Ball bearing

Abstract

A ball bearing includes an inner ring having a raceway surface, an outer ring having a raceway surface, a plurality of rolling elements rollably disposed between the raceway surface of the inner ring and the raceway surfaces of the outer ring, and a resin cage configured to retain the plurality of rolling elements between the inner ring and the outer ring. The cage is a crown type cage having an annular base portion and a plurality of pockets formed in an axial end face of the annular base portion, in which the pockets retain the rolling elements. An axial distance between an axial position of a center of gravity of the cage and a curvature center of a spherical or cylindrical inner surface of each of the pockets is 0.6 or more times a radius of curvature of the inner surface. A hybrid vehicle transmission has this ball bearing.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This FIG. 1 is a partial sectional view of a ball bearing according to a first embodiment of the invention;Embodiment 1

According to the ball bearing of the third embodiment, since the annular opening portion 51 is formed at the axial supply side between the inner circumferential portion 5c of the lubricant guide 5 fixed to the outer ring 32 and the outer circumferential portion of the inner ring 31, the lubricating oil can be introduced into the interior of the bearing from the annular opening portion 51. Then, the lubricating oil that flows into the interior of the bearing flows into the sliding portions between the balls 3 and the crown type cage 34 by centrifugal force after having flowed towards the radially inner side of the cage 34 and is discharged to the outside of the bearing from an annular opening opened at the axial discharge side between the inner and outer rings 31, 32 in such a state that the flow rate is increased further by centrifugal force. Note that arrows in FIG. 31 indicate the flow of lubricating oil.

In this way, since the lubricating oil supplied into the interior of the bearing flows into the sliding portions between the balls 3 and the crown type cage 34 from the radially inner side of the cage 34 by centrifugal force, the wear of the cage 34 can be suppressed which is caused by the sliding of the balls 3 on the cage 34 which tends to be generated easily when rotating at high speeds without employing a device such as a lubrication nozzle which requires extra space and cost. As a result, the rotation of the crown type cage 34 with run-out can be prevented, thereby making it possible to realize a long life of the bearing. In addition, since the lubricating oil can be discharged to the outside of the bearing in such a state that the flow rate is increased by centrifugal force, the ingress and egress of lubricating oil can be implemented effectively, thereby making it possible to prevent the increase in both temperature and torque of the bearing.

In addition, since the resin crown type cage 34 can be injection molded, cages can be mass produced, and hence, lubricating conditions can be improved while suppressing costs. The ball-guided crown type cage 34 can contribute to the reduction in torque.

Additionally, by making the inside diameter Ds of the lubricant guide 5 equal to or smaller than the inside diameter Dh of the crown type cage 34, the lubricating oil that has entered the interior of the bearing from the annular opening portion 51 can flow in towards the radially inner side of the crown type cage 34 in a more ensured fashion. In addition, an excessive lubricant can be prevented from entering the interior of the bearing.

Since the radial widthwise center 4h of the crown type cage 34 is offset towards the radially inner side of the bearing from the center O3 of the ball 3, the holding amount of the balls 3 by the crown type cage 34 can be increased, whereby the warp of the crown type cage 34 can be suppressed.

In addition, since the center O3 of the ball 3 is offset to the discharge side S2 of the lubricating oil, a large distance can be secured between the lubricant guide 5 disposed at the supply side 51 of the lubricating oil and the ball 3. Consequently, due to the space between the ball 3 and the lubricant guide 5 being expanded, the axial thickness of the base portion 4a of the crown type cage 34 facing the supply side S1 of the lubricating oil, that is, the bottom thickness J of the spherical pocket 4c can be increased. As a result, the rotation of the crown type cage 34 with run-out can be suppressed.

Additionally, since the tapered cutout 1c is provided at the shoulder portion 1b of the inner ring 31 which is situated on the side where the lubricant guide 5 is disposed, the inside diameter Ds of the lubricant guide 5 can made small, while ensuring that the annular opening portion 51 into which the lubricating oil flows is kept slightly larger. As a result, the lubricating oil can be introduced towards the radially inner side of the crown type cage 34 in an ensured fashion, facilitating the introduction of the lubricating oil to the sliding portions between the spherical pockets 4c and the balls 3.

