Patent Publication Number: US-2020300351-A1

Title: Driving apparatus for electric vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. 119 to Korean Patent Application No. 10-2019-0032618, filed on Mar. 21, 2019, the disclosure of which is hereby incorporated by reference in its entirety. 
     BACKGROUND 
     The present disclosure relates to a driving apparatus for an electric vehicle. 
     In recent years, electric vehicles using electric power as a power source have been actively developed in place of vehicles using oil as a power source. 
     The electric vehicle comprises a battery for supplying electric power and a driving apparatus which operates by the battery to rotate an axle. The driving apparatus comprises a driving motor for generating power through electric power supplied from the battery and a transmission device (or a gear box) for connecting the driving motor with the axle. 
     The transmission device may be understood as a device for deceleration or gear shifting. Specifically, the power generated by the driving motor is transmitted to the transmission device and the power transmitted to the transmission device is decelerated or changed and transmitted to the axle. 
     Korean Patent Laid-Open Publication No. 10-2015-0004108 (Publication Date: Jan. 12, 2015) discloses a double-reduction driving apparatus for a hybrid and electric vehicle. 
     The reduction driving apparatus disclosed in the above-described document comprises an input shaft connected to a driving motor, an intermediate shaft, and an output shaft, and the output shaft comprises a first gear and a second gear. 
     In addition, the output shaft is provided with a shift sleeve (or a synchronizer) selectively coupled to the first gear or the second gear, such that the shift sleeve slips to shift the gear to the first gear or the second gear according to a gear shifting command. 
     However, the reduction driving apparatus disclosed in the above-described document has the following problems. 
     First, since the conventional reduction driving apparatus for an electric vehicle does not have a clutch for interrupting power between the motor and the transmission device at the time of gear shifting, impact may occur due to input torque of the motor when the gear is put out for gear shifting. 
     Second, impact occurring during gear shifting may be reduced by adding a clutch for interrupting power between the motor and the transmission device. However, in this case, product cost may increase due to addition of the clutch. 
     Third, since the conventional synchronizer for gear shifting comprises a plurality of parts such as a hub, a sleeve, a ring, a fork, a cone, and a friction material and has a complicated structure, it is difficult to assemble the synchronizer. Therefore, misassembling may occur and defective products may occur. 
     SUMMARY 
     An object of the present disclosure is to solve the problem by providing a driving apparatus for an electric vehicle capable of minimizing impact due to input torque of a motor at the time of gear shifting without a clutch for interrupting power between the motor and a transmission device. 
     Another object of the present disclosure is to solve the problem by providing a driving apparatus for an electric vehicle capable of primarily performing speed synchronization between an input shaft and a gear through motor control and secondarily performing speed synchronization between the input shaft and the gear through a rotating magnetic field. 
     Another object of the present disclosure is to solve the problem by providing a driving apparatus for an electric vehicle in which the structure of a synchronizer for gear shifting is very simple and the number of parts is remarkably reduced. 
     A driving apparatus for an electric vehicle according to an embodiment of the present disclosure may comprise a driving motor and a transmission device coupled to the driving motor and configured to receive a driving force of the driving motor. 
     The transmission device may comprise an input shaft connected to a rotation shaft of the driving motor and comprising a first driving gear and a second driving gear, a synchronizer disposed between the first driving gear and the second driving gear and selectively coupled to the first driving gear or the second driving gear, an intermediate shaft comprising a first shift gear coupled to the first driving gear and a second shift gear coupled to the second driving gear, and an output shaft coupled to the intermediate shaft. 
     In particular, the synchronizer may comprise a first coupling ring coupled to the first driving gear and comprising a first magnet, a second coupling ring coupled to the second driving gear and comprising a second magnet, and a sleeve disposed between the first coupling ring and the second coupling ring and comprising a winding coil. 
     According to the configuration of the synchronizer, since speed synchronization between an input shaft and a gear may be primarily performed through motor control and speed synchronization between the input shaft and the gear may be secondarily performed through a rotating magnetic field, it may be possible to minimize impact due to input torque of a motor at the time of gear shifting, without a clutch for interrupting power between the motor and a transmission device. In addition, since the structure of a synchronizer for gear shifting can be very simple, the number of parts can be remarkably reduced, and product costs can be reduced. 
