JP2021089040A - Slide component for bearing and hub unit bearing - Google Patents

Abstract

To provide a structure of a slide component for bearing that has an uneven surface for excellently securing reduction effect on frictional force molded while molding costs are suppressed.SOLUTION: A slide component for bearing (retainer 5) has a slide surface (an inner surface of a pocket 24), and is formed of a polymer composition. The polymer composition includes a polymer and a filler mixed with the polymer. The filler is composed of particles which are made of a material having a smaller coefficient of linear expansion than the polymer and have no ridge part on surfaces. The slide surface is a surface molded of the polymer composition by injection, and has many fine recesses formed through molding shrinkage of the polymer composition in the injection molding and holding a lubricant.SELECTED DRAWING: Figure 4

Description

The present invention relates to sliding parts for bearings such as cages and seal members, and hub unit bearings that rotatably support wheels of automobiles with respect to suspension devices.

The hub unit bearing is formed between an outer member having a double-row outer ring track on the inner peripheral surface, an inner member having a double-row inner ring track on the outer peripheral surface, and a double-row outer ring track and a double-row inner ring track. It is provided with a plurality of rolling elements arranged in. When the hub unit bearing is assembled to the automobile, one of the outer member and the inner member is coupled and fixed to the suspension device, and the other member of the outer member and the inner member is connected and fixed. The wheels are supported and fixed.

The hub unit bearing is a cage that holds the rolling element so that it can roll, and a sealing device that closes the axial end opening of the internal space existing between the inner peripheral surface of the outer member and the outer peripheral surface of the inner member. And further prepare. The cage has pockets at a plurality of locations in the circumferential direction, and the rolling elements are rotatably held in the pockets. The sealing device includes a sealing member having a sealing lip, and the surface of the tip end portion of the sealing lip is slidably contacted with the mating surface.

By the way, in recent years, there has been an increasing demand for lower torque of hub unit bearings in order to improve fuel efficiency and efficiency of automobiles. As a method of reducing the torque of the hub unit bearing, for example, a sliding contact portion between the inner surface (sliding contact surface) of the pocket of the cage (sliding component for bearing) and the surface of the rolling element, or a sealing member (sliding for bearing). It is conceivable to reduce the frictional force between the surface (sliding contact surface) of the tip of the seal lip constituting the component) and the sliding contact portion with the mating surface.

According to Japanese Patent Application Laid-Open No. 2002-155949 (Patent Document 1), in order to reduce the frictional force between the inner surface of the pocket of the cage and the surface of the rolling element, the inner surface of the pocket is formed of an uneven surface. Therefore, a structure is described in which the contact area between the inner surface of the pocket and the surface of the rolling element is reduced, and the lubricant can be easily held on the inner surface of the pocket. Further, the publication describes a method of molding the inner surface of a pocket into an uneven surface by using a mold having an uneven shape when the cage is manufactured by injection molding of a synthetic resin.

Japanese Patent Application Laid-Open No. 2012-193835 (Patent Document 2) describes the tip of the seal lip in order to reduce the frictional force between the surface of the tip of the seal lip and the mating surface of the sealing member. A structure is described in which the contact area between the surface of the tip of the seal lip and the mating surface is reduced by forming the surface with an uneven surface, and the lubricant can be easily held on the surface of the tip of the seal lip. There is. Further, in the same publication, when a seal member is manufactured by rubber injection molding (vulcanization molding), a method of molding the surface of the tip portion of the seal lip into an uneven surface by using a mold having an uneven shape is described. Are listed.

Japanese Unexamined Patent Publication No. 2002-155949 Japanese Unexamined Patent Publication No. 2012-193835

In the conventional structure as described above, in order to form the inner surface of the pocket of the cage and the surface of the tip of the seal lip into the uneven surface, the inner surface of the mold is subjected to costly mechanical processing, thereby causing unevenness. It is necessary to form a shape. Therefore, the molding cost of the cage and the sealing member tends to be high.

In particular, in the case of a cage, injection molding is generally performed by axial draw molding, which allows a large number of pieces to be taken. Since the angle difference between the two is large, it is difficult to form the uneven shape by scraping or crushing the uneven shape at the time of mold release.

Also, in the case of the seal member, vulcanization molding is performed in the cavity sandwiched between the upper mold and the lower mold, so that the surface of the radial lip is in the direction of the uneven shape and the direction of die cutting when the mold is released after molding. Since the angle difference is large, it is difficult to form the uneven shape by scraping or crushing the uneven shape at the time of mold release.

Further, when the inner surface of the pocket of the cage and the surface of the tip of the seal lip are formed into an uneven surface by a mold in which an uneven shape is formed by mechanical processing, the formed uneven surface becomes sharp. It often has a ridge, and the lubricant is scraped off by the ridge, which may reduce the effect of reducing the frictional force.

In view of the above circumstances, the present invention realizes a structure of a sliding component for a bearing and a hub unit bearing in which a concave-convex surface for satisfactorily ensuring the effect of reducing frictional force is molded while suppressing a molding cost. It is an object.

