Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Patent
1993-05-26
1995-03-21
Miller, Carl S.
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
123198D, F02M 3302
Patent
active
053986610
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The following relates to a method and an arrangement for checking the operability of a tank-venting system on a motor vehicle having an internal combustion engine.
BACKGROUND OF THE INVENTION
From U.S. Pat. No. 5,193,512, a tank-venting system is known which has: a tank with a tank-pressure sensor; an adsorption filter, which is connected to the tank via a tank-connecting line and has a venting line blockable by a shutoff valve; and, a tank-venting valve which is connected to the adsorption filter via a valve line. The tank-venting system assembled in this manner is checked as to operability according to the following method: a check is made as to whether an operating condition is present, for example full load, in which no significant underpressure can be built up in the tank after closing the shutoff valve and opening the tank-venting valve; if such a condition is present, the method is interrupted; otherwise, the following steps follow: closing the shutoff valve; opening the tank-venting valve; measuring the underpressure building up in the tank; and, determining the tank-venting system as not operational if a pregiven underpressure is not reached.
In the mentioned publication, a variant of the method is also disclosed according to which the shutoff valve and the tank-venting valve are closed and a check is made as to whether a pregiven overpressure builds up within a pregiven time span because of vaporizing fuel. If this is the case, the tank-venting valve is opened and a check is made whether a lambda control on the internal combustion engine has to carry out a lean correction. If this is the case, the tank-venting system is determined as being operational.
The arrangement described in the above-mentioned publication for checking the operability of a tank-venting apparatus includes units for performing the above-mentioned steps.
It has been shown that it is not possible to determine relatively small holes in the tank-venting apparatus with the method mentioned above. Accordingly, the problem existed to provide a method and an arrangement for checking the operability of a tank-venting apparatus on a motor vehicle having an internal combustion engine with which it is possible to also reliably determine relatively small holes.
SUMMARY OF THE INVENTION
The method of the invention for checking the operability of a tank-venting apparatus configured as described above on a motor vehicle equipped with an internal combustion engine includes the following steps: tank-venting apparatus and interrupting the check when pregiven operating variable values are not obtained for which values a reliable statement as to operability is possible; only during the test method including the engine and tank-venting apparatus and interrupting the check of the development of underpressure when the operating variable values show that the measured tank pressure values permit no reliable statement as to the operability of the apparatus; the method when the gradient of the underpressure buildup lies below a threshold; measured during the test method including engine and tank-venting apparatus and interrupting the check of the decay of underpressure when the operating variable values indicate that the measured tank pressure values permit no reliable information as to the operability of the apparatus; gradient of underpressure decay lies above a threshold, otherwise, determining the apparatus as being operable at that time; and,
What is essential for the method of the invention is that it is interrupted when values of operating variables, which can be measured only during the method, indicate that the method cannot supply a reliable statement. In addition, values of operating variables can still be monitored in a conventional manner with these operating variables being measurable already at the start of the method. Preferably, the monitored operating variables are especially those which are related to a gassing of the fuel. This is for the following reasons.
The buildup of underpressure in the tank is cau
REFERENCES:
patent: 5191870 (1993-03-01), Cook
patent: 5193512 (1993-03-01), Steinbrenner et al.
patent: 5220896 (1992-06-01), Blumenstock
patent: 5295472 (1994-03-01), Otsuka
patent: 5297579 (1994-03-01), Cook
patent: 5299545 (1994-04-01), Koroda
patent: 5305724 (1994-04-01), Chikamatsu
patent: 5333589 (1994-08-01), Otsura
patent: 5339788 (1994-08-01), Blumenstock
patent: 5345917 (1994-09-01), Maruyama
Blumenstock Andreas
Denz Helmut
Miller Carl S.
Ottesen Walter
Robert & Bosch GmbH
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