JP6879810B2 - Optical encoder - Google Patents

Description

The present invention relates to an optical encoder incorporated in a machine tool, a semiconductor manufacturing apparatus, or the like to detect the position of a movable member.

The present invention relates to an optical encoder having a position detection unit that outputs a detection signal that changes in a sinusoidal manner with respect to a relative displacement between the scale unit and the slider unit. In particular, the present invention relates to an absolute encoder including a plurality of position detection units such as a lower digit and an upper digit. 7 and 8 show a schematic structure of a conventional absolute encoder.

The absolute encoder includes a scale unit 10, a slider unit 15, and a calculation unit 30 that performs various calculations. The scale unit 10 has a long glass scale 11 in the moving direction of the movable member (hereinafter referred to as "horizontal direction"). The upper girder scale 21 and the lower girder scale 20 are formed on the glass scale 11 side by side in the vertical direction. The upper girder scale 21 and the lower girder scale 20 are both composed of a plurality of slits arranged in the horizontal direction, and the slit pitch of the upper girder scale 21 (slit arrangement pitch) is the slit pitch of the lower girder scale 20. Greater than. The slider unit 15 has a light emitting unit 18 and a light receiving unit 19 located on both sides of the glass scale 11 in the thickness direction. The light emitting unit 18 outputs parallel light. The light receiving unit 19 converts the light transmitted through the scales 20 and 21 into an electric signal (detection signal) after being irradiated from the light emitting unit 18. The calculation unit 30 calculates position data indicating the position of the slider unit 15 within the range of the scale length based on the detection signal output from the light receiving unit 19. The arithmetic unit 30 may be, for example, a microcomputer in which an arithmetic program is incorporated, or a device in which a general-purpose CPU and a memory are combined.

The glass scale 11 has a lower digit scale 20 having a small slit pitch and capable of detecting with extremely high resolution, and an upper digit scale 21 having a large slit pitch and a low resolution but a wider absolute position detection range. Is included. Then, by combining the position data obtained in relation to the scales of the lower digit and the upper digit, position detection having both high resolution and absolute position detection is possible. Further, as shown in FIG. 7, by assembling the glass scale 11 and the light receiving unit 19 attached to the slider unit 15 at a constant distance, an appropriate signal strength can be obtained.

The light receiving unit 19 is composed of a light receiving element 16 and an index glass 17. In the light receiving unit 19, the upper digit detection unit 23 corresponding to the upper digit scale 21 and the lower digit detection unit 22 corresponding to the lower digit scale 20 are arranged in the vertical direction, and a signal is output from each detection unit. To. The amplitude of the detection signal output from the lower girder detection unit 22 having a small slit pitch increases or decreases depending on the distance (gap) between the glass scale 11 and the light receiving unit 19, and is increased or decreased from the upper girder detection unit 23 having a large slit pitch. The output detection signal has a structure that is hardly affected by the distance between the glass scale 11 and the light receiving unit 19.

The parallel light output from the light emitting unit 18 passes through the glass scale 11 and the index glass 17, and is incident on a plurality of light receiving elements 16 attached to the back surface of the index glass 17. The light receiving element 16 that constitutes the detection unit of each of the upper and lower digits is divided into signals a1 that change in a sinusoidal manner with respect to displacement, and signals a2 and a1 that change in phase 180 degrees with respect to a1 and change in a sinusoidal manner. On the other hand, four signals, b1 which has a 90-degree phase difference and changes in a sinusoidal shape, and b2, which has a 180-degree phase difference from b1 and changes in a sinusoidal shape, are output. That is, the detection signals of the detection units 22 and 23 include four signals, signal a1, signal a2, signal b1, and signal b2. In the following, the signals a1, a2, b1 and b2 output from the high-order light receiving element 16 are referred to as Ha1, Ha2, Hb1 and Hb2, respectively, with an H at the beginning. Further, the signals a1, a2, b1, and b2 output from the lower digit light receiving element 16 are referred to as Ma1, Ma2, Mb1, and Mb2, respectively, with an M at the beginning.

