Patent Publication Number: US-2015061423-A1

Title: Motor driving apparatus and vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2013-184441 filed with the Japan Patent Office on Sep. 5, 2013, the entire content of which is hereby incorporated by reference. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a motor driving apparatus and a vehicle. 
     2. Related Art 
     Conventionally, there is known a motor driving apparatus includes a motor including a first winding and a second winding (for example, refer to JP-A-2010-17055). The motor driving apparatus disclosed in JP-A-2010-17055 includes a motor, a winding switcher, and an inverter (power converter). The motor includes a first winding for high-speed driving and the second driving winding for low-speed driving. The winding switcher switches between connection states of the two windings of the motor. 
     In general, in such a conventional motor driving apparatus including a motor, a winding switcher, and a power converter as disclosed in JP-A 2010-17055, the winding switcher and the power converter are directly mounted on the side surfaces of the motor, respectively. In other words, the winding switcher and the power converter are individually mounted on different portions on the side surfaces of the motor. 
     SUMMARY 
     A motor driving apparatus includes: a motor including a first winding and a second winding; a winding switcher configured to switch between connection states of the first winding and the second winding of the motor; and a power converter connected to the motor. The motor, the power converter, and the winding switcher are disposed in a direction approximately orthogonal to an axial direction of the motor in order of the motor, the power converter, and the winding switcher. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram illustrating an entire configuration of a vehicle according to a first embodiment; 
         FIG. 2  is a side view of an entire configuration of a motor drive unit according to the first embodiment; 
         FIG. 3  is an exploded perspective view of the motor drive unit illustrated in  FIG. 2 ; 
         FIG. 4  is an exploded perspective view of the motor drive unit illustrated in  FIG. 3  viewed from the side opposite to the side in  FIG. 3 ; 
         FIG. 5  is a perspective view of the motor drive unit illustrated in  FIG. 2  viewed from obliquely below; 
         FIG. 6  is a perspective view of the motor drive unit illustrated in  FIG. 5  viewed from the side opposite to that in  FIG. 5 ; 
         FIG. 7  is a perspective view of the motor drive unit illustrated in  FIG. 2  viewed obliquely from above; 
         FIG. 8  is a top view of an inverter housing portion in the motor drive unit according to the first embodiment; 
         FIG. 9  is a diagram illustrating the inverter housing portion illustrated in  FIG. 8 , in the state prior to mounting of the inverter and a controller; 
         FIG. 10  is a perspective view of an inverter bus-bar wiring in the motor drive unit according to the first embodiment; 
         FIG. 11  is a perspective view of the inverter bus-bar wiring illustrated in  FIG. 10  viewed from the side opposite to that in  FIG. 10 ; 
         FIG. 12  is a cross-section view of  FIG. 6  taken along line  200 - 200 ; 
         FIG. 13  is an axial view of the motor drive unit illustrated in  FIG. 2 ; 
         FIG. 14  is a top view of a second housing portion in the motor drive unit according to the first embodiment; 
         FIG. 15  is a diagram illustrating the second housing portion illustrated in 
         FIG. 14 , in the state prior to mounting of the winding switcher; 
         FIG. 16  is a perspective view of a low-speed winding bus-bar wiring in the motor drive unit according to the first embodiment; 
         FIG. 17  is a perspective view of the low-speed winding bus-bar wiring illustrated in  FIG. 16  viewed from the side opposite to that in  FIG. 16 ; 
         FIG. 18  is a cross-section view of  FIG. 6  taken along line  300 - 300 ; 
         FIG. 19  is a side view of a first cooling flow passage in the motor drive unit according to the first embodiment; 
         FIG. 20  is a top view of the first cooling flow passage in the motor drive unit according to the first embodiment; 
         FIG. 21  is a bottom view of the first cooling flow passage in the motor drive unit according to the first embodiment; 
         FIG. 22  is a block diagram illustrating an entire configuration of a vehicle according to a second embodiment; 
         FIG. 23  is a cross-section view of a motor drive unit according to the second embodiment; and 
         FIG. 24  is a top view of a second housing portion in a motor drive unit according to a modification example of the first and second embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, for purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing. 
     A motor driving apparatus according to a first aspect of the present disclosure includes: a motor including a first winding and a second winding; a winding switcher configured to switch between connection states of the first winding and the second winding of the motor; and a power converter connected to the motor. The motor, the power converter, and the winding switcher are disposed in a direction approximately orthogonal to an axial direction of the motor in order of the motor, the power converter, and the winding switcher. 
     In the motor driving apparatus according to the first aspect, the motor, the power converter, and the winding switcher are disposed in a direction approximately orthogonal to the axial direction of the motor in order of the motor, the power converter, and the winding switcher, as described above. In other words, the power converter and the winding switcher are disposed to overlap the motor (at positions orthogonal to the motor) viewed from a direction orthogonal to the axis of the motor (rotation axis) (in the direction in which the power converter and the winding switcher are disposed). Thus, the winding switcher and the power converter can be mounted to the motor without having to rotate the motor around the axis, facilitating the work of mounting the winding switcher and the power converter. As a result, an improvement can be made in workability in mounting the winding switcher and the power converter. 
     In addition, the motor driving apparatus according to the first aspect may further includes a first housing portion including a motor housing portion for housing the motor and a power converter housing portion for housing the power converter, and a second housing portion that is stacked on the first housing portion in the direction approximately orthogonal to the axial direction of the motor in the first housing portion and is configured to house the winding switcher. In this configuration, the first housing portion and the second housing portion may be disposed at positions adjacent to each other and may be integrally joined each other. Further, the second housing portion may overlap the first housing portion (at a position orthogonal to the first housing portion) viewed from the direction orthogonal to the axis of the motor (rotation axis) (in the direction in which the second housing portion is disposed). 
