EP2748439A1

EP2748439A1 - Dosing system for a liquid reducing agent

Info

Publication number: EP2748439A1
Application number: EP12733139.5A
Authority: EP
Inventors: Ewgenij Landes; Peter Boehland
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2011-08-26
Filing date: 2012-07-09
Publication date: 2014-07-02
Anticipated expiration: 2032-07-09
Also published as: CN103782002A; JP6012732B2; US9562455B2; EP2748439B1; US20140227120A1; CN103782002B; JP2014524542A; DE102011081628A1; WO2013029849A1

Abstract

Proposed is a dosing module for injecting liquid urea-water solution into the exhaust tract of an internal combustion engine, which dosing module is composed of two pumps, specifically a delivery pump (5) and an aeration pump (15). This permits firstly the injection of urea-water solutions and secondly safe and reliable ventilation of the system when the internal combustion engine is to be shut down.

Description

description

title

Dosing systems for a liquid reducing agent

State of the art

In internal combustion engines that operate according to the diesel process, an SCR catalytic converter is often provided in the exhaust system in order to meet the environmental requirements. So that the SCR catalyst can convert the NOx compounds contained in the exhaust gas into water and nitrogen, must

liquid urea or a liquid urea-water solution (reducing agent) are injected into the exhaust line upstream of the SCR catalyst. For this purpose, a metering system comprising a tank, a

Pump and a dosing module, similar to the injector one

Fuel injection system works, used. The pump is also called

Delivery module designated. The task of the delivery module or the pump is to suck urea-water solution from a tank and build up a sufficient pressure on the pressure side, so that the liquid urea-water solution is finely atomized as soon as the dosing opens demand-controlled. The injector, like the delivery module, is connected to a control unit of the internal combustion engine and is opened and closed by it as required.

The same applies to the operation of the feed pump. Since urea-water solution has the property of freezing at low temperatures and increasing its volume by about 1 1%, measures must be taken to prevent damage to the dosing system caused by freezing

To prevent urea-water solution.

For this purpose it is known from DE 10 2004 054 238 to aerate lines carrying urea-water solution. For this purpose, the pump is designed with a reversible conveying direction or a valve is provided for reversing the conveying direction of the pump. From DE 10 2009 029 408 it is known in the metering a 4/2

Integrate directional control valve. In a first switching position of the 4/2-way valve, the pump promotes reducing agent from the tank to the metering module. When the internal combustion engine is to be turned off, the 4/2-way valve is brought into the second switching position, so that the pump of the delivery module liquid

Promotes reducing agent from the dosing into the tank and thereby ventilated parts of the dosing. This presupposes that the dosing module is open and that air or exhaust gas can flow from the exhaust gas tract into the dosing system.

Partial aeration of the metering system produces a compressible air bubble, so that when the remaining residues of the reducing agent in the metering system freeze, the resulting ice pressure is so low that no damage to the metering system occurs. However, such a 4/2-way valve is prone to failure and expensive.

Disclosure of the invention

The metering system according to the invention according to claim 1 is characterized in that it is very cost-effective and reliable emptying or ventilation of the metering after switching off the

Internal combustion engine guaranteed. Because the ventilation pump according to the invention only serves to aerate or empty the dosing system, a very low flow rate is sufficient. Also, only low demands are placed on the delivery pressure of the ventilation pump. As a result, the ventilation pump according to the invention is less expensive than a 4/2-way valve. In addition, such a pump is less prone to failure than a switchable 4/2-way valve. The feed pump according to the invention and / or the inventive

Ventilation pump are preferably designed as diaphragm pumps. However, the invention is not limited to diaphragm pumps. Other types known in the art may also be used. It has proved to be particularly advantageous if the inventive

Feed pump and / or the venting pump of an electromagnetic (Linear) actuator, which is also referred to as a solenoid, is driven. Then namely, can be dispensed with an implementation of the rotational movement of an electric motor, for example in an oscillating conveying movement of the pump.

The direct drive of the diaphragm pump via an electromagnetic actuator allows to easily and inexpensively detect the injected amount of the reducing agent over the stroke of the actuator very accurately. For example, from the course of the armature current through the

electromagnetic actuator can be deduced on the stroke of the actuator. The stroke of the actuator is a direct measure of the amount of reducing agent delivered. Therefore, it is possible to dispense with a separate pressure sensor without degrading the metering accuracy of the metering system according to the invention.

In order to optimize the function of the feed pump and / or the venting pump, a check valve is provided in each case on the suction side and / or the delivery side of both pumps. Alternatively, it is also possible that on the suction side and / or the delivery side of the feed pump and / or the

Venting each a throttle or aperture is provided. In many applications, it is advantageous if a check valve is provided both on the suction side, as well as on the delivery side. Alternatively, it is also possible to provide either on the suction side or the delivery side, a throttle or a diaphragm on the pressure side or the suction side

Provide check valve.

