Device For Supplying A Reducing Agent Solution Into An Exhaust System And Corresponding Exhaust System, Method and Vehicle

Abstract

A device for supplying reducing agent solution into an exhaust system, includes a reservoir for reducing agent solution and a delivery device for delivering reducing agent solution from the reservoir to a reducing agent infeed configuration. A delivery height to be overcome between the reservoir and the reducing agent infeed configuration is less than 1.5 meters and the delivery device includes a diaphragm pump. The device permits the dosed metering of reducing agent solution into an exhaust system of an internal combustion engine regardless of prevailing boundary conditions, in particular regardless of the position of the device, which is for example influenced by a position of a corresponding automobile. In particular, it is thus also possible to ensure reliable metering of reducing agent solution into the exhaust system even when the automobile or motor vehicle is traveling over grades. A corresponding exhaust system, method and utility vehicle are also provided.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority, under 35 U.S.C. §119, of German Patent Application DE 10 2008 022 517.7, filed May 7, 2008; the prior application is herewith incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device for supplying a reducing agent solution into the exhaust system of an internal combustion engine, a corresponding exhaust system, a corresponding method and a vehicle using a corresponding device in an exhaust system. The preferred field of application of the present invention is supplying a urea-water solution in the exhaust system of mobile internal combustion engines, such as for example of automobiles.

With the ever more stringent exhaust-gas standards in many countries around the world, additional measures for the reduction of the nitrogen oxide content in the exhaust gas are necessary to reduce nitrogen oxides. One such option is selective catalytic reduction (SCR) of the nitrogen oxides, in which a reducing agent is introduced into the exhaust gas. The reducing agent selectively reduces nitrogen oxides (NO_x) to form nitrogen. One possible reducing agent is ammonia. Ammonia is conventionally stored on board motor vehicles not in pure form, but rather in the form of a so-called ammonia precursor. For example, urea-water solutions are commercially available and are marketed, for example, under the trademark AdBlue or Denoxium, are carried on board automobiles in an additional tank and are then metered to the exhaust gas depending on the nitrogen oxide content thereof.

In order to ensure the functionality and efficiency of the selective catalytic reduction, it is necessary for the corresponding reducing agent solution to be reliably supplied regardless of the operating conditions of the motor vehicle, in particular regardless of the position of the motor vehicle. At the same time, it must be ensured in that case that the tank in which the reducing agent solution is stored is easily accessible for refilling the tank.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a device for supplying a reducing agent solution into an exhaust system and a corresponding exhaust system, method and vehicle, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and at least alleviate the problems known from the prior art. In particular, the invention should ensure a reliable supply of reducing agent solution to the exhaust system regardless of position, wherein in particular it is also sought to provide that corresponding reservoirs are simultaneously easily accessible.

With the foregoing and other objects in view there is provided, in accordance with the invention, a device for supplying a reducing agent solution into an exhaust system, in particular of an internal combustion engine. The device comprises a reservoir for the reducing agent solution, a reducing agent infeed configuration, and a delivery device, including a diaphragm pump, for delivering the reducing agent solution from the reservoir to the reducing agent infeed configuration. The reservoir and the reducing agent infeed configuration define a delivery height therebetween of less than 1.5 meters to be overcome.

In this case, the expression reducing agent solution is to be understood to mean a solution of a reducing agent which acts selectively on nitrogen oxides, or a solution of the precursor of the reducing agent, in particular an aqueous solution of at least urea. An exhaust system is to be understood in particular to mean an exhaust system including an SCR catalytic converter, and also preferably a hydrolysis catalytic converter situated upstream of the SCR catalytic converter. A reducing agent infeed configuration is to be understood to mean a device for feeding the reducing agent solution into the exhaust system, in particular in the form of droplets or a jet. The reducing agent infeed configuration may in particular be operated in an intermittent or pulsed fashion.

