Calculation and Verification of the Real-Time Working Characteristics of a Viscous Coupling

Abstract

During operation, the shear friction between the silicone oil and the plates of a viscous coupling (VC) will generate heat and increase the temperature of the silicone oil, inflate the volume, increase the internal pressure, and eventually deliver more torque, in what is called hump operation mode. Temperature is the root cause of the change of the operation characteristics in VCs. In this paper, the heat-transfer model for a VC is established based on the thermodynamical theory. The capacity of the heat transmission of each part of the VC are calculated to obtain the temperature of silicone oil. The real-time shear torque of the VC is finally obtained. Then, the theoretical analysis on hump phenomenon was done. The internal pressure was obtained by analyzing the characteristics of ideal gas, and the maximum torque during the hump phenomenon was calculated. The simulation of the key parameters and the entire working process for the VC were carried out based on the proposed calculation model. A prototype of a viscous limited-slip differential (VLSD) was developed to test the output torque characteristics. The test results were quite consistent with the simulation results, and the accuracy of the calculation model was verified.

Keywords

• viscous coupling (VC)
• viscous limited-slip differential (VLSD)
• torque characteristic
• thermodynamics