Development of CAE Technology for the Design Support of Piston Pin Circlip

This study focuses on the technology for establishing design criteria for the piston pin circlip (hereinafter referred to as "circlip"), which is a component that holds the engine piston pin. During the development of high-revving engines, failure of the piston sometimes becomes a problem, and the main factors are fatigue failure of the piston and falling of the piston pin. The falling of the piston pin is caused by the circlip disengaging from the groove by the inertial force due to the vertical motion of the piston. The circlip is compressed to the size of the piston circlip groove and assembled to the piston. Therefore, in order to prevent the circlip from falling out, it is necessary to compress it more and increase the reaction force acting on the groove. However, this measure raises concerns about the deterioration of the ease of assembly of the circlip. Therefore, it is necessary to establish evaluation criteria that prevent the circlip from disengaging and deterioration of its ease of assembly. To enable appropriate design of the circlip during the engine specifications review phase, we developed the following two technologies. The first is the development of a surrogate model that predicts the amount of plastic deformation of the circlip due to compression during the circlip assembly process and thermal loads during engine warm-up. This surrogate model was created using data obtained from actual measurement tests and CAE analysis, using a regression model. The second is the development of CAE technology that predicts the likelihood of the circlip disengaging, considering the amount of plastic deformation. These technologies were developed to support the optimization of circlip design and to contribute to improving the reliability of the engine.