Systems and methods for operating a lift pump

Patent metadata

Field	Value
Publication number	US-10077733-B2
Application number	US-201615353535-A
Country	US
Kind code	B2
Filing date	Nov 16, 2016
Priority date	Nov 16, 2016
Publication date	Sep 18, 2018
Grant date	Sep 18, 2018

Abstract

Methods and systems are provided for operating a lift pump of an engine fuel system. In one example, a method may comprise predicting when a fuel rail pressure will decrease below a threshold assuming that a lift pump remains off. The method may further comprise powering on the lift pump before the fuel rail pressure decreases below to the threshold to prevent fuel rail pressure from decreasing below the threshold.

First claim

The invention claimed is:

1. A method comprising:
maintaining a lift pump off that supplies fuel to a fuel rail;
while the lift pump is maintained off, predicting when a fuel rail pressure will decrease below a threshold based on fuel injection rates; and
based on the prediction, powering on the lift pump before the fuel rail pressure decreases below the threshold such that actual fuel rail pressures do not decrease below the threshold.

2. The method of claim 1 , further comprising estimating what a minimum future fuel rail pressure would be were the lift pump to be powered on at a current instance based on one or more of fuel line stiffness, fuel injection rates, and a lift pump spin-up period, where the minimum future fuel rail pressure is a fuel rail pressure at which the lift pump would begin to add pressure to the fuel rail.

3. The method of claim 2 , wherein the powering on the lift pump is initiated in response to the minimum future fuel rail pressure decreasing to within a threshold difference of the threshold, such that future fuel rail pressures do not decrease below the threshold.

4. The method of claim 2 , where the lift pump spin-up period is estimated based on one or more of a predicted fuel rail pressure profile and an amount of electrical power to be supplied to the lift pump when powering on the lift pump.

5. The method of claim 2 , wherein the minimum future fuel rail pressure decreases for increases in one or more of the fuel line stiffness, fuel injection rates, and lift pump spin-up period.

6. The method of claim 2 , further comprising maintaining a voltage supplied to the lift pump at a lower first level prior to the fuel rail pressure reaching the minimum fuel rail pressure, and in response to the fuel rail pressure reaching the minimum fuel rail pressure, increasing the voltage supplied to the lift pump.

7. The method of claim 6 , wherein the increasing the voltage supplied to the lift pump comprises first stepping up the voltage from the lower first level to an intermediate second level, and then ramping up the voltage from the intermediate second level to a higher third level over a duration.

8. The method of claim 6 , wherein the increasing the voltage supplied to the lift pump comprises ramping up the voltage from the lower first level to a higher second level over a duration.

9. The method of claim 1 , wherein the powering on the lift pump comprises electrically powering the lift pump for a duration, and where the method further comprises powering off the lift pump after the duration.

10. The method of claim 1 , wherein the powering on the lift pump comprises electrically powering the lift pump until the fuel rail pressure increases to a higher second threshold, and where the method further comprises powering off the lift pump in response to the fuel rail pressure increasing above the higher second threshold.

11. A method comprising:
predicting when a fuel rail pressure will decrease below a threshold;
calculating a desired instance to power on a lift pump based on a lift pump delay period, where the desired instance precedes when the fuel rail pressure is predicted to decrease below the threshold;
stepping up a voltage supplied to the lift pump from zero to a first level at the desired instance; and
ramping up the voltage supplied to the lift pump from the first level after the desired instance.

12. The method of claim 11 , wherein the predicting when the fuel rail pressure will decrease below the threshold is determined based on one or more of fuel line stiffness and fuel injection rates.

13. The method of claim 11 , further comprising maintaining the voltage supplied to the lift pump at the first level for a duration before ramping up the voltage.

14. The method of claim 11 , wherein the lift pump delay period comprises a duration that passes from the instance the lift pump is powered on to when the lift pump begins adding pressure to the fuel rail.

15. The method of claim 11 , where the lift pump delay period is determined by maintaining the fuel rail pressure at the threshold while powering on the lift pump, and recording how long it takes for the lift pump to begin adding pressure to the fuel rail.

16. The method of claim 11 , where the calculating the desired instance to power on the lift pump is additionally based on one or more of fuel compressibility and fuel injection rates.

17. The method of claim 11 , further comprising detecting a faulty check valve when fuel compressibility increases by more than a threshold rate.

18. A system comprising:
a lift pump;
a fuel line coupled to the lift pump and comprising a fuel rail, the fuel rail including one or more fuel injectors, the fuel line delivering fuel from the lift pump to the fuel injectors;
a check valve positioned in the fuel line between the lift pump and the fuel rail for maintaining fuel pressure downstream of the check valve, between the check valve and the fuel injectors; and
a controller in electrical communication with the lift pump, the controller including computer readable instructions stored in non-transitory memory for:
while the lift pump is off, predicting a decay profile for the fuel pressure downstream of the check valve;
determining an instance to power on the lift pump based on the decay profile and a delay period of the lift pump such that the fuel pressure downstream of the check valve does not decrease below a threshold; and
powering on the lift pump at the determined instance, before the fuel pressure downstream of the check valve reaches the threshold.

19. The system of claim 18 , wherein the fuel rail comprises a port fuel injection rail, and where the fuel injectors inject fuel into an intake manifold, upstream of one or more engine cylinders.

20. The system of claim 18 , wherein the controller further includes instruction stored in non-transitory memory for powering the lift pump at a voltage sufficient to increase fuel line pressure upstream of the check valve to the threshold, and then increasing the voltage supplied to the lift pump as desired in response to the fuel rail pressure decreasing to within a threshold difference above the threshold.

Assignees

• Ford Global Tech Llc

Inventors

• Trzeciak Justin
• Ulrey Joseph Norman
• Pursifull Ross Dykstra

Classifications

• F02M63/0054

  Check valves (F02M59/462, F02M59/464 take precedence) · CPC title

• F02M69/465

  of fuel rails · CPC title

• F02D41/3082 Primary

  Control of electrical fuel pumps · CPC title

• F02D41/3845

  by controlling the flow into the common rail, e.g. the amount of fuel pumped · CPC title

• F02D41/3854

  with elements in the low pressure part, e.g. low pressure pump · CPC title