In addition, since the bent wall 5d extending towards the interior of the bearing is provided at the inner circumferential portion 5c of the lubricant guide 5, the lubricating oil that flows in from the annular opening portion 51 secured formed between the inner circumferential portion 5c of the lubricant guide 5 and the outer circumferential portion of the inner ring 31 can be guided positively in the direction of the inner circumferential portion of the crown type cage 34 by overcoming the centrifugal force.

Additionally, since the edges 4e of the inner circumferential portion of the spherical pocket 4c of the crown cage 34 are chamfered or rounded, even when the edges 4e are brought into contact with the ball 3, the concentration of stress on the cage side 34 can be relaxed, thereby making it possible to reduce the wear of the cage 34. In particular, when the inside diameter of the crown type cage 34 is reduced, while the edges 4e become sharp, by chamfering or rounding the edges 4e, a reduction in wear can be realized.

In addition, since the inside diameter Ds of the lubricant guide 5 is equal to or smaller than the revolution diameter PCD of the ball 3 and is more preferably equal to or smaller than the inside diameter of the crown type cage, it becomes possible to increase the performance of sending the lubricating oil to the portions requiring lubrication by the lubricant guide 5, thereby making it possible to improve the lubricating conditions of the bearing. In particular, when the shortest distance y between the outer circumferential portion of the inner ring 31 and the inner circumferential portion 5c of the lubricant guide 5 is 9% or more of the diameter Dw of the ball 3, a reduction in rotation of the crown type cage 34 with run-out can be realized. Further, when the shortest distance y between the outer circumferential portion of the inner ring 31 and the inner circumferential portion 5c of the lubricant guide 5 is 11% or more of the diameter Dw of the ball 3, a reduction in rotation of the crown type cage 34 with run-out can be realized in a more ensured fashion.

FIG. 35 shows a ball bearing according to a first modified example of the third embodiment. In this ball bearing, a through hole 5e which allows for the passage of lubricating oil is provided near an outer circumference of a lubricant guide 5 which is situated further radially inwards than relative to an inner circumferential portion of an outer ring 32. By adopting this configuration, since the lubricating oil can freely escape through the through hole 5e provided near the outer circumference of the lubricant guide 5, the replacement efficiency of lubricating oil can be increased in a region R in an interior of the bearing which is situated on an outer circumferential side of the interior of the bearing, thereby making it possible to prevent the portion in question from being heated. The other configurations and advantages are similar to those of the third embodiment of FIG. 31.

FIGS. 36A to 36E show ball bearings according to a second modified example to a sixth modified example of the third embodiment, respectively. Note that these modified examples have the same configurations and advantages as those of the third embodiment except portions that will be described below.

A ball bearing according to the second modified example shown in FIG. 36A has a stepped cutout 1d formed at a shoulder portion 1b of an inner ring 31 in place of the tapered cutout 1c.

A ball bearing according to the third modified example shown in FIG. 36B has a stepped cutout 1d formed at a shoulder portion 1b of an inner ring 31 in place of the tapered cutout 1c. Further, a bent wall 5d extends as far as a position where it enters a circumferential side of a base portion 4a of a crown type cage 34.

A ball bearing according to the fourth modified example shown in FIG. 36C has a stepped cutout 1d formed at a shoulder portion 1b of an inner ring 31 in place of the tapered cutout 1c. However, a lubricant guide 5 has no bent wall 5d. In this case, since no bent wall 5d is present, lubricating oil that flows in from an annular opening portion 51 tends to be directed in an outside diameter direction by centrifugal force. However, since kinetic energy is given to the lubricating oil at a point in time when the lubricating oil flows into an interior of the bearing from the annular opening portion 51, the lubricating oil can satisfactorily be guided to the inner circumferential portion of the crown type cage 34.

A ball bearing according to the fifth modified example shown in FIG. 36D has a configuration in which no cutout is formed at a shoulder portion 1b of an inner ring 31, and an inner circumferential portion of a crown type cage 34 lies close to an outside diameter surface of the inner ring 31. In addition, a lubricant guide 5 has no bent wall 5d.

A ball bearing according to the sixth modified example shown in FIG. 36E has a configuration in which no cutout is formed at a shoulder portion 1b of an inner ring 31. In addition, a crown type cage 34 is used in which a center of a radial width of the cage 34 coincides with the center of a ball 3, so that the contact of an inner circumferential portion of the crown type cage 34 with an outside diameter surface of the inner ring 31 is suppressed. In addition, the inside diameter of a lubricant guide 5 becomes smaller than an inside diameter of the cage 34 by employing the cage 34, facilitating the passage of lubricating oil between an inner circumferential side of the cage 34 and the inner ring 31.

