Manual transmission (MT) is still the most preferred solution for emerging markets due to the lower cost of ownership and maintenance coupled with a higher transmission efficiency. In this regard, continuous improvement of the transmission shift quality is quite essential to meet the growing customer expectations. In the present work, a detailed evaluation of the gear-shift impulse (experienced at the gear-shift knob) is conducted between two different architectures of a manual, high-torque (450 Nm input torque) inline transmission meant for a sports utility vehicle (SUV). The conventional manual inline transmission architecture comprises a common gear pair at the input of the transmission. While this input reduction architecture is the most widely used architecture, having the common gear pair at the output of the transmission is also another option.
The synchronizers of the manual transmission need to match the speed of the rotating components just before the gear-shifting event. The axial force required to achieve the synchronization depends heavily on the synchronizer torque capacity, reflected inertia of the rotating components, speed difference, and time required for synchronization. For the same synchronizer torque capacity, it is observed that a significant reduction (~ 40%) of the required axial force is possible by selecting the output reduction architecture. A reduction in the reflected inertia and speed difference are the main reasons for the observed results. Since the axial force requirement at the synchro-sleeve is directly proportional to the gear-shift force required at the gear-shift knob, a similar benefit could be achieved in the gear-shift impulse measured at the knob. The theoretical calculations are validated with the experimental measurements conducted through a sophisticated Gear Shift Quality Assessment (GSQA) equipment of RICARDO make. Detailed calculations of reflected inertia and speed difference in each operating gear along with the layout comparison are presented to support the measurement results.
The benefit of the output reduction architecture could be utilized either to reduce the gear-shift impulse or to reduce the cost by going for a lesser capacity synchronizer. Moreover, a reduced synchronizer capacity helps package the complete synchronizer pack (synchro rings, sleeve, hub, clutch body ring) with a reduced packaging space requirement.