WO2023135689A1

WO2023135689A1 - Rolling bearing and wave generator of strain wave gear deivce

Info

Publication number: WO2023135689A1
Application number: PCT/JP2022/000776
Authority: WO
Inventors: 教夫城越
Original assignee: 株式会社ハーモニック・ドライブ・システムズ
Priority date: 2022-01-12
Filing date: 2022-01-12
Publication date: 2023-07-20
Also published as: TW202334563A

Abstract

In a ball bearing (1), outer ring inner peripheral surface portions (23, 24) of an outer ring (2) that are adjacent to an outer ring raceway surface (22) and inner ring outer peripheral surface portions (33, 34) of an inner ring (3) that are adjacent to an inner ring raceway surface (32) are subjected to processing such as shot peening-surface roughening or femtosecond laser nanotexturing to obtain a processed surface with a high wettability with respect to a base oil component of grease. Exudation of the base oil component of the grease located around the outer ring raceway surface (22) and the inner ring raceway surface (32) is facilitated and the base oil component is efficiently supplied to the outer ring raceway surface (22) and the inner ring raceway surface (32). The occurrence of a shortage of lubricant in the outer ring raceway surface and the inner ring raceway can be prevented or suppressed.

Description

Wave generator for rolling bearings and strain wave gearing

The present invention relates to a rolling bearing such as a ball bearing in which a plurality of rolling elements are rotatably inserted between an outer ring and an inner ring, and a wave generator for a strain wave gearing.

Rolling bearings are used, for example, as bearings for wave generators in wave gear devices. The wave generator includes a rigid plug and a wave generator bearing (rolling bearing) attached to the elliptical outer peripheral surface of the plug in an elliptically bent state. It is necessary to supply a lubricant such as grease to the wave generator bearing to keep the rolling parts of the rolling elements in an appropriate lubricated state.

In Patent Document 1, in a wave generator of a strain wave gearing device, a lubricant is held in an inner ring of a vibration generator bearing (wave generator bearing) mounted on an outer peripheral surface of a vibration generator (wave generator plug). A lubricating reservoir is provided to prevent the vibration generator bearing from running out of lubricant. In Patent Document 2, in order to improve the ability to form an oil film between the rolling elements and the raceway surface, minute grooves are formed on the raceway surface. Further, in Patent Document 3, on both sides or one side of the contact passage area where dynamic pressure is likely to be generated due to the sliding of the rolling elements on the raceway surface, concave streaks having an oil reservoir function are formed to form a sufficient oil film. are doing.

Japanese Unexamined Patent Application Publication No. 2015-190600 Japanese Unexamined Patent Application Publication No. 2005-321048 Japanese Patent Application Laid-Open No. 2009-108901

In conventional rolling bearing lubricant supply mechanisms, the raceway surfaces of the outer and inner rings are improved to prevent insufficient lubrication. However, no attention has been paid to the outer ring inner peripheral surface portion of the outer ring other than the raceway surface, or the inner ring outer peripheral surface portion of the inner ring other than the raceway surface, from the viewpoint of promoting the supply of the lubricant, and no proposals have been made for that purpose. not

In view of this point, the object of the present invention is to utilize the outer ring inner peripheral surface portion other than the outer ring raceway surface and the inner ring outer peripheral surface portion other than the inner ring raceway surface to prevent insufficient lubrication on the outer ring raceway surface and the inner ring raceway surface. To provide a rolling bearing which prevents such occurrence. Another object of the present invention is to provide a wave generator for a strain wave gear device using the rolling bearing as a wave generator bearing.

The present invention relates to a rolling bearing comprising an outer ring, an inner ring, and a plurality of rolling elements that roll on the outer ring raceway surface formed on the inner peripheral surface of the outer ring and the inner ring raceway surface formed on the outer peripheral surface of the inner ring. ,
One or both of an inner peripheral surface portion of the inner peripheral surface of the outer ring adjacent to the outer ring raceway surface and an outer peripheral surface portion of the outer peripheral surface of the inner ring adjacent to the inner ring raceway surface are provided with a treated surface. cage,
The treated surface is characterized in that wettability with respect to the base oil component of the lubricant is higher than that of the outer ring raceway surface or the inner ring raceway surface adjacent to the treated surface.

The treated surfaces with high wettability to the base oil components of lubricants such as grease and lubricating oil are roughened by shot peening, nano-texturing, etc. on the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring. It can be obtained by rubbing.

Further, the wave generator of the strain wave gearing device of the present invention includes the rolling bearing having the above-described configuration as a wave generator bearing, and the wave generator includes a rigid wave generator plug having an elliptical outer peripheral surface, and the and a wave generator bearing that is attached and fixed to the elliptical outer peripheral surface of the wave generator plug and is bent into an elliptical shape. In this case, the outer ring side treated surface and the inner ring side treated surface are formed as treated surfaces having high wettability with respect to the base oil component of the lubricant. In addition, since insufficient lubrication tends to occur in the portion where the long axis of the ellipse is located, it is desirable to form the inner ring side treated surface at least in a predetermined angular range including the long axis.

