JP2017181473A - Position transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position transducer that can achieve a stable output even when a temperature varies.SOLUTION: A position transducer includes: a rotary member that has a protrusion face protruding around a rotary shaft of a rotation limit motor at a part in a circumferential direction of the rotary shaft of the rotation limit motor, and is attached to the rotary shaft to rotate together with the rotary shaft; a diffusion light source that is arranged so as to oppose the protrusion face; and a detector that is composed of two pairs of photodiode arrays, in which each photodiode array is composed of first and second photodiodes that are monolithically formed on the same chip, and the protrusion face is irradiated with light from the diffusion light source, and thereby on the first and second photodiodes, an image is formed that moves in the circumferential direction, and each photodiode array outputs a first signal corresponding to a light reception area by the first photodiode and a second signal corresponding to a light reception area by the second photodiode; and a signal processing circuit that compensates for a temperature change component of the first signal using the second signal.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a position transducer.

  There is known a position converter mounted on a rotation-restricted motor that drives an optical component such as a mirror for scanning laser light.

  For example, Patent Document 1 discloses a so-called transmission-type optical position detection device (position converter) that detects a rotation angle of a rotating element. The position detection device of Patent Document 1 includes a single light source that provides a uniform and wide-angle optical field in the major axis direction of a rotating element, and a plurality of sectors that are aligned around the major axis and receive light from the light source. An optical sensor and a light blocking member connected to the rotating element and rotating around the major axis to periodically block a portion of the light illuminating the optical sensor. There is no obstacle in the space between the light source and the light sensor except for the light blocking member, and the light from the light source directly irradiates the light sensor portion that is not blocked by the light blocking member. The linear output from the light sensor is used to measure the angular position of the rotating element.

  Patent Document 2 discloses a so-called reflection-type optical position converter that detects the rotation angle of a rotation limiting motor. The position converter of Patent Document 2 is attached to a rotation shaft of a rotation limiting motor, and is disposed so as to face a reflector having a plurality of reflection surfaces protruding radially from the rotation shaft and a central portion of the reflection surface of the reflector. The same number of diffused light sources as the number of reflective surfaces, and behind the reflectors as viewed from the diffused light sources, are placed on the fixed side of the rotation limiting motor so as to surround the reflectors at a distance from the reflectors. It has a diffused light absorbing member that absorbs irradiation light from a diffused light source that did not hit, and a plurality of detectors that are mounted on the same circuit board as the diffused light source and detect an image reflected by the reflector. The diffused light source and the plurality of detectors are respectively arranged in accordance with the angle formed by the plurality of reflecting surfaces.

  Patent Document 3 discloses a light-receiving photodiode having an open light-receiving surface, a compensation photodiode manufactured on the same semiconductor chip as the light-receiving photodiode and having a light-receiving surface covered with a metal vapor-deposited film, and a light-receiving photodiode. An optical receiver circuit having an amplifier that amplifies the output signal of the compensation photodiode and an operational amplifier that amplifies the difference between the amplified signals and effectively reducing the dark current of the photodiode to zero is disclosed.

Japanese translation of PCT publication No. 2002-512364 Japanese Patent No. 5595550 JP 59-28389

  In the position converter, when a temperature change occurs due to heat generation of each member during operation, the peak sensitivity wavelength of the detector, the light emission amount of the diffuse light source, the light emission wavelength and the light emission distribution, the light blocking member or the reflector The shape, the distance between the detector and the reflector, the reflectance of the reflector, the light absorptivity of the diffused light absorbing member, and the like change. These characteristic changes due to temperature cause a drift, which is an output change of the position converter, and therefore the accuracy of detecting the rotation angle is lowered. In order to increase the detection accuracy of the position transducer, it is necessary to devise signal processing for the output signal of the detector to suppress the occurrence of drift due to temperature changes.

  Accordingly, an object of the present invention is to provide a position converter that can obtain a stable output even when the temperature changes.

  A rotation member that has a protruding surface that protrudes around the rotation shaft at a part of the rotation shaft of the rotation limiting motor, and that is mounted on the rotation shaft and rotates together with the rotation shaft, and is disposed to face the protruding surface. A detector comprising a diffused light source and two pairs of photodiode arrays, each photodiode array comprising a first and a second photodiode monolithically formed on the same chip, and a projecting surface By irradiating light from the diffusion light source, an image moving in the circumferential direction is formed on the first and second photodiodes, and the first signal corresponding to the light receiving area of the first photodiode is formed. And a detector that outputs each of the second signals corresponding to the light receiving area of the second photodiode array, and the temperatures of the two first signals output by the pair of photodiode arrays. Position transducer, characterized in that a signal processing circuit for compensating the change component by using two second signal output by the pair of photodiode array is provided.

  In the position converter, the signal processing circuit includes a first subtracter that generates a difference signal between the second signals output from the pair of photodiode arrays, and a second photodiode for the first photodiode. An amplifier that amplifies the difference signal with an amplification factor that is inversely proportional to the area ratio of the first and second subtracters that subtract the output signal of the amplifier from the sum signal of the first signals output by the pair of photodiode arrays. It is preferable to have.

  The position converter is installed behind the rotating member as viewed from the diffused light source, on the fixed side of the rotation limiting motor so as to surround the rotating member at a distance from the rotating member, and from the diffused light source that does not hit the protruding surface The rotating member is a reflector having a reflecting surface as a projecting surface, and the detector is disposed on the reflecting surface on the same side as the diffusing light source. It is preferable that they are arranged to face each other.

  According to the position converter, a stable output can be obtained even if the temperature changes.

