Abstract:
The electric motor control unit of this electric vehicle is disposed at a first primary surface and/or a facing second primary surface of a plate-shaped member disposed along the anterior-posterior direction of the electric vehicle and having a higher rigidity than peripheral components or vehicle-configuring elements. An electricity storage device is connected to the electric motor control unit by means of wiring and is disposed on the vehicle cabin side of the plate-shaped member in the anterior-posterior direction. Furthermore, the electric motor control unit is provided with a low-voltage circuit unit and a high-voltage circuit unit. The high-voltage circuit unit is disposed on the vehicle cabin side in the anterior-posterior direction with respect to the low-voltage circuit unit.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an electric vehicle having an electric motor controller configured to control an electric motor that propels a vehicle. More particularly, the present invention relates to an electric vehicle which is capable of protecting the electric motor controller when impact force is applied to the electric vehicle from the front or rear end thereof. 
       BACKGROUND ART 
       [0002]    There has been proposed a technology for protecting an electric motor controller on an electric vehicle at the time of vehicle collision {U.S. Patent Application Publication No. 2010/0283337 (hereinafter referred to as “US 2010/0283337 A1”)}. According to US 2010/0283337 A1, an objection thereof is to provide a vehicle drive apparatus which appropriately protects a power control unit against an external impact thereon (see Abstract and paragraph [0008]). 
         [0003]    In order to achieve the above object, the vehicle drive apparatus, denoted by  20 , according to US 2010/0283337 A1 includes motor generators MG 1 , MG 2  for generating driving forces and a power control unit (PCU)  21  integrally combined with the motor generators MG 1 , MG 2  for controlling the motor generators MG 1 , MG 2  (see paragraph [0027]). The PCU  21  includes a low-voltage circuit section  71  to which a relatively low voltage is applied, a high-voltage circuit section  75  disposed at a rear side of the vehicle relative to the low-voltage circuit section  71  and to which a relatively high voltage is applied, and a cooling plate  72  for cooling the high-voltage circuit section  75 , the cooling plate  72  being disposed between the low-voltage circuit section  71  and the high-voltage circuit section  75  in the longitudinal direction of the vehicle (see Abstract, paragraphs [0055], [0057] through [0059], and  FIG. 4 ). 
         [0004]    According to US 2010/0283337 A1, when the vehicle drive apparatus  20  is subjected to an impact from the front end of the vehicle, the low-voltage circuit section  71  absorbs the impact, and the cooling plate  72  that serves to increase the mechanical strength of the front side of the high-voltage circuit section  75  buffers the impact which reaches the high-voltage circuit section  75  to which a high voltage is applied, thereby protecting the PCU  21  from the impact appropriately (see paragraphs [0010] and [0064]). On the rear side of the high-voltage circuit section  75 , a water jacket  74 , a portion of an MG 2 /inverter case  64  (a right wall of the water jacket  74  in  FIG. 4 ), and the motor generator MG 2  are disposed (see  FIGS. 4 through 6 ). 
       SUMMARY OF INVENTION 
       [0005]    According to US 2010/0283337 A1, as described above, the low-voltage circuit section  71  and the cooling plate  72  are used to protect the high-voltage circuit section  75 . However, the invention of US 2010/0283337 A1 is based on the idea of protecting the high-voltage circuit section  75  with the low-voltage circuit section  71 , and thus the low-voltage circuit section  71  is not protected. 
         [0006]    According to US 2010/0283337 A1, furthermore, the high-voltage circuit section  75  is sandwiched between the cooling plate  72 , and the water jacket  74 , the portion of the MG 2 /inverter case  64  and the motor generator MG 2  in the longitudinal directions of the vehicle. Consequently, when the vehicle drive apparatus  20  is subjected to an impact from the front end of the vehicle, the high-voltage circuit section  75  may possibly be stuck between and damaged by these components, i.e., the cooling plate  72 , the water jacket  74 , the portion of the MG 2 /inverter case  64 , and the motor generator MG 2 . 
         [0007]    According to US 2010/0283337 A1, moreover, the high-voltage circuit section  75  is disposed on a rear cooling surface of the cooling plate  72 , but not on a front cooling surface thereof. Therefore, the cooling plate  72  tends to be large in size. 
         [0008]    The present invention has been made in view of the above problems. It is an object of the present invention to provide an electric vehicle which offers improved protection to an electric motor controller in the event of an impact along the longitudinal directions of the vehicle. 
