Rotary encoder

Abstract

To provide a rotary encoder capable of easily adjusting the size of a gap between a disk and a light receiving element.SOLUTION: A rotary encoder 1 comprises: a base 20; a cylindrical hole 21 provided in the base 20; a bearing holding cylinder 22 inserted into the cylindrical hole 21; a bearing 23 held by the bearing holding cylinder 22; a rotating shaft 24 rotatably provided on the base 20 via the bearing 23; a disk 30 provided on the rotating shaft 24; an LED 31 provided on the base 20; and a photodiode 32 provided opposite to the LED 31 across the disk 30, wherein the cylindrical hole 21 has a female thread 25, and the bearing holding cylinder 22 has a male thread 26, and the female thread 25 of the cylindrical hole 21 and the male thread 26 of the bearing holding cylinder 22 are screwed together.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rotary encoder, and more particularly to an optical rotary encoder. [Background technology]

[0002] A known configuration of a conventional rotary encoder is described in Patent Document 1. The rotary encoder described in Patent Document 1 has a rotating shaft to which a disk having an optical pattern is fixed, a bearing provided on the outer diameter of the rotating shaft, and a bearing retaining cylinder provided on the outer diameter of the bearing and holding the bearing. The bearing retaining cylinder is inserted into and fitted into the center hole of a base, and the axial position of the bearing retaining cylinder is adjusted to fine-tune the size of the gap between the disk and the light-receiving element, and then an adhesive is injected between the bearing retaining cylinder and the center hole to fix the position of the disk. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 5-27616 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the rotary encoder described in Patent Document 1, the size of the gap between the disk and the light receiving element is fine-tuned by fitting the bearing retaining cylinder into the central hole and adjusting the axial position of the bearing retaining cylinder. However, factors such as changes in the frictional force between the bearing retaining cylinder and the central hole make it difficult to fine-tune the axial position of the bearing retaining cylinder, which creates the problem of making it difficult to fine-tune the size of the gap between the disk and the light receiving element.

[0005] The present invention has been made to solve such problems, and has as its object to provide a rotary encoder that allows the size of the gap between the disk and the light receiving element to be easily adjusted. [Means for solving the problem]

[0006] In order to solve the above problems, the rotary encoder of the present invention comprises a base, a cylindrical hole provided in the base, a bearing retaining tube inserted into the cylindrical hole, a bearing held in the bearing retaining tube, a rotating shaft rotatable relative to the base via the bearing, a disk provided on the rotating shaft, a light-emitting element provided on the base, and a light-receiving element provided opposite the light-emitting element across the disk, wherein the cylindrical hole has a female threaded portion and the bearing retaining tube has a male threaded portion, and the female threaded portion of the cylindrical hole and the male threaded portion of the bearing retaining tube are screwed together.

[0007] The bearing retainer may further include an adhesive for bonding the cylindrical hole and the bearing retainer tube together. The cylindrical hole may include a metallic cylindrical member disposed therein, and the female thread may be formed inside the metallic cylindrical member. The bearing retainer may also have a nut that screws onto the male thread of the bearing retainer to secure the metallic cylindrical member and the bearing retainer. [Effects of the Invention]

[0008] The rotary encoder of this invention can easily adjust the size of the gap between the disk and the light receiving element by screwing together the female threaded portion of the cylindrical hole provided in the base and the male threaded portion provided in the bearing retaining tube, which holds the bearing that rotatably supports the rotating shaft on which the disk is mounted. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a front cross-sectional view of a rotary encoder according to a first embodiment. [Figure 2] FIG. 10 is a front cross-sectional view of a rotary encoder according to a second embodiment. [Figure 3] FIG. 11 is a front cross-sectional view of a rotary encoder according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Embodiment 1 A rotary encoder according to a first embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a front cross-sectional view of the rotary encoder 1 according to the first embodiment. The rotary encoder 1 is an optical rotary encoder and has a cylindrical base 20. The base 20 has a cylindrical hole 21. A cylindrical bearing retaining tube 22 is provided in the inner diameter portion of the cylindrical hole 21. A bearing 23 is provided in the inner diameter portion of the bearing retaining tube 22. A hollow rotating shaft 24 is provided inside the bearing 23. That is, the bearing retaining tube 22 holds the bearing 23 between the base 20 and the rotating shaft 24. A disk 30 having an optical pattern formed on its surface is attached to the end of the rotating shaft 24. The surface of the disk 30 is arranged so that it is approximately perpendicular to the axial direction of the rotating shaft 24, and the disk 30 is arranged to be rotatable around the rotating shaft 24. In the first embodiment, the end of the rotating shaft 24 in the axial direction where the disk 30 is attached is called the upper side, and the end where the disk 30 is not attached is called the lower side. Furthermore, the base 20, the bearing holder cylinder 22, and the rotary shaft 24 may be made of a metal such as stainless steel, or may be made of a resin.

