Abstract:
A housing for an electronic apparatus having heat generating components, such as a rectifier, comprises a bottom panel ( 4   a ), at least one side panel ( 4   c,    4   d,    4   e,    4   f ) and a lid ( 4   b ). According to the invention, the whole housing is adapted do constitute a heat sink.

Description:
TECHNICAL FIELD OF THE INVENTION  
         [0001]    The present invention relates to a housing for an electronic apparatus having heat generating components, such as a rectifier, comprising a bottom panel, at least one side panel and a lid. This Application claims priority to Swedish Patent Application No. 0003189-9 filed on Sep. 8, 2000, the entire disclosure of which is incorporated by reference herein. The invention also relates to an electronic apparatus having heat generating components, such as a rectifier, comprising such a housing and a printed circuit board, and to a method of assembling such an electronic apparatus.  
           [0002]    Such a housing as well as such an electronic apparatus and methods of assembling such electronic apparatuses are generally known in the art and are marketed by Emerson Energy Systems AB.  
         OBJECT OF THE INVENTION  
         [0003]    The object of the invention is to provide a housing and an electronic apparatus having improved heat transfer properties and an improved method of assembling such an electronic apparatus.  
         SUMMARY OF THE INVENTION  
         [0004]    This has been achieved by a housing and an electronic apparatus of the initially defined kind, wherein the whole housing is adapted do constitute a heat sink.  
           [0005]    It has also been achieved by a method of the initially defined kind, including selecting a housing completely made of metal and comprising a lid and a first unit having a bottom panel and at least one side panel, providing a printed circuit board with components, providing said first unit with said printed circuit board, providing said first unit with a lid, such that it covers the printed circuit board. Hereby is achieved efficient cooling of all components in the housing.  
           [0006]    Preferably, said bottom panel and said at least one side panel are formed in metal as an integrated first unit, wherein said first unit is adapted to receive said lid formed in metal and constituting a second unit. Hereby, a housing constituted by solely two components is achieved.  
           [0007]    Suitably, at least said first unit is provided with integrated surface enlargements formed in one piece together with the rest of said first unit. Hereby, separate mounting of surface enlargements into the housing is avoided.  
           [0008]    Advantageously, said surface enlargements protrude from the interior surface of the first unit into the interior of the housing.  
           [0009]    Preferably, at least one air inlet opening is provided for allowing cooling air to enter the housing, and wherein at least one of said surface enlargements is associated with at least one opening for allowing air to pass through from the interior to the exterior of the housing. Hereby, cooling of the components by natural convection is achieved.  
           [0010]    Suitably, said air inlet opening is adapted to receive a fan for drawing air through said air inlet opening and for creating a pressure higher than the atmospheric pressure inside the housing. Hereby, cooling of the components by forced convection is achieved.  
           [0011]    Preferably, the housing it is made of an aluminium alloy. Hereby is achieved an inexpensive manufacturing of the housing and that heat transfer is allowed through the whole housing to the exterior thereof.  
           [0012]    Preferably, said bottom panel is substantially rectangular forming four edges, and wherein a side panel is formed in one piece with the bottom panel along each edge, and wherein said side panels are formed as one piece. Hereby, the first unit is formed as a unitary piece. 
