Patent Publication Number: US-2021175772-A1

Title: Techniques for sub-micron radial alignment of electric motor components and air flow management to extend motor lifespan

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/944,068 filed on Dec. 5, 2019, which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This specification generally relates to electric motors, and in particular, to techniques for sub-micron radial alignment of motor components, and diffuser devices for use in electric motors that divert airflow to generate one or more air jets for cooling core motor components such as windings and rotor assemblies. 
     BACKGROUND INFORMATION 
     Electric motors are used in a wide range of consumer and industrial applications. A wide variety of electric motors are available, and electric motors tend to fall into one of two broad motor types, namely brushed and brushless. 
     A brushed DC motor, for example, has permanent magnets on the outside of its structure and a spinning armature on the inside. The permanent magnets, which are stationary on the outside, are called the stator. The armature, which rotates and contains an electromagnet, is called the rotor. In a brushed DC motor, the rotor spins 180-degrees when an electric current is run to the armature. For sustained rotation, poles of the electromagnet must flip. As the rotor rotates, the brushes make contact with the stator, flipping the magnetic field and allowing the rotor to spin a full 360-degrees. 
     On the other hand, brushless DC motors do not contain brushes and use a DC current. A brushless DC motor is essentially flipped inside out, eliminating the need for brushes to flip the electromagnetic field. In brushless DC motors, for instance, the permanent magnets are on the rotor, and the electromagnets are on the stator. Circuitry can then charge the electromagnets in the stator to rotate the rotor a full 360-degrees. 
     In either case, radial alignment of the rotor within an electric motor significantly impacts motor performance and reliability. For instance, angular and/or radial misalignment of a rotor shaft can significantly impact nominal power/torque of a motor, introduce acoustic noise (e.g., via vibration), and ultimately lead to premature component failure based on, for instance, asymmetric loading along the associated rotor shaft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the teaching of the present specification and are not intended to limit the scope of what is taught in any way. 
         FIG. 1  shows an example electric motor in accordance with an embodiment of the present disclosure. 
         FIG. 2  shows a bottom view of the electric motor of  FIG. 1  in accordance with an embodiment of the present disclosure. 
         FIG. 3  shows the electric motor of  FIG. 1  partially exploded in accordance with an embodiment of the present disclosure. 
         FIG. 4  shows a cross-sectional view of the electric motor of  FIG. 1  in accordance with an embodiment. 
         FIG. 5  shows another cross-sectional view of the electric motor of  FIG. 1  during a radial alignment stage of manufacturing, in accordance with an embodiment. 
         FIG. 6  shows another cross-sectional view of the electric motor of  FIG. 1  after performing a radial alignment stage of manufacturing, in accordance with an embodiment. 
         FIG. 7  shows a rotor assembly coupled to, and radially aligned, with an associated fan/impeller based on a step feature of the rotor assembly, in accordance with an embodiment of the present disclosure. 
         FIG. 8  shows the rotor assembly of  FIG. 7  prior to insertion into a rotor bore of an electric motor, in accordance with an embodiment of the present disclosure. 
         FIG. 9  shows the rotor assembly of  FIG. 7  after insertion into a rotor bore of an electric motor, in accordance with an embodiment. 
         FIG. 10A  shows an example lock nut in accordance with an embodiment. 
         FIG. 10B  shows another cross-sectional view of the electric motor of  FIG. 1  in accordance with an embodiment. 
         FIG. 11  shows a perspective view of a diffuser suitable for use within an electric motor consistent with the present disclosure. 
         FIG. 12  shows a side view of the diffuser of  FIG. 11  in accordance with an embodiment. 
         FIG. 13  shows a bottom view of the diffuser of  FIG. 11  in accordance with an embodiment. 
         FIG. 14  shows an example shroud for use within an electric motor consistent with the present disclosure. 
         FIG. 15  shows a cross-sectional view of the example shroud of  FIG. 14  in accordance with an embodiment. 
         FIG. 16  shows a perspective view of another example diffuser suitable for use within an electric motor consistent with the present disclosure. 
         FIG. 17  shows a side view of the diffuser of  FIG. 16 . 
         FIG. 18  shows another perspective view of the diffuser of  FIG. 16 . 
         FIG. 19  shows another example shroud for use within an electric motor consistent with the present disclosure. 
         FIG. 20  shows a cross-sectional view of the example shroud of  FIG. 19  in accordance with an embodiment. 
         FIG. 21  shows a cross-sectional view of the electric motor of  FIG. 1  in accordance with an embodiment. 
         FIG. 22A  shows another example shroud for use within an electric motor consistent with the present disclosure. 
         FIG. 22B  shows a cross-section of the shroud of  FIG. 22A  in accordance with an embodiment. 
         FIG. 22C  shows a seal insert device suitable for use in the shroud of  FIG. 22A , in accordance with an embodiment. 
         FIG. 23A  shows another example electric motor consistent with the present disclosure. 
         FIG. 23B  shows a side view of the electric motor of  FIG. 23A . 
         FIG. 23C  shows a cross-sectional view of the electric motor of  FIG. 23B  taken along the line C-C, in accordance with an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     As discussed above, radial alignment of the rotor shaft within an electric motor significantly impacts motor performance and reliability. Electric motors, such as brushless DC (BLDC) motors, can be formed from multiple portions/segments that get sandwiched together in a stack arrangement. For instance, some electric motors include housing portions that couple together with a stator assembly disposed therebetween. The housing portions and stator assembly can each include an aperture/through hole that align to collectively provide a rotor bore. However, as each component of the motor gets coupled together, varying amounts of deviation gets introduced. This deviation ultimately compounds as each component introduces additional misalignment such that the resulting bore has an end-to-end deviation of up to 150 microns, or worse. Ideally, the resulting bore has an end-to-end deviation of zero microns, e.g., perfectly concentric, but such a zero-micron deviation is difficult to achieve in practice. This is due to inherent manufacturing deviations in motor components, and manufacturing processes that simply cannot identify and compensate for such deviations. Minute deviations introduced by each successive motor component can ultimately compound and result in substantial radial misalignment of a rotor shaft. 
     Such end-to-end deviations along the rotor bore tend to proportionally introduce asymmetric loading of a rotor shaft and significantly reduce operational lifespan of a motor, e.g., due to rotor assembly wear and generated heat, as well as introduce acoustic noise due to vibrations. 