         [0009]    According to the present invention, there is provided an electric vehicle including an electric motor configured to propel the vehicle, an electric storage device configured to supply electric power to the electric motor, an electric motor controller configured to control the electric motor by use of the electric power supplied from the electric storage device to the electric motor, and a peripheral component or a vehicle component of the vehicle which is disposed around the electric motor controller, wherein the electric motor controller is disposed on at least one of a first principal surface and a second principal surface, which is opposite to the first principal surface, of a plate-like member disposed along a longitudinal direction of the vehicle, the plate-like member being more rigid than the peripheral component or the vehicle component, and the electric storage device is disposed more closely to a passenger compartment of the vehicle than the plate-like member in the longitudinal direction of the vehicle, and connected to the electric motor controller by electric wires. 
         [0010]    According to the present invention, the plat-like member is more rigid than the peripheral component or the vehicle component and lies along longitudinal directions of the vehicle. When an impact force is applied to the electric vehicle toward the passenger compartment along the longitudinal direction of the vehicle so that the peripheral component or the vehicle component presses the plate-like member, the plate-like member is prevented from being crushed in the longitudinal directions of the vehicle. Therefore, the electric motor controller that is disposed on at least one of the first and second principal surfaces of the plate-like member can be prevented from being damaged. If the electric motor controller is disposed on both the first and second principal surfaces of the plate-like member, then the electric motor controller is prevented from being damaged on both of the first and second principal surfaces. 
         [0011]    According to the present invention, furthermore, the electric motor controller is disposed on at least one of the first and second principal surfaces of the plate-like member. Therefore, when the plate-like member is pressed by the peripheral component or the vehicle component upon collision of the vehicle and is displaced so as to slide in the longitudinal direction of the vehicle, the electric motor controller can be prevented from being pressed between the plate-like member and the peripheral component or vehicle component. 
         [0012]    According to the present invention, moreover, if the electric motor controller is disposed on both the first and second principal surfaces of the plate-like member, then the plate-like member can be prevented from being increased in size compared to a case where the electric motor controller is disposed on one of the first and second principal surfaces. 
         [0013]    According to the present invention, in addition, the electric storage device is disclosed more closely to the passenger compartment of the vehicle than the plate-like member in the longitudinal direction of the vehicle, and connected to the electric motor controller by electric wires. Consequently, when the peripheral component or the vehicle component presses the plate-like member toward the passenger compartment upon collision of the vehicle, the electric wires are displaced toward the electric storage device, or stated otherwise, in a direction in which the electric wires shrink. Therefore, the electric wires that interconnect the electric storage device and the electric motor controller can be prevented from being stretched and damaged. 
         [0014]    The electric motor controller may include a low-voltage circuit section to which a relatively low prescribed voltage is applied and a high-voltage circuit section to which a voltage higher than the voltage applied to the low-voltage circuit section is applied. The high-voltage circuit section may be disposed more closely to the passenger compartment than the low-voltage circuit section in the longitudinal direction of the vehicle. Consequently, when the peripheral component or the vehicle component presses the plate-like member toward the passenger compartment upon collision of the vehicle, the low-voltage circuit section undergoes the impact earlier than the high-voltage circuit section. Therefore, the high-voltage circuit section can be further effectively prevented from being damaged. 
         [0015]    In the above arrangement, the high-voltage circuit section is disposed more closely to the passenger compartment than the low-voltage circuit section in the longitudinal direction of the vehicle. Therefore, the high-voltage circuit section and the low-voltage circuit section can be positioned in different areas separated in the longitudinal direction of the vehicle on the first or second principal surface of the plate-like member. Therefore, even if the high-voltage circuit section and the low-voltage circuit section are disposed on one principal surface of the plate-like member, the high-voltage circuit section can be prevented from being positioned relatively closely to the low-voltage circuit section. As a result, noise that the low-voltage circuit section receives from the high-voltage circuit section is reduced, and hence the low-voltage circuit section can be prevented from malfunctioning in the electric motor controller. 
         [0016]    The high-voltage circuit section may have high-voltage terminals disposed on the first principal surface or the second principal surface of the plate-like member most closely to the passenger compartment, and the electric wires may be connected to the electric storage device and the high-voltage terminals of the high-voltage circuit section. Consequently, when the peripheral component or the vehicle component presses the plate-like member toward the passenger compartment upon collision of the vehicle, the other components than the high-voltage terminals and the electric wires undergo the impact earlier than the high-voltage terminals and the electric wires. Therefore, the high-voltage terminals and the electric wires can be further effectively prevented from being damaged. In addition, as the length of the electric wires that interconnect the electric storage device and the electric motor controller can be relatively shortened, power loss caused by the electric wires can be reduced. 
