Abstract:
A power conversion apparatus capable of cheaply securing safety and achieving watertightness. The power conversion apparatus ( 100 ) has: a charging device ( 14 ) for charging from an external power source ( 20 ) to a cell ( 30 ); an inverter ( 13 ) for converting the current of the cell ( 30 ) from direct current to alternating current and supplying the current to a motor ( 40 ); and a junction box ( 15 ) for relaying an electrical connection. The inverter ( 13 ), the charging device ( 14 ), and the junction box ( 15 ) are contained in a single housing. Also, the charging device ( 14 ) and the junction box ( 15 ) are electrically connected, and the junction box ( 15 ) and the inverter ( 13 ) are electrically connected. Also, the junction box ( 15 ) and the inverter ( 13 ) are connected by a bus bar ( 16 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a power conversion apparatus and a junction box to be installed in a vehicle. 
       BACKGROUND ART 
       [0002]    In recent years, electric vehicles (EVs) or plug-in hybrid electric vehicles (PHEVs) have become popular. These vehicles each include: a battery; a charging apparatus configured to charge the battery using an external power supply (commercial power supply); an inverter configured to convert a direct current from the battery to an alternating-current; and a motor configured to drive a wheel of the vehicle using the alternating-current from the inverter (e.g., see Patent Literature (hereinafter, referred to as “PTL”)  1 . These devices are electrically connected to each other. 
       CITATION LIST 
     Patent Literature 
     PTL 1 
     Japanese Patent Application Laid-Open No. 2012-240477 
     SUMMARY OF INVENTION 
     Technical Problem 
       [0003]    The technique disclosed in PTL 1 adopts a harness as a means for electrical connection, thus connecting devices respectively housed in different casings to each other via a harness. Accordingly, the technique disclosed in PTL 1 has the following problems. 
         [0004]    More specifically, the harness is exposed to the outside of each casing, so that processing to coat the harness with an insulator and/or waterproofing needs to be applied to the harness in order to ensure safety. Such processing requires costs. 
         [0005]    Moreover, use of a harness requires custom processing for a connection portion of the harness in each connection-target device. Such processing requires costs as well. 
         [0006]    An object of the present invention is to ensure safety as well as to achieve complete waterproofing without additional costs. 
       Solution to Problem 
       [0007]    A power conversion apparatus according to an aspect of the present invention includes: a charging apparatus that charges a battery using an external power supply; an inverter that converts a current of the battery from a direct current to an alternating-current and that supplies the alternating-current to a motor; and a junction box that relays electrical connection, in which the inverter, the charging apparatus, and the junction box are housed in a single casing, and the charging apparatus and the junction box are electrically connected to each other while the junction box and the inverter are electrically connected to each other, in which the junction box and the inverter are connected to each other via a bus bar. 
         [0008]    A junction box according to an aspect of the present invention includes a protruding portion to be inserted into an opening formed in a partition member of a casing that is internally divided into a plurality of spaces by the partition member, in which the protruding portion includes an insulation portion and serves as a connection portion for a bus bar. 
       Advantageous Effects of Invention 
       [0009]    According to the present invention, it is made possible to ensure safety as well as to achieve complete waterproofing without additional costs. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0010]      FIG. 1  is a block diagram illustrating an example of a power conversion apparatus according to Embodiment 1 of the present invention; 
           [0011]      FIG. 2  is an exploded perspective view illustrating an example of the power conversion apparatus according to Embodiment 1 of the present invention; 
           [0012]      FIG. 3  is a lateral cross-sectional view illustrating an example of the vicinity of a fastening portion of the power conversion apparatus according to Embodiment 1 of the present invention; 
           [0013]      FIG. 4  is a lateral cross-sectional view illustrating an example of the vicinity of a bus bar according to Embodiment 1 of the present invention; 
           [0014]      FIGS. 5A and 5B  are each a lateral cross-sectional view illustrating an example of a vehicle installation position for the power conversion apparatus according to Embodiment 1 of the present invention; 
           [0015]      FIG. 6  is an exploded perspective view illustrating an example of a power conversion apparatus according to Embodiment 2 of the present invention; 
           [0016]      FIG. 7  is an exploded perspective view illustrating an example of the structures of work windows and lids of the power conversion apparatus according to Embodiment 2 of the present invention; 
           [0017]      FIG. 8  is a perspective view illustrating an example of how the lids are fixed to the work windows of the power conversion apparatus according to Embodiment 2 of the present invention; 
           [0018]      FIG. 9  is a front view illustrating an example of the work windows of the power conversion apparatus according to Embodiment 2 of the present invention; 
           [0019]      FIG. 10  is a front view illustrating an example of how a first lid is fixed to the work window of the power conversion apparatus according to Embodiment 2 of the present invention; 
           [0020]      FIG. 11  is a front view illustrating an example of how the first lid and a second lid are fixed to the work windows of the power conversion apparatus according to Embodiment 2 of the present invention; and 
           [0021]      FIG. 12  is a plan view illustrating an example of an interlock mechanism of the power conversion apparatus according to Embodiment 2 of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiment 1 
       [0022]    Hereinafter, a description will be given of a power conversion apparatus according to Embodiment 1 of the present invention with reference to the accompanying drawings. 
