Friction gear

Abstract

A friction transmission device (100) is provided with: an input race (14); planetary rolling bodies (20) disposed around a rotation axis of the input race (14) and in contact with the input race (14); an output race (30) in contact with the planetary rolling bodies (20) and linked to an output shaft (32); and a first support race (26) and a second support race (28) in contact with the planetary rolling bodies (20), the friction transmission device being configured such that lines of extension of normal vectors at contact points of the planetary rolling bodies (20) with each race form a quadrilateral.

Description

TECHNICAL FIELD

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

[0002] There is known a continuously variable transmission capable of achieving an infinitely large speed ratio, which is called an IVT (Infinitely Variable Transmission). For example, a transmission is described in Patent Literature 1, which has a plurality of planetary assemblies arranged at a certain angle around an axis. The transmission is provided with a first traction ring which is in contact with the planetary assemblies and cannot rotate, a second traction ring which is in contact with the planetary assemblies to transmit power, a first carrier member which is combined with one end of the shaft center of the planetary assemblies, a second carrier member which is combined with the other end of the shaft center of the planetary assemblies, and a speed control mechanism which adjusts the tilt angle of the planetary assemblies.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2015-232402 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] It is expected that the transmission is used for a plurality of uses such as a robot or a self-propelled vehicle. In order to make the transmission used for a plurality of uses, it is expected to reduce the manufacturing cost thereof. However, the transmission described in Patent Literature 1 is complicatedly combined with a plurality of members in order to support the rotation of the planetary assemblies, and thus it is difficult to reduce the manufacturing cost.

[0008] The present application has been achieved in view of such a problem, and an object thereof is to provide a friction transmission device capable of reducing the manufacturing cost.

[0009] MEANS FOR SOLVING THE PROBLEMS

[0010] In order to solve the above problem, the friction transmission device of one embodiment of the present application is provided with an input race, a planetary rolling body which is arranged around the rotation axis of the input race and is in contact with the input race, an output race which is in contact with the planetary rolling body and is connected to an output shaft, and a first support race and a second support race which are in contact with the planetary rolling body, the friction transmission device being configured such that the extension line of the normal vector at the contact point of the planetary rolling body with each race forms a quadrilateral.

[0011] In addition, any combination of the above configuration requirements or a manner in which the configuration requirements or expressions of the present application are replaced with each other between a method, a system, and the like is also effective as a manner of the present application.

[0012] EFFECT OF THE INVENTION

[0013] According to the present application, a frictional transmission device capable of reducing manufacturing cost is provided. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a front view schematically showing an example of the frictional transmission device according to the first embodiment.

[0015] Figure 2 is a sectional view showing a cross section of the frictional transmission device of Figure 1 along the line A-A.

[0016] Figure 3 is a side view showing the periphery of the coupling of the frictional transmission device of Figure 1

[0017] Figure 4 is an explanatory view for explaining the operation of the frictional transmission device of Figure 1

[0018] Figure 5 is an explanatory view for explaining the support structure of the planetary rolling body of Figure 1

[0019] Figure 6 is a sectional view showing the periphery of the planetary rolling body of the frictional transmission device according to the second embodiment.

[0020] Figure 7 is a schematic view showing the relationship between the race and the rolling body of the frictional transmission device of Figure 6

[0021] is a graph conceptually showing the influence of the diameter error of the rolling body of the frictional transmission device of Figure 8 Figure 6

[0022] Figure 9 is a graph showing the relationship between the number of the rolling body of the frictional transmission device of Figure 6 and the offset amount of the center position of the input shaft.

[0023] Figure 10 is a sectional view showing the frictional transmission device according to the first modified example.

[0024] Figure 11 is a sectional view showing the frictional transmission device according to the second modified example.

[0025] Figure 12 is a sectional view showing the frictional transmission device according to the third modified example.

[0026] Figure 13 is a sectional view showing the frictional transmission device according to the fourth modified example. ​​​​​

[0027] Figure 14 is a sectional view showing a frictional transmission device of a fifth modification example. DETAILED DESCRIPTION

[0028] Hereinafter, the best mode for carrying out the present application will be described with reference to the accompanying drawings. In the embodiments and modification examples, the same or equivalent constituent elements and members are denoted by the same symbols, and repeated description is appropriately omitted. Also, in order to facilitate understanding, the size of each member in the drawings is appropriately enlarged or reduced. Also, in each drawing, a part of a member which is not important for the description of the embodiments is omitted.

[0029] Also, the terms including first, second, and the like are used for the description of various constituent elements, but the terms are used only for the purpose of distinguishing one constituent element from another constituent element, and the terms are not used to limit the constituent elements.

[0030] [First Embodiment]

[0031] Reference Figure 1 The structure of a frictional transmission device 100 according to the first embodiment of the present application will be described. Figure 1 is a front view schematically showing an example of the frictional transmission device 100 according to the present embodiment. Figure 2 is a sectional view schematically showing the frictional transmission device 100. The drawing shows a cross section taken along the A-A line of Figure 1 .

[0032] The frictional transmission device 100 is configured as follows: by rotating the input race to cause the planetary rolling bodies to perform rotation and revolution, and outputting the generated rotational component from the output shaft coupled to the output race to a driven device (not shown).

[0033] The frictional transmission device 100 mainly includes a transmission mechanism 10, a relative position changing mechanism 60, and a coupling 70. The transmission mechanism 10 is a mechanism that transmits the rotation input from a motor 50 after performing speed conversion to the coupling 70. The relative position changing mechanism 60 is a mechanism that changes the relative positions of the races of the transmission mechanism 10. The coupling 70 is a mechanism that absorbs misalignment between the output race of the transmission mechanism 10 and the output shaft.

