JP2013083673A - Detection unit and encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detection unit for detecting the rotation amount of a motor shaft in which credibility as an encoder is improved easily.SOLUTION: A detection unit includes a light-receiving element array where plural light receiving elements for outputting output signals corresponding to the quantity of incident light are arranged in a predetermined direction, and a light source for applying light to at least part of a code plate. The plural light receiving elements are respectively provided so that the width of an effective domain in a width direction vertical to the predetermined direction is changed according to the light quantity distribution.

Description

  The present invention relates to a detection unit, an encoder, and an output signal correction method suitable for application when detecting the rotation amount of a motor shaft.

  2. Description of the Related Art Conventionally, an encoder for detecting the rotation amount of a motor shaft includes a rotary code plate on which an incremental pattern and an absolute pattern are formed, and a detection unit provided so as to face the rotary code plate. FIG. 5 is a plan view showing this type of detection unit. In this detection unit 2, as shown in FIG. 5, a point light source 22 and two light receiving element arrays 23 and 24 are provided on a silicon substrate 21. Here, one light receiving element array 23 is composed of, for example, twelve light receiving elements 25 formed in the same size, and the other light receiving element array 24 is formed, for example, six light receiving elements formed in the same size. 26. Further, a signal processing circuit 7 is connected to these light receiving elements 25 and 26.

  When the rotation amount of the motor shaft is detected by this encoder, the light emitted from the point light source 22 is reflected by the incremental pattern and the absolute pattern of the rotary code plate and enters the light receiving element arrays 23 and 24, respectively. By the conversion, output signals S1 and S2 proportional to the amount of incident light are output from the light receiving elements 25 and 26, respectively. Then, these output signals S1 and S2 are signal-processed by the signal processing circuit 7, and the rotation amount of the motor shaft is calculated (see, for example, Patent Document 1).

Japanese Patent Laying-Open No. 2005-121593 (paragraphs [0009] and [0010], FIGS. 2 and 3)

  However, the light emitted from the point light source 22 is divergent light, and the distance of the optical path from the point light source 22 through the incremental pattern to the light receiving elements 25 and 26 differs depending on the light receiving elements 25 and 26. Incident light has uneven illuminance (light quantity per unit area of the light receiving elements 25 and 26). Here, since the light receiving elements 25 and 26 are formed in the same size, a difference occurs in the amount of incident light. Then, since the output values of the output signals from the light receiving elements 25 and 26 are different for each of the light receiving elements 25 and 26, if the amount of light emitted from the point light source 22 fluctuates for some reason, the function of the encoder (the rotation angle) There is a risk that the accuracy of the encoder will be hindered and the reliability of the encoder will be reduced. Therefore, in order to avoid such a situation, it is troublesome to add to the signal processing circuit 7 a process for adjusting the difference between the output values of the output signals from the light receiving elements 25 and 26.

  In view of such circumstances, it is an object of the present invention to provide a detection unit, an encoder, and an output signal correction method capable of easily increasing the reliability as an encoder.

  The present invention pays attention to the fact that the output signal from the light receiving element depends not only on the amount of incident light but also on the output characteristics of the light receiving element itself (effective area of the light receiving surface, element sensitivity, etc.). The above-described object is achieved by appropriately changing the characteristics according to the amount of incident light.

  That is, the first detection unit (2) according to the present invention is provided with a plurality of light receiving elements (25, 26) for outputting output signals (S1, S2) corresponding to the amount of incident light to the signal processing circuit (7). A plurality of light receiving elements having different amounts of incident light incident on the plurality of light receiving elements, wherein the plurality of light receiving elements have an output value of an output signal from a light receiving element having a low amount of incident light and The detection unit is characterized in that the output characteristics are set so that the output value of the output signal from the light receiving element having a high amount of light is substantially equal.

  An encoder (1) according to the present invention is an encoder including the detection unit (2).

  The output signal correction method according to the present invention includes a detection unit (2) provided with a plurality of light receiving elements (25, 26) for outputting output signals (S1, S2) corresponding to the amount of incident light to the signal processing circuit (7). Output signal correction method applied to the light receiving element, and when there is a difference in the amount of incident light incident on the light receiving element, the output value of the output signal from the light receiving element with a low amount of incident light and the amount of incident light The output signal correction method is characterized in that the output value of the output signal from the light receiving element having a high value is substantially equal.

  Here, in order to explain the present invention in an easy-to-understand manner, the description has been made in association with the reference numerals of the drawings representing the embodiments. However, it goes without saying that the present invention is not limited to the embodiments.

