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Internal combustion engines experience severe valve train wear and the reduction of valve seat and seat insert wear has been a long-standing issue. In this work, worn valve seats and inserts were examined to obtain a fundamental understanding of the wear mechanisms and the results were applied in developing new valve seat insert materials. The new exhaust valve insert material for gasoline engines is a sintered alloy steel containing Co-base hard particles, with lead infiltrated only for inserts used in unleaded gasoline engines. The new intake valve insert material for gasoline engines is a high-Mo sintered steel, obtained through transient liquid phase sintering and with copper precipitated uniformly. This material can be used for both leaded and unleaded gasoline engines. Valve and valve seat insert wear has long been an issue of concern to engine designers and manufacturers.

In recent years, demands for increased output and low fuel consumption in automobile engines have been mounting. Light weight and high performance is demanded of the main operating parts, such as pistons. In response to these demands, the crown thickness and pin boss unit thickness has been reduced by tremendous improvements in the fatigue strength, compared to strength obtained by conventional methods, by utilizing Squeeze Casting techniques. In addition, the thickness of the inside face of the pistons has been reduced by making use of a split core. Furthermore, by manufacturing a cooling gallery, the heat load has been reduced; by introduction of hollow regions, an extremely light weight and compact piston has been developed. Three new techniques are indicated here. Firstly, the technique of attaining soundness in material and excellent fatigue strength by the Squeeze Casting technique, which is superior to those attained by conventional methods.

Many studies have been reported concerning fundamental tribological research aimed at reducing the severe valve train wear that occurs in internal combustion engines. In this paper, cam follower wear was theoretically and experimentally analyzed at the material development stage. Statistical methods have been applied to practical use in determining the material properties quantitatively. Based on the results, a method for predicting cam follower wear has been derived which has made it possible to develop new valve train systems more efficiently. Further, a guideline for developing new wear resistant materials was also clarified. Finally, the precision high chrominum cast iron rocker arm is described, along with its application to a new NISSAN high-performance 4-cylinder DOHC engine, as an example of the use of this method to develop new wear-resistant materials.