JP7630245B2 - Ball bearings - Google Patents

Description

This invention relates to ball bearings.

Ball bearings are often used to support rotating shafts in automobiles, industrial machinery, and other equipment. In general, a ball bearing has an inner ring, an outer ring arranged coaxially and radially outward of the inner ring, a number of balls arranged in the annular space between the inner ring and the outer ring, and a cage that holds the balls.

As an example of a cage, as disclosed in Patent Document 1, a resin cage (a so-called crown cage) is known that has a cage ring portion that extends circumferentially adjacent to the area through which the balls pass, and a cantilever-shaped cage claw portion that extends axially from the cage ring portion between adjacent balls in the circumferential direction. The cage claw portion has a ball guide surface that faces the surface of the ball, and this ball guide surface is a concave spherical surface that conforms to the surface of the ball so as to embrace the ball.

Patent No. 3035766

In recent years, in the field of electric vehicles such as EVs (battery electric vehicles) and HEVs (hybrid electric vehicles), efforts are being made to increase the speed of electric motors in order to reduce their size and weight. Ball bearings that support the rotating shaft to which the rotation of such electric motors is input are sometimes used under conditions where the dmn value (ball pitch circle diameter dm (mm) × rotation speed n (min ^-1 )) exceeds 2 million.

The inventors of this application have considered using a crown cage in ball bearings that support rotating shafts that rotate at high speeds in EVs, HEVs, and other vehicles.

However, it has been found that when a crown-shaped cage is used in a ball bearing that rotates at high speed, the centrifugal force acting on the cantilever-shaped cage claws causes torsional deformation in the cage annular portion that tilts the cage claws radially outward, and the cage claws themselves also undergo bending deformation radially outward, and these deformations may cause the cage claws to interfere with the balls. If the cage claws interfere with the balls, this can cause heat to build up in the ball bearing.

The problem that this invention aims to solve is to provide a ball bearing in which the plastic cage is less likely to deform due to centrifugal force when used at high speeds.

In order to solve the above problems, the present invention employs the following configuration for a ball bearing.
With the inner circle,
an outer ring provided coaxially on the radially outer side of the inner ring;
A plurality of balls are mounted in an annular space formed between the inner ring and the outer ring;
a resin cage that holds the plurality of balls;
an inner periphery of the outer ring is provided with an outer ring raceway groove with which the balls roll and contact, and a pair of outer ring groove shoulders located on both axial sides of the outer ring raceway groove;
The resin cage has a cage annular portion extending in a circumferential direction adjacent to an area through which the balls pass, and a cantilever-shaped cage claw portion extending in an axial direction from the cage annular portion between the balls adjacent in the circumferential direction,
an axial length of the cage claw portion is set to be greater than an axial width of the outer ring raceway groove,
a base-side guided surface that is in sliding contact with one of the pair of outer ring groove shoulders is formed on a radially outer surface of the cage annular portion,
a tip-side guided surface that comes into sliding contact with the other of the pair of outer ring groove shoulders is formed on a radially outer surface of an axial end portion on a tip side of the cage claw portion,
A ball bearing characterized in that the base side guided surface and the tip side guided surface have a cross-sectional shape along the circumferential direction formed into an arc shape that protrudes radially outward.

In this way, the root side guided surface is formed in an arc shape with a cross section along the circumferential direction protruding outward in the radial direction, so that an oil film is formed between the root side guided surface and one of the outer ring groove shoulders due to the wedge film effect, and the oil film creates a fluid lubrication state between the root side guided surface and the outer ring groove shoulder, making it possible to keep the contact resistance between the cage and the outer ring extremely small. Similarly, the tip side guided surface is formed in an arc shape with a cross section along the circumferential direction protruding outward in the radial direction, so that an oil film is formed between the tip side guided surface and the other outer ring groove shoulder due to the wedge film effect, and the oil film creates a fluid lubrication state between the tip side guided surface and the outer ring groove shoulder, making it possible to keep the contact resistance between the cage and the outer ring extremely small. Therefore, it is possible to prevent abnormal heat generation due to the sliding resistance of the contact portion between the cage and the outer ring. In addition, one of the pair of outer ring groove shoulders supports the cage ring from the radial outside, and the other supports the axial end of the tip of the cage claw from the radial outside, so the cage claw is less likely to bend radially outward. Therefore, even when used at high speeds, the cage ring is prevented from being twisted by the centrifugal force applied to the cage claw, and the cage claw itself is prevented from being bent radially outward.

The cage claw portion has a circumferentially opposed surface that faces the ball in a circumferential direction,
It is preferable that the portion of the circumferential opposing surface that receives the balls circumferentially be configured in a planar shape extending parallel to a straight line connecting the center of the retainer annular portion and the center of the retainer claw portion so that the circumferential opposing surface does not interfere with the balls when the retainer claw portion moves radially outward due to centrifugal force.

In this way, because the circumferentially facing surfaces of the retainer claws are flat, it is possible to prevent the circumferentially facing surfaces of the retainer claws from interfering with the balls when the retainer claws move radially outward due to centrifugal force acting on the retainer claws. In addition, the shear resistance of the lubricant generated between the circumferentially facing surfaces of the retainer claws and the balls is kept low, making it possible to suppress heat generation in the ball bearing.

It is preferable to provide R-chamfering to the axial end edge of the base side guided surface farther from the retainer claw portion and the axial end edge of the tip side guided surface farther from the retainer ring portion.

In this way, an oil film can be effectively formed between the base guided surface and one of the outer ring groove shoulders by the wedge film effect, and an oil film can also be effectively formed between the tip guided surface and the other outer ring groove shoulder by the wedge film effect.

It is preferable to form an escape recess extending in the circumferential direction with an axial width wider than the axial width of the outer ring raceway groove between the root side guided surface and the tip side guided surface on the radially outer surface of the cage claw portion.

