Apparatus for monitoring air leakage into fuel supply system for internal combustion engine

• US 5,347,971 A
• Filed: 06/07/1993
• Issued: 09/20/1994
• Est. Priority Date: 06/08/1992
• Status: Expired due to Term

• Current Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Original Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Inventors: Kobayashi, Yasunori, Morita, Yoshiyuki, Sugiura, Tsuguo
• Primary Examiner(s): Miller, Carl S.
• Application Number:
  US08/072,757
• Time in Patent Office: 470 Days
• Field of Search: 123/520, 123/521, 123/198 D, 123/518, 123/516, 123/519
• US Class Current: 123/520
• CPC Class Codes: F02M 2025/0845 Electromagnetic valves
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system

Abstract

An apparatus for monitoring air leakage into a fuel supply system for an internal combustion engine is provided. This system comprises a pressure sensor for detecting a pressure level in a fuel supply passage of the fuel supply system which communicates between a fuel tank and an intake passage of the engine and providing a signal indicative thereof, an air leakage control valve for leaking ambient air into the fuel supply passage at a preselected rate, and an air leakage monitoring unit for detecting a first pressure in the fuel supply system when the air leakage control valve is closed to restrict the leakage of the ambient air and a second pressure when the air leakage control valve is open to leak the ambient air into the fuel supply passage, the air leakage monitoring unit providing an alarm signal indicating that there is a preselected amount of air leakage in the fuel supply system based on a difference between the first and second pressures.

Claims

1. An apparatus for monitoring a degree of airtightness of a fuel supply system of an internal combustion engine comprising:

a purge control valve which modifies a purge flow rate of fuel vapor from a fuel tank into an intake passage of the engine;

orifice means for allowing ambient air to be introduced into the fuel supply system at a preselected flow restriction;

air leakage control valve means arranged in series with said orifice means to selectively establish fluid communication through said orifice means;

pressure detecting means for detecting pressure in the fuel supply system to provide a signal indicative thereof; and

air leakage detecting means for determining a first pressure variation in the fuel supply system after said purge control valve is closed while the air leakage control valve means is closed and a second pressure variation in the fuel supply system after the purge control valve is closed while said air leakage control valve means is opened to allow the orifice to introduce the ambient air into the fuel supply system, said leakage detecting means determining a degree of airtightness of the fuel supply system based on a difference between the first and second pressure variations.

2. An air-fuel mixture control system for an internal combustion engine which is operable to supply intake air from an air cleaner into the engine through an intake passage disposing therein a throttle valve, store in a canister fuel vapors generated in a fuel tank, and supply the fuel vapors stored in the canister through a purge control valve into a portion of the intake passage downstream of the throttle valve, comprising:

pressure detecting means for detecting pressure in a fuel supply system having a line extending from the fuel tank to the canister and providing a signal indicative thereof;

orifice means, arranged between the air cleaner and the fuel supply system, for leaking air into the fuel supply system at a preselected air leakage restriction;

an air leakage passage disposing therein an air leakage control valve which is operable to selectively allow and restrict the air leakage through said orifice means; and

a failure detecting means responsive to the signal from said pressure detecting means for comparing a pressure variation in the fuel supply system while said air leakage control valve is closed after the purge control valve is closed with a pressure variation in the fuel supply system while said air leakage control valve is opened after the purge control valve is closed, to detect a failure of the fuel supply system.

3. An air-fuel mixture control system as set forth in claim 2, wherein said canister has an opening exposed to atmospheric pressure, and further comprising a canister opening control valve which blocks communication through the opening of said canister when said failure detecting means detects the failure of the fuel supply system.

4. An air-fuel mixture control system as set forth in claim 3, wherein the opening of said canister is communicated with the air cleaner along with said air leakage passage.

5. An air-fuel mixture control system as set forth in claim 3, wherein said failure detecting means includes:

means for closing the canister opening control valve when detecting the failure of the fuel supply system;

means for opening tile purge control valve with the canister opening control valve being closed to introduce negative pressure created in the intake passage downstream of the throttle valve into the fuel supply system;

means for closing the purge control valve after detecting a condition where the negative pressure in the fuel supply system has become a preselected level;

means for opening the air leakage control valve with the purge control valve being closed after the negative pressure has become the preselected level;

means for detecting the variation in pressure detected by said pressure detecting means in a preselected period of time the air leakage control valve is closed with the purge control valve being closed after the negative pressure has become the preselected level;

means for detecting the variation in pressure detected by said pressure detecting means in a preselected period of time the air leakage control valve is open with the purge control valve being closed after the negative pressure has become the preselected level; and

means for comparing the pressure variation when the air leakage control valve is closed with the pressure variation when the air leakage control valve is open to detect the failure of the fuel supply system.

6. An air-fuel mixture control system as set forth in claim 2, wherein the preselected air leakage restriction of said orifice means is set to a preselected allowable air leakage value, said failure detection means determines that the fuel supply system is malfunctioning when the pressure variation when the air leakage control valve is open is smaller than a value twice the pressure variation when the air leakage control valve is closed.

7. An apparatus for monitoring an air leakage around a fuel supply system for an internal combustion engine comprising:

a pressure sensor for detecting a pressure level in a fuel supply passage of the fuel supply system, which communicates between a fuel tank and an intake passage of the engine and provides a signal indicative thereof;

valve means adapted to be opened and closed for selectively introducing ambient air into the fuel supply passage and blocking the introduction of the ambient air into the fuel supply pages; and

air leakage monitoring means, responsive to the signal from said pressure sensor, for determining a first pressure in the fuel supply system when said valve means is closed to restrict the introduction of the ambient air and a second pressure when said valve means is open to introduce the ambient air into the fuel supply passage, said air leakage monitoring means including pressure difference determining means for determining a difference between the first and second pressures and providing a signal indicating that there is a preselected amount of air leaking around the fuel supply system based on the difference between the first and second pressures.

8. An apparatus for monitoring an air leakage around a fuel supply system for an internal combustion engine comprising:

a pressure sensor that detects a pressure level in a fuel supply passage of the fuel supply system, the fuel supply passage communicating between a fuel tank and an intake passage of the engine and providing a signal indicative thereof;

valve means designed to be opened and closed fore selectively introducing ambient air into the fuel supply passage and blocking the introduction of the ambient air into the fuel supply passage; and

air leaking monitoring means, responsive to the signal from said pressure sensor, for detecting a first pressure variation in the fuel supply passage after communication is blocked between the fuel supply passage and the intake passage of the engine and a second pressure variation in the fuel supply passage after said valve means is opened to introduce the ambient air into the fuel supply passage while communication between the fuel supply passage and the intake passage is blocked, said air leakage monitoring means including a pressure variation determining means for determining a difference between the first and second pressure variations to determine that a failure occurs in the fuel supply when the difference between the first and second pressure variations is lower than a preselected value.