speed reducer

Abstract

To provide a speed reducer capable of preventing a non-round cam from being fixed eccentrically to a center shaft.SOLUTION: A speed reducer has an input shaft 21, a wave motion generator A3, a flexible contact member A2, an annular contact member A1, and a fixing portion 70. The wave motion generator has a non-round cam 62 and rotates about a center shaft as a center. The wave motion generator is brought into contact with the flexible contact member from a radial inner side. The flexible contact member is brought into contact with the annular contact member from the radial inner side. The fixing portion fixes the non-round cam to the input shaft. The input shaft has a connection portion to be connected to the non-round cam. The non-round cam has a through hole 62a. The connection portion is disposed in the through hole from an axial one side of the non-round cam. A part of the annular member is disposed in the through hole from the axial other side of the non-round cam. A connecting member is disposed on the center shaft and axially presses the annular member to the non-round cam in a state of axially penetrating through the annular member and connected to the connection portion.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a speed reducer.

Background Art

[0002] In a conventional harmonic gear speed reducer, the wave generator includes a transmission cylinder portion and a connection ring portion installed coaxially (for example, Patent Document 1). The output shaft is connected to the transmission cylinder portion via an adjustment expansion sleeve. The connection ring portion is connected to the rigid wheel via a flexible wheel.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in a conventional harmonic gear speed reducer, the adjustment expansion sleeve is fixed to the transmission cylinder portion by a plurality of screws arranged around the output shaft. Therefore, due to the order of tightening the plurality of screws and the variation in the tightening torque of the plurality of screws, there is a possibility that the transmission cylinder portion (non-circular cam) is fixed eccentrically with respect to the output shaft (central axis).

[0005] The present disclosure has been made in view of the above problems, and an object thereof is to provide a speed reducer capable of suppressing the non-circular cam from being fixed eccentrically with respect to the central axis.

Means for Solving the Problems

[0006] An exemplary speed reducer of a motor reduces the rotational speed of a motor. The speed reducer comprises an input shaft, a wave generator, a flexible contact member, an annular contact member, and a fixed part. The input shaft rotates about a central axis. The wave generator has a non-circular cam having different outer diameters depending on its circumferential position, and rotates about the central axis. The wave generator contacts the flexible contact member from the radially inner side. The flexible contact member contacts the annular contact member from the radially inner side. The fixed part fixes the non-circular cam to the input shaft. The flexible contact member rotates relative to the annular contact member in response to the rotation of the wave generator. The input shaft has a coupling part that connects to the non-circular cam. The non-circular cam has a through hole that penetrates the non-circular cam axially on the central axis. The coupling part is positioned in the through hole from one axial side of the non-circular cam. The fixing portion comprises an annular member and a connecting member. A portion of the annular member is positioned in the through hole from the other axial side of the non-circular cam. The connecting member is positioned on the central axis and, when connected to the connecting portion by passing through the annular member in the axial direction, presses the annular member against the non-circular cam in the axial direction. [Effects of the Invention]

[0007] According to this exemplary disclosure, a reduction gear can be provided that can prevent a non-circular cam from being fixed eccentrically with respect to the central axis. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a perspective view showing a speed reducer according to an embodiment of the present disclosure. [Figure 2] Figure 2 is a longitudinal cross-sectional view of the speed reducer along the line II-II in Figure 1. [Figure 3] Figure 3 is a vertical cross-sectional view showing a magnified portion of the gearbox and motor shown in Figure 2. [Figure 4] Figure 4 is a perspective view showing the rotating shaft, magnet holding member, and magnet according to this embodiment. [Figure 5A] Figure 5A is a perspective view showing the magnet holding member according to this embodiment. [Figure 5B] Figure 5B is a perspective view showing the axis of rotation according to this embodiment. [Figure 6] Figure 6 is a plan view showing the axis of rotation according to this embodiment. [Figure 7] Figure 7 is a vertical cross-sectional view showing an enlarged portion of the gearbox shown in Figure 3. [Figure 8] Figure 8 is a cross-sectional view along the line VIII-VIII in Figure 7. [Figure 9] Figure 9 is a perspective view showing the fixed part, non-circular cam, shim ring, and rotation axis according to this embodiment. [Figure 10A] Figure 10A is a perspective view showing the annular member according to this embodiment. [Figure 10B] Figure 10B is a perspective view showing a non-circular cam according to this embodiment. [Figure 11] Figure 11 is a side view showing the process of fixing the non-circular cam according to this embodiment to the rotating shaft. [Figure 12A] Figure 12A is a perspective view showing a magnet holding member of a speed reduction device according to a first modified example of this embodiment. [Figure 12B] Figure 12B is a perspective view showing the rotation axis of the reduction gear according to the first modified example of this embodiment. [Figure 12C] Figure 12C is a plan view showing the rotation axis of the reduction gear according to the first modified example of this embodiment. [Figure 13A] Figure 13A is a perspective view showing a magnet holding member of a speed reduction device according to a second modified example of this embodiment. [Figure 13B] Figure 13B is a perspective view showing the rotation axis of the reduction gear according to a second modified example of this embodiment. [Figure 13C] Figure 13C is a plan view showing the rotation axis of the reduction gear according to a second modified example of this embodiment. [Figure 14A] Figure 14A is a perspective view showing a magnet holding member of a reduction gear according to a third modified example of this embodiment. [Figure 14B] Figure 14B is a perspective view showing the rotation axis of a reduction gear according to a third modified example of this embodiment. [Figure 14C] FIG. 14C is a plan view showing the rotating shaft of the speed reduction device according to the third modification of the present embodiment. [Figure 15] FIG. 15 is a perspective view showing the annular member of the speed reduction device according to the fourth modification of the present embodiment.

Mode for Carrying Out the Invention

[0009] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and the description thereof will not be repeated. Also, in the drawings, for ease of understanding, the X-axis, Y-axis, and Z-axis of the three-dimensional orthogonal coordinate system are appropriately shown.

[0010] Also, in this specification, the direction parallel to the central axis AX of the speed reducer and the motor is described as the "axial direction AD", the direction orthogonal to the central axis AX is described as the "radial direction RD", and the direction along the arc centered on the central axis AX is described as the "circumferential direction CD". The "radial direction RD" may be any direction as long as it is orthogonal to the central axis AX, and is not particularly limited. Also, in this specification, the "parallel direction" does not mean strictly parallel, but includes, for example, a case where it is parallel to such an extent that the effects in the present disclosure are achieved. Also, in this specification, the "orthogonal direction" does not mean strictly orthogonal, but includes, for example, a case where it is orthogonal to such an extent that the effects in the present disclosure are achieved.

[0011] Furthermore, in this specification, "bottomed cylindrical shape", "bottomed circular cylindrical shape", "bottomed rectangular cylindrical shape", "cylindrical shape", "circular cylindrical shape", "annular shape", "circular annular shape", "circular ring shape", "elliptical shape", "columnar shape", "circular columnar shape", "flat plate shape", "flat plate状", "circular plate shape", and "rectangular parallelepiped shape", "rectangular shape" do not represent a shape in a strict sense, but include, for example, a shape to such an extent that the function of the speed reduction device in the present disclosure can be realized.

[0012] The reduction gear SR according to an embodiment of the present disclosure will be described with reference to Figures 1 to 11. Figure 1 is a perspective view showing the reduction gear SR. The reduction gear SR shown in Figure 1 reduces the rotational speed. The rotational speed refers to, for example, the number of rotations per unit time. Specifically, the reduction gear SR converts rotational motion at a first rotational speed into rotational motion at a second rotational speed lower than the first rotational speed.

