Torque transmission mechanism

Abstract

To provide a torque transmission mechanism which does not need an inner pin.SOLUTION: A torque transmission mechanism includes: a first member having a circular column shape and configured to be rotatable around a rotation axis, the first member including an outer peripheral surface provided with a first zigzag-shaped groove extending around the rotation axis; a second member having an annular shape surrounding the first member and configured to be rotatable around the rotation axis, the second member including an inner peripheral surface provided with a second zigzag-shaped groove extending around the rotation axis; one or more first rolling members disposed in and configured to be rollable in the first groove and in the second groove; and a first regulating member disposed between the first member and the second member and configured to allow movement of the first rolling members along the rotation axis and regulate movement of the first rolling members around the rotation axis.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a torque transmission mechanism. [Background technology]

[0002] Regarding torque transmission mechanisms, an eccentric oscillation type reduction mechanism is disclosed in Patent Document 1. In the reduction mechanism of Patent Document 1, torque transmission is achieved by transmitting the rotation component of the external gear to a carrier body via an inner pin. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-132364 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technique of Patent Document 1, when the mechanism is in operation, a load in the shear direction is generated on the inner pin that is responsible for torque transmission, which may cause the inner pin to break. [Means for solving the problem]

[0005] According to one aspect of the present disclosure, there is provided a torque transmission mechanism comprising: a first member having a cylindrical shape and configured to be rotatable about a rotation axis, the first member having an outer circumferential surface with a first zigzag groove extending about the rotation axis, a second member having an annular shape surrounding the first member and configured to be rotatable about the rotation axis, the second member having an inner circumferential surface with a second zigzag groove extending about the rotation axis, one or more first rolling members disposed in the first groove and the second groove and configured to be rollable within the first groove and the second groove, and a first restricting member disposed between the first member and the second member and configured to allow movement of the first rolling members along the rotation axis and restrict movement of the first rolling members about the rotation axis. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 2 is a perspective view showing a schematic configuration of a torque transmission mechanism according to the first embodiment. [Figure 2] FIG. 2 is an exploded perspective view showing a schematic configuration of a torque transmission mechanism according to the first embodiment. [Figure 3] Cross-sectional view of FIG. 1 taken along line III-III. [Figure 4] IV-IV cross section of Figure 1. [Figure 5] FIG. 2 is a first explanatory diagram of the torque transmission mechanism according to the first embodiment. [Figure 6] FIG. 4 is a second explanatory diagram of the torque transmission mechanism according to the first embodiment. [Figure 7] FIG. 10 is a cross-sectional view schematically showing the general configuration of a torque transmission mechanism according to a second embodiment. [Figure 8] Cross-sectional view of VIII-VIII in Figure 7. [Figure 9] FIG. 10 is a cross-sectional view schematically showing the general configuration of a torque transmission mechanism according to a third embodiment. [Figure 10] FIG. 10 is a cross-sectional view schematically showing the general configuration of a torque transmission mechanism according to a fourth embodiment. [Figure 11] FIG. 11 is a perspective view showing a schematic configuration of a torque transmission mechanism according to a fifth embodiment. [Figure 12] FIG. 11 is an exploded perspective view showing a schematic configuration of a torque transmission mechanism according to a fifth embodiment. [Figure 13] XIII-XIII cross section of Figure 11. [Figure 14] XIV-XIV cross section of Figure 11. [Figure 15] FIG. 6 is an explanatory diagram of a first example of a torque transmission mechanism according to another embodiment. [Figure 16] FIG. 10 is an explanatory diagram of a second example of a torque transmission mechanism according to another embodiment. [Figure 17] FIG. 10 is an explanatory diagram of a third example of a torque transmission mechanism according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] A. First embodiment: FIG. 1 is a perspective view showing a schematic configuration of a torque transmission mechanism 100 according to a first embodiment. FIG. 2 is an exploded perspective view showing a schematic configuration of the torque transmission mechanism 100. FIG. 1 shows arrows indicating mutually orthogonal X, Y, and Z directions. The X and Y directions are parallel to a horizontal plane, and the Z direction is a vertically upward direction. The arrows indicating the X, Y, and Z directions are also shown in other figures as appropriate so that the illustrated directions correspond to those in FIG. 1. In the following description, when specifying the direction, positive and negative signs are used in combination to indicate the direction indicated by the arrow in each figure, with "+" indicating the direction indicated by the arrow and "-" indicating the opposite direction. Hereinafter, the +Z direction will also be referred to as "up" and the -Z direction as "down."

[0008] In this embodiment, the torque transmission mechanism 100 is configured as a reduction gear device. As shown in Figures 1 and 2, the torque transmission mechanism 100 includes a first member 130, a second member 150, one or more first rolling members 170, and a first restricting member 190. Furthermore, the torque transmission mechanism 100 in this embodiment includes a first bearing portion 201 and a second bearing portion 202.

[0009] The torque transmission mechanism 100 in this embodiment has an overall cylindrical shape. The torque transmission mechanism 100 is disposed so that the rotation axis AX of the torque transmission mechanism 100 is aligned with the Z direction. In this embodiment, the rotation axis AX corresponds to the rotation axis of the first member 130 and the rotation axis of the second member 150. In this disclosure, the term "cylindrical shape" includes a solid cylindrical shape and a hollow cylindrical shape. In addition, hereinafter, the direction along the rotation axis AX will also be referred to as the rotation axis AX direction.

[0010] The circumferential direction DC of the torque transmission mechanism 100 corresponds to the circumferential direction of the first member 130 and the circumferential direction of the second member 150. In the present disclosure, the circumferential direction DC is defined as the counterclockwise direction when the torque transmission mechanism 100 is viewed from the +Z direction side. Furthermore, hereinafter, unless otherwise specified, "counterclockwise" means the counterclockwise direction when the torque transmission mechanism 100 is viewed from the +Z direction side. The same applies to "clockwise" as well.

[0011] The first member 130 has a cylindrical shape. More specifically, the first member 130 has a hollow cylindrical shape. The first member 130 is disposed such that its axial direction is along the Z direction. In this embodiment, the first member 130 is disposed at the innermost position in the horizontal direction among the components of the torque transmission mechanism 100. The first member 130 is configured to be rotatable around the rotation axis AX of the torque transmission mechanism 100. As shown in FIG. 2 , the first member 130 has an outer peripheral surface 131. A first groove 132 is provided in the outer peripheral surface 131. The first groove 132 has a zigzag shape that extends around the rotation axis AX on the outer peripheral surface 131. In this specification, the term "zigzag shape" refers to a shape that travels back and forth in a certain direction one or more times while extending in a direction perpendicular to that direction. In other words, the zigzag shape has one or more turning points. The turning points of the zigzag shape may be sharp or rounded. The details of the first groove 132 will be described later.

[0012] As shown in FIGS. 1 and 2, the second member 150 has an annular shape surrounding the first member 130. That is, the inner diameter of the second member 150 is larger than the outer diameter of the first member 130. The second member 150 is disposed so that its axial direction is along the Z direction. In this embodiment, the second member 150 is disposed at the outermost position in the horizontal direction among the components of the torque transmission mechanism 100. The second member 150 is configured to be rotatable around the rotation axis AX. As shown in FIG. 2, the second member 150 has an inner circumferential surface 151. A second groove 152 is provided in the inner circumferential surface 151. The second groove 152 has a zigzag shape that extends around the rotation axis AX on the inner circumferential surface 151. The second groove 152 will be described in detail later.

[0013] FIG. 3 is a cross-sectional view taken along line III-III of FIG. 1. FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 1. As shown in FIGS. 3 and 4 , the first rolling member 170 is disposed in the first groove 132 and the second groove 152 between the first member 130 and the second member 150. The first rolling member 170 is configured to be able to roll in the first groove 132 and the second groove 152. Specifically, the first rolling member 170 rolls in the first groove 132 and the second groove 152 so as to be disposed at a position where the first groove 132 and the second groove 152 intersect when viewed along the radial direction of the torque transmission mechanism 100. As the first rolling member 170 rolls in the first groove 132, the first rolling member 170 and the first member 130 move relative to each other. Furthermore, as the first rolling member 170 rolls in the second groove 152, the first rolling member 170 and the second member 150 move relative to each other. In this embodiment, the first rolling member 170 has a spherical shape. The first rolling member 170 is configured as a so-called steel ball, for example, and is made of stainless steel, iron or steel. As will be described later, the first rolling member 170 transmits torque between the first member 130 and the second member 150.

[0014] In this embodiment, the first rolling members 170 include rolling members 170A, 170B, 170C, 170D, and 170E. When there is no need to distinguish between the rolling members 170A to 170E, they are also simply referred to as first rolling members 170. When the torque transmission mechanism 100 is viewed from the +Z direction side, the rolling members 170A, 170B, 170C, 170D, and 170E are arranged in this order in the circumferential direction DC.

[0015] 3 and 4, the first restricting member 190 is disposed between the first member 130 and the second member 150. In this embodiment, the first restricting member 190 has a hollow cylindrical shape as a whole. The first restricting member 190 is disposed such that the axial direction of the first restricting member 190 is aligned with the Z direction.

[0016] The first restricting member 190 has a main body portion 191, a first flange portion 192, and a second flange portion 193. The main body portion 191 is a portion of the first restricting member 190 that is disposed within the annular portion of the second member 150. The first flange portion 192 is an annular flange portion that constitutes the lower end of the first restricting member 190. The second flange portion 193 is an annular flange portion that constitutes the upper end of the first restricting member 190. As shown in FIGS. 1 and 4 , the first flange portion 192 is not disposed within the annular portion of the second member 150, but is disposed below the lower end of the first member 130 and the lower end of the second member 150. In a similar manner, the second flange portion 193 is disposed above the upper end of the first member 130 and the upper end of the second member 150. In this embodiment, the first flange portion 192 is formed integrally with the main body portion 191. The second flange portion 193 is formed as a cap separate from the main body portion 191 and is fixed to the main body portion 191 via bolts 194. The outer diameter of the main body portion 191 is smaller than the inner diameter of the second member 150. On the other hand, the outer diameters of the first flange portion 192 and the second flange portion 193 are larger than the inner diameter of the second portion. The inner diameter of the main body portion 191 is larger than the outer diameter of the first member 130. On the other hand, the inner diameters of the first flange portion 192 and the second flange portion 193 are smaller than the outer diameter of the first member 130. The inner diameter of the first flange portion 192 is approximately the same as the inner diameter of the second flange portion 193. The outer diameter of the first flange portion 192 is approximately the same as the outer diameter of the second flange portion 193 .

