Low evaporative emission fuel system depressurization via solenoid valve

• US 7,066,152 B2
• Filed: 09/03/2004
• Issued: 06/27/2006
• Est. Priority Date: 09/03/2004
• Status: Expired due to Fees

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Motor Company
• Inventors: Pursifull, Ross D., Yu, Dequan, Kempfer, Stephen T., Vint, Matti K., Stroia, Kathleen H.
• Primary Examiner(s): MOULIS, THOMAS N
• Application Number:
  US10/934,975
• Publication Number:
  US 20060048752A1
• Time in Patent Office: 662 Days
• Field of Search: 123/467, 123/198.D, 123/198.DB, 123/514, 123/510, 123/511
• US Class Current: 123/467
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system
• CPC Class Codes: F02M 25/0827 by monitoring engine running conditions
• CPC Class Codes: F02M 63/0215 by draining or closing fuel conduits

Abstract

A fuel delivery system is provided with a fuel solenoid valve to minimize fuel leakage and evaporative emissions during diurnal cycles by preventing pressure buildup as the temperature of the fuel system rises. The fuel solenoid valve is located between a pressurized side of the delivery system and a fuel tank. In one embodiment, the fuel solenoid valve is closed when the engine is running or when the engine is off and the rail is hot. When the fuel rail cools down, the solenoid valve opens to bleed a desired amount of fuel thereby creating a fuel vapor space. Thereafter, during hot soak conditions of the diurnal cycles when the fuel rail is hot again while the engine is off, the pressure will rise due to the thermal expansion of the fuel and the created fuel vapor space minimizes further rising of the fuel pressure. Further, by adjusting the solenoid valve opening time, the pressure rising limit may be set at a desired pressure to minimize injector leakage.

Claims

1. A fuel delivery system for an engine, comprising:

a fuel tank to contain a volume of fuel;

a fuel pump in fluid communication with the fuel tank to pressurize the fuel;

a fuel rail in fluid communication with the fuel pump to receive the pressurized fuel;

an injector in fluid communication with the fuel rail to supply the pressurized fuel to the engine;

a first valve in fluid communication with the fuel rail to maintain the fuel in a pressurized state;

a second valve in fluid communication with the fuel rail to relieve the pressurized state of the fuel when the engine is not operating; and

a solenoid valve, provided between a pressurized side of the fuel delivery system and the fuel tank, being operably opened via a control unit after key-off to drain fuel into the fuel tank.

2. A fuel delivery system for an engine of claim 1, wherein the solenoid valve being opened to drain fuel after key-off enables creation of vapor space in the fuel delivery system.

3. A fuel delivery system for an engine of claim 1, wherein the fuel delivery system is an electronic return-less fuel system (ERFS).

4. The fuel delivery system for an engine of claim 1, wherein the fuel delivery system is a mechanical return-less fuel system (MRFS).

5. A fuel delivery system for an engine of claim 4, wherein the solenoid valve is in fluid communication with the fuel rail downstream of a fuel filter.

6. The fuel delivery system for an engine of claim 1, further comprising a third valve in fluid communication with the fuel rail, the third valve being located upstream from the solenoid valve.

7. The fuel delivery system for an engine of claim 6, wherein relieving the pressurized state via the solenoid valve and the third valve occurs when the fuel pressure exceeds about a predetermined fuel push out pressure.

8. The fuel delivery system for an engine of claim 1, further comprising a fuel orifice in fluid communication with the fuel rail, the fuel orifice being located inline with the solenoid valve.

9. A method for minimizing fuel leakage during diurnal cycles in a fuel delivery system of an engine, comprising:

determining when an ignition key has been turned from an on position to an off position; and

after the key is turned to the off position, opening a solenoid valve to drain an amount of fuel from a fuel rail of the fuel delivery system to a fuel tank of the fuel delivery system.

10. The method for minimizing fuel leakage during diurnal cycles of claim 9, further comprising opening the solenoid valve for a predetermined time duration.

11. The method for minimizing fuel leakage during diurnal cycles of claim 9, further comprising:

determining whether a fuel rail pressure has dropped below a first desirable pressure level;

determining whether the fuel rail pressure has exceeded a second desirable pressure, the second desirable pressure being above the first desirable pressure; and

opening the solenoid valve to drain the amount of fuel within a specified time interval during which the second desirable pressure was exceeded.

12. The method for minimizing fuel leakage during diurnal cycles of claim 9, further comprising:

allowing an amount of time to elapse after the key is turned to the off position to insure that the fuel rail has cooled off; and

opening the solenoid valve to drain the amount of fuel within a specified time interval during which a desirable fuel rail pressure was exceeded.

