Internal rotational motion transmission device

Abstract

To reduce costs and enhance a degree of freedom for design, in an inscribed rotational motion transmission device.SOLUTION: An inscribed rotational motion transmission device comprises: an intermediate engagement part (cam member) 38 that is arranged between a first engagement part (inner ring cam engagement surface) 34B of an inner ring member 34 and a second engagement part (cam engagement surface) 30 of an outer ring member 28 and can engage with the first engagement part 34B and the second engagement part 30. In an approach region A1 where the inner ring member 34 and the outer ring member 28 are close to each other in a circumferential direction within a specified range, the intermediate engagement part 38 performs engagement to be able to transmit torque in at least one direction. In a region (separation region) B1 away from the approach region A1 in the circumferential direction, the intermediate engagement part 38 does not perform engagement not to be able to transmit the torque.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an internal contact type rotational motion transmission device.

Background Art

[0002] Conventionally, an internal contact type planetary gear device is known, which includes an internal gear gear having internal teeth on its inner peripheral portion, and an external gear gear having external teeth with a smaller number of teeth than the internal teeth on its outer peripheral portion and meshing with the internal gear gear. The internal gear gear is connected to the input side, and the external gear gear is connected to the output side (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the tooth profile used in the internal contact type rotational motion transmission device as described above, the involute tooth profile is frequently used. However, the involute tooth profile has problems in that tooth cutting takes time and cost. Further, in the internal contact type rotational motion transmission device as described above, in the case of the involute tooth profile, there is a problem that involute interference or trochoid interference easily occurs between the internal teeth and the external teeth.

[0005] Therefore, an object of the present invention is to reduce costs and increase the design freedom in an internal contact type rotational motion transmission device.

Means for Solving the Problems

[0006] As a means of solving the above problems, a first aspect of the present invention provides an inner ring member (34) having a first central axis (C1) and a first engaging portion (34B) on its outer circumference (34A), and an outer ring member having a second central axis (C2) eccentric with respect to the first central axis (C1), disposed on the outer circumference side of the inner ring member (34), and having a second engaging portion (30) on its inner circumference (28B) facing the outer circumference (34A) of the inner ring member (34) ( 28) and an intermediate engaging portion (38, 38') positioned between the first engaging portion (34B) and the second engaging portion (30) and capable of engaging with the first engaging portion (34B) and the second engaging portion (30), wherein the intermediate engaging portion (38, 38') engages between the first engaging portion (34B) and the second engaging portion (30) when the inner ring member (34) and the outer ring member (28) attempt to rotate relative to each other. The cam members (38, 38') are movable to transmit torque, and the first engaging portion (34B) and the second engaging portion (30) are cylindrical cam engaging surfaces (34B, 30) into which the cam members (38, 38') engage. The cam members (38, 38') are characterized in that, in an approach region (A1) where the inner ring member (34) and the outer ring member (28) are close within a specified range in the circumferential direction of one of the cam engaging surfaces (34B, 30), they frictionally contact the first engaging portion (34B) and the second engaging portion (30) to engage and operate, enabling the transmission of torque in at least one direction between the inner ring member (34) and the outer ring member (28). In a region (B1) in the circumferential direction that avoids the approach region (A1), the cam members (38, 38') do not engage and are unable to transmit torque. This configuration allows for cost reduction by providing a cam member that functions as an internal or external tooth between the inner and outer ring members in an internal rotational motion transmission device. This eliminates the need for gear tooth machining of the inner and outer rings. Furthermore, because there is no interference with involute tooth profiles, it becomes possible to combine two reference circle diameters, which was not possible with involute or other tooth profiles. When this device is applied to a power transmission path equipped with a one-way clutch that utilizes the wedge effect of the cam member, the function of the device can be realized by a one-way clutch that operates only in the approach area, thus reducing the number of parts and weight.

