JP2021025614A - Ball bearing - Google Patents

Abstract

To provide a ball bearing for a wave-motion gear reduction gear which can secure lubrication performance while preventing the intrusion of foreign matter.SOLUTION: A ball bearing 1 interposed between an elliptical cam 4 of a wave-motion gear reduction gear and a flexible spline 3 comprises: an inner ring 5 which is deformed into an elliptical shape by fitment with the cam 4; an outer ring 6 elliptically deformed with the elliptical deformation of the inner ring 5; and an annular shield 11 for covering an opening at one side of a bearing space in an axial direction between the inner ring 5 and the outer ring 6. The shield 11 is located at an opening edge 14 side of the flexible spline 3, an inner ring part 11b of the shield 11 is fit into a seal fitting groove 4b of the cam 4 by pressure-insertion, and the shield 11 is brought into a state of rotating integrally with the cam 4. A labyrinth seal 30 is formed between an outer ring part 11c of the shield 11 and an internal peripheral part of the outer ring 6.SELECTED DRAWING: Figure 1

Description

The present invention relates to ball bearings incorporated in a strain wave gearing reducer.

The strain wave gearing reducer includes a circular spline, a flexspline, an elliptical cam, and a ball bearing interposed between the flexspline and the elliptical cam. The ball bearing is elastically deformed into an elliptical shape by being fitted into the elliptical cam. The flexspline is elastically deformed into an elliptical shape by the outer ring of an elliptical ball bearing.

The flexspline is meshed with the circular spline at two points in its elliptical major axis direction. When the elliptical ball bearing rotates integrally with the rotation of the elliptical cam, the direction of the elliptical long axis changes in the direction of rotation, and the meshing position of the circular spline and the flexspline moves in the rotation direction, and the flexspline and Relative rotation occurs with the circular spline. The relative rotation is taken out as a deceleration rotation (see, for example, Patent Document 1).

Explaining with reference to FIG. 7, the flexspline 100 is generally made of a thin metal material, and has a tubular portion 101 that opens at one end in the axial direction and a bottom 102 that is continuous with the tubular portion 101 at the other end in the axial direction. It is in the shape of a cup formed by. The ball bearing 110 has an outer diameter surface portion 112 in which the outer ring 111 is formed in a cylindrical surface shape between the chamfered portions on both outer peripheral surfaces, and there is no seal that opens both sides in the axial direction between the outer ring 111 and the inner ring 113. , So-called open type.

The inside of the tubular portion 101 of the flexspline 100 is filled with grease (not shown), and the ball bearing 110 is used by grease lubrication.

Here, the tubular portion 101 of the flexspline 100 is inclined toward the outer diameter side toward the opening edge 103 side at two elliptical locations (on the cross section shown in the drawing) in the long axis direction. Therefore, the cylindrical outer diameter surface portion 112 of the outer ring 111 is in a linear contact state in which the inclined tubular portion 101 and the end of the outer diameter surface portion 112 on the bottom 102 side are in contact with each other.

Creep is likely to occur between the outer diameter surface portion 112 of the outer ring 111 and the tubular portion 101 of the flexspline 100, which are in a linear contact state. There is a possibility that wear may occur between the outer diameter surface portion 112 of the outer ring 111 where creep occurs and the tubular portion 101 of the flexspline 100.

For this reason, there arises a problem that metal powder generated by wear invades from one end side in the axial direction between the outer ring 111 and the inner ring 113 of the ball bearing and hinders the lubrication of the ball bearing. Further, as described above, since the ball bearing 110 is a so-called open type, there is a problem that grease leaks.

In order to solve this problem, a strain wave gearing reducer having a sealing member between the outer ring of the ball bearing and the housing has been proposed (see Patent Document 2). The sealing member is in contact with the housing, and the sealing member can prevent grease leakage from the ball bearings and metal powder from entering the ball bearings due to wear between the outer ring of the ball bearings and the flexspline. it can.

Jikkenhei 7-332442 Japanese Unexamined Patent Publication No. 2018-168956

However, in the strain wave gearing reducer described in Patent Document 2, the seal member is in contact with the housing. Therefore, when the strain wave gearing speed reducer is operated, there is a possibility that the torque increases due to the friction between the seal member and the housing, and foreign matter due to the wear of the seal member itself may enter the ball bearing.

Therefore, the present invention is to provide a ball bearing for a strain wave gearing that can secure lubricity while preventing foreign matter from entering.