[0013] As shown in Figure 1, the reduction gear SR comprises a motor 100 and a reduction gear 200. The motor 100 drives the reduction gear 200. The reduction gear 200 reduces the rotational speed of the motor 100. Specifically, the reduction gear 200 converts the rotational motion of the motor 100 at a first rotational speed to rotational motion at a second rotational speed lower than the first rotational speed.

[0014] Figure 2 is a longitudinal cross-sectional view of the reduction gear SR along the line II-II in Figure 1. As shown in Figure 2, the reduction gear SR further includes a main board SB0. Circuits and a microcomputer are arranged on the main board SB0. The main board SB0 is arranged along the axial direction AD. The main board SB0 spans the motor 100 and the reduction gear 200.

[0015] The motor 100 includes a motor body 1, a magnetic encoder 3, a motor housing 7, a wall member 9, a plurality of fixing members 11, and a rotating shaft 21. Figure 2 shows one fixing member 11. The magnetic encoder 3 is an example of an "encoder".

[0016] The motor body 1 rotates the rotation axis 21 around the central axis AX. The central axis AX is an imaginary line that runs along the longitudinal direction of the rotation axis 21 and passes through the center of the rotation axis 21. The motor body 1 has a rotor RT and a stator ST. The rotor RT rotates around the central axis AX. In other words, the rotor RT is the rotor of the motor body 1. The rotor RT is fixed to the rotation axis 21. Therefore, when the rotor RT rotates, the rotation axis 21 rotates. In other words, the rotation axis 21 rotates together with the rotor RT. The rotor RT is positioned around the central axis AX. The rotor RT is positioned inside the radial direction RD of the stator ST. In other words, the motor 100 is an inner rotor type motor. Note that the motor 100 may also be an outer rotor type motor. The stator ST is the stator of the motor body 1. The stator ST is positioned around the central axis AX.

[0017] When the motor body 1 is driven, the rotating shaft 21 rotates about the central axis AX. The rotating shaft 21 extends in the axial direction AD. The rotating shaft 21 has, for example, a substantially cylindrical shape. The rotating shaft 21 is made of, for example, metal. The material of the rotating shaft 21 is, for example, an alloy containing iron.

[0018] The magnetic encoder 3 detects the rotation of the rotating shaft 21. The magnetic encoder 3 then outputs rotation information indicating the rotational position or rotational angle of the rotating shaft 21 to the microcomputer on the main board SB0.

[0019] The motor housing 7 houses the motor body 1 and the magnetic encoder 3. The motor housing 7 has, for example, a roughly bottomed rectangular cylindrical shape. The motor housing 7 is fixed to the wall member 9 by a plurality of fixing members (not shown), such as screws.

[0020] The wall member 9 is positioned between the motor body 1 and the reduction gear 200. The wall member 9 has a substantially flat plate shape and a substantially rectangular shape.

[0021] Each fixing member 11 secures the stator ST to the wall member 9. The fixing member 11 is, for example, a screw. The screw is, for example, a bolt or a screw.

[0022] The gear reducer 200 includes a rigid internal gear A1, a flexible external gear A2, a wave generator A3, a plurality of internal gear fixing members 74, an external gear fixing member 75, an annular member 76, an output rotating body 77, a first output bearing 81, a second output bearing 85, a gear reducer housing 86, and a cover 87. The rigid internal gear A1 corresponds to an example of an "annular contact member". The flexible external gear A2 corresponds to an example of a "flexible contact member".

[0023] The reduction gear 200 is a device that reduces the input rotational motion by utilizing the differential between a rigid internal gear A1 and a flexible external gear A2. In this embodiment, the rotating shaft 21 functions as the input shaft of the reduction gear 200. Therefore, it can also be considered that the reduction gear 200 has a rotating shaft 21.

[0024] The rigid internal gear A1 is approximately annular. In the example in Figure 2, the rigid internal gear A1 is approximately annular. The rigid internal gear A1 is fixed to the reduction gear housing 86 by a plurality of internal gear fixing members 74. Specifically, each internal gear fixing member 74 is screwed into the reduction gear housing 86 while passing through the rigid internal gear A1. As a result, the rigid internal gear A1 is fixed to the reduction gear housing 86 by the tightening of the internal gear fixing members 74. The internal gear fixing members 74 are, for example, screws. The screws are, for example, bolts or screws.

[0025] A flexible external gear A2 contacts a rigid internal gear A1 from the inside of the radial direction RD. The flexible external gear A2 is flexible. A wave generator A3 contacts the flexible external gear A2 from the inside of the radial direction RD. The wave generator A3 has different outer diameters depending on its position in the circumferential direction CD. A rotating shaft 21 is coupled to the wave generator A3. Therefore, as the rotating shaft 21 rotates, the wave generator A3 rotates around its central axis AX. In the example in Figure 2, the wave generator A3 is approximately elliptical. The wave generator A3 is a mechanism that causes the flexible external gear A2 to bend and deform.

[0026] The flexible external gear A2 rotates relative to the rigid internal gear A1 in response to the rotation of the wave generator A3. In the example shown in Figure 2, the flexible external gear A2 functions as the output shaft of the reduction gear 200. As a result, the reduction gear 200 reduces the rotational motion input from the rotating shaft 21, which functions as the input shaft, and outputs the reduced rotational motion from the flexible external gear A2, which functions as the output shaft.

[0027] The flexible external gear A2 is fixed to the output rotor 77 by an external gear fixing member 75 via an annular member 76. The annular member 76 is a substantially annular member. The annular member 76 is, for example, a bush. The annular member 76 is, for example, made of metal. The material of the annular member 76 is, for example, an iron-containing alloy. The external gear fixing member 75 is screwed onto the axial AD end of the output rotor 77 via the annular member 76. As a result, the flexible external gear A2 is tightened between the annular member 76 and the end of the output rotor 77, fixing the flexible external gear A2 to the output rotor 77. The external gear fixing member 75 is, for example, a screw. The screw is, for example, a bolt or a screw. Furthermore, as will be described later, the rotation of the flexible external gear A2 relative to the output rotor 77 in the circumferential direction CD is restricted.

[0028] The flexible external gear A2, which functions as an output shaft, is fixed to the output rotating body 77, and the relative rotation of the flexible external gear A2 with respect to the output rotating body 77 is restricted, so that the rotation of the flexible external gear A2 is transmitted to the output rotating body 77. Therefore, the output rotating body 77 rotates about the central axis AX at the same rotational speed as the flexible external gear A2.

[0029] The first output bearing 81 is substantially annular. The first output bearing 81 is positioned between the outer circumferential surface 77a of the output rotor 77 and the inner circumferential surface 86a of the reduction gear housing 86. The first output bearing 81 has an inner ring 82, an outer ring 83, and a plurality of balls 84. The inner ring 82 is fixed to the outer circumferential surface 77a of the output rotor 77. The outer ring 83 is fixed to the inner circumferential surface 86a of the reduction gear housing 86. The plurality of balls 84 are interposed between the inner ring 82 and the outer ring 83 and are arranged along the circumferential direction CD. The first output bearing 81 is, for example, a ball bearing.

