Friction transmission device

Abstract

To provide a friction transmission device which can transmit higher torque.SOLUTION: A friction transmission device 100 of the present embodiment comprises a planetary rolling body 20 arranged around a rotating shaft La, a first support bearing ring 26 and a second support bearing ring 28 contacting with the planetary rolling body 20, and a pressing force impartment mechanism 7 for generating a pressing force to a contact face between the second support bearing ring 28 and the planetary rolling body 20 by pressing the second support bearing ring 28 thereto. The friction transmission device 100 has a cover 67 for covering the friction transmission device 100 from an axial direction, the pressing force impartment mechanism 7 has a pressing part 72 for pressing the second support bearing ring 28, and the pressing force impartment mechanism 7 has an abutment part 56b abutting on the cover 67 in a position in which the abutment part is superimposed on the pressing part 72 in the axial direction, or is constituted integrally with the cover 67.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a friction transmission. [Background technology]

[0002] A continuously variable transmission capable of an infinitely large gear ratio, called an IVT (Infinitely Variable Transmission), is known. In Patent Document 1, the present applicant disclosed a technology for a friction transmission device including an input raceway, planetary rolling elements, and an output raceway. In this device, the planetary rolling elements are disposed around the rotation axis of the input raceway and contact the input raceway, and the output raceway is in contact with the planetary rolling elements and connected to the output shaft. This device also has a plurality of support raceways in contact with the planetary rolling elements, and changes the speed of the rotation input to the input raceway and outputs it from the output shaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 182001 Summary of the Invention [Problem to be solved by the invention]

[0004] Friction transmissions are expected to be used in many applications, such as robots and self-propelled vehicles. In order to be installed in a variety of applications, it is desirable for the friction transmission to be able to transmit a larger torque. However, in conventional friction transmissions, the mechanism for applying preload between the planetary rolling elements and the raceways is complicated, making it difficult to increase the transmission torque of the friction transmission.

[0005] SUMMARY OF THE PRESENT EMBODIMENT In view of the above problems, an object of the present invention is to provide a friction transmission device capable of transmitting a larger torque. [Means for solving the problem]

[0006] In order to solve the above problems, a friction transmission device according to one embodiment of the present invention is a friction transmission device including planetary rolling elements arranged around a rotation axis, first and second support raceways in contact with the planetary rolling elements, and a pressing force imparting mechanism that presses the second support raceway to generate a pressing force on a contact surface between the second support raceway and the planetary rolling elements, and includes a cover that covers the friction transmission device in the axial direction. The pressing force imparting mechanism has a pressing portion that presses the second support raceway. The pressing force imparting mechanism has an abutting portion that abuts against the cover at a position that axially overlaps with the pressing portion, or is configured integrally with the cover.

[0007] Any combination of the above components, or mutual substitution of the components or expressions of the present invention between methods, systems, etc. are also valid aspects of the present invention. Effect of the Invention

[0008] According to the present invention, it is possible to provide a friction transmission capable of transmitting a larger torque. [Brief description of the drawings]

[0009] [Figure 1] 1 is a perspective view showing an example of a friction transmission device according to an embodiment; [Diagram 2] 2 is a cross-sectional view showing a cross section of the friction transmission device taken along line AA in FIG. 1. [Diagram 3] 2 is a perspective view showing an input race of the friction transmission of FIG. 1. [Figure 4] 2 is a perspective view showing a first support bearing ring of the friction transmission of FIG. 1. [Diagram 5] 2 is a perspective view showing a planetary rolling element of the friction transmission of FIG. 1. [Figure 6] 2 is a perspective view showing a cage of the friction transmission of FIG. 1. [Figure 7] 2 is a perspective view showing a planetary rolling element unit of the friction transmission of FIG. 1. [Figure 8] 2 is a perspective view showing a second support ring of the friction transmission of FIG. 1. FIG. [Figure 9]2 is a perspective view showing an output race of the friction transmission device of FIG. 1. [Figure 10] 2 is a perspective view showing a roller cage of the friction transmission of FIG. 1. [Figure 11] 2 is a perspective view showing a pressing cam of the friction transmission device of FIG. 1. [Figure 12] FIG. 2 is a perspective view showing a cover of the friction transmission device of FIG. [Figure 13] 2 is a schematic diagram illustrating the operation of a pressing force imparting mechanism of the friction transmission device of FIG. 1. [Figure 14] 2 is a perspective view showing a speed ratio control mechanism of the friction transmission of FIG. 1. [Figure 15] 2 is a cross-sectional view showing a spigot portion of the pressing force imparting mechanism of FIG. 1. [Figure 16] FIG. 4 is a cross-sectional view showing a second configuration example of the friction transmission device of the embodiment. [Figure 17] FIG. 17 is a perspective view showing a cover of the second configuration example of FIG. 16. [Figure 18] 4 is a cross-sectional view showing a support structure for a pressing cam of a friction transmission device according to a reference example. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described below based on preferred embodiments with reference to the drawings. In the embodiments, reference examples, and modified examples, the same or equivalent components and members are given the same reference numerals, and duplicated descriptions are omitted as appropriate. The dimensions of the members in each drawing are enlarged or reduced as appropriate for ease of understanding. Some of the members that are not important for explaining the embodiments are omitted in each drawing.

[0011] In addition, although terms including ordinal numbers such as first, second, etc. are used to describe various components, these terms are used only for the purpose of distinguishing one component from another component, and the components are not limited by these terms.

[0012] [Embodiment] First, the overall configuration of a friction transmission 100 according to an embodiment of the present disclosure will be described. Fig. 1 is a perspective view showing an example of a friction transmission 100 according to an embodiment. The friction transmission 100 has a casing 37 that encloses an internal mechanism, an input shaft 64, an output member 32, and an attachment member 38. The attachment member 38 is a brim-shaped member provided on the outer periphery of the casing 37 in order to attach the friction transmission 100 to an external device (not shown).

[0013] The friction transmission device 100 is configured such that the rotation input to the input shaft 64 rotates the input raceway, thereby causing the planetary rolling elements to rotate and revolve about their axes, and the rotational components thus generated are output to a driven device (not shown) from the output member 32 connected to the output raceway.

