초록 ▼

An arrangement for determining purge valve flow tolerance for use with evaporative emissions control systems includes developing an equation based on data relating purge valve duty cycle to flow, wherein the equation describes a flow curve with reference to a first axis and a second axis. The arrang

An arrangement for determining purge valve flow tolerance for use with evaporative emissions control systems includes developing an equation based on data relating purge valve duty cycle to flow, wherein the equation describes a flow curve with reference to a first axis and a second axis. The arrangement further includes using the equation as a base equation for flow, and adapting the equation for part-to-part tolerance as a function of an intercept point of the equation with respect to the first axis, wherein the first axis relates to duty cycle.

대표청구항 ▼

1. A method for determining purge valve flow tolerance for use with evaporative emissions control systems, comprising:developing an equation based on data relating purge valve duty cycle to rate of flow, wherein the equation describes a flow curve with reference to a first axis and a second axis;usi

1. A method for determining purge valve flow tolerance for use with evaporative emissions control systems, comprising:developing an equation based on data relating purge valve duty cycle to rate of flow, wherein the equation describes a flow curve with reference to a first axis and a second axis;using the equation as a base equation for rate of flow;applying a pulse width modulated current to the purge valve;measuring O2 feedback to determine a rate of flow through the purge valve for a duty cycle of the pulse width modulated current;determining whether the purge valve is open or closed based on the measured O2 feedback, andadapting the equation for part-to-part tolerance as a function of an intercept point of the equation with respect to the first axis, wherein the first axis relates to duty cycle. 2. The method of claim 1, further comprising collecting the data relating purge valve duty cycle to rate of flow. 3. The method of claim 2, wherein said step of collecting the data comprises:applying pulse width modulated current to a purge valve;modifying a duty cycle of the current; andmeasuring a plurality of rates of flow through the purge valve for a plurality of duty cycles. 4. The method of claim 3, wherein said step of measuring a plurality of rates of flow through the purge valve for a plurality of duty cycles comprises measuring exactly two rates of flow for exactly two duty cycles. 5. The method of claim 1, wherein said step of developing an equation comprises fitting the data relating purge valve duty cycle to rate of flow into a point slope equation. 6. The method of claim 5, wherein said step of using the equation as the base equation for rate of flow comprises using a y-intercept form of the point slope equation as the base equation for rate of flow. 7. The method of claim 1, wherein said step of determining whether the purge valve is open or closed comprises determining that the purge valve is open, and said step of adapting the equation for part-to-part tolerance comprises establishing the intercept point based on the duty cycle. 8. The method of claim 1, wherein said step of determining whether the purge valve is open or closed comprises determining that the purge valve is closed, and said step of adapting the equation for part-to-part tolerance comprises increasing the duty cycle of the pulse width modulated current by a predetermined amount. 9. The method of claim 1, wherein said step of determining whether the purge valve is open or closed comprises waiting a predetermined amount of time. 10. The method of claim 1, wherein said step of determining whether the purge valve is open or closed comprises determining whether the rate of flow exceeds a minimum detectable rate of flow. 11. The method of claim 1, wherein said step of adapting the equation for part-to-part tolerance further comprises closing a vent valve to produce a sealed environment under pressure substantially regulated by operation of the purge valve. 12. The method of claim 11, wherein said step of determining whether the purge valve is open or closed includes determining that the purge valve is open, and wherein said step of adapting the equation for part-to-part tolerance further comprises opening the vent valve. 13. A purge valve flow tolerance determination system for use with evaporative emissions control systems, comprising:a memory storing an equation based on data relating purge valve duty cycle to rate of flow, wherein the equation describes a flow curve with reference to a first axis and a second axis;a purge valve operation module adapted to operate a purge valve based on the equation; andan adaptation module using an O2 sensor for determining rate of flow through the purge valve and using the determined rate of flow to adapt the equation for part-to-part tolerance as a function of an intercept paint of the equation with respect to the first axis, wherein the first axis relates to duty cycle. 14. The system of claim 13, further comprisin g a power source applying pulse width modulated current to the purge valve. 15. The system of claim 13, wherein said adaptation module is adapted to adjust duty cycle of the pulse width modulated current while sensing rate of flow through the purge valve, and to determine whether the purge valve is open or closed based on the rate of flow. 16. The system of claim 15, wherein said adaptation module is adapted to establish the intercept point based on a particular duty cycle causing the purge valve to begin to open. 17. The system of claim 16, wherein said adaptation module is adapted to recursively increase the duty cycle of the pulse width modulated current by a predetermined amount, wait a predetermined amount of time, and determine whether the rate of flow exceeds a minimum detectable rate of flow. 18. The system of claim 13, wherein said equation describes a curve having a slope formed by fitting the data into a point-slope equation. 19. The system of claim 18, wherein said purge valve operation module is adapted to determine a particular duty cycle y for a desired purge valve behavior x according to:wherein a y axis relates to duty cycle, on x axis relates to rate of flow, m relates to the slope, and b relates to an intercept point on the y axis. 20. The system of claim 18, wherein said adaptation module is operable to determine the intercept point on the y axis at a time the purge valve initially opens by sensing an initial opening or the purge valve based on rate of flow, and by equating a duty cycle producing the initial opening with the intercept point on the y axis. 21. The system of claim 13, wherein said adaptation module is operable to close a vent valve, thereby producing a sealed environment under pressure substantially regulated by operation of the purge valve. 22. The method of claim 21, wherein said adaptation module is operable to open the vent valve once adaptation of the equation has been substantially completed.