JP3633670B2 - Position encoder - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a position encoder.
[0002]
[Prior art]
FIG. 5 is a configuration diagram of a conventional optical transmission type position encoder, FIG. 6 is a circuit diagram of a signal processing circuit thereof, and FIG. 7 is a diagram showing operation waveforms of each part. In FIG. 5, the light from the light source 1 passes through the collimator lens 2, the displacement signal pattern 4 having a slit pattern with a constant pitch on the first scale 3, and a reference position composed of a transmission part and a non-transmission part at a predetermined position. The second scale 6 is irradiated through the signal pattern 5 '. The second scale 6 has four constant signal displacement signal patterns 7-1 to 7-4 and a reference position signal pattern 8 each having a different phase in order to generate signals having different phases by 90 degrees. 'Is formed. The light passing through the second scale 6 irradiates the displacement signal light receiving elements 11-1 to 11-4 and the reference position signal light receiving element 13 '. The light obtained by the light receiving elements 11-1 to 11-4 is supplied from the amplifiers 21-1 to 21-4 of the displacement signal generation circuit unit 60 (FIG. 6) to voltage signals v _a , corresponding to the light amounts as shown in FIG. Converted to v _b , v _a ′, and v _b ′. Further, the digital signals (displacement signals) V _A and V _B are converted by the comparators 22-1 to 22-2. When the moving body passes through the reference position to move in a predetermined direction, the amount of light received by the light receiving element 13 'is changed, by the amplifier 21-5 of the reference position signal generating circuit 70 into a voltage signal v _z as shown in FIG. 7 Converted. Detected by the comparator 22-3 points to reach the level v _c with a voltage signal v _z, and outputs the step-shaped reference position signal V _Z. After the reference position signal _VZ becomes H level, it is obtained from the rising edges of the respective phases of the displacement signals V _A and V _{B of} the displacement signal generating circuit 60 and their inverted signals V _A ′ and V _B ′. The amount of movement of the moving body from the reference position can be detected by counting the number of pulses using the pulse signal generated at the rising edge of the displacement signal V _A as the first pulse among the pulse signals V _p to be generated.
[0003]
[Problems to be solved by the invention]
The reference position signal needs to be able to define one specific period of the displacement signal, which is a periodic signal. As the resolution of the encoder increases, the length of the period of the displacement signal becomes shorter, and accordingly, the required accuracy of the reference position signal becomes higher. If the reference position signal is a transmissive type provided on the first scale, the change in the amount of transmitted light at the boundary between the transmissive part and the non-transmissive part is reflected, and if it is a reflective type, the reflected light at the boundary between the reflective part and the non-reflective part. Is detected through a thin slit provided on the second scale. In order to secure the S / N of this detection signal and obtain a signal of a certain level, it is necessary to increase the slit width of the second scale shape to some extent. For this reason, the slope of the detection signal becomes gentle, and the change in the level of the detection signal due to the change in the characteristics of the element and the change in the mechanical mounting state greatly affects the position where the reference position signal is generated, and the required performance cannot be secured. It was. That is, there is a problem in that the required accuracy of the reference position signal cannot be realized for increasing the resolution of the displacement signal.
[0004]
In a system using three grids as disclosed in British Patent Application No. 44522/74 (Japanese Patent Publication No. 60-23282), when this is applied to a reflective linear encoder, the displacement signal is Although it has a feature that a signal having a good S / N can be obtained even if the gap between the first scale and the second scale is relatively large, with respect to the reference position signal, if the gap is increased, the spread of light or signal due to diffraction There is a problem in that a highly accurate reference position signal cannot be obtained due to a decrease in level.
[0005]
An object of the present invention is to provide a position encoder capable of obtaining a reference position signal with high accuracy.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the position encoder of the present invention comprises:
A displacement signal generating means for generating a periodic displacement signal with respect to the relative position displacement of the relatively moving detection object;
A reference position temporary signal generating means for generating a pulse-like or step-like reference position temporary signal in the vicinity of a reference position for relative movement of the detection object;
An auxiliary signal having a period different from the period of the displacement signal, and an auxiliary signal generating means for generating the auxiliary signal that forms a periodic relative position with the displacement signal ;
Beat period generating means for generating a beat period signal which is a repetition period of the relative phase of the displacement signal and the auxiliary signal;
Displacement signal counting means for counting the displacement signal based on the beat cycle signal after the provisional reference position temporary signal is generated.