[0014] FIG. 2 is a cross-sectional view showing a longitudinal section of the friction transmission 100 taken along line AA. FIG. 2 shows a state in which the mounting member 38 has been removed. The friction transmission 100 mainly includes an input mechanism 2, a transmission mechanism 3, an output mechanism 5, a pressing force imparting mechanism 7, and a speed ratio control mechanism 6. The input mechanism 2 is a mechanism that transmits the rotation input from the prime mover to the input raceway 14. The transmission mechanism 3 is a mechanism that changes the speed of the rotation transmitted to the input raceway 14 and transmits it to the output raceway 30. The output mechanism 5 is a mechanism that outputs the rotation transmitted to the output raceway 30 from the output member 32 to the driven device. The pressing force imparting mechanism 7 imparts an axial pressing force to the transmission mechanism 3. The speed ratio control mechanism 6 is a mechanism that changes the relative positions of the raceways of the transmission mechanism 3 to control the speed ratio.

[0015] The input mechanism 2 will be described with reference to Fig. 2. The input mechanism 2 according to the embodiment includes an input shaft 64, a ball spline nut 65, an input bearing 66, a cover 67, a first oil seal S1, a shaft 68, a shaft cap 69, an input race 14, a sleeve 15, a first support race 26, and a bearing 27 for the first race.

[0016] Hereinafter, the direction along the rotation axis La of the input race 14 will be referred to as the "axial direction," and the circumferential direction and radial direction of a circle centered on the rotation axis La will be referred to as the "circumferential direction" and the "radial direction," respectively. For convenience, one side in the axial direction (the right side in the drawing) will be referred to as the "input side," and the other side (the left side in the drawing) will be referred to as the "anti-input side."

[0017] Unless otherwise specified, the circular parts surrounding the rotation axis La of each member of the friction transmission 100 are formed around the rotation axis La. The centers of these circular parts may be shifted from the rotation axis La within a margin of error.

[0018] The input shaft 64 is an input section to which rotation from a prime mover is input. The prime mover in this embodiment is the motor 50, and the input shaft 64 is connected to a motor shaft 51 to which the rotation of the motor 50 is output. The ball spline nut 65 transmits the rotation of the input shaft 64 to a shaft 68, and supports the shaft 68 so that it can move in the axial direction. The input shaft 64 has an outer cylinder that houses the ball spline nut 65. The ball spline nut 65 is key-connected to the input shaft 64 by a key 65k, and rotates integrally with the input shaft 64. The shaft 68 is axially movable relative to the ball spline nut 65, and rotates integrally with the ball spline nut 65.

[0019] The cover 67 is a hollow disk-shaped member that covers a part or all of the input side of the friction transmission 100, and has a hollow portion 67c that surrounds the rotation axis La. The cover 67 is fixed to the input side of the casing 37 by a plurality of bolts B1. The input bearing 66 is disposed between the hollow portion 67c and the ball spline nut 65, and supports the ball spline nut 65 and the input shaft 64 so that they can rotate relative to each other. The outer ring of the input bearing 66 is supported by the hollow portion 67c, and the inner ring supports the input shaft 64. The input bearing 66 in this example is a ball bearing. The first oil seal S1 is disposed on the input side of the input bearing 66 in the hollow portion 67c, and seals the input bearing 66.

[0020] The shaft 68 is a rod-shaped shaft extending in the axial direction, and has an axial groove (not shown) through which balls pass. The input side of the shaft 68 is accommodated in the ball spline nut 65, and the tip of the shaft 68 extends further toward the anti-input side than the planetary rolling elements 20. The shaft cap 69 is a member that regulates the positional relationship between the shaft 68 and the first support raceway 26. The shaft cap 69 has a cup shape that is composed of a disk portion 69b and a cylindrical portion 69c that extends from the outer periphery of the disk portion 69b toward the input side. The tip of the shaft 68 is inserted into the cylindrical portion 69c, and is fixed to the disk portion 69b by a bolt B3 that passes through the disk portion 69b.

[0021] The input raceway 14 will be described with reference to Fig. 3. In Figs. 3 to 12, 14, and 16, (A) shows a view from diagonally above the non-input side, and (B) shows a view from diagonally above the input side. Fig. 3 is a perspective view showing the input raceway 14. In the example of Fig. 3, the input raceway 14 is formed integrally with a sleeve 15.

[0022] The sleeve 15 is a hollow cylindrical member fixed to the outer periphery of the shaft 68 by interference fit or the like, and has a first cylindrical portion 15b and a second cylindrical portion 15c from the input side toward the non-input side. The first cylindrical portion 15b is surrounded by the control portion bearing 63 and rotatably supported by the control portion bearing 63. The second cylindrical portion 15c is continuous with the first cylindrical portion 15b at a portion having a larger diameter than the first cylindrical portion 15b. A step portion 15d is formed at the boundary between the first cylindrical portion 15b and the second cylindrical portion 15c. A circumferential groove 15g is provided around the first cylindrical portion 15b, in which a retaining ring W1 is attached to regulate the positional relationship with the control portion bearing 63.

[0023] The input race 14 is a hollow cylindrical member fixed to the outer periphery of the shaft 68, has a larger diameter than the second cylindrical portion 15c, and is continuous with the second cylindrical portion 15c. The input race 14 is a hole into which the shaft 68 is fitted, and has a hollow portion 14e penetrating from the non-input side of the input race 14 to the input side of the sleeve 15. A rolling surface 14h that contacts the planetary rolling element 20 is provided on the outer periphery of the input race 14. The input race 14 has a bearing receiving portion 14j for receiving a part of the input side of the first race bearing 27. The bearing receiving portion 14j in this example is a circular recess recessed from the end face of the non-input side of the input race 14 to the input side.

[0024] The input raceway 14 is a member for supporting the planetary rolling elements 20 in a predetermined position and transmitting rotation to the planetary rolling elements 20. The rolling surface 14h is a surface on which the planetary rolling elements 20 roll, and is in point contact or surface contact with the planetary rolling elements 20. The rolling surface 14h may be inclined in the axial direction and the radial direction. The rolling surface 14h may include a tapered surface that reduces in diameter toward the input side. The rolling surface 14h may be a curved surface such as a flat surface or a concave surface, but in this example, it is a convex surface.

[0025] The first support race 26 will be described with reference to FIG. 4. FIG. 4 is a perspective view showing the first support race 26. The first support race 26 is a cylindrical member that fits around the outer periphery of the shaft 68 and is rotatably supported by the shaft 68, and is a hollow cylindrical member having approximately the same diameter as the input race 14. The first support race 26 has a through hole 26d that surrounds the shaft 68. A rolling surface 26h that contacts the planetary rolling element 20 is provided on the outer periphery of the first support race 26. The first support race 26 has a bearing accommodating portion 26j for accommodating a part of the anti-input side of the first race bearing 27. The bearing accommodating portion 26j in this example is a circular recess that is recessed from the end face of the anti-input side of the first support race 26 toward the anti-input side.

