Abstract:
A twisting device comprises at least one conductor coupler configured to engage a plurality of the conductors and at least one drive operably connected to the conductor coupler. The at least one drive is configured to rotate the conductor coupler in order to bend the plurality of the conductors and simultaneously move the conductor coupler in an axial direction relative to the electric machine component. An associated method of bending conductors positioned in a component of an electric machine comprises first engaging a plurality conductors with a conductor coupler. Thereafter, the plurality of conductors are bent by rotating the conductor coupler while simultaneously moving the conductor coupler in an axial direction relative to the component of the electric machine.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional patent application No. 61/123,227, filed Apr. 7, 2008, the contents of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     This application relates to the field of electric machines, and more particularly, electric machines having bent conductor windings. 
     Electric machines are important components of conventional internal combustion engine automobiles. For example, electric machines typically serve as starting motors to crank automobile engines. Other electric machines serve as alternators that generate electricity from engine motion and deliver power to automobile loads. Electric machines are also very important in modern hybrid electric vehicles (HEVs), serving as a core component in the HEV&#39;s electric drive system. 
     The electric machine in many HEVs comprises a laminated stator stack with a plurality of rectangular windings inserted into the stator slots. In order to insert the windings into the stator slots, U-shaped segmented conductors (also referred to herein as “hairpins” or “U-shaped bars”) of rectangular cross-section are utilized. These hairpins are created by cutting a rectangular conductor into many segments with each segment having a certain length. The straight segments of wire are then bent and twisted into U-shaped conductors (or “hairpin” conductors) with the proper span for the electric machine. Next, the U-shaped conductors are inserted into the slots of the stator core from an insertion end of the stator. After the U-shaped conductors are inserted into the slots, the legs of the hairpin conductors extend from a connection end of the stator in multiple radial rows of conductors. These leg ends are then bent to appropriate positions before connections are made between the conductors.  FIG. 7  shows a plurality of bent conductors  12  provided in an outer row of conductors for an exemplary stator core  14 . An exemplary four layer conductor arrangement is disclosed in U.S. Pat. No. 7,034,428 to Cai et al., the contents of which are incorporated herein by reference. 
     Precise bending (also referred to herein as “twisting”) of the leg ends of the U-shaped conductors facilitates proper connections between the conductors. However, it can be difficult to bend the conductor ends the exact amount required for a proper connection. In particular, there is relatively little space between the conductors at the end of the stator, and this alone makes access to the conductors and any associated movement required for bending of the conductors difficult. Furthermore, the metal conductors are resilient and tend to spring back to some extent toward their original position after they are bent. This makes precise bending to a desired degree or to a desired location difficult. Furthermore, when a conductor is bent, the height profile of the conductor is changed. In particular, the greater the degree of bending required, the lower the final height profile of the bent conductor. With current bending machines, the rotation and height positioning are not independent. An inability to adapt to the changing height of the conductor during bending may result in an improper bend. 
     In view of the foregoing, it would be advantageous to provide a method and device for twisting stator windings in a more precise fashion. It would also be advantageous if such twisting could be done quickly and with relative ease. It would also be advantageous if such twisting could be accomplished while adapting the system to accommodate for both the rotational offset and the height change in the conductors during the twisting process. 
     SUMMARY 
     In at least one embodiment, a method of bending conductors positioned in a component of an electric machine comprises first engaging a plurality conductors with a conductor coupler. Thereafter, the plurality of conductors are bent by rotating the conductor coupler while simultaneously moving the conductor coupler in an axial direction relative to the component of the electric machine. 
     In at least one embodiment, the step of bending the conductor coupler comprises rotating the conductor coupler in a first rotational direction while simultaneously moving the conductor coupler in an axial direction toward the component of the electric machine and then rotating the conductor coupler in a second rotational direction opposite the first rotational direction in order to bend the plurality of the conductors to a desired position. 
     The conductor coupler may be a first conductor coupler with a second conductor coupler coaxial with the first conductor coupler. The second conductor coupler engages a second plurality of the conductors which are bent by rotating the second conductor coupler opposite the direction of rotation of the first conductor coupler. Simultaneous with the rotation of the second conductor coupler, the second conductor coupler is moved in the axial direction relative to the component of the electric machine. Servomotors may be used to drive the first and second conductor couplers in both the rotational direction as well as the axial direction. 
