Claims:We Claim

1. A high pressure fuel pump (10), said high pressure fuel pump (10) comprising;
a housing (12);
a plunger (14) positioned within a pumping chamber defined within said housing (12), said plunger (14) comprising:
a solid portion (16);
a first vertical groove (18) defined in said solid portion, said first vertical groove (18) adapted to channel pressurized fuel from said pumping chamber to an inlet portion of said high pressure fuel pump (10);
a helical groove (20) in flow communication with said first vertical groove (18), said helical groove (20) adapted to channel pressurized fuel that flows through the first vertical groove (18) to the inlet portion of said high pressure fuel pump (10); characterized in that
a second vertical groove (22) defined in said solid portion, the second vertical groove (22) extending from a top portion (24) of said plunger (14) to said helical groove (20), the second vertical groove (22) adapted to channel pressurized fuel that flows through the second vertical groove (22) to the inlet portion of said high pressure fuel pump (10) via the helical groove (20).

2. The high pressure fuel pump (10) in accordance with Claim 1 wherein a width of the second vertical groove (22) is smaller than a width of the first vertical groove (18).

3. The high pressure fuel pump (10) in accordance with Claim 1 wherein a depth of the second vertical groove (22) is lesser than a depth of the first vertical groove (18).
, Description:Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[0001] This invention relates to a high pressure fuel pump, and more specifically to a plunger of the high pressure fuel pump.

Background of the invention
[0002] GB 784948 A describes dough pieces on a conveyer that are sprayed before baking with liquid fat intermittently delivered by spraying nozzles connected respectively to the cylinders of a multi-cylinder pump and the operation of the latter is so timed, in relation to the speed of the conveyer, that each dough piece is subjected to several collective discharges while passing the spraying nozzles. The conveyer belt is carried on rollers journalled in brackets and its top run extends flush with the top of casing and is supported on flat strips or small rollers. One roller is driven through gearing including reduction gear-box by an electric motor. The output shaft of the gear-box is connected by a chain (or belt) to the shaft of a high pressure pump. Edible fat is contained in a tank heated by a thermostatically-controlled electric heater and flows through a pipe to the intake of the pump which has three plungers working in three cylinders each connected by a pipe to a nozzle. Each pump cylinder communicates with a common suction chamber through inlet ports which are shut off during the latter part of the delivery stroke, the trapped oil having access to a circumferential helical groove so that, at a point determined by the angular position of the plunger, it uncovers one of the inlet ports and terminates delivery by allowing oil to return to the suction chamber. The output is controlled by rotating the plungers by a rack-rod. Means are provided on each nozzle for altering the type of discharge produced. The dough pieces are placed on the conveyer at its right-hand end and travel through a sheet-metal tunnel to a hood containing the nozzles and thence to a second tunnel.

Brief description of the accompanying drawings
[0003] Figure 1 illustrates a high pressure fuel pump in one embodiment of the invention.
[0004] Figure 2 illustrates a plunger of the high pressure fuel pump in one embodiment of the invention.

Detailed description of the embodiments
[0005] Figure 1 illustrates a high pressure fuel pump 10. The high pressure fuel pump 10 comprises a housing 12, and a plunger 14 positioned within a pumping chamber defined within the housing 12. The plunger 14 comprises a solid portion 16, and a first vertical groove 18 defined in the solid portion 16, the first vertical groove 18 adapted to channel pressurized fuel from the pumping chamber to an inlet portion of the high pressure fuel pump 10. A helical groove 20 is in flow communication with the first vertical groove 18, the helical groove 20 adapted to channel pressurized fuel that flows through the first vertical groove 18 to the inlet portion of the high pressure fuel pump 10. A second vertical groove 22 is defined in the solid portion 16, the second vertical groove 22 extending from a top portion 24 of the plunger 14 to the helical groove 20, the second vertical groove 22 adapted to channel pressurized fuel that flows through the second vertical groove 22 to the inlet portion of the high pressure fuel pump 10 via the helical groove 20.

[0006] In the exemplary embodiment, a high pressure fuel pump 10 is described. The high pressure fuel pump 10 comprises a housing 12 that is used to house a plurality of components of the high pressure fuel pump 10. A plunger 14 is positioned within the pumping chamber that is defined within the housing 12. In the exemplary embodiment, the plunger 14 comprises a solid portion 16 that is defined all along the length of its shaft that reciprocates within the housing 12 and delivers pressurized fuel from the pumping chamber of the high pressure fuel pump 10 to a fuel injector.
[0007] Figure 2 illustrates a plunger 14 of the high pressure fuel pump 10 in one embodiment of the invention. A first vertical groove 18 is defined in the solid portion 16 of the plunger 14 that extends from a top portion 24 of the plunger 14 along a sidewall of the plunger 14 and culminates in the helical groove 20. More specifically, the first vertical groove 18 is adapted to channel pressurized fuel from the pumping chamber of the high pressure fuel pump 10 to an inlet portion of the high pressure fuel pump 10 via the helical groove 20. In the exemplary embodiment, the helical groove 20 is in flow communication with the first vertical groove 18, wherein the helical groove 20 is adapted to channel pressurized fuel that flows through the first vertical groove 18 to the inlet portion of the high pressure fuel pump 10.

