JP2004348562A - Incremental encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the number of transmission lines and to deal accurately with the unevenness of signal switching timing under the rotation control of a motor. <P>SOLUTION: The incremental encoder includes a signal line 13 mounted in an AC motor to output U-phase signal, V-phase signal, and W-phase signal for detecting the pole position of the AC motor by power-on and to output A-phase signal, B-phase signal, and Z-phase signal for controlling the rotational speed and positioning the AC motor after the AC motor starts rotating. The incremental encoder further includes a phase change detecting circuit 15 for detecting the change of any phase signal of A-phase signal, B-phase signal and Z-phase signal by the rotation of the AC motor at the rotation starting time to switch U-phase signal, V-phase signal and W-phase signal transmitted to the signal line 13 to A-phase signal, B-phase signal, and Z-phase signal based on the output of the phase change detecting circuit 15 and to transmit A-phase signal, B-phase signal, and Z-phase signal through the signal line. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an incremental encoder used by being incorporated in a brushless motor such as a three-phase AC servomotor.
[0002]
[Prior art]
Servo motors used for rotating and driving various machines such as industrial robots include DC servo motors with brushes and AC servo motors without brushes (DC brushless servo motors). The demand for AC servomotors is increasing.
[0003]
Rotary encoders incorporated into AC servomotors as position detectors for servo systems are broadly classified into incremental and absolute types. The former absolute type is widely used in various robot servomotors and the like because it does not require an origin return operation. On the other hand, the latter incremental type is widely used because of its low cost, and occupies the mainstream as a rotary encoder for AC servo.
[0004]
FIG. 3 shows an output stage of a general incremental encoder. In this incremental encoder, an A-phase signal and a B-phase signal having a phase difference of 90 ° from each other so that the rotation direction of the rotor can be discriminated, a Z-phase signal that generates one pulse per rotation of the rotor to indicate the origin reference, and AC A U-phase signal, a V-phase signal, and a W-phase signal indicating the position of the magnetic pole of the rotor are provided as detection signals to switch the energized phase of the servomotor.
[0005]
Here, in the incremental encoder, A-phase, B-phase, Z-phase and U-phase, V-phase, and W-phase signals, and signals having a 180 ° phase to improve the S / N ratio (hereinafter, shown in FIG. For convenience, A- phase, B- phase, Z- phase and U- phase, V- phase, and W- phase signals) are output as detection signals.
[0006]
Incremental encoder, U-phase, U-phase signal, V-phase, V-phase signal, W-phase, line driver 1u the W-phase signal outputs respectively, 1 v, a line driver unit 1 consisting of 1 w, A-phase, A-phase signal, A line driver unit 2 composed of line drivers 2a, 2b, 2z for outputting B-phase, B- phase, Z-phase, and Z- phase signals, respectively, and these U-phase, U- phase signal, V-phase, V- phase signal, W In addition to the signal lines 3 for the phase, W- phase signal, A-phase, A- phase signal, B-phase, B- phase signal, Z-phase, and Z- phase signal, from the Vcc and GND power supply lines 4 for supplying internal power It has a total of 14 transmission lines (for example, see Patent Document 1).
[0007]
[Patent Document 1]
JP-A-5-157581
[Problems to be solved by the invention]
Incidentally, the above-described incremental encoder requires a total of 14 transmission lines including 12 signal lines 3 and 2 power supply lines 4. Since such a large number of transmission lines are required, there is a problem that the mass productivity of the product is poor, and the possibility of erroneous wiring to the device or disconnection of the transmission line increases.
[0009]
Therefore, in Patent Document 1 described above, a U- phase signal, a U- phase signal, a V- phase signal, a V- phase signal, a W-phase signal, and a W- phase signal are output to the signal line 3 within a predetermined set time after the power is turned on. After the elapse, the A-phase, A- phase signal, B-phase, B- phase signal, Z-phase, and Z- phase signal are transmitted to the same signal line 3 as described above, thereby reducing the number of transmission lines. In Patent Literature 1, a power-on timer 5 for switching a signal to be output to a signal line after a predetermined set time from power-on is provided (see FIG. 4).
[0010]
However, if the elapsed time from power-on is monitored by the power-on timer 5 and the signal output to the signal line 3 is switched when a certain set time has elapsed as in Patent Document 1, the signal switching is not performed. May be difficult to perform accurately.
[0011]
In other words, since there is a temporal variation in the above-described signal switching timing in controlling the rotation of the AC servomotor, it is difficult to perform accurate signal switching in monitoring based on a fixed set time by the power ON timer 5. In addition, the time set by the power ON timer 5 must be adjusted in accordance with the signal switching timing, and it is difficult to cope with the variation in the signal switching timing.
