Evap canister purge prediction for engine fuel and air control

• US 20050240336A1
• Filed: 04/23/2004
• Published: 10/27/2005
• Est. Priority Date: 04/23/2004
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Reddy, Sam R.
• Granted Patent: US 7,305,975 B2
• Time in Patent Office: Days
• US Class Current: 701/103
• CPC Class Codes: F02D 2041/1433 using a model or simulation of the system
• 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 41/0045 Estimating, calculating or determining the purging rate, amount, flow or concentration
• CPC Class Codes: F02M 25/089 Layout of the fuel vapour installation
• CPC Class Codes: F02M 37/106 the pump being installed in a sub-tank

Abstract

In a system and a method for purging a vapor storage canister having adsorbed fuel vapor (or hydrocarbon vapor) by drawing air through the storage canister the storage canister being coupled with an engine having a system for controlling the amount of fuel provided to the engine, the amount of fuel vapor in the purge is estimated using a model that predicts fuel vapor concentration in the purge vapor. The engine controller uses the estimated amount of fuel vapor and air brought into the engine from the evaporative vapor storage canister for better control of engine air and fuel during purging.

Claims

1. A method for controlling amounts of air and fuel introduced to an engine during purge of hydrocarbon vapor from a canister containing adsorbed hydrocarbon vapor, comprising the steps of:

providing an initial value, C_HC0, for the concentration of hydrocarbon vapor in the canister containing adsorbed hydrocarbon vapor;

drawing air into the canister containing adsorbed hydrocarbon vapor and withdrawing from the canister a volume of purge vapor containing desorbed hydrocarbon vapor;

calculating a concentration of desorbed hydrocarbon vapor in the purge vapor; and

using purge vapor volume and concentration of hydrocarbon vapor in the purge vapor to calculate the amounts of purge hydrocarbon vapor and purge air and adjusting an amount of fuel to be taken from the fuel tank and an amount of intake air based on the amounts of purge hydrocarbon vapor and purge air.

2. A method for controlling amounts of air and fuel introduced to an engine during purge of hydrocarbon vapor from a canister containing adsorbed hydrocarbon vapor according to claim 1, wherein C_HC0 is measured by monitoring the fuel injection rate with and without canister purge at steady state engine operation.

3. A method for controlling amounts of air and fuel introduced to an engine during purge of hydrocarbon vapor from a canister containing adsorbed hydrocarbon vapor according to claim 1, wherein C_HC0 is estimated from purge canister and/or vehicle conditions.

4. A method for controlling amounts of air and fuel introduced to an engine during purge of hydrocarbon vapor from a canister containing adsorbed hydrocarbon vapor according to claim 1, wherein the concentration of desorbed hydrocarbon vapor in the purge vapor is calculated using a curve fitted to experimentally measured values for hydrocarbon concentration in the purge vapor as a function of commanded purge vapor volume for a specific vehicle, purge canister, absorbent, and purge conditions.

5. A method for controlling amounts of air and fuel introduced to an engine during purge of hydrocarbon vapor from a canister containing adsorbed hydrocarbon vapor according to claim 1, wherein the concentration of desorbed hydrocarbon vapor in the purge vapor is calculated using a model that predicts exponential decrease for hydrocarbon concentration in the purge vapor from the initial hydrocarbon concentration with continuing purge.

6. A method for controlling amounts of air and fuel introduced to an engine during purge of hydrocarbon vapor from a canister containing adsorbed hydrocarbon vapor according to claim 1, wherein the concentration of hydrocarbon in the purge vapor, C_HC, is calculated from an equation:

C_HC═

C_HC0EXP(−

(α

C_HC0+β

)V), in which

V is the cubic feet of commanded purge volume;

C_HC0 is the initial concentration of hydrocarbon vapor in the purge;

C_HC is the concentration of hydrocarbon vapor in the purge after V cubic feet of commanded purge volume; and

α and

β

are constants, the values of which depend on the particular engine and make of vehicle.

7. A method for controlling amounts of air and fuel introduced to an engine during purge of hydrocarbon vapor from a canister containing adsorbed hydrocarbon vapor according to claim 1, wherein the concentration of hydrocarbon in the purge vapor, C_HC, is calculated using a model combining material balance and isotherm equations.

8. A method for controlling amounts of air and fuel introduced to an engine during purge of hydrocarbon vapor from a canister containing adsorbed hydrocarbon vapor according to claim 1, wherein the concentration fraction of hydrocarbon C_HC in the purge vapor is determined from a ratio of its partial pressure P to the atmospheric pressure P_atm using the equation

C_HC=P/P_atm,

wherein

9. A method of operating a vehicle having

an internal combustion engine with an air induction system,

a fuel tank connected to the engine to supply fuel to the engine,

an electronic engine control module comprising a programmed microprocessor controlling fuel delivery to the engine and intake air to the engine, and

a canister to adsorb vapor from the fuel tank comprising a vapor inlet coupled to the fuel tank and a purge outlet coupled to the air induction system, comprising steps of:

adsorbing fuel vapor from the fuel tank into the canister through the vapor inlet;

desorbing fuel vapor from the canister through the purge outlet by opening the purge valve through a signal from the electronic engine control module and drawing air through the canister into the air induction system;

calculating the concentration of desorbed hydrocarbon vapor in the purge vapor;

using the concentration of desorbed hydrocarbon vapor and purge vapor volume to calculate the amounts of purge hydrocarbon vapor and purge air and

using the electronic engine control module to adjust fuel delivery from the fuel tank to the engine and/or the amount of intake air in response to the calculated amounts of purge hydrocarbon vapor and purge air.

10. A controller having an algorithm for determining the concentration of hydrocarbon vapor in purge vapor drawn from a canister containing adsorbed hydrocarbon vapor, said algorithm including

steps for providing an initial concentration of hydrocarbon in purge vapor;

steps for determining commanded purge volume and purge vapor composition; and

steps for calculating purge air correction and purge hydrocarbon correction and applying the corrections in engine air and fuel intake calculations.

11. A controller according to claim 10, wherein the purge vapor composition is determined using a curve fitted to experimentally measured values for hydrocarbon concentration in the purge vapor as a function of commanded purge vapor volume for a specific vehicle, purge canister, absorbent, and purge conditions.

12. A controller according to claim 10, wherein the purge vapor composition is determined using a model that predicts exponential decrease for hydrocarbon concentration in the purge vapor from the initial hydrocarbon concentration with continuing purge.

13. A controller according to claim 10, wherein the purge vapor composition is determined using a model combining material balance and isotherm equations.

14. A vehicle having

an internal combustion engine with an air induction system,

a fuel tank connected to the engine to supply fuel to the engine,

an electronic engine control module comprising a programmed microprocessor controlling fuel and air delivery to the engine, and

a canister to adsorb vapor from the fuel tank comprising a vapor inlet coupled to the fuel tank, a purge outlet coupled to the air induction system, and an air inlet,

wherein the microprocessor is programmed to estimate concentration of hydrocarbon vapor in purge air drawn from the canister from an equation that predicts a decrease of fuel vapor concentration in the purge air from an initial fuel vapor concentration in the purge air and

further wherein the electronic engine control module adjusts fuel and air delivery to the engine in response to the estimated concentration of hydrocarbon vapor in the purge air.

15. A vehicle according to claim 14, wherein the equation predicts exponential decrease for hydrocarbon concentration in the purge vapor from the initial hydrocarbon concentration with continuing purge.

16. A vehicle according to claim 14, wherein the equation combines material balance and isotherm equations.