JP7401990B2 - ball bearing - Google Patents

Description

The present invention relates to a ball bearing incorporated in a wave gear reducer.

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

The flexspline is engaged with the circular spline at two points in the long axis direction of the ellipse. When the elliptical ball bearing rotates together with the rotation of the elliptical cam, the direction of the long axis of the ellipse changes in the direction of rotation, and the position where the circular spline and flexspline engage moves in the rotational direction, causing the flexspline and Relative rotation occurs between the circular spline and the circular spline. The relative rotation is extracted as decelerated rotation (for example, see Patent Document 1).

To explain with reference to FIG. 7, the flexspline 100 is generally made of a thin metal material, and includes a cylindrical portion 101 that is open at one end in the axial direction, and a bottom 102 that is continuous with the cylindrical portion 101 at the other end in the axial direction. It is cup-shaped. In the ball bearing 110, an outer ring 111 has an outer diameter surface part 112 formed in a cylindrical shape between chamfered parts on both sides of the outer periphery, and there is no seal that opens on both sides in the axial direction between the outer ring 111 and the inner ring 113. , is a so-called open type.

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

Here, the cylindrical portion 101 of the flexspline 100 is inclined toward the opening edge 103 side toward the outer diameter side at two locations (on the illustrated cross section) in the long axis direction of the ellipse. Therefore, the cylindrical outer diameter surface portion 112 of the outer ring 111 is in a linear contact state in which it contacts the inclined cylinder portion 101 at the end of the outer diameter surface portion 112 on the bottom 102 side.

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

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

In order to solve this problem, a wave gear reducer including a seal 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 prevents grease from leaking from the ball bearing and metal powder generated due to wear between the outer ring of the ball bearing and the flexspline from entering the ball bearing. can.

Utility Model Publication No. 7-332442 Japanese Patent Application Publication No. 2018-168956

However, in the strain wave gear reducer described in Patent Document 2, the sealing member is in contact with the housing. For this reason, during operation of the wave gear reducer, there is a possibility that torque may increase due to friction between the seal member and the housing, and foreign matter may enter the ball bearing due to wear of the seal member itself.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a ball bearing for a wave gear reducer that can ensure lubricity while preventing the intrusion of foreign substances.

In order to solve the above problems, the present invention provides a ball bearing interposed between an elliptical cam and a flexspline of a strain wave gear reducer, and an inner ring that is deformed into an elliptical shape by fitting with the cam. , an outer ring that is deformed into an elliptical shape as the inner ring is deformed into an elliptical shape, a rolling element disposed in a bearing space formed between the inner ring and the outer ring, and an opening on one axial side of the bearing space. an annular sealing member, the sealing member is located on the opening edge side of the flexspline in the axial direction, and the end face on one axial side of the inner ring is located closer in the axial direction than the end face on the one axial side of the cam. located on the inside, the inner peripheral part of the seal member is fixed to one side in the axial direction of the outer peripheral part of the cam, and between the outer peripheral part 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 bearing ring width smaller than the bearing ring width of the outer ring, and an end face on one axial side of the inner ring is located axially inward than an end face on one axial side of the outer ring. A configuration can be adopted.

Further, the inner ring has a bearing ring width that is the same as the bearing ring width of the outer ring, and end faces of the inner ring and the outer ring on one axial side are located axially inward than the end face of the cam on one axial side. It is possible to adopt the following configuration.

Further, the sealing member is a shield formed from a metal plate, the shield has a flange-shaped outer ring portion bent inward in the axial direction on its outer circumferential portion, and the labyrinth seal includes the outer ring portion and the outer ring. It is possible to adopt a structure in which the inner circumferential surface of the

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

This 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, thereby preventing foreign matter from entering the flexspline from the opening on the one axial side of the bearing space. can do.

In addition, since the seal member rotates together with the cam and a labyrinth seal is formed between the outer circumference of the seal member and the inner circumference of the outer ring, the grease in the flexspline and the bearing space is removed from the shaft of the bearing space. It is possible to prevent leakage to the outside from the opening on one side of the direction.

A vertical cross-sectional view of a wave gear reducer equipped with a ball bearing according to a first embodiment of the present invention Front view of wave gear reducer equipped with ball bearings as above Cross-sectional view showing the same ball bearing as above A longitudinal sectional view showing a ball bearing according to a second embodiment of the invention A longitudinal sectional view showing a ball bearing according to a third embodiment of the invention A longitudinal sectional view showing a modification of the ball bearing according to the third embodiment of the invention Vertical cross-sectional view showing a wave gear reducer equipped with conventional ball bearings

Hereinafter, a first embodiment of the present invention will be described based on the drawings. As shown in FIGS. 1 to 3, a ball bearing 1 according to this embodiment is for a wave gear reducer. This wave gear reducer includes a circular spline 2, a flexspline 3, a cam 4, and a ball bearing 1 interposed between the flexspline 3 and the cam 4.

