JP7530766B2 - Plastic cage for tapered roller bearing and tapered roller bearing - Google Patents

Description

This invention relates to a plastic retainer for a tapered roller bearing and a tapered roller bearing using the plastic retainer for a tapered roller bearing.

Tapered roller bearings, which are bearings capable of supporting radial and axial loads simultaneously, are often used in automobile transmissions and differential mechanisms (see, for example, Patent Document 1).

The tapered roller bearing in Patent Document 1 has an outer ring with a tapered outer ring raceway surface on its inner circumference, an inner ring with a tapered inner ring raceway surface on its outer circumference facing the inner diameter side of the outer ring raceway surface, a number of tapered rollers assembled at intervals in the circumferential direction between the outer ring raceway surface and the inner ring raceway surface, and an annular cage that maintains the circumferential spacing of the tapered rollers. A large rib that guides the large end faces of the tapered rollers is formed on the outer circumference of the inner ring. When the bearing rotates, the large end faces of the tapered rollers and the large rib of the inner ring support part of the axial load through sliding contact.

The above-mentioned tapered roller bearings are lubricated by a splash lubrication method in which the bearings are lubricated by droplets of lubricating oil splashed up by the rotation of the gears, a pressure-fed lubrication method in which lubricating oil pumped by pressure from an oil pump is directly supplied to the bearing, and an oil bath lubrication method in which the bearing is used with part of it immersed in lubricating oil stored in an oil bath. Here, when the bearing is rotating, lubricating oil is continuously supplied to the tapered roller bearing from the outside, but when the bearing is stopped, the supply of lubricating oil from the outside to the tapered roller bearing stops. Therefore, if the tapered roller bearing is stopped for a long period of time, much of the lubricating oil adhering to the tapered roller bearing will flow off, and when the tapered roller bearing is then started, it is easy for insufficient lubrication to occur.

In particular, in recent years, there has been a trend to use lower viscosity lubricants and reduce the amount of lubricant in automobile transmissions and differential mechanisms in order to reduce energy loss caused by the agitation resistance of the lubricant. As a result, when a tapered roller bearing is stopped for an extended period of time, the amount of lubricant remaining in the tapered roller bearing is likely to be insufficient, and when the tapered roller bearing is subsequently started, there is a risk of a sudden rise in temperature between the large end faces of the tapered rollers and the large rib of the inner ring.

JP 2007-024168 A International Publication No. 2011/062188

By the way, a retainer for a tapered roller bearing that can lubricate the area between the large end faces of the tapered rollers and the large rib of the inner ring even when the supply of lubricating oil to the tapered roller bearing from outside is stopped is known, as shown in Figures 5 and 11 of Patent Document 2.

The retainer for the tapered roller bearing shown in FIG. 5 and FIG. 11 of Patent Document 2 has a large diameter side rim portion that extends in the circumferential direction of the retainer along the large end faces of multiple tapered rollers that are spaced apart in the circumferential direction of the retainer, a small diameter side rim portion that extends in the circumferential direction of the retainer along the small end faces of the multiple tapered rollers, and multiple pillar portions that connect the large diameter side rim portion and the small diameter side rim portion by passing between adjacent tapered rollers in the circumferential direction of the retainer, and the large diameter side rim portion and the multiple pillar portions define multiple pockets that respectively accommodate multiple tapered rollers. The large diameter side rim portion has a large diameter side pocket surface that faces the large end faces of each tapered roller, a large diameter side rim inner surface that extends from the inner end of the retainer in the radial direction of the large diameter side pocket surface in a direction away from the large end faces of the tapered rollers and faces inward in the radial direction of the retainer, and an oil-retaining recess that opens across and between the large diameter side pocket surface and the large diameter side rim inner surface.

When the tapered roller bearing is rotating, this retainer for tapered roller bearings collects some of the lubricating oil flowing inside the bearing in an oil-retaining recess formed in the large-diameter rim of the retainer. Then, when the bearing stops and then starts rotating again, the lubricating oil flowing out of the oil-retaining recess lubricates the area between the large end faces of the tapered rollers and the large rib of the inner ring.

In the case of the retainer for the tapered roller bearing shown in FIG. 5 and FIG. 11 of Patent Document 2, the inner circumferential surface of the large diameter rim portion facing inward in the radial direction of the retainer is formed in a cylindrical shape parallel to the axial direction of the retainer, or is formed in a tapered shape with the inner diameter gradually decreasing as it moves away from the large end face of the tapered roller in the axial direction of the retainer in order to guide the lubricating oil adhering to the surface of the inner circumferential surface of the large diameter rim toward the large end face of the tapered roller.

Here, the inventor of the present application noticed the following problem when attempting to manufacture a tapered roller bearing cage such as that shown in FIG. 5 and FIG. 11 of Patent Document 2 by resin molding using a mold.

That is, since the retainer for the tapered roller bearing is a truncated cone shape with the small diameter side of the rim portion and the large diameter side of the rim portion, when this retainer for the tapered roller bearing is manufactured by resin molding using a metal mold, a female mold with a tapered cavity and a male mold with a tapered core are used. Here, as in Figures 5 and 11 of Patent Document 2, if the inner peripheral surface of the large diameter side rim is cylindrical in shape parallel to the axial direction of the retainer or tapered in shape with the inner diameter decreasing as it moves away from the large end face of the tapered roller, it is difficult to release the male mold from the molded product, and it was noticed that there is a problem that moldability is deteriorated because it is in a so-called forced removal state.

The problem that this invention aims to solve is to provide a plastic cage for tapered roller bearings that is less susceptible to a sudden rise in temperature between the large end faces of the tapered rollers and the large ribs of the inner ring when the tapered roller bearing starts, and that has excellent moldability.

