Bearing device for a wheel

A bearing device for a wheel has a stem shaft of an outer joint member of a constant-velocity universal joint fit and inserted in a hole of a hub wheel, the stem shaft and hub wheel being coupled through an intermediation of a recess-projection fitting structure. Projections extending in an axial direction are provided on one of the stem shaft and an inner diameter surface of the hole of the hub wheel. The projections are press-fit into another of the stem shaft and the inner diameter surface of the hole along the axial direction. Recesses that adhere to and fit the projections are formed in the other. An end on an inboard side of the hub wheel is caulked to an outer diameter side to form a caulking section and preload is applied to a roller bearing by the caulking section.

TECHNICAL FIELD

The present invention relates to a bearing device for a wheel for supporting wheels to freely rotate relative to a vehicle body in a vehicle such as an automobile.

BACKGROUND ART

The bearing device for a wheel has evolved from a structure called first generation in which roller bearings in double rows are independently used to second generation in which a vehicle body attachment flange is integrally provided in an outer member. Further, third generation in which one inner raceway surface of the roller bearings in double rows is integrally formed with an outer circumference of a hub wheel integrally having a wheel attachment flange has been developed and fourth generation in which a constant-velocity universal joint is integrated with the hub wheel and the other inner raceway surface of the roller bearings in double rows is integrally formed with an outer circumference of an outer joint member configuring the constant-velocity universal joint has been developed.

For example, the bearing device for a wheel called third generation is described in Patent Document 1. The bearing device for a wheel called third generation includes, as illustrated inFIG. 39, a hub wheel152having a flange151extending in an outer diameter direction, a constant-velocity universal joint154having an outer joint member153fixed to this hub wheel152, and an outer member155disposed on an outer circumferential side of the hub wheel152.

The constant-velocity universal joint154includes the outer joint member153, an inner joint member158disposed in a cup-shaped section157of this outer joint member153, a ball159disposed between this inner joint member158and the outer joint member153, and a retainer160that retains this ball159. A spline section161is formed on an inner circumferential surface of a center hole of the inner joint member158. An end spline section of a shaft (not shown) is inserted into this center hole, whereby the spline section161on the inner joint member158side and the spline section on the shaft side are engaged.

The hub wheel152has a cylindrical shaft section163and the flange151. A short-cylindrical pilot section165, on which a wheel and a brake rotor (not shown) are mounted, is protrudingly provided on an outer end surface164(end surface on an out board side) of the flange151. The pilot section165includes a large-diameter first section165aand a small-diameter second section165b. The brake rotor is externally fit in the first section165aand the wheel is externally fit in the second section165b.

A notch section166is provided in an outer circumferential surface at an end on the cup-shaped section157side of the shaft section163. An inner ring167is fit in this notch section166. A first inner raceway surface168is provided near a flange on an outer circumferential surface of the shaft section163of the hub wheel152. A second inner raceway surface169is provided on an outer circumferential surface of the inner ring167. A bolt inserting hole162is provided in the flange151of the hub wheel152. A hub bolt for fixing the wheel and the brake rotor to this flange151is inserted into this bolt inserting hole162.

In the outer member155, outer raceway surfaces170and171in two rows are provided on an inner circumference thereof and the flange (vehicle body attachment flange)151is provided on an outer circumference thereof. The first outer raceway surface170of the outer member155and the first inner raceway surface168of the hub wheel152are opposed to each other. The second outer raceway surface171of the outer member155and the raceway surface169of the inner ring167are opposed to each other. Rolling elements172are interposed between the second outer raceway surface171and the raceway surface169.

A stem shaft173of the outer joint member153is inserted into the shaft section163of the hub wheel152. In the shaft section173, a screw section174is formed at an end of a reverse cup-shaped section thereof. A spline section175is formed between this screw section174and the cup-shaped section157. A spline section176is formed on an inner circumferential surface (inner diameter surface) of the shaft section163of the hub wheel152. When this stem shaft173is inserted into the shaft section163of the hub wheel152, the spline section175on the stem shaft173side and the spline section176on the hub wheel152side are engaged.

A nut member177is screwed onto the screw section174of the stem shaft173projecting from the shaft section163. The hub wheel152and the outer joint member153are connected. An inner end surface (rear surface)178of the nut member177and an outer end surface179of the shaft section163come into contact with each other and an end surface180on a shaft section side of the cup-shaped section157and an outer end surface181of the inner ring181come into contact with each other. In other words, when the nut member177is tightened, the hub wheel152is nipped by the nut member177and the cup-shaped section157through an intermediation of the inner ring167.

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

Conventionally, as described above, the spline section175on the stem shaft173side and the spline section176on the hub wheel152side are engaged. Therefore, because it is necessary to apply spline machining to both the stem shaft173side and the hub wheel152side, cost increases. When the stem shaft173is press-fit into the hub wheel152, recesses and projections of the spline section175on the stem shaft173side and the spline section176on the hub wheel152side need to be aligned. If the stem shaft173is press-fit into the hub wheel152by aligning tooth surfaces thereof, recessed and projected teeth are likely to be damaged (torn). If the stem shaft173is press-fit into the hub wheel152by aligning the spline sections to a large diameter of the recessed and projected teeth rather than aligning the tooth surfaces, a backlash in a circumferential direction tends to occur. If there is the backlash in the circumferential direction in this way, transferability of rotation torque is low and noise tends to occur. Therefore, when the stem shaft173is press-fit into the hub wheel152by the spline fitting as in the prior art, it is difficult to solve both the damages to the recessed and projected teeth and the backlash in the circumferential direction.

Further, it is necessary for the nut member177to be screwed on the screw section174of the stem shaft173projecting from the shaft section163. Thus, the assembly work involves screw fastening operation, resulting in a rather poor workability. Further, the number of components is large, resulting in a rather poor component controllability.

Even if adhesion of a male spline and a female spline is improved in the spline fitting to prevent the backlash in the circumferential direction from occurring, if driving torque acts, it is likely that relative displacement occurs in the male spline and the female spline. If such relative displacement occurs, fretting wear occurs. The splines are likely to cause abrasion because of dust of the wear. Consequently, it is likely that a backlash occurs in a spline fitting region or stable torque transmission cannot be performed.

In view of the above-mentioned problems, it is an object of the present invention to provide a bearing device for a wheel that can realize suppression of a backlash in a circumferential direction and is excellent in workability of connection of a hub wheel and an outer joint member of a constant-velocity joint member, can perform stable torque transmission over a long period of time and is excellent in maintainability because separation of the hub wheel and the outer joint member of the constant-velocity universal joint is possible, and can perform stable torque transmission over a long period of time.

Means for Solving the Problems

A first bearing device for a wheel according to the present invention includes an outer member having an inner circumference in which outer raceway surfaces in double rows are formed; an inner member that has, on an outer circumference thereof, inner raceway surfaces in double rows opposed to the outer raceway surfaces and includes an inner ring and a hub wheel provided with flanges for attachment to a wheel; and rolling elements in double rows interposed between the outer raceway surfaces of the outer member and the inner raceway surfaces of the inner member, a stem section of an outer joint member of a constant-velocity universal joint being fit and coupled to an inner diameter of the hub wheel, in which: projections extending in an axial direction are provided in one of a stem shaft of the outer joint member and an inner diameter surface of a hole of the hub wheel, the projections are press-fit into another along the axial direction, and recesses that adhere to and fit on the projections are formed on the another by this press fitting to configure the recess-projection fitting structure in which entire fitting contact regions of the projections and the recesses adhere to each other; and an end on an inboard side of the hub wheel is caulked to an outer diameter side to form a caulking section, an inner ring of a roller bearing externally fit in the hub wheel is fixed by this caulking section, preload is applied to the roller bearing, and the caulking section and a back surface of a mouth section of the outer joint member of the constant-velocity universal joint opposed to this caulking section are brought into contact with each other.

With the bearing device for a wheel according to the present invention, the bearing device for a wheel includes the recess-projection fitting structure for integrating the hub wheel and the stem shaft of the outer joint member of the constant-velocity universal joint fit and inserted into the hole of the hub wheel. Therefore, a bolt and the like are unnecessary in coupling the stem shaft and the hub wheel. In the recess-projection fitting structure, entire fitting contact regions of projections and recesses are in close contact with each other. Therefore, in this fitting structure, a gap in which a backlash occurs is not formed in a diameter direction and a circumferential direction.

Because the end of the hub wheel is caulked and preload is applied to the roller bearing, it is unnecessary to apply preload with the mouth section of the outer joint member.

The caulking section of the hub wheel and the back surface of the mouth section of the outer joint member of the constant-velocity universal joint opposed to this caulking section are brought into contact with each other. Therefore, bending rigidity in a stem shaft direction is improved. This bending rigidity is caused by secondary moment generated during a joint high actuation angle and axial load input from a tire side during turning.

It is preferable to provide a shaft slip-off preventing structure for regulating slip-off of the stem shaft from the hub wheel between the stem shaft of the outer joint member of the constant-velocity universal joint and the inner diameter surface of the hub wheel. It is possible to prevent the outer joint member of the constant-velocity universal joint from slipping off from the hub wheel in the axial direction by providing the shaft slip-off preventing structure.

The shaft slip-off preventing structure is a hook structure formed by plastically deforming a cylindrical section, which is provided at a shaft end of the stem shaft, outward in a diameter direction with swinging and caulking by a swinging caulking jig. Therefore, it is possible to reduce caulking load during caulking compared with expansion of a diameter by pushing in the caulking jig in the axial direction without swinging the caulking jig.

The recess-projection fitting structure allows separation by application of drawing force in the axial direction. That is, if drawing force in the axial direction is applied to the stem shaft of the outer joint member, it is possible to remove the outer joint member from the hole of the hub wheel. After the stem shaft of the outer joint member is drawn out from the hole of the hub wheel, if the stem shaft of the outer joint member is press-fit into the hole of the hub wheel again, it is possible to configure the recess-projection fitting structure in which the entire fitting contact regions of the projections and the recesses are in close contact with each other.

The hub wheel and the stem shaft of the outer joint member can be fixed through an intermediation of a bolt coupling means provided on a device axis and having a screw hole and a bolt member screwed in this screw hole. Consequently, because the hub wheel and the stem shaft of the outer joint member are fixed through an intermediation of the bolt coupling means, slip-off in the axial direction of the stem shaft of the outer joint member from the hub wheel is regulated.

The bolt coupling means includes a shaft press-fitting guide structure section of the outer joint member that guides the bolt member during re-press fitting after the separation.

The bolt member has a screw section and a non-screw section, and the shaft press-fitting guide structure section has a bolt inserting hole through which the non-screw section of the bolt member is inserted. When a diameter difference between a hole diameter of the bolt inserting hole and a shaft diameter of the non-screw section of the bolt member is represented as Δd5 and a diameter difference between a stem shaft outer diameter of the outer joint member in the recess-projection fitting structure and a hub wheel inner diameter in the recess-projection fitting structure is represented as Δd6, a relation between the diameter differences can be 0<Δd5<Δd6.

In other words, the diameter difference between the hole diameter of the bolt inserting hole and the shaft diameter of the non-screw section of the bolt member is set smaller than the diameter difference between the stem shaft outer diameter of the outer joint member and the hub wheel inner diameter in the recess-projection fitting structure. The bolt inserting hole functions as a guide when the stem shaft of the outer joint member is press-fit.

It is preferable to provide an inner wall for partitioning an inside of the hole of the hub wheel in the hole, and provide the bolt inserting hole in this inner wall. Rigidity of the shaft press-fitting guide structure section is improved by this inner wall.

A seal material may be interposed at least one of between the caulking section of the hub wheel and an opposed surface of the outer joint member opposed to the caulking section and between a bearing surface of the bolt member of the bolt coupling means and a receiving surface for receiving this bearing surface.

It is preferable to set contact surface pressure between the caulking section of the hub wheel and the back surface of the mouth section is set to be equal to or lower than 100 MPa. When this contact surface pressure exceeds 100 MPa, noise is likely to be caused. In other words, when torque load is large, a difference occurs in twisting amounts of the outer joint member of the constant-velocity universal joint and the hub wheel. Sudden slip occurs in the contact section of the outer joint member of the constant-velocity universal joint and the hub wheel because of this difference, and noise occurs. On the other hand, when the contact surface pressure is equal to or lower than 100 MPa, it is possible to prevent sudden slip from occurring and suppress occurrence of noise.

The projections of the recess-projection fitting structure are provided in the stem shaft of the outer joint member of the constant-velocity universal joint, at least hardness of ends in the axial direction of the projections is set higher than that of an inner diameter section of the hole of the hub wheel, and the stem shaft is press-fit into the hole of the hub wheel from an axial direction end side of the projections. Thus, recesses that adhere to and fit in the projections are formed on the inner diameter surface of the hole of the hub wheel by the projections, and the recess-projection fitting structure may be configured. Further, the projections of the recess-projection fitting structure are provided on the inner diameter surface of the hole of the hub wheel, at least hardness of ends in the axial direction of the projections is set higher than that of an outer diameter section of the stem shaft of the outer joint member of the constant-velocity universal joint, and the projections on a hub wheel side are press-fit into the stem shaft of the outer joint member from an axial direction end side of the projections. Thus, recesses that adhere to and fit in the projections are formed on an outer diameter surface of the stem shaft of the outer joint member by the projections, and the recess-projection fitting structure may be configured.

