JPH0630719U - Optical rotary position detector - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent the eccentricity of the shaft and disk in the optical rotary position detector. [Structure] The optical rotational position detecting device includes a moving member composed of a disk 1 and is attached to a rotating shaft. A spiral slit 1 along the circumferential direction of the surface of the disk 1.
7 are formed. A light source and a light receiving element are arranged so as to face each other with a disk 1 in between. The light receiving element has a longitudinal light receiving surface A arranged along the radial direction of the disk 1, receives the transmitted light from the slit 17 that moves in the radial direction with rotation, and outputs a rotational position detection signal. Output. The disc 1 is attached to the shaft via a plurality of tongues 14 that are radially formed radially inward from the circumferential end surface 13 of the central opening 11. The tongue piece 14 is elastically deformable according to the shaft outer diameter S, and the tip 15 thereof forms a free shaft mounting hole 16 adapted to the shaft outer diameter S.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an optical transmission type rotational position detecting device. More specifically, the present invention relates to a shaft mounting structure for a rotating disk having slits formed in a spiral shape.

[0002]

[Prior art]

 Conventionally, various types of optical rotational position detecting devices are known. For example, Japanese Patent Application Laid-Open No. 60-225024 discloses a structure using a rotating disk having slits formed in a spiral shape. As shown in FIG. 5, the optical rotational position detecting device having this structure is provided with a disc 102 rotatably around a shaft 101 serving as a rotating shaft. The disk 102 is made of a light-shielding material such as a thin metal plate, and a spiral slit 103 is formed on the surface thereof from the center of rotation along the circumferential direction. A light source 104 is fixedly arranged so as to irradiate the disk 102 with incident light. Further, the light receiving element 105 is fixedly arranged at a position directly facing the light source 104 via the disc 102. The light receiving element 105 is provided with a longitudinal light receiving surface 106 arranged along the radial direction of the disc 102, and receives the transmitted light from the slit width portion that moves in the radial direction as the disc 102 rotates. Outputs a rotational position detection signal.

FIG. 6 shows the relationship between the rotation angle of the rotating disk 102 and the detection signal. As the disc rotates, the light passing through the spiral slit moves along the light receiving surface having a long shape. The light receiving element outputs a detection signal according to the light receiving position of the light transmitted through the slit. When the center of rotation and the center of spiral are completely coincident, the light receiving position moves in the radial direction in proportion to the rotation angle. Therefore, the rotation angle and the detection signal have a linear relationship in principle.

[0004]

[Problems to be solved by the device]

 Generally, the detection signal of the position detection device or the potentiometer is mainly evaluated by linearity (absolute linearity) and smoothness. Smoothness is a measure of the smoothness of the detection signal and the deviation from the ideal output. This smoothness may cause a problem in the case of a contact type wire-wound potentiometer, but it hardly causes a problem in a contact type resistance band type or a non-contact type optical type. Therefore, absolute linearity is the most important evaluation item for non-contact potentiometers. The factors that impair the absolute linearity include the shape error of the spiral slit, the mounting error of the rotating disc, the relative displacement of the fixed light source and the rotating disc, and the relative displacement of the fixed light receiving element and the rotating disc. To be Among these factors, the eccentricity of the shaft and rotating disk has a significant effect on absolute linearity. With this eccentricity, the light receiving position of the slit transmitted light is not proportional to the rotation angle, and the linearity is significantly impaired.

Conventionally, the shaft mounting hole provided in the center of the rotating disk has been processed into a circular shape. In order to minimize the above-mentioned eccentricity error, the hole diameter accuracy of the shaft mounting hole was precision machined to the machining limit, and the shaft outer diameter inserted into this mounting hole was also finished with high accuracy. In this way, conventionally, by increasing the dimensional accuracy of each component, the amount of eccentricity between the shaft and the rotating disk has been minimized (for example, 20 μm or less). However, the influence of the eccentricity error on the detection signal is very large, and the linearity is reduced by about 1% at the eccentricity amount of 20 μm. This decrease in linearity is usually close to the permissible limit, and there is a problem that there is almost no margin in design even though parts with the highest level of finishing accuracy are used.

In an optical potentiometer using a rotating disk made of a glass plate material having a predetermined rigidity, the eccentricity can be adjusted by tapping the side edge of the assembled glass disk. . However, when a rotating disk in which a spiral slit is formed by etching on a thin metal plate having a thickness of about 0.1 mm is used, it cannot be adopted because of the possibility of deformation if such eccentricity adjustment is performed.

[0007]

[Means for Solving the Problems]

 In view of the above-mentioned problems of the conventional technique, an object of the present invention is to provide a mounting structure capable of effectively preventing eccentricity when mounting a rotating disk made of, for example, a metal thin plate or the like on a shaft. The following measures have been taken in order to achieve this object. That is, the optical rotational position detecting device according to the present invention is basically composed of a moving member and a fixed light source and a fixed light receiving element arranged on both sides of the moving member. The moving member consists of a disk mounted on a shaft that serves as the center of rotation, and spiral slits are formed along the circumferential direction of the surface. The fixed light source irradiates the moving member with incident light. The light receiving element has a longitudinal light receiving surface arranged along the radial direction of the disk, and receives transmitted light from a slit that moves in the radial direction with rotation, and outputs a rotational position detection signal. In this structure, the disc is mounted on the shaft via a plurality of tongues that are radially formed from the circumferential end surface of the central opening toward the inner side in the radial direction. Preferably, the tip of each tongue has an arc shape. The curvature of this arc shape is set smaller than the outer radius of the shaft. The center of this curvature coincides with the center of the circular central opening formed in the disk.