     Thus, the present disclosure is generally directed to techniques for radial alignment of motor components relative to each other to achieve an electric motor with a rotor bore having sub-micron end-to-end deviation, e.g., end-to-end deviation of less than 50 microns, and preferably less than 10 microns. In more detail, a rotor bore alignment tool is disclosed herein that can be inserted between multiple motor components, and more particularly, apertures/through holes defined by each of the motor components such as housing sections and a stator assembly. The rotor bore alignment tool includes expandable members that can be selectively transitioned to an extended position to cause each of the motor components to be radially aligned prior to securely coupling the same in a so-called “stack” to form a motor. Once the motor components are securely coupled together, e.g., via adhesive and/or screws, the resulting motor includes a rotor shaft extending from end-to-end that preferably includes a sub-micron deviation of less than 10 microns, and more preferably less than or equal to 5 microns, for example. 
     In an embodiment, an electric motor includes a first housing portion defining a first rotor receptacle to receive and couple to a first end of a rotor assembly. The electric motor further includes a second housing portion defining a second rotor receptacle to receive and couple to a second end of the rotor assembly, the first and second housing portions are configured to couple together and collectively provide a rotor bore to receive the rotor assembly. A rotor assembly is disposed within the rotor bore, with the rotor assembly comprising a shaft and first and second bearings coupled concentrically along the shaft. The first bearing can be disposed within the first rotor receptacle of the first housing portion and the second bearing can be disposed within the second rotor receptacle of the second housing portion. The shaft and associated first and second bearings are preferably radially aligned with each other based on the rotor bore collectively provided by the first and second housing portions having an end-to-end offset deviation of preferably less than 10 microns, and more preferably less than or equal to 5 microns. 
     Turning to the Figures,  FIGS. 1-4  illustrate a motor  100  consistent with an embodiment of the present disclosure. The motor  100  is preferably configured as an electric motor, and more preferably as a brushless DC (BLDC) motor. Note, the present disclosure illustrates and describes various aspects and features with specific reference to BLDC motors. However, this disclosure is not limited in this regard, and the present disclosure is equally applicable to other electric motor types, e.g., brushed motors, with minor modification. 
     The motor  100  includes a housing shown collectively as  102  and individually as first, second and third housings portions  102 - 1 ,  102 - 2 , and  102 - 3  respectively (See  FIG. 3 ). The housing  102  may therefore also be referred to herein as a multi-part or multi-portion housing. The housing  102  may be formed from, for example, plastic, metal, or any other suitably ridged material. Preferably, each portion of the housing  102  comprises a thermoplastic with a relatively high heat resistance and tensile strength. For example, the housing  102  is preferably formed from Acrylonitrile butadiene styrene (ABS). 
     With specific reference to  FIG. 3 , each of the housing portions  102 - 1  to  102 - 3  are configured to radially align with each other along longitudinal axis  150  such that an aperture/through hole of each generally aligns when the same are coupled together during manufacture. As discussed further below, each of the housing portions  102 - 1  to  102 - 3  can include relatively large manufacturing tolerances to allow for relatively coarse-grain adjustment prior to subsequent radial alignment (e.g., via an extendable mandrel consistent with the present disclosure) and attachment/fixation stages. 
     Continuing on, the first housing portion  102 - 1  includes a base with a plurality of mating projections extending therefrom along the longitudinal axis  150 . The mating projections are configured to interlock with corresponding mating sections of the second housing portion  102 - 2 . Thus, the first and second housing portions may be configured to couple together via the mating projections, which may also be referred to herein as interlocking mating portions or simply interlocking portions. 
     The mating projections preferably include an offset alignment tolerance of up to 50 microns or more, and more preferably between 100-150 microns. The offset alignment tolerance allows for radial displacement of the first and second housing portions  102 - 1 ,  102 - 2  relative to each other as discussed in further detail below. 
     In addition, the mating projections are also preferably configured to maintain angular alignment of the first and second housing portions  102 - 1 ,  102 - 2 . This angular alignment can be maintained by supplying a compressive force (or clamping force) along the longitudinal axis  150  that causes the first and second housing portions  102 - 1 ,  102 - 2 , to be displaced towards each other and sandwiched together via extendable mandrels/members during manufacture, as will be discussed further below. 
     Continuing on, the first housing portion  102 - 1  further defines a first rotor receptacle  104 - 1  and the second housing portion  102 - 2  further defines a second rotor receptacle  104 - 2  based at least in part on the aforementioned respective apertures/through holes. The first and second housing portions  102 - 1 ,  102 - 2  further define a stator cavity  105 , which may also be referred to herein as simply a cavity, for receiving and aligning a stator assembly, e.g., stator assembly  111 , with an associated rotor assembly, e.g., rotor assembly  106 . 
     In more detail, each of the stator components of the stator assembly  111  are radially aligned along longitudinal axis  150  and are configured to couple together in a sandwich/stack configuration. As shown in  FIG. 3 , the stator components of the stator assembly  111  include a first winding liner  110 - 1  followed by a stator stack  112  and second winding liner  110 - 2 . The stator stack  112  can comprise a plurality of laminations. For instance, the stator stack  112  can comprise a plurality of iron laminations radially-aligned with each other. 
     The first and second winding liners  110 - 1 ,  110 - 2  are configured to receive and hold windings  108  at predefined positions relative to the stator stack  112  within the stator cavity  105  such that the windings  108  get arrayed about rotor assembly  106  within the housing  102 . The windings  108  can comprise, for instance, copper or other suitable material. Thus, the stator components couple together and collectively provide a radially-aligned stator assembly disposed within the stator cavity  105 . 
     As shown in  FIG. 3 , the rotor assembly is shown collectively at  106  and individually at  106 - 1  to  106 - 4 . The rotor assembly  106  comprises a shaft  106 - 4  and a plurality of components concentrically coupled to the shaft  106 - 4 . In particular, the rotor assembly  106  includes a first bearing  106 - 1 , a second bearing  106 - 2  and a magnet  106 - 3 , each coaxially and concentrically coupled to the shaft  106 - 4 . 