In order to solve the above problems, the present invention provides a resin cage for a tapered roller bearing having the following configuration.
a large diameter side rim portion extending in a circumferential direction of the cage along large end faces of a plurality of tapered rollers arranged at intervals in the circumferential direction of the cage;
a small diameter side rim portion extending in a circumferential direction of the cage along small end faces of the plurality of tapered rollers;
a plurality of pillar portions that pass between adjacent tapered rollers in a circumferential direction of the cage and connect the large diameter side rim portion and the small diameter side rim portion,
the large diameter side rim portion, the small diameter side rim portion and the plurality of column portions define a plurality of pockets for accommodating the plurality of tapered rollers, respectively;
the large diameter side rim portion, the small diameter side rim portion, and the plurality of column portions are integrally molded from a resin composition,
In a resin retainer for a tapered roller bearing, the large diameter side rim portion has a large diameter side pocket surface facing the large end faces of each of the tapered rollers, a large diameter side rim inner circumferential surface extending from an inner end of the large diameter side pocket surface in a direction away from the large end faces of the tapered rollers and facing inward in the radial direction of the retainer, and an oil-retaining recessed portion opening across between the large diameter side pocket surface and the large diameter side rim inner circumferential surface,
A plastic retainer for a tapered roller bearing, characterized in that the large diameter side rim inner surface is formed with a tapered inclination such that the inner diameter gradually increases as it moves away from the large end face of the tapered roller in the axial direction of the retainer.

In this way, the inner peripheral surface of the large diameter side rim is formed with a tapered inclination such that the inner diameter gradually increases as it moves away from the large end face of the tapered roller in the axial direction of the cage. Therefore, when a resin cage for a tapered roller bearing is resin molded using a female mold with a tapered cavity and a male mold with a tapered core, the male mold is easy to release from the resin cage for a tapered roller bearing, resulting in excellent moldability.

In addition, when the tapered roller bearing is rotating, some of the lubricating oil flowing inside the bearing is stored in an oil-retaining recess formed in the large diameter rim portion of the resin cage for tapered roller bearings, and then when the bearing stops temporarily and starts rotating again, the lubricating oil flowing out of the oil-retaining recess can lubricate the area between the large end faces of the tapered rollers and the large rib of the inner ring. As a result, when the tapered roller bearing starts, a sudden rise in temperature is unlikely to occur between the large end faces of the tapered rollers and the large rib of the inner ring.

The inclination angle θ of the inner peripheral surface of the large diameter rim relative to the axial direction of the cage is preferably set in the range of 0°<θ≦10°.

By setting the inclination angle θ to 10° or less, when a resin retainer for a tapered roller bearing is resin molded using a female mold with a tapered cavity and a male mold with a tapered core, it is possible to prevent the resin retainer for a tapered roller bearing from sticking to the female mold when the male and female molds are released from the resin retainer for the tapered roller bearing. Furthermore, by setting the inclination angle θ to be greater than 0°, excellent moldability can be ensured.

It is preferable that the oil-retaining recess is formed so that, in a cross section perpendicular to the circumferential direction of the cage, the inner surface of the oil-retaining recess has an L-shaped cross section that is bent to connect between a central position in the cage radial direction of the large-diameter pocket surface and a central position in the cage axial direction of the large-diameter rim inner peripheral surface.

In this way, the oil-retaining recess does not penetrate the cage axially, so the lubricating oil that flows from the small diameter side to the large diameter side inside the bearing due to the pumping action while the bearing is rotating can be reliably stored in the oil-retaining recess formed in the large diameter rim part of the resin cage for tapered roller bearings. Therefore, when the tapered roller bearing starts, the space between the large end faces of the tapered rollers and the large rib of the inner ring can be effectively lubricated.

It is preferable to form a convex portion on the inner peripheral surface of the large diameter rim, which extends continuously around the entire circumference in the circumferential direction of the cage, on the side farther from the large end face of the tapered roller than the position where the inner surface of the oil-retaining recess connects to the inner peripheral surface of the large diameter rim.

In this way, a resin retainer for a tapered roller bearing is resin molded using a female mold with a tapered cavity and a male mold with a tapered core, and when the male mold and female mold are released from the resin retainer for the tapered roller bearing, the male mold catches on the convex portion on the inner circumferential surface of the large diameter rim and pulls the resin retainer for the tapered roller bearing in the axial direction of the retainer, preventing the resin retainer for the tapered roller bearing from sticking to the female mold.

In addition, the convex portion is located farther from the large end face of the tapered roller than the position where the inner surface of the oil-retaining recess connects to the inner circumferential surface of the large diameter rim, and extends continuously around the entire circumference of the cage. Therefore, when the lubricating oil that flows from the small diameter side to the large diameter side inside the bearing due to the pumping action while the bearing is rotating is received by the oil-retaining recess, the lubricating oil that overflows from the oil-retaining recess is blocked by the convex portion and can be retained on the inner circumferential surface of the large diameter rim. This makes it possible to lubricate the area between the large end face of the tapered roller and the large rib of the inner ring particularly effectively when the tapered roller bearing starts.

It is preferable to set the height of the protrusion in the cage radial direction relative to the base of the protrusion on the side closer to the large end face of the tapered roller to 1.0 mm or less.

In this way, when a plastic retainer for a tapered roller bearing is resin molded using a female mold with a tapered cavity and a male mold with a tapered core, it is possible to reliably release the male mold from the plastic retainer for a tapered roller bearing.

It is preferable that the protrusions are formed so that their cross-sectional shape perpendicular to the circumferential direction of the cage is arc-shaped.

In this way, when a plastic retainer for a tapered roller bearing is resin molded using a female mold with a tapered cavity and a male mold with a tapered core, it becomes possible to smoothly release the male mold from the plastic retainer for the tapered roller bearing.

It is preferable to use a resin composition in which an elastomer is added to a resin material.

In this way, the flexibility of the plastic cage for tapered roller bearings is increased, so that when the plastic cage for tapered roller bearings is resin molded using a female die with a tapered cavity and a male die with a tapered core, the male and female dies can be released from the plastic cage for tapered roller bearings smoothly. In addition, when assembling the bearings, the cage is expanded in diameter while being installed, so the increased flexibility also improves assembly.

It is preferable to further add fiber reinforcing material to the resin material.

In this way, the fiber reinforcement material can compensate for the loss in strength of the plastic retainer for tapered roller bearings caused by adding elastomer to the resin material. This makes it possible to achieve the moldability and assembly of the plastic retainer for tapered roller bearings, as well as the strength of the plastic retainer for tapered roller bearings.

