DE102007028480A1

DE102007028480A1 - SCR device

Info

Publication number: DE102007028480A1
Application number: DE102007028480A
Authority: DE
Inventors: Rainer Haeberer
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2007-06-21
Filing date: 2007-06-21
Publication date: 2008-12-24
Also published as: WO2008155270A1

Abstract

The invention relates to an SCR device (1) with at least one first reservoir (3) for a reducing agent (19) and at least one first suction line (5), with which the reducing agent (19) can be removed from the first reservoir (3). In order to provide an SCR device (1), which can be operated reliably even when a reservoir (3) for reducing agent (19) runs empty or threatens to run empty, and yet easy and kosteng produced,) a valve device (27) is associated, which closes the first suction line (5) partially or completely, when a level (31) of the reducing agent (19) in the first reservoir (3) reaches or falls below a minimum value (41) at least approximately.

Description

State of the art
The The invention relates to an SCR device having at least a first one Reservoir and at least a first suction line.
It It is known that the nitrogen oxide content in the exhaust gas of an internal combustion engine can be reduced by a selective catalytic reduction (SCR). For this purpose, the exhaust gas is an immediate reducing substance such as ammonia or a precursor supplied, which only releases reducing substances in the exhaust gas. For example, as a precursor a urea-water solution can be used. ammonia becomes in the selective catalytic reduction with nitrogen monoxide and converted nitrogen dioxide to molecular nitrogen and water. The selective catalytic reduction takes place in an SCR catalyst instead of.
For storage of the exhaust gas to be supplied substance (reducing agent) in a motor vehicle suitable tank systems are used. Such a vehicle tank is for example from the DE 10 2006 027 487 A1 known. This vehicle tank is subdivided into a first reservoir and a second reservoir, the first reservoir having a first suction line and the second reservoir having a second suction line. More reducing agent is sucked in via the two suction lines than is needed to reduce the exhaust gas to the maximum, and excess reducing agent is returned to the second storage container. The second reservoir is connected to the first reservoir via an overflow, so that when reaching a maximum level of the second reservoir, the reducing agent can also flow back into the first reservoir.
Disclosure of the invention
task The invention is to provide an SCR device which also then reliably operated when a reservoir for reducing agent runs empty or run empty threatens, and yet easy and inexpensive to produce is.
These The object is achieved by an SCR device having the features of the claim 1 solved. Advantageous developments are mentioned in subclaims. For the invention important features also go from the subsequent description and the drawings, wherein the features alone or in different combinations may be important without being explicitly mentioned again.
at the realization of the SCR device according to the invention is achieved that no disturbing the operation of the SCR device Air over the first suction line in the SCR device can get. It is thus ensured that the SCR device until the minimum level is reached can work.
in this connection can be provided that when empty first reservoir the suction line is completely closed. This is the first reservoir during operation of the SCR device completely emptied, and it passes because of the closed still no air in the SCR device, so that the SCR device after refilling the first Reservoir must not be vented.
It It is particularly preferred that the SCR device has a second Reservoir and a second suction line, wherein both suction lines connected to a common pumping direction and the minimum level for the level first reservoir is selected such that the two reservoirs partially closed first suction line at least approximately simultaneously from the pumping device can be emptied. The valve device throttles So a flow through the first suction line from a certain Level in the first reservoir such that the two storage containers at least approximately simultaneously be emptied by the pumping device. Depending on the version The flow through the first suction line will be late, but then throttled so much that the pumping means the reducing agent mainly from the second reservoir extracts. Ideally, the minimum level is the level of the reducing agent in the first reservoir or the reducing agent flow through the first suction line when closed Valve device chosen so that when the second reservoir has become empty, even the first reservoir emptied is. This can advantageously particularly simple and inexpensive valve devices are used, which do not fully seal the first suction line when closed.
It can also be provided that the first reservoir already at partially emptied second reservoir is deflated, reducing the structure of the SCR device and the vote their individual components are further simplified with each other.