[0007]
According to the position encoder of the present invention, one period from one rising edge of the displacement signal to the next rising edge or from the falling edge to the next falling edge is from the rising edge of the auxiliary signal to the next rising edge or from the rising edge. It is in the middle of a period from the falling edge to the next falling edge.
[0008]
In the position encoder of the present invention, the beat cycle generation means counts up at one rising edge or falling edge of the displacement signal, and the count value is cleared at one rising edge or falling edge of the auxiliary signal. Alternatively, the counter includes a counter that counts up at one rising edge or falling edge of the auxiliary signal and the count value is cleared at one rising edge or falling edge of the displacement signal. A beat cycle signal is generated every time.
In the position encoder according to the present invention, the period of the auxiliary signal is 5/4 times the period of the displacement signal.
[0009]
[Action]
The present invention, reference position signal v _Z Instead of immediately starts to count the pulse V _p after rises, the beat period signal V _RZ after reference tentative position signal V _T is generated in the reference pulse V The count of _p is started.
Here, the reference position temporary signal V _T may be generated in one specific cycle of the beat cycle signal having a sufficiently longer cycle than the displacement signal.
[0010]
Therefore, according to the present invention, a highly accurate reference position signal can be obtained.
[0011]
【Example】
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a first embodiment of the present invention, FIG. 2 is a circuit diagram of a signal processing circuit, and FIG. 3 is a diagram showing operation waveforms of each part.
[0012]
The light from the light source 1 passes through the collimator lens 2, the patterns on the first scale 3, and the patterns on the second scale 6 to the light receiving elements 11-1 to 11-4, 12-1, 12-2, and 13. Irradiate. Optical signals detected by the respective light receiving elements 11-1 to 11-4, 12-1, 12-2, and 13 are converted into necessary electrical signals by the signal processing circuit shown in FIG.
[0013]
The pattern 4 on the first scale 3 in FIG. 1, the patterns 7-1 to 7-4 on the second scale 6, the light receiving elements 11-1 to 11-4, and the displacement signal generating circuit unit 30 shown in FIG. Displacement signal generating means for generating displacement signals V _A and V _B having a constant period according to the displacement of the position of the moving moving body is constituted. The pattern 5 on the first scale 3 in FIG. 1, the pattern 8 on the second scale 6, the light receiving element 13, and the reference position temporary signal generation circuit unit 50 shown in FIG. 2 are stepped reference positions in the vicinity of the reference position. Reference position temporary signal generating means for generating the temporary signal V _T is configured. The pattern 9 on the first scale 3 in FIG. 1, the patterns 10-1 to 10-2 on the second scale 6, the light receiving elements 12-1 to 12-2, and the auxiliary signal generation circuit unit 40 shown in FIG. The auxiliary signal generating means for generating the auxiliary signal V _OZ having a slightly different period from the period of the signals V _A and V _B is configured. The beat cycle signal generation means 24 in the auxiliary signal generation circuit section 40 shown in FIG. 2 receives the displacement signal V _A and the auxiliary signal V _OZ and generates a beat cycle signal _VRZ .