  According to the present invention, when there is a difference in the amount of incident light to each light receiving element, the output value of the output signal is corrected on the light receiving element side and the uniformity of the output signal is improved. Therefore, it is not necessary to perform troublesome processing, and the reliability as an encoder can be easily improved.

It is sectional drawing which shows the reflection type absolute encoder which concerns on Embodiment 1 of this invention. FIG. 3 is a plan view of the rotary code plate according to the first embodiment. FIG. 3 is a plan view of the detection unit according to the first embodiment. It is a top view which shows the detection unit which concerns on Embodiment 2 of this invention. It is a top view which shows the conventional detection unit.

Embodiments of the present invention will be described below.
Embodiment 1 of the Invention
1 to 3 are diagrams according to Embodiment 1 of the present invention.
First, the configuration will be described.

  As shown in FIG. 1, the reflective absolute encoder 1 has a rotary code plate 3 that is attached to the tip of the motor shaft 6 so as to rotate synchronously with the motor shaft 6. As shown in FIG. 2, the rotary code plate 3 has a disc-shaped rotary substrate 4, and a boss portion 4 a that is fitted to the tip end portion of the motor shaft 6 at the center of the rotary substrate 4. Is formed. A circumferential incremental pattern 8 is formed on the upper surface of the rotating substrate 4 so that the center thereof coincides with the axial center CT1 of the motor shaft 6. The incremental pattern 8 is not connected to the reflection pattern region 8a. The reflection pattern areas (areas not subjected to patterning) 8b are alternately arranged. Further, a circumferential absolute pattern 9 is formed on the upper surface of the rotating substrate 4 concentrically with the incremental pattern 8 so that the center thereof coincides with the axis CT1 of the motor shaft 6 inside the incremental pattern 8. The absolute pattern 9 is a pattern in which a reflective pattern region 9a and a non-reflective pattern region (region not subjected to patterning) 9b are arranged by, for example, an Nth order M-sequence pattern.

  Further, as shown in FIG. 1, a printed wiring board 5 is disposed above the rotation code plate 3, and a detection unit is provided on the lower surface of the printed wiring board 5 (that is, the surface on the rotation code plate 3 side). 2 is attached at a position facing the incremental pattern 8 and the absolute pattern 9.

  And this detection unit 2 has the silicon substrate 21 of a rectangular plate shape as shown in FIG. On the silicon substrate 21, a point light source 22 such as an LED (light emitting diode) is provided as a light emitting element at the center thereof, and two light receiving element arrays 23 and 24 face each other with the point light source 22 interposed therebetween. Arranged in a shape.

  Here, one light receiving element array 23 is for detecting the incremental pattern 8, and as shown in FIG. 3, twelve photodiodes formed in a rectangular shape having the same size (shape and size). The light receiving elements 25 such as phototransistors are arranged in an arc shape corresponding to the incremental pattern 8 and are adjacent to each other to form the light receiving element array 23. In FIG. 3, these light receiving elements 25 are shown in a straight line for convenience.

  Then, as shown in FIG. 3, these light receiving elements 25 correspond to the light quantity distribution of incident light by light shielding films 27 of various sizes (specifically, from the point light source 22 through the incremental pattern 8). The effective area changes (in proportion to the square of the distance of the optical path to the light receiving element 25). That is, of the twelve light receiving elements 25, the two light receiving elements 25 located at both ends (the light receiving element 25 farthest from the point light source 22) are not provided with the light shielding film 27. The entire surface is an effective region and the effective area matches the area of the light receiving surface, and part of the light receiving surface (both left and right ends) is masked (covered) by the light shielding film 27 for the remaining 10 light receiving elements 25. ), The effective area is reduced in such a manner that the circumferential width of the effective region is reduced. In addition, the effective area of the light receiving element 25 varies in proportion to the square of the distance of the optical path from the point light source 22 to the light receiving element 25 through the incremental pattern 8 with respect to the size (circumferential width) of these light shielding films 27. As shown, the light receiving element 25 closer to the point light source 22 is larger.

  The other light receiving element array 24 is for detecting the absolute pattern 9, and as shown in FIG. 3, six photodiodes formed in a rectangular shape having the same size (shape and size), The light receiving elements 26 such as phototransistors are arranged in an arc shape corresponding to the absolute pattern 9 and are adjacent to each other to form the light receiving element array 24. In FIG. 3, these light receiving elements 26 are shown in a straight line for convenience.

