Patent Publication Number: US-2021195787-A1

Title: Electrical equipment comprising a busbar cooled by two faces of a heatsink

Description:
TECHNICAL FIELD 
     The present invention relates to the field of electrical equipment, in particular for electric or hybrid vehicles, and more precisely relates to the cooling of electrical systems such as inverters connected to the motor in electrical motorization systems. 
     PRIOR ART 
     It is known to use electrical equipment that has busbars. In particular, such busbars are intended to convey electrical energy from an interface, in particular an external interface, of the electrical equipment to an internal component of the electrical equipment. For example, the busbar connects a terminal of the electrical equipment with a capacitor of the electrical equipment. The busbar generally comprises a leadframe, in particular made of metal, maintained by a body made from an electrically insulating material, in particular plastic. Electronic components can be received on the busbar in order to allow for a filtering of the signal flowing in the leadframe. During the passing of the current in the busbar, the heat given off by the electrical conductor and/or the filtering components can damage the other components of the electrical equipment, in particular the capacitor, which already generates heat via the Joule effect due to its own operation. 
     To cool the busbars, it is known to have them pass along a cooling box provided with a system for circulating a cooling liquid. However, this can be insufficient, in particular when the electrical equipment is operating at a high voltage, i.e. at a voltage higher than 60V, even 80V or 100V or 400V or 800V. In particular, the electrical equipment can operate between 50 kW and 300 kW. 
     A cooling solution is therefore sought that allows for an improved dissipation of heat of leadframes. 
     SUMMARY 
     For this purpose, a piece of electrical equipment is proposed comprising:
         a heatsink comprising an internal volume delimited by at least two opposite faces,   a busbar,
 
the busbar coming against said two opposite faces of the heatsink in such a way as to be cooled by the heatsink.
       

     The busbar is therefore cooled by the two opposite faces of the heatsink. In the prior art, only one face of the heatsink is used to cool the busbar. Thus, thanks to the integration of the busbar with the heatsink, the cooling of the busbar is increased in relation to the prior art. In particular, said busbar comes into direct contact with said two opposite faces of the heatsink, or comes against the opposite faces of the heatsink via one or more intermediate layers. 
     According to an embodiment, the busbar extends along the two opposite faces in such a way as to surround the heatsink. 
     According to an embodiment, the heatsink comprises a first side at which said two opposite faces are connected, said busbar extending along said heatsink from the first side returning to said first side. 
     In an alternative, an input terminal and an output terminal of the busbar are at said first side of the heatsink. 
     In an alternative, the heatsink comprises a second side at which said two opposite faces are connected, said second side being opposite the first side. Said busbar extends along said heatsink from the first side to the second side, then from the second side to the first side. 
     According to an embodiment, the busbar comprises two portions assembled together, the first portion coming against a first of said faces of the heatsink and the second portion coming against the second of said faces of the heatsink, in such a way as to surround the heatsink. 
     According to an alternative, the first portion and the second portion of the busbar are assembled together at second edge of the heatsink. 
     According to an embodiment, the busbar is made from a single piece by surrounding the heatsink. 
     According to an embodiment, the busbar comprises a coating surrounding a leadframe, the coating comprising an opening coming across from a portion of the heatsink, the opening comprising an electrically insulating heatsink material in such a way as to improve the cooling of said leadframe. 
     According to an embodiment, the busbar supports at least one electrical component. In an alternative, the electrical component is an EMC filtering component. 
     In an alternative, the electrical component is sandwiched between the busbar and the heatsink. 
     According to an embodiment, at least one of said faces of the heatsink is configured to cool other components on at least one surface not covered by the busbar. 
     According to an alternative, the first face of the heatsink receives an electronic power module and the second face of the heatsink receives a capacitive module at surfaces not covered by the busbar. 
     According to an alternative, the heatsink comprises at least one cooling channel configured to receive a cooling fluid, the cooling channel being at least partially in the zone not covered by the busbar, and the portion of the heatsink surrounded by the busbar being devoid of a cooling channel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood and other details, characteristics and advantages of the invention shall appear when reading the following description given as a non-limiting example in reference to the accompanying figures. 
         FIG. 1  shows a perspective view of an example of a piece of electrical equipment according to the invention. 
         FIG. 2  shows a perspective view of the electrical equipment of  FIG. 1 , wherein the busbar is provided with components. 
         FIG. 3  shows a cross-section view of the electrical equipment of  FIG. 2 . 
         FIG. 4  shows an exploded view of the electrical equipment of  FIG. 2 . 
