Encoder, motor, and encoder adjustment method

Abstract

This encoder includes a rotary disk, a protruding part provided coaxially with a shaft at one end of the shaft, and a boss that supports the rotary disk between the rotary disk and the one end of the shaft. A through-hole in which a screw thread is formed is formed on the inner circumferential surface of the boss. After the boss is engaged with the protruding part of the shaft, an adjustment tool is screwed into the through-hole of the boss through an opening formed in the rotary disk, and the position of the boss on the center axis of the shaft is adjusted using the adjustment tool.

Description

Encoder, motor, and encoder adjustment method

[0001] The present disclosure relates to an encoder, a motor, and an encoder adjustment method.

[0002] Encoders are used to detect the rotation speed of a rotating body, such as the output shaft of a motor. Optical encoders include a light source, a light receiving unit, and a rotating disk arranged between the light source and the light receiving unit (see, for example, Patent Document 1 and Patent Document 2). As is well known, the rotating disk, on which a plurality of slits are formed, is arranged coaxially with the rotating body or arranged to rotate synchronously with the rotating body.

[0003] Japanese Utility Model Application Publication No. 04-063020 Japanese Patent Application Publication No. 2012-141248

[0004] To improve the detection accuracy of the encoder, it is necessary to maintain an appropriate and constant gap between the rotating disk and the light receiving unit, and to suppress variations in the height of the rotating disk.Furthermore, it is also necessary to simplify the encoder configuration and reduce the encoder's weight.

[0005] There is a demand for an encoder, a motor, and an encoder adjustment method with a simple configuration that can improve detection accuracy.

[0006] According to a first aspect of the present disclosure, there is provided an encoder comprising: a rotating disk having at least one slit that transmits light output from a light source; a protrusion provided coaxially with one end of a shaft that is to rotate integrally with the rotating disk; and a boss that is disposed between the rotating disk and the one end of the shaft and supports the rotating disk, wherein a through hole with a thread formed on the inner peripheral surface of the boss is formed coaxially with the shaft; and after the boss is engaged with the protrusion of the shaft, an adjustment tool is passed through an opening formed in the rotating disk and screwed into the through hole of the boss, and the adjustment tool is used to adjust the position of the boss on the central axis of the shaft.

[0007] The objects, features, and advantages of the present disclosure will become more apparent from the following description of the embodiments taken in conjunction with the accompanying drawings.

[0008] FIG. 1 is an axial cross-sectional view of a motor including an encoder according to the present disclosure. FIG. 2 is an axial cross-sectional view of an encoder according to a first embodiment. FIG. 3 is a partial axial cross-sectional view of an encoder according to a first embodiment. FIG. 4 is a partial axial cross-sectional view of an encoder according to a second embodiment. FIG. 5 is a partial axial cross-sectional view of an encoder according to a fifth embodiment. FIG. 6 is a flowchart showing the processing of FIGS. 3A to 3E. FIG. 7 is a partial axial cross-sectional view of an encoder according to a second embodiment. FIG. 8 is a partial axial cross-sectional view of an encoder according to a prior art.

[0009] Embodiments of the present disclosure will now be described with reference to the accompanying drawings. Corresponding components will be designated by common reference numerals throughout the drawings. FIG. 1 is an axial cross-sectional view of a motor equipped with an encoder according to the present disclosure. As shown in FIG. 1 , the motor 1 includes a stator 9 and a rotor 10 rotatably supported by the stator 9. A first bearing 7 and a second bearing 8 are disposed on the inner circumferential surface of the stator 9. A shaft 5 that passes through the rotor 9 is rotatably supported by the stator 9 via the first bearing 7 and the second bearing 8. An encoder 6 that detects the rotation speed of the shaft 5 is attached to one end of the stator 9. The following describes the encoders 6, 6a, 6b, and 6c attached to the shaft 5 of the motor 1; however, the encoder 6 may also be attached to a rotating body other than the shaft 5 of the motor 1.

[0010] 2 is an axial cross-sectional view of the encoder 6a according to the first embodiment. The encoder 6a mainly includes a bottomed housing 11, a lid 12 that engages with the housing 11, a rotary disk 20 disposed between the housing 11 and the lid 12, and a boss 30 that connects the rotary disk 20 to the shaft 5.