[0034] (Transmission mechanism)

[0035] The transmission mechanism 10 will be described. The transmission mechanism 10 mainly includes an input shaft 12, an input collar 14, an input shaft bearing 18, planetary rolling bodies 20, a first support collar 26, a second support collar 28, an output collar 30, an output shaft 32, a main bearing 34, an oil seal 36, first and second housings 40, 42. Hereinafter, the direction along the center axis La of the input shaft 12 will be referred to as the "axial direction", and the circumferential direction and the radial direction of a circle centered on the center axis La will be referred to as the "circumferential direction" and the "radial direction", respectively. Also, hereinafter, for convenience of explanation, one side in the axial direction (the right side in the drawing) will be referred to as the input side, and the other side in the axial direction (the left side in the drawing) will be referred to as the input opposite side. The input collar 14, the first support collar 26, the second support collar 28, and the output collar 30 will sometimes be referred to simply as collars, and the planetary rolling bodies 20 will sometimes be referred to simply as rolling bodies.

[0036] If a rotational input is applied to the motor 50, the input shaft 12 rotates about the center axis La. The input shaft 12 of the present embodiment is a cylindrical member extending in the axial direction. The input collar 14 is fixed to the outer periphery of the input shaft 12, and thus rotates integrally with the input shaft 12. The input opposite side of the input shaft 12 is connected to the inner ring of the input shaft bearing 18. The outer ring of the input shaft bearing 18 supports the first support collar 26. The first support collar 26 is annularly disposed around the input shaft 12 with a gap therebetween. The input shaft 12 and the first support collar 26 are configured to be relatively rotatable.

[0037] The end portion of the input side of the input shaft 12 is connected to the relative position changing mechanism 60. The input shaft 12 moves in the axial direction by driving of the relative position changing mechanism 60. The rotor 52 of the motor 50 is annularly disposed around the outer peripheral portion of the input side of the input shaft 12. The input shaft 12 is movably supported in the axial direction by the rotor 52. The spline groove 12s provided to the outer peripheral surface of the input shaft 12 and the spline groove 51s provided to the inner peripheral surface of the rotor 52 are engaged with each other with a gap therebetween.

[0038] The input collar 14 rotates about the center axis La integrally with the input shaft 12. The input collar 14 is in contact with the planetary rolling bodies 20, and as the input collar 14 rotates, the planetary rolling bodies 20 are caused to revolve and orbit. The input collar 14 can be formed separately from the input shaft 12, but in this example, is formed integrally with the input shaft 12. The input collar 14 is a substantially disc-shaped member, and has a rolling surface 14h on the input opposite side thereof. The rolling surface 14h is a surface for rolling of the planetary rolling bodies 20, and is in substantially point contact with the planetary rolling bodies 20. The rolling surface 14h is inclined with respect to the axial direction and the radial direction. The rolling surface 14h includes a tapered surface that is tapered in diameter toward the input opposite side. The rolling surface 14h can be a curved surface such as a convex surface or a concave surface, but in this example is a flat surface.

[0039] The input shaft bearing 18 is provided between the end portion of the input shaft 12 on the opposite side of the input and the first support collar 26. The kind of bearing is not particularly limited, but in the present embodiment, the input shaft bearing 18 is a rolling bearing having spherical rolling bodies. The input shaft bearing 18 has an inner ring attached to the input shaft 12 and an outer ring fixed to the first support collar 26.

[0040] The first support collar 26 and the second support collar 28 hold the posture and position of the planetary rolling bodies 20 within a certain range. The first support collar 26 and the second support collar 28 are configured to be arranged apart from each other with the planetary rolling bodies 20 therebetween and to be arranged in opposition to each other. The first support collar 26 is arranged on the input opposite side and radially inner side of the second support collar 28.

[0041] The first support collar 26 has a ring shape that surrounds the input shaft 12 with a gap therebetween. The first support collar 26 has a rolling surface 26h on the input side. The rolling surface 26h is a surface for the planetary rolling bodies 20 to roll on, and substantially point contacts the planetary rolling bodies 20. The rolling surface 26h is inclined with respect to the axial direction and the radial direction. The rolling surface 26h includes a tapered surface that is reduced in diameter toward the input side. The rolling surface 26h can be a curved surface such as a convex surface or a concave surface, but in this example, it is a flat surface. The first support collar 26 is freely rotatable with respect to the input shaft 12 and the planetary rolling bodies 20, and is sometimes referred to as an idler collar.

[0042] The second support collar 28 has a ring shape that surrounds the input shaft 12 and the planetary rolling bodies 20. The second support collar 28 has a rolling surface 28h on the input opposite side. The rolling surface 28h is a surface for the planetary rolling bodies 20 to roll on, and substantially point contacts the planetary rolling bodies 20. The rolling surface 28h is inclined with respect to the axial direction and the radial direction. The rolling surface 28h includes a tapered surface that is reduced in diameter toward the input side. The rolling surface 28h can be a curved surface such as a convex surface or a concave surface, but in this example, it is a flat surface. The rolling surface 28h of the second support collar 28 is generally opposed to the rolling surface 26h of the first support collar 26, and the planetary rolling bodies 20 are interposed therebetween.

[0043] The second support collar 28 is fixed to the inner circumferential side of the second housing 42. The second support collar 28 can be formed separately from the second housing 42, but in this example, it is formed integrally with the second housing 42.

[0044] The output collar 30 is in contact with the planetary rolling bodies 20, and rotates about the center axis La along with the rotation of the planetary rolling bodies 20. The output collar 30 is coupled to the output shaft 32 via the coupling 70, and the coupling 70 and the output shaft 32 rotate along with the rotation of the output collar 30.

[0045] The output race 30 has a ring shape that surrounds the input shaft 12 and the planetary rolling body 20. The output race 30 has a rolling surface 30h on the input side. The rolling surface 30h is a surface on which the planetary rolling body 20 rolls, and substantially point contacts the planetary rolling body 20. The rolling surface 30h is inclined with respect to the axial direction and the radial direction. The rolling surface 30h includes a tapered surface that is tapered in diameter as it goes toward the input opposite side. The rolling surface 30h can be a curved surface such as a convex surface or a concave surface, but is a flat surface in this example. The rolling surface 30h of the output race 30 is substantially opposed to the rolling surface 14h of the input race 14, and the planetary rolling body 20 is interposed between the rolling surface 30h of the output race 30 and the rolling surface 14h of the input race 14.

