Method for manufacturing rolling bearing unit

Abstract

Construction is achieved that is capable of preventing the formation of radial streaks in the tip-end surfaces of teeth of hub-side face splines 21. When a swing center distance is taken to be L, a swing angle that is the inclination angle of the center axis of a roll 30 with respect to a main hub body 8 is taken to be , the pitch diameter of the hub-side face splines 21 is taken to be D.sub.h, the number of teeth of the hub-side face splines 21 is taken to be N.sub.h, and the number of teeth of a processing surface 31 of the roll 30 is taken to be N.sub.r, the position relationship of the main hub body 8 and the roll 30, or in other words, at least one of the swing center distance L, the swing angle , and the pitch circle diameter D.sub.h is regulated so that the relationship Nh/Nr=cos +(2L/D.sub.h).Math.sin is satisfied.

Claims

1. A manufacturing method for a rolling bearing unit that comprises: a main hub body and an inner ring; the main hub body having an inner-ring raceway on one side in the axial direction of the rolling bearing unit that is provided around an outer-circumferential surface of a middle section in the axial direction of the main hub body, a cylindrical section that is provided on a portion near the end on the other side in the axial direction of the main hub body, and a crimped section that is provided on an end section on the other side in the axial direction of the main hub body and extends outward in the radial direction from the end section on the other side in the axial direction of the cylindrical section; the inner ring having an inner-ring raceway on the other side in the axial direction around an outer-circumferential surface of the inner ring, and fitting around the cylindrical section; and the crimped section having a surface on the one end in the axial direction that constrains a surface on the other end in the axial direction of the inner ring, and a surface of the other end in the axial direction on which hub-side face splines are provided; the manufacturing method for a rolling bearing unit comprising; a step of forming the hub-side face splines on the surface of the other end in the axial direction of the crimped section by using a roll having a center axis that is inclined with respect to the center axis of the main hub body and a processing surface provided with plural teeth, and with the processing surface of the roll pressed against the surface of the other end in the axial direction of the crimped section, causing the roll to rotate around the center axis of the main hub body, and causing the roll to rotate around the center axis of the roll due to engagement between the processing surface of the roll and the surface of the other end in the axial direction of the crimped section; when causing the roll to rotate around the center axis of the main hub body with the processing surface of the roll pressed against the surface of the other end in the axial direction of the crimped section, spacing of the teeth that are formed on the processing surface at a location in the radial direction of a portion of the processing surface of the roll where the tip end of one of the teeth formed on the processing surface of the roll first comes in contact with the surface of the other end in the axial direction of the crimped section, and spacing of teeth of the hub-side face splines at a location in the radial direction of a portion of the surface of the other end in the axial direction of the crimped section where the surface of the other end in the axial direction of the crimped section first comes in contact with the tip end of the one of the teeth formed on the processing surface of the roll being made to coincide.

2. The manufacturing method for a rolling bearing unit according to claim 1, wherein in a state in which the processing surface of the roll is pressed against the surface of the other end in the axial direction of the crimped section, when a swing center distance that is the distance in the axial direction of the main hub body between an intersecting point of the center axis of the main hub body and the center axis of the roll and an imaginary plane that includes the surface of the other end in the axial direction of the crimped section is taken to be L; a swing angle that is the inclination angle of the center axis of the roll with respect to the center axis of the main hub unit is taken to be ; a diameter of an imaginary circle the center of which is the center axis of the main hub body and the radius of which is the distance between the center axis of the main hub body and the location in the radial direction of the portion of the surface of the other end in the axial direction of the crimped section where the surface of the other end in the axial direction of the crimped section first comes in contact with the tip end of the one of the teeth formed on the processing surface of the roll is taken to be D.sub.h; the number of teeth of the hub-side face splines is taken to be N.sub.h; and the number of teeth formed on the processing surface of the roll is taken to be N.sub.r; at least one of the swing center distance L, the swing angle , and the pitch circle diameter D.sub.h is regulated so that the relationship
N.sub.r/N.sub.h=cos +(2L/D.sub.h).Math.sin is satisfied.

