Patent Publication Number: US-2017355272-A1

Title: In-vehicle structure of electric-power converter

Description:
INCORPORATION BY REFERENCE 
     The disclosure of Japanese Patent Application No. 2016-117126 filed on Jun. 13, 2016 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an in-vehicle structure of an electric-power converter that converts electric power of an electric power source into driving electric power for a traction motor. 
     2. Description of Related Art 
     An electric vehicle includes an electric-power converter configured to convert electric power of an electric power source into driving electric power for a traction motor. Note that the “electric vehicle” in the present specification includes not only an automobile provided with only an electric motor as a power source, but also an automobile provided with both a motor and an engine configured to generate a driving force for traveling. Further, the “electric vehicle” described in the present specification also includes a car provided with an electric power source (e.g., a fuel cell) other than a battery. 
     One type of the electric vehicle includes a traction motor and an electric-power converter provided in a front compartment (a space in front of a cabin). The electric-power converter may be fixed onto a motor housing in which a motor is accommodated (e.g., Japanese Patent Application Publication No. 2012-95482 (JP 2012-95482 A)). In one type of the electric-power converter, a connector for connecting a wiring harness for power supply to an auxiliary battery is provided on a top face of the electric-power converter (e.g.,  FIG. 1  in Japanese Patent Application Publication No. 2015-133803 (JP 2015-133803 A)). Note that the auxiliary battery is a battery configured to supply electric power to a device (e.g., a control board in the electric-power converter) operating with a voltage lower than a drive voltage for a traction motor. 
     SUMMARY 
     One type of the electric-power converter includes a capacitor configured to restrain a high-frequency fluctuation in a voltage of electric power supplied from an electric power source, and a discharge circuit configured to discharge the capacitor. The electric-power converter discharges the capacitor upon receipt of an instruction signal (a discharge instruction signal) from another device connected to a sensor (a pre-crash safety sensor, an air bag sensor, and the like) that detects a collision. Accordingly, a housing for the electric-power converter is provided with a connector (a signal connector) to which a wiring harness for signal communication to transmit the instruction signal is connected. Conventionally, the signal connector might be also provided on a top face of the electric-power converter similarly to the connector of JP 2015-133803 A. 
     When the electric-power converter is fixed onto a motor housing, the electric-power converter is placed in front of a cowl top. The cowl top curves like a halfpipe in order to store a wiper pivot therein, and its upper part sticks out toward a vehicle front side when viewed from a vehicle width direction. In a case where the signal connector is provided on the top face of the electric-power converter, when the electric-power converter that has received a collision load moves rearward at the time of a front collision or an oblique collision, the signal connector might make contact with the cowl top provided on a rear side. When the signal connector makes contact with the cowl top, the signal connector is damaged, so that a discharge instruction signal transmitted via the signal connector might not reach a discharge circuit and the discharge circuit might not operate appropriately. The present specification provides a structure in which a signal connector for transmitting a discharge instruction signal can hardly break at the time of a collision. 
     The present specification discloses an in-vehicle structure of an electric-power converter that converts electric power of an electric power source into driving electric power for a traction motor. In order to prevent contact between a signal connector and a cowl top at the time of a collision, it is conceivable that the signal connector is changed to be placed on a front face of the electric-power converter, on a rear face thereof at a position lower than the cowl top, or on a side face thereof facing in a vehicle width direction. However, the front face easily receives an impact at the time of a front collision, so the front face is not suitable for protection of the signal connector. At the position lower than the cowl top on the rear face, a high-voltage connector to which a power cable through which the electric power of the electric power source is transmitted to the electric-power converter is connected might be provided. Accordingly, in a range, of the rear face, which is lower than the cowl top, it might be difficult to secure a space in which the signal connector is placed. In view of this, in the in-vehicle structure described in the present specification, a signal connector is placed on the side face of the electric-power converter, the side face being facing in the vehicle width direction. With such a configuration, the signal connector can hardly break at the time of a collision in comparison with a case where the signal connector is placed in the other places. 
