Cylinder head assembly having a hybrid valve seat insert

Abstract

A cylinder head assembly for an internal combustion engine includes a main body, a valve seat insert, and at least one flow passage extending through the main body. The main body may be formed from a first material and defines a recess configured to cooperate with an associated cylinder bore and piston to form a combustion chamber. The flow passage may extend through the main body from the recess. The valve seat insert may be disposed within the recess proximate to an end of the flow passage. The valve seat insert includes a thermally conductive layer of powdered metal having an upper side disposed adjacent to the main body, a hardness layer of powdered metal, and a machining layer of powdered metal.

What is claimed is: 
     
         1 . A cylinder head assembly for an internal combustion engine comprising:
 a main body formed from a first material and defining a recess configured to cooperate with an associated cylinder bore and piston for forming a combustion chamber;   at least one flow passage extending through the main body from the recess; and   a valve seat insert disposed within the recess proximate to an end of the at least one flow passage   wherein the valve seat insert includes a thermally conductive layer of powdered metal having an upper side disposed adjacent to the main body, a hardness layer of powdered metal, and a machining layer of powdered metal having a lower side exposed to the associated cylinder bore and piston.   
     
     
         2 . The cylinder head assembly as defined in  claim 1  wherein the thermally conductive layer of powdered metal has a thermal conductivity which is greater than 350 W/(m-K), the hardness layer of powdered metal has a hardness which is greater than Rc 35, and the machining layer of powdered metal includes free machining steel alloy. 
     
     
         3 . The cylinder head assembly as defined in  claim 2  wherein the hardness layer of powdered metal is disposed between the machining layer of powdered metal and the thermally conductive layer of powdered metal. 
     
     
         4 . The cylinder head assembly as defined in  claim 2  further comprising:
 a transition region defined between the thermally conductive layer and the hardness layer of powdered metal; 
 wherein the transition region includes a mixture of powdered metal from the thermally conductive layer and hardness layer. 
 
     
     
         5 . The cylinder head assembly as defined in  claim 2  wherein the valve seat insert is formed by a sintering process. 
     
     
         6 . The cylinder head assembly as defined in  claim 5  wherein the valve seat insert defines a ring-like configuration. 
     
     
         7 . The cylinder head assembly as defined in  claim 6  further comprising a secondary hardness layer disposed along an inner surface of the ring wherein the secondary hardness layer is positioned between the thermally conductive layer and the machining layer. 
     
     
         8 . The cylinder head assembly as defined in  claim 6  wherein all or a portion of the machining layer is configured to be machined away from the valve seat insert. 
     
     
         9 . The cylinder head assembly as defined in  claim 7  wherein a portion of the machining layer is configured to be machined away from the valve seat insert.