A Method to Assess Grease Temperature Response in CVJ Applications

The constant velocity joint (CVJ) has seen increased usage driven by the growth of front wheel drive vehicles over the last 30 years. The CVJ provides a smooth, dynamic connection between the output of the axle or gearbox and the driving wheels of the vehicle. The seemingly simple device, however, requires specially designed greases to maximize protection of the internal components from distress and provide optimum performance and service life. One measure of potential distress in the CVJ can be related to temperature rise which is a reflection of the friction and wear properties of the grease employed.

A test rig was designed and a method created to evaluate the temperature response of different greases used in a CVJ. The test rig was designed to allow a wide range of speeds, torques and shaft angles to be used. The rig uses a unique temperature pickup system to allow for dynamic measurement of the grease temperature in the boot. The test method described here is based on calculated road load power requirements needed to move a compact vehicle over a wide range of speeds and road grade conditions. The resulting 27 step test matrix evaluates the response of the test grease over 9 speed - torque levels and 3 shaft angle settings. The method shows that different greases can be distinguished by their stabilized operating temperature over a variety of operating conditions using the test rig and method described here.