Cylinder for internal combustion engine and method of treating inner wall surface of the cylinder

Abstract

There is provided a cylinder for an internal combustion engine, wherein the inner wall surface of the cylinder which constitutes a slide-contacting surface for the piston is treated with a metal plating which is minimal in burden to the environment, excellent in abrasion resistance and hard enough to endure the practical use of the cylinder, thus making it possible to dispense with a finishing work such as honing work. The cylinder is featured in that the inner wall surface of the cylinder which is adapted to be slidably contacted with a piston is electroplated in a plating bath comprising a nickel plating solution containing a boron compound such as trimethylamine borane, dimethylamine borane, etc.

1 . A cylinder for an internal combustion engine, which is made of an aluminum alloy and is featured in that an inner wall surface of said cylinder which is adapted to be slidably contacted with a piston is electroplated in a plating bath comprising a nickel plating solution containing a boron compound such as trimethylamine borane, dimethylamine borane, etc.  
     
     
         2 . The cylinder according to  claim 1 , wherein a layer formed on said inner wall surface by said electroplating is employed, as it is, as a finished surface without a finishing work by means of honing, etc.  
     
     
         3 . The cylinder according to  claim 1  or  2 , wherein the layer formed by said electroplating has a Vickers hardness of 650 to 750(Hv[50 gf]).  
     
     
         4 . The cylinder according to any one of  claims 1  to  3 , wherein a deviation in thickness of the layer formed by said electroplating all over said inner wall surface is confined within 15 μm.  
     
     
         5 . The cylinder according to any one of  claims 1  to  4 , which is adapted to be used as a cylinder for a small air-cooled two-stroke gasoline engine to be employed in a portable power working machine, said cylinder being constructed such that a head portion constituting the combustion chamber of the engine is formed integral with a barrel portion into which the piston is slidably inserted.  
     
     
         6 . A method of treating the inner wall surface of the cylinder for an internal combustion engine, said method comprising a step of electroplating an inner wall surface of said cylinder which is adapted to be slidably contacted with a piston by making use of a plating bath comprising a nickel plating solution containing a boron compound such as trimethylamine borane, dimethylamine borane, etc.