  Then, as shown in FIG. 3, these light receiving elements 26 correspond to the light quantity distribution of incident light by light shielding films 28 of various sizes (specifically, from the point light source 22 through the absolute pattern 9). The effective area changes (in proportion to the square of the distance of the optical path to the light receiving element 26). That is, of the six light receiving elements 26, the two light receiving elements 26 (the light receiving elements 26 farthest from the point light source 22) located at both ends are not provided with the light shielding film 28. The entire surface is an effective region, and the effective area is equal to the area of the light receiving surface. For the remaining four light receiving elements 26, part of the light receiving surface (both left and right ends) is masked (covered) by the light shielding film 28. ), The effective area is reduced in such a manner that the circumferential width of the effective region is reduced. In addition, the effective area of the light receiving element 26 varies in proportion to the square of the distance of the optical path from the point light source 22 through the absolute pattern 9 to the light receiving element 26. As shown, the light receiving element 26 closer to the point light source 22 is larger.

  Further, these light receiving elements 25 and 26 are connected to a signal processing circuit 7 on the printed wiring board 5 as shown in FIG.

Next, the operation will be described.
When detecting the amount of rotation (relative rotation angle, absolute angle position, etc.) of the motor shaft 6 using the absolute encoder 1 having the above-described configuration, the rotary code plate 3 is attached to the tip of the motor shaft 6. In this state, divergent light is emitted from the point light source 22.

  Then, the divergent light from the point light source 22 is reflected by the incremental pattern 8 of the rotary code plate 3 and then enters the light receiving element array 23 of the detection unit 2 as shown in FIG. As a result, in each light receiving element 25 of the light receiving element array 23, an output signal (charge or the like) S1 proportional to the amount of incident light is time-sequentially sent to the signal processing circuit 7 by photoelectric conversion, as shown in FIG. Is output. In response to this, the signal processing circuit 7 sequentially reads and processes the output value of the output signal S1, and calculates the relative rotation angle of the motor shaft 6.

  At this time, the light emitted from the point light source 22 is divergent light, and the distance of the optical path from the point light source 22 through the incremental pattern 8 to the light receiving element 25 is different for each light receiving element 25. As described above, since the effective area changes corresponding to the light quantity distribution of the incident light, the output signal S1 output from each light receiving element 25 to the signal processing circuit 7 is uniform. This is because the output value of the output signal S1 from the light receiving element 25 where the amount of incident light is low is equal to the output value of the output signal S1 from the light receiving element 25 where the amount of incident light is high. As a result, the relative rotation angle of the motor shaft 6 can be accurately calculated.

  The light receiving element array 23 for detecting the incremental pattern 8 outputs signals of four phases of 0 °, 90 °, 180 ° and 270 ° so that the rotation direction (forward / reverse direction) of the motor shaft 6 can be determined. Output. Then, the signal processing circuit 7 calculates the differential between the 0 ° signal and the 180 ° signal and the differential between the 90 ° signal and the 270 ° signal, respectively, so that the rotation direction of the rotary code plate 3 and thus the motor shaft 6 is calculated. Is determined.

  Further, divergent light from the point light source 22 is reflected by the absolute pattern 9 of the rotary code plate 3 and then enters the light receiving element array 24 of the detection unit 2 as shown in FIG. As a result, in each light receiving element 26 of the light receiving element array 24, an output signal (charge or the like) S2 proportional to the amount of incident light is time-sequentially sent to the signal processing circuit 7 by photoelectric conversion, as shown in FIG. Is output. In response to this, in the signal processing circuit 7, the output value of the output signal S2 is sequentially read and subjected to signal processing, and the absolute angular position of the motor shaft 6 is calculated.

  At this time, the light emitted from the point light source 22 is divergent light, and the distance of the optical path from the point light source 22 through the absolute pattern 9 to the light receiving element 26 is different for each light receiving element 26. As described above, since the effective area changes corresponding to the light quantity distribution of the incident light, the output signal S2 output from each light receiving element 26 to the signal processing circuit 7 is uniform. This is because the output value of the output signal S2 from the light receiving element 26 where the amount of incident light is low is equal to the output value of the output signal S2 from the light receiving element 26 where the amount of incident light is high. As a result, the absolute angular position of the motor shaft 6 can be accurately calculated.

  Thus, in the light receiving elements 25 and 26, the output signals S1 and S2 output to the signal processing circuit 7 are uniform. Therefore, the reliability of the absolute encoder 1 can be easily increased without adding processing for adjusting the difference between the output values of the output signals S1 and S2 to the signal processing circuit 7.

