Abstract:
The present invention in one embodiment is an engine cooling fan module including a motor having a horizontally extending motor shaft, at least one plastic brush guide defining a guide axis aligned with the motor shaft, the at least one plastic brush guide including a first side wall portion extending along the guide axis, a second side wall portion generally opposite the first side wall portion, and a top portion extending between the first side wall portion and the second side wall portion, the second side wall portion defining a radial slot opened at an inner portion of the plastic brush guide, a brush slidingly positioned within the plastic brush guide, and a shunt electrically coupled to the brush and extending through the radial slot.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to electric motors or generators and, more specifically, to electric motors having a brush assembly used to create an electrical connection between a power supply and a commutator. 
       BACKGROUND 
       [0002]    Electric motors and generators are used in a variety of applications. One such application is in small electric motors which are commonly utilized in engine cooling fan modules (ECF modules). In general, a typical motor includes field windings that surround a centrally located shaft, which is rotatable mounted in the ECF motor. A commutator is mounted on the motor shaft and placed in electrical contact with a power supply by two or more brushes spaced about the commutator and in contact with the commutator. 
         [0003]    Traditionally, motor components have been supported on a skeletal frame made of metal to provide adequate support. Recently, non-metal molded motor frames and housings have been incorporated in an attempt to reduce the weight of the motor. Even in such light weight applications, the commutator brushes must be supported within the motor frame. In some designs, metal brush guides or brush boxes are attached to a plastic base, and the metal boxes support the brushes. Metal brush boxes are effective heat conductors and, as such, can help to cool the brushes. The metal brush boxes, however, exhibit undesired deformation during assembly operations, and add excessive weight. 
         [0004]    In other designs, plastic brush guides are incorporated. While effectively reducing the weight of the motor, plastic is significantly less effective at removing heat from the brushes. The reduced cooling ability lessens the efficiency of the motor. Additionally, because of structural concerns when using plastic as opposed to metal, the electrical shunt which connects the brush to other electrical components in a device is routed through an upper wall of the plastic brush guide. This horizontal extension adds to the overall height requirements of the motor which can be problematic for ECF motor applications. 
         [0005]    Accordingly, there is a need for a plastic brush guide which allows for improved heat conduction away from brushes housed therein. An ECF module that incorporates a brush guide which does not unduly increase the horizontal height of the motor portion of the ECF module would be further beneficial. 
       SUMMARY 
       [0006]    The present invention in one embodiment is an ECF module including a motor having a horizontally extending motor shaft, at least one plastic brush guide defining a guide axis aligned with the motor shaft, the at least one plastic brush guide including a first side wall portion extending along the guide axis, a second side wall portion generally opposite the first side wall portion, and a top portion extending between the first side wall portion and the second side wall portion, the second side wall portion defining a radial slot opened at an inner portion of the plastic brush guide, a brush slidingly positioned within the plastic brush guide, and a shunt electrically coupled to the brush and extending through the radial slot. 
         [0007]    In a further embodiment, an ECF module includes a horizontally extending motor shaft, at least one brush guide including a first side wall portion supported by a top portion of the at least one brush guide, a brush slidingly positioned within the brush guide, and a shunt electrically coupled to the brush and extending through a radially oriented slot located beneath the first side wall portion, wherein the first side wall portion is plastic. 
         [0008]    These and other advantages and features of the present invention may be discerned from reviewing the accompanying drawings and the detailed description of a preferred embodiment of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The present invention may take form in various system and method components and arrangement of system and method components. The drawings are only for purposes of illustrating exemplary embodiments and are not to be construed as limiting the invention. 