Projecting direction intermediate regions of the projections are arranged on a recess forming surface before the formation of the recesses. When the projections are provided in the stem shaft of the outer joint member, a maximum diameter dimension of a circle connecting vertexes of the plural projections is set larger than an inner diameter dimension of the hub wheel shaft hole in which the recesses are formed. A diameter dimension of a circle connecting bottoms among the projections is set smaller than an inner diameter dimension of the shaft fitting hole of the hub wheel. On the other hand, an outer diameter dimension of the stem shaft of the outer joint member is set larger than a minimum diameter dimension of a circle connecting vertexes of the plural projections provided in the hole of the hub wheel, and set smaller than the diameter dimension of the circle connecting the bottoms among the projections of the hub wheel hole.

It is preferable to set a circumferential direction thicknesses of the projecting direction intermediate regions of the projections smaller than a circumferential direction dimension in positions corresponding to the intermediate regions among the projections adjacent to one another in the circumferential direction. By setting the circumferential direction thicknesses in this way, it is possible to set a sum of the circumferential direction thicknesses of the projecting direction intermediate regions of the projections smaller than a sum of circumferential direction thicknesses in positions corresponding to the intermediate regions in the projections on the other side that fit in among the projections adjacent to one another in the circumferential direction.

It is preferable to arrange the recess-projection fitting structure while avoiding a position right below the raceway surface of the roller bearing. In other words, if the shaft section is press-fit into the hole of the hub wheel, the hub wheel expands. Hoop stress is generated on the raceway surface of the roller bearing by this expansion. The hoop stress means force for expanding a diameter in the outer diameter direction. Therefore, when the hoop stress is generated on the bearing raceway surface, there is a fear that the hoop stress reduces rolling fatigue life and causes a crack. Therefor, it is possible to suppress generation of the hoop stress on the bearing raceway surface by arranging the recess-projection fitting structure while avoiding a position right below the raceway surface of the roller bearing.

It is preferable to provide a pocket section that stores an extruded portion caused by the recess formation by the press fitting. It is possible to provide the pocket section that stores the extruded portion caused by the recess formation by the press fitting and provide the pocket section on the inner diameter surface of the hole of the hub wheel. The extruded portion is equivalent to a volume of a material in the recesses in which the recess fitting regions of the projection are fit in. The extruded portion includes the material extruded from the recesses to be formed, the material cut for forming the recesses, or the material extruded and cut. It is preferable to provide the pocket section for storing the extruded portion on a press fitting start end side of the projections of the stem shaft and provide a collar section for centering with the hole of the hub wheel on an axial direction opposite projection side of this pocket section.

Effect of the Invention

The bearing device for a wheel according to the present invention includes the recess-projection fitting structure for integrating the hub wheel and the stem shaft of the outer joint member of the constant-velocity universal joint fit and inserted into the hole of the hub wheel. Therefore, it is possible to eliminate a backlash in the circumferential direction of the recess-projection fitting structure section.

The caulking section and the back surface of the mouth section of the outer joint member are brought into contact with each other, whereby bending rigidity in the stem shaft direction is improved, the stem shaft becomes robust against bending, and a high-quality product excellent in durability is obtained. Moreover, positioning during press fitting can be realized by this contact. Consequently, dimension accuracy of this bearing device for a wheel is stabilized, it is possible to secure stable length as axial direction length of the recess-projection fitting structure disposed along the axial direction and realize improvement of torque transmission performance. Further, a seal structure can be configured by this contact. It is possible to prevent intrusion of foreign matters into the recess-projection fitting structure from the caulking section side of this hub wheel. The recess-projection fitting structure can maintain a stable fit state over a long period of time.

Because the end of the hub wheel is caulked and preload is applied to the roller bearing, it is unnecessary to apply preload with the mouth section of the outer joint member. Therefore, it is possible to press-fit the stem shaft of the outer joint member without taking into account preload and realize improvement of connectability (assemblability) of the hub wheel and the outer joint member.

With the shaft slip-off preventing structure, it is possible to effectively prevent the stem shaft of the outer joint member from slipping off in the axial direction from the hole of the hub wheel. Consequently, it is possible to maintain a stable connected state and realize improvement of a quality of the bearing device for a wheel. Therefore, nut fastening work is unnecessary when the stem shaft and the hub wheel are coupled. Therefore, it is possible to easily perform assembly work, realize a reduction in cost in the assembly work, and realize a reduction in weight.

It is possible to remove the outer joint member from the hole of the hub wheel by applying drawing force in the axial direction to the stem shaft of the outer joint member. Therefore, it is possible to realize improvement of workability (maintainability) of repairing and inspection of components. Moreover, by press-fitting the stem shaft of the outer joint member into the hole of the hub wheel again after repairing and inspection of the components, it is possible to configure the recess-projection fitting structure in which the entire fitting contact regions of the projections and the recesses are in close contact with each other. Therefore, it is possible to configure the bearing device for a wheel, which can perform stable torque transmission, again.

In the bearing device for a wheel in which the hub wheel and the constant-velocity universal joint are fixed through an intermediation of the bolt coupling means, slip-off in the axial direction of the stem shaft of the outer joint member from the hub wheel is regulated. It is possible to maintain a stable connected state.

Because the shaft slip-off preventing structure is a hook structure formed by plastically deforming the cylindrical section outward in the diameter direction, screw fastening in the prior art can be omitted. Therefore, it is unnecessary to form the screw section projecting from the hole of the hub wheel in the shaft section. It is possible to realize a reduction in weight, omit screw fastening work, and realize improvement of assembly workability. Moreover, caulking load during caulking may be relatively small. It is possible to increase the thickness of the caulking section and surely bring the inner diameter surface of the hub wheel and the outer diameter surface of the caulking section into contact with each other. Consequently, it is possible to provide a more robust slip-off preventing mechanism (structure). Further, because such a robust slip-off preventing mechanism (structure) is provided, bending rigidity of the shaft section is improved and the shaft section becomes robust against bending. If the caulking load during caulking can be reduced, it is possible to prevent deformation of a region that receives load (a load receiving section of the outer joint member of the constant-velocity universal joint, for example, a step surface provided on the outer diameter surface of the outer joint member, an opening side end surface of the outer joint member, etc.).

Because the diameter difference between the hole diameter of the bolt inserting hole and the shaft diameter of the non-screw section of the bolt member is set smaller than the diameter difference between the stem shaft outer diameter of the outer joint member and the hub wheel inner diameter in the recess-projection fitting structure, the bolt inserting hole functions as a guide when the stem shaft of the outer joint member is press-fit. It is possible to perform more stable re-press fitting.

The rigidity of the shaft press-fit guide structure section is improved and press fitting of the stem shaft of the outer joint member is more stabilized by the inner wall of the hole of the hub wheel.

If a seal material is interposed between the caulking section of the hub wheel and the opposed surface of the outer joint member opposed to the caulking section, it is possible to prevent intrusion of rainwater, foreign matters, and the like into the recess-projection fitting structure from a space between the caulking section and the opposed surface. If a seal material is interposed between a bearing surface of the bolt shaft of the bolt coupling means and a receiving surface that receives the bearing surface, it is possible to prevent intrusion of rainwater, foreign matters, and the like into the recess-projection fitting structure from a space between the bearing surface and the receiving surface.

If contact surface pressure between the caulking section of the hub wheel and the back surface of the mouth section is equal to or lower than 100 MPa, it is possible to prevent sudden slip from occurring and suppress occurrence of noise. Consequently, it is possible to configure a silent bearing device for a wheel.

The projections of the recess-processing fitting structure are provided in the stem shaft of the outer joint member of the constant-velocity universal joint, the hardness of the axial direction ends of the projections is set higher than that of the inner diameter section of the hole of the hub wheel, and the stem shaft is press-fit in the hole of the hub wheel from the axial direction end side. As a result, it is possible to increase the hardness on the stem shaft side and improve the rigidity of the stem shaft. The projections of the recess-projection fitting structure are provided on the inner diameter surface of the hole of the hub wheel, the hardness of the axial direction ends of the projections is set higher than that of the outer diameter section of the stem shaft of the outer joint member of the constant-velocity universal joint, and the projections on the hub wheel side are press-fit in the stem shaft of the outer joint member from the axial direction end side thereof. As a result, it is unnecessary to perform hardness treatment (heat treatment) on the stem shaft side. Therefore, the outer joint member of the constant-velocity joint is excellent in productivity.

By setting the circumferential direction thickness of the projecting direction intermediate region of the projections smaller than a dimension in positions corresponding to the intermediate regions among the projections adjacent to one another in the circumferential direction, it is possible to increase the circumferential direction thickness of the projecting direction intermediate regions of the projections on the side in which the recesses are formed (projections among the formed recesses). Therefore, it is possible to increase a shearing area of the projections on the opposite side (projections having low hardness among the recesses because the recesses are formed) and secure torsion strength. Moreover, because tooth thickness of the projections on the high hardness side is small, it is possible to reduce press-fitting load and realize improvement of press-fitting properties.

Generation of hoop stress on the bearing raceway surface is suppressed by arranging the recess-projection fitting structure while avoiding a position right below the raceway surface of the roller bearing. Consequently, it is possible to prevent occurrence of a deficiency of the bearing such as a reduction in rolling fatigue life, occurrence of a crack, and stress corrosion crack.

By providing the pocket section for storing the extruded portion caused by recess formation by the press fitting, it is possible to hold (maintain) the extruded portion in this pocket. The extruded portion does not enter the inside of the vehicle and the like on the outside of the device. In other words, it is possible to keep the extruded portion stored in the pocket section, it is unnecessary to perform removal processing for the extruded portion, and it is possible to realize a reduction in assembly work man-hour and realize improvement of assembly workability and cost reduction.

By providing the collar section for centering with the hole of the hub wheel on the opposite projection side in the axial direction of the pocket section, ejection of the extruded portion in the pocket section to the collar section side is eliminated. The extruded portion is more stably stored. Moreover, because the collar section is used for centering, it is possible to press-fit the stem shaft into the hub wheel while preventing decentering. Therefore, it is possible to highly accurately connect the outer joint member and the hub wheel and perform stable torque transmission.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention are described below with reference toFIGS. 1 to 41. A bearing device for a wheel according to a first embodiment is illustrated inFIG. 1. In this bearing device for a wheel, a hub wheel1, roller bearings2in double rows, and a constant-velocity universal joint3are integrated and the hub wheel1and a stem shaft12of an outer joint member of the constant-velocity universal joint3fit and inserted into a hole22of the hub wheel1are coupled through an intermediation of a recess-projection fitting structure M.

The constant-velocity universal joint3mainly includes an outer ring5as an outer joint member, an inner ring6as an inner joint member arranged on the inner side of the outer ring5, plural balls7provided between the outer ring5and the inner ring6to transmit torque, and a cage8provided between the outer ring5and the inner ring6and adapted to retain the balls7. An end section10aof a shaft10is press-fitted into a shaft hole inner diameter6aof the inner ring6to effect spline fitting, whereby connection with the shaft10is effected so as to allow torque transmission. A stop ring9for preventing shaft slipping-off is fit in the end section10aof the shaft10.

The outer ring5includes a mouth section11and a stem section (shaft section)12, and the mouth section11is formed in a cup-like shape open at its one end. In an inner spherical surface13thereof, there are formed plural axially extending guiding grooves (track grooves)14at equal circumferential intervals. The inner ring6has in an outer spherical surface15thereof plural axially extending guiding grooves (track grooves)16formed at equal circumferential intervals.

The track grooves14of the outer ring5and the track grooves16of the inner ring6are paired with each other, and one ball7as a torque transmission element (torque transmission member) is incorporated into a track formed by each pair of track grooves14,16so as to be capable of rolling. The balls7are provided between the track grooves14of the outer ring5and the track grooves16of the inner ring6to transmit torque. The cage8is slidably provided between the outer ring5and the inner ring6, with an outer spherical surface thereof coming in contact with the inner spherical surface13of the outer ring5and an inner spherical surface thereof coming in contact with the outer spherical surface15of the inner ring6. While in this example the constant-velocity universal joint is of the undercut free type, in which each track grooves14,16has a linear straight section provided to a groove bottom. It is also possible to adopt a constant-velocity universal joint of some other type such as the zepper type in which the linear straight section is not provided to the bottom.

Further, the opening of the mouth section11is stopped by a boot18. The boot18includes a large diameter section18a, a small diameter section18b, and a bellows section18cconnecting the large diameter section18aand the small diameter section18b. The large diameter section18ais fitted onto the opening of the mouth section11, and is fastened in this state by a boot band19a. Further, the small diameter section18bis fitted onto a boot attachment section10bof the shaft10, and is fastened in this state by a boot band19b.