[0046] The planetary rolling body 20 is arranged at a prescribed interval in the circumferential direction, and is a plurality of (for example, six). In order to hold the plurality of planetary rolling bodies 20 in the desired position, a retainer can be provided, but in the present embodiment, a retainer is not provided. The structure without a retainer is advantageous in terms of manufacturing cost, size of the device, mass of the device, and the like. In addition, the number of planetary rolling bodies 20 is not particularly limited, and can be less than six or more than six, but is preferably six to twelve.

[0047] Hereinafter, when the rolling surface 30h of the output race 30, the rolling surface 14h of the input race 14, the rolling surface 26h of the first support race 26, and the rolling surface 28h of the second support race 28 are collectively referred to, they will be simply referred to as "rolling surfaces".

[0048] The planetary rolling body 20 is in contact with four rolling surfaces, and thus its axial position, radial position, and posture are restricted. The shape of the planetary rolling body 20 can be any shape as long as it is a shape that is in contact with four rolling surfaces so that its posture is determined and can roll while being in contact with the four rolling surfaces. The planetary rolling body 20 of the present embodiment is a rotating body obtained by rotating an ellipse or an oblong about a short axis (hereinafter referred to as "oblong ball"). Also, in the present specification, a circle formed by intersecting a plane passing through the center of the short axis of the planetary rolling body 20 and orthogonal to the rotation axis Lb with the outer peripheral surface of the planetary rolling body 20 is referred to as an "equator". In this example, the equator is a large circle formed by intersecting a plane orthogonal to the rotation axis Lb with the outer peripheral surface of the planetary rolling body 20.

[0049] The inclination of the rotation axis Lb of the planetary rolling body 20 with respect to the central axis La varies depending on the relative positions of the four rolling surfaces. That is, there are cases where the rotation axis Lb is parallel to the central axis La and cases where the rotation axis Lb is inclined with respect to the central axis La.

[0050] The ratio Ra (= axial dimension / radial dimension) of the axial dimension of the planetary rolling element 20 to the radial dimension of the planetary rolling element 20 in the state where the rotation axis Lb of the planetary rolling element 20 is parallel to the central axis La is described. If the ratio Ra is large, it is possible that the planetary rolling element 20 rotates around an analog rotation axis orthogonal to the original rotation axis Lb. From the viewpoint of suppressing this phenomenon, the ratio Ra is preferably 1 or less, more preferably 0.8 or less, and further preferably 0.6 or less. The ratio Ra can be 0.1 or more.

[0051] Reference Figure 3 The coupling 70 is described. Figure 3 is a side view showing the periphery of the coupling 70. In this drawing, a part is shown in cross section. The coupling 70 is provided between the output collar 30 and the output shaft 32. The coupling 70 absorbs misalignment between the output collar 30 and the output shaft 32. The coupling 70 can be any structure as long as it can absorb eccentricity on the input side and the opposite side of the input.

[0052] The coupling 70 of the present embodiment has a disc portion 72, a plurality of (for example, two) first rollers 74 disposed on the input side of the disc portion 72, and a plurality of (for example, two) second rollers 76 disposed on the opposite side of the input of the disc portion 72. The central axes of the two first rollers 74 extend in the radial direction, and these rollers are symmetrically disposed with respect to the central axis La. The central axes of the two second rollers 76 extend in the radial direction, and these rollers are symmetrically disposed with respect to the central axis La. The central axes of the first rollers 74 and the central axes of the second rollers 76 are orthogonal to each other. Hereinafter, when collectively referring to the first rollers 74 and the second rollers 76, they are simply referred to as "rollers".

[0053] A first recess 74d that accommodates the first rollers 74 is provided on the input side of the disc portion 72, and a second recess 76d that accommodates the second rollers 76 is provided on the opposite side of the input. A collar-side recess 30d that accommodates the first rollers 74 is provided on the opposite side of the input of the output collar 30 at a position corresponding to the first recess 74d. An output shaft-side recess 32d that accommodates the second rollers 76 is provided on the input side of the output shaft 32 at a position corresponding to the second recess 76d. Hereinafter, when collectively referring to the first recess 74d, the second recess 76d, the collar-side recess 30d, and the output shaft-side recess 32d, they are referred to as "roller recesses".

[0054] As Figure 3As shown, the bottom of the roll recess is formed by a centrally deep inclined surface in the circumferential direction, which, when viewed radially, has a V-shaped cross-section. The sides of each roll contact the V-shaped inclined surface. The rolls are supported within the roll recess with a radial clearance between them and the recess. The roll recess allows rotation of the rolls and restricts their radial movement within the clearance. Radial misalignment is absorbed by the radial movement of the rolls within the clearance. Misalignment in the inclined direction is absorbed by the movement of the bottom of the roll recess along the sides of the rolls.

[0055] The disc portion 72 functions as a spring that flexes axially. Therefore, by using the disc portion 72 as a spring, the preload applied to each race can be adjusted. Furthermore, when torque is applied to the coupling 70, the axial load applied to the output race 30 increases due to the V-shaped inclination at the bottom. Therefore, the coupling 70 can increase or decrease the contact load between each race and the planetary rolling elements according to the transmitted torque. In this way, the coupling 70 absorbs the misalignment (eccentricity) between the output race 30 and the output shaft 32 while transmitting the rotation of the output race 30 to the output shaft 32.

[0056] The output shaft 32 is connected to the output ring 30 via a coupling 70 and rotates as the output ring 30 rotates. The output shaft 32 is sometimes referred to as the output flange. In this embodiment, the output shaft 32 has a generally disc-shaped shape and is rotatably supported on the first housing 40 via a main bearing 34. A driven device is connected to the input side of the output shaft 32.

[0057] like Figure 2 As shown, the main bearing 34 is disposed between the output shaft 32 and the first housing 40, supporting the output shaft 32 so that it can rotate relative to the first housing 40. The type of bearing is not particularly limited, but in this embodiment, the main bearing 34 is a crossed roller bearing with cylindrical rollers as rolling elements. The inner ring of the main bearing 34 is integrally formed with the output shaft 32, and the outer ring of the main bearing 34 is integrally formed with the first housing 40.