In an advantageous embodiment of the metering system according to the invention, a second check valve is provided on the suction side of the ventilation pump parallel to the first check valve, wherein the reverse direction of the second

Check valve of the reverse direction of the first check valve

is opposite.

This makes it possible, the ventilation pump according to the invention as

Insert pressure compensation element. Namely, when operating the Delivery pump in the pressure line an inadmissibly high pressure, damage to the dosing or the pressure line may result.

In the metering system according to the invention, the ventilation pump is used during operation of the feed pump as a pressure compensation element. Namely, if in the pressure line so high pressure prevails that he is the first

The non-return valve on the suction side of the aeration pump opens, then the high pressure from the pressure line acts on the diaphragm of the aeration pump. This membrane can yield to this pressure by expanding towards the electric actuator. As a result, the volume on the pressure side of the metering system according to the invention increases and the pressure peak is reduced.

Alternatively, it is also possible, the pressure-side check valve in the

Design vent line so that it opens when an inadmissibly high pressure in the pressure line and thus a part of the

Feed pump pumped urea water solution from the pressure line flows back into the suction line. As a result, an effective pressure limitation is also achieved. Again, no additional costs are required.

Of course, a combination of the two variants, namely the elastic deformation of the membrane of the ventilation pump and the opening of the vent line can be realized.

In a further advantageous embodiment of the invention, it is provided that a throttle or a diaphragm is provided on the pressure side of the ventilation pump parallel to the check valve. By this, the electric actuator can be made smaller. This reduces the electrical power consumption and reduces the weight and space requirements.

A particularly advantageous embodiment of the invention provides that in a diaphragm pump, the membrane vent line on the pressure side or the suction side of the venting pump closes when the actuator is de-energized. As a result, the ventilation pump according to the invention assumes the function of a switchable directional valve without additional expenditure of components. This is possible because the conveying work, ie when the membrane presses reducing agent from the pumping chamber into the venting line, from one to the membrane acting spring is done. This spring is biased by the electromagnetic actuator during the suction stroke of the feed pump.

By a suitable structural design, it is therefore easily possible that the membrane of the spring on the connection of the

Ventilation line is pressed in the pump housing and thus closes.

In order to increase the sealing effect or the maximum pressure in the delivery chamber against which the diaphragm of the ventilation pump can shut off the ventilation line, a cross-sectional constriction in the housing can be provided. This cross-sectional constriction may be formed simultaneously as a throttle or aperture.

Furthermore, it is possible to increase the tightness or the maximum holding pressure / closing pressure of the diaphragm by forming an annular bead which surrounds the end of the pressure line or the suction line. This results in an increased surface pressure between the bead and the

Membrane, so that also the tightness of the as controllable directional control valve

used diaphragm pump is increased. Again, the cost of the additional bead are negligible, since the housing of the pump is usually made as a plastic injection molded part or as a cast metal part and thus incur no additional manufacturing costs for the bead.

Alternatively, it is also possible, in the case of a currentless actuator of the delivery pump and / or the ventilation pump, to exert the membrane directly or indirectly a closing force on a valve member of the check valves. As a result, the tightness of the check valves is increased. Again, this can be done without additional

Manufacturing costs are achieved. This improved tightness makes it possible to simultaneously reduce the bias of the closing springs in the check valves. This will cause the electromagnetic actuator

reduces the promotional work to be applied and as a result can

electromagnetic actuator be made smaller, more energy efficient and cost-effective. This is an aspect that affects both the aeration pump and the delivery pump. In order to achieve a particularly compact design, it is further provided that the ventilation pump is integrated in the feed pump. This not only has advantages in terms of the hydraulics of the dosing system, but also has the advantage that the signal lines for controlling both pumps can be guided together into the housing.

In addition, there is the advantage that with freezing reducing agent in the feed pump, the ventilated delivery chamber of the ventilation pump, yes as

Compensation volume for the reductant located in the feed pump is located in the immediate vicinity of the feed pump and thereby the

Pressure equalization between the two pumps is very possible.

According to an advantageous embodiment of the metering system according to the invention according to claim 13, at least one capacitor is provided, so that the stored in the capacitor electrical charge for energizing the electric actuator of the ventilation pump can be used. Since a capacitor can deliver the stored electric charge very quickly, it is possible to act on the actuator of the aeration pump very quickly and with large currents in an emergency, so that the membrane is suddenly raised and a very rapid suction of liquid reducing agents through the Ventilation pump takes place. Through this dynamic suction process, a so-called impulse back suction of liquid reducing agent takes place. This impulse back is ultimately nothing more than the exploitation of

Elasticity of the pressure line and the pressurized liquid reducing agent therein. At a sudden pressure drop springs

in a sense, the pressure line together and thereby promotes a small amount of liquid reducing agent in the direction of the ventilation pump. This results in that at least a portion of the pressure line, but also the metering module is no longer filled with liquid reducing agent, but with air or exhaust gases. This has reduced the risk of ice pressure damage.

