DE102008054800A1 - Device for supplying medium i.e. aqueous urea solution, to internal combustion engine of commercial motor vehicle, has medium flowing into supply line in direction tempered by another medium, and line arranged in area of supply lines - Google Patents

Abstract

The device has a supply line (5) integrated into a pump (14) and attached to a tank (16) for receiving a medium i.e. aqueous urea solution (8), which is injected into an exit gas line by a controllable injection valve. The medium flowing into the supply line in a direction (26) is tempered by another medium. The latter medium flows in a return line in another direction (28), where the return line is arranged in a passage area (24) of the supply line and another supply line. The supply line forms a counter flowing device with a return pipe (2).

Description

State of the art

In a vehicle powered by diesel fuel, among other things, the pollutant NOx must be significantly reduced due to the stricter exhaust gas legislation in Europe and the USA in the coming years. One method that is used is the SCR process, in which the pollutant NOx is reduced to N ₂ and H ₂ O with the aid of a reducing agent on a catalyst. SCR (Selective Catalytic Reduction) refers to the technique of selective catalytic reduction of nitrogen oxides in exhaust gases of combustion plants and engines. The chemical reaction of the reduction is selective, which means that not all exhaust gas components are reduced, only the nitrogen oxides (NO, NO ₂ ). The reaction requires ammonia (NH ₃ ), which is added to the exhaust gas. The products of the reaction are water (H ₂ O) and nitrogen (N ₂ ). Chemically, the reaction is a transformation of the nitrogen oxides with ammonia to nitrogen. There are two types of catalysts: one type essentially comprises titanium dioxide, vanadium pentoxide and tungsten oxide, the other uses zeolites.

The object of the vehicle catalytic converter is the chemical conversion of the combustion pollutants hydrocarbon (H _m C _n ), carbon monoxide (CO) and nitrogen oxides (NO _x ) to carbon dioxide (CO ₂ ), water (H ₂ O) and nitrogen (N ₂ ) by oxidation respectively Reduction. Depending on the engine operating point and optimum operating conditions, conversion rates close to 100% can be achieved.

The greater the efficiency of internal combustion engines is optimized, the higher the combustion temperature. At high combustion temperatures, however, more and more nitrogen oxides NO _{x are formed} , which are for example significantly involved in the formation of summer smog.

In vehicle technology, therefore, the SCR process is used to reduce emissions of diesel vehicles, especially commercial vehicles. Thus, these diesel vehicles can EU-5 emissions standard fulfill. The required ammonia is not used directly, ie in pure form, but in the form of an aqueous urea solution (AdBlue). The composition is in the DIN 70070 regulated. The solution is placed in front of the SCR catalyst in the exhaust line, z. B. by means of a metering pump or an injector injected. From the urea-water solution produced by a hydrolysis reaction ammonia and water. The ammonia thus produced can react in the SCR catalyst at the appropriate temperature with the nitrogen oxides in the exhaust gas. The amount of injected urea depends on the engine's nitrogen oxide emissions and thus on the current speed and torque of the engine. The consumption of urea-water solution is depending on the raw emission of the engine about 2% to 8% of the diesel fuel used. It must therefore be carried a corresponding separate tank volume.

Of the Reason that the required ammonia is not is carried in a pure form, is the danger this substance. Ammonia affects the skin and mucous membranes (in particular also on the eyes) corrosive, moreover forms with air an explosive mixture.

To is a medium, for. B. aqueous urea solution (AdBlue) with additives, in front of the SCR catalyst in the exhaust pipe injected by means of a metering valve. To protect against freezing So far, an electrically heated line is used to to keep the system functioning at minus temperatures. However, such a device is costly.

The NO _x minimization of diesel engines can first by internal engine measures, ie the targeted influence of combustion, eg. B. by a partial exhaust gas recirculation, done. However, this is possible only within narrow limits, otherwise the soot emission increases and the engine power drops. The use of SCR catalysts optimally reduces the NO _x emissions of diesel vehicles.