         [0023]      FIG. 1  is a block diagram illustrating a configuration example of the power conversion apparatus according to Embodiment 1. 
         [0024]    In  FIG. 1 , power conversion apparatus  100  is an apparatus to be installed in a vehicle such as an EV and includes: casings  11  and  12 ; inverter  13 , which serves as a power conversion circuit; charging apparatus  14 ; and junction box  15 . In power conversion apparatus  100 , a single casing is formed by combination of casing  11  (an example of a first casing) and casing  12  (an example of a second casing) and is divided into casings  11  and  12  by partition member  10 . Partition member  10  is a member serving as the bottom of casing  12  (hereinafter, may be referred to as “bottom member”). 
         [0025]    Casings  11  and  12  are molded using an aluminum cast, for example, and are heat-resistant and rigid. Casings  11  and  12  are ensured for airtightness in order to prevent entry of a water droplet or dust or the like into casing  11  and  12 , respectively. 
         [0026]    Casing  11  includes inverter  13  in an inner portion (an example of a first space) of casing  11 . Inverter  13  converts a direct current (or DC-power) supplied from battery  30  to a three-phase alternating-current (or AC power) and outputs the current to motor  40 . 
         [0027]    Meanwhile, casing  12  includes charging apparatus  14  and junction box  15  in an inner portion (an example of a second space) of casing  12 . Charging apparatus  14  includes an AC-DC conversion circuit and/or a DC-DC conversion circuit and receives power from external power supply  20  and generates a charging voltage for battery  30 . Junction box  15  is an apparatus configured to relay electrical connection between battery  30 , charging apparatus  14 , and inverter  13  and also to distribute the flow of power, and is called an electricity distribution box. 
         [0028]    Charging apparatus  14  is electrically connected to external power supply (commercial power supply)  20  via an external connector (not illustrated) and electrically connected to junction box  15 . For example, charging apparatus  14  and junction box  15  are connected via a bus bar. 
         [0029]    Junction box  15  is connected to battery  30  via a harness, for example. Thus, charging apparatus  14  converts power from external power supply  20  into a direct current from an alternating-current, and charges, via junction box  15 , battery  30 , which is installed in the vehicle. Battery  30  is a secondary battery configured to store power for driving motor  40 . 
         [0030]    Inverter  13  is electrically connected to motor  40  and is also electrically connected to junction box  15 . Inverter  13  and junction box  15  are connected to each other via bus bar  16 . Bus bar  16  is made of metal (e.g., made of copper) and has the positive pole and negative pole. Bus bar  16  passes through opening  17 , which is formed in partition member  10 , and connects inverter  13  and junction box  15  together. Thus, inverter  13  converts a current supplied from battery  30  via junction box  15  to an alternating-current (e.g., three-phase alternating-current) and supplies the current to motor  40 , which is mounted in a vehicle. Motor  40  drives a wheel of the vehicle using the alternating-current. 
         [0031]      FIG. 2  is an exploded perspective view illustrating a configuration example of the power conversion apparatus according to Embodiment 1. 
         [0032]    In  FIG. 2 , power conversion apparatus  100  is separated into casings  11  and  12 , and lid  18 . Casings  11  and  12 , and lid  18  are each made of metal. 
         [0033]    Casings  11  and  12  each substantially has an open-top cuboid shape. Casing  12  is superimposed on and fastened with casing  11 . Bottom member  10  of casing  12  serves as a lid portion of casing  11  when superimposed on chasing  11 . Meanwhile, the opening of casing  12  is covered by lid  18 . Note that, how casings  11  and  12  are fastened together will be described using  FIG. 3 , hereinafter. 
         [0034]    In  FIG. 2 , external power supply connection portion  19 , which is disposed on a side surface of casing  12 , serves as an interface for connection with external power supply  20 . In addition, casing  12  includes a battery connection portion (not illustrated), which serves as an interface for connection with battery  30 , and which is disposed on a side surface opposite to the side surface where external power supply connection portion  19  is disposed. Moreover, a motor connection portion (not illustrated), which serves as an interface for connection with motor  40  is disposed on the bottom of casing  11 . 
         [0035]    In  FIG. 2 , casing  12  includes one interlock (not illustrated). This interlock detects that lid  18  has been opened (open state of lid  18 ). With this detection, the current in power conversion apparatus  100  is controlled to stop. Although it will be described hereinafter, a fastening portion for fastening casings  11  and  12  is disposed within each casing. Accordingly, the user always needs to remove lid  18  of casing  12  in order for the user to touch the inside of casing  11 . This configuration eliminates the need for an interlock to detect an opening state of the lid in casing  11 . Stated differently, the interlock of casing  12  also serves as the interlock for casing  11 . 
         [0036]      FIG. 3  is a lateral cross-sectional view illustrating a configuration example of the fastening portion of power conversion apparatus  100  according to Embodiment 1. 
         [0037]    The fastening portion for fastening casings  11  and  12  is disposed inside casings  11  and  12 . In  FIG. 3 , the fastening portion is formed of screw  21  and screw hole  22 , for example. Screw hole  22  is formed in each of casings  11  and  12 . When casing  11  is appropriately superimposed on casing  12 , single screw hole  22 , which is a through hole, is formed. Casings  11  and  12  are fastened together by inserting screw  21  into screw hole  22 . Note that, although only one position of the fastening portion is illustrated in  FIG. 3 , it is preferred that a plurality of fastening portions identical to the fastening portion mentioned above be disposed inside of each casing. 