2 is a longitudinal sectional view of the position converter 100. FIG. It is the longitudinal cross-sectional view of the position converter 100 seen from 90 degree side with respect to FIG. 1A. 3 is an exploded perspective view of the position converter 100. FIG. It is the perspective view which showed the position converter 100 partially broken. It is an enlarged view of the surface of the diffused light absorption member 3d. It is a top view of the butterfly-shaped reflector 7. It is a figure which shows arrangement | positioning of the detector 11 on the printed circuit board 6. FIG. 3 is a circuit diagram of a signal processing circuit 13 of the position converter 100. FIG. It is a figure which shows the positional relationship of photodiode A1, A2, B1, B2 and butterfly-shaped image 12a, 12b, 12c. It is the graph which showed the relationship between the position converter output Vo and a rotation angle. 3 is a longitudinal sectional view of the position converter 200. FIG. It is a longitudinal cross-sectional view of the position converter 200 when the butterfly-shaped reflector 7 of FIG. 8A rotates 90 degrees. It is a figure which shows arrangement | positioning of the detector 11a of the position converter 200. FIG. It is typical sectional drawing for demonstrating the structure of a photodiode array. 3 is a circuit diagram showing a main part of a signal processing circuit 13 of the position converter 100. FIG. 3 is a circuit diagram showing a main part of a signal processing circuit 14 of the position converter 200. FIG. 4 is a longitudinal sectional view of the position converter 300. FIG. It is a figure which shows arrangement | positioning of the detector 11b of the position converter 300. FIG.

  Hereinafter, the position converter will be described in detail with reference to the drawings. However, it should be understood that the present invention is not limited to the drawings or the embodiments described below.

  FIG. 1A is a longitudinal sectional view of the position transducer 100. FIG. 1B is a longitudinal sectional view of the position transducer 100 as viewed from the side of 90 degrees with respect to FIG. 1A. FIG. 1C is an exploded perspective view of the position converter 100. FIG. 1D is a perspective view of the position converter 100 with a part thereof broken away.

  The position converter 100 includes a rotation limiting motor 1, a diffused light absorber 3, an LED die 4, a case 5, a printed circuit board 6, a butterfly reflector 7, a detector 11, and the like. The position converter 100 is a reflective optical position converter that detects the rotation angle of the rotation limiting motor 1 by detecting the light emitted from the LED die 4 and reflected by the butterfly reflector 7 with the detector 11. It is.

  The rotation limiting motor 1 has a rotating shaft 2 at the end of the rotor 10, and the rotating shaft 2 is supported by a bearing 8. A reflector mounting portion 2 a protrudes from the tip of the rotating shaft 2. A butterfly reflector 7 is attached to the reflector attachment portion 2a. The butterfly reflector 7 is an example of a rotating member, and rotates together with the rotating shaft 2 by driving the rotation limiting motor 1.

  A diffused light absorber 3 is disposed at an upper portion of the rotation limiting motor 1 with a distance from the butterfly reflector 7. As shown in FIG. 1D, the diffused light absorber 3 includes a disc-shaped portion 3c, a trapezoid-shaped portion 3a formed near the center of the disc-shaped portion 3c, and a through-hole formed in the center of the trapezoid-shaped portion 3a. And a hole 3b. The diffused light absorber 3 is attached to the upper end of the rotation limiting motor 1 so that the rotating shaft 2 passes through the through hole 3b. The diffused light absorber 3 is incorporated in a cylindrical case 5.

  The diffused light absorber 3 and the case 5 are fixed members that are not rotated by the rotation limiting motor 1. A diffused light absorbing member 3 d (see FIG. 2) that absorbs light from the LED die 4 is disposed on the surface of the fixed-side diffused light absorber 3 and the case 5 that is spaced from the reflecting surface of the butterfly reflector 7. Has been. That is, the internal space formed by the diffused light absorber 3 and the case 5 is surrounded by the diffused light absorbing member 3d. The diffused light absorber 3 and the case 5 absorb the light emitted from the LED die 4 and not hitting the butterfly reflector 7 by the diffused light absorbing member 3d.

  FIG. 2 is an enlarged view of the surface of the diffused light absorbing member 3d. The diffused light absorbing member 3d is a black member that has been subjected to a surface treatment, and has a three-dimensional and complicated microstructure such as irregularities having a pitch and a height that match the wavelength of light on its surface. The diffused light absorption member 3d confines and absorbs the light by repeatedly reflecting the incident light L on the surface with this fine structure (stray light effect). The surface treatment is performed by a method such as vapor deposition, plating, inorganic baking coating, or electrostatic flocking.

  A printed circuit board 6 (an example of a circuit board) is attached on the case 5. As shown in FIG. 1A, the LED die 4 is mounted on the lower surface of the printed circuit board 6 at a position corresponding to the center of the rotating shaft 2. The LED die 4 is disposed on the printed circuit board 6 so as to face the butterfly reflector 7. The LED die 4 is a diffusion light source that emits light from one point and emits the emitted light with a predetermined spread. In FIG. 1A and FIG. 1B, the light irradiated from LED die 4 is shown by the arrow. In the position converter 100, for example, aluminum gallium arsenide (AlGaAs) having a peak wavelength of 870 nm is used as the LED die 4.

  A connector 9 having a 10-pin terminal is attached to the printed circuit board 6. Each pin of the connector 9 is electrically connected to each land of a pattern (not shown) formed on the printed circuit board 6 by soldering or the like. In FIG. 1C, five pins 9a are visible, and the remaining pins are located behind the connector and are not visible. Each pin is connected to a pattern connected to the terminals of the detector 11 and the LED die 4. The connector 9 is electrically coupled to a female (or male) connector (not shown) to which a connection terminal of a signal processing circuit or the like is connected.

