Patent Publication Number: US-2023163671-A1

Title: Radial and axial type hybrid motor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefits of Korean Patent Application No. 10-2021-0163823, filed on Nov. 24, 2021, the disclosure of which is incorporated herein by reference in its entirety 
     TECHNICAL FIELD 
     The present disclosure relates to a radial and axial type hybrid motor. 
     BACKGROUND 
     The description in this section merely provides background information related to the present disclosure and does not necessarily constitute the prior art. 
     As the motorization of vehicles intensifies, the demand for non-rare-earth motors is increasing. As non-rare-earth motors that can practically replace permanent magnet synchronous motors (PMSM), inductor motors (IM) are attracting attention, and therefore, active research is being done to improve the performance of induction motors. 
     An induction motor largely consists of a stator and a rotor, and rotates the rotor by using a rotating magnetic field generated by a stator winding and an induced current generated by the rotating magnetic field. 
     The performance of induction motors, such as power factor and efficiency, decreases with the increasing number of poles. For this reason, most induction motors have a small number of poles, around 2 to 8 poles, and this makes end coils relatively longer. 
     Meanwhile, stator winding methods are largely categorized as concentrated winding or distributed winding. The distributed winding is a winding method in which a coil of each phase is distributed in two or more slots, which has the advantage of less harmonics compared to the concentrated winding. In the case of inductor motors, the distributed windings are generally used to minimize harmonic components generated by rotor and stator slots. A disadvantage of distributed windings is that their end coils are longer than those of concentrated windings. 
     Such an increase in the length of end coils leads to an increase in the axial length of induction motors and consequently an increase in the overall volume of the induction motors. 
     SUMMARY 
     According to at least one embodiment, the present disclosure provides a hybrid motor including a rotor, a radial stator facing the circumference of the rotor, a first axial stator facing a first side of the rotor, and a second axial stator facing a second side of the rotor. The rotor includes a plurality of conduction bars arranged in radial and axial directions, corresponding to the radial stator and the first and second axial stators, and a plurality of end-rings electrically connecting the plurality of conduction bars. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG.  1 A  is an exploded perspective view schematically illustrating a hybrid motor according to an exemplary embodiment of the present disclosure. 
         FIG.  1 B  is a partial cross-sectional perspective view schematically illustrating a hybrid motor according to an exemplary embodiment of the present disclosure. 
         FIG.  2    is a perspective view schematically illustrating a conductor bar structure of a radial induction motor of the prior art. 
         FIG.  3 A  is a perspective view schematically illustrating a conduction bar structure of a hybrid motor according to an exemplary embodiment of the present disclosure. 
         FIG.  3 B  is a horizontal cross-sectional view schematically illustrating a conduction bar structure of a hybrid motor according to another exemplary embodiment of the present disclosure. 
         FIG.  4    is a graph showing torque-slip characteristics of a hybrid motor according to an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure provides a radial and axial type hybrid motor that can increase torque without increasing volume in comparison to conventional induction motors, by placing an axial stator in an empty space inside an end coil and arranging conduction bars radially on both sides of a rotor. 
     Hereinafter, some embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, like reference numerals preferably designate like elements, although the elements are shown in different drawings. Further, in the following description of some embodiments, a detailed description of related known components and functions when considered to obscure the subject of the present disclosure will be omitted for the purpose of clarity and for brevity. 
     Additionally, various terms such as first, second, A, B, (a), (b), etc., are used solely for the purpose of differentiating one component from others but not to imply or suggest the substances, the order or sequence of the components. Throughout this specification, when parts “include” or “comprise” a component, they are meant to further include other components, not excluding thereof unless there is a particular description contrary thereto. The terms such as “unit,” “module,” and the like refer to units for processing at least one function or operation, which may be implemented by hardware, software, or a combination thereof. 
       FIG.  1 A  is an exploded perspective view schematically illustrating a hybrid motor according to an exemplary embodiment of the present disclosure. 
       FIG.  1 B  is a partial cross-sectional perspective view schematically illustrating a hybrid motor according to an exemplary embodiment of the present disclosure. 
     Referring to  FIG.  1 A , the hybrid motor according to an exemplary embodiment of the present disclosure may include all or part of a rotor  100 , a radial stator  110 , and axial stators  120 . 
