Patent Publication Number: US-2021178893-A1

Title: In-wheel motor

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2019-0175610, filed on Dec. 26, 2019, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Field of the Disclosure 
     The present disclosure relates to a high-output, high-torque in-wheel motor having a power line-taken-out structure. 
     2. Description of Related Art 
     In-wheel motors may be used in moving means. The moving means may be operated using electricity as a power source. 
     The in-wheel motor may be powered by a motor assembly disposed in a rim. 
     The motor assembly may include a stator and a rotor. The power generated from the motor assembly may be transmitted directly to a wheel of the in-wheel motor without passing through additional power transmission devices. 
     The wheel wound around the rim of the in-wheel motor may rotate using electricity as a power source. 
     In contrast to moving means in related art, the in-wheel motor may have a relatively simple structure because the in-wheel motor does not require a driving device and a power transmission device having complicated structures. 
     Therefore, the in-wheel motor may enable weight reduction of the moving means and reduces energy loss generated during power transmission. 
     The in-wheel motor may include a tire, a rim, a motor assembly, and a shaft. 
     The tire may surround and be coupled to the rim. The motor assembly may include a stator and a rotor, and be disposed in the rim. The shaft may be connected through a center of the stator. 
     The stator of the in-wheel motor may receive power through an externally connected power line (or a taken-out line). When the power is supplied to the stator, the rotor may rotate around the stator. 
     As the rotor is connected to the rim, the rim rotates when the rotor rotates, and the tire coupled to an outer ring of the rim also rotates. 
     As the required output of single-person electric scooters and electric vehicles increases, a diameter of a power line for supplying power to the in-wheel motor is also increasing. 
       FIG. 1  is a schematic view showing an in-wheel motor in related art. An in-wheel motor  10  in the related art includes a tire  20 , a rim  30 , a motor assembly  40  including a stator  41  and a rotor  43 , a gear assembly  50  including a sun gear  51 , a planetary gear  53 , and a carrier  55 , a shaft  60 , a bearing  80 , and a cover  90 . 
     The in-wheel motor  10  in the related art includes a power line  70 . The power line  70  supplies power to the stator  41 . 
     Further, for the in-wheel motor  10  in the related art, a shaft  60  defines a hollow  61  to take out the power line  70  to an outside thereof. The power line  70  was taken out toward a setting direction (W 1 ) through the hollow  61  defined at the shaft  60 . 
       FIG. 2  is a side view showing a power line  70  taken out from an in-wheel motor in related art. 
     The power line  70  includes a three-phase (U, V, W) power line. The three-phase power line  70  is entirely taken out through a narrow hollow  61  defined at cross section of the shaft  60 . 
     If a diameter of the power line  70  is increased to satisfy high-output, high-torque conditions, the in-wheel motor in the related art may have difficulty in taking out the power line  70  to an outside thereof due to the structure of the in-wheel motor in related art. 
     Further, as the diameter of the power line  70  increases, a size of the hollow  61  is increased to provide a taken-out space of the power line  70 . As a result, an end of the shaft  60  becomes thinner, thereby degrading structural rigidity of the shaft  60 . 
     Therefore, there is a need for a technical solution to not degrade the structural rigidity of the shaft  60  even if the diameter of the power line  70  is increased to provide a high-output, high-torque in-wheel motor. 
     As a related art document, CN001098191C discloses an electric wheel hub assembly. The electric wheel hub assembly in the related art discloses a power line being taken out to an end of a shaft. 
     However, as a size of an end of the shaft is determined by standard, it is difficult to increase the size of the end of the shaft. For this reason, when the diameter of the power supply line is increased to meet high-output, high-torque conditions, it is difficult to take out the power line. 
     In addition, there is a difficulty in processing a hole in the shaft in a diagonal direction and reliability against vibration is deteriorated. Furthermore, performing waterproof and dustproof functions using a bond has a problem in durability and product reliability may be degraded. 
     RELATED ART DOCUMENT 
     (Patent Document 1) CN001098191C 
     SUMMARY OF THE DISCLOSURE 
     The present disclosure provides an in-wheel motor capable of not degrading structural rigidity of a shaft even when a diameter of a power line is increased to provide a high-power, high-torque in-wheel motor. 
     The present disclosure also provides an in-wheel motor capable of increasing the diameter of the power line to provide a high-power, high-torque in-wheel motor as well as improving overall structural rigidity of each of a shaft and a bearing. 
