A material for each of the hub shafts 1 of the driving and driven wheel bearing apparatuses D and F (the axle bearing apparatus of the invention) is formed into a predetermined shape, for example, by forging, and a through hole 5 having an inner diameter d is formed axially through a center portion of a cylindrical portion 4 in concentric relation thereto. The inner diameter d of this through hole 5 is smaller than an outer diameter of a spline shaft of a constant velocity joint which is to be fitted into a female spline portion 9 formed on an inner surface of the through hole 5 in the hub shaft 1 of the driving wheel bearing apparatus D.
The hub shaft 1 of the driven wheel bearing apparatus F is finally formed by finishing end faces of a flange 2 and an outer peripheral surface of the cylindrical portion 4 of its hub shaft material by machining.
Similarly, with respect to the hub shaft 1 of the driving wheel bearing apparatus D, the cylindrical portion 4, etc., of its hub shaft material are finished by machining, and further the inner diameter of the through hole 5 is enlarged, that is, formed into a larger diameter d1. This inner diameter d1 corresponds to an inner diameter defined by grooves in the spline shaft of the above-mentioned constant velocity joint. Then, the female spline portion 9 is axially formed on the inner surface of the diameter-enlarged through hole 5. As a result, a wall thickness t1 of the cylindrical portion 4 of the hub shaft 1 of the driving wheel bearing apparatus D is smaller than a wall thickness t of the cylindrical portion 4 of the hub shaft 1 of the driven wheel bearing apparatus F (t1<t).
When a bearing portion 10 is press-fitted on the cylindrical portion 4 of the hub shaft 1 of the driven wheel bearing apparatus F, the bearing portion 10 is tightened since the cylindrical portion 4 has the increased wall thickness t and hence increases rigidity, so that axial clearances of the bearing portion 10 are reduced (become smaller).
On the other hand, when a bearing portion 10 is press-fitted on the cylindrical portion 4 of the driving wheel bearing apparatus D, the amount of change (reduction) of axial clearances of the bearing portion 10 is smaller as compared with the driven wheel bearing apparatus F, since the cylindrical portion 4 has the reduced wall thickness t1 and hence has low rigidity. However, when the spline shaft of the constant velocity joint is fitted into the female spline portion 9 of the hub shaft 1, the bearing portion 10 is tightened by this spline shaft, so that the axial clearances of the bearing portion 10 are reduced as described above.
In this case, the wall thickness t of the cylindrical portion 4 of the hub shaft 1 of the driven wheel bearing apparatus F is set to a predetermined value obtained by calculation, and by doing so, the amount of reduction of the axial clearances of the bearing portion 10 of the driven wheel bearing apparatus F and the amount of reduction of the axial clearance of the bearing portion 10 of the driving wheel bearing apparatus D can be made generally equal to each other.
Thus, in the invention, the wall thickness t of the cylindrical portion 4 of the hub shaft 1 of the driven wheel bearing apparatus F is larger than the wall thickness t1 of the cylindrical portion 4 of the hub shaft 1 of the driving wheel bearing apparatus D, thereby the former cylindrical portion 4 has the higher rigidity. Therefore the axial clearances of the two bearing portions 10 press-fitted respectively on the cylindrical portions 4 of the hub shafts 1 of the driven and driving wheel bearing apparatuses F and D can be made generally equal to each other.
In the invention, the hub shaft material having the through hole 5 beforehand formed in the cylindrical portion 4 is prepared, and part of this hub shaft material is finished to provide the hub shaft 1 for the driven wheel bearing apparatus F. With respect to the driving wheel bearing apparatus D, part of the hub shaft material is finished, and then the through hole 5 is enlarged in diameter, and then the female spline portion 9 is formed on the inner surface of the diameter-enlarged through hole 5, thereby providing the hub shaft 1 for the driving wheel bearing apparatus D. Therefore, the common hub shaft (hub shaft material) 1 can be used for the driven and driving wheel bearing apparatuses F and D. Therefore, the production and inventory management are easier, and besides the costs can be reduced. Rolling elements 13 of the bearing portion 10 may be balls.
In the above description, although the present invention is applied to the illustrated axle bearing apparatus, the invention is not limited to it, but can be applied to any other suitable axle bearing apparatus. The rolling elements 13 of the bearing portion 10 may be balls.
Number | Date | Country | Kind |
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P2006-220896 | Aug 2006 | JP | national |