The calculation unit 30 uses two signals MA (= Ma1-Ma2) that change in a sinusoidal shape and are 90 degrees out of phase with each other from the four signals Ma1, Ma2, Mb1, and Mb2 output by the light receiving element 16 of the lower digit detection unit 22. ) And MB (= Mb1-Mb2) are calculated. Further, the calculation unit 30 calculates the amplitude MAMP = (MA ² + MB ² ) ^0.5 of the detection signal from the signals MA and MB. Since this amplitude MAMP increases or decreases depending on the distance (gap) between the glass scale 11 and the light receiving unit 19, it is possible to detect the gap Gap from the amplitude MAMP.

Further, the calculation unit 30 receives two signals HA (= Ha1-Ha2) that change in a sinusoidal shape and have a 90-degree phase difference from the four signals Ha1, Ha2, Hb1, Hb2 output by the light receiving element 16 of the upper digit detection unit 23. ) And HB (= Hb1-Hb2) are calculated. Further, the calculation unit 30 calculates the amplitude HAMP = (HA ² + HB ² ) ^0.5 of the detection signal from the signals HA and HB. Since the amplitude HAMP of the upper digit detection unit 23 is hardly affected by the distance (gap) between the glass scale 11 and the light receiving unit 19, the temperature change of the light emitting unit 18 or the like becomes the change of the amplitude HAMP as it is.

Utilizing this characteristic, the calculation unit 30 calculates HRATE = HAMPINI / HAMP, which is the ratio of the initial amplitude value HAMPINI of the high-order digit detection unit 23 to the signal amplitude HAMP, and as shown in Equation 1, the high-order digit The amplitude change ratio HRATE is multiplied by the signal amplitude MAMP of the lower digit detection unit 22, and the amplitude MAMP1 of the gap-dependent signal is calculated. This amplitude MAMP1 becomes a gap-dependent signal in which the influence of temperature is added (error caused by temperature is corrected). Instead of the above calculation method, as disclosed in Patent Document 1, the gap may be calculated by the ratio of the sum and the difference using the four-phase signal.

MAMP1 = MAMP x HRATE (1)

By using the above-mentioned technique, it is possible to provide an absolute encoder that does not cause a position detection error such as lost motion and eliminates cost-increasing factors.

Japanese Unexamined Patent Publication No. 2016-50886 Japanese Unexamined Patent Publication No. 2013-113634

In the conventional technique, the influence when the light receiving unit 19 is mounted at an angle relative to the glass scale 11 is not taken into consideration, and since the absolute amount of the gap cannot be detected, the defective mounting position can be accurately detected. Could not be detected. Further, in the conventional technique, the signal is corrected in consideration of the influence of temperature, but the error due to the inclination is not taken into consideration, and the gap cannot be detected with sufficient accuracy. Here, the inclination means that the light receiving unit 19 rotates around an axis perpendicular to the 11th surface of the glass scale, as shown in FIG.

Therefore, if the scale unit 10 and the slider unit 15 are incorrectly attached, the scale unit 10 and the slider unit 15 interfere with each other, and in the worst case, the scale unit 10 and the slider unit 15 are damaged and become unusable. Will end up. Further, as disclosed in Patent Document 1, there is also a method of calculating the gap by the ratio of the signal amplitude calculated by the calculation of the sum and the difference using the four-phase signal, but the amount of change in the signal amplitude due to the temperature is The signal amplitude calculated by the sum and the signal amplitude calculated by the difference are different. Therefore, this method has a problem that not only the temperature cannot be corrected but also the detection error increases due to the change in the ambient temperature.

The optical encoder disclosed in the present specification is a glass scale elongated in the horizontal direction, and includes a glass scale in which a plurality of scales composed of a plurality of slits arranged in the horizontal direction are arranged in the vertical direction. The position detection unit, which is a light receiving unit facing the glass scale through a predetermined gap and outputs a detection signal that changes according to the relative displacement of the scale unit and the slider unit in the lateral direction, has a corresponding scale. A plurality of light receiving units arranged in the vertical direction and a calculation unit for calculating position data indicating the position of the light receiving unit based on the detection signal are provided so as to face each other, and the light receiving unit is at least first detected. The calculation unit includes a first position detection unit that outputs a signal and a second position detection unit that outputs a second detection signal, and the calculation unit is based on a detection signal output from at least one position detection unit. The second position detection unit has a parallel quadrilateral light receiving element, and the calculation unit has an amplitude of the second detection signal. It is characterized in that the inclination is acquired based on the above.

