Patent Publication Number: US-2023142145-A1

Title: Electrical heating device comprising earthing means

Description:
FIELD OF THE INVENTION 
     The invention relates to a heating device for an air-conditioning housing, comprising earthing means. The invention also relates to an air-conditioning housing comprising such a heating device. It is particularly applicable in the field of motor vehicles. 
     PRIOR ART 
     Electrical heating devices are known that are intended to be integrated into vehicle air-conditioning housings. This involves either additional radiators, combined with heating radiators traversed by a heat transfer fluid, in heat engine vehicles, or main radiators in electric or hybrid vehicles. 
     Such heating devices comprise a heating body accommodating heating units provided with heating elements supplied with electric current by electrodes. For electrical safety reasons, the heating elements and their power supply electrodes may need to be insulated from the outside. To this end, the heating units comprise tubes, with the heating elements and their electrode being located therein, the inner surface of the tube being provided with an electrically insulating layer for insulating the heating elements and their electrode. 
     These heating devices comprise a distribution unit capable of controlling the current circulating in the heating units, in particular via an electronic board. 
     Several elements equally forming part of the heating body and of the distribution unit necessarily must be earthed as a safety measure. 
     By way of a reminder, the earth is the conductive part of electrical hardware liable to be touched by an individual, which hardware is not normally powered but which can be powered in the event of an insulation fault in the active parts of this hardware. 
     Thus, all the metal frames of the heating device must be earthed for safety reasons. In motor vehicles with metal bodywork, the bodywork is used as an electrical earth. 
     It is customary for each metal element of the heating device to be connected to a stud, which is connected to the earth, i.e. to the bodywork in the example of a motor vehicle. This particularly involves metal elements liable to be in contact with high current in the event of a current leak. 
     This involves an increase in the connections, often corresponding to earth cables, between each metal element and the stud. These connections to the stud are sometimes difficult to integrate due to the limited space available inside the heating device. Moreover, there is a risk of interference between these connections and others present inside the heating device. 
     SUMMARY OF THE INVENTION 
     The aim of the present invention is to overcome the different disadvantages mentioned above using a heating device allowing its metal elements to be earthed by means of simple and easy construction inside the heating body and the distribution unit, and where there is no risk of interference. 
     This aim is achieved by means of a heating device for an air-conditioning housing conventionally comprising a heating body supplied with current for heating an air flow traversing said heating body, the heating body comprising heating elements traversed by said current and being located in electrically insulated tubes of the heating elements, said heating elements being controlled via a distribution unit, the heating device comprising means for earthing a plurality of metal elements distributed in the heating body and the distribution unit. 
     This device is mainly characterized in that said earthing means comprise a single earthing circuit traversing the heating body and the distribution unit and formed by arranging said metal elements in series through direct contact between said metal elements. 
     The main idea of this invention involves providing a single earthing circuit, formed by a chain of metal earthing elements. In this chain, the metal elements directly touch in pairs, so as to provide the electrical continuity. Thus, a path of metal elements in series exists inside the heating device, forming the earthing circuit. Each metal element forms a link of the electrical chain. 
     Specific wiring no longer needs to be implemented when assembling the heating device, which saves a considerable amount of time. 
     The earthing circuit is thus simplified, especially since it requires fewer components, and those remaining are shorter and simpler than usual. 
