Method for manufacturing a hub unit bearing and hub unit bearing

Abstract

To provide a method of manufacturing a hub unit bearing capable of preventing trouble such as noise, seizure, and peeling of a surface layer surface due to burrs by preventing burrs produced when a fitted cylinder part of a hub is ground from separating when an inner ring is pressed in the fitted cylinder part, and the hub unit bearing.SOLUTION: A hub 30 of a hub unit bearing 10 comprises a hub shaft 31 which has a rotary flange 32 and a small-diameter step part 33, and an inner ring 41 which is pressed in and fixed to the small-diameter step part 33. The hub shaft 31 has an inclined part 34 which gradually decreases in diameter axially inward on an axially inner side of a fitted cylinder part 33a of the small-diameter step part 33. The hub shaft 31 is formed through a lathe turning process of forming the fitted cylinder part 33a and the inclined part 34 through lathe turning, and a grinding process of grinding an inner ring raceway 30a, the fitted cylinder part 33a, and a part of the inclined part 34 to form a dull part 34a. A border 36 between a lathe turning surface 58 and a ground surface 57 of the dull part 34a is provided at the inclined part 34 so as to have a diameter smaller than an inner diameter d of an inner diameter surface 41a of the inner ring 41 to be pressed in.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a hub unit bearing and a hub unit bearing. [Background Art]

[0002] Hub unit bearings are generally widely used to rotatably support wheels of vehicles such as automobiles with respect to suspension devices. In a hub unit bearing, a hub, which is a rotating wheel, supports and fixes a wheel constituting the wheel and a rotating member for braking on the mounting surface of a rotating flange, and rotates via rolling elements relative to an outer ring that is a stationary wheel.

[0003] The hub is configured by combining a hub shaft and an inner ring. The hub shaft is provided with a rotating flange, has an inner ring raceway in the axially outer row formed on the outer peripheral surface of the axially intermediate portion, and further has a small-diameter stepped portion on the axially inner side. A fitting cylindrical portion is formed on the small-diameter stepped portion, and an inner ring having an inner ring raceway in the axially inner row on the outer peripheral surface is externally fitted and fixed by interference fitting.

[0004] The hub shaft is subjected to turning from the thick portion with which a seal lip is in sliding contact, across the inner ring raceway surface of the axially outer row and the fitting cylindrical portion of the small-diameter stepped portion. A heat-treated hardened layer is formed on the turned outer peripheral surface, and then grinding is performed to smooth the surface.

[0005] For example, in the rolling bearing unit described in Patent Document 1, as shown in FIG. 7, the grinding of the hub shaft is performed by rotating the magnet chuck coupled to the axially outer surface of the rotating flange of the hub shaft by magnetic coupling force, thereby rotating the hub shaft. In this process, the outer peripheral surface of the hub shaft is rotatably supported by the tip end of a shoe to position the hub shaft in the radial direction. Then, the outer peripheral surface of the form grinding wheel formed by a diamond wheel is pressed against the outer peripheral surface of the hub shaft, and plunge cut grinding (a grinding method in which the axial position of the grinding wheel does not move) is performed on the outer peripheral surface of the hub shaft. [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-23976 [Overview of the initiative] [Problems that the invention aims to solve]

[0007] Incidentally, plunge-cut grinding is a process in which the normal force is greater than the tangential force due to the abrasive grains having a negative rake angle. Therefore, burrs are likely to occur between the grinding surface 57 and the pre-machined turning surface 58, that is, on the axially inner portion of the fitting cylindrical part 33a into which the inner ring 41 is fitted. Since the full-form grinding wheel 4, formed by the diamond wheel 3, has poorer cutting performance than a single-stone dressed grinding wheel, burrs are even more likely to occur between the grinding surface 57 and the turning surface 58.

[0008] On the other hand, the inner diameter surface 41a of the inner ring 41 that fits onto the fitting cylindrical portion 33a is subjected to oscillation grinding (the rotating grinding wheel 5 moves back and forth in the axial direction), as shown in Figure 8. As mentioned above, the grinding process has a high normal force, so both ends 41b of the inner diameter surface 41a of the inner ring 41 tend to become rounded due to the action of the edge load, and burrs are unlikely to occur.

[0009] Therefore, when the inner ring 41 is press-fitted into the fitting cylindrical portion 33a of the hub shaft 31 during the assembly of the hub unit bearing, burrs may separate from the hub shaft 31 and become hair-like metal fragments (hair burrs). If these hair burrs enter the bearing portion (raceway surface and rolling area of ​​the rolling elements), they may cause abnormal noise, seizure, and peeling of the surface layer.

