JP6684631B2 - Position converter - Google Patents

Description

  The present invention relates to position converters.

  A position converter mounted on a rotation-limited motor that drives an optical component such as a mirror for scanning laser light is known. For example, in US Pat. No. 6,037,049, an illumination source is provided that directs illumination to an illumination reflector that rotates with the rotor of a rotation limited motor, and a plurality of detector areas adjacent to the illumination source that receive modulated reflected illumination from the illumination reflector. A position transducer system for a limited rotation motor including is disclosed.

  Patent Document 2 discloses a structure of an optical system of an optical rotary encoder. The encoder has a light source provided near the rotation center line of the rotation shaft, and an optical pattern that is attached to the rotation shaft so as to be rotatable around the rotation center line and that includes a light-transmitting portion and a light-shielding portion that are alternately formed in the circumferential direction. The rotary scale has a space between the rotary scale and the rotary scale and reflects the light from the light source into a parallel light flux whose width does not change substantially in a cross section including the rotation center line. The light source includes a reflector that irradiates the light portion so that the light transmitted through the light transmitting portion is directed to the periphery of the light source, and a light receiving element that receives the light transmitted through the light transmitting portion. The optical rotary encoder of Patent Document 2 is a converter that obtains position information by detecting bright and dark light from a reflector with a detector and encoding it in a subsequent circuit.

  Patent Document 3 relates to an encoder as in Patent Document 2, and discloses an optical system using a reflective cylindrical surface. In this encoder, a module including a photodetector and a light source is arranged facing the drum. Stripe-shaped non-reflective regions are provided at equal intervals on the circumferential surface of the drum. The light from the light source is applied to the drum, and the reflected light is detected by the photodetector. Japanese Patent Application Laid-Open No. 2004-242242 discloses an encoder-specific optical system that irradiates light on a non-reflective region arranged in a stripe shape on a surface of a drum and a reflective region between them and detects a rotational position of the non-reflective region from the reflected light. Systems and detection schemes are disclosed.

  Patent Document 4 discloses a structure of a rotary motor that detects a rotational position. In this rotary motor, in order to detect its rotational position, a butterfly-shaped diffusion surface having an angle width of 90 degrees is attached to the rotor shaft. The diffusion surface has a disk-shaped opaque surface near the center (see FIG. 1B of Patent Document 4). A lens is arranged facing the diffusion surface, and a stationary detector is installed behind it. As a light source, four LEDs are arranged on both sides of the lens. The light emitted from the four LEDs is reflected by the rotating diffusing surface, and the reflected light is collected by the lens and received by the stationary detector. In the rotary motor of Patent Document 4, the LED and the detector are arranged not in the same surface but in different spaces, and light is emitted from each of the four LED light sources toward the reflecting surface.

  In Patent Document 5, a reflector attached to a rotation shaft of a rotation limiting motor and having a plurality of reflecting surfaces radially protruding from the rotation shaft, and a reflector arranged to face a central portion of the reflecting surface of the reflector. It was installed on the fixed side of the rotation limiting motor so as to surround the reflector at a distance from the reflector, behind the reflector when viewed from the diffused light source, and as many diffused light sources as there were surfaces, and did not hit the reflective surface. A diffused light absorbing member that absorbs the light emitted from the diffused light source, and a plurality of detectors that are mounted on the same circuit board as the diffused light source and that detect the image reflected by the reflector are provided. As for the detector of (1), a position converter which is arranged according to an angle formed by a plurality of reflecting surfaces is disclosed.

Japanese Patent Publication No. 2009-542178 JP, 2004-340929, A JP, 2005-164588, A British Patent Application Publication No. 2264781 Patent No. 5595550

  Originally, the output signal of the detector of the position converter should change linearly within the range of the rotation angle (mechanical angle) required for detection in accordance with the rotation angle of the rotation limiting motor. However, in reality, distortion appears in a part of the waveform of the output signal. Therefore, if the range of the rotation angle used for detection is widened, this distortion adversely affects the detection accuracy.

  Therefore, an object of the present invention is to widen the angle range in which the linearity of the output signal of the detector is maintained with respect to the rotation angle of the rotation limiting motor of the position converter.

  A reflector mounted on the rotation axis of the rotation limiting motor and having a plurality of reflecting surfaces radially protruding from the rotation axis, a diffuse light source mounted on the circuit board facing the plurality of reflecting surfaces, and viewed from the diffuse light source. And a diffused light absorbing member that is installed behind the reflector on the fixed side of the rotation limiting motor so as to surround the reflector at a distance from the reflector and absorbs the light emitted from the diffused light source that did not hit the reflecting surface. , Having a plurality of pairs of photodiodes mounted on the circumference centered on a position directly above the rotation axis on the circuit board, receiving images of light reflected by a plurality of rotating reflecting surfaces, and And a detector that outputs a signal that changes according to the light-receiving area of the image formed by the two photodiodes that make up each of the photodiodes. Are inclined to one another in the plane of the plate, the position transducer, characterized in that two photodiodes are arranged with a gap of the same angle on the circumference is provided.

In the above position converter, the angle of the gap is preferably larger than 4 degrees and smaller than 40 degrees.
In the above position converter, the diffused light source is preferably composed of a plurality of LED dies, and each of the plurality of LED dies is preferably arranged inside the gap on the circuit board.

