Systems and methods for diagnosing components in a vehicle evaporative emissions system

Patent metadata

Field	Value
Publication number	US-10451010-B2
Application number	US-201615248817-A
Country	US
Kind code	B2
Filing date	Aug 26, 2016
Priority date	Aug 26, 2016
Publication date	Oct 22, 2019
Grant date	Oct 22, 2019

Abstract

Methods and systems are provided for conducting a canister purging operation and for rationalizing components of a vehicle evaporative emission system. In one example, after completion of a refueling event, a first fuel vapor canister purge operation is conducted to desorb hydrocarbon light ends from the fuel vapor canister, and subsequently the canister is heated to desorb hydrocarbon heavy ends from the canister, which are routed to a hydrocarbon sensor to rationalize the hydrocarbon sensor, before being purged to engine intake in a second purging operation. In this way, a fuel vapor storage canister may be thoroughly cleaned of hydrocarbon light ends and hydrocarbon heavy ends, while additionally indicating whether a canister heating element, and a hydrocarbon sensor positioned between the canister and atmosphere, are functioning as desired.

First claim

The invention claimed is:

1. A method comprising:
capturing and storing fuel vapors in a fuel vapor canister positioned in a vehicle evaporative emission system, the fuel vapor canister removably coupled to a fuel tank that provides fuel to an engine that propels a vehicle;
actively routing fuel vapors from the fuel vapor canister into a vent line coupling the fuel vapor canister to atmosphere; and
diagnosing one or more evaporative emission system components responsive to the routing.

2. The method of claim 1 , wherein actively routing fuel vapors from the fuel vapor canister into the vent line includes activation of a canister heating element coupled to and/or within the fuel vapor canister to promote desorption of fuel vapors stored in the fuel vapor canister.

3. The method of claim 2 , wherein actively routing fuel vapors from the fuel vapor canister further comprises:
sealing the fuel vapor canister from atmosphere, from an intake manifold of the engine, and from the fuel tank during activation of the canister heating element; and
responsive to the canister heating element being activated for a predetermined duration of time or until a predetermined canister temperature is reached:
unsealing the fuel vapor canister from atmosphere while maintaining the fuel vapor canister sealed from the intake manifold and from the fuel tank.

4. The method of claim 3 , further comprising:
monitoring the vent line via a hydrocarbon sensor for a presence of fuel vapors subsequent to activation of the canister heating element and unsealing the fuel vapor canister from atmosphere;
wherein diagnosing one or more evaporative emission system components includes indicating that both the canister heating element and the hydrocarbon sensor are functioning as desired responsive to an indication of the presence of fuel vapors in the vent line.

5. The method of claim 4 , further comprising:
purging fuel vapors to the intake manifold of the engine by unsealing the fuel vapor canister from the intake manifold while maintaining the fuel vapor canister unsealed from atmosphere to draw fresh air through the fuel vapor canister;
wherein the purging is conducted responsive to either an indication of fuel vapors in the vent line, or responsive to a predetermined time duration elapsing subsequent to activation of the canister heating element and unsealing of the fuel vapor canister from atmosphere, without the indication of fuel vapors in the vent line.

6. The method of claim 5 , further comprising:
purging fuel vapors to the intake manifold of the engine prior to activating the canister heating element to promote desorption of hydrocarbon light ends from the fuel vapor canister; and
wherein diagnosing the canister heating element and the hydrocarbon sensor is not conducted during or prior to purging of hydrocarbon light ends.

7. The method of claim 6 , wherein activating the canister heating element subsequent to purging the fuel vapor canister of hydrocarbon light ends serves to promote desorption of hydrocarbon heavy ends stored within the fuel vapor canister that are not purged during purging of the fuel vapor canister in an absence of activation of the canister heating element.

