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Fuel consumption and exhaust gas emission regulations are being tightened around the world year by year. Electric vehicles are needed to reduce carbon dioxide emissions. Especially, Plug-in hybrid heavy-duty vehicles (PHEVs) are expected to become widespread. PHEVs enable all-electric modes, as well as hybrid modes, using both engines and electric motors, but the control system significantly affects the characteristics of fuel consumption and gas emission. In this study, we used new testing machine (we call extended HILS) to analyze the fuel consumption and gas emission for different plug-in hybrid control systems and investigated the optimal control method for PHEVs.

Next-generation vehicles which include the Electric Vehicles, the Hybrid Electric Vehicles and the Plug-in Hybrid Electric Vehicles are researched and expected to reduce carbon dioxide (CO2) emission in the future. In order to reduce the emissions of the heavy-duty diesel plug-in hybrid electric vehicles (PHEV), it is necessary to provide the high exhaust-gas temperature and to keep the exhaust-gas aftertreatment system effective. The engine starting condition of the PHEV is cold, and the engine start and stop is repeated. And, the engine load of the PHEV is assisted by the electric motor. Therefore, the exhaust-gas aftertreatment system of the PHEV is not able to get the enough high exhaust-gas temperature. And, the warm-up of the exhaust-gas aftertreatment system for the PHEV is spent the long time. So, it is worried about a bad effect on the emission characteristics of the PHEV.

At interurban transportation, improvement of fuel economy of hybrid electric heavy-duty diesel vehicles, which assist drive-axle by using regeneration energy, is minimum, compared to heavy-duty diesel vehicles. One of the factors is that hybrid electric heavy-duty vehicles are not able to balance regeneration energy (input) and power energy (output) at high speed driving. One reason is not opportunity to operate of braking at high speed driving for the heavy-duty vehicle. In this research, we focus on the method used for the battery energy, and propose a new concept of hybrid electric system to efficiently utilize battery energy. That system consists of electrical booster for supercharging intake air into engine cylinder. We have confirmed the feasibility of the electric system of a new HEV concept by using the simulation I created.

Next-generation vehicles which include Electric Vehicles (EV) and Hybrid Electric Vehicles (HEV) are researched and expected to reduce CO2 emissions in the future. Generally, the main factor to support high efficiency of EV and HEV is the idle stop, motor assistance and regenerative braking. The vehicle mechanism of HEV is complex, compared with conventional internal combustion engine vehicle. Certification test method of gas emissions and fuel consumption is used driving mode, which is currently reflecting the typical driving conditions in the market. And driving mode of certification test is established focusing on the reproducibility of driving by conventional internal combustion engine vehicles. It is necessary to consider that the driving mode for the vehicle used regenerative energy is reflected correctly. And high accuracy certification test method for next generation HEVs is necessary in order to evaluate exhaust gas and fuel economy.

Next-generation vehicles which include Electric Vehicles and Hybrid Electric Vehicles are studied and expected to reduce carbon dioxide emissions. The number of small delivery hybrid trucks has increased in the commercial vehicle class. The engine load of a commercial hybrid truck is reduced by using an electric motor. Fuel economy of the hybrid truck is improved with the assist. On the other hand, exhaust-gas temperature is decreased, and it has a negative effect on the purification performance of aftertreatment system. In this report, the fuel performance and emission gas characteristics of marketed small hybrid trucks were surveyed using the chassis dynamometer test system.

From the perspective of improving the atmospheric environment, evaluating the fuel efficiency and exhaust gas emissions when using actual vehicles on real roads is necessary. Passenger vehicles apply RDE (real driving emission) test. However, unlike passenger vehicles, there are many types and models of heavy-duty vehicles; thus, evaluating all of these types using real driving emission tests is difficult. Therefore, we investigated the possibility of an alternative evaluation of heavy-duty vehicle based on a simulation method that uses a vehicle model for part of the evaluation. This alternative evaluation method is a combination of the “engine HILS (hardware-in-the-loop simulation)” method, developed in previous studies and can perform tests based on vehicle speed and driving wind that is reproduced in the engine bench to appropriately cool the engine and various devices.

In order to improve the fuel economy of the heavy duty trucks at a highway driving condition, the heavy duty hybrid trucks with new type of hybrid electric assist engine system were proposed at the previous report. The new system consists of a downsizing diesel engine with a two-stage charging structure, which has an electric supercharger with bypass circuit and a conventional turbocharger, the hybrid electric motor and the small-capacity battery. The electric power consumption of an electric supercharger is equivalent to the amount of the regeneration power produced during high-speed driving where the opportunity of the regeneration is small. In this report, an electric supercharger for the heavy duty hybrid truck was produced experimentally. First, the engine performance and exhaust emissions were investigated using the 4 cylinder diesel engine equipped with an electric supercharger.