  FIG. 3 is a top view of the butterfly-shaped reflector 7. The butterfly reflector 7 has a mounting hole 7a for fitting to the reflector mounting portion 2a of the rotary shaft 2 by fitting, and projects around the rotary shaft 2 at a part of the central portion in the circumferential direction. Butterfly-shaped flat reflective surface 7b. The butterfly reflector 7 has a reflective surface 7b that is a reflective region, but does not have a non-reflective region. The light emitted from the LED die 4 and hitting the reflection surface 7b of the butterfly reflector 7 is reflected toward the detector 11 by the reflection surface 7b. On the other hand, of the light emitted from the LED die 4, the light passing through the region other than the reflection surface 7 b and passing through the back surface side of the butterfly reflector 7 is absorbed by the diffused light absorbing member 3 d.

  The butterfly reflector 7 is manufactured by processing a mirror-finished metal plate by cold rolling or the like into a butterfly shape by etching or wire cutting. The reflectance of the butterfly reflector 7 may be further improved by depositing aluminum, silver, gold or the like on the reflecting surface 7b and applying a metal coating.

  FIG. 4 is a diagram showing the arrangement of the detectors 11 on the printed circuit board 6. The detector 11 includes four photodiode dies A1, A2, B1, and B2, and is disposed on the same side as the LED die 4 with respect to the butterfly-shaped reflector 7 so as to face the reflecting surface 7b. The photodiodes A1, A2, B1, and B2 are disposed around the LED die 4 on the lower surface of the printed circuit board 6. Each photodiode is composed of a silicon wafer having a sensitivity wavelength of 800 to 900 nm. The spectral sensitivity wavelengths of the photodiodes A1, A2, B1, and B2 are preferably the same as the peak wavelength of the LED die 4. The LED die 4 and the photodiodes A1, A2, B1, and B2 are directly mounted on the printed circuit board 6 without being packaged (chip-on-board).

  The photodiodes A1, A2, B1, and B2 are mounted such that the photodiodes A1 and A2 face each other and the photodiodes B1 and B2 face each other with the LED die 4 arranged at the center point of the printed circuit board 6 interposed therebetween. Yes. Furthermore, the photodiodes A1 and B1 are mounted close to each other, and the photodiodes B2 and A2 are mounted close to each other. On the printed circuit board 6, photodiodes A1 and A2 are connected in parallel, and photodiodes B1 and B2 are connected in parallel.

  The butterfly-shaped image emitted from the LED die 4 and reflected by the butterfly-shaped reflector 7 moves with the rotation of the rotation limiting motor 1. The detector 11 receives the image of the reflected light from the plurality of rotating reflecting surfaces 7b and outputs a signal that changes in accordance with the ratio of the light receiving area of the image between the two photodiodes. Specifically, the photodiodes A1 and A2 and the photodiodes B1 and B2 receive the images and output photocurrents Ia and Ib corresponding to the areas of the respective light receiving regions. The photocurrents Ia and Ib are converted into currents and voltages by the signal processing circuit 13 to be described below to become voltages Va and Vb, respectively. This voltage difference Va−Vb becomes the output of the position converter 100.

  FIG. 5 is a circuit diagram of the signal processing circuit 13 of the position converter 100. Although not shown in FIGS. 1A to 1D, the position converter 100 is a signal processing circuit 13 that converts photocurrents from the photodiodes A 1, A 2, B 1, and B 2 according to the rotation angle of the rotation limiting motor 1 into voltage signals. Have

The photocurrent Ia that is the output of the photodiodes A1 and A2 is input to the current-voltage converter 21a. The photocurrent Ib that is the output of the photodiodes B1 and B2 is input to the current-voltage conversion unit 21b. The output voltage Va of the current-voltage conversion unit 21a and the output voltage Vb of the current-voltage conversion unit 21b are input to the subtracter 22 and subjected to subtraction processing. The position converter output Vo processed by the signal processing circuit 13 is:
Vo = (Ia−Ib) Vref / (Ia + Ib) (1)
It becomes. Vref is a reference voltage.

  Further, the signal processing circuit 13 includes an AGC circuit 28a that performs temperature compensation and linearity compensation with respect to a temperature change that cannot be compensated for by the optical system in order to obtain a highly accurate position conversion output. The output voltage Va of the current-voltage converter 21a and the output voltage Vb of the current-voltage converter 21b are led to the AGC circuit 28a and added by the adder 23. This added output is compared with the reference voltage Vref by the comparator 24. The output of the comparator 24 is integrated by the integrating circuit 25 and amplified by the current amplifier 26a. Thereby, the current If is supplied to the LED 20 through the resistor 27.

  FIGS. 6A to 6C are diagrams showing the positional relationship between the photodiodes A1, A2, B1, and B2 and the butterfly-shaped images 12a, 12b, and 12c. Images irradiated to the photodiodes A1, A2, B1, and B2 from the butterfly-shaped reflector 7 are rotated by the rotation limiting motor 1 as shown in images 12a, 12b, and 12c in FIGS. 6 (a) to 6 (c). Move by angle.

  Hereinafter, the area of the light receiving regions of the photodiodes A1 and A2 is referred to as Sa, and the light receiving regions of the photodiodes A1 and A2 are referred to as “Sa regions”. Similarly, the area of the light receiving regions of the photodiodes B1 and B2 is Sb, and the light receiving regions of the photodiodes B1 and B2 are referred to as “Sb regions”. FIGS. 6A to 6C show a case where the Sa region is larger than the Sb region, a case where the Sa region and the Sb region are the same size, and a case where the Sa region is smaller than the Sb region.

