JPH0640812U - Optical rotary position detector - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] In an optical rotational position detector, prevents eccentricity between the shaft and the disk, and suppresses elastic strain deformation of the disk. [Structure] A spiral slit 17 is formed along the circumferential direction of the surface of the thin disk 1. A light source and a light receiving element are arranged to face each other via the disc 1. 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 elastic tongues 14 radially formed from the circumferential end surface 13 of the central opening 11 toward the inner side in the radial direction. The tongue piece 14 is elastically deformable according to the shaft outer diameter S, and the tip 15 forms a free shaft mounting hole 16 adapted to the shaft outer diameter S. A strain absorbing hole 12 is provided at the base of each elastic tongue piece 14 to absorb the elastic deformation of the tongue piece 14 and prevent the tongue piece 14 from expanding to the slit 17.

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 thin plate disk having a predetermined slit pattern.

[0002]

[Prior art]

 Conventionally, various types of optical rotational position detecting devices are known. For example, Japanese Patent Laid-Open No. Sho 60-225024 discloses a structure using a rotating thin plate disk having slits formed in a spiral pattern. As shown in FIG. 6, in the optical rotary position detecting device having this structure, a disc 102 is attached so as to be rotatable around a shaft 101 serving as a rotary 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 along the circumferential direction from the center of rotation. A light source 104 is fixedly arranged so as to face the disk 102 and irradiate incident light. Further, a 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 has a long-shaped light-receiving surface 106 arranged along the radial direction of the disk 102, and receives and rotates the transmitted light from the slit width portion that moves in the radial direction as the disk 102 rotates. Outputs a position detection signal.

FIG. 7 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 the contact type antibody type or 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 Of 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 remarkably impaired. Conventionally, the shaft mounting hole provided in the center of the rotating disk was machined into a perfect circle. In order to minimize the above-mentioned eccentricity error, the hole diameter accuracy of the shaft mounting hole was machined to the machining limit, and the shaft outer diameter inserted into this mounting hole was also processed with high accuracy. In this way, conventionally, by increasing the dimensional accuracy of each component, the amount of eccentricity between the shaft and the rotary disk has been suppressed to a minimum (for example, 20 μm or less). However, the influence of the eccentricity error on the detection signal is very large, and a linearity decrease of about 1% is brought about by the eccentricity amount of 10 μm. This decrease in linearity is usually close to the permissible limit, and there is a problem that there is almost no margin in the design despite the use of parts with the highest level of finishing accuracy. In an optical potentiometer using a rotating disc made of a glass plate material having a predetermined rigidity, the eccentricity can be adjusted by tapping the side end of the assembled glass disc. However, the thickness is 0. If a rotating disk with a spiral slit pattern formed on a thin metal plate of about 1 mm by etching is used, such eccentricity adjustment may cause plastic deformation and cannot be used. It is also possible to adjust the eccentricity by adjusting the outer diameter of each shaft to the shaft mounting hole, but this is not practical because the cost required for machining the shaft increases.

[0005]

[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. At the same time, the purpose is to suppress the elastic strain deformation that occurs when attaching the thin metal disk to the shaft. The following measures were taken to achieve this purpose. That is, the optical rotational position detecting device according to the present invention comprises, as a basic constituent element, 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 is a thin disk mounted on a shaft that serves as the center of rotation, and has a predetermined slit pattern formed along the circumferential direction of the surface thereof. This slit pattern has, for example, a spiral shape. The fixed light source irradiates the moving member with incident light. The light-receiving element has a light-receiving surface arranged along the disk and receives transmitted light from a slit pattern that moves with rotation and outputs a rotation position detection signal. When the slit pattern has a spiral shape, the light-receiving surface has a long shape along the radial direction of the disk, and receives transmitted light from the spiral slit width portion that moves in the radial direction with rotation.

In this structure, the thin disk is mounted on the shaft via a plurality of elastic tongues that are radially formed inward from the circumferential end surface of the central opening. The tip of each elastic tongue has an arc shape, and the radius of the inscribed circle is set to be smaller than the outer radius of the shaft. The center of this inscribed circle coincides with the center of the circular central opening formed in the thin disk. Further, as a feature of the present invention, a strain absorbing hole is provided in the thin disk along the base of the radial elastic tongue. Preferably, each elastic tongue itself is also provided with additional strain absorbing holes.

The basic configuration concept of the present invention is not limited to the above-described optical rotational position detecting device, but includes a widely rotating shaft and a thin disk having a predetermined pattern mounted on the shaft. Can be applied to the rotating body. That is, the thin disk is mounted eccentrically on the shaft through a plurality of elastic tongues that are formed radially inward from the circumferential end surface of the central opening, and the base of the radial elastic tongues is attached. It is characterized by the provision of absorption holes for strain generated by elastic deformation along the.

