Automotive Synchronizer with Asymetric Toothing 2011-01-0724

In automotive Transmission especially in Manual shift Transmission, a mechanism is provided for smooth and quick shifting of gears known as Synchronizer. A synchronizer mechanism having a Sliding shift sleeve, synchronizer ring, clutch body and clutch body ring as the main components to shift the gears smoothly. A synchronizer ring and Clutch body ring having outer tooth with inclined faces i.e. chamfer on their end facing towards gear shift sleeve, having inclination faces to mesh with the same inclined faces of blocker ring and clutch body ring for smooth shifting with less effort. Generally in cold environment certain forces are acting inside the Transmission to reduce the speed of rotating elements, these force are called drag forces. Mostly these drag force are generated due to high viscosity of transmission oil and large Inertia of masses of rotating elements, bearings and oil seals friction etc.. When the rotational speed of gearwheel and the shift sleeve becomes zero after synchronization, and sleeve starts to travel towards the clutch body ring via Blocker ring then these drag forces further reduce the speed of gearwheel and hence arise of scraping Noise known as “Cold Clash or Cold scratch”. This paper presents the method to avoid the Scraping Noise and smoothen the shifting of Gear. To reduce this cold clash the inclination or chamfer on the end faces of Sleeve tooth and Clutch Body ring tooth are so designed asymmetrically in such a manner that the check faces 30 leading in the sense of direction of rotation 25 have a greater axial displacement than the check faces 31 trailing in the sense of direction of rotation as shown in Figure-1. This ensures that sliding sleeve exerts the pressure on the blocker ring even after achieving the synchronous speed, to allow the gearwheel to rotate with synchronous speed against existence of drag or high braking forces acting on transmission, particular due to high viscosity of cold transmission oil which affects the synchronizer performance.