Friction transmission device

Abstract

A friction transmission device (100) is provided with: an input track wheel (14); planetary rolling bodies (20) arranged around the rotational axis (La) of the input orbital wheel (14) and in contact with the input orbital wheel (14); an output orbital wheel (30) that is in contact with the planetary rolling bodies (20) and is connected to an output member (32); and a first support raceway wheel (26) and a second support raceway wheel (28) which are in contact with the planetary rolling bodies (20). A speed ratio changing mechanism (6) is provided, and the speed ratio changing mechanism (6) changes the speed ratio by changing the relative positions of the two outer side rail wheels. In the gear ratio changed by the speed ratio changing mechanism (6), the maximum absolute value of the positive side gear ratio and the maximum absolute value of the negative side gear ratio are different from each other, and the shapes of a first contact surface (20d) and a second contact surface (20c) where the planetary rolling bodies (20) are in contact with the two outer raceway wheels are different from each other.

Description

Technical Field

[0001] This disclosure relates to a friction transmission device. Background Technology

[0002] A continuously variable transmission (CVT) called IVT (Infinitely Variable Transmission) is known, capable of achieving an infinitely large gear ratio. In Patent Document 1, the applicant discloses a friction transmission device comprising an input guide wheel, planetary rolling elements, and an output guide wheel. In this device, the planetary rolling elements are arranged around the rotation axis of the input guide wheel and contact the input guide wheel, while the output guide wheel contacts the planetary rolling elements and is connected to the output shaft. Furthermore, the device has multiple support guide wheels in contact with the planetary rolling elements, and the rotation input to the input guide wheel is speed-changed and output from the output shaft.

[0003] Previous technical documents Patent documents Patent Document 1: International Publication No. 2021 / 182001 Summary of the Invention

[0004] The technical problem to be solved by the invention Friction drives hold promise for applications in various fields, including robotics and automated guided vehicles. By altering the orientation of constituent components through mechanical inputs used for gear ratio control, friction drives can change the gear ratio across the range of output rotation, from the reverse side to the forward side. However, in conventional devices, the gear ratio characteristics on the forward and reverse sides are symmetrical, resulting in limitations in effectively utilizing the gear ratio range depending on the application.

[0005] This disclosure is made in view of such issues, and its purpose is to provide a friction transmission device that can make more efficient use of the gear ratio range.

[0006] means for solving technical problems To address the aforementioned issues, one embodiment of the friction drive device disclosed herein includes: an input track wheel; planetary rolling elements disposed around the rotation axis of the input track wheel and in contact with the input track wheel; an output track wheel in contact with the planetary rolling elements and connected to an output component; and first and second support track wheels in contact with the planetary rolling elements. The friction drive device has a speed ratio changing mechanism that alters the speed ratio by changing the relative positions of two inner drive wheels located inside the planetary rolling elements and two outer track wheels located outside the planetary rolling elements among the input track wheel, output track wheel, first support track wheel, and second support track wheel. The speed ratio changed by the speed ratio changing mechanism satisfies the following: the maximum absolute value of the speed ratio on the positive side where the output rotation is in the same direction as the input rotation and the maximum absolute value of the speed ratio on the negative 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 and second contact surfaces of the planetary rolling elements in contact with the two outer track wheels are different from each other.

[0007] Furthermore, any combination of the above-mentioned constituent elements, or a solution that substitutes the constituent elements or expressions of this disclosure for each other in methods, systems, etc., is also valid as an implementation of this disclosure.

[0008] Invention Effects According to this disclosure, a friction drive device that can more effectively utilize the range of speed ratios is provided. Attached Figure Description

[0009] Figure 1 This is a perspective view showing an example of the friction drive device according to the embodiment.

[0010] Figure 2 Is displaying along Figure 1 A cross-sectional view of the friction drive device along line AA.

[0011] Figure 3 It is a display Figure 1 A three-dimensional view of the input track wheel of the friction drive device.

[0012] Figure 4 It is a display Figure 1 A perspective view of the first support track wheel of the friction drive device.

[0013] Figure 5 It is a display Figure 1 A three-dimensional view of the planetary rolling elements of a friction drive device.

[0014] Figure 6 It is a display Figure 1 A perspective view of the cage of a friction drive device.

[0015] Figure 7 It is a display Figure 1A perspective view of the planetary rolling element unit of a friction drive device.

[0016] Figure 8 It is a display Figure 1 A perspective view of the second support track wheel of the friction drive device.

[0017] Figure 9 It is a display Figure 1 A three-dimensional view of the output track wheel of the friction drive device.

[0018] Figure 10 It is a display Figure 1 A perspective view of the output component of a friction drive device.

[0019] Figure 11 It is a display Figure 1 A three-dimensional view of the pressure cam of a friction drive device.

[0020] Figure 12 It is a display Figure 1 A perspective view of the roller cage of a friction drive device.

[0021] Figure 13 It is a display Figure 1 A three-dimensional view of the cover of the friction drive device.

[0022] Figure 14 It is displayed Figure 13 A three-dimensional diagram showing the state in which the specified components are installed on the cover.

[0023] Figure 15 It is used for explanation Figure 1 A schematic diagram of the operation of the clamping force application mechanism of the friction drive device.

[0024] Figure 16 It is a display Figure 1 A three-dimensional view of the speed ratio changing mechanism of the friction transmission device.

[0025] Figure 17 This is a cross-sectional view showing a first structural example of the friction drive device according to the embodiment.

[0026] Figure 18 This is a cross-sectional view showing a second structural example of the friction drive device according to the embodiment.

[0027] Figure 19 This is a cross-sectional view showing a third structural example of the friction drive device according to the embodiment.

[0028] Figure 20 This is a cross-sectional view showing the fourth structural example of the friction drive device according to the embodiment.

[0029] Figure 21This is a cross-sectional view showing the fifth structural example of the friction drive device according to the embodiment.

[0030] Figure 22 This is a cross-sectional view showing the sixth structural example of the friction drive device according to the embodiment.

[0031] Figure 23 This is a cross-sectional view showing the structure of a friction drive device for reference examples. Detailed Implementation

[0032] Hereinafter, preferred embodiments of the present disclosure will be described with reference to the accompanying drawings. In the embodiments and variations, identical or equivalent constituent elements and components are labeled with the same symbols, and repeated descriptions are omitted where appropriate. Furthermore, for ease of understanding, the dimensions of the displayed components are appropriately enlarged or reduced in the accompanying drawings. Also, in the accompanying drawings, components that are not essential to the explanation of the embodiments are omitted.

[0033] Furthermore, terms including ordinal numbers such as 1 and 2 are used to describe various constituent elements, but such terms are only used for the purpose of distinguishing one constituent element from other constituent elements, and the constituent elements are not limited by such terms. Implementation

[0034] First, the overall structure of the friction transmission device 100 according to the embodiments of the present invention will be described. Figure 1 This is a perspective view showing an example of the friction transmission device 100 according to the embodiment. Figure 2 This is a longitudinal cross-sectional view showing the friction drive 100 along line AA. The friction drive 100 has a housing 37 surrounding the internal mechanism, an input shaft 64, an output component 32, and a mounting component 38. The mounting component 38 is a flange-shaped component provided on the outer periphery of the housing 37 for mounting the friction drive 100 to an external device (not shown). Figure 2 The image shows the state after the mounting component 38 has been removed.