     The electric-power converter described in the present specification is fixed onto a motor housing in which a motor is accommodated and is also placed in front of a cowl top. A high-voltage connector to which a power cable through which the electric power of the electric power source is transmitted to the electric-power converter is connected is provided on a surface of the electric-power converter at a position lower than the cowl top, the surface being facing toward a vehicle rear side. The electric-power converter includes a capacitor configured to restrain a high-frequency fluctuation in a voltage of the electric power supplied from the electric power source, and a discharge circuit configured to discharge the capacitor. A signal connector to which a wiring harness for communication of a discharge instruction signal to operate the discharge circuit at a time of a collision is connected is provided on a side face of the electric-power converter, the side face facing in a vehicle width direction. The signal connector is provided on the side face of the electric-power converter and on a vehicle front side relative to a rear end of the electric-power converter, the side face of the electric-power converter being facing in the vehicle width direction. With such a configuration, when the electric-power converter moves backward at the time of a collision, the electric-power converter makes contact with the cowl top earlier than the signal connector so as to push the cowl top rearward. Besides, the signal connector is provided on the side face of the electric-power converter and on the vehicle front side relative to the rear end of the electric-power converter. Accordingly, even if the cowl top deforms and partially enters a lateral side of the electric-power converter, the cowl top thus deforming hardly hits the signal connector. As such, when the signal connector is provided on the side face of the electric-power converter and on the front side relative to the rear end of the electric-power converter, it is possible to avoid such a situation that the signal connector makes contact with the cowl top. With the in-vehicle structure, it is possible to reduce the possibility that the signal connector is damaged, as compared with a case where the signal connector is placed on the front face of the electric-power converter. 
     The signal connector may be positioned at a height similar to the cowl top, but it is preferable that the signal connector be provided on the electric-power converter at a position lower than the cowl top. In the former case, when the electric-power converter moves backward, the rear end of the electric-power converter makes contact with the cowl top so as to push the cowl top rearward. Accordingly, the signal connector provided on the side face of the electric-power converter which faces in the vehicle width direction is less likely to make contact with the cowl top. In the latter case, it is further possible to reduce the possibility that the signal connector makes contact with the cowl top. 
     Note that the high-voltage connector to which a power cable for transmission of electric power of the electric power source is connected is connected to the rear face of the electric-power converter at a position lower than the cowl top. With this structure, it is also possible to avoid such a situation that the high-voltage connector makes contact with the cowl top at the time of a collision. Technical details described in the present specification and further improvements thereof are described in “DETAILED DESCRIPTION OF EMBODIMENTS.” 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: 
         FIG. 1  is a block diagram of a driving system of a hybrid vehicle that employs an electric-power converter targeted for an in-vehicle structure of an embodiment; 
         FIG. 2  is a perspective view illustrating a device layout in a front compartment of the hybrid vehicle; 
         FIG. 3  is a view of the electric-power converter provided in the vehicle when viewed from a vehicle front side; 
         FIG. 4  is a sectional view taken along a line IV-IV in  FIG. 3 ; 
         FIG. 5  is a view of an electric-power converter in a conventional in-vehicle structure when viewed from a vehicle width direction; 
         FIG. 6  is a view illustrating an in-vehicle structure of a modification (a view of an electric-power converter when viewed from the vehicle width direction); 
         FIG. 7  is three face views illustrating a component layout inside a case of the conventional electric-power converter, and (A) is a plan view, (B) is a side view, and (C) is a rear view; and 
         FIG. 8  is three face views illustrating a component layout inside a case of the electric-power converter employed in the in-vehicle structure of the embodiment, and (A) is a plan view, (B) is a side view, and (C) is a rear view. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The following describes an in-vehicle structure of an embodiment with reference to the drawings. The in-vehicle structure of the embodiment is applied to a hybrid vehicle including two motors and one engine for traveling.  FIG. 1  illustrates a block diagram of a driving system of a hybrid vehicle  90 . Output shafts of two motors  8   a,    8   b  and an output shaft of an engine  91  are connected to a power distribution mechanism  92 . The power distribution mechanism  92  combines output torques of the motors  8   a,    8   b  and an output torque of the engine  91  appropriately, and transmits a resultant torque to an axle  93 . The power distribution mechanism  92  is more specifically a planetary gear, and the motor  8   a  is connected to its sun gear, the engine  91  is connected to its carrier, and the motor  8   b  and the axle  93  are connected to its ring gear. The power distribution mechanism  92  may transmit a part of the torque of the engine  91  to the motor  8   a  and may transmit a remaining torque to the axle  93 . In that case, the motor  8   a  generates electric power with the part of the torque of the engine  91 . Further, the power distribution mechanism  92  may transmit a torque of the axle  93  to the motors  8   a,    8   b  when a driver steps on a brake pedal. In that case, the motors  8   a,    8   b  generate electric power with the torque transmitted from the axle. The electric power obtained by the electric-power generation is used for charging of a high-voltage battery  3 . 