  According to the above position converter, the angular range in which the linearity of the output signal of the detector is maintained with respect to the rotation angle of the rotation limiting motor is widened as compared with the case where this configuration is not provided.

3 is a vertical cross-sectional view of the position converter 100. FIG. FIG. 1B is a vertical cross-sectional view of the position converter 100 viewed from the side of 90 degrees with respect to FIG. 1A. 3 is an exploded perspective view of the position converter 100. FIG. It is the perspective view which partially cut away and showed position converter 100. It is an enlarged view of the surface of diffused light absorption member 3d. It is a top view of the butterfly shape 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 photodiodes A1, A2, B1, B2 and butterfly-shaped images 12a, 12b, 12c. 6 is a graph showing the relationship between the position converter output Vo and the rotation angle. It is a figure which shows arrangement | positioning of the LED die of the position converter 30. FIG. 6 is a diagram for comparing the length of the optical distance from the LED die to the detector in the position converters 100, 200, 30. It is a figure which shows arrangement | positioning of the LED die of the position converter 40,50,60. It is a figure which shows the arrangement | positioning of the LED die of the position converter 70, and the detector 11a. It is a figure for demonstrating the range of the magnitude | size of the clearance gap G between the photodiodes of a detector. It is the figure which showed the waveform of output voltage Va, Vb of the current voltage conversion part 21a, 21b in the position converters 100, 70. It is a graph which showed the error of the detection angle in position converters 100 and 70. It is a figure which shows the arrangement | positioning of the LED die of the position converter 90, and the detector 11c.

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

  FIG. 1A is a vertical cross-sectional view of the position converter 100. 1B is a vertical cross-sectional view of the position converter 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 showing the position converter 100 with a part thereof cut 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-shaped reflector 7, a detector 11 and the like. The position converter 100 detects the light emitted from the LED die 4 and reflected by the butterfly-shaped reflector 7 by the detector 11 to detect the rotation angle of the rotation limiting motor 1. Is.

  The rotation limiting motor 1 has a rotating shaft 2 at an end of a rotor 10, and the rotating shaft 2 is supported by a bearing 8. A reflector mounting portion 2 a projects from the tip of the rotary shaft 2. The butterfly reflector 7 is attached to the reflector attachment portion 2a. The butterfly-shaped reflector 7 is driven by the rotation limiting motor 1 to rotate together with the rotating shaft 2.

  A diffused light absorber 3 is arranged above the rotation limiting motor 1 at a distance from the butterfly reflector 7. As shown in FIG. 1D, the diffused light absorber 3 includes a disc-shaped portion 3c, a trapezoidal portion 3a formed near the center of the disc-shaped portion 3c, and a penetrating hole formed in the center of the trapezoidal 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 do not rotate depending on the rotation limiting motor 1. A diffused light absorbing member 3d (see FIG. 2) that absorbs light from the LED die 4 is arranged on the surface of the diffused light absorber 3 on the fixed side and the case 5 which are spaced from the reflecting surface of the butterfly-shaped reflector 7. Has been done. That is, the internal space formed by the diffused light absorber 3 and the case 5 is surrounded by the diffused light absorber 3d. The diffused light absorber 3 and the case 5 absorb the light emitted from the LED die 4 and not hitting the butterfly-shaped 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 fine structure such as unevenness having a pitch and a height that match the wavelength of light on the surface thereof. The diffused light absorbing member 3d traps and absorbs the incident light L on its surface by repeatedly reflecting it by 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 placed on and attached to 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 arranged on the printed circuit board 6 so as to face the butterfly-shaped 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 FIGS. 1A and 1B, the light emitted from the LED die 4 is indicated by an arrow. In the position converter 100, as the LED die 4, for example, aluminum gallium arsenide (AlGaAs) having a peak wavelength of 870 nm is used.

  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 board 6 by soldering or the like. In FIG. 1C, the 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. A female (or male) connector (not shown) to which a connection terminal of a signal processing circuit or the like is connected is electrically coupled to the connector 9.

  FIG. 3 is a top view of the butterfly reflector 7. The butterfly-shaped reflector 7 has a mounting hole 7a at the center for mounting it on the reflector mounting portion 2a of the rotating shaft 2 by fitting, and has a butterfly-shaped flat reflecting surface 7b protruding from the center. The butterfly-shaped reflector 7 has a reflecting surface 7b that is a reflecting area, but does not have a non-reflecting area. The light emitted from the LED die 4 and hitting the reflecting surface 7b of the butterfly-shaped reflector 7 is reflected by the reflecting surface 7b toward the detector 11. On the other hand, of the light emitted from the LED die 4, the light passing through the area other than the reflecting surface 7b and passing through to the back surface side of the butterfly reflector 7 is absorbed by the diffused light absorbing member 3d.

  The butterfly-shaped 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-shaped reflector 7 may be further improved by vapor-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 is composed of four photodiode dies, and these photodiodes A1, A2, B1 and B2 are arranged around the LED die 4 on the lower surface of the printed board 6. Each photodiode is composed of a silicon wafer having a sensitivity wavelength of 800 to 900 nm. The LED die 4 and the photodiodes A1, A2, B1 and B2 are directly mounted on the printed board 6 without being packaged (chip on board).