     A vehicle according to a second aspect of the present disclosure includes: a vehicle main body unit; and a motor drive unit that is provided within the vehicle main body unit. The motor drive unit includes: a motor including a first winding and a second winding; a winding switcher configured to switch between connection states of the first winding and the second winding of the motor; and a power converter connected to the motor, and the motor, the power converter, and the winding switcher are disposed in a direction approximately orthogonal to an axial direction of the motor, in order of the motor, the power converter, and the winding switcher. 
     In the vehicle according to the second aspect, the motor, the power converter, and the winding switcher are disposed in the direction approximately orthogonal to the axial direction of the motor in order of the motor, the power converter, and the winding switcher, as described above. The winding switcher and the power converter can be therefore mounted the motor without having to rotate the motor around the axis, facilitating the work of mounting the winding switcher and the power converter. As a result, the workability in mounting the winding switcher and the power converter can be improved. 
     The foregoing motor driving apparatus and vehicle can be provided with improved workability in mounting the winding switcher and the power converter. 
     Hereinafter, embodiments will be described with reference to the drawings. 
     First Embodiment 
     Referring to  FIG. 1 , a configuration of a vehicle  100  according to a first embodiment will be described. However, the configuration illustrated in  FIG. 1  is an example of a “configuration of a vehicle including a winding switch-type motor drive unit.” 
     As illustrated in  FIG. 1 , the vehicle  100  includes a vehicle main body unit  101 , a motor drive unit  10  provided within the vehicle main body unit  101 , and a battery unit  20  connected to the motor drive unit  10 . The motor drive unit  10  is an example of a “motor driving apparatus.” 
     The motor drive unit  10  is configured to include an inverter  1 , a smoothing capacitor  2 , a motor  3 , a winding switcher  4 , a controller  5 , and a power source unit  6 . The inverter  1  is an example of a “power converter.” 
     The inverter  1  is configured to convert direct-current power input from the battery unit  20  into alternating power in three phases (U phase, V phase, and W phase), and output the same to the motor  3 . The inverter  1  has direct-current input terminals TP 1  and TN 1  connected to the battery unit  20  and alternating-current output terminals TU 1 , TV 1 , and TW 1  connected to the motor  3 . Terminals TP 2  and TN 2  of the smoothing capacitor  2  are connected to the direct-current terminals TP 1  and TN 1  of the inverter  1 , respectively. The smoothing capacitor  2  is provided to smooth out direct-current power input from the battery unit  20 . 
     The inverter  1  is also configured to include six switch elements Q 1 , Q 2 , Q 3 , Q 4 , Q 5 , and Q 6  for power conversion. The switch elements Q 1  and Q 2  are configured to perform power conversion in U phase. The switch elements Q 3  and Q 4  are configured to perform power conversion in V phase. The switch elements Q 5  and Q 6  are configured to perform power conversion in W phase. The switch elements Q 1  to Q 6  are formed by semiconductors including SiC, for example. 
     The motor  3  is configured to be driven in correspondence with alternating-current power of three phases supplied from the inverter  1 . The motor  3  is configured to include a three-phase winding  3   a  for high-speed driving, and three-phase windings  3   a  and  3   b  for low-speed driving. The winding  3   a  is an example of a “first winding” and a “high-speed driving winding.” The windings  3   a  and  3   b  are examples of a “second winding” and a “low-speed driving winding.” 
     The windings  3   a  and  3   b  are connected electrically in series. Respective terminals TU 2 , TV 2 , and TW 2  in the phases (U phase, V phase, and W phase) at one side of the winding  3   a  are connected to the inverter  1 . Respective terminals TU 3 , TV 3 , and TW 3  of phases at the other side of the winding  3   a  and one side of the winding  3   b  are connected to a diode bridge DB 1  described later in the winding switcher  4 . Respective terminals TU 4 , TV 4 , and TW 4  at the other side of the winding  3   b  are connected to a diode bridge DB 2  described later in the winding switcher  4 . 
     The winding switcher  4  has the function of switching connection states between the windings  3   a  and  3   b  of the motor  3 . Specifically, the winding switcher  4  is configured to include a high-speed winding switch SW 1  and a low-speed winding switch SW 2 . The high-speed winding switch SW 1  is a switch for short-circuiting the terminals TU 3 , TV 3 , and TW 3  of the motor  3 . The low-speed winding switch SW 2  is a switch for short-circuiting the terminals TU 4 , TV 4 , and TW 4  of the motor  3 . The high-speed winding switch SW 1  and the low-speed winding switch SW 2  are formed by semiconductors including SiC, for example. 
     The winding switcher  4  is configured to include the diode bridge DB 1  and a capacitor C 1 . The diode bridge DB 1  has terminals TU 5 , TV 5 , and TW 5  connected to the terminals TU 3 , TV 3 , and TW 3  of the motor  3 , respectively. The capacitor C 1  protects the winding  3   a  of the motor  3 . The high-speed winding switch SW 1 , the diode bridge DB 1 , the capacitor C 1 , and the smoothing capacitor  2  are connected electrically in parallel to each other. 
     The winding switcher  4  is also configured to include the diode bridge DB 2  and a capacitor C 2 . The diode bridge DB 2  has terminals TU 6 , TV 6 , and TW 6  connected to the terminals TU 4 , TV 4 , and TW 4  of the motor  3 , respectively. The capacitor C 2  protects the windings  3   a  and  3   b  of the motor  3 . The low-speed winding switch SW 2 , the diode bridge DB 2 , the capacitor C 2 , and the smoothing capacitor  2  are connected electrically in parallel to each other. 