In this way, it is possible to prevent the boundary portion between the outer ring groove shoulder and the outer ring raceway groove from sliding against the radially outer surface of the cage ring portion or the radially outer surface of the cage claw portion. As a result, it is possible to prevent the radially outer surface of the cage ring portion or the radially outer surface of the cage claw portion from wearing locally at the position corresponding to the boundary portion between the outer ring groove shoulder and the outer ring raceway groove.

It is preferable to form an oil reservoir groove on the radially inner surface of the retainer claw portion, the oil reservoir groove extending axially from the tip of the retainer claw portion toward the retainer ring portion.

In this way, the lubricant that is scattered to the outer diameter side by centrifugal force can be collected in the oil collection groove and then supplied to the inner ring.

The annular space has an opening at one end in the axial direction, and the annular space has an annular seal member.
the retainer annular portion has a retainer-side sliding surface that is in sliding contact with the seal member while facing the retainer in the axial direction,
the seal member has a seal-side sliding surface that is in sliding contact with the cage-side sliding surface,
It is preferable to adopt a configuration in which a plurality of axial protrusions, each of which has an axially convex arc-shaped cross-sectional shape along the circumferential direction, is formed at a constant pitch in the circumferential direction on one of the retainer side sliding surface and the seal side sliding surface.

In this way, multiple axial protrusions, each of which has an axially convex arc-shaped cross section along the circumferential direction, are formed at a constant pitch on one of the sliding surfaces of the retainer side and the seal side, so that an oil film is formed between the axial protrusions and the sliding surface due to the wedge film effect, and the oil film creates a fluid lubrication state between the axial protrusions and the sliding surface, making it possible to keep the contact resistance between the retainer and the seal member extremely small. This makes it possible to prevent abnormal heat generation due to the sliding resistance of the contact area between the retainer and the seal member. In addition, since the retainer ring portion is provided in sliding contact with the seal member, the axial thickness of the retainer ring portion can be set large, making it possible to increase the rigidity of the retainer ring portion. Therefore, even when used at high speed rotation, it is possible to suppress torsional deformation of the retainer ring portion due to the centrifugal force received by the retainer claw portion.

It is preferable that the axial protrusion has a parallel apex portion in which the height of the axially convex arc-shaped apex in the circumferential cross section is constant along the radial direction, and an inclined apex portion in which the height of the axially convex arc-shaped apex in the circumferential cross section gradually decreases from the radial outer end of the parallel apex portion toward the radial outward direction.

In this way, when the bearing rotates at a low speed and the centrifugal force applied to the retainer claws is relatively small, an oil film can be formed between the parallel tops of the axial protrusions and the sliding surface due to the wedge film effect. Also, when the bearing rotates at a high speed and the centrifugal force applied to the retainer claws is relatively large, an oil film can be formed between the parallel tops and inclined tops of the axial protrusions and the sliding surface due to the wedge film effect, with the retainer annular portion undergoing relatively large torsional deformation. In this way, it is possible to stably form an oil film between the retainer and the seal member due to the wedge film effect, regardless of the rotational speed of the bearing.

It is preferable that the inclined apex has an R-shape in cross section perpendicular to the circumferential direction that smoothly connects to the parallel apex.

In this way, the inclined apex and the parallel apex are smoothly connected, so when an oil film is formed between the parallel apex and the inclined apex and the sliding surface due to the wedge film effect when the retainer annular portion is in a state where a relatively large torsional deformation occurs, the oil film can be formed stably.

The multiple axial protrusions are preferably positioned at a position overlapping the pitch circle of the ball or radially outward from that position.

In this way, when the centrifugal force acting on the cage claw portion causes twisting deformation in the cage ring portion in a direction that tilts the cage claw portion radially outward, the cage side sliding surface and the seal side sliding surface can be prevented from coming into contact at a position radially outwardly of the axial protrusion due to the twisting deformation.

It is preferable to adopt a configuration in which the axial end of the annular space opposite the axial end blocked by the sealing member is open without a sealing member so that lubricant supplied from the outside can be received in the annular space.

This allows the base side guided surface and the tip side guided surface to be sufficiently lubricated, ensuring the formation of an oil film using a wedge film.

It is particularly suitable for use as a bearing in an electric vehicle transmission that slows down the rotation of the electric motor in the electric vehicle.

In the ball bearing of this invention, the root guided surface is formed in an arc shape with a cross section along the circumferential direction protruding radially outward, so that an oil film is formed between the root guided surface and one of the outer ring groove shoulders due to the wedge film effect, and the oil film creates a fluid lubrication state between the root guided surface and the outer ring groove shoulder, making it possible to keep the contact resistance between the cage and the outer ring extremely small. Similarly, the tip guided surface is formed in an arc shape with a cross section along the circumferential direction protruding radially outward, so that an oil film is formed between the tip guided surface and the other outer ring groove shoulder due to the wedge film effect, and the oil film creates a fluid lubrication state between the tip guided surface and the outer ring groove shoulder, making it possible to keep the contact resistance between the cage and the outer ring extremely small. Therefore, it is possible to prevent abnormal heat generation due to the sliding resistance of the contact portion between the cage and the outer ring. In addition, one of the pair of outer ring groove shoulders supports the cage ring from the radial outside, and the other supports the axial end of the tip of the cage claw from the radial outside, so the cage claw is less likely to bend radially outward. Therefore, even when used at high speeds, the cage ring is prevented from being twisted by the centrifugal force applied to the cage claw, and the cage claw itself is prevented from being bent radially outward.

