Failure diagnosis apparatus for evaporative fuel processing system
First Claim
1. A failure diagnosis apparatus for diagnosing a failure within an evaporative fuel processing system which includes a fuel tank, a canister having adsorbent for adsorbing evaporative fuel generated in said fuel tank, an air passage connected to said canister for communicating said canister with the atmosphere, a first passage for connecting said canister and said fuel tank, a second passage for connecting said canister and an intake system of an internal combustion engine, and a purge control valve provided in said second passage, said failure diagnosis apparatus comprising:
- pressure detecting means for detecting a pressure in said evaporative fuel processing system;
control means for controlling an opening of said purge control valve by changing a duty ratio of a drive signal which drives said purge control valve;
first filtering means for performing a first filtering of the pressure detected by said pressure detecting means,second filtering means for performing a second filtering of the pressure detected by said pressure detecting means, a second passing frequency band of the second filtering being narrower than a first passing frequency band of the first filtering; and
flow rate abnormality determining means for determining a flow rate abnormality of a purge gas flowing in said second passage, based on the filtered pressures outputted from said first and second filtering means.
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Accused Products
Abstract
A failure diagnosis apparatus for diagnosing a failure of an evaporative fuel processing system. The system includes a fuel tank, a canister having adsorbent for adsorbing evaporative fuel generated in the fuel tank, an air passage connected to the canister for communicating the canister with the atmosphere, a first passage for connecting the canister and the fuel tank, a second passage for connecting the canister and an intake system of an internal combustion engine, and a purge control valve provided in the second passage. A pressure in the evaporative fuel processing system is detected. An opening of the purge control valve is controlled by changing a duty ratio of a drive signal which drives the purge control valve. First and second filterings of the detected pressure are performed. A second passing frequency band of the second filtering is narrower than a first passing frequency band of the first filtering. A flow rate abnormality of a purge gas flowing in the second passage is determined based on the filtered pressures.
30 Citations
18 Claims
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1. A failure diagnosis apparatus for diagnosing a failure within an evaporative fuel processing system which includes a fuel tank, a canister having adsorbent for adsorbing evaporative fuel generated in said fuel tank, an air passage connected to said canister for communicating said canister with the atmosphere, a first passage for connecting said canister and said fuel tank, a second passage for connecting said canister and an intake system of an internal combustion engine, and a purge control valve provided in said second passage, said failure diagnosis apparatus comprising:
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pressure detecting means for detecting a pressure in said evaporative fuel processing system; control means for controlling an opening of said purge control valve by changing a duty ratio of a drive signal which drives said purge control valve; first filtering means for performing a first filtering of the pressure detected by said pressure detecting means, second filtering means for performing a second filtering of the pressure detected by said pressure detecting means, a second passing frequency band of the second filtering being narrower than a first passing frequency band of the first filtering; and flow rate abnormality determining means for determining a flow rate abnormality of a purge gas flowing in said second passage, based on the filtered pressures outputted from said first and second filtering means. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A failure diagnosis method for diagnosing a failure of an evaporative fuel processing system which includes a fuel tank, a canister having adsorbent for adsorbing evaporative fuel generated in said fuel tank, an air passage connected to said canister for communicating said canister with the atmosphere, a first passage for connecting said canister and said fuel tank, a second passage for connecting said canister and an intake system of an internal combustion engine, and a purge control valve provided in said second passage, said failure diagnosis method comprising the steps of:
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a) detecting a pressure in said evaporative fuel processing system; b) controlling an opening of said purge control valve by changing a duty ratio of a drive signal which drives said purge control valve; c) performing a first filtering of the detected pressure, d) performing a second filtering of the detected pressure, a second passing frequency band of the second filtering being narrower than a fierst passing frequency band of the first filtering; and e) determining a flow rate abnormality of a purge gas flowing in said second passage, based on the filtered pressures obtained by filtering of said steps c) and d). - View Dependent Claims (8, 9, 10, 11, 12)
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13. A computer program embodied on a computer-readable medium, for causing a computer to carry out a failure diagnosis method for diagnosing a failure of an evaporative fuel processing system which includes a fuel tank, a canister having adsorbent for adsorbing evaporative fuel generated in said fuel tank, an air passage connected to said canister for communicating said canister with the atmosphere, a first passage for connecting said canister and said fuel tank, a second passage for connecting said canister and an intake system of an internal combustion engine, and a purge control valve provided in said second passage, said failure diagnosis method comprising the steps of:
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a) detecting a pressure in said evaporative fuel processing system; b) controlling an opening of said purge control valve by changing a duty ratio of a drive signal which drives said purge control valve; c) performing a first filtering of the detected pressure, d) performing a second filtering of the detected pressure, a second passing frequency band of the second filtering being narrower than a first passing frequency band of the first filtering; and e) determining a flow rate abnormality of a purge gas flowing in said second passage, based on the filtered pressures obtained by filtering of said steps c) and d). - View Dependent Claims (14, 15, 16, 17, 18)
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Specification