[0007] A second aspect of the present invention is characterized in that, in the first aspect described above, the cam member (38) is capable of transmitting torque in one direction between the inner ring member (34) and the outer ring member (28), but is not capable of transmitting torque in the reverse direction. This configuration allows the clutch to operate in one direction only and rotate freely in the opposite direction, thus reducing the number of parts and weight.

[0008] A third aspect of the present invention is that, in the first aspect described above, a plurality of cam members (38, 38') are arranged in the circumferential direction of the member (34) that holds itself among the inner ring member (34) and the outer ring member (28), and the plurality of cam members (38, 38') are arranged alternately in the circumferential direction, with a first cam member (38) capable of transmitting torque in a first direction between the inner ring member (34) and the outer ring member (28) and a second cam member (38') capable of transmitting torque in a second direction opposite to the first direction. With this configuration, by arranging multiple first cam members and second cam members, whose torque transmission directions are opposite to each other, alternately, for example, every other cam member as shown in Figure 5, it is possible to provide an internal rotational motion transmission device that can transmit torque in both forward and reverse rotation, even though it does not have gear teeth. [Effects of the Invention]

[0009] According to the present invention, it is possible to reduce costs and increase design flexibility in an internal rotational motion transmission device. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view including a cross-section of a planetary gear system according to an embodiment of the present invention. [Figure 2] This is an explanatory diagram of the configuration of the planetary gear system described above. [Figure 3] This is an explanatory diagram showing the internal rotational motion transmission device included in the planetary gear system described above, viewed from the axial direction. [Figure 4]Figure 3 is a magnified view of the main part, where (A) represents the meshing region in a gear and (B) represents the free region. [Figure 5] This is an explanatory diagram corresponding to Figure 3, which shows an application example of the internal rotational motion transmission device described above. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a perspective view including a cross-section of the planetary gear system 10 of the embodiment. Figure 2 is an explanatory diagram of the configuration of the planetary gear system 10. Figure 3 is an explanatory diagram of the internal rotational motion transmission device 10A included in the planetary gear system 10, viewed from the axial direction. The planetary gear system 10 shown in Figures 1 and 2 has a casing 12. The casing 12 is divided into a pair of bottomed cylindrical case components 12A and 12B. The casing 12 forms a base member, which will be described later, and defines a cylindrical transmission chamber 14 having a central axis C1.

[0012] The casing 12 supports a cylindrical rotary input member 18 within the transmission chamber 14 via bearings 16 and 17. The rotary input member 18 is rotatably supported around a central axis C1. The rotary input member 18 is connected to a rotary output member 22 of an electric motor 20 located in the transmission chamber 14. The rotary input member 18 corresponds to the rotor member of the electric motor 20 and is rotationally driven around the central axis C1 by the power supply to the electric motor 20.

[0013] Referring to Figures 2 and 3, the rotation input member 18 has an eccentric hole 24, such as a circular hole, which is eccentric with respect to the rotation center (central axis C1) by an eccentricity E. The eccentric hole 24 is eccentric downwards in the figures. That is, at the lower end position in the figures, the distance from the outer diameter of the rotation input member 18 to the inner diameter of the eccentric hole 24 is AE, whereas at the upper end position in the figures, the distance from the outer diameter of the rotation input member 18 to the inner diameter of the eccentric hole 24 is A+E.

[0014] An outer ring member 28 is supported in the eccentric hole 24 by a bearing 26 so as to be rotatable relative to it. The outer ring member 28 integrally has an outer circumference 28A that is received so as to be rotatable relative to the central axis C2 of the eccentric hole 24, and an inner circumference 28B provided coaxially with the outer circumference 28A. The inner circumference 28B has a flat cylindrical cam engagement surface 30 (see Figure 3) formed over its entire circumference in the circumferential direction. In the figure, the symbol B indicates the radius of the inner circumference 28B. For illustrative purposes, gear teeth are shown in Figure 1 instead of the cam engagement surface 30. The outer ring member 28 and the bearing 26 are eccentric with an eccentricity amount E to match the eccentric hole 24. In Figure 3, the outer ring member 28 and the bearing 26 are shown in shaded areas.