3. The manufacturing method for a rolling bearing unit according to claim 1, wherein in a state in which the processing surface of the roll is pressed against the surface of the other end in the axial direction of the crimped section, after one of a swing center distance L that is the distance in the axial direction of the main hub body between an intersecting point of the center axis of the main hub body and the center axis of the roll and an imaginary plane that includes the surface of the other end in the axial direction of the crimped section, and a swing angle that is the inclination angle of the center axis of the roll with respect to the center axis of the main hub body has been set to an arbitrary value; a relationship between the value of the other of the swing center distance L and the swing angle , and the difference between the spacing of the teeth that are formed on the processing surface of the roll, and the spacing of the teeth of the hub-side face splines is found in order that specified values are employed for a pitch circle diameter D.sub.h of an imaginary circle the center of which is the center axis of the main hub body and the radius of which is the distance between the center axis of the main hub body and the location in the radial direction of the portion of the surface of the other end in the axial direction of the crimped section where the surface of the other end in the axial direction of the crimped section first comes in contact with the tip end of the one tooth of the teeth formed on the processing surface of the roll, and the number of teeth N.sub.h of the hub-side face splines, and from that relationship, the value of the other of the swing center distance L and the swing angle is set so that the difference is 0.

4. A rolling bearing unit comprising: at least a main hub body and an inner ring; wherein the main hub body has an inner-ring raceway on one side in the axial direction of the rolling bearing unit that is provided around an outer-circumferential surface of a middle section in the axial direction of the main hub body, a cylindrical section that is provided on a portion near the end on the other side in the axial direction of the main hub body, and a crimped section that is provided on an end section on the other side in the axial direction of the main hub body and extends outward in the radial direction from the end section on the other side in the axial direction of the cylindrical section; the inner ring has an inner-ring raceway around the outer-circumferential surface of the inner ring, and fits around the cylindrical section; the crimped section has a surface on the one end in the axial direction that constrains a surface on the other end in the axial direction of the inner ring, and a surface of the other end in the axial direction on which hub-side face splines are provided; and radial streaks due to orbital forging for forming hub-side face splines are not formed in the tip-end surfaces of the teeth of the hub-side face splines.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a cross-sectional view illustrating an example of a manufacturing method for a rolling bearing unit of the present invention.

(2) FIGS. 2A to 2C illustrate three examples of diagrams for finding the relationship of the swing center distance L, pitch circle diameter D.sub.r and pitch difference P in a second example of an embodiment of the present invention.

(3) FIG. 3 is a graph illustrating the relationship between the swing center distance L and pitch difference P in the second example of an embodiment of the present invention.

(4) FIG. 4 is a graph illustrating the relationship between the swing angle and pitch difference P in a third example of an embodiment of the present invention.

(5) FIG. 5 is a cross-sectional view of an example of conventional construction of a wheel-drive bearing unit in which a wheel-support bearing unit, which is one kind of a rolling bearing that is the object of the present invention, is assembled.

(6) FIG. 6 is cross-sectional view illustrating an example of a conventional manufacturing method for a rolling bearing unit.

(7) FIG. 7 is an enlarged perspective view of the main part of hub-side face splines, and is for explaining the problems in a conventional manufacturing method for a rolling bearing unit.

MODES FOR CARRYING OUT INVENTION

First Example

(8) A first example of an embodiment of the present invention is explained using FIG. 1. A feature of the present invention, including this example, is the prevention of radial streaks 32 (refer to FIG. 7) that are formed in the tip-end surfaces of teeth of hub-side face splines 21 due to orbital forging when forming the hub-side face splines 21 by performing orbital forging on a surface of the other end in the axial direction of a crimped section 20. The procedure for manufacturing each of the members of a rolling bearing unit 1 (refer to FIG. 5) by performing a plastic working process such as a forging process and the like, and performing a cutting process such as turning and the like, and a finishing process such as polishing on a metal material, is the same as in a conventionally known manufacturing method for a rolling bearing unit.

