Development of Joint Sheet Gasket with Reduced Amount of Aramid Fibers 2018-32-0026
Gasket made of joint sheet is widely used for mating surfaces of an engine and a transmission. Ahead of the law enforcement of banning of asbestos usage, Honda had already started to apply non-asbestos gasket using aramid fibers as the substitute material for asbestos all over the world. However, aramid fiber is very expensive while the sealing performance of a joint sheet largely depends on the added amount of aramid fibers. Therefore, when it is adopted, the resulting cost increase becomes an issue. Accordingly, we designed a material aiming at the cost reduction while maintaining the required reliabilities for a joint sheet in real applications mainly by reducing the amount of aramid fibers. According to the required characteristics for a joint sheet, the constituent materials of the middle layer were optimized by combining glass fibers with coarse-grained silica as a reinforcement substance into highly fibrillated aramid fibers as the base material. In addition, the material structure was optimized by adding a skin layer superior in shape-following and sealing against the fastened object. By combining these measures, reduction of aramid fiber amount was achieved without sacrificing required properties. Furthermore, by constructing a dynamic evaluation method considering the operating environment of the engine, it was made possible to evaluate the joint sheet specific performances with high accuracy. As a result, it enabled the development of a joint sheet using a less amount of aramid fibers, realizing low cost together with superior sealing performance with the long lasting durability.