         [0038]      FIG. 4  is a lateral cross-sectional view illustrating a configuration example for a position around the bus bar of power conversion apparatus  100  according to Embodiment 1. Note that, illustration of the fastening portion (screw  21  and screw hole  22 ) illustrated in  FIG. 3  is omitted in  FIG. 4 . 
         [0039]    In  FIG. 4 , junction box  15  is formed in a partially protruding shape. The partially protruding portion of junction box  15  is referred to as protruding portion  24  and is inserted into opening  17  and serves as a connection portion (insertion port) for bus bar  16 . Protruding portion  24  includes a portion near the opening which is formed as insulation portion  23 . Furthermore, as described above, bus bar  16  passes through opening  17  and connects inverter  13  and junction box  15  together. 
         [0040]      FIGS. 5A and 5B  are each a lateral cross-sectional view illustrating an example of an in-vehicle installation position of power conversion apparatus  100  according to Embodiment 1. Hereinafter, two examples illustrated in  FIGS. 5A and 5B  will be described, respectively. Note that, the charging apparatus, junction box, inverter, motor, and battery are denoted by “CHG,” “JB,” “INV,” “M,” and “BAT,” respectively, in  FIGS. 5A and 5B . 
         [0041]      FIG. 5A  illustrates an example in which power conversion apparatus  100  is installed in a front portion of vehicle  1 . In  FIG. 5A , battery  30  is installed in a bottom portion (e.g., under the passenger seat) of vehicle  1 . Junction box  15  is installed at a position that allows junction box  15  to be connected to battery  30  with the shortest distance in casing  12 . As described above, junction box  15  and battery  30  are connected together via a harness. 
         [0042]      FIG. 5B  illustrates an example in which power conversion apparatus  100  is installed in a rear portion of vehicle  1 . In  FIG. 5B , battery  30  is installed in a bottom portion (e.g., under the passenger seat) of vehicle  1 . Junction box  15  is installed at a position that allows junction box  15  to be connected to battery  30  with the shortest distance in casing  12 . As described above, junction box  15  and battery  30  are connected together via a harness. 
         [0043]    Power conversion apparatus  100  according to Embodiment 1 described above can bring about the following effects. 
         [0044]    Power conversion apparatus  100  according to Embodiment 1 is characterized in that inverter  13 , charging apparatus  14 , and junction box  15  are housed in a single casing, and charging apparatus  14  and junction box  15  are electrically connected to each other while junction box  15  and inverter  13  are electrically connected to each other, and junction box  15  and inverter  13  are connected to each other via bus bar  16 . More specifically, in power conversion apparatus  100  according to Embodiment 1, a charging apparatus, a junction box, and an inverter are electrically connected to each other in a single casing, so that the casing itself can serve as a cover for the electrically connected portions between these devices. In addition, the electrical connection according to Embodiment 1 allows the charging apparatus, the junction box and the inverter to be disposed while being fixed at certain positions within a limited space inside the casing. For this reason, there is no need to use a harness. Accordingly, power conversion apparatus  100  according to Embodiment 1 can ensure safety and achieve complete waterproofing without additional costs. 
         [0045]    In addition, power conversion apparatus  100  according to Embodiment 1 is characterized in that power conversion apparatus  100  includes a single casing in which two spaces obtained by dividing the space inside the casing using partition member  10 , while inverter  13  and junction box  15  are placed in the two different spaces, respectively, but connected to each other via bus bar  16  passing through opening  17 , which is formed in portion member  10 . More specifically, in power conversion apparatus  100  according to Embodiment 1, an inverter and a junction box are electrically connected to each other within a single casing, so that the casing itself can serve as a cover for the electrical connection portion of the two devices. In addition, the electrical connection according to Embodiment 1 requires no use of a harness because the charging apparatus, the junction box and the inverter are fixed at certain positions within the limited space, which is the space inside the casing. Accordingly, power conversion apparatus  100  according to Embodiment 1 can ensure safety and achieve complete waterproofing without additional costs. 
         [0046]    Power conversion apparatus  100  according to Embodiment 1 is characterized in that battery  30  is installed in a rear portion or a bottom portion of vehicle  1  while junction box  15  is installed at a position that makes the distance between junction box  15  and the battery shortest within power conversion apparatus  100 . Thus, power conversion apparatus  100  according to Embodiment 1 can reduce the length of the harness connecting the junction box and the battery together, thus reducing the costs. Note that, higher safety can be achieved in the arrangement illustrated in  FIG. 5B  than in the arrangement in  FIG. 5A . More specifically, in  FIG. 5A , it is possible for the user to touch power conversion apparatus  100  when the hood is open, so that this arrangement is not very safe. Meanwhile, in  FIG. 5B , the user cannot touch power conversion apparatus  10  disposed inside the trunk, even when a rear door is open, so that this arrangement is safe. 
         [0047]    Moreover, in power conversion apparatus  100  according to Embodiment 1, protruding portion  24 , which is a part of junction box  15 , includes insulation portion  23  and is inserted through opening  17  and serves as a connection portion for bus bar  16 . Thus, power conversion apparatus  100  according to Embodiment 1 can avoid an unsafe situation that may occur when the bus bar comes into contact with a metal-made opening because the screw of the fastening portion comes loose, for example. 
