Abstract:
A structure and methodology of fabrication for a cost effective multipole motor adapted to high volume manufacture. The apparatus includes a low cost housing within which a stator assembly comprised of interchangeable stator electromagnets is installed. A rotor assembly including a plurality of sense magnets and motor magnets integrated onto a rotor shaft is also used. A cover assembly is attached to complete the device. The cover assembly includes a lead frame interconnection assembly and a magnetic sensor adapted to detect the passing of sense magnets to determine the position of the rotor shaft.

Description:
TECHNICAL FIELD  
         [0001]    The invention relates to a multiple pole electromagnetic motor design and method of assembling.  
         BACKGROUND OF THE INVENTION  
         [0002]    The expansion in use of electric motors in numerous consumer applications leads to a desire for more efficient and cost effective manufacture and fabrication of the same. Multiple pole motors of various types are well known in the art. One such existing motor of the aforementioned general type is depicted in FIGS. 1A and 1B. In reference to those figures, such a motor is typically fabricated from a complex machined stator assembly requiring detailed, expensive, labor-intensive operations. Further, such a machined stator assembly is commonly machine wound and installed into a housing, yet not readily or easily removed or replaced.  
           [0003]    The machined stator assembly would also typically employ interconnections that are commonly hand-connected or soldered to terminals for external connection. Soldered or hand connected terminals are commonly time-consuming to complete and difficult to repair. Soldering has also received significant scrutiny for its environmental and health related impacts in recent years. The rotor of such an existing motor is conventionally mounted by employing two or more bearings at each end of the shaft configured in such a way as to constrain both radial and axial displacement.  
           [0004]    As is clear, there are many design, construction, and assembly limitations within the existing art. The existing art is not conducive to providing a lower cost motor, nor is it adapted to high volume manufacture. The above-identified drawbacks of the prior art are overcome by the structure and method described herein.  
         SUMMARY OF THE INVENTION  
         [0005]    The invention provides a lower cost motor that is readily adapted to high volume manufacture. Specifically, the invention is directed to an apparatus and method of fabrication of a cost-effective multipole motor in high volumes. The motor assembly includes a housing, a stator assembly, a rotor assembly, and a cover assembly. The stator assembly, which is comprised of interchangeable stator electromagnets, is installed into the low cost housing. The rotor assembly includes a plurality of sense magnets and motor magnets integrated onto a rotor shaft. The cover assembly attaches to an end of the housing, and includes a magnetic sensor, a lead frame interconnection assembly, and an external electrical connector. The magnetic sensor is adapted to detect the passing of sense magnets that are on the rotor shaft, and provides for determining the position of the rotor shaft. The lead frame interconnection assembly provides for electrical connection between the external connector, and the sense magnets and the motor magnets. This eliminates a printed circuit board and hand wiring. These and other features of the invention will become apparent to those skilled in the art upon reading and understanding the following detailed description of the embodiments. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    Referring now to the drawings wherein like elements are numbered alike in the several FIGURES:  
         [0007]    [0007]FIG. 1A depicts a cross sectional view of a prior art design multipole motor;  
         [0008]    [0008]FIG. 1B depicts a drive end view of the multipole motor of FIG. 1A;  
         [0009]    [0009]FIG. 2 is an elevation view, partially in cross-section, of the multipole motor of the present invention;  
         [0010]    [0010]FIG. 3 is a plan view, partially in cross-section of the multipole motor of FIG. 2;  
         [0011]    [0011]FIG. 4 is a perspective view of the stator winding of the present invention; and  
         [0012]    [0012]FIG. 5 is a perspective view of the cover assembly of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]    The present invention may be utilized in various types of motors and other rotational devices such as motors employed in a vehicle control system. One embodiment of the invention, by way of illustration is described herein as it may be applied to a multipole motor utilized in an air control valve. While this embodiment of the invention is shown and described, it will be appreciated by those skilled in the art that the invention is not limited to air control valves alone, but may be applied to multipole motors and their applications in general.  
         [0014]    Referring now to FIGS. 1A and 1B, a multipole motor  12  is shown that includes a complex machined stator assembly  13  that requires detailed, expensive, labor-intensive operations to manufacture. It also includes a shaft  18 , a shaft bearing  16 , and a rotor iron and magnets  14 . The machined stator assembly  13  is commonly machine wound and installed into a housing  15 , yet is not readily or easily removed or replaced.  