     The diode bridge DB 1  includes six diodes D 11 , D 12 , D 13 , D 14 , D 15 , and D 16 . These diodes D 11 , D 12 , D 13 , D 14 , D 15 , and D 16  rectify alternating currents in the three phases (U phase, V phase, and W phase) output from the terminals TU 3 , TV 3 , and TW 3  of the motor  3 . The diodes D 11  and D 12  are configured to rectify an alternating current in U phase. The diodes D 13  and D 14  are configured to rectify an alternating current in V phase. The diodes D 15  and D 16  are configured to rectify an alternating current in W phase. Two diodes D 17  and D 18  are provided on a direct-current output side of the diode bridge DB 1 . 
     Similarly, the diode bridge DB 2  includes six diodes D 21 , D 22 , D 23 , D 24 , D 25 , and D 26 . These diodes D 21 , D 22 , D 23 , D 24 , D 25 , and D 26  rectify alternating currents in the three phases (U phase, V phase, and W phase) output from the terminals TU 4 , TV 4 , and TW 4  of the motor  3 . The diodes D 21  and D 22  are configured to rectify an alternating current in U phase. The diodes D 23  and D 24  are configured to rectify an alternating current in V phase. The diodes D 25  and D 26  are configured to rectify an alternating current in W phase. Two diodes D 27  and D 28  are provided on a direct-current output side of the diode bridge DB 2 . 
     The controller  5  is configured to control the inverter  1  and the winding switcher  4  by outputting control signals (inverter control signal, control signal for high-speed winding switch, and control signal for low-speed winding switch) to the inverter  1  and the winding switcher  4 . The power source unit  6  is configured to supply power source for operating the switch elements Q 1  to Q 6  of the inverter  1  (inverter gate power source) to the inverter  1 . The power source unit  6  is also configured to supply a power source for operating the high-speed winding switch SW 1  and the low-speed winding switch SW 2  of the winding switcher  4  (a gate power source for high-speed winding switch and a gate power source for low-speed winding switch) to the winding switcher  4 . 
     Next, referring to  FIGS. 2 to 21 , a configuration of the motor drive unit  10  according to the first embodiment will be described. 
     As illustrated in  FIGS. 2 to 7 , the motor drive unit  10  includes a first housing portion  11 , a second housing portion  12 , a first cover portion  13 , and a second cover portion  14 . The first housing portion  11  houses the motor  3  and the inverter  1 . The second housing portion  12  houses the winding switcher  4 . The first cover portion  13  covers a non-load side (X2-direction side) of the first housing portion  11 . The second cover portion  14  covers an upper side of the second housing portion  12  (in a Z1 direction). 
     The first housing portion  11  includes a motor housing portion  111  for housing the motor  3  and an inverter housing portion  112 . The inverter housing portion  112  is disposed on a side surface of the motor housing portion  111  (in the Z1 direction) to house the inverter  1 . The motor housing portion  111  has an almost cylindrical shape. As illustrated in  FIG. 4 , the motor housing portion  111  is opened at the non-load side (X2-direction side) of the motor housing portion  111 . Provided at the non-load side of the motor housing portion  111  is a resolver housing portion  113  at which a resolver  15  is disposed. The resolver housing portion  113  (at the non-load side (X2-direction side) of the motor housing portion  111 ) is configured such that the first cover portion  13  is attached thereto by screw members  16 . As illustrated in  FIG. 3 , a flange  17  is attached to a load side (X1-direction side) of the motor housing portion  111 . As illustrated in  FIG. 2 , the motor  3  has a shaft  3   c  configured to protrude from the flange  17  in the axial direction (X direction). The inverter housing portion  112  is an example of a “power converter housing portion.” In addition, the motor housing portion  111  and the inverter housing portion  112  of the first housing portion  11  may be integrally formed. Alternatively, the motor housing portion  111  and the inverter housing portion  112  may be separately formed and then integrally joined together. 
     As illustrated in  FIGS. 3 and 4 , the inverter housing portion  112  has a box shape opened at the upper side (in the Z1 direction). As illustrated in  FIG. 12 , the inverter  1  is disposed on a bottom surface of the inverter housing portion  112 . In the first embodiment, the controller  5  configured to control the winding switcher  4  and the inverter  1  is disposed at the inverter housing portion  112 . The controller  5  is disposed on the outer side than the inverter  1  in a direction approximately orthogonal (Z1 direction) to the axial direction of the inverter  1  (axial direction of the motor  3 ). Specifically, a plurality of column portions  112   c  is integrally provided at the inverter housing portion  112 . The controller  5  is disposed at the upper side of the column portions  112   c  (upper side of the inverter  1 ) in the state of being supported by the column portions  112   c.    
     In the first embodiment, as illustrated in  FIG. 8 , an inverter bus-bar wiring  51  is provided to connect the inverter  1  and the motor  3 . In addition, as illustrated in  FIG. 9 , the first housing portion  11  is provided with a first hole portion  112   a  that establishes a communication between the motor housing portion  111  and the inverter housing portion  112 . The inverter bus-bar wiring  51  is configured to penetrate through the first hole portion  112   a . A motor connector  51   c  (refer to  FIG. 13 ) is disposed at the non-load side of the motor housing portion  111  (resolver housing portion  113 ) (refer to  FIG. 13 ). The first hole portion  112   a  is formed in an almost rectangular shape to extend from an end at the Y1-direction side to an end at the Y2-direction side of the inverter housing portion  112  at the X2-direction side of the inverter housing portion  112  in plan view (viewed from the Z1 direction). The inverter bus-bar wiring  51  is an example of a “first bus-bar wiring.” 
