JP7584556B2 - Wave generator for wave gearing and wave gearing - Google Patents

Description

The present invention relates to a wave generator for a wave gear device and a wave gear device.

The lifespan (durability) of a strain wave gear device is primarily determined by the durability of the bearings in the wave generator that generates wave motion in the strain wave gear device. In the case of ball bearings, the rolling elements are spherical balls, so stress is concentrated at the apex (support) of the ball, which is a factor in reducing durability.

For this reason, it has been proposed to use roller bearings in which the support parts of the rolling elements come into line contact (see, for example, Patent Document 1).

JP 2011-190826 A

However, the above conventional roller bearings have a problem in that they are significantly affected by coning (a phenomenon in which the flexspline of a strain wave gear device is deformed into an elliptical cone shape when a wave generator is inserted into the flexspline). The occurrence of coning places a large load on the axial ends of the rollers of the roller bearing, concentrating stress on the outer circumferential surface of the rollers (particularly the axial ends of the outer circumferential surface of the rollers). Such stress concentration can be a factor in, for example, a decrease in the durability of the wave generator and thus of the strain wave gear device, an increase in energy loss (a decrease in power transmission efficiency), etc.

The object of the present invention is to provide a wave generator for a wave gear device and a wave gear device in which stress concentration caused by coning is reduced.

(1) The wave generator of the wave gearing according to the present invention comprises a cam member having a non-circular contour and a roller bearing mounted on the outer peripheral surface of the cam member, in which the roller of the roller bearing includes a roller sliding surface on the outer peripheral surface of the roller that includes the center of the roller outer peripheral surface in the roller axial direction, and at least one of two roller sliding surface regions on either side of the center of the roller outer peripheral surface in the roller axial direction of the roller sliding surface includes a reduced diameter surface tapered toward the roller axial end of the roller.

(2) In the wave generator of the wave gear device described above in (1), it is preferable that the roller diameter reduction surface is a curved surface that is curved radially outward.

(3) In the wave generator of the wave gear device described above in (1) or (2), it is preferable that the roller sliding surface is a curved surface that has a maximum diameter at the center of the roller outer circumferential surface in the roller axial direction and is curved so as to be convex radially outward.

(4) In the wave generator of the wave gear device of any one of (1) to (3) above, the reference diameter φA1 of the roller and the diameter φA2 of the roller axial end of the reduced diameter surface can satisfy the condition 60≦(φA2/φA1)×100≦99.

(5) In the wave generator of the wave gear device of any one of (1) to (4) above, it is preferable that the roller bearing is provided with a retainer that holds the rollers, and the retainer holds the axial end of the outer circumferential surface of the rollers.

(6) In the wave generator of the wave gear device of any one of (1) to (5) above, it is preferable that the roller bearing is provided with a retainer that holds the rollers, and the retainer holds the rolling direction sliding portion of the roller sliding surface Fs.

(6) In the wave generator of the wave gear device described above in (5), the roller bearing may include a plurality of the retainers.

(7) In the wave generator of the wave gear device described above in (5) or (6), the retainer may be made of resin or light metal.

(8) In the wave generator of the wave gear device of any one of (1) to (7) above, the roller bearing may be configured to include at least one of an inner ring and an outer ring.

(9) In the wave generator of the wave gear device of any one of (1) to (7) above, the roller bearing may be configured to bring the rollers into contact with the cam member and the flexspline.

(10) The wave gear device according to the present invention comprises a circular spline, a flexspline, and any one of the wave generators described above in (1) to (9).

The present invention provides a wave generator for a wave gear device and a wave gear device in which stress concentration caused by coning is reduced.

FIG. 1 is a front view showing a wave gear device according to an embodiment of the present invention, viewed from the axial input side, the wave gear device including a wave generator according to a first embodiment of the present invention. FIG. 2 is a front view showing a roller bearing, which is one component of the strain wave gear device of FIG. 1 . FIG. 3 is a plan view partially and diagrammatically showing the assembled state of the rollers of the roller bearing in FIG. 2 and the cage that holds the rollers, with the cage developed flat. XX cross-sectional view of FIG. 3. FIG. 4 is a front view of FIG. 2 is a cross-sectional view showing the wave gear device of FIG. 1 , the cross section including the major axis of a cam member. FIG. 1 is a cross-sectional view showing a conventional strain wave gear device, the cross section including the major axis of a cam member. FIG. 11 is a plan view partially and diagrammatically showing an assembled state of the rollers of a roller bearing of a wave generator according to a second embodiment of the present invention, the rollers of the roller bearing and the cage that holds the rollers, with the cage laid out flat. FIG. 8 is a front view of FIG. This is a cross-sectional view taken along the line YY in FIG. 7. FIG. 11 is a partial and schematic front view of a roller bearing of a wave generator according to a third embodiment of the present invention, showing the assembled state of the rollers of the roller bearing and the cage that holds the rollers, with the cage laid out flat. 11 is a cross-sectional view taken along the line XX of FIG. 10 . 11 is a cross-sectional view showing the assembled state of FIG. 10, taken along line YY of FIG. FIG. 10 is a front view illustrating a roller bearing of a wave generator according to a fourth embodiment of the present invention. 14 is a plan view partially and diagrammatically showing the assembled state of the rollers of the roller bearing of FIG. 13 and the cage that holds the rollers, with the cage laid out flat. FIG. This is a cross-sectional view taken along the line XX in FIG. 14. FIG. 15 is a front view of FIG. This is a cross-sectional view taken along the line YY in FIG. 14. FIG. 13 is a front view illustrating a roller bearing of a wave generator according to a fifth embodiment of the present invention. 19 is a plan view partially and diagrammatically showing the assembled state of the rollers of the roller bearing of FIG. 18 and the cage that holds the rollers, with the cage laid out flat. FIG. This is a cross-sectional view taken along the line XX in Figure 19. FIG. 20 is a front view of FIG. 19 . This is a cross-sectional view taken along the line YY in FIG. 19. FIG. 13 is a partial and schematic front view of a roller bearing of a wave generator according to a sixth embodiment of the present invention, showing the assembled state of the rollers of the roller bearing and the cage that holds the rollers, with the cage laid out flat. This is a cross-sectional view taken along the line XX in Figure 23. FIG. 24 is a front view of FIG. 23. This is a cross-sectional view taken along the line YY in FIG. 23. FIG. 13 is a plan view partially and diagrammatically showing an assembled state of the rollers of a roller bearing of a wave generator according to a seventh embodiment of the present invention, the rollers of the roller bearing and the cage that holds the rollers, with the cage laid out flat. This is a cross-sectional view of Figure 27 taken along the line XX.

Below, we will explain the wave generator and wave gear device of the wave gear device according to an exemplary embodiment of the present invention, with reference to the drawings.

Here, the axial direction refers to the direction in which the axis (central axis) extends. Also, the "axial direction" refers to the direction perpendicular to the axial direction. Furthermore, the "axial direction" can also be called the "radial direction" when the axis is used as the reference (center). In particular, when referring to the radial direction, the side closer to the axis is called the "radial inner side" and the side farther from the axis is called the "radial outer side". Also, in the following description, the same reference numerals are used for substantially identical parts.