[0014]
Next, the operation of this embodiment will be described with reference to the operation waveform diagram of FIG. When the moving body moves in a certain direction, the outputs v _a , v _b , v _a ′, v _b ′ from the operational amplifiers 21-1 to 21-4 of the displacement signal generation circuit unit 30 in FIG. It becomes a wavy signal. 3A shows the signals v _a and v _a ′, and FIG. 3B shows the signals v _b and v _b ′. The signals v _a and v _a ′ and the signals v _b and v _b ′ are respectively compared in voltage by comparators 22-1 and 22-2, and digital signals (displacement signals) V _A and V _B (FIG. 3D, ( E)). Further, inverted signals V _A ′ and V _B ′ (waveform not shown) are generated by the inverters 23-1 and 23-2. For a specific circuit for detecting the rising edge of each of the displacement signals V _A , V _B , V _A ′, and V _B ′ and generating the pulsed signal V _p (V _p shown in FIG. (Not shown) is created. Outputs (auxiliary signals) v _OZ and v _OZ ′ from the operational amplifiers 21-6 and 21-7 of the auxiliary signal generation circuit unit 40 of FIG. 2 are 180 ° in the vicinity of the reference position as shown in FIG. It is a sinusoidal signal with a different phase. The signals v _oz and v _oz ′ are compared in voltage by the comparator 22-4, and become a digital signal (auxiliary signal) V _oz (FIG. _3F ). In this embodiment, the period of the auxiliary signal V _OZ is 5/4 times the period of the displacement signals V _A and V _B. Regarding the phases of the auxiliary signal V _OZ and the displacement signals V _A and V _B , one period from the rising edge of the displacement signal V _A to the next rising edge is from the rising edge of the auxiliary signal V _OZ to the next rising edge. The positional relationship between the displacement signal pattern and the auxiliary signal pattern of the first scale 3 and the second scale 6 is determined so as to be in the center of one period. Next, the displacement signal V _A and the auxiliary signal V _OZ are applied to the beat cycle signal generation means 24. The beat cycle signal generating means 24 has a counter inside to detect a specific relative phase state periodically generated between the displacement signal V _A and the auxiliary signal V _OZ and is displaced as shown in FIG. signal counts up at the rising edge of V _a, the count value is cleared on the rising edge of the auxiliary signal V _OZ. From the beat cycle signal generating means 24, a portion having a count number of 2 as shown in FIG. 3 (H) is output as a beat cycle signal _VRZ . The cycle of the beat cycle signal V _RZ is five times that of the displacement signal V _A. When the moving body passes through the reference position and moves in a predetermined direction, the reference position temporary signal V _T rises. Next, the displacement signal counting means (not shown) detects the first beat cycle signal V _RZ after the rise of the temporary reference position signal V _T and outputs the pulse signal V _p synchronized with this beat cycle signal V _RZ as the first. Pulse counting is performed as a pulse. As can be understood from the above description, the temporary reference position signal V _T may be generated within one specific cycle of the beat cycle signal V _RZ . Further, the phase accuracy between the displacement signal V _A and the auxiliary signal V _OZ for outputting the beat cycle signal V _RZ with a correct cycle may be ± 36 ° when the cycle of the auxiliary signal V _OZ is 360 °. The accuracy can be realized relatively easily. Therefore, the pulse count start point of the pulse signal V _p of the position signal is stabilized, an accurate position signal.
[0015]
Although a detailed embodiment is not shown, by limiting the number of slits of each of the slit patterns 10-1 and 10-2 of the auxiliary signal generating means, the beat cycle signal _VRZ is generated only at one place, The reference position temporary signal generating means can be omitted.
[0016]
In the present embodiment, the phase relationship between the auxiliary signal V _OZ and the displacement signal V _A is defined by the rising edges of both signals, but the falling edges may have the same phase relationship. In this case, the counter of the beat cycle signal generating means 24 operates at the falling edges of both signals. Further, the displacement signal V _B may be used instead of the displacement signal V _A.
[0017]
FIG. 4 is a block diagram showing a second embodiment of the present invention, which is an application example to a reflective linear encoder using so-called three gratings.
[0018]
The displacement signal is such that the light that has passed through the patterns 14-1 and 14-2 provided on the front surface of the light source 1 on the second scale 6 is reflected by the pattern 4 on the first scale 3. Light passes through patterns 7-1 and 7-4, and light from pattern 14-2 passes through patterns 7-2 and 7-3, and light receiving elements 11-1, 11-2, 11 corresponding to the respective positions. It is obtained by irradiating −3, 11-4. As for the auxiliary signal, the light that has passed through the pattern 15 provided on the front surface of the light source 1 on the second scale 6 is reflected by the pattern 9 on the first scale 3, and passes through the patterns 10-1 and 10-2. It is obtained by irradiating the light receiving elements 12-1 and 12-1 corresponding to the positions. The temporary reference position signal is obtained by irradiating the light receiving element 13 through the slit 8 after the light passing through the light transmitting portion 16 on the front surface of the light source 1 on the second scale 6 is reflected by the pattern 5 on the first scale 3. It is done. The phase relationship between the period of the auxiliary signal and the displacement signal and the signal processing method are the same as in the first embodiment.