The hub wheel1includes, as illustrated inFIG. 1andFIG. 5, a cylindrical section20, and a flange21provided at the out board side end section of the cylindrical section20. A hole22of the cylindrical section20includes a shaft section fitting hole22a, a tapered hole22bon the out board side, and a large diameter section22con the in-board side. Between the shaft section fitting hole22aand the large diameter section22c, there is provided a taper section (tapered hole)22d. This taper section22dis reduced in diameter along a press-fitting direction in coupling the hub wheel1and the stem shaft12of the outer ring5. A tilt angle θ1of the taper section22dis set to, for example, 15° to 75°. The outboard side is an outer side of the vehicle in a state in which the bearing device is attached to the vehicle and the inboard side is an inner side of the vehicle in the state in which the bearing device is attached to the vehicle.

The roller bearing2includes an inner ring24fit in a step section23provided on the inboard side of the cylinder section20of the hub wheel1and an outer member25externally fit from the cylinder section20to the inner ring24of the hub wheel1. In the outer member25, outer raceway surfaces (outer races)26and27in two rows are provided on an inner circumference thereof. The first outer raceway surface26and a first inner raceway surface (inner race)28provided on an outer circumference of the shaft section of the hub wheel1are opposed to each other. The second outer raceway surface27and a second inner raceway surface (inner race)29provided on an outer circumferential surface of the inner ring24are opposed to each other. Balls as rolling elements30are interposed between the first outer raceway surface26and the first inner raceway surface28and between the second outer raceway surface27and the second inner raceway surface29. Therefore, in this bearing device for a wheel, the hub wheel1and the inner ring24configure an inner member39of the roller bearing2. Seal members S1and S2are inserted in both openings of the outer member25.

A knuckle34(seeFIG. 26, etc.) extending from a suspension system for a vehicle body not shown in the figure is attached to the outer ring as the outer member25. An entire outer surface of the outer member25is formed as a cylindrical surface. This cylindrical surface is set as a press-fitting surface25ain which the knuckle34is press-fit. Consequently, the outer member25can be press-fit into a cylindrical inner diameter surface of the knuckle. In this case, it is desirable to set to regulate, with a tightening margin between the knuckle press-fitting surface25aand the knuckle inner diameter surface, relative shift in an axial direction and a circumferential direction of the knuckle34and the outer member25. For example, when mating surface pressure×mating area between the outer member25and the knuckle34is mating load, a value obtained by dividing this mating load with equivalent radial load of this bearing for a wheel is set as a creep occurrence limit coefficient. A design specification for the outer member25, i.e., a fitting margin between the outer member25and the knuckle is set by taking into account this creep occurrence limit coefficient in advance.

Therefore, it is possible to prevent slip-off in the axial direction and creep in the circumferential direction of the outer member25with the tightening margin between the knuckle press-fitting surface25aof the outer member25and the knuckle inner diameter surface of the knuckle34. The creep means that the bearing slightly moves in the circumferential direction because of insufficiency of the mating margin, machining accuracy failure of the fitting surface, or the like and the mating surface changes to a mirror surface and, in some case, the fitting surface involves score, and seizure or adhesion occurs. As illustrated inFIG. 26and the like, it is preferable to provide circumferential direction grooves in the knuckle press-fitting surface25aof the outer member25and an inner diameter surface34aof the knuckle34, respectively, and a lock ring61for slip-off prevention is inserted between those circumferential direction grooves.

In this case, the end on the inboard side of the hub wheel1is caulked and the inner ring24is pressed to the outboard side by the caulking section31, whereby preload is applied to this bearing2. Consequently, the inner ring24can be fastened to the hub wheel1. An end surface24aon the inboard side of the inner ring24is pressed to the outboard side along the axial direction by the caulking section31. An end surface24bon the outboard side of the inner ring24comes into contact or press-contact with the end surface23aof the step section23. A bolt inserting hole32is provided in the flange21of the hub wheel1. A hub bolt33for fixing a wheel and a brake rotor to this flange21are inserted into this bolt inserting hole32.

As illustrated inFIG. 2, the recess-projection fitting structure M is formed, for example, of axially extending projections35provided to the stem shaft12, and recesses36formed in the inner diameter surface of the hole section22of the hub wheel1(inner diameter surface37of shaft section fitting hole22ain this case). The entire regions of the fitting contact regions38of the projections35and the recesses36of the hub wheel1fit in the projections35are held in close contact. Plural projections35are arranged at a predetermined circumferential pitch on the outer peripheral surface of the opposite mouse side of the stem shaft12, and plural recesses36to be fit in the projections35are formed circumferentially in the inner diameter surface37of the shaft section fitting hole22aof the hole22of the hub wheel1. That is, over the circumferential entire periphery, the projections35and the recesses36fit-engaged thereto are tightly fit in each other.

In this case, the respective projections35are formed in a triangular shape (ridge shape) having a vertex of a projected R shape in section. Fitting contact regions (recess fitting regions)38of the projections35are ranges A illustrated inFIG. 2Band ranges from halfway sections of the ridges in section to the tops of the ridges. A gap40is formed further on an inner diameter side than an inner diameter surface37of the hub wheel1between the projections35adjacent to each other in the circumferential direction.

In this way, the hub wheel1and the stem shaft12of the outer ring5of the constant-velocity universal joint3can be connected through an intermediation of the recess-projection fitting structure M. In connecting the hub wheel1and the stem shaft12, because the end on the inboard side of the hub wheel1is caulked and preload is applied to the roller bearing2by the caulking section31as described above, it is unnecessary to apply preload to the inner ring24in the mouth section11of the outer ring5. However, in the present invention, the end of the hub wheel1(in this case, an outer end surface31aof the caulking section31) and an opposed surface of the outer ring5opposed to the end of the hub wheel1(back surface11aof the mouth section11) are brought into contact with each other. Contact surface pressure in this case is set to be equal to or smaller than 100 MPa.

Incidentally, the shaft slip-off preventing structure M1is provided between the end of the stem shaft12of the outer ring5and the inner diameter surface37of the hub wheel1. This shaft slip-off preventing structure M1includes an expanded-diameter caulking section (tapered locking piece)65that extends from the end of the stem shaft12of the outer ring5to the outboard side and locks to a tapered hole22b. In other words, the expanded-diameter caulking section65includes a ring-like member that increases in diameter from the inboard side to the outboard side. At least a part of an outer circumferential surface65athereof comes into press-contact or contact with the tapered hole22b.

In this bearing device for a wheel, foreign-matter intrusion preventing means W for preventing intrusion of foreign matters into the recess-projection fitting structure M are respectively provided further on the inboard side (the inner side of the vehicle in the state in which the bearing device is attached to be vehicle) than the recess-projection fitting structure M and further on the outboard side (the outer side of the vehicle in the state in which the bearing device is attached to the vehicle) than the recess-projection fitting structure M.

The out board side foreign-matter intrusion prevention means W2can be formed of a seal material (not shown) provided between the tapered locking piece65described above constituting an engagement section and the inner diameter surface of the tapered hole22b. In this case, a seal material is applied to the tapered locking piece65. That is, there is applied a seal material (seal agent) selected from among various resins curable after the application and capable of exerting sealing property between the tapered locking piece65and the inner diameter surface of the tapered hole22b. Note that, as this seal material, there is selected one that does not deteriorate in the atmosphere in which this bearing device for a wheel is used.

The foreign-matter intrusion preventing means W1on the inboard side can be configured by bringing the outer end surface31aof the caulking section31of the hub wheel1and the back surface11aof the mouth section11into contact with each other. A seal material (seal agent) may be applied to at least one of the outer end surface31aand the back surface11a.

It is also possible to provide a seal material in the fitting contact region38between the projections35and the recesses36, and in a gap40, thereby forming a foreign-matter intrusion prevention means W (W3). In this case, there is applied to the surfaces of the projections35a seal material (seal agent) selected from among various resins curable after the application and capable of exerting sealing property in the fitting contact region38.

When this bearing device for a wheel is assembled, as described later, the recesses36are formed by the projections35by press-fitting the stem shaft12of the outer ring5into the hub wheel1. When the stem shaft12is press-fit into the hub wheel1, a material is extruded from the recesses36formed by the projections35and an extruded portion45(seeFIG. 3) is formed. The extruded portion45is equivalent to a volume of the material of the recesses36in which recess fitting regions of the projections35are fit in. The extruded portion45includes the material extruded from the recesses36to be formed, the material cut for forming the recesses36, or the material extruded and cut. Therefore, in the bearing device for a wheel illustrated inFIG. 1and the like, a pocket section50for storing the extruded portion45is provided to the stem shaft12.

The pocket section50is formed by providing a circumferential direction groove51at a shaft edge of a spline41of the stem shaft12. The expanded-diameter caulking section (tapered locking piece)65configuring the shaft slip-off preventing structure M1is formed further on an opposite spline side than the circumferential direction groove51.

A method of fitting the recess-projection fitting structure M is described. In this case, as illustrated inFIG. 5, thermosetting treatment is applied to an outer diameter section of the stem shaft12of the outer ring5of the constant-velocity universal joint3. The spline41including projections41aand recesses41balong the axial direction is formed in this hardened layer H. Therefore, the projections41aof the spline41are hardened and changes to the projections35of the recess-projection fitting structure M. A range of the hardened layer H in this embodiment is, as indicated by a cross hatching section, from an outer edge of the spline41to a part of a bottom wall of the mouth section11of the outer ring5. As this thermosetting treatment, various kinds of heat treatment such as induction hardening and carburizing and quenching can be adopted. The induction hardening is a hardening method employing the principle of inserting a section necessary for hardening into a coil through which a high-frequency current flows, generating Joule heat with an electromagnetic induction action, and heating a conductive substance. The carburizing and quenching is a method of causing carbon to intrude/spread from the surface of a low carbon material and performing hardening after that. A hardened layer H1by the induction hardening is formed on the outer diameter side of the hub wheel1and the inner diameter side of the hub wheel is left in an unhardened state. A range of the hardened layer H1in this embodiment is, as indicated by a cross hatching section, from a base section of the flange21to near the caulking section of the step section23in which the inner ring24fits.

If the induction hardening is performed, the surface can be hard and hardness of a material in the inside can be kept. Therefore, the inner diameter side of the hub wheel1can be maintained in the unhardened state. The inner diameter surface37side of the hole22of the hub wheel1is an unhardened section not subjected to the thermosetting treatment (in an unhardened state). A hardness difference between the hardened layer H of the stem shaft12of the outer ring5and the unhardened section of the hub wheel1is set to be equal to or larger than 20 points in HRC. Specifically, the hardness of the hardened layer H is set to about 50 HRC to 65 HRC and the hardness of the unhardened section is set to about 10 HRC to 30 HRC.

In this case, a projecting direction intermediate region of the projections35corresponds to a position of a recess forming surface before recess formation (in this case, the inner diameter surface37of the hole22of the hub wheel1). That is, as illustrated inFIG. 4, an inner diameter dimension D of the inner diameter surface37of the hole22is set smaller than a maximum outer diameter of the projections35, i.e., a maximum diameter dimension (circumscribed circle) D1of a circle connecting vertexes of the projections35as the projections41aof the spline41and is set larger than an outer diameter dimension of a shaft outer diameter surface among the projections, i.e., a maximum diameter dimension D2(seeFIG. 5) of a circle connecting bottoms of the recesses41bof the spline41. In other words, the dimensions are set in a relation of D2<D<D1.

The spline41can be formed by various machining methods such as component rolling, cutting, pressing, and drawing, which are publicly known and used conventional means. As the thermosetting treatment, various kinds of heat treatment such as induction hardening and carburizing and quenching can be adopted.

As illustrated inFIG. 5, before the stem shaft12of the outer ring5is press-fit into the hole22of the hub wheel1, a cylindrical section66for configuring the expanded-diameter caulking section65is projected from an outer circumferential edge of the end surface12aof the stem shaft12along the axial direction. An outer diameter D4of the cylindrical section66is set smaller than an inner diameter dimension D of a fitting hole22aof the hole22. As described later, this cylindrical section66functions as a guide section for centering during press fitting of the hub wheel1of the stem shaft12into the hole22. Further, an inner diameter D3of a large diameter section22cof the hub wheel1is set larger than the maximum diameter dimension (circumscribed circle diameter) D1. If the outer diameter D4of the cylindrical section66is the same as or larger than a hole diameter of the fitting hole22a, the cylindrical section66itself is press-fit into the fitting hole22a. When the cylindrical section66is press-fit, if the cylindrical section66is decentered, the projections35of the recess-projection fitting structure M are press-fit in this state. The shaft section12and the hub wheel1are connected in a state in which the axis of the stem shaft12and the axis of the hub wheel1are not aligned. Further, if the outer diameter D4of the cylindrical section66is too smaller than the hole diameter of the fitting hole22a, the cylindrical section66does not function as the guide section for centering. Therefore, it is preferable to set a very small gap between the outer diameter surface of the cylindrical section66and the inner diameter surface of the fitting hole22aof the hole22to about 0.01 mm to 0.2 mm.

