Abstract:
A thermoelectric device, for example a thermoelectric generator, for a motor vehicle may include a housing defining a housing interior, and the housing may include a first housing part and a second housing part. The housing may further include a fluid-tight thermally insulating element for thermally insulating at least one first housing part portion of the first housing part from the second housing part. The thermal insulating element may include a separating joint fully encompassing the at least one first housing part portion along a circumferential direction. The separating joint may include at least one opening along the circumferential direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to a German Patent Application No. 10 2014 218 787.7 filed on Sep. 18, 2014, and International Patent Application No. PCT/EP2015/068036 filed on Aug. 5, 2015, the contents of which are hereby incorporated by reference in their entirely. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a thermoelectric device, more particularly a thermoelectric generator, for a motor vehicle. 
       BACKGROUND 
       [0003]    Understood by the term “thermoelectricity” is the reciprocal influencing of temperature and electricity and their conversion into each other. Thermoelectric materials make use of this influencing. However, in order as thermoelectric generators to produce electrical energy from waste heat so-called heat pumps are also utilised if through the use of electrical energy heat is to be transported from a temperature reservoir at a lower temperature into one with a higher temperature. 
         [0004]    Known from German patent application DE 10 2014 208 433.4 which was not yet published at the time of the present application is a thermoelectric device of this type, especially for a motor vehicle, comprising a housing which surrounds a first and a second housing part and least partially encompasses a housing interior. 
         [0005]    Precisely the cited thermoelectric heat pumps are used in motor vehicle technology for the cooling of a wide variety of different components, such as, for example, modern lithium ion batteries which develop considerable amounts of waste heat. However, such thermoelectric heat pumps can also be used in electric motor vehicles as combined heating and cooling devices, for example for controlling the temperature of the passenger space, especially as they exhibit a considerably higher degree of efficiency than conventional electrical resistance heaters. In motor vehicles with an internal combustion engine, by means of thermoelectric generators the waste heat produced in the exhaust during the combustion process can partly be converted into electrical energy and fed into the on-board network of the motor vehicle. The waste heat converted into electrical energy can thus be utilised to a considerable extent in order to reduce the energy consumption of the motor vehicle to a necessary minimum and thereby prevent the unnecessary emission of waste gases such as CO 2 . There are therefore many different areas of application of thermoelectric devices in motor vehicle construction. In each of said areas of application it is of decisive importance to achieve as high a degree of efficiency as possible in order to convert heat into electrical energy or vice versa as effectively as possible. 
         [0006]    Thermoelectric devices and/or thermoelectric generators typically comprise a plurality of thermoelectric elements made of a thermoelectrically active material which form the actual thermo-electric module. This thermoelectric module is typically arranged in a housing made of metal as on the one hand a housing of this type has the necessary high degree of thermal conductivity and, on the other hand, it can be very simply assembled and sealed, mostly through joining at least two housing parts to each other by means of a welded connection. 
         [0007]    Precisely this fluid-tight fastening of the housing parts of the housing to each other is of considerable importance as the housing interior accommodating the thermoelectric module has to protected against the penetration of various media such as water, exhaust gas, salt etc. As in conventional thermoelectric devices, and in particular in the already cited thermoelectric generators, for the functional creation of a hot and cold side at least two housing parts must be thermally insulated from each other as well as possible, the fundamental problem arises of connecting the housing parts to each other in a manner that is as stable and fluid-tight as possible, as well as thermally insulating. 
       SUMMARY 
       [0008]    It is therefore the object of the present invention to create an improved embodiment of a thermoelectric device in which the above-described problem is largely, or even completely, eliminated. 
         [0009]    This object is solved by the subject matter of the independent patent claims. Preferred forms of embodiment are the subject matter of the dependent patent claims. 
         [0010]    The basic concept of the invention is accordingly to provide a thermoelectric device, in particular a thermoelectric generator with a fluid-tight, thermal insulating element which insulates at least one housing part section of a first housing part from a second housing part of the device housing. In this way said housing wall section can be used as the hot side of the thermoelectric device or the thermoelectric generator and the area of the first housing part complementary to the housing wall section as well as the second housing parts can be used as the cold side or vice-versa. Through the fluid-tight design of the thermal insulating element according to the invention it is simultaneously ensured that no unwanted media, such as water, salt or also dirt particles can penetrate into the housing interior delimited by the housing. 
