Claims:CLAIMS

We Claim

1. A high pressure fuel pump (10), said high pressure fuel pump (10) comprising:
a housing (12), and a plunger (14) adapted to reciprocate within a pumping chamber defined within said housing (12);
a helix groove (16) defined on an outer circumference of said plunger (14), the helix groove (16) adapted to channel pressurized fuel from within the pumping chamber defined within said housing (12) to a fuel gallery (20) during an end of a pumping stroke of said plunger (14);
a stop groove (18) defined at an end of the helix groove (16), the stop groove (18) adapted to channel pressurized fuel from within the pumping chamber defined within said housing (12) to said fuel gallery (20) during a stop condition of said high pressure fuel pump (10), and wherein said plunger (14) is adapted to be rotated to facilitate varying an orientation of the helix groove (16) and the stop groove (18) for different loading conditions of said high pressure fuel pump (10);
a barrel (22) positioned between said plunger (14) and said housing (12); characterized in that
a partial circumferential groove (24) defined from an end of said plunger (14) that is proximate to the pumping chamber defined within said housing (12) and extending along a longitudinal axis of said plunger (14), the partial circumferential groove (24) adapted to vary a delivery timing of pressurized fuel from the pumping chamber defined within the housing (12) of said high pressure fuel pump (10) to a fuel injector.

2. The high pressure fuel pump (10) in accordance with Claim 1, wherein a diameter of the partial circumferential groove (24) is smaller than a diameter of said plunger (14), and wherein the partial circumferential groove (24) is sized such that a film of fuel is formed between the partial circumferential groove (24) and the barrel (22) at higher pumping speeds of said plunger (14) of said high pressure fuel pump (10).

3. The high pressure fuel pump (10) in accordance with Claim 1, wherein the partial circumferential groove (24) extends from the stop groove (18) defined at an end of the helix groove (16) at its first end to a displacement that is equal to a maximum operating range of said plunger and along an outer circumference of said plunger (14).

4. The high pressure fuel pump (10) in accordance with Claim 1, wherein the partial circumferential groove (24) extends from the stop groove (18) defined at an end of the helix groove (16) at its first end to a displacement that is equal to a desired working range of said plunger and along an outer circumference of said plunger (14).

5. The high pressure fuel pump (10) in accordance with Claim 1, wherein the partial circumferential groove (24) is of a uniform diameter along a circumference of said plunger (14).

6. The high pressure fuel pump (10) in accordance with Claim 1, wherein a diameter of the partial circumferential groove (24) is defined by a user.

7. The high pressure fuel pump (10) in accordance with Claim 1, wherein a length of the partial circumferential groove (24) is defined by a user.
, 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 partial circumferential groove defined in a plunger of the high pressure fuel pump.

Background of the invention
[0002] IN 202041037038 describes a high pressure fuel pump. The high pressure fuel pump comprises a housing, and a plunger adapted to reciprocate within a pumping chamber defined within the housing. A helix groove is defined on an outer circumference of the plunger. The helix groove is adapted to channel pressurized fuel from within the pumping chamber defined within the housing to a fuel gallery during an end of a pumping stroke of the plunger. A stop groove is defined at an end of the helix groove. The stop groove is adapted to channel pressurized fuel from within the pumping chamber defined within the housing to the fuel gallery during a stop condition of the high pressure fuel pump. The plunger is adapted to be rotated to facilitate varying an orientation of the helix groove and the stop groove for different loading conditions of the high pressure fuel pump. A barrel is positioned between the plunger and the housing. A partial circumferential groove is defined from an end of the plunger that is proximate to the pumping chamber defined within the housing and extending along a longitudinal axis of the plunger. The partial circumferential groove is adapted to vary a delivery timing of pressurized fuel from the pumping chamber defined within the housing of the high pressure fuel pump to a fuel injector.

