FUEL PUMP

A fuel pump having a housing which defines a pump chamber with an inlet and an outlet. A piston is reciprocally mounted in the pump chamber. An inlet valve is mounted fluidly in series between the pump chamber and the housing inlet which opens and closes the inlet in synchronism with the reciprocation of the piston. A rotary valve is mounted fluidly in series with the housing outlet and the rotary outlet valve is rotatably driven in synchronism with reciprocation of the piston. The rotary valve is configured so that it is fluidly open only at one or more predetermined angular positions of the rotary outlet valve. The open and close timings of the rotary inlet and outlet valves are completely controlled by a motor in order to control the fuel pressure, especially to avoid excessive fuel compression and resulting fuel pressure fluctuation.

With reference first toFIG. 1, a fuel pump10according to the present invention is shown having a housing12. The fuel pump defines an internal pump chamber14having an inlet16and an outlet18.

The fuel pump inlet16is fluidly connected to a source20of fuel, such as a fuel tank. Conversely, the housing outlet18is fluidly connected to one or more fuel injectors22, preferably through a fuel rail24. The fuel injectors22, in turn, supply fuel to an internal combustion engine26(illustrated only diagrammatically) which is preferably a direct injection internal combustion engine.

A piston28is reciprocally mounted to the fuel pump housing12. Although any means may be used to reciprocally drive the piston28, preferably a multi-lobe cam30is mechanically coupled to the piston28. The cam30is preferably mechanically coupled to the drive shaft for the engine26so that the cam30rotates in synchronism with the engine rotation.

Rotation of the cam30reciprocally drives the piston28as indicated by arrow32. Consequently, the piston28reciprocates between a pressure or compression stroke in which the piston28moves in a direction into the pump chamber14and an induction stroke in which the piston28moves outwardly from the pump chamber14.

With reference now toFIGS. 1,2,4A and4B, a rotary inlet valve34is rotatably mounted within a cylindrical recess36formed in the pump housing12. This recess36, furthermore, is fluidly positioned in between a fuel inlet passage38fluidly connected to the inlet16and the pump chamber14.

The fuel inlet valve34is generally cylindrical in shape but includes a radially inwardly extending recess40at a predetermined angular position of the valve34. Consequently, at a predetermined angular position for the rotary valve34illustrated inFIG. 4A, the opening40registers with both the fuel inlet passageway38and the pump chamber14to establish fluid communication between the pump chamber14and the source20of fuel. Conversely, at other rotational positions such as shown inFIG. 4B, the valve34closes the inlet passageway38from the pump chamber14.

Similarly, with reference toFIGS. 1,2, and3, a generally cylindrical outlet valve42is rotatably mounted within a cylindrical recess44in the housing14which is fluidly in series between the fuel pump outlet18and the pump chamber14. The rotary outlet valve42, like the inlet valve34, also includes a radially inwardly extending recess46at a predetermined angular position of the outlet valve42. Thus, at predetermined rotational positions of the outlet valve42the opening46registers with both the outlet18and the pump chamber14as shown inFIG. 2to establish fluid communication from the pump chamber14and to the fuel injectors22through the outlet18and fuel rail24. At other rotational positions, such as shown inFIG. 3, the recess46does not register with the outlet18thus fluidly closing the pump chamber14from the outlet18.

The rotation of the inlet valve34and outlet valve42within their respective valve seats36and44, respectively, are synchronized with each other. Although different means may be used to synchronize the rotation of the inlet valve34with the outlet valve42, as illustrated inFIGS. 1 and 2, a shaft48extends across the pump chamber14and is connected at one end to the inlet valve34and at its other end to the outlet valve42. In doing so, the inlet valve34and outlet valve42, which may be a one piece construction, are rotationally mechanically synchronized.

The rotation of the inlet valve34and outlet valve42is synchronized with the reciprocation of the piston28so that the opening40of the inlet valve34fluidly connects the fuel pump inlet16to the pump chamber14only during the induction or outward stroke of the piston28. Similarly, the opening46in the outlet valve42fluidly connects the pump chamber14to the fuel outlet18only during the compression or inward stroke of the piston28into the fuel chamber14.

With reference toFIG. 1, although different means may be utilized to rotatably drive the inlet valve34and outlet valve42in synchronism with the reciprocation of the piston28, preferably a controllable motor50, such as a DC controllable motor or stepper motor, mechanically synchronizes the rotation of the inlet valve34and outlet valve42with reciprocation of the piston28under control of the engine control unit (ECU)52, other means may also be utilized to synchronize the rotation of the valves34and42with the piston32. For example, the valves34and42may be mechanically coupled to the drive mechanism for the cam30in order to achieve synchronism between the valve opening and the piston reciprocation.

With reference now toFIGS. 5A and 5B,FIG. 5Aillustrates an alternate design for the piston28′ in which the piston28′ includes a through notch54. This through notch54is greater in width than the diameter of the shaft48so that portions of the piston28′ extend around the shaft48during reciprocation of the piston28′. Similarly, a modified piston28″ is illustrated inFIG. 5Bin which a closed through notch56is formed through the piston28″. The shaft48extends through this through notch56.

The inlet valve34and outlet valve42thus far described contain a single opening or notch40or46, respectively. As such, as thus far described, the inlet valve34and outlet valve42rotate once for each full reciprocation of the piston28in the pump chamber14. However, as shown inFIG. 6, two or more circumferentially equidistantly spaced notches, such as three notches58, may be provided in the inlet valve34′ and the outlet valve42′. Where multiple notches or openings are formed in the inlet valve34′ and outlet valve42′, the inlet valve34′ and outlet valve42′ open three times during a single rotation of the inlet valve34′ and outlet valve42′. Consequently, the motor50, or other drive mechanism, rotatably drives the inlet valve34′ and outlet valve42′ at a reduced speed so that the inlet valve34′ and outlet valve42′ rotate one full revolution for each three reciprocations of the cam28. It will be understood, of course, that the illustration of three notches for both the inlet valve34′ and outlet valve42′ is by way of example only and that more, or fewer, notches or openings in the valves may also be used.

Optionally, the valve rotation may be decelerated before each valve closure to reduce shock resulting from rapid valve closure.

A primary advantage of Applicant's fuel pump construction is that since the rotary outlet valve42is actively and fully controlled through the shaft48together with the rotary inlet valve34, the excessive fuel compression in the chamber14by the previously known outlet check valves is eliminated or at least reduced, the previously known pressure fluctuations and pulsations in the fuel system, and especially in the fuel rail24, are reduced together with the noise (sound and vibration) caused by such pressure pulsations. Furthermore, the inlet valve and outlet valve merely rotate in their valve seats in the fuel pump housing which completely eliminates the impact noise of the previously known fuel pump valves as they open and close.

A still further advantage of the invention is that the precise opening and closing of both the inlet and outlet of the pump chamber can be completely controlled by one motor.

A still further advantage of the present invention is that, since the rotation of the inlet and outlet valves are absolutely synchronized, when the inlet valve is open, the outlet valve is closed and vice versa.

Having described our invention, however, many modifications thereto will become apparent to those skilled in the art to which it pertains without deviation from the spirit of the invention as defined by the scope of the appended claims.