DE102008043778A1 - Method for level measuring in tank receiving liquid, involves detecting driving condition indicative dimension, where level characterizing dimension is evaluated as function of driving condition indicative dimension - Google Patents

Abstract

The method involves detecting driving condition indicative dimension, where the level characterizing dimension is evaluated as a function of driving condition indicative dimension. The evaluation of sensors (101,102,103) is evaluated at different driving conditions which are characterized by two driving condition indicative dimension. Independent claims are included for the following: (1) a device for level measuring in a tank receiving liquid, particularly a urea water solution; (2) a computer program for executing the level measuring method; and (3) a computer program product with program code.

Description

The The invention relates to a method and a device for level measurement in one a liquid, in particular a urea water solution receiving container after the genus of independent Claims.

State of the art

The Reduction of nitrogen oxide emissions with excess air working internal combustion engines, especially in diesel internal combustion engines, can with the help of the so-called Selective Catalytic Reduction technology (SCR). In this case, nitrogen oxide becomes nitrogen and water vapor reduced. As a reducing agent come either gaseous Ammonia or ammonia in aqueous solution or Urea in aqueous solution for use. Of the Urea serves as ammonia carrier and is with the help a metering system in front of a built-in the exhaust system hydrolysis catalyst injected and converted by hydrolysis to ammonia, which is then in a so-called SCR or Denox catalyst reduced nitrogen oxides. One Such dosing system has a container for receiving the Dosing agent in the form of a liquid, in particular the Urea water solution on. For a proper The function of the SCR system is knowledge of the fluid level required in the urea water solution tank. By doing In particular, the system must have the level of the solution be continuously monitored to see about the urea consumption and the function of the catalyst and the quality of the urea solution to be able to make a statement. To the level sensors are high due to the aggressive properties of the urea solution Requirements made.

in the State of the art are different methods for level determination known. For example, there are continuously detecting level sensors, For example, electric level sensors with a Resistance path whose resistance depends on Fluid level changes, or mechanical sensors, for example, in the form of floats, on the surface of the liquid swim and with a swivel joint and a corresponding electrical decline the rotational position are provided, and the like.

From the DE 100 57 934 A1 is a method and an apparatus for measuring in a container, in particular a fuel tank, located liquid volume out, in which the level sensor is laid along the inside of the conversion of the fuel tank and there continuously detects the liquid level.

In the DE 103 24 009 A1 a differential pressure sensor for measuring the height of the liquid in a tank, in particular the tank of a urea dosing system is described, with a first pressure receiving means for measuring a pressure at the bottom of the tank and a second pressure receiving means for measuring a reference pressure in an upper region of the tank. From the thus measured differential pressure is closed to the liquid level in the tank.

About that In addition, there are sensors that only in a single place the Detect the presence or absence of fluid. Such discrete sensors detect defined liquid levels. They are advantageous because of their lower production costs, easier assembly etc.

A However, continuous level detection is discrete Sensors are not possible without further ado.

Of the The present invention is therefore based on the problem, a method and to provide a device with discrete level sensors a continuous recording of the level height in a tank installed in a vehicle in any driving conditions of the vehicle allows.

Disclosure of the invention

The Method for level measurement in a liquid, in particular, a urea water solution receiving tank with the features of claim 1 triggers the problem individual, discrete level information a continuous Level in any driving conditions of a vehicle to investigate. The level information is not only by at least one, preferably a plurality of level sensors, but also by recording and evaluating driving status indicators Sizes determined.

For this becomes a level characterizing the level depending on at least one driving state indicator Evaluated sizes and from this to the in the Tank located amount of liquid closed. Different In terms of the basic idea of the invention, it is the tank contents to cause vibrations due to the inertia of its mass, which characteristic signal patterns on one or more sensors produce. These signal patterns contain information about the level. Therefore, if below from driving state indicators Sizes are spoken, so are in particular also such accelerations and delays meant that the liquid in the tank to corresponding vibrations stimulate.

By the in the dependent claims listed measures are advantageous developments, refinements and improvements of the method specified in the independent claim possible.

