Abstract:
An electronic control unit ( 1 ) having a housing ( 2 ) containing a circuit board ( 5 ). The housing ( 2 ) includes a base ( 3 ) and a cover ( 4 ) between which the circuit board ( 5 ) is located, and the unit being characterised in that the base ( 3 ) and the cover ( 4 ) are connected to one another via interference fit interengagement around at least a major part of a peripheral edge ( 20 ) of the cover ( 4 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a 35 U.S.C. §371 National Phase Application of PCT/EP2016/052145, filed Feb. 2, 2016, which claims the benefit of priority to European Patent Application Serial No.: 15153702.4, filed Feb. 3, 2015, the contents of which are incorporated herein by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to an electronic control unit, and more particularly to an electronic control unit of a type having a housing containing a circuit board. 
         [0003]    Although the electronic control unit of the present invention has been found to be particularly suitable for use in the environment of a motor vehicle, and will thus be described with particular reference to that technical area, it is to be appreciated that the present invention is not limited to the field of motor vehicles. 
       BACKGROUND 
       [0004]    Modern motor vehicles are equipped with a vast array of electronic circuitry to manage operation of the vehicle and to ensure the safety of occupants in the case of an accident. For example, the use of airbags is now common and airbag systems require sophisticated electronics to monitor the motion of the motor vehicle to ensure that the airbags are properly deployed, and deployed in an appropriate manner to provide protection in a given accident situation. Furthermore, so called active safety systems such as adaptive cruise control systems, forward collision warning and braking systems, blind spot monitoring systems, and lane departure warning systems are becoming increasingly common and all require sophisticated electronic circuitry. A modern motor vehicle therefore includes a significant number of electronic control units (ECUs). 
         [0005]    In the environment of a motor vehicle, it is important for ECUs to be adequately sealed in order to prevent environmental influences (such as the ingress of water, dust etc.) from affecting ECU performance. Additionally, it can be advantageous in many installations to ensure that ECUs provide good heat dissipation from their internal circuit boards, and to ensure that the circuit boards are securely retained in position, noting that there are usually very considerable vibrations occurring during operation of a motor vehicle. 
         [0006]    Additionally, motor vehicle manufacturers are continuously striving to reduce the componentry of their vehicles, which means that producers of various electronic systems for installation in motor vehicles are generally striving to reduce the cost involved in their production, and to simplify their production. 
         [0007]    It is an object of the present invention to provide an improved electronic control unit, which may be suitable for use in a motor vehicle. 
         [0008]    According to the present invention, there is provided an electronic control unit having a housing containing a circuit board, wherein the housing comprises a base and a cover between which the circuit board is located, the unit being characterised in that the base and the cover are inter-engaged via an interference fit connection extending around at least a major part of a peripheral edge of the cover. 
         [0009]    Preferably, the interference fit connection involves elastic deformation of said cover around its peripheral edge. 
         [0010]    Advantageously, the cover is resiliently deformable. 
         [0011]    Conveniently, the peripheral edge of the cover engages an inwardly directed surface of the base. 
         [0012]    Advantageously, the peripheral edge of the cover is received within a groove formed around the base as a snap-fit. 
         [0013]    Optionally, the groove is formed around the inwardly directed surface. 
         [0014]    Preferably, the circuit board is clampingly engaged between said base and said cover. 
         [0015]    Conveniently, a first side of the circuit board contacts the base, and an opposing second side of the circuit board contacts the cover. 
         [0016]    Advantageously, the first and second sides of the circuit board respectively contact the base and the cover around a peripheral region of the circuit board. 
         [0017]    Preferably, the second side of the circuit board contacts a re-entrant region of the cover which is depressed inwardly of the base. 
         [0018]    Conveniently, the re-entrant region of the cover is spaced inwardly of the peripheral edge of the cover. 
         [0019]    Advantageously, the unit further comprises a peripheral seal adjacent the interference fit inter-engagement. 
         [0020]    Preferably, the seal extends around the circuit board, and is located between the peripheral edge of the cover and the re-entrant region of the cover. 
         [0021]    Conveniently, both the base and the cover are formed of heat conductive material. 
