Optimal Design of Roller One Way Clutch for Starter Drives 2004-01-1151

The starter drive clutch is a one way roller clutch and a key component in a starter motor that is used to crank internal combustion engines. The starter drive clutch transmits torque from an electrical motor to a ring gear mounted on a cranking shaft in an engine thus cranks the engine. The clutch also prevents the whole starter from damage caused by extremely high load and/or extremely high speed applied to the starter pinion from the engine.

Drive slippage and barrel cracking are two major failure modes for the starter drive[1]. Insufficient torque capacity results in drive slippage while excessive high hoop stress on the clutch barrel ring causes barrel crack. To eliminate drive slippage failure, the clutch should be designed with high torque capacity. High torque capacity, however, is a cause of high hoop stress on the barrel that may result in the cracked barrel failure. Higher torque capacity and lower hoop stress are two completely opposite design directions. So, an optimal design approach should be applied to the clutch design. The optimal design of the clutch is maximizing torque capacity of the clutch and minimizing hoop stress on the barrel. Thus, optimization of the clutch is to design a clutch to achieve maximum torque and minimum hoop stress. To achieve this goal, an optimization model is derived based on the mechanism of the clutch. A sensitivity analysis is used to select the most effective parameters for the optimization in this multiple variables optimization. A constant strut angle is introduced to reduce changing strut angle during the clutch works. Finally, a case study shows this optimal design approach improved clutch design.