Claims:We Claim

1. A high pressure fuel pump (10), said high pressure fuel pump (10) comprising:
a housing (12);
a barrel (13) positioned within said housing (12), and secured within said housing (12);
a plunger (14) positioned within said barrel (13), said plunger (14) adapted to reciprocate within said barrel (13) to facilitate channeling pressurized fuel to a fuel injector;
a vertical groove (16) defined in said plunger (14), the vertical groove (16) adapted to extend along a sidewall of said plunger (14);
a pinion (18) secured around an outer circumference of said plunger (14), said pinion (18) adapted to rotate said plunger (14) to facilitate aligning the vertical groove (16) with a fuel inlet port (20) that is defined in said barrel (13);
a rack (22) adapted to mesh against said pinion (18), a translation of said rack (22) by a predetermined linear displacement adapted to cause a rotation of said pinion (18) by a corresponding predetermined angular displacement, the rotation of said pinion (18) by the corresponding predetermined angular displacement causes a rotation of said plunger (14) by the corresponding predetermined angular displacement to facilitate aligning the vertical groove (16) with the fuel inlet port (20) that is defined in said barrel (13); characterized in that
a stepper motor (24) secured to said rack (22) and adapted to translate said rack (22) against said pinion (18) by the predetermined linear displacement to facilitate rotating said pinion (18) by the corresponding predetermined angular displacement, the rotation of said pinion (18) by the corresponding predetermined angular displacement causes a rotation of said plunger (14) by the predetermined angular displacement to facilitate aligning the vertical groove (16) with the fuel inlet port (20) that is defined in said barrel (13).

2. The high pressure fuel pump (10) in accordance with Claim 1, further comprising an electronic control unit (26) in electronic communication with said stepper motor (24), the electronic control unit (26) adapted to actuate said stepper motor (24) to facilitate translating said rack (22) against said pinion (18) by the predetermined linear displacement to facilitate rotating said pinion (18) by the corresponding predetermined angular displacement, the rotation of said pinion (18) by the corresponding predetermined angular displacement causes a rotation of said plunger (14) by the corresponding predetermined angular displacement to facilitate aligning the vertical groove (16) with the fuel inlet port (20) that is defined in said barrel (13).

3. The high pressure fuel pump (10) in accordance with Claim 1, wherein said stepper motor (24) is secured to said rack (22) by means of a coupling mechanism
, 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 stepper motor for controlling a rotational displacement of a plunger of the high pressure fuel pump.

Background of the invention
[0002] US 2018306179 AA describes a positive displacement pump that includes at least two pumping chambers and associated plungers. Each plunger is driven by an associated variable speed motor, such as a stepper motor, in a reciprocating motion. The stepper motor varies speed during each stroke of the plunger. A controller controls speed and direction of each stepper motor. Each stepper motor is coupled to a leadscrew having an associated guide rod mounted on the leadscrew to move along the leadscrew as the leadscrew rotates and actuates an associated plunger. The controller varies the speed, displacement, and duration of the stepper motors' steps to maintain a constant outflow without pulses.

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 with a stepper motor / ECU assembly secured to a rack and pinion gear arrangement in the plunger of the high pressure fuel pump in one embodiment of the invention.

Detailed description of the embodiments
[0005] A high pressure fuel pump 10 is described. The high pressure fuel pump 10 comprises a housing 12. A barrel 13 is positioned within the housing 12, and secured within the housing 12. A plunger 14 is positioned within the barrel 13, the plunger 14 adapted to reciprocate within the barrel 13 to facilitate channeling pressurized fuel to a fuel injector. A vertical groove 16 is defined in the plunger 14, the vertical groove 16 adapted to extend along a sidewall of the plunger 14. A pinion 18 is secured around an outer circumference of the plunger 14. The pinion 18 is adapted to rotate the plunger 14 to facilitate aligning the vertical groove 16 with a fuel inlet port 20 that is defined in the barrel 13. A rack 22 is adapted to mesh against the pinion 18, a translation of the rack 22 by a predetermined linear displacement adapted to cause a rotation of the pinion 18 by a corresponding predetermined angular displacement. The rotation of the pinion 18 by the corresponding predetermined angular displacement causes a rotation of the plunger 14 by the corresponding predetermined angular displacement to facilitate aligning the vertical groove 16 with the fuel inlet port 20 that is defined in the barrel 13. A stepper motor 24 is secured to the rack 22, and adapted to translate the rack 22 against the pinion 18 by the predetermined linear displacement to facilitate rotating the pinion 18 by the corresponding predetermined angular displacement. The rotation of the pinion 18 by the corresponding predetermined angular displacement causes a rotation of the plunger 14 by the predetermined angular displacement to facilitate aligning the vertical groove 16 with the fuel inlet port 20 that is defined in the barrel 13.