         [0022]    Advantageously, at least a major part of the peripheral edge of the cover is rounded. 
         [0023]    Optionally, the peripheral edge of the cover has a shape comprising rounded corners. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    So that the invention may be more readily understood, and so that further features thereof may be appreciated, embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: 
           [0025]      FIG. 1  is a perspective view from below of an electronic control unit in accordance with the present invention; 
           [0026]      FIG. 2  is a perspective view from above of the unit illustrated in  FIG. 1 ; 
           [0027]      FIG. 3  is a cross-sectional view through the unit, taken along line Ill-Ill in  FIG. 1 ; 
           [0028]      FIG. 4  is an enlarged cross-sectional view, similar to that of  FIG. 3 , but which shows only part of the unit and which illustrates an initial step in the assembly of the unit; 
           [0029]      FIG. 5  is a view corresponding to that of  FIG. 4 , but which illustrates a subsequent step in the assembly of the unit; 
           [0030]      FIG. 6  is another view corresponding to those of  FIGS. 4 and 5 , but which illustrates a final step in the assembly of the unit; and 
           [0031]      FIG. 7  is a view similar to that of  FIG. 4 , and which shows schematically a heat dissipation function of the assembled unit. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    Turning now to consider the drawings in more detail,  FIGS. 1 and 2  illustrate an electronic control unit (ECU)  1  in accordance with an embodiment of the present invention. The ECU has a housing  2  which includes a base  3  and a cover  4  which are inter-engaged to form the housing  2 . As illustrated most clearly in  FIG. 3 , the housing  2  of the ECU  1  contains a circuit board  5  which may be, for example, a printed circuit board in the conventional manner. 
         [0033]    Both the base  3  and the cover  4  of the housing  2  are formed from a material having good thermal conductivity properties. Some embodiments are configured such that the base  3  and the cover  4  are formed of metal, although it is to be appreciated that other heat conductive materials could be used instead of metal. The base  3  and the cover  4  may both be formed from the same material. However, the base  3  is configured to be substantially rigid while the cover  4  is configured so as to be resiliently deformable, and so they may be formed from different materials in order to achieve these characteristics. 
         [0034]    As illustrated most clearly in  FIG. 2 , the outside of the base  3 , on its side opposite the cover  4 , is provided with a plurality of integrally formed and spaced-apart heat sink fins  6  in order to improve dissipation of heat generated by the circuit board  5  to the surrounding atmosphere. The base  3  also has a peripheral mounting flange  7  with a plurality of mounting apertures  8  to facilitate its connection to a suitable mounting structure, for example in a motor vehicle. 
         [0035]    As illustrated in  FIG. 3 , the base  3  defines a recessed opening  9  through which the circuit board  5  may be inserted so as to be positioned within an interior volume of the housing  2  which is formed when the base  3  and the cover  4  are inter-engaged. More particularly, it will be noted that the base presents an upstanding (in the orientation illustrated in  FIG. 3 ) support ring  10  which extends generally around the interior volume inside the recessed opening  9  and on which the circuit board  5  is supported around its peripheral region. As will thus be appreciated, the underside surface  11  of the circuit board  5  contacts the base  3  around the support ring  10 , but is otherwise spaced from the inner surfaces of the base  3  so that a void  12  is formed between the majority of the circuit board  5  and the base  3  within the support ring  10 . However, the base  3  may include an upstanding central formation  13  in order to provide additional support to a central region of the circuit board  5  or to an electrical component  5   a  mounted to the circuit board as illustrated in  FIG. 3 . 
         [0036]    As illustrated most clearly in  FIGS. 3 and 4 to 6 , the opening  9  of the base  3  is defined by a peripheral sidewall  14  which defines an inwardly directed surface  15 . A peripheral groove  16  is preferably formed in and around the sidewall  14  as illustrated in  FIGS. 4 to 6 , at a position spaced slightly below the upper edge  17  of the sidewall  14 . Additionally, the ECU  1  may include a peripheral seal  18 , such as an elastomeric O-ring type seal, which is seated in a seal recess  19  provided in the base  3  adjacent the sidewall  14 , but spaced below the upper edge  17  and the groove  16 . The seal  18  thus extends around the outside of the peripheral edge of the circuit board  5  in spaced relation thereto. 
