Roller drive mechanism for GDI pump
In a high pressure fuel supply system, a variable speed motor asynchronously actuates a pumping piston with a drive mechanism including a circular cam with cam roller, having an axis that is offset from the axis of the cam drive shaft. A rolling or sliding cam follower is rigidly connected to the piston, and a piston retainer is operatively connected among the piston, the cam follower and the cam roller. As the cam shaft rotates, the cam roller rotates eccentrically relative to the cam shaft while maintaining contact with the cam follower, thereby reciprocating the follower and the piston along the actuation axis, in corresponding charging and pumping strokes of the piston.
1. 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 valve connected to the body, wherein the inlet valve is in fluid communication with the pumping chamber;
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 circular cam roller and the cam;
a cam follower connected to the piston, wherein the cam follower includes a roller that contacts the circular cam roller with a mutually rolling relationship as the cam rotates;
a piston retainer operatively connected among the piston, the cam follower and the circular cam roller for biasing the piston and cam follower toward the circular 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, wherein the variable speed electric motor is situated in a housing that is connected to the pump body,
whereby as the cam shaft continuously rotates, the circular 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.
2. The pump of claim 1 , wherein the piston retainer maintains a direct transfer of force between the circular cam roller and the piston such that the piston stroke follows a sinusoidal rate of displacement though a fully charging stroke and a fully pumping stroke corresponding to cam rotation between bottom dead center and top dead center.
3. The pump of claim 1 , wherein
the pump is connected to a fuel supply circuit including a common rail;
the fuel supply circuit is connected to an electronic control unit that receives input signals commensurate with fuel pressure in the common rail, engine speed, and a rotational position of the cam; and
the electronic control unit delivers a control signal to the variable speed electric motor for rotating the cam at a speed different from the engine speed.
4. The pump of claim 1 , wherein the cam follower defines a flat face that contacts the circular cam roller with a sliding relationship as the cam rotates.
5. The pump of claim 4 , wherein the piston retainer is a spring that wraps more than 180 degrees around the cam follower and the circular cam roller.
6. The pump of claim 1 , wherein the cam roller bearing is a journal bearing.
7. The pump of claim 1 , wherein the cam roller bearing is selected from the group consisting of ball-type, roller-type, or needle type.
8. The pump of claim 1 , wherein during one rotation of the cam shaft the piston is reciprocally displaced through a charging stroke between top dead center and bottom dead center and a pumping stroke between bottom dead center and top dead center and the piston stroke follows a rate of displacement that decelerates as the piston approaches top dead center and bottom dead center.
9. The pump of claim 1 , wherein the piston retainer, cam follower, circular cam roller, cam, and camshaft are situated in the housing that is connected to the pump body, and a camshaft bearing in the housing supports rotation of the cam shaft.
10. The pump of claim 1 , wherein the piston retainer, the cam follower, the circular cam roller, the cam, and the cam shaft are situated in the housing that is connected to the pump body where the variable speed electric motor is situated.
11. 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 valve connected to the body, wherein the inlet valve is in fluid communication with the pumping chamber;
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 circular cam roller and the cam;
a cam follower connected to the piston, wherein the cam follower includes a roller that contacts the circular cam roller with a mutually rolling relationship as the cam rotates;
a piston retainer operatively connected among the piston, the cam follower and the circular cam roller for biasing the piston and cam follower toward the circular cam roller; and
a variable speed electric motor operatively connected to said cam shaft, wherein the variable speed electric motor is configured to rotate said cam shaft and said circular cam independently of an engine crankshaft of the gasoline direct injection engine when the gasoline direct injection engine is running,
whereby as the cam shaft continuously rotates, the circular 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;
wherein the pump is connected to a fuel supply circuit including a common rail;
wherein the fuel supply circuit is connected to an electronic control unit that receives input signals commensurate with fuel pressure in the common rail and engine speed; and
wherein the electronic control unit delivers a control signal to the variable speed electric motor for rotating the cam at a speed different from the engine speed.
12. The pump of claim 11 wherein the cam shaft is free of any connection to the crankshaft of the gasoline direct injection engine.
13. The pump of claim 11 , wherein the electronic control unit is further configured to receive input signals commensurate with a rotational position of the cam.
14. The pump of claim 11 , wherein the piston retainer, the cam follower, the circular cam roller, the cam, and the cam shaft and the variable speed electric motor are situated in a housing that is connected to the pump body.
15. 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 valve connected to the body, wherein the inlet valve is in fluid communication with the pumping chamber;
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 circular cam roller and the cam;
a cam follower connected to the piston, wherein the cam follower includes a roller that contacts the circular cam roller with a mutually rolling relationship as the cam rotates;
a piston retainer operatively connected among the piston, the cam follower and the circular cam roller for biasing the piston and cam follower toward the circular cam roller; and
a variable speed electric motor operatively connected to said cam shaft, wherein the variable speed electric motor is configured to rotate said cam shaft at a speed independent of a rotational speed of an engine crankshaft of the gasoline direct injection engine and independent of any rotational speed corresponding to the rotational speed of the engine crankshaft of the gasoline direct injection engine,
whereby as the cam shaft continuously rotates, the circular 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.
16. The pump of claim 15 wherein the variable speed electric motor is configured to rotate said cam shaft at a speed different from any rotational speed corresponding to the rotational speed of the engine crankshaft when the engine is running.
17. The pump of claim 15 , wherein the pump is connected to a fuel supply circuit including a common rail;
the fuel supply circuit is connected to an electronic control unit that receives input signals commensurate with fuel pressure in the common rail, engine speed, and a rotational position of the cam; and
the electronic control unit delivers a control signal to the variable speed electric motor for rotating the cam at a speed different from the engine speed.
18. The pump of claim 15 , wherein the piston retainer, the cam follower, the circular cam roller, the cam, and the cam shaft and the variable speed electric motor are situated in a housing that is connected to the pump body.