Friction transmission device

Abstract

A friction transmission device 100 comprises: an input raceway ring 14; a planetary rolling element 20 that is disposed around a rotation axis La of the input raceway ring 14 and comes into contact with the input raceway ring 14; an output raceway ring 30 that comes into contact with the planetary rolling element 20 and is connected to an output member 32; and a first support raceway ring 26 and a second support raceway ring 28 that come into contact with the planetary rolling element 20. The friction transmission device includes a speed ratio changing mechanism 6 that changes the speed ratio by changing the relative positions of two outer raceway rings. The gear ratio changed by the speed ratio changing mechanism 6 is configured such that the maximum amount of an absolute value of the gear ratio on the positive side and the maximum amount of an absolute value of the gear ratio on the negative side are different from each other, and shapes of a first contact surface 20d and a second contact surface 20c that come into contact with the two outer raceway rings of the planetary rolling element 20 are different from each other.

Description

Friction transmission

[0001] The present disclosure relates to friction transmissions.

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

[0003] International Publication No. 2021 / 182001

[0004] Friction transmissions are expected to be used in many applications, such as robots and self-propelled vehicles. Friction transmissions can change the gear ratio from the reverse rotation side to the forward rotation side by changing the orientation of the components using mechanical input for gear ratio control. However, conventional devices have symmetrical gear characteristics between the forward and reverse rotation sides, which means that the gear ratio range cannot be used more effectively in some applications.

[0005] The object of the present disclosure has been made in view of the above-mentioned problems, and is to provide a friction transmission device that can more effectively use the range of gear ratios.

[0006] In order to solve the above problems, one aspect of the friction transmission device disclosed herein is a friction transmission device comprising an input raceway, planetary rolling elements arranged around the rotation axis of the input raceway and in contact with the input raceway, an output raceway in contact with the planetary rolling elements and connected to an output member, and first and second support raceways in contact with the planetary rolling elements, and further comprising a speed ratio change mechanism that changes the speed ratio by changing the relative positions of two inner drive rings among the input raceway, output raceway, first support raceway, and second support raceway that are located inside the planetary rolling elements, and two outer raceways that are located outside the planetary rolling elements. The speed ratio changed by the speed ratio change mechanism is configured so that the maximum absolute value of the positive side speed ratio, where the output rotation is in the same direction as the input rotation, is different from the maximum absolute value of the negative side speed ratio, where the output rotation is in the opposite direction to the input rotation, and the shapes of the first and second contact surfaces that come into contact with the two outer raceways of the planetary rolling elements are different from each other.

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

[0008] According to the present disclosure, it is possible to provide a friction electric device that can more effectively use the range of gear ratios.

[0009] 13 is a perspective view showing an example of a friction transmission device according to an embodiment. FIG. 13 is a cross-sectional view showing a cross section taken along line A-A of the friction transmission device of FIG. 1. FIG. 13 is a perspective view showing an input raceway of the friction transmission device of FIG. 1. FIG. 13 is a perspective view showing a first support raceway of the friction transmission device of FIG. 1. FIG. 13 is a perspective view showing a planetary rolling element of the friction transmission device of FIG. 1. FIG. 13 is a perspective view showing a cage of the friction transmission device of FIG. 1. FIG. 13 is a perspective view showing a planetary rolling element unit of the friction transmission device of FIG. 1. FIG. 13 is a perspective view showing a second support raceway of the friction transmission device of FIG. 1. FIG. 13 is a perspective view showing an output raceway of the friction transmission device of FIG. 1. FIG. 13 is a perspective view showing an output member of the friction transmission device of FIG. 1. FIG. 13 is a perspective view showing a pressing cam of the friction transmission device of FIG. 1. FIG. 13 is a perspective view showing a roller cage of the friction transmission device of FIG. 1. FIG. 13 is a perspective view showing a state in which predetermined members are attached to the cover of FIG. 13. FIG. 13 is a schematic view illustrating the operation of a pressing force imparting mechanism of the friction transmission device of FIG. 1. FIG. 13 is a perspective view showing a speed ratio changing mechanism of the friction transmission device of FIG. 1. FIG. 13 is a cross-sectional view showing a first configuration example of a friction transmission device according to an embodiment. Fig. 1 is a cross-sectional view showing a second configuration example of a friction transmission device of an embodiment; Fig. 2 is a cross-sectional view showing a third configuration example of a friction transmission device of an embodiment; Fig. 3 is a cross-sectional view showing a fourth configuration example of a friction transmission device of an embodiment; Fig. 4 is a cross-sectional view showing a fifth configuration example of a friction transmission device of an embodiment; Fig. 5 is a cross-sectional view showing a sixth configuration example of a friction transmission device of an embodiment; Fig. 6 is a cross-sectional view showing the configuration of a friction transmission device of a reference example.

[0010] The present disclosure will be described below based on preferred embodiments with reference to the drawings. In the embodiments and modified examples, identical or equivalent components and members are designated by the same reference numerals, and redundant explanations will be omitted where appropriate. Furthermore, the dimensions of the members in each drawing are enlarged or reduced as appropriate for ease of understanding. Furthermore, some members that are not important for explaining the embodiments are omitted from the drawings.

[0011] Furthermore, terms including ordinal numbers such as first and second are used to describe various components, but these terms are used only to distinguish one component from another and do not limit the components.

[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 the friction transmission 100 according to the embodiment. FIG. 2 is a cross-sectional view showing a longitudinal section of the friction transmission 100 taken along line A-A. The friction transmission 100 has a casing 37 that surrounds the internal mechanism, an input shaft 64, an output member 32, and an attachment member 38. The attachment member 38 is a flange-shaped member provided on the outer periphery of the casing 37 to attach the friction transmission 100 to an external device (not shown). FIG. 2 shows the state in which the attachment member 38 has been removed.

