WO2008155270A1

WO2008155270A1 - Scr device

Info

Publication number: WO2008155270A1
Application number: PCT/EP2008/057271
Authority: WO
Inventors: Rainer Haeberer
Original assignee: Robert Bosch Gmbh
Priority date: 2007-06-21
Filing date: 2008-06-11
Publication date: 2008-12-24
Also published as: DE102007028480A1

Abstract

The invention relates to an SCR device (1) having at least one first storage container (3) for a reducing agent (19), and at least one first suction line (5), by means of which the reducing agent (19) can be removed from the first storage container (3). In order to create an SCR device (1) that may also be reliably operated if a storage container (3) for a reducing agent (19) runs empty, or is at risk of running empty, while still allowing simple and cost-effective production thereof, the invention provides that a valve unit (27) is associated with the first suction line (5), the valve unit closing the first suction line (5) partially or completely if a fill level (31) of the reducing agent (19) in the first storage container (3) at least approximately approaches a minimum value (41), or falls below the same.

Description

description

title

SC R device

State of the art

The invention relates to an SC R device with at least one first reservoir and at least one first suction line.

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, a directly reducing substance such as ammonia or a precursor is supplied to the exhaust, which releases substances reducing the exhaust only. As a precursor, for example, a urea-water solution can be used. Ammonia is converted to molecular nitrogen and water by selective catalytic reduction with nitrogen monoxide and nitrogen dioxide. The selective catalytic reduction takes place in an S C R catalyst.

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 known for example from DE 10 2006 027 487 Al. 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 upon reaching a maximum level of the second reservoir, the reducing agent can also flow back into the first reservoir.

Disclosure of the invention

The object of the invention is to provide an SCR device that can be operated reliably even when a reservoir for reducing agent runs empty or threatens to run empty, and yet is easy and inexpensive to produce.

This object is achieved by an SCR device having the features of claim 1. Advantageous developments are mentioned in subclaims. Features which are important for the invention will become apparent from the following description and the drawing, wherein the features alone or in different combinations may be important without being explicitly referred to again.

When realizing the SCR device according to the invention, it is achieved that no air interfering with the operation of the SCR device can reach the SCR device via the first suction line. It is thus ensured that the SCR device can operate without interference until the minimum value of the filling level has been reached.

It can be provided that when the first reservoir is empty, the suction line is completely closed. Thus, the first reservoir during operation of the SCR device is completely emptied, and it passes because of the sealed first suction line yet no air in the SCR device, so that the SCR device must not be vented after refilling the first reservoir.

It is particularly preferred that the SCR device has a second reservoir and a second suction line, wherein both suction lines are connected to a common pumping device and the minimum value for the filling level is selected in the first reservoir so that the two reservoirs are at least approximately simultaneously emptied from the pumping device at partially closed first suction line. The valve device thus throttles a flow through the first suction line from a certain level in the first reservoir such that the two reservoirs at least approximately simultaneously from the

Pumping device to be emptied. Depending on the design of the flow through the first suction line is late, but then throttled so strong that the pumping device removes the reducing agent mainly from the second reservoir. Ideally, the minimum value of the level of the reducing agent in the first reservoir or the reducing agent flow through the first suction line with closed valve device is selected so that when the second reservoir has become empty, and the first reservoir is emptied. In this case, advantageously particularly simple and inexpensive valve devices can be used, which do not completely seal the first suction line in the closed position.

It can also be provided that the first reservoir is already emptied with partially emptied second reservoir, whereby the structure of the SCR device and the coordination of their individual components with each other are further simplified.

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 refilling, the first suction line does not have to be vented at all, which speeds up recommissioning. 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 device may comprise a valve element, which is designed as a buoyant body or coupled to such, wherein the buoyant body is arranged in the first reservoir or a communicating with this space, and the valve means may comprise at least one of the valve element completely or partially closable opening, the in the open state connects the first suction line with the first reservoir. With the help of a buoyant body can on simple and thus cost-effective and robust in operation, the

Valve device as a function of the level of the first reservoir, that is, the height of the liquid level of the first reservoir, are actuated. A structurally particularly favorable valve device can be realized in that the valve element itself is designed as a buoyant body.

It can be provided that the valve element and / or the buoyant body are / is formed as a hollow body, which has the advantage of good structural stability and therefore robustness during operation, with good sealing function in the case of the valve element. As a buoyant body but in principle also foam body o. Ä. In question.

