JPH0123048B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for measuring relatively large travel distances with high resolution and accuracy.

Measuring instruments with relatively small travel distances include linear gauges, Magnescales, and Inductosin, all of which have high resolution and precision within the range of 1 to 10 μm. These configurations are based on a scale in which transmitting parts such as slits, magnetic poles, and coils are arranged at minute equal pitches, and a detector having two receiving parts such as a light source, a light receiving element, a magnetic flux responsive head, and a coil. The two receivers are arranged opposite each other, and the appropriate transmitters are offset from each other by 1/4 of the pitch of the transmitter. Therefore,
Each time the scale and detector are moved relative to each other by one pitch of the transmitting section, a periodic output will be generated at each receiving section of the detector, and the periodic outputs will be 90 degrees (mechanical) from each other. Distance is 1/4 of transmitter pitch)
It will have a phase difference of .

Therefore, by introducing these two periodic outputs into the direction determining section and determining the phase advance or lag of the other periodic output with respect to one periodic output as a reference, the relative movement direction of the scale and the detector is determined. By generating a discrimination output according to the discrimination output, and switching the periodic output or the output obtained by multiplying it via the multiplication section to the addition and subtraction input terminals of the counting section, scale and detection can be performed. The relative moving distance of the container is converted into the count value of the counter.

Therefore, the measurement resolution of the above-mentioned measuring device is the moving distance represented by one count of the counting section, and this is determined by the array pitch of the transmitter and the multiplication rate of the periodic output generated in the detector each time the array pitch moves. Determined by. Therefore, in principle, it is possible to perform higher resolution measurements by making the array pitch of the transmitter as small as possible and increasing the multiplication factor, but in order to ensure accuracy, it is necessary to It is necessary to form the pitch and multiply accurately.

By the way, when forming a transmitting part using minute bits like this, the longer the scale, the more difficult it becomes both technically and pharmaceutically, including problems with the manufacturing equipment. The only high-precision, high-resolution measuring instruments available are those for measuring relatively small travel distances.

The present invention eliminates the above-mentioned drawbacks and utilizes a relatively short scale that allows the production of a transmitting section with high precision and minute bits, and in the longitudinal direction of the scale,
A plurality of detectors are arranged at appropriate intervals shorter than the entire length of the scale, and the periodic outputs of the detectors placed adjacent to each other are introduced into the switching control section and the phase shift calculation section to calculate the period of both detectors. A switching output corresponding to the presence or absence of a digital output and a shift distance output corresponding to a phase shift between the periodic outputs of both detectors are generated, and a detector or a multiplier connected to the counting section is selectively selected according to the switching output. At the same time, the output of the deviation distance between the detectors before and after the switching is added to the counting section to correct the deviation distance within the transmitter pitch caused by the installation position error between the detectors before and after the switching. This is what I did. Hereinafter, embodiments of the present invention will be described in detail using a linear gauge as an example.

This uses a relatively short scale, and measures approximately twice the travel distance under the resolution and accuracy of the measuring instrument.

In FIG. 1, the linear gauge has a spindle 4 supported in a housing 5 so as to be movable only in the vertical direction, the lower part of the spindle 4 protruding from the bottom surface of the housing 5, and a slit in the housing 5. A scale 1 arranged at an equal pitch P is fixed to the spindle 4, and pairs of light sources and light receiving elements 23 and 21 and 24 and 22 are fixed to the inner wall of the casing 5, facing each other with the scale 1 sandwiched between them. Light receiving elements 21, 22
A detection slit plate 25 having an appropriate number of slits with the same pitch as the scale 1 is fixed on the opposing surface of the scale 1, and the light source and light receiving element pairs 23, 21 and 2
4 and 22 is set to (n+1/4)P of the slit pitch P (where n is an integer and is an appropriate number determined depending on the size of the light receiving element).

Therefore, in the above linear gauge,
the light source and light receiving element pairs 23 and 21 and 24 and 22, and the detection slit plate 2 facing them;
5 serves as a detector 2, each pair thereof serves as a receiving section, and the slit of scale 1 serves as a transmitting section.

Above this detector 1, there are components similar to those of the detector 1, namely, two pairs of light sources and light receiving elements 33, 31 and 3 arranged at (n+1/4)P distance from each other.
4 and 32, and a detector 3 consisting of a detection slit plate 35 fixed to the opposing surface of the light receiving elements 31 and 32 is disposed. Thus, the distance between the light receiving element 21 on the lower side of the detector 2 and the light receiving element 31 on the upper side of the detector 3 is approximately L.

