Thermal Compensating Tapered Roller Bearing for Enhancement of Transmission and Transaxle Performance

Automotive transmissions and transaxles use aluminum housings for weight reduction and tapered roller bearings for increased reliability. The initial bearing setting is obtained by using selective shims to account for tolerance variations of the transmission or transaxle components.

Aluminum transmission and transaxle housings have a coefficient of thermal expansion approximately twice that of steel shafts and bearings. This difference results in a change to the initial bearing setting, as temperatures vary. For a direct bearing mounting arrangement (cup adjusted), the bearing setting becomes looser as the operating temperature increases, and tighter as the temperature decreases.

Improved operating bearing setting is achieved through the use of a thermal compensating bearing. This bearing incorporates an elastomeric ring in the outer race, or cup, which responds to temperature variations and maintains a close bearing setting range for improved bearing and transmission/transaxle performance. This paper describes the principles of a thermal compensating bearing and also provides test results illustrating the advantage of reducing transmission and transaxle shift force.