Abstract:
The invention relates to a device for cooling a metering module ( 10 ) for dispensing a process liquid/auxiliary agent into the exhaust gas system of an internal combustion engine. The metering module ( 10 ) comprises a housing ( 12 ) with a plurality of housing sections ( 19 ), ( 20 ), ( 28 ), ( 29 ). A first housing section ( 19 ), ( 20 ), on which a supply line ( 18 ) for the process liquid/auxiliary agent is located, is situated in a region ( 62 ) of the metering module ( 10 ) that is exposed to varying temperatures, said section being made of metal.

Description:
BACKGROUND OF THE INVENTION 
     DE 44 36 397 B4 relates to a device for the aftertreatment of exhaust gases. The device comprises an exhaust manifold system, in which a reduction catalytic converter is arranged for reducing NO x  constituents of the exhaust gas from the internal combustion engine. The device further comprises a metering device, comprising an electrically controlled metering valve for the metered introduction of a reducing agent into the flow of exhaust gas delivered to the catalytic converter, as a function of a value for the NO x  content of the exhaust gas stored in the mapping for various operating parameters of the internal combustion and the catalytic converter. The valve for controlling the air feed is an electrically controlled control valve, which is arranged downstream of outlet aperture of the metering valve and the outlet aperture of which opens directly into the exhaust gas flow from the internal combustion engine. The control valve is accommodated by a body with a cooling medium flowing round it, so that the control valve is cooled. 
     US 2008/0236147 A1 discloses an injection system, which as part of the selective catalytic reduction on a motor vehicle is used for reducing NO x  fractions in the exhaust gas. According to this solution the injection system comprises an injector, which is supplied with current via an electrical connection. Situated within the electrical connection is an electrical contact which is configured to receive a connector of a connection lead. 
     The subject matter of US 2010/0108020 A1 is a connection system for electrical leads which are laid in hazardous areas, such as, for example, in an area in which there is a risk of explosion, for example in the surroundings of an internal combustion engine. The connection system disclosed is suitable for the electrical connection of leads of various sensors and components. The connection system comprises a protective rubber sleeve and a cap, which is provided with an internal thread. Here the protective rubber sleeve serves as an electrical and thermal insulator and is compressed in the assembled state of the connection system. 
     DE 10 2009 060 065 A1 discloses a fluid line for urea-water solutions in NO x  reduction devices which function on the selective catalytic reduction (SCR) principle. The fluid line is made from a thermoplastic vulcanizate. The thermoplastic vulcanizate has rubber-like characteristics and is also known as a thermoplastic elastomer. An outstanding characteristic of the thermoplastic vulcanizate is its high resistance to aggressive fluids and it possesses a very high flexibility and an outstanding pliability. According to DE 10 2009 060 065 A1 a fluid line produced from a thermoplastic vulcanizate is used for connecting tanks, pumps and injection nozzles or to accommodate couplings. 
     In metering modules, which are used as part of exhaust gas aftertreatment systems, use is made of injection valves which serve for urea metering. In order to get as close as possible to the exhaust gas flow with the valve tip of the injection valve, the valve fixture in these metering modules is actively cooled. This is done through a connection of the valve body to the coolant circuit of the vehicle. This ensures that, even when the valve is positioned close to the exhaust gas, in operation the valve tip temperature does not exceed 120° C. Where in a metering module a connection fitting, made of plastic (PA66) and affording contact with the supply feed for the automotive fluid/additive, runs outside the cooling element, it is exposed to the ambient temperature and in critical operating states, such as at high ambient temperatures, for example, may heat up in operation or in the event of heat soak. 
     In such cases a high heat input may pass via the plastic connection fitting into the O-ring situated under the former and serving for sealing purposes. 
     SUMMARY OF THE INVENTION 
     According to the invention it is proposed that in a departure from the materials hitherto used the connection fitting of the metering module now be made from a metal. This means that the connection fitting stands up better to the high thermal loads in operation and to those occurring in the event of a heat soak, and to the mechanical stresses. Through the choice of material for the connection fitting and the associated improvement in the thermal conduction to the sealing element between the connection fitting and the injection valve of the metering module, it is possible to dispense entirely with a soft seal constituting a potential leakage point. 
     According to the invention it is proposed to connect the connection fitting directly to the injection valve of the metering module and to constitute a circumferential seal, for example by making a cohesive material connection such as laser welding. On the one hand this eliminates the soft seal, which as mentioned above has to be classed as very temperature-critical, and on the other it increases the robustness of this sealing considerably compared to the use of a soft seal. 
