Claims:We Claim

1. A high pressure fuel pump (10), said high pressure fuel pump (10) comprising:
a housing (12);
an element (8) positioned within said housing (12), the element (8) comprising a barrel (32) and a plunger (14) positioned within said barrel (32), said plunger (14) adapted to reciprocate within said barrel (32);
a vertical groove (16) defined in said plunger (14), the vertical groove (16) adapted to extend along a sidewall of said plunger (14) and adapted to channel fuel that is present within a pumping chamber (40) that is defined within said barrel (32) through the vertical groove (16); characterized in that
a variable pitch helix groove (18) in flow communication with the vertical groove (16) and extending angularly along a sidewall of said plunger (14), the variable pitch helix groove (18) comprising a first shallow helix groove (20) having a first angle with reference to a horizontal axis, and a second steep helix groove (22) in flow communication with the first shallow helix groove (20) and having a second angle with reference to the horizontal axis, wherein the first angle between the first shallow helix groove (20) and the horizontal axis is lower than the second angle between the second steep helix groove (22) and the horizontal axis.

2. The high pressure fuel pump (10) in accordance with Claim 1, wherein a first end of the first shallow helix groove (20) is in flow communication with the vertical groove (16), the first shallow helix groove (20) extending partially along an outer circumference of said plunger (14) from the vertical groove (16) to an opposite second end of the first shallow helix groove (20).
3. The high pressure fuel pump (10) in accordance with Claim 2, wherein a first end of the second steep helix groove (22) is in flow communication with the opposite second end of the first shallow helix groove (20), the second steep helix groove extending partially along an outer circumference of said plunger (14) from the opposite second end of the first shallow helix groove (20) to an opposite second end of the second steep helix groove (22).

4. The high pressure fuel pump (10) in accordance with Claim 1, wherein a length of the first shallow helix groove (20) and a length of the second steep helix groove (22) are each pre-defined by a user based on a user specific application, the first shallow helix groove (20) operable at a lower speed and lower load operating condition of said high pressure fuel pump (10), the second steep helix groove (22) operable at a higher speed and higher load operating condition of said high pressure fuel pump (10).

5. The high pressure fuel pump (10) in accordance with Claim 1, wherein the length of the first shallow helix groove (20) is sized such that when said plunger (14) translates towards its top dead center position, a lower quantity of pressurized fuel is delivered during the lower speed and lower load operating condition of said high pressure fuel pump (10) when a fuel inlet port (42) translates from a top of said plunger (14) until the fuel inlet port (42) becomes aligned with the first shallow helix groove (20).

6. The high pressure fuel pump (10) in accordance with Claim 1, wherein the length of the second steep helix groove (22) is sized such that when said plunger (14) translates towards its top dead center position, a higher quantity of pressurized fuel is delivered during the higher speed and higher load operating condition of said high pressure fuel pump (10) when a fuel inlet port (42) translates from a top of said plunger (14) until the fuel inlet port (42) becomes aligned with the second steep helix groove (22).
, 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 variable pitch helix groove that is defined in a plunger of the high pressure fuel pump.

Background of the invention
[0002] IN 202141019725 describes a high pressure fuel pump. The high pressure fuel pump comprises a housing. An element is positioned within the housing. The element comprises of a barrel and a plunger, the plunger adapted to reciprocate within the barrel. A vertical groove is defined in the plunger. The vertical groove is adapted to extend along a sidewall of the plunger. A helix groove is in flow communication with the vertical groove, and extends angularly along a sidewall of the plunger. The helix groove comprises an upper edge having a first angle with reference to a horizontal axis, a lower edge having a second angle with reference to the horizontal axis, and a connecting edge that connects the upper edge and the lower edge. The first angle between the upper edge and the horizontal axis is greater than the second angle between the lower edge and the horizontal axis.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates a high pressure fuel pump illustrating a variable pitch helix groove defined in the plunger in one embodiment of the invention.