[0010] The present invention has been made in view of the aforementioned problems, and its purpose is to provide a hub unit bearing that can suppress the separation of burrs generated when grinding the fitting cylindrical portion of the hub from the hub shaft, thereby preventing problems such as abnormal noise, seizure, and peeling of the surface caused by the burrs. [Means for solving the problem]

[0011] The above objective of the present invention is achieved by the following configuration. [1] An outer ring having a double row of outer ring raceways on its inner surface, A hub shaft having a rotating flange on the axially outward side to which a wheel and a braking rotating member are attached, and a small-diameter stepped portion formed on the axially inward side, and a hub comprising at least one inner ring press-fitted and fixed to the small-diameter stepped portion of the hub shaft, and having double rows of inner ring raceways on its outer circumference facing the double rows of outer ring raceways, A plurality of rolling elements are arranged to roll freely between the double-row outer ring raceway and the double-row inner ring raceway, A method for manufacturing a hub unit bearing comprising, The hub shaft is provided continuously on the axially inward side of the fitting cylindrical portion of the small-diameter stepped portion, and has an inclined portion that gradually decreases in diameter as it extends axially inward. A turning process for turning the fitting cylindrical portion and the inclined portion, A grinding step in which the fitting cylindrical portion and a part of the inclined portion are ground to form a roughened portion on the inclined portion by grinding, Equipped with, The boundary between the turned surface and the ground surface of the slack portion, located in the inclined portion, is positioned at a location where the diameter is smaller than the inner diameter of the inner ring before press-fitting. A method for manufacturing a hub unit bearing.

[0012] [2] An outer ring having a double row of outer ring raceways on its inner surface, A hub shaft having a rotating flange on the axially outward side to which a wheel and a braking rotating member are attached, and a small-diameter stepped portion formed on the axially inward side, and a hub comprising at least one inner ring press-fitted and fixed to the small-diameter stepped portion of the hub shaft, and having double rows of inner ring raceways on its outer circumference facing the double rows of outer ring raceways, A plurality of rolling elements are arranged to roll freely between the double-row outer ring raceway and the double-row inner ring raceway, Equipped with, A hub unit bearing comprising: a hub shaft including the hub, the rotating flange, the axially outer row of inner ring raceways among the double-row inner ring raceways, and a fitting cylindrical portion provided in the axially inner row with respect to said inner ring raceways; and an inner ring including the axially inner row of inner ring raceways among said double-row inner ring raceways and externally fitted onto said fitting cylindrical portion, said hub shaft has an inclined portion continuously provided on an axially inner side of the fitting cylindrical portion of the small-diameter step portion, the diameter of the inclined portion gradually decreasing toward the axially inner side, a boundary between a turned surface and a ground surface is provided on said inclined portion, the boundary between the turned surface and the ground surface is provided at a position having a smaller diameter than an inner diameter of said inner ring before press-fitting, the hub unit bearing.

Effects of the Invention

[0013] According to the method for manufacturing a hub unit bearing and the hub unit bearing of the present invention, burrs generated when grinding the fitting cylindrical portion and the inclined portion of the hub are prevented from separating during press-fitting of the inner ring onto the fitting cylindrical portion, thereby preventing failures such as abnormal noise, seizure, and peeling of the surface layer caused by burrs.

Brief Description of the Drawings

[0014] [Figure 1] It is a cross-sectional view of a hub unit bearing for a driven wheel according to a first embodiment of the present invention. [Figure 2] (a) is a cross-sectional view showing a state where an inner ring is externally fitted onto the fitting cylindrical portion of the hub shaft shown in FIG. 1, and (b) is an enlarged view of a portion surrounded by circle II in FIG. 2(a). [Figure 3] It is a cross-sectional view of a hub unit bearing for a driving wheel according to a second embodiment of the present invention. [Figure 4] (a) is a cross-sectional view showing a state where an inner ring is externally fitted onto the fitting cylindrical portion of the hub shaft shown in FIG. 3, and (b) is an enlarged view of a portion surrounded by circle IV in FIG. 4(a). [Figure 5] It is a cross-sectional view of a hub unit bearing for a driven wheel according to a third embodiment of the present invention. [Figure 6]It is a cross-sectional view of a hub unit bearing for a drive wheel according to a fourth embodiment of the present invention. [Figure 7] It is a grinding processing diagram of the outer peripheral surface of a hub shaft by a conventional full-form grinding wheel. [Figure 8] It is a grinding processing diagram of the inner diameter surface of an inner ring. Mode for Carrying Out the Invention

[0015] Hereinafter, a method for manufacturing a hub unit bearing and a hub unit bearing according to each embodiment of the present invention will be described in detail with reference to the drawings. Regarding the axial direction of the hub unit bearing 10, the "axially outer side" refers to the left side in FIG. 1, which is the outer side of the vehicle body when the hub unit bearing 10 is assembled to an automobile. Conversely, the right side in FIG. 1, which is the center side of the vehicle body when the hub unit bearing 10 is assembled to an automobile, that is, the axially inner side, is referred to as the "axially inner side".