[0008]

[Action]

 In the present invention, the elastic tongues arranged radially in the central opening of the thin disk can be elastically deformed according to the outer diameter of the inserted shaft, and the tip having an arc shape is adapted to the outer diameter of the shaft. A free shaft mounting hole is formed. The shaft inserted into the free shaft mounting hole is supported by the plurality of elastic tongues in a balanced state from the surroundings. The elastic tongues are evenly bent, and the shaft and the rotating disk are concentrically connected to each other.

Further, according to the present invention, the strain absorbing holes are provided in the thin disk along the base of the radial elastic tongue. The strain absorbing holes are for effectively absorbing the strain deformation of the elastic tongue that occurs when the thin disk is attached to the shaft, and preventing the slit pattern from being adversely affected. If the strain generated in the central elastic tongue is transmitted to the peripheral portion, a step is generated between the inner end and the outer end of the spiral slit, and an error appears in the detection signal.

[0010]

【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 is made of a light-shielding material such as a thin metal plate and has a plate thickness of, for example, about 0.1 mm and a diameter dimension of, for example, about 20 mm. The disc 1 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 in the center of the disk 1, and its center coincides with the center O of the disk 1. A plurality of elastic tongues 14 are radially formed from the circumferential end 13 of the opening 11 toward the inner side in the radial direction. In this example, the six elastic 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 radius of curvature and inscribed circle of this arc shape is set to be slightly smaller than the outer radius of the outer shape of the shaft. The center of the inscribed circle coincides with the center O of the rotary disk 1. Each tongue piece 14 is elastically deformable according to the shaft outer diameter S, and its tip 15 forms a free shaft mounting hole 16 adapted to the shaft outer diameter S.

The strain absorbing holes 12 are provided along the base of the elastic tongue pieces 14 which are radially arranged. The strain absorbing hole 12 effectively absorbs the elastic strain of the tongue piece 14 that occurs when it is engaged with the shaft, and prevents the deformation from expanding toward the periphery of the disk 1. In this example, the strain absorbing holes 12 are arranged in a line along the circumferential direction so as to surround the circular opening 11. However, the present invention is not limited to this, and a plurality of rows of strain absorbing holes 12 may be concentrically provided.

On the peripheral portion of the surface of the disk 1, a spiral slit 17 is formed which gradually expands from the center along the circumferential direction. The slit 17, the plurality of tongue pieces 14, and the strain absorbing hole 12 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 formula, r represents a radial distance from the center O to the spiral, θ represents a rotation angle of the disk 1, ro represents a spiral radial distance when θ 1 is 0, and K is a proportional constant. 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 1.

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, when the disk 1 rotates clockwise in the illustrated state, 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 are coincident with each other, the light receiving position 18 moves in proportion to the rotation angle, and thus the ideal absolute linearity is obtained. 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 figure, a plurality of elastic tongues 14 project from the central opening of the disk 1, and the tip 15 thereof has an arc shape. The center of the inscribed circle 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 aforementioned shaft outer diameter S means the outer diameter of the rotor bush 3. The end surface 31 of the insertion portion of the rotor bush 3 is processed into a tapered shape. The distal end 15 of the elastic tongue 14 described above is processed into an arc shape so as to just contact the tapered portion. By doing so, the center of the disc 1 and the rotation axis 21 of the shaft 2 are aligned with each other, and the positions can be aligned concentrically. If the rotor bush 3 does not have a taper, it becomes 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, the shaft 2 can be supported more easily than in the case of a straight shape, and the 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 the parts, free mounting holes can be formed that match the individual shafts, so it is possible to eliminate the eccentricity between the shaft 2 and the disk 1. it can.

In addition, as shown in (B), each tongue piece 14 is connected to the peripheral portion of the disk 1 via the strain absorbing hole 12. Therefore, even if the tongue piece 14 is elastically deformed in the press-fitting process, there is no fear that the strain is effectively absorbed by the absorption hole 12 and propagated to the peripheral portion of the disk 1. If the strain absorbing hole 12 were not provided, the strain would be concentrated on the root of the tongue due to the deformation of the elastic tongue 14. Furthermore, this distortion is not absorbed at all, and is propagated to the entire disk. Therefore, when the spiral slit is formed on the disk as shown in FIG. 1, a slight step is generated between the inner end side and the outer end side, and there is a possibility that the detection signal may include an error. . Also, when the elastic strain disappears due to stress relaxation due to temperature rise, etc., the slit shape changes subtly.