         [0017]    The high-voltage circuit section may include an inverter configured to convert a DC voltage from the electric storage device into an AC voltage and at least one of a first converter configured to step up or down the DC voltage from the electric storage device and a second converter configured to convert an AC voltage from an external power supply into a DC voltage. The inverter may be disposed on one of the first principal surface and the second principal surface of the plate-like member, and the at least one of the first converter and the second converter may be disposed on the other of the first principal surface and the second principal surface. Therefore, the inverter and the first converter or the second converter, each in the form of a high-voltage circuit, can be positioned on mutually different surfaces of the plate-like member. The plate-like member is thus prevented from increasing in size while it effectively cools the inverter and the first converter or the second converter, which each are a heat generator. 
         [0018]    If the electric wires are connected to the electric storage device and the high-voltage terminals of the high-voltage circuit section, then the high-voltage circuit section may include high-voltage bus bars interconnecting the high-voltage terminals, and the inverter, the first converter, or the second converter. 
         [0019]    The low-voltage circuit section may have a communication line configured to supply a signal for operating the inverter, the first converter, or the second converter. The high-voltage circuit section may include a current sensor connected to a supply line configured to supply the AC voltage from the inverter to the electric motor, and the low-voltage circuit section may include a communication line configured to control the current sensor. The high-voltage circuit section may include contactors connected between charging connectors and the electric storage device, and the low-voltage circuit section may include communication lines configured to control the contactors. 
         [0020]    The plate-like member may include, for example, a cooling plate having coolant channels configured to pass a coolant therethrough. 
         [0021]    The peripheral component may include a radiator for the coolant or a radiator supporting frame supporting the radiator. The vehicle component may include a front bumper member or a rear bumper member, for example. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0022]      FIG. 1  is an overall schematic block diagram of an electric power system, a cooling system, and their related components of an electric vehicle according to an embodiment of the present invention; 
           [0023]      FIG. 2  is a sectional perspective view showing partial structural details and positional relationship of a power control unit (hereinafter referred to as “PCU”) on the electric vehicle; 
           [0024]      FIG. 3  is a side elevational view schematically showing the layout of the PCU and its related components on the electric vehicle; 
           [0025]      FIG. 4  is a plan view showing specific component layout and wiring details on an upper principal surface (hereinafter referred to as “upper surface”) of a cooling portion; 
           [0026]      FIG. 5  is a bottom view showing, in a vertically reversed fashion, specific component layout and wiring details on a lower principal surface (hereinafter referred to as “lower surface”) of the cooling portion; 
           [0027]      FIG. 6A  is a view showing the manner in which a radiator is displaced when the electric vehicle collides on its front end; 
           [0028]      FIG. 6B  is a view showing the manner in which the radiator is brought into contact with the PCU when the electric vehicle collides on its front end; and 
           [0029]      FIG. 7  is a side elevational view schematically showing the layout of the PCU and its related components on an electric vehicle according to a modification. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
     A. Embodiment: 
     1. Description of Overall Arrangement: 
     [1-1. Overall Arrangement] 
       [0030]      FIG. 1  shows in schematic block form an electric power system  100 , a cooling system  200 , and their related components of an electric vehicle  10  (hereinafter referred to as “vehicle  10 ”) according to an embodiment of the present invention.  FIG. 2  shows in sectional perspective partial structural details and positional relationship of a power control unit  12  (hereinafter referred to as “PCU  12 ”) mounted as an electric motor controller on the electric vehicle  10 . 
         [0031]    As shown in  FIG. 1 , the electric power system  100  of the vehicle  10  includes the PCU  12 , a traction motor  14  (hereinafter referred to as “motor  14 ”) as an electric motor, a high-voltage battery  16  (hereinafter referred to as “battery  16 ”) as an electric storage device, a 12-volt system  18 , a normal charging connection  20 , and a quick charging connection  22 . 