The sliding component for a bearing of the present invention has a sliding contact surface that is in sliding contact with another member, and is composed of a polymer composition.
The polymer composition comprises a polymer and a filler mixed in the polymer.
The filler is composed of particles having no ridge on the surface, which are made of a material having a coefficient of linear expansion smaller than that of the polymer.
The sliding contact surface is a surface formed by injection molding or vulcanization molding of the polymer composition, and a lubricant formed by molding shrinkage of the polymer composition in the injection molding or vulcanization molding. It has a large number of minute recesses for holding.

In one aspect of the sliding component for bearings of the present invention, the amount of the filler mixed in the polymer composition is 10% by weight or more and 30% by weight or less, and the size of the particles constituting the filler is 5 μm or more. It is 50 μm or less.

In one aspect of the sliding bearing component of the present invention, the sliding bearing component has pockets for rotatably holding the rolling element at a plurality of locations in the circumferential direction, and the sliding contact surface is the pocket. A cage, which is the inner surface of the polymer, and the polymer is a thermoplastic resin.

In one aspect of the sliding component for bearings of the present invention, the sliding component for bearings is a sealing member having a seal lip and the sliding contact surface is the surface of the tip end portion of the seal lip, and the polymer. Is rubber.

The first aspect of the hub unit bearing of the present invention is arranged between an outer member having an outer ring track on the inner peripheral surface, an inner member having an inner ring track on the outer peripheral surface, and the outer ring track and the inner ring track. The cage is provided with a plurality of rolling elements and a cage having pockets at a plurality of locations in the circumferential direction and holding the rolling elements in the pockets so that the rolling elements can roll freely. It is a part.

A second aspect of the hub unit bearing of the present invention is arranged between an outer member having an outer ring track on the inner peripheral surface, an inner member having an inner ring track on the outer peripheral surface, and the outer ring track and the inner ring track. A plurality of rolling elements and a sealing device having a sealing member for closing the axial end opening of the internal space existing between the inner peripheral surface of the outer member and the outer peripheral surface of the inner member. , The sealing member is a sliding component for a bearing of the present invention.
When the hub unit bearing of the present invention is carried out, the first aspect and the second aspect may be carried out at the same time.

According to the sliding component for bearings of the present invention, the effect of reducing the frictional force can be satisfactorily secured, and the molding cost can be suppressed.

FIG. 1 is a cross-sectional view of the hub unit bearing of the first example of the embodiment. FIG. 2 is a view of the cage of the first example of the embodiment as viewed from the opening side of the pocket with respect to the axial direction. FIG. 3 is a view of the cage of the first example of the embodiment as viewed from the rim portion side in the axial direction. FIG. 4 is a cross-sectional view taken along the line AOA of FIG. FIG. 5 is an enlarged view of part B of FIG. FIG. 6 is an enlarged view of part C of FIG. FIG. 7 is a cross-sectional view schematically showing the vicinity of the surface of the sliding component for bearing (retainer, seal member) of the first example of the embodiment in an enlarged manner.

A first example of the embodiment of the present invention will be described with reference to FIGS. 1 to 7.

The hub unit bearing 1 of this example is an inner ring rotation type and is for a drive wheel, and has an outer ring 2 corresponding to an outer member and a hub 3 corresponding to an inner member, each of which is a rolling element. A ball 4, a pair of cages 5, and a seal ring 6 and a combination seal ring 7, each of which is a sealing device, are provided.

Regarding the hub unit bearing 1, the inside in the axial direction is the right side in the width direction of the vehicle when assembled to the vehicle, and the outside in the axial direction is the width direction of the vehicle when assembled to the vehicle. It is the left side of FIG. 1 which is the outside.

The outer ring 2 is made of a hard metal such as medium carbon steel. The outer ring 2 has a double-row outer ring tracks 8a and 8b on the inner peripheral surface, and has a stationary flange 9 protruding outward in the radial direction at an axial intermediate portion. The stationary flange 9 has support holes 10 penetrating in the axial direction at a plurality of locations in the circumferential direction in the middle portion in the radial direction. The outer ring 2 is supported and fixed to the suspension device by a support bolt screwed into the support hole 10 of the stationary flange 9, and does not rotate even when the wheel rotates.

The hub 3 has a double-row inner ring tracks 11a and 11b on the outer peripheral surface, and is arranged coaxially with the outer ring 2 on the inner side in the radial direction of the outer ring 2. The hub 3 has a rotary flange 12 projecting outward in the radial direction at a portion located on the outer side in the axial direction from the outer end in the axial direction of the outer ring 2, and has a cylinder at the outer end in the axial direction. It has a shaped pilot unit 13. The rotary flange 12 has mounting holes 14 penetrating in the axial direction at a plurality of locations in the circumferential direction in the middle portion in the radial direction. A stud 15 is press-fitted into each of the mounting holes 14. The rotating body for braking such as a disc or a drum, and the wheels constituting the wheels are provided with the pilot portion 13 inserted into the central hole provided in the central portion and at a plurality of locations in the circumferential direction in the radial intermediate portion. With the stud 15 inserted into the through hole, the hub nut is screwed into the tip of the stud 15 to be coupled to the rotating flange 12.