Figure 1 shows a schematic diagram of a strain wave gear device 1 according to one embodiment of the present invention, viewed from the axial input side.

In FIG. 1, symbol O1 is the central axis of the wave gear device 1. The wave gear device 1 outputs input from one axial side to the other axial side at the central axis O1 (hereinafter simply referred to as "axis O1") of the wave gear device 1. In this embodiment, the front side of the drawing is the one axial side (axial input side), and the back side of the drawing is the other axial side (axial output side).

The wave gear device 1 includes a circular spline 2, a flexspline 3, and a wave generator 4 according to the first embodiment of the present invention.

The circular spline 2 is a ring member. The circular spline 2 is arranged so that the central axis of the circular spline 2 is coaxial with the axis O1. A plurality of internal teeth 2a are formed on the inner circumference of the circular spline 2 and are spaced apart in the circumferential direction around the axis O1. The circular spline 2 is preferably a member having high rigidity, for example, a rigid body. The circular spline 2 can be formed, for example, from a metal or a resin such as engineering plastic. In this embodiment, the circular spline 2 is fixed to a case (not shown) of the strain wave gear device 1.

The flexspline 3 is a cup-shaped member having an opening A3. The flexspline 3 is also arranged so that the central axis of the flexspline 3 is coaxial with the axis O1. A plurality of external teeth 3a are formed on the outer periphery of the flexspline 3 and are spaced apart in the circumferential direction around the axis O1. The flexspline 3 is a deformable member. The external teeth 3a of the flexspline 3 can be locally engaged with a plurality of internal teeth 2a formed on the circular spline 2 by deformation of the flexspline 3. The flexspline 3 can also be formed from, for example, a metal or a resin such as engineering plastic.

In this embodiment, the flexspline 3 has a cylindrical portion 3b with the axis O1 as the central axis. The external teeth 3a are formed on the outer periphery of the cylindrical portion 3b on the axial input side. Furthermore, as shown in FIG. 6A, the flexspline 3 has a bottom portion 3c. The flexspline 3 is formed into a cup shape by closing one end of the cylindrical portion 3b with the bottom portion 3c. The flexspline 3 has an opening portion A3 on the side opposite the bottom portion 3c in the axial direction. The opening portion A3 can accommodate the wave generator 4. In this embodiment, the output shaft (not shown) of the wave gear device 1 is connected to the bottom portion 3c.

The wave generator 4 generates a wave motion in the flexspline 3 in the circumferential direction about the axis O1. As shown in FIG. 1, the wave generator 4 includes a cam member 5 having a non-circular contour and a roller bearing 6 mounted on the outer peripheral surface of the cam member 5.

In this embodiment, an input shaft 11 is connected to the cam member 5. Power from a motor (not shown) or the like is transmitted to the input shaft 11. This allows the cam member 5 to rotate around the axis O1. The central axis (rotation axis) of the input shaft 11 is coaxial with the axis O1. That is, in this disclosure, the wave generator 4 is arranged on the same axis as the axis O1, with the axis O1 being the central axis.

The cam member 5 has a non-circular shape when viewed in the axial direction (when viewed from the extension direction of the axis O1). Like the circular spline 2, the cam member 5 is preferably a member having high rigidity, for example, a rigid body. The cam member 5 can also be formed, for example, from a metal or a resin such as engineering plastic. The outer peripheral surface F5 of the cam member 5 functions as a cam surface.

In this embodiment, the cam member 5 is of a two-lobe type. As shown in FIG. 1, the two-lobe type is an elliptical shape when viewed in the axial direction. However, the cam member 5 is not limited to a two-lobe type. For example, the cam member 5 may be of a multi-lobe type. Specific examples of the cam member 5 include a triangular three-lobe type and a rectangular four-lobe type.

In this embodiment, the roller bearing 6 is a radial roller bearing. The roller bearing 6 receives a force applied in the radial direction. The roller bearing 6 has a plurality of rollers 7 arranged in the circumferential direction around the axis O1. The rollers 7 are members having high rigidity, for example, rigid bodies. The rollers 7 can be formed, for example, from metal or resin such as engineering plastic. The rollers 7 are each arranged at intervals in the circumferential direction around the axis O1 by a cage 8.

The roller bearing 6 is equipped with a cage 8 that holds the rollers 7. The cage 8 rotatably holds each of the rollers 7. The rollers 7 are positioned at regular intervals around the axis O1 by the cage 8. The cage 8 is a deformable, endless, band-shaped member that has no terminus. The cage 8 can also be formed from, for example, metal or resin such as engineering plastic.

Figure 2 shows the roller bearing 6 removed from the strain wave gear device 1. In this embodiment, the roller bearing 6 is configured to include an inner ring 9 and an outer ring 10. The inner ring 9 and the outer ring 10 are each circular raceways that hold the rollers 7 so that they can roll. As shown in Figure 2, in the initial state of the roller bearing 6, the inner ring 9 and the outer ring 10 are each arranged coaxially with the same axis (e.g., axis O1) as the central axis. Furthermore, in this embodiment, the roller bearing 6 is equipped with a cage 8A, which will be described later.

As shown in FIG. 1, the roller bearing 6 can be deflected to the contour shape of the outer peripheral surface F5 of the cam member 5 (elliptical in this embodiment) by fitting the inner ring 9 to the outer peripheral surface F5 of the cam member 5. Therefore, the flexspline 3 can also be deflected to the contour shape of the outer peripheral surface F5 of the cam member 5 (elliptical in this embodiment) by fitting the inner peripheral surface of the flexspline 3 to the outer ring 10 of the roller bearing 6.

The wave generator 4 can bend the flexspline 3 in a non-circular shape to mesh the external teeth 3a of the flexspline 3 with the internal teeth 2a of the circular spline 2. In this disclosure, the internal teeth 2a of the circular spline 2 and the external teeth 3a of the flexspline 3 mesh with each other at two positions on the long axis of the cam member 5. There is a difference in the number of teeth (2 in this embodiment) between the number of teeth ZR of the internal teeth 2a of the circular spline 2 and the number of teeth ZF of the external teeth 3a of the flexspline 3. In FIG. 1, the symbol P indicates the meshing portion between the internal teeth 2a of the circular spline 2 and the external teeth 3a of the flexspline 3. As shown in FIG. 1, in this embodiment, the meshing portion P is located on the two long axis sides of the cam member 5.

The wave gear device 1 converts the rotational motion of the wave generator 4 into wave motion of the flexspline 3 that occurs between the wave generator 4 and the circular spline 2. This allows the wave gear device 1 to decelerate the input rotation from the wave generator 4, and then output the decelerated input rotation as output rotation from the flexspline 3.

Specifically, when the cam member 5 rotates together with the input shaft 11 around the axis O1, the cam member 5 can rotate the flexspline 3 relative to the circular spline 2 via the roller bearing 6. As a result, when the cam member 5 is rotated, the meshing portion P moves in the opposite direction to the rotational direction of the cam member 5 relative to the circular spline 2. For example, when the cam member 5 rotates clockwise around the axis O1, the meshing portion P moves counterclockwise around the axis O1 relative to the circular spline 2. In this embodiment, the meshing portion P moves one mesh with the circular spline 2 in the opposite direction to the rotational direction of the cam member 5 every time the cam member 5 rotates 180 degrees around the axis O1. Therefore, according to the wave gear device 1, the input rotation from the input shaft 11 is reversed and output as a reduced rotation from the flexspline 3.