[0016] (First Embodiment) First, the hub unit bearing 10 for a driven wheel according to the present embodiment will be described. As shown in FIG. 1, the hub unit bearing 10 for a driven wheel includes an outer ring 20, a hub 30, a plurality of balls (rolling elements) 51 arranged in two rows rotatably between the inner peripheral surface of the outer ring 20 and the outer peripheral surface of the hub 30, a pair of cages 52 that respectively hold the plurality of balls 51 in the two rows at substantially equal intervals in the circumferential direction, a seal ring 53a, and a combined seal ring 53b.

[0017] The outer ring 20 is provided with a mounting flange 21 on its outer peripheral surface. By coupling and fixing the mounting flange 21 to a knuckle of a suspension device (not shown) with mounting bolts, the outer ring 20 does not rotate while being supported by the suspension device. On the inner peripheral surface of the outer ring 20, two rows of outer ring raceways 20a, 20a parallel to each other are formed spaced apart from each other.

[0018] The hub 30 is arranged coaxially with the outer ring 20, radially inward from the outer ring 20, and comprises a hub shaft 31 and an inner ring 41 fitted and fixed to a small-diameter stepped portion 33 of the hub shaft 31. The hub shaft 31 is solid, and a rotating flange 32 extending radially outward from its outer circumferential surface is formed at its axial outer end (left side in the figure). Multiple hub bolts 55 for fastening a tire wheel and brake rotor (not shown) are provided on the rotating flange 32 at approximately equal intervals in the circumferential direction.

[0019] Referring also to Figure 2, the hub shaft 31 is provided with an inner ring raceway 30a on the outer circumferential surface of the axially inner side of the rotating flange 32, and a small-diameter stepped portion 33 is formed at the axially inner end (right side in the figure) of the inner ring raceway 30a. On the outer circumferential surface of the small-diameter stepped portion 33, a fitting cylindrical portion 33a, an inclined portion 34 that gradually decreases in diameter as it moves axially inward, and a crimping cylindrical portion 35 are formed in this order. After the inner ring 41 is fitted onto the fitting cylindrical portion 33a, the inner ring 41 is fixed to the hub shaft 31 by a crimping portion 35a formed by crimping the crimping cylindrical portion 35 radially outward. In this embodiment, the inclined portion 34 is formed in a position opposite to the chamfered portion between the inner diameter surface 41a and the axial end surface of the inner ring 41 when the inner ring 41 is fitted onto it, in order to facilitate deformation during crimping.

[0020] The inner ring 41 has an inner ring raceway 40a on its outer circumference and is positioned axially by being sandwiched between the axial end face 33b of the small-diameter stepped portion 33 and the crimping portion 35a, and is fixed to the hub shaft 31. Furthermore, by pressing the inner ring 41 axially against the hub shaft 31 through this crimping process, an appropriate preload is applied.

[0021] As a result, the inner ring raceway 30a of the hub shaft 31 and the inner ring raceway 40a of the inner ring 41 are formed corresponding to the outer ring raceways 20a, 20a of the outer ring 20, respectively. Multiple balls 51, which are held rotatably by the retainer 52, are arranged at equal intervals in the circumferential direction on the two rows of raceways composed of the inner ring raceways 30a, 40a and the outer ring raceways 20a, 20a.

[0022] Multiple balls 51 are arranged in a back-to-back configuration, contacting the outer ring raceways 20a, 20a and inner ring raceways 30a, 40a at predetermined contact angles. This allows the hub 30 to rotate relative to the outer ring 20.

[0023] The seal ring 53a and the combined seal ring 53b are positioned between the axial outer end of the outer ring 20 and the axial middle portion of the hub shaft 31, and between the axial inner end of the outer ring 20 and the axial inner end of the inner ring 41, closing both sides of the internal space 22 in which the multiple rolling elements 51 are provided.