[0011] A female thread 25 is formed on the inner diameter surface of the cylindrical hole 21. A male thread 26 that can be threaded onto the female thread 25 is formed on the outer diameter surface of the bearing retaining tube 22. An LED 31 is mounted on an LED substrate 31a provided on the base 20 on the underside of the disk 30. A photodiode 32 is mounted on a photodiode substrate 32a on the upper side of the disk 30, facing the LED 31 along the axial direction. The LED 31 is an LED that emits light of any wavelength, such as infrared or visible light, and the photodiode 32 is a photodiode that can detect light of the wavelength emitted by the LED 31. A gap A is provided between the lower surface of the photodiode 32 and the upper surface of the disk 30. The LED 31 constitutes a light-emitting member, and the photodiode 32 constitutes a light-receiving member.

[0012] The rotary encoder 1 also has a cylindrical case 40 that houses the base 20, bearing retaining cylinder 22, bearing 23, rotating shaft 24, disk 30, LED 31, and photodiode 32. A mounting nut 41 is provided below the bearing 23 and is threaded onto a threaded portion formed on the lower end of the rotating shaft 24. The mounting nut 41 comes into contact with the bearing 23 and is threaded onto the rotating shaft 24 to prevent the rotating shaft 24 from moving in the axial direction.

[0013] Next, a method of assembling the rotary encoder 1 according to the first embodiment will be described. First, the photodiode substrate 32a and the photodiode 32 are provided inside the case 40. Next, the disk 30 is fixed to the upper end of the rotating shaft 24. Next, the disk 30 and the rotating shaft 24 are housed inside the case 40. Next, the base 20, the LED substrate 31a, and the LED 31 are housed inside the case 40. Next, the bearing 23 is attached to the inner diameter portion of the bearing retaining tube 22, and the bearing retaining tube 22 is inserted into the cylindrical hole 21 of the base 20. As a result, the inner diameter surface of the upper part of the cylindrical hole 21 and the outer diameter surface of the upper part of the bearing retaining tube 22 rub against each other as the bearing retaining tube 22 is inserted into the cylindrical hole 21. Next, by rotating the bearing retaining tube 22 in the screw tightening direction, the female threaded portion 25 in the lower part of the cylindrical hole portion 21 and the male threaded portion 26 in the lower part of the bearing retaining tube 22 are screwed together, and the bearing retaining tube 22 is inserted into the cylindrical hole portion 21.

[0014] The bearing retainer tube 22 is inserted into the cylindrical hole 21 while the female thread 25 at the lower portion of the cylindrical hole 21 and the male thread 26 at the lower portion of the bearing retainer tube 22 are threadedly engaged. Therefore, by adjusting the rotation distance of the bearing retainer tube 22, the size of the gap A between the underside of the photodiode 32 and the upper surface of the disk 30 can be easily fine-tuned. Therefore, while the cylindrical hole 21 and the bearing retainer tube 22 are threadedly engaged, light is emitted from the LED 31. While checking the output of the photodiode 32 corresponding to the light detected by the photodiode 32, the rotation distance of the bearing retainer tube 22 is adjusted to fine-tune the size of the gap A between the photodiode 32 and the upper surface of the disk 30. After appropriately adjusting the size of the gap A between the photodiode 32 and the upper surface of the disk 30, a mounting nut 41 is threadedly engaged with the lower end of the rotating shaft 24 to fix the rotating shaft 24 so that it does not move in the axial direction. In this manner, the rotary encoder 1 can be assembled.

[0015] In conventional rotary encoders, the size of the gap between the disc and the light-receiving element mounted on the rotating shaft is fine-tuned by fitting a bearing retaining cylinder into the cylindrical hole of the base and adjusting the axial position of the bearing, but factors such as changes in the frictional force between the bearing retaining cylinder and the center hole make it difficult to fine-tune the axial position of the bearing retaining cylinder, which in turn makes it difficult to fine-tune the gap between the disc and the light-receiving element. In contrast, in the rotary encoder 1 according to the first embodiment, the base 20 and bearing 23 are fixed by threading the female thread portion 25 of the cylindrical hole 21 into the male thread portion 26 of the bearing retaining cylinder 22, which has the advantage of facilitating fine adjustment of the axial position of the disc 30 and fine adjustment of the gap A between the photodiode 32 and the upper surface of the disc 30.