     The first bearing  106 - 1  is disposed at a first end of the shaft  106 - 4  and gets at least partially inserted into the first rotor receptacle  104 - 1 . To this end, the first bearing  106 - 1  may be sized/dimensioned with a diameter that is substantially identical to that of the diameter of the first rotor receptacle to ensure a “snug” fit without axial play/slop. 
     The second bearing  106 - 2  is disposed adjacent a second end of the shaft  106 - 4 . The second bearing  106 - 2  gets at least partially inserted into the second rotor receptacle  104 - 2 . The second bearing  106 - 2  is also sized/dimensioned such that the same couples into the second rotor receptacle  104 - 2  without axial play. 
     The magnet  106 - 3  is preferably fixedly coupled at a midpoint of the shaft  106 - 4 , e.g., via an adhesive or other attachment approach, such that rotation of the shaft  106 - 4  causes rotation of the magnet  106 - 3 . 
     As further shown, the second winding liner  110 - 2  is followed by a diffuser  114 , a fan (or impeller)  116 , a hub  118 , and the third housing portion  102 - 3 . The third housing portion  102 - 2  may also be referred to as a shroud. 
     Turning to  FIG. 4 , and with additional reference to  FIG. 3 , a cross-sectional view of the motor  100  is shown after components of the same have been radially aligned and securely coupled together. As shown, a shaft bore (also referred to herein a simply a bore) gets collectively formed by the apertures/through holes of each component of the motor  100  aligning along longitudinal axis  150 , with the bore having a maximum nominal end-to-end offset deviation. 
     An end-to-end offset deviation in the context of a motor bore generally refers herein to the largest amount of radial deviation between each radially/concentrically aligned hole/aperture. For example, a radial deviation/displacement of 50 microns between the apertures/through holes of the first and second housing portions  102 - 1 ,  102 - 2 , introduces an end-to-end offset deviation of at least 50 microns, e.g., assuming no other motor components have a greater misalignment amount. 
     The example bore of  FIG. 4  preferably has an end-to-end offset deviation of between 10-50 microns, 10 microns+−5 microns, and more preferably less than or equal to 5 microns. Aspects and features of the present disclosure recognize that the smaller the end-to-end offset deviation is for the bore, the longer the potential operational lifespan of the motor  100 . Stated differently, the closer the bore of the motor  100  gets to essentially a zero-deviation opening/bore, e.g., a perfectly concentric bore, the longer the theoretical lifespan of the motor  100  based on the shaft  106 - 4  of the rotor assembly  106  having symmetric loading along its length. Likewise, it is desirable to have the shaft  106 - 4  be disposed concentrically within the bore of the motor, e.g., without angular misalignment. This alignment is also commonly referred to as perpendicular alignment of the shaft  106 - 4  relative to the housing  102  of the motor. 
     In any event, one aspect of the present disclosure achieves sub-micron end-to-end offset deviation for the bore of the motor  100  to increase maximum motor lifespan, and reduce or otherwise mitigate motor component wear and motor acoustics caused by misaligned rotor shafts. 
       FIGS. 5 and 6  demonstrate one example approach for achieving the aforementioned sub-micron offset deviation for the bore of an electric motor. As shown, prior to insertion of the rotor assembly  106  into the bore of the motor  100 , an extendable mandrel  124  is inserted therein, with the extendable mandrel  124  being in a retracted orientation/position. The extendable mandrel  124  may also be referred to herein as a rotor bore alignment device. The extendable mandrel  124  may be formed with an elongated shaft having a substantially uniform diameter along its entire length and an overall length greater than or equal to the length of an associated rotor bore. Preferably, the diameter of the shaft of the extendable mandrel  124  remains within +−10 microns, and more preferably less than or equal to 5 microns, along the entire length. 
     As shown, the extendable mandrel  124  includes a plurality of extendable members, namely first, second and third extendable members  126 - 1 ,  126 - 2 ,  126 - 3 , respectively. The extendable mandrel  124  may include more or less extendable mandrels depending on a desired configuration. Preferably, the extendable mandrel  124  includes at least one extendable mandrel. 
     Each extendable member is disposed along the shaft of the extendable mandrel  124  at a predetermined position. As shown, each of the first, second and third extendable members  126 - 1 ,  126 - 2 ,  126 - 3 , are disposed at different locations along the shaft of the extendable mandrel  124 . The locations of each extendable member are preferably predefined to align with component(s) of the motor  100 , and more preferably, at least the first housing portion  102 - 1 , the second housing portion  102 - 2 , and the stator assembly  111 . 
     For example, and as shown in  FIG. 5 , the extendable mandrel  124  is preferably configured to be inserted into the bore of the motor  100  and prevented from further insertion by flange  128  of the extendable mandrel  124  engaging outer surfaces of the motor  100 . Each of the first, second, and third extendable members  126 - 1 ,  126 - 2 , and  126 - 3  may therefore be disposed at predetermined locations along the extendable mandrel  124  at locations that, when the extendable mandrel  124  gets disposed within the bore of the motor  100 , align each extendable member with a target component of the motor  100 , as discussed in greater detail below. 
     The extendable mandrel  124  further includes an actuating member (or arrangement)  130  and a sleeve  132 . The sleeve  132  includes slidable sections that travel in a linear manner along the longitudinal axis of the extendable mandrel  124 . The sleeve  132  preferably defines angled surfaces forming V-shaped grooves  134 . Each V-shaped groove preferably extends radially about the shaft of the extendable mandrel  124 . Each extendable member  126 - 1  to  126 - 3  is disposed within an associated V-shaped groove. The sleeve  132  may then slidably increase the width of each V-shaped groove to allow the extendable members  126 - 1  to  126 - 3  to transition into the retracted orientation such that the same extend radially from the shaft to a first distance of D 1 , such as shown in  FIG. 5 . The first distance D 1  may be configured to allow for slidable insertion of the extendable mandrel  124  into the bore of the motor  100 . 