[0024] Next, the manufacturing method of the hub shaft 31 will be described. As shown in Figure 2, the hub shaft 31 is formed by turning from the axially inner side surface 32a of the rotating flange 32, through the inner ring raceway 30a, to the outer surface of the small-diameter stepped portion 33 which includes the fitting cylindrical portion 33a, the inclined portion 34, and the crimping cylindrical portion 35, thereby forming the general shape of the outer surface (turning process). The outer diameter D2 of the fitting cylindrical portion 33a is formed to be larger in diameter than the outer diameter D1 of the crimping cylindrical portion 35, and the fitting cylindrical portion 33a and the crimping cylindrical portion 35 are smoothly continuous by the inclined portion 34.

[0025] Then, a heat-treated hardened layer (not shown) is formed on the outer circumferential surface of the rotating flange 32, from the axially inner side surface 32a to the inclined portion 34, including the inner ring raceway 30a, by high-frequency induction hardening or the like. In addition, plunge-cut grinding is performed on the outer circumferential surface of the rotating flange 32, from the axially inner side surface 32a to a part of the inclined portion 34, including the inner ring raceway 30a, using a full-form grinding wheel 4 as shown in Figure 7 (grinding process).

[0026] In this configuration, the axially inner end face of the total grinding wheel 4 is set to grind a portion of the axially outer side of the inclined portion 34 while smoothing it out. As a result, a smoothed portion 34a with a curved cross-section that smoothly continues from the fitting cylindrical portion 33a to the inclined portion 34 is formed on a portion of the axially outer side of the inclined portion 34.

[0027] As a result, the inclined portion 34 has both a grinding surface 57 and a turning surface 58. That is, a boundary 36 is formed between the grinding surface 57 and the turning surface 58 in the inclined portion 34, and a burr (not shown) is formed on the turning surface side of the boundary 36.

[0028] The axial position of the boundary 36 where the burr is formed is set so that the outer diameter D3 of the boundary 36 is smaller than the inner diameter d of the inner diameter surface 41a of the inner ring 41 before press-fitting. That is, the following relationship exists between the outer diameters of the fitting cylindrical portion 33a, the boundary 36, the crimping cylindrical portion 35, and the inner diameter of the inner diameter surface 41a of the inner ring 41 before press-fitting.

[0029] Outer diameter D2 of fitting cylindrical portion 33a > Inner diameter d of inner diameter surface 41a of inner ring 41 before press-fitting > Outer diameter D3 of boundary 36 > Outer diameter D1 of crimping cylindrical portion 35

[0030] The inner ring 41 is then press-fitted into the fitting cylindrical portion 33a, and the crimping cylindrical portion 35 is crimped radially outward to form a crimped portion 35a, thereby fixing it to the hub shaft 31. At this time, since the inner diameter d of the inner ring 41 is larger than the outer diameter D3 of the boundary 36 where the burr is formed, the inner surface of the inner ring 41 does not come into contact with the burr formed at the boundary 36 when the inner ring 41 is press-fitted. Therefore, there is no risk of the burr separating from the hub shaft 31 and becoming hair-like metal fragments (beard burrs), and problems such as abnormal noise, seizing, and peeling of the surface due to the burr can be prevented.

[0031] (Second Embodiment) Next, the drive wheel hub unit bearing 10A of the second embodiment will be described with reference to Figures 3 and 4. The hub unit bearing 10A for the drive wheel of the second embodiment includes a hollow hub shaft 31 with a female spline 37 formed on its inner circumferential surface, and a male spline of a spline shaft (not shown) is fitted into the female spline 37 of the hub shaft 31.

[0032] Furthermore, the hub shaft 31 of this embodiment does not have the crimping cylindrical portion 35 (see Figure 2) of the first embodiment, and the axial inner end face 31a of the hub shaft 31 is located axially outward from the axial inner end face 41c of the inner ring 41 that fits into the fitting cylindrical portion 33a of the small diameter stepped portion 33. Therefore, the inner ring 41 is positioned and fixed axially relative to the hub shaft 31 by, for example, the axially outward end face of the spline shaft coming into contact with the axial inner end face 41c of the inner ring 41.

[0033] In such a hub shaft 31, a chamfered portion 34 is formed as an inclined surface on the axial inner side of the fitting cylindrical portion 33a, that is, between the fitting cylindrical portion 33a of the small-diameter stepped portion 33 and the axial inner end face 31a of the hub shaft 31.