         [0015]    [0015]FIGS. 2 and 3 depict one embodiment of the invention as illustrated by application to a multipole motor  30 . The motor  30  includes a housing  40 , a stator assembly  60 , a rotor assembly  80 , and a cover assembly  100 . The housing  40  as depicted, is designed to simplify manufacture and facilitate assembly. This has been accomplished by redesigning certain components for ease of manufacture and assembly. For example, the housing  40  may be fabricated of molded plastic or an aluminum casting. Further, the housing  40  may incorporate the actuated device, e.g. an air control valve  46 . Additionally, the housing  40  is configured in a manner that allows the stator electromagnets  62  to be modular and interchangeably arranged within the housing  40 . Such a process saves considerable effort and time in fabrication. The housing  40  includes a plurality of cavities shaped and sized to receive the plurality of stator electromagnets  62 . The housing  40  also includes a cavity to accommodate a shaft bearing  82 .  
         [0016]    In this embodiment, the housing  40  combines the encasement for the motor and air control valve  46  in a single structure. The housing  40  at the motor portion is primarily cubic. The four sides are essentially square, the bottom is the actuated device  46 , and the top is open, and interfaces and mates with the cover assembly  100  (FIG. 5). The top portion of the housing  40  includes a cutout, stepped, lip  42  in the wall thickness about the perimeter to facilitate mating and sealing with the cover assembly  100  (FIG. 5). The cover assembly  100  includes a similar, but opposite mating lip  118  on its sides. The housing  40  includes openings for the shaft bearing  82  and a second bearing  84 . The housing  40  also includes four posts  44 , placed near each corner, that are cylindrically shaped. These posts  44  are positioned such that alignment posts  116  (FIG. 5) on the cover assembly  100  enter and engage the respective mating posts  44  in the housing  40  upon assembly, thereby assuring proper alignment of the cover assembly  100  to the housing  40 . Further, each of the four posts  44  in the housing  40  may receive a fastener (e.g. be threaded) for securing the cover assembly  100  to the housing  40 .  
         [0017]    Referring again to FIGS. 2 and 3, the stator assembly  60  is modular in structure, comprised of a plurality of interchangeable stator electromagnets  62  cylindrical in shape, each characterized by an interchangeable, cylindrical, ferromagnetic core  64  around which an interchangeable, cylindrical, bobbin wound, stator winding  66  is arranged. The stator winding  66 , shown in FIG. 4, is annular in shape of approximately the same length as the core  64  such that when the core  64  is inserted into the vacant center portion of the annular stator winding  66 , the assembly resembles a cylinder. In this embodiment four such stator electromagnets  62  are employed to comprise a stator assembly  60 . The stator electromagnets  62  are placed in the housing  40  and arranged in a particular orientation that facilitates engagement and interface of the connection portion  68  with the insulation displacement terminals  102  of the cover assembly  100 . This orientation is such that the flat portion of the tops of each cylindrically shaped stator electromagnet  62  and connection portion  68  are rotated about an axis parallel to the axis of rotation of the rotor assembly  80 . Therefore the connection portion  68  is closest to each corner of the housing  40 . The connection portion  68  includes two wires, each electrically connected to an end of the stator winding  66 .  
         [0018]    The rotor assembly  80  is comprised of a rotor shaft  86 , a rotor iron  65 , a plurality of motor magnets  88 , a plurality of sense magnets  90 , and a shaft bearing  82 . The rotor shaft  86  is cylindrically shaped and made of material suitable to attach the motor magnets, sense magnets and other devices. It is designed with sufficient strength to transfer the rotational forces of the motor  30  to the actuated device, and bear a load from the actuated device, i.e. the air control valve. A longitudinal axis of the rotor shaft  86  is concentric to the longitudinal axis of the stator assembly.  
         [0019]    The shaft bearing  82  maintains radial constraint and provides axial constraint of the rotor shaft  86 . The shaft bearing  82  and second bearing  84  may comprise a sleeve, ball, or roller bearing. The shaft bearing  82  is rigidly affixed to the rotor shaft  86  approximately mid-length with its inner ring, and to the housing  40  with its outer ring. The rotation of the rotor assembly  80  is further facilitated and radially restricted by the second bearing  84  mounted near end of the rotor shaft  86  in proximity to the actuated device  46 . Those skilled in the art will understand that such a configuration provides the necessary mechanical constraints on the rotor shaft  86 , while also providing for rotational freedom while limiting translation. Further, it is understood that such a configuration provides greater radial constraint of the rotor shaft  86  in proximity to the actuated device  46  and thereby allows for tighter control of tolerances on the actuated device  46  interface with the housing  40 .  
         [0020]    The rotor iron  65  is a flat disk that is operably attached to the rotor shaft  86  near one end. The plane of the rotor iron  65  is perpendicular to and concentric to the longitudinal axis of the rotor shaft  86 . Affixed to the rotor iron  65  are a plurality of motor magnets  88 . The motor magnets  88  are also concentric with the rotor shaft  86  and positioned in a manner such that the flux lines radiate parallel to the axis of rotation of the rotor shaft  86 . The motor magnets  88  are arranged to provide maximal torque per motor diameter by utilizing a distribution that allows the motor magnets  88  to occupy the maximum possible diameter within a given size housing  40 . That is, the outer diameter of the motor magnets  88  is nearly equivalent to the inner diameter of the housing  40 . This configuration allows the invention as embodied to produce torque levels in excess of those produced by conventionally designed similarly sized motors where the motor magnets are typically placed at a radius smaller than the stator.  