The stem shaft12of the outer ring5is inserted (press-fit) into the hub rig1in a state in which the axis of the hub wheel1and the axis of the outer ring5of the constant-velocity universal joint are aligned. A seal material is applied to the surface of the projection35in advance. When the stem shaft12is inserted, because the taper section22dthe decreases in diameter along a press-fitting direction is formed in the hole22of the hub wheel1, this taper section22dcan form a guide at the start of press fitting. The diameter dimension D of the inner diameter surface37of the hole22, the maximum diameter dimension D1of the projections35, and the outer diameter dimension (diameter dimension) D2of the recess bottoms of the spline41are in the relation described above. Moreover, the hardness of the projections35is larger than the hardness of the inner diameter surface37of the hole22by 20 points or more. Therefore, if the shaft10is press-fit into the hole22of the inner ring6, the projections35bite in the inner diameter surface37. The projections35form the recesses36, in which the projections35fit, along the axial direction.

Because the shaft10is press-fit in the hole22in this away, as illustrated inFIG. 3, the extruded portion45to be formed is stored in the pocket section50while curling. In other words, a part of the material scraped off or extruded from the inner diameter surface of the hole22enters the pocket section50.

According to the press fitting, as illustrated inFIG. 2, the entire fitting contact regions38of the projections35at the end of the stem shaft12and the recesses36fit therein adhere to each other. In other words, a shape of the projections35is transferred onto a recess formation surface on the opposite side (in this case, the inner diameter surface37of the hole22). When the shape is transferred, because the projections35bite in the inner diameter surface37of the hole22, the hole22is slightly expanded in diameter and allows movement in the axial direction of the projections35. If the movement in the axial direction stops, the hole22decreases in diameter to return to the original diameter. In other words, the hub wheel1is elastically deformed in the diameter direction when the projections35are press-fit, and preload equivalent to this elastic deformation is applied to a tooth surface of the projections35(surface of the recess fitting region). Therefore, it is possible to surely form the recess-projection fitting structure M in which the entire recess fitting regions of the projections35adhere to the recesses36corresponding thereto.

That is, a female spline42adhering to the spline (male spline)41on the stem shaft12side is formed on the inner diameter surface of the hole22of the hub wheel1by the male spline41. Further, a space between the fitting contact regions38of the projections35and the recesses36are sealed by the seal material applied to the surface of the projections35.

The recess-projection fitting structure M is configured as described above. The recess-projection fitting structure M in this case is arranged avoiding positions right below the raceway surfaces26,27,28, and29of the roller bearing2. Positions avoiding the positions right below the raceway surfaces26,27,28, and29are positions not corresponding to ball contacting positions of the raceway surfaces26,27,28, and29in the diameter direction.

In this recess-projection fitting structure M, as illustrated inFIG. 4, when a diameter difference (D1-D) between the maximum diameter dimension D1of the stem shaft12and the inner diameter dimension D of the fitting hole22aof the hole22of the hub wheel1is represented as Δd, the height of the projections35provided on the outer diameter surface of the stem shaft12is represented as h, and a ratio of the diameter difference and the height is represented as Δd/2h, a relation among the diameter difference, the height, and the ratio is 0.3<Δd/2h<0.86. Consequently, the projecting direction intermediate regions (height direction intermediate regions) of the projections35are surely arranged on the recess formation surface before recess formation. Therefore, the projections35bite in the recess formation surface during press fitting and the recesses36can be surely formed.

When the stem shaft12of the outer ring5is press-fit in the hole22of the hub wheel1, a step surface G is provided on the outer diameter surface of the mouth section11of the outer ring5as illustrated inFIG. 1and the like. A press-fitting jig Konly has to be engaged with this step surface G to apply press-fitting load (axial direction load) from this press-fitting jig K to the step surface G. Note that the step surface G can be formed by a circumferential direction groove provided on the outer diameter surface of the mouth section11.

The press-fitting jig K can be formed by a ring-like member47made of, for example, a split mold. In other words, the ring-like member47includes plural (at least two) segments47aand is formed in a ring shape by combining the segments47a. The ring-like member47formed by combining the segments47ain the ring shape includes a main body annular section57, a taper section58connected to this main body annular section57, and an inner collar section59projecting from this taper section58to the inner diameter side.

Therefore, the inner collar section59of the press-fitting jig K is set in contact with the step surface G formed by the circumferential direction groove. In this state, load (pressing force) in an arrow E direction (axial direction) ofFIG. 1is applied to the press-fitting jig55. Consequently, this load can be applied to the outer ring5through an intermediation of an inner collar section53engaged with the step surface G. The stem shaft12of the outer ring5can be pressed-fit into the hole22of the hub wheel1. To apply the axial direction load to the press-fitting jig K, various axial direction reciprocating mechanisms such as a press mechanism, a cylinder mechanism, and a ball screw mechanism can be used. The step surface G can be formed by recesses disposed at a predetermined pitch along the circumferential direction rather than being formed by the circumferential direction groove. Further, the step surface G may be formed by projected streaks or projections rather than the groove or the recesses.

When the stem shaft12is press-fit into the hole22of the hub wheel1in a state of the outer ring5alone of the constant-velocity universal joint3illustrated inFIG. 9or a state in which the outer ring5, the inner ring6, the ball7, and the cage8are assembled as illustrated inFIG. 10rather than a state of a drive shaft assembly, a method of applying press-fitting load to an end surface5aon the inboard side of the outer ring5may be adopted. The stem shaft12can be press-fit without providing the step surface G on the outer diameter surface of the outer ring5. In other words, the jig K1illustrated inFIG. 8can be used. The jig K1can be formed by a bottomed short cylindrical member. In other words, the jig K1includes a main body section98made of a cylindrical member and a bottom wall99that blocks the opening on the inboard side of this main body section98. InFIGS. 9 and 10, a Rzeppa constant-velocity universal joint in which groove bottoms of the track grooves14and16are formed by arc sections is illustrated inFIGS. 9 and 10. Even when the stem shaft12is press-fit by the outer ring5alone or the like in this way, the constant-velocity universal joint may be other constant-velocity universal joints such as an undercut free type in which the groove bottoms of the track grooves14and16have linear straight sections.

In a state in which the stem shaft12of the outer ring5is press-fit in the hole22of the hub wheel1, and the stem shaft12of the outer ring5and the hub wheel1are integrated through an intermediation of the recess-projection fitting structure M, as illustrated inFIG. 6, the cylindrical section66projects from the fitting hole22ato the tapered hole22bside.

Therefore, this cylindrical section66is expanded in diameter by using a jig67illustrated inFIGS. 6 to 8. The caulking jig67includes a columnar main body section67aand a distal end swelling section67bprovided on a distal end surface of this main body section67a. In this case, the distal end swelling section67bcan be loosely fit in the cylindrical section66. An outer circumferential surface of the distal end swelling section67bis formed as a gentle radius section on a main body section side thereof.

In this case, the distal end swelling section67bof the caulking jig67is fit in the cylindrical section66. As illustrated inFIGS. 7 and 8and the like, the caulking jig67is swung while being pressed in an arrow α direction. The swinging is to swing the caulking jig67with a device axis O as a rotation axis, and with an intersection of a jig axis O1and the device axis O as a fulcrum such that the jig axis O1tilts relative to the device axis O. Consequently, a circumferential wall surface of the distal end swelling section67bpresses an inner diameter surface of the cylindrical section66to an outer diameter side. Therefore, the cylindrical section66is plastically deformed outward in the diameter direction and the expanded-diameter caulking section (tapered locking piece)65illustrated inFIG. 1is formed. The shaft slip-off preventing structure M1is formed in a hook structure in which the cylindrical section66provided at the shaft end of the stem shaft12is plastically deformed outward in the diameter direction by the swinging caulking by the swinging caulking jig67.

In this case, in order to support the outer ring5of the constant-velocity universal joint3, for example, the jig K illustrated inFIG. 7and the jig K1illustrated inFIG. 8can be used. The jig K can receive axial direction load by the swinging caulking through an intermediation of the inner collar section53engaged with the step surface G. In the jig K1, a main body section98is fit in the opening side of the mouth section11of the outer ring5and an inner surface99aof a bottom wall99is brought into contact with the opening end11bof the mouth section11. In this way, the jib K1can receive the axial direction load by the swinging caulking.

Certain degree of load is applied during press fitting (when the stem shaft12is press-fit into the hub wheel1) to strike the back surface11aof the outer ring5of the constant-velocity universal joint3against the caulking section31. After the load is removed, contact surface pressure of a striking section of the back surface11a(end surface31aof caulking section31) is reduced by spring-back of the outer ring5of the constant-velocity universal joint3. When the cylindrical section66is caulked, load is applied in the axial direction. After the caulking, the contact surface pressure of the striking section of the back surface11a(end surface31aof caulking section31) can be reduced by spring-back of the stem shaft12. Therefore, this contact surface pressure can be set to be equal to or lower than 100 MPa.

In the present invention, it is possible to surely form the recess-projection fitting structure M in which the entire fitting contact regions38of the projections35of the stem shaft12and the recesses36of the hub wheel1adhere to each other. Moreover, it is unnecessary to form spline sections and the like in a member in which the recesses36are formed. The bearing device for a wheel is excellent in productivity. Further, phase alignment of the splines is unnecessary. It is possible to realize improvement of assemblability, prevent damage to the tooth surfaces during press fitting, and maintain a stable fit state.

In the recess-projection fitting structure M, because the entire fitting contact regions38of the projections35and the recesses36adhere to each other, a gap in which a backlash occurs is not formed in the diameter direction and the circumferential direction. Therefore, the entire fitting regions contribute to torque transmission, stable torque transmission is possible, and noise is not caused.

Because the shaft slip-off preventing structure M1is a hook structure in which the cylindrical section is plastically deformed outward in the diameter direction, screw fastening as in the conventional art can be omitted. Therefore, it is unnecessary to form a screw section projecting from the hole22of the hub wheel1in the stem shaft12. It is possible to realize a reduction in weight, omit screw fastening work, and realize improvement of assembly workability.

With this shaft slip-off preventing structure M1, it is possible to effectively prevent the stem shaft12of the outer joint member from slipping off in the axial direction from the hole22of the hub wheel1. Consequently, it is possible to maintain a stable connected state and realize improvement of a quality of the bearing device for a wheel. Moreover, caulking load during caulking may be relatively small. It is possible to increase the thickness of this caulking section65and bring the caulking section65into press-contact with the hub wheel inner diameter surface through an intermediation of large press-contact force. Consequently, it is possible to provide a firmer slip-off preventing mechanism (structure). Further, because such a firm slip-off preventing mechanism (structure) M1is provided, bending rigidity of the stem shaft12is improved and the stem shaft12is robust against bending. If the caulking load during caulking can be reduced, it is possible to prevent deformation of a region that receives load (load receiving section of the outer joint member of the constant-velocity universal joint3, e.g., a step surface provided on the outer diameter surface of the outer joint member and an opening side end surface of the outer joint member).

The caulking section31and the back surface11aof the mouth section11of the outer ring5are set in contact with each other, whereby bending rigidity in the axial direction is improved, the shaft becomes robust against bending, and a high-quality product excellent in durability is obtained. Moreover, positioning during press fitting can be realized by this contact. Consequently, dimension accuracy of this bearing device for a wheel is stabilized, it is possible to secure stable length as axial direction length of the recess-projection fitting structure M disposed along the axial direction and to realize improvement of torque transmission performance. Further, a seal structure can be configured by this contact. It is possible to prevent intrusion of foreign matters into the recess-projection fitting structure M from this caulking section31side. The recess-projection fitting structure M can maintain a stable fit state over a long period of time.

Because the end of the hub wheel1is caulked and preload is applied to the roller bearing2, it is unnecessary to apply preload with the mouth section11of the outer ring5. Therefore, it is possible to press-fit the stem shaft12of the outer ring5without taking into account preload and realize improvement of connectability (assemblability) of the hub wheel1and the outer ring5.

When the contact surface pressure between the caulking section31of the hub wheel1and the back surface11aof the mouth section11exceeds 100 MPa, noise is likely to be caused. When torque load is large, a difference occurs in torsion amounts of the outer ring5of the constant-velocity universal joint3and the hub wheel1. Sudden slip occurs in the contact section of the outer ring5of the constant-velocity universal joint3and the hub wheel1because of this difference and noise occurs. On the other hand, when the contact surface pressure is equal to or lower than 100 MPa as in the present invention, it is possible to prevent sudden slip from occurring and suppress occurrence of noise. Consequently, it is possible to configure a silent bearing device for a wheel. Even if the contact surface pressure is equal to or lower than 100 MPa, it is preferable to set the contact surface pressure to be equal to or higher than surface pressure with which a seal structure can be configured.

By providing the pocket section50for storing the extruded portion45caused by recess formation by the press fitting, it is possible to hold (maintain) the extruded portion45in this pocket section50. The extruded portion45does not enter the inside of the vehicle and the like on the outside of the device. In other words, the extruded portion45can be kept stored in the pocket section50. It is unnecessary to perform removal processing for the extruded portion45. It is possible to realize a reduction in assembly work man-hour and realize improvement of assembly workability and cost reduction.