FIG. 1 is a cross-sectional view showing a ball bearing according to a first embodiment of the present invention. 2 is a cross-sectional view taken along line II-II of FIG. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 2 is an enlarged cross-sectional view of the vicinity of the retainer ring portion of the ball bearing shown in FIG. A cross-sectional view taken along line V-V in FIG. FIG. 2 is a perspective view of the cage of FIG. 1 as seen from the cage claw portion side. FIG. 2 is an enlarged view of the vicinity of the seal lip of the seal member of FIG. 1 . 8 is a cross-sectional view taken along line VIII-VIII of FIG. Schematic diagram of an electric vehicle transmission incorporating the ball bearing of FIG. FIG. 4 is a cross-sectional view showing a ball bearing according to a second embodiment of the present invention. 11 is a cross-sectional view taken along line XI-XI of FIG. 12 is a cross-sectional view taken along line XII-XII of FIG. FIG. 11 is a perspective view of the cage of FIG. 10 as viewed from the cage claw portion side. FIG. 11 is a cross-sectional view showing a ball bearing according to a third embodiment of the present invention. 15 is a cross-sectional view taken along line XV-XV of FIG. 16 is a cross-sectional view taken along line XVI-XVI of FIG. FIG. 15 is a perspective view of the cage of FIG. 14 as viewed from the cage claw portion side. FIG. 13 is an enlarged cross-sectional view of the vicinity of a retainer annular portion of a ball bearing according to a fourth embodiment of the present invention; 19 is a cross-sectional view taken along line XIX-XIX of FIG. FIG. 13 is an enlarged cross-sectional view of the vicinity of a retainer annular portion of a ball bearing according to a fifth embodiment of the present invention. 21 is a cross-sectional view taken along line XXI-XXI of FIG.

Figure 1 shows a ball bearing 1 according to a first embodiment of the present invention. This ball bearing 1 has an inner ring 2, an outer ring 3 arranged coaxially on the radial outside of the inner ring 2, a number of balls 5 assembled at intervals in the circumferential direction in an annular space 4 formed between the inner ring 2 and the outer ring 3, an annular seal member 6 that closes one of the end openings on both sides of the axial direction of the annular space 4, and a plastic retainer 7 (hereinafter simply referred to as "retainer 7") that maintains the circumferential spacing of the balls 5.

On the outer periphery of the inner ring 2, an inner ring raceway groove 8 with which the balls 5 roll and make contact, a pair of inner ring groove shoulders 9 located axially outside the inner ring raceway groove 8, and a sliding recess 10 located axially outside the inner ring groove shoulders 9 are formed. The inner ring raceway groove 8 is an arc groove with a concave arc-shaped cross section along the surface of the balls 5, and is formed extending circumferentially through the axial center of the outer periphery of the inner ring 2. The pair of inner ring groove shoulders 9 are bank-shaped parts extending circumferentially on both sides of the inner ring raceway groove 8 in the axial direction. The sliding recess 10 is a circumferentially extending recess formed adjacent to the axial outside of the inner ring groove shoulders 9. A seal lip 11 provided at the inner diameter end of the seal member 6 is in sliding contact with the inner surface of the sliding recess 10. In the figure, the surface of the inner surface of the sliding recess 10 with which the seal lip 11 makes sliding contact is a cylindrical surface having a constant outer diameter along the axial direction.

On the inner circumference of the outer ring 3, there are formed an outer ring raceway groove 12 with which the balls 5 roll and make contact, a pair of outer ring groove shoulders 13 located axially outward of the outer ring raceway groove 12, and a seal fixing groove 14 located axially outward of the outer ring groove shoulders 13. The outer ring raceway groove 12 is an arc groove with a concave arc-shaped cross section along the surface of the balls 5, and is formed extending circumferentially through the axial center of the inner circumference of the outer ring 3. The pair of outer ring groove shoulders 13 are bank-shaped parts extending circumferentially on both sides of the outer ring raceway groove 12 in the axial direction. The seal fixing groove 14 is a groove extending circumferentially formed adjacent to the axial outside of the outer ring groove shoulders 13. An engagement portion 15 provided on the outer diameter side end of the seal member 6 is engaged and fixed in the seal fixing groove 14.

The ball 5 is radially sandwiched between the outer ring raceway groove 12 and the inner ring raceway groove 8. The axial width dimension of the outer ring raceway groove 12 is greater than half the diameter of the ball 5. Also, the axial width dimension of the inner ring raceway groove 8 is greater than half the diameter of the ball 5.

As shown in FIG. 4, the seal member 6 is an annular member formed by vulcanizing and bonding a rubber material 17 (e.g., nitrile rubber, acrylic rubber, etc.) to the surface of an annular core metal 16. The seal member 6 has a fitting portion 15 that fits into the seal fixing groove 14, an annular plate portion 18 that extends radially inward from the fitting portion 15, and a seal lip 11 that slides against the inner surface of the sliding recess 10. The core metal 16 has an annular plate-shaped flange portion 19 and a cylindrical portion 20 that is bent axially inward along the radial outer end of the flange portion 19. The flange portion 19 is embedded in the annular plate portion 18 of the seal member 6, and the cylindrical portion 20 is embedded in the fitting portion 15 of the seal member 6.

As shown in FIG. 1, the seal member 6 is provided only on one of the end openings on both axial sides of the annular space 4. In other words, the axial end on the side of the annular space 4 that is blocked by the seal member 6 (the right side in the figure) is open without the seal member 6 so that lubricating oil supplied from the outside can be received into the annular space 4.

The cage 7 has a cage annular portion 21 that extends circumferentially adjacent to the area through which the balls 5 pass, and cage claw portions 22 that extend axially from the cage annular portion 21 between the circumferentially adjacent balls 5. The cage annular portion 21 and the cage claw portions 22 are seamlessly formed as a single piece from a resin composition. The resin composition forming the cage annular portion 21 and the cage claw portions 22 can be made of resin material only, but here, a resin material with added fiber reinforcing material is used.

Polyamide (PA) or super engineering plastics can be used as the base resin material for the resin composition. As polyamides, polyamide 46 (PA46), polyamide 66 (PA66), polynonamethylene terephthalamide (PA9T), etc. can be used. As super engineering plastics, polyether ether ketone (PEEK) and polyphenylene sulfide (PPS) can be used. As fiber reinforcing materials to be added to the resin material, glass fiber, carbon fiber, aramid fiber, etc. can be used.

