Method of processing a shaft for hub unit

Abstract: The present invention discloses a processing method for a shaft for a hub unit comprising a shaft body portion (2) and a radial outward flange (3) provided on one end thereof. The processing method comprises the steps of: machining, on a root portion (5) of the flange (3), an internal diameter surface (7) and a side (8) of an annular portion (6) extending in a direction of axis X-X of the shaft body portion (2) and in a direction opposite to the shaft body portion (2); and clamping the internal diameter surface (7) with the side (8) of the annular portion (6) being a reference, in which clamped state a flange side (9) on the annular portion (5) side and an outer peripheral surface (10) of the shaft body portion are machine-finished.

Description: FIELD OF THE INVENTION The present invention relates to a method of processing a shaft for a hub unit, for example, a hub unit for automobiles. DE-A-4 015 231 discloses a method of processing a shaft which corresponds to the preamble of claim 1. DESCRIPTION OF THE RELATED ART A hub unit heretofore known is shown in Fig. 2. A shaft 20 has a shaft body portion 21 and a radial outward flange 22 provided on one end thereof. A roller bearing 23 is mounted on an outer peripheral surface 21a of the shaft body portion 21 of the shaft 20 and fixed by means of a nut 24 threadedly mounted on an end of the shaft body portion 21. The flange 22 is formed at its root portion 25 with an annular portion 26 which extends in a direction opposite to the shaft body portion 21. The shaft 20 is formed by forging, an internal diameter face 27 of the annular portion 26 is in the form of a forged surface of a bevel face, and at the time of forging thereof, a rotating dog 28 is formed. This rotating dog 28 is used when the flange 22 and the outer peripheral surface 21a of the shaft body portion 21 are subjected to machining or polishing with both center holes 29 and 30 being a reference. In this hub unit, the shaft 20 is processed by forging as described above. After that, processing is finished in one of two cases, in one case of which a side 22a of the flange 22 on the annular portion 26 side which constitutes a mounting surface relative to a mating member not shown and the outer peripheral surface 21a of the shaft body portion 21 which is a mounting surface of the roller bearing 23 are machined, and in the other case of which they are polished after machining. In the case where the machining is carried out, the center holes 29 and 30 formed in opposite ends of the shaft body portion 21 are clamped by centers 31 and 32 (Fig.3A) of a machining device, and the shaft 20 is rotated through the dog 28 of the annular portion 26 whereby the flange side 22a and the outer peripheral surface 21a of the shaft body portion 21 are machined. In the case where polishing is carried out, the polishing is carried out in two steps as shown in Fig. 3A and Fig. 3B. That is, in Fig. 3A, the center holes 29 and 30 formed in opposite ends of the shaft body portion 21 are clamped by the centers 31 and 32 of the polishing device, and the shaft 20 is rotated through the dog 28 of the annular portion 26 to first polish the flange side 22a, thus completing the first step. Subsequently, in the second step, in Fig. 3B, the flange side 22a after polishing is supported by a packing plate 33 and received by a shoe 34, and the outer peripheral surface 21a of the shaft body portion 21 is polished with the flange side 22a being a reference. In the above-described processing methods, the following problem sometimes occurs unless the management of the processing reference is sufficiently carried out. That is, in the machining, in the case where the axes of the center holes 29 and 30 are formed in the opposite ends of the shaft body portion 21, the flange side 22a and the outer peripheral surface 21a of the shaft body portion 21 are machined without being attended by stable rotation. Therefore, a deflection of the flange side 22a relative to the shaft body portion 21 cannot be suppressed. Further, since the polishing is carried out in two steps, in the case where the polishing is carried out in the state in which in the second step, foreign matter is moved in and between the flange side 22a and the packing plate 33, there occurs a problem in that a right-angled degree between the flange side 22a and the axis of the shaft body portion 21 fails to be maintained, so that the deflection of the flange side 22a relative to the shaft body portion 21 cannot be suppressed. SUMMARY OF THE INVENTION An object of the present invention is to provide a processing method capable of suppressing a deflection of a flange relative to a shaft body portion of a shaft for a hub unit. The constitution of the processing method for the shaft for the hub unit according to the present invention is as follows. The present invention provides a processing method for a shaft for a hub unit comprising a shaft body portion and a radial outward flange provided on one end of the shaft body portion, comprising the steps of: machining, on a root portion of the flange, an internal diameter surface and a side of an annular portion extending in a direction opposite to the shaft body portion, and clamping the internal diameter portion with the side of the annular portion being a reference, in which clamped state a flange side on the annular portion side and an outer peripheral surface of the shaft body portion are machine-finished. In the processing method for the shaft for the hub unit according to the present invention, the deflection of the flange relative to the shaft body portion can be suppressed by the constitution as described above. Further, since no center holes are formed in opposite ends of the shaft body portion, there provides an effect that the number of steps of processing are reduced. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an explanatory view of a processing method for a shaft for a hub unit according to one embodiment of the present invention. Fig. 2 is a sectional view of a conventional hub unit. Figs. 3A and 3B are respectively explanatory views of a processing method for a shaft for a hub unit according to prior art. DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described hereinafter with reference to the drawings. The construction of the entire hub unit is generally the same as in Figs. 3A and 3B described above in connection with the conventional apparatus except that both the center holes 29, 30 and the rotating dog 28 are not formed. Therefore, a duplicate explanation is omitted and only the portion of the processing method for the shaft for the hub unit according to the present invention will be explained. Referring to Fig. 1, a shaft 1 for a hub unit has a shaft body portion 2 and a radial outward flange 3 provided on one end thereof. A roller bearing 23 is mounted on an outer peripheral surface 10 of the shaft body portion 2 of the shaft 1, as shown in Fig. 2, and fixed by means of a nut 24 threadedly mounted on a thread portion 4 in the end of the shaft body portion 2. The flange 3 is formed at its root portion 5 with an annular portion 6 extending in a direction of axis X-X of the shaft body portion 2 and in a direction opposite to the shaft body portion 2. An internal diameter surface 7 and a side 8 of the annular portion 6 are machined after the shaft 1 has been forged. Preferably, the internal diameter surface 7 of the annular portion 6 is formed parallel with the axis X-X, and the side 8 of the annular portion 6 is formed vertically to the axis X-X. After this, the side 8 of the annular portion is supported by a jig B so that the internal diameter surface 7 is clamped by a jig A with the side 8 being a reference. In this clamped state, a side 9 (a mounting surface onto a mating member not shown) of the flange 3 on the side of the annular portion 6 and the outer peripheral surface 10 of the shaft body portion 2 are machine-finished. The deflection of the flange 3 relative to the shaft body portion 2 can be suppressed merely by the machining as described. As an incidental effect, it is possible to omit the polishing. Further, since the center holes are not formed in opposite ends of the shaft body portion 2 of the shaft 1, as in the shaft of the conventional apparatus, the processing of the center holes is not necessary to reduce the number of processing steps.

