DE102009027693A1 - Dosing module for a liquid reducing agent - Google Patents

Abstract

The invention relates to a metering module (10) for a liquid reducing agent, in particular a urea-water solution, for injecting the reducing agent into an exhaust pipe of an internal combustion engine. The metering module (10) has a housing (14, 16) which encloses a metering device (18) and a drive unit (36) which actuates the metering device (18). The metering device (18) and the drive unit (36) are inserted as separate assemblies in the housing (14, 16), at least the area of the drive unit (36) being coverable by an adapter ring (42) and the metering device (18) and the Adapter ring (42) are sealingly connected to the housing.

Description

The invention relates to a metering module for a liquid reducing agent, in particular a urea-water solution according to the preamble of claim 1.

State of the art

The emission limit values for nitrogen oxides demanded by the legislature require exhaust aftertreatment devices in motor vehicles and commercial vehicles which, for example, carry out a selective catalytic reduction (SCR) of the nitrogen oxides contained in the raw emissions of the internal combustion engine. In this case, a liquid reducing agent (eg urea-water solution) is injected into the exhaust pipe of an internal combustion engine as needed in order to enable the selective catalytic reduction of nitrogen oxides in an SCR catalyst. The urea decomposes into ammonia (NH ₃ ), which reacts with the nitrogen oxides (NO _X ) of the exhaust gas and converts them into harmless water (H ₂ O) and harmless nitrogen (N ₂ ). This so-called SCR process for exhaust gas purification is known from the prior art.

The DE 10 2007 043 532 A1 describes a metering module for metering the urea-water solution in an exhaust system of an internal combustion engine, in which a drive unit and a metering device are provided and between a unit of the drive unit and a unit of the metering device, a membrane is arranged. The metering device and a serving for transmitting a force on the diaphragm on the metering actuator of the drive unit form separate components. The drive unit is attached to a holding body of the metering device via a housing by means of an adhesive or screw connection. At the tightness to the interior of the dosing and the cooling of the dosing no requirements are set.

Disclosure of the invention

The object of the invention is to further develop a metering module of the type mentioned above such that the interior of the metering module remains essentially uninfluenced by external influences. In addition, the dosing is to be compact and lower by its design, the manufacturing and installation costs.

The object is achieved in that the metering device and the drive unit are used as separate modules in the housing, wherein the drive unit is positioned by an adapter ring in the housing and then fixed and the metering device and the drive unit are sealingly connected to the housing. In the case of the drive unit, the seal can be sealed with a sealing cap.

The housing of the metering module is a substantially cylindrical body and according to the invention designed such that a metering device with the membrane and the drive unit can each be inserted into the housing. The side of the housing with the drive unit used is tightly sealed by the adapter ring and the sealing cap, taking into account an electrical contacting of the electromagnet actuating the drive unit, by suitable means. In a corresponding manner, the opposite side of the housing is sealed with the metering device by suitable means. This means that the dosing module is composed of different, separately manufactured assemblies during assembly, but then forms a hermetically sealed unit.

As a result, the reliability of the dosing is not affected even with a dipped completely in water dosing. Such a situation arises, for example, whenever a commercial vehicle (eg a tractor) is used in a submerged paddy field. An improved general protection against dirt and spray is also given.

Features which are important for the invention can also be found in the following description and in the drawing, wherein the features, both alone and in different combinations, can be important for the invention without any explicit reference being made thereto. Advantageous developments can be found in the subclaims.

Advantageously, the metering device according to the invention and / or the adapter ring according to the invention is connected to the housing by welding and / or caulking. Both represent indissoluble and dense connections, since during caulking a non-positive and positive connection between two workpieces is produced by plastic deformation. This deformation of an edge region of the workpiece takes place in such a way that they become indissolubly wedged into one another. In contrast to welding, wherein both workpieces must be made of metal and enter into a cohesive connection, can be joined together by caulking different materials, such as. Plastic and metal. This allows the production of, for example, the adapter ring or the housing also made of plastic. Alternatively it is also a cohesive connection, such as soldering, conceivable.

