Isuzu has developed a diesel hybrid truck targeting the distribution truck market based on the new Elf commercial vehicle. The new hybrid truck enables a reduction in vehicle maintenance costs and a reduction in driver fatigue in addition to substantial improvement in fuel economy owing to effective recovery of kinetic energy during deceleration utilizing the feature of the Smoother-E Autoshift system, the proprietary technology of Isuzu. The following are the objectives and outline of development.

Recently, the increase in the average temperature due to the effect of earth-warming gases, such as CO, is a focus of attention as an environmental issue. In the Kyoto Protocol, Japan agreed to reduce the emissions of earth warming gases by 6% from the level in 1990 by the year 2012, and the reduction of CO emitted from automobiles, i.e., an improvement in fuel efficiency, and the reduction of particulate matter (PM) emitted from diesel vehicles is an urgent issue.
Isuzu introduced the compressed natural gas (CNG) vehicle as a low emission vehicle that emits virtually no PM, and it is becoming popular with urban customers where PM pollution is a pressing issue. However CNG vehicle requires CNG stations (establishment of infrastructure), and one of the reasons that prevent the spread of CNG vehicles in non-urban areas will be the uneven distribution of CNG stations into urban areas. Because the new hybrid vehicle is based on a diesel vehicle, which utilizes diesel fuel, its use is not restricted by infrastructure and can be used anywhere, urban or rural. In the hybrid vehicle, kinetic energy during deceleration generates electricity, which is stored in the battery, and the electric energy helps to start and accelerate the engine with a torque assist from the electric motor. Improvement of fuel efficiency and reduction of CO emissions are also realized. When combined with reduced idling, a 35% improvement in fuel efficiency can be realized. By installing the well-received Diesel Particulate Defuser (DPD) installed on the Elf introduced in 2004, emissions of PM are substantially reduced.

Fig. 1 Outside View of the Hybrid Vehicle

To fully utilize the feature of the hybrid vehicle (utilization of kinetic energy during deceleration) six model types shown in Table 1 are introduced targeting distribution trucks that frequently accelerate, decelerate, and stop.
The number of requests to reduce the vehicle life cycle cost has recently increased, and the manufacturer should satisfy such requests. In response, the Smoother-E Autoshift system (optional equipment in the Elf truck and compatible with the A/T restricted license) is equipped as standard, and results in
(1) No need for clutch plate replacement
(2) Reduction of driver fatigue
(3) Hiring of drivers with A/T restricted license
Idling stop is also standard to further improve fuel economy and reduce emissions of CO.