         [0011]    A thermoelectric device according to the invention comprises a housing which delimits a housing interior and comprises a first and a second housing part. According to the invention the housing comprises a thermal insulating element for the thermal insulation of at least one housing part portion of the first housing part from the second housing part. 
         [0012]    In a preferred form of embodiment the thermal insulating element can be designed as a separating joint which fully surrounds the housing part portion. The separating joint extends along a circumferential direction and along this circumferential direction has at least one opening. Particularly preferably the separating joint can even have several such openings as with an increasing number of openings the thermal conductivity provided by the separating joint decreases. The at least one opening can be designed as a through slit extending along the circumferential direction. In order to provide the insulating element with the required tightness at least one of the openings can be closed in a fluid-tight manner by means of a foil. The foil is preferably made of a metal as in this case it can be particularly easily joined to the casing in order to close the at least one seal. This can be take place, in particular, by means of a soldered or welded connection. 
         [0013]    In order to limit the loss of mechanical rigidity associated with an opening to a minimum, in a particularly preferred form of embodiment the separating joint is provided with at least two, preferably with a plurality of openings, which are interrupted by struts integrally formed on the first housing part. By means of such struts the housing part portion to be insulated is connected to the area of the first housing part complimentary thereto. This results in the desired increase in the rigidity of the first housing part. 
         [0014]    In a further preferred form of embodiment which can be combined with the previously described forms of embodiment, the first housing part is in the form of a housing pot with a pot base and with a pot collar projecting from the pot base towards the second housing part and encompassing the pot base. In addition, the second housing part is designed as a housing cover which is applied to the pot collar and can close the interior of the housing. In terms of manufacturing such an arrangement with a housing pot and a housing cover is particularly simple to produce and is thus associated with particularly low manufacturing costs. 
         [0015]    Particularly expediently the pot base and pot collar can be formed integrally on each other. 
         [0016]    Alternatively, however, the pot base and the pot collar can also be separate components which are fastened to each other by means of the thermal insulating element. 
         [0017]    In an advantageous further embodiment of the invention the separating joint is arranged in the pot collar and completely encompasses the pot base. In this scenario the separating joint for encompassing the housing part portion of the first housing part extends adjacent to the pot collar along an outer edge section of the pot base. In this way the central area of the pot base is thermally insulated both from the remaining areas of the first housing part as well as the second housing part and can thus be used as a hot or cold side. 
         [0018]    In a further preferred form of embodiment the thermal insulating element is a bellows-like structure in the pot cover extending along the circumferential direction and completely encompassing the pot base. By way of such a bellows-like structure thermomechanical stresses in and between the two housing parts occurring as a result of the temperature difference between the hot and cold side can be considerably reduced. Additionally, such a bellows structure exhibits a high thermal resistance and also meets the requirements of the invention with regard to fluid tightness. 
         [0019]    To increase the thermal resistance of the bellow-like structure it is proposed to reduce a wall thickness of the pot collar in the region of the bellows-like structure in relation to the wall thickness in the remaining area of the pot collar. In the case of a suitable design of the wall thickness the bellows-like structure can also be provided with resilient properties through which thermo-mechanical stresses in the first housing part can again be reduced. 
         [0020]    Particularly expediently the pot collar can project from the pot base essentially at a right angle or at an obtuse or acute angle. In this way the housing interior, which is delimited by the two housing parts, can be used particularly effectively for the arrangement of the thermoelectric module. 
         [0021]    In another preferred form of embodiment the two housing parts are in the form of essentially flat housing walls. The thermal insulating element is designed as hollow-cylindrical frame made of a thermally insulating material, in particular a ceramic material. The two end faces of the frame are fastened to the first or the second housing part by means of a bonded connection or adhesive connection. 
