The present invention relates to a bearing apparatus of a type used for bearing a driven shaft of an automobile and having a rotational speed detector which detects the rotational speed of the wheels connecting with the shaft so that the wheels do not lock, when brakes are suddenly applied, by controlling the brakes according to the detected rotational speed.
A conventional bearing apparatus of the above type is shown in FIG. 5 (according to Japanese Laid-open Patent Application No. 63-166601). This bearing apparatus has a cylindrically shaped outside member 50 fixed to a chassis of an automobile (not shown), a cylindrically shaped inside member 51 which includes a driven shaft and which is coaxially positioned inside of the outside member 50, rolling elements 52 in double rows which roll between a raceway surface 50a of the outside member 50 and a raceway surface 51f of the inside member 51, and retainers 53 which hold the rolling elements 52. The inside member 51 has a flange 51b at its one end 51a to which a wheel (not shown) is mounted, and a detected member 51e on the other end 51c. The detected member 51e has multiple projections 51d spaced apart at even intervals in a circumferential direction. A closed-end, cylindrically shaped cover 54 is provided at the end 50b of the outside member 50 in such a manner as to enclose the detected member 51e. A rotational speed detector 55 is fixed in said cover 54 and held in such a manner as to be opposed to said detected member 51e at a specified distance.
Mounting of the rotational speed detector 55 in the cover 54 is accomplished by first mounting the cover 54 to the end 50b of the outside member 50, and then press fitting the rotational speed detector 55 into a hole 54a of the cover 54. According to this mounting method for the rotational speed detector 55, it is impossible to place a jig having a strike surface inside of the cover 54 and to press fit the rotational speed detector until the rotational speed detector 55 is mounted. Therefore, the rotational speed detector 55 cannot be readily and precisely positioned relative to the detected member 51e. It might be possible to control the insertion of the rotational speed detector 55 by controlling the dimension (dimension d in FIG. 5) of a portion of the rotational speed detector projecting outwardly in the axial direction from the cover 54. However, there can be variations in said dimension in the axial direction. Therefore, precise positioning of the rotational speed detector 55 relative to the detected member 51e cannot be performed even with this method.
Because sufficiently high precision cannot thus be obtained in positioning the rotational speed detector 55 relative to the detected member 51e, the conventional bearing apparatus presents the problem of low precision in the rotational speed detection.
Furthermore, because the rotational speed detector 55 is fixed in the cover 54 by press fitting, the seal performance of the cover is low at the fitting portion, and water and other foreign matter can penetrate inside the cover. An additional problem concerns the gradual loosening of the cover at the fitting portion due to vibrations.