         [0032]    The PCU  12  includes an inverter  30 , a motor electronic control unit  32  (hereinafter referred to as “motor ECU  32 ”), a charger  34  (second converter), a pair of normal charging connectors  36 , a step-down DC/DC converter  38  (first converter), a pair of contactors  40 , a pair of quick charging connectors  42 , a pair of battery connectors  44  (high-voltage terminals), current sensors  46 , a through terminal base  48  (see  FIG. 2 , etc.), and a low-voltage coupler  49 . The inverter  30  and the motor ECU  32  jointly make up a power module  50 . As shown in  FIG. 2 , the PCU  12  is encased in a casing  52  which comprises an upper member  54  and a lower member  56 . 
         [0033]    As shown in  FIG. 1 , the cooling system  200  of the vehicle  10  has a coolant pump  60 , a cooling plate  62  (plate-like member), and a radiator  64  (a peripheral component or a vehicle component). The cooling plate  62  serves as part of the PCU  12  and is disposed in the casing  52  ( FIG. 2 ). 
         [0034]    The electric power system  100  and the cooling system  200  are controlled by an integrated electronic control unit  70  (hereinafter referred to as “integrated ECU  70 ”) (see  FIG. 1 ). The integrated ECU  70  controls the vehicle  10  in its entirety. 
         [0035]    Incidentally, in  FIG. 1 , the positional relationship of the components is not shown. The layout of the components of the PCU  12  will be described later with reference to  FIGS. 2 through 5 . 
       [1-2. Driving System] 
       [0036]    The motor  14  comprises a three-phase AC brushless motor. The motor  14  generates a drive force F [N] or a torque [N·m] for the vehicle  10  based on electric power supplied from the battery  16  through the inverter  30 . The motor  14  also generates electric power [W] by operating in a regenerative mode (hereinafter referred to as “regenerated electric power Preg”) and supplies the regenerated electric power Preg to the battery  16 , thereby charging the battery  16 . The regenerated electric power Preg may be supplied to the 12-volt system  18  or unillustrated auxiliaries. 
         [0037]    The inverter  30 , which is a three-phase bridged inverter, converts direct current into alternating current. The inverter  30  converts direct current into three-phase alternating current and supplies the three-phase alternating current to the motor  14 . The inverter  30  also converts alternating current generated by the motor  14  operated in the regenerative mode, into direct current, and supplies the direct current to the battery  16 . 
         [0038]    The motor  14  and the inverter  30  operate while the vehicle  10  is being driven in both power and regenerative modes (hereinafter, the vehicle  10  will be driven in the power and regenerative modes unless specified otherwise). 
         [0039]    The battery  16  comprises an electric storage device (energy storage device) including a plurality of battery cells. The battery  16  may be a lithium ion secondary battery, a nickel hydrogen secondary battery, a capacitor, or the like. In the present embodiment, the battery  16  is a lithium ion secondary battery. The battery  16  is connected to a pair of first electric power lines  80  of the PCU  12  through the battery connectors  44  (see  FIG. 1 ) that provides a connection between the inside and outside of the casing  52  (see  FIG. 2 ). 
         [0040]    The motor ECU  32  controls the inverter  30  based on commands from the integrated ECU  70  and output signals from various sensors including the current sensors  46 , etc., thereby controlling output power (propulsive power) of the motor  14 . In  FIG. 1 , communication lines between the motor ECU  32  and other parts are omitted from illustration. 
       [1-3. DC/DC Converter  38  and 12-Volt System  18 ] 
       [0041]    On the basis of a command from the integrated ECU  70 , the DC/DC converter  38  steps down a high voltage on the first electric power lines  80  for high-voltage, into a low voltage, and supplies the low voltage to the 12-volt system  18 . 
         [0042]    The 12-volt system  18  has a 12-V battery  90  and a 12-V load  92  (auxiliary). The components of the 12-volt system  18  can operate while the vehicle  10  is being driven and while the battery  16  is being charged by an external circuit. 
       [1-4. External Charging System] 
       [0043]    As shown in  FIG. 1 , the charger  34  is connected to a normal charging power supply  110  (external power supply), which is external to the vehicle  10 , through the normal charging connection  20  which is connected to the normal charging connectors  36  and a pair of second electric power lines  120  for low-voltage. The charger  34  converts an AC voltage, e.g., 120 V, from the normal charging power supply  110  into a DC voltage, steps up the DC voltage into a high DC voltage, and supplies the high DC voltage to the first electric power lines  80  for high-voltage. 
         [0044]    As shown in  FIG. 1 , the contactors  40  are connected to a quick charging power supply  112 , which is external to the vehicle  10 , through the quick charging connection  22  which is connected to the quick charging connectors  42  and a pair of third electric power lines  122  for high-voltage. The contactors  40  supply an output voltage, e.g., 240 V, from the quick charging power supply  112  to the first electric power lines  80  for high-voltage. 