[0017] As shown in FIGS. 2 to 4 , the main body 191 has slits 195. In this embodiment, the main body 191 has five slits 195. The slits 195 are configured as openings extending along the rotation axis AX, i.e., in the Z direction. Walls 196 of the main body 191 are disposed between the openings of the slits 195. The walls 196 correspond to the walls defining the openings of the slits 195 in the circumferential direction DC. As shown in FIGS. 2 and 4 , in this embodiment, the lower ends of the openings of the slits 195 are defined by the first flange 192. Furthermore, as shown in FIG. 4 , the upper ends of the openings of the slits 195 are defined by the second flange 193. The opening width of the openings of the slits 195 in the circumferential direction DC is slightly larger than the diameter of the first rolling member 170. Furthermore, the opening length of the slits 195 in the Z direction is larger than the opening width of the slits 195.

[0018] The first restricting member 190 has a first restricting portion 199. The first restricting portion 199 allows movement of the first rolling member 170 along the rotation axis AX, i.e., movement in the Z direction. On the other hand, the first restricting portion 199 restricts movement of the first rolling member 170 around the rotation axis AX. In this embodiment, the first restricting portion 199 includes a restricting portion 199A, a restricting portion 199B, a restricting portion 199C, a restricting portion 199D, and a restricting portion 199E. Hereinafter, when the restricting portions 199A to 199E are not distinguished from one another, they will each be simply referred to as a first restricting portion 199. The first restricting portion 199 will also be simply referred to as a restricting portion.

[0019] Specifically, in this embodiment, first restricting portion 199 has slit portion 195, which allows and restricts movement of first rolling member 170. For example, rolling member 170A is disposed within slit portion 195 of restricting portion 199A. As a result, movement of rolling member 170A in the Z direction along slit portion 195 is permitted. On the other hand, movement of rolling member 170A around rotation axis AX is restricted by wall portion 196 that defines slit portion 195. Similarly, rolling members 170B to 170E are disposed within slit portions 195 of restricting portions 199B to 199E, respectively. Note that the number of first rolling members 170 is preferably determined taking into account, for example, the strength of first restricting member 190. Specifically, the greater the number of first rolling members 170, the greater the total opening area of ​​each slit portion 195 in first restricting member 190, which may reduce the strength of first restricting member 190. It is preferable to set the number of first rolling members 170 to a number small enough to prevent such a reduction in strength.

[0020] The first bearing portion 201 is disposed between the first member 130 and the first restricting member 190. The first bearing portion 201 holds the first member 130 rotatably about the rotation axis AX relative to the first restricting member 190. The first bearing portion 201 is configured using various bearings, such as a ball bearing or a needle bearing. In this embodiment, two first bearing portions 201 are provided. Each first bearing portion 201 is press-fitted and fixed to the outside of the upper end and the outside of the lower end of the first member 130, respectively, and supports the upper end and the lower end of the first member 130. The first bearing portion 201 on the lower end side of the first member 130 is disposed inside the main body portion 191 so as to contact the upper surface of the first flange portion 192. The first bearing portion 201 on the upper end side of the first member 130 is disposed inside the main body portion 191 so as to contact the lower surface of the second flange portion 193. As a result, the movement of the first member 130 in the Z direction relative to the first restricting member 190 is restricted, and the first member 130 is held rotatably relative to the first restricting member 190.

[0021] The second bearing portion 202 is disposed between the second member 150 and the first restricting member 190. The second bearing portion 202 holds the second member 150 rotatably about the rotation axis AX relative to the first restricting member 190. The second bearing portion 202 may be formed, for example, by various bearings, similar to the first bearing portion 201. In this embodiment, two second bearing portions 202 are provided. Each second bearing portion 202 is press-fitted and fixed to the inside of the upper end and the inside of the lower end of the second member 150, respectively, and supports the upper and lower ends of the second member 150. The second bearing portion 202 on the lower end side of the second member 150 is disposed outside the main body portion 191 so as to contact the upper surface of the first flange portion 192. The second bearing portion 202 on the upper end side of the second member 150 is disposed outside the main body portion 191 so as to contact the lower surface of the second flange portion 193. As a result, the movement of the second member 150 in the Z direction relative to the first restricting member 190 is restricted, and the second member 150 is held rotatably relative to the first restricting member 190.

[0022] FIG. 5 is a first explanatory diagram of the torque transmission mechanism 100. FIG. 5 shows an outer peripheral surface 131t and an inner peripheral surface 151t. The outer peripheral surface 131t corresponds to the outer peripheral surface 131 when unfolded. The inner peripheral surface 151t corresponds to the inner peripheral surface 151 when unfolded. FIG. 5 shows the outer peripheral surface 131t and the inner peripheral surface 151t superimposed on each other. Also, in FIG. 5, each first restricting portion 199 is schematically indicated by a dashed line. Also, in FIG. 5, each first rolling member 170 is schematically indicated by hatching.

[0023] FIG. 5 shows the angle θ at the outer peripheral surface 131 and the inner peripheral surface 151. The angle θ increases as one moves in the circumferential direction DC. The angular position A0 of 0 degrees and the angular position A360 of 360 degrees shown in FIG. 5 are the same position. In this embodiment, the restricting portion 199A is located at the angular position A0. To facilitate understanding of the technology, FIG. 5 shows the rolling member 170A and the restricting portion 199A near the angular position A0 and the angular position A360, respectively. However, in reality, there is only one rolling member 170A and one restricting portion 199A.

[0024] In FIG. 5 , the first grooves 132 are indicated by thick lines. The first grooves 132 have a closed ring shape that goes around the outer peripheral surface 131 in the circumferential direction DC. The first grooves 132 as a whole have a periodic wave shape that moves back and forth in the Z direction on the outer peripheral surface 131 and advances along the circumferential direction DC. That is, when the first grooves 132 are considered as waves, the direction of advance of the first grooves 132 is along the circumferential direction DC, and the direction of vibration of the first grooves 132 is the Z direction. Specifically, the first grooves 132 have a triangular wave shape. The first grooves 132 have one period. That is, the first grooves 132 have one peak 132m and one valley 132v. The peak 132m and the valley 132v have a pointed shape. The positions of the peaks 132m in the Z direction are approximately the same. Furthermore, the positions of the valleys 132v in the Z direction are approximately the same. That is, when the first grooves 132 are regarded as waves, the amplitude of the first grooves 132 is approximately constant. Each peak and valley corresponds to a turning point of the zigzag shape described above. In this embodiment, the peaks are located on the +Z direction side of the valleys. In other embodiments, the positional relationship between the peaks and valleys may be reversed.

[0025] The second grooves 152 have a closed ring shape that goes around the inner circumferential surface 151 in the circumferential direction DC. The second grooves 152 as a whole have a periodic wave shape that moves back and forth in the Z direction on the inner circumferential surface 151 and advances along the circumferential direction DC. That is, when the second grooves 152 are considered as waves, the direction of advancement of the second grooves 152 is along the circumferential direction DC, and the direction of vibration of the second grooves 152 is the Z direction. Specifically, the second grooves 152 have a triangular wave shape. The second grooves 152 have a different period from the first grooves 132. Specifically, the second grooves 152 have 12 periods. That is, the second grooves 152 have 12 peaks 152m and 12 valleys 152v. The peaks 152m and the valleys 152v have pointed shapes. The positions of the peaks 152m in the Z direction are substantially the same as the positions of the peaks 132m in the Z direction. The positions of the valleys 152v in the Z direction are substantially the same as the positions of the valleys 132v in the Z direction. In other words, when the second grooves 152 are regarded as waves, the amplitude of the second grooves 152 is substantially constant and substantially the same as the amplitude of the first grooves 132.

[0026] In this embodiment, one of the first member 130 and the second member 150 is used as an input shaft, and the other is used as an output shaft in the torque transmission mechanism 100. The following describes the operation of the torque transmission mechanism 100 when the first member 130 is used as the input shaft.

[0027] Fig. 6 is a second explanatory diagram of the torque transmission mechanism 100. Fig. 6 shows a state in which the first member 130 serving as the input shaft has rotated in the circumferential direction DC around the rotation axis AX by a rotation angle θ1 from the state shown in Fig. 5. In the example shown in Fig. 6, the rotation angle θ1 is 60 degrees.