The mounting hole of the rotary flange may be formed by a female screw hole. In this case, by screwing the hub bolt through which the through hole provided in the braking rotating body and the through hole provided in the wheel are inserted into the mounting hole, the braking rotating body and the wheel are attached to the rotating flange. Bond and fix.

The hub 3 has a spline hole 16 penetrating in the axial direction at the center thereof. The tip of the drive shaft, which is rotationally driven directly or via a transmission, is spline-engaged with the spline hole 16 by a drive source such as an engine or an electric motor. When the automobile is running, the hub 3 is rotationally driven by the drive shaft to rotationally drive the wheels and the rotating body for braking that are coupled and fixed to the rotary flange 12 of the hub 3.

The hub 3 of this example is a combination of an inner ring 17 and a hub ring 18.

The inner ring 17 is made of a hard metal such as bearing steel. The inner ring 17 has an inner ring track 11a on the outer peripheral surface, which is inside in the axial direction among the double-row inner ring tracks 11a and 11b.

The hub ring 18 is made of a hard metal such as medium carbon steel. The hub ring 18 has an inner ring raceway 11b on the outer side in the axial direction among the double-row inner ring raceways 11a and 11b at the axially intermediate portion of the outer peripheral surface. The hub ring 18 has a rotary flange 12 protruding outward in the radial direction at a portion located on the outer side in the axial direction with respect to the inner ring track 11b on the outer side in the axial direction, and has a cylindrical shape at an end portion on the outer side in the axial direction. It has a pilot unit 13 of the above. Further, the hub ring 18 has a spline hole 16 penetrating in the axial direction at the center thereof.

The hub ring 18 has a fitting cylinder portion 19 having a smaller outer diameter than a portion adjacent to the outer side in the axial direction and the inner ring 17 being externally fitted in a portion located inside the inner ring track 11b on the outer side in the axial direction. Have. The hub ring 18 further has a caulking portion 20 that bends radially outward from the axially inner end of the fitting cylinder portion 19 and presses the axially inner end surface of the inner ring 17. That is, the hub 3 of this example has a stepped surface 21 existing at an axially outer end of the fitting cylinder portion 19 and a caulking portion in a state where the inner ring 17 is externally fitted to the fitting cylinder portion 19 of the hub ring 18. The inner ring 17 is sandwiched between the inner ring 17 and the hub ring 17 from both sides in the axial direction, and the inner ring 17 and the hub ring 18 are coupled and fixed. However, the inner ring and the hub ring can also be connected and fixed with nuts.

A plurality of balls 4 are arranged between the outer ring orbits 8a and 8b of the double row and the inner ring orbits 11a and 11b of the double row, one in each row, separated from each other in the circumferential direction, and the respective rows. It is rotatably held by the cage 5 of the above. As a result, the hub 3 is rotatably supported inward in the radial direction of the outer ring 2. In this example, the ball 4 is used as the rolling element, but a tapered roller can also be used as the rolling element. Further, in this example, the pitch circle diameter of the balls 4 in the inner row in the axial direction and the pitch circle diameter of the balls 4 in the outer row in the axial direction are the same as each other. It can also be applied to PCD type hub unit bearings having different diameters in which the pitch circle diameter and the pitch circle diameter of the rolling elements in the outer row in the axial direction are different from each other.

The cage 5, which is a sliding component for bearings, is a crown-type cage made of synthetic resin, and as shown in FIGS. 2 to 4, the annular rim portion 22 and the rim portion 22 are equally spaced in the circumferential direction. A pillar portion 23 that protrudes unilaterally in the axial direction and outward in the radial direction is provided from a plurality of locations. The portion surrounded on three sides by the rim portion 22 and the pair of pillar portions 23 adjacent to each other in the circumferential direction is a pocket 24 for holding the ball 4 so as to be rollable. The inner surface of the pocket 24, which is the sliding contact surface, is composed of a partially spherical or partially cylindrical concave surface whose radius of curvature is slightly larger than the radius of curvature of the surface (rolling surface) of the ball 4.

Regarding the cage 5, one side in the axial direction is the right side for the cage 5 in the right column of FIG. 1 and the left side for the cage 5 in the left column of FIG. Further, regarding the cage 5, the other side in the axial direction is the left side for the cage 5 in the right column of FIG. 1 and the right side for the cage 5 in the left column of FIG.

In this example, the surface of the cage 5 including the inner surface of the pocket 24 has a large number of minute recesses α1 (see FIG. 7, which is a schematic cross-sectional view showing the vicinity of the surface in an enlarged manner). The opening peripheral edge of the recess α1 is not a sharp ridge but a smooth convex curved surface. That is, the surface of the cage 5 is composed of a fine uneven surface S1 having a large number of such minute recesses α1 and having no sharp ridges.

Grease, which is a lubricant, is sealed in a substantially cylindrical internal space 25 that exists between the inner peripheral surface of the outer ring 2 and the outer peripheral surface of the hub 3 and on which the balls 4 are arranged. The rolling contact portion between the surface of the ball 4 and the outer ring tracks 8a and 8b and the inner ring tracks 11a and 11b, and the sliding contact portion between the surface of the ball 4 and the inner surface of the pocket 24 of the cage 5 are enclosed in the internal space 25. It is lubricated with grease. In particular, in this example, a large number of minute recesses α1 provided on the inner surface of the pocket 24 are used as a grease reservoir for holding grease.