[0026] The first support raceway 26 is a member for supporting the planetary rolling element 20 in a predetermined position. The rolling surface 26h is a surface on which the planetary rolling element 20 rolls, and is in point contact or surface contact with the planetary rolling element 20. The rolling surface 26h may be inclined in the axial direction and the radial direction. The rolling surface 26h may include a tapered surface that reduces in diameter toward the non-input side. The rolling surface 26h may be a curved surface such as a flat surface or a concave surface, but is a convex surface in this example. The first support raceway 26 is freely rotatable with respect to the shaft 68 and the planetary rolling element 20, and may be referred to as an idle raceway.

[0027] The first bearing ring 27 is a thrust bearing that rotatably supports the first support bearing ring 26 relative to the input bearing ring 14. For example, the first bearing ring 27 can be composed of two rings facing each other in the axial direction and a number of spheres interposed between the two rings.

[0028] See also Figures 5 to 9. The transmission mechanism 3 of the embodiment includes a plurality of planetary rolling elements 20, a cage 21, an input race 14, a first support race 26, a second support race 28, and an output race 30. The input race 14, the first support race 26, the second support race 28, and the output race 30 are collectively referred to as "races."

[0029] 5 is a perspective view showing the planetary rolling element 20. A plurality of planetary rolling elements 20 (for example, five) are arranged at a predetermined interval in the circumferential direction. The number of planetary rolling elements 20 is not particularly limited and may be less than or more than five, but is preferably 5 to 12. The planetary rolling element 20 has a contact surface 20a that contacts the rolling surface 14h of the input race 14, a contact surface 20b that contacts the rolling surface 26h of the first support race 26, a contact surface 20c that contacts the rolling surface 28h of the second support race 28, and a contact surface 20d that contacts the rolling surface 30h of the output race 30.

[0030] The rolling surfaces 14h, 26h, 28h, and 30h of the raceways are collectively referred to as the rolling surfaces of the raceways. The contact surfaces 20a, 20b, 20c, and 20d are collectively referred to as the contact surfaces of the planetary rolling elements. The contact surfaces 20a and 20b may be flat or convex, but in this example they are concave. The contact surfaces 20c and 20d may be flat or concave, but in this example they are convex.

[0031] The planetary rolling body 20 is regulated in its axial position, radial position and attitude by contacting the rolling surface of the raceway. The shape of the planetary rolling body 20 may be any shape as long as its attitude is determined by contacting the rolling surface of the raceway and it can roll while contacting the rolling surface of the raceway. The planetary rolling body 20 of the embodiment is a rotating body obtained by rotating a trapezoid whose upper base and legs are curved around a predetermined axis. The predetermined axis is an axis parallel to the lower base of the trapezoid and spaced apart from the lower base on the opposite side to the upper base. In this specification, the circle formed by the intersection of a plane (hereinafter referred to as the "equatorial plane") that passes through the center of the upper base of the trapezoid and is perpendicular to the rotation axis Lb of the planetary rolling body 20 and the outer circumferential surface of the planetary rolling body 20 is referred to as the "equator". In this example, the equator 20e is a circle formed by the intersection of the equatorial plane and the outer circumferential surface of the planetary rolling body 20.

[0032] The inclination of the rotation axis Lb of the planetary rolling element 20 with respect to the rotation axis La varies depending on the relative position of the rolling surface of the raceway. That is, the rotation axis Lb may be parallel to the rotation axis La or may be inclined with respect to the rotation axis La.

[0033] 6 is a perspective view showing the retainer 21. The friction transmission 100 of the embodiment includes the retainer 21 for retaining the multiple planetary rolling elements 20 at desired positions. The retainer 21 restricts the circumferential movement of the multiple planetary rolling elements 20. The retainer 21 retains the multiple planetary rolling elements 20 at predetermined intervals in the circumferential direction so as to prevent the planetary rolling elements 20 from contacting each other. The retainer 21 has two ring portions 22 and multiple (e.g., five) pillar portions 23. The ring portions 22 and the pillar portions 23 of the retainer 21 can be integrally formed from resin or metal.

[0034] The two ring portions 22 are arranged axially apart, sandwiching the planetary rolling element 20 therebetween. The ring portion 22 is a hollow annular portion having a central hole 22c. The multiple pillar portions 23 are strip-shaped members extending in the axial direction, and are arranged between the multiple planetary rolling elements 20 at predetermined intervals in the circumferential direction. One end of the pillar portion 23 is fixed to the outer periphery of one ring portion 22, and the other end is fixed to the outer periphery of the other ring portion 22. In other words, the pillar portion 23 is bridged between the two ring portions 22. A pocket 24 for holding the planetary rolling element 20 is formed between two adjacent pillar portions 23.

[0035] 7 is a perspective view showing the planetary rolling element unit 4. A plurality of planetary rolling elements 20 are incorporated into each pocket 24 of the cage 21 to constitute the planetary rolling element unit 4. The planetary rolling elements 20 are held in the pockets 24 so as to be rotatable.

[0036] FIG. 8 is a perspective view showing the second support raceway 28. The second support raceway 28 has a ring shape that surrounds the sleeve 15 and the planetary rolling element 20. The second support raceway 28 has a rolling surface 28h on the opposite input side and a cam surface 28p on the input side. The rolling surface 28h is a surface on which the planetary rolling element 20 rolls, and is in point contact or surface contact with the planetary rolling element 20. The rolling surface 28h is inclined in the axial direction and the radial direction. The rolling surface 28h includes a tapered surface that reduces in diameter toward the input side. The rolling surface 28h in this example is a conical surface composed of a flat surface. Since the conical surface is a concave surface, the contact surface 20c, which is a convex surface, and the rolling surface 28h are in uneven contact.

[0037] The cam surface 28p has a plurality of (for example, six) concave cam grooves 28j each consisting of a first inclined surface 28f and a second inclined surface 28g. The cam grooves 28j have a V-shape when viewed radially from the outer diameter side. The plurality of cam grooves 28j are arranged at predetermined intervals in the circumferential direction and are connected to each other by a connection surface 28e. The connection surface 28e can be formed parallel to a plane perpendicular to the rotation axis La. The first inclined surface 28f is inclined with respect to the plane perpendicular to the rotation axis La. The second inclined surface 28g is inclined in the opposite direction to the first inclined surface 28f with respect to the plane perpendicular to the rotation axis La.

[0038] The second support race 28 is fitted into the inner peripheral surface of the casing 37 so as to be slidable in the axial direction. A pressing force in the axial direction toward the non-input side is applied to the second support race 28 from the cam surface 28p by the pressing force applying mechanism 7. The pressing force presses the planetary rolling elements 20 against the output race 30.