So provides an advantageous embodiment, at the same time several, the level at several different levels characterizing positions in the container characterizing To capture sizes, these sizes depending on the at least one driving state indicative Evaluate size and compare with each other and from the comparison to the amount of liquid disposed in the container close. By evaluating the at different Positions in the tank detected level information in conjunction with the driving status indicators is a precise determination of levels possible in the tank. This takes into account Method also changing driving conditions, for example by acceleration or deceleration while driving a Vehicle caused states. The procedure does not allow only the detection of states with higher precision, but also a plausibility of the results by inclusion the driving status indicators.

According to one very advantageous embodiment is provided that the several, the fill levels characterizing Sizes through several at different filling levels arranged sensors are detected. This is through interpolation and extrapolation a quasi-continuous level determination possible with discrete sensors.

According to one Embodiment is provided on a quantity of liquid close in the tank when the level sensors generate predetermined characteristic signal patterns. These signal patterns take into account given driving state indicators, for example, accelerations or decelerations of the vehicle.

So For example, it may be provided that at an unaccelerated or delayed tank on at least partial filling is closed when some of the sensors indicate the presence the liquid characterizing continuous signal generate and the rest of the sensors a the absence of the Liquid characterizing continuous signal produce.

On an accelerated or delayed partially filled Tank is closed on the other hand, if at least part of the sensors generate a pulsating signal and the rest of the sensors a Presence of liquid characterizing continuous Signal or the absence of the fluid generate a characterizing continuous signal. If, for example three sensors in different filling levels are arranged, for example, the middle sensor generates pulsating signal, which is located under it in the tank, that is a lower level sensor detects the presence fluid characterizing continuous signal and the one above, that is, the one above higher level detecting sensor a the absence the liquid characterizing continuous signal.

The above-described embodiments of the method can be combined with each other. For example, the provision a level at a not accelerated or not delayed tank are compared with the level signal with an accelerated or delayed tank.

The The invention further relates to a device for implementation the method in which the level sensors in different Level heights are arranged and the signals these level sensors in a circuit device, which also supplied driving stateindicative quantities be processed.

The Finally, the invention also relates to a computer program and a computer program product to be executed of the method are suitable.

Brief description of the drawings

embodiments are shown in the drawing and closer in the following description explained.

In FIG. 1 is a schematic view of an invention Apparatus for carrying out the inventive Process illustrated.

embodiments the invention

Shown in the figure is a tank 100 For example, a urea water solution tank containing a urea water solution 110 up to a filling level 111 located. Arranged at different heights are sensors 101 . 102 . 103 which detect a level 1 level, for example a 15% liquid fill, a level 2 level, such as a 50% liquid fill, and a level 3 level, such as a 90% liquid fill.

The signals of these sensors 101 . 102 . 103 are in a signal preprocessing device 120 preprocessed and via signal lines 121 a multiplexer MUX 130 fed. From there they can be reached via a CAN bus, for example 131 to an engine control unit 200 where they are in a dedicated circuit device 210 or in a program implemented for this purpose 210 are processed.

The control device or the circuit device 210 or the corresponding program will also be indicative of driving status 300 , For example, the acceleration or deceleration signals characterizing supplied.

The through the level sensors 101 . 102 . 103 recorded values are evaluated as a function of the driving state-indicative quantities. The basic idea of the invention is to determine a continuous fill level from a few, discrete fill level information and also to take account of driving state-indicative variables to increase the precision of the fill level determination, that is, for example, accelerations or delays that regularly occur in vehicles that characterize variables. In this case, both a level determination is made by a plurality of superimposed level sensors in non-accelerated or non-decelerated vehicle and closed by interpolation or extrapolation to a corresponding level, as well as a level determination in a delayed or accelerated vehicle and determination of the level. By detecting signal patterns, the level is closed.

With In other words, the essence of the method described below in it, a liquid in a jar, here in a tank by accelerating the vessel to vibrate or "sloshing" to stimulate and due this swinging a determination of the fluid level make.

During the acceleration process arises in the edge area of the tank 100 due to the inertia of the liquid an increased level. Is the level of the tank 100 sufficiently close below the next level sensor, the latter will emit a signal characterizing the presence of liquid during the acceleration process.

