GB2282225A

GB2282225A - Device for determining the level of a medium and process for controlling an engine

Info

Publication number: GB2282225A
Application number: GB9418590A
Authority: GB
Inventors: Peter Knoll
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1993-09-28
Filing date: 1994-09-15
Publication date: 1995-03-29
Also published as: SE9403248D0; FR2710744A1; DE4332946A1; SE9403248L; SE9403248A0; GB9418590D0

Description

2282225 Measuring device f or determining the level of a medium and

Drocess for controlling the engine State-of-the-art

The invention is based on a measuring device for determining the level of a medium according to the f orm of independent Claim 1. In motor vehicles with a catalyzer f or the engine exhaust gases the exact amount of residual fuel must be determined. With tank level sensors previously used in practice it is quiEe possible to make particularly sensitive measurements in the end region, the so-called residual region. However, a precise definition of a specific residual quantity is possible only with difficulty. Furthermore, it is known that in the case of motor vehicles with catalyzers, total draining of the fuel tank is to be avoided. The catalyzer can be damaged after refilling the tank and operating the internal combustion machine. Consequently, complete emptying of the fuel tank should be avoided at all costs.

Advantages of the invention The measuring device according to the invention for determining the level of a medium allows a residual quantity to be determined very accurately. Emptying of the fuel tank and the inevitable resulting damage to the catalyzer can be prevented by combining the process according to the invention with control of the engine. In principle, the process can be employed in conjunction with all tank level sensors, but due to the special design of the bottom of the tank a precisely defined residual quantity of material for implementing the process is prescribed in a simple manner. - Due to the steps described in the sub-claims, advantageous further forms of the measuring device cited in the main claim are possible.

Drawing Embodiments of the invention are illustrated in the drawing and explained in more detail in the description below. Figure I shows a section through a schematic representation of the measuring device and Figure 2 shows a block diagram for implementing the process.

Description of the embodiments

A sealed tank that can be used in all kinds of motor vehicles is denoted by 10 in Figure 1. A level sensor 12 projects through an opening 11 in the tank 10. A recess 14, to whose lowest point the level sensor 12 extends, is formed in the bottom of the tank 10. Furthermore, a line 16 leads from the lowest point 15 of the recess 14 to the engine of the internal combustion machine, not shown. The size of the recess 14, i.e. the medium located in the recess 14 of the tank 10 is matched to the required remaining running distance of the engine. If the tank is used in passenger vehicles, the recess 14 contains a volume of approximately 0.5 litres. For passenger vehicles currently on the market a remaining running distance of 5 to 10 km is therefore possible. Should a cylindrical shape be chosen for the recess 14, the recess 14 would have a diameter of 10 cm and a depth of around 6.4 cm. However, it is important that a precisely defined residual volume can be set or stipulated in a simple way.

The level sensor 12 has an external jacket 20 that is pressed against the lowest point 15 of the recess 14 with the aid of a spring 21. A rod 22, e. g. made of metal, steel, etc. that is attached via fixing components 23 to the jacket 20, is located in the jacket 20. The rod 22 is adjusted so that its lower end, i.e. its end projecting into the recess 14, does not rest on the bottom of the recess 14, but has a specific clearance of 1 mm, for example, and thus can freely oscillate. In the head 24 of the level sensor 12 is arranged a current-carrying coil 25 via which the rod is excited into oscillation. This involves ultrasonic oscillations whose resonant frequency changes as a function of the height of the medium in the tank 10. This means that the resonant frequency of the rod 22 varies according to the height of the medium in the tank 10. The resonant frequency is further processed in the conventional known manner as an indication of the level of the medium in the tank and is therefore not shown here. The level of the medium in the tank 10 could alsq be determined with the aid of other tank level sensors. Tank level sensors that operate with ultrasonic oscillations, however, facilitate a relatively accurate measurement in the lower region, i.e. in the region of the recess 14. Regions of the rod 22 could thus be provided with different measurement sensitivities, for example by coating the rod 22 in different ways or by suitable shaping of the rod, e.g. with thick or thin areas.

