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

• US 10,451,010 B2
• Filed: 08/26/2016
• Issued: 10/22/2019
• Est. Priority Date: 08/26/2016
• 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.
• Primary Examiner(s): Nguyen, Robert T
• Application Number:
  US15/248,817
• Publication Number:
  US 20180058384A1
• Time in Patent Office: 1,152 Days
• CPC Class Codes: F02D 41/0032 Controlling the purging of the canister as a function of the engine operating conditions
• CPC Class Codes: F02D 41/0037 for diagnosing the engine diagnosis of purge control systems F02M25/0809
• CPC Class Codes: F02D 41/0042 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 Class Codes: F02D 41/1454 the characteristics being an oxygen content or concentration or the air-fuel ratio
• CPC Class Codes: F02D 41/221 relating to the failure of actuators or electrically driven elements
• CPC Class Codes: F02D 41/222 relating to the failure of sensors or parameter detection devices
• CPC Class Codes: F02M 2025/0881 with means to heat or cool the canister
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system
• CPC Class Codes: F02M 25/0854 Details of the absorption canister
• CPC Class Codes: Y02T 10/40 Engine management systems

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.

Claims

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 with respect to stoichiometry being indicated during purging in the second condition, and without the indication of fuel vapors in the vent line subsequent to activation of the canister heating element prior to purging in the second condition; and

indicating the canister heating element is not functioning as desired responsive to the absence of an indication of the rich air/fuel ratio during purging in the second condition subsequent to activation of the canister heating element and unsealing of the fuel vapor storage canister from atmosphere, and without an indication of fuel vapors in the vent line.

18. A system for a vehicle, comprising:

a fuel vapor canister positioned in an evaporative emission system;

a fuel tank positioned in a fuel system;

an engine with an intake manifold and an exhaust manifold;

a canister purge valve positioned in a purge conduit between the fuel vapor canister and the intake manifold;

a fuel tank isolation valve positioned in a conduit between the fuel tank and the fuel vapor canister;

a canister vent valve positioned in a vent line between the fuel vapor canister and atmosphere;

a canister heating element, coupled to and/or within the fuel vapor canister;

a secondary bleed canister positioned in the vent line between the fuel vapor canister and the canister vent valve;

a hydrocarbon sensor positioned in the vent line between the fuel vapor canister and the secondary bleed canister; and

a controller, storing instructions in non-transitory memory that, when executed, cause the controller to;

responsive to an indication of completion of a refueling event;

in a first condition, purge fuel vapors stored in the fuel vapor canister to the intake manifold of the engine for combustion by commanding open the canister purge valve and the canister vent valve without prior activation of the canister heating element;

in a second condition, purge fuel vapors stored in the fuel vapor canister to the intake manifold of the engine for combustion by commanding open the canister purge valve and the canister vent valve after activation of the canister heating element; and

diagnose whether the canister heating element and the hydrocarbon sensor are functioning as desired in the second condition, but not the first condition;

where the first condition is commenced prior to the second condition after completion of the refueling event.

19. The system of claim 18, wherein the controller further stores instructions in non-transitory memory that, when executed, cause the controller to:

in the second condition, command or maintain closed the canister purge valve, the canister vent valve, and the fuel tank isolation valve during activation of the canister heating element until activation of the canister heating element has been conducted for a predetermined time duration or until a canister temperature reaches a canister temperature threshold, and then command open the canister vent valve while maintaining the canister purge valve and the fuel tank isolation valve closed to route desorbed fuel vapors into the vent line; and

indicate that both the canister heating element and the hydrocarbon sensor are functioning as desired responsive to an indication of a presence of fuel vapors in the vent line as monitored by the hydrocarbon sensor.

20. The method of claim 19, further comprising:

an exhaust gas oxygen sensor positioned in the exhaust manifold;

wherein the controller further stores instructions in non-transitory memory that, when executed, cause the controller to;

indicate an air/fuel ratio via the exhaust gas oxygen sensor in both the first and second conditions;

during the second condition, indicate the canister heating element is functioning as desired and that the hydrocarbon sensor is not functioning as desired responsive to a rich air/fuel ratio and an absence of fuel vapors in the vent line; and

indicate the canister heating element is not functioning as desired responsive to an absence of the rich air/fuel ratio during purging in the second condition.