         [0022]    In a further preferred form of embodiment the thermal insulating element is designed in such a way that it not only thermally insulates one housing part portion of the first housing part from the remaining area of the first housing part complementary thereto, but thermally insulates the entire first housing part from the second housing part. In this way the entire first housing part is available as a hot or cold side of the thermoelectric device or the thermoelectric generator. 
         [0023]    In an advantageous further development of the invention not only the first housing part but also the second housing part is provided with a pot base and a pot collar which projects away from the pot base towards the first housing part and encompasses the pot base. In this form of embodiment the two pot collars can be arranged at a distance from one another so that between the two pot collars an opening is formed which fluidically connects the housing interior with the outside environment. However, this opening is closed in a fluid-tight manner by a metallic foil. It is conceivable to apply the metallic foil to the two pot collars by way of a soldered connection or another suitable bonded connection. 
         [0024]    In another preferred form of embodiment which is associated with particularly low manufacturing costs an inner side of the pot collar of the first housing part is fastened by means of a bonded connection to an outer side of the pot collar of the second housing part or vice-versa. Alternatively an adhesive connection can also be considered in order to attach the two pot collars to each other. 
         [0025]    Particularly stable mechanical connection of the two housing parts to each other can be achieved if the pot collar of the first and/or the second housing part merges into a flange section projecting outwards from the pot collar and arranged essentially in parallel to the pot base. 
         [0026]    Other important features and advantages of the invention are set out in the sub-claims, the drawings and the associated description of the figures of the drawings. 
         [0027]    The features cited above and the features still to be explained below are of course not only usable in the combinations indicated in each case, but also in other combinations or alone without departing from the framework of the present invention. 
         [0028]    Preferred examples of embodiment of the invention are shown in the drawings and will be explained in more detail in the following description wherein the same reference symbols relate to identical or similar or functionally identical components. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    In each case: 
           [0030]      FIGS. 1 to 12  schematically show various examples of thermoelectric devices according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    Roughly schematically and in longitudinal section,  FIG. 1  shows a first example of a thermoelectric device  1  according to the invention. The device  1  comprises a housing  2  with a first housing part  3   a  and a second housing part  3   b.  The housing  2  delimits a housing interior  4  in which a thermoelectric module  5  is arranged in a manner known to the relevant person skilled in the art. This comprises a plurality of thermoelectric elements  6  made of a thermoelectrically active material such a bismuth telluride, for example, which are arranged adjacent to each other in the housing interior  4  and are electrically connected to each other by means of electrically conducting conductor bridges  7 . The thermoelectric elements  6  are attached to the first or second housing part  3   a,    3   b  via a first or second electrical insulator  7   a,    7   b  made of an electrically isolating, but thermally conducting material, so that the first housing part  3   a  can act in a known manner as a hot side and the second housing part  3   b  as a cold side, or vice-versa. 
         [0032]    The detailed technical implementation of the thermoelectric module  5  is not the key point of the invention described here and will not be explained in more detail below. In  FIGS. 2 to 12 , for reasons of clarity the thermoelectric module  5  of  FIG. 1  is only shown in the form of a quadrilateral rectangle which is given reference number  5 . 
         [0033]    The housing  2  has a fluid-tight thermal insulating element  8  by means of which a housing part portion  9  of the first housing part  3   a  is thermally insulated from the area  10  of the housing part  3   a  complementary to the housing part portion  9  as well as from the second housing part  3   b.    
         [0034]    Here, “thermally insulating” is understood to mean that the thermal insulating device  8  has greatly increased thermal resistance compared with the housing parts  3   a,    3   b  so that thermal interaction of the thermally insulated housing part portion  9  with the remaining housing part portions is at least greatly reduced, ideally even completely stopped. 
         [0035]    According to  FIG. 1  the first housing part  3   a  is designed as a housing pot  11  with a pot base  12  and with a pot collar  13  projecting from the pot base  12  towards the second housing section  3   b.  In the example in  FIG. 1  the pot base  12  and the pot collar  13  are formed integrally on each other. The pot collar  13  encompasses the pot base  12 . In contrast the second housing part  3   b  is designed as a pot cover  14  which is applied on the pot collar  13  of the first housing part  3   a  and closes an opening  15  of the first housing part  3   a  or the housing pot  11  encompassed by the pot collar  13 . 
