DE102008050138A1 - Method for assigning measuring signal of fill level sensor to liquid amount in fuel container of motor vehicle, involves obtaining Measuring signals of sensor, and using characteristics curves for determining assignment of measuring signal - Google Patents

Abstract

The method involves providing a characteristic curves, and filling a defined amount of liquid into a liquid container i.e. fuel container (10). Measuring signals of a fill level sensor (14) is obtained, and characteristics are determined from the characteristic curves based on combination of the defined amount and the measuring signals. The characteristics curves are used for determining the assignment of the measuring signal. The characteristics curves are determined by determination of offset of the characteristic curves to an axis. An independent claim is also included for a motor vehicle comprising a display unit.

Description

The The invention relates to a method for assigning a measurement signal a level sensor in a liquid container, in particular in a fuel tank, predetermined Type for a motor vehicle or in or on a motor vehicle, and although to assign such a measurement signal to an amount of in the container of the predetermined type befindlicher liquid.

To the Purposes of such assignment are so far calibration measurements carried out. This gradually becomes more and more liquid filled in the container, with the amount of filled liquid is known. It will then constantly or repeatedly the measuring signal of the level sensor, from the closed to the level of the level can be determined, and this measurement signal or this height is paired with the value of each filled amount of liquid used as the measuring point of a calibration curve.

Subsequently a control unit uses the calibration curve obtained in this way due to measuring signals of the level sensor, a level indicator to drive in the vehicle.

The recording of a calibration curve for the purpose of associating a measurement signal of a filling level sensor with an amount of liquid in the associated container is known, for example, from US Pat U.S. Patent 4,406,152 described.

in the U.S. Patent 5,752,409 It is described that a calibration curve is calculated on the basis of a limited number of measured values.

The Deriving a complete calibration curve turns out to be due to the fact that in the prior art the liquid container gradually filled must be as laborious. In addition, the liquid container often be unfilled after calibrating with it it can be transported more safely and with less fuel consumption.

It Object of the invention, a method for assigning a measurement signal a level sensor to a liquid amount in the associated container to provide simple, fast and easy to carry out is.

The Task is achieved by a method with the features according to claim 1 solved.

According to the invention initially given a characteristic form. The characteristic curve is preferably chosen so that when used as a characteristic, ie if the characteristic shape in a predetermined manner in a coordinate system is placed, the dependence of the measurement signal of the Amount for a liquid container of the predetermined type exemplifies. At typical placement the characteristic, defines z. B. by the distance of a point of Characteristic to the axis on which the quantity is plotted and defined characteristic curve set for this axis (ie at a defined distance a second point to this axis), the resulting Characteristic, for example, be the standard characteristic that the container due to the target rules would have, if there is no There would be manufacturing tolerances.

at The inventive method will now be a defined amount of liquid in the liquid container filled. Furthermore, a measurement signal of the level sensor won. Now, a characteristic curve is made using the characteristic shape based on the combination of definition over the defined filled amount and obtained at least one measurement signal established. The characteristic thus obtained is used to determine the desired assignment.

Thereby, it is not assumed that a characteristic form is assumed in advance more a variety of measurements as required in the prior art. It is sufficient a measured value, namely the defined Amount of liquid to the characteristic in a coordinate system (eg, plotted with the amount of liquid on the x-axis and the measurement signal or the level derived from the measurement signal Plotted on the y-axis) to place clearly. By selecting the defined amount, the range can be selected set the characteristic, the most precise the reality reproduces. Is the defined amount not more than 20% of the maximum fillable in the liquid container Target quantity, gives the characteristic especially with almost empty liquid container the reality is very good again. This is advantageous because because a motor vehicle driver has very accurate information about must have the amount of liquid in the container, if the container is almost empty.

Theoretically, it would be possible to compress or spread the characteristic at a fixed scale in order to account for a systematic deviation of the liquid container from standard conditions of the liquid container of the predetermined type: For example, if the liquid container in one direction wider than the desired width, more liquid can be filled , If the characteristic curve is adapted to the standard shape of the liquid container, it must be spread open, so that the level height must be divided into a predetermined amount by a value that accurately reflects how much of the liquid container in question is wider than a normal liquid container is.

