Friction transmission

Abstract

To provide a friction transmission device capable of reducing surface pressure.SOLUTION: A friction transmission device 100 comprises: an input bearing ring 14; a planetary rolling element 20 arranged around a rotational axial line of the input bearing ring 14, and in contact with the input bearing ring 14; an output bearing ring 30 that is in contact with the planetary rolling elements 20, and is connected to an output member 32; and a first support bearing ring 26 and a second support bearing ring 28 that are in contact with the planetary rolling elements 20. At least one of the input bearing ring 14, the output bearing ring 30, the first support bearing ring 26 and the second support bearing ring 28 is a convex-concave contact bearing ring that is in concave-concave contact with the planetary rolling elements 20.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] There is known a continuously variable transmission called IVT (Infinitely Variable Transmission) that enables an infinite transmission ratio. The applicant has disclosed in Patent Document 1 a technology of a friction transmission device including an input orbital gear, a planetary rolling body, and an output orbital gear. In this device, the planetary rolling body is arranged around the rotation axis of the input orbital gear and contacts the input orbital gear, and the output orbital gear contacts the planetary rolling body and is connected to the output shaft. Further, this device has a plurality of support orbital gears that contact the planetary rolling body, and变速 the rotation input to the input orbital gear and outputs it from the output shaft.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Friction transmission devices are expected to be used in many applications such as robots and self-propelled vehicles. In order for friction transmission devices to be used in more applications, it is desirable to reduce the contact surface pressure between the planetary rolling body and the orbital gear and extend their lifespan. However, in conventional friction transmission devices, it has been difficult to lower the surface pressure because there is a limit to expanding the contact area.

[0005] An object of the present invention is to provide a friction transmission device that can lower the surface pressure more.

Means for Solving the Problems

[0006] To solve the above problems, a friction transmission device according to one aspect of the present invention comprises 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 that is in contact with the planetary rolling elements and connected to an output member, and a first support raceway and a second support raceway that are in contact with the planetary rolling elements, wherein at least one of the input raceway, output raceway, first support raceway and second support raceway is an uneven contact raceway that makes uneven contact with the planetary rolling elements.

[0007] Furthermore, any combination of the above components, or in which the components or expressions of the present invention are mutually substituted among methods, systems, etc., are also valid embodiments of the present invention. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view showing an example of a friction transmission device according to an embodiment. [Figure 2] This is a cross-sectional view of the friction transmission device in Figure 1, showing a cross-section along line AA. [Figure 3] Figure 1 is a perspective view showing the input raceway of the friction transmission system. [Figure 4] Figure 1 is a perspective view showing the first support raceway of the friction transmission device. [Figure 5] Figure 1 is a perspective view showing the planetary rolling elements of a friction transmission system. [Figure 6] Figure 1 is a perspective view showing the retainer of the friction transmission device. [Figure 7] Figure 1 is a perspective view showing the planetary rolling element unit of the friction transmission device. [Figure 8] Figure 1 is a perspective view showing the second support raceway of the friction transmission device. [Figure 9] Figure 1 is a perspective view showing the output raceway of the friction transmission system. [Figure 10] Figure 1 is a perspective view showing the output member of the friction transmission device. [Figure 11] Figure 1 is a perspective view showing the press cam of the friction transmission device. [Figure 12]Figure 1 is a perspective view showing the roller retainer of the friction transmission device. [Figure 13] Figure 1 is a perspective view showing the cover of the friction transmission device. [Figure 14] Figure 13 is a perspective view showing the cover with the specified components attached. [Figure 15] Figure 1 is a schematic diagram illustrating the operation of the pressing force application mechanism of the friction transmission device. [Figure 16] Figure 1 is a perspective view showing the speed ratio control mechanism of the friction transmission device. [Figure 17] This is an explanatory diagram illustrating the support structure of the planetary rolling element in Figure 1. [Modes for carrying out the invention]

[0009] The present invention will be described below with reference to the drawings, based on preferred embodiments. In embodiments and modifications, the same or equivalent components and members will be denoted by the same reference numerals, and redundant explanations will be omitted as appropriate. In addition, the dimensions of the members in each drawing will be enlarged or reduced as appropriate for ease of understanding. Furthermore, some members that are not important for explaining the embodiments will be omitted from the drawings.

[0010] Furthermore, while terms including ordinal numbers such as "first" and "second" are used to describe various components, these terms are used solely to distinguish one component from others, and do not limit the components themselves.

[0011] [Embodiment] First, the overall configuration of the friction transmission device 100 according to the embodiments of the present disclosure will be described. FIG. 1 is a perspective view showing an example of the friction transmission device 100 according to the embodiment. FIG. 2 is a cross-sectional view showing a longitudinal section along the line A-A of the friction transmission device 100. The friction transmission device 100 includes a casing 37 that surrounds the internal mechanism, an input shaft 64, an output member 32, and a mounting member 38. The mounting member 38 is a flange-shaped member provided on the outer periphery of the casing 37 for attaching the friction transmission device 100 to an external device (not shown). FIG. 2 shows a state where the mounting member 38 is removed.

[0012] The friction transmission device 100 is configured to cause the input race to rotate by the rotation input to the input shaft 64, thereby causing the planetary rolling elements to rotate and revolve, and outputting the generated rotational component from the output member 32 connected to the output race to a driven device (not shown).

