Abstract:
The invention relates to a metering device ( 10 ) for introducing a process liquid or auxiliary agent into a flow pipe of an internal combustion engine, in particular for introducing a reducing agent into an exhaust gas pipe ( 12 ). Said device comprises an injection valve ( 22 ) and a receiving device ( 50 ) comprising a heat sink element ( 46 ) and a cover element ( 48 ). The injection valve ( 22 ) and the receiving device ( 50 ) are combined to form a structural unit by means of bonded connections ( 62, 64 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to a dosing device, comprising an injection valve and a receiving device which are combined to form a structural unit by way of cohesive connections. 
         [0002]    In known dosing devices for liquid reducing agents, such as are known for example from DE 10 2008 041 486, a dosing module is used which comprises a dosing unit, for example a dosing valve, for the injection of a reducing agent into the exhaust-gas region and which is held by a holding device or an adapter by means of which a connection to the exhaust tract is realized. To be able to introduce the reducing agent into the exhaust gas in an optimum manner, the dosing module must be positioned as close as possible to the hot exhaust tract, wherein maximum temperatures of 700° C. are reached in the exhaust tract of internal combustion engines. Owing to this inevitably high introduction of heat into the dosing module, there is the risk of overheating of the materials, for example of those used for insulators and seals, which permanently impairs the functionality of the dosing unit. For reasons relating to component strength and material protection against overheating, cooling devices are known which are intended to ensure a limit temperature of the dosing module, which is not to be exceeded, of approximately 150° C. 
         [0003]    DE 10 2009 047 375 A1 discloses a dosing module for the dosing of a reducing agent into the exhaust tract of an internal combustion engine, which dosing module is assigned a cooling device. Aside from passive cooling by way of cooling fins on the dosing module, use is made of a cooling body filled with a fluid. For example, a cooling housing comprises a metal sleeve and plastics parts, wherein said cooling housing may be of multi-part form and is sealed off by way of O-rings and is mounted on a receiving sleeve of the dosing module. 
         [0004]    WO 2012/049175 discloses a holder for an injector, for example for the introduction of a liquid substance into an exhaust gas of an internal combustion engine, wherein the injector is received entirely in a main body and a cap. The main body is formed from metal sheets which are connected to one another, for example by way of a brazed or welded connection, which metal sheets together form a ring-shaped chamber, wherein the injector accommodated therein is radially enclosed by said ring-shaped chamber and thus constitutes a heat barrier. The ring-shaped chamber, which is partially delimited by the housing of the injector, is charged with a cooling medium. The main body and injector housing are adhesively bonded, or connected in positively locking fashion by way of flanging, to one another in the abutment regions. The leak-tightness of the system is achieved by way of at least one seal which supplements the adhesive connections. The use of elastomers for sealing, mounting and/or insulation limits the maximum admissible temperature of the dosing module. Furthermore, the protection of the dosing valve installed in a dosing module with respect to the surroundings, for example spray water, or, on the exhaust-gas side, with respect to the reducing agent, is ensured only to a limited extent. 
       SUMMARY OF THE INVENTION 
       [0005]    According to the invention, a dosing device for the introduction of an operating or auxiliary substance into a flow pipe of an internal combustion engine is proposed, comprising an injection valve and a receiving device which comprises a cooling body element and a cover element, wherein the injection valve and the receiving device are combined to form a structural unit by way of cohesive connections. A dosing device of said type may be used in particular as part of an exhaust-gas aftertreatment system for the denitrogenization of the exhaust gases of internal combustion engines, wherein a reducing agent, for example aqueous urea solution (AdBlue®) is injected into the exhaust pipe of an internal combustion engine. 
         [0006]    The dosing device comprises, inter alia, a dosing module which has, arranged in a receiving device, a dosing unit, for example an injection valve, also referred to as dosing valve or injector. The receiving device at least partially, preferably substantially completely, surrounds the injection valve. Furthermore, the receiving device has an attachment region for the connection of the dosing device to the exhaust pipe. 
         [0007]    The receiving device is in the form of a multi-part construction comprising at least one cooling body element and one cover element, and is designed to receive the injection valve. The injection valve, at its lower end which faces toward the exhaust pipe and on which a spray hole disk is positioned, is cohesively connected by way of a welded connection to the receiving device or to the cooling body element of the receiving device. Said welded connection imparts a sealing action with respect to the exhaust gas and ensures low thermal resistance between the cooling body element and the spray hole disk received on the lower end of the injection valve. 
