Claims:We Claim

1. An algorithm (10) for a stepper motor for controlling a rotational displacement of a plunger of a high pressure fuel pump, the algorithm (10) comprising the steps of:
extracting (12) a data set by an engine control unit, the data set comprising a number of engine rotations per minute, an accelerator pedal position, a control lever position, and a load imposed on the high pressure fuel pump;
obtaining (14) from a plurality of characteristic curves of a first data map of pump speed vs. quantity of fuel to be delivered, a required quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector;
obtaining (16) from a plurality of characteristic curves of a second data map of effective stroke length vs. quantity of fuel to be delivered from the high pressure fuel pump to the fuel injector, a required effective stroke length corresponding to the required quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector; and
de-actuating (18) the stepper motor by the engine control unit, the de-actuation of the stepper motor by the engine control unit facilitates rotating the plunger of the high pressure fuel pump such that a fuel inlet port of the high pressure fuel pump is aligned with a stop groove of the plunger to facilitate discharging pressurized fuel from a pumping chamber of the high pressure fuel pump to a fuel gallery via the fuel inlet port when the required effective stroke length corresponding to the required quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector has been attained by the plunger.

2. The algorithm (10) for a stepper motor for controlling a rotational displacement of a plunger of a high pressure fuel pump in accordance with Claim 1, wherein extracting (12) the data set by the engine control unit further comprises extracting (12) the data set comprising the number of engine rotations per minute, the accelerator pedal position, the control lever position, and the load imposed on the high pressure fuel pump by means of an engine speed sensor, an accelerator pedal position sensor, a control lever position sensor, and a load sensor respectively.

3. The algorithm (10) for a stepper motor for controlling a rotational displacement of a plunger of a high pressure fuel pump in accordance with Claim 1, wherein obtaining (14) from a plurality of characteristic curves of a first data map of pump speed vs. quantity of fuel to be delivered further comprises obtaining the plurality of characteristic curves of the first data map of pump speed vs. quantity of fuel to be delivered during a calibration procedure of the high pressure fuel pump.

4. The algorithm (10) for a stepper motor for controlling a rotational displacement of a plunger of a high pressure fuel pump in accordance with Claim 1, wherein obtaining (16) a plurality of characteristic curves of a second data map of effective stroke length vs. quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector further comprises obtaining (16) the plurality of characteristic curves of the second data map of effective stroke length vs. quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector during a calibration procedure of the high pressure fuel pump.

5. The algorithm (10) for a stepper motor for controlling a rotational displacement of a plunger of a high pressure fuel pump in accordance with Claim 4, wherein obtaining (18) the plurality of characteristic curves of the second data map of effective stroke length vs. quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector during a calibration procedure of the high pressure fuel pump wherein a correlation between the quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector and the effective stroke length of the plunger is quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector is equal to pi * radius of the plunger * radius of the plunger * effective stroke length of the plunger.

6. The algorithm (10) for a stepper motor for controlling a rotational displacement of a plunger of a high pressure fuel pump in accordance with Claim 4, wherein de-actuating (18) the stepper motor by the engine control unit further comprises rotating the plunger of the high pressure fuel pump by the restoring motion of the stepper motor such that the fuel inlet port of the high pressure fuel pump is aligned with the stop groove of the plunger to facilitate discharging pressurized fuel from a pumping chamber of the high pressure fuel pump to a fuel gallery via the fuel inlet port when the required effective stroke length corresponding to the required quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector has been attained by the plunger.

7. The algorithm (10) for a stepper motor for controlling a rotational displacement of a plunger of a high pressure fuel pump in accordance with Claim 4, wherein de-actuating (18) the stepper motor by the engine control unit further comprises rotating the plunger of the high pressure fuel pump by means of a restoring spring member such that the fuel inlet port of the high pressure fuel pump is aligned with the stop groove of the plunger to facilitate discharging pressurized fuel from a pumping chamber of the high pressure fuel pump to a fuel gallery via the fuel inlet port when the required effective stroke length corresponding to the required quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector has been attained by the plunger.

, 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 an algorithm for a stepper motor for controlling a rotational displacement of a plunger of the high pressure fuel pump.