           [0010]      FIG. 1  depicts an exploded perspective view of an ECF module incorporating features of the present invention; 
           [0011]      FIG. 2  depicts an exploded perspective view of the electric motor of the ECF module of  FIG. 1 ; 
           [0012]      FIG. 3  depicts a top perspective view of a brush plate of the commutator and armature assembly of  FIG. 2  showing four brush guides; 
           [0013]      FIG. 4  depicts a bottom perspective view of the brush plate of  FIG. 3 ; 
           [0014]      FIG. 5  depicts a lateral cross-sectional view of a brush and plastic brush guide; 
           [0015]      FIG. 6  depicts a cross-sectional view looking toward the bottom of the brush guide of  FIG. 5  with the brush removed; 
           [0016]      FIG. 7  depicts a top perspective view of the brush guide of  FIG. 5  with the brush removed to show a spring slot in the side wall opposite to the side wall through which a shunt extends when a brush is inserted within the plastic brush guide; 
           [0017]      FIG. 8  depicts a cross-sectional view looking toward the top of the brush guide of  FIG. 5  with the brush removed 
           [0018]      FIG. 9  depicts a top perspective view of a plastic brush guide of the brush plate of  FIG. 3  with a spring and brush inserted into the brush guide; 
           [0019]      FIG. 10  depicts a top plan view of the spring of  FIG. 9 ; 
           [0020]      FIG. 11  depicts a side plan view of the spring of  FIG. 9   
           [0021]      FIG. 12  depicts a cross-sectional view of a plastic brush guide with a spring loaded therein; 
           [0022]      FIG. 13  depicts a top plan view of a “C” type poka yoke post spaced apart from a stanchion of the brush guide of  FIG. 12  and a spring slot of the brush guide; 
           [0023]      FIG. 14  depicts a top plan view of the “C” type poka yoke post of  FIG. 13  with a spring loaded in the brush guide and wedged by a spring slot and the poka yoke post; 
           [0024]      FIG. 15  depicts a top plan view of a “5” type poka yoke post spaced apart from a stanchion of the brush guide of  FIG. 12  and a spring slot of the brush guide; and 
           [0025]      FIG. 16  depicts a top plan view of the “5” type poka yoke post of  FIG. 15  with a spring loaded in the brush guide and wedged by a spring slot and an area formed by a tail limiter and the midpoint of the poka yoke post. 
       
    
    
     DESCRIPTION 
       [0026]    An ECF module generally designated  100  is shown in  FIG. 1 . The ECF module  100  includes a shroud  102 , an electric motor assembly  104 , and a fan  106 . The electric motor assembly  104 , shown in more detail in  FIG. 2 , includes a housing  108 , a brush holder and armature assembly  110 , and a bearing end plate assembly  112 . The brush holder and armature assembly  110  includes a horizontally oriented output shaft  114 , an armature assembly  116 , a commutator  118 , and a brush holder assembly  120 . The electric motor assembly  104  is used to rotate the fan  106  to provide cooling to associated components. 
         [0027]    The brush holder assembly  120  includes a brush plate  140  shown in  FIGS. 3 and 4 . The brush plate  140  includes four brush guides  142 ,  144 ,  146 , and  148  positioned about a commutator shaft opening  150 . The brush guides  142 ,  144 ,  146 , and  148  are plastic and each define a respective guide axis (only guide axes  152  and  154  of plastic brush guides  142  and  144 , respectively are shown for purpose of clarity). The guide axes are perpendicular to a commutator axis  156  which is coaxial with the output shaft  114 . Accordingly, when the electric motor assembly  104  is assembled and the commutator  118  is positioned within the commutator shaft opening  150 , the guide axes intersect the commutator  118 . 
         [0028]    The brush guides  142 ,  144 ,  146 , and  148  (also referred to herein alternatively as “plastic guides”, “plastic brush boxes” and “plastic brush guides”) are substantially identical and are further described with reference to brush guide  142  and further reference to  FIGS. 5-8 . The brush guide  142  includes a base portion  170  and an upper portion  172  ( FIG. 5 ). As used herein, “upper” refers to a location farther away from the bearing end plate assembly  112  and “lower” refers to a location closer to the bearing end plate assembly  112 . The upper portion  172  in one embodiment is integrally formed with the base portion  170 . In another embodiment, the upper portion  172  is separately formed and connected to the base portion  170  using a desired joining process. 
         [0029]    The base portion  170  includes two support tracks  174  and  176  which define a ventilation channel  178  therebetween. The support tracks  174  and  176  and ventilation channel  178  extend radially outwardly of the upper portion  172  as shown in  FIG. 6 . On the lower side of the base portion  170 , a plurality of stiffening members  180  are formed (see  FIG. 4 ). The stiffening members  180  include radial members  182  and  184 , and cross members  186  and  188 . The radial members  182  and  184  extend radially outwardly from the commutator shaft opening  150 . In one embodiment, the radial members  182  and  184  are radially coextensive with the upper portion  172 . In other embodiments, the radial members  182  and  184  extend only partially along the radial extent of the upper portion  172 . The stiffening members  180  increase the rigidity of the base portion  170  without unduly increasing the weight of the base portion  170 . 