     On the other hand, the sleeve  132  may then slidably decrease the width of each V-shaped groove, e.g., via linear movement along the shaft of the extendable mandrel  124 , and as a result “pinch” and displace the extendable members to transition the same to an extended position/orientation, with the displacement of the extendable members causing the same increase in overall diameter and extend radially outwards from the shaft of the extendable mandrel  124  to a second distance D 2 . Preferably, the first distance D 1  measures preferably between 0 and 100 microns, and more preferably less than 10 microns. In one preferred example, the overall diameter of the extendable mandrel  124  with the extendable members in the retracted orientation may then preferably measure about 9.25 mm. Preferably, the second distance D 2  measures preferably between 500-800 microns, and more preferably, 500+−100 microns. In one preferred example, the overall diameter of the extendable mandrel  124  with the extendable members in the extended orientation may then preferably measure about 9.7 to 10.0 mm. In this preferred example, the outer diameter of the extendable mandrel  124  increases/decreases in a uniform manner along the entire length of the same such that the extendable members extend from the shaft of the extendable mandrel  124  at a distance that is within +−5 microns of each other when transitioning from the retracted to the extended orientations, and vice-versa. 
     Each extendable member  126 - 1  to  126 - 3  preferably comprises a material with an elasticity that allows for the aforementioned increase in overall diameter, and thus by extension, allows for each of the extendable members  126 - 1  to  126 - 3  to extend to the second distance D 2  as a result as being displaced by an associated V-groove. Likewise, the material elasticity of the extendable members  126 - 1  to  126 - 3  preferably allows the same to return to an original state and decrease in overall diameter to the first distance D 1  based on the V-grooves being increased and width, for example. Some such example materials with suitable elasticity and stiffness include, for example, Nitrile Butadiene Rubber (NBR), Carboxylated Nitrile Butadiene Rubber (XNBR), and/or Fluroelastomers (e.g. VITON™). Note, other approaches to expanding the overall diameter of the extendable mandrel  124  is within the scope of this disclosure and the provided examples are not intended to be limiting. 
     Continuing on, actuation of the extendable members  126 - 1  to  126 - 3  can occur based on rotation of the actuating member  130 . As shown in  FIG. 5 , the actuating member  130  is a threaded screw/shaft that, in response to rotation of the same, causes linear displacement/movement of the sleeve  132 . Thus, the actuating member  130  and sleeve  132  may also be pneumatic &amp; hydraulic as well as a rack and pinion arrangement, with the rack and pinion arrangement configured to translate the rotational movement of the actuating member  130  to linear movement of the sleeve  132 . 
     Thus, when the extendable mandrel  124  gets inserted into the bore of the motor  100 , the extendable mandrel  124  reaches a predefined position (or alignment position) based on, for instance, the flange  128  bottoming out on sidewalls of the first housing portion  102 - 1 . At the predefined position, the first extendable member  126 - 1  preferably aligns with the first housing portion  102 - 1 , the second extendable member  126 - 2  preferably aligns with the stator assembly  111  and the third extendable member  126 - 3  preferably aligns with the second housing portion  102 - 2 . 
     The first, second and third extendable members  126 - 1  to  126 - 3  may then be transitioned to an extended position based on, for example, a hydraulic component (not shown) that securely couples to the actuating member  130  and causes rotation of the same. In response, the sleeve  132  then slidably engages the extendable members, e.g., by reducing the width of each corresponding V-groove, and slidably displaces the extendable members. 
     In response, the first, second and third extendable members  126 - 1  to  126 - 3  increase in diameter and extend radially to the second distance D 2 . Preferably, each of the first, second and third extendable members  126 - 1  to  126 - 3  extend at substantially the same rate and distance in a synchronized manner based on the actuating member  130 . In any event, as the first, second and third extendable members  126 - 1  to  126 - 3  transition to the extended position, a force is then applied along a direction that is substantially transverse relative to the shaft of the extendable mandrel  124 , and more importantly, the bore of the motor  100 . In response, each of the first housing portion  102 - 1 , the stator assembly  111 , and the second housing portion  102 - 2  get radially displaced by the substantially transverse force transferred by virtue of the aligned first, second and third extendable members  126 - 1 ,  126 - 2 ,  126 - 3  being transitioned to the extended position. 
     Notably, the aforementioned radial displacement is achieved at least in part by an offset alignment tolerance  120  (See  FIGS. 4 and 5 ) that gets collectively provided by the first and second housing portions  102 - 1 ,  102 - 2 . In particular, the interlocking sections that allow the first and second housing portions  102 - 1 ,  102 - 2  to couple together can be manufactured to allow for a predefined amount of radial displacement in the order of 50 to 100 microns, for example, to provide the offset alignment tolerance  120 . Thus, when the extendable mandrel  124  transitions to the extended orientation, the offset alignment tolerance  120  allows for the first and second housing portions  102 - 1 ,  102 - 2  to be displaced along a direction that extends substantially transverse relative to the bore of the motor  100 . The result of such displacement is a radial alignment of the first and second housing portions  102 - 1 ,  102 - 2  that achieves sub-micron radial alignment of the bore collectively formed therebetween (See e.g.,  FIG. 6 ). 
     Notably, the extendable members of the extendable mandrel  124  can also introduce a compressive/clamping force that causes the first and second housing portions  102 - 1 ,  102 - 2  to be displaced towards each other such that angular alignment of the bore of the motor  100  is achieved by ensuring that the interlocking portions of the first and second housing portions  102 - 1 ,  102 - 2  directly couple with each other, e.g., without a gap formed therebetween. 
     Subsequent to the first and second housing portions  102 - 1 ,  102 - 2  being brought into the aforementioned sub-micron radial alignment by the extendable mandrel  124 , the first and second housing portions  102 - 1 ,  102 - 2  may be securely coupled to each other via an adhesive and/or locking device. For instance, an adhesive may be disposed on surfaces forming the interface between the first and second housing portions  102 - 1 ,  102 - 2 . Alternatively, or in addition to adhesives, a bolt (e.g., a metal bolt/rod) or screw may be inserted through the first and second housing portions  102 - 1 ,  102 - 2 . In scenarios where a screw is utilized, the screw can optionally include a self-tapping head for penetrating the housing portions. 
     After securely coupling the first and second housing portions  102 - 1 ,  102 - 2  to each other, the extendable mandrel  124  may be transitioned back to a retracted orientation, e.g., based on rotation of the actuating member  130 . The extendable mandrel  124  may then be extracted from the bore of the motor  100 . 
