Abstract:
The invention relates to a delivery module for a dosage system used to introduce a reducing agent into the exhaust gas tract of an internal combustion engine. The delivery module has a housing, which accommodates various components, and which is produced as an injection moulded component. A heating system is integrated in the vicinity of the center of the housing. The housing has at least one chamber for receiving additional components.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a 35 USC 371 application of PCT/EP 2007/062413 filed on Nov. 15, 2007. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a delivery module for a dosage system used to introduce a reducing agent into the exhaust gas tract of an internal combustion engine. 
     2. Description of the Prior Art 
     In motor vehicles with internal combustion engines, because of the increasingly stringent laws regarding exhaust gases expected in the next few years, the pollutant NOx contained in the exhaust gas of internal combustion engines must be reduced. One currently used method for this is the SCR process (Selective Catalytic Reduction), in which the pollutant NOx is reduced to N 2  or H 2 O, using liquid reducing agent. The reducing agent used, as a rule in liquid form, is received in a tank and is fed by a delivery module from the tank via a line to a metering module for injecting the reducing agent into the exhaust gas. The goal is to position the metering system, with its components, that is, tank delivery module lines, metering module, and the like, outside the passenger compartment of the motor vehicle, since at elevated temperatures, ammonia (NH 3 ) forms from the aqueous urea solution used as the reducing agent. With this concept of accommodating the entire metering system that carries the reducing agent outside the passenger compartment, it is assured that in the event of leaks in the metering system that carries the reducing agent, or in the event of an accident, no NH 3  formation can occur in the passenger compartment. Stringent demands are made of the delivery module, which includes such components as a pressure sensor, pump, scavenging valves, filter, heater, contact means of the components, and the like, in terms of being splashproof and being capable of fording flooded roads, and in particular of having corrosion resistance. Since the components of the metering system that carry the reducing agent are disposed outside the passenger compartment, they are exposed to a greater extent to temperature fluctuations and to the influence of splashing water and de-icing salt, in contrast to a disposition of those components in the passenger compartment. 
     These demands in terms of being splashproof and having fording ability as well as corrosion resistance are attended to, in systems used until now, by providing that the components of the entire metering system, that is, the aforementioned components comprising the tank delivery module, lines, and metering module, are accommodated in a separate housing. An internal cable harness connects the individual components to a central plug, which is mounted on the housing and by way of which the task of electrical contacting is shifted to the outside. The components accommodated inside the housing communicate with one another hydraulically via heatable hoses. These heatable hoses end at an inlet and outlet piece on the housing and are thus shifted to the hose connections outside the common housing. Once the components are mounted inside this housing, the housing is closed, sealed off from the environment with its components, via a separate lid. In a different concept for meeting this demand, all the components of the delivery module for the system carrying the reducing agent are embodied as individual components that are already splashproof and have fording ability. The individual components are mounted on a circuit board or mounting plate or the like and are sealed off by seals at an interface between the components and the plate. The hydraulic communication of the components is effected inside a plate or mounting block (circuit board). Each individual component designed to be splashproof and capable of fording flooded roads has its own contact means. A heater is also connected to the plate. 
     The embodiment described at the outset above is relatively large, since the individual components are accommodated in a common housing. Because of the hydraulic communication of the components with one another via hoses and because of the electrical triggering of the individual components with a central plug via a cable harness, the common housing in the first version sketched at the outset is extremely expensive and requires an extremely large amount of space. In addition to the components accommodated in a common housing, the hydraulic lines also each require heaters, which have an adverse effect on cost and space and in an individual case must be procured from the automobile manufacturer with regard to the required specifications. in the other versions it is a prerequisite that each of the individual components, on their own, meet the demands made for a component mounted outside the passenger compartment with regard to splashproofness, fording ability or corrosion resistance. This can be extremely complicated, since in the SCR process, some of the components are actuated via levers, as in the case of the reversing valve for the pump. An eccentric drive mechanism may be actuated by an actuation magnet or an electric drive mechanism. These are not compact, rotationally symmetrically embodied individual components that operate independently of one another; on the contrary, they are components which are in engagement with one another in manifold ways. This makes separate sealing for each component, as is known in the second embodiment previously chosen and known from the prior art, extremely difficult. Moreover, heating the components of an SCR system that are accommodated outside a common mounting block and received there proves extremely difficult, especially with regard to heat transfer from a heat source to the individual components received on a common mounting block. 