[0016] Furthermore, in conventional rotary encoders, the bearing retaining tube is fitted into the cylindrical hole of the base, and the size of the gap between the disc and the light-receiving element is adjusted, and then the base and the bearing retaining tube are adhesively fixed together. This requires a lot of labor for adhesive during manufacturing of the rotary encoder, and poor adhesion can lead to misalignment between the base and the bearing. In contrast, in the rotary encoder 1 according to the first embodiment, the base 20 and the bearing retaining tube 22 are fixed together by threading the female thread portion 25 of the cylindrical hole 21 into the male thread portion 26 of the bearing retaining tube 22. This eliminates the need to adhesively fix the cylindrical hole 21 and the bearing retaining tube 22 together, thereby reducing the labor required for assembling the rotary encoder. Furthermore, by not adhesively fixing the cylindrical hole 21 and the bearing retaining tube 22 together, the fixation between the base 20 and the bearing retaining tube 22 can be released as needed, and the rotary encoder 1 can be easily disassembled.

[0017] Furthermore, in conventional rotary encoders, a flange portion may be provided at the lower end of the cylindrical hole of the base to prevent the bearing retainer tube from falling out of the cylindrical hole when the bearing retainer tube is fitted into the cylindrical hole of the base. However, in this case, there is a problem in that more man-hours are required to provide the flange portion when manufacturing the rotary encoder. In contrast, in the rotary encoder according to the first embodiment, the base 20 and the bearing 23 are fixed by threading the female thread portion 25 of the cylindrical hole 21 into the male thread portion 26 of the bearing retainer tube 22. This eliminates the need to form a flange portion at the lower end of the cylindrical hole 21, and reduces the man-hours required to manufacture the rotary encoder 1.

[0018] In addition, in conventional rotary encoders, the bearing retainer tube is inserted into and fitted to the cylindrical hole of the base, the position of the bearing retainer tube relative to the base is adjusted, and the size of the gap between the photodiode and the upper surface of the disc is adjusted. Then, a fixing screw is threaded into the base along the radial direction of the disc, and the tip of the fixing screw abuts against the bearing retainer tube, thereby screwing and fixing the bearing retainer tube to the base. In such conventional rotary encoders, the fixing screw is inserted along the radial direction of the disc, and its tip abuts against the bearing retainer tube, which causes a problem of radial pressure on the bearing retainer tube and the rotating shaft, resulting in eccentricity of the disc. In contrast, in the rotary encoder 1 according to the first embodiment, the base 20 and the bearing retainer tube 22 are fixed by threading the female thread portion 25 of the cylindrical hole 21 into the male thread portion 26 of the bearing retainer tube 22, which has the advantage of preventing eccentricity of the disc 30.

[0019] As described above, the rotary encoder 1 according to the first embodiment comprises a base 20, a cylindrical hole 21 provided in the base 20, a bearing retaining tube 22 inserted into the cylindrical hole 21, a bearing 23 held by the bearing retaining tube 22, a rotating shaft 24 rotatably mounted on the base 20 via the bearing 23, a disk 30 mounted on the rotating shaft 24, an LED 31 mounted on the base 20, and a photodiode 32 positioned opposite the LED 31 across the disk 30, and the cylindrical hole 21 has a female threaded portion 25, and the bearing retaining tube 22 has a male threaded portion 26, and the female threaded portion 25 of the cylindrical hole 21 and the male threaded portion 26 of the bearing retaining tube 22 are threadedly engaged with each other, so that the size of the gap A between the disk 30 and the photodiode 32 can be easily adjusted.

[0020] Embodiment 2 Next, a rotary encoder according to a second embodiment of the present invention will be described. In the following embodiments, the same reference symbols as those in Fig. 1 designate the same or similar components as those in the first embodiment, and detailed descriptions thereof will be omitted. The rotary encoder according to the second embodiment is the rotary encoder according to the first embodiment, except that an adhesive is injected between the cylindrical hole and the bearing retaining tube. 2 is a front cross-sectional view of a rotary encoder 1a according to the second embodiment. An adhesive injection section 50 is provided between the cylindrical hole 21 of the rotary encoder 1a and the bearing retaining tube 22. An adhesive is injected into the adhesive injection section 50. The adhesive injected into the adhesive injection section 50 can be any suitable adhesive, such as an epoxy resin adhesive. The other configurations are the same as those of the first embodiment.

