WO2009010569A1

WO2009010569A1 - Device and method for metering a reducing agent into an exhaust gas system of a vehicle

Info

Publication number: WO2009010569A1
Application number: PCT/EP2008/059412
Authority: WO
Inventors: Peter Bauer; Rainer Bentz; Joachim Frank; Hermann Ketterl
Original assignee: Continental Automotive Gmbh
Priority date: 2007-07-18
Filing date: 2008-07-17
Publication date: 2009-01-22
Also published as: DE102007033470B4; DE102007033470A1

Abstract

The invention relates to a device for metering a reducing agent, such as for example a urea solution, into the exhaust gas system of a vehicle. The aim of the invention is to provide a metering system which allows an improved pressure reduction. This aim is achieved by a metering device (10) for metering a reducing agent into the exhaust system of a vehicle by means of a metering valve device (20). Said metering device comprises a reservoir (12) containing the reducing agent (14), a first line (18) connecting the reservoir to the metering valve device, a filter device and, downstream thereof, a pump device (24) being arranged in the first line, and a pressure evacuation device (28) being connected to the first line to evacuate pressure from the first line.

Description

description

Apparatus and method for metering a reducing agent into an exhaust tract of a vehicle

The invention relates to an apparatus and a method for metering a reducing agent, such as a urea solution, into an exhaust tract of a vehicle.

In the operation of internal combustion engines produced exhaust gas which pollutants, such as HC, CO, NOx, etc., contains. For various pollutants, such as HC, CO, NOx particles, there are legal regulations that limit pollutant emissions during operation of an internal combustion engine. To meet these legal requirements, a purification of the exhaust gas is usually necessary. For this purpose, an emission control system is usually used. In the case of lean-burn engines, such as diesel engines, Otto lean-burn engines, special NOx-reducing processes based on NOx storage catalysts or SCR catalysts are increasingly being used. SCR catalytic converters require a reducing agent for NOx reduction; ammonia (NH3) is currently the usual reducing agent. This reducing agent is today usually produced by injection of a urea-water solution, such as AdBlue, Denoxium, etc., and its hydrolysis in the exhaust system of the internal combustion engine or "on board" of the respective vehicle and then fed to the SCR catalyst However, the reductant represents a challenge in terms of robustness, reliability and cost-effectiveness.

Current systems known from the prior art employ a membrane pump suitable for conveying the reducing agent from a storage tank to the place of conversion into ammonia (NH.sub.3), which is suitable for the urea-water solution medium. The systems, which are based on a backflow system, have a very elaborate and expensive 4/2 way valve. This valve realizes an empty pumping without the pump direction reversal. In addition, these systems require a valve for flushing the pipes and controlling the temperature in the pipe system. Furthermore, it is pumped back, ie against the conveying direction. This can be done on the one hand with fresh air or on the other hand by exhaust through the open injector. However, the latter has the disadvantage that it can lead to a blockage of the injector. The state of the art involves injecting the reducing agent via an injector into a generator or directly into the exhaust system.

From EP 1 656 986 Al a urea dosing device is known. The urea dosing device comprises a reservoir for the reducing agent. This is connected via a first line with a 2/2-way valve, which introduces the reducing agent in the exhaust system. Between the reservoir and the metering valve, a pump and then a filter is arranged. The pump pumps the reducing agent to the exhaust gas tract, wherein the reducing agent is metered into the exhaust tract via the actuation of the metering valve. In this case, the pump is designed such that it can also transport the reducing agent from the metering valve back into the storage container. This makes it possible to pump the reducing agent in the first line back into the reservoir and to empty the first line completely. In addition, a second line is provided, which is switchable via a 2/2-way valve. If, during operation of the pump, an excess of reducing agent is transported via the first line to the valve and as a result excessively high pressure results, the valve in the second line is opened to reduce the pressure and an excess flow of reducing agent can be applied via the second line Return the line to the storage tank.

Furthermore, a metering system is known from DE 10 2004 054 238 A1. The metering system has a storage tank with a urea solution as a reducing agent. The pros Ratstank is connected via a line with a pump, various filters and a metering valve, via which the reducing agent is metered into a metering point of a Abgaseinlassbereichs a catalyst. Furthermore, an area of the delivery line between the feed pump and the metering valve opposite to the normal operation conveying direction can be emptied. In this case, the conveying direction of the feed pump is reversed and the urea solution is conveyed back into the storage tank counter to the usual normal operation in the conveying direction. A vent valve located upstream of the metering valve is opened and the metering valve is closed.

Furthermore, systems are known from the prior art, which are based on a dead-headed system (without return, only feed). However, such systems can be destroyed in certain external conditions, such as frost, if they do not have sufficient measures, such as pressure relief or expansion possibilities for the reducing agent. In addition, it is not possible with a diaphragm pump to reduce the pressure in the pressure line if desired.