The present invention also provides a tapered roller bearing using the above-mentioned resin cage for a tapered roller bearing, having the following configuration.
An outer ring having a conical outer ring raceway on its inner circumference;
an inner ring having a conical inner ring raceway surface on an outer periphery thereof facing an inner diameter side of the outer ring raceway surface;
a plurality of tapered rollers assembled at intervals in a circumferential direction between the outer ring raceway surface and the inner ring raceway surface;
and the resin cage for a tapered roller bearing, which maintains the circumferential spacing of the plurality of tapered rollers,
The inner ring is a tapered roller bearing having a large rib that contacts the large end faces of each of the tapered rollers.

The oil-retaining recess is preferably positioned within the area of the large-diameter pocket surface that faces the large end face of the tapered roller so as not to protrude beyond that area.

This prevents the lubricating oil that has accumulated in the oil-retaining recess from dropping and being lost from outside the large end face of the tapered roller, making it possible to effectively retain the lubricating oil between the large end face of the tapered roller and the oil-retaining recess in the large diameter side rim portion.

When the tapered roller has a circular recess in the center of the large end face, it is preferable to provide two oil-retaining recesses for each pocket, on both sides of the circular recess in the circumferential direction of the cage.

In this way, the oil-retaining recesses are arranged on both sides of the retainer in the circumferential direction, sandwiching the circular recess, so that the lubricating oil that has accumulated in the oil-retaining recesses can be prevented from dropping and being lost between the large diameter pocket surface of the large diameter rim portion and the circular recess on the large end surface of the tapered roller. This makes it possible to effectively retain the lubricating oil between the large end surface of the tapered roller and the oil-retaining recess on the large diameter rim portion.

It is preferable that the opening area of the oil-retaining recess on the large diameter pocket surface side that faces the annular portion of the large end face of each tapered roller excluding the circular recess is 50% or more of the opening area of the oil-retaining recess on the large diameter pocket surface side.

This effectively prevents the lubricating oil that has accumulated in the oil-retaining recess from dropping and being lost between the large diameter pocket surface of the large diameter rim portion and the circular recess on the large end surface of the tapered roller.

It is preferable that the two oil-retaining recesses on either side of the circular recess in the circumferential direction of the cage are each formed in a polygonal shape having two or more corners where adjacent inner surfaces of the oil-retaining recesses intersect when viewed in the axial direction of the cage.

In this way, the lubricating oil comes into contact with each of the adjacent inner surfaces of the oil-retaining recess at the corners of the oil-retaining recess, and the surface tension of the lubricating oil makes it easier for the lubricating oil to be retained within the oil-retaining recess. Therefore, by adopting a polygonal oil-retaining recess with two or more corners, the lubricating oil in the oil-retaining recess is prevented from flowing out of the oil-retaining recess due to its own weight while the bearing is stopped, and the lubricating oil can be reliably retained within the oil-retaining recess even when the bearing is stopped for an extended period of time. As a result, it is possible to reliably lubricate the area between the large end faces of the tapered rollers and the large rib of the inner ring when the tapered roller bearing starts.

The plastic retainer for tapered roller bearings of this invention has a large diameter side rim inner peripheral surface that is tapered so that the inner diameter gradually increases as it moves away from the large end face of the tapered roller in the axial direction of the retainer. Therefore, when the plastic retainer for tapered roller bearings is resin molded using a female mold with a tapered cavity and a male mold with a tapered core, the male mold is easy to release from the plastic retainer for tapered roller bearings, and has excellent moldability. In addition, when the tapered roller bearing rotates, some of the lubricating oil flowing inside the bearing is stored in an oil-retaining recess formed in the large diameter side rim part of the plastic retainer for tapered roller bearings, and when the bearing stops and then starts rotating again, the lubricating oil flowing out of the oil-retaining recess can lubricate the area between the large end face of the tapered rollers and the large rib of the inner ring. Therefore, when the tapered roller bearing starts, a sudden rise in temperature is unlikely to occur between the large end face of the tapered rollers and the large rib of the inner ring.

FIG. 1 is a cross-sectional view taken along an axial plane of a tapered roller bearing incorporating a resin retainer for a tapered roller bearing according to a first embodiment of the present invention. An enlarged cross-sectional view of the vicinity of the oil-retaining recess of FIG. FIG. 2 is a perspective view of the plastic cage for tapered roller bearing shown in FIG. 1, viewed from the small diameter side. FIG. 2 is a perspective view of the plastic cage for tapered roller bearing shown in FIG. 1, viewed in the cage axial direction from the small diameter side. FIG. 5 is a diagram showing a modified example in which the number of oil-retaining recesses in the resin cage for tapered roller bearing shown in FIG. 4 is reduced to one. FIG. 5 is a diagram showing a state in which lubricating oil is held in the corners of the oil-retaining recesses of the plastic cage for the tapered roller bearing shown in FIG. 4 . FIG. 2 is a diagram showing a state in which the male and female dies used for injection molding the plastic cage for the tapered roller bearing shown in FIG. 1 are closed. FIG. 8 is a diagram showing the state in which the male and female dies shown in FIG. 7 are opened and released from the resin retainer for a tapered roller bearing. FIG. 3 is a view showing a resin retainer for a tapered roller bearing according to a second embodiment of the present invention, corresponding to FIG. 2; 10A is a diagram showing a modified example of the protrusion shown in FIG. 9 , and FIG. 10B is a diagram showing another modified example of the protrusion shown in FIG. 9 . FIG. 10 is a diagram showing a state in which a male mold and a female mold for injection molding the resin retainer for the tapered roller bearing shown in FIG. 9 are closed. FIG. 12 is a diagram showing a state in which the female die shown in FIG. 11 has been released from the resin cage for a tapered roller bearing. A diagram showing the analysis results of the amount of oil retained in an oil-retaining recess when the bearing is stopped, when one oil-retaining recess is provided per pocket. A diagram showing the analysis results of the amount of oil retained in the oil-retaining recesses when the bearing is stopped, when two oil-retaining recesses are provided per pocket.