[0021] Next, a method for assembling the rotary encoder 1a of the second embodiment will be described. When the bearing retaining tube 22 is inserted into the cylindrical hole 21 of the base 20, the female thread 25 at the lower part of the cylindrical hole 21 is threadedly engaged with the male thread 26 at the lower part of the bearing retaining tube 22, the rotation distance of the bearing retaining tube 22 is adjusted, and the size of the gap A between the photodiode 32 and the upper surface of the disk 30 is finely adjusted. The steps are the same as those in the first embodiment. Next, after adjusting the gap A between the photodiode 32 and the upper surface of the disk 30 to an appropriate size, adhesive is injected into the adhesive injection part 50 between the cylindrical hole 21 and the bearing retaining tube 22 to bond and fix the cylindrical hole 21 and the bearing retaining tube 22. Next, a mounting nut 41 is threaded onto the lower end of the rotating shaft 24 to fix the rotating shaft 24 so that it does not move in the axial direction.

[0022] As such, the rotary encoder of this second embodiment has an adhesive that bonds the cylindrical hole portion 21 and the bearing retaining tube 22, and therefore can more reliably prevent the size of the gap A between the photodiode 32 and the disk 30 from fluctuating after adjusting the size of the gap A.

[0023] Embodiment 3 Next, a rotary encoder according to a third embodiment of the present invention will be described. The rotary encoder according to the third embodiment differs from the rotary encoder according to the first embodiment in that an inserter is provided inside the cylindrical hole 21 of the base 20. FIG. 3 is a front cross-sectional view of a rotary encoder 1b according to the third embodiment. The base 20 of the third embodiment is made of a resin material. An inserter 27, which is a cylindrical member made of a metal such as stainless steel, is provided inside the cylindrical hole 21 of the base 20 and is molded integrally with the base 20. The inserter 27 is provided so that its axial direction coincides with the axial direction of the rotating shaft 24. A female thread 25 is formed on the inner diameter surface of the lower part of the inserter 27, and this female thread 25 is threadedly engaged with the male thread 26 of the bearing retaining tube 22. An inserter nut 28, which is threadedly engaged with the male thread 26 of the bearing retaining tube 22, is provided below the inserter 27. The inserter 27 constitutes a metallic cylindrical member. The other configurations are the same as those of the first embodiment.

[0024] Next, a method of assembling the rotary encoder 1b of the third embodiment will be described. First, the photodiode substrate 32a and the photodiode 32 are provided inside the case 40. Next, the disk 30 is fixed to the upper end of the rotating shaft 24. Next, the disk 30 and the rotating shaft 24 are housed inside the case 40. Next, the base 20 having the inserter 27 integrally molded in the cylindrical hole 21, the LED substrate 31a, and the LED 31 are housed inside the case 40.

[0025] Next, the bearing 23 is attached to the inner diameter portion of the bearing retainer tube 22, and the bearing retainer tube 22 is inserted into the inserter 27. This fits the bearing 23 onto the outer periphery of the rotating shaft 24. At this time, the inner diameter surface of the upper portion of the inserter 27 rubs against the outer diameter surface of the upper portion of the bearing retainer tube 22 as the bearing retainer tube 22 is inserted into the inserter 27. Next, by rotating the bearing retainer tube 22 in the screw tightening direction, the female thread portion 25 of the lower portion of the inserter 27 and the male thread portion 26 of the lower portion of the bearing retainer tube 22 of the bearing 23 are threadedly engaged with each other, and the bearing retainer tube 22 is inserted into the inserter 27.

[0026] Because the bearing retainer tube 22 is inserted into the cylindrical hole 21 while the female thread portion 25 on the lower portion of the inserter 27 and the male thread portion 26 on the lower portion of the bearing retainer tube 22 are threadedly engaged, adjusting the rotation distance of the bearing retainer tube 22 makes it possible to fine-tune the size of the gap A between the underside of the photodiode 32 and the upper surface of the disk 30. Therefore, while the inserter 27 and the bearing retainer tube 22 are threadedly engaged, light is emitted from the LED 31, and the rotation distance of the bearing retainer tube 22 is adjusted while checking the output of the photodiode 32 corresponding to the light detected by the photodiode 32, thereby fine-tuning the size of the gap A between the photodiode 32 and the upper surface of the disk 30. Once the gap A between the photodiode 32 and the upper surface of the disk 30 has been adjusted to an appropriate size, an inserter nut 28 is threadedly engaged with the lower side of the inserter 27 to fix the bearing retainer tube 22 to the inserter 27 so as not to move axially. Next, a mounting nut 41 is screwed onto the lower end of the rotary shaft 24 to fix the rotary shaft 24 so that it does not move in the axial direction. In this way, the rotary encoder 1b can be assembled.