Incidentally, some conventional wave generators are known to use roller bearings in order to improve durability. However, roller bearings in wave gearing devices have the problem that stress concentrates on the axial ends of the rollers when coning occurs. Specifically, as shown in FIG. 1, when roller bearings are used in a wave gearing device, coning occurs in the flexspline 3 (a phenomenon in which the flexspline 3 is deformed into an elliptical cone shape when the wave generator 4 is inserted into the flexspline 3). Coning tends to concentrate stress on the axial ends of the outer circumferential surface of the rollers. Such stress concentration can be a factor in, for example, a decrease in the durability of the wave generator and, ultimately, the wave gearing device, an increase in energy loss (a decrease in power transmission efficiency), and the like.

Figure 3 partially and diagrammatically shows the assembled state of the rollers 7 and the cage 8A with the cage 8A flattened out.

As shown in FIG. 3, in this embodiment, the roller 7 includes a roller sliding surface Fs on the outer peripheral surface 71 of the roller 7 (hereinafter also referred to as the "roller outer peripheral surface 71"), which includes the roller axial center C of the roller outer peripheral surface 71. At least one of the two roller sliding surface regions RS of the roller sliding surface Fs, which are located on either side of the roller axial center C of the roller outer peripheral surface 71, includes a roller reduced diameter surface Fr that tapers toward the roller axial end 72 of the roller 7 (hereinafter also simply referred to as the "roller axial end 72").

In this embodiment, roller 7 is a cylindrical member extending along roller axis O7. Here, "roller axis O7" refers to the central axis of roller 7, which is surrounded by roller outer peripheral surface 71. Furthermore, "roller axial direction" refers to the direction in which roller axis O7 extends. Furthermore, "radial direction" refers to the direction perpendicular to roller axis O. Furthermore, "radial inner side" refers to the side closer to roller axis O7, and "radial outer side" refers to the side farther from roller axis O7.

In this embodiment, the roller outer peripheral surface 71 is a cylindrical surface with the roller axis O7 as the central axis. The roller 7 can rotate around the roller axis O7. In this embodiment, the roller 7 has two roller axial ends 72 spaced apart in the roller axial direction. In this embodiment, the roller axial end 72 is circular with the roller axis O7 as the center. In this embodiment, the roller outer peripheral surface 71 is continuous with each of the two roller axial ends 72.

The above-mentioned "roller axial center C" refers to the portion of the roller outer circumferential surface 71 that is located at the center between the two roller axial ends 72. In this embodiment, the diameter φ1 of the roller axial center C is the maximum diameter of the roller 7. Also, in this embodiment, the diameter φ2 of the roller axial end 72 is the minimum diameter of the roller 7. Note that, in this embodiment, the diameters φ2 of the two roller axial ends 72 are the same.

In this embodiment, the roller sliding surface Fs is the roller outer peripheral surface 71. Also, in this embodiment, the roller reduced diameter surface Fr is the sliding surface Fs excluding the center C in the roller axial direction. Specifically, the roller reduced diameter surface Fr is the roller sliding surface Fs of either one of the sliding surfaces Fs of the two roller sliding surface regions RS. In other words, in this embodiment, the roller 7 has two roller reduced diameter surfaces Fr.

In FIG. 3, a portion of the endless, band-shaped retainer 8A is shown in a flattened state. The retainer 8A has an opening A8 for partially exposing the rollers 7. The opening A8 is an opening that passes through the retainer 8A. The retainer 8A has a plurality of openings A8. The openings A8 are spaced apart in the circumferential direction of the retainer 8A.

The retainer 8A has two endless band-like circumferentially extending portions 8a spaced apart in the width direction, and a plurality of bridge portions 8b that connect the two circumferentially extending portions 8a in the width direction and are spaced apart in the circumferential direction. In this embodiment, the opening A8 is a rectangular opening defined by the two circumferentially extending portions 8a and the two bridge portions 8b that connect the two circumferentially extending portions 8a in a plan view as shown in FIG. 3.

In this embodiment, the roller outer peripheral surface 71 coincides with the roller sliding surface Fs. In this embodiment, the roller sliding surface Fs is a surface that can be in sliding contact with each of the cage 8A, the inner ring 9, and the outer ring 10.

In this embodiment, the roller 7 has two roller reduced diameter surfaces Fr. Each of the two roller reduced diameter surfaces Fr tapers toward the roller axial end 72.

In this embodiment, the roller 7 is a so-called entasis-shaped cylindrical member in which the roller outer peripheral surface 71 is bulged outward in the radial direction. In this embodiment, the roller outer peripheral surface 71 bulges outward in the radial direction so that the roller axial center C of the roller outer peripheral surface 71 has a maximum diameter. In other words, in this embodiment, the roller sliding surface Fs bulges outward in the radial direction so that the roller axial center C of the roller outer peripheral surface 71 has a maximum diameter. Therefore, in this embodiment, the roller sliding surfaces Fs of the two roller sliding surface regions RS are each tapered toward the roller axial end 72. In other words, in this embodiment, the roller 7 has two reduced diameter surfaces Fr sandwiching the roller axial center C of the roller outer peripheral surface 71.

In addition, in this embodiment, the retainer 8A holds the roller axial end of the roller outer peripheral surface 71. In this embodiment, the roller axial end of the roller outer peripheral surface 71 is the roller axial end of the roller sliding surface Fs. In other words, in this embodiment, the roller axial end of the roller outer peripheral surface 71 is the roller axial end 73 of the roller reduced diameter surface Fr. That is, in this embodiment, the retainer 8A holds the roller reduced diameter surface Fr of the roller sliding surface Fs.

In addition, in this embodiment, the retainer 8A has pockets 81 that rotatably hold the rollers 7. In this embodiment, the retainer 8A has two pockets 81 to correspond to one roller 7. The two pockets 81 are arranged at an interval in the width direction of the retainer 8A. The two pockets 81 are connected to the opening A8. In this embodiment, the pockets 81 are formed in the circumferentially extending portion 8a of the retainer 8A. As a result, in this embodiment, the retainer 8A holds the roller axial end of the roller outer circumferential surface 71, i.e., the two roller reduced diameter surfaces Fr, for one roller 7.

Figure 4 is a cross-sectional view taken along line X-X in Figure 3. The X-X cross section is a cross section including the roller axis O7. In Figure 4, the symbol C indicates the center C in the roller axis direction.

In this embodiment, the roller reduced diameter surface Fr is a curved surface that curves radially outward.