     The present disclosure further provides an in-wheel motor having a structure in which a power line the diameter of which is increased to provide a high-output, high-torque in-wheel motor may be easily taken out of a shaft and improvements in waterproof and dustproof functions. 
     The objects of the present disclosure are not limited to the above-mentioned objects, and other objects and advantages of the present disclosure which are not mentioned may be understood by the following description and more clearly understood based on the embodiments of the present disclosure. It will also be readily understood that the objects and the advantages of the present disclosure may be implemented by features defined in claims and a combination thereof. 
     According to an aspect of the present disclosure, there may be provided an in-wheel motor capable of not degrading structural rigidity of the shaft even when the diameter of a power line is increased to provide a high-power, high-torque in-wheel motor. 
     In addition, according to an aspect of the present disclosure, there may be provided an in-wheel motor capable of increasing the diameter of a power line to provide a high-power, high-torque in-wheel motor as well as improving the overall structural rigidity of each of a shaft and a bearing. 
     In addition, according to an aspect of the present disclosure, there may be provided an in-wheel motor having improvement in waterproof and dustproof functions. 
     An in-wheel motor according to an embodiment of the present disclosure includes a rim, a shaft, a motor assembly, a cover, and a bearing. 
     The tire may surround and be coupled to the outer ring of the rim. 
     The shaft may be connected to the rim through the center of the rim. 
     The motor assembly includes a stator connected and coupled to the shaft in the rim, and a rotor surrounding the stator and rotated around the stator. 
     The cover may be coupled to an opening of the rim to block the motor assembly disposed inside the rim from the outside of the rim and have a center through which the shaft may pass. 
     A bearing is positionally constrained at an inside of the cover and may contact and support the shaft. 
     For the in-wheel motor according to an embodiment of the present disclosure, the shaft includes a first shaft body and a second shaft body to take out the power line through an inner diameter portion of the bearing without degrading the rigidity of the shaft. 
     The first shaft body may extend outward through the center of each of the rim and the cover. 
     The second shaft body has a diameter larger than that of the first shaft body and may be disposed between the stator and the bearing. 
     In this case, a power line for supplying power to the motor assembly and a sensor line may be inserted in a radial direction of the second shaft body between the stator and the bearing, and may be taken out in a longitudinal direction of the second shaft body. 
     The second shaft body may have a first end defining a stator press-fit surface to which the stator is press-fit and a second end defining a bearing contact surface to which the bearing contacts. 
     In addition, the second shaft body includes a first hole disposed between the stator press-fit surface and the bearing contact surface and defined in a radial direction of the second shaft body to insert the power line taken out from the stator. 
     In addition, the second shaft body includes a second hole intersecting with the first hole and defined in a longitudinal direction of the second shaft body to take out the power line inserted through the first hole. 
     In this case, the second hole may be spaced apart from the first shaft body by a predetermined distance and may be defined at a position close to the inner diameter of the bearing. 
     In addition, the second shaft body may have a power line-taken-out path through which the power line passes through and is taken out in an L-shaped shape. 
     The power line-taken-out path includes a first power line-taken-out path into which the power line is inserted in the radial direction of the second shaft body through the first hole and a second power line-taken-out path intersecting with the power line-taken-out path and in which the power line is inserted in a longitudinal direction of the second shaft body from an end of the first power line-taken-out path and is taken out through the second hole. 
     In addition, the second shaft body includes a groove defined along an outer edge of the second hole, and an O-ring inserted into the groove. 
     In addition, the in-wheel motor according to an embodiment of the present disclosure further includes a sealing cap coupled to a surface of the second shaft body to block the O-ring disposed between the second shaft body and the sealing cap. 
     The sealing cap has a center through which the first shaft body protrudes and has a larger diameter than that of the second shaft body to block the second shaft body from outside. Accordingly, excellent long-term waterproof and dustproof performance may be achieved in contrast to an epoxy bonding methods in the related art, thereby increasing a product lifespan and preventing product failure. 
     The power line may be a three-phase power line. Each of the first hole and the second hole may have an area having a diameter larger than a total diameter of the three-phase power line. 
     The second hole may be spaced apart from the first shaft body, defined at a cross section of the second shaft body, and have an arc-shape. 
     In this case, a length of the arc of the second hole may be larger than the total diameter of the three-phase power line. 
     In addition, a width of the second hole may be larger than the diameter of each of the three-phase power lines. 