In this case, Inc the current value of the slope, HAMP the amplitude of the current of the second detection signal, HAMPINI the amplitude of the second detection signal in the reference state defined, ICOF a predetermined coefficient, when the JCOF , The calculation unit may calculate the slope based on the formula of Inc = ICOF × (HAMP-HAMPINI) + JCOF.

Further, the slit pitch of the scale corresponding to the first position detection unit is smaller than the slit pitch of the scale corresponding to the second position detection unit, and the calculation unit determines the amplitude of the first detection signal. The gap may be acquired based on the corrected first amplitude corrected according to the temperature and the slope. In this case, the gap Gap,, the corrected first amplitudes MAMP2, amplitude MA M PINI of the first detection signal in a predetermined reference state, GCOF a predetermined coefficient, when the HCOF, the arithmetic unit, The gap may be calculated based on the formula Gap = GCOF × (MAMP2-MAMPINI) + HCOF.

Further, the calculation unit obtains a value obtained by multiplying the amplitude of the first detection signal by a temperature correction coefficient for correcting the change in amplitude due to the temperature change, and adding the error in the amplitude due to the inclination to the value. It may be calculated as the corrected first amplitude. In this case, the amplitude of the first detection signal is MAMP, the corrected first amplitude is MAMP2, the temperature correction coefficient is HRATE1, the slope is Inc, and the amplitude of the first detection signal when the slope is zero is MAMPmax. When the coefficients of are CCOF, DCOF, and ECOF, the calculation unit calculates the ^{corrected first amplitude based on the formula of MAMP2 = MAMP × HRATE1 + {MAMPmax- (CCOF × Inc 2} + DCOF × Inc + ECOF)}. May be good.

Further, the second position detection unit has a light receiving element having a substantially parallel quadrilateral shape, the temperature correction coefficient is HRATE1, the amplitude of the second detection signal is HAMP, and the second detection signal in a predetermined reference state. When the amplitude of is HAMPINI, the slope is Inc, and the predetermined coefficient is FCOF, the calculation unit may calculate based on the formula of HRATE1 = HAMPINI / (HAMP + FCOF × Inc).

According to the optical encoder disclosed in the present specification, since the tilt is acquired, it is possible to accurately detect whether or not the tilt is excessive. Further, by correcting the amplitude of the detection signal according to the inclination, the gap can be acquired more accurately. As a result, interference due to incorrect mounting of the scale unit and slider unit can be eliminated, and after the mounting adjustment is completed, a large margin to the alarm level that occurs when the signal drops or rises can be taken, so maintenance and maintenance can be performed. The labor can be reduced. In addition, since it can be realized by embedded software without adding a structure and a function for maintaining a distance between the scale unit and the slider unit, there is no new cost increase.

It is an external view of an optical encoder. It is a figure which shows the relationship between the inclination of a light receiving unit, and the position data difference. It is a figure which shows an example of the change of the position data difference with respect to the inclination. It is a figure which shows an example of the change of the amplitude of the detection signal of the lower digit detection part with respect to the inclination. It is a figure which shows an example of the change of the amplitude of the detection signal of the upper digit detection part with respect to the inclination. It is a figure which shows an example of the change of the lower digit amplitude after correction with respect to a gap. It is a figure which shows the structure of the conventional optical encoder. It is a figure which shows the structure of the glass scale, the light emitting unit, and the light receiving unit in the conventional optical encoder.

Hereinafter, the configuration of the optical encoder will be described. The same parts as those in the prior art will be described below by omitting or simplifying the description. FIG. 1 is an external view of an optical encoder. In FIG. 1, the slider unit 15 moves in the left-right direction on the paper surface. Further, in FIG. 1, both the light receiving unit 19 and the glass scale 11 are shown by broken lines because they are covered with the cover of the scale unit 10 and cannot be seen. Further, FIG. 2 is a diagram showing the relationship between the inclination of the light receiving unit 19 and the position data difference. Although the light receiving unit 19 is shown by shifting it in the vertical direction in FIG. 2, the light receiving unit 19 and the glass scale 11 actually face each other as is clear from FIGS. 1 and 8.