A further advantageous embodiment of the metering system according to the invention provides that the feed pump and / or the aeration pump comprises an electric actuator with a magnet and an armature, a diaphragm, a valve-membrane plate and a valve plate, and that between the Valve diaphragm plate and the valve plate is a rubber plate as a valve element and sealing element is present.

Through this sandwich structure of the feed pump and / or the

Venting pump check valves according to the invention and 7oder throttles can be produced in a simple and inexpensive manner. For example, for an additional check valve to provide only an additional breakthrough in the valve plate and provide corresponding recesses acting as a valve element rubber plate.

Similarly, it is possible that the valve diaphragm plate and the diaphragm of the ventilation pump together with the electric actuator form a controllable shut-off valve. Again, no significant additional manufacturing costs are required.

In a further advantageous embodiment of the invention, a valve plate is formed on the armature, which works together with a sealing bead of the valve diaphragm plate as a switchable way or check valve. Furthermore, it is provided that the membrane is arranged offset in the stroke direction to the valve disk on the armature. This makes it possible, on the one hand, the pressure prevailing in the delivery chamber to some extent on the back of the

Valve plate acts and thus this against the sealing seat in the

Valve diaphragm plate presses. This increases the tightness. At the same time it is possible that the membrane evades in the stroke direction and thus degrades a pressure peak. Thus, the membrane can work as a pressure compensation element. In order to be able to determine the elasticity of the membrane structurally within narrow limits, it is advantageous for the membrane to be wave-shaped in cross-section

embody. At the same time it is advantageous if the armature of the electric actuator limits the travel of the membrane in the stroke direction, so that no bursting or tearing of the membrane is to be feared when the membrane is subjected to impermissible high pressures.

Further advantages and advantageous embodiments of the invention are the following drawings, the description and the claims removable. Show it: a block diagram of a first embodiment of a metering system according to the invention, the embodiment of Figure 1 when ventilating the system, the block diagram of a second embodiment in which the ventilation as a diaphragm pump running aeration pump at the same time as a controlled check valve in normal operation of the metering, a third embodiment of a metering system according to the invention with a throttle instead of a check valve on the suction side of the ventilation pump, a further embodiment of a metering system according to the invention with a throttle on the pressure side / delivery side of the ventilation pump according to the invention, a further embodiment of a metering system according to the invention, in which the membrane of the feed pump is used as a controlled check valve.

Figures 7 and 8 further embodiments according to the invention

Dosing systems and the

Figures 9 to 16 constructive details of various embodiments of inventive ventilation pumps.

FIG. 1 shows a first exemplary embodiment of a metering system according to the invention as a block diagram. In a tank 1 is liquid reducing agent (urea-water solution). If necessary, a feed pump 5 sucks liquid reducing agent out of the tank via a suction line 3 and conveys it via a pressure line 7 to a metering module 9

Designations suction line 3 and pressure conveying line 7 refer to the Normal operation of the metering system, namely, when reducing agent is conveyed from the tank to the metering module 9.

The metering module 9 can be represented in the block diagram as a combination of a throttle 1 1 and a switchable 2/2 way valve 13. The directional valve

13 is closed when de-energized. Then no liquid reducing agent is injected into the exhaust system of the internal combustion engine (not shown). When the feed pump 5 delivers and thus the reducing agent in the pressure line 7 is under an elevated pressure, the directional control valve 13 can be opened by the engine control unit (not shown), so that liquid

Reducing agent is atomized by the throttle 1 1 in the dosing 9 and is finely distributed in the exhaust pipe of the internal combustion engine is injected.

About the delivery pressure of the feed pump 5 and the opening time of the directional control valve 13, the injected into the exhaust tract amount of the liquid reducing agent can be controlled. In the metering system according to the invention is parallel to the feed pump, but with opposite conveying direction a

Ventilation pump 15 provided according to the invention. When the feed pump 5 is in operation, the venting pump 15 is out of order

Operation and vice versa. However, there are also operating states of the

Dosing system according to the invention in which neither of the two pumps 5, 15 is in operation. On the suction side and the delivery side of the feed pump 5 is a respective

Check valve 17, 19 provided. Similarly, on the suction side and the pressure side of the venting pump 15 are also

Check valves 21 and 23 are provided. Since the conveying directions of

Feed pump 15 and the venting pump 15 are opposite, the locking directions of the check valves 17, 19 and 21, 23 are directed opposite.