         [0030]    The upper portion  172  includes a first side wall  190  which extends from the base portion  170  to a top wall  192  along substantially the entire length (i.e., along the guide axis  152 ) of the brush guide  142 . Two support stanchions  194  and  196  extend upwardly from the brush plate  140  along an outer side  198  of the side wall  190 . The stanchions  194  and  196  are substantially identical to the stanchions  200  and  202 , respectively, of the brush guide  144  (see  FIG. 3 ). The side wall  190  terminates at the inner stanchion  194 . A lip  204  extends radially inwardly from the inner stanchion  194  and defines a spring slot  206  as shown most clearly in  FIG. 7 . 
         [0031]    Returning to  FIG. 5 , the side wall  190  further includes an inner side  210 . As used herein, when describing a lateral view, “inner” and “outer” refer to location with respect to the guide axis of the respective plastic brush guide, with an “inner” location being closer to the guide axis than an “outer” location. The inner side  210  includes two side guide portions  212  and  214  and two generally opposing ramps  216  and  218 . The lower ramp  216  extends upwardly and laterally outwardly from the lower side guide portion  212  to a middle side wall portion  220  while the upper ramp  218  extends downwardly and laterally outwardly from the upper side guide portion  214  to the middle side wall portion  216 . 
         [0032]    The top wall  192  includes a main wall portion  230  and a stiffening member  232  (see  FIG. 7 ). The main wall portion  230  includes three ventilation ports  234 ,  236 , and  238  best seen in  FIG. 8 . The ventilation ports  234 ,  236 , and  238  extend from an upper surface  240  of the main wall portion  230  to a ventilation channel  242 . The ventilation channel  242  is defined between two lower guide surfaces  244  and  246  of the main wall portion  230 . The stiffening member  232  includes two radially extending stiffening portions  248  and  250  along with two cross members  252  and  254 . 
         [0033]    Generally opposite to the first side wall  190  is a second side wall  260 . The side wall  260  includes a lip  262  which is supported by the base portion  170 . The lip  262  extends radially outwardly from the commutator shaft opening  150  to a stanchion  264 . The stanchion  264  and the top wall  192  support an upper side wall portion  266  which extends above the lip  262 . The lip  262  and the upper side wall portion  266  define a shunt slot  268  which is opened to the radially inward side of the side wall  260  (i.e., the portion of the side wall  260  closest to the commutator shaft opening  150 ). The top wall  192  thus functions as a cantilever, supported on one side by the side wall  190  and the stanchions  194 / 196 , and supporting a load in the form of the upper side wall portion  266  on the opposite side. 
         [0034]    The lip  262  includes a side guide surface  270  generally laterally opposite to the side guide surface  212 , and a stepped portion  272  which is located laterally outwardly from the side guide surface  270  as shown in  FIG. 5 . The upper side wall portion  266  includes a side guide surface  274  generally laterally opposite to the side guide surface  214 , and a stepped portion  276  which is located laterally outwardly from the side guide surface  274  as shown in  FIG. 5 . 
         [0035]    The radially oriented shunt slot  268  allows for a lower overall height to the brush plate  140 . As used herein, “radially oriented” means that the slot is oriented such that the length of the slot in the radial direction is greater than the height of the slot in the horizontal direction (i.e., along the commutator axis  156 ). As seen most easily in  FIG. 5 , when a brush  280  is positioned within the plastic brush guide  142 , a shunt  282  can be connected to the side of the brush  280  and exit out of the shunt slot  268  on the lateral side of the plastic brush guide  142 . This low profile connection is also shown in  FIG. 9 . In  FIG. 9 , a brush  290  is loaded within the brush guide  144  and a shunt  292  connected to the brush  290  extends through a shunt slot  294 . 
         [0036]    The configuration of the brush guides  142 ,  144 ,  146 , and  148  also provides for increased air circulation which is needed for plastic brush guides since plastic is not a good conductor of heat and the non-plastic brushes generate a large amount of heat. The ventilation channel  178  (see  FIGS. 5 and 6 ) provides cooling along the bottom of the brush  280 . The ventilation channel  242  (see  FIGS. 5 and 8 ) provides cooling along the upper surface of the brush  280 . The ventilation ports  234 ,  236 , and  238  allow for increased air flow through the ventilation channel  242 . Cooling along one side of the brush  280  is provided by airflow through the open shunt slot  268  as well as the stepped portions  272  and  276  which are located laterally outwardly from the guide surfaces  270 / 274 . The other lateral side of the brush  280  is cooled by airflow through the middle side wall portion  220  which is laterally outwardly offset from the guide surfaces  212 / 214  and the brush  280 . 