[0012]
In view of the above, the present invention has been proposed in view of the above problems, and aims to reduce the number of transmission lines and accurately cope with signal switching timing variations caused by motor rotation control. It is to provide an incremental encoder.
[0013]
[Means for Solving the Problems]
As a technical means for achieving the object, the present invention is mounted on an AC motor, and outputs a U-phase signal, a V-phase signal, and a W-phase signal for detecting a magnetic pole position of the AC motor when the power is turned on. An incremental encoder having a signal line for outputting an A-phase signal, a B-phase signal, and a Z-phase signal for controlling the rotational speed of the AC motor and positioning the AC motor after the AC motor starts rotating. A phase change detection circuit that detects that any one of the A-phase signal, the B-phase signal, and the Z-phase signal has changed due to rotation of the motor; and a signal line based on the output of the phase change detection circuit. The transmitted U-, V-, and W-phase signals are switched to A-, B-, and Z-phase signals, and the A-, B-, and Z-phase signals are transmitted on the signal lines. And wherein the door.
[0014]
In the incremental encoder according to the present invention, a U-phase signal, a V-phase signal, and a W-phase signal are output to a signal line when the power is turned on, and the A-phase signal, the B-phase signal, and the Z-phase signal are output by the rotation of the AC motor at the start of rotation. When any one of the signals changes, the change in the phase signal is detected by a phase change detection circuit, and the U-phase signal, V-phase signal, and W-phase signal transmitted to the signal line based on the detection result. The signal is switched to an A-phase signal, a B-phase signal, and a Z-phase signal.
[0015]
As described above, a signal transmitted on the signal line based on a change in any one of the A-phase signal, the B-phase signal, and the Z-phase signal is converted from the U-phase signal, the V-phase signal, the W-phase signal to the A-phase signal, By switching to the phase signal and the Z-phase signal, it is possible to accurately cope with a variation in signal switching timing that occurs in controlling the rotation of the AC motor.
[0016]
When performing the signal switching by the above-described phase change detection circuit, two line driver units that respectively output the U-phase signal, the V-phase signal, the W-phase signal, the A-phase signal, the B-phase signal, and the Z-phase signal are used. In this case, the signal lines of these two line driver units may be connected in common. Further, if the circuit configuration includes a single line driver unit that outputs one of the U-phase signal, the V-phase signal, the W-phase signal or the A-phase signal, the B-phase signal, and the Z-phase signal, A single line driver unit can be used in place of the two line driver units required for signals, V-phase signals, W-phase signals and A-phase signals, B-phase signals, and Z-phase signals.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the incremental encoder according to the present invention will be described in detail below.
[0018]
The incremental encoder of the embodiment shown in FIG. 1 is attached to a light-emitting element 17 and a shaft to which rotation of a rotor of a motor is transmitted, and has optical slits (rotation slits) of U, V, W, A, B, and Z phases. Rotating plate 18 and a fixing plate 19 provided to separate the light passing through the rotating plate 18 with higher precision, and having U, V, W, A, B, and Z-phase optical slits (fixed slits). And a light receiving element 20 for converting an optical signal of each phase into an electric signal.
[0019]
In this incremental encoder, a U-phase signal, a V-phase signal, and a W-phase signal for detecting a magnetic pole position of a rotor in an AC motor when the power is turned on, the number of rotations of the AC motor are controlled, and the rotor is positioned. A phase signal, B phase signal, and Z phase signal. In order to drive the motor, it is necessary to detect the magnetic pole position of the rotor, so that a U-phase signal, a V-phase signal, and a W-phase signal are required.
It is possible to start rotation of the motor by reading the magnetic pole position when the power is turned on.
[0020]
The U-phase signal, the V-phase signal, and the W-phase signal indicate the magnetic pole position of the rotor for switching the energized phase of the AC servomotor, and are generally two or four pulses per rotation of the rotor. The A-phase signal and the B-phase signal have a phase difference of 90 ° from each other so that the rotation direction of the rotor can be determined, and is about 500 to 4000 pulses per rotation of the rotor. The Z-phase signal indicates one reference point by generating one pulse in one rotation of the rotor. Therefore, the above-mentioned A-phase signal and B-phase signal have very fine resolution.
[0021]
For example, when the motor has four poles, the U-phase signal, the V-phase signal, and the W-phase signal output two pulses in one rotation of the rotor, and the phase of each phase signal is shifted by 30 °. On the other hand, when the A-phase signal and the B-phase signal are set to 360 pulses per one rotation of the rotor, after monitoring the rotation of the motor, the A-phase signal and the B-phase signal can be monitored without monitoring the U-phase signal, the V-phase signal, and the W-phase signal. By monitoring the phase signals, it can be expected that the U-phase signal, the V-phase signal, and the W-phase signal change every 30 pulses of the A- and B-phase signals. However, in this case, a maximum shift of 30 ° has occurred.