     For the in-wheel motor according to an embodiment of the present disclosure, the stator includes a stator core coupled to the shaft and a plurality of coils disposed on the stator core. 
     The stator core may be press-fitted and coupled to the stator press-fit surface. 
     In addition, the second shaft body includes a first protrusion protruding outward from the stator press-fit surface, having an annular shape, and configured to support at least one surface of the stator core when the stator core is press-fitted to the stator press-fit surface. 
     Further, the second shaft body includes a second protrusion protruding outward from the bearing contact surface, having an annular shape, and configured to support at least one surface of the bearing. 
     In addition, the in-wheel motor according to an embodiment of the present disclosure includes a first bearing disposed between the motor assembly and the first shaft body and a second bearing disposed between a side body of the rim and the first shaft body. 
     In this case, the bearing contacting the bearing contact surface provided at the second end of the second shaft body may have an inner diameter that is larger than that of each of the first bearing and the second bearing. As the size of the bearing increases, a lifespan of the bearing is increased. Stiffness of the bearing is improved, thereby improving durability. 
     An in-wheel motor according to another embodiment of the present disclosure includes a rim, a shaft, a motor assembly, a gear assembly, a cover, and a bearing. The shaft includes the first shaft body and the second shaft body. The power line may be inserted in a radial direction of the second shaft body between the stator and the bearing, and may be taken out in a longitudinal direction of the second shaft body. 
     For the in-wheel motor according to another embodiment of the present disclosure, a gear assembly includes a sun gear, a planetary gear, and a carrier. 
     The sun gear may be disposed on a same centerline as the rotor. A plurality of planetary gears may be provided to surround a periphery of the sun gear. The carrier may have a frame shape and connect the plurality of planetary gears. 
     According to the present disclosure, the structural rigidity of the shaft may not be deteriorated even when the diameter of the power line is increased to provide a high-output, high-torque in-wheel motor. 
     Specifically, the inner diameter of the bearing is increased and the diameter of a portion of the shaft is increased to provide a power line-taken-out space and not to degrade the structural rigidity of the shaft. 
     In addition, as the size of the bearing is increased, a lifespan of the bearing is increased. Further, stiffness of the bearing is improved, thereby improving durability thereof. 
     In addition, the size of the shaft increases and a number of hollows defined in the shaft is increased. Therefore, the in-wheel motor may have weight reduction and improve ride comfort. 
     In addition, the degradation of the rigidity of the shaft may be prevented, which results from defining a hollow at a cross-section of the shaft, thereby advantageously obtaining overall rigidity of the shaft. 
     In addition, according to the present disclosure, in contrast to other structures sealing the taken-out portion using the epoxy bond or the like, the O-ring and the sealing cap are used at the taken-out portion of the power line, thereby significantly improving the waterproof and dustproof functions. 
     Hereafter, further effects of the present disclosure, in addition to the above-mentioned effect, are described together while describing specific matters for implementing the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view showing an in-wheel motor in related art. 
         FIG. 2  shows a power line-taken-out structure of an in-wheel motor in related art. 
         FIG. 3  is a schematic cross-sectional view showing an example in-wheel motor. 
         FIG. 4  is an enlarged view showing an example power line-taken-out structure of an in-wheel motor. 
         FIG. 5  is a schematic perspective view showing an example shaft of an in-wheel motor. 
         FIG. 6  is a side view showing an example power line-taken-out structure of an in-wheel motor. 
         FIG. 7  is an enlarged view showing area “A” of  FIG. 5 . 
         FIG. 8  is a perspective view showing an example sealing cap used for an in-wheel motor. 
         FIG. 9  is an image showing an example impact load analysis result of an in-wheel motor. 
         FIG. 10  is an image of an example static load analysis result of an in-wheel motor. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY IMPLEMENTATIONS 
     Some embodiments of the present disclosure will be described in detail with reference to the accompanying drawings, such that a person having ordinary knowledge in the art to which the present disclosure pertains may easily implement the technical idea of the present disclosure. The present disclosure may, however, be embodied in different manners and should not be construed as limited to example embodiments set forth herein. 
     A description not relating to the present disclosure is omitted to clearly describe the present disclosure and same reference numerals can be used to refer to same or similar components throughout the disclosure. Further, some embodiments of the present disclosure are described in detail with reference to exemplary drawings. Reference now should be made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same or similar components. Further, a detailed description of a well-known configuration or function relating to the present disclosure may be omitted if it unnecessarily obscures the gist of the present disclosure. 
