JPS608714A - Absolute position detection type optical shaft encoder - Google Patents

Abstract

PURPOSE:To reduce the control error without being influenced by temperature and secular change by using a code disc where a position detection code consisting of the bright part of a triangular waveform and a discrimination code consisting of the dark part and the bright part of a square waveform are recorded. CONSTITUTION:A code disc 25A is provided with the first track T1 where the position detection code which increases or reduces linearly the quantity of transmitted light from a collimator lens 12 in accordance with the rotation angular position and consists of a bright part C of the triangular waveform is recorded, the second track T2 where the discrimination code consisting of a dark part D of the square waveform through which a parallel light is not transmitted at all and a bright part C of the square waveform through which all of the parallel light is transmitted is recorded for the purpose of discriminating the direction of the inclination of the bright part C of the triangular waveform, and the third track T3 for compensation of light quantity consisting of only the bright part C of the square waveform. An absolute position is detected by the first photodetector 42, the rotation angular position is discriminated by the second photodetector 43, and the quantity of light is compensated by the third photodetector 44 and a light quantity compensating circuit 13. If the same type photodetectors are used for all photodetectors, the control error is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an absolute position detection type optical single shaft encoder, and in particular to a code disc in which a position detection code consisting of the portion between the triangular waveforms and a discrimination code consisting of the dark and bright portions of the square waveform are recorded. The present invention relates to an absolute position detection type optical single shaft encoder.

Prior art A conventional absolute position detection type optical single shaft encoder has two
Logical value of decimal code ``7''. ``θ'' is defined as the part on the code disk of this shaft encoder that transmits 6 lights (hereinafter referred to as bright part) and the part that does not transmit 1 light (hereinafter referred to as bright part).
It's called the dark side. ).

It is recorded as. To do this, the code disk required a number of code trunks equal to the number of bits of the unary code to be recorded. In addition, the number of light sources and light-receiving elements used to read the code was required to be equal to the number of bits of the binary code.

OBJECTS OF THE INVENTION The present invention uses a logical value ``'7'' of a λ-adic code as in conventional devices to detect an absolute position.

Instead of using a code disk on which bright and dark areas corresponding to 0'' are recorded, a position detection code consisting of the area between the triangular waveforms and a discrimination code consisting of the dark and bright areas of the square waveform are recorded instead. An object of the present invention is to provide an absolute position detection type optical single shaft encoder using a code disk.

Another object of the present invention is to compensate for variations in the light emission output of a light source and the light reception output of a light receiving element due to changes in temperature and over time.

Structure of the Invention Accordingly, the present invention provides an optical system that emits parallel light, and a code disk whose position also includes a portion between triangular waveforms that linearly increases or decreases the amount of transmitted light of the parallel light according to its rotational angular position. In order to determine the direction of the inclination of the first track in which the detection code is recorded and between the triangular waveforms, there is a discrimination code consisting of a rectangular waveform dark area that does not transmit any parallel light and a rectangular waveform bright area that transmits all parallel light. the code disk having a recorded first track; a first light-receiving element that detects the amount of light transmitted through the first track and converts it into a seventh electric signal;
a light receiving section having a first light receiving element that detects the amount of light transmitted through the track and converts it into a second electrical signal; and electronically processing the first and first electrical signals to determine the absolute position of the code disk. and an absolute position signal generating means for generating an analog output signal or a digital output signal indicating the absolute position of the input shaft of the absolute position calibration type optical shaft encoder and thus detecting the absolute position of the code disk attached to this input shaft. You can. Furthermore, a third waveform for light intensity compensation consisting only of square waveform bright areas is provided.
A track is provided on the code disk, a third light-receiving element is provided in the light-receiving section for detecting a change in lrr of the parallel light transmitted through the third track, and converting the detected change into a third electrical signal. By providing the optical system with a light amount compensation circuit that adjusts the amount of light so that the amount of light is always constant, it is possible to obtain a shaft encoder that is independent of temperature and changes over time.

Furthermore, by using the same type of elements for the first, first, and third light receiving elements.

Control errors can be reduced.

EMBODIMENT OF THE INVENTION Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention, in which an optical system 10 includes a light source //, a collimator lens saw that converts the light emitted from the light source // into parallel light, and a light amount compensation circuit (to be described in detail later).
It consists of 3 parts. The code disc, 20A, is attached to the input shaft 30 of the shaft encoder, and the code disc, 20A, is attached to the input shaft 30 of the shaft encoder and is rotated from the collimator lens saw according to the rotational angular position of the code disc, 2OA, the details of which are shown in FIGS. A first track T/ on which a position detection code consisting of a bright part C of a triangular waveform that linearly increases/decreases the transmitted light M: of the parallel light M: is recorded. In order to determine the direction of inclination of part 0, the dark part of the square waveform that does not transmit all the parallel light (C) and the bright part C of the square waveform that transmits all the parallel light.
A second track T, on which a discrimination code consisting of 2.
and a third beam for light amount compensation consisting only of the bright part C of the square waveform.
It has a track T3. 1 and 3 are examples in which the only triangular waveform interval C is recorded on the first track TI of the code disk, but as shown in FIGS. 4 and 5, the first track TI λ triangular waveform intervals O may be recorded in the TI, or three or more triangular waveform intervals O may be recorded, although not shown. In short, the number of triangular waveform intervals may be determined depending on the resolution required of the code disk. To explain in detail, the code disk 20B shown in FIGS. 9 and 5 is a first track T/ on which a position detection code consisting of an area C between two triangular waveforms is recorded, and each triangular waveform light. A square waveform dark area is formed depending on the direction of the slope of the section C, and a square waveform dark area is formed corresponding to one track T2A in which the square waveform bright area O is recorded and one of the inter-triangular waveform areas. The other track T, in which a square waveform bright portion C is recorded corresponding to the other triangular waveform interspace, a first track consisting of 2B, and a third trunk consisting only of a square waveform bright portion C. It has T3. In addition.