         [0037]    Turning now to consider the cover  4  in more detail, it will immediately be noted that the cover  4  is sized and shaped to be received within the recessed opening  9  of the base  3 , to thereby close the interior volume of the housing  2  with the circuit board  5  located therein and between the base  3  and the cover  4 . In this regard it will be noted that the cover  4  has a shape defined by its peripheral edge  20  which is generally rectangular but with rounded corners. It is envisaged that in other embodiments the cover  4  may have a generally oval shape, which will thus also be rounded. The peripheral sidewall  14  of the base  3  thus has a corresponding shape in order to ensure intimate contact with the peripheral edge  20  of the cover  4  around at least a major extent of its length. 
         [0038]    As indicated above, the cover  4  is formed of a heat conductive material such as metal. Additionally, it is to be noted that the cover is configured so as to be resiliently deformable. It is therefore envisaged that the cover  4  may be pressed from metal plate. 
         [0039]    As illustrated most clearly in  FIGS. 1 and 2 , the cover has a relatively large central region  21  which may be substantially planar. Around the central region  21  there is provided a re-entrant region  22  which is depressed inwardly of the base  3  when the cover  4  is fitted to the base  3  as illustrated in  FIGS. 1 and 3  and as will be described in more detail hereinbelow. As will be noted, the re-entrant region  22  of the cover is spaced inwardly of the peripheral edge  20  of the cover  4 . 
         [0040]    The outermost extent of the re-entrant region  22  is defined by an upturned bend in the metal of the cover which defines a small shoulder  23  between the re-entrant region  22  and a planar region  24  around the outside of the re-entrant region. In the peripheral region of the cover  4 , there is defined an upturned lip  25  which terminates in the peripheral edge  20  of the cover  4 . 
         [0041]    As illustrated in  FIGS. 1 and 2 , the sidewall  14  of the base  3  may include an opening  26  to accommodate an electrical connector  27  affixed to the circuit board  5  in order to facilitate electrical connection of the ECU to other circuitry. 
         [0042]    Turning now to consider  FIGS. 4 to 6 , the manner in which the base  3  and the cover  4  are inter-engaged will now be described in more detail. These Figures all show the circuit board  5  supported around its periphery by the support ring  10  of the base  3 , such that the underside surface  11  of the circuit board  5  is in contact with the support ring  10 . 
         [0043]      FIG. 4  shows the cover  4  positioned above the base  3  prior to engagement with the base  3 , and thus shows the cover in its natural, relaxed and un-deformed, condition. As will be noted, in this condition, the cover  4  is too large to fit inside the opening  9  of the base as defined by its peripheral sidewall  14 . The upturned flange  25  of the cover  4  thus rests against the upper edge of the base sidewall  14 . Additionally, it is to be noted that the base  3  is shown received within a supporting tool  28 . 
         [0044]    In order to inter-engage the base  3  and the cover  4 , the cover  4  is pressed downwardly towards the base. This may be achieved by applying downwards pressure via a pressing tool configured to bear against the upper surface of the planar region  24  of the cover, preferably around the entire extent of the cover  4 , so as to apply a downwards force F to the cover as denoted by arrow F in  FIG. 5 . Alternatively, however, the cover  4  may be pressed downwardly towards the base  3  by applying downwards pressure via a pressing tool configured to bear instead against the re-entrant region  22  of the cover, preferably around the entire extent of the re-entrant region, so as to apply a downwards force to the cover as denoted by arrow F′ in FIG.  5 . In either case, the applied downwards pressure is thus effective to urge the cover  4  towards the base  3 . In more detail, and as shown in  FIG. 5 , because of the inherent deformability of the cover  4 , and the relative rigidity of the base  3 , the peripheral region of the cover  4  will thus be elastically and plastically deformed as the upturned flange  25  is forced past the upper edge  17  of the sidewall  14 . This may be further facilitated by the provision of a chamfer on the inside of the upper edge  17  as illustrated. 
         [0045]    The cover  4  is thus deformed by bending about the connection between the upturned flange  25  and the planar region  24 , and by bending about the shoulder  23  between the planar region  24  and the re-entrant region  22 . 