[0028] As shown in FIG. 6 , as the first member 130 rotates around the rotation axis AX, each of the first rolling members 170 rolls in the first groove 132 and the second groove 152. Specifically, as the first member 130 rotates, the first rolling members 170 roll along a path Pt1 in the first groove 132. The length of the path Pt1 in the circumferential direction DC corresponds to the rotation angle θ1. Specifically, the path Pt1 is a path whose start point S1 is the position of the first rolling member 170 in the first groove 132 before the first member 130 starts to rotate, and whose end point E1 is a position in the circumferential direction DC from the start point by an amount corresponding to the rotation angle θ1. In FIG. 6 , as an example of the path Pt1, the path Pt1 for the rolling member 170A is indicated by dotted hatching. When the first rolling member 170 rolls along the path Pt1, movement of the first rolling member 170 around the rotation axis AX is restricted, and the first rolling member 170 moves only in the Z direction in accordance with the first groove 132. As a result, the position of the first rolling member 170 in the circumferential direction DC does not change, but the position of the first rolling member 170 in the Z direction changes according to the position of the path Pt1 in the Z direction. Furthermore, by rolling along the path Pt2 in the second groove 152 while moving in the Z direction in this manner, the first rolling member 170 transmits torque to the second member 150 via the second groove 152, causing the second member 150 to rotate around the rotation axis AX. The path Pt2 is a path where the change in position of the first rolling member 170 in the rotation axis AX direction when passing through the path Pt2 is the same as the change in position of the first rolling member 170 in the rotation axis AX direction when passing through the path Pt1. 6, as an example of the path Pt2, the path Pt2 for the rolling member 170A is indicated by dotted hatching. As a result, the second member 150 rotates around the rotation axis AX by a rotation angle θ2 corresponding to the length of the path Pt2 in the circumferential direction DC, i.e., the length in the circumferential direction DC between the start point S2 and the end point E2 of the path Pt2. The ratio of the rotation angle θ2 to the rotation angle θ1 corresponds to the ratio of the period T1 of the first grooves 132 to the period T2 of the second grooves 152. That is, the reduction ratio RR1a in this case corresponds to the value obtained by dividing the period T1 by the period T2.As shown by the white arrow in Figure 6, it can also be said that the first rolling member 170, such as rolling member 170A, moves through the first groove 132 and the second groove 152 relative to the first member 130 and the second member 150 in the direction opposite to the rotational direction of the first member 130 and the second member 150.

[0029] The operation of the torque transmission mechanism 100 when the second member 150 is used as the input shaft is substantially the same as the operation of the torque transmission mechanism 100 when the first member 130 is used as the input shaft. In this case, the first rolling member 170 rolls in the first groove 132 due to the rotation of the second member 150, thereby transmitting torque to the first member 130 via the first groove 132. Furthermore, the reduction ratio RR1b in this case corresponds to the value obtained by dividing the period T2 by the period T1. That is, in this case, the rotation input to the torque transmission mechanism 100 via the second member 150 is accelerated and output via the first member 130.

[0030] As shown in FIG. 5 , each first rolling member 170 is disposed at an intersection position CP where the first groove 132 and the second groove 152 intersect when viewed along the radial direction DR. The intersection position CP includes a first intersection position CP1, a second intersection position CP2, a third intersection position CP3, and a fourth intersection position CP4. The first intersection position CP1 is a position where the first positive portion P1 and the second positive portion P2 intersect. The first positive portion P1 is a portion of the first groove 132 that extends from the valley portion 132v toward the peak portion 132m in the forward direction of the circumferential direction DC. The second positive portion P2 is a portion of the second groove 152 that extends from the valley portion 152v toward the peak portion 152m in the forward direction of the circumferential direction DC. The second intersection position CP2 is a position where the first negative portion N1 and the second negative portion N2 intersect. The first negative portion N1 is a portion of the first groove 132 that extends from the peaks 132m toward the valleys 132v toward the forward side in the circumferential direction DC. The second negative portion N2 is a portion of the second groove 152 that extends from the peaks 152m toward the valleys 152v toward the forward side in the circumferential direction DC. The third intersection position CP3 is a position where the first positive portion P1 and the second negative portion N2 intersect. The fourth intersection position CP4 is a position where the first negative portion N1 and the second positive portion P2 intersect. Note that the first positive portion P1 and the first negative portion N1 both include the apex of the peaks 132m and the apex of the valleys 132v. Note that the second positive portion P2 and the second negative portion N2 both include the apex of the peaks 152m and the apex of the valleys 152v.

[0031] In this embodiment, each first rolling member 170 is disposed at the first intersecting position CP1 or the second intersecting position CP2. As a result, the rotation directions of the first member 130 and the second member 150 are the same. Note that in other embodiments, each first rolling member 170 may be disposed at the third intersecting position CP3 or the fourth intersecting position CP4. In this case, the rotation directions of the first member 130 and the second member 150 are opposite to each other.

[0032] According to the torque transmission mechanism 100 of the present embodiment described above, the first rolling members 170 disposed in the first groove 132 of the first member 130 and the second groove 152 of the second member 150 are configured to be able to roll within the first groove 132 and the second groove 152. Within the first groove 132 and the second groove 152, movement of the first rolling members 170 along the rotation axis AX is permitted, while movement of the first rolling members 170 around the rotation axis AX is restricted. Therefore, torque can be transmitted between the first member 130 and the second member 150 without using a torque transmission pin.

[0033] Furthermore, in this embodiment, the number of peaks 132m and valleys 132v of the first grooves 132 is different from the number of peaks 152m and valleys 152v of the second grooves 152. According to this embodiment, the rotation speed between the first member 130 and the second member 150 can be reduced depending on the number of peaks 132m and valleys 132v of the first grooves 132 and the number of peaks 152m and valleys 152v of the second grooves 152. That is, the rotation speed between the first member 130 and the second member 150 can be reduced depending on the difference between the period T1 of the first grooves 132 and the period T2 of the second grooves 152. Furthermore, in this embodiment, various reduction ratios can be achieved with a high degree of freedom by arbitrarily changing the combination of the period T1 and the period T2.

[0034] In this embodiment, the first rolling member 170 has a spherical shape. Therefore, the first rolling member 170 can roll more smoothly in the first groove 132 and the second groove 152. As a result, wear of the first member 130, the second member 150, the first rolling member 170, and the first restricting member 190 can be suppressed.

[0035] Furthermore, in this embodiment, first rolling member 170 includes one rolling member 170A and another rolling member 170B. In this way, torque can be transmitted between first member 130 and second member 150 using rolling member 170A and rolling member 170B. Therefore, for example, the load on each first rolling member 170 can be reduced compared to a configuration in which rolling member 170A is provided.

[0036] Furthermore, providing multiple first rolling members 170 as in this embodiment makes it easier to uniquely determine the rotational direction of the second member 150 relative to the first member 130, or the rotational direction of the first member 130 relative to the second member 150. Specifically, for example, if only the rolling member 170A is provided, when the rolling member 170A approaches the crest 152m or the valley 152v of the second groove 152 due to rotation of the first member 130 as an input shaft, the rolling member 170A can move in either direction in the circumferential direction DC within the second groove 152. As a result, the second member 150 can rotate both in the forward direction of the circumferential direction DC and in the reverse direction of the circumferential direction DC, which may result in a phenomenon in which the second member 150 reciprocates in a closed space in the circumferential direction DC. This phenomenon is particularly likely to occur when the rotation speed of the first member 130 or the second member 150 is low. Note that this phenomenon can also occur when second member 150 is used as an input shaft. On the other hand, if rolling member 170B is provided in addition to rolling member 170A, for example, when rolling member 170A approaches peak portion 152m or valley portion 152v, rolling member 170B can be positioned in a portion of second groove 152 other than peak portion 152m and valley portion 152v. In this case, the movement direction of rolling member 170B within second groove 152 is uniquely determined, and therefore the movement direction of rolling member 170B within second groove 152 and the rotation direction of second member 150 are also uniquely determined.

[0037] Furthermore, in this embodiment, the first member 130 can be rotated more smoothly relative to the first restricting member 190 via the first bearing portion 201 disposed between the first member 130 and the first restricting member 190.

[0038] In addition, in this embodiment, the second member 150 can be rotated more smoothly relative to the first restricting member 190 via the second bearing portion 202 arranged between the second member 150 and the first restricting member 190.

[0039] In this embodiment, the first groove 132 and the second groove 152 each have a triangular wave shape. Therefore, the amount of movement of the first rolling member 170 in the Z direction per unit rotation angle of the first member 130 or the second member 150 is substantially constant at each position in the first groove 132 and each position in the second groove 152. This allows the first member 130 to rotate more stably relative to the second member 150, or vice versa. As a result, more stable deceleration can be achieved between the first member 130 and the second member 150. Furthermore, compared to a case where the first groove 132 or the second groove 152 has a zigzag shape with rounded peaks and valleys, such as a sinusoidal shape, torque transmission efficiency at the peaks and valleys can be improved. As a result, torque can be transmitted more efficiently between the first member 130 and the second member 150.

[0040] B. Second embodiment: FIG. 7 is a cross-sectional view schematically illustrating the overall configuration of a torque transmission mechanism 100b according to the second embodiment. FIG. 8 is a cross-sectional view taken along line VIII-VIII of FIG. 7. FIG. 7 illustrates cross sections of the torque transmission mechanism 100b along the X and Y directions. FIG. 8 illustrates cross sections of the torque transmission mechanism 100b along the X and Z directions. As shown in FIGS. 7 and 8, in this embodiment, unlike the first embodiment, a third groove 162 is provided on the outer peripheral surface 161 of the second member 150b. The torque transmission mechanism 100b further includes a third member 230, one or more second rolling members 250, and a second restricting member 270. The torque transmission mechanism 100b according to this embodiment is similar to the first embodiment unless otherwise specifically described. Note that FIGS. 7 and 8 illustrate an example in which the number of first rolling members 170 and the number of second rolling members 250 are four. 7 and 8, the first groove 132, the second groove 152, and the third groove 162 are each schematically indicated by dashed lines. In addition, in Figures 7 and 8, members such as the first bearing portion 201 and the second bearing portion 202 are omitted as appropriate.

[0041] The third groove 162 has a zigzag shape that extends around the rotation axis AX on the outer circumferential surface 161. The third groove 162 is configured, for example, in substantially the same manner as the first groove 132. In this embodiment, the third groove 162 has a closed ring shape that goes around the outer circumferential surface 161 in the circumferential direction DC. The third groove 162 as a whole has a periodic wave shape that moves back and forth on the outer circumferential surface 161 along the rotation axis AX and advances along the circumferential direction DC. Specifically, the third groove 162 has a triangular wave shape. The period T3 of the third groove 162 may be the same as or different from the period T1 and the period T2. In this embodiment, the period T3 is 1. The positions of the peaks of the third groove 162 in the Z direction are substantially the same. Furthermore, the positions of the valleys of the third groove 162 in the Z direction are substantially the same.