[0015] The casing 12 supports the shaft portion 36 of the inner ring member 34 via a bearing 32 within the transmission chamber 14 and the rotating input member 18. The inner ring member 34 is rotatably supported around its own central axis C3. The central axes C1 to C3 are parallel to each other. Hereinafter, the direction along each central axis C1 to C3 will be referred to as the axial direction, the direction perpendicular to each central axis C1 to C3 will be referred to as the radial direction, and the direction of rotation around each central axis C1 to C3 will be referred to as the circumferential direction.

[0016] The inner ring member 34 has an outer circumference 34A that is radially opposite to the inner circumference 28B of the outer ring member 28. The outer circumference 34A holds a plurality of cam members 38 (see Figure 3) along its entire circumference. In the figure, the symbol D indicates the radius of the outer circumference 34A. For illustrative purposes, gear teeth are shown in Figure 1 instead of cam members 38.

[0017] Referring to Figure 3, the cam member 38 can frictionally engage with the inner ring cam engagement surface 34B (outer circumference 34A) of the inner ring member 34 and the cam engagement surface 30 (inner circumference 28B) of the outer ring member 28 under the oscillating motion of the outer ring member 28. The outer diameter R1 of the outer circumference of the cam member 38 (the outer diameter of the circle connecting the outer circumference ends t1 of the engagement surfaces 38a of each cam member 38 with the cam engagement surface 30) is smaller than the inner diameter R2 of the cam engagement surface 30 of the inner circumference 28B of the outer ring member 28. The transmission of rotational motion from the outer ring member 28 to the inner ring member 34 is reduced by a reduction ratio corresponding to the values ​​of the outer circumference 34A and the inner circumference 28B, as well as the shape of the cam member 38. The shaft portion 36 of the inner ring member 34 becomes the rotational output member of the planetary gear system 10.

[0018] The rotating input member 18, the inner ring member 34, and the outer ring member 28 are arranged along the same plane orthogonal to the central axes C1 to C3. In FIG. 2, for the sake of illustration, the rotating input member 18 and the outer ring member 28 are shown offset from each other in the axial direction.

[0019] The central axis C3 of the inner ring member 34 and the central axis C1 of the rotating input member 18 may be arranged on the same axis. Thereby, the rotating input member 18 of the planetary gear device 10 and the shaft portion 36 forming the rotating output member are arranged on the same axis. In the embodiment, the central axis C1 may be referred to as the central axis of the inner ring member 34.

[0020] The outer ring member 28 is held (connected) to the casing 12 by a holding mechanism (connecting mechanism) 40 so as to be non-rotatable relative to the casing 12 and swingable. The "non-rotatable relative" allows the outer ring member 28 to swing along a circular locus with an eccentricity E as the radius.

[0021] The holding mechanism 40 includes a cylindrical phase regulation pin 42 along the axial direction. The phase regulation pin 42 is inserted into a through hole F penetrating the outer ring member 28 in the axial direction. The axial end portions of the phase regulation pin 42 are respectively engaged with circular bottomed holes 46 formed in the case components 12A and 12B located on both sides in the axial direction of the outer ring member 28. When the inner diameter of the bottomed hole 46 is the same as the inner diameter of the through hole F and the outer diameter of the phase regulation pin 42, the inner diameter of the bottomed hole 46 has a difference of twice the eccentricity E from the outer diameter of the phase regulation pin 42 and is made larger. When the inner diameter of the through hole F is larger than the outer diameter of the phase regulation pin 42 by the eccentricity E, the inner diameter of the bottomed hole 46 is the same as the inner diameter of the through hole F.

[0022] Thereby, the holding mechanism 40 allows the outer ring member 28 to eccentrically swing due to the eccentricity E with respect to the casing 12 without changing the rotational phase of the outer ring member 28 with respect to the casing 12. In the outer ring member 28, the through hole F and the second through hole G having a slightly larger diameter than the through hole F are alternately formed in the circumferential direction.

