Patent Publication Number: US-2011073363-A1

Title: Circuit module and electric vehicle including the same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a circuit module and an electric vehicle including the same. 
     2. Description of the Background Art 
     Examples of an electric vehicle include a two-wheeled electric vehicle provided with a battery system, a power converter, a motor and a drive wheel. During traveling of the two-wheeled electric vehicle, the power converter converts electric power supplied from the battery system into electric power (driving power) required for driving the drive wheel. 
     The power converter includes electronic circuits such as an inverter circuit. Therefore, in the case of providing the power converter in the two-wheeled electric vehicle that is used outdoors, liquid such as rainwater must be reliably prevented from coming in contact with the electronic circuits of the power converter and connections between the electronic circuits and wires. 
     JP 9-199871 A discloses an example of waterproof construction of an electronic device. In the electronic device having the waterproof construction of JP 9-199871 A, a lower case and an upper case are joined through a waterproof rubber gasket, thereby forming a main body that accommodates a substrate. A hole for passing a harness therethrough is formed in part of the waterproof rubber gasket. The harnesses are passed through the holes of the waterproof rubber gasket, and one end of the harness is soldered to the substrate inside the main body. 
     Applying the waterproof construction of the electronic device disclosed in JP 9-199871 A is considered in order to ensure waterproofness of the power converter of the two-wheeled electric vehicle and the connections between the power converter and the wires. 
     However, applying the waterproof construction of JP 9-199871 A to the power converter makes it difficult to replace the wires. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a circuit module which can be reliably waterproofed and in which wires can be easily replaced, and an electric vehicle including the same. 
     (1) According to an aspect of the present invention, a circuit module includes a first casing having an internal space, an electronic circuit accommodated in the internal space of the first casing, a terminal electrically connected to the electronic circuit and drawn out of the first casing, a terminal holder provided outside the first casing, having an internal region in which the terminal is held, and having a first joint region that surrounds the internal region, a wire, and a cover having a second joint region that corresponds to the first joint region of the terminal holder, and formed to cover the internal region of the terminal holder, wherein the second joint region of the cover is joined to the first joint region of the terminal holder while one end of the wire is connected to the terminal in the internal region of the terminal holder and the other end of the wire is drawn out to an external space. 
     In the circuit module, the electronic circuit is accommodated in the internal space of the first casing, and the terminal electrically connected to the electronic circuit is drawn out of the first casing. The terminal is held in the internal region of the terminal holder provided outside the first casing. The terminal holder has the first joint region that surrounds the internal region. The cover has the second joint region corresponding to the first joint region of the terminal holder. The one end of the wire is connected to the terminal in the internal region of the terminal holder while the other end of the wire is drawn out to the external space. In this state, the second joint region of the cover is joined to the first joint region of the terminal holder. 
     In this manner, the waterproofness of the electronic circuit is ensured by the first casing. A connection between the terminal and the wire is closed by the terminal holder and the cover. This ensures waterproofness of the connection between the terminal and the wire. In this case, removing the wire from the terminal allows the wire to be easily removed from the terminal holder without disassembling the first casing. As a result, the circuit module can be reliably waterproofed and the wire is easily replaced. 
     (2) The circuit module may further include a seal member arranged on the first joint region to surround the internal region of the terminal holder, and having a plurality of holes that pass the seal member from the external space to the internal region, wherein the terminal may include a plurality of terminals, and the wire may include a plurality of wires, the plurality of wires can be inserted through the plurality of holes, respectively, of the seal member, the plurality of terminals may be held in the internal region of the terminal holder, the wires inserted through the plurality of holes of the seal member may be connected to the plurality of terminals, respectively, in the internal region of the terminal holder, and the second joint region of the cover may be joined to the first joint region of the terminal holder through the seal member. 
     In this case, the seal member is arranged on the first joint region to surround the internal region of the terminal holder, and has the plurality of holes that pass the seal member from the external space to the internal region. The plurality of wires are inserted through the plurality of holes, respectively, of the seal member, and connected to the plurality of terminals, respectively, held in the internal region of the terminal holder. In this state, the second joint region of the cover is joined to the first joint region of the terminal holder through the seal member. 
     Accordingly, the internal region including connections between the terminals and the wires are closed by the terminal holder, the cover and the seal member. This improves the waterproofness of the connections between the terminals and the wires. 
     The plurality of wires are integrated with the seal member. This causes the plurality of wires to be easily handled, and prevents erroneous connections between the plurality of wires and the plurality of terminals. 
     (3) The seal member may include a plurality of seal members, the first joint region may include a plurality of first joint regions, the second joint region may include a plurality of second joint regions, the terminal holder may have a plurality of internal regions in which the plurality of terminals are held, and the plurality of first joint regions that surround the plurality of internal regions, respectively, the cover may have the plurality of second joint regions that correspond to the plurality of first joint regions of the terminal holder, and the plurality of wires inserted through the plurality of holes of the plurality of seal members, respectively, may be connected to the plurality of terminals in the plurality of internal regions of the terminal holder, respectively, and the plurality of second joint regions of the cover may be joined to the plurality of first joint regions of the terminal holder through the plurality of seal members. 
     In this case, the plurality of wires are inserted through the holes of the plurality of seal members, respectively, and connected to the plurality of terminals held in the plurality of internal regions of the terminal holder, respectively. In this state, the plurality of second joint regions of the cover are joined to the plurality of first joint regions of the terminal holder through the plurality of seal members, respectively. 
     Accordingly, the plurality of wires and the plurality of terminals are independently integrated, respectively, through the plurality of seal members, and the internal regions including the respective connections between the wires and the terminals are closed by the common terminal holder and the common cover. As a result, the wires and the seal members can be integrally handled, respectively, and the respective connections between the plurality of wires and the plurality of terminals can be closed by the common terminal holder and the common cover, so that the plurality of wires can be reliably attached and removed in the smaller number of operation steps. 
     (4) The terminal holder may be formed such that the seal member can be fitted in the terminal holder, and the seal member may have a first surface and a second surface, and may be shaped so as to be fitted in the terminal holder while the first surface is opposite to the first joint region, and may be shaped so as not to be fitted in the terminal holder while the second surface is opposite to the first joint region. 
     In this case, although the seal member can be fitted in the terminal holder while the first surface is opposite to the first joint region of the terminal holder, the seal member cannot be fitted in the terminal holder while the second surface is opposite to the first joint region of the terminal holder. 
     Therefore, the seal member is prevented from being directed opposite to the normal direction between the terminal holder and the cover. Accordingly, the seal member can be easily and accurately attached. 
     (5) The first casing may have electrical conductivity, the terminal may be electrically insulated from the first casing, the wire may have a core and a shield conductor, the core may be connected to the terminal, and the shield conductor may be electrically connected to the first casing. 
     In this case, the core of the wire is connected to the terminal that is electrically insulated from the first casing. The shielded conductor of the wire is electrically connected to the first casing having electrical conductivity. Thus, the first casing functions as a shield of the electronic circuit. This allows the electronic circuit to be shielded with simple configuration and operation. 
     (6) The terminal may include a plurality of terminals, and the wire may include a plurality of wires, the terminal holder may have a plurality of grooves that are provided corresponding to the plurality of wires and cause the internal region and the external space to communicate with each other, the circuit module may further include a plurality of seal members that are formed so as to be fitted in the plurality of grooves of the terminal holder, respectively, and each have a hole that passes the seal member from the external space to the internal region, and the plurality of wires can be inserted through the holes of the plurality of seal members, respectively, the plurality of terminals are held in the internal region of the terminal holder, the plurality of wires inserted through the holes of the plurality of seal members may be connected to the plurality of terminals in the internal region of the terminal holder, and the second joint region of the cover may be joined to the first joint region of the terminal holder through the plurality of seal members. 
     In this case, the plurality of seal members are fitted in the plurality of grooves that cause the internal region of the terminal holder and the external space to communicate with each other. The plurality of wires are inserted through the holes of the plurality of seal members, and connected to the plurality of terminals in the internal region of the terminal holder, respectively. In this state, the second joint region of the cover is joined to the first joint region of the terminal holder. 
     Accordingly, portions between the plurality of grooves of the terminal holder and the plurality of seal members are sealed, and a portion between the first joint region of the terminal holder and the second joint region of the cover is sealed. Therefore, the internal region including connections between the terminals and the wires is closed by the terminal holder, the cover and the seal member. This results in improved waterproofness of the connections between the terminals and the wires. 
     The plurality of seal members and the plurality of grooves are provided corresponding to the plurality of wires. This allows the wires to be separately removed from the terminals. Thus, replacement operation of the wires can be efficiently performed. 
     (7) The circuit module may further include a second casing provided outside the first casing, wherein the terminals, the terminal holder and the cover may be accommodated in the second casing, and the plurality of wires may be drawn out from the second casing to the external space, and the first casing and the second casing may have electrical conductivity. 