The ventilation pump 15 is hydraulically integrated via a ventilation line 25 in the suction line 3 and the pressure line 7 of the feed pump 5. The suction-side section of the ventilation line with respect to the ventilation pump 15 25 has the reference numeral 25.1 The reference to the ventilation pump 15 pressure-side portion of the vent line 25 has the reference numeral 25.2

In the normal operation of the dosing shown in Figure 1, the check valves 21 and 23 block the vent line 25, as long as the pressure in the pressure line 7 below the opening pressure of said

Check valves is located.

In Figure 2, the same embodiment of the invention

Dosing system shown in the operating mode aeration. In this case, the

Feed pump 5 out of service and the aeration pump 15 promotes liquid reducing agent from the metering module 9 in the tank 1 back. So that

Venting pump 15 can ventilate the dosing 9 and a portion of the pressure line 7, the 2/2-way valve 13 of the dosing 9 is open. This switching position is shown in FIG.

In the ventilation of the metering system shown in Figure 2 lock the

Check valves 17 and 17 sections of the suction line 3 and the pressure line 7 from, as long as the delivery pressure of the aeration pump 15 7 below the

Opening pressure of said check valves is.

Once the ventilation process is completed, the directional control valve 13 of the metering module 9 are closed again and the aeration pump 15 is turned off. After the aeration process, both the metering module 9 and parts of the

Pressure line 7, the vent line 25 and the venting pump 15 filled with air or exhaust gas. Thus, the still filled with liquid reducing agents areas of the dosing, namely especially the feed pump 5, the suction line 3 and a part of the pressure line 7, the aforementioned air-filled areas are available as a compensating volume, if the

Reducing agent freezes. This will help freeze the

Reducing agent resulting forces reduced so much that no damage to the feed pump 5 or the lines 3, 7 are more to be feared. This is especially true when the feed pump 5 and the venting pump 15 are arranged in a common housing. FIG. 3 shows a second embodiment of the metering system according to the invention. An essential difference to the first

Embodiment is that designed as a diaphragm pump venting pump 15 is designed so that whenever the

Venting pump is de-energized, the diaphragm of the aeration pump 15 the

Ventilation line 25 closes. This is represented by a switchable directional control valve 26. Preferably, the section 25.2 of the vent line 25 is closed, although the directional control valve 26 is located in the section 25.1.

As soon as the actuator of the ventilation pump 15 is energized, the membrane releases the ventilation line 25 again, so that the mode of operation explained with reference to FIGS. 1 and 2 is restored. The ventilation pump 15 according to the second embodiment thus additionally has the function of a controlled shut-off valve 26. Because this no additional components are needed, this additional functionality is achieved at no extra cost.

The use of the feed pump as a controlled shut-off valve 26 has the advantage that, by appropriate design of the cross-section of the

Vent line 25 this with a very low spring pressure, the spring acting on the membrane, can be sealed. This eliminates the

Necessity to design one of the two check valves 21, 23 in the ventilation line so that they are still tight with respect to the operating pressure of the feed pump 5. The opening pressure of the check valves 21 and 23 should be as low as possible because the electromagnetic actuator of the venting pump 15 must overcome the opening pressure at each stroke. The lower the opening pressure, the smaller and lighter the actuator can be made. Therefore, when using the diaphragm of the ventilation pump 15 as an additional shut-off valve, not only the opening pressure of the check valves 21, 23 can be reduced, but the electromagnetic actuator of the ventilation pump 15 can be made smaller, which saves costs and installation space. In addition, this also reduces the electrical energy required for the drive of the ventilation pump 15th In the embodiment shown in Figure 4, a suction throttle 27 is provided on the suction side of the venting pump 15 instead of a check valve 21 (see Figures 1 to 3). Since the suction throttle 27 ultimately in

Substantially consists only of a cross-sectional constriction in the vent line 25, thereby the number of required components is further reduced, which has a positive effect on the manufacturing cost and the robustness of the

dosing system according to the invention.

As can be seen from FIG. 5, the non-return valve 23 on the pressure side of the aeration pump 15 can also be replaced by a delivery throttle 29.

It is important, however, that in the ventilation line 25 at least one

Check valve is present.

It goes without saying that the membranes of the feed pump 5 and the venting pump 15 can be driven not only by an electromagnetic actuator, but also by an electric motor. It can also be another pump principle such. B. a piston pump, a gear pump, a vane pump u. a. be used more. The check valves 17, 19, 21 and / or 23 may as needed and

Design are loaded with spring elements, so that their opening pressure is adjustable by the biasing force of the springs within wide limits. As explained with reference to the exemplary embodiments according to FIGS. 4 and 5, they can also be partially replaced by throttles.

Any necessary filters in the suction side 3, the pressure line 7 and / or the vent line 25 are partially required in practical applications, but not shown for reasons of clarity. The same applies to a pressure sensor or a flow sensor. If possible, however, the installation of such sensors is dispensed with, since they drive the costs upwards. If required, an additional electric heater can be installed. However, this is not necessary in many cases, because the waste heat of the pump drive is usually sufficient to freeze the

Prevent dosing. Of course, this does not apply to the liquid reducing agent in the tank 1. Here is in many cases a heater required at least for thawing the frozen reducing agent (not shown).