  For example, when the butterfly-shaped images are images 12a, 12b, and 12c, the rotation angles are assumed to be positive, 0, and negative, respectively. Then, in the case of FIG. 6A, since the area difference is Sa−Sb> 0, the output voltage of the position converter 100 becomes Va−Vb> 0 corresponding to the rotation angle being positive. In the case of FIG. 6B, since the area difference is Sa−Sb = 0, the output voltage of the position converter 100 is Va−Vb = 0 corresponding to the rotation angle being 0. In the case of FIG. 6C, since the area difference is Sa−Sb <0, the output voltage of the position converter 100 becomes Va−Vb <0 corresponding to the negative rotation angle.

  FIG. 7 is a graph showing the relationship between the position converter output Vo and the rotation angle. As shown in FIG. 7, the position transducer output increases in proportion to the rotation angle.

In general, the conversion coefficient of photocurrent with respect to the illuminance from the reflector is Kr, the light receiving area from the reflector is Sa and Sb, the reflectance of the reflector is αr, and the conversion coefficient of the photocurrent with respect to the illuminance from the diffused light absorber is Ke. When the total area of the photodiode is represented by S, the light receiving area of reflection from the diffused light absorber is represented by S-Sa and S-Sb, and the reflectance of the diffused light absorber is represented by βr, the photocurrents Ia and Ib of the photodiode are ,
Ia = Kr · Sa · αr + Ke · (S−Sa) · βr (2)
Ib = Kr · Sb · αr + Ke · (S−Sb) · βr (3)
It becomes. By substituting these into equation (1), an output Vo close to the actual value is calculated.

  When the optical distance until the diffused light reaches the detector via the reflector and the optical distance until the diffused light reaches the detector via the diffused light absorber are substantially the same, βr relative to αr If the ratio is not reduced, good contrast cannot be obtained, and the S / N ratio deteriorates. In order to increase the signal as the position converter, it is necessary to increase the forward current of the LED, so that the junction temperature of the LED light source rises and affects the temperature change of the LED light source.

  As shown in FIG. 6B, when Sa = Sb, the numerator term in the equation (1) is zero, so that the output of the position converter does not change with temperature. However, as shown in FIGS. 6 (a) and 6 (c), when Sa ≠ Sb, the ratio of βr to αr changes depending on the temperature. Occur. Due to this drift, as shown in FIG. 7, the gradient of the proportional relationship between the position transducer output Vo and the rotation angle changes. This drift is called “gain drift”. A highly accurate position transducer is required to have as little gain drift as possible. Further, by keeping the above Ke or βr small, the expression (1) can be made closer to the ideal. That is, gain drift can be reduced.

  Since the reflected light attenuates in inverse proportion to the square of the optical distance, in the position converter 100, the diffused light absorber can be obtained by appropriately taking the distance from the butterfly-shaped reflector 7 to the fixed-side diffused light absorber 3. The conversion coefficient Ke of the photocurrent with respect to the illuminance from 3 is reduced. Thereby, the S / N ratio is improved as compared with the case where the reflective region and the non-reflective region are provided on the same plane of the reflector. Moreover, the influence of the change of the emission wavelength with respect to the temperature of the LED die 4 and the influence of the change in the absorptance of the diffused light absorber 3 due to the temperature rise are reduced, and the stability of the output with respect to temperature is improved.

  In the position converter 100, the reflective region and the non-reflective region are configured by the butterfly-shaped reflector 7 and the diffused light absorber 3 installed on the fixed side at a distance from the reflector. As a result, even if reflective or non-reflective particles are attached to the reflector, the image irradiated on the detector is hardly adversely affected. Further, in the position converter 100, since the reflective region and the non-reflective region are separate members, it is easy to use a high reflection film and a high light absorption film, respectively. Furthermore, since the butterfly-shaped reflector 7 does not have a non-reflective region, the butterfly-shaped reflector 7 has low inertia, which is advantageous for high-speed response of the rotation limiting motor 1.

  FIG. 8A is a longitudinal sectional view of the position converter 200. 8B is a longitudinal sectional view of the position converter 200 when the butterfly-shaped reflector 7 of FIG. 8A is rotated 90 degrees. The position converter 200 differs from the position converter 100 shown in FIGS. 1A to 1D only in the configuration of the LED die and the detector. In other respects, the configuration of the position converter 200 is the same as that of the position converter 100. Hereinafter, the position converter 200 will be described with respect to differences from the position converter 100, and description of points that are common to the position converter 100 will be omitted.

  The position converter 200 has two LED dies 4a and 4b mounted on the lower surface of the printed circuit board 6 by chip-on-board. The LED dies 4 a and 4 b are disposed on the lower surface of the printed circuit board 6 so as to face the butterfly reflector 7 at a position corresponding to the center of the rotary shaft 2. The LED dies 4 a and 4 b are both the same diffused light source and irradiate light toward the butterfly reflector 7. In FIG. 8A and FIG. 8B, the light irradiated from LED die 4a, 4b is shown by the arrow.

  By using two LED dies as the diffused light source, the intensity of the emitted light is averaged, and variations due to individual differences of the LEDs are averaged. For this reason, the output of the position converter 200 is more stable than the position converter 100. Further, in the position converter 200, even if the forward current of the LED is made lower than that of the position converter 100, the same output as that obtained when the number of LED dies is one can be obtained. For this reason, in the position converter 200, it becomes possible to reduce the forward current of the LED while maintaining a good S / N ratio. Further, if the forward current of the LED is reduced, the influence of the junction temperature of the LED is reduced, and the stability of the output with respect to the temperature is further improved. By reducing the forward current of the LED, there is also an effect that power saving and long life of the LED can be achieved.