[0058] like Figure 2 As shown, the oil seal 36 is disposed on the opposite side of the input of the main bearing 34 between the output shaft 32 and the first housing 40. The oil seal 36 suppresses leakage of lubricant from the main bearing 34 and reduces the intrusion of foreign matter into the main bearing 34.

[0059] like Figure 2As shown, the first and second housings 40, 42 are hollow substantially cylindrical members and function as a housing of the friction transmission device 100. The first and second housings 40, 42 include: the first housing 40 which mainly surrounds the output shaft 32; and the second housing 42 which is connected to the input side of the first housing 40 and mainly surrounds the coupling 70 and the transmission mechanism 10. The first housing 40 is connected to the second housing 42 by a bolt B2. A second support collar 28 is provided on the inner peripheral side of the second housing 42. A flange portion 42f is provided on the outer peripheral side of the second housing 42. The flange portion 42f is connected to a motor housing 54 described later by a bolt B1, whereby the second housing 42 is connected to the motor 50.

[0060] Reference Figure 2 The motor 50 will be described. The kind of the motor 50 is not particularly limited, but in the present embodiment, the motor 50 is an inner rotor type brushless motor having a motor shaft 51. The motor 50 mainly includes the motor shaft 51, a rotor 52, a stator 53, a motor housing 54, a first cover portion 56, a second cover portion 57, and a pair of motor bearings 58. The motor shaft 51 is a hollow shaft having a hollow portion 51c for advancing and retreating of a linear motion shaft 66 described later. The motor shaft 51 is supported to the first cover portion 56 and the second cover portion 57 by the pair of motor bearings 58 which are arranged apart in the axial direction. The rotor 52 has a main body portion 52b integrally formed on the outer periphery of the motor shaft 51, and a cylindrical magnet 52m fixed to the outer periphery of the main body portion 52b and having a prescribed magnetic pole.

[0061] The stator 53 has a stator core 53s which opposes the magnet 52m across a magnetic gap, and an armature winding 53c provided to the stator core 53s. The motor housing 54 is a cylindrical member fixed to the outer periphery of the stator core 53s. The first cover portion 56 is a disc-shaped member which closes the input side opposite side of the motor housing 54. The second cover portion 57 is a disc-shaped member which closes the input side of the motor housing 54. The first cover portion 56, the motor housing 54, and the second cover portion 57 are integrated by a bolt B1 and are connected together with the flange portion 42f.

[0062] Reference Figure 2 The relative position changing mechanism 60 will be described. As described above, the relative position changing mechanism 60 is a mechanism which changes the relative positions of the input collar 14, the output collar 30, the first support collar 26, and the second support collar 28. The relative position changing mechanism 60 need only be able to change the relative positions between one or more of these four collars and the remaining collars. The relative position changing mechanism 60 of the present embodiment has a moving mechanism 62 which integrally moves the input collar 14 and the first support collar 26 in the axial direction.

[0063] The moving mechanism 62 is a linear actuator having a linear motion shaft 66 that advances and retreats within the hollow portion 51c of the motor shaft 51, and an actuator body 64 that generates a driving force in the axial direction of the linear motion shaft 66. The linear motion shaft 66 has a circular rod shape that extends in the axial direction. A portion of the actuator body 64 is housed in the hollow portion 51c of the motor shaft 51. The moving mechanism 62 is not particularly limited in structure as long as it is capable of advancing and retreating the linear motion shaft 66. For example, the linear motion shaft 66 can be driven by a stepping motor, or can be moved in the axial direction without rotation by the driving of a voice coil motor or the like. The moving mechanism 62 of the present embodiment drives the linear motion shaft 66 to move in the axial direction by converting rotational motion into linear motion using a ball screw mechanism.

[0064] An extension portion 62f that extends toward the radial direction outer side is provided on the actuator body 64. The extension portion 62f is fixed to the second cover portion 57 by a bolt B3, whereby the actuator body 64 is coupled to the motor 50.

[0065] A coupling hole 12h that is recessed toward the opposite side of the input is provided on the end portion of the input shaft 12 on the input side. The front end of the linear motion shaft 66 is housed in the coupling hole 12h. A coupling bearing 68 is provided between the linear motion shaft 66 and the coupling hole 12h. The outer ring of the coupling bearing 68 is fixed to the coupling hole 12h, and the inner ring of the coupling bearing 68 is fixed to the front end of the linear motion shaft 66. By adopting this structure, the input shaft 12 and the linear motion shaft 66 are coupled in a manner that allows them to rotate relative to each other. In addition, in the case where the linear motion shaft 66 moves in a non-rotating state, the linear motion shaft 66 and the input shaft 12 can be coupled without passing through the coupling bearing 68.

[0066] If the linear motion shaft 66 moves in the axial direction, the input shaft 12 also moves in the axial direction, and as a result, the input collar 14 and the first support collar 26 move toward the input side or the opposite side of the input, and the relative relationship between them and the output collar 30 and the second support collar 28 changes. By changing the relative relationship between them, the speed change ratio Rs of the transmission mechanism 10 changes. Thus, in the present embodiment, the speed change ratio Rs can be changed by a simple structure that moves the input shaft 12 in the axial direction. Furthermore, since the linear motion shaft 66 is disposed in the hollow portion 51c of the motor shaft 51, the device can be made compact.

[0067] Reference Figure 4 The operation of the transmission mechanism 10 will be described. Figure 4is an explanatory view for explaining the action of the transmission mechanism 10. In this view, each rolling surface is depicted as a curved surface, but each rolling surface is flat in a contact region that contacts the planetary rolling body 20. If the input race 14 rotates, the planetary rolling body 20 revolves around the revolution axis while rotating on its own axis Lb. In this example, the revolution axis of the planetary rolling body 20 coincides with the central axis La, and therefore the central axis La will be described as the revolution axis hereinafter.