FIG. 2 shows an example of a light receiving unit 19 including two detection units, a lower digit detection unit 22 (first position detection unit) and an upper digit detection unit 23 (second position detection unit). The upper digit detection unit 23 and the lower digit detection unit 22 are arranged in the vertical direction, and the corresponding upper digit scale 21 and the lower digit scale 20 are also arranged in the vertical direction. The upper girder detection unit 23 has a configuration in which parallelogram light receiving elements 16 for each of the four phase signals are arranged in a laterally distributed manner, while the lower girder detection unit 22 receives light of each of the four phase signals. It has a configuration in which the elements 16 are arranged in a laterally dispersed manner. The calculation unit 30 in the slider unit 15 calculates the position data MPOS and HPOS of the light receiving unit 19 based on the detection signals output from the detection units 22 and 23. As the method for calculating the position data MPOS and HPOS, for example, the prior art disclosed in Patent Document 1 and the like can be used, and thus detailed description thereof is omitted here.

Here, as shown in FIG. 2, in the case of a configuration in which two types of detection units are arranged in the vertical direction, the positions calculated based on the detection signals of the detection units 22 and 23 according to the inclination of the light receiving unit 19. There is a difference in data MPOS and HPOS. This will be described with reference to FIG. In an optical encoder having two scales 20 and 21 having different slit pitches, as shown on the left side of FIG. 2, when the postures of the glass scale 11 and the light receiving unit 19 are the same (the long side of the light receiving unit 19 is (When parallel to the long side of the glass scale 11), the detection signal of the upper digit detection unit 23 and the detection signal of the lower digit detection unit 22 are signals with reference to the same position a. On the other hand, as shown on the right side of FIG. 2, when the light receiving unit 19 is tilted around an axis perpendicular to the glass scale 11 (when the light receiving unit 19 is tilted in the direction of the white arrow with respect to the glass scale 11), the upper girder. The detection signal of the detection unit 23 is based on the position a, whereas the detection signal of the lower digit detection unit 22 is based on the position b. In this way, the reference positions of the detection signals of the upper girder detection unit 23 and the lower girder detection unit 22 are relatively displaced depending on the degree of relative inclination of the glass scale 11 and the light receiving unit 19.

As a result, the difference Diff (= HPOS-MPOS) of the position data relative to the position data HPOS calculated from the detection signal of the upper digit detection unit 23 and the position data MPOS calculated from the detection signal of the lower digit detection unit 22 becomes. appear. Since this relative position data difference Diff increases or decreases according to the inclination, it is possible to detect the relative inclination Inc between the glass scale 11 and the light receiving unit 19.

Specifically, a method of calculating the inclination will be described. FIG. 3 is a diagram showing the relationship between the inclination Inc of the light receiving unit 19 having the above-mentioned structure and the position data difference Diff. The slope Inc shows a monotonous decrease with respect to the position data difference Diff between the lower digit detection unit 22 and the upper digit detection unit 23. Therefore, the slope Inc can be approximated by a linear function as shown in the following equation 1.
Inc = ACOF × (Diff-DiffINI) + BCOF (1)

ACOF and BCOF are coefficients that change depending on the structure of the detection unit composed of the light receiving element 16 and the index glass 17. Further, DiffINI is a position data difference in a reference state set in consideration of an attachment error between the slider unit 15 and the light receiving unit 19. In the above equation, by setting Diff-DiffINI as a variable, it is possible to detect the current slope Inc as an absolute quantity, assuming that the initial setting is horizontal (slope is 0 degrees) or the slope is the variable BCOF degree. It is possible. When the slope IncINI in the reference state is 0 degrees (horizontal), the coefficient BCOF = 0. Further, the above equation 1 is an example, and another method may be used if the slope Inc is obtained based on the position data difference Diff. For example, a map recording the correspondence between the position data difference Diff or (Diff-DiffINI) and the inclination Inc is stored, and the obtained position data difference Diff or (Diff-DiffINI) is compared with the map. The current slope Inc may be acquired.

Next, a method of correcting the error of the amplitude MAMP of the detection signal of the lower digit detection unit 22 will be described. The amplitude MAMP includes the amount of change due to the temperature change and the amplitude error due to the slope Inc. Therefore, when correcting the amplitude MAMP, the amplitude error ErrMAMP due to the slope Inc can be added to the value corrected by multiplying the amplitude MAMP by the temperature correction coefficient HRATE1 for correcting the amplitude change due to the temperature change. Good. That is, the corrected lower digit amplitude MAMP2 is MAMP2 = MAMP × HRATE1 + ErrMAMP.