Figure 1 shows a tapered roller bearing using a resin retainer 1 for tapered roller bearings according to a first embodiment of the present invention. This tapered roller bearing has an outer ring 3 having a tapered outer ring raceway surface 2 on its inner circumference, an inner ring 5 having a tapered inner ring raceway surface 4 on its outer circumference, a number of tapered rollers 6 assembled at intervals in the circumferential direction between the outer ring raceway surface 2 and the inner ring raceway surface 4, and a resin retainer 1 for tapered roller bearings (hereinafter simply referred to as "resin retainer 1") that maintains the spacing between the multiple tapered rollers 6.

The inner ring 5 is arranged coaxially inside the outer ring 3. The outer circumference of the inner ring 5 is formed with an inner ring raceway surface 4, a small rib 7 located on the small diameter side of the inner ring raceway surface 4, and a large rib 8 located on the large diameter side of the inner ring raceway surface 4. The inner ring raceway surface 4 faces the inner diameter side of the outer ring raceway surface 2. The tapered rollers 6 are in rolling contact with the outer ring raceway surface 2 and the inner ring raceway surface 4. When the bearing rotates, each tapered roller 6 revolves around the axis of the inner ring 5 (i.e. the axis of the resin cage 1) between the outer ring raceway surface 2 and the inner ring raceway surface 4 while rotating on its own axis.

The tapered rollers 6 are arranged at intervals in the circumferential direction of the resin cage 1, with the center line (not shown) of each tapered roller 6 located on an imaginary conical surface (pitch cone) centered on the axis of the annular resin cage 1. The tapered roller 6 has a conical rolling surface 9, a small end face 10 connected to the small diameter side of the rolling surface 9, and a large end face 11 connected to the large diameter side of the rolling surface 9. A circular recess 12 (see Figure 4) is formed in the center of the large end face 11. The rolling surface 9 is the portion of the surface of the tapered roller 6 that rolls and comes into contact with the outer ring raceway surface 2.

The small rib 7 is formed to protrude radially outward from the inner ring raceway surface 4 so as to face the small end face 10 of the tapered roller 6. The small rib 7 restricts the tapered roller 6 from moving toward the smaller diameter side, preventing the tapered roller 6 from falling off the inner ring raceway surface 4. The large rib 8 is formed to protrude radially outward from the inner ring raceway surface 4 so as to face the large end face 11 of the tapered roller 6. When the bearing rotates, the large end face 11 of the tapered roller 6 and the large rib 8 of the inner ring 5 support part of the axial load through contact involving sliding.

The resin cage 1 has a large diameter side rim portion 13 that extends circumferentially along the large end face 11 of each tapered roller 6, a small diameter side rim portion 14 that extends circumferentially along the small end face 10 of each tapered roller 6, and a number of pillar portions 15 that pass between adjacent tapered rollers 6 in the cage circumferential direction and connect the large diameter side rim portion 13 and the small diameter side rim portion 14.

The large diameter side rim portion 13, the small diameter side rim portion 14, and the multiple pillar portions 15 define multiple pockets 16 that each house a multiple tapered roller 6. Here, the large diameter side rim portion 13 and the small diameter side rim portion 14 define both ends of the pocket 16 in the axial direction of the cage, and the pillar portions 15 define both ends of the pocket 16 in the circumferential direction of the cage. The large diameter side rim portion 13 is formed with a large diameter side pocket surface 17 that faces the large end face 11 of the tapered roller 6, and the small diameter side rim portion 14 is formed with a small diameter side pocket surface 18 that faces the small end face 10 of the tapered roller 6.

The large diameter side pocket surface 17 is formed at an incline with respect to the cage radial direction (the vertical direction in the figure) so as to face parallel to the large end face 11 of the tapered roller 6. The small diameter side pocket surface 18 is also formed at an incline with respect to the cage radial direction (the vertical direction in the figure) so as to face parallel to the small end face 10 of the tapered roller 6.

The column portion 15 is formed with a roller guide surface 19 that guides the rolling surface 9 on the outer circumference of the tapered roller 6, and a triangular recess 20 located at the end of the column portion 15 on the large diameter side rim portion 13 side. The triangular recess 20 is a recess that is recessed in the cage circumferential direction relative to the roller guide surface 19. As shown in Figures 7 and 8, when the resin cage 1 is resin molded using a male mold 21 and a female mold 22, the triangular recess 20 is the portion through which the portion of the female mold 22 that molds the large diameter side pocket surface 17 passes.

As shown in FIG. 1, the triangular recess 20 is a triangular recess with one side being the corner where the large diameter pocket surface 17 and the column portion 15 intersect, as viewed in the circumferential direction of the resin retainer 1, and the width in the radial direction of the retainer gradually decreases as it approaches the small diameter side rim portion 14 from that side. As viewed in the circumferential direction of the resin retainer 1, one side of the triangular recess 20 on the outer side in the retainer radial direction coincides with the outer periphery of the resin retainer 1, and one side of the triangular recess 20 on the inner side in the retainer circumferential direction extends parallel to the retainer axial direction or inclined in a direction gradually approaching the axis of the retainer from the large diameter side to the small diameter side in the retainer axial direction.

The large diameter rim portion 13, small diameter rim portion 14, and multiple pillar portions 15 that make up the cage are molded seamlessly from a resin composition. The resin composition that forms the cage can be made of resin material alone, but here, a resin material to which an elastomer and fiber reinforcement material have been added is used.

Polyamide (PA) or super engineering plastics can be used as the base resin material of the resin composition. As the polyamide, polyamide 66 (PA66), polyamide 46 (PA46), polynonamethylene terephthalamide (PA9T), etc. can be used. As the super engineering plastic, polyphenylene sulfide (PPS) can be used. It is preferable to use PPS as the base resin material of the resin composition that forms the resin retainer 1, since PPS has excellent heat resistance, oil resistance, and low water absorption. The elastomer added to the resin material is, for example, a thermoplastic elastomer.

As fiber reinforcement to be added to the resin material, glass fiber, carbon fiber, aramid fiber, etc. can be used. When glass fiber is used as the fiber reinforcement, the glass fiber content in the fiber reinforcement can be 10 to 50% by weight (preferably 20 to 40% by weight, more preferably 25 to 35% by weight). The combination of the types of resin material, elastomer, and fiber reinforcement can be freely selected as appropriate.

