Patent Publication Number: US-6661140-B2

Title: Brushless motor having housing enabling alignment of stator and sensor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation-In-Part of application U.S. Ser. No. 10/014,711, now U.S. Pat. No. 6,570,284, entitled Brushless Motor Having Double Insulation, filed Dec. 11, 2001 in the U.S. Patent and Trademark Office. The contents of the aforementioned Application are incorporated herein by reference, and the benefit of priority to the same Application is claimed under 35 U.S.C. §120. 
    
    
     FIELD OF INVENTION 
     The invention relates generally to electronically commutated brushless motors, such as switched reluctance motors, high frequency induction motors, brushless AC motors, and brushless DC motors. More particularly, the invention relates to an electronically commutated brushless motor design and assembly process that provides a robust brushless motor capable of meeting the unique functional requirements in various applications, such as portable table saws, miter saws, site saws, and TGS-type combination saws. Specifically, the invention relates to an electronically commutated brushless motor design which accurately aligns the stator stack to the rotor position by molding a sensor bridge, in which an optical sensor is installed, from the same core side of the mold as are stator locating ribs, which orient the position of the stator. 
     BACKGROUND OF THE INVENTION 
     Prior art electronically commutated brushless motors suffer from various limitations. One limitation is a restriction of airflow through the motor. In a typical universal motor housing, air is drawn in through vents in an end cap, passes over a brush gear assembly and windings, through a fan and exhausts out the other end of the motor. 
     In an electronically commutated brushless motor, air is also drawn in through an end cap but first must pass around the periphery of an electronics control module, installed at one axial end of the housing, before the air can pass through the rest of the motor. Thus, the electronics control module, which includes a potting boat holding an encapsulated printed circuit board (PCB), impedes the airflow by causing the air to first pass around the electronics control module. After passing around the electronics control module the air passes down through channels created by extruded fins of aluminum heat sinks, thereby cooling electronic components attached to the heat sinks. The air then continues over stator windings, passes through and around the stator, through a fan and exhausts out through the end of the motor. Thus, in electronically commutated brushless motors the electronics control module restricts the airflow through the motor. 
     The obstruction to airflow in electronically commutated brushless motors is further compounded by the housing molding process. To effectively mold and produce the housing, it must have draft added on both its internal (core) and external (cavity) sides. Since the geometry at the mouth of the housing is fixed by mounting interface requirements with existing products, the draft closes (i.e., narrows) the housing down about the electronics control module, thereby further restricting the airflow around the electronics control module and through the motor. 
     A second limitation of known electronically commutated brushless motors is that the motor is typically longer than a typical universal motor. Due to the overall length, electronically commutated brushless motors are difficult to utilize in many power tools where it is desirable to keep the overall axial length of the motor, or housing, as short as possible. This is especially true with saws, such as miter saws and other saws, because when the saw (and the motor coupled to the saw) is tilted at an angle, an extra long motor housing can cause interference with a fence or the table of the saw. For example, in a TGS-type combination saw, the axial length of the motor housing must be short enough so that it does not protrude beyond the frame of the saw. If it does, it will prevent the table from being flipped over. 
     As another example, the axial length of the motor in a small portable table saw should be short enough such that when attached to the saw gear case, the motor housing should fit inside the skirt that forms the base of the table. As yet another example, in a miter saw, where the bevel and miter functions will require the end of the motor to be tipped towards the table, the axial length of the motor needs to sufficiently short such that the motor will not contact the table fence when it is articulated into a tilted position for a bevel or miter cut. 
