Patent Publication Number: US-6699076-B2

Title: Connector assembly with metal oxide varistor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The application claims priority to U.S. Provisional Application No. 60/328,776, which was filed on Oct. 9, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to connector assembly for an electronic control unit that incorporates surge protection directly into a connector housing. 
     Electronic control units can be used in various vehicle applications to transmit signals to control vehicle devices such as an airbag assembly, for example. The electronic control unit includes a printed circuit board mounted within a housing. A connector assembly is used to electrically connect the printed circuit board to the respective vehicle device. A surge protection device is incorporated into the electronic control unit to divert extra current to ground when operating voltages exceed a predetermined voltage limit. 
     One example of a surge protection device is a metal oxide varistor (MOV). The MOV typically includes a piece of metal oxide material in the middle that is joined to a power line and a grounding line by a pair of semiconductors. Traditionally, the MOV is mounted directly to the printed circuit board. Mounting the MOV on the printed circuit board itself takes up valuable space that could be used for other components or which prevents the size of the printed circuit board from being reduced to be used in applications requiring smaller electronic control unit modules. 
     Thus, it is desirable to have an electronic control unit that includes surge protection without requiring a surge protection device to be incorporated into the printed circuit board itself, as well as overcoming the other above-mentioned deficiencies with the prior art. 
     SUMMARY OF THE INVENTION 
     A connector assembly for an electronic control unit includes a metal oxide varistor (MOV) that diverts current when system operating voltages exceed a predetermined voltage limit. The MOV is directly incorporated into the connector assembly to reduce the size of an associated printed circuit board. 
     In one disclosed embodiment, the connector assembly is used to connect the printed circuit board to a vehicle device. The connector assembly includes a first connector that cooperates with the printed circuit board and a second connector that cooperates with the vehicle device. The MOV is mounted within one of the first or second connector housing members. 
     Preferably, the connector housing has a mount interface that includes a pair of holes. The MOV has a central body portion with a pair of transversely extending legs. The legs are received within the holes to directly connect the MOV to the connector housing. The connector assembly and MOV are soldered together to establish a secure connection for the assembly. 
     The subject system and method incorporates the MOV into the connector assembly for an electronic control unit to increase space on the associated printed circuit board for other components, or optionally, allow the size of the printed circuit board to be reduced. These and other features of the present invention can be best understood from the following specifications and drawings, the following of which is a brief description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of an electric control unit for controlling a vehicle device, which incorporates the subject invention. 
     FIG. 2 is an exploded view of a connector assembly for the electronic control unit incorporating the subject invention. 
     FIG. 3 is a front view of the assembly of FIG. 2 showing the metal oxide varistor in an installed position. 
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     An electronic control unit (ECU) is shown generally at  10  in FIG.  1 . The ECU  10  includes a housing  12  that encloses a printed circuit board (PCB)  14  as known. The ECU  10  is preferably connected to a vehicle device  16 , such as an airbag assembly for example, with a connector assembly  18 . 
     The connector assembly  18  includes a first connector  20  operably associated with the PCB  14  and a second connector  22  operably associated with the vehicle device  16 . The first  20  and second  22  connectors are mated together to electrically connect the ECU  10  to the vehicle device  16 . 
     As shown in FIG. 2, a metal oxide varistor (MOV)  24  is installed within the connector assembly  18  to divert current when operating voltages exceed a predetermined voltage limit. The MOV  24  can be installed within either the first  20  or second  22  connector. 
     The MOV  24  serves as a surge protection device to dissipate voltage surges or spikes in the connection, to ground. A surge protection device such as the MOV  24  forms a connection between a “hot” power line and a ground line. Typically a MOV  24  includes a piece of metal oxide material in the middle and is joined to the power and grounding lines by a pair of semiconductors. 
     The semiconductors have a variable resistance that is dependent on voltage. When voltage is below a certain level, the electrons in the semiconductors flow in such a way as to create a very high resistance. When the voltage exceeds that level, the behavior of the electrons is modified to create a lower resistance. When the operating voltage is normal, the MOV  24  does nothing. When the voltage surges or spikes, the MOV  24  operates to conduct a significant portion of current to eliminate or reduce the extra voltage. 
     Once the extra current is diverted through the MOV  24  to ground, the voltage returns to a normal operating level and the resistance of the MOV  24  returns to the high level. Thus, the MOV  24  only diverts the surge current while still allowing the standard current to continue powering the respective vehicle device  16 . 
     The first  20  and second  22  connectors of the connector assembly  18  each include a housing portion  26 . The housing portion  26  includes a first support structure  28  for a first plurality of leads  30  and a second support structure  32  for a second plurality of leads  34 . The first  28  and second  32  support structures are preferably spaced apart from one another be a predetermined distance that depends on the number and types of leads  30 ,  34  used in the connector assembly  18 . A base  36  of the housing portion  26  includes a mount interface  38  for attachment of the MOV  24 . The mount interface  38  is located between the first  28  and second  32  support structures. 
     The mount interface  38  preferably includes a pair of holes  40  that are pre-formed in the base  36 . The holes  40  are centrally located within the housing portion  26  at approximately an equal distance from the first  30  and second  34  plurality of leads. 
     The MOV  24  includes a central body portion  42  with a pair of transversely extending legs  44 . The legs  44  are received within the holes  40  to directly mount the MOV  24  to the housing portion  26 . Once the legs  44  are inserted into the holes  40  and the first  20  and second  22  connectors are mated together, the MOV  24  and connectors  20 ,  22  are soldered together to form a secure connection between the ECU  10  and the vehicle device  16 . The soldering process is well known in the art and thus will not be discussed in detail. An assembled MOV  24  in the connector housing portion  26  is shown in FIG.  3 . 
     Mounting the MOV  24  directly within the connector assembly  18  removes the MOV from is traditional position on the PCB  14  and allows the overall size of the PCB  14  to be reduced, or optionally, frees up additional space on the PCB  14  for other components. By placing the MOV  24  in the connector assembly  18 , a space savings of more than 80 square millimeters has been realized on the top side of the PCB  14  and a space savings of approximately 400 square millimeters has been realized on the solder side of the PCB  14 . 
     Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.