       [1-5. Cooling System  200 ] 
       [0045]    As described above, the cooling system  200  has the coolant pump  60 , the cooling plate  62 , and the radiator  64 . The cooling plate  62  serves as a so-called heat sink. Specifically, the cooling plate  62  includes a first cooling surface (i.e., an upper surface  130  as a first principal surface) and a second cooling surface (i.e., a lower surface  132  as a second principal surface). On each of the cooling surfaces, various circuit components including the charger  34 , the DC/DC converter  38 , the power module  50 , etc. are arranged. Then, coolant (not shown) is passed through the interior of the cooling plate  62  so as to cool the circuit components. 
         [0046]    As shown in  FIG. 2 , the cooling plate  62  has cooling fins  140  and coolant channels  142  therein. The coolant pump  60  delivers the coolant through the coolant channels  142  (see  FIG. 2 ). The cooling plate  62  is made of aluminum, for example, and is more rigid than the peripheral components including the radiator  64 , a front assembly  66 , etc. 
       [1-6. Integrated ECU  70 ] 
       [0047]    The integrated ECU  70  manages the vehicle  10  in its entirety. According to the present embodiment, for example, the integrated ECU  70  controls the motor ECU  32 , the charger  34 , the DC/DC converter  38 , the contactors  40 , and the coolant pump  60  of the cooling system  200  through the low-voltage coupler  49  and communication lines  144  (signal lines). 
       2. Layout of Components: 
     [2-1. Layout of PCU  12  on Vehicle  10 ] 
       [0048]      FIG. 3  schematically shows in side elevation the layout of the PCU  12  and its related components on the vehicle  10 . As shown in  FIG. 3 , the PCU  12  is disposed forwardly of a passenger compartment  150  of the vehicle  10 . The radiator  64  is disposed forwardly of the PCU  12 , and the front assembly  66  is disposed forwardly of the radiator  64 . The front assembly  66  includes a front bumper member  67  and a radiator supporting frame  68 . The motor  14  is disposed below the PCU  12 , which is connected to the motor  14  by a first high-voltage DC cable  152  (hereinafter referred to as “first cable  152 ”). 
         [0049]    The battery  16  is disposed below the passenger compartment  150 , i.e., below front seats and rear seats, not shown. The battery  16  is connected to the PCU  12  through a second high-voltage DC cable  154  (hereinafter referred to as “second cable  154 ”) that includes electric wires. As shown in  FIG. 3 , the first cable  152  and the second cable  154  are disposed so as to hang loosely. 
         [0050]    The cooling plate  62  of the PCU  12  lies along the longitudinal directions of the vehicle  10 , i.e., horizontally in  FIG. 3 . More specifically, the cooling plate  62  is disposed along the longitudinal directions of the vehicle  10 , i.e., horizontally, with the upper surface  130  facing upwardly (upwardly in  FIG. 3 ) and the lower surface  132  facing downwardly (downwardly in  FIG. 3 ). An upper circuit component group  156  is disposed on the upper surface  130  of the cooling plate  62 , whereas a lower circuit component group  158  is disposed on the lower surface  132  of the cooling plate  62 . The upper circuit component group  156  and the lower circuit component group  158  include circuit components (to be described in detail later) of the electric power system  100 . In  FIG. 3 , the casing  52  is omitted from illustration. 
         [0051]    According to the present embodiment, the PCU  12  and its related components are arranged as described above to thereby provide various advantages which will be described in detail later. 
       [2-2. Arrangement and Layout of the Upper Circuit Component Group  156  and the Lower Circuit Component Group  158 ] 
       [0052]      FIG. 4  is a plan view showing specific component layout and wiring details on the upper surface  130  of the cooling plate  62 .  FIG. 5  is a bottom view showing, in a vertically reversed fashion, specific component layout and wiring details on the lower surface  132  of the cooling plate  62 . In  FIGS. 4 and 5 , the terms “FRONT”, “REAR”, “LEFT”, and “RIGHT” refer to directions as viewed from the viewpoint of the driver in the direction of travel of the vehicle  10 .  FIG. 5  shows the specific component layout and wiring details in the vertically reversed fashion for an easier understanding of the positional relationship of the components. Stated otherwise,  FIG. 5  shows the layout as viewed from a plan-view side of the casing  52 . It should be noted that when the layout is viewed from the plan-view side of the casing  52 , the forward, rearward, leftward, and rightward directions of the components in  FIG. 4  and in  FIG. 5  coincide respectively with each other. 