         [0036]    As can also been seen from  FIG. 1  the thermal insulating element  8  is designed as a separating joint  16  completely encompassing housing section portion  9 . The separating joint  16  extends along a circumferential direction and along this circumferential direction has an opening  17  which is closed in a fluid-tight manner by means of a foil  18  made of metal. For this the foil  18  is connected to the two housing parts  3   a,    3   b  in bonded or adhesive manner. In  FIG. 1  the separating joint  16  has precisely one opening  17  in the form of a circumferential slit running along the pot collar  13 . 
         [0037]    In a variant of the example of  FIG. 1  shown in  FIG. 2  the separating joint along the circumferential direction has a plurality of openings  17  which are interrupted by struts  20 . In addition, the example in  FIG. 2  differs from that in  FIG. 1  in that the thermal insulating element  8  in the form of a separating joint  16  is not arranged in the pot collar  13  but in the pot base  12 . To encompass the housing part portion  9  the separating joint  16  thus extends adjacently to the pot collar  10  along an outer edge section  19  of the pot base  12 . 
         [0038]    By means of the struts  20  the housing part portion  9  is connected to the area  10  of the first housing part  3   a  complementary thereto. As shown in  FIG. 2  the struts can be designed as separate components which are connected to the two housing parts  3   a,    3   b  by adhesion or by means of a bonded connection. Alternatively, however, the struts  20  can also be integrally formed on the first housing part  3   a.  In this scenario it is conceivable that to produce such struts the openings  17  are punched out of the first housing part  3   a.    
         [0039]      FIG. 3  shows a further variant of the example of  FIG. 1 . In this example the separating joint  16  has precisely one opening  17 , provided in the pot collar  13  and completely surrounding the pot base  12 , which is closed in a fluid-tight manner by way of an adhesive or a sealing element, more particularly made of an elastomer, or a plug part or a sealing mass—all these component are designated  21  in  FIG. 3 . In a further variant it is also conceivable to combine the variants in  FIGS. 2 and 3 , which means that several openings  17 , interrupted by struts  20 , are closed in a fluid-tight manner with the components  21 . 
         [0040]    In the example of  FIG. 4  the second housing part  3   b  also has a pot base  22  and a pot collar  23  which encompasses the pot base  22  and projects away from the pot base  22  towards the first housing part  3   a.  As  FIG. 4  clearly shows the two pot collars  13 ,  23  are arranged at a distance from one another. Between the two pot collars  13 ,  33  there is an opening  25  which fluidically connects the housing interior  4  with the external environment  24  and which is part of the thermal insulating element  8 . The opening  25  can be designed in an analogue manner to the separating joint  16  according to  FIGS. 1 to 3  so that the explanations relating to the separating joint  15  with reference to  FIGS. 1 and 3  expressly also apply to the variant in  FIG. 4 . In the example in  FIG. 4  the opening  25  is closed in a fluid-tight manner by means of a metallic foil  18  fastened at the end of the two housing parts  3   a,    3   b  by way of a soldered connection. 
         [0041]    In the example in  FIG. 5  the pot collar  23  is produced separately from the second housing part  3   b.  The pot collar  23  can be fastened to the pot base  22  of the second housing part by means of a bonded connection. In accordance with  FIG. 5  one end section  33  of the pot collar  13  overlaps with an end section  34  of the pot collar  23 . The two pot collars  13 ,  23  are dimensioned in such a way that between an outer side  27  of the pot collar  23  and an inner side  26  of the pot collar  13  a circumferential intermediate space  32  is formed which brings about the desired thermal insulation. The intermediate space  32  is closed or covered in a fluid-tight manner by a metal foil  18  which is soldered onto the outside of the two pot collars  13 ,  23 . Outer side  27  of the pot collar  23  is fastened of the second housing part  3   b.  In the sample in  FIG. 5  said metal foil  18  in synergy with the intermediate space  32  forms the thermal insulating element. 