[0030] The second output bearing 85 and the first output bearing 81 are arranged side by side in the axial direction A and D. The second output bearing 85 is substantially annular in shape. The second output bearing 85 is positioned between the outer circumferential surface 77a of the output rotating body 77 and the inner circumferential surface 86a of the reduction gear housing 86. The second output bearing 85 has an inner ring 82, an outer ring 83, and a plurality of balls 84. Otherwise, the configuration of the second output bearing 85 is the same as that of the first output bearing 81.

[0031] By providing the first output bearing 81 and the second output bearing 85, the output rotating body 77 can rotate relative to the reduction gear housing 86.

[0032] The gearbox housing 86 houses a rigid internal gear A1, a flexible external gear A2, a wave generator A3, an external gear fixing member 75, an annular member 76, a first output bearing 81, a second output bearing 85, and a portion of the output rotating body 77. In the example shown in Figure 2, the external shape of the gearbox housing 86 is approximately a rectangular parallelepiped. The gearbox housing 86 also has a roughly cylindrical housing space SP. The gearbox housing 86 is fixed to the wall member 9 by a plurality of fixing members (not shown), such as screws.

[0033] The cover 87 covers the axial AD end of the reduction gear housing 86. The output rotor 77 passes through the cover 87 and protrudes outward from the cover 87.

[0034] Next, the motor 100 will be described in detail with reference to Figure 3. Figure 3 is a longitudinal cross-sectional view showing an enlarged portion of the reduction gear 200 and the motor 100 shown in Figure 2. As shown in Figure 3, the motor 100 includes a substrate SB1, a substrate SB2, a magnet holding member 5, a first bearing 30, a second bearing 35, and a plurality of support members 93.

[0035] Circuits are formed on each of the substrates SB1 and SB2. Each of the substrates SB1 and SB2 is electrically connected to the main substrate SB0. Substrate SB1 has, for example, a roughly rectangular shape. Substrate SB1 is positioned with a gap in the axial direction AD relative to substrate SB2. Substrates SB1 and SB2 are roughly perpendicular to the axial direction AD. Substrate SB1 is supported by a plurality of support members 93. Each support member 93 is fixed to substrate SB2. Substrate SB2 has, for example, a roughly annular shape and extends radially outward RD with respect to the central axis AX. Substrate SB2 is fixed to the stator ST.

[0036] A portion of the magnetic encoder 3 is arranged on the substrate SB1. The magnetic encoder 3 has a magnet 91 and a magnetic sensor 92. The magnet 91 is, for example, a permanent magnet. The magnet 91 has, for example, a substantially cylindrical shape. The magnet holding member 5 holds the magnet 91. Specifically, the magnet 91 is fixed to the magnet holding member 5. The magnet holding member 5, which holds the magnet 91, is then fixed to the first end E1 of the rotating shaft 21. The material of the magnet holding member 5 is a non-magnetic material. For example, the magnet holding member 5 is made of aluminum or synthetic resin.

[0037] The rotating shaft 21 has a first end E1 and a second end E2. The first end E1 is one end of the axial direction AD of the rotating shaft 21. The second end E2 is the other end of the axial direction AD of the rotating shaft 21. The second end E2 is coupled to the reduction gear 200. The second end E2 corresponds to an example of a "connection part".

[0038] The magnetic encoder 3 detects the rotation of the rotating shaft 21 based on the change in the magnetic field of the magnet 91, which rotates together with the rotating shaft 21.

[0039] Specifically, the magnet 91 is positioned at an axial distance A and D relative to the magnetic sensor 92. The magnetic sensor 92 detects changes in the magnetic field caused by the magnet 91, which rotates together with the rotation axis 21. In other words, the magnetic sensor 92 detects the rotational position or rotational angle of the rotation axis 21 as a change in the magnetic field and outputs rotational information indicating the rotational position or rotational angle of the rotation axis 21 to the microcomputer on the main board SB0. The magnetic sensor 92 includes, for example, a Hall element. The magnetic sensor 92 is placed on the board SB1.

[0040] The motor body 1 has a stator case 54. The stator case 54 has a substantially bottomed cylindrical shape. The stator case 54 also has a hole through which the central axis AX passes. The stator case 54 is fixed to the wall member 9 by a fixing member 11. The stator case 54 houses the stator ST. The stator ST is fixed to the stator case 54. The stator ST has a stator core 51, an insulator 52, and a plurality of coils 53.

[0041] The stator core 51 is positioned around a central axis AX. The stator core 51 is arranged around the central axis AX and is substantially annular in shape. The stator core 51 is made of, for example, laminated steel sheets formed by stacking thin sheets of electromagnetic steel in the axial direction AD. The insulator 52 electrically insulates the stator core 51 from the coil 53. The insulator 52 is made of an insulating material. The insulator 52 covers at least a portion of the stator core 51. The insulator 52 is arranged in a substantially annular shape around the central axis AX. The insulator 52 may be made of multiple separate members or of a single member. The coil 53 is made by winding a conductor around the stator core 51 via the insulator 52.

[0042] The rotor RT comprises a rotor yoke 41 and a magnet 42. The magnet 42 is, for example, a permanent magnet. The magnet 42 has, for example, a substantially annular shape. The rotor RT may also have a plurality of magnets arranged in the circumferential direction CD. The rotor yoke 41 is made of, for example, a magnetic material. The rotor yoke 41 has a substantially bottomed cylindrical shape. The rotor yoke 41 also has a hole through which the rotating shaft 21 passes. The rotor yoke 41 is fixed to the rotating shaft 21.

[0043] The magnet 42 is fixed to the outer surface of the rotor yoke 41 in the radial direction RD. In other words, the motor 100 is an SPM (Surface Permanent Magnet) motor. Alternatively, the magnet 42 may be fixed inside the rotor yoke 41. In other words, the motor 100 may be a so-called IPM (Interior Permanent Magnet) motor. The magnet 42 and the stator core 51 face each other with a gap in the radial direction RD.

[0044] The first bearing 30 is substantially annular. The first bearing 30 is positioned between the outer circumferential surface of the rotating shaft 21 and the inner circumferential surface of the inner cylinder portion 541 of the stator case 54. The first bearing 30 has an inner ring 32, an outer ring 33, and a plurality of balls 34. The inner ring 32 is fixed to the outer circumferential surface of the rotating shaft 21. The outer ring 33 is fixed to the inner circumferential surface of the inner cylinder portion 541 of the stator case 54. The plurality of balls 34 are interposed between the inner ring 32 and the outer ring 33 and are arranged along the circumferential direction CD. The first bearing 30 is, for example, a ball bearing.

[0045] The second bearing 35 and the first bearing 30 are positioned with a gap between them in the axial direction AD. By placing a spacer 39 and a wave washer 40 between the second bearing 35 and the first bearing 30, the gap between the second bearing 35 and the first bearing 30 is maintained at a constant level. The spacer 39 has a substantially bottomed cylindrical shape.

[0046] The second bearing 35 is substantially annular in shape. The second bearing 35 is positioned between the outer circumferential surface of the rotating shaft 21 and the inner circumferential surface of the inner cylindrical portion 541 of the stator case 54. The second bearing 35 has an inner ring 32, an outer ring 33, and a plurality of balls 34. Otherwise, the configuration of the second bearing 35 is the same as that of the first bearing 30.

[0047] By providing the first bearing 30 and the second bearing 35, the rotating shaft 21 can rotate relative to the motor housing 7.