There Preferably, the characteristic curve is adapted to a measuring point which is is located in the lower branch of the characteristic curve (ie at a lower defined value) was filled in), plays such a Spread then but not outstanding role. It is sufficient for sufficient precision in the assignment, if only the offset of the characteristic to the axis on the the amount is plotted, set and the characteristic shape simply put into the coordinate system with this offset becomes. Under "offset" is here the distance of a Point of the characteristic curve to the axis, on which quantity is plotted, understood, with the remaining characteristic parallel to the axis, on the the measuring signal or the level height is applied, is moved. By the distance of the one point the distances of the other points of the characteristic curve form to the axis on which the quantity is applied automatically. The parallel shift The characteristic curve in the coordinate system can also be determined by this be that the distance between two predetermined points in the characteristic shape to the axis on which the quantity is applied. These distances should then differ by a predetermined distance from each other, which is determined by the characteristic shape. In the area below this offset dominates the assignment, a possible compression or spreading the characteristic would contribute little. If the characteristic shape is placed only in the coordinate system suitable By setting the offset, you can do that Carry out the procedure very simply, because it is enough actually a single measuring point.

typical Level sensors are on the lid of the container attached and sticking down, often taking the floor not reach the container. This can be a lot be filled with liquid without these is detected by the level sensor. This amount of liquid can vary due to manufacturing tolerances, and this leaves also in the method according to the invention consider. It must then be determined during filling from which filled in the container Quantity of level sensor is filled captured by liquid. This information may be at the Interpretation of the measuring signals of the level sensor (assignment to a level) can be used. She can also join It can be used to set the defined amount defined quantity namely be chosen so that slightly larger than the filling amount is from which the level sensor is filled captured by liquid. Additionally or alternatively This information can also be used when defining the characteristic curve, in particular used in determining the above offset.

The Invention is also reflected in a motor vehicle, a liquid container with a level sensor further comprising a display unit for indicating the level due to of measured values of the level sensor, wherein the Display unit is controlled in operation by a control unit. The control unit is intended to be measuring signals of the level sensor receive and access to a according to the inventive method have obtained characteristic. This characteristic can then serve the amount of liquid received by the control unit assigned. Due to the assignment then the display unit controlled, z. B. the display unit digitally the amount of indicate liquid in the container, the control unit based on the measured values using the characteristic determined.

following is a preferred embodiment of the invention below Referring to the drawing, in which

1 schematically shows a cross section through a liquid container,

2 shows a characteristic that illustrates the dependence of the level height of the filled volume of liquid and

3 illustrates how the characteristic is off 2 undergoes a change in order to arrive at a desired characteristic.

The inventive method is preferably used in connection with fuel tanks for trucks, which have a very high capacity of up to several hundred liters of fuel. Such a fuel tank 10 is in 1 shown in section. On the lid 12 of the fuel tank is a level sensor 14 suspended. The level sensor 14 extends perpendicularly towards the ground 16 of the fuel tank 10 without reaching this ground.

The level sensor 14 should be able to determine the amount of filled liquid, indicated in volume units. Depending on the height H of the liquid level, the level sensor emits other signals. These signals are in the present case transformed into information on the height H.

2 gives an exemplary characteristic 18 again, that for a fuel tank 10 the relationship between height H and filled volume V reflects. In the present case, the characteristic curve passes through 18 the origin of the coordinate system: At height H = 0, of course, the volume V = 0 is filled. Through the characteristic 18 becomes a Kennlini enform defined.

Now in the fuel tank 10 filled a predetermined amount of fuel. In the present case, this is 40 liters. 1 It can be seen that a quantity of x liters with x <40 in the fuel tank 10 is fillable before the liquid is the level sensor 14 reached. The fact that 40 liters are filled, the level sensor can measure a level height H, in this case of H = 550 mm. It is now so that the characteristic 18 as in the clipping 2 according to 3 illustrated, includes the point P1, which is assigned to a fill level of 540 mm according to a filled volume of 40 liters. If at the actual fuel tank 10 the level is 550 mm, it means that the fuel tank 10 slightly less liquid per unit of height than the standard container to which the characteristic 18 is defined.