     As shown in  FIG. 7 , the shaft  106 - 4  of the rotor assembly  106  can include a plurality of step (or shoulder) features including at least first and second step features  134 - 1 ,  134 - 2 . The first step feature  134 - 1  allows for an end of the shaft  106 - 4  to get inserted into an aperture/through hole of the impeller  116  and “bottom” out against the first step  134 - 1 . Thus, the first step feature  134 - 1  can operate as a mechanical stop that allows for the fan to achieve the aforementioned perpendicular alignment with the shaft  106 - 4 . 
     The second step feature  134 - 2  includes a projection configured to engage a corresponding groove within the motor  100  and prevent further insertion into the bore of the motor  100 . For instance, as shown in  FIGS. 8 and 9 , the rotor assembly  106  gets inserted into the bore of the motor  100 . The second step feature  134 - 2  then engages groove  136  of the second housing portion  102 - 2 , which acts as a mechanical stop to prevent further insertion of the rotor assembly  106 . Thus, the second step feature  134 - 2  of the rotor assembly  106  and the groove  136  of the second housing portion  102 - 2  ensure that the rotor assembly  106  gets inserted to a predefined position within the bore of the motor  100  by preferably simply bottoming out. Thus, perpendicular alignment of the rotor assembly  106  and insertion to a predefined location within the bore of the motor  100  can be achieved by virtue of the mechanical stops provided by the first and second step features  134 - 1 ,  134 - 2  of the rotor assembly  106 . 
     As shown in  FIG. 10B , bearing pre-loading may be achieved via a spring-loaded bearing sleeve consistent with the present disclosure. As shown, the bore of the motor  100 , and more particularly, the first bearing receptacle  104 - 1  is provided at least in part by a bearing sleeve  138 . The bearing sleeve  138  includes a diameter to receive at least a portion of the first bearing  106 - 1  of the rotor assembly  106 . 
     A locking cap  140 , such as shown more clearly in  FIG. 10A , then couples to the bearing sleeve  138  in a radially and axially aligned orientation, e.g., based on a threaded portion of the locking cap  140  and a corresponding threaded slot of the bearing sleeve  138 . The locking cap  140  provides an annular disk that extends substantially transverse relative to the rotor assembly  106  and bore of the motor  100 . A spring device  142 , such as a wavy washer as shown, gets disposed between the sidewalls of the first housing portion  102 - 1  and a surface defining the annular disk of the locking cap  140 . As further shown, the first housing portion  102 - 1 , and more particularly an outer sidewall thereof, defines a confining recess for receiving and holding the spring device  142  in alignment with the locking cap  140 . 
     The spring device  142  then provides a spring bias force along an axis that extends substantially parallel with the longitudinal axis of the rotor assembly  106  and bore of the motor  100 , and along a direction substantially away from the motor  100 . This spring bias force thus “pulls” (or draws away) the bearing sleeve  138  to introduce preloading on to the first bearing  106 - 1 . 
     The bearing sleeve  138  can comprise a material with a thermal expansion coefficient less than that of the material forming the first housing portion  102 - 1 . Thus, expansion of the first housing portion  102 - 1 , e.g., based on heat generated during operation of the motor  100 , can occur in a direction substantially parallel with the bore of the motor  100  without causing misalignment of the first bearing  106 - 1 . Instead, the bearing sleeve  138  maintains pressure/force against the first bearing  106 - 1 , which can be generally understood as a force that “pulls” the rotor assembly  106  towards the locking cap  140 . However, the rotor assembly  106  remains in radial alignment and fixed within the bore of the motor  100  based on, for example, the second step feature  134 - 2  that engages groove  136  of the second housing portion  102 - 2 . 
       FIGS. 11-13  show an embodiment of the diffuser  114  of  FIG. 3  in isolation. As shown, the diffuser  114  includes a cylindrical body  144  defining an opening/aperture  146  to allow a shaft of the rotor assembly  106  to extend therethrough along the longitudinal axis  150  (See  FIGS. 1 and 3 ). The diffuser  114  further comprises a band  148  (or rim) disposed concentrically with and surrounding the cylindrical body  144 . The band  148  includes a side wall that extends substantially parallel with the longitudinal axis  150 . The band  148  is disposed adjacent to a first end  152 - 1  of the cylindrical body  144 . 
     The diffuser  114  further defines a plurality of fins  154  extending radially from the cylindrical body  144 . The plurality of fins  154  may also be referred to herein as curved air displacement fins or air displacement fins. Such fins may not necessarily include a curved profile, such as shown in  FIGS. 11-13 , and can include other shapes and profiles depending on a desired configuration. 
     Each fin of the plurality of fins  154  adjoins the cylindrical body  144  to the band  148  based on a first portion extending from the first end  152 - 1  of the cylindrical body  144  along a direction substantially transverse relative to the longitudinal axis  150 , and a second portion  156  extending from the band  148  and tapering to a position adjacent the second end  152 - 2  of the cylindrical body  144 . Thus, the band  148  only partially encompasses/surrounds the curved air displacement fins such that a tapered section, e.g., generally shown at  156 , of each of the air displacement fins is exposed to air and forms a blade-like (or wing) structure for displacement of air. 
     As shown in  FIG. 13 , the plurality of fins  154  further define a plurality of air diverting channels shown generally at  158 . As shown in  FIG. 13 , the diffuser  114  defines at least three of such air diverting channels  158 . The air diverting channels  158  are configured generate air jets that extend substantially transverse with the longitudinal axis  150  such that the generated air jets induce cooling across windings  108  and/or the rotor assembly  106  within the motor  100  (See  FIGS. 1 and 4 ). This advantageously introduces cooling for core components within the motor  100  and can increase operational lifespan, limit thermal expansion, and allow for the motor  100  to maintain nominal power over a longer period of time relative to un-cooled motor configurations. 
       FIGS. 14-15  show the third housing portion  102 - 3  of  FIG. 3  in isolation. The third housing portion  102 - 3  may also be referred to as a shroud. As shown, one end of the third housing portion  102 - 3  defines an aperture  199  for receiving air within the housing  102  ( FIG. 10B ). 
       FIGS. 16-18  collectively show another example embodiment a diffuser  214  suitable for use in the motor  100  of  FIGS. 1-4  and/or the motor  100 ′ of  FIG. 23A . The diffuser  214  can be configured similar to that of diffuser  114  discussed above to generate air jets within a motor, the description of which will not be repeated for brevity. 
