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] The present disclosure relates to a high-pressure fuel pump for an internal combustion engine.

Background of the invention
[0002] The high-pressure fuel pump delivers fuel that is received from a fuel filter into a common rail under high pressure. For this purpose, the camshaft of the high-pressure fuel pump is driven by the engine and translates the pump pistons to generate the required high pressure. The injection of fuel to the common rail is achieved by the reciprocation of a plunger inside the cylinders of the high pressure fuel pump. In the current design of the plunger, a stop groove and a helix groove that are defined on the body of the plunger are in flow communication with one another. The helix groove allows for the flow of fuel from a pumping chamber to a fuel gallery via a fuel inlet port that is defined in a barrel.

[0003] Therefore, as the load acting on the high-pressure fuel pump is increased from a low load to a high load, the quantity of pressurized fuel that is delivered from the pumping chamber to a fuel injector increases in direct proportion to a stroke length of the plunger i.e. the fuel inlet port traverses from a top of the plunger until the helix groove comes in flow communication with the fuel inlet port. As the plunger is rotated, the quantity of pressurized fuel that is delivered from a pumping chamber to the common rail or the high-pressure circuit increases in direct proportion to the stroke length of the plunger as the fuel inlet port translates from the top portion of the plunger until the fuel inlet port becomes aligned with the rotating helix groove. However due to the construction of the stop groove and the helix groove, at low loads or idle condition a secondary fuel injection occurs when the fuel inlet port is closed by a lower edge of the helix groove.

[0004] Indian Patent application IN 201641018154 A describes a fuel pump having helix grooves for a main injection and a post injection. The helix grooves are disposed on diametrically opposite sides of a plunger. The helix groove associated with the main injection event and the helix groove associated with the post injection event are spaced in an axial direction such that the post injection event occurs after the main injection event. As the fuel in a plunger chamber is pressurized by a movement of the plunger, the helix groove associated with the main injection event first aligns with a leak port, marking the completion of the main injection. Therein, the helix groove associated with the post injection event aligns with an inlet port, marking the completion of the post injection. A start limiting groove for preventing post injection at lower engine loads is also connected to the helix groove associated with the post injection event.

Brief description of the accompanying drawings
[0005] An embodiment of the invention is described with reference to the following accompanying drawings:
[0006] Figure 1 depicts a high-pressure fuel pump (100) in one embodiment of the invention;
[0007] Figure 2 depicts a plunger (103) that is positioned within a barrel (102) of the high-pressure fuel pump (100) in one embodiment of the invention;
[0008] Figure 3 illustrates the relative movement of plunger (103) with respect to an inlet (107) in one embodiment of the invention.

Detailed description of the invention
[0009] Figure 1 depicts a high-pressure fuel pump (100) for an internal combustion engine. The high-pressure fuel pump (100) comprises a housing (101), a barrel (102) and a plunger (103) that is adapted to reciprocate within a pumping chamber (106) that is defined within the barrel (102) assembled onto the housing (101) of the high-pressure fuel pump (100). In the exemplary embodiment, a plunger (103) is adapted to reciprocate within the pumping chamber (106) that is defined within the housing (101) and deliver pressurized fuel to a fuel injector (not shown) that is in flow communication with the high-pressure fuel pump (100).

[0010] A helix groove (105) is defined on an outer circumference of the plunger (103), the helix groove (105) adapted to channel pressurized fuel from within the pumping chamber (106) defined within the barrel (102) to a fuel gallery (108) during an end of a pumping stroke of the plunger (103). The most important non-limiting feature of the present invention is the design and construction of a stop groove (104). The helix groove (105) is in flow communication with an inlet port (107) that is defined in the barrel (102) when the plunger (103) translates upwardly by a predetermined displacement. The alignment of the helix groove (105) with the inlet port (107) discharges the high pressure fuel that is present in the pumping chamber (106) of the high-pressure fuel pump (100) at the end of the pumping stroke to the low pressure fuel gallery (108) via the helix groove (105) and via the inlet (107) port respectively.

