Claims:We Claim

1. A fuel injection pump (10), said fuel injection pump (10) comprising:
a housing (12), said housing (12) comprising a cylindrical bore (14) defined therein;
a piston (16) positioned within said cylindrical bore (14) and adapted to reciprocate within said cylindrical bore (14), said piston (16) comprising:
a first axial bore (18) extending in an axial direction and along an outer circumference of said piston (16), and a helical groove (20) extending from the first axial bore (18) through the outer circumference of said piston (16); characterized in that
a second axial bore (22) extending along the longitudinal axis of said piston (16) and through an axis of said piston (16);
a first cross hole (24) extending from the second axial bore (22) to the outer circumference of said piston (16), said first cross hole (24) positioned above said helical groove (20) and adapted to supply pressurized fuel from the second axial bore (22) to the outer circumference of said piston (16) when the first cross hole (24) is aligned with a fuel supply path (26); and
a second cross hole (28) extending from the second axial bore (22) to the outer circumference of said piston (16), said second cross hole (28) positioned below said helical groove (20) and adapted to supply pressurized fuel from the second axial bore (22) to the outer circumference of said piston (16) when the second cross hole (28) is aligned with the fuel supply path (26).

2. The fuel injection pump (10) in accordance with Claim 1 wherein the fuel supply path (26) is a fuel inlet supply path, and wherein a diameter of the fuel inlet supply path is increased to allow a greater inflow of fuel into the cylindrical bore (14) of said fuel injection pump (10).

3. The fuel injection pump (10) in accordance with Claim 1 wherein a stiffness of a spring that is secured to a fuel discharge valve of the fuel injection pump (10) is increased to allow for a faster closing of the fuel discharge valve once fuel is channeled out of the fuel injection pump (10).

4. The fuel injection pump (10) in accordance with Claim 1 wherein a diameter of the helical groove (20) is reduced to facilitate retaining a greater quantity of fuel within said cylindrical bore (14) of said fuel injection pump (10) after fuel is discharged from said cylindrical bore (14) of said fuel injection pump (10) to the fuel supply path (26) via the helical groove (20) so as to facilitate discharging fuel that is within the cylindrical bore (14) of said fuel injection pump (10) to the fuel supply path (26) via the second cross hole (28) when the second cross hole (28) is aligned with the fuel supply path (26).

5. A piston (16) of a fuel injection pump (10), said piston (16) comprising:
a first axial bore (18) extending along a longitudinal axis of said piston (16) and along an outer circumference of said piston (16), and a helical groove (20) extending from the first axial bore (18) through the outer circumference of said piston (16); characterized in that
a second axial bore (22) extending along the longitudinal axis of said piston (16) and through an axis of said piston (16);
a first cross hole (24) extending from the second axial bore (22) to the outer circumference of said piston (16), said first cross hole (24) positioned above said helical groove (20) and adapted to supply pressurized fuel from the second axial bore (22) to the outer circumference of said piston (16) when the first cross hole (24) is aligned with a fuel supply path (26); and
a second cross hole (28) extending from the second axial bore (22) to the outer circumference of said piston (16), said second cross hole (28) positioned below said helical groove (20) and adapted to supply pressurized fuel from the second axial bore (22) to the outer circumference of said piston (16) when the second cross hole (28) is aligned with the fuel supply path (26).

6. The piston (16) of the fuel injection pump (10) in accordance with Claim 5 wherein the fuel supply path (26) is a fuel inlet supply path, and wherein a diameter of the fuel inlet supply path is increased to allow a greater inflow of fuel into a cylindrical bore (14) of said fuel injection pump (10).

7. The piston (16) of the fuel injection pump (10) in accordance with Claim 5 wherein a stiffness of a spring that is secured to a fuel discharge valve of the fuel injection pump (10) is increased to allow for a faster closing of the fuel discharge valve once fuel is channeled out of the fuel injection pump (10).

8. The piston (16) of the fuel injection pump (10) in accordance with Claim 5 wherein a diameter of the helical groove (20) is reduced to facilitate retaining a greater quantity of fuel within a cylindrical bore (14) of said fuel injection pump (10) after fuel is discharged from the cylindrical bore (14) of said fuel injection pump (10) to the fuel supply path (26) via the helical groove (20) so as to facilitate discharging fuel that is within the cylindrical bore (14) of said fuel injection pump (10) to the fuel supply path (26) via the second cross hole (28) when the second cross hole (28) is aligned with the fuel supply path (26).

, 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 fuel injection pump, and more specifically to an axial hole that is formed in a piston of the fuel injection pump.