  Moreover, in the light receiving element arrays 23 and 24, since the effective area of the light receiving elements 25 and 26 can be increased / decreased only by changing the width of the light shielding films 27 and 28, the detection unit 2 can be manufactured easily.

[Embodiment 2 of the Invention]
FIG. 4 is a diagram according to Embodiment 2 of the present invention.
In the second embodiment, as shown in FIG. 4, in order to equalize the output signals S1 and S2 output from the plurality of light receiving elements 25 and 26 to the signal processing circuit 7, the radial directions of these light receiving elements 25 and 26 are used. The configuration is the same as that of the first embodiment described above except that the width is changed in accordance with the light amount distribution of the incident light.

  That is, the twelve light receiving elements 25 have the same circumferential width as shown in FIG. 4, and the radial width is the distance of the optical path from the point light source 22 through the incremental pattern 8 to the light receiving element 25. The light receiving element 25 farther from the point light source 22 is larger so that the area (effective area) of the light receiving surface of the light receiving element 25 changes in proportion to the square of. The six light receiving elements 26 have the same circumferential width, and the radial width is proportional to the square of the distance of the optical path from the point light source 22 through the absolute pattern 9 to the light receiving element 26. The light receiving element 25 farther from the point light source 22 is larger so that the area (effective area) of the light receiving surface of the light receiving element 26 changes.

In addition, about the same component as Embodiment 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted.
Therefore, according to this Embodiment 2, there exists the same effect as Embodiment 1 mentioned above.

[Other Embodiments of the Invention]
In the first embodiment described above, the case where the light receiving surfaces of the light receiving elements 25 and 26 are masked with the light shielding films 27 and 28 to reduce the effective area has been described. However, it is possible to reduce the effective area of the light receiving surface by reducing the size of the light receiving elements 25 and 26 without using the light shielding films 27 and 28.

  In the second embodiment described above, the case where the size of the light receiving elements 25 and 26 themselves is reduced in the light receiving elements 25 and 26 has been described. However, the effective area can be reduced by masking the light receiving surface with a light shielding film.

  Further, in the first embodiment described above, the case where the effective area is changed by changing the circumferential width of the effective region in the light receiving elements 25 and 26 will be described. In the second embodiment described above, the light receiving element 25 is described. 26, the case where the effective area is changed by changing the radial width of the effective region has been described. However, both the circumferential width and the radial width of the effective region may be changed.

  Furthermore, in the first and second embodiments described above, the effective areas of the light receiving elements 25 and 26 correspond to the light quantity distribution of the incident light in order to make the output signals S1 and S2 from the plurality of light receiving elements 25 and 26 uniform. The case of setting has been described. However, the output signals S1 and S2 from the light receiving elements 25 and 26 receive not only the effective area of the light receiving elements 25 and 26 but also the element sensitivity of the light receiving elements 25 and 26 (that is, the light reception when light of a certain intensity is received). Based on the idea that it also depends on the output values of the output signals S1 and S2 of the elements 25 and 26, it is also possible to set the element sensitivities of the light receiving elements 25 and 26 corresponding to the light quantity distribution of the incident light. Alternatively, both the effective area of the light receiving elements 25 and 26 and the element sensitivity may be set.

  In the first and second embodiments described above, the reflection type absolute encoder 1 has been described. However, as long as the light quantity distribution of the incident light of the light receiving elements 25 and 26 is clear, the invention is applied to the absolute encoder 1 other than the reflection type. Can also be applied. For example, even if the transmissive absolute encoder 1 is used as diffuse light without collimating the diffused light from the point light source 22 with a collimating lens (convex lens), Usefulness becomes remarkable. Even if the light emitted from the point light source 22 is not divergent light, there may be a difference in the amount of incident light of the light receiving elements 25 and 26. In such a case, the usefulness of the present invention is remarkable. Become.

  In the first and second embodiments, the modular type absolute encoder 1 has been described. However, the present invention can also be applied to the hollow shaft type absolute encoder 1.

  Further, in the first and second embodiments, the absolute encoder 1 has been described. However, as long as the detection unit 2 having a difference in the amount of incident light incident on the plurality of light receiving elements 25 and 26 is provided, the absolute encoder 1 is used. The present invention can also be applied to other encoders (for example, an incremental encoder).

  Moreover, although Embodiment 1 and 2 mentioned above demonstrated the case where the point light source 22 was used as a light emitting element, it is also possible to substitute a line light source and a surface light source.

