METHOD FOR LIFT PUMP CONTROL

• US 20160153385A1
• Filed: 12/02/2014
• Published: 06/02/2016
• Est. Priority Date: 12/02/2014
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Pursifull, Ross Dykstra
• Granted Patent: US 9,771,909 B2
• Time in Patent Office: Days
• CPC Class Codes: F02D 2041/3881 with multiple common rails, e.g. one rail per cylinder bank, or a high pressure rail and a low pressure rail
• CPC Class Codes: F02D 2200/0602 Fuel pressure
• CPC Class Codes: F02D 2250/02 Fuel evaporation in fuel rails, e.g. in common rails
• CPC Class Codes: F02D 41/3094 the fuel injection being effected by at least two different injectors, e.g. one in the intake manifold and one in the cylinder
• CPC Class Codes: F02D 41/3845 by controlling the flow into the common rail, e.g. the amount of fuel pumped
• CPC Class Codes: F02D 41/3854 with elements in the low pressure part, e.g. low pressure pump
• CPC Class Codes: F02D 41/402 Multiple injections
• CPC Class Codes: F02M 59/102 Mechanical drive, e.g. tappets or cams F02M45/063 takes precedence
• CPC Class Codes: F02M 63/0285 having more than one common rail

Abstract

Methods and systems are provided for controlling a low pressure pump in port fuel direct injection (PFDI) engines. One method includes, when operating a high pressure pump in a default pressure mode, pulsing the low pressure pump when pressure in a high pressure fuel rail decreases below a threshold. The method further includes, when operating the high pressure pump in a variable pressure mode, pulsing the low pressure pump based on presence of fuel vapor at an inlet of the high pressure pump.

Claims

1. A method, comprising:

when operating a high pressure pump in a default pressure mode,

pulsing a low pressure pump when pressure in a high pressure fuel rail decreases below a threshold; and

when operating the high pressure pump in a variable pressure mode,

pulsing the low pressure pump based on presence of fuel vapor at an inlet of the high pressure pump.

2. The method of claim 1, wherein an electronically-controlled solenoid valve is deactivated when the high pressure pump is operated in default pressure mode.

3. The method of claim 2, wherein the electronically-controlled solenoid valve is activated when the high pressure pump is operated in variable pressure mode, and wherein the pressure in the high pressure fuel rail is regulated via the electronically-controlled solenoid valve.

4. The method of claim 1, wherein pulsing the low pressure pump includes pulsing the low pressure pump at full voltage.

5. The method of claim 1, wherein pulsing the low pressure pump includes pulsing the low pressure pump for short durations.

6. The method of claim 1, further comprising, when operating the high pressure pump in variable pressure mode, not pulsing the low pressure pump when pressure in the high pressure fuel rail decreases below the threshold.

7. The method of claim 1, wherein when operating the high pressure pump in the variable pressure mode, presence of fuel vapor at the inlet of the high pressure pump is determined when an increase in pressure in the high pressure fuel rail during a pump stroke is less than an expected increase.

8. The method of claim 1, wherein pressure in the high pressure fuel rail is measured via a fuel rail pressure sensor, and wherein the low pressure pump is pulsed based on a measurement of pressure during a compression stroke in the high pressure pump.

9. A system, comprising:

a port fuel direct injection (PFDI) engine;

a direct injection fuel pump including a piston, a compression chamber, a cam for moving the piston, a solenoid activated check valve positioned at an inlet of the direct injection fuel pump, and a pressure relief valve positioned upstream of the solenoid activated check valve for regulating pressure in the compression chamber during a default pressure mode;

a high pressure fuel rail fluidically coupled to the direct injection fuel pump;

a sensor coupled to the high pressure fuel rail for monitoring fuel rail pressure;

a lift pump fluidically coupled to the high pressure fuel rail via the direct injection fuel pump; and

a controller having executable instructions stored in a non-transitory memory for;

during a first condition,

pulsing the lift pump based on a decrease in pressure in the high pressure fuel rail below a threshold; and

during a second condition,

pulsing the lift pump based on detection of fuel vapor at an inlet of the direct injection fuel pump.

10. The system of claim 9, wherein the first condition includes operation of the direct injection fuel pump in the default pressure mode by deactivating the solenoid activated check valve, and wherein a default pressure of the direct injection fuel pump is determined by the pressure relief valve positioned upstream of the solenoid activated check valve.

11. The system of claim 9, wherein the second condition includes operation of the direct injection fuel pump in a variable pressure mode, and wherein the solenoid activated check valve is activated and adjusted based on the pressure in the high pressure fuel rail.

12. The system of claim 11, wherein during the second condition, the lift pump is not pulsed when pressure in the high pressure fuel rail decreases below the threshold.

13. The system of claim 12, wherein fuel vapor at the inlet of the direct injection fuel pump is detected when a measured change in pressure of the high pressure fuel rail during a compression stroke of the direct injection fuel pump is lower than an expected change in pressure of the high pressure fuel rail.

14. A method for a fuel system, comprising:

during default pressure operation of a direct injection pump,

disabling a solenoid activated check valve; and

pulsing a lift pump responsive to a decrease in fuel rail pressure below a threshold; and

during variable pressure operation of the direct injection pump,

enabling the solenoid activated check valve; and

pulsing the lift pump responsive to a condition other than the decrease in fuel rail pressure below the threshold.

15. The method of claim 14, wherein pulsing the lift pump during variable pressure operation responsive to a condition other than the decrease in fuel rail pressure includes a condition when fuel vapor is detected at an inlet to the direct injection pump.

16. The method of claim 14, wherein pulsing the lift pump during default pressure operation of the direct injection pump is in response to the decrease in fuel rail pressure when measured during a compression stroke in the direct injection pump.

17. The method of claim 16, wherein pulsing the lift pump includes pulsing the lift pump at full voltage.

18. The method of claim 16, wherein pulsing the lift pump includes pulsing the lift pump for predetermined durations.

19. The method of claim 14, further comprising, during variable pressure operation of the direct injection pump, adjusting the solenoid activated check valve responsive to changes in fuel rail pressure, and wherein the changes in fuel rail pressure are measured by a pressure sensor coupled to a high pressure fuel rail.