JPH11118524A - Reference position detector for optical position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reference position detector for an optical position detector for obtaining an accurate reference position signal with satisfactory high speed response. SOLUTION: The reference position detector for an optical position detector comprises a zero signal track 22 having one position shielding part 22A formed on a round on a rotary plate 10, a zero signal detector 41 having an open track 23 having no shielding part formed to detect the track 22, and a threshold signal detector 42 for detecting the open track 23. In this case, the detection signal -z by the detector 41 is compared with the detection signal (r) by the detector 42, and hence a reference position signal Z is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference position detector for generating a reference position signal once per rotation of a rotating plate in an optical position detecting device for optically detecting the amount of rotation of the rotating plate.

[0002]

2. Description of the Related Art There is an incremental rotary encoder as an optical position detecting device for optically detecting the amount of rotation of a rotary plate.

As shown in a conceptual diagram in FIG. 3, an incremental type rotary encoder includes a rotary plate 10 rotatably supported by a rotary shaft 11 and a rotary slit 2 in a radial direction.
The rotation signal tracks 21 are formed by arranging the rotation signal tracks 1A in a circle around the rotation shaft 11, and a rotation amount detector 30 is disposed at a position corresponding to the rotation signal track 21. Are configured to optically detect the rotation slit 21A of the rotation signal track 21 and output a rotation signal corresponding to the rotation amount of the rotating plate 10. Thus, the rotation amount of the rotating plate can be known by counting the rotation signal from the rotation amount detector 30.

In such a rotary encoder, the zero signal track 22 formed on the rotating plate 10 is
And a reference position detector 40 disposed at a position corresponding to the single slit track 24, outputs a reference position signal of one pulse for one rotation of the rotating plate 10, and resets the external position counter and detects the origin position. To be used.

[0005] The reference position detector 40 includes a light emitting device 41 with a rotating plate 10 and a slit plate 50 disposed adjacent thereto interposed therebetween.
A, 43A and the light receivers 41B, 43B are arranged to face each other, and respective detection signals by the light receivers 41B, 43B are -z,
The reference position signal: Z is generated by comparing and combining z with the voltage comparator 44.

[0006] The zero signal track 22 is formed with a shielding portion 22A at one location on the circumference, and the single slit track 24 is formed so as to be shielded over the entire circumference except for the slit 24A at one location on the circumference.

The slit plate 50 has a transmitting portion 52 formed at a position corresponding to a position between the light emitting device 41A and the light receiving device 41B, and has a slit 54A at a position corresponding to a position between the light emitting device 43A and the light receiving device 43B. A light shielding portion 54 is formed.

The pair of the light emitter 41A and the light receiver 41B and the pair of the light emitter 43A and the light receiver 43B are arranged at the same position in the circumferential direction with respect to the rotating plate 10 and the shielding part of the zero signal track 22 is provided. 22A and the slit 24A of the single slit track 24 are set at the same position in the circumferential direction of the rotating plate 10, whereby the shielding section 22A of the zero signal track 22 shields the optical path from the light emitter 41A to the light receiver 41B. The opening of the optical path from the light emitting device 43A to the light receiving device 43B due to the coincidence of the slit 24A of the single slit track 24 and the slit 54A of the shielding portion 54 is performed once every rotation of the rotating plate 10 in synchronization. As shown in FIG. 4, the detection signal: -z from the light receiver 41B has a negative peak, and the detection signal: z from the light receiver 43B has a positive peak.

[0009] The photodetector 4 which becomes a pulse of the opposite phase to the above
The reference position signal: Z is generated by comparing and synthesizing the detection signal: -z from 1B with the detection signal: z from the light receiver 43B by the voltage comparator 44.

That is, a reference position signal: Z is generated by using the light-dark change detection signal: -z from the light receiver 41B and the dark-light change detection signal: z from the light receiver 43B as an original signal. It is something that is to be done.

[0011]

By the way, in the photodiode used as the light receiving device in the above configuration, a time lag is required between the light receiving and the output because of the setup time. On the other hand, the output is rapidly reduced due to the interruption of the light reception.