[0006] Figure 1 illustrates the high pressure fuel pump 10 in one embodiment of the invention. The high pressure fuel pump 10 comprises a housing 12. A barrel 13 is positioned within the housing 12, and is secured within the housing 12. A plunger 14 is positioned within the barrel 13, wherein the plunger 14 is adapted to reciprocate within the barrel 13 and translate from the bottom dead center position to the top dead center position. As the plunger 14 translates from its bottom dead center position to its top dead center position, fuel is delivered from 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.
[0007] The vertical groove 16 is adapted to channel pressurized fuel from the pumping chamber of the high pressure fuel pump 10 to a fuel inlet port 20 that is in flow communication with the vertical groove 16. From the fuel inlet port 20, the pressurized fuel is discharged from the pumping chamber to the fuel gallery of the high pressure fuel pump 10 as will be explained in more detail hereinafter.

[0008] Figure 2 illustrates a plunger with a stepper motor / ECU assembly secured to a rack and pinion gear arrangement in the plunger of the high pressure fuel pump in one embodiment of the invention. In an exemplary embodiment, a pinion 18 is secured around an outer circumference of the plunger 14. More specifically, when the pinion 18 is rotated via external means, the pinion 18 is adapted to rotate the plunger 14. The rotation of the plunger 14 facilitates aligning the vertical groove 16 with a fuel inlet port 20 that is defined in the barrel 13. Similarly, when the pinion 18 is rotated in an opposite direction via external means, the vertical groove 16 is rotated away from the fuel inlet port 20 that is defined in the barrel 13, such that the fuel inlet port 20 is wedged between the solid portion of the plunger 14 and the barrel 13 of the high pressure fuel pump 10. The fuel inlet port 20 that is wedged between the solid portion of the plunger 14 and the barrel 13 of the high pressure fuel pump 10 prevents pressurized fuel from the element chamber from flowing into the fuel inlet port 20 via the vertical groove 16.

[0009] In an exemplary embodiment, a rack 22 is adapted to mesh against the pinion 18 that is secured to the plunger 14 of the high pressure fuel pump 10. When the rack 22 is translated by a predetermined linear displacement, the pinion 18 is adapted to be rotated by a corresponding predetermined angular displacement that is proportional to the predetermined linear displacement of the rack 22. As the pinion 18 is secured to the plunger 14 of the high pressure fuel pump 10, the rotation of the pinion 18 by the corresponding predetermined angular displacement causes a rotation of the plunger 14 by the same predetermined angular displacement. As the plunger 14 of the high pressure fuel pump 10 is rotated, the fuel inlet port 20 that is defined in the barrel 13 becomes misaligned with the vertical groove 16. Similarly, when the rack 22 is translated in an opposite direction by the predetermined linear displacement, the pinion 18 is adapted to be rotated in the opposite direction by the corresponding predetermined angular displacement that is proportional to the predetermined linear displacement of the rack 22. The rotation of the pinion 18 in the opposite direction by the corresponding predetermined angular displacement causes a rotation of the plunger 14 in the opposite direction by the same predetermined angular displacement. As the plunger 14 of the high pressure fuel pump 10 is rotated in the opposite direction by the same predetermined angular displacement, the fuel inlet port 20 that is defined in the barrel 13 becomes aligned with the vertical groove 16 to facilitate discharging pressurized fuel from the pumping chamber of the high pressure fuel pump 10.

[0010] In an exemplary embodiment, a stepper motor 24 is secured to the rack 22. More specifically, the stepper motor 24 that is secured to the rack 22 is adapted to translate the rack 22 against the pinion 18 by the predetermined linear displacement. The stepper motor 24 that is secured to the rack 22 and is adapted to translate the rack 22 by the predetermined linear displacement facilitates rotating the pinion 18 by the corresponding predetermined angular displacement. Therefore, the rotation of the pinion 18 by the corresponding predetermined angular displacement causes a rotation of the plunger 14 by the predetermined angular displacement to facilitate aligning the vertical groove 16 with the fuel inlet port 20 that is defined in the barrel 13.

