C-Shaped Synchronizer Spring-theoretical Analysis and Validation 2012-01-2002

This paper presents the analysis and experimental validation of c-spring and its stiffness properties in the gear shift synchronizer system.

A synchronizer assembly for a transmission comprises of a synchronizer hub carried by a torque delivery shaft and a cone clutch member carried by a gear and a synchronizer blocking ring. The gear shift sleeve is meshing over the teeth of the clutch hub. The c-spring is positioned in the inner circumference of the rim position of the clutch hub and strut keys will be positioned at the slots on the clutch hub, which are usually 120 degree apart. As the sleeve moves while gear shifting, it pushes down the strut keys which compress the C-spring radially inward; this gives the strut load.

The strut keys, which are pushed down by the sleeve, will apply force on the c-spring from radial directions. Since the c-spring is in the shape of an arc it is assumed as a curved beam for the analysis. One half of the spring is taken for the analysis, which gives the shape of a bent beam and beam equation is applied to arrive at the empirical relation connecting the section modulus of the spring and the stiffness of the spring. Equations depicting the correlation between section modulus and other critical parameters related to c-spring design are also derived.

The validation of the analysis was done on the bench test rig set up. Simulation was done on the rig such that radial forces are acting on the c-spring, deflecting it radially, thus correlating the simulation with the assumptions considered while analyzing the problem. Validation was done on c-springs of different section modulus and varying cross-sectional area, to arrive at a better correlation with the theoretical analysis done. Synchronizer pack of a manual transmission with strut keys was taken as the experimental set up for validation. Validation was done for one hundred thousand cycles each for the all the samples and thus correlating the theoretical result with the actual result. Periodic change in the c-spring stiffness is noted in the test rig validation stage and the effect of scragging on the c-spring functioning is also studied.

The strut load while shifting the gear, which determines the shifting quality, depends upon the stiffness of the c-spring. Factors which play a role in determining the stiffness and resultant stresses of a c-spring are studied in this paper.