         FIG. 5  shows a detailed view of an alternative of the electrical equipment of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     The electrical equipment  100  such as shown in  FIG. 1  comprises a heatsink  2 , which comprises an internal volume delimited by at least two opposite faces  20   a ,  20   b . In the example shown, a portion of the heatsink  2  called main portion  2   a , can comprise a cooling channel  21  configured to receive a cooling fluid. Another portion of the heatsink, called auxiliary portion  2   b , is then devoid of a cooling channel. The auxiliary portion  2   b  is in particular cooled by heat conduction from the auxiliary portion  2   b  to the main portion  2   a  where the heat is drained by the cooling fluid flowing in the cooling channel  21 . In other words, the auxiliary portion  2   b  forms a protrusion of material from the main portion  2   a . By not providing a cooling channel in the auxiliary portion  2   b , its size and the final size of the electrical equipment  100  are thus limited. The heatsink  2  can have a substantially rectangular shape. However, the auxiliary portion  2   b  could receive a cooling channel, which would increase its size but would improve the heat dissipation at the auxiliary portion  2   b . But an auxiliary portion  2   b  devoid of a cooling channel is sufficient for a cooling of a busbar, in particular such as described hereinafter. The auxiliary portion  2   b  could be made from a material different from that of the main portion  2   a . In particular the auxiliary portion  2   b  could be made of a material with a thermal conductivity that is higher than that of the main portion  2   a . For example, the main portion  2   a  is made from aluminum and the auxiliary portion  2   b  is made from copper. However, the cost could be substantially higher. 
     The two opposite faces  20   a ,  20   b  can have a substantially identical contour. They can be superimposed in a substantially parallel manner. The contours of the two opposite faces  20   a ,  20   b  are in particular connected by a wall  3  all along the contours. Alternatively, the contours of the two opposite faces can be connected directly between them, in particular without a wall  3 . For the positioning of a component or for the passing of a connection, or other, the opposite faces  20   a ,  20   b  can comprise notches, openings or other differences with respect to the other opposite face  20   a ,  20   b.    
     The electrical equipment comprises a busbar  4 . The busbar  4  can comprise two leadframes  41   a ,  41   b , in particular a negative leadframe  41   a  and a positive leadframe  41   b . The leadframes  41   a ,  41   b  are in particular made of metal, for example of copper. They form rigid parts which are maintained together by a coating  42  made of an electrically insulating material, deposited for example by overmolding. In  FIG. 1 , a portion of the coating  42  is not shown in order to render the leadframes  41   a ,  41   b  visible. The leadframes  41   a ,  41   b  connect in particular terminals of the electrical equipment  100  with a capacitor of the electrical equipment  100 . 
     The busbar  4  comes into contact against the two opposite faces  20   a ,  20   b  of the heatsink  2  in such a way as to be cooled by the heatsink  2 . Thus, the busbar  4  benefits from the two faces of the heatsink  2  to be cooled. The integration of the busbar  4  into the electrical equipment  100  is improved in relation to the prior art. The cooling of the busbar  4  is improved while still controlling the size of the electrical equipment  100 . The busbar  4  extends in particular along two opposite faces  20   a ,  20   b  of the heatsink  2  in such a way as to surround the heatsink  2 . The busbar  4  can therefore be cooled over its entire length. The surfaces of the busbar  4  that are cooled are therefore increased with respect to the prior art. The cooling of the busbar  4  is then higher, the risk of damage by the heat therefore decreases substantially. Furthermore, by surrounding the heatsink  2 , the busbar  4  is integrated with the heatsink  2 . 
     In particular, the busbar  4  starts from a first side  3   a  of the heatsink  2 ; extends along the auxiliary portion  2   b , in particular along the portion of the first face  20   a  comprised in the auxiliary portion  2   b . The busbar  4  then joins the second face  20   b  by a second side  3   b  of the heatsink  2 , and again runs along the auxiliary portion  2   b , in particular along the portion of the second face  20   b  comprised in the auxiliary portion  2   b , to return to the first side  3   a . Thus, the busbar  4  forms a loop around the heatsink  2 , in particular around the auxiliary portion  2   b . Returning to the first side  3   a , the electrical connections to the busbar  4 , for example the connection to a terminal of the electrical equipment  100  or the connection to a capacitor of the electrical equipment  100 , can be provided on the same side  3   a  of the heatsink  2 . In particular from an industrial standpoint, during the manufacturing of the electrical equipment  100 , this arrangement makes it possible to connect the busbar  4  more easily. The two connections can therefore be carried out from the same side of the heatsink  2 , without turning over the electrical equipment  100 ; which makes it possible to save a manufacturing step and time as well. Unnecessary manipulations of the electrical equipment  100  during the assembly are therefore avoided and/or a quality inspection is therefore facilitated. In particular, the second side  3   b  is opposite the first side  3   a . However, this second side  3   b  could be a side of the heatsink  2  which is adjacent to the first side  3   a.    