Here, the amplitude error ErrMAMP due to the slope Inc will be examined. FIG. 4 is a graph showing a change in the amplitude MAMP of the detection signal of the lower digit detection unit 22 with respect to the slope Inc. As is clear from FIG. 4, the amplitude MAMP of the detection signal of the lower digit detection unit 22 has a characteristic that changes in the shape of a quadratic curve with respect to the relative inclination Inc between the glass scale 11 and the light receiving unit 19. Have. By correcting this, it is possible to reduce the gap detection error with respect to the relative inclination Inc between the glass scale 11 and the light receiving unit 19.

Specifically, the amplitude MAMP of the lower digit detection unit 22 shown in FIG. 4 can be approximated by a quadratic curve as shown in Equation 2. Note that CCOF, DCOF, and ECOF are coefficients that change depending on the mounting state of the light receiving unit 19 and the slider unit 15.
MAMP = CCOF x Inc ² + DCOF x Inc + ECOF (2)

Here, if the amplitude MAMP when the light receiving unit 19 is not tilted with respect to the glass scale 11, that is, when the amplitude MAMP is arranged at Inc = 0 is set to the maximum amplitude MAMPmax, the amplitude error ErrMAMP is changed from the maximum amplitude MAMPmax to the amplitude MAMP. Is subtracted from. That is, the amplitude error ErrMAMP is expressed by Equation 3.
ErrMAMP
= MAMPmax- (CCOF x Inc ² + DCOF x Inc + ECOF) (3)

Therefore, the corrected lower digit amplitude MAMP2 can be calculated by Equation 4.
MAMP2 = MAMP x HRATE1 + ErrMAMP
= MAMP x HRATE1 + {MAMPmax- (CCOF x Inc ² + DCOF x Inc + ECOF)} (4)

Next, the calculation of the temperature correction coefficient HRATE1 will be described. The temperature correction coefficient HRATE1 can be expressed as the ratio of the amplitude HAMPINI in the reference state to the amplitude HAMP of the detection signal of the current upper digit detection unit 23. The amplitude HAMPINI is an amplitude HAMP obtained at an appropriate gap position, an appropriate attitude, and a specified temperature.

Here, the current amplitude HAMP includes an error due to the slope Inc. Therefore, for the calculation of the temperature correction coefficient HRATE1, the corrected upper digit amplitude HAMP1 in which the amplitude HAMP is corrected by the error caused by the slope Inc is used.

FIG. 5 is a graph showing a change in the amplitude HAMP of the detection signal of the upper digit detection unit 23 with respect to the slope Inc. Since the light receiving element 16 of the upper girder detection unit 23 is a parallelogram, the amplitude HAMP shows a monotonically decreasing amplitude change with respect to the slope Inc, as shown in FIG. Therefore, the corrected upper digit amplitude HAMP1 can be calculated by the following formula 5, and the temperature correction coefficient HRATE1 can be calculated by the following formula 6. The FCOF is a coefficient that changes depending on the shape of the light receiving element 16 of the upper girder detection unit 23.
HAMP1 = HAMP + FCOF x Inc (5)
HRATE1 = HAMPINI / HAMP1 (6)

Next, a method of calculating the gap from the corrected lower digit amplitude MAMP2 in which the error due to the slope and the temperature is corrected will be described. The corrected lower digit amplitude MAMP2 calculated from the above equation 4 increases or decreases depending on the gap between the glass scale 11 and the light receiving unit 19. FIG. 6 is a diagram showing a change in amplitude MAMP2 with respect to a gap. As shown in FIG. 6, since the corrected lower digit amplitude MAMP2 exhibits monotonous increase with respect to the gap, it can be approximated by a linear function. Equation 7 is an example of an equation for calculating the gap gap. Note that GCOF and HCOF are coefficients determined by the structure of the slit of the glass scale 11 and the light receiving unit 19, and MAMPINI is the signal amplitude in the reference state where the gap is an appropriate value.
Gap = GCOF × (MAMP2-MAMPINI) + HCOF (7)

This makes it possible to detect the current gap Gap as an absolute quantity. The HCOF indicates a gap in the reference state, that is, an appropriate gap.