Therefore, when the reference position signal is formed as the original signal from the light-to-dark change detection signal and the dark-to-light change detection signal by the photodetector as in the above-described conventional configuration, the change from dark to light is detected. Detection signal from the light receiver (the slit 24A of the single slit track 24 is
Receiver 4 that receives light by matching with slit 54A of No. 4
The detection signal (z) from 3B is a detection signal from the light receiver that detects the change from light to dark (the shielding portion 2 of the zero signal track 22).
2A is delayed with respect to the detection signal: -z) that changes by blocking the optical path from the light emitting device 41A to the light receiving device 41B, and thus is generated based on these original signals: -z, z as shown in FIG. The generated reference position signal: Z causes a delay. Also, since the peak portions of the two original signals: -z and z are synthesized, the mutual variation of the output signal is large with respect to the variation of the bias and the amplitude.

As a result, there is a problem that the high-speed response is inferior and a high-precision reference position signal cannot be obtained, and the rotation signal is also shifted.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a reference position detector of an optical position detection device capable of obtaining a reference position signal with high speed response and high accuracy. The purpose is to:

[0015]

According to the present invention, there is provided a reference position detector for an optical position detecting apparatus according to the present invention, wherein a rotatable rotatable plate has a radially detected slit at the center of rotation. An optical position detection device, which is arranged circularly around and optically detects the slit to be detected by a rotation amount detector and outputs a signal corresponding to the rotation amount of the rotation plate, wherein one rotation of the rotation plate A reference position detector that generates a reference position signal once every time, wherein the rotating plate is formed with a zero signal track having a shielding portion formed at one location on the circumference and an open track without a shielding portion. A zero signal detection unit that detects the zero signal track, and a threshold signal detection unit that detects the open track, and compares a detection signal from the zero signal detection unit with a detection signal from the threshold signal detection unit to determine a reference. Characterized in that it is configured to generate a preamble signal.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a conceptual configuration diagram of an incremental type rotary encoder as an optical position detection device to which a configuration example of a reference position detector of the optical position detection device of the present invention is applied.

The illustrated rotary encoder 1 includes a rotation amount detector 30 that outputs a signal corresponding to the rotation amount of the rotating plate 10 at a position corresponding to the slit portion 20 of the rotating plate 10,
A reference position detector 4 which is one configuration example of the reference position detector according to the present invention which outputs a reference position signal of one pulse per rotation.
0 is arranged.

The rotary plate 10 is rotatable about a rotary shaft 11, and the slit portion 20 is a rotary signal track in which radial rotary slits 21A are circularly formed around the rotary shaft 11 as detected slits. 21 and a zero signal track 22 having a shield part 22A formed on the circumference.
And an open track 23 having no shielding over the entire circumference.

A slit plate 50 is provided adjacent to the slit portion 20 of the rotary plate 10, and a pair of fixed slits 51A and 51B are provided in the slit plate 50 at positions corresponding to the rotation signal tracks 21. Transmission portions 52 and 53 are formed at positions corresponding to the signal track 22 and the single slit track 23, respectively.

The rotation amount detector 30 includes a pair of detection units 30A and 30B for forming two rotation signals having phases shifted from each other.
The detectors 30A and 30B are respectively provided with the light emitters 31A and 31B and the light receivers 32A and 32B with the rotation signal track 21 and the fixed slits 51A and 51B therebetween (with the rotation plate 10 and the slit plate 40 therebetween). Are arranged facing each other.

As a result, the amount of light emitted from the light emitters 31A and 31B and reaching the light receivers 32A and 32B is controlled by the rotating plate 10A.
The rotation slit 21A of the rotation signal track 21 becomes maximum when the rotation slit 21A of the rotation signal track 21 coincides with the fixed slits 51A, 51B of the slit plate 50, and the rotation slit 21A of the rotation signal track 21 becomes fixed slits 51A, 5A of the slit plate 50.
1B, which is the minimum in a state where it coincides with the light opaque portion,
With the rotation of the rotating plate 10, the light receivers 32A and 32B output a waveform signal corresponding to the rotating slit 21A.

Fixed slits 51A, 51B of fixed plate 50
Are formed with a phase shift by a predetermined amount. Therefore, a waveform signal having a phase shift is output from the photodetectors 32A and 32B. One rotation signal is output.

The reference position detector 40 detects the zero signal track 2
A zero signal detection unit 41 in which a light-emitting device 41A and a light-receiving device 41B are opposed to each other with the second track 2 and the transmission unit 52 therebetween (with the rotating plate 10 and the slit plate 50 therebetween);
And a threshold signal detection unit 42 in which the light emitter 42A and the light receiver 42B are arranged to face each other across the slit 53 (with the rotation plate 10 and the slit plate 50 therebetween), and a zero signal detection unit 41 and a threshold signal detection unit 42. A voltage comparator 44 receives the detection signal: -z, r differentially and outputs a reference position signal: Z.