[0023] The planetary gear unit 10 has a rotation input member 18 that is driven to rotate around the central axis C1 by an electric motor 20, and also has a phase regulating pin 42 and a bottomed hole 46. As a result, the outer ring member 28 eccentrically oscillates in the eccentric hole 24 with a circular trajectory whose radius is the eccentricity amount E, without changing the rotational phase relative to the casing 12. Due to the eccentric oscillation of the outer ring member 28, the inner ring member 34 rotates at a reduced speed around the central axis C1 under the engagement of the cam engagement surface 30 and the cam member 38.

[0024] In this example, a planetary gear system 10 that incorporates a reduction gear into the motor does not require a crank mechanism such as a crankshaft, and by simply forming an eccentric hole 24 in the rotating input member 18, the axis length and weight of the planetary gear system 10 can be shortened. By arranging the rotating input member 18, the inner ring member 34, and the outer ring member 28 on the same plane, the axis length of the planetary gear system 10 can be further shortened, and the planetary gear system 10 can be made more compact. By arranging the central axis C1 of the inner ring member 34 and the central axis C1 of the rotating input member 18 on the same axis, the structure of the casing 12 that supports the inner ring member 34 and the rotating input member 18 can be simplified.

[0025] <Internal rotational motion transmission device 10A> Figure 4 is a magnified view of the main part of Figure 3, where (A) shows the meshing region described later, and (B) shows the free region described later.

[0026] Referring to Figure 3, the internal rotary motion transmission device 10A is composed of an inner ring member 34 and an outer ring member 28. Instead of gears, the internal rotary motion transmission device 10A transmits power using mechanical friction meshing, which is used in one-way clutches. The one-way clutch is an existing configuration that is installed in the power transmission path of various machines, and transmits the forward rotation torque of the driving member to the driven member, but does not transmit the reverse rotation torque of the driving member to the driven member. In addition to the type in which a cam is meshed between the inner and outer rings as in the embodiment, the one-way clutch can also be made of other cam structures, such as a type using rollers and wedge grooves.

[0027] The internal rotational motion transmission device 10A comprises an outer ring member 28 having a cam engagement surface 30 on its inner circumference 28B, and an inner ring member 34 holding a plurality of cam members 38 arranged in the circumferential direction on its outer circumference 34A. A flat, cylindrical inner ring cam engagement surface (first engagement portion) 34B is formed on the outer circumference 34A of the inner ring member 34, extending over its entire circumference, and is capable of engaging with the cam members 38 when they mesh together. As described above, the outer ring member 28 eccentrically oscillates with a circular trajectory whose radius is the eccentricity E with respect to the central axis C1, without changing its rotational phase with respect to the casing 12. Due to the eccentric oscillation of the outer ring member 28, the inner ring member 34 rotates at a reduced speed around the central axis C1 under the engagement of the cam engagement surface 30, the cam members 38, and the inner ring cam engagement surface 34B. In Figure 3, the central axis C2 of the outer ring member 28 is located below the central axis C1 of the inner ring member 34 in the figure.

[0028] Referring to Figures 3 and 4(A), the upper region A1 in Figure 3, in the circumferential direction of the outer ring member 28, is the proximity region A1 where the cam member 38 of the inner ring member 34 approaches the cam engagement surface 30. In proximity region A1, the cam engagement surface 30 of the outer ring member 28 contacts the cam member 38 of the inner ring member 34, and torque transmission becomes possible when the cam member 38 meshes due to frictional engagement. In other words, proximity region A1 is the meshing region of the inner ring member 34 and the outer ring member 28. In proximity region A1, torque transmission is possible when the outer ring member 28 rotates relative to the inner ring member 34 in the direction of arrow F1 in the figure (hereinafter referred to as the forward rotation direction). Even in proximity region A1, when the outer ring member 28 rotates relative to the inner ring member 34 in the opposite direction to arrow F1 in the figure (hereinafter referred to as the reverse rotation direction), the meshing effect of the cam member 38 does not operate, and torque transmission becomes impossible.

