Diagnostic system for detecting leakage of fuel vapor from purge system
First Claim
1. A leakage diagnostic system for making a judgment of leakage of a fuel purge system based on a rising rate of pressure in purge passage means between a fuel tank and an intake system of an engine isolated from the atmosphere after lowering the interior of the purge passage below a specified negative pressure level, said leakage diagnostic system comprising:
- pressure regulating means for developing negative pressure in said purge passage means;
operation detection means for detecting a pressure level of the inside of said purge passage means; and
control means for controlling said pressure regulating means to cause a specified change in said negative pressure level, comparing a change in said negative pressure level caused within a specified period of time with a predetermined judging value, delivering a judgment of leakage from said fuel purge system when said change is larger than said predetermined judging value, and maintaining said predetermined judging when said change becomes greater than said predetermined judging value within a specified time from an engine start and increasing said predetermined judging with a passage of time when said change becomes greater than said predetermined judging value after said predetermined time from an engine start so as to make it harder to deliver said judgement of leakage.
1 Assignment
0 Petitions
Accused Products
Abstract
A leakage diagnostic system for making a judgement of leakage of a fuel purge system, which has in order from the side of a fuel tank a control valve, a canister and a purge valve disposed in a purge passage and a relief valve isolating the canister from the atmosphere, based on a rising rate of pressure in the purge passage between the fuel tank and the intake system isolated from the atmosphere after lowering and keeping the interior of the purge passage below specified negative pressure level for a specified period of time. When the interior of the fuel tank increases above a threshold level after a specified period of time, the leakage diagnostic system delivers a judgement of leakage of the purge system.
45 Citations
12 Claims
-
1. A leakage diagnostic system for making a judgment of leakage of a fuel purge system based on a rising rate of pressure in purge passage means between a fuel tank and an intake system of an engine isolated from the atmosphere after lowering the interior of the purge passage below a specified negative pressure level, said leakage diagnostic system comprising:
-
pressure regulating means for developing negative pressure in said purge passage means; operation detection means for detecting a pressure level of the inside of said purge passage means; and control means for controlling said pressure regulating means to cause a specified change in said negative pressure level, comparing a change in said negative pressure level caused within a specified period of time with a predetermined judging value, delivering a judgment of leakage from said fuel purge system when said change is larger than said predetermined judging value, and maintaining said predetermined judging when said change becomes greater than said predetermined judging value within a specified time from an engine start and increasing said predetermined judging with a passage of time when said change becomes greater than said predetermined judging value after said predetermined time from an engine start so as to make it harder to deliver said judgement of leakage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. A leakage diagnostic system for making a judgment of leakage of a fuel purge system based on a rising rate of pressure in a purge passage connected between a fuel tank and an intake system of an engine isolated from the atmosphere after lowering the interior of the purge passage below a specified negative pressure level, said leakage diagnostic system comprising:
-
a purge valve installed in said purge passage; a negative pressure sensor for detecting a pressure level of negative pressure introduced into said purge passage through said purge valve; and a control unit for counting a time after an engine start, controlling said purge valve to open to admit said negative pressure into said purge passage, comparing a change in level of said negative pressure in said purge passage caused within a specified period of time with a predetermined judging value, judging that there occurs leakage from said fuel purge system when said change is larger than said predetermined judging value, and increasing said predetermined judging value within a specified time counted from said engine start. - View Dependent Claims (11, 12)
-
Specification