     The hybrid vehicle  90  includes the high-voltage battery  3  configured to supply electric power to the motors  8   a,    8   b.  The high-voltage battery  3  is a lithium-ion secondary battery, for example, and its output voltage is 100 volts or more. An electric-power converter  10  is connected between the high-voltage battery  3  and the motors  8   a,    8   b.  The electric-power converter  10  converts electric power of the high-voltage battery  3  into driving electric power for the motors  8   a,    8   b.  More specifically, the electric-power converter  10  boosts the electric power of the high-voltage battery  3  and converts the electric power thus boosted into an alternating current. Note that a system main relay  4  is connected between the high-voltage battery  3  and the electric-power converter  10 . The system main relay  4  is opened and closed in conjunction with a main switch (not shown). 
     The following describes a circuit configuration of the electric-power converter  10 . The electric-power converter  10  includes a first voltage converter circuit  19 , two inverter circuits  16   a,    16   b,  a second voltage converter circuit  24 , and a circuit substrate  25 . The first voltage converter circuit  19  is a so-called bidirectional DC-DC converter having a step-up function and a step-down function. The first voltage converter circuit  19  can boost a voltage of output power of the high-voltage battery  3  and supply it to the inverter circuits  16   a,    16   b  (the step-up function). Further, the first voltage converter circuit  19  can reduce a voltage of electric power (electric power generated by the motors  8   a,    8   b ) from the inverter circuits  16   a,    16   b  and supply it to the high-voltage battery  3  (the step-down function). The first voltage converter circuit  19  includes a filter capacitor  21 , a reactor  22 , and two serially-connected power transistors  17   a,    17   b.  A reflux diode is connected to each of the power transistors  17   a,    17   b  in an inverse parallel manner. A circuit structure of the first voltage converter circuit  19  is well known, so its detailed description is omitted. The power transistors  17   a,    17   b  are driven by a control circuit provided in the circuit substrate  25 . Note that the two serially-connected power transistors  17   a  and  17   b  are accommodated in one power module  18   a  as hardware. 
     Two inverter circuits  16   a,    16   b  are connected to a high-voltage side of the first voltage converter circuit  19 . Structures of the inverter circuits  16   a,    16   b  will be described. The inverter circuit  16   a  includes three sets of two power transistors connected in series. Power transistors  17   c  and  17   d  are connected in series, power transistors  17   e  and  17   f  are connected in series, and power transistors  17   g  and  17   h  are connected in series. A reflux diode is connected to each of the power transistors  17   c  to  17   h  in an inverse parallel manner. Three sets of serially-connected circuits are connected in parallel to each other. Each of the power transistors is driven by a control circuit provided on the circuit substrate  25 , so that an alternating current is output from a midpoint of each of the serial connections. The alternating currents output from three midpoints form a three-phase alternating current. The three-phase alternating current thus output from the inverter circuit  16   a  is supplied to the motor  8   a.  As hardware, the serial connection of the power transistors  17   c  and  17   d  is accommodated in a power module  18   b,  the serial connection of the power transistors  17   e  and  17   f  is accommodated in a power module  18   c,  and the serial connection of the power transistors  17   g  and  17   h  is accommodated in a power module  18   d.    
     Since the second inverter circuit  16   b  has the same structure as the inverter circuit  16   a,  a description thereof is omitted. A three-phase alternating current output from the inverter circuit  16   b  is supplied to the motor  8   b.  The inverter circuit  16   b  also includes three sets of two serially-connected power transistors, and those serial connections are accommodated in three power modules  18   e  to  18   g,  respectively. In the following description, the plurality of power transistors  17   a  to  17   h  may be referred to generally as a power transistor group  17 . 
     A smoothing capacitor  23  is connected between the first voltage converter circuit  19  and the inverter circuits  16   a,    16   b.  The smoothing capacitor  23  and the aforementioned filter capacitor  21  are provided so as to restrain a high-frequency fluctuation in a voltage of electric power supplied from the high-voltage battery  3 . 
     A second voltage converter circuit  24  is connected to the high-voltage battery  3 , in addition to the first voltage converter circuit  19 . The second voltage converter circuit  24  reduces an output voltage of the high-voltage battery  3  to a drive voltage of accessories. The “accessories” is a general term of a device group operating at a voltage lower than the drive voltage of the motors  8   a,    8   b,  and its operating voltage is around 10 to 50 volts. The circuit substrate  25  provided in the electric-power converter  10  and a HV controller  6  that controls a whole system of the hybrid vehicle  90  belong to the accessories. The electric power, the voltage of which is reduced by the second voltage converter circuit  24 , is supplied to the circuit substrate  25 , the HV controller  6 , other accessories, and an auxiliary battery  5 . The auxiliary battery  5  is provided so as to supply electric power to the accessories while electric power is not supplied from the electric-power converter  10 . The auxiliary battery  5  and negative electrodes of the accessories are electrically conductive to each other via a vehicle body (a body ground G). 