[0039] FIG. 9 is a perspective view showing the output race 30. The output race 30 has a hollow circular shape that surrounds the shaft 68 and the shaft cap 69. The output race 30 has a rolling surface 30h on the input side. The rolling surface 30h is a surface on which the planetary rolling elements 20 roll, and is in point contact or surface contact with the planetary rolling elements 20. The rolling surface 30h is inclined in the axial direction and the radial direction. The rolling surface 30h includes a tapered surface that reduces in diameter toward the opposite input side. In this example, the rolling surface 30h is a conical surface composed of a flat surface. Since the conical surface is a concave surface, the contact surface 20d, which is a convex surface, and the rolling surface 30h are in uneven contact.

[0040] The output race 30 contacts the planetary rolling elements 20 and rotates about the rotation axis La as the planetary rolling elements 20 rotate. The output race 30 is connected to an output member 32 of the output mechanism 5, and the output member 32 rotates as the output race 30 rotates. The output race 30 has a connecting hole 30e that surrounds the rotation axis La and penetrates in the axial direction. The connecting hole 30e is provided with a recess 30k that meshes with the parallel key 35. The output race 30 is provided with a circular protrusion 30b that protrudes toward the opposite input side.

[0041] The operation of the transmission mechanism 3 will be described. When the input race 14 rotates, the planetary rolling elements 20 revolve around the revolution axis while rotating around the rotation axis Lb. In this example, the revolution axis of the planetary rolling elements 20 coincides with the rotation axis La, so the following description will be given assuming that the rotation axis La is the revolution axis.

[0042] When the first support race 26 rotates freely and the second support race 28 is stationary and non-rotating, an output rotation obtained by multiplying the input rotation by the speed ratio R is output to the output race 30. The speed ratio R is determined according to the shape of the planetary rolling elements 20 and the inclination of the spinning shaft Lb with respect to the rotation axis La. Therefore, the speed ratio R can be changed by changing the inclination of the spinning shaft Lb. The embodiment includes a speed ratio control mechanism 6 in order to change the speed ratio R by changing the inclination of the spinning shaft Lb. The speed ratio control mechanism 6 will be described later.

[0043] The output mechanism 5 will be described with reference to Fig. 2. The output mechanism 5 includes an output race 30, a thrust bearing 33, an output member 32, an output bearing 34, a second oil seal S2, and a casing 37.

[0044] The casing 37 functions as an outer shell that encloses the internal mechanism of the friction transmission 100. The casing 37 is a cylindrical member having a cylindrical portion 37b and an inward protruding portion 37h. A cover 67 is fixed to the input side end of the cylindrical portion 37b of the casing 37. The inward protruding portion 37h is a ring-shaped portion that protrudes radially inward from the inner periphery of the cylindrical portion 37b. The output bearing 34 is accommodated on the opposite input side of the inward protruding portion 37h of the cylindrical portion 37b.

[0045] The output bearing 34 is disposed between the output member 32 and the cylindrical portion 37b, and the input side of the output bearing 34 is supported by the inner protruding portion 37h. The output bearing 34 rotatably supports the output member 32. The output bearing 34 in this example is a cross roller bearing. The outer ring of the output bearing 34 is supported by the casing 37. The inner ring of the output bearing 34 supports the output member 32.

[0046] The second oil seal S2 is disposed on the inner circumferential surface of the cylindrical portion 37b on the anti-input side of the output bearing 34, and provides a seal between the inside of the friction transmission 100 and the outside.

[0047] The thrust bearing 33 rotatably supports the output race 30. The thrust bearing 33 is disposed between the inner protrusion 37h and the output race 30 in the axial direction. The thrust bearing 33 has a ring shape that is accommodated in the annular space between the casing 37 and the circular protrusion 30b of the output race 30. That is, the thrust bearing 33 fits onto the outer periphery of the circular protrusion 30b. The thrust bearing 33 in this example includes a hollow disk-shaped rolling ring 33e and a plurality of rolling elements 33b that roll on the rolling ring 33e. As an example, the rolling elements 33b are rollers.

[0048] The output member 32 is a substantially circular member having an output annular portion 32b and a connecting portion 32d. The output annular portion 32b is a circular portion, and a driven device is connected to the opposite side to the input side. A retaining ring W2 is attached to the outer periphery of the output annular portion 32b to regulate the positional relationship with the output bearing 34. The output annular portion 32b is supported by the output bearing 34.

[0049] The connecting portion 32d is a hollow circular portion that protrudes from the output annular portion 32b toward the input side. The outer periphery of the connecting portion 32d fits into the inner periphery of the output race 30, and a parallel key 35 is inserted between them. With this configuration, the output member 32 is connected to the output race 30. In this state, the output member 32 and the output race 30 are relatively movable in the axial direction and rotate integrally in the circumferential direction. The tip of the shaft 68 and a shaft cap 69 are housed in the inner periphery of the connecting portion 32d.

[0050] The pressing force imparting mechanism 7 will be described with reference to Fig. 2 and Figs. 10 to 13. The pressing force imparting mechanism 7 converts the rotational motion of the preload raceway into linear motion of the preload raceway to impart a preload to the transmission mechanism 3. In the example of Fig. 2, the second support raceway 28 functions as the preload raceway. The pressing force imparting mechanism 7 includes a pressing cam 56, a roller cage 52, a roller 53, a cover 67, and the second support raceway 28.

[0051] FIG. 10 is a perspective view showing the roller 53 and the roller retainer 52. The roller retainer 52 is a hollow disk-shaped member having a through hole 52c, and is disposed between the cam surface 28p of the second support raceway 28 and the pressing cam surface 56p of the pressing cam 56. The roller retainer 52 has a plurality of (for example, six) pockets 52b disposed at a predetermined interval in the circumferential direction. The pockets 52b are rectangular holes when viewed from the axial direction. A plurality of (for example, six) rollers 53 are provided corresponding to the cam grooves 56j. The rollers 53 have a cylindrical shape and are rotatably accommodated in the pockets 52b. The roller retainer 52 has a cutout portion 52k in which a part of the circumferential direction is cut out at a position corresponding to the radial protruding portion 62c of the control ring 62 in order to allow the control shaft 61 of the speed ratio control mechanism 6 to penetrate to the outside of the cover 67.