The cage claw portion 22 is formed in a cantilever shape with one axial end fixed to the cage annular portion 21 as a fixed end and the other axial end as a free end. The axial length of the cage claw portion 22 is set to be greater than the axial width of the outer ring raceway groove 12. The cage claw portion 22 has a constant shape with no change in radial thickness in the axial direction.

As shown in Figures 1 and 6, a root-side guided surface 23 that slides against one of the pair of outer ring groove shoulders 13 is formed on the radial outer surface of the cage ring portion 21 at a position corresponding to the root of the cage claw portion 22. In addition, a tip-side guided surface 24 that slides against the other of the pair of outer ring groove shoulders 13 is formed on the radial outer surface of the axial end portion on the tip side of the cage claw portion 22.

As shown in FIG. 5, the root side guided surface 23 has a cross-sectional shape along the circumferential direction formed in an arc shape that protrudes radially outward. Here, "protruding radially outward" means that the shape protrudes radially outward with respect to a circle concentric with the retainer annular portion 21. The tip side guided surface 24 (see FIG. 6) also has a cross-sectional shape along the circumferential direction formed in an arc shape that protrudes radially outward. The cross section along the circumferential direction of the root side guided surface 23 and the cross section along the circumferential direction of the tip side guided surface 24 have the same shape. The radii of curvature of the cross sections along the circumferential direction of the root side guided surface 23 and the tip side guided surface 24 can be set to be smaller than 1/2 the radius of the inner diameter of the outer ring groove shoulder portion 13 and larger than 1/10 the radius of the inner diameter of the outer ring groove shoulder portion 13.

As shown in FIG. 6, in this embodiment, the root side guided surface 23 and the tip side guided surface 24 are a continuous, straight surface in the axial direction so that no recess is formed between the root side guided surface 23 and the tip side guided surface 24.

As shown in FIG. 3, the axial edge 25 of the base guided surface 23, which is far from the retainer claw portion 22, is R-chamfered. Here, R-chamfering refers to providing a corner shape such that the cross section perpendicular to the circumferential direction is a convex arc shape, as shown in FIG. 4. As shown in FIG. 3, the axial edge 26 of the tip guided surface 24, which is far from the retainer annular portion 21, is also R-chamfered.

As shown in FIG. 2, the retainer claw portion 22 has a circumferentially opposed surface 27 that faces the balls 5 in the circumferential direction. The portion of the circumferentially opposed surface 27 that receives the balls 5 in the circumferential direction has a planar shape that extends parallel to an imaginary line connecting the center of the retainer annular portion 21 and the center of the retainer claw portion 22 when viewed in the axial direction so that the circumferentially opposed surface 27 does not interfere with the balls 5 when the retainer claw portion 22 moves radially outward due to centrifugal force. Here, the center of the retainer annular portion 21 is at the same position as the center of the inner ring 2 or the center of the outer ring 3. Also, the center of the retainer claw portion 22 is at the midpoint of a pair of circumferentially opposed surfaces 27 located on both circumferential sides of the retainer claw portion 22 when viewed in the axial direction.

As shown in FIG. 3, the portion of the circumferential facing surface 27 that receives the balls 5 in the circumferential direction extends straight in the axial direction without any circumferential inclination when viewed radially so as not to generate an axial component force when the balls 5 are received. The cage annular portion 21 has an axial facing surface 28 that faces the balls 5 in the axial direction. The circumferential facing surface 27 and the axial facing surface 28 are connected in a concave arc shape in cross section.

As shown in Figures 7 and 8, the inner diameter end of the seal lip 11 is provided with a number of protrusions 29 spaced apart in the circumferential direction, which come into sliding contact with the sliding recess 10 on the outer periphery of the inner ring 2. The protrusions 29 are formed to extend in a direction perpendicular to the circumferential direction. As shown in Figure 8, each protrusion 29 has a convex arc-shaped cross section.

The above-mentioned ball bearing 1 can be used as a bearing for an electric vehicle transmission 30 that reduces the rotation speed of an electric motor 31 of an electric vehicle such as an EV (battery electric vehicle) or HEV (hybrid electric vehicle), as shown in Fig. 9. The bearing for this electric vehicle transmission 30 rotates at a wide range of rotation speeds from low to high speeds while the vehicle is running, and when the bearing rotates at the highest speed, it is used under conditions where the dmn value (pitch circle diameter of balls 5 (mm) x rotation speed (min ^-1 )) exceeds 2 million.

The transmission shown in FIG. 9 includes a stator 32 of an electric motor 31, a rotor 33 of the electric motor 31, a rotating shaft 34 connected to the rotor 33, a ball bearing 1 that rotatably supports the rotating shaft 34, a second rotating shaft 35 and a third rotating shaft 36 arranged parallel to the rotating shaft 34, a first gear train 37 that transmits the rotation of the rotating shaft 34 to the second rotating shaft 35, and a second gear train 38 that transmits the rotation of the second rotating shaft 35 to the third rotating shaft 36. The stator 32 is an annular stationary member, and the rotor 33 as a rotating member is arranged inside the stator 32. When electricity is applied to the stator 32, the rotor 33 rotates due to the electromagnetic force acting between the stator 32 and the rotor 33, and the rotation of the rotor 33 is input to the rotating shaft 34.

As shown in Fig. 5, the base guided surface 23 of this ball bearing 1 is formed in an arc shape with a cross section along the circumferential direction that protrudes radially outward, so that an oil film is formed between the base guided surface 23 and one of the outer ring groove shoulders 13 due to the wedge film effect, and the oil film creates a fluid lubrication state between the base guided surface 23 and the outer ring groove shoulder 13, making it possible to keep the contact resistance between the cage 7 and the outer ring 3 extremely small. Similarly, the tip guided surface 24 shown in Fig. 1 is also formed in an arc shape with a cross section along the circumferential direction that protrudes radially outward, so that an oil film is formed between the tip guided surface 24 and the other outer ring groove shoulder 13 (left outer ring groove shoulder 13) due to the wedge film effect, and the oil film creates a fluid lubrication state between the tip guided surface 24 and the outer ring groove shoulder 13, making it possible to keep the contact resistance between the cage 7 and the outer ring 3 extremely small. This prevents abnormal heat generation caused by sliding resistance at the contact points between the cage 7 and the outer ring 3.

