DE102008000932A1 - Device for dosing a liquid reducing agent - Google Patents

Abstract

A device (110) for metering a liquid reducing agent (112) into an exhaust system is proposed. In particular, the device (110) can be used to reduce nitrogen oxides in an exhaust gas. The device (110) comprises at least one working container (114) for storing a working amount of the liquid reducing agent (112). Furthermore, at least one metering module (132) is provided, as well as at least one delivery line (120) and at least one delivery pump (130). Furthermore, the device (110) comprises at least one storage container (216) for storing a storage amount of the liquid reducing agent (112), preferably an amount exceeding the working amount. The storage container (216) is connected to the working container (114) via at least one bearing line (218). In the bearing line (218) at least one bearing pump (220) and a leakage flow check valve (320) for pumping liquid reducing agent (112) from the storage container (216) to the working container (114) is added.

Description

State of the art

The The invention is based on known devices for dosing liquid Reducing agents or other pollutant-reducing liquids in an exhaust system. Such devices are used for example in the automotive industry used to pollutants in an exhaust an internal combustion engine to reduce. Furthermore, the concerns Invention A method of operating the dosing apparatus of the liquid reducing agent.

at Internal combustion engines, especially diesel-powered Internal combustion engines must be due in the next Years of tightened emissions legislation The proportion of nitrogen oxides in the exhaust gas can be reduced. to Reduction of the nitrogen oxide content in the exhaust gas becomes, for example, a Selective Catalytic Reduction (SCR) performed at the nitrogen oxides with the help of reducing agents to nitrogen and water are reduced. As a reducing agent, for example an aqueous urea solution used. Also other methods of chemical reduction of pollutants are known.

at the SCR is usually the reducing agent in a Tank stored and via a line from the tank to a dosing module promoted. The dosing module becomes the reducing agent For example, in an exhaust pipe, for example in the range of a catalyst, injected.

Such a mixture delivery device for introducing a reducing agent into an exhaust system of an internal combustion engine is in EP 0 928 884 A2 described. In this case, a urea-water solution is introduced by means of a pump under pressure and the addition of compressed air in front of a catalyst to effect the reduction of nitrogen oxides in the exhaust gas. In addition to a reducing agent consumption tank, the apparatus shown also has a reducing agent reservoir from which can be refilled via a equipped with a return valve line urea-water solution in the reducing agent consumption tank.

by virtue of the harsh environmental conditions under which the systems in the Practice must be used, stand the known systems however, faced with numerous challenges which sometimes require a high system complexity. One difficulty, for example, is that in many Cases a pumping of the reducing agent with great effort connected is. If, for example, a conveyor both for dosing and for pumping liquid Reducing agent between storage container and working container used, this pumping is either only by means of a complex control possible, or in a wake of the system, d. H. if the vehicle is parked. The latter process takes several minutes, in many cases a high level of noise occurs.

Farther represents the now regularly required Error detection in the sense of a so-called on-board diagnosis (OBD) high challenges to the systems. In particular, the connection between storage container and working container must be monitored, what with a coupling of dosing and pumping is not always easy. Such are usually taken in the pumping circuit valves, which are difficult to monitor are, so it is in case of leaks of such valves in normal operation overfilling the storage container can come.

A another challenge is the temperature range, in which the systems are commonly used. Specifications require a system uptime down to temperatures of about -40 ° C. Depending on the design the reducing agent, in particular depending on the addition of antifreeze, is the benchmark of liquid reducing agents (for Example of a urea-water solution), however far above this temperature, for example at about -11 ° C. Accordingly, the systems must be designed ice pressure resistant which, in known systems usually only by consuming heating of the lines can be realized. For example, must usually the connecting line between storage containers and working container be configured heated. valves, which are included in this line must be in the Usually ice pressure resistant to be chosen, which is not in all cases possible without major technical effort is.

From the post-published DE 10 2006 06 1732 For example, an SCR system is known in which a liquid reducing agent is injected into the exhaust line of an internal combustion engine when required in order to enable the catalytic reduction of nitrogen oxides in an SCR catalyst. An embodiment of this SCR system includes a first tank and a storage tank.

Advantages of the invention

It is a device for dosing a liquid reducing agent proposed in an exhaust system, the above-described Disadvantages of the prior art avoids.

The proposed device may, for example, in the context of the above Pollutant reduction can be used in the context of SCR process. Instead of a liquid reducing agent in the true sense, other pollutant-reducing fluid media can be used.

