Systems and methods for intelligent vehicle evaporative emissions diagnostics

Patent metadata

Field	Value
Publication number	US-10718282-B2
Application number	US-201816134128-A
Country	US
Kind code	B2
Filing date	Sep 18, 2018
Priority date	Dec 22, 2016
Publication date	Jul 21, 2020
Grant date	Jul 21, 2020

Abstract

Methods and systems are provided for cleaning a fuel vapor storage canister positioned in an evaporative emissions control system of a vehicle. In one example, a method comprises sealing a fuel system of the vehicle for descending an altitude change that is predicted in advance, and subsequent to the vehicle descending the altitude change, unsealing the fuel system to passively purge fuel vapors stored in the fuel vapor storage canister to a fuel tank of the vehicle. In this way, bleed through emissions from the fuel vapor storage canister may be reduced, and engine operation may be improved.

First claim

The invention claimed is:

1. A method comprising:
sealing a fuel system of a vehicle in response to predicting an altitude change, and then the vehicle descending the altitude change, the altitude change predicted in advance of the vehicle descending the altitude change; and
in response to determining that the vehicle has finished descending the altitude change, unsealing the fuel system to passively purge fuel vapors stored in a fuel vapor storage canister to a fuel tank of the vehicle.

2. The method of claim 1 , wherein the altitude change predicted in advance occurs along a learned driving route that is learned over time.

3. The method of claim 1 , wherein the altitude change predicted in advance is based on a vehicle operator-selected or passenger-selected driving route.

4. The method of claim 1 , wherein the altitude change that is predicted in advance results in development of a negative pressure in the fuel system with respect to atmospheric pressure that is at least a predetermined negative pressure.

5. The method of claim 4 , wherein the predetermined negative pressure is −8 InH2O.

6. The method of claim 1 , further comprising:
unsealing the fuel system to passively purge fuel vapors stored in the fuel vapor storage canister to the fuel tank while the vehicle is descending the altitude change, under conditions where a predetermined passive purge threshold negative pressure is reached in the fuel system during the descending the altitude change; and
resealing the fuel system in response to pressure in the fuel system being within a threshold of atmospheric pressure during the descending the altitude change.

7. The method of claim 6 , wherein the predetermined passive purge threshold negative pressure is −16 InH2O.

8. The method of claim 6 , wherein unsealing the fuel system to passively purge fuel vapors stored in the fuel vapor storage canister to the fuel tank while the vehicle is descending the altitude change, and resealing the fuel system in response to the pressure in the fuel system being within the threshold of atmospheric pressure occurs any number of times during the descending the altitude change.

9. The method of claim 1 , further comprising:
subsequent to the descending the altitude change and prior to unsealing the fuel system to passively purge fuel vapors stored in the fuel vapor storage canister, monitoring pressure in the sealed fuel system and indicating an absence of undesired evaporative emissions stemming from the fuel system in response to the pressure in the sealed fuel system remaining below a pressure bleedup threshold for a predetermined time duration.

10. The method of claim 1 , further comprising:
monitoring a temperature change of the fuel vapor storage canister during the passively purging the fuel vapors to the fuel tank; and
indicating a loading state of the fuel vapor storage canister based on the temperature change.

11. A method comprising:
during a driving cycle, passively purging a fuel vapor storage canister of a vehicle that captures and stores fuel vapors from a fuel system via sealing the fuel system for a duration that the vehicle travels a predicted altitude descent, in response to predicting the altitude descent, and then unsealing the fuel system in response to determining that the predicted altitude descent is completed to route fuel vapors from the fuel vapor storage canister to a fuel tank of the fuel system; and
adjusting an aggressiveness of a subsequent active purge of the fuel vapor storage canister as a function of the passive purge.

12. The method of claim 11 , wherein the predicted altitude descent comprises either a learned altitude change or is inferred from a selected route.

13. The method of claim 11 , wherein the active purge comprises a purging event of the fuel vapor storage canister that relies on a vacuum communicated to the fuel vapor storage canister from an engine of the vehicle; and
wherein adjusting the aggressiveness of the active purge includes reducing an initial rate at which a canister purge valve positioned in a purge line that couples the fuel vapor storage canister to the engine is duty cycled for conducting the active purge as compared to a situation where the aggressiveness of the active purge is not adjusted.

14. The method of claim 13 , wherein adjusting the aggressiveness of the active purge further comprises adjusting a ramp rate at which the duty cycle of the canister purge valve is increased during the active purge.

15. The method of claim 11 , further comprising:
monitoring a temperature change of the fuel vapor storage canister during the passively purging of the fuel vapor storage canister in order to indicate a loading state of the fuel vapor storage canister; and
wherein adjusting the aggressiveness of the active purge includes cancelling the active purge in response to an indication that the loading state of the fuel vapor storage canister is below a canister load threshold.

16. A system for a vehicle, comprising:
a fuel system that includes a fuel tank that is selectively fluidically coupled to a fuel vapor storage canister via a fuel tank isolation valve, the fuel vapor storage canister positioned in an evaporative emissions system and where the fuel vapor storage canister is selectively fluidically coupled to atmosphere via a canister vent valve and to an intake of an engine via a canister purge valve;
an onboard navigation system; and
a controller with computer readable instructions stored on non-transitory memory that when executed, cause the controller to:
in response to an indication that the vehicle is within a threshold distance of an altitude descent predicted to result in development of at least a predetermined vacuum level in the fuel system and evaporative emissions as indicated via the onboard navigation system, couple the fuel system to the evaporative emissions system via commanding open the fuel tank isolation valve and then seal the fuel system and the evaporative emissions system via commanding closed the canister vent valve;
maintain a target vacuum in the fuel system and the evaporative emissions system during the altitude descent via duty cycling the canister vent valve;
conduct a test for a presence or an absence of undesired evaporative emissions stemming from the fuel system and/or the evaporative emissions system via monitoring a pressure bleedup in the fuel system and the evaporative emissions system which are sealed from atmosphere, just subsequent to the altitude descent;
unseal the fuel system and the evaporative emissions system in response to a determination as to the presence or the absence of undesired evaporative emissions stemming from the fuel system and/or the evaporative emissions system; and
adjust an aggressiveness of a subsequent active purging operation of the fuel vapor storage canister based on whether the presence or the absence of undesired evaporative emissions is indicated.

17. The system of claim 16 , wherein the controller stores further instructions to indicate the presence of undesired evaporative emissions stemming from the fuel system and/or the evaporative emissions system in response to the pressure bleedup exceeding a predetermined pressure bleedup threshold and/or in response to a pressure bleedup rate exceeding a predetermined pressure bleedup rate, within a predetermined duration of time.

18. The system of claim 16 , wherein the controller stores further instructions to actively purge the canister in the subsequent active purging operation via commanding open the canister vent valv

Assignees

• Ford Global Tech Llc

Inventors

• Dudar Aed M

Classifications

• F02D41/004 Primary

  Control of the valve or purge actuator, e.g. duty cycle, closed loop control of position · CPC title

• F02D2041/225

  Leakage detection · CPC title

• F02D2200/0802

  Temperature of the exhaust gas treatment apparatus · CPC title

• F02D2200/702

  Road conditions · CPC title

• G07C5/0841

  Registering performance data (recording measured values G01D; information storage G11B) · CPC title