[0042] As shown in FIG. 7, the third member 230 has an annular shape surrounding the second member 150b. That is, the inner diameter of the third member 230 is larger than the outer diameter of the second member 150b. In this embodiment, the third member 230 is disposed at the outermost position in the horizontal direction among the components of the torque transmission mechanism 100b. The third member 230 is configured to be rotatable around the rotation axis AX. As shown in FIGS. 7 and 8, the third member 230 has an inner circumferential surface 231. A fourth groove 232 is provided in the inner circumferential surface 231.

[0043] The fourth groove 232 has a zigzag shape that extends around the rotation axis AX on the inner circumferential surface 231. The fourth groove 232 is configured, for example, in a manner substantially similar to the second groove 152. The fourth groove 232 has a closed ring shape that extends around the inner circumferential surface 231 in the circumferential direction DC. The fourth groove 232 has a periodic wave shape that moves back and forth along the rotation axis AX on the inner circumferential surface 231 and advances along the circumferential direction DC. Specifically, the fourth groove 232 has a triangular wave shape. The fourth groove 232 has a period T4 that is different from the period T3. That is, the number of peaks and valleys of the third groove 162 is different from the number of peaks and valleys of the fourth groove 232. The period T4 may be the same as or different from the period T1 or T2. In this embodiment, the magnitude relationship between the period T4 and the period T3 is the same as the magnitude relationship between the period T2 and the period T1. Specifically, the period T4 in this embodiment is 12. The positions in the Z direction of the peaks of the fourth grooves 232 are substantially the same and are substantially the same as the positions in the Z direction of the peaks of the third grooves 162. Furthermore, the positions in the Z direction of the valleys of the fourth grooves 232 are substantially the same and are substantially the same as the positions in the Z direction of the valleys of the third grooves 162.

[0044] The second rolling member 250 is configured, for example, in substantially the same manner as the first rolling member 170. The second rolling member 250 is disposed in the third groove 162 and the fourth groove 232 between the second member 150b and the third member 230. The second rolling member 250 is configured to be able to roll in the third groove 162 and the fourth groove 232. Specifically, the second rolling member 250 rolls in the third groove 162 and the fourth groove 232 so as to be disposed at a position where the third groove 162 and the fourth groove 232 intersect when viewed along the radial direction of the torque transmission mechanism 100b. The second rolling member 250 in this embodiment has a spherical shape, similar to the first rolling member 170. The second rolling member 250 transmits torque between the second member 150b and the third member 230.

[0045] The second restricting member 270 is configured, for example, in substantially the same manner as the first restricting member 190. In this embodiment, the second restricting member 270 has a hollow cylindrical shape as a whole. The second restricting member 270 is disposed between the second member 150b and the third member 230. The second restricting member 270 allows movement of the second rolling member 250 along the rotation axis AX and restricts movement of the second rolling member 250 around the rotation axis AX. Note that, for example, bearings substantially similar to the first bearing 201 and the second bearing 202 may be disposed between the second restricting member 270 and the second member 150b and between the second restricting member 270 and the third member 230. That is, these bearings hold the second member 150b or the third member 230 rotatably about the rotation axis AX relative to the second restricting member 270.

[0046] In this embodiment, similar to the first embodiment, deceleration is achieved between the first member 130 and the second member 150b via the first rolling member 170. Furthermore, in this embodiment, deceleration is achieved between the second member 150b and the third member 230 via the second rolling member 250. The behavior of the third member 230 relative to the second member 150b is substantially the same as the behavior of the second member 150b relative to the first member 130. For example, when the first member 130 is used as an input shaft, a reduction ratio RR1a is achieved between the first member 130 and the second member 150b, and a reduction ratio RR2a is achieved between the second member 150b and the third member 230. The reduction ratio RR2a corresponds to the value obtained by dividing the period T3 by the period T4. As a result, a reduction ratio RR3a is achieved between the first member 130 as the input shaft and the third member 230 as the output shaft. The reduction ratio RR3a corresponds to the product of the reduction ratio RR1a and the reduction ratio RR2a. Furthermore, when the third member 230 is used as the input shaft, the reduction ratio RR2b is realized between the third member 230 and the second member 150b, and the reduction ratio RR1b is realized between the second member 150b and the first member 130. The reduction ratio RR2b corresponds to the value obtained by dividing the period T4 by the period T3. As a result, the reduction ratio RR3b is realized between the third member 230 as the input shaft and the first member 130 as the output shaft. The reduction ratio RR3b corresponds to the product of the reduction ratio RR1b and the reduction ratio RR2b. In other words, in this case, the rotation input to the torque transmission mechanism 100b is accelerated and then output.

[0047] According to the torque transmission mechanism 100b of the second embodiment described above, the second rolling members 250 are disposed in the third grooves 162 provided in the outer peripheral surface 161 of the second member 150b and in the fourth grooves 232 provided in the inner peripheral surface 231 of the third member 230 surrounding the second member 150b. The second rolling members 250 are configured to be able to roll within the third grooves 162 and the fourth grooves 232. Movement of the second rolling members 250 along the rotation axis AX is permitted, while movement of the second rolling members 250 around the rotation axis AX is restricted. The number of peaks and valleys in the third grooves 162 is different from the number of peaks and valleys in the fourth grooves 232. This configuration allows the rotation speed to be reduced in stages between the first member 130 and the second member 150b and between the second member 150b and the third member 230. Therefore, for example, a higher reduction ratio can be achieved without excessively increasing the pitch of the second grooves 152 and the fourth grooves 232. As a result, for example, an increase in the pitch of the second grooves 152 and the fourth grooves 232 can be prevented from increasing the size of the second member 150b and the third member 230, and a higher reduction ratio can be achieved while configuring the torque transmission mechanism 100b in a more space-saving manner. Furthermore, for example, an increase in the pitch of the second grooves 152 and the fourth grooves 232 can be prevented from excessively reducing the size of the first rolling member 170 and the second rolling member 250, and a higher reduction ratio can be achieved while suppressing a decrease in durability of the torque transmission mechanism 100b. Note that in other embodiments, for example, a fourth member may be provided outside the third member 230 to achieve more gradual reduction in speed.

[0048] C. Third embodiment: FIG. 9 is a cross-sectional view schematically illustrating the overall configuration of a torque transmission mechanism 100c according to a third embodiment. Similar to FIG. 8, FIG. 9 illustrates a cross section of the torque transmission mechanism 100c along the X and Z directions. Unlike the first embodiment, this embodiment includes a first corresponding groove 139 on the outer peripheral surface 131c of the first member 130c. Furthermore, a second corresponding groove 159 is provided on the inner peripheral surface 151c of the second member 150c. One or more third rolling members 280 are disposed in the first corresponding groove 139 and the second corresponding groove 159. Furthermore, the first restricting member 190 includes a second restricting portion 205. The torque transmission mechanism 100c according to this embodiment is similar to the first embodiment unless otherwise specifically described.

[0049] The first corresponding groove 139 is arranged alongside the first groove 132 in the Z direction. In this embodiment, the first corresponding groove 139 is arranged on the +Z direction side of the first groove 132. The first corresponding groove 139 is a groove that corresponds to the first groove 132 and has a zigzag shape that corresponds to the first groove 132. Specifically, the first corresponding groove 139 has the same period as the first groove 132. That is, the first corresponding groove 139 has a periodic wave shape with the same number of peaks 139m and valleys 139v as the peaks 132m and valleys 132v of the first groove 132. In this embodiment, the first groove 132 and the first corresponding groove 139 are arranged so that the peaks 132m of the first groove 132 and the valleys 139v of the first corresponding groove 139 face each other. In addition, for example, the portion of the first member 130c in which the first groove 132 is provided and the portion in which the first corresponding groove 139 is provided may be formed separately, and the first member 130c may be formed by fixing the two stacked portions together.

[0050] The second corresponding groove 159 is arranged alongside the second groove 152 in the Z direction. In this embodiment, the second corresponding groove 159 is arranged on the +Z direction side of the second groove 152. The second corresponding groove 159 is a groove that corresponds to the second groove 152 and has a zigzag shape that corresponds to the second groove 152. Specifically, the second corresponding groove 159 has the same period as the second groove 152. That is, the second corresponding groove 159 has a periodic wave shape having the same number of peaks 159m and valleys 159v as the peaks 152m and valleys 152v of the second groove 152. Furthermore, the number of peaks 139m and valleys 139v of the first corresponding groove 139 is different from the number of peaks 159m and valleys 159v of the second corresponding groove 159. In this embodiment, the second groove 152 and the second corresponding groove 159 are arranged so that the peaks 152m of the second groove 152 face the valleys 159v of the second corresponding groove 159. Note that the second member 150c may be configured such that, for example, the portion where the second groove 152 is provided and the portion where the second corresponding groove 159 is provided are separate members, similar to the first member 130c.

[0051] The third rolling member 280 is configured to be able to roll within the first corresponding groove 139 and the second corresponding groove 159. The third rolling member 280 is configured, for example, in substantially the same manner as the first rolling member 170. The third rolling member 280 transmits torque between the first member 130 and the second member 150 in substantially the same manner as the first rolling member 170. The second restricting portion 205 allows movement of the third rolling member 280 along the rotation axis AX and restricts movement of the third rolling member 280 around the rotation axis AX. The second restricting member 270 is configured, for example, in substantially the same manner as the first restricting portion 199. Specifically, in this embodiment, first restricting member 190 is provided with slit portion 195c that extends in the Z direction from first groove 132 and second groove 152 to first corresponding groove 139 and second groove 152, and slit portion 195c allows and restricts movement of first rolling member 170 and third rolling member 280. Note that in other embodiments, for example, first restricting portion 199 and second restricting portion 205 may each have separate slit portions, and each slit portion may allow and restrict movement of first rolling member 170 and third rolling member 280.

