Reduction of Cranking Noise from High Voltage Starter for One-Motor Two-Clutch Hybrid Systems 2017-01-1167

In this paper, we propose a high voltage brushless AC starter that contributes to improved fuel efficiency and a reduction in the cost of the one-motor two-clutch hybrid system, which we call a 1MG2CL system. We have named it the HV starter, and it is composed of an AC motor, inverter and pinion with a shift mechanism. One of the issues with the 1MG2CL system is the high electrical energy when starting an ICE as it switches over from EV drive to HEV drive. While the ICE is starting, the main motor has to crank the ICE via the clutch; the clutch slips to absorb the main motor power, so the main motor has to output a high power to overcome the loss. Therefore, to contribute to reducing the electrical power by eliminating clutch slip losses, we developed an HV starter as a dedicated ICE starting device. Thanks to the reduction in electrical power, the HV starter is able to improve fuel efficiency and reduce system costs.

However, the major issue is the cranking noise generated by the pinion mechanism of the starter. We have developed a noise control strategy to solve this issue. The concept is to reduce the dependency of the pinion operation on the starter. We aim to utilize the ICE inertia energy in the later cranking process instead of starter cranking. Using the HV starter, which is a high power and controllable AC motor, we have managed to control the cranking noise to the target level, which is equal to the road noise during EV driving.