The small diameter side rim portion 14 has an inward flange shape that extends radially inward of the cage from the connection position with the column portion 15, intersecting the pitch cone. The pitch cone is an imaginary conical surface that is the path of the rotation axis of the tapered roller 6 as it revolves around the outer ring 3 and the inner ring 5 while rotating on its own axis.

As shown in FIG. 2, the large diameter side rim portion 13 has a large diameter side pocket surface 17, a large diameter side rim inner surface 23 that extends from the inner end of the large diameter side pocket surface 17 in the cage radial direction away from the large end surface 11 of the tapered roller 6, and an oil-retaining recess 24 that opens across between the large diameter side pocket surface 17 and the large diameter side rim inner surface 23. The large diameter side rim inner surface 23 is the surface of the large diameter side rim portion 13 that faces inward in the cage radial direction. The large diameter side rim inner surface 23 faces the outer circumferential surface of the large flange 8 in the cage radial direction.

The large diameter side rim inner circumferential surface 23 is formed with a tapered inclination such that the inner diameter gradually increases as it moves away from the large end face 11 of the tapered roller 6 in the cage axial direction. The inclination angle θ of the large diameter side rim inner circumferential surface 23 with respect to the cage axial direction is set in the range of 0°<θ≦10° (at least 0°<θ≦20°). The large diameter side rim inner circumferential surface 23 is a conical surface that extends linearly in a cross section perpendicular to the cage circumferential direction. The end of the large diameter side rim inner circumferential surface 23 close to the large end face 11 of the tapered roller 6 is aligned in the cage radial direction with the end of one side of the triangular recess 20 of the column portion 15 on the inner side in the cage circumferential direction close to the large diameter side rim portion 13.

As shown in FIG. 2, the oil-retaining recess 24 is formed so that, in a cross section perpendicular to the cage circumferential direction, the inner surface of the oil-retaining recess 24 is bent and connected to the middle position of the large diameter side pocket surface 17 in the cage radial direction and the middle position of the large diameter side rim inner peripheral surface 23 in the cage axial direction. The inner surface of the oil-retaining recess 24 has an inner bottom surface 25 facing the cage radially inward, and an inner wall surface 26 that rises inward in the cage radial direction from the end of the inner bottom surface 25 farther from the large end surface 11 of the tapered roller 6 in the cage axial direction to reach the large diameter side rim inner peripheral surface 23. The inner bottom surface 25 extends parallel to the cage axial direction in the figure, but may be inclined at an inclination angle of 10° or less with respect to the cage axial direction. The inner wall surface 26 extends parallel to the cage radial direction.

As shown in Fig. 3, two oil-retaining recesses 24 are provided for each pocket 16, spaced apart in the circumferential direction of the cage. When lubricating oil is received in these oil-retaining recesses 24, a force (hereinafter referred to as a retention force F1) acts on the lubricating oil in the oil-retaining recesses 24, which tends to keep the oil in the oil-retaining recesses 24 even when an external force such as gravity acts on the oil, due to the surface tension of the lubricating oil. When the retention force F1 is greater than the gravity F2 acting on the lubricating oil, the lubricating oil is effectively retained in the oil-retaining recesses 24. The retention force F1 is calculated by the following formula.
F1 = γ × L × cosθ
Here, L is the wetted edge length (the total length of the inner surface of the oil-retaining recess 24 in contact with the lubricating oil), and θ is the contact angle of the lubricating oil with the resin composition constituting the resin cage 1 .
On the other hand, the gravity F2 acting on the lubricating oil is calculated by the following formula.
F2 = g × ρ × V
where g is the acceleration of gravity (standard acceleration of free fall), ρ is the density of the lubricant, and V is the volume of the lubricant.
For example, when the surface tension of the lubricating oil is γ=30 (mN/m), the contact angle θ=18.5 (°), the wetted edge length L=2.8×10 ^-3 (m), the lubricating oil density ρ=0.850 (g/cm ³ ), and the lubricating oil volume V=0.49 (mm ³ ), F1=8.0×10 ^-5 N. At this time, the gravity F2 acting on the lubricating oil is F2=4.0×10 ^-6 N. Therefore, F1≧F2, and the lubricating oil in the oil-retaining recesses 24 is held in the oil-retaining recesses 24 by the surface tension. The oil-retaining recesses 24 can be formed so that the volume of each oil-retaining recess 24 is 3.00 (mm ³ ) or less.

As shown in FIG. 4, both of the oil-retaining recesses 24 are arranged within the area of the large-diameter pocket surface 17 facing the large end face 11 of the tapered roller 6 so as not to protrude beyond the area (the area inside the large end face 11 of the tapered roller 6 shown by the dashed line in the figure) that faces the large end face 11 of the tapered roller 6. Here, the large end face 11 is a surface that includes the chamfered portion 27 (see FIG. 2) on the outer periphery of the end portion on the large diameter side of the tapered roller 6.

The two oil-retaining recesses 24 are arranged on either side of the circular recess 12 in the circumferential direction of the cage, with the circular recess 12 sandwiched between the two oil-retaining recesses 24. The circular recess 12 is the entire portion recessed from the annular flat portion of the large end face 11 toward the inner diameter side (including the chamfered portion formed along the periphery of the circular recess 12).

The opening area of the oil-retaining recesses 24 on the large-diameter pocket surface 17 side facing the annular portion of the large end face 11 of each tapered roller 6 excluding the circular recesses 12 (the portion inside the outer circle and outside the inner circle shown by the dashed line in the figure) is 50% or more (preferably 60% or more, more preferably 80% or more; 100% in the figure) of the opening area of the oil-retaining recesses 24 on the large-diameter pocket surface 17 side. In the figure, the two oil-retaining recesses 24 are arranged so that no portion of them enters the area of the large-diameter pocket surface 17 facing the circular recesses 12 (the inner circle portion shown by the dashed line in the figure).

The two oil-retaining recesses 24 on either side of the circular recess 12 in the circumferential direction of the cage are each formed in a polygonal shape (square shape in the figure) with two or more corners 28 (two in the figure) where adjacent inner surfaces of the oil-retaining recesses 24 intersect when viewed in the axial direction of the cage, as shown in FIG. 4.