[0052] In this embodiment, the at least one first rolling member 170 is configured to be located at the peak 132m of the first groove 132 when the at least one third rolling member 280 is located at the valley 139v of the first corresponding groove 139. Furthermore, the at least one first rolling member 170 is configured to be located at the peak 152m of the second groove 152 when the at least one third rolling member 280 is located at the valley 159v of the second corresponding groove 159. Fig. 9 shows how the one rolling member 280p included in the third rolling member 280 is located at the valley 139v and the valley 159v when the one rolling member 170p included in the first rolling member 170 is located at the peak 132m and the peak 152m. Also shown is a state in which one rolling member 280q included in third rolling member 280 is located at peaks 139m and 159m when one rolling member 170q included in first rolling member 170 is located at valleys 132v and 152v. Note that, although not shown, when rolling member 170p is located at valleys 132v and 152v, rolling member 280p is located at peaks 139m and 159m. Similarly, when rolling member 170q is located at peaks 132m and 152m, rolling member 280q is located at valleys 139v and 159v.

[0053] According to the torque transmission mechanism 100c of the third embodiment described above, the third rolling member 280 disposed in the first corresponding groove 139 provided in the outer peripheral surface 131c of the first member 130c and the second corresponding groove 159 provided in the inner peripheral surface 151c of the second member 150c is configured to be able to roll within the first corresponding groove 139 and the second corresponding groove 159. Movement of the third rolling member 280 along the rotation axis AX is permitted, while movement of the third rolling member 280 around the rotation axis AX is restricted. This allows torque to be transmitted between the first member 130 and the second member 150 using the first rolling member 170 and the third rolling member 280. This reduces the load on each rolling member. Note that in other embodiments, for example, two or more first corresponding grooves 139 may be provided in the first member 130, and two or more second corresponding grooves 159 may be provided in the second member 150.

[0054] Furthermore, in this embodiment, when the rolling member 170p is located at the peaks 132m and 152m, the rolling member 280p is located at the valleys 139v and 159v. This allows the first rolling member 170 and the third rolling member 280 to move in opposite directions in the direction of the rotation axis AX, thereby preventing the torque transmission mechanism 100c from swinging in the direction of the rotation axis AX due to the movement of the first rolling member 170 and the third rolling member 280. Furthermore, in this embodiment, the first groove 132 and the first corresponding groove 139 are arranged so that the peaks 132m of the first groove 132 face the valleys 139v of the first corresponding groove 139. Furthermore, the second groove 152 and the second corresponding groove 159 are arranged so that the peaks 152m of the second groove 152 face the valleys 159v of the second corresponding groove 159. 9, the first rolling member 170 and the third rolling member 280 can be arranged so that their positions in the X direction are the same. As a result, as in this embodiment, for example, the pair of the first rolling member 170 and the third rolling member 280 can be arranged within one slit portion 195c, and the movement of the pair of the first rolling member 170 and the third rolling member 280 can be permitted and restricted by the slit portion 195c. In this way, with a simpler configuration, it is possible to prevent the torque transmission mechanism 100c from swinging in the direction of the rotation axis AX.

[0055] D. Fourth embodiment: Fig. 10 is a cross-sectional view schematically showing the overall configuration of a torque transmission mechanism 100d according to the fourth embodiment. Similar to Figs. 8 and 9, Fig. 10 shows a cross section of the torque transmission mechanism 100d taken along the X and Z directions. Unlike the first embodiment, the torque transmission mechanism 100d according to this embodiment has a first reduction gear unit 101, a second reduction gear unit 102, and a connecting member 103. The torque transmission mechanism 100d according to this embodiment is similar to the first embodiment in the respects that are not specifically described.

[0056] The first reduction gear unit 101 has the same configuration as the torque transmission mechanism 100 in the first embodiment. The second reduction gear unit 102 has, for example, substantially the same configuration as the first reduction gear unit 101. The second reduction gear unit 102 includes a fourth member 330, a fifth member 350, one or more fourth rolling members 370, and a third restricting member 390. Note that in other embodiments, for example, the components of the second reduction gear unit 102 and the components of the first reduction gear unit 101 may be interchanged. The second reduction gear unit 102 is disposed alongside the first reduction gear unit 101 in the Z direction. As a result, the fourth member 330 and the fifth member 350 are disposed alongside the first member 130 and the second member 150 in the Z direction. Specifically, in this embodiment, the second reduction section 102 is positioned on the +Z direction side of the first reduction section 101, so that the fourth member 330 and the fifth member 350 are positioned on the +Z direction side of the first member 130 and the second member 150.

[0057] The fourth member 330 corresponds to the first member 130 in the first reduction gear section 101 and is configured, for example, substantially similar to the first member 130. The fourth member 330 has a cylindrical shape. The fourth member 330 is configured to be rotatable around the rotation axis AX. The fourth member 330 has an outer peripheral surface 331 on which a fifth groove 332 is provided. The fifth groove 332 is configured, for example, substantially similar to the first groove 132. The fifth groove 332 has a zigzag shape that extends around the rotation axis AX and goes around the outer peripheral surface 131 in the circumferential direction DC. The fifth groove 332 has a periodic wave shape having peaks 332m and valleys 332v and has a period T5. The period T5 may be the same as or different from the periods T1 and T2. In this embodiment, the period T5 is 1. In this embodiment, the first grooves 132 and the fifth grooves 332 are arranged such that the peaks 132m of the first grooves 132 and the valleys 332v of the fifth grooves 332 face each other.

[0058] The fifth member 350 corresponds to the second member 150 in the first reduction gear section 101 and is configured, for example, in a manner substantially similar to the second member 150. The fifth member 350 has an annular shape that surrounds the fourth member 330. The fifth member 350 is configured to be rotatable around the rotation axis AX. The fifth member 350 has an inner circumferential surface 351 in which a sixth groove 352 is provided. The sixth groove 352 is configured, for example, in a manner substantially similar to the second groove 152. The sixth groove 352 has a zigzag shape that extends around the rotation axis AX and goes around the inner circumferential surface 351 in the circumferential direction DC. The sixth groove 352 has a periodic wave shape having peaks 352m and valleys 352v. The number of peaks 332m and valleys 332v of the fifth groove 332 is different from the number of peaks 352m and valleys 352v of the sixth groove 352. That is, the period T6 of the sixth grooves 352 is different from the period T5 of the fifth grooves 332. The period T6 may be the same as or different from the period T1 or T2. In this embodiment, the magnitude relationship between the periods T6 and T5 is the same as the magnitude relationship between the periods T2 and T1. Specifically, the period T6 in this embodiment is 12. In this embodiment, the second grooves 152 and the sixth grooves 352 are arranged so that the peaks 152m of the second grooves 152 and the valleys 352v of the sixth grooves 352 face each other.

[0059] The fourth rolling member 370 corresponds to the first rolling member 170 in the first reduction gear section 101 and is configured, for example, in substantially the same manner as the first rolling member 170. The fourth rolling member 370 is disposed in the fifth groove 332 and the sixth groove 352 and is configured to be able to roll within the fifth groove 332 and the sixth groove 352.

[0060] The third restricting member 390 corresponds to the first restricting member 190 in the first reduction gear section 101 and is configured, for example, in substantially the same manner as the first restricting member 190. The third restricting member 390 is disposed between the fourth member 330 and the fifth member 350. The third restricting member 390 allows movement of the fourth rolling member 370 along the rotation axis AX while restricting movement of the fourth rolling member 370 around the rotation axis AX. Similar to the first restricting member 190, for example, the third restricting member 390 allows and restricts movement of the fourth rolling member 370 by using a slit portion.

[0061] The connecting member 103 connects the first reduction gear part 101 and the second reduction gear part 102. More specifically, the connecting member 103 connects the second member 150 and the fourth member 330 rotatably around the rotation axis AX. In this embodiment, the connecting member 103 is disposed between the second member 150 and the fourth member 330 in the Z direction, and is fixed to an upper end of the second member 150 and a lower end of the fourth member 330.

[0062] In this embodiment, similarly to the second embodiment, it is possible to realize a stepwise rotation speed between the first member 130 and the second member 150 in the first reduction section 101, and between the fourth member 330 and the fifth member 350 in the second reduction section 102. Specifically, for example, when the first member 130 is used as the input shaft, a reduction ratio RR1a is realized between the first member 130 and the second member 150 in the first reduction section 101. At this time, the rotation of the second member 150 is transmitted to the fourth member 330 via the connecting member 103. Furthermore, in the second reduction section 102, reduction is realized between the fourth member 330 and the fifth member 350 via the fourth rolling member 370. In this case, the reduction ratio RR4a realized between the fourth member 330 and the fifth member 350 corresponds to the value obtained by dividing the period T5 by the period T6. As a result, a reduction gear ratio RR5a is realized between the first member 130 as the input shaft and the fifth member 350 as the output shaft. The reduction gear ratio RR5a corresponds to the product of the reduction gear ratios RR1a and RR4a. Furthermore, when the fifth member 350 is used as the input shaft, a reduction gear ratio RR4b is realized between the fifth member 350 and the fourth member 330 in the second reduction section 102, and a reduction gear ratio RR1b is realized in the first reduction section 101. As a result, a reduction gear ratio RR5b is realized between the fifth member 350 as the input shaft and the first member 130 as the output shaft. The reduction gear ratio RR5b corresponds to the product of the reduction gear ratios RR1b and RR4b. In other words, in this case, the rotation input to the torque transmission mechanism 100d is accelerated and then output.