[0035] The friction drive 100 is configured such that the rotation input via the input shaft 64 causes the input track wheel to rotate, thereby causing the planetary rolling elements to rotate and revolve, and the resulting rotational component is output from the output component 32 connected to the output track wheel to the driven device (not shown).

[0036] The friction drive device 100 mainly includes an input mechanism 2, a transmission mechanism 3, an output mechanism 5, a clamping force application mechanism 7, and a speed ratio changing mechanism 6. The input mechanism 2 transmits the rotation input from the prime mover (not shown) to the input track wheel 14. The transmission mechanism 3 transmits the rotation transmitted to the input track wheel 14 at a different speed to the output track wheel 30. The output mechanism 5 outputs the rotation transmitted to the output track wheel 30 from the output component 32 to the driven device. The clamping force application mechanism 7 applies an axial clamping force to the transmission mechanism 3. The speed ratio changing mechanism 6 controls the speed ratio by changing the relative positions of the track wheels of the transmission mechanism 3.

[0037] Reference Figure 2 The input mechanism 2 will be described below. The input mechanism 2 in 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 track wheel 14, a sleeve 15, a first support track wheel 26, and a bearing 27 for the first track wheel.

[0038] Hereinafter, the direction along the rotation axis La of the input track wheel 14 will be referred to as the "axial direction", and the circumferential direction and radial direction of the circle centered on the rotation axis La will be referred to as the "circumferential direction" and "radial direction", respectively. Furthermore, for convenience, one side of the axial direction (right side in the figure) will be referred to as the "input side", and the other side (left side in the figure) will be referred to as the "opposite input side".

[0039] Unless otherwise specified, the circular portions of each component of the friction drive 100 surrounding the rotation axis La are formed with the rotation axis La as the center. Furthermore, the centers of these circular portions may deviate from the rotation axis La within a tolerance range.

[0040] Input shaft 64 is the input section for inputting the rotation of the prime mover. In this embodiment, the prime mover is a motor 50, and input shaft 64 is connected to motor shaft 51, which outputs the rotation of motor 50. A ball spline nut 65 transmits the rotation of input shaft 64 to shaft 68 and supports shaft 68 so that it can move axially. Input shaft 64 has an outer cylinder that houses the ball spline nut 65. The ball spline nut 65 is keyed to input shaft 64 via key 65k, thereby rotating integrally with input shaft 64. Shaft 68 is axially movable relative to ball spline nut 65 and rotates integrally with ball spline nut 65.

[0041] The cover 67 is a hollow disc-shaped component covering the input side of the friction drive 100, and it has a hollow portion 67c surrounding the rotation axis La. The cover 67 is fixed to the input side of the housing 37 by a plurality of bolts B1. The input bearing 66 is disposed between the hollow portion 67c and the ball spline nut 65, and rotatably supports the ball spline nut 65 and the input shaft 64. The outer ring of the input bearing 66 is supported in the hollow portion 67c, and the inner ring supports the input shaft 64. In this example, the input bearing 66 is a ball bearing. A first oil seal S1 is disposed on the input side of the input bearing 66 in the hollow portion 67c, thereby sealing the input bearing 66.

[0042] Shaft 68 is an axially extending rod-shaped shaft with axial grooves (not shown) for balls to pass through. The input side of shaft 68 is received within a ball spline nut 65, and the end of shaft 68 extends further into the opposite direction of the input than the planetary rolling elements 20. Shaft cap 69 is a component that limits the positional relationship between shaft 68 and the first support track wheel 26. Shaft cap 69 has a cup shape consisting of a disc portion 69b and a cylindrical portion 69c extending from the outer periphery of the disc portion 69b toward the input side. The end of shaft 68 is inserted into the cylindrical portion 69c and secured to the disc portion 69b by a bolt B3 passing through the disc portion 69b.

[0043] Reference Figure 3 The input track wheel 14 is described below. Figures 3 to 12 and Figure 16 In the diagram, (A) represents the view viewed from the opposite side above the input, and (B) represents the view viewed from the side above the input. Figure 3 It is a 3D view of the input track wheel 14. Figure 3 The input track wheel 14 is integrated with the sleeve 15.

[0044] The sleeve 15 is a hollow cylindrical component fixed to the outer periphery of the shaft 68 by means of interference fit or the like, and has a first cylindrical portion 15b and a second cylindrical portion 15c from the input side toward the opposite side of the input. The first cylindrical portion 15b is surrounded by the control bearing 63 and is rotatably supported by the control bearing 63. The second cylindrical portion 15c is a portion with a diameter larger than that of 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. A circumferential groove 15g is provided on the first cylindrical portion 15b for mounting a retaining ring W1, which is used to limit the positional relationship between the retaining ring W1 and the control bearing 63.

[0045] The input track wheel 14 is a hollow cylindrical component fixed to the outer periphery of the shaft 68. Its diameter is larger than that of the second cylindrical portion 15c, and it is continuous with the second cylindrical portion 15c. The input track wheel 14 has a hole for the shaft 68 to be inserted, which extends from the input-opposite side of the input track wheel 14 to the input side of the sleeve 15 through a hollow portion 14e. A rolling surface 14h that contacts the planetary rolling element 20 is provided on the outer periphery of the input track wheel 14. The input track wheel 14 has a bearing receiving portion 14j for accommodating a portion of the input side of the bearing 27 for the first track wheel. In this example, the bearing receiving portion 14j is a circular recess that is recessed from the input-opposite end face of the input track wheel 14 to the input side.

[0046] The input track wheel 14 is a component used to support the planetary rolling element 20 in a predetermined posture and to transmit rotation to the planetary rolling element 20. The rolling surface 14h is a surface for the planetary rolling element 20 to roll on, and it has point or surface contact with the planetary rolling element 20. The rolling surface 14h can be inclined relative to the axial and radial directions. The rolling surface 14h may include a tapered surface with a reduced diameter towards the input side. The rolling surface 14h can be a flat surface or a concave surface, but in this example it is a convex surface.

[0047] Reference Figure 4 The first support track wheel 26 will be described. Figure 4 This is a perspective view showing the first support track wheel 26. The first support track wheel 26 is a cylindrical component that fits into the outer periphery of the shaft 68 and is rotatably supported on the shaft 68. It is a hollow cylindrical component with a diameter approximately the same as that of the input track wheel 14. The first support track wheel 26 has a through hole 26d surrounding the shaft 68. A rolling surface 26h that contacts the planetary rolling element 20 is provided on the outer periphery of the first support track wheel 26. The first support track wheel 26 has a bearing receiving portion 26j for accommodating a portion of the bearing 27 for the first track wheel on the input-opposite side. In this example, the bearing receiving portion 26j is a circular recess that is recessed from the input-side end of the first support track wheel 26 towards the input-opposite side.