[0048] Next, the rotating shaft 21, the magnet holding member 5, and the magnet 91 will be described with reference to Figure 4. Figure 4 is a perspective view showing the rotating shaft 21, the magnet holding member 5, and the magnet 91. As shown in Figure 4, the magnet holding member 5 has a holding portion 5a. The holding portion 5a has a substantially bottomed cylindrical shape. The holding portion 5a holds the magnet 91.

[0049] The rotating shaft 21 has a first fitting portion 22. The first fitting portion 22 is located at the first end E1. As shown in Figures 3 and 4, a magnet holding member 5 holding a magnet 91 is fitted into the first fitting portion 22 in the axial direction AD. The first fitting portion 22 is an example of a "fitting portion".

[0050] Specifically, the magnet holding member 5 has a second fitting portion 5b. The second fitting portion 5b is fitted into the first fitting portion 22 of the rotating shaft 21. The second fitting portion 5b is an example of a "part of the member".

[0051] Figure 5A is a perspective view showing the magnet holding member 5. As shown in Figure 5A, in the magnet holding member 5, the second fitting portion 5b protrudes in the axial direction AD from the bottom surface 505 of the holding portion 5a. In other words, the second fitting portion 5b is a convex portion. Specifically, the second fitting portion 5b has a first convex portion 510 and a second convex portion 520.

[0052] The first protrusion 510 projects from the bottom surface 505 of the holding portion 5a in the axial direction AD. The first protrusion 510 extends in a first direction D1. The first direction D1 intersects with the axial direction AD. In the example of Figure 5A, the first direction D1 is approximately perpendicular to the axial direction AD. The first direction D1 is approximately parallel to the radial direction RD. The end face 511 of the first protrusion 510 in the first direction D1 is curved. Specifically, the first protrusion 510 is curved convexly outward in the radial direction RD.

[0053] The second protrusion 520 projects from the bottom surface 505 of the holding portion 5a in the axial direction AD. The second protrusion 520 extends in the second direction D2. The second direction D2 intersects the first direction D1. The second direction D2 intersects the axial direction AD. In the example of Figure 5A, the second direction D2 is approximately perpendicular to the axial direction AD and the first direction D1. The second direction D2 is approximately parallel to the radial direction RD. The end face 521 of the second protrusion 520 in the second direction D2 is curved. Specifically, the second protrusion 520 is curved convexly outward in the radial direction RD.

[0054] The second protrusion 520 intersects with the first protrusion 510. In the example of Figure 5A, the second protrusion 520 is approximately perpendicular to the first protrusion 510. The intersection 515 of the second protrusion 520 and the first protrusion 510 is curved. Specifically, the intersection 515 is curved in a concave shape toward the radial side RD.

[0055] Figure 5B is a perspective view showing the rotating shaft 21. As shown in Figure 5B, the first fitting portion 22 has a shape that conforms to the second fitting portion 5b (Figure 5A). Specifically, the first fitting portion 22 is recessed in the axial direction AD toward the reduction gear 200 (Figure 3) relative to the end face 21a of the first end E1 in the axial direction AD. In other words, the first fitting portion 22 is recessed in the axial direction AD toward the second end E2 relative to the end face 21a of the first end E1 in the axial direction AD. Therefore, according to this embodiment, machining of the rotating shaft 21 is easier compared to the case where the first fitting portion 22 protrudes in the axial direction AD. As a result, the formation of the first fitting portion 22 at the first end E1 is easier. This is particularly effective when the rotating shaft 21 is made of metal.

[0056] Figure 6 is a plan view showing the rotation axis 21. In Figure 6, the second fitting portion 5b of the magnet holding member 5 is shown by a dashed line. In this case, a gap has been made between the second fitting portion 5b and the first fitting portion 22 for the sake of clarity in the drawing. In reality, the second fitting portion 5b and the first fitting portion 22 are in contact. This is also true for Figures 12C, 13C, and 14C, which will be discussed later.

[0057] As shown in Figure 6, when the second fitting portion 5b of the magnet holding member 5 is fitted into the first fitting portion 22, the first fitting portion 22 has a shape that restricts one of the rotating shaft 21 and the magnet holding member 5 from rotating relative to the other in the circumferential direction CD. Therefore, according to this embodiment, it is possible to suppress the rotation of the magnet holding member 5 and the magnet 91 (Figure 4) relative to the rotating shaft 21 around the central axis AX.

[0058] Specifically, the first fitting portion 22 faces the second fitting portion 5b of the magnet holding member 5 in the circumferential direction CD.

[0059] When the second fitting portion 5b is fitted into the first fitting portion 22, the end face 21a of the first end portion E1 in the axial direction AD contacts the bottom surface 505 (Figure 5A) of the holding portion 5a.

[0060] In addition, the shape of the first fitting portion 22 restricts the radial movement RD of the magnet holding member 5. Therefore, eccentricity of the magnet 91 (Figure 4) held by the magnet holding member 5 with respect to the central axis AX can be suppressed. In other words, by fitting the second fitting portion 5b of the magnet holding member 5, in which the magnet 91 is held, to the first fitting portion 22 of the rotating shaft 21, the magnet holding member 5 can be attached to the rotating shaft 21 while suppressing eccentricity of the magnet 91 with respect to the central axis AX. As a result, the detection accuracy of rotation information of the rotating shaft 21 by the magnetic encoder 3 can be improved.

[0061] Specifically, the first fitting portion 22 faces the second fitting portion 5b of the magnet holding member 5 in the radial direction RD.

[0062] More specifically, as shown in Figures 5B and 6, the first fitting portion 22 has a first recess 23 and a second recess 24. The first recess 23 and the second recess 24 intersect. Therefore, the first fitting portion 22 has four corners CN. In contrast, the second fitting portion 5b of the magnet holding member 5 has four curved intersecting portions 515 (Figure 5A). Therefore, contact between the intersecting portions 515 and the corners CN is suppressed, and the second fitting portion 5b can be smoothly fitted into the first fitting portion 22. In the example of Figures 5B and 6, the first recess 23 and the second recess 24 are substantially perpendicular to each other.

[0063] The first recess 23 is recessed in the axial direction AD toward the reduction gear 200 (Figure 2). In other words, the first recess 23 is recessed in the axial direction AD toward the second end E2. The first recess 23 extends in the first direction D1. Therefore, it is possible to restrict the movement of the magnet holding member 5 and the magnet 91 (Figure 4) in the radial direction RD (for example, the second direction D2) intersecting the first direction D1. In addition, the second recess 24 is recessed in the axial direction AD toward the reduction gear 200. In other words, the second recess 24 is recessed in the axial direction AD toward the second end E2. The second recess 24 extends in the second direction D2. Therefore, it is possible to restrict the movement of the magnet holding member 5 and the magnet 91 in the radial direction RD (for example, the first direction D1) intersecting the second direction D2. According to this embodiment, by providing the first recess 23 and the second recess 24, the movement of the magnet holding member 5 and the magnet 91 in the radial direction RD can be easily restricted. As a result, the eccentricity of the magnet 91 with respect to the central axis AX can be easily suppressed with a simple configuration.

[0064] Specifically, the first recess 23 penetrates the first end E1 in the first direction D1. In addition, the length L1 of the second recess 24 in the second direction D2 is shorter than the length L2 of the first end E1 in the second direction D2. Therefore, according to this embodiment, the first recess 23 and the second recess 24 can be easily formed in the first end E1. In other words, the processing required to form the first recess 23 and the second recess 24 in the first end E1 is easy.