The The device described has at least one working container for storing a working amount of the liquid reducing agent, at least one metering module, at least one delivery line and at least one pump on. Single components can also be present several times, for example several Work container as part of a device for mixing fluid media. The feed pump is preferably as a diaphragm pump trained, as such pumps are inherently ice pressure resistant. The delivery line can be fully or partially heated be.

In the delivery line can accommodate at least one reversing valve be, preferably a 4/2-way valve (although other Embodiments are possible), which is designed to in a conveying direction of the feed pump, a flow direction to reverse, at least in part, through the support line. In this way, the device can for example be operated in this way be that in a normal operation liquid reducing agent through the feed pump from the work container is transported to the dosing, for example, the above to perform the described SCR process. After a shutdown the normal operation, or even in a state in which the device For example, you can prepare for a hibernation a wake of the feed pump can be used to the delivery line to empty into the working tank and to ventilate in whole or in part. In this way, even without costly measures, one high ice pressure resistance achieved.

additionally at least one working container is at least a storage container for storing a storage amount of provided liquid reducing agent, which preferably before exceeds the maximum storable in the work container amount of work. Typically, the working container has a capacity in the range of 1 to 15 liters, for example in the range between 5 to 8 liters, and more preferably about 6 liters. The storage container has a capacity between 15 liters and 100 liters, preferably in the range between 20 and 50 liters, and especially preferably at about 30 liters.

Of the Storage container is over with the working container connected at least one bearing line, in which a bearing pump for pumping liquid reducing agent and a leakage flow shut-off valve is included. It is advantageously as a bearing pump a Diaphragm pump used because this pump principle has a high ice pressure resistance.

advantageously, So is the bearing line as a separate hydraulic connection between designed the storage and working container. Thus, a surveillance this hydraulic connection, which preferably no valves has to realize in a simple manner. That's enough This advantageous development of the invention, the requirements to an on-board diagnosis as these are easy to monitor is. The pumping operation may occur during operation of the device (ie during dosing of the liquid reducing agent) respectively. As a bearing pump, for example, turn a diaphragm pump can be used, which is inherently ice pressure resistant. In this Fall can also be due to the ice pressure resistance of the diaphragm pump the hydraulic line between storage and working vessels run unheated, since these are not simultaneously must be used for dosing, and there, in particular when using the volumes described above, in the working container contained reducing agent volume for a longer Operation, for example, operation over a frosty period away, enough. The pumping process, for example, over a separate control device, which, for example by means of at least one sensor, a level of the liquid Reducing agent in the working container includes. The control device For example, can act on a speed of the bearing pump.

Brief description of the drawings

embodiments The invention is illustrated in the drawings and in the following Description explained in more detail.

It demonstrate:

1 a device for dosing a liquid reducing agent with a working container and a reversing valve in the form of a 4/2-way valve;

2 a device with a 2-tank system;

3 in the 2 illustrated device in the venting operation; and

4 a device according to the invention with a 2-tank system.

In 1 is an example of a device 110 for dosing a liquid reducing agent 112 shown. The liquid reducing agent 112 is in a work container 114 recorded, wel For example, with level sensors 116 for monitoring the amount of liquid in the working container 114 can be equipped. The data of the level sensors 116 for example, to a control device 118 be transmitted, for example, a microcomputer, for example, to generate appropriate warning signals when the work container 114 must be refilled.

Furthermore, a delivery line 120 provided, which in this case the subsections 122 . 124 . 126 and 128 having. In the delivery line is a delivery pump 130 recorded, which liquid reducing agent 112 from the work container 114 through the support line 120 to a dosing module 132 promoted. For example, this dosing module can 132 to act an injection valve for injecting the liquid reducing agent in an exhaust tract, for example, a pressure-controlled injection valve. Such injectors are for example in EP 0 928 884 A2 and the prior art described therein, so that the exact embodiment should not be discussed here. In addition to an immediate injection of the liquid reducing agent 112 An injection with admixture of additives or gases is also considered.

Furthermore, in the delivery line 120 a reversing valve 134 added. This reversing valve is designed in the illustrated embodiment as a 4/2-way valve and thus has four inputs. Each of the sections described above 122 to 128 the support line 120 is connected to one of the inputs.

In normal operation of the device 110 is the first section 122 with the second section 124 connected, and the third section 126 with the fourth section 128 , In this way, via the feed pump 130 liquid reducing agent from the working tank 114 to the dosing module 132 be pumped to be injected there into the exhaust.