[0008]

[Action]

 In the present invention, the tongues arranged radially in the central opening of the disk can be elastically deformed according to the outer diameter of the shaft to be inserted, and the arcuate tip of the tongue allows free shaft attachment suitable for the outer diameter of the shaft. A hole is formed. The shaft inserted into the free shaft mounting hole is supported by the plurality of tongues in a balanced state from the surroundings. The tongues are evenly bent, and the shaft and the rotating disk are concentrically connected to each other.

[0009]

【Example】

 Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic plan view showing a rotary disk which is a main component of an optical rotary position detecting device according to the present invention. The disk 1 made of a light-shielding material such as a thin metal plate is attached to a shaft (not shown), and is rotationally displaced with the rotation center O as a reference. The outer peripheral shape of the shaft is shown by a dotted line S. A circular opening 11 is provided at the center of the disk 1, and its center coincides with the center O of the disk 1. A plurality of tongue pieces 14 are radially formed from the circumferential end portion 13 of the opening 11 toward the inner side in the radial direction. In this example, six tongue pieces 14 are arranged at 60 ° intervals, but the number is not limited to this. The tip 15 of each tongue 14 preferably has an arc shape. The curvature of this arc shape is set to be slightly smaller than the outer radius of the shaft outer diameter S. The center of curvature coincides with the center O of the rotating disk 1. Each tongue piece 14 is elastically deformable according to the shaft outer diameter S, and a tip 15 thereof forms a free shaft mounting hole 16 adapted to the shaft outer diameter S.

A spiral slit 17 that gradually expands from the center along the circumferential direction is formed on the peripheral portion of the surface of the disk 1. The slit 17 and the plurality of tongue pieces 14 can be simultaneously formed by etching or the like. This spiral is geometrically drawn with the center O of the disk 1 as a reference, and is represented by r = kθ + ro. In this equation, r represents the radial distance from the center O to the screw, θ represents the rotation angle of the disk 1, ro represents the spiral radial distance when θ is 0, and K is a proportional multiplier. is there. In the figure, ro represents the minimum radial distance at one end of the spiral. The draft angle of the spiral slit 17 defines the rotation angle detection range. As is clear from the above equation, the spiral radial distance r is proportional to the rotation angle θ.

A light receiving element is fixedly arranged on the lower surface side of the disk 1, and is provided with a light receiving surface A having a longitudinal shape along the radial direction. Although not shown, a light source is fixedly arranged on the upper surface side of the disk 1 so as to face the light receiving surface A. The transmitted light that has passed through the slit 17 is incident on the light receiving surface A 1. The light receiving position 18 moves in the radial direction along the light receiving surface A as the disk 1 rotates. For example, in the illustrated state, when the disc 1 rotates clockwise, the light receiving position 18 moves from the inner end side of the light receiving surface A toward the outer end side. As can be understood from the above spiral formula, when the rotation center of the shaft and the center O of the disk 1 coincide, the light receiving position 18 moves in proportion to the rotation angle, so the ideal absolute straight line Sex is obtained. In other words, removing the eccentricity between the shaft and the disk results in ideal linearity.

FIG. 2 is a schematic view showing the work of attaching the disc to the shaft. (A) shows an alignment state, (B) shows a press-fitting process. As shown in the drawing, a plurality of tongue pieces 14 are projected from the central opening of the disk 1, and the tip 15 thereof has an arc shape. The center of curvature of the arc shape 15 coincides with the center of the disk 1. On the other hand, a rotor bush 3 is integrally fixed to the tip of the shaft 2. Therefore, in this case, the shaft outer diameter S described above means the outer diameter of the rotor bush 3. The end surface 31 of the insertion portion of the rotor bush 3 is tapered. The tip 15 of the tongue piece 14 described above is processed into an arc shape so as to just contact the tapered portion. By doing so, the center of the disk 1 and the rotation axis 21 of the shaft 2 coincide with each other, and concentric positioning is possible. If the rotor bush 3 does not have a taper, it will be difficult to position the disc 1 and the shaft 2, and the disc 1 may tilt. Since the tip 15 of the tongue has an arcuate shape, it is easier to support the shaft 2 than in the case of a straight shape, and positioning is stabilized.

From the state shown in (A), pressure is evenly applied to the disk 1 along the direction of the rotation axis 21. As shown in (B), all the tongue pieces 14 are elastically deformed similarly, and the shaft 2 is inserted while maintaining the concentric state. In this way, even if the shaft outer diameter S contains an error due to variations in the finishing accuracy of parts, free mounting holes can be formed that match the individual shafts, so the eccentricity between the shaft 2 and the disk 1 can be eliminated. it can.

