Valve lifter and forming and processing method therefor

Abstract

A forming and processing method for a valve lifter. The forming and processing method includes the steps of: (a) forming a hole in the valve lifter at a site where a cam is slidably contacted with; (b) forming a diameter-increasing section along an edge of the valve lifter, the edge defining a part of the hole and being located on a side with which the cam is slidably contacted; and (c) carrying out a surface treatment to whole of a surface of the valve lifter which surface is on the side with which the cam is slidably contacted.

1 . A forming and processing method for a valve lifter, comprising the steps of: 
 forming a hole in the valve lifter at a site where a cam is slidably contacted with;    forming a diameter-increasing section along an edge of the valve lifter, the edge defining a part of the hole and being located on a side with which the cam is slidably contacted; and    carrying out a surface treatment to whole of a surface of the valve lifter which surface is on the side with which the cam is slidably contacted.    
   
   
       2 . A forming and processing method as claimed in  claim 1 , wherein the surface treatment is carried out in an area extending from the whole of the surface with which the cam is slidably contacted to inside of the hole through the diameter-increasing section formed along the annular edge of the valve lifter.  
   
   
       3 . A forming and processing method as claimed in claims  1 , wherein the diameter-increasing section is formed to have a round surface in section.  
   
   
       4 . A forming and processing method as claimed in  claim 3 , wherein the round surface of the diameter-increasing section has a radius of curvature within a range of from 0.05 to 0.2 mm in section.  
   
   
       5 . A forming and processing method as claimed in  claim 1 , wherein the diameter-increasing section is formed tapered.  
   
   
       6 . A forming and processing method as claimed in  claim 1 , wherein the surface treatment is a diamond-like carbon treatment.  
   
   
       7 . A forming and processing method as claimed in  claim 6 , wherein a lapping treatment is carried out after the diamond-like carbon treatment.  
   
   
       8 . A forming and processing method as claimed in  claim 1 , wherein a crown surface of the valve lifter is spherically formed.  
   
   
       9 . A forming and processing method as claimed in  claim 1 , wherein forming the hole is carried out after carrying out a surface processing of a crown section and inner and outer peripheral surface of a skirt section of the valve lifter.  
   
   
       10 . A forming and processing method as claimed in  claim 1 , wherein the hole is a lubricating oil supply hole and formed during cold forging of the valve lifter.  
   
   
       11 . A forming and processing method as claimed in  claim 1 , wherein the diameter-increasing section is formed after a heat treatment and a surface polishing which are carried out after the hole is formed.  
   
   
       12 . A forming and processing method as claimed in  claim 1 , the surface treatment is carried out after rinsing the valve lifter carried out after the diameter-increasing section is formed.  
   
   
       13 . A valve lifter, comprising: 
 a crown section formed with a hole at a site where a cam is slidably contacted and having an edge of the valve lifter, the edge defining a part of the hole, a diameter-increasing section being formed along the edge;    a skirt section formed integral with an outer peripheral edge of the crown section; and    a surface treatment layer formed on whole of a surface with which the cam is slidably contacted and on an area extending from the diameter-increasing section to inside of the hole.    
   
   
       14 . A valve lifter as claimed in  claim 13 , wherein the crown section and the skirt section are formed of an iron-based metal.  
   
   
       15 . A valve lifter as claimed in  claim 14 , wherein a minute recess is formed on the surface treatment layer.  
   
   
       16 . A valve lifter, comprising: 
 a crown section formed with a circular recess and an oil hole formed to communicate with the recess so as to pierce the crown section;    a skirt section formed integral with an outer peripheral edge of the crown section;    a shim accommodated in the recess and formed with a hole piercing the shim, a diameter-increasing section being formed along an edge defining a part of the hole; and    a surface treatment layer formed on whole of a surface with which the cam is slidably contacted and on an area extending from the diameter-increasing section to inside of the hole.    
   
   
       17 . A valve lifter as claimed in  claim 16 , wherein a minute recess is formed at the surface treatment layer.  
   
   
       18 . A valve lifter as claimed in  claim 16 , wherein the crown section and the skirt section are formed of an aluminum alloy, and the shim is formed of an iron-based metal.  
   
   
       19 . A valve lifter as claimed in  claim 16 , an annular oil groove is formed to communicate with inside of the recess, wherein the oil hole is formed to communicate with a first position of the oil groove so as to pierce the crown section, wherein the hole in the shim is formed at a second position corresponding to the oil groove.  
   
   
       20 . A valve lifter as claimed in  claim 16 , wherein the hole is an air hole through which air flows.