Furthermore, it can be provided that the valve device has a valve housing with at least one flat seat for the valve element. A flat seat seals well with the valve device closed and allows the realization of a low overall height by a flat housing. In such a case, the inlet openings of the valve device for removing the reducing agent can be arranged at a low point of the first reservoir, so that even at a low level of the first reservoir still reducing agent can be removed.

It can be provided that the valve housing has a disc-shaped or annular disc-shaped portion and that the opening is formed on an upper side of this section. Due to the disc-shaped structure of the section, which has the opening, and thereby possible disc-like construction of the valve element results in spite of the overall relatively flat basic structure of the entire valve device, a fairly large contact surface between the valve housing and the valve element to which relatively many or relatively large closable openings can be attached. About the opened

Valve device can therefore be removed high amounts of liquid per unit time.

It can further be provided that the valve element has a flat seat facing the first metal plate and / or the flat seat has a valve element facing the second metal plate. In this way, a high dimensional stability is achieved, so that the valve device closes well. This in turn means that a flow through the first suction line when the valve device is closed is relatively low or completely disappears.

It is particularly preferred that the valve body is annular and radially guided on a nozzle portion of the valve housing, wherein the nozzle portion is at least approximately orthogonal to the disk-shaped or annular disk-shaped portion. By using such a nozzle portion, lateral sliding of the valve body is easily prevented, resulting in reliable and reproducible closing when necessary.

It is preferred that the first suction line is connected to the nozzle section. The nozzle section thus has a double function, there is no additional component or an additional section for connecting the first

Suction line are provided on the valve device, so that the valve device can be realized with a small number of parts.

Alternatively it can be provided that the valve device has a valve housing with a sleeve-like and in the operating position at least approximately vertical portion in the wall of the opening (s) in the sense of a slide valve is / are present. 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 a schematic representation:

Figure 1 shows an SCR device according to a first preferred

Embodiment of the present invention;

Figure 2 shows an SCR device according to a second preferred

Embodiment of the present invention;

Figure 3 is a sectional side view of a valve device;

Figure 4 is a section along the line IV-IV of Figure 3; and

Figure 5 is a sectional side view of a variant of the valve device.

Embodiments of the invention

FIG. 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. The two suction lines 5, 9 are connected upstream to a common pumping device 11. Downstream of the pumping device 11, a return line 13 with a throttle 15 and fluidly parallel thereto, a metering valve 17, not further considered here, for metering a reducing agent 19 into the exhaust gas of an internal combustion engine are arranged. The second reservoir 7 and the first reservoir 3 are interconnected by an overflow 21, and the first Suction line 5 and the second suction line 9 has a first throttle 23 and a second throttle 25.

This valve device 27 is located at a lowest point 29 of the first reservoir 3. The valve device 27 is such that it partially closes the first suction line 5 when 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.

During operation of the SCR device 1, the pumping device 11 via the two suction lines 5, 9 promotes reducing agent 19 from the two storage containers 3, 7 to the metering valve 17. In the reducing agent 19 between the pumping device 11 and the metering valve 17 existing system pressure p below Use of a suitable pressure control device (not shown) kept constant. For pressure control also contributes to the return line 13 together with throttle 15. Furthermore, the pumping device 11 is dimensioned such that more reducing agent 19 is conveyed than consumed by the metering valve 17. 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 so one upon the other that when the valve device 27 is open, a return flow (arrow 37) present in the return line 13 is greater than the second reducing agent flow 35. This results in the second reservoir 7 always being filled to the level of the overflow 21 and reducing agent when the valve device 27 is open 19 via the overflow 21 from the second reservoir. 7 flows into the first reservoir 3. The overflow 21 thus prevents an excessive rise of a liquid level (arrow 39) of the reducing agent 19 contained in the second reservoir 7.

If the filling level, that is to say the liquid level 31 of the first storage container 3, reaches a minimum value (arrow 41), the valve device 27 closes and throttles the first reducing agent flow 33 so that the filling level 31 of the first storage container 3 decreases only comparatively slowly. As a result of this additional throttling of the first reducing agent flow 33, it is achieved that the second reducing agent flow 35 is significantly greater than the first reducing agent flow 33. The reducing agent 19 is thus sucked out of the second storage tank 7, 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 thus causes that upon reaching or falling below the minimum level 41 in the first reservoir 3, the second reducing agent flow 35 is increased at the expense of the first reducing agent flow 33 such that the second reservoir 7 is gradually emptied. In this case, the valve device 27 is dimensioned such that the throttled by the valve means 27 first reducing agent flow 33 has a value which leads to an at least approximately simultaneous emptying of the two reservoirs 3, 7. This means that the first reservoir 3 is only emptied when the second reservoir 7 is at least approximately emptied.