       
    
    
     DRAWING SUMMARY  
       [0013]    In the following, the invention will be described in more detail with reference to the accompanying drawings, in which  
         [0014]    [0014]FIG. 1 is a perspective view of a three phase rectifier provided with heat sink bodies,  
         [0015]    [0015]FIG. 2 is an exploded view of the rectifier shown in FIG. 1,  
         [0016]    [0016]FIG. 3 is a magnification of FIG. 2,  
         [0017]    [0017]FIG. 4 illustrates the heat sink body shown in FIG. 1 and a spring device,  
         [0018]    [0018]FIG. 5 a  is a perspective view of the rectifier shown in FIG. 1, but from the opposite direction,  
         [0019]    [0019]FIG. 5 b  is a plan view of the rectifier shown in FIG. 5 a    
         [0020]    [0020]FIG. 5 c  is a schematic representation of the compression of a spring device,  
         [0021]    [0021]FIGS. 6 a - 6   d  illustrate different embodiments of spring devices,  
         [0022]    [0022]FIGS. 7 a - 7   c  illustrate different embodiments of fins of the heat sink bodies shown in FIG. 1 
         [0023]    [0023]FIG. 8 illustrates air flow through the rectifier shown in FIGS.  1 - 7   c    
         [0024]    [0024]FIGS. 9 a - 9   d  illustrate a one phase rectifier, and  
         [0025]    [0025]FIG. 10 illustrates air flow through the rectifier of FIGS. 9 a - 9   d.   
     
    
     DETAILED DESCRIPTION  
       [0026]    [0026]FIG. 1 shows a rectifier  2  mounted in a housing  4 , of which the top and three of the side panels have been omitted for reasons of clarity.  
         [0027]    The rectifier  2  has three layers of printed circuit boards  6   a,    6   b,    6   c,  each provided with heat a sink body  8   a,    8   b  and  8   c.    
         [0028]    The rectifier  2  is a three phase rectifier. Accordingly, each layer is a rectifier for one of the three phases.  
         [0029]    [0029]FIG. 2 shows in an exploded view how the printed circuit boards  6   a,    6   b,    6   c  have been stacked on top of one another to form the compact unit shown in FIG. 1.  
         [0030]    [0030]FIG. 3 shows in an exploded view from above: Screws  10  to be introduced into through holes  11   a    11   b  in each heat sink body and to be fastened in nuts  11   b  arrannged on the bottom of the housing  4 , for the assembly of the three layers of printed circuit boards  6   a,    6   b,    6   c  shown in FIGS. 1 and 2. Thereafter in consecutive order: The uppermost heat sink body  8   a,  upper insulation strips  12 , the uppermost printed circuit board  6   a,  provided with electronic components  14  to be cooled by the heat sink body  8   a,  lower insulation strips  16 , four spring devices  18  and the middle heat sink body  8   b.    
         [0031]    [0031]FIG. 4 shows the heat sink body  8   b  provided with a plurality of cooling fins or pins  20   a,    20   b,  divided by an air gap  21 . On top of a pair of fins there is provided a protrusion  22 . The thermal insulation body is provided with a pair of openings  24 , adapted to receive the corresponding pair of protrusions  22 . The fins  20   a  supporting the spring device  18  are lower than the ones surrounding  20   b  the spring device  18 . In fact, the surrounding fins of the heat sink body  8   c  are adapted to support a portion of the lower surface  23  of the heat sink body  8   b.  In the same manner, the surrounding fins of the heat sink body  8   b  are adapted to support the heat sink body  8   a,  whereas the surrounding fins of the heat sink body  8   a  are adapted to support the not shown lid.  
         [0032]    The lower surface  23  of each heat sink body  8   a,    8   b,    8   c  is furthermore arranged with a cut-out  23   a  for leaving space for each spring device  18  and the components  14 .  
         [0033]    Of course, instead of providing the cut-out  23   a  and the lower fins  20   a  for leaving space for each spring device  18  and the components  14 , the space could have been formed by providing a deeper cut-out in the lower surface  23 , thereby providing fins of equal length.  
         [0034]    Alternatively, it could have been possible to provide an even lower surface  23 , thereby providing even lower fins  20   a.  However in that case, there would be no space for spring devices  18  and components underneath the lowest heat sink body  8   c  (cf. FIG. 5 b ).  
         [0035]    The cross-section of the spring device  18  has the form of a Z making it resilient. The spring device  18  is furthermore made of a resilient material, such as spring steel, but could as well be made of e.g. a plastic material as the spring device  18  itself is not intended to substantially contribute to heat transfer, but to provide a springing effect, which will be discussed below. It should be noted in this context that spring steel has bad heat transfer properties.  