     The busbar  4  comprises in particular two portions  4   a ,  4   b  assembled together in such a way as to surround the heatsink  2 . The first portion  4   a  comes against the first face  20   a  of the heatsink  2 ; and the second portion  4   b  comes against the second face  20   b  of the heatsink  2 . Thus, the assembly of the busbar  4  around the heatsink  2  can be done in several steps. In particular, the first portion  4   a  and the second portion  4   b  of the busbar  4  are assembled together at the second side  3   b  of the heatsink  2 . In particular, the leadframes  41   a ,  41   b  each comprise a first portion coming against the first face  20   a  and a second portion coming against the second face  20   b . As shown for example in  FIG. 4 , ends  5   a ,  5   b  of the first portions of the leadframes  41   a ,  41   b  come against respective ends  5   c ,  5   d  of the second portions of the leadframes  41   a ,  41   b . These ends  5   a ,  5   b ,  5   c ,  5   d  are connected by welding, brazing, screwing or any other means of fastening. The arrangement described hereinabove allows for an assembly of the busbar  4  with the heatsink  2  along a single axis. 
     Alternatively, the busbar  4  could be of a single piece by surrounding the heatsink  2 . The leadframes  41   a ,  41   b  are then each of a single piece, and in particular extend continuously from the first face  20   a  to the second face  20   b . This alternative makes it possible on the contrary to save parts, for example parts that connect the first  4   a  and second  4   b  portions of the busbar  4 , and/or pre-assembly steps. Furthermore, any assembly in an incorrect direction is avoided. 
     As for example shown in  FIG. 5 , the coating  42  of the busbar  4  can comprise one or more openings  40  facing the heatsink  2 . The opening  40  exposes in particular a surface of the leadframe  41   a ,  41   b . This opening  40  is then filled with an electrically insulating material, but which conducts heat which acts in such a way as to improve the cooling of the leadframe  41   a ,  41   b . The material can be a thermal grease or a flexible material, such as for example a “gap pad”® or any other material with the dual characteristics of electrical insulation and thermal conduction. 
     As for example shown in  FIGS. 2, 3 and 4 , the busbar  4  can support components  12 ,  16 . In particular filtering components  12  and magnetic cores  16 , required for filtering. These components  12 ,  16  can be assembled on an electronic board  14 , which itself is mounted on the busbar  4 , in particular on the coating  42  of the busbar  4 . The electronic board  14  receives in particular electrical elements of small size, of which a direct assembly on the busbar  4  would be difficult. The filtering makes it possible to decrease the EMC electromagnetic field linked to the current flowing in the busbar  4  so as to protect the components of the electrical equipment  100 . Other components can be placed on another electronic board and connected to the busbar  4  by cables, bundles or a rigid connector. 
     Alternatively, the components  12 ,  16  can be mounted directly on the busbar  4 , without the intermediary of the electronic board  14 . In this case the components  12 ,  16  can be welded, brazed or fastened by any other method of fastening on the busbar  4 . 
     In particular, the busbar  4  comes against the heatsink  2  at the auxiliary portion  2   b  of the heatsink  2 . The busbar  4  covers only one zone on the heatsink  2 . Preferably, the busbar  4  covers only one zone of the auxiliary portion  2   b  of the heatsink  2 . The remainder of the heatsink  2 , in particular the portions of the first  20   a  and second  20   b  faces located in the main portion  2   a , can receive other components to cool them. For example, in  FIG. 1 , an opening  22  in the first face  20   a  of the heatsink  2  is closed by a plate carrying an electronic power module. The plate, by closing the opening  22  of the first face  20   a  contributes in particular in forming the cooling channel located in the main portion  2   a  of the heatsink  2 . For example, as shown in  FIG. 4 , a portion  201   b  of the second face  20   b  located in the main portion  2   b  can receive a capacitor that will be cooled by the main portion  2   a . As the power module and the capacitor generally give off a lot of heat by the Joule effect, it is advantageous to arrange them on the main portion  2   a  of the heatsink. 
     In an alternative not shown, the components  12 ,  16  can be sandwiched between the busbar  4  and the heatsink  2 , which improves the cooling of the components  12 ,  16 . In this particular case, the structure of the faces  20   a ,  20   b  of the heatsink  2  can be adapted to the size of the components  12 ,  16 . The surface of the heatsink  2  against which the components  12 ,  16  come can take the different heights and shapes of the components  12 ,  16  into account in order to ensure the cooling thereof. For example, starting from the heatsink  2 , there is firstly a layer of a flexible material  42 , electrically insulating but thermally conducting, then the component  12 ,  16 , followed by the electronic board  14  and the busbar  4 . Such an arrangement in a sandwich furthermore allows for a firm hold of the components  12 ,  16 . Degradation by vibration is then attenuated. The longevity of the electrical equipment  100  is increased.