FIGS. 37A to 37D show ball bearings according to seventh to tenth modified examples of the third embodiment, respectively. For example, in the third embodiment, while the lubricant guide 5 is attached directly to the shoulder portion of the outer ring 32, as in the seventh and eighth modified examples shown in FIGS. 37A and 37B, respectively, a side plate 35, 45 may be provided on an external surface of an outer ring 32, and an annular projecting portion 35a provided on the side plate 35 or the side plate 45 itself may be used as a lubricant guide. In addition, as in the ninth and tenth modified examples shown in FIGS. 37C and 37D, respectively, an inwardly facing flange portion 55, 65 may be provided on a housing 50, 60 to which an outer ring 32 is fixed so as to face inwards, and an annular projecting portion 35a provided on the flange portion 55 or the flange portion 65 itself may be used as a lubricant guide.

By adopting this configuration, the number of components can be reduced. In addition, the step of crimping the outer circumferential end of the lubricant guide into the engagement groove in the outer ring can also be omitted, whereby costs are reduced. In addition, in the seventh to tenth modified examples, compared with the configuration in which the lubricant guide is fixed to the outer ring 32, a space can easily be provided at one axial side between an inner ring 31 and the outer ring 32, thereby making it possible to increase the thickness of a base portion 4a of a cage 34.

Further, in the third embodiment, while the shield plate, which is not in contact with the outer circumferential surface of the shoulder portion 1b of the inner ring 31 is used as the lubricant guide, in the case of a contact seal is used, a supply hole may be provided on an inner circumferential portion side of the lubricant guide.

In addition, as cages to which the invention can be applied, the invention can also be applied to other cages which include a ribbon type pressed cage and a duplex cage made by bringing two members into engagement with each other.

Next, an example of a test for measuring a radial play of a cage will be described by using a ball bearing shown in FIG. 38. This ball bearing has substantially the same configuration as that of the ball bearing according to the fourth modified example shown in FIG. 36C. In Test 1, an outside diameter Dl of an end portion of a shoulder portion 1b of an inner ring 31 is changed, and in Test 2, an inside diameter Ds of a lubricant guide 15 is changed.

<Test 1>

In Test 1, as an index of wear loss, an increased amount of a radial play of a cage as compared with a new cage was surveyed while changing y/Dw (gap/ball diameter) by changing the outside diameter Dl of the end portion of the shoulder portion 1b of the inner ring 31 with the inside diameter Ds of the lubricant guide 15 fixed at 51.8 mm. The configuration of the bearing and testing conditions were as follows.

<Configuration of Bearing>

• • Bearing Type: 6909 (PCD=56.5 mm)
  • Ball Diameter: 6.7 mm
  • Cage: Crown Type Cage having Spherical Pockets
  • Cage Material Nylon 46 reinforced with 25% Glass Fibers
  • Distance Db between Base Portion of Cage and Lubricant Guide Portion of Lubricant Guide: 1 mm
  • Cage Inside Diameter: 51.8 mm

<Testing Conditions>

• • Rotation speed: 30000 rpm
  • Temperature of Lubricating Oil Supplied: 120° C.
  • Lubrication Method Supply of Mineral Oil of VG24 through Forced Lubrication (0.1 L/min)
  • Load: 2500 N
  • Testing Time: 20 Hr

The results of the test are shown in Table 1 and in FIG. 39.

	TABLE 1
	Inner Ring	Opening		Radial Play of
	Outside	Amount		Cage (mm) (Difference
	Diameter (mm)	(mm)	y/Dw	from New Product)
	51.4	0.2	3	heat-seizure
	51.2	0.3	5	1.13
	50.8	0.5	7	0.61
	50.6	0.6	9	0.18
	50.4	0.7	10	0.06
	49.8	1.0	15	0.04
	48.4	1.7	25	0.07

It is seen from the results of the wear test shown in FIG. 39 that when y/Dw is 9% or larger, the improvement in starting time of rotation with run-out of the bearing comes almost to a saturation, and when y/Dw is 11% or larger, the improvement in starting time of rotation with run-out of the bearing comes completely to a saturation. It is verified from this fact that when y/Dw is 9% or larger and is preferably 11% or larger, a large effect can be obtained on the reduction of rotation with run-out of the ball bearing. In addition, when y/Dw is 3% or smaller, an annular opening portion 51 is so narrow that lubricating oil cannot be supplied sufficiently, resulting in heat-seizure of the bearing.

