Claims
- 1. A method of purging a canister containing an absorbent, the canister being connected to a fuel tank to permit therein to evaporated fuel from the fuel tank to be absorbed by the absorbent, the canister having a purge air inlet and a purge air outlet connected to one end of a purge passage having therein a flow control valve, the purge passage having an opposite end connected to an induction passage of an internal combustion engine at a portion downstream of a throttle valve disposed in the induction passage, the method comprising the steps of:
- detecting flow of intake air passing through the induction passage at a portion upstream of the throttle valve and generating an intake air flow indicative signal indicative of the detected flow of intake air;
- deriving an intake air flow rate from said intake air flow indicative signal;
- calculating a product of said derived intake air flow rate and a purge rate;
- incrementing a counter by a value proportional to said calculated product;
- determining a target value of said purge rate in response to said counter; and
- adjusting the flow control valve in response to said determined target value of said purge rate.
- 2. A method as claimed in claim 1, wherein said purge rate is expressed as,
- PR=(Q.sub.PA /Q.sub.IA).times.100
- where,
- PR: purge rate,
- Q.sub.PA : flow rate of purge air,
- Q.sub.IA : flow rate of intake air.
- 3. A method as claimed in claim 2, wherein said counter is expressed as,
- CNT=Q.sub.IA .times.PR.times.KDUTY
- where,
- CNT: counter
- KDUTY: constant.
- 4. A method as claimed in claim 3, wherein said step of determining said target value of said purge rate includes a step of performing a table look-up of a table containing various values of said purge rate against various values of said counter.
- 5. A method as claimed in claim 4, wherein, for the same target value of a deviation from the stoichiometry, said various values of said purge rate depend on varying air fuel ratios of the purge air.
- 6. A method as claimed in claim 1, wherein when said counter exceeds a predetermined value, said purge rate is fixed at the minimum value.
- 7. A method of purging a canister containing an absorbent, the canister being connected to a fuel tank to permit therein to evaporated fuel from the fuel tank to be absorbed by the absorbent, the canister having a purge air inlet and a purge air outlet connected to one end of a purge passage having therein a flow control valve, the purge passage having an opposite end connected to an induction passage of an internal combustion engine at a portion downstream of a throttle valve disposed in the induction passage, the method comprising the steps of:
- detecting flow of intake air passing through the induction passage at a portion upstream of the throttle valve and generating an intake air flow indicative signal indicative of the detected flow of intake air;
- deriving an intake air flow rate from said intake air flow indicative signal;
- calculating a product of said derived intake air flow rate and a purge rate;
- incrementing a counter by a value proportional to said calculated produce;
- determining a target value of said purge rate out of various values of said purge rate contained in a table in response to said counter, the arrangement being such that, with a predetermined target value of deviation from the stoichiometry, said various values of said purge rate contained in said table are dependent on various values of said counter; and
- adjusting the flow control valve in response to said determined target value of said purge rate.
- 8. A method as claimed in claim 7, wherein said purge rate is expressed as,
- PR=(Q.sub.PA /Q.sub.IA).times.100
- where,
- PR: purge rate,
- Q.sub.PA : flow rate of purge air,
- Q.sub.IA : flow rate of intake air.
- 9. A method as claimed in claim 8, wherein said counter is expressed as,
- CNT=Q.sub.IA .times.PR.times.KDUTY
- where,
- CNT: counter
- KDUTY: constant.
- 10. A method of purging a canister containing an absorbent, the canister being connected to a fuel tank to permit thereinto evaporated fuel from the fuel tank to be absorbed by the absorbent, the canister having a purge air inlet and a purge air outlet connected to one end of a purge passage having therein a flow control valve, the purge passage having an opposite end connected to an induction passage of an internal combustion engine at a portion downstream of a throttle valve disposed in the induction passage, the method comprising the steps of:
- accumulating an amount of fuel vapor purged from the canister after the engine starts;
- storing the accumulated purge fuel vapor amount at least for a predetermined time after the engine stops;
- detecting a time interval between a time at which the engine stops and a time at which the engine restarts;
- setting a purge rate characteristic based on the accumulated purge fuel vapor amount stored when the engine starts and the detected time interval, the purge rate characteristic defining purge rate as a function of accumulated purge fuel vapor amount after the engine starts;
- calculating a purge rate according to the set purge rate characteristic; and
- adjusting the flow control valve to provide the calculated purge rate.