It is also possible that the metering device and / or the sealing cap are connected by a snap connection, in particular a cooperating with a snap ring snap connection with the housing. In snap connections, the elasticity of at least one material, usually plastic or steel, exploited the components to be joined for the connection of two workpieces. In snap connections, a joining part deforms elastically and then hooked into intended attack projections releasably or permanently with the other joining part. In this case, the snap connection can be in the attack projections outside or inside.

The circlip surrounding the snap connection is essentially a captive. This is a particularly assembly-friendly embodiment, which allows an assembly without significant expenditure of time.

It is also possible that the metering device and / or the sealing cap are connected by a flared connection with the housing. It is understood by a crimped the forming of a rim round or oval metallic sheets with a crimping machine or by hand. The sheet is compressed during forming. For this one uses a flaring iron, d. H. a tool that has a rounded edge. The crimp connection can also guarantee a secure and tight connection.

It is also possible that the metering device and / or the sealing cap are connected by a self-clinch connection with the housing. In a self-clinching connection, crimping is effected by press-fitting a locking element, for example into a groove. This too can guarantee a secure and tight connection.

Allen mounting options in common is that can be dispensed with the known wear and aging-prone elastomer sealing elements in the thermally and chemically highly loaded reducing agent area. Moreover, the fixing possibilities themselves are essentially likewise not subject to any aging. This makes the device inexpensive and durable.

It is also advantageous that the metering device has an integral part of a flange for attachment to the exhaust pipe. The metering device is thus integrated in the flange. It can be dispensed with a holding body for the metering device, the holding function takes over the material of the flange. This eliminates an additional connection point between the housing of the dosing and the metering device, which would also be sealed. This leads to a compact dosing module. In addition, the manufacturing and assembly costs are reduced.

Furthermore, it is advantageous that the metering module can be cooled by coolant. For this purpose, the metering module, in particular in the region of the flange and / or in the region of the sealing cap, preferably has circulating coolant channels. This can be cooled especially the thermally heavily loaded area of the dosing, which is in communication with the exhaust pipe. But it is also possible that the sealing cap also has coolant channels for cooling the drive unit. When the sealing cap extends to the flange, the entire dosing module can be cooled via the coolant channels in the sealing cap. This has the advantage that on the one hand the cooling water connections can be kept away from the sensitive flange area, that is, as desired, but can preferably be provided in the region of the electrical contacting in the opposite region of the flange at one end of the sealing cap. On the other hand, the ambient temperature of the thermosensitive magnetic coil of the electromagnet can be limited to the cooling water temperature. As a result, the electrical plug contacts can be contacted largely cold. The cooling ensures that the metering module is protected from the effects of water and dirt and also from the effects of temperature.

Hereinafter, exemplary embodiments of the invention will be explained by way of example with reference to FIGS. Show it:

1 a schematic representation of a metering module in longitudinal section in a first embodiment;

2 a schematic representation of a metering module in longitudinal section in a second embodiment;

3 a schematic representation of the housing of the metering valve 1 in detail with a further possibility for its attachment in the flange;

4 a schematic representation of the housing of the metering valve 1 in detail with a further possibility for its attachment in the flange;

5 a schematic representation of the sealing cap 1 or 2 in detail in a second embodiment;

6 a schematic representation of an alternative to the sealing cap 1 . 2 or 5 in detail;

7 a schematic representation of a second mounting possibility of the sealing cap 5 in detail;

8th a schematic representation of a third attachment possibility of the sealing cap 5 in detail; and

9 a schematic representation of a fourth mounting possibility of the sealing cap 5 in detail.

Detailed description

1 shows a dosing module 10 for injecting a reducing agent into an unillustrated exhaust pipe of an internal combustion engine in a first embodiment. The dosing module 10 includes one with a flange 12 trained pedestal 14 which is in a cylindrical housing 16 passes. flange 12 , Pedestal 14 and housing 16 So are one piece and preferably made of stainless steel. The flange 12 has an opening in the middle, into which a metering device acting as a valve group 18 is formed, accurately inserted and through a weld 19 is permanently attached. This is at the same time the inside of the dosing module 10 sealed to the outside. Alternatively, the valve group 18 Also be fixed by caulking, a snap connection, a flare, a self-clinch connection or a screw connection. The flange 12 is with screws 20 attached to the exhaust pipe, not shown.

