Two-piece friction-welded piston

摘要

A two-piece piston is formed by friction welding an upper member to a lower member, wherein the upper and lower members are precision cast to net final dimensions such that no post-casting machining is required prior to the friction-welding process. The upper member includes a substantially flat crown and combustion surface extending radially inward from the crown. The lower member includes a pair of opposing skirts, each having a bore formed therethrough for receiving a connecting rod pin. The upper member and lower member each include at least two corresponding connecting surfaces that form a welded joint therebetween when the upper and lower members are friction welded together. The finished piston includes an integral cooling oil reservoir adjacent to the combustion surface.

主权项

1. A piston for use in an internal combustion engine, said piston comprising:
an upper member, wherein said upper member is precision cast to net final dimensions, and said upper member includes a crown and a combustion surface extending radially inward from said crown, said upper member further including a first upper connecting surface and a second upper connecting surface, wherein said first and second upper connecting surfaces are concentrically oriented; and a lower member, wherein said lower member is precision cast to net final dimensions, said lower member having a pair of opposing skirts, each skirt having a bore formed therethrough, and said lower member further including a first lower connecting surface and a second lower connecting surface, wherein said first and second lower connecting surfaces are concentrically oriented; wherein said lower member is integrally connected to said upper member by friction welding such that said first upper connecting surface and said first lower connecting surface form a continuous first welded joint therebetween and said second upper connecting surface and said second lower connecting surface form a continuous second welded joint therebetween, wherein in the formation of the foregoing welded joints, the heat which is necessary to raise the temperature of the connecting surfaces to the level required to form a welded joint is solely and exclusively generated by the friction created by the continuous relative rotation between said upper member and said lower member as one of said upper member and said lower member is rotated and other of said upper member and said lower member is fixed, and applying pressure to either or both of the joining surfaces until the welded joint is completed upon which the rotation ceases, wherein said upper member and said lower member require no additional post-casting machining in order to friction weld together said upper member and said lower member.