The seal ring 6 closes the axially outer opening of the internal space 25. As a result, foreign matter such as muddy water may enter the internal space 25 from the external space through the axially outer opening of the internal space 25, or the grease sealed in the internal space 25 may leak to the external space. It is preventing.

As shown in FIG. 5, the seal ring 6 includes a core metal 26 and a seal member 27 which is a sliding component for bearings.

The core metal 26 is formed in an annular shape as a whole by bending and molding a metal plate such as a mild steel plate into a substantially L-shaped cross section. The core metal 26 is internally fitted and fixed to the axially outer end of the outer ring 2.

The seal member 27 is made of rubber and is fixed to the core metal 26 by vulcanization adhesion. The seal member 27 has three seal lips 28a, 28b, 28c. One of these seal lips (radial lips) 28a has the surface of the tip portion, which is the sliding contact surface, slidably contacting the outer peripheral surface of the axial intermediate portion of the hub 3, which is the mating surface, over the entire circumference, and the rest. In each of the two seal lips (axial lips) 28b and 28c, the surface of the tip portion, which is the sliding contact surface, is slidably contacted with the inner surface surface of the rotating flange 12 which is the mating surface in the axial direction over the entire circumference.

In this example, the surface of the seal member 27, including the surface of the tip of each of the three seal lips 28a, 28b, 28c, has a large number of minute recesses α2 (see FIG. 7). The opening peripheral edge of the recess α2 is not a sharp ridge but a smooth convex curved surface. That is, the surface of the seal member 27 is composed of a fine uneven surface S2 having many such minute recesses α2 and having no sharp ridges.

The surface of the tip of each of the three seal lips 28a, 28b, 28c and the sliding contact portion between the outer peripheral surface of the axial intermediate portion of the hub 3 or the axial inner surface of the rotary flange 12 which is the mating surface are lubricated with grease. It is lubricated. In particular, in this example, a large number of minute recesses α2 provided on the surface of the tip portions of the three seal lips 28a, 28b, and 28c are used as a grease reservoir for holding grease.

The combination seal ring 7 is mounted between the inner peripheral surface of the axially inner end of the outer ring 2 and the outer peripheral surface of the axially inner end of the hub 3 to close the axially inner opening of the internal space 25. As a result, foreign matter such as muddy water may enter the internal space 25 from the external space through the axially inner opening of the internal space 25, or the grease sealed in the internal space 25 may leak to the external space. It is preventing.

As shown in FIG. 6, the combination seal ring 7 includes a slinger 29 and a seal ring 30.

The slinger 29 has an L-shaped cross section and is formed in an annular shape as a whole by bending and molding a rust-preventive metal plate such as a stainless steel plate or a rust-preventive mild steel plate. The slinger 29 has a slinger cylindrical portion 31 that is fitted and fixed to the outer peripheral surface of the axially inner end of the hub 3, and a ring shape that is bent outward in the radial direction from the axially inner end of the slinger cylindrical portion 31. It has a slinger side plate portion 32 of the above.

The seal ring 30 includes a core metal 33 and a seal member 34 which is a sliding component for bearings.

The core metal 33 has a substantially L-shaped cross section and is formed in an annular shape as a whole by bending and molding a metal plate such as a mild steel plate. The core metal 33 is bent inward in the radial direction from the axially outer end of the core metal cylindrical portion 35 and the core metal cylindrical portion 35 that are internally fitted and fixed to the inner peripheral surface of the axially inner end portion of the outer ring 2. It has a substantially circular ring-shaped core metal side plate portion 36.

The seal member 34, which is a sliding component for bearings, is made of rubber and is fixed to the core metal 33 by vulcanization adhesion. The seal member 34 includes three seal lips 37a, 37b, 37c. One of the seal lips (radial lips) 37a has the surface of the tip portion, which is the sliding contact surface, slidably contacting the outer peripheral surface of the slinger cylindrical portion 31, which is the mating surface, over the entire circumference. In each of the remaining two seal lips (axial lips) 37b and 37c, the surface of the tip portion, which is the sliding contact surface, is slidably contacted with the axial outer surface of the slinger side plate portion 32, which is the mating surface, over the entire circumference. There is.

In this example, the surface of the seal member 34, including the surface of the tip of each of the three seal lips 37a, 37b, 37c, has a large number of minute recesses α2 (see FIG. 7). The opening peripheral edge of the recess α2 is not a sharp ridge but a smooth convex curved surface. That is, the surface of the seal member 34 is composed of a fine uneven surface S2 having many such minute recesses α2 and having no sharp ridges.

The surface of the tip of each of the three seal lips 37a, 37b, 37c and the sliding contact portion between the outer peripheral surface of the slinger cylindrical portion 31 or the axial outer surface of the slinger side plate portion 32, which is the mating surface, are lubricated by grease. Has been done. In particular, in this example, a large number of minute recesses α2 provided on the surface of the tip portions of the three seal lips 37a, 37b, and 37c are used as a grease reservoir for holding grease.