It is further preferred that the valve device is arranged at a container-side end of the first suction line and / or at a lowest point of the first storage container. In the first case, after a refill, the first Sauglei be vented at all, which speeds up the restart. In the second case, the volume of the reservoir is optimally utilized. In addition, an actuating device which responds to the minimum level of the filling level of the first storage container can be integrated into the valve device in a particularly simple manner or be mounted in the spatial vicinity of the valve device. Because when reaching or exceeding the minimum value is a liquid level of the reducing agent in the vicinity of the lowest point of the first reservoir and thus also in the vicinity of the valve device. Elaborate actuators or controls are therefore not required for the operation of the valve device.
The Valve means may comprise a valve element which serves as a buoyant body is formed or coupled with such, wherein the buoyant body in the first reservoir or communicating with this Space is arranged, and the valve means may be at least one the valve element completely or partially closable opening have, in the open state, the first suction line with the first reservoir connects. With the help of a buoyant body can to simple and therefore cost-effective and robust in operation Make the valve device depending on the level the first reservoir, that is from the Height of the liquid level of the first storage container, be operated. A structurally particularly favorable Valve device can be realized by that the valve element itself formed as a buoyant body is.
in this connection can be provided that the valve element and / or the buoyant body are formed as a hollow body / is, which has the advantage of good structural stability and therefore robustness in operation has, with good sealing function in the case of the valve element. As a buoyancy body but in principle also foam body o. Ä. in question.
Of Furthermore, it can be provided that the valve device a Valve housing with at least one flat seat for having the valve element. A flat seat seals when closed Valve device good and allows the realization of a small Height by a flat housing. In such a can the inlet openings of the valve device for removing the reducing agent at a low point of the first Reservoir are arranged so that even at a low level of the first reservoir still reducing agent can be removed.
in this connection can be provided that the valve housing a disc-shaped or annular disc-shaped portion and that the opening is formed on an upper side of this section. By the disc-shaped construction of the section, the opening has, and thereby a possible disc-like structure of the valve element results despite the overall relatively flat basic structure the whole valve device a fairly large contact surface between valve housing and valve element, at the relatively many or relatively large closable openings can be attached. about the open valve device can therefore high quantities of liquid per unit time to be removed.
in this connection can be further provided that the valve element is a flat seat facing first metal plate and / or the flat seat a the valve element having facing second metal plate. That way, one becomes achieved high dimensional stability, so that the valve device good closes. This in turn means that a flow through the first suction line with closed valve device relatively is low or completely disappears.
It It is particularly preferred that the valve body is annular and at a nozzle portion of the valve housing radially is guided, wherein the nozzle section at least approximately orthogonal to the disk-shaped or annular disk-shaped Section is. Using such a nozzle section is a lateral sliding away of the valve body to simple Way, resulting in a reliable and reproducible Close performs when needed.
in this connection it is preferred that the first suction line to the nozzle section connected. The nozzle section thus has a double function, it no additional component or additional Section for connecting the first suction line to the valve device be provided, so that the valve device with a small Part number can be realized.
alternative can be provided that the valve means a valve housing with a sleeve-like and operational position at least has approximately vertical section, in the wall of which the opening (s) is present in the sense of a slide valve / are. In this way the valve device can be made particularly compact become.
Brief description of the drawings
Hereinafter, exemplary embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. Like elements bear the same reference numerals and are usually described only once in detail. In the drawing show in schemati shear representation:
1 an SCR device according to a first preferred embodiment of the present invention;
2 an SCR device according to a second preferred embodiment of the present invention;
3 a sectional side view of a valve device;
4 a section along the line IV-IV from 3 ; and
5 a sectional side view of a variant of the valve device.
embodiments the invention
1 shows an SCR device 1 with separate storage containers. The SCR device 1 has a first reservoir 3 with a first suction line 5 and a second reservoir 7 with a second suction line 9 on. The two suction lines 5 . 9 are upstream of a common pumping device 11 connected. Downstream of the pumping device 11 are a return line 13 with a throttle 15 as well as fluidically parallel thereto a not closer considered dosing valve 17 for dosing a reducing agent 19 arranged in the exhaust gas of an internal combustion engine. The second reservoir 7 and the first reservoir 3 are through an overflow 21 connected to each other, and the first suction line 5 or the second suction line 9 has a first throttle 23 or a second throttle 25 on.