[0034] Therefore, as shown in Figure 4, in this embodiment, the outer circumferential surface of the hub shaft 31 is turned from the axially inner side surface 32a of the rotating flange 32, via the inner ring raceway 30a, to the fitting cylindrical portion 33a and the chamfered portion 34 which is an inclined surface, to form the general shape of the outer circumferential surface (turning process). The outer diameter D2 of the fitting cylindrical portion 33a is formed to be larger in diameter than the outer diameter D1 of the axially inner end of the chamfered portion 34 (the axially inner end surface 31a of the hub shaft 31).

[0035] Then, a heat-treated hardened layer (not shown) is formed on the outer circumferential surface of the rotating flange 32 from the axially inner side surface 32a to the chamfered portion 34 by high-frequency induction hardening or the like. Furthermore, plunge-cut grinding is performed on the outer circumferential surface of the rotating flange 32 from the axially inner side surface 32a to a part of the chamfered portion 34 using a full-form grinding wheel 4 as shown in Figure 7 (grinding process).

[0036] In this process, the axially inner end face of the total grinding wheel 4 is ground down by smoothing the axially outer portion of the chamfered portion 34 to form a smoothed portion 34a. Therefore, the chamfered portion 34 has a grinding surface 57 and a turning surface 58. A burr (not shown) is formed on the turning surface side of the boundary 36 between the grinding surface 57 and the turning surface 58.

[0037] However, in this embodiment as well, the axial position of the boundary 36 where the burr is formed is set to a position where the outer diameter D3 of the boundary 36 is smaller than the inner diameter d of the inner diameter surface 41a of the inner ring 41 before press-fitting. That is, the following relationship exists between the outer diameters of the fitting cylindrical portion 33a and the boundary 36 and the inner diameter of the inner diameter surface 41a of the inner ring 41 before press-fitting.

[0038] Outer diameter D2 of the fitting cylindrical portion 33a > Inner diameter d of the inner diameter surface 41a of the inner ring 41 before press-fitting > Outer diameter D3 of the boundary 36

[0039] Therefore, in this embodiment, the inner diameter d of the inner ring 41 of the drive wheel hub unit bearing 10A is larger than the outer diameter D3 of the boundary 36 where the burr is formed. As a result, when the inner ring 41 is pressed in, the inner surface of the inner ring 41 does not come into contact with the burr formed at the boundary 36. Consequently, there is no risk of the burr separating from the hub shaft 31, and problems such as abnormal noise, seizure, and peeling of the surface caused by the burr can be prevented. Other configurations and operations are the same as those of the driven wheel hub unit bearing 10 in the first embodiment.

[0040] (Third embodiment) Next, a hub unit bearing 10B for the driven wheel according to the third embodiment of the present invention will be described with reference to Figure 5. The hub unit bearing 10B for the driven wheel according to this embodiment mainly differs from the hub unit bearing 10 for the driven wheel according to the first embodiment in that it uses tapered rollers 61 as rolling elements.

[0041] As shown in Figure 5, the driven wheel hub unit bearing 10B of this embodiment comprises an outer ring 20, a hub 30, a plurality of tapered rollers 61 which are rolling elements arranged in two rows so as to be rotatable between the inner circumferential surface of the outer ring 20 and the outer circumferential surface of the hub 30, a pair of cages 62 which each hold the plurality of tapered rollers 61 in the two rows at substantially equal intervals in the circumferential direction, and a seal ring 53 which is arranged at the axial outer end of the outer ring 20.

[0042] Similar to the first embodiment, the outer ring 20 is provided with a mounting flange 21 on its outer circumference, and the mounting flange 21 is connected and fixed to a knuckle of a suspension device (not shown) with mounting bolts, so that it does not rotate while supported by this suspension device. In addition, two rows of outer ring raceways 20a, 20a are formed on the inner circumference of the outer ring 20, spaced apart from each other, and these two rows of outer ring raceways 20a are inclined in a direction in which the diameter increases as they move away from each other in the axial direction.

[0043] The hub 30 comprises a hub shaft 31 having a rotating flange 32 and a small-diameter stepped portion 33, and a pair of inner rings 63A and 63B fitted and fixed to the hub shaft 31, and is arranged coaxially with the outer ring 20 on the radially inner side of the outer ring 20. The pair of inner rings 63A and 63B each have an inner ring raceway 63a. The two rows of inner ring raceways 63a are formed opposite to the two rows of outer ring raceways 20a of the outer ring 20. The two rows of inner ring raceways 63a are inclined in a direction in which the diameter increases as they move away from each other in the axial direction.

