EP0404919A1

EP0404919A1 - Liquid level gauge

Info

Publication number: EP0404919A1
Application number: EP19900901793
Authority: EP
Inventors: Walter Holzer
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-01-19
Filing date: 1990-01-17
Publication date: 1991-01-02
Also published as: WO1990008303A1; DE3929344A1

Abstract

Un indicateur de niveau, notamment pour réservoirs (1) de carburant de véhicules, comprend un capteur (26) électrique de mesure agencé dans le réservoir de carburant et un dispositif d'affichage (22). Afin de compenser des différences de pression lors de la mesure du niveau de remplissage du réservoir de carburant et de pouvoir ainsi en reconnaître le niveau de remplissage par une mesure directe de la pression hydrostatique, un capteur de mesure pourvu d'une sonde (21) de mesure de la pression différentielle qui sert à mesurer la pression hydrostatique du carburant est agencé au fond ou dans la zone postérieure du réservoir de carburant, la prise (32) de pression de référence de la sonde étant reliée au réservoir de carburant au-dessus du niveau de carburant. En outre, un réservoir d'air (5) est agencé dans le réservoir de carburant afin de séparer la zone contenant du liquide de la zone contenant de l'air, la prise de pression de référence de la sonde de mesure de la pression différentielle étant reliée à la zone contenant de l'air.A level indicator, in particular for vehicle fuel tanks (1), comprises an electrical measurement sensor (26) arranged in the fuel tank and a display device (22). In order to compensate for pressure differences when measuring the filling level of the fuel tank and thus to be able to recognize the filling level by direct measurement of the hydrostatic pressure, a measurement sensor provided with a probe (21) for measuring the differential pressure which is used to measure the hydrostatic pressure of the fuel is arranged at the bottom or in the rear region of the fuel tank, the reference pressure tap (32) of the probe being connected to the fuel tank above fuel level. In addition, an air tank (5) is arranged in the fuel tank in order to separate the area containing liquid from the area containing air, the reference pressure tap of the differential pressure measurement probe. being connected to the area containing air.

Description

Level indicator

The task of indicating the fill level of a fuel tank, particularly in vehicles, has hitherto been achieved almost exclusively by a float, which in most cases acts on a measuring instrument via a variable resistor.

The mechanical structures and devices required for this are relatively complicated and therefore also prone to failure. An electronic measurement of the hydrostatic pressure, which would meet today's demands for reliability and simplicity, cannot be carried out easily because the pressure conditions in the tank, e.g. of a motor vehicle, constantly changing.

The gasoline pump causes a negative pressure in the container when removing the fuel, so that a built-in pressure measuring probe, for. B. in the bottom of the container, under certain circumstances would report "empty", even if the container were full.

On the other hand, high ambient temperatures, e.g. B. in summer, to the fact that an overpressure arises in the Treobstoff container, which could fake a full state even when the tank is empty.

In order to compensate for these pressure differences so that the level can be recognized with a direct measurement of the hydrostatic pressure, it is proposed according to the invention to arrange a differential pressure measuring probe in the bottom or in the lower region of the fuel tank as a measuring value transmitter, and the reference pressure connection with the fuel tank to connect above the fuel level.

This measure makes it possible to actually record the fill level as a measured value and to use a display device, e.g. to feed a display instrument. The use of a fill level indicator according to the invention is particularly advantageous in all cases where a float system for fill level indication cannot be installed due to the shape of the fuel tank or the installation of space-consuming devices in the fuel tank. These include the arrangement of flexible inner containers (DE 37 14401 AI) in fuel containers. In patent application P 39 00499.6, the disclosure content of which is intended to be fully encompassed by the present disclosure, a fuel container is separated into a liquid region and an air region by installing an air bubble. In this case, it is proposed according to the invention to connect the reference pressure connection to the interior of the air bubble.

A level indicator according to the invention with a differential pressure measuring probe does not hinder the installation of an air bubble in the tank.

It is even possible to design such a tank as a pressure tank, which largely reduces the formation of gasoline vapors, without the level indicator values being influenced by the excess pressure in the tank.

The arrangement of a fill level indicator according to the invention is particularly simple in a fuel container with an air bubble that is permanently connected to the atmospheric environmental pressure, since in such a case the reference pressure connection can also be connected to the atmospheric ambient pressure. In this case, the reference pressure connection can even be closed to avoid contamination or external influences. By using a differential pressure measuring probe, especially in combination with a fuel tank with an air bubble, it is actually possible to determine the fill level by measuring the hydrostatic pressure, to implement these values analog or digitally and to display them as fill levels on the display device. It is irrelevant whether the display is on a scale, on a display or via symbols, or in any other way.