By providing the collar section52for centering with the hole22of the hub wheel1on an opposite projection side in the axial direction of the pocket section50, ejection of the extruded portion45in the pocket section50to the guide section side is eliminated. The extruded portion45is more stably stored. Moreover, because the guide section is used for centering, it is possible to press-fit the stem shaft12into the hub wheel1while preventing decentering. Therefore, it is possible to highly accurately connect the outer joint member and the hub wheel1and perform stable torque transmission.

Further, by arranging the projecting direction intermediate regions of the projections35on the recess formation surface before recess formation, the projections35bite in the recess formation surface during press fitting and the recesses36can be surely formed. In other words, it is possible to sufficiently secure a press-fitting margin for the opposite side of the projections35. Consequently, moldability of the recess-projection fitting structure M is stabilized, no fluctuation in press-fitting load occurs, and stable torsion strength can be obtained.

Because the guide section for centering, i.e., the cylindrical section66is provided in the stem shaft12, the stem shaft12can be press-fit into the hub wheel1without causing decentering to thereby stably perform formation of the recesses36by the projections35. Therefore, it is possible to highly accurately configure the recess-projection fitting structure M. Further, because the taper section22dcan configure a guide at the start of press fitting, it is possible to press fit the stem shaft12of the outer ring5into the hole22of the hub wheel1without causing decentering to thereby perform stable torque transmission.

In the embodiment illustrated inFIG. 1and the like, the projections35of the recess-projection fitting structure M is provided in the stem shaft12of the outer ring5, the hardness in the axial direction end of the projections35is set higher than that of the hole inner diameter section of the hub wheel1, and the stem shaft12is press-fit into the hole22of the hub wheel1. Therefore, it is possible to increase the hardness on the shaft side and improve rigidity of the shaft.

Generation of hoop stress on the bearing raceway surface is suppressed by arranging the recess-projection fitting structure M avoiding a position right below the raceway surface of the roller bearing2. Consequently, it is possible to prevent occurrence of deficiencies of the bearing such as a reduction in rolling fatigue life, occurrence of a crack, and stress corrosion crack.

As in this embodiment, teeth with a module equal to or smaller than 0.5 are used in the spline41formed in the stem shaft12. Therefore, it is possible to realize improvement of moldability of this spline41and realize a reduction in press-fitting load. Because the projections35can be formed by a spline normally formed in the shaft of this kind, it is easy to form the projections35at low cost.

The outer circumferential surface25aof the outer member25of the bearing2is fit and built in the knuckle34on the vehicle body side. The fitting and building-in means that the outer member25is completed to be built in the knuckle34by fitting the outer member25in the knuckle34. The outer member25can be built in the knuckle34by press-fitting, for example, the outer circumferential surface25aof the cylindrical surface shape of the outer member25into the cylindrical inner circumferential surface34aof the knuckle34.

When a diameter difference between the outer diameter dimension D1of the stem shaft12and the inner diameter dimension D of the fitting hole22of the hub wheel1is represented as Δd, the height of the projection is represented as h, and a ratio of the diameter difference and the height is represented as Δd/2h, a relation among the diameter difference, the height, and the ratio is 0.3<Δd/2h<0.86. Therefore, it is possible to sufficiently secure a press-fitting margin of the projections35. In other words, when Δd/2h is equal to or smaller than 0.3, torsion strength falls. If Δd/2h exceeds 0.86, the entire projections35bite in the opposite side because of very small decentering and press-fit tilt during press fitting, moldability of the recess-projection fitting structure M is deteriorated, and press-fitting load suddenly increases. When moldability of the recess-projection fitting structure M is deteriorated, because not only torsion strength falls but also an expansion amount of the hub wheel outer diameter increases, there is a problem in that, for example, the function of the bearing2inserted in the hub wheel1is affected and rotation life is reduced. On the other hand, by setting Δd/2h to 0.3 to 0.86, moldability of the recess-projection fitting structure M is stabilized, fluctuation in press-fitting load is eliminated, and stable torsion strength can be obtained.

Because the taper section22dcan form a guide at the start of press fitting, it is possible to press-fit the stem shaft12of the outer ring5into the hole22of the hub wheel1without causing decentering and perform stable torque transmission. Further, because the outer diameter D4of the cylindrical section66is set smaller than the inner diameter dimension D of the fitting hole22aof the hole22, the cylindrical section66functions as a centering member. Therefore, it is possible to press-fit the stem shaft into the hub wheel while preventing decentering and perform more stable press fitting.

The stem shaft12of the outer ring5can be effectively prevented from slipping off from the hole22of the hub wheel1(in particular, slipping off in the axial direction to the shaft side) by the shaft slip-off preventing structure M1. Consequently, it is possible to maintain a stable connection state and realize improvement of a quality of the bearing device for a wheel. Because the shaft slip-off preventing structure M1is the tapered locking piece65, screw fastening in the past can be omitted. Therefore, it is unnecessary to form a screw section projecting to the stem shaft12from the hole22of the hub wheel1. It is possible to realize a reduction in weight, omit screw fastening work, and improve assembly workability. Moreover, in the tapered locking piece65, because a part of the stem shaft12of the outer ring5only has to be expanded, it is possible to easily perform formation of the shaft slip-off preventing structure M1. In the movement of the stem shaft12of the outer ring5in the reverse joint direction, pressing force in a direction for further press-fitting the stem shaft12is necessary. Therefore, positional shift in the reverse joint direction of the stem shaft12of the outer ring5extremely hardly occurs. Even if the stem shaft12shifts in this direction, because the bottom of the mouth section11of the outer ring comes into contact with the caulking section31of the hub wheel1, the stem shaft12of the outer ring5does not slip off from the hub wheel1.

Note that, because the projections35can be formed by a spline normally formed in a shaft of this type, it is possible to easily form the projections35at low cost.

When the recesses36are formed by press-fitting the stem shaft12into the hub wheel1, work hardening occurs on the recesses36side. The work hardening means that, when plastic deformation (plastic working) is applied to an object, resistance against deformation increases as a degree of deformation increases and the object becomes harder than a material not subjected to deformation. Therefore, according to plastic deformation during press fitting, the inner diameter surface37of the hub wheel1on the recesses36side hardens. It is possible to realize improvement of rotation torque transmission performance.

The inner diameter side of the hub wheel11is relatively soft. Therefore, it is possible to realize improvement of fittability (adhesiveness) in fitting the projections35of the outer diameter surface of the stem shaft12of the outer ring5in the recesses36of the hole inner diameter surface of the hub wheel1. It is possible to accurately suppress a backlash from occurring in the diameter direction and the circumferential direction.

The end expanded-diameter caulking section (tapered locking piece)65that engages with the inner diameter surface of the hub wheel1(in this case, the inner diameter surface of the tapered hole22b) through an intermediation of the seal material (seal member configuring the foreign-matter intrusion preventing means W2) is provided further on the outboard side than the recess-projection fitting structure M. Therefore, it is possible to prevent intrusion of foreign matters from a side further on the outboard side than the recess-projection fitting structure M.

Further on the inboard side than the recess-projection fitting structure M, the seal structure (foreign-matter intrusion preventing means W1) can be configured by contact of the outer end surface31aof the caulking section31and the back surface11aof the mouth section11of the outer ring5. It is possible to prevent intrusion of foreign matters from the inboard side with this seal structure.

In this way, as in the embodiment, the foreign-matter intrusion preventing means W1and W2are provided further on the inboard side than the recess-projection fitting structure M and further on the outboard side than the recess-projection fitting structure M. Intrusion of foreign matters from both end sides in the axial direction of the recess-projection fitting structure M is prevented. Therefore, it is possible to stably prevent deterioration in adhesiveness over a long period of time.

Further, the foreign-matter intrusion preventing means W3formed by interposing the seal material is provided between the fitting contact regions38of the projections35and the recesses36. Therefore, it is possible to prevent intrusion of foreign matters between the fitting contact regions38and reliability of foreign-matter intrusion prevention is improved.

During press fitting, axial direction pressing force can be applied to the outer ring5through an intermediation of the step surface G on the outer diameter surface of the outer ring5of the constant-velocity universal joint3. In other words, an axial direction pressing force applying region can be secured and the vicinity of the stem shaft of the outer ring5as the press-fitting shaft can be pressed. Therefore, it is possible to perform stable press fitting.

A recessed groove may be provided on the outer diameter surface of the outer ring5of the constant-velocity universal joint3to form a diameter direction end surface of this recessed groove as the step surface G. Alternatively, a protrusion may be provided on the outer diameter surface of the outer ring5to form a diameter direction end surface of this protrusion as the step surface G. In those cases, reliability of securing of the axial direction pressing force applying regions is improved. As a result, it is possible to perform more stable press-fitting work.

When the stem shaft12is press-fit in a state in which a boot and a shaft are not attached rather than the drive shaft assembly state, if press-fitting load is applied to the end surface5aon the inboard side of the outer ring5to perform press-fitting work, it is unnecessary to provide the step surface G on the outer diameter surface of the outer ring5. It is possible to press fit the stem shaft12at low cost.

When the cylindrical section66is expanded in diameter, the jig67illustrated inFIG. 11may be used. This jig67includes a columnar main body section68and a truncated cone section69connected to a distal end of this main body section68. In the truncated cone section69of the jig67, a tilt angle of a tilting surface69athereof is set substantially the same as a tilt angle of the tapered hole22band an outer diameter of a distal end of the truncated cone section69is set to a dimension same as or slightly smaller than the inner diameter of the cylindrical section66. The truncated cone section69of the jig67is fit in through an intermediation of the tapered hole22bto apply load in the arrow α direction, whereby diameter expanding force in an arrow β direction in which this cylindrical section66increases in diameter is applied to the inner diameter side of the cylindrical section66illustrated inFIG. 6. When the truncated cone69of the jig67is fit in, at least a part of the cylindrical section66is pressed to the inner diameter surface side of the tapered hole22band is in press-contact or contact with the inner diameter surface of the tapered hole22bthrough an intermediation of the seal material configuring the foreign-matter intrusion preventing means W2. Therefore, the shaft slip-off preventing structure M1can be configured. When load in the arrow α direction of the jig67is applied, this bearing device for a wheel needs to be fixed not to move in the arrow α direction. However, a part of the hub wheel1, the constant-velocity universal joint3, and the like only has to be received by a fixed member. The inner diameter surface of the cylindrical section66may be formed in a tapered shape increasing in diameter to the shaft end side. If the inner diameter surface of the cylindrical section66is formed into such a shape, it is possible to mold the inner diameter surface with forging. This leads to a reduction in cost.

Further, in order to reduce load in the arrow α direction of the jig67, a notch may be cut in the cylindrical section66or a conical surface of the truncated cone section69of the jig67may be partially arranged in a circumferential direction. When the notch is cut in the cylindrical section66, it is easy to expand the cylindrical section66in diameter. When the conical surface of the truncated cone section69of the jig67is partially arranged in the circumferential direction, a region where the cylindrical section66is expanded in diameter is a part on the circumference. Therefore, it is possible to reduce push-in load of the jig67.

Next,FIG. 13illustrates a second embodiment. In this case, in the hole22of the hub wheel1, a stepped surface22eextending in the diameter direction is provided between the tapered hole22band the shaft fitting hole22a. The expanded-diameter caulking section65engages with this stepped surface22e.

That is, the expanded-diameter caulking section65plastically deformed outward in the diameter direction by swinging caulking by the swinging caulking jig67is molded. That is, the expanded-diameter caulking section65in this case is folded to bend at a substantially right angle with respect to the axis of the device. The end surface on the inboard side thereof comes into contact or press-contact with the stepped surface22e.

Other components of the bearing device for a wheel illustrated inFIG. 12are the same as those of the bearing device for a wheel illustrated inFIG. 1. Therefore, the components same as those illustrated inFIG. 1are denoted by the same reference symbols and description of the components is omitted. Therefore, the bearing device for a wheel illustrated inFIG. 13also realizes operations and effects same as those of the bearing device for a wheel illustrated inFIG. 1.

FIG. 14illustrates a third embodiment. The shaft slip-off preventing structure M1of this bearing device for a wheel is configured by providing a tapered locking piece70that projects to the outer diameter direction in apart of the stem shaft12rather than forming the cylindrical section66illustrated inFIG. 4in advance.

In this case, a jig71illustrated inFIG. 15is used. The jig71includes a columnar main body section72and a short cylindrical section73connected to a distal end of this main body section72. A notch74is provided at a distal end of an outer circumferential surface of the short cylindrical section73. Therefore, a distal end wedge section75is formed in the jig71. As illustrated inFIG. 16, if the distal end wedge section75is driven (load in the arrow α direction is applied), a sectional shape of this distal end wedge section75is a tilting surface, and the outer diameter side of the end of the stem shaft12is expanded in diameter by the notch74forming this tilting surface.