In the above system, when the spindle 1 moves upward (or downward) from the state shown in FIG. The moire fringes formed by the slits of the slit plate 25 change periodically as the slit pitch moves, and the amount of light reaching the light receiving elements 21 and 22 from the light sources 23 and 24 changes periodically. The light receiving elements 21 and 22 generate a voltage output that changes periodically each time the scale 1 moves through its slit pitch. The waveforms of the voltage outputs generated in the light receiving elements 21 and 22 are sinusoidal, and as a result of the arrangement positions of the elements 21 and 22 being different, they have a phase difference of 90 degrees. When scale 1 moves upward and downward, the phase of one voltage output with respect to the other voltage output is 90
It will be reversed by a degree.

Next, when the scale 1 moves further upward with the movement of the spindle 1 and faces the light receiving element 31 below the detector 3, a periodic voltage output begins to be generated in the light receiving element 31 in the same manner as described above. Then, when the scale 1 moves further upward by 1/4 pitch, the scale 1 faces the upper light-receiving element 32, and a periodic voltage output starts to be generated.
Then, when scale 1 moves further upwards,
The lower end of the scale 1 is the light receiving element 2 below the detector 2.
1. As a result of passing through the arrangement position of the upper light receiving element 22, the voltage output of the light receiving elements 21 and 22 becomes constant.

As a result of the above, each of the detectors 2 and 3 detects the advance or delay of one of the periodic voltage outputs generated in the light receiving elements 21 and 22, 31 and 32 with respect to the other, thereby moving the spindle 4. The direction will be determined, and if the presence or absence of voltage output of the light receiving elements 21, 22, 31, and 32 of both detectors 2 and 3 is detected, the detector facing the scale 1 will be determined. become.

In addition, when detecting the phase shift between the light receiving elements 21 and 31 or 22 and 32 on the lower or upper side of the detectors 2 and 3, the shift distance within the slit pitch due to the initial placement position error of the detectors 2 and 3 can be calculated. It will be done.

Next, depending on the detection result of the presence or absence of the periodic output described above, the detectors connected to the counter are switched, and the counter In addition, when switching between detectors, it is necessary to correct the deviation distance caused by the error in the placement of both detectors.

The processing circuit will be explained below.

In FIG. 2, the periodic voltage output generated in each of the light receiving elements 21, 22, 23, 24 of the detectors 2, 3 is shaped into a rectangular wave by waveform shaping sections 6, 7, 8, 9. , the outputs of the waveform shaping sections 6 and 7 are:
The outputs of the waveform shaping sections 8 and 9 are introduced into the multiplication section 11 and the direction discrimination section 12, and the outputs of the waveform shaping sections 8 and 9 are introduced into the multiplication section 14 and the direction discrimination section, respectively. In the multipliers 11 and 13, the rising and falling edges of the input rectangular waves are differentiated and combined to form a pulse output multiplied by 4,
The output is sent to the switching unit 17 of the switching control unit, and the direction determining units 12 and 14 output signals to the waveform shaping units 7 and 8 based on the outputs of the waveform shaping units 6 and 8, respectively.
detects the phase of the output, and sends a discrimination output to the switching unit 17 only when the phase is delayed. On the other hand, the switching output generating section 16 of the switching control section shapes the outputs of the waveform shaping sections 6 and 9, that is, the periodic outputs of the lower light receiving element 21 of the detector 1 and the upper light receiving element 32 of the detector 2. output has been introduced. Both shaped outputs have a phase difference of 90 degrees, and therefore,
As shown in FIG. 3a, when the scale 1 moves from the detector 2 to the detector 3 and faces the detector 3, an output is generated at the light receiving element 21 and then 90
An output is generated at the light-receiving element 32 with a phase delay of 100 degrees, and conversely, as shown in b, when the scale 1 moves from the detector 3 to the detector 2 and faces the detector 2, the light-receiving element 32 90 after the output occurs on 32
An output is generated at the light-receiving element 21 with a phase delay of degrees. This switching output generation section 16 determines the generation timing of the outputs of both the light receiving elements 21 and 32 when both the light receiving elements 21 and 32 are in a state where outputs are generated. When the output of the light receiving element 32 is generated later, the switching output is sent to the switching unit 17, and in the opposite way, after the output of the light receiving element 32 is generated, the switching output is sent to the switching unit 17.
If an output occurs, the transmission of the switching output is stopped.

As a result, after the state shown in FIG. 3a, scale 1
The switching output continues to be generated while the scale 1 continues to move toward the detector 3, and after that, after the scale 1 moves toward the detector 2 and reaches the state shown in FIG. 3b, the switching output continues. Sending out the output is stopped, and thereafter, no switching output is sent out until the scale 1 moves toward the detector 3 again and enters the state shown in (a).

The switching section 17 is connected to this switching output generating section 16.
The conduction of the pulse outputs of the multipliers 11 and 13 is selectively switched in accordance with the switching output of and the discrimination outputs of the direction discrimination sections 12 and 14, and the details will be explained below with reference to FIG.

