Leak-check apparatus of fuel-vapor-processing system, fuel-temperature estimation apparatus and fuel-temperature-sensor diagnosis apparatus

• US 20030019286A1
• Filed: 07/25/2002
• Published: 01/30/2003
• Est. Priority Date: 07/25/2001
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Miwa, Makoto, Maegawa, Yoshinori, Wakahara, Keiji, Morinaga, Syujiro
• Granted Patent: US 6,807,851 B2
• Time in Patent Office: Days
• US Class Current: 73/118.1
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system

Abstract

A fuel-vapor-processing system for an engine has a canister for accumulating fuel evaporation gas. The system has a leak-check apparatus for checking a leak on passages. The leak-check apparatus includes a leak-check means for carrying out leak-check processing when the engine if in a stopped state. The leak-check means operates only if a predetermined condition is satisfied. It is thus possible to reduce the number of times the leak-check processing is carried out and, hence, possible to reduce power consumption. For example, only if a relatively small leak is detected when the engine is in a running state, the leak-check processing is carried out in a stopped state to verify existence of such a leak. In the leak-check processing, the temperature of fuel, detected by a sensor or an estimated value, may be taken into consideration.

Claims

1. A leak-check apparatus for an engine'"'"'s fuel-vapor-processing system wherein:

a canister is provided on a connecting pipe linking a fuel tank to an intake pipe of the engine;

fuel evaporation gas resulting from evaporation of fuel in the fuel tank is absorbed into the canister;

the amount of the fuel evaporation gas purged from the canister to the intake pipe is controlled by opening and closing a purge valve provided on the downstream side of the canister according to a running state of the engine; and

a fresh air passage of the canister is opened and closed by a canister valve,

the leak-check apparatus comprising;

an engine-running-state leak-check means for checking a leak in the fuel-vapor-processing system in a running state of the engine; and

an engine-stopped-state leak-check means for checking a leak in the fuel-vapor-processing system in a stopped state of the engine,

wherein the engine-stopped-state leak-check means checks a leak in the fuel-vapor-processing system when the engine-running-state leak-check means determines existence of a leak in the fuel-vapor-processing system.

2. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 1 wherein:

the engine-running-state leak-check means has a leak-magnitude detection means for determining a detected leak of evaporated fuel in the fuel-vapor-processing system to be a high-degree leak or as a low-degree leak;

if leak-magnitude detection means determines that a detected leak of evaporated fuel in the fuel-vapor-processing system is a high-degree leak, the detected leak is regarded as an abnormality of the fuel-vapor-processing system;

if leak-magnitude detection means determines that a detected leak of evaporated fuel in the fuel-vapor-processing system is a low-degree leak, the detected leak is regarded as a preliminarily leak determination; and

the engine-stopped-state leak-check means checks a leak in the fuel-vapor-processing system when the engine-running-state leak-check means determines existence of a preliminarily leak determination in the fuel-vapor-processing system.

3. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 1, the leak-check apparatus further having:

an engine-running-state-leak-check-execution-condition determination means for determining whether a condition for execution of leak-check processing in a running state of the engine is satisfied;

a pressure detection means for detecting a pressure in the fuel-vapor-processing system;

a negative-pressure introduction means for introducing a negative pressure into the fuel-vapor-processing system by opening the purge valve; and

an engine-running-state hermetically sealing means for hermetically sealing the fuel-vapor-processing system after introduction of a negative pressure into the fuel-vapor-processing system by the negative-pressure introduction means by closing the purge valve and the canister valve,

wherein, if the engine-running-state-leak-check-execution-condition determination means determines that the condition for execution of leak-check processing in a running state of the engine is satisfied, then

the negative-pressure introduction means introduces a negative pressure into the fuel-vapor-processing system by opening the purge valve;

then

the engine-running-state hermetically sealing means hermetically seals the fuel-vapor-processing system by closing the purge valve and the canister valve; and

then

the engine-running-state leak-check means checks a leak in the fuel-vapor-processing system on the basis of a pressure, which is detected in the fuel-vapor-processing system while the fuel-vapor-processing system is being hermetically sealed, and an engine-running-state criterion value.

4. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 3, the leak-check apparatus further having:

an engine-stopped-state-leak-check-execution-condition determination means for determining whether a condition for execution of leak-check processing in a stopped state of the engine is satisfied;

a pressure detection means for detecting a pressure in the fuel-vapor-processing system; and

an engine-running-state hermetically sealing means for hermetically sealing the fuel-vapor-processing system by closing the purge valve and the canister valve,

wherein engine-stopped-state leak-check means checks a leak in the fuel-vapor-processing system on the basis of a pressure, which is detected in the fuel-vapor-processing system while the fuel-vapor-processing system is being hermetically sealed by the engine-running-state hermetically sealing means, and an engine-running-state criterion value.

5. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 4, the leak-check apparatus further having a residual-fuel-amount detection means for detecting an amount of residual fuel left in the fuel tank, wherein the engine-running-state criterion value and/or the engine-stopped-state criterion value are corrected on the basis of the amount of residual fuel left in the fuel tank.

6. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 4, the leak-check apparatus further having:

a return pipe for returning an excessive portion of fuel supplied by a fuel pump back to the fuel tank; and

a fuel-temperature detection means for detecting a fuel temperature of the fuel tank,

wherein the engine-running-state criterion value and/or the engine-stopped-state criterion value are corrected on the basis of the fuel temperature.

7. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 1, the leak-check apparatus further having a first leak-check-processing-allowing timer for measuring the lapse of a first predetermined time by carrying out a counting operation, wherein leak-check processing is executed when a result of the count operation carried out by the first leak-check-processing-allowing timer indicates that the first predetermined time has lapsed since detection of a leak of fuel evaporation gas by the engine-stopped-state leak-check means or the engine-running-state leak-check means.

8. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 4, the leak-check apparatus further having a second leak-check-processing-allowing timer for measuring the lapse of a second predetermined time by carrying out a counting operation since immediately preceding detection of a leak of fuel evaporation gas by the engine-stopped-state leak-check means or the engine-running-state leak-check means, wherein, if the engine-stopped-state leak-check means has not carried out leak-check processing after immediately preceding detection of a leak of fuel evaporation gas by the engine-stopped-state leak-check means or the engine-running-state leak-check means and a result of the count operation carried out by the second leak-check-processing-allowing timer indicates that the second predetermined time has lapsed since the immediately preceding detection of a leak, the leak-check-execution condition to be determined by the engine-stopped-state-leak-check-execution-condition determination means is made more lenient.

9. A leak-check apparatus for an engine'"'"'s fuel-vapor-processing system wherein:

a canister is provided on a connecting pipe linking a fuel tank to an intake pipe of the engine;

fuel evaporation gas resulting from evaporation of fuel in the fuel tank is absorbed into the canister;

the amount of the fuel evaporation gas purged from the canister to the intake pipe is controlled by opening and closing a purge valve provided on the downstream side of the canister according to a running state of the engine; and

a fresh air passage of the canister is opened and closed by a canister valve,

the leak-check apparatus comprising;

an engine-running-state leak-check means used for checking a leak in the fuel-vapor-processing system in a running state of the engine and provided with a means for determining a normal state of the fuel-vapor-processing system; and

an engine-stopped-state leak-check means used for checking a leak in the fuel-vapor-processing system in a stopped state of the engine and provided with a means for determining a normal state of the fuel-vapor-processing system,

wherein, when the engine-stopped-state leak-check means confirms existence of a leak in the fuel-vapor-processing system in a stopped state of the engine, only the engine-running-state leak-check means determines a normal state of the engine.

10. A leak-check apparatus for an engine'"'"'s fuel-vapor-processing system for purging evaporation gas resulting from evaporation of fuel in a fuel tank to an intake system of the engine,

the leak-check apparatus comprising:

an internal-pressure detection means for detecting a pressure of the fuel-vapor-processing system including the fuel tank;

a hermetically sealing means for sustaining a hermetically sealed state of the fuel-vapor-processing system at least during a leak-check period after the start of a stopped state of the engine; and

a leak-check means for checking existence or nonexistence of a leak in the fuel-vapor-processing system on the basis of a pressure detected by the internal-pressure detection means during the leak-check period after the start of a stopped state of the engine.

11. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 10, wherein the leak-check period is an interval during which the pressure of the fuel-vapor-processing system including no leak in a stopped state of the engine is a positive pressure or shorter than the interval.

12. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 10, wherein the leak-check period is an interval during which the pressure of the fuel-vapor-processing system including no leak in a stopped state of the engine is increasing to reach a maximum value or shorter than the interval.

13. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 10, wherein the hermetically sealing means hermetically seals the fuel-vapor-processing system right after the engine is put in a stopped state.

14. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 10, wherein the leak-check means:

computes a cumulative value of differences between pressures detected by the internal-pressure detection means during the leak-check period and a reference voltage over a processing period; and

checks existence or non-existence of a leak in the fuel-vapor-processing system on the basis of the cumulative value.

15. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 10, wherein the leak-check means checks existence or non-existence of a leak in the fuel-vapor-processing system on the basis of variations in pressure detected by the internal-pressure detection means during the leak-check period.

16. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 10, wherein the leak-check means checks existence or non-existence of a leak in the fuel-vapor-processing system on the basis of a maximum value of pressures detected by the internal-pressure detection means during the leak-check period.

17. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 10, the leak-check apparatus further having:

a fuel-temperature determination means for determining a fuel temperature of the fuel tank; and

a leak-check-execution-condition determination means for determining whether execution of leak-processing is allowed or inhibited on the basis of a fuel temperature determined by the fuel-temperature determination means.

18. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 17, wherein the fuel-temperature determination means estimates a fuel temperature on the basis of an operating state of the engine prior to a stopped state or a running history of the engine prior to the stopped state.

19. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 17, wherein the leak-check means corrects the leak-check period on the basis of a fuel temperature determined by the fuel-temperature determination means.

20. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 17, wherein the leak-check means changes a leak-check criterion on the basis of a fuel temperature determined by the fuel-temperature determination means.

21. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 10, the leak-check apparatus further having a residual-fuel-amount detection means for detecting an amount of residual fuel left in the fuel tank, wherein the leak-check means changes a leak-check criterion on the basis of a residual-fuel amount detected by the residual-fuel-amount detection means.

22. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 10, the leak-check apparatus further having:

a generated-evaporation-gas-amount determination means for determining an amount of evaporation gas generated prior to a stopped state of the engine; and

a leak-check-execution-condition determination means for determining whether execution of leak-check processing is allowed or inhibited on the basis of a generated-evaporation-gas amount determined by the generated-evaporation-gas-amount determination means.

23. A leak-check apparatus for an engine'"'"'s fuel-vapor-processing system for purging evaporation gas resulting from evaporation of fuel in a fuel tank to an intake system of the engine,

the leak-check apparatus comprising:

an internal-pressure detection means for detecting a pressure of the fuel-vapor-processing system including the fuel tank;

a hermetically sealing means, which is used for hermetically sealing the fuel-vapor-processing system during a leak-check period after the start of a stopped state of the engine and is used for ending hermetical sealing of the fuel-vapor-processing system for temporary exposure of the fuel-vapor-processing system to the atmosphere each time the pressure of the fuel-vapor-processing system reaches a predetermined limit pressure in order to let the pressure of the fuel-vapor-processing system drop to an atmospheric pressure before again hermetically sealing the fuel-vapor-processing system; and

a leak-check means for checking existence or nonexistence of a leak in the fuel-vapor-processing system on the basis of a pressure detected by the internal-pressure detection means during the leak-check period after the start of a stopped state of the engine.

24. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 23, wherein the leak-check means cumulates pressures, which are detected by the internal-pressure detection means during the leak-check means, over a predetermined processing period and checks existence or non-existence of a leak in the fuel-vapor-processing system on the basis of a cumulative value obtained as a result of cumulating the pressures.

25. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 24, wherein, in an operation carried out by the leak-check means to cumulate the fuel-vapor-processing system'"'"'s pressures detected by the internal-pressure detection means, the pressures detected by the internal-pressure detection means to be cumulated by the leak-check means are corrected by the leak-check means according to the number of times the pressures of the fuel-vapor-processing system reach a predetermined limit pressure.

26. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 23, wherein the leak-check means checks existence or non-existence of a leak in the fuel-vapor-processing system on the basis of the number of times pressures of the fuel-vapor-processing system reach a predetermined limit pressure during the leak-check period.

27. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 26, wherein the leak-check means determines that no leak exists in the fuel-vapor-processing system and stops checking existence or non-existence of a leak in the fuel-vapor-processing system as a count attains a predetermined value where the count is the number of times pressures of the fuel-vapor-processing system reach a predetermined limit pressure during the leak-check period.

28. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 23, wherein the leak-check means checks existence or non-existence of a leak in the fuel-vapor-processing system on the basis of a time required by a pressure of the fuel-vapor-processing system to reach a predetermined limit pressure.

29. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 28, wherein the leak-check means determines that a leak exists in the fuel-vapor-processing system and stops checking existence or non-existence of a leak in the fuel-vapor-processing system as a pressure of the fuel-vapor-processing system has not reached a predetermined limit -pressure even after a predetermined time has lapsed since the start of processing to check existence or non-existence of a leak in the fuel-vapor-processing system.

30. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 23, wherein the fuel tank is made of resin.

