Patent Publication Number: US-2011052161-A1

Title: Heating Device

Description:
The invention is directed to a heating device of a type known from DE 10 2006 018 784 B4. 
     In the case of the known heating device, an extruded part is used that includes openings that extend transversely to the extrusion direction and through which a fluid to be heated can flow. The disadvantage of the known heating device is that an additional working step must be carried out on an extruded part to create the openings. The object of the present invention, therefore, is to demonstrate a way in which this effort can be avoided. 
     SUMMARY OF THE INVENTION 
     In a heating device according to the invention, several extruded parts are held next to each other by a holder transversely to the flow direction. Advantageously, a fluid to be heated can flow along the extruded parts, thereby eliminating the need for openings that extend transversely to the extrusion direction. In the case of a heating device according to the invention, a fluid to be heated preferably flows in the longitudinal direction, along the tubes formed by the extruded parts. However, it is also possible to design a heating device according to the invention such that a fluid to be heated flows between adjacent tubes transversely to their longitudinal direction. The extruded tubes are preferably single-pieced, but can also be composed of multiple pieces, e.g. be composed of a U-shaped profile or a C-shaped profile and a sealing cover strip. 
     A heating device according to the invention preferably includes at least one power rail to which a plurality of contact plates is connected. The power rail extends from the contact plates connected thereto to a holder that holds the tubes containing the heating elements. A heating device according to the invention preferably includes a plurality of power rails, each of which contacts contact plates that extend at one end out of tubes situated in a row. The holder preferably comprises a supply rail to which a plurality of power rails is connected. If the tubes are used to provide a ground connection, then a single supply rail is sufficient. Preferably, however, the heating elements are electrically insulated against the tubes and are each disposed between two contact plates. Particularly preferably, these two contact plates extend out of the tubes at opposite ends. In this preferred case, the holder contains two supply rails, to each of which one half of the contact plates is connected. The two supply rails are preferably disposed on the same end of the heating device e.g. on the same frame part. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further details and advantages of the invention are explained using embodiments, with reference to the attached drawings. Parts that are identical or corresponding are labelled using the same reference numerals. The drawings show: 
         FIG. 1  an embodiment of a heating device according to the invention; 
         FIG. 2  a front view of  FIG. 1 ; 
         FIG. 3  a side view of  FIG. 1 ; 
         FIG. 4  a view of the heating device from above; 
         FIG. 5  a view of the heating device from below; 
         FIG. 6  a further embodiment of a heating device; and 
         FIG. 7  a schematic depiction of the components disposed in the tubes of the heating device. 
     
    
    
     DETAILED DESCRIPTION 
     The heating device shown in  FIGS. 1 through 5  comprises several extruded parts  2  that are arranged side by side and held by a holder designed as a frame. The frame is composed of four joined frame parts i.e. an upper frame part  1   a,  a lower frame part  1   b,  and two lateral frame parts  1   c.  Extruded parts  2 , which are disposed next to each other in the frame transversely to the flow direction, contain tubes  2   a.  Tubes  2   a  of various extruded parts  2  are situated in rows. In the embodiment shown, these rows extend parallel to lateral frame parts  1   c.    
     In the embodiment shown, each extruded part  2  includes five tubes  2   a  in which heating elements  7  are disposed; heating elements  7  are shown in  FIG. 7 . In the figures, only one tube  2   a  of each extruded part  2  can be seen in each case since remaining tubes  2   a  are covered by power rails  3  that contact contact plates (not depicted) that extend out of tubes  2   a.    
     Preferably, heating elements  7  in tubes  2   a  are each disposed between two contact plates  8  that are electrically insulated against tubes  2   a  and extend out of tubes  2   a  at different ends. It is also possible, however, for each heating element  7  to contact only a single contact plate  8  and to form a ground connection via extruded parts  2 . 
     Power rails  3  can be designed as plastic-enclosed sheet-metal strips. The sheet-metal strips are preferably coated with a plastic jacket. The plastic jacket can also be slid onto the sheet-metal strips. The plastic jacket of the contact rails can have openings in a few places to facilitate the contacting of contact plates which extend out of tubes  2   a.  The contact plates are preferably bent at their ends. For example, the contact plates having bent ends can bear resiliently against the power rails. It is also possible to bend tabs out of power rails  3 , that bear against the contact plates. 