If the number of triangular waveform segments recorded on the first track is -, the second trunk consists of (n+/) tracks, where n is θ or a positive integer. ) and the square waveform dark areas and square waveform bright areas are recorded alternately.

Returning to FIG. 1, the parallel light transmitted through the sign disk 20k reaches the light receiving section OG which is arranged to face the optical system 7'0 with the sign disk 20A in between. This light receiving part 0 is a fixed sill l provided with an opening (not shown).
-4'/, first light receiving element 11.2. First light receiving element/
/3 and a third light receiving element 2<2. The first light-receiving element 11.2 is a light-receiving element for absolute position detection, and detects the amount of parallel light that has passed through the first track TI of the code disk 20A and through the opening of the fixed slit lIl. The absolute position of the input shaft 30 of the shaft encoder, that is, the code disk 2OA attached to this input shaft 301c, is detected and converted into a first electrical signal. Second light receiving element +
! 3 is a light receiving element for discrimination that discriminates the direction of inclination of the bright portion of the triangular waveform recorded on the first track T/.

The light leakage s of the parallel light transmitted through the first track T2 of the code disk 20A and through the fixed aperture 20A is detected and converted into a first electrical signal.

The third light-receiving element Kuda is a light-receiving element for compensating the amount of parallel light from the light source /1, that is, from the collimator lens /2, and transmits the light through the third track T3 of the sign disk θA and the opening of the fixed slit 4/. Changes in the amount of parallel light that has passed through due to temperature or changes over time are detected and converted into a third electrical signal.

Here, the first photodetector element t3 of '7 $2
respective seventh electrical signals S/, detected and converted by
A second electrical signal S (for example, voltage) and a code disk 20A
The relationship between the rotation angle and the rotation angle is as shown in FIG. 1st
Points a and a+ in the electric signal S of are at the same voltage (mV
), and these points a and a' correspond to the rotational angular positions x 6 and y O of the code disk 2OA, respectively. Therefore, the first light receiving element 3 discriminates between the rotational angular positions X0 and Yo. In other words, in the first electrical signal S2 generated by the first light receiving element q3, the part where voltage is generated is given the logical value "/", and the part where no voltage is produced is given the logical value "0".
Then, the rotational angular position X0 can be determined as the position of the logical value "θ", and the rotational angular position Y0 can be determined as the position of the logical value "/".

This also applies when the code disks OB shown in FIGS. 9 and 5 are used. The coding system in this invention is, for example, when a code of 2n is used, and when the code disk θA is used, the square wave recorded in the first trunk T2 represents the digit 1, and ko.Hereinafter, 2 1st place up to °
This is represented by the triangular wave recorded on trunk T/.

Similarly, when the sign disk θB is used, the 2n digit is represented by the square wave recorded on the other track lever B of the second track, and the - digit is recorded on one track T, 2A. represents a square wave and sn! Thereafter, the triangular wave recorded on the first track T/ represents the digit up to 2 degrees.

Returning the explanation to Figure 1 again, it is an absolute position signal generating means! O is electrically connected to the first light receiving element lI2 and linearly amplifies the first electric signal S/ to generate a sign disk -θA.
A linear amplifier S/, which generates an analog output signal indicating the absolute position of , is electrically connected to the first light-receiving element lI3 and shapes the waveform of the first electric signal S to produce a logical value "/" and O.
A waveform shaping circuit 52 converts the sign into a sign of ``'', and combines the analog output signal of the linear amplifier S/ with the logic value sign of the left λ of the waveform shaping circuit to generate an analog output signal indicating the absolute position of the sign disk 20A. If necessary, the absolute position signal generating means Sθ converts the analog output signal of the linear amplifier 5/ from analog to digital to generate a digital output signal indicating the absolute position of the code disk, 2OA. It may also include an analog/digital (A/D) converter S.

The light amount compensation circuit 13 in the optical system lO is connected to the third light receiving element lI.
electrically connected to the The light emitting output of the light source l/ and the first light receiving element l, the first light receiving element +! Since the light receiving output of 3 and the third light receiving element <19 varies depending on the temperature or changes over time, the third light receiving element 11 detects only the change in the light amount of the parallel light from the light source//therefore, the collimating lens 12. This third electrical signal is fed back to the light intensity compensation circuit 13 to adjust the light intensity of the light source l/ so that the output of the third light receiving element group l, that is, the third electrical signal is always constant. Control so that

Note that if the same type of elements are used for the first light-receiving element Kuko, the first light-receiving element l13, and the third light-receiving element ++, control errors can be reduced.