Because most fuel tanks in the bottom are one

Own tank emptying device, it is recommended according to the invention to integrate the measuring probe or the connection of the measuring probe with this tank emptying device.

It is equally advantageous to combine the measuring probe or its connection with a petrol withdrawal connection located in the bottom. This avoids additional breakthroughs in the bottom of the fuel tank and simplifies assembly.

There has recently been a tendency not to provide any openings in the bottom of fuel tanks, but rather to use all components from above, if possible. An extremely advantageous embodiment according to the invention consists in also designing the pressure measuring probe to be insertable into the fuel tank from above, the measuring probe being fastened to the lower end of a holder which also has the reference pressure connection above the fuel level. The bracket can e.g. B. be a tube that not only receives the electrical lines, but contains an opening in the upper area as a reference pressure connection.

Various measuring methods can be used to implement a transducer with a differential pressure measuring probe. According to the invention, the use of a membrane system is particularly proposed, the deformation of which is magnetically measured and evaluated.

Another type of measurement of the deformation of the membrane system is according to the invention by means of a Hall generator and corresponding evaluation.

According to the invention, methods are also suitable which detect and evaluate the deformation of an electronic bridge circuit.

As an example, FIG. 1 shows schematically the arrangement of a fill level indicator according to the invention in a normal fuel tank (1).

After removing the cover (10), the fuel (4) is filled through the filler neck (2) and fed to the engine via the fuel line (6). The display instrument (22) is intended to show the respective level (8) of the fuel.

The pressure measuring probe (21) with its transducer (26) is connected either directly or via a connecting line (7) to the bottom (19) of the fuel tank (1). The reference pressure is connected to the tank (1) from line (17) above the fuel level. The power supply takes place, as is customary in motor vehicles, via a battery (20), which is usually connected on one side to ground (18). The line (12) supplies the pressure measuring probe with voltage and the connection (23) passes the evaluated data to the display instrument (22), which is usually also 1-pole to ground (18). Depending on which measuring method is used for the transmitter, and depending on the spatial conditions, these connecting lines can be combined to form multi-pole cable harnesses.

In modern on-board networks, it may even be expedient to provide data evaluation using a central on-board computer.

In Figure 1 is also the summary of the line (7) and the fuel line (6) in a common component (11), which, for. B. already exists as a tank emptying device.

Figure 2 shows the corresponding arrangement of a transducer according to the invention with differential pressure measuring probe in a safety tank with air bubble, according to patent application P 39 00 499.6.

In this example, there is an air container (5) in the form of an air bubble in the fuel tank (1), which inflates more or less depending on the filling state, that is, "unfolds". This process is indicated schematically by the folds (9). The air tank (5) floats on the surface (8) of the fuel (4), so to speak, and is aerated via the ventilation connection (3). Since such fuel tanks can also be operated in a simple manner as "pressure tanks", the pressure measuring probe (21) is connected to the interior of the air tank (5) via line (17). The line (17) and the ventilation connection (3) are sealed by a closure (15) in the bulge (14) of the air container (5).

A particularly simple design is possible in such a fuel container with an air bubble if the ventilation connection (3) is in direct contact with the outside air, so that there is always atmospheric pressure inside the air container. In In such a case, line (17) can be dispensed with at all and atmospheric pressure can be used as the reference pressure.

In this case, it is even possible and recommended to close the reference pressure connection in order to avoid unwanted contamination.

For the rest, all comments apply as they were given for Figure 1.

3 and FIG. 4 schematically show two exemplary embodiments of a sensor (26) with a differential pressure probe (21). In the example in FIG. 3, the measured value probe (21) consists of a housing (28) which is divided by a flexible membrane (16) into the actual measuring chamber (29) with its connection (31) and the reference pressure chamber (30) with its connection ( 32).

The static liquid pressure acts in the measuring chamber (29) on the membrane (19) and deforms it more or less depending on the filling state. The deformation of the membrane (16) is sensed by the sensor (26) and converted into electrical information. The pressure in the reference pressure chamber (30) ensures that this difference is compensated for in the event of an overpressure or underpressure in the fuel tank above the liquid.

Figure 4 shows a corresponding structure with a double membrane (17), the interior (33) of which serves as a measuring chamber. The connection (31) is connected directly to the interior (33). In this case, the entire interior of the housing (28) serves as the reference pressure chamber (30). The reference pressure connection (32) corresponds to FIG. 3.

The advantage of an arrangement according to the invention corresponding to FIG. 4 consists in the fact that the double membrane (17) has twice as large deformations as the dimensions and dimensions of a single membrane (16).