In order to solve the above problems, the present invention has a ball bearing interposed between an elliptical cam of a wave gear reducer and a flexspline, and an inner ring that is deformed into an elliptical shape by fitting with the cam. Covers the outer ring that is deformed into an elliptical shape with the elliptical deformation of the inner ring, the rolling element arranged in the bearing space formed between the inner ring and the outer ring, and the opening on one side of the bearing space in the axial direction. An annular seal member is provided, the seal member is located on the opening edge side of the flexspline in the axial direction, and the end face on one side of the inner ring in the axial direction is axially more than the end face on the one side in the axial direction of the cam. It is located inside, and the inner peripheral portion of the seal member is fixed to one side of the outer peripheral portion of the cam in the axial direction, and is between the outer peripheral portion of the seal member and the inner peripheral surface of the outer ring. A configuration in which a labyrinth seal is formed can be adopted.

Further, the inner ring has a raceway ring width smaller than the raceway ring width of the outer ring, and the end face on one side in the axial direction of the inner ring is located axially inside the end face on one side in the axial direction of the outer ring. Can be adopted.

Further, the inner ring has the same raceway ring width as the raceway ring width of the outer ring, and the end faces of the inner ring and the outer ring on one side in the axial direction are located axially inside the end face on one side in the axial direction of the cam. It is possible to adopt the configuration that is used.

Further, the seal member is a shield formed of a metal plate, the shield has a flange-shaped outer ring portion bent inward in the axial direction on the outer peripheral portion thereof, and the labyrinth seal has the outer ring portion and the outer ring portion. A configuration formed between the inner peripheral surface and the inner peripheral surface of the can be adopted.

Further, the sealing member is formed of an elastic body and a core metal for reinforcing the elastic body, the elastic body has a lip located on the outer peripheral portion thereof, and the labyrinth seal is formed on the lip and the inner peripheral surface of the outer ring. The configuration formed between the two can be adopted.

Since the present invention includes a sealing member that covers the opening on one axial side of the bearing space formed between the inner ring and the outer ring, it prevents foreign matter from entering the flexspline from the opening on one axial direction of the bearing space. can do.

Further, since the seal member rotates integrally with the cam and a labyrinth seal is formed between the outer peripheral portion of the seal member and the inner peripheral surface of the outer ring, the grease in the flexspline and the bearing space is the axis of the bearing space. It is possible to prevent leakage from the opening on one side of the direction to the outside.

Longitudinal sectional view of a strain wave gearing reducer including ball bearings according to the first embodiment of the present invention. Front view of a strain wave gearing reducer equipped with the same ball bearings Cross-sectional view showing the same ball bearing Longitudinal sectional view showing a ball bearing according to a second embodiment of the present invention. Longitudinal sectional view showing a ball bearing according to a third embodiment of the present invention. Longitudinal sectional view showing a modified example of the ball bearing according to the third embodiment of the present invention. Longitudinal section showing a strain wave gearing reducer with conventional ball bearings

Hereinafter, the first embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 1 to 3, the ball bearing 1 according to this embodiment is for a strain wave gearing speed reducer. This strain wave gearing reducer includes a circular spline 2, a flex spline 3, a cam 4, and a ball bearing 1 interposed between the flex spline 3 and the cam 4.

The ball bearing 1 is a cage that maintains a circumferential distance between the inner ring 5, the outer ring 6, a row of balls 9 that are interposed between the raceway groove 7 of the inner ring 5 and the raceway groove 8 of the outer ring 6, and these balls 9. A shield 11 which is a sealing member covering an opening on one side in the axial direction of the bearing space between the inner ring 5 and the outer ring 6 is provided. An odd number of balls 9 are usually arranged between the track grooves 7 and 8. The inner ring 5 and the outer ring 6 are made of metal.

Hereinafter, the "axial direction" refers to a direction along the bearing central axis (not shown) of the ball bearing 1. By design, the bearing central axis of the ball bearing 1 is set coaxially with the central axes of the raceway rings of the inner ring 5 and the outer ring 6, and is set coaxially with the rotation axis of the wave gear reducer. Hereinafter, the direction perpendicular to the bearing center axis is referred to as "diameter direction", and the circumferential direction around the bearing center axis is referred to as "circumferential direction".