[0044] In other words, the hub shaft 31 of this embodiment does not have an inner ring raceway on its outer circumference. Instead, a small-diameter stepped portion 33 is formed from the outer circumference axially inward of the rotating flange 32 to the axially inward end face. The small-diameter stepped portion 33 has a cylindrical fitting cylindrical portion 33a, similar to the first embodiment, and is formed in the order of a sloping portion 34 that gradually decreases in diameter as it moves axially inward, and a crimping cylindrical portion 35 (not shown in Figure 5). After fitting a pair of inner rings 63A and 63B onto the small-diameter stepped portion 33, the pair of inner rings 63A and 63B are axially positioned and fixed to the hub shaft 31 by a crimping portion 35a formed by crimping the crimping cylindrical portion 35 of the small-diameter stepped portion 33 radially outward.

[0045] The inner rings 63A and 63B are constructed in a cylindrical shape and have an inner ring raceway 63a on the outer circumferential surface of the axial intermediate portion. The inner rings 63A and 63B also have a large flange portion 63b that protrudes radially outward from the large-diameter end adjacent to the large-diameter side of the inner ring raceway 63a in the axial direction, and a small flange portion 63c that protrudes radially outward from the small-diameter end adjacent to the small-diameter side of the inner ring raceway 63a in the axial direction.

[0046] In the illustrated example, the axially outer opening of the internal space 22 between the inner surface of the outer ring 20 and the outer surface of the hub 30 is sealed by a combination seal ring 53 assembled between the inner surface of the axially outer end of the outer ring 20 and the outer surface of the large flange portion 63b of the axially outer inner ring 63A. Furthermore, the axially inner opening of the outer ring 20 is sealed by a cap 65 made of a non-magnetic material that is fitted and fixed to the axially inner end of the outer ring 20. In addition, an annular encoder 66, which constitutes a rotational speed detection device, is fitted and fixed to the outer surface of the large flange portion 63b that constitutes the axially inner inner ring 63B.

[0047] The manufacturing method for the hub shaft 31 in this embodiment is the same as the manufacturing method for the hub shaft 31 in the first embodiment described in Figure 2. Of the outer circumferential surface of the small-diameter stepped portion 33, which includes the turned fitting cylindrical portion 33a, the inclined portion 34, and the crimping cylindrical portion 35, the fitting cylindrical portion 33a and a part of the inclined portion 34 are ground, and the outer diameter of the boundary 36 between the ground surface 57 and the turned surface 58 formed on the inclined portion 34 is smaller than the inner diameter surface of the inner rings 63A and 63B before press-fitting. As a result, the inner surfaces of the inner rings 63A and 63B do not come into contact with the burrs formed at the boundary 36 when the inner rings 63A and 63B are press-fitted, and there is no risk of the burrs separating from the hub shaft 31, thus preventing problems such as abnormal noise, seizing, and peeling of the surface caused by the burrs. Other configurations and operations are the same as those of the driven wheel hub unit bearing 10 in the first embodiment.

[0048] (Fourth Embodiment) The drive wheel hub unit bearing 10C of this embodiment will be described with reference to Figure 6. In the drive wheel hub unit bearing 10C of the fourth embodiment, tapered rollers 61 are used as rolling elements, similar to the driven wheel hub unit bearing 10B of the third embodiment, and a male spline of a spline shaft (not shown) is fitted to the female spline 37 of the hub shaft 31, similar to the drive wheel hub unit 10A of the second embodiment. However, in the hub 30, the axially outer inner ring raceway 63a is formed on the hub shaft 31, and the axially inner inner ring raceway 63a is formed on the inner ring 63B, and the small diameter stepped portion 33 of the hub shaft 31 is formed axially inward from the axially outer inner ring raceway 63a.

[0049] Furthermore, similar to the second embodiment, the hub shaft 31 is formed such that its axial inner end face 31a is located axially outward from the axial inner end face 63d of the inner ring 63B that fits into the fitting cylindrical portion 33a of the small diameter stepped portion 33. In addition, a chamfered portion 34 is formed as an inclined surface on the axial inner side of the fitting cylindrical portion 33a, that is, between the fitting cylindrical portion 33a of the small diameter stepped portion 33 and the axial inner end face 31a of the hub shaft 31.

[0050] Therefore, similar to the second embodiment, by performing turning and grinding, the outer diameter D3 of the boundary 36 between the ground surface 57 and the turned surface 58 formed on the chamfered portion 34 is set to a position smaller than the inner diameter d of the inner ring 63B before press-fitting, so that the inner diameter surface of the inner ring 63B does not come into contact with the burr formed at the boundary 36 when the inner ring 63B is press-fitted. Therefore, there is no risk of the burr separating from the hub shaft 31, and problems such as abnormal noise, seizing, and peeling of the surface due to the burr can be prevented. Other configurations and operations are the same as those of the driven wheel hub unit bearing 10 in the first embodiment.