Background of the invention
[0002] IN 202141024100 describes a high pressure fuel pump. The high pressure fuel pump comprises a housing. A barrel is positioned within the housing, and secured within the housing. A plunger is positioned within the barrel, the plunger adapted to reciprocate within the barrel to facilitate channeling pressurized fuel to a fuel injector. A vertical groove is defined in the plunger, the vertical groove adapted to extend along a sidewall of the plunger. A pinion is secured around an outer circumference of the plunger, the pinion adapted to rotate the plunger to facilitate aligning the vertical groove with a fuel inlet port that is defined in the barrel. A rack is adapted to mesh against the pinion, a translation of the rack by a predetermined linear displacement adapted to cause a rotation of the pinion by a corresponding predetermined angular displacement. The rotation of the pinion by the corresponding predetermined angular displacement causes a rotation of the plunger by the corresponding predetermined angular displacement to facilitate aligning the vertical groove with the fuel inlet port that is defined in the barrel. A stepper motor is secured to the rack, and is adapted to translate the rack against the pinion by the predetermined linear displacement to facilitate rotating the pinion by the corresponding predetermined angular displacement. The rotation of the pinion by the corresponding predetermined angular displacement causes a rotation of the plunger by the predetermined angular displacement to facilitate aligning the vertical groove with the fuel inlet port that is defined in the barrel.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates an algorithm for the stepper motor for controlling a rotational displacement of the plunger of the high pressure fuel pump in one embodiment of the invention.

Detailed description of the embodiments
[0004] An algorithm 10 for a stepper motor for controlling a rotational displacement of a plunger of a high pressure fuel pump is described. The algorithm 10 comprises the steps of extracting 12 a data set by an engine control unit, the data set comprising a number of engine rotations per minute, an accelerator pedal position, a control lever position, and a load imposed on the high pressure fuel pump. The algorithm 10 further comprises obtaining 14 from a plurality of characteristic curves of a first data map of pump speed vs. quantity of fuel to be delivered, a required quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector, and obtaining 16 from a plurality of characteristic curves of a second data map of effective stroke length vs. quantity of fuel to be delivered from the high pressure fuel pump to the fuel injector, a required effective stroke length corresponding to the required quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector. The algorithm 10 further comprises de-actuating 18 the stepper motor by the engine control unit, the de-actuation of the stepper motor by the engine control unit facilitates rotating the plunger of the high pressure fuel pump such that a fuel inlet port of the high pressure fuel pump is aligned with a stop groove of the plunger to facilitate discharging pressurized fuel from a pumping chamber of the high pressure fuel pump to a fuel gallery via the fuel inlet port when the required effective stroke length corresponding to the required quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector has been attained by the plunger.

[0005] Figure 1 illustrates an algorithm 10 for the stepper motor for controlling a rotational displacement of the plunger of the high pressure fuel pump in one embodiment of the invention. The algorithm 10 for the stepper motor for controlling a rotational displacement of a plunger of a high pressure fuel pump comprises the steps of extracting 12 a data set by an engine control unit. The data set that is extracted by the engine control unit comprises a number of engine rotations per minute from an engine speed sensor, an accelerator pedal position from an accelerator pedal position sensor, a control lever position from a control lever position sensor, and a load that is imposed on the high pressure fuel pump by an engine load sensor. Once the data set is extracted by the engine control unit based on the above parameters, based on the output of the data set, the engine control unit determines a required quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector. More specifically, the engine control unit obtains 14 from a plurality of characteristic curves of a first data map of pump speed vs. pump quantity, a required quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector. The characteristic curves of the first data map of pump speed vs. quantity of fuel to be delivered are themselves obtained during a calibration procedure of the high pressure fuel pump. During the calibration procedure of the high pressure fuel pump, the plot of pump speed on the x-axis and the fuel quantity to be delivered on the y-axis gives rise to a series of characteristic curves of the variation of the quantity of fuel that is delivered from the high pressure fuel pump to the fuel injector based on the variation in the pump speed due to the rotation of the cam shaft of the high pressure fuel pump.