[0063] In this embodiment, at least one first rolling member 170 is configured to be located at the peak 132m of the first groove 132 when at least one fourth rolling member 370 is located at the valley 332v of the fifth groove 332. Furthermore, the first rolling member 170 is configured to be located at the peak 152m of the second groove 152 when at least one fourth rolling member 370 is located at the valley 352v of the sixth groove 352. Fig. 10 shows how one rolling member 170p included in the fourth rolling member 370 is located at the valley 332v and the valley 352v when one rolling member 170p included in the first rolling member 170 is located at the peak 132m and the peak 152m. Also shown is a state in which one rolling member 170q included in first rolling member 170 is located at valley portion 132v and valley portion 152v, and one rolling member 370q included in fourth rolling member 370 is located at peak portion 332m and peak portion 352m. Note that, although not shown, when rolling member 170p is located at valley portion 132v and valley portion 152v, rolling member 370p is located at peak portion 332m and peak portion 352m. Similarly, when rolling member 170q is located at peak portion 132m and peak portion 152m, rolling member 370q is located at valley portion 332v and valley portion 352v.

[0064] According to the torque transmission mechanism 100d of the fourth embodiment described above, the first reduction gear unit 101 and the second reduction gear unit 102 are arranged side by side in the Z direction, and the second member 150 of the first reduction gear unit 101 and the fourth member 330 of the second reduction gear unit 102 are connected by the connecting member 103 to be rotatable around the rotation axis AX. In the second reduction gear unit 102, the fourth rolling members 370 are arranged in the fifth groove 332 of the fourth member 330 and the sixth groove 352 of the fifth member 350 and are configured to be able to roll within the fifth groove 332 and the sixth groove 352. Within the fifth groove 332 and the sixth groove 352, the fourth rolling member 370 is allowed to move along the rotation axis AX and is also allowed to move around the rotation axis AX. Furthermore, the number of peaks 332m and valleys 332v in the fifth groove 332 is different from the number of peaks 352m and valleys 352v in the sixth groove 352. This allows the rotation speed to be reduced in stages between the first member 130 and the second member 150 and between the fourth member 330 and the fifth member 350, thereby achieving a higher reduction ratio while conserving space in the radial direction for the torque transmission mechanism 100d. In other embodiments, for example, other reduction units may be coupled to the first reduction unit 101 or the second reduction unit 102 to achieve even more gradual reduction. Furthermore, for example, the configuration of the third embodiment may be combined with the configuration of the fourth embodiment to achieve even more gradual reduction.

[0065] Furthermore, in this embodiment, when the rolling member 170p is located at the peaks 132m and 152m, the rolling member 370p is located at the valleys 332v and 352v. This allows the first rolling member 170 and the fourth rolling member 370 to move in opposite directions along the rotation axis AX, thereby preventing the torque transmission mechanism 100d from swinging in the direction of the rotation axis AX due to the movement of the first rolling member 170 and the fourth rolling member 370.

[0066] E. Fifth embodiment: FIG. 11 is a perspective view showing a schematic configuration of a torque transmission mechanism 100e in a fifth embodiment. FIG. 12 is an exploded perspective view showing a schematic configuration of the torque transmission mechanism 100e. FIG. 13 is a cross-sectional view taken along XIII-XIII in FIG. 11. FIG. 14 is a cross-sectional view taken along XIV-XIV in FIG. 11. In this embodiment, the configuration of a first restricting member 190e is different from that of the first embodiment. Points of the torque transmission mechanism 100e in this embodiment that are not particularly described are the same as those in the first embodiment.

[0067] As shown in FIGS. 11, 12, and 14, the first restricting member 190e in this embodiment includes a columnar member 211, a first annular member 215, and a second annular member 220. As shown in FIG.

[0068] The first annular member 215 has a circular ring shape. The first annular member 215 is disposed such that the axial direction of the first annular member 215 is along the Z direction. The first annular member 215 is provided with a plurality of first through holes 216. The first through holes 216 penetrate the first annular member 215 in the Z direction. In this embodiment, the first annular member 215 is provided with ten first through holes 216.

[0069] The second annular member 220 has a circular ring shape. The second annular member 220 is disposed such that the axial direction of the second annular member 220 is along the Z direction. The second annular member 220 is provided with a plurality of second through holes 221. The second through holes 221 penetrate the second annular member 220 in the Z direction. In this embodiment, the second annular member 220 is provided with ten second through holes 221 corresponding to the ten first through holes 216.

[0070] In this embodiment, ten columnar members 211 are provided corresponding to the ten first through holes 216 and second through holes 221. The columnar members 211 have an overall cylindrical shape. The columnar members 211 are arranged such that their axial directions are along the Z direction. The columnar members 211 have a head portion 212 and a shaft portion 213. The head portion 212 has a diameter larger than the opening diameters of the first through holes 216 and the second through holes 221. The head portion 212 forms the upper end portion of the columnar member 211. The shaft portion 213 has a diameter slightly smaller than the opening diameters of the first through holes 216 and the second through holes 221. Each columnar member 211 is inserted into the second through holes 221 and the first through holes 216 from the +Z direction side. That is, the shaft portion 213 of each columnar member 211 is disposed in the first through-hole 216 and the second through-hole 221, respectively. The head portion 212 of each columnar member 211 is disposed on the +Z direction side of the second annular member 220. The lower end portion of each columnar member 211 is fixed to the first annular member 215 via a fixing member 225 and the first through-hole 216, respectively. The fixing member 225 is formed of, for example, a bolt and a washer. With this configuration, the columnar members 211 are connected to each other in the horizontal direction by the first annular member 215 and the second annular member 220.

[0071] As shown in FIGS. 12 and 14 , the columnar members 211 are connected to each other in the horizontal direction, thereby forming openings between adjacent columnar members 211 in the circumferential direction DC. In this embodiment, first rolling members 170 are disposed in five of these openings Op. The opening width of each opening Op in the circumferential direction DC is slightly larger than the diameter of the first rolling member 170. The opening length of each opening Op in the Z direction is larger than the opening width of each opening Op. Similar to the slit portion 195 described in the first embodiment, the openings Op allow movement of each first rolling member 170 in the Z direction and restrict movement of each first rolling member 170 around the rotation axis AX. Specifically, movement of the first rolling member 170 around the rotation axis AX is restricted by the columnar members 211 that define the openings Op. In this way, the first restricting member 190e in this embodiment allows and restricts movement of each first rolling member 170 by using the openings Op. The first regulating member 190e and the first regulating member 190 described in the first embodiment are similar in that they allow and regulate the movement of the first rolling member 170 by means of a groove-shaped opening extending in the Z direction.

[0072] The torque transmission mechanism 100e in the fifth embodiment described above can also reduce the rotational speed between the first member 130 and the second member 150 in accordance with the first groove 132 and the second groove 152 via the first rolling member 170, without using a pin for torque transmission.

[0073] In addition, a configuration similar to that of the first regulating member 190e in the fifth embodiment may be applied, for example, to the second regulating member 270 described in the second embodiment or the third regulating member 390 described in the fourth embodiment.

[0074] F. Other Embodiments: (F-1) In each of the above embodiments, first rolling member 170 has a spherical shape. However, first rolling member 170 does not have to be spherical as long as it can roll within first groove 132 and second groove 152. For example, first rolling member 170 may have a curved shape other than a sphere that allows it to roll within first groove 132 and second groove 152.

[0075] (F-2) In each of the above embodiments, a plurality of first rolling members 170 are provided. However, the number of first rolling members 170 may be one. Furthermore, as long as torque transmission by the torque transmission mechanism 100 is possible and each first rolling member 170 can be arranged in the first groove 132 and the second groove 152, the number of first rolling members 170 and the arrangement of the first rolling members 170 may be arbitrary. For example, the number of first rolling members 170 may be two or more and four or less, or six or more. Similarly, the number and arrangement of the second rolling members 250, the third rolling members 280, and the fourth rolling members 370 may be arbitrary. Furthermore, the numbers of the first rolling members 170, the second rolling members 250, the third rolling members 280, and the fourth rolling members 370 may be the same or different.

[0076] (F-3) In each of the above embodiments, the first bearing portion 201 is provided, but it does not have to be provided. Similarly, the second bearing portion 202 does not have to be provided.

[0077] (F-4) In each of the above embodiments, the period T1 of the first grooves 132 is smaller than the period T2 of the second grooves 152, but the period T1 may be larger than the period T2. In this case, when the first member 130 is used as an input shaft, acceleration is achieved between the first member 130 and the second member 150. Furthermore, when the second member 150 is used as an input shaft, deceleration is achieved between the second member 150 and the first member 130. Furthermore, in a substantially similar manner, the period T3 may be larger than the period T4. Furthermore, in a substantially similar manner, the period T5 may be larger than the period T6.

[0078] (F-5) In the above embodiment, the first grooves 132 and the second grooves 152 have a triangular wave shape, but they do not have to have a triangular wave shape. For example, the first grooves 132 and the second grooves 152 may have a zigzag shape such as a sinusoidal shape or a sawtooth wave shape. Similarly, the third grooves 162, the fourth grooves 232, the fifth grooves 332, and the sixth grooves 352 do not have to have a triangular wave shape.

[0079] (F-6) In the above embodiments, the number of peaks 132m and valleys 132v of the first groove 132 is different from the number of peaks 152m and valleys 152v of the second groove 152, but they may be the same. In this case, the period T1 of the first groove 132 is the same as the period T2 of the second groove 152. In other words, the torque transmission mechanism 100 does not have to be configured as a reduction gear device.