     Specifically, the first coupling ring and the second coupling ring may be configured to surround a circumference of the input shaft. At this time, the driving apparatus may further comprise a first bearing disposed between an outer circumferential surface of the input shaft and the first driving gear. The first bearing may rotatably support the first driving gear, and the first coupling ring may be configured to be inserted into an outer circumferential surface of the first driving gear. The driving apparatus may further comprise a second bearing disposed between an outer circumferential surface of the input shaft and the second driving gear. The second bearing may rotatably support the second driving gear, and the second coupling ring may be configured to be inserted into an outer circumferential surface of the second driving gear. 
     The sleeve may be configured to surround a circumference of the input shaft. The first magnet and the second magnet may be arranged to face each other. 
     The first coupling ring may comprise a plurality of first magnets spaced apart from each other in a circumferential direction, and the second coupling ring may comprise a plurality of second magnets spaced apart from each other in a circumferential direction. 
     The winding coil may be disposed between the first magnet and the second magnet. That is, the first magnet, the winding coil, and the second magnet may overlap one another in an axial direction. 
     The winding coil may comprise a plurality of winding coils wound inside the sleeve, and the plurality of winding coils may be spaced apart from each other inside the sleeve in a circumferential direction. 
     The input shaft may further comprise a brush configured to apply current to the winding coil. A wire extending from the brush may be configured to be connected to a controller along a cavity of the input shaft. 
     The driving apparatus may further comprise an actuator configured to move the sleeve in an axial direction on an outer circumferential surface of the input shaft. Therefore, the sleeve may be selectively coupled to the first driving gear or the second driving gear. 
     The driving apparatus may further comprise a cone formed at one side of at least one of the first coupling ring or the second coupling ring. The cone may be selectively coupled to a portion of the sleeve. The cone may comprise a first cone formed at one side of the first coupling ring and a second cone formed at one side of the second coupling ring in accordance with the first cone. 
     The first cone may protrude from an exterior of the first coupling ring toward the sleeve, and the second cone may protrude from an exterior of the second coupling toward the sleeve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing the configuration of a driving apparatus for an electric vehicle according to an embodiment of the present disclosure. 
         FIG. 2  is a cross-sectional view showing a transmission device according to an embodiment of the present disclosure. 
         FIG. 3  is a cross-sectional view showing the configuration of a synchronizer according to an embodiment of the present disclosure. 
         FIG. 4  is a view showing the configuration of a coupling ring according to an embodiment of the present disclosure. 
         FIG. 5  is a view showing the configuration of a sleeve according to an embodiment of the present disclosure. 
         FIG. 6  is a view showing a state in which the sleeve according to the embodiment of the present disclosure is placed at a neutral position. 
         FIG. 7  is a view showing a state in which the sleeve according to the embodiment of the present disclosure is moved to a first coupling ring side. 
         FIG. 8  is a view showing a state in which the sleeve according to the embodiment of the present disclosure is moved to a second coupling ring side. 
         FIG. 9  is a view showing synchronization between a coil and a magnet according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. 
     In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific preferred embodiments in which the present disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present disclosure, and it is understood that other embodiments may be utilized and that logical structural, mechanical, electrical, and chemical changes may be made without departing from the spirit or scope of the invention. To avoid detail not necessary to enable those skilled in the art to practice the present disclosure, the description may omit certain information known to those skilled in the art. The following detailed description is, therefore, not to be taken in a limiting sense. 
     Also, in the description of embodiments, terms such as first, second, A, B, (a), (b) or the like may be used herein when describing components of the present disclosure. Each of these terminologies is not used to define an essence, order or sequence of a corresponding component but used merely to distinguish the corresponding component from other component(s). It should be noted that if it is described in the specification that one component is “connected,” “coupled” or “joined” to another component, the former may be directly “connected,” “coupled,” and “joined” to the latter or “connected”, “coupled”, and “joined” to the latter via another component. 