[0029] Referring to Figures 3 and 4(B), the lower region B1 in Figure 3, circumferentially, is a separation region B1 where the cam member 38 of the inner ring member 34 is separated from the cam engagement surface 30. For illustrative purposes, Figure 4(B) shows the corresponding part of Figure 3 inverted vertically. In separation region B1, the cam engagement surface 30 of the outer ring member 28 does not contact the cam member 38 of the inner ring member 34, and the cam member 38 does not mesh and operate in either forward or reverse rotation, making torque transmission impossible. In other words, separation region B1 is a free region where the inner ring member 34 and the outer ring member 28 can rotate relative to each other. (In the free region shown in the figure, the cams are separated for clarity, but in reality, there may be cases where the cams are in contact but the meshing action does not work.)

[0030] As described above, the internal rotational motion transmission device 10A in the above embodiment comprises an inner ring member 34 having a first central axis C1 and a first engaging portion 34B on its outer circumference 34A, an outer ring member 28 having a second central axis C2 eccentric with respect to the first central axis C1, positioned on the outer circumference side of the inner ring member 34 and having a second engaging portion 30 on its inner circumference 28B facing the outer circumference 34A of the inner ring member 34, and an intermediate engaging portion 38 positioned between the first engaging portion 34B and the second engaging portion 30 and capable of engaging with the first engaging portion 34B and the second engaging portion 30, wherein the intermediate engaging portion 38 engages with the first engaging portion 34B and the second engaging portion 30 when the inner ring member 34 and the outer ring member 28 attempt to rotate relative to each other. A cam member 38 is provided that meshes and operates between the inner ring member 34 and the outer ring member 28 to transmit torque. The first engaging portion 34B and the second engaging portion 30 are cylindrical cam engaging surfaces 34B and 30 into which the cam member 38 engages. In the approach region A1 where the inner ring member 34 and the outer ring member 28 are within a specified range in the circumferential direction of one of the cam engaging surfaces 34B and 30, the cam member 38 frictionally contacts the first engaging portion 34B and the second engaging portion 30 to mesh and operates, enabling the transmission of torque in at least one direction between the inner ring member 34 and the outer ring member 28. In the circumferential direction, the cam member 38 does not mesh and cannot transmit torque in the area (separated region) B1 that avoids the approach region A1.

[0031] According to this configuration, in the internal rotary motion transmission device 10A, a cam member 38 that functions as an internal or external tooth is provided between the inner ring member 34 and the outer ring member 28, eliminating the need for gear tooth cutting on the inner and outer rings and reducing costs. Furthermore, because there is no interference with involute tooth profiles, it becomes possible to combine two reference circle diameters, which was not possible with involute or other tooth profiles. When this device is applied to a power transmission path equipped with a one-way clutch that uses the wedge effect of the cam member 38 to transmit torque only in the forward rotation direction, the function of the device can be realized by a one-way clutch that operates only in the approach region A1, thus reducing the number of parts and weight.

[0032] In the internal rotational motion transmission device 10A described above, the cam member 38 is capable of transmitting torque in one direction between the inner ring member 34 and the outer ring member 28, but is not capable of transmitting torque in the reverse direction. That is, multiple cam members 38 are arranged in a line in the circumferential direction of the inner ring member 34 that holds it, and are inclined so that the outer circumference, when viewed from the axial direction, is positioned towards the reverse direction. This configuration allows the clutch to operate in one direction only and rotate freely in the opposite direction, thus reducing the number of parts and weight.

