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In order to reduce diesel NOx emissions, aftertreatment methods including LNT (Lean NOx Trap) and urea SCR (Selective Catalytic Reduction) have been researched. One of the shortcomings of urea SCR is its NOx reduction performance degradation at low exhaust gas temperatures and possible emission of unregulated byproducts. Here, a new type of a urea-dosing device to overcome these shortcomings is studied. This dosing device actively produces ammonia without depending upon the exhaust gas temperature, and designed for onboard application. The device incorporates an electrically heated bypass with a hydrolysis catalyst. An injector supplies urea solution into the bypass. The bypass is heated only when thermolysis is needed to produce ammonia (NH3). The hydrolysis catalyst further assists in the production of NH3. The ammonia gas obtained is then mixed with the main exhaust gas flow.

The urea-SCR system is one of the most promising aftertreatment systems for future automotive diesel engines. We developed a urea dosing device with twin urea injectors for onboard applications, to enhance the NOx reduction performance at low exhaust temperatures and to lower the electric power consumption of the SCR system. The injectors operate with a single-phase urea solution, without air assist. Of the injectors, one is used to supply urea to a bypass passage routing the exhaust, during low exhaust temperatures. The other injector is located on the wall of the main exhaust duct, directly supplying urea to the exhaust. This direct injection method has a uniform spray distribution problem. A set of impact plates were used to distribute the spray. Impact plates have a high potential for deposition, but use of film boiling was considered. A thermal analysis was conducted and as a result, deposit conditions were theoretically derived. This was confirmed through experiments.

We have predicted the hill climbing performance of a batteryless motorized-four-wheel-drive (M4WD) system. With this type of M4WD system, the engine drives the front wheels, and an electric motor drives the rear wheels. The electrical power to the motor is supplied directly by the M4WD generator (water-cooled alternator for M4WD use only) driven by the engine. The system is small and simple due to this batteryless powertrain. However, predicting hill climbing performance is complex due to the power tradeoff between the front and rear wheels. We clarify nonlinear mechanical and electrical power flow models, and discuss how our M4WD vehicle simulator using these power flow models is able to predict hill climbing performance. The performance we predicted agreed well with the actual performance of a prototype vehicle.

A potentiometer-type throttle-position sensor, wiring, a connector, and a cover for the throttle drive mechanism are integrated in order to reduce the size of an electronic-throttle-control actuator. The throttle-position sensor inside the integrated cover showed a large signal deviation when the environmental temperature changed. This output deviation was caused by the temperature expansion of the plastic material of the integrated cover. With the aim of decreasing the output deviation, we analyzed the temperature sensitivity of the throttle-position-sensor output in order to find optimum location for arc-shaped resistor track, and we increased the rigidity of the plastic gear-cover in order to decrease the effect of the temperature expansion.

An electronic throttle actuator with a faster response time and reduced peak current was aimed for the DI-G engine. An qualitative analysis of the drivetrain of the throttle actuator is performed. It was found that to obtain faster response, inertia, motor inductance, and motor resistance need to be reduced, while the reduction gear ratio has an optimal value. On the other hand, to reduce the peak current, motor inductance, motor resistance and the reduction gear ratio must be increased. Based on this analysis, a more detailed numerical calculation is done and design parameters are optimized. An actuator with optimized parameters is prototyped and showed 20% faster response time and 50% lower peak current.

The hot-wire(H/W) element of an air flow sensor has a tendency to indicate lower than actual flow rate when subjected to large-amplitude oscillatory flow. First, the causes for this measurement error is investigated and a new dynamic model for H/W is proposed. The dynamic model is a combination of the static non-linearity output characteristic of the H/W element and the dynamic response of the H/W element. Second, a signal processing method is developed to correct the measurement error of the H/W by inversing the proposed H/W dynamic model. The result shows that by using this signal processing method, the measurement error of the H/W is reduced.