Here, the lubrication state between the sliding surfaces is divided into a boundary lubrication state and a fluid lubrication state. The boundary lubrication state refers to a state in which the sliding surfaces are lubricated with an oil film consisting of several molecular layers (about ^10-5 to ^10-6 mm) of lubricating oil adsorbed on each sliding surface, and the fine unevenness of the sliding surfaces directly contact each other. On the other hand, the fluid lubrication state refers to a state in which an oil film (for example, about ^10-3 to ^10-1 mm) is formed between the sliding surfaces due to the wedge film effect, and the oil film does not cause direct contact between the sliding surfaces (a state in which only indirect contact occurs through the oil film). When the wedge film effect occurs and the state of fluid lubrication is reached, the sliding resistance becomes almost zero, making it possible to use the sliding surfaces at high peripheral speeds that were previously impossible.

In addition, as shown in FIG. 1, in this ball bearing 1, one of the pair of outer ring groove shoulders 13 (the right outer ring groove shoulder 13) supports the retainer annular portion 21 from the radial outside, and the other outer ring groove shoulder 13 (the left outer ring groove shoulder 13) supports the axial end portion of the tip side of the retainer claw portion 22 from the radial outside, so that the retainer claw portion 22 is less likely to bend radially outward. Therefore, even when used at high speeds, the centrifugal force applied to the retainer claw portion 22 can be prevented from causing torsional deformation in the retainer annular portion 21, and the retainer claw portion 22 itself can be prevented from being bent radially outward.

As shown in FIG. 3, the axial edge 25 of the base guided surface 23 on the side farther from the retainer claw portion 22 and the axial edge 26 of the tip guided surface 24 on the side farther from the retainer annular portion 21 of the ball bearing 1 are rounded. This allows an oil film to be effectively formed between the base guided surface 23 and one of the outer ring groove shoulders 13 (the right outer ring groove shoulder 13) shown in FIG. 1 by the wedge film effect, and also allows an oil film to be effectively formed between the tip guided surface 24 and the other outer ring groove shoulder 13 (the left outer ring groove shoulder 13) by the wedge film effect.

As shown in FIG. 2, the portion of the circumferentially facing surface 27 of the ball bearing 1 that receives the balls 5 in the circumferential direction has a planar shape that extends parallel to the line connecting the center of the retainer annular portion 21 and the center of the retainer claw portion 22. This prevents the circumferentially facing surface 27 of the retainer claw portion 22 from interfering with the balls 5 when the retainer claw portion 22 moves radially outward due to the centrifugal force acting on the retainer claw portion 22. In addition, the shear resistance of the lubricating oil generated between the circumferentially facing surface 27 of the retainer claw portion 22 and the balls 5 is kept low, so heat generation in the ball bearing 1 can also be suppressed.

In addition, because the axial end of the ball bearing 1 is open on the side opposite the axial end of the annular space 4 that is blocked by the sealing member 6, the base guided surface 23 and the tip guided surface 24 can be sufficiently lubricated, and a wedge-film oil film can be reliably formed.

In the above embodiment, an oil-lubricated ball bearing 1 using lubricating oil as the lubricant for lubricating the inside of the bearing has been described as an example, but this invention can also be applied to a grease-lubricated ball bearing 1 using grease as the lubricant for lubricating the inside of the bearing. Grease is a semi-solid lubricant that contains lubricating oil and a thickener that is dispersed in the lubricating oil.

Figures 10 to 13 show a ball bearing 1 according to the second embodiment. Parts corresponding to those in the first embodiment are given the same reference numerals and will not be described.

As shown in Figures 10 and 12, an oil reservoir groove 40 is formed on the radial inner surface of the retainer claw portion 22, extending axially from the tip of the retainer claw portion 22 toward the retainer annular portion 21. As shown in Figure 10, the oil reservoir groove 40 is cut into the radial inner surface of the retainer 7 at a position radially opposite the inner ring groove shoulder 9 of the pair of inner ring groove shoulders 9 that is closer to the retainer annular portion 21. In other words, the oil reservoir groove 40 is a groove that does not penetrate in the axial direction. Note that the oil reservoir groove 40 can also be formed by penetrating the radial inner surface of the retainer 7 in the axial direction.

As shown in Figures 11 and 13, the oil reservoir groove 40 is formed in the circumferential center of the radially inner surface of the retainer claw portion 22. The oil reservoir groove 40 has a semicircular cross-sectional shape. The oil reservoir groove 40 may have a triangular cross-sectional shape or a rectangular cross-sectional shape.

In this embodiment, the ball bearing 1 is capable of collecting lubricating oil that is scattered toward the outer diameter side due to centrifugal force in the oil collection groove 40 and supplying the lubricating oil to the inner ring 2.

Furthermore, the ball bearing 1 of this embodiment has the same effects as the first embodiment.

Figures 14 to 17 show a ball bearing 1 according to the third embodiment. Parts corresponding to those in the first and second embodiments are given the same reference numerals and will not be described.

As shown in FIG. 17, an escape recess 41 is formed on the radial outer surface of the retainer claw portion 22 between the root guided surface 23 and the tip guided surface 24. In other words, the radial outer surface of the retainer claw portion 22 is a stepped surface in which the root guided surface 23, the escape recess 41, and the tip guided surface 24 are arranged in order along the axial direction.