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 that reciprocates within a barrel 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 adapted to reciprocate within a pumping chamber defined within the housing 12. A helix groove 16 is defined on an outer circumference of the plunger 14. The helix groove 16 is adapted to channel pressurized fuel from within the pumping chamber defined within the housing 12 to a fuel gallery 20 during an end of a pumping stroke of the plunger 14. A stop groove 18 is defined at an end of the helix groove 16. The stop groove 18 is adapted to channel pressurized fuel from within the pumping chamber defined within the housing 12 to the fuel gallery 20 during a stop condition of the high pressure fuel pump 10. The plunger 14 is adapted to be rotated to facilitate varying an orientation of the helix groove 16 and the stop groove 18 for different loading conditions of the high pressure fuel pump 10. A barrel 22 is positioned between the plunger 14 and the housing 12. A partial circumferential groove 24 is defined from an end of the plunger 14 that is proximate to the pumping chamber defined within the housing 12 and extending along a longitudinal axis of the plunger 14. The partial circumferential groove 24 is adapted to vary a delivery timing of pressurized fuel from the pumping chamber defined within the housing 12 of the high pressure fuel pump 10 to a fuel injector.

[0006] Figure 1 illustrates a high pressure fuel pump 10. The high pressure fuel pump 10 comprises a housing 12. In the exemplary embodiment, a plunger 14 is adapted to reciprocate within a pumping chamber that is defined within the housing 12 and deliver pressurized fuel to a fuel injector (not shown) that is in flow communication with an outlet of the high pressure fuel pump 10.

[0007] Figure 2 illustrates a plunger 14 that is positioned within the barrel 22 of the high pressure fuel pump 10. A helix groove 16 is defined on an outer circumference of the plunger 14. The helix groove 16 is in flow communication with a fuel inlet port 30 that is defined in the barrel 22 when the plunger 14 translates upwardly by a predetermined displacement. The alignment of the helix groove 16 with the fuel inlet port 30 discharges the high pressure fuel that is present in the pumping chamber of the high pressure fuel pump 10 at the end of the pumping stroke to a low pressure fuel gallery 20 via the helix groove 16 and via the fuel inlet port 30 respectively.

[0008] In an exemplary embodiment, a stop groove 18 is defined at an end of the helix groove 16. The stop groove 18 is adapted to channel pressurized fuel from within the pumping chamber that is defined within the housing 12 to the fuel gallery 20 during a stop condition of the high pressure fuel pump 10. More specifically, during a stop condition of the high pressure fuel pump 10, the plunger 14 of the high pressure fuel pump 10 is rotated such that the stop groove 18 that is defined at the end of the helix groove 16 is in flow communication with the fuel inlet port 30. Therefore, the pressurized fuel from within the pumping chamber that is defined within the housing 12 is channeled to the fuel gallery 20 via the stop groove 18 and via the fuel inlet port 30 with no pressurization and delivery of fuel occurring from the pumping chamber of the high pressure fuel pump 10.

[0009] In an exemplary embodiment, the plunger 14 is adapted to be rotated to facilitate varying an orientation of the helix groove 16 and the stop groove 18 for different loading conditions of the high pressure fuel pump 10. More specifically, from the stop condition of the high pressure fuel pump 10 which results in the complete fuel being discharged from the pumping chamber to the fuel gallery 20 via the stop groove 18 and via the fuel inlet port 30, the fuel is continuously discharged from the pumping chamber to the fuel gallery 20 via the helix groove 16 and via the fuel inlet port 30 for different displacement positions of the fuel inlet port 30 from the helix groove 16 as the plunger 14 is rotated from the stop position to a maximum load position. As the plunger 14 is continuously rotated from the position where the helix groove 16 / stop groove 18 is in alignment with the fuel inlet port 30, at the maximum load position of the plunger 14, the displacement between the fuel inlet port 30 and the helix groove 16 is maximum. The maximum displacement between the fuel inlet port 30 and the helix groove 16 results in the maximum fuel delivery quantity that is delivered from the pumping chamber of the high pressure fuel pump 10 to the engine before the helix groove 16 becomes aligned with the fuel inlet port 30. The alignment of the helix groove 16 with the fuel inlet port 30 after the maximum quantity of fuel is delivered from the pumping chamber of the high pressure fuel pump 10 to the engine causes all the fuel that is within the pumping chamber to be delivered to the fuel gallery 20 via the helix groove 16 and via the fuel inlet port 30 of the high pressure fuel pump 10.

