JPS5822914A - Zero point detecting device of photoelectric encoder - Google Patents

Abstract

PURPOSE:To obtain an exact zero point detecting signal having no directional error, by detecting 2 kinds of zero point reference signals being opposite in polarity, at a desired zero point position. CONSTITUTION:On a main scale 10, 2 rows of zero point detecting optical lattices 10c, 10d are provided, and on each lattice 10c, 10d, its light screening part and light transmitting part are provided in reverse to each other. Also, at a position opposed to the lattices 10c, 10d, a zero point detecting optical lattice 12c is provided on an index scale 12. At the side of the lattice 12c, zero point detecting photodetectors 20, 22 are placed at a position opposed to the lattices 10c, 10d, light, and shade of light are detected, and zero point reference signals 200, 202 being opposite in polarity are supplied to a comparator 24. Subsequently, a comparison output 204 is converted to a pulse 26, and a zero point detecting signal 206 is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a zero point detection device for a photoelectric encoder, in particular, a zero point reference signal obtained from a zero point detection optical grating provided on a pair of scales that move relative to each other as physical quantities change, to accurately determine the zero point position of a scale. This invention relates to an improvement of a zero point detection device.

Photoelectric encoders are suitable for detecting changes in length or physical quantities as accurate electrical signals in length measuring instruments, coordinate measuring machines, positioning of machine tools, etc., and are used in various fields as linear or rotary encoders. It has been put into practical use.

In the photoelectric encoder I, the electrical detection signal is normally processed as a current signal that is supplied to the current sensor. A zero point detection device is provided to indicate the position.

Figure 1 shows the main parts of a general photoelectric encoder I.
The main scale lO and the index scale 12 form a linear lid encoder.

Both scales 10 and 12 have optical gratings on their surfaces in which light-shielding parts and light-transmitting parts are arranged alternately. Two pairs of optical gratings are formed by the two provided optical gratings 12a and 12b,
Two detection signals, which will be described later, are obtained from both pairs of optical gratings.

Both the optical gratings 12 and 12b provided on the index scale 12 are arranged in alignment with different phases, for example, a phase difference of 9σ, and therefore, due to the relative movement of both scales 10 and 12, two types of different phases can be generated. It becomes possible to obtain a detection signal of

That is, a light emitter 14 made of a light emitting diode or the like is provided on one side of the main scale IO, and C2 light receivers 16.1B are provided on the other side facing the light emitter 14 via both scales 10.12. Both light receivers 16 and 18 are arranged at positions facing the optical gratings 12m and 12b, respectively. Therefore, in the example, main scale 1
0 or the index scale 12 in response to a change in length or physical quantity, the amount of light transmitted through the pair of optical gratings changes, and both light receivers 16 and 18 electrically detect periodic changes in the amount of light. It becomes possible to obtain it as a signal.

In a normal case, the detection signal is detected as a sine wave signal and a cosine wave signal with a 90" phase difference, and these are converted into a Callan-Thonors signal by a processing circuit (not shown) at a subsequent stage, and changes in length or physical quantity are detected. It can be displayed as a digital value or used as another control signal.

In order to detect the zero point position of the scale, the main scale 10 in the figure, the main scale 10 and the index scale 12 are provided with zero point detection optical gratings 10c and 1, respectively.
2C, and these optical gratings IQc, 12G are each formed from a light shielding part and a light transmitting part arranged in the same manner as the optical gratings 10, 12, 1.12b, or are used as an optical grating for zero point detection. c4I is formed from special random nog turns. So [, index scale 1
A light receiver 20 for zero point detection is provided opposite to the optical grating 12c for zero point detection of No. 2, and when the zero point of the main scale 10 faces the index scale 12, the light receiver 20 can output a zero point reference signal. This allows the zero point reference signal to be used to reset the count value to make an absolute measurement or as any other comparison signal.

The zero point position of the scale may be a single position or a plurality of arbitrarily selected positions within the entire length of the scale, and one or more of these zero point reference signals can be used as desired.

According to the above-mentioned general photoelectric encoder, the zero point reference signal can be obtained from the above explanation, but in the conventional device, this zero point reference signal is processed as follows.

FIG. 2 shows a conventional zero point detection circuit, in which the zero point reference signal 100 shown in FIG. is converted into a zero point detection signal 106 synchronized with its leading edge by a pulse forming circuit 24 consisting of a differentiating circuit or a one-shot circuit, and this is supplied to a subsequent processing circuit.

According to the conventional device described above, the zero point detection signal 106 can be easily obtained with a simple circuit configuration and has five rows of points, but since the comparison output 104 has a pulse width that cannot be ignored, the main scale 10 There is a problem in that a directional error occurs in the zero point detection signal 106 depending on the direction of movement.