[0048] The first support track wheel 26 is a component used to support the planetary rolling element 20 in a predetermined posture. The rolling surface 26h is the surface from which the planetary rolling element 20 rolls, and it makes point or surface contact with the planetary rolling element 20. The rolling surface 26h can be inclined relative to the axial and radial directions. The rolling surface 26h may include a tapered surface with a reduced diameter towards the opposite side of the input. The rolling surface 26h can be a flat surface or a concave surface, but in this example it is a convex surface. The first support track wheel 26 is freely rotatable relative to the shaft 68 and the planetary rolling element 20, and is sometimes referred to as a floating track wheel.

[0049] The first track wheel bearing 27 is a thrust bearing that rotatably supports the first support track wheel 26 on the input track wheel 14. For example, the first track wheel bearing 27 may consist of two rings opposed in the axial direction and a plurality of balls located between the two rings.

[0050] Reference Figure 2 and Figures 5-9 The transfer mechanism 3 will be described below. The transfer mechanism 3 of the embodiment includes a plurality of planetary rolling elements 20, a cage 21, an input track wheel 14, a first support track wheel 26, a second support track wheel 28, and an output track wheel 30. The input track wheel 14, the first support track wheel 26, the second support track wheel 28, and the output track wheel 30 are collectively referred to as "track wheels".

[0051] Figure 5 This is a perspective view showing the planetary rolling elements 20. Multiple planetary rolling elements 20 are arranged at predetermined intervals in the circumferential direction (e.g., 5). The number of planetary rolling elements 20 is not particularly limited and may be less than or more than 5, 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 track wheel 14, a contact surface 20b that contacts the rolling surface 26h of the first support track wheel 26, a contact surface 20c that contacts the rolling surface 28h of the second support track wheel 28, and a contact surface 20d that contacts the rolling surface 30h of the output track wheel 30.

[0052] The rolling surfaces 14h, 26h, 28h, and 30h of these orbital wheels are collectively referred to as the rolling surfaces of the orbital wheels. 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 can be flat or convex, but in this example, they are concave. Contact surfaces 20c and 20d can be flat or concave, but in this example, they are convex.

[0053] The planetary rolling element 20 is restricted in its axial position, radial position, and orientation through contact with the rolling surface of the orbital wheel. As long as the orientation of the planetary rolling element 20 is determined by its contact with the rolling surface of the orbital wheel and it can roll while in contact with the rolling surface of the orbital wheel, the shape of the planetary rolling element 20 can be any shape. Figure 5 As shown, the planetary rolling body 20 in this embodiment is a rotating body obtained by rotating a trapezoid with a curved upper base and waist about a predetermined axis. The predetermined axis is an axis located on the side of the trapezoid away from the upper base and parallel to that lower base. Furthermore, in this specification, the circle formed by the intersection of a plane passing through the center of the upper base of the trapezoid and orthogonal to the rotation axis Lb of the planetary rolling body 20 (hereinafter referred to as the "equatorial plane") and the outer peripheral surface of the planetary rolling body 20 is called the "equatorial plane". In this example, the equatorial plane 20e is the circle formed by the intersection of the equatorial plane and the outer peripheral surface of the planetary rolling body 20.

[0054] The inclination of the rotation axis Lb of the planetary rolling element 20 relative to the rotation axis La varies depending on the relative position of the rolling surfaces of the orbital wheel. That is, the rotation axis Lb can be parallel to the rotation axis La or inclined relative to the rotation axis La.

[0055] Figure 6 This is a perspective view showing the cage 21. The friction drive device 100 of this embodiment includes a cage 21 for holding a plurality of planetary rolling elements 20 in a desired position. The cage 21 restricts the circumferential movement of the plurality of planetary rolling elements 20. The cage 21 holds the plurality of planetary rolling elements 20 circumferentially at predetermined intervals to prevent the planetary rolling elements 20 from contacting each other. The cage 21 has two annular portions 22 and a plurality (e.g., 5) column portions 23. The cage 21 may be integrally molded from resin or metal for the annular portions 22 and column portions 23.

[0056] Two annular portions 22 are axially separated from the planetary rolling elements 20. Each annular portion 22 is a hollow ring-shaped section having a central hole 22c. A plurality of pillar portions 23 are axially extending strip-shaped members, arranged circumferentially between the planetary rolling elements 20 at predetermined intervals. One end of each pillar portion 23 is fixed to the outer periphery of one annular portion 22, and the other end is fixed to the outer periphery of the other annular portion 22. That is, the pillar portions 23 are positioned between two annular portions 22. Pockets 24 for holding the planetary rolling elements 20 are formed between adjacent pillar portions 23.

[0057] Figure 7 This is a three-dimensional view showing planetary rolling element 4. (Example) Figure 7 As shown, multiple planetary rolling elements 20 are assembled into pockets 24 of the cage 21, thereby forming a planetary rolling element unit 4. The planetary rolling elements 20 are rotatably held in the pockets 24.

[0058] Figure 8 This is a perspective view showing the second support track wheel 28. The second support track wheel 28 has an annular shape surrounding the sleeve 15 and the planetary rolling element 20. The second support track wheel 28 has a rolling surface 28h on the opposite side of the input and a cam surface 28p on the input side. The rolling surface 28h is the surface for the planetary rolling element 20 to roll, and it has point contact or surface contact with the planetary rolling element 20. The rolling surface 28h is inclined relative to the axial and radial directions. The rolling surface 28h includes a tapered surface with a reduced diameter towards the input side. In this example, the rolling surface 28h is a conical surface composed of flat surfaces. Since the conical surface is concave, it forms a concave-convex contact with the convex contact surface 20c.

[0059] The cam surface 28p has multiple (e.g., 6) concave cam grooves 28j formed by the first inclined surface 28f and the second inclined surface 28g. When viewed radially from the outer diameter side, the cam grooves 28j are V-shaped.

[0060] Multiple cam grooves 28j are arranged circumferentially at predetermined intervals and are connected by connecting surfaces 28e. The connecting surfaces 28e can be formed parallel to a plane orthogonal to the rotation axis La. A first inclined surface 28f is inclined relative to the plane orthogonal to the rotation axis La. A second inclined surface 28g is inclined relative to the plane orthogonal to the rotation axis La in the opposite direction to the first inclined surface 28f.

[0061] The second support track wheel 28 is axially slidably fitted into the inner circumferential surface of the housing 37. The second support track wheel 28 is subjected to a clamping force from the cam surface 28p toward the opposite side of the axial input by the clamping force application mechanism 7. The clamping force presses the planetary rolling element 20 toward the output track wheel 30.

[0062] Figure 9 This is a perspective view of the output track wheel 30. The output track wheel 30 has an annular shape surrounding the shaft 68 and the cap 69. The output track wheel 30 has a rolling surface 30h on the input side. The rolling surface 30h is the surface for the planetary rolling element 20 to roll, and it has point contact or surface contact with the planetary rolling element 20. The rolling surface 30h is inclined relative to the axial and radial directions. The rolling surface 30h includes a tapered surface with a reduced diameter facing the opposite side of the input. In this example, the rolling surface 30h is a conical surface composed of flat surfaces. Since the conical surface is concave, it forms a concave-convex contact with the convex contact surface 20d.