     A third limitation of known electronically commutated brushless motors is the inability to insure proper alignment of the registering means on the rotor shaft with the rotor pole, and the position sensor with the stator during the assembly process. The registering means could be any suitable registering means such as an interrupter or a magnet, and the position sensor could any suitable sensor such as an optical sensor or a Hall Effect sensor. In typical electronically commutated brushless motors, the position of the registering means, relative to the position sensor, determines the position of the rotor, relative to the stator. In electronically commutated brushless motors it is critically important to know the exact position of the rotor when the electronic switching signals, which switch the direction of the flux in the motor winding(s), are provided by an electronic controller. If the alignment of the registering means with the rotor pole is off, or the alignment of the position sensor with the stator is not precisely set, then the position of the registering means, as detected by the position sensor, will provide an inaccurate indication of the position of the rotor, relative to the stator. If the position of the rotor is not accurately determined, the electronic switching motor will very quickly lose power and torque. 
     A fourth limitation of known electronically commutated brushless motors is meeting the requirements for double insulated construction as described by Underwriters Laboratories (UL) and other compliance agencies. Double insulated motor designs, which eliminate the need for a ground wire in the power cord, have been implemented on universal motors. This is a preferred construction for hand held and table mounted power tools since the alternative, grounded tools, rely on there being a solid ground connection available on a job site, which often is not the case. The basic requirement is that the design must provide at least two levels of insulation between live components, such as the windings, and any metallic components, such as the shaft or screws, that are accessible to the user. Known electronically commutated brushless motors do not implement a double insulated construction design. 
     Therefore, it would be desirable to provide an electronically commutated brushless motor design that provides increased airflow through the motor. It would further be desirable provide an electronically commutated brushless motor having an overall axial length suitable for applications requiring a shorter motor. Even further, it would be desirable to provide an electronically commutated brushless motor design that insures accurate alignment of the optical encoder with the rotor poles, and accurate alignment of the optical sensor with the stator during assembly of the motor. Further yet, it would be desirable to provide an electronically commutated brushless motor that implements a double insulated design without significantly increasing the cost or complicating the manufacturability and/or assembly of the overall motor. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention relates to an electronically commutated brushless motor design, which overcomes the various drawbacks described above. In a preferred form, the invention relates to brushless AC motor, although it will be appreciated that the invention is also applicable to brushless DC motors. 
     In one aspect of the present invention a housing of the motor is provided with a draft angle that increases the airflow through the housing to allow more efficiently cooling of the motor. 
     In a second aspect of the present invention the electronically commutated brushless motor design provides a capacitor mounting arrangement that allows the overall axial length of the motor to be made shorter. The film capacitors associated with the electronic control system for the motor are mounted on an independent circuit board. The circuit board is adapted to slide into a housing protrusion, or bulge, formed on the sidewall of the housing rather than being positioned at one axial end of the housing. This allows the overall axial length of the housing to be made shorter, thereby allowing a wider range of applications for the motor in which the motor must be articulated into different positions without interfering with other components of its associated tool. 
     In a third aspect of the present invention the electronically commutated brushless motor provides a housing that allows accurate alignment of a stator and a position sensor, such as an optical sensor, relative to each other. This is accomplished by using a housing molding core that produces a housing that includes both a bridge on which the position sensor is mounted, and stator locating ribs. Typically, the molding core for the housing forms locating ribs on an interior surface of the housing, which are used to precisely align the stator when it is inserted into the housing, but does not include a mounting bridge for the position sensor. By molding the housing to include both a position sensor mounting bridge and the stator locating ribs, variances in the positioning of the position sensor, relative to the stator, are avoided. Therefore, the position sensor and the stator will be accurately aligned when installed, without the need for time consuming alignment procedures, or tests, during the assembly of the motor. 