By selective catalytic reduction, nitrogen oxides are largely removed from the exhaust gas. In contrast to the use of a diesel particulate filter, there is no additional fuel consumption. This advantage also applies to the alternative technology for the reduction of nitrogen oxides by means of a NO _x storage catalytic converter, which, like the DPF, requires a temporary avoidance of optimum combustion conditions. The main disadvantage of using SCR technology, eg. As in trucks, results from the required ammonia in the form of a urea solution or other media. Due to its special properties, this fuel must be carried in a stainless steel or plastic tank and sprayed continuously into the exhaust gas flow. This results in addition to the SCR catalyst and the injection system, the need for a second, usually smaller tank in addition to the fuel tank. There are a number of attempts to reduce the storage problem by using higher storage density materials or by bypassing the direct generation of ammonia from fuel in the vehicle. Since this, however, so far failed to succeed, has SCR technology with AdBlue tank, SCR catalyst and fuel injection control is available to nearly all major truck manufacturers EU-5 emissions standard enforced.

Disclosure of the invention

Around achieving high throughput rates on the SCR catalyst, it is important that the preparation of the reducing agent to the nozzle or injection nozzle in liquid form and evenly Good quality with the required pressure reaches the nozzle.

According to the invention proposed that the flowed through by the medium supply line with the help of a facility that directly or indirectly to the Internal combustion engine or connected to the exhaust system is to a certain operating temperature and / or flow rate can be adjusted, which is chosen such that a certain Pressure of the medium in the area of an injection point at the exhaust system is guaranteed. The heat energy present in the exhaust system can cost-effectively flowed through by the medium Supply line are provided, so that on a complex, separate heating in the pipe system, especially in the supply, can be dispensed with. The heat energy required for the piping system can easily elsewhere on the internal combustion engine z. B. removed from the cooling water and the pipe system to provide. For this purpose, the supply line corresponding to a nearby heat source. This ensures that it is very cold as well as hot Days the medium flowing through the supply line always to the optimum temperature and thus to the optimum degree of viscosity is set, so that thereby the desired conveying speed or Flow rate of the medium reached and thus the required Amount of medium for insertion into the exhaust system available is provided. Another advantage of being promoted in a cycle Medium in the supply lines leads in particular at very high temperatures to avoid outgassing and thus to avoid blistering in the medium, so that with the inventive Arrangement and design of the supply line no spray problem occurs when the medium is injected into the exhaust system. It is also advantageous that the medium exactly in the required Amount can be introduced.

Due to the advantageous embodiment of the delivery system, an optimal selective catalytic reduction of the nitrogen oxides from the exhaust gas can be achieved. In contrast to the diesel particulate filter (DPF), there is no additional fuel consumption. This advantage also applies to the alternative technology for the reduction of nitrogen oxides by means of a NO _x storage catalytic converter, which, like the DPF, requires a temporary avoidance of optimum combustion conditions of the internal combustion engine.

in the Feeding system, whether as a hose-in-hose system or be it executed as a pipe-in-pipe system, freezing or Outgassing thereby prevents a defined amount of medium in the Tube or pipe or flows back into a return line, by a fixed aperture or optionally by an adjustable Valve on the tank can be controlled very well. Another advantage the hose-hose system is the elimination of an electrical, separately to be contacted heating hose. This allows Assembly time and energy can be saved.

Advantageous is to use a supply line of the delivery system in to integrate and connect the pump or a pressure vessel to connect the tank to the medium, which is over a controllable valve is connected to the exhaust system.

A additional possibility exists according to a Development of the invention in that the supply is in operative connection with a countercurrent device. Further it is advantageous that the countercurrent device with the same Medium is flowed through as the supply line the feed system, which is preferably aqueous urea solution is. This leads to a continuous summer Cooling, allowing outgassing of the medium and thus the very disturbing blistering in the medium is avoided, the the injection of the medium in the exhaust system be prevented. In the winter The medium can be heated to the desired temperature and thereby for the flow rate of the Medium viscosity required to be changed, so that the injector in front of the exhaust system is always optimal can work.

According to one preferred embodiment of the invention Solution is finally provided that the countercurrent device includes a second conduit located within the supply conduit or these sheathed. Of particular importance is for the present invention that the second, internal conduit at least partially coaxial in the feed line of the delivery system taken and designed as a return line. These Arrangement is space-saving and inexpensive and leaves also easily retrofit to existing equipment.

In connection with the design and arrangement according to the invention, it is advantageous that the second, internally extending line is connected to a distributor and to a return control valve closed, which is directly or indirectly connected to the tank for the aqueous urea solution. The distributor connected to the second line designed as a return line and the return control valve are connected to a drain line connected to the tank. About this part of the medium, preferably aqueous urea solution, flows back into the tank.

