WO2010077188A1

WO2010077188A1 - Urea level metering device.

Info

Publication number: WO2010077188A1
Application number: PCT/SE2008/000750
Authority: WO
Inventors: Sigurd Sonderegger; Magnus Bernhardsson
Original assignee: Volvo Lastvagnar Ab
Priority date: 2008-12-29
Filing date: 2008-12-29
Publication date: 2010-07-08
Also published as: WO2010077188A8

Abstract

The invention relates to a urea level metering device (10) particularly for use in a urea tank (16) of a vehicle, particularly a commercial vehicle, more particularly a truck, comprising a sensor body (18) with one or more sensing units (42; 42a) and a level indicator (34) for indicating a urea level in the urea tank (16) by activating one or more of the sensing units (42; 42a), wherein a sensor device (14) is provided for detecting a contamination in the urea tank (16) comprising one or more contamination indicators (38) coupled to the sensor body (18).

Description

D E S C R I P T I O N

Urea Level Metering Device.

TECHNICAL FIELD

The invention relates to a urea level metering device according to the preamble of claim 1.

BACKGROUND OF THE INVENTION

In modern vehicles, particularly commercial vehicles, more particularly trucks, urea is used for after treatment of exhaust gas in catalytic converters with selective catalytic reduction (SCR). It is known to measure the level of urea in a urea tank by a level metering device comprising a sensor body with a multitude of REED sensors indicating the level of urea dependent on a signal provided by a floater which floats on the urea.

The presence of a contamination, particularly hydrocarbons such as fuel, in particular diesel, in the urea tank will negatively affect components, such as a urea pump, a urea injector, a catalyst, etc. Hence detecting a contamination in a urea tank is an important issue.

WO 98/38663 A1 discloses a sensor with a switching arrangement for triggering an alarm in the event of the content of a brake fluid container being contaminated by hydrocarbon. A plastics body which swells in the contaminating liquid displaces the floater in a liquid container in the same direction which determines of movement of the floater when the liquid level decreases. The floater can trigger an alarm when the liquid is contaminated in the same way as when the liquid level drops significantly.

SUMMARY OF THE INVENTION It is an object of the invention to provide a urea level metering device which provides increased safety for attached components against contamination with hazardous materials.

The object is achieved by the features of the independent claim. The other claims and the description disclose advantageous embodiments of the invention.

A urea level metering device particularly for use in a urea tank of a vehicle, particularly a commercial vehicle, more particularly a truck, comprising a sensor body with one or more sensing units and a level indicator for indicating a urea level in the urea tank by activating one or more of the sensing units, wherein a sensor device is provided for detecting a contamination in the urea tank comprising one or more contamination indicators coupled to the sensor body.

Favourably, as a response of an interaction of the coupling member with the contamination the one or more contamination indicators can float or can be locked relative to the sensor body. According to the invention at least one coupling member can be used which changes its shape, i.e. swells or shrinks or disintegrates or dissolves, as a result of contact with a contamination, particularly hydrocarbons, more particular fuel, e.g. diesel, being present in the urea tank. The change of shape of the coupling member can be used to create a signal, in particular an electrical signal, which in turn may be transmitted to some kind of warning system. Accordingly ,_a contamination in the urea tank can be easily and reliably detected.