31. A leak-check apparatus provided for a fuel-vapor-processing system of an engine according to claim 23, the leak-check apparatus further having a leak-check-execution-condition determination means for determining whether leak-check processing is allowed or inhibited according to a result of determination of a parameter having a correlation with a state of generation of evaporation gas in the fuel tank.

32. A leak-check apparatus for an engine'"'"'s fuel-vapor-processing system for purging evaporation gas resulting from evaporation of fuel in a fuel tank to an intake system of the engine,

the leak-check apparatus having a leak-check means for carrying out leak-check processing to check a leak in the fuel-vapor-processing system, wherein, when the engine is put in a stopped state in the course of the leak-check processing, the leak-check means continues an operation to supply power to components required for continuing the leak-check processing and continues the leak-check processing till an end of the leak-check processing.

33. A leak-check apparatus provided for an engine'"'"'s fuel-vapor-processing system according to claim 32, wherein, when the leak-check means continues the leak-check processing till an end of the leak-check processing, the leak-check means discontinues the operation to supply power to the components immediately after the end of the leak-check processing.

34. A leak-check apparatus provided for an engine'"'"'s fuel-vapor-processing system according to claim 32, wherein, if existence or non-existence of a leak in the fuel-vapor-processing system cannot be determined even after a predetermined time has lapsed since the start of a stopped state of the engine, the leak-check means discontinues the operation to supply power to the components and aborts the leak-check processing.

35. A leak-check apparatus provided for an engine'"'"'s fuel-vapor-processing system according to claim 32, wherein the leak-check means:

hermetically seals the fuel-vapor-processing system including the fuel tank after introducing a predetermined pressure into the fuel-vapor-processing system at the start of the leak-check processing; and

checks existence or non-existence of a leak in the fuel-vapor-processing system by monitoring variations in pressure in the hermetically sealed fuel-vapor-processing system; and

discontinues the operation to supply power to components and aborts the leak-check processing if the engine is put in a stopped state while the predetermined pressure is being introduced into the fuel-vapor-processing system.

36. A fuel-temperature estimation apparatus for estimating a fuel temperature of a fuel tank employed in an engine in a running state of the engine, the fuel-temperature estimation apparatus comprising:

a fuel-temperature-increase estimation means for estimating an increase in fuel temperature in the fuel tank on the basis of an operating condition in the running state of the engine; and

a fuel-temperature-decrease estimation means for estimating a decrease in fuel temperature in the fuel tank on the basis of a vehicle speed and/or an intake-air temperature or on the basis of information having correlations with the vehicle speed and/or the intake-air temperature,

wherein a present estimated value of the fuel temperature is updated on the basis of a fuel-temperature increase estimated by the fuel-temperature-increase estimation means and a fuel-temperature decrease estimated by the fuel-temperature-decrease estimation means.

37. A fuel-temperature estimation apparatus according to claim 36, wherein the fuel-temperature-increase estimation means estimates a fuel-temperature increase caused by exhaust-gas heat dissipated to the fuel tank.

38. A fuel-temperature estimation apparatus according to claim 36, wherein the fuel-temperature-increase estimation means estimates an increase in fuel temperature on the basis of the engine'"'"'s revolution speed and/or load.

39. A fuel-temperature estimation apparatus according to claim 36, wherein:

the fuel-temperature estimation apparatus is applied to a fuel system in which an excessive portion of fuel supplied by a fuel pump from the fuel tank to a fuel injection valve is returned to the fuel tank; and

the fuel-temperature-increase estimation means estimates a fuel-temperature increase caused by exhaust-gas heat dissipated to the fuel tank as well as a fuel-temperature increase caused by the excessive portion returned from the fuel injection valve to the fuel tank.

40. A fuel-temperature estimation apparatus according to claim 36 wherein:

the fuel-temperature estimation apparatus is applied to a fuel system with a configuration including a fuel pump installed in the fuel tank; and

the fuel-temperature-increase estimation means also estimates a fuel-temperature increase caused by heat dissipated by the fuel pump in the fuel tank.

41. A fuel-temperature estimation apparatus according to claim 36, wherein the fuel-temperature-increase estimation means and the fuel-temperature-decrease estimation means each have a correction means for correcting a present fuel-temperature estimated value on the basis of an amount of residual fuel left in the fuel tank and/or a previous fuel-temperature estimated value.

42. A fuel-temperature estimation apparatus according to claim 36, wherein the fuel-temperature-increase estimation means and the fuel-temperature-decrease estimation means each estimate a fuel-temperature initial value at the present start of the engine on the basis of a fuel-temperature estimated value estimated in a previous stopped state of the engine, a lapse of time since the previous stopped state of the engine till the present start of the engine and an ambient temperature or information having a correlation with the ambient temperature.