         [0048]    Moreover, power conversion apparatus  100  according to Embodiment 1 is characterized in that a single casing is divided into the first and the second spaces using partition member  10 , while casing  11 , which forms the first space, and casing  12 , which forms the second space, are separable, and that casings  11  and  12  include fastening portions for fastening casings  11  and  12  together in the first and the second spaces, respectively. Stated differently, the fastening portions are included inside the respective casings. Thus, power conversion apparatus  100  according to Embodiment 1 can be reduced in length of the lateral width of the entire casing by the length (width) of the fastening portions, which would otherwise be added to the lateral width of the entire casing when the fastening portions are formed outside the respective casings. 
         [0049]    Moreover, power conversion apparatus  100  according to Embodiment 1 is characterized in that casing  12  is superimposed on and fastened to the casing  11  inside casings  11  and  12 , while power conversion apparatus  100  according to Embodiment 1 includes, in casing  12 , only one interlock to detect an open state of lid  18  of casing  12 . Thus, power conversion apparatus  100  according to Embodiment 1 does not need to include an interlock in casing  11 , thereby making it possible to obtain effects including simplification in shape, a cost reduction for the interlock itself, and a reduction in the number of components required for installation of the interlock, for example. 
         [0050]    Junction box  15  according Embodiment 1 is characterized by including protruding portion  24  to be inserted into opening  17 , while protruding portion  24  includes insulation portion  23  and serves as a connection portion for bus bar  16 . Thus, the junction box according to Embodiment 1 makes it possible to avoid an unsafe situation that may occur when the bus bar comes into contact with the metal-made opening portion because the screw of the fastening portion comes loose, for example. 
         [0051]    The description has been given of Embodiment 1 of the present invention, but the description is an example only, and the following modifications are possible, for example. 
         [0052]    For example, an example is used to describe Embodiment 1, in which junction box  15  is included in casing  12  together with charging apparatus  14 , but the present invention is not limited to this example. For example, junction box  15  may be included in casing  11  together with inverter  13 . 
         [0053]    For example, an example is used to describe Embodiment 1, in which an unsafe situation that may occur when bus bar  16  comes into contact with opening  17  is avoided by including insulation portion  23  in protruding portion  24  of junction box  15 , but the present invention is not limited to this example. For example, junction box  15  itself may be formed using an insulator (e.g., resin), or the portion of partition member  10  where opening  17  is formed may be coated using an insulating member. Thus, as in the case of the presence of insulation portion  23  of protruding portion  24 , it is made possible to avoid an unsafe situation that may occur when bus bar  16  comes into contact with opening portion  17  because screw  21  comes loose, for example. 
         [0054]    Furthermore, a configuration is used to describe Embodiment 1, in which battery  30  is installed in a bottom portion of vehicle  1 , but the present invention is not limited to this configuration. For example, battery  30  may be installed in a front portion or rear portion of the vehicle. In this configuration, junction box  15  is installed at a position that makes the distance between junction box  15  and battery  30  shortest in casing  12 . 
         [0055]    Furthermore, although a configuration in which inverter  13 , charging apparatus  14 , and junction box  15  are housed in power conversion apparatus  100  in Embodiment 1, for example, the present invention is not limited to this configuration, and another device may be installed in power conversion apparatus  100 . For example, a DC/DC converter may be housed in power conversion apparatus  100 . Such a DC/DC converter is used to supply power to an auxiliary battery (12V), for example, and reduces a high voltage of battery  30  to 12V and outputs the power. Housing the DC/DC converter within power conversion apparatus  100  (e.g., within casing  12 ) increases the number of high voltage cables covered by power conversion apparatus  100 , thereby making it possible to further enhance the safety. 
         [0056]    In Embodiment 1, a description has been given of a configuration in which power conversion apparatus  100  includes a single casing formed by combination of casings  11  and  12  while partition member  10  serves as a bottom member for casing  12 , but the present invention is not limited to this configuration. For example, a single casing without combination of a plurality of casings (single casing that cannot be separated into a plurality of casings) may be employed. Moreover, partition member  10  may be a member that simply divides a space. Note that, the number of partition members  10  is not limited to one, and may be two or more. 
       Embodiment 2 
       [0057]    Hereinafter, a description will be given of a power conversion apparatus according to Embodiment 2 of the present invention with reference to the accompanying drawings. 
       Background and Problems According to Embodiment 2 
       [0058]    In recent years, vehicles provided with a running motor, such as hybrid electric vehicles (HEVs), plug-in HEVs (PHEVs), or electric vehicles (EVs) have become popular. These vehicles may be provided with a high-output motor such as a motor for driving a lifting machine, a crane, or a power compressor. 
         [0059]    These vehicles are provided with a power conversion apparatus configured to convert power between an external power supply, a storage battery, and a motor, in addition to a storage battery for supplying power. Such a power conversion apparatus is provided with a charging circuit that generates a charging voltage for the storage battery from the external power supply or an inverter circuit that converts a direct current of the storage battery to a three-phase alternating-current and outputs the current to the motor, for example. 
