Patent ID: 7341205

Claim:
A fuel injection nozzle for DME fuel, which is mounted in each combustion chamber of a light oil fuel diesel engine and is for driving the Light oil fuel diesel engine by using DME fuel, comprising: a nozzle body having a fuel injection hole with a total injection hole area to attain an injection amount of the DME fuel which enables an engine output comparable to light oil fuel to be obtained; and a needle valve provided to be capable of reciprocating to the fuel injection hole and having a tip part of a substantially right circular cone shape, characterized in that the needle valve is configured to form a valve closed state as the tip part is seated on a valve seat part of the nozzle body at a position before the fuel injection hole, and to form a valve open state as the tip part is lifted to be separated from the valve seat part, and the needle valve is lifted from the valve closed state to shift into the valve open state, so that a fuel flow path of the DME fuel from an inside of the nozzle body to the fuel injection hole is defined, the tip part of a substantially right circular cone shape, of the needle valve has a shape set by a center diameter for defining a minimum flow path area of the fuel flow oath defined as a minimum interval between the needle valve at full lift and the valve seat part, a seat diameter of a seat part which is positioned on a root side with respect to the center diameter and is for coming in contact with the valve seat part and blocking communication with the fuel injection hole, and a shaft diameter of a needle valve body, and the tip part of the needle valve is shaped such that a size of the center diameter is made closer to that of the seat diameter by positioning the center diameter closer to the seat diameter, to such a degree that an injection amount of the DME fuel which enables an engine output characteristic comparable to light oil fuel to be obtained is attained with the minimum flow path area of the fuel flow path defined by the center diameter with the needle valve at full lift, according to the total injection hole area of the fuel injection hole.