After completion of the acceleration process, a vibration pattern is established, which is defined by the natural frequency of the system and thus by the liquid properties, the tank geometry, ie the tank dimensions and in particular the liquid level. For example, is the level in the tank 100 below one of the discrete sensors, for example below the sensor 102 As shown in the figure, the sensor becomes 102 generate a "pulsating" signal when "vibrating" the liquid. In contrast, the sensor shows 101 , which is constantly covered by the liquid and remains covered even when vibrating liquid, a continuous, the presence of liquid characterizing signal. The sensor 103 , which is not wetted by liquid even when swinging, however, indicates a continuous, the absence of liquid characterizing signal.

By modeling this vibration pattern, the level can be calculated. It will be in the controller 200 For example, previously deposited certain vibration patterns that suggest empirically determined levels.

A major advantage of the method is that the necessary for the evaluation required driving state variables, such as acceleration states or deceleration states of the engine control unit 200 Any information of acceleration, speed, etc. or of ABS signals, wheel speed signals, ESP signals, signals from an automatic transmission, which is available anyway, can be derived and determined.

The method described above can either - as mentioned - in the form of a corresponding circuit 210 , for example, part of the controller 200 can be realized. Particularly advantageously, the method described above is implemented as a computer program, for example as a subroutine in the control unit 200 , The program code may be stored on a machine-readable medium that the controller 200 can read.

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

• DE 10057934 A1 [0004]
• - DE 10324009 A1 [0005]

Claims (11)

Method for filling level measurement in a tank receiving a liquid, in particular a urea water solution ( 100 ), characterized by the following steps: - at least one driving state-indicative variable ( 300 ) detected; A variable characterizing the level at at least one point characterizing a tank level (Level 1, Level 2, Level 3) is detected; The size characterizing the level is evaluated as a function of the at least one driving state-indicative variable and from this to the one in the tank ( 100 ) amount of liquid is closed. A method according to claim 1, characterized in that - at the same time a plurality of filling levels at a plurality of different level heights characterizing points (Level 1, Level 2, Level 3) in the tank 100 characterizing quantities are detected; That these variables are dependent on the at least one driving state-indicative variable ( 300 ) and compared with each other, and that from the comparison to that in the tank ( 100 ) liquid is closed. A method according to claim 2, characterized in that the plurality of variables characterizing the level by a plurality of at different level heights (Level 1, Level 2, Level 3) arranged, the presence of liquid detecting sensors ( 101 . 102 . 103 ). Method according to claim 3, characterized in that the presence of an amount of liquid in the tank ( 100 ) is closed when the sensors ( 101 . 102 . 103 ) generate predefinable signal patterns. A method according to claim 4, characterized in that in an unaccelerated or delayed tank on an at least partially filled tank ( 100 ) is closed when a part of the sensors ( 101 . 102 . 103 ) generate a continuous signal characterizing the presence of liquid and the remainder produce a continuous signal characterizing the absence of liquid. A method according to claim 4, characterized in that an accelerated or delayed, at least partially filled tank ( 100 ) is closed when at least a part of the sensors ( 101 . 102 . 103 ) generate a pulsating signal and the rest of the sensors ( 101 . 102 . 103 ) generate a continuous signal characterizing the presence of liquid and / or a continuous signal characterizing the absence of liquid. Method according to claim 6, characterized in that from the pulsating signal of the at least one part of the sensors ( 101 . 102 . 103 ) and from the continuous, the presence of liquid characterizing signal and / or the absence of liquid characterizing signal of the rest of the sensors ( 101 . 102 . 103 ) is closed to the capacity in the tank. Method according to one of the preceding claims, characterized in that the evaluation of the sensors ( 101 . 102 . 103 ) are evaluated on at least two different driving conditions, which are characterized by at least two driving state indicative quantities. Device for detecting the level in a tank, in particular in a tank ( 100 ) for a urea water solution, characterized by - presence of liquid-sensing sensors arranged at different levels (Level 1, Level 2, Level 3) ( 101 . 102 . 133 ), - at least one, at least one driving state active variable ( 300 ) sensor and - an evaluation device ( 210 ) for evaluating the signals of the tank level sensors as a function of the driving state indicator variable output by the at least one sensor detecting the driving condition (US Pat. 300 ). Computer program which carries out all steps of a method according to one of claims 1 to 8, when it is stored on a computing device, in particular the control device ( 200 ) runs an internal combustion engine. Computer program product with program code, which is stored on a machine-readable carrier, for carrying out the method according to one of claims 1 to 8, when the program is stored on a computer or the control unit ( 200 ) is performed.