     The rotor  100  may include a plurality of conduction bars  102  that are arranged in radial and axial directions, an end-ring  104  where the plurality of conduction bars  102  are electrically connected, and a rotor core  106  with a plurality of slots where the conduction bars  102  are arranged (or inserted). Here, the axial direction refers to the direction of the axis of rotation of the rotor  100 , and the radial direction refers to a direction perpendicular to the axis of rotation. The rotor core  106  may have a cylindrical structure with a shaft hole formed at the center. Accordingly, the rotor  100  is near-cylindrical as a whole. A detailed structure of the conduction bars  102  according to an exemplary embodiment of the present disclosure will be described below with reference to  FIGS.  3 A and  3 B . 
     The radial stator  110  may be disposed to face the circumference of the rotor  100 . The radial stator  110  may include a first stator core  112  providing a magnetic flux path and a first coil  114  wound on the first stator core  112 , and generate a rotating magnetic field through a current applied to the first coil  114 . Here, as illustrated in  FIG.  1 B , a portion of the first coil  114  exposed out of slots in the first stator core  112  is referred to as an end coil  116 . 
     The axial stators  120  may be disposed to face both sides of the rotor  100 . Each axial stator  120  may include a second stator core  122  providing a magnetic flux path and a second coil  124  wound on the second stator core  122 , and generate a rotating magnetic field through a current applied to the second coil  124 . 
     Referring to  FIG.  1 B , the axial stators  120  may be disposed inside the end coil  116 . According to an embodiment of the present disclosure, the height of the axial stators  120  may be designed to be smaller than the height (or length) of the end coil  116 , in order to increase torque density without increasing volume in comparison to conventional radial induction motors having the radial stator  110 , but not necessarily limited to this. 
     Meanwhile, in the radial stator  110  and the axial stators  120 , the first coil  114  and the second coil  124  may be connected and wound as a single body at the position of each pole and receive a current from an inverter (not shown), or the first coil  114  and the second coil  124  may be separately wound and receive currents from their respective inverters. In other words, the radial stator  110  may receive current from a first inverter (not shown) while the axial stators  120  may receive current from a second inverter (not shown). 
     When the radial stator  110  and the axial stators  120  receive currents from their respective inverters, the radial stator  110  and the axial stators  120  may be selectively driven depending on load conditions. For example, both the radial stator  110  and the axial stators  120  may be driven during high-load operation, and either the radial stator  110  or the axial stators  120  may be driven during low-load operation. In this way, efficiency may be improved. 
     Moreover, when the radial stator  110  and the axial stators  120  receive currents from their respective inverters, a rotating magnetic field generated by the axial stators  120  may rotate at synchronous or asynchronous speed with respect to the rotor  100 . The inverter supplying current to the second coil  124  may be controlled such that the rotating magnetic field generated by the axial stators  120  rotates at synchronous or asynchronous speed with respect to the mechanical rotation speed of the rotor  100 . 
     On the other hand, when the radial stator  110  and the axial stators  120  receive currents from the same inverter, the rotating magnetic field generated by the axial stators  120  may rotate at asynchronous speed with respect to the rotor  100 . 
     Prior to describing a conduction bar structure of a hybrid motor according to an exemplary embodiment of the present disclosure, a conduction bar structure of a conventional radial induction motor will be described below with reference to  FIG.  2   . 
       FIG.  2    is a perspective view schematically illustrating a conduction bar structure of a conventional radial induction motor. 
     Referring to  FIG.  2   , the rotor of the radial induction motor includes a plurality of conduction bars  200  arranged radially from the axis of rotation and an end-ring  210  provided on both ends of the conduction bars  200 , that interconnects the plurality of conduction bars  200 . Here, the conduction bars  200  are arranged radially from the axis of rotation so that their length direction is parallel to the axial direction of the rotor. 
     Meanwhile, the stator of the radial induction motor may include a coil wound in such a way as to correspond to the conduction bars  200 , and may be identical or similar to the radial stator  110  according to an embodiment of the present disclosure. 
       FIG.  3 A  is a perspective view schematically illustrating a conduction bar structure of a hybrid motor according to an exemplary embodiment of the present disclosure. 