     Exemplary embodiments of the present disclosure will be described below in detail with reference to the accompanying drawings in which the same reference numbers are used throughout this specification to refer to the same or like parts. In describing the present disclosure, a detailed description of known functions and configurations will be omitted when it may obscure the subject matter of the present disclosure. The accompanying drawings are used to help easily understood the technical idea of the present disclosure and it should be understood that the idea of the present disclosure is not limited by the accompanying drawings. 
     It will be understood that, although the terms first, second, A, B, (a), (b), etc. may be used herein to describe various elements of the present disclosure, these terms are only used to distinguish one element from another element and essential, order, or sequence of corresponding elements are not limited by these terms. It will be understood that when one element is referred to as “being connected to”, “being coupled to”, or “accessing” another element, one element may “be connected to”, “be coupled to”, or “access” another element via a further element although one element may be directly connected to or may directly access another element. 
       FIG. 1  is a block diagram showing the configuration of a driving apparatus for an electric vehicle according to an embodiment of the present disclosure. 
     Referring to  FIG. 1 , the driving apparatus for the electric vehicle (hereinafter referred to as a “driving apparatus”)  100  according to the embodiment of the present disclosure may comprise a driving motor  100 , a transmission device  200  and driving wheels  300 . 
     The driving motor  100  may generate driving force by applied current. 
     Specifically, the driving motor  100  may comprise a stator and a rotor disposed inside the stator. The stator may be fixed to a motor housing, and the rotor may be rotatably disposed inside the stator. In addition, when electric power (AC current) may be applied to the stator, the rotor may rotate by electromagnetic force. 
     The stator and the rotor may be provided in a cylindrical shape with a hollow formed therein. Specifically, the insides of the stator and the rotor may be opened in an axial direction. In addition, the rotor may be axially disposed inside the stator and a rotor shaft may be radially disposed inside the rotor. 
     The rotor shaft may be understood as a component for connecting the rotor with the below-described transmission device. The rotor shaft may be composed of a hollow shaft and may be rotated with the rotor. 
     The transmission device  200  may convert power generated by the driving motor  100  into required rotational force according to a speed and may transmit the rotational force to an axle. The transmission device  200  may comprise a plurality of gears, which may be shifted according to the shift ratio of the plurality of gears. 
     The transmission device  200  may comprise a gear box for transmitting driving force or rotational force of the driving motor  100  to the axle. The gear box may comprise a shaft coupled with the plurality of gears and bearings. 
     The driving wheels  300  may rotate by rotational force transmitted from the transmission device  200  to the axle. A plurality of driving wheels  300  may be provided to support the load of the electric vehicle. The plurality of driving wheels  300  may enable the electric vehicle to travel through rolling on the ground. 
     The driving apparatus  10  may further comprise a controller  400 . 
     The controller  400  may control driving of the driving motor  100  and the transmission device  200 . The controller  400  may apply electric power or AC current to the driving motor  100 . The controller  400  may adjust a frequency to control the driving force or the rotational speed of the driving motor  100 . 
     The driving apparatus  10  may further comprise an actuator  500 . 
     The actuator  500  may control driving of a synchronizer included in the transmission device  200 . The actuator  500  may control slipping of a sleeve included in the synchronizer according to a gear shifting command of the controller  400 , thereby smoothly shifting gears. 
       FIG. 2  is a cross-sectional view showing a transmission device according to an embodiment of the present disclosure. 
     Referring to  FIG. 2 , the transmission device  200  according to the embodiment of the present disclosure may comprise an input shaft  210 , an intermediate shaft  220  and an output shaft  230 . 
     The input shaft  210  may be connected with the rotor shaft or the rotation shaft of the driving motor  100  to receive the driving force generated in the driving motor  100 . 
     The input shaft  210  may be referred to as a “driving shaft”. 
     The transmission device  200  may further comprise a first driving gear  211  and a second riving gear  212  coupled to an outer circumferential surface of the input shaft  210 . 
     The first driving gear  211  and the second driving gear  212  may be installed to surround the circumference of the input shaft  210 . The diameter of the first driving gear  211  may be less than that of the second driving gear  212 . The first driving gear  211  and the second driving gear  212  may be sequentially spaced apart from the front end of the input shaft  210 . 
