US Patent 7794216 High-pressure pump

A plunger is inserted into a slide hole of a cylinder body provided between a pressurizing chamber and a drive cam, so as to reciprocate within the slide hole. The drive cam and a coil spring move the plunger toward the drive cam so that fuel is sucked into the pressurizing chamber, and also move the plunger toward the pressurizing chamber so that the fuel in the pressurizing chamber is pressurized. A clearance between the plunger and a wall of the slide hole forms a flow passage of the fuel discharged from the pressurizing chamber. In the high-pressure fuel pump constructed as above, a fluid reservoir is provided in the flow passage. The capacity of the fluid reservoir increases as the plunger moves toward the drive cam, and decreases as the plunger moves toward the pressurizing chamber.