Consequently, at least a part of this tapered locking piece70comes into press-contact or contact with the inner diameter surface of the tapered hole22b. Therefore, like the tapered locking piece65illustrated inFIG. 1and the like, such a tapered locking piece70can effectively prevent the stem shaft12of the outer ring5from slipping off in the axial direction from the hole22of the hub wheel1. Consequently, it is possible to maintain a stable connected state and realize improvement of a quality of the bearing device for a wheel. An inner diameter surface of the distal end wedge section75may be formed in a tapered shape.

FIG. 17illustrates a fourth embodiment. The shaft slip-off preventing structure M1of this bearing device for a wheel is configured by an outer collar-like locking piece76formed by caulking apart of the stem shaft12to project in the outer diameter direction. In this case, in the hole22of the hub wheel1, the stepped surface22eis provided between the fitting hole22aand the tapered hole22b. The outer collar-like locking piece76locks to this stepped surface22e.

In this shaft slip-off preventing structure M1, a jig77illustrated inFIG. 18is used. This jig77includes a cylindrical member78. An outer diameter D5of the cylindrical member78is set larger than an outer diameter D7of the end of the stem shaft12and an inner diameter D6of the cylindrical member78is set smaller than the outer diameter D7of the end of the stem shaft12.

Therefore, if axes of this jig77and the stem shaft12of the outer ring5are aligned and load is applied in the arrow α direction to the end surface12aof the stem shaft12by an end surface77aof the jig77in this state in which the axes are aligned, as illustrated inFIG. 13, an outer circumferential side of the end surface12aof the stem shaft12is crushed and the outer collar-like locking piece76can be formed.

Because the above-mentioned outer collar-like locking piece76engages with the stepped surface22e, like the tapered locking piece65illustrated inFIG. 1and the like, the outer collar-like locking piece76can effectively prevent the stem shaft12of the outer ring5from slipping off in the axial direction from the hole22of the hub wheel1. Consequently, it is possible to maintain a stable connected state and realize improvement of a quality of the bearing device for a wheel.

If the jig77illustrated inFIG. 18is used, as illustrated inFIG. 20A, the outer collar-like locking piece76is formed along a circumferential direction. Therefore, if pressing sections are disposed at a predetermined pitch (e.g., 90° pitch) along the circumferential direction as a jig, as illustrated inFIG. 20B, plural outer collar-like locking pieces76are arranged at the predetermined pitch along the circumferential direction. Even if the plural outer collar-like locking piece76are arranged at the predetermined pitch along the circumferential direction as illustrated inFIG. 20B, because the outer collar-like locking pieces76locks to the stepped surface22e, it is possible to effectively prevent the stem shaft12of the outer ring5from slipping off in the axial direction from the hole22of the hub wheel1.

As the shaft slip-off preventing structure M1, bolt and nut coupling may be used as illustrated inFIG. 21of a fifth embodiment, a lock ring may be used as illustrated inFIG. 22of a sixth embodiment, or coupling means such as welding may be used as illustrated inFIG. 23of a seventh embodiment.

InFIG. 21, a screw shaft section80is connected to the stem shaft12and a nut member81is screwed on this screw shaft section80. The nut member81is brought into contact with the stepped surface22eof the hole22. Consequently, the stem shaft12is regulated from slipping off from the hole22of the hub wheel1to the shaft side.

InFIG. 22, a shaft extending section83is provided further on the outboard side than the spline41. A circumferential direction groove84is provided in this shaft extending section83and a lock ring85is fit in this circumferential direction groove84. In the hole22of the hub wheel1of the stem shaft12, a step section22fto which the lock ring85locks is provided between the fitting hole22aand the tapered hole22b. Consequently, the lock ring85locks to the step section22fto regulate the stem shaft12from slipping off from the hole22of the hub wheel1to the shaft side.

InFIG. 23, an end outer circumferential surface of the stem shaft12and an opening edge on the step surface22eside of the fitting hole22aare joined by welding. Consequently, the stem shaft12is regulated from slipping off from the hole22of the hub wheel1to the shaft side. In this case, a welding region108may be disposed over the entire circumference or may be disposed at a predetermined pitch along the circumferential direction.

In the bearing device for a wheels illustrated inFIGS. 13,14,17,21,22,23, and the like, the foreign-matter intrusion preventing means W1, W2, and W3can be configured. InFIG. 13, the foreign-matter intrusion preventing means W2can be formed by interposing the seal material between the expanded-diameter caulking section65and the stepped surface22e. InFIG. 14, the foreign-matter intrusion preventing means W2can be formed by interposing the seal material between the tapered locking piece70and the inner diameter surface of the tapered hole22b. InFIG. 17, the foreign-matter intrusion preventing means W2can be formed by interposing the seal material between the outer collar-like locking piece76and the stepped surface22e. InFIG. 22, the foreign-matter instruction preventing means W2can be formed by the fit lock ring85. InFIG. 23, the foreign-matter intrusion preventing means W2can be formed by the welding region108over the entire circumference. The foreign-matter intrusion preventing means W1and W3are the same as those in the bearing device for a wheel illustrated inFIG. 1

Further on the inboard side than the recess-projection fitting structure M, the seal structure (foreign-matter intrusion preventing means W1) can be configured by contact of the outer end surface31aof the caulking section31and the back surface11aof the mouth section11of the outer ring5. It is possible to prevent intrusion of foreign matters from the inboard side with this seal structure.

In this way, as in the above-mentioned embodiment, the foreign-matter intrusion preventing means W1and W2are provided further on the inboard side than the recess-projection fitting structure M and further on the outboard side than the recess-projection fitting structure M. Therefore, intrusion of foreign matters from both end sides in the axial direction of the recess-projection fitting structure M is prevented. Therefore, it is possible to more stably prevent deterioration in adhesiveness over a long period of time.

Further, because the foreign-matter intrusion preventing means W3formed by interposing the seal material is provided between the fitting contact regions38of the projections35and the recesses36, it is possible to prevent intrusion of foreign matters between the fitting contact regions38. As a result, reliability of foreign-matter intrusion prevention is improved.

In the bearing device for a wheel according to the present invention, as illustrated inFIG. 24illustrating a seventh embodiment, the shaft slip-off preventing structure M1does not have to be provided. In this case, as illustrated inFIG. 25, in the circumferential direction groove51, a side51aon the spline41side is a plane orthogonal to the axial direction and a side51bon an opposite spline side is a taper surface that increases in diameter from a groove bottom51cto the opposite spline side. A disc-like collar section52for centering is provided further on the opposite spline side than the side51bof the circumferential direction groove51. An outer diameter dimension D4aof the collar section52is set the same as or slightly smaller than the hole diameter of the fitting hole22aof the hole22. In this case, a very small gap t is provided between an outer diameter surface52aof the collar section52and the inner diameter surface of the fitting hole22aof the hole22.

By providing, in the axial direction of the pocket section50, the collar section52for centering with the hole22of the hub wheel1on the opposite projection side, ejection of the extruded portion45in the pocket section50to the collar section52side is eliminated. Therefore, the extruded portion45is more stably stored. Moreover, because the collar section52is used for centering, it is possible to press-fit the stem shaft12into the hub wheel1while preventing decentering. Therefore, it is possible to highly accurately connect the outer ring5and the hub wheel1and to perform stable torque transmission.

Because the collar section52is used for centering during press fitting, it is preferable to set an outer diameter dimension thereof to a degree slightly smaller than a hole diameter of the fitting hole22aof the hole22of the hub wheel1. If the outer diameter dimension of the collar section52is the same as or larger than the hole diameter of the fitting hole22a, the collar section52itself is press-fit into the fitting hole22a. When the collar section52is press-fit into the fitting hole22a, if the collar section52and the fitting hole22aare decentered, the projections35of the recess-projection fitting structure M are press-fit in this state and the stem shaft12and the hub wheel1are connected in a state in which the axis of the stem shaft12and the axis of the hub wheel1are not aligned. If the outer diameter dimension of the collar section52is smaller than the hole diameter of the fitting hole22a, the collar section52does not function as a section for centering. Therefore, it is preferable to set the very small gap t between the outer diameter surface52aof the collar section52and the inner diameter surface of the fitting hole22aof the hole22to about 0.01 mm to 0.2 mm.

Note that, as illustrated inFIGS. 24 and 25, when the shaft slip-off preventing structure M1is not provided, the collar section52as the section for centering of the stem shaft12may be omitted.

Next,FIG. 26is a diagram of a bearing device for a wheel in which the hub wheel1and the stem shaft12of the outer joint member of the constant-velocity universal joint3fit and inserted in the hole22of the hub wheel1are separably coupled through an intermediation of the recess-projection fitting structure M.

The hub wheel1in this case has, as illustrated inFIGS. 26 and 30, the cylinder section20and the flange21provided at the end on the outboard side of the cylinder section20. The hole22of the cylinder section20has the shaft fitting hole22aand the tapered hole22bon the outboard side. An inner wall22gprojecting in an inner diameter direction is provided between the shaft fitting hole22aand the tapered hole22b. A recessed dent section63is provided on an end surface on an opposite shaft fitting hole side of this inner wall22g.

The hole22has the large diameter section22con an opening side further on an opposite inner wall side than the shaft fitting hole22aand a small diameter section48further on an inner wall side than the shaft fitting hole22a. The taper section22dis provided between the large diameter section22cand the shaft fitting hole22a. This taper section22ddecreases in diameter along a press-fitting direction in coupling the hub wheel1and the stem shaft12of the outer ring5.

A screw hole64opening to the end surface on the outboard side is provided in an axis section of the stem shaft12of the outer ring5. An opening of the screw hole64is formed as a taper section64aexpanded toward an opening side. A small diameter section12bis provided at the end on the outboard side of the stem shaft12. In other words, the stem shaft12includes a main body section12ahaving a large diameter and the small diameter section12b.

A bolt member54is screwed in the screw hole64of the stem shaft12from the outboard side. The bolt member54includes, as illustrated inFIGS. 26 and 30, a flanged head54aand a screw shaft54b. The screw shaft54bhas a non-screw section55aon a proximal end side and a screw section55bon a distal end side. In this case, a through hole56is provided in the inner wall22g, the shaft54bof the bolt member54is inserted through this through hole56, and the screw section55bis screwed in the screw hole64of the stem shaft12. As illustrated inFIG. 32, a hole diameter D12of the through hole56is set slightly larger than a shaft diameter (outer diameter) D11of the non-screw section55aof the shaft54b. Specifically, the hole diameter D12is set such that a difference between the hole diameter D12and the shaft diameter D11is about 0.05 mm<D12−D11<0.5 mm. Note that, a maximum outer diameter of the screw section55bis set the same as or slightly smaller than the outer diameter of the non-screw section55a.

In this bearing device for a wheel, as illustrated inFIG. 27, a shaft press-fitting guide section M6for performing guide for press fitting of the stem shaft12during press fitting is provided on a projection press-fitting start side. In this case, the shaft press-fitting guide section M6includes a female spline44provided in the taper section22dof the hole22. That is, as illustrated inFIG. 28A, guiding recesses44aare provided at a predetermined pitch (in this case, a pitch same as the arrangement pitch for the projections35) along the circumferential direction on the shaft fitting hole22aside of the taper section22d.

In this case, as illustrated inFIG. 27, a bottom diameter dimension D16of the guiding recesses44ais set larger than the maximum outer diameter of the projections35, i.e., the maximum diameter dimension (circumscribed circle diameter) (shaft outer diameter) D1of the circle connecting the vertexes of the projections35as the projections41aof the spline41. As illustrated inFIG. 28A, diameter direction gaps C1are formed between the vertexes of the projections35and the bottoms of the guiding recesses44a.

When this bearing device for a wheel is assembled (when the stem shaft12of the outer ring3of the constant-velocity universal joint is press-fit in the hub wheel1), the respective projections35of the stem shaft12are fit in the respective guiding recesses44aof the shaft press-fitting guide section M6. Consequently, the axis of the hub wheel1and the axis of the outer ring5coincide with each other. When the projections35are fit in the guiding recesses44a, because an end on the recess-projection fitting structure side of the guiding recess44ais a flat surface97a(seeFIG. 27) orthogonal to a press-fitting direction, the end can receive press-fitting start end surfaces35aof the projections35, and the stem shaft12can be press-fit from this state. When the stem shaft12is press-fit, as described above, the inner diameter dimension D of the inner diameter surface37of the shaft fitting hole22a, the maximum diameter dimension D1of the projections35, and the outer diameter dimension (diameter dimension) D2of the recess bottom of the spline41are in the relation described above. Moreover, the hardness of the projections35is larger than the hardness of the inner diameter surface37by 20 points or more. Therefore, if the stem shaft12is press-fit into the hole22of the hub wheel1, the projections35bite in the inner diameter surface37. The projections35form the recesses36, in which the projections35fit, along the axial direction.

After press fitting, the bolt member54is screwed in the screw hole64of the stem shaft12from the outboard side. By screwing the bolt member54in the screw hole64of the stem shaft12in this way, a flange section60of the head54aof the bolt member54is fit in the recessed dent section63of the inner wall22g. Consequently, the hub wheel1is nipped by the head54aof the bolt member54and the recess-projection fitting structure M or by the head54aof the bolt member54and the bottom surface (back surface)11aof the mouth section11. The hub wheel1and the constant-velocity universal joint3are integrated. In this way, bolt coupling means M5on the device axis in which the hub wheel1and the stem shaft12of the outer ring5are connected is formed by the bolt member54, the screw hole64in which this bolt member54is screwed, and the like.