[0063] The output track wheel 30 contacts the planetary rolling element 20 and rotates around the rotation axis La as the planetary rolling element 20 rotates. The output track wheel 30 is connected to the output component 32 of the output mechanism 5, thereby causing the output component 32 to rotate as the output track wheel 30 rotates. The output track wheel 30 has a connecting hole 30e that extends axially around the rotation axis La. The connecting portion 32d of the output component 32 is inserted into the connecting hole 30e. The connecting hole 30e is provided with a recess 30k that engages with a flat key 35 provided on the outer periphery of the connecting portion 32d. The output track wheel 30 is provided with a circular protrusion 30b that protrudes toward the opposite side of the input.

[0064] The operation of the transmission mechanism 3 will be explained. If the input track wheel 14 rotates, the planetary rolling element 20 rotates around its rotation axis Lb and revolves around its revolution axis. In this example, the revolution axis of the planetary rolling element 20 coincides with the rotation axis La, therefore, the rotation axis La will be used as the revolution axis in the following explanation.

[0065] When the first support track wheel 26 rotates freely and the second support track wheel 28 remains stationary, an output rotation multiplied by the input rotation by the gear ratio R is output to the output track wheel 30. The gear ratio R depends on the shape of the planetary rolling element 20 and the inclination of the rotation axis Lb relative to the rotation axis La. Therefore, the gear ratio R can be changed by altering the inclination of the rotation axis Lb. In this embodiment, a gear ratio changing mechanism 6 is provided to change the gear ratio R by altering the inclination of the rotation axis Lb. The gear ratio changing mechanism 6 will be described later.

[0066] Reference Figure 2 , Figure 10 The output mechanism 5 is described below. Figure 2 As shown, the output mechanism 5 includes an output track wheel 30, an output track wheel bearing 33, an output component 32, an output bearing 34, a second oil seal S2, and a housing 37. The housing 37 functions as an outer shell surrounding the internal mechanisms of the friction drive device 100. The housing 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, and a clamping cam 56 is sandwiched between the cylindrical portion 37b and the cover 67. The inner protrusion 36 is an annular portion that protrudes radially inward from the inner circumference of the cylindrical portion 37b. The output bearing 34 is accommodated on the cylindrical portion 37b at a position opposite to the input side, further away from the inner protrusion 36.

[0067] An output bearing 34 is disposed between the output component 32 and the cylindrical portion 37b, with its input side supported by an inner protrusion 36. The output bearing 34 rotatably supports the output component 32. In this example, the output bearing 34 is a crossed roller bearing. The outer ring of the output bearing 34 is supported by the cylindrical portion 37b, and the inner ring supports the output component 32.

[0068] The second oil seal S2 is disposed on the inner circumferential surface of the cylinder 37b on the opposite side of the input of the output bearing 34, thereby closing (sealing) the inside and outside of the friction drive 100.

[0069] The output track wheel bearing 33 rotatably supports the output track wheel 30 on the inner protrusion 36 of the housing 37. The output track wheel bearing 33 is axially positioned between the inner protrusion 36 and the output track wheel 30. The output track wheel bearing 33 has an annular shape that is accommodated within the annular space between the cylindrical portion 37b and the circular protrusion 30b of the output track wheel 30. That is, the output track wheel bearing 33 is fitted into the outer periphery of the circular protrusion 30b. In this example, the output track wheel bearing 33 is a thrust bearing comprising a ring and a plurality of rollers rolling on that ring.

[0070] Figure 10This is a perspective view of the output component 32. The output component 32 is a generally circular component, and from the opposite side of the input, it has a flange portion 32b, a middle portion 32c, and a connecting portion 32d. The flange portion 32b is a disc-shaped portion and has a plurality of (e.g., 6) threaded holes 32m on the opposite side of the input for bolting with the driven device. The plurality of threaded holes 32m are arranged at predetermined intervals on the circumference around the rotation axis La.

[0071] The intermediate portion 32c is a circular portion that is continuous with the input side of the flange portion 32b and has a diameter smaller than that of the flange portion 32b. A circumferential groove 32g is provided on the outer periphery of the intermediate portion 32c for mounting a retaining ring W2, which restricts the positional relationship between the retaining ring W2 and the output bearing 34. The intermediate portion 32c is supported by the output bearing 34.

[0072] The connecting portion 32d is a circular portion that is continuous with the input side of the intermediate portion 32c and has a diameter smaller than that of the intermediate portion 32c. A fixing key 35 is fixed to the outer periphery of the connecting portion 32d by bolt B2. The key 35 engages with the recess 30k of the connecting hole 30e. With the connecting portion 32d inserted into the connecting hole 30e, the output component 32 is connected to the output track wheel 30. In this state, the output component 32 and the output track wheel 30 can move relative to each other axially and rotate integrally circumferentially. A circular recess 32e is provided on the input side of the connecting portion 32d, recessed axially towards the opposite side of the input. The circular recess 32e is a circular recess surrounding the rotation axis La, and has an inner diameter and depth capable of accommodating the end of the shaft 68 and the shaft cap 69 with a clearance.

[0073] Reference Figure 2 , Figure 11 , Figure 12 , Figure 13 , Figure 14 and Figure 15 The clamping force application mechanism 7 will be described. The clamping force application mechanism 7 converts the rotational motion of the second support track wheel 28 into the linear motion of the second support track wheel 28, applying a preload force to the transmission mechanism 3. For example... Figure 2 As shown, the clamping force application mechanism 7 includes a clamping cam 56, a roller retainer 52, a roller 53, a cover 67, and a second support track wheel 28. Figure 11 This is a perspective view showing the clamping cam 56. The clamping cam 56 is an annular component with a through hole 56c, and it is disposed between the cylindrical portion 37b and the cover 67. The clamping cam 56 has a plurality of bolt holes 56d for the bolt B1 to pass through. The plurality of bolt holes 56d are disposed at positions offset from the rotation axis La and are arranged at predetermined intervals in the circumferential direction. The clamping cam 56 has a notch 56k formed by cutting off a portion in the circumferential direction to allow the control shaft 61 of the speed ratio changing mechanism 6 to pass through.

[0074] The clamping cam 56 has a cam surface 56p on the input-opposite side. The cam surface 56p has a plurality of (e.g., six) concave cam grooves 56j formed by a first inclined surface 56f and a second inclined surface 56g. When viewed radially from the outer diameter side, the cam grooves 56j have a V-shaped shape. The plurality of cam grooves 56j are arranged circumferentially at predetermined intervals and are connected by connecting surfaces 56e. The connecting surfaces 56e can be formed parallel to a plane orthogonal to the rotation axis La. The first inclined surface 56f is inclined relative to the plane orthogonal to the rotation axis La. The second inclined surface 56g is inclined relative to the plane orthogonal to the rotation axis La in the direction opposite to that of the first inclined surface 56f.

[0075] Figure 12 This is a perspective view showing the roller 53 and the roller cage 52. The roller cage 52 is an annular component with a through hole 52c, and it is disposed between the cam surface 28p of the second support track wheel 28 and the cam surface 56p of the clamping cam 56. The roller cage 52 has a plurality (e.g., 6) of pockets 52b arranged circumferentially at predetermined intervals. The pockets 52b are rectangular holes when viewed from the axial direction. A plurality (e.g., 6) of rollers 53 are provided corresponding to the cam grooves 56j. The rollers 53 have a cylindrical shape and are rotatably received in the pockets 52b. The roller cage 52 has a notch 52k formed by cutting off a portion in the circumferential direction to receive the radial protrusion 62c of the speed ratio changing mechanism 6.