     In this case, the electronic circuit is accommodated in the first casing having electrical conductivity, and the terminals are accommodated in the second casing having electrical conductivity. Thus, the electronic circuit and the terminals are shielded. As a result, entry of noise from the external space into the electronic circuit and the terminals can be suppressed, and emission of noise from the electronic circuit and the terminals to the external space can be suppressed. 
     (8) According to another aspect of the present invention, an electric vehicle includes a power converter composed of the circuit module according to the one aspect of the present invention, a battery system arranged to supply electric power to the power converter, a motor driven by the power converter, and a drive wheel rotated by a torque generated by the motor. 
     In the electric vehicle, the electric power is supplied from the battery system to the power converter. The electric power converted by the power converter is applied to the motor, thereby rotating the motor. The torque generated by the motor causes the drive wheel to rotate, so that the electric vehicle moves. 
     The power converter is constituted by the circuit module according to the one aspect of the present invention. Therefore, waterproofness of the power converter is ensured by the first casing even when the electric vehicle is used in wet weather or on a flooded road. The internal region including the connection between the terminal electrically connected to the power converter and the wire is closed by the terminal holder and the cover. Thus, waterproofness of the connection between the terminal and the wire is ensured. In this case, removing the wire from the terminal allows the wire to be easily removed from the terminal holder without disassembling the first casing. As a result, the circuit module can be reliably waterproofed and the wire can be easily replaced. 
     According to the present invention, the circuit module can be reliably waterproofed, and the wire can be easily replaced. 
     Other features, elements, characteristics, and advantages of the present invention will become more apparent from the following description of preferred embodiments of the present invention with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a side view of a two-wheeled electric vehicle according to a first embodiment of the present invention; 
         FIG. 2  is a block diagram for explaining a control system of the two-wheeled electric vehicle of  FIG. 1 ; 
         FIG. 3  is an external perspective view of a power converter constituted by a circuit module according to the first embodiment of the present invention; 
         FIG. 4  is a plan view of the power converter of  FIG. 3 ; 
         FIG. 5  is an exploded perspective view of the power converter of  FIGS. 3 and 4 ; 
         FIG. 6  is an exploded perspective view of the power converter of  FIGS. 3 and 4 ; 
         FIG. 7  is a perspective view and a plan view of a terminal holder of  FIG. 5 ; 
         FIG. 8  is a perspective view of a rubber gasket to which a motor power line group is attached; 
         FIG. 9  is a perspective view of a rubber gasket to which an electric power line group is attached; 
         FIG. 10  is a bottom view of a terminal cover; 
         FIG. 11  is a bottom view of a terminal cover; 
         FIG. 12  is a vertical sectional view taken along the line A-A of  FIG. 4 ; 
         FIG. 13  is a plan view showing another example of the terminal holder; 
         FIG. 14  is a plan view showing another example of the rubber gaskets; 
         FIG. 15  is a plan view showing another example of the terminal covers; 
         FIG. 16  is a plan view showing still another example of the terminal holder; 
         FIG. 17  is a plan view showing still another example of the rubber gaskets; 
         FIG. 18  is an exploded perspective view showing another example of a wire connector; 
         FIG. 19  is a bottom view of a terminal cover in the wire connector of  FIG. 18 ; 
         FIG. 20  is an external perspective view of a power converter constituted by a circuit module according to a second embodiment of the present invention; 
         FIG. 21  is an exploded perspective view of the power converter of  FIG. 20 ; 
         FIG. 22  is an exploded perspective view of the power converter of  FIG. 20 ; 
         FIG. 23  is a perspective view and a plan view of a terminal holder of  FIG. 21 ; 
         FIG. 24  is a bottom view of a top cover; 
         FIG. 25  is a perspective view showing another example of the top cover of a connection casing; and 
         FIG. 26  is a perspective view showing still another example of the top cover of the connection casing. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     [1] First Embodiment 
     (1) Two-Wheeled Electric Vehicle 
     Description will be made of a circuit module and an electric vehicle including the same according to a first embodiment of the present invention while referring to the drawings. In the following paragraphs, a two-wheeled electric vehicle is described as an example of the electric vehicle.  FIG. 1  is a side view of the two-wheeled electric vehicle according to the first embodiment of the present invention. As shown in  FIG. 1 , the two-wheeled electric vehicle  600  according to the present embodiment includes a vehicle body frame  610 , a front fork  611 , a handle  620 , a main body  630 , a seat  640 , a swing arm  650 , a motor  660 , a front wheel  691  and a rear wheel  692 . In the following description, front, rear, left and right means front, rear, left and right directions seen from a position of a driver seated on the seat  640  of the two-wheeled electric vehicle  600 . 
     The vehicle body frame  610  is of an underbone type, and provided to extend in a front-to-rear direction in a lower portion of the two-wheeled electric vehicle  600 . The front fork  611  is attached to a front end portion of the vehicle body frame  610  so as to swing from side to side. The front wheel  691  is attached to a lower end portion of the front fork  611 . The handle  620  is attached to an upper end portion of the front fork  611 . The handle  620  includes an accelerator  621  ( FIG. 2 , described below) and a brake  622  ( FIG. 2 , described below). Details will be described in the following paragraphs. 
     The main body  630  is attached to a portion from the center to the rear of the vehicle body frame  610 . A power converter  100 , a main controller  631  and a battery system  632  are provided in the main body  630 . The power converter  100  is constituted by the circuit module according to the present embodiment. Details of the power converter  100 , the main controller  631  and the battery system  632  will be described below. The seat  640  is provided in an upper end portion of the main body  630 . 
     The swing arm  650  is attached to a rear end portion of the vehicle body frame  610  to extend in the rear direction. In this state, a rear end portion of the swing arm  650  can swing in an up-and-down direction with respect to the vehicle body frame  610 . The motor  660  is provided at a rear end of the swing arm  650 . The rear wheel  692  is attached to a rotation shaft of the motor  660 . Thus, a torque generated by the motor  660  is transmitted to the rear wheel  692  through the rotation shaft during operation of the motor  660 . 
     Next, a control system of the two-wheeled electric vehicle  600  of  FIG. 1  is described.  FIG. 2  is a block diagram for explaining the control system of the two-wheeled electric vehicle  600  of  FIG. 1 . 
     As shown in  FIG. 2 , the two-wheeled electric vehicle  600  includes the power converter  100 , the main controller  631 , the battery system  632 , the accelerator  621 , the brake  622 , a rotation speed sensor  651  and the motor  660  as components of the control system that adjusts the torque of the rear wheel  692 . 
     Here, the accelerator  621  includes an accelerator grip  621   a  and an accelerator detector  621   b , and the brake  622  includes a brake lever  622   a  and a brake detector  622   b . The rotation speed sensor  651  is incorporated in the motor  660  of  FIG. 1 . The motor  660  incorporates a decelerator in the present embodiment. 
     The battery system  632  includes a plurality of battery modules and a battery ECU (Electronic Control Unit). The plurality of battery modules of the battery system  632  are connected to the motor  660  through the power converter  100 . 
     The battery ECU of the battery system  632  is connected to the main controller  631 . This causes an amount of charge of the plurality of battery modules to be applied from the battery ECU to the main controller  631 . 
     The accelerator  621 , the brake  622  and the rotation speed sensor  651  are connected to the main controller  631 . The main controller  631  is composed of a CPU (Central Processing Unit) and a memory, or composed of a microcomputer, for example. 
     When the driver operates the accelerator grip  621   a , the accelerator detector  621   b  detects an operation amount of the accelerator grip  621   a  with reference to an unoperated state. The detected operation amount of the accelerator grip  621   a  is applied to the main controller  631 . 
     When the brake lever  622   a  is operated by the driver, the brake detector  622   b  detects an operation amount of the brake lever  622   a  with reference to an unoperated state. The detected operation amount of the brake lever  622   a  is applied to the main controller  631 . 
     The rotation speed sensor  651  detects the rotation speed of the motor  660 . The detected rotation speed is applied to the main controller  631 . 
     In this manner, information including the amount of charge of the battery modules, the operation amount of the accelerator grip  621   a , the operation amount of the brake lever  622   a , the rotation speed of the motor  660  and so on is applied to the main controller  631 . The main controller  631  performs charge/discharge control of the battery modules and power conversion control of the power converter  100  based on the information. 
     Electric power generated by the battery modules is supplied from the battery system  632  to the power converter  100  at the time of starting and accelerating the two-wheeled electric vehicle  600  based on the accelerator operation, for example. 
     Furthermore, the main controller  631  calculates a torque to be transmitted to the rear wheel  692  as a commanded torque based on the given operation amount of the accelerator grip  621   a , and applies a control signal based on the commanded torque to the power converter  100 . 
     The power converter  100  converts the electric power supplied from the battery system  632  into electric power (driving power) required for driving the rear wheel  692  based on the control signal given from the main controller  631 . Accordingly, the driving power converted by the power converter  100  is supplied to the motor  660 , and the torque of the motor  660  based on the driving power is transmitted to the rear wheel  692 . 