DE 199 47 197 A1 discloses a device for metering in a reducing agent by means of a metering valve device into an exhaust gas tract of a vehicle. There is provided a reservoir containing the reducing agent. The reservoir is connected via a first line with a metering valve device. In the first line, a filter element and then a pump device is provided. There is a pressure relief device connected to the first line to release the pressure from the first line.

DE 100 47 516 A1 discloses a method and a device for dosing a reducing agent for the removal of

Nitrogen oxides from the exhaust gases known. The reducing agent is arranged in a storage container and is fed via a line by means of a pump to a metering device. leads. Parallel to the pump, a return line is provided, in which a check valve is arranged.

The object of the invention is therefore to provide a metering device and a method which allows an improved pressure reduction.

According to the invention, this object is achieved by providing a method and a metering device for metering in a reducing agent, in which a first line connects a storage container with a metering valve device. In this case, first a filter device is arranged in the first line and then a pump device. A pressure relief device, such as a valve device, is connected to the first line in such a way that pressure can be released from the first line.

In addition, in the embodiment according to the invention, at least one temperature sensor device is provided, which determines, for example, the temperature of the reducing agent in the first line, the reservoir and / or an ambient temperature. This temperature determination can additionally or alternatively be used to determine the pressure in order to control the pressure relief device accordingly. For example, the pressure relief device can be opened at low temperatures to minimize ice pressure in the system.

This has the advantage that a pressure release can be achieved very easily by a corresponding actuation of the pressure relief device, without a pumping back via the pump device is necessary. As a result, a pump device with only one conveying direction can also be used. In addition, the filter device allowed before the

Pump device, or upstream thereof is arranged that the pump means and the metering device not so can easily clog and thereby a reliable operation of the metering device is ensured.

According to one embodiment of the invention, the pressure relief device is connected on the one hand to the reservoir and on the other hand to the first line to the pump means. This has the advantage that, for example, during freezing of the reducing agent in the reservoir, this can be pumped back into the reservoir through circular pumping via the valve device in order to counteract freezing.

In another embodiment of the invention, the pressure relief device is connected on the one hand with the first line in front of the filter device and on the other hand with the first line following the pump device. This has the advantage that the pressure-lowering device can be combined, for example, with a pressure and / or temperature sensor in a housing and, for example, does not have to be attached to the storage container.

According to a further embodiment of the invention, the pressure relief device is connected on the one hand to the first line after the filter device and on the other hand to the first line following the pump device. This has the advantage that the filter device can be flushed through when reducing agent is discharged through the valve device to reduce the pressure.

In a further embodiment of the invention, the pump device, for example, a pump which promotes only in one direction, for example, a diaphragm pump. Since the pressure reduction takes place via the valve device, a pump device with two delivery directions is not necessary.

In another embodiment, a pressure sensor device is provided in the first line, for example between the pump device and the metering device. The Pressure sensor device determines the pressure in the first line by means of at least one pressure sensor in order to release pressure via the pressure-lowering device if one or more staggered reference values are exceeded.

According to another embodiment of the invention, at least one heating device is provided on the first conduit and / or the reservoir. In this way, the reducing agent can be additionally heated to prevent freezing in frost.

The invention will be explained in more detail with reference to various embodiments in the accompanying drawings. It shows:

1 is a schematic view of a metering device according to a first embodiment of the invention, FIG. 2 is a schematic view of a metering device according to a second embodiment of the invention, FIG. 3 is a schematic view of a metering device according to a third embodiment of the invention, FIG Top view of the dosing device according to the second embodiment, and Fig. 5 is a side perspective view of the dosing device according to the second embodiment.

In all figures, identical or functionally identical elements and devices have been provided with the same reference numerals, unless stated otherwise.

In Fig. 1, a first embodiment of the dosing device 10 according to the invention is shown. In this case, the metering device 10 is connected to a reservoir 12 for a reducing agent 14, such as a urea-water solution or an ammonia solution. In the reservoir 12, a suction device 16, such as an intake pipe or tank tube, is provided, which is connected via a first line 18 with a metering valve device 20. The dosing Valve device 20 is arranged, for example, on an exhaust gas tract of a motor vehicle (not shown) in order to meter reducing agent 14 into the exhaust gas tract of a motor vehicle, for example into the exhaust gas inlet region of a catalytic converter. Alternatively, the metering valve device 20 can also inject the reducing agent via an injector into a generator instead of directly into the exhaust gas tract. The reducing agent 14, such as a urea solution, thereby causing toxic nitrogen oxides in the exhaust gas can be converted to nitrogen.