The cam 4 can rotate integrally with the first axis S1 in the circumferential direction. The flexspline 3 is rotatable in the circumferential direction integrally with the second axis S2 arranged on the same axis as the first axis S1. As shown in FIG. 3, the cam 4 has an outer peripheral portion 4a formed in an elliptical shape. The outer peripheral portion 4a of the cam 4 has a seal fitting groove 4b formed on one side in the axial direction on the entire circumference.

The circular spline 2 is made of metal. A predetermined number of internal teeth 2a are provided on the inner circumference of the circular spline 2 in the circumferential direction.

The flexspline 3 is made of metal. The flexspline 3 has a cup shape formed by a tubular portion 12 and a bottom portion 13 continuous with the other end in the axial direction of the tubular portion 12. The inside of the tubular portion 12 is formed in a cylindrical surface shape. The tip of the tubular portion 12 on one side in the axial direction is an opening edge 14 that opens on one side in the axial direction of the flexspline 3.

On the outer periphery of the tubular portion 12 of the flexspline 3, external teeth 3a that mesh with the internal teeth 2a of the circular spline 2 are provided along the circumferential direction. In this embodiment, the number of external teeth 3a of the flexspline 3 is two less than the number of internal teeth 2a of the circular spline 2. The number of internal teeth 2a and the number of external teeth 3a can be appropriately set under the condition that the number of external teeth 3a is smaller than the number of internal teeth 2a. The second axis S2 is connected to the central portion of the bottom portion 13.

The inner ring 5 of the ball bearing 1 is fitted so as to rotate integrally with the outer peripheral portion 4a of the cam 4. The inner ring 5 has a raceway ring width smaller than the raceway ring width of the outer ring 6. The raceway ring width of the inner ring 5 is formed to have a width dimension smaller than the axial width of the cam 4.

The end face on one side in the axial direction of the inner ring 5 is located axially inside the end face on one side in the axial direction of the cam 4. The axial positions of the end face on the other side of the inner ring 5 in the axial direction and the end face on the other side in the axial direction of the cam 4 match.

The raceway ring width of the outer ring 6 is formed to have the same width dimension as the axial width of the cam 4. The end faces on both sides of the outer ring 6 in the axial direction coincide with the end faces on both sides in the axial direction of the cam 4.

A plurality of balls 9 are arranged in a bearing space formed between the inner ring 5 and the outer ring 6. A plurality of balls 9 are rotatably held by the cage 10 at intervals in the circumferential direction. As the cage 10, for example, one shape cage can be adopted.

The shield 11 is formed of an annular metal plate and covers an axially one-sided opening of the bearing space between the inner ring 5 and the outer ring 6. As shown in FIG. 3, the shield 11 has an annular flat plate portion 11a, an inner ring portion 11b provided on the inner peripheral edge of the flat plate portion 11a, and an outer ring portion 11c provided on the outer peripheral edge of the flat plate portion 11a. ing. The shield 11 is manufactured by a known means such as pressing a stainless steel plate such as SUS304.

As shown in FIG. 2, the flat plate portion 11a is formed in an annular shape in which the inner peripheral edge and the outer peripheral edge form an ellipse. The inner peripheral edge and the outer peripheral edge of the flat plate portion 11a are formed so that their major axes match. A tapered portion 11d extending inward in the axial direction and inward in the radial direction is formed on the inner peripheral side portion of the flat plate portion 11a. The flat plate portion 11a is reinforced by the tapered portion 11d.

The inner ring portion 11b is curved outward in the axial direction from the inner peripheral edge of the flat plate portion 11a. The inner ring portion 11b has an elliptical shape along the outer peripheral portion 4a of the cam 4, and is fitted into the seal fitting groove 4b by press fitting.

The outer ring portion 11c is formed in a flange shape inward in the axial direction from the outer peripheral edge of the flat plate portion 11a. The outer ring portion 11c has an elliptical shape along the inner peripheral surface of the outer ring 6, and a labyrinth seal 30 is formed between the outer ring portion 11c and the inner peripheral surface of the outer ring 6.

In the shield 11, the inner ring portion 11b is press-fitted into the seal fitting groove 4b in a state where the long axis of the outer peripheral edge of the flat plate portion 11a and the long axis of the cam 4 match. By this fitting, the shield 11 rotates integrally with the cam 4. Further, a labyrinth seal 30 is formed on the entire circumference between the outer ring portion 11c of the shield 11 and the inner peripheral surface of the outer ring 6.