In this case, as in the above case, it is preferable to set contact surface pressure between the caulking section31of the hub wheel and the back surface11aof the mouth section111ato be equal to or lower than 100 MPa. In this embodiment, the gap is provided between the end surface on the outboard side of the stem shaft12and the inner wall22g. However, the end surface on the outboard side of this stem shaft12and the inner wall22gmay be brought into contact with each other. By bringing the end surface on the outboard side of this stem shaft12and the inner wall22ginto contact with each other in this way, it becomes easy to set the contact surface pressure.

In this case, when a diameter difference between the hole diameter D12of the bolt inserting hole56and the shaft diameter D11of the non-screw section55aof the bolt member54is represented as Δd5 and a diameter difference in the recess-projection fitting structure M between the outer diameter dimension D1of the outer ring5and the inner diameter D of the hub wheel1is represented as Δd6, a relation between the diameter differences is 0<Δ5d<Δd6.

In this case, as illustrated inFIG. 40, a seal material100may be interposed between a bearing surface60aof the bolt member54and the inner wall22g. For example, the seal material100(seal agent) made of various kinds of resin that is hardened after application and can display sealing performance between the bearing surface60aand the bottom of the recessed dent section63of the inner wall22gonly has to be applied to the bearing surface60aof the bolt member54. As this seal material100, a material that is not deteriorated in an atmosphere in which this bearing device for a wheel is used is selected. The seal material100may be applied to the inner wall22gside or may be applied to the bearing surface60aside and the inner wall22gside.

Further, the end surface31aof the caulking section31and the bottom back surface11aof the mouth section11are set in contact with each other. However, as illustrated inFIG. 41, a seal material200(seal agent) may be interposed between the end surface31aof the caulking section31and the bottom back surface11aof the mouth section11. In this case, the seal material200may be applied to the end surface31aside, may be applied to the bottom back surface11aside, or may be applied to the end surface31aand the bottom back surface11a.

In this embodiment, slip-off in the axial direction of the stem shaft12from the hub wheel1is regulated by the bolt coupling means M5. As a result, it is possible to perform stable torque transmission over a long period of time.

By interposing the seal material between the bearing surface60aof the bolt member54, which fixes the hub wheel1and the stem shaft12of the outer ring5, and the inner wall22gor interposing the seal material between the end surface31aof the caulking section31and the bottom back surface11aof the mouth section11, intrusion of rainwater and foreign matters into the recess-projection fitting structure M from this bolt member54is prevented and it is possible to realize improvement of quality.

Incidentally, if the bolt member54is removed by screwing back the bolt member54from the state illustrated inFIG. 26, the hub wheel1can be drawn out from the outer ring5. In other words, fitting force of the recess-projection fitting structure M is such that the outer ring5can be drawn out by applying drawing force equal to or larger than predetermined force to the outer ring5.

For example, the hub wheel1and the constant-velocity universal joint3can be separated by a jig90illustrated inFIG. 31. The jig90includes a base91, a pressing bolt member93screwed in a screw hole92of this base91to be capable of screed in and back, and a screw shaft96screwed in the screw hole64of the stem shaft12. A through hole94is provided in the base91. The bolt33of the hub wheel1is inserted through this through hole94and a nut member95is screwed on this bolt33. When the nut member95is screwed on the bolt33, the base91and the flange21of the hub wheel1are superimposed and the base91is attached to the hub wheel1.

In this way, after the base91has been mounted to the hub wheel1, or before mounting the base91, the screw shaft96is screwed on the screw hole64of the stem shaft12so that a base section76amay protrude to the out board side from the inner wall22g. The protruding amount of the base section96ais set larger than the axial length of the recess-projection fitting structure M. The screw shaft96and the pressing bolt member93are arranged in the same axis (on the axis of the bearing device for a wheel).

After that, the pressing bolt member93is screwed on the screw hole92of the base91from the out board side, and in this state, the bolt member93is caused to threadedly advance in the direction of the arrow. In this process, the screw shaft96and the pressing bolt member93are arranged in the same axis (on the axis of the bearing device for a wheel). Therefore, with this threading advancement, the pressing bolt member93presses the screw shaft96in an arrow direction. This causes the outer ring5to move in the arrow direction with respect to the hub wheel1, and the hub wheel1is removed from the outer ring5.

Further, in the state in which the outer ring5is removed from the hub wheel1, it is possible to connect the hub wheel1and the outer ring5together again by using, for example, the bolt member54. That is, as a state in which the base91is removed from the hub wheel1, and the screw shaft76is removed from the stem shaft12, projections35of the stem shaft12is fit in the guiding recesses44aas illustrated inFIG. 34A. Consequently, phases of the male spline41on the stem shaft12side and the female spline42of the hub wheel1formed by the previous press-fitting are aligned. When the phases are aligned, as illustrated inFIG. 28A, the diameter direction gaps C1are formed between the vertexes of the projections35and the bottoms of the guiding recesses44a.

Next, in this state, as illustrated inFIG. 33, the bolt member54is screwed on the screw hole64of the stem shaft12through an intermediation of the through-hole56, and the bolt member54is caused to threadedly advance with respect to the screw hole64. As a result, as illustrated inFIG. 34B, the stem shaft12is gradually fitted into the hub wheel1. When the stem shaft12fits in the hub wheel1, the hole22is slightly expanded in diameter and allows entrance in the axial direction of the stem shaft12. The stem shaft12enters until the bottom back surface11aof the mouth section11comes into contact with the end surface31aof the caulking section31. In this case, at the same time, as illustrated inFIG. 34C, the end surfaces35aof the projections35come into contact with end surfaces36aof the recesses36. When the movement in the axial direction is stopped, the hole22decreases in diameter to return to the original diameter. Consequently, as in the previous press fitting, it is possible to surely configure the recess-projection fitting structure M in which the entire recess fitting regions of the projections35adhere to the recesses36corresponding thereto.

The opening of the screw hole64of the stem shaft12is formed as a taper section50aopening toward the opening side. Therefore, there is an advantage that the screw shaft54band the bolt member54are easily screwed in the screw hole64.

Incidentally, in the first time (press fitting for molding the recesses36on the inner diameter surface37of the hole22), because press-fitting load is relatively large, for press fitting, it is necessary to use a press machine or the like. On the other hand, in press fitting in the second time, because press-fitting load is smaller than the press-fitting load in the first time. Therefore, it is possible to stably and accurately press-fit the stem shaft12into the hole22of the hub wheel1without using the press machine or the like. Therefore, it is possible to separate and connect the outer ring5and the hub wheel1on the site.

Moreover, when a diameter difference between the hole diameter D12of the bolt inserting hole56and the shaft diameter D11of the non-screw section55aof the bolt member54is represented as Δd5 and a diameter difference between the outer diameter D1of the outer ring5in the recess-projection fitting structure M and the inner diameter dimension D of the hub wheel1in the recess-projection fitting structure M is represented as Δd6, a relation between the diameter differences is 0<Δd5<Δd6. Therefore, the diameter difference between the hole diameter D12of the bolt inserting hole56and the shaft diameter D11of the non-screw section55aof the bolt member54is set smaller than the diameter difference between the outer diameter D1of the outer ring5and the inner diameter dimension D of the hub wheel1. The bolt inserting hole56is formed as the shaft press-fitting guide structure section M3during re-press fitting of the stem shaft12of the outer ring5. In other words, the bolt coupling means M5includes the shaft press-fitting guide structure section M3. During re-press fitting, press fitting of the stem shaft12is guided by the shaft press-fitting guide structure section M3without being decentered. Therefore, stable re-press fitting is possible. The projections35fit in the recesses36formed previous time without being decentered, whereby it is possible to realize improvement of re-assemblability.

By applying the drawing force in the axial direction to the stem shaft12of the outer ring5in this way, the outer ring5can be removed from the hole22of the hub wheel1. Therefore, it is possible to realize improvement of workability for repairing and inspection (maintainability) of components. Moreover, by press-fitting the stem shaft12of the outer ring5into the hole22of the hub wheel1again after the repairing and inspection of the components, the recess-projection fitting structure M in which the entire fitting contact regions38of the projections35and the recesses36adhere to each other can be configured. Therefore, it is possible to configure again a bearing device for a wheel capable of performing stable torque transmission.

The shaft press-fitting guide section M6has the guiding recess44afor aligning a phase of the projections35and a phase of the other recesses36. Therefore, when the stem shaft12of the outer joint member is press-fit into the hole22of the hub wheel1again, the stem shaft12fits in the recesses36formed by the previous press fitting and does not damage the recesses36. Therefore, it is possible to highly accurately configure again the recess-projection fitting structure M in which a gap that causes a backlash is not formed in the diameter direction and the circumferential direction.

By forming a gap, for example, between the vertexes of the projections35and the bottoms of the guiding recesses44a, the projections35can be easily fit in the guiding recesses44ain a pre-press fitting process. Moreover, the guiding recesses44ado not hinder press-fitting of the projections35. Therefore, it is possible to realize improvement of assemblability.

When the axial direction length of the through hole56is too short, the through hole56cannot function as a stable guide. Conversely, when the axial direction length of the through hole56is too long, the thickness dimension of the inner wall22gbecomes large, whereby the axial direction length of the recess-projection fitting structure M cannot be secured, and the weight of the hub wheel1becomes large. Therefore, it is possible to make various changes taking into account those disadvantages.

In the embodiment, as illustrated inFIG. 28A, the diameter direction gaps C1are formed between the vertexes of the projections35and the bottoms of the guiding recesses44a. However, as illustrated inFIG. 28B, circumferential direction gaps C2and C2may be formed between the sides of the projections35and the sides of the guiding recesses44a. As illustrated inFIG. 28C, the diameter direction gaps C1may be formed between the vertexes of the projections35and the bottoms of the guiding recesses44aand the circumferential direction gaps C2may be formed between the sides of the projections35and the sides of the guiding recesses44a. By forming such gaps, it is possible to easily fit the projections35in the guiding recesses44ain the pre-press fitting process. Moreover, the guiding recesses44ado not hinder press fitting of the projections35.

In the spline41illustrated inFIG. 2, the pitch of the projections41aand the pitch of the recesses41bare set to the same value. Thus, in the above-mentioned embodiment, as illustrated inFIG. 2B, a circumferential direction thickness L of projecting direction intermediate regions of the projections35, and a circumferential direction dimension L0in a position corresponding to the intermediate region between the projections35adjacent to each other in the circumferential direction are substantially the same.

On the other hand, as illustrated inFIG. 35A, a circumferential direction thickness L2of the projecting direction intermediate regions of the projections35may be smaller than a circumferential direction dimension L1in a position corresponding to the intermediate region between the projections35adjacent to each other in the circumferential direction. In other words, in the spline41formed in the stem shaft12, the circumferential direction thickness (tooth thickness) L2of the projecting direction intermediate regions of the projections35is set smaller than the circumferential direction thickness (tooth thickness) L1of projecting direction intermediate regions of projections43on the hub wheel1side that fit in among the projections35.

Therefore, a sum Σ(B1+B2+B3+ . . . ) of tooth thicknesses of the projections35in the entire circumference on the stem shaft12side is set smaller than a sum Σ(A1+A2+A3+ . . . ) of tooth thicknesses of the projections43(projecting teeth) on the hub wheel1side. Consequently, it is possible to increase a shearing area of the projections43on the hub wheel1side and secure torsion strength. Moreover, because the tooth thickness of the projections35is small, it is possible to reduce press-fitting load and realize improvement of press-fitting performance. When a sum of circumferential direction thicknesses of the projections35is set smaller than a sum of circumferential direction thicknesses of the projections43on the opposite side, it is unnecessary to set the circumferential direction thickness L2of all the projections35smaller than the dimension L1in the circumferential direction between the projections35adjacent to each other in the circumferential direction. In other words, even if the circumferential direction thickness of arbitrary projections35among the plural projections35is the same as or larger than a dimension in the circumferential direction between the projections adjacent to each other in the circumferential direction, a sum of circumferential direction thicknesses only has to be smaller than a sum of dimensions in the circumferential direction.

The projections35inFIG. 35Aare trapezoidal in section. However, a shape of the projections35may be an involute tooth shape as illustrated inFIG. 35B.

The shaft press-fitting guide section M6may be that illustrated inFIG. 36. InFIG. 36A, the end on the recess-projection fitting structure M side of the guiding recess44ais a tilting surface97bthat decreases in diameter along a press-fitting direction (press-fitting progress direction). In other words, a tilt angle η3of the tilting surface97bis, for example, about 45°.

InFIGS. 36B and 36C, a diameter direction depth dimension of the guiding recess44adecreases along the press-fitting direction. InFIG. 36B, the end on the recess-projection fitting structure M side is the flat surface97aorthogonal to the press-fitting direction. InFIG. 36C, the end on the recess-projection fitting structure M side is the tilting surface97bthat decreases in diameter along the press-fitting direction (press-fitting progress direction).