[0065] More specifically, the first protrusion 510 of the second fitting portion 5b is fitted into the first recess 23. Therefore, the first recess 23 faces the first protrusion 510 in the circumferential direction CD. In addition, the second protrusion 520 of the second fitting portion 5b is fitted into the second recess 24. Therefore, the second recess 24 faces the second protrusion 520 in the circumferential direction CD.

[0066] Furthermore, the first recess 23 has a pair of wall surfaces Wa and Wb that face each other in the circumferential direction CD. The pair of wall surfaces Wa and Wb extend in the first direction D1. The pair of wall surfaces Wa and Wb restrict the movement of the magnet holding member 5 in the second direction D2 and the rotation of the circumferential direction CD. Furthermore, the second recess 24 has a pair of wall surfaces Wc and Wd that face each other in the circumferential direction CD. The pair of wall surfaces Wc and Wd extend in the second direction D2. The pair of wall surfaces Wc and Wd restrict the movement of the magnet holding member 5 in the first direction D1 and the rotation of the circumferential direction CD.

[0067] Next, the details of the speed reducer 200 will be described with reference to Figures 7 and 8. Figure 7 is a longitudinal cross-sectional view showing an enlarged portion of the speed reducer 200 shown in Figure 3.

[0068] As shown in Figure 7, in the reduction gear 200, the flexible external gear A2 has a cylindrical portion A21, an annular portion A22, and a protruding portion A23. The cylindrical portion A21 is flexible. The cylindrical portion A21 is substantially cylindrical. In the example in Figure 7, the cylindrical portion A21 is substantially cylindrical. The cylindrical portion A21 of the flexible external gear A2 contacts one end of the rigid internal gear A1 in the axial direction AD from the inside in the radial direction RD. The annular portion A22 is substantially annular. In the example in Figure 7, the annular portion A22 is substantially circular. The annular portion A22 is a flat plate-like portion that is less flexible than the cylindrical portion A21. The annular portion A22 is the part that extends radially inward from the other end of the cylindrical portion A21 in the axial direction AD.

[0069] The projection A23 protrudes from the annular portion A22 in the axial direction AD. The projection A23 extends along the circumferential direction CD. For example, the projection A23 consists of two arc portions extending along the circumferential direction CD. In this case, a convex portion is positioned between the two adjacent arc portions in the circumferential direction CD, protruding in the axial direction AD from the axial end AD of the output rotor 77. Thus, the relative rotation of the flexible external gear A2 with respect to the output rotor 77 is restricted. In addition, by screwing the external gear fixing member 75 onto the end of the output rotor 77, the projection A23 is tightened toward the output rotor 77 by the annular member 76. As a result, the rotation of the flexible external gear A2, which is the output shaft, is efficiently transmitted to the output rotor 77.

[0070] The rigidity of the rigid internal gear A1 is higher than the rigidity of the cylindrical portion A21 of the flexible external gear A2. Therefore, the rigid internal gear A1 can be considered substantially rigid.

[0071] The wave generator A3 is fixed to the rotating shaft 21. The wave generator A3 has a wave bearing 61 and a non-circular cam 62. The wave bearing 61 is flexible. The wave bearing 61 is located radially RD inside the cylindrical portion A21 of the flexible external gear A2. The non-circular cam 62 expands in an annular shape around the central axis AX. In the example in Figure 3, the non-circular cam 62 is approximately elliptical. The non-circular cam 62 has different outer diameters depending on the position in the circumferential direction CD. The wave bearing 61 is positioned along the outer circumferential surface of the non-circular cam 62 and is approximately elliptical in shape.

[0072] The second end E2 of the rotating shaft 21 is connected to the non-circular cam 62. Specifically, the reduction gear 200 has a fixed part 70. The fixed part 70 fixes the non-circular cam 62 to the rotating shaft 21. The reduction gear 200 also has a shim ring 73. This will be described later.

[0073] Figure 8 is a cross-sectional view along the line VIII-VIII in Figure 7. As shown in Figure 8, the rigid internal gear A1 has a plurality of internal teeth A10 on its inner circumferential surface. The plurality of internal teeth A10 are arranged at a constant pitch along the circumferential direction CD.

[0074] The flexible external gear A2 has multiple external teeth A20 on the outer circumferential surface near one end of the axial direction AD. In other words, multiple external teeth A20 are provided on the outer circumferential surface near one end of the axial direction AD of the cylindrical portion A21. The multiple external teeth A20 are arranged at a constant pitch along the circumferential direction CD.

[0075] In wave generator A3, the non-circular cam 62 is connected to the rotating shaft 21, which serves as the input shaft. Therefore, the non-circular cam 62 rotates around its central axis AX at the rotational speed before deceleration due to the rotation of the rotating shaft 21. The non-circular cam 62 has an elliptical cam profile. In other words, the non-circular cam 62 has different outer diameters depending on the position CD in the circumferential direction. In further terms, the outer edge of the non-circular cam 62 is approximately elliptical.

[0076] The wave bearing 61 is a flexible bearing located radially RD inside the cylindrical portion A21 of the flexible external gear A2. The wave bearing 61 is substantially annular. The wave bearing 61 is, for example, a ball bearing. The wave bearing 61 has an inner ring 65, a plurality of balls 66, and an elastically deformable outer ring 67. The inner ring 65 is fixed to the outer circumferential surface of the non-circular cam 62. The plurality of balls 66 are interposed between the inner ring 65 and the outer ring 67 and are arranged along the circumferential direction CD. The outer ring 67 elastically deforms (flexes) via the inner ring 65 and the balls 66 to reflect the cam profile of the rotating non-circular cam 62. The outer ring 67 also contacts the inner circumferential surface of the portion of the cylindrical portion A21 of the flexible external gear A21 that has the external teeth A20. Specifically, the outer ring 67 is fixed to the inner circumferential surface of the portion of the cylindrical portion A21 that has the external teeth A20. The wave generator A3 has different outer diameters depending on the position CD in the circumferential direction, and rotates at the rotational speed before deceleration around the central axis AX inside the radial RD of the rigid internal gear A1.

[0077] Next, the fixed part 70, the non-circular cam 62, the shim ring 73, and the rotating shaft 21 will be described with reference to Figures 7, 9, and 10. Figure 9 is a perspective view showing the fixed part 70, the non-circular cam 62, the shim ring 73, and the rotating shaft 21. Figure 10A is a perspective view showing the annular member 72. Figure 10B is a perspective view showing the non-circular cam 62.

[0078] As shown in Figure 9, the fixing portion 70 has a connecting member 71 and an annular member 72. The connecting member 71 is positioned on the central axis AX. The connecting member 71 has a head 71a and a shaft portion 71b. The head 71a has a substantially cylindrical shape. The head 71a protrudes radially RD from the shaft portion 71b. The shaft portion 71b has a substantially cylindrical shape. The shaft portion 71b extends axially AD from the head 71a. The shaft portion 71b is positioned on the central axis AX. Screw threads (not shown) are formed on the shaft portion 71b. The connecting member 71 functions as a male screw. The connecting member 71 is, for example, a bolt or a screw. The connecting member 71 is, for example, made of metal. For example, the material of the connecting member 71 is an alloy containing iron.