Next, the flow of calculating the gap gap by the calculation unit 30 will be described. The calculation unit 30 stores in advance the initial amplitudes HAMPINI and MAMPINI, the reference position data difference DiffINI, and various coefficients ACOF to HCOF. If it becomes necessary to calculate the gap gap, the calculation unit 30 calculates the position data HPOS and MPOS based on the detection signals output from the two detection units 22 and 23. In addition, the amplitudes HAMP and MAMP of each detection signal are calculated. ^{Incidentally, HAMP = {(Ha1-Ha2} ) 2 + (Hb1-Hb2) 2} is ^{0.5, MAMP = {(Ma1-} Ma2) 2 + (Mb1-Mb2) 2} ^0.5.

If the position data HPOS and MPOS can be calculated, the calculation unit 30 calculates the current slope Inc according to Equation 1. If the slope Inc is obtained, the calculation unit 30 subsequently substitutes the slope Inc obtained in Equation 5 to calculate the amplitude HAMP1 after tilt correction, and further, based on Equation 6, the temperature correction coefficient HRATE1 Is calculated.

If the temperature correction coefficient HRATE1 can be calculated, the calculation unit 30 substitutes the obtained temperature correction coefficient HRATE1, the slope Inc, and the amplitude MAMP into the equation 4 to calculate the corrected lower digit amplitude MAMP2. If the corrected lower digit amplitude MAMP2 is obtained, the calculation unit 30 substitutes the amplitude MAMP2 into the equation 7 to calculate the gap Gap. The calculation unit 30 may determine the appropriateness of mounting the light receiving unit 19, and thus the slider unit 15, based on the obtained gap Gap and inclination Inc.

As is clear from the above description, according to the optical encoder disclosed in the present specification, it is possible to produce and inspect the optical encoder and reproduce the mounting in a state where the accuracy is guaranteed, and the deviation from the proper mounting position. It is possible to grasp the amount (tilt, gap). As a result, the scale unit 10 and the slider unit 15 can be attached without interfering with each other.

Here, the coefficients ACOF, BCOF, FCOF, GCOF, and HCOF used in each equation are coefficients that are determined once the structures of the scale unit 10 and the light receiving unit 19 are determined, and are measured in advance and used as initial values in the internal storage device. It is held in (calculation unit 30). Further, since the coefficients CCOF, DCOF, and ECOF are also the coefficients determined by attaching the slider unit 15 and the light receiving unit 19, they can be measured in advance in the same manner, or can be calculated in real time by the sequential least squares method or the like. Good.

In the above description, it is assumed that the intensity of the light from the light emitting unit 18 is not uneven and there is no variation in the characteristics of the plurality of light receiving elements. Since the signals b1 and b2 include errors such as amplitude, offset, and phase difference, the detection accuracy is further improved by using a signal corrected for the errors.

Further, in the above description, in order to avoid cost increase, a signal that is hardly affected by the gap between the glass scale 11 and the light receiving unit 19 is used without adding any parts, but the temperature is used by using the temperature sensor. The temperature may be compensated by measuring the change in the amount of light due to the above in advance and preparing a table or the like in the internal storage device. Therefore, in this case, the temperature correction coefficient HRATE1 may be specified, for example, by comparing the detection value of the temperature sensor with the table without using Equation 6.

Further, the above-mentioned calculation method is an example, and at least the other configurations may be changed as appropriate as long as the inclination Inc of the light receiving unit 19 with respect to the glass scale 11 is calculated. For example, in the above description, the slope Inc is used as the variable in the formulas 4 and 5, but a variable (Diff-DiffINI) may be used instead of the slope Inc. Moreover, each of the various formulas described above is an example, and may be changed as appropriate. Further, in the above description, various parameters are calculated using mathematical formulas, but various parameters may be acquired by comparing with a map or table stored in advance without using mathematical formulas.

Further, in the description so far, the slope Inc is acquired based on the position data difference Diff, but the slope Inc may be acquired based on the amplitude HAMP of the detection signal of the upper digit detection unit 23. Specifically, when a light receiving unit 19 having a light receiving element having a parallelogram is used as in the correction of the temperature correction coefficient, it is also possible to obtain the slope Inc from the amount of increase / decrease in the signal amplitude by the following equation 8. Is. ICOF and JCOF are coefficients that change depending on the arrangement and structure of the detection unit composed of the light receiving element 16 and the index glass 17.
Inc = ICOF × (HAMP-HAMPINI) + JCOF (8)

Further, in the description so far, an optical encoder having two scales and two detection units has been illustrated, but the number of scales and detection units may be more than two as long as they are two or more, respectively.