Particularly, the sensor device can be integrated in a fluid level measuring device for measuring the level of urea in a urea tank. Such prior art fluid level measuring devices are known have a vertical bar and a floater arranged on the bar. Dependent on the current level of urea the floater takes a position relative to the bar which gives an electrical signal unique to the current fluid level. Favourably, the contamination indicator can use the same wiring, feedthroughs and connections as the level indicator. It is not necessary to adapt the urea tank or to provide additional connections. Advantageously, existing urea tanks can be easily retrofitted with such a sensor device. According to a favourable embodiment of the invention, the sensor device can be coupled to the sensor body in a region not in use for the level indication yielding a compact construction of the level metering device. Particularly, the interaction of the coupling member with the contamination can e.g. cause a movement of the at least one contamination indicator relative to the sensor body. Thus a change from a first operational state (below a predetermined contamination level) into a second operational state (at or above a predetermined contamination level) can be directly detected by the sensing units to create the signal. By using a contamination indicator for detecting a contamination it is possible to combine the sensor device detecting contamination with the level metering device in an easy and space efficient way. The level metering device can work independently of the contamination detecting device and thus is able to give information about the level of urea even if contamination has been detected. In particular, it is possible to add a second floater to a vertical bar of a level metering device in the lower region of the level metering device. The contamination indicator may be connected to the bottom of the urea tank or of the level metering device via the coupling member. This implies that a change of the shape of the coupling member will change the position of the contamination indicator relative to the vertical bar. The already existing equipment for receiving signals from the level indicator of the level metering device can also be used for receiving a corresponding signal from the contamination indicator as an indication of contamination being present in the urea tank. This reduces the engineering effort andjhe costs for a contamination detector.

According to a further favourable embodiment of the invention, the one or more contamination indicators can be fixed in a position by at least one coupling member as long as a content of the contamination is below a predetermined level. The level metering device can operate undisturbed.

According to a further favourable embodiment of the invention, the one or more contamination indicators can be disconnected from the position in the presence of the contamination at or above a predetermined level. An error signal can be issued as a reaction of the movement of the one or more contamination indicators. According to a further favourable embodiment of the invention, the one or more contamination indicators can be locked in the position in the presence of the contamination at or above a predetermined level. This enforced fixation of the contamination indicator can be particularly used in an embodiment when the contamination indicator is integrated in the level indicator. If no error signal related to a malfunction of the level indicator is issued and the urea level is estimated to have changed and the level indicator does not respond accordingly, it can be derived that a contamination is present in the urea tank.

According to a further favourable embodiment of the invention, one or more of the contamination indicators are floatable in urea. When released from the original position at the level metering device in case of contamination, the contamination indicator can behave like a floater and its movement detected e.g. by REED switchs. In this way, already existing floaters for the level metering device can be used for the contamination detection.

According to a further favourable embodiment of the invention, one or more contamination indicators can be integrated in the level indicator. In this case it is favourable to provide the contamination indicators with contamination sensitive material which swells and locks the level indicator in the presence of the contamination.

According to a further favourable embodiment of the invention, at least one contamination indicators can be functionally arranged in series with the level indicator. Particularly, the contamination indicator can be arranged in an area of the level metering device not used for the level metering.

According to a further favourable embodiment of the invention, at least one contamination indicator can be functionally arranged in parallel with the level indicator, so that the range of the level-metering-portion can be expanded to the bottom of the urea tank. Further it is easy to retrofit an existing level metering device with such a contamination sensor device. According to a further favourable embodiment of the invention, the level metering device can comprise one or more REED switches. REED switches can be connected to an electrical circuit for detecting electrical signals for detecting the contamination. REED switches are well-suited for fluid level metering devices since they are sealed in tubes, so that the contacts are protected from corrosion or other chemical influences. As the moving parts are small and lightweight, REED switches can switch very fast. REED switches can be switched through walls, so that they in particular can be embedded in the sensor body. Due to their encapsulated construction, REED switches can be used e.g. in sensible ambient, such as explosion-prone areas.

According to a further favourable embodiment of the invention, one or more REED switches can be responsive to at least one contamination indicator. The contamination indicator can use the same sensors employed by the level metering device. Additional to the other advantages of REED switches, a combination with the contamination indicator allows to detect easily, reliably and exactly each movement of the contamination indicator relative to the REED contact or a fixation of the contamination indicator. For this the contamination indicator particularly can comprise a magnetic field for switching the REED switches. Particularly the contamination indicator can comprise a permanent magnet for that purpose.