[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 own 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] 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 change mechanism 6. The input mechanism 2 is a mechanism that transmits rotation input from a prime mover (not shown) to an 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 an output raceway 30. The output mechanism 5 is a mechanism that outputs the rotation transmitted to the output raceway 30 from an output member 32 to a driven device. The pressing force imparting mechanism 7 imparts an axial pressing force to the transmission mechanism 3. The speed ratio change mechanism 6 is a mechanism that controls the speed ratio by changing the relative positions of the raceways of the transmission mechanism 3.

[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 bearing ring 14, a sleeve 15, a first support bearing ring 26, and a first bearing ring bearing 27.

[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 portions 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 portions may be offset from the rotation axis La within a margin of error.

[0018] The input shaft 64 is an input portion to which rotation from a prime mover is input. In this embodiment, the prime mover is the motor 50, and the input shaft 64 is connected to a motor shaft 51 to which rotation of the motor 50 is output. The ball spline nut 65 transmits the rotation of the input shaft 64 to the 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-coupled 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 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 with 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 in 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 axial grooves (not shown) through which balls pass. The input side of the shaft 68 is housed 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 race 26. The shaft cap 69 has a cup shape consisting 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 fixed to the disk portion 69b by a bolt B3 that passes through the disk portion 69b.

[0021] The input race 14 will be described with reference to Figure 3 as well. In Figures 3 to 12 and 16, (A) is a view from diagonally above the non-input side, and (B) is a view from diagonally above the input side. Figure 3 is a perspective view of the input race 14. The input race 14 in the example of Figure 3 is formed integrally with the 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, from the input side to the non-input side, a first cylindrical portion 15b and a second cylindrical portion 15c. 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 formed around the first cylindrical portion 15b, into which a snap 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 that penetrates from the non-input side of the input race 14 to the input side of the sleeve 15. A rolling surface 14h that comes into contact with the planetary rolling elements 20 is provided on the outer periphery of the input race 14. The input race 14 has a bearing accommodating portion 14j for accommodating a portion of the input side of the first race bearing 27. In this example, the bearing accommodating portion 14j is a circular recess that is recessed from the end face of the non-input side of the input race 14 toward the input side.

[0024] The input raceway 14 is a member that supports the planetary rolling elements 20 in a predetermined position and transmits rotation to the planetary rolling elements 20. The rolling surface 14h is the 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 and radial directions. The rolling surface 14h may include a tapered surface that narrows in diameter toward the input side. The rolling surface 14h may be a flat surface or a curved surface such as 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 as well. FIG. 4 is a perspective view showing the first support race 26. The first support race 26 is a cylindrical member that fits onto the outer periphery of the shaft 68 and is rotatably supported by the shaft 68. It is a hollow cylindrical member with approximately the same diameter as the input race 14. The first support race 26 has a through hole 26d that circumscribes the shaft 68. A rolling surface 26h that comes into contact with the planetary rolling elements 20 is provided on the outer periphery of the first support race 26. The first support race 26 has a bearing accommodating portion 26j that accommodates a portion of the non-input side of the first race bearing 27. In this example, the bearing accommodating portion 26j is a circular recess that is recessed from the input-side end face of the first support race 26 toward the non-input side.

[0026] The first support race 26 is a member for supporting the planetary rolling elements 20 in a predetermined position. The rolling surface 26h is the 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 26h may be inclined in the axial and radial directions. 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 flat surface or a curved surface such as a concave surface, but in this example it is a convex surface. The first support race 26 is freely rotatable with respect to the shaft 68 and the planetary rolling elements 20, and is sometimes referred to as an idler race.

[0027] The first bearing ring bearing 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 bearing 27 can be configured with two rings facing each other in the axial direction and a plurality of spheres interposed between the two rings.

[0028] The transmission mechanism 3 will be described with reference to Figures 2 and 5 to 9. The transmission mechanism 3 of this 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 elements 20. A plurality of planetary rolling elements 20 (for example, five) are arranged at predetermined intervals in the circumferential direction. The number of planetary rolling elements 20 is not particularly limited and may be more or less than five, but is preferably 5 to 12. Each planetary rolling element 20 has a contact surface 20a that contacts the rolling surface 14h of the input raceway 14, a contact surface 20b that contacts the rolling surface 26h of the first support raceway 26, a contact surface 20c that contacts the rolling surface 28h of the second support raceway 28, and a contact surface 20d that contacts the rolling surface 30h of the output raceway 30.

[0030] The rolling surfaces 14h, 26h, 28h, and 30h of these 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 axial position, radial position, and orientation of the planetary rolling elements 20 are restricted by contact with the rolling surfaces of the raceways. The shape of the planetary rolling elements 20 may be any shape as long as their orientation is determined by contact with the rolling surfaces of the raceways and they can roll while in contact with the rolling surfaces of the raceways. As shown in FIG. 5 , the planetary rolling elements 20 of this embodiment are rotating elements obtained by rotating a trapezoid whose upper base and legs are curved around a predetermined axis. The predetermined axis is an axis parallel to and spaced from the lower base of the trapezoid on the opposite side of the upper base. In this specification, the "equator" refers to a 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 elements 20 and the outer circumferential surface of the planetary rolling elements 20. 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 elements 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 bearing ring. In other words, the rotation axis Lb may be parallel to the rotation axis La or may be inclined with respect to the rotation axis La.

[0033] FIG. 6 is a perspective view showing the cage 21. The friction transmission 100 of this embodiment is equipped with the cage 21 for holding the plurality of planetary rolling elements 20 in desired positions. The cage 21 restricts circumferential movement of the plurality of planetary rolling elements 20. The cage 21 holds the plurality of planetary rolling elements 20 at predetermined intervals in the circumferential direction so as to prevent contact between the planetary rolling elements 20. The cage 21 has two ring portions 22 and a plurality (e.g., five) of column portions 23. The ring portions 22 and column portions 23 of the cage 21 can be integrally formed from resin or metal.