[0068] The contact points of the planetary rolling body 20 with the input race 14, the first support race 26, the second support race 28, and the output race 30 are set as an input contact point 14c, a first support contact point 26c, a second support contact point 28c, and an output contact point 30c. As shown in Figure 4 the revolution radii of the contact points 14c, 26c, 28c, 30c are set as Rbg, Rhb, Rbm, Rbn, and the revolution radii of the contact points 14c, 26c, 28c, 30c are set as Rg, Rh, Rm, Rn.

[0069] In a case where the first support race 26 freely rotates and the second support race 28 does not rotate and is stationary, the ratio (hereinafter, referred to as "speed change ratio Rs") of the rotational speed ω2 of the output race 30 to the rotational speed ω1 of the input race 14 is shown in the following mathematical expression 1.

[0070] [mathematical expression 1]

[0071]

[0072] In the state of Figure 4 , the planetary rolling body 20 has a posture in which the input side of the rotation axis Lb is close to the central axis La. If the positions of the input race 14 and the first support race 26 are changed toward the input side by the relative position changing mechanism 60, the posture of the planetary rolling body 20 is changed to a posture in which the input opposite side of the rotation axis Lb is close to the central axis La. As a result, the revolution radii and the revolution radii of each contact point are changed, and the speed change ratio Rs is also changed. In this way, by changing the posture of the planetary rolling body 20 by changing the relative positions of each race, it is possible to change the speed change ratio Rs of the transmission mechanism 10. Conversely, by supporting the posture of the planetary rolling body 20 to be constant, the speed change ratio Rs is maintained to be constant.

[0073] In order to suppress the posture variation of the planetary rolling body 20, as one example, a structure in which an axis member is provided on the planetary rolling body 20 along the rotation axis Lb and the axis member is supported by a bearing, as described in Patent Literature 1, can be adopted. At this time, the planetary rolling body 20 is supported by the axis member. In the present embodiment, the planetary rolling body 20 is not supported by the axis member, but is supported by the input race 14, the output race 30, the first support race 26, and the second support race 28.

[0074] Reference Figure 5 A structure in which the planetary rolling body 20 is supported by each race will be described. Figure 5 is an explanatory view for explaining a structure in which the planetary rolling body 20 is supported by each race. In this view, the extension lines of each vector on a plane including the center axis La and the rotation axis Lb are shown. As shown in the view, in the present embodiment, the extension lines of the normal vectors at the contact points of the planetary rolling body and each race form a quadrangle. According to the shape of the planetary rolling body 20, a quadrangle based on the extension lines is not formed, and the posture of the planetary rolling body 20 becomes unstable. Figure 5

[0075] As shown in the view, with respect to the normal vector 14v at the input contact point 14c, the normal vector 26v at the first support contact point 26c, the normal vector 28v at the second support contact point 28c, and the normal vector 30v at the output contact point 30c, the extension lines 14m, 26m, 28m, and 30m of the normal vectors thereof intersect each other to form a quadrangle 20s. According to this structure, the posture of the planetary rolling body 20 is uniquely determined, and the posture of the planetary rolling body 20 is maintained without being supported by the shaft member. In addition, if the quadrangle 20s is a convex quadrangle (a quadrangle having no corner with an internal angle of 180 degrees or more), the stability of the posture is further improved. Figure 5

[0076] According to the shape of the planetary rolling body 20, the area of the quadrangle 20s sometimes becomes too small. If the area of the quadrangle 20s becomes too small, the posture of the planetary rolling body 20 can become unstable. From the viewpoint of making the posture stable, the area of the quadrangle 20s is preferably 4% or more, more preferably 25% or more, and further preferably 60% or more of the cross-sectional area of the planetary rolling body 20. The area of the quadrangle 20s can be set to 15% or more of the cross-sectional area of the planetary rolling body 20.

[0077] According to the shape of the planetary rolling body 20, the directions of the normal vectors of the opposite sides of the quadrangle 20s sometimes become the same direction. If the directions of the normal vectors of the opposite sides of the quadrangle 20s are the same, the posture of the planetary rolling body 20 can become unstable. Therefore, the present embodiment is configured such that the normal vectors of the opposite sides of the quadrangle are in opposite directions. Specifically, the normal vector 14v and the normal vector 30v are in opposite directions, and the normal vector 26v and the normal vector 28v are in opposite directions. At this time, since the position and the orientation of the planetary rolling body 20 are restricted by each race, the posture of the planetary rolling body 20 becomes more stable. Also, if the normal vectors of two sides adjacent to each other of the quadrangle 20s are both directed toward a corner or both directed away from the corner, the posture becomes more stable. ​​

[0078] If the contact surfaces of the races and the planetary rolling bodies 20 are flat surfaces, the contact area increases, which results in an increase in mechanical loss, and if the contact surfaces are curved surfaces, the manufacturing time increases. Therefore, in the present embodiment, with respect to the contact surfaces of the input contact point 14c, the first support contact point 26c, the second support contact point 28c, and the output contact point 30c, the races are flat surfaces, and the surfaces of the planetary rolling bodies 20 that face the races are curved surfaces. At this time, the increase in mechanical loss is suppressed, and the manufacturing of the components becomes easy. The curved surfaces of the planetary rolling bodies 20 are not particularly limited, but in this example, the curved surfaces have the profile of an involute curve.

[0079] Next, the operation of the friction transmission device 100 having the above-described structure will be described. If rotational power is transmitted from the motor shaft 51 to the input shaft 12, the input race 14 rotates about the center axis La. By the rotation of the input race 14, the planetary rolling bodies 20 generate rotation and revolution. The rotation of the planetary rolling bodies 20 is transmitted to the output race 30, and the output race 30 rotates at the above-described speed change ratio Rs. The rotation of the output race 30 is output to the output shaft 32 via the coupling 70. If the relative position changing mechanism 60 changes the positions of the input race 14 and the first support race 26, the speed change ratio Rs changes.