[0013] The friction transmission device 100 mainly includes an input mechanism 2, a transmission mechanism 3, an output mechanism 5, a pressing force applying 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 race 14. The transmission mechanism 3 is a mechanism that changes the speed of the rotation transmitted to the input race 14 and transmits it to the output race 30. The output mechanism 5 is a mechanism that outputs the rotation transmitted to the output race 30 from the output member 32 to the driven device. The pressing force applying mechanism 7 applies an axial pressing force to the transmission mechanism 3. The speed ratio control mechanism 6 is a mechanism that controls the speed ratio by changing the relative positions of the respective races of the transmission mechanism 3.

[0014] The input mechanism 2 will be described with reference to FIG. 2. The input mechanism 2 of 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 first race bearing 27.

[0015] Hereinafter, the direction along the rotation axis La of the input raceway 14 will be referred to as the "axial direction," and the circumferential and radial directions of the circle centered on that rotation axis La will be referred to as the "circumferential direction" and "radial direction," respectively. Also, for convenience, hereafter, one side of the axial direction (right side in the diagram) will be referred to as the "input side," and the other side (left side in the diagram) will be referred to as the "anti-input side."

[0016] Unless otherwise specified, the circular portions surrounding the rotation axis La of each component of the friction transmission device 100 are formed with the rotation axis La as the center. However, the centers of these circular portions may be offset from the rotation axis La within a margin of error.

[0017] The input shaft 64 is an input unit to which rotation from the prime mover is input. In this embodiment, the prime mover is a 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 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-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.

[0018] The cover 67 is a hollow disc-shaped member that covers the input side of the friction transmission device 100 and has a hollow portion 67c surrounding 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 positioned 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 ball spline nut 65. In this example, the input bearing 66 is a ball bearing. The first oil seal S1 is positioned on the input side of the input bearing 66 in the hollow portion 67c and seals the input bearing 66.

[0019] The shaft 68 is a rod-shaped shaft extending in the axial direction and has an axial groove (not shown) through which a ball passes. The input side of the shaft 68 is housed in a ball spline nut 65, and the tip of the shaft 68 extends away from the planetary rolling element 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 consisting of a disc portion 69b and a cylindrical portion 69c extending from the outer circumference of the disc portion 69b toward the input side. The tip of the shaft 68 is inserted into the cylindrical portion 69c and fixed to the disc portion 69b by a bolt B3 that passes through the disc portion 69b.

[0020] The input raceway 14 will be explained with reference to Figure 3. In Figures 3 to 12 and Figure 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 showing the input raceway 14. In the example of Figure 3, the input raceway 14 is formed integrally with the sleeve 15.

[0021] The sleeve 15 is a hollow cylindrical member fixed to the outer circumference of the shaft 68 by a compression fit or the like, and has a first cylindrical portion 15b and a second cylindrical portion 15c extending from the input side to the non-input side. The first cylindrical portion 15b is surrounded by the control bearing 63 and rotatably supported by the control bearing 63. The second cylindrical portion 15c is a larger diameter portion than the first cylindrical portion 15b and is continuous with the first cylindrical portion 15b. A stepped portion 15d is formed at the boundary between the first cylindrical portion 15b and the second cylindrical portion 15c. The first cylindrical portion 15b has a circumferential groove 15g on which a washer W1 is fitted to regulate the positional relationship with the control bearing 63.

[0022] The input raceway 14 is a hollow cylindrical member fixed to the outer circumference of the shaft 68, having a larger diameter than the second cylindrical portion 15c and being continuous with the second cylindrical portion 15c. The input raceway 14 has a hollow portion 14e that is a hole into which the shaft 68 is fitted, and which penetrates from the non-input side of the input raceway 14 to the input side of the sleeve 15. A rolling surface 14h that contacts the planetary rolling elements 20 is provided on the outer circumference of the input raceway 14. The input raceway 14 has a bearing housing portion 14j for housing a part of the input side of the first raceway bearing 27. In this example, the bearing housing portion 14j is a circular recess that is recessed from the non-input end face of the input raceway 14 toward the input side.

[0023] 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 makes point contact or surface contact with the planetary rolling elements 20. The rolling surface 14h may be inclined with respect to the axial and radial directions. The rolling surface 14h may include a tapered surface that decreases 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.

[0024] The first support raceway 26 will be described with reference to Figure 4. Figure 4 is a perspective view showing the first support raceway 26. The first support raceway 26 is a cylindrical member fitted to the outer circumference of the shaft 68 and rotatably supported by the shaft 68, and is a hollow cylindrical member with approximately the same diameter as the input raceway 14. The first support raceway 26 has a through hole 26d that surrounds the shaft 68. A rolling surface 26h that contacts the planetary rolling elements 20 is provided on the outer circumference of the first support raceway 26. The first support raceway 26 has a bearing housing portion 26j for housing a part of the non-input side of the bearing 27 for the first raceway. In this example, the bearing housing portion 26j is a circular recess that is recessed toward the non-input side from the end face of the first support raceway 26 toward the non-input side.

[0025] The first support raceway 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 it makes point contact or surface contact with the planetary rolling elements 20. The rolling surface 26h may be inclined with respect to the axial and radial directions. The rolling surface 26h may include a tapered surface that decreases 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 in this example it is a convex surface. The first support raceway 26 is freely rotatable relative to the shaft 68 and the planetary rolling elements 20, and is sometimes referred to as a free-rotating raceway.