According to a further favourable embodiment of the invention, the coupling member can comprise at least one of rubber, polycarbonate, polymethyl methacrylate, polystyrene, ethylene-propylene-terpolymer (EPDM). Those materials are very sensitive for contamination comprising hydrocarbon, e.g. fuel, such as diesel. They can react in the contaminating liquid and dependent on the design of the sensor device can release, move or fix the relevant contamination indicator for activating one or more sensing units. For instance, the contamination indicator attached with the coupling member can be released and float (in case of a floater) or drop to the bottom of the tank which can be detected by adequate sensor units.

According to a further favourable embodiment of the invention, at least one contamination indicator in a first operational state can be embedded in the coupling member. In contact with the contamination the contamination indicator can be released or, when the coupling member increases in volume when in contact with the contamination, can be locked to a desired position. In particular a floater of the level metering device can be coated with the material of the coupling member on the inside surface directed towards the vertical bar. If contamination is present the coupling member will swell and the floater will get stuck on the bar. Then it can be noticed that the measured level of urea does not changed despite the fact that urea is injected. This can be detected as an indication that contamination is present in the urea tank.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention together with the above-mentioned and other objects and advantages may best be understood from the following detailed description of the embodiments, but not restricted to the embodiments, wherein is shown schematically:

Fig. 1 a first embodiment of a level metering device for urea comprising a sensor device for detecting a contamination in a urea tank according to the invention; Fig. 2 a detail drawing of the level metering device of Fig. 1 in the area there in a first operational state;

Fig. 3 a detail drawing of the level metering device of Fig. 1 in the area there in a second operational state;

Fig. 4 a urea pumping system comprising a level metering device similar to that of Figs. 1 to 3; Fig. 5 a second embodiment of a level metering device for urea comprising a sensor device for detecting a contamination in a urea tank according to the invention, wherein the sensor device has a separate rod as sensor-body portion; Fig. 6 a detail drawing of the level metering device of Fig. 5 in the area

VI/VII there in a first operational state; Fig. 7 a detail drawing of the level metering device of Fig. 5 in the area

VI/VII there in a second operational state; and

Fig. 8 a third embodiment of a level metering device for urea comprising a sensor device for detecting a contamination in a urea tank according to the invention, wherein one combined floater is used for both, level measurement and detecting the contamination.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

In the drawings, equal or similar elements are referred to by equal reference numerals. The drawings are merely schematic representations, not intended to portray specific parameters of the invention. Moreover, the drawings are intended to depict only typical embodiments of the invention and therefore should not be considered as limiting the scope of the invention.

Fig. 1 depicts schematically a first embodiment of a level metering device 10 for urea 12 comprising a sensor device 14 for detecting a contamination comprising hydrocarbon, particularly diesel, in a urea tank 16 of a truck. The level metering device 10 and the sensor device 14 are shown in detail in Fig. 2 in a first operational state without contamination (or wit contamination below a predetermined level) present and in Fig. 3 in a second operational state with contamination (at or above a predetermined level) present.

The sensor device 14 comprises a sensor body 18, which comprises as a vertical rod 20.

The upper end of the sensor body 18 is fixed in a connecting block 22 for electrical lines 24 of the sensor device 14 and the level metering device 10. The electrical lines 24 are shown in Figs. 2 and 3. The connecting block 22 is supported in an upper wall of the urea tank 16. The lower end of the vertical rod 20 is connected to a horizontal base rod 26. The complete device 10 may be fixed on the top of the tank. The horizontal rod 26 may consist of a urea suction pipe with a urea filter at its end and a coil containing engine coolant to defrost the tank 16 in cold climate conditions.

The rod 20 of the sensor body 18 is divided in a level-metering-device portion 28, which is above a float stop 30, shown in Figs. 2 and 3, and a contamination- sensor-device portion 32 below the float stop 30. For clarity reasons, the float stop 30 is not represented in Fig. 1.