Furthermore it is advantageous that to the distributor and / or the return control valve a third conduit for a gaseous medium, z. B. compressed air, is connected, with the help of the medium through the in the distributor or in the area of the return control valve and / or overpressure formed in the second line the tank is transported. This device can be in one Emergency running situation are used when, for example, hazardous goods be transported. In such an emergency situation, the truck will generated and constantly available compressed air flow into the third line and overpressure generate in the area of the return control valve, so that With the help of the pressure effect thus formed a forced emptying of the system and thus freezing the System is prevented.

So can implement a "emergency stop" function.

Around achieving high throughput rates on the SCR catalyst, it is important that the preparation of the reducing agent to the injection nozzle in liquid form with the desired viscosity gets to the injection nozzle. This is only possible when the supply to the pump unit, which advantageously designed Line and injector for spray preparation flawless works. So that the medium optimally transports to the nozzle The second, inner pipe is a hose pipe or pipe line in the supply line, which also as Hose line or can be designed as a pipe line, installed. This hose-in-hose line ensures a constant Flow of medium from the heated storage tank via the return flow back into the tank. The hose-in-hose pipe can also be designed as a tube-in-tube configuration. The pressure can help in a simple and beneficial way with help in a third Conduction of incoming compressed air are generated.

Brief description of the drawings

Based In the drawings, the invention will be described in more detail below.

It shows:

1 a supply and return line of a device for supplying a medium, in particular an aqueous urea solution, in front of a catalyst from a tank by means of a pump;

2 a schematic representation of a 3/2-way valve for blowing compressed air,

3 an end of a supply and return line for aqueous urea solution and

4 the interconnected components of the system for introducing reducing agent into the exhaust gas tract of the internal combustion engine.

embodiments

The representation according to 1 is a device for supplying a medium, in particular an aqueous urea solution 8th to remove in the exhaust tract of an internal combustion engine.

The device has a schematically illustrated tank 16 to, for receiving a medium, which is preferably aqueous urea solution 8th or another reducing agent. The Tank 16 can be designed as a steel or plastic container and be housed in the protected area of the fuel tank.

The Tank 16 may be formed as a tank unit from which the medium, preferably a reducing agent such as. B. aqueous urea solution 8th , with the help of an in 1 Injector, not shown in an exhaust tract 18 (see 4 ) of an internal combustion engine, where it is metered into the desired amount in an exhaust gas line. For this purpose is located on the exhaust pipe 19 a controllable or controllable by the engine electronics injection valve 17 with which the supply of the medium 8th can be optimally controlled or regulated.

The Tank 16 is at an in 1 shown supply line 5 connected and via an injection valve 17 with the exhaust tract 18 connected, so that the medium, preferably aqueous urea solution 8th , in the desired way in the exhaust pipe 19 sprayed or injected. The injection valve 17 , z. B. as injector or designed as a control or regulating valve is connected to the control device of the vehicle electronics, which according to the detected parameter values, the inlet of the medium 8th to an SCR catalyst 21 ( 4 ) in the exhaust tract 18 controls or regulates. SCR means selective catalytic reduction in which the pollutant is NO, with the aid of a reducing agent in a catalyst to N ₂ and H ₂ O. is reduced. The chemical reaction of the reduction is selective, which means that not all exhaust gas components are reduced, only the nitrogen oxides (NO, NO ₂ ). The reaction requires ammonia (NH ₃ ), which is added to the exhaust gas. The products of the reaction are water (H ₂ O) and nitrogen (N ₂ ).

The Tank 16 can be heated according to a variant with the help of an integrated heater to the medium 8th to temper so far that it easily to the injector 17 the exhaust tract 18 can be promoted.

According to another, inexpensive variant, the medium flows by means of a device such. B. a pump 14 or a pressure accumulator, not shown in the drawing, through the supply line 5 , in which a certain operating temperature prevails, which is chosen so that the proper inflow of the medium 8th to an injection valve 17 in front of the catalyst 21 the exhaust tract 18 is ensured, regardless of the prevailing outside temperatures. According to 1 encased the feed line 5 the return line 2 , so that a temperature equalization between the in the inflow direction 26 entering medium 8th and that through the return line 2 in the outflow direction 28 flowing medium 8th takes place. As shown in 1 is the supply line 5 as a tee 3 formed, on which the return line 2 from the supply line 5 led out and sealed. An inflow side of the T-piece 3 is by reference numerals 30 , an exit side by reference numerals 32 characterized. Between the jacket of the return line 2 and the inner wall of the supply line 5 extends an annulus 24 , which is the flow area for the medium 8th in the inflow direction 26 forms. As shown in the illustration 1 moreover, it becomes the medium 8th , which via the return line 2 from the tee 3 exit, into the tank 16 guided, in which a suction nozzle of the pump 14 to promote the tank 16 stocked medium 8th located.