[0026] The first raceway bearing 27 is a thrust bearing that rotatably supports the first support raceway 26 with respect to the input raceway 14. For example, the first raceway bearing 27 can be composed of two rings facing each other in the axial direction and a plurality of spheres interposed between the two rings.

[0027] The transmission mechanism 3 will be explained with reference to Figures 2, 5 to 9. The transmission mechanism 3 of this embodiment includes a plurality of planetary rolling elements 20, a retainer 21, an input orbital ring 14, a first support orbital ring 26, a second support orbital ring 28, and an output orbital ring 30. The input orbital ring 14, the first support orbital ring 26, the second support orbital ring 28, and the output orbital ring 30 are collectively referred to as "orbital rings".

[0028] Figure 5 is a perspective view showing the planetary rolling elements 20. Multiple planetary rolling elements 20 are arranged at predetermined intervals in the circumferential direction (for example, 5). The number of planetary rolling elements 20 is not particularly limited and may be less than or more than 5, but 5 to 12 is preferred. The planetary rolling elements 20 have 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.

[0029] 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. Contact surfaces 20a and 20b may be flat or convex, but in this example they are concave. Contact surfaces 20c and 20d may be flat or concave, but in this example they are convex.

[0030] The planetary rolling elements 20 have their axial position, radial position, and orientation restricted by contact with the rolling surfaces of the raceway wheels. The shape of the planetary rolling elements 20 can be any shape as long as its orientation is determined by contact with the rolling surfaces of the raceway wheels and it can roll while in contact with the rolling surfaces of the raceway wheels. As shown in Figure 5, the planetary rolling elements 20 of the embodiment are a body of rotation obtained by rotating a trapezoid whose upper base and legs are curved around a predetermined axis. The predetermined axis is an axis that is spaced apart from the lower base of the trapezoid on the opposite side of the upper base and is parallel to the lower base. In this specification, the circle formed when the outer surface of the planetary rolling elements 20 intersects with a plane (hereinafter referred to as the "equator 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 is called the "equator". In this example, the equator 20e is the circle formed when the equatorial plane intersects with the outer surface of the planetary rolling elements 20.

[0031] The inclination of the rotation axis Lb of the planetary rolling element 20 with respect to the rotation axis La changes depending on the relative position of the rolling surfaces of the orbital rings. In other words, the rotation axis Lb can be either parallel to the rotation axis La or inclined with respect to the rotation axis La.

[0032] Figure 6 is a perspective view showing the retainer 21. The friction transmission device 100 of the embodiment includes a retainer 21 to hold a plurality of planetary rolling elements 20 in desired positions. The retainer 21 restricts the circumferential movement of the plurality of planetary rolling elements 20. The retainer 21 holds the plurality of planetary rolling elements 20 at predetermined intervals in the circumferential direction so as to avoid contact between the planetary rolling elements 20. The retainer 21 has two ring portions 22 and a plurality (e.g., five) column portions 23. The retainer 21 can be integrally formed from resin or metal, with the ring portions 22 and column portions 23 being made from the same material.

[0033] The two ring portions 22 are positioned axially apart, flanking the planetary rolling element 20. Each ring portion 22 is a hollow annular section having a central hole 22c. The multiple column portions 23 are strip-shaped members extending axially, and are positioned between the multiple planetary rolling elements 20 at predetermined intervals in the circumferential direction. One end of each column portion 23 is fixed to the outer circumference of one ring portion 22, and the other end is fixed to the outer circumference of the other ring portion 22. In other words, the column portions 23 are spanned between the two ring portions 22. A pocket 24 is formed between two adjacent column portions 23 to hold the planetary rolling element 20.

[0034] Figure 7 is a perspective view showing the planetary rolling element unit 4. As shown in Figure 7, multiple planetary rolling elements 20 are incorporated into each pocket 24 of the retainer 21 to constitute the planetary rolling element unit 4. The planetary rolling elements 20 are rotatably held within the pockets 24.

[0035] Figure 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 non-input side and a cam surface 28p on the input side. The rolling surface 28h is the surface on which the planetary rolling element 20 rolls and makes point or surface contact with the planetary rolling element 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 flat surfaces.

[0036] The cam surface 28p has a plurality (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 by connecting surfaces 28e. The connecting surfaces 28e can be formed parallel to a plane perpendicular to the axis of rotation La. The first inclined surface 28f is inclined with respect to the plane perpendicular to the axis of rotation 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 axis of rotation La.

[0037] The second support raceway 28 is fitted to the inner surface of the casing 37 so as to be axially slidable. The second support raceway 28 is subjected to a pressing force from the cam surface 28p toward the axial opposite input side by the pressing force application mechanism 7. This pressing force presses the planetary rolling elements 20 against the output raceway 30.

[0038] Figure 9 is a perspective view showing the output raceway 30. The output raceway 30 has a ring shape that surrounds the shaft 68 and the shaft cap 69. The output raceway 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 it makes point or surface contact with the planetary rolling elements 20. The rolling surface 30h is inclined with respect to 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 flat surfaces.

