DE102010043937A1 - Method for detecting refueling operation of urea in auxiliary tank in selective catalyst reduction (SCR) system of motor vehicle, involves stopping the filling operating cycle by comparing stored value and current value of fuel level - Google Patents

Abstract

The level of fuel in auxiliary tank in selective catalyst reduction system is detected (110) by a level sensor, after detecting standstill state of the tank for predetermined waiting time. A subsequent filling operating cycle is started (132) based on the detected level of fuel in tank. The filling operating cycle is stopped on the basis of a comparison (140) between the stored value and current value of fuel level in tank. Independent claims are included for the following: (1) computer program for detecting refueling operation of fuel tank; and (2) computer program product for detecting refueling operation of fuel tank.

Description

The invention relates to a method for detecting a refueling operation of a tank subjected to movements, in particular a tank of an SCR system of a motor vehicle. The subject matter of the present invention is also a computer program and a computer program product with a program code which is stored on a machine-readable carrier for carrying out the method.

State of the art

Fill levels of liquids, for example tank levels in vehicles, are detected, for example, by tank level sensors or sensors. In this case, tank level gauge, which allow continuous detection of the level and level gauge, which only detect whether liquid is present at a donor position or not, so-called "discrete" level sensor, distinguished. The former are for example in fuel tanks of vehicles in use, the latter are preferably used in, for example, additional tanks, such as SCR systems.

In modern diesel vehicles, the so-called SCR technology is used. This is understood to mean the selective catalytic reduction of nitrogen oxides in exhaust gases of internal combustion engines as well as, moreover, of combustion plants. The chemical reaction of the reduction is selective. This means that not all exhaust gas components are reduced, only nitrogen oxides (NO, NO ₂ ). The reaction requires ammonia, which is added to the exhaust gas. The products of the reaction are water and nitrogen.

In vehicles, the required ammonia is no longer used in pure form, but in the form of an aqueous urea solution. The solution is injected into the exhaust line before the SCR catalyst, for example by means of a metering pump or an injector. From the urea-water solution formed by a hydrolysis reaction ammonia and water. The ammonia thus produced can react in a special SCR catalyst at the appropriate temperature with the nitrogen oxides in the exhaust gas. The amount of injected urea depends on the (engine) nitrogen oxide emission and thus on the instantaneous engine speed and torque. The consumption of the urea-water solution depends on the raw emissions of the engine about 2-8% of the consumed diesel fuel. For this reason, a tank with urea-water solution must be installed in the vehicle and the level in this tank must be recorded. The sensor signals generated by both continuous level sensors and discrete level sensors in a liquid-filled reservoir in a vehicle are strongly influenced by driving dynamics factors, such as acceleration and deceleration, cornering accelerations, uphill gradients and downhill gradients.

In order to plausibilize the signals of a level sensor of a tank, the acceleration and deceleration processes and the like, is seen from the DE 10 2010 029 775.5 a prominent method to determine the road inclination and to assess the signals depending on the roadway inclination.

The level signals - regardless of the type of detection, ie whether they are detected by means of continuous level sensors or discrete fill level or level sensors - must be recorded very precisely as exhaust gas-relevant quantities very precisely. In particular, influences due to the driving dynamics or the road condition should be largely eliminated.

If there is no reducing agent in the tank, the permissible emission values are exceeded. In order not to let this state occur, the driver of a vehicle must be warned in good time before falling below a residual amount, which allows a certain residual range, and be asked to refuel. The refueling of a urea-water solution is usually carried out as part of the service program during workshop visits of the vehicle by the workshop staff. Refueling, however, can also be done by the driver himself. It can be assumed that the driver does not completely fill the tank, but merely fills a minimum amount stipulated in the manual of the vehicle into the tank. This amount of refueling should be detected quickly and reliably.

To preclude erroneous fueling detection due to, for example, vehicle bank angles, systems known in the art are believed to move the vehicle. In addition, a slosh signal is processed. The signal is filtered. Since the signal changes after a refueling process, the filter effect must be adjusted accordingly. Such a function is difficult to apply because of its high complexity, moreover, it proves to be less robust, so that incorrect Nachzustankungserkennungen may occur, in particular, the driver himself refills can not be distinguished from a complete filling of the SCR tank due to a service performed become.

It is therefore an object of the invention to provide a method for detecting a refueling operation of a tank subject to movement, and more particularly a tank of an SCR system, which enables a precise detection of refueling and in particular refueling operations.

Disclosure of the invention

Advantages of the invention

• – nach Erkennen eines Stillstands des Tanks wird eine vorgebbare Wartezeit gewartet;
• – nach Ablauf der Wartezeit wird der Füllstand mittels wenigstens eines Levelsensors erfasst und gespeichert;
• – zu Beginn eines darauffolgenden Fahrzyklus wird der Füllstand mittels des wenigstens einen Levelsensors erfasst und auf der Basis eines Vergleichs zwischen dem gespeicherten Wert und dem aktuellen Wert des Füllstands auf einen Betankungsvorgang geschlossen.