  In the first and second embodiments described above, the absolute encoder 1 that detects the rotation amount of the motor shaft 6, that is, the rotary encoder has been described. However, it goes without saying that the present invention can be applied to a linear encoder (linear sensor).

  In the first and second embodiments described above, the case where the output signals S1 and S2 output from the plurality of light receiving elements 25 and 26 to the signal processing circuit 7 are equalized has been described. However, these output signals S1 and S2 It is not always necessary to achieve the uniformity of 100%, and the uniformity of these output signals S1 and S2 may be improved as much as possible.

  In the first and second embodiments described above, the detection unit 2 including the light receiving element array 23 including the 12 light receiving elements 25 and the light receiving element array 24 including the six light receiving elements 26 has been described. The number of 25 and 26 may be any number as long as it is plural (two or more).

  The present invention can be widely applied to various encoders such as a rotary encoder and a linear encoder.

1 …… Absolute encoder (encoder)
2 ... Detection unit 3 ... Rotation code plate 4 ... Rotation board 4a ... Boss part 5 ... Printed wiring board 6 ... Motor shaft 7 ... Signal processing circuit 8 ... Incremental pattern 8a ... Reflection pattern area 8b …… Non-reflective pattern region 9 …… Absolute pattern 9a …… Reflective pattern region 9b …… Non-reflective pattern region 21 …… Silicon substrate 22 …… Point light source (light emitting element)
23, 24... Light receiving element array 25, 26... Light receiving element 27, 28 .. Light shielding film S1, S2.

Claims (11)

A light receiving element array in which a plurality of light receiving elements that output an output signal corresponding to the amount of incident light are arranged in a predetermined direction;
A light source for irradiating at least a part of the code plate,
The detection unit, wherein the plurality of light receiving elements are provided by changing an effective area width in a width direction perpendicular to the predetermined direction in accordance with a light amount distribution of the light. 2. The detection unit according to claim 1, wherein the plurality of light receiving elements are provided such that an effective area in the width direction is narrowed toward a light receiving element closer to the light source in the predetermined direction. 3. The plurality of light receiving elements are provided such that, of both ends in the width direction, an end opposite to the light source is positioned along the predetermined direction. Detection unit. The detection unit according to any one of claims 1 to 3, further comprising a second light receiving element array provided at a position different from the light receiving element array. A light receiving element array in which a plurality of light receiving elements that output an output signal corresponding to the amount of incident light are arranged in a predetermined direction;
A light source for irradiating at least a part of the code plate,
The detection unit, wherein each of the plurality of light receiving elements is provided with a light shielding film that changes an area of the light receiving surface in the predetermined direction according to a light amount distribution of the light. A light receiving element array in which a plurality of light receiving elements that output an output signal corresponding to the amount of incident light are arranged in a predetermined direction;
A light source for irradiating at least a part of the code plate,
Each of the plurality of light receiving elements is provided with a light shielding film that changes an area of a light receiving surface in a width direction perpendicular to the predetermined direction according to a light amount distribution of the light. The light-shielding film provided on the plurality of light-receiving elements is provided so that a light-receiving element closer to the light source in the predetermined direction has a smaller area of the light-receiving surface. The detection unit described in 1. An encoder comprising the detection unit according to any one of claims 1 to 7. A sign plate having an absolute pattern and an incremental pattern;
A light source for irradiating at least part of the code plate;
A plurality of first light receiving elements that are movable in a predetermined direction with respect to the code plate and that output an output signal corresponding to the amount of light through the absolute pattern are arranged in a predetermined direction. A light receiving element array;
A plurality of second light receiving elements that are movable relative to the code plate in the predetermined direction and that output an output signal corresponding to the amount of light through the incremental pattern are arranged in the predetermined direction. Two light receiving element arrays,
The plurality of first light receiving elements are respectively provided by changing the width of the effective area in the width direction perpendicular to the predetermined direction according to the light quantity distribution of the light. The plurality of second light receiving elements are respectively provided by changing a width of an effective region in a width direction perpendicular to the predetermined direction according to a light amount distribution of the light. Encoder. A light receiving element array in which a plurality of light receiving elements that output an output signal corresponding to the amount of incident light are arranged in a predetermined direction;
A light source for irradiating at least a part of the code plate,
The detection unit, wherein the plurality of light receiving elements are covered with a light shielding unit that changes an area of a light receiving surface in a width direction perpendicular to the predetermined direction according to a light amount distribution of the light.

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