The ball bearing 1 includes an inner ring 5, an outer ring 6, a row of balls 9 interposed between a raceway groove 7 of the inner ring 5 and a raceway groove 8 of the outer ring 6, and a retainer that maintains the circumferential spacing between these balls 9. 10, and a shield 11 which is a sealing member that covers an opening on one axial side of the bearing space between the inner ring 5 and the outer ring 6. An odd number of balls 9 are usually arranged between each raceway groove 7, 8. Inner ring 5 and outer ring 6 are made of metal.

Hereinafter, the "axial direction" refers to a direction along the bearing center axis (not shown) of the ball bearing 1. The bearing center axis of the ball bearing 1 is designed to be coaxial with the center axes of the inner ring 5 and outer ring 6, and also coaxial with the rotational axis of the wave gear reducer. Hereinafter, the direction perpendicular to the bearing center axis will be referred to as the "radial direction," and the circumferential direction around the bearing center axis will be referred to as the "circumferential direction."

The cam 4 is rotatable in the circumferential direction integrally with the first shaft S1. The flexspline 3 is rotatable in the circumferential direction together with a second shaft S2 arranged on the same axis as the first shaft 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 around the entire circumference on one side in the axial direction.

The circular spline 2 is made of metal. A predetermined number of internal teeth 2a are provided on the inner periphery 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 cylindrical portion 12 and a bottom portion 13 that is continuous with the other end of the cylindrical portion 12 in the axial direction. The inside of the cylindrical portion 12 is formed into a cylindrical surface shape. The tip of the cylindrical portion 12 on one axial side forms an opening edge 14 that opens on one axial side of the flexspline 3 .

On the outer periphery of the cylindrical 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 fewer 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. A second shaft S2 is connected to the center of the bottom portion 13.

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

An end surface of the inner ring 5 on one axial side is located axially inward than an end surface of the cam 4 on one axial side. The end face of the inner ring 5 on the other axial side and the end face of the cam 4 on the other side in the axial direction match in axial position.

The bearing ring width of the outer ring 6 is formed to have the same width dimension as the axial width of the cam 4. The axially opposite end surfaces of the outer ring 6 are aligned with the axially opposite end surfaces of the cam 4, respectively.

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 a cage 10 at intervals in the circumferential direction. The cage 10 can be, for example, a two-shaped cage.

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

As shown in FIG. 2, the flat plate portion 11a is formed into an annular shape with an inner peripheral edge and an outer peripheral edge forming an ellipse. The inner circumferential edge and outer circumferential edge of the flat plate portion 11a are formed such that their long axes coincide with each other. A tapered portion 11d that extends 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 axially outward 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 press-fitted into the seal fitting groove 4b.

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

The inner ring part 11b of the shield 11 is press-fitted into the seal fitting groove 4b with the long axis of the outer peripheral edge of the flat plate part 11a and the long axis of the cam 4 matching. Due to this fitting, the shield 11 rotates together 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 onto the outer peripheral portion 4a of the cam 4. Along with this elliptical deformation, the outer ring 6 is pushed through the balls 9, thereby being elastically deformed into an elliptical shape. In this state, the outer ring 6 of the ball bearing 1 is press-fitted inside the cylindrical portion 12 of the flexspline 3, so that the cylindrical portion 12 of the flexspline 3 is also elastically deformed into an elliptical shape.

When the elliptical ball bearing 1 rotates together with the rotation of the cam 4, the direction of the long axis of the ellipse changes in the direction of rotation, and the position where the internal teeth 2a of the circular spline 2 and the external teeth 3a of the flex spline 3 mesh moves in the rotational direction, and two relative rotations occur between the circular spline 2 and the flexspline 3 in one rotation. The relative rotation is taken out from the second shaft S2 as decelerated rotation.

This embodiment is configured as described above. In the ball bearing 1 of the wave gear reducer having this configuration, the present invention includes a 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 through the opening on one side in the direction.

Further, the shield 11 rotates together 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, the grease in the flexspline 3 and the bearing space can be prevented from leaking to the outside, and the lubricity of the ball bearing 1 can be ensured.

Here, the wave gear 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 this 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 flex spline 3 in the axial direction. Therefore, it is possible to keep the grease in the bearing space of the ball bearing 1, and a good lubrication state can be maintained.

FIG. 4 shows a ball bearing according to a second embodiment of the invention. The ball bearing 1 of the second embodiment is different from the above-described first embodiment in that the sealing member is formed of an elastic body 21 and a core metal 22 that reinforces the elastic body 21. In other configurations, the same configurations as in the first embodiment are given the same reference numerals, and the description thereof will be omitted.

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

The sealing member has a fitting portion 21 a provided around the entire inner peripheral edge of the elastic body 21 and a lip 21 b provided around the entire 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 press-fitted into the seal fitting groove 4b of the cam 4, and the seal member rotates together with the cam 4.