[0011] As can be seen from FIG. 2 , an opening is formed in the bottom of the housing 11. A light source 28 is disposed in the bottom of the housing 11, and a light receiving unit 29 is disposed on the inner surface of the lid 12 at a position corresponding to the light source 28. The positional relationship between the light source 28 and the light receiving unit 29 may be reversed. Furthermore, the encoder 6 a does not necessarily include the housing 11 and the lid 12. Furthermore, as is well known, the rotating disk 20 has at least one slit 25 formed in its radial direction. Light output from the light source 28 reaches the light receiving unit 29 through the at least one slit 25.

[0012] A protrusion 4 is provided at the tip of the shaft 5, coaxially with the shaft 5. The protrusion 4 is preferably cylindrical and has a diameter smaller than that of the shaft 5. A boss 30 is engaged around the protrusion 4.

[0013] The boss 30 includes a support portion 31 that supports one surface of the rotary disk 20, and an enclosing portion 32 that extends from the support portion 31 and encloses the outer circumferential surface of the protrusion 4. Strictly speaking, the enclosing portion 32 of the boss 30 is press-fit into the protrusion 4, thereby engaging the boss 30 with the protrusion 4 of the shaft 5. The boss 30 is preferably formed from metal or hard resin. The height of the enclosing portion 32 at the central axis O of the shaft 5 is preferably greater than the height of the protrusion 4. The lower end of the enclosing portion 32 can abut against the end surface of the shaft 5.

[0014] 2, in order to support the lower surface of the rotary disk 20, the diameter of the support portion 31 is preferably larger than the diameter of the surrounding portion 32. An opening 21 is formed in the center of the rotary disk 20, and a through hole 33 is formed in the center of the support portion 31 of the boss 30. The opening 21 and the through hole 33 are preferably coaxial with the central axis O of the shaft 5. In addition, the diameter of the opening 21 is preferably larger than the diameter of the through hole 33. As will be described later, a screw thread is formed on the inner peripheral surface of the through hole 33 of the boss 30.

[0015] 3A to 3E are partial axial cross-sectional views of the encoder, and Fig. 3F is a flowchart showing the processing of Fig. 3A to 3E. Hereinafter, the position adjustment of the boss 30 and / or the rotating disk 20 in the encoder of the present disclosure will be described with reference to Fig. 3A to 3F. At least one of the steps described below may be performed by an operator, or may be performed automatically by a single or multiple articulated robots.

[0016] 3A, the rotary disk 20 is fixed to the upper surface of the support portion 31 of the boss 30 so that the central axis O of the rotary disk 20 is coaxial with the through-hole 33. As a result, the rotary disk 20 and the boss 30 become integrated.

[0017] Next, the surrounding portion 32 of the boss 30 is engaged with the protruding portion 4 of the shaft 5. The inner circumferential surface of the surrounding portion 32 and the outer circumferential surface of the protruding portion 4 have the same shape. The surrounding portion 32 is then press-fitted into the protruding portion 4 until the lower end of the surrounding portion 32 reaches one end of the shaft 5 (step S11). Note that a visual sensor (not shown) disposed on the side of the shaft may be used to determine whether the lower end of the surrounding portion 32 has reached one end of the shaft 5.

[0018] Next, as shown in FIG. 3B , the adjuster 39 is inserted into the through hole 33 of the boss 30 through the through hole 33 of the rotary disk 20. The adjuster 39 is a bolt or screw having a thread formed on the outer circumferential surface of its shaft. Alternatively, a rod having a thread formed on its outer circumferential surface may be used as the adjuster 39. As shown in FIG. 3C , a thread is formed on the inner circumferential surface of the through hole 33, so that the adjuster 39 screws into the through hole 33. Then, the adjuster 39 is rotated in a predetermined direction A1, for example, clockwise (step S12).

[0019] The adjustment tool 39 continues to rotate until the tip of the adjustment tool 39 reaches the end face of the protrusion 4. Whether the tip of the adjustment tool 39 has reached the end face of the protrusion 4 may be determined, for example, by a torque sensor (not shown) provided on the hand of the articulated robot. In this case, it can be determined that the tip of the adjustment tool 39 has reached the end face of the protrusion 4 when the torque detected by the torque sensor exceeds a predetermined value (step S13).

[0020] 3D, the measuring device 61 is disposed so as to face the outer peripheral surface of the surrounding portion 32 of the boss 30. In FIG. 3D, the measuring device 61 is provided on the end surface of the stator 9, but the measuring device 61 may be provided in another location.

[0021] The measuring device 61 measures the height T of the rotating disk 20 integrated with the boss 30. In other words, the height T is the distance between the rotating disk 20 and the end face of the stator 9. Alternatively, the height T may be the distance between the boss 30 and the end face of the stator 9. In the present disclosure, the positions of the boss 30 and the rotating disk 20 on the central axis of the shaft are adjusted by adjusting the height T.

