Patent ID: 7500472

Claim:
A fuel injection valve comprising: a needle valve including a base material; an opposite member including a base material whose sliding section is in slidable contact with a sliding section of the base material of the needle valve in presence of fuel for an automotive vehicle; and a hard carbon thin film coated on at least one of the sliding sections of the base materials of the needle valve and the opposite member, the hard carbon thin film having a surface hardness ranging from 1500 to 4500 kg/mm 2 in Knoop hardness, a film thickness ranging from 0.3 to 2.0 μm, and a surface roughness (Ry) (μm) which satisfies a relationship represented by the following formula (A): Ry < (0.75− Hk/ 8000) ×h + 0.0875 (A) where h is the thickness (μm) of the hard carbon thin film; and Hk is the surface hardness in Knoop hardness (kg/mm 2 ) of the hard carbon thin film.