JP2009030618A - Rolling bearing unit for drive wheel and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a spline shaft from becoming difficult to be inserted into a spline hole 17a. <P>SOLUTION: An inner ring 4 is externally fixedly fitted onto a small diameter step part 15a by shrink fit. After forming a caulked part 24, the mutually opposed groove side surfaces of the portions out of the female spline grooves 27a, 27a forming a spline hole 17a corresponding to the axial inner end of the spline hole 17a are tilted in the direction of separating from each other toward the inner end opening edge of the spline hole 17a. As necessary, the inner end part inner peripheral surface of the spline hole 17a is formed in a conical concave tapered surface part 29 so tilted that the inner diameter is increased toward the axial inner side. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention supports driving wheels (front wheels of FF vehicles, rear wheels of FR vehicles, MR vehicles and RR vehicles, all wheels of 4WD vehicles) supported by an independent suspension so as to be rotatable with respect to the suspension device. The present invention relates to an improvement in a rolling bearing unit for a driving wheel used for rotationally driving the driving wheel and a manufacturing method thereof.

  In order to rotatably support the wheel with respect to the suspension device, various types of driving wheel rolling bearing units in which an outer ring and an inner ring are rotatably combined via a rolling element are used. For example, Patent Literatures 1 to 4 and the like describe a driving wheel rolling bearing unit 1 as shown in FIGS. The driving wheel rolling bearing unit 1 is configured such that a hub 3 and an inner ring 4 are rotatably supported on a radially inner side of an outer ring 2 via a plurality of rolling elements 5 and 5. Out of these, the outer ring 2 is coupled and fixed to the knuckle 7 constituting the suspension device by the first flange 6 provided on the outer peripheral surface thereof, and does not rotate during use. Further, double row outer ring raceways 8 and 8 are provided on the inner peripheral surface of the outer ring 2, and the hub 3 and the inner ring 4 are rotatably supported concentrically with the outer ring 2 on the inner diameter side of the outer ring 2. Yes.

  Further, the hub 3 is an outer end in the axial direction of the outer peripheral surface {outside with respect to the axial direction is a side which is the outer side in the width direction of the vehicle in the assembled state to the automobile, 6 (a), FIG. 7, FIG. 19 (a) on the right side. Same throughout the specification and claims. } A second flange 11 for supporting the wheel 9 constituting the wheel and the disc 10 constituting the disc brake as a braking device is provided on the side closer to the end. The wheel 9 and the disk 10 are coupled and fixed to the outer surface of the second flange 11 by a stud 12 and a nut 13. Also, a first inner ring raceway 14 is formed in the middle portion of the outer peripheral surface of the hub 3, and the inner end in the axial direction {inner with respect to the axial direction is the side that is the central side in the width direction of the vehicle when assembled to the automobile. The right side of FIGS. 1, 2, 8 to 16, the left side of FIGS. 6 (a), 7 and 19 (a). Same throughout the specification and claims. The inner ring 4 having the second inner ring raceway 16 formed on the outer peripheral surface thereof is fixed to the small-diameter step portion 15 corresponding to the fitting cylindrical surface portion described in the claims. is doing.

  A spline hole 17 is provided at the center of the hub 3. A spline shaft 19 constituting a constant velocity joint 18 is inserted into the spline hole 17 from the inner side to the outer side in the axial direction. Then, a nut 21 is screwed into a male screw portion 20 provided at a portion protruding from the outer end surface of the hub 3 at the outer end portion of the spline shaft 19, and further tightened, whereby the constant velocity joint 18 and the driving wheel The rolling bearing unit 1 is coupled and fixed to each other. In this state, the inner end surface in the axial direction of the inner ring 4 abuts on the outer end surface in the axial direction of the outer ring 22 for the constant velocity joint constituting the constant velocity joint 18, so that the inner ring 4 comes out of the small diameter step portion 15. There is no displacement. At the same time, an appropriate preload is applied to each of the rolling elements 5 and 5.

  The shape of each component of the constant velocity joint 18 is the same as that of a well-known Zepper type or Barfield type constant velocity joint, and is not related to the gist of the present invention. The description is omitted. Further, as shown in FIG. 15, a cylindrical portion 23 existing at a portion protruding inward in the axial direction from the inner ring 4 fitted on the small diameter step portion 15a at the inner end in the axial direction of the hub 3a A structure in which a caulking portion 24 is formed by caulking and spreading (plastic deformation) and the inner end surface of the inner ring 4 is suppressed by the caulking portion 24 is also described in Patent Document 1 and the like and has been conventionally known. Even in such a structure, an appropriate preload is applied to the rolling elements 5 and 5 in a state where the inner end face of the inner ring 4 is suppressed by the caulking portion 24.

  Incidentally, even if the inner end surface of the inner ring 4 as shown in FIGS. 13 to 14 is configured to be held down by the outer ring 22 for constant velocity joints, the inner end surface of the inner ring 4 as shown in FIG. Conventionally, the operation of forming the spline hole 17 in the central portion of the hubs 3 and 3a and the operation of assembling the constituent members have been performed as follows, even if the structure is held down. First, in a state before assembling the constituent members including the inner ring 4 to the hub 3 (3a), broaching is performed on the inner peripheral surface of the raw hole provided at the center of the hub 3 (3a) to form the spline hole. The female spline part for comprising 17 is formed. Next, in a state where the constituent members other than the inner ring 4 are assembled to the hub 3 (3a), the inner ring 4 is tightened to the small diameter step portion 15 provided at the inner end of the hub 3 (3a). Fit and fix. Then, after the caulking portion 24 (see FIG. 15) is formed as necessary, the spline shaft 19 constituting the constant velocity joint 18 is inserted into the spline hole 17 as shown in FIG. The rolling bearing unit 1 and the constant velocity joint 18 are combined.

