder characterized by being arranged as an electrode pattern. The rotating substrate is provided with a continuous belt-like secondary induction electrode on the outer diameter side and inner diameter side tracks on the entire circumference in the circumferential direction, and a plurality of tracks at a predetermined pitch in the circumferential direction are provided on the track between the outer diameter side and the inner diameter side. The excitation electrodes are connected to the secondary induction electrodes on the outer diameter side and the inner diameter side alternately in the circumferential direction,
The fixed substrate is provided with a continuous belt-shaped primary induction electrode on the outer diameter side and the inner diameter side of the track on the entire circumference in the circumferential direction, and on the track between the outer diameter side and the inner diameter side in the circumferential direction from the pitch. By providing a plurality of detection electrodes at a pitch of 1 / multiple or less,
2. The electrostatic rotary encoder according to claim 1, wherein the electrodes are electrodes for generating A phase and B phase signals.

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