Evaporative emissions diagnostics for a multi-path purge ejector system

Patent metadata

Field	Value
Publication number	US-10107233-B2
Application number	US-201615370606-A
Country	US
Kind code	B2
Filing date	Dec 6, 2016
Priority date	Dec 6, 2016
Publication date	Oct 23, 2018
Grant date	Oct 23, 2018

Abstract

Methods and systems are provided for diagnosing a high load purge line of a boosted engine system for undesired evaporative emissions. In one example, a method for diagnosing the high load purge line includes drawing vacuum in the high load purge line under natural aspiration conditions and concurrently purging a fuel vapor canister. In this way, the high load purge line may be diagnosed for undesired evaporative emissions without disrupting a canister purge schedule.

First claim

The invention claimed is:

1. A method, comprising:
in a first condition, purging fuel vapors from a fuel vapor canister through an ejector unit into an air intake system of an engine without simultaneously conducting a test for undesired evaporative emissions on a high load purge line coupled between the ejector unit and the air intake system; and
in a second condition, purging fuel vapors from the fuel vapor canister while simultaneously conducting the test for undesired evaporative emissions on the high load purge line.

2. The method of claim 1 , wherein the high load purge line is coupled between the ejector unit and the air intake system through a check valve, which in turn is coupled to an air compressor, the air compressor supplying compressed air into the air intake system.

3. The method of claim 1 , wherein the first condition includes purging fuel vapors from the fuel vapor canister under boosted conditions or under natural aspiration conditions.

4. The method of claim 1 , wherein the second condition includes purging fuel vapors from the fuel vapor canister under natural aspiration conditions but not under boosted conditions.

5. The method of claim 1 , wherein the second condition includes an indication of an absence of undesired evaporative emissions upstream of the ejector unit.

6. The method of claim 1 , wherein conducting the test for undesired evaporative emissions on the high load purge line further comprises:
monitoring a fuel system pressure via a fuel tank pressure transducer coupled to a fuel tank which is coupled to the fuel vapor canister; and
indicating a presence or absence of undesired evaporative emissions in the high load purge line as a function of a fuel system pressure threshold during purging fuel vapors from the fuel vapor canister while simultaneously conducting the test for undesired evaporative emissions on the high load purge line in the second condition.

7. The method of claim 6 , further comprising:
indicating a manifold air pressure in an intake manifold included within the air intake system via a manifold air pressure sensor positioned in the intake manifold; and
adjusting the fuel system pressure threshold for indicating the presence or absence of undesired evaporative emissions in the high load purge line as a function of the indicated manifold air pressure.

8. The method of claim 6 , further comprising:
wherein both the first condition and the second condition include duty cycling a canister purge valve positioned in a purge line between the ejector unit and the fuel vapor canister;
wherein both the first condition and the second condition include commanding or maintaining open a canister vent valve positioned in a vent line between the fuel vapor canister and atmosphere; and
wherein the second condition further includes adjusting the fuel system pressure threshold for indicating the presence or absence of undesired evaporative emission in the high load purge line as a function of the canister purge valve duty cycle.

9. A method comprising:
indicating a presence or an absence of undesired evaporative emissions upstream of an ejector unit in a vehicle with an engine having an air intake system which may be configured to operate under either boosted or natural aspiration conditions; and
responsive to an indication of the absence of undesired evaporative emissions upstream of the ejector unit:
indicating the presence or absence of undesired evaporative emissions in a high load purge line positioned between the ejector unit and the air intake system by drawing a vacuum simultaneously on both the high load purge line and upstream of the ejector unit.

10. The method of claim 9 , wherein indicating the presence or absence of undesired evaporative emissions upstream of the ejector unit includes duty cycling a canister purge valve positioned between the ejector unit and a fuel vapor canister, the fuel vapor canister positioned in a canister-side of an evaporative emissions system, the canister-side of the evaporative emissions system coupled to a fuel system including a fuel tank configured to provide fuel to the engine;
commanding closed a canister vent valve positioned in a vent line between the fuel vapor canister and atmosphere;
drawing a vacuum on the fuel system and the canister-side of the evaporative emissions system by communicating vacuum from the ejector unit to the fuel system and the canister-side of the evaporative emissions system during boosted conditions until a predetermined fuel system pressure is reached;
sealing the fuel system and the canister-side of the evaporative emissions system from atmosphere responsive to the predetermined fuel system pressure being reached; and
indicating the absence of undesired evaporative emissions responsive to pressure bleed-up below a pressure bleed-up threshold, or responsive to a pressure bleed-up rate below a predetermined pressure bleed-up rate.

11. The method of claim 10 , wherein drawing the vacuum simultaneously on both the high load purge line and the canister-side of the evaporative emissions system is not conducted during boosted conditions.

12. The method of claim 10 , wherein drawing the vacuum simultaneously on both the high load purge line and the canister-side of the evaporative emissions system further comprises:
duty cycling the canister purge valve;
commanding or maintaining open the canister vent valve;
closing a check valve positioned between the high load purge line and the air intake system; and
drawing vacuum on the fuel system, the canister-side of the evaporative emissions system, and the high load purge line by communicating vacuum from the air intake system under natural aspiration conditions to the fuel system, the canister-side of the evaporative emissions system, and the high load purge line.

13. The method of claim 12 , wherein drawing vacuum simultaneously on the fuel system, the canister-side of the evaporative emissions system, and the high load purge line draws atmospheric air across the fuel vapor canister to purge fuel vapors stored in the fuel vapor canister to the air intake system to be combusted by the engine.

14. The method of claim 12 , wherein indicating the presence or absence of undesired evaporative emissions in the high load purge line further comprises:
indicating the absence of undesired evaporative emissions in the high load purge line responsive to pressure in the fuel system reaching a predetermined negative pressure threshold while drawing the vacuum simultaneously on both the high load purge line and the canister-side of the evaporative emissions system.

15. The method of claim 14 , further comprising:
indicating a manifold air pressure in an intake manifold of the air intake system via a manifold air pressure sensor positioned in the intake manifold; and
adjusting the predetermined negative pressure threshold as a function of the indicated manifold air pressure;
wherein adjusting the threshold as a function of the indicated manifold air pressure includes making the threshold more negative as the indicated manifold air pressure decreases with respect to atmospheric pressure and making the threshold less negative as the indicated manifold air pressure increases with respect to atmospheric pressure.

16. The method of claim 14 , further comprising;
adjusting the predetermined negative pressure threshold as a function of the duty cycle of the canister purge valve;
wherein adjusting the predetermined negative pressure threshold as a function of the duty cycle of the canister purge valve includes making the threshold more negative as

Assignees

• Ford Global Tech Llc

Inventors

• Dudar Aed M
• Bohr Scott A
• Werner Matthew
• Masucci Matthew

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

• F02M25/0818 Primary

  having means for pressurising the evaporative emission space · CPC title

• B01D53/0454

  Controlling adsorption (controlling temperature swing adsorption B01D53/0462, controlling pressure swing adsorption B01D53/047) · CPC title

• F02D41/26

  using computer, e.g. microprocessor · CPC title

• B01D2257/7022

  Aliphatic hydrocarbons · CPC title