[0039] The output raceway 30 is in contact with the planetary rolling elements 20 and rotates around the rotation axis La as the planetary rolling elements 20 rotate. The output raceway 30 is connected to the output member 32 of the output mechanism 5, and the output member 32 rotates as the output raceway 30 rotates. The output raceway 30 has a connecting hole 30e that surrounds the rotation axis La and penetrates axially. The connecting portion 32d of the output member 32 is fitted into the connecting hole 30e. The connecting hole 30e is provided with a recess 30k that engages with a parallel key 35 provided on the outer circumference of the connecting portion 32d. The output raceway 30 is provided with a circular protrusion 30b that projects toward the opposite side of the input.

[0040] The operation of the transmission mechanism 3 will now be explained. When the input orbital wheel 14 rotates, the planetary rolling element 20 rotates around its rotation axis Lb while revolving around its orbital axis. In this example, the orbital axis of the planetary rolling element 20 coincides with the rotation axis La, so the rotation axis La will be used as the orbital axis in the following explanation.

[0041] When the first support orbital 26 rotates freely and the second support orbital 28 is stationary and not rotating, the output orbital 30 outputs an output rotation obtained by multiplying the input rotation by the gear ratio R. The gear ratio R is determined according to the shape of the planetary rolling element 20 and the inclination of the rotation axis Lb with respect to the rotation axis La. Therefore, the gear ratio R can be changed by changing the inclination of the rotation axis Lb. The embodiment includes a gear ratio control mechanism 6 to change the gear ratio R by changing the inclination of the rotation axis Lb. The gear ratio control mechanism 6 will be described later.

[0042] The output mechanism 5 will be described with reference to Figures 2 and 10. As shown in Figure 2, the output mechanism 5 includes an output raceway 30, an output raceway 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 surrounding the internal mechanism of the friction transmission device 100. The casing 37 has a cylindrical portion 37b and an inner protrusion 36. A cover 67 is fixed to the input side of the cylindrical portion 37b, sandwiching a press cam 56. The inner protrusion 36 is a ring-shaped portion that protrudes radially inward from the inner circumference of the cylindrical portion 37b. The output bearing 34 is housed on the side of the cylindrical portion 37b opposite the input side to the inner protrusion 36.

[0043] The output bearing 34 is positioned between the output member 32 and the cylindrical portion 37b, and the input side of the output bearing 34 is supported by the inner overhang 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.

[0044] The second oil seal S2 is positioned on the inner circumferential surface of the cylindrical portion 37b on the side opposite to the input of the output bearing 34, and seals the space between the inside and outside of the friction transmission device 100.

[0045] The output raceway bearing 33 rotatably supports the output raceway 30 with respect to the inner protrusion 36 of the casing 37. The output raceway bearing 33 is positioned axially between the inner protrusion 36 and the output raceway 30. The output raceway bearing 33 has a ring shape that is housed in the annular space between the cylindrical portion 37b and the circular protrusion 30b of the output raceway 30. In other words, the output raceway bearing 33 fits onto the outer circumference of the circular protrusion 30b. In this example, the output raceway bearing 33 is a thrust bearing including a ring and a plurality of rollers that roll on the ring.

[0046] Figure 10 is a perspective view showing the output member 32. The output member 32 is a substantially circular member as a whole, and has a flange portion 32b, an intermediate portion 32c, and a connecting portion 32d, in order from the non-input side. The flange portion 32b is a disc-shaped part and has a plurality (for example, 6) tapped holes 32m on the non-input side for bolt connection to the driven device. The plurality of tapped holes 32m are arranged at predetermined intervals on the circumference surrounding the rotation axis La.

[0047] The intermediate portion 32c is a circular portion with a smaller diameter than the flange portion 32b and is continuous with the input side of the flange portion 32b. A circumferential groove 32g is provided around the outer circumference of the intermediate portion 32c, into which a washer W2 is fitted to regulate the positional relationship with the output bearing 34. The intermediate portion 32c is supported by the output bearing 34.

[0048] The connecting portion 32d is a circular portion that is continuous with the input side of the intermediate portion 32c and has a smaller diameter than the intermediate portion 32c. A fixing parallel key 35 is fixed to the outer circumference of the connecting portion 32d by 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 raceway 30. In this state, the output member 32 and the output raceway 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 in the opposite direction to the input side in the axial direction. The circular recess 32e is a circular recess surrounding the axis of rotation La and has an inner diameter and depth that can accommodate the tip of the shaft 68 and the shaft cap 69 with a gap in between.

[0049] The pressing force application mechanism 7 will be described with reference to Figures 2, 11, 12, 13, 14, and 15. The pressing force application mechanism 7 converts the rotational motion of the second support raceway 28 into linear motion of the second support raceway 28 and applies preload to the transmission mechanism 3. As shown in Figure 2, the pressing force application mechanism 7 includes a pressing cam 56, a roller holder 52, a roller 53, a cover 67, and the second support raceway 28. Figure 11 is a perspective view showing the pressing cam 56. The pressing cam 56 is a ring-shaped member having a through hole 56c and is positioned between the cylindrical portion 37b and the cover 67. The pressing cam 56 has a plurality of bolt holes 56d for passing bolts B1 through. The plurality of bolt holes 56d are arranged 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 its circumferential direction is cut out in order to allow the control shaft 61 of the speed ratio control mechanism 6 to pass through.

[0050] The pressing cam 56 has a cam surface 56p on the side opposite to the input. The cam surface 56p has a plurality (for example, 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 plurality of cam grooves 56j are arranged at predetermined intervals in the circumferential direction and are connected by connecting surfaces 56e. The connecting surfaces 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.

