Knowledge of Automotive Drive Systems - Synchronizer Chapter

　　Due to the fact that the input shaft and output shaft of the transmission rotate at their respective speeds, there is a synchronization issue when shifting gears. Forcefully meshing two gears with different rotational speeds will inevitably result in impact collision and damage to the gears. Therefore, the shifting of old style transmissions should adopt a "two foot clutch" method, with upshifts staying in neutral for a moment and downshifts requiring the throttle valve to be filled in neutral to reduce the gear speed difference. But this operation is quite complex and difficult to master accurately. Therefore, the designer created a "synchronizer" to achieve consistent speed and smooth meshing of the gears to be meshed through the synchronizer.

　　There are two types of synchronizers: atmospheric pressure and inertia.

　　At present, all synchronous transmissions use inertia synchronizers, which are mainly composed of joint sleeves, synchronous locking rings, etc. Its characteristic is to achieve synchronization through friction.

　　The engagement sleeve, synchronous lock ring, and the gear ring to be engaged all have chamfers (locking angles), and the inner conical surface of the synchronous lock ring contacts the outer conical surface of the gear ring to be engaged, generating friction. The locking angle and conical surface have been appropriately selected in the design. The friction between the conical surface allows the gear sleeve to quickly synchronize with the gear ring, while also producing a locking effect to prevent the gears from meshing before synchronization.

　　When the inner conical surface of the synchronous lock ring comes into contact with the outer conical surface of the gear ring to be engaged, the gear speed rapidly decreases (or increases) to be equal to the synchronous lock ring speed under the action of friction torque. The two rotate synchronously, and the speed of the gear relative to the synchronous lock ring is zero, so the inertia torque also disappears at the same time. At this time, under the pushing force, the engagement sleeve is unobstructed and engages with the synchronous lock ring gear, and further engages with the gear ring of the gear to be engaged to complete the shifting process.