EP1257738B1 - Device and method for monitoring a tank ventilation system - Google Patents

Abstract

The invention relates to a device and method for monitoring a tank ventilation system on a motor vehicle, with a tank ventilation valve (7), comprising an engine speed sensor (10), an air flow sensor (12) and/or an idle controller (13) to provide an air flow signal and an analytical unit (14), which compares the change in engine speed and air flow on opening and closing the ventilation valve, with at least one threshold value (16). According to the invention, the monitoring of the tank ventilation system may be improved, whereby the analytical unit is arranged, such that a combined reaction value is generated from the engine speed, with closed and opened tank ventilation valve and the air flow, with closed and opened tank ventilation valve and which is to be compared with a threshold value.

Description

The invention relates to a method and a device for checking a tank ventilation system according to the preambles of claims 1 and 2, respectively.

It is known to open the tank venting valve of a tank ventilation system to check its functionality specifically and close. The engine response to the opening or closing of the tank vent valve is then examined. For example, the speed and air mass change when the tank vent valve is opened or closed. For most systems, however, it is only known to compare each operating date individually with a threshold value in order to check the functionality of the tank ventilation system as a whole.

However, depending on how quickly an idle controller responds to changes made by opening or closing the tank vent valve, different responses occur. With a slow idle speed controller, it will mostly come to a reaction at the speed. In a fast idle controller, it will predominantly come to a reaction in the air mass. Moreover, of course, all intervening reactions are possible in which both the speed and the measured or piloted air mass changes. Overall, this means that the particular reaction is strong depends on the application. In the event that the speed and the air mass change simultaneously, the amplitudes of each individual signal can vary in size. Overall, this leads to a poor signal to noise ratio.

From DE 44 01 887 A1 discloses a method for the diagnosis of components of a tank ventilation system is known, in which among other things at two different tank vent valve positions each quotient of a measured air mass and stored in a map of a control unit air mass (among others depends on the speed) be formed. If the two quotients differ by a predetermined amount, the proper function of the tank-venting valve is concluded.

In WO 90/13738 a method for checking the controllability of a tank venting valve and an idling actuator is described. Here, the knowledge is used that the internal combustion engine supplied air / fuel mixture is possibly changed by opening the tank vent valve. Depending on whether there is a change, and if so, which change is present, reactions of a lambda control and / or an idling control can be evaluated.

The object of the present invention is to provide a method and a device for checking a tank ventilation system, which or which permits an accurate and correct checking of the functionality independently of the applications of an idle controller.

This object is achieved by the features specified in claim 1 and by the features specified in claim 2.

A core idea of the present invention can be found in the fact that the respective individual variables (operating data) are not individually compared with their own threshold value. Rather, the various changes in the individual variables are combined into an overall reaction, which is then assessed. at the assessment You can then make the known comparison with a threshold.

The method according to the invention or the device according to the invention is based on the assumption that the respective air masses and rotational speeds behave approximately proportionally to one another when the engine is idling (n.about.ml). In particular, it is assumed that with a closed tank venting valve, the quotient of air mass and speed is approximately constant (ml ₀ : n ₀ = approximately constant).

As a rule, the air volume additionally supplied via the tank ventilation valve is not measured or determined. Therefore, the engine is provided with open tank vent valve more air available, as this is pre-controlled via the idler actuator. The total air mass with an open tank venting valve thus results from the measured air mass (ml) as well as the additional air mass (ml _TEV ) flowing in via the tank venting valve.

Instead of an air mass (ml) measured with an air mass sensor, the pre-controlled air mass setpoint (ml_soll) of the idle controller could also be used as air mass signal. This is particularly advantageous if the measured air mass value is not fine enough dissolvable or fluctuates too much. Of course, the use of the air mass setpoint as air mass signal is also suitable even if no air mass sensor is present.

In the present invention, a relative change in the air mass is calculated from the air mass and the engine speed with the tank vent valve open and the air mass and the speed when the tank vent valve is closed. The relative air mass results from a difference of the quotient of the speed when the tank vent valve is open and the speed when the tank vent valve is closed on the one hand and the quotient of the air mass with the tank vent valve open and the air mass with the tank vent valve closed on the other hand.

Fig. 1

ein schematisches Blockdiagramm einer Ausführungsform der vorliegenden Erfindung und

Fig. 2

eine Darstellung eines einfachen Verfahrens zum Betrieb der Vorrichtung gemäß Fig. 1.

The present invention will be explained in more detail below with reference to an embodiment and with reference to the accompanying drawings. The drawings show in

Fig. 1

a schematic block diagram of an embodiment of the present invention and

Fig. 2

a representation of a simple method for operating the device according to FIG. 1.

In Fig. 1, a motor 1 with an exhaust passage 5 and a suction 3 is shown in a schematic block diagram manner. In the intake 3, a throttle valve 2 and an air mass meter 12 are arranged in series. The air mass meter 12 detects the air mass moving through an intake passage and outputs a corresponding signal to an evaluation device 14.

In addition, a speed sensor 10 is provided in the engine 1, which also outputs its speed signal to the evaluation unit 14. In the evaluation unit 14, a threshold value 16 is also stored.