     In at least one embodiment four layers of conductors are positioned in the electric machine component. A separate and independent conductor coupler is brought into contact with each of the four layers of conductors. The conductor couplers are used to precisely twist/bend of the conductors. Servos are used to drive and control the position of each of the conductor couplers. The rotation and height of each conductor layer of the stator is controlled independently using the servo control. Accordingly, the machine uses eight axes to position four layers of conductors: four axis are used for rotational positioning and four axis for height positioning. 
     The above described features and advantages, as well as others, will become more readily apparent to those of ordinary skill in the art by reference to the following detailed description and accompanying drawings. While it would be desirable to provide a method and device that provides one or more of these or other advantageous features as may be apparent to those reviewing this disclosure, the teachings disclosed herein extend to those embodiments which fall within the scope of any appended claims, regardless of whether such embodiments accomplish one or more of the above-mentioned advantages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a diagrammatic view of a conductor twisting device including a twisting portion and a connection arrangement; 
         FIG. 2  shows a perspective view of a plurality of connection cylinders of the connection arrangement of  FIG. 1 ; 
         FIG. 3A  shows the connection cylinders of  FIG. 2  assembled to form the connection arrangement; 
         FIG. 3B  shows a cross-sectional view of the assembled connection arrangement along line B-B of  FIG. 3A ; 
         FIG. 4  shows a side view of a portion of a toothed rim of one of the connection cylinders of  FIG. 2  opposite the slotted rim of the connection cylinder; 
         FIG. 5  shows a perspective view of the conductor twisting device of  FIG. 1  without the conductor coupler; 
         FIG. 6A  shows a top cutaway view of the conductor twisting device of  FIG. 5 ; 
         FIG. 6B  shows a front view of the barrels of the conductor twisting device of  FIG. 6A  along the axis of the barrels; and 
         FIG. 7  shows a close-up view of a group of bent conductors extending from the connection end of a stator. 
     
    
    
     DESCRIPTION 
     With reference to  FIG. 1 , a diagrammatic view of a conductor twisting device  40  is shown engaging a stator  14  and stator conductors  12 . The twisting device  40  includes a twisting portion  44  configured to rotate about axis  41 . The twisting device  44  releasably engages a connection arrangement  20  along a toothed interlock  37 . The connection arrangement  20  engages the conductors  12  which extend from the stator core  14 . The stator core  14  is held in a stationary position on the twisting device  40  using the stator clamp  42 . Rotation of the twisting device  44  about the axis  41  results in rotation of the connection arrangement  20  and the engaged conductors  12 . 
     With reference to  FIG. 2 , an exemplary unassembled connection arrangement  20  is shown for use with the electric machine twisting device disclosed herein. The connection arrangement  20  comprises a plurality of separate conductor couplers in the form of cylinders  22 ,  24 ,  26  and  28 . Each of the cylinders  22 ,  24 ,  26 ,  28  are assembled in a concentric fashion to form the connection arrangement  20 . Each of the cylinders includes an elongated central body provided between a slotted rim  30  on one end and a toothed rim  34  (see  FIG. 3B ) on the opposite end. 
       FIG. 3A  shows and end view of the slotted rims  30  of each of the cylinders  22 ,  24 ,  26 ,  28  when assembled concentrically to form the connection arrangement  20 . Each slotted rim  30  includes a plurality of slots  32  provided as holes or cavities in the rim  30 . The slots  32  are designed and dimensioned to receive the ends of the conductors  12  provided in the stator core  14 . Thus, the leg ends of the conductors fit down into the slots  32  provided on the rim  30  in a direction parallel to the center axis of the cylinders. The slots  32  are generally configured to match the cross-sectional shape of the conductors. However, the slots  32  are slightly larger than the conductor ends, thus allowing the conductors to be easily inserted into the slots. 
       FIG. 3B  shows a cross-sectional view of the assembled cylinders  22 ,  24 ,  26 ,  28  which form the connection arrangement  20 . As shown in  FIG. 3B , the cylinders  22 ,  24 ,  26 ,  28  are nested in concentric fashion about axis  41  to form the connection arrangement  20 . Each cylinder  22 ,  24 ,  26 ,  28  includes a toothed rim  34  opposite the slotted rim  30 . The slotted rims  30  of each cylinder  22 ,  24 ,  26 ,  28  are generally closer together than the toothed rims  34 . However, it will be recognized that each of the cylinders  22 ,  24 ,  26  and  28  are independent of the other cylinders of the connection arrangement  20 . Accordingly, each of the cylinders  22 ,  24 ,  26  and  28  is capable of independent rotation about axis  41  and independent linear movement along axis  41  without resulting in movement of the other cylinders of the connection arrangement  20 . 