         [0008]    The injection valve that is received in the receiving device is sealed off with respect to the surroundings also by way of the cover element, which is an element of the receiving device. The injection valve is connected by way of a welded connection to the cover element in an abutment region, and the cover element is in turn connected preferably by way of a cohesive connection, in particular a weld seam, to the cooling body element. The cohesive connections of the individual components by way of welding offers the advantage, inter alia, of substantially complete sealing of the injection valve, without use being made of further sealing elements and thus of materials that are unfavorable with regard to temperature stability. 
         [0009]    The cooling body element and cover element are preferably manufactured from thin-walled components, in particular metal sheets, which are connected preferably cohesively to one another. The cooling body element may likewise be a multi-part construction comprising multiple elements connected to one another, wherein a cohesive connection in abutment regions of the individual elements is preferable. 
         [0010]    The cooling body element has a structure of complex shape, which forms inter alia a cavity which can be charged with a cooling medium. A cavity formed in this way provides a ring-shaped chamber, wherein a cooling medium inlet and outlet is provided on the cooling body element in order for the ring-shaped chamber to be charged with cooling medium. The cavity at least partially, preferably substantially completely, surrounds the received injection valve and provides a large receiving volume for the cooling medium. Furthermore, the ring-shaped chamber of the cooling body element may be divided by way of dividing elements such that the cooling medium is conducted within the ring-shaped chamber along a flow path which is configured for optimum cooling of the injection valve. The cooling medium that enters at low temperature passes along the flow path for example into the region of the injection valve, in which relatively high temperatures prevail. Owing to the temperature conditions, an improved cooling action for the injection valve is achieved. Depending on the usage situation and cooling power to be provided, the cooling medium that enters may also have other flow paths imparted to it in the region of the injection valve. Furthermore, by way of the predefined flow path, the flow of the cooling medium is influenced such that a predominantly turbulent flow exists, and dead spaces are substantially avoided, wherein the dissipation of heat is improved. The cooling medium may be a liquid or a gas mixture, for example cooling water, water, fuel or reducing agent or air. 
         [0011]    Furthermore, the receiving device is designed such that the injection valve is surrounded by the cooling body element in the manner of a sleeve, wherein a radial sleeve chamber that is formed between the injection valve and the cooling body element extends in particular as far as into the region of the tip of the injection valve. The sleeve chamber, which is sealed off with respect to the surroundings, may accommodate a medium, for example air, thermally conductive paste, oil or other suitable media which assist a transfer of heat between injection valve and cooling body element. 
         [0012]    For the radial retention of the injection valve in the receiving device, it is furthermore provided that, in the radial sleeve chamber formed between injection valve and cooling body element, there is arranged a holding element which positions the injection valve radially. The holding element may be designed in the form of a ring-shaped thermally conductive body, such that a heat flow entering the injection valve from the tip is dissipated by way of thermal contact to the holding element and onward to the cooling body element. Thus, by way of the holding element, a simple fastening of the injection valve to the receiving device, and an effective dissipation of heat into the cooling body element of the receiving device, are achieved. 
         [0013]    The injection valve and receiving device are subject to different length expansions in the event of temperature changes, which length expansions lead to mechanical stresses in particular at the connecting points. For the elastic compensation of different thermal changes in length of the injection valve on the one hand and of the receiving device on the other hand, at least one expansion compensation means is provided. The at least one expansion compensation means, which is for example integrated into the cover element, preferably compensates all of the occurring length differences of the components that are connected to one another. In one embodiment, the expansion compensation means may be in the form of a spring element or a corrugated bellows, and may be arranged between the injection valve and receiving device. 
         [0014]    A refinement of the dosing device provides that an electrical terminal and an actuation means of the injection valve for the control of the dosing of reducing agent are provided, wherein the cover element comprises a corresponding leadthrough which has a means for sealing with respect to the surroundings. For example, a fastening may be realized by way of a positively locking connection by means of flanging. 
         [0015]    By way of the solution proposed according to the invention, of the dosing device having an injection valve and having a receiving device connected thereto to form a structural unit by way of cohesive connections, optimum protection with respect to external media, for example spray water, is achieved. Simple structural measures and reduced manufacturing outlay for the receiving device, comprising a cooling body element and a cover element, reduce the manufacturing costs and the weight of the construction. 
         [0016]    For the injection valve, which is cooled in optimized fashion, increased robustness with respect to temperature loads is realized. In particular, because the reducing agent that is introduced into the exhaust pipe by the injection valve changes into the vapor phase in the presence of a temperature higher than 140° C. to 160° C., it is possible, with an improved dissipation of heat, to prevent boiling within the injection valve. Owing to the improved cooling of the injection valve in combination with insulation with respect to the surroundings, the arrangement of the dosing device for a reducing agent can be optimized. 