     According to the various embodiments of the invention, which can be taken together or separately: 
     the heating device comprises a metal heat dissipation plate, through which the earthing circuit passes; 
     the heating device comprises an electrical connection element between the heating body and said plate; 
     the tubes are electrically connected together via heat sinks that are electrically conductive, the earthing circuit successively traversing these tubes and these heat sinks; 
     said electrical connection element is disposed between the plate and a tube forming part of the heating body; 
     said electrical connection element is disposed between the plate and a heat sink forming part of the heating body; 
     said electrical connection element is disposed between the plate and a metal flange forming part of the heating body and in contact with at least one heat sink: the metal flange can comprise an inter-heat sink plate, located between two adjacent heat sinks, or can comprise a plate located between a heat sink and a lateral side of the frame delimiting the heating body; 
     said electrical connection element is disposed between the plate and any other conductive element of the heating body; 
     said electrical connection element is disposed between the plate and any other conductive element electrically connected to the heating body; 
     said electrical connection element comprises a clip with a flexible strip able to provide electrical continuity between said plate and the heating body; 
     the clip comprises a first section able to attach to an edge of the plate and a second section with the flexible strip in abutment on the heating body; 
     said plate comprises a perforated plate, with the first section of the clip comprising a free end, on which a shoulder is produced that is inserted into a perforation of the plate, providing resilient fitting of the clip in the plate; 
     the second section has a V-shape with a branch connected to the first section and a free branch corresponding to said flexible strip that is able to deform by reducing the angle of the V in order to exert a constant pressure against the heating body; 
     said electrical connection element comprises a metal pin traversing an orifice in said plate that is provided to this end, said pin being able to provide electrical continuity between said plate and the heating body; 
     said electrical connection element comprises a metal part that is fixed, on the one hand, to the heating body by soldering or by any other technique providing electrical continuity between the heating body and the metal part and, on the other hand, to said plate by resilient fitting in a groove in the plate that is provided to this end; 
     the distribution unit comprises an electronic control board, on which heat releasing components are fixed, said plate being in contact with these components: it particularly involves transistors; 
     the fin type heat sinks extend from the tubes and touch between two adjacent tubes: the earthing circuit passes through these heat sinks; 
     said plate is connected, via a metal connection bar traversing the distribution unit, to an earthing stud disposed at the input of the distribution unit; 
     said connection bar is molded in the housing and forms an insert: this molding hides part of the earthing circuit and protects this part from other components disposed in the distribution unit. Indeed, the molding prevents any contact of this part of the circuit with the other components. The molding also allows any risk of detachment of the bar due to vibrations of the on-board heating device to be avoided. Advantageously, the bar forms an insert in the housing, which allows the protective housing to be stiffened. In this way, it is possible to equally combine an earthing function with a function for stiffening the protective housing, by means of a single bar. This combining of these functions also helps to make the distribution unit more compact; 
     said connection bar is made from an electrically conductive metal material, of the aluminum, steel, brass type; 
     said protective housing is made from an electrically insulating material, of the plastic type; 
     said bar comprises:
         a first end electrically connected to the plate;   a central part molded in the housing;   a second free end molded in the housing and connected to an earthing stud;       

     the bar extends orthogonal to the plate; 
     the bar extends over substantially the entire length of the electronic board and at a distance from the electronic board: this allows any contact with the components fixed on the electronic board to be avoided. 
     The invention also relates to an air-conditioning housing comprising a heating device as described above. 
    
    
     
       PRESENTATION OF THE FIGURES 
       The invention will be better understood, and other aims, details, features and advantages thereof will become more clearly apparent from the following detailed explanatory description of at least one embodiment of the invention, which is provided by way of a purely illustrative and non-limiting example, with reference to the appended schematic drawings. 
       In these drawings: 
         FIG.  1    shows a perspective view of a heating device according to the invention; 
         FIG.  2    is an exploded view of  FIG.  1   , more specifically showing the distribution unit according to the invention; 
         FIG.  3    shows a perspective view of an electrical connection element between a tube of the heating body and the plate of the distribution unit; 
         FIG.  4    is an exploded view of the electrical connection element according to  FIG.  3   ; 
         FIG.  5    shows a perspective view of an earthing bar connected to the plate. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG.  1   , the invention relates to an electrical heating device  1 . It involves, for example, a heating device  1 , called high-voltage heating device, i.e. intended to be powered by a direct (DC) or alternating (AC) current having an electrical voltage of more than 60 V, in particular between 60 and 1000 V, more specifically between 180 and 600 V, and/or allowing heating power to be released into the air, or having electrical power consumption of more than 2 kW, in particular between 2 kW and 10 kW. Said heating device  1  comprises a heating body  2  supplied with electric current for heating an air flow traversing said heating body  2 . 
     Said heating body  2  in this case has a substantially parallelepipedal configuration extending on the surface. It is intended to be positioned transverse to the air flow to be heated. More specifically, said air flow is intended to be oriented perpendicular to said heating body  2 , i.e. perpendicular to the plane of  FIG.  1   . 