     In a fourth aspect of the present invention the electronically commutated brushless motor incorporates a double insulation (DI) feature, thereby eliminating the need for a direct ground cable in the power cord. The DI design includes insulating strips between the stator and stator windings, and an insulating sleeve disposed between the rotor shaft and the rotor laminations. Therefore, there are two layers of insulation between metal parts accessible to a user and parts of the motor in which electrical current flows. Alternatively, the motor housing, which supports the stator, is also constructed of a non-conductive material. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and accompanying drawings, wherein; 
     FIG. 1 is a perspective view of a electronically commutated brushless motor in accordance with a preferred embodiment of the present invention; 
     FIG. 2 is an exploded view of the motor shown in FIG. 1, showing how the components of the motor are assembled; 
     FIG. 3 is an exploded view of the interior of the distal end of the motor housing shown in FIG. 2; 
     FIG. 4 is an exploded view of the distal end of the motor shown in FIG. 2, showing how the components at the distal end of the motor are assembled; 
     FIG. 5 is an exploded view of the housing shown in FIG. 4, showing how film capacitors are slideably inserted into a motor housing bulge; 
     FIG. 6 is an exploded view of a stator stack shown in FIG. 2; 
     FIG. 7 is an exploded view of the stator and rotor assembly shown in FIG. 2; 
     FIG. 8 is cross-sectional view of the motor shown in FIG. 1; and 
     FIG. 9 is a schematic of the housing of the motor shown in Figure, showing the location of the parting line of the core and cavity used to mold the housing. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is a perspective view of an electronically commutated brushless motor  10  in accordance with a preferred embodiment of the present invention. Motor  10  is a self-contained motor, which can be bolted directly onto a gearbox or other support means of a product, such as a power tool. Motor  10  includes a plastic motor housing  14  having an integrally formed bulge  18  protruding from an outer surface of a sidewall of the motor housing, wherein a plurality of capacitors (not shown) are inserted. Housing  14  is closed at a distal end by a vented end cap  22  and closed at the opposing proximal end by a bearing end cap  26 . 
     FIG. 2 is an exploded view of motor  10  (shown in FIG. 1) showing how the components of motor  10  are assembled. A stator stack  30 , a rotor  34  and a baffle  38  are fitted annularly inside housing  14 . Stator stack  30  comprises a stack of steel laminations fitted with stator windings (described in reference to FIG. 6 below). The stator windings are sequentially energized with electric current, thereby generating a revolving magnetic field. Stator stack  30  is precisely positioned within housing  14  using a plurality of locating ribs  40  formed on an inside surface  14   a  of a sidewall of housing  14 . In the preferred embodiment, stator stack  30  is then pressed into housing  14 , having an interference fit such that locating ribs  40  fit into stator channels  42  integrally formed in stator stack  30 , thereby maintaining an angular alignment of stator stack  30  to housing  14 . Stator stack  30  is secured in place with two screws (not shown). In an alternate embodiment, stator stack  30  is pressed into housing  14 , having an interference fit such that the geometry of stator stack  30  closely fitted against locating ribs  40  maintains the angular alignment of stator stack  30  to housing  14 . 
     Rotor  34  has no windings and is supported between a first bearing  44 , supported by bearing end cap  26 , and a second bearing  46 , supported by an integral bearing support (not shown), incorporated into motor housing  14 . Rotor  34  includes a shaft  50 , an insulating tube, or sleeve,  54 , a stack of steel laminations  58 , and a cooling fan  62  that helps to direct air through the motor  10 . Stack  58  is assembled by interlocking, welding, cleating, or bonding the steel laminations together. Insulating tube  54  is pressed onto shaft  50  and rotor stack  58  is pressed onto insulating tube  54 . Shaft  50  connects to a product gearbox (not shown), which in turn is coupled to a tool element such as a saw blade. The revolving magnetic field created by the stator windings imparts a force on rotor stack  58  causing rotor stack  58  to revolve about an axis of shaft  50 , thereby transferring torque to shaft  50 , which in turn delivers torque to gears in the product gearbox. Rotor stack  58  includes a plurality of four rotor poles  68 , although it will be appreciated that a greater or lesser plurality of rotor poles  68  could be incorporated. 