[0034] The two ring portions 22 are arranged axially apart, with the planetary rolling elements 20 sandwiched between them. The ring portion 22 is a hollow, annular portion having a central hole 22c. The multiple pillar portions 23 are strip-shaped members extending axially, and are arranged circumferentially at predetermined intervals between the multiple planetary rolling elements 20. One end of each 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 spans between the two ring portions 22. A pocket 24 for holding the planetary rolling elements 20 is formed between two adjacent pillar portions 23.

[0035] Fig. 7 is a perspective view showing the planetary rolling element unit 4. As shown in Fig. 7, a plurality of planetary rolling elements 20 are incorporated into each pocket 24 of the cage 21 to form the planetary rolling element unit 4. The planetary rolling elements 20 are rotatably held in the pockets 24.

[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 elements 20. The second support raceway 28 has a rolling surface 28h on the non-input side and a cam surface 28p on the input side. The rolling surface 28h is the 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 28h is inclined with respect to the axial and radial directions. The rolling surface 28h includes a tapered surface that narrows in diameter toward the input side. In this example, the rolling surface 28h is a conical surface composed of a flat surface. Because the conical surface is concave, 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 (e.g., 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 connecting surfaces 28e. The connecting surfaces 28e can be formed parallel to a plane perpendicular to the rotation axis La. The first inclined surfaces 28f are inclined relative to the plane perpendicular to the rotation axis La. The second inclined surfaces 28g are inclined in the opposite direction to the first inclined surfaces 28f relative to the plane perpendicular to the rotation axis La.

[0038] The second support race 28 is fitted onto the inner peripheral surface of the casing 37 so as to be slidable in the axial direction. A pressing force is applied to the second support race 28 from the cam surface 28p toward the non-input side in the axial direction 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 ring 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 the 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 and radial directions. The rolling surface 30h includes a tapered surface that narrows in diameter toward the non-input side. In this example, the rolling surface 30h is a conical surface composed of a flat surface. Because the conical surface is concave, the contact surface 20d, which is a convex surface, and the rolling surface 30h are in uneven contact.

[0040] The output bearing ring 30 contacts the planetary rolling elements 20 and rotates about the rotation axis La as the planetary rolling elements 20 rotate. The output bearing ring 30 is connected to an output member 32 of the output mechanism 5, and the output member 32 rotates as the output bearing ring 30 rotates. The output bearing ring 30 has a connecting hole 30e that surrounds the rotation axis La and penetrates in the axial direction. A connecting portion 32d of the output member 32 is fitted into the connecting hole 30e. A recess 30k that engages with a parallel key 35 provided on the outer periphery of the connecting portion 32d is provided in the connecting hole 30e. The output bearing ring 30 is provided with a circular protrusion 30b that protrudes toward the non-input side.

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

[0042] When the first support bearing ring 26 rotates freely and the second support bearing ring 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 bearing ring 30. The speed ratio R is determined according to the shape of the planetary rolling elements 20 and the inclination of the rotation axis Lb with respect to the rotation axis La. Therefore, the speed ratio R can be changed by changing the inclination of the rotation axis Lb. This embodiment includes a speed ratio change mechanism 6 in order to change the speed ratio R by changing the inclination of the rotation axis Lb. The speed ratio change mechanism 6 will be described later.

[0043] The output mechanism 5 will be described with reference to FIGS. 2 and 10 . As shown in FIG. 2 , the output mechanism 5 includes an output bearing ring 30, an output bearing ring bearing 33, an output member 32, an output bearing 34, a second oil seal S2, and a casing 37. The casing 37 functions as an outer shell that encloses the internal mechanism of the friction transmission 100. The casing 37 has a cylindrical portion 37b and an inward protruding portion 36. A cover 67 is fixed to the input side of the cylindrical portion 37b, with a pressing cam 56 sandwiched between them. The inward protruding portion 36 is a ring-shaped portion that protrudes radially inward from the inner periphery of the cylindrical portion 37b. The output bearing 34 is housed on the opposite input side of the inward protruding portion 36 of the cylindrical portion 37b.

[0044] 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 36. The output bearing 34 rotatably supports the output member 32. In this example, the output bearing 34 is a cross roller bearing. The outer ring of the output bearing 34 is supported by the cylindrical portion 37b, and the inner ring supports the output member 32.

[0045] The second oil seal S2 is disposed on the inner peripheral surface of the cylindrical portion 37b on the non-input side of the output bearing 34, and seals between the inside and outside of the friction transmission device 100.

[0046] The output race bearing 33 rotatably supports the output race 30 relative to the inward protruding portion 36 of the casing 37. The output race bearing 33 is disposed axially between the inward protruding portion 36 and the output race 30. The output race bearing 33 has a ring shape that is housed in the annular space between the cylindrical portion 37b and the circular protruding portion 30b of the output race 30. In other words, the output race bearing 33 fits onto the outer periphery of the circular protruding portion 30b. The output race bearing 33 in this example is a thrust bearing that includes a ring and a plurality of rollers that roll on the ring.

[0047] 10 is a perspective view showing the output member 32. The output member 32 is a generally circular member overall, and includes, from the non-input side, a flange portion 32b, an intermediate portion 32c, and a connecting portion 32d. The flange portion 32b is a disk-shaped portion, and includes a plurality of (e.g., six) tapped holes 32m on the non-input side for bolt connection to a driven device. The plurality of tapped holes 32m are arranged at predetermined intervals on a circumference surrounding the rotation axis La.

[0048] The intermediate portion 32c is continuous with the input side of the flange portion 32b and is a circular portion with a smaller diameter than the flange portion 32b. A circumferential groove 32g is formed around the outer periphery of the intermediate portion 32c, and a retaining ring W2 is fitted to the intermediate portion 32c to regulate the positional relationship with the output bearing 34. The intermediate portion 32c is supported by the output bearing 34.

