Abstract:
An electric motor has a housing closed at one end by an end plate assembly including a motor driver transistor. The transistor is mounted on a disk and is connected to brushes by lead frames that have ends terminating in a projection integral for connection to an electronic control unit associated with the motor.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates generally to electric motors with motor driver transistors and, in particular, to an electric motor with an integrated motor driver transistor.  
           [0002]    Electric motor drivers that utilize electronic switching devices such as transistors, for control, are well known in the art. Motor driver transistors have generally been installed remotely from the electric motor to which they are connected. A typical location for a motor driver transistor is in the Electronic Control Unit (ECU) of the system of which the motor is a part. An example of such a system is an automobile ABS braking system. The ECU functions to control the operation of the system, including the operation of the electric motor which may be attached to a hydraulic pump or the like. Locating the motor driver transistor on the ECU poses a number of inherent problems, including greater difficulty in managing the electric current through the ECU. Another problem is the difficulty in dissipating the heat generated by the combined electronic components of the ECU and the motor driver transistor; the heat dissipation is necessary for the circuits of the motor driver transistor and ECU to operate within their respective safe operating zones. Yet another problem in locating the motor driver transistor on the ECU is the design condition where the power connector is located on the ECU housing. This makes the ECU housing larger in size.  
           [0003]    It is desirable to remedy the electric current and heat load problems associated with ECUs that contain motor driver transistors. It is also desirable to reduce the size of the ECU, and further to be able to move the power connector from the ECU housing to the motor housing. It is also desirable to provide a motor diagnostic and monitoring means as part of the motor housing in order to observe the performance of the electric motor and thereby diagnose problems with motor operation.  
           [0004]    The primary objective of the present invention is to integrate a motor driver transistor within an electric motor and thereby reduce the size and cost of the ECU. Another objective of the present invention is to integrate the power connector into the motor end plate and remove the power connector from the ECU housing, which will also reduce the size and cost of the ECU. A further objective of the present invention is to integrate a current sensing resistor and/or a motor diagnostics line with the electric motor. The ability to measure the electric motor current can enhance the performance of the motor and the electrical system of which it is a component.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention achieves the objectives noted above by providing a novel electric motor end plate with an integrated motor driver transistor. By integrating the motor driver transistor as part of the motor housing end plate, the electric current control and thermal load management of the ECU can be improved.  
           [0006]    Prior art electric motors that utilized motor driver transistors, as noted above, located the motor driver transistor remotely from the motor. The present invention incorporates the electronic switching device, or motor driver transistor, as a part of the end plate of the electric motor housing, which permits the ECU to be of a much smaller size. This novel integrated motor driver transistor allows the power connection to be moved from the ECU to the motor housing, which also permits the ECU to be of a much smaller size. In addition, the novel integrated motor driver transistor allows the motor to be fitted with at least two types of diagnostic circuits. These circuits, when connected to proper instrumentation, are able to provide better monitoring and diagnosis of the motor under operating conditions. The present invention contemplates integrating a power connector, a motor connector or both types of connectors as part of the end plate of the electric motor housing. The present invention also contemplates utilizing a field effect transistor (FET) or a bipolar junction transistor (BJT) as the motor driver transistor, but those skilled in the art will recognize that other types of electronic switching devices may be used while still remaining within the scope of the invention.  
           [0007]    A preferred embodiment of the present invention is disclosed having an electric motor with the novel integrated motor driver transistor.  
           [0008]    Another embodiment of the present invention is disclosed having an electric motor with the integrated motor driver transistor and an integral motor connector.  
           [0009]    Yet another embodiment of the present invention is disclosed having an electric motor with the integrated motor driver transistor, an integral motor connector, and an integral motor diagnostics line.  
           [0010]    Still another embodiment of the present invention is disclosed having an electric motor with the integrated motor driver transistor, an integral motor connector, and an integral current sensing resistor. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0011]    The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which:  
         [0012]    [0012]FIG. 1 is an end elevation view of an electric motor having an end plate assembly in accordance with the present invention;  
         [0013]    [0013]FIG. 2 is a cross-sectional view of the end plate assembly shown in FIG. 1; FIG. 3 is an end elevation view of a second embodiment of the electric motor shown in FIG. 1;  
         [0014]    [0014]FIG. 4 is an end elevation view of a third embodiment of the electric motor shown in FIG. 1; and  
         [0015]    [0015]FIG. 5 is an end elevation view of a fourth embodiment of the electric motor shown in FIG. 1. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]    Referring to FIGS. 1 and 2, an electric motor end plate is indicated generally at  2  and includes a generally tubular housing  4  that receives a bearing  6  in one end opening. Not shown are an opposite end of the housing  4 , and conventional rotor and stator components. A disk  8  with an aperture in its center is also received in the housing  4  and surrounds the bearing  6 . The disk  8  serves as a heat sink for the electric motor end plate  2  and is preferably constructed of an electrically insulated yet thermally conductive material, such as aluminum with a nonconductive coating. The bearing  6 , preferably of a ball or roller bearing type, rotatably supports a motor shaft  10 , and a hollow, generally cylindrical motor commutator  12  receives the shaft  10  at a point farther along the axis of the shaft  10 , as best seen in FIG. 2. At least two motor brushes  14  contact the circumference of the commutator  12 . At least one of the brushes  14  is electrically connected to an integral motor driver transistor  16 . The brushes  14  and the commutator  12  alternate fields in the rotor (not shown) to provide torque to rotate the shaft  10  in a manner well known in the art.  
