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When the alkali metal-supported catalyst was treated at 830°C, the NOx conversion decreased because the alkali metals in the catalyst layer gradually moved to the cordierite honeycomb layer and reacted with the cordierite elements. This phenomena decreased to be added the basic metal oxide (α) in the catalyst layer. The improved catalyst with α 2 showed higher performance than the conventional catalyst in the model gas test. Moreover, the emission values of NOx, HC, and CO were 50% or less than Japanese domestic regulation values even after 830°C×60h heat treatment in a vehicle test.

A new type of lean NOx catalyst has been developed with improved thermal resistance. This lean NOx catalyst contains precious metals and NO2 adsorbents. The precious metals are used mainly for the oxidation reaction of NO, and the NO2 adsorbents are for the adsorption removal of generated NO2. The thermal resistance of the catalyst was raised by paying attention to the following points. 1) Improvement of thermal resistance for the NO oxidation activity by addition of a different precious metal element. 2) Prevention of thermal degradation of the NO2 adsorbent by addition of a new metal oxide. For item 1, Pd was added to the catalyst which had already included Pt. By having Pd coexist with Pt, the precious metal dispersion was kept high even after heat treatment, so the NO oxidizing ability was improved. For item 2, thermal degradation of NO2 adsorbent was prevented by addition of the new metal oxide (B) to the adsorbent.

Sulfur oxides endurance and heat resistance of the conventional catalyst were improved from the studies using synthetic model gas and vehicle test. The NOx purification performance was improved for lean NOx catalyst deteriorated due to SOx poising. However, the trapped SOx could be removed with CO in rich gas at 600°C. Moreover, the SOx removal could be promoted with a SOx release material (γ1). On the other hand, heat resistance of the catalyst has been improved by using new mixed metal oxides (C) as a NO2 adsorbent. The improved catalyst which contained γ1 and C showed superior heat resistance at 800°C and SOx durability compared to the conventional lean NOx catalyst in the model gas test. Also, in the vehicle test, the emission values of NOx, HC, and CO were 50% or less than J-ULEV regulation standards. These results show that the improved catalyst has a good purification performance of exhaust gas from a lean burn vehicle.

Development is proceeding on catalysts which separate the NOx in lean exhaust gas by adsorption and then reduce the adsorbed NOx in combustion exhaust gas with the stoichiometric or a slightly richer air fuel ratio, as well as exhaust conversion technology that uses these catalysts. Amidst this research it has been found that catalysts containing mixed metal oxides exhibit superior NOx adsorption performance, so the authors prepared a mixed metal oxide catalyst by adding precious metals and promoters, etc. The resulting catalyst has high heat resistance and also offers excellent SOx durability. These properties were presumed to be due to an adsorbent including the mixed metal oxide, and the relation between the physical properties and NOx conversion properties of the catalyst was investigated.

The purpose of this study is to develop a shaker teat method for analyzing and evaluating the dynamic characteristics of the total power plant vibration system more rapidly and precisely than the conventional engine running test. A power plant is excited at the connecting rods of both end cylinders, lubricating crank journals and crankpins. The shaker test was proved effective by comparing it with the engine running test. The results of both tests are equivalent in resonant frequency, mode shape, and vibration control effect. Furthermore, the multiple input burst random excitation was put into practical use for improving the reciprocity and coherence, and for reducing the measurement time. Based on this study, we have developed a power plant system with greatly reduced vibration amplitude.

Recently, the quietness of the passenger compartment has become an important quality for a vehicle, and as a result, various improvements have been made to reduce the passenger compartment noise level. Particularly engine noise, a major source of interior noise, has been studied for many years and has recently been reduced to an acceptable level. As a result, air intake noise, which was a relatively minor noise source in the past, has rapidly become a noticeable noise source. This paper describes a newly developed air intake system testing apparatus, which enables us to evaluate intake noise at an early stage of engine development and also describes how the new apparatus and approach was used to develop a low-noise air intake system. This apparatus, called the PULSATION SIMULATOR, reproduces intake pulsations in the actual engine using its cylinder head and reproduces intake air flow precisely.

Recently engine sound quality is becoming more noticeable as noise level in a vehicle passenger compartment has been decreasing. It is necessary to reduce such discomforting noise as rumbling noise in order to improve engine sound quality. This paper describes the experimental study to find out causes of rumbling noise in an engine structure and several investigations to reduce rumbling noise. Some new approaches have been introduced to evaluate the influence of an combustion impact, the movement of a crankshaft, timing of rumbling noise and so on. The result shows that the primary cause of rumbling noise is the movement of a crankshaft due to the impact of combustion and next is the vibration characteristics of the engine-transmission assembly (power plant). Finally superior engine sound quality is achieved by increasing counterweights and stiffness of a crankshaft and also by optimizing the spark advance and improving vibration characteristics of various engine parts.