         [0046]    Continued application of the downwards pressing force F pushes the cover  4  downwardly into the recessed opening  9  of the base  3  until the peripheral edge  20  of the cover moves past the groove  16  in the sidewall  14 , whereupon the inherent resiliency of the cover  4  causes the peripheral edge  20  to spring outwardly into engagement with the groove as snap fit, as illustrated in  FIG. 6 . Nevertheless, even when the peripheral edge  20  of the cover is engaged in the groove  16  in this manner, the cover will still be elastically deformed on account of having been pressed into the smaller opening  9  of the base  3 . The base  3  and the cover  4  are thus inter-engaged via an interference fit connection which extends around the peripheral edge  20  of the cover  4  such that the peripheral edge  20  is pressed into intimate engagement with the groove  16 . The connection is therefore substantially watertight around its entire extent. 
         [0047]    Nevertheless, as illustrated in  FIG. 6 , when the peripheral edge  20  of the cover  4  is received in the groove  16 , the planar region  24  of the cover engages and bears against the seal  18 , causing a slight deformation of the seal  18 . This supplements the substantially watertight seal provided by the interference fit connection between the peripheral edge  20  of the cover  4  and the groove  16 . 
         [0048]    Furthermore, as also illustrated in  FIG. 6 , when the cover  4  is fully engaged with the base  3  as described above, the undersurface of the re-entrant region  22  of the cover contacts and bears down on the upper surface  27  of the circuit board  5 , around the peripheral region of the circuit board  5 , thereby clamping the peripheral region of the circuit board securely between the support ring  10  of the base  3  and the re-entrant region  22  of the cover  4 . 
         [0049]    The ECU of the present invention thus provides for very simple and convenient inter-engagement between the base  3  and the cover  4  of the housing  2 , which additionally provides good protection against the ingress of water into the housing  2  between the base  3  and the cover  4 , whilst also ensuring that the circuit board  5  is securely held in position within the housing  2 . 
         [0050]    However the ECU of the present invention also offers additional benefits in terms of heat dissipation. Having regard to  FIG. 7 , the arrows illustrate schematically the dissipation of heat from the circuit board  5  into both the cover  4  and the base  3  by virtue of its direct contact with both and the fact that the base  3  and the cover  4  are both made from heat conductive material. 
         [0051]    Whilst the invention has been described above with reference to a specific embodiment, it is to be appreciated that various modifications can be made without departing from the scope of the claimed invention. For example, in some variants it is envisaged that the interengagement between the peripheral edge  20  of the cover  4  and the peripheral groove  16  in the sidewall  14  of the base  3  can be further secured by a process of mechanical caulking (plastic deformation) in which the upper edge  17  of the sidewall  14  of the base is stamped or otherwise deformed at a plurality of positions spaced-apart around the periphery of the upper edge  17 . These spaced-apart deformations can be created, for example, by sharply driving a blunt tool downwardly against the upper edge  17  of the sidewall  14  in order to displace the material of the base  3  locally into even tighter mechanical engagement with the peripheral edge  20  of the cover, thereby effectively locking the peripheral edge  20  of the cover  4  into tight engagement with the groove  16  formed around the sidewall  14  of the base  3 . 
         [0052]    It is also proposed that in some embodiments the groove  16  formed around the sidewall  14  of the base  3  could be discontinuous so as to form a series of discrete groove portions spaced-apart around the sidewall  14  rather than a single entirely peripheral groove as described above. 
         [0053]    As indicated above, whilst in preferred embodiments the base  3  and the cover  4  are both made from metal, other heat conductive materials could be used instead. For example, the base  3  and/or the cover  4  could be formed from plastics material (such as fiber-reinforced plastic) having a plurality of metal particles (such as aluminium particles) distributed therein in order to provide appropriate heat conductive properties. It is envisaged that in some embodiments the base  3  could be formed from this type of conductive plastic material, whilst the cover  4  could be formed from metal. 
         [0054]    The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof. 
         [0055]    While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention. 
         [0056]    While the above description constitutes the preferred embodiment of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.