Roller drive mechanism for gdi pump

A high pressure fuel supply pump for a gasoline direct injection engine, comprising:

• a pump body;
• a single pumping bore in the body, partially defining a pumping chamber;
• a single pumping piston reciprocating in the bore along an actuation axis, with one end further defining the pumping chamber and another end projecting out of the body for reciprocal driving by a rotating circular cam;
• an inlet control valve connected to the body for supplying low pressure feed fuel through the body to the pumping chamber during a charging stroke of the piston;
• an outlet check valve connected to the body for discharging pressurized fuel from the pumping chamber through the body during a pumping stroke of the piston;
• a cam shaft outside the body, extending along a cam shaft axis that is perpendicular to and intersects the actuation axis;
• the circular cam rigidly connected to the cam shaft, having a cam axis that is perpendicular to and intersects the actuation axis, and is offset from the cam shaft axis;
• a circular cam roller surrounding the cam;
• a cam roller bearing interposed between the cam roller and the cam;
• a cam follower connected to the piston;
• a piston retainer operatively connected among the piston, the cam follower and the cam roller for biasing the piston and cam follower toward the cam roller;
• and
• a variable speed electric motor operatively connected to rotate said cam shaft and said circular cam independently of the gasoline direct injection engine,
• whereby as the cam shaft continuously rotates, the cam roller rotates eccentrically relative to the cam shaft and through the piston retainer and cam follower, converts the rotating motion of the cam shaft into a linearly reciprocal stroke of the piston in the pumping chamber.