Abstract:
Disclosed herein is a vehicle dynamoelectric machine electrical system. The system includes, a housing having a boss, and at least one electrically insulative member in operable communication with the boss and capable of electrically isolating the housing from a bracket configured to mount the housing.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The increasing power density of vehicle dynamoelectric machines has resulted in some dynamoelectric machines using housings of the machine as heat sinks for electrical components and circuits. Designers typically connect the negative of a circuit to the housing and the housing is electrically connected to the vehicle ground through mounting to a bracket. This system often works fine; however, in some applications disruptive electromagnetic interference (EMI) can emanate from the vehicle ground due to this grounding methodology. Systems and methods to reduce or minimize the EMI would be well received in the industry. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0002]    Disclosed herein is a vehicle dynamoelectric machine electrical system. The system includes, a housing having a boss, and at least one electrically insulative member in operable communication with the boss and capable of electrically isolating the housing from a bracket configured to mount the housing. 
         [0003]    Further disclosed herein is a method of controlling electrical transients in a vehicle electrical system. The method includes, electrically connecting a negative portion of a circuit of a dynamoelectric machine to a housing, and electrically insolating the housing from a bracket securing the dynamoelectric machine to a vehicle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
           [0005]      FIG. 1  depicts a perspective view of a dynamoelectric machine having a grounding system disclosed herein with a cover of the dynamoelectric machine removed; and 
           [0006]      FIG. 2  depicts a cross sectional view through a dynamoelectric machine mounting bolt. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0007]    A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
         [0008]    Referring to  FIG. 1 , an embodiment of the vehicle dynamoelectric machine grounding system  10  disclosed herein is illustrated. The system  10 , among other things, includes a dynamoelectric machine  14 , shown here as an alternator, a circuit  18  having a positive portion  22  electrically connected to a positive (B+) terminal  26  and a negative portion  30  electrically connected to a negative (B−) terminal  34  and electrically connected to a housing  38 . The negative portion  30  and B− terminal  34  are electrically connected to the housing  38  by a plurality of negative diodes  42  that are press fitted into and electrically connected to the housing  38  directly, or a separate member that is electrically connected to the housing  38 . This press fit between the diodes  42  and the housing  38  allow heat generated in the diode  42  to efficiently pass into the housing  38  thereby using the housing  38  as a heat sink. A bracket  46  and one or more of bolt(s)  50  structurally mounts the housing  38  to an engine block  40 . Electrically nonconductive insulators  54  electrically insulate the housing  38  from the bolt(s)  50  and the bracket  46  as will be described in detail with reference to  FIG. 2  below. As such, the housing  38  is electrically insolated from the bracket  46  and engine block  40 , unlike grounding systems that are typical in automotive and heavy-duty vehicle applications. A cable  58  connected to the B− terminal  34  is connected directly to a negative terminal  59  of a battery  60 . Similarly, a cable  62 , connected to the B+ terminal  26 , is directly connected to a positive terminal  61  of the battery  60 . 
         [0009]    The high capacitance of the battery  60  allows large amounts of current to flow to and from the battery  60  with little resistance. By connecting the negative portion  30  of the circuit  18 , shown herein as a regulator, directly to the battery  60  through the cable  58 , and not via engine parts and components of a vehicle frame (not shown), EMI is much easier to control. This is due to the control over mechanical parameters, such as, size, shape and routing and electrical parameters, such as, resistance, inductance and capacitance, for example, available with the cable  58  that is not available with a ground that runs through multiple paths of multiple vehicle components. 
         [0010]    Referring to  FIG. 2 , the alternator  14 , in this embodiment, is structurally mounted to the bracket  46  by the one or more bolt(s)  50 , with two bolts  50  being shown and two bolts  50  being hidden from view (in  FIG. 2 ) on a backside of the alternator  14 . Each of the bolts  50  passes through a hole  66  in a boss  70  protruding from the housing  38  and a hole  74  in a flange  78  of the bracket  46 . Additionally, each bolt  50  passes through nonconductive insulators  54  that electrically insulate the bolt  50  and bracket  46  from the housing  38 . The insulators  54  consist of three portions, a first insulating portion  54 A, a second insulating portion  54 B and a third insulating portion  54 C. The portions  54 A and  54 B are flat with holes  82  and  86  therethrough respectively, through which the bolt  50  passes. The first insulating portion  54 A electrically insulates a first surface  94  of the boss  70  from a head  90  of the bolt  50 . Similarly, the second insulating portion  54 B electrically insulates a second surface  102  of the boss  70  from the flange  78 . The third, cylindrically shaped, insulating portion  54 C electrically insulates an inner surface  106  of the boss  70  from a shaft  110  of the bolt  50 . The bolt  50  is threadably engaged with threaded hole  114  in the engine block  40  to axially compress the first insulating portion  54 A, the boss  70 , the second insulating portion  54 B and the flange  78  between the engine block  40  and the head  90 . Alternately the bolt  50  can be threaded into a threaded hole in the bracket directly. It should be noted that the three insulating portions  54 A,  54 B,  54 C, although disclosed in this embodiment as being three separate parts, may be combined as two parts or even as a single part depending upon specifics of a particular application and methods of assembly employed. The portions  54 A,  54 B and  54 C may be fabricated of any suitably durable insulating material, such as, ceramic, polymeric, elastomeric or paper, for example. 
         [0011]    While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.