         [0017]    The connection of the injection valve to the receiving device by way of cohesive welded connections offers optimum sealing without the use of additional seals, which are problematic with regard to their temperature stability. 
         [0018]    Further advantages include the fact that the receiving device, and/or the cooling body element and the cover element, can be manufactured from thin metal sheets, whereby a weight saving and simple manufacturing are possible. Furthermore, the cooling body element can, by way of dividing elements, be designed optimally for the throughflow of a cooling medium. 
         [0019]    Furthermore, the mounting of the injection valve, and the compensation of expansions induced by temperature changes in the dosing device according to the invention, can be made possible in a simple manner. In accordance with the solution proposed according to the invention, the injection valve is virtually completely surrounded by the cooling medium. The cooling medium jacket surrounding the injection valve as a thermal barrier is virtually complete in a radial direction. With the solution proposed according to the invention, it can furthermore be achieved that the injection valve can be installed in optimum fashion in a manner dependent on its installation location and its operating conditions. In a manner dependent on whether the injection valve is used at an installation location exposed to high temperatures or at a location which is sensitive with regard to acoustics, it is possible to realize an appropriate attachment of the injection valve in optimum fashion in a receiving device for the injection valve. With regard to a temperature-resistant installation location, improved heat dissipation can be allowed for through the selection of suitable materials and of a suitable temperature level of the cooling medium. By contrast, if the injection valve is used in an acoustically sensitive location, then by way of correspondingly optimized installation, sound propagation in the receiving device of the injection valve can be realized without the provision of sound transmission bridges. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    Further advantages and embodiments of the subjects according to the invention will be illustrated by the drawings and discussed in more detail in the following description. 
           [0021]    In the drawings: 
           [0022]      FIG. 1  shows a cross section through a dosing device with a holder and with an integrated injection valve, and 
           [0023]      FIG. 2  shows a cross section through a design variant of a dosing device proposed according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]      FIG. 1  shows a dosing device  10  for use in SCR systems for the dosing of reducing agent into an exhaust pipe  12 , wherein an exhaust-gas flow passes through the exhaust pipe  12  in a flow direction B. The exhaust-gas flow originates from an internal combustion engine which is not illustrated in  FIG. 1  and to which, at the outlet side, the exhaust pipe  12  is connected. The dosing device  10  comprises a main body  14  which is formed from a first metal sheet  16  and from a second metal sheet  17 , which are connected to one another in an abutment region or an overlap region by way of a brazed connection  18 . The metal sheets  16  and  17  are spaced apart from one another and form a ring-shaped chamber  20 . Furthermore, in the main body  14 , there is received an injection valve  22 , the housing of which is denoted by  24 . The contour of the first metal sheet  16  is in this case selected such that a matching receptacle  26  for the injection valve  22  is formed. The injection valve  22  forms, with the first metal sheet  16  and the second metal sheet  17 , abutment regions which are formed as adhesive connections  28  and  30 , wherein the ring-shaped chamber  20  is delimited at one side by the first and the second metal sheet  16 ,  17  and at the other side by the housing  24  of the injection valve  22 . For the purposes of sealing the ring-shaped chamber  20 , an additional seal  32 , for example in the form of an O-ring, is additionally provided, adjacent to the adhesive connection  28 . On the second metal sheet  17  there are provided a cooling medium inlet  34  and a cooling medium outlet  36 , by way of which the ring-shaped chamber  20  is charged with a cooling medium. Above the main body  14  there is provided a cap  38  on which there is provided an injection fluid port  40 . The cap  38  and the main body  14  are connected to one another by way of a brazed connection that is not explicitly illustrated. Illustrated between the main body  14  and the cap  38  is an electrical terminal  42  of the injection valve  22 , wherein control lines may also be connected there. For the compensation of a change in volume of an injection fluid situated within the dosing device  10  as a result of formation of ice, a disk spring as an expansion compensation means  44  is provided in the region of the cap  38 . 
         [0025]      FIG. 2  shows a possible design variant of the dosing device  10  proposed according to the invention, wherein similar elements are denoted correspondingly to the designations used in  FIG. 1 . 