FIG. 3 is a schematic view showing a reference example of a mounting structure for a disc and a shaft. In this reference example, after the rotor bush 3 is press-fitted into the shaft 2 to be integrally fixed, the rotor bush 3 is directly inserted into the central circular opening 19 of the disc 1 and fixed by the SE ring 4. If there is no dimensional error between the outer diameter S of the rotor bush 3 and the circular opening 19, eccentricity does not occur. However, in reality, there is a limit to the processing accuracy, so the error cannot be completely eliminated. Therefore, the circular opening 19 of the disk 1 must be set larger than the outer diameter S of the rotor bush by the machining accuracy, so that there is a possibility that eccentricity exists between the disk 1 and the shaft 2 at the time of design. It will be. The machining accuracy of the rotor bush and disk is 0.01 mm and 0.03 mm, respectively, and the maximum eccentricity is 0.02 mm. When the length of the light-receiving surface is 2.5 mm, the absolute linearity decreases by 0.5% when the eccentricity is 0.01 mm. Therefore, the absolute linearity is reduced by 1% at the maximum.

FIG. 4 is a schematic cross-sectional view showing the overall configuration of the optical rotational position detecting device according to the present invention. Bearings 6a and 6b and a light source 7 are attached to the main body 5. The light source 7 is composed of, for example, an LED or the like. The shaft 2 is inserted into the pair of bearings 6a and 6b. A rotor bush 3 is press-fitted into one end of the shaft 2 and abuts against a bearing 6b. The bearing 6a side is fixed by a G ring 8. Further, a coil spring 9 is interposed between the pair of bearings 6a and 6b, and pressure is applied from the inside to press the bearings 6a and 6b outward, respectively. Thereby, the play in the thrust direction of the shaft 2 is reduced. The rotating disk 1 is mounted on the rotor bush 3 and is fixed by the SE ring 4. As described above, a plurality of radially arranged tongue pieces 14 are provided at the center opening of the disk 1 and elastically contact the outer circumference of the rotor bush 3. Further, a spiral slit 17 is formed around the surface of the disk 1. The light source 7 is positioned and fixed to the main body 5 so as to illuminate the slit 17. On the other hand, the light receiving element 10 is mounted on the circuit board 51 on which the signal detection circuit is mounted. The light receiving element 10 is arranged so as to face the light source 7 via the disk 1. The circuit board 51 is fixed to the main body 5 via a board holder 52.

The light emitted from the light source 7 is converted into substantially parallel light by the lens member 71 and illuminates the rotating disk 1. This irradiation light reaches the light receiving surface A of the light receiving element 10 after passing through the spiral slit 17. When the disk 1 rotates, the light receiving position of the slit transmitted light moves on the light receiving surface A along the radial direction. This amount of movement is linear with the rotation angle.

[0017]

[Effect of device]

 As described above, according to the present invention, a plurality of radial tongue pieces are provided at the shaft mounting position of the rotating disk. By attaching the rotating disk to the shaft via this tongue, it is possible to easily ensure the concentricity between the shaft and the disk without increasing the number of assembly steps and the number of parts. Therefore, it is possible to secure the absolute linearity of the detection signal with respect to the rotation angle.

[Brief description of drawings]

FIG. 1 is a plan view showing a rotary disk which is a main component of an optical rotary position detecting device according to the present invention.

FIG. 2 is a schematic view showing an operation of incorporating a rotary disc into a shaft.

FIG. 3 is a schematic diagram showing a reference example of a mounting structure of a rotating disk and a shaft.

FIG. 4 is a cross-sectional view showing an overall configuration of an optical rotational position detecting device according to the present invention.

FIG. 5 is a perspective view showing a conventional optical rotational position detecting device.

FIG. 6 is a graph showing a relationship between a rotation angle of the optical rotary position detecting device and a detection signal.

[Explanation of symbols]

 1 disk 2 shaft 3 rotor bush 5 main body 6a bearing 6b bearing 7 light source 10 light receiving element 11 circular opening 14 tongue piece 15 tip 17 slit A light receiving surface O center S shaft outer diameter

Claims (4)

[Scope of utility model registration request] 1. A rotating member, a moving member formed of a disk mounted on the shaft and having a spiral slit formed along the circumferential direction of the surface thereof, and a fixed light source for irradiating the moving member with incident light. , A fixed light receiving element that has a light receiving surface of a longitudinal shape arranged along the radial direction of the disk and that receives transmitted light from a slit that moves in the radial direction with rotation and outputs a rotational position detection signal. In the optical rotational position detecting device, the disk is mounted on the shaft via a plurality of tongues radially formed from the circumferential end surface of the central opening toward the inner side in the radial direction. Rotational position detector. 2. The optical rotary position detector according to claim 1, wherein each tongue tip has an arc shape. 3. The optical rotary position detecting device according to claim 2, wherein the curvature of the arc shape is smaller than the outer radius of the shaft. 4. The optical rotation according to claim 2, wherein the tongue piece is elastically deformable according to the outer diameter of the shaft, and a free shaft mounting hole adapted to the outer diameter of the shaft is formed by the tip of the tongue. Position detection device.