[0011] The stop groove (104) is defined on the body of the plunger (103) at an angle inclined with respect to a vertical axis of the plunger (103). The stop groove (104) is in flow communication with the helix groove (105). The plunger (103) is adapted to be rotated to facilitate varying an orientation of the helix groove (105) and the stop groove (104) for different loading conditions and operating speeds of the high pressure fuel pump (100). The inclination of the stop groove (104) ensures flow communication between the stop groove and the inlet port (107) of the fuel gallery (108) during the translation of the plunger (103) to a top dead center position. Further, the inclination of the stop groove (104) makes an obtuse angle with respect to the inlet port (107). The inclination of the stop groove (104) is designed so as to prevent a secondary fuel injection from occurring during the translation of the plunger (103) to a top dead center position.

[0012] It should be understood at the outset that, although exemplary embodiments are illustrated in the figures and described below, the present disclosure should in no way be limited to the exemplary implementations illustrated in the drawings and described below. A working of the present invention is explained with respect to figure 2.

[0013] Figure 2 illustrates a plunger (103) that is positioned within the barrel (102) of the high-pressure fuel pump (100). In the current design of the plunger (103), the stop groove (104) and the helix groove (105) are in flow communication with one another. The helix groove (105) allows for the flow of pressurized fuel from the pumping chamber (106) to the fuel gallery (108) via a fuel inlet port (107) that is defined in a barrel (102).

[0014] Therefore, as the load acting on the high-pressure fuel pump (100) is increased from a low load to a high load, the quantity of pressurized fuel that is delivered from the pumping chamber (106) to a fuel injector increases in direct proportion to a stroke length of the plunger (103) i.e. the fuel inlet port (107) traverses from a top of the plunger (103) until the helix groove (105) comes in flow communication with the fuel inlet (107) port. As the plunger (103) is rotated, the quantity of pressurized fuel that is delivered from the pumping chamber (106) to the fuel injector increases in direct proportion to the stroke length of the plunger (103) as the fuel inlet port (107) translates from the top portion of the plunger (103) until the fuel inlet (107) port becomes aligned with the rotating helix groove (105). However, the stop groove (104) extends vertically from the top of the plunger (103) until it culminates at a portion that is along a longitudinal length of the plunger (103) as shown in Fig. 1. Therefore, once the plunger (103) is rotated by means of a governor that is secured to a control sleeve of the plunger (103) via a rack and pinion gear assembly, the fuel inlet port (107) is rotated away from the stop groove (104). Once the fuel inlet port (107) rotates away from the stop groove (104) such that the fuel inlet port (107) is no longer in flow communication with the stop groove (104), and is located between the top of the plunger (103) and the helix groove (105), as the plunger (103) is translating towards its top dead center position, pressurization and subsequent pressurized fuel delivery from the high pressure fuel pump (100) to the fuel injector occurs until the fuel inlet port (107) is in flow communication with the helix groove (105).

[0015] In addition, once the plunger (103) continues translating towards its top dead center position, secondary fuel injection occurs when the fuel inlet port (107) is closed by a lower edge of the helix groove (105). In order to exploit the axial portion of the plunger (103) in the low idle region of the high pressure fuel pump (100) that exists adjacent to the stop groove (104), an inclined stop groove (104) is proposed in this invention report that enables fuel injection operation of the high pressure fuel pump (100) at a lower angular displacement of the fuel inlet port (107) with reference to the angular stop groove (104), while at the same time preventing secondary fuel injection from occurring from the high pressure fuel pump (100) to the fuel injector. Figure 3 illustrates the relative movement of the plunger (103) with respect to the inlet port (107).Figure 3(a) is the present or conventional design of the helix groove (105) and the stop groove (104), whereas figure 3(b) depicts the proposed construction and design of the helix groove (105) and the stop groove (104).