[0051] In particular, in hub unit bearings 10B and 10C equipped with tapered rollers as rolling elements, such as in the third and fourth embodiments, the hoop stress on the small flange portion 63c and the large flange portion 63b of the inner rings 63A and 63B is high, making burr separation likely. When burrs enter between the abutting surfaces of the pair of inner rings 63A and 63B, the preload becomes unstable, and if the burrs are crushed between the abutting surfaces of the pair of inner rings 63A and 63B, the burrs are more likely to enter the raceway surface due to the flow of grease. For this reason, the present invention is particularly suitably applicable to hub unit bearings 10B and 10C equipped with tapered rollers.

[0052] Furthermore, the present invention is not limited to the embodiments described above, and can be modified, improved, etc., as appropriate.

[0053] As described above, the following matters are disclosed in this specification: (1) An outer ring having a double row of outer ring raceways on its inner circumference, A hub shaft having a rotating flange on the axially outward side to which a wheel and a braking rotating member are attached, and a small-diameter stepped portion formed on the axially inward side, and a hub comprising at least one inner ring press-fitted and fixed to the small-diameter stepped portion of the hub shaft, and having double rows of inner ring raceways on its outer circumference facing the double rows of outer ring raceways, A plurality of rolling elements are arranged to roll freely between the double-row outer ring raceway and the double-row inner ring raceway, A method for manufacturing a hub unit bearing comprising: The hub shaft is provided continuously on the axially inward side of the fitting cylindrical portion of the small-diameter stepped portion, and has an inclined portion that gradually decreases in diameter as it extends axially inward. A turning process for turning the fitting cylindrical portion and the inclined portion, A grinding step in which the fitting cylindrical portion and a part of the inclined portion are ground to form a roughened portion on the inclined portion by grinding, Equipped with, The boundary between the turned surface and the ground surface of the slack portion, located in the inclined portion, is positioned at a location where the diameter is smaller than the inner diameter of the inner ring before press-fitting. A method for manufacturing a hub unit bearing. With this configuration, when grinding the fitting cylindrical portion and inclined portion of the hub, burrs that form at the boundary between the turned surface and the ground surface of the inclined portion are prevented from separating when the inner ring is pressed into the fitting cylindrical portion, thereby preventing problems such as abnormal noise, seizing, and peeling of the surface caused by burrs.

[0054] (2) Tapered rollers are used as the rolling elements, The method for manufacturing a hub unit bearing according to (1), wherein the inner ring has a small flange and a large flange on both sides of the inner ring raceway in the axial direction. This configuration is suitable for use in hub unit bearings where tapered rollers are used, as the hoop stress on the small flange portion 63c and the large flange portion 63b of the inner rings 63A and 63B is high, making burr separation more likely.

[0055] (3) The method for manufacturing a hub unit bearing according to (1), wherein the hub shaft further comprises a crimping cylindrical portion provided continuously on the axially inward side of the inclined portion, the outer surface of which is formed by a turning process. With this configuration, even in a configuration where the inner ring is fixed to the hub shaft by a crimping portion, burrs generated at the boundary between the turned surface and the ground surface of the inclined portion can be prevented from separating when the inner ring is pressed into the fitting cylindrical portion.

[0056] (4) The method for manufacturing a hub unit bearing according to (1), wherein the inclined portion of the hub shaft constitutes a chamfered portion formed between the fitting cylindrical portion and the axial end face. With this configuration, even in a setup where the inner ring is fixed to the hub shaft by pressing the axial end face of the inner ring with another member, it is possible to prevent burrs generated at the boundary between the turned surface and the ground surface of the inclined portion from separating when the inner ring is pressed into the fitting cylindrical portion.

[0057] (5) An outer ring having a double row of outer ring raceways on its inner circumference, A hub shaft having a rotating flange on the axially outward side to which a wheel and a braking rotating member are attached, and a small-diameter stepped portion formed on the axially inward side, and a hub comprising at least one inner ring press-fitted and fixed to the small-diameter stepped portion of the hub shaft, and having double rows of inner ring raceways on its outer circumference facing the double rows of outer ring raceways, A plurality of rolling elements are arranged to roll freely between the double-row outer ring raceway and the double-row inner ring raceway, A hub unit bearing equipped with, The hub shaft is provided continuously on the axially inward side of the fitting cylindrical portion of the small-diameter stepped portion, and has an inclined portion that gradually decreases in diameter as it extends axially inward. The inclined portion is provided with a boundary between the turning surface and the grinding surface. The boundary between the turned surface and the ground surface is positioned at a location where the diameter is smaller than the inner diameter of the inner ring before press-fitting. Hub unit bearing. With this configuration, when grinding the fitting cylindrical portion and inclined portion of the hub, burrs that form at the boundary between the turned surface and the ground surface of the inclined portion are prevented from separating when the inner ring is pressed into the fitting cylindrical portion, thereby preventing problems such as abnormal noise, seizing, and peeling of the surface caused by burrs. [Explanation of symbols]