     Rotor  34  further includes a registering means  66 , such as an interrupter. As used herein registering means  66  is referred to as interrupter  66 , but it will be appreciated that registering means  66  could be any other suitable registering means, such as a magnet. Interrupter  66  has a plurality of four vanes  66   a , only three of which are visible in FIG.  2 . Interrupter  66  is a plastic part that fits on the distal, or rear, end of shaft  50  and interfaces with a position sensor (described below in reference to FIG. 3) to provide data relating to a rotor position and a rotor speed to the electronic controller. Slipping or spinning of the outer diameter (OD) of second bearing  46  is prevented by a compliant material (not shown) that fits between the OD of bearing  46  and the wall of the bearing support, such as a rubber plug or rubber boot. After stator  30 , baffle  38  and rotor  34  are annularly fitted into housing  14 , bearing end plate  26  is fitted over first bearing  44  and onto locating points at the mouth of housing  14 , then secured to plastic housing  14  with four screws (not shown). 
     FIG. 3 is an exploded view of the interior of the distal end of motor housing  14  (shown in FIG.  2 ). Behind the integral bearing support (not shown) of housing  14  is a bridge  70 , which supports, as well as substantially encloses, a position sensor  74 . In the preferred embodiment, position sensor  74  comprises an optical sensor and is herein referred to optical sensor  74 . However, it will be appreciated that position sensor  74  could comprise any other suitable position sensor, for example, a Hall Effect sensor. Bridge  70  is integrally formed with, and protrudes from, and an end wall  72  of housing  14 . Optical sensor  74  is inserted under an upper portion  70   a  of the bridge  70  such that it fits substantially within a hollow area  71  inside the bridge. Optical sensor  74  includes tabs  74   a  and  74   b , with tab  74   a  including an aperture  75  and tab  74   b  including an aperture  77 . Optical sensor  74  is attached at tab  74   b  to the bridge  70  by a fastener (not shown) which extends through an aperture  80  formed in upper portion  70   a  of bridge  70  and through aperture  77 . End wall  72  includes a pair of mounting bosses  72   a  and  72   b  projecting outwardly therefrom. Boss  72   a  includes a blind hole  72   c  and  72   b  includes a through hole  72   d.  Tab  74   a  of optical sensor  74  is laid over mounting boss  72   a  such that aperture  75  and through hole  72   d  are aligned. 
     Once fitted into bridge  70 , as described above, optical sensor  74  is covered with a hollow plastic opaque sensor cap  78 . Optical sensor  74  is bounded above by cap  78  and below by second bearing  46 , which form a sealed chamber for housing optical sensor  74 . The sealed chamber protects optical sensor  74  from contamination by dirt, dust, oil and moisture, and accidental triggering by external light sources. Additionally, the distal end of motor housing  14  includes a boss  81  used in attaching vented end cap  22  (shown in FIG. 1) to the distal end of motor housing  14 . 
     Optical sensor  74  interfaces with interrupter  66  (shown in FIG. 2) to provide data relating to rotor  34  position and speed. As shaft  50  and interrupter  66  rotate, the passing of vanes  66   a  of interrupter  66  is detected by optical sensor  74 , which provides data to a main control PCB (described below in reference to FIG.  4 ). The main control PCB utilizes the data to determine information critical to proper operation of the motor  10 , such as the relative position of rotor stack  58  to stator stack  30  (shown in FIG. 2) and the speed of rotor stack  58 . Therefore, the alignment of interrupter vanes  66   a  to rotor poles  68  (shown in FIG.  2 ), and the alignment of stator stack  30  to optical sensor  74  is very important for proper motor operation. 
     Proper alignment of stator stack  30  relative to optical sensor  74  during assembly of motor  10  is accomplished by molding bridge  70  and the stator locating ribs  40  from the same core side of the mold. Bridge  70  includes the sensor mounting structure, such as aperture  80  and mounting boss  72   b,  which precisely orient optical sensor  74  within bridge  70 . Stator locating ribs  40  are keyed to stator stack channels  42  (shown in FIG. 2) such that stator stack  30  is fitted into housing  14  in a precise orientation. Therefore, the mold tooling that defines the sensor mounting features in bridge  70  also defines locating ribs  40 . The fact that both bridge  70  and the stator locating ribs  40  are incorporated into the core side of the mold insures that these important structural components are integrally formed on the same part (i.e. housing  14 ). This serves to ensure that alignment of the optical sensor  74  relative to the position of stator stack  30  is controlled with great accuracy and further reduces the chance of misalignment of stator stack  30  during assembly of motor  10 . It will also be appreciated that this significantly reduces assembly time because particular care does not need to be taken in carefully aligning these components during assembly of the motor  10 . 