Detailed description of the embodiments
[0004] A high pressure fuel pump 10 is described. The high pressure fuel pump 10 comprises a housing 12, and an element 8 positioned within the housing 12. The element 8 comprises a barrel 32 and a plunger 14 positioned within the barrel 32. The plunger 14 is adapted to reciprocate within the barrel 32. A vertical groove 16 is defined in the plunger 14. The vertical groove 16 is adapted to extend along a sidewall of the plunger 14, and is adapted to channel fuel that is present within a pumping chamber 40 that is defined within the barrel 32 through the vertical groove 16. A variable pitch helix groove 18 is in flow communication with the vertical groove 16 and extends angularly along a sidewall of the plunger 14. The variable pitch helix groove 18 comprises a first shallow helix groove 20 having a first angle with reference to a horizontal axis, and a second steep helix groove 22 in flow communication with the first shallow helix groove 20 and having a second angle with reference to the horizontal axis. The first angle between the first shallow helix groove 20 and the horizontal axis is lower than the second angle between the second steep helix groove 22 and the horizontal axis.

[0005] Figure 1 illustrates a plunger 14 of a high pressure fuel pump 10 in one embodiment of the invention. In an exemplary embodiment, the high pressure fuel pump 10 comprises a housing 12. An element 8 is positioned within the housing 12. The element 8 comprises a barrel 32 and a plunger 14 positioned within the barrel 32 of the high pressure fuel pump 10. The plunger 14 is adapted to reciprocate within the barrel 32 of the high pressure fuel pump 10 and translate from its bottom dead center position towards its the top dead center position. As the plunger 14 translates from its bottom dead center position towards its the top dead center position, pressurized fuel is delivered from the pumping chamber 40 of the high pressure fuel pump 10 to a fuel injector, and therein supplied to an engine cylinder for combustion. A vertical groove 16 is defined in the plunger 14, wherein the vertical groove 16 is adapted to extend along a sidewall of the plunger 14. The vertical groove 16 is adapted to channel pressurized fuel from the pumping chamber 40 of the high pressure fuel pump 10 to a variable pitch helix groove 18 that is in flow communication with the vertical groove 16. From the variable pitch helix groove 18, the pressurized fuel is discharged from the pumping chamber 40 to the fuel gallery of the high pressure fuel pump 10 via the fuel inlet port 42 that is defined in the barrel 32.

[0006] In an exemplary embodiment, the variable pitch helix groove 18 is defined in the plunger 14 of the high pressure fuel pump 10. The variable pitch helix groove 18 is in flow communication with the vertical groove 16, and extends angularly along a sidewall of the plunger 14. When the plunger 14 reciprocates within the barrel 32 of the high pressure fuel pump 10, the plunger 14 is rotated by means of the governor of the high pressure fuel pump 10. As the plunger 14 translates towards the top dead center position, the variable pitch helix groove 18 comes in flow communication with the fuel gallery of the high pressure fuel pump 10. Therein, the fuel from the pumping chamber 40 of the high pressure fuel pump 10 flows through the variable pitch helix groove 18 via the vertical groove 16, and is finally discharged to the fuel gallery via the fuel inlet port 42. In an exemplary embodiment, the variable pitch helix groove 18 extends downwardly towards a bottom portion of the plunger 14. More specifically, the variable pitch helix groove 18 extends downwardly towards the bottom portion of the plunger 14 from the vertical groove 16 at one end to an opposite second end of the variable pitch helix groove 18 at its opposite second end.