     SUMMARY AND ADVANTAGES OF THE INVENTION 
     According to the invention, it is proposed that a component of the metering system for introducing a reducing agent into the exhaust gas of an internal combustion engine be embodied as a primary component in such a way that further components can be integrated with the selected primary component in drawerlike or modular fashion, so that a compact complete unit is obtained. In practice, a reversing valve, for instance, which may for instance be a 4/2-way valve, can be selected as the primary component, in the housing of which drawerlike compartments or drawerlike chambers for the other components, such as a delivery module of the metering system, can be embodied for introducing a reducing agent into the exhaust gas of an internal combustion engine. According to the invention, it is proposed that the housing of the selected primary component be provided with a plurality of drawers. Since the housing of the primary component is fabricated economically, offering a high degree of design freedom, in the course of the plastic injection molding process, the chambers required for the drawers can be made relatively simply from plastic. Further components, such as a pressure sensor and at least one filter on the compression side, can easily be inserted into these drawers in the housing of the primary component. Once the applicable component has been built into the particular drawer provided for it in the housing of the primary component, individual chambers can be closed via separate plastic lids. The closure of the individual chambers via separate plastic lids can be done for instance by way of securing a lid to the drawer by means of a clip connection or screw connection or by embodying material-locking connection, for instance in the course of the plastic friction welding. 
     Depending on the degree of tightness of the individual chambers that is required, which depends on the component accommodated therein, elastomer seals can be let in between the chamber and the lid as seals. Elastomer seals may be dispensed with, for instance, if a material-locking connection is created along the opening of the chamber, receiving the drawer, in the housing of the primary component and in the lid that closes it. The electrical triggering of a component that is accommodated in its particular chamber in the housing of the primary component may be done for instance via a plug connection integrally injected onto the lid. Contacting of the component with the plug can be done via a pigtail connection, which can be plugged onto the particular component to be contacted electrically, between the component and the plug. Optionally, the plug housing integrally molded onto the lid can be provided with openings. If the particular component to be contacted electrically has plug prongs, then the plug, upon completion of the component and lid upon assembly can protrude from inward through the openings into the inner plug region and thus complete an electrical plug on the delivery module end. 
     Advantageously, a heater can be injection-molded into the housing of the primary component, which housing is preferably made in the course of the plastic injection molding process and in which the various chambers are embodied for receiving the drawers and components. If this heater is injection-molded directly into the plastic housing, then in contrast to a screwed-on heater, which is in contact at most at one point and thus can transmit heat via this one side in the course of the heat conduction, considerably better heat input into the drawers accommodated in the housing of the primary components, or in other words into the components integrated with these drawers, can be achieved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is describe in further detail below in conjunction with the drawings, in which: 
         FIG. 1  shows an embodiment in accordance with the prior art, in which the components of the delivery module of a metering system are accommodated in a common housing that is sealed off from the outside and is electrically contacted; 
         FIG. 2  shows a further embodiment in accordance with the prior art, in which individual components, each meeting exterior demands, are received on a common mounting block; and 
         FIG. 3  shows a delivery module proposed according to the invention for a metering system for introducing a reducing agent, in which in the housing of a primary component, a plurality of further components of the delivery module of a metering system are accommodated. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In  FIG. 1 , a first embodiment of a delivery module according to the prior art can be seen in which the components of a delivery module of a metering system are integrated with a common housing that is sealed off from the outside. 
     It can be seen from  FIG. 1  that a plurality of components  26 ,  28 ,  30  of a delivery module for delivering a reducing agent inside a metering system are disposed inside a central housing  10 . In  FIG. 1 , the first component  26 , second component  28 , and third component  30  are secured to the bottom of the central housing  10 . The central housing  10  is closed by a lid  12 , which is sealed off by means of a sealing ring  16  extending all the way around. A central plug with a cable harness  14  is integrated with the lid  12 , and by way of it the individual components  26 ,  28 ,  30  are electrically contacted inside the central housing  10 . An inlet  18  extends into the central housing  10  through its bottom, and the reducing agent leaves the central housing  10  via a return  20 . Both the inlet  18  and the return  20  each have a respective connection piece  32 . The individual components  26 ,  28 ,  30  that are disposed inside the central housing  10  communicate with one another by hydraulic hoses  22 , by way of which the reducing agent, via the inlet  18 , reaches the inside of the first component  26  and from there the inside of the second component  28 , to which the return  20  is connected via the connection piece  32 . The hydraulic hoses  22  are each surrounded by a helical heating coil  24 , which requires a relatively high heating capacity. The version shown in  FIG. 1  is relatively large, since the components  26 ,  28 ,  30  are all accommodated in the central housing  10 . Because of the hydraulic communication of the components  26 ,  28 ,  30  via hydraulic hoses  22  and the electrical triggering of the components by means of the cable harness  14  on the lid  12 , this embodiment is extremely expensive and requires an extremely large amount of space. Both the hydraulic hoses  22  and the individual components  26 ,  28 ,  30  each require heaters, which with regard to the hydraulic hoses  22  can be formed by the heating coils  24 . Separate heating elements are required for each of the components  26 ,  28 ,  30 . 