The level-metering-device portion 28 is for measuring the level 36 of urea 12 in the urea tank 16. The contamination-sensor-device portion 32 is for detecting contamination in the urea 12.

A level-metering floater as level indicator 34 is movable longitudinally on the level- metering-device portion 28 of the sensor body 18. The level indicator 34 is floatable in urea 12 indicating the urea level 36 in the urea tank 16.

The float stop 30 prevents the level indicator 34 from moving to the contamination- sensor-device portion 32, in case the urea level 36 goes below the float stop 30.

A contamination indicator 38 embodied as a floater is located on the contamination-sensor-device portion 32. The contamination-detecting floater 38 is also floatable in urea 12, but in a first operational state, shown in Figs. 1 and 2, where no contamination is present in the urea 12, the contamination indicator 38 is fixed relative to the base rod 26 by means of a coupling member 40. For clarity reasons, the coupling member 40 is not represented in Fig. 1 , but in Figs. 2 and 3. As can be seen in Fig. 2, in the first operational state the contamination indicator 38 is partly embedded in the coupling member 40 and so is coupled to the coupling member 40. The contamination indicator 38 can also be embedded completely in the coupling member 40 in the first operational state.

The coupling member 40 is made of contamination sensitive rubber, which can be deformed when interacting with the contamination. By deforming, the coupling member 40 releases the contamination indicator 38, so that in the second operational state, shown in Fig. 3, the contamination indicator 38 moves due to its buoyancy - or due to another force such as applied by an elastic element working against coupling member 40 - in the urea 12 longitudinally on the contamination- sensor-device portion 32 of the sensor body 18. The float stop 30 prevents the contamination indicator 38 from moving to the level-metering-device portion 28. By this, the contamination indicator 38 is functionally arranged in series with the level- metering-device portion 28 and its level indicator 34.

Alternatively, the contamination indicator 38 can be held between two biased elastic tension elements, for example two rubber bands. One of the tension elements can be adapted for interacting with the contamination, so that the contamination indicator 38 moves if contamination is present. By using elastic tension elements, the contamination detection advantageously is mostly insensitive to vibrations and independent of gravity.

As can be seen in Figs. 2 and 3, the vertical rod 20 of the sensor body 18 comprises five REED switches 42 as sensing units. The upper three REED switches 42 belong to an electrical circuit of the level-metering-device portion 28. The lower two REED switches 42 belong to a electrical circuit of the contamination-sensor-device portion 32.

The REED switches 42 of the level-metering-device portion 28 are electrically parallel to each other connected with two electrical lines 24. The REED switches 42 of the contamination-sensor_:device portion 32 are electrically parallel to each other connected with two different electrical lines. Each electrical line 24 is connected by means of the connecting block 22 via a line 44 with an electronic unit 46. For clarity reasons, only the connections of the upper REED switch 42 of the level-metering-device portion 28 to the corresponding electrical lines 24 are shown in Figs. 1 and 2. The electrical lines from the contamination-sensor-device portion 32 and the corresponding lines from the connecting block 22 to the electronic unit 46 are not shown in the figures.

One of the electrical lines 24 of each circuit is subdivided in sections with specific electrical resistances. Between two of those sections each, one of the REED switches 42 is connected to this sectionized electrical line 24. If one of the REED switches 42 of the circuit is activated, an electrical loop will be realised by the corresponding lines 44, the electrical lines 24 and the activated REED switch 42. By this, all sections of the sectioned electrical line 24, which are between the connecting block 22 and the activated REED switch 42, are switched in series and so are the corresponding specific electrical resistances. Depending on which REED switch 42 is activated, the total resistance as the sum of the resistances in the loop varies, which results in different voltage output for each REED switch 42. The specific voltage output will be detected by the electronic unit 46. However, the electrical scheme can look different with regard to the connection of the quality REED switches 42 to get a specific voltage for each REED switch 42. It is also possible to use one common adequate circuit for both, the level-metering-device portion 28 and the contamination-sensor-device portion 32.