     Power rails  3  extend transversely to diametrically opposed frame parts  1   a,    1   b  and, in the embodiment shown, plug into frame parts  1   a,    1   b.  The heating device is therefore easy to assemble. However, it is not absolutely necessary for power rails  3  to extend from one frame part la to a diametrically opposed frame part  1   b.  It is also possible for power rails  3  to terminate at a distance away from one of these frame parts, e.g. the lower frame part  1   b.    
     Power rails  3  are connected via the frame to the electrical system of a motor vehicle. For this purpose, power rails  3  extend into upper frame part  1   a,  on which at least one supply rail  4  is mounted, and to which a plurality of power rails  3  is connected. In the embodiment shown, contact plates  9 , each of which is contacted by one of the power rails  3 , extend out of tubes  2   a  at both ends. Accordingly, in the embodiment shown, one half of power rails  3  should be connected to positive potential and one half of power rails  3  should be contacted to negative potential. Two supply rails  4  are therefore provided in the embodiment shown. Supply rails  4  preferably extend in the same frame part  1   a,  although they can also be disposed at opposite ends of the heating device and, therefore, in diametrically opposed frame parts. Supply rails  4  can carry connection elements  4   a  that are designed e.g. as projections that extend transversely to supply rails  4 . Due to the connection on diametrically opposed sides of tube  2   a,  a large distance between the two terminal potentials advantageously results, thereby increasing safety, especially in high-voltage applications. 
     The frame can include a printed circuit board  5  on frame part  1   a  on which supply rails  4  are installed. Supply rails  4  can be designed as conductor tracks on printed circuit board  5 , or they can be designed e.g. as separate pieces of sheet metal, as is the case in the embodiment shown. Printed circuit board  5  can carry one or more power semiconductors  6  for controlling the heating device. Printed circuit board  5  can carry a heat sink  6  to utilize the heat dissipated from power semiconductors  6  or other electronic components disposed on printed circuit board  5 . 
     Extruded parts  2  are fastened to lateral frame parts  1   c  e.g. by being plugged in or hooked in. Lateral frame parts  1   c,  to which extruded parts  2  are fastened, preferably extend parallel to power rails  3 . In the embodiment shown, the frame carries eleven extruded parts  2 , each of which contains five tubes  2   a.  The number of tubes  2   a  per extruded part  2  can be selected freely within wide limits, as can the number of extruded parts  2 . In general, it is favorable to have two to five tubes per extruded part, and four to fifteen, in particular six to twelve, adjacently disposed extruded parts. 
     Extruded parts  2  preferably include heat-dissipation fins  2   b  to improve heat dissipation. Heat-dissipation fins  2   b  extend out of a base plate. Preferably, heat-dissipation fins  2   b  extend on both sides of the base plate. Instead of or in addition to heat-dissipation fins  2   b,  it is also possible to use additional tubes  2   a  that are not filled with heating elements  7 . 
     Preferably, one contact plate  8  contacts only one single heating element  7  i.e. tubes  2   a  do not contain more than one heating element  7  each. However, it is also possible for each contact plate  8  to contact a plurality of heating elements  7 , e.g. two to five heating elements, that are disposed one behind the other in a tube  2   a.    
     Extruded parts  2  can be stacked one on top of the other, and they can touch each other. Preferably, however, adjacent extruded parts  2  do not touch each other, and are therefore disposed at a distance from each other, as shown in the figures. This has the advantage that any manufacturing tolerances of extruded parts  2  can be compensated for by the distances provided between them, 
     PTC heating elements are preferably used as heating elements  7 , that is, heating elements having a positive temperature coefficient that increases abruptly once a critical temperature is reached. Ceramic heating elements are particularly suitable, for instance those based on barium titanate. 