[0076] Figure 13 This is a perspective view of the cover 67. The cover 67 is a hollow disk-shaped component having a hollow portion 67c surrounding the rotation axis La, and it is fixed to the input side of the housing 37. The cover 67 has a plurality of bolt holes 67d for the bolt B1 to pass through. The plurality of bolt holes 67d are arranged at positions offset from the rotation axis La, and are arranged at predetermined intervals in the circumferential direction, and communicate with the bolt holes 56d of the clamping cam 56. The cover 67 has a through hole 67e for the control shaft 61 to pass through. The through hole 67e is located at a position offset from the rotation axis La, and is arranged on the inner circumferential side of the bolt hole 67d.

[0077] A sleeve bearing 57 and a cylindrical seal 58 are installed on the through hole 67e (see also...). Figure 2 The sleeve bearing 57 has a plate-shaped flange portion that contacts the input side of the cover 67 and a cylindrical portion that is embedded in the through hole 67e. It may be formed, for example, of sintered metal. The sleeve bearing 57 facilitates the axial movement of the control shaft 61 and inhibits lubricant leakage. A cylindrical seal 58 is disposed in the through hole 67e on the input side of the sleeve bearing 57 and functions as an oil seal to inhibit lubricant leakage.

[0078] The hollow portion 67c has a circumferentially provided an annular stepped portion 67h that contacts the input side of the input bearing 66, and a circumferential groove 67g for mounting the retaining ring W3. The retaining ring W3, which contacts the opposite side of the input bearing 66, is installed in the circumferential groove 67g. The axial position of the input bearing 66 is restricted by the retaining ring W3 and the annular stepped portion 67h.

[0079] Figure 14 This is a perspective view showing the main components of the speed ratio changing mechanism 6 and the clamping force applying mechanism 7 mounted on the cover 67. The clamping cam 56 and the roller retainer 52 are mounted overlappingly on the opposite side of the input of the cover 67. In this state, the notches 56k and 52k are aligned circumferentially with the through hole 67e. Furthermore, the control ring 62 is mounted as a radially protruding portion 62c (see also...). Figure 16 The control ring 62 is accommodated in the central space of the clamping cam 56 and the roller retainer 52, and the control shaft 61 protrudes from the input side of the cover 67 after passing through the central hole of the sleeve bearing 57 and the cylindrical seal 58.

[0080] Figure 15 This is a schematic diagram illustrating the operation of the clamping force application mechanism 7, showing cam surface 28p, roller 53, and cam surface 56p. The clamping cam 56 is fixed to the housing and stationary, while the second support track wheel 28 rotates due to rotational force (torque) as the planetary rolling element 20 rotates. Figure 15 (A) represents the state without rotational force. Figure 15 (B) indicates the state of being subjected to rotational force.

[0081] like Figure 15 As shown in (B), if the second support track wheel 28 rotates, the relative position between the cam groove 28j and the cam groove 56j shifts as indicated by arrow W, and the roller 53 climbs up the first inclined plane 56f and the second inclined plane 28g. As a result, the reaction force F0 from the roller 53 acts on the inclined plane, and the component of the reaction force F0 becomes the clamping force F, pressing the second support track wheel 28 towards the opposite side of the input. The clamping force F presses the second support track wheel 28, the planetary rolling element 20, the output track wheel 30, and the output track wheel bearing 33 towards the inward protrusion 36, thereby acting as the preload of the transmission mechanism 3 (see also...). Figure 2 ).

[0082] If the load from the driven device increases, and the preload between the output track wheel 30 and the planetary rolling element 20 is insufficient, the proportion of the rotational force input from the input track wheel 14 to the planetary rolling element 20 transmitted to the second support track wheel 28 increases. If the rotational force of the second support track wheel 28 increases, the component of the rotational force of the second support track wheel 28, i.e., the clamping force F, increases, thereby increasing the preload. If the load from the driven device decreases, the rotational force transmitted to the second support track wheel 28 decreases through the opposite mechanism, and the clamping force F and the preload also decrease. In this way, the clamping force application mechanism 7 can apply a corresponding clamping force to the transmission mechanism 3 according to the load from the driven device, thereby automatically adjusting the preload.

[0083] Reference Figure 2 and Figure 16 The speed ratio changing mechanism 6 is explained. Figure 16 This is a perspective view showing the speed ratio changing mechanism 6. As described above, the speed ratio changing mechanism 6 controls the speed ratio R by changing the relative position of the input track wheel 14 of the transmission mechanism 3. Figure 2 As shown, the speed ratio changing mechanism 6 includes a control shaft 61, a control ring 62, and a control bearing 63. The control shaft 61 is a rod-shaped component extending axially from a position radially offset from the rotation axis La, with its input-opposite end mounted on a radially protruding portion 62c of the control ring 62. The radial position of the control shaft 61 can be radially offset further outward than the input shaft 64, or radially offset further outward than the input track wheel 14. The control ring 62 is an annular component with a hollow portion 62e. In the hollow portion 62e, to support the control bearing 63, an annular extension 62f extends radially inward from the input-opposite portion of the hollow portion 62e, and a circumferential groove 62g is provided for mounting a retaining ring W4. The axial movement of the control bearing 63 is restricted by the annular extension 62f and the retaining ring W4.

[0084] A control 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 bearing 63 rotatably supports the sleeve 15 to the speed ratio changing 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 crossed roller bearing. The control shaft 61 extends from the radial protrusion 62c toward the input side, passes through the clamping 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 input-opposite side of the control ring 62 is received within the through hole 52c of the roller cage 52.

[0085] The operation of the speed ratio changing mechanism 6 will be explained. When an axial driving force is input from the actuator to the control shaft 61, the control ring 62 moves axially. As the control ring 62 moves, the control bearing 63, sleeve 15, input track wheel 14, first track wheel bearing 27, first support track wheel 26, shaft 68, and shaft cap 69 move together. At this time, the second support track wheel 28 and the output track wheel 30 are stationary in the axial direction, so the rotation axis Lb of the planetary rolling element 20 is inclined relative to the rotation axis La.

[0086] When the input track wheel 14 and the first support track wheel 26 move to the opposite side of the input, the opposite side of the rotation axis Lb moves away from the rotation axis La, and the input side of the rotation axis Lb moves closer to the rotation axis La, resulting in tilting. As a result, the rotation radius and revolution radius of each contact point between each track wheel 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 drive 100 increases with the increase of the tilt relative to the rotation axis La. Similarly, when the input track wheel 14 and the first support track wheel 26 move to the input side, the rotation axis Lb tilts to the opposite side, and the gear ratio R of the friction drive 100 decreases with the increase of the tilt relative to the rotation axis La. By keeping the position of the control shaft 61 fixed, the posture of the planetary rolling element 20 remains unchanged, thereby keeping the gear ratio R constant.