         [0053]    As shown in  FIG. 4 , the contactors  40 , the quick charging connectors  42 , the current sensors  46 , the low-voltage coupler  49 , and the power module  50  are disposed on the upper surface  130  of the cooling plate  62 . As shown in  FIG. 5 , the charger  34 , the DC/DC converter  38 , and the battery connectors  44  are disposed on the lower surface  132  of the cooling plate  62 . 
         [0054]    In  FIGS. 4 and 5 , thick wires  160  represent high-voltage bus bars and correspond to the first electric power lines  80  in  FIG. 1 . An area where the high-voltage bus bars  160  are located will hereinafter be referred to as a high-voltage circuit section  162 . Thin wires  164  represent a low-voltage harness for supplying low-voltage signals for operating circuit components and correspond to the communication lines  144  in  FIG. 1 . An area where the low-voltage harness  164  is located will hereinafter be referred to as a low-voltage circuit section  166 . 
         [0055]    The cooling plate  62  has a plurality of through regions  170 ,  172 ,  174 ,  176  defined therein which interconnect the upper surface  130  and the lower surface  132 . The through regions  170 ,  172 ,  174 ,  176  correspond to the through terminal base  48  shown in  FIG. 2  and equivalent through terminal bases, not shown. 
         [0056]    On both of the upper surface  130  and the lower surface  132 , the high-voltage bus bars  160  are positioned more closely to the rear side of the vehicle  10 , i.e., to the passenger compartment  150 , than the low-voltage harness  164 . Therefore, when an impact force is applied from the front end of the vehicle  10 , the low-voltage harness  164  side firstly undergoes (absorbs) the impact force. Owing thereto, it becomes easy to protect the high-voltage bus bars  160 . 
         [0057]    On the lower surface  132 , the battery connectors  44  are positioned most closely to the rear side of the vehicle  10 , i.e., to the passenger compartment  150 . Therefore, when an impact force is applied from the front end of the vehicle  10 , the low-voltage harness  164  side firstly undergoes (absorbs) the impact force. Owing thereto, it becomes easy to protect the battery connectors  44 . 
       3. Operation and Advantages of the Present Embodiment Upon Frontal Collision: 
       [0058]      FIGS. 6A and 6B  illustrate operation and advantages of the present embodiment upon frontal collision. Specifically,  FIG. 6A  is a view showing the manner in which the radiator  64  is displaced when the vehicle  10  collides on its front end, and  FIG. 6B  is a view showing the manner in which the radiator  64  is brought into contact with the PCU  12  when the vehicle  10  collides on its front end. 
         [0059]    According to the present embodiment, the cooling plate  62  (plate-like member) is more rigid than the radiator  64  and lies along the longitudinal directions of the vehicle  10 . Thus, when the radiator  64  presses the cooling plate  62  under an impact force applied toward the passenger compartment  150  along the longitudinal direction of the vehicle  10 , the cooling plate  62  is prevented from being crushed in the longitudinal direction of the vehicle  10 . Consequently, the circuit components of the PCU  12 , i.e., the upper circuit component group  156  and the lower circuit component group  158 , which are disposed on the upper and lower surfaces  130 ,  132  of the cooling plate  62  are prevented from being damaged. 
         [0060]    According to the present embodiment, furthermore, the circuit components of the PCU  12 , i.e., the upper circuit component group  156  and the lower circuit component group  158 , are disposed on the upper and lower surfaces  130 ,  132  of the cooling plate  62 . Therefore, when the cooling plate  62  is pressed by the radiator  64  upon collision of the vehicle  10  and is displaced so as to slide in the longitudinal direction of the vehicle  10 , the PCU  12  can be prevented from being pressed between the cooling plate  62  and the radiator  64 . 
         [0061]    According to the present embodiment, moreover, since the circuit components of the PCU  12 , i.e., the upper circuit component group  156  and the lower circuit component group  158 , are disposed on both the upper and lower surfaces  130 ,  132  of the cooling plate  62 , the cooling plate  62  can be prevented from getting larger in size, compared to a case where the circuit components of the PCU  12  are disposed on one of the upper and lower surfaces  130 ,  132 . 
