Performance Evolution of a One-motor Two-Clutch Parallel Full Hybrid System

This paper describes the performance evolution and key breakthroughs of the world's first one-motor two-clutch (1M2CL) parallel full hybrid system without a torque converter that was developed and implemented on a hybrid luxury sedan in November 2010. The high potential of this hybrid system was brought out further to improve fuel economy without sacrificing acceleration performance. The resultant second generation of the 1M2CL parallel full hybrid system was applied to a hybrid premium sports sedan in August 2013. In order to improve these performance attributes, the following key technical measures were adopted: 1. Motor torque during the EV mode was increased to expand the EV drive region. 2. Maximum motor torque and battery power at engine startup were boosted to reduce the engine start time. 3. Integrated control of the motor and clutches was improved. 4. Mechanical efficiencies were improved for higher fuel economy. Increasing the motor torque was an especially key technical measure for expanding the EV drive region and reducing the engine start time. That was achieved by confirming system durability based on extensive data obtained in public road testing. As a result, the motor torque in the EV mode and at engine start was increased by 20 Nm over that of the firstgeneration system. Owing to these breakthrough advances, both fuel economy and acceleration time was improved from the first-generation system to achieve the fastest acceleration of all vehicles in its category.