[0079] As shown in Figures 9 and 10A, the annular member 72 has a substantially frustoconical shape that tapers toward the second end E2 of the rotation axis 21. The annular member 72 has a through hole 72a. The through hole 72a penetrates the annular member 72 in the axial direction AD on the central axis AX. The shaft portion 71b of the connecting member 71 penetrates the through hole 72a in the axial direction AD. The through hole 72a is a substantially cylindrical space. The annular member 72 is made of, for example, metal. For example, the material of the annular member 72 is an alloy containing iron. The annular member 72 is, for example, a bush.

[0080] The non-circular cam 62 has a through hole 62a. The through hole 62a penetrates the non-circular cam 62 in the axial direction AD on the central axis AX. The through hole 62a is a substantially cylindrical space. A part of the annular member 72 is positioned in the through hole 62a.

[0081] The non-circular cam 62 has a cam body 623 and a cam projection 624. The cam body 623 has an elliptical cam profile. In other words, the cam body 623 has different outer diameters depending on the position of the circumferential CD. In other words, the outer edge of the cam body 623 is approximately elliptical. The wave bearing 61 (Figure 8) is positioned along the outer circumferential surface of the cam body 623 and is approximately elliptical in shape.

[0082] The cam projection 624 protrudes in the axial direction AD from the end face of the cam body 623 toward the side opposite to where the motor 100 (Figure 3) is located. The cam projection 624 has a substantially annular shape.

[0083] Furthermore, as shown in Figure 10B, the non-circular cam 62 has a first inner surface 621 and a second inner surface 622. The first inner surface 621 and the second inner surface 622 form a through hole 62a. The first inner surface 621 includes the inner surface of the cam body 623. The second inner surface 622 includes the inner surface of the cam projection 624. The second inner surface 622 has a shape that widens towards the side opposite to where the motor 100 (Figure 3) is located.

[0084] Returning to Figure 9, the shim ring 73 has a substantially cylindrical shape. The shim ring 73 is positioned on the opposite side of the fixed portion 70 from the non-circular cam 62.

[0085] The second end E2 of the rotating shaft 21 has a substantially cylindrical shape. The second end E2 has a recess 21b. The recess 21b is recessed in the axial direction AD toward the first end E1. Screw threads (not shown) are formed in the recess 21b. The second end E2 functions as a female thread. The second end E2 passes through the shim ring 73. The second end E2 is coupled to the non-circular cam 62. The second end E2 is positioned in the through hole 62a of the non-circular cam 62.

[0086] Furthermore, the rotating shaft 21 has an annular surface 25. The annular surface 25 is approximately circular. The annular surface 25 extends radially outward RD from the end 21e of the second end E2 that is furthest from the annular member 72 in the axial direction AD.

[0087] Referring again to Figure 7, we will explain the state in which the second end E2 of the rotating shaft 21 is coupled to the non-circular cam 62. As shown in Figure 7, the second end E2 is coupled to the non-circular cam 62. The fixing part 70 then fixes the non-circular cam 62 to the second end E2. Specifically, the second end E2 is positioned in the through hole 62a from one axial AD side of the non-circular cam 62. In other words, the second end E2 is positioned in the through hole 62a from the side where the motor 100 (Figure 2) is located. The second end E2 passes through the shim ring 73.

[0088] On the other hand, a portion of the annular member 72 is positioned in the through hole 62a from the other axial AD side of the non-circular cam 62. In other words, a portion of the annular member 72 is positioned in the through hole 62a from the opposite side of the motor 100 (Figure 2) relative to the non-circular cam 62.

[0089] The coupling member 71 is positioned on the central axis AX. The coupling member 71 penetrates the annular member 72 axially AD and connects to the second end E2, pressing the annular member 72 against the non-circular cam 62 in the axial direction AD. As a result, the non-circular cam 62 is fixed to the rotating shaft 21. In particular, because the coupling member 71 and the annular member 72 are positioned on the central axis AX, it is possible to suppress the non-circular cam 62 from being fixed eccentrically with respect to the central axis AX. Therefore, fluctuations in the force acting from the external teeth A20 of the flexible external gear A2 to the internal teeth A10 of the rigid internal gear A1 during rotation can be suppressed. As a result, excessive force acting from the internal teeth A10 to the external teeth A20 can be suppressed, improving the durability of both the external teeth A20 and the internal teeth A10. Furthermore, the meshing between the internal teeth A10 and the external teeth A20 can be maintained to efficiently achieve the reduction ratio specified in the product specifications.

[0090] Furthermore, in this embodiment, the annular member 72 ensures a relatively wide seating surface, thereby suppressing plastic deformation of the seating surface. As a result, the fixing of the non-circular cam 62 by tightening the connecting member 71 becomes stronger. The head 71a of the connecting member 71 contacts the annular member 72 while tightening the annular member 72.

[0091] In particular, the annular member 72 has a frustoconical shape that tapers towards the second end E2. Therefore, the contact area between the annular member 72 and the inner circumferential surface 620 of the non-circular cam 62 can be increased. As a result, the annular member 72 becomes less likely to slip against the inner circumferential surface 620 of the non-circular cam 62, and the non-circular cam 62 can be more firmly fixed to the rotating shaft 21. Specifically, the circumferential surface 72d of the annular member 72 and the second inner circumferential surface 622 of the non-circular cam 62 are in contact. On the other hand, the outer circumferential surface of the second end E2 is in contact with the first inner circumferential surface 621 of the non-circular cam 62.

[0092] Furthermore, in this embodiment, the axial AD end 72b of the annular member 72 and the axial AD end 21c of the second end E2 are spaced apart and face each other in the axial AD. Therefore, a gap GP is formed between the end 72b of the annular member 72 and the end 21c of the second end E2. As a result, the annular member 72 and the rotating shaft 21 do not come into contact. Thus, even if there are dimensional tolerances between the annular member 72 and the rotating shaft 21, the connecting member 71 can be screwed into the second end E2 until the desired fastening force is secured.

[0093] Furthermore, in this embodiment, a portion 625 on one side of the non-circular cam 62 in the axial direction AD is pressed against the annular surface 25 of the rotating shaft 21 in the axial direction AD. Therefore, the non-circular cam 62 is sandwiched between the annular member 72 and the annular surface 25 and tightened by the connecting member 71. As a result, the non-circular cam 62 can be more firmly fixed to the rotating shaft 21.

[0094] A portion 625 on one side of the non-circular cam 62 in the axial direction AD is the surface 626 on the axial direction AD of the non-circular cam 62 that faces the annular surface 25 in the axial direction AD via the shim ring 73. In other words, a portion 625 on one side of the non-circular cam 62 in the axial direction AD is a substantially annular region surrounding the through hole 62a in the circumferential direction CD.

[0095] In particular, in this embodiment, a portion 625 on one side of the non-circular cam 62 in the axial direction AD is pressed against the annular surface 25 of the rotating shaft 21 in the axial direction AD via a shim ring 73. That is, the shim ring 73 is positioned between the surface 626 of the non-circular cam 62 and the annular surface 25. Therefore, a decrease in the fastening force of the connecting member 71 due to aging can be suppressed. Note that the shim ring 73 may be omitted. In this case, a portion 625 on one side of the non-circular cam 62 in the axial direction AD will be in contact with the annular surface 25 of the rotating shaft 21.

[0096] Next, with reference to Figure 11, the procedure for fixing the non-circular cam 62 to the rotating shaft 21 will be explained. Figure 11 is a side view showing the procedure for fixing the rotating shaft 21 to the non-circular cam 62.