[0019]
Although the optical position encoder has been described above, the present invention can also be applied to a magnetic position encoder.
[0020]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a highly accurate reference position signal that can correspond to the high resolution of the encoder.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of the present invention.
FIG. 2 is a circuit diagram of a signal processing circuit according to the first embodiment.
FIG. 3 is a diagram illustrating operation waveforms of respective units of the first embodiment.
FIG. 4 is a block diagram showing a second embodiment of the present invention.
FIG. 5 is a configuration diagram of a conventional optical transmission type position encoder.
6 is a circuit diagram of a signal processing circuit of the conventional example of FIG.
7 is a diagram showing operation waveforms of respective parts of the conventional example of FIG. 5;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Light source 2 Collimator lens 3 1st scale 4 Displacement signal pattern 5 on 1st scale 3 Reference position temporary signal pattern 5 'on 1st scale 3 Reference position signal pattern 6 2nd scale 7 2nd scale 6 Displacement signal pattern 8 Reference position temporary signal pattern 8 'on the second scale 6 Reference position signal pattern 9 Auxiliary signal pattern 10 on the first scale 3 Auxiliary signal pattern 11 on the second scale 6 Displacement signal Light receiving element for auxiliary signal 12 Light receiving element for auxiliary signal 13 Light receiving element for reference position temporary signal 13 ′ Light receiving element for reference position signal 14 Displacement signal pattern 15 provided on the front surface of the light source on the second scale 6 On the second scale 6 Auxiliary signal pattern 16 provided on the front surface of the light source The reference position temporary signal light transmitting portions 21-1 to 21-21 provided on the front surface of the light source on the second scale 6. 7 Amplifiers 22-1 to 22-4 Comparators 23-1, 23-2 Inverter 24 Beat period signal generating means 30, 60 Displacement signal generating circuit unit 40 Auxiliary signal generating circuit unit 50 Reference position temporary signal generating circuit unit 70 Reference Position signal generation circuit unit V _A , V _B displacement signal V _OZ auxiliary signal V _RZ beat period signal V _T reference position temporary signal V _z reference position signal V _p pulse signal

Claims (4)

A displacement signal generating means for generating a periodic displacement signal with respect to the relative position displacement of the relatively moving detection object;
A reference position temporary signal generating means for generating a pulse-like or step-like reference position temporary signal in the vicinity of a reference position for relative movement of the detection object;
An auxiliary signal having a period different from the period of the displacement signal, and an auxiliary signal generating means for generating the auxiliary signal that forms a periodic relative phase with the displacement signal ;
Beat period generating means for generating a beat period signal which is a repetition period of the relative phase of the displacement signal and the auxiliary signal;
A position encoder having displacement signal counting means for counting the displacement signal with reference to the beat period signal after the provisional reference position temporary signal is generated. One period from one rising edge of the displacement signal to the next rising edge or from the falling edge to the next falling edge is a period from the rising edge of the auxiliary signal to the next rising edge or from the falling edge to the next. The position encoder according to claim 1, wherein the position encoder is in the middle of a period up to a falling edge. The beat cycle generation means counts up at one rising edge or falling edge of the displacement signal, and the counter whose count value is cleared at one rising edge or falling edge of the auxiliary signal or one of the auxiliary signals Each time the rising edge or falling edge of the displacement signal is counted up and the count value is cleared at one rising edge or falling edge of the displacement signal. The position encoder according to claim 1, wherein the position encoder generates the beat period signal. The position encoder according to any one of claims 1 to 3, wherein a period of the auxiliary signal is 5/4 times a period of the displacement signal.

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