This object is achieved in a method for detecting a fueling operation of a tank subjected to movements, in particular of a tank of an SCR system of a motor vehicle, by the following steps:

• - After detecting a standstill of the tank a predetermined waiting time is waited;
• - After the waiting time, the level is detected and stored by means of at least one level sensor;
• - At the beginning of a subsequent drive cycle, the level is detected by means of the at least one level sensor and closed on the basis of a comparison between the stored value and the current value of the level on a refueling operation.

The invention makes use of the fact that refueling can only take place while stationary. In this phase, therefore, a level detection is made. The level determined and stored in this way is compared with a level detected in a subsequent driving cycle and from this a refueling process is concluded.

By detecting the level at rest of the vehicle driving dynamics influences or influences due to the route profile to the level can be completely excluded. In this way, a level detection is possible even with a discrete level or level sensor (DLS), which has only a number of arranged at different heights pins and insofar can only determine whether the liquid has a higher liquid level than one or more of the pins , In other words, a precise Nachgefankungserkennung also possible with relatively simple design and therefore inexpensive discrete level sensors.

Advantageous embodiments and further developments of the method are the subject of the dependent claims on claim 1.

Thus, the predeterminable waiting time is advantageously chosen so that it is long enough for calming the sloshing in the tank, but at the same time shorter than the time from which it would be possible after vehicle standstill refueling urea-water solutions. The time is preferably between 10 and 60 seconds, in particular between 15 and 30 seconds, and especially between 20 and 25 seconds. After 20 to 25 seconds, the sloshing in the tank has decreased so much that a signal distortion can be largely excluded, conversely, after such a short time is not expected that already hard-water solution is refilled.

The detection of a standstill of the tank, for example, by means of a speedometer signal and / or other, the movement and acceleration of a vehicle detecting sensors, in particular acceleration sensors, yaw rate sensors and the like. This sensor is present in many modern vehicles anyway. Already the tacho signal provides a very reliable statement about the stoppage of the vehicle and thus a standstill of the tank.

The comparison of the fill level value detected in the idle state of the tank with the aid of the discrete level sensor with the fill level value detected with the aid of the discrete level sensor in a subsequent drive cycle is preferably such that when the measured current value characterizing the fill level is stored Value is different by a predefinable size, a refueling is concluded. The predeterminable variable may be, for example, a difference, but it may also be, for example, a signal which characterizes the different wetting of the pins in both cases, or the like.

The method can be implemented very advantageously as a computer program and run on a computer, in particular the control unit of an internal combustion engine. In this case, a computer program product with program code that is stored on a machine-readable carrier can be provided. This makes it possible to "play in" the program into existing ECUs as it were and to provide appropriate (subsequent) extensions to existing SCR systems that have discrete level sensors. This is especially because no additional hardware is required. Rather, it is the hardware already used in SCR systems, i. H. the discrete level sensor (DLS) used to implement the method.

Brief description of the drawings

The method of recognizing a refueling operation of a tank subjected to movement will be described below in connection with FIG Drawing explained in more detail. In the figure, a flowchart of an embodiment of the method according to the invention is shown schematically.

Embodiments of the invention

The method described below is used in SCR systems of motor vehicles that have a known discrete level sensor (DLS). Such discrete level sensors have a plurality of pins stacked in a tank. Wetting of the pins leads to a change in the output signal of such level sensors. Depending on the number of wetted, stacked pins, a statement about the level can be made. Such sensors do not allow continuous level detection, but only allow the detection of the presence of a liquid in a certain height in the tank, namely the height at which each of the pin is arranged. These discreet level sensors (DLS) are inexpensive to produce and essentially provide very reliable signals, but a precise detection of the tank level is only possible with them to a limited extent. In particular, with such discrete level sensors Nachgemankungsvorgänge small amounts can not be detected easily. Such refueling is required if the reducing agent, i. H. the urea-water solution in the SCR tank is running out. In this case, the driver must be warned and made aware of the remaining range remaining. If there is no reducing agent in the tank, the statutory emission limits are exceeded, which should be avoided. The refilling of the SCR tank with reducing agent now takes place not only workshop in the service, but can also be made by the driver himself, in which case only a minimum amount is refilled according to the vehicle handbook. The aim of the invention is to reliably detect such refueling. This is not easily possible because a vehicle is continuously subjected to acceleration and deceleration processes, both longitudinal and lateral accelerations. In addition, the route profile, z. B. driving on very large slopes or gradients affect the liquid level in the SCR tank. This could be eliminated in principle by appropriate filtering of the signals. However, such filter functions are difficult to apply due to the high complexity. In addition, they prove to be less robust, so that incorrect Nachzustankungserkennungen can not be excluded.

