Mitsubishi Fuso Buses and Trucks

Daimler’s Japanese brand Mitsubishi Fuso is employing a series hybrid for its city bus. Since 2004, five Aero HEV vehicles have been successfully used in three Japanese cities, where they have each been driven around 150,000 kilometers without encountering any problems.

The diesel engine is transversely mounted in the rear of the bus. The engine operates within an optimized characteristic map and drives a generator, which supplies energy to two electric motors located right behind the rear axle. By means of a special transmission, the motors’ torque is transferred to a portal axle. As with other advanced hybrid vehicles, the Aero HEV’s roof-mounted batteries are rechargeable lithium-ion packs.

At the end of September 2007, Mitsubishi Fuso presented the second generation of the bus under the designation Aero Star Eco Hybrid. The low-entry bus with 65 seats now has a compact four-cylinder diesel engine with only 4.9 liters of displacement. The engine delivers 132 kW (180 hp) and is used exclusively to supply electricity. The engine drives a fast-running generator that supplies two electric motors with 79 kW each.

When waiting at a red light or a bus stop, the diesel engine is automatically switched off. That’s why the vehicle’s doors and accessory components such as the auxiliary steering pump, air compressor, and air conditioning are operated electrically. The bus also starts off solely with electric power, and the diesel engine does not begin to supply electricity until medium speeds are reached. The kinetic energy produced by braking is converted into electricity and fed back into the batteries (recovery).

Mitsubishi Fuso presented its first battery-powered city bus back in 1973. In 1994, the company introduced a system for recovering braking energy. Among the brand’s environmentally compatible vehicles is also a natural gas-powered city bus that was presented in 2000.

The most successful hybrid truck to date is the Mitsubishi Canter Eco Hybrid. Around 200 units of the light truck have rolled off the assembly line since it was first presented in summer 2006. The Canter Eco Hybrid was the first light truck to satisfy Japan’s new strict emissions limits. In addition, the vehicle impresses with its very low fuel consumption, which is around 20 percent lower than that of a comparable diesel engine.

The core component of the drive system is a three-liter four-cylinder diesel engine delivering 92 kW (125 hp) and 294 Nm of torque. In relation to the vehicle’s total weight, the drive system is very compact and light. The vehicle has an exhaust gas recirculation system and a particulate filter. Linked to the internal combustion engine is a 35 kW electric motor that serves as a generator when braking. The recovered braking energy is stored in lithium-ion batteries with a capacity of 1.9 kWh.

The Canter Eco Hybrid switches between operating modes, depending on the driving situation. The electric motor is used to get the truck moving, and the diesel engine kicks in during rapid acceleration. The engine is responsible for driving power when the truck rolls along at a steady rate. When the vehicle is not moving, a start-stop function switches off the idling engine. With a vehicle weight of 2.9 tons and a GVW of 7.5 tons, the Eco-Canter has a high payload despite its hybrid drive system.

As a result of its success in Japan, the Canter Eco Hybrid will now be introduced to Europe as well. The first batch of ten vehicles recently commenced a three-year test period at a customer in the UK. Although the vehicles’ powertrain is technologically identical to that used in Japan, the trucks have been modified in line with European legal requirements and the engines have been adapted to meet European emissions regulations.

Using the Canter as the base vehicle, Mitsubishi Fuso displayed the first hybrid concept model of a dump truck at the Tokyo Motor Show 2007. An outstanding feature of the Canter Eco-D is the structure’s electrically operated dump function. The use of an electric drive significantly reduces noise and emissions, as the required energy is obtained from the batteries while the diesel engine remains turned off during dumping. The system could conceivably also drive other additional components such as cranes or boom lifts. The vehicle is equipped with the same parallel drive concept as the Canter Eco Hybrid.