Systems and methods for fuel vapor canister purge

Patent metadata

Field	Value
Publication number	US-9822719-B2
Application number	US-201615064811-A
Country	US
Kind code	B2
Filing date	Mar 9, 2016
Priority date	Mar 9, 2016
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

Abstract

Methods and systems are provided for controlling the purging of a fuel vapor canister coupled to a vehicle fuel tank, configured for capturing and storing vapors emanating from the tank. In one example, two canister purge valves are coupled in series in a fuel vapor conduit between the fuel vapor canister and engine intake, one at the intake manifold and one at the fuel vapor canister, such that fine control over the introduction of fuel vapors into the engine is maintained via the purge valve at the intake manifold, while thorough purging of the fuel vapor canister may be regulated via the purge valve at the fuel vapor canister. In this way, fuel vapors in the fuel vapor canister may be effectively purged to intake, thus reducing the potential for undesired evaporative emissions.

First claim

The invention claimed is:

1. A method comprising:
regulating purging of vapors stored in a storage canister into an engine intake with a first valve coupled to the intake and a second valve coupled to the canister, by transitioning between:
under first conditions during the purging, regulating flow through the first valve, and not through the second valve; and
under second, different, conditions during the purging, regulating flow through the second valve, and not through the first valve.

2. The method of claim 1 , wherein the first conditions comprise: vapor load of the canister above a threshold; or, vapor state of the canister not known.

3. The method of claim 1 , wherein the second conditions comprise: vapor load of the canister below a threshold; or, a rich response to an initiation of the purging not indicated from an air/fuel sensor positioned in an exhaust of an engine.

4. The method of claim 1 , further comprising maintaining the second valve fully open when a vapor load is above a threshold and maintaining the first valve fully open when the vapor load is below the threshold.

5. A method for a vehicle comprising:
purging fuel vapors stored in a fuel vapor canister to an intake manifold of an engine;
during a canister purging with a canister vent valve open, duty cycling a first canister purge valve and commanding open a second canister purge valve; and
stopping duty cycling the first canister purge valve, opening the first canister purge valve, and commencing duty cycling the second canister purge valve responsive to a canister load below a threshold canister load.

6. The method of claim 5 , wherein the first canister purge valve and the second canister purge valve are arranged in series.

7. The method of claim 5 , wherein opening the first canister purge valve and duty cycling the second canister purge valve increases air flow through the fuel vapor canister as compared to duty cycling the first canister purge valve and opening the second canister purge valve.

8. The method of claim 5 , wherein opening the first canister purge valve and duty cycling the second canister purge valve results in a desorption of hydrocarbons from the fuel vapor canister that are not desorbed during duty cycling the first canister purge valve and commanding open the second canister purge valve.

9. The method of claim 8 , wherein the desorption of hydrocarbons from the fuel vapor canister that are not desorbed during duty cycling the first canister purge valve and commanding open the second canister purge valve reduces undesired evaporative emissions.

10. The method of claim 5 , further comprising:
indicating an exhaust gas air/fuel ratio via an exhaust gas sensor; and
wherein indicating canister load is further based on the exhaust air/fuel ratio as measured by the exhaust gas sensor.

11. The method of claim 5 , further comprising:
indicating a temperature of the fuel vapor canister at one or more locations via one or more temperature sensors positioned within the fuel vapor canister; and
wherein indicating canister load is further based on a temperature decrease while purging the fuel vapor canister.

12. The method of claim 5 , wherein purging fuel vapors stored in the fuel vapor canister to the intake manifold further comprises:
selectively coupling the fuel vapor canister to atmosphere via the canister vent valve;
selectively coupling the intake manifold to the fuel vapor canister via opening the first and second canister purge valves;
wherein engine intake manifold vacuum draws fresh air into the fuel vapor canister; and
wherein air drawn into the fuel vapor canister desorbs hydrocarbons from the fuel vapor canister and engine intake manifold vacuum routes the desorbed hydrocarbons to the engine for combustion.