Notwithstanding this is provided in an embodiment not shown that the valve means 27, the first suction line 5 completely closes as soon as the first reservoir 3 is emptied as far as possible. The closing of the valve device 27 then causes the pumping device 11 sucks reducing agent 19 exclusively from the second reservoir 7. The present invention may also be applied to SCR devices 1 having a multi-part tank as shown in FIG. In this second embodiment, the first reservoir 3 has a surge pot 43, in which the valve device 27 is located. The swirl pot 43 is connected to a remainder 44 of the first storage container 3 via a shield valve 45. Within the swirl pot 43 is the second reservoir 7. Since the second reservoir 7 is arranged in the swirl pot 43 of the first reservoir 3, the overflow 21 of the second reservoir 7 is simply formed by an upper edge or an upper edge of the second reservoir 7.

The operation of the second embodiment of the SCR device 1 shown in Figure 2 is substantially identical to the operation of the first embodiment shown in Figure 1, as regards the operation of the valve means 27, but there is a function provided mainly by the umbrella valve 45 the coupling of 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 is not moved, always open when the level of the remainder 44 of the first reservoir 3 is higher than the level of the swirl pot 43. So it can reducing agent 19 refill from the rest 44 of the first reservoir 3 in the swirl pot 43 when it is sucked out of this reducing agent 19. Movements of the SCR device 1, which occur, for example, during operation of a motor vehicle in which the SCR device 1 is installed, lead to sloshing movements of the reducing agent 19 within the reservoir 3, 7. The shield valve 45 prevents the reducing agent 19 from the swirl pot 43 flows back directly into the rest 44 of the first reservoir 3, so that the probability that the valve device 27 is not immersed due to such sloshing movements for a short time in the reducing agent 19 and thus air can get into the first suction line 5, is low.

In the following, two implementation possibilities of the valve device 27 will be described in more detail. Each of these two implementation possibilities of the valve device 27 may be used in any of the two embodiments of the entire SC R apparatus described above.

As shown in Figure 3, a valve means 27 may be provided which has an annular disk-shaped valve member 51 which is formed from a buoyant body 52 in the form of a hollow body 53 with a mounted below the hollow body 53 first metal plate 55. Furthermore, the valve device 27 has a valve housing 57 which is arranged on an annular disk-shaped, in operating position horizontal section 58 on or in its upper side 62, which comprises an annular metal plate 63, flat seats 59 with inlet openings 61. In addition, the valve device 27 has a nozzle section 65 for radially guiding the valve element 51 and for connecting the first suction line 5. The valve device 27 is arranged in the first reservoir 3 such that a longitudinal axis 67 of the valve device 27 extends at least approximately vertically in the normal operating position of the SCR device 1.

As can be seen from FIG. 4, the upper side 62 has eight inlet openings 61. However, different from this, a different number of inlet openings 61 may be provided. The inlet openings 61 are arranged in a circular pattern, but in another embodiment can also be arranged in other ways. Finally, the geometry of the inlet openings 61, which is circular in the embodiment shown in FIG. 4, can be varied.

As long as only a certain small amount of reducing agent 19 is present in the first reservoir 3, the inlet openings 61 are immersed in the reducing agent 19, because the valve means 27 is disposed at the lowest point 29 of the first reservoir 3. If the hollow body 53 of the valve element 51 also lies in the reducing agent 19, then it experiences a buoyancy force (arrow 69) which acts against a weight force (arrow 71) of the valve element 51.

If the liquid level 31 in the first storage container 3 is significantly above a lower edge 73 of the first suction line 5, then the valve element 51 sits on this Edge 73, and the vertical movement of the valve element 51 is limited upward. If the liquid level 31 in the first storage container 3 is as shown in FIG. 3, clearly below the lower edge 73 of the first suction line 5, ie still significantly above the inlet openings 61, then the valve element 51 does not abut on this lower edge 73, that is Valve member 51 can move freely in the vertical direction. In this case, a diving depth d of the valve element 51 adjusts so that the buoyant force 69 and the weight force 71 correspond. In this case, the first metal plate 55 is located with a pointing to the second metal plate 63 sealing surface 75 of the valve member 51 below the liquid level 31. Achieved the liquid level 31, as shown in Figure 3 with a dashed line 41, the minimum value, then the valve member 51 sits with the Sealing surface 75 on the flat seats 59 and throttles so the first reducing agent flow 33. When sinking liquid level 31 so the valve means 27 is closed, well before the liquid level 31 reaches the plane of the inlet openings 61. The first reducing agent flow 33 is throttled so strongly when the first valve device 27 is closed that the liquid level 31 only reaches the plane of the inlet openings 61 when the second reservoir 7 is also approximately emptied.