     In such an embodiment of the metering module the direct connection between the connection fitting and the injection valve would allow forces occurring in the pressure line, which in operation manifest themselves as vibrations, for example, to act directly on the injection valve, so that additional relief of the injection valve has to be provided. The injection valve of the metering module can be relieved of forces caused by the pressure line and inevitably occurring in operation, for example, by suitably connecting the connection fitting, now made of metal, to a connection plate, for example. This is likewise preferably done by forming a cohesive material connection, such as a laser weld seam, for example. The forces inevitably introduced into the injection valve via the connection fitting during operation can thereby be dissipated via the connection plate to a cooling element enclosing the injection valve. The injection valve can thereby be relieved of mechanical forces. 
     In a further advantageous embodiment of the solution underlying the invention the injection valve is axially held on the connection plate solely by way of the connection fitting attachment. A locking plate that would otherwise be necessary can be dispensed with, so that an additional weight and cost advantage can be achieved. 
     The solution proposed according to the invention makes it possible to create a temperature-resistant connection fitting which does not sustain any damage, even when it is exposed to very high ambient temperatures. 
     Since the solution proposed according to the invention opens up the possibility of creating a cohesive material connection between the connection fitting and the injection valve, the problem of sealing, which is bound to occur where a temperature-sensitive soft seal is used, is eliminated. The sealing, preferably in the form of a laser weld seam, is firstly temperature-resistant and secondly it is leak-tight. A selection of special soft seal materials can now be eliminated as can the soft seal itself. The latter is usually embodied as an O-ring. The solution proposed according to the invention eliminates this critical sealing site. 
     Furthermore, by exchanging plastic for metal the solution proposed according to the invention affords an increase in the strength of the connection fitting. Since in the solution proposed according to the invention the seal in the form of an O-ring made from a soft seal material can be dispensed with, the elimination of this particular component allows the valve to be shortened. This in turn has a beneficial effect on the design space needed for installation of the metering module, so that design space advantages can be secured in terms of the vehicle packaging. In addition, in assembling the metering module proposed according to the invention the production operations involving the fitting of the soft seal and the fitting of the locking plate securing the metering valve in an axial direction can be eliminated. The elimination of the locking plate moreover has an advantageous impact on the overall weight of the metering module. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is described in more detail below with reference to the drawing, in which: 
         FIG. 1  shows a perspective representation of a metering module, which is enclosed by a multipart cooling element and 
         FIG. 2  shows a representation of a metering module in which a connection fitting is made of metal and is joined to an injection valve by a cohesive material connection. 
     
    
    
     DETAILED DESCRIPTION 
     The metering module described below with reference to  FIGS. 1 and 2  is a metering module for introducing an automotive fluid/additive, in particular a reducing agent such as urea or a urea-water solution, for example, into the exhaust tract of an internal combustion engine. Temperatures ranging between 100° C. and 160° C. can occur in the immediate surroundings of the metering module  10  proposed according to the invention. Higher or lower temperature levels may also prevail depending on the intended purpose and the installed location. The automotive fluid/additive, in particular a reducing agent such as urea or a urea-water solution, for example, serves to reduce the NO x  constituents which are present in the exhaust gas from internal combustion engines, to H 2 O and N 2 . The device proposed according to the invention for cooling a metering module  10  may also be used in other metering devices which are to be operated within a specific temperature range as cooling for these. 
       FIG. 1  shows that a metering valve of a metering module  10  is enclosed by a complete encapsulation  12 , which represents a second housing. The complete encapsulation  12  comprises an upper shell  20 , which may be embodied in cap form, for example, and a plastic cover  17 , which may be produced in particular from a material having elastic characteristics, such as a plastic material, for example, or a rubber. In addition the encapsulation  12  comprises a middle shell  28 , together with a guide sleeve  32  arranged below the former, and below that a lower shell  29 , into which a cupped insert  24  is inserted as is shown only partially in  FIG. 1 . 
     As can be seen from the perspective representation according to  FIG. 1 , the metering valve of the metering module  10  is entirely enclosed by the components  17 ,  20 ,  28  and  29  enumerated above. Only a lower end of the cupped insert  24  protrudes below the lower shell  29  of the complete encapsulation  12  of the metering module  10 . 
     As can also be seen from the perspective representation according to  FIG. 1 , a cooling fluid inlet  22  is situated in the circumferential face of the lower shell  29 . Situated opposite this in the circumferential face of the middle shell  28  is a cooling fluid return  26 . 