A diaphragm pump is to be understood in particular to mean a pump in which the medium to be delivered is separated from the drive of the pump by a diaphragm. The delivery takes place through the use of a deformation of the diaphragm. The diaphragm may preferably be driven mechanically or hydraulically. The diaphragm is elastically deformable and is preferably formed from metal and/or plastic. The use of the diaphragm pump as a delivery device is advantageous since it is thereby possible to prevent the pump drive from coming into contact with the reducing agent solution and in particular urea-water solution. The urea-water solution can crystallize out and, depending on the temperature, reactions may occur which lead to depositions. The pump drive is advantageously protected from those effects through the use of the diaphragm.

The reservoir, delivery device and reducing agent infeed configuration are preferably connected through the use of a corresponding line. The expression “delivery height” is to be understood to mean the total level difference to be overcome between the lowest point of the reservoir and the reducing agent infeed configuration. In particular, the delivery height is also selected according to the invention in such a way that reliable dosing of the reducing agent solution is ensured even in the case of a corresponding automobile presently being situated on common grades or slopes. It is nevertheless possible to position the reservoir such that the reservoir is still easily accessible from the outside and can therefore easily be refilled.

The device according to the invention can in particular be used in exhaust systems of internal combustion engines, preferably of diesel engines.

In accordance with another feature of the device of the invention, the reducing agent infeed configuration and the delivery device are constructed in such a way that a geometric spacing of at least 300 mm (millimeters) is provided between them.

This minimum spacing ensures that thermal damage to the delivery device as a result of the waste heat of the exhaust system does not occur, since the reducing agent infeed configuration is provided in contact with the exhaust system in order to be able to feed reducing agent solution into the exhaust system. The geometric spacing is preferably even at least 400 mm.

In accordance with a further feature of the device of the invention, the delivery device includes a pump, in particular a magnet pump.

The delivery device as a pump is to be understood to mean that the delivery device is not a dosing pump but rather a delivery pump, through the use of which a pressure at the reducing agent infeed configuration can be predefined. A magnet pump is to be understood in particular to mean a pump in which a movement of corresponding pump parts takes place through the use of a magnetic coupling.

In accordance with an added feature of the device of the invention, the diaphragm pump has a hydraulic diaphragm drive. The hydraulic diaphragm drive preferably includes magnetically movable components.

The use of a hydraulic diaphragm drive can advantageously be controlled in a simple manner and permits in particular very precise dosing of the pump capacity, since different diaphragm positions can be set in a simple and precise manner. The use of a hydraulic diaphragm drive which includes magnetically movable components is advantageous since the corresponding forces can be transmitted in this case substantially with little wear.

In accordance with an additional feature of the device of the invention, the reducing agent infeed configuration includes a nozzle.

Through the use of the reducing agent infeed configuration which is constructed as a nozzle, it is advantageously possible to provide a fine vaporization of the reducing agent solution as it enters into the exhaust system. This leads to improved evaporation and conversion of the reducing agent solution, since a larger surface area is provided for the evaporation.

In accordance with yet another feature of the device of the invention, the reducing agent infeed configuration includes a valve.

In this case, the dosing of the corresponding quantity takes place in a simple manner by maintaining a pressure upstream of the reducing agent infeed configuration and opening the corresponding valve, wherein the quantity of reducing agent solution to be dosed can be dosed through a traversable cross section which is opened up by the valve and the opening duration of the valve. It is advantageously also possible in this connection for a return line to be provided from the reducing agent infeed configuration to the reservoir and/or to the delivery device.

In accordance with yet a further feature of the device of the invention, the reducing agent solution includes an aqueous solution at least of urea.

This is to be understood in particular to mean a solution such as is marketed under the trademarks AdBlue or Denoxium, wherein further substances may be present in aqueous solution in addition to urea. The further substances may, for example, include additives, such as for example ammonium formate, which lower the freezing point of the urea-water solution. This means that the corresponding parts, in particular walls, of the device according to the invention which come into contact with the reducing agent solution are constructed in such a way that they are not corroded by the urea-water solution. A refinement is preferable in which the contact regions are composed at least partially of a metal which includes chromium and nickel. Preferable materials in this case are steels with a chromium content of at least 17 wt % (percent by weight) and a nickel content of at least 10 wt %. The steel preferably has additions of titanium, niobium and/or molybdenum. The molybdenum content is in particular at least 2 wt %. It is particularly preferable to use steels with the following material numbers according to the DIN EN (German Institute for Standardization, German Edition of European Standards) 10088 (list of stainless steels) standard: 1.4301, 1.4306, 1.4311, 1.4541, 1.4550, 1.4401, 1.4404, 1.4571, 1.4429, 1.4435, 1.4426, 1.4439.