The lip 21b has an elliptical outer circumferential surface facing the inner circumferential surface of the outer ring 6. A labyrinth seal 30 is formed around the entire circumference between the outer peripheral surface of the lip 21b and the inner peripheral surface of the outer ring 6.

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

FIG. 5 shows a ball bearing according to a third embodiment of the invention. The ball bearing 1 of the third embodiment has the following features: the inner ring 5 has the same bearing ring width as the outer ring 6; It differs from the first embodiment described above in that it is located axially more inward than the end face. In other configurations, the same configurations as in the first embodiment are given the same reference numerals, and the description thereof will be omitted.

In the ball bearing 1 of this embodiment, the raceway widths of the inner ring 5 and the outer ring 6 are the same. In addition, the inner ring 5 is press-fitted into the outer peripheral part 4a of the cam 4 with the end surfaces of the inner ring 5 and the outer ring 6 on the other axial side aligned with the end surface of the cam 4 on the other side 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 radially outward. An outer ring portion 11c is formed on the outer peripheral edge of the flat plate portion 11a so as to face inward in the axial direction.

The tip edge of the outer ring portion 11c is located axially inward from the end surface of the outer ring 6 on one axial side. Similarly to the first embodiment, 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.

In addition, as shown in FIG. 6, the shield 11 may have a middle ring part 11e formed axially inward on the flat plate part 11a. The middle ring portion 11e of the flat plate portion 11a is located at a position where the shield 11 does not interfere with the balls 9 and the retainer 10. By providing the middle ring part 11e, the position of the outer ring part 11c of the shield 11 can be brought closer to the outer ring 6 in the axial direction.

Further, the sealing member may be an annular member in which an elastic body is reinforced with a core metal formed from a metal plate. This sealing member is provided so that the elastic body covers the entire core bar except for the inner surface of the radially intermediate portion of the core bar. This elastic body has a fitting portion formed on the inner periphery and a lip formed on the outer periphery. A fitting portion of the elastic body is press-fitted into a seal fitting groove 4b of the cam 4, and a labyrinth seal 30 is formed between the lip and 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 Raceway groove 9 Ball 10 Cage 11 Shield 11a Flat plate part 11b Inner ring part 11c Outer ring part 12 Cylindrical part 13 Bottom part 14 Opening edge 21 Elastic body 21a Fitting part 21b Lip 22 Core bar 30 Labyrinth seal S1 First shaft S2 Second shaft

Claims (5)

In a wave gear reducer including a ball bearing (1) interposed between an elliptical cam (4) and a flexspline (3),
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 as the inner ring (5) deforms into an elliptical shape; ) and an outer ring (6), a rolling element (9) disposed in a bearing space formed between the outer ring (6), and an annular sealing member covering an opening on one axial side 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 axial side of the inner ring (5) is located on the one axial side of the cam (4). The inner peripheral part of the seal member is fixed to one side of the outer peripheral part (4a) of the cam (4) in the axial direction, and the outer peripheral part of the seal member A labyrinth seal (30) is formed between the part and the inner peripheral surface of the outer ring (6).The outer circumference of the cam (4) has a seal fitting groove (4b) formed around the entire circumference on one side in the axial direction, and the inner circumference of the seal member has a seal fitting groove (4b) formed around the entire circumference on one side in the axial direction, and the inner circumference of the seal member has a seal fitting groove (4b) formed on the entire circumference on one side in the axial direction. Fitted into the matching groove (4b)characterized by Wave gear reducer. The inner ring (5) has a bearing ring width smaller than the bearing ring width of the outer ring (6), and the inner ring (5) has an end face on one axial side of the outer ring (6). 2. The wave gear reducer according to claim 1, wherein the wave gear reducer is located axially more inward than the wave gear reducer. The inner ring (5) has the same bearing ring width as that of the outer ring (6), and one end surface of the inner ring (5) and the outer ring (6) in the axial direction is aligned with the cam (4). 2. The wave gear reducer according to claim 1, wherein the wave gear reducer is located axially inner than an end face on one axial side. The sealing member is a shield (11) formed from a metal plate, and the shield (11) has a flange-shaped outer ring part (11c) bent inward in the axial direction on its outer peripheral part, and the labyrinth seal ( 30) is formed between the outer ring portion (11c) and the inner peripheral surface of the outer ring (6) , the wave gear reducer according to any one of claims 1 to 3. The sealing member is formed of an elastic body (21) and a core metal (22) reinforcing the elastic body (21), the elastic body (21) has a lip (21b) located on its outer periphery, and The wave gear reduction gear according to any one of claims 1 to 3, characterized in that a labyrinth seal (30) is formed between the lip (21b) and the inner peripheral surface of the outer ring (6).

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