The throttle valve 2 is acted upon, inter alia, by an idle controller 13, which emits an air mass desired value ml_soll corresponding to the throttle valve opening degree to the evaluation device 14.

Furthermore, a tank ventilation system is provided, of which in the present case only the tank ventilation valve 7 is shown with a supply channel 6. Via the supply channel 6, the air flowing through the tank vent valve 7 is supplied to the intake area 3. The tank venting valve 7 can be closed or opened (see control by arrow shown).

Depending on the switching state of the tank ventilation valve 7, a motor reaction takes place in the form of a change in the engine speed and / or the air mass flowing through the intake area 3.

A review of the tank ventilation system is now carried out in the present embodiment in such a way that first with closed tank vent valve 7, the air mass ml ₀ and the associated speed n _{0 is} detected (step 50 in Fig. 2).

Then, the tank-venting valve 7 is opened (step 52).

Subsequently, the air mass ml and the associated speed n with the tank vent valve 7 is detected (step 54).

Subsequently, in step 56, a total reaction value is calculated. In the present embodiment, it is assumed that when the engine is idling the air mass and the speed are approximately proportional (n ~ ml). It follows that the quotient of air mass and speed is approximately constant: $$\frac{m{l}_0}{n_0}\approx \mathrm{const},$$

When the tank venting valve 7 is open, on the other hand, a total air mass ml + ml _TEV results, where ml _{TEV describes} the air mass via the tank venting valve 7.

This results in the equation: $$\frac{m{l}_0}{n_0}=\frac{ml+m{l}_{\mathrm{TEV}}}{n}$$

After a transformation one obtains from it: $$\frac{m{l}_{\mathrm{TEV}}}{m{l}_0}=\frac{n}{n_0}-\frac{ml}{m{l}_0}$$

The quotient of ml _TEV / ml ₀ denotes the relative change in the air mass. In the present case, this is also the total reaction value, which describes the overall motor reaction.

Advantageously, the tank vent valve 7 is continuously, i. open in a ramp shape or in a staircase. At the same time, steps 54, 56 and 58 are executed. If you reach the threshold in step 58, the tank vent valve 7 does not need to be opened further.

Of course, one can also carry out the reaction evaluation from an open tank vent valve to a closed tank vent valve. When the method is carried out in both directions, maximum information is obtained from the respective targeted opening or closing of the tank-venting valve and an associated diagnostic certainty.

The total reaction value, in this case the relative change in the air mass, is then compared with the threshold value 16 and, depending on the undershooting or exceeding of the threshold value, receives information as to whether the tank venting valve 7 and the tank ventilation system are functioning properly overall.

If the air mass signal originating from the air mass meter 12 fluctuates too much, it is possible to resort to the desired air mass setpoint ml_soll coming from the idling controller 13, which is then used as a substitute for the air mass value ml to be measured per se.

With the present invention, one is relatively independent of an application of the idle controller. Moreover, one achieves a better noise ratio than with the aforementioned method. Moreover, the tank vent valve does not have to be opened widely until a certain reaction occurs. This therefore means a minor disturbance of idling during a test run. Incidentally, the present method is simpler than the method originally used, since one must apply only one size, namely the overall reaction.

Claims (2)

1. A device for testing a tank ventilation system with a tank ventilation valve in a motor vehicle, comprising an engine speed sensor (10), an air mass sensor (12) and/or an idle controller (13) for providing an air mass signal, as well as an evaluation unit (14), which compares the changes in speed and air masses with at least one threshold value when the tank ventilation valve is opened and closed, characterised in that the evaluation unit (14) is designed in such a way as to calculate a relative change in the air mass (ml_TEV/ml₀) from the air mass and the engine speed when the tank ventilation valve (ml, n) is opened and from the air mass and speed when the tank ventilation valve (ml₀, n₀) is closed, wherein the relative air mass (ml_TEV/ml₀) is calculated as the difference in the quotients of the speed when the tank ventilation valve (n) is opened and the speed when the tank ventilation valve (no) is closed, on the one hand, and, on the other hand, the air mass when the tank ventilation valve (ml) is opened and the air mass when the tank ventilation valve (ml₀) is closed.
2. A method for testing a tank ventilation system comprising the steps of detecting the engine speed when the tank ventilation valve (no) is closed, detecting the engine speed when the tank ventilation valve (n) is opened, detecting or determining an air mass when the tank ventilation valve (ml₀) is closed, detecting or determining an air mass when the tank ventilation valve (ml) is opened, characterised in that a relative change in the air mass (ml_TEV/ml₀) is calculated from the air mass and the speed when the tank ventilation valve (ml, n) is opened and from the air mass and the speed when the tank ventilation valve (ml₀, n₀) is closed, wherein the relative air mass (ml_TEV/ml₀) is calculated as the difference in the quotients of the speed when the tank ventilation valve (n) is opened and the speed when the tank ventilation valve (no) is closed , on the one hand, and, on the other hand, the air mass when the tank ventilation valve (ml) is opened and the air mass when the tank ventilation valve (ml₀) is closed.

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