- 11. A method as claimed in claim 10, wherein the time interval is derived from an engine coolant temperature.
- 12. A method as claimed in claim 10, wherein the purge rate increases at an increasing rate as the stored accumulated purge fuel vapor amount increases and as the detected time interval decreases.
- 13. A method as claimed in claim 12, wherein the time interval is derived from an engine coolant temperature.
- 14. A method as claimed in claim 12, wherein the purge rate has an initial value used for purge rate control when engine starts, the initial value increasing as the accumulated purge fuel vapor amount increases.
- 15. A method as claimed in claim 14, wherein the time interval is derived from an engine coolant temperature.
- 16. A method of purging a canister containing an absorbent, the canister being connected to a fuel tank to permit thereinto evaporated fuel from the fuel tank to be absorbed by the absorbent, the canister having a purge air inlet and a purge air outlet connected to one end of a purge passage having therein a flow control valve, the purge passage having an opposite end connected to an induction passage of an internal combustion engine at a portion downstream of a throttle valve disposed in the induction passage, the method comprising the steps of:
- detecting engine operating conditions;
- calculating a required purge flow rate based on the detected engine operating conditions;
- controlling the flow control valve based on the detected engine operating conditions and the calculated required purge flow rate;
- calculating a maximum possible purge flow rate based on the detected engine operating conditions;
- selected a lower one of the required purge flow rate and the maximum possible purge flow rate after the engine starts; and
- correcting the required purge flow rate based on the selected purge flow rate.
- 17. A method as claimed in claim 16, wherein the detected engine operating conditions include a flow cross sectional area of the induction passage and an engine speed, and wherein the maximum possible purge flow rate is calculated based on the induction passage flow cross sectional area and the engine speed.
- 18. A method as claimed in claim 16, wherein an upper purge rate limit is set at a ratio of a maximum flow cross sectional area of the purge passage obtained when the flow control valve opens fully with respect to an flow cross sectional area of the induction passage, and wherein the maximum possible purge flow rate is calculated based on the upper purge rate limit.
- 19. A method as claimed in claim 18, wherein the maximum possible purge flow rate calculated based on the upper purge rate limit is accumulated when the target purge rate exceeds the upper purge rate limit.
- 20. A method as claimed in claim 16, wherein the engine operating conditions include an engine intake manifold negative pressure, and wherein the maximum possible purge flow rate is calculated based on the engine intake manifold negative pressure.
- 21. A method as claimed in claim 16, wherein the detected engine operating conditions include an intake air flow rate, and wherein the required purge flow rate is calculated based on the intake air flow rate and a target purge rate calculated based on the accumulated purge flow rate, the target purge rate being a target percentage of the purge flow rate with respect to the intake air flow rate.
- 22. A method as claimed in claim 21, wherein the detected engine operating conditions include a flow cross sectional area of the induction passage and an engine speed, and wherein the maximum possible purge flow rate is calculated based on the induction passage flow cross sectional area and the engine speed.
- 23. A method as claimed in claim 21, wherein an upper purge rate limit is set at a ratio of a maximum flow cross sectional area of the purge passage obtained when the flow control valve opens fully with respect to an flow cross sectional area of the induction passage, and wherein the maximum possible purge flow rate is calculated based on the upper purge rate limit.
- 24. A method as claimed in claim 23, wherein the maximum possible purge flow rate calculated based on the upper purge rate limit is accumulated when the target purge rate exceeds the upper purge rate limit.
- 25. A method as claimed in claim 21, wherein the engine operating conditions include an engine intake manifold negative pressure, and wherein the maximum possible purge flow rate is calculated based on the engine intake manifold negative pressure.