In the rolling bearing of the present invention, the portion other than the raceway surface of the inner or outer ring is roughened by shot peening or nano-textured by femtosecond laser processing or the like to form a treated surface with improved wettability. As a result, the exudation of the base oil component from the lubricant such as grease located around the inner ring raceway surface or the outer ring raceway surface is promoted, and the base oil component of the lubricant is efficiently applied to the inner ring raceway surface and the outer ring raceway surface. supplied. As a result, it is possible to prevent or suppress the occurrence of lubricant starvation on the outer ring raceway surface and the inner ring raceway surface. In particular, the effect of improving the lubrication of the wave generator bearing of the strain wave gearing is expected.

(a) is a longitudinal section showing a ball bearing to which the present invention is applied, (b) is an explanatory view showing an outer ring-side treated surface formed on the inner peripheral surface of the outer ring, and (c) is a It is explanatory drawing which shows the formed inner ring side processing surface. 1(a) is a schematic longitudinal sectional view showing the overall configuration of a cup-type strain wave gearing to which the present invention is applied, and FIG. 1(b) is a schematic end view thereof. (a) is an end view showing a wave generator plug and a wave generator bearing of a wave generator, (b) is an explanatory diagram showing an outer ring-side treated surface formed on an outer ring, and (c) is an inner ring. It is explanatory drawing which shows the formed inner ring side processing surface.

Embodiments of the present invention will be described below with reference to the drawings. The following embodiments relate to a wave gear device using a ball bearing to which the present invention is applied and a rolling bearing according to the present invention as a wave generator bearing. The invention is not limited to these embodiments. For example, the present invention is similarly applicable to rolling bearings other than ball bearings.

(Embodiment 1)
FIG. 1(a) is a longitudinal section showing a ball bearing to which the present invention is applied, FIG. 1(b) is an explanatory view showing an outer ring side treated surface formed on the inner peripheral surface of the outer ring, and FIG. ) is an explanatory view showing the inner ring side treated surface formed on the outer peripheral surface of the inner ring. A ball bearing 1 comprises an outer ring 2, an inner ring 3, and a plurality of balls 4 arranged therebetween. The balls 4 are held at regular intervals by retainers (not shown). The rolling portions of the outer ring 2 and the inner ring 3 on which the balls 4 roll are lubricated with a lubricant (not shown). For example, grease (not shown) filled between the outer ring 2 and the inner ring 3 lubricates.

A circular inner peripheral surface 21 of the outer ring 2 is formed with an outer ring raceway surface 22 having a cross section curved in an arc shape and having a constant width at a central portion in the direction of the axis 1a. They are

surface portions

23 and 24 . The inner

peripheral surface portions

23 and 24 of the outer ring are treated surfaces having a predetermined surface roughness, for example, by shot peening. Alternatively, the inner

peripheral surface portions

23 and 24 of the outer ring are processed surfaces subjected to nano-texturing by femtosecond laser processing or the like. For example, the outer ring raceway surface 22 is ground after roughening the circular inner peripheral surface 21 of the outer ring material before the outer ring raceway surface 22 is formed. As a result, the outer ring 2 is obtained in which the outer ring inner

peripheral surface portions

23 and 24 having high wettability with respect to the base oil component of the grease are arranged on both sides of the outer ring raceway surface 22 . In FIG. 1(b), the outer ring inner

peripheral surface portions

23 and 24, which are treated surfaces, are shown as shaded portions.

Similarly, on the circular outer peripheral surface 31 of the inner ring 3, an inner ring raceway surface 32 having a cross section curved in an arc shape and having a constant width is formed at the central portion in the direction of the axis 1a. They are outer

peripheral surface portions

33 and 34 . The inner ring outer

peripheral surface portions

33 and 34 are treated surfaces having a predetermined surface roughness by, for example, shot peening. Alternatively, the inner ring outer

peripheral surface portions

33 and 34 are processed surfaces subjected to nano-texturing by femtosecond laser processing or the like. By performing such a surface treatment, wettability to the base oil component of the grease is made higher than that of the adjacent inner ring raceway surface 32 . Also in FIG. 1(c), inner ring outer

peripheral surface portions

33 and 34, which are treated surfaces, are shown as shaded portions.

