Abstract:
A power supply apparatus for an electric bicycle is disclosed. The apparatus may include i) a battery pack and ii) a keybox connected to the battery pack and controlling on/off operations of the power supply apparatus. The keybox may further include i) a key set configured to receive a key cylinder that is moveable according to the rotation of a key inserted into the key box, ii) a contact terminal that includes a first plurality of sub-terminals, iii) a terminal base including at least one second sub-terminal connectable to and detachable from at least one of the first sub-terminals and iv) a keybox case configured to receive the key set, the contact terminal, and the terminal base. The terminal base may have a plate shape with a polygonal periphery surface at least part of which contacts an inner portion of the keybox case.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2010-00128956 filed on Dec. 16, 2010, in the Korean Intellectual Property Office, and entitled: “POWER SUPPLY APPARATUS FOR ELECTRIC BICYCLE” which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     The described technology generally relates to a power supply apparatus for an electric bicycle 
     2. Description of the Related Technology 
     Electric bicycles, which include a battery and a motor, are widely used by people of all ages. The battery of an electric bicycle supplies power to a driving device of the electric bicycle. The driving device is generally installed on the front wheel of the electric bicycle, the upper middle portion of the electric bicycle, or the rear portion thereof. The driving device includes a starter switch that is located at a side portion of the battery to control the on/off operation of the battery. 
     SUMMARY 
     One inventive aspect is a power supply apparatus for an electric bicycle, which includes a keybox where a battery pack is electrically connected to a starter switch, to fix a contact between a terminal and a wire even when the key is inserted and rotated in the keybox, thereby reducing a resistance at the contact. 
     Another aspect is a power supply apparatus for an electric bicycle which includes: a battery pack including a plurality of bare cells and a protection circuit module electrically connected to the bare cells; a keybox connected to the battery pack through a wire to control on/off operations; and a case receiving the battery pack and the keybox, wherein the keybox includes: a key set receiving a key cylinder that is moved forward or rearward according to an operation of an inserted key; a contact terminal that is moved by a shaft adjacent to the key cylinder and includes connection parts having different polarities from each other; a terminal base including a terminal from which the connection part contacts or is removed to control the on/off operations; and a keybox case receiving the key set, the contact terminal, and the terminal base, wherein the terminal base has a plate shape with a polygonal periphery surface to contact an inner portion of the keybox case. 
     A portion of the terminal may protrude from a side of the terminal base and contacts the connection part of the contact terminal, and another portion of the terminal may protrude from another side of the terminal base and is connected to the battery pack. The terminal may be coupled through soldering to a wire connected to an electrode of the battery pack. 
     The terminal may have a polygonal side surface connected to the battery pack. The terminal may pass through the terminal base, and the terminal base may have a hole having at least one polygonal portion. 
     The connection part may be provided with a contact spring to be adjacent to a center of a rear surface thereof, and the contact spring may be fitted on the shaft. 
     The rear surface of the connection part may be adjacent to a plurality of contact springs. 
     The power supply apparatus may further include a polygonal fixing cover that fixes the terminal base. 
     The terminal base may be pentagonal or hexagonal. The power supply apparatus may further include a pentagonal or hexagonal fixing cover that fixes the terminal base. Another aspect is a power supply apparatus for an electric bicycle, comprising: a battery pack comprising a plurality of bare cells and a protection circuit module electrically connected to the bare cells; a keybox connected to the battery pack through a wire and configured to control on/off operations of the power supply apparatus; and a case configured to receive the battery pack and the keybox, wherein the keybox comprises: a key set configured to receive a key cylinder that is configured to move forward or backward according to the rotation of a key inserted into the key box; a contact terminal that is movable by a shaft adjacent to the key cylinder and includes a first plurality of sub-terminals having different polarities from each other; a terminal base including at least one second sub-terminal which is connectable to and detachable from at least one of the first sub-terminals so as to control the on/off operations; and a keybox case configured to receive the key set, the contact terminal, and the terminal base, wherein the terminal base has a plate shape with a polygonal periphery surface at least part of which contacts an inner portion of the keybox case. 
     In the above apparatus, a portion of the second sub-terminal protrudes from a first side of the terminal base and contacts at least one of the first sub-terminals, wherein another portion of the second sub-terminal protrudes from a second side of the terminal base and is connected to the battery pack, and wherein the first and second sides are opposing each other. In the above apparatus, the terminal is connected to an electrode of the battery pack via a wire. In the above apparatus, the second sub-terminal has a polygonal side surface connected to the battery pack. In the above apparatus, the second sub-terminal passes through the terminal base, and wherein the terminal base has a hole having at least one polygonal portion. 
     The above apparatus further comprises at least one contact spring formed on the shaft, wherein the contact spring is closer to the contact terminal than the terminal base. In the above apparatus, the first sub-terminals comprise a pair of sub-terminals, and wherein the at least one second sub-terminal comprises a pair of second sub-terminals which are connectable to and detachable from the first sub-terminals, respectively. The above apparatus further comprises a polygonal fixing cover configured to fixe the terminal base to the keybox case. In the above apparatus, the polygonal periphery surface of the terminal base is pentagonal or hexagonal. The above apparatus further comprises a pentagonal or hexagonal fixing cover configured to fixe the terminal base to the keybox case. 
     Another aspect is a power supply apparatus for an electric bicycle, comprising: a battery pack comprising a plurality of bare cells; a keybox connected to the battery pack and configured to control on/off operations of the power supply apparatus, wherein the keybox comprises: a movable contact terminal comprising a first pair of sub-terminals; and a terminal base comprising a second pair of sub-terminals which are connectable to and detachable from the first pair of sub-terminals so as to control the on/off operations, wherein the terminal base has a polygonal periphery surface at least part of which contacts an inner portion of the keybox case. 
     In the above apparatus, the keybox further comprises a key set configured to receive a key cylinder that is configured to move forward or backward according to the rotation of a key inserted into the key box. In the above apparatus, the keybox further comprises a keybox case configured to receive the key set, the contact terminal, and the terminal base. The above apparatus further comprises a polygonal fixing cover configured to fix the terminal base to the keybox case. 
     In the above apparatus, the contact terminal is movable by a shaft adjacent to the key cylinder. In the above apparatus, the first pair of sub-terminals have different polarities from each other, wherein the second pair of sub-terminals have different polarities from each other, wherein the first pair of sub-terminals are connected to the second pair of sub-terminals having the same polarities. In the above apparatus, each of the second pair of sub-terminals has a circular shape or a polygonal shape. In the above apparatus, the polygonal periphery surface of the terminal base is pentagonal or hexagonal. 
     Another aspect is a power supply apparatus for an electric bicycle, comprising: a battery pack comprising a plurality of bare cells; a keybox connected to the battery pack and configured to control on/off operations of the power supply apparatus; and a case configured to receive the battery pack and the keybox, wherein the keybox comprises: a key set configured to receive a key cylinder that is configured to move forward or backward according to the rotation of a key inserted into the key box; a movable contact terminal comprising at least one first sub-terminal; and a terminal base comprising at least one second sub-terminal which is connectable to and detachable from the first sub-terminal and the battery pack, wherein the terminal base has a polygonal perimeter, and wherein at least part of the terminal base engages an inner portion of the keybox to a sufficiently tight degree such that the terminal base does not move upon the rotation of the key. 
     In the above apparatus, the polygonal perimeter has a pentagonal or hexagonal shape. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating a power supply apparatus for an electric bicycle according to an embodiment. 
         FIG. 2  is a circuit diagram illustrating an operation of the power supply apparatus of  FIG. 1 . 
         FIG. 3  is a perspective view illustrating the inner upper end of the power supply apparatus of  FIG. 1 . 
         FIG. 4  is a perspective view illustrating a keybox of  FIG. 3 . 
         FIG. 5  is an exploded perspective view illustrating the keybox of  FIG. 3 . 
         FIG. 6  is a side view illustrating a portion A of  FIG. 5 . 
         FIG. 7  is a perspective view illustrating a contact terminal of  FIG. 3 . 
         FIG. 8A  is a perspective view illustrating a keybox according to another embodiment. 
         FIG. 8B  is a perspective view illustrating a keybox according to another embodiment. 
         FIG. 9  is a perspective view illustrating a keybox according to another embodiment. 
         FIG. 10  is a cross-sectional view taken along line A-A′ of  FIG. 9 . 
         FIG. 11  is a perspective view illustrating a terminal of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION 
     Generally, a starter switch for a battery driving device is used to perform a start-off operation or a start-on operation according to the rotation of a key. The starter switch typically includes a narrow land part that is exposed out of a terminal of a terminal base. The terminal base may rotate according to the rotation of the key. The rotation of the terminal base causes a defective contact between the terminal and the wire. When the terminal is used over a long period of time, the position on a housing is dislocated, and this decreases its reliability. 
     Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. 
     Referring to  FIGS. 1 through 6 , a power supply apparatus  100  for an electric bicycle according to an embodiment includes a battery pack  110 , a keybox  120 , wires  130 , and a case  140 . 
     The power supply apparatus  100  supplies power to drive an electric bicycle. A key  121  is inserted into a side portion of the keybox  120  to control an on-off operation. A contact terminal  123  is connected to or detached from a terminal  127  according to the rotation of the inserted key  121 , so that the keybox  120  can control power supply. 
     The battery pack  110  includes bare cells (not shown) and a protection circuit module (not shown), which are electrically connected to each other. 
     The bare cell includes an electrode assembly (not shown), a first electrode tab (not shown), and a second electrode tab (not shown). In one embodiment, the electrode assembly is formed by winding a negative electrode plate (not shown), a positive electrode plate (not shown), and a separator (not shown). The first electrode tab and the second electrode tab have different polarities from each other. The first and second electrode tabs are electrically connected to the positive electrode plate and the negative electrode plate, respectively. The bare cells of the power supply apparatus  100  are electrically connected to each other to output and store a large amount of electricity. 
     The keybox  120  includes a key set  122 , the contact terminal  123 , a keybox case  125 , a case cover  126 , the terminal  127 , and a terminal base  128 . The case cover  126  may include a fixing cover  129 . 
     In one embodiment, the keybox case  125  has an open front portion, an open rear portion, and a hollow middle portion. The case cover  126  covers the keybox case  125 . The key set  122  for receiving the key  121  is disposed at the front side of the keybox case  125 . A key cylinder  122   a  of the key set  122  moves forward or backward within the keybox case  125 . The key cylinder  122   a  is spaced a predetermined distance from the contact terminal  123 . The key  121  rotates to move the key cylinder  122   a  to the rear portion of the keybox case  125 , and thus, the contact terminal  123  contacts a portion of the terminal  127 . In one embodiment, the terminal base  128  has a polygonal periphery surface as shown in  FIG. 5 . The periphery surface of the terminal base  128  may have a pentagon, hexagon or other polygonal shape. This applies to the remaining embodiments. In one embodiment, as shown in  FIG. 3 , at least part of the periphery surface contacts an inner portion of the fixing cover  129 . In one embodiment, the periphery surface sufficiently tightly contacts the inner portion of the fixing cover  129  so as to substantially prevent the terminal base  128  from moving even when the key  121  rotates. As a result, an increase of resistance at terminal contacts can be substantially prevented. 
     The key set  122  includes a key insertion recess (not shown) and the key cylinder  122   a.    
     When the key  121  inserted into the key insertion recess (not shown) rotates in an on-direction (e.g., clockwise or counterclockwise), the key cylinder  122   a  moves to the rear portion of the keybox case  125 . A protrusion (not shown) may be disposed at an end of the key cylinder  122   a . The protrusion passes through a center hole (not shown) of a catching portion  122   b  to push an extension  122   c . When the key  121  rotates in an off-direction (e.g., counterclockwise or clockwise), the key cylinder  122   a  moves to the front portion of the keybox case  125 . 
     The key cylinder  122   a  may include pins (not shown) corresponding to the shape of the key  121 , an inner cylinder (not shown), and an outer cylinder (not shown). When the key  121  is inserted into and rotated in the on-direction, the pins (not shown) unlock the key set  122 . The key  121  is received in the center of the inner cylinder (not shown). The inner cylinder (not shown) may have a hole such that the pins (not shown) are inserted into a surface corresponding to the shape of the key  121 . When the key  121  rotates in the on-direction, the outer cylinder (not shown) moves to the rear portion of the keybox case  125 . 
     In one embodiment, the contact terminal  123  includes a hole  123   b  and connection portions (hereinafter to be interchangeably used with sub-terminals)  123   a  disposed at positions to contact the terminal  127  that is, for example, tetragonal or circular. The connection portions  123   a  may have a concave and convex shape according to the distance between the contact terminal  123  and the terminal  127 . In one embodiment, the contact terminal  123  includes a pair of first sub-terminals having different polarities from each other. In one embodiment, the terminal  127  includes a pair of second sub-terminals having different polarities from each other. Each pair of the sub-terminals may have substantially the same function. The contact terminal  123  contacts the terminal  127  via the corresponding pairs of sub-terminals each having the same polarity. 
     The connection portion  123   a  contacts a first end of a shaft  125   a . A second end of the shaft  125   a  is adjacent to the extension  122   c . In one embodiment, the diameter of the hole  123   b  is smaller than that of the shaft  125   a . When the extension  122   c  pushes the second end of the shaft  125   a , the shaft  125   a  is not removed from the hole  123   b , and thus, the contact terminal  123  moves. Guide recesses (not shown) may be disposed at the upper and lower sides of the contact terminal  123 . The guide recesses (not shown) prevent a removal of the contact terminal  123 . Bars  123   e  are fixed at both ends of the contact terminal  123 , and move along recesses  123   d  disposed in the keybox case  125 . When the extension  122   c  pushes the second end of the shaft  125   a , the contact terminal  123  moves along the recesses  123   d  and contacts the front surface of the terminal  127 . 
     Referring to  FIG. 6 , a contact spring  124  is fitted on the shaft  125   a . A portion of the contact spring  124  is fixed to the keybox case  125 . When the shaft  125   a  moves the contact terminal  123  to the terminal  127 , the contact spring  124  maximally extends. At this point, the contact terminal  123  contacts the terminal  127 . On the contrary, when the key  121  rotates in the off-direction, the shaft  125   a  moves away from the terminal  127 . At this point, the contact terminal  123  is detached from the terminal  127  by resilient force of the maximally extended contact spring  124 . At this point, the contact spring  124  corresponds to rear surfaces of the recesses  123   d.    
     The terminal  127  is disposed within the keybox case  125 , and is formed at a position corresponding to the rear surface of the contact terminal  123 . The terminal  127  protrudes out of the keybox case  125  and is electrically connected to the battery pack  110 . 
     In one embodiment, the terminal base  128  has a plate shape with a polygonal periphery surface. The terminal base  128  includes the terminal  127  at a position corresponding to the contact terminal  123 . The polygonal terminal base  128  is fixed to the keybox case  125  to maintain a constant contact resistance at the terminal  127 . 
     Referring to  FIG. 2 , when the key  121  rotates in the on-direction, the resistance value of a contact of the terminal  127  affects the resistance value of the battery pack  110 . When the terminal base  128  rotates according to the rotation of the key  121 , the contact resistance of the keybox  120  varies, and thus, inner resistance values are uneven, and the dispersion of inner resistances are increased. Thus, the terminal base  128  is substantially fixed to maintain a substantially constant contact resistance, and the life of the battery pack  110  is increased. 
     Table 1 shows a discharge time and an operation time when an inner resistance value increases in  FIG. 2 . 
     
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Discharge Time 
                 Operation Time 
               
               
                 Keybox × IR 
                 (SOC = 0%) 
                 (28 V cut off) 
               
               
                   
               
             
             
               
                  0 mΩ 
                 6290[s] 
                 6130[s] 
               
               
                 100 mΩ 
                 6170[s] 
                 5950[s] 
               
               
                 230 mΩ 
                 6010[s] 
                 5680[s] 
               
               
                 300 mΩ 
                 5920[s] 
                 5520[s] 
               
               
                   
               
             
          
         
       
     
     As shown in Table 1, when the inner resistance (Keybox×IR) increases, the discharge time and the operation time are decreased. 
     The case cover  126  includes the fixing cover  129 . In one embodiment, the inner portion of the fixing cover  129  has a polygonal shape that is substantially the same as the shape of the terminal base  128 . Thus, the fixing cover  129  contacts the periphery of the terminal base  128 . Since the fixing cover  129  prevents the rotation of the terminal base  128  due to the rotation of the key  121 , the resistance at the contact of the terminal  127  is decreased. 
     The wires  130  include wires  130   a ,  130   b ,  130   c , and  130   d . The wire  130  contacts the rear surface of the terminal  127 , and thus, is electrically connected to the battery pack  110 . 
     If the terminal base  128  rotates, the contact resistance at the contact where the terminal  127  is connected to the wire  130   c  varies, and thus, an inner resistance value is uneven. Thus, according to the current embodiment, the contact between the wire  130   c  and the terminal  127  may be substantially fixed to decrease a resistance value. 
     The case  140  includes a case body  141  and an upper case  142 . The case body  141  receives the battery pack  110 . The upper case  142  has a hole (not shown) to insert the key  121  into the key box  120 . 
       FIG. 8A  is a perspective view illustrating a keybox  220  according to another embodiment. 
     In one embodiment, as shown in  FIG. 8A , the keybox  220  includes a terminal base  228  that is pentagonal. The power supply apparatus according to the current embodiment will now be described with respect to the terminal base  228 . In addition, like reference numerals denote like elements in the current embodiment and the previous one of  FIGS. 1 through 6 , and detailed descriptions thereof will be omitted here. 
     In one embodiment, the terminal base  228  has a plate shape with a pentagonal periphery surface. The periphery surface of the terminal base  228  contacts the inner portion of the fixing cover  129  and is fixed. The terminal base  228  may substantially uniformly maintain the contact resistance between a terminal  227  and the wire  130 . In this case, the fixing cover  129  may have a pentagonal shape that is substantially the same as the shape of the terminal base  228 . 
       FIG. 8B  is a perspective view illustrating a keybox  320  according to another embodiment. In one embodiment, as shown in  FIG. 8B , the keybox  320  includes a terminal base  328  that is hexagonal. Thus, the power supply apparatus according to the current embodiment will now be described with respect to the terminal base  328 . In addition, like reference numerals denote like elements in the current embodiment and the previous ones of  FIGS. 1 through 7 , and detailed descriptions thereof will be omitted here. 
     In one embodiment, the terminal base  328  has a plate shape with a hexagonal periphery surface. The periphery surface of the terminal base  328  contacts the inner portion of the fixing cover  129 . The terminal base  328  may substantially uniformly maintain the contact resistance between a terminal  327  and the wire  130 . In this case, the fixing cover  129  may have a hexagonal shape that is substantially the same as the shape of the terminal base  328 . 
       FIG. 9  is a perspective view illustrating a keybox  420  according to another embodiment.  FIG. 10  is a cross-sectional view taken along line A-A′ of  FIG. 9 .  FIG. 11  is a perspective view illustrating a terminal of  FIG. 9 . A power supply apparatus according to the current embodiment includes the battery pack  110 , the keybox  420 , the wires  130 , and the case  140 . In one embodiment, as shown in FIGS.  10  and  11 , the keybox  420  includes a terminal  427  has a polygonal portion. Thus, the power supply apparatus according to the current embodiment will now be described with respect to the terminal  427 . In addition, like reference numerals denote like elements in the current embodiment and the previous ones of  FIGS. 1 through 8B , and detailed descriptions thereof will be omitted here. 
     The terminal  427  includes a wire contact  427   a , a body  427   b , and a terminal contact  427   c . The terminal  427  passes through the terminal base  428 . In one embodiment, the terminal base  428  has a hole  428   a  that has at least one polygonal portion. The hole  428   a  has substantially the same shape as that of the wire contact  427   a . The hole  428   a  prevents the movement of the terminal  427  due to the rotation of the key  121  or external force. 
     Although the wire contact  427   a  is polygonal in the current embodiment, the body  427   b  and the terminal contact  427   c  may be circular or polygonal in another embodiment. A through central portion  428   b  of the terminal base  428  may have a shape corresponding to the shape of the body  427   b.    
     Table 2 shows inner resistance values of the keybox  420 . 
     
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                 Experimental 
                 Comparison 
               
               
                   
                 Inner Resistance at 
                 Example 
                 Example 
               
               
                   
                 Contact 
                 (mΩ) 
                 (mΩ) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Mean Value 
                 8 
                 37 
               
               
                   
                 Standard Deviation 
                 2 
                 37 
               
               
                   
                 Maximum Value 
                 15 
                 201 
               
               
                   
                 Minimum Value 
                 6 
                 7 
               
               
                   
                 Range 
                 9 
                 194 
               
               
                   
                 Number of times of 
                 100 
                 96 
               
               
                   
                 measuring 
               
               
                   
                   
               
             
          
         
       
     
     A terminal base and a terminal of the comparison example are circular. In the comparison example, the terminal base rotates (moves) to vary a contact resistance of the terminal, and thus, the inner resistance values are uneven. 
     Thus, according to the current embodiment, since the contact is substantially fixed, the inner resistance values can be decreased, and a substantially uniform contact resistance can be maintained. 
     According to one embodiment, the rotation of the terminal base is prevented even when the key rotates, the resistance at the contact between the terminal and the wire is decreased, thereby increasing the life of the battery pack. 
     According to at least one of the disclosed embodiments, since the shape of the terminal base and the shape of the terminal are improved, the coupling force with the wire can be improved. 
     Embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the following claims.