With the objects of the invention in view, there is also provided an exhaust system, comprising a hydrolysis catalytic converter, an SCR catalytic converter, and a device according to the invention for supplying a reducing agent. The reducing agent infeed configuration of the device for supplying a reducing agent is disposed upstream of the hydrolysis catalytic converter and upstream of the SCR catalytic converter.

The hydrolysis catalytic converter is in particular also provided upstream of the SCR catalytic converter. The urea-water solution is introduced into the exhaust system upstream of the hydrolysis catalytic converter, wherein a hydrolysis reaction of the urea to form ammonia occurs as the urea-water solution impinges on the hydrolysis catalytic converter. It is also possible, depending on the temperature in the exhaust system, for thermolysis to take place to form ammonia and isocyanic acid before the urea-water solution impinges on the hydrolysis catalytic converter, with the isocyanic acid then also being converted into ammonia on the hydrolysis catalytic converter. The hydrolysis catalytic converter is preferably constructed in such a way that a substantially complete conversion to ammonia takes place even in the case of the maximum quantity of reducing agent solution being metered. It is preferable for more than 98 wt % of the urea to be converted into ammonia.

With the objects of the invention in view, there is furthermore provided a method for operating or using an exhaust system of a mobile internal combustion engine. The method or use comprises supplying a reducing agent solution in the exhaust system of the mobile internal combustion engine with a device according to the invention.

In the case of mobile internal combustion engines in particular, such as for example in motor vehicles, especially passenger cars and trucks, the available installation space is limited, so that it is usually possible for only very small pumps to be installed as a delivery device. In this case, the use of a device according to the invention helps, as a result of the limitation according to the invention of the maximum required delivery height, to create a dosing system, which provides reliable dosing for the reducing agent solution even in the case of extreme grades or slopes.

In accordance with another mode of the method or use of the invention, the reducing agent solution includes an aqueous solution at least of urea.

With the objects of the invention in view, there is concomitantly provided a utility vehicle, comprising an exhaust system including a hydrolysis catalytic converter, an SCR catalytic converter, and a device according to the invention for supplying a reducing agent solution. The reducing agent infeed configuration of the device for supplying a reducing agent solution is disposed upstream of the hydrolysis catalytic converter and upstream of the SCR catalytic converter.

In this case, a utility vehicle is to be understood in particular to mean trucks, forklift trucks, construction machines, such as for example bucket excavators, cranes, caterpillar vehicles and/or wheel loaders, as well as agricultural machines, such as for example tractors, combine harvesters, harvesting vehicles and/or soil cultivation vehicles.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in a device for supplying a reducing agent solution into an exhaust system and a corresponding exhaust system, method and vehicle, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a fragmentary, diagrammatic, partly sectional view of a first exemplary embodiment of a device according to the invention;

FIG. 2 is a view similar to FIG. 1 of a second exemplary embodiment of a device according to the invention;

FIG. 3 is a view similar to FIGS. 1 and 2 of a third exemplary embodiment of a device according to the invention;

FIG. 4 is a fragmentary, partly sectional view of an example of a diaphragm pump for use as a delivery device in a device according to the invention; and

FIG. 5 is a view similar to FIG. 4 of a second example of a diaphragm pump for use as a delivery device in a device according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now in detail to the figures of the drawings, without being restricted to the exemplary embodiments and details shown therein, and first, particularly, to FIG. 1 thereof, there is seen a diagrammatic illustration of a first exemplary embodiment of a device 1 according to the invention for supplying a reducing agent solution 2 into an exhaust system 3 of a non-illustrated internal combustion engine. The reducing agent solution 2 is an aqueous solution of at least urea. The exhaust system 3 is part of a motor vehicle, in particular of a truck, especially with a diesel drive, and has a hydrolysis catalytic converter 4 and an SCR catalytic converter 5. The hydrolysis catalytic converter 4 is situated upstream of the SCR catalytic converter 5 in a throughflow direction 6 of the exhaust gas through the exhaust system 3.