14 and 15, the relief recess 41 extends in the circumferential direction with an axial width wider than the axial width of the outer ring raceway groove 12. Here, as shown in FIG. 14, the relief recess 41 is arranged so as to cover the entire axial width of the outer ring raceway groove 12. That is, the end of the relief recess 41 on the side of the root side guided surface 23 is arranged at a position shifted toward the one outer ring groove shoulder 13 side from the boundary portion between one of the pair of outer ring groove shoulders 13 (the outer ring groove shoulder 13 on the side closer to the retainer annular portion 21) and the outer ring raceway groove 12. Also, the end of the relief recess 41 on the side of the tip side guided surface 24 is arranged at a position shifted toward the other outer ring groove shoulder 13 side from the boundary portion between the other of the pair of outer ring groove shoulders 13 (the outer ring groove shoulder 13 on the side farther from the retainer annular portion 21) and the outer ring raceway groove 12. Both axial ends of the relief recess 41 are inclined and cut upward toward the base guided surface 23 and the tip guided surface 24.

As shown in FIG. 15, the relief recess 41 is recessed relative to the base guided surface 23 (or the tip guided surface 24) so that its inner surface is located at a position radially inwardly retreated from the base guided surface 23 (or the tip guided surface 24). In the figure, the inner surface of the relief recess 41 is a flat surface perpendicular to the radial direction.

As shown in FIG. 14, the ball bearing 1 of this embodiment has an escape recess 41 formed between the root guided surface 23 and the tip guided surface 24, so that the boundary portion between the outer ring groove shoulder 13 and the outer ring raceway groove 12 can be prevented from sliding against the radially outer surface of the retainer annular portion 21 or the radially outer surface of the retainer claw portion 22. Therefore, it is possible to prevent the radially outer surface of the retainer annular portion 21 or the radially outer surface of the retainer claw portion 22 from wearing locally at the position corresponding to the boundary portion between the outer ring groove shoulder 13 and the outer ring raceway groove 12.

In addition, the ball bearing 1 of this embodiment has the same effects as the first and second embodiments.

Figures 18 and 19 show a ball bearing 1 according to the fourth embodiment. Parts corresponding to those in the first embodiment are given the same reference numerals and will not be described.

As shown in FIG. 18, the axial thickness of the retainer annular portion 21 is approximately the same as the axial spacing between the balls 5 and the seal member 6 (specifically, 95% or more and less than 100% of the axial spacing between the balls 5 and the seal member 6). The retainer annular portion 21 has a retainer-side sliding surface 42 that is in sliding contact with the seal member 6 opposite in the axial direction, and the seal member 6 has a seal-side sliding surface 43 that is in sliding contact with the retainer-side sliding surface 42.

As shown in FIG. 19, a plurality of axial protrusions 44 are formed at a constant pitch in the circumferential direction on the retainer side sliding surface 42. Each axial protrusion 44 is formed so that its cross-sectional shape along the circumferential direction is an axially convex arc shape. The axial height of the axial protrusions 44 is set to 5% or less of the circumferential width dimension of the axial protrusions 44. In the figure, the axial height of the axial protrusions 44 is exaggerated to make the presence of the axial protrusions 44 easier to understand. On the other hand, the seal side sliding surface 43 is an annular flat surface perpendicular to the axial direction, and no axial protrusions 44 are formed.

As shown in FIG. 18, the axial protrusion 44 is positioned at a position overlapping the pitch circle of the balls 5 (a virtual circle connecting the centers of multiple balls 5) or radially outward from that. Here, "the axial protrusion 44 is positioned at a position overlapping the pitch circle of the balls 5" means that the virtual cylindrical surface passing through the pitch circle of the balls 5 passes through the position of the axial protrusion 44, and "the axial protrusion 44 is positioned radially outward from the pitch circle of the balls 5" means that the entire axial protrusion 44 is positioned radially outward from the virtual cylindrical surface passing through the pitch circle of the balls 5. In the figure, the axial protrusion 44 is positioned radially outward from the pitch circle of the balls 5.

The axial protrusion 44 has a parallel apex 45, a first inclined apex 46, and a second inclined apex 47. The parallel apex 45 is a portion in which the height of the axially convex arc-shaped apex in the circumferential cross section is constant along the radial direction. The first inclined apex 46 is a portion in which the height of the axially convex arc-shaped apex in the circumferential cross section gradually decreases from the radial outer end of the parallel apex 45 toward the radial outward direction. The second inclined apex 47 is a portion in which the height of the axially convex arc-shaped apex in the circumferential cross section gradually decreases from the radial inner end of the parallel apex 45 toward the radial inward direction. As shown in FIG. 18, the first inclined apex 46 has a cross-sectional shape perpendicular to the circumferential direction that is R-shaped so as to smoothly connect with the parallel apex 45. The second inclined apex 47 also has a cross-sectional shape perpendicular to the circumferential direction that is R-shaped so as to smoothly connect with the parallel apex 45.

As shown in FIG. 19, this ball bearing 1 has a plurality of axial protrusions 44 formed at a constant pitch on the retainer side sliding surface 42, whose cross-sectional shape along the circumferential direction is an axially convex arc shape. An oil film is formed between the axial protrusions 44 and the seal side sliding surface 43 due to the wedge film effect, and this oil film creates a fluid lubrication state between the axial protrusions 44 and the seal side sliding surface 43, making it possible to keep the contact resistance between the retainer 7 and the seal member 6 extremely small. This makes it possible to prevent abnormal heat generation due to the sliding resistance at the contact area between the retainer 7 and the seal member 6.

In addition, as shown in FIG. 18, this ball bearing 1 has the retainer annular portion 21 in sliding contact with the seal member 6, so that the axial thickness of the retainer annular portion 21 can be set large, making it possible to increase the rigidity of the retainer annular portion 21. Therefore, even when used at high speeds, torsional deformation of the retainer annular portion 21 due to the centrifugal force applied to the retainer claw portion 22 can be suppressed.