     The representation according to  FIG. 2  shows a metering module in which a connection fitting is made of metal and is connected by a cohesive material joint to an injection valve. 
     The cross section according to  FIG. 2  shows that a metering valve  30  is completely enclosed by the encapsulation  12 . The encapsulation  12  here comprises the upper shell  20 . Extending through the upper shell  20  is the automotive fluid/additive inlet  18 , via which in particular a reducing agent, such as urea or a urea-water solution, for example, is delivered to the metering module  10 .  FIG. 2  shows that this inlet  18  may be formed at an angle to a connection fitting  19  and is encapsulated by the upper shell  20  with a flange covering an upper end face of the metering valve  30 . For its part the upper shell  20  comprises a cavity  42 , which is separated from the cooling fluid by a dividing rib  60  against the middle shell  28 , though the cavity  44  of which the cooling fluid is able to flow. As can additionally be seen from the sectional representation according to  FIG. 2 , the upper shell  20 , in the area of a connector  16  or an electrical plug contact  36 , comprises an air gap portion, which is part of an air gap insulation  14  of the electrical plug contact  16  or  36  of the metering module  10 . 
     Situated below the upper shell  20 , which is part of the encapsulation  12  of the metering module  10 , is a middle shell, which is identified by the reference numeral  28 . The middle shell  28  comprises a seat  40 , into which the upper shell  20  defining the cavity  42  is inserted. 
     The middle shell  28  also encloses the metering valve  30 , which in previous solutions was secured in an axial direction by the locking plate  34  still represented in  FIG. 2 . In the solution proposed according to the invention the locking plate  34  still drawn in in  FIG. 2  can be dispensed with, since the axial locking of the metering valve  30  is now provided by the cohesive material connection, that is to say the second connecting seam  72  between the reducing agent inlet  18  of the connection fitting  19  and the corresponding connection of the metering valve body  30  in an axial direction. 
     The middle shell  28  is seated on a guide sleeve  32 . For its part the guide sleeve  28  is accommodated on an insert  24  of substantially cupped design. 
     It can be seen from the sectional representation according to  FIG. 2  that the middle shell  28  comprises the cavity  44 , through which the cooling fluid flows and which at the same time also contains a first air gap portion  54  and a second air gap portion  56 . The first air gap portion  54  and the second air gap portion  56  are separated from the cavity  44  by a dividing rib  60 , which is formed in the middle shell  28 . In particular, the profile of the dividing rib  60  in the middle shell  28  is selected in such a way that the first air gap portion  54  and the adjoining second air gap portion  56  extend along the electrical plug contact  36  towards the plug contact cover  17 . The dividing rib  60 , which separates the first air gap portion  54  and the second air gap portion  56  from the cavity  44  through which the cooling fluid flows, terminates at a wall end  52  of the middle shell  28 . Also situated there, as on the opposite side of the upper shell, is a latching connection  50 , cf. position  48  in  FIG. 2 . The plug contact cover  17  is detachably latched at both of the latching points  48  and  50 , which are formed on the upper shell  20  on the one hand and on the middle shell  28  on the other. As already explained in connection with  FIG. 1 , the plug contact cover  17  is detachably connected to the outside of the middle shell  28  by a latch  48  on the upper shell  20  and by a latch  50  opposite the former. 
     Cooling through the air gap insulation  14  at the air gap portions  38 ,  54  and  56 , as represented in  FIG. 2 , is afforded in the area of the electrical contacts  36 . It can also be seen from  FIG. 2  that the middle shell  28  represents a “hybrid component”, which both comprises an air gap insulation in the area of the electrical plug contact  36  and which on the other hand contains at least one cavity  44 , which is forcibly cooled, that is to say it has cooling fluid flowing through it. 
     The lower shell  29  is situated below the guide sleeve  32 , as can be seen from the bottom area of  FIG. 2 . For its part the lower shell  29  receives the cupped insert denoted by the reference numeral  24 . Temperatures of 120° C. and above can occur at the bottom end of the metering module  10 . For this reason the cooling fluid inlet  22 , into which the cooling fluid overflows into the lower shell  29  and thence into a cavity  66  of the cupped insert  24 , is situated in the area of the lower shell  29 . The injection nozzle, via which a spray mist of automotive fluid/additive and air is injected into the exhaust tract of the internal combustion engine, is also situated in the bottom area of the metering valve  30 . Since operation dictates that the highest temperatures occur here, the cooling fluid inlet  22  is situated in this part of the metering module  10  so as to optimize the cooling effect, in order to ensure an optimum dissipation of heat in the area of the high temperatures occurring there. 