FIG. 6 shows a further exemplary embodiment of a metering system according to the invention. In this embodiment, the feed pump

5 as a diaphragm pump and can be used in a similar manner as explained with reference to Figure 3, as a switchable shut-off valve 28. Therefore, reference is made in this regard to what has been said in connection with the aeration pump 15 in FIG.

Figure 7 shows a block diagram of another embodiment of the metering system according to the invention. In this embodiment, parallel to the first check valve 21 on the suction side of the

Ventilation pump 15, a second check valve 31 is provided. The

Locking directions and the passage directions of the check valves 21 and 31 are opposite.

If, for example, during operation of the feed pump 5 in the pressure line 7, an impermissibly high pressure occurs, then opens the first

Check valve 21. As a result, the membrane (not shown in FIG

7) of the ventilation pump 15 is subjected to the higher pressure and the

Membrane evades due to the higher pressure. As a result, the volume of the delivery chamber in the aeration pump 15 is increased and the pressure peak thereby partially reduced. As soon as the pressure in the pressure line 7 returns to normal values, the elastic membrane of the ventilation pump

15 via the second check valve 31 previously in the delivery chamber

absorbed amount of liquid urea water solution back into the

Push back the pressure line until a pressure equalization is achieved. If the overpressure in the pressure line 7 is very high, it may also happen that the check valve 23 opens on the pressure side of the aeration pump 15 and thus a portion of the conveyed by the pump 5 liquid from the pressure line 7 is returned to the suction line 3 , This also causes a pressure reduction to permissible values or a pressure limitation. Thus, the system according to the invention is very robust and takes no damage even when impermissibly high pressures occur. In the embodiment according to FIG. 8, a throttle 33 is provided parallel to the check valve 23 on the pressure side of the aeration pump 15. Through this throttle, it is possible to make the electric actuator smaller

perform. It has been found that, especially if the

Diaphragm of the ventilation pump 15 as an additional shut-off valve 26

Pressure holding valve 26 is formed during the suction phase of the feed pump 5, a strong negative pressure in the delivery chamber of the venting pump 15 can form, because the delivery chamber via the vent line 25 and the check valve 23 is connected to the suction line 3. The blocking effect of the check valve 23 prevents a pressure equalization between the delivery chamber of the ventilation pump 15 and the suction line 3, when there is a negative pressure in the delivery chamber.

This negative pressure in the delivery room can only be overcome by a very strong electric actuator. By the throttle according to the invention it is ensured that a pressure equalization between the delivery chamber of

Ventilation pump 15 and the suction line 3 can take place when there is negative pressure in the delivery chamber. As a result, the drive power of the electric actuator can be reduced, which has a positive effect on space requirements and weight of the electric actuator. Further details can be found in the

Figures 14-16 and their descriptions.

In Figure 9 is a longitudinal section through an embodiment of a

ventilation pump 15 according to the invention.

The electric actuator 35 essentially comprises an electromagnet 37 and an armature 39. Between the magnet 37 and the armature 39, a spring 41 is present, which the armature 39 in the figure 9 to the left against a

Membrane 43 presses. The membrane 43 is sealingly clamped on the outside with a bead 44 in the housing 47 of the ventilation pump 15 so that there is no liquid in FIG. 9 to the right of the membrane 43. On the other side of the membrane 43, a delivery chamber 45 of the ventilation pump 15 is formed in the housing 47. In the housing 47 of the ventilation pump 15 are in addition to the delivery chamber 45 and the connections of the sections 25.1 and 25.2 of

Ventilation line 25 indicated. In this case, by the reference numeral 25.1, the suction-side connection of the ventilation pump 15 to the ventilation line 25th designated during the connection 25.2 the pressure-side connection of the ventilation pump 15 to the ventilation line 25. The

Check valves 21 and 23 are not shown in FIG. In the region of the pressure-side connection 25.2, an annular sealing seat 49 is formed in the housing 47.

If the electric actuator is de-energized, then the spring 41 presses the armature 39 and with it the membrane 43 against the sealing seat 49, so that the connection 25.2 of the ventilation line 25 is closed. As soon as the electric actuator 35 is energized, the magnet 37 moves the armature 39 to the right in FIG. 9 so that the membrane 43 lifts off from the sealing seat 49 and thus a hydraulic connection is established between the connection 25.1 and the delivery chamber 45. Thus, the ventilation pump 15 according to the invention is according to the

Embodiment of Figure 9 at the same time a controllable directional control valve, which closes the port 25.2 of the vent line 25 in the currentless switched actuator 35. This functionality requires no additional components. It is achieved by a clever design and tuning of the diaphragm 43, the pump housing or the sealing seat 49 and the electric actuator 35. This results in no additional costs in the production.