After parking the vehicle, the feed pump points 130 a caster on. This caster (which may also be artificially extended, for example, by a short-term continued operation of the feed pump 130 ) can be used selectively to the hydraulic system of the device 110 To vent with exhaust gas from the exhaust system. For this purpose, see the illustration in 3 referenced, which is the reversing valve 134 in the corresponding switch position for ventilation shows. In this switching position is the subsection 122 with the subsection 126 connected, and the subsection 124 with the subsection 128 , Because the feed pump 130 their pumping direction has not reversed, is now the conveying direction in the subsections 128 and 122 vice versa, so that still in the delivery line 120 present liquid reducing agent 112 back to the work container 114 is pumped. Subsequently, exhaust gas, for example via the nozzle openings of the dosing 132 , from the exhaust system (not shown) in the delivery line 120 pumped and thus ventilated with exhaust gas. In this way the device becomes 110 For example, prepared for a standstill of the vehicle at low temperatures (for example, at temperatures below -11 ° C). This embodiment gives the device 110 and the individual components a high ice crushing strength.

In the 2 and 3 is a further developed embodiment of the device 110 according to 1 shown. The device 110 indicates, however, as opposed to 1 , a work system 210 and a storage system 212 on. The work system 210 is essentially designed as the device 110 according to 1 and in turn has a work container 114 , a promotion line 120 , a pump 130 , a reversing valve 134 and a dosing module 132 on. Furthermore, again a level sensor 116 and a control device 118 intended. Accordingly, to the design of the individual elements largely to the description 1 to get expelled. The representation in 2 shows the reversing valve 134 in normal operation, ie in a switching position, which the switching position of the reversing valve 134 in 1 equivalent. In contrast, shows 3 the reversing valve 134 in the second switching position, ie in a ventilation switching position, which also above based 1 has been described. The 2 and 3 are therefore described together below.

In contrast to 1 has the device 110 according to 2 still in the subsection 128 the support line 120 a filter 214 on. This filter 214 can essentially serve to block the dosing 132 For example, by particles or ice crystals to prevent. In addition or alternatively, filters can also be provided in further subsections. Also in 1 illustrated device 110 can with appropriate filters 214 be designed.

Next to the workstation 210 is the device according to the 2 and 3 opposite to the illustration in 1 essentially by the addition of the storage system 210 further training. This storage system 210 has a storage container 216 on. This is preferably equipped with a larger maximum filling volume than the working container 114 and serves to stock a storage amount of the liquid reducing agent 112 , In contrast to the work container 114 which is preferred for operation at low temperatures heated working container is configured, the storage container 216 be designed as an unheated container. In this case, a freezing of the liquid reducing agent 112 deliberately accepted, since preferably the work container 114 is configured to supply the vehicle stored therein during a cold period with the amount of work stored therein. Like the work container 114 is also the storage container 216 with a level sensor 116 equipped, which in turn, for example, signals to the control device 118 so that, for example, low level warning messages of the storage container 216 can be issued.

The storage container 216 is with the work container 114 over a camp line 218 connected. About this camp line 218 can the work container 114 from the storage container 216 with liquid reducing agent 112 be supplied. The camp administration 218 thus forms a separate hydraulic path, which with the delivery line 120 of the work system 210 not communicating.

To pump over from the storage container 216 in the work container 114 in normal operation of the device 110 to ensure is in the camp line 218 a bearing pump 220 provided, which is designed as a single pump. Under a single pump is to be understood as a pump in which only small demands are placed on the life, such as a pump with a brush motor. Preferably, as a bearing pump 220 in turn uses a diaphragm pump, as this is inherently ice pressure resistant. Again, in the camp administration 218 a filter 214 added, which the protection of the bearing pump 220 serves.

The pumping, so the promotion of liquid reducing agent 112 from the storage container 216 in the work container 114 , in this example, depending on the fluid level in the working container 114 controlled. Accordingly, the control device 118 , which via level signals of the working container 114 has, according to the Lagerpum PE 220 act. For example, at low level by the control device 118 the bearing pump 220 be switched on or off. Alternatively, a stepless control, for example, a speed of the bearing pump 220 , conceivable.

Due to the separate hydraulic paths is in the in the 2 and 3 shown example, the hydraulic system of the work system 210 and the hydraulic system of the storage system 212 separated from each other. This facilitates a separate diagnosis of both systems 210 . 212 significantly what can be used as part of an on-board diagnosis. Accordingly, additional sensors may be provided to monitor leaks, for example. Furthermore, the Umpumpgeräusche when in the 2 and 3 shown variant compared to conventional systems negligible. Because the bearing pump 220 is preferably designed as a diaphragm pump, which is ice-resistant, can also be the bearing line 218 run unheated.