  However, when the inner ring 4 is externally fitted and fixed to the small diameter step portion 15 after the spline hole 17 is processed as described above, the axial direction of the spline hole 17 in a state where the inner ring 4 is externally fitted and fixed to the small diameter step portion 15. It is inevitable that the inner end portion shrinks slightly inward in the radial direction. That is, the inner ring 4 is fitted and fixed to the small-diameter step portion 15 by an interference fit (the inner diameter of the inner ring 4 in a free state <the outer diameter of the small-diameter step portion 15 in a free state). A large force directed inward in the radial direction acts on the small-diameter step portion 15 that is thin. Based on such a force, the inner end portion in the axial direction of the spline hole 17 is elastically deformed radially inward, and the inner peripheral surface of the inner end portion of the spline hole 17 is reduced in diameter (each female spline groove). And the inner diameter of the inscribed circle of each female spline tooth and the overpin diameter are reduced). If the inner peripheral surface of the inner end portion of the spline hole 17 is thus reduced in diameter, it becomes difficult to insert the spline shaft 19 into the spline hole 17, and the wheel drive rolling bearing unit 1 and the constant velocity joint 18 are assembled. It becomes difficult.

  In order to prevent such inconvenience, as shown in FIG. 16, Patent Document 5 discloses a state before the inner ring 4 (see, for example, FIGS. 13 to 15) is externally fixed to the small diameter step portion 15 by an interference fit. A tapered surface 26 having a conical concave shape inclined in a direction in which the inner diameter increases toward the inner side in the axial direction on the inner peripheral surface of the inner end of the raw hole (preparation hole) 25 before broaching for forming the female spline groove. Techniques for providing the are described. More specifically, by providing the tapered surface portion 26 on the inner peripheral surface of the inner end portion in the axial direction of the raw hole 25 in this manner, the inner ring 4 is tightly fitted and fixed to the small diameter step portion 15 in the state described above. The inner peripheral surface of the spline hole 17 is formed in a single cylindrical shape (straight shape) over the entire axial direction. By adopting such a technique, it is possible to prevent the spline shaft 19 (see, for example, FIG. 3) from being easily inserted into the spline hole 17 and to assemble the wheel drive rolling bearing unit 1 and the constant velocity joint 18. It is thought that work can be performed easily.

  Further, in Patent Document 6, prior to the outer ring being fitted and fixed to the small-diameter step portion by interference fitting, the small-diameter step portion is fitted and fixed to the small-diameter step portion by interference fitting. A technique is described in which a female spline portion for forming a spline hole is formed in a state in which it is elastically deformed in the same manner or slightly larger than that in which it is elastically deformed. Even when such a technique is adopted, the inner peripheral surface of the spline hole can be made into a single cylindrical shape (straight shape) in a state where the inner ring 4 is fitted and fixed to the small diameter step portion 15 by interference fitting. For this reason, it becomes difficult to insert the spline shaft into the spline hole, and the wheel drive rolling bearing unit and the constant velocity joint can be easily assembled.

  In addition, in the case of a conventionally known wheel drive rolling bearing unit 1 including the structures described in Patent Documents 5 and 6 as described above, as shown in FIGS. The tooth thickness S of each male spline tooth 28, 28 of the spline shaft 19 is made smaller than the groove width W of each female spline groove 27, 27 (W> S). However, as it is, the spline hole 17 and the spline shaft 19 are likely to rattle. That is, when the spline hole 17 and the spline shaft 19 tend to rotate relative to each other with a neutral state therebetween, the groove side surfaces of the female spline grooves 27 and 27 and the teeth of the male spline teeth 28 and 28 are provided. There is a possibility that the side surfaces collide with each other to generate abnormal noise (collision noise), or damage such as premature wear is likely to occur on the groove side surfaces and the tooth side surfaces. In order to prevent such inconvenience, the male spline teeth 28, 28 of the spline shaft 19 are formed with a twist angle α with respect to the central axis of the spline shaft 19 as shown in FIG. However, it has been performed conventionally.

  If such a configuration is adopted, as the spline shaft 19 is inserted into the spline hole 17, the apparent tooth thickness of the male spline teeth 28, 28 increases by an amount corresponding to the twist angle α. In a state after completion, the tooth side surfaces of the male spline teeth 28, 28 of the spline shaft 19 and the side surfaces of the female spline grooves 27, 27 of the spline hole 17 are connected to both end portions (both edges of the spline hole 17). ), That is, contact is made at points a and b in FIG. And based on such contact | abutting, the above inconvenience accompanying the shakiness of the said spline shaft 19 and the spline hole 17 can be prevented. When power is transmitted, the tooth side surfaces of the male spline teeth 28 and 28 and the groove side surfaces of the female spline grooves 27 and 27 that face each other based on elastic deformation are entirely axially between the point a and the point b. Crawl and touch. From the aspect of ensuring the allowable transmission torque and ensuring the durability at the spline engaging portion while preventing the rattling, the tooth thickness S of each male spline tooth 28, 28 and the female spline groove 27, The smaller the difference (gap) from the groove width W of 27, and the larger the distance between the points a and b (contact distance), the better.