     Here, the term “front end” means one end (the left end in  FIG. 2 ) of the input shaft  210  connected to the rotation shaft of the driving motor  100  and the term “rear end” means the other end (the right end in  FIG. 2 ) corresponding to the opposite side of the front end of the input shaft  210 . 
     In addition, the transmission device  200  may further comprise a plurality of bearings  213  and  214  coupled to the outer circumferential surface of the input shaft  210 . 
     The plurality of bearings  213  and  214  may include the first bearing  213  rotatably supporting the first driving gear  211  and the second bearing  214  rotatably supporting the second driving gear  212 . 
     The first bearing  213  may be provided between the outer circumferential surface of the input shaft  210  and the first driving gear  211  to rotatably support the first driving gear  211 . 
     The second bearing  214  may be provided between the outer circumferential surface of the input shaft  210  and the second driving gear  212  to rotatably support the second driving gear  212 . 
     In addition, the transmission device  200  may further comprise a synchronizer  600  coupled to the outer circumferential surface of the input shaft  210 . 
     The synchronizer  600  may be provided between the first driving gear  211  and the second driving gear  212 . The synchronizer  600  may be selectively engaged with the first driving gear  211  or the second driving gear  212 , as the sleeve slides in the axial direction (to the left or right in the figure) according to the gear shifting command of the controller  400 . 
     The transmission device  200  may further comprise a plurality of ball bearings  215  and  216  provided on the outer circumferential surface of the input shaft  210 . 
     The plurality of ball bearings  215  and  216  may include the first ball bearing  215  disposed at the front side of the input shaft  210  and the second ball bearing  216  disposed at the rear side of the input shaft  210 . 
     Specifically, the first ball bearing  215  may be disposed at the front side of the first driving gear  211 , and the second ball bearing  216  may be disposed on the rear end of the input shaft  210 . Therefore, both ends of the input shaft  210  may be rotatably supported by the plurality of bearings  215  and  216 . 
     The intermediate shaft  220  may receive torque and rotational force from the input shaft  210 . The intermediate shaft  220  may change the received torque and rotational force and may then transmit the changed torque and rotational force to the output shaft  230 . The intermediate shaft  220  may be a hollow shaft. 
     The intermediate shaft  220  may be referred to as a “shift shaft” or an “idle shaft”. 
     The transmission device  200  may further comprise a first shift gear  221  and a second shift gear coupled to the outer circumferential surface of the intermediate shaft  220 . 
     The diameter of the first shift gear  221  may be greater than that of the second shift gear  222 . The first shift gear  221  and the second shift gear  222  may be sequentially spaced apart from the front end of the intermediate shaft  220 . 
     The first shift gear  221  and/or the second shift gear  222  may be formed integrally with the intermediate shaft  220 . 
     The first shift gear  221  may be engaged with the first driving gear  211  and the second shift gear  222  may be engaged with the second driving gear  212 . 
     The transmission device  200  may further comprise a plurality of bearings  223  and  224  provided on the outer circumferential surface of the intermediate shaft  220 . 
     The plurality of bearings  223  and  224  may include a front bearing  223  disposed on the front end of the intermediate shaft  220  and a rear bearing  224  disposed on the rear end of the intermediate shaft  220 . Therefore, both ends of the intermediate shaft  220  may be rotatably supported by the plurality of bearings  223  and  224 . 
     The transmission device  200  may further comprise a driven gear  225  provided on the outer circumferential surface of the intermediate shaft  220 . 
     The driven gear  225  may transmit the increased or decreased torque and rotational force to the output shaft  230  through the first shift gear  221  or the second shift gear  222 . 
     Specifically, the driven gear  225  may be disposed between the first shift gear  221  and the second shift gear  222 . The driven gear  225  may be integrally formed on the outer circumferential surface of the intermediate shaft  220  through spline coupling. 
     The output shaft  230  may receive the increased/decreased torque and rotational force through the intermediate shaft  220 . The output shaft  230  may transmit the received torque and rotational force to the axle to rotate the driving wheels  300 . The output shaft  230  may be connected to the axle. In addition, both ends of the output shaft  230  may be connected to the axle. 
     The output shaft  230  may be a hollow shaft. The output shaft  230  may comprise the axle. 