Background of the invention
[0002] GB 1411844 A describes lubricating pumps for internal combustion engines. The lubricating pump for an I.C. engine, e.g. a two-stroke, has its output controlled according to the engine throttle setting, and comprises a piston rotated by a worm and worm-wheel drive and reciprocated by the action of an annular face cam formed on the worm-wheel and biased towards a peg by a spring, the piston stroke being adjustable by a longitudinally movable stop member having a tapered cam surface engageable by a stop pin formed on the end of the piston and defining a pumping chamber, an axial groove in the piston connecting the pumping chamber alternately to an inlet port and an outlet port. The stop member is movable against a spring by a cable connected to the engine throttle control, the minimum stroke setting being adjustable by the screw. The stop pin and the seal assembly may be of different diameters to vary the pump capacity. A passage conveys lubricant from the inlet to the actuating mechanism chamber having an air venting screw.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates a piston of a fuel injection pump in one embodiment of the invention.

Detailed description of the embodiments
[0004] Figure 1 illustrates a fuel injection pump 10. The fuel injection pump 10 comprises a housing 12. The housing 12 comprises a cylindrical bore 14 defined therein. A piston 16 is positioned within the cylindrical bore 14 and adapted to reciprocate within the cylindrical bore 14. The piston 16 comprises a first axial bore 18 extending in an axial direction and along an outer circumference of the piston 16, and a helical groove 20 extending from the first axial bore 18 through the outer circumference of the piston 16. A second axial bore 22 extends along the longitudinal axis of the piston 16 and through an axis of the piston 16. A first cross hole 24 extends from the second axial bore 22 to the outer circumference of the piston 16, the first cross hole 24 positioned above the helical groove 20 and adapted to supply pressurized fuel from the second axial bore 22 to the outer circumference of the piston 16 when the first cross hole 24 is aligned with a fuel supply path 26. A second cross hole 28 extends from the second axial bore 22 to the outer circumference of the piston 16, the second cross hole 28 positioned below the helical groove 20 and adapted to supply pressurized fuel from the second axial bore 22 to the outer circumference of the piston 16 when the second cross hole 28 is aligned with the fuel supply path 26.

[0005] The fuel injection pump 10 comprises a housing 12. The housing 12 of the fuel injection pump 10 comprises a plurality of mechanical components that are integrated within the fuel injection pump 10 and is used to deliver pressurized fuel to a fuel injector (not shown). In the exemplary embodiment, the housing 12 of the fuel injection pump 10 comprises a cylindrical bore 14 that is defined therein. A piston 16 is positioned within the cylindrical bore 14 and is adapted to reciprocate within the cylindrical bore 14. The reciprocatory movement of the piston 16 within the cylindrical bore 14 causes fuel to be delivered from the cylindrical bore 14 of the fuel injection pump 10 to the fuel injector (not shown).

[0006] The piston 16 of the fuel injection pump 10 comprises a first axial bore 18 that extends along a longitudinal axis of the piston 16. More specifically, the first axial bore 18 extends along an outer circumference of the piston 16 and is adapted to allow fuel to flow along the outer circumference of the piston 16. A helical groove 20 extends from the first axial bore 18 and along an outer circumference of the piston 16. More specifically, when fuel is channeled through the first axial bore 18, the fuel flows through the first axial bore 18 and along the helical groove 20 that extends from the first axial bore 18 and along the outer circumference of the piston 16. When the fuel supply path 26 of the fuel injection pump 10 is aligned with the helical groove 20, the fuel that flows through the first axial bore 18 is channeled to the fuel supply path 26 of the fuel injection pump 10 via the helical groove 20. In an exemplary embodiment, a diameter of the helical groove 20 is reduced with reference to the diameter of helical grooves of previously known fuel injection pumps to facilitate retaining a greater quantity of fuel within the cylindrical bore 14 of the fuel injection pump 10 after fuel is discharged from the cylindrical bore 14 of the fuel injection pump 10 to the fuel supply path 26 via the helical groove 20.

[0007] A second axial bore 22 extends along the longitudinal axis of the piston 16 and through an axis of the piston 16. More specifically, a first end of the axial bore 22 is in flow communication with the cylindrical bore 14 of the fuel injection pump 10 and receives fuel that is within the cylindrical bore 14 of the fuel injection pump 10. A first cross hole 24 extends from the second axial bore 22 to the outer circumference of the piston 16. More specifically, the first cross hole 24 is positioned above the helical groove 20 and is adapted to supply pressurized fuel from the second axial bore 22 to the outer circumference of the piston 16 when the first cross hole 24 is aligned with the fuel supply path 26. In the exemplary embodiment, the first cross hole 24 is positioned above the helical groove 20 and is adapted to supply pressurized fuel from the second axial bore 22 to the outer circumference of the piston 16 in order to end pilot injection of the fuel injection pump 10 and marks the beginning of the main injection event from the fuel injection pump 10.

[0008] A second cross hole 28 extends from the second axial bore 22 to the outer circumference of the piston 16. More specifically, the second cross hole 28 is positioned below the helical groove 20 and is adapted to supply pressurized fuel from the second axial bore 22 to the outer circumference of the piston 16 when the second cross hole 28 is aligned with the fuel supply path 26. In the exemplary embodiment, the second cross hole 28 is positioned below the helical groove 20 and is adapted to supply pressurized fuel from the second axial bore 28 to the outer circumference of the piston 16 via the second cross hole 28 in order to end post injection of the fuel injection pump 10.