[0010] A barrel 22 is positioned between the plunger 14 and the housing 12. The barrel 22 comprises the fuel inlet port 30 extending from an inner surface of the barrel 22 to an outer surface of the barrel 22, and in flow communication with the fuel gallery 20 of the high pressure fuel pump 10. In the exemplary embodiment, the fuel inlet port 30 is adapted to channel pressurized fuel from the helix groove 16 that is defined in the outer circumference of the plunger 14 to the fuel gallery 20 during the end of the pumping stroke of the plunger 14 for different loading positions of the high pressure fuel pump 10. Alternatively, the fuel inlet port 30 is adapted to channel pressurized fuel from the stop groove 18 of the plunger 14 to the fuel gallery 20 during the stop condition of the high pressure fuel pump 10.

[0011] In the exemplary embodiment, a partial circumferential groove 24 is defined from an end of the plunger 14 that is proximate to the pumping chamber defined within the housing 12. More specifically, the partial circumferential groove 24 that is defined from an end of the plunger 14 that is proximate to the pumping chamber defined within the housing 12 extends along a longitudinal axis of the plunger 14. In an exemplary embodiment, the partial circumferential groove 24 extends around a circumference of the plunger 14 from one end of the stop groove 18 defined at an end of the helix groove 16 at its first end to a displacement that is equal to a maximum operating range of the plunger and along an outer circumference of the plunger 14. In an alternate exemplary embodiment, the partial circumferential groove 24 extends partially around the outer circumference of the plunger 14 from an end of the stop groove 18 until the termination of the helix groove 16. In yet another alternate exemplary embodiment, the partial circumferential groove 24 extends partially around the outer circumference of the plunger 14 from the stop groove 18 defined at an end of the helix groove 16 at its first end to a displacement that is equal to a desired working range of the plunger and along an outer circumference of the plunger 14. As will be explained in further detail below, the partial circumferential groove 24 is adapted to vary a delivery timing of pressurized fuel from the pumping chamber of the high pressure fuel pump 10 to a fuel injector.

[0012] In an exemplary embodiment, a diameter of the partial circumferential groove 24 is smaller than a diameter of the plunger 14. More specifically, the diameter of the partial circumferential groove 24 is sized such that a film of fuel can be created between the partial circumferential groove 24 and the barrel 22. The film of fuel that is created between the partial circumferential groove 24 and the barrel 22 exists for higher pumping speeds of the plunger 14 of the high pressure fuel pump 10. The partial circumferential groove 24 in the present embodiment extends from the stop groove 18 that is defined at an end of the helix groove 16 at its first end to a displacement that is equal to a maximum operating range of the plunger, and along an outer circumference of the plunger 14. Therefore, the beginning of the partial circumferential groove 24 is aligned with the beginning of the helix groove 16 / stop groove 18, and the partial circumferential groove 24 culminates at the culmination of the helix groove 16 that is equal to the maximum operating range of the plunger 14 and along the outer circumference of the plunger 14. Moreover, the partial circumferential groove 24 extends along an outer circumference of the plunger 14 from an end of the plunger 14 that is adjoining the pumping chamber to a portion along the longitudinal axis of the plunger 14. The length of the partial circumferential groove 24 is predetermined by a user based on a user specific application, and may be a design parameter that may be varied by the user.

[0013] In an alternate exemplary embodiment, the partial circumferential groove 24 in the present embodiment extends from the stop groove 18 that is defined at the end of the helix groove 16 at its first end to a displacement that is equal to a desired working range of the plunger and along an outer circumference of the plunger 14. Therefore, the beginning of the partial circumferential groove 24 is aligned with the beginning of the stop groove 18 / beginning of the helix groove 16, and the partial circumferential groove 24 culminates at a displacement that is equal to a desired working range of the plunger. Moreover, the partial circumferential groove 24 extends along an outer circumference of the plunger 14 from an end of the plunger 14 that is adjoining the pumping chamber to a portion that is along the longitudinal axis of the plunger 14. The length of the partial circumferential groove 24 is predetermined by the user based on the user specific application, and may be a design parameter that may be varied by the user.