       FIG. 2  shows an embodiment in which the individual components each meet the exterior demands and are received on a mounting block. 
     From  FIG. 2 , it can be seen that a mounting block  40  has one connection piece  32  each for one inlet  18  and one return  20  for a reducing agent. The mounting block  40  includes a first side  42 , on which the first component  26  and the second component  28  of the delivery module for a reducing agent are received, while the third component  30  is located on a second side  44  of the mounting block  40 . In this version, each of the components  26 ,  28 ,  30  associated with the sides  42 ,  44  of the mounting block  40  are independently splashproof, capable of fording flooded roads, and highly corrosion resistant, or in other words each meets the demands summarized in general by the term “exterior demands”. It should also be noted that the components  26 ,  28 ,  30  shown in  FIG. 2  are connected to the on-board electrical system of the motor vehicle via electrical contact means  46 . 
     The embodiment shown in  FIG. 2  has the prerequisite on the one hand that each of the components  26 ,  28  and  30  employed meet the exterior demands individually. However, in practice this can present problems, since in SCR metering systems, the components are actuated in part via levers (such as the reversing valve for pumps or eccentric elements) by an actuation magnet or an electric motor. Accordingly, they are not compact, rotationally symmetrical individual components that function independently of one another but on the contrary are components  26 ,  28 ,  30  that are in engagement with one another. Moreover, sealing each component separately against splashing water and flooded roads is extremely difficult and increases costs greatly. Moreover, heating the individual components proves extremely difficult, since the heat transfer by the mounting block  40  from it to the various components  26 ,  28 ,  30  disposed on the sides  42  and  44  can be done only on one side, which means that a great deal of heat is lost to the environment. 
     From  FIG. 3 , a delivery module designed according to the invention can be seen, in which individual components are integrated with drawers or chambers. 
     From  FIG. 3 , it can be seen that a primary component of the delivery module  50  includes a plastic housing  52 . The plastic housing  52  of the primary component is as a rule an injection-molded component, and it may be produced for instance by an aluminum injection molding process or a plastic injection molding process, which allows great freedom in terms of design with regard to the geometry and the subdivision of the housing  52  into individual chambers or drawers. The housing  52 , shown in section in  FIG. 3 , which is preferably a housing made in the course of the plastic injection molding process, includes outer housing walls  54 , at least one inner wall  56 , a lid  58  that is removable from the housing  52 , and a bottom face identified by reference numeral  60 . 
     The delivery module  50  shown in  FIG. 3  is a selected primary component of a metering system for introducing a reducing agent into the exhaust system of an internal combustion engine. The 4/2-way valve shown here as an example serves as a reversing valve  70 , with whose housing  52  the components described in further detail hereinafter are integrated in modular fashion. The housing  52  in which the reversing valve  70  is accommodated simultaneously, in the embodiment proposed according to the invention, forms the housing for the other components of the delivery module  50 . The delivery module  50  includes further components, such as at least one pressure sensor and a filter, disposed on the compression side, for filtering the reducing agent. Via the filter provided on the compression side, it is assured that only particle-free reducing agent is metered into the exhaust system of the engine. 
     The delivery module  50  is in turn a component of a metering system, which besides the delivery module  50  also includes a metering module, in which a metering valve, not shown in conjunction with the present invention, is accommodated. 
     It can be seen from  FIG. 3  that the bottom face  60 , for instance, of the selected primary component, that is, the delivery module  50 , has a seal  62 , by way of which the outer housing walls  54  placed on the bottom face  60  are sealed off. 
     In the housing  52  of the primary component selected, that is, the delivery module  50 , a first chamber  64  is embodied, which can also be called a drawer. Also located inside the housing  52 , which is preferably produced in the course of the plastic injection molding process, is a second chamber  66 , which serves to receive a heater  82 . Finally, it can be seen from  FIG. 3  that a third chamber  68  is separated from the first chamber  64  by the inner wall  56 . The chambers  64 ,  66 ,  68 , which can also be called drawers, represent separate receiving chambers for the further components to be accommodated in the housing  52  of the selected primary component, that is, the delivery module  50 . These further components are for instance a drive mechanism  80 , which as a rule is an electric drive mechanism; the heater  82  already mentioned; and an actuation magnet  86  as well as a pump  90 . 
     Also accommodated in the delivery module  50  are the components, not shown in further detail in  FIG. 3 , comprising a pressure sensor and a filter on the compression side. Analogously to the components already listed, that is, the drive mechanism  80 , heater  82 , actuation magnet  86  and pump  90 , these can be accommodated in separate chambers of the housing  52  of the delivery module  50 . 