The inner ring 5 of the ball bearing 1 is elastically deformed into an elliptical shape by being fitted to the outer peripheral portion 4a of the cam 4. Along with this elliptical deformation, the outer ring 6 is pushed through the ball 9 to be elastically deformed into an elliptical shape. In this state, the outer ring 6 of the ball bearing 1 is press-fitted into the tubular portion 12 of the flexspline 3, so that the tubular portion 12 of the flexspline 3 is also elastically deformed into an elliptical shape.

When the elliptical ball bearing 1 rotates integrally with the rotation of the cam 4, the direction of the elliptical long axis changes in the rotation direction, and the position where the internal teeth 2a of the circular spline 2 and the external teeth 3a of the flexspline 3 mesh with each other. Moves in the direction of rotation, and two relative rotations are generated between the circular spline 2 and the flexspline 3 in one round. The relative rotation is taken out from the second axis S2 as a deceleration rotation.

This embodiment is configured as described above. In the ball bearing 1 of the wave gear reducer having this configuration, in the present invention, the axis of the bearing space is provided by providing the shield 11 that covers the opening on one side in the axial direction of the bearing space between the inner ring 5 and the outer ring 6. It is possible to prevent foreign matter from entering the flexspline 3 from the opening on one side in the direction.

Further, the shield 11 rotates integrally with the cam 4, and a labyrinth seal 30 is formed between the outer ring portion 11c of the shield 11 and the inner peripheral surface of the outer ring 6. Therefore, it is possible to prevent the grease in the flexspline 3 and the bearing space from leaking to the outside, and the lubricity of the ball bearing 1 is ensured.

Here, the strain wave gearing speed reducer is often used in a vertical axis state in which the first shaft S1 and the second shaft S2 are arranged in the vertical direction. When the opening edge 14 of the flexspline 3 is located below, the grease tends to move downward toward the opening edge 14 of the flexspline 3 due to its own weight.

In the present invention, the ball bearing 1 is provided with a shield 11 on one side in the axial direction of the ball bearing 1 which is the opening edge 14 side of the flexspline 3 in the axial direction. Therefore, the grease can be retained in the bearing space of the ball bearing 1, and a good lubrication state can be maintained.

A ball bearing according to a second embodiment of the present invention is shown in FIG. The ball bearing 1 of the second embodiment is different from the first embodiment described above in that the sealing member is formed of the elastic body 21 and the core metal 22 for reinforcing the elastic body 21. In other configurations, the same configurations as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

The seal member of the ball bearing 1 of this embodiment is an annular member in which the elastic body 21 is reinforced by a core metal 22 formed of a metal plate. The elastic body 21 is provided so as to cover the entire core metal 22 except for the inner surface side of the radial intermediate portion of the core metal 22.

The sealing member has a fitting portion 21a provided on the entire circumference of the inner peripheral edge of the elastic body 21, and a lip 21b provided on the entire circumference of the outer peripheral edge of the elastic body 21. The fitting portion 21a is formed in an elliptical shape along the inner surface of the seal fitting groove 4b of the cam 4. The fitting portion 21a is fixed to the seal fitting groove 4b of the cam 4 by press fitting, and the seal member rotates integrally with the cam 4.

The lip 21b has an elliptical outer peripheral surface facing the inner peripheral surface of the outer ring 6. The outer peripheral surface of the lip 21b forms a labyrinth seal 30 on the entire circumference between the outer peripheral surface and the inner peripheral surface of the outer ring 6.

The ball bearing 1 of this embodiment includes a seal member between the outer ring 6 and the inner ring 5 that covers an opening on one side in the axial direction of the bearing space. Therefore, as in the first embodiment, it is possible to prevent foreign matter from entering the flexspline 3 through the opening of the bearing space on one side in the axial direction.

A ball bearing according to a third embodiment of the present invention is shown in FIG. In the ball bearing 1 of the third embodiment, the inner ring 5 has the same raceway ring width as the raceway ring width of the outer ring 6, and the end faces of the inner ring 5 and the outer ring 6 on one side in the axial direction are on one side in the axial direction of the cam 4. It differs from the above-described first embodiment in that it is located axially inside the end face. In other configurations, the same configurations as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the ball bearing 1 of this embodiment, the inner ring 5 and the outer ring 6 have the same raceway ring width. Further, the inner ring 5 is press-fitted into the outer peripheral portion 4a of the cam 4 in a state where the end faces of the inner ring 5 and the outer ring 6 on the other side in the axial direction match the end faces of the cam 4 on the other side in the axial direction in the axial direction. There is.