[0051] Figure 12 is a perspective view showing the roller 53 and the roller retainer 52. The roller retainer 52 is a ring-shaped member having a through hole 52c and is positioned between the cam surface 28p of the second support raceway 28 and the cam surface 56p of the press cam 56. The roller retainer 52 has a plurality (e.g., six) of pockets 52b arranged at predetermined intervals in the circumferential direction. The pockets 52b are rectangular holes when viewed from the axial direction. A plurality (e.g., six) of 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 retainer 52 has a notch 52k in which a portion in the circumferential direction is cut out to allow the control shaft 61 of the speed ratio control mechanism 6 to pass through.

[0052] Figure 13 is a perspective view showing the cover 67. The cover 67 is a hollow disc-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 through. The plurality of bolt holes 67d are arranged at predetermined intervals in the circumferential direction at a position offset from the rotation axis La, and communicate with the bolt holes 56d of the press cam 56. The cover 67 has a through hole 67e for passing the control shaft 61 through. The through hole 67e is located at a position offset from the rotation axis La and is positioned on the inner circumference side of the pitch circle of the bolt holes 67d.

[0053] A sleeve bearing 57 and a cylindrical seal 58 are installed in the through hole 67e (see also Figure 2). The sleeve bearing 57 has a plate-shaped flange portion 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 facilitates the axial movement of the control shaft 61 and suppresses the outflow of lubricant. The cylindrical seal 58 is positioned on the input side of the sleeve bearing 57 in the through hole 67e and functions as an oil seal that suppresses the outflow of lubricant.

[0054] The hollow portion 67c is provided with a circumferential stepped portion 67h that contacts the input side of the input bearing 66, and a circumferential groove 67g in which a washer W3 is fitted. The washer W3 that contacts the non-input side of the input bearing 66 is fitted into the circumferential groove 67g. The axial position of the input bearing 66 is restricted by the washer W3 and the circumferential stepped portion 67h.

[0055] Figure 14 is a perspective view showing the main components of the speed ratio control mechanism 6 and the pressing force application mechanism 7 mounted on the cover 67. The pressing cam 56 and the roller retainer 52 are mounted on top of each other on the non-input side of the cover 67. In this state, the notches 56k and 52k are aligned with the through hole 67e in the circumferential direction. The control ring 62 is mounted so that its radially protruding portion 62c (see also Figure 16) is accommodated in the notches 56k and 52k. The control ring 62 is housed in the central space between the pressing cam 56 and the roller retainer 52, and the control shaft 61 protrudes from the input side of the cover 67 by passing through the central hole of the sleeve bearing 57 and the cylindrical seal 58.

[0056] Figure 15 is a schematic diagram illustrating the operation of the pressing force application mechanism 7, showing the cam surface 28p, roller 53, and cam surface 56p. The pressing cam 56 is fixed to the casing and stationary, while the second support raceway 28 rotates as it receives rotational force (torque) in conjunction with the rotation of the planetary rolling elements 20. Figure 15(A) shows the state without rotational force, and Figure 15(B) shows the state with rotational force.

[0057] As the second support raceway 28 rotates, the relative positions of the cam groove 28j and the cam groove 56j shift as shown by arrow W in Figure 15(B), causing the roller 53 to ride up onto the first inclined surface 56f and the second inclined surface 28g. As a result, a drag force F0 from the roller 53 is applied to the inclined surface, and the component of the drag force F0 becomes a pressing force F, which presses the second support raceway 28 against 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 output raceway bearing 33 against the inner overhang 36, functioning as a preload for the transmission mechanism 3 (see also Figure 2).

[0058] When the load from the driven device increases and the preload between the output raceway 30 and the planetary rolling elements 20 becomes insufficient, the proportion of the rotational force input from the input raceway 14 to the planetary rolling elements 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 by the opposite mechanism, and both the pressing force F and the preload decrease. In this way, the pressing force application mechanism 7 can apply a pressing force F corresponding to the load from the driven device to the transmission mechanism 3, and the preload can be automatically adjusted.

[0059] The speed ratio control mechanism 6 will be described with reference to Figures 2 and 16. Figure 16 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 gear ratio R by changing the relative position of the input raceway 14 of the transmission mechanism 3. As shown in Figure 2, the speed ratio control 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 that extends axially at a position radially offset from the rotation axis La, and its non-input end is attached to the radially protruding portion 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 it may be offset radially outward from the input raceway 14. The control ring 62 is a ring-shaped member having a hollow portion 62e. The hollow portion 62e is provided with a circumferential extension 62f extending radially inward from the non-input side of the hollow portion 62e, and a circumferential groove 62g into which a washer W4 is fitted, in order to support the control unit bearing 63. The axial movement of the control unit bearing 63 is restricted by the circumferential extension 62f and the washer W4.

[0060] The control bearing 63 is positioned between the hollow portion 62e of the control ring 62 and the first cylindrical portion 15b of the sleeve 15. The control bearing 63 rotatably supports the sleeve 15 with respect to the speed ratio control mechanism 6. The outer ring of the control bearing 63 is supported by the hollow portion 62e of the control ring 62, and the inner ring supports the first cylindrical portion 15b. In this example, the control bearing 63 is a cross roller bearing. The control shaft 61 extends from the radial projection 62c to the input side, passes through the press 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 axial driving force. The non-input side of the control ring 62 is housed in the through hole 52c of the roller retainer 52.

