Patent ID: 8919186

Claim:
A fuel pressure measuring device for use in a fuel injection system for an internal combustion engine which supplies fuel from an accumulator in which the fuel is accumulated to a fuel injection valve through a high-pressure pipe and sprays the fuel from a spray hole formed in a nozzle body of the fuel injection valve, the fuel pressure measuring device comprising: a thin-walled portion which is formed in the nozzle body defining a high-pressure fuel path which communicates between an inlet of the fuel injection valve into which the fuel is inputted and the spray hole of the fuel injection valve and through which the fuel flows to the spray hole which is opened by a needle to be moved within the nozzle body to spray the fuel, the thin-walled portion being defined by a locally thin wall thickness of the path member and the thin-walled portion having a first and a second surface opposed to each other through a thickness of the thin-walled portion, the first surface being directly exposed to the fuel flowing through the high-pressure fuel path; and a strain sensor which is attached to the second surface of the thin-walled portion to measure strain of the thin-walled portion arising from pressure of the flowing fuel in the high-pressure fuel path when the spray hole is opened to spray the fuel by the needle being moved within the nozzle body.