<Test 2>

In Test 2, in a ball bearing as shown in FIG. 38, as an index of wear loss, an increased amount of a radial play of a cage as compared with a new cage was surveyed while changing the inside diameter Ds of a lubricant guide 15 with an outside diameter Dl of an inner ring 31 fixed at 48.4 mm. However, y/Dw was set to be 11% or more at which the starting time of rotation with run-out of the bearing stayed in the saturation region at all times in Test 1. The configuration of the bearing and testing conditions were the same as those of Test 1.

The results of the test are shown in Table 2 and in FIG. 40.

TABLE 2
			Radial Play of
Annular	Opening		Cage (mm)
Plate Inside	Amount		(Difference from
Diameter (mm)	(mm)	y/Dw	New Product)	Remarks
61.5	6.6	97	1.21	Outer Ring
				Inside Diameter
59.0	5.3	79	1.23
56.6	4.1	60	0.90	Bearing PCD
54.0	2.8	41	0.20
51.8	1.7	25	0.07	Cage Inside
				Diameter
50.0	0.8	12	0.06

It is seen from the results of the wear test shown in FIG. 40 that the wear loss starts to decrease somewhen at a pint in time when the inside diameter of the lubricant guide starts to be lowered to and beyond the PCD of the bearing. It can be considered that this is because lubricating oil is made difficult to flow into a cage 34 and much of the lubricating oil then starts to flow to a radially inner side of the cage 34. This effect comes almost to a saturation when the inside diameter Ds of the lubricant guide 15 is lowered to and beyond the inside diameter Dh of the cage 34. It is seen from these facts that the inside diameter Ds of the lubricant guide 15 should be equal to or smaller than the PCD of the bearing and be preferably equal to or smaller than the inside diameter Dh of the cage 34.

<Test 3>

Next, heat generation amounts were compared by changing only the radius of curvature R of the grooves in the raceway surfaces of the inner ring and the outer ring in the dimensions of the bearing in the bearings used in Test 1 which indicated the smallest play amount, the outside diameter of the inner ring being 49.8 mm, the opening amount being 1.0 mm, and y/Dw of the bearing being 15%, respectively. The results of Test 3 are shown in FIG. 41. In a graph in FIG. 41, an axis of abscissae denotes Ri=radius of curvature R of groove in raceway surface of inner ring/ball diameter, and an axis of ordinates denotes a ratio of heat generation amounts when a heat generation amount when Re=radius of curvature of groove in raceway surface of outer ring/ball diameter=0.52 and Ri=0.52 is referred to as 1.0. It is seen from the test results shown in FIG. 41 that irrespective of radius of curvature R of the groove in the raceway surface of the outer ring, it is favorable when the radius of curvature R of the groove in the raceway surface of the inner ring is equal to or larger than 53% (Ri≥0.53), in which not much heat is generated.

Thus, while the embodiments embodiment and the modified examples example thereof have been described, the invention is not limited to the embodiments embodiment and the modified examples example thereof, and hence, it is obvious to those skilled in the art to which the invention pertains that various alterations and modifications can be made thereto without departing from the spirit and scope of the invention. For example, the materials, shapes, dimensions, numbers and disposition locations can be altered or modified as required.

In addition, the characteristics of the embodiments and the modified examples thereof may be combined together.

Additionally, in the embodiments embodiment and the modified examples example thereof, while the deep groove ball bearing is described as the ball bearing to which the invention is applied, the invention can be applied to other various types of ball bearings (for example, angular contact ball bearings and self aligning ball bearings).

INDUSTRIAL APPLICABILITY

The invention provides the ball bearing which can suitably be used even under high-temperature, high-speed conditions and a hybrid vehicle transmission.