     Meanwhile, the motor  660  functions as a power generation system at the time of decelerating the two-wheeled electric vehicle  600  based on the brake operation. In this case, the power converter  100  converts regenerated electric power generated by the motor  660  to electric power suitable for charging the battery modules, and supplies the electric power to the battery module. This causes the battery modules to be charged. 
     Here, the power converter  100  includes a circuit board  30  ( FIG. 5 , described below) in the two-wheeled electric vehicle  600  according to the present embodiment. The power converter  100  also includes a signal line group  20   b  for connecting the circuit board  30  ( FIG. 5 , described below) and the main controller  631 . The power converter  100  also includes an electric power line group  20   c  for connecting the circuit board  30  ( FIG. 5 , described below) and the battery system  632 . Furthermore, the power converter  100  includes a motor power line group  20   a  for connecting the circuit board  30  ( FIG. 5 , described below) and the motor  660 . Each of the signal line group  20   b , the electric power line group  20   c  and the motor power line group  20   a  is constituted by a plurality of harnesses. 
     Hereinafter, description is made of details of the power converter  100 . 
     (2) Configuration of the Power Converter 
       FIG. 3  is an external perspective view of the power converter  100  constituted by the circuit module according to the first embodiment of the present invention.  FIG. 4  is a plan view of the power converter  100  of  FIG. 3 . 
     As shown in  FIGS. 3 and 4 , the power converter  100  is constituted by a converter main body  10  and a wire connector  20 . 
     The circuit board  30  ( FIG. 5 ), described below, is accommodated in a box-shaped main body casing  10 C in the converter main body  10 . The main body casing  10 C is composed of a lower casing  110  having an upper opening, and a top cover  120  that closes the upper opening of the lower casing  110 . The main body casing  10 C is formed of an electrically conductive material such as aluminum. 
     The lower casing  110  has four side surfaces and a bottom surface. A wire connector  20  is integrally formed with the lower casing  110  to extend sideward from one side surface. 
     In the present embodiment, the wire connector  20  includes a first connector portion  20   x , a second connector portion  20   y  and a third connector portion  20   z . One ends of the motor power line group  20   a , the signal line group  20   b  and the electric power line group  20   c  of  FIG. 3  are connected to the first connector portion  20   x , the second connector portion  20   y  and the third connector portion  20   z , respectively. The first connector portion  20   x  and the third connector portion  20   z  have waterproof construction. 
     The motor power line group  20   a  and the signal line group  20   b  are each constituted by the three harnesses  21 , and the electric power line group  20   c  is constituted by the two harnesses  21 . 
       FIGS. 5 and 6  are exploded perspective views of the power converter  100  of  FIGS. 3 and 4 . 
     Electronic circuits such as an inverter circuit for driving the motor  660  of  FIG. 2  are mounted on the circuit board  30 . The circuit board  30  is accommodated within the lower casing  110 . 
     As shown in  FIG. 5 , three terminals  30   a ,  30   b ,  30   c  corresponding to the motor power line group  20   a  of  FIG. 3  are formed on an upper surface of the circuit board  30 . Two terminals  30   d ,  30   e  corresponding to the electric power line group  20   c  of  FIG. 3  are formed on the upper surface of the circuit board  30 . Each of the terminals  30   a  to  30   e  has a screw hole for connecting a strip-shaped bus bar BB thereto. Three terminals (not shown) corresponding to the signal line group  20   b  of  FIG. 3  are also formed on the circuit board  30 . 
     The wire connector  20  is constituted by two supports  110   x ,  110   y  shown in  FIG. 5 , a terminal holder  11  shown in  FIG. 5 , rubber gaskets  23   a ,  23   c  shown in  FIG. 6  and terminal covers  12   a ,  12   b ,  12   c  shown in  FIG. 6 . 
     As shown in  FIG. 5 , the two supports  110   x ,  110   y  are integrally formed with a distance therebetween on the one side surface of the lower casing  110 . Each of the two supports  110   x ,  110   y  has a constant width, and extends in a horizontal direction. A tip portion of each of the two supports  110   x ,  110   y  is bent upward. 
     Three concave portions a, b, c, each of which has a semicircular shape in cross section, corresponding to the motor power line group  20   a  of  FIG. 3  are formed at an upper end of the tip portion of the support  110   x . Two concave portions d, e, each of which has a semicircular shape in cross section, corresponding to the electric power line group  20   c  of  FIG. 3  are formed at an upper end of the tip portion of the support  110   y . The terminal holder  11  made of resin is mounted on the two supports  110   x ,  110   y.    
       FIG. 7  ( a ) is a perspective view of the terminal holder  11  of  FIG. 5 , and  FIG. 7  ( b ) is a plan view of the terminal holder  11  of  FIG. 5 . 
     As shown in  FIG. 7  ( a ), the terminal holder  11  is made of a plate-like member having a rectangular shape, and has an upper surface  11 A, a lower surface  11 B, one end surface  11 C and the other end surface  11 D. 
     A plurality of concave grooves g 1 , g 2 , g 3 , g 7 , g 8  are formed parallel to one another on the upper surface  11 A of the terminal holder  11  to extend from the one end surface  11 C to portions near the other end surface  110 . A plurality of concave grooves g 4 , g 5 , g 6  are formed parallel to one another between the concave grooves g 1 , g 2 , g 3  and the concave grooves g 7 , g 8  to extend from the one end surface  11 C to the other end surface  11 D. 
     The three concave grooves g 1 , g 2 , g 3  correspond to the motor power line group  20   a  of  FIG. 3 , and formed in the first connector portion  20   x  of  FIG. 3 . The three concave grooves g 4 , g 5 , g 6  correspond to the signal line group  20   b  of  FIG. 3 , and formed in the second connector portion  20   y . The two concave grooves g 7 , g 8  correspond to the electric power line group  20   c  of  FIG. 3 , and formed in the third connector portion  20   z . A tip portion of each of the concave grooves g 1 , g 2 , g 3 , g 7 , g 8  is formed to have a semicircular shape in cross section. An entire portion of each of the concave grooves g 4 , g 5 , g 6  is formed to have a semicircular shape in cross section. 
     A joint region CR 1  is formed on the upper surface  11 A to surround the three concave grooves g 1 , g 2 , g 3  in an integrated manner excluding the tip portions of the concave grooves g 1 , g 2 , g 3 . A joint region CR 2  is formed on the upper surface  11 A to surround the two concave grooves g 7 , g 8  in an integrated manner excluding the tip portions of the concave grooves g 7 , g 8 . A region inside the joint region CR 1  is referred to as an internal region IR 1 , and a region inside the joint region CR 2  is referred to as an internal region IR 2 . 
     The concave grooves g 1 , g 2 , g 3  are symmetrically arranged with respect to a center line CL 1   a  of the internal region IR 1  in this example. Here, the center line CL 1   a  is a straight line passing through the center of two sides of the internal region IR 1  that are parallel to the one end surface  11 C. The concave grooves g 7 , g 8  are symmetrically arranged with respect to a center line CL 2   a  of the internal region IR 2 . Here, the center line CL 2   a  is a straight line passing through the center of two sides of the internal region IR 2  that are parallel to the one end surface  11 C. 
     As shown in  FIG. 7  ( b ), a slit S 1  parallel to the one end surface  11 C is formed to vertically penetrate the terminal holder  11  from the lower surface  11 B to the internal region  1 R 1 . A slit S 2  parallel to the one end surface  11 C is formed to vertically penetrate the terminal holder  11  from the lower surface  11 B to the internal region IR 2 . 
     The tip portion of the support  110   x  of  FIG. 5  is inserted from the lower surface  11 B into the slit S 1 , and the tip portion of the support  110   y  of  FIG. 5  is inserted from the lower surface  11 B into the slit  82 . In this state, upper surfaces of the three concave portions a, b, c of the support  110   x  are substantially flush with upper surfaces of the three concave grooves g 1 , g 2 , g 3  of the terminal holder  11 . Upper surfaces of the two concave portions d, e of the support  110   y  are substantially flush with upper surfaces of the two concave grooves g 7 , g 8  of the terminal holder  11  (see  FIG. 6 ). 
     As shown in  FIG. 7  ( b ), a plurality of slits H 1 , H 2 , H 3 , H 4 , H 5  that are parallel to the lower surface  11 B and extend from the other end surface  110  into the concave grooves g 1 , g 2 , g 3 , g 7 , g 8 , respectively, are formed in the terminal holder  11 . 
     The foregoing strip-shaped bus bar BB is inserted in each of the plurality of slits H 1 , H 2 , H 3 , H 4 , H 5  (see  FIG. 5 ). One ends of the plurality of bus bars BB are exposed inside the concave grooves g 1 , g 2 , g 3 , g 7 , g 8 . Each of the plurality of bus bars BB is formed of copper, for example, and has connection holes at its both ends. 