On signals caused by the REED switches 42, the electronic unit 46 is adapted to start a warning procedure which can comprise a warning signal and/or a control procedure for a urea pump (not shown).

The REED switches 42 are responsive to a movement of the contamination indicator 38 and the level indicator 34 relative to the rod 20 of the sensor body 18. For this the contamination indicator 38 and the level indicator 34 each comprise a permanent magnet (not shown). When the contamination indicator 38 or the level indicator 34 reaches one of the REED switches 42 this will cause the REED switch 42 to close and a specific voltage signal is being sent to the electronic unit 46. The amplitude of the voltage signal is dependent on the REED switch 42 caused to be closed, which can be identified by the electronic unit 46 accordingly. Since the location of each REED switch 42 on the rod 20 is known, the position and the movement of the contamination indicator 38 and the level -indicator 34 can be obtained.

The specific voltages of the from the lowest to the topmost are by way of example 0,5 Volt, 0,7 Volt, 0,9 Volt, 1 ,1 Volt and 1 ,3 Volt. The specific voltages are shown in Figs. 2 and 3 each to the left of the respective REED switch 42. Depending on a actual system used, the voltages can differ from these values. In the first operational state where the urea in the urea tank 16 is free of contamination (Fig. 2), the contamination indicator 38 is caused to activate the REED switch 42 on the lower end of the contamination-sensor-device portion 32. Hence the electronic unit 46 receives a voltage signal of 0,5 Volt. This is identified by the electronic unit 46 as being uncritical, as there is no contamination in the urea tank 16.

Further, the electronic unit 46 receives a voltage signal of 1 ,1 Volt from one REED switch 42 in the mid-position of the level-metering-device portion 28.

The electronic unit 46 identifies this voltage signal resulting from the level indicator 34 being elevated by the urea level 36 in the range of the REED switch 42 in the , mid-position of the level-metering-device portion 28. This indicates that urea 12 should be added to the urea tank 16. A warning signal can then be sent to a display unit (not shown) indicating that the urea tank 16 should be refilled with urea 12. The electronic unit 46 can be adapted to identify if urea 12 should be filled up as soon as it receives a signal voltage of 1 ,3 Volt or 1 ,1 Volt from one of the two topmost REED switches 42. If the urea level 36 decreases (not shown in the Figs.) and the level indicator 34 activates the lowest REED switch 42 of the level-metering-device portion 28, the signal voltage of 0,9 Volt will be received by the electronic unit 46. The electronic unit 46 identifies this signal as the urea level 36 being too low. A stop signal can be send to the urea pump.

In the second operational state shown in Fig. 3 the contamination indicator 38 is caused to activate the upper REED switch 42 of the contamination-sensor-device portion 32 as a response of the interaction of the coupling member 40 with the contamination. Hence the electronic unit 46 receives a voltage signal of 0,7 Volt. The electronic unit 46 now recognizes that a contamination is present in the urea tank 16. A stop signal can be sent to the urea pump to prevent that urea pump system components and further devices which are supplied by the urea pump system are negatively affected by the contamination. Further, a warning signal can be send to the display unit for informing that contamination is present in the urea tank 16. Fig. 4 shows a more realistic representation of a urea supply system 50 comprising a level metering device 10 with a sensor device 14 for detecting a contamination in a urea tank 16 similar to that of Figs. 1 to 3 to which is referred to fro a detailed explanation of the components. The urea supply system 50 shown in Fig 4 comprises also a suction and return pipe for urea, as well as of a coil for engine coolant, used for defrosting of urea. Particularly, the urea suction and urea return pipes as well as a coolant coil are all using the same opening in the tank 16.

Figs. 5 to 7 depict a second embodiment of a level metering device 10 for urea 12, wherein the sensor body 18 comprises a second vertical rod 20a which includes the contamination-sensor-device portion 32. The second rod 20a is arranged parallel to the first rod 20 with the level-metering-device portion 28. The lower end of the second rod 20a is connected to the base rod 26. The upper end is free and comprises the float stop 30. The float stop 30 prevents that the contamination- detecting floater 38 leaves the contamination-sensor-device portion 32 if being released by the coupling member 40 due to interaction with the contamination.