[0022]
Therefore, if the Z-phase signal is made coincident with the start of the U-phase signal, it is possible to correct the above-mentioned maximum 30 ° shift when the Z-phase signal is input. Therefore, the motor is driven with a maximum of 30 ° deviation per rotation of the rotor. However, the motor is controlled by the U-phase signal, V-phase signal, and W-phase signal only when the power is turned on. , A-phase signal, B-phase signal, and Z-phase signal to control the motor.
[0023]
Here, in the incremental encoder, U-phase, V-phase, W-phase and A-phase, B-phase, and Z-phase signals, and signals having a 180 ° phase to improve the S / N ratio (hereinafter, U- phase, V- phase) , W- phase, A- phase, B- phase, and Z- phase signals) are output as detection signals.
[0024]
The output stage of the incremental encoder includes a line driver unit 11 including line drivers 11u, 11v, and 11w for outputting U-phase, U- phase signals, V-phase, V- phase signals, W-phase, and W- phase signals, respectively. , A line driver unit 12 that incorporates line drivers 12a, 12b, and 12z that output A- phase signals, B-phase, B- phase signals, Z-phase, and Z- phase signals, respectively. A phase change detection circuit for detecting that any one of the B-phase signal and the Z-phase signal has changed, and switching the output from the line driver unit to the line driver unit based on the detection result;
[0025]
Each of the line drivers 11u, 11v, 11w, 12a, 12b, 12z of the two line driver units 11, 12 receives U-phase, V-phase, W-phase signals and A-phase, B-phase, Z-phase signals, and , U phase signal, V phase, V phase signal, W phase, W phase signal and A phase, A phase signal, B phase, B phase signal, Z phase, Z phase signal are output. Further, the phase change detection circuit 15 receives the A-phase, B-phase, and Z-phase signals as input, and outputs a signal from the line driver unit 11 based on a change in any one of the A-phase, B-phase, and Z-phase signals. A control signal for switching to the driver unit 12 is output to each of the line drivers 11u, 11v, 11w, 12a, 12b, 12z.
[0026]
In this incremental encoder, at the output stage, U-phase, U- phase signal, V-phase, V- phase signal, W-phase, W- phase signal and A-phase, A- phase signal, B-phase, B- phase signal, Z-phase, Z- phase The signal line 13 of each of the two line driver units 11 and 12 for outputting a signal is connected in common, so that the U phase, the U phase signal and the A phase, the A phase signal, the V phase, the V phase signal and the B , B- phase signal, W-phase, and six signal lines 13 shared by the W- phase signal and the Z-phase and Z- phase signals, and a total of eight power supply lines 14 including Vcc and GND power supply line 14 for supplying internal power. With transmission lines.
[0027]
In this incremental encoder, the U-phase, U- phase signal, V-phase, V- phase signal, W-phase, and W- phase signals are output from the line drivers 11u, 11v, and 11w of the line driver unit 11 to the signal line 13 when the power is turned on. When the AC motor starts rotating, the A-phase signal, the B-phase signal, and the Z-phase signal are output thereafter, but any one of the A-phase signal, the B-phase signal, and the Z-phase signal is output according to the rotation of the AC motor at the start of the rotation. Is detected by the phase change detection circuit 15, and based on the detection of the change in the phase signal, the output of the line driver unit 11 is invalidated by the phase change detection By enabling the output of, the U-phase, U- phase signal, V-phase, V- phase signal, W-phase, and W- phase signal transmitted to the signal line 13 are converted to the A-phase and the A- phase. Switch to signal, B phase, B phase signal, Z phase, Z phase signal.
[0028]
A phase thus phase change detection circuit 15, B-phase, a change in either phase signal of Z phase signal, the signal U-phase to transmit a signal line 13, U-phase signal, V-phase, V-phase signal , W-phase, W- phase signal to A-phase, A- phase signal, B-phase, B- phase signal, Z-phase, Z- phase signal, the signal switching that occurs in controlling the rotation of the AC motor is A-phase. , B-phase, and Z-phase signals, if the changes in the A-phase, B-phase, and Z-phase signals are monitored, it is possible to quickly and accurately respond to variations in signal switching timing. .
[0029]
In the above embodiment, the U-phase, the U- phase signal and the A- phase signal, the A- phase signal, the V- phase signal, the V- phase signal and the B- phase, the B- phase signal, the W-phase, the W- phase signal and the Z-phase signal, and the Z- phase signal respectively In the above, the case where the signal line 13 is shared has been described. However, the present invention is not limited to this. For example, the circuit configuration shown in FIG. 2 can be adopted.