[0052] 11 is a perspective view showing the pressing cam 56. The pressing cam 56 is a hollow disk-shaped member having a through hole 56c, and is disposed between the roller cage 52 and the cover 67 in the axial direction. The pressing cam 56 has a notch 56k in which a part of the pressing cam 56 is cut out in the circumferential direction at a position corresponding to the radial protruding portion 62c of the control ring 62 in order to allow the control shaft 61 of the speed ratio control mechanism 6 to penetrate to the outside of the cover 67.

[0053] The pressing cam of the pressing force imparting mechanism has a first spigot portion 56n that spigot-fits with the cover 67. The first spigot portion 56n is provided on the outer circumferential surface of the pressing cam .

[0054] The pressing cam 56 has a pressing cam surface 56p on the opposite input side. The pressing cam surface 56p is composed of an arrangement surface 56a on which the rollers 53 are arranged, and a non-arrangement surface 56e on which the rollers 53 are not arranged. The arrangement surface 56a has a concave cam groove 56j consisting of a first inclined surface 56f and a second inclined surface 56g. The pressing cam surface 56p has a plurality of arrangement surfaces 56a (for example, six). The cam groove 56j has a V-shape when viewed in the radial direction from the outer diameter side. The multiple cam grooves 56j are arranged at predetermined intervals in the circumferential direction, and are connected to each other by the non-arrangement surface 56e.

[0055] The non-placement surface 56e can be formed parallel to a plane perpendicular to the rotation axis La. The first inclined surface 56f is inclined with respect to the plane perpendicular to the rotation axis La. The second inclined surface 56g is inclined in the opposite direction to the first inclined surface 56f with respect to the plane perpendicular to the rotation axis La.

[0056] The pressing cam 56 has a plurality of connected parts 56h arranged at a predetermined interval in the circumferential direction at a position offset from the rotation axis La. The connected parts 56h in this example are bolt holes penetrating in the axial direction and arranged at equal intervals in the circumferential direction. The connected parts 56h do not need to be arranged at strictly equal intervals, and may deviate from the equal intervals within the margin of error. In the example of FIG. 11, three connected parts 56h are provided at intervals of 120°. The connected parts 56h penetrate in the axial direction from the non-placement surface 56e. The pressing cam 56 is fixed to the cover 67 by a bolt B5 passing through the connected parts 56h and screwing into a screw hole 67f provided in the cover 67.

[0057] The cover 67 will be described with reference to Figures 1, 2, and 12. Figure 12 is a perspective view showing the cover 67. The cover 67 is a hollow disk-shaped member having a hollow portion 67c surrounding the rotation axis La. The cover 67 has a plurality of (e.g., 15) bolt holes 67d arranged at predetermined intervals in the circumferential direction at positions offset from the rotation axis La. The cover 67 is fixed to the input side of the casing 37 by screwing a plurality of bolts B1 into the input side of the casing 37 through the bolt holes 67d.

[0058] The cover 67 has a through hole 67e for passing the control shaft 61 therethrough. The through hole 67e is disposed at a position offset from the rotation axis La and on the inner circumferential side of the pitch circle of the bolt hole 67d. A plurality of screw holes 67f are provided on the non-input side of the cover 67 at a position offset from the rotation axis La and disposed at predetermined intervals in the circumferential direction. In the example of FIG. 12, three screw holes 67f are provided at intervals of 120°.

[0059] The hollow portion 67c is provided with a circumferential step 67h in contact with the input side of the input bearing 66, and a circumferential groove 67g in which a retaining ring W3 is attached. The retaining ring W3 in contact with the non-input side of the input bearing 66 is attached to the circumferential groove 67g. The axial position of the input bearing 66 is regulated by the retaining ring W3 and the circumferential step 67h.

[0060] The pressing cam 56 is fixed to the opposite input side of the cover 67, and the roller retainer 52 is attached to overlap the opposite input side of the pressing cam 56. The control ring 62 is housed in the hollow portion of the pressing cam 56 and the roller retainer 52, and the control shaft 61 penetrates a cylindrical seal 58 attached to a through hole 67e and protrudes from the cover 67 to the input side. The cylindrical seal 58 functions as an oil seal that suppresses the outflow of lubricant.

[0061] The operation of the pressing force imparting mechanism 7 will be described with reference to Fig. 2 and Fig. 13. Fig. 13 is a diagram for explaining the operation of the pressing force imparting mechanism 7, and shows the cam surface 28p, the roller 53, and the pressing cam surface 56p. The pressing cam 56 is fixed to the cover 67 and is stationary, and the second support raceway 28 receives a rotational force (torque) as the planetary rolling body 20 rotates, and rotates within a certain range. Fig. 13(A) shows a state in which no rotational force is being received, and Fig. 13(B) shows a state in which a rotational force is being received.

[0062] 13(B), when the second support raceway 28 rotates, the relative positions of the cam grooves 28j and 56j shift as indicated by the arrow W, and the rollers 53 ride up onto the first inclined surfaces 56f and the second inclined surfaces 28g. As a result, a reaction force F0 from the rollers 53 is applied to the inclined surfaces, and a component force of the reaction force F0 becomes a pressing force F, which presses the second support raceway 28 to the non-input side. The pressing force F presses the second support raceway 28, the planetary rolling elements 20, the output raceway 30, and the thrust bearing 33 against the inward protrusion 37h, and functions as a preload for the transmission mechanism 3.

[0063] The preload adjustment function of the pressing force imparting mechanism 7 will be described. When the load from the driven device increases and the preload between the output raceway 30 and the planetary rolling element 20 becomes insufficient, the proportion of the rotational force input from the input raceway 14 to the planetary rolling element 20 that is transmitted to the second support raceway 28 increases. When the rotational force of the second support raceway 28 increases, the pressing force F, which is a component of the rotational force of the second support raceway 28, increases, and the preload increases. When the load from the driven device decreases, the rotational force transmitted to the second support raceway 28 decreases due to the reverse mechanism, and the pressing force F and preload also decrease. In this way, the pressing force imparting mechanism 7 can impart a pressing force F corresponding to the load from the driven device to the transmission mechanism 3, and automatically adjust the preload.

[0064] The speed ratio control mechanism 6 will be described with reference to Figs. 2, 3, and 14. Fig. 14 is a perspective view showing the speed ratio control mechanism 6. As described above, the speed ratio control mechanism 6 is a mechanism that controls the speed ratio R by changing the relative position of the input raceway 14 of the transmission mechanism 3. The speed ratio control mechanism 6 includes a control shaft 61, a control ring 62, and a control section bearing 63. The control shaft 61 is a rod-shaped member that extends in the axial direction at a position radially offset from the rotation axis La, and its opposite input end is attached to a radial protruding portion 62c of the control ring 62. The radial position of the control shaft 61 may be a position that is offset radially outward from the input shaft 64, or may be a position that is offset radially outward from the input raceway 14. The control ring 62 is a hollow annular member having a hollow portion 62e. A circumferential extension 62f extending radially inward from the non-input side of the hollow portion 62e and a circumferential groove 62g in which a retaining ring W4 is attached are provided around the hollow portion 62e in order to support the control portion bearing 63. The axial movement of the control portion bearing 63 is restricted by the circumferential extension 62f and the retaining ring W4.