     In an alternate embodiment, bridge  70  supports a plurality of position sensors  74 , as would be utilized in multiphase brushless motors. In this embodiment the plurality of position sensors  74  are inserted under bridge  70 , covered above with sensor cap  78 , and bounded below by second bearing  46  in the same fashion as described above in reference to a single position sensor  74 . Therefore, bridge  70  accurately aligns each position sensor  74  with respect to each other position sensor  74 , and molding bridge  709  and stator locating ribs  40  from the same core side of the mold accurately aligns all position sensors  74  relative to stator stack  30 . 
     FIG. 4 is an exploded view of the distal end of motor  10  (shown in FIG. 2) showing how the components at the distal end of motor  10  are assembled. A main control PCB  82  fits behind optical sensor  74  while preferably a pair of capacitors  86 , for example, large film capacitors, are mounted on a capacitor PCB  94  and housed in the bulge  18  integrated into the side of the motor housing  14 . 
     Main control PCB  82  is potted in epoxy resin inside a plastic potting boat  98 , which fits onto plastic boss  81  and another plastic boss (not shown) that extend up from motor housing  14 . Additionally, main control PCB  82  has two wing-shaped aluminum heat sinks  102  and  106  fitted on opposite peripheral edges of main control PCB  82 . Four switching devices, in one preferred form comprising insulated gated bipolar transistors (IGBTs), are secured to one of heat sinks  102  and  106 , and also soldered to main control PCB  82 . Additionally, four diodes are fitted to the other one of heat sinks  102  and  106 . After all of components  74 ,  78 ,  82 ,  94  and  98  are inserted into housing  14 , vented end cap  22  is placed over the components and secured to housing  14 . 
     There are multiple connections (not shown) to main control PCB  82 , which include the incoming AC power, connections to the motor leads, connections to optical sensor  74 , and finally signal level leads coming from the various switches on the product, such as a trigger switch, a table position latch switch, or speed control potentiometers. These connections may be either directly soldered to main control PCB  82  and secured with potting compound or connected using terminals. All the external leads, such as AC power and signal level switch inputs, are bundled into a single, multi-conductor cable (not shown) which exits motor housing  14  on the side opposite bulge  18 . 
     FIG. 5 is an exploded view of motor housing  14  (shown in FIG.  4 ), showing how capacitors  86  are slideably inserted into motor housing bulge  18 . In order to implement brushless motor  10  in applications where a typical universal motor is commonly utilized, the overall axial length of the motor must be similar to the axial length of typical universal motors. 
     In the preferred embodiment, motor housing  14  includes the integrally formed bulge  18 , formed on a side of housing  14 . The bulge  18  houses capacitors  86 , thereby minimizing the overall axial length of motor  10 . Capacitors  86  are soldered onto capacitor PCB  94  and then strapped to capacitor PCB  94  using fasteners  110 , such as nylon cable ties. Stiffeners  114 , which preferably comprise lengths of plastic each having a longitudinal groove, are attached to the two opposing longitudinal edges of capacitor PCB  94 , thereby adding structural rigidity to capacitor PCB  94 . In one embodiment, stiffeners  114  are temporarily attached to capacitor PCB  94 , for example, using clips or a snap fitting. In an alternate embodiment, stiffeners  114  are permanently attached to capacitor PCB  94 , for example, using glue or a bracket riveted to both capacitor PCB  94  and stiffeners  114 . Stiffeners  114  fit into corresponding channels  116  along the inside wall of motor housing bulge  18 . In the preferred embodiment, stiffeners  114  are drafted, and thus have a tapered shape. 