         [0042]    The example in  FIG. 6  differs from the example according to  FIG. 5  in that an outer side  30  of the pot collar  13  of the first housing part  3   a  is attached by means of a bonded connection  28  or an adhesive connection  29  to an inner side of the pot collar  23  of the second housing part  3   b.  The bonded connection  28  or the adhesive connection  29  thus closes the circumferentially formed intermediate space  32  between the end sections  33 ,  34  of the pot collars. In the example in  FIG. 5  the bonded connection  28  or the adhesive connection  29  in synergy with the intermediate space  32  forms the thermal insulating element  8 . 
         [0043]    The example in  FIG. 7  shows a combination of the examples of  FIGS. 5 and 6 . According to this pot collar  23  is integrally formed on the pot base  13  of the second housing part  3   b.  The outer side  27  of the pot collar  23  is opposite the inner side  26  of the pot collar  13  so that between these the intermediate space is formed  32 . The inner side  26  of the pot collar  13  of the first housing part  3   a  is attached by means of a bonded connection  28  or an adhesive connection  29  to the outer side  27 ,  31  of the pot collar  23  of the second housing part  3   b.  In an analogue manner to the example in  FIG. 6 , the bonded connection  28  or the adhesive connection  29  closes the circumferential intermediate space  32  formed between the end sections  33 ,  34  of the pot collars  13 ,  23  in a fluid-tight manner. The thermal insulation element  8  is thus formed by the bonded connection  28  or the adhesive connection and the intermediate space  32  closed by these. 
         [0044]      FIG. 8  illustrates a further variant in which from the pot base  12  the pot collar  13  of the first housing part  3   a  merges into a flange section  35  projecting away from the pot collar  12  and arranged essentially in parallel to the pot base  12 . An intermediate space  32  between the flange section  35  and the second housing part  3   b  produced as a housing cover  14  is closed by means of a bonded connection  28  or the adhesive connection  29  between the end section  35  and the housing cover  14  and is in this way sealed in a fluid-tight manner. The thermal insulating element  8  is formed by the bonded connection  28  or the adhesive connection  29  and the intermediate space  29  closed by these. 
         [0045]      FIG. 9  shows a combination of the variants of  FIGS. 4 and 8 . In the example in  FIG. 9  both pot collars  23 ,  33  have flange sections  35 ,  36  projecting outwards between which an intermediate space  32  or an opening  25  between the two pot collars  13 ,  23  by means of a bonded connection  28  or an adhesive connection  29  between the two pot collars  13 ,  23 . In this way the housing interior  4  is also sealed off against the external environment  24  of the housing  2  and is sealed in this way. The thermal insulating element  8  is formed by the bonded connection  38  or the adhesive connection and the intermediate space  32  closed by these. 
         [0046]    The variant in  FIG. 10  differs from the variant in  FIG. 7  in that the pot collar  23  of the second housing part  3   b  projects orthogonally from the pot base  22 . In contrast the pot collar  13  of the first housing part  3   a  projects, like the example in  FIG. 7 , at an obtuse angle from the housing pot  12  of the first housing part  3   a.  This produces an enlarged intermediate space  32  between the two pot collars  13 ,  23 . More volume for the material of the bonded connection  28 —typically soldering tin—or the adhesive connection—typically adhesive—is thus available. 
         [0047]    In the example in  FIG. 11  the thermal insulating element  8  comprises a bellows-like structure  37  extending along the circumferential direction in the pot collar  13  of the first housing part  13  and completely encompassing the pot base  12 . In the area of the bellows-like structure a wall thickness of the pot collar  13  can be reduced compared with a wall thickness in the remaining areas of the pot collar  13  and/or of the pot base  12  complementary to the bellow-like structure. 
         [0048]    Finally attention is also drawn to the illustration in  FIG. 12 . In the example in  FIG. 12  both housing parts  3   a,    3   b  of the housing  2  are designed as essentially flat housing walls  38   a,    38   b.  In this scenario the thermal insulating element  8  is in the form of a hollow cylindrical frame  39  made of an insulating material, more particular of a ceramic material. The two face ends  40   a,    40   b  of the frame  39  facing the two housing walls  38   a,    39   b  are respectively attached to the first and the second housing part  3   a,    3   b  by means of a bonded connection  29  or an adhesive connection  29 .