  By the way, as described above, in the case of the inventions described in Patent Documents 5 and 6, in a state where the constituent members of the wheel drive rolling bearing unit 1 are assembled to the hub 3 (3a), {the small diameter step portion 15 (15a) The inner ring 4 is externally fixed by interference fitting (with a caulking portion 24 formed as necessary)}, and the inner peripheral surface of the spline hole 17 is formed in a single cylindrical shape over the entire axial direction (spline hole Each female spline groove constituting 17 can be straightened over the axial direction). However, in the case of such a structure, a certain degree of assembling property (easy assembling) with the counterpart spline shaft 19 can be ensured. For example, the overpin diameter of the spline hole 17 varies toward the lower limit of the standard. In some cases, it may be difficult to insert the spline shaft 19 into the spline hole 17. In order to prevent such an inconvenience, it is conceivable that the overpin diameter is highly regulated (strict standard), but there is a possibility that the manufacturing cost may increase. On the other hand, if the dimensional tolerance between the spline hole 17 and the spline shaft 19 is set large in order to ensure assemblability, the rattling in the circumferential direction can be sufficiently achieved even with the twist angle α as described above. There is a possibility that it will not be suppressed. In addition, there is Patent Document 7 as another publication related to the present invention.

JP 2003-139174 A JP 2002-274118 A JP 2002-327715 A JP 2002-283804 A JP 2005-240942 A JP 2005-297728 A JP 2002-339959 A

  In view of the circumstances as described above, the rolling bearing unit for driving wheels of the present invention and the manufacturing method thereof can be used even when the overpin diameter of the spline hole varies due to, for example, inevitable manufacturing errors. The present invention has been invented to realize a structure and a manufacturing method thereof in which a spline shaft can be easily inserted into the inside thereof, and the backlash in the circumferential direction between the spline shaft and the spline hole can be sufficiently suppressed.

The rolling bearing unit for driving wheels of the present invention and the rolling bearing unit for driving wheels that is the object of the manufacturing method thereof include an outer ring, a hub, an inner ring, and a plurality of rolling elements.
Of these, the outer ring has a first flange for coupling and fixing to the suspension device on the outer peripheral surface, and a double row outer ring raceway on the inner peripheral surface.
Further, the hub has a spline (including serration) hole at the center, and a second flange for supporting and fixing the drive wheel near the axial outer end of the outer peripheral surface at the axial intermediate portion of the outer peripheral surface. Each of the first inner ring raceways has a fitting cylindrical surface portion near the inner end in the axial direction of the outer peripheral surface.
The inner ring has a second inner ring raceway on the outer peripheral surface, and is fitted and fixed to the fitting cylindrical portion by an interference fit.
Further, a plurality of rolling elements are provided between the double row outer ring raceway and the first and second inner ring raceways so as to be freely rollable.

In particular, in the rolling bearing unit for a drive wheel according to claim 1, of the female spline grooves constituting the spline hole in a state in which the inner ring is externally fitted and fixed to the fitting cylindrical portion. The groove side surfaces facing each other in the portion corresponding to the inner end portion in the axial direction of the spline hole are inclined toward each other toward the inner edge opening edge of the spline hole (the groove width is directed inward in the axial direction). Make it bigger).
Of the inner peripheral surface of the spline hole, the portion corresponding to the portion in which the groove side surfaces of the female spline grooves are inclined away from each other as described above, that is, the inner periphery of the inner end of the spline hole in the axial direction. If necessary, the surface is a conical concave tapered surface portion inclined in a direction in which the inner diameter increases toward the inner side in the axial direction. However, for example, by increasing the depth of each male spline groove of the spline shaft that engages with the spline hole, the bottom surface of each male spline groove and the inner peripheral surface of each spline hole (each female spline) If it is possible to prevent interference with the tooth surface and the top surface of the teeth, it is not always necessary to use a tapered concave surface portion as described above. Even when the conical concave tapered surface portion is not used, it is essential to incline the groove side surfaces of the female spline grooves in directions away from each other as described above.

  Further, the cylindrical portion existing in the portion protruding inward in the axial direction from the inner ring externally fitted to the fitting cylindrical surface portion at the inner end portion of the hub is caulked and spread outward in the diameter direction to form a caulking portion. When the inner ring is coupled and fixed to the hub by suppressing the axial inner end face of the inner ring with a caulking portion, the inner ring is fixed to the fitting cylindrical surface portion with an interference fit and the caulking portion is fixed. (The inner peripheral surface of the inner end portion of the spline hole is a conical concave tapered surface portion inclined in a direction in which the inner diameter increases toward the inner side in the axial direction. Of the female spline grooves constituting the spline hole, the mutually facing groove side surfaces of the portion corresponding to the axial inner end portion (tapered surface portion) of the spline hole are directed toward the inner end opening edge of the spline hole. Directions away from each other Tilting (increasing as towards the groove width in the axial direction inside).

  Further, in the case of implementing the driving wheel rolling bearing unit of the present invention as described above, preferably, the side surfaces of the grooves inclined in the direction away from each other are inclined with respect to the central axis of the hub. The angle is set to be equal to or smaller than the twist angle of each male spline tooth of the spline shaft engaged with the spline hole. And by comprising in this way, the tooth | gear side surface of each male spline tooth | gear of this spline shaft and each said groove | channel side surface are contact | abutted by the axial direction both ends (both ends edge) of the said spline hole.

  Further, in the method for manufacturing a driving wheel rolling bearing unit according to the third aspect of the present invention, the inner ring is tightly fitted to the fitting cylindrical surface portion in order to manufacture the driving wheel rolling bearing unit as described above. Prior to external fitting and fixing, the fitting cylindrical surface portion is gripped by the gripping means. In addition, the spline hole is formed by reducing the inner diameter of the gripping means that grips the fitting cylindrical surface portion from the outer diameter in the free state of the fitting cylindrical surface portion. The inner circumferential surface of the inner end portion in the axial direction of the inner hole is fixed by external fitting of the inner ring to the fitting cylindrical surface portion (and a caulking portion is formed at the inner end portion of the fitting cylindrical surface portion if necessary). The elastic deformation is greater than the elastic deformation inward in the engagement direction. In this case, if necessary, the inner peripheral surface of the inner end portion in the axial direction of the element hole is elastically deformed greatly inward in the radial direction as compared with the outer side as it goes inward in the axial direction.