[0087] The operation of the friction drive device 100 with the above-described structure will be explained. If rotation is transmitted from the motor shaft 51 to the input shaft 64, the input track wheel 14 rotates around the rotation axis La. The rotation of the input track wheel 14 causes the planetary rolling elements 20 to rotate on their own axis and revolve around the axis. The rotation of the planetary rolling elements 20 is transmitted to the output track wheel 30, which rotates at a speed corresponding to the gear ratio R. The rotation of the output track wheel 30 is output to the output component 32 via the output mechanism 5. If the positions of the input track wheel 14 and the first support track wheel 26 are changed by the speed ratio changing mechanism 6 (hereinafter simply referred to as "position T"), the gear ratio R also changes.

[0088] The characteristic structure of this disclosure will now be described. The friction drive device 100 of the embodiment is configured such that a first shape parameter related to the first contact surface 20d, which contacts the rolling surface 30h of the output track wheel 30 of the planetary rolling body 20, and a second shape parameter related to the second contact surface 20c, which contacts the rolling surface 28h of the second support track wheel 28 of the planetary rolling body 20, are different from each other. That is, the first contact surface 20d and the second contact surface 20c, which contact the planetary rolling body 20 with the two outer track wheels, have different shapes. The shape parameter related to the contact surface in contact with the rolling surface is a variable that defines the rolling surface, the contact surface, and the contact point. In other words, in the friction drive device 100, the rolling surface 30h and the first contact surface 20d, and the rolling surface 28h and the second contact surface 20c, are asymmetrical with respect to the equatorial plane. The specific structure will be described later.

[0089] To facilitate understanding of the characteristic structure, the contact structure between the planetary rolling element 20 and each orbital wheel in Reference Example 200 will be described. Reference Example 200 was conceived by the inventors of this application during the development of this embodiment. Figure 23 (A) shows the structure of the planetary rolling element 20 and each orbital wheel of Reference Example 200. Figure 23 (B) shows the speed ratio control characteristic G of Reference Example 200. Figure 23 (A) shows the profiles (hereinafter referred to as “section curves”) that appear on the cross sections of the planetary rolling body 20, input track wheel 14, first support track wheel 26, second support track wheel 28 and output track wheel 30 on a plane including the central axis La and the rotation axis Lb.

[0090] The difference between Reference Example 200 and the Implementation Method is that its first shape parameter and second shape parameter are configured to be identical to each other. In Reference Example 200, the rolling surface 30h and the first contact surface 20d, and the rolling surface 28h and the second contact surface 20c are symmetrical with respect to the equatorial surface.

[0091] The speed ratio control characteristic G of Reference Example 200 will be explained. Figure 23In diagram (B), the horizontal axis represents the position T of the speed ratio changing 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), and a negative value indicates that the output rotation is in the opposite direction to the input rotation (reverse rotation). Furthermore, the larger the absolute value of the speed ratio R, the higher the output rotation speed. Also, a speed ratio R = 0 (zero) indicates that the output rotation = 0, i.e., no rotation. That is, in the friction drive, the speed ratio R can be changed by moving the position T of the speed ratio changing mechanism 6 from the neutral position Tp to one side and from the neutral position Tp to the other side. The position T where the rotation axis Lb of the planetary rolling element 20 is parallel to the rotation axis La of the input track wheel 14 is called the neutral position Tp. In the diagram representing the speed ratio control characteristic G, the position T is represented by its relative value to the neutral position Tp.

[0092] like Figure 23 As shown in (B), in Reference Example 200, the speed ratio changing mechanism 6 is configured such that the movable amount N1 from the neutral position Tp to one side and the movable amount N2 from the neutral position Tp to the other side are the same. The movable amount of the speed ratio changing mechanism 6 is set such that the contact point does not exceed the rolling surface of the planetary rolling element or the raceway surface of the track wheel, and the error of the gear ratio is within an acceptable range. The speed ratio control characteristic G of Reference Example 200 is symmetrical on the positive and negative sides of the gear ratio R, and sometimes cannot be applied to applications that require increasing the gear ratio R on one side. Therefore, the friction transmission device 100 of the embodiment has a first shape parameter and a second shape parameter that are different from each other, so that it can be applied to applications that require increasing the gear ratio R on one side. The first shape parameter and the second shape parameter are collectively referred to as "shape parameters". Hereinafter, several structural examples will be described with reference to them.

[0093] (Examples of the first and second structures) Reference Figure 17 and Figure 18 The first and second structural examples of the friction transmission device 100 of the embodiment will be described. Figure 17 (A) represents the first structural example of the planetary rolling body 20 and each orbital wheel. Figure 17 (B) represents the speed ratio control characteristic G of the first structural example. Figure 18 (A) represents the second structural example of the planetary rolling body 20 and each orbital wheel. Figure 18 (B) represents the speed ratio control characteristic G of the second structural example.

[0094] In the first and second structural examples, the maximum outer diameter K1 of the first contact surface 20d and the maximum outer diameter K2 of the second contact surface 20c of the planetary rolling element 20 are different from each other. In the first structural example, the maximum outer diameter K1 of the first contact surface 20d is smaller than the maximum outer diameter K2 of the second contact surface 20c. The maximum outer diameters K1 and K2 are examples of shape parameters. In the second structural example, the maximum outer diameter K1 of the first contact surface 20d is larger than the maximum outer diameter K2 of the second contact surface 20c.

[0095] Furthermore, in the first and second structural examples, as shown in the speed ratio control characteristic G, the speed ratio changing mechanism 6 is configured such that the movable amount N1 from the neutral position Tp to one side and the movable amount N2 from the neutral position Tp to the other side are different from each other.

[0096] In the first structural example, the movable amount N1 on the positive side is greater than the movable amount N2 on the negative side, the maximum value (absolute value) M1 of the gear ratio R on the positive side is greater than that in the reference example, and the maximum value (absolute value) M2 of the gear ratio R on the negative side is less than that in the reference example. That is, the maximum value (absolute value) M1 of the gear ratio R on the positive side is less than the maximum value (absolute value) M2 of the gear ratio R on the negative side.

[0097] In the second structural example, the movable amount N2 on the negative side is greater than the movable amount N1 on the positive side, the maximum value (absolute value) M2 of the gear ratio R on the negative side is greater than that in the reference example, and the maximum value (absolute value) M1 of the gear ratio R on the positive side is less than that in the reference example. That is, the maximum value (absolute value) M2 of the gear ratio R on the negative side is less than the maximum value (absolute value) M1 of the gear ratio R on the negative side. The first structural example is suitable for applications requiring high-speed rotation on the positive side, and the second structural example is suitable for applications requiring high-speed rotation on the negative side.

[0098] (Examples of structures 3 and 4) Reference Figure 19 and Figure 20 The third and fourth structural examples of the friction transmission device 100 of the embodiment will be described. Figure 19 (A) represents the third structural example of the planetary rolling body 20 and each orbital wheel. Figure 19 (B) represents the speed ratio control characteristic G of the third structural example. Figure 20 (A) represents the fourth structural example of the planetary rolling body 20 and each orbital wheel. Figure 20 (B) represents the speed ratio control characteristic G of the fourth structural example.

