Method and apparatus for diagnosing leakage of fuel vapor treatment unit
First Claim
1. A method of diagnosing leakage of a fuel vapor treatment unit which temporarily adsorbs fuel vapor from a fuel tank of an internal combustion engine into an adsorption means and then draws this into an engine intake system under predetermined engine operating conditions, said method comprising the steps of;
- setting a judgment level based on a drive current of an electric pump for when air is pumped by said electric pump via a reference orifice having a reference aperture diameter, anddiagnosing the presence of fuel vapor leakage by comparing a drive current of said electric pump for when air is pumped by said electric pump bypassing said reference orifice and into piping to be leak diagnosed of said fuel vapor treatment unit, with said set judgment level, and further comprising the step of;
comparing the drive current of said electric pump for when air is pumped via said reference orifice, with a reference level, and when the drive current deviates from the reference level, stopping said leakage diagnosis.
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Accused Products
Abstract
With a fuel vapor treatment unit where fuel vapor of an internal combustion engine which has been temporarily adsorbed into an adsorption device is drawn into an engine intake system under predetermined engine operating conditions, a judgment level is set based on a drive current of an electric pump for when air is pumped by the electric pump via a reference orifice having a reference aperture diameter, and the presence of fuel vapor leakage is diagnosed by comparing a drive current of the electric pump for when air is pumped by the electric pump bypassing the reference orifice and into piping to be leak diagnosed of the fuel vapor treatment unit, with the set judgment level. Moreover, the drive current of the electric pump for when air is pumped via the reference orifice is compared with a reference level, and when the drive current deviates from the reference level, the leakage diagnosis is stopped. Furthermore, refuelling judgment is performed, and the leakage diagnosis is started after judging that refuelling is completed. In this way, erroneous diagnosis due to blockage or contamination of the reference orifice, or erroneous diagnosis due to diagnosis being made during refuelling can be prevented, enabling an improvement in leakage diagnosis accuracy.
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Citations
8 Claims
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1. A method of diagnosing leakage of a fuel vapor treatment unit which temporarily adsorbs fuel vapor from a fuel tank of an internal combustion engine into an adsorption means and then draws this into an engine intake system under predetermined engine operating conditions, said method comprising the steps of;
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setting a judgment level based on a drive current of an electric pump for when air is pumped by said electric pump via a reference orifice having a reference aperture diameter, and diagnosing the presence of fuel vapor leakage by comparing a drive current of said electric pump for when air is pumped by said electric pump bypassing said reference orifice and into piping to be leak diagnosed of said fuel vapor treatment unit, with said set judgment level, and further comprising the step of; comparing the drive current of said electric pump for when air is pumped via said reference orifice, with a reference level, and when the drive current deviates from the reference level, stopping said leakage diagnosis. - View Dependent Claims (2, 3, 4)
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5. A leakage diagnosis apparatus for a fuel vapor treatment unit, said apparatus comprising a fuel vapor treatment unit which temporarily adsorbs fuel vapor from a fuel tank of an internal combustion engine into an adsorption means and then draws this into an engine intake system under predetermined engine operating conditions, and also comprising;
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judgment level setting means for setting a judgment level based on a drive current of an electric pump for when air is pumped by said electric pump via a reference orifice having a reference aperture diameter, and leakage diagnosis means for diagnosing the presence of fuel vapor leakage by comparing a drive current of said electric pump for when air is pumped by said electric pump bypassing the reference orifice and into piping to be leak diagnosed of said fuel vapor treatment unit, with said set judgment level, and further comprising; leakage diagnosis stopping means for comparing the drive current of said electric pump for when air is pumped via said reference orifice, with a reference level, and when the drive current deviates from the reference level, stopping diagnosis by said leakage diagnosis means. - View Dependent Claims (6, 7, 8)
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Specification