  And in this state, the female spline part for comprising the said spline hole in the said elementary hole is formed, for example by broaching. Note that the female spline portion is straight (over a single cylindrical surface and has an overpin diameter of the entire axial direction) in a state where the broaching is performed while being elastically deformed as described above. Is the same). And after forming the female spline part in this way, after releasing the elastic deformation by expanding the inner diameter of the gripped part to be larger than the outer diameter of the fitting cylindrical surface part, The inner ring is fixed by external fitting with an interference fit. In this state, the inner peripheral surface of the inner end portion of the spline hole is a conical concave tapered surface portion inclined in a direction in which the inner diameter increases toward the inner side in the axial direction, and each female spline constituting the spline hole. The groove side surfaces of the groove corresponding to the inner end portion (tapered surface portion) in the axial direction of the spline hole are inclined toward each other toward the inner end opening edge of the spline hole.

  Note that the amount of elastic deformation of the inner peripheral surface of the inner end portion of the spline hole can be easily adjusted by restricting the inner diameter of the gripping means that grips the fitting cylindrical surface portion. Then, based on the regulation of the inner diameter, the desired tapered surface portion and the groove are formed in a state where the inner ring is externally fitted and fixed to the fitting cylindrical surface portion by crimping (a caulking portion is formed if necessary). Make sure the sides are formed. For example, the inner diameter of the inner peripheral surface of the gripping means is made smaller than the inner diameter of the inner ring so that a desired tapered surface portion and groove side surface can be obtained. If necessary, the inner peripheral surface of the gripping means may be a conical concave tapered surface portion that is inclined in a direction in which the inner diameter becomes smaller toward the inner side in the axial direction, and the inclination angle and inner diameter of the gripping tapered surface portion. The amount of inclination between the tapered surface portion and the groove side surfaces can also be adjusted by regulating the dimensions and the like. Note that the gripping tapered surface portion and the cross-sectional shape of the tapered surface portion can be not only linear but also curved (having a large curvature radius) if necessary.

According to the rolling bearing unit for a drive wheel and the manufacturing method thereof of the present invention configured as described above, even if the overpin diameter of the spline hole varies due to unavoidable manufacturing errors, for example, The spline shaft can be easily inserted, and rattling in the circumferential direction between the spline shaft and the spline hole can be sufficiently suppressed.
That is, even when the inner ring is fitted and fixed to the fitting cylindrical surface portion by an interference fit (and a caulking portion is also formed if necessary), {the inner peripheral surface of the inner end portion of the spline hole becomes more inward in the axial direction. It becomes a conical concave tapered surface portion inclined in the direction of increasing the inner diameter. In other words, among the female spline portions (female spline teeth, female spline grooves) constituting the spline hole, the opening end portion on the side where the spline shaft is inserted is tightened by fitting the inner ring to the fitting cylindrical surface portion. Even in a state of being deformed inward in the radial direction based on fitting and fixing (and forming a caulking portion as necessary), the tapered surface portion is inclined in a direction in which the inner diameter increases toward the opening side. Along with this, among the female spline grooves of the spline hole, the mutually opposite groove side surfaces of the portion corresponding to the axial inner end portion (tapered surface portion) of the spline hole are the inner end openings of the spline hole. Inclined in directions away from each other toward the edge. For this reason, the overpin diameter of the inner end opening of the spline hole can be set to the opening side even when the inner ring is externally fixed to the fitting cylindrical surface part by an interference fit (even if a caulking part is formed if necessary). Can be as large as possible. Therefore, for example, even if the overpin diameter of the spline hole varies toward the lower limit of the standard, the spline shaft can be easily placed in the spline hole on the basis of the inclination of the tapered surface part and the groove side surfaces as described above. Can be inserted into.

  In order to provide the tapered surface portion as described above and to incline the side surfaces of the grooves, as described in claim 3, the fitting cylindrical surface portion is clamped by the gripping means, and the inner ring is tightly fitted to the fitting cylindrical surface portion. In the state where the spline hole is elastically deformed to a greater extent than it is elastically deformed inward in the engagement direction based on external fixation (and forming a caulking portion at the inner end portion of the fitting cylindrical surface portion if necessary). A female spline groove may be formed. Thus, the taper surface portion is provided and the processing operation for inclining the side surfaces of the grooves is not troublesome, and the manufacturing cost does not increase easily. And when the structure described in Claim 2 is employ | adopted, the tooth | gear side surface of a male spline tooth and each groove | channel side surface of a spline groove | channel can be made to contact | abut at the both ends (both ends edge) of the said spline hole. That is, even if the groove side surfaces facing each other at the opening end of the female spline groove are inclined away from each other toward the opening edge as described above, the axis of each groove side surface and the tooth side surface of the male spline tooth Sufficient contact length in the direction can be ensured (as in the case of not inclining). As a result, the spline shaft can be easily inserted, and the allowable transmission torque, durability, and rattling of the spline engaging portion can be prevented in a high level.

  1 to 12 show an example of an embodiment of the present invention. The feature of this example is that the inner ring 4 is externally fitted and fixed to the small diameter step portion 15a corresponding to the fitting cylindrical surface portion described in the claims formed at the axially inner end portion of the hub 3b ( Further, the shape and size of the spline hole 17a formed in the center portion of the hub 3b is regulated with the caulking portion 24 formed, and the spline shaft 19 can be easily inserted into the spline hole 17a. This is to prevent the rattling in the circumferential direction between the spline shaft 19 and the spline hole 17a sufficiently. Since the basic structure itself of the wheel drive rolling bearing unit 1 is the same as the structure shown in FIGS. 13 to 15 described above, description of equivalent parts will be omitted or simplified. Explained.