         [0017]    The motor driver transistor  16  is connected electrically in series with the commutator  12  and the brushes  14 . The motor driver transistor  16  is connected electrically in series with the commutator  12  and the brushes  14 . The motor driver transistor  16  has a control contact  18  and a ground contact  20 . For embodiments using a field effect transistor (FET) as the motor driver transistor  16 , the control contact  18 , the case contact of the transistor  16  and the ground contact  20  typically are the gate, drain, and source. For embodiments using a bipolar junction transistor (BJT) as the motor driver transistor  16 , the control contact  18 , case contact of the transistor  16 , and ground contact  20  typically are the base, collector, and emitter. The electrical connections between the various electrical components are made by lead frames that are bonded to the disk  8  in order to dissipate the heat generated by the motor  2  and the transistor  16 . The disk  8  also helps hold the lead frames in place during the plastic overmolding process mentioned below. The lead frames are flat plates shaped to fit within the housing  4  and are constructed of electrically conductive material, for example tin-plated brass or tin-plated copper. A radial projection  22  on the circumference of the motor end plate  2  contains terminal ends of at least three lead frames that provide external power and signals to the electric motor (not shown) attached to the motor end plate  2 . A motor driver transistor control lead frame  24  connects an output signal from an ECU (not shown) to the control contact  18  on the motor driver transistor  16 . A ground lead frame  26  connects the ground polarity of a power source, such as an automotive alternator or battery (not shown) to the ground contact  20  on the motor driver transistor  16 . A positive lead frame  28  connects the positive polarity of the power source (not shown) to one of the motor brushes  14 . An additional lead frame  30  connects the case contact of the motor driver transistor  16  and the other one of the brushes  14 . While the electric motor end plate  2  has been shown with a radial projection  22 , those skilled in the art will realize that, alternatively, the electric motor end plate  2  may not include a radial projection  22 , and the lead frames  24 ,  26 , and  28  may be attached to electric wire connections (not shown) extending from the motor end plate  2 , while still remaining within the scope of the invention.  
         [0018]    Referring now to FIG. 2, a plastic overmold or end plate  32  is formed during the construction of the motor  2  to set the various components in place after the parts have been placed in their correct positions and to provide the projection  22 . The overmold/end plate  32  functions as an end wall closing the open end of the housing  4  and retaining the bearing  6  and the disk  8  while providing sliding support for the brushes  14 . A lead frame  37  in FIG. 2 is shown only for the purpose of representing the axial position of the previously mentioned lead frames  24 ,  26 ,  28 , or  30 , relative to the metal disk  8 , the motor brushes  14 , and the motor driver FET  16 . An O-ring  34 , set in an annular channel  36  in the plastic overmold  32 , seals the shaft  10  and the bearing  6  of the motor  2  when abutted against an adjacent surface (not shown) of, for example, a pump.  
         [0019]    Referring to FIG. 3, the motor indicated generally at  2 A contains many of the same elements as in FIG. 1, but further has two projections from the end plate  32 A. The first projection  38 , in the same location as the projection  22  in FIG. 1, is a two-pin power connector that supplies power from a power source (not shown), such as an automobile battery or alternator. The power connector  38  contains two lead frames, a ground lead frame  26 A and a positive lead frame  28 A, which perform the same function as the ground lead frame  26  and the positive lead frame  28  shown in FIG. 1. By locating the power connector  38  as part of the end plate  32 A, the ECU (not shown) can be made smaller. A second radial projection  40  from the end plate  32 A is an integral motor connector that is used to electrically connect through various lead frames the ECU (not shown) to the motor  2 A. The integral motor connector  40  contains terminal ends of at least three lead frames, including the ground lead frame  26 A and the positive lead frame  28 A. The integral motor connector  40  further contains a motor driver transistor control lead frame  24 A that connects an output signal from the ECU (not shown) to the control contact  18  on the motor driver transistor  16 . While the electric motor end plate  2 A has been shown with a power connector  38 , those skilled in the art will realize that, alternatively, the electric motor end plate  2  may not include a radial projection  38 , and the lead frames  24 A,  26 A, and  28 A may be attached to electric wire connections (not shown) extending from the motor end plate  2 , while still remaining within the scope of the invention.  
         [0020]    Referring to FIG. 4, the motor indicated generally at  2 B contains many of the same elements as in FIG. 3, including the power connector  38  and the integral motor connector  40 , but the integral motor connector  40  contains the ends of four lead frames. The ground lead frame  26 A, the positive lead frame  28 A, and the motor driver transistor control lead frame  24 A perform the same function as in FIG. 3. A fourth lead frame, a motor diagnostics lead frame  30 A, also extends into the projection  40  and connects the ECU (not shown) to the case contact of the motor driver FET  16 . The motor diagnostics lead frame  30 A also connects the motor driver FET  16  with one of the motor brushes  14 . The ability to diagnose the functioning of the motor  2 B during operating conditions can enhance the performance of the entire electrical system.  
         [0021]    Referring to FIG. 5, the motor indicated generally at  2 C contains many of the same elements as in FIGS. 3 and 4, including the power connector  38  and the integral motor connector  40 , but the motor  2 C further contains a current sensing resistor  44  that is mounted on the end plate  32 A. The current sensing resistor  44  is electrically connected in series with the gate contact  20  of the motor driver transistor  16  (by a motor transistor current monitoring lead frame  42 ) and a ground lead frame  26 B that terminates in both the power connector  38  and the integral motor connector  40 . As in FIG. 3, the lead frame  30  electrically connects the case contact of the motor driver transistor  16  with one of the motor brushes  14 , and a motor driver transistor control lead frame  24 A is provided to connect the ECU (not shown) to the control contact  18  of the motor driver transistor  16 . The ability to measure the current of the motor assists in diagnosis and enhances control of the motor under operating conditions.  
         [0022]    In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.