[0049] The connecting portion 32d is continuous with the input side of the intermediate portion 32c and is a circular portion with a smaller diameter than the intermediate portion 32c. A fixing parallel key 35 is fixed to the outer periphery of the connecting portion 32d with a bolt B2. The parallel key 35 engages with a recess 30k in the connecting hole 30e. With the connecting portion 32d fitted into the connecting hole 30e, 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. A circular recess 32e is provided on the input side of the connecting portion 32d, recessed axially toward the opposite input side. The circular recess 32e is a circular recess surrounding the rotation axis La and has an inner diameter and depth that allow the tip of the shaft 68 and the shaft cap 69 to be accommodated with a gap therebetween.

[0050] The pressing force applying mechanism 7 will be described with reference to FIGS. 2 , 11 , 12 , 13 , 14 , and 15 . The pressing force applying mechanism 7 converts the rotational motion of the second support bearing ring 28 into linear motion of the second support bearing ring 28 to apply a preload to the transmission mechanism 3. As shown in FIG. 2 , the pressing force applying mechanism 7 includes a pressing cam 56, a roller retainer 52, a roller 53, a cover 67, and the second support bearing ring 28. FIG. 11 is a perspective view showing the pressing cam 56. The pressing cam 56 is a ring-shaped member having a through hole 56 c and is disposed between the cylindrical portion 37 b and the cover 67. The pressing cam 56 has a plurality of bolt holes 56 d for passing bolts B1 therethrough. The plurality of bolt holes 56 d are disposed at predetermined intervals in the circumferential direction at positions offset from the rotation axis La. The pressing cam 56 has a notch 56k in which a part of the circumferential direction is cut out to allow the control shaft 61 of the speed ratio change mechanism 6 to pass through.

[0051] The pressing cam 56 has a cam surface 56p on the non-input side. The cam surface 56p has multiple (e.g., six) concave cam grooves 56j each consisting of a first inclined surface 56f and a second inclined surface 56g. The cam grooves 56j have a V-shape when viewed radially 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 connecting surfaces 56e. The connecting surfaces 56e can be formed parallel to a plane perpendicular to the rotation axis La. The first inclined surfaces 56f are inclined with respect to the plane perpendicular to the rotation axis La. The second inclined surfaces 56g are inclined in the opposite direction to the first inclined surfaces 56f with respect to the plane perpendicular to the rotation axis La.

[0052] FIG. 12 is a perspective view showing the rollers 53 and the roller cage 52. The roller cage 52 is a ring-shaped member having a through hole 52c and is disposed between the cam surface 28p of the second support raceway 28 and the cam surface 56p of the pressing cam 56. The roller cage 52 has multiple (e.g., six) pockets 52b arranged at predetermined intervals in the circumferential direction. The pockets 52b are rectangular holes when viewed from the axial direction. Multiple (e.g., six) rollers 53 are provided corresponding to the cam grooves 56j. The rollers 53 have a cylindrical shape and are rotatably housed in the pockets 52b. The roller cage 52 has a notch 52k, which is a cutout portion cut out in part of the circumferential direction, to accommodate the radial protrusion 62c of the speed ratio change mechanism 6.

[0053] 13 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, and is fixed to the input side of the casing 37. The cover 67 has a plurality of bolt holes 67d for passing bolts B1. The plurality of bolt holes 67d are arranged at predetermined intervals in the circumferential direction at positions offset from the rotation axis La, and communicate with the bolt holes 56d of the pressing cam 56. The cover 67 has a through hole 67e for passing the control shaft 61 therethrough. The through hole 67e is arranged at a position offset from the rotation axis La and on the inner circumferential side of the pitch circle of the bolt holes 67d.

[0054] A sleeve bearing 57 and a cylindrical seal 58 are fitted into the through hole 67e (see also FIG. 2). The sleeve bearing 57 has a plate-shaped flange that contacts the non-input side of the cover 67 and a cylindrical portion that fits into the through hole 67e, and can be made of, for example, sintered metal. The sleeve bearing 57 smooths the axial movement of the control shaft 61 and prevents the outflow of lubricant. The cylindrical seal 58 is located on the input side of the sleeve bearing 57 in the through hole 67e and functions as an oil seal that prevents the outflow of lubricant.

[0055] The hollow portion 67c is provided with a circumferential step 67h that contacts the input side of the input bearing 66 and a circumferential groove 67g in which a snap ring W3 is fitted. The snap ring W3 that contacts the non-input side of the input bearing 66 is fitted in the circumferential groove 67g. The axial position of the input bearing 66 is regulated by the snap ring W3 and the circumferential step 67h.

[0056] FIG. 14 is a perspective view showing the state in which the main components of the speed ratio change mechanism 6 and the pressing force applying mechanism 7 are attached to the cover 67. The pressing cam 56 and the roller cage 52 are attached to the non-input side of the cover 67, overlapping each other. In this state, the notches 56k and 52k are circumferentially aligned with the through-hole 67e. The control ring 62 is attached so that the radial protrusion 62c (see also FIG. 16) is received in the notches 56k and 52k. The control ring 62 is received in the central space of the pressing cam 56 and the roller cage 52, and the control shaft 61 passes through the central holes of the sleeve bearing 57 and the cylindrical seal 58 and protrudes from the input side of the cover 67.

[0057] 15 is a diagram for schematically explaining the operation of the pressing force applying mechanism 7, showing the cam surface 28p, the roller 53, and the cam surface 56p. The pressing cam 56 is fixed to the casing and remains stationary, and the second support raceway 28 receives a rotational force (torque) and rotates as the planetary rolling elements 20 rotate. Fig. 15(A) shows a state in which no rotational force is being applied, and Fig. 15(B) shows a state in which a rotational force is being applied.

[0058] 15(B), when the second support race 28 rotates, the relative positions of the cam grooves 28j and 56j shift as indicated by the arrow W, causing the rollers 53 to ride up onto the first inclined surfaces 56f and the second inclined surfaces 28g. As a result, a reaction force F0 is applied from the rollers 53 to the inclined surfaces, and a component of the reaction force F0 becomes a pressing force F, pressing the second support race 28 to the non-input side. The pressing force F presses the second support race 28, planetary rolling elements 20, output race 30, and output race bearing 33 against the inward projection 36, and functions as a preload for the transmission mechanism 3 (see also FIG. 2).