  The wheel drive rolling bearing unit 1 of this example protrudes inward in the axial direction from the inner ring 4 that is externally fitted to the small-diameter step portion 15a at the inner end of the hub 3b, similarly to the structure shown in FIG. The cylindrical portion 23 existing in the portion is caulked and spread outward in the diametrical direction to form a caulking portion 24, and the caulking portion 24 suppresses the inner end surface in the axial direction of the inner ring 4, thereby causing the inner ring 4 to move to the hub 3 b. It is fixed to the joint. In the case of this example, the inner ring 4 is externally fixed to the small-diameter step portion 15a with an interference fit, and the caulking portion 24 is formed, as shown in FIG. The inner peripheral surface of the inner end portion is a tapered concave surface portion 29 that is inclined in a direction in which the inner diameter increases toward the inner side in the axial direction. In the case of this example, as shown in FIG. 2, the state before the caulking portion 24 (FIG. 1) is formed, that is, the inner ring 4 is externally fixed to the small diameter step portion 15a by an interference fit, Even before the cylindrical portion 23 is caulked, the inner peripheral surface of the inner end portion of the spline hole 17a becomes a conical concave tapered surface portion 29 inclined in a direction in which the inner diameter increases toward the inner side in the axial direction. Yes. Then, with such a tapered surface portion 29, the inner ring 4 is externally fitted and fixed to the small diameter step portion 15a as described above, and the caulking portion 24 is formed, and the inner edge opening edge of the spline hole 17a is formed. Similarly, the inner diameter D is made larger than the inner diameter d of the outer end opening edge (D> d).

In the case of this example, as described above, the inner ring 4 is externally fixed to the small-diameter step portion 15a by an interference fit and the caulking portion 24 is formed, as shown in FIG. Of the female spline grooves 27a, 27a constituting 17a, the mutually facing groove side surfaces of the portion corresponding to the tapered surface portion 29 are inclined in directions away from each other toward the inner end opening edge of the spline hole 17a. (The groove width of the inner end portion is increased toward the inner side in the axial direction. The groove width W _{i of the} inner end portion> the groove width W _o of the outer end portion). That is, the mutually facing groove side surfaces of the inner end portions of the female spline grooves 27a and 27a are inclined portions 36 and 36 that are inclined in a direction away from each other toward the inner end opening edge. Further, the inclination angle β of the inclined portions 36, 36 inclined in the direction away from each other with respect to the virtual plane including the central axis of the hub 3b is set to each male spline tooth 28, 28 of the spline shaft 19 which is the counterpart member. The twist angle α is set to be equal to or smaller than (β ≦ α). By configuring in this way, the side surfaces of the male spline teeth 28, 28 of the spline shaft 19 and the side surfaces of the female spline grooves 27a, 27a are connected to both end portions (both end edges) of the spline hole 17a. ), That is, contact at points a and b in FIG. On the other hand, as shown in FIG. 7, when the inclination angle β of the inclined portions 36, 36 of each female spline groove 27a is larger than the twist angle α of the male spline teeth 28, 28 (β> α), The distance (the distance between a and b) of the contact position between each tooth side surface and each groove side surface becomes small. In such a case, the amount of distortion of each of the male spline teeth 28, 28 tends to be large, and it is difficult to ensure durability and allowable transmission torque, for example, it is difficult to ensure strength. Incidentally, the inclination angle β of each inclined portion 36, a groove length of a tilted portion is L, the groove width of the inner end opening edge and W _i, has an outer end opening edge of the groove width (slope When the groove width of the non-existing portion is W _o , β = tan ⁻¹ [{(W _i −W _o ) / 2} / L]. Then, in relation to the twist angle α of each of the male spline teeth 28, 28, the amount of expansion of the female spline grooves 27 a, 27 a (W _i −W _o ) and the groove length of the inclined portion By regulating L, the distance between the contact positions (distance between a and b) is secured.

  The wheel drive rolling bearing unit 1 as described above is manufactured as follows. First, as shown in FIG. 8, a cylindrical material is subjected to forging and turning, machining such as drilling, threading, and grinding as necessary, and surface treatment such as heat treatment and coating. The hub 3b is formed. Next, before the inner ring 4 is fitted and fixed to the small-diameter step portion 15a provided at the inner end of the hub 3b, the hub 3b is connected to the center portion of the hub 3b as shown in FIG. It supports to the processing apparatus 31 for forming a female spline part in the internal peripheral surface of the raw hole 30 provided in this. This processing device 31 is capable of gripping the small-diameter step portion 15a, and the inner diameter of the portion that grips the small-diameter step portion 15a is larger and smaller than the outer diameter in the free state of the small-diameter step portion 15a. And a cutting means (not shown) for forming a female spline portion for forming the spline hole 17a in the raw hole 30. Of these, the cutting means is constituted by a broach for performing broaching on the inner peripheral surface of the raw hole 30, and in the state where the small diameter step portion 15 a is gripped by the gripping means 32, A female spline portion is formed on the inner peripheral surface of the raw hole 30 by being pushed into the hole 30.

