METHOD AND SYSTEM FOR PURGE CONTROL

• US 20160290285A1
• Filed: 04/01/2015
• Published: 10/06/2016
• Est. Priority Date: 04/01/2015
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Dudar, Aed M., Werner, Matthew
• Granted Patent: US 9,970,393 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F01N 5/04 the devices using kinetic energy
• CPC Class Codes: F02B 37/183 Arrangements of bypass valves or actuators therefor
• CPC Class Codes: F02M 2025/0881 with means to heat or cool the canister
• CPC Class Codes: F02M 25/089 Layout of the fuel vapour installation
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

Methods and systems are provided for purging a fuel vapor canister during conditions when purge vacuum is limited, such as during boosted conditions. An exhaust-driven purge pump is used to flow positive pressure air through a canister, and purge the canister to a compressor inlet. The air is heated during the pressurization, improving hydrocarbon desorption from the canister.

Claims

1. A method for an engine, comprising:

during boosted engine operation,

purging a fuel vapor canister to a compressor inlet with positive pressure drawn from an exhaust-driven pump.

2. The method of claim 1, further comprising, adjusting an output of the exhaust-driven pump via a wastegate.

3. The method of claim 2, wherein the adjusting includes, decreasing an opening of the wastegate to increase an output of the exhaust-driven pump responsive to actual canister purge rate being lower than a desired canister purge rate.

4. The method of claim 3, wherein the opening of the wastegate is further adjusted based on a fuel tank pressure, the opening increased as the fuel tank pressure increases.

5. The method of claim 3, wherein the opening of the wastegate is further adjusted based on a temperature of air directed from the exhaust-driven pump into the canister.

6. The method of claim 1, wherein the purging includes closing a first purge valve coupled between the canister and an engine intake while opening a second purge valve coupled between the canister and an outlet of the exhaust-driven pump.

7. The method of claim 6, wherein the purging further includes closing one or more of a vent valve coupled in a vent line of the canister, and a vapor blocking valve coupled between the canister and a fuel tank.

8. The method of claim 7, further comprising, during non-boosted engine operation, while an intake manifold vacuum level is higher than a threshold vacuum, purging the fuel vapor canister to the engine intake, downstream of an intake throttle, with negative pressure drawn from the engine intake;

and while the intake manifold vacuum level is lower than the threshold vacuum, purging the fuel vapor canister to the compressor inlet with positive pressure drawn from the exhaust-driven pump.

9. The method of claim 8, wherein the purging during non-boosted engine operation includes opening each of the first purge valve and the canister vent valve while closing the second purge valve.

10. An engine method, comprising:

during a first purging condition, adjusting an exhaust-driven positive pressure pump via a wastegate to flow fuel vapors from a canister to a compressor inlet; and

during a second purging condition, applying negative pressure from an intake manifold to draw fuel vapors from the canister to an engine intake.

11. The method of claim 10, wherein during the first purging condition, the engine is operated with boost and wherein during the second purging condition, the engine is operated with natural aspiration.

12. The method of claim 10, wherein during the first purging condition, heated air is drawn into the canister and wherein during the second purging condition, ambient air is drawn into the canister.

13. The method of claim 10, wherein an output of the exhaust-driven positive pressure pump is adjusted via a wastegate, the method further comprising, during the first purging condition, adjusting an opening of the wastegate based on each of a canister purge rate and a boost pressure.

14. The method of claim 10, wherein during the first purging condition, a first canister purge valve coupled between the canister and the engine intake is closed and a second canister purge valve coupled between the canister and the compressor inlet is open, and wherein during the second purging condition, the first canister purge valve is open and the second canister purge valve is closed.

15. The method of claim 14, wherein during the first purging condition, a vent valve coupled between the canister and atmosphere is closed, and wherein during the second purging condition, the vent valve is open.

16. An engine system, comprising:

an engine including an intake;

a turbocharger including an intake compressor and an exhaust turbine;

a fuel system including a fuel tank coupled to a fuel vapor canister;

a first purge valve coupled between the canister and the intake;

a second purge valve coupled between the canister and the compressor;

a pump operated using engine exhaust received from downstream of the turbine;

a wastegate for adjusting an output of the pump; and

a controller with computer-readable instructions stored on non-transitory memory for;

operating in a first purging mode to flow ambient air, via the pump, through the canister and flow fuel vapors from the canister to an inlet of the compressor; and

operating in a second purging mode to flow ambient air, via intake manifold vacuum, through the canister and flow fuel vapors from the canister to the intake, downstream of an intake throttle.

17. The system of claim 16, wherein the operating in the first purging mode in response to canister purging conditions being met while the engine is operating with boost from the turbocharger, and wherein the operating in the second purging mode in response to canister purging conditions being met while the engine is operating without boost from the turbocharger.

18. The system of claim 16, wherein operating in the first mode includes operating with the first purge valve closed and the second purge valve open, and wherein operating in the second mode includes operating with the first purge valve open and the second purge valve closed.

19. The system of claim 18, wherein operating in the first mode further includes adjusting an opening of the wastegate based on a canister purge rate and a boost pressure of the turbocharger, and wherein operating in the second mode further includes maintaining an opening of the wastegate.

20. The system of claim 16, wherein the ambient air flowed while operating in the first mode is at a higher temperature than the ambient air flowed while operating in the second mode.