13. The method for minimizing fuel leakage during diurnal cycles of claim 12, wherein the amount of elapsed time is about two hours to five hours.

14. The method for minimizing fuel leakage during diurnal cycles of claim 12, wherein the amount of elapsed time is about three hours.

15. The method for minimizing fuel leakage during diurnal cycles of claim 9, further comprising:

inferring that a fuel rail pressure has dropped below a first desirable pressure level from a measured fuel rail temperature via a temperature transducer;

determining whether the fuel rail pressure has exceeded a second desirable pressure, the second desirable pressure being above the first desirable pressure; and

opening the solenoid valve to drain a desirable amount of fuel within a specified time interval during which the second desirable pressure was exceeded.

16. The method for minimizing fuel leakage during diurnal cycles of claim 9, further comprising:

allowing the amount of time to elapse after the key is turned to the off position to insure that the fuel rail has cooled off;

determining whether the fuel rail pressure has exceeded a desirable pressure before opening the solenoid valve to drain a desirable amount of fuel; and

determining whether the fuel rail pressure has dropped below another desirable pressure before opening the solenoid valve to ingest fuel from the fuel tank.

17. A fuel delivery system for an engine, comprising:

a fuel tank to contain a volume of fuel;

a fuel pump in fluid communication with the fuel tank to pressurize the fuel;

a fuel rail in fluid communication with the fuel pump to receive the pressurized fuel;

an injector in fluid communication with the fuel rail to supply the pressurized fuel to the engine;

a first valve in fluid communication with the fuel rail to maintain the fuel in a pressurized state;

a second valve in fluid communication with the fuel rail to relieve the pressurized state of the fuel when the engine is not operating;

a solenoid valve, provided between a pressurized side of the fuel delivery system and the fuel tank, being operably opened during key-on and the engine is off to reduce fuel pressure until the injector is open, and after an ignition key has been turned from an on position to an off position to drain fuel into the fuel tank; and

a fuel orifice in fluid communication with the fuel rail, the fuel orifice being positioned upstream from the solenoid valve.

18. A method for minimizing fuel leakage in a fuel delivery system of an engine while the engine is off, the fuel delivery system comprising a fuel tank containing a volume of fuel, a fuel pump, a fuel rail, an injector, a first valve, a second valve, a solenoid valve, and a fuel orifice, the method comprising:

determining whether an ignition key is turned to an on position;

determining whether the solenoid valve is open, and closing the solenoid valve if determined to be open;

determining whether a fuel pressure has exceeded a target level;

opening the solenoid valve and increasing a flow of the fuel pump when the fuel pressure has exceeded the pressure target value;

determining whether a fuel flow of the injector is above a flow speed; and

closing the solenoid valve and reducing the fuel pump flow once the injector fuel flow is above the flow speed.

19. A method for minimizing fuel leakage in a fuel delivery system of an engine while the engine is off, the fuel delivery system comprising a fuel tank containing a volume of fuel, a fuel pump, a fuel rail, an injector, a first valve, a second valve, a solenoid valve, and a fuel orifice, the method comprising:

determining whether an ignition key is turned to an off position;

evaluating a fuel temperature in the fuel rail via one of measurement and inference;

computing a minimal positive pressure, the minimal positive pressure enabling the fuel delivery system to minimize fuel leakage for a substantially volatile fuel at the evaluated temperature;

opening periodically the solenoid valve when the fuel pressure has exceeded a predetermined pressure value, the predetermined pressure value being greater than the minimal positive pressure.

20. A method for minimizing fuel leakage of claim 19, wherein the predetermined pressure value is minimally greater that the minimum positive pressure.

21. A fuel delivery system for an engine, comprising:

a fuel tank to contain a volume of fuel;

a fuel pump in fluid communication with the fuel tank to pressurize the fuel;

a fuel rail in fluid communication with the fuel pump to receive the pressurized fuel;

an injector in fluid communication with the fuel rail to supply the pressurized fuel to the engine;

a first valve in fluid communication with the fuel rail to maintain the fuel in a pressurized state;

a second valve in fluid communication with the fuel rail to relieve the pressurized state of the fuel when the engine is not operating;

a solenoid valve, provided between a pressurized side of the fuel delivery system side and the fuel tank, being operably opened during key-on and the engine is off to reduce fuel pressure until the injector is open, and after key-off to drain fuel into the fuel tank;

a fuel orifice in fluid communication with the fuel rail, the fuel orifice being located upstream from the solenoid valve; and

a third valve in fluid communication with the fuel rail, the third valve being located upstream from the fuel orifice.

22. The fuel delivery system for an engine of claim 21, further comprising a controlling module comprising a fuel pump controller, a solenoid controller and a pressure transducer.