     The heating body  2  comprises heating elements (not shown) traversed by said current. The heating elements are, for example, PTC (Positive Temperature Coefficient) effect resistors. 
     The heating elements are located inside metal tubes  4 . In order to avoid any electrical contact between the heating elements and the tubes  4 , an electrically insulating and thermally conductive layer of material coats the inner surface of the tubes  4 . 
     Each tube  4 /heating elements assembly forms what is referred to as a heating unit. Said heating units are selectively supplied with current. This is understood to mean that each heating unit is supplied with current independently of the other units and therefore can be traversed by a different current, in particular in terms of its intensity, from the currents traversing the other heating units. The value of the current that is used in this case is particularly the value of the average current or of the effective current. 
     The heating body  2  can comprise heat sinks  13 , for example, fins, in thermal contact with the tubes  4 . The heat sinks  13  are particularly positioned between said tubes  4 . For the sake of clarity, only some heat sinks  13  extending from the end tubes  4  have been shown, so as not to overload  FIG.  1   . 
     Said heating body  2  comprises a frame  5 , in particular made of plastic material, accommodating said heating units and being used to support said tubes  4 . 
     Intermediate bars  14  are also provided between the tubes  4  in order to hold them in position. 
     Preferably, the heating device  1  further comprises a distribution unit  3  able to control the current circulating in said heating body  2 . 
     Said distribution unit  3  is advantageously configured to control the current supplying the heating body  2 , in particular the various heating units, for example, using controlled switches, allowing respective control of a circulation of current in each of the heating units. It particularly involves transistors  12 , for example, of the Mosfet or IGBT type, particularly operating by pulse width modulation. These transistors  12  are particularly shown in  FIG.  5    and are mounted on a T-shaped electronic board  11 , therefore having a central axis of symmetry. 
     Said distribution unit  3  comprises a housing  8 , shown in  FIGS.  1 ,  2 ,  6  and  7   , which completely covers said electronic board  11  and which comprises a connection face  83  used for mounting and/or mechanically fixing the heating body  2 . This housing  8  is preferably made from a plastic material, having electrically insulating properties, and is obtained by molding. 
     When the heating elements operate, the transistors  12  release a considerable amount of heat. In order to avoid any overheating inside the housing  8 , a heat dissipation plate  6  is provided in the heating device  1 . This plate  6  comprises a perforated sheet, positioned in a plane parallel to the plane of the heating body  2 , and located in front of the tubes  4  so that the air flow traversing the heating body  2  also traverses this perforated plate  6 . Thus, this plate  6  helps to heat the air flow. 
     The plate  6  is mainly made up of a perforated body  63 , which extends from the lugs (hidden by the transistors  12  in  FIG.  5   ) able to come into contact with transistors  12  so as to draw the calories emanating from the transistors  12 . The plate  6  thus heats up, via the transistors  12 , and is subsequently cooled via the air flow. 
     In such a heating device  1 , it is essential that the metal elements are earthed, so as to electrically safeguard them. 
     To this end, an earthing circuit exists that traverses the whole of the heating device  1 , so that each metal element can be connected thereto. In particular, this earthing circuit is made up of a series of metal elements positioned in series and in direct contact in pairs, and thus forming the circuit. 
     At the heating body  2 , the tubes  4 , as well as the heat sinks  13  and the intermediate bars  14 , are metal. In the configuration of the heating device  1  according to the invention, the heat sinks  13  are all connected to a tube  4  through direct contact, and the heat sinks  13  of two adjacent tubes  4  meet and are also in direct contact, or meet at an intermediate bar  14 . Consequently, the entire row of tubes  4 , of heat sinks  13  and of intermediate bars  14  are in electrical contact with each other, and the earthing circuit thus passes through all the tubes  4 , the heat sinks  13  and the intermediate bars  14  of the heating body  2 . 
     At the output of this row of tubes  4 , of heat sinks  13  and of intermediate bars  14 , an electrical connection element  7  is disposed between an end tube  4  and the perforated plate  6 , as is particularly shown in  FIGS.  2 ,  3  and  5   . This electrical connection element  7  provides the electrical continuity between the row of tubes  4  and the perforated plate  6 . 