[0059] When the load from the driven device increases and the preload between the output race 30 and the planetary rolling elements 20 becomes insufficient, an increasing proportion of the rotational force input from the input race 14 to the planetary rolling elements 20 is transmitted to the second support race 28. When the rotational force of the second support race 28 increases, the pressing force F, which is a component of the rotational force of the second support race 28, increases, and the preload increases. When the load from the driven device decreases, the rotational force transmitted to the second support race 28 decreases due to the opposite 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 to the transmission mechanism 3 according to the load from the driven device, thereby automatically adjusting the preload.

[0060] The speed ratio change mechanism 6 will be described with reference to FIGS. 2 and 16 . FIG. 16 is a perspective view showing the speed ratio change mechanism 6. As described above, the speed ratio change mechanism 6 controls the speed ratio R by changing the relative position of the input bearing ring 14 of the transmission mechanism 3. As shown in FIG. 2 , the speed ratio change mechanism 6 includes a control shaft 61, a control ring 62, and a control unit bearing 63. The control shaft 61 is a rod-shaped member extending axially at a position radially offset from the rotation axis La, and its non-input end is attached to a radial protrusion 62c of the control ring 62. The radial position of the control shaft 61 may be offset radially outward from the input shaft 64 or from the input bearing ring 14. The control ring 62 is a ring-shaped member having a hollow portion 62e. The hollow portion 62e is provided with a circumferential extending portion 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 fitted, in order to support the control portion bearing 63. The axial movement of the control portion bearing 63 is restricted by the circumferential extending portion 62f and the retaining ring W4.

[0061] 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 relative to the speed ratio change mechanism 6. The outer ring of the control section bearing 63 is supported in the hollow portion 62e of the control ring 62, and the inner ring supports the first cylindrical portion 15b. In this example, the control section bearing 63 is a cross roller bearing. The control shaft 61 extends from the radial protrusion 62c to the input side, penetrates the pressing cam 56 and the cover 67, and protrudes from the input side of the cover 67. The control shaft 61 is connected to an actuator (not shown) that outputs driving force in the axial direction. The non-input side of the control ring 62 is housed in the through hole 52c of the roller cage 52.

[0062] The operation of the speed ratio change mechanism 6 will now 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 unit 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, the second support race 28 and output race 30 are stationary in the axial direction, so the rotation axis Lb of the planetary rolling element 20 is tilted with respect to the rotation axis La.

[0063] When the input race 14 and the first support race 26 move toward the opposite input side, the opposite input side of the rotation axis Lb moves away from the rotation axis La, and the input side of the rotation axis Lb tilts toward the rotation axis La. As a result, the rotation radius and revolution radius of each contact point between each race and the planetary rolling elements 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 race 14 and the first support race 26 move toward the input side, the rotation axis 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 a constant position of the control shaft 61, the attitude of the planetary rolling elements 20 remains constant, and the speed ratio R is maintained constant.

[0064] The operation of the friction transmission 100 configured as described above will now be described. When rotation is transmitted from the motor shaft 51 to the input shaft 64, the input race 14 rotates about 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 corresponding to the gear ratio R. The rotation of the output race 30 is output to the output member 32 via the output mechanism 5. When the positions of the input race 14 and the first support race 26 (hereinafter simply referred to as "position T") are changed by the gear ratio change mechanism 6, the gear ratio R also changes.

[0065] The characteristic configuration of the present disclosure will be described below. In the friction transmission 100 of this embodiment, a first shape parameter for a first contact surface 20d that contacts the rolling surface 30h of the output raceway 30 of the planetary rolling element 20 and a second shape parameter for a second contact surface 20c that contacts the rolling surface 28h of the second support raceway 28 of the planetary rolling element 20 are different from each other. In other words, the shapes of the first contact surface 20d and the second contact surface 20c that contact the two outer raceways of the planetary rolling element 20 are different from each other. The shape parameter for the contact surface that contacts the rolling surface is a variable that defines the rolling surface, contact surface, and contact point. In other words, in the friction transmission 100, the rolling surface 30h and the first contact surface 20d, and the rolling surface 28h and the second contact surface 20c are asymmetric with respect to the equatorial plane. Specific configurations will be described later.

[0066] To facilitate understanding of the characteristic configuration, the contact configuration of the planetary rolling elements 20 and each bearing ring of Reference Example 200 will be described. Reference Example 200 was created by the present inventor during the process of developing this embodiment. Fig. 23(A) shows the configuration of the planetary rolling elements 20 and each bearing ring of Reference Example 200, and Fig. 23(B) shows the speed ratio control characteristic G of Reference Example 200. Fig. 23(A) shows the contour lines (hereinafter referred to as "sectional curves") that appear in each cross section of the planetary rolling elements 20, input bearing ring 14, first support bearing ring 26, second support bearing ring 28, and output bearing ring 30 in a plane including the center axis La and the rotation axis Lb.

[0067] Reference example 200 differs from the embodiment in that the first shape parameters and the second shape parameters are configured to be the same. In reference example 200, rolling surface 30 h and first contact surface 20 d, and rolling surface 28 h and second contact surface 20 c are configured symmetrically with respect to the equatorial plane.

[0068] The speed ratio control characteristic G of the reference example 200 will be explained. In FIG. 23(B), the horizontal axis represents the position T of the speed ratio change mechanism 6, and the vertical axis represents the speed ratio R (output rotation / input rotation). In the speed ratio R, a positive value indicates that the output rotation is in the same direction as the input rotation (forward rotation), while a negative value indicates that the output rotation is in the opposite direction to the input rotation (reverse rotation). The larger the absolute value of the speed ratio R, the higher the output rotation speed. A speed ratio R = 0 (zero) indicates that the output rotation is 0, i.e., no rotation. In other words, in a friction transmission, the speed ratio R can be changed by moving the position T of the speed ratio change mechanism 6 from the neutral position Tp to one side or from the neutral position Tp to the other side. The position T at which the rotation axis Lb of the planetary rolling element 20 is parallel to the rotation axis La of the input raceway 14 is called the neutral position Tp. In the diagram showing the speed ratio control characteristic G, the position T is shown as a relative value with respect to the neutral position Tp.