[0080] Next, the features of the friction transmission device 100 will be described. In the friction transmission device 100, the extension lines of the normal vectors at the contact points of the planetary rolling bodies 20 and the races form a quadrilateral, and thus the posture of the planetary rolling bodies 20 becomes more stable than in the case where the extension lines do not form a quadrilateral. Since the structure for maintaining the posture of the planetary rolling bodies 20 becomes simple, the manufacturing cost can be reduced.

[0081] In the friction transmission device 100, the planetary rolling bodies 20 are not supported by shaft members but are supported by the input race 14, the output race 30, the first support race 26, and the second support race 28, and thus the manufacturing cost of the shaft members and the surrounding members thereof can be reduced.

[0082] [Second Embodiment]

[0083] Reference Figures 6-9 A friction transmission device 100 according to a second embodiment of the present application will be described. In the drawings and the description of the second embodiment, the same symbols are attached to the constituent elements and the members that are the same as or equivalent to those of the first embodiment. The description that is repeated in the first embodiment is appropriately omitted, and the structure that is different from that of the first embodiment will be mainly described. The friction transmission device 100 of the present embodiment is different from that of the first embodiment in the shape of the rolling bodies and the shape of the contact portions of the rolling bodies and the races, and the other structures are the same. Therefore, these different points will be mainly described.

[0084] Figure 6 FIG. 21 is a sectional view showing the periphery of the planetary rolling body 20 of the friction transmission device 100 representing an embodiment. In the description of the first embodiment, an example in which the curved surface of the planetary rolling body 20 has a profile of an involute curve is shown, but in the present embodiment, the contact portion in contact with the race in the axial section of the planetary rolling body 20 is a circular arc. In this example, the curved surface of the contact portion in contact with each race 14, 26, 28, 30 in the axial section of the planetary rolling body 20 has a profile of a circular arc curve. At this time, since the profile of the raceway surface of the planetary rolling body 20 is a circular arc, the rolling body machining, the measurement of the profile after machining, and their management become easy, and are advantageous in terms of cost reduction and quality stabilization.

[0085] Reference Signs List Figure 6 The position of the contact point of the rolling body will be described. As shown by the broken line in FIG. 21, if the positions of the contact point of the planetary rolling body 20 in contact with the inner race and the contact point in contact with the outer race overlap, stress will be concentrated at this point, which can cause fatigue accumulation, which can lead to a reduction in the life of the planetary rolling body 20. Therefore, in the present embodiment, the respective contact points of the inner race and the outer race disposed at positions overlapping each other when viewed in the radial direction in contact with the planetary rolling body 20 are axially offset from each other. Figure 6

[0086] Specifically, as shown in FIG. 22, the input race 14 and the second support race 28 are disposed at positions overlapping each other when viewed in the radial direction, and the contact point 14c of the planetary rolling body 20 in contact with the input race 14 and the contact point 28c of the planetary rolling body 20 in contact with the second support race 28 are axially offset from each other. For example, in order to achieve this structure, the contact angle θ1 of the rolling surface 14h (indicated by a solid line in FIG. 22) of the input race 14 can be set to be different from the contact angle θ2 of the rolling surface 28h of the second support race 28. Figure 6 Figure 6 Further, the output race 30 and the first support race 26 are disposed at positions overlapping each other when viewed in the radial direction, and the contact point 30c of the planetary rolling body 20 in contact with the output race 30 and the contact point 26c of the planetary rolling body 20 in contact with the first support race 26 are axially offset from each other. For example, in order to achieve this structure, the contact angle θ3 of the rolling surface 26h (indicated by a solid line in FIG. 23) of the first support race 26 can be set to be different from the contact angle θ4 of the rolling surface 30h of the output race 30.

[0087] Figure 6

[0088] Thus, by making the contact angles of the raceway surfaces of the inner ring side and the outer ring side different and axially offsetting the contact points of the races of the inner ring side and the races of the outer ring side, it is possible to disperse the stress of the rolling body and thus reduce the accumulation of fatigue, and thus it is possible to extend the life.​​​​

[0089] Reference Figure 6 A recess in the rolling element will be described. The shape and size of the rolling element have manufacturing variations. It can be considered that if the size variation of the planetary rolling element is large and the rigidity of the planetary rolling element is high, the surface pressure of the contact portion locally becomes too large, which can cause a reduction in the life. Therefore, the planetary rolling element 20 of the present embodiment has a recess 22 in the center portion. The recess 22 can be a bottomed hole, but in this example, the recess 22 is a through hole. By providing the recess 22 in the center portion, the planetary rolling element 20 can be deflected according to the contact load acting on the raceway surface, so the influence of the size variation of the rolling element can be suppressed, and thus the life can be extended.

[0090] Reference Figure 7 , Figure 8 and Figure 9 The influence of the diameter variation of the rolling element on the shift of the center position of the input shaft 12 will be described. Figure 7 is a diagram showing the relationship between the race and the rolling element. In order to facilitate understanding, the race and the rolling element are shown in two dimensions in this diagram. In this diagram, the race on the radially outer side is shown as the outer race and the race on the radially inner side is shown as the inner race, and the outer race and the inner race are shown by circles. All of the rolling elements (rolling elements 1 to 6) are in contact with the outer race and the inner race. D1 shows the diameter of the outer race, and P0 shows the center position of the input shaft 12.

[0091] Figure 8 is a diagram conceptually showing the influence of the diameter error of the rolling element on the center position of the input shaft 12. In this diagram, P1 shows the contact point of the rolling element 1 with the outer race, P4 shows the contact point of the rolling element 4 on the opposite side from the rolling element 1 with the outer race, and P0 shows the center position of the input shaft 12 when all of the rolling elements 1 to 6 are the same diameter. As shown in Figure 8 , in the case where the diameter of the rolling element 1 is larger than the diameters of the other rolling elements 2 to 6 by d1, the center position of the input shaft 12 is shifted from P0 as shown by P0d. That is, the shift amount of the center position of the input shaft 12 can be calculated from the geometrical relationship of Figure 8 .