Such an embodiment is particularly advantageous in the case of measuring probes in which the atmospheric pressure can serve as a reference pressure, because in such a case only the double membrane (17) has to be pressure-tight. Since the surrounding atmospheric pressure serves as the reference pressure, the connection (32) can remain open, or the housing (28) can be closed tightly, so that the constant internal pressure in the chamber (30) is always present as the reference pressure.

Figure 5 shows schematically an embodiment of a level indicator (21), which is combined with the fuel extraction line (6) in a bottom screw (11).

Such bottom screw connections (11), which are very often present in the bottom (19) of the fuel tank, can be used to accommodate the level indicator thanks to their small dimensions, without having to make an additional opening in the bottom (19) of the fuel tank (1). The bottom screw connection (11) is normally fastened with a nut (27) in the bottom (19) with the addition of a seal (25). The internal connection (31) takes up the hydrostatic pressure of the fuel, the reference pressure is supplied to the connection (32). The sieve (24) prevents dirt from getting into the fuel line (6).

Figure 6 shows a particularly advantageous embodiment of a level indicator according to the invention, in which a breakthrough in the bottom (19) of the fuel tank (1) can be avoided. The level indicator (21) is attached to a tube (34) which is mounted in a cover (35). The connection (31) to the measuring chamber is shown laterally in this case, and the pipe (34) with the connection (32) receives the reference pressure above the level (8) of the fuel (4). The electrical lines (23, 12) can also be led out in the tube (34), which of course must be tightly cast in at the upper end of the tube (34).

The example in FIG. 6 clearly shows how flexible the attachment and design of a fill level indicator according to the invention is.

In the case of fuel containers with an air bubble, a flexible hose can also be used instead of the tube (34), which rests against the inner wall of the fuel container; it only has to be noted that the connection (32) for the reference pressure is always above the level (8 ) of the fuel (4) remains. This is easily possible by providing this opening near the cover (35).

The schematically illustrated examples cannot exhaustively describe the possibilities according to the invention, they merely serve to better understand the inventive idea. Of course, all other methods for pressure measurement or for electronic data processing can also be used, provided that they satisfy the object of the invention.

In particular, FIG. 2 gives constructive suggestions when combining a fuel tank with an air bubble and a level indicator according to the invention. However, the drawings are in no way to be interpreted as restrictive.

The technical advantages of an electronic level indicator exist not only in a reliable and inexpensive solution to the task, but also bring further improvements.

So it is z. B. possible to interpret the display by averaging over time so that influences on the system when driving through curves or gradients are suppressed.

ZF.ICHNUNG LEGEND

Fuel tank 29 measuring chamber filler neck 30 reference pressure chamber ventilation connection 31 fuel connection 32 "air tank 33 interior fuel line 34 pipe connecting line 35 cover level (surface) folding cover component line

Bead Closure Membrane Double Membrane Ground Soil Battery Pressure Probe Display Instrument Connection Strainer Gasket Sensor Mother Housing

Claims

-MP claims

1. Level indicator, in particular for fuel tanks of vehicles, consisting of an electrical sensor in the area of the fuel tank and a display device, characterized in that a sensor with a differential pressure measuring probe for measuring the hydrostatic pressure of the fuel is arranged in the bottom or in the rear area of the fuel tank, and the reference pressure connection of the measuring probe is connected to the fuel tank above the fuel level.

2. Level indicator according to claim 1, so that an air tank is present in the fuel tank which separates the liquid area from the air area and the reference pressure connection of the differential pressure measuring probe is connected to the air area.

3. Level indicator according to claim 1 and 2, so that the air area of the fuel tank is constantly open to the atmospheric ambient pressure and the reference pressure connection of the differential pressure measuring probe is also open to the atmospheric pressure.

4. level indicator according to claim 3, d a d u r c h g e k e n n z e i c h n e t that the reference pressure connection is closed.

5. Level indicator according to one or more of the preceding claims, characterized in that the measuring probe or its connection integrated with the tank emptying device -λ ^{~ j}

is.

6. Level indicator according to one or more of the preceding claims, that the measuring probe or its connection is combined with the gasoline extraction connection.

7. Level indicator according to one or more of the preceding claims, that the measuring probe can be inserted into the fuel tank from above and is fastened to the lower end of a holder which also contains the reference pressure connection above the fuel level.

8. Level indicator according to one or more of the preceding claims, that a diaphragm system is present as a measuring probe, the deformation of which is measured and evaluated by means of a magnetic transducer.

9. Level indicator according to one or more of the preceding claims, that the deformation of the membrane system is measured and evaluated by means of a Hall generator as a measuring value transmitter.

10. Level indicator according to one or more of the preceding claims, that the deformation is measured and evaluated by means of an electronic bridge circuit as a measuring value transmitter.