[0008] When the first vertical groove 18 is aligned with the pumping chamber of the high pressure fuel pump, fuel flows from the pumping chamber of the high pressure fuel pump through the first vertical groove 18, from where it is channeled back to the inlet portion of the high pressure fuel pump 10. As the plunger 14 of the high pressure fuel pump 10 is rotated, the first vertical groove 18 rotates such that a smaller fraction of pressurized fuel is channeled from the pumping chamber of the high pressure fuel pump 10 to the inlet portion of the high pressure fuel pump 10 via the helical groove 20. As the first vertical groove 18 continues to rotate, the flow of fuel from the pumping chamber to the inlet portion of the high pressure fuel pump 10 via the helical groove 20 is stopped due to the non-alignment of the first vertical groove 18 with the pumping chamber of the high pressure fuel pump 10.

[0009] In the exemplary embodiment, a second vertical groove 22 is defined in the solid portion. The second vertical groove 22 extends from the top portion 24 of the plunger 14 to the helical groove 20. More specifically, the second vertical groove 22 is adapted to channel pressurized fuel that flows through the second vertical groove 22 to the inlet portion of the high pressure fuel pump 10 via the helical groove 20. In an exemplary embodiment, a width of the second vertical groove 22 is smaller than a width of the first vertical groove 18. Therefore, once the second vertical groove 22 is aligned with the pumping chamber of the high pressure fuel pump 10 due to the rotation of the plunger 14, the pressurized fuel from the pumping chamber of the high pressure fuel pump 10 is channeled to the inlet portion of the high pressure fuel pump 10 via the second vertical groove 22 then via the helical groove 20 respectively. Moreover, in the exemplary embodiment, a depth of the second vertical groove 22 is lesser than a depth of the first vertical groove 18. Therefore, the volume of the pressurized fuel that is channeled from the pumping chamber of the high pressure fuel pump 10 to the inlet portion of the high pressure fuel pump 10 via the second vertical groove 22 and via the helical groove 20 is lesser than the volume of the pressurized fuel that is channeled from the pumping chamber of the high pressure fuel pump 20 to the inlet portion of the high pressure fuel pump 10 via the first vertical groove 18 and via the helical groove 20 respectively.

[0010] A working of the high pressure fuel pump 10 is described as an example. As the first vertical groove 18 of the plunger 14 is aligned with the pumping chamber of the high pressure fuel pump 10 and the fuel inlet path, the fuel from the pumping chamber flows through the first vertical groove 18 and to the fuel inlet path via the helical groove 20. As the rack that is secured to the plunger 14 translates, the plunger 14 is rotated. As the plunger 14 rotates, the quantity of fuel that is delivered from the pumping chamber to the fuel inlet path via the first vertical groove 18 and via the helical groove 20 decreases. As the plunger continues to rotate, the first vertical groove 18 is completely misaligned with the fuel inlet path of the high pressure fuel pump 10. Therefore, at this point the flow of fuel from the pumping chamber of the high pressure fuel pump 10 to the fuel inlet path via the first vertical groove 18 of the high pressure fuel pump is completely stopped. As the plunger 14 continues its ascent, the fuel that is present in the pumping chamber of the high pressure fuel pump 10 gets pressurized and delivered to the fuel injector.

[0011] If the governor that controls the control rack that is secured to the plunger 14 of the high pressure fuel pump 10 fails, the control rack is translated to cause the plunger 14 to rotate such that there is high flow of fuel from the pumping chamber of the high pressure fuel pump 10 to the fuel inlet path of the fuel injector. To prevent this from occurring, the second vertical groove 22 is provided in the plunger 14 of the high pressure fuel pump 10. As the plunger rotates, the second vertical groove 22 gets aligned with the fuel inlet path of the high pressure fuel pump 10. Therein, the pressurized fuel from the pumping chamber of the high pressure fuel pump 10 is delivered to the fuel inlet path via the second vertical groove 22. Therefore, the fuel that is present in the pumping chamber of the high pressure fuel pump 10 is not pressurized and is not delivered from the high pressure fuel pump 10 to the fuel injector. Instead, the pressurized fuel from the pumping chamber of the high pressure fuel pump 10 flows to the fuel inlet path via the second vertical groove 22 and the helical groove 20 respectively. Hence, the presence of the second vertical groove 22 in the plunger 14 of the high pressure fuel pump 10 acts as a safety mechanism to cause the pressurized fuel that is present in the pumping chamber of the high pressure fuel pump 10 from flowing to the fuel inlet path via the second vertical groove 22 and the helical groove 20 instead of getting further pressurized and delivered from the high pressure fuel pump 10 to the fuel injector.

[0012] It must be understood that the embodiments explained above are only illustrative and do not limit the scope of the disclosure. Many modifications in the embodiments with regard to dimensions of various components are envisaged and form a part of this invention. The scope of the invention is only limited by the scope of the claims.