[0065] The control section bearing 63 is disposed between the hollow portion 62e of the control ring 62 and the first cylindrical portion 15b of the sleeve 15. The control section bearing 63 rotatably supports the sleeve 15 with respect to the speed ratio control mechanism 6. An outer ring of the control section bearing 63 is supported in the hollow portion 62e of the control ring 62, and an inner ring supports the first cylindrical portion 15b. The control section bearing 63 in this example is a cross roller bearing. The control shaft 61 extends from the radial protrusion 62c to the input side, penetrates the cover 67, and protrudes to the input side of the cover 67. The control shaft 61 is connected to an actuator (not shown) that outputs a driving force in the axial direction. The non-input side of the control ring 62 is accommodated in the through hole 52c of the roller retainer 52.

[0066] The operation of the speed ratio control mechanism 6 will be described. When an axial driving force is input from the actuator to the control shaft 61, the control ring 62 moves in the axial direction. In conjunction with the movement of the control ring 62, the control section bearing 63, sleeve 15, input race 14, first race bearing 27, first support race 26, shaft 68 and shaft cap 69 move integrally. At this time, since the second support race 28 and the output race 30 are stationary in the axial direction, the rotation axis Lb of the planetary rolling element 20 tilts with respect to the rotation axis La.

[0067] When the input raceway 14 and the first support raceway 26 move toward the opposite input side, the opposite input side of the rotating shaft Lb moves away from the rotation axis La, and the input side of the rotating shaft Lb tilts toward the rotation axis La. As a result, the rotation radius and revolution radius of each contact point between each raceway and the planetary rolling element 20 change, and the speed ratio R also changes. The speed ratio R (output rotation / input rotation) of the friction transmission 100 increases as the inclination with respect to the rotation axis La increases. Similarly, when the input raceway 14 and the first support raceway 26 move toward the input side, the rotating shaft Lb tilts toward the opposite side, and the speed ratio R of the friction transmission 100 decreases as the inclination with respect to the rotation axis La increases. By maintaining the position of the control shaft 61 constant, the attitude of the planetary rolling element 20 becomes constant, and the speed ratio R is kept constant.

[0068] The operation of the friction transmission 100 configured as above will be described. When rotation is transmitted from the motor shaft 51 to the input shaft 64, the input race 14 rotates around the rotation axis La. The rotation of the input race 14 causes the planetary rolling elements 20 to rotate and revolve. The rotation of the planetary rolling elements 20 is transmitted to the output race 30, which rotates at a speed according to the speed ratio R. The rotation of the output race 30 is output to the output member 32 through the output mechanism 5. When the positions of the input race 14 and the first support race 26 are changed by the speed ratio control mechanism 6, the speed ratio R also changes.

[0069] Hereinafter, a description will be given of the characteristic configuration of the friction transmission 100 of the embodiment. One of the characteristics of the friction transmission 100 of the embodiment is the support structure of the pressing portion 72 that presses the second support race 28. As an example, the second support race 28 has a pressing cam 56 as the pressing portion 72.

[0070] (Reference example) A specific support structure of the pressing portion 72 of the pressing force imparting mechanism 7 will be described. In order to facilitate understanding of the characteristic configuration, a support structure of the pressing portion 72 in a reference example 200 of a friction transmission device will be described. The reference example 200 was created by the present inventor in the process of developing this embodiment. The pressing portion 72 in the reference example 200 is a pressing cam 56. FIG. 18 is a cross-sectional view showing the support structure of the pressing cam 56 in the reference example 200.

[0071] The reference example 200 differs from the friction transmission 100 of the embodiment in that the casing 37 and the cover 67 are fixed to each other by a bolt B1 while sandwiching the pressing cam 56, but the other configurations are the same as those of the embodiment. In the reference example 200, the pressing cam 56 has a flange 56m that protrudes in the radial direction from the outer periphery. The flange 56m is accommodated in the axial space between a recess 37d provided on the input side of the casing 37 and a recess 67b provided on the opposite input side of the cover 67. The flange 56m is provided with 15 through holes 56d provided at positions corresponding to the bolt holes 67d of the cover 67. The cover 67 and the flange 56m are fixed to the input side of the casing 37 by screwing the bolt B1 into the casing 37 through the bolt hole 67d and the through hole 56d.

[0072] In the reference example 200, bending stress is applied to the flange 56m of the pressing cam 56 by the axial load (reaction force of the pressing force) generated by the pressing force applying mechanism 7. This is because there is a large radial offset between the position (pressing cam surface 56p) where the reaction force of the pressing cam 56 is received and the support position of the flange. Therefore, if the transmission torque is increased in the reference example 200, the reaction force of the pressing force also increases, and the bending stress generated in the flange 56m also increases, resulting in a lack of strength in this portion. This is disadvantageous in increasing the transmission torque. Below, several configuration examples for improving the strength of the pressing portion 72 will be described.

[0073] (First configuration example) A first configuration example of the friction transmission 100 of the embodiment will be described with reference to Figures 2, 11, 12, and 15. In the first configuration example, the pressing portion 72 is a pressing cam 56, and the pressing cam 56 has an abutment portion 56b that abuts against the cover 67 at a position that overlaps with the pressing cam 56 in the axial direction. In other words, the abutment portion 56b on the input side of the pressing cam 56 abuts against the cover 67 at the position of the pressing cam surface 56p that receives the reaction force of the pressing force. With this configuration, almost no bending stress is generated in the pressing cam 56. The pressing cam 56 is fixed to the cover 67 by passing the bolt B5 through the connected portion 56h and screwing it into the screw hole 67f of the cover 67 while the pressing cam 56 abuts against the cover 67.

