Leak diagnosis system for evaporative emission control system

• US 5,408,866 A
• Filed: 11/17/1993
• Issued: 04/25/1995
• Est. Priority Date: 11/25/1992
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Kishimoto, Yoichi, Kawamura, Katsuhiko, Matsuno, Osamu
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): WIGGINS, JOHN DAVID
• Application Number:
  US08/153,516
• Time in Patent Office: 524 Days
• Field of Search: 73/40, 73/40.5, 73/49.7, 73/118.1, 123/516, 123/518, 123/520
• US Class Current: 73/40
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system

Abstract

A leak diagnosis system which diagnoses a leak condition of an evaporative emission control system for an internal combustion engine. The leak diagnosis system detects a changing speed of a pressure in the evaporative emission control system for plural times during when the evaporative emission control system is put into a negative pressure condition by the negative pressure of the engine and is then closed by a purge-cut valve. The leak diagnosis system diagnoses a leak condition of the evaporative emission control system according to the detected plural pressure changing speeds while taking a fuel condition in the evaporative emission control system into consideration on the basis of the detected plural pressure changing speeds. Accordingly, the leak condition in the evaporative emission control system is accurately diagnosed without being effected by the fuel condition.

Claims

1. A leak diagnosis system for an evaporative emission control system of an internal combustion engine, said leak diagnosis system comprising:

a pressure detecting means detecting a pressure in the evaporative emission control system which is connected to an intake system of the internal combustion engine;

a leak diagnosis means comprising a pressure changing speed calculating means which calculates the pressure changing speed on the basis of the signal from said pressure detecting means and a fuel condition detecting means which obtains a fuel condition in the evaporative emission control system according to the pressure changing speed, said leak diagnosis means diagnosing the leak condition in the evaporative emission control system according to the fuel condition and the pressure changing speed.

12. A leak diagnosis system as claimed in claim 1, wherein the evaporative emission control system comprises a charcoal canister which is communicated with an intake side of the internal combustion engine through a purge conduit, a purge-cut valve being disposed in the purge conduit, said charcoal canister being communicated with a fuel tank through an adsorbing conduit through a check valve.

2. A leak diagnosis system for an evaporative emission control system of an internal combustion engine, said leak diagnosis system comprising:

a pressure detecting means detecting a pressure in the evaporative emission control system which is connected to an intake system of the internal combustion engine;

a leak diagnosis means comprising a pressure drop speed detecting means which obtains a pressure drop speed by detecting the pressure in the evaporative emission control system upon communicating the evaporative emission control system with the intake side of the internal combustion engine and a pressure buildup speed detecting means which obtains a pressure buildup speed by detecting the pressure in the evaporative emission control system upon closing the communication between the evaporative emission control system and the internal combustion engine, said leak diagnosis means diagnosing the leak condition of the evaporative emission control system according to the detected pressure drop speed and the detected pressure buildup speed.

3. A leak diagnosis system as claimed in claim 2, wherein said leak diagnosis means diagnoses the leak condition on the basis of a variation of one of the pressure drop speed and the pressure buildup speed which variation is obtained by detecting pressure for at least two points which are different in measured time.

7. A leak diagnosis system as claimed in claim 2, wherein the evaporative emission control system comprises a check valve which is disposed between a fuel tank and a charcoal canister, a bypass passage which bypasses the check valve, and a bypass valve which is disposed in the way of the bypass passage and is opened when the leak diagnosis is implemented.

13. A leak diagnosis system as claimed in claim 2, wherein said leak diagnosis means calculates first pressure build up speed near a predetermined negative pressure and a second pressure build up speed near the atmospheric pressure on the basis of the signal from said pressure detecting means, said leak diagnosis means calculating a difference between the first pressure changing speed and the second pressure changing speed, said leak diagnosis comparing the calculated difference with a predetermined decision value for judging the leakage of the evaporative emission control system.

4. A leak diagnosis system for an evaporative emission control system of an internal combustion engine system, said leak diagnosis system comprising:

a pressure detecting means detecting a pressure in the evaporative emission control system which is connected to an intake system of the internal combustion engine;

an inner space volume detecting means detecting an inner space volume of the evaporative emission control system;

a leak diagnosis means detecting a pressure changing speed according to a signal from said pressure detecting means upon setting the pressure in the evaporative emission control system at a predetermined condition, said leak diagnosis means diagnosing the leak condition of the evaporative emission control system according to the calculated pressure changing speed and the detected inner space volume.

