Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Reexamination Certificate
1999-08-11
2001-05-22
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
C073S040000
Reexamination Certificate
active
06234152
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for checking the operability of a vessel and especially of a tank-venting system. The tank-venting system includes a tank and an adsorption filter having a venting line. The adsorption filter is connected to the tank via a connecting line and the system further includes a tank-venting valve which is connected to the adsorption filter via a valve line. In the method, an overpressure is introduced into the vessel compared to atmospheric pressure with a pressure source. To determine a pressure trace, the operating variable of the pressure source is detected during introduction of the overpressure and a conclusion is drawn therefrom as to the presence of a leak.
BACKGROUND OF THE INVENTION
A method of this kind for checking the operability of a tank-venting system is disclosed, for example, in U.S. Pat. No. 5,890,474 and in U.S. patent application Ser. No. 09/263,787, filed Mar. 5, 1999.
In many cases, it is desirable to undertake the check of the operability of the tank-venting system in vehicles only within certain temperature ranges. The diagnosis of the tank-venting system should not be carried out above or below certain ambient temperatures because, on the one hand, the service life of the seal elements in the valves, lines and the like is shortened by high temperatures and, on the other hand, the reliable operability of components of this kind cannot be guaranteed at low temperatures.
SUMMARY OF THE INVENTION
It is an object of the invention to improve a method for checking the operability of a vessel and especially of a tank-venting system in that a detection of the ambient temperature is made with the least possible complexity.
The method of the invention is for checking the operability of a tank-venting system of a vehicle having an engine. The tank-venting system includes: a tank; an adsorption filter having a venting line; a first connecting line connecting the adsorption filter to the tank; a tank-venting valve; and, a second connecting line connecting the tank-venting valve to the adsorption filter. The method includes the steps of: providing a pressure source for introducing an overpressure into the tank-venting system with the pressure source having operating characteristic variables; drawing a conclusion as to the ambient temperature from one of the operating characteristic variables and determining whether the ambient temperature lies within a pregiven temperature interval; only if the ambient temperature lies within the pregiven temperature interval, then introducing an overpressure into the tank-venting system relative to atmospheric pressure; detecting one of the operating characteristic variables of the pressure source as the overpressure is introduced into the tank-venting system to obtain a pressure trace of the pressure in the tank-venting system; and, drawing a conclusion as to the presence of a leak in the tank-venting system from the pressure trace.
The detection of the ambient temperature from one or more operating variables of the pressure source and the determination of the pressure trace from these operating characteristic variables have the significant advantage that additional temperature sensors are not needed. By applying overpressure to the vessel only when the detected temperature lies within a pregiven temperature interval ensures that a check of the operability of the vessel only takes place in the pregiven desired temperature interval and that a check of this kind affords reliable test results.
Advantageously, a pump driven by an electric motor is used as the pressure source and the ambient temperature is determined from the coil resistance of the electric motor of this pump. In this way, one can advantageously use electric variables which must anyway be detected for the determination of the pressure trace to check as to operability.
In principle, it would be possible to detect the operating characteristic variables of the pressure source in advance based on a comparison leak and to store the same in a memory to compare operating variables, which are detected in later measurements, to these operating characteristic values stored in the memory and to draw a conclusion as to the presence of a leak. In this way, the conclusion as to the presence of a leak can be reached relatively precisely. However, it is not possible, for example, to consider deterioration effects of the tank-venting system or of the vehicle or even other variables which influence the measurement with this method.
For the above reason, an especially advantageous solution provides for applying overpressure alternately to the tank-venting system and a reference leak and that the operating characteristic variables of the pressure source are detected during the introduction of the pressure into the tank-venting system and during the introduction of the pressure into the reference leak and the two operating characteristic variables are compared and the presence of a leak is concluded therefrom. This advantageous solution considers especially the different operating states of the vehicle and especially also operating states which are caused by deterioration.
The provision of a reference leak has, in addition, the significant advantage that representative comparative operating characteristic variables for a leak, which is present, do not have to be stored and the memory can therefore be omitted.
An advantageous embodiment provides that the reference leak can be connected in parallel to the tank-venting system and this provides an especially good reference measurement.
In another advantageous embodiment, the reference leak is simulated by a controlled partially opened tank-venting valve. For this reason, an additional reference leak branch in the tank-venting system can be omitted. With this controlled partial opening of the tank-venting valve, any desired leak size can be realized in an especially advantageous manner.
REFERENCES:
patent: 5349935 (1994-09-01), Mezger et al.
patent: 5460141 (1995-10-01), Denz et al.
patent: 5553577 (1996-09-01), Denz et al.
patent: 5890474 (1999-04-01), Schnaibel et al.
patent: 6105557 (2000-08-01), Schnaibel et al.
Fritz Thorsten
Reuschenbach Lutz
Castro Arnold
Dolinar Andrew M.
Ottesen Walter
Robert & Bosch GmbH
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