In the reference position detector 40 having the above configuration, the detection signal z from the zero signal detector 41 is rotated by the rotating plate 10 so that the shield 22A of the zero signal track 22 reaches from the light emitter 41A to the light receiver 41B. Blocking the optical path produces a negative peak. On the other hand, the threshold signal detector 42 continuously outputs the detection signal r at a constant voltage, and therefore, the voltage comparator 44 sets the reference signal corresponding to the change of the detection signal: -z with the detection signal r as a threshold. Generate and output Z.

In this configuration, the reference position signal: Z is formed on the basis of the output signal (detection signal: -z) from the light receiver 42B that changes rapidly with the decrease in the amount of light received.
For this reason, as in the case of forming a reference position signal using a positive peak generated by receiving light as an original signal, deterioration of high-speed response due to a set-up time from light reception to output of the light receiver and error of rotation signal error. There is no occurrence
A high-speed responsive high-precision reference position signal can be obtained, and no deviation occurs with respect to the rotation signal.

Also, since one peak portion is pulsed at a constant voltage threshold value, the output signal cross-talk caused by a change in bias and amplitude is smaller than that in which the two original signal peak portions are combined. The variation is small and the accuracy is not reduced.

The above configuration example is an application of the present invention to an incremental rotary encoder. However, the invention is not limited to this, and is also applicable to an encoder having another configuration that optically detects a slit to form an output signal. It is possible. In the case of an encoder that already has a reference signal, such as an encoder for excitation control of an AC servomotor, the reference signal can be used as the detection signal: r, so that the threshold signal detection unit 42 becomes unnecessary. is there.

[0028]

As described above, according to the reference position detector of the optical position detecting device according to the present invention, the rotating plate has:
A zero signal track in which a shield portion is formed at one location on the circumference, an open track without a shield portion are formed, a zero signal detector for detecting the zero signal track, and a threshold signal detector for detecting the open track. The detection signal from the zero signal detection unit and the detection signal from the threshold signal detection unit are compared to form a reference position signal. A reference position signal is generated based on the detection signal from the zero signal detector.

For this reason, as in the case where the reference position signal is formed by using the positive peak generated by receiving light as an original signal, deterioration of high-speed response due to setup time from reception to output and error of rotation signal are reduced. There is no occurrence, a high-precision reference position signal with good responsiveness can be obtained, and there is no deviation with respect to the rotation signal, and one peak portion is pulsed with a constant voltage threshold. As a result, the mutual variation of the output signal due to the change in the bias and the amplitude is smaller and the accuracy is less reduced as compared with the case where the peak portions of the two original signals are combined.

[Brief description of the drawings]

FIG. 1 is a conceptual configuration diagram of a rotary encoder to which a configuration example of a reference position detector of an optical position detection device according to the present invention is applied.

FIG. 2 is a waveform diagram showing a generation state of a reference position signal by a reference position detector.

FIG. 3 is a conceptual diagram of a rotary encoder as a conventional example.

FIG. 4 is a waveform diagram showing a generation state of a reference position signal in a conventional rotary encoder.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 rotary encoder (optical position detecting device) 10 rotating plate (detected member) 21A rotating slit (detected slit) 22 zero signal track 23 open track 30 rotation amount detector 40 reference position detector 41 zero signal detector 42 threshold Signal detection unit -z detection signal (detection signal by zero signal detection unit) r detection signal (detection signal by threshold signal detection unit) Z reference position signal

Claims (1)

[Claims] 1. A rotating plate provided rotatably has a plurality of slits to be detected in a radial direction arranged in a circle around the center of rotation thereof, and the slits to be detected are optically detected by a rotation amount detector. An optical position detection device that outputs a signal corresponding to a rotation amount of a rotating plate, wherein the reference position signal is generated once for one rotation of the rotating plate, and the rotating plate is shielded at one location on the periphery. A zero signal track in which a portion is formed, an open track without a shielding portion is formed, and a zero signal detection unit that detects the zero signal track, and a threshold signal detection unit that detects the open track, A reference position detector for an optical position detection device, wherein a reference signal is generated by comparing a detection signal from a zero signal detection unit with a detection signal from the threshold signal detection unit.