As shown in Figures 7 and 8, the resin cage 1 can be manufactured by resin molding using a male die 21 and a female die 22 that can be separated in the cage axial direction. The male die 21 is a die having a tapered core 29 that molds the surface of the column portion 15 of the resin cage 1 that faces inward in the cage radial direction, and the female die 22 is a die having a tapered cavity 30 that molds the surface of the column portion 15 of the resin cage 1 that faces outward in the cage radial direction. Here, the small diameter side pocket surface 18 and roller guide surface 19 of the resin cage 1 shown in Figure 1 are molded by the male die 21, and the large diameter side rim inner peripheral surface 23 shown in Figure 2 is also molded by the male die 21. On the other hand, the large diameter side pocket surface 17 and triangular recess 20 of the resin cage 1 shown in Figure 1 are molded by the female die 22.

In recent years, there has been a trend to use lower viscosity lubricants or reduce the amount of lubricant in automobile transmissions and differential mechanisms in order to reduce energy loss caused by the agitation resistance of the lubricant. As a result, when tapered roller bearings are used in automobile transmissions and differential mechanisms, the amount of lubricant remaining in the tapered roller bearing is likely to be insufficient when the tapered roller bearing is stopped for an extended period of time, and there is a risk of a sudden rise in temperature between the large end face 11 of the tapered roller 6 and the large rib 8 of the inner ring 5 shown in Figure 1 when the tapered roller bearing is subsequently started.

To address this problem, the tapered roller bearing of this embodiment stores some of the lubricating oil flowing inside the bearing in the oil-retaining recess 24 formed in the large diameter side rim portion 13 of the resin cage 1 when the tapered roller bearing is rotating, and then when the bearing stops temporarily and starts rotating again, the lubricating oil flowing out of the oil-retaining recess 24 can lubricate the area between the large end face 11 of the tapered roller 6 and the large rib 8 of the inner ring 5. Therefore, when the tapered roller bearing starts, a sudden rise in temperature is unlikely to occur between the large end face 11 of the tapered roller 6 and the large rib 8 of the inner ring 5.

In addition, the resin cage 1 has a large diameter side rim inner peripheral surface 23 that is tapered so that the inner diameter gradually increases as it moves away from the large end face 11 of the tapered roller 6 in the cage axial direction. As a result, as shown in Figures 7 and 8, when the resin cage 1 is resin molded using a female die 22 and a male die 21, the male die 21 is easily released from the resin cage 1, resulting in excellent moldability.

As shown in FIG. 2, the inclination angle θ of the large diameter side rim inner peripheral surface 23 of this resin retainer 1 relative to the retainer axial direction is set to 10° or less (at least 20° or less). Therefore, as shown in FIG. 7 and FIG. 8, when the resin retainer 1 is resin molded using the female mold 22 and the male mold 21, and the male mold 21 and the female mold 22 are released from the resin retainer 1, it is possible to prevent the resin retainer 1 from sticking to the female mold 22.

As shown in FIG. 2, the resin cage 1 has an oil-retaining recess 24 formed in such a way that it has an L-shaped cross section in a cross section perpendicular to the cage circumferential direction, and the oil-retaining recess 24 does not penetrate in the cage axial direction. This means that the lubricating oil that flows from the small diameter side to the large diameter side inside the bearing due to the pump action while the bearing is rotating can be reliably received and stored in the oil-retaining recess 24 formed in the large diameter side rim portion 13 of the resin cage 1. As a result, when the tapered roller bearing starts, the space between the large end faces 11 of the tapered rollers 6 and the large rib 8 of the inner ring 5 can be effectively lubricated.

In addition, since the resin cage 1 is formed from a resin composition in which an elastomer is added to a resin material, the resin cage 1 has high flexibility. Therefore, when the resin cage 1 is resin molded using the female die 22 and the male die 21, and the male die 21 and the female die 22 are released from the resin cage 1, the resin cage 1 can be released smoothly.

In addition, this resin cage 1 has fiber reinforcement added to the resin material, so the fiber reinforcement can compensate for the loss in strength of the resin cage 1 caused by adding elastomer to the resin material. Therefore, it is possible to achieve the moldability and assembly properties of the resin cage 1 as well as the strength of the resin cage 1.

In addition, as shown in FIG. 4, the above-mentioned tapered roller bearing has an oil-retaining recess 24 that is located within the area of the large diameter side pocket surface 17 that faces the large end face 11 of the tapered roller 6 and does not extend beyond the area, so that the lubricating oil that has accumulated in the oil-retaining recess 24 can be prevented from falling and being lost from outside the large end face 11 of the tapered roller 6. This makes it possible to effectively retain lubricating oil between the large end face 11 of the tapered roller 6 and the oil-retaining recess 24 of the large diameter side rim portion 13.

In addition, as shown in FIG. 4, the tapered roller bearing described above has two oil-retaining recesses 24 on both sides of the circular recess 12 in the circumferential direction of the cage for each pocket 16, so that the lubricating oil accumulated in the oil-retaining recesses 24 can be prevented from dropping and being lost between the large diameter side pocket surface 17 of the large diameter side rim portion 13 and the circular recess 12 of the large end face 11 of the tapered roller 6. Therefore, it is possible to effectively retain the lubricating oil between the large end face 11 of the tapered roller 6 and the oil-retaining recess 24 of the large diameter side rim portion 13.

In addition, as shown in FIG. 4, the opening area of the oil-retaining recess 24 on the large-diameter pocket surface 17 side of the tapered roller bearing, which faces the annular portion of the large end face 11 of each tapered roller 6 excluding the circular recess 12, is 50% or more (preferably 60% or more, more preferably 80% or more; in FIG. 4, 100%) of the opening area of the oil-retaining recess 24 on the large-diameter pocket surface 17 side, so that the lubricating oil accumulated in the oil-retaining recess 24 can be effectively prevented from falling and being lost between the large-diameter pocket surface 17 of the large-diameter rim portion 13 and the circular recess 12 of the large end face 11 of the tapered roller 6.