       FIG. 4  shows a side view of a portion of the toothed rim of one of the cylinders  22 ,  24 ,  26  or  28 . The toothed rim  34  is provided on the opposite end of the cylinder from the slotted rim  30 . The toothed rim  34  includes a plurality of teeth  36  that encircle the end of the cylinder. Depressions  38  are provided between each of the teeth  36 . 
     With reference now to  FIG. 5 , a perspective view of a conductor twisting device  40  is shown without the connection arrangement  20  positioned in the device  40 . The conductor twisting device  40  comprises a stator clamp portion  42  and a conductor twisting portion  44 , with a tooling area  48  provided in between. A stator (not shown in  FIG. 5 ) is positioned in a staging area  46  of the clamp portion  42  with the conductor ends of the stator extending toward the twisting portion  44 . The clamp portion  42  is configured to hold the stator core  14  stationary while the conductors  12  in the stator are twisted. Thus, the staging area  46  and clamp portion  42  provide a seat for the stator core  14  when the conductors  12  of the stator are bent using the conductor twisting device  40 . A stator drive arrangement  43  is operable to move the clamp  42  and stator in a linear direction toward or away from the tooling area  48  of the twisting device  40 . 
     While not show in  FIG. 5 , it will be recognized that the connection arrangement  20  is configured for insertion in the tooling area  48  of the twisting device  40  with the toothed rims  34  of the connection arrangement (see  FIG. 4 ) facing the twisting portion  44  and the slotted rims  30  of the connection arrangement facing the clamp portion  42 . The conductor ends extending from the stator are then inserted into the slots  32  on the connection arrangement  30 , with each layer of conductors inserted into a different one of the coaxial cylinders  22 ,  24 ,  26 ,  28  (see  FIG. 3 ). Thus, rotation of one of the cylinders  22 ,  24 ,  26 ,  28  results in twisting of the conductors in the associated layer. 
     At the opposite end of the connection arrangement from the stator, the toothed rims  34  releasably engage the twisting portion  44  of the twisting device  40 . With reference to  FIGS. 5 ,  6 A and  6 B, the twisting portion  44  comprises a yoke  50  and a plurality of concentric barrels  52 ,  54 ,  56 ,  58  (best seen in  FIGS. 6A and 6B ). Each of the concentric barrels  52 ,  54 ,  56  or  58  is independently rotatable with respect to the other barrels (i.e., in a rotational or “circumferential” direction, as noted by arrow  81 ). Furthermore, each of the concentric barrels  52 ,  54 ,  56  or  58  is moveable in the axial direction toward or away from the clamping portion  42  (i.e., a “linear” direction as noted by arrow  71 ). Toothed portions on the ends of the concentric barrels are configured to engage the toothed rims  34  on the connection arrangement, forming a toothed interlock  37  between the concentric barrels  52 ,  54 ,  56 ,  58  and the concentric cylinders  22 ,  24 ,  26 ,  28 . This toothed interlock secures the cylinders  22 ,  24 ,  26 ,  28  to the barrels  52 ,  54 ,  56 ,  58  when the barrels are rotated or moved in a rotational direction or a linear direction toward the staging area  46 . However, the cylinders  22 ,  24 ,  26 ,  28  may be released from the barrels  52 ,  54 ,  56 ,  58  when the barrels are moved in a linear direction away from the staging area  46 . 
     The concentric barrels  52 ,  54 ,  56 ,  58  are operably mounted within a frame  80 . In addition, a total of eight servo motors are mounted to the frame  80 . The eight servo motors include four servo motors  62 ,  64 ,  66  and  68  of a first set  60  and four servo motors  72 ,  74 ,  76  and  78  of a second set  70 . The servo motors of the first set  60  are configured to provide rotational adjustment to the barrels  52 ,  54 ,  56  and  58 . The servo motors of the second set  70  are configured to provide linear adjustment to the barrels  52 ,  54 ,  56  and  58 . 
     As best seen in  FIG. 6A , the second set  70  of servo motors are connected to arms  73 ,  75 ,  77  and  79  that extend from the servo to the barrel. When the second set  70  of servo motors operate, the arms  73 ,  75 ,  77 ,  79  move and result in the barrels  52 ,  54 ,  56  and  58  also moving in a lateral direction (i.e., a linear direction indicated by arrow  71  in  FIG. 6 ). Accordingly, the second set  70  of servo motors are operable to control linear movement of the barrels  52 ,  54 ,  56 ,  58 . 