  FIG. 9 is a diagram showing the arrangement of the detectors 11 a of the position converter 200. FIG. 9 shows the positional relationship between the LED die and the detector on the printed circuit board 6 shown in FIGS. 1A to 1D for the position converter 200. In FIG. 9, the shape of the image formed by irradiating the reflected light from the butterfly-shaped reflector 7 onto the printed circuit board 6 is also shown by being overlaid with broken lines.

  The detector 11a of the position converter 200 includes four photodiode arrays 15 to 18, and is disposed on the same side as the LED dies 4a and 4b with respect to the butterfly-shaped reflector 7 so as to face the reflecting surface 7b. Yes. The photodiode arrays 15 to 18 are mounted on the lower surface of the printed circuit board 6 by chip-on-board. The photodiode arrays 15 and 16 are close to each other, and the photodiode arrays 17 and 18 are also close to each other, but the LED dies 4a and 4b are sandwiched between the photodiode arrays 15 and 16 and the photodiode arrays 17 and 18. Away.

  In the position converter 200, the LED dies 4a and 4b and the photodiode arrays 15 to 18 are arranged so that the LED die 4a and the photodiode arrays 15 and 16 correspond, and the LED die 4b and the photodiode arrays 17 and 18 correspond. Is arranged. For this reason, the emitted light from the LED die 4a is reflected by one reflecting surface 7b of the butterfly-shaped reflector 7, and the reflected light is received mainly by the photodiode arrays 15 and 16. The light emitted from the LED die 4 b is reflected by the other reflecting surface 7 b of the butterfly reflector 7, and the reflected light is received mainly by the photodiode arrays 17 and 18.

  Each of the photodiode arrays 15 to 18 includes two photodiodes monolithically formed on the same chip. Specifically, the photodiode array 15 is photodiodes A1 and A3, the photodiode array 16 is photodiodes B1 and B3, the photodiode array 17 is photodiodes A2 and A4, and the photodiode array 18 is photodiode B2, Each is configured with B4. The photodiodes A1, A2, B1, and B2 are examples of the first photodiode, and are provided for detecting the rotation angle of the rotation limiting motor 1. The photodiodes A3, A4, B3, and B4 are examples of the second photodiode, and are provided to compensate for the temperature change component of the output signal from the detector 11a.

  On the lower surface of the printed circuit board 6, the photodiodes A1, A2, B1, and B2 are arranged on the same circumference with the center O at a position immediately above the rotating shaft 2 (see FIG. 1C and the like). A4, B3, and B4 are arranged on the same circumference outside. The photodiodes A1 and A3 and the photodiodes A2 and A4 face each other across the center O, and the photodiodes B1 and B3 and the photodiodes B2 and B4 also face each other across the center O.

  FIG. 10A and FIG. 10B are schematic cross-sectional views for explaining the structure of the photodiode array. For example, the photodiode array 15 includes a p-type contact layer 102, a light absorption layer 103, an electric field control layer 104, an electron transit layer 105, and an n-type contact layer 106 on a substrate 101 as shown in FIG. One laminated structure that is sequentially laminated is formed by patterning as shown in FIG. 10B by a known etching technique. That is, the photodiodes A1 and A3 of the photodiode array 15 are integrated (monolithically) formed on the same substrate (chip), and the p layer and the n layer are derived from a common semiconductor layer. Have the same characteristics. The same applies to the photodiodes B1 and B3, the photodiodes A2 and A4, and the photodiodes B2 and B4 of the photodiode arrays 16 to 18.

  The photodiodes A1, A2, B1, and B2 have the same light receiving area, and the photodiodes A3, A4, B3, and B4 also have the same light receiving area. However, the light receiving areas of the photodiodes A1, A2, B1, and B2 are larger than the light receiving areas of the photodiodes A3, A4, B3, and B4. On the printed circuit board 6, photodiodes A1 and A2, photodiodes A3 and A4, photodiodes B1 and B2, and photodiodes B3 and B4 are connected in parallel.

  Light is irradiated from the LED dies 4a and 4b and reflected by the reflecting surface 7b of the butterfly reflector 7 to form a butterfly-shaped image on the photodiode arrays 15 to 18, and this image is the rotation limiting motor 1. It moves in the circumferential direction with the rotation of. The detector 11a receives an image of the reflected light from the reflecting surface 7b, and outputs a signal that changes in accordance with the ratio of the light receiving area between the two photodiode arrays. Specifically, the photodiode arrays 15 and 16 output photocurrents Ia1, Ia3, Ib1, and Ib3 corresponding to the light receiving areas of the photodiodes A1, A3, B1, and B3. The photodiode arrays 17 and 18 output photocurrents Ia2, Ia4, Ib2, and Ib4 according to the light receiving areas of the photodiodes A2, A4, B2, and B4. The photocurrents Ia1, Ia2, Ib1, and Ib2 are examples of the first signal, and the photocurrents Ia3, Ia4, Ib3, and Ib4 are examples of the second signal.

  FIG. 11 is a circuit diagram illustrating a main part of the signal processing circuit 13 of the position converter 100. FIG. 11 shows a portion other than the AGC circuit 28a in the signal processing circuit 13 shown in FIG. The signal processing circuit 13 includes current-voltage conversion units 21a and 21b, and the photocurrent generated by the photodiode is converted into a voltage and output. In FIG. 11, for the sake of simplicity, the current-voltage conversion unit 21a , 21b are omitted and shown as a signal processing circuit for current. Also, the LED 20 and the resistor 27 are not shown in FIG.