         [0062]    According to the present embodiment, in addition, the battery  16  is disposed more closely to the passenger compartment  150  than the cooling plate  62  along the longitudinal direction of the vehicle  10 , and is connected to the PCU  12  by the second cable  154  (see  FIG. 3 ). Consequently, when the radiator  64  presses the cooling plate  62  toward the passenger compartment  150  upon frontal collision of the vehicle  10 , the second cable  154  is displaced toward the battery  16 , or stated otherwise, in a direction in which the second cable  154  shrinks. Therefore, the second cable  154 , which interconnects the battery  16  and the PCU  12 , can be prevented from being stretched and damaged. 
         [0063]    According to the present embodiment, the high-voltage circuit section  162  is positioned more closely to the passenger compartment  150  than the low-voltage circuit section  166  along the longitudinal direction of the vehicle  10  (see  FIGS. 4 and 5 ). Consequently, when the radiator  64  presses the cooling plate  62  toward the passenger compartment  150  upon frontal collision of the vehicle  10 , the low-voltage circuit section  166  undergoes (absorbs) the impact earlier than the high-voltage circuit section  162 . Therefore, the high-voltage circuit section  162  can be further effectively prevented from being damaged. 
         [0064]    Inasmuch as the high-voltage circuit section  162  is positioned more closely to the passenger compartment  150  than the low-voltage circuit section  166  in the longitudinal direction of the vehicle  10 , the high-voltage circuit section  162  and the low-voltage circuit section  166  can be positioned in different areas separated in the longitudinal direction of the vehicle  10  on the upper or lower surface  130 ,  132  of the cooling plate  62 . Therefore, even if the high-voltage circuit section  162  and the low-voltage circuit section  166  are disposed on one principal surface (the upper surface  130  or the lower surface  132 ) of the cooling plate  62 , the high-voltage circuit section  162  can be prevented from being positioned relatively closely to the low-voltage circuit section  166 . As a result, any noise that the low-voltage circuit section  166  receives from the high-voltage circuit section  162  is reduced, and hence the low-voltage circuit section  166  can be prevented from malfunctioning in the PCU  12 . 
         [0065]    According to the present embodiment, the high-voltage circuit section  162  has the battery connectors  44  (high-voltage terminals) disposed on the lower surface  132  of the cooling plate  62  most closely to the passenger compartment  150 , and the second cable  154  is connected to the battery  16  and the battery connectors  44 . Consequently, when the radiator  64  presses the cooling plate  62  toward the passenger compartment  150  upon frontal collision of the vehicle  10 , the other components than the battery connectors  44  and the second cable  154  undergo (absorb) the impact earlier than the battery connectors  44  and the second cable  154 . Therefore, the battery connectors  44  and the second cable  154  can be further effectively prevented from being damaged. In addition, as the length of the second cable  154 , which interconnects the PCU  12  and the battery  16 , can be relatively shortened, power loss caused by the second cable  154  can be reduced. 
         [0066]    According to the present embodiment, the high-voltage circuit section  162  has the inverter  30 , the charger  34 , and the DC/DC converter  38 , with the inverter  30  (power module  50 ) being disposed on the upper surface  130  of the cooling plate  62  (see  FIG. 4 ) and the charger  34  and the DC/DC converter  38  being disposed on the lower surface  132  of the cooling plate  62  (see  FIG. 5 ). Therefore, the inverter  30 , and the charger  34  and the DC/DC converter  38 , each in the form of a high-voltage circuit, can be positioned on mutually different surfaces of the cooling plate  62 . The cooling plate  62  can be thus prevented from increasing in size, while it cools the inverter  30 , the charger  34 , and the DC/DC converter  38 , which each are a heat generator. 
       B. Modifications: 
       [0067]    The present invention is not limited to the above embodiment, but may employ various arrangements based on the disclosure of the present description. For example, the present invention may employ the following arrangements: 
         [0000]    1. Objects in which the Invention may be Incorporated 
         [0068]    In the above embodiment, the PCU  12  is incorporated in the electric vehicle  10 . However, the PCU  12  may be incorporated in other objects. For example, the PCU  12  may be incorporated in a movable body such as a ship or an aircraft, for example. 
         [0069]    In the above embodiment, only the motor  14  is used as the drive source of the vehicle  10 . However, the present invention is not limited to the above case. For example, the present invention is also applicable to another vehicle such as a vehicle (hybrid vehicle) having an engine in addition to the motor  14  or a vehicle (fuel cell vehicle) having a fuel cell in addition to the motor  14 . 