  The photodiodes A1, A2, B1 and B2 are mounted so that the photodiodes A1 and A2 face each other and the photodiodes B1 and B2 also face each other with the LED die 4 arranged at the center point of the printed circuit board 6 interposed therebetween. There is. Further, the pair of photodiodes A1 and B1 are mounted close to each other, and the other pair of photodiodes B2 and A2 are also mounted close to each other. Further, on the printed circuit board 6, the photodiodes A1 and A2 are connected in parallel, and the 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 as the rotation limiting motor 1 rotates. The detector 11 receives the image of the light reflected by the plurality of rotating reflecting surfaces 7b and outputs a signal that changes according to the ratio of the light receiving area of the image between the two photodiodes forming each pair. Specifically, the photodiodes A1 and A2 and the photodiodes B1 and B2 receive the image and output the photocurrents Ia and Ib corresponding to the areas of the respective light receiving regions. The photocurrents Ia and Ib are current-voltage converted by the signal processing circuit 13 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 includes a signal processing circuit 13 for converting a photocurrent generated by the photodiodes A1, A2, B1, B2 according to the rotation angle of the rotation limiting motor 1 into a voltage signal. Have.

The photocurrent Ia that is the output of the photodiodes A1 and A2 is input to the current-voltage converter 21a. Further, the photocurrent Ib which is the output of the photodiodes B1 and B2 is input to the current-voltage converter 21b. The output voltage Va of the current-voltage converter 21a and the output voltage Vb of the current-voltage converter 21b are input to the subtractor 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)
Becomes Vref is a reference voltage.

  Further, the signal processing circuit 13 has an AGC circuit 28a for performing temperature compensation and linearity compensation for a temperature change that cannot be compensated 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 guided to the AGC circuit 28a and added by the adder 23. The 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. As a result, the current If is supplied to the LED 20 via the resistor 27.

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

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

  For example, when the butterfly-shaped images are the images 12a, 12b, and 12c, the rotation angles are 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 positive rotation angle. Further, in the case of FIG. 6B, 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 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. The position transducer output increases in proportion to the rotation angle, as shown in FIG.

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, Sb, the reflectance of the reflector is α, and the conversion coefficient of the photocurrent with respect to illuminance from the diffuse light absorber is Ke. , S is the total area of the photodiode, S-Sa and S-Sb are the light receiving areas of reflection from the diffused light absorber, and β is the reflectance of the diffused light absorber, and the photocurrents Ia and Ib of the photodiode are ,
Ia = Kr · Sa · α + Ke · (S−Sa) · β (2)
Ib = Kr · Sb · α + Ke · (S−Sb) · β (3)
Becomes By substituting these into the equation (1), the output Vo that is close to the actual value is calculated.

  If the optical distance for diffused light to reach the detector through the reflector and the optical distance for diffused light to reach the detector through the diffuser light absorber are substantially the same, then β for α If the ratio is not decreased, good contrast cannot be obtained and the S / N ratio deteriorates. Since it is necessary to increase the forward current of the LED in order to increase the signal as the position converter, the junction temperature of the LED light source rises, which affects the temperature change of the LED light source.

  As shown in FIG. 6B, when Sa = Sb, the numerator term of the equation (1) becomes zero, so that the output change of the position converter due to temperature does not occur. However, as shown in FIGS. 6A and 6C, in the case of Sa ≠ Sb, the ratio of β to α changes depending on the temperature. Therefore, when the temperature changes, the drift, which is the change in the output of the position converter, changes. Occur. Due to this drift, as shown in FIG. 7, the slope of the proportional relationship between the position converter output Vo and the rotation angle changes. This drift is called "gain drift". A highly accurate position converter requires that the gain drift be as small as possible. Also, by keeping the above Ke or β small, it becomes possible to approximate equation (1) to the ideal. That is, it is possible to reduce the gain drift.

  Since the reflected light is attenuated in inverse proportion to the square of the optical distance, in the position converter 100, by appropriately setting 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. This improves the S / N ratio as compared with the case where the reflective area and the non-reflective area are provided on the same plane of the reflector. Further, 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 of the absorptance of the diffused light absorber 3 due to the temperature rise are reduced, and the stability of the output with respect to the temperature is improved.

  Further, in the position converter 100, the reflection area and the non-reflection area are composed of the butterfly-shaped reflector 7 and the diffused light absorber 3 installed on the fixed side with a distance from the reflector. As a result, even if the reflective or non-reflective particles adhere to the reflector, the image irradiated on the detector is less likely to be adversely affected. Further, in the position converter 100, since the reflective area and the non-reflective area are separate members, it becomes easy to form the high reflective film and the high light absorbing film respectively. Furthermore, since the butterfly-shaped reflector 7 has no non-reflection area, it has a low inertia, which is advantageous for the high-speed response of the rotation limiting motor 1.

  FIG. 8 is a diagram showing the arrangement of the LED dies of the position converter 30. The position converter 30 is different from the position converter 100 shown in FIGS. 1A to 1D only in the number and mounting position of LED dies that are diffuse light sources. The configuration of the position converter 30 is otherwise the same as that of the position converter 100. FIG. 8 shows the positional relationship between the LED die and the photodiode on the printed circuit board 6 shown in FIGS. 1A to 1D for the position converter 30. Further, in FIG. 8, the shape of the image formed by irradiating the printed substrate 6 with the reflected light from the rotating butterfly-shaped reflector 7 is also shown by the broken line 7 in a superposed manner.