[0080] For example, FIG. 15 is an explanatory diagram of a torque transmission mechanism 100f, which is a first example of a torque transmission mechanism according to another embodiment. FIG. 16 is an explanatory diagram of a torque transmission mechanism 100g, which is a second example of a torque transmission mechanism according to another embodiment. FIGS. 15 and 16 show an outer peripheral surface 131t and an inner peripheral surface 151t, similar to FIG. 5. In the example of FIGS. 15 and 16, the number of peaks 132m and valleys 132v of the first groove 132 is the same as the number of peaks 152m and valleys 152v of the second groove 152f, i.e., one peak. In the example of FIGS. 15 and 16, rolling members 170A and 170B are provided as the first rolling member 170, and restricting portions 199A and 199B are provided as the first restricting portion 199. 15, when the outer peripheral surface 131t and the inner peripheral surface 151t are viewed along the radial direction DR, the first member 130 and the second member 150f are arranged so that the peaks 132m of the first grooves 132 and the valleys 152v of the second grooves 152f are positioned at the same positions in the circumferential direction DC, that is, so that the phases of the first grooves 132 and the second grooves 152f are opposite. In this way, when rotation is input to one of the first member 130 and the second member 150f, a rotation in the opposite direction to the input rotation can be output from the other member. Furthermore, as shown in FIG. 16 , when the outer peripheral surface 131t and the inner peripheral surface 151t are viewed along the radial direction DR, the first member 130 and the second member 150f can be arranged so that the peaks 132m of the first grooves 132 and the peaks 152m of the second grooves 152f are positioned at the same positions in the circumferential direction DC, i.e., so that the phases of the first grooves 132 and the second grooves 152f are the same. Note that in FIG. 16 , the first grooves 132 and the second grooves 152f are shown offset from each other for ease of understanding, but in reality, the first grooves 132 and the second grooves 152f overlap. In this way, when rotation is input to one of the first member 130 and the second member 150f, rotation in the same direction as the input rotation can be output from the other member. In this way, even if the periods T1 and T2 are the same, torque transmission can be achieved between the first member 130 and the second member 150f without using a torque transmission pin.Furthermore, using the same first member 130, second member 150f, and first regulating member 190, it is possible to easily configure a forward-rotation type torque transmission mechanism that outputs rotation in the same direction as the input rotation, and a reverse-rotation type torque transmission mechanism that outputs rotation in the opposite direction to the input rotation.

[0081] (F-7) In the third embodiment, the peaks 132m of the first groove 132 and the valleys 139v of the first corresponding groove 139 face each other, and the peaks 152m of the second groove 152 and the valleys 159v of the second corresponding groove 159 face each other. However, the peaks 132m and the valleys 139v do not have to face each other. Also, the peaks 152m and the valleys 159v do not have to face each other. In this case, for example, the peaks 132m and the valleys 139v may face each other, but the peaks 152m and the valleys 159v may not face each other. Also, for example, the peaks 152m and the valleys 159v may face each other, but the peaks 132m and the valleys 139v may not face each other. Similarly, in the fourth embodiment, the peaks 132m of the first grooves 132 and the valleys 332v of the fifth grooves 332 do not have to face each other. Also, the peaks 152m of the second grooves 152 and the valleys 352v of the sixth grooves 352 do not have to face each other.

[0082] FIG. 17 is an explanatory diagram of a torque transmission mechanism 100h, which is a third example of a torque transmission mechanism according to another embodiment. Similar to FIG. 5, FIG. 17 illustrates an outer peripheral surface 131t and an inner peripheral surface 151t. Similar to the third embodiment, the torque transmission mechanism 100h includes a first groove 132 and a first corresponding groove 139, and a second groove 152h and a second corresponding groove 159h. In the example of FIG. 17, the number of peaks 152m and valleys 152v of the second groove 152h is two, and the number of peaks 159m and valleys 159v of the second corresponding groove 159h is two. In the example of FIG. 17, the first rolling member 170 includes a rolling member 170A and a rolling member 170B, and the first restricting portion 199 includes a restricting portion 199A and a restricting portion 199B. Further, rolling members 280A and 280B are provided as third rolling members 280, and restricting portions 205A and 205B are provided as second restricting portion 205. Restricting portions 205A and 205B each have a slit portion extending in the Z direction, similar to restricting portions 199A and 199B. Restricting portions 205A and 205B allow movement of rolling members 280A and 280B along rotation axis AX, respectively, and restrict movement of rolling members 280A and 280B around rotation axis AX, using the respective slit portions. In the example of FIG. 17 , unlike the third embodiment, peak portion 132m and valley portion 139v do not face each other, and peak portion 152m and valley portion 159v do not face each other. However, in the example of FIG. 17 , as in the third embodiment, at least one first rolling member 170 is positioned on the crest 132m of the first groove 132 when at least one third rolling member 280 is positioned on the valley 139v of the first corresponding groove 139. Furthermore, at least one first rolling member 170 is positioned on the crest 152m of the second groove 152 when at least one third rolling member 280 is positioned on the valley 159v of the second corresponding groove 159h. Note that FIG. 17 shows a state in which the rolling member 170A is positioned on the crest 132m and the crest 152m, and the rolling member 280A is positioned on the valley 139v and the valley 159v. In this way, as in the third embodiment, it is possible to suppress swinging of the torque transmission mechanism 100h in the Z direction due to movement of the first rolling member 170 and the third rolling member 280.In this way, even in a configuration in which the peaks 132m and valleys 139v do not face each other and the peaks 152m and valleys 159v do not face each other, the torque transmission mechanism 100h can be prevented from swinging in the Z direction.

[0083] G. Other forms: The present disclosure is not limited to the above-described embodiments and can be realized in various forms without departing from the spirit thereof. For example, the present disclosure can also be realized in the following forms. The technical features in the above embodiments corresponding to the technical features in each form described below can be appropriately replaced or combined to solve some or all of the problems of the present disclosure or to achieve some or all of the effects of the present disclosure. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted.

[0084] (1) According to a first aspect of the present disclosure, there is provided a torque transmission mechanism comprising: a first member having a cylindrical shape and configured to be rotatable about a rotation axis, the first member having an outer circumferential surface with a zigzag-shaped first groove extending about the rotation axis; a second member having an annular shape surrounding the first member and configured to be rotatable about the rotation axis, the second member having an inner circumferential surface with a zigzag-shaped second groove extending about the rotation axis; one or more first rolling members disposed in the first groove and the second groove and configured to be rollable within the first groove and the second groove; and a first restricting member disposed between the first member and the second member, the first rolling member allowing movement along the rotation axis and restricting movement of the first rolling member about the rotation axis. According to this aspect, torque can be transmitted between the first member and the second member via the first rolling member in accordance with the first groove and the second groove, without using a pin for torque transmission.

[0085] (2) In the above embodiment, the first groove and the second groove may have a periodic wave shape having one or more peaks and valleys, and the number of peaks and valleys in the first groove may be different from the number of peaks and valleys in the second groove. According to this embodiment, the rotation speed between the first member and the second member can be reduced depending on the number of peaks and valleys in the first groove and the number of peaks and valleys in the second groove.

[0086] (3) In the above embodiment, the first rolling member may have a spherical shape. According to this embodiment, the first rolling member can roll more smoothly.

[0087] (4) In the above embodiment, the first rolling member may include one rolling member and another rolling member, and the first restricting member may have one restricting portion that allows movement of the one rolling member along the rotation axis and restricts movement of the first rolling member around the rotation axis, and another restricting portion that allows movement of the other rolling member along the rotation axis and restricts movement of the other rolling member around the rotation axis. According to this embodiment, it is possible to reduce the load on each rolling member.

[0088] (5) In the above aspect, a first bearing portion may be disposed between the first member and the first restricting member, and configured to rotatably hold the first member relative to the first restricting member. According to this aspect, the first member can be rotated more smoothly relative to the first restricting member via the first bearing portion.

[0089] (6) In the above aspect, a second bearing portion may be disposed between the second member and the first restricting member, and configured to rotatably hold the second member relative to the first restricting member. According to this aspect, the second member can be rotated more smoothly relative to the first restricting member via the second bearing portion.

[0090] (7) In the above embodiment, the outer peripheral surface of the second member is provided with a zigzag-shaped third groove extending around the rotation axis, and the torque transmission mechanism further includes: a third member having an annular shape surrounding the second member and configured to be rotatable around the rotation axis, the third member having an inner peripheral surface on which a zigzag-shaped fourth groove extending around the rotation axis is provided; one or more second rolling members arranged in the third groove and the fourth groove and configured to be able to roll within the third groove and the fourth groove; and a second restricting member arranged between the second member and the third member and allowing movement of the second rolling member along the rotation axis and restricting movement of the second rolling member around the rotation axis, wherein the third groove and the fourth groove have a periodic wave shape having one or more peaks and valleys, and the number of peaks and valleys of the third groove may be different from the number of peaks and valleys of the fourth groove. According to this embodiment, the rotation speed can be reduced stepwise between the first member and the second member and between the second member and the third member, thereby achieving a higher reduction ratio.

[0091] (8) In the above embodiment, a first corresponding groove corresponding to the first groove may be provided on the outer peripheral surface of the first member and aligned with the first groove in the direction of the rotation axis, a second corresponding groove corresponding to the second groove may be provided on the inner peripheral surface of the second member and aligned with the second groove in the direction of the rotation axis, the torque transmission mechanism may further include one or more third rolling members disposed in the first corresponding groove and the second corresponding groove and configured to be able to roll within the first corresponding groove and the second corresponding groove, and the first restricting member may further permit movement of the third rolling members along the rotation axis and restrict movement of the third rolling members around the rotation axis. This embodiment may reduce the load on each rolling member.

[0092] (9) In the above aspect, the first groove and the first corresponding groove may each have a periodic wave shape having the same number of peaks and valleys, the second groove and the second corresponding groove may each have a periodic wave shape having the same number of peaks and valleys, and at least one of the first rolling members may be configured to be positioned on the peaks of the first groove when at least one of the third rolling members is positioned on the valleys of the first corresponding groove, and to be positioned on the peaks of the second groove when the at least one third rolling member is positioned on the valleys of the second corresponding groove. According to this aspect, the first rolling member and the third rolling member can be moved in opposite directions in the rotational axis direction, and oscillation of the torque transmission mechanism in the rotational axis direction due to movement of the first rolling member and the third rolling member in the rotational axis direction can be suppressed.

[0093] (10) In the above embodiment, the first groove and the first corresponding groove may be arranged so that the peaks of the first groove face the valleys of the first corresponding groove, and the second groove and the second corresponding groove may be arranged so that the peaks of the second groove face the valleys of the second corresponding groove. This embodiment makes it possible to suppress swinging of the torque transmission mechanism in the rotation axis direction with a simpler configuration.