(9) A wheel-support rolling bearing unit 1, which is one example of a rolling bearing unit that is the object of the manufacturing method of the present invention, includes a main hub unit 8 and an inner ring 9 (refer to FIG. 5). The main hub unit 8 includes an inner-ring raceway 11a on one side in the axial direction that is provided around the outer-circumferential surface of the middle section in the axial direction of the main hub unit 8, a cylindrical section 19 that is provided in a portion near the other end in the axial direction of the main hub unit 8, and a crimped section 20 that is provided on the other end in the axial direction of the main hub unit 8 and extends outward in the radial direction of the other end section in the axial direction of the cylindrical section 19. The inner ring 9 has an inner-ring raceway lib around the outer-circumferential surface of the inner ring 9, and is fitted around the cylindrical section 19. The crimped section 20 has a surface on the one end in the axial direction that constrains the surface of the other end in the axial direction of the inner ring 9, and a surface on the other end in the axial direction on which hub-side face splines 21 (uneven surface in the circumferential direction) are provided.

(10) When assembling the wheel-support rolling bearing 1, first, an outer ring 3 is arranged around the circumference of the main hub unit 8, and a plurality of rolling bodies 5 are arranged between an outer-ring raceway 7a on the one side in the axial direction and an inner-ring raceway 11a on the one side in the axial direction, and held by a retainer 29a on the one side in the axial direction. Next, rolling bodies 5 are arranged around the circumference of the inner-ring raceway 11b on the other side in the axial direction that is formed around the outer-circumferential surface of the inner ring 9 and held by a retainer 29b on the other side in the axial direction; and in this state, the inner ring 9 is fitted with an interference fit around a small-diameter stepped section 12 that is formed by a cylindrical section 19 that extends from the middle section in the axial direction of the main hub body 8 to the other side in the axial direction. Together with this outer fitting work, the rolling surfaces of the rolling bodies 5 in the row on the other side in the axial direction are brought into contact with an outer-ring raceway 7b on the other side in the axial direction that is formed around the inner-circumferential surface of a portion near the other end in the axial direction of the outer ring 3. After that, in the state before forming the crimped section 20, of the cylindrical section 19 that extends in the axial direction from a portion near the other end in the axial direction of the main hub body 8 to the other end section in the axial direction, a portion that protrudes toward the other side in the axial direction from an opening on the other side in the axial direction of the inner ring 9 is plastically deformed outward in the radial direction to form a crimped section 20 on the other end section in the axial direction of the main hub body 8. The inner ring 9 is fastened to the main hub body 8 by constraining the other end surface in the axial direction of the inner ring 9 in the axial direction by the one end surface in the axial direction of the crimped section 20.

(11) Hub-side face splines 21 are formed by using a roll 30 having a center axis that is inclined with respect to the center axis of the main hub body 8 to perform orbital forging on the other end surface in the axial direction of the crimped section 20 of the wheel-support rolling bearing unit 1 that is assembled in this way. More specifically, with the processing surface of the roll 30 pressed against the other end surface in the axial direction of the crimped section 20, hub-side face splines 21 are formed by causing the roll 30 to rotate around the center axis of the main hub body 8, and by causing the roll 30 to rotate around the center axis of the roll 30 due to the engagement between the processing surface of the roll 30 and the other end surface in the axial direction of the crimped section 20.

(12) In this embodiment, when performing orbital forging on the other end surface in the axial direction of the crimped section 20, the spacing (pitch in the circumferential direction of the teeth that are formed on the processing surface) P.sub.r of the teeth that are formed on the processing surface 31 at a location in the radial direction of a portion of the processing surface 31 of the roll 30 where the tip end of one tooth of the plural teeth that are formed on the processing surface 31 of the roll 30 first comes in contact with the other end surface in the axial direction of the crimpled section 20, and the spacing (pitch in the circumferential direction of the hub-side face splines 21 that are to be formed on the other end surface in the axial direction of the crimped section 20) P.sub.h of the teeth of the hub-side face splines 21 at a location in the radial direction of a portion of the other end surface in the axial direction of the crimped section 20 where the other end surface in the axial direction of the crimped section 20 first comes in contact with the tip end of one tooth of the plural teeth formed on the processing surface 31 of the roll 30 are made to coincide. In other words, the difference P (=P.sub.rP.sub.h) between the pitch P.sub.r in the circumferential direction of the teeth formed on the processing surface 31 and the pitch P.sub.h in the circumferential direction of the hub-side face splines 21 that are to be formed on the other end surface in the axial direction of the crimped section 20 is made to be 0.