     Further, the terms “connected,” “coupled,” or the like are used such that, where a first component is connected or coupled to a second component, the first component may be directly connected or able to be connected to the second component, or one or more additional components may be disposed between the first and second components, or the first and second components may be connected or coupled through one or more additional components. 
     Hereinafter, an in-wheel motor according to an embodiment of the present disclosure is described in detail with reference to accompanying drawings. 
     In-Wheel Motor 
       FIG. 3  is a schematic cross-sectional view showing an example in-wheel motor.  FIG. 4  is an enlarged view of a portion of an in-wheel motor corresponding to a power line-taken-out structure. 
     An in-wheel motor  1000  according to an embodiment of the present disclosure is a high-power, high-torque in-wheel motor and may not reduce structural rigidity of the shaft  100  even when a diameter of a power line  900  is increased. 
     In particular, the in-wheel motor  1000  according to an embodiment of the present disclosure may increase a size of each of the shaft  100  and a bearing  510  supporting the shaft  100 , thereby significantly improving structural rigidity thereof. 
     In addition, the in-wheel motor  1000  according to an embodiment of the present disclosure may have greater improvement in waterproof and dustproof functions. 
     The in-wheel motor  1000  according to an embodiment of the present disclosure includes a shaft  100 , a rim  200 , a motor assembly  300 , a cover  410 , and a bearing  510 . 
     In addition, the in-wheel motor  1000  according to the embodiment of the present disclosure may further include a gear assembly  700 . 
     The shaft  100  may include at least two bodies  110  and  130  having different diameters such that a power line  900  having increased diameter is taken out through an area having an inner diameter of the bearing  510  without deteriorating its structural rigidity. 
     The two bodies  110  and  130  may be referred to as a first shaft body  110  and a second shaft body  130 . 
     The first shaft body  110  may pass through a center of each of the rim  200  and the cover  410  and protrudes from both sides of the in-wheel motor  1000  by a predetermined length. 
     The first shaft body  110  may have a shape and a diameter corresponding to a shape and a diameter of the shaft  60  (see  FIG. 1 ) of the in-wheel motor  10  in the related art (see  FIG. 1 ). 
     The in-wheel motor  10  in the related art (see  FIG. 1 ) includes a hollow  61  defined at the shaft  60  to take out the power line  70  (see  FIG. 1 ), but the first shaft body  110  according to the embodiment of the present disclosure does not include the hollow  61 . 
     Therefore, the overall rigidity of the shaft  100  may not be degraded, and rather, the rigidity of the shaft  100  may be significantly improved due to the structure of the second shaft body  130 . 
     The second shaft body  130  is an example component of the shaft  100  and has a larger diameter than that of the first shaft body  110 . 
     The second shaft body  130  may be disposed between the stator  310  (e.g., a stator core  311 ) and a bearing  510 . 
     As the second shaft body  130  has a larger diameter than that of the first shaft body  110 , a size of an inner diameter of the bearing  510  may be increased compared to other bearings. Therefore, the rigidity of the bearing  510  is improved, a lifespan of the bearing  510  is increased, and durability of the bearing  510  is improved. 
     A power line  900  refers to a line taken out from an inside of the in-wheel motor  1000  to an outside of the in-wheel motor  1000  to supply power to the motor assembly  300  (e.g., the stator  310 ). 
     The power line  900  may include a line supplying power to a sensor (e.g., a Hall sensor) of the in-wheel motor  1000 . 
     The power line  900  is inserted between the stator  310  and the bearing  510  in a radial direction of the second shaft body  130 . Subsequently, the inserted power line  900  moves in a longitudinal direction of the second shaft body  130 . Thereafter, as shown in  FIG. 3 , the power line  900  is taken out to outside through a space having the inner diameter of the bearing  510  at a position spaced apart from the first shaft body  110 . 
     According to an embodiment of the present disclosure, the power line  900  with an increased diameter may be taken out to the outside of the in-wheel motor  1000  without degrading the rigidity of the first shaft body  110  corresponding to the shaft  60  in the related art (see  FIG. 1 ). 
     Components of the shaft  100  for obtaining the power line-taken-out structure of the in-wheel motor  1000  are described along with a description with respect to  FIGS. 5 to 7 . 
     Hereinafter, the remaining components of the in-wheel motor  1000  according to an embodiment of the present disclosure except for the shaft  100  are described in detail. 