  The detector 11 of the position converter 30 is the same as that of the position converter 100, and is located on a circle C centered on a point O immediately above the rotary shaft 2 (see FIG. 1C etc.) on the printed circuit board 6. It has a plurality of pairs of photodiodes A1, A2, B1, B2 mounted. The photodiodes A1, A2, B1, and B2 have a width in the radial direction of a circle centered on the point O, and in FIG. A circle passing through the center of the photodiode is shown. As can be seen from FIG. 8, each of the photodiodes A1, A2, B1, and B2 has two arc-shaped ends extending along the circumference C and two straight ends extending in the radial direction of the circumference C. And a department.

  Further, the position converter 30 has two LED dies 4a and 4b mounted on the lower surface of the circuit board 6 by chip-on-board so as to face the butterfly-shaped reflector 7. The LED die 4a is inside the fan-shaped region D1 determined by the length of the arc occupied by the pair of photodiodes A1 and B1 on the circumference, and the center of the diameter corresponding to the rotary shaft 2 immediately above the rotary shaft 2. It is arranged outside the region C1. The LED die 4b is arranged inside the fan-shaped area D2 defined by the length of the arc occupied by the other pair of photodiodes A2 and B2 on the circumference and outside the central area C1. Since it is not possible to arrange the LED dies on the light receiving surface of the photodiode in a stacked manner, more accurately, the fan-shaped region D1 is defined by the arcuate end and the point O on the side closer to the point O of the photodiodes A1 and B1. This is a fixed area. Similarly, the fan-shaped region D2 is a region defined by the arc-shaped ends of the photodiodes A2 and B2 on the side closer to the point O and the point O.

  In the position converter 30, the LED dies 4a and the pair of photodiodes A1 and B1 correspond to each other, and the LED die 4b and the other pair of photodiodes A2 and B2 correspond to each other. Photodiodes A1, A2, B1 and B2 are arranged. Therefore, the light emitted from the LED die 4a is reflected by the one reflecting surface 7b of the butterfly-shaped reflector 7, and the reflected light is mainly received by the photodiodes A1 and B1. Light emitted from the LED die 4b is reflected by the other reflecting surface 7b of the butterfly-shaped reflector 7, and the reflected light is mainly received by the photodiodes A2 and B2.

  The signal processing circuit of the position converter 30 is the same as the signal processing circuit 13 shown in FIG. 5 except that two LEDs 20 are connected in series.

  9A to 9C are diagrams for comparing the lengths of the optical distances from the LED dies to the detectors in the position converters 100, 200, and 30. FIG. 9A shows a part of a vertical cross section of the position converter 100 shown in FIG. 1A. FIG. 9B has two LED dies 4a and 4b at the position corresponding to the center of the rotary shaft 2 on the lower surface of the printed circuit board 6, and the other configurations are the same as those of the position converter 100. A part of the vertical cross section of the converter 200 is shown. Further, FIG. 9C shows a part of a vertical cross section of the position converter 30 shown in FIG. The LED die 4 of the position converter 100 and the LED dies 4a and 4b of the position converter 200 are arranged inside the central region C1 having a diameter corresponding to the rotary shaft 2 just above the rotary shaft 2. On the other hand, the LED dies 4a and 4b of the position converter 30 are arranged outside the central region C1 as described above.

  9A to 9C, the optical paths L1 to L3 of light emitted from the LED die 4 or the LED dies 4a and 4b, reflected by the butterfly-shaped reflector 7 and reaching the detector 11 are indicated by arrows. Shows. The mounting position of the detector 11 is the same in all of the position converters 100, 200, 30. On the other hand, the mounting position of the LED die is located at the center of the center region C1 in the position converter 100, but in the position converters 200 and 30, the mounting position of the LED die moves away from the center of the center region C1 in this order and approaches the mounting position of the detector 11. Therefore, as can be seen by comparing FIGS. 9A to 9C, the optical path L2 of the position converter 200 is shorter than the optical path L1 of the position converter 100, and the optical path L3 of the position converter 30 is shorter. Is even shorter. Therefore, in the position converter 30, the optical distance from the LED dies 4a, 4b to the detector 11 via the butterfly-shaped reflector 7 is shorter than that of the position converters 100, 200. The amount increases, which improves the S / N ratio.

  Further, by using two LED dies as the diffused light source, the intensity of the emitted light is averaged, and the variations due to individual differences of the LEDs are averaged. Therefore, the position converter 30 has a more stable output than the position converter 100. Further, in the position converter 30, even when the forward current of the LED is made lower than that in the position converter 100, the same output as that obtained when there is one LED die is obtained. Therefore, in the position converter 30, it becomes possible to reduce the forward current of the LED while maintaining a good S / N ratio. Furthermore, 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 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.