In this embodiment, the roller outer peripheral surface 71 has a so-called entasis-shaped outer shape. In this embodiment, the roller outer peripheral surface 71 is curved radially outward so that the roller axial center C of the roller outer peripheral surface 71 has the maximum diameter. In other words, in this embodiment, the roller sliding surface Fs is a curved surface that is curved radially outward so that the roller axial center C of the roller outer peripheral surface 71 has the maximum diameter. In this embodiment, the roller reduced diameter surface Fr is disposed at two positions in the roller axial direction sandwiching the roller axial center C. As a result, in one roller 7 according to this embodiment, the two roller reduced diameter surfaces Fr are each a bowl-shaped curved surface that is curved radially outward. In this embodiment, the roller reduced diameter surface Fr tapers from the roller axial center C of the roller outer peripheral surface 71 as a base point, so as to approach the roller axis O7 as it moves from the roller axial center C of the roller outer peripheral surface 71 to the roller axial end 72.

In this embodiment, the roller sliding surface Fs is a curved surface that has a maximum diameter at the center C of the roller outer peripheral surface 71 in the roller axis direction and is curved so as to be convex toward the radially outward direction. Referring to FIG. 4, in this embodiment, the cross-sectional contour line that forms the roller sliding surface Fs is a curve that is curved toward the radially outward direction so that the center C of the roller outer peripheral surface 71 in the roller axis direction has a maximum diameter in the X-X cross section including the roller axis O7. Specifically, as shown in FIG. 4, the cross-sectional contour line that forms the roller sliding surface Fs is a curve with a radius of curvature R7 that is perpendicular to the roller axis O7 and has a center OR on a radial axis that passes through the center C of the roller outer peripheral surface 71 in the roller axis direction. Note that the curved shape may be a polynomial function of a second degree, a third degree, an ellipse, a trigonometric function, a hyperbola, or a logarithmic curve, in addition to a circle. Furthermore, as an embodiment, the radius of curvature R7 may be infinite (i.e., a straight line). As a result, in this embodiment, the roller sliding surface Fs has a maximum diameter at the center C of the roller axial direction of the outer circumferential surface 71, and is a curved surface that is convex radially outward, or a polygonal surface.

In this embodiment, the roller axial center C of the outer peripheral surface 71 is a linear portion that extends annularly around the roller axis O7. However, the roller outer peripheral surface 71 can be configured as a uniform diameter surface so that a certain range from the roller axial center C of the roller outer peripheral surface 71 to the middle of the roller axial end 72 is straight, and the roller axial end of the uniform diameter surface from the roller axial end 72 to the roller axial end 72 can be configured as a roller reduced diameter surface Fr.

The retainer 8A has a pocket 81 in each of the two circumferentially extending portions 8a for rotatably retaining the rollers 7. In this embodiment, the pocket 81 is formed on the inner peripheral surface of the retainer 8A (the peripheral surface on the side of the cam member 5). Furthermore, the pocket 81 is connected in the width direction to the opening A8 formed in the retainer 8A. In other words, the pocket 81 is a recess that opens to the opening A8 of the retainer 8A in the width direction of the retainer 8A.

In this embodiment, the pocket 81 is formed by a bottom surface 81a and a side surface 81b. The bottom surface 81a of the pocket 81 slidably holds the roller outer peripheral surface 71. In this embodiment, the bottom surface 81a of the pocket 81 slidably holds the roller axial end 73 of the roller reduced diameter surface Fr. The roller axial end 73 of the roller reduced diameter surface Fr is connected to the roller axial end 72. In addition, the side surface 81b of the pocket 81 slidably holds the roller axial end 72. As a result, the retainer 8A can rotatably protrude the sliding surface Fs excluding the roller axial end 73 of the roller reduced diameter surface Fr to the outer peripheral surface of the retainer 8A (the peripheral surface on the side of the flexspline 3) through the opening A8 while suppressing the roller 7 from falling out to the outside of the width direction of the retainer 8A.

Figure 5 shows a front view of Figure 3. Here, the front view of Figure 3 is a view showing the assembled state of the roller 7 and the cage 8A from the width direction of the cage 8A. As shown by the solid line in Figure 4 and the dashed line in Figure 5, the pocket 81 has a curved shape that matches the outer shape of the roller axial direction end 73 of the roller reduced diameter surface Fr. This allows the roller 7 to rotate smoothly around the roller axis O7 inside the pocket 81.

In this embodiment, the roller axial direction end 73 of the roller reduced diameter surface Fr can slide against the inner surface of the pocket 81 of the retainer 8A so that the roller 7 can rotate around the roller axis O7. In addition, in this embodiment, the part of the roller outer peripheral surface 71 that protrudes from the opening A8 of the retainer 8A can be slidably contacted with the inner peripheral surface of the outer ring 10 as the roller sliding surface Fs or as part of the roller reduced diameter surface Fr. Furthermore, in this embodiment, the part of the roller outer peripheral surface 71 opposite to the side held by the retainer 8A can be slidably contacted with the outer peripheral surface of the inner ring 9 as the roller sliding surface Fs or as part of the roller reduced diameter surface Fr. As a result, in this embodiment, the roller 7 can slidably roll between the inner ring 9 and the outer ring 10 while contacting each of the retainer 8A, the inner ring 9, and the outer ring 10.

Figure 6A is a cross-sectional view showing a schematic diagram of the strain wave gear device 1. In Figure 6A, the strain wave gear device 1 in Figure 1 is shown in a cross section including the axis O1 and the major axis of the cam member 5. However, in Figure 6A, the cage 8 is omitted.

The flexspline 3 of the strain wave gear device is a cup-shaped member having an opening A3. Referring to FIG. 6A, the peripheral wall 3b of the flexspline 3 is bent at a bent portion 3p so as to form a portion 3b1 that holds the roller bearing 6 after assembly.

However, when a typical roller with a straight outer peripheral surface is used, as shown in FIG. 6B, a large load is applied to the axial end of the roller bearing 6 on the side of the bottom 3c of the flexspline 3 in the radial direction inward of the axis O1. For this reason, when coning occurs, a large stress is concentrated on the axial end of the roller outer peripheral surface 71 on the side of the bottom 3c of the flexspline 3, out of the two axial ends of the roller. Such stress concentration can be a factor in, for example, a decrease in the durability of the wave generator and ultimately the wave gear device, an increase in energy loss (a decrease in power transmission efficiency), etc.

In contrast, in this embodiment, the roller axial end of the roller outer peripheral surface 71 is configured with a roller reduced diameter surface Fr that tapers toward the roller axial end 72. In this case, the flexspline 3 can deform along the roller reduced diameter surface Fr relative to the roller 7. In other words, the roller 7 according to this embodiment maintains the shape of the flexspline 3 in a state close to the state before assembly, as shown in area Z in FIG. 6A. That is, the roller 7 according to this embodiment reduces stress concentration that can occur at the roller axial end of the roller outer peripheral surface 71 due to the occurrence of coning. Therefore, the roller 7 according to this embodiment improves the durability of the wave generator 4 and thus the wave gear device 1, and improves energy efficiency (power transmission efficiency), for example.

On the other hand, FIG. 6B is a cross-sectional view showing a conventional wave gear device in a simplified manner. In FIG. 6B, the conventional wave gear device is shown in a cross section including the axis O1 and the major axis of the cam member 5. However, FIG. 6B also omits the cage that holds the rollers 70.