In the figure, the multiplied pulses from the multipliers 11 and 13 are introduced into the AND gates 71 and 72, respectively, and their conduction is controlled by the switching signal generator 1, respectively.
It is controlled by the inverted output and switching output of the switching output No. 6. Therefore, the AND gate 71 is conductive while the transmission of the switching output is stopped and transmits the multiplied pulse to the next AND gates 73 and 74, and the AND gate 72 is conductive while the switching output is being transmitted. Then, the multiplied pulse is sent to the next AND gates 75 and 76. That is, while the scale 1 moves from the position shown in FIG. 3a to face the detector 3, a pulse obtained by multiplying the periodic output of the detector 3 is sent out, and the scale 1 detects the signal from the position shown in FIG. 3b. While moving opposite the detector 2, a pulse that is a multiplication of the periodic output of the detector 2 is sent out.

Next, the conduction of the AND gates 73 and 74, and the conduction of the AND gates 75 and 76 are controlled by the discrimination outputs of the direction discrimination sections 12 and 14, respectively.
3 and 75 are conductive while the discrimination output is being sent out, and AND gates 74 and 76 are conductive while the discrimination output is being stopped, allowing the multiplied pulses introduced therethrough to pass through. In this case, as described above, the discrimination output is sent out while scale 1 is moving upward, so the AND gates 73 and 75 end up
The AND gates 74 and 76 are conductive while the scale 1 is moving upward, and the AND gates 74 and 76 are conductive while the scale 1 is moving downward. A multiplied pulse is sent out from AND gate 73 or 74, and if scale 1 faces detector 3, a multiplied pulse is sent out from AND gate 75 or 76 depending on the direction of movement. Below, during the upward movement of scale 1, AND gate 73 or 7
The multiplied pulse passing through the AND gate 74 or 76 is inputted to the addition terminal of the counting section 18 via the OR circuit 77, and the multiplied pulse passing through the AND gate 74 or 76 during the downward movement of the scale is counted via the OR circuit 78. The signals are input to the subtraction terminal of the unit 18, and are added or subtracted.

Next, 19 is a phase shift calculating section, which inputs each output of the waveform shaping sections 6 and 8, 7 and 9, measures the phase shift time and period of each output, and calculates the ratio thereof. an arithmetic circuit that calculates and stores the deviation distance when the detectors 2 and 3 are arranged;
It consists of a memory circuit. This shift distance is determined by pressing the lower end of the spindle 4 against a constant velocity cam in advance, moving the spindle 4 upward at a constant velocity, and then measuring the phase shift time at a position where the scale 1 faces both the detectors 2 and 3. This is calculated from the period, and this is due to the error in the installation distance between detectors 2 and 3 (light receiving element 2
The spacing between 1 and 31 and between 22 and 32 must be set to an integral multiple of the slit pitch, but it is inevitable that deviations will occur during setting, and when the pitch becomes minute, it is difficult to adjust it mechanically.)
corresponds to Below, this memorized deviation distance is
It is added to the counting section 18 while the switching output is being sent out, and is removed when the switching output is stopped being sent out.

In the above system, when the scale 1 is facing the detector 2 as shown in FIG. 1 and moves upward along with the upward movement of the spindle 4, the light receiving elements 21 and 22 periodically output occurs,
It is multiplied by 4 by the multiplier 11. At this time, since no periodic output is generated in the light receiving element 32 of the detector 3, no switching output is sent out from the switching output generator 16, and the AND gate 71 (FIG. 4)
becomes conductive and the multiplied pulse passes through the AND gate 73,
74, but as a result of the discrimination output being sent from the direction discrimination section 12, only the AND gate 73 becomes conductive, and the multiplied pulse that passes through it is sent to the OR circuit 77.
The signal is added to the addition terminal of the counting unit 18 via the pulse generator 18, and the multiplied pulses are added and counted. Therefore, each time the spindle 4 moves by 1/4 of the slit pitch of the scale 1, the count value of the counter 18 increases by one count. When the spindle 4 moves further upwards from this state, the scale 1 faces the detector 3, and a periodic output is generated in the love light element 32 above it, a switching output is sent out from the switching output generator 16. , the AND gate 72 becomes conductive,
AND gate 71 is shut off. As a result, a pulse obtained by multiplying the periodic output generated in the light-receiving elements 31 and 32 of the detector 3 by the multiplier 13 is applied to the AND gates 75 and 76, but since the discrimination output is sent from the direction discrimination section 14, and gate 75
only conducts, and the pulse that passes through it is applied to the addition terminal of the counting section 18 via the OR circuit 77,
The multiplied pulses are counted. Therefore,
Even if the moving distance of the spindle exceeds the entire length of the scale 1, the count value of the counting section 18 will continuously increase in accordance with the moving distance. Further, at the same time as this switching output is sent out, the shift distance stored in the phase shift calculating section 19 is also added to the counting section 18.