Next, a method of manufacturing the cage 5 will be described. The cage 5 is manufactured by injection molding of a synthetic resin. That is, the method for manufacturing the cage 5 includes an injection molding step of a synthetic resin.

In this example, as the synthetic resin constituting the cage 5, the polymer composition X1 containing the base material and the filler mixed in the base material is used (see FIG. 7). The base material is composed of polymer P1. The filler is composed of particles Q1 having no ridge on the surface, which is made of a material having a coefficient of linear expansion smaller than that of the polymer P1.

The polymer P1 is a polyamide resin (PA (linear expansion rate: 5.9 × 10 ^-5 / K)), a polyphenylene sulfide resin (PPS (linear expansion rate: 5.5 × 10 ^-5 / K)), and a polyacetal resin (. It is a thermoplastic resin such as POM (linear expansion rate: 8.5 × 10 ^{-5 / K).}

The particle Q1 is preferably composed of a material having a linear expansion coefficient of 5 × 10 ^-6 / K or less, and examples of the material include silicic anhydride (linear expansion rate: 0.5 × 10 ^-6 / K) and glass. (Coefficient of linear expansion: 3 × 10 ^-6 / K), graphite (coefficient of linear expansion: 5 × 10 ^-6 / K) and the like can be used. In order to form the uneven surface S1 by the injection molding step described later, it is preferable that the coefficient of linear expansion of the material constituting the particles Q1 is as small as possible.

As the shape of the particle Q1, any shape such as an elliptical sphere, a bean shape, and a bale shape can be adopted in addition to the sphere as shown in FIG. 7 as long as the surface does not have a ridge. In order to form the uneven surface S1 by the injection molding step described later, it is preferable that the shape of the particles Q1 is as close to a sphere as possible (substantially spherical).

The size of the particle Q1 can be, for example, 5 μm or more and 50 μm or less, and preferably 10 μm or more and 30 μm or less. In the present invention, the particle size is the size of the particles defined by the sieving method defined in JIS Z 8801. In order to form the uneven surface S1 by the injection molding step described later, it is preferable that the sizes of the particles Q1 constituting the filler are as uniform as possible (almost the same size).

The amount of the filler (particle Q1) mixed in the polymer composition X1 can be, for example, 10% by weight or more and 30% by weight or less, and preferably 10% by weight or more and 20% by weight or less.

The injection molding process for manufacturing the cage 5 is a mold formed by combining a fixed mold having a molten resin filling port and not moving and a movable mold that moves in the axial direction of the cage 5 with respect to the fixed mold. This is done using a device. In this example, the inner surfaces of the two molds (fixed mold and movable mold) that form the surface of the cage 5 are smooth flat surfaces or curved surfaces F (see FIG. 7) in which minute irregularities do not exist. When performing the injection molding process, the polymer composition X1 that has been heated and melted is filled into the cavity defined between the inner surfaces of the two molds in the state where the two molds are closest to each other (the heat-melted polymer composition X1). Pour in). Then, the cage 5 is formed by cooling and solidifying the polymer composition X1 in the cavity.

In particular, in this example, the polymer P1 existing near the surface is shrunk by the molding shrinkage (shrinkage of about 2 to 4% by volume) that occurs when the polymer composition X1 is cooled and solidified (solidified) in this way. , A fine uneven surface S1 (see FIG. 7) having a large number of minute concave portions α1 and having no sharp ridges is formed on the surface. Generally, when injection molding is performed, the particle Q1 which is a filler is not exposed on the surface, the particle Q1 exists at a position sunk from the surface, and the polymer P1 is formed between the surface side of the cage 5 of the particle Q1 and the particle Q1. I'm filling it up. Since the particle Q1 which is a filler is originally a solid, molding shrinkage does not occur, and molding shrinkage occurs only in the polymer P1. Therefore, the portion covering the particle Q1 is convex on the surface, and the space between the particles Q1 is concave. An uneven surface is formed. Further, since the linear expansion rate of the material constituting the particles Q1 is smaller than the linear expansion rate of the polymer P1, when the polymer composition X1 is cooled from the injection molding temperature (more than the melting temperature of the polymer P1, for example, 250 ° C. or more). The polymer P1 shrinks more than the particles Q1 present near the surface. As a result, the minute concave portion α1 based on the molding shrinkage generated at the portion located between the particles Q1 on the surface further grows, so that the fine uneven surface S1 having no sharp ridge is formed on the surface. Will be done. Note that, in FIG. 7, a plurality of particles Q1 are schematically drawn in a spherical shape of the same size in a neatly arranged state. However, in reality, the shapes and sizes of the plurality of particles Q1 are often different, and the spacing between the particles Q1 differs depending on the location. Then, the larger the distance between the particles Q1, that is, the larger the volume of the polymer P1, the larger the shrinkage amount, and the recess α1 having a size (width and depth) corresponding to the shrinkage amount is formed. The size of the concave portion α1 constituting the uneven surface S1 can be adjusted by appropriately selecting the size of the particles Q1 and the amount of the particles Q1 mixed in the polymer composition X1.