     The rim  200  is a circular rigid member forming a wheel. A tire  800  surrounds and is coupled to an outer ring of the rim  200 . The rim  200  may further include a tire separation prevention protrusion to maintain the coupled state of the tire  800 , at the outer ring thereof. 
     The rim  200  includes a predetermined accommodation space. A plurality of components including the shaft  100 , the motor assembly  300 , and the gear assembly  700  are coupled to each other and the plurality of coupled components are accommodated in the accommodating space of the rim  200 . 
     The motor assembly  300  is disposed inside the rim  200  and surrounds and is coupled to the shaft  100 . 
     The motor assembly  300  includes a stator  310  and a rotor  330 . 
     The stator  310  is connected to the shaft  100 . For example, the stator core  311  may be press-fitted and coupled to the second shaft body  130 . 
     The stator  310  may receive power for driving the motor from outside through the power line  900 . 
     The stator  310  includes a stator core  311  surrounding and press-fitted to the second shaft body  130  in the rim  200  and a plurality of coils  313 . The plurality of coils  313  may be disposed in a circumferential direction along a circumference of the stator core  311 . 
     The rotor  330  is spaced apart from the stator  310  by a predetermined distance (i.e., there is a space between the rotor  330  and the stator  310 ) and may surround the stator  310 . 
     For example, the rotor  330  includes a rotor core  331  and a plurality of magnets  333 . The plurality of magnets  333  are coupled to the rotor core  331  and face the plurality of coils  313  of the stator  310 . 
     When the power is supplied to the stator  310  by the power line  900 , an electromagnetic force is generated between the coil  313  of the stator  310  and the magnet  333  of the rotor  330 . The rotor  330  rotates around the stator  310  based on the generated electromagnetic force. 
     When the rotor  330  rotates, the rim  200  connected to the rotor  330  rotates. The tire  800  mounted at the outer ring of the rim  200  rotates about the fixed shaft  100  as a central axis based on the rotation of the rim  200 . 
     The cover  410  covers an opening defined at a side surface of the rim  200  and blocks the inside of the rim  200  from the outside of the rim  200 . 
     The cover  410  blocks the inside of the rim  200  from the outside of the rim  200  to protect a plurality of components vulnerable to water, such as the motor assembly  300 . 
     The cover  410  is coupled to the opening of the rim  200  and has a disk shape, and the shaft  100  is coupled through a center of the cover  410 . In addition, a bearing  510  is disposed between the cover  410  and the shaft  100 . 
     The bearing  510  is positionally constrained to contact and support the second shaft body  130  from the inside of the cover  410 . 
     The bearing  510  reduces contact friction between the cover  410  and the shaft  100  when the cover  410  coupled to the rim  200  rotates. 
     The gear assembly  700  is disposed inside the rim  200  and controls a rotational speed of the rotor  330 . 
     The gear assembly  700  includes a sun gear  710 , a planetary gear  730 , and a carrier  750 . 
     The sun gear  710  has a same centerline as the rotor  330 . A plurality of planetary gears  730  may be provided to surround a periphery of the sun gear  710 . The carrier  750  refers to a frame member connecting the plurality of planetary gears  710 . 
     According to an embodiment of the present, the in-wheel motor  1000  may include at least one Hall sensor substrate and the Hall sensor substrate may be disposed between the motor assembly  300  and the cover  410 . For example, the Hall sensor substrate may include a plurality of Hall sensors to stably and accurately measure a magnetic force of the motor assembly  300 . 
     The in-wheel motor  1000  according to an embodiment of the present disclosure may further include two bearings  520  and  530  (see  FIG. 3 ) in addition to the bearing  510  disposed between the second shaft body  130  and the cover  410 . 
     The first bearing  520  is disposed between the motor assembly  300  and the first shaft body  110  and reduces mutual contact friction. 
     The second bearing  530  is disposed between the side body  420  of the rim  200  and the first shaft body  110  and reduces the mutual contact friction. 
     As the second shaft body  130  has a larger diameter than that of the first shaft body  110 , the bearing  510  in contact with the second shaft body  130  has a larger inner diameter than that of each of the first bearing  520  and the second bearing  530  in contact with the first shaft body  110 . 
     Shaft and Power Line-Taken-Out Structure 
       FIG. 5  is a schematic perspective view showing an example shaft of an in-wheel motor.  FIG. 6  is a side view showing an example in-wheel motor having a power line-taken-out structure.  FIG. 7  is an enlarged view showing area “A” of  FIG. 5 . 