That is, the main scale 100 is changed to the index scale 1.
When moving in the direction of the arrow B in FIG.
When the zero point detection signal 1 shown in FIG.
06' occurs, resulting in a signal shifted by the pulse width of the comparison output 104.

This directional error will not cause a count error in any direction as long as it is within the pulse interval of the count pulse signal obtained from the photoreceiver 16, 18, but it will affect the response speed of the encoder and processing circuit. Taking this into consideration, the tolerance range for this directional error becomes extremely small, and in the conventional device, the zero point reference signal 100 or the comparison output 104
The pulse width of the reference voltage 10c and 12c must be set extremely small for this reason, and very strict precision is required when processing the optical gratings 10c and 12c for zero point detection.
2 near the top of the zero point reference signal Zoo, there is a problem that the zero point cannot be detected or an erroneous signal is mixed in when the amount of light emission decreases or when noise occurs.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide an improved zero point detection device that can obtain an accurate zero point detection signal without directional errors. □ In order to achieve the above object, the present invention includes a main scale having aligned optical gratings, and an index scale having two optical gratings aligned with mutually different phases. In a photoelectric encoder that detects two types of signals with different phases from the brightness and darkness of light transmitted or reflected by both optical grating pairs by relatively moving the scale, two types of zero point reference signals with different polarities are detected at a desired zero point position. The present invention is characterized in that a zero point detection means is provided for obtaining the zero point reference signal, and outputs a zero point detection signal when the two zero point reference signals intersect.

Preferred embodiments of the present invention will be described below based on the drawings.

A first embodiment of the present invention is shown in FIG. 4, and the same members as those in the conventional device shown in FIG.

A characteristic feature of the present invention is that two types of zero point reference signals with different polarities are detected at a desired zero point position. For this reason, in the embodiment shown in FIG. Two rows of zero point detection optical gratings 10c, 10 arranged in parallel in the moving direction of the mower 0! These optical gratings 10c and 10d consist of a hatched light-shielding part and a light-transmitting part other than the hatched part. It is provided.

Optical grating 10C110 for zero point detection of the main scale 10
The index scale 12 is provided with an optical grating 12C for zero point detection at a position opposite to the main scale 1.
It is understood that the brightness of the transmitted light from the light emitter 14 changes at the zero point position due to the cooperation of the zero-side optical gratings 10c and 10d and the zero-side optical grating 12c. On the side of the zero point detection optical grating 12- of the index scale 12, there is an optical grating 10c%10d of the main scale 10 even.
Zero point detection light receivers 20 and 22 are located opposite each other.
is arranged, and the light/darkness of the light is detected by the light receiver 20.22.
can be output as an electrical detection signal.

The outputs of the zero point detection light receiver 20122 form zero point reference signals 200 and 202 having different polarities, respectively, and the zero point reference signals are processed by the processing circuit shown in FIG. 5, and the waveform thereof is shown in FIG. There is. As is clear from FIG. 6, both zero point reference signals 200 and 202 have waveforms that are inverted at the boundary between the light shielding part and the light transmitting part of the zero point detection optical grating 10c10d. A state in which a plurality of zero point positions are set along the movement direction is shown, and one zero point reference signal 20 is set for each zero point position.
0 and 202 are reversed to have opposite polarities.

Therefore, in the present invention, the zero point reference signal 200
．． As shown in FIG. 5, the zero point detection signal 206 can be obtained very easily by comparing the signals 202 with each other using the comparator 24 and converting the comparison output 204 into a Norsing circuit 26. Become.

FIG. 7 shows a second embodiment of the present invention, in which the same members as those in the first embodiment are given the same reference numerals and their explanations will be omitted.

A characteristic feature of the second embodiment is that the main scale 10 has one row of zero point detection optical gratings, and from this one row of zero point detection optical gratings 12c, two types of zero points with opposite polarities are In order to obtain a signal, the index scale 1:l has two zero point detection optical gratings 12c, 12 arranged at a predetermined distance in the moving direction of the main scale 10.
d, and the zero point detection light receiver 20.22 is disposed at a position facing the cough optical gratings 12c, 12d.

In this embodiment, the optical grating 12c for zero point detection of the main scale 10 has its light shielding portions and light transmitting portions arranged at equal intervals, and the light receivers 20 and 22 provided on the index scale 12 also have gaps between them. The gap is set to be equal to the gap between the light shielding part and the light transmitting part.

Therefore, when one photoreceiver 20 outputs a zero point reference signal with an increasing characteristic facing the boundary from the light-transmitting portion to the light-transmitting portion, the other photoreceiver 20 outputs the zero point reference signal facing the boundary from the light-transmitting portion to the light-shielding portion. and outputs a zero point reference signal with decreasing characteristics. Therefore, the fifth
As described in FIGS. and 6, by comparing both zero point reference signals having different polarities, it becomes possible to obtain an accurate zero point detection signal when both characteristics intersect.

