Experimental Investigation of Efficiency Enhancement of Manual Transmission Gearbox Synchronizer Rings for the Enrichment of Gearshift Quality

In developing countries, manual transmissions are leading the market due to their efficiency and low cost. In a manual transmission, the synchronizers play a vital role in defining the gear shift quality. Manual transmission vehicles are getting refined for a pleasant driving experience. The gear shift quality is one of the unique selling points for the vehicle, so the automakers are focusing on the reduction of the gear shift forces. In a manual transmission, the synchronizers are used to match the speed difference between the upstream and downstream inertia for the gear-shifting process. The synchronizers have conical friction surfaces to generate friction and cone torque. The increase in cone torque reduces the gear shift impulse. The cone torque can be increased with mismatch tolerance in the frictional surfaces. In this technique, two cone angles are used for the frictional surfaces. The applied force on the synchronizer tooth compresses the synchronizer ring and closes the non-uniform clearance between the frictional surfaces. This generates uniform surface pressure and increases the cone torque. The design is validated for the increase in cone torque using the synchronizer test rig. The mismatch tolerance increases the cone torque and reduces the synchronization time. Due to the mismatch, after the synchronization, the synchronizer ring tries to come back to its original position. This avoids the sticking of the synchronizer ring over the gear cone. This quickly reduces the gear shift forces after synchronization. The gear shift quality is validated on the vehicle using the Gear Shift Quality Analyzer. The results confirm that the mismatch tolerance enhances the gear shift quality more than the conventional method of tolerancing of the frictional surfaces.