8. The method of claim 5 , further comprising:
indicating an air/fuel ratio via an exhaust gas oxygen sensor positioned in an exhaust manifold of the engine during purging fuel vapors to the intake manifold of the engine; and
indicating the canister heating element is functioning as desired but that the hydrocarbon sensor is not functioning as desired responsive to a rich air/fuel ratio with respect to stoichiometry being indicated during purging, and without the indication of fuel vapors in the vent line subsequent to activation of the canister heating element prior to purging.

9. The method of claim 8 , further comprising:
indicating the canister heating element is not functioning as desired responsive to the absence of an indication of a rich air/fuel ratio during purging subsequent to activation of the canister heating element and unsealing of the fuel vapor canister from atmosphere, and without the indication of fuel vapors in the vent line.

10. The method of claim 1 , further comprising:
preventing undesired evaporative emissions from being released to atmosphere during actively routing fuel vapors from the fuel vapor canister into the vent line by capturing fuel vapors in a secondary bleed canister positioned in the vent line between the fuel vapor canister and atmosphere.

11. A method comprising:
sequentially purging fuel vapors stored in a fuel vapor storage canister to an intake manifold of a vehicle engine, the fuel vapor storage canister removably coupled to a vehicle fuel tank which supplies fuel to the engine, by, in a first condition, purging the fuel vapor storage canister of hydrocarbon light ends, and subsequently, in a second condition, purging the fuel vapor storage canister of hydrocarbon heavy ends.

12. The method of claim 11 , wherein purging fuel vapors from the fuel vapor storage canister to the intake manifold in both the first condition and the second condition includes coupling the fuel vapor storage canister to the intake manifold and to atmosphere, to draw atmospheric air through the fuel vapor storage canister and into the intake manifold.

13. The method of claim 11 , further comprising:
promoting desorption of fuel vapors from the fuel vapor storage canister via activation of a canister heating element;
wherein the first condition includes purging the fuel vapor storage canister before activation of the canister heating element; and
wherein the second condition includes purging the fuel vapor storage canister subsequent to activation of the canister heating element.

14. The method of claim 13 , wherein purging the fuel vapor storage canister before activation of the canister heating element desorbs hydrocarbon light ends in the first condition, but not hydrocarbon heavy ends; and
wherein activation of the canister heating element subsequent to purging the fuel vapor storage canister of hydrocarbon light ends in the first condition promotes desorption of hydrocarbon heavy ends that are subsequently purged to the intake manifold in the second condition.

15. The method of claim 13 , wherein activation of the canister heating element is conducted with the fuel vapor storage canister sealed from the intake manifold, from the fuel tank, and from atmosphere; and
wherein subsequent to activation of the canister heating element for a predetermined duration, or responsive to a canister temperature reaching a predetermined canister temperature threshold, unsealing the fuel vapor storage canister from atmosphere, to route desorbed fuel vapors into a vent line coupling the fuel vapor storage canister to atmosphere.

16. The method of claim 15 , further comprising:
indicating a presence or an absence of fuel vapors in the vent line via a hydrocarbon sensor; and
indicating that both the hydrocarbon sensor and the canister heating element are functioning as desired responsive to the indication of the presence of fuel vapors in the vent line subsequent to activation of the canister heating element.

17. The method of claim 16 , further comprising:
indicating an air/fuel ratio via an exhaust gas oxygen sensor positioned in an exhaust manifold of the engine during purging fuel vapors to the intake manifold of the engine;
indicating the canister heating element is functioning as desired but that the hydrocarbon sensor is not functioning as desired responsive to a rich air/fuel ratio wit

Assignees

• Ford Global Tech Llc

Inventors

• Dudar Aed M

Classifications

• F02D41/0037

  for diagnosing the engine (diagnosis of purge control systems F02M25/0809) · CPC title

• F02D41/0032

  Controlling the purging of the canister as a function of the engine operating conditions · CPC title

• F02D41/0042

  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

• F02D41/222

  relating to the failure of sensors or parameter detection devices · CPC title

• Y02T10/40

  Engine management systems · CPC title