     It can also be seen from the sectional representation according to  FIG. 2  that, after entering through the cooling fluid inlet  22  and flowing through the cavity  66  of the cupped insert  24 , the cooling fluid flows via at least one passage  46  to the cavity  44  above the base of the middle shell  28 . As  FIG. 2  shows, passages  46  in the guide sleeve  32  and in the base of the middle shell  28  align with one another, so that after flowing through the cupped insert  24  the cooling fluid passes into the cavity  44  in the middle shell  28 . After passing through the cavity  44  in the middle shell  28 , which is imperviously separated by the dividing rib  60  from the air gap portions  54 ,  56 , the cooling fluid, warmed by the waste heat from the metering module  10  as it flows around the latter, leaves the cavity  44  in the middle shell  28  at the cooling fluid return  26 , as represented in  FIG. 2 . The passages  46  ensure transfer of the cooling fluid from the cavity  66  in the cupped insert  24  into at least the one cavity  44  in the middle shell  28  of the encapsulation  12 . 
       FIG. 2  furthermore shows that an exposed area  62 , that is to say an area that is neither liquid nor air-cooled, and which in particular comprises the area of the connection fitting  19 , is situated on the metering module  10 . In addition,  FIG. 2  shows that an insulated area  64  is situated below the exposed area  62 . In this area cooling ensues due to an air gap insulation  14 , starting from the cavity  42 , which is defined by the upper shell  20  in cap form. Situated below this insulated area  64  of the metering module  10  is a water-cooled area  66 , which is cooled by the cooling fluid, which circulates through the various cavities  58  and  44  via the cooling water inlet  22  and the cooling water return  26 . A dividing rib, which inside the middle shell  28  separates the first air gap portion  54  from the middle shell cavity  44 , is denoted by the reference numeral  60 . 
     The representation according to  FIG. 2  shows that the connection fitting  19  has a connection plate  74  running circularly, for example, around the reducing agent inlet  18 . In the solution proposed according to the invention this connection plate  74  of circular form, for example, is connected in the area of a first connecting seam  70  by a cohesive material joint to the connection fitting  19  made of metal. The first connecting seam  70  serves for the transmission of force, that is to say for transmitting forces acting on the reducing agent inlet  18  to the metering module  10 . The first connecting seam  70  is preferably formed as a laser weld seam between the connection plate  74  and an area of the cap-shaped upper shell  20  of the connection fitting  19  situated opposite the former. In addition, the representation according to  FIG. 2  shows that the reducing agent inlet  18  of the connection fitting  19  is connected to an end face of the metering valve body  30  by a cohesive material joint along a second connecting seam  72 . The connection fitting  19  is configured to be connected in an ungraduated rotational position to the metering valve body  30  of the metering module  10 . The cohesive material connecting seam  72  between the reducing agent inlet  18  of the connection fitting  19  and the corresponding connection of the metering valve body  30  is likewise made as a laser weld seam. This second connecting seam  72  constitutes a fluid seal, formed between the metering valve body  30  and the reducing agent inlet  18  of the connection fitting  19 . The fluid seal represented by the second connecting seam  72  serves to protect the cavity  42  against the ingress of reducing agent. The dividing wall  34 , which separates the cavity  42  from the middle shell cavity  44  for the cooling medium, serves to seal the two media cavities  42  and  44  off from one another, the dividing wall  34  being seated on the external geometry of the metering valve body  30 . 
     The solution according to  FIG. 2  and in particular the first connecting seam  70  between the circumferential connection plate  74  on the one hand and the inside of the upper shell part  20 , made in the form of a metal cap, on the other provide mechanical relief for the metering valve body  30 . The forces reduced by the connection fitting  19  are transmitted to the cooling element, that is to say the complete encapsulation  12 , via the connection fitting  19  and are not transmitted directly to the metering module  10  enclosed by the complete encapsulation  12 . 
     In the representation according to  FIG. 2  the locking plate  34  has still been drawn in for the purposes of clarification. It can be seen that in  FIG. 2  the axial locking plate  34  engages in a corresponding groove on the circumferential face of the metering valve  30 , thereby securing this component in an axial direction. This locking plate  34  is dispensed with, since the task of axially securing the metering valve  30  is now assumed by the second connecting seam  72 , as represented in  FIG. 2 .