     Stiffeners  114  are slideably inserted into corresponding channels  116 , which are also drafted, however the shape of stiffeners  114  and corresponding channels  116  are not so limited. End slots (not shown) at the base of motor housing bulge  18  and in vented end cap  22  (shown in FIG. 1) capture the ends of capacitor PCB  94 . Capacitor PCB  94  is electrically connected to main control PCB  82  using flexible lead wires  118  inserted through an aperture  120  in the side wall of housing  14 . Preferably lead wires  118  comprise a ribbon cable, but could be any other suitable electrical connecting means. 
     FIG. 6 is an exploded view of stator stack  30  (shown in FIG.  2 ). In the preferred embodiment stator stack  30  comprises a stack of laminations, known as a “unified stack”, which are interlocked, welded, cleated, or bonded to one another. A plurality of first insulating strips  122  are formed into the shape of stator slots  124 , inserted into stator slots  124  before windings or coils  126  are inserted into stator slots  124 , and extend at either end of stator stack  30 . A plurality of second insulating strips  128  (shown in FIG.  7 ), commonly known as “topsticks” or “coil stays”, are wedged between windings  126  and the mouth of stator slots  124  after windings  126  are inserted into stator slots  124 , and extend at either end of stator stack  30 . First insulating strips  122  and second insulating strips  128  provide a layer of electrical insulation between current carrying components of motor  10  and metal parts of motor  10  that a user would normally come into contact with, referred to herein as “accessible metal”. For example, if motor  10  is used in a hand held power saw, rotor shaft  50  is considered accessible metal because it connects through conducting a metal-to-metal interface with the saw gearbox, which connects through a conducting metal-to-metal interface to a saw blade. 
     FIG. 7 is an exploded view of stator stack  30  (shown in FIG.  6 ), rotor stack  58 , and shaft  50  (shown in FIG. 2) showing a double insulation feature implemented in accordance with a preferred embodiment of motor  10  of present invention. Electronically commutated brushless motor  10  (shown in FIG. 2) includes two layers of electrical insulation between accessible metal and parts of motor  10  in which electrical current flows. One layer of insulation comprises insulation tube  54  between shaft  50  and rotor lamination stack  58 . Insulation tube  54  is constructed of a non-conductive, electrically insulating material such as fiberglass. Insulation tube  54  is pressed onto shaft  50  and rotor lamination stack  58  is then pressed onto insulation tube  54 . 
     Another layer of insulation comprises the plurality of first insulating strips  122  and the plurality of second insulating strips  128 . First insulating strips  122  are constructed of an electrically insulating material and fit into stator slots  124  prior to stator windings  126 , such that first insulating strips provide a first portion of an electrical barrier between stator windings  126  and stator laminations  30 . Second insulating strips  128  are also constructed of an electrically insulating material and are fitted into stator slots  124  after windings  126 , such that second insulating strips  128  provide a second portion of an electrical barrier between stator winding  126  and stator laminations  30 . The combination of first insulating strips  122  and second insulating strips  128  totally encompass the part of stator winding  126  inserted into stator slots  124 , thereby providing a complete electrical barrier between winding  126  and stator stack  30 . The insulating material used to construct first insulating strips  122  and second insulating strips  128  can be any suitable insulating material, for example, Mylar®, or a laminated composite of Mylar® with other materials such as rag paper or Nomex®. 
     Thus, insulating tube  54  disposed between shaft  50  and rotor stack  58 , and the combination of first insulating strips  122  and second insulating strips  128  disposed between stator stack  30  and windings  126 , provide a double insulation barrier against possible electrical shock should a user come into contact with accessible metal if a malfunction has occurred in the motor that would otherwise cause electrical current to be in contact with accessible metal portion of the tool. 