         [0026]    In the dosing device  10 , a cooling body element  46  and a cover element  48  are combined to form a receiving device  50 , said cooling body element and cover element being sealingly connected to one another for example by way of a weld seam  49 . The dosing device  10  is arranged on the exhaust pipe  12 , wherein, for example, a flange connection  52  is provided, by way of which the dosing device  10  can be connected to the exhaust pipe  12 . Alternatively, said connection may also be produced by way of a welded connection or by flanging. The dosing device  10  comprises the injection valve  22  or an injector, by way of which the reducing agent, for example AdBlue®, is introduced into the exhaust-gas flow. The temperature of the exhaust gas flowing in the flow direction B may reach 700° C. at this location. Accordingly, at this location, the exhaust pipe  12  is heated, whereby the injection valve  22 , and in particular its lower end on which a spray hole disk  54  is situated, is subject to extremely high thermal loads. Accordingly, cooling of the injection valve  22  is necessary, which cooling prevents damage to the dosing device  10 . 
         [0027]    According to the invention, cooling is achieved by way of a cooling body element  46  in the form of a thin-walled construction. The cooling body element  46  may be manufactured from multiple metal sheets which have a structure of greater or lesser complexity and which are welded to one another at corresponding abutment regions. In the design variant as per  FIG. 2 , the metal sheets  16 ,  17  are formed in a structure and are cohesively connected to one another at welded connections  56 . 
         [0028]    The metal sheets  16 ,  17  thus connected to one another delimit the ring-shaped chamber  20  which can be charged with a cooling medium via the cooling medium inlet and outlet  34 ,  36 . As cooling medium, use may be made of a liquid, for example water, cooling water, fuel or the reducing agent. Also illustrated in  FIG. 2  are dividing elements  58  which further divide the ring-shaped chamber  20 , wherein the individual regions of the ring-shaped chamber  20  that are thus formed are in fluidic contact with one another via openings  60  provided on the dividing elements  58 . In this way, the cooling medium has imparted to it a flow path which permits optimized cooling. 
         [0029]    The injection valve  22  is received in the receiving device  50 , wherein the cooling body element  46  substantially completely surrounds the injection valve  22 . The injection valve  22  is, at its lower end in the region of the spray hole disk  54 , connected sealingly to the receiving device  50 , that is to say to the cooling body element  46 , by way of a cohesive connection in the form of a weld seam  62 . Furthermore, the injection valve  22  is, at its upper end, connected to the cover element  48  of the receiving device  50 , likewise cohesively by way of a welded connection  64 , in an abutment region. Thus, the injection valve  22  is received in the receiving device  50 , wherein said injection valve is sealed off with respect to the surroundings by way of welded connections, without the need for additional sealing elements. 
         [0030]    Furthermore, a holding element  66  is provided for the radial positioning of the injection valve  22  in the receiving device  50 , which holding element is provided in a radial sleeve chamber  68  formed between the injection valve  22  and the cooling body element  46 . The holding element  66  may be in the form of a ring-shaped thermally conductive body and held in the receiving device  50 , or in the radial sleeve chamber  68 , with an interference fit. In this way, the injection valve  22  is also held at least indirectly in the receiving device  50 , and heat dissipation is realized. The sleeve chamber  68 , which is sealed off by way of the welded connections in the form of weld seams  62  and  64 , can be filled with a medium which serves for the improved dissipation of the heat that is introduced into the injection valve  22  from the lower end. Suitable media are air, thermally conductive paste, oil etc., wherein, for more efficient cooling owing to improved heat transfer, the thermally conductive medium substantially surrounds the injection valve  22  as far as into the region of the spray hole disk  54 . 
         [0031]    The injection valve  22  and the receiving device  50  exhibit different changes in volume or length in the event of temperature changes. To realize compensation of the different thermal changes in length, an expansion compensation element  70  is received between the receiving device  50 , in particular the cover element  48 , and the injection valve  22 . The expansion compensation element  70  may be in the form of a disk spring or, as indicated in  FIG. 2 , in the form of a corrugated bellows, wherein a relative movement is possible for pressure relief purposes. 
         [0032]    Furthermore, on the cover element  48 , there is provided a leadthrough  72  for an electric actuation means, indicated by an electrical terminal  74  of the injection valve  22 , wherein the leadthrough  72  has a seal  76 . 
         [0033]    A major advantage of this embodiment consists in that, owing to the cohesive connections of the individual components of the dosing device  10 , no additional sealing elements have to be provided. Furthermore, the lightweight construction of the receiving device  50  advantageously makes it possible to realize an inexpensive construction which is optimized with regard to cooling of the injection valve  22  received therein. 
         [0034]    The invention is not restricted to the exemplary embodiments described here and to the aspects highlighted therein. Rather, within the scope specified by the claims, numerous modifications are possible which fall within the capabilities of a person skilled in the art.