When the electric actuator 35 is energized abruptly by the discharge of one or more capacitors (not shown), then the armature 39 is attracted very quickly and with great force, so that a strong and sudden pressure drop in the region of the pressure line 7 and a portion 25.1 of Ventilation line 25 takes place. Due to the elasticity of the pressure line 7 or the vent line 25 and the liquid therein and pressurized, the sudden pressure relief causes a portion of the liquid contained in the pressure line 7 is pressed by the venting pump 15 in the direction of the tank. This is also done with a. However, very fast conveying stroke of the aeration pump 15 ensures partial ventilation of the dosing module 9 and the pressure line 7, so that even during the subsequent freezing of the system no damage caused by ice pressure. This highly dynamic process is referred to in the context of the invention as pulse back suction and is also in all Inventive embodiments of dosing

or ventilation pumps 15 can be used.

In the figure 10, another embodiment of a ventilation according to the invention is also shown partially in section. In this

Embodiment is a sandwich-like structure of the ventilation pump 15 to recognize well. From top to bottom connects to the armature 39, the membrane 43 with its bead 44 and a valve-diaphragm plate 51 at.

In this embodiment, it is also easy to see that at the lower end of the armature 39 in Figure 10, a valve plate 53 is formed, which is encapsulated with rubber or a similar elastic material. The membrane 43 is made of the same rubber material and is positively connected to the armature 39.

However, there is a certain distance between the valve disk 53 and the membrane 43 in the axial stroke direction of the armature 39, so that the pressure prevailing in the pumping chamber 45 is also shown in FIG. 10 "from above"

Valve plate 53 acts. As a result, the pressure prevailing in the delivery chamber 45 simultaneously acts as a hydraulic closing force, which presses the valve disk 53 against the sealing seat 49 in the valve membrane plate 51.

In the exemplary embodiment illustrated in FIG. 10, the membrane 43 has a wave-shaped cross section. As a result, the membrane 43 becomes more elastic and can thus yield more easily when the pressure in the delivery chamber 45 increases. Then the membrane 43 in FIG. 10 deviates upward in the direction of the armature 39 until it rests against the armature 39. This ensures that even with the occurrence of extremely large excess pressures in the delivery chamber 45, the membrane 43 does not tear.

In the valve diaphragm plate 51 are still more connections, namely the port 25.1 and a port 25.3 visible. The pressure-side outlet 25.2 of the ventilation pump 15 is covered by the valve disk 53 in FIG. The port 25.3 provides the hydraulic connection to the second

Check valve 31 (see Figure 7) ago, when the inventive Ventilation pump 15 is still used at the same time as a pressure compensation element.

Figure 1 1 shows a detail of Figure 10 further enlarged and to a

Valve plate 57 and a rubber plate 55 added. Below the valve membrane plate 51, a rubber plate 55 and a valve plate 57 are arranged. The valve diaphragm plate 51, the rubber plate 55 and the

Valve plate 57 form below the port 25.1, the check valve 21, the locking direction in Figure 1 1 runs from top to bottom. The

Passage direction is indicated by an arrow 59. To clarify which portions of the components 51, 55 and 57 form the check valve 21, these portions are enclosed by a dashed line.

In the valve plate 57, a circumferential ridge 61 is formed, which cooperates with a corresponding web 63 of the valve-diaphragm plate 51 so that it clamps the rubber plate 55 sealing. Coaxially with the web 61, a sealing seat 65 is formed in the valve plate 57, on which the rubber plate 55 rests when the check valve 21 is closed. The sealing seat 65 and the web 61 together with the rubber plate 55 define an annular channel 67. Above the annular channel 67, a plurality of arc-shaped openings 69 are recessed in the rubber plate 55.

If now the check valve 21 of the pressure line 7 (not shown in Figure 1 1) via the vent line 25 with the in the pressure line. 7

prevailing pressure is applied and this pressure is greater than the

Opening pressure of the check valve 21, then lifts the rubber plate 55 from the sealing seat 65 and thereby creates a hydraulic connection to the annular channel 67 in the valve plate 57. From the annular channel 67, the reducing agent passes through apertures 69 in the rubber plate 55 in the Pumping chamber 45 of the ventilation pump flow.

This means that reducing agent can flow in the direction of the arrow 59 through the bore 69 in the valve plate 57, when the difference between that in the bore 71 and the delivery chamber 45 is large enough. Once the pressure of the reducing agent in section 25.1 of

Ventilation line 25, which communicates with the pressure line 7, under the Opening pressure of the check valve 21 decreases, the rubber plate 55 lowers due to their elasticity back to the sealing seat 65 and thus closes the delivery chamber 45th

The second check valve 31 has the same structure but the

opposite passage direction. Therefore, the annular channel 73 and the sealing seat 75 are disposed in the valve-membrane plate 51.

