This application discloses an aluminum alloy cylinder head for an internal combustion engine having an integral valve stem guide bore therein with integral wear resistant end portions of the bore formed by an integrally bonded but different metal alloy for forming the wear resistant end portions.
Aluminum alloy cylinder head with a valve guide bore to support a stem portion of a valve, said valve guide bore being integral with said cylinder head and having end means enhancing the wear resistance of the bore to rubbing by movement of the valve stem against said cylinder head, said cylinder head being formed with a relatively thick portion which is positioned at a location where said valve stem guide bore is desireable, said wear resistance means created by forming pockets at opposite ends of said thick portion, filling said pockets with a wear resistant alloy which integrally bonds with the aluminum alloy, and boring said guide bore through said filled material and said thick portion whereby said guide bore is produced with a cylindrical surface characterized by a midportion of relatively soft aluminum alloy and opposite end portions formed of wear resistant alloy.
In a conventional aluminum cylinder head, a tubular metal valve guide or sleeve is press fitted into a bore in the aluminum cylinder head. Without this separate valve guide, a rubbing stem portion of a valve quickly wears away at the soft aluminum or aluminum alloy of the cylinder head. This resultants in sloppy and non-axial valve movements and also the passage of relatively large quantities of lubricating oil to the engine combustion chamber by travel between the valve stem and the cylinder head.
Specifically, the cylinder head has a bore with integral portions of wear resistant metal alloy defferent from the head's aluminum alloy. The guide bore is formed by machining pockets into the cylinder head's aluminum alloy at end of a valve guide bore. Subsequently, a metal deposit technique is utilized to fuse a powdered metal alloy to the aluminum cylinder head and fill the pockets with a copper based alloy. Subsequently, a bore through the deposited material and through the cylinder head forms a valve guide bore with a wear resistant 'collar' or annullus formed at either end of the guide bore.
The steps for manufacturing the sleeveless aluminum cylinder head been indicated above in the description of the apparatus but further detail is included hereafter. Obviously, the first step is casting the cylinder head of aluminum. As previously stated, cast aluminum has insufficent hardeness to provide a durable cylinder head capable of long resisting wear by movement of a steel valve stem in a bore.
Although only a single embodiment of the subject valvetrain drive apparatus has been illustrated in the drawings and described in detail above, modifications will be readily apparent to one skilled in the art and the invention is to be described and defined.