2 shows a schematic representation of a 3/2-way valve for blowing compressed air.

The medium flows through the 3/2-way valve 8th , in particular aqueous urea solution, via the supply line 5 to the injection valve 17 and from there via the further, second, internal return line 2 turn into the tank 16 back. This includes the coaxially arranged, further internal return line 2 at the end a panel 22 , The aperture 22 can, for example, as a perforated disc with the circumference of the return line 2 potted, stamped or stamped on it, or fastened in any other way. From the annulus 24 between the lateral surface of the return line 2 and from the inner wall of the supply line 5 limited, the medium flows 8th over the aperture 22 in the from the supply line 5 enclosed return line 2 one and through this in the outflow direction 28 the tank 16 to.

This in 2 schematically shown 3/2-way valve 12 is used to rinse the feeding system in case of "emergency stop" in the event of a dangerous situation.

In the case of a power failure z. B. stored in a compressed air storage in a truck, a compressed air reservoir at a pressure level of 5 to 9 bar. This can be used during a power failure to flush the dosing system for the medium 8th , in particular aqueous urea solution, are used. This is done via a compressed air line 9 an admission of the return line 2 with compressed air 11 , By the concern of the compressed air 11 with a compressed air level in the order of 5 bar to 9 bar on the one hand, the 3/2-way valve 12 trained, rinsed and the medium 8th via a drainage line 10 in the tank 16 expelled, on the other hand drives the compressed air 11 the medium 8th also from the return line 2 in the outflow direction 28 in the tank 16 out.

In case of failure, the controllable pump is formed 14 operated in the opposite direction. When sucking back the controllable pump is formed 14 operated in the opposite direction. This means that the original pressure side becomes the suction side and the original suction side to the pressure side. By sucking back on the controllable pump 14 can the medium 8th , which is preferably aqueous urea solution, from the conduit system, in particular from the annulus 24 , between the supply line 5 and the internally arranged, from the supply line 5 Coaxially enclosed, further line 2 be sucked off, leaving the annulus 24 essentially free of medium 8th is.

3 shows an end of a supply and return line for a medium, in particular aqueous urea solution.

The representation according to 3 it can be seen that this is an end piece 34 is. 3 shows that the feed line 5 that from the medium 8th , in particular aqueous urea solution, in the inflow direction 26 is flowed through, the return line 2 Coaxially encloses. Between the lateral surface of the return line 2 and the inner wall of the supply line 5 the annulus runs 24 as already related to 1 in the explanation of the T-piece 3 shown.

At the end of the supply line 5 , just before the injection valve 17 , which in the in 3 only schematically indicated exhaust pipe 19 protrudes, is the connection for the compressed air line 9 which is used to blow out the metering system for a medium 8th , in particular aqueous urea solution, serves, should there be a dangerous situation, such. B. enter a power failure. As shown in the illustration 3 shows, is the return line 2 through a panel 22 locked in the wall of the return line 2 punched, stamped or materially connected to this can be. If an accident occurs, the pump 14 , compare illustration according to 1 , in the reverse direction, ie in the Rücksaugmodus be driven, the supply line 5 sucked dry. The empty eyes in the area of the tail 34 is by blowing in the compressed air 11 still supported via their connecting piece. Furthermore, via the injection of compressed air 11 in the tail 34 an empty flushing of the return line 2 from medium 8th , which in the outflow direction 28 back to the tank 16 is expelled. This will ensure that the medium 8th , which is in particular aqueous urea solution which freezes below an outside temperature of -11 ° C, from the lines 2 and 5 and optionally the tee 3 and expelled from the valve, so that it can not freeze there and builds up an increase in volume during freezing and thus an ice pressure, which could destroy the components.

In connection with the embodiments according to 1 and 3 It should be noted that it is in the illustrated routing of the return line 2 , encased by the supply line 5 , is a counterflow. In this countercurrent flow is through the warm exhaust system via the return line 2 returning tempered medium 8th a preheating of the in the inflow direction 26 the supply line 5 passing medium 8th , which is in particular an aqueous urea solution, without providing a separately operated and to be provided electrical heating device. It will be the temperature differences between the back-flowing medium 8th and the injector 17 inflowing medium 8th exploited.