Claims: A method of processing a shaft (1) for a hub unit comprising a shaft body portion (2), a radially outwardly extending flange (3) provided at one end of said shaft body portion and having a flange root portion (5), and an annular portion (6) extending from the flange root portion in a direction opposite to and oriented coaxially to said shaft body portion, characterized in that the method comprises the steps of: machining at the annular portion (6) an internal diameter surface (7) and a front side (8) thereof; and clamping the internal diameter surface (7) with the side (8) of said annular portion (6) being a reference, in which clamped state a radially extending side surface (9) on said flange (3) located on the side of said annular portion (6) and an outer peripheral surface (10) of said shaft body portion (2) are machine-finished. The method of processing a shaft according to claim 1, characterized in that no center holes (29, 30) in opposite ends of said shaft body portion (2) are processed.

Inventors: KAWATANI TERUYUKI, SHIMIZU KOICHI, KAWATANI, TERUYUKI, SHIMIZU, KOICHI, Kawatani, Teruyuki, c/o Koyo Seiko Co., Ltd., Shimizu, Koichi, c/o Koyo Seiko Co., Ltd.
Applicants: KOYO SEIKO CO, KOYO SEIKO CO., LTD.
Application year: 1998
Main classification: F16C1
IPC codes: B23P13, B23B5, B23Q3