Flow damper

A flow damper for controlling a flow of fuel flowing from a rail main body that accumulates pressure of high-pressure fuel into an injector that injects fuel, the flow damper comprising:

• a valve body that is fastened to the rail main body and has a fuel passage therein, wherein:
• the fuel passage communicates between a fuel hole of the rail main body and the injector;
• and
• the fuel passage includes a piston sliding hole on its rail main body-side;
• a piston that is slidably held on an inner circumferential surface of the piston sliding hole;
• a spring that urges the piston in an opposite direction from a direction of fuel flowing through the fuel passage;
• and
• a cap that includes a small diameter portion and a large diameter portion, wherein:
• the small diameter portion is fitted into the inner circumferential surface of the piston sliding hole with a gap between the small diameter portion and the piston sliding hole;
• and
• the large diameter portion is located between the valve body and the rail main body.