Claims

1. A ball bearing comprising:

an inner ring comprising an outer circumferential surface wherein the outer circumferential surface has a tapered portion extending from an axial end of the inner ring to a first shoulder portion of the inner ring and defining a boundary of an annular supply opening, a second shoulder portion of the inner ring defining a portion of an annular discharge opening, and a raceway groove provided between the first shoulder portion of the inner ring and the second shoulder portion of the inner ring, the raceway groove defining a raceway surface on an in the outer circumferential surfacethereof;

an outer ring comprising an inner circumferential surface wherein the inner circumferential surface has a first shoulder portion of the outer ring having an engagement groove nearer to an axial end of the outer ring than to an opposite axial end of the outer ring, a second shoulder portion of the outer ring defining another portion of the annular discharge opening, and a raceway groove provided between the first shoulder portion of the outer ring and the second shoulder portion of the outer ring, the raceway groove of the outer ring defining a raceway surface on an in the inner circumferential surfacethereof; and

a plurality of balls rollably disposed between the raceway surface of the raceway groove of the inner ring and the raceway surface of the raceway groove of the outer ring;

a cage configured to retain the plurality of balls at intervals in a circumferential direction, the cage being a crown type cage comprising a base portion and a plurality of pillar portions protruded on an axial end face of axially from the base portion, the bails balls being accommodated in spherical pockets formed between the pillar portions; and

an annular lubricant guide fixed to in fixed engagement with the engagement groove of the outer ring at an axial end portion of the outer ring and extending towards a shoulder portion the tapered portion of the inner ring,

wherein an annular opening portion is formed between an inner circumferential portion of the lubricant guide and the outer circumferential surface of the inner ring to supply lubricating oil into an interior of the ball bearing, and

wherein the tapered portion of the inner ring faces an inner circumferential portion of the lubricant guide,

wherein the ball bearing is used under an environment in which the lubricating oil is supplied from one side in an axial direction with respect to the balls and is discharged from the other side in the axial direction with respect to the balls,

wherein the lubricant guide is provided only on said one a first side in the an axial direction with respect to the balls, the other side being an annular the annular supply opening is formed between the inner circumferential portion of the lubricant guide and the tapered portion of the inner ring to supply lubricating oil into an interior of the ball bearing, and the discharge opening extending is on a second side in the axial direction with respect to the balls and extends radially between the outer ring inner circumferential surface and the inner ring outer circumferential surface to discharge the lubricating oil from the interior of the ball bearing, and

wherein the ball bearing is used in an environment in which the lubricating oil is supplied from the first side in the axial direction with respect to the balls and is discharged from the second side in the axial direction with respect to the balls,

wherein the base portion of the cage is disposed to face said one the first side in the axial direction; and

wherein the inner circumferential portion of the lubricant guide comprises a bent wall extending toward the interior of the bearing;

wherein a radial widthwise center of the cage is offset radially inwards relative to a center of each of the balls,

wherein the center of each of the balls is offset towards the second side in the axial direction relative to axial widthwise centers of the inner ring and the outer ring,

wherein an inside diameter of the lubricant guide is smaller than an inside diameter of the cage, and

wherein a shortest distance between the tapered portion of the inner ring and the inner circumferential portion of the lubricant guide is 11% or more of the diameter of each of the balls.

2. The ball bearing as set forth in claim 1,

wherein a radial widthwise center of the cage is offset radially inwards than a center of each of the balls.

3. The ball bearing as set forth in claim 1, wherein a center of each of the balls is offset toward the other side in the axial direction than axial widthwise centers of the inner ring and the outer ring.

4. The ball bearing as set forth in claim 1, wherein the shoulder portion of the inner ring that faces the inner circumferential portion of the lubricant guide comprises at least one of a tapered cutout portion and a stepped cutout portion.

5. The ball bearing as set forth in claim 1, wherein the inner circumferential portion of the lubricant guide comprises a bent wall which is bent toward the interior of the bearing.

6. The ball bearing as set forth in claim 1, wherein an edge edges of an inner circumferential portion portions of the spherical pocket pockets of the cage is are chamfered or rounded.

7. The ball bearing as set forth in claim 1, wherein an inside diameter of the lubricant guide is equal to or smaller than an inside diameter of the cage, and

wherein a shortest distance between the outer circumferential portion of the inner ring and the inner circumferential portion of the lubricant guide which form the annular opening portion is 11% or more of the diameter of the ball.

8. The ball bearing as set forth in claim 1, wherein the lubricant guide and a housing to which the outer ring is fixed are formed as a one-piece structure.