The device 1 includes a reservoir 7 for a urea-water solution and a delivery device 8. The reducing agent solution 2 can be delivered from the reservoir 7 to a reducing agent infeed configuration by the delivery device 8. The reducing agent infeed configuration is constructed as a nozzle 9 in this exemplary embodiment. According to the invention, the delivery device 8 includes a diaphragm pump. The reducing agent solution 2 is injected, preferably in the form of a plurality or a multiplicity of small droplets, into the exhaust system 3 through the use of the nozzle 9 during operation. The nozzle 9 is provided upstream of the hydrolysis catalytic converter 4 and upstream of the SCR catalytic converter 5. The reservoir 7, the pump 8 and the nozzle 9 are connected to one another through the use of lines 10. During operation, the delivery device 8 delivers the reducing agent solution 2 to the nozzle 9 through the line 10. According to the invention, a delivery height 11 between the reservoir 7 and the nozzle 9 is less than 1.5 m, preferably less than 1.0 m and in particular less than 0.5 m. The delivery height is the total geodetic height which must be overcome from the lowest point of the reservoir 7 or of the line 10 to the nozzle 9. In this case, depending on the construction of the device 1, it is possible for stepped delivery to take place, that is to say the delivery height 11 can be composed of different partial delivery heights. The delivery height 11 is then defined as the sum of the partial delivery heights.

The urea-water solution is provided to the hydrolysis catalytic converter 4 as a result of the delivery of the reducing agent solution 2 through the nozzle 9. The urea-water solution 2 evaporates either in the exhaust system 3 before impinging on the hydrolysis catalytic converter 4, or evaporates on the hydrolysis catalytic converter 4. The conversion to form ammonia is catalyzed on the hydrolysis catalytic converter 4. It is preferably possible for an at least partial thermolysis to take place, in which isocyanic acid and ammonia are generated from urea. The isocyanic acid is likewise converted by the hydrolysis catalytic converter 4 to form ammonia. According to the invention, a geometric spacing 27 between the nozzle 9 and the delivery device 8 is at least 300 mm in order to protect the delivery device 8 from thermal damage as a result of waste heat of the exhaust system 3.

FIG. 2 diagrammatically shows a second exemplary embodiment of a device 1 according to the invention. The second exemplary embodiment has a different configuration of the lines 10, such that the delivery height 11 is defined differently in this case too. The delivery height 11 is defined as a height difference from the lowest point of the line 10 to the height of the nozzle 9.

FIG. 3 diagrammatically shows a third exemplary embodiment of a device 1 according to the invention. In this case, instead of a nozzle, a valve 12 is provided, through which the reducing agent solution 2 can be metered to the exhaust system 3. The valve 12 therefore constitutes an alternative reducing agent infeed configuration within the context of the present invention. The valve 12 is connected through a return line 13 to the reservoir 7, in such a way that the reducing agent solution 2 is circulated. In this case, the delivery device 8 builds up and maintains a pressure, and the quantity of reducing agent solution 2 which is to be metered is determined through the use of corresponding clocking and opening of the valve 12. The delivery height 11, which according to the invention is less than 1.5 m, is calculated in this case as a height difference between the lowest point of the return line 13 and the highest point of the line 10.

FIG. 4 diagrammatically shows a first example of a diaphragm pump 14 for use as a delivery device 8 in a device 1 according to the invention. The diaphragm pump 14 has a diaphragm 15 which separates a delivery chamber 16 from a drive chamber 17. The drive chamber 17 includes a diaphragm drive 18. In the example according to FIG. 4, the diaphragm drive 18 includes a piston 19 which can be moved through the use of a magnet drive 20. The magnet drive 20 includes non-illustrated coils which can be connected to a non-illustrated power supply and through the use of which an upward and downward movement of the piston 19 can be generated depending on the operation of the corresponding coils. The piston 19 can be pressed against the diaphragm 15 through the use of the magnet drive 20, as a result of which the diaphragm 15 is deformed. The piston 19 and diaphragm 15 are joined to one another, preferably through the use of technical joining, in such a way that the diaphragm 15 can also be deformed out of the delivery chamber 16 by using the piston 19, by virtue of the diaphragm 15 being pulled by using the piston 19. The preferred manner of producing the technical joining connection is by brazing. However, a sintering process or even welding may be used as well.

