Valve for Controlling Gas Exchange, Especially in Internal Combustion Engines

Abstract

A valve for controlling gas exchange, especially in internal combustion engines, comprises, at a valve stem, a stem end and at the other end thereof a valve cone. The valve cone and/or the valve stem are configured as hollow metal elements in such a manner that the hollow elements are entirely or partially filled with a metal foam. The interfaces between the metal and the metal foam are interlinked on the molecular level

1 . A valve for control of gas exchange, especially in internal combustion engines, comprising a valve cone at one end of a valve stem, the valve stem and/or valve cone being formed as hollow metal parts having a cavity filled at least partly with metal foam to form a metal-foam body, wherein the metal-foam body formed in the valve cavity is bonded metallically at the molecular level at the interfaces with the hollow metal parts forming the valve.  
   
   
       2 . A valve according to  claim 1 , wherein the metal foam is processed in such a way that it has closed or open pores.  
   
   
       3 . A valve according to  claim 1 , wherein the metal foam has a metal matrix comprising between 5 and 20 volume percent.  
   
   
       4 . A valve according to  claim 3 , wherein the metal foam has a metal matrix comprising between 8 and 10 volume percent.  
   
   
       5 . A valve according to  claim 1 , wherein the metal foam is formed by a metal matrix based on AlSi7.  
   
   
       6 . A valve according to  claim 5 , wherein the average density of the metal foam is approximately 0.5 g/cm 3 .  
   
   
       7 . A valve according to  claim 5 , wherein as starting material for the metal foam there is chosen a powder mixture such that a blowing agent will generate a foam volume of approximately five times that of the starting material under the effect of heat.  
   
   
       8 . A valve according to  claim 1 , wherein the valve stem and the valve cone are completely filled with metal foam.  
   
   
       9 . A valve according to  claim 1 , wherein a metal envelope forming the valve is welded together from a plurality of portions, which are made of like or unlike materials.  
   
   
       10 . A valve according to  claim 9 , wherein a valve head comprises the valve cone made in one piece with the valve stem as well as a valve sealing plug, joined to one another by electric welding.  
   
   
       11 . A valve according to  claim 9 , wherein the valve stem comprises a portion of Nimonic80A at the head end of the valve as well as an end portion of hardenable material surrounding the stem end of the valve, the two portions being joined to one another by friction welding.  
   
   
       12 . A valve according to  claim 11 , wherein the end portion is made of X45CrSi93 (DIN 1.4718).  
   
   
       13 . A method for manufacturing a valve according to  claim 1 , comprising introducing starting material for the metal foam through one open end of the valve stem in such a way that the metal foam completely fills the valve cavity under the effect of heat, and its quantity is adjusted to swell beyond the filling end, after which the excess quantity of metal foam is removed and the filling opening is sealed by welding.