At a tank end 26 the first suction line 5 there is a valve device 27 , This valve device 27 is at a lowest point 29 of the first reservoir 3 , The valve device 27 is designed to be the first suction line 5 partially closes when a level, that is, a liquid level (arrow 31 ) of the reducing agent 19 in the first storage container 3 reaches or falls below a minimum value. In the present context, the term "reducing agent" is understood as meaning both an immediately reducing substance such as ammonia or a precursor which releases substances that reduce the exhaust gas first.
In an operation of the SCR device 1 promotes the pumping device 11 over the two suction lines 5 . 9 reducing agent 19 from the two storage containers 3 . 7 to the metering valve 17 , This is one in the reducing agent 19 between the pumping device 11 and the metering valve 17 existing system pressure p using a suitable pressure control device (not shown) kept constant. For pressure control also carries the return line 13 velvet throttle 15 at. Furthermore, the pumping device 11 so dimensioned that more reducing agent 19 promoted as by the metering valve 17 is consumed. The excess reducing agent 19 flows through the return line 13 through the throttle 15 in the second reservoir 7 ,
The first throttle 23 limits a first reducing agent flow (arrow 33 ) through the first suction line 5 , and the second throttle 25 limits a second reducing agent flow (arrow 35 ) through the second suction line 9 , The two throttles 23 . 25 and the throttle 15 are coordinated so that when the valve device is open 27 one in the return line 13 existing return flow (arrow 37 ) is greater than the second flux of reducing agent 35 , As a result, when the valve device is open 27 the second reservoir 7 always up to the height of the overflow 21 is filled and reducing agent 19 over the overflow 21 from the second reservoir 7 in the first reservoir 3 flows. The overflow 21 prevents an excessive rise of a liquid level (arrow 39 ) of the second reservoir 7 contained reducing agent 19 ,
Reaches the level, so the liquid level 31 of the first reservoir 3 , a minimum value (arrow 41 ), closes the valve device 27 and throttles the first reductant flow 33 , so the level 31 of the first reservoir 3 only comparatively slowly decreases. By this additional throttling of the first reducing agent flow 33 is achieved that now the second reducing agent flow 35 is significantly larger than the first reducing agent flow 33 , The reducing agent 19 So now mainly from the second reservoir 7 sucked off, to such an extent that the second reducing agent flow 35 is greater than the return flow 37 , This in turn means that the level 39 of the second reservoir 7 decreases.
The closing of the valve device 27 So that, when reaching or falling below the minimum level 41 in the first storage container 3 the second reducing agent flow 35 at the expense of the first reductant flow 33 is increased such that the second reservoir 7 is gradually emptied. In this case, the valve device 27 dimensioned so that by the valve device 27 throttled first reductant flow 33 has a value that leads to an at least approximately simultaneous emptying of both reservoirs 3 . 7 leads. That is, the first reservoir 3 only then emptied when the second reservoir 7 is at least approximately emptied.
Notwithstanding this, it is provided in an embodiment, not shown, that the valve device 27 the first suction line 5 completely closes as soon as the first reservoir 3 as much as possible is emptied. The closing of the valve device 27 then causes the pumping device 11 exclusively from the second reservoir 7 reducing agent 19 sucks.
The present invention may also be applied to SCR devices 1 that, as in 2 shown to have a multi-part tank can be applied. In this second embodiment, the first reservoir 3 a swirl pot 43 on, in which the valve device 27 located. The swirl pot 43 is with a rest 44 of the first reservoir 3 via a screen valve 45 connected. Inside the baffle pot 43 is the second reservoir 7 , Since the second reservoir 7 in the swirl pot 43 of the first reservoir 3 is arranged, the overflow 21 of the second reservoir 7 simply by an upper edge or an upper edge of the second reservoir 7 educated.
The functioning of in 2 shown second embodiment of the SCR device 1 is with the functioning of in 1 shown first embodiment, what the operation of the valve device 27 Essentially, identical, but it comes mainly through the umbrella valve 45 provided function of coupling the swirl pot 43 with the rest 44 of the first reservoir 3 added. The umbrella valve 45 acts as a check valve and is under ideal conditions and when the SCR device 1 not moved, always open when the level of the rest 44 of the first reservoir 3 higher than the level of the swirl pot 43 , So it can be reducing agent 19 from the rest 44 of the first reservoir 3 in the swirl pot 43 Refill, if from this reducing agent 19 is sucked off. Movements of the SCR device 1 For example, when operating a motor vehicle in which the SCR device 1 is installed, lead to sloshing of the reducing agent 19 inside the reservoir 3 . 7 , The umbrella valve prevents this 45 that reducing agent 19 from the swirl pot 43 immediately in the rest 44 of the first reservoir 3 flows back, reducing the likelihood that the valve device 27 due to such sloshing movements temporarily not in the reducing agent 19 immersed and thus air in the first suction line 5 can reach, is low.