(13) Therefore, more specifically, the swing center distance L that is the distance in the axial direction of the main hub body 8 between the intersecting point of the center axis of the main hub body 8 and the center axis of the roll 30 in a state in which the processing surface 31 of the roll 30 is pressed against the other end surface in the axial direction of the crimped section 20 and an imaginary plane that includes the other end surface in the axial direction of the crimped section 20, and the swing angle that is the inclination angle of the center axis of the roll 30 with respect to the center axis of the main hub body 8 are regulated to as to satisfy the relationship given in Expression (1).
N.sub.r/N.sub.h=cos +(2L/D.sub.h).Math.sin (1)

(14) In Expression (1), D.sub.h indicates the diameter of an imaginary circle (pitch circle diameter of the hub-side face splines 21) the center of which is taken to be the center axis of the main hub body 8, and the radius of which is taken to be the distance between the center axis of the main hub body 8 and the location in the radial direction of the portion of the other end surface in the axial direction of the crimped section 20 where the other end surface in the axial direction of the crimped section 20 first comes in contact with the tip end of one tooth of the plural teeth that are formed on the processing surface 31 of the roll 30. Moreover, N.sub.h indicates the number of teeth of the hub-side face splines 21, and N.sub.r indicates the number of teeth that are formed on the processing surface 31 of the roll 30.

(15) The reason for matching the pitch P.sub.r in the circumferential direction of the teeth that are formed on the processing surface 31 with the pitch P.sub.h in the circumferential direction of the hub-side face splines 21 that are to be formed on the other end surface in the axial direction of the crimped section 20 by satisfying the relationship of this kind of Expression (1) is as described below.

(16) The pitch P.sub.r in the circumferential direction of the teeth that are formed on the processing surface 31 of the roll 30 is expressed by Expression (2), and the pitch P.sub.h in the circumferential direction of the hub-side face splines 21 that are to be formed on the other end surface in the axial direction of the crimped section 20 is expressed by the Expression (3).
P.sub.r=D.sub.r/N.sub.r(2)
Ph=D.sub.h/N.sub.h(3)

(17) In Expression (2), D.sub.r indicates the diameter of an imaginary circle (pitch circle diameter of teeth that are formed on the processing surface 31) the center of which is taken to be the center axis of the roll 30, and the radius of which is taken to be the distance between the center axis of the roll 30 and the location in the axial direction of the portion of the processing surface 31 of the roll 30 where the tip end of one tooth of the plural teeth that are formed on the processing surface 31 first comes in contact with the other end surface in the axial direction of the crimped section 20. From Expression (2) and Expression (3), the pitch difference P (=P.sub.rP.sub.) can expressed as in Expression (4).
P=(D.sub.r/N.sub.rD.sub.h/N.sub.h)(4)

(18) The relationship between the pitch circle diameter D.sub.h of the hub-side face splines 21 and the pitch circle diameter D.sub.r of the teeth that are formed on the processing surface 31 of the roll 30, can be expressed by Expression (5) as can be clearly seen from FIG. 1.
D.sub.r/2=(D.sub.h/2+L.Math.tan ).Math.cos (5)

(19) By substituting Expression (5) into Expression (4), an Expression (6) is obtained.
P=.Math.{(D.sub.h/N.sub.r).Math.cos +(2L/N.sub.r).Math.sin D.sub.h/N.sub.h}(6)

(20) As can be clearly seen from Expression (6), the pitch difference P changes as the swing center distance L or the swing angle changes. Here, when the pitch difference P is taken to be P=0, Expression (4) can be expressed by Expression (7).
D.sub.r/N.sub.r=D.sub.h/N.sub.h(7)

(21) From Expression (7) and Expression (5), it is possible to derive Expression (1).

