Patent Publication Number: US-2020296803-A1

Title: Heating device

Description:
BACKGROUND OF THE INVENTION 
     The invention is based on a heating device, a tank installation unit and a method for producing a heating device. 
     Heating devices comprising heating elements and heat distribution bodies are already known, for example, from DE102011084962, but the heating elements in said heating devices are designed as prefabricated or piecemeal PTC heating elements with which contact can be made via busbars. In this case, a thermally conductive body which is coupled to the heating elements is encapsulated by injection molding with a plastics layer. 
     Tank installation units comprising heating devices of this kind, which tank installation units can also have or be fitted with a conveyor pump, a sensor system, e.g. a filling level sensor system, and a filter device for example in addition to said heating devices, are known from DE102015200168. Tank installation units of this kind can be flange-connected to the opening of a tank, for example in the base region of the tank, or can be arranged in the region of the opening and welded to the tank wall. Arrangements of this kind allow only a specific diameter of the tank installation unit which has an installation space-limiting effect on all of the structural parts located on the carrier of the tank installation unit. 
     SUMMARY OF THE INVENTION 
     The heating device and the tank installation unit according to the invention and the production method according to the invention have the advantage over the above prior art of a simplified construction and the ability to provide improved functioning. There is no need for any undefined calking or grouting processes, fragile insulation ceramics, prefabricated PTC elements or separate busbars. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the invention are illustrated in the drawing and explained in more detail in the following description. 
       In the drawing, 
         FIG. 1  shows a heating device, 
         FIG. 2  shows a ram contact, and 
         FIG. 3  shows a tank installation unit. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a perspective view of a heating device  10 . Said heating device comprises a sheet-like heating element  14  which is elongate in the present exemplary embodiment and is arranged between two thermally conductive bodies  12 . The thermally conductive bodies  12  are manufactured, for example, from aluminum. The thermally conductive bodies are preferably symmetrical identical parts, as depicted. At their ends along their longitudinal extent, said thermally conductive bodies have recesses  16  which serve to position and, respectively, to lock the heating device on a base plate or the like, for example by way of a snap-action/clamping connection. 
     The heating element  14  is manufactured from a heatable, i.e. electrically conductive plastic. Said plastic may be, for example, high-density polyethylene (“HDPE”) to which graphite containing a mass fraction, in particular, of 30 to 45 percent of the total mass of the heating element has been added. Here, the two thermally conductive bodies  12  are adhesively bonded to one another by means of this electrically conductive plastics material. If HDPE containing said graphite admixture is used, the heating element exhibits a self-regulating behavior, that is to say, with an electrical voltage applied between the two thermally conductive bodies, the electrical resistance significantly increases when the temperature rises or when it exceeds a certain threshold value. The thermal dissipation to a liquid environment is optimized with the two thermally conductive bodies which are of simple construction and composed of aluminum. Said thermally conductive bodies give off heat which is created between them in an effective manner and over a large surface area. 
     For permanent connection of these thermally conductive aluminum bodies, they are correspondingly pretreated on the contact side which faces the heating element  14  in the finished state of the heating device. To this end, a rough surface (mean roughness depth Rz 36 . . . 100) is provided, preferably by means of plasma treatment. The thermally conductive aluminum bodies are then clamped in a mold. The contact layer or the material which then forms the heating element  14  is then injected. The thermally conductive aluminum bodies are then fixedly connected to one another. In a further step, they are placed into a different mold and suitably positioned, so that they can be encapsulated by injection molding all the way around with (non-electrically conductive) high-density polyethylene for the purpose of corrosion protection. 
     In a preferred variant of the production method, electrical contacts, in particular in the form of ram contacts, are initially pressed in after said process of encapsulation by injection molding. As a result, the production method is simplified. This facilitates the sealing of the contact region in the mold for encapsulation by injection molding. 
       FIG. 2  shows, by way of example, a ram contact  18  of this kind which has a twin-wing ram terminal  20  at one end and a connection region  22  at the other bent-away end. Here, the two wings of the ram terminal  20  can be rammed or pressed into the region of the two flanks  17  (see  FIG. 1 ) of a thermally conductive body  12  which are each adjacent to a recess  16 . This is done on in each case at least one pair  17  of flanks of this kind for each thermally conductive body, in order to be able to excite an electric current flow, which generates ohmic heat, across the thermally conductive bodies through the heating element  14  in the case of heat requirement. 
     The finished heating device  10  can become, for example, a constituent part of a tank installation unit, wherein the heating device  10 , in the region of its recesses  16 , can be welded to a base region of the tank installation unit. 
     A tank installation unit  24  of this kind especially for being fitted in a base region of a liquid tank is illustrated in  FIG. 3 . The fluid-tight connection of the tank installation unit  24  to the liquid tank is made at the edge of a base region  32  of the tank installation unit, for example by welding to the tank base. The base region or carrier  32  is fitted with various functional components, a conveyor pump  26 , a filling level sensor system  30  and a filter device  34  being illustrated by way of example. Further examples include electrical and/or hydraulic connections for electrically actuating functional components or for transporting away the liquid which is stored in the tank. The heating device  10  is then positioned at a suitable location in order to be able to readily heat temperature-critical locations, in particular in order to keep warm or to thaw regions at risk of freezing to a sufficient extent in order to ensure continuous transportation of liquid out of the tank using the conveyor pump. 
     The heating device is suitable, in particular, for tank installation units for storage containers which can be filled with an aqueous urea solution in order to provide this reducing agent for selective catalytic reduction of nitrogen oxides of an internal combustion engine of a motor car. The heating device can also be used for heating or thawing other liquids, and can also be provided for other purposes in the field of heating, in particular, liquids.