[0094] (11) In the above embodiment, the fourth member has a cylindrical shape and is configured to be rotatable around the rotation axis, the fourth member having an outer circumferential surface on which a zigzag-shaped fifth groove extending around the rotation axis is provided; a fifth member has an annular shape surrounding the fourth member and is configured to be rotatable around the rotation axis, the fifth member having an inner circumferential surface on which a zigzag-shaped sixth groove extending around the rotation axis is provided; fourth rolling members arranged in the fifth groove and the sixth groove and configured to be able to roll in the fifth groove and the sixth groove; and a fourth rolling member arranged between the fourth member and the fifth member and configured to roll in the fourth rolling member. a third restricting member that allows movement of a moving member along the rotation axis and restricts movement of the fourth rolling member around the rotation axis, and a connecting member that connects the second member and the fourth member so that they can rotate around the rotation axis, wherein the fourth member and the fifth member are arranged side by side with the first member and the second member in the direction of the rotation axis, and the fifth groove and the sixth groove have a periodic wave shape having one or more peaks and valleys, and the number of peaks and valleys in the fifth groove may be different from the number of peaks and valleys in the sixth groove. According to this embodiment, the rotation speed can be reduced in stages between the first member and the second member and between the fourth member and the fifth member, and a higher reduction ratio can be achieved while configuring a torque transmission mechanism in a more space-saving manner in the radial direction.

[0095] (12) In the above aspect, the first groove and the fifth groove may each have the same number of peaks and valleys, the second groove and the sixth groove may each have the same number of peaks and valleys, and at least one of the first rolling members may be configured to be located on the peaks of the first groove when at least one of the fourth rolling members is located on the valleys of the fifth groove, and to be located on the peaks of the second groove when the at least one fourth rolling member is located on the valleys of the sixth groove. According to this aspect, the first rolling member and the fourth rolling member can be moved in opposite directions in the rotational axis direction, and oscillation of the torque transmission mechanism in the rotational axis direction due to movement of the first rolling member and the fourth rolling member in the rotational axis direction can be suppressed.

[0096] (13) In the above aspect, the first groove and the second groove may have a triangular wave shape. According to this aspect, more efficient torque transmission can be achieved between the first member and the second member. [Explanation of symbols]

[0097] 100, 100b, 100c, 100d, 100e, 100f, 100g, 100h... torque transmission mechanism, 101... first reduction gear portion, 102... second reduction gear portion, 103... connecting member, 130, 130c... first member, 131, 131c, 131t... outer peripheral surface, 132... first groove, 132m... crest portion, 132v... valley portion, 139... first corresponding groove, 139m... crest portion, 139v... valley portion, 150, 150b, 150c, 150f... second member, 151, 151c, 151t...inner peripheral surface, 152, 152f, 152h...second groove, 152m...ridge portion, 152v...valley portion, 159, 159h...second corresponding groove, 159m...ridge portion, 159v...valley portion, 161...outer peripheral surface, 162...third groove, 170...first rolling member, 170A, 170B, 170C, 170D, 170E, 170p, 170q...rolling members, 190, 190e...first restricting member, 191...main body portion, 192...first flange portion, 193...second flange portion, 194...bolt 195, 195c...slit portion, 196...wall portion, 199...first restricting portion, 199A, 199B, 199C, 199D, 199E...restricting portion, 201...first bearing portion, 202...second bearing portion, 205...second restricting portion, 205A, 205B...restricting portion, 211...columnar member, 212...head portion, 213...shaft portion, 215...first annular member, 216...first through hole, 220...second annular member, 221...second through hole, 225...fixing member, 230...third member, 2 31...inner peripheral surface, 232...fourth groove, 250...second rolling member, 270...second restricting member, 280...third rolling member, 280A, 280B, 280p, 280q...rolling members, 330...fourth member, 331...outer peripheral surface, 332...fifth groove, 332m...ridge portion, 332v...valley portion, 350...fifth member, 351...inner peripheral surface, 352...sixth groove, 352m...ridge portion, 352v...valley portion, 370...fourth rolling member, 370p, 370q...rolling member, 390...third restricting member

Claims

1. a first member having a cylindrical shape and configured to be rotatable around a rotation axis, the first member having an outer circumferential surface provided with a first groove having a zigzag shape extending around the rotation axis; a second member having an annular shape surrounding the first member and configured to be rotatable around the rotation axis, the second member having an inner circumferential surface provided with a second groove having a zigzag shape extending around the rotation axis; one or more first rolling members disposed in the first groove and the second groove and configured to be able to roll within the first groove and the second groove; a first restricting member disposed between the first member and the second member, allowing movement of the first rolling member along the rotation axis and restricting movement of the first rolling member around the rotation axis.

2. 2. The torque transmission mechanism according to claim 1, the first groove and the second groove have a periodic wave shape having one or more peaks and valleys, A torque transmission mechanism, wherein the number of peaks and valleys of the first groove is different from the number of peaks and valleys of the second groove.

3. 2. The torque transmission mechanism according to claim 1, The torque transmission mechanism, wherein the first rolling member has a spherical shape.

4. 2. The torque transmission mechanism according to claim 1, the first rolling member includes one rolling member and another rolling member, a torque transmission mechanism, wherein the first regulating member has one regulating portion that allows movement of the one rolling member along the rotation axis and regulates movement of the first rolling member around the rotation axis, and another regulating portion that allows movement of the other rolling member along the rotation axis and regulates movement of the other rolling member around the rotation axis.

5. 2. The torque transmission mechanism according to claim 1, The torque transmission mechanism further includes a first bearing portion disposed between the first member and the first restricting member, the first bearing portion holding the first member rotatably relative to the first restricting member.

6. 2. The torque transmission mechanism according to claim 1, The torque transmission mechanism further includes a second bearing portion disposed between the second member and the first restricting member, the second bearing portion holding the second member rotatably relative to the first restricting member.

7. 3. The torque transmission mechanism according to claim 2, a third groove having a zigzag shape extending around the rotation axis is provided on the outer circumferential surface of the second member, The torque transmission mechanism further comprises: a third member having an annular shape surrounding the second member and configured to be rotatable around the rotation axis, the third member having an inner circumferential surface provided with a fourth groove having a zigzag shape extending around the rotation axis; one or more second rolling members disposed in the third groove and the fourth groove and configured to be able to roll within the third groove and the fourth groove; a second restricting member that is disposed between the second member and the third member, that allows movement of the second rolling member along the rotation axis and restricts movement of the second rolling member around the rotation axis, the third groove and the fourth groove have a periodic wave shape having one or more of the peaks and valleys, a number of the peaks and valleys of the third groove and a number of the peaks and valleys of the fourth groove that are different from each other;

8. 2. The torque transmission mechanism according to claim 1, a first corresponding groove having a zigzag shape corresponding to the first groove is provided on an outer peripheral surface of the first member and is aligned with the first groove in the direction of the rotation axis; a second corresponding groove having a zigzag shape corresponding to the second groove is provided on an inner peripheral surface of the second member and is aligned with the second groove in the direction of the rotation axis; the torque transmission mechanism further includes one or more third rolling members disposed in the first corresponding groove and the second corresponding groove and configured to be able to roll within the first corresponding groove and the second corresponding groove; The first restricting member further allows movement of the third rolling member along the rotation axis and restricts movement of the third rolling member around the rotation axis.

9. 9. The torque transmission mechanism according to claim 8, the first groove and the first corresponding groove each have a periodic wave shape having the same number of peaks and valleys; the second groove and the second corresponding groove each have a periodic wave shape having the same number of peaks and valleys, A torque transmission mechanism, wherein at least one of the first rolling members is configured to be positioned on the crest portion of the first groove when at least one of the third rolling members is positioned on the valley portion of the first corresponding groove, and to be positioned on the crest portion of the second groove when the at least one third rolling member is positioned on the valley portion of the second corresponding groove.

10. 10. The torque transmission mechanism according to claim 9, the first groove and the first corresponding groove are arranged such that the peaks of the first groove and the valleys of the first corresponding groove face each other; The second groove and the second corresponding groove are arranged so that the peaks of the second groove and the valleys of the second corresponding groove face each other.

11. 3. The torque transmission mechanism according to claim 2, further comprising: a fourth member having a cylindrical shape and configured to be rotatable around the rotation axis, the fourth member having an outer circumferential surface provided with a zigzag-shaped fifth groove extending around the rotation axis; a fifth member having an annular shape surrounding the fourth member and configured to be rotatable around the rotation axis, the fifth member having an inner circumferential surface provided with a sixth groove having a zigzag shape extending around the rotation axis; a fourth rolling member disposed in the fifth groove and the sixth groove and configured to be able to roll within the fifth groove and the sixth groove; a third restricting member disposed between the fourth member and the fifth member, the third restricting member allowing movement of the fourth rolling member along the rotation axis and restricting movement of the fourth rolling member around the rotation axis; a connecting member that connects the second member and the fourth member rotatably around the rotation axis, the fourth member and the fifth member are arranged alongside the first member and the second member in the direction of the rotation axis, the fifth groove and the sixth groove have a periodic wave shape having one or more of the peaks and valleys, a number of the peaks and valleys of the fifth groove and a number of the peaks and valleys of the sixth groove that are different from each other;

12. 12. The torque transmission mechanism according to claim 11, the first groove and the fifth groove each have the same number of peaks and valleys, the second groove and the sixth groove each have the same number of peaks and valleys, a torque transmission mechanism, wherein at least one of the first rolling members is configured to be positioned on the crest portion of the first groove when at least one of the fourth rolling members is positioned on the valley portion of the fifth groove, and is configured to be positioned on the crest portion of the second groove when the at least one fourth rolling member is positioned on the valley portion of the sixth groove.

13. 13. A torque transmission mechanism according to any one of claims 1 to 12, The torque transmission mechanism, wherein the first groove and the second groove have a triangular wave shape.

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