  FIGS. 10A to 10C are views showing the arrangement of the LED dies of the position converters 40, 50 and 60, respectively. The position converters 40 and 50 differ from the position converter 100 shown in FIGS. 1A to 1D only in the number of LED dies and the mounting position. The position converter 60 is different from the position converter 100 shown in FIGS. 1A to 1D only in the number and mounting position of LED dies and the shape of the photodiode. The configuration of the position converters 40, 50, 60 is otherwise the same as that of the position converter 100. 10A to 10C show positional relationships between the LED die and the photodiode on the printed circuit board 6 shown in FIGS. 1A to 1D for the position converters 40, 50, and 60. In addition, in FIGS. 10A to 10C, the shapes of the images formed by irradiating the printed board 6 with the reflected light from the rotating butterfly-shaped reflector 7 are also overlapped by the broken line 7 Shows.

  The position converter 40 shown in FIG. 10A includes the LED dies 4a and 4b mounted inside the fan-shaped regions D1 and D2 and outside the center region C1 as well as the position converter 30. It has an LED die 4c mounted in the center. The LED die 4c is an example of a central diffused light source mounted on the central region C1 of the printed circuit board 6 so as to face the plurality of reflecting surfaces 7b of the butterfly-shaped reflector 7. In the position converter 40, the three LED dies 4a, 4b, 4c are arranged on a straight line on the lower surface of the printed circuit board 6. If the LED die is inside the fan-shaped regions D1 and D2 and outside the central region C1 like the position converter 40, another LED die may be mounted on the central region C1. Further, like the position converter 40, the number of LED dies (diffuse light sources) does not have to be the same as the number of reflecting surfaces 7 b of the butterfly-shaped reflector 7.

  The position converter 50 shown in FIG. 10B has four LED dies 4d, 4e, 4f and 4g, which are the same in number as the photodiodes A1, A2, B1 and B2 of the detector 11. The LED dies 4d and 4e are mounted inside the fan-shaped region D1 and outside the center region C1, and the LED dies 4f and 4g are mounted inside the fan-shaped region D2 and outside the center region C1. In the position converter 50, the four LED dies 4d, 4e, 4f, 4g are arranged in a rectangular shape so as to correspond to the four photodiodes A1, B1, A2, B2, respectively. Like the position converter 50, a plurality of LED dies may be mounted in each of the fan-shaped region D1 and the fan-shaped region D2.

  The position converter 60 shown in FIG. 10C has a detector 11 ′ composed of four photodiodes A1 ′, A2 ′, B1 ′, B2 ′ instead of the detector 11 of the position converter 100. . Although the photodiodes A1, A2, B1 and B2 described so far are formed on a rectangular chip, the photodiodes A1 ′, A2 ′, B1 ′ and B2 ′ are shown in FIG. As shown, each is formed on a chip in which a part of the side facing the central region C1 is cut out.

  Further, the position converter 60 is mounted in the LED die 4a mounted in the chip notch E1 of the photodiodes A1 'and B1' and in the chip notch E2 of the photodiodes A2 'and B2'. LED die 4b. The LED dies 4a and 4b of the position converter 60 are inside the fan-shaped regions D1 and D2 on the lower surface of the printed circuit board 6 and are regions directly above the central portion of the butterfly-shaped reflector 7 except the reflecting surface 7b. Is located outside the central region C2. The central region C2 is a circular region centered on the point O, like the central region C1, and has a larger area than the central region C1. Like the position converter 60, the chip of each photodiode may be cut away to bring the LED die closer to the photodiode than the position converters 30-50.

  In the position converters 40 and 50, a plurality of LED dies are arranged between the central region C1 facing the rotation shaft 2 of the rotation limiting motor 1 and the detector 11. As a result, the arrangement position of the LED die is closer to the detector than when the LED die is arranged only inside the central region C1. Therefore, also in the position converters 40 and 50, similarly to the position converter 30, the amount of light received by the detector 11 increases and the S / N ratio improves. Also, in the position converters 40 and 50, the intensity of emitted light is averaged by using a plurality of LED dies. Particularly in the position converter 50, since the LED dies 4d, 4e, 4f, 4g are arranged in a square shape corresponding to the photodiodes A1, B1, A2, B2, the LED dies are arranged between each LED die and each photodiode. The distance becomes uniform and the effect of this averaging becomes stronger. Further, also in the position converters 40 and 50, as in the position converter 30, since the LED current is reduced, the stability of the output with respect to temperature is also improved.

  Further, in the position converter 60, a plurality of LED dies are arranged between the detector 11 'and the central region C2 facing the central portion other than the reflecting surface 7b of the butterfly-shaped reflector 7. Therefore, in the position converter 60, the optical distance from the LED dies 4a and 4b to the detector 11 ′ is shorter than that in the position converters 30 to 50, and the amount of light received by the detector 11 ′ is further increased. , S / N ratio is improved. Further, in the position converter 60, the distance between the LED dies is longer than that in the position converters 30 to 50, so that the photodiodes of each pair mainly receive light from one of the LED dies arranged close to each other. Therefore, the amount of light received by each photodiode is made more uniform.

  In the position converters 50 and 60 shown in FIGS. 10B and 10C, the LED die may be additionally arranged in the center of the central region C1. In the position converter 60 as well, like the position converter 50, a total of four LED dies are provided in the notches E1 and E2 so as to correspond to the photodiodes A1 ′, A2 ′, B1 ′, and B2 ′, respectively. You may arrange.