     For a shaft  100  of an in-wheel motor  1000  according to an embodiment of the present disclosure, as shown, a power line  900  having an increased diameter is taken out through a space having an inner diameter of a bearing  510  without degrading structural rigidity thereof. 
     The shaft  100  includes a first shaft body  110  and a second shaft boy  130  having different diameters. 
     The first shaft body  110  may pass through a center of each of a rim  200  and a cover  410 , protrudes from both sides of the in-wheel motor  1000  by a predetermined length. 
     The first shaft body  110  may have a shape and a diameter corresponding to a shape and a diameter of the shaft  60  (see  FIG. 1 ) of the in-wheel motor  10  in related art (see  FIG. 1 ). However, the first shaft body  110  does not include the hollow  61 , thereby preventing degradation in overall rigidity of the shaft  100 . 
     The second shaft body  130  is an example component of the shaft  100  and has a diameter larger than a diameter of the first shaft body  110 . The second shaft body  130  may have a diameter-increased shape such that the overall rigidity of the shaft  100  is improved. 
     The second shaft body  130  is disposed between the stator core  311  and the bearing  510 . 
     The power line  900  is inserted in the radial direction of the second shaft body  130  between the stator  310  and the bearing  510 , is curved in a longitudinal direction of the second shaft body  130  by 90 degrees, and is taken out to outside. 
     That is, the power line  900  is not taken out to outside at the first shaft body  110 , but is taken out to outside through the second shaft body  120  disposed at the inner diameter of the bearing  510  (see  FIG. 4 ). 
     Therefore, even if the diameter of the power line  900  is increased to satisfy the high-power and high-torque performance of the in-wheel motor  1000 , the power line  900  is taken out only through the second shaft body  130 , and thus, the rigidity of the first shaft body  110  is not degraded. 
     Referring to  FIG. 5 , the second shaft body  130  has a first end defining a stator press-fit surface  131  into which the stator core  311  is press-fit. 
     In addition, the second shaft body  130  has a second end defining the bearing contact surface  133  to which the bearing  510  contacts. 
     Referring to  FIG. 4 , a structure in which the stator core  311  is press-fitted into the stator press-fit surface  131  and the structure in which the bearing  510  contacts the bearing contact surface  133 . 
     The second shaft body  130  includes a first hole  135  and a second hole  136  to provide a structure in which the power line  900  is taken out. 
     Specifically, the first hole  135  is defined between the stator press-fit surface  131  and the bearing contact surface  133  and penetrates a circumference of the second shaft body  130 , that is, an outer circumferential surface of the second shaft body  130 . 
     For example, the first hole  135  may be defined in the radial direction of the second shaft body  130  in order for the power line  900  taken out from the stator  310  (see  FIG. 4 ) to be inserted through the first hole  135 . 
     The second hole  136  intersects with the first hole  135  and is defined at a side of the second shaft body  130 . The second hole  136  may be defined in the longitudinal direction of the second shaft body  130  to take out the power line  900  inserted through the first hole  135 . 
     In this case, the second hole  136  may be spaced apart from the first shaft body  110  and defined at a position near the inner diameter of the bearing  510  (see  FIG. 4 ). 
     According to this structure, the power line  900  may be taken out to an outside thereof through the second hole  136 , and thus, the rigidity of the first shaft body  110  may not be degraded. Further, even when the diameter of the power line  900  is increased, the size of the second hole  136  may be easily increased using the second shaft body  130 . As a result, the in-wheel motor may have a power line-taken-out structure for achieving high-output, high-torque performance. 
     The second shaft body  130  may include a power line-taken-out path  190  (see  FIG. 4 ) through which the power line  900  passes and is taken out in an L-shape. 
     Referring to  FIG. 4 , the power line-taken-out path  190  includes a first power line-taken-out path  191  and a second power line-taken-out path  193 . 
     The first power line-taken-out path  191  refers to a longitudinal path through which the power line  900  is inserted through the first hole  135  (see  FIG. 5 ) in the radial direction of the second shaft body  130 . 
     The second power line-taken-out path  193  intersects with the first power-taken-out path  191  and is defined in a horizontal direction. 
     The second power line-taken-out path  193  refers to a path through which the power line  900  passes in the longitudinal direction of the second shaft body  130  from an end of the first power line-taken-out path  191  and is taken out in an outward direction (W 2 ) through the second hole  136  (see  FIG. 5 ). 