     As illustrated in  FIGS. 10 and 11 , the inverter bus-bar wiring  51  is extended along the Y direction and has a first portion  51   b  and a second portion  51   d . The first portion  51   b  is provided with three inverter connectors  51   a  to be connected to the inverter  1 . The second portion  51   d  is extended in the Z direction. The second portion  51   d  is provided with three motor connectors  51   c  to be connected to the motor  3  side. In addition, as illustrated in  FIG. 8 , the inverter bus-bar wiring  51  is disposed at the X2-direction side of the inverter  1 . Further, as illustrated in  FIGS. 12 and 13 , the second portion  51   d  (motor connectors  51   c ) of the inverter bus-bar wiring  51  extending in the Z direction is disposed at the non-load side (X2-direction side, resolver housing portion  113 ) of the first housing portion  11  through the first hole portion  112   a.    
     As illustrated in  FIGS. 14 and 15 , the second housing portion  12  is provided with a high-speed winding switcher  41  and a low-speed winding switcher  42 . The high-speed winding switcher  41  includes the high-speed winding switch SW 1  and the diode bridge DB 1  (refer to  FIG. 1 ). The low-speed winding switcher  42  includes the low-speed winding switch SW 2  and the diode bridge DB 2 . The high-speed winding switcher  41  is disposed at the load side (X1-direction side) of the second housing portion  12 . The low-speed winding switcher  42  is disposed at the non-load side (X2-direction side) of the second housing portion  12 . 
     In the first embodiment, a high-speed winding bus-bar wiring  43  is provided to connect the high-speed winding switcher  41  and the motor  3 . In addition, a low-speed winding bus-bar wiring  44  is provided to connect the low-speed winding switcher  42  and the motor  3 . Further, as illustrated in  FIG. 15 , the second housing portion  12  is provided with second hole portions  12   a  that establish a communication between the second housing portion  12  and the first housing portion  11  (inverter housing portion  112 ). The high-speed winding bus-bar wiring  43  and the low-speed winding bus-bar wiring  44  are configured to penetrate through the second hole portions  12   a  and the first hole portion  112   a  (refer to  FIG. 9 ). The motor connector  43   c  (refer to  FIG. 13 ) and the motor connector  44   c  (refer to  FIG. 13 ) are disposed at the non-load side (X2-direction side) of the motor housing portion  111  (resolver housing portion  113 ). As illustrated in  FIG. 15 , the second hole portions  12   a  are disposed at the X2-direction side of the second housing portion  12 , and at an end in the Y1-direction side and an end at the Y2-direction side in plan view (viewed from the Z1 direction). These second hole portions  12   a  are formed in an almost rectangular shape. The high-speed winding bus-bar wiring  43  and the low-speed winding bus-bar wiring  44  are examples of a “second bus-bar wiring.” 
     As illustrated in  FIGS. 16 and 17 , the low-speed winding bus-bar wiring  44  is extended along the X direction. The low-speed winding bus-bar wiring  44  has a first portion  44   b  and a second portion  44   d . The first portion  44   b  is provided with three switcher connectors  44   a  to be connected to the low-speed winding switcher  42 . The second portion  44   d  is extended in the Z direction. The second portion  44   d  is provided with three motor connectors  44   c  to be connected to the motor  3  side. In addition, as illustrated in  FIG. 14 , the low-speed winding bus-bar wiring  44  is disposed at the Y1-direction side of the low-speed winding switcher  42 . Further, as illustrated in  FIGS. 13 and 18 , the second portion  44   d  (motor connectors  44   c ) of the low-speed winding bus-bar wiring  44 , extending in the Z direction, is disposed at the resolver housing portion  113  at the non-load side (X2-direction side) of the first housing portion  11  through the second hole portion  12   a  and the first hole portion  112   a.    
     As illustrated in  FIG. 14 , the high-speed winding bus-bar wiring  43 , as with the low-speed winding bus-bar wiring  44 , is extended along the X direction, and has a first portion  43   b  and a second portion  43   d . The first portion  43   b  is provided with three switcher connectors  43   a  to be connected to the high-speed winding switcher  41 . The second portion  43   d  is extended in the Z direction. The second portion  43   d  is provided with three motor connectors  43   c  (refer to  FIG. 13 ) to be connected to the motor  3  side. In addition, the high-speed winding bus-bar wiring  43  is disposed at Y2-direction side of the high-speed winding switcher  41 . 
     As illustrated in  FIG. 13 , the second portion  43   d  extended in the Z direction (motor connector  43   c ) of the high-speed winding bus-bar wiring  43  is disposed at the resolver housing portion  113  at the non-load side (X2-direction side) of the first housing portion  11  through the second hole portions  12   a  and the first hole portion  112   a.    
     In the first embodiment, as illustrated in  FIG. 12 , the second housing portion  12  houses the winding switcher  4 . The first housing portion  11  houses the motor  3  and the inverter  1 . The first housing portion  11  and the second housing portion  12  are stacked in a direction approximately orthogonal (Z direction) to the axial direction of the motor  3  (X direction). That is, the first housing portion  11  and the second housing portion  12  are disposed adjacent to each other and integrally joined together. Specifically, the motor housing portion  111  for housing the motor  3 , the inverter housing portion  112  for housing the inverter  1 , and the second housing portion  12  for housing the winding switcher  4  are disposed (connected) in the Z1 direction in order of the motor housing portion  111 , the inverter housing portion  112 , and the second housing portion  12 . Thus, the motor  3 , the inverter  1 , and the winding switcher  4  are disposed in the direction approximately orthogonal (Z1 direction) to the axial direction of the motor  3  (X direction) in order of the motor  3 , the inverter  1 , and the winding switcher  4 . 