In addition, as shown in FIG. 6, the two oil-retaining recesses 24 on either side of the circular recess 12 in the circumferential direction of the cage are each formed in a polygonal shape having two or more corner portions 28 where adjacent inner surfaces of the oil-retaining recesses 24 intersect when viewed in the axial direction of the cage, so that the oil-retaining recesses 24 have a high ability to retain lubricating oil.

That is, at the corners 28 of the oil-retaining recess 24, the lubricating oil comes into contact with each of the adjacent inner surfaces of the oil-retaining recess 24, so the surface tension of the lubricating oil makes it easier for the lubricating oil to be retained in the oil-retaining recess 24. Therefore, as shown in FIG. 6, by adopting a polygonal oil-retaining recess 24 having two or more corners 28, the lubricating oil in the oil-retaining recess 24 is prevented from flowing out of the oil-retaining recess due to its own weight while the bearing is stopped, and the lubricating oil can be reliably retained in the oil-retaining recess 24 even when the bearing is stopped for a long period of time. As a result, it is possible to reliably lubricate the area between the large end faces 11 of the tapered rollers 6 and the large rib 8 of the inner ring 5 when the tapered roller bearing starts. For example, as shown in FIG. 5, if there is only one oil-retaining recess 24 per pocket 16, there will be only two corners 28 per pocket 16, whereas as shown in FIG. 6, if there are two oil-retaining recesses 24 per pocket 16, four corners 28 can be secured per pocket 16, making it possible to increase the total amount of lubricating oil that can be held in the oil-retaining recesses 24 per pocket 16.

Figure 9 shows the resin cage 1 of the second embodiment. The only difference from the first embodiment is that a protrusion 31 has been added, and the other configuration is the same as the first embodiment. Therefore, parts corresponding to the first embodiment are given the same reference numerals and descriptions are omitted.

A protrusion 31 is formed on the large diameter side rim inner circumferential surface 23, extending continuously around the entire circumference in the circumferential direction of the cage, on the side farther from the large end face 11 of the tapered roller 6 than the position where the inner surface of the oil-retaining recess 24 connects to the large diameter side rim inner circumferential surface 23.

The height h of the protrusion 31 in the cage radial direction relative to the base of the protrusion 31 on the side closer to the large end face 11 of the tapered roller 6 is set to 1.0 mm or less (at least 2.0 mm or less).

The protrusion 31 is formed so that its cross-sectional shape perpendicular to the circumferential direction of the cage is arc-shaped.

As shown in Figures 11 and 12, this resin cage 1 is resin molded using a female die 22 and a male die 21, and when the male die 21 and female die 22 are released from the resin cage 1, the male die 21 catches on the convex portion 31 on the inner peripheral surface 23 of the large diameter rim and pulls the resin cage 1 in the cage axial direction, preventing the resin cage 1 from sticking to the female die 22. The resin cage 1 shown in Figure 12 is released from the male die 21 using an ejection pin (not shown) built into the male die 21.

In addition, in this resin cage 1, the convex portion 31 is located on the far side from the large end face 11 of the tapered roller 6 relative to the position where the inner surface of the oil-retaining recess 24 connects to the large diameter side rim inner circumferential surface 23, and extends continuously around the entire circumference of the cage. Therefore, when the lubricating oil that flows inside the bearing from the small diameter side to the large diameter side due to the pump action during bearing rotation is received by the oil-retaining recess 24, the lubricating oil that overflows from the oil-retaining recess 24 is blocked by the convex portion 31 and can be retained on the large diameter side rim inner circumferential surface 23. Therefore, when the tapered roller bearing starts, it is possible to lubricate the area between the large end face 11 of the tapered roller 6 and the large rib 8 of the inner ring 5 particularly effectively.

In addition, the height h of the protrusion 31 in the radial direction of the cage is set to 1.0 mm or less in this resin cage 1, so that when the resin cage 1 is resin-molded using the female die 22 and the male die 21, as shown in Figures 11 and 12, the male die 21 can be reliably released from the resin cage 1.

The protrusion 31 may have a rectangular cross-sectional shape as shown in FIG. 10(a) or a trapezoidal cross-sectional shape as shown in FIG. 10(b). However, if a circular arc cross-sectional shape is used as shown in FIG. 9, it is possible to smoothly release the male die 21 from the resin retainer 1 when the resin retainer 1 is resin-molded using the female die 22 and male die 21 as shown in FIGS. 11 and 12.

The following analysis was performed to confirm that providing two oil-retaining recesses 24 per pocket 16, as in the above embodiment, is more effective at retaining lubricating oil than providing one oil-retaining recess 24 per pocket 16.

<Analysis conditions>
Unsteady fluid analysis using multiphase flow (VOF) Bearing size: φ34mm x φ62mm x 16mm
Bearing speed: 6000 rpm
Temperature: constant at 120°C Lubricating oil: ATF (dynamic viscosity at 120°C is 3.90 ^mm2 /sec)
Inflow conditions: Oil supply amount: 100 mL/min (oil flows in from the small diameter end face side of the outer ring)
The area from 9.6 mm to 49.6 mm from the small diameter side end face of the outer ring is filled with oil.
Outlet conditions: Pressure outlet initial conditions: Air, 0 m/s, 0 MPa (gauge pressure)

<Analysis Contents>
1. Rotate the bearing and allow the lubricant to flow in.
2. 0.5 seconds after the start of rotation, the rotation of the bearing is stopped and the bearing is allowed to reach a steady state where the flow of lubricating oil ceases.
3. In the steady state where the flow of lubricating oil has completely stopped, check the amount of oil remaining in the oil-retaining recess (after 2.5 seconds).

<Analysis results>
Fig. 13 shows the analysis results when one oil-retaining recess 24 is provided per pocket 16 as shown in Fig. 5, and Fig. 14 shows the analysis results when two oil-retaining recesses 24 are provided per pocket 16 as shown in Fig. 6. These analysis results show that in a steady state where the flow of lubricating oil ceases, a large amount of lubricating oil remains in the corners 28 of the oil-retaining recesses 24. Furthermore, when two oil-retaining recesses 24 are provided per pocket 16, the total amount of remaining oil in the two oil-retaining recesses was ^0.248 mm3 in the analysis results shown in Fig. 14. This amount of remaining oil was approximately twice the amount of remaining oil in the analysis results shown in Fig. 13 when one oil-retaining recess 24 is provided per pocket 16. From these analysis results, it can be confirmed that when two oil-retaining recesses 24 are provided per pocket 16, as in the above embodiment, compared to when one oil-retaining recess 24 is provided per pocket 16, the number of corner portions 28 of the oil-retaining recesses 24 is greater, and therefore lubricating oil can be effectively retained in the oil-retaining recesses 24 per pocket 16.