  FIG. 11 is a diagram showing the arrangement of the LED die of the position converter 70 and the detector 11a. The position converter 70 differs from the position converter 100 shown in FIGS. 1A-1D only in the number of LED dies and the shape of the detector. Otherwise, the configuration of the position converter 70 is the same as that of the position converter 100. FIG. 11 shows the positional relationship of the position converter 70 between the LED die and the photodiode on the printed circuit board 6 shown in FIGS. 1A to 1D. Further, in FIG. 11, the shape of an image formed by irradiating the printed board 6 with the reflected light from the rotating butterfly-shaped reflector 7 is also shown by the broken line 7 in a superposed manner.

  The position converter 70 has two LED dies 4a and 4b mounted on the lower surface of the printed circuit board 6 inside a central region C1 facing the rotation axis 2 of the rotation limiting motor 1.

  The position converter 70 also has a detector 11a including four photodiodes A1, A2, B1, and B2. The photodiodes A1, A2, B1 and B2 are the same as those of the position converter 100, but in the detector 11a of the position converter 70, the arrangement of the photodiodes A1, A2, B1 and B2 is detected by the position converter 100. Different from the container 11. As shown in FIG. 11, in the detector 11a, the rectangular chips of the pair of photodiodes A1 and B1 are inclined to each other in the plane of the printed circuit board 6, and the rectangular chips of the other pair of photodiodes A2 and B2 are arranged. The chips are also inclined to each other in the plane of the printed circuit board 6. Further, the photodiodes A1 and B1 and the photodiodes A2 and B2 have a gap G of the same angle on a circle C centered on a point O immediately above the rotation axis 2 (see FIG. 1C etc.) on the printed circuit board 6. It is arranged with a space.

  In the example shown in FIG. 11, the angle of the gap G is 14 degrees. This angle is defined by the end of one photodiode (for example, the right end of the photodiode A1 in FIG. 11) and the end of the other photodiode (for example, the left end of the photodiode B1 in FIG. 11) forming a pair. Part) is the size of the angle formed by. In the example shown in FIG. 11, the opening angle of one reflecting surface 7b of the butterfly-shaped reflector 7 is 60 degrees, and the angle formed by two opposing ends of each photodiode is 50 degrees.

  The signal processing circuit of the position converter 70 is the same as the signal processing circuit 13 shown in FIG. 5 except that two LEDs 20 are connected in series.

  12A and 12B are views for explaining the range of the size of the gap G between the photodiodes of the detector. In these drawings, the positional relationship between the LED die and the photodiode on the printed circuit board 6 shown in FIGS. 1A to 1D is shown, and the shape of the image by the reflected light from the butterfly-shaped reflector 7 is also superposed with reference numeral 7. Shows. 12A is a diagram of the position converter 100, and FIG. 12B is a diagram of the position converter 80 in which the gap G is maximized from a practical viewpoint. The position converter 80 is different from the position converter 70 shown in FIG. 11 only in the size of the corners of the gap G, and in other respects, the position converter 80 has the same configuration as that of the position converter 70. Is.

  In the detector 11 of the position converter 100 shown in FIG. 12A, unlike the detector 11a of the position converter 70, the rectangular chips of the photodiodes A1 and B1 are not inclined with respect to each other, and the other pair of The rectangular chips of the photodiodes A2 and B2 are also not tilted. In the detector 11, the size of the angle formed by the end of one photodiode and the end of the other photodiode forming a pair is 4 degrees. Therefore, it is necessary that the angle of the gap G is larger than 4 degrees.

  The position converter 80 shown in FIG. 12B has a detector 11b composed of four photodiodes A1, A2, B1 and B2. In the detector 11b of the position converter 80, the rectangular chips of the pair of photodiodes A1 and B1 are inclined with respect to each other within the plane of the printed circuit board 6, and the rectangular chips of the other pair of photodiodes A2 and B2 are also included. , Are inclined to each other in the plane of the printed circuit board 6. In the detector 11b, the angle of the gap G is 40 degrees. Further, in the position converter 80, the opening angle of one reflecting surface 7b of the butterfly-shaped reflector 7 is 86 degrees, and the angle formed by the two opposing ends of each photodiode is 50 degrees.

  In order to function as a position converter, when the butterfly-shaped reflector 7 rotates, an image of the reflected light on the reflecting surface 7b is formed, so that the difference in the light receiving area between the two photodiodes forming a pair. Needs to occur. Therefore, the upper limit of the angle of the gap G depends on the size of the opening angle of the reflecting surface 7b. In the position converter 80, the opening angle of the reflecting surface 7b is widened as compared with the position converter 100, but there is a limit to the range in which the opening angle of the reflecting surface 7b can be expanded. When the angle of the gap G is set to 40 degrees or more, when the butterfly-shaped reflector 7 rotates, a difference in light receiving area between two photodiodes forming a pair is less likely to occur. Further, if the angle of the gap G is set to 40 degrees or more, the inclination of the chips of the respective photodiodes becomes large, and there is a risk that the chips will contact each other between the photodiodes A1 and B2 and between the photodiodes B1 and A2. Therefore, practically, the angle of the gap G is preferably smaller than 40 degrees.

