Abstract
Valve seats assembled to the bottom of the cylinder head prevent the gas leakage in the ignition chamber adhering closely to the valves and need high abrasion resistance even the valves hammer valve seats repeatedly in the high temperature. The general ways to insert the valve seat into the cylinder head are freezing of valve seat press fitting and heating of head press fitting. Due to their high manufacture cost and lower inferiority rate, a new method called an ambient temperature press fitting is appeared. It can reduce a manufacture line installation cost, a running cost and field claims. But its theoretical background has not been proved yet. In order to develop a reasonable measure for the reliability, the hoop strain of valve seat is considered, which has not been tried before. The hoop strain and reaction force of the valve seat during the tight-fitting process were measured and the process FEA simulation of ambient temperature press fitting was performed. The FEA results showed a good relationship with the measured data. As the results, the proper range of the hoop strain is defined. And the range can be used as a guideline of the tight-fitting reliability when designing the interference tolerance of the valve seat and the cylinder head for the new engine. That scenario was proved in a real engine durability test.
Keywords: Cylinder Head, Valve seat, Press fitting, FEA, Simulation