This ball bearing 1 can also be installed in locations where the space required for installation is narrow and the width of the bearing needs to be kept small (i.e., locations where, in the past, it was necessary to abandon the use of sealed ball bearings and instead use open-type ball bearings with both axial ends open without the seal member 6).

In addition, as shown in FIG. 18, this ball bearing 1 employs an axial protrusion 44 having a parallel apex 45 and a first inclined apex 46, so that when the bearing rotates at a low speed and the centrifugal force received by the retainer claw portion 22 is relatively small, an oil film can be formed between the parallel apex 45 of the axial protrusion 44 and the seal side sliding surface 43 due to the wedge film effect. When the bearing rotates at a high speed and the centrifugal force received by the retainer claw portion 22 is relatively large, an oil film can be formed between the parallel apex 45 and the first inclined apex 46 of the axial protrusion 44 and the seal side sliding surface 43 in a state in which the retainer annular portion 21 has undergone a relatively large torsional deformation. In this way, it is possible to stably form an oil film between the retainer 7 and the seal member 6 due to the wedge film effect, regardless of the rotation speed of the bearing.

As shown in FIG. 18, the cross-sectional shape of the first inclined apex 46 perpendicular to the circumferential direction of this ball bearing 1 is R-shaped, and the first inclined apex 46 and the parallel apex 45 are smoothly connected. Therefore, when an oil film is formed between the parallel apex 45 and the first inclined apex 46 and the seal side sliding surface 43 due to the wedge film effect when the retainer annular portion 21 is in a state where a relatively large torsional deformation occurs, the oil film can be formed stably.

In addition, as shown in FIG. 18, the axial protrusion 44 of this ball bearing 1 is positioned at a position overlapping the pitch circle of the balls 5 or radially outward from that. Therefore, when the centrifugal force acting on the retainer claw portion 22 causes torsional deformation in the retainer annular portion 21 in a direction tilting the retainer claw portion 22 radially outward, the torsional deformation can be prevented from causing the retainer side sliding surface 42 and the seal side sliding surface 43 to come into contact at a position radially outward from the axial protrusion 44.

The ball bearing 1 of this embodiment has the same effect as the first embodiment. Furthermore, it is possible to add the configurations of the second and third embodiments to the ball bearing 1 of this embodiment.

20 and 21 show a ball bearing 1 according to the fifth embodiment. The fourth embodiment differs in that an axial protrusion 44 is provided on the cage-side sliding surface 42, which is one of the cage-side sliding surface 42 and the seal-side sliding surface 43, whereas the fifth embodiment differs in that an axial protrusion 44 is provided on the seal-side sliding surface 43; otherwise, the configuration is the same. Therefore, parts corresponding to the fourth embodiment are given the same reference numerals and will not be described.

21, a plurality of axial protrusions 44 are formed at a constant pitch in the circumferential direction on the seal side sliding surface 43. The axial protrusions 44 are molded in a mold on the rubber material 17 that constitutes the seal member 6. Each axial protrusion 44 is formed so that the cross-sectional shape along the circumferential direction is an axially convex arc shape. The axial height of the axial protrusions 44 is set to 5% or less of the circumferential width dimension of the axial protrusions 44. In the figure, the axial height of the axial protrusions 44 is exaggerated to make the presence of the axial protrusions 44 easier to understand. On the other hand, the retainer side sliding surface 42 is an annular plane perpendicular to the axial direction, and no axial protrusions 44 are formed.

As shown in FIG. 20, the axial protrusion 44 is positioned at a position overlapping the pitch circle of the balls 5 (an imaginary circle connecting the centers of the multiple balls 5) or radially outward from the pitch circle.

The axial protrusion 44 has a parallel apex 45, a first inclined apex 46, and a second inclined apex 47. The parallel apex 45 is a portion in which the height of the axially convex arc-shaped apex in a cross section along the circumferential direction is constant along the radial direction. The first inclined apex 46 is a portion in which the height of the axially convex arc-shaped apex in a cross section along the circumferential direction gradually decreases from the radial outer end of the parallel apex 45 toward the radial outward direction. The second inclined apex 47 is a portion in which the height of the axially convex arc-shaped apex in a cross section along the circumferential direction gradually decreases from the radial inner end of the parallel apex 45 toward the radial inward direction. The first inclined apex 46 has a cross-sectional shape perpendicular to the circumferential direction that is R-shaped so that it smoothly connects to the parallel apex 45. The second inclined apex 47 also has a cross-sectional shape perpendicular to the circumferential direction that is R-shaped so that it smoothly connects to the parallel apex 45.

As shown in FIG. 21, this ball bearing 1 has a plurality of axial protrusions 44 formed at a constant pitch in the circumferential direction on the seal side sliding surface 43, whose cross-sectional shape along the circumferential direction is an axially convex arc shape. An oil film is formed between the axial protrusions 44 and the retainer side sliding surface 42 due to the wedge film effect, and this oil film creates a fluid lubrication state between the axial protrusions 44 and the retainer side sliding surface 42, making it possible to keep the contact resistance between the retainer 7 and the seal member 6 extremely small. This makes it possible to prevent abnormal heat generation due to the sliding resistance at the contact area between the retainer 7 and the seal member 6.

In addition, as shown in FIG. 20, this ball bearing 1 employs an axial protrusion 44 having a parallel apex 45 and a first inclined apex 46. Therefore, when the bearing rotates at a low speed and the centrifugal force applied to the retainer claw portion 22 is relatively small, an oil film can be formed between the parallel apex 45 of the axial protrusion 44 and the retainer side sliding surface 42 due to the wedge film effect. When the bearing rotates at a high speed and the centrifugal force applied to the retainer claw portion 22 is relatively large, an oil film can be formed between the parallel apex 45 and the first inclined apex 46 of the axial protrusion 44 and the retainer side sliding surface 42 in a state in which the retainer annular portion 21 has undergone a relatively large torsional deformation. In this way, it is possible to stably form an oil film between the retainer 7 and the seal member 6 due to the wedge film effect, regardless of the rotation speed of the bearing.