The contamination indicator 38 is similar to the first embodiment movable on the contamination-sensor-device portion 32 and in the first operational state without contamination held by the coupling member 40 in the lower position, which is shown in Fig. 6. The second operational state with contamination in the urea tank 16 is shown in Fig. 7. The contamination indicator 38 so is functionally arranged in parallel with the level-metering-device portion 28 and its level indicator 34 nf th^p sensor body 18.

The contamination sensor device 14 works similar to that of the first embodiment. The contamination-sensor-device portion 32 comprises two separate REED switches 42a similar to the two REED switches 42 of the contamination-sensor- device portion 32 of the first embodiment. The lower REED switches 42a is adapted to create a 0,5 Volt signal if activated by the contamination indicator 38, the upper one is adapted to create a 0,7 Volt signal if activated. The electrical lines 24 lead from the REED switches 42a to the connecting block 22 and to corresponding lines 44. For clarity reasons only two of the four lines 44 of the REED switches 42a and the REED switches 42 are depicted in Fig. 7. Different to the first embodiment, the level-metering-device portion 28 extends over the complete first rod 20 until the base rod 26 at the bottom of the urea tank 16, so that the two REED switches 42 on the lower end can also be used for level metering. Thus it is possible to adapt the electronic unit 46 in a way that the stop signal for the urea pump is only created when the level indicator 34 reaches the REED switches 42 on the lower end of the level-metering-device portion 28. The lowermost of the two REED switches 42 is adapted to create a 0,5 Volt signal if activated by the level indicator 34, the second lowest REED switches 42 is adapted to create a 0,7 Volt signal if activated.

In the second embodiment, alternatively, for the level-metering-device portion 28 and the contamination-sensor-device portion 32 one common adequate electronic circuit can be used with only two electrical lines 24 and two lines 44. In this case, different output voltages for the lower two REED switches 42 of the level-metering- device portion 28 and the two REED switches 42a of the contamination-metering- device portion 32 will be used. For example for the REED switches 42a voltages of 0,5 and 0,7 V can be used. The level measurement can start at the lowest REED switch 42 with 0,9 V. The second REED switch 42 gives a voltage of 1 ,1 V and so on.

Fig. 8 shows a third embodiment of a level metering device 10 for urea 12 comprising a sensor device 14 for detecting a contamination in a urea tank 16. Unlike to the first two embodiments, a coupling member 40a is integrated as a coating or as inserts of contamination sensitive rubber on the inner surface of a combined level-metering/ contamination indicator 38 surrounding a combined level-metering-device/sensor device portion 28 of the sensor body 18. A separate contamination-sensor-device portion and a separate contamination-detecting floater are not necessary.

Instead of causing a movement of the level-metering/ contamination indicator 38 the interaction of the coupling member 40a with the contamination causes in the third embodiment an enforced fixation of the floater relative to the sensor body 18. The electronic unit 46 identifies the presence of the contamination in that the signal voltage of the REED switches 42 does not change, if urea 12 is filled in the urea tank 16 since the level indicator / contamination indicator 38 does not move although the urea level 36 rises.

The invention is not limited to urea tanks 16 of trucks. The invention can also be applied for other kinds of vehicles, particularly commercial vehicles. The invention can further be applied to other kinds of urea tanks 16 in particular for after treatment of exhaust gas in catalytic converters with selective catalytic reduction (SCR).

The contamination-detecting system can also be sensitive for contamination different from diesel or another hydrocarbon.

Instead of sensor bodies 18 comprising vertical rods 20; 20a, other kinds of sensor bodies can be used. For example instead of the rods 20; 20a open hollow cylinders can be employed, in which one or more floaters are movable.