[0074] The spigot portion of the pressing force imparting mechanism 7 of the first configuration example will be described. FIG. 15 is a cross-sectional view showing the spigot portion of the pressing force imparting mechanism 7. The first configuration example has a spigot portion to ensure the radial positional accuracy of the pressing force imparting mechanism 7. Specifically, the pressing cam 56 of the pressing force imparting mechanism 7 has a first spigot portion 56n that fits with the cover 67 and a second spigot portion 56q that fits with the casing 37. The first spigot portion 56n and the second spigot portion 56q are provided integrally and continuously with the outer circumferential surface of the pressing cam 56. A surrounding portion 67k that surrounds the pressing cam 56 is provided on the opposite input side of the cover 67, and the first spigot portion 56n fits with the inner circumferential surface 67n of the surrounding portion 67k. The casing 37 includes a surrounding portion 37k that surrounds the pressing cam 56 at the input side end of the cylindrical portion 37b. The second spigot portion 56q is spigot-fitted into the inner circumferential surface 37q of the surrounding portion 37k of the cylindrical portion 37b of the casing 37.

[0075] While the cover 67 needs to be machined into various shapes depending on requirements, the cam surface 28p needs to have hardness. Therefore, in the first configuration example, the pressing cam 56 is separate from the cover 67, and the hardness of the pressing cam 56 is greater than the hardness of the cover 67. By making them separate, the cam surface 28p can be formed from a high-hardness material, and the cover 67 can be formed from an easy-to-machine material, so that both hardness and ease of machining can be achieved at low cost.

[0076] According to the first configuration example, by eliminating the flange that is subjected to bending stress, it is possible to ensure strength and increase the transmission torque.

[0077] (Second configuration example) A second configuration example of the friction transmission 100 of the embodiment will be described with reference to Figs. 16 and 17. Fig. 16 is a cross-sectional view showing the second configuration example of the friction transmission 100. Fig. 17(A) is a perspective view of the cover 167 of the second configuration example seen from diagonally above the non-input side. Fig. 17(B) is a perspective view of the cover 167 of the configuration example seen from diagonally above the input side. The second configuration example differs from the first configuration example in that the pressing portion 72 is formed integrally with the cover 167, and other configurations are similar. Therefore, overlapping explanations will be omitted, and the differences from the first configuration example will be mainly explained.

[0078] As shown in Fig. 17(B), the input side of cover 167 is similar to the input side of cover 67 of the first configuration example (see also Fig. 12), and there are no differences. As shown in Fig. 17(A), cover 167 differs from cover 67 of the first configuration example in that a pressing portion 72 having a pressing cam surface 56p is provided on the non-input side. The pressing portion 72 can be considered as a pressing cam integrated with cover 167. The pressing cam surface 56p of cover 167 differs from pressing cam surface 56p of pressing cam 56 of the first configuration example (see also Fig. 11) in that it does not have connected portion 56h, but the other configurations are the same.

[0079] According to the second configuration example, since the pressing portion 72 is integrated with the cover 167, it is easier to ensure strength against the reaction force of the pressing force than in the reference example, and it is possible to increase the transmitted torque. Also, in the second configuration example, under the same condition of the transmitted torque, the cover 167 including the pressing portion 72 can be configured to be thinner in the axial direction than in the reference example.

[0080] The operation and effect of the friction transmission 100 of the embodiment will be described. The friction transmission 100 of the embodiment is a friction transmission device including a planetary rolling element 20 arranged around a rotation axis La, a first support raceway 26 and a second support raceway 28 in contact with the planetary rolling element 20, and a pressing force imparting mechanism 7 that presses the second support raceway 28 to generate a pressing force on the contact surface between the second support raceway 28 and the planetary rolling element 20. The friction transmission 100 has a cover 67 that covers the friction transmission 100 in the axial direction, and the pressing force imparting mechanism 7 has a pressing portion 72 that presses the second support raceway 28, and the pressing force imparting mechanism 7 has an abutting portion 56b that abuts against the cover 67 at a position that axially overlaps with the pressing portion 72, or is configured integrally with the cover 67.

[0081] According to this configuration, since the pressing portion 72 (pressing cam 56) is fixed to the cover 67, almost no bending stress due to the reaction force of the pressing force is generated in the pressing portion 72. Therefore, it is possible to eliminate the insufficient strength of the pressing portion 72, and in turn, it is possible to provide a friction transmission capable of transmitting a larger torque.

[0082] As an example, the pressing force imparting mechanism 7 includes a cam surface 28p provided on the second support raceway 28, a pressing cam 56 axially facing the cam surface 28p, and a plurality of rollers 53 arranged between the cam surface 28p and the pressing cam 56 and functioning as a pressing section 72, the pressing cam 56 has a pressing cam surface 56p configured with an arrangement surface 56a on which the plurality of rollers 53 are arranged and a non-arrangement surface 56e on which the plurality of rollers 53 are not arranged, a connected portion 56h for connecting to the cover 67 is provided on the non-arrangement surface 56e, and the pressing force imparting mechanism 7 is integrally configured with the cover 67 by connecting the connected portion 56h to the cover 67. In this case, compared to the case where the connected portion 56h is provided on the arrangement surface 56a, the connected portion 56h is provided on the non-arrangement surface 56e, so that interference between the rollers 53 and the connected portion 56h can be avoided.

[0083] As an example, the connected portions 56h are disposed at equal intervals in the circumferential direction, which can improve the variation in strength due to the position in the circumferential direction.

[0084] As an example, the pressing force imparting mechanism 7 has a first spigot portion 56n that abuts radially with and fits into the cover 67. In this case, since the first spigot portion 56n functions as a guide, when the pressing force imparting mechanism 7 is attached to the cover 67, they can be easily fitted together.

[0085] As an example, the friction transmission 100 has a casing 37 that surrounds the planetary rolling elements 20 and is connected to a cover 67, and the pressing force imparting mechanism has a second spigot portion 56q that abuts radially with the casing 37 and fits in the spigot portion 56q. In this case, since the second spigot portion 56q functions as a guide, when the pressing force imparting mechanism 7 is attached to the casing 37, they can be easily fitted together.

[0086] As an example, the pressing force imparting mechanism 7 includes a cam surface 28p provided on the second support raceway 28, a pressing cam 56 axially opposed to the cam surface 28p, and a plurality of rollers 53 disposed between the cam surface 28p and the pressing cam 56. The pressing cam 56 is separate from the cover 67, and the hardness of the pressing cam 56 is greater than the hardness of the cover 67. In this case, the cam surface 28p can be formed from a high-hardness material, and the cover 67 can be formed from an easy-to-machine material, so that both hardness and ease of machining can be achieved at low cost.

[0087] As an example, the pressing portion 72 is formed integrally with the cover 167. In this case, it is easy to ensure the strength against the reaction force of the pressing force, and it becomes possible to increase the transmission torque.

[0088] The above is a description of the embodiment.