[0007] In an exemplary embodiment, the height of origination of the variable pitch helix groove 18 from the top of the plunger 14 is minimum adjoining the vertical groove 16. Conversely, the height of termination of the variable pitch helix groove 18 from the top of the plunger 14 is maximum at the end of the variable pitch helix groove 18 that is farthest away from the vertical groove 16. Therefore, between the point of origination of the variable pitch helix groove 18 and the point of termination of the variable pitch helix groove 18, the variable pitch helix groove 18 may have any user desired profile. In the exemplary embodiment, the profile of the variable pitch helix groove 18 between the point of origination of the variable pitch helix groove 18 and the point of termination of the variable pitch helix groove 18 is that of a linear stepped profile having a first length and a first angle extending partially around the circumferential length of the plunger 14, and a second length and a second angle extending partially from the termination of the first length and around the circumferential length of the plunger 14. In an alternate exemplary embodiment, the profile of the variable pitch helix groove 18 between the point of origination of the variable pitch helix groove 18 and the point of termination of the variable pitch helix groove 18 is that of a parabolic stepped profile.

[0008] In an exemplary embodiment, the variable pitch helix groove 18 that is in flow communication with the vertical groove 16 extends angularly along a sidewall of the plunger 14. The variable pitch helix groove 18 comprises a first shallow helix groove 20 having a first angle with reference to a horizontal axis. In addition, the variable pitch helix groove 18 comprises a second steep helix groove 22 that is in flow communication with the first shallow helix groove 20 and having a second angle with reference to the horizontal axis. A connecting edge 24 connects an upper edge of the second steep helix groove 22 with a lower edge of the second steep helix groove 22. More specifically, the first angle between the first shallow helix groove 20 and the horizontal axis is lower than the second angle between the second steep helix groove 22 and the horizontal axis.

[0009] In an exemplary embodiment, a first end of the first shallow helix groove 20 that is in flow communication with the vertical groove 16 extends partially and angularly along a sidewall of the plunger 14. More specifically, the first shallow helix groove 20 extends partially along an outer circumference of the plunger 14 from the vertical groove 16 to an opposite second end of the first shallow helix groove 20. In addition, a first end of the second steep helix groove 22 is in flow communication with the opposite second end of the first shallow helix groove 20 and is adapted to receive pressurized fuel that flows through the first shallow helix groove 20. The second steep helix groove 22 extends partially along an outer circumference of the plunger 14 from the second end of the first shallow helix groove 20 to an opposite second end of the second steep helix groove 22.

[0010] In an exemplary embodiment, a length of the first shallow helix groove 20 and a length of the second steep helix groove 22 are each pre-defined by a user based on a user specific application. More specifically, the first shallow helix groove 20 that is defined on the plunger 14 of the high pressure fuel pump 10 is operable at a lower speed and lower load operating condition of the high pressure fuel pump 10. In addition, the second steep helix groove 22 is operable at a higher speed and higher load operating condition of the high pressure fuel pump 10. Therefore, based on the user definition of lower load and lower speed operating condition of the high pressure fuel pump 10, the length of the first shallow helix groove 20 is pre-determined by the user based on the user specific application. Moreover, based on the user definition of higher load and higher speed operating condition of the high pressure fuel pump 10, the length of the second steep helix groove 22 is pre-determined by the user based on the user specific application. In an exemplary embodiment, a length of the first shallow helix groove 20 may be equal to a length of the second steep helix groove 22. In an alternate exemplary embodiment, a length of the first shallow helix groove 20 may be lower than a length of the second steep helix groove 22 based on the user specific application. Therefore, an aspect ratio between the first shallow helix groove 20 and the second steep helix groove 22 is a variable parameter that is defined by the user based on the user specific application.

[0011] In an exemplary embodiment, the length of the first shallow helix groove 20 is sized such that when the plunger 14 translates towards its top dead center position, a lower quantity of pressurized fuel is delivered from the high pressure fuel pump 10 to the fuel injector during the low speed and low load operating condition of the high pressure fuel pump 10. More specifically, due to the lower angle of inclination of the first shallow helix groove 20 with reference to the horizontal axis, when the fuel inlet port 42 translates from a top of the plunger 14 towards the first shallow helix groove 20, the fuel inlet port 42 becomes aligned with the first shallow helix groove 20 much faster. As the fuel inlet port 42 becomes aligned with the first shallow helix groove 20 much faster, the quantity of pressurized fuel that is delivered from the high pressure fuel pump 10 to the fuel injector is correspondingly lower.