[0033] <Application Examples> Figure 5 is an explanatory diagram corresponding to Figure 3, showing an internal rotational motion transmission device 110A, which is an application example of the above embodiment. In the internal rotational motion transmission device 10A of the above embodiment, the device was configured to function as a one-way clutch that could transmit torque only in the forward direction and not in the reverse direction. That is, all of the multiple cam members 38 were inclined such that the outer circumference, when viewed from the axial direction, was positioned towards the reverse direction.

[0034] In contrast, the internal rotational motion transmission device 110A in the application example has a first cam member 38 that transmits torque in the forward direction (direction of arrow F1) and a second cam member 38' that transmits torque in the reverse direction (direction of arrow F1') arranged alternately, thereby enabling torque transmission without slippage in either forward or reverse rotation. Specifically, the first cam member 38 is inclined so that the outer circumference is closer to the reverse direction when viewed from the axial direction, and the second cam member 38' is inclined so that the outer circumference is closer to the forward direction, and these are arranged alternately, for example, every other cam member. To stabilize the rotation in the application example, it is also possible to insert a rotating body such as a roller between the first cam member 38 and the second cam member 38' to facilitate rotation. The first cam member 38 and the second cam member 38' may be arranged alternately, for example, every other cam member.

[0035] In the internal rotational motion transmission device 110A of the application example, multiple cam members 38, 38' are arranged in a line in the circumferential direction of the member that holds itself within the inner ring member 34 and the outer ring member 28. The multiple cam members 38, 38' are arranged alternately in the circumferential direction, with a first cam member 38 capable of transmitting torque in a first direction between the inner ring member 34 and the outer ring member 28, and a second cam member 38' capable of transmitting torque in a second direction opposite to the first direction. With this configuration, by arranging the first cam member 38 and the second cam member 38', which have opposite torque transmission directions, alternately at intervals such as every other cam member, it is possible to provide an internal rotational motion transmission device 110A that can transmit torque in both forward and reverse rotation, even though it does not have gear teeth.

[0036] It should be noted that the present invention is not limited to the above embodiments, and for example, the configuration in which the cam members 38, 38' are held by the inner ring member 34 is not limited to the configuration in which the cam members 38, 38' are held by the outer ring member 28 or held between the outer ring member 28 and the inner ring member 34. However, it is preferable that the cam members 38, 38' are not held on the eccentric side because this reduces the energy consumed by the oscillating motion of the cam members 38, 38'. The configuration is not limited to one in which the outer ring member 28 eccentrically oscillates without changing its rotational phase, and this eccentric oscillation causes the inner ring member 34 to rotate at a reduced speed around the central axis C1. For example, a normal gear transmission configuration in which the inner ring member 34 and the outer ring member 28 have their central positions fixed and rotation is transmitted solely by the rotation of the inner ring member 34 and the outer ring member 28 may also be used.

[0037] In a pair of rotating members that transmit rotational motion while being externally tangent to each other, one member may hold a cam member and the other may form a cylindrical cam engagement surface. Alternatively, both members of the pair may form cylindrical cam engagement surfaces, with a cam member interposed between them. Even if the axes of the pair of rotating members are not parallel to each other, such as in bevel gears, rotational motion can be transmitted depending on the shape of the cam member. Rotating members with parallel axes are not limited to those that transmit rotational motion by engaging in the radial direction, but may also transmit rotational motion by engaging in the axial direction, such as in axial bearings. Furthermore, the configuration in the above embodiment is just one example of the present invention, and various modifications are possible without departing from the spirit of the invention, such as replacing the components of the embodiment with well-known components. [Explanation of symbols]

[0038] 10A, 110A Internal Rotational Motion Transmission Device 28 Outer ring member 28B Inner circumference 30 Second engagement portion, cam engagement surface 34 Inner ring member 34A outer periphery 34B First engagement portion, inner ring cam engagement surface 38 Intermediate engaging portion, cam member, first cam member 38' Intermediate engagement portion, cam member, second cam member A1 Approach area B1 Separation area C1 First center axis C2 Second central axis C3 Third central axis

