Valve lifter for internal combustion engine

Abstract

A valve lifter for an automotive internal combustion engine. The valve lifter includes a main body formed of one of an aluminum alloy and an iron-based alloy as a base material and having a top surface and a side surface which are respectively in slidable contact with opposite members in presence of at least one of a lubricating oil and a lubricant. Additionally, a hard carbon thin film is formed on the main body to cover the top surface and the side surface, the hard carbon thin film containing hydrogen atom in an amount of not more than 1 atomic %.

1 . A valve lifter for an internal combustion engine, comprising 
 a main body formed of a metal as a base material and having a top surface and a side surface which are respectively in slidable contact with opposite members in presence of a lubricant; and    a hard carbon thin film formed on the main body to cover the top surface and the side surface, the hard carbon thin film containing hydrogen atom in an amount of not more than 20 atomic %.    
   
   
       2 . A valve lifter as claimed in  claim 1 , wherein the lubricant contains at least one friction modifier selected from the group consisting of ashless fatty acid ester friction modifier and ashless aliphatic amine friction modifier.  
   
   
       3 . A valve lifter as claimed in  claim 2 , wherein the at least one friction modifier has a C 6 -C 30  hydrocarbon chain and is contained in an amount of 0.05 to 3.0% by mass based on a total mass of the at least one of a lubricating oil and a lubricant.  
   
   
       4 . A valve lifter as claimed in  claim 2 , wherein the lubricant contains at least one compound selected from the group consisting of polybutenyl succinimide and a derivative of polybutenyl succinimide.  
   
   
       5 . A valve lifter as claimed in  claim 4 , wherein the at least one compound selected from the group consisting of polybutenyl succinimide and a derivative of polybutenyl succinimide is contained in an amount of 0.1 to 15% by mass based on a total mass of the one of the lubricating oil and lubricant.  
   
   
       6 . A valve lifter as claimed in  claim 2 , wherein the lubricating oil contains zinc dithiophosphate in an amount of 0.1% or less by mass in terms of a phosphorus element based on a total mass of the at least one of a lubricating oil and a lubricant. oil and a lubricant.  
   
   
       7 . A valve lifter as claimed in  claim 1 , wherein the lubricant has a main component which is a compound containing hydroxyl group.  
   
   
       8 . A valve lifter as claimed in  claim 7 , wherein the compound is at least one of alcohols.  
   
   
       9 . A valve lifter as claimed in  claim 8 , wherein the at least of alcohols is at least one of glycerol and ethylene glycol.  
   
   
       10 . A valve lifter as claimed in  claim 1 , wherein the main body includes a top wall section and a side wall section which are integral with each other, the top wall section having the top surface, the side wall section having the side surface.  
   
   
       11 . A valve lifter as claimed in  claim 1 , wherein the metal is at least one of aluminum alloy and an iron-based alloy.  
   
   
       12 . A valve lifter as claimed in  claim 1 , wherein the lubricant includes a lubricating oil.  
   
   
       13 . A valve lifter as claimed in  claim 1 , wherein the hard carbon thin film contains hydrogen atom in an amount of not more than 10 atomic %.  
   
   
       14 . A valve lifter as claimed in  claim 1 , wherein the hard carbon thin film contains hydrogen atom in an amount of not more than 0.5 atomic %.  
   
   
       15 . A valve lifter as claimed in  claim 1 , wherein the hard carbon thin film contains hydrogen atom in an amount of not more than 1 atomic %.  
   
   
       16 . A method of making a valve lifter for an internal combustion engine, comprising: 
 preparing a main body of the valve lifter, formed of one of an aluminum alloy and an iron-based alloy as a base material and having a top surface and a side surface;    forming a hard carbon thin film on the main body to cover the top surface and the side surface by a PVD process, the hard carbon thin film containing hydrogen atom in an amount of not more than 20 atomic %; and    providing a lubricant between the main body of the valve lifter and the hard carbon thin film.