13. A system for a vehicle comprising:
a fuel tank configured within a fuel system;
a fuel vapor canister configured within an evaporative emissions system, and coupled to the fuel tank that provides fuel to an internal combustion engine;
an intake manifold of the internal combustion engine, coupled to the fuel vapor canister via a first canister purge valve and a second canister purge valve;
a canister vent valve, positioned between the fuel vapor canister and atmosphere; and
a controller storing instructions in non-transitory memory, that when executed, cause the controller to:
purge stored fuel vapors to the intake manifold of the engine for combustion by coupling the fuel vapor canister to atmosphere via the canister vent valve by commanding open the canister vent valve, and applying engine intake manifold vacuum to the fuel vapor canister by opening one or more of the canister purge valves to draw fresh air across the fuel vapor canister to desorb fuel vapors;
in a first condition during purging, purging stored fuel vapors to the intake manifold of the engine by applying a first pressure drop between the intake manifold and the fuel vapor canister;
in a second condition during purging, purging stored fuel vapors to the intake manifold of the engine by applying a second pressure drop between the intake manifold and the fuel vapor canister;
wherein the first pressure drop is greater than the second pressure drop;
wherein the first condition includes duty cycling the first canister purge valve and commanding open the second canister purge valve;
wherein the second condition includes opening the first canister purge valve and duty cycling the second canister purge valve; and
wherein the first and second canister purge valves are arranged in series.

14. The system of claim 13 , wherein:
a distance between the intake manifold and the second canister purge valve is equivalent to a distance between the fuel vapor canister and the first canister purge valve.

15. The system of claim 13 , wherein:
the first canister purge valve and the second canister purge valve are both normally closed solenoid-actuated valves.

16. The system of claim 13 , wherein:
the first canister purge valve is mounted at the intake manifold, and the second canister purge valve is mounted at the fuel vapor canister.

17. The system of claim 13 , further comprising:
an exhaust gas sensor positioned in an exhaust manifold of the engine;
wherein the controller further stores instructions in non-transitory memory, that when executed, cause the controller to:
indicate an exhaust air/fuel ratio via the exhaust gas sensor; and
during the first condition and the second condition, indicate a fuel vapor canister load based on the indicated exhaust air/fuel ratio.

18. The system of claim 17 , wherein the controller further stores instructions in non-transitory memory, that when executed, cause the controller to:
purge stored fuel vapors according to the first condition responsive to a canister load above a predetermined threshold canister load or an unknown canister load; and
purge stored fuel vapors according to the second condition responsive to the canister load below the predetermined threshold canister load.

19. The system of claim 17 , wherein the controller further stores instructions in non-transitory memory, that when executed, cause the controller to:
during the first and second conditions, adjust the duty cycle of the first or second canister purge valve based on one or more of engine operating conditions, and/or canister load.

20. The system of claim 17 , further comprising:
the first and second canister purge valves arranged in parallel, not in series, the first canister purge valve close-coup

Assignees

• Ford Global Tech Llc

Inventors

• Dudar Aed M
• Ignasiak Donald
• Yang Dennis Seung-Man
• Pearce Russell Randall
• Peters Mark W
• Kragh Niels Christopher

Classifications

• F02M25/0836

  Arrangement of valves controlling the admission of fuel vapour to an engine, e.g. valve being disposed between fuel tank or absorption canister and intake manifold · CPC title

• F02M25/0854

  Details of the absorption canister · CPC title

• F02D41/0042 Primary

  Controlling the combustible mixture as a function of the canister purging, e.g. control of injected fuel to compensate for deviation of air fuel ratio when purging · CPC title

• F02M35/10222 Primary

  Exhaust gas recirculation [EGR]; Positive crankcase ventilation [PCV]; Additional air admission, lubricant or fuel vapour admission · CPC title

• F02M25/089

  Layout of the fuel vapour installation · CPC title