         [0060]    The power conversion apparatus includes a power conversion circuit to which a high voltage is applied or in which a high voltage is generated, so that it is a common practice to configure the power conversion circuit to be covered by a casing (see, e.g., Japanese Patent Applications Laid-open No. 2003-009301 and No. 2005-143200). The casing is ensured for airtightness in order to prevent entry of a water drop or dust, for example. 
         [0061]    During a vehicle assembly process, a process of assembling a power conversion apparatus of a production unit to a vehicle may include a step of connecting a power output cable (e.g., output cable for supplying a driving current to a motor) to the power conversion apparatus. A cable through which a large current flows requires sure connection. For this reason, as a connection method for such a cable, a connection method of inserting a cable into a casing of a power conversion apparatus and directly connecting the cable to a connection portion is employed, normally, instead of a connection method using a connector. Connecting a cable to the connection portion is performed by inserting a screw driver or the like through a work window of the casing. 
         [0062]    The connection portion is provided at a plurality of positions, e.g., three connection portions where three-phase alternating-current is outputted. The plurality of connection portions are disposed while being spaced apart from each other in general in consideration of securing a predetermined insulation distance or of the influence of a magnetic field. For this reason, the work window for a plurality of connection portions is formed as a window hole that is long in a direction where the connection portions are aligned or a plurality of window holes aligned in a direction identical to that of the plurality of connection portions. 
         [0063]    When the casing of the power conversion apparatus is provided with a work window, an interlock mechanism is required, which ensures safety when the work window is opened. To be more specific, such an interlock mechanism is a mechanism in which an interlock switch turns and blocks supply of power when the lid of the work window is removed. 
         [0064]    However, when the work window is formed in a range that is long in a certain direction, there arises a problem of how a lid partially forming the interlock mechanism should be formed. 
         [0065]    For example, when a configuration is employed in which a metal lid is adopted and fastened to the casing via a gasket, high airtightness can be ensured. However, providing the lid with a mechanism (e.g., protrusion) to turn an interlock switch makes molding difficult compared with the case where the lid is made of resin, and causes an increase in the number of manufacturing steps, thus causing an increase in costs. 
         [0066]    Meanwhile, when a configuration is employed in which a resin-made lid including an O-ring is fastened to the casing, the mechanism (e.g., protrusion) to turn an interlock switch can be formed in the lid with low costs and a high degree of freedom by resin molding. For example, a protrusion having an optimum shape can be easily formed in the lid. However, when a lid that is long in a certain direction such as a rectangular shape is to be sealed, an O-ring having a similar shape needs to be prepared. In this case, there arises a problem in that it is difficult to keep the airtightness by the O-ring as the length of the certain direction becomes long. 
         [0067]    Moreover, when a plurality of sets of work windows and lids are to be independently provided for a plurality of connection portions, there arises a problem in that it is required to prepare the number of interlock mechanisms for the number of lids. 
         [0068]    For the reasons mentioned above, in Embodiment 2, it is made possible to ensure airtightness for a work window of a power conversion apparatus and to achieve easiness of the manufacturing of an interlock mechanism. 
       Description of Embodiment 2 
       [0069]    The basic configuration of power conversion apparatus  100  according to Embodiment 2 is similar to the configuration illustrated in  FIG. 1 , so that the description will not be repeated. Hereinafter, a description will be given of differences from Embodiment 1. 
         [0070]    [Configuration of Work Window] 
         [0071]    In power conversion apparatus  100  according to Embodiment 2, casing  11  includes two work windows  111  and  112  for directly connecting three-phase output cables  42  to inverter  13  as illustrated in  FIG. 6 . 
         [0072]      FIG. 7  is an exploded perspective view illustrating a structure of the work windows and lids of the power conversion apparatus according to Embodiment 2.  FIG. 8  is a perspective view illustrating how the lids are fixed to the work windows.  FIG. 9  is a front view illustrating the work windows.  FIG. 10  is a front view illustrating how a first lid is fixed to a work window.  FIG. 11  is a front view illustrating first and second lids are fixed to the work windows. 
         [0073]    As illustrated in  FIG. 9 , work windows  111  and  112  are through holes passing through casing  11  from outside of casing  11  to inside thereof. Work windows  111  and  112  are formed at positions where three connection portions  131  face work windows  111  and  112 . Three connection portions  131  are regions where connection terminals  42   a  of three output cables  42  for transmitting a three-phase alternating-current to motor  40  and the output terminals of inverter  13  are fixedly attached together using screws, for example. 
         [0074]    Three connection portions  131  are disposed while being spaced apart from each other because of the magnetic influence and a need to secure a predetermined insulation distance. Three connection portions  131  are aligned in a row in parallel with a substrate of inverter  13 . 
         [0075]    Three output cables  42  are inserted into the inside of casing  11  via three through holes at a lower portion of casing  11 , respectively. The airtightness for the three through holes is secured by fastening three cable clamps  42   b.    
         [0076]    Work window  111 , which is one of the two work windows (hereinafter, may be referred to as “first work window  111 ”) has an elongated hole shape that is long in a certain direction. More specifically, work window  111  has a rectangular shape that is long in the direction in which three connection portions  131  are aligned (rectangular with rounded corners). Two connection portions  131  face work window  111 . 
