Single vs. Multi-cone synchronizers with carbon friction lining – a comparison of load limits and deterioration behavior

Synchronizers are widely used in gear boxes of car and truck transmissions. Optimizing costs and improving the efficiency of gear boxes require knowledge about the relative load limits of single and multi-cone synchronizers with carbon friction linings and their corresponding deterioration mechanisms. Load limits for single and multi-cone synchronizers with carbon friction lining used in cars were determined experimentally using the component test rig SSP-180 and compared against each other. Different load stages were run in life cycle tests and the influences of sliding velocity, friction work and frictional power were investigated. The synchroniz-ers’ failure mode is described and the novel specific value μ_min,grad is introduced that is able to quantify the deterioration of different synchronizer systems. During life cycle tests at the same specific load level, the single cone synchronizers, contrary to expectations, displayed greater damage compared to the multi-cone synchronizers. Calculations of the friction surface temperature in thermo-mechanical simulations, in combination with experiments on the test rig, show that the maximum temperature during the engagement has a significant influence on deterioration and endurance life of synchronizers with carbon friction lining.