The roller 70 is a cylindrical member whose outer peripheral surface is a straight outer peripheral surface along the roller axis O7 (an outer peripheral surface of equal diameter along the roller axis O7). In this case, as shown in area Z in FIG. 6B, the straight outer peripheral surface of the roller 70 causes the peripheral wall 3b of the flexspline 3 to protrude radially outward from the bent portion 3p of the flexspline 3 on the long axis side of the cam member 2. Therefore, in conventional wave generators and, in turn, conventional wave gear devices, there are problems such as reduced durability of the wave generator and, in turn, increased energy loss (reduced power transmission efficiency) due to stress concentration that can occur due to coning.

In addition, in the wave generator 4 according to this embodiment, and in the wave gear device 1 according to this embodiment, the roller diameter reduction surface Fr is a curved surface that curves radially outward. In this case, it is more effective in reducing stress concentration caused by coning.

In particular, in the wave generator 4 according to this embodiment, and in the wave gear device 1 according to this embodiment, the roller sliding surface Fs is a curved surface that has a maximum diameter at the center C in the roller axial direction of the roller outer peripheral surface 71 and is curved so as to be convex toward the radially outward direction. In this case, it is even more effective in reducing stress concentration caused by coning.

By the way, when using roller bearings in a wave generator, and therefore in a wave gear device, it is possible to obtain a large load capacity in a limited space by increasing the number of rollers and packing them closer together.

However, in the case of conventional wave generators, and therefore wave gear devices, there is room for improvement in the arrangement of the rollers in order to increase the number of rollers. Also, in the case of conventional wave generators, and therefore wave gear devices, there is room for improvement in the arrangement of the rollers in order to increase the number of rollers when the rollers are held by a cage. For example, conventional cages need to leave a certain amount of space between the rollers in order to hold the rolling direction ends of the outer circumferential surfaces of the rollers.

In contrast, according to the wave generator 4 of this embodiment, and thus the wave gear device 1 of this embodiment, the retainer 8A retains the roller axial end 73 of the roller reduced diameter surface Fr. When retaining the roller axial end 73 of the roller reduced diameter surface Fr, it is not necessary to retain the rolling direction end of the roller outer circumferential surface 71. In this case, the interval in the rolling direction between adjacent rollers 7 in the circumferential direction around the axis O1 can be narrowed, and the rollers 7 can be positioned close to each other in the rolling direction. Therefore, according to the wave generator 4 and thus the wave gear device 1, the rollers 7 can be efficiently packed together, thereby efficiently increasing the number of the rollers 7. As a result, according to the wave generator 4 of this embodiment, and thus the wave gear device 1 of this embodiment, a large load capacity can be obtained within a limited space. Furthermore, according to the wave generator 4 and thus the wave gear device 1, the provision of the retainer 8A makes it possible to suppress the occurrence of skew (tilt of the rollers).

It is preferable that the reference diameter φA1 of the roller 7 and the diameter φA2 of the roller axial end of the roller reduced diameter surface Fr satisfy the following condition (1).

[Equation 1]
60≦(φA2/φA1)×100≦99...(1)

Here, the reference diameter φA1 is the maximum diameter of the roller 7. In this embodiment, the reference diameter φA1 is the diameter φ1 of the roller axial center C of the roller outer peripheral surface 71. Also, in this embodiment, the diameter φA2 of the axial end of the roller reduced diameter surface Fr is the diameter φ2 of the roller axial end 72 of the roller 7.

When the above condition (1) is satisfied, the inclination angle of the roller reduced diameter surface Fr relative to the roller axis O7 (axis O1) or the inclination angle of the roller sliding surface Fs relative to the roller axis O7 (axis O1) is greater than the inclination angle of the flexspline 3 relative to the axis O1 (roller axis O7) on the long axis side of the cam member 5 when the flexspline 3 in a perfectly circular state protrudes radially outward from the bent portion 3p of the peripheral wall 3b on the long axis side of the cam member 5. Therefore, when the above condition (1) is satisfied, if coning is likely to occur in the flexspline 3, the flexspline 3 or the outer ring 10 can be inclined along the roller reduced diameter surface Fr. As a result, according to this embodiment, stress concentration due to coning can be easily and efficiently suppressed.

Figure 7 is a plan view partially and diagrammatically showing the assembled state of the rollers 7 of the roller bearing of the wave generator 4 according to the second embodiment of the present invention, and the retainer 8A that holds the rollers 7, with the retainer 8A flattened out. Figure 8 is a front view of Figure 7. Figure 9 is a Y-Y cross-sectional view of Figure 7.

In this embodiment, the retainer 8A is a modified example of the retainer 8A described in the first embodiment. In this embodiment, the retainer 8A holds the rolling direction sliding portion 74 of the roller sliding surface Fs in addition to the roller axial end portion 73 of the roller reduced diameter surface Fr. Here, the rolling direction sliding portion 74 of the roller sliding surface Fs is a radial portion extending in the roller width direction, including the roller axial center portion C of the roller outer peripheral surface 71. In this embodiment, the rolling direction sliding portion 74 of the roller sliding surface Fs is arranged at two positions in the circumferential direction of the retainer 8A, sandwiching the roller axis O7, in a plan view as shown in FIG. In this embodiment, the rolling direction sliding portions 74 of the two roller outer peripheral surfaces 71 are each held by the bridge portion 8b of the retainer 8. In this case, the number of rollers 7 can be more efficiently increased by more efficiently packing the rollers 7 adjacent to each other in the circumferential direction around the axis O1. As a result, the wave generator 4 of this embodiment, and therefore the wave gear device 1 of this embodiment, can achieve a greater load capacity within a limited space.

In FIG. 7, the symbol ΔC denotes the distance between adjacent rollers 7 in the circumferential direction around the axis O1. The distances ΔC between the rollers 7 can be the same or different. The symbol L8 denotes the circumferential length of the suspension portion 8b. The distance ΔC between the rollers 7 can be adjusted, for example, by appropriately setting the circumferential length L8 of the suspension portion 8b. For example, the distance ΔC between the rollers 7 can be adjusted to the limit where adjacent rollers 7 do not come into contact with each other, as shown in FIG. 8.

As shown in FIG. 9, in this embodiment, the rolling direction sliding portion 74 of the roller sliding surface Fs is the center C of the roller sliding surface Fs in the roller axis direction. Therefore, in this embodiment, the rolling direction sliding portion 74 of the roller outer peripheral surface 71 is in point contact with the radially inner edge of the circumferential end edge of the suspension portion 8b of the retainer 8A. However, the rolling direction sliding portion 74 of the roller sliding surface Fs can be in line contact along the roller axis O7, as described below. Alternatively, it can be in surface contact by being rotatably accommodated in a pocket 82 formed in the suspension portion 8b of the retainer 8A, as described below.

The roller bearing 6 according to the first and second embodiments described above has been described as having only one retainer 8A that holds the roller 7 from the flexspline 3 side to the cam member 5 side, but the roller bearing 6 can be configured with multiple retainers 8.

Figure 10 is a partial and schematic front view of a roller bearing of a wave generator 4 according to a third embodiment of the present invention, showing an assembled state of the rollers 7 of the roller bearing and the cages 8A, 8B that hold the rollers 7, with the cages 8A, 8B flattened out. Figure 11 is a cross-sectional view taken along line X-X in Figure 10. Figure 12 is a cross-sectional view showing the assembled state of Figure 10, which corresponds to the cross-section taken along line Y-Y in Figure 7.