     The transmission device  200  may further comprise an output gear  231  coupled to the outer circumferential surface of the output shaft  230 . 
     The output gear  231  may be engaged with the driven gear  225  to receive the torque and the rotational force from the intermediate shaft  230 . The output gear  231  may be connected to a differential gear unit  232 . 
     The transmission device  200  may further comprise the differential gear unit  232  provided inside the output shaft  230 . 
     The differential gear unit  232  may comprise a differential gear case, a differential gear and a differential shaft. The driven gear  225  may be disposed outside the differential gear unit  232 . 
       FIG. 3  is a cross-sectional view showing the configuration of a synchronizer according to an embodiment of the present disclosure,  FIG. 4  is a view showing the configuration of a coupling ring according to an embodiment of the present disclosure, and  FIG. 5  is a view showing the configuration of a sleeve according to an embodiment of the present disclosure. 
     Referring to  FIGS. 3 to 5 , the synchronizer  600  according to the embodiment of the present disclosure may be provided outside the input shaft  210  and may be selectively engaged with the first driving gear  211  or the second driving gear  212 . 
     The synchronizer  600  may comprise a plurality of coupling rings  610  and  620  disposed outside the input shaft  210 . The plurality of coupling rings  610  and  620  may include the first coupling ring  610  disposed to surround the circumference of the input shaft  210  and the second coupling ring  620  spaced apart from the first coupling ring  610  in the axial direction. 
     Specifically, the first coupling ring  610  and the second coupling ring  620  may have a ring shape and have through-holes  611  and  621  formed therein, respectively. The input shaft  210  may be disposed in the through-holes  611  and  621 . The first coupling ring  610  and the second coupling ring  620  may have a symmetrical structure. 
     The first coupling ring  610  and the second coupling ring  620  may be disposed outside the input shaft  210 . At this time, the first coupling ring  610  may be fixed to the outer surface of the first driving gear  211  and the second coupling ring  620  may be fixed to the outer surface of the second driving gear  212 . 
     According to the present embodiment, the first coupling ring  610  may be inserted into the outer circumferential surface of the first driving gear  211  to rotate with the first driving gear  211 . The first coupling ring  610  may be fixed to the outside corresponding to the rear end of the first driving gear  211 . 
     The second coupling ring  620  may be inserted into the outer circumferential surface of the second driving gear  212  to rotate with the second driving gear  212 . The second coupling ring  620  may be fixed to the outside corresponding to the front end of the second driving gear  212 . 
     The first coupling ring  610  and the second coupling ring  620  may be disposed to face each other. The first coupling ring  610  and the second coupling ring  620  may be spaced apart from each other in the axial direction. 
     The synchronizer  600  may further comprise a plurality of magnets  630  and  640  provided in the first coupling ring  610  and the second coupling ring  620 . 
     The plurality of magnets  630  and  640  may include the first magnet  630  provided in the first coupling ring  610  and the second magnet  640  provided in the second coupling ring  620 . The first magnet  630  and the second magnet  640  may include permanent magnets. 
     Specifically, the first magnet  630  may be provided inside the first coupling ring  610  and the second magnet  640  may be provided inside the second coupling ring  620 . At this time, the first magnet  630  and the second magnet  640  may be disposed to face each other. 
     According to one embodiment, the first magnet  630  may include a plurality of magnets spaced apart from each other inside the first coupling ring  610  in the circumferential direction. 
     That is, in  FIG. 4 , the first magnet  630  may include eight magnets spaced apart from each other in the circumferential direction. The eight magnets may be spaced apart from each other at the same interval. 
     In addition, the second magnet  640  may include a plurality of magnets spaced apart from each other inside the second coupling ring  620  in the circumferential direction. 
     That is, in  FIG. 4 , the second magnet  640  may include eight magnets spaced apart from each other in the circumferential direction. The eight magnets may be spaced apart from each other at the same interval. 
     In summary, each of the first magnet  630  and the second magnet  640  may include a plurality of magnets having a circular band shape in the circumferential direction of the first coupling ring  610  and the second coupling ring  620 . 
     In addition, the synchronizer  600  may further comprise a sleeve  650  provided on the outer circumferential surface of the input shaft  210  and a coil  660  provided inside the sleeve  650 . 
     The sleeve  650  may be formed in a cylindrical shape and may have a through-hole  651  formed therein. In addition, the input shaft  210  may be received in the through-hole  650  of the sleeve  650 . 
     In addition, a plurality of poles, on which the coil  660  is wound, may be provided inside the sleeve  650 . The plurality of poles may be spaced apart from each other inside the sleeve  650  in the circumferential direction. 
     Meanwhile, although not shown, a hub (not shown) may be provided between the sleeve  650  and the input shaft  210 . The hub may be coupled to the outer circumferential surface of the input shaft  210  and connected to the sleeve  650 . In addition, the sleeve  650  may move in the axial direction in a state of being supported by the hub. The sleeve  650  may be connected with the actuator  500  to slip in the axial direction by on/off operation of the actuator  500 . 
     The sleeve  650  may be located between the first coupling ring  610  and the second coupling ring  620 . At this time, the sleeve  650  may be moved by the actuator  500  in the axial direction and may be selectively coupled with the first coupling ring  610  or the second coupling ring  620 . That is, the sleeve  650  may be moved to be close to the first coupling ring  610  or the second coupling ring  620 . 
     The coil  660  may be installed inside the sleeve  650  to perform an electromagnet function. The coil  660  may be wound along the inside of the sleeve  650  in the circumferential direction. The coil  660  may be magnetized when constant current flows in the coil  660  and may return to an original state when current is interrupted. 
     According to one embodiment, the coil  660  may include a plurality of winding coils wound inside the sleeve  650 . The plurality of winding coils may be wound on the poles provided inside the sleeve  650 . That is, the plurality of winding coils may be spaced apart from each other inside the sleeve  650  in the circumferential direction. 
     That is, in  FIG. 5 , the coil  660  may include eight winding coils spaced apart from each other in the circumferential direction of the sleeve  650 . The eight winding coils may be spaced apart from each other at the same interval. The eight winding coils may be disposed in correspondence with the eight magnets configuring the first magnet  630  and/or the second magnet  640 . 
     In addition, the coil  660  may be fixed to the inside of the sleeve  650  and may be moved in the axial direction according to slipping of the sleeve  650 . In this case, the coil  660  may become close to the first magnet  630  or the second magnet  640 . 
     In addition, the coil  660  may be disposed to face the first magnet  630  and the second magnet  640 . That is, the first magnet  630  may overlap the coil  660  and the second magnet  640  in the axial direction. 
     Hereinafter, the configuration and operation of the synchronizer will be described in greater detail with reference to the drawing. 
       FIG. 6  is a view showing a state in which the sleeve according to the embodiment of the present disclosure is placed at a neutral position. 
     Referring to  FIG. 6 , as described above, the synchronizer  600  may be located in a space between the first coupling ring  610  and the second coupling ring  620 . 
     Specifically, the coil  660  of the sleeve  650  may be disposed between the first magnet  630  of the first coupling ring  610  and the second magnet  640  of the second coupling ring  620 . At this time, one surface or the front surface of the coil  660  may face the first magnet  630  and the other surface or the rear surface of the coil  660  may face the second magnet  640 . 
     As shown in  FIG. 6 , the sleeve  650  may be located at a middle point between the first coupling ring  610  and the second coupling ring  620 . That is, in the sleeve  650 , the distance L 1  between the front surface of the sleeve  650  and the first coupling ring  610  may be equal to the distance L 2  between the front surface of the sleeve  650  and the second coupling ring  620 . 
     The middle point between the first coupling ring  610  and the second coupling ring  620  may be referred to as a “neutral position” or an “initial position”. That is, when the sleeve  650  is located at the neutral position, the distance L 1  between the sleeve  650  and the first coupling ring  610  may be equal to the distance L 2  between the sleeve  650  and the second coupling ring  620 . 
     Meanwhile, the radial width W 1  of the first magnet  630  may be equal to the radial width W 2  of the second magnet  640 . In addition, the radial width W 3  of the coil  660  may be equal to the width W 1  of the first magnet  630  or the width W 2  of the second magnet  640 . That is, the coil  660  and the first and second magnets  630  and  640  may be aligned. 
     According to the present embodiment, a virtual line connecting the outer surface  661  of the coil  660  and the outer surfaces  631  and  641  of the first and second magnets  630  and  640  may form a straight line. In addition, a virtual line connecting the inner surface  662  of the coil  660  and the inner surfaces  632  and  642  of the first and second magnets  630  and  640  may form a straight line. 
     By such a configuration, when the coil  660  moves toward the first magnet  630  or the second magnet  640 , speed synchronization between the coil  660  and the first magnet  630  or the second magnet  640  may be easily performed by a rotating magnetic field. 
     Meanwhile, the synchronizer  600  may further comprise a brush  670  for applying current to the coil  660 . The brush  60  may be provided inside the input shaft  210 . 
     Specifically, the brush  60  may be disposed in a brush hole  210   b  extending from a cavity  210   a  of the input shaft  210  in the radial direction. In addition, the brush  60  may be electrically connected to the controller  400  through a wire  671 . In this case, the wire  671  may extend from the brush  60  to the controller  400  through the brush hole  210   b  and the cavity  210   a.    
     The brush  60  may be brought into contact with a slip ring by spring tension to selectively supply current to the coil  660 . 
     In addition, the synchronizer  600  may further comprise cones  680  and  690  for coupling with the sleeve  650 . The cones  680  and  690  may be provided in the first coupling ring  610  and the second coupling ring  620 , respectively. 
     Specifically, the cones  680  and  690  may include the first cone  680  provided inside the first coupling ring  610  and the second cone  690  provided inside the second coupling ring  620 . 
     The first cone  680  may protrude from one side of the first coupling ring  610  toward the sleeve  650 , and the second cone  690  may protrude from one side of the second coupling ring  620  toward the sleeve  650 . Each of the first cone  680  and the second cone  690  may be formed to have a conical friction surface. In addition, the first cone  680  and the second cone  690  may be brought into contact with the friction surface formed at one side of the sleeve  650  to match or synchronize the rotational speeds of the gears. 
     Meanwhile, the sleeve  650  may include an outer sleeve  651  forming an outer portion and an inner sleeve  652  forming an inner portion. Friction surfaces  652   a  which may be brought into contact with the first cone  680  and the second cone  690  may be formed at both sides of the inner sleeve  652 . 
     That is, the first cone  680  and the second cone  690  may be provided at points corresponding to the friction surfaces  652   a  of the inner sleeve  652 . Therefore, when the sleeve  650  is moved in the axial direction, the friction surfaces  652   a  of the inner sleeve  652  may be coupled with the first cone  680  or the second cone  690  and thus the sleeve  650  and the first driving gear  211  or the second driving gear  212  may be coupled. 
     Although the friction surfaces  652   a  are described as being provided in the inner sleeve  652  in the present embodiment, the present disclosure is not limited thereto. For example, the friction surfaces may be provided in the outer sleeve  651 . In this case, the first cone  680  and the second cone  690  may be disposed at corresponding points of the outer sleeve  651 . 
     Alternatively, the friction surfaces may be formed in the inner sleeve  652  and the outer sleeve  651 . 
       FIG. 7  is a view showing a state in which the sleeve according to the embodiment of the present disclosure is moved to a first coupling ring side,  FIG. 8  is a view showing a state in which the sleeve according to the embodiment of the present disclosure is moved to a second coupling ring side, and  FIG. 9  is a view showing synchronization between a coil and a magnet according to an embodiment of the present disclosure. 
     First, referring to  FIG. 7 , when a first gear shifting command is input through an operation unit or the controller  400  of the electric vehicle, the controller  400  may increase or decrease the rotational speed of the driving motor  100 . That is, the controller  400  may decrease the rotational speed of the driving motor  100  to match the rotational speed of the rotor shaft with the first driving gear  211 . 
     In addition, the controller  400  may generate a magnetic field, by enabling current to flow in the coil  660  when a relative speed between the rotor shaft and the first driving gear  211  is very low. The controller  400  may control the actuator  500  such that the sleeve  650  may move toward the first coupling ring  610  corresponding to the first driving gear  211 . 