[0022] 3D includes a plurality of photoelectric sensors 62 arranged side by side parallel to the central axis of the shaft 5. The light projection directions of the plurality of photoelectric sensors 62 are perpendicular to the central axis of the shaft 5. The height T described above is measured from the positions of the photoelectric sensors where the light projected from the plurality of photoelectric sensors 62 is blocked by the rotating disk 20. Although not shown in the drawing, the measurement device 61 may also include a plurality of light receiving elements arranged opposite each of the plurality of photoelectric sensors 62.

[0023] Alternatively, a distance sensor may be used as the measuring device 61. In this case, the measuring direction of the distance sensor is arranged so as to be perpendicular to the surface of the rotating disk 20 and the end face of the stator 9. Then, the height T described above is measured by subtracting the distance between the distance sensor and the surface of the rotating disk 20 from the distance between the distance sensor and the end face of the stator 9, which has been measured in advance. Naturally, measuring devices 61 with other configurations may also be used.

[0024] As shown in Fig. 3D, while measuring the height T with the measuring device 61, the adjuster 39 is rotated in a predetermined direction A1 (step S14). As a result, the boss 30 and the rotating disk 20 move in a direction away from the stator 9. Because the lower end of the adjuster 39 abuts against the protruding portion 4, the boss 30 and the rotating disk 20 move upward in the direction of arrow A2. As a result, a gap is formed between the lower end of the surrounding portion 32 and the end face of the shaft 5, as shown in Fig. 3D.

[0025] With regard to the height T, an ideal height T0 is determined in advance by experiment, simulation, or the like. When the height T reaches the ideal height T0 while the adjuster 39 is being rotated in the predetermined direction A1, the rotation of the adjuster 39 is stopped (step S15). This completes the adjustment of the positions of the boss 30 and the rotary disk 20 with respect to the central axis O of the shaft 5.

[0026] 3E, the adjuster 39 is rotated in another predetermined direction A3, for example, counterclockwise (step S16). As a result, the ideal height T0 is maintained by the boss 30 and the rotary disc 20, and only the adjuster 39 moves away from the protrusion 4. Finally, the adjuster 39 is released from the boss 30 (step S17).

[0027] In this way, the final encoder 6a etc. in the present disclosure does not include the adjuster 39. Therefore, it is possible to simplify the configuration of the encoder 6a etc. and reduce the weight of the encoder 6a etc.

[0028] 6 is an axial cross-sectional view of a conventional encoder. In the encoder 6′ shown in FIG. 6, with the rotary disk 20 fixed to the boss 30, the position of the encoder can be adjusted simply by press-fitting the boss 30 into the protruding portion 4, thereby causing the lower end of the surrounding portion 32 to reach one end of the shaft 5.

[0029] In this case, however, the positions of the boss 30 and the rotating disk 20 are affected by the dimensional tolerances of the shaft 5, the stator 9, the boss 30, the rotating disk 20, etc. Therefore, there is a large variation in the height of the rotating disk 20, and the interpolation accuracy is not stable.

[0030] In addition, in the encoder 6' shown in Figure 6, with the rotating disk 20 fixed to the boss 30, the boss 30 is pressed into the protrusion 4 while measuring the height T, and the pressing of the boss 30 is stopped when the ideal height is reached, thereby adjusting the encoder.

[0031] However, in this case, the surrounding portion 32 of the boss 30 does not reach one end of the shaft 5. Therefore, there is a possibility that the rotating disk 20 may be fixed at an angle from a plane perpendicular to the central axis of the shaft 5, and therefore, the rotating disk 20 may experience surface wobble.

[0032] In this regard, in the present disclosure, since the through hole 33 is formed in the boss 30, it is possible to raise the boss 30 and the rotating disk 20 to the ideal height T0 using the adjuster 39 after the lower end of the surrounding portion 32 has reached one end of the shaft 5. Therefore, the above-mentioned problem does not occur in the present disclosure. In other words, the present disclosure can provide an encoder 6a that suppresses variation in the height of the rotating disk 20 and has stable interpolation accuracy. Furthermore, in the present disclosure, the rotating disk 20 can be fixed to a surface perpendicular to the central axis of the shaft 5, and it is also possible to suppress surface wobble of the rotating disk 20.