Effects of the Invention According to the present invention, the absolute position of the code disk can be determined by using a code disk on which a position detection code consisting of a bright portion of a triangular waveform and a discrimination code consisting of dark and bright portions of a square waveform are recorded. It can be output as an analog signal or a digital signal, is not affected by R1 degree or change over time, and has the advantage of having a small control error.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a plan view of a code disk used in the embodiment shown in FIG. 1, and FIG. 3 is a block diagram of the code disk shown in FIG. Figure 6 is a linear representation of each symbol on the board. Figure 6 is a plan view of another code disk. Figure S is a linear representation of each symbol on the code disk of the 8g diagram. FIG. 2 is a graph diagram showing the relationship between the electric signal generated by the light receiving section and the rotation angle of the code disk. 10 is an optical system, 11 is a light source, /:1 is a collimator lens, /3 is a light amount compensation circuit 1.20A and 10B are sign disks,
T/ is the first track, T, 2 is the second track, T
Core A is one track of the first trunk, T2B is the other trunk of the first truck, T3 is the eighth trunk, and C is the light section. D is the dark area, and 3θ is the input axis of the shaft encoder. lIO is a light receiving unit, ri/ is a fixed slit, Kuyu is a first light receiving element, 473 is a first light receiving element, 4t is a third light receiving element, go is an absolute position signal generating means, 31 is a linear amplifier% tacho is a waveform shaping circuit. 3 is a logic circuit, and 1 on the left is an A/D converter. Patent applicant: Tamagawa Seiki Co., Ltd. Tori 6* Figure 2, Figure 4

Claims (1)

[Claims] / Position detection consisting of an optical system that emits parallel light, and a triangular waveform bright portion that is a sign disk and linearly increases or decreases the amount of transmitted light of the parallel light according to its rotational angular position. A first track on which a code is recorded, and a determination comprising a rectangular waveform dark part that does not transmit any of the parallel light and a square waveform bright part that transmits all the parallel light in order to determine the direction of the inclination of the triangular waveform bright part. the code disc having a second trunk on which a code is recorded; a first light receiving element that detects an amount of light transmitted through the second trunk and converts the detected amount of light into a first electrical signal; an absolute position signal generating means for electronically processing the signal and the first electric signal to generate an output signal indicating the absolute position of the code disk. encoder. 2. The absolute position detection type optical shaft encoder according to claim 1, wherein the optical system includes a light source that emits light and a collimator lens that converts the light into parallel light. 3 The absolute position signal generating means is an IJ near amplifier that linearly amplifies the first electric signal from the first light receiving element to generate an analog output signal indicating the absolute position of the code disk, and a first light receiving element. A waveform shaping circuit that shapes the second electrical signal from the output signal and converts it into a logic value "/" and "θ" sign, and a logic circuit that combines the analog output signal and the logic value sign. An absolute position detection type scientific shaft encoder according to the first or second range. The absolute position signal generating means according to claim 3 has an analog/digital command converter inserted between the linear amplifier and the logic circuit to generate a digital output signal indicating the absolute position of the code disk. Position detection type optical single shaft encoder. ! The only triangular waveform interval is recorded on the seventh track,
The first track is composed of seven tracks, and rectangular waveform dark areas and rectangular waveform bright areas are recorded corresponding to the direction of inclination of the inter-triangular waveform areas, respectively.
! 11. The absolute position detection type optical single shaft encoder according to any one of items 1 to 7. In the first track, λ triangular waveform interparts are recorded,
The first track consists of one track, and a rectangular waveform dark part and a rectangular waveform bright part are recorded in one of these tracks, respectively, depending on the direction of the slope of the inter-triangular waveform part. However, in the other track, a square waveform dark part is recorded corresponding to one of the two triangular waveform intervals, and a square waveform bright part is recorded corresponding to the other of the one triangular waveform interval. An absolute position detection type optical single shaft encoder according to any one of claims 1 to 7. 2 In the first track: 1n triangular waveform interstices are recorded, and the first track consists of (n+/) tracks (YL, n is O or a positive integer) and has a rectangular shape. An absolute position detection type optical single shaft encoder according to any one of claims 1 to 7, wherein dark waveform portions and square waveform bright portions are recorded alternately. The code disk has a third track for light intensity compensation consisting only of square waveform bright areas, and the light receiving section detects changes in the light intensity of the parallel light transmitted through the third track from the optical system due to temperature or changes over time. an eighth that detects and converts it into a third electrical signal;
Claims 7 to 6 have a light receiving element, and the optical system includes a light amount compensation circuit that adjusts the scene so that the third electric signal is always constant. Absolute position detection type scientific shaft encoder. The absolute position detection type optical single shaft encoder according to claim 7, wherein the first, first and third light receiving elements are of the same type.