【正文】 ? Low tension piston rings ? Carburized connecting rods The roller coaxial VTEC structure (Fig. 11) is an adaptation of technology used in the Honda S2021 (high output sportscar engine) to a singlecam VTEC mechanism. The camshaft drive loss was reduced by 70% using a needle roller bearing in the area where the rocker arm slides on the camshaft. In addition, simultaneous reduction in both weight and size were achieved by incorporating the VTEC switching piston into the roller bearing inner shaft. Piston microdimple treatment consists of treating the surface of the piston skirt to create a microdimple surface. This increases the oil film retention performance and can reduce friction by approximately 30% when lowfriction oil is used. Figure 11. Section view of Roller VTEC These effects resulted in the development of a 0W20 grade low viscosity oil that plies with ILSAC standards. The friction reducing effects of superlow viscosity oil were measured by engine motoring. These measurement results are shown in Fig. 12. In the current technology engine, the HTHS viscosity at the limit friction value was approximately mPas. Being used together with the advanced low friction engine, the limit value was lower than the current technology engine These low friction technologies have vastly reduced the overall engine friction, as shown in Fig. 13. In total, they have realized a reduction in friction of 10% or more pared to a conventional liter engine design . Figure 12. Limit in friction reduction Figure 13. Engine friction . WEIGHT REDUCTION – The structure and materials of almost all parts in this engine have been reviewed with the aim of creating the lightest engine in the world in the liter class. This weight reduction extends even to the skeleton structure technology and materials technology fields carburized connecting rods as used on the S2021 (high output sportscar engine). Carburization strength enhancement technology contributes greatly to increasing engine operational speed. We applied this strength enhancement technology to create a slim connecting rod design for the IMA engine. This resulted in a weight reduction of approximately 30% pared to conventional connecting rods. Most oil pans are made of steel plate or aluminum alloy. Conventional magnesium materials have had problems withstanding the high temperatures of engine oil. In contrast to conventional materials, which experience a significant drop in creep strength at 120176。C or higher, we have developed a new magnesium oil pan (Fig. 14) which ensures sufficient creep strength up to 150176。C. Figure 14. Magnesium Oil Pan This oil pan is fastened using steel bolts with aluminum washers to prevent galvanic corrosion. The oil pan weight is 35% lighter than an aluminum oil pan, for a reduction in weight that is parable to the ratio between the specific masses of the two metals. In order to expand the application of plastic parts, plastic materials were adopted for the intake manifold, cylinder head cover, water pump pulley, and intake system parts. These changes brought the discrete dry weight of the engine to less than 60 kg, which is the lightest weight in the world for the liter class. . EXHAUST EMISSION PERFORMANCE – Technology for simultaneously achieving both lean burn and low exhaust emissions was adopted in this engine, achieving a notable reduction in NOx emissions. Combustion was improved by putting the exhaust system to the rear of the engine (Fig. 15). In addition, the exhaust manifold was integrated with the cylinder head and a NOx adsorption catalyst which reduces NOx emissions during lean burn operation was also newly developed. Figure 15. Section view of emission system . Integrated Exhaust Manifold and Cylinder Head – Conventional cylinder heads have independent exhaust ports for each cylinder and a separate exhaust manifold acts to converge these exhaust ports into a single port is then mounted to the head. However, the new head on the Insight has a structure which converges the exhaust ports into a single port inside the head, as shown in Fig. 16. This greatly reduces the weight. In addition, the small heat radiating surface area reduces the exhaust gas heat loss, thus enabling early catalyst activation. Figure 16. View of Head . Lean NOx Catalyst – The catalyst system on the Insight bines a conventional threeway catalyst with NOx adsorbing materials. The NOx conversion mechanism of the newly developed catalyst is shown in Fig. 17. The NOx in the exhaust gas is adsorbed and separated by the NOx adsorption action of the catalyst during lean engine operating conditions. Conventional threeway catalyst operation reduces part of the NOx to nitrogen and oxidizes most of the HC and CO to CO2 and H2O during lean operation. However, since the exhaust gas contains large amounts of oxygen, there is relatively little NOx reduction with the threeway catalyst and most of the NOx is stored on the surface of the adsorbing material. When the exhaust is held at the theoretical air fuel ratio (stoichiometry) or richer airfuel ratio, the adsorbed NOx is reduced to nitrogen using HC and CO as reducing agents. The adsorbent is regenerated at the same time. Thus, NOx, HC and CO are effectively converted using the threeway catalytic action of the catalyst bined with the NOx adsorber. This type of catalyst exhibits superior conversion performance during both lean operation and stoichiometric operation by switching between lean and stoichiometry operating conditions. It is essential to create a regenerative atmosphere before the NOx adsorption capacity bees overloaded. This catalyst directly adsorbs NOx during lean burn engine operation and the adsorbed NOx is then reduced and exhausted as harm