High pressure fuel pump and fuel supply system

A high pressure fuel pump for delivering fuel, which is suctioned into a pressurizing chamber from a low pressure fuel pump through a suction passage, to a supply destination after pressurizing the fuel in the pressurizing chamber with a plunger, the high pressure fuel pump comprising:

• a pump body that slidably supports the plunger and forms the suction passage, the pressurizing chamber, a cam receiving chamber, a release passage, an internal pressure variable chamber and a communication passage, wherein the pressurizing chamber is communicated with the suction passage and the release passage through a connection, and the release passage is communicated with the cam receiving chamber which receives a drive cam that is configured to drive the plunger, and an internal pressure of the internal pressure variable chamber is increased and decreased in response to reciprocation of the plunger, and the communication passage communicates between the internal pressure variable chamber and the cam receiving chamber;
• a control valve that is configured to open and close the connection;
• and
• a controller that is configured to control an operation of the control valve, wherein:
• the controller is configured to place the control valve in an opening state where the control valve opens the connection to supply the fuel from the suction passage to the pressurizing chamber through the connection in a suction stroke, during which the plunger is driven toward a suction side for suctioning the fuel into the pressurizing chamber;
• the controller is configured to place the control valve in a closing state where the control valve closes the connection at a closing timing in a delivery stroke, during which the plunger is driven toward a delivery side for delivering the fuel out of the pressurizing chamber upon pressurization of the fuel after the suction stroke;
• the controller is configured to maintain the control valve in the opening state to relieve the fuel, which is pressurized by the plunger, from the pressurizing chamber to the cam receiving chamber through the connection and the release passage during the delivery stroke until the closing timing reaches after a start of the delivery stroke;
• the pump body forms a drain passage that drains the fuel from the cam receiving chamber to a fuel tank;
• a passage cross-sectional area of a portion of the release passage is reduced on a side of the cam receiving chamber, at which the suction passage is placed, to form a release flow restricting portion;
• and
• a passage cross-sectional area of at least-a portion of the drain passage is reduced in comparison to a passage cross-sectional area of the release flow restricting portion.