Method and system for fuel vapor management

Patent metadata

Field	Value
Publication number	US-9797322-B2
Application number	US-201414252665-A
Country	US
Kind code	B2
Filing date	Apr 14, 2014
Priority date	Apr 14, 2014
Publication date	Oct 24, 2017
Grant date	Oct 24, 2017

Abstract

Methods and systems are provided for improving the efficiency of canister purge completion. Based on engine operating conditions, a canister is purged to a compressor inlet or a throttle outlet. During purging conditions, as canister loads change, a purge flow through the canister is varied so that a fixed preselected portion of total engine fueling is delivered as fuel vapors.

First claim

The invention claimed is:

1. A method for an engine, comprising:
receiving purge flow from a fuel system canister concurrently at each of a first location upstream of a compressor and a second location downstream of an intake throttle;
adjusting the purge flow to be a preselected proportion of total engine fuel including maintaining a fuel vapor fraction of the total engine fuel as engine fueling changes with load even if a higher purge flow rate is possible.

2. The method of claim 1 , wherein the total engine fuel includes a total of liquid fuel and fuel vapors, and wherein the preselected proportion includes substantially 20% of the total engine fuel.

3. The method of claim 1 , wherein the purge flow received at the first location is received via an aspirator coupled in a compressor bypass path.

4. The method of claim 3 , wherein the purge flow received at the second location is received via a canister purge valve.

5. The method of claim 1 , wherein an amount of purge flow received at the first location relative to the second location is based on engine operating conditions including one or more of manifold pressure, boost pressure, and canister load.

6. The method of claim 5 , wherein a higher amount of purge flow is received at the first location relative to the second location when manifold pressure is higher than barometric pressure, when the boost pressure is higher, when boost is enabled, or when the canister load is lower.

7. The method of claim 1 , wherein the adjusting includes limiting the purge flow when the fuel vapor fraction reaches the preselected proportion of total engine fuel, the method further comprising adjusting engine liquid fueling based on the purge flow to maintain engine combustion at or around stoichiometry.

8. A method for an engine, comprising:
receiving purge flow from a fuel system canister at a first location upstream of a compressor and a second location downstream of an intake throttle at mutually exclusive conditions; and
across the mutually exclusive conditions, maintaining the purge flow at a preselected proportion of total engine fueling even as the total engine fueling changes with engine load from a minimum engine fueling level to a maximum engine fueling level, wherein maintaining the purge flow at the preselected proportion of total engine fueling includes applying a lower purge flow rate at higher canister load and a higher purge flow rate at lower canister load.

9. The method of claim 8 , wherein receiving purge flow at mutually exclusive conditions includes receiving purge flow downstream of the intake throttle during a first condition when manifold pressure is lower than barometric pressure, and receiving purge flow upstream of the compressor during a second condition, mutually exclusive to the first condition, when manifold pressure is higher than barometric pressure.

10. The method of claim 9 , wherein the purge flow is received in an intake manifold using intake vacuum during the first condition, and wherein the purge flow is received in the intake manifold using vacuum generated at an aspirator coupled in a compressor bypass path during the second condition.

11. The method of claim 10 , wherein a rate of purge flow is adjusted during the first condition by adjusting an opening of a purge valve, the opening of the purge valve based on canister load, and wherein the rate of purge flow is adjusted during the second condition by adjusting an opening of an aspirator shut-off valve, the opening of the aspirator shut-off valve based on the canister load.

12. The method of claim 8 , further comprising transitioning between the mutually exclusive conditions and continuously maintaining the purge flow at the preselected proportion immediately before and immediately after the transition.

13. The method of claim 12 , wherein the continuously maintaining includes, as the engine is transitioned from a first condition of lower engine fueling to a second condition of higher engine fueling, increasing engine airflow, and wherein the preselected proportion is substantially 20% of total engine fueling.

14. An engine system, comprising:
an engine including an intake;
an intake throttle;
an intake compressor;
a compressor bypass path including a valved aspirator;
a fuel system canister;
a first purge conduit coupling the canister to the engine intake via a canister purge valve;
a second purge conduit coupling the canister to the engine intake via the valved aspirator; and
a controller with computer readable instructions for:
selectively purging the canister to the engine intake via one or more of the first conduit and the second conduit, the selection based on manifold pressure; and
limiting a purge fuel vapor flow received in the engine intake to be a predefined proportion of total engine fuel as engine fueling level changes with engine load even if a higher purge flow rate is possible, the total engine fuel including a total of the purge fuel vapor flow and liquid fuel received in the engine.

15. The system of claim 14 , wherein limiting the purge fuel vapor flow includes adjusting the purge flow so that the total of the purge fuel vapor flow and liquid fuel received in the engine is at or around stoichiometry.

16. The system of claim 15 , wherein the predefined proportion includes a maximum of 20% purge.

17. The system of claim 14 , wherein the selectively purging includes purging via the first conduit at lower manifold pressure, purging via the second conduit at higher manifold pressure, and purging via each of the first and second conduit at a manifold pressure intermediate the higher and lower manifold pressures.

18. The system of claim 17 , wherein purging via the first conduit includes opening the canister purge valve to purge to the engine intake using intake vacuum, downstream of the intake throttle, and wherein purging via the second conduit includes opening a valve of the valved aspirator to purge to the engine intake using aspirator vacuum, upstream of the intake throttle, and upstream of the intake compressor.

19. The system of claim 14 , wherein purging via the second conduit further includes opening a compressor bypass valve coupled in the compressor bypass path.

20. The system of claim 14 , wherein the selectively purging is further based on the engine load, the canister purged via the first conduit at higher engine load and purged via the second conduit at lower engine load.

Assignees

• Ford Global Tech Llc

Inventors

• Pursifull Ross Dykstra
• Kragh Niels Christopher

Classifications

• F02D2250/41

  Control to generate negative pressure in the intake manifold, e.g. for fuel vapor purging or brake booster · 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

• F02M35/10222

  Exhaust gas recirculation [EGR]; Positive crankcase ventilation [PCV]; Additional air admission, lubricant or fuel vapour admission · CPC title

• F02D41/0002

  Controlling intake air · CPC title

• F02B37/16

  by bypassing charging air · CPC title