46. A fuel-temperature estimation apparatus having an engine-running-state fuel-temperature estimation apparatus equivalent to a fuel-temperature estimation apparatus according to claim 36 and an engine-stopped-state fuel-temperature estimation apparatus equivalent to a fuel-temperature estimation apparatus according to claim 43.

47. A fuel-temperature estimation apparatus according to claim 46, wherein, in a stopped state of the engine, the fuel-temperature estimation means of the engine-stopped-state fuel-temperature estimation apparatus updates an engine-stopped-state fuel-temperature estimated value by setting an initial value of the engine-stopped-state fuel-temperature estimated value at an engine-running-state fuel-temperature estimated value estimated by the engine-running-state fuel-temperature estimation apparatus'"'"'s fuel-temperature-increase estimation means or fuel-temperature-decrease estimation means.

48. A leak-check apparatus comprising a fuel-temperature estimation apparatus according to claim 36 and a leak-check means for checking a leak in an fuel-vapor-processing system of an engine in a running state of the engine, wherein the leak-check means uses a fuel-temperature estimated value estimated by the fuel-temperature estimation apparatus as a fuel-check execution condition determination parameter and/or a leak-check parameter.

49. A leak-check apparatus according to claim 48, wherein, as one of fuel-check execution conditions, a fuel-temperature estimated value estimated by the fuel-temperature estimation apparatus is required to be not greater than a predetermined value.

54. An abnormality diagnosis apparatus for diagnosing a fuel-temperature sensor for detecting a temperature of fuel in a fuel tank for a sensor abnormality, the abnormality diagnosis apparatus comprising:

a fuel-temperature estimation apparatus according to claim 36;

and

an abnormality diagnosis means for diagnosing the fuel-temperature sensor for a sensor abnormality on the basis of a relation between fuel-temperature estimated values estimated by the fuel-temperature estimation apparatus and fuel-temperature detection values output by the fuel-temperature sensor.

55. An abnormality diagnosis apparatus according to claim 54, wherein the abnormality diagnosis means diagnoses the fuel-temperature sensor for a sensor abnormality on the basis of a relation between variations in the fuel-temperature estimated value estimated over a predetermined period and variations in the fuel-temperature detection value output over the predetermined period.

43. A fuel-temperature estimation apparatus having a fuel-temperature estimation means for estimating a fuel temperature of a fuel tank employed in an engine in a stopped state of the engine, wherein an estimated value of the fuel temperature in the stopped state of the engine is updated on the basis of a lapse of time since the start of the stopped state or information having a correlation with the lapse of time.

44. A fuel-temperature estimation apparatus according to claim 43, wherein an estimated value of the fuel temperature in the stopped state of the engine is updated on the basis of a lapse of time since the start of the stopped state and an ambient temperature or on the basis of information having correlations with the lapse of time and the ambient temperature.

45. A fuel-temperature estimation apparatus according to claim 43, wherein the fuel-temperature estimation means has a correction means for correcting a present fuel-temperature estimated value on the basis of an amount of residual fuel left in the fuel tank.

50. A leak-check apparatus comprising a fuel-temperature estimation apparatus according to claim 43 and a leak-check means for checking a leak in an fuel-vapor-processing system of an engine in a stopped state of the engine, wherein the leak-check means uses a fuel-temperature estimated value estimated by the fuel-temperature estimation apparatus as a fuel-check execution condition determination parameter and/or a leak-check parameter.

51. A leak-check apparatus according to claim 50, wherein, in a stopped state of the engine, the leak-check means checks a leak in the fuel-vapor-processing system on the basis of a relation between variations in fuel-temperature estimated value estimated by the fuel-temperature estimation apparatus and variations in fuel-tank internal pressure.

52. A leak-check apparatus according to claim 51, wherein, in a stopped state of the engine, the leak-check means carries out leak-check processing to check a leak in the fuel-vapor-processing system on the basis of the variation in fuel-tank internal pressure over a period beginning at the start of the leak-check processing and ending at a time the fuel-temperature estimated value estimated by the fuel-temperature estimation apparatus becomes equal to or smaller than a predetermined value.

53. A leak-check apparatus according to claim 50, wherein, as one of fuel-check execution conditions, a fuel-temperature estimated value estimated by the fuel-temperature estimation apparatus right after or right before the start of a stopped state of the engine is required to be greater than a predetermined value.