     As described above, the tip portions of the supports  110   x ,  110   y  of the lower casing  110  are inserted in the slits S 1 , S 2  of the terminal holder  11 . This causes the terminal holder  11  to be fixed to the lower casing  110  as shown in  FIG. 5 . The connection holes at one ends of the plurality of bus bars BB are positioned in the concave grooves g 1 , g 2 , g 3 , g 7 , g 8  of the terminal holder  11 , and the connection holes at the other ends of the plurality of bus bars BB are positioned on the plurality of terminals  30   a ,  30   b ,  30   c ,  30   d ,  30   e  of the circuit board  30 . 
     In this state, the other ends of the plurality of bus bars BB are connected to the screw holes of the plurality of terminals  30   a ,  30   b ,  30   c ,  30   d ,  30   e  of the circuit board  30  by screws  31  through the connection holes. 
     The three harnesses  21  constituting the signal line group  20   b  are fitted in the three concave grooves g 4 , g 5 , g 6  of the terminal holder  11 , respectively, and ends of the three harnesses  21  are electrically connected to the circuit board  30 . Concave grooves each having a semicircular shape and being opposite to the three concave grooves g 4 , g 5 , g 6  of the terminal holder  11  are formed on a lower surface of the terminal cover  12   b . The terminal cover  12   b  is formed of resin. The terminal cover  12   b  is mounted on the terminal holder  11  to cover the harnesses  21  in the concave grooves g 4 , g 5 , g 6  of the terminal holder  11 . 
     In this state, an internal space of the lower casing  110  is filled with resin, and the top cover  120  is attached to the lower casing  110 . 
       FIG. 8  is a perspective view of the rubber gasket  23   a  to which the motor power line group  20   a  is attached.  FIG. 9  is a perspective view of the rubber gasket  23   c  to which the electric power line group  20   c  is attached. 
     As shown in  FIG. 8 , the rubber gasket  23   a  has a rectangular shape corresponding to the joint region CR 1  of the upper surface  11 A of the terminal holder  11 . The rubber gasket  23   a  surrounds the internal region IR 1  while being arranged on the joint region CR 1  of the upper surface  11 A of the terminal holder  11 . 
     Three cylindrical attachment portions F each having a through hole h that penetrates the rubber gasket  23   a  from the outside to the inside are integrally formed at a distance from one another at one side of the rubber gasket  23   a . The inner diameter of each of the through holes h is substantially equal to the diameter of each harness  21  of the motor power line group  20   a . Screw holes H are formed at four corners of the rubber gasket  23   a.    
     The three through holes h and three attachment portions F are symmetrically arranged with respect to a center line CU b of the rubber gasket  23   a  in this example. Here, the center line CL 1   b  is a straight line passing through the midpoint of the one side of the rubber gasket  23   a  at which the through holes h are formed and the midpoint of the other side being opposite thereto. 
     As shown in  FIG. 9 , the rubber gasket  23   c  has a rectangular shape corresponding to the joint region CR 2  of the upper surface  11 A of the terminal holder  11 . The rubber gasket  23   c  surrounds the internal region  1 R 2  while being arranged on the joint region CR 2  of the upper surface  11 A of the terminal holder  11 . 
     Two cylindrical attachment portions F each having a through hole h that penetrates the rubber gasket  23   c  from the outside to the inside are integrally formed at a distance from each other at one side of the rubber gasket  23   c . The inner diameter of each of the through holes h is substantially equal to the diameter of the harness  21  of the electric power line group  20   c . Screw holes H are formed at four corners of the rubber gasket  23   c.    
     The two through holes h and two attachment portions F are symmetrically arranged with respect to a center line CL 2   b  of the rubber gasket  23   c  in this example. Here, the center line CL 2   b  is a straight line passing through the midpoint of the one side of the rubber gasket  23   c  at which the through holes h are formed and the midpoint of the other side being opposite thereto. 
     Each of the harnesses  21  constituting the motor power line group  20   a  of  FIG. 8  and the electric power line group  20   c  of  FIG. 9  is a coaxial cable composed of a core  21   a , insulating films  21   b ,  21   d  and a shield line  21   c . An outer periphery of the core  21   a  is covered with the insulating film  21   b , the shield line  21   c  and the insulating film  21   d , A solderless terminal  22  is attached to the core  21   a  exposed at a tip portion of each harness  21 . 
     The three harnesses  21  of  FIG. 8  are inserted through the through holes h of the rubber gasket  23   a , respectively. The solderless terminal  22  attached to the tip portion of each harness  21  is positioned inside the rubber gasket  23   a . The two harnesses  21  of  FIG. 9  are inserted through the through holes h of the rubber gasket  23   c . The solderless terminal  22  attached to the tip portion of each harness  21  is positioned inside the rubber gasket  23   c.    
     As shown in  FIG. 6 , the rubber gasket  23   a  is arranged on the joint region CR 1  of the upper surface  11 A of the terminal holder  11 , and the three attachment portions F are fitted in the three concave grooves g 1 , g 2 , g 3  of the terminal holder  11 , respectively, while the three harnesses  21  constituting the motor power line group  20   a  are inserted in the rubber gasket  23   a.    
     In this state, the three solderless terminals  22  positioned inside the rubber gasket  23   a  are connected to the respective bus bars BB exposed in the three concave grooves g 1 , g 2 ,  93  by screws  24   a.    
     Similarly, the rubber gasket  23   c  is arranged on the joint region CR 2  of the upper surface  11 A of the terminal holder  11 , and the two attachment portions F are fitted in the two concave grooves g 7 , g 8  of the terminal holder  11 , respectively, while the two harnesses  21  constituting the electric power line group  20   c  are inserted in the rubber gasket  23   c.    
     In this state, the two solderless terminals  22  positioned inside the rubber gasket  23   c  are connected to the respective bus bars BB exposed in the two concave grooves g 7 , g 8  by screws  24   a.    
     The terminal cover  12   a  made of resin is attached to the joint region CR 1  (FIG.,  7  ( a )) of the upper surface  11 A of the terminal holder  11  with the rubber gasket  23   a  sandwiched therebetween. 
       FIG. 10  is a bottom view of the terminal cover  12   a . As shown in  FIG. 10 , a joint region CR 3  is formed at a peripheral edge portion on a lower surface of the terminal cover  12   a . The joint region CR 3  has a rectangular shape corresponding to the joint region CR 1  of the upper surface  11 A of the terminal holder  11 . The joint region CR 3  projects downward as compared with a region inside thereof. Three concave grooves g 9 , g 10 , g 11  each having a semicircular shape corresponding to the attachment portion F (see  FIG. 8 ) of the rubber gasket  23   a  are formed at one side of the joint region CR 3 , Screw holes H are formed at four corners of the terminal cover  12   a.    
     The concave grooves g 9 , g 10 , g 11  are symmetrically arranged with respect to a center line CL 1   c  of the joint region CR 3  in this example. Here, the center line CL 1   c  is a straight line passing through the midpoint of the one side of the joint region CR 3  at which the concave grooves g 9 , g 10 , g 11  are formed and the midpoint of the other side being opposite thereto. 
     The joint region CR 3  of the terminal cover  12   a  is arranged on the rubber gasket  23   a , and the concave grooves g 9 , g 10 , g 11  are positioned on the three attachment portions F of the rubber gasket  23   a , respectively. In this state, the terminal cover  12   a  is attached to the upper surface  11 A of the terminal holder  11  by screws  13  (see  FIG. 6 ) with the rubber gasket  23   a  sandwiched therebetween. 
     Accordingly, the terminal holder  11 , the rubber gasket  23   a  and the terminal cover  12   a  form a closed space above the internal region IR 1  of the terminal holder  11 . 
     Similarly, the terminal cover  12   c  made of resin is attached to the joint region CR 2  ( FIG. 7  ( a )) of the upper surface  11 A of the terminal holder  11  with the rubber gasket  23   c  sandwiched therebetween. 
       FIG. 11  is a bottom view of the terminal cover  12   c . As shown in  FIG. 11 , a joint region CR 4  is formed at a peripheral edge portion on a lower surface of the terminal cover  12   c . The joint region CR 4  has a rectangular shape corresponding to the joint region CR 2  of the upper surface  11 A of the terminal holder  11 . The joint region CR 4  projects downward as compared with a region inside thereof. Two concave grooves g 15 , g 16  each having a semicircular shape corresponding to the attachment portion F (see  FIG. 9 ) of the rubber gasket  23   c  are formed at one side of the joint region CR 4 . Screw holes H are formed at four corners of the terminal cover  12   c.    
     The concave grooves g 15 , g 16  are symmetrically arranged with respect to a center line CL 2   c  of the joint region CR 4  in this example. Here, the center line CL 2   c  is a straight line passing through the midpoint of the one side of the joint region CR 4  at which the concave grooves g 15 , g 16  are formed and the midpoint of the other side being opposite thereto. 
     The joint region CR 4  of the terminal cover  12   c  is arranged on the rubber gasket  23   c , and the concave grooves g 15 , g 16  are positioned on the two attachment portions F of the rubber gasket  23   c , respectively. In this state, the terminal cover  12   c  is attached to the upper surface  11 A of the terminal holder  11  by screws  13  (see  FIG. 6 ) with the rubber gasket  23   c  sandwiched therebetween. 