[0014] The partial circumferential groove 24 is of a uniform diameter and is defined along the outer circumference of the plunger 14. More specifically, from the origination of the partial circumferential groove 24 until the termination of the partial circumferential groove 24, the diameter of the partial circumferential groove 24 is uniform for the rationale which will be explained in further detail below. In addition, in an exemplary embodiment, a diameter of the partial circumferential groove 24 is determined by a user based on the user’s requirement for a specific application. Moreover, the length of the partial circumferential groove 24 that extends from the pumping chamber of the high pressure fuel pump 10 along the longitudinal axis of the plunger 14 is determined by the user based on the user’s requirement for a specific application.

[0015] A working of the high pressure fuel pump 10 is described as an example. When the plunger 14 of the high pressure fuel pump 10 reciprocates within the pumping chamber and delivers pressurized fuel to a fuel injector at higher pumping speeds, a film of fuel is formed between the partial circumferential groove 24 that is defined in the plunger 14 and the barrel 22 of the high pressure fuel pump 10. As the partial circumferential groove 24 comes in flow communication with the fuel inlet port 30 of the high pressure fuel pump 10, the film of fuel continues to be maintained between the partial circumferential groove 24 that is defined in the plunger 14 and the barrel 22 of the high pressure fuel pump 10. The film of fuel that continues to be maintained between the partial circumferential groove 24 that is defined in the plunger 14 and the barrel 22 of the high pressure fuel pump 10 maintains the current pressure of fuel in the pumping chamber of the high pressure fuel pump 10 that is delivered to the fuel injector even when the fuel inlet port 30 is in flow communication with the partial circumferential groove 24. This is because the top portion of the film of fuel that fills the partial circumferential groove acts like the top portion of the plunger 14, thereby not allowing the fuel from the pumping chamber to be discharged into the fuel gallery 20 via the fuel inlet port 30 even when the fuel inlet port 30 comes in flow communication with the film of fuel that exists between the circumferential groove 24 and the barrel 22.

[0016] As the plunger 14 is rotated by a control rod owing to a decrease in the speed of the engine, the viscous forces that are required to collapse the film of fuel between the partial circumferential groove 24 that is defined in the plunger 14 and the barrel 22 of the high pressure fuel pump 10 exceeds the inertial forces that are responsible for maintaining the film of fuel between the partial circumferential groove 24 that is defined in the plunger 14 and the barrel 22 of the high pressure fuel pump 10. As the partial circumferential groove 24 that is defined in the plunger 14 comes in flow communication with the fuel inlet port 30 of the high pressure fuel pump 10, the film of fuel that collapses between the partial circumferential groove 24 that is defined in the plunger 14 and the barrel 22 of the high pressure fuel pump 10 is channeled to the fuel gallery 20 of the high pressure fuel pump 10 via the fuel inlet port 30. Therefore, a portion of the fuel from the pumping chamber of the high pressure fuel pump 10 flows downwardly due to gravity between the plunger 14 and the barrel 22, thereby decreasing the pressure of fuel as well as the quantity of pressurized fuel within the pumping chamber of the high pressure fuel pump 10 that is delivered to the fuel injector. Moreover, due to a delay in the pressurization of fuel in the pumping chamber that consequently occurs due to the downward flow of fuel between the plunger 14 and the barrel 22, the fuel is delivered from the high pressure fuel pump 10 at a later time in contrast with a time at which the fuel was originally delivered from the high pressure fuel pump 10. The delivery of fuel from the high pressure fuel pump 10 at the later time in contrast with the time at which the fuel was originally delivered from the high pressure fuel pump 10 causes a retardation in the delivery timing of pressurized fuel from the pumping chamber defined within the housing 12 of the high pressure fuel pump 10 to the fuel injector. As the speed of the high pressure fuel pump 10 decreases further at lower fuel pumping speeds, the film of fuel that is formed between the partial circumferential groove 24 that is defined in the plunger 14 and the barrel 22 of the high pressure fuel pump 10 continues to reduce in fuel film level from a top surface of the partial circumferential groove 24 until a bottom surface of the partial circumferential groove 24. As the film of fuel approaches the bottom surface of the partial circumferential groove 24, the plunger 14 of the high pressure fuel pump 10 is rotated to a position where the stop groove 18 becomes aligned with the fuel inlet port 30 that is defined in the barrel 22 of the high pressure fuel pump 10. At the position where the stop groove 18 becomes aligned with the fuel inlet port 30 that is defined in the barrel 22 of the high pressure fuel pump 10, all of the fuel that is present within the pumping chamber of the high pressure fuel pump 10 is discharged into the fuel gallery 20 via the stop groove 18 such that no pressurization and delivery of fuel occurs from the pumping chamber of the high pressure fuel pump 10 to the fuel injector.

