Abstract:
The present disclosure provides an electric motor for use in a vehicle. The disclosure includes a stator comprising a plurality of stator coils separated by the stator core. The stator coils have insulation thereon. The disclosure further includes an abrasion resistant layer covering at least a portion of the stator coil. The abrasion resistant layer is a porous material capable of resisting the abrasive effect of particulate matter within the air used to cool the motor.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates generally to electric motors. More specifically, it relates to an improved process for the protection of coil insulation in electric motors cooled with air containing abrasive particles.  
         BACKGROUND OF THE INVENTION  
         [0002]    Locomotives and large industrial trucks typically use electric motors to mobilize the vehicle. Diesel engines on the vehicle are attached alternators to generate electricity to power the motors, and air from the external environment vehicle is used to cool the motors. For example, U.S. Pat. No. 6,148,940 discloses an AC motorized wheel arrangement that uses air from the exterior of an industrial truck to cool a pair of drive motors. Typically, these vehicles are utilized in environments that have a high concentration of grit and dust. Because the electric motors use air for cooling the motors that has been taken from the work environment with little or no filtering, the cooling air has a sandblasting effect when circulated through the motor. It has been found that this sandblasting effect can eventually erode the insulation from stator coils used to energize the stators of the motor and cause failure of the motor.  
         SUMMARY OF THE INVENTION  
         [0003]    The present invention provides an electric motor for use in a vehicle. The invention comprises a stator comprising a plurality of stator coils inserted into the stator core. The stator coils are made of copper conductors having insulation thereon. The invention further comprises an abrasion resistant layer covering at least a portion of the stator coil. The abrasion resistant layer is a porous material capable of resisting the abrasive effect of particulate matter within the air used to cool the motor. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]    The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself, however, both as to organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings, where like numerals represent like components, in which:  
         [0005]    [0005]FIG. 1 is a sectional side view of one embodiment of the present invention;  
         [0006]    [0006]FIG. 2 is a partial cut out and perspective view of the embodiment of FIG. 1;  
         [0007]    FIGS.  3 - 6  are respective rear, side, perspective, and top views of a cooling embodiment of the present invention;  
         [0008]    [0008]FIG. 7 is a side view of a portion of a motor frame having cooling air holes;  
         [0009]    [0009]FIG. 8 is a partial view of the stator, stator coils and abrasion resistant layer of an embodiment of the present invention;  
         [0010]    [0010]FIG. 9 is a side and top view of a insertion of the abrasion resistant layer of an embodiment of the present invention.  
         [0011]    [0011]FIG. 10 is a top view of the felt being held in place by the tip of the wedge and a small felt pad. This process is to secure the felt prior to VPI. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0012]    [0012]FIG. 1 is a sectional side view of one embodiment of the present invention, and FIG. 2 is a partial cut out and perspective view of the embodiment of FIG. 1. An AC motorized wheel arrangement  1  of the present invention includes an AC motor  10 , a transmission  12 , a wheel frame  14 , a wheel hub  16 , and a service brake  18 . A truck with which the motorized wheel will be used is shown in block form as element  34  in FIG. 2.  
         [0013]    A single motorized wheel is shown in FIGS. 1 and 2. In practice, two motorized wheels are used with the other, unshown motorized wheel substantially similar to a mirror image of that shown in FIG. 1. For purposes of the present invention, as shown in FIG. 1, the term “outboard side” with respect to a motorized wheel, means a portion of the motorized wheel in the direction of the outboard arrow (away from a center line of the truck) and the term “inboard side” refers to a portion of the motorized wheel in the direction of the inboard arrow.  
         [0014]    Wheel frame  14  supports the motorized wheel components and includes a flange  20  that can be bolted directly to an axle box  36  of the truck. In one embodiment, a motor frame  15  of the AC motor is mounted with bolts  13  on a portion of the wheel frame on the inboard side of the wheel, and the transmission is mounted to a portion of the wheel frame on the outboard side of the wheel. The wheel frame provides a standard interface to the truck and thus permits easy removal and replacement of the motorized wheel assembly from the truck.  
         [0015]    Roller bearings  22  are situated between the wheel frame and the wheel hub for supporting the wheel hub and allowing it to turn on the outside of the wheel frame. The wheel hub is turned by the transmission. Rims  30  and tires  32  are mounted to and rotate with the wheel hub.  
         [0016]    The service brake is mounted between the frame flange  20  and wheel hub  16 . This is a useful position for the service brake for two reasons: (1) the brake is between the rotating portion (wheel hub) and the stationary portion (wheel frame) of the wheel and (2) the brake can be oil cooled with the wheel frame geometry in the area of the brake providing a reservoir of cooling oil for the brake.  