[0069] As shown in FIG. 23B , in the reference example 200, the speed ratio change mechanism 6 is configured so that the amount of movement N1 from the neutral position Tp to one side and the amount of movement N2 from the neutral position Tp to the other side are the same. The amount of movement of the speed ratio change mechanism 6 is set within a range where the contact point does not extend beyond the rolling surfaces of the planetary rolling elements or the raceway surfaces of the bearing rings and where the error in the speed ratio is acceptable. The speed ratio control characteristic G of the reference example 200 is symmetrical between the positive and negative sides of the speed ratio R, and may not be applicable to applications where the speed ratio R on one side is increased. Therefore, the friction transmission 100 of the embodiment has different first and second shape parameters so that it can be applied to applications where the speed ratio R on one side is increased. The first and second shape parameters are sometimes collectively referred to simply as "shape parameters." Below, several configuration examples will be described.

[0070] (First and Second Configuration Examples) First and second configuration examples of the friction transmission 100 of this embodiment will be described with reference to Figures 17 and 18. Figure 17(A) shows a first configuration example of the planetary rolling elements 20 and each raceway ring, and Figure 17(B) shows the speed ratio control characteristic G of the first configuration example. Figure 18(A) shows a second configuration example of the planetary rolling elements 20 and each raceway ring, and Figure 18(B) shows the speed ratio control characteristic G of the second configuration example.

[0071] In the first and second configuration examples, the outermost diameter K1 of the first contact surface 20d and the outermost diameter K2 of the second contact surface 20c of the planetary rolling element 20 are different from each other. In the first configuration example, the outermost diameter K1 of the first contact surface 20d is smaller than the outermost diameter K2 of the second contact surface 20c. The outermost diameter K1 and the outermost diameter K2 are examples of shape parameters. In the second configuration example, the outermost diameter K1 of the first contact surface 20d is larger than the outermost diameter K2 of the second contact surface 20c.

[0072] Furthermore, in the first and second configuration examples, as shown in the speed ratio control characteristic G, the amount of movement N1 of the speed ratio change mechanism 6 from the neutral position Tp to one side and the amount of movement N2 from the neutral position Tp to the other side are configured to be different from each other.

[0073] In the first configuration example, the amount of movement N1 to the positive side is greater than the amount of movement N2 to the negative side, the maximum amount (absolute value) M1 of the positive side gear ratio R is greater than in the reference example, and the maximum amount (absolute value) M2 of the negative side gear ratio R is smaller than in the reference example. In other words, the maximum amount (absolute value) M1 of the positive side gear ratio R is smaller than the maximum amount (absolute value) M2 of the negative side gear ratio R.

[0074] In the second configuration example, the amount of movement N2 toward the negative side is greater than the amount of movement N1 toward the positive side, the maximum amount (absolute value) M2 of the negative side gear ratio R is greater than in the reference example, and the maximum amount (absolute value) M1 of the positive side gear ratio R is smaller than in the reference example. In other words, the maximum amount (absolute value) M2 of the negative side gear ratio R is smaller than the maximum amount (absolute value) M1 of the negative side gear ratio R. The first configuration example is suitable for applications requiring high speed rotation on the positive side, and the second configuration example is suitable for applications requiring high speed rotation on the negative side.

[0075] (Third and Fourth Configuration Examples) Third and fourth configuration examples of the friction transmission 100 of this embodiment will be described with reference to Figures 19 and 20. Figure 19(A) shows a third configuration example of the planetary rolling elements 20 and each raceway ring, and Figure 19(B) shows the speed ratio control characteristic G of the third configuration example. Figure 20(A) shows a fourth configuration example of the planetary rolling elements 20 and each raceway ring, and Figure 20(B) shows the speed ratio control characteristic G of the fourth configuration example.

[0076] In the third and fourth configuration examples, when the rotation axis Lb of the planetary rolling element 20 is parallel to the rotation axis La of the input race 14, the radial distance D1 from the rotation axis Lb of the contact point 30c on the first contact surface 20d and the radial distance D2 from the rotation axis Lb of the contact point 28c on the second contact surface 20c are different from each other. In the third configuration example, the radial distance D1 is smaller than the radial distance D2. In the fourth configuration example, the radial distance D1 is larger than the radial distance D2. The radial distances D1 and D2 are examples of shape parameters.

[0077] To achieve this configuration, in the third and fourth configuration examples, the inclination angle θ1 of the region of the rolling surface 30h of the output race 30 that contacts the planetary rolling elements 20 relative to the rotation axis La and the inclination angle θ2 of the region of the rolling surface 28h of the second support race 28 that contacts the planetary rolling elements 20 relative to the rotation axis La are different from each other. In the third configuration example, the inclination angle θ1 is larger than the inclination angle θ2. In the fourth configuration example, the inclination angle θ1 is smaller than the inclination angle θ2. The inclination angles θ1 and θ2 are examples of shape parameters.

[0078] 19B, in the third configuration example, the amount of movement N1 to the plus side and the amount of movement N2 to the minus side are relative distances from the neutral position Tp and are equal to each other, with the maximum amount (absolute value) M1 of the speed ratio R on the plus side being larger than that of the reference example, and the maximum amount (absolute value) M2 of the speed ratio R on the minus side being smaller than that of the reference example. Furthermore, at the neutral position Tp, the speed ratio R is not zero but is offset by M0 to the plus side. The third configuration example is suitable for applications requiring high-speed rotation on the plus side.