Instead of being made of rubber, the coupling member 40; 40a can also be made of another contamination sensitive material, for example polycarbonate, polymethyl methacrylate, polystyrene and/or EPDM or the like.

In the first and second embodiment the contamination indicator 38 can also be adapte_d_to_stay embedded in the coupling member_.40 in the second operational state. For example, the coupling member 40 can be arranged such that it is released from the base rod 26 when interacting with a contamination. The coupling member 40 also can be adapted to swell and to move actively the contamination indicator 38 as a result of interacting with the contamination.

In the first and second embodiment, instead of the contamination indicator 38 being embedded in the coupling member 40, vice versa, the coupling member 40 can be embedded in the contamination indicator 38 for coupling.

Instead of REED switches 42; 42a other kinds of sensing units can be used, which are in particular contactless and/or electrical. In the first and third embodiment it is possible that the sensor body 18 comprises more or less then five REED switches 42. In the second embodiment it is also possible the more or less than seven REED switches 42 and 42a are used.

The REED switches 42; 42a can also be adapted to create specific voltages different from 0,5 Volt, 0,7 Volt, 0,9 Volt, 1 ,1 Volt and 1 ,3 Volt. For instance, a urea level metering device may use a voltage range between 0 to 5 Volts instead. The level indicator 34 may use REED switches corresponding to the voltage range between 0,5 and 4,5 Volts. Voltages above 4,5 Volts or below 0,5 Volts are reserved for indicating an error of the level metering device. Thus, the contamination indicator 38 may use REED switches below 0,5 Volts. If the contamination indicator 38 is activated, e.g. released by the coupling device 40 by contact with the contamination, an error signal can be issued.

Claims

C L A I M S

1. A urea level metering device (10) particularly for use in a urea tank (16) of a vehicle, particularly a commercial vehicle, more particularly a truck, comprising a sensor body (18) with one or more sensing units (42; 42a) and a level indicator (34) for indicating a urea level in the urea tank (16) by activating one or more of the sensing units (42; 42a), wherein a sensor device (14) is provided for detecting a contamination in the urea tank (16) comprising one or more contamination indicators (38) coupled to the sensor body (18).

2. The urea level metering device according to claim 1 , characterized in that the sensor device (14) is coupled to the sensor body (18) in a region not in use for the level indication.

3. The urea level metering device according to claim 1 or 2, characterized in that the one or more contamination indicators (38) are fixed in a position by at least one coupling member (40, 40a) as long as a content of the contamination is below a predetermined level.

4. The urea level metering device according to claim 3, characterized in that the one or more contamination indicators (38) are disconnected from the position in the presence of the contamination at or above a predetermined level.

5. The urea level metering device according to claim 3, characterized in that the one or more contamination indicators (38) are locked in the position in the presence of the contamination at or above a predetermined level.

6. The urea level metering device according to any preceding claim, characterized by that one or more of the contamination indicators (38) are floatable in urea (12).

7. The urea level metering device according to any preceding claim, characterized by that one or more contamination indicators (38) are integrated in the level indicator (34).

8. The urea level metering device according to any preceding claim, characterized in that at least one contamination indicators (38) is functionally arranged in series with the level indicator (34).

9. The urea level metering device according to any preceding claim, characterized in that at least one contamination indicator (38) is functionally arranged in parallel with the level indicator (34).

10. The urea level metering device according to any preceding claim, characterized in that the sensing unit (42, 42a) comprises one or more REED switches.

11. The urea level metering device according to any preceding claim, characterized in that one or more REED switches are responsive to at least one contamination indicator (38).

12. The urea level metering device according to any preceding claim, characterized in that the coupling member (40; 40a) is comprises at least one of rubber, polycarbonate, polymethyl methacrylate, polystyrene, EPDM.

13. The urea level metering device according to any preceding claim, characterized in that at least one contamination indicator (38) in a first operational state embedded in the coupling member (40).