Development of Toyota Mild Hybrid System (THS-M) with 42V PowerNet

For the first time ever a hybrid system using a 42-V power supply system has been developed for better fuel economy, lower emissions and urban environment. And Toyota Mild Hybrid System (THS-M), which is the first mass production vehicle with dual voltage(42V/14V) has been launched to the Japanese market In August, 2001. This paper introduces the system configuration, features and gives actual vehicle evaluation results. The system has a motor generator (hereinafter M/G) connected to the engine crankshaft via a belt, in place of the alternator on a conventional vehicle. The electronic control of the M/G has five functions: restarting the stopped engine, driving the vehicle when starting, driving auxiliaries when the engine Is stopped, power generation during ordinary traveling and regenerative braking on deceleration braking. By restarting the engine via a belt with motor driving control, a smooth starting without discomfort is achieved. Furthermore, using this motor to drive auxiliaries during Idle increases the number of idle stop opportunities. Installing this system on a direct injection 3.0 liter engine with a 5-speed automatic transmission improves fuel economy by about 40% in the Japanese standard urban mode, when compared to the average fuel consumption of vehicles in the same class without the system.