     When a vehicle has a collision, the control circuit provided on the circuit substrate  25  drives the power transistor group  17  in response to a signal (a discharge instruction signal) from the HV controller  6 , so as to discharge the capacitors  21 ,  23 . More specifically, the control circuit controls the power transistor group  17  so that the electric power of the capacitors  21 ,  23  is discharged through the reactor  22  and the motors  8   a,    8   b.  The circuit substrate  25 , the first voltage converter circuit  19 , and the inverter circuits  16   a,    16   b  at the time of discharging the capacitors  21 ,  23  may be generally referred to as a discharge circuit  26  for convenience of description. 
     An air bag sensor  7  (an acceleration sensor) is connected to the HV controller  6 . When the vehicle has a collision, the air bag sensor  7  transmits, to the HV controller  6 , a signal (a collision detection signal) indicative of the collision. More specifically, when a magnitude (a magnitude of acceleration) of the collision that the vehicle has exceeds a predetermined threshold, the air bag sensor  7  transmits the collision detection signal to the HV controller  6 . Upon receipt of the collision detection signal from the air bag sensor  7 , the HV controller  6  opens the system main relay  4  and transmits a discharge instruction signal to the electric-power converter  10 . 
     A connector connected to the electric-power converter  10  will be described. Four connectors are provided in the electric-power converter  10 . One of them is a connector (a signal connector  14 ) to which a wiring harness  52  for communication of the discharge instruction signal and a low-voltage power supply harness  59  for transmitting electric power of the auxiliary battery  5  to the circuit substrate  25  are connected. Note that, in  FIG. 1 , only one line is illustrated as the wiring harness  52 , but the wiring harness  52  can include other various signal lines. Another one of them is a connector (a high-voltage connector  12 ) to which a cable (a high-voltage power supply cable  51 ) for transmitting electric power of the high-voltage battery  3  to the electric-power converter  10  is connected. Further another one of them is a connector (a low-voltage connector  13 ) to which a cable (a low-voltage power supply cable  54 ) for transmitting output power of the second voltage converter circuit  24  to the auxiliary battery  5  is connected. Although not illustrated in  FIG. 1 , another communication cable (the after-mentioned communication cable  55 ) is also connected to the low-voltage connector  13 . The communication cable  55  is a cable that connects the HV controller  6 , which is a superior control device of the electric-power converter  10 , to the second voltage converter circuit  24  inside the electric-power converter  10 . The HV controller  6  monitors a residual quantity of the auxiliary battery  5 , and controls the second voltage converter circuit  24  depending on the residual quantity. The communication cable  55  is provided for that purpose. The last one of them is a connector (a motor cable connector  15 ) to which a motor power cable  53  for transmitting output alternating currents of the inverter circuits  16   a,    16   b  to the motors  8   a,    8   b  is connected. 
     Next will be described an arrangement of the electric-power converter  10  on the vehicle and an arrangement of the connectors described above.  FIG. 2  is a perspective view illustrating a device layout in a front compartment FC of the hybrid vehicle  90 . In a coordinate system in  FIG. 2 , an F-axis indicates a vehicle front side, an H-axis indicates a vehicle width direction, and a V-axis indicates a vehicle upper side. In  FIGS. 3 to 6  to be described later, each axis in their coordinate systems indicates the same meaning as above. In  FIG. 2 , an engine hood is not illustrated. 
     The engine  91 , a transaxle  37 , the electric-power converter  10 , the auxiliary battery  5 , and the like are provided in the front compartment FC. Note that various components are further provided in the front compartment FC, but components other than the above components are not described herein. In the transaxle  37 , the traction motors  8   a,    8   b,  the power distribution mechanism  92 , and a differential gear are accommodated. The transaxle  37  can be expressed as a motor housing in which the traction motors  8   a,    8   b  are accommodated. The transaxle  37  is connected to the engine  91  in the vehicle width direction. As has been described earlier, the output shaft of the engine  91 , the output shafts of the motors  8   a,    8   b,  and the axle  93  (the differential gear) are connected to the power distribution mechanism  92  inside the transaxle  37 . The engine  91  and the transaxle  37  are suspended between two side members  94  extending in a vehicle front-rear direction below the front compartment FC. Note that one of the body side members is covered and therefore not observable in  FIG. 2 . 
     The electric-power converter  10  is fixed onto the transaxle  37  via a front bracket  36  and a rear bracket  35 . 