4 shows a device according to the invention, the components thereof, if provided with the same reference numerals as in 2 or 3 provided, not described again. Unlike the arrangement after 2 is on the suction side 323 opposite pressure side 325 the bearing pump 220 a leakage control valve 320 in the camp administration 218 arranged. This leakage control valve 320 prevents unwanted filling of the working container 114 , in particular by from the storage container 216 trailing medium, which can otherwise happen at correspondingly different levels of fill in the two containers relative to a common horizontal or movements of the medium due to the movements of the motor vehicle. Furthermore, the metering module is an electrically switchable valve 1320 performed; especially when the metering valve is closed 1320 continue from the feed pump 130 Promoted medium can via a return path 308 in a container, preferably the working container 114 as in 4 imaged, be traced back. The return path 308 branches on the suction side 333 opposite pressure side 335 the feed pump 130 and ends in the work container 114 , with recirculated medium in the return path 308 arranged throttle 310 has to go through. This throttle can optionally be preceded by a filter not shown in detail. The return path can here, as in 4 shown, at least at higher levels in the work container 114 immersed in the medium or, alternatively, be arranged in the region of the working container, that it does not dive into the medium located in the working container even at a maximum level in the working container.

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

• - EP 0928884 A2 [0004, 0023]
• - DE 102006061732 [0008]

Claims (12)

Contraption ( 110 ) for dosing a liquid reducing agent ( 112 ) in an exhaust system, in particular for the reduction of nitrogen oxides in an exhaust gas, comprising at least one working container ( 114 ) for storing a working amount of the liquid reducing agent ( 112 ), at least one dosing module ( 132 ), at least one support line ( 120 ) and at least one delivery pump ( 130 ), further comprising at least one storage container ( 216 ) for storing a storage amount of the liquid reducing agent ( 112 ), preferably a quantity exceeding the working quantity, the storage container ( 216 ) with the working container ( 114 ) via at least one warehouse line ( 218 ), characterized by at least one in the stock line ( 218 ) received bearing pump ( 220 ) for pumping liquid reducing agent ( 112 ) from the storage container ( 216 ) to the working container ( 114 ), whereas in the camp 218 ), preferably on the pressure side ( 325 ) of the bearing pump ( 220 ), a leakage control valve ( 320 ) is arranged. Device according to claim 1, characterized in that the dosing module ( 132 ) as an electrically switchable valve ( 1320 ) is trained. Apparatus according to claim 1 or 2, characterized in that from the pressure side ( 335 ) of the feed pump ( 130 ) a return path ( 308 ) branches off. Apparatus according to claim 3, characterized in that the return path ( 308 ) to the working container ( 114 ) or to the storage container ( 216 ). Apparatus according to claim 3 or 4, characterized in that in the return path, a throttle ( 310 ), optionally with upstream filter, is arranged. Contraption ( 110 ) according to one of the preceding claims, characterized in that the bearing pump ( 220 ) has a diaphragm pump. Contraption ( 110 ) according to one of the preceding claims, characterized by a control device ( 118 ), wherein the control device ( 118 ) at least one sensor ( 116 ) for detecting a fill level of the liquid reducing agent ( 112 ) in the working container ( 114 ), wherein the control device ( 118 ) is arranged to circulate the liquid reducing agent ( 112 ) from the storage container ( 216 ) in the working container ( 114 ) according to the level of the working container ( 114 ) to control. Contraption ( 110 ) according to one of the preceding claims, characterized by at least one in the delivery line ( 120 ) reversal valve ( 134 ), which is designed to be a flow direction through the delivery line ( 120 ) at least partially reverse. Contraption ( 110 ) according to the preceding claim, characterized in that the reversing valve ( 134 ) comprises a 4/2-way valve. Contraption ( 110 ) according to the preceding claim, characterized in that a first of the inputs of the 4/2-way valve with the working container ( 114 ), wherein a second of the inputs of the 4/2-way valve with the dosing ( 132 ) and wherein in each case a third and a fourth of the inputs of the 4/2-way valve with two different ends of the feed pump ( 130 ) are connected. Contraption ( 110 ) according to one of the preceding claims, characterized in that the feed pump ( 130 ) has a diaphragm pump. Method for operating a device for dosing a liquid reducing agent with a storage container, a working container and a bearing line ( 218 ) between the storage container and the working container according to one of the preceding claims, characterized in that at least at times liquid reducing agent ( 112 ) from the storage container ( 216 ) to the working container ( 114 ) is pumped and that in this case the liquid reducing agent in the bearing line ( 218 ) arranged leakage control valve ( 320 ) goes through.