         [0021]    There is also a plurality of sense magnets  90  provided to detect rotation of the rotor assembly  80  and thus the motor  30 . This attachment alleviates later assembly and thus saves fabrication effort. The sense magnets  90  combined with the magnetic sensor  104  (FIG. 5) provide position-sensing capability. The sense magnets  90  positioned circumferentially around a distal portion of a first end of the rotor shaft  86  and are integrated thereon. The sense magnets  90  align axially with a flux carrier  112  and a magnetic sensor  104  (FIG. 5) of the cover assembly  100  (FIG. 5). The changing magnetic field is detected by the magnetic sensor  104 , which outputs a voltage responsive to the passing of each of the sense magnets  90  and therefore the position of the rotor assembly  80 .  
         [0022]    [0022]FIG. 5 depicts the cover assembly  100 , which is comprised of a cover  106  upon which is mounted an external electrical connector  108 , the flux carrier  112 , the magnetic sensor  104 , and a lead frame interconnection assembly  110 .  
         [0023]    In this embodiment, the cover  106  is primarily rectangular in shape with four sides and a base. The external electrical connector  108  protrudes through one of the sides. The cover  106  also includes a base upon which the magnetic sensor  104  and the lead frame interconnection assembly  110  are mounted. Furthermore, the cover  106  includes four alignment posts  116 , placed near each corner of the cover  106  cylindrically shaped and positioned such that the posts enter and engage mating posts  44  in the housing  40  upon assembly. The sides of the cover  106  include a cutout, stepped, mating lip  118  (FIG. 2) in the wall thickness about the perimeter to facilitate mating and sealing with the housing  40  (FIGS. 2 and 3). The cover  106  is also configured to mate and be attached to the housing  40  in a manner that allows the insulation displacement terminals  102  to be forcibly and securely compressed upon the connection portion  68  of the stator winding  66 . This provides electrical connectivity to each stator assembly  60 .  
         [0024]    The external electrical connector  108  of this embodiment is approximately rectangular with semicircular sides on the shorter sides. One skilled in the art will understand that the connector can take many shapes and configurations appropriate with a specific design, or to accommodate a specific connector. In this embodiment the longer sides lie in a plane parallel to the base of the cover  106 . The external electrical connector  108  is connected to the magnetic sensor  104  and insulation displacement terminals  102  via the lead frame assembly  110 . The lead frame assembly  110  is integrated with the insulation displacement terminals  102  and the magnetic sensor  104 , thus eliminating separate interconnects, hand connections, and a circuit substrate.  
         [0025]    The flux carrier  112  is approximately annular in shape and resembles two crescent-like halves placed together to form a journal. It has a cylindrical center portion sized to accept an end of the rotor shaft  86  with the integrated sense magnets  90 . The flux carrier  112  is positioned on the cover  106  such that the cylindrical center portion is concentric with the rotor shaft  86  when assembled. The rotor shaft  86  can enter and engage the journal when the cover assembly is attached to the housing  40 , thus placing the integrated sense magnets  90  on the rotor shaft in close proximity to the magnetic sensor  104 . The flux carrier  112  provides an aperture  114  at the mating points of the two halves within which the magnetic sensor  104  is positioned.  
         [0026]    The insulation displacement terminals  102  are positioned orthogonal to the base of the cover  106  and positioned on the cover  106  in a manner such that they are aligned with the connection portion  68  of the stator winding  66  of each stator assembly  60 . The insulation displacement terminals  102  are bifurcated terminals formed as part of the lead frame assembly  110 . They are configured to accept, hold, and make electrical contact with the wire at the connection portion  68  of the stator winding  66  of each stator assembly  60  when the cover assembly  100  is assembled onto the housing  40 .  
         [0027]    The invention can also include multipole motors where the longitudinal axis of the rotor shaft  86  is parallel to but eccentric to the housing  40 . In this instance, corresponding adaptations to the cover assembly  100 , rotor assembly  80 , and stator assembly  60  will be made to accommodate the eccentricity while still maintaining the essence of the apparatus and assembly.  
         [0028]    It will be understood that one skilled in the art may make modifications to the embodiment shown herein within the scope and intent of the claims. The invention has been described with specific reference to the preferred embodiments and modifications thereto. Further modifications and alterations may occur to others upon reading and understanding the specification. It is intended to include all such modifications and alterations insofar as they come within the scope of the invention.