     However, and as shown in  FIGS. 16-18 , the diffuser  214  does not include the outer rim/band  148  (See  FIG. 11 ). This disclosure has identified that omitting the rim/band  148  around the diffuser improves aerodynamic performance of the diffuser  214  by reducing the potential for cross-current air flows to form along surfaces of the associated fins, e.g., eddy formations, and the potential for undesirable air recirculation within the housing of a motor, as is discussed in greater detail below. 
     As shown, the diffuser  214  includes a cylindrical body  244  defining an opening/aperture  246  to allow a shaft of the rotor assembly  106  to extend therethrough along the longitudinal axis  150  (See  FIG. 3 ). The cylindrical body  244  may also be referred to herein as a diffuser body or simply a body. 
     The diffuser  214  further defines a plurality of fins  254  that extend radially from the cylindrical body  244  such that plurality of fins  254  extend substantially transverse relative to the rotor assembly  106  when the same extends through the opening  246 . The plurality of fins  254  can be evenly distributed around the diameter of the cylindrical body  244  and preferably include a uniform distance between each fin. The fins  254  may also be referred to herein as curved air displacement fins or simply curved fins. 
     Preferably, the plurality of fins  254  are formed with the cylindrical body  244  as single, monolithic piece of material. For example, the cylindrical body  244  and fins  254  may be formed from a single piece of composite and/or thermoset plastic. However, this disclosure is not necessarily limited in this regard and the cylindrical body  244  and fins  254  may be formed as separate pieces comprising the same or different material. 
     As shown in  FIGS. 16 and 17 , each fin of the plurality of fins  254  preferably includes a curved profile and extend radially from the cylindrical body  244  to an overall length L 1 . Preferably, the overall length L 1  measures between 4 and 6 mm, and more preferably, at least a distance of 5 mm. In one example configuration, the overall length L 1  measures between 10% to 50% of the radius R 1  of the cylindrical body  244 . 
     Each fin of the plurality of fins  254  include top and bottom surfaces  270 - 1 ,  270 - 2  that extend from a first end  272 - 1  to a second end  272 - 2 . The top and bottom surfaces  270 - 1 ,  270 - 2 , are disposed opposite each other and extend at a predetermined angle ( 0 ) relative to the top surface  252  defining a first end of the cylindrical body  244  (See  FIG. 17 ). Preferably, the predetermined angle (θ) measures between 25-50 degrees, and more preferably, 30 to 35 degrees. 
     Each fin of the plurality of fins  254  preferably extend from the first end  272 - 1  to the second end  272 - 1  to an overall height of H 2 . Preferably, the overall height H 2  measures between 13 and 16 mm. In one example configuration, the overall height H 2  measures equal to or greater than the overall height H 1  of the cylindrical body  244 . Preferably, the overall height H 1  measures between 9 and 10 mm. 
     As shown in  FIG. 17 , each fin of the plurality of fins  254  preferably include a first end  272 - 1  with a distal surface that is substantially flush with the top surface  252  defining the first end of the cylindrical body  244 . Each fin of the plurality of fins  254  further preferably includes a second end  272 - 2  that extends beyond a bottom surface  257  that defines a second end of the cylindrical body  244 . 
     Preferably, the width W 1  ( FIG. 16 ) from the first end  272 - 1  to the second end  272 - 2  of each fin of the plurality of fins  254  varies to provide a taper at one or both ends. The width W 1  of each fin of the plurality of fins  254  can measure between 1 and 2 mm, for example. More preferably, the width of W 1  of each fin of the plurality of fins  254  along their respective entire length measures a maximum of 10-25% (0.1 to 0.25) of the overall length L 1  each fin extends from the cylindrical body  244 . Thus, the ratio of the width W 1  of each fin relative to the length L 1  can be between 0.2:1.0 and 0.25:1.0, although other ratios are within the scope of this disclosure. Accordingly, each fin of the plurality of fins  254  can provide a blade-like structure to displace air and diffuse the same into a motor during operation. 
     As discussed above, the diffuser  214  shown in  FIGS. 16-18  includes a rimless configuration that does not include rim/band  148  (See  FIG. 11 ). Thus, each fin of the plurality of fins  254  can include a distal portion relative to the cylindrical body  244  that does not couple to an adjoining rim structure. Stated differently, each fin of the plurality of fins  254  preferably couples to the cylindrical body  244  along a region of each fin that is proximate the cylindrical body  244  such that the distal end of each fin relative to the cylindrical body  244  is fully/entirely exposed (e.g., to air). As shown in  FIG. 17 , this can include the distal end provided by surface  259 , which extends substantially transverse relative to the first and second surfaces  270 - 1 ,  270 - 2  and adjoins the same, being (fully) exposed to air. 
     Thus, air may then flow along the first and/or second surfaces  270 - 1 ,  270 - 2  in a first direction that extends from the first end  272 - 1  to the second end  272 - 2  of each fin, and also in a second direction which is transverse to the first direction to allow air to flow radially outwards away from the cylindrical body  244  without being obstructed/impeded by, for instance, surfaces defining the rim  148  (See  FIG. 11 ). This may advantageously increase aerodynamic performance by minimizing or otherwise reducing eddy formations which can reduce the overall amount of air that recirculates/stagnates within the housing of the motor. 
       FIGS. 19-20  shows an example third housing portion  102 - 3 ′ consistent with aspects of the present disclosure. The third housing portion  102 - 3 ′ can be utilized with the motor  100  of  FIG. 1  and/or motor  100 ′ of  FIG. 23A  as the third housing portion  102 - 3 / 2302 - 3 . The third housing portion  102 - 3 ′ may also be referred to herein as a shroud. 
     The third housing portion  102 - 3 ′ preferably includes a dome-shaped profile that defines an inner cavity  1904 . The third housing portion  102 - 3 ′ can include other shapes/profiles and the example shown in  FIGS. 19-20  is not intended to be limiting. 
     The third housing portion  102 - 3 ′ further defines an aperture  1906  at an end which is in communication with the inner cavity  1904 . Note, the aperture  1906  can provide the aperture  199  (See  FIG. 10B ) when coupled to a motor. The third housing portion  102 - 3 ′ further preferably provides a plurality of shoulder/step features shown as first, second and third step features  1902 - 1 ,  1902 - 2 ,  1902 - 3  respectively. The particular number of step features shown in  FIGS. 19-20  are not intended to be limiting and more or less step features may be utilized depending on a desired configuration. 
     As discussed in greater detail below, the one or more such step features may be utilized as a mechanical stop to allow for insertion of one or more sealant devices (also referred to herein as seal devices) to block air from entering/exiting a motor  100  via gaps formed between the third housing portion  102 - 3 , rotor assembly  106  and fan/impeller  116 . 
       FIG. 22A  shows a cross-sectional view of an example third housing portion  2202 - 3  that includes a cavity  2204  defined by inner sidewall  2256 . The cavity  2204  may at least partially define an impeller windage chamber when the third housing portion  2202 - 3  is coupled to a motor. The example third housing portion  2202 - 3  may be utilized within the motor  100  and/or motor  100 ′ of  FIGS. 1 and 23A , for example. 
     As further shown, the inner sidewall  2256  defines a plurality of riblets/projections  2258  that extend into the cavity  2204 . Each of the riblets/projections of the plurality of riblets  2258  extend substantially parallel relative to each other and form a spiral pattern preferably along the entire inner diameter of the cavity  2204 . 
     The plurality of riblets  2258  are preferably angled to guide air along a direction that extends substantially parallel with the longitudinal axis of the motor, e.g., longitudinal axis  150  of motor  100  (See  FIG. 4 ), when the third housing portion  2102 - 3  is coupled to the same. Thus, the plurality of riblets  2258  can also define at least a portion of an impeller compression chamber within the motor  100 . The plurality of riblets  2258  can be formed of the same material as the third housing portion  2202 - 3 , such as ABS plastic, or from a different material such as Polyphenylene sulfide (PPS) or steel. 
     As further shown in  FIG. 22A  and the partially-exploded view of  FIG. 22B , the third housing portion  2202 - 3  can include a first seal insert  2262 . The first seal insert  2262  is preferably formed of a deformable material such as a foam material, although other materials for the first seal insert  2262  are within the scope of this disclosure such as rubber. For example, the first seal insert  2262  may comprise Polytetrafluoroethylene, rubber, and/or nylon. 
     The first seal insert  2262  preferably includes a plurality of annular rings/projections  2280  that extend radially from a body. The projections  2280  may also be referred to herein as O-rings. Preferably, the plurality of annular rings  2280  are configured to extend into corresponding grooves  2278  defined by the third housing portion  2202 - 3  such as shown in  FIG. 22A . One example of such grooves is shown more clearly as grooves  2178  in the cross-sectional view of  FIG. 21 . 
     Alternatively, the first seal insert  2262  may be implemented as a ring that does not necessarily include annular rings/projections  2280 . For example, and as shown in  FIG. 22C , the first seal insert  2262 ′ can include a substantially smooth outer surface. The first seal insert  2262 ′ may be utilized when, for instance, the third housing portion  2202 - 3  does not include the grooves  2278 . 
     In any event, the first seal insert  2262 ′ may then advantageously provide an axial seal  2244  at a distal end/lip of the third housing portion  2202 - 3  (See  FIG. 22A ) adjacent the surfaces defining aperture  2206 , and/or a radial seal based on the annular projections  2280  (See  FIG. 22B ), for example. 
     Referring to  FIGS. 23A-23B  another example motor  100 ′ is shown in accordance with aspects of the present disclosure. The motor  100 ′ may be configured substantially similar to that of motor  100 , the teachings of which are equally applicable and will not be repeated for brevity. Notably, the motor  100 ′ can also include sub-micron radial alignment for the associated rotor assembly utilizing, for instance, the extendable mandrel  124  as discussed above. 
     However, and as shown, the motor  100 ′ includes a housing shown collectively as  2302  and individually as first, second and third housing portions  2302 - 1 ,  2302 - 2 ,  2302 - 3  respectively that include one or more pressure regulator valves  2390 . 
     Preferably, the one or more pressure regulator valves  2390  are disposed along the third housing portion  2302 - 3 , and more preferably, at a location of the third housing portion  2302 - 3  that is proximate to the impeller windage/compression chamber  2392  (See  FIG. 23C ). 
     Each pressure regulator valve of the one or more pressure regulator valves  2390  can include a nozzle that extends away from the third housing portion  2302 - 3 . Preferably, each nozzle extends radially from the third housing portion  2303 - 3 , such as shown in  FIGS. 23A-23C . Each nozzle can include a barbed profile as shown to allow for a friction fit with associated hosing/tubes, although other nozzle profiles are within the scope of this disclosure. 
       FIG. 23C  shows a cross-sectional view of the motor  100 ′ taken along line C-C of  FIG. 23B , in accordance with an embodiment of the present disclosure. 
     As shown, each valve of the one or more pressure regulator valves  2390  includes a first end that extends from the third housing portion  2303 - 3  and that defines an inlet. The inlet fluidly communicates with valve actuator  2391 . The valve actuator  2391  selectively fluidly couples passageway  2394  with the inlet based on, for instance, the air pressure within the passageway  2394  falling below a predetermined threshold value. The predetermined threshold value may be selected to maintain a pressure within the impeller windage chamber  2392  at a target pressure. For example, the target pressure may be about atmospheric +−10 PSI, and the valve actuator  2391  may therefore be configured to open based on air pressure within the passageway  2394  falling below a first predetermined pressure value of −15 PSI, for example. 
     Notably, the passageway  2394  being disposed at a distal end of the motor  100 ′ (e.g., adjacent the aperture  2399 ) allows for a pressure differential to be introduced along shoulder  2398  of the impeller  2316  relative to the impeller windage chamber  2392 . The valve actuator  2391  may therefore be configured to induce the pressure differential along the shoulder  2398  such that the air pressure proximate the same is greater than the air pressure within the impeller windage chamber  2392 . One such example differential includes the air pressure proximate the shoulder  2398  of the impeller  2316  being at least 0.1-0.2% greater than the air pressure within the impeller windage chamber  2392 . 