となる。ただし、ＩａはフォトダイオードＡ１，Ａ２による光電流の和であり、ＩｂはフォトダイオードＢ１，Ｂ２による光電流の和である。また、Ｉｒｅｆは参照電流である。 Let α be the temperature coefficient of the photodiodes A1 and A2, and β be the temperature coefficient of the photodiodes B1 and B2. The temperature coefficient α is a coefficient representing the change amount of the photocurrent of the photodiode A2 with respect to the photocurrent of the photodiode A1 when the temperature changes. Similarly, the temperature coefficient β is a coefficient representing the change amount of the photocurrent of the photodiode B2 with respect to the photocurrent of the photodiode B1 when the temperature changes. In consideration of the characteristic change due to temperature, when the equation (1) is rewritten into the equation for current, the output signal Iout of the position converter 100 is

It becomes. However, Ia is the sum of photocurrents from the photodiodes A1 and A2, and Ib is the sum of photocurrents from the photodiodes B1 and B2. Iref is a reference current.

  If the temperature coefficients α and β are equal, the terms α and β, which are temperature change components in the equation (4), cancel out with the denominator numerator. However, in practice, the temperature characteristics of the photodiodes A1 and A2 and the photodiodes B1 and B2 are different. Therefore, α and β are not the same, and the temperature change component in the equation (4) remains. Occur. Therefore, the signal processing circuit of the position converter 200 compensates for the temperature change component of the output signals of the photodiodes A1, A2, B1, and B2 using the output signals of the photodiodes A3, A4, B3, and B4.

  FIG. 12 is a circuit diagram showing a main part of the signal processing circuit 14 of the position converter 200. Also in the signal processing circuit 14, the photocurrent generated by each photodiode is converted into a voltage and output. However, in FIG. 12, for simplicity, the description of the current-voltage conversion unit is omitted, and the signal processing circuit for the current As shown. The signal processing circuit 14 also has the same LED 20 as the signal processing circuit 13 of FIG. 5 (however, the position converter 200 has two LEDs corresponding to the LED dies 4a and 4b), a resistor 27A, and an AGC circuit 28a. However, since it is not necessary for the description, it is omitted in FIG.

  As shown in FIG. 12, the signal processing circuit 14 includes a temperature compensation circuit 30 including a subtractor 31, an amplifier 32, a subtracter 33, a subtracter 34, an amplifier 35, and a subtracter 36. The temperature compensation circuit 30 generates temperature change components of two photocurrents Ia1, Ia2 (or Ib1, Ib2) for each of the pair of photodiode arrays 15, 17 and the other pair of photodiode arrays 16, 18. Compensation is performed using the other two photocurrents Ia3 and Ia4 (or Ib3 and Ib4). For example, for the photodiode arrays 15 and 17, the signal processing circuit 14 subtracts the temperature change component included in the photocurrents Ia3 and Ia4 from the combined signal of the photocurrents Ia1 and Ia2, thereby changing the temperature change included in the combined signal. Compensate the component. The same applies to the photodiode arrays 16 and 18.

  The subtractor 31 is an example of a first subtracter, and generates a difference signal between the photocurrent Ia3 output from the photodiodes A3 and A4 of the photodiode arrays 15 and 17 and the photocurrent (1 + α) Ia4. However, the coefficient α is a temperature coefficient representing the amount of change in the photocurrent of the photodiode A4 with respect to the photocurrent of the photodiode A3 when the temperature changes. Since the light receiving areas of the photodiodes A3 and A4 are the same, the generated photocurrents are also equal, and Ia3 = Ia4. Therefore, the difference signal generated by the subtractor 31 is (1 + α) Ia4−Ia3 = αIa4.

  The amplifier 32 amplifies the output signal αIa4 of the subtractor 31 with an amplification factor that is inversely proportional to the area ratio of the photodiodes A3 and A4 to the photodiodes A1 and A2. Assuming that the light receiving areas of the photodiodes A3 and A4 are 1 / K of the light receiving areas of the photodiodes A1 and A2, the amplifier 32 amplifies the output signal of the subtractor 31 by K times. As a result, the level of the temperature compensation photocurrent Ia4 is adjusted to the level of the angle detection photocurrent Ia2, so that the output signal of the amplifier 32 is KαIa4 = αIa2. Since the photodiodes A1 and A3 and the photodiodes A2 and A4 have the same temperature characteristics, the temperature coefficient representing the amount of change in the photocurrent of the photodiode A2 with respect to the photocurrent of the photodiode A1 when the temperature changes is also as described above. The same value α.

  The subtractor 33 is an example of a second subtracter, and the output signal of the amplifier 32 is obtained from the sum signal of the photocurrent Ia1 and the photocurrent (1 + α) Ia2 output from the photodiodes A1 and A2 of the photodiode arrays 15 and 17. Subtract αIa2. The difference signal generated by the subtractor 33 is Ia1 + (1 + α) Ia2−αIa2 = Ia1 + Ia2. This is set as Ia (Ia1 + Ia2 = Ia).

  The subtractor 34 is an example of a first subtracter, and generates a difference signal between the photocurrent Ib3 output from the photodiodes B3 and B4 of the photodiode arrays 16 and 18 and the photocurrent (1 + β) Ib4. However, the coefficient β is a temperature coefficient representing the amount of change in the photocurrent of the photodiode B4 with respect to the photocurrent of the photodiode B3 when the temperature changes. Since the light receiving areas of the photodiodes B3 and B4 are the same, the generated photocurrents are also equal, and Ib3 = Ib4. Therefore, the difference signal generated by the subtractor 34 is (1 + β) Ib4−Ib3 = βIb4.