     The first set of servos  60  are also connected to the barrels  52 ,  54 ,  56 ,  58  with arms. These arms reach the barrels through openings  82 ,  84 ,  86 ,  88  in the barrel mounting cylinders  90 ,  92  connected to the frame  80 . The arms that extend through the openings  82 ,  84 ,  86 ,  88  are best seen in  FIG. 5 , but only two of the arms  63  and  67  are shown in  FIG. 5 . Arm  63  extends through opening  82  and arm  67  extends through opening  86 . When the first set  60  of servo motors operate, the arms  63  and  67  move, resulting in rotation of the barrels  52 ,  54 ,  56 ,  58  which are pivotably connected to the arms. Accordingly, the first set  60  of servo motors are operable to control rotational movement of the barrels. 
     In operation, the stator core  14  is mounted in a stationary position on the twisting device  40  with the conductors of the stator inserted in the slots of the connection arrangement  20 . When the barrels  52 ,  54 ,  56 ,  58  are rotated about their axes in the circumferential direction  81  by the first set of servo motors  60 , the conductors are twisted. In at least one embodiment, the conductors are twisted in opposite directions in alternating layers. Thus, barrels  52  and  54  are rotated one direction by the servo motors, while barrels  54  and  56  are rotated in opposite directions. 
     When any barrel  52 ,  54 ,  56 ,  58  is rotated it is also moved in the liner direction  71  toward the stator core  14  by the motors in the second set  70  of servo motors. This also results in linear movement of the associated cylinders  22 ,  24 ,  26 ,  28 . This linear movement is made to account for the reduction in height of the conductor ends as they are twisted in the stator. By moving the barrels  52 ,  54 ,  56 ,  58  (and the associated cylinders  22 ,  24 ,  26 ,  28 ), the device  40  ensures that the conductor ends remain fully seated in the slots  32  of the cylinders  22 ,  24 ,  26 ,  28  during the twisting process. In other words, as the conductors  12  are rotated by the cylinders  22 ,  24 ,  26 ,  28 , the conductors tend to pull away from the cylinders. However, because the cylinders  22 ,  24 ,  26  and  28  also move in the linear direction toward the stator core  14  when the cylinders are rotated, the conductors  12  are not allowed to escape the slots  32  in the cylinders. Thus, the dual action of rotation and linear movement of the barrels  52 ,  54 ,  56 ,  58  and the associated cylinders  22 ,  24 ,  26  and  28  helps ensure that the conductors  12  are properly twisted by the twisting device  40 . 
     By using servo motors to perform the twisting motion, the twisting device  40  may be used to more precisely twist the conductors. In particular, the servo motors may be operated to provide an amount of over-twist to the conductors (i.e., rotation past the desired amount). After an over-twist, the servo motors are used to provide a slight amount of reverse twist to the conductors. The reverse twist returns the conductors back to their desired twisted location for connection. This process of over-twist and return (or reverse twist) reduces the tendency of the conductors to spring back toward their original position and out of the proper connection position. 
     In addition to the foregoing, it will be recognized the servo-motors may be utilized to provide feedback information related to the position of the barrels  53 ,  54 ,  56 ,  58  and associated cylinders  22 ,  24 ,  26 ,  28  during the twisting process. In particular, the servomotors are provided with a rotary encoder on a back portion of each servomotor. The positions of the linear actuators that move the barrels  52 ,  54 ,  56   58  of the twisting device  40  are synchronized with the encoders by using home position switches. This information related to the position of an associated barrel may then be used to determine the extent to which the servomotors should be driven to achieve a desired amount of barrel movement. In particular, the servomotors may be connected to a microprocessor which uses the feedback information to drive each servomotor a precise amount in order to achieve a precise amount of rotational or linear movement of the associated barrel. It will also be recognized that the feedback information may also be provided in other manners. For example, optical sensors may be used to determine the extent of rotational or linear movement of one or more of the barrels  52 ,  54 ,  56 ,  58  or cylinders  22 ,  24 ,  26  or  28 . In this case, the motor or other actuator may be driven until the optical sensor indicates that the barrel or cylinder has moved the desired amount. 
     Although the present invention has been described with respect to certain preferred embodiments, it will be appreciated by those of skill in the art that other implementations and adaptations are possible. For example, while the embodiments disclosed herein have been directed to stator windings, the machine and method disclosed herein could also be used to twist other windings, such as rotor windings. As another example, although the current twisting device has been described with four barrels and four associated cylinders, fewer or more barrels or cylinders may be utilized, depending on the number of conductor layers to be twisted. Moreover, there are advantages to individual advancements described herein that may be obtained without incorporating other aspects described above. Therefore, the spirit and scope of any claims should not be limited to the description of the preferred embodiments contained herein.