[0097] As shown in Figure 11, the tip 15X of the tool TL1 is fitted into the first fitting portion 22 of the first end E1 of the rotating shaft 21. Specifically, the tip 15X of the tool TL1 has a pair of blades 15a and a pair of blades 15b. The pair of blades 15a are fitted into the first recess 23 of the first fitting portion 22. The pair of blades 15b are fitted into the second recess 24 (Figure 5B) of the first fitting portion 22. The tool TL1 is kept stationary so as not to rotate in the circumferential direction CD. The tool TL1 is, for example, a Phillips screwdriver. The tool TL1 corresponds to an example of a "component".

[0098] Meanwhile, the connecting member 71, in which the annular member 72 is inserted into the shaft portion 71b, is screwed into the second end portion E2 by the tool TL2. Specifically, the connecting member 71 is screwed into the second end portion E2 by the tool TL2 rotating the connecting member 71 in the circumferential direction CD. In this case, since the tip portion 15X of the tool TL1 is fitted into the first fitting portion 22, the rotation axis 21 is prevented from rotating in the circumferential direction CD. Therefore, the connecting member 71 can be effectively screwed into the second end portion E2 by the tool TL2. As a result, tightening by the connecting member 71 can be performed stably. The tool TL2 is, for example, a hexagonal wrench.

[0099] In other words, according to this embodiment, by providing the first fitting portion 22 on the rotating shaft 21, the reduction gear 200 can be effectively fixed to the rotating shaft 21 of the motor 100 when the task of fixing the reduction gear 200 to the rotating shaft 21 of the motor 100 is required.

[0100] As described above with reference to Figure 11, the tool TL1 is fitted into the first fitting portion 22 of the rotating shaft 21 in the axial direction AD. The first fitting portion 22 has a shape that restricts the rotation of either the rotating shaft 21 or the tool TL1 relative to the other in the circumferential direction CD. Furthermore, the shape of the first fitting portion 22 restricts the radial movement RD of the tool TL1.

[0101] (First variation) A first modified example of this embodiment will be described with reference to Figure 12. The first modified example differs from the embodiment described with reference to Figure 5B in that the first fitting portion 22x has a substantially polygonal recess. The differences between the first modified example and the embodiment described above will be mainly described below.

[0102] Figure 12A is a perspective view showing the magnet holding member 5A of the reduction gear SR according to the first modified example. Figure 12B is a perspective view showing the rotating shaft 21A of the reduction gear SR according to the first modified example. Figure 12C is a plan view showing the rotating shaft 21A of the reduction gear SR according to the first modified example.

[0103] As shown in Figure 12A, the magnet holding member 5A has a second fitting portion 5x. The second fitting portion 5x protrudes from the bottom surface 505 of the holding portion 5a in the axial direction AD. The second fitting portion 5x is polygonal prism-shaped. In the example of Figure 12A, the second fitting portion 5x is hexagonal prism-shaped. Specifically, the second fitting portion 5x has a plurality of wall surfaces W2 arranged in the circumferential direction CD. Adjacent wall surfaces W2 in the circumferential direction CD form an obtuse angle. However, adjacent wall surfaces W2 in the circumferential direction CD may form an acute angle or a right angle. The magnet holding member 5A corresponds to an example of a "member". The second fitting portion 5x corresponds to an example of a "part of a member".

[0104] On the other hand, as shown in Figure 12B, the rotating shaft 21A has a first fitting portion 22x. The first fitting portion 22x is recessed in the axial direction AD toward the reduction gear 200 (Figure 3) relative to the end face 21a of the first end E1. In other words, the first fitting portion 22x is recessed in the axial direction AD toward the second end E2. A magnet holding member 5A, which holds a magnet 91 (Figure 4), is fitted into the first fitting portion 22x in the axial direction AD. The first fitting portion 22x is an example of a "fitting portion".

[0105] Specifically, as shown in Figure 12C, the second fitting portion 5x of the magnet holding member 5A is fitted into the first fitting portion 22x of the rotating shaft 21A. The first fitting portion 22x has a shape that restricts one of the rotating shaft 21A and the magnet holding member 5A from rotating relative to the other in the circumferential direction CD. Furthermore, the shape of the first fitting portion 22x restricts the movement of the magnet holding member 5A in the radial direction RD. In detail, the first fitting portion 22x has a plurality of wall surfaces W1 arranged in the circumferential direction CD. Adjacent wall surfaces W1 in the circumferential direction CD form an obtuse angle. However, adjacent wall surfaces W1 in the circumferential direction CD may form an acute angle or a right angle.

[0106] When fixing the non-circular cam 62 to the rotating shaft 21A, a hexagonal wrench, for example, is used as the tool TL1 (Figure 10).

[0107] (Second variation) A second modification of this embodiment will be described with reference to Figure 13. The second modification mainly differs from the embodiment described with reference to Figure 5B in that the first fitting portion 22y has a protrusion. The differences between the second modification and the embodiment described above will be mainly explained below.

[0108] Figure 13A is a perspective view showing the magnet holding member 5B of the reduction gear SR according to the second modified example. Figure 13B is a perspective view showing the rotating shaft 21B of the reduction gear SR according to the second modified example. Figure 13C is a plan view showing the rotating shaft 21B of the reduction gear SR according to the second modified example.

[0109] As shown in Figure 13A, the magnet holding member 5B has a second fitting portion 5y. The second fitting portion 5y is recessed in the axial direction AD from the bottom surface 505 of the holding portion 5a. Specifically, the second fitting portion 5y includes a first recess 95 and a second recess 96. The first recess 95 and the second recess 96 are recessed in the axial direction AD from the bottom surface 505 of the holding portion 5a. The first recess 95 extends in a first direction D1. The second recess 96 extends in a second direction D2. The magnet holding member 5B corresponds to an example of a "member". The second fitting portion 5y corresponds to an example of a "part of a member".

[0110] Specifically, the first recess 95 has a pair of wall surfaces W4 and W5 that face each other in the circumferential direction CD. The pair of wall surfaces W4 and W5 extend in the first direction D1. The second recess 96 also has a pair of wall surfaces W6 and W7 that face each other in the circumferential direction CD. The pair of wall surfaces W6 and W7 extend in the second direction D2.

[0111] On the other hand, as shown in Figure 13B, the rotating shaft 21 has a first fitting portion 22y. The first fitting portion 22y protrudes in the axial direction AD from the end face 21a of the first end portion E1. A magnet holding member 5B, which holds the magnet 91 (Figure 4), is fitted into the first fitting portion 22y in the axial direction AD. The first fitting portion 22y is an example of a "fitting portion".

[0112] Specifically, the first fitting portion 22y has a first protrusion 23y and a second protrusion 24y. The first protrusion 23y and the second protrusion 24y project in the axial direction AD relative to the end face 21a of the first end portion E1. The first protrusion 23y extends in the first direction D1. The second protrusion 24y extends in the second direction D2.

[0113] As shown in Figure 13C, the second fitting portion 5y of the magnet holding member 5B is fitted into the first fitting portion 22y of the rotating shaft 21B. The first fitting portion 22y has a shape that restricts one of the rotating shaft 21B and the magnet holding member 5B from rotating relative to the other in the circumferential direction CD. Furthermore, the shape of the first fitting portion 22y restricts the radial movement RD of the magnet holding member 5B.