  The gripping means 32 has a plurality of (for example, 3 to 4) gripping members 33, 33 that are displaceable in the radial direction of the small diameter step portion 15a at equal intervals in the circumferential direction of the small diameter step portion 15a. It is provided and has a structure like a chuck of a machine tool. Further, the gripping members 33 and 33 are respectively displaced in synchronism with each other in the radial direction of the small diameter step portion 15a by the driving means 34 such as a hydraulic cylinder (in the radial direction of the small diameter step portion 15a). It is configured so that the load can be applied evenly. Further, the inner side surfaces (surfaces facing and abutting the outer peripheral surface of the small diameter step portion 15a) 35, 35 of the gripping members 33, 33 are partially cylindrical surfaces having a curvature radius substantially equal to the radius of the small diameter step portion 15a. It is in the shape. And by displacing each said holding member 33,33 to the radial direction of the said small diameter step part 15a, the internal diameter of the part which hold | grips this small diameter step part 15a, ie, the inner surface 35 of these each holding member 33,33, The inner diameter of the intermittent cylindrical surface constituted by 35 can be expanded and reduced more than the outer diameter of the small diameter step portion 15a.

  In addition, in the state which displaced each said holding member 33,33 most inward with respect to the radial direction of the said small diameter step part 15a, each inner surface 35,35 of these each holding member 33,33 which is a partial cylindrical surface Preferably constitutes a single cylindrical surface. Further, in this state, the inner diameter of the cylindrical surface constituted by each of the inner surfaces 35 is smaller than the outer diameter of the small diameter step portion 15a in the free state. In the case of this example, in this state, the inner diameter of the cylindrical surface is made smaller than the inner diameter of the inner ring 4 that is externally fixed to the small-diameter step portion 15a. By regulating the inner diameter of the cylindrical surface in this manner, the amount of elastic deformation of the inner peripheral surface of the inner end portion of the raw hole 30 (spline hole 17a) is set to a desired value when forming a female spline portion described later. Can be adjusted. Further, if necessary, the inner side surfaces 35, 35 of the gripping members 33, 33 can be tapered conical tapered surface portions that are inclined in a direction in which the inner diameter decreases toward the inner side in the axial direction. On the other hand, the intermittent cylindrical surface formed by the inner side surfaces 35, 35 of the gripping members 33, 33 in a state where the gripping members 33, 33 are displaced outwardly in the radial direction of the small diameter step portion 15a. Is larger than the outer diameter (in a free state) of the small-diameter step portion 15a.

  When the hub 3b is attached to the processing apparatus 31 configured as described above, first, the gripping members 33 and 33 configuring the gripping means 32 are displaced outward in the radial direction of the small diameter step portion 15a. The diameter of the intermittent cylindrical surface constituted by the inner side surfaces 35, 35 of the gripping members 33, 33 is made larger than the outer diameter of the small-diameter step portion 15a in the free state. In this state, the small diameter step portion 15a is inserted inside the gripping members 33, 33, and the gripping members 33, 33 are displaced inward in the radial direction by the driving means 34. The side surfaces 35 and 35 are brought into contact with the outer peripheral surface of the small diameter step portion 15a. In this state, as shown in FIG. 9, the hub 3 b is gripped (supported) by the gripping means 32 constituting the processing device 31. Further, in this example, the gripping members 33 and 33 are further displaced inward in the radial direction of the small diameter step portion 15a by the driving means 34 from this state, and the small diameter step portion 15a is radially inward. Apply the load to go.

  That is, the inner diameter of the intermittent cylindrical surface constituted by the inner side surfaces 35, 35 of the gripping members 33, 33 is made smaller than the outer diameter of the small-diameter step portion 15a, and as shown exaggeratedly in FIG. The inner peripheral surface of the inner end portion in the axial direction of the raw hole 30 is elastically deformed radially inward. In the case of this example, as described above, the inner side surfaces 35, 35 of the respective gripping members 33, 33 are in a state where the gripping members 33, 33 are displaced in the most inward in the radial direction of the small diameter step portion 15a. A single cylindrical surface (a single conical concave surface if necessary) is formed. In this state, the inner diameter of the single cylindrical surface is smaller than the inner diameter of the inner ring 4. Accordingly, the inner peripheral surface of the inner end portion of the raw hole 30 is based on the fact that the inner ring 4 is fitted and fixed to the small-diameter step portion 15a by being fitted with the gripping members 33 and 33 being displaced in this manner. The elastic deformation is larger than the elastic deformation. In this state, on the inner peripheral surface of the inner end portion in the axial direction of the raw hole 30, the portion overlapping the grip members 33 and 33 in the axial direction protrudes radially inward from the other portions over the entire circumference. .

  Then, in a state where the inner peripheral surface of the inner end portion of the element hole 30 is elastically deformed in this way, a broach constituting the cutting means is pushed into the element hole 30 to form a spline hole 17a as shown in FIG. In addition, when this spline hole 17a is formed by providing a round blade in this broach, you may process simultaneously the front end surface of each female spline tooth | gear which comprises this spline hole 17a. In addition to wet processing using ordinary cutting oil and cutting fluid, broaching such as this is not limited to semi-dry processing, cutting oil or cutting fluid with reduced usage of cutting oil or cutting fluid, considering the environment. Dry processing that is not used may be employed. Thus, in the state where each female spline tooth is formed on the inner peripheral surface of the spline hole 17a, the inner peripheral surface of the spline hole 17a is uniform (straight) in the axial direction (inward in the radial direction). The protruding part disappears).

  Then, if the female spline teeth are formed in this way, as shown in FIG. 12, the gripping members 33, 33 are displaced radially outward of the small diameter step portion 15a, and the gripping members 33, The diameter of the inscribed circle of the inner side surfaces 35, 35 of the 33 is made larger than the outer diameter of the small diameter step portion 15 a, and the hub 3 b is removed from the gripping means 32. In this state, the inner circumferential surface of the inner end portion in the axial direction of the spline hole 17a becomes a tapered surface portion 29 inclined in a direction in which the outer diameter increases toward the inner side in the axial direction. That is, the female spline teeth are formed as described above in a state where the inner peripheral surface of the inner end portion of the spline hole 17a is elastically deformed radially inward. Many parts are cut. For this reason, in the state where the gripping members 33, 33 are displaced radially outward to release the elastic deformation, the inner circumferential surface of the inner end portion in the axial direction of the spline hole 17a is inclined as described above. At the same time, among the female spline grooves 27a, 27a constituting the spline hole 17a, the groove side surfaces of the portions corresponding to the tapered surface portion 29 are opposed to each other as shown in FIG. The spline holes 17a are inclined away from each other toward the inner end opening edge (inclined portions 36, 36 are formed).