It is thus possible, through the use of a corresponding deflection of the piston 19, to obtain different degrees of deformation of the diaphragm 15. Depending on the deformation of the diaphragm and depending on the position of an inlet valve 21 and of an outlet valve 22, it is therefore possible for a fluid to be fed from an inlet line 23 into an outlet line 24, depending on whether the diaphragm 15 is deformed into the delivery chamber 16 or out of the delivery chamber 16.

FIG. 5 shows a further example of a diaphragm pump 14 which can be used as a delivery device 8 in a device 1 according to the invention. In contrast to the first example, the diaphragm drive 18 does not have a mechanical construction but rather has a hydraulic construction. Above the diaphragm 15, the drive chamber 17 is constructed so as to widen conically. A hydraulic liquid 25 is provided within a free space. The pressure of the hydraulic liquid 25 can be varied through the use of a delivery piston 26. The diaphragm 15 is thereby deformed into the delivery chamber 16 or out of the delivery chamber 16. The delivery piston 26 is moved through the use of a magnet drive 20. The diaphragm 15 is preferably formed of a metal, although may fundamentally also be formed of a corresponding plastic.

The device 1 according to the invention advantageously permits dosed metering of the reducing agent solution 2 into an exhaust system 3 of an internal combustion engine regardless of the prevailing boundary conditions, in particular regardless of the position of the device 1 which is, for example, influenced by a position of a corresponding automobile. In particular, it is thus also possible to ensure reliable metering of the reducing agent solution 2 into the exhaust system 3 even when the automobile or motor vehicle is traveling over grades or inclines.

Claims

1. A device for supplying a reducing agent solution into an exhaust system, the device comprising:

a reservoir for the reducing agent solution;

a reducing agent infeed configuration; and

a delivery device, including a diaphragm pump, for delivering the reducing agent solution from said reservoir to said reducing agent infeed configuration;

said reservoir and said reducing agent infeed configuration defining a delivery height therebetween of less than 1.5 meters to be overcome.

2. The device according to claim 1, wherein said reducing agent infeed configuration and said delivery device define a geometric spacing of at least 300 mm therebetween.

3. The device according to claim 1, wherein said diaphragm pump of said delivery device is a magnet pump.

4. The device according to claim 1, wherein said diaphragm pump has a hydraulic diaphragm drive.

5. The device according to claim 4, wherein said hydraulic diaphragm drive includes magnetically movable components.

6. The device according to claim 1, wherein said reducing agent infeed configuration includes a nozzle.

7. The device according to claim 1, wherein said reducing agent infeed configuration includes a valve.

8. The device according to claim 1, wherein the reducing agent solution includes an aqueous solution at least of urea.

9. An exhaust system, comprising:

a hydrolysis catalytic converter;

an SCR catalytic converter; and

a device according to claim 1 for supplying a reducing agent solution;

said reducing agent infeed configuration of said device for supplying a reducing agent solution being disposed upstream of said hydrolysis catalytic converter and upstream of said SCR catalytic converter.

10. A method for operating an exhaust system of a mobile internal combustion engine, the method comprising the following steps:

supplying a reducing agent solution in the exhaust system of the mobile internal combustion engine with a device according to claim 1.

11. The method according to claim 10, wherein the reducing agent solution includes an aqueous solution at least of urea.

12. A utility vehicle, comprising:

an exhaust system including: a hydrolysis catalytic converter; an SCR catalytic converter; and a device according to claim 1 for supplying a reducing agent solution; said reducing agent infeed configuration of said device for supplying a reducing agent solution being disposed upstream of said hydrolysis catalytic converter and upstream of said SCR catalytic converter.

13. A utility vehicle, comprising a device according to claim 1.