     In the first embodiment, as illustrated in  FIGS. 3 and 4 , a surface of the inverter housing portion  112  at the second housing portion  12  side (upper surface  112   b ) and a surface of the second housing portion  12  at the inverter housing portion  112  side (lower surface  12   d ) are configured to have almost the same shape (almost rectangular shape) in plan view. In addition, the second housing portion  12  is stacked on the inverter housing portion  112  to cover the inverter housing portion  112 . Specifically, the second housing portion  12  is attached to the upper side of the first housing portion  11  (in the Z1 direction) by the screw members  16  to block the opening of the first housing portion  11 . Further, the second housing portion  12  has a box shape opened at the upper side (in the Z1 direction). The second housing portion  12  has a second cover portion  14  attached by the screw members  16  to cover the opening of the second housing portion  12 . 
     In the first embodiment, as illustrated in  FIG. 13 , the motor connector  44   c  of the low-speed winding bus-bar wiring  44 , the motor connector  43   c  of the high-speed winding bus-bar wiring  43 , and the motor connector  51   c  of the inverter bus-bar wiring  51  are disposed in parallel to each other (in a Y direction) viewed from the axial direction at the non-load side of the motor housing portion  111  (resolver housing portion  113 ). Specifically, viewed from the axial direction, the motor connector  44   c  of the low-speed winding bus-bar wiring  44  and the motor connector  43   c  of the high-speed winding bus-bar wiring  43  are disposed at the Y1-direction side and Y2-direction side of the resolver housing portion  113 , respectively. In addition, the motor connector  51   c  of the inverter bus-bar wiring  51  is disposed to be sandwiched between the motor connector  44   c  of the low-speed winding bus-bar wiring  44  and the motor connector  43   c  of the high-speed winding bus-bar wiring  43 . 
     In the first embodiment, as illustrated in  FIG. 18 , a first cooling flow passage  61  configured to cool the motor  3  and the inverter  1  is provided between the motor  3  and the inverter  1  in the first housing portion  11  (between the motor housing portion  111  and the inverter housing portion  112 ). The first cooling flow passage  61  is configured such that a cooling liquid flows therethrough. In addition, the first cooling flow passage  61  is extended to the vicinities of the motor connector  44   c  of the low-speed winding bus-bar wiring  44  and the motor connector  43   c  of the high-speed winding bus-bar wiring  43  so as to be opposed to the motor connector  44   c  of the low-speed winding bus-bar wiring  44  and the motor connector  43   c  of the high-speed winding bus-bar wiring  43  disposed at the non-load side of the motor housing portion  111  (resolver housing portion  113 ) viewed from the axial direction (refer to  FIG. 13 ). The first cooling flow passage  61  is an example of a “first cooler.” 
     The first cooling flow passage  61  is provided within the motor housing portion  111  to surround the motor  3  circumferentially. Specifically, as illustrated in  FIG. 19  (side view),  FIG. 20  (top view), and  FIG. 21  (bottom view), the first cooling flow passage  61  is formed to have a plurality of straight portions. These straight portions are extended within the first housing portion  11  (at the motor housing portion  111  and between the motor housing portion  111  and the inverter housing portion  112 ) from the vicinity of the end at the X1-direction side to the vicinity of the end at the X2-direction side in the X direction. The plurality of straight portions extended in the X direction are alternately folded in U shape and connected to each other at the end at the X1-direction side and the end at the X2-direction side. This forms a series of flow passages configured to let a cooling liquid flow from the one end to the other end of the first cooling flow passage  61 . 
     In the first embodiment, as illustrated in  FIG. 18 , a second cooling flow passage  62  configured to cool the winding switcher  4  is provided at a bottom portion  12   c  of the second housing portion  12  at the first housing portion  11  side (at the Z2-direction side). The second cooling flow passage  62  is connected to the first cooling flow passage  61 . This forms a series of flow passages configured to let a cooling liquid flow from the one end of the first cooling flow passage  61  to the other end of the second cooling flow passage  62 . The first cooling flow passage  61  and the second cooling flow passage  62  are connected together by a connection pipe  18  as illustrated in  FIGS. 4 and 5 . The cooling liquid is flown in from an inlet  19   a  provided at the motor housing portion  111  and flown out from an outlet  19   b  provided at the second housing portion  12  disposed at the upper side. The second cooling flow passage  62  is an example of a “second cooler.” 
     In the first embodiment, the second housing portion  12  for housing the winding switcher  4  is configured to be attachable/detachable to/from the first housing portion  11  together with the winding switcher  4 . Even if the second housing portion  12  is detached together with the winding switcher  4 , the motor  3  can be driven as a non-winding switch-type motor by connecting (short-circuiting) the low-speed drive winding  3   b.    
     As illustrated in  FIGS. 4 and 5 , the inverter housing portion  112  is configured such that a battery cable  71  connected to the battery unit  20  and a signal cable  72  connected to the controller  5  are mounted thereto. 
     According to the first embodiment, the following advantages can be obtained. 