- 26. A system for purging a canister containing an absorbent, the canister being connected to a fuel tank to permit thereunto evaporated fuel from the fuel tank to be absorbed by the absorbent, the canister having a purge air inlet and a purge air outlet connected to one end of a purge passage, the purge passage having an opposite end connected to an induction passage of an internal combustion engine at a portion downstream of a throttle valve disposed in the induction passage, the system comprising:
- means for detecting flow of intake air passing through the induction passage at a portion upstream of the throttle valve and generating an intake air flow indicative signal indicative of the detected flow of intake air;
- a control unit which derives an intake air flow rate from said intake air flow indicative signal; calculates a product of said derived intake air flow rate and a purge rate; increments a counter by a value proportional to said calculated produce; determines target value of said purge rate in response to said counter; and produces an output signal in response to said determined target value of said purge rate; and
- means for controlling the purge passage in response to said control signal.
- 27. A system as claimed in claim 26, wherein said controlling means includes a flow control valve in the purge passage.
- 28. A system for purging a canister containing an absorbent, the canister being connected to a fuel tank to permit thereinto evaporated fuel from the fuel tank to be absorbed by the absorbent, the canister having a purge air inlet and a purge air outlet connected to one end of a purge passage, the purge passage having an opposite end connected to an induction passage of an internal combustion engine at a portion downstream of a throttle valve disposed in the induction passage, the system comprising:
- means for detecting flow of intake air passing through the induction passage at a portion upstream of the throttle valve and generating an intake air flow indicative signal indicative of the detected flow of intake air;
- a control unit which derives an intake air flow rate from said intake air flow indicative signal; calculates a product of said derived intake air flow rate and a purge rate; increments a counter by a value proportional to said calculated produce; determines a target value of said purge rate out of various values of said purge rate contained in a table in response to said counter, the arrangement having such that, with a predetermined target value of deviation from the stoichiometry, said various values of said purge rate contained in said table are dependent on various values of said counter; and produces a control signal in response to said determined target value; and
- means for controlling the purge passage in response to said control signal.
- 29. A system as claimed in claim 28, wherein said controlling means includes a flow control valve in the purge passage.
- 30. A system for purging a canister containing an absorbent, the canister being connected to a fuel tank to permit thereinto evaporated fuel from the fuel tank to be absorbed by the absorbent, the canister having a purge air inlet and a purge air outlet connected to one end of a purge passage having therein a flow control valve, the purge passage having an opposite end connected to an induction passage of an internal combustion engine at a portion downstream of a throttle valve disposed in the induction passage, the system comprising:
- means for accumulating an amount of fuel vapor purged from the canister after the engine starts;
- means for storing the accumulated purge fuel vapor amount at least for a predetermined time after the engine stops;
- means for detecting a time interval between a time at which the engine stops and a time at which the engine restarts;
- means for setting a purge rate characteristic based on the accumulated purge fuel vapor amount stored when the engine starts and the detected time interval, the purge rate characteristic defining purge rate as a function of accumulated purge fuel vapor amount after the engine starts;
- means for calculating a purge rate according to the set purge rate characteristic; and
- means for adjusting the flow control valve to provide the calculated purge rate.
- 31. A system as claimed in claim 30, wherein said time interval detecting means includes means for deriving the time interval from an engine coolant temperature.
- 32. A system as claimed in claim 30, wherein said purge rate characteristic setting means includes means for setting a purge rate characteristic defining a purge rate increasing at an increasing rate as the stored accumulated purge fuel vapor amount increases and as the detected time interval decreases.
- 33. A system as claimed in claim 32, wherein said time interval detecting means includes means for deriving the time interval from an engine coolant temperature.
- 34. A system as claimed in claim 32, wherein said purge rate characteristic setting means includes means for setting a purge rate having an initial value used for purge rate control when engine starts, the initial value increasing as the accumulated purge fuel vapor amount increases.
- 35. A system as claimed in claim 34, wherein said time interval detecting means includes means for deriving the time interval from an engine coolant temperature.