     Accordingly, the terminal holder  11 , the rubber gasket  23   c  and the terminal cover  12   c  form a closed space above the internal region IR 2  of the terminal holder  11 . 
       FIG. 12  is a vertical sectional view of the power converter  100  taken along the line A-A of  FIG. 4 . As shown in  FIG. 12 , the solderless terminal  22  attached to the harness  21  constituting the motor power line group  20   a  ( FIG. 4 ) is connected to the bus bar BB in the closed space above the internal region IR 1  of the terminal holder  11  in the first connector portion  20   x . This causes the three harnesses  21  of the motor power line group  20   a  to be electrically connected to the three terminals  30   a ,  30   b ,  30   c  ( FIG. 5 ) of the circuit board  30 , respectively, through the bus bars BB. 
     The shield lines  21   c  of the three harnesses  21  are held while abutting against the concave portions a, b, c of the support  110   x  of the lower casing  110 , respectively. Note that  FIG. 12  only shows the concave portion b. This causes the shield lines  21   c  of the three harnesses  21  of the motor power line group  20   a  to be electrically connected to the lower casing  110 . 
     As described above, the third connector portion  20   z  has substantially the same configuration as the first connector portion  20   x . Therefore, also in the third connector portion  20   z , the solderless terminal  22  attached to the harness  21  constituting the electric power line group  20   c  ( FIG. 4 ) is connected to the bus bar BB in the closed space above the internal region IR 2  of the terminal holder  11 . This causes the two harnesses  21  of the electric power line group  20   c  to be electrically connected to the two terminals  30   d ,  30   e  ( FIG. 5 ) of the circuit board  30 , respectively, through the bus bars BB. 
     The shield lines  21   c  of the two harnesses  21  are held while abutting against the concave portions d, e of the support  110   y  of the lower casing  110 , respectively. This causes the shield lines  21   c  of the two harnesses  21  of the electric power line group  20   c  to be electrically connected to the lower casing  110 . 
     (3) Effects 
     (3-a) The Circuit Module 
     The circuit board  30  is accommodated in the internal space of the main body casing  10 G. The inside of the main body casing  10 C is filled with resin. This ensures waterproofness of the circuit board  30 . 
     The internal region IR 1  including the respective connections between the bus bars BB extending from the circuit board  30  and the three harnesses  21  of the motor power line group  20   a  is closed by the terminal holder  11 , the terminal cover  12   a  and the rubber gasket  23   a  in the outside of the main body casing  10 C. This ensures waterproofness of the internal region IR 1  including the respective connections between the bus bars BB and the three harnesses  21  of the motor power line group  20   a . In this case, the terminal cover  12   a  is removed from the terminal holder  11 , and the rubber gasket  23   a  in which the harnesses  21  of the motor power line group  20   a  are inserted is removed from the terminal holder  11 , so that the harnesses  21  of the motor power line group  20   a  can be easily removed without disassembling the main body casing  10 G. As a result, the motor power line group  20   a  and the bus bars BB can be reliably waterproofed, and the motor power line group  20   a  can be easily replaced. 
     Similarly, the internal region IR 2  including the respective connections between the bus bars  88  extending from the circuit board  30  and the two harnesses  21  of the electric power line group  20   c  is closed by the terminal holder  11 , the terminal cover  12   c  and the rubber gasket  23   c  in the outside of the main body casing  10 C. This ensures waterproofness of the internal region IR 2  including the respective connections between the bus bars BB and the two harnesses  21  of the electric power line group  20   c . In this case, the terminal cover  12   c  is removed from the terminal holder  11 , and the rubber gasket  23   c  in which the harnesses  21  of the electric power line group  20   c  are inserted is removed from the terminal holder  11 , so that the harnesses  21  of the electric power line group  20   c  can be easily removed without disassembling the main body casing  10 C. As a result, the electric power line group  20   c  and the bus bars BB can be reliably waterproofed, and the electric power line group  20   c  can be easily replaced. 
     ( 3 - b ) Shielding of the Main Body Casing 
     The core  21   a  of the harness  21  is connected to the bus bar BB, which is electrically insulated from the main body casing  100 , through the solderless terminal  22 . The shield line  21   c  of the harness  21  is electrically connected to the main body casing  10 C having electrical conductivity. Thus, the main body casing  10 C functions as a shield of the circuit board  30 . Accordingly, the circuit board  30  can be shielded with simple configuration and operation. 
     (3-c) The Motor Power Line and the Electric Power Line 
     The three harnesses  21  of the motor power line group  20   a  are inserted through the three through holes h of the rubber gasket  23   a , respectively, thereby being integrated with the rubber gasket  23   a . As a result, the three harnesses  21  of the motor power line group  20   a  are easily handled, and the three harnesses  21  of the motor power line group  20   a  are prevented from being improperly connected to the three bus bars BB. 
     The two harnesses  21  of the electric power line group  20   c  are inserted through the two through holes h of the rubber gasket  23   c , respectively, thereby being integrated with the rubber gasket  23   c . As a result, the two harnesses  21  of the electric power line group  20   c  are easily handled, and the two harnesses  21  of the electric power line group  20   c  are prevented from being improperly connected to the two bus bars BB. 
     (3-d) The Two-Wheeled Electric Vehicle 
     The electric power is supplied from the battery system  632  to the power converter  100  in the two-wheeled electric vehicle  600  of  FIG. 1 . The electric power converted in the power converter  100  is applied to the motor  660 , thereby causing the motor  660  to rotate. The torque generated by the motor  660  causes the rear wheel  692  to rotate, so that the two-wheeled electric vehicle moves. 
     The power converter  100  is constituted by the circuit module shown in  FIGS. 3 to 6 . Therefore, waterproofness of the power converter  100  is ensured by the main body casing  10 C that is molded of resin even when the two-wheeled electric vehicle  600  is used in wet weather or on a flooded road. The respective connections between the bus bars BB of the power converter  100  and the motor power line group  20   a  and between the bus bars BB of the power converter  100  and the electric power line group  20   c  are closed by the terminal holder  11 , the terminal covers  12   a ,  12   c  and the rubber gaskets  23   a ,  23   c . This ensures waterproofness of the respective connections between the bus bars BB and the motor power line group  20   a  and between the bus bars BB and the electric power line group  20   c . In this case, the harnesses  21  of the motor power line group  20   a  and the electric power line group  20   c  are removed from the bus bars BB, so that the motor power line group  20   a  and the electric power line group  20   c  can be easily removed from the power converter  100  without disassembling the main body casing  10 C. As a result, the respective connections between the power converter  100  and the motor power line group  20   a  and between the power converter  100  and the electric power line group  20   c  can be reliably waterproofed, and the motor power line group  20   a  and the electric power line group  20   c  can be easily replaced. 
     (4) Other Examples of the Terminal Holder, the Rubber Gasket and the Terminal Cover 
       FIG. 13  is a plan view showing another example of the terminal holder  11 .  FIG. 14  is a plan view showing another example of the rubber gaskets  23   a ,  23   c .  FIG. 15  is a plan view showing another example of the terminal covers  12   a ,  12   c.    
     In the example of  FIG. 13 , the concave grooves g 1 , g 2  g 3  of the terminal holder  11  are asymmetrically arranged with respect to the center line CL 1   a  of the internal region IR 1 . 
     Similarly, the concave grooves g 7 , g 8  of the terminal holder  11  are asymmetrically arranged with respect to the center line CL 2   a  of the internal region  1 R 2 . 
     In the example of  FIG. 14  ( a ), the through holes h and the attachment portions F at the one side of the rubber gasket  23   a  are asymmetrically arranged with respect to the center line CL 1   b  of the rubber gasket  23   a.    
     In the example of  FIG. 14  ( b ), the through holes h and the attachment portions F at the one side of the rubber gasket  23   c  are asymmetrically arranged with respect to the center line CL 2   b  of the rubber gasket  23   c.    
     In the example of  FIG. 15  ( a ), the concave grooves g 9 , g 10 , g 11  are asymmetrically arranged with respect to the center line CL 1   c  of the joint region CR 3 . 
     In the example of  FIG. 15  ( b ), the concave grooves g 15 , g 16  are asymmetrically arranged with respect to the center line CL 2   c  of the joint region CR 4 . 
     In this case, the rubber gasket  23   a , in which the three harnesses  21  constituting the motor power line group  20   a  are inserted, is prevented from being arranged between the joint region CR 1  of the terminal holder  11  and the joint region CR 3  of the terminal cover  12   a  with one surface and the other surface of the rubber gasket  23   a  arranged in the opposite manner. 
     This prevents the two harnesses  21  to be fitted in the concave grooves g 1 , g 3 , respectively, from being erroneously fitted in the concave grooves g 3 , g 1 , respectively. As a result, improper connection between the motor power line group  20   a  and the circuit board  30  is inhibited. 
     Similarly, the rubber gasket  23   c , in which the two harnesses  21  constituting the electric power line group  20   c  are inserted, is prevented from being arranged between the joint region CR 2  of the terminal holder  11  and the joint region CR 4  of the terminal cover  12   c  with one surface and the other surface of the rubber gasket  23   c  arranged in the opposite manner. 
     This prevents the two harnesses  21  to be fitted in the concave grooves g 7  g 8 , respectively, from being erroneously fitted in the concave grooves g 8 , g 7 , respectively. As a result, improper connection between the electric power line group  20   c  and the circuit board  30  is inhibited. 
     (5) Still Other Examples of the Terminal Holder and the Rubber Gasket 
       FIG. 16  is a plan view showing still another example of the terminal holder  11 .  FIG. 17  is a plan view showing still another example of the rubber gaskets  23   a ,  23   c.    
     In the example of  FIG. 16 , a projection  14   a  is formed between the other end surface  11 D of the terminal holder  11  and the other end of the concave groove g 3 . A projection  14   c  is formed between the other end surface  110  of the terminal holder  11  and the other end of the concave groove g 8 . 
     In the example of  FIG. 17  ( a ), a wide portion W 1  having a larger width than the other portion is formed in part of the other side of the rubber gasket  23   a  that is opposite to the one side at which the through holes h are formed. The wide portion W 1  is positioned on the opposite side to the projection  14   a  of the terminal holder  11  of  FIG. 16  with respect to the center line Cub. This causes a concave portion  15   a  to be formed in a position corresponding to the projection  14   a  of the terminal holder  11 . 
     In the example of  FIG. 17  ( b ), a wide portion W 2  having a larger width than the other portion is formed in part of the other side of the rubber gasket  23   c  that is opposite to the one side at which the through holes h are formed. The wide portion W 2  is positioned on the opposite side to the projection  14   c  of the terminal holder  11  of  FIG. 16  with respect to the center line CL 2   b . This causes a concave portion  15   c  to be formed in a position corresponding to the projection  14   c  of the terminal holder  11 . 
     When the one surface of the rubber gasket  23   a  in which the three harnesses  21  constituting the motor power line group  20   a  are inserted is arranged on the joint region CR 1  of the terminal holder  11 , the projection  14   a  of the terminal holder  11  is fitted in the concave portion  15   a  of the motor power line group  20   a.    
     In this manner, the rubber gasket  23   a , in which the three harnesses  21  constituting the motor power line group  20   a  are inserted, is prevented from being arranged between the joint region CR 1  of the terminal holder  11  and the joint region CR 3  of the terminal cover  12   a  with the one surface and the other surface of the rubber gasket  23   a  arranged in the opposite manner. 
     This prevents the two harnesses  21  to be fitted in the concave grooves g 1 , g 3 , respectively, from being erroneously fitted in the concave grooves g 3 , g 1 , respectively. As a result, improper connection between the motor power line group  20   a  and the circuit board  30  is inhibited. 
     Similarly, when the one surface of the rubber gasket  23   c  in which the two harnesses  21  constituting the electric power line group  20   c  are inserted is arranged on the joint region CR 2  of the terminal holder  11 , the projection  14   c  of the terminal holder  11  is fitted in the concave portion  15   c  of the electric power line group  20   c.    
     In this manner, the rubber gasket  230 , in which the two harnesses  21  constituting the electric power line group  20   c  are inserted, is prevented from being arranged between the joint region CR 2  of the terminal holder  11  and the joint region CR 4  of the terminal cover  12   c  with the one surface and the other surface of the rubber gasket  23   c  arranged in the opposite manner. 
     This prevents the two harnesses  21  to be fitted in the concave grooves g 7  g 8 , respectively, from being erroneously fitted in the concave grooves g 8 , g 7 , respectively. As a result, improper connection between the rubber gasket  23   c  and the circuit board  30  is inhibited. 
     (6) Another Example of the Wire Connector 
       FIG. 18  is an exploded perspective view showing another example of the wire connector  20 , and  FIG. 19  is a bottom view of a terminal cover  12   d  in the wire connector  20  of  FIG. 18 . 
     In the example of  FIG. 18 , the first connector portion  20   x , the third connector portion  20   z  and the second connector portion  20   y  are arranged to line up in this order. Therefore, the first connector portion  20   x  and the third connector portion  20   z  having the waterproof construction are adjacent to each other. Thus, the joint region CR 1  and the joint region CR 2  are arranged adjacent to each other. In this example, the common terminal cover  12   d  made of resin is used instead of the terminal covers  12   a ,  12   c  of  FIGS. 10 and 11 . 
     As shown in  FIG. 19 , the joint regions CR 3 , CR 4  corresponding to the joint regions CR 1 , CR 2  of the terminal holder  11 , respectively, are formed on a lower surface of the terminal cover  12   d . One side of the joint region CR 3  and one side of the joint region CR 4  are integrated and used in common. 
     Each of the joint regions CR 3 , CR 4  projects downward as compared with the region inside thereof. The three concave grooves g 9 , g 10 , g 11  each having the semicircular shape corresponding to the attachment portion F of the rubber gasket  23   a  are formed at the one side of the joint region CR 3 . The two concave grooves g 15 , g 16  each having a semicircular shape corresponding to the attachment portion F of the rubber gasket  23   c  are formed at the one side of the joint region CR 4 . Screw holes H are formed in a peripheral portion of the terminal cover  12   d.    
     The joint regions CR 3 , CR 4  of the terminal cover  12   d  are arranged on the rubber gaskets  23   a ,  23   c , respectively, and the concave grooves g 9 , g 10 , g 11 , g 15 , g 16  are positioned on the five attachment portions F of the rubber gaskets  23   a ,  23   c , respectively. In this state, the terminal cover  12   d  is attached to the upper surface  11 A of the terminal holder  11  by screws  13  with the rubber gaskets  23   a ,  23   c  sandwiched therebetween. 
     In this manner, the common terminal cover  12   d  is used for the first connector portion  20   x  and the third connector portion  20   z  in this example. Accordingly, the plurality of wires (the motor power line group  20   a  and the electric power line group  20   c  in this example) can be reliably attached and removed in the smaller number of operation steps as compared with the case where the terminal cover is attached to each of the first connector portion  20   x  and the third connector portion  20   z.    
     (7) Still Another Example of the Wire Connector 
     Since the signal line group  20   b  is less frequently replaced, the signal line group  20   b , unlike the motor power line group  20   a  and the electric power line group  20   c , is waterproofed by resin molding inside the main body casing  10 C in the circuit module and the electric vehicle including the same according to the above-described embodiment. However, the present invention is not limited to this. The signal line group  20   b  may be waterproofed by a terminal holder and a terminal cover outside the main body casing  10 C, similarly to the motor power line group  20   a  and the electric power line group  20   c.    
     While the joint regions CR 3 , CR 4  of the terminal covers  12   a ,  12   c ,  12   d  are joined to the joint regions CR 1 , CR 2  of the terminal holder  11  through the rubber gaskets  23   a ,  23   c  in the foregoing embodiment, the present invention is not limited to this. The joint regions CR 1 , CR 2  of the terminal holder  11  and the joint regions CR 3 , CR 4  of the terminal covers  12   a ,  12   c ,  12   d  may be directly joined to each other, respectively, not through the rubber gaskets  23   a ,  23   c  if airtightness between the terminal holder  11  and the terminal covers  12   a ,  12   c ,  12   d  is maintained. 
     [2] Second Embodiment 
     Description will be made of a circuit module according to a second embodiment while referring to differences from the circuit module according to the first embodiment. 
     (1) Configuration of the Power Converter 
       FIG. 20  is an external perspective view of the power converter  100  constituted by the circuit module according to the second embodiment of the present invention. As shown in  FIG. 20 , the power converter  100  is constituted by the converter main body  10  and the wire connector  20 . 
     Similarly to the first embodiment, the main body casing  10 C of the converter main body  10  is composed of the lower casing  110  having the upper opening, and the top cover  120  that closes the upper opening of the lower casing  110 . The lower casing  110  has the four side surfaces and the bottom surface. The wire connector  20  is integrally formed in the lower casing  110  so as to extend sideward from one side surface. 
     The wire connector  20  is composed of a lower casing  130  having the upper opening, and a top cover  140  that closes the upper opening of the lower casing  130 . The lower casing  130  has three side surfaces and a bottom surface. A connection casing  20 C and a signal line connecter portion  20 S are integrally formed to line up on the one side surface of the lower casing  110  of the converter main body  10 . The main body casing  10 C, the connection casing  20 C excluding the top cover  140 , and the signal line connector portion  20 S are formed of electrically conductive materials such as aluminum. The top cover  140  is formed of an electrically conductive material such as stainless steel. 
     The first connector portion  20   x , the third connector portion  20   z  and the second connector portion  20   y  are arranged to line up in this order in the present embodiment. One ends of the motor power line group  20   a , the signal line group  20   b  and the electric power line group  20   c  are connected to the first connector portion  20   x , the second connector portion  20   y  and the third connector portion  20   z , respectively. The first connector portion  20   x  and the third connector portion  20   z  have waterproof construction. The motor power line group  20   a  and the signal tine group  20   b  are each constituted by the three harnesses  21 , and the electric power line group  20   c  is constituted by the two harnesses  21 . 
       FIGS. 21 and 22  are exploded perspective views of the power converter  100  of  FIG. 20 . As shown in  FIGS. 21 and 22 , the first connector portion  20   x  and the third connector portion  20   z  of the wire connector  20  are constituted by the connection casing  20 C (the lower casing  130  and the top cover  140 ), a terminal holder  11   b  made of resin, a plurality of bushings  25   a ,  25   c  and a terminal gasket  150 . The second connector portion  20   y  of the wire connector  20  is constituted by a signal line connector portion  11 S and the signal line connector portion  20 S of the lower casing  130 . The signal line connector portion  11 S is integrally formed with the terminal holder  11   b . The top cover  120  of the main body casing  10 C is not shown in  FIG. 21 . 
     Three concave portions A, B, C each having a semicircular shape in cross section and corresponding to the three harnesses  21  of the motor power line group  20   a  (see  FIG. 20 ) and two concave portions D, E corresponding to the two harnesses  21  of the electric power line  20   c  (see  FIG. 20 ) are formed on one side surface of the lower casing  130  that is opposite to the one side surface of the lower casing  110 . The terminal holder lib is fitted in the lower casing  130 . 
       FIG. 23  ( a ) is a perspective view of the terminal holder  11   b  of  FIG. 21 , and  FIG. 23  ( b ) is a plan view of the terminal holder  11   b  of  FIG. 21 . As shown in  FIG. 23  ( a ), the terminal holder lib has a flat and rectangular parallelepiped shape, and has an upper surface  11 E, a lower surface  11 F, one end surface  11 G and the other end surface  11 H. The signal line connector portion  118  is formed to line up along the other end surface  11 H of the terminal holder  11   b.    
     A plurality of concave grooves  917 , g 18 , g 19 , g 23 , g 24  are formed parallel to one another on the upper surface  11 E of the terminal holder  11   b  to extend from the one end surface  11 G to portions near the other end surface  11 H. Three concave grooves g 20 , g 21 , g 22  are formed parallel to one another on a lower surface of the signal line connector portion  11 S. 
     The three concave grooves g 17  to g 19  correspond to the motor power line group  20   a  of  FIG. 20 , and formed within the first connector portion  20   x  of  FIG. 20 . The two concave grooves g 23 , g 24  correspond to the electric power line group  20   c  of  FIG. 20 , and formed within the third connector portion  20   z . The three concave grooves g 20  to g 22  correspond to the signal line group  20   b  of  FIG. 20 , and formed within the second connector portion  20   y  of  FIG. 20 . A tip portion of each of the concave grooves g 17  to g 19 , g 23 , g 24  is formed to have a semicircular shape in cross section. Each of the concave grooves g 20  to g 22  is formed to have a semicircular shape in cross section from its one end surface to its other end surface. 
     A joint region CR 5  is formed on the upper surface  11 E to surround the concave grooves g 17  to g 19 , g 23 , g 24  in an integrated manner excluding tip portions of the concave grooves g 17  to g 19 , g 23 , g 24 . A region inside the joint region CR 5  is referred to as an internal region  1 R 3 . 
     The terminal holder  11   b  is fitted in the lower casing  130 . In this state, upper surfaces of the concave portions A to E formed on the one side surface of the lower casing  130  are substantially flush with upper surfaces of the tip portions of the concave grooves g 17  to g 19 , g 23 , g 24  formed on the one end surface  11 G of the terminal holder  11   b  (see  FIG. 22 ). 
     As shown in  FIG. 23  ( b ), a plurality of slits H 6 , H 7 , H 8 , H 9 , H 10  that extend from the other end surface  11 H into the concave grooves g 17  to g 19 , g 23 , g 24 , respectively, are formed to extend parallel to the lower surface  11 F in the terminal holder  11   b.    
     The strip-shaped bus bar BB is inserted in each of the plurality of slits H 6  to H 10  (see  FIG. 21 ). One ends of the plurality of bus bars BB are exposed inside the concave grooves g 17  to g 19 , g 23 , g 24 . Each of the plurality of bus bars BB is formed of copper, for example, and has connection holes at its both ends. 
     The connection holes at one ends of the plurality of bus bars BB are positioned in the concave grooves g 17  to g 19 , g 23 , g 24  of the terminal holder  11   b , and the connection holes at the other ends of the plurality of bus bars BB are positioned on the plurality of terminals  30   a  to  30   e  (see  FIG. 5 ) of the circuit board  30 . In this state, the other ends of the plurality of bus bars BB are connected to the screw holes of the plurality of terminals  30   a  to  30   e  of the circuit board  30  by the screws  31  through the connection holes. 
     Concave grooves g 25 , g 26 , g 27  each having a semicircular shape in cross section are formed on an upper surface of the signal line connector portion  20 S to be opposite to the three concave grooves g 20  to g 22  of the signal line connector portion  11 S. The three harnesses  21  constituting the signal line group  20   b  are fitted in the three concave grooves g 25  to g 27  of the signal line connector portion  205 , respectively, and ends of the three harnesses  21  are electrically connected to the circuit board  30  (see  FIG. 5 ). 
     After that, the three harnesses  21  constituting the signal line group  20   b  are fitted in the three concave grooves g 20  to g 22  of the signal line connector portion  11 S. In this state, the internal space of the lower casing  110  is filled with resin, and the top cover  120  is attached to the lower casing  110 . 
     Each of the plurality of bushings  25   a  has a substantially rectangular parallelepiped shape, and is formed of rubber. The bushings  25   a  each have a lower portion in a semicircular shape in cross section, and can be fitted in the tip portions of the concave grooves g 17  to g 19  formed in the one end surface  11 G of the terminal holder  11   b . The bushings  25   a  each have a flat upper surface. 
     A through hole is formed in each bushing  25   a , and the harness  21  of the motor power line group  20   a  is inserted through the through hole. The inner diameter of the through hole is substantially equal to the diameter of the harness  21  of the motor power line group  20   a . The harnesses  21  constituting the motor power line group  20   a  of  FIG. 20  each have the same configuration as the harness  21  of  FIG. 8 . After each harness  21  is inserted through the through hole of the bushing  25   a , the solderless terminal  22  is attached to the core  21   a  (see  FIG. 8 ) exposed at the tip portion as shown in  FIG. 22 . 
     The bushings  25   a  are fitted in the tip portions of the concave grooves g 17  to g 19  while the harnesses  21  of the motor power line group  20   a  are inserted through the bushings  25   a . Thus, the tip portions of the concave grooves g 17  to g 19  of the terminal holder  11   b  and the lower surfaces of the bushings  25   a  adhere to each other, respectively, while being waterproofed. The upper surfaces of the bushings  25   a  are substantially flush with the upper surface  11 E of the terminal holder  11   b  (see  FIG. 23 ). In this state, the solderless terminals  22  attached to the harnesses  21  are connected to the bus bars BB exposed in the three concave grooves g 17  to g 19  by the screws  24   a  as shown in  FIG. 22 . 
     Similarly, each of the plurality of bushings  25   c  has a substantially rectangular parallelepiped shape, and is formed of rubber. The bushings  25   c  each have a lower portion in a semicircular shape in cross section, and can be fitted in the tip portions of the concave grooves g 23 , g 24  formed in the one end surface  110  of the terminal holder  11   b . The bushings  25   c  each have a flat upper surface. 
     A through hole is formed in each bushing  25   c , and the harness  21  of the electric power line group  20   c  is inserted through the through hole. The inner diameter of the through hole is substantially equal to the diameter of the harness  21  of the electric power line group  20   c . The harnesses  21  constituting the electric power line group  200  of  FIG. 20  each have the same configuration as the harness  21  of  FIG. 9 . After each harness  21  is inserted through the through hole of the bushing  25   c , the solderless terminal  22  is attached to the core  21   a  (see  FIG. 9 ) exposed at the tip portion as shown in  FIG. 22 . 
     The bushings  25   c  are fitted in the tip portions of the concave grooves g 23 , g 24  while the harnesses  21  of the electric power line group  20   c  are inserted through the bushings  25   c . Thus, the tip portions of the concave grooves g 23 , g 24  of the terminal holder  11   b  and the lower surfaces of the bushings  25   c  adhere to each other, respectively, while being waterproofed. The upper surfaces of the bushings  25   c  are substantially flush with the upper surface  11 E of the terminal holder  11   b  (see  FIG. 23 ). In this state, the solderless terminals  22  attached to the harnesses  21  are connected to the bus bars BB exposed in the two concave grooves g 23 , g 24  by the screws  24   a  as shown in  FIG. 22 . 
     Then, the terminal gasket  150  made of rubber is mounted on the joint region CR 5  (see  FIG. 23  ( a )) of the upper surface  11 E of the terminal holder  11   b . As shown in  FIG. 24 , a joint region CR 6  is formed at a peripheral edge portion on a lower surface of the top cover  140 . The joint region CR 6  has a rectangular shape that corresponds to the joint region CR 5  of the upper surface  11 E of the terminal holder  11   b . Screw holes H are formed at a peripheral portion of the top cover  140 . 