In the figure 1 1 are associated with the second check valve 31

Breakthroughs 77 visible in the rubber plate 55 only to a small extent.

In comparison of the two check valves 21 and 31 it is clear that the sealing seat 75 of the second check valve 31 is smaller than the diameter of the sealing seat 65 of the first check valve 21. Thus, with the same thickness of the rubber plate 55, the opening pressure of the two check valves 21 and 31 can be adjusted , As already explained in connection with FIG. 7, it is advantageous if the opening pressure of the second

Check valve 31 is higher than that of the first check valve 21, which is structurally implemented by the smaller diameter of the sealing seat 75.

Already from the figure 1 1 it is clear that it is possible with minimal cost, one or more check valve 21, 23, 31 in the inventive

To integrate aeration pump 15. As a result, different variants of the ventilation pump 15 according to the invention can be produced by replacing the valve membrane plate 51 or the valve plate 57.

FIG. 12 shows a side view of the exemplary embodiment according to FIG. 11. In this, the check valve 23, which connects the delivery chamber 45 with the pressure-side section 25.2 of the ventilation line 25, can be clearly seen. The passage direction of the check valve 23 is indicated by an arrow 79. Again, the same structure is recognizable.

In the embodiment shown in Figure 12, an outer sealing seat 49.2 and an inner sealing seat 49.1 are formed in the valve diaphragm plate 51 on which the valve plate 53 rests when the actuator 35 is de-energized, so that a particularly good sealing of the delivery chamber 45th to the print side of the Ventilation pump 15 takes place. The inner sealing bead 49.1 results in a leakage-free sealing possible by the spring 41 applied closing forces. This is of particular importance when the vehicle is parked and a full run of the pressure line 7 and / or the dosing and / or the

Exhaust system should be reliably prevented without the spring 41 and thus the magnet 37 must be larger than absolutely necessary.

In the valve-membrane plate 51, a sealing seat 81 and an annular channel 83 is formed, which forms the check valve 23 together with the rubber plate 55. In this illustration, it is easy to see how the valve plate 53 with the

Sealing seat 49 cooperates and thereby relieves the second check valve 23.

FIG. 12 also clearly shows that the magnet 37 has a toroidal recess which compensates for the lifting or elastic deformation of the

Membrane 43 limited. As a result, damage to the membrane 43 in the event of inadmissibly high pressures in the delivery chamber 45 can be avoided.

A shoulder 85 on the armature 39 serves on the one hand to the fact that the compression spring 41 can be supported on the anchor, on the other hand, this paragraph 85 for guiding the

Ankers 39 in the magnet 37 serve.

13, the rubber plate 55 is transparent and "from below", so that the sealing seats in the valve-membrane plate 51 and parts of the membrane 43 are also visible

Diameter of the check valves 21, 23 and 31 clearly.

The check valve 23 has the largest bore, so that it opens at a small overpressure in the delivery chamber, if not the valve plate 53 closes this valve. As a result, during operation of the aeration pump 15 of the

Energy requirement minimized. In contrast, the second check valve 31 on the suction side of the ventilation pump 15 has the smallest diameter of the

Sealing seat 75, so that this check valve opens only at relatively high pressure. In the figures 14 to 16 is another embodiment of a

ventilation pump 15 according to the invention.

The check valves 21 and 23 are slightly different in construction than those described above. However, their function is unchanged. In FIGS. 14 and

It is easy to see how the membrane 43 rests on the sealing seat 49, which surrounds the connection 25.1 in the valve plate 51.

Especially in FIG. 15, which shows an enlarged detailed illustration of FIG. 14, it can also be clearly seen that the membrane 43 is attached to another

Bead 87 rests. The delivery chamber 45 thus has an annular geometry and is bounded radially on the outside by the bead 87 and on the inside by the sealing seat 49. If, during operation of the feed pump 5 (see, for example, FIG. 1), liquid reducing agent is sucked out of the tank, the pressure in the suction line 3 briefly drops. As a result, the check valve 23 opens in the pressure-side part in the ventilation line 25 and as a result, the pressure in the pumping chamber 45 also decreases. This low pressure in the delivery chamber 45 is maintained because of the blocking effect of the check valve 23 even if ambient pressure prevails in the suction line 3 again.

This low pressure in the delivery chamber 45 causes the membrane 43 is pulled against the valve plate 51 and against the sealing seat 49 and the bead 87, so to speak. This means that a huge force of the

Anchor 39 or by the magnet 37 must be applied to lift the armature 39 and with it the membrane 43 of the sealing seat 49 and the bead 87. This would require a large and expensive electric actuator 35.

