1. Field of the Invention
This invention relates in general to setting antifriction bearings, and more particularly to a method and apparatus for pre-loading pinion tapered roller bearings.
2. Description of the Prior Art
Conventionally, a shaft that rotates within a housing requires bearings of some type to support it in the housing, and where the shaft must rotate with precision or carry significant radial and axial loads, the bearings are often single row tapered roller bearings. When mounted in pairs, these bearings must be adjusted against each other to control an end play or preload in the bearings, or in other words, to bring the bearing to the proper setting. Too much end play detracts from the stability of the shaft. Preload, while keeping the shaft rotating about a fixed axis, if excessive, will produce too much friction within the bearings and cause them to experience early failure.
Within a pair of single row tapered roller bearings the setting depends on the axial spacing between the inner races or cones of the two bearings and the axial spacing between the outer races or cones of the two bearings. Various procedures and appliances exist for determining the proper spacing. Changing the spacing between the cones will alter the setting for the combination.
Tapered roller bearings find widespread use in automotive equipment—from small automobiles to large trucks. In the typical rear wheel drive vehicle, the longitudinal drive or propeller shaft is connected to a pinion shaft, which forms part of a vehicle's axle assembly. The pinion shaft typically rotates on two single row tapered roller bearings, which are located in a housing or differential carrier. The pinion shaft must rotate with considerable precision, lest the pinion carried by it will not mesh properly with a large ring gear in the differential assembly and thereby produce noise and excessive wear. To achieve this precision, the pinion shaft and the housing must not only be machined accurately, but the bearings must be set properly to a condition of slight preload where no radial or axial end play exists in the pinion shaft. The preload in the bearings imparts rigidity to the shaft, but too much preload will cause the bearings to overheat and fail prematurely. On the other hand, too little preload may cause the bearings to acquire end play, and this likewise decreases the life of the bearings and introduces radial and axial play into the shaft.
Several procedures exist for setting these bearings. One of the procedures for setting the pinion shaft bearings of automotive axles controls the setting of the bearings with a shim located between the inner cone of a rear bearing of the pinion shaft and a bearing support surface formed on the pinion shaft for axially supporting the inner cone of the rear bearing. Typically, the inner cone of the rear bearing is clamped between the pinion shaft and an end yoke, which is in turn secured by a nut, with the shim determining the distance between the two cones and hence the setting of the bearings.
However, a process of selecting a thickness of the shim remains a complex and laborious task, since it in essence relied on a trial and error procedure. With each new shim, the pinion shaft would be rotated to determine the amount of torque transmitted by the bearings, and when the torque fell within an acceptable range, one assumed that the assembly contained the shim of a proper thickness.