         [0077]    The other one of the work windows, which is work window  112  (hereinafter, may be referred to as “second work window  112 ”) is a hole having substantially the same vertical and horizontal lengths. More specifically, work window  112  has substantially a circular shape, or an ellipse shape which has a slightly long side in a certain direction than in the other direction. One connection portion  131  faces work window  112 . 
         [0078]    [Configuration of Lid of Work Window] 
         [0079]    As illustrated in  FIG. 7 , casing  11  includes a plurality of lids  51  and  52  for closing work windows  111  and  112 , respectively. 
         [0080]    First lid  51  is provided for closing first work window  111  and is a metal lid formed by processing a plate. Lid  51  is fastened to casing  11  via bolts or the like with highly rigid gasket  511  interposed therebetween. Note that, as long as the material has rigidity, lid  51  does not have to be metal. 
         [0081]    Second lid  52  is provided for closing second work window  112  and is integrally molded using a resin. Note that, lid  52  includes projection  522  (equivalent to an operation portion), which pushes interlock switch  135  (see  FIG. 12 ), to be described, hereinafter. Lid  52  may be formed to have both a metal portion and a resin portion by insert molding or outsert molding. 
         [0082]    Lid  52  is fastened to casing  11  via bolts. Elastic O-ring  521  (e.g., rubber O-ring) is fitted to lid  52 . O-ring  521  is placed between lid  52  and work window  112 , thus sealing the gap between lid  52  and work window  112 . 
         [0083]    Lid  52  includes superimposed portion  52   a , which is superimposed over one of the lids, lid  51  (hereinafter, may be referred to as “first lid  51 ”) when lid  52 , which is the other one of the lids (hereinafter, may be referred to as “second lid  52 ”) is fastened to casing  11 . Superimposed portion  52   a  is configured to be superimposed over fastening portion  51   a  of lid  51  (outside of the casing), e.g., superimposed over the bolts used for fastening lid  51 . With this configuration, as illustrated in  FIGS. 8 and 11 , while lid  52  is fastened, bolts for first lid  51  are hidden to prevent lid  51  from being unfastened. More specifically, this structure prevents first lid  51  from being opened unless lid  52  is opened. 
         [0084]    Projection  113  is formed near work window  112  corresponding to lid  52  so as to prevent lid  52  from being attached to the wrong side. 
         [0085]    [Configuration of Interlock Mechanism] 
         [0086]      FIG. 12  is a plan view illustrating an interlock mechanism of the power conversion apparatus according to Embodiment 2. 
         [0087]    Power conversion apparatus  100  according to Embodiment 2 includes an interlock mechanism for ensuring safety when work windows  111  and  112  are released. 
         [0088]    The interlock mechanism includes: interlock switch  135 , which is disposed inside casing  11 ; and projection  522 , which responds to interlock switch  135  and turns the switch. 
         [0089]    Interlock switch  135  is a contact switch that turns when arm  135   a  is pushed in, for example. Inverter  13  includes a blocking circuit that allows input of power to the inverter when arm  135   a  is pushed in and that blocks input of power to the inverter when arm  135   a , which has been pushed in is released. 
         [0090]    As has been described above, projection  522  is formed in lid  52  and protrudes into the inside of casing  11  from work window  112  so as to push arm  135   a  of interlock switch  135  while lid  52  is fastened. 
         [0091]    Interlock switch  135  may not be a contact switch and may be a proximity sensor switch that turns the state of the switch when projection  522  comes closer to the switch. 
         [0092]    [Installation Process to Vehicle] 
         [0093]    As in Embodiment 1, power conversion apparatus  100  according to Embodiment 2 is installed in a vehicle. The installation of power conversion apparatus  100  will be described with reference to  FIGS. 5A and 5B , hereinafter. 
         [0094]    Vehicle  1  illustrated in  FIG. 5A  is an example in which running motor  40  is disposed near a front wheel axle. Battery  30  is installed in a bottom portion (e.g., under the passenger seat) of vehicle  1 . In this case, it is favorable to install power conversion apparatus  100  at a front position of vehicle  1  that allows power conversion apparatus  100  to be connected to motor  40  with the shortest distance. 
         [0095]    Vehicle  1  in  FIG. 5B  is an example in which running motor  40  is disposed near a rear wheel axle. Battery  30  is installed in a bottom portion (e.g., under the passenger seat) of vehicle  1 . In this case, it is favorable to install power conversion apparatus  100  at a rear position of vehicle  1  that allows power conversion apparatus  100  to be connected to motor  40  with the shortest distance. 
         [0096]    In the step of installing power conversion apparatus  100  in vehicle  100 , the step of connecting output cable  42  to inverter  13  is required after installation of power conversion apparatus  100  of a unit production to vehicle  1  or during the installation. 
         [0097]    In the step of connecting the cable, as illustrated in  FIGS. 7 and 9 , while lids  51  and  52  are released, the operator connects connection terminals  42   a  of three output cables  42  to connection portions  131  of inverter  13 . Since lid  52  is removed, interlock switch  135  is turned off, thus blocking input of power to inverter  13 . Accordingly, the connection work can be performed while safety is ensured. 