For this purpose, a filter element 22 is initially provided in the first line 18 and then a pump device 24 thereafter. The filter element 22 serves, for example, to filter out existing solid particles or crystals, for example to prevent clogging of the pump device 24 and the metering valve device 20. The pumping device 24 in this case transports the reducing agent 14 in one direction, i. from the reservoir 12 to the metering valve device 20. In this case, for example, a diaphragm pump can be used as a pump device 24. In principle, however, it is also conceivable to provide a pump device 24 which not only conveys in one direction but can convey in two directions, i. For example, the reducing agent 14 can also promote back into the reservoir 12.

The pressure in the first line 18 is determined via a pressure sensor device 26 which is arranged, for example, between the pump device 24 and the metering valve device 20. For this purpose, at least one pressure sensor can be provided. Optionally, in addition, at least one temperature sensor may also be provided which measures, for example, the temperature in the first conduit 18, the reservoir 12 and / or an ambient temperature. In this way, it can be determined whether, for example, the reducing agent 14 is freezing. In particular, urea solution tends to freeze relatively quickly. When freezing expands the reducing agent 14, since it is a liquid, so that the pressure in the first conduit 18 increases. In order to counteract this increase in pressure, a pressure relief device 28 is provided according to the invention, which may have, for example, a valve device 28. The valve device may, for example, have at least a 2/2-way valve or another suitable valve.

In addition to a valve device, the pressure relief device optionally also have a throttle, to name just another example of the design of a pressure relief device. However, the invention is not limited to this example. It will be apparent to one of ordinary skill in the art that there are a variety of other possible configurations for a pressure relief device that can be used to vent pressure from a conduit.

In the following, the invention will be described with reference to a valve device 28 as an example of a pressure relief device.

This valve device 28 is in the first embodiment, as shown in Fig. 1, on the one hand connected via a second line 30 to the reservoir 12 and the other with the first line 18 following the pump means 24. Sets, for example, in the winter freezing the urea solution, so the urea solution expands in the first line 18 and can damage the line during further freezing. In order to release the pressure that arises in the process, the additional valve device 28 is opened accordingly. As a result, a portion of the reducing agent 14 can be discharged back into the reservoir 12 in this case. This has the advantage that destruction of the components of the dosing device 10 can be prevented when freezing occurs. Furthermore, by a corresponding actuation of the valve device 28, ie, for example with regard to the opening frequency and / or the degree of opening of the valve, the pressure drop construction in the dosing device 10 are made variable and thereby also the components of the dosing device 10 are spared.

Furthermore, a so-called. Circulation pumping of the reducing agent 14 during thawing is possible. This means that pumped liquid reducing agent 14 can be pumped back into the reservoir 12 and there again thawing of further reducing agent 14 causes. This has the advantage that the thawing time can be reduced.

Basically, however, the invention and the embodiments discussed below are not limited only to this case of freezing and thawing. The function of the additional valve device 28 is quite generally that the valve device 28 is used to cause a pressure reduction when the pressure sensor and / or temperature sensor means 26, 32 determines that the pressure threatens to be too high at least in the first line 18 , It can be dispensed with a special pump device with which the reducing agent 14 is pumped back into the reservoir 12. A pumping device which therefore pumps only in one direction, i. from the reservoir 12 to the metering valve device 20 is sufficient.

In Fig. 2, a second dosing device 10 according to the invention is shown. This dosing device 10 differs from the dosing device 10 of the first embodiment in that the additional valve device 28 is connected via a second line 30 once with the first line 18 in front of the filter element 22 and once with the first line 18 to the pump device 24. Dies has the advantage that no additional connection to the reservoir 12 has to be created. Furthermore, in the second embodiment, to lower the pressure, the pump means 24 and the filter element 22 can be bypassed, the valve means 28 need not be attached in the vicinity or directly to the reservoir 12, but Also be provided spaced therefrom, as will be explained below with reference to FIGS. 4 and 5.

FIG. 3 furthermore shows a third embodiment of the dosing device 10 according to the invention. In this case, the additional valve device 28 is connected via a second line 30 once with the first line 18 to the filter element 22 and once with the first line 18 following the pump means 24. This arrangement in which the valve means 28 parallel to the pump means

24, has the advantage that the filter element 22 can be rinsed. This is done by reducing reducing agent 14 via the valve device 28 in order to reduce the pressure in the first line 18. In this case, the reducing agent 14 flows back through the filter element 22 and rinses it in this case. Another advantage of the second and third embodiments is that the components need not all be mounted to the reservoir 12, such as the additional valve means 28, but may be mounted at other locations outside of the reservoir 12. The valve device 28 can also be used as a kind of heating for adjacent parts.