       FIG. 3  illustrates a view of the electric-power converter  10  provided in the vehicle when viewed from the vehicle front side and  FIG. 4  illustrates a sectional view taken along a line IV-IV in  FIG. 3 .  FIG. 4  corresponds to a view of the electric-power converter  10  provided in the vehicle when viewed in the vehicle width direction. After  FIG. 2 , an in-vehicle structure of the electric-power converter  10  is indicated by a reference sign  2 . In  FIG. 3 , the engine hood that covers the front compartment FC is not illustrated. In  FIG. 4 , in order to assist understanding, an internal structure of the transaxle  37  and the like is not illustrated. In the following description, with reference to  FIGS. 3, 4  as well as  FIG. 2 , the in-vehicle structure  2  of the electric-power converter  10 , particularly, an arrangement of the signal connector  14  will be described. 
     As illustrated in  FIG. 4 , due to the front bracket  36  and the rear bracket  35 , a gap is secured between a top face of the transaxle  37  and the electric-power converter  10 . This is to protect the electric-power converter  10  from the vibration of the engine  91  and the vibration of the motors  8   a,    8   b.  Although not illustrated herein, a damping bush is sandwiched between the front bracket  36  and the electric-power converter  10  and between the rear bracket  35  and the electric-power converter  10 . The electric-power converter  10  is supported by the front bracket  36  and the rear bracket  35 , and therefore, at the time of a front collision, the electric-power converter  10  may move backward upon receipt of a collision load from the front side. 
     The low-voltage connector  13  is provided on a surface of the electric-power converter  10 , the surface facing the vehicle front side, and the signal connector  14  and the motor cable connector  15  are provided on a side face of the electric-power converter  10 , the side face facing in the vehicle width direction. The signal connector  14  is attached on the vehicle front side relative to a rear end of the electric-power converter  10 . The high-voltage connector  12  is provided on a surface of the electric-power converter  10 , the surface facing a vehicle rear side. As has been described earlier, the low-voltage power supply cable  54  (a cable for transmitting output power of the second voltage converter circuit  24  to the auxiliary battery  5 ) and the communication cable  55  are connected to the low-voltage connector  13 , and the wiring harness  52  for communication of the discharge instruction signal and the low-voltage power supply harness  59  are connected to the signal connector  14 . Note that various signal cables are bundled up in the wiring harness  52  as well as the signal cable for communication of the discharge instruction signal, so the wiring harness  52  is illustrated thickly in  FIGS. 3, 4 . The motor power cable  53  (a cable for transmitting output alternating currents of the inverter circuits  16   a,    16   b  to the motors  8   a,    8   b ) is connected to the motor cable connector  15 . The high-voltage power supply cable  51  (a cable for transmitting electric power of the high-voltage battery  3  to the electric-power converter  10 ) is connected to the high-voltage connector  12 . 
     A cowl top  31  made of metal is placed on the vehicle rear side of the front compartment FC. The cowl top  31  extends in the vehicle width direction, and as illustrated in  FIG. 4 , a section cut along a plane expanding in the vehicle front-rear direction (an F-axis direction in the figure) and a vehicle up-down direction (a V-axis direction in the figure) has a curved shape opened upward. In other words, the cowl top  31  has a shape like a halfpipe opened upward. The cowl top  31  curves so that its bottom face gradually becomes high toward the vehicle front side. A rear edge of the cowl top  31  makes contact with a lower ledge of a windshield  99 , and an engine hood  97  that covers the front compartment FC makes contact with its front edge (see  FIG. 4 ). A wiper pivot  34  is placed inside the curve in an upper part of the cowl top  31 . The wiper pivot  34  is supported by a pivot holder  98 . The pivot holder  98  is fixed to the cowl top  31 . The upper part of the cowl top  31  that is opened upward is covered with a cowl louver  32  made of resin. An upper end of the wiper pivot  34  penetrates through the cowl louver  32 , and a part thereof is exposed. A wiper  33  is connected to a part of the wiper pivot  34  which sticks out from the cowl louver  32 . Note that the wiper  33  is not illustrated in  FIG. 4 . A dash panel  96  continues below the cowl top  31 . The dash panel  96  is a metal plate that separates the front compartment FC from a cabin. Note that the cowl top  31  may be called a cowl top panel. 