[0033] With this configuration, in the present disclosure, the gap between the rotary disk 20 and the light receiving portion 29 can be maintained appropriately and constantly, thereby improving the detection accuracy of the encoder 6a.

[0034] Figure 4 is a partial axial cross-sectional view of an encoder according to a second embodiment. In an encoder 6b shown in Figure 4, two through holes 33a, 33b are formed in the support portion 31 of the boss 30. These through holes 33a, 33b extend parallel to the central axis of the shaft 5 in the region inside the enclosure portion 32. Threads similar to those described above are formed on the inner circumferential surfaces of these through holes 33a, 33b. Adjusters 39a, 39b are threadedly engaged with these through holes 33a, 33b, respectively. The adjusters 39a, 39b function in the same manner as the adjuster 39 described above, but the diameters of the adjusters 39a, 39b may be smaller than the diameter of the adjuster 39.

[0035] In this case, the positions of the rotating disk 20 and the boss 30 on the central axis O of the shaft 5 are adjusted in the same manner as described above. In the second embodiment, in addition to adjusting the height T of the rotating disk 20 and the boss 30, it is possible to adjust the height of the rotating disk 20 so as to further reduce in-plane variations of the rotating disk 20. For this purpose, it is preferable that the adjusters 39a, 39b do not contact each other. Note that the use of three or more adjusters is also within the scope of the present disclosure, and it will be understood that in such cases, in-plane variations in the height of the rotating disk 20 can be reduced even more precisely.

[0036] 5 is a partial axial cross-sectional view of an encoder according to a third embodiment. In the encoder 6c shown in FIG. 5, a cylindrical recess 34 is formed on the end surface of the protrusion 4. A screw thread is formed on the inner circumferential surface of the recess 34. However, the diameter of the recess 34 is smaller than the diameter of the through-hole 33.

[0037] Another adjuster 38 is threaded into the recess 34. The other adjuster 38 is a bolt or screw with a thread formed on the outer circumferential surface of its shaft. The diameter of the shaft of the other adjuster 38 is smaller than the diameters of the shafts of the adjuster 39, etc. However, the diameter of the head of the other adjuster 38 is larger than the diameter of the through-hole 33.

[0038] In the third embodiment, as described with reference to Fig. 3F etc., the positions of the rotary disk 20 and the boss 30 are adjusted using the adjuster 39. Then, if it is determined in steps S14 and S15 of Fig. 3F that the height T has become greater than the ideal height T0, the adjuster 39 is rotated in another predetermined direction A3, for example, counterclockwise, and the adjuster 39 is removed from the encoder 6c.

[0039] Next, the other adjusting tool 38 is passed through the through-hole 33 and screwed into the recess 34 of the protruding portion 4. When the other adjusting tool 38 is then rotated in a predetermined direction A1, for example, clockwise, the rotary disc 20 and the boss 30 move toward the shaft 5 together with the other adjusting tool 38.

[0040] As described above, the height T is measured by the measuring device 61, and when the height T has decreased to the ideal height T0, the rotation of the other adjusting tool 38 is stopped and the other adjusting tool 38 is rotated in another predetermined direction A3, for example, counterclockwise, to remove the other adjusting tool 38. It will be understood that this allows readjustment even if the height T has become greater than the ideal height T0.

[0041] At least one of the embodiments described above has the effect of providing an encoder with a simple configuration that can improve detection accuracy.

[0042] Although the embodiments of the present disclosure have been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible to these embodiments without departing from the gist of the invention or the concept and spirit of the present invention derived from the content of the claims and their equivalents. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical formulas are used in the description of the above-described embodiments. Furthermore, appropriate combinations of several of the above-described embodiments are within the scope of the present disclosure.