The shield 11 has a tapered portion 11d on the inner peripheral side of the flat plate portion 11a. The flat plate portion 11a extends outward in the radial direction. An outer ring portion 11c is formed on the outer peripheral edge of the flat plate portion 11a inward in the axial direction.

The tip edge of the outer ring portion 11c is located axially inside the end surface on one side of the outer ring 6 in the axial direction. Similar to the first embodiment, the outer ring portion 11c of the shield 11 forms a labyrinth seal 30 with the inner peripheral surface of the outer ring 6.

As shown in FIG. 6, the shield 11 may have a middle ring portion 11e formed on the flat plate portion 11a inward in the axial direction. The position of the central ring portion 11e on the flat plate portion 11a is provided at a position where the shield 11 does not interfere with the ball 9 and the cage 10. By providing the middle ring portion 11e, the position of the outer ring portion 11c of the shield 11 can be brought closer to the outer ring 6 in the axial direction.

Further, the seal member may be an annular member in which an elastic body is reinforced with a core metal formed of a metal plate. This sealing member is provided so that the elastic body covers the entire core metal except for the inner surface side of the radial intermediate portion of the core metal. This elastic body has a fitting portion formed on the inner peripheral portion and a lip formed on the outer peripheral portion. The fitting portion of the elastic body is fixed to the seal fitting groove 4b of the cam 4 by press fitting, and the lip forms a labyrinth seal 30 with the inner peripheral surface of the outer ring 6.

1 Ball bearing 2 Circular spline 3 Flex spline 4 Cam 4a Outer circumference 4b Seal fitting groove 5 Inner ring 6 Outer ring 7, 8 Track groove 9 Ball 10 Cage 11 Shield 11a Flat plate part 11b Inner ring part 11c Outer ring part 12 Cylinder part 13 Bottom 14 Opening edge 21 Elastic body 21a Fitting part 21b Lip 22 Core metal 30 Labyrinth seal S1 First axis S2 Second axis

Claims (5)

In the ball bearing (1) interposed between the elliptical cam (4) and the flexspline (3) of the strain wave gearing reducer,
An inner ring (5) that is deformed into an elliptical shape by fitting with the cam (4), an outer ring (6) that is deformed into an elliptical shape by the elliptical deformation of the inner ring (5), and the inner ring (5). ) And the rolling element (9) arranged in the bearing space formed between the outer ring (6), and an annular sealing member covering the opening on one side in the axial direction of the bearing space.
The sealing member is located on the opening edge (14) side of the flexspline (3) in the axial direction, and the end surface on one side in the axial direction of the inner ring (5) is on the one side in the axial direction of the cam (4). It is located inward in the axial direction from the end face, and the inner peripheral portion of the seal member is fixed to one side in the axial direction of the outer peripheral portion (4a) of the cam (4). A ball bearing characterized in that a labyrinth seal (30) is formed between the portion and the inner peripheral surface of the outer ring (6). The inner ring (5) has a raceway ring width smaller than the raceway ring width of the outer ring (6), and the end face on one side in the axial direction of the inner ring (5) is the end face on one side in the axial direction of the outer ring (6). The ball bearing according to claim 1, wherein the ball bearing is located inward in the axial direction. The inner ring (5) has the same bearing ring width as the raceway ring width of the outer ring (6), and the end faces of the inner ring (5) and the outer ring (6) on one side in the axial direction of the cam (4). The ball bearing according to claim 1, wherein the ball bearing is located inside in the axial direction with respect to the end face on one side in the axial direction. The sealing member is a shield (11) formed of a metal plate, and the shield (11) has a flange-shaped outer ring portion (11c) bent inward in the axial direction on the outer peripheral portion thereof, and the labyrinth seal (11c). 30) The ball bearing according to any one of claims 1 to 3, wherein the outer ring portion (11c) is formed between the outer ring portion (11c) and the inner peripheral surface of the outer ring (6). The sealing member is formed of an elastic body (21) and a core metal (22) that reinforces the elastic body (21), and the elastic body (21) has a lip (21b) located on the outer peripheral portion thereof. The ball bearing according to any one of claims 1 to 3, wherein the labyrinth seal (30) is formed between the lip (21b) and the inner peripheral surface of the outer ring (6).

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