[0092] Figure 9 is a diagram showing the relationship between the number of rolling elements and the shift amount of the center position of the input shaft 12. In this diagram, the result of calculating the shift amount of the center position of the input shaft 12 from the number of rolling elements using the geometrical relationship of Figure 8 is shown. In this diagram, the horizontal axis shows the number of rolling elements, and the vertical axis shows the relative value of the shift amount of the center position of the input shaft 12 divided by a prescribed unit amount. According to Figure 9It is known from the study that, in the case where the number of rolling elements is odd, the shift in the center position of the input shaft 12 caused by the diameter deviation of the rolling elements is smaller than in the case where the number of rolling elements is even. Based on this result, the present embodiment is configured to have an odd number (for example, seven) of planetary rolling elements 20, thereby reducing the influence of the diameter deviation of the rolling elements.

[0093] According to the present embodiment, the same effects as those of the first embodiment are obtained. Also, in the present embodiment, since the contact portions of the planetary rolling elements are circular arcs, manufacturing becomes easy. Also, in the present embodiment, since the contact points of the inner and outer are offset from each other in the axial direction, it is possible to disperse the stress of the rolling elements. Also, in the present embodiment, since the recess is provided in the center portion, it is possible to suppress the influence of the size deviation of the rolling elements. Also, in the present embodiment, since an odd number of rolling elements are provided, it is possible to suppress the influence of the diameter deviation of the rolling elements.

[0094] The above describes examples of the embodiments of the present application in detail. The above embodiments are merely specific examples for implementing the present application. The contents of the embodiments are not intended to limit the technical scope of the present application, and various design changes such as changes, additions, and deletions of the constituent elements can be made within the scope of the idea of the present application defined in the technical concept. In the above embodiments, the contents that can be subjected to such design changes are described with the phrases "of the embodiment", "in the embodiment", and the like, but this does not mean that the contents without such phrases are not allowed to be subjected to design changes. Also, the hatching lines on the cross sections of the drawings are not intended to limit the material of the object to which the hatching lines are applied.

[0095] Hereinafter, a modified example will be described. In the drawings and the description of the modified example, the same reference numerals are applied to the constituent elements and members that are the same as or equivalent to those of the embodiments. The description that is repeated with the embodiments is appropriately omitted, and the structures that are different from the embodiments will be mainly described.

[0096] [First Modified Example]

[0097] Figure 10 is a cross-sectional view that shows a friction transmission device 200 according to the first modified example, and corresponds to Figure 2 The present modified example differs from the embodiments mainly in the shapes of the planetary rolling elements 20 and the respective races, and the other structures are the same. Therefore, the different structures will be described. The planetary rolling elements 20 of the present modified example are rotation bodies obtained by rotating a rectangle having a round corner R. The planetary rolling elements 20 have curved surface portions 20h formed by rotating the round corner R. The rolling surfaces 14h, 26h, 28h, and 30h are in contact with the curved surface portions 20h. The friction transmission device 200 operates in the same manner as the embodiments.

[0098] [Second Modification]

[0099] Figure 11 is a cross-sectional view of a friction transmission device 300 according to a second modification, which corresponds to Figure 2 The second modification differs from the embodiment mainly in the shapes of the planetary rolling body 20 and the respective races, and the other structures are the same. Therefore, the different structures will be described. The planetary rolling body 20 of the second modification is a rotating body obtained by rotating a figure having a curved portion near the intersection of two sides of the apex side of a triangle about the other side. The planetary rolling body 20 has a substantially rhombic cross section. The planetary rolling body 20 has a curved surface portion 20h formed by the rotation of the curved portion. The respective races have shapes that contact the curved surface portion 20h of the planetary rolling body 20. The rolling surfaces 14h, 26h, 28h, 30h contact the curved surface portion 20h. The friction transmission device 300 operates in the same manner as the embodiment and has the same features.

[0100] [Third Modification]

[0101] Figure 12 is a cross-sectional view of a friction transmission device 400 according to a third modification, which corresponds to Figure 2 The third modification differs from the embodiment mainly in the shapes of the planetary rolling body 20 and the respective races, and the other structures are the same. Therefore, the different structures will be described. The planetary rolling body 20 of the third modification is a rotating body obtained by rotating a figure having a curved portion on two sides of the apex side of a pentagon constituted of a semicircle and a pentagon protruding from the center of the circular arc of the semicircle toward the side opposite to the chord of the semicircle about the chord of the semicircle. In the planetary rolling body 20, the equatorial portion is convexly protruded so as to have a circumferential convex portion 20c. The planetary rolling body 20 has a curved surface portion 20h formed by the rotation of the curved portion of the pentagon. The rolling surfaces 14h, 26h contact regions corresponding to the circular arc of the semicircle, and the rolling surfaces 28h, 30h contact the curved surface portion 20h. The friction transmission device 400 operates in the same manner as the embodiment and has the same features.

[0102] [Fourth Modification]

[0103] Figure 13 is a cross-sectional view of a friction transmission device 500 according to a fourth modification, which corresponds to Figure 2The present modification differs from the embodiment mainly in the shapes of the planetary rolling body 20, the respective races, the output race 30, the disc portion 72, and the output shaft 32, and is identical in other structures. Therefore, the different structures will be described. The planetary rolling body 20 of the present modification is a rolling body obtained by rotating a figure in which a rectangle having a V-shaped recess in one side thereof is rotated with the side opposite to the side having the recess as the center. The planetary rolling body 20 has a circumferential recess 20d in which the equator is recessed in a circumferential shape, and a curved portion 20h is formed in the circumferential recess 20d. The rolling surfaces 14h, 26h, 28h, and 30h are in contact with the curved portion 20h.

[0104] The first roller 74 and the first recess 74d are provided on the input side opposite side of the disc portion 72, and the second roller 76 and the second recess 76d are provided on the input side of the disc portion 72. The output race 30 has a disc-shaped portion 30b provided on the input side opposite side of the disc portion 72 with a gap, and a cylindrical extension 30e extending from the outer periphery of the disc-shaped portion 30b toward the input side. A rolling surface 30h is provided on the end portion of the cylindrical extension 30e on the input side, and a race side recess 30d is provided on the input side of the disc-shaped portion 30b.