[0061] The operation of the speed ratio control mechanism 6 will now be explained. 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 raceway 14, first raceway bearing 27, first support raceway 26, shaft 68, and shaft cap 69 move together. At this time, the second support raceway 28 and the output raceway 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.

[0062] When the input raceway 14 and the first support raceway 26 move to the non-input side, the non-input side of the rotation axis Lb moves away from the rotation axis La, and the input side of the rotation axis Lb tilts closer to the rotation axis La. As a result, the rotation radius and orbital radius of each contact point between each raceway and the planetary rolling element 20 change, and the gear ratio R also changes. The gear 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 to the input side, the rotation axis Lb tilts to the opposite side, and the gear ratio R of the friction transmission 100 decreases as the inclination with respect to the rotation axis La increases. By keeping the position of the control shaft 61 constant, the attitude of the planetary rolling element 20 remains constant, and the gear ratio R is kept constant.

[0063] The operation of the friction transmission device 100 configured as described above will now be explained. When rotation is transmitted from the motor shaft 51 to the input shaft 64, the input raceway 14 rotates around the axis of rotation La. The rotation of the input raceway 14 causes the planetary rolling elements 20 to rotate and revolve. The rotation of the planetary rolling elements 20 is transmitted to the output raceway 30, and the output raceway 30 rotates at a speed corresponding to the gear ratio R. The rotation of the output raceway 30 is output to the output member 32 through the output mechanism 5. When the positions of the input raceway 14 and the first support raceway 26 are changed by the gear ratio control mechanism 6, the gear ratio R also changes.

[0064] The characteristic configuration of this disclosure will be explained with reference to Figures 2 and 17. Figure 17 is a diagram illustrating a configuration in which the planetary rolling element 20 is supported by each orbital ring. This diagram shows the contour lines (hereinafter referred to as "cross-sectional curves") that appear in the cross-sections of the planetary rolling element 20, the input orbital ring 14, the first support orbital ring 26, the second support orbital ring 28, and the output orbital ring 30 in a plane containing the central axis La and the rotation axis Lb.

[0065] In a friction transmission system, if both the contact surface of the planetary rolling element and the rolling surface of the raceway ring that contacts the planetary rolling element on the radially inner side are convex, then they make convex-convex contact with each other. Convex-convex contact refers to contact where both of the two contacting surfaces are convex. When such convex-convex contact occurs, the contact stress at the contact point increases, and the lifespan of the contact point tends to be shortened. Therefore, in this embodiment, at least one of the raceway rings among the input raceway ring 14, output raceway ring 30, first support raceway ring 26, and second support raceway ring 28 makes convex-concave contact with the planetary rolling element 20. Convex-concave contact refers to contact where one of the two contacting surfaces is convex and the other is concave.

[0066] In the example shown in Figure 17, the input raceway 14 and the planetary rolling elements 20 are in uneven contact, and the first support raceway 26 and the planetary rolling elements 20 are in uneven contact. Specifically, the rolling surface 14h of the input raceway 14 is convex, and the contact surface 20a of the planetary rolling elements 20 that contacts the rolling surface 14h is concave, so they are in uneven contact with each other. Similarly, the rolling surface 26h of the first support raceway 26 is convex, and the contact surface 20b of the planetary rolling elements 20 that contacts the rolling surface 26h is concave, so they are in uneven contact with each other. In this case, the contact stress at the contact points is lower than in the case of convex-convex contact, and the lifespan of the contact points can be extended. Note that the curvature of the convex surface in uneven contact is set to be greater than the curvature of the concave surface on the other side.

[0067] Figure 17 shows the extensions of each normal vector. Depending on the shape of the planetary rolling element, the extensions may not form a quadrilateral, in which case the orientation of the planetary rolling element becomes unstable. Therefore, the planetary rolling element 20 of the embodiment has a shape that allows a quadrilateral to be formed by the extensions of the normal vectors at the contact points between the planetary rolling element 20 and each raceway.

[0068] As shown in Figure 17, the extensions of the normal vectors 14v at contact point 14c, 26v at contact point 26c, 28v at contact point 28c, and 30v at contact point 30c intersect to form a quadrilateral Q. In this case, the orientation of the planetary rolling element 20 is uniquely determined, and the planetary rolling element 20 can maintain a constant orientation. Furthermore, in the example in Figure 17, the lengths of the two sides 14m and 26m located radially inward of the quadrilateral Q are longer than the lengths of the two sides 28m and 30m located radially outward. In this case, the orientation of the planetary rolling element 20 is even more stable.

[0069] As an example, simulations suggest that the lengths of the two sides (14m and 26m) should preferably be at least twice the length of the two sides (28m and 30m), and more preferably four times or more. In this example, the lengths of the two sides (14m and 26m) are set to at least 4.3 times the length of the two sides (28m and 30m). Furthermore, simulations show that the lengths of the two sides (14m and 26m) can be set to 20 times or less the length of the two sides (28m and 30m).