As shown in FIG. 20, the cross-sectional shape of the first inclined apex 46 perpendicular to the circumferential direction of this ball bearing 1 is R-shaped, and the first inclined apex 46 and the parallel apex 45 are smoothly connected. Therefore, when an oil film is formed between the parallel apex 45 and the first inclined apex 46 and the retainer side sliding surface 42 due to the wedge film effect when the retainer annular portion 21 is in a state where a relatively large torsional deformation occurs, the oil film can be formed stably.

Other effects are the same as those of the fourth embodiment.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

Reference Signs List 1 Ball bearing 2 Inner ring 3 Outer ring 4 Annular space 5 Ball 6 Seal member 7 Resin cage 12 Outer ring raceway groove 13 Outer ring groove shoulder 21 Cage annular portion 22 Cage claw portion 23 Root side guided surface 24 Tip side guided surfaces 25, 26 Axial edge 27 Circumferentially opposing surface 30 Transmission for electric vehicle 31 Electric motor 40 Oil reservoir groove 41 Relief recess 42 Cage side sliding surface 43 Seal side sliding surface 44 Axial projection 45 Parallel apex 46 First inclined apex

Claims (9)

Inner circle (2) and
an outer ring (3) provided coaxially on the radially outer side of the inner ring (2);
A plurality of balls (5) are assembled in an annular space (4) formed between the inner ring (2) and the outer ring (3);
A resin cage (7) that holds the plurality of balls (5),
An outer ring raceway groove (12) with which the balls (5) roll and come into contact is provided on an inner periphery of the outer ring (3), and a pair of outer ring groove shoulders (13) are located on both axial sides of the outer ring raceway groove (12),
The resin retainer (7) has a retainer annular portion (21) extending in the circumferential direction adjacent to a passing area of the balls (5), and a cantilever-shaped retainer claw portion (22) extending in the axial direction from the retainer annular portion (21) between the balls (5) adjacent in the circumferential direction,
The axial length of the cage claw portion (22) is set to be greater than the axial width of the outer ring raceway groove (12),
a base-side guided surface (23) that is in sliding contact with one of the pair of outer ring groove shoulders (13) is formed on a radially outer surface of the retainer annular portion (21);
a tip-side guided surface (24) that is in sliding contact with the other of the pair of outer ring groove shoulder portions (13) is formed on a radially outer surface of an axial end portion on a tip side of the cage claw portion (22);
The base side guided surface (23) and the tip side guided surface (24) have a cross-sectional shape along the circumferential direction formed into an arc shape that protrudes radially outward,
a radius of curvature of a cross section along a circumferential direction of the base side guided surface (23) and the tip side guided surface (24) is set to be smaller than 1/2 of a radius of an inner diameter of the outer ring groove shoulder portion (13) and larger than 1/10 of a radius of an inner diameter of the outer ring groove shoulder portion (13) ;
The annular space (4) has an opening at one end in the axial direction, and an annular seal member (6) is provided to close the opening at one end of the annular space (4).
The retainer annular portion (21) has a retainer-side sliding surface (42) which is in sliding contact with the seal member (6) while facing the retainer in the axial direction,
The seal member (6) has a seal-side sliding surface (43) that is in sliding contact with the cage-side sliding surface (42),
a plurality of axial projections (44) having an axially convex arc-shaped cross-sectional shape along the circumferential direction are formed at a constant pitch on one of the retainer-side sliding contact surface (42) and the seal-side sliding contact surface (43) ;
The ball bearing is characterized in that the axial protrusion (44) has a parallel apex (45) in which the height of the axially convex arc-shaped apex in a cross section taken along the circumferential direction is constant along the radial direction, and an inclined apex (46) in which the height of the axially convex arc-shaped apex in a cross section taken along the circumferential direction gradually decreases from the radial outer end of the parallel apex (45) toward the radial outward direction. The cage claw portion (22) has a circumferentially opposing surface (27) that faces the ball (5) in the circumferential direction,
2. A ball bearing as described in claim 1, wherein the portion of the circumferential opposing surface (27) that receives the balls (5) in the circumferential direction has a planar shape extending parallel to a straight line connecting the center of the retainer annular portion (21) and the center of the retainer claw portion (22) so that the circumferential opposing surface (27) does not interfere with the balls (5) when the retainer claw portion (22) moves radially outward due to centrifugal force. A ball bearing according to claim 1 or 2, in which the axial end edge (25) of the base side guided surface (23) farther from the retainer claw portion (22) and the axial end edge (26) of the tip side guided surface (24) farther from the retainer annular portion (21) are R-chamfered. A ball bearing according to any one of claims 1 to 3, in which a relief recess (41) is formed between the root side guided surface (23) and the tip side guided surface (24) on the radial outer surface of the retainer claw portion (22), and extends in the circumferential direction with an axial width wider than the axial width of the outer ring raceway groove (12). A ball bearing according to any one of claims 1 to 4, in which an oil reservoir groove (40) is formed on the radially inner surface of the retainer claw portion (22) and extends axially from the tip of the retainer claw portion (22) toward the retainer annular portion (21). 6. The ball bearing according to claim 1, wherein the inclined apex portion (46) has a cross-sectional shape perpendicular to the circumferential direction that is an R-shape that smoothly connects to the parallel apex portion (45). 7. A ball bearing according to claim 1 , wherein the plurality of axial projections (44) are arranged at a position overlapping with a pitch circle of the balls (5) or radially outward therefrom. A ball bearing as described in any one of claims 1 to 7, wherein the axial end of the annular space ( 4 ) opposite to the axial end blocked by the sealing member (6) is open without a sealing member (6) so as to receive lubricant supplied from the outside into the annular space (4). 9. The ball bearing according to claim 1, which is used as a bearing for an electric vehicle transmission (30) that reduces the rotation of an electric motor (31) of the electric vehicle.

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