Next, when the spindle 4 starts to be moved downward from this state, the direction determining section 14 no longer sends out the determination output, the AND gate 75 is cut off, the AND gate 76 is conductive, and the AND gate 7
The multiplied pulse introduced from 2 is sent to the subtraction terminal of the counting section 18 via the OR circuit 78 to perform subtraction counting. Therefore, from now on, the count value of the counting unit 18 will decrease in accordance with the descending distance of the spindle.

Subsequently, when the spindle 4 is further moved downward, the scale 1 faces the detector 2, and a periodic output is generated in the light receiving element 21 below, the switching output generation section 16 stops sending out the switching output. stop,
AND gate 71 becomes conductive and AND gate 72 is cut off. As a result, a pulse obtained by multiplying the periodic output of the detector 2 by the multiplier 11 is applied to the AND gates 73 and 74, but since no discrimination output is sent from the direction discriminator 12 at this time, the AND gate 74 The pulse that has passed therethrough is applied to the subtraction terminal of the counting section 18 via the OR circuit 78, and is subtracted and counted. Therefore, even if the spindle 4 moves downward by a distance exceeding its entire length, the count value of the counting section 18 will continuously decrease in accordance with the moving distance. Also, at the same time as this switching output stops sending out,
The shift distance added to the counting section 18 from the phase shift calculating section 19 is subtracted.

As a result of the above, the moving distance of the spindle 4 is continuously converted into the count value of the counting unit 18 over a distance approximately twice the total length of the scale 1.

In addition, in the above-mentioned embodiment, an example was shown in which the movement distance is approximately twice the total length of the scale 1, but the number of detectors is further increased and arranged upward, and adjacent detectors are arranged in the same manner as above. The measurement range is expanded by switching.

Furthermore, although the above embodiment is a case in which the present invention is applied to a linear gauge, a detector consisting of two receivers is placed opposite to a scale in which the receivers are arranged, and the relative moving distance is measured. The moving distance measuring device can be implemented in the same manner as described above.

Further, in the above embodiment, the case where the outputs generated in the detectors 2 and 3 are multiplied by 4 is illustrated, but depending on the required measurement resolution and accuracy, the multiplier section may be omitted, or conversely, the output may be further multiplied. It's okay.

In addition, in the above embodiment, the calculation of the phase shift calculation section is performed using the ratio of the phase shift time between the periodic outputs and the period of the periodic outputs, but the light receiving elements 21, 22, 3
The same result can be obtained by simultaneously sampling and holding the voltage outputs generated at 1 and 32, calculating the phase shift θ from the voltages V ₂₁ , V ₂₂ , V ₃₁ , and V ₃₂ using the following formula to find the shift distance. be.

θ = tan ^-1 (V ₃₁ /V ₃₂ ) - tan ^-1 (V ₂₁ /V ₂₂ ) As described above, the present invention is applicable to short scales in which transmitting parts are arranged with high resolution and high precision. , a plurality of detectors are arranged in the longitudinal direction at intervals shorter than the entire length of the scale, and the periodic output of the counting detector is switched depending on the facing state of the adjacent detector and the scale, and when switching is performed, the output is switched. Since the phase shift distance between the front and rear detectors is corrected, it is possible to continuously measure with high accuracy and resolution up to a moving distance greater than the entire length of the scale.

[Brief explanation of drawings]

Fig. 1 is a perspective view of essential parts showing an example of implementing the present invention in a linear gauge, Fig. 2 is a block diagram showing an embodiment of the processing circuit of the present invention, and Fig. 3 shows the opposing view of a detector and a scale. A model diagram showing the relationship, FIG. 4 is a block diagram showing an embodiment of the switching section of FIG. 3. 1: Scale, 2, 3: Detector, 21, 22,
31, 32: Light receiving element, 23, 24, 33, 3
4: light source, 25, 35: detection slit plate, 11,
13: Multiplication section, 16: Switching output generation section, 17: Switching section, 18: Counting section, 19: Phase shift calculation section.

Claims (1)

[Claims] 1. A scale with transmitting parts arranged in minute pitches is placed opposite the detector, and each time the scale and the detector move a certain distance relative to each other, the periodic output generated in the detector is extracted, and the periodic output or the multiplication of the periodic output is obtained. In a moving distance measuring device in which the output multiplied through the scale is counted by the counting section, there are a plurality of said detectors, each of which is arranged in the longitudinal direction of the scale at an interval shorter than the entire length of the scale. The periodic outputs of the detectors arranged in the above are introduced into the switching control section and the phase shift calculation section to correspond to the switching output depending on the presence or absence of periodic outputs of both detectors and the phase shift between the periodic outputs of both detectors. selectively switches a detector or a multiplier connected to the counter according to the switching output, and adds the shift distance output between the detectors before and after the switching to the counter. A moving distance measuring device characterized by: