Patent Publication Number: US-11050264-B2

Title: Wireless power transmission apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of co-pending U.S. patent application Ser. No. 16/213,542 filed on Dec. 7, 2018, which is a Continuation of U.S. patent application Ser. No. 14/831,685 filed on Aug. 20, 2015 (now U.S. Pat. No. 10,193,352 issued on Jan. 29, 2019), which is a Continuation of U.S. patent application Ser. No. 14/709,075 filed on May 11, 2015 (now U.S. Pat. No. 9,450,423 issued on Sep. 20, 2016), which claims the priority benefit under 35 U.S.C. § 119(a) to Korean Patent Application Nos. 10-2015-0014965 filed in the Republic of Korea on Jan. 30, 2015, and 10-2014-0131402 filed in the Republic of Korea on Sep. 30, 2014, all of which are hereby expressly incorporated by reference into the present application. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The disclosure relates to a wireless power charging system, and more particularly to a wireless power transmission apparatus of a wireless power charging system. 
     Discussion of the Related Art 
     In general, various electronic devices are equipped with batteries and driven using power charged in the batteries. In this case, the battery is replaceable with new one, and rechargeable in the electronic device. To this end, the electronic device is equipped with a connector for the connection with an external charging device. In other words, the electronic device is electrically connected with the charging device through the connector. However, as the connector in the electronic device is exposed to the outside, the connector may be contaminated with foreign matters or shorted by moisture. In this case, connection failure occurs between the connector and the charging device, so that the battery in the electronic device may not be charged with power. 
     In order to solve the above problem, there has been suggested a wireless power charging system to wirelessly charge the electronic device with power. The wireless power charging system includes a wireless power transmission apparatus and a wireless power reception apparatus. The wireless power transmission apparatus wirelessly transmits power and the wireless power reception apparatus wirelessly receives power. The electronic device may include the wireless power reception apparatus, or may be electrically connected with the wireless power reception apparatus. In this case, the wireless power reception apparatus must be arranged within a preset charging area of the wireless power transmission apparatus. In particular, when the wireless power charging system is realized through a resonance scheme, it is important that the wireless power transmission apparatus is designed to have a constant coupling coefficient regardless of the location of the wireless power reception apparatus. Otherwise, the variation range of a transmission power amount to be adjusted in the wireless power transmission apparatus must be increased according to the locations of the wireless power reception apparatus. Accordingly, the realization cost of the wireless power charging system may be increased and the efficiency of the wireless power charging system may be degraded. 
     SUMMARY OF THE INVENTION 
     The disclosure provides a wireless power transmission apparatus having more improved power transmission efficiency. More particularly, the disclosure provides a wireless power transmission apparatus having a chargeable area more enlarged as the wireless power transmission apparatus has a constant coupling coefficient according to locations. 
     In order to accomplish the above object of the disclosure, there is provided a wireless power transmission apparatus including a mounting member, an upper transmission coil on the mounting member, a lower transmission coil under the mounting member, a first terminal connected with an outer connection part of the upper transmission coil and an inner connection part of the lower transmission coil, and a second terminal connected with an inner connection part of the upper transmission coil and an outer connection part of the lower transmission coil. The upper transmission coil and the lower transmission coil are bilaterally symmetrical to each other about a central axis between the first and second terminals. 
     According to the wireless power transmission apparatus of the disclosure, as a plurality of transmission coils are formed symmetrically to each other, magnetic fields formed by the transmission coils have vertical and horizontal symmetrical shapes. Accordingly, the coupling coefficient between the wireless power transmission apparatus and the wireless power reception apparatus can be constant according to the locations of the wireless power transmission apparatus. Accordingly, the variation range of a transmission power amount to be adjusted in the wireless power transmission apparatus can be reduced, so that the realization cost of the wireless power charging system can be reduced and the efficiency of the wireless power charging system can be improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing a typical wireless power charging system; 
         FIGS. 2 a , 2 b , 2 c , 2 d , and 2 e    are circuit diagrams showing equivalent circuits of a wireless transmission unit and a wireless reception unit of  FIG. 1 ; 
         FIG. 3  is a block diagram showing a typical wireless power transmission apparatus; 
         FIG. 4  is an exploded perspective view showing a typically wireless transmission unit; 
         FIG. 5  is a circuit diagram showing an equivalent circuit of the typical wireless transmission unit; 
         FIG. 6  is a graph to explain a coupling coefficient of a typical wireless reception unit; 
         FIG. 7  is an exploded perspective view showing a wireless transmission unit according to a first embodiment of the disclosure; 
         FIGS. 8 a  and 8 b    are plan views showing an upper transmission coil of  FIG. 7 ; 
         FIGS. 9 a  and 9 b    are plan views showing a lower transmission coil of  FIG. 7 ; 
         FIG. 10  is a circuit diagram showing an equivalent circuit of the wireless transmission unit according to the first embodiment of the disclosure; 
         FIG. 11  is a graph to explain a coupling coefficient of the wireless transmission unit according to the first embodiment of the disclosure; 
         FIG. 12  is an exploded perspective view showing a wireless transmission unit according to a second embodiment of the disclosure; 
         FIGS. 13 a  and 13 b    are plan views showing an upper transmission coil of  FIG. 12 ; 
         FIGS. 14 a  and 14 b    are plan views showing a lower transmission coil of  FIG. 12 ; 
         FIG. 15  is a graph to explain a coupling coefficient of a wireless transmission unit according to the second embodiment of the disclosure; 
         FIG. 16  is an exploded perspective view showing a wireless transmission unit according to a third embodiment of the disclosure; 
         FIGS. 17 a  and 17 b    are plan views showing an upper transmission coil of  FIG. 16 ; 
         FIGS. 18 a  and 18 b    are plan views showing a lower transmission coil of FIG.  16 ; 
         FIG. 19  is a graph to explain a coupling coefficient of a wireless transmission unit according to the third embodiment of the disclosure; and 
         FIG. 20  is a view showing a realization example of the wireless transmission unit according to the third embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, embodiments of the disclosure will be more described with reference to accompanying drawings. In this case, it is noted that the same reference numerals are assigned to the same elements as much as possible. In addition, the details of well known functions or configurations that may make the subject matter of the embodiments unclear will be omitted in the following description. 
       FIG. 1  is a block diagram showing a typical wireless power charging system, and  FIGS. 2 a , 2 b , 2 c , 2 d , and 2 e    are circuit diagrams showing equivalent circuits of a wireless transmission unit and a wireless reception unit showing in  FIG. 1 . 
     Referring to  FIG. 1 , a typical wireless power charging system  10  includes a wireless power transmission apparatus  20  and a wireless power reception apparatus  30 . 
     The wireless power transmission apparatus  20  is connected with a power supply  11  to receive power from the power supply  11 . In addition, the wireless power transmission apparatus  20  wirelessly transmits power. In this case, the wireless power transmission apparatus  20  may transmit AC power. In this case, the wireless power transmission apparatus  20  transmits the power through various charging schemes. The charging schemes include an electromagnetic induction scheme, a resonance scheme, and an RF/micro wave radiation scheme. In other words, at least one of the charging schemes is preset to the wireless power transmission apparatus  20 . In addition, the wireless power transmission apparatus  20  may transmit power through the preset charging scheme. The wireless power transmission apparatus  20  includes a wireless transmission unit  21 . 
     The wireless power reception apparatus  30  wirelessly receives power. In this case, the wireless power reception apparatus  30  may receive AC power. In addition, the wireless power reception apparatus may convert the AC power into DC power. In this case, the wireless power reception apparatus  30  receives power through various charging schemes. The charging schemes include an electromagnetic induction scheme, a resonance scheme, and an RF/micro wave radiation scheme. In other words, at least one of the charging schemes is preset to the wireless power reception apparatus  30 . In addition, the wireless power reception apparatus  30  may receive power the preset charging scheme. In addition, the wireless power reception apparatus  30  may be driven using power. The wireless power reception apparatus  30  includes a wireless reception unit  31 . 
     In this case, in order for the wireless power transmission apparatus  20  to transmit power to the wireless power reception apparatus  30 , the charging scheme of the wireless power transmission apparatus  20  is identical to that of the wireless power reception apparatus  30 . 
     For example, when the wireless power transmission apparatus  20  and the wireless power reception apparatus  30  employ the electromagnetic induction scheme as the charging scheme thereof, the wireless transmission unit  21  and the wireless reception unit  31  may be expressed as the circuit shown in  FIG. 2 a   . The wireless transmission unit  21  may include a transmission induction coil  23 . In this case, the transmission induction coil  23  may be represented as a transmission inductor L 1 , and the wireless reception unit  31  may include a reception induction coil  33 . In this case, the reception induction coil  33  may be represented as a reception inductor L 2 . Accordingly, when the reception induction coil  33  is provided in opposition to the transmission induction coil  23 , the transmission induction coil  23  may transmit power to the reception induction coil  33  through the electromagnetic induction scheme. 
     Meanwhile, when the wireless power transmission apparatus  20  and the wireless power reception apparatus  30  employ the resonance scheme as the charging scheme thereof, the wireless transmission unit  21  and the wireless reception unit  31  may be expressed as the circuits shown in  FIGS. 2 b , 2 c , 2 d   , and  2   e.    
     The wireless transmission unit  21  may include a transmission induction coil  25  and a transmission resonance coil  26  as shown in  FIGS. 2 b  and 2 d   . In this case, the transmission induction coil  25  may be provided in opposition to the transmission resonance coil  26 . In addition, the transmission induction coil  25  may be represented as a first transmission inductor L 11 . In addition, the transmission resonance coil  26  may be represented as a second transmission inductor L 2  and a transmission capacitor C 1 . In this case, the second transmission inductor L 2  and the transmission capacitor C 1  may be connected with each other in parallel to form a closed loop. In addition, the wireless transmission unit  21  may include a transmission resonance coil  27  as shown in  FIGS. 2 c  and 2 e   . In this case, the transmission resonance coil  27  may be represented as the transmission inductor L 1  and the transmission capacitor C 1 . In this case, the transmission inductor L 1  and the transmission capacitor C 1  may be connected with each other in serial. 
     In addition, the wireless reception unit  31  may include a reception resonance coil  35  and a reception induction coil  36  as shown in  FIGS. 2 b  and 2 e   . In this case, the reception resonance coil  35  and the reception induction coil  36  may be provided in opposition to each other. In addition, the reception resonance coil  35  may be represented as a reception capacitor C 2  and a first reception inductor L 21 . In this case, the reception capacitor C 2  and the first reception inductor L 21  may be connected with each other in parallel to form a closed loop. The reception induction coil  36  may be represented as a second reception inductor L 22 . In addition, the wireless reception unit  31  may include a reception resonance coil  37  as shown in  FIGS. 2 c  and 2 d   . In this case, the reception resonance coil  37  may be represented as the reception inductor L 2  and the reception capacitor C 2 . In this case, the reception inductor L 2  and the reception capacitor C 2  may be connected with each other in serial. 
     Accordingly, when the reception resonance coil  35  is provided in opposition to the transmission resonance coil  26 , the transmission resonance coil  26  may transmit power to the reception resonance coil  35  through the resonance scheme. In this case, the transmission induction coil  25  may transmit power to the transmission resonance coil  26  through the electromagnetic induction scheme, and the transmission resonance coil  26  may transmit power to the reception resonance coil  35  through the resonance scheme. In addition, the transmission resonance coil  26  may directly transmit power to the reception resonance coil  35  through the resonance scheme. In addition, the reception resonance coil  35  may receive power from the transmission resonance coil  26  through the resonance scheme, and the reception induction coil  36  may receive power from the reception resonance coil  35  through the electromagnetic induction scheme. In addition, the reception resonance coil  35  may receive power from the transmission resonance coil  26  through the resonance scheme. 
     A quality factor and a coupling coefficient are important in the wireless power charging system  10 . In this case, as the quality factor and the coupling coefficient have a larger value, the efficiency of the wireless power charging system  10  is improved. 
     The quality factor may refer to an index of energy that may be stored in the vicinity of the wireless power transmission apparatus  20  or the wireless power reception apparatus  30 . The quality factor may vary according to the operating frequency (w), the shape, the size, and the material of the transmission coil  23 ,  25 ,  26 , or  27  of the wireless transmission unit  21 , or the reception coil  33 ,  35 ,  36 , or  37  of the wireless reception unit  31 . The quality factor may be calculated an equation of Q=ω*L/R. In the above equation, L refers to the inductance of the transmission coil  23 ,  25 ,  26 , or  27  or the reception coil  33 ,  35 ,  36 , or  37  and R refers to resistance corresponding to the quantity of power loss caused in the transmission coil  23 ,  25 ,  26 , or  27  or the reception coil  33 ,  35 ,  36 , or  37 . The quality factor may have a value of 0 to infinity. 
     The coupling coefficient represents the degree of magnetic coupling between the wireless power transmission apparatus  20  and the wireless power reception apparatus  30 . In this case, the coupling coefficient may be determined depending on the relative position and the distance between the transmission coil  23 ,  25 ,  26 , or  27  of the wireless power transmission apparatus  21  and the reception coil  33 ,  35 ,  36 , or  37 . The coupling coefficient has a value ranging from 0 to 1. 
       FIG. 3  is a block diagram showing a typical wireless power transmission apparatus. 
     Referring to  FIG. 3 , a typical wireless power transmission apparatus  40  includes a wireless transmission unit  41 , an interface unit  43 , an oscillator  45 , a power conversion unit  47 , a detection unit  49 , and a control unit  51 . 
     The wireless transmission unit  41  wirelessly transmits power in the wireless power transmission apparatus  40 . In this case, the wireless transmission unit  41  transmits power through multiple charging schemes. In this case, the charging schemes include an electromagnetic induction scheme, a resonance scheme, and an RF/micro wave radiation scheme. The wireless transmission unit  41  may include at least one transmission coil. In this case, the transmission coil may include at least one of a transmission induction coil and a transmission resonance coil according to the charging scheme of the transmission coil. 
     The interface unit  43  provides an interface with the power supply  11  in the wireless power transmission apparatus  40 . In other words, the interface unit  43  is connected with the power supply  11 . In this case, the interface unit  43  may be connected with the power supply  11  through a wired scheme. In addition, the interface unit  43  receives power from the power supply  11 . The interface unit  43  receives DC power from the power supply  11 . 
     The oscillator  45  generates an AC signal. In this case, the oscillator  45  generates the AC signal corresponding to the charging scheme of the wireless transmission unit  41 . In this case, the oscillator  45  generates the AC signal to have a predetermined frequency. 
     The power conversion unit  47  converts power to be provided for the wireless transmission unit  41 . In this case, the power control unit  51  receives DC power from the interface unit  43  and receives the AC signal from the oscillator  45 . In addition, the power conversion unit  47  generates AC power using the DC power and the AC signal. In this case, the power conversion unit  47  may amplify the AC signal for the use of the AC signal. In addition, the power conversion unit  47  outputs the AC power to the wireless transmission unit  41 . The power conversion unit  47  may have a push-pull type structure. In the push-pull type structure, paired switches, paired transistors, or paired predetermined circuit blocks are alternately operated and alternately output a response. 
     The detection unit  49  detects a power transmission state of the wireless power transmission apparatus. In this case, the detection unit  49  may detect the intensity of current between the power conversion unit  47  and the wireless transmission unit  41 . In this case, the detection unit  49  may detect the intensity of current at an output terminal of the power conversion unit  47  or an input terminal of the wireless transmission unit  41 . The detection unit  49  may include a current sensor. In this case, the current sensor may include a current transformer (CT). 
     The control unit  51  controls the whole operations of the wireless power transmission apparatus  40 . The control unit  51  operates the wireless transmission unit  41  to wirelessly transmit power. In this case, the control unit  51  controls the power conversion unit  47  to supply power to the wireless transmission unit  41 . To this end, the control unit  51  operates the wireless transmission unit  41  to determine the existence of the wireless power reception apparatus  30  ( FIG. 1 ). In this case, the control unit  51  controls the detection unit  49  to determine the existence of the wireless power reception apparatus  30 . In other words, the control unit  51  determines the existence of the wireless power reception apparatus  30  according to the power transmission state of the wireless power transmission apparatus  40 . If the wireless power reception apparatus  30  exists, the control unit  51  operates the wireless transmission unit  41  to wirelessly transmit power. 
     In this case, as the wireless power transmission apparatus  40  approaches the wireless power reception apparatus  30 , the intensity of current detected by the detection unit  49  may be increased, which represents that the coupling coefficient between the wireless power transmission apparatus and the wireless power reception apparatus is a high value. Meanwhile, as the wireless power transmission apparatus  40  is gradually spaced apart from the wireless power reception apparatus  30 , the intensity of current detected by the detection unit  49  may be decreased, which represents that the coupling coefficient between the wireless power transmission apparatus and the wireless power reception apparatus is a low value. 
       FIG. 4  is an exploded perspective view showing a typically wireless transmission unit,  FIG. 5  is a circuit diagram showing an equivalent circuit of the typical wireless transmission unit, and  FIG. 6  is a graph to explain a coupling coefficient of a typical wireless reception unit. 
     Referring to  FIG. 4 , a typical wireless transmission unit  60  includes a mounting member  61 , a first terminal  63 , a second terminal  65 , a transmission coil  67 , and a shielding member  69 . In this case, the wireless transmission unit  60  transmits power through the resonance scheme. 
     The mounting member  61  supports the first terminal  63 , the second terminal  65 , and the transmission coil  67 . In this case, the mounting member  61  may be formed at a single layer structure, or may be formed at a multi-layer structure. The mounting member  61  includes a printed circuit board (PCB), a flexible PCB (FPCB), or a film. 
     The first terminal  63  and the second terminal  65  alternately apply current to the transmission coil  67 . In addition, the first and second terminals  63  and  65  alternately output current from the transmission coil  67 . For example, when the first terminal  63  applies current to the transmission coil  67 , the second terminal  65  outputs current from the transmission coil  67 . Meanwhile, when the second terminal  65  applies current to the transmission coil  67 , the first terminal  63  outputs current from the transmission coil  67 . In this case, the first and second terminals  63  and  65  may be connected with the power conversion unit  47  ( FIG. 3 ). 
     The first and second terminals  63  and  65  are mounted on the mounting member  61 . In this case, the first and second terminals  63  and  65  are arranged on one surface of the mounting member  61 . In other words, the first and second terminals  63  and  65  are arranged on a top surface or a bottom surface of the mounting member  61 . In addition, the first and second terminals  63  and  65  may include a conductive material. 
     The transmission coil  67  transmits power according to a preset charging scheme. The charging scheme includes an electromagnetic induction scheme, a resonance scheme or an RF/micro wave radiation scheme. In this case, the transmission coil  67  operates at a predetermined resonance frequency band to transmit power. In this case, if current is transmitted along the transmission coil  67 , an electromagnetic field may be formed around the transmission coil  67 . 
     The transmission coil  67  is mounted on the mounting member  67 . In this case, the transmission coil  67  is provided on one surface of the mounting member  61 . In other words, the transmission coil  67  is arranged on a top surface or a bottom surface of the mounting member  61 . In this case, the transmission coil  67  is formed in one-turn. For example, the transmission coil  67  may be formed in a circular shape or a rectangular shape. In addition, the transmission coil  67  is connected with the first and second terminals  63  and  65  at both end portions thereof. In this case, the transmission coil  67  may be represented as one inductor as shown in  FIG. 5 . In addition, the transmission coil  67  may include a conductive material. In addition, the transmission coil  67  may include a conductive material and an insulating material, and the conductive material may be coated with the insulating material. 
     The shielding member  69  isolates the transmission coil  67 . In other words, the shielding member  69  isolates the transmission coil  67  from other components of the wireless power transmission apparatus  40  (see  FIG. 3 ). In this case, the shielding member  69  has a predetermined physical property. In this case, the physical property includes permeability (p). The permeability of the shielding member  69  may be maintained at a resonance frequency band of the transmission coil  67 . Accordingly, the loss rate of the shielding member  69  may be reduced at the resonance frequency band of the transmission coil  67 . 
     In general, the coupling coefficient between the wireless transmission unit  60  and the wireless reception unit  31  (see  FIG. 1 ) is not a constant according to the locations as shown in  FIG. 6 . In other words, the coupling coefficient between the wireless transmission unit  60  and the wireless reception unit  31  is increased toward a wire of the transmission coil  67 . This is because the intensity of a magnetic field is increased toward the wire of the transmission coil  67 . Accordingly, the coupling coefficient between the wireless transmission unit  60  and the wireless reception unit  31  has a low value at a location corresponding to the center of the transmission coil  67 . Therefore, a chargeable area of the wireless transmission unit  60  is narrow. 
       FIG. 7  is an exploded perspective view showing a wireless transmission unit according to a first embodiment of the disclosure.  FIGS. 8 a  and 8 b    are plan views showing an upper transmission coil of  FIG. 7 .  FIGS. 9 a  and 9 b    are plan views showing a lower transmission coil of  FIG. 7 .  FIG. 10  is a circuit diagram showing an equivalent circuit of the wireless transmission unit according to the first embodiment of the disclosure. In addition,  FIG. 11  is a graph to explain a coupling coefficient of the wireless transmission unit according to the first embodiment of the disclosure. 
     Referring to  FIGS. 7, 8   a ,  8   b ,  9   a , and  9   b , a wireless transmission unit  100  according to the present embodiment includes a mounting member  110 , a first terminal  120 , a second terminal  130 , an upper transmission coil  140 , a lower transmission coil  160 , and a shielding member  180 . In this case, the wireless transmission unit  100  transmits power through a resonance scheme. 
     The mounting member  110  supports the first and second terminals  120  and  130  and the upper and lower transmission coils  140  and  160 . In this case, the mounting member  100  may be formed at a single layer structure or may be formed at a multi-layer structure. In addition, the mounting member  110  may include a PCB, an FPCB, or a film. 
     The first and second terminals  120  and  130  alternately apply current to the upper and lower transmission coils  140  and  160 . In addition, the first and second terminals  120  and  130  alternately output current from the upper and lower transmission coils  140  and  160 . For example, when the first terminal  120  applies current to the upper and lower transmission coils  140  and  160 , the second terminal  130  outputs current from the upper and lower transmission coils  140  and  160 . On the contrary, when the second terminal  130  applies current to the upper and lower transmission coils  140  and  160 , the first terminal  120  outputs current from the upper and lower transmission coils  140  and  160 . In this case, the first and second terminals  120  and  130  may be connected with an output terminal of the power conversion unit  47  (see  FIG. 3 ). 
     The first and second terminals  120  and  130  are mounted on the mounting member  110 . In this case, the first and second terminals  120  and  130  are arranged on one surface of the mounting member  110 . In other words, the first and second terminals  120  and  130  are arranged on a top surface or a bottom surface of the mounting member  110 . The first and second terminals  120  and  130  are withdrawn from an opposite surface of the mounting member  110 . In other words, the first and second terminals  120  and  130  are withdrawn from the top surface or the bottom surface of the mounting member  110 . In this case, the first terminal  120  includes a first terminal via (not shown) formed through the mounting member  110 , and may be withdrawn through the first terminal via. In addition, the second terminal  130  includes a second terminal via (not shown) formed through the mounting member  110 , and may be withdrawn through the second terminal via. In addition, the first and second terminals  120  and  130  may include a conductive material. In this case, a Y axis serves as a central axis passing between the first and second terminals  120  and  130 . In this case, the interval between the Y axis serving as the central axis and the first terminal  120  may be equal to the interval between the central axis and the second terminal  130 . In other words, when a perpendicular is drawn from the first terminal  120  onto the Y axis, the distance between the first terminal  120  and the foot of the perpendicular may be equal to the distance between the second terminal  130  and the foot of a virtual perpendicular when the virtual perpendicular is drawn from the second terminal  130  onto the Y axis. 
     In addition, an X axis may be defined perpendicularly to the Y axis. In this case, on the assumption that an intersection point between the Y and X axes is zero, the Y axis may be divided into a positive Y (Y) axis and a negative Y (−Y) axis based on the 0 point, and the X axis may be divided into a positive X (X) axis and a negative X (−X) axis. In addition, the zero point serving as the intersection point may be defined as a central point. In other words, when the upper and lower transmission coils  140  and  160  are mounted on the mounting member  110 , the zero point may serve as the central point of the upper and lower transmission coils  140  and  160  in terms of a position. In addition, a first quadrant may be defined by the Y axis and the X axis, a second quadrant may be defined by the −Y axis and the X axis, a third quadrant may be defined by the −Y axis and the −X axis, and a fourth quadrant may be defined by the Y axis and the −X axis. In this case, the first terminal  120  may be provided in the first quadrant, and the second terminal  130  may be provided in the fourth quadrant. 
     The upper and lower transmission coils  140  and  160  transmit power according to a preset charging scheme. In this case, the upper and lower transmission coils  140  and  160  are mutually coupled to each other to transmit power. In other words, the upper and lower transmission coils  140  and  160  transmit power in cooperation with each other. In this case, the charging scheme includes an electromagnetic induction scheme, a resonance scheme, and an RF/micro wave radiation scheme. In addition, the upper and lower transmission coils  140  and  160  may be coupled to each other through the electromagnetic induction scheme. In addition, the upper and lower transmission coils  140  and  160  operate at a predetermined resonance frequency band to transmit power. In this case, when the upper and lower transmission coils  140  and  160  operate, the electromagnetic field may be formed around the upper and lower transmission coils  140  and  160 . 
     The upper and lower transmission coils  140  and  160  are mounted on the mounting member  110 . In this case, the upper transmission coil  140  is arranged on one surface of the mounting member  110 , and the lower transmission coil  160  is arranged on an opposite surface of the mounting member  110 . In other words, the upper transmission coil  140  is provided on the top surface of the mounting member  110 , and the lower transmission coil  160  is provided on the bottom surface of the mounting member  110 . 
     In addition, the upper and lower transmission coils  140  and  160  are connected with the first and second terminals  120  and  130 , respectively. In other words, the upper transmission coil  140  is connected with the first and second terminals  120  and  130  at both end portions thereof, and the lower transmission coil  160  is connected with the first and second terminals  120  and  130  at both end portions thereof. In addition, the upper and lower transmission coils  140  and  160  have a bilaterally symmetrical shape about the Y axis serving as the central axis. In this case, the upper and lower transmission coils  140  and  160  may have the shape shown in  FIG. 10 . In other words, the upper and lower transmission coils  140  and  160  may be represented as inductors connected with each other in parallel. 
     In addition, the upper and lower transmission coils  140  and  160  may include conductive materials. In addition, the upper and lower transmission coils  140  and  160  may include a conductive material and an insulating material, and the conductive material may be coated with the insulating material. 
     The upper transmission coil  140  includes an outer connection part  141 , an outer coil part  143 , an extension part  145 , an inner coil part  147 , and an inner connection part  149 . 
     The outer connection part  141  is connected with the first terminal  120 . In this case, the outer connection part  141  extends from the first terminal  120 . For example, when the first terminal  120  is provided at the right side of the Y axis, the outer connection part  141  may extend at the right side of the Y axis serving as the central axis. In other words, the outer connection part  141  starts from the first terminal  120  and extends in the negative Y (−Y) axis direction by a predetermined length in parallel to the Y axis. In this case, the predetermined length is a length corresponding to an extent that the outer connection part  141  may be provided only at the first quadrant without extending to the second quadrant. 
     The outer coil part  143  is provided at the outermost part of the upper transmission coil  140 . In addition, the outer coil part  143  is connected with the outer connection part  141 . In this case, the outer coil part  143  extends from the outer connection part  141 . The outer coil part  143  is formed in one-turn. For reference, the one-turn represents that a coil extends in a circular shape or a rectangular shape. For example, when the first terminal  120  is provided at the right side of the Y axis serving as the central axis, the outer coil part  143  may extend from the outer connection part  141  clockwise. In addition, the outer coil part  143  may extend from the right side of the Y axis serving as the central axis to the left side of the Y axis serving as the central axis. In detail, the outer coil part  143  may include a first outer coil part  143   a  provided at the first quadrant, a second outer coil part  143   b  provided at the second quadrant, the third outer coil part  143   c  provided at the third quadrant, and the fourth outer coil part  143   d  provided at the fourth quadrant, and the first to fourth outer coil parts  143   a  to  143   d  are integrated with each other. The first outer coil part  143   a  may extend to an intersection between the first outer coil part  143   a  and the X axis from a terminated point of the outer connection part  141 . In other words, the first outer coil part  143   a  extends in parallel to the X axis in the positive X (X) axis direction from the terminated point of the outer connection part  141 . Then, the first outer coil part  143   a  extends in parallel to the Y axis in the negative Y (−Y) axis direction. When the direction of the first outer coil part  143   a  is changed from the negative Y (−Y) axis direction from the positive X (X) axis direction, the direction of the first outer coil part  143   a  may be changed with a predetermined curvature. In addition, the second outer coil part  143   b  may extend from the terminated point of the first outer coil part  143   a  to the intersection between the second outer coil part  143   b  and the Y axis. In other words, the second outer coil part  143   b  extends in parallel to the Y axis in the negative Y (−Y) axis direction from the terminated point of the first outer coil part  143   a , and extends in parallel to the X axis in the negative X (−X) axis direction. When the direction of the second outer coil part  143   b  is changed from the negative Y (−Y) axis direction to the negative X (−X) axis direction, the direction of the second outer coil part  143   b  may be changed with a predetermined curvature. In addition, the third outer coil part  143   c  may extend from the terminated point of the second outer coil part  143   b  to the intersection between the third outer coil part  143   c  and the X axis. In other words, the third outer coil part  143   c  extends in parallel to the X axis in the negative X (−X) axis direction from the terminated point of the second outer coil part  143   b , and extends in parallel to the Y axis in the positive Y (Y) axis direction. When the direction of the third outer coil part  143   c  is changed from the negative X (−X) axis direction to the positive Y (Y) axis direction, the direction of the third outer coil part  143   c  may be changed with a predetermined curvature. In addition, the fourth outer coil part  143   d  may extend from the terminated point of the third outer coil part  143   c  to the intersection between the fourth outer coil part  143   d  and the Y axis. In other words, the fourth outer coil part  143   d  extends in parallel to the Y axis in the positive Y (Y) axis direction from the terminated point of the third outer coil part  143   c , and extends in parallel to the X axis in the positive X (X) axis direction. When the direction of the fourth outer coil part  143   d  is changed from the positive Y (Y) axis direction to the positive X (X) axis direction, the direction of the fourth outer coil part  143   d  may be changed with a predetermined curvature 
     In addition, the first outer coil part  143   a  and the second outer coil part  143   b  are symmetrical to each other about the X axis, the first outer coil part  143   a  and the fourth outer coil part  143   d  are symmetrical to each other about the Y axis, and the first outer coil part  143   a  and third outer coil part  143   c  are symmetrical to each other about a origin (0). 
     Meanwhile, although description has been made regarding that the first to fourth outer coil parts  143   a ,  143   b ,  143   c , and  143   d  partially have a linear shape and partially have a curved shape with a curvature, the embodiment is not limited thereto. In other words, the whole shape of the first to fourth outer coil parts  143   a ,  143   b ,  143   c , and  143   d  may have an oval shape or a circular shape. Accordingly, when the first outer coil part  143   a  extends in the positive X (X) axis direction, the distance between the first outer coil part  143   a  and the X axis may be gradually decreased. When the first outer coil part  143   a  extends in the negative Y (−Y) axis direction, the distance between the first outer coil part  143   a  and the Y axis may be gradually increased. In addition, when the second outer coil part  143   b  extends in the negative Y (−Y) axis direction, the distance between the second outer coil part  143   b  and the Y axis may be gradually decreased. When the second outer coil part  143   b  extends in the negative X (−X) axis direction, the distance between the second outer coil part  143   b  and the X axis may be gradually increased. In addition, when the third outer coil part  143   c  extends in the negative X (−X) axis direction, the distance between the third outer coil part  143   c  and the X axis may be gradually decreased. When the third outer coil part  143   c  extends in the negative Y (−Y) axis direction, the distance between the third outer coil part  143   c  and the Y axis may be gradually increased. In addition, when the fourth outer coil part  143   d  extends in the positive Y (Y) axis direction, the distance between the fourth outer coil part  143   d  and the Y axis may be gradually decreased. When the fourth outer coil part  143   d  extends in the positive X (X) axis direction, the distance between the fourth outer coil part  143   d  and the X axis may be gradually increased. Accordingly, the whole shape of the outer coil part  143  may have a circular shape or an oval shape. 
     The extension part  145  is connected with the outer coil part  143 . In this case, the extension part  145  extends from a terminated point of the fourth outer coil part  143   d . The extension part  145  extends inward of the outer coil part  143 . For example, when the first terminal  120  is provided at the right side of the Y axis serving as the central axis, the extension part  145  may extend from the left side of the Y axis serving as the central axis in parallel to the Y axis in the negative Y (−Y) axis direction by a predetermined length. The predetermined length may be a length corresponding to an extent that the extension part  145  may be provided only at the fourth quadrant without extending to the third quadrant. 
     The inner coil part  147  extends from a terminated point of the extension part  145 . In addition, the inner coil part  147  is connected with the extension part  145 . In this case, the inner coil part  147  is provided inward of the outer coil part  143 . In other words, the inner coil part  147  has a radius less than that of the outer coil part  143 . In this case, the inner coil part  147  is formed in a half-turn. For reference, the half-turn represents that a coil extends at any one of left and right sides of a central axis in a circular shape or a rectangular shape. For example, when the first terminal  120  is provided at the right side of the central axis, the inner coil part  147  may extend from the extension part  145  counterclockwise. In addition, the inner coil part  147  may extend at the left side of the Y axis serving as the central axis. In detail, the inner coil part  147  may include a first inner coil part  147   a  provided at the fourth quadrant and a second inner coil part  147   b  provided at the third quadrant in which the first and second inner coil parts  147   a  and  147   b  are integrated with each other. In addition, the first inner coil part  147   a  extends from a terminated point of the extension part  145  in the negative X (−X) axis direction, and extends in the negative Y (−Y) axis direction until the first inner coil part  147   a  meets the X axis. When the direction of the first inner coil part  147   a  is changed from the negative X (−X) axis direction to the negative Y (−Y) axis direction, the direction of the first inner coil part  147   a  may be changed with a predetermined curvature. In addition, the second inner coil part  147   b  extends from a terminated point of the first inner coil part  147   a  in the negative Y (−Y) axis direction, and extends in the positive X (X) axis direction in the third quadrant. When the direction of the second inner coil part  147   b  is changed from the negative Y (−Y) axis direction to the positive X (X) axis direction, the direction of the second inner coil part  147   b  may be changed with a predetermined curvature. Meanwhile, although description has been made regarding that the first and second inner coil parts  147   a  and  147   b  partially have a linear shape and partially have a curved shape with a curvature, the embodiment is not limited thereto. In other words, the whole shape of the first and second inner coil parts  147   a  and  147   b  may have an oval shape or a rectangular shape. Accordingly, when the first inner coil part  147   a  extends in the negative X (−X) axis direction, the distance between the first inner coil part  147   a  and the X axis may be constant or gradually decreased. When the first inner coil part  147   a  extends in the negative Y (−Y) axis direction, the distance between the first inner coil part  147   a  and the Y axis may be constant or may be gradually increased. In addition, when the second inner coil part  147   b  extends in the negative Y (−Y) axis direction, the distance between the second inner coil part  147   b  and the Y axis may be constant or gradually decreased. When the second inner coil part  147   b  extends in the positive X (X) axis direction, the distance between the second inner coil part  147   b  and the X axis may be constant or may be gradually increased. 
     Meanwhile, the first inner coil part  147   a  may be symmetrical to the second inner coil part  147   b  about the X axis. 
     The inner connection part  149  is connected with the inner coil part  147 . In addition, the inner connection part  149  is connected with the second terminal  130 . In this case, the inner connection part  149  extends from the inner coil part  147  to the second terminal  130 . For example, when the second terminal  130  is provided at the left side of the Y axis serving as the central axis, the inner connection part  149  may extend at the right side of the central axis. In detail, the inner connection part  149  extends in parallel to the Y axis in the positive Y (Y) axis direction from a terminated point of the second inner coil part  147   b , so that the inner connection part  149  may be connected with the second terminal  130 , and may be provided at the third quadrant and fourth quadrant. In addition, the inner connection part  149  may include at least one connection via (not shown) formed through the mounting member  110 . In other words, the inner connection part  149  may be connected with the second terminal  130  by passing the bottom surface of the mounting member  110  through the connection via, so that the inner connection part  149  does not make contact with the lower transmission coil  160 . 
     Meanwhile, the lower transmission coil  160  includes an outer connection part  161 , an outer coil part  163 , an extension part  165 , an inner coil part  167 , and an outer connection part  169 . 
     The outer connection part  161  is connected with the second terminal  130 . The outer connection part  161  extends from the second terminal  130 . For example, when the second terminal  130  is provided at the left side of the central axis, the outer connection part  161  may extend at the left side of the central axis. 
     The outer coil part  163  is provided at the outermost part of the lower transmission coil  160 . In addition, the outer coil part  163  is connected with the outer connection part  161 . In this case, the outer coil part  163  extends from the outer connection part  161 . In this case, the outer coil part  163  is formed in one-turn. For example, when the second terminal  130  is provided at the left side of the central axis, the outer coil part  163  may extend counterclockwise from the outer connection part  161 . In addition, the outer coil part  163  may extend from the left side of the central axis to the right side of the central axis. 
     The extension part  165  is connected with the outer coil part  163 . In this case, the extension part  165  extends from the outer coil part  163 . In this case, the extension part  165  extends inward of the outer coil part  163 . For example, when the second terminal  130  is provided at the left side of the central axis, the extension part  165  may extend at the right side of the central axis. 
     The inner coil part  167  extends from the extension part  165 . In addition, the inner coil part  167  is connected with the extension part  165 . In this case, the inner coil part  167  is provided inward of the outer coil part  163 . In other words, the inner coil part  167  has a radius less than that of the outer coil part  163 . In this case, the inner coil part  167  is formed in a half-turn. For example, when the second terminal  130  is provided at the left side of the central axis, the inner coil part  167  may extend clockwise from the extension part  165 . In addition, the inner coil part  167  may extend at the right side of the central axis. 
     The inner connection part  169  is connected with the inner coil part  167 . In addition, the inner connection part  169  is connected with the first terminal  120 . In this case, the inner connection part  169  extends from the inner coil part  167  to the first terminal  120 . For example, when the first terminal  120  is provided at the right side of the central axis, the inner connection part  169  may extend at the right side of the central axis. In addition, the inner connection part  169  may include at least one connection via (not shown) passing through the mounting member  110 . In other words, the inner connection part  169  may be connected with the first terminal  120  by passing the top surface of the mounting member  110  through the connection via so that the inner connection part  169  does not make contact with the upper transmission coil  140 . 
     In addition, the upper transmission coil  140  has the same current application direction as that of the lower transmission coil  160 . For example, when the current application direction of the upper transmission coil  140  is a clockwise direction, the current application direction of the lower transmission coil  160  is a clockwise direction. Meanwhile, when current is transmitted inward through the upper transmission coil  140 , current is transmitted outward through the lower transmission coil  160 . For example, when current is transmitted to the first terminal  120 , current may be inward transmitted through the upper transmission coil  140 , and transmitted outward through the lower transmission coil  160 . In addition, when current is transmitted outward through the upper transmission coil  140 , current is inward transmitted through the lower transmission coil  160 . For example, when current is transmitted to the second terminal  130 , current may be transmitted outward through the upper transmission coil  140 , and current may be transmitted inward through the lower transmission coil  160 . 
     In other words, the outer coil part  143  of the upper transmission coil  140  vertically faces the outer coil part  163  of the lower transmission coil  160 . In addition, the outer connection part  141 , the extension part  145 , the inner coil part  147 , and the inner connection part  149  of the upper transmission coil  140  are provided in opposition to the outer connection part  161 , the extension part  165 , the inner coil part  167 , and the inner connection part  169  of the lower transmission coil  160 , respectively, about the central axis. Accordingly, the upper and lower transmission coils  140  and  160  have a bilaterally symmetrical shape about the central axis. 
     Hereinafter, the bilaterally symmetrical shape of the upper and lower transmission coils  140  and  160  will be described in detail. Since the extension part  165  of the lower transmission coil  160  is provided at the first quadrant, the extension part  165  of the lower transmission coil  160  may be symmetrical to the extension part  145  of the upper transmission coil  140  about the Y axis. In addition, the outer coil part  163  of the lower transmission coil  160  may include a first outer coil part  163   a  provided at the fourth quadrant, a second outer coil part  163   b  provided at the third quadrant, a third outer coil part  163   c  provided at the second quadrant, and the fourth outer coil part  163   d  provided at the first quadrant. The first outer coil part  163   a  of the lower transmission coil  160  may be symmetrical to the first outer coil part  143   a  of the upper transmission coil  140  about the Y axis. The second outer coil part  163   b  of the lower transmission coil  160  may be symmetrical to the second outer coil part  143   b  of the upper transmission coil  140  about the Y axis. The third outer coil part  163   c  of the lower transmission coil  160  may be symmetrical to the third outer coil part  143   c  of the upper transmission coil  140  about the Y axis. The fourth outer coil part  163   d  of the lower transmission coil  160  may be symmetrical to the fourth outer coil part  143   d  of the upper transmission coil  140  about the Y axis. In addition, the inner coil part  167  of the lower transmission coil  160  may include a first inner coil part  167   a  provided at the first quadrant and a second inner coil part  167   b  provided at the second quadrant. The first inner coil part  167   a  of the lower transmission coil  160  may be symmetrical to the first inner coil part  147   a  of the upper transmission coil  140  about the Y axis, and the second inner coil part  167   b  of the lower transmission coil  160  may be symmetrical to the second inner coil part  147   b  of the upper transmission coil  140  about the Y axis. An inner connection part  169  of the lower transmission coil  160  may be symmetrical to the inner connection part  149  of the upper transmission coil  140  about the Y axis, so that the inner connection part  169  of the lower transmission coil  160  may be provided at the second quadrant or the first quadrant. 
     The distance between the outer coil part  143  and the inner coil part  147  of the upper transmission coil  140  and the distance between the outer coil part  163  and the inner coil part  167  of the lower transmission coil  160  may be formed corresponding to ½ of the size of the reception coil. In addition, the distance between the outer coil part  143  and the inner coil part  147  of the upper transmission coil  140  may be formed to the extent that a position where the coupling coefficient between the outer coil part  143  of the upper transmission coil  140  and the reception coil becomes maximized is matched with a position where the coupling coefficient between the inner coil part  147  and the reception coil becomes zero. Similarly, the distance between the outer coil part  163  and the inner coil part  167  of the lower transmission coil  160  may be formed to the extent that a position where the coupling coefficient between the outer coil part  163  of the lower transmission coil  160  and the reception coil becomes maximized is matched with a position where the coupling coefficient between the inner coil part  167  and the reception coil becomes zero. 
     The shielding member  180  isolates the upper transmission coil  140  from the lower transmission coil  160 . In other words, the shielding member  180  isolates the upper and lower transmission coils  140  and  160  from other components of the wireless power transmission apparatus  40  (see  FIG. 3 ). In this case, the shielding member  180  has a predetermined physical property. In this case, the physical property includes permeability (p). The permeability of the shielding member  180  may be maintained at a resonance frequency band of the upper and lower transmission coils  140  and  160 . Accordingly, the loss rate of the shielding member  180  may be reduced at the resonance frequency band of the upper and lower transmission coils  140  and  160 . 
     The shielding member  180  supports the mounting member  110 , the first terminal  120 , the second terminal  130 , the upper transmission coil  140 , and the lower transmission coil  160 . In addition, the shielding member  180  is formed of ferrite. In other words, the shielding member  180  may include metallic powders and a resin material. For example, the metallic powders may include soft magnetic metal powders, aluminum (Al), metal silicon, or an iron oxide (FeO; Fe 3 O 4 ; Fe 2 O 3 ). In addition, the resin material may include thermoplastic resin, for example polyolefin elastomer. 
     According to the present embodiment, the coupling coefficient between the wireless transmission unit  100  and the wireless reception unit  31  (see  FIG. 1 ) is substantially constant according to locations as shown in  FIG. 11 . The coupling coefficient between the wireless transmission unit  100  and the wireless reception unit  31  is formed equally to an average value of a first coupling coefficient formed between the outer coil part  143  of the upper transmission coil  140  and the outer coil part  163  of the lower transmission coil  160  and a second coupling coefficient formed between the inner coil part  147  of the upper transmission coil  140  and the inner coil part  167  of the lower transmission coil  160 . Accordingly, the coupling coefficient between the wireless transmission unit  100  and the wireless reception unit  31  has a higher value even if the wireless reception unit  31  approaches the centers of the upper and lower transmission coils  140  and  160 . Accordingly, the chargeable area of the wireless transmission unit  100  is enlarged. 
       FIG. 12  is an exploded perspective view showing a wireless transmission unit according to a second embodiment of the disclosure.  FIGS. 13 a  and 13 b    are plan views showing an upper transmission coil of  FIG. 12 .  FIGS. 14 a  and 14 b    are plan views showing a lower transmission coil of  FIG. 12 .  FIG. 15  is a graph to explain a coupling coefficient of a wireless transmission unit according to the second embodiment of the disclosure. 
     Referring to  FIGS. 12, 13   a ,  13   b ,  14   a , and  FIG. 14 b   , a wireless transmission unit  200  according to the present embodiment includes a mounting member  210 , a first terminal  220 , a second terminal  230 , an upper transmission coil  240 , a lower transmission coil  260 , and a shielding member  280 . Since components of the present embodiment are similar to the above-described components, the details thereof will be omitted in the following description. In other words, the present embodiment may have the same description as that of the above-described embodiment since the outer coil part  243  of the upper transmission coil  240  includes first to fourth outer coil parts  243   a ,  243   b ,  243   c , and  243   d , which are the same as the first to fourth outer coil parts  143   a ,  143   b ,  143   c , and  143   d  according to the above-described embodiment in terms of shapes and arrangement relationships. The present embodiment may have the same description as that of the above-described embodiment since the first inner coil part  247  of the upper transmission coil  240  includes a (1-1) th  inner coil part  247   a  and a (1-2) th  inner coil part  247   b , which are the same as the first and second inner coil parts  147   a  and  147   b  according to the above-described embodiment in terms of shapes and arrangement relationships. The present embodiment may have the same description as that of the above-described embodiment since the outer connection part  241  and the first extension part  245  are the same as the outer connection part  141  and the extension part  145  according to the above-described embodiment in terms of shapes and arrangement relationships. 
     The upper transmission coil  240  includes an outer connection part  241 , an outer coil part  243 , a first extension part  245 , a first inner coil part  247 , a second extension part  249 , a second inner coil part  251 , and an inner connection part  253 . 
     The outer connection part  241  is connected with the first terminal  220 . In this case, the outer connection part  241  extends from the first terminal  220 . For example, when the first terminal  220  is provided at the right side of the Y axis, the outer connection part  241  may extend at the right side of the Y axis serving as the central axis. 
     The outer coil part  243  is provided at the outermost part of the upper transmission coil  240 . In addition, the outer coil part  243  is connected with the outer connection part  241 . In this case, the outer coil part  243  extends from the outer connection part  241 . The outer coil part  243  is formed in one-turn. For example, when the first terminal  220  is provided at the right side of the central axis, the outer coil part  243  may extend from the outer connection part  241  clockwise. In addition, the outer coil part  243  may extend from the right side of the central axis to the left side of the central axis. 
     The first extension part  245  is connected with the outer coil part  243 . In this case, the first extension part  245  extends from the outer coil part  243 . In this case, the first extension part  245  extends inward of the outer coil part  243 . For example, the first terminal  220  is provided at the right side of the central axis, the first extension part  245  may extend from the left side of the central axis. 
     The first inner coil part  247  extends from a terminated point of the first extension part  245 . In addition, the first inner coil part  247  extends from the first extension part  245 . In this case, the first inner coil part  247  is provided inward of the outer coil part  243 . In other words, the first inner coil part  247  has a radius less than that of the outer coil part  243 . In this case, the first inner coil part  247  is formed in a half-turn. For example, when the first terminal  220  is provided at the right side of the central axis, the first inner coil part  247  may extend from the first extension part  245  counterclockwise. In addition, the first inner coil part  247  may extend at the left side of the Y axis serving as the central axis. 
     The second extension part  249  is connected with the first inner coil part  247 . In this case, the second extension part  249  extends from a terminated point of the first inner coil part  247 . In this case, the second extension part  249  extends inward of the first inner coil part  247 . For example, when the first terminal  220  is provided at the right side of the Y axis serving as the central axis, the second extension part  249  may extend from the left side of the central axis to the right side of the central axis. In other words, the second extension part  249  may extend from the third quadrant to the second quadrant across the Y axis. In more detail, the second extension part  249  may extend with the directionality from an XY plane to a (−X)(−Y) plane. 
     The second inner coil part  251  is connected with the second extension part  249 . In this case, the second inner coil part  251  extends from a terminated point of the second extension part  249 . In this case, the second inner coil part  251  has a radius less than that of the first inner coil part  247 . In this case, the second inner coil part  251  is formed in a half-turn. For example, when the first terminal  220  is provided at the right side of the Y axis serving as the central axis, the second inner coil part  251  may extend from the second extension part  249  counterclockwise. In addition, the second inner coil part  251  may extend from the right side of the central axis to the left side of the central axis. In detail, the second inner coil part  251  may include a (2-1) th  inner coil part  251   a  provided at the second quadrant and a (2-2) th  inner coil part  251   b  provided at the first quadrant. The (2-1) th  inner coil part  251   a  may extend in parallel to the X axis or with a vertical distance from the X axis, which is gradually decreased, in the positive X (X) axis direction. Then, the (2-1) th  inner coil part  251   a  may extend in parallel to the Y axis or with a vertical distance from the Y axis, which is gradually increased, in the positive Y (Y) axis direction. The (2-2) th  inner coil part  251   b  may extend in parallel to the Y axis or with a vertical distance from the Y axis, which is gradually decreased, in the positive Y (Y) axis direction. Then, the (2-2) th  inner coil part  251   b  may extend in parallel to the X axis or with a vertical distance from the X axis, which is gradually increased, in the negative X (−X) axis direction. In addition, the (2-1) th  inner coil part  251   a  and the (2-2) th  inner coil part  251   b  may be symmetrical to each other about the X axis except for the shapes of the (2-1) th  inner coil part  251   a  and the (2-2) th  inner coil part  251   b  at a starting point and a terminated point thereof. 
     The inner connection part  253  is connected with the second inner coil part  251 . In addition, the inner connection part  253  is connected with the second terminal  230 . In this case, the inner connection part  253  extends from a terminated point of the second inner coil part  251 , that is, a terminated point of the (2-2) th  inner coil part  252   b  toward the second terminal  230  in parallel to the Y axis in the positive Y (Y) axis direction. For example, when the second terminal  230  is provided at the left side of the Y axis serving as the central axis, the inner connection part  253  may extend at the left side of the central axis. In addition, the inner connection part  253  may include at least one connection via (not shown) formed through the mounting member  210 . In other words, the inner connection part  253  may be connected with the second terminal  230  by passing the bottom surface of the mounting member  210  through the connection via so that the inner connection part  253  does not make contact with the lower transmission coil  260 . 
     Meanwhile, the lower transmission coil  260  includes an outer connection part  261 , an outer coil part  263 , a first extension part  265 , a first inner coil part  267 , a second extension part  269 , a second inner coil part  271 , and an inner coil part  273 . 
     In other words, the present embodiment may have the same description as that of the above-described embodiment since the outer coil part  263  of the lower transmission coil  260  includes first to fourth outer coil parts  263   a ,  263   b ,  263   c , and  263   d , which are the same as the first to fourth outer coil parts  163   a ,  163   b ,  163   c , and  163   d  according to the above-described embodiment in terms of shapes and arrangement relationships. The present embodiment may have the same description as that of the above-described embodiment since the first inner coil part  267  of the upper transmission coil  260  includes a (1-1) th  inner coil part  267   a  and a (1-2) th  inner coil part  267   b , which are the same as the first and second inner coil parts  167   a  and  167   b  according to the above-described embodiment in terms of shapes and arrangement relationships. The present embodiment may have the same description as that of the above-described embodiment since the outer connection part  261  and the first extension part  265  are the same as the outer connection part  161  and the extension part  165  according to the above-described embodiment in terms of shapes and arrangement relationships. 
     The outer connection part  261  is connected with the second terminal  230 . The outer connection part  261  extends from the second terminal  230 . For example, when the second terminal  230  is provided at the left side of the central axis, the outer connection part  261  may extend at the left side of the central axis. 
     The outer coil part  263  is provided at the outermost part of the lower transmission coil  260 . In addition, the outer coil part  263  is connected with the outer connection part  261 . In this case, the outer coil part  263  extends from the outer connection part  261 . In this case, the outer coil part  263  is formed in one-turn. For example, when the second terminal  230  is provided at the left side of the central axis, the outer coil part  263  may extend counterclockwise from the outer connection part  261 . In addition, the outer coil part  263  may extend from the left side of the central axis to the right side of the central axis. 
     The first extension part  265  is connected with the outer coil part  263 . In this case, the first extension part  265  extends from the outer coil part  263 . In this case, the first extension part  265  extends inward of the outer coil part  263 . For example, when the second terminal  230  is provided at the left side of the central axis, the first extension part  265  may extend at the right side of the central axis. 
     The first inner coil part  267  is connected with the first extension part  265 . In addition, the first inner coil part  267  extends from the first extension part  265 . In this case, the first inner coil part  267  is provided inward of the outer coil part  263 . In other words, the first inner coil part  267  has a radius less than that of the outer coil part  263 . In this case, the first inner coil part  267  is formed in a half-turn. For example, when the second terminal  230  is provided at the left side of the central axis, the first inner coil part  267  may extend clockwise from the first extension part  265 . In addition, the first inner coil part  267  may extend at the right side of the central axis. 
     The second inner connection part  269  is connected with the first inner coil part  267 . In addition, the second inner connection part  269  extends from the first inner coil part  267 . In this case, the second extension part  269  extends inward of the first inner coil part  267 . For example, when the second terminal  230  is provided at the left side of the central axis, the second extension part  269  may extend from the right side of the central axis to the left side of the central axis. 
     The second inner coil part  271  is connected with the second extension part  269 . In addition, the second inner coil part  271  extends from the second extension part  269 . In this case, the second inner coil part  271  has a radius less than that of the first inner coil part  267 . In this case, the second inner coil part  271  is formed in a half-turn. For example, when the second terminal  230  is provided at the left side of the central axis, the second inner coil part  271  may extend clockwise from the second extension part  269 . In addition, the second inner coil part  271  may extend from the left side of the central axis to the right side of the central axis. 
     The inner connection part  273  is connected with the second inner coil part  271 . In addition, the inner connection part  273  is connected with the first terminal  220 . In this case, the inner connection part  273  extends from the second inner coil part  271  to the first terminal  220 . For example, when the first terminal  220  is provided at the right side of the central axis, the inner connection part  273  may extend at the right side of the central axis. In addition, the inner connection part  273  may include at least one connection via (not shown) formed through the mounting member  210 . In other words, the inner connection part  273  may be connected with the first terminal  220  by passing the top surface of the mounting member  210  through the connection via so that the inner connection part  273  does not make contact with the upper transmission coil  240 . 
     In other words, the outer coil part  243  of the upper transmission coil  240  vertically faces the outer coil part  263  of the lower transmission coil  260 . In addition, the outer connection part  241 , the first extension part  245 , the first inner coil part  247 , the second extension part  259 , the second inner coil part  251 , and the inner connection part  253  of the upper transmission coil  240  are provided in opposition to the outer connection part  261 , the first extension part  265 , the first inner coil part  267 , the second extension part  269 , the second inner coil part  271 , and the inner connection part  273  of the lower transmission coil  260 , respectively, about the central axis. Accordingly, the upper and lower transmission coils  240  and  260  have a bilaterally symmetrical shape about the central axis. In other words, the description of the symmetrical shape according to the first embodiment may be applicable to the present embodiment. According to the present embodiment, the second inner coil part  271  of the lower transmission coil  260  making a difference from the previous embodiment may include (2-1) th  and (2-2) th  inner coil parts  271   a  and  271   b . The (2-1) th  inner coil part  271   a  of the lower transmission coil  260  may be symmetrical to the (2-1) th  inner coil part  251   a  of the second inner coil part  251  provided in the upper transmission coil  240  and provided at the second quadrant about the Y axis. The (2-2) th  inner coil part  271   b  of the lower transmission coil  260  may be symmetrical to the (2-2) th  inner coil part  251   b  of the second inner coil part  251  provided in the upper transmission coil  240  and provided at the first quadrant about the Y axis. 
     In this case, the distance between the outer coil part  243  and the first inner coil part  247  of the upper transmission coil  240  and the distance between the outer coil part  263  and the first inner coil part  267  of the lower transmission coil  260  may be formed corresponding to ½ of the size of the reception coil. Meanwhile, the distance between the outer coil part  243  and the inner coil part  247  of the upper transmission coil  240  may be formed to the extent that a position where the coupling coefficient between the outer coil part  243  of the upper transmission coil  240  and the reception coil becomes maximized is matched with a position where the coupling coefficient between the second inner coil part  251  and the reception coil becomes zero. Similarly, the distance between the outer coil part  263  and the second inner coil part  271  of the lower transmission coil  260  may be formed to the extent that a position where the coupling coefficient between the outer coil part  263  of the lower transmission coil  260  and the reception coil becomes maximized is matched with a position where the coupling coefficient between the second inner coil part  271  and the reception coil becomes zero. 
     According to the present embodiment, the coupling coefficient between the wireless transmission unit  200  and the wireless reception unit  31  (see  FIG. 1 ) is substantially constant according to locations as shown in  FIG. 15 . In other words, the coupling coefficient between the wireless transmission unit  200  and the wireless reception unit  31  is formed equally to an average value of a first coupling coefficient formed between the outer coil part  243  of the upper transmission coil  240  and the outer coil part  263  of the lower transmission coil  260 , a second coupling coefficient formed between the first inner coil part  247  of the upper transmission coil  240  and the first inner coil part  267  of the lower transmission coil  260 , and a third coupling coefficient between the second inner coil unit  251  of the upper transmission coil  240  and the second inner coil unit  271  of the lower transmission coil  260 . Accordingly, the coupling coefficient between the wireless transmission unit  200  and the wireless reception unit  31  has a higher value even if the wireless reception unit  31  approaches the centers of the upper and lower transmission coils  240  and  260 . Accordingly, the chargeable area of the wireless transmission unit  200  is enlarged. 
       FIG. 16  is an exploded perspective view showing a wireless transmission unit according to a third embodiment of the disclosure, and  FIGS. 17 a  and 17 b    are plan views showing an upper transmission coil of  FIG. 16 .  FIGS. 18 a  and 18 b    are plan views showing a lower transmission coil of  FIG. 16 .  FIG. 19  is a graph to explain a coupling coefficient of a wireless transmission unit according to the third embodiment of the disclosure.  FIG. 20  is a view showing a realization example of the wireless transmission unit according to the third embodiment of the disclosure. 
     Referring to  FIGS. 16, 17   a ,  17   b ,  18   a , and  18   b , a wireless transmission unit  300  includes a mounting member  310 , a first terminal  320 , a second terminal  330 , an upper transmission coil  340 , a lower transmission coil  360 , and a shielding member  380 . Since components of the present embodiment are similar to corresponding components of the previous embodiment, the details of the components of the disclosure will be omitted. 
     The upper transmission coil  340  includes an outer connection part  341 , an outer coil part  343 , a first extension part  345 , a first inner coil part  347 , a second extension part  349 , a second inner coil part  351 , a third extension part  353 , a third inner coil part  354 , a fourth extension part  355 , a fourth inner coil part  357 , and an inner connection part  358 . 
     The outer connection part  341  is connected with the first terminal  320 . In this case, the outer connection part  341  extends from the first terminal  320  in parallel to the Y axis in the negative Y (−Y) axis direction. For example, when the first terminal  320  is provided at the right side of the Y axis serving as the central axis, the outer connection part  341  may extend at the right side of the Y axis serving as the central axis. In other words, the outer connection part  341  starts from the first terminal  320  and extends in parallel to the Y axis in the negative Y (−Y) axis direction by a predetermined length. In this case, the predetermined length is a length corresponding to an extent that the outer connection part  341  may be provided only at the first quadrant without extending to the second quadrant. 
     The outer coil part  343  is provided at the outermost part of the upper transmission coil  340 . In addition, the outer coil part  343  is connected with the outer connection part  341 . In this case, the outer coil part  343  extends from a terminated point of the outer connection part  341 . The outer coil part  343  is formed in one-turn. For example, when the first terminal  320  is provided at the right side of the central axis, the outer coil part  343  may extend clockwise from the outer connection part  341 . In addition, the outer coil part  343  may extend from the right side of the central axis to the left side of the Y axis serving as the central axis. 
     In detail, the outer coil part  343  may include a first outer coil part  343   a  provided at the first quadrant, a second outer coil part  343   b  provided at the second quadrant, the third outer coil part  343   c  provided at the third quadrant, and the fourth outer coil part  343   d  provided at the fourth quadrant, and the first to fourth outer coil parts  343   a  to  343   d  are integrated with each other. The first outer coil part  343   a  may extend to an intersection between the first outer coil part  343   a  and the X axis from a terminated point of the outer connection part  341 . In other words, the first outer coil part  343   a  extends in parallel to the X axis in the positive X (X) axis direction from the terminated point of the outer connection part  341 . Then, the first outer coil part  343   a  extends in parallel to the Y axis in the negative Y (−Y) axis direction. When the direction of the first outer coil part  343   a  is changed from the negative Y (−Y) axis direction from the positive X (X) axis direction, the direction of the first outer coil part  343   a  may be changed with a predetermined curvature. In addition, the second outer coil part  343   b  may extend from the terminated point of the first outer coil part  343   a  to the intersection between the second outer coil part  343   b  and the Y axis. In other words, the second outer coil part  343   b  extends in parallel to the Y axis in the negative Y (−Y) axis direction from the terminated point of the first outer coil part  343   a , and extends in parallel to the X axis in the negative X (−X) axis direction. When the direction of the second outer coil part  343   b  is changed from the negative Y (−Y) axis direction to the negative X (−X) axis direction, the direction of the second outer coil part  343   b  may be changed with a predetermined curvature. In addition, the third outer coil part  343   c  may extend from the terminated point of the second outer coil part  343   b  to the intersection between the third outer coil part  343   c  and the X axis. In other words, the third outer coil part  343   c  extends in parallel to the X axis in the negative X (−X) axis direction from the terminated point of the second outer coil part  343   b , and extends in parallel to the Y axis in the positive Y (Y) axis direction. When the direction of the third outer coil part  343   c  is changed from the negative X (−X) axis direction to the positive Y (Y) axis direction, the direction of the third outer coil part  343   c  may be changed with a predetermined curvature. In addition, the fourth outer coil part  343   d  may extend from the terminated point of the third outer coil part  343   c  to the intersection between the fourth outer coil part  343   d  and the Y axis. In other words, the fourth outer coil part  343   d  extends in parallel to the Y axis in the positive Y (Y) axis direction from the terminated point of the third outer coil part  343   c , and extends in parallel to the X axis in the positive X (X) axis direction. When the direction of the fourth outer coil part  343   d  is changed from the positive Y (Y) axis direction to the positive X axis direction, the direction of the fourth outer coil part  343   d  may be changed with a predetermined curvature. 
     In addition, the first outer coil part  343   a  and the second outer coil part  343   b  may be symmetrical to each other about the X axis, and the first outer coil part  343   a  and the fourth outer coil part  343   d  may be symmetrical to each other about the Y axis. The first outer coil part  343   a  and the third outer coil part  343   c  may be symmetrical to each other about the origin (0). 
     Meanwhile, although description has been made regarding that the first to fourth outer coil parts  343   a ,  343   b ,  343   c , and  343   d  partially have a linear shape and partially have a curved shape with a curvature, the embodiment is not limited thereto. In other words, the whole shape of the first to fourth outer coil parts  343   a ,  343   b ,  343   c , and  343   d  may have an oval shape or a circular shape. Accordingly, when the first outer coil part  343   a  extends in the positive X (X) axis direction, the distance between the first outer coil part  343   a  and the X axis may be gradually decreased. When the first outer coil part  343   a  extends in the negative Y (−Y) axis direction, the distance between the first outer coil part  343   a  and the Y axis may be gradually increased. In addition, when the second outer coil part  343   b  extends in the negative Y (−Y) axis direction, the distance between the second outer coil part  343   b  and the Y axis may be gradually decreased. When the second outer coil part  343   b  extends in the negative X (−X) axis direction, the distance between the second outer coil part  343   b  and the X axis may be gradually increased. In addition, when the third outer coil part  343   c  extends in the negative X (−X) axis direction, the distance between the third outer coil part  343   c  and the X axis may be gradually decreased. When the third outer coil part  343   c  extends in the positive Y (Y) axis direction, the distance between the third outer coil part  343   c  and the Y axis may be gradually increased. In addition, when the fourth outer coil part  343   d  extends in the positive Y (Y) axis direction, the distance between the fourth outer coil part  343   d  and the Y axis may be gradually decreased. When the fourth outer coil part  343   d  extends in the positive X (X) axis direction, the distance between the fourth outer coil part  343   d  and the X axis may be gradually increased. Accordingly, the whole shape of the outer coil part  343  may have a circular shape or an oval shape. 
     The extension part  345  is connected with the outer coil part  343 . In this case, the extension part  345  extends from a terminated point of the outer coil part  343 . The extension part  345  extends inward of the outer coil part  343 . For example, when the first terminal  320  is provided at the right side of the Y axis serving as the central axis, the extension part  345  may extend from the left side of the Y axis serving as the central axis. 
     The first inner coil part  347  is connected with the first extension part  345 . The first inner coil part  347  extends from a terminated point of the first extension part  345 . Accordingly, the first extension part  345  may connect the terminated point of the outer coil part  343  with a starting point of the first inner coil part  347  across the Y axis. In this case, the first inner coil part  347  is provided inward of the outer coil part  343 . In other words, the first inner coil part  347  has a radius less than that of the outer coil part  343 . In this case, the first inner coil part  347  is formed in a half-turn. For example, when the first terminal  320  is provided at the right side of the Y axis serving as the central axis, the first inner coil part  347  may extend from the first extension part  345  clockwise. In addition, the first inner coil part  347  may extend at the right side of the Y axis serving as the central axis. In addition, the distance from the origin to the first inner coil part  347  may be shorter than the distance from the origin to the outer coil part  343 . In this case, the distance between the first inner coil part  347  and the outer coil part  343  may be formed to the extent that the first inner coil part  347  and the outer coil part  343  are significantly close to each other. 
     In addition, the first inner coil part  347  may include a (1-1) inner coil part  347   a  provided at the first quadrant and a (1-2) th  inner coil part  347   b  provided at the second quadrant, in which the (1-1) th  inner coil part  347   a  is integrated with the (1-2) th  inner coil part  347   b . In addition, the (1-1) th  inner coil part  347   a  extends from the terminated point of the first extension part  345  to the intersection between the (1-1) th  inner coil part  347   a  and the X axis. In other words, the (1-1) th  inner coil part  347   a  may extend in parallel to the X axis or with a vertical distance from the X axis, which is gradually decreased, in the positive X (X) axis direction and may extend in parallel to the Y axis or with a vertical distance from the Y axis, which is gradually decreased, in the negative Y (−Y) axis direction. When the direction of the (1-1) th  inner coil part  347   a  is changed from the negative Y (−Y) axis direction from the positive X (X) axis direction, the direction of the (1-1) th  inner coil part  347   a  may be changed with a predetermined curvature. In addition, the (1-2) th  inner coil part  347   b  extends from the terminated point of the (1-1) th  inner coil part  347   a  within the second quadrant. In other words, the (1-2) th  inner coil part  347   b  may extend in parallel to the Y axis or with a vertical distance from the Y axis, which is gradually decreased, in the negative Y (−Y) axis direction, and may extend in parallel to the X axis or with a vertical distance from the X axis, which is gradually decreased, in the negative X (−X) axis direction. When the direction of the (1-2) th  inner coil part  347   b  is changed from the negative Y (−Y) axis direction from the negative X (−X) axis direction, the direction of the (1-2) th  inner coil part  347   b  may be changed with a predetermined curvature. In addition, the (1-1) th  inner coil part  347   a  and the (1-2) th  inner coil part  347   b  may be symmetrical to each other about the X axis. 
     The second extension part  349  is connected with the first inner coil part  347 . In this case, the second extension part  349  extends from the terminated point of the first inner coil part  347 . In this case, the second extension part  349  extends inward of the first inner coil part  347 . For example, when the first terminal  320  is provided at the right side of the central axis, the second extension part  349  may extend from the right side of the central axis to the left side of the Y axis serving as the central axis. In other words, the second extension part  349  may extend from the second quadrant to the third quadrant across the Y axis. In more detail, the second extension part  349  may extend with the directionality from an (X)(−Y) plane to a (−X)(Y) plane. 
     The second inner coil part  351  is connected with the second extension part  349 . In addition, the second inner coil part  351  extends from the terminated point of the second extension part  349 . In this case, the second inner coil part  351  has a radius less than that of the first inner coil part  347 . In this case, the second inner coil part  351  is formed in a half-turn. For example, when the first terminal  320  is provided at the right side of the Y axis serving as the central axis, the second inner coil part  351  may extend clockwise from the second extension part  329 . In addition, the second inner coil part  351  may extend at the left side of the Y axis serving as the central axis. 
     In detail, the second inner coil part  351  may include a (2-1) th  inner coil part  351   a  provided at the third quadrant and a (2-2) th  inner coil part  351   b  provided at the fourth quadrant, in which the (2-1) th  inner coil part  351   a  is integrated with the a (2-2) th  inner coil part  351   b . In addition, the (2-1) th  inner coil part  351   a  extends in the negative X (−X) axis direction from the terminated point of the second extension part  349  and extends in the positive Y (Y) axis until the (2-1) th  inner coil part  351   a  meets the X axis. When the direction of the (2-1) th  inner coil part  351   a  is changed from the negative X (−X) axis direction to the positive Y (Y) axis direction, the direction of the (2-1) th  inner coil part  351   a  may be changed with a predetermined curvature. In addition, the (2-2) inner coil part  351   b  extends in the positive Y (Y) axis direction from the terminated point of the (2-1) th  inner coil part  351   a  and extends in the positive X (X) axis direction within the fourth quadrant. When the direction of the (2-2) th  inner coil part  351   b  is changed from the positive Y (Y) axis direction to the positive X (X) axis direction, the direction of the (2-1) th  inner coil part  351   a  may be changed with a predetermined curvature. Meanwhile, although description has been made regarding that the (2-1) th  inner coil part  351   a  and the (2-2) th  inner coil part  351   b  partially have a linear shape and partially have a curved shape with a curvature, the embodiment is not limited thereto. In other words, the whole shape of the (2-1) th  inner coil part  351   a  and the (2-2) th  inner coil part  351   b  may have an oval shape, a circular shape, or a rectangular shape. Accordingly, when the (2-1) th  inner coil part  351   a  extends in the negative X (−X) axis direction, the distance between the (2-1) th  inner coil part  351   a  and the X axis may be constant or gradually decreased. When the (2-1) th  inner coil part  351   a  extends in the positive Y (Y) axis direction, the distance between the (2-1) th  inner coil part  351   a  and the Y axis may be constant or gradually increased. In addition, when the (2-2) th  inner coil part  351   b  extends in the positive Y (Y) axis direction, the distance between the (2-2) th  inner coil part  351   b  and the Y axis may be constant or gradually decreased. When the (2-2) th  inner coil part  351   b  extends in the positive X (X) axis direction, the distance between the (2-2) th  inner coil part  351   b  and the X axis may be constant or gradually increased. 
     Meanwhile, the (2-1) th  inner coil part  351   a  and the (2-2) th  inner coil part  351   b  may be symmetrical to each other about the X axis except for the shapes of the (2-1) th  inner coil part  351   a  and the (2-2) th  inner coil part  251   b  at a starting point and a terminated point thereof. 
     The third extension part  353  is connected with the second inner coil part  351 . In this case, the third extension part  353  extends in parallel to the Y axis in the negative Y (−Y) axis direction from the terminated point of the second inner coil part  351 , that is, the terminated point of the (2-2) th  inner coil part  351   b . In this case, the third extension part  353  extends inward of the second inner coil part  351 . For example, when the first terminal  320  is provided at the right side of the Y axis serving as a central axis, the third extension part  353  extends from the left side of the central axis to the right side of the Y axis serving as the central axis. 
     The third inner coil part  354  is connected with the third extension part  353 . In this case, the third inner coil part  354  extends from the terminated point of the third extension part  353 . In this case, the third inner coil part  354  has a radius less than that of the second inner coil part  351 . In this case, the third inner coil part  354  is formed in a half-turn. For example, when the first terminal  320  is provided at the right side of the central axis, the third inner coil part  354  may extend clockwise from the third extension part  353 . In addition, the third inner coil part  354  may extend at the right side of the central axis. 
     In detail, the third inner coil part  354  may include a (3-1) th  inner coil part  354   a  provided at the first quadrant and a (3-2) th  inner coil part  354   b  provided at the second quadrant. The (3-1) th  inner coil part  354   a  may extend in parallel to the X axis or with the vertical distance from the X axis, which is gradually decreased, in the positive X (X) axis direction, and may extend in parallel to the Y axis or with the vertical distance from the Y axis, which is gradually increased, in the negative Y (−Y) axis direction. The (3-2) th  inner coil part  354   b  may extend in parallel to the Y axis or with the vertical distance from the Y axis, which is gradually decreased, in the negative Y (−Y) axis direction, and may extend in parallel to the X axis or with the vertical distance from the X axis, which is gradually increased, in the negative X (−X) axis direction. In addition, the (3-1) th  inner coil part  354   a  and the (3-2) th  inner coil part  354   b  may be symmetrical to each other about the X axis except for the shapes of the (3-1) th  inner coil part  354   a  and the (3-2) th  inner coil part  354   b  at a starting point and a terminated point thereof. 
     The fourth extension part  355  is connected with the third inner coil part  354 . In this case, the fourth extension part  355  extends from a terminated point of the third inner coil part  354 , that is, the terminated point of the (3-2) th  inner coil part  354   b . In this case, the fourth extension part  355  extends inward of the third inner coil part  354 . For example, when the first terminal  320  is provided at the right side of the Y axis serving as the central axis, the fourth extension part  355  may extend from the right side of the central axis to the left side of the Y axis serving as the central axis. In other words, the fourth extension part  355  may extend from the second quadrant from the third quadrant across the Y axis. In more detail, the fourth extension part may extend in the positive Y (Y) axis direction with the directionality from an X(−Y) plane to a (−X)Y plane. 
     The fourth inner coil part  357  is connected with the fourth extension part  355 . In this case, the fourth inner coil part  357  extends from the terminated point of the fourth extension part  355 . In this case, the fourth inner coil part  357  has a radius less than that of the third inner coil part  354 . In this case, when the fourth inner coil part  357  is formed in a half-turn. For example, when the first terminal  320  is provided at the right side of the Y axis serving as the central axis, the fourth inner coil part  357  may extend clockwise from the fourth extension part  355 . In addition, the fourth inner coil part  357  may extend at the left side of the Y axis serving as the central axis. 
     In detail, the fourth inner coil part  357  may include a (4-1) th  inner coil part  357   a  provided at the third quadrant and a (4-2) th  inner coil part  357   b  provided at the fourth quadrant. The (4-1) inner coil part  357   a  may extend in the negative X (−X) axis direction and extend in the positive Y (Y) axis direction while the whole shape of the (4-1) th  inner coil part  357   a  has a predetermined curvature. The (4-2) th  inner coil part  357   b  may extend in the positive Y (Y) axis direction and extend in the positive X (X) axis direction while the whole shape of the (4-2) th  inner coil part  357   b  has a predetermined curvature. In addition, the (4-1) th  inner coil part  357   a  and the (4-2) th  inner coil part  357   b  may be symmetrical to each other about the X axis. The inner connection part  358  is connected with the fourth inner coil part  357 . In addition, the inner connection part  358  is connected with the second terminal  330 . In this case, the inner connection part  358  extends along the Y axis in the positive Y (Y) axis direction from the terminated point of the fourth inner coil part  357 , that is, the terminated point of the (4-2) inner coil part  357   b  toward the second terminal  330 . For example, when the second terminal  330  is provided at the left side of the Y axis serving as the central axis, the inner connection part  358  may extend at the left side of the Y axis serving as the central axis. In addition, the inner connection art  358  may include at least one connection via (not shown) formed through the mounting member  310 . In other words, the inner connection part  358  may be connected with the second terminal  330  by passing the bottom surface of the mounting member  310  through the connection via when the inner connection part  358  does not make contact with the lower transmission coil  360 . 
     Meanwhile, the lower transmission coil  360  according to the disclosure includes an outer connection part  361 , an outer coil part  363 , a first extension part  365 , a first inner coil part  367 , a second extension part  369 , a second inner coil part  371 , a third extension part  373 , a third inner coil part  374 , a fourth extension part  375 , a fourth inner coil part  377 , and an inner connection part  378 . 
     The outer connection part  361  is connected with the second terminal  330 . In this case, the outer connection part  361  extends from the second terminal  330 . For example, when the second terminal  330  is provided at the left side of the central axis, the outer connection part  361  may extend at the left side of the central axis. 
     The outer coil part  363  is provided at the outermost part of the lower transmission coil  360 . In addition, the outer coil part  363  is connected with the outer connection part. In this case, the outer coil part  363  extends from the outer connection part  361 . In this case, the outer coil part  363  is formed one-turn. For example, when the second terminal  330  is provided at the left side of the central axis, the outer coil part  363  may extend counterclockwise from the outer connection part  361 . In addition, the outer coil part  363  may extend from the left side of the central axis to the right side of the central axis. 
     The first extension part  365  is connected with the outer coil part  363 . In this case, the first extension part  365  extends from the outer coil part  363 . In this case, the first extension part  365  extends inward of the outer coil part  363 . For example, when the second terminal  330  is provided at the left side of the central axis, the first extension part  365  may extend at the right side of the central axis. 
     The first inner coil part  367  is connected with the first extension part  365 . In addition, the first inner coil part  367  extends from the first extension part  365 . In this case, the first inner coil part  367  is provided inward of the outer coil part  363 . In other words, the first inner coil part  367  has a radius less than that of the outer coil part  363 . In this case, the first inner coil part  367  is formed in a half-turn. For example, when the second terminal  330  is provided at the left side of the central axis, the first inner coil part  367  may extend counterclockwise from the first extension part  365 . In addition, the first inner coil part  367  may extend at the left side of the central axis. 
     The second extension part  369  is connected with the first inner coil part  367 . In this case, the second extension part  369  extends from the first inner coil part  367 . In this case, the second extension part  368  extends inward of the first inner coil part  367 . For example, when the second terminal  330  is provided at the left side of the central axis, the second extension part  369  may extend from the left side of the central axis to the right side of the central axis. 
     The second inner coil part  371  is connected with the second extension part  369 . In addition, the second inner coil part  371  extends from the second extension part  369 . In this case, the second inner coil part  371  has a radius less than that of the first inner coil part  367 . In this case, the second inner coil part  371  is formed in a half-turn. For example, when the second terminal  330  is provided at the left side of the central axis, the second inner coil part  371  may extend counterclockwise from the second extension part  369 . In addition, the second inner coil part  371  may extend at the right side of the central axis. 
     The third extension part  373  is connected with the second inner coil part  371 . In this case, the third extension part  373  extends from the second inner coil part  371 . In this case, the third extension part  373  extends inward of the second inner coil part  371 . For example, when the second terminal  330  is provided at the left side of the central axis, the third extension part  373  may be extend at the left side of the central axis. 
     The third inner coil part  374  is connected with the third extension part  373 . In this case, the third inner coil part  374  extends from the third extension part  373 . In this case, the third inner coil part  374  has a radius less than that of the second inner coil part  371 . In this case, the third inner coil part  374  is formed in a half-turn. For example, when the second terminal  330  is provided at the left side of the central axis, the third inner coil part  374  may be extend counterclockwise from the third extension part  373 . In addition, the third inner coil part  373  may extend at the left side of the central axis. 
     The fourth extension part  375  is connected with the third inner coil part  374 . In this case, the fourth extension part  375  extends from the third inner coil part  374 . In this case, the fourth extension part  375  extends inward of the third inner coil part  374 . For example, when the second terminal  330  is provided at the left side of the central axis, the fourth extension part  375  may extend from the left side of the central axis to the right side of the central axis. 
     The fourth inner coil part  377  is connected with the fourth extension part  375 . In this case, the fourth inner coil part  377  extends from the fourth extension part  375 . In this case, the fourth inner coil part  377  has a radius less than that of the third inner coil part  374 . In this case, the fourth inner coil part  377  is formed in a half-turn. For example, when the second terminal  330  is provided at the right side of the central axis, the fourth inner coil part  377  may be extend counterclockwise from the fourth extension part  375 . In addition, the fourth inner coil part  377  may extend at the right side of the central axis. 
     The inner connection part  378  is connected with the fourth inner coil part  377 . In addition, the inner connection part  378  is connected with the first terminal  320 . In this case, the inner connection part  378  extends from the fourth inner coil part  377 . For example, when the first terminal  320  is provided at the right side of the central axis, the inner connection part  378  may extend at the right side of the central axis. In addition, the inner connection part  378  may include at least one connection via (not shown) formed through the mounting member  310 . In other words, the inner connection part  378  may be connected with the first terminal  320  by passing the bottom surface of the mounting member  310  through the connection via so that the inner connection part  378  does not make contact with the upper transmission coil  340 . 
     In other words, the outer coil part  343  of the upper transmission coil  340  vertically faces the outer coil part  363  of the lower transmission coil  360 . In addition, the outer connection part  341 , the first extension part  345 , the first inner coil part  347 , the second extension part  349 , the second inner coil part  351 , the third extension part  353 , the third inner coil part  354 , the fourth extension part  355 , the fourth inner coil  357 , and the inner connection part  358  of the upper transmission coil  340  mutually face the outer connection part  361 , the first extension part  365 , the first inner coil part  367 , the second extension part  369 , the second inner coil part  371 , the third extension part  373 , the third inner coil part  374 , the fourth extension part  375 , the fourth inner coil part  377 , and the inner connection part  378  of the lower transmission coil  360  about the central axis. Accordingly, the upper transmission coil  340  is bilaterally symmetrical to the lower transmission coil  360  about the central axis. 
     Regarding the details of the symmetrical shape, similarly, the first outer coil part  343   a  provided at the first quadrant, the second outer coil part  343   b  provided at the second quadrant, the third outer coil part  343   c  provided at the third quadrant, and the fourth outer coil part  343   d  provided at the fourth quadrant in the upper transmission coil  340 , the outer coil part  363  of the lower transmission coil  360  may include a first outer coil part  363   a  provided at the fourth quadrant, the second outer coil part  363   b  provided at the third quadrant, the third outer coil part  363   c  provided at the second quadrant, and the fourth outer coil part  363   d  provided at the first quadrant. Similarly to the first inner coil part  347  of the upper transmission coil  340  including the (1-1) th  inner coil part  347   a  provided at the first quadrant and the (1-2) th  inner coil part  347   b  provided at the second quadrant, the first inner coil part  367  of the lower transmission coil  360  may include a (1-1) th  inner coil part  367   a  provided at the fourth quadrant and a (1-2) th  inner coil part  367   b  provided at the third quadrant. In addition, similarly to the second inner coil part  351  of the upper transmission coil  340  including the (2-1) th  inner coil part  351   a  provided at the third quadrant and the (2-2) th  inner coil part  351   b  provided at the fourth quadrant, the second inner coil part  371  of the lower transmission coil  360  may include a (2-1) th  inner coil part  371   a  provided at the second quadrant and a (2-1) th  inner coil part  371   a  provided at the first quadrant. In addition, similarly to the third inner coil part  354  of the upper transmission coil  340  including the (3-1) th  inner coil part  354   a  provided at the first quadrant and the (3-2) th  inner coil part  354   b  provided at the second quadrant, the third inner coil part  374  of the lower transmission coil  360  may include a (3-1) th  inner coil part  374   a  provided at the fourth quadrant and the (3-2) th  inner coil part  374   b  provided at the third quadrant. In addition, similarly to the fourth inner coil part  357  of the upper transmission coil  340  including the (4-1) th  inner coil part  357   a  provided at the third quadrant and the (4-2) th  inner coil part  357   b  provided at the fourth quadrant, the fourth inner coil part  377  of the lower transmission coil  360  may include a (4-1) th  inner coil part  377   a  provided at the second quadrant and a (4-2) th  inner coil part  377   b  provided at the first quadrant. In addition, the outer connection part  361  of the lower transmission coil  360  may be symmetrical to the outer connection part  341  of the upper transmission coil  340  about the Y axis, and the outer coil part  363  of the lower transmission coil  360  may be symmetrical to the outer coil part  343  of the upper transmission coil  340  about the Y axis. The first extension part  365  of the lower transmission coil  360  may be symmetrical to the first extension part  345  of the upper transmission coil  340  about the Y axis, and the first inner coil part  367  of the lower transmission coil  360  may be symmetrical to the first inner coil part  347  of the upper transmission coil  340  about the Y axis. The second extension part  369  of the lower transmission coil  360  may be symmetrical to the second extension part  349  of the upper transmission coil  340  about the Y axis, and the second inner coil part  371  of the lower transmission coil  360  may be symmetrical to the second inner coil part  351  of the upper transmission coil  340  about the Y axis. The third extension part  373  of the lower transmission coil  360  may be symmetrical to the third extension part  353  of the upper transmission coil  340  about Y axis, and the third inner coil part  374  of the lower transmission coil  360  may be symmetrical to the third inner coil part  354  of the upper transmission coil  340  about the Y axis. The fourth extension part  375  of the lower transmission coil  360  may be symmetrical to the fourth extension part  355  of the upper transmission coil  340  about the Y axis, and the fourth inner coil part  377  of the lower transmission coil  360  may be symmetrical to the fourth inner coil  357  of the upper transmission coil  340 . The inner connection part  378  of the lower transmission coil  360  may be symmetrical to the inner connection part  358  of the upper transmission coil  340  about the Y axis. 
     In this case, the distance between the outer coil part  343  and the second inner coil part  351  of the upper transmission coil  340  and the distance between the outer coil part  363  and the second inner coil part  371  of the lower transmission coil  360  may be formed corresponding to ½ of the size of the reception coil. Meanwhile, the distance between the outer coil part  343  and the third inner coil part  354  of the upper transmission coil  340  may be formed to the extent that a position where the coupling coefficient between the outer coil part  343  of the upper transmission coil  340  and the reception coil becomes maximized is matched with a position where the coupling coefficient between the third inner coil part  354  and the reception coil becomes zero. Similarly, the distance between the outer coil part  363  and the third inner coil part  374  of the lower transmission coil  360  may be formed to the extent that a position where the coupling coefficient between the outer coil part  363  of the lower transmission coil  360  and the reception coil becomes maximized is matched with a position where the coupling coefficient between the third inner coil part  374  and the reception coil becomes zero. 
     According to the present embodiment, the coupling coefficient between the wireless transmission unit  300  and the wireless reception unit  31  (see  FIG. 1 ) is substantially constant according to locations as shown in  FIG. 19 . In other words, the coupling coefficient between the wireless transmission unit  300  and the wireless reception unit  31  is formed equally to an average value of a first coupling coefficient formed between the outer coil part  343  of the upper transmission coil  340  and the outer coil part  363  of the lower transmission coil  360 , a second coupling coefficient formed between the second inner coil part  351  of the upper transmission coil  240  and the second inner coil part  371  of the lower transmission coil  360 , and a third coupling coefficient between the third inner coil unit  354  of the upper transmission coil  340  and the third inner coil unit  374  of the lower transmission coil  360 . Accordingly, the coupling coefficient between the wireless transmission unit  300  and the wireless reception unit  31  has a higher value even if the wireless reception unit  31  approaches the centers of the upper and lower transmission coils  340  and  360 . In addition, as the first inner coil part  347  is provided closely to the outer coil part  343  in the upper transmission coil  340 , and the first inner coil  367  is provided closely to the outer coil part  363  in the lower transmission coil  360 , the first coupling coefficient has a higher value. Accordingly, the chargeable area of the wireless transmission unit  300  is enlarged. 
     For example, the wireless transmission unit  300  according to the present embodiment may be realized as shown in following table I and  FIG. 20 . In this case, in the upper transmission coil  340 , the distance between the outer coil part  343  and the first inner coil part  347  may be about 5.2 mm, the distance between the first inner coil part  347  and the second inner coil part  351  may be about 34 mm, the distance between the second inner coil part  351  and the third inner coil part  354  may be about 32.4 mm, and the distance between the third inner coil part  354  and the fourth inner coil part  357  may be about 83.5 mm. Similarly, in the lower transmission coil  360 , the distance between the outer coil part  363  and the first inner coil part  367  may be about 5.2 mm, the distance between the first inner coil part  367  and the second inner coil part  371  may be about 34 mm, the distance between the second inner coil part  371  and the third inner coil part  374  may be about 32.4 mm, and the distance between the third inner coil part  374  and the fourth inner coil part  377  may be about 83.5 mm. 
     Further, in the mounting member  310 , the width in the Y axis direction may be about 180.5 mm, and the width in the X axis direction may be about 129 mm. In the outer coil part  343  of the upper transmission coil  340  or the outer coil part  363  of the lower transmission coil  360 , the width in the Y axis direction is about 179.5 mm and the width in the X axis direction may be about 128 mm. In the first inner coil part  347  of the upper transmission coil  340  or the first inner part  367  of the lower transmission coil  360 , the width in the Y axis may be about 174.3 mm. The maximum distance between the first inner coil part  347  of the upper transmission coil  340  and the first inner coil part  367  of the lower transmission coil  360  in the X axis direction may be about 122.8 mm. In the second inner coil part  351  of the upper transmission coil  340  or the second inner coil part  371  of the lower transmission coil  360 , the width in the Y axis direction may be about 140.3 mm. In the third inner coil part  354  of the upper transmission coil  340  or the third inner coil part  374  of the lower transmission coil  360 , the width in the Y axis direction may be about 107.9 mm. In the fourth inner coil part  357  of the upper transmission coil  340  or the fourth inner coil part  377  of the lower transmission coil  360 , the width in the Y axis direction may be about 24.4 mm. The distance in a starting point between the second extension part  349  of the upper transmission coil  340  and the second extension part  369  of the lower transmission coil  360  in the X direction may be about 7.04 mm. The distance in a terminated point between the second extension part  349  of the upper transmission coil  340  and the second extension part  369  of the lower transmission coil  360  in the X direction may be about 10.29 mm. The vertical distance between the inner connection part  358  of the upper transmission coil  340  and the inner connection part  378  of the lower transmission coil  360  may be about 2.6 mm. A circular arc of an area having a curvature of the outer coil part  343  of the upper transmission coil  340  or the outer coil part  363  of the lower transmission coil  360  provides about R 302 mm as a radius of a circle, and a circular arc of an area having a curvature of the second inner coil part  351  of the upper transmission coil  340  or the second inner coil part  371  of the lower transmission coil  360 , which is spaced apart from the X axis, provides about 20 mm as a radius of a circle. A circular arc of an area having a curvature and close to the X axis provides about R 269.1 mm as a radius of a circle. A circular arc of an area having a curvature and closer to the X axis provides about R 270.8 mm as a radius of a circle. A circular arc of an area having a curvature of the third inner coil part  354  of the upper transmission coil  340  or the third inner coil part  374  of the lower transmission coil  360 , which is located at the negative Y (−Y) area and spaced apart from the X axis, provides about R 15.4 mm as a radius of a circle. A circular arc of an area having a curvature and close to the X axis at a positive Y (Y) axis area provides about R 17 mm as a radius of a circle. A circular arc of an area having a curvature and closer to the X axis at a positive Y (Y) axis area provides about R 160.88 mm as a radius of a circle. A circular arc of an area having a curvature and closer to the X axis at a negative Y (−Y) axis area provides about R 162.56 mm as a radius of a circle. A circular arc of an area having a curvature of the fourth inner coil part  357  of the upper transmission coil  340  or the fourth inner coil part  377  of the lower transmission coil  360  provides about R 15.1 mm as a radius of a circle. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Items 
                 Description 
               
               
                   
                   
               
             
            
               
                   
                 Length of mounting member 
                 180.5 mm  
               
               
                   
                 Width of mounting member 
                 129.0 mm  
               
               
                   
                 Thickness of mounting member 
                 0.80 mm 
               
               
                   
                 Thickness of upper transmission coil 
                 0.05 mm 
               
               
                   
                 Thickness of lower transmission coil 
                 0.05 mm 
               
               
                   
                 Thickness of shielding member 
                 0.80 mm 
               
               
                   
                 Permeability of shielding member 
                 100 
               
               
                   
                   
               
            
           
         
       
     
     According to the disclosure, as the upper transmission coil  140 ,  240  or  340  and the lower transmission coil  160 ,  260  or  360  are symmetrical to each other, the magnetic fields formed by the upper transmission coil  140 ,  240  or  340  and the lower transmission coil  160 ,  260  or  360  may have uniform shapes. In other words, when the upper transmission coil  140 ,  240  or  340  and the lower transmission coil  160 ,  260  or  360  are operated, the shape of the magnetic fields can be uniformly maintained without change. The magnetic fields may have vertical and horizontal symmetrical shapes in the upper transmission coil  140 ,  240  or  340  and the lower transmission coil  160 ,  260  or  360 . Accordingly, the coupling coefficient between the wireless power transmission apparatus  100 ,  200 , or  300  and the wireless power reception apparatus  30  (see  FIG. 1 ) may be constantly distributed according to the locations of the wireless power transmission apparatus  100 ,  200 , or  300 . Accordingly, as the chargeable area of the wireless power transmission apparatus  100 ,  200 , or  300  is enlarged, the power transmission efficiency of the wireless power transmission apparatus  100 ,  200 , or  300  can be improved. 
     Although embodiments of the disclosure have been described only for the illustrative purpose of the technical concept of the disclosure, 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.