5. A leak diagnosis means as claimed in claim 4, wherein said inner space volume detecting means detects the inner space volume by detecting a fuel remaining amount in a fuel tank.

6. A leak diagnosis system as claimed in claim 4, wherein said leak diagnosis means diagnoses the leak condition of the evaporative emission control system according to the inner space volume and the variation of the pressure changing speeds between at least two points in the evaporative emission control system.

8. A leak diagnosis system as claimed in claim 4, wherein the evaporative emission control system comprises a check valve which is disposed between a fuel tank and a charcoal canister, a bypass passage which bypasses the check valve, a bypass valve which is disposed in the way of the bypass passage and opens when the leak diagnosis is implemented.

9. A leak diagnosis system for an evaporative emission control system applied to an internal combustion engine for an automotive vehicle, said leak diagnosis system comprising:

a pressure detecting means detecting a pressure in the evaporative emission control system and outputting a signal indicative of the pressure in the evaporative emission control system; and

a leak diagnosing means calculating at least one of a first pressure changing speed in the evaporative emission control system when the evaporative emission control system is communicated with an intake side of the internal combustion engine and a second pressure changing speed in the evaporative emission control System when the evaporative emission control system is shut out from communication with an intake side of the internal combustion engine for plural times on the basis of the signal from the pressure detecting means, said leak diagnosing means diagnosing a leak condition of the evaporative emission control system according to the variation of the calculated first and second pressure changing speed or speeds.

10. A leak diagnosis system for an evaporative emission control system applied to an internal combustion engine for an automotive vehicle, said leak diagnosis system comprising:

a pressure detecting means detecting a pressure in the evaporative emission control system under a predetermined condition and outputting a signal indicative of the pressure in the evaporative emission control system;

a leak diagnosing means diagnosing a leak condition of the evaporative emission control system according to the signal from said pressure detecting means and a decision value which is previously stored in said leak diagnosis means;

a fuel vapor generating amount calculating means calculating the generating amount of fuel vapor in the evaporative emission control system; and

a leak decision value correcting means correcting the decision value according to the calculated fuel vapor generating amount.

11. A leak diagnosis system for an evaporative emission control system applied to an internal combustion engine for an automotive vehicle, the evaporative emission control system having an evaporative fuel adsorbing means which temporally adsorbs evaporative fuel from a fuel tank and from which the adsorbed evaporative fuel is purged in the internal combustion engine under a predetermined engine operating condition, said leak diagnosis system comprising:

a check valve disposed between the evaporative fuel adsorbing means and the fuel tank, said check valve supplying the evaporative fuel from the fuel tank to the evaporative fuel adsorbing means when a pressure in the fuel tank is higher than a predetermined value;

a pressure detecting means detecting the pressure in a closed space between the fuel tank and said check valve; and

a leak diagnosing means diagnosing a leak condition of the closed space according to the detected pressure and a decision value previously stored in said diagnosing means after detecting a condition that the pressure in the closed space is higher than a predetermined pressure which is higher than the atmospheric pressure.

14. A leak diagnosis system for an evaporative emission control system of an internal combustion engine, said leak diagnosis system comprising:

a pressure detecting means for detecting a pressure in the evaporative emission control system which is connected to an intake system of the internal combustion engine and outputting a signal indicative of the pressure in the evaporative emission control system;

a pressure changing speed calculating means for calculating first pressure changing speed near a predetermined negative pressure and a second pressure changing speed near the atmospheric pressure on the basis of the signal from said pressure detecting means;

a difference calculating means for calculating a difference between the first pressure changing speed and the second pressure changing speed; and

a comparing means for comparing the difference calculated in said difference calculating means with a predetermined decision value in order to diagnose the leakage of the evaporative emission control system.

15. A leak diagnosis system for an evaporative emission control system of an internal combustion engine, said leak diagnosis system comprising:

pressure detecting means for detecting a pressure in the evaporative emission control system which is connected to an intake system of the internal combustion engine and outputting a signal indicative of the pressure in the evaporative emission control system;

a pressure changing speed calculating means for calculating pressure changing speed on the basis of the signal from said pressure detecting means;

a calculating means for calculating a gradient of the pressure changing speed by means of a single regression analysis upon detecting the pressure changing speed for at least two points; and

a comparing means for comparing the gradient with a predetermined decision value in order to diagnose the leakage of the evaporative emission control system.