       2. PCU  12  and Motor  14 : 
     [2-1. Arrangement of PCU  12  and Motor  14 ] 
       [0070]    In the above embodiment, the PCU  12  is disposed forwardly of the passenger compartment  150 . However, the present invention is not limited to such an arrangement.  FIG. 7  schematically shows in side elevation the layout of the PCU  12  and its related components on an electric vehicle  10 A (hereinafter also referred to as “vehicle  10 A”) according to a modification. On the vehicle  10 A shown in  FIG. 7 , the PCU  12 , the motor  14 , the first cable  152 , and the second cable  154  are disposed rearwardly of the passenger compartment  150 . Further, a rear panel  180  and a rear bumper member  182  are disposed rearwardly of the PCU  12 , the motor  14 , the first cable  152 , and the second cable  154 . The layout according to the modification offers the same advantages as the above embodiment when an impact force is applied to the vehicle  10 A from the rear end of the vehicle  10 A. In this case, the cooling plate  62  is made more rigid than peripheral components, e.g., the rear panel  180  and the rear bumper member  182 , which may possibly be brought into contact with the cooling plate  62  upon rear collision. 
       [2-2. Layout and Arrangement in PCU  12 ] 
       [0071]    In the above embodiment, the circuit components (constituent elements) such as the power module  50 , etc. are disposed on the upper surface  130  of the cooling plate  62 , whereas the circuit components such as the charger  34 , the DC/DC converter  38 , etc. are disposed on the lower surface  132  of the cooling plate  62 . However, the circuit components on the upper and lower surfaces  130 ,  132  may be disposed as desired. 
         [0072]    In the above embodiment, the circuit components, i.e., the upper circuit component group  156  and the lower circuit component group  158 , are disposed respectively on the upper and lower surfaces  130 ,  132  of the cooling plate  62 . However, the circuit components may be disposed on only either one of the upper and lower surfaces  130 ,  132 . In this case, the cooling plate  62  may have only one of the upper and lower surfaces  130 ,  132  as a cooling surface. 
         [0073]    In the above embodiment, the cooling plate  62  is disposed between the upper circuit component group  156  and the lower circuit component group  158 . However, the plate-like member disposed between the upper circuit component group  156  and the lower circuit component group  158  may not be a cooling member. Instead of the cooling plate  62 , an insulating member may be disposed between the upper circuit component group  156  and the lower circuit component group  158 . In this case, the cooling plate  62  may be disposed at least over the upper circuit component group  156  or beneath the lower circuit component group  158 . 
         [0074]    In the above embodiment, the cooling plate  62  lies horizontally along the longitudinal directions of the vehicle  10 . However, the cooling plate  62  may be disposed otherwise insofar as it lies along the longitudinal directions of the vehicle  10 . For example, the cooling plate  62  may lie vertically along the longitudinal directions of the vehicle  10 . In this case, the circuit components can be disposed on the left and right sides of the cooling plate  62  with respect to the vehicle  10 . 
       [2-3. Arrangement of Motor  14 ] 
       [0075]    In the above embodiment, the motor  14  comprises a three-phase AC brushless motor. However, the motor  14  may be another motor insofar as it can propel the vehicle  10 . For example, the motor  14  may comprise s three-phase AC brush motor, a single-phase AC motor, or a DC motor. 
       3. Others: 
       [0076]    In the above embodiment, the radiator  64  is illustrated as a peripheral component or vehicle component which tends to contact the PCU  12  upon frontal collision. However, the peripheral component or vehicle component which may possibly contact the PCU  12  upon frontal collision is not limited to the radiator  64 , but may be the front assembly  66  including the front bumper member  67  and the radiator supporting frame  68 , for example. The peripheral component or vehicle component which may possibly contact the PCU  12 , referred to above, is a peripheral component or vehicle component which may possibly contact the PCU  12  upon frontal collision in a case where the PCU  12  is disposed forwardly of the passenger compartment  150 . If such a peripheral component or vehicle component may possibly contact the PCU  12 , the cooling plate  62  can be made more rigid than the peripheral component or vehicle component. 
         [0077]    If the PCU  12  is disposed forwardly of the passenger compartment  150 , then the cooling plate  62  only has to be made more rigid than the peripheral component or vehicle component that may possibly contact the PCU  12  upon frontal collision, but is not necessarily required to be made more rigid than peripheral components, e.g., the motor  14 , that are present on the upper side or the lower side of the cooling plate  62  (upper and lower directions in  FIG. 3 ).