[0070] When the lengths of the two sides, 14m and 26m, are long, the angle of the normal to the radial direction at the contact point between the input raceway 14, the first support raceway 26 and the planetary rolling elements becomes smaller. When this angle becomes smaller, the axial component of the contact load vector (consisting of a radial component and a central axis component) at the contact point becomes smaller, and the contact load decreases. Also, when this angle becomes smaller, the curvature of the cross-sectional curve including the central axis at the contact surfaces 20a and 20b (concave surfaces) of the planetary rolling elements 20 becomes smaller, and the relative curvature of the contact point becomes smaller. As a result, the contact stress (surface pressure) can be reduced.

[0071] The input raceway 14 and the first support raceway 26, located radially inward of each raceway, are referred to as the inner raceways 14 and 26. The second support raceway 28 and the output raceway 30, located radially outward of each raceway, are referred to as the outer raceways 28 and 30. In the example shown in Figure 17, the rolling surfaces 14h and 26h on which the planetary rolling elements 20 of the inner raceways 14 and 26 roll are convex surfaces (inner convex surfaces), and the contact surfaces 20a and 20b of the planetary rolling elements 20 with the inner raceways 14 and 26 are concave surfaces (inner concave surfaces of the planetary rolling elements). The inner raceways 14 and 26 tend to have higher surface pressure than the outer raceways 28 and 30, but this configuration can reduce the surface pressure on the inner raceways 14 and 26.

[0072] In this example, the contact surfaces 20a and 20b of the planetary rolling element 20 that contact the inner raceways 14 and 26 are concave surfaces, and are collectively referred to as inner concave surfaces (inner concave surfaces of the planetary rolling element) 20a and 20b. The contact surfaces 20c and 20d of the planetary rolling element 20 that contact the outer raceways 28 and 30 are convex surfaces, and are collectively referred to as outer convex surfaces (outer convex surfaces of the planetary rolling element) 20c and 20d. By having inner concave surfaces 20a and 20b and outer convex surfaces 20c and 20d, the planetary rolling element 20 can form convex-concave contact with the inner raceways 14 and 26, and convex-flat contact with the outer raceways 28 and 30, thereby avoiding convex-convex contact. Therefore, the contact stress at the contact points can be reduced. Convex-flat contact refers to contact where one of two contacting surfaces is convex and the other is flat.

[0073] As shown in Figure 17, the first raceway bearing 27 is positioned between the two drive wheels 14 and 26 that contact the inner concave surfaces 20a and 20b of each raceway 14, 26, 28, and 30. In this case, the thrust load received from the input raceway 14 can be supported, and the speed difference between the input raceway 14 and the first support raceway 26 can be tolerated with low loss. Furthermore, since the first raceway bearing 27 is surrounded by the input raceway 14 and the first support raceway 26, the dedicated space for the first raceway bearing 27 can be reduced, which is advantageous for miniaturization.

[0074] As shown in Figure 17, the inner concave surfaces 20a and 20b are constructed as continuous curved surfaces. When the speed is changed, the relative position of the planetary rolling elements 20 and the inner raceways 14 and 26 changes, so by making the inner concave surfaces 20a and 20b continuous curved surfaces, the speed change range can be widened. In addition, since the inner concave surfaces 20a and 20b can be machined continuously, they can be easily manufactured.

[0075] In this example, the cross-sectional curves of the inner concave surfaces 20a and 20b are circular arcs. In this case, the way the surfaces contact each other does not change easily when shifting speeds, allowing for smoother shifting.

[0076] In this example, the cross-sectional curves of the outer convex surfaces 20c and 20d are involute curves or circular arcs. In this case, the gear changes can be made smoothly.

[0077] The cross-sectional curves of the rolling surfaces 14h and 26h on which the planetary rolling elements 20 of the inner raceways 14 and 26 roll are circular arcs. In this case, the speed can be changed smoothly.

[0078] The features of the friction transmission device 100 configured as described above will now be explained. The friction transmission device 100 comprises an input raceway 14, planetary rolling elements 20 arranged around the rotation axis of the input raceway 14 and in contact with the input raceway 14, an output raceway 30 in contact with the planetary rolling elements 20 and connected to an output member 32, and a first support raceway 26 and a second support raceway 28 in contact with the planetary rolling elements 20, wherein 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 uneven contact raceway that makes uneven contact with the planetary rolling elements 20.

[0079] This configuration allows for a friction transmission device that reduces contact stress, or surface pressure, at the contact points compared to cases with convex-convex contact. Lower surface pressure extends the lifespan of the contact points, allowing the friction transmission device to be applied to a wider range of applications.

[0080] The present invention has been described above based on several embodiments. These embodiments are illustrative, and it will be 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. Accordingly, the description and drawings herein should be treated as illustrative rather than limiting.

[0081] (modified version) The following describes modified examples. In the drawings and descriptions of the modified examples, components and parts that are the same as or equivalent to those in the embodiments are denoted by the same reference numerals. Descriptions that overlap with those in the embodiments will be omitted as appropriate, and the descriptions will focus on the configurations that differ from those in the embodiments.

[0082] In the description of the embodiment, an example was shown in which the cross-sectional curves of the inner concave surfaces 20a and 20b are circular arcs, but there are no restrictions on these cross-sectional curves. For example, these cross-sectional curves may be curves drawn by quadratic functions (parabolas), ellipses, ovals, etc.

[0083] In the description of the embodiments, examples were shown where the cross-sectional curves of the outer convex surfaces 20c and 20d are involute curves or circular arcs, but there are no restrictions on these cross-sectional curves. For example, these cross-sectional curves may be curves drawn by quadratic functions, ellipses, ovals, etc.