     The joint region CR 6  of the top cover  140  is arranged on the joint region CR 5  of the upper surface  11 E of the terminal holder lib with the terminal gasket  150  sandwiched therebetween. In this state, the top cover  140  is attached to the lower casing  130  by the screws  13  (see  FIG. 22 ) with the terminal gasket  150 , the bushings  25   a ,  25   c  and the terminal holder  11   b  sandwiched therebetween. Here, the upper surface  11 E of the terminal holder lib and the upper surfaces of the bushings  25   a ,  25   c  adhere to the lower surface of the terminal gasket  150  while being waterproofed. Accordingly, the terminal holder  11   b  and the top cover  140  form a closed space above the internal region IR 3  of the terminal holder  11   b.    
     As shown in  FIG. 21 , one end  141  of the top cover  140  corresponding to the one end surface  11 G of the terminal holder  11   b  is bent downward in the present embodiment. This prevents the one end  141  of the top cover  140  from being deflected when the top cover  140  is attached to the lower casing  130  by the screws  13 . 
     The thickness of the top cover  140  may be increased in order to prevent the top cover  140  from being deflected. In this case, the one end  141  of the top cover  140  may not be bent. 
     In the first connector portion  20   x , the solderless terminals  22  attached to the harnesses  21  constituting the motor power line group  20   a  are connected to the bus bars BB within the closed space above the internal region IR 3  of the terminal holder  11   b . Accordingly, the three harnesses  21  of the motor power line group  20   a  are electrically connected to the three terminals  30   a ,  30   b ,  30   c  (see  FIG. 5 ) of the circuit board  30 , respectively, through the bus bars BB. 
     Also in the third connector portion  20   z , the solderless terminals  22  attached to the harnesses  21  constituting the electric power line group  20   c  are connected to the bus bars BB within the closed space above the internal region IR 3  of the terminal holder  11   b . Accordingly, the two harnesses  21  of the electric power line group  20   c  are electrically connected to the two terminals  30   d ,  30   e  (see  FIG. 5 ) of the circuit board  30 , respectively, through the bus bars BB. 
     (2) Effects 
     In the present embodiment, the plurality of bushings  25   a  are fitted in the plurality of concave grooves g 17  to g 19 , which cause the internal region IR 3  of the terminal holder  11   b  and the external space to communicate with each other. The plurality of harnesses  21  constituting the motor power line group  20   a  are inserted through the through holes of the plurality of bushings  25   a , respectively, and connected to the bus bars BB in the internal region IR 3  of the terminal holder  11   b.    
     Similarly, the plurality of bushings  25   c  are fitted in the plurality of concave grooves g 23 , g 24 , which cause the internal region IR 3  of the terminal holder  11   b  and the external space to communicate with each other. The plurality of harnesses  21  constituting the electric power line group  20   c  are inserted through the through holes of the plurality of bushings  25   c , respectively, and connected to the bus bars BB in the internal region IR 3  of the terminal holder  11   b.    
     In this state, the joint region CR 6  of the top cover  140  is joined to the joint region CR 5  of the terminal holder  11   b  with the terminal gasket  150  sandwiched therebetween. Accordingly, spaces between the plurality of concave grooves g 17  to g 19 , g 23 , g 24  of the terminal holder  11   b  and the plurality of bushings  25   a ,  25   c  are sealed, and a space between the joint region CR 5  of the terminal holder  11   b  and the joint region CR 6  of the top cover  140  is sealed. Thus, the internal region IR 3  including the connections between the bus bars BB and the harnesses  21  is closed by the terminal holder  11   b , the top cover  140 , the terminal gasket  150  and the bushings  25   a ,  25   c . This results in improved waterproofness of the connections between the bus bars BB and the harnesses  21 . 
     The plurality of bushings  25   a  and the plurality of concave grooves g 17  to g 19  are provided corresponding to the plurality of harnesses  21  constituting the motor power line group  20   a . Similarly, the plurality of bushings  25   c  and the plurality of concave grooves g 23 , g 24  are provided corresponding to the plurality of harnesses  21  constituting the electric power line group  20   c . This allows the harnesses  21  to be separately removed from the bus bars BB. As a result, replacement operation of the harnesses  21  can be efficiently performed. 
     The circuit board  30  is accommodated in the main body casing  10 C having electrical conductivity, and the one ends of the bus bars BB are accommodated in the connection casing  20 C having electrical conductivity. This causes the circuit board  30  and the bus bars BB to be shielded. As a result, entry of noise from the external space into the circuit board  30  and the bus bars BB can be suppressed, and emission of noise from the circuit board  30  and the bus bars BB to the external space can be suppressed. 
     (3) Another example of the Top Cover of the Connection Casing 
       FIG. 25  is a perspective view showing another example of the top cover  140  of the connection casing  20 C. In the example of  FIG. 25 , the one end  141  of the top cover  140  corresponding to the one end surface  11 G of the terminal holder  11   b  of  FIG. 23  ( b ) is not bent, and the other end  142  of the top cover  140  corresponding to the other end surface  11 H of the terminal holder  11   b  is bent upward. This prevents the other end  142  of the top cover  140  from being deflected when the top cover  140  is attached to the lower casing  130  by the screws  13 . 
     The other end  142  of the top cover  140  may be bent downward. Also in this case, the other end  142  of the top cover  140  is prevented from being deflected when the top cover  140  is attached to the lower casing  130  by the screws  13 . 
     (4) Still Another Example of the Top Cover of the Connection Casing 
       FIG. 26  is a perspective view showing still another example of the top cover  140  of the connection casing  20 C. Similarly to the example of  FIG. 21 , the one end  141  of the top cover  140  corresponding to the one end surface  11 G of the terminal holder  11   b  of  FIG. 23  ( b ) is bent downward in the example of  FIG. 26 . In addition, the other end  142  of the top cover  140  corresponding to the other end surface  11 H of the terminal holder lib is bent downward. This prevents the one end  141  and the other end  142  of the top cover  140  from being deflected when the top cover  140  is attached to the lower casing  130  by the screws  13 . 
     (5) While the solderless terminal  22  is attached to the core  21   a  of each harness  21  that is exposed at the tip portion after the harnesses  21  constituting the motor power line group  20   a  and the harnesses  21  constituting the electric power line group  20   c  are inserted through the through holes of the bushings  25   a ,  25   c , respectively, in the present embodiment, the present invention is not limited to this. The harnesses  21  constituting the motor power line group  20   a  and the harnesses  21  constituting the electric power line group  20   c  may be inserted through the through holes of the bushings  25   a ,  25   c , respectively, after the solderless terminal  22  is attached to the core  21   a  of each harness  21 . 
     Similarly, in the first embodiment, the solderless terminal  22  may be attached to the core  21   a  of each harness  21  exposed at the tip portion after the harnesses  21  constituting the motor power line group  20   a  and the harnesses  21  constituting the electric power line group  20   c  are inserted through the through holes h of the rubber gaskets  23   a ,  23   c , respectively, and the harnesses  21  constituting the motor power line group  20   a  and the harnesses  21  constituting the electric power line group  20   c  may be inserted through the through holes h of the rubber gaskets  23   a ,  23   e , respectively, after the solderless terminal  22  is attached to the core  21   a  of each harness  21 . 
     [3] Correspondences between Elements in the Claims and Parts in Embodiments 
     In the following paragraph, non-limiting examples of correspondences between various elements recited in the claims below and those described above with respect to various preferred embodiments of the present invention are explained. 
     In the above-described embodiments, the main body casing  10 C is an example of a first casing, the circuit board  30  is an example of an electronic circuit, the bus bar BB is an example of a terminal, the internal regions IR 1  to IR 3  are examples of an internal region, the joint regions CR 1 , CR 2 , CR 5  are examples of a first joint region, and the terminal holders  11 ,  11   b  are examples of a terminal holder. The through hole h is an example of a hole, the rubber gaskets  23   a ,  23   c  and the bushings  25   a ,  25   c  are examples of a seal member, the harness  21  is an example of a wire, the joint regions CR 3 , CR 4 , CR 6  are examples of a second joint region, the terminal covers  12   a ,  12   c  or  12   d  or the top cover  140  is an example of a cover, and the wire connector  20  is an example of a wire connector. The core  21   a  is an example of a core, the shield line  21   c  is an example of a shield conductor, the concave grooves g 17  to g 19 , g 23 , g 24  are examples of a groove, and the connection casing  20 C is an example of a second casing. The power converter  100  is an example of a power converter, the battery system  632  is an example of a battery system, the motor  660  is an example of a motor, the rear wheel  692  is an example of a drive wheel, and the two-wheeled electric vehicle  600  is an example of an electric vehicle. 
     As each of various elements recited in the claims, various other elements having configurations or functions described in the claims can be also used. 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.