Then, as described above, the polymer composition X1 is cooled and solidified in the cavity to form the cage 5, and then the movable mold is moved in the axial direction to open the cavity, and the cage 5 is taken out from the cavity.

Further, regarding the method for manufacturing the cage 5, a secondary heating (annealing) step of heating the intermediate material obtained by the injection molding step as described above can be added. By increasing the crystallinity of the polymer P1 and shrinking the polymer P1 by adding such a secondary heating step, an uneven surface S1 having a deeper concave portion α1 can be obtained.

Next, a method of manufacturing the seal members 27 and 34 constituting the seal rings 6 and 30 will be described. The sealing members 27 and 34 are manufactured by vulcanization molding of rubber.

In this example, the polymer composition X2 containing the base material and the filler mixed in the base material is used as the rubber constituting the sealing members 27 and 34 (see FIG. 7). The base material is composed of polymer P2. The filler is composed of particles Q2 having no ridges on the surface, which are made of a material having a coefficient of linear expansion smaller than that of the polymer P2. In this example, the polymer composition X2 is appropriately provided with a vulcanizing agent, a plasticizer, a reinforcing material such as carbon black or silica sand, a lubricant such as wax (wear improving agent, friction improving agent), etc., if necessary. It is added and mixed.

The polymer P2 is fluororubber (FKM (coefficient of linear expansion: 0.1 to 1 × 10 ^-4 / K)) and nitrile rubber (NBR (coefficient of linear expansion: 2.2 to 2.4 × 10 ^-4 / K)). ), Silicone rubber (VMQ (coefficient of linear expansion: 2.5 to ⁴ × 10 -4 / K)) and other rubber materials.

The particles Q2 are preferably composed of a material having a linear expansion coefficient of 5 × 10 ^-6 / K or less, and examples of the material include silicic anhydride (linear expansion rate: 0.5 × 10 ^-6 / K) and glass. (Coefficient of linear expansion: 3 × 10 ^-6 / K), graphite (coefficient of linear expansion: 5 × 10 ^-6 / K) and the like can be used. In order to form the uneven surface S2 by the vulcanization molding step described later, it is preferable that the coefficient of linear expansion of the material constituting the particles Q2 is as small as possible.

As the shape of the particle Q2, any shape such as an elliptical sphere, a bean shape, and a bale shape can be adopted in addition to the sphere as shown in FIG. 7 as long as the surface does not have a ridge. In order to form the uneven surface S2 by the vulcanization molding step described later, it is preferable that the shape of the particles Q2 is as close to a sphere as possible (substantially spherical).

The size of the particles Q2 can be, for example, 5 μm or more and 50 μm or less, and preferably 5 μm or more and 25 μm or less. In order to form the uneven surface S2 by the vulcanization molding step described later, it is preferable that the sizes of the particles Q2 constituting the filler are as uniform as possible (almost the same size).

The amount of the filler (particle Q2) mixed in the polymer composition X2 can be, for example, 10% by weight or more and 30% by weight or less, and preferably 15% by weight or more and 25% by weight or less.

The vulcanization molding step for manufacturing the seal members 27 and 34 is performed by using a mold apparatus formed by combining an upper mold and a lower mold that move in perspective with each other. In this example, the inner surfaces of the two molds (upper mold and lower mold) that form the surfaces of the sealing members 27 and 34 are smooth flat surfaces or curved surfaces F in which minute irregularities do not exist. When performing the vulcanization molding step, the core metal (26, 33) and the unvulcanized polymer composition X2 premolded in the lower mold (polymer composition X2 in which the polymer P2 is in the state of unvulcanized rubber) Place the lump, close the upper mold (with the two molds closest to each other), and bond the cores 26 and 33 with the rubber in the cavity defined between the inner surfaces of these molds. , Vulcanization molding.

In particular, in this example, due to the molding shrinkage (shrinkage of about 4 to 6% by volume) generated when the polymer composition X2 is vulcanized (crosslinked) in this way, the polymer P2 existing in the vicinity of the surface is subjected to the surface. By contracting more than the particles Q2 existing in the vicinity, a fine uneven surface S2 (see FIG. 7) having a large number of minute recesses α2 and having no sharp ridges is formed on the surface. When vulcanization molding is performed, the unvulcanized rubber becomes a free-flowing liquid state, so that the particles Q2 as the filler are not exposed to the surface and the particles Q2 are exposed from the surface as in the case of injection molding of the cage 5. It exists at the sunken position, and the polymer P2 fills the space between the sliding contact surface side of the seal lip (28a to 28c, 37a to 37c) of the particle Q2 and the particle Q2. Since the particle Q2, which is a filler, is not rubber, shrinkage due to vulcanization molding does not occur, and molding shrinkage due to vulcanization occurs only in the polymer P2. Therefore, the portion covering the particle Q2 is convex on the surface, and the particle Q2 An uneven surface is formed. Further, the linear expansion rate of the material constituting the particles Q2 shrinks more than the particles Q2 existing near the surface when the polymer composition X2 is cooled from the vulcanization molding temperature (for example, 250 ° C. or higher). To do. As a result, of the surface, the minute concave portions α2 generated between the particles Q2 due to the shrinkage due to vulcanization molding further grow, so that the fine uneven surface S2 having no sharp ridge is formed on the surface. To. The size of the concave portion α2 constituting the uneven surface S2 can be adjusted by appropriately selecting the size of the particles Q2, the amount of the particles Q2 mixed in the polymer composition X2, and the like. Further, since the shrinkage of rubber due to vulcanization molding is larger than the molding shrinkage of synthetic resin and the linear expansion coefficient of rubber is smaller than the linear expansion coefficient of resin, the size of particles Q2 is smaller than that of synthetic resin, and the polymer composition. The amount of the particles Q2 mixed in X2 is preferably larger than that in the case of the synthetic resin.