     Then, as shown in  FIG. 9 , attraction may be generated by polarity (N-polarity or S-polarity) formed in the coil  660  and polarity (S-polarity or N-polarity) formed in the first magnet  630 , and the relative speed between the rotor shaft and the first driving gear  211  may converge on zero by such attraction. Additionally, when the sleeve  650  is further moved to the first coupling ring  610 , the friction surfaces  652   a  of the sleeve  650  and the friction surface of the first cone  680  may be brought into contact with each other, thereby synchronizing the rotational speeds of the rotor shaft and the gear. 
     In summary, the rotational speed of the input shaft  210  and the rotational speed of the first driving gear  211  may be primarily synchronized by current control of the driving motor  100 , and the rotational speed of the input shaft  210  and the rotational speed of the first driving gear  211  may be secondarily synchronized by electromagnetic force between the coil  660  and the first magnet  630 . Finally, the sleeve  650  may be coupled with the first cone  680  when the relative speed between the input shaft  210  and the first driving gear  211  is very low, such that the input shaft  210  and the first driving gear  211  may be fully synchronized. 
     Meanwhile, referring to  FIG. 8 , when a second gear shifting command is input through an operation unit or the controller  400  of the electric vehicle, the controller  400  may increase or decrease the rotational speed of the driving motor  100 . That is, the controller  400  may decrease the rotational speed of the driving motor  100  to match the rotational speed of the rotor shaft with the second driving gear  212 . 
     In addition, the controller  400  may generate a magnetic field, by enabling current to flow in the coil  660  when a relative speed between the rotor shaft and the second driving gear  212  is very low. The controller  400  may control the actuator  500  such that the sleeve  650  may move toward the second coupling ring  620  corresponding to the second driving gear  212 . 
     Then, as shown in  FIG. 9 , attraction may be generated by polarity (N-polarity or S-polarity) formed in the coil  660  and polarity (S-polarity or N-polarity) formed in the first magnet  630 , and the relative speed between the rotor shaft and the second driving gear  212  may converge on zero by such attraction. Additionally, when the sleeve  650  is further moved to the second coupling ring  620 , the friction surfaces  652   a  of the sleeve  650  and the friction surface of the second cone  690  may be brought into contact with each other to fully synchronize the rotational speeds of the rotor shaft and the gear. 
     In summary, the rotational speed of the input shaft  210  and the rotational speed of the second driving gear  212  may be primarily synchronized by current control of the driving motor  100 , and the rotational speed of the input shaft  210  and the rotational speed of the second driving gear  212  may be secondarily synchronized by electromagnetic force between the coil  660  and the second magnet  640 . Finally, the sleeve  650  may be coupled with the second cone  690  when the relative speed between the input shaft  210  and the second driving gear  212  is very low, such that the input shaft  210  and the second driving gear  212  may be fully synchronized. 
     The driving apparatus for the electric vehicle according to the embodiment of the present disclosure having the above configuration has the following effects. 
     First, the synchronizer for gear shifting may comprise a first coupling ring fixed to a first driving gear and comprising a first magnet, a second coupling ring fixed to a second driving gear and comprising a second magnet, and a sleeve provided between the first coupling ring and the second coupling ring and comprising a winding coil. 
     Therefore, since speed synchronization between the input shaft and the gear may be primarily performed through motor control and speed synchronization between the input shaft and the gear may be secondarily performed through a rotating magnetic field, it may be possible to minimize impact due to input torque of the motor at the time of gear shifting without a clutch for interrupting power between the motor and the transmission device. 
     Second, the conventional synchronizer substantially uses a mechanical friction material for speed synchronization between the motor and the gear. However, in the present disclosure, since a friction material for speed synchronization between the motor and the gear may not be necessary, it may be possible to improve product reliability and increase a product lifespan. 
     Third, since the synchronizer of the present disclosure may have a simpler structure and a smaller number of parts as compared to the conventional synchronizer, the product cost may be reduced, and a defect rate may be reduced. 
     Fourth, in the present disclosure, since the capacity of the vehicle may be capable of being changed according to the level of the current applied to the motor or the coil, it may not be necessary to change design according to the capacity of the vehicle. 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.