[0084] In the description of the embodiment, an example was shown in which the cross-sectional curves of the rolling surfaces 14h and 26h on which the planetary rolling elements 20 of the inner raceways 14 and 26 roll are circular arcs, but there are no restrictions on these cross-sectional curves. For example, these cross-sectional curves may be curves drawn by quadratic functions, ellipses, ovals, etc.

[0085] In the description of the embodiment, an example was shown in which the rolling surfaces 30h and 28h are conical surfaces composed of flat surfaces, but these may also be curved surfaces such as convex or concave surfaces.

[0086] The configuration of the input bearing 66 is not limited and may be, for example, a bearing having rollers as rolling elements. Similarly, the configuration of the first raceway bearing 27 is not limited and may be, for example, a bearing having rollers as rolling elements. Furthermore, the configuration of the output raceway bearing 33 is not limited and may be, for example, a bearing having spheres as rolling elements. Similarly, the configuration of the output bearing 34 is not limited and may be, for example, a bearing having spheres as rolling elements.

[0087] The configuration of the control unit bearing 63 is not limited, and may include, for example, a bearing with balls as rolling elements, a thrust bearing, a sliding bearing, etc.

[0088] For example, in the pressing force application mechanism 7, a sphere may be provided instead of a roller 53, and the pocket 52b of the roller holder 52, the cam groove 56j of the pressing cam 56, and the cam groove 28j of the second support raceway ring 28 may each have a shape corresponding to the sphere.

[0089] For example, in the pressing force application mechanism 7, the roller 53 and roller holder 52 may be eliminated, and the cam groove 28j of the second support raceway 28 may be made into a convex cam peak with a V-shaped slope, and the cam groove 56j of the pressing cam 56 may be in direct contact with it. Conversely, the region corresponding to the cam groove 56j of the pressing cam may be the cam peak.

[0090] Each of these modifications produces the same functions and effects as the embodiments.

[0091] Any combination of the embodiments and modifications described above is also useful as an embodiment of the present invention. The new embodiments resulting from these combinations possess the combined effects of both the respective embodiments and modifications. [Explanation of symbols]

[0092] 2 Input mechanism, 3 Transmission mechanism, 4 Planetary rolling element unit, 5 Output mechanism, 6 Speed ​​ratio control mechanism, 7 Pressing force application mechanism, 14 Input raceway, 20 Planetary rolling element, 20c Contact surface, 20e Equator, 21 Cage, 22 Ring section, 23 Column section, 26 First support raceway, 27 Bearing for first raceway, 28 Second support raceway, 28p Cam surface, 30 Output raceway, 32 Output member, 33 Bearing for output raceway, 34 Output bearing, 37 Casing, 52 Roller cage, 53 Roller, 56 Pressing cam, 61 Control shaft, 62 Control ring, 64 Input shaft, 66 Input bearing, 67 Cover, 68 Shaft, 100 Friction transmission device.

Claims

1. 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 that is in contact with the planetary rolling elements and connected to an output member; and a first support raceway and a second support raceway that are in contact with the planetary rolling elements, At least one of the input orbital, output orbital, first support orbital, and second support orbital is an uneven contact orbital that makes uneven contact with the planetary rolling element. The aforementioned uneven contact raceway includes an inner raceway located radially inward, The input raceway, the output raceway, the first support raceway, and the second support raceway include an outer raceway located radially outward. The inner raceway has an inner convex surface whose contact surface with the planetary rolling element is a convex surface, The planetary rolling element has an inner concave surface, the contact surface with the inner raceway ring is a concave surface, in this friction transmission device.

2. The planetary rolling body has a quadrilateral formed by the extension of the normal vectors at the contact points with the input orbital, the output orbital, the first support orbital, and the second support orbital. The friction transmission device according to claim 1, wherein the lengths of the two sides of the rectangle located radially inward from the axis of rotation are longer than the lengths of the two sides located radially outward from the axis of rotation.

3. The planetary rolling elements are arranged in a plurality at predetermined intervals in the circumferential direction, The friction transmission device according to claim 1 or 2, further comprising a retainer for restricting the circumferential movement of a plurality of planetary rolling elements.

4. The friction transmission device according to claim 1, wherein the planetary rolling element has an outer convex surface of the planetary rolling element, the contact surface with the outer raceway ring being a convex surface.

5. The inner raceway is the input raceway and the first support raceway which is spaced apart in the axial direction from the input raceway. The input raceway is configured to be movable in the axial direction. The friction transmission device according to any one of claims 1 to 4, wherein a thrust bearing is disposed between the input raceway and the first support raceway.

6. The inner raceway is the input raceway and the first support raceway which is spaced apart in the axial direction from the input raceway. The inner concave surface of the planetary rolling element is configured as a continuous curved surface, The friction transmission device according to claim 4 or 5, wherein the continuous curved surface makes uneven contact with both the inner convex surface of the input raceway and the inner convex surface of the first support raceway.

7. The friction transmission device according to any one of claims 1 to 6, wherein the cross-sectional curve of the inner concave surface of the planetary rolling element is a circular arc.

8. The friction transmission device according to any one of claims 1 to 7, wherein the cross-sectional curve of the inner convex surface is a circular arc.

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