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Diagnosis apparatus and method for an evapo-purge system

  • US 5,780,728 A
  • Filed: 04/25/1995
  • Issued: 07/14/1998
  • Est. Priority Date: 04/27/1994
  • Status: Expired due to Fees
First Claim
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1. A diagnosis apparatus for an evapo-purge system having a canister for storing an evaporated fuel generated from a fuel tank, an intake pipe connected to an engine for inducing air thereof, and a purge line connected to said canister, comprising:

  • a purge control valve installed in the purge line for controlling purge flow rate;

    a directional valve connected between the intake pipe and the purge line via a first tube diverged from the intake pipe and a second tube diverged from the purge line;

    a pressure sensor, in a general mode, communicated with the intake pipe through the first diverged tube by switching the directional valve and measuring a pressure in the intake pipe and, in a evapo-purge mode, communicated with the purge line through the second diverged tube by switching the directional valve and measuring pressures in the purge line when the purge control valve is closed and open; and

    discriminating means for discriminating the state of the evapo-purge system;

    wherein when the evapo-purge system is concluded to be normal, the measured value of pressure in the purge line produced when the purge control valve is closed can be regarded as equivalent to atmospheric pressure so that the measured value is adapted for some other control of the engine, and is concluded to be abnormal when the measured values are of a difference falling outside a predetermined range between pressure in the purge line produced when the purge control valve is closed and pressure in the purge line produced when the purge control valve is open.

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