Sandooja, A., "Double Indexing Synchronizer - To Amplify the Synchronizer Capacity," SAE Technical Paper 2012-01-2003, 2012, doi:10.4271/2012-01-2003.
Manual transmissions, dual clutch transmissions and automatic manual transmissions use a synchronizer mechanism to have smooth gear shifting inside the gearbox and good shift feel inside the driver's cabin. Smooth gear shifting is related to the time required to complete the synchronization process inside the gearbox and a good shift feel related to the force required to shift the gear inside the driver's cabin. Moreover, good shift feel depends on efficiency of gear shifter mechanism, driveline vibrations and double bumps.Transmission gear shifting performance is the major concern area for all automotive and commercial sectors of vehicles. Transmission gear shifting performance in synchromesh gearbox depends on the capacity of synchronizer to produce sufficient frictional torque in required synchronization time and shifting force on the lever. It has been observed during downshift, of low gears in automotive and all gears in commercial gearboxes, high shift force is required because of large gear reduction ratio. Therefore multicone synchronizers are used in low gears to get good shift comfort. But multicone synchronizers have some disadvantages as compared to single cone, such as cost against performance and additional components increase the complexity of synchronizer mechanism.This paper presents a higher level of transmission gear shifting performance, which amplifies the frictional torque on synchronizer without changing the shift force at the shift lever. Furthermore, synchronization time is reduced by keeping the same shift force at the shift lever. Hence, the capacity of conventional single cone synchronizer can be significantly increased by using the concept of Double Indexing. This paper provides the mathematical and analytical results and simulation of gear shifting performance, measured on test rig and in dynamic condition of vehicle.