FIGS. 4 and 5 show an example of the second embodiment according to the invention. Therein, first a tank extraction pipe 34 is shown, which is introduced into a storage container. The reservoir has been omitted for reasons of clarity. Only the tank wall 36 of the reservoir is shown. The tank removal tube 34 is provided with a heating device in order to heat up the reducing agent, such as the urea solution, at low temperatures in winter and to prevent freezing. In this case, a first line 18 is connected to the tank extraction pipe 34. In the first line 18, a filter element 22 is arranged downstream of the tank extraction pipe 34 and subsequently a pump device 24 for pumping the reducing agent from the reservoir to the metering valve device 20. In this case, as shown in FIG. shows, the additional pressure relief device or here valve device 28 is not attached to the reservoir but provided spaced therefrom to other components.

For comparison, the valve device 28 of the first embodiment, which is arranged on the tank wall 36 of the storage container, is shown purely schematically in FIGS. 4 and 5 as well. However, this is not mandatory. In principle, the valve device 28 may also be mounted in a different position than the storage container in the first embodiment.

Furthermore, the valve device 28 and its connection with the first line 18 may be included for the diagnosis of the filter element state, the system tightness and / or the pump malfunction. For example, it can be concluded in the second embodiment, when the pressure reduction is slowed down, that the filter element 22 may be damaged or clogged, since the reducing agent 14 does not flow back optimally through the filter element 22. Furthermore, it can also be concluded from the pressure reduction via the valve device 28 on the system tightness. About the circular pumping, as has been described with reference to the first embodiment can, for example, on the

Pump function are closed. Furthermore, the valve device 28 can also be included, for example for diagnosing the system with respect to freezing, thawing and / or system emergency operations. In this case, reducing means 14 can be circulated via the valve device 28, for example in freezing or thawing phases.

As already mentioned above, the valve device 28 is merely an example of a pressure relief device. The statements made above on the valve device 28 therefore also apply correspondingly to any other form of pressure relief device.

Claims

claims

A metering device (10) for metering a reducing agent (14) by means of a metering valve device (20) into an exhaust tract of a vehicle, comprising: a reservoir (12) containing the reducing agent (14), a first conduit (18) containing the reservoir (12) to the metering valve means (20), wherein in the first conduit (18) a filter element (22) and then a pump means (24) is arranged, and wherein a pressure relief means (28) with the first line (18) is connected to vent pressure from the first conduit (18), wherein at least one temperature sensing device (32) is provided on the dosing device (10), for example in the first conduit (18), at the temperature of the reducing agent (14) of the reservoir (12) and / or to determine the ambient temperature, wherein the pressure in the first line (18) via the pressure discharge means (28) is discharged when the of the temperature sensor means ( 32) measured temperature exceeds or falls below a predetermined threshold.

2. Dosing device according to claim 1, characterized in that the pressure relief device (28) on the one hand to the reservoir (12) is connected and on the other hand with the first line (18) following the pump means (24).

3. Dosing device according to claim 1 or 2, characterized in that the pressure relief device (28) on the one hand with the first line (18) in front of the filter element (22) is connected and on the other hand with the first Line (18) is connected to the pump means (24).

4. Dosing device according to at least one of claims 1, 2 or 3, characterized in that the pressure relief device (28) on the one hand with the first line (18) is connected to the filter element (22) and on the other hand with the first line (18). connected to the pump device (24).

5. Dosing device according to at least one of claims 1 to 4, characterized in that the pump device (24) is for example a pump with a pump direction, for example a diaphragm pump.

6. Dosing device according to at least one of claims 1 to 5, characterized in that in the first conduit (18) has a pressure sensor means (26) is provided for determining the pressure in the first conduit (18).

7. Dosing device according to claim 6, characterized in that the pressure in the first conduit (18) via the pressure discharge means (28) is discharged when the pressure in the first conduit (18) exceeds a predetermined threshold.

8. Dosing device according to at least one of claims 1 to 7, characterized in that a heating device on the first conduit (18) and / or the storage container (12) is provided.

9. Dosing device according to at least one of claims 1 to 8, characterized in that the reducing agent (14) is a urea solution or an ammonia solution.

10. Dosing device according to at least one of claims 1 to 9, characterized in that the pressure Lasseinrichtung example, a valve device (28), and / or has a throttle.

11. Vehicle with a metering device (10) for injecting a reducing agent (14) into an exhaust gas tract of the vehicle according to at least one of claims 1 to 10.

12. A method for dosing a reducing agent by means of a Dosierventileinrichtung in an exhaust system of a vehicle, with a reservoir containing the reducing agent, with a first line which connects the reservoir with the Dosierventileinrichtung, wherein in the first conduit a filter element and then a Pump means is arranged, wherein a pressure relief device is connected to the first line to discharge the pressure from the first conduit, wherein at least one temperature sensor means is provided on the metering device, for example in the first conduit to determine the temperature of the reducing agent, wherein the pressure in the first conduit is discharged via the pressure relief device when the temperature measured by the temperature sensor device exceeds or falls below a predetermined threshold value.