     In order to describe the advantage of the in-vehicle structure  2  in  FIGS. 2 to 4 ,  FIG. 5  illustrates an in-vehicle structure  102  of an electric-power converter  100  including a signal connector  114  provided on its top face, as a comparative example. Differences between  FIG. 4  and  FIG. 5  are only a mounted position of the signal connector and whether another communication cable  55  is provided or not.  FIG. 4  and  FIG. 5  have the same positional relationship between the electric-power converter  10  (the electric-power converter  100  in the comparative example) and the cowl top  31 . A broken line A in  FIGS. 4 and 5  indicates a height of a bottom end of the cowl top  31 . As has been described earlier, the electric-power converter  10  (the electric-power converter  100 ) is supported on the transaxle  37  by the front bracket  36  and the rear bracket  35 . At the time of a front collision, the electric-power converter  10  may move backward due to a collision load from the front side. Further, when the electric-power converter  10  (the electric-power converter  100 ) is fixed onto the transaxle  37 , the electric-power converter  10  (the electric-power converter  100 ) is placed in front of the cowl top  31 . In the meantime, as has been described earlier, the cowl top  31  has such a shape that its bottom face gradually becomes high toward the vehicle front side. When the signal connector  114  is provided on the top face of the electric-power converter  100  as illustrated in  FIG. 5 , the signal connector  114  makes contact with the cowl top  31  at the time when the electric-power converter  100  moves backward, so that the signal connector  114  might be damaged. As described above with reference to  FIG. 1 , at the time of a collision, the electric-power converter  10  (the electric-power converter  100 ) receives a discharge instruction signal via the wiring harness  52  and the signal connector  14  (the signal connector  114 ), so as to discharge the capacitor provided therein. In a case of the in-vehicle structure  102  of  FIG. 5 , when the signal connector  114  is damaged due to the contact with the cowl top  31  at the time of the collision, the discharge instruction signal might not reach a circuit substrate  25  inside the electric-power converter  100 . In the meantime, in a case of the in-vehicle structure  2  of the embodiment ( FIG. 4 ), a part of the signal connector  14  is positioned higher than a bottom end of the cowl top  31 , but the signal connector  14  is provided on the side face of the electric-power converter  10  which faces in the vehicle width direction. When the electric-power converter  10  moves backward, the electric-power converter  10  makes contact with the cowl top  31  earlier than the signal connector  14  so as to push the cowl top  31  rearward. Accordingly, the signal connector  14  provided on the surface of the electric-power converter  10  which faces in the vehicle width direction can avoid the contact with the cowl top  31 . Note that, when the electric-power converter  10  moves backward to push the cowl top  31  rearward, the cowl top  31  is bent by a corner of a boundary between the side face and the rear face of the electric-power converter  10 . A part of the cowl top  31  comes close to the side face of the electric-power converter  10 . Since the signal connector  14  is positioned on the vehicle front side relative to the rear end of the electric-power converter  10 , the signal connector  14  can hardly hit the cowl top  31  that is bent to come close thereto. In the in-vehicle structure  2  of the embodiment, it is possible to avoid such a situation that the signal connector  14  collides with the cowl top  31  at the time when the electric-power converter  10  moves backward, so that the discharge instruction signal is transmitted to the discharge circuit provided therein. As a result, the internal capacitor is discharged surely. 
     An in-vehicle structure  2   a  of a modification is illustrated in  FIG. 6 . In the in-vehicle structure  2  of  FIG. 4 , a part of the signal connector  14  is positioned higher than the bottom end of the cowl top  31 . In the in-vehicle structure  2   a  of  FIG. 6 , a signal connector  14   a  is provided at a position lower than the bottom end of the cowl top  31 . With such a configuration, it is possible to more surely protect the signal connector  14   a  from a collision with the cowl top  31  at the time of a front collision. 
     In the in-vehicle structure  2  of  FIG. 4  and the in-vehicle structure  2   a  of  FIG. 6 , the high-voltage connector  12  is provided on the surface (the rear face) of the electric-power converter  10  at a position lower than the cowl top  31 , the surface facing the vehicle rear side. Accordingly, even if the electric-power converter  10  moves backward, the high-voltage connector  12  does not make contact with the cowl top  31 . Hereby, the high-voltage connector  12  is protected, and it is avoided that a conductor to which a high voltage is applied is exposed. Further, the providing of the high-voltage connector  12  on the rear face of the electric-power converter  10  has such an advantage that, even if the vehicle collides with an obstacle from a lateral side of the vehicle, the high-voltage connector  12  can hardly be damaged. 
     Below are notes regarding the in-vehicle structure described in the embodiment. The electric-power converter  10  employed in the in-vehicle structure of the embodiment includes the signal connector  14  ( 14   a ) provided on a side face of its housing. The providing of the signal connector  14  ( 14   a ) on the side face of the housing has such an advantage that moisture content can hardly enter the housing in comparison with a case where the signal connector  14  ( 14   a ) is provided on the top face of the housing. 
