Malfunction diagnosis apparatus for evaporated fuel purge system

• US 5,954,034 A
• Filed: 10/21/1997
• Issued: 09/21/1999
• Est. Priority Date: 10/21/1996
• Status: Expired due to Term

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Takagi, Naoya
• Primary Examiner(s): MILLER, CARL STUART
• Application Number:
  US08/955,399
• Time in Patent Office: 700 Days
• Field of Search: 123/518, 123/519, 123/520, 123/521, 123/198 D
• US Class Current: 123/520
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system

Abstract

A malfunction diagnosis apparatus for an evaporated fuel purge system comprises an evaporated fuel processing unit, an air valve arranged between a canister and the atmosphere wherein, when the air valve is open, the canister communicates with the atmosphere and, when the air valve is closed, the canister is sealed from the atmosphere, means for setting, based on an engine operating condition, a time required to lower a pressure within a least a portion of the evaporated fuel processing unit to a predetermined negative value, means for detecting an atmospheric pressure and means for changing the introduction time of the negative pressure in accordance with the atmospheric pressure. Means are provided for determining whether a failure of the evaporated fuel processing unit has occurred based on a pressure change in the system during a predetermined testing time after the predetermined negative pressure has been introduced into the evaporated fuel processing unit by closing the air valve and opening for the changed introduction time the purge control valve.

Claims

1. A malfunction diagnosis apparatus for an evaporated fuel purge system for an internal combustion engine comprising:

an evaporated fuel processing unit for absorbing in an absorbent contained within a canister evaporated fuel from a fuel tank, and for purging, under predetermined operating conditions of the engine, the absorbed in the canister into an intake system of the engine via a purge control valve;

an air valve arranged between the canister and the atmosphere wherein, when the air valve is open, the canister communicates with the atmosphere and, when the air valve is closed, the canister is sealed from the atmosphere;

introduction time setting means for setting, based on an engine operating condition, a time required to lower a pressure within at least a portion of the evaporated fuel processing unit to a predetermined negative value;

atmospheric pressure detecting means for detecting an atmospheric pressure;

introduction time changing means for changing the introduction time of the negative pressure in accordance with the atmospheric pressure;

malfunction judging means for judging whether a failure of the evaporated fuel processing unit has occurred based on a pressure change in the system during a predetermined testing time after the predetermined negative pressure has been introduced into the evaporated fuel processing unit by closing the air valve and opening for the changed introduction time the purge control valve, wherein the testing time begins when the purge control valve is closed after the changed introduction time has elapsed.

2. A malfunction diagnosis apparatus according to claim 1, wherein the introduction time changing means obtains the introduction time (t) based on a target negative pressure (Pr), the atmospheric pressure (Pa), a purged flow amount (Qp) and a volume of the portion of the evaporated fuel processing unit into which the negative pressure has been introduced (V), according to the following expression:

space="preserve" listing-type="equation">t=K×

(Pr×

V)/(Pa×

Qp),

where K is a constant.