The valve group 18 comprises a holding body or housing 22 , which is a metering valve 24 with a valve element 26 holds. The valve element 26 acts in the outflow direction of the reducing agent with a valve seat 28 together. The base 14 also has an inlet 30 for the reducing agent and a bore 32 for the guidance of cooling water. The feed 30 , as well as all components, which come into contact with the reducing agent, are made of stainless steel and / or ausuktionsmittelbeständigem aluminum.

Contrary to the outflow direction of the reducing agent is the valve group 18 from a membrane 34 limited. This is followed by a drive unit 36 for actuating the metering valve 24 over the membrane 34 at. In the drive unit 36 becomes one on the membrane 34 adjoining spring-loaded anchor bolt 38 from an electromagnet 40 actuated. In the embodiment shown, the drive unit 36 from the flange 12 opposite side into the housing 16 used.

The drive unit 36 is at the opposite end to the anchor bolt 38 through an adapter ring 42 secured and through a first weld 43 with the drive unit 36 and through a second weld 44 with the housing 16 secured. Other mounting options, such as. The above, are possible. On the adapter ring 42 is a sealing cap 46 provided, which simultaneously realizes an electrical connection and a guide for the electrical supply. The sealing cap 46 could also have a cooling water connection (in 1 not shown). The sealing cap 46 is in a widened area 48 of the housing 16 let in and by caulking 50 secured. The sealing cap 46 is sealed by an O-ring (not numbered).

2 shows a second, more compact embodiment of the dosing 10 , In this case and for the following figures, it applies that such elements and areas which are functionally equivalent to elements and areas of the dosing module 10 from 1 , bear the same reference numerals and will not be explained again in detail. In this embodiment, the valve group 18 integral part of the base 14 and the flange 12 , That means on the holding body 22 from 1 can be waived. This is the cylindrical part of the housing 16 a separate component on the pedestal 14 fitted accurately and with a weld 52 is tightly fastened. Other mounting options, such as. The above, are possible. In this embodiment, the valve group 18 in the flange 12 and the drive unit 36 from the flange 12 opposite side into the housing 16 used.

3 shows the holding body 22 of the metering valve 24 out 1 with a second possibility for its attachment in the flange 12 in detail. The holding body 22 is to the interior of the dosing module 10 made substantially conical. In this case, the holding body sits 22 precisely fitting in the opening of the flange 12 , The holding body 22 is by caulking 56 additionally fixed and sealed. In addition, the holding body is located 22 to the interior of the dosing module 10 at a stop shoulder 58 at.

4 shows the housing (holding body) 22 of the metering valve 24 out 1 with a third possibility for fixing it in the flange 12 in detail. This is a profiling of the holding body 22 used. Instead of the stop shoulder 58 Here is a self-clinch attachment 60 provided at the a bead 61 by a forming process during the pressing of the holding body 22 in the flange 12 is effected. In this case, the holding body acts 22 as a forming tool, which the bead 61 in the flange 12 ausformt. The flange 12 should preferably made of aluminum or another good formable material consist. This self-clinch connection or caulking fixes and seals the holding body 22 to the flange 12 in addition to the caulking 56 from.

5 shows a second embodiment of the sealing cap 46 out 1 or 2 in detail. Here is the sealing cap 46 to the flange 12 pulled down so that on the cylindrical housing 16 (out 1 or 2 ) can be omitted. The sealing cap 46 is preferably made of plastic and is on a projecting flange from the outflow opening ring 62 on the flange 12 attached. The ring 62 has some play on the sealing cap 46 on. In two radial circumferential grooves of the ring 62 are O-rings 64 let in that the sealing cap 46 to the flange 12 caulk. The sealing cap 46 has inside essentially the drive unit 36 on, with the electromagnet (in 5 not visible) of the drive unit 36 via a cold plug contact 66 and one in 5 electrical connection arranged above the plug contact 68 is supplied with electrical energy. On the right side has the sealing cap 46 a cooling water connection 70 on, one in the sealing cap 46 integrated circulating cooling water supply 72 realized. A drain for the cooling water is not visible.

6 shows an alternative embodiment of the sealing cap 46 out 1 . 2 or 5 in detail. Here is the cold plug contact 66 designed as a Rammkontakt and the electrical connection 68 to the ramming contact 66 staggered.