Claims

1. An inner ring member (34) having a first central axis (C1) and a first engaging portion (34B) on its outer circumference (34A), An outer ring member (28) having a second central axis (C2) eccentric with respect to the first central axis (C1), positioned on the outer circumference side of the inner ring member (34), and having a second engaging portion (30) on the inner circumference (28B) facing the outer circumference (34A) of the inner ring member (34), The system includes an intermediate engaging portion (38) positioned between the first engaging portion (34B) and the second engaging portion (30), which is capable of engaging with the first engaging portion (34B) and the second engaging portion (30), The intermediate engaging portion (38) is a cam member (38) that engages with the first engaging portion (34B) and the second engaging portion (30) to transmit torque when the inner ring member (34) and the outer ring member (28) attempt to rotate relative to each other, and the first engaging portion (34B) and the second engaging portion (30) are cylindrical cam engaging surfaces (34B, 30) into which the cam member (38) engages. When the outer ring member (28) rotates relative to the inner ring member (34) in one direction in which torque can be transmitted, the cam member (38) frictionally contacts the first engagement portion (34B) and the second engagement portion (30) in the approach region (A1) where the inner ring member (34) and the outer ring member (28) approach within a specified range in the circumferential direction of one of the cam engagement surfaces (34B, 30), thereby engaging and operating, and enabling the transmission of the torque in one direction between the inner ring member (34) and the outer ring member (28). The cam member (38) is an internal rotational motion transmission device that, when the outer ring member (28) rotates relative to the inner ring member (34) in one direction in which torque can be transmitted, does not engage in the meshing operation and cannot transmit torque in the region (B1) in the circumferential direction that avoids the approach region (A1).

2. The internal rotational motion transmission device according to claim 1, characterized in that, during the meshing operation, the cam member (38) rotates both the inner ring member (34) and the outer ring member (28) in the same direction, enabling the transmission of torque in the same direction between the inner ring member (34) and the outer ring member (28), while preventing the transmission of torque in the opposite direction.

3. An inner ring member (34) having a first central axis (C1) and a first engaging portion (34B) on its outer circumference (34A), An outer ring member (28) having a second central axis (C2) eccentric with respect to the first central axis (C1), positioned on the outer circumference side of the inner ring member (34), and having a second engaging portion (30) on the inner circumference (28B) facing the outer circumference (34A) of the inner ring member (34), The system includes intermediate engaging portions (38, 38') positioned between the first engaging portion (34B) and the second engaging portion (30), which are capable of engaging with the first engaging portion (34B) and the second engaging portion (30), The intermediate engaging portion (38, 38') is a cam member (38, 38') that engages with the first engaging portion (34B) and the second engaging portion (30) to transmit torque when the inner ring member (34) and the outer ring member (28) attempt to rotate relative to each other, and the first engaging portion (34B) and the second engaging portion (30) are cylindrical cam engaging surfaces (34B, 30) into which the cam member (38, 38') engages. The cam members (38, 38') engage in frictional contact with the first engaging portion (34B) and the second engaging portion (30) in the approach region (A1) where the inner ring member (34) and the outer ring member (28) are close together within a specified range in the circumferential direction of one of the cam engagement surfaces (34B, 30), thereby enabling the transmission of the torque in at least one direction between the inner ring member (34) and the outer ring member (28). The cam members (38, 38') do not engage in the meshing operation in the region (B1) that avoids the approach region (A1) in the circumferential direction, and thus are unable to transmit torque. The cam members (38, 38') are arranged in a plurality in the circumferential direction of the member (34) that holds itself among the inner ring member (34) and the outer ring member (28), An internal rotational motion transmission device characterized in that a plurality of cam members (38, 38') are arranged alternately in the circumferential direction, with a first cam member (38) capable of transmitting the torque in a first direction between the inner ring member (34) and the outer ring member (28), and a second cam member (38') capable of transmitting the torque in a second direction opposite to the first direction.

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