  FIG. 13 is a diagram showing waveforms of output voltages Va and Vb of the current-voltage converters 21a and 21b in the position converters 100 and 70. The horizontal axis represents the time t, and the vertical axis represents the voltage V. Curves a and b are waveforms of the output voltage Va of the photodiodes A1 and A2 and the output voltage Vb of the photodiodes B1 and B2 in the position converter 100, respectively. Curves a'and b'are the waveforms of the output voltage Va of the photodiodes A1 and A2 and the output voltage Vb of the photodiodes B1 and B2 in the position converter 70 shown in FIG. 11, respectively. That is, the curves a and b are the voltage waveforms of the position converter in which the gap G is not substantially formed between the photodiodes of each pair, and the curves a ′ and b ′ are the waveforms of the photodiodes of each pair. It is a waveform of the voltage of the position converter in which a gap G is formed. Since the voltage value changes according to the rotation angle of the rotation limiting motor 1, FIG. 13 also shows the correspondence relationship between the rotation angle and the waveform.

  In the waveform of the output voltage of the position converter 100, distortion is seen in the area surrounded by the broken circle in FIG. However, the range of the rotation angle (mechanical angle) actually used in the position converter 100 is only about 30 degrees shown in FIG. The waveform distortion occurs outside this range, and the output waveform of the voltage changes linearly with the rotation angle within the illustrated range of 30 degrees. Therefore, at the rotation angle of 30 degrees, the position converter 100 can be used without being affected by the waveform distortion.

  Also in the waveform of the output voltage of the position converter 70, distortion is seen in the portion surrounded by the broken circle in FIG. However, in the case of the position converter 70, since the gap G is provided between each pair of photodiodes, the phase of the waveform of the output voltage Vb with respect to the waveform of the output voltage Va is greater than that of the position converter 100. Running late. Therefore, in the position converter 70, as shown in FIG. 13, the output waveform of the voltage is linear with respect to the rotation angle within the range of 30 ° + Δθ, which is wider than 30 ° by Δθ (about 10 °). Is changing. In other words, in the position converter 70, as compared with the position converter 100, the region where the linear portions of the output waveforms of the two photodiodes forming a pair overlap is widened.

  Therefore, in the position converter 70, even if the range of the rotation angle of the rotation limiting motor 1 is made wider than that of the position converter 100, the distorted portion on the waveform does not fall within the waveform portion corresponding to the angle range. Therefore, the position converter 70 can be used at a rotation angle of 30 degrees + Δθ, which is wider than the position converter 100 by Δθ, without being affected by the waveform distortion.

  14 (a) and 14 (b) are graphs showing the errors in the detected angles in the position converters 100 and 70, respectively. The horizontal axis of each graph represents the rotation angle θ (mechanical angle) of the rotation limiting motor 1, and the vertical axis represents the error E (%) between the actual rotation angle and the angle detected by the position converters 100 and 70. Represents The rotation angle indicates a range of 30 degrees from −15 degrees to +15 degrees.

  In the case of the position converter 100 shown in FIG. 14A (the position converter in which the gap G is not substantially formed between the photodiodes of each pair), the width of the error E is 0.381%. is there. On the other hand, in the case of the position converter 70 shown in FIG. 14B (position converter in which the gap G of 14 degrees is formed between each pair of photodiodes), the width of the error E is 0.035. %. If the width of the error E is within 0.1%, it can be said that the output waveform of the voltage linearly changes with the rotation angle in practical use. Therefore, it is understood that by forming the gap G between the photodiodes of each pair, the angular range in which the linearity of the output signal of the detector is maintained with respect to the rotation angle of the rotation limiting motor is widened.

  FIG. 15 is a diagram showing the arrangement of the LED die of the position converter 90 and the detector 11c. The position converter 90 is different from the position converter 70 shown in FIG. 11 only in the mounting position of the LED die and the size of the corner of the gap G. In other respects, the position converter 90 has the same structure as the position converter 90. It is the same as that of the container 70. FIG. 15 shows the positional relationship between the LED die and the photodiode on the printed circuit board 6 shown in FIGS. 1A to 1D for the position converter 90, and also the shape of the image formed by the reflected light from the butterfly-shaped reflector 7. Reference numeral 7 is shown in an overlapping manner.

  The position converter 90 has a detector 11c including four photodiodes A1, A2, B1 and B2. In the detector 11c, the rectangular chips of the pair of photodiodes A1 and B1 are inclined to each other in the plane of the printed circuit board 6, and the rectangular chips of the other pair of photodiodes A2 and B2 are also arranged on the printed circuit board 6. They are inclined to each other in the plane. In the detector 11c, the angle of the gap G is 30 degrees. The position converter 90 includes the LED die 4a mounted on the lower surface of the printed circuit board 6 inside the gap G between the photodiodes A1 and B1 forming one pair, and the photodiode A2 forming another pair. , B2 and the LED die 4b mounted inside the gap G. When the LED die is arranged in the gap G, the angle of the gap G is optimally about 30 degrees, which is larger than 14 degrees of the position converter 70 shown in FIG.