[0006] The engine control unit obtains 16 from a plurality of characteristic curves of a second data map of effective stroke length vs. quantity of fuel to be delivered from the high pressure fuel pump to the fuel injector. The characteristic curves of the second data map of effective stroke length vs. quantity of fuel to be delivered from the high pressure fuel pump to the fuel injector are themselves obtained during a calibration procedure of the high pressure fuel pump. During the calibration procedure of the high pressure fuel pump, the plot of effective stroke length on the x-axis and the quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector on the y-axis gives rise to a series of characteristic curves of the variation of the effective stroke length of the plunger that is attained during which fuel is delivered from the pumping chamber to the fuel injector via a delivery valve before the helix groove becomes aligned with the fuel inlet port. This variation in the effective stroke length of the plunger is based on the variation in the pump speed due to a variable rotation of the cam shaft of the high pressure fuel pump. More specifically, at lower pump speeds at lower rotations of the cam shaft of the high pressure fuel pump, the effective stroke length of the plunger that is attained during which fuel is delivered from the pumping chamber to the fuel injector via the delivery valve before the helix groove becomes aligned with the fuel inlet port is lower. Conversely, at higher pump speeds at higher rotations of the cam shaft of the high pressure fuel pump, the effective stroke length of the plunger that is attained during which fuel is delivered from the pumping chamber to the fuel injector via the delivery valve before the helix groove becomes aligned with the fuel inlet port is higher.

[0007] In the exemplary embodiment, a correlation between the quantity of fuel that is delivered from the pumping chamber of the high pressure fuel pump to the fuel injector and the effective stroke length of the plunger is that the quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector is equal to pi * radius of the plunger * radius of the plunger * effective stroke length of the plunger. This is because the quantity of fuel that is delivered from the pumping chamber of the high pressure fuel pump to the fuel injector is equal to the area of cross-section that is swept by the plunger multiplied by the effective stroke length that the plunger has to traverse to deliver pressurized fuel from the pumping chamber to the fuel injector before the helix groove of the plunger becomes aligned with the fuel inlet port that is defined within the barrel of the high pressure fuel pump. The alignment of the helix groove of the plunger with the fuel inlet port that is defined within the barrel of the high pressure fuel pump causes pressurized fuel to be delivered from the pumping chamber to the fuel gallery of the high pressure fuel pump via the helix groove and via the fuel inlet port respectively.

[0008] The algorithm 10 for the stepper motor for controlling a rotational displacement of a plunger of a high pressure fuel pump comprises de-actuating 18 the stepper motor by the engine control unit when the effective stroke length has been attained by the plunger that corresponds to the required quantity of pressurized fuel that is required to be delivered from the pumping chamber to the fuel injector. The de-actuation of the stepper motor by the engine control unit facilitates rotating the plunger of the high pressure fuel pump such that the fuel inlet port that is defined in the barrel of the high pressure fuel pump is aligned with a stop groove of the plunger. The alignment of the fuel inlet port that is defined in the barrel of the high pressure fuel pump with the stop groove of the plunger due to the de-actuation of the stepper motor by the engine control unit facilitates discharging pressurized fuel from the pumping chamber of the high pressure fuel pump to the fuel gallery via the fuel inlet port.

[0009] The mechanism for the rotation of the plunger of the high pressure fuel pump is now described. When the stepper motor is de-actuated by the engine control unit, the stepper motor is restored back to its original position. Due to the restoring motion of the stepper motor back to its original position, the plunger of the high pressure fuel pump is rotated back to its original position such that the fuel inlet port of the high pressure fuel pump is aligned with the stop groove of the plunger. The restoring motion of the stepper motor back to its original position facilitates discharging pressurized fuel from the pumping chamber of the high pressure fuel pump to the fuel gallery via the fuel inlet port when the required effective stroke length corresponding to the required quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector has been attained by the plunger.

[0010] An alternate exemplary mechanism for the rotation of the plunger of the high pressure fuel pump is now described. When the stepper motor is de-actuated by the engine control unit, the stepper motor is restored back to its original position. Due to the restoring motion of the stepper motor back to its original position, the plunger of the high pressure fuel pump is rotated back to its original position such that the fuel inlet port of the high pressure fuel pump is aligned with the stop groove of the plunger. Moreover, the plunger of the high pressure fuel pump is rotated to facilitate restoring the plunger back to its initial position by means of a restoring spring member (not shown) that is coupled between the plunger of the high pressure fuel pump and the stepper motor. The restoring spring member that causes the rotation of the plunger back to its initial position causes the fuel inlet port to be aligned with the stop groove of the plunger. The restoring motion of the stepper motor back to its original position due to the force that is imparted to the plunger by the restoring spring member facilitates discharging pressurized fuel from the pumping chamber of the high pressure fuel pump to the fuel gallery via the fuel inlet port when the required effective stroke length corresponding to the required quantity of fuel that is to be delivered from the high pressure fuel pump to the fuel injector has been attained by the plunger.

[0011] 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.