- 36. A system for purging a canister containing an absorbent, the canister being connected to a fuel tank to permit thereinto evaporated fuel from the fuel tank to be absorbed by the absorbent, the canister having a purge air inlet and a purge air outlet connected to one end of a purge passage having therein a flow control valve, the purge passage having an opposite end connected to an induction passage of an internal combustion engine at a portion downstream of a throttle valve disposed in the induction passage, the system comprising:
- means for detecting engine operating conditions;
- means for calculating a required purge flow rate based on the detected engine operating conditions;
- means for controlling the flow control valve based on the detected engine operating conditions and the calculated required purge flow rate;
- means for calculating a maximum possible purge flow rate based on the detected engine operating conditions;
- means for selecting a lower one of the required purge flow rate and the maximum possible purge flow rate after the engine starts; and
- means for correcting the required purge flow rate based on the selected purge flow rate.
- 37. A system as claimed in claim 36, wherein the engine operating condition detecting means includes means for detecting a flow cross sectional area of the induction passage and means for detecting an engine speed, and wherein the maximum possible purge flow rate calculating means includes means for calculating the maximum possible purge flow rate based on the induction passage flow cross sectional area and the engine speed.
- 38. A system as claimed in claim 36, wherein the engine operating condition detecting means includes means for detecting a flow cross sectional area of the induction passage, wherein the maximum possible purge flow rate calculating means includes means for setting an upper purge rate limit at a ratio of a maximum flow cross sectional area of the purge passage obtained when the flow control valve opens fully with respect to an flow cross sectional area of the induction passage, and means for calculating the maximum possible purge flow rate based on the upper purge rate limit.
- 39. A system as claimed in claim 38, wherein the accumulating means includes means for accumulating the maximum possible purge flow rate calculated based on the upper purge rate limit when the target purge rate exceeds the upper purge rate limit.
- 40. A system as claimed in claim 36, wherein the engine operating condition detecting means includes means for detecting an engine intake manifold negative pressure, and wherein the maximum possible purge flow rate calculating means includes means for calculating the maximum possible purge flow rate based on the engine intake manifold negative pressure.
- 41. A system as claimed in claim 36, wherein the engine operating condition detecting means includes means for detecting an intake air flow rate, and wherein the required purge flow rate calculating means includes means for calculating the required purge flow rate based on the intake air flow rate and a target purge rate calculated based on the accumulated purge flow rate, the target purge rate being a target percentage of the purge flow rate with respect to the intake air flow rate.
- 42. A system as claimed in claim 41, wherein the engine operating condition detecting means includes means for detecting a flow cross sectional area of the induction passage and means for detecting an engine speed, and wherein the maximum possible purge flow rate calculating means includes means for calculating the maximum possible purge flow rate based on the induction passage flow cross sectional area and the engine speed.
- 43. A method as claimed in claim 41, wherein the engine operating condition detecting means includes means for detecting a flow cross sectional area of the induction passage, and wherein the maximum possible purge flow rate calculating means includes means for setting an upper purge rate limit at a ratio of a maximum flow cross sectional area of the purge passage obtained when the flow control valve opens fully with respect to an flow cross sectional area of the induction passage, and means for calculating the maximum possible purge flow rate based on the upper purge rate limit.
- 44. A system as claimed in claim 43, wherein the accumulating means includes means for accumulating the maximum possible purge flow rate calculated based on the upper purge rate limit when the target purge rate exceeds the upper purge rate limit.
- 45. A system as claimed in claim 41, wherein the engine operating condition detecting means includes means for detecting an engine intake manifold negative pressure, and wherein the maximum possible purge flow rate calculating means includes means for calculating the maximum possible purge flow rate based on the engine intake manifold negative pressure.
Priority Claims (3)
Number |
Date |
Country |
Kind |
5-051744 |
Mar 1993 |
JPX |
|
6-094716 |
May 1994 |
JPX |
|
6-094717 |
May 1994 |
JPX |
|
RELATED APPLICATIONS
This application is a continuation-in-part of U.S. Ser. No. 08/208,897, filed on Mar. 14, 1994, now abandoned.
US Referenced Citations (13)
Foreign Referenced Citations (2)
Number |
Date |
Country |
53-19729 |
Jun 1978 |
JPX |
63-39787 |
Aug 1988 |
JPX |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
208897 |
Mar 1994 |
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