[New Car Technology] "Outlander PHEV" hybrid power system

Mitsubishi Motors unveiled the hybrid system of its plug-in hybrid electric vehicle (PHEV) Outlander PHEV in September 2012 (Figure 1). The Outlander PHEV is scheduled to be launched in Japan in early 2013 and will be launched in Europe and North America later.

Appearance. Photo taken from one side of the disassembled prototype.

The hybrid system consists of a 2.0L gasoline engine, a generator, and two motors. Although the engine power can be transmitted to the wheels, it is usually driven by the motor that generates electricity from the engine. Compared with other companies' PHEVs that have been launched, it is closer to the "Chevrolet Volt" of General Motors in the United States, which is mainly based on the motor, than the Toyota "Prius PHV" that emphasizes the driving force of the engine, and can be said to be a "range-extended engine pure electric vehicle."

The front part is equipped with an engine that serves as both an engine and a motor, and the rear part is equipped with another motor (Figure 2). One of its features is that since there is an inverter at the front and rear, hybrid power can be achieved with only the front parts. In the future, "it is envisioned that a derivative model using only the front system will be manufactured" (Ryugo Nakao, director of Mitsubishi Motors and general manager of the development department).

Figure 2: Hybrid system using a generator and two motors
A generator and a motor are installed at the front, and another motor is installed at the rear. The rear motor is basically the same as that of the i-MiEV. A lithium-ion rechargeable battery pack is installed under the floor.

From the front structure, the drive shaft is directly connected to the generator and engine and the motor (Figure 3). A clutch is also set between the engine and the drive shaft. The rear motor is also directly connected to the drive shaft.

Figure 3: Composition of the hybrid system
From the front, the drive shaft is directly connected to the generator-cum-engine and the motor. A clutch is provided between the engine and the drive shaft.

Normally, the clutch is used to disconnect the engine from the drive shaft, and the engine is used exclusively for power generation. The vehicle is driven by the power of the front and rear motors directly connected to the drive shaft. When a large driving force is required, such as when going uphill or accelerating at high speed, the clutch is connected to transmit the engine power to the drive shaft.

The generator and two motors are manufactured by Meidensha, and the generator has an output of 70kW. The front motor has a maximum output of 60kW and a maximum torque of 137N·m, while the rear motor has 60kW and 195N·m.

The reason why the front motor has less torque than the rear motor is because the front space is small. The rear motor of the new PHEV is basically the same as the "i-MiEV". Although the front is also the same, since it is based on a gasoline car, the generator and motor need to be stored in the space of the gearbox. Therefore, in order to reduce the size of the front motor, the torque is reduced.

A lithium-ion rechargeable battery manufactured by Lithium Energy Japan is installed under the floor. The power capacity is 12kWh and the voltage is about 300V. A full charge can travel more than 55km in pure electric vehicle mode. The weight of the hybrid system is about 270kg, and the battery accounts for about half. It is also equipped with a function to supply power to external devices from the battery through the vehicle socket.