4 shows the system in a possible overall presentation.

The representation according to 4 can be seen that starting from the tank 16 in which the medium 8th is stockpiled, an intake to the suction end of the pump 14 extends. From the pump 14 from the supply line extends 5 with the interposition of a T-piece 3 to the injection valve 17 which is in the exhaust pipe 19 protrudes. To improve the heat dissipation are in the end 34 according to 3 the supply line 5 at its outer periphery a number of the heat dissipation favors ribs. The representation according to 4 can also be seen that in the supply line 5 leading to the injector 17 extends, a return line 2 coaxially, over which heated medium 8th to the tee 3 flowing back. An entry side of the tee 3 is by reference numerals 30 , Its exit side by reference numerals 32 based on the inflow direction 26 of the medium 8th designated. At the tee 3 is essentially coaxial in the lead 5 recorded return line 2 , the tempered medium 8th leads, from the supply line 5 sealed out. As shown in the illustration 4 shows, the flows at the tee 3 from the supply line 5 led out return line 2 also in the tank 16 , Parallel to this embodiment, as in connection with 2 already explained, another drain pipe 10 from the valve 12 in the tank 16 run so that in case of an emergency stop function, a rapid emptying of the dosing system for introducing the medium 8th in the exhaust tract 18 the internal combustion engine is guaranteed.

As shown in the illustration 4 further, the exhaust tract comprises 18 in the exhaust pipe 19 for example, a diesel particulate filter 20 and the SCR catalyst 21 , Between these components, ie the DPF 20 and the SCR catalyst 21 , lies the Einosierungsstelle for the medium 8th , which is in particular aqueous urea solution, in which of the exhaust pipe 19 guided exhaust gas of the internal combustion engine.

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 non-patent literature

• - EU 5 emission standard [0004]
• - DIN 70070 [0004]
• - EU-5 emission standard [0008]

Claims (9)

Device for feeding a medium, in particular an aqueous urea solution ( 8th ), in front of a catalyst ( 21 ) from a tank ( 16 ) by means of a pump ( 14 ) via a supply line ( 5 ) and an injection valve ( 17 ) in an exhaust tract ( 18 ) of an internal combustion engine, characterized in that the medium ( 8th ) located in the supply line ( 5 ) in a first direction ( 26 ) flows through the medium ( 8th ), which in a second direction ( 28 ) in a flow cross-section ( 24 ) of the supply line ( 5 ) arranged return line ( 12 ) flows, is tempered. Apparatus according to claim 1, characterized in that the supply line ( 5 ) into the pump ( 14 ) and connected to the tank ( 16 ) for receiving the medium ( 8th ) connected via a controllable injection valve ( 17 ) in an exhaust pipe ( 19 ) is injected or sprayed. Apparatus according to claim 1 or 2, characterized in that the supply line ( 5 ) with the return line ( 2 ) forms a countercurrent device. Device according to one of the preceding claims, characterized in that the return line ( 2 ) from the same medium ( 8th ), in particular aqueous urea solution, is flowed through, like the supply line ( 5 ). Apparatus according to claim 3, characterized in that the countercurrent device, the return line ( 2 ) located within the supply line ( 5 ) or from this to form an annular space ( 24 ) is sheathed. Apparatus according to claim 5, characterized in that the return line ( 2 ) at least partially coaxial in the supply line ( 5 ) is recorded. Device according to one of the preceding claims, characterized in that the return line ( 2 ) on a tee ( 3 ) and / or to a 3/2-way valve ( 12 ) connected directly or indirectly to the tank ( 16 ) connected is. Device according to one of the preceding claims, characterized in that the with the return line ( 2 ) connected tee ( 3 ) and the 3/2-way valve ( 12 ) with one to the tank ( 16 ) connected drain line ( 10 ), over which part of the medium ( 8th ), in particular aqueous urea solution ( 8th ), into the tank ( 16 ) flows back. Device according to one of the preceding claims, characterized in that the tee ( 3 ) and / or the 3/2-way valve ( 12 ) a compressed air line ( 9 ) is connected to a gaseous medium, with the aid of which the medium ( 8th ), in particular aqueous urea solution, through which in the T-piece ( 3 ) or in the area of the 3/2-way valve ( 12 ) and / or in the return line ( 2 ) formed in the tank ( 16 ).