[0017] As the speed of the high pressure fuel pump 10 is increased, the control rod rotates the plunger 14 of the high pressure fuel pump 10 towards the full load position. Consequently, the higher speed of the plunger 14 of the high pressure fuel pump 10 causes the inertial forces that are responsible for maintaining the film of fuel between the partial circumferential groove 24 that is defined in the plunger 14 and the barrel 22 of the high pressure fuel pump 10 to exceed the viscous forces that are required to collapse the film of fuel between the partial circumferential groove 24 that is defined in the plunger 14 and the barrel 22 of the high pressure fuel pump 10. Therefore, even when the fuel inlet port 30 that is defined in the barrel 22 of the high pressure fuel pump 10 comes in flow communication with the partial circumferential groove 24 that is defined in the plunger 14 when the plunger 14 translates towards the top dead center position, the film of fuel that is formed between the partial circumferential groove 24 that is defined in the plunger 14 and the fuel inlet port 30 that is defined in the barrel 22 does not collapse, and is therefore maintained steady. Consequently, the pressure of fuel as well as the quantity of the pressurized fuel that is delivered from the pumping chamber of the high pressure fuel pump 10 to the fuel injector continues to be maintained at the same operating level for higher loads and higher operating speed conditions of the high pressure fuel pump 10 during the normal operating range of the high pressure fuel pump 10. As the pressure of fuel as well as the quantity of the pressurized fuel that is delivered from the pumping chamber of the high pressure fuel pump 10 to the fuel injector continues to be maintained at the same operating level, there is no delay in the pressurization of fuel and the delivery of fuel from the pumping chamber of the high pressure fuel pump 10 to the fuel injector. Therefore, there is an advance in the delivery timing of pressurized fuel from the pumping chamber defined within the housing 12 of the high pressure fuel pump 10 to the fuel injector in contrast with the retardation in the delivery timing of pressurized fuel from the pumping chamber defined within the housing 12 of the high pressure fuel pump 10 to the fuel injector that occurs at lower pumping speeds of the high pressure fuel pump 10.

[0018] The uniform diameter of the partial circumferential groove 24 that extends from the origination of the partial circumferential groove 24 proximate to the stop groove 18 until the termination of the partial circumferential groove 24 that is farthest away from the stop groove facilitates a uniform thickness of the film of fuel to be maintained between the partial circumferential groove 24 of the plunger 14 and the barrel 22 of the high pressure fuel pump 10 for different operating speeds of the high pressure fuel pump 10. More specifically, at different operating speeds of the high pressure fuel pump 10, different concentric levels of the uniform thickness of the film of fuel are maintained between the partial circumferential groove 24 that is defined in the plunger 14 and the barrel 22 of the high pressure fuel pump 10. Each concentric level of the film of fuel extends around the circumference of the partial circumferential groove 24 from the origination of the stop groove 18 until the termination of the partial circumferential groove 24, and represents a state of dynamic equilibrium between the inertial forces and the viscous forces that are responsible for maintaining the film of fuel and collapsing the film of fuel between the partial circumferential groove 24 of the plunger 14 and the barrel 22 of the high pressure fuel pump 10 respectively.

[0019] In an exemplary embodiment, the partial circumferential groove 24 extends from the stop groove 18 that is defined at an end of the helix groove 16 at its first end to a displacement that is equal to a maximum operating range of the plunger, and along an outer circumference of the plunger 14. In an alternate exemplary embodiment, the partial circumferential groove 24 extends from the stop groove 18 that is defined at an end of the helix groove 16 at its first end to a displacement that is equal to a desired operational working range of the plunger 14 and along an outer circumference of the plunger 14.

[0020] 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