Method and arrangement for venting a tank

Details Method and arrangement for venting a tank Method and arrangement for venting a tank

1993-09-22

1994-12-13

Wolfe, Willis R.

Internal-combustion engines

Charge forming device

Including exhaust gas condition responsive means

123520, F02M 2508, F02D 4114

Patent

active

053721179

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention relates to a method and an arrangement for alternately carrying out phases with and without tank venting during operation of an internal combustion engine equipped with a tank-venting assembly.


BACKGROUND OF THE INVENTION

U.S. Pat. No. 4,705,007 describes a method according to which phases with and without tank venting (namely, tank-venting phases and base-adaptation phases) alternate in a fixed raster. 5 minutes are provided for the tank-venting time span and 1 minute is provided for the base-adaptation time span. In practice, the first time duration is more likely to be somewhat shorter and the second somewhat longer.
The duration of the tank-venting time span together with the characteristic variables of the tank assembly and of the corresponding engine determine the size of the adsorption filter in which fuel vapor is adsorbed from the tank. These variables also determine the diameter of the tank-venting valve with the aid of which the adsorption filter is purged with air. The size of the adsorption filter and the cross section of the tank-venting valve must be so dimensioned that, even for the largest possibly occurring fuel vapor quantity, essentially all fuel vapor can be adsorbed during the base-adaptation time spans and can again be desorbed during the tank-venting time spans.
In the technology, the problem generally is present to operate arrangements according to such methods and to so configure the arrangements that the components are used in the most purposeful manner possible. This problem applied correspondingly also to methods and arrangements for carrying out phases with and without tank venting during operation of an internal combustion engine with a tank-venting assembly.


SUMMARY OF THE INVENTION

A method of the invention of this kind is characterized in that the ratio of the time spans with and without tank venting is no longer fixed; instead, the ratio is selected to be dependent upon operating data of the engine or of the tank-venting assembly.
The arrangement of the invention includes a sequence control for alternately carrying out phases with and without tank venting. The sequence control is so configured that it selects the ratio of phase durations in dependence upon operating data of the engine or of the tank-venting assembly.
The method and arrangement can use participating components with greater flexibility than was previously possible because this method and this arrangement no longer use a fixed pregiven time reference for the above-mentioned phases.
In a preferred embodiment, the method includes the following steps: during the tank venting; and, increased with respect to a base ratio when the value of the measured variable exceeds an upper threshold value.
According to another variation, tank venting is carried out at full load without lambda control always with a completely open tank-venting valve. This variation is based upon the recognition that no base adaptation can be carried out in the phases without tank venting during full load without lambda control so that it is more purposeful to utilize the entire time for tank venting. The valve is not used much because the valve is held continuously open in lieu of being clocked.
According to a third variation, a diagnostic method is started to determine the operability of the tank-venting assembly during a tank-venting phase. The diagnostic method requires a temporary closure of the tank-venting valve. Immediately with the closing of the valve, a base-adaptation phase is started and the next tank-venting phase is extended at least partially as compensation for the interrupted previous phase. In this way, the time for diagnosis is at the same time purposefully utilized for adaptation.
It is especially advantageous to utilize all above-mentioned variations in common.
The method having a variable ratio of the above-mentioned time spans makes possible that the adsorption filter and the tank-venting valve can be configured for the throughput of an average quantity of fuel from the tank ve

REFERENCES:
patent: 4467769 (1984-08-01), Matsumura
patent: 4705007 (1987-11-01), Plapp et al.
patent: 5048493 (1991-09-01), Orzel et al.
patent: 5085194 (1992-02-01), Kuroda et al.
patent: 5125385 (1992-06-01), Frinzel
patent: 5150689 (1992-09-01), Yano et al.
patent: 5193512 (1993-03-01), Steinbrenner et al.
patent: 5265577 (1993-11-01), Denz et al.

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