(22) In the manufacturing method for a rolling bearing unit of the present invention, when providing hub-side face splines 21 on the other end surface in the axial direction of the crimped section 20 by performing orbital forging, the spacing (pitch in the circumferential direction of the hub-side face splines 21 that are to be formed on the other end surface in the axial direction of the crimped section 20) P.sub.h of the teeth of the hub-side face splines 21 at a location in the radial direction of a portion of the other end surface in the axial direction of the crimped section 20 where the other end surface in the axial direction of the crimped section 20 first comes in contact with the tip end of one tooth of the plural teeth that are formed on the processing surface 31 of the roll 30, and the spacing (pitch in the circumferential direction of the teeth that are formed on the processing surface 31 of the roll 30) P.sub.r of the teeth that are formed on the processing surface 31 at a location in the radial direction of a portion of the processing surface 31 of the roll 30 where the tip end of one tooth of the plural teeth that are formed on the processing surface 31 of the roll 30 first comes in contact with the other end surface in the axial direction of the crimped section 20 are made to coincide (P.sub.h=P.sub.r).

(23) As a result, it is possible to prevent radial streaks 32 such as illustrated in FIG. 7 from being formed on the tip-end surfaces of each of the teeth of the hub-side face splines 21, and it is possible to prevent damage such as peeling from occurring on the other end surface in the axial direction of the crimped section 20. Therefore, when forming a wheel-drive bearing unit such as illustrated in FIG. 5 by combining a wheel-support rolling bearing unit 1 that was made according to the production method of this embodiment with a universal joint outer ring 2, it is possible to properly maintain an engaged state between the hub-side face splines 21 and the joint-side face splines 26, and to sufficiently maintain the life of the wheel-support rolling bearing unit 1.

(24) Furthermore, the pitch P.sub.r in the circumferential direction of the teeth that are formed on the processing surface 31 and the pitch P.sub.h in the circumferential direction of the hub-side face splines 21 that are to be formed on the other end surface in the axial direction of the crimped section 20 are made to coincide by regulating the swing center distance L and the swing angle . Therefore, it is possible to form various shapes (number of teeth N.sub.h, pitch circle diameter D.sub.h) of hub-side face splines 21 by adjusting the swing center distance L and the swing angle without having to replace the roll 30.

(25) In the manufacturing method for a rolling bearing unit of this embodiment, the pitch circle diameter D.sub.h of the hub-side face splines 21, the number N.sub.h of hub-side face splines 21, and the number N.sub.r of teeth formed on the processing surface 31 of the roll 30 are taken to be specified values, and the swing center distance L and the swing angle are regulated so that the relationship of Expression (1) is satisfied. However, in the present invention, the positional relationship between the main hub body 8 and the roll 30 can be set with other parameters taken to be specified values, and it is possible to regulate at least any one of the swing center distance L, the swing angle , and the pitch circle diameter D.sub.h of the hub-side face splines 21.

Second Example

(26) A second example of an embodiment will be explained using FIG. 1 to FIG. 3. In this example, first, the swing angle that is the inclination angle of the center axis of the roll 30 with respect to the center axis of the main hub body 30 is set to an arbitrary value. After that, the relationship (see FIG. 3) of the swing center distance L, which is the distance between the intersecting point of the center axis of the main hub body 8 and the center axis of the roll 30 and an imaginary plane that includes the other end surface in the axial direction of the crimped section 20, and the difference P (=P.sub.rP.sub.h) between the pitch P.sub.r in the circumferential direction of the teeth that are formed on the processing surface 31 of the roll 30 and the pitch P.sub.h in the circumferential direction of the hub-side face splines 21 is found.

(27) With the swing angle that is the inclination angle of the center axis of the roll 30 with respect to the center axis of the main hub body 8 fixed, a plurality of combinations (three in this example) of swing center distances L and pitch circle diameters D.sub.r of the teeth that are formed on the processing surface 31 of the roll 30 for giving a specified shape (number of teeth N.sub.h, pitch circle diameter D.sub.h) to the hub-side face splines 21 are found from diagrams such as illustrated in FIG. 2. Combinations of swing angle distance L, pitch circle diameters D.sub.h, D.sub.r and number of teeth N.sub.h, N.sub.r that were found in this way are given in the following Table 1.