         [0036]    The spring device  18  is provided with strips  26  divided by slits  28 . The strips  26  are joined at one end by an elongated portion  30  attached to a plate  32  of metal or plastic, transversal to the strips  26 , and at the other end by an elongated member  34 .  
         [0037]    [0037]FIG. 5 a  shows the rectifier  2  from the opposite direction, compared to in FIG. 1, and FIG. 5 b  is a front view of the rectifier  2  shown in FIG. 5 a.  A fan  36  for drawing air through the rectifier is arranged at the end of the housing where no heat sink body is provided.  
         [0038]    During assembly, the spring devices  18  are placed on the bottom of the housing  4 . On top of the spring devices  18 , lower insulation strips  12  are arranged. Thereafter, the printed circuit board  6   c  is arranged such that the components  14  mounted thereon contact the strips  26  of a corresponding spring device  18 . On top of the components  14 , the upper insulation strips  16  are arranged. The heat sink body  8   c  is then placed on top of the printed circuit board  6   c,  such that the components  14  thereof contact the heat sink  8   c  via the upper insulation strips  12 .  
         [0039]    On the lower fins  20   a  of the heat sink body  8   c,  spring devices  18  are arranged, on top of which lower insulation strips  16 , components mounted on printed circuit board  6   b,  upper insulation strips  14  and heat sink body  8   b.  On top of the lower fins  20   a,  spring devices etc are arranged in a corresponding manner.  
         [0040]    The uppermost heat sink body  8   a  is provided with lower fins  20   a,  but no spring device etc. is arranged there. The reason for the provision of lower fins  20   a  on the heat sink body  8   a  is simply to avoid high production costs caused by the use of differently shaped heat sink bodies.  
         [0041]    The screws  10  are now inserted through the holes  11   a  and tightened by means of the nuts  11   b.  During tightening thereof, the strips  26  of the spring devices  18  will be pressed together, in particular the strips  26  bearing against the components  14 .  
         [0042]    The strips  26  are intended to be compressed to a predetermined extent, in order to provide a predetermined pressure on the components  14 , such that a desired cooling effect from the heat sink body is achieved. Thus, as can be seen in FIG. 5 c,  if a component is thicker than the average component, the cut-out  23   a  in the lower surface  23  of the heat sink body arranged on top of that component, must be made deeper than the rest of the cut-out. The same occurs if a component does not have the same lateral extension, i.e. does not compress the same number of strips  26 .  
         [0043]    [0043]FIG. 6 a  shows an alternative embodiment of the spring device  18 , according to which embodiment the strips  26  divided by slits  28  have free ends at one end, i.e. no second elongated portion  34  is provided.  
         [0044]    [0044]FIG. 6 b  shows another alternative embodiment, according to which the strips  26  divided by slits  28  have a semi-circular cross-section.  
         [0045]    [0045]FIG. 6 c  shows yet another alternative embodiment, according to which the strips  26  divided by slits  28  have the cross-section of a pair of reversed Z.  
         [0046]    Furthermore, in FIGS. 6 a - 6   c,  no plate  32  has been shown, even though the plate  32  may be provided also in this embodiment.  
         [0047]    [0047]FIG. 6 d  shows another alternative embodiment of the spring device  18 . The strips  26  divided by slits  28  are unevenly distributed over the elongated portion  30 . The strips  26  are not inter-connected, as is also the case in the spring device shown in FIG. 6 a.  This kind of spring device is advantageous as is can be completely adapted to a particular set-up of components, i.e. with different lateral dimensions and thicknesses.  