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 0.1% when the amount of eccentricity is 0.01 mm. Therefore, the absolute linearity is reduced by 2% 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. A thin disk 1 is mounted on the rotor bush 3 and is fixed by an SE ring 4. As described above, a plurality of elastic tongues 14 arranged in a radial pattern are provided in the central opening of the disk 1, and elastically contact the outer circumference of the rotor bush 3. A spiral slit 17 is formed around the surface of the disk 1. Further, the strain absorbing hole 12 is provided at the base of each elastic tongue piece 14 so that the elastic deformation of the tongue piece 14 does not reach the slit 17 portion. 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 detection signal circuit is mounted. The light receiving element 10 is arranged so as to face the light source 7 via the disc 1. The circuit board 51 is fixed to the main body 5 via a board holder 52.

The light emitted from the disk 7 is made into substantially parallel light by the lens member 71, and irradiates 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.

Finally, another embodiment of the optical rotational position detecting device according to the present invention will be described with reference to FIG. FIG. 5 shows a plan view of the rotating disk, which basically has the same structure as that of the rotating disk shown in FIG. 1, and corresponding parts are designated by corresponding reference numerals to facilitate understanding. . The difference from the embodiment shown in FIG. 1 is that each elastic tongue 14 itself is provided with an additional strain absorbing hole 12a. The additional strain absorbing hole 12a adjusts the elastic force of the tongue piece 14 and absorbs the strain deformation to some extent. In this example, the strain absorbing hole 12 provided at the base of each tongue piece 14 and the additional strain absorbing hole 12a provided in the tongue piece itself are connected in two stages to more effectively absorb the elastic deformation. . A plurality of beams 17a are provided substantially in the center of the draft angle range of the spiral slit 17, and the inner region and the outer region separated by the slit 17 are connected to each other to prevent the bending deformation of the rotary disk 1. To prevent.

[0021]

[Effect of device]

 As described above, according to the present invention, a plurality of radial elastic tongues are provided at the shaft mounting position of the rotating disk. By attaching the rotating disk to the shaft via this tongue piece, it is possible to easily ensure the concentricity of 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. In addition, a strain absorption hole is provided at the base of the elastic tongue, preventing elastic deformation that occurs when it is attached to the shaft from expanding to the slit, and stabilizing the detection signal. Is obtained. The basic concept of the present invention is not limited to the above-described optical rotary position detecting device, but has a wider range of application. That is, it can be generally applied to a rotating body composed of a rotating shaft and a thin plate disk mounted on the shaft and having a predetermined pattern, and has a great industrial utility value.

[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 plan view showing a rotary disk used in another embodiment of the optical rotational position detecting device according to the present invention.

FIG. 6 is a perspective view showing a conventional optical rotational position detecting device.

FIG. 7 is a graph showing a relationship between a rotation angle and a detection signal of the optical rotary position detector.

[Explanation of symbols]

 1 thin plate 2 shaft 3 rotor bush 5 main body 6a bearing 6b bearing 7 light source 10 light receiving element 11 circular opening 12 strain absorption hole 12a additional strain absorption hole 14 elastic tongue 15 tip 17 slit A light receiving surface O center S shaft outer diameter

Claims (3)

[Scope of utility model registration request] 1. A rotating member, a moving member having a thin disk mounted on the shaft and having a slit pattern formed along the circumferential direction of the surface thereof, and a fixed light source for irradiating the moving member with incident light. In an optical rotational position detection device comprising a fixed light receiving element that receives transmitted light from a slit pattern that moves with rotation and has a light receiving surface that is arranged along a thin disk, and that outputs a rotational position detection signal, The thin disk is mounted on the shaft through a plurality of elastic tongues that are formed radially inward from the circumferential end surface of the central opening, and the tip of each elastic tongue has an arc shape. An optical rotational position detecting device having a radius of an inscribed circle set to be smaller than an outer radius of the shaft, and a strain absorbing hole provided in a thin disk along the root of the radial elastic tongue. 2. The optical rotary position detecting device according to claim 1, wherein each elastic tongue itself is provided with an additional strain absorbing hole. 3. A rotating body comprising a rotating shaft and a thin disk mounted on the shaft and having a predetermined pattern, wherein the thin disk is radially formed from a circumferential end surface of a central opening toward a radial inner side. A rotary body, which is eccentrically mounted on the shaft via a plurality of elastic tongues, and is provided with an absorption hole for strain generated by elastic deformation along the root of the radial elastic tongue.