     Referring to  FIG. 7 , the second shaft body  130  includes a groove  137  defined along an outer edge of the second hole  136 . 
     The groove  137  may have a shape corresponding to that of the second hole  136 , may be disposed near an edge of the second hole  136 , and may have a predetermined depth. 
     At least a portion of an O-ring  150  as an additional sealing means is inserted into the groove  137  defined at the outer portion of the second hole  136  to improve the waterproof and dustproof functions. 
     The O-ring  150  may be made of various materials and have various shapes. Therefore, the present disclosure is not limited to the shape of the illustrated O-ring  150  and various shapes of O-ring that are obvious to those skilled in the art may be used without limitation. 
     In addition, a plurality of grooves  137  may be provided. Although not shown, the plurality of grooves  137  may be defined outside of the second hole  136  and spaced apart from one another by a predetermined distance. In addition, each of the plurality of O-rings  150  is partially inserted into one of the plurality of grooves  137  to further improve the waterproof and dustproof performance. 
     Referring to  FIG. 8 , the second shaft body  130  according to an embodiment of the present disclosure may further include a sealing cap  160 . 
     The sealing cap  160  is coupled to a surface of the second shaft body  130  defining the second hole  136  (see  FIG. 7 ) to block the O-ring  150  (see  FIG. 7 ) disposed between the second shaft body and the sealing cap, and has a disk-shaped member. 
     For example, the sealing cap  160  includes a hole at a center thereof, the first shaft body  110  passes through the central hole, and protrudes from a side surface of the in-wheel motor  1000 . 
     In addition, the sealing cap  160  has a diameter larger than that of the second shaft body  130  to cover the side surface of the second shaft body  130  and blocks the side surface of the second shaft body  130  from an outside thereof. 
     The second shaft body  120  having the power line-taken-out structure may be structurally completely sealed using the O-ring  150  and the sealing cap  160  to achieve excellent waterproof and dustproof performance for a long time compared to using an epoxy bond. In addition, the O-ring  150  may be replaced as necessary, thereby improving product durability and reliability. 
     For the in-wheel motor  1000  according to an embodiment of the present disclosure, the power line  900  may include a three-phase (i.e., U, V, W) power line (see  FIG. 6 ). 
     Referring to  FIG. 5 , each of the first hole  135  and the second hole  136  may have an area with a diameter larger than a total diameter of the three-phase power line  900 . Accordingly, even when the diameter of the power line is increased, the power line  900  may be easily taken out to outside through the first hole  135  and the second holes  136  defined at the second shaft body  130 . 
     As a specific example, referring to  FIG. 7 , the second hole  136  has an arc-shape, is not defined at a protruding portion of the first shaft body  110 , but defined at a cross-section of the second shaft body  130 . 
     If the second hole  136  has an arc-shape, a length (L 1 ) of the arc of the second hole  136  may be larger than a sum of the diameters of the three-phase power line  900  (see  FIG. 6 ). In addition, a width (L 2 ) of the second hole  136  may be larger than the diameter of each of the three-phase power lines  900  (see  FIG. 6 ). 
     Accordingly, the three-phase power line  900  (see  FIG. 6 ) may be taken out to outside through the second hole  136 . In addition, if the diameter of the power line is further increased as necessary, the length and the width of the arc of the second hole  136  may be increased. 
     In addition, when a number of power lines are changed or the diameter of the power line is changed as necessary, a number of second holes  136  may be added and a plurality of second holes  136  may be provided. 
     Referring to  FIG. 7 , the second shaft body  130  includes a first protrusion  132  and a second protrusion  134 . 
     The first protrusion  132  has an annular shape and protrudes outward from the stator press-fit surface  131 . Referring to  FIG. 4 , the first protrusion  132  supports at least a portion of the stator core  311  when the stator core  311  is press-fit into the stator press-fit surface  131 , thereby improving structural stability thereof. 
     The second protrusion  134  has an annular shape and protrudes outward from a bearing contact surface  133 . Referring to  FIG. 4 , the second protrusion  134  supports at least a portion of the bearing  510  when the bearing  510  contacts the bearing contact surface  133  and accurately guides the contact position of the bearing  510 , thereby improving assembly precision and structural stability thereof. 
