Systems and methods for controlling purge flow from a vehicle fuel vapor storage canister

Patent metadata

Field	Value
Publication number	US-11008963-B2
Application number	US-201916566822-A
Country	US
Kind code	B2
Filing date	Sep 10, 2019
Priority date	Sep 10, 2019
Publication date	May 18, 2021
Grant date	May 18, 2021

Abstract

Methods and systems are provided for improving efficiency of purging a fuel vapor storage canister included in an evaporative emissions control system of a vehicle. In one example, a method includes controlling a duty cycle of a canister purge valve to purge fuel vapors stored in a fuel vapor storage canister to an engine of the vehicle, and adjusting a flow rate at which the fuel vapors are purged to the engine independently of the duty cycle by controlling a magnitude of a voltage supplied to the canister purge valve during the purging.

First claim

The invention claimed is:

1. A method comprising:
during a first purge event, controlling a duty cycle of a canister purge valve to purge fuel vapors stored in a fuel vapor storage canister to an engine of a vehicle while supplying voltage to the canister purge valve at a default magnitude of voltage that is based on current vehicle operating parameters; and
during a second purge event, controlling the duty cycle of the canister purge valve to purge fuel vapors stored in the fuel vapor storage canister to the engine, and adjusting a flow rate at which the fuel vapors are purged to the engine independently of the duty cycle by controlling the voltage supplied to the canister purge valve during the second purge event to an adjusted magnitude that is different than the default magnitude.

2. The method of claim 1 , wherein adjusting the flow rate includes increasing the flow rate by increasing the magnitude of the voltage supplied to the canister purge valve relative to the default magnitude; and
decreasing the flow rate by decreasing the magnitude of the voltage supplied to the canister purge valve relative to the default magnitude.

3. The method of claim 1 , further comprising controlling the voltage supplied to the canister purge valve during the second purge event by adjusting an output voltage of a smart alternator.

4. The method of claim 1 , further comprising, during both the first purge event and the second purge event, learning a fuel vapor concentration being inducted to the engine from the fuel vapor storage canister during the respective purge event; and
wherein controlling the duty cycle during both the first purge event and the second purge event comprises sequentially ramping up the duty cycle of the canister purge valve during the respective purge event as a function of the learned fuel vapor concentration.

5. The method of claim 4 , further comprising adjusting the flow rate in response to an indication that there is a degraded voltage supply to the canister purge valve.

6. The method of claim 5 , further comprising indicating that there is the degraded voltage supply to the canister purge valve based on a determination of a voltage drop across an electrical connection between an onboard energy storage device and the canister purge valve, in comparison to a baseline voltage drop across the connection between the onboard energy storage device and the canister purge valve.

7. The method of claim 4 , wherein the fuel vapor storage canister receives fuel vapors from a fuel tank of the vehicle and further comprising:
adjusting the flow rate in response to an indication of a fuel tank pressure greater than a threshold fuel tank pressure during the purging.

8. The method of claim 4 , further comprising monitoring an output from a hydrocarbon sensor positioned in a vent line stemming from the fuel vapor storage canister that couples the fuel vapor storage canister to atmosphere; and
adjusting the flow rate in response to an indication that fuel vapors are entering into the vent line as indicated via the output from the hydrocarbon sensor immediately prior to or during the purging.

9. The method of claim 4 , further comprising monitoring a canister temperature via a canister temperature sensor positioned within a threshold distance of a vent port of the fuel vapor storage canister; and
adjusting the flow rate in response to an indication that the canister temperature is increasing near the vent port as indicated via the canister temperature sensor immediately prior to or during the purging.

10. A system for a vehicle, comprising:
a fuel vapor storage canister that receives fuel vapors from a fuel tank;
a canister purge valve for purging fuel vapors stored at the fuel vapor storage canister to an engine;
a smart alternator that charges an onboard energy storage device; and
a controller with computer readable instructions stored on non-transitory memory that when executed, cause the controller to:
raise an output voltage of the smart alternator during a canister purging event in response to an indication that a fuel vaporization rate of fuel in the fuel tank is greater than a first threshold fuel vaporization rate during the canister purging event.

11. The system of claim 10 , further comprising:
a fuel tank pressure transducer; and
wherein the controller stores further instructions to indicate that the fuel vaporization rate of fuel in the fuel tank is greater than the first threshold fuel vaporization rate under conditions where a fuel tank pressure as monitored via the fuel tank pressure transducer is greater than a non-zero positive pressure threshold with respect to atmospheric pressure during and/or immediately prior to the canister purging event.

12. The system of claim 10 , further comprising:
a hydrocarbon sensor positioned in a vent line that couples the fuel vapor storage canister to atmosphere; and
wherein the controller stores further instructions to indicate that the fuel vaporization rate of fuel in the fuel tank is greater than the first threshold fuel vaporization rate in response to an indication that fuel vapors are migrating into the vent line as monitored via the hydrocarbon sensor, immediately prior to and/or during the canister purging event.

13. The system of claim 10 , further comprising:
a canister temperature sensor positioned in the fuel vapor storage canister within a threshold distance of a vent port of the fuel vapor storage canister; and
wherein the controller stores further instructions to indicate that the fuel vaporization rate of fuel in the fuel tank is greater than the first threshold fuel vaporization rate in response to an increase in canister temperature as monitored via the canister temperature sensor immediately prior to and/or during the canister purging event.

14. The system of claim 10 , wherein the controller stores further instructions to reduce the output voltage of the smart alternator during the canister purging event in response to an indication that the fuel vaporization rate has been reduced from being greater than the first threshold fuel vaporization rate to less than a second threshold fuel vaporization rate, where the second threshold fuel vaporization rate is equal to or less than the first threshold fuel vaporization rate.

15. The system of claim 10 , further comprising:
an exhaust gas oxygen sensor;
wherein the controller stores further instructions to learn a concentration of fuel vapors being inducted to the engine during the canister purging event based at least in part on output from the exhaust gas oxygen sensor; and
wherein the controller stores further instructions to sequentially increase a duty cycle of the canister purge valve as a function of the learned concentration of fuel vapors being inducted to the engine, where raising the output voltage of the smart alternator is in addition to sequentially increasing the duty cycle of the canister purge valve.

16. A method comprising:
determining that a voltage supply to a canister purge valve is degraded; and
in response to the determination, increasing a magnitude of a voltage provided to the canister purge valve that is duty cycled in order to purge fuel vapors from a fuel vapor storage canister to an engine of a vehicle, where the magnitude of the voltage provided to the canister purge valve is a function of a determined amount of degradation of the voltage supply to the canister purge valve.

17. The method of claim 16 , further comprising comparing an actual voltage drop between an onboard energy source and the canister purge valv

Assignees

• Ford Global Tech Llc

Inventors

• Dudar Aed M
• Bohr Scott Alan
• Werner Matthew

Classifications

• F02M2025/0881

  with means to heat or cool the canister · CPC title

• F02M25/0854

  Details of the absorption canister · CPC title

• 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

• F02D41/22

  Safety or indicating devices for abnormal conditions {(in air/fuel ratio feedback systems F02D41/1495, in electric control linkage F02D11/107, in purge control systems F02M25/0809)} · CPC title

• F02D41/0045

  Estimating, calculating or determining the purging rate, amount, flow or concentration · CPC title