         [0037]    The configuration of the plastic brush guides  142 ,  144 ,  146 , and  148  further simplifies loading of brushes into the brush guides  142 ,  144 ,  146 , and  148  as described with initial reference to  FIG. 9 . In  FIG. 9 , a portion of a spring  300  is depicted on the side of the brush guide  144  opposite to the side which includes the shunt slot  294 . The spring  300 , also shown in  FIGS. 10 and 11 , includes a coil portion  302 , a shoulder  304 , a shank  306 , and a tail  308 . 
         [0038]    The coil portion  302  is sized to fit within the brush guide  144  hole. By way of example,  FIG. 12  depicts a partial cross sectional view of the brush guide  144  with the spring  300  positioned therein. The brush guide  144  includes a middle wall portion  310  located between two ramps  312  and  314 . The brush guide  144  further includes a spring slot  316  shown in  FIG. 13  (the spring  300  is not shown in  FIG. 13 ).  FIG. 13  also shows a “C” type poka-yoke post  318  spaced apart from the stanchion  200 . 
         [0039]    Referring now to  FIGS. 10-13 , the coil  302  is formed with a diameter  320  that is slightly less than the minimum distance between the middle side wall portion  310  and the side of the brush  290  farthest from the middle side wall portion (see also  FIG. 9 ). The height  322  of the coil  302  is sized to be slightly less than the height of the middle side wall portion  310  while the thickness  324  of the spring  300  at the shoulder  304  is sized slightly less than the width of the spring slot  316 . The length of the shoulder  304  is selected such that the shoulder  304  extends from the spring slot  316  to a location just past the stanchion  200  as shown in  FIG. 14 . The length of the shank  306  is selected such that the shank  306  extends from the shoulder  304  to a location just beyond a midpoint  326  of the poka-yoke post  318 . 
         [0040]    Accordingly, when the spring  300  is positioned within the brush guide  144  as in  FIG. 12 , the lower and upper ramps  312 / 314  maintain the coil  302  therebetween without generating excess friction as the coil  302  is wound/unwound. This allows the coil  302 , which is positioned outwardly of the brush  290 , to provide a relatively constant pressure on the brush  290 . 
         [0041]    Additionally, the shoulder  304  fits within the spring slot  316  (see  FIG. 14 ) while the tail  308  is at a location beyond the midpoint  326 . The configuration of the spring slot  316 , the post  318 , and the spring  300  thus ensures that the spring is properly inserted. Moreover, once the spring  300  is thus wedged into position, the potential for dislodgement of the spring as the brush  290  is loaded is reduced. Specifically, as the brush  290  is loaded into the brush guide  144 , by pushing the outer end of the brush  290  radially outwardly against the coil  302  within the brush guide  144 , the tail  308  is wedged more tightly against the post  318  and the shoulder  304  is wedged against the spring slot  316 , thereby reducing the potential for dislodgement. 
         [0042]    A poka-yoke arrangement may further be used to ensure that the correctly sized spring is used with a particular brush guide. By way of example, the spring  300  must have a sufficiently long shank  306  in order to position the tail  308  beyond the midpoint  326  of the “c” type post  318  of  FIG. 14 . Of course, if a spring with a shank that is too long is used, an incorrectly sized spring may still be loaded. This type of mistake may be averted by incorporating a “5” type post like the post  340  of  FIG. 15 . 
         [0043]    The post  340  is similar to the post  318  and is shown adjacent to the brush guide  144 . The post  340  includes a midpoint  342  that is spaced apart from the stanchion  200 . The post  340  further includes a tail limiter  344 . Accordingly, so long as a properly sized spring is used, the tail  308  will fit in the space between the midpoint  342  and the tail limiter  344  as depicted in  FIG. 16 . A spring with a shank that is too short or too long, however, will not fit properly. 
         [0044]    While the present invention has been illustrated by the description of exemplary processes and system components, and while the various processes and components have been described in considerable detail, applicant does not intend to restrict or in any limit the scope of the appended claims to such detail. Additional advantages and modifications will also readily appear to those skilled in the art. The invention in its broadest aspects is therefore not limited to the specific details, implementations, or illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant&#39;s general inventive concept.