[0016] In the proposed invention, the stop groove (104) extends at an inclined angle from the top of the plunger (103) until it culminates at a length that is proportionately equal to a longitudinal length of the vertical stop groove (104). The angle of the angular stop groove (104) with reference to the inlet (107) port is empirically defined based on a user specific application. As the plunger (103) begin to rotate due to the rotational torque imposed by the governor on the plunger (103) via the control sleeve and via the rack and pinion gear assembly (not shown) that is secured to the control sleeve of the plunger (103), the fuel inlet port (107) is rotated away from the stop groove (104). Due to the inclined nature of the stop groove (104), the angular displacement required to rotate the fuel inlet (107) port away from the angular stop groove (104) and enter into a fuel injection operation region of the high-pressure fuel pump (100) is higher than the angular displacement that is required to rotate the fuel inlet port (107) and enter into the fuel injection operation region as is in the case of the vertical stop groove (104). By enabling the fuel injection operation of the high-pressure fuel pump (100) at a higher angular displacement of the fuel inlet (107) port with reference to the angular stop groove (104), the low idle operating region of the high-pressure fuel pump (100) may be extended in contrast with a plunger (103) employing a vertical stop groove (104).
[0017] In the case of a shallow pitch element, in the low idle operating region of the high pressure fuel pump (100), secondary fuel injection occurs in case of a vertical stop groove (104) that is defined in the plunger (103) This is because, once the fuel inlet (107) port translates through the helix groove (105) and crosses the lower edge of the helix groove (105), the closure of the fuel inlet (107) port by the lower edge of the helix groove (105) of the high pressure fuel pump (100) causes further pressurization and consequently delivery of the pressurized fuel from the pumping chamber (106) of the high pressure fuel pump (100) to the fuel injector. However, due to the inclined nature of the angular stop groove (104), once the fuel inlet (107) port crosses the lower edge of the helix groove (105) of the plunger (103), the fuel inlet (107) port continues to remain in flow communication with the angular stop groove (104). As the plunger (103) of the high-pressure fuel pump (100) continues to translate towards its top dead center position, a greater portion of the fuel inlet port (107) comes in flow communication with the angular stop groove (104). Consequently, all the fuel from the pumping chamber (106) flows into the fuel inlet port (107) via the angular stop groove (104) with no further pressurization and secondary injection of fuel occurring from the pumping chamber (106) of the high-pressure fuel pump (100) to the fuel injector.

[0018] This idea to develop an inclined or angular stop groove (104) prevents secondary fuel injection of pressurized fuel from the pumping chamber (106) to the fuel injector from occurring. A further advantage of the inclined stop groove (104) is the ease of machinability. By means of a simple milling operation, the angle of the stop groove (104) may be adjusted to facilitate passing a milling cutter on the plunger (103) at the required stop groove (104) angle to obtain the required angular stop groove (104) at the required depth from the top of the plunger (103).

[0019] It must be understood that the embodiments explained in the above detailed description are only illustrative and do not limit the scope of this invention. Any modification in the embodiments with regard to dimensions of various components are envisaged and form a part of this invention. The scope of this invention is limited only by the claims.

, Claims: We Claim:
1. A high-pressure fuel pump (100), said high pressure fuel pump (100) comprising: a housing (101), and a plunger (103) adapted to reciprocate within a pumping chamber (106) defined within the barrel (102) assembled onto the housing (101) of the high-pressure fuel pump (100);
a helix groove (105) defined on an outer circumference of said plunger (103), the helix groove (105) adapted to channel pressurized fuel from within the pumping chamber (106) defined within said housing (101) to a fuel gallery (108) during an end of an effective stroke length of said plunger (103); characterized in that high pressure fuel pump (100):
a stop groove (104) defined on the body of said plunger (103) at an angle inclined with respect to a vertical axis of said plunger (103), the stop groove (104) in flow communication with the helix groove (105), said plunger (103) is adapted to be rotated to facilitate varying an orientation of the helix groove (105) and the stop groove (104) for different loading conditions of said high pressure fuel pump (100).

2. The high-pressure fuel pump (100) as claimed in claim 1, wherein the inclination of the stop groove (104) ensures continuous flow communication between a fuel inlet port (107) and the stop groove (104) during the translation of the plunger (103) to its top dead center position.
3. The high-pressure fuel pump (100) as claimed in claim 1, wherein the inclination of the stop groove (104) makes an obtuse angle with respect to the fuel inlet port (107) of the fuel gallery (108).

4. The high-pressure fuel pump (100) as claimed in claim 1, wherein the inclination of the stop groove (104) is designed so as to prevent a secondary fuel injection from occurring during the translation of the plunger (103) to its top dead center position.