         [0098]    Upon completion of the connection work, as illustrated in  FIG. 10 , the operator fastens first lid  51  to casing  11 . Next, as illustrated in  FIG. 11 , second lid  52  is fastened to casing  11 . Fastening the lids to casing  11  can ensure high airtightness for casing  11 . Fastening second lid  52  to casing  11  turns on interlock switch  135  and enables power supply to inverter  13 . 
         [0099]    As described above, with power conversion apparatus  100  according to Embodiment 2, second lid  52  is fastened so as to partially overlap first lid  51 . Accordingly, providing the interlock mechanism that interlocks with the opening and closing of second lid  52  alone makes it possible to ensure safety related to opening of work windows  111  and  112 . More specifically, first lid  51  cannot be removed unless second lid  52  is removed. 
         [0100]    Moreover, in Embodiment 2, a plurality of lids  51  and  52  are provided for closing work windows  111  and  112 , respectively. Thus, even in a configuration in which work windows  111  and  112  are each formed in a range that is long in a certain direction for a plurality of connection portions disposed while being spaced apart from each other, second lid  52 , which requires the operation portion (e.g., protrusion) of the interlock mechanism, can be formed in a small shape (or a shape having substantially the same vertical and lateral dimensions). Thus, use of a resin-made lid for second lid  52  allows the operation portion (e.g., projection) of the interlock mechanism to be formed easily at low costs and also makes it possible to ensure high airtightness easily with an O-ring. 
         [0101]    In Embodiment 2, first lid  51 , which requires no operation portion (e.g., projection) of the interlock mechanism, and work window  111 , which corresponds to first lid  51 , are formed in a shape that is long in a certain direction and placed at a position where two connection portions  131  face lid  51  and work window  111 . Thus, the number of components can be reduced, and the efficiency of connection work is improved as well. 
         [0102]    Embodiment 2 of the present invention has been described thus far, but the description provided above is only an example. Accordingly, the following modifications are possible, for example. 
         [0103]    In Embodiment 2, the configuration in which power supply to inverter  13  is blocked when work windows  111  and  112  are opened has been described as an example of the interlock mechanism. However, the interlock mechanism may be configured to block at least application of a high voltage to connection portions  131 . 
         [0104]    In Embodiment 2, the configuration including two work windows  111  and  112 , and two lids  51  and  52  has been described as an example, but a configuration including “n” work windows and “n” lids (where “n” is a natural number equal to or greater than three) may be employed. In this case, the “n” lids are each configured to partially overlap another lid and are configured in such a manner that the lids except the last lid cannot be removed unless another lid is removed. In this configuration, the operation portion (e.g., projection) of the interlock mechanism is formed in the lid to be fastened last. 
         [0105]    Moreover, in Embodiment 2, a configuration including two work windows  111  and  112  and two lids  51  and  52  has been described as an example, but a configuration including one work window and two lids may be employed. In this configuration, while a first lid covers the entire circumference of one work window, a through hole serving as a small work window may be formed in a part of the first lid, and a second lid is configured to cover the work window formed in the first lid. 
         [0106]    In Embodiment 2, the configuration in which second lid  52  partially overlaps fastening portion  51   a  (bolts) of first lid  51  has been described as an example. However, it is also possible to employ a configuration in which second lid  52  overlaps a portion of first lid  51  other than the fastening portion of first lid  51 , thereby making first lid  51  unremovable unless second lid  52  is removed. Moreover, it is also possible to employ a configuration in which first and second lids  51  and  52  are configured to be collectively fastened to casing  11  at a portion where first and second lids  51  and  52  overlap each other. For example, a configuration in which insertion holes that overlap each other are formed in first and second lids  51  and  52 , respectively, and one bolt is inserted through both of the insertion holes to fasten first and second lids  51  and  52  to casing  11 . 
         [0107]    In Embodiment 2, work windows  111  and  112  have been described as work windows for connection of output cables  42  of motor  40 , a work window for connection of a terminal of a harness for power input, or work windows for various purposes may be provided. 
         [0108]    Moreover, in Embodiment 2, inverter  13 , charging apparatus  14 , and junction box  15  have been described as examples of the circuit to be housed in a casing of the power conversion apparatus. However, as a circuit to be housed in a casing of the power conversion apparatus, only an inverter or a charging apparatus, or various high voltage circuits to which a high voltage is applied or in which a high voltage is generated may be employed. 
       Summary of Aspects of the Invention 
       [0109]    Next, a description will be given of an overview of aspects according to the present invention. 
         [0110]    A power conversion apparatus according to a first aspect includes: a charging apparatus that charges a battery using an external power supply; an inverter that converts a current of the battery from a direct current to an alternating-current and that supplies the alternating-current to a motor; and a junction box that relays electrical connection, in which the inverter, the charging apparatus, and the junction box are housed in a single casing, and the charging apparatus and the junction box are electrically connected to each other while the junction box and the inverter are electrically connected to each other, in which the junction box and the inverter are connected to each other via a bus bar. 
         [0111]    A power conversion apparatus according to a second aspect is the power conversion apparatus according to the first aspect further including a DC/DC converter in the casing. 
         [0112]    A power conversion apparatus according to a third aspect is the power conversion apparatus according to the first aspect in which the charging apparatus and the inverter are each connected to the battery via the junction box. 