  The amplifier 35 amplifies the output signal βIb4 of the subtractor 34 with an amplification factor that is inversely proportional to the area ratio of the photodiodes B3 and B4 to the photodiodes B1 and B2. If the light receiving areas of the photodiodes A3 and A4 are 1 / K of the light receiving areas of the photodiodes A1 and A2, the light receiving areas of the photodiodes B3 and B4 are also 1 / K of the light receiving areas of the photodiodes B1 and B2. The amplifier 35 amplifies the output signal of the subtractor 34 K times. As a result, the level of the temperature compensation photocurrent Ib4 is adjusted to the level of the angle detection photocurrent Ib2, so that the output signal of the amplifier 35 becomes KβIb4 = βIb2. Since the photodiodes B1 and B3 and the photodiodes B2 and B4 have the same temperature characteristics, the temperature coefficient representing the amount of change in the photocurrent of the photodiode B2 with respect to the photocurrent of the photodiode B1 when the temperature changes is also as described above. The same value β.

  The subtractor 36 is an example of a second subtracter, and the output signal of the amplifier 35 is obtained from the sum signal of the photocurrent Ib1 and the photocurrent (1 + β) Ib2 output from the photodiodes B1 and B2 of the photodiode arrays 16 and 18. βIb2 is subtracted. The difference signal generated by the subtracter 36 is Ib1 + (1 + β) Ib2−βIb2 = Ib1 + Ib2. This is set as Ib (Ib1 + Ib2 = Ib).

  The subsequent signal processing is the same as that of the signal processing circuit 13. That is, the output signal Ia of the subtracter 33 and the output signal Ib of the subtractor 36 are input to the subtractor 22, and the difference signal Ia−Ib becomes the output Iout of the position converter 200. Further, the output signal Ia of the subtractor 33 and the output signal Ib of the subtractor 36 are added by the adder 23, and the sum signal Ia + Ib is compared with the reference current Iref by the comparator 24. Although not shown in FIG. 12, the output of the comparator 24 is integrated by the integrating circuit 25 of FIG. 5, and further amplified by the current amplifier 26a to obtain the current If supplied to the LED 20.

  As described above, the detector 11a of the position converter 200 includes the four photodiode arrays 15 to 18 each composed of two photodiodes formed from a common semiconductor layer on the same chip. The signal processing circuit 14 uses the photocurrents of the photodiodes A3, A4, B3, and B4 to compensate for the temperature change components (terms including the temperature coefficients α and β) of the photocurrents of the photodiodes A1, A2, B1, and B2. To do. Since the photodiodes A1, A3, photodiodes A2, A4, photodiodes B1, B3 and photodiodes B2, B4 have the same temperature characteristics, the temperature change components are extracted from the photocurrents Ia3, Ia4 and the photocurrents Ib3, Ib4, respectively. By subtracting it, the temperature change components of the photocurrents Ia1 and Ia2 and the photocurrents Ib1 and Ib2 are canceled out. Therefore, in the position converter 200, the occurrence of gain drift due to a temperature change is suppressed, and a stable output can be obtained even if the temperature changes.

  The photodiodes A1 and A3, photodiodes B1 and B3, photodiodes A2 and A4, and photodiodes B2 and B4 of the photodiode arrays 15 to 18 are as shown in FIGS. 10A and 10B, respectively. It must be formed from a common semiconductor layer on the same chip. If the photodiodes A1 and A3 formed on different chips are used, the temperature characteristics are different from each other, so that the signal processing of the signal processing circuit 14 cannot cancel the temperature change component. The same applies to the photodiodes B1 and B3, the photodiodes A2 and A4, and the photodiodes B2 and B4.

  The position converter 200 has two LED dies 4a and 4b, but instead of providing a plurality of LED dies, for example, a rectangular LED chip is used, and the central portion thereof is covered with a light-shielding component. One light source may be used. Moreover, you may use LED with a big chip area as a diffused light source. The material of the optical element may be changed and light in the visible light region may be used. Moreover, in order to efficiently direct the diffused light of the LED die toward the butterfly reflector, a hemispherical lens may be provided using a highly thixotropic transparent resin or glass.

  The LED die is preferably mounted directly on the printed circuit board so that the diffused light of the LED die is not directly applied to the photodiode. However, the LED die and the photodiode are not necessarily arranged on the same plane.

  As the reflector, for example, a resin that is made into a butterfly shape with a metal mold or the like and is provided with a reflecting surface by plating or the like may be used. Further, a reflector having a hole in the center may be fixed by press fitting as well as fitting to the rotation shaft of the rotation limiting motor. By attaching the reflector to the rotating shaft by fitting, alignment work with the rotating shaft is unnecessary, and the manufacturing cost is reduced.

  For the diffused light absorbing member, an aluminum material with black matte may be used. Further, a non-reflective coating agent such as black nickel plating or a black resin may be used. When light in the visible light region is used, an anodized film (black matte alumite) may be used as the diffused light absorbing member.

  Practically, the distance from the reflecting surface of the butterfly reflector to the diffused light absorber is preferably about 0.2 mm to 5 mm. In addition, when there is a member on the fixed side of the rotation limiting motor at a distance at which light reaching the detector from other than the reflector is sufficiently attenuated, the diffused light absorbing member may not be disposed on the member on the fixed side. When the inner surface of the case is sufficiently away from the detector, the inner surface of the case may not be covered with the diffused light absorbing member.

  The detector 11a and the signal processing circuit 14 of the position converter 200 can be applied not only to the reflection type optical position converter but also to the transmission type optical position converter. Therefore, in the following, an example in which the above signal processing is applied to a transmissive optical position transducer will be described.