[0011] In an exemplary embodiment, an electronic control unit 26 is in electronic communication with the stepper motor 24 and controls the motion of the stepper motor 24. More specifically, the output signal provided by the electronic control unit 26 is adapted to actuate the stepper motor 24. The actuation of the stepper motor 24 facilitates translating the rack 22 against the pinion 18 by the predetermined linear displacement. The translation of the rack 22 by the predetermined linear displacement facilitates rotating the pinion 18 by the corresponding predetermined angular displacement that is proportional to the predetermined linear displacement of the rack 22. Further, the rotation of the pinion 18 by the corresponding predetermined angular displacement causes a rotation of the plunger 14 by the corresponding predetermined angular displacement. The rotation of the plunger 14 by the predetermined angular displacement due to the actuation of the stepper motor 24 facilitates misaligning the vertical groove 16 with the fuel inlet port 20 that is defined in the barrel 13. In a similar manner, when the electronic control unit 26 disengages from the stepper motor 24 by deactivating the output signal that is supplied to the stepper motor 24, the stepper motor 24 is deactuated.

[0012] The deactuation of the stepper motor 24 facilitates translating the rack 22 against the pinion 18 by the predetermined linear displacement in an opposite direction to the translation of the rack 22 against the pinion 18 as in the earlier case when the stepper motor 24 was actuated. The translation of the rack 22 by the predetermined linear displacement in an opposite direction to the translation of the rack 22 against the pinion 18 as was in the earlier case when the stepper motor 24 was actuated facilitates rotating the pinion 18 by the corresponding predetermined angular displacement in an opposite direction. The rotation of the pinion 18 by the corresponding predetermined angular displacement in the opposite direction to the rotation of the pinion 18 as was in the earlier case when the stepper motor 24 was actuated facilitates rotating the plunger 14 by the corresponding predetermined angular displacement in an opposite direction. The rotation of the plunger 14 by the corresponding predetermined angular displacement in the opposite direction due to the deactuation of the stepper motor 24 facilitates aligning the vertical groove 16 with the fuel inlet port 20 that is defined in the barrel 13. The alignment of the vertical groove 16 with the fuel inlet port 20 that is defined in the barrel 13 facilitates discharging pressurized fuel from the pumping chamber to the fuel gallery of the high pressure fuel pump 10 via the vertical groove 16 and via the fuel inlet port 20.

[0013] In an exemplary embodiment, the stepper motor 24 is secured to the rack 22 by means of a coupling mechanism. Therefore, any coupling mechanism that is known in the art may be used to secure the stepper motor 24 to the rack 22. A working of the high pressure fuel pump 10 is now described as an example.

[0014] When the ECU 26 actuates the stepper motor 24, the pinion 18 is rotated by means of the rack 22, thereby moving the vertical groove 16 away from the fuel inlet port 20 just when the top of the plunger 14 closes the fuel inlet port 20 during its translation towards its top dead center position. The fuel inlet port 20 is now covered between the solid portion of the plunger 14 and the barrel 13 of the high pressure fuel pump 10. Therefore, no fuel from the pumping chamber of the high pressure fuel pump 10 is delivered to the fuel gallery via the fuel inlet port 20. Pressurization begins and fuel is delivered from the pumping chamber to the fuel injector, as the plunger 14 continues translating upwardly towards its top dead center position. The ECU 26 is incorporated with a data set for the required effective stroke. The data set is based on the engine/ pump RPM, accelerator pedal position, control lever position, Etc., and the corresponding fueling quantity/required effective stroke length. When the required effective stroke length of the plunger 14 is attained that corresponds to the required quantity of fuel that is to be delivered from the pumping chamber, the ECU 26 deactuates the stepper motor 24. The plunger 14 is rotated back to its initial position, with the fuel inlet port 20 becoming aligned with the vertical groove 16 due to the restoring motion of the stepper motor 24.

[0015] Fuel from the pumping chamber is discharged to the fuel gallery via the vertical groove 16 and the via the fuel inlet port 20. When it is required to deliver an increased quantity of pressurized fuel from the pumping chamber of the high pressure fuel pump 10 to the fuel injector, the ECU 26 deactuates the stepper motor 24 at the corresponding increased effective stroke length of the plunger 14. The plunger 14 is rotated back to its initial position at the increased stroke length after the increased quantity of pressurized fuel is delivered to the fuel injector. Therefore, the oscillatory movement of the plunger 14 by means of the stepper motor 24 closes / opens the fuel inlet port 20 to the vertical groove 16 at different stroke lengths of the plunger 14 that correspond to the different quantities of fuel that are required to be delivered from the pumping chamber of the high pressure fuel pump 10 to the fuel injector.

[0016] 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.