Analytical Studies on Sealing Design for CVJ Boot 2004-01-1324

This paper presents a new concept of thermoplastic polyester elastomer boot (here in after referred to as TPEE boot) fitted for inboard, constant velocity universal joint (here in after referred to as CVJ). The CVJ has an irregularly shaped, tri-lobed housing for the purpose of weight and noise reduction. In this investigation, we carried out a series of analysis using FEM to develop the boot design. Our successful TPEE boot comprises two distinct features: (1) a boot with its inner surface sealing portion shaped to fit the outer surface of tri-lobe CVJ housing, and (2) a grommet to be fitted onto the boot and fastened by a clamp from the outside.

Conventional boots for CVJ with tri-lobe shaped housing usually have a sealing portion of cylindrical profile, and a bushing is applied therein to fill the clearance between the CVJ housing and the boot sealing portion. The novel concept described herein is a particular method of applying a grommet outside of the boot. Therefore, when a clamp is applied and fastened thereon, satisfactory contact pressure is established between the CVJ housing and the TPEE boot. In addition, the clamping force is directly applied on the CVJ housing, which enhances the sealing performance of the boot. Because of the TPEE material for the boot, the low temperature effects have been taken into consideration. By means of FEA, we predicted the formation of clearance caused by a difference in thermal shrinkage between the CVJ housing and the boot. We also carried out FEA to determine if there is grease leakage through the boot sealing portion arising from the boot slip at the start of rotation at low temperature operating condition. Based on the FEA results, we developed a more robust TPEE boot that could provide satisfactory sealing under any operating conditions.