[0027] In the third embodiment, the base 20 and the bearing retainer tube 22 are joined by threading the female threaded portion 25 of the metal inserter 27, which is integrally molded with the resin base 20, onto the male threaded portion 26 of the bearing retainer tube 22. Therefore, compared to a case where the female threaded portion of the base is made of resin and the male threaded portion of the bearing retainer tube are directly threaded together, in the third embodiment, there is less play between the female threaded portion 25 and the male threaded portion 26 and dimensional accuracy is increased, allowing for more accurate adjustment of the gap A between the photodiode 32 and the upper surface of the disk 30. Furthermore, because the inserter 27 is made of metal, the bearing retainer tube 22 is less likely to slip relative to the inserter 27 and fall off. Another advantage is that no adhesive is required between the inserter 27 and the bearing retainer tube 22.

[0028] In this way, in the rotary encoder 1b of this embodiment 3, the cylindrical hole portion 21 includes an inserter 27 provided therein, and the female thread portion 25 is formed inside the inserter 27. Therefore, by threading the female thread portion 25 of the metal inserter 27 into the male thread portion 26 of the bearing retaining tube 22 of the bearing 23, the size of the gap A between the photodiode 32 and the upper surface of the disk 30 can be adjusted with greater precision.

[0029] Furthermore, the rotary encoder 1b has an inserter nut 28 that screws onto the male threaded portion 26 of the bearing retaining tube 22 and secures the inserter 27 to the bearing retaining tube 22, thereby more securely connecting the inserter 27 to the bearing retaining tube 22 and preventing the bearing retaining tube 22 from falling off.

[0030] Although the inserter 27 of the third embodiment is made of stainless steel, it may be made of any other type of metal, such as brass.

[0031] In the third embodiment, an appropriate adhesive may be injected into the space between the inserter 27 and the bearing retainer tube 22 as an adhesive injection section, if necessary. This allows the inserter 27 and the bearing retainer tube 22 to be bonded more firmly.

[0032] Furthermore, in the first to third embodiments of the present application, an LED 31 is used as the light-emitting element and a photodiode 32 is used as the light-receiving element, but this is not limited to this, and other types of light-emitting elements may be used as the light-emitting element instead of the LED 31, and other types of light-receiving elements, such as a phototransistor, may be used as the light-receiving element instead of the photodiode 32.

[0033] Furthermore, the rotary encoders 1, 1a, and 1b according to the first to third embodiments of the present invention are optical rotary encoders, but the configurations of the first to third embodiments may also be used for magnetic rotary encoders.

[0034] Furthermore, the components included in the first to third embodiments of the present invention and the components included in the variations thereof can be used in appropriate combination.

[0035] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims. [Explanation of symbols]

[0036] 20 Foundation 21 Cylindrical hole 22 Bearing retainer tube 23 Bearings 24 Rotation Axis 25 Female thread 26 Male thread 27 Inserter (metallic inner cylindrical member) 28 Inserter nut (nut) 30 discs 31 LED (light-emitting component) 32 Photodiode (light receiving element)

Claims

1. A base (20); A cylindrical hole (21) provided in the base (20); a bearing retaining tube (22) inserted into the cylindrical hole (21); a bearing (23) held in the bearing holding tube (22); a rotation shaft (24) rotatably provided with respect to the base (20) via the bearing (23); a disk (30) provided on the rotating shaft (24); a light-emitting member (31) provided on the base (20); a light receiving member (32) provided opposite the light emitting member across the disk (30); Equipped with The cylindrical hole (21) has an internal thread (25), The bearing retaining cylinder (22) has a male thread portion (26), The female threaded portion (25) of the cylindrical hole (21) and the male threaded portion (26) of the bearing retaining tube (22) are threadedly engaged with each other.

2. 2. The rotary encoder according to claim 1, further comprising an adhesive for bonding the cylindrical hole (21) and the bearing retaining tube (22).

3. 2. The rotary encoder according to claim 1, wherein the cylindrical hole portion (21) includes a metallic cylindrical member (27) provided therein, and the female thread portion (25) is formed inside the metallic cylindrical member (27).

4. 4. The rotary encoder according to claim 3, further comprising a nut (28) that screws onto the male threaded portion (26) of the bearing retaining tube (22) and secures the metal cylindrical member (27) and the bearing retaining tube (22).

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