(28) TABLE-US-00001 TABLE 1 Pitch Circle Diameter of Pitch Circle Swing Number of the Face Diameter of Center Face Spline Splines Number of the Roll Distance L Teeth D.sub.h Roll Teeth D.sub.r [mm] N.sub.h [mm] N.sub.r [mm] (A) 8.5 31 85.2 30 91.0 (B) 5.3 31 85.2 30 87.6 (C) 0.8 31 85.2 30 82.8

(29) The pitch difference P is calculated by substituting the swing center distance L, pitch circle diameters D.sub.h, D.sub.r, and number of teeth N.sub.h, N.sub.r into Expression (4). As illustrated in FIG. 3, a linear function relationship is established between the pitch difference P and the swing center distance L. By finding from FIG. 3 the swing center distance L where the pitch difference P becomes 0 (approximately 3.1 mm in the example in FIG. 3), it is possible to make the pitch P.sub.r in the circumferential direction of the teeth that are formed on the processing surface 31 of the roll 30 and the pitch P.sub.h in the circumferential direction of the hub-side face splines 21 when performing orbital forging. The construction and function of the other parts are the same as in the case of the first example of an embodiment.

Third Example

(30) A third example of an embodiment will be explained using FIG. 1 and FIG. 4. In this example, first the swing center distance L that is the distance in the axial direction of the main hub body 8 between the intersecting point of the center axis of the main hub body 8 and the center axis of the roll 30 and an imaginary plane that includes the other end surface in the axial direction of the crimped section 20 is set to an arbitrary value. After that, the relationship (see FIG. 4) of the swing angle , which is the inclination angle of the center axis of the roll 30 with respect to the center axis of the main hub body 8, and the difference P (=P.sub.rP.sub.h) between the pitch P.sub.r in the circumferential direction of the teeth that are formed on the processing surface 31 of the roll 30 and the pitch P.sub.h in the circumferential direction of the hub-side face splines 21 is found. In other words, with the swing center distance L, which is the distance in the axial direction of the main hub body 8 between the intersecting point of the center axis of the main hub body 8 and the center axis of the roll 30 and an imaginary plane that includes the other end surface in the axial direction of the crimped section 20, fixed, a plurality of combinations (six in this example) of swing angles and pitch circle diameters D.sub.r of the teeth that are formed on the processing surface 31 of the roll 30 for giving a specified shape (number of teeth N.sub.h, pitch circle diameter D.sub.h) to the hub-side face splines 21 are found.

(31) Next, the pitch difference P is calculated by substituting the swing angle and pitch circle diameter D.sub.r into Expression (4). FIG. 4 illustrates the relationship of the pitch difference P and the swing angle . By finding FIG. 4 the swing angle where the pitch difference P becomes 0 (approximately 5.5 degrees in the example in FIG. 4), it is possible to make the pitch P.sub.r in the circumferential direction of the teeth that are formed on the processing surface 31 of the roll 30 and the pitch P.sub.h in the circumferential direction of the hub-side face splines 21 coincide. The construction and functions of the other parts are the same as those in the first example of an embodiment.

INDUSTRIAL APPLICABILITY

(32) When embodying the present invention, from the aspect of obtaining hub-side face splines having a specified shape, preferably the pitch difference P is made to be 0 by at least one of the swing angle and the swing center distance L of the roll as done in each of the examples of an embodiment. However, when it is not necessary to strictly regulate the shape of the hub-side face splines, the pitch difference P can also be made to be 0 by adjusting the pitch circle diameter of the teeth of the hub-side face splines.

EXPLANATION OF REFERENCE NUMBERS

(33) 1 Wheel-support bearing unit 2 Universal joint outer ring 3 Outer ring 4 Hub 5 Rolling body 6 Stationary-side flange 7a, 7b Outer-ring raceway 8 Main hub body 9 Inner ring 10 Rotating-side flange 11a, 11b Inner-ring raceway 12 Small-diameter stepped section 13 Center hole 14 Small-diameter section 15 Bolt 16 Rod section 17 Male threaded section 18 Head section 19 Cylindrical section 20 Crimped section 21 Hub-side face splines 22 Mouth section 23 End wall section 24 Shaft section 25 Threaded hole 26 Joint-side face splines 27 Universal-joint inner ring 28 Ball 29a, 29b Retainer 30 Roll 31 Processing surface