In this embodiment, the roller bearing includes a retainer 8A that holds the roller 7 from the flexspline 3 side to the cam member 5 side, as well as a retainer 8B that holds the roller 7 from the cam member 5 side to the flexspline 3 side.

As shown in FIG. 11, in the retainer 8B, the pocket 81 is formed on the outer peripheral surface of the retainer 8B (the peripheral surface on the side of the flexspline 3). Furthermore, in the retainer 8B, the pocket 81 is connected in the width direction to the opening A8 formed in the retainer 8B. That is, the pocket 81 is a recess that opens to the opening A8 of the retainer 8B in the width direction of the retainer 8B. As with the retainer 8A, the retainer 8B can also rotatably protrude the sliding surface Fs, excluding the roller axial end 73 of the roller reduced diameter surface Fr, through the opening A8 to the inner peripheral surface of the retainer 8B (the peripheral surface on the side of the cam member 5), while suppressing the roller 7 from falling out to the outside in the width direction of the retainer 8B.

In this embodiment, the roller bearing is configured with multiple retainers 8A, 8B. In this case, the occurrence of skew can be further suppressed.

As shown in FIG. 12, in this embodiment, the roller sliding portion 74 of the roller sliding surface Fs of the cage 8A is in point contact with the radially inner edge of the circumferential edge of the suspension portion 8b of the cage 8A. Furthermore, in this embodiment, the roller sliding portion 74 of the roller sliding surface Fs of the cage 8B can also be in point contact with the radially outer edge of the circumferential edge of the suspension portion 8b of the cage 8B. As a result, according to this embodiment, the number of rollers can be increased more efficiently by packing the rollers 7 more efficiently, as in the case of a single cage 8. Furthermore, according to this embodiment, the rollers 7 can be handled as one unit together with the two cages 8A and 8B.

Figure 13 is a front view that shows a roller bearing 6 of a wave generator 4 according to a fourth embodiment of the present invention. Figure 14 is a plan view that shows, partially and generally, the assembled state of the rollers 7 of the roller bearing of Figure 13 and the cage 8C that holds the rollers 7, with the cage 8C flattened out. Figure 15 is a cross-sectional view taken along line X-X of Figure 14. Figure 16 is a front view of Figure 14. Figure 17 is a cross-sectional view taken along line Y-Y of Figure 14.

As shown in FIG. 13, the circumferentially extending portion 8a of the retainer 8C is configured like a wall that annularly covers the axial side of the rollers 7. As shown in FIG. 14, the bridge portion 8b of the retainer 8C extends between the two circumferentially extending portions 8a in the width direction of the retainer 8C and is connected to each of the two circumferentially extending portions 8a.

The pocket 81 of the retainer 8C is constituted by a through hole formed in the circumferentially extending portion 8a of the retainer 8C. The through hole penetrates the circumferentially extending portion 8a of the retainer 8C in the width direction of the retainer 8C. In this embodiment, as shown in FIG. 15, the pocket 81 has a curved shape that matches the outer shape of the roller axial end 73 of the roller reduced diameter surface Fr. This allows the roller 7 to rotate smoothly around the roller axis O7 inside the pocket 81.

As shown in FIG. 16, in this embodiment, the portion of the roller outer peripheral surface 71 that protrudes radially outward from the opening A8 can be brought into sliding contact with the inner peripheral surface of the outer ring 10. Also, in this embodiment, the portion of the roller outer peripheral surface 71 that protrudes radially inward from the opening A8 can be brought into sliding contact with the outer peripheral surface of the inner ring 9. In this embodiment, the suspension parts 8b of the retainer 8C are arranged at intervals in the circumferential direction at a radially outer position (flexspline 3 side) and a radially inner position (cam member 5 side) as shown in FIG. 17. The suspension parts 8b arranged radially outward define the radially outer opening A8 between the suspension parts 8b in the circumferential direction. The suspension parts 8b arranged radially inward define the radially inner opening A8 between the suspension parts 8b in the circumferential direction.

The retainer 8C according to this embodiment is a tubular retainer with a rectangular cross-sectional shape. The retainer 8C allows a plurality of rollers 7 to be rotatably housed inside the retainer 8C. In this case, the rollers 7 and the retainer 8C can be treated as a single unit in which the rollers 7 are housed inside the retainer 8C.

The pockets 81 of the retainer 8 can also be arranged in the circumferential direction of the retainer 8.

Figure 18 is a front view that shows a roller bearing 6 of a wave generator 4 according to a fifth embodiment of the present invention. Figure 19 is a plan view that shows, partially and generally, the assembled state of the rollers 7 of the roller bearing of Figure 18 and the retainer 8D that holds the rollers 7, with the retainer 8D flattened out. Figure 20 is a cross-sectional view taken along line X-X of Figure 19. Figure 21 is a front view of Figure 19. Figure 22 is a cross-sectional view taken along line Y-Y of Figure 19.

As shown in FIG. 18, the retainer 8D is open on one axial side of the opening A8. In this embodiment, the opening A8 is open on one widthwise side of the retainer 8D as shown in FIG. 19. One of the two roller axial ends 72 is held in the width direction by the widthwise inner surface 83 of the circumferentially extending portion 8a of the retainer 8D as shown in FIG. 20.

In this embodiment, the retainer 8D holds the rolling direction sliding portion 74 of the roller sliding surface Fs. In this case, the holding force of the retainer 8D is larger than that when the roller axial end 73 of the roller sliding surface Fs is held. In addition, generally, the axial length of the roller is larger than the diameter of the roller. For this reason, even if one of the two circumferential extending portions 8a of the retainer 8D is released, as in the case of the retainer 8D, the holding force is greater when the rolling direction sliding portion 74 of the roller sliding surface Fs is held, so that the holding force is improved compared to when the roller axial end 73 of the roller sliding surface Fs is held. Therefore, according to this embodiment, the retainer 8D can be configured to increase the holding force of the roller 7 by increasing the holding area of the roller sliding surface Fs while keeping the distance of the roller 7 the same, compared to other embodiments.

As shown in FIG. 21, for example, the retainer 8D has pockets 82 that rotatably hold the rollers 7. In this embodiment, the pockets 82 are formed on the inner peripheral surface (the peripheral surface on the cam member 5 side) of the retainer 8D. In this embodiment, the pockets 82 hold the rolling direction sliding portion 74 of the roller sliding surface Fs. The pockets 82 are arranged at intervals in the circumferential direction of the retainer 8D. In this embodiment, the retainer 8D has a pair of pockets 82 for each roller 7, arranged in the circumferential direction on either side of the opening A8. Each of the pair of pockets 82 is connected to the same opening A8. In this embodiment, the pockets 82 are formed on the inner surface (the surface on the cam member 5 side) of the bridge portion 8b of the retainer 8D.

21, in this embodiment, the portion of the roller outer peripheral surface 71 that protrudes from the radially outer side of the retainer 8D can be in slidable contact with the inner peripheral surface of the outer ring 10 as the roller sliding surface Fs or as part of the roller reduced diameter surface Fr. Also, in this embodiment, the portion of the roller outer peripheral surface 71 that protrudes from the radially inner side of the retainer 8D can be in slidable contact with the outer peripheral surface of the inner ring 9 as the roller sliding surface Fs or as part of the roller reduced diameter surface Fr.