A third embodiment of the present invention is shown in FIG.
The same members as those in the embodiment are given the same reference numerals, and the description thereof will be omitted.

In the third embodiment, the optical grating 12c for zero point detection provided on the main scale 10 is arranged in one row, and furthermore, the optical grating 12c for zero point detection provided at the position facing the optical grating for zero point detection is arranged in one row. The number of light receivers 20 is one. Then, in order to detect a zero point detection signal from one row of zero point detection optical gratings 12c and one zero point detection light receiver 20, a ninth
The zero point detection circuit shown in the figure is used.

In FIG. 9, an inverting circuit 28 is provided to invert the zero point reference signal 200 of the zero point detection light receiver 20, and a zero point detection signal is generated from the zero point reference signal 200 and an inverted zero point reference signal 2001 having a different polarity from the inverting circuit 28. 206 is detected. That is, in the waveform diagrams of FIGS. 9 and 10, if the comparator 24 compares the zero point reference signal 200 and the inverted zero point reference signal 200', an accurate zero point detection signal 206 can be obtained when both characteristics intersect. I can do it.

As described above, according to the present invention, it is possible to easily obtain a strong zero point detection signal that is not affected by changes in the mechanical gap of the encoder or changes in the amount of light. The lattice has the advantage of being easy to process because its nodata turns are extremely simple. Further, according to the present invention, there is no error in the moving direction of the scale, which is extremely effective, especially when a plurality of zero point positions are required as in the embodiment.

[Brief explanation of drawings]

Fig. 1 is a perspective view of the main parts showing the schematic configuration of a general photoelectric encoder, Fig. 2 is a zero point detection circuit diagram of Fig. 1, Fig. 3 is a waveform diagram of the main parts of Fig. 2, and Fig. 4 is a diagram of the main parts of Fig. 2. A perspective view of a main part showing a preferred embodiment of a photoelectric encoder incorporating a zero point detection device according to the present invention, FIG. 5 is a photoelectric detection circuit diagram in FIG. 4, and FIG.
FIG. 7 is a perspective view of the main part showing the second embodiment of the present invention, FIG. 8 is a perspective view of the main part showing the third embodiment of the invention, and FIG.
The zero point detection circuit diagram in the figure, FIG. 1θ is the waveform diagram of FIG. 9. 10--Main scale, 12...in, dex scale, 10m, 12m, 12b--Optical grating, 10c, 10d
, 12c - Optical grating for zero point detection, 14 - Light emitter, 16.18 - Light receiver, 20.22 - Light receiver for zero point detection, 24 - Comparator, 26 - Pulsing Circuit, 28--Inverting circuit, 200.202--Zero point reference signal, 200'--Inverted zero point reference signal, 206--Zero point detection signal. Figure 1 10d' 5VU Figure 6 06 11E? ! ! ! ! 1 2c

Claims (1)

[Scope of Claims] (1) A main scale having optical gratings arranged in alignment, and an index scale having two optical gratings arranged in alignment with mutually different phases, wherein both scales are moved relative to each other. In a photoelectric encoder that detects two types of signals with different phases from the brightness and darkness of light transmitted or reflected by both optical grating pairs, zero point detection means obtains two types of zero point reference signals with different polarities at a desired zero point position. A zero point detection device for a photoelectric encoder, characterized in that the zero point detection device for a photoelectric encoder is provided with: and outputs a zero point detection signal when the two zero point reference signals intersect. (2. In the apparatus described in claim (1), the main scale is provided with at least two rows of zero point detection optical gratings arranged in parallel along the movement direction of the main scale. A zero point detection device for a photoelectric encoder, characterized in that it detects a zero point reference signal of opposite polarity. The optical grating for zero point detection has light shielding parts and light transmitting parts arranged at equal intervals corresponding to a plurality of desired zero point positions, and the light shielding and light transmitting intervals of the zero point detecting optical grating are arranged at equal intervals. A zero point detection device for a photoelectric encoder, characterized in that two light receivers for zero point detection are provided on the index scale at the same interval as , and a zero point reference signal of opposite polarity is detected from both of the light receivers. ) In the apparatus according to claim (1), the main scale is provided with a line of zero point detection optical gratings along its movement direction, and the zero point detection optical gratings are arranged in a row corresponding to a plurality of desired zero point positions. The light-shielding portions and the light-transmitting portions are arranged at regular intervals, and one zero-point detection light receiver is provided at a position facing the zero-point detection optical grating, and the zero-point reference signal of the zero-point detection light receiver and its A zero point detection device for a photoelectric encoder, characterized in that a zero point detection signal is detected when it crosses an inverted zero point reference signal.