     Preferably, a first seal insert  2262  provides an airtight seal, e.g., with surfaces defining the impeller  2316 , and prevents the communication of air from outside of the motor  100 ′ from entering into the shoulder  2398  of the impeller  2316 . Accordingly, air may be then substantially prevented from recirculating along the shoulder  2398  of the impeller  2316  and instead directed over the components of the motor  100 ′ within the housing  2302  (See  FIG. 23A ). 
     As further shown in  FIG. 23C , the diffuser  2314  can include the rim-less configuration as discussed above with regard to  FIGS. 16 and 17 . This may further increase air flow through the motor  100 ′ and minimize or otherwise reduce air recirculation. Accordingly, the motor  100 ′ may then achieve a greater overall efficiency based on increased air flow by removing heat generated at the stator assembly within the motor  100 ′. 
     In accordance with an aspect a method for aligning sections of an electric motor during manufacturing is disclosed. The method comprising coupling a stator assembly between first and second housing portions to collectively provide a rotor bore extending therethrough, inserting an extendable mandrel into the rotor bore, the extendable mandrel having a retracted position and an extended position, the retracted position to provide the extendable mandrel with an outer diameter substantially equal to or less than a diameter for the rotor bore to allow insertion therein, transitioning the extendable mandrel to the extended position to radially displace the first housing portion, second housing portion, and the stator assembly relative to each other such that the rotor bore extending therethrough has an end-to-end axial offset deviation of less than 50 microns and more preferably less than 10 microns, and securing the first and second housing portions to each other subsequent to transitioning the extendable mandrel to the extended position within the rotor bore such that the rotor bore maintains the end-to-end axial offset deviation after the extendable mandrel gets removed from the rotor bore. 
     The method can further include inserting the extendable mandrel into the rotor bore further includes inserting the extendable mandrel to a predefined position within the rotor bore. Inserting the extendable mandrel to the predefined position can further include bottoming-out a flange of the extendable mandrel against an outer sidewall of the first or second housing portion. 
     In the method, inserting the extendable mandrel to the predefined position can further comprise aligning extendable members of the extendable mandrel with each of the first housing portion, the stator assembly, and the second housing portion. In the method, transitioning the extendable mandrel to the extended position preferably causes axial displacement of the first housing portion, the stator assembly, and the second housing portion based on the aligned plurality of extendable members. In the method, securing the first and second housing portions to each other can further comprise disposing an adhesive on an interface between the first and second housing portions. In the method, securing the first and second housing portions to each other can further comprise inserting a screw therebetween. 
     In accordance with another aspect of the present disclosure an electric motor is disclosed. The electric motor comprising a first housing portion defining a first rotor receptacle to receive and couple to a first end of a rotor assembly, a second housing portion defining a second rotor receptacle to receive and couple to a second end of the rotor assembly, the first and second housing portions configured to couple together and collectively provide a rotor bore to receive the rotor assembly, and a rotor assembly disposed within the rotor bore, the rotor assembly comprising a shaft and first and second bearings coupled concentrically along the shaft, the first bearing being disposed within the rotor receptacle of the first housing portion and the second bearing being disposed within the rotor receptacle of the second housing portion. 
     The electric motor can further include a sleeve disposed in the first rotor receptacle, the sleeve defining an aperture to receive at least a portion of the first bearing, a locking cap radially aligned and coupled with the sleeve, the locking cap providing an annular disk extending substantially transverse relative to the rotor assembly, and a spring disposed between the first housing portion and annular disk to provide a spring force in a direction substantially parallel to the rotor assembly and away from the first housing portion, the spring force to preload the first bearing. 
     In the electric motor, the first housing portion can comprise a first material having a first thermal expansion coefficient and the sleeve can comprise a second material having a second thermal expansion coefficient, the second thermal expansion coefficient being less than the first. In the electric motor, the second housing portion can include a groove adjacent the rotor bore, the groove to engage a step feature of the rotor assembly and prevent further insertion of the same. In the electric motor, the spring can comprise a spring washer, and wherein the spring washer is preferably disposed in a confining recess defined by an outer sidewall of the first housing portion. 
     In accordance with an aspect of the present disclosure an electric motor is disclosed. The electric motor comprising a first housing portion defining a first rotor receptacle to receive and couple to a first end of a rotor assembly, a second housing portion defining a second rotor receptacle to receive and couple to a second end of the rotor assembly, the first and second housing portions configured to couple together and collectively provide a rotor bore to receive the rotor assembly, and a rotor assembly disposed within the rotor bore, the rotor assembly comprising a shaft and at least a first bearing coupled concentrically along the shaft, the first bearing being disposed within the first rotor receptacle of the first housing portion or within the second rotor receptacle of the second housing portion, and wherein the shaft and first bearing are radially aligned with each other based on the rotor bore collectively provided by the first and second housing portions having an end-to-end offset deviation of less than 10 microns. 
     In accordance with another aspect of the present disclosure a rotor bore alignment device for radial alignment of a bore collectively provided by a plurality of housing portions of an electric motor is disclosed. The rotor bore alignment device comprising a shaft, the shaft having at least one extendable member disposed at a predefined location along the shaft, the at least one extendable member to selectively transition from a retracted orientation to an extended orientation, the retracted orientation causing the at least one extendable member to radially extend from the shaft to a first distance D 1 , and the extended orientation causing the at least one extendable member to radially extend from the shaft to a second distance D 2 , the second distance D 2  being greater than the first distance D 1 , and wherein the shaft is configured to slidably couple into the bore to a predefined position, the predefined position to align the at least one extendable member with at least a first motor component of the electric motor such that transitioning of the at least one extendable member to the extended orientation causes radial alignment of the first motor component with a second motor component of the electric motor. 
     In accordance with an aspect of the present disclosure a diffuser for use with an electric motor is disclosed. The diffuser comprising a cylindrical body defining an opening to allow a shaft of a rotor assembly to extend therethrough, and a plurality of curved air displacement fins extending radially from the cylindrical body. 
     While the principles of the disclosure have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the disclosure. Other embodiments are contemplated within the scope of the present disclosure in addition to the exemplary embodiments shown and described herein. It will be appreciated by a person skilled in the art that an electric motor may embody any one or more of the features contained herein and that the features may be used in any particular combination or sub-combination. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present disclosure, which is not to be limited except by the claims.