[0105] The output shaft 32 has an output shaft main body portion 32b, a tubular extension 32e extending from the end surface on the input side of the output shaft main body portion 32b toward the input side, and a flange portion 32f protruding in the radial direction from the end portion on the input side of the tubular extension 32e. The flange portion 32f has a wheel disc shape provided on the input side of the disc portion 72 with a gap. An output shaft side recess 32d is provided on the input side opposite side of the flange portion 32f. The friction transmission device 500 operates in the same manner as the embodiment, and has the same features.

[0106] [Fifth Modification]

[0107] Figure 14 is a sectional view of a friction transmission device 600 of the fifth modification, which corresponds to Figure 13 The present modification differs from the fourth modification mainly in the shapes of the planetary rolling body 20 and the respective races, and is identical in other structures. Therefore, the different structures will be described. The planetary rolling body 20 of the present modification is a rolling body obtained by rotating a rectangle having a V-shaped recess in one side thereof with the side opposite to the side having the recess as the center. The planetary rolling body 20 has a circumferential recess 20d in which the equator is recessed in a circumferential shape, and a curved portion 20h is formed in the circumferential recess 20d. The rolling surfaces 14h, 26h, 28h, and 30h are in contact with the curved portion 20h. The friction transmission device 600 operates in the same manner as the embodiment, and has the same features.

[0108] [Other Modifications]

[0109] In the description of the embodiments, an example in which two support races 26, 28 are provided is shown, but the present application is not limited to this, and three or more support races can be provided.

[0110] In the description of the embodiments, an example in which the first support race 26 is free to rotate and the second support race 28 is stationary is shown, but the present application is not limited to this. The first support race 26 can be stationary and the second support race 28 can be free to rotate.

[0111] In the description of the embodiments, the input race 14 is disposed on the radially inner side and the output race 30 is disposed on the radially outer side with respect to the axis of rotation of the planetary rolling elements 20. However, the present application is not limited to this, and the input race 14 can be disposed on the outer side and the output race 30 can be disposed on the inner side, or both can be disposed on the inner side, or both can be disposed on the outer side.

[0112] The above-described modifications also have the same effects and advantages as the embodiments.

[0113] Any combination of the components of the above-described embodiments and modifications is also effective as an embodiment of the present application. The new embodiments produced by the combination have the effects of each of the embodiments and modifications combined.

[0114] Industrial Applicability

[0115] The present application can be used as a friction transmission device.

[0116] Explanation of Symbols

[0117] 10 - transmission mechanism, 12 - input shaft, 14 - input race, 18 - input shaft bearing, 20 - planetary rolling elements, 26 - first support race, 28 - second support race, 30 - output race, 32 - output shaft, 34 - main bearing, 40 - first housing, 42 - second housing, 50 - motor, 60 - relative position changing mechanism, 62 - moving mechanism, 66 - linear motion shaft, 70 - coupling, 100 - friction transmission device.

Claims

1. A friction drive device comprising: an input ring; planetary rolling elements disposed about a rotation axis of the input ring and in contact with the input ring; an output ring in contact with the planetary rolling elements and connected to an output shaft, the output ring being capable of changing the speed of rotation from the input ring and outputting it to the output shaft; and a first support ring and a second support ring in contact with the planetary rolling elements, characterized in that... The first support ring and the second support ring are respectively capable of rotating relative to the output ring. The input collar is positioned on one side of the radial outer and radial inner sides relative to the planetary rolling element. The first support collar is disposed on the side where the input collar is disposed, and is rotatable relative to the input collar. The extensions of the normal vectors at the contact points between the planetary rolling element and each ring form a quadrilateral.

2. The friction transmission device according to claim 1, characterized in that, The normal vectors of the opposite sides of the quadrilateral are oriented in opposite directions.

3. A friction drive device comprising: an input ring; planetary rolling elements disposed about a rotation axis of the input ring and in contact with the input ring; an output ring in contact with the planetary rolling elements and connected to an output shaft, the output ring being capable of changing the speed of rotation from the input ring and outputting it to the output shaft; and a first support ring and a second support ring in contact with the planetary rolling elements, characterized in that... The first support ring and the second support ring are respectively capable of rotating relative to the output ring. The input collar is positioned on one side of the radial outer and radial inner sides relative to the planetary rolling element. The first support collar is disposed on the side where the input collar is disposed, and is rotatable relative to the input collar. The planetary rolling elements are not supported by the shaft components but are supported by the input ring, the output ring, the first support ring, and the second support ring.

4. The friction transmission device according to any one of claims 1 to 3, characterized in that, It has a relative position changing mechanism that changes the relative positions of the input collar, the output collar, the first support collar, and the second support collar.

5. The friction transmission device according to claim 4, characterized in that, The relative position changing mechanism includes a moving mechanism that moves the input collar and the first support collar together along the axial direction.

6. The friction transmission device according to claim 5, characterized in that, The moving mechanism has a linear motion axis that moves forward and backward within the hollow portion of the motor shaft.

7. The friction transmission device according to any one of claims 1 to 6, characterized in that, It has a coupling that absorbs misalignment between the output ring and the output shaft.

8. The friction transmission device according to any one of claims 1 to 7, characterized in that, Each of the rings is a flat surface, while the surface of the planetary rolling element opposite to each of the rings is a curved surface.

9. The friction transmission device according to claim 8, characterized in that, In the axial section of the planetary rolling element, the contact portion that contacts the raceway is an arc.

10. The friction transmission device according to any one of claims 1 to 9, characterized in that, Either the first support ring or the second support ring is positioned to overlap with the input ring when viewed radially. The contact points between the planetary rolling element and the input race and the contact points between the planetary rolling element and the race are axially offset from each other.

11. The friction transmission device according to any one of claims 1 to 10, characterized in that, The planetary rolling element has a recess in its center.

12. The friction transmission device according to any one of claims 1 to 11, characterized in that, It has an odd number of the planetary rolling bodies.

Images