In the ball bearing 1 having this configuration, the grease filled between the outer ring 2 and the inner ring 3 covers the circular inner peripheral surface 21 of the outer ring 2 and the circular outer peripheral surface 31 of the inner ring 3 with a lubricating film. Both sides of the outer ring raceway surface 22 are connected to outer ring inner

peripheral surface portions

23 and 24 with high wettability, and both sides of the inner ring raceway surface 32 are also connected to inner ring outer

peripheral surface portions

33 and 34 with high wettability. The exudation of the base oil component from the grease around the outer ring raceway surface 22 and the inner ring raceway surface 32 is promoted by the outer ring inner

peripheral surface portions

23 and 24 and the inner ring outer

peripheral surface portions

33 and 34 with high wettability. As a result, the oil component of the grease is efficiently supplied to the adjacent outer ring raceway surface 22 and inner ring raceway surface 32 . As a result, the outer ring raceway surface 22 and the inner ring raceway surface 32 can be prevented or suppressed from running out of oil.

(Embodiment 2)
FIG. 2(a) is a schematic longitudinal sectional view showing the overall configuration of a cup-type strain wave gearing (hereinafter simply referred to as "wave gearing") to which the present invention is applied, and FIG. 2(b) is a schematic thereof. FIG. 4 is an end view; The strain wave gearing 100 comprises an annular rigid internal gear 120, a cup-shaped flexible external gear 130 coaxially arranged inside this, and an elliptical outline wave generator fitted inside this. 140.

The external gear 130 has a body portion 131, a diaphragm 132 and a boss 133, and has a cup shape as a whole. The trunk portion 131 has a cylindrical shape and is radially flexible. One end of the trunk portion 131 is an open end 134 , and external teeth 135 are formed on the outer peripheral surface portion of the trunk portion on the side of the open end 134 . A diaphragm 132 extends radially inward continuously from the other end of the body portion 131 . An annular boss 133 is formed continuously with the inner peripheral edge of the diaphragm 132 . Boss 133 is a rigid portion for attaching external gear 130 to another member (not shown). The internal gear 120 is arranged to surround the external teeth 135 of the external gear 130 . The external teeth 135 can mesh with the internal teeth 121 formed on the inner peripheral surface of the internal gear 120 .

The wave generator 140 comprises a hollow hub 141 , a rigid wave generator plug 143 attached to the outer circumference thereof via an Oldham coupling 142 , and a wave generator plug 143 fitted to an elliptical plug outer peripheral surface 144 of the wave generator plug 143 . It consists of generator bearings 145 . By the wave generator 140, the portion of the body portion 131 of the external gear 130 where the external teeth 135 are formed is bent from the initial perfect circle shape to an elliptical shape. The external teeth 135 mesh with the internal teeth 121 of the internal gear 120 at both ends of the major axis Lmax of the ellipse.

The wave generator bearing 145 (rolling bearing) comprises a radially flexible circular outer ring 146 and inner ring 147, and a plurality of balls 148 (rolling elements) mounted therebetween so as to be able to roll. It has The wave generator bearing 145 is fitted inside the external gear 130 while being bent into an elliptical shape by the wave generator plug 143, and holds the external gear 130 and the wave generator plug 143 in a relatively rotatable state. are doing. The wave generator plug 143 is connected to a high speed rotating input shaft (not shown). Balls 148 inserted between the elliptically bent outer ring 146 and inner ring 147 perform rolling motion along the outer ring raceway surface 146a and the inner ring raceway surface 147a. can smoothly rotate relative to each other with a small torque. The inner peripheral surface of the inner ring 147 of the wave generator bearing 145 is fixed to the elliptical plug outer peripheral surface 144 of the wave generator plug 143 by press fitting and adhesive.

When the wave generator 140 rotates around the central axis 100a, the meshing positions of the two

gears

120 and 130 rotate in the circumferential direction. Due to this rotation, relative rotation occurs between the external gear 130 and the internal gear 120 according to the difference in the number of teeth between the external gear 135 and the internal gear 121 . For example, if the internal gear 120 is fixed and the wave generator 140 is used as a high-speed rotation input element, the external gear 130 serves as a deceleration rotation output element, and the rotation is reduced according to the difference in the number of teeth between the two

gears

120 and 130. Output is retrieved.

FIG. 3(a) is an end view showing the wave generator bearing 145 of the wave generator 140, and FIG. 3(b) is an explanatory diagram showing the outer ring side treated surface formed on the outer ring 146. FIG. c) is an explanatory view showing the inner ring side treated surface formed on the inner ring 147. FIG. An outer ring raceway surface 146 a curved in an arc is formed on the inner peripheral surface of the outer ring 146 . Outer ring inner

peripheral surface portions

146b and 146c on both sides of the outer ring raceway surface 146a are treated surfaces (hatched portions in FIG. 3B) that are nanotextured by femtosecond laser processing or the like. For example, the outer ring inner

peripheral surface portions

146b and 146c are outer ring side treated surfaces in which a lubricating groove pattern is formed as a surface nano-texture over the entire circumference.