         [0113]    A power conversion apparatus according to a fourth aspect is the power conversion apparatus according to the first aspect in which the battery is installed in a rear portion or a bottom portion of a vehicle, and the junction box is installed at a position that allows the junction box to be connected to the battery in the casing with a shortest distance between the junction box and the battery. 
         [0114]    A power conversion apparatus according to a fifth aspect is the power conversion apparatus according to the first aspect, in which the casing is internally divided into a plurality of spaces by a partition member, in which the casing includes the inverter and the junction box in different spaces, respectively, and the inverter and the junction box are connected to each other via the bus bar that passes through an opening formed in the partition member. 
         [0115]    A power conversion apparatus according to a sixth aspect is the power conversion apparatus according to the fifth aspect, in which a portion of the partition member where the opening is formed is insulated and coated. 
         [0116]    A power conversion apparatus according to a seventh aspect is the power conversion apparatus according to the fifth aspect, in which the junction box at least includes a portion that includes an insulation portion, that is inserted through the opening, and that serves as a connection portion for the bus bar. 
         [0117]    A power conversion apparatus according to an eighth aspect is the power conversion apparatus according to the fifth aspect, in which the casing is internally divided into a first space and a second space by the partition member, a first casing that forms the first space and a second casing that forms the second space are separable from each other, and the first and the second casings include fastening portions in the first and the second spaces, respectively, the fastening portions being included for fastening the first and the second casings together. 
         [0118]    A power conversion apparatus according to a ninth aspect is the power conversion apparatus according to the eighth aspect, in which the second casing includes a lid, in which, when the second casing is fastened to the first casing while being superimposed on the first casing, only the second casing includes an interlock that detects an open state of the lid of the second casing. 
         [0119]    A power conversion apparatus according to a tenth aspect is the power conversion apparatus according to the first aspect further including: a work window that is formed in the casing and that passes through the casing from an outer side of the casing to an inner side of the casing; a plurality of lids for closing the work window; and an interlock mechanism that interlocks with open and closed states of the plurality of lids, in which the plurality of lids include a first lid and a second lid that is fixed to the casing while superimposed over a part of the first lid, in which the interlock mechanism includes: an interlock switch disposed inside the casing; and an operation portion that is formed in the second lid, the operation portion being configured to respond to the interlock switch and to turn the interlock switch. 
         [0120]    A power conversion apparatus according to an eleventh aspect is the power conversion apparatus according to the tenth aspect further including a fastening portion at a portion where the second lid overlaps the first lid, the fastening portion being configured to fasten the first lid to the casing. 
         [0121]    A power conversion apparatus according to a twelfth aspect is the power conversion apparatus according to the tenth aspect further including three connection portions facing the work window, the three connection portions being used for a three-phase cable for conducting a three-phase alternating-current, in which the work window includes a window hole that is long in one direction or a plurality of window holes that are aligned in one direction or combination of the window hole and the plurality of widow holes. 
         [0122]    A power conversion apparatus according to a thirteenth aspect is the power conversion apparatus according to the twelfth aspect, in which the first lid is a metal lid and closes a portion of the work window where two of the three connection portions face the work window, and the second lid includes at least a resin-made portion and closes a portion of the work window where the remaining connection portion of the three connection portions faces the work window. 
         [0123]    A power conversion apparatus according to a fourteenth aspect is the power conversion apparatus according to the tenth aspect, in which the first lid is a metal lid that is fixed to the casing with a gasket interposed between the lid and the casing, and the second lid includes at least a resin-made portion and is fixed to the casing with an O-ring interposed between the lid and the casing. 
         [0124]    A power conversion apparatus according to a fifteenth aspect is the power conversion apparatus according to the first aspect, in which the inverter is an inverter circuit that outputs the alternating-current to the motor to be installed in a vehicle. 
         [0125]    A junction box according to a sixteenth aspect includes a protruding portion to be inserted into an opening formed in a partition member of a casing that is internally divided into a plurality of spaces by the partition member, in which the protruding portion includes an insulation portion and serves as a connection portion for a bus bar. 
         [0126]    The disclosures of Japanese Patent Applications No. 2013-078544, filed on Apr. 4, 2013, No. 2013-078546, filed on Apr. 4, 2013, and No. 2013-140526, filed on Jul. 4, 2013 including the specifications, drawings and abstracts, are incorporated herein by reference in their entireties. 
       INDUSTRIAL APPLICABILITY 
       [0127]    The present invention is applicable to a power conversion apparatus to be installed in a vehicle. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1  Vehicle 
           10  Partition member (bottom member) 
           11 ,  12  Casing 
           13  Inverter 
           14  Charging apparatus 
           15  Junction box 
           16  Bus bar 
           17  Opening 
           18  Lid 
           19  External power supply connection portion 
           20  External power supply 
           21  Screw 
           22  Screw hole 
           23  Insulation portion 
           24  Protruding portion 
           30  Battery 
           40  Motor 
           42  Output cable 
           42   a  Connection terminal 
           42   b  Cable clamp 
           51  Lid (first lid) 
           51   a  Fastening portion 
           52  Lid (Second lid) 
           522  Projection (operation portion) 
           52   a  Superimposed portion 
           100  Power conversion apparatus 
           111 ,  112  Work window 
           113  Projection 
           131  Connection portion 
           135  Interlock switch 
           135   a  Arm 
           511  Gasket 
           521  O-ring