[0030]
The incremental encoder of this embodiment replaces the two line driver units 11 and 12 in the above-described embodiment with a U-phase, U- phase signal, V-phase, V- phase signal, W-phase, W- phase signal or A-phase, A- phase. A single line driver unit 21 having line drivers 21ua, 21vb, and 21wz for outputting any of a phase signal, a B phase, a B phase signal, a Z phase, and a Z phase signal is provided.
[0031]
That is, the switching circuit 16 is interposed between the phase change detection circuit 15 and the line driver unit 21 described in the above embodiment. The switching circuit 16 includes a plurality of switching elements 16a, 16b, 16z, 16u, 16v, 16w, and 16p. Each line driver 21ua, 21vb, 21wz of the line driver unit 21 based on the output of the phase change detection circuit 15. Is switched to any one of a U-phase, V-phase, W-phase signal or an A-phase, B-phase, or Z-phase signal.
[0032]
In the incremental encoder of this embodiment, the U-phase, U- phase signal, V-phase, V- phase signal, W-phase, and W- phase signal are supplied from the line drivers 21ua, 21vb, and 21wz of the line driver unit 21 to the signal line 13 by turning on the power. The phase change detection circuit 15 detects the change of any one of the A-phase signal, the B-phase signal, and the Z-phase signal due to the rotation of the AC motor at the start of rotation.
[0033]
Each line driver 21ua, 21vb, 21wz of the line driver unit 21 is switched by the switching elements 16a, 16b, 16z, 16u, 16v, 16w, 16p of the switching circuit 16 based on the detection result of the phase change detection circuit 15. Are switched from U-phase, V-phase, and W-phase signals to A-phase, B-phase, and Z-phase signals, and by this switching, the A-phase and A- phase signals are transmitted from the line drivers 21ua, 21vb, and 21wz to the signal line 13. , B-phase, B- phase signal, Z-phase, and Z- phase signal.
[0034]
As described above, since the switching circuit 16 including the switching elements 16a, 16b, 16z, 16u, 16v, 16w, and 16p is interposed between the phase change detection circuit 15 and the line driver unit 21, the U-phase and the U- phase A, A , B, B , Z, and Z signals are output by a single line driver unit 21 that outputs signals, V, V , W, and W signals. Therefore, a single line driver unit 21 can be used in place of the two line driver units 11 and 12 of the above-described embodiment.
[0035]
【The invention's effect】
According to the present invention, there is provided a phase change detection circuit that detects that any one of the A-phase signal, the B-phase signal, and the Z-phase signal has changed due to the rotation of the AC motor at the start of rotation. The U-phase signal, V-phase signal, and W-phase signal transmitted to the signal line are switched to the A-phase signal, the B-phase signal, and the Z-phase signal based on the output of the phase change detection circuit, and the A-phase signal, By transmitting the B-phase signal and the Z-phase signal, the number of transmission lines can be reduced, and variation in signal switching timing caused by motor rotation control can be accurately handled.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an embodiment of an incremental encoder according to the present invention.
FIG. 2 is a circuit diagram showing another embodiment of the present invention.
FIG. 3 is a circuit diagram showing a general example of an incremental encoder.
FIG. 4 is a circuit diagram showing a conventional example of an incremental encoder.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Line driver unit 11u, 11v, 11w Line driver 12 Line driver unit 12a, 12b, 12z Line driver 13 Signal line 14 Power supply line 15 Phase judgment circuit

Claims (3)

It is attached to an AC motor and outputs a U-phase signal, a V-phase signal, and a W-phase signal for detecting the magnetic pole position of the AC motor when the power is turned on. An incremental encoder having a signal line for outputting an A-phase signal, a B-phase signal, and a Z-phase signal for positioning,
A phase change detection circuit for detecting that any one of the A-phase signal, the B-phase signal, and the Z-phase signal has changed due to the rotation of the AC motor at the start of rotation; Switches the U-phase signal, V-phase signal, and W-phase signal transmitted to the signal line to the A-phase signal, the B-phase signal, and the Z-phase signal on the basis of the A-phase signal, the B-phase signal, and the Z-phase signal. An incremental encoder for transmitting a signal. Claims: Two line driver units for respectively outputting the U-phase signal, the V-phase signal, the W-phase signal, the A-phase signal, the B-phase signal, and the Z-phase signal, and the signal lines of the two line driver units are commonly connected. Item 1. The incremental encoder according to Item 1. 2. The incremental encoder according to claim 1, further comprising a single line driver unit that outputs one of the U-phase signal, the V-phase signal, the W-phase signal, the A-phase signal, the B-phase signal, and the Z-phase signal. 3.

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