[0058] 10, 10B Drive wheel hub unit bearing (hub unit bearing) 10A, 10C Drive Wheel Hub Unit Bearing (Hub Unit Bearing) 20 Outer ring 20a Outer ring track 21 Mounting flange 30 Hubs 30a, 40a, 63a Inner track 31 Hub axle 33 Small diameter stepped section 33a Fitting cylindrical part 34 Inclined section, chamfered section 34a Sloppy Club 35. Cylindrical part for crimping 36. Boundary between the turned surface and the ground surface 41, 63A, 63B inner ring 51 Ball (rolling element) 57 Grinding surface 58 Turning surface 61. Cone roller (rolling element) d Inner diameter of the inner ring D1 Outer diameter of the cylindrical part for crimping D2 Outer diameter of the fitting cylindrical part Outer diameter of the boundary at D3

Claims

1. An outer ring having a double row of outer ring raceways on its inner circumference, A hub shaft having a rotating flange on the axially outward side to which a wheel and a braking rotating member are attached, and a small-diameter stepped portion formed on the axially inward side, and a hub comprising at least one inner ring press-fitted and fixed to the small-diameter stepped portion of the hub shaft, and having double rows of inner ring raceways on its outer circumference facing the double rows of outer ring raceways, A plurality of rolling elements are arranged to roll freely between the double-row outer ring raceway and the double-row inner ring raceway, A method for manufacturing a hub unit bearing comprising: The hub shaft is provided continuously on the axially inward side of the fitting cylindrical portion of the small-diameter stepped portion, and has an inclined portion that gradually decreases in diameter as it is directed axially inward. A turning process for turning the fitting cylindrical portion and the inclined portion, A grinding step in which the fitting cylindrical portion and a part of the inclined portion are ground to form a roughened portion on the inclined portion by grinding, Equipped with, The boundary between the turned surface and the ground surface of the sloping portion, provided in the inclined portion, is positioned at a location where the diameter is smaller than the inner diameter of the inner ring before press-fitting. The inner ring is press-fitted into the fitting cylindrical portion of the small-diameter stepped portion without contacting the boundary. A method for manufacturing hub unit bearings.

2. Tapered rollers are used as the rolling elements. The method for manufacturing a hub unit bearing according to claim 1, wherein the inner ring has a small flange and a large flange on both sides of the inner ring raceway in the axial direction.

3. The method for manufacturing a hub unit bearing according to claim 1, wherein the hub shaft further comprises a crimping cylindrical portion provided continuously on the axially inward side of the inclined portion, the outer surface of which is formed by a turning process.

4. The method for manufacturing a hub unit bearing according to claim 1, wherein the inclined portion of the hub shaft constitutes a chamfered portion formed between the fitting cylindrical portion and the axial end face.

5. An outer ring having a double row of outer ring raceways on its inner circumference, A hub shaft having a rotating flange on the axially outward side to which a wheel and a braking rotating member are attached, and a small-diameter stepped portion formed on the axially inward side, and a hub comprising at least one inner ring press-fitted and fixed to the small-diameter stepped portion of the hub shaft, and having double rows of inner ring raceways on its outer circumference facing the double rows of outer ring raceways, A plurality of rolling elements are arranged to roll freely between the double-row outer ring raceway and the double-row inner ring raceway, A hub unit bearing equipped with, The hub shaft is provided continuously on the axially inward side of the fitting cylindrical portion of the small-diameter stepped portion, and has an inclined portion that gradually decreases in diameter as it is directed axially inward. A portion of the inclined portion has a curved cross-sectional area that extends smoothly from the fitting cylindrical portion to the inclined portion. The inclined portion is provided with a boundary between the turning surface and the grinding surface of the sloping portion. The boundary between the turned surface and the ground surface of the slack portion is provided at a position where the diameter is smaller than the inner diameter of the inner ring before press-fitting. After press-fitting, the inner ring is not in contact with the boundary. Hub unit bearing.

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