The following method according to the invention described in connection with the figure enables a precise recognition of refueling, in particular also with the aid of a discrete level sensor. The basic idea of the invention is to carry out the fill level in a standstill phase of the vehicle or of the tank and to compare the fill level detected in this way with the fill level which is detected during a subsequent drive cycle and to make statements about refueling.

An embodiment of the method will be described below in conjunction with the figure. After a start 100 is first in a query 110 checked whether the vehicle is stationary. This can be done for example on the basis of the speedometer signal. If the tacho signal indicates 0, it must be assumed that the vehicle is not moving. Alternatively or additionally, the signals of other sensors that are provided in modern vehicles, such as acceleration sensors or yaw rate sensors or the like, can be detected and evaluated. If in the query 110 no standstill is detected, before step 110 jumps back. However, when a stoppage is detected, in one step 120 first set a time parameter t to 0: t = 0.

In a subsequent step 121 the time parameter is increased by a predefinable increase value Δt: t = t + Δt.

In a subsequent query 123 it is checked whether the time parameter t has reached a predefinable waiting time t _w , so it is checked whether t = t _w . If not, before step 121 jump back and there is a further increase time of the parameter: t = t + Δt.

However, when the waiting time is reached, the level becomes one step 130 measured and the measured level value F1 stored as a level value F: F = F1.

The waiting time t _w is chosen so that on the one hand it is ensured that a sloshing tank has calmed down, ie that sloshing operations are largely completed. In addition, the time is chosen so short that it is ensured that a refueling of the SCR tank has not taken place. The time is selected, for example, at an interval of 10 to 60 seconds, and more preferably in a range of 20 to 25 seconds. After 20 to 25 seconds, the sloshing is reduced so much that a faulty level detection can be virtually ruled out, at the same time can be assumed that a refueling has not occurred.

In a subsequent step 132 a check is made as to whether a subsequent drive cycle has started Has. This can in turn be checked with the help of, for example, the tachometer signal. If the tacho signal has assumed a value greater than 0, it must be assumed that the vehicle has set in motion again. In a corresponding manner, the above-mentioned sensor signals of acceleration sensors, yaw rate sensors and the like can also be evaluated. If the query 132 indicates that a drive cycle has not started yet, before step 132 jumped back and, so to speak, waited until a driving cycle began. If this is the case, the level is detected and the new level F2 compared with the stored level F1. This is done in one step 134 the difference ΔF = F2 - F1 formed and in a query 140 checked whether ΔF is greater than a predeterminable level value F _V. If this is the case, it must be assumed that refueling has taken place. This will be done in one step 141 spent and in one step 142 the level F2 is stored as the current level F _A and further processed. If, on the other hand, the query 140 indicates that the difference is greater .DELTA.F F _V is not, in step 145 issued that no refueling has occurred. In this case, before step 110 jump back and the procedure begins again. Both the value F2 and the value F1 or, for example, an average value of these two values (F1 + F2) / 2 can be used as the current fill level value F _A.

The method can be implemented as a computer program, it can be stored on a computer program product, which can be read, for example, from a control unit of a vehicle. In this way, retrofitting of existing systems is readily possible, since additional hardware for realizing the method according to the invention is not required.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010029775 [0005]

Claims (6)

Method for detecting a refueling operation of a tank subjected to movements, in particular a tank of an SCR system of a motor vehicle, characterized by the following steps - After detecting a standstill of the tank a predetermined waiting time is waited; - After the waiting time, the level is detected and stored by means of at least one level sensor; - At the beginning of a subsequent drive cycle, the level is detected by means of the at least one level sensor and closed on the basis of a comparison between the stored value and the current value of the level on a refueling operation. A method according to claim 1, characterized in that the waiting time is chosen so long that a sloshing of the liquid disposed in the tank has subsided as far as possible and at the same time so short that it can be assumed that refueling of the tank has not taken place, in particular Time is chosen so that it is between 10 to 60 seconds, in particular between 15 to 30 seconds and preferably between 20 and 25 seconds. A method according to claim 1, characterized in that the detection of a standstill of the tank by means of a speedometer signal and / or further the movement and acceleration of a vehicle detecting sensors, in particular acceleration sensors, yaw rate sensors takes place. A method according to claim 1, characterized in that when the measured current value characterizing the level is different from the stored value by a predeterminable size, a refueling is concluded. Computer program that executes all steps of a method according to one of claims 1 to 4, when it runs on a computing device, in particular the control unit of a vehicle. 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 4, when the program is executed on a computer or a control unit of a vehicle.

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