If the end on the recess-projection fitting structure side of the guiding recess44ais the flat surface97aorthogonal to the press-fitting direction, when the stem shaft12is press-fit into the hole22, this flat surface97acan receive the stem shaft12. If the end is the tilting surface97b, the projections35can be stably fit in the recesses36on the opposite side from the guiding recess44a. Even if the diameter direction depth of the guiding recesses44adecreases along the press-fitting direction, the projections35can be stably fit in the recesses36on the opposite side from the guiding recesses44a.

Next,FIG. 37illustrates another embodiment. In this case, the inner wall22gis not provided in the hub wheel1. Instead of this inner wall22g, a ring member86is inserted in the hole22of the hub wheel1. In other words, a ring fitting notch section86is provided in the hole22of the hub wheel1and a ring member87is fit in this ring fitting notch section86. When the ring member87is fit in the ring fitting notch section86, the ring member87engages with a notch end surface86aof the ring fitting notch section81. It is preferable that clearance between an outer diameter of the ring member87and an inner diameter of the ring fitting notch section81be reduced as much as possible or the ring member87is press-fit into the ring fitting notch section86.

A bolt inserting hole88through which the bolt member54is inserted is formed in the ring member87. In this bolt inserting hole88, as in the bolt inserting hole56according to the first embodiment, when a diameter difference between the hole diameter D12and the shaft diameter D11of the non-screw section55aof the bolt member54is represented as Δd5 and a diameter difference between the outer diameter D1of the outer ring5and the inner diameter dimension D of the hub wheel1in the recess-projection fitting structure M is represented as Δd6, a relation between the diameter differences is 0<Δd5<Δd6.

Other components of a bearing device for a wheel illustrated inFIG. 38are the same as those of the bearing device for a wheel illustrated inFIG. 26. Therefore, components same as those inFIG. 26are denoted by the same reference symbols and description of the components is omitted.

Therefore, the bearing device for a wheel illustrated inFIG. 38realizes operations and effects same as those of the bearing device for a wheel illustrated inFIG. 26. Moreover, because the bolt inserting hole88is formed in the ring member80separate from the hub wheel1, the bolt inserting hole88can be highly accurately and stably formed. Even when, for example, the ring member87is damaged, the ring member87can be replaced. It is unnecessary to replace the entire hub wheel1. Therefore, it is possible to realize a reduction in cost.

In this embodiment, the spline41forming the projections35is formed on the stem shaft12side. Hardening treatment is applied to this spline41of the stem shaft12and the inner diameter surface of the hub wheel1is not hardened (a row material). On the other hand, as illustrated inFIG. 38, a spline111(including projected streaks111aand recessed streaks111b) subjected to hardening treatment may be formed on the inner diameter surface of the hole22of the hub wheel1. Hardening treatment may not be applied to the stem shaft12. This spline111can also be formed by various machining methods such as broaching, cutting, pressing, and drawing, which are publicly known and used means. As thermosetting treatment, various kinds of heat treatment such as induction hardening, and carburizing and quenching can be adopted.

In this case, the projecting direction intermediate regions of the projections35correspond to positions of the recess forming surface before recess formation (outer diameter surface of the stem shaft12). In other words, a diameter dimension (minimum diameter dimension of the projections35) D8of a circle connecting the vertexes of the projections35as the projections111aof the spline111is set smaller than an outer diameter dimension D10of the stem shaft12. A diameter dimension (inner diameter dimension of fitting hole inner diameter surfaces among the projections) D9of a circle connecting bottoms of the recesses111bof the spline111is set larger than the outer diameter dimension D10of the stem shaft12. In other words, a relation among the diameter dimensions and the outer diameter dimension is D8<D10<D9.

If the stem shaft12is press-fit into the hole22of the hub wheel1, the recesses36in which the projections35on the hub wheel1side are fit can be formed on the outer circumferential surface of the stem shaft12by the projections35. Consequently, the entire fitting contact regions38of the projections35and the recesses that fit on the projections35adhere to each other.

The fitting contact regions38are ranges B illustrated inFIG. 38Band ranges from halfway sections to the tops of the ridges in section of the projections35. A gap112is formed further on an outer diameter side than the outer circumferential surface of the stem shaft12between the projections35adjacent to each other in the circumferential direction.

In the bearing device for a wheel illustrated inFIG. 38, as in the bearing device described above, it is preferable to provide the shaft press-fitting guide section M6. In this case, the guiding recesses44bonly have to be provided on the stem shaft12side. The diameter direction gaps C1can be formed between the vertexes of the projections35and the bottoms of the guiding recesses44a, the circumferential direction gaps C2and C2can be formed between the sides of the projections35and the sides of the guiding recesses44a, or the diameter direction gaps C1and the circumferential direction gaps C2and C2can be formed.

In the case illustrated inFIG. 38, as in the case described above, the extruded portion45is formed by press fitting. Therefore, it is preferable to provide the pocket section50that stores this extruded portion45. Because the extruded portion45is formed on the mouth side of the stem shaft12, the pocket section50is provided on the hub wheel1side.

In the bearing device for a wheel in which the projections35of the recess-projection fitting structure M are provided on the inner diameter surface37of the hole22of the hub wheel1, the hardness of the axial direction ends of the projections35is set higher than that of the outer diameter section of the stem shaft12of the outer ring5, and the stem shaft12is press-fit as described above, it is unnecessary to perform hardness treatment (heat treatment) on the stem shaft12side. Therefore, the bearing device of vehicle is excellent in productivity of the outer joint member (outer ring5) of the constant-velocity universal joint.

The embodiments of the present invention have been described. However, the present invention is not limited to the embodiments and various modifications of the embodiments are possible. For example, the shape of the projections35of the recess-projection fitting structure M is triangular in section in the embodiment illustrated inFIG. 2and is trapezoidal in section in the embodiment illustrated inFIG. 35A. Besides, projections of various shapes such as a semicircular shape, a semi-elliptical shape, and a rectangular shape can be adopted. An area, the number, and a circumferential direction disposing pitch, and the like of the projections35can also be arbitrarily changed. In other words, it is unnecessary to form the spline41or111and form the projections41aor111aof this spline41or111as the projections35of the recess-projection fitting structure M. The projections35may be something like keys or may form wavy mating surfaces of a curved line shape. In short, it is sufficient that the projections35disposed along the axial direction are press-fit into the opposite side, the recesses36adhering to and fitting in the projections35can be formed on the opposite side by the projections35, the entire fitting contact regions38of the projections35and the recesses that fit in the projections35adhere to each other, and rotation torque can be transmitted between the hub wheel1and the constant-velocity universal joint3.

The hole22of the hub wheel1may be a deformed-shape hole such as a polygonal hole other than a circular hole. A sectional shape of the end of the stem shaft12fit and inserted into this hole22may be a deformed-shape section such as a polygon other than a circular section. Further, when the stem shaft12is press-fit into the hub wheel1, only press-fitting start ends of the projections35have hardness higher than that of the regions where the recesses36are formed. Therefore, it is unnecessary to set the hardness of the entire projections35high. InFIG. 2and the like, the gap40is formed. However, the projections35may bite in the inner diameter surface37of the hub wheel1up to the recesses among the projections35. As a hardness difference between the projections35side and the side of the recess formation surface formed by the projections35, as described above, it is preferable to set the hardness difference to be equal to or larger than 20 points in HRC. As long as the projections35can be press-fit, the hardness difference may be smaller than 20 points.

The end surfaces (press-fitting start ends) of the projections35are the surfaces orthogonal to the axial direction in the embodiments. However, the end surfaces may be surfaces tilting at a predetermined angle with respect to the axial direction. In this case, the end surfaces may tilt to the opposite projection side from the inner diameter side to the outer diameter side or may tilt to the projection side.

A shape of the pocket section50only has to be a shape that can store (house) the extruded portion45to be caused. Therefore, a capacity of the pocket section50only has to be capable of storing the extruded portion45to be caused.

Further, it is also possible to provide small recesses arranged at a predetermined circumferential pitch in the inner diameter surface37of the hole22of the hub wheel1. It is necessary for the small recesses to have a volume smaller than that of the recesses36. By thus providing the small recesses, it is possible to improve the press-fitting property of the projections35. That is, by thus providing the small recesses, it is possible to reduce the capacity of the extruded portion45formed during press fitting of the projections35, and hence it is possible to reduce the press-fitting resistance. Further, because the extruded portion45can be made smaller, it is possible to reduce the volume of the pocket section50, making it possible to improve the processability of the pocket section50and the strength of the stem shaft12. The small recesses may be of various shapes such as a triangular, a semi-elliptical, or a rectangular shape, and the number of small recess can also be set arbitrarily.

While welding is adopted as the coupling means illustrated inFIG. 23, it is also possible to adopt adhesive instead of welding. Further, it is also possible to use rollers as the rolling elements30of the bearing2. Further, while in the above-mentioned embodiment the third generation bearing device for a wheel is described, it is also possible to adopt the first or second generation bearing device for a wheel. Note that, when press fitting the projections35, it is possible to move the member on which the projections35are formed, with the member in which the recesses36are formed being stationary. Conversely, it is also possible to move the member in which the recesses36are formed, with the member on which the projections35are formed being stationary. Further, it is also possible to move both of them. Note that, in the constant-velocity universal joint3, the inner ring6and the shaft10may be integrated with each other through the intermediation of the recess-projection fitting structure M as described with reference to the above-mentioned embodiments.

The seal material interposed between the bearing surface60aof the bolt member54, which fixes by a bolt the hub wheel1and the stem shaft12, and the inner wall22gis formed by applying the resin to the bearing surface60aside of the bolt member54in the embodiments. However, conversely, the resin may be applied to the inner wall22gside. The resin may be applied to the bearing surface60aside and the inner wall22gside. When the bolt member54is screwed in, if the bearing surface60aof the bolt member54and the bottom surface of the recessed dent section63of the inner wall22gare excellent in adhesiveness, such a seal material can also be omitted. In other words, it is possible to improve adhesiveness of the bolt member54with the bearing surface60aby grinding the bottom surface of the recessed dent section63. It goes without saying that, even if the bottom surface of the recessed dent section63is not ground and is in a so-called turning finish state, the seal material can be omitted as long as adhesiveness can be exerted.

As the guiding recesses44a, as illustrated inFIGS. 28A,28B, and28C, the gaps C1and C2are formed among the projections35. A dimension of those gaps only has to be a dimension that does not cause decentering and shaft misalignment during press fitting and prevents the projections35from coming into press-contact with the inner surfaces of the guiding recesses44ato cause an increase in press-fitting load. The axial direction length of the guiding recesses44acan be arbitrarily set. If the guiding recesses44aare long in the axial direction, this is preferable in alignment. However, an upper limit of the axial direction length is limited because of the axial direction length of the hole22of the hub wheel1. Conversely, if the axial direction length of the hole22of the hub wheel1is small, the guiding recesses44ado not function as a guide and decentering and shaft misalignment are likely to occur. Therefore, it is necessary to determine the axial direction length of the guiding recesses44ataking into account those points.

A sectional shape of the guiding recesses44ais not limited to that illustrated inFIG. 4as long as the projections35can fit in the guiding recesses44a. The sectional shape can be variously changed according to a sectional shape and the like of the projections35. The number of guiding recesses44adoes not have to be the same as the number of projections35and may be smaller or larger than the number of projections35. In short, several projections35only have to fit in several guiding recesses44aand a phase of the projections35and a phase of the recesses36formed in the previous press fitting only have to coincide with each other.

The tilt angle θ3of the tilting surfaces97bof the ends of the guiding recesses44aand the tilt angle θ4of the bottoms of the guiding recesses44acan also be arbitrarily changed. If the tilt angle θ3of the tilting surfaces97bis close to 90°, the tilting surfaces97bare functionally the same as the flat surfaces97aorthogonal to the press-fitting direction. If the tilt angle θ3is small, the guiding recesses44aare long and the axial direction length of the recess-projection fitting structure M is small. If the tilt angle θ1of the bottoms is large, it is difficult to form the guiding recesses44a. Conversely, if the tilt angle θ1is small, the function of the tilted guiding recesses44acannot be exerted. Therefore, it is necessary to set the tilt angles θ3and θ4taking into account those points.

The outer member25of the roller bearing2in the embodiments does not include a vehicle body attachment flange. However, the outer member25may include the vehicle body attachment flange.

INDUSTRIAL APPLICABILITY

The present invention can be applied to bearing devices for a wheel of the first generation having the structure in which roller bearings in double rows are independently used, the second generation in which a vehicle body attachment flange is integrally provided in an outer member, the third generation in which an inner raceway surface on one side of the roller bearings in double rows is integrally formed with an outer circumference of a hub wheel integrally having a wheel attachment flange, and the fourth generation in which a constant-velocity universal joint is integrated with the hub wheel and an inner raceway surface of the other side of the roller bearings in double rows is integrally formed with an outer circumference of an outer joint member configuring the constant-velocity universal joint.