[0012] In an exemplary embodiment, the length of the second steep helix groove 22 is sized such that when the plunger 14 translates towards its top dead center position, a higher quantity of pressurized fuel is delivered from the high pressure fuel pump 10 to the fuel injector during the higher speed and higher load operating conditions of the high pressure fuel pump 10. More specifically, due to the higher angle of inclination of the second steep helix groove 22 with reference to the horizontal axis, when the fuel inlet port 42 translates from the top of the plunger 14 towards the second steep helix groove 22, the fuel inlet port 42 becomes aligned with the second steep helix groove 22 much slower than in the case when the fuel inlet port was aligned with the first shallow helix groove 20. As the fuel inlet port becomes aligned with the second steep helix groove 22 much slower than in the case when the fuel inlet port 42 was aligned with the first shallow helix groove 20, the quantity of pressurized fuel that is delivered from the pumping chamber 40 of the high pressure fuel pump 10 to the fuel injector is correspondingly higher.

[0013] A working of the high pressure fuel pump 10 is now described as an example. The variable pitch helix groove allows the flow of fuel from the pumping chamber 40 of the high-pressure fuel pump 10 to a low-pressure fuel gallery via the fuel inlet port 42 that is defined in the barrel 32 of the high-pressure fuel pump 10. Therefore, as the load acting on the high-pressure fuel pump 10 is low, and the operating speed of the high pressure fuel pump 10 is low, the fuel inlet port 42 translates from the top of the plunger 14 until it becomes aligned with the first shallow helix groove 20. As the angle of inclination of the first shallow helix groove 20 with reference to the horizontal axis is lower, the time taken for the fuel inlet port 42 to translate from the top of the plunger 14 until it becomes aligned with the first shallow helix groove 20 is lower. Therefore, a lower quantity of pressurized fuel is delivered from the high pressure fuel pump 10 to the fuel injector in the first shallow helix groove 20 regime at low loads and low operating speeds of the high pressure fuel pump 10. As the load acting on the high-pressure fuel pump 10 is high, and the operating speed of the high pressure fuel pump 10 is high, the fuel inlet port 42 translates from the top of the plunger 14 until it becomes aligned with the second steep helix groove 22. As the angle of inclination of the second steep helix groove 22 with reference to the horizontal axis is higher, the time taken for the fuel inlet port 42 to translate from the top of the plunger 14 until it becomes aligned with the second steep helix groove 22 is higher. Therefore, a higher quantity of pressurized fuel is delivered from the high pressure fuel pump 10 to the fuel injector in the second steep helix groove 22 regime at high loads and high operating speeds of the high pressure fuel pump 10.

[0014] The variable pitch helix groove 18 therefore is adapted to deliver a lower quantity of pressurized fuel from the high pressure fuel pump 10 to the fuel injector at lower pumping speeds and lower loads acted on the high pressure fuel pump 10 by aligning the fuel inlet port 42 with the first shallow helix groove 20 in the first operating regime of the high pressure fuel pump 10. Conversely, the variable pitch helix groove 18 is adapted to deliver a higher quantity of pressurized fuel from the high pressure fuel pump 10 to the fuel injector at higher pumping speeds and higher loads acted on the high pressure fuel pump 10 by aligning the fuel inlet port 42 with the second steep helix groove 22 in the second operating regime of the high pressure fuel pump 10. Therefore, a single variable pitch helix groove 10 of varying angle of inclinations of the helix groove with reference to the horizontal axis may be used to meet the demands of varying quantities of pressurized fuel that is required to be delivered from the high pressure fuel pump 10 to the fuel injector at a low speed and a low load operating regime of the high pressure fuel pump 10 as well as at a high speed and a high load operating regime of the high pressure fuel pump 10.

[0015] 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.