[0114] When fixing the non-circular cam 62 to the rotating shaft 21A, a Phillips screwdriver, for example, is used as the tool TL1 (Figure 10).

[0115] (Third variation) A second modification of this embodiment will be described with reference to Figure 14. The second modification mainly differs from the embodiment described with reference to Figure 5B in that the first fitting portion 22z has a substantially polygonal protrusion. The differences between the third modification and the above embodiment will be mainly described below.

[0116] Figure 14A is a perspective view showing the magnet holding member 5C of the reduction gear SR according to the third modified example. Figure 14B is a perspective view showing the rotating shaft 21C of the reduction gear SR according to the third modified example. Figure 14C is a plan view showing the rotating shaft 21C of the reduction gear SR according to the third modified example.

[0117] As shown in Figure 14A, the magnet holding member 5C has a second fitting portion 5z. The second fitting portion 5z is recessed in the axial direction AD from the bottom surface 505 of the holding portion 5a. The second fitting portion 5z is a polygonal prism-shaped recess. In the example of Figure 14A, the second fitting portion 5z is a hexagonal prism-shaped recess. Specifically, the second fitting portion 5z has a plurality of wall surfaces W9 arranged in the circumferential direction CD. Adjacent wall surfaces W9 in the circumferential direction CD form an obtuse angle. However, adjacent wall surfaces W9 in the circumferential direction CD may form an acute angle or a right angle. The magnet holding member 5C corresponds to an example of a "member". The second fitting portion 5z corresponds to an example of a "part of a member".

[0118] On the other hand, as shown in Figure 14B, the rotating shaft 21C has a first fitting portion 22z. The first fitting portion 22z protrudes in the axial direction AD from the end face 21a of the first end portion E1. A magnet holding member 5C, which holds the magnet 91 (Figure 4), is fitted into the first fitting portion 22z in the axial direction AD. The first fitting portion 22z is an example of a "fitting portion".

[0119] Specifically, as shown in Figure 14C, the second fitting portion 5z of the magnet holding member 5C is fitted into the first fitting portion 22z of the rotation shaft 21C. The first fitting portion 22z has a shape that restricts one of the rotation shaft 21C and the magnet holding member 5C from rotating relative to the other in the circumferential direction CD. Furthermore, the shape of the first fitting portion 22z restricts the movement of the magnet holding member 5C in the radial direction RD. In detail, the first fitting portion 22z has a plurality of wall surfaces W8 arranged in the circumferential direction CD. Adjacent wall surfaces W8 in the circumferential direction CD form an obtuse angle. However, adjacent wall surfaces W8 in the circumferential direction CD may form an acute angle or a right angle.

[0120] When fixing the non-circular cam 62 to the rotating shaft 21A, a wrench, for example, is used as the tool TL1 (Figure 10).

[0121] (Fourth variation) A fourth modification of the present invention will be described with reference to Figure 15. The fourth modification mainly differs from the embodiment described with reference to Figure 10A in that the annular member 72A for fixing the non-circular cam 62 to the rotating shaft 21 is not frustoconical. The differences between the fourth modification and the embodiment described above will be mainly explained below.

[0122] Figure 15 is a perspective view showing an annular member 72A according to the fourth modified example. As shown in Figure 15, the annular member 72A has a cylindrical portion 721 and an annular portion 720. The cylindrical portion 721 has a substantially cylindrical shape. The cylindrical portion 721 extends axially AD from the annular portion 720 toward the side where the motor 100 (Figure 2) is located. The cylindrical portion 721 is positioned in the through hole 62a (Figure 7) of the non-circular cam 62. The annular portion 720 has a substantially annular shape. The annular portion 720 expands radially RD outward from the axial AD end of the cylindrical portion 721. The head 71a (Figure 7) of the coupling member 71 contacts the annular portion 720, and the annular member 72A is tightened by the head 71a.

[0123] Embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from its spirit. Furthermore, the multiple components disclosed in the above embodiments can be modified as appropriate. For example, some components from all the components shown in one embodiment may be added to the components of another embodiment, or some components from all the components shown in one embodiment may be deleted from the embodiment.

[0124] Furthermore, the drawings schematically show each component in order to facilitate understanding of the invention, and the thickness, length, number, spacing, etc. of each component shown may differ from the actual dimensions due to the convenience of drawing creation. Also, the configuration of each component shown in the above embodiments is merely an example and is not particularly limiting, and it goes without saying that various modifications are possible without substantially departing from the effects of the present invention.

[0125] In the speed reducer 200 described with reference to Figures 2 and 3, a flexible external gear A2 was described as an example of a "flexible contact member," and a rigid internal gear A1 was described as an example of an "annular contact member." However, the "flexible contact member" and the "annular contact member" are not particularly limited, as long as they can convert rotational motion at a first rotational speed to rotational motion at a second rotational speed lower than the first rotational speed. For example, when the speed reducer 200 performs reduction using traction (friction), the "flexible contact member" may be flexible but not have external teeth, and the "annular contact member" may be elastic but not have internal teeth. In this case, the outer circumferential surface of the "flexible contact member" contacts the inner circumferential surface of the "annular contact member" via a lubricating oil film.

[0126] Furthermore, the shapes of the first fitting portions 22, 22x~22z and the second fitting portions 5b, 5x~5z are not particularly limited, as long as the movement of the magnet holding members 5, 5A~5C and the tool TL1 in the circumferential direction CD and radial direction RD is restricted. For example, each of the first fitting portion and the second fitting portion may have a convex portion and a concave portion. [Industrial applicability]

[0127] This disclosure can be used, for example, in a gearbox. [Explanation of Symbols]

[0128] 21 Rotation axis (input axis) 25 Annular surface 62 Non-circular cam 62a through hole 70 Fixed part 71 Connecting member 72 Annular member 100 motor 200 reducer A1 Rigid internal gear (annular contact member) A2 Flexible external gear (flexible contact member) A3 Wave Generator E1 1st end E2 2nd end (joint part)

Claims

1. A reduction gear that reduces the rotational speed of a motor, An input axis that rotates around a central axis, A wave generator having a non-circular cam with different outer diameters depending on its circumferential position, and rotating about the central axis, The wave generator contacts a flexible contact member from the radially inward direction, The flexible contact member contacts an annular contact member from the radially inner side, A fixing part for fixing the non-circular cam to the input shaft It has, The flexible contact member rotates relative to the annular contact member in accordance with the rotation of the wave generator. The input shaft has a coupling portion that connects to the non-circular cam, The non-circular cam has a through hole that penetrates the non-circular cam axially on the central axis, The coupling portion is positioned in the through hole from one axial side of the non-circular cam, The fixing portion has an annular member and a connecting member. A portion of the annular member is positioned in the through hole from the other axial side of the non-circular cam. The connecting member is positioned on the central axis and, in a state where it penetrates the annular member axially and is connected to the connecting portion, presses the annular member axially against the non-circular cam. The annular member has a frustoconical shape that tapers towards the joint, The through hole of the non-circular cam has a shape that widens towards the other axial side of the non-circular cam, corresponding to the frustoconical shape of the annular member. A gearbox in which the axial end of the frustoconical shape of the annular member and the axial end of the connecting portion are spaced apart and face each other in the axial direction.

2. The input shaft has an annular surface that extends radially outward from the end of the coupling portion furthest from the annular member in the axial direction, The gearbox according to claim 1, wherein a portion of one axial side of the non-circular cam is pressed axially against the annular surface.

Images