Then, as described above, the polymer composition X2 is vulcanized and molded in the cavity to form the seal members 27 and 34, and the seal members 27 and 34 are adhered to the core metal 26 and 33, and then the upper mold is formed. Is opened (with the two molds separated from each other), and the sealing members 27 and 34 and the cores 26 and 33 (seal rings 6 and 30) are taken out from this cavity.

Further, regarding the manufacturing method of the sealing members 27 and 34, a secondary heating (secondary vulcanization) step of heating the intermediate material obtained by the vulcanization molding step as described above can be added. By adding such a secondary heating step, the cross-linking of the polymer P2 is advanced and the polymer P2 is contracted, so that the uneven surface S2 having the deeper concave portion α2 can be obtained.

In the hub unit bearing 1 of this example as described above, the inner surface of the pocket 24 of the cage 5 is composed of a fine uneven surface S1 having a large number of minute recesses α1 and having no sharp ridge. Then, these recesses α1 are used as a grease reservoir for holding the grease. Further, since the uneven surface S1 does not have a sharp ridge portion, the inconvenience that the grease adhering to the surface of the ball 4 is scraped off by such a ridge portion does not occur. Therefore, it is possible to maintain a good lubrication state of the sliding contact portion between the inner surface of the pocket 24 and the surface of the ball 4 for a long period of time, and to keep the frictional force of the sliding contact portion small for a long period of time. Further, the inner surface of the pocket 24 is in sliding contact with the surface of the ball 4 at a portion (convex portion) excluding the concave portion α1. That is, the sliding contact area between the inner surface of the pocket 24 and the surface of the ball 4 can be reduced by the amount of the recess α1. Therefore, also in this respect, the frictional force of the sliding contact portion between the inner surface of the pocket 24 and the surface of the ball 4 can be suppressed to be small for a long period of time. As described above, in the structure of this example, the frictional force of the sliding contact portion can be suppressed to be small, so that the torque of the hub unit bearing 1 can be reduced.

Further, in the structure of this example, the surface of the tip of the seal lips (28a, 28b, 28c) (37a, 37b, 37c) constituting the seal members 27, 34 has a sharp ridge having many minute recesses α2. It is composed of a fine uneven surface S2 having no portion. Then, such a recess α2 is used as a grease reservoir for holding the grease. Further, since the uneven surface S2 does not have a sharp ridge portion, such a ridge portion allows the mating surface ((the outer peripheral surface of the axial intermediate portion of the hub 3 or the axial inner surface of the rotating flange 12), (slinger cylinder). There is no inconvenience that the grease adhering to the outer peripheral surface of the portion 31 or the axial outer surface of the slinger side plate portion 32) is scraped off. Therefore, the lubrication state of the sliding contact portion between the surface of the tip portion of the seal lip (28a, 28b, 28c) (37a, 37b, 37c) and the mating surface is maintained well for a long period of time, and the frictional force of the sliding contact portion is maintained. Can be kept small for a long period of time. Further, the surface of the tip portion of the seal lip (28a, 28b, 28c) (37a, 37b, 37c) is in sliding contact with the mating surface at a portion (convex portion) excluding the concave portion α2. That is, the sliding contact area between the surface of the tip of the seal lip (28a, 28b, 28c) (37a, 37b, 37c) and the mating surface can be reduced by the amount of the recess α2. Therefore, also in this respect, the frictional force between the surface of the tip of the seal lip (28a, 28b, 28c) (37a, 37b, 37c) and the sliding contact portion between the mating surface can be kept small for a long period of time. As described above, in the structure of this example, the frictional force of the sliding contact portion can be suppressed to be small, so that the torque of the hub unit bearing 1 can be reduced.

Further, in this example, of the inner surface of the mold used when the cage 5 is manufactured by injection molding, the portion where the inner surface of the pocket 24 is molded is also referred to as a smooth surface F having no minute irregularities. For example, the inner surface of the pocket 24 can be molded into the concave-convex surface S1 by utilizing the molding shrinkage of the synthetic resin without giving the portion a concave-convex shape by subjecting the portion to a costly mechanical process. .. Therefore, the molding cost of the cage 5 can be suppressed as much as the costly mechanical processing becomes unnecessary.