[0079] 20B, in the fourth configuration example, the amount of movement N1 to the plus side and the amount of movement N2 to the minus side are relative distances from the neutral position Tp and are equal to each other, and the maximum amount (absolute value) M2 of the speed ratio R on the minus side is larger than that of the reference example, and the maximum amount (absolute value) M1 of the speed ratio R on the plus side is smaller than that of the reference example. Also, at the neutral position Tp, the speed ratio R is not zero but is offset by M0 to the minus side. The fourth configuration example is suitable for applications requiring high speed rotation on the minus side.

[0080] (Fifth and Sixth Configuration Examples) Fifth and sixth configuration examples of the friction transmission 100 of this embodiment will be described with reference to Figures 21 and 22. Figure 21(A) shows a fifth configuration example of the planetary rolling elements 20 and each raceway ring, and Figure 21(B) shows the speed ratio control characteristic G of the fifth configuration example. Figure 22(A) shows a sixth configuration example of the planetary rolling elements 20 and each raceway ring, and Figure 22(B) shows the speed ratio control characteristic G of the sixth configuration example.

[0081] In the friction transmission device 100 of the embodiment, the first, second, third, and fourth configuration examples can be combined with each other within a configurable range. The fifth configuration example is a combination of the first and third configuration examples, and the sixth configuration example is a combination of the second and fourth configuration examples.

[0082] In the fifth and sixth configuration examples, when the rotation axis Lb of the planetary rolling element 20 is parallel to the rotation axis La of the input race 14, the radial distance D1 and the radial distance D2 are different from each other, the outermost diameter K1 and the outermost diameter K2 are different from each other, and the inclination angle θ1 and the inclination angle θ2 are different from each other. In the fifth configuration example, the outermost diameter K1 is smaller than the outermost diameter K2, the inclination angle θ1 is larger than the inclination angle θ2, and the radial distance D1 is smaller than the radial distance D2. In the sixth configuration example, the outermost diameter K1 is larger than the outermost diameter K2, the inclination angle θ1 is smaller than the inclination angle θ2, and the radial distance D1 is larger than the radial distance D2.

[0083] In the fifth configuration example, as shown in FIG. 21B, the amount of movement N1 to the plus side and the amount of movement N2 to the minus side are relative distances from the neutral position Tp, with the amount of movement N1 to the plus side being greater than the amount of movement N2 to the minus side, the maximum amount (absolute value) M1 of the speed ratio R on the plus side being greater than in the reference example, and the maximum amount (absolute value) M2 of the speed ratio R on the minus side being smaller than in the reference example. Furthermore, at the neutral position Tp, the speed ratio R is not zero but is offset by M0 to the plus side. The fifth configuration example is more suitable for applications requiring high-speed rotation on the plus side.

[0084] In the sixth configuration example, as shown in FIG. 22B, the amount of movement N1 to the positive side and the amount of movement N2 to the negative side are relative distances from the neutral position Tp, with the amount of movement N2 to the negative side being greater than the amount of movement N1 to the positive side, the maximum amount (absolute value) M2 of the speed ratio R on the negative side being greater than that of the reference example, and the maximum amount (absolute value) M1 of the speed ratio R on the positive side being smaller than that of the reference example. Furthermore, at the neutral position Tp, the speed ratio R is not zero but is offset by M0 to the negative side. The sixth configuration example is more suitable for applications requiring high-speed rotation on the negative side.

[0085] The following describes the operation and effect of the friction transmission device 100 of the embodiment. The friction transmission device 100 of the embodiment is a friction transmission device that includes an input raceway 14, planetary rolling elements 20 that are arranged around the rotation axis La of the input raceway 14 and in contact with the input raceway 14, an output raceway 30 that is in contact with the planetary rolling elements 20 and is connected to an output member 32, and a first support raceway 26 and a second support raceway 28 that are in contact with the planetary rolling elements 20. The gear ratio change mechanism 6 changes the speed ratio by changing the relative positions of the two inner driving rings located inside the planetary rolling elements 20 out of the input ring 14, output ring 30, first support ring 26 and second support ring 28, and the two outer driving rings located outside the planetary rolling elements 20. The gear ratio changed by the gear ratio change mechanism 6 is configured so that the maximum absolute value M1 of the gear ratio on the plus side, where the output rotation is in the same direction as the input rotation, and the maximum absolute value M2 of the gear ratio on the minus side, where the output rotation is in the opposite direction to the input rotation, are different from each other, and the shapes of the first contact surface 20d and the second contact surface 20c that come into contact with the two outer rings of the planetary rolling elements 20 are different from each other.

[0086] According to this configuration, the first contact surface 20d and the second contact surface 20c have different shapes, making it possible to increase the speed ratio R (absolute value) on one of the plus and minus sides of the speed ratio R. This allows the speed ratio R on one side to be larger than in a symmetrical configuration, making it possible to more effectively use the range of the speed ratio R according to the needs of the application. Furthermore, the friction transmission 100 of the embodiment can be applied when an engine is used as the prime mover, but is particularly suitable when the prime mover is a servo motor whose rotation speed can be controlled over a wide range.

[0087] As an example, in the friction transmission 100, at least one of the input raceway 14, the output raceway 30, the first support raceway 26, and the second support raceway 28 is an asymmetrical contact raceway that comes into asymmetrical contact with the planetary rolling elements 20. In this case, the contact stress at the contact portion is lower than in the case of asymmetrical contact, and the life of the contact portion can be extended.

[0088] As an example, the friction transmission 100 is configured so that the amount of movement of the speed ratio change mechanism 6 from the neutral position to one side is different from the amount of movement of the speed ratio change mechanism 6 from the neutral position to the other side. In this case, since the amount of movement is different, it is possible to increase the speed ratio R (absolute value) on one side of the plus side and minus side of the speed ratio R, which has a larger amount of movement.

[0089] As an example, in the friction transmission 100, the outermost diameter of the first contact surface 20d and the outermost diameter of the second contact surface 20c of the planetary rolling element 20 are different from each other. In this case, the amount of movement is greater on one side of the contact surface with the larger outermost diameter than on the other side with the smaller outermost diameter, so the speed ratio R (absolute value) on one side can be increased.