From the calculated gap gap, it is determined whether or not the preset upper and lower limits of the allowable mounting gap are exceeded by this technology, and if it is exceeded, the GER, which is a warning signal of the gap, is output to a higher-level device such as a control device. .. In addition, from the calculated tilt Inc, it is determined whether or not the preset allowable mounting tilt upper limit and lower limit are exceeded, and if it is exceeded, the tilt warning signal IER is output to a higher-level device such as a control device. In addition to displaying gaps and tilts, it is possible to alert workers and prevent interference.

10 scale unit, 11 glass scale, 15 slider unit, 16 light receiving element, 17 index glass, 18 light emitting unit, 19 light receiving unit, 20 low digit scale, 21 high digit scale, 22 low digit detector, 23 high digit detector, 30 Arithmetic unit.

Claims (7)

A glass scale that is long in the horizontal direction and has a plurality of scales composed of a plurality of slits arranged in the horizontal direction arranged in the vertical direction.
The position detection unit, which is a light receiving unit facing the glass scale via a predetermined gap and outputs a detection signal that changes according to the relative lateral displacement of the glass scale and the slider unit, has a corresponding scale. With the light receiving units arranged in the vertical direction so as to face each other,
A calculation unit that calculates position data indicating the position of the light receiving unit based on the detection signal, and
With
The light receiving unit includes at least a first position detection unit that outputs a first detection signal and a second position detection unit that outputs a second detection signal.
The calculation unit acquires an axial inclination of the light receiving unit perpendicular to the glass scale surface based on the detection signals output from at least one position detection unit.
The second position detection unit has a parallelogram light receiving element, and has a parallelogram light receiving element.
The calculation unit acquires the slope based on the amplitude of the second detection signal.
An optical encoder characterized by this. The optical encoder according to claim 1.
When the current value of the slope is Inc, the current amplitude of the second detection signal is HAMP, the amplitude of the second detection signal in the specified reference state is HAMPINI, and the predetermined coefficients are ICOF and JCOF.
The calculation unit calculates the slope based on the formula Inc = ICOF × (HAMP-HAMPINI) + JCOF.
An optical encoder characterized by this. The optical encoder according to claim 1 or 2.
The slit pitch of the scale corresponding to the first position detection unit is smaller than the slit pitch of the scale corresponding to the second position detection unit.
The calculation unit acquires the gap based on the corrected first amplitude obtained by correcting the amplitude of the first detection signal according to the temperature and the inclination.
An optical encoder characterized by this. The optical encoder according to claim 3.
The gap Gap,, the corrected first amplitudes MAMP2, amplitude MA M PINI of the first detection signal in a predetermined reference state, GCOF a predetermined coefficient, when the HCOF,
The calculation unit calculates the gap based on the formula of Gap = GCOF × (MAMP2-MAMPINI) + HCOF.
An optical encoder characterized by this. The optical encoder according to claim 3 or 4.
The calculation unit corrects the value obtained by multiplying the amplitude of the first detection signal by the temperature correction coefficient for correcting the change in amplitude due to the temperature change and adding the error in the amplitude due to the inclination to the value. An optical encoder characterized in that it is calculated as the rear first amplitude. The optical encoder according to claim 5.
The amplitude of the first detection signal is MAMP, the corrected first amplitude is MAMP2, the temperature correction coefficient is HRATE1, the slope is Inc, the amplitude of the first detection signal at zero slope is MAMPmax, and a predetermined coefficient is used. When CCOF, DCOF, ECOF are used,
The calculation unit calculates the corrected first amplitude based on the formula of MAMP2 = MAMP × HRATE1 + {MAMPmax− (CCOF × Inc ² + DCOF × Inc + ECOF)}.
An optical encoder characterized by this. The optical encoder according to claim 5 or 6.
The second position detection unit has a light receiving element having a substantially parallel quadrilateral shape.
When the temperature correction coefficient is HRATE1, the amplitude of the second detection signal is HAMP, the amplitude of the second detection signal in a predetermined reference state is HAMPINI, the slope is Inc, and the predetermined coefficient is FCOF.
The calculation unit calculates based on the formula of HRATE1 = HAMPINI / (HAMP + FCOF × Inc).
An optical encoder characterized by this.

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