     Tubes  2   a  that contain heating elements  7  are preferably square tubes, as shown in the drawings. After the PTC elements and contact plates  9  have been installed, tubes  2   a  can be molded by compression to improve the thermal coupling. To simplify the installation of heating elements  7  in tubes  2   a,  it is advantageous to use assembly frames  13  which hold heating elements  7  and contact plates  9 . Assembly frames  13  can be slid onto contact plates  9 , for example. It is also possible to injection-mold assembly frames  13  around contact plates  9 . Assembly frames  13  can include, in particular, receptacles  14  for heating elements  7 . 
     A further embodiment of a heating device according to the invention is shown schematically in  FIG. 6 . Similar to the embodiment described above, the heating device is composed of several extruded parts  2  that are disposed side by side transversely to the flow direction and are held by a holder  1   a,    1   c.    
     The main difference from the above-described embodiment is that the inflow direction, which is indicated by arrows in  FIG. 6 , of the fluid to be heated extends transversely to the longitudinal direction of tubes  2   a  and, therefore, transversely to the extrusion direction. Mutually engaged heat-dissipation fins  2   b  of extruded parts  2  define a serpentine flow path. Similar to the above-described embodiment, extruded parts are adjacently disposed transversely to the direction of flow. 
     The heating device is shown in  FIG. 6  as viewed perpendicularly to the inflow direction and in the extrusion direction. Power rails  3  and the curved ends of contact plates  8  therefore overlap extruded parts  2 . In  FIG. 6 , power rails  3 , holder I a, and contact plates  8  are shaded or appear to be transparent, to ensure that extruded parts  2  disposed underneath them are clearly visible. 
     Power rails  3  are disposed in holder part  1   a  which is situated in the plane of the drawing. Power rails  3  can be connected directly or via a printed circuit board  5 . 
     The plane defined by holder part  1   a  and holder parts  1   c  is then transverse to the inflow direction shown in  FIG. 6 . Holder part la that connects the two holder parts  1   c  shown therefore extends along the plane in which power rails  3  shown in  FIG. 6  are disposed. 
     In the embodiment shown in  FIG. 6 , the holder can form a frame. In contrast to the above-described embodiment, the longitudinal direction of tubes  2   a  and, therefore, the direction of extrusion then extend in the plane of the frame. 
     In  FIG. 6 , two tubes  2   a  are shown, one behind the other in the direction of flow, that is, each extruded part  2  includes two tubes  2   a.  It is also possible, however, to have more than two tubes  2   a,  or a different number of tubes  2   a.    
     Furthermore, the embodiment shows the arrangement of tubes  2   a  in uniform rows. However, it is also possible for tubes  2   a  to be offset relative to adjacent extruded parts  2 . 
     Extruded parts  2  are preferably fastened to holder part  1   c  by clamping. In that case, holding elements of holder part  1   c  clamp with fins  2   b  of extruded parts  2 . 
     The layout in tube  2   a  is shown in  FIG. 7 . Each tube  2   a  contains two identical contact plates  8 , between which at least one square heating element  7  composed of a PTC ceramic (positive temperature coefficient) is disposed. One assembly frame  13  is mounted on each contact plate  8  and defines receptacles  14  for heating elements  7 . Assembly frame  13  is preferably composed of plastic and can be slid onto contact plates  8 . However, assembly frame  13  can also be injected around contact plates  8 . 
     In the embodiment shown, and as shown in  FIG. 7 , assembly frame  13  exposes a back side of contact plates  8 , which faces away from heating elements  7 . Contact plates  8  include an electrically insulating layer  15 , which is a strip of Kapton film in the embodiment shown, on their side facing away from heating elements  7 . 
     Ends  9  of contact plates  8  that are connected to power rails  3  are angled. Ends  9  can be fastened to power rails  3  e.g. using rivets or screws. 
     The layout shown in  FIG. 7  can be used for both of the embodiments described above. 
     REFERENCE NUMERALS  
       1   a  Holder part 
       1   b  Holder part 
       1   c  Holder part 
       2  Extruded part 
       2   a  Tube 
       2   b  Heat-dissipation fins 
       3  Power rail 
       4  Supply rail 
       4   a  Terminal elements 
       5  Printed circuit board 
       6  Power semiconductor 
       7  Heating element 
       8  Contact plate 
       9  End of the contact plate 
       13  Assembly frame 
       14  Recess 
       15  Insulating layer