Optimum Design of Return and Cushion Springs for Automatic Transmission Clutches

Clutches and brakes are important elements in automatic transmissions in terms of function, number of parts and design works involved. Among the many design options and variables involved in the clutch and brake design, selection of return and cushion spring types and their characteristics are important for positive disengagement and better shift quality. However, not much information is available on the advantages and disadvantages of various return and cushion spring types, such as Multiple Round Wire Coil Springs, Flat Wire Wave Coil Springs, Disk Springs and Wave Springs.

In this paper, the functions and design requirements of return and cushion springs are reviewed. In order to provide some design guide lines for engineers, sample designs of return and cushion springs have been made using round wire coil, flat wire wave coil, disk and wave springs. A comparison of the results in terms of space, weight, cost and transmission performance is also provided.