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 Plastic cage for tapered roller bearing 2 Outer ring raceway surface 3 Outer ring 4 Inner ring raceway surface 5 Inner ring 6 Tapered roller 8 Large rib 10 Small end face 11 Large end face 12 Circular recess 13 Large diameter side rim portion 14 Small diameter side rim portion 15 Pillar portion 16 Pocket 17 Large diameter side pocket surface 23 Large diameter side rim inner peripheral surface 24 Oil-retaining recess 28 Corner portion 31 Convex portion θ Inclined angle h Height

Claims (11)

a large diameter side rim portion (13) extending in a circumferential direction of the cage along large end faces (11) of a plurality of tapered rollers (6) arranged at intervals in the circumferential direction of the cage;
a small diameter side rim portion (14) extending in a circumferential direction of the cage along small end faces (10) of the plurality of tapered rollers (6);
a plurality of pillar portions (15) passing between adjacent tapered rollers (6) in a circumferential direction of the cage and connecting the large diameter side rim portion (13) and the small diameter side rim portion (14),
the large diameter side rim portion (13), the small diameter side rim portion (14) and the plurality of pillar portions (15) define a plurality of pockets (16) for accommodating the plurality of tapered rollers (6),
The large diameter side rim portion (13), the small diameter side rim portion (14), and the plurality of pillar portions (15) are integrally molded from a resin composition,
The large diameter side rim portion (13) has a large diameter side pocket surface (17) facing the large end faces (11) of the tapered rollers (6), a large diameter side rim inner circumferential surface (23) extending from an inner end of the large diameter side pocket surface (17) in the radial direction of the cage in a direction away from the large end faces (11) of the tapered rollers (6) and facing inward in the radial direction of the cage, and an oil-retaining recess (24) opening across between the large diameter side pocket surface (17) and the large diameter side rim inner circumferential surface (23),
the oil-retaining recess (24) is formed such that, in a cross section perpendicular to the circumferential direction of the cage, an inner surface of the oil-retaining recess (24) presents an L-shaped cross section that is bent to connect between a middle position in the cage radial direction of the large-diameter side pocket surface (17) and a middle position in the cage axial direction of the large-diameter side rim inner circumferential surface (23),
The large diameter side rim inner peripheral surface (23) is formed in a tapered shape inclined such that the inner diameter gradually increases as it moves away from the large end surface (11) of the tapered roller (6) in the cage axial direction ,
A resin retainer for a tapered roller bearing, characterized in that an inclination angle θ of the large diameter side rim inner surface (23) with respect to the retainer axial direction is set in the range of 0°<θ≦10°. 2. A plastic cage for a tapered roller bearing according to claim 1, wherein a convex portion (31) is formed on the large diameter side rim inner circumferential surface (23) on a side farther from the large end faces (11) of the tapered rollers (6) with respect to a position where the inner surface of the oil-retaining recess (24) connects to the large diameter side rim inner circumferential surface (23). The convex portion (31) extends continuously around the entire circumferential direction of the cage. 3. A plastic cage for a tapered roller bearing according to claim 2, wherein a height (h) of the protrusion (31) in a radial direction of the cage relative to a base of the protrusion (31) on a side closer to the large end face (11) of the tapered roller (6 ) is set to 1.0 mm or less. 4. The resin cage for a tapered roller bearing according to claim 2 , wherein the protrusion (31) is formed so that a cross section perpendicular to the circumferential direction of the cage is arc-shaped. 5. The resin cage for a tapered roller bearing according to claim 1, wherein the resin composition is a resin material to which an elastomer has been added. 6. The resin cage for a tapered roller bearing according to claim 5 , wherein a fiber reinforcing material is further added to said resin material. An outer ring (3) having a conical outer ring raceway surface (2) on its inner circumference;
an inner ring (5) having a conical inner ring raceway surface (4) on its outer periphery, the inner ring raceway surface (5) facing the inner diameter side of the outer ring raceway surface (2);
a plurality of tapered rollers (6) assembled at intervals in the circumferential direction between the outer ring raceway surface (2) and the inner ring raceway surface (4);
and a resin cage (1) for a tapered roller bearing according to any one of claims 1 to 6 , which maintains a circumferential interval between the plurality of tapered rollers (6),
The inner ring (5) is a tapered roller bearing having a large rib (8) that contacts the large end face (11) of each of the tapered rollers (6). 8. The tapered roller bearing according to claim 7, wherein the oil-retaining recess (24) is arranged within a region of the large diameter side pocket surface (17) that faces the large end face (11) of the tapered roller (6) so as not to protrude outside the region of the large diameter side pocket surface (17) that faces the large end face (11) of the tapered roller ( 6 ). 9. The tapered roller bearing according to claim 7 or 8, wherein the tapered roller (6) has a circular recess (12) in the center of the large end face (11), and two of the oil-retaining recesses (24) are provided for each pocket ( 16 ), on both sides in the circumferential direction of the cage that sandwich the circular recess ( 12). 10. The tapered roller bearing according to claim 9, wherein an opening area of the oil-retaining recess (24) on the large diameter side pocket surface (17) side that faces an annular portion of the large end face (11) of each tapered roller ( 6 ) excluding the circular recess (12) is 50% or more of an opening area of the oil-retaining recess (24) on the large diameter side pocket surface (17) side. 11. A tapered roller bearing according to claim 9 or 10, wherein the two oil-retaining recesses (24) on either side in the circumferential direction of the retainer sandwiching the circular recess (12) are each formed in a polygonal shape having two or more corner portions (28) where adjacent inner surfaces of the oil-retaining recesses ( 24 ) intersect when viewed in the axial direction of the retainer.

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