     In the first embodiment, as described above, the motor  3 , the inverter  1 , and the winding switcher  4  are disposed in the direction approximately orthogonal to the axial direction of the motor  3 , in order of the motor  3 , the inverter  1 , and the winding switcher  4 . This makes it possible to mount the winding switcher  4  and the inverter  1  to the motor  3  without having to rotate the motor  3  around the axis. This facilitates the work of mounting the winding switcher  4  and the inverter  1 , allowing an improvement in workability in mounting the winding switcher  4  and the inverter  1 . 
     In the first embodiment, as described above, the motor drive unit  10  includes the first housing portion  11  and the second housing portion  12  for housing the winding switcher  4 . The first housing portion  11  includes the motor housing portion  111  for housing the motor  3  and the inverter housing portion  112  for housing the inverter  1 . The second housing portion  12  is stacked on the first housing portion  11  in the direction approximately orthogonal to the axial direction of the motor  3  in the first housing portion  11 . Thus, the second housing portion  12  is disposed at the outer peripheral side (for example, the outermost side) of the direction approximately orthogonal to the axial direction of the motor  3  in the first housing portion  11 . This makes it possible to easily perform maintenance of the winding switcher  4  housed in the second housing portion  12  without having to rotate the motor  3  around the axis, allowing an improvement in workability in maintenance of the winding switcher  4 . 
     In the first embodiment, as described above, the first housing portion  11  is provided with the first hole portion  112   a  that establishes a communication between the inverter housing portion  112  and the motor housing portion  111 . This facilitates installing of the wirings or the like from the inverter housing portion  112  to the motor housing portion  111 . In addition, the wirings for connecting the inverter  1  and the motor  3  (high-speed/low-speed winding wirings) become short significantly. This decreases a space needed for the wirings, which makes it possible to reduce the motor drive unit  10  in size and weight. As a result, the motor drive unit  10  has a smaller portion producing heat and thus can be improved in reliability. 
     In the first embodiment, as described above, the inverter bus-bar wiring  51  is connected to the inverter  1 . In addition, the motor connector  51   c  of the inverter bus-bar wiring  51  is disposed at the non-load side of the motor housing portion  111  through the first hole portion  112   a  of the inverter housing portion  112 . Thus, the motor connector  51   c  of the inverter bus-bar wiring  51  is disposed at the non-load side of the motor housing portion  111 . This can improve workability in connecting the motor connector  51   c  of the inverter bus-bar wiring  51  to the wirings of the motor  3  in contrast to the case where the motor connector  51   c  is disposed at the load side without a margin in space due to arrangement of the drive shaft and the like. 
     In the first embodiment, as described above, the second housing portion  12  is provided with the second hole portions  12   a  that establish a communication between the second housing portion  12  and the first housing portion  11 . This makes it possible to easily install the wirings and the like from the second housing portion  12  to the inverter housing portion  112 . In addition, the wirings for connecting the inverter  1  and the winding switcher  4  become short significantly. This decreases a space needed for the wirings, which makes it possible to reduce the motor drive unit  10  in size and weight. As a result, the motor drive unit  10  has a smaller portion producing heat and thus can be improved in reliability. 
     In the first embodiment, as described above, the low-speed winding bus-bar wiring  44  and the high-speed winding bus-bar wiring  43  are provided to connect the winding switcher  4  and the motor  3 . The motor connector  44   c  of the low-speed winding bus-bar wiring  44  and the motor connector  43   c  of the high-speed winding bus-bar wiring  43  are disposed at the non-load side of the motor housing portion  111  through the second hole portions  12   a  and the first hole portion  112   a . Thus, the motor connector  44   c  of the low-speed winding bus-bar wiring  44  and the motor connector  43   c  of the high-speed winding bus-bar wiring  43  are disposed at the non-load side of the motor housing portion  111 . This can improve workability in connecting the low-speed winding bus-bar wiring  44  and the high-speed winding bus-bar wiring  43  to the motor  3  in contrast to the case where the motor connectors  43   c  and  44   c  are disposed at the load side without a margin in space due to arrangement of the drive shaft and the like. 
     In the first embodiment, as described above, the motor connector  44   c  of the low-speed winding bus-bar wiring  44  and the motor connector  43   c  of the high-speed winding bus-bar wiring  43 , and the motor connector  51   c  of the inverter bus-bar wiring  51  are disposed in parallel to each other viewed from the axial direction. This makes it possible to perform the operation of connecting the low-speed winding bus-bar wiring  44  and the high-speed winding bus-bar wiring  43  to the motor  3  and the operation of connecting the inverter bus-bar wiring  51  to the motor  3  at the same time (in the same connection process), allowing a further improvement in workability in performing the connections. 
     In the first embodiment, as described above, the first cooling flow passage  61  configured to cool the motor  3  and the inverter  1  is provided between the motor  3  and the inverter  1  in the first housing portion  11 . The first cooling flow passage  61  is extended to the vicinity of the low-speed winding bus-bar wiring  44  and the high-speed winding bus-bar wiring  43  so as to be opposed to the motor connector  44   c  of the low-speed winding bus-bar wiring  44  and the motor connector  43   c  of the high-speed winding bus-bar wiring  43  at the non-load side of the motor housing portion  111 , when viewed from the axial direction. Thus, the cooling liquid flowing through the first cooling flow passage  61  can efficiently cool the motor connector  44   c  of the low-speed winding bus-bar wiring  44  and the motor connector  43   c  of the high-speed winding bus-bar wiring  43 , preventing deterioration due to heat in the motor connector  44   c  and the motor connector  43   c.    