     According to an embodiment of the present disclosure, the in-wheel motor may increase the diameter of the power line to achieve the high-output, high-torque performance of the in-wheel motor. Furthermore, the all components may have simple assembly structure, thereby improving assembly convenience. In addition, the second shaft body  130  has the increased diameter and the bearing  510  has the increased inner diameter, thereby improving the structural rigidity thereof and improving the waterproof and dustproof functions using the O-ring  150  and the sealing cap  160 . 
       FIGS. 9 and 10  show a result of stiffness analysis of an in-wheel motor of the present disclosure. 
     Referring to  FIG. 9 , the illustrated analysis result image shows an impact load analysis result for a shaft  100  of an in-wheel motor manufactured according to an embodiment of the present disclosure. 
     When an impact load of  50 G is applied to the shaft  100  of the in-wheel motor manufactured according to an embodiment of the present disclosure, the shaft  100  of the in-wheel motor manufactured according to an embodiment of the present disclosure has a pressure of a Max 67.2 Mpa, which corresponds to 5.1 times of standard safety factor of a material, for example, SM45c. Therefore, sufficient rigidity of the shaft  100  of the in-wheel motor manufactured according to an embodiment of the present disclosure is obtained. 
     Referring to  FIG. 10 , the illustrated analysis result image shows a static load analysis result for a shaft  100  of an in-wheel motor manufactured according to an embodiment of the present disclosure. 
     When a vertical load of  1200  N is applied to the shaft  100  of the in-wheel motor manufactured according to an embodiment of the present disclosure, the shaft  100  of the in-wheel motor manufactured according to an embodiment of the present disclosure has a pressure of a Max 62.4 MPa, which corresponds to 5.5 times of a standard safety factor of a material, for example, SM45C. Therefore, sufficient rigidity of the shaft  100  of the in-wheel motor manufactured according to an embodiment of the present disclosure is obtained. 
     The in-wheel motor  1000  according to an embodiment of the present disclosure may take out the power line to outside and the rigidity of the shaft  100  may be further improved even when the diameter of the power line is increased. 
     According to the configurations and the operations of the present disclosure, even when the diameter of the power line is increased to implement the high-power, high-torque in-wheel motor, the structural rigidity of the shaft may not be degraded. 
     Particularly, the inner diameter of the bearing is increased and the diameter of a portion of the shaft is increased such that the power line having the increased diameter may be smoothly taken out to outside without degrading the rigidity of the shaft. 
     Furthermore, as the size of the bearing is increased, a lifespan of the bearing is increased and the rigidity of the bearing may be improved. Thus, the durability of the bearing may be improved. 
     Furthermore, the size of the shaft increases and a number of hollows defined in the shaft increases, thereby reducing weight of the in-wheel motor and improving ride comfort. In addition, weight-reduction processing such as providing a hollow at the cross-section of the shaft may not be performed, thereby preventing degradation of the shaft. 
     In addition, in contrast to sealing the taken-out portion using the epoxy bond in the related art, the in-wheel motor according to the configuration and the operation of the present disclosure may dispose the O-ring at the taken-out portion of the power line and use the sealing cap to entirely cover the second shaft body. Therefore, even when used for a long period of time, the in-wheel motor according to the present disclosure may obtain the excellent waterproof and dustproof functions, thereby increasing a product lifespan. 
     While the present disclosure has been described with reference to the embodiments shown in the drawings, it will be understood that it is merely illustrative and many variations and equivalent other embodiment are possible from the above for those skilled in the art. Therefore, the true technical protection scope of the present disclosure should be defined by claims below. 
     DESCRIPTION OF SYMBOLS 
     
         
         
           
               100 : Shaft 
               110 : First shaft body 
               130 : Second shaft body 
               131 : Stator press-fit surface 
               132 : First protrusion 
               133 : Bearing contact surface 
               134 : Second protrusion 
               135 : First hole 
               136 : Second hall 
               137 : Groove 
               150 : O-ring 
               160 : Sealing cap 
               190 : Power line-taken-out path 
               191 : First power line-taken-out path 
               193 : Second power line-taken-out path 
               200 : Rim 
               300 : Motor assembly 
               310 : Stator 
               311 : Stator core 
               313 : Coil 
               330 : Rotor 
               331 : Rotor core 
               331 : Magnet 
               410 : Cover 
               420 : Side body 
               510 : Bearing 
               520 : First bearing 
               530 : Second bearing 
               700 : Gear assembly 
               710 : Sun gear 
               730 : Planetary gear 
               750 : Carrier 
               800 : Tire 
               900 : Power line 
               1000 : In-wheel motor