The 7 . 8th and 9 show as variants for representation in 5 further attachment possibilities of the sealing cap 46 on the flange 12 with simultaneous sealing with the flange 12 , The sealing cap 46 is at each of the flange 12 opposite the outflow opening projecting ring 62 on the flange 12 attached.

In 7 indicates the lower edge of the sealing cap 46 an inward protruding projection 74 on, in the manner of a snap connection in a circumferential groove 76 of the flange 12 intervenes. The snap connection is by means of a from the outside to the sealing cap 46 applied circlip 78 secured against opening. The sealing properties are characterized by an in 5 above the projection 74 arranged O-ring 64 reached. In addition, the sealing cap has 46 in 5 a centering pin 80 on that in the sealing cap 46 is integrated and the drive unit 36 in the sealing cap 46 positioned correctly.

In 8th indicates the lower edge of the sealing cap 46 an outward protrusion 74 on, in the manner of a snap connection in a circumferential groove 76 of the flange 12 intervenes. The snap connection is by means of a from the inside to the sealing cap 46 applied circlip 78 secured against opening.

9 shows the attachment of the sealing cap 46 by means of a crimp connection 82 , This is the electrical connector 68 opposite end of the sealing cap 46 in a recess 84 of the flange 12 admitted. By forming one on the flange 12 trained envisaged margins 86 with a crimping machine or by hand will be the edge 86 against the sealing cap 46 pressed. This causes a solidification of the material and ensures a secure and tight attachment.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102007043532 A1 [0003]

Claims (10)

Dosing module ( 10 ) for a liquid reducing agent, in particular a urea-water solution, for injecting the reducing agent into an exhaust pipe of an internal combustion engine, wherein the metering module ( 10 ) a housing ( 14 . 16 ), which has a metering device ( 18 ) and a metering device ( 18 ) actuating drive unit ( 36 ), characterized in that the metering device ( 18 ) and the drive unit ( 36 ) as separate assemblies in the housing ( 14 . 16 ) are used, wherein at least the area of the drive unit ( 36 ) through an adapter ring ( 42 ) in the housing ( 14 . 16 ) is positioned and / or fixed and the metering device ( 18 ) are sealingly connected to the housing, wherein the drive unit ( 36 ) with the adapter ring ( 42 ) additionally with a sealing cap ( 46 ) is sealed. Dosing module ( 10 ) according to claim 1, characterized in that the metering device ( 18 ) and / or the adapter ring ( 42 ) by welding and / or caulking with the housing ( 14 . 16 ) are connected. Dosing module ( 10 ) according to one of claims 1 or 2, characterized in that the metering device ( 18 ) and / or the sealing cap ( 46 ) by a snap connection ( 74 . 76 ), in particular one with a retaining ring ( 78 ) cooperating snap connection ( 74 . 76 ), with the housing ( 14 . 16 ) are connected. Dosing module ( 10 ) according to claim 3, characterized in that the snap connection ( 74 . 76 ) in intended attack surfaces ( 76 ) is outside or inside. Dosing module ( 10 ) according to one of the preceding claims, characterized in that the metering device ( 18 ) and / or the sealing cap ( 46 ) by a crimp connection ( 82 ) with the housing ( 14 . 16 ) are connected. Dosing module ( 10 ) according to one of the preceding claims, characterized in that the metering device ( 18 ) and / or the sealing cap ( 46 ) by a screw connection to the housing ( 14 . 16 ) are connected. Dosing module ( 10 ) according to one of the preceding claims, characterized in that the metering device ( 18 ) and / or the sealing cap ( 46 ) by a self-clinch attachment ( 60 ) with the housing ( 14 . 16 ) are connected. Dosing module ( 10 ) according to claim 1, characterized in that the metering device ( 18 ) as an integral part of a flange ( 12 ) for attachment to the exhaust pipe. Dosing module ( 10 ) according to one of the preceding claims, characterized in that the metering module ( 10 ) is coolable by coolant. Dosing module ( 10 ) according to claim 9, characterized in that the dosing module ( 10 ), in particular in the region of the flange ( 12 ), and / or in the region of the sealing cap ( 46 ) Coolant channels ( 32 . 72 ) having.

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