     In the first embodiment, as described above, the second cooling flow passage  62  configured to cool the winding switcher  4  is connected to the first cooling flow passage  61 . The second cooling flow passage  62  is provided on the bottom portion  12   c  of the second housing portion  12  at the first housing portion  11  side. This can cool the winding switcher  4  by the cooling liquid flowing through the second cooling flow passage  62 , preventing the winding switcher  4  from causing deterioration and malfunction due to heat. 
     In the first embodiment, as described above, the controller  5  configured to control the winding switcher  4  and the inverter  1  is disposed at the inverter housing portion  112 . This allows the controller  5  to be separated from the motor  3  producing relatively high feat, preventing the controller  5  from causing deterioration and malfunction due to heat produced by the motor  3 . 
     In the first embodiment, as described above, the surface of the inverter housing portion  112  (upper surface  112   b ) at the second housing portion  12  side and the surface of the second housing portion  12  (lower surface  12   d ) at the inverter housing portion  112  side are configured to have almost the same shape in plan view. Thus, the surface of the second housing portion  12  (lower surface  12   d ) at the inverter housing portion  112  side can be used as a lid configured to cover the inverter housing portion  112 . This eliminates the need to provide a separate lid configured to cover the inverter housing portion  112 . As a result, the configuration of the motor drive unit  10  can be simplified. 
     In the first embodiment, as described above, the second housing portion  12  for housing the winding switcher  4  is configured to be attachable/detachable to/from the first housing portion  11  together with the winding switcher  4 . Thus, the motor drive unit  10  can be configured as a motor drive unit dedicated for low-speed driving by detaching the second housing portion  12  together with the winding switcher  4  and connecting (short-circuiting) the winding  3   b  for low-speed driving. 
     Second Embodiment 
     Next, referring to  FIGS. 22 and 23 , a configuration of a vehicle  102  according to a second embodiment will be described. In the second embodiment, unlike in the first embodiment, a DC-DC converter is connected in parallel to the inverter. 
     As illustrated in  FIG. 22 , in a motor drive unit  10   a  of the vehicle  102 , a DC-DC converter  7  is connected in parallel to the inverter  1 . The DC-DC converter  7  has the function of converting a high voltage into a low voltage and outputting the same (that is, the function of subjecting a direct-current voltage to voltage conversion). The DC-DC converter  7  also has a converter module including a semiconductor element (not illustrated) and a printed wiring substrate (not illustrated). The motor drive unit  10   a  is an example of a “motor driving apparatus.” 
     As illustrated in  FIG. 23 , the DC-DC converter  7  is disposed between the winding switcher  4  and the inverter  1  in the motor drive unit  10   a . Specifically, the DC-DC converter  7  is disposed at a second housing portion  12   e  for housing the winding switcher  4  so as to be opposed to the winding switcher  4  via the second cooling flow passage  62 . That is, the DC-DC converter  7  is disposed at the lower side of the second cooling flow passage  62 . Thus, the DC-DC converter  7  is cooled by a cooling liquid flowing through the second cooling flow passage  62 . Other configurations and advantages of the second embodiment are the same as those of the first embodiment. 
     The embodiments disclosed herein are examples in all respects and should not be considered to be limitative. The scope of the present disclosure is indicated not by the foregoing descriptions of the embodiments but by the scope of the claims. Further, the scope of the present disclosure includes all modifications in the sense equal to the scope of the claims and within the scope of the claims. 
     For example, in the examples of the first and second embodiments, the motor drive unit is mounted in the vehicle. Alternatively, the motor drive unit may be mounted in a device other than a vehicle. 
     In the examples of the first and second embodiments, the inverter housing portion for housing the inverter and the second housing portion for housing the winding switcher are stacked and thereby the winding switcher and the inverter are disposed along the direction approximately orthogonal to the motor axis. Alternatively, the winding switcher may be disposed at the inverter housing portion. In this configuration, the winding switcher and the inverter are disposed in the direction approximately orthogonal to the motor axis, within the inverter housing portion. 
     In the examples of the first and second embodiments, the winding switcher is connected to the low-speed winding bus-bar wiring and the high-speed winding bus-bar wiring. Alternatively, the winding switcher may be connected to cable-like wirings, for example. 
     In the examples of the first and second embodiments, the inverter bus-bar wiring is connected to the inverter. Alternatively, the inverter may be connected to cable-like wirings, for example. 
     In the examples of the first and second embodiments, the low-speed winding bus-bar wiring, the high-speed winding bus-bar wiring, and the motor connector of the inverter bus-bar wiring are disposed at the resolver housing portion so as to be adjacent to one another in the horizontal direction. Alternatively, the low-speed winding bus-bar wiring, the high-speed winding bus-bar wiring, and the motor connector of the inverter bus-bar wiring may be disposed so as not to be adjacent to one another. 
     In the examples of the first and second embodiments, the motor, the winding switcher, and the inverter are cooled by a cooling liquid flowing through the first cooling flow passage and the second cooling flow passage. Alternatively, the motor, the winding switcher, and the inverter may be cooled by a cooling member not using a cooling liquid (for example, an air-cooling device or a cooling element). 
     In the examples of the first and second embodiments, the first cooling flow passage configured to cool the motor and the inverter and the second cooling flow passage configured to cool the winding switcher are connected together. Alternatively, the first cooling flow passage and the second cooling flow passage may not be connected together. The first cooling flow passage and the second cooling flow passage may cool separately the motor and the inverter, and the winding switcher. 
     In the examples of the first and second embodiments, the cooling liquid is flown from the lower side (motor housing portion) to the upper side (second housing portion). Alternatively, the cooling liquid may be flown from the upper side (second housing portion) to the lower side (motor housing portion). 