[0043] The following supplementary notes are further disclosed regarding the above embodiments and variations. (Supplementary Note 1) An encoder comprising: a rotating disk having at least one slit that transmits light output from a light source; a protrusion provided coaxially at one end of a shaft that is to rotate integrally with the rotating disk; and a boss disposed between the rotating disk and the one end of the shaft and supporting the rotating disk, wherein a threaded through-hole is formed in the inner peripheral surface of the boss coaxially with the shaft, and after engaging the boss with the protrusion of the shaft, an adjuster is passed through an opening formed in the rotating disk and screwed into the through-hole of the boss, and the adjuster is used to adjust the position of the boss on the central axis of the shaft. (Supplementary Note 2) The encoder according to Supplementary Note 1, wherein the position of the boss is adjusted after the tip of the adjuster is abutted against the end face of the protrusion. (Supplementary Note 3) The encoder according to Supplementary Note 1, wherein the adjuster is removed from the boss after the position of the boss has been adjusted. (Supplementary Note 4) The encoder according to Supplementary Note 1, wherein the opening and the through hole are formed coaxially with the central axis of the shaft. (Supplementary Note 5) The encoder according to Supplementary Note 1, wherein a plurality of through holes are formed in the boss, and a plurality of adjusters are passed through the opening of the rotating disk and screwed into each of the plurality of through holes in the boss, and the position of the boss on the central axis of the shaft and the position of the rotating disk with respect to a plane perpendicular to the central axis are adjusted using the plurality of adjusters. (Supplementary Note 6) The encoder according to Supplementary Note 1, wherein a recess is formed coaxially with the central axis of the shaft on an end face of the protrusion. (Supplementary Note 7) A motor equipped with the encoder according to Supplementary Note 1.(Supplementary Note 8) An encoder adjustment method comprising: preparing a boss having an enclosing portion and a support portion, the support portion having a through hole with a thread formed on its inner peripheral surface; supporting a rotary disk on the support portion of the boss, thereby making an opening formed in the rotary disk and the through hole of the boss coaxial; engaging the enclosing portion of the boss with a protrusion provided coaxially at one end of a shaft; passing an adjusting tool through the opening of the rotary disk and screwing it into the through hole of the boss; and adjusting the position of the boss on the central axis of the shaft using the adjusting tool. (Supplementary Note 9) The encoder adjustment method according to Supplementary Note 8, wherein the position of the boss is adjusted after a tip of the adjusting tool is abutted against an end face of the protrusion. (Supplementary Note 10) The encoder adjustment method according to Supplementary Note 8, wherein the adjusting tool is removed from the boss after adjusting the position of the boss.

[0044] REFERENCE SIGNS LIST 1 motor 4 protrusion 5 shaft 6, 6a to 6c encoder 9 stator 10 rotor 11 housing 12 lid 20 rotating disk 25 slit 28 light source 29 light receiving portion 30 boss 31 support portion 32 surrounding portion 33, 33a, 33b through hole 38 other adjustment tool 39, 39a, 39b adjustment tool 61 measuring device 62 photoelectric sensor

Claims

1. An encoder comprising: a rotating disk having at least one slit for transmitting light output from a light source; a protrusion provided coaxially with the shaft at one end of the shaft that should rotate integrally with the rotating disk; and a boss disposed between the rotating disk and the one end of the shaft for supporting the rotating disk. A through hole with a thread formed on the inner peripheral surface of the boss is formed coaxially with the shaft. After engaging the boss with the protrusion of the shaft, a adjuster is passed through an opening formed in the rotating disk and screwed into the through hole of the boss, and the position of the boss on the central axis of the shaft is adjusted using the adjuster.

2. The encoder according to claim 1, wherein the position of the boss is adjusted after the tip of the adjuster is abutted against the end face of the protrusion.

3. The encoder according to claim 1, wherein the adjuster is removed from the boss after the position of the boss is adjusted.

4. The encoder according to claim 1, wherein the opening and the through hole are formed coaxially with the central axis of the shaft.

5. A plurality of through holes are formed in the boss. A plurality of adjusters are passed through the openings of the rotating disk and screwed into the respective through holes of the boss, and the position of the boss on the central axis of the shaft and the position of the rotating disk with respect to a plane perpendicular to the central axis are adjusted using the plurality of adjusters. The encoder according to claim 1.

6. The encoder according to claim 1, wherein a concave portion is formed coaxially with the central axis of the shaft on the end face of the protrusion.

7. A motor to which the encoder according to claim 1 is attached.

8. An encoder adjustment method, comprising: preparing a boss having a surrounding portion and a supporting portion, and having a through hole with a thread formed on the inner peripheral surface thereof formed in the supporting portion; supporting a rotating disk on the supporting portion of the boss, so that an opening formed in the rotating disk and the through hole of the boss are coaxially aligned; engaging the surrounding portion of the boss with a protrusion provided coaxially with the shaft at one end of the shaft; passing an adjuster through the opening of the rotating disk and screwing it into the through hole of the boss; and adjusting the position of the boss on the central axis of the shaft using the adjuster.

9. The encoder adjustment method according to claim 8, wherein after abutting the tip of the adjuster against the end face of the protruding portion, the position of the boss is adjusted.

10. The encoder adjustment method according to claim 8, wherein after adjusting the position of the boss, the adjuster is removed from the boss.

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