  Then, after machining and surface treatment as necessary, as shown in FIG. 2, components other than the inner ring 4 are assembled to the hub 3b, and then provided at the inner end of the hub 3b. The inner ring 4 is fitted and fixed to the small-diameter step portion 15a by an interference fit, and a caulking portion 24 is formed as shown in FIG. In the case of this example, even if the inner peripheral surface of the axial inner end portion of the spline hole 17a is displaced radially inward based on such an interference fit (and the formation of the caulking portion 24), The conical concave tapered surface portion 29 that is inclined in the direction in which the inner diameter increases toward the inner side in the axial direction remains on the inner peripheral surface of the end portion. Further, in this state, among the female spline grooves 27a, 27a constituting the spline hole 17a, the mutually opposite groove side surfaces of the portion corresponding to the tapered surface portion 29 are the inner end opening edges of the spline hole 17a. Inclined in directions away from each other as it goes to.

In the case of this example as described above, the spline shaft 19 can be easily inserted into the spline hole 17a even when the overpin diameter of the spline hole 17a varies due to, for example, inevitable manufacturing errors. Further, rattling in the circumferential direction between the spline shaft 19 and the spline hole 17a can be sufficiently suppressed.
That is, even when the inner ring 4 is fitted and fixed to the small-diameter step portion 15a with an interference fit, and the caulking portion 24 is further formed, the inner diameter of the inner end portion of the spline hole 17a increases toward the inner side in the axial direction. The conical concave tapered surface portion 29 that is inclined in the remaining direction remains. In other words, among the female spline portions (female spline teeth, female spline grooves 27a, 27a) constituting the spline hole 17a, the opening end portion on the side where the spline shaft 19 is inserted is connected to the inner ring 4 with a small diameter step portion. Even in a state of being deformed inward in the radial direction based on the fact that the crimping portion 24 is formed while being externally fitted and fixed to 15a, the tapered surface portion 29 is inclined in a direction in which the inner diameter increases toward the opening side. At the same time, among the female spline grooves 27a, 27a of the spline hole 17a, the mutually facing groove side surfaces of the portion corresponding to the tapered surface portion 29 are directed toward the inner end opening edge of the spline hole 17a. Tilt away from each other. Therefore, the overpin diameter D _o of the inner end opening of the spline hole 17a (see FIG. 3) can be obtained even when the inner ring 4 is fitted and fixed to the small-diameter step portion 15a with an interference fit. Can be increased toward the opening side. Therefore, for example, even if the overpin diameter of the spline hole 17a varies toward the lower limit of the standard, the spline hole 17a has the spline hole 29a in the spline hole 17a on the basis of the margin of the tapered surface portion 29 and the groove side surfaces as described above. The shaft 19 can be easily inserted.

  In order to provide the tapered surface portion 29 as described above and to incline the side surfaces of the grooves, as described above, the small diameter step portion 15a is clamped by the gripping means 32 and the inner ring 4 is tightened to the small diameter step portion 15a. The female spline grooves 27a and 27a may be formed in the spline hole 17a in a state of being elastically deformed larger than elastically deforming radially inward based on the fitting fixing and the caulking portion 24. Thus, the taper surface portion 29 is provided, and the processing operation for inclining the side surfaces of the grooves is not troublesome, and the manufacturing cost does not increase easily. In addition, in this example, each male side of the spline shaft 19 that engages with the spline hole 17a has an inclination angle β with respect to a virtual plane including the central axis of the hub 3b of the side surfaces of the grooves inclined in directions away from each other. The spline teeth 28 and 28 have a twist angle α or less, and the side surfaces of the male spline teeth 28 and 28 of the spline shaft 19 and the side surfaces of the grooves are brought into contact with both ends of the spline hole 27a. That is, as described above, even when the groove side surfaces facing each other at the opening ends of the female spline grooves 27a and 27a are inclined away from each other toward the opening edge, these groove side surfaces and the male spline teeth 27 and 28 are inclined. A sufficient contact length with respect to the tooth side surface in the axial direction can be ensured (as in the case of not inclining). For this reason, the structure in which the spline shaft 19 can be easily inserted can secure the allowable transmission torque, ensure the durability, and prevent the spline engaging portion from rattling.

  If the heat treatment applied to the hub 3b is performed before the female spline portion is formed, the female spline portion can be free from heat treatment deformation. However, the heat treatment may be performed after the female spline portion is formed. Further, the caulking portion 24 can be formed with a relatively small load in a state where a restraining jig such as the spline shaft 19 is fitted in the spline hole 17a as described in, for example, Patent Document 7. It is preferable to perform by swaging caulking. In this way, if the caulking portion 24 is formed by swing caulking, the amount by which the inner diameter of the inner end portion in the axial direction of the spline hole 17a is reduced due to the formation of the caulking portion 24 can be reduced.