     In the examples of the first and second embodiments, the high-speed winding switcher  41  and the low-speed winding switcher  42  are shifted from each other in the X direction (refer to  FIG. 14 ). Alternatively, as illustrated in the modification example of  FIG. 24 , the high-speed winding switcher  41  and the low-speed winding switcher  42  may be disposed adjacent to each other in the Y direction. Thus, the high-speed winding switcher  41  and the low-speed winding switcher  42  can be disposed at the second hole portion  12   a  side (X2-direction side), shortening the lengths of the high-speed winding bus-bar wiring and the low-speed winding bus-bar wiring along the X direction. 
     In the example of the second embodiment, switching takes place between the high-speed driving winding and the low-speed driving winding. Alternatively, switching may take place between windings other than the high-speed driving winding and the low-speed driving winding, for example, a low-torque winding and a high-torque winding. 
     In the example of the second embodiment, the DC-DC converter is disposed at the second housing portion for housing the winding switcher, so as to be opposed to the winding switcher via the cooling flow passage. Alternatively, the DC-DC converter may be disposed at the second housing portion so as to be adjacent to the winding switcher. Still alternatively, the DC-DC converter may be disposed at a place other than the second housing portion (for example, within the inverter housing portion). 
     The embodiment in the present disclosure may be first to twelfth motor driving apparatus and the first vehicle as described below. The first motor driving apparatus includes: a motor including a first winding and a second winding; a winding switcher configured to switch between connection states of the first winding and the second winding of the motor; and a power converter connected to the motor, wherein the motor, the power converter, and the winding switcher are stacked in a direction approximately orthogonal to an axial direction of the motor in order of the motor, the power converter, and the winding switcher. 
     The second motor driving apparatus is configured such that the first motor driving apparatus further includes: a first housing portion that includes a motor housing portion for housing the motor and a power converter housing portion for housing the power converter; and a second housing portion that is stacked on the first housing portion in the direction approximately orthogonal to the axial direction of the motor and is configured to house the winding switcher. 
     The third motor driving apparatus is configured such that, in the second motor driving apparatus, the first housing portion is provided with a first hole portion that connects the power converter housing portion and the motor housing portion. 
     The fourth motor driving apparatus is configured such that the third motor driving apparatus further includes a first bus-bar wiring that connects the power converter and the motor, wherein the first bus-bar wiring penetrates through the first hole portion, and a motor connector of the first bus-bar wiring is disposed at a non-load side of the motor housing portion. 
     The fifth motor driving apparatus is configured such that, in any of the second to fourth motor driving apparatus, the second housing portion is provided with a second hole portion that connects the second housing portion and the first housing portion. 
     The sixth motor driving apparatus is configured such that the fifth motor driving apparatus further includes a second bus-bar wiring that connects the winding switcher and the motor, wherein the first housing portion is provided with a first hole portion that connects the power converter housing portion and the motor housing portion, the second bus-bar wiring penetrates through the second hole portion and the first hole portion, and a motor connector of the second bus-bar wiring is disposed at the non-load side of the motor housing portion. 
     The seventh motor driving apparatus is configured such that the sixth motor driving apparatus further includes a first bus-bar wiring that connects the power converter and the motor, wherein the motor connector of the first bus-bar wiring and the motor connector of the second bus-bar wiring are aligned in the horizontal direction viewed from the axial direction. 
     The eighth motor driving apparatus is configured such that any of the second to seventh motor driving apparatus further includes a first cooler that is provided at least between the motor and the power converter in the first housing portion and configured to cool the motor and the power converter; and a second bus-bar wiring that connects the winding switcher and the motor, wherein the first cooler is extended to the vicinity of the second bus-bar wiring so as to be opposed to the motor connector of the second bus-bar wiring disposed at the non-load side of the motor housing portion viewed from the axial direction. 
     The ninth motor driving apparatus is configured such that the eighth motor driving apparatus further includes a second cooler that is connected to the first cooler, provided on a bottom portion of the second housing portion at the first housing portion side, and configured to cool the winding switcher. 
     The tenth motor driving apparatus is configured such that any of the second to ninth motor driving apparatus further includes a controller that is disposed at the power converter housing portion and configured to control the power converter and the winding switcher. 
     The eleventh motor driving apparatus is configured such that, in any of the second to tenth motor driving apparatus, at least a surface of the power converter housing portion at the second housing portion side and a surface of the second housing portion at the power converter housing portion are configured to have almost the same shape in plan view. 
     The twelfth motor driving apparatus is configured such that, in any of the first to eleventh motor driving apparatus, the first winding and the second winding include a high-speed driving winding and a low-speed driving winding, respectively. 
     The thirteenth motor driving apparatus is configured such that, in any of the second to twelfth motor driving apparatus, the second housing portion for housing the winding switcher is configured to be attachable/detachable to/from the first housing portion together with the winding switcher. 
     The first vehicle includes a vehicle main body unit and a motor drive unit that is provided within the vehicle main body unit, wherein the motor drive unit includes: a motor including a first winding and a second winding; a winding switcher configured to switch between connection states of the first winding and the second winding of the motor; and a power converter connected to the motor, and the motor, the power converter, and the winding switcher are stacked in a direction approximately orthogonal to an axial direction of the motor, in order of the motor, the power converter, and the winding switcher. 
     The foregoing detailed description has been presented for the purposes of illustration and description. Many modifications and variations are possible in light of the above teaching. It is not intended to be exhaustive or to limit the subject matter described herein to the precise form disclosed. Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims appended hereto.