Similarly, on the outer peripheral surface of the inner ring 147, an inner ring raceway surface 147a having an arc-shaped cross section is formed. Inner ring outer

peripheral surface portions

147b and 147c on both sides of the inner ring raceway surface 147a are treated surfaces (hatched portions in FIG. 3(c)) that are nanotextured by femtosecond laser processing or the like. For example, the inner ring outer

peripheral surface portions

147b and 147c are inner ring side treated surfaces in which a lubricating groove pattern is formed as a surface nano-texture over the entire circumference.

The lubrication groove pattern is composed of linear lubrication grooves extending linearly, curvedly, or in a wavy shape. The lubricating grooves have a width and depth of several tens of nanometers to several micrometers, and are arranged at a pitch of several tens of nanometers to several micrometers. The lubricating groove pattern retains a lubricating film of grease and guides the base oil component of the grease in the axial direction toward the adjacent outer ring raceway surface 146a and inner ring raceway surface 147a. The lubricating grooves are formed so that the orientation direction of the lubricating grooves includes a directional component toward the axial direction so that the base oil component oozing out of the grease can be guided in the axial direction.

In the wave generator bearing 145 of the wave generator 140, the exudation of the base oil component from the grease positioned around the outer ring raceway surface 146a and the inner ring raceway surface 147a causes the outer ring inner

peripheral surface portions

146b and 146c with high wettability to be exuded. , inner ring outer

peripheral surface portions

147b, 147c. As a result, the oil component of the grease is efficiently supplied to the adjacent outer ring raceway surface 146a and inner ring raceway surface 147a. As a result, the outer ring raceway surface 146a and the inner ring raceway surface 147a can be prevented or suppressed from running out of oil.

In the wave generator bearing 145 flexed into an elliptical shape by the wave generator plug 143, a plurality of balls 148 positioned at both ends of the long axis Lmax of the ellipse are tightly spaced between the outer ring 146 and the inner ring 147. It is in a state of being in point contact with the outer ring raceway surface 146a and the inner ring raceway surface 147a and rolling. The remaining balls 148 positioned at portions other than both ends of the long axis Lmax have a gap between the outer ring raceway surface 146a and the inner ring raceway surface 147a, and are held in a loose state in which they can freely roll. Although it varies depending on the operating conditions of the strain wave gearing 100, the portions where the balls 148 in the loose state are located are roughly as follows. Regarding positive and negative angles, the counterclockwise direction is the positive direction and the clockwise direction is the negative direction with respect to the minor axis Lmin. At most, it is part of the angular range from about -75° to about +75° centered on the minor axis Lmin. At a minimum, it is the portion of the angular range from about -40° to about +40° about the minor axis Lmin. The greater the speed reduction ratio, the wider the angular range. For example, the angle range is wider when the reduction gear is 160 than when the speed reduction ratio is 30. Accordingly, the portion where the tight ball 148 is located is a portion of an angular range from about −15° to +15° at a minimum and about −50° to +50° at a maximum about the long axis Lmax. is the portion of the angular range to Insufficient lubrication of the inner ring raceway surface 147a tends to occur in a portion where the long axis of the elliptical shape on which the balls roll in a tight state is located. Therefore, it is desirable to form the inner ring side treated surface at least in a predetermined angular range including the long axis (for example, in a range of approximately ±50°).

Claims

A rolling bearing comprising an outer ring, an inner ring, and a plurality of rolling elements rolling on the outer ring raceway surface formed on the inner peripheral surface of the outer ring and the inner ring raceway surface formed on the outer peripheral surface of the inner ring,
One or both of an inner peripheral surface portion of the inner peripheral surface of the outer ring adjacent to the outer ring raceway surface and an outer peripheral surface portion of the outer peripheral surface of the inner ring adjacent to the inner ring raceway surface are provided with a treated surface. cage,
A rolling bearing, wherein the treated surface has higher wettability to a base oil component of a lubricant than the outer ring raceway surface or the inner ring raceway surface adjacent to the treated surface.
In claim 1,
A rolling bearing in which the treated surface is a shot peened or textured surface.
A wave generator for a strain wave gearing,
a rigid wave generator plug with an elliptical outer circumference;
a wave generator bearing attached and fixed to the elliptical outer peripheral surface and flexed in an elliptical shape,
A wave motion generator for a strain wave gearing, wherein the wave motion generator bearing is the rolling bearing according to claim 1 .
In claim 3,
The treated surfaces include an outer ring side treated surface and an inner ring side treated surface,
A wave generator for a strain wave gearing device, wherein the inner ring-side treated surface and the outer ring-side treated surface are surfaces subjected to shot peening processing or nano-texturing, respectively.