Patent ID: 7926745

Claim:
A fuel injection valve comprising: a valve seat that has a valve seat portion with a conical space defined therein and tapered toward an injection hole; a needle that has a valve portion formed with a curved surface for abutment with said valve seat portion and a column-shaped sliding portion located upstream of said valve seat portion; and a guide body that holds said sliding portion in a slidable manner; wherein fuel to be injected from said injection hole is adjusted by opening and closing a gap between said valve portion and said valve seat portion; wherein, assuming that a radius of curvature in an axial direction of said valve portion at a point at which said valve portion and said valve seat portion are in abutment with each other is R and an outer diameter of said sliding portion is D, R is greater than D/2, and wherein, assuming that a seat diameter in the form of the diameter of an abutment circle in which said valve seat portion and said valve portion are in abutment with each other is S and a seat angle in the form of an inner angle at a vertex of said conical space is θ, the following expression is satisfied: S< 2 ×R ×sin(90 degrees−θ/2).