Instead of the characteristic curve 18 by replacing a completely new characteristic, the characteristic becomes 18 only according to the arrow 20 offset, in the direction of the H-axis. The point P1 is imaged on the point P2, which according to the height at 40 liters instead of 540 mm is actually 550 mm.

In the following, the characteristic thus obtained 18 ' arising from the original characteristic 18 , that is, the original shape of the curve, using only an offset between the points P1 and P2 has been determined. It remains irrelevant that a perfect characteristic for the real fuel tank over the characteristic 18 would have to be compressed along the H-axis. The characteristic 18 ' In particular, it no longer goes through the origin of the coordinate system. By shifting the characteristic 18 to the characteristic 18 ' out according to the arrow 20 is therefore not a characteristic representing the actual conditions 18 ' receive. The characteristic 18 ' but it reflects the conditions in the area in which it is of particular interest, namely at low level: the driver of the truck, in which the fuel tank 10 is used, must have information about how far he can drive when the fuel tank 10 approaching its complete emptying. The size of 40 liters is chosen so that the offset in the lower part of the curve 18 is defined.

The method has the advantage that it is not necessary to record a large number of measured values. At best, it may prove useful to determine the size x liter and to take it into account when determining the characteristic curve. In principle, however, one single measured value, namely the one to the point P2, is sufficient. The characteristic curve according to the characteristic 18 is offset so far in the direction of the H-axis, that the point P2 is exactly on the characteristic. By recording only one measuring point, the method can be carried out quickly. For transporting the truck after determining the characteristic curve 18 ' is the fuel tank 10 largely empty. This is advantageous so that the motor vehicle (the truck) with the fuel tank 10 has a low weight when it is transported, z. B. on a ship or a railway car. Typically, this is done by defining the characteristic 18 ' in the factory of the production of the motor vehicle, in which the fuel tank 10 is used, and the motor vehicle is subsequently transported to its place of use without driving and needing fuel. Superfluous fuel in the motor vehicle increases its weight and thus the transport costs. There is little fuel in the fuel tank in the present case 10 after determining the characteristic 18 ' to transport.

10

Fuel tank

12

cover

14

level sensor

16

ground

18.18 '

characteristics

20

arrow

H

height

P1, P2

Points

V

volume

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 4406152 [0004]
• US 5752409 [0005]

Claims (5)

Method for assigning a measuring signal of a filling level sensor ( 14 ) in a liquid container ( 10 ), in particular a fuel tank, for or in or on a motor vehicle, to an amount of liquid in the tank, comprising the steps of: - specifying a characteristic shape, - filling a defined amount of liquid into the liquid tank ( 10 ) and subsequently - obtaining at least one measuring signal of the filling level sensor ( 14 ), - definition of a characteristic ( 18 ' ) from the characteristic shape based on the combination (P2) of a defined amount and obtained at least one measurement signal, and - using the characteristic thus obtained to determine the assignment. Method according to Claim 1, in which the characteristic curve ( 18 ) by specifying an offset of the characteristic curve ( 18 ) to the axis on which the quantity is plotted, the characteristic curve ( 18 ' ). Method according to Claim 1 or 2, in which, during filling, it is ascertained from which amount of liquid filled into the container the level sensor ( 14 ) detects the filling of liquid, and in which this information in the interpretation of the measured signals, in determining the defined amount and / or in the determination of the characteristic ( 18 ' ) is used. Method according to one of the preceding claims, where the defined amount is at most 20% of the maximum can be filled in the liquid container Target quantity is. Motor vehicle comprising a liquid container with a filling level sensor ( 14 ), further comprising a display unit for indicating the filling level on the basis of measured values of the filling level sensor ( 14 ), wherein the display unit is controllable by a control unit, which is for receiving measurement signals from the level sensor ( 14 ), the control unit having access to a characteristic obtained according to the method of one of the preceding claims.