         [0017]    The AC motor converts electrical energy to mechanical energy that turns a shaft  24  connected to the transmission. In one embodiment the transmission comprises a double reduction transmission, and the shaft is connected to a high speed portion  26  of transmission  12 . The high speed portion of the transmission then turns the low-speed portion  28  of the transmission that is bolted to the wheel hub with bolts  27  and  29  through a torque tube  31 .  
         [0018]    FIGS.  3 - 6  are respective rear, side, perspective, and top views of a cooling embodiment of the present invention. As shown in FIG. 4, one or more blowers  33  in the front of the truck supply cooling air to axle box  36  through air inlet duct  35 . As shown in FIGS. 3 and 6, cooling air from the axle box enters the motors through air holes  21  which are provided in motor frames  15  (which are secured with bolts  13  to flanges  20  of frames  14  of wheels  450  and  452 ). FIG. 7 shows a portion of the stator core  500  and the stator frame  702  with axial vent holes  705 . The stator coil  502  is held in the stator slot by a wedge  704  that is driven into the slot over the coil. Air enters the motors from the outboard ends of the motors and passes through motors  10  toward the inboard ends. The motors are attached to an air outlet housing element  410  that directs the air through an opening  425  in the rear of the axle box.  
         [0019]    As shown in FIGS. 4 and 5 the outlet housing preferably includes a cylindrical portion  414  having two circular openings  412  corresponding to the two motors. The outlet housing can be attached to the motors with any appropriate device. In one embodiment, the motors are bolted to the outlet housing with bolts  423 . The outlet housing can be tapered to provide a smaller air outlet opening  419  that is shown as a rectangular portion  418 . In one embodiment, the outlet housing can be angled in a downward direction. Tilting the outlet housing downwards is useful for preventing debris from falling into the air outlet from the truck body or from the top of the axle box.  
         [0020]    The rectangular portion of the outlet housing can be attached to a hose  422  by a housing coupler  420  which can further narrow the available air path, and the hose can be coupled by an axle box coupler  424  to create an opening having the same diameter as the axle box opening. In one embodiment, outlet housing  410  and couplers  420  and  424  comprise sheet steel, hose  422  comprises a flexible air duct hose, and cover  426  comprises steel.  
         [0021]    As shown in FIG. 5, in one embodiment outlet housing  410  may comprise three portions: two side cowlings  415  and a center wrap portion  417 . This structure provides easy access for bolting the cowlings  415  to the frames of motors  10 . Housing coupler  420  may be secured with bolts  454  to the side cowlings. Center wrap portion  417  may include tabs  429  that fit through loops  421  of the housing coupler to secure the center wrap portion of the outlet housing to the housing coupler.  
         [0022]    Although hose  422  and couplers  420  and  424  are shown as having circular cross-sections, the present invention does not require a specific shape for the cross sections. Furthermore, the air path does not need to be narrowed in the manner shown in FIGS.  3 - 6 .  
         [0023]    [0023]FIG. 8 shows the stator  500  of one of the motors. The stator coils  502  are separated by the stator core  506 . To prevent gritty air entering the outboard ends of the motors (FIG. 6) from abrading the insulation of stator  500 , the exposed surfaces of the coils  502  are covered with an abrasion resistant layer  508 . The abrasion resistant layer  508  is preferably a porous strip material that is pliable and has a temperature rating of at least 160 degrees Celsius. The abrasion resistant layer  508  most preferably comprises a felt material that exhibits good dimensional stability and little swelling when saturated with varnish (described below). The term varnish is used generally to describe an impregnating resin which, when cured, provides dielectric strength, moisture resistance and mechanical bonding. Additionally, felt is preferred due to its ability to absorb and retain a large quantity of varnish.  
         [0024]    The abrasion resistant layer  508  is woven between each stator coil  502  as shown in FIG. 9. Alternatively, the abrasion resistant layer may comprise several small strips  510  that together comprise the abrasion resistant layer  508 . The abrasion resistant layer is held in place by the tip of the wedge ( 704 ) next to the core and by the small felt strips ( 510 ) inserted between the coils shown in FIG. 10. After installation, abrasion resistant layer  508  is subjected to a known VPI (vacuum-pressure-impregnation) process that saturates the abrasion resistant later  508  with varnish and then is baked to harden the varnish. While the abrasion resistant layer is described pliable, the abrasion resistant layer could be a premolded strip or several premolded portions.  
         [0025]    The hardened, varnish-impregnated abrasion resistant layer  508  exhibits excellent resistance to the “sandblasting” effect of the cooling air blown through the motor and protects the stator coil insulation from erosion. Further, the abrasion resistant layer fills the air gap between the stator coils  502  thereby reducing noise that would other wise be transmitted through the air gap. As a result, the noise wads used in AC electric motors to suppress the operating noise of the motor are no longer required.  
         [0026]    While only certain preferred features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.