[0099] In the third and fourth structural examples, when the rotation axis Lb of the planetary rolling element 20 is parallel to the rotation axis La of the input track wheel 14, the radial distance D1 from the contact point 30c on the first contact surface 20d to the rotation axis Lb and the radial distance D2 from the contact point 28c on the second contact surface 20c to the rotation axis Lb are different from each other. In the third structural example, the radial distance D1 is smaller than the radial distance D2. In the fourth structural example, the radial distance D1 is greater than the radial distance D2. The radial distances D1 and D2 are examples of shape parameters.

[0100] To achieve this structure, in the third and fourth structural examples, the tilt angle θ1 of the rolling surface 30h of the output track wheel 30 relative to the rotation axis La in the region contacting the planetary rolling body 20 and the tilt angle θ2 of the rolling surface 28h of the second support track wheel 28 relative to the rotation axis La in the region contacting the planetary rolling body 20 are different from each other. In the third structural example, the tilt angle θ1 is greater than the tilt angle θ2. In the fourth structural example, the tilt angle θ1 is less than the tilt angle θ2. The tilt angles θ1 and θ2 are examples of shape parameters.

[0101] In the third structural example, such as Figure 19 As shown in (B), the movable amount N1 on the positive side and the movable amount N2 on the negative side are relative distances from the neutral position Tp, and they are equal. The maximum value (absolute value) M1 of the gear ratio R on the positive side is greater than that in the reference example, and the maximum value (absolute value) M2 of the gear ratio R on the negative side is less than that in the reference example. Furthermore, at the neutral position Tp, the gear ratio R is not zero, but is offset to the positive side by an amount M0. The third structural example is suitable for applications requiring high-speed rotation on the positive side.

[0102] In the fourth structural example, as Figure 20 As shown in (B), the movable amount N1 on the positive side and the movable amount N2 on the negative side are relative distances from the neutral position Tp, and they are equal. The maximum value (absolute value) M2 of the gear ratio R on the negative side is greater than that in the reference example, while the maximum value (absolute value) M1 of the gear ratio R on the positive side is less than that in the reference example. Furthermore, at the neutral position Tp, the gear ratio R is not zero, but is offset to the negative side by an amount M0. The fourth structural example is suitable for applications requiring high-speed rotation on the negative side.

[0103] (Examples of structures 5 and 6) refer to Figure 21 , Figure 22 The fifth and sixth structural examples of the friction transmission device 100 of the embodiment will be described. Figure 21 (A) represents the fifth structural example of the planetary rolling body 20 and each orbital wheel. Figure 21 (B) represents the speed ratio control characteristic G of the fifth structural example. Figure 22 (A) represents the sixth structural example of the planetary rolling body 20 and each orbital wheel. Figure 22 (B) represents the speed ratio control characteristic G of the sixth structural example.

[0104] In the friction transmission device 100 of the embodiment, the first structural example, the second structural example, the third structural example, and the fourth structural example can be combined with each other within the range of possible configurations. The fifth structural example is a combination of the first structural example and the third structural example, and the sixth structural example is a combination of the second structural example and the fourth structural example.

[0105] In the fifth and sixth structural examples, when the rotation axis Lb of the planetary rolling element 20 is parallel to the rotation axis La of the input track wheel 14, the radial distances D1 and D2 are different, the maximum outer diameters K1 and K2 are different, and the tilt angles θ1 and θ2 are different. In the fifth structural example, the maximum outer diameter K1 is smaller than the maximum outer diameter K2, the tilt angle θ1 is larger than the tilt angle θ2, and the radial distance D1 is smaller than the radial distance D2. In the sixth structural example, the maximum outer diameter K1 is larger than the maximum outer diameter K2, the tilt angle θ1 is smaller than the tilt angle θ2, and the radial distance D1 is larger than the radial distance D2.

[0106] In the fifth structural example, as Figure 21 As shown in (B), the movable amount N1 on the positive side and the movable amount N2 on the negative side are relative distances from the neutral position Tp. The movable amount N1 on the positive side is greater than the movable amount N2 on the negative side. The maximum value (absolute value) M1 of the gear ratio R on the positive side is greater than that in the reference example, while the maximum value (absolute value) M2 of the gear ratio R on the negative side is less than that in the reference example. Furthermore, at the neutral position Tp, the gear ratio R is not zero, but is offset to the positive side by an amount M0. The fifth structural example is more suitable for applications requiring high-speed rotation on the positive side.

[0107] In the sixth structural example, as Figure 22 As shown in (B), the movable amount N1 on the positive side and the movable amount N2 on the negative side are relative distances from the neutral position Tp. The movable amount N2 on the negative side is greater than the movable amount N1 on the positive side. The maximum value (absolute value) M2 of the gear ratio R on the negative side is greater than that in the reference example, while the maximum value (absolute value) M1 of the gear ratio R on the positive side is less than that in the reference example. Furthermore, at the neutral position Tp, the gear ratio R is not zero, but is offset to the negative side by an amount M0. The sixth structural example is more suitable for applications requiring high-speed rotation on the negative side.

[0108] The operation and effects of the friction drive device 100 according to the embodiment will be explained. The friction drive device 100 according to the embodiment includes: an input track wheel 14; a planetary rolling element 20, which is arranged around the rotation axis La of the input track wheel 14 and in contact with the input track wheel 14; an output track wheel 30, which is in contact with the planetary rolling element 20 and connected to an output member 32; and a first support track wheel 26 and a second support track wheel 28, which are in contact with the planetary rolling element 20. The friction transmission device has a speed ratio changing mechanism 6. The speed ratio changing mechanism 6 changes the speed ratio by changing the relative position of the two inner motor wheels located inside the planetary rolling body 20 and the two outer track wheels located outside the planetary rolling body 20 among the input track wheel 14, output track wheel 30, first support track wheel 26 and second support track wheel 28. The speed ratio changed by the speed ratio changing mechanism 6 satisfies the following: the maximum absolute value M1 of the positive side speed ratio where the output rotation is in the same direction as the input rotation and the maximum absolute value M2 of the negative side speed ratio 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 of the planetary rolling body 20 in contact with the two outer track wheels are different from each other.

[0109] According to this structure, by employing an asymmetrical structure in which the shapes of the first contact surface 20d and the second contact surface 20c are different from each other, the absolute value of the gear ratio R on one side (positive or negative) can be increased. Therefore, compared with a symmetrical structure, the gear ratio R on one side can be increased, thereby allowing for more efficient utilization of the range of gear ratio R according to the requirements of the application. Furthermore, the friction drive device 100 of this embodiment can also be applied to cases where an engine is used as the prime mover, but it is particularly suitable for cases where a servo motor capable of controlling the rotational speed over a wide range is used as the prime mover.

[0110] As an example, in the friction drive device 100, at least one of the input track wheel 14, output track wheel 30, first support track wheel 26, and second support track wheel 28 is a concave-convex contact track wheel that makes concave-convex contact with the planetary rolling element 20. In this case, compared with the convex-convex contact case, the contact stress at the contact portion is reduced, thereby extending the service life of the contact portion.

[0111] As an example, in the friction transmission device 100, the speed ratio changing mechanism 6 is configured such that the amount of movement of the mechanism from the neutral position to one side is different from the amount of movement of the mechanism from the neutral position to the other side. In this case, since the amount of movement is different, the speed ratio R (absolute value) of the side with the larger amount of movement can be increased, both on the positive and negative sides of the speed ratio R.