[0009] In an exemplary embodiment, the fuel supply path 26 is a fuel inlet supply path. More specifically, the diameter of the fuel inlet supply path 26 is increased to allow a greater inflow of fuel into the cylindrical bore 14 of the fuel injection pump 16. As the first cross hole 24 and the second cross hole 28 allow the fuel to be supplied from the second axial bore 22 to the fuel supply path 26, the quantity of fuel that is retained within the cylindrical bore 14 of the fuel injection pump 10 significantly decreases. Therefore, the quantity of fuel that is retained within the cylindrical bore 14 of the fuel injection pump 10 for main injection is reduced. Therefore, an increase in the diameter of the fuel supply path 26 allows a greater quantity of fuel to be channeled into the cylindrical bore 14 of the fuel injection pump 10. Therefore, the release of fuel from the fuel injection pump 10 via the first cross hole 24 and the second cross hole 28 does not significantly reduce the quantity of fuel that is available in the cylindrical bore 14 of the fuel injection pump 10 for the main injection event.

[0010] A working of the fuel injection pump 10 is described as an example. As the piston 16 that is within the cylindrical bore 14 of the fuel injection pump 10 begins translating towards the top dead center, the fuel that is within the fuel supply path 26 begin flowing into the cylindrical bore 14 of the fuel injection pump 10. Due to the larger diameter of the fuel supply path 26 in comparison to fuel injection pumps known in the art, a greater quantity of fuel is channeled into the cylindrical bore 14 of the fuel injection pump 10 via the fuel supply path 26. Once the piston 16 of the fuel injection pump 10 crosses the fuel supply path 26, the fuel that is present within the cylindrical bore 14 of the fuel injection pump 10 gets compressed by the piston 16. Once the pressure within the cylindrical bore 14 of the fuel injection pump 10 exceeds the threshold pressure that is required to open the fuel outlet valve, the fuel outlet valve is opened, thereby channeling the fuel from the cylindrical bore 14 of the fuel injection pump 10 to the fuel injector.

[0011] As the piston 16 of the fuel injection pump 10 continues rising, the first cross hole 24 that extends from the second axial bore 22 to the outer circumference of the piston 16 is aligned with the fuel supply path 26. Therefore, the first cross hole 24 that is positioned above the helical groove 20 is adapted to supply pressurized fuel from the second axial bore 22 to the outer circumference of the piston 16 when the first cross hole 24 is aligned with the fuel supply path 26. As the fuel flows out of the cylindrical bore 14 of the fuel injection pump 10 via the first cross hole 24, the pressure of the fuel within the cylindrical bore 14 of the fuel injection pump 10 decreases. The decrease in the pressure of the fuel within the cylindrical bore 14 of the fuel injection pump 10 causes the fuel outlet supply valve to close, thereby ending pilot injection. As the piston 16 of the fuel injection pump 10 continues rising, the first cross hole 24 that extends from the second axial bore 22 to the outer circumference of the piston 16 also rises, thereby closing the first cross hole 24 connection with the fuel supply path 26. This causes the fuel that is present within the cylindrical bore 14 of the fuel injection pump 10 to get compressed and delivered from the fuel injection pump 10 to the fuel injector, thereby causing main injection of the fuel injection pump 10.

[0012] When the helical groove 20 that extends from the first axial bore 18 through the outer circumference of the fuel injection pump 10 is aligned with the fuel supply path 26, fuel from the cylindrical bore 14 of the fuel injection pump 10 is channeled to the fuel supply path 26 via the first axial bore 18 and the helical groove 20. The flow of fuel through the helical groove 20 causes the pressure of fuel within the cylindrical bore 14 of the fuel injection pump 10 to decrease, thereby causing the fuel outlet supply valve to close, and ending the main injection event. As the piston 16 of the fuel injection pump 10 continues rising, the helical groove 20 that extends from the first axial bore 18 to the outer circumference of the piston 16 also rises, thereby closing the helical groove 20 connection with the fuel supply path 26. This causes the fuel that is present within the cylindrical bore 14 of the fuel injection pump 10 to get compressed and delivered from the fuel injection pump 10 to the fuel injector thereby causing post injection of the fuel injection pump 10.

[0013] As the piston 16 of the fuel injection pump 10 continues rising, the second cross hole 28 that extends from the second axial bore 22 to the outer circumference of the piston 16 is aligned with the fuel supply path 26. Therefore, the second cross hole 28 that is positioned below the helical groove 20 is adapted to supply pressurized fuel from the second axial bore 22 to the outer circumference of the piston 16 when the second cross hole 28 is aligned with the fuel supply path 26. As the fuel flows out of the cylindrical bore 14 of the fuel injection pump 10 via the second cross hole 28, the pressure of the fuel within the cylindrical bore 14 of the fuel injection pump 10 decreases. The decrease in the pressure of fuel within the cylindrical bore 14 of the fuel injection pump 10 causes the fuel outlet supply valve to close, thereby ending post injection.

[0014] 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.