In the following, two implementation possibilities of the valve device 27 describe in more detail. Each of these two implementation possibilities of the valve device 27 can be used in any of the two embodiments of the entire SCR device described above.
As in 3 shown, a valve device 27 be provided, which is an annular disk-shaped valve element 51 comprising, a buoyancy body 52 in the form of a hollow body 53 with one below the hollow body 53 attached first metal plate 55 is formed. Furthermore, the valve device 27 a valve housing 57 on, which on a ring-shaped, horizontal in operational position section 58 on or in its top 62 which is an annular metal plate 63 includes, flat seats 59 with inlet openings 61 are arranged. In addition, the valve device 27 a spigot section 65 for radial guidance of the valve element 51 and for connecting the first suction line 5 on. The valve device 27 is so in the first reservoir 3 arranged that a longitudinal axis 67 the valve device 27 in the normal operating position of the SCR device 1 at least approximately vertical.
How out 4 can be seen, has the top 62 eight inlet openings 61 on. However, different from this, a different number of inlet openings 61 be provided. The inlet openings 61 are arranged in a circular pattern, but in another embodiment may be arranged in other ways. Finally, the geometry of the inlet openings 61 in the in 4 shown embodiment is circular, can be varied.
As long as only a certain small amount of reducing agent 19 in the first reservoir 3 is present, are the inlet openings 61 into the reducing agent 19 dipped, because the valve device 27 at the lowest point 29 of the first reservoir 3 is arranged. Is also the hollow body 53 of the valve element 51 in the reducing agent 19 , he experiences a buoyancy force (arrow 69 ), which against a weight force (arrow 71 ) of the valve element 51 acts.
Is the liquid level 31 in the first storage container 3 well above a lower edge 73 the first suction line 5 , then the valve element sits 51 on this edge 73 on, and the vertical movement of the valve element 51 is limited to the top. Is the liquid level 31 in the first storage container 3 as in 3 shown, well below the lower edge 73 the first suction line 5 So still significantly above the inlet openings 61 , then beats the valve element 51 not at this lower edge 73 on, that is the valve element 51 can move freely in the vertical direction. In this case, a diving depth d of the valve element 51 so that the buoyancy force 69 and the weight 71 correspond. there there is the first metal plate 55 with one to the second metal plate 63 facing sealing surface 75 of the valve element 51 below the liquid level 31 , Reached the liquid level 31 , as in 3 with a dashed line 41 shown, the minimum value, then sits the valve element 51 with the sealing surface 75 on the flat seats 59 and throttles the first reducing agent flow 33 , With sinking liquid level 31 So is the valve device 27 closed, well before the liquid level 31 the level of the inlet openings 61 reached. The first reductant flow 33 is at closed first valve means 27 so much choked off that the liquid level 31 only then the level of the inlet openings 61 achieved, although the second reservoir 7 is almost empty.
Another exemplary realization of the valve device 27 represents the in 5 shown slide valve construction. The valve housing 57 here has a sleeve-like vertical section in operational position 77 on. That as a hollow body 53 executed valve element 51 is inside the sleeve-like section 77 slidably mounted. A pressure equalization opening 79 serves to a largely unhindered movement of the valve element 51 within the sleeve-like section 77 sure. The inlet openings 61 are in a wall 80 of the sleeve-like section 77 , On its underside has the sleeve-like section 77 a stop 81 on that the movement of the valve element 51 limited to the bottom.
At a liquid level 31 in the first storage container 3 , which is above an inwardly bent upper edge 83 of the sleeve-like section 77 lies, limits this edge 83 the vertical movement of the valve element 51 up. Is the liquid level 31 within the first reservoir 3 below the upper edge 83 of the sleeve-like section 77 , then the immersion depth d of the valve element 51 so that the weight and buoyancy of the valve element 51 correspond. This valve device 27 is like that in the 3 and 4 shown valve device 27 designed so that the valve element 51 the inlet openings 61 with sinking liquid level 31 closes before the liquid level 31 the inlet openings 61 reached. Also with this valve device 27 So is a throttling of the first reducing agent flow 33 even before the complete emptying of the first storage container 3 reached.
Both variants of the valve device 27 can be designed such that they fall below a certain level of the reducing agent 19 the first suction line 5 completely close.
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 102006027487 A1 [0003]