         [0048]    [0048]FIGS. 7 a,    7   b  and  7   c  show alternative forms and distributions of the cooling fins or pins  20 . In FIG. 7 a,  the fins have a rectangular cross-section, and are distributed in a parallel relation ship across the elongated extension of a support plate  38 . In FIG. 7 b,  they have a circular cross-section and are evenly distributed over the support plate  38 . In FIG. 7 c,  they have a rectangular cross-section, but they are arranged at an angle to the elongated extension of said support plate  38 .  
         [0049]    In FIG. 8, one layer of printed circuit board with mounted heat sink body is shown. The fan  36  draws air of about 50° C. into the housing and over components not contacted by the heat sink bodies  8   a,    8   b    8   c.  The temperature has thus risen to about 57° C. when entering the spaces  21  between the fins  20 ,  20   b.  The components  14  generate heat that is transferred to the corresponding heat sink bodies  8   a,    8   b  or  8   c.  The air passes the fins  20   a,    20   b  and is heated to about 71° C. by heat transferred therefrom, i.e. the heat sink bodies  8   a,    8   b,    8   c  are cooled by the air.  
         [0050]    It should be noted that the bottom and the lid of the housing are active cooling surfaces connected to the heat sink bodies.  
         [0051]    The pin formed fins shown in FIG. 8 may be exchanged to the form of fins shown in FIG. 7 c.    
         [0052]    By arranging the heat sink bodies on three sides of the housing, it has been possible to produce a compact rectifier that fits into a rack of standard size. By arranging three such layers on top on one another, it has been possible to produce a compact three phase rectifier.  
         [0053]    Furthermore, a rectifier adapted to be assembled in an automated way is achieved.  
         [0054]    [0054]FIGS. 9 a,    9   b,    9   c  and  9   d  show a one phase rectifier from different angles.  
         [0055]    The housing  4  is made of a bottom panel  4   a,  a lid  4   b  and side panels  4   c,    4   d,    4   e,    4   f.  The side panels and the bottom panel constitute an integrated unit. All six sides of the housing  4  is made of an aluminium alloy.  
         [0056]    The side panel  4   f  is provided with a pair of fans  36  for distribution of air inside the housing  4 . The opposite panel  4   d  is provided with heat sink body  8  comprising a plurality of fins  20 , divided by an air gap  21 . One further heat sink body  52  in the form of a rectangular parallelepiped is integrated with the bottom panel  4   a.  It should thus be understood, that the whole housing  4  constitutes a heat sink for the over all cooling of the rectifier, whereas the heat sink bodies  8  and  52  constitute contacting members for heat transmission from the individual components. In order to improve the heat transfer properties of the bottom and the lid, they are provided with surface enlargements  53 .  
         [0057]    Closest to the heat sink body  8 , an insulation member  12  is mounted, on top of which, the components  14  mounted on a printed circuit board  6  are arranged.  
         [0058]    Closest to the lid  4   a,  the spring device  18  of the kind shown in FIG. 6 d  is arranged, on top of which an insulation member  16 , covering a large part of the lid&#39;s inside, is arranged. On top of the heat transfer body  52 , an insulation member  54  is arranged. The component to be cooled by the heat transfer body  52  has been omitted in the figure for reasons of clarity.  
         [0059]    During assembly of the housing  4 , the lid  4   b,  including the spring device  18  and the insulation member  16 , are mounted above the printed circuit board  6 . The strips  26  of the spring device  18  are adapted to contact each of the components  14 .  
         [0060]    The lid  4   b  is then screwed onto the side panels  4   c - 4   f,  during which operation, the strips  26  will be pressed towards the portion  32 , so that a predetermined pressure is applied on each component, in the same manner as discussed above regarding the three phase rectifier.  
         [0061]    Thus a very fast assembly of the rectifier is achieved, in particular as it is adapted to be assembled by an industrial robot.  
         [0062]    [0062]FIG. 10 shows the air flow trough the rectifier of FIGS. 9 a - 9   d.  Air is drawn over the surface enlargements  53  and through the openings  21  of the heat sink body  8 .