     In the case of the housing  52  shown in section in  FIG. 3  and preferably produced in the course of the plastic injection molding process, the heater  82  can either be introduced into the second chamber  66 , embodied separately in the interior of the housing  52 , or it can already be injection-molded into the housing in the course of production of the housing  52 . Both embodiment possibilities are feasible. Disposing the heater  82  in the center of the hollow space in the housing  52 —as shown in FIG.  3 —offers the possibility that the heat produced by the heater  82  can simultaneously, in the course of the heat conduction or by convection, be transferred to the components comprising the drive mechanism  80 , actuation magnet  86  and pump  90  that are disposed in the interior of the housing in the various chambers  64 ,  66  and  68 , without requiring separate lines for this purpose. The embodiment proposed by the invention offers the advantage that given a suitable disposition and suitable configuration of the heater  82  and its physical contact with the reversing valve  70  or the inner wall  56 , very good, uniformly effective heating of the housing  52  can be achieved. While in the case of the heater  82  as shown in  FIG. 3 , heat transfer from heat conduction is effected between the horizontally extending leg of the heater  82  and the housing of the reversing valve  70  and heat transfer also takes place in the course of heat conduction from the leg, bent by 90°, of the heater  82  via the inner wall  56  to the actuation magnet  86  disposed in the third chamber  68 , a heat transfer is established in the course of convection from the top side of the leg, bent by 90°, to the pump  90  and to the drive mechanism  80  received in the first chamber  64 . 
     The chambers  64 ,  66 ,  68  shown in  FIG. 3  may be closed by lid elements, for instance. The lid elements can either be joined materially to the housing  52  via material-locking connection after the introduction of the various components  80 ,  90 ,  86  and  70  into the chambers  64 ,  66 ,  68 , intended for them, in the interior of the housing  52 , so that the components disposed in the various chambers  64 ,  66 ,  68  are sealed off from environmental factors such as splashing water, de-icing salt, dirt, and so forth; that is, they meet all of the “exterior demands” made of them. Securing the lids that close the chambers  64 ,  66 ,  68  can moreover be done via clip connections or screw connections or the like. Depending on the degree of tightness regard to external environmental factors that is required of the individual chambers  64 ,  66 ,  68 , elastomer seals (see reference numeral  62 ) may also be used. The electrical triggering, for instance of the actuation magnet  86  or of the drive mechanism  80 , can be effected both via plug contacts embodied in each of the lids that close the respective chambers  68  and  64 , or—as shown in FIG.  3 —via plug prongs  72 , which pass through openings  74 ,  76 ,  78  in the bottom face  60  or in an outer housing wall  54 . Ideally, the plug prongs  72 , for instance of the drive mechanism  80 , heater  82 , or also the actuation magnet  86 , after passing through the openings  74 ,  76 ,  78  in the bottom face  60  or the outer housing wall  54  end in plug modules, by way of which the various components  80 ,  82  and  86  to be electrically contacted can be electrically contacted. The plug prongs  72  of the components  80 ,  86  and  90  to be contacted electrically, to name these examples, extend from the inside of the housing  52  through the housing openings  74 ,  76 ,  78  in the outer housing wall  54  or the bottom face  60  into corresponding plug contacts, on which the housing  52  of the reversing valve  70 , selected as a primary component and having the nature of a 4/2-way valve, is embodied. 
     For the sake of completeness, it will be noted that the housing  52  of the reversing valve  70  embodied as a 4/2-way valve, with the first chamber  64 , the second chamber  66 , and the third chamber  68 , offers receiving chambers both for the components  80 ,  82  and for the components  86  and  90 . The actuation magnet  86  is likewise electrically contacted via plug contacts  72  that extend through housing openings  78  in the outer housing wall  54  and has a tappet  92 . The tappet  92  is rotatably connected to a lever, by way of which in turn the reversing valve  70 , which may for instance be embodied as a 4/2-way valve, is actuatable. 
     Thus after the selection of a primary component of the delivery module  50 , whose housings  52  embody chambers  64 ,  66 ,  68  or drawers serving as housings for further components  80 ,  82 ,  86  and  90 , offers the advantage that components interacting with one another, such as the actuation magnet  86  and the reversing valve  70 , can likewise meet the exterior demands, since they are adequately encapsulated and durably protected against environmental factors, such as the parameters listed at the outset, that is, splashing water, flooded roads, de-icing salt, and corrosion. In the embodiment shown in  FIG. 2 , the exterior demands can be met only at comparatively high effort and expense, since the components  26 ,  28 ,  30  received there on the sides  42 ,  44  of the mounting block  40  are exposed to the environmental factors virtually without protection from them. 
     The foregoing relates to the preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.