A special process f or sampling the residual amount of material in the recess 14 and for the associated control of the engine of the internal combustion machine is represented in the block diagram in Figure 2. Here it is important that the engine of the internal combustion machine is switched off when the residual quantity in the tank 10 is the minimum possible, in order to prevent damage to the engine exhaust gas catalyzer when put into service again. However, when a specified amount that more or less corresponds to the volume of the recess 14 is reached, the driver of the internal combustion machine should first be warned and informed of the imminent switchingof f of the engine. In this connection, the measured value determined by the level sensor 12 is continuously checked in a microprocessor or an electrical circuit (computer) and compared to a specified set-point. The residual quantities given below are to be taken only as a definite example related to motorcars. If the measured level corresponds to a residual quantity v that is greater than 0. 5 litres, the computer returns directly to the original scan in a loop and a new value, determined by the level sensor 12, is input or sampled. On the other hand, if a residual quantity v is reached, that in the example used here is between 0.2 litres and 0.5 litres, an alarm device is actuated by the electrical circuit. This can be a visual as well as an audible warning signal. It would also be possible to arrange for both warning signals to be triggered in combination with each other. If this warning signal is sounded, the driver of the internal combustion machine knows that there is only suf f icient fuel in the tank 10 f or a f ew kilometres and that the engine of the internal combustion machine will soon be switched of f automatically. The alarm device can only remain permanently switched on as long as the residual quantity of the medium is within the range stated above. However, it would also be possible if, for example, the audible warning signal would continuously become louder as the residual quantity v becomes smaller. The computer now remains in this sampling loop as long as the medium in the tank 10 or in the recess 14 has not fallen below the specif ied minimum value; in this example 0.2 litres. On the other hand, if the tank 10 is emptied still further and the minimum residual quantity falls below 0.2 litres in this example, then the engine of the internal combustion machine is switched off automatically by the computer or the associated electrical circuit. This can be achieved, for example, by interrupting the ignition. This automatically prevents complete emptying of the tank and consequent destruction of the engine exhaust gas catalyzer.

Claims

1. measuring device for determining the level of a medium in a tank (10) with the aid of a sensor (12), characterized in that a recess (14) for holding a minimum residual quantity v of the medium to be determined is provided in the bottom (13) of the tank (10), and that the end of the sensor (12) projects into this recess (14).

2. Measuring device according to Claim 1, characterised in that the outlet (16) of the tank (10) is located in the region of the recess (14).

3. Measuring device according to Claim 1 or 2, characterised in that the sensor (12) has at least two different sensitivity ranges, whereby the most sensitive range includes the medium in the recess (14).

4. Measuring device according to one of the Claims 1 to 3, characterised in that the sensor (12) has an external jacket (20) that is pressed against the bottom (15) of the recess (14) by a spring (21), that a rod (22) that is attached to the jacket (20) by means of fixing components (23) is arranged inside the jacket (20) and is excited into oscillation by a coil (25).

5. Measuring device according to one of the Claims 1 to 4, characterised in that where the jacket (20) rests on the bottom (15) the rod (22) stands clear of the bottom (15) so that the rod (22) can freely oscillate.

6. Process for controlling the engine of an internal combustion machine in relation to the quantity of the medium remaining in the tank (10), whereby the medium is fed to the engine if the quantity of medium in the tank (10) exceeds the value x, whereby alarm, devices are activated in the range of the quantity of medium between x and y, and whereby if the quantity of medium falls below y the engine of the internal combustion machine is switched off.

I-

7. Process according to Claim 6, characterised in that the process is determined by a measuring device according to one of the Claims 1 to 5.

8. Process according to Claim 6 or 7, characterised in that the alarm devices are switched on until the quantity of medium falls below y.

9. Process according to one of the Claims 6 to 8, characterised in that the alarm device is of a visual and/or an audible type.

10. A measuring device substantially as herein described with reference to the accompanying drawings.

11. A process substantially as herein described with reference to the accompanying drawings.

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