     In an alternate embodiment housing  14  is constructed of a non-conductive material, thereby providing a supplemental layer of insulation within motor  10 , in addition to the double insulation barrier described above. In another alternate embodiment, stator stack  30  is installed into motor housing using a non-conductive intermediate device, such as a molded plastic cradle, housing, or sleeve (not shown) into which stator stack  30  is inserted prior to being installed in housing  14 . In this embodiment the plastic cradle would house stator stack  30  and would then fit into housing  14  thereby providing an alternate supplemental layer of insulation between parts of motor  10  in which electrical current flows and accessible metal. 
     FIG. 8 is cross-sectional view of motor  10  (shown in FIG.  2 ). In the electronically commutated brushless motor  10 , air is drawn in through vented end cap  22 , passes around the periphery of potting boat  98  and main control PCB  82 , through channels created by extruded fins of aluminum heat sinks  102  and  106 , continues over stator windings  126 , passes through and around stator stack  30 , through cooling fan  62 , and exhausts out bearing end cap  26 . 
     Potting boat  98  and main PCB  82  impede this airflow by causing an obstruction to a more direct flow of air into heat sinks  102  and  106 . The obstruction to airflow is further compounded by the molding process of housing  14 . To effectively mold and produce housing  14 , it must have draft added on both its internal core and external cavity sides of the mold. The draft closes the space between an internal wall of housing  14  and potting boat  98 , thereby further restricting the airflow around through the motor. 
     FIG. 9 is a schematic of the housing  14  (shown in FIG.  2 ), showing the location of the parting line of the core and cavity used to mold housing  14 . Housing  14  is designed to provide more area at the distal end, or rear, of housing  14  than known electronically commutated brushless motor housings. The increased area provides greater space around potting boat  98  (shown in FIG.  4 ), which allows improved airflow through the motor  10  (shown in FIG.  1 ). 
     Generally, when designing molding tools for a motor housing, such as motor housing  14 , a specified angle of draft θ in the core, and a specified angle of draft α in the cavity, are designed into the molding tools to make removal of the housing from the mold easier. The draft incorporated into the core and cavity create taper in the sidewall of the housing that extends away from a parting line between the core and cavity. Specifically, draft angle α in the cavity creates taper in an exterior surface of the housing. 
     The interfacing surface at which the core and cavity meet, and separate, during the molding process is referred to as the parting line. Draft angles θ and α are measured from a plane perpendicular to the parting line. Since draft angle α creates taper in the exterior surface, the further the parting line is away from the distal end of the housing, or the closer the parting line is to the proximal end, the smaller the outside diameter of the distal end of the housing will be. The inside diameter of the distal end of the housing directly relates to the outside diameter. Thus, the further away the parting line is from the distal end of the housing, the smaller the inside diameter of the distal end will be, thereby providing less area for air to flow in the distal end of the housing. 
     Referring to FIG. 9, the parting line of housing  14  is shown located closer to the distal end “D” of housing  14 , rather than at, or near, the proximal end “P” of housing  14 , as is generally the case in known motor housings. Having the parting line located closer to the distal end D of housing  14  reduces the amount of taper of exterior surface  130 , and therefore provides an increased outside diameter of the distal end, which in turn provides an increased inside diameter of the distal end of housing  14 . The increased inside diameter increases the area at the distal end, thereby providing more room for air to flow around potting boat  98  (shown in FIG.  4 ). 
     Therefore, electronically commutated brushless motor  10  provides a modular motor that fits the existing mounting schemes for typical universal motors. Motor  10  includes a housing having a bulge wherein two large capacitors are placed, thereby providing a brushless motor having an overall axial length comparable to typical universal motors. Additionally, proper alignment of the position sensor to the stator is achieved by molding the mounting features for both the position sensor and the stator using the same molding core. Furthermore, motor  10  implements a double insulation design in an electronically commutated brushless motor. Even further, the design of motor  10  provides improved airflow through the motor by moving the parting line of the molding core and cavity, thereby permitting the housing to be molded using less taper, which in turn allows more space for air to flow around the electronics control module of the motor. 
     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.