[0089] The above description is based on the embodiments. These embodiments are merely examples, and it is understood by those skilled in the art that various modifications and changes are possible within the scope of the claims of the present invention, and that such modifications and changes are also within the scope of the claims of the present invention. Therefore, the description and drawings in this specification should be treated as illustrative rather than restrictive.

[0090] (Modification) The following describes the modified examples. In the drawings and description of the modified examples, the same or equivalent components and members as those in the embodiment are denoted by the same reference numerals. Descriptions that overlap with the embodiment will be omitted as appropriate, and the description will focus on configurations that differ from the embodiment.

[0091] In the explanation of the second configuration example, an example was shown in which pressing portion 72 is formed integrally with cover 167, but they may be formed separately and then connected to be integrated. When formed integrally, it is necessary to form the entire portion with high hardness, but when connected to be integrated, pressing portion 72 can be formed from a high hardness material and cover 167 can be formed from a material that is easy to process.

[0092] In the embodiment described above, an example has been given in which the cover 67 covers the entire friction transmission 100 in the axial direction, but the cover may be configured to cover only a portion of the friction transmission in the axial direction.

[0093] Although an example has been shown in which the output member 32 and the output race 30 are key-connected by the parallel key 35, there are no limitations to this connection structure. Any connection structure may be used as long as they are relatively movable in the axial direction and rotate integrally in the circumferential direction, and for example, a spline connection, an involute spline connection, or a connection using an elastic body such as a spring that has low rigidity in the axial direction and high rigidity in the circumferential direction can be used.

[0094] In the description of the embodiment, an example has been given in which the rolling surfaces 30h and 28h are conical surfaces constituted by flat surfaces, but these may also be curved surfaces such as convex surfaces or concave surfaces.

[0095] The configuration of the input bearing 66 is not limited, and may be, for example, a bearing having rollers as rolling elements. The configuration of the first raceway bearing 27 is not limited, and may be, for example, a bearing having rollers as rolling elements. The configuration of the thrust bearing 33 is not limited, and may be, for example, a bearing having spheres as rolling elements. The configuration of the output bearing 34 is not limited, and may be, for example, a bearing having spheres as rolling elements.

[0096] The configuration of the control section bearing 63 is not limited, and may be, for example, a bearing having balls as rolling elements, a thrust bearing, a sliding bearing, or the like.

[0097] For example, the pressing force imparting mechanism 7 may have a sphere instead of the roller 53, and the pocket 52b of the roller retainer 52, the cam groove 56j of the pressing cam 56, and the cam groove 28j of the second support raceway 28 may each have a shape corresponding to the sphere.

[0098] For example, in the pressing force imparting mechanism 7, the roller 53 and the roller retainer 52 may be eliminated, and the cam groove 28j of the second support race 28 may be a convex cam lobe having a V-shaped slope, which the cam groove 56j of the pressing cam 56 directly contacts. Conversely, the area of ​​the pressing cam corresponding to the cam groove 56j may be a cam lobe.

[0099] The positional relationship of each component of the friction transmission, including the first support raceway 26 and the second support raceway 28, is not limited to the example shown in the embodiment. These positional relationships may be different from those in the embodiment as long as they do not contradict the description of the claims of the present invention. For example, the positional relationship between the first support raceway 26 and the second support raceway 28 may be different from that in the embodiment.

[0100] In the description of the embodiment, the input race 14 is disposed radially inward and the output race 30 is disposed radially outward with respect to the rotation axis of the planetary rolling elements 20. However, this is not limited to this, and the input race 14 may be disposed on the outside and the output race 30 on the inside, or both may be disposed on the inside, or both may be disposed on the outside.

[0101] In the description of the embodiment, an example has been shown in which the cover 67 covers a part of the input side of the friction transmission 100 in the axial direction, but this is not limited to this. For example, a part of the casing may be protruded inward, and the protruding part may be used as a cover that covers the input side of the friction transmission in the axial direction.

[0102] The pressing cam 56 may be configured to have the contact portion 56b as a separate body from the cover 67, or may be configured to be integral with the cover 67.

[0103] Each of these modified examples provides the same functions and effects as the embodiment.

[0104] Any combination of the above-described embodiments and modifications is also useful as an embodiment of the present invention. A new embodiment resulting from the combination has the combined effects of the respective embodiments and modifications. [Explanation of symbols]

[0105] 7 pressing force imparting mechanism, 20 planetary rolling element, 26 first support raceway, 28 second support raceway, 28p cam surface, 32d connecting portion, 33b rolling element, 37 casing, 53 roller, 56 pressing cam, 56a arrangement surface, 56e non-arrangement surface, 56h connected portion, 56n first spigot portion, 56q second spigot portion, 67, 167 cover, 72 pressing portion, 100 friction transmission device.

Claims

1. A friction transmission device including: planetary rolling elements arranged around a rotation axis; a first support raceway and a second support raceway in contact with the planetary rolling elements; and a pressing force applying mechanism that presses the second support raceway to generate a pressing force on a contact surface between the second support raceway and the planetary rolling elements, A cover is provided to cover the friction transmission from the axial direction. the pressing force applying mechanism has a pressing portion that presses the second support race, The pressing force imparting mechanism has an abutment portion that abuts against the cover at a position that axially overlaps with the pressing portion, or is a friction transmission device that is integral with the cover.

2. the pressing force imparting mechanism includes a cam surface provided on the second support raceway, a pressing cam that faces the cam surface in the axial direction, and a plurality of rollers that are disposed between the cam surface and the pressing cam and function as the pressing portion, the pressing cam has a pressing cam surface including an arrangement surface on which the rollers are arranged and a non-arrangement surface on which the rollers are not arranged, A connection portion for connection to the cover is provided on the non-placement surface, The friction transmission device according to claim 1 , wherein the pressing force imparting mechanism is integrally formed with the cover by connecting the connected portion and the cover.

3. The friction transmission device according to claim 2 , wherein the connected portions are arranged at equal intervals in the circumferential direction.

4. 2. The friction transmission according to claim 1, wherein the pressing force imparting mechanism has a first spigot portion that abuts against the cover in a radial direction and is spigot-fitted therewith.

5. a casing that surrounds the planetary rolling elements and to which the cover is connected, 5. The friction transmission device according to claim 4, wherein the pressing force imparting mechanism has a second spigot portion that abuts against the casing in a radial direction and is spigot-fitted therewith.

6. the pressing force imparting mechanism includes a cam surface provided on the second support raceway, a pressing cam axially opposed to the cam surface, and a plurality of rollers disposed between the cam surface and the pressing cam, The pressing cam is separate from the cover, 2. The friction transmission device according to claim 1, wherein the hardness of the pressing cam is greater than the hardness of the cover.

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