  In the position converter 90, the arrangement positions of the LED dies 4a and 4b are closer to the photodiodes A1, A2, B1 and B2 than in the position converter 70. Therefore, in the position converter 90 as well as the position converter 70, in addition to the effect of widening the angular range in which the linearity of the output signal of the detector is maintained with respect to the rotation angle of the rotation limiting motor, the position converters 30 to 30 Similar to 60, the amount of light received by the detector 11c is increased and the S / N ratio is also improved.

  In the position converter 70, the two LED dies 4a and 4b are mounted inside the central region C1, but in the position converter in which the gap G is formed between each pair of photodiodes, the number of LED dies is May be 1 or 3 or more. Also in the position converter that forms the gap G between each pair of photodiodes, as shown in FIGS. 8, 10A, and 10B, a plurality of LED dies are connected to the fan-shaped region D1. It may be arranged inside D2 and outside the central region C1. Alternatively, as shown in FIG. 10C, the photodiode chip may be cut out, and a plurality of LED dies may be arranged in the cutout.

  Instead of providing a plurality of LED dies, for example, a rectangular LED chip may be used and its central portion may be covered with a light-shielding component to form two light sources. Alternatively, an LED having a large chip area may be used as the diffused light source. Light in the visible light region may be used by changing the material of the optical element. Further, in order to efficiently direct the diffused light of the LED die to the butterfly-shaped reflector, a hemispherical lens may be provided using a transparent resin or glass having high thixotropy.

  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 do not necessarily have to be coplanar.

  As the reflector, for example, a resin formed in a butterfly shape with a metal mold or the like may be plated to provide a reflection surface. Further, the 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 fitting the reflector onto the rotary shaft by fitting, the alignment work with the rotary shaft becomes unnecessary, and the manufacturing cost is reduced.

  A black matte aluminum material may be used for the diffused light absorbing member. Alternatively, a non-reflective coating agent such as black nickel plating or a black resin may be used. When using light in the visible light region, an anodic oxide coating (black matte alumite) may be used as the diffused light absorbing member.

  As the distance from the reflecting surface of the butterfly-shaped reflector to the diffused light absorber is wider, the improvement effect is higher, but in practice it is preferably about 0.2 mm to 5 mm. If the fixed-side member of the rotation limiting motor is located at a distance where the light reaching the detector from other than the reflector is sufficiently attenuated, the diffused light absorbing member may not be arranged on the fixed-side member. When the inner surface of the case is sufficiently separated from the detector, the inner surface of the case does not have to be covered with the diffused light absorbing member.

  The photodiode die is preferably provided with fan-shaped blanks on the surface by vapor deposition of aluminum or the like so as to shield unnecessary portions of the detector from light. Further, in order to reduce variations in characteristics, it is preferable to use the four photodiodes taken out from locations close to each other in one wafer. Further, the spectral sensitivity wavelength of the photodiode is preferably the same as the peak wavelength of the above LED.

  For the purpose of improving the mounting accuracy of the four photodiodes, for example, a photodiode array in which the photodiodes A1 and B1 are paired may be manufactured. In addition, a P-layer substrate may be used for the photodiode array in order to share the signal processing circuit in the subsequent stage. Further, two pairs of photodiode arrays, that is, the photodiodes A1 and B1 and the photodiodes A2 and B2, may be used by hollowing out the region where the LED die is mounted. Alternatively, a photodiode array formed monolithically may be used, and LEDs corresponding to each may be arranged.

1 Rotation Limiting Motor 2 Rotation Shaft 3 Diffused Light Absorber 4, 4a, 4b, 4c, 4d, 4e, 4f, 4g LED Die 5 Case 6 Printed Circuit Board 7 Butterfly Shape Reflector 8 Bearing 9 Connector 10 Rotor 11, 11 ', 11a, 11b, 11c Detector 12a, 12b, 12c Image 13 Signal processing circuit 30, 40, 50, 60, 70, 80, 90, 100, 200 Position converter A1, A2, A1 ', A2', B1, B2 , B1 ′, B2 ′ Photodiode C1, C2 Central region D1, D2 Fan-shaped region E1, E2 Notched part G Gap

Claims (3)

A reflector having a plurality of reflecting surfaces attached to the rotation shaft of the rotation limiting motor and radially protruding from the rotation shaft;
A diffused light source mounted on the circuit board so as to face the plurality of reflection surfaces,
Behind the reflector when viewed from the diffused light source, installed on the fixed side of the rotation limiting motor so as to surround the reflector with a distance from the reflector, from the diffused light source that did not hit the reflective surface A diffused light absorbing member that absorbs the irradiation light of
It has a plurality of pairs of photodiodes mounted on a circumference centered on a position directly above the rotation axis on the circuit board, receives an image of light reflected by the plurality of rotating reflecting surfaces, and A detector that outputs a signal that changes according to the light receiving area of the image by the two photodiodes forming a pair,
In each of the plurality of pairs of photodiodes, the chips of the two photodiodes forming the pair are inclined to each other in the plane of the circuit board, and the two photodiodes form a gap of the same angle on the circumference. It is laid out,
A position converter characterized by the above.   The position converter according to claim 1, wherein the angle of the gap is larger than 4 degrees and smaller than 40 degrees.   The position converter according to claim 1 or 2, wherein the diffused light source is composed of a plurality of LED dies, and each of the plurality of LED dies is arranged inside the gap on the circuit board.

Images