According to the invention, therefore, a throttle 33 is formed in the valve plate 57, which connects the delivery chamber 45 with the ventilation line 25.2 or indirectly with the suction line 3 (see the block diagram in Figure 8 and Figure 16). The throttle 33 ensures a pressure equalization between the suction line 3 and the delivery chamber 45, so that the forces for lifting the membrane 43 from

Sealing seat 49 and the bead 87 are required to be drastically reduced. As a result, a smaller electrical actuator 35 can be used, which saves costs and installation space. In addition, the power requirement of the

Ventilation pump 15 according to the invention.

Claims

claims

1. metering system for urea-water solution comprising a delivery module with a feed pump (5), a metering module (9) and a tank (1), wherein the feed pump (5) and the tank (1) via a suction line (3 ), and wherein the feed pump (5) and the metering module (9) via a pressure line (7) are interconnected, characterized in that parallel to the

Feed pump (5), a venting pump (15) is arranged, and that the

Ventilation pump (15) is connected on the suction side to the dosing module (9) and on the pressure side to the tank (1).

2. dosing system according to claim 1, characterized in that the feed pump (5) and / or the venting pump (15) is designed as a diaphragm pump.

3. dosing system according to claim 1 or 2, characterized in that the

Feed pump (5) and / or the ventilation pump (15) of a

electromagnetic actuator (35) is driven.

4. Dosing system according to one of the preceding claims, characterized in that on the suction side and the delivery side of the feed pump (5) and / or the aeration pump (15) each have a first check valve (17, 19, 21, 23) is provided.

5. Dosing system according to one of the preceding claims, characterized in that on the suction side of the feed pump (5) and / or the venting pump (15), a throttle (27, 33) or a diaphragm is provided.

6. dosing system according to claim 4 or 5, characterized in that on the

Suction side of the aeration pump (15) parallel to the first check valve (21) a second check valve (31) is provided, that the locking direction of the second check valve (31) opposite to the reverse direction of the first check valve (21), and that the opening pressure of second check valve (31) is higher than the opening pressure of the first check valve (21). (Figure 7)

7. Dosing system according to one of claims 4 to 6, characterized in that on the pressure side (25.2) of the aeration pump (15) parallel to the first

Check valve (23) a throttle (33) or aperture is provided. (Figure 8)

8. Dosing system according to one of claims 3 to 7, characterized in that in the currentless actuator (35) of the feed pump (5) and / or the aeration pump (15) has a membrane (43) the pressure line (7), the suction line ( 3) or the

Ventilation line (25) closes.

9. dosing system according to claim 7 or 8, characterized in that the throttle (27) or aperture at the end of the pressure line (7), the suction line (3) or the ventilation line (25) is arranged, which of the membrane (43) is closed when the actuator (35) is de-energized.

10. dosing system according to claim 6, characterized in that the end of

Pressure line (7), the suction line (3) or the vent line (25), which is closed by the membrane (43) with currentless actuator (35) is surrounded by a sealing seat (49, 65, 81).

11. Dosing system according to one of claims 3 to 10, characterized in that in currentless actuator (35) of the feed pump (5) and / or the venting pump (15) the membrane (43) directly or indirectly a closing force on a valve member of a Check valve (17, 19, 21, 23) exercises.

12. dosing system according to one of the preceding claims, characterized in that the ventilation pump (15) in the feed pump (5) is integrated.

13. Dosing system according to one of the preceding claims, characterized in that at least one capacitor is present, and that stored in the capacitor electrical charge of the capacitor, for energizing the

electric actuator (35) of the ventilation pump (15) can be used.

14. Dosing system according to one of the preceding claims, characterized in that the feed pump (5) and / or the aeration pump (15) comprises an electric actuator (35) with a magnet (37) and an armature (39), a membrane (43) , a valve-membrane plate (51) and a valve plate (57), and that between the valve diaphragm plate (51) and the valve plate (57) a rubber plate (55) is provided as a valve element and sealing element.

15. Dosing system according to claim 14, characterized in that the valve membrane plate (51) and the membrane (45) of the venting pump (15) form a controllable directional or check valve (26). (Figures 9 to 16)

16. Dosing system according to claim 14 or 15, characterized in that the valve membrane plate (51), the rubber plate (55) and the valve plate (57) has a first suction-side check valve (21), a second suction-side check valve (31), a pressure-side check valve (23) and / or a throttle (27, 29, 33) form. (Figures 4, 5, 7 and 8)

17. Dosing system according to one of claims 14 to 16, characterized in that on the armature (39), a valve plate (53) is formed, and that the valve disc (53) with the material of the membrane (43) is encapsulated, and that the Membrane (43) offset in the stroke direction to the valve disc (53) on the armature (39) is arranged.

18. Dosing system according to one of the preceding claims, characterized in that the membrane (43) is designed in a wave-like manner in cross-section.

19. Dosing system according to one of claims 14 to 18, characterized in that the armature (37) limits the travel of the membrane (43) in the stroke direction.