As shown in FIG. 22, the pocket 82 has a curved shape that matches the outer shape of the rolling direction sliding portion 74 of the roller sliding surface Fs. This allows the roller 7 to rotate smoothly around the axis O7 inside the pocket 81.

The pocket 82 can be formed by closing an open portion formed in the width direction of the retainer 8D. In this case, the open portion formed in the width direction of the retainer 8D can be closed by two circumferentially extending portions 8a of the retainer 8D. The roller bearing can also be configured to include multiple retainers 8D.

Figure 23 is a plan view partially and diagrammatically showing the assembled state of rollers 7 of a roller bearing of a wave generator according to a sixth embodiment of the present invention, and a retainer 8E that holds the rollers 7, with the retainer 8E flattened out. Figure 24 is a cross-sectional view taken along line X-X in Figure 23. Figure 25 is a front view of Figure 23. Figure 26 is a cross-sectional view taken along line Y-Y in Figure 23.

As shown in FIG. 23, the opening A8 of the retainer 8E is a rectangular opening defined by two circumferentially extending portions 8a and two bridge portions 8b. In this embodiment, the opening A8 has a circumferential length shorter than the roller axial ends 72 of the rollers 7. In this embodiment, the two roller axial ends 72 of the rollers 7 are each held in the width direction by the widthwise inner surfaces 83 of the circumferentially extending portions 8a of the retainer 8E, as shown in FIG. 24.

In this embodiment, the roller bearing includes a retainer 8E (hereinafter also referred to as the "radial outer retainer 8E") that holds the roller 7 from the flexspline 3 side to the cam member 5 side, as well as a retainer 8E (hereinafter also referred to as the "radial inner retainer 8E") that holds the roller 7 from the cam member 5 side to the flexspline 3 side.

As shown in FIG. 25, in the radially outer retainer 8E, the pocket 82 is a circumferential side edge of the bridge portion 8b of the retainer 8E that is formed on the inner peripheral surface of the radially outer retainer 8E (the peripheral surface on the side of the cam member 5) and forms the widthwise contour of the opening A8. As shown in FIG. 26, the circumferential side edge of the bridge portion 8b of the radially outer retainer 8E is configured by an inclined surface when viewed in the width direction of the retainer 8E (when viewed from the width direction of the retainer 8E).

As shown in FIG. 26, the pocket 82 of the radially outer retainer 8E is an inclined surface that inclines from the radially outer side toward the radially inner side so that the circumferential length of the opening A8 increases. In the radially outer retainer 8E, the pocket 82 holds the roller 8 rotatably by making line contact with the radial portion 74 of the roller sliding surface Fs along the width direction on the inner peripheral surface side of the bridge portion 8b.

In addition, in the radially inner retainer 8E, the pocket 82 is a circumferential side edge of the suspension portion 8b of the retainer 8E that is formed on the outer peripheral surface of the radially inner retainer 8E (the peripheral surface on the side of the flexspline 3) and forms the widthwise contour of the opening A8. As shown in FIG. 26, the circumferential side edge of the suspension portion 8b of the retainer 8E is configured by an inclined surface when viewed in the width direction of the retainer 8E.

As shown in FIG. 26, the pocket 82 of the radially inner retainer 8E is an inclined surface that inclines from the radially outer side toward the radially inner side so that the circumferential length of the opening A8 decreases. In the radially inner retainer 8E, the pocket 82 can rotatably retain the roller 8 by making line contact with the radial portion 74 of the roller sliding surface Fs along the width direction on the outer circumferential surface side of the bridge portion 8b.

Figure 27 is a partial and schematic front view of a roller bearing of a wave generator according to a seventh embodiment of the present invention, showing the assembled state of the roller 7 of the roller bearing and the cage 8F that holds the roller 7, with the cage 8F flattened out. Figure 28 is a cross-sectional view taken along line X-X of Figure 27.

In this embodiment, the roller 7 can rotate around the roller axis O7. In this embodiment, the roller 7 includes a roller body 7a and two shafts 7b connected to the roller axial end of the roller body 7a. In this embodiment, the roller outer peripheral surface 71 of the roller 7 is composed of the roller body outer peripheral surface 75 of the roller body 6a and the shaft outer peripheral surfaces 76 of the two shafts 7b. The roller body outer peripheral surface 75 and the shaft outer peripheral surface 76 each constitute a roller sliding surface Fs. In this embodiment, the roller body outer peripheral surface 75 has a so-called entasis-shaped cylindrical shape in which the roller axial direction center C of the roller outer peripheral surface 71 is bulged outward in the radial direction. In this embodiment, the roller body outer peripheral surface 75 bulges outward in the radial direction so that the roller axial direction center C of the roller outer peripheral surface 71 has a maximum diameter. In other words, in this embodiment, the roller sliding surface Fs of the roller body 7a bulges outward in the radial direction so that the roller axial direction center C of the roller outer peripheral surface 71 has a maximum diameter. For this reason, in this embodiment, the roller sliding surfaces Fs of the two roller sliding surface regions RS of the roller body 7a each taper toward the roller axial end 72. In other words, in this embodiment, the roller 7 also has two reduced diameter surfaces Fr on either side of the roller axial center C of the roller outer peripheral surface 71, as in the other embodiments.

In FIG. 28, the symbol φ1 is the diameter of the roller axial center of the roller body outer peripheral surface 75. In this embodiment, the diameter φ1 is the diameter of the roller axial center C of the roller outer peripheral surface 71. Furthermore, the symbol φ2 is the diameter of the roller axial end 72 of the roller 7. In this embodiment, the roller axial end 72 of the roller 7 is the roller axial end of the shaft 7b. Furthermore, in this embodiment, the symbol φ3 is the diameter of the roller axial end of the roller body 7a. In this embodiment, the diameters φ3 of the two roller axial ends of the roller body 7a are the same. Furthermore, in this embodiment, the diameters φ2 of the two roller axial ends 72 of the roller 7 are the same.

In this embodiment, the pocket 81 of the retainer 8F holds the shaft outer circumferential surface 76 of the shaft 7b as the roller axial end of the roller outer circumferential surface 71. This allows the retainer 8F to prevent the roller 7 from falling out to the outside in the width direction of the retainer 8F, while allowing the roller sliding surface Fs of the roller body 7a, excluding the shaft outer circumferential surface 76 of the shaft 7b, to rotatably protrude through the opening A8 to the outer circumferential surface of the retainer 8F (the peripheral surface on the side of the flexspline 3).

In the roller bearing according to this embodiment, the roller axial end of the roller body outer circumferential surface 75 is configured with a tapered diameter surface Fr that tapers toward the roller axial end 72. In this case, the flexspline 3 can be deformed along the roller reduced diameter surface Fr of the roller body 7a with respect to the roller 7. In other words, the roller 7 according to this embodiment maintains the shape of the flexspline 3 in a state close to the state before assembly, as shown in area Z in FIG. 6A. That is, the roller 7 according to this embodiment reduces stress concentration that may occur at the roller axial end of the roller outer circumferential surface 71 due to the occurrence of coning. Therefore, the roller 7 according to this embodiment, like the roller 7 according to other embodiments not having the shaft 7b, improves the durability of the wave generator 4 and thus the wave gear device 1, and improves the energy efficiency (power transmission efficiency).