  FIG. 13 is a longitudinal sectional view of the position converter 300. FIG. 14 is a diagram illustrating the arrangement of the detectors 11 b of the position converter 300. FIG. 14 shows a cross section of the position transducer 300 along the line XIV-XIV in FIG. The position converter 300 is a transmissive optical position converter having the same basic configuration as the position detection device of Patent Document 1, and includes a rotation limiting motor 1, an LED light source 40, a case 5, a butterfly-shaped light shield 7 ′, and a detector. 11b and the like. The position converter 300 detects the rotation angle of the rotation limiting motor 1 by detecting the light emitted from the LED light source 40 and reaching the detector 11b without being blocked by the butterfly-shaped light shield 7 '.

  In the position converter 300, instead of the LED dies 4a and 4b, the butterfly reflector 7 and the detector 11a of the position converter 200, the point having the LED light source 40, the butterfly light shield 7 'and the detector 11b is converted. Different from the vessel 200. The position converter 300 is different from the position converter 200 in that it does not have the diffused light absorber 3. In other respects, the configuration of the position converter 300 is the same as that of the position converter 200, and therefore, the points common to the position converter 200 are denoted by the same reference numerals and redundant description is omitted. To do.

  The butterfly-shaped light-shielding device 7 ′ is an example of a rotating member. Like the butterfly-shaped reflector 7 shown in FIG. And has two projecting surfaces 7 b ′ that are attached to the rotating shaft 2 and rotate together with the rotating shaft 2. In FIG. 14, the shape of the butterfly-shaped light shield 7 ′ is also overlapped with a broken line. Since the butterfly-shaped light shield 7 'partially shields the light emitted from the LED light source 40, unlike the butterfly-shaped reflector 7, it does not have a reflecting surface and is formed by, for example, resin molding. The

  The LED light source 40 is an example of a diffused light source, and is disposed in the center of the upper end of the case 5 so as to face the protruding surface 7b 'of the butterfly-shaped light shield 7'. The LED light source 40 is composed of an LED die 4c and a resin-made hemispherical curved window 41 covering the LED die 4c, and full-angle toward the butterfly-shaped light shield 7 'and the detector 11b below the case 5. Irradiate light with uniform intensity.

  Unlike the detector 11a of the position converter 200, the detector 11b is arranged on the opposite side to the LED light source 40 with respect to the butterfly-shaped light shield 7 ′, but the same four photodiode arrays as the detector 11a. It consists of 15-18. Light is emitted from the LED light source 40 and is shielded by the projecting surface 7b ′ of the butterfly-shaped light shield 7 ′, so that a butterfly-shaped image (shadow) is formed on the photodiode arrays 15-18. As the rotation limiting motor 1 rotates, it moves in the circumferential direction. The detector 11b outputs a signal that changes in accordance with the ratio of the light receiving area between the photodiode arrays 15 and 16 and between the photodiode arrays 17 and 18.

  Although not shown, the signal processing circuit of the position converter 300 is the same as the signal processing circuit 14 of the position converter 200 shown in FIG. Similarly to the signal processing circuit 14, the signal processing circuit of the position converter 300 uses the photocurrents of the photodiodes A3, A4, B3, and B4, and the temperature change component of the photocurrents of the photodiodes A1, A2, B1, and B2. To compensate. Therefore, the position converter 300 can also suppress the occurrence of gain drift due to a temperature change, and a stable output can be obtained even if the temperature changes.

DESCRIPTION OF SYMBOLS 1 Rotation limiting motor 2 Rotating shaft 3 Diffuse light absorber 4, 4a, 4b, 4c LED die 5 Case 6 Printed circuit board 7 Butterfly-shaped reflector 8 Bearing 9 Connector 10 Rotor 11, 11a, 11b Detector 12a, 12b, 12c Image 13, 14 Signal processing circuit 15, 16, 17, 18 Photodiode array 31, 33, 34, 36 Subtractor 32, 35 Amplifier 100, 200, 300 Position converter A1, A2, A3, A4, B1, B2, B3 , B4 Photodiode

Claims (3)

A rotating member that has a protruding surface that protrudes around the rotating shaft at a part of the circumferential direction of the rotating shaft of the rotation limiting motor, and is attached to the rotating shaft and rotates with the rotating shaft;
A diffused light source disposed opposite the protruding surface;
A detector comprising two pairs of photodiode arrays, each photodiode array comprising a first and second photodiodes monolithically formed on the same chip, and the diffused light source on the protruding surface When the light from the first photodiode is irradiated, an image moving in the circumferential direction is formed on the first and second photodiodes, and a first signal corresponding to the light receiving area of the first photodiode is formed. And a detector from which each photodiode array outputs a second signal corresponding to the light receiving area of the second photodiode,
A signal processing circuit for compensating for a temperature change component of the two first signals output from the pair of photodiode arrays using the two second signals output from the pair of photodiode arrays;
A position converter characterized by comprising: The signal processing circuit includes:
A first subtractor for generating a difference signal between the second signals output by a pair of photodiode arrays;
An amplifier that amplifies the difference signal at an amplification factor that is inversely proportional to the area ratio of the second photodiode to the first photodiode;
A second subtracter for subtracting the output signal of the amplifier from the sum signal of the first signals output by the pair of photodiode arrays;
The position transducer according to claim 1, comprising: From the diffused light source that is installed behind the rotating member as viewed from the diffused light source, on the fixed side of the rotation limiting motor so as to surround the rotating member at a distance from the rotating member, and does not hit the protruding surface Further having a diffused light absorbing member that absorbs the irradiation light of
The rotating member is a reflector having a reflecting surface as the protruding surface,
3. The position converter according to claim 1, wherein the detector is disposed on the same side as the diffused light source with respect to the reflector so as to face the reflecting surface. 4.

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