     The conduction bars  102  may include a plurality of first conduction bars  300  corresponding to the radial stator  110  and a plurality of second conduction bars  310  connected to both ends of the first conduction bars  300  and corresponding to the axial stators  120 . 
     A plurality of first conduction bars  300  are circumferentially arranged on the circumference of the rotor  100 , and a plurality of second conduction bars  310  are radially arranged on both sides of the rotor  100 . Specifically, according to an embodiment of the present disclosure, the first conduction bars  300  are arranged radially from the axis of rotation so that their length direction is parallel to the axial direction of the rotor  100 , and the second conduction bars  310  are arranged radially from the axis of rotation so that their length direction is parallel to the radial direction of the rotor  100 . 
     End-rings  104  are provided on one end of the second conduction bars  310  to electrically and mechanically connect the plurality of second conduction bars  310 . Specifically, one end of each second conduction bar  310  is electrically and mechanically connected to any one of the end-rings  104 , and the other end of each second conduction bar  310  is electrically and mechanically connected to any one of the first conduction bars  300 . Accordingly, the first conduction bars  300 , the second conduction bars  310 , and the end-rings  104  are electrically connected as a single body. 
     According to an embodiment of the present disclosure, when a rotating magnetic field generated by the radial stator  110  induces currents in the first conduction bars  300 , the induced currents flow to the second conduction bars  310  as well, and an axial magnetic flux is created by the radial currents flowing through the second conduction bars  310 . 
     Likewise, when a rotating magnetic field generated by the axial stators  120  induces currents in the second conduction bars  310 , the induced currents flow to the first conduction bars  300  as well, and a radial magnetic flux is created by the axial currents flowing through the first conduction bars  300 . 
     Accordingly, with the addition of torque generated by the radial magnetic flux and torque generated by the axial magnetic flux, the conduction bar structure according to an embodiment of the present disclosure can form more magnetic flux compared to the conduction bar structure of  FIG.  2   , and this may increase overall average torque. 
     The conduction bar structure according to an embodiment of the present disclosure may be similar in concept to the way in which the second conduction bars  310  on both sides are arranged and spread out along the circumference of the rotor. Accordingly, given that the radius of the rotor is constant, the hybrid motor according to an embodiment of the present disclosure may provide the same level of output as the radial induction motor whose rotor has a longer axial length (and therefore larger volume). 
     Furthermore, according to an embodiment of the present disclosure, as the second conduction bars  310  are arranged on both sides of the rotor  100 , the radius and width of the end-ring  104  may be shorter, and the magnetic flux path may be longer, compared to the conduction bar structure of  FIG.  2   , thereby improving driving torque characteristics. 
       FIG.  3 B  is a horizontal cross-sectional view schematically illustrating a conduction bar structure of a hybrid motor according to another exemplary embodiment of the present disclosure. 
     Referring to  FIG.  3 B , the first conduction bars  300  and/or the second conduction bars  310  according to another embodiment of the present disclosure may be distorted to have a skew at a predetermined angle. By distorting the first conduction bars  300  and/or the second conduction bars  310  to a skewed shape, torque ripple may be reduced, and therefore noise and/or vibration characteristics of the motor may be improved. 
       FIG.  4    is a graph showing torque-slip characteristics of a hybrid motor according to an exemplary embodiment of the present disclosure. 
     In  FIG.  4   , “With axial type” represents a hybrid motor according to an embodiment of the present disclosure, and “Without axial type” represents a radial induction motor. 
     Referring to  FIG.  4   , it can be seen that the hybrid motor according to an embodiment of the present disclosure has more torque than the radial induction motor. 
     As described above, according to an embodiment of the present disclosure as described above, it is possible to increase torque without increasing volume in comparison to conventional induction motors, by placing an axial stator in an empty space inside an end coil and arranging conduction bars radially on both sides of a rotor. 
     Although embodiments of the present disclosure have been described for illustrative purposes, those having ordinary skill in the art should appreciate that various modifications, additions, and substitutions are possible, without departing from the idea and scope of the present disclosure. Therefore, embodiments of the present disclosure have been described for the sake of brevity and clarity. The scope of the technical idea of the present embodiments is not limited by the illustrations. Accordingly, those having ordinary skill should understand the scope of the present disclosure should not be limited by the above explicitly described embodiments but by the claims and equivalents thereof.