Hitting the road with hybrids: Kenworth launches two hybrid trucks for city delivery and utility truck applications.(TECHNOLOGY OF CLEAN AIR)

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Start-stop driving applications, such as delivery, have long been considered the ideal application for hybrid vehicles, as energy generated during braking is captured, it charges the hybrid system's batteries. Truck manufacturers, such as Kenworth Truck Co., are also realizing the benefits of hybrids in other applications such as utility trucks. Kenworth has introduced a hybrid variation for both delivery and utility applications.

Competing in the medium-duty range, Kenworth offers a delivery and utility hybrid trucks for its Class 6 T270 (19,501 to 26,000 lb. GVWR) and Class 7 T370 (26,001 to 33,000 lb. GVWR) truck models. Both models of the trucks are equipped with the Eaton hybrid system and powered by a PACCAR PX-6 diesel engine, a derivative of the Cummins ISB engine. The PX-6 engine is rated up to 300 hp at 2600 rpm, has up to 660 lb.ft. of torque and is equipped with a Cummins Filtration air filter and 56 gal. fuel tank.

Eaton is the system integrator for the hybrid system. The delivery truck consists of a dry clutch, Eaton UltraShift six-speed fully automated transmission, 60 hp 130 Amp motor/generator, a 340 Vdc lithium-ion battery package and a power management system.

The power management system is the brains of the Eaton hybrid system, telling the motor/generator to either propel or store energy. When the truck is started, the motor/generator acts as a starter--taking the place of the standard 12 V system. When the engine is at idle or when it is accelerating the truck, the power management system tells the motor/ generator to act as a propulsion motor by providing energy assistance to the engine as the vehicle gets up to speed, using electricity stored in the battery.

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At lower travel speeds, the truck primarily runs on electrical power from the motor and battery, as this provides enough energy to propel the truck without placing a load on the engine. When the truck reaches higher speeds, it runs in a blended mode, combining engine and electric motor power, which augments the engine with nearly 60 hp and allows it to run at a lower operating speed.