Claims

SCR device ( 1 ) with at least one first storage container ( 3 ) for a reducing agent ( 19 ) and at least one first suction line ( 5 ), with which the reducing agent ( 19 ) the first reservoir ( 3 ), characterized in that the first suction line ( 5 ) a valve device ( 27 ) associated with the first suction line ( 5 ) partially or completely closes when a level ( 31 ) of the reducing agent ( 19 ) in the first storage container ( 3 ) a minimum value ( 41 ) reaches or falls below at least approximately.
SCR device ( 1 ) according to claim 1, characterized in that when empty first storage tank ( 3 ) the first suction line ( 5 ) is completely closed.
SCR device ( 1 ) according to claim 1 or 2, characterized in that it comprises a second reservoir ( 7 ) and a second suction line ( 9 ), both suction lines ( 5 . 9 ) with a common pumping device ( 11 ) and the minimum value ( 41 ) for the filling level ( 31 ) in the first storage container ( 3 ) is selected such that the two storage containers ( 3 . 7 ) with partially closed first suction line ( 5 ) at least approximately simultaneously from the pumping device ( 11 ) are emptied.
SCR device ( 1 ) according to one of the preceding claims, characterized in that the valve device ( 27 ) at a container end ( 26 ) of the first suction line ( 5 ) and / or at a lowest point ( 29 ) of the first storage container ( 3 ) is arranged.
SCR device ( 1 ) according to one of the preceding claims, characterized in that the valve device ( 27 ) a valve element ( 51 ), which serves as buoyancy body ( 52 ) is formed or coupled to such, wherein the buoyant body ( 52 ) in the first storage container ( 3 ) or a communicating with this space is arranged, and that the valve device ( 27 ) at least one of the valve element ( 51 ) completely or partially closable opening ( 61 ), which in the open state, the first suction line ( 5 ) with the first reservoir ( 3 ) connects.
SCR device ( 1 ) according to claim 5, characterized in that the valve element ( 51 ) and / or the buoyancy body ( 52 ) as a hollow body ( 53 ) are / is formed.
SCR device ( 1 ) according to claim 5 or 6, characterized in that the valve device ( 27 ) a valve housing ( 57 ) with at least one flat seat ( 59 ) for the valve element ( 51 ) having.
SCR device ( 1 ) according to claim 7, characterized in that the valve housing ( 57 ) a disc-shaped or ring-shaped portion ( 58 ), and that the opening ( 61 ) on a top side ( 62 ) of this section ( 58 ) is trained.
SCR device ( 1 ) according to claim 7 or 8, characterized in that the valve element ( 51 ) a flat seat ( 59 ) facing first metal plate ( 55 ) and / or the flat seat ( 59 ) a the valve element ( 51 ) facing second metal plate ( 63 ) having.
SCR device ( 1 ) according to one of claims 8 or 9, characterized in that the valve element ( 51 ) annularly and at a nozzle section ( 65 ) of the valve housing ( 57 ) is guided radially, wherein the nozzle section ( 65 ) at least approximately orthogonal to the disk-shaped or annular disk-shaped portion ( 58 ).
SCR device ( 1 ) according to claim 10, characterized in that at the nozzle section ( 65 ) the first suction line ( 5 ) connected.
SCR device ( 1 ) according to claim 5 or 6, characterized in that the valve device ( 27 ) a valve housing ( 57 ) with a sleeve-like and in the operating position at least approximately vertical section ( 77 ), in whose wall ( 80 ) the opening ( 61 ) in the sense of a slide valve ( 27 ) is available.