A further exemplary realization of the valve device 27 represents the slide valve construction shown in FIG. 5. Here, the valve housing 57 has a sleeve-like section 77 which is vertical in the operating position. The designed as a hollow body 53 valve member 51 is slidably mounted within the sleeve-like portion 77. A pressure compensation opening 79 serves to ensure a largely unhindered movement of the valve element 51 within the sleeve-like portion 77. The inlet openings 61 are located in a wall 80 of the sleeve-like portion 77. On its underside, the sleeve-like portion 77 has a stop 81 which limits the movement of the valve element 51 downwards.

At a liquid level 31 in the first reservoir 3, which is above an inwardly bent upper edge 83 of the sleeve-like portion 77 limited this edge 83, the vertical movement of the valve element 51 upwards. If the liquid level 31 within the first storage container 3 lies below the upper edge 83 of the sleeve-like portion 77, then the immersion depth d of the valve element 51 adjusts to correspond to the weight force and the buoyancy force of the valve element 51. This valve device 27, like the valve device 27 shown in FIGS. 3 and 4, is constructed in such a way that the valve element 51 closes the inlet openings 61 when the liquid level 31 sinks, before the liquid level 31 reaches the inlet openings 61. Even with this valve device 27, therefore, a throttling of the first reducing agent flow 33 is achieved even before the complete emptying of the first storage container 3.

Both variants of the valve device 27 can be designed such that they completely close the first suction line 5 when falling below a certain level of the reducing agent 19.

Claims

claims

1. SC R device (1) with at least a first reservoir (3) for a reducing agent (19) and at least a first suction line (5), with which the reducing agent (19) the first reservoir (3) can be removed, characterized in that the first suction line (5) is assigned a valve device (27) which partially or completely closes the first suction line (5) when a filling level (31) of the reducing agent (19) in the first storage container (3) has a minimum value (41 ) reaches or falls below at least approximately.

2. SC R device (1) according to claim 1, characterized in that when the first empty storage container (3), the first suction line (5) is completely closed.

3. SC R device (1) according to claim 1 or 2, characterized in that it comprises a second reservoir (7) and a second suction line (9), wherein both suction lines (5, 9) with a common pumping device (11) are connected 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) are closed at least approximately simultaneously by the pumping device (2) when the first suction line (5) is partially closed. 11) can be emptied.

4. SC R device (1) according to any one of the preceding claims, character- ized in that the valve means (27) at a container side end

(26) of the first suction line (5) and / or at a lowest point (29) of the first storage container (3) is arranged.

5. SC R device (1) according to one of the preceding claims, characterized in that the valve device (27) comprises a valve element (51), which is designed as a buoyancy body (52) or coupled to such, wherein the buoyancy body (52) is arranged in the first reservoir (3) or a space communicating therewith, and in that the valve device (27) has at least one opening (61) which can be completely or partially closed by the valve element (51) connects the first suction line (5) with the first reservoir (3).

6. SC R device (1) according to claim 5, characterized in that the valve element (51) and / or the buoyancy body (52) are formed as a hollow body (53) / is.

7. SC R device (1) according to claim 5 or 6, characterized in that the valve device (27) has a valve housing (57) with at least one flat seat (59) for the valve element (51).

8. SC R device (1) according to claim 7, characterized in that the valve housing (57) has a disc-shaped or annular disk-shaped portion (58), and that the opening (61) on an upper side (62) of this portion (58) is trained.

9. SC R device (1) according to claim 7 or 8, characterized in that the valve element (51) a flat seat (59) facing the first metal plate (55) and / or the flat seat (59) a the valve element (51) having facing second metal plate (63).

10. SC R device (1) according to any one of claims 8 or 9, characterized in that the valve element (51) is annular and radially guided on a nozzle portion (65) of the valve housing (57), wherein the nozzle portion (65) at least is approximately orthogonal to the disc-shaped or annular disc-shaped portion (58).

11. SC R device (1) according to claim 10, characterized in that the first suction line (5) is connected to the nozzle section (65).

12. SC R 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 Be operating position at least approximately vertical portion (77), in the wall (80), the opening (61) in the sense of a slide valve (27) is present.