Further, in this example, since the inner surface of the mold used when the cage 5 is manufactured by injection molding is a smooth surface F having no minute irregularities, when the cage 5 is taken out from the cavity (at the time of mold release). ), The uneven shape of the uneven surface S1 is not crushed by the inner surface of the mold even if strict molding condition control is not performed. Therefore, the molding cost of the cage 5 can be suppressed because it is not necessary to strictly control the molding conditions.

Further, in this example, among the inner surfaces of the mold used when the seal members 27 and 34 are manufactured by vulcanization molding, the surface of the tip of the seal lip (28a, 28b, 28c) (37a, 37b, 37c) is used. Even if the portion to be molded is a smooth surface F in which there are no minute irregularities, in other words, the rubber molding shrinkage even if the portion is mechanically processed to increase the cost and does not have an uneven shape. Can be used to mold the surface of the tip of the seal lip (28a, 28b, 28c) (37a, 37b, 37c) into the uneven surface S2. Therefore, the molding cost of the sealing members 27 and 34 can be suppressed because the costly mechanical processing is not required.

Further, in this example, since the inner surface of the mold used when the sealing members 27 and 34 are manufactured by vulcanization molding is a smooth surface F having no minute irregularities, the sealing members 27 and 34 are taken out from the cavity. At that time (at the time of mold release), the uneven shape of the uneven surface S2 is not scraped or crushed by the inner surface of the mold. Therefore, the molding cost (inspection cost and defective loss) of the sealing members 27 and 34 can be suppressed.

In this example, the case where the present invention is applied to the hub unit bearing for the drive wheel in which the hub 3 is driven by the drive shaft has been described. However, the present invention has described the case where the hub is not driven by the drive shaft in the hub unit bearing for the driven wheel. It can also be applied to.

In the hub unit bearing 1 of this example, the outer ring 2 constitutes a stationary wheel supported and fixed to the suspension device, and the hub 3 constitutes a rotating body for braking and a rotating wheel supporting the wheel, so-called inner ring rotation. Has a mold structure. However, the present invention is a so-called outer ring rotation type in which the outer member constitutes a rotating body for braking and a rotating wheel that supports the wheel, and the inner member constitutes a stationary wheel that is supported and fixed to the suspension device. It can also be applied to hub unit bearings.

The sliding component for bearings of the present invention is not limited to the hub unit bearing, and can be used by assembling to various bearings.

1 Hub unit bearing 2 Outer ring 3 Hub 4 Ball 5 Cage 6 Seal ring 7 Combination seal ring 8a, 8b Outer ring track 9 Static flange 10 Support hole 11a, 11b Inner ring track 12 Rotating flange 13 Pilot part 14 Mounting hole 15 Stud 16 Spline hole 17 Inner ring 18 Hub ring 19 Fitting cylinder part 20 Caulking part 21 Step surface 22 Rim part 23 Pillar part 24 Pocket 25 Internal space 26 Core metal 27 Sealing member 28a, 28b, 28c Seal lip 29 Slinger 30 Sealing ring 31 Slinger Cylindrical part 32 Slinger side plate 33 Core metal 34 Sealing member 35 Core metal cylindrical part 36 Core metal side plate 37a, 37b, 37c Seal lip

Claims (6)

A sliding component for bearings that has a sliding contact surface that slides into contact with other members and is made of a polymer composition.
The polymer composition comprises a polymer and a filler mixed in the polymer.
The filler is composed of particles having no ridge on the surface, which are made of a material having a coefficient of linear expansion smaller than that of the polymer.
The sliding contact surface is a surface formed by injection molding or vulcanization molding of the polymer composition, and a lubricant formed by molding shrinkage of the polymer composition in the injection molding or vulcanization molding. Has a large number of tiny recesses for holding,
Sliding parts for bearings. The amount of the filler mixed in the polymer composition is 10% by weight or more and 30% by weight or less.
The size of the particles constituting the filler is 5 μm or more and 50 μm or less.
The sliding component for a bearing according to claim 1. It has pockets for holding the rolling elements freely at a plurality of locations in the circumferential direction, and is used as a cage in which the sliding contact surface is the inner surface of the pockets.
The polymer is a thermoplastic resin,
The sliding component for a bearing according to claim 1 or 2. Used as a sealing member having a sealing lip, the sliding contact surface being the surface of the tip of the sealing lip.
The polymer is rubber,
The sliding component for a bearing according to claim 1 or 2. An outer member having an outer ring track on the inner peripheral surface,
An inner member having an inner ring track on the outer peripheral surface and
A plurality of rolling elements arranged between the outer ring track and the inner ring track,
A cage having pockets at a plurality of locations in the circumferential direction and holding the rolling element in a rollable manner is provided in the pockets.
The cage is the sliding component for bearings according to claim 3.
Hub unit bearing. An outer member having an outer ring track on the inner peripheral surface,
An inner member having an inner ring track on the outer peripheral surface and
A plurality of rolling elements rotatably arranged between the outer ring track and the inner ring track, and
A sealing device having a sealing member for closing the axial end opening of the internal space existing between the inner peripheral surface of the outer member and the outer peripheral surface of the inner member is provided.
The sealing member is the sliding component for bearings according to claim 4.
Hub unit bearing.

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