[0112] As an example, in the friction transmission device 100, the maximum outer diameter of the first contact surface 20d of the planetary rolling element 20 is different from the maximum outer diameter of the second contact surface 20c. In this case, since the side with the larger maximum outer diameter of the contact surface has a greater amount of movement than the side with the smaller maximum outer diameter, the gear ratio R (absolute value) on that side can be increased.

[0113] As an example, in the friction transmission device 100, when the rotation axis of the planetary rolling element 20 is parallel to the rotation axis La, the radial distance from the contact point on the first contact surface 20d to the rotation axis is different from the radial distance from the contact point on the second contact surface 20c to the rotation axis. For example, when the radial distance D1 < the radial distance D2, the positive gear ratio R (absolute value) can be increased, and when the radial distance D1 > the radial distance D2, the negative gear ratio R (absolute value) can be increased.

[0114] As an example, in the friction drive device 100, when the rotation axis of the planetary rolling element 20 is parallel to the rotation axis La, the tilt angle of the rolling surface of the output track wheel 30 relative to the rotation axis in the region contacting the planetary rolling element 20 and the tilt angle of the rolling surface of the second support track wheel 28 relative to the rotation axis in the region contacting the planetary rolling element 20 are different from each other. For example, when the tilt angle θ1 > the tilt angle θ2, the gear ratio R (absolute value) on the positive side can be increased. For example, when the tilt angle θ1 < the tilt angle θ2, the gear ratio R (absolute value) on the negative side can be increased.

[0115] The present disclosure has been described above based on several embodiments. Those skilled in the art should understand that these embodiments are merely examples, and various modifications and alterations can be made, and such modifications and alterations are also within the scope of this disclosure. Therefore, the descriptions and drawings in this specification should not be considered limiting, but rather illustrative.

[0116] (Variation example) The following describes modified examples. In the accompanying drawings and descriptions of the modified examples, the same reference numerals are used to denote the same or equivalent components and parts as in the embodiment. Descriptions that are repeated in the embodiment are omitted where appropriate, and the focus is on describing structures that differ from the embodiment.

[0117] In the description of the embodiment, an example is shown where the output component 32 and the output track wheel 30 are keyed together by a flat key 35, but this connection structure is not limited. The connection structure can be any structure that allows them to move relative to each other in the axial direction and rotate integrally in the circumferential direction; for example, a spline connection, an involute spline connection, or a connection using an elastic body such as a spring with low axial stiffness and high circumferential stiffness can be used.

[0118] In the description of the implementation, examples of rolling surfaces 30h and 28h being conical surfaces composed of flat surfaces are shown, but they can also be curved surfaces such as convex or concave surfaces.

[0119] The structure of the input bearing 66 is not limited; for example, it can be a bearing with rollers as rolling elements. Similarly, the structure of the bearing 27 for the first track wheel is not limited; for example, it can be a bearing with rollers as rolling elements. Furthermore, the structure of the bearing 33 for the output track wheel is not limited; for example, it can be a bearing with balls as rolling elements. And the structure of the output bearing 34 is not limited; for example, it can be a bearing with balls as rolling elements.

[0120] The structure of the control bearing 63 is not limited; for example, it can be a bearing with a ball as a rolling element, a thrust bearing, a sliding bearing, etc.

[0121] For example, in the clamping force application mechanism 7, a ball can be used instead of a roller 53, and the pocket 52b of the roller holder 52, the cam groove 56j of the clamping cam 56 and the cam groove 28j of the second support track wheel 28 each have a shape corresponding to the ball.

[0122] For example, the clamping force application mechanism 7 can also be structured as follows: omitting the roller 53 and roller retainer 52, setting the cam groove 28j of the second support track wheel 28 as a convex cam ridge with a V-shaped bevel, and making the cam groove 56j of the clamping cam 56 in direct contact with it. Alternatively, the area corresponding to the cam groove 56j of the clamping cam can also be a cam ridge.

[0123] In the description of the implementation, the input track wheel 14 is arranged radially inward and the output track wheel 30 is arranged radially outward relative to the rotation axis of the planetary rolling element 20. However, it is not limited to this; the input track wheel 14 may be arranged on the outer side and the output track wheel 30 on the inner side, or both may be arranged on the inner side, or both may be arranged on the outer side.

[0124] These variations perform the same functions and effects as the implementation method.

[0125] Any combination of the above-described embodiments and modifications is also effective as an embodiment of the present invention. New embodiments resulting from combinations possess the effects of both the combined embodiments and modifications.

[0126] Industrial availability This disclosure relates to friction drive devices.

[0127] Symbol Explanation 6-Speed ​​ratio changing mechanism, 14-Input track wheel, 14h-Rolling surface, 20-Planetary rolling element, 20a, 20b, 20c, 20d-Contact surfaces, 26-First support track wheel, 26h-Rolling surface, 28-Second support track wheel, 28c-Contact point, 28h-Rolling surface, 30-Output track wheel, 30c-Contact point, 30h-Rolling surface, 32-Output component, 100-Friction transmission device.

Claims

1. A friction drive device comprising: an input track wheel; planetary rolling elements disposed about a rotation axis of the input track wheel and in contact with the input track wheel; an output track wheel in contact with the planetary rolling elements and connected to an output component; and a first support track wheel and a second support track wheel in contact with the planetary rolling elements, wherein, The friction transmission device has a speed ratio changing mechanism, which changes the speed ratio by altering the relative positions of the two inner motor wheels located inside the planetary rolling body and the two outer track wheels located outside the planetary rolling body among the input track wheel, the output track wheel, the first support track wheel, and the second support track wheel. The gear ratio changed by the speed ratio changing mechanism satisfies the following: the maximum absolute value of the gear ratio on the positive side where the output rotation is in the same direction as the input rotation and the maximum absolute value of the gear ratio on the negative side where the output rotation is in the opposite direction to the input rotation are different from each other. The shapes of the first and second contact surfaces of the planetary rolling element that contact the two outer orbital wheels are different from each other.

2. The friction transmission device according to claim 1, wherein, At least one of the input track wheel, the output track wheel, the first support track wheel, and the second support track wheel is a concave-convex contact track wheel that makes concave-convex contact with the planetary rolling element.

3. The friction transmission device according to claim 1 or 2, wherein, The friction drive device is configured such that the amount of movement of the speed ratio changing mechanism from the neutral position to one side is different from the amount of movement from the neutral position to the other side.

4. The friction transmission device according to claim 3, wherein, The maximum outer diameter of the first contact surface of the planetary rolling element is different from the maximum outer diameter of the second contact surface.

5. The friction drive device according to any one of claims 1 to 4, wherein, When the rotation axis of the planetary rolling element is parallel to the rotation axis, the radial distance from the contact point on the first contact surface to the rotation axis is different from the radial distance from the contact point on the second contact surface to the rotation axis.

6. The friction transmission device according to claim 5, wherein, When the rotation axis of the planetary rolling element is parallel to the rotation axis, the tilt angle of the rolling surface of the output track wheel relative to the rotation axis in the area in contact with the planetary rolling element and the tilt angle of the rolling surface of the second support track wheel relative to the rotation axis in the area in contact with the planetary rolling element are different from each other.

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