PURPOSE: To make it possible to maintain the stable insulation quality of a needle valve for a long period of time by forming an insulating layer around the needle valve by means of placing between them an intermediate layer which has a high bonding strength to the needle valve and the insulating layer and which is made up of a material whose thermal expansion coefficient is between them.
CONSTITUTION: On the surface 8a of the large diameter section of a needle valve 8, an intermediate layer 25 is formed, consisting of titanium nitride whose thermal expansion coefficient is between that of iron used as a material for the needle valve 8 and that of SiO2 used as a material for an insulating layer 26, and which has a high bonding strength to iron and SiO2. These intermediate layer 25 and insulating layer 26 are each formed by use of the techniques of sputtering, iron plating, etc. In this way, with the insulating layer tightly bonded to the needle valve and with the difference in thermal expansion coeffcient between the needle valve and the insulating layer, the distortion within the insulating layer is reduced, thus it is possible to form the insulating layer which is extremely good in peeling resistance.
KASATANI MASASHI
ABE TATSUHIKO
Next Patent: ENGINE