     In the electric-power converter  10  of the embodiment, the wiring harness  52  for communication of the discharge instruction signal and the low-voltage power supply harness  59  for transmitting electric power of the auxiliary battery  5  to the circuit substrate  25  are connected to the signal connector  14  ( 14   a ). The low-voltage power supply harness  59  may be a structure connected to the electric-power converter  10  not by the signal connector  14  ( 14   a ), but by other connectors. 
     The in-vehicle structure  2 ,  2   a  of the embodiment is applied to a hybrid vehicle including motors and an engine. The in-vehicle structure described in the present specification is also preferably applied to an electric vehicle or a fuel-cell vehicle that does not include an engine. 
     The wiring harness  52  of the embodiment corresponds to one example of a “wiring harness for communication of a discharge instruction signal” in Claims. The transaxle  37  in which the motors  8   a,    8   b  are accommodated corresponds to one example of a “motor housing” in Claims. 
     In the electric-power converter  100  of  FIG. 5 , the signal connector  114  is provided on its top face, and in the electric-power converter  10  of  FIG. 4 , the signal connector  14  is provided on the side face facing in the vehicle width direction. The reason why the position of the signal connector can be changed from the top face of the electric-power converter  100  to the surface that faces in the vehicle width direction is because the components accommodated in the housing of the electric-power converter  10  are downsized and the layout thereof is changed. The following describes the difference between a component layout inside the electric-power converter  100  of  FIG. 5  and a component layout inside the electric-power converter  10  of  FIG. 4 .  FIG. 7  is a schematic view of the component layout of the electric-power converter  100  of  FIG. 5 , and  FIG. 8  is a schematic view of the component layout of the electric-power converter  10  of  FIG. 4 . In  FIGS. 7, 8 , (A) indicates a plan view, (B) indicates a side view, and (C) indicates a rear view. In the coordinate system in the figures, an X-axis corresponds to the vehicle front-rear direction, a Y-axis corresponds to the vehicle width direction, and a Z-axis corresponds to the vehicle up-down direction. In the following description, for convenience of description, an X-axis positive direction is referred to as a “front side,” and an X-axis negative direction is referred to as a “rear side.” Further, a Z-axis positive direction is referred to as an “upper side,” and a Z-axis negative direction is referred to as a “lower side.” A Y-axis direction is referred to as the vehicle width direction. 
     In three face views of  FIGS. 7, 8 , only a contour of the housing is indicated by a broken line so that the component layout inside the housing can be understood. Further, in the plan view of (A) of  FIG. 7 , the circuit substrate  25  and the signal connector  114  are not illustrated. In the plan view of (A) of  FIG. 8 , the circuit substrate  25  is not illustrated. In  FIGS. 7, 8 , wiring lines that connect the components to each other are not illustrated except for an inner cable  67  of  FIG. 7 . 
     The electric-power converter  100  and the electric-power converter  10  have the same outside diameter dimension (length L×width W×height H). The component layout of the electric-power converter  100  will be described first. In the electric-power converter  100 , a converter unit  66   a  is placed in a lowermost layer of a case. The converter unit  66   a  corresponds to the second voltage converter circuit  24  in  FIG. 1 . The low-voltage connector  13  is placed in front of the converter unit  66   a.  As illustrated in  FIG. 5 , the low-voltage connector  13  is exposed on a front face (a surface that faces toward the vehicle front side) of the electric-power converter  100 . 
     A cooler  64  is placed so as to make contact with a top face of the converter unit  66   a.  A reactor  22  is placed so as to make contact with a top face of the cooler  64 . A power stack  61  is placed in front of the reactor  22 . The power stack  61  is a device in which the plurality of power modules  18   a  to  18   g  described in  FIG. 1  and a plurality of cooling plates (not shown) are laminated. In  FIGS. 7, 8 , the power stack  61  is simply illustrated as a rectangular solid. The aforementioned cooler  64  mainly cools down the converter unit  66   a  and the reactor  22 . The power modules  18   a  to  18   g  with a large amount of heat generation are cooled by the plurality of cooling plates in the power stack  61 . 
     A current sensor unit  62  is placed on one side of the power stack  61  in the vehicle width direction, and a smoothing capacitor  23  is placed on the other side. The current sensor unit  62  is a unit for measuring a current of each phase of two sets of three-phase alternating currents. A part (a part exposed from the case of the electric-power converter  100 ) of the current sensor unit  62  corresponds to the aforementioned motor cable connector  15 . 