[0090] As an example, in the friction transmission 100, when the rotation axis of the planetary rolling element 20 is parallel to the rotation axis La, the radial distance from the rotation axis to the contact point on the first contact surface 20d is different from the radial distance from the rotation axis to the contact point on the second contact surface 20c. For example, when the radial distance D1 is smaller than the radial distance D2, the positive speed ratio R (absolute value) can be increased, and when the radial distance D1 is larger than the radial distance D2, the negative speed ratio R (absolute value) can be increased.

[0091] As an example, in the friction transmission 100, when the rotation axis of the planetary rolling elements 20 is parallel to the rotation axis La, the inclination angle of the region of the rolling surface of the output race 30 that contacts the planetary rolling elements 20 relative to the rotation axis is different from the inclination angle of the region of the rolling surface of the second support race 28 that contacts the planetary rolling elements 20 relative to the rotation axis. For example, if the inclination angle θ1 is greater than the inclination angle θ2, the positive speed ratio R (absolute value) can be increased. For example, if the inclination angle θ1 is less than the inclination angle θ2, the negative speed ratio R (absolute value) can be increased.

[0092] The present disclosure has been described above based on several embodiments. These embodiments are merely examples, and it will be understood by those skilled in the art that various modifications and variations are possible and that such modifications and variations are also within the scope of the present disclosure. Therefore, the descriptions and drawings in this specification should be treated as illustrative rather than restrictive.

[0093] (Modifications) Modifications will be described below. In the drawings and descriptions of the modifications, the same components and members as those in the embodiment will be denoted by the same reference numerals. Explanations that overlap with the embodiment will be omitted as appropriate, and the description will focus on the configurations that differ from the embodiment.

[0094] In the description of the embodiment, an example has been shown in which the output member 32 and the output bearing ring 30 are key-coupled by the parallel key 35, but there are no limitations on these coupling structures. These coupling structures may be any structure that allows them to move relatively in the axial direction and rotate integrally in the circumferential direction, and for example, spline coupling, involute spline coupling, or coupling using an elastic body such as a spring that has low rigidity in the axial direction and high rigidity in the circumferential direction may be employed.

[0095] In the description of the embodiment, an example has been shown in which the rolling surfaces 30h and 28h are conical surfaces formed of flat surfaces, but these may also be curved surfaces such as convex or concave surfaces.

[0096] 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 bearing ring 27 is not limited, and may be, for example, a bearing having rollers as rolling elements. The configuration of the output bearing ring 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.

[0097] The configuration of the control section bearing 63 is not limited, and may be, for example, a bearing having spheres as rolling elements, a thrust bearing, a sliding bearing, or the like.

[0098] For example, the pressing force applying 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.

[0099] For example, the pressing force applying mechanism 7 may be configured so that the roller 53 and the roller retainer 52 are eliminated, and the cam groove 28j of the second support raceway 28 is a convex cam lobe with a V-shaped slope, which is in direct contact with the cam groove 56j of the pressing cam 56. Conversely, the area of ​​the pressing cam corresponding to the cam groove 56j may be a cam lobe.

[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] Each of these modifications provides the same functions and effects as the embodiment.

[0102] Any combination of the above-described embodiments and modifications is also useful as an embodiment of the present disclosure. A new embodiment resulting from the combination has the combined effects of the combined embodiments and modifications.

[0103] The present disclosure relates to friction transmissions.

[0104] 6 Speed ​​ratio change mechanism, 14 Input raceway, 14h Rolling surface, 20 Planetary rolling element, 20a, 20b, 20c, 20d Contact surface, 26 First support raceway, 26h Rolling surface, 28 Second support raceway, 28c Contact point, 28h Rolling surface, 30 Output raceway, 30c Contact point, 30h Rolling surface, 32 Output member, 100 Friction transmission device.

Claims

1. A friction transmission comprising an input raceway, planetary rolling elements arranged around the rotation axis of the input raceway and in contact with the input raceway, an output raceway in contact with the planetary rolling elements and connected to an output member, and first and second support raceways in contact with the planetary rolling elements, wherein the friction transmission further comprises a speed ratio change mechanism that changes the speed ratio by changing the relative positions of two inner driving rings among the input raceway, output raceway, first support raceway, and second support raceway, which are located inside the planetary rolling elements, and two outer raceways located outside the planetary rolling elements, wherein the speed ratio changed by the speed ratio change mechanism has a maximum absolute value different between the plus side speed ratio in which the output rotation is in the same direction as the input rotation and the minus side speed ratio in which the output rotation is in the opposite direction to the input rotation, and wherein the shapes of the first and second contact surfaces in contact with the two outer raceways of the planetary rolling elements are different from each other.

2. The friction transmission device according to claim 1, wherein at least one of the input raceway, the output raceway, the first support raceway and the second support raceway is a convex-concave contact raceway that comes into convex-concave contact with the planetary rolling elements.

3. A friction transmission device as set forth in claim 1 or 2, wherein the amount of movement of said speed ratio change mechanism from the neutral position to one side is different from the amount of movement of said speed ratio change mechanism from the neutral position to the other side.

4. A friction transmission as set forth in claim 3, wherein the outermost diameter of said first contact surface of said planetary rolling element and the outermost diameter of said second contact surface are different from each other.

5. A friction transmission device as described in any one of claims 1 to 4, wherein when the rotation axis of the planetary rolling body is parallel to the rotation axis, the radial distance from the rotation axis of the contact point on the first contact surface to the radial distance from the rotation axis of the contact point on the second contact surface to the rotation axis is different from each other.

6. A friction transmission device as described in claim 5, wherein, when the rotation axis of the planetary rolling elements is parallel to the rotation axis, the inclination angle of the region of the rolling surface of the output raceway that contacts the planetary rolling elements with respect to the rotation axis is different from the inclination angle of the region of the rolling surface of the second support raceway that contacts the planetary rolling elements with respect to the rotation axis.

Images