     With reference to  FIGS.  3  and  4   , which show a possible example of the invention, the electrical connection element  7  comprises a clip  7  formed by: 
     a first inverted U-shaped section  71  that is positioned astride the upper edge  62  of the perforated plate  6 ; 
     a second V-shaped section  72 , a branch  75  of which is connected to the first section  71  and the free branch  74  of which comprises a flexible strip  74  coming into abutment against the outer wall of the tube  4 . 
     More specifically, the angle of the V is designed so that the flexible strip  74  exerts sufficient pressure on the tube  4  so that the electrical contact is properly established. 
     The first section  71  and the second section  72  of the clip  7  comprise a shared branch  75 . 
     The free end of the first section  71  is provided with a shoulder  73  directed toward the inside of the clip  7  and designed so as to be able to penetrate inside a perforation  61  of the perforated plate  6 , so as to provide resilient fitting of the clip  7  in the plate  6 . 
     Any other shape of the clip  7  can be contemplated. The invention is not limited to this precise shape of a clip  7 . In particular, it is possible to contemplate an electrical connection element assuming the shape of a pin fixed to the plate  6  and to the tube  4  via orifices, or even a connection element comprising a part that is clipped into a groove produced in the plate  6 . In general, the connection element can assume any possible shape, as long as it connects the plate  6  to the tube  4  while providing electrical continuity. 
     This electrical connection element is made up of a metal material. 
     The earthing circuit passes through this electrical connection element, then through the perforated plate  6 . 
     The earthing circuit subsequently continues through a metal bar  9 , for example, made of aluminum, steel or brass, passing above the whole of the electronic board  11  along its axis of symmetry, as is particularly shown in  FIG.  5   . This bar  9  orthogonally extends from the perforated plate  6 . 
     The bar  9  comprises:
         a first end  91  fixed to the perforated plate  6 ;   a central part  94  extending over the electronic board  11 ;   a second free end  92  connected to an earthing stud  10 .       

     More specifically, the first end  91  comprises a lug that is perpendicular to the central part  94 . It is soldered, for example, to a central tab  64  extending from the perforated body  63  of the plate  6 . It can be fixed by any other means for ensuring electrical continuity between the perforated plate  6  and the bar  9 . 
     Even more specifically, the second end  92  comprises an orifice, into which the earthing stud  10  is bolted. The bar  9  comprises a shoulder  93  located immediately upstream of the second end  92 . 
     The earthing circuit thus ends at the stud  10 . In the case of a motor vehicle, for example, this stud  10  will be connected to the bodywork of the vehicle, which forms the earthing reference. 
     The earthing circuit can also follow the opposite direction, i.e. by traversing the stud, the bar, the plate, the clip, then the row of tubes/fins/intermediate bars. 
     Advantageously, this bar  9  is molded in the protective housing  8 , as shown in  FIG.  1   . Such molding also allows the bar  9  to be positioned at a distance from the electronic board  11  in order to avoid any contact with the components of the board  11 . 
     In particular, the central part  94  and the second end  92  of the bar  9  are fully embedded in the material of the protective housing  8 . The first end  91  for its part is flush with the housing  8 . An upper layer of plastic material and a lower layer of plastic material exist that form part of the protective housing  8  and sandwich the bar  9 . 
     The bar  9  thus comprises an insert, which is particularly used to stiffen the housing  8 . Thus, in addition to its earthing function, the bar  9  is used to consolidate the housing  8 . The stud  10  projects from the protective housing  8  in order to be accessible so that it can be connected to the earth. 
     In this way, no particular wiring needs to be implemented inside the heating device  1  in order to earth metal elements. All the metal elements of the heating device  1  come into contact with each other, in series, so as to form a single earthing circuit traversing the heating device  1 . 
     The invention also relates to an air-conditioning housing comprising a heating device  1  as described above. Said air-conditioning housing comprises a body for circulating the air flow, inside which body said heating device  1  is located. 
     With respect to the above description, the optimal dimensional relationships for the parts of the invention, including variations in size, materials, shapes, function and modes of operation, assembly and use, are considered to be clear and obvious to a person skilled in the art, and all the relationships equivalent to that which is illustrated in the drawings and to that which is described in the brief are deemed to be included in the present invention.