Sectional drawing which shows one example of embodiment of this invention. Sectional drawing shown in the state before forming a caulking part. The figure equivalent to the AA cross section of FIG. 1 which shows the state which measures the overpin diameter of a spline hole. The figure equivalent to the BB cross section of FIG. 1 shown in the state which inserted the spline shaft in the spline hole. The C section enlarged view of FIG. It is a figure for demonstrating the twist angle of a male spline tooth, (a) is DD sectional drawing of FIG. 5, (b) is sectional drawing seen from the left of (a). Sectional drawing similar to (a) of FIG. 6 for demonstrating the necessity to control the inclination | tilt angle of the groove | channel side surface of a female spline groove | channel. Sectional drawing which shows the hub before forming a spline hole. Sectional drawing which shows the state which supported the hub in the processing apparatus. Then, sectional drawing which shows the state which carried out elastic deformation of the axial direction inner-end part internal peripheral surface of the raw hole which should be processed into a spline hole by a holding means. Then, sectional drawing which shows the state which processed the raw hole into the female spline hole. Then, sectional drawing which shows the state which cancelled | released the elastic deformation of the inner peripheral part inner peripheral part of a spline hole. Sectional drawing which shows the 1st example of conventional structure in the assembly | attachment state to a suspension apparatus. Sectional drawing which takes out and shows the rolling bearing unit for a wheel drive. Sectional drawing similar to FIG. 14 which shows the 2nd example of conventional structure. Sectional drawing which takes out only a hub and shows the 3rd example of conventional structure. Sectional drawing which shows the spline engaging part of conventional structure. The E section enlarged view of FIG. The figure similar to FIG. 6 for demonstrating the spline engaging part of a conventional structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rolling bearing unit for driving wheels 2 Outer ring 3, 3a, 3b Hub 4 Inner ring 5 Rolling element 6 First flange 7 Knuckle 8 Outer ring raceway 9 Wheel 10 Disc 11 Second flange 12 Stud 13 Nut 14 First inner ring raceway 15 , 15a Small diameter step portion 16 Second inner ring raceway 17, 17a Spline hole 18 Constant velocity joint 19 Spline shaft 20 Male thread portion 21 Nut 22 Outer ring for constant velocity joint 23 Cylindrical portion 24 Caulking portion 25 Elementary hole 26 Tapered surface portion 27, 27a Female Spline groove 28 Male spline teeth 29 Tapered surface portion 30 Raw hole 31 Processing device 32 Gripping means 33 Gripping member 34 Driving means 35 Inner side surface 36 Inclined portion

Claims (3)

An outer ring, a hub, an inner ring, and a plurality of rolling elements are provided. Of these, the outer ring has a first flange for coupling and fixing to the suspension device on the outer peripheral surface, and a double row outer ring raceway on the inner peripheral surface. The hub has a spline hole at the center, and a second flange for supporting and fixing the drive wheel near the axial outer end of the outer peripheral surface at the axial intermediate portion of the outer peripheral surface. The first inner ring raceway has a fitting cylindrical surface portion on the axially inner end portion of the outer peripheral surface, and the inner ring has a second inner ring raceway on the outer peripheral surface, and the fitting cylindrical portion. The rolling elements are fixedly fitted to each other by an interference fit, and each of the rolling elements is provided between the double row outer ring raceway and the first and second inner ring raceways so as to be capable of rolling. In the drive wheel rolling bearing unit
Each of the female spline grooves constituting the spline hole in the state where the inner ring is externally fitted and fixed to the fitting cylindrical portion, the portions corresponding to the inner ends in the axial direction of the spline hole are opposed to each other. A rolling bearing unit for a drive wheel, characterized in that the groove side surfaces are inclined toward each other toward the inner end opening edge of the spline hole.   The angle of inclination of the groove side surfaces inclined in the direction away from each other with respect to the central axis of the hub is made equal to or less than the twist angle of each male spline tooth of the spline shaft engaged with the spline hole, and the tooth side surface of the male spline tooth of this spline shaft The rolling bearing unit for a drive wheel according to claim 1, wherein the side surfaces of the grooves are brought into contact with both end portions in the axial direction of the spline holes. An outer ring, a hub, an inner ring, and a plurality of rolling elements are provided. Of these, the outer ring has a first flange for coupling and fixing to the suspension device on the outer peripheral surface, and a double row outer ring raceway on the inner peripheral surface. The hub has a spline hole at the center, and a second flange for supporting and fixing the drive wheel near the axial outer end of the outer peripheral surface at the axial intermediate portion of the outer peripheral surface. The first inner ring raceway has a fitting cylindrical surface portion on the axially inner end portion of the outer peripheral surface, and the inner ring has a second inner ring raceway on the outer peripheral surface, and the fitting cylindrical portion. The rolling elements are fixedly fitted to each other by an interference fit, and each of the rolling elements is provided between the double row outer ring raceway and the first and second inner ring raceways so as to be capable of rolling. A method of manufacturing a rolling bearing unit for a drive wheel,
Prior to external fitting and fixing the inner ring to the fitting cylindrical surface portion, the fitting cylindrical surface portion is gripped by the gripping means, and the inner diameter of the portion of the gripping means that grips the fitting cylindrical surface portion. By reducing the diameter of the fitting cylindrical surface portion from the outer diameter in the free state, the inner peripheral surface of the inner end portion in the axial direction of the raw hole for forming the spline hole is formed, and the inner ring is attached to the fitting cylindrical surface portion. After forming a female spline portion for forming the spline hole in the element hole in a state where the spline hole is elastically deformed to a greater extent than elastically deforming inward in the engagement direction based on the external fitting fixed by interference fit, After releasing the elastic deformation by expanding the inner diameter of the gripped part larger than the outer diameter of the fitting cylindrical surface portion, the inner ring is fitted and fixed to the fitting cylindrical surface portion by external fitting, and in this state, Each female spline constituting the spline hole Among them, the side surfaces of the grooves corresponding to the inner end of the spline hole in the axial direction are inclined toward each other toward the inner end opening edge of the spline hole. Manufacturing method.

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