     A filter capacitor  21  is placed behind the reactor  22 . An inner connector  63  is positioned above the filter capacitor  21 . The high-voltage connector  12  is placed behind the inner connector  63 . The circuit substrate  25  is placed above the smoothing capacitor  23 , the power stack  61 , and the inner connector  63 . The inner connector  63  is connected to the converter unit  66   a  by the inner cable  67 , and an upper end of the inner connector  63  is connected to the circuit substrate  25 . The circuit substrate  25  controls the converter unit  66   a  via the inner connector  63  and the inner cable  67 . 
     The signal connector  114  is connected to the top face of the circuit substrate  25 . An upper part of the signal connector  114  is exposed from the top face of the electric-power converter  100 . That is, the signal connector  114  is provided on the top face of the electric-power converter  100 . 
     With reference to  FIG. 8 , the following describes the inner layout of the electric-power converter  10 . In the electric-power converter  10 , a cooler  64  is placed in a bottom end of a housing, and a converter unit  66   b  is placed thereon. The converter unit  66   b  corresponds to the second voltage converter circuit  24  in  FIG. 1 . The converter unit  66   b  is downsized in comparison with the converter unit  66   a  of  FIG. 7 , and its length in the vehicle front-rear direction is shortened. In the electric-power converter  10 , the converter unit  66   b  is shortened, so that the reactor  22  is placed behind the converter unit  66   b.  Further, in the electric-power converter  100 , the inner connector  63  is placed above the reactor  22 , but in the electric-power converter  10 , the inner connector  63  and the inner cable  67  can be eliminated. The reason is as follows. As has been described earlier, the electric-power converter  10  (and the electric-power converter  100 ) is connected to the superior HV controller  6 , and the HV controller  6  controls the second voltage converter circuit  24  (the converter unit  66   b ). In the electric-power converter  100 , a communication line from the HV controller  6  is connected to the signal connector  114  on the top face of the electric-power converter  100 , and the converter unit  66   a  and the HV controller  6  are connected to each other via the signal connector  114 , the inner connector  63 , and the inner cable  67 . In the electric-power converter  10  of the embodiment, the communication cable (the communication cable  55 ) from the HV controller  6  is connected to the low-voltage connector  13  placed on the front face of the electric-power converter  10 . The HV controller  6  is connected to the converter unit  66   b  via the communication cable  55  and the low-voltage connector  13  positioned right in front of the converter unit  66   b.  With this structure, the inner connector  63  and the inner cable  67  can be eliminated. 
     Further, in the electric-power converter  10 , a capacitor unit  68  is placed on a lateral side of a power stack  61 . The capacitor unit  68  accommodates two capacitor elements therein. One capacitor element corresponds to the filter capacitor  21  of  FIG. 1 , and the other capacitor element corresponds to the smoothing capacitor  23  of  FIG. 1 . In comparison with the electric-power converter  100 , the electric-power converter  10  employs small capacitor elements and unifies two capacitor elements as one unit, so as to increase space efficiency. 
     With such differences, the electric-power converter  10  can secure a sufficient space on the lateral side (the side along the vehicle width direction) of the circuit substrate  25 , so that the signal connector  14  can be placed in the space. 
     The embodiment of the in-vehicle structure of an electric-power converter configured to convert electric power of an electric power source into driving electric power for a traction motor may be defined as follows. The electric-power converter is fixed onto a motor housing in which the motor is accommodated, the electric-power converter is provided ahead of a cowl top in a front-rear direction of a vehicle, a high voltage connector is configured to connect to a power cable that transmits the electric power of the electric power source to the electric-power converter, the high voltage connector is provided on a rear surface of the electric-power converter in the front-rear direction of the vehicle, the high voltage connector is provided at a position lower than the cowl top, the electric-power converter includes a capacitor configured to restrain a high-frequency fluctuation in a voltage of the electric power supplied from the electric power source, and a discharge circuit configured to discharge the capacitor, a signal connector is configured to connect to a wiring harness that transmits a discharge instruction signal for operating the discharge circuit to the discharge circuit at a time of a collision, the signal connector is provided on one of right and left side surfaces of the electric-power converter in a width direction of the vehicle, and the signal connector is provided ahead of a rear end of the electric-power converter in the front-rear direction of the vehicle. The specific example of the disclosure has been explained in detail. However, the example is for illustration only, and does not limit the scope of the claims. The technique described in the scope of the claims includes the foregoing example with various modifications and changes. Each of and various combinations of the technical elements explained in this specification and the drawings achieve technical utility, and the technical elements are not limited to the combination stated in the claims at the time of filing. The technique explained in this specification and the drawings as an example is able to achieve the plurality of objectives simultaneously, and has technical utility by achieving one of the objectives.