In addition, according to this embodiment, the roller sliding surface Fs can also be provided on the outer circumferential surface 76 of the shaft 7b.

In this embodiment, the retainer 8 is made of resin or light metal. The retainer 8 can be made of a resin material such as a flexible light metal alloy or a light metal alone, for example, an aluminum alloy, a magnesium alloy, a titanium alloy, or an element thereof, or an engineering plastic such as PEEK (polyether ether ketone), PPS (polyphenylene sulfide), or POM (polyoxymethylene). When the retainer 8 is made of resin or light metal, the wave generator 4, and therefore the wave gear device 1, can be easily manufactured by using existing materials.

In this embodiment, the roller bearing 6 is configured to include an inner ring 9 and an outer ring 10. That is, in this embodiment, the roller bearing 6 is a so-called raced bearing that includes the races (races) of the inner ring 9 and the outer ring 10. When the roller bearing 7 includes the inner ring 9, the radially inner portion (cam member 5 side) of the roller 7 rolls on the inner peripheral surface (raceway surface) of the inner ring 9. In this case, the roller 7 can be smoothly rolled on the cam member 5 side. When the roller bearing 7 includes the outer ring 10, the radially outer portion (flexspline 3 side) of the roller 7 rolls on the inner peripheral surface (raceway surface) of the outer ring 10. In this case, the roller 7 can be smoothly rolled on the flexspline 3 side. In particular, when the roller bearing 6 includes the inner ring 9 and the outer ring 10, the roller bearing 6 can be easily handled as an independent roller bearing. However, the roller bearing 6 can be configured to include at least one of the inner ring 9 and the outer ring 10.

On the other hand, the roller bearing 6 can also be configured so that the rollers 7 are in contact with the cam member 5 and the flexspline 3. In this case, the roller bearing 6 does not have races (raceway rings) for the inner ring 9 and the outer ring 10. A roller bearing 6 configured in this way is called, for example, a raceless bearing. In this case, the wave generator 4, and therefore the wave gear device 1, can be made smaller.

The above is merely an exemplary embodiment of the present invention, and various modifications are possible within the scope of the claims. For example, the reduced diameter surface Fr may be at least one of the two roller sliding surfaces Fs sandwiching the roller axial center C of the roller outer peripheral surface 71. For example, the reduced diameter surface Fr may be only the side of the two roller sliding surfaces Fs sandwiching the roller axial center C of the roller outer peripheral surface 71 that is closer to the bottom 3c of the flexspline 3. In addition, in each of the above-mentioned embodiments, the roller reduced diameter surface Fr is a curved surface that curves radially outward, but it can be a flat surface (so-called tapered surface) that linearly tapers at a constant inclination toward the roller axial end 72. In the above description, the power transmission path of the wave gear device 1 has the wave generator 4 as an input and the flexspline 3 as an output, but this is not limited to this. For example, the power transmission path of the wave gear device 1 may have the flexspline 3 as an input and the wave generator 4 as an output. In addition, the configurations (items) used in each of the above-mentioned embodiments can be added to or substituted for each other.

DESCRIPTION OF SYMBOLS 1: Strain wave gear device, 2: Circular spline, 2a: Internal teeth, 3: Flexspline, 3a: External teeth, 3b: Cylindrical portion, 3c: Bottom portion, 4: Wave generator, 5: Cam member, 6: Roller bearing, 7: Roller, 7a: Roller body, 7b: Shaft, 71: Roller outer peripheral surface (roller outer peripheral surface), 72: Roller axial end of roller, 73: Roller axial end of roller outer peripheral surface, 74: Rolling direction sliding portion of roller sliding surface, 75: Roller body outer peripheral surface of roller body, 76: Shaft outer peripheral surface of shaft, 8: Cage, 8a: Circumferential extension portion, 8b: Bridge portion, 8A to 8F: Cage, 81: Pocket, 82: Pocket, 83: Width direction inner surface of circumferential extension portion of cage, 9: Inner ring, 10: Outer ring, 11: input shaft, C: axial center of outer peripheral surface of roller, A8: opening of cage, Fr: roller reduced diameter surface, Fs: roller sliding surface, O1: central axis of strain wave gear device, O7: central axis of roller, φA1: reference diameter of roller, φA2: diameter of roller axial end of reduced diameter surface, φ1: diameter of roller axial center of outer peripheral surface of roller, φ2: diameter of roller axial end, φ3: diameter of roller axial end of outer peripheral surface of roller body

Claims (8)

A wave generator for a wave gear device comprising a cam member having a non-circular contour and a roller bearing mounted on an outer peripheral surface of the cam member,
a roller of the roller bearing includes, on an outer peripheral surface of the roller, a roller sliding surface including a center portion of the outer peripheral surface in a roller axial direction;
the outer peripheral surface of the roller is curved radially outward so that the center of the outer peripheral surface in the roller axial direction has a maximum diameter, so that the roller sliding surface is a curved surface that is convex radially outward so that the center of the outer peripheral surface in the roller axial direction has a maximum diameter,
At least one of two roller sliding surface regions of the roller sliding surface, which are disposed on either side of a center portion in the roller axial direction of the outer peripheral surface of the roller, includes a roller reduced diameter surface tapered toward an end in the roller axial direction of the roller, and the roller reduced diameter surface is a curved surface curved toward the radially outward side,
a reference diameter φA1 of the roller and a diameter φA2 of the roller axial direction end of the reduced diameter surface of the roller satisfy the condition 60≦(φA2/φA1)×100≦99,
a wave generator for a wave gear device in which the inclination angle of the roller reduced diameter surface with respect to the roller axis or the inclination angle of the roller sliding surface with respect to the roller axis is greater than the inclination angle of the flexspline with respect to the roller axis on the long axis side of the cam member when the flexspline in a perfectly circular state protrudes radially outward from a bent portion of the peripheral wall of the flexspline as a base point on the long axis side of the cam member, and when coning may occur in the flexspline, the flexspline or the outer ring of the roller bearing can be inclined along the roller reduced diameter surface . The wave generator of claim 1, wherein the roller bearing is provided with a retainer that holds the rollers, and the retainer holds the axial end of the outer circumferential surface of the rollers. The wave generator of the wave gear device described in claim 1, wherein the roller bearing is provided with a retainer that holds the rollers, and the retainer holds the rolling direction sliding portion of the roller sliding surface Fs. 4. The wave generator of claim 2 , wherein the roller bearing comprises a plurality of the cages. 4. The wave generator of a wave gear device according to claim 2 , wherein the cage is made of resin or light metal. The wave generator of claim 1, wherein the roller bearing is configured to have at least one of an inner ring and an outer ring. The wave generator of claim 1, wherein the roller bearing is configured to bring the rollers into contact with the cam member and the flexspline. A wave gear device comprising a circular spline, a flexspline, and the wave generator described in claim 1.

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