Patent Publication Number: US-2021167659-A1

Title: Motor drive device for vehicles

Description:
TECHNICAL FIELD 
     The present invention relates to a motor drive device for vehicles, and particularly relates to a wiring structure of signal cables in a motor drive device for vehicles. 
     BACKGROUND ART 
     Motor drive devices for vehicles include a casing that defines its enclosure, and a motor unit disposed within the casing. Inside the casing are arranged a power line for supplying electric power to the motor unit and a signal cable (signal line) for transmitting detection signals of various sensors to the vehicle body, and these cables are drawn out from the casing to the outside. 
     Among the motor drive device for vehicles, an in-wheel motor drive device disposed in an inner hollow region (within the wheel) of the wheel is particularly required to be lightweight and compact as much as possible, due to the mountability to the vehicle and in terms of enhancing driving performance. Therefore, in order to dispose the various cables within the limited space without interfering with peripheral components, many thoughts have been given to the protection structure of the cables within the casing and the fixing structure for improving wire connection workability. 
     Japanese Unexamined Patent Publication No. 2012-206709 (Patent Document 1) discloses a structure that passes a power cable (power line) that supplies electric source to the motor unit through the inside of a motor support shaft. Moreover, as a method for improving workability of wire connection, use of a socket (connector) as in Japanese Unexamined Patent Publication No. 2016-068605 (Patent Document 2) is also broadly implemented. 
     Japanese Unexamined Patent Publication No. 2016-111862 (Patent Document 3) discloses a wire fixing structure for preventing cables from being pinched in an assembling process of a motor drive device for vehicles. 
     CITATION LIST 
     Patent Literatures 
     [Patent Document 1] Japanese Unexamined Patent Publication No. 2012-206709 
     [Patent Document 2] Japanese Unexamined Patent Publication No. 2016-068605 
     [Patent Document 3] Japanese Unexamined Patent Publication No. 2016-111862 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the technique of Patent Document 1, the power line is not positioned and fixed at the point of closing the housing (side portion). Therefore, the wired state of the power line within the housing cannot be directly (visually) confirmed at the time of completing the assembling. For example, a method can be considered in which the wired state of the power line is managed by the length of the wire from a wire inlet of a through hole of a motor shaft, however the tension applied on the cable within the housing and the bent state and clearance from the peripheral components will vary depending on the way the assembly work is performed. 
     On the other hand, in the technique of Patent Document 3, a signal cable of a revolution sensor attached and fixed to an inner edge surface of a rear cover is arranged in a radial and vertical direction along this inner end surface, and provides a fixing unit on a passage of this signal cable. Furthermore, the technique employs a housing structure that prevents the cable from being pinched at a position that becomes a blind spot when attaching the rear cover to an end portion of the motor casing in an axial direction. Therefore, the technique of Patent Document 3 can eliminate to the utmost degree the possibility of malfunctioning due to the signal cable wired state during assembly and after completion of the drive device. 
     However, the technique of Patent Document 3 can only be applied to a wiring structure that arranges the signal cable of the sensor attached on the inner end surface of the rear cover in the radial direction, and that draws this signal cable to a terminal box positioned on an outer peripheral side of the motor casing. That is to say, in a motor drive device in which an external connector of the signal cable is provided for example on the rear cover, the technique of Patent Document 3 cannot be applied to the wiring structure of the signal cable from the sensor fixed to the motor casing or the reducer unit casing to the external connector. Therefore, even with such motor drive device, there has been a demand for a technique to improve the reliability of the wired state of the signal cable upon completion of the assembly. 
     The present invention is accomplished to overcome the above problem, and an object thereof is to provide a motor drive device for vehicles that allows for improving the reliability of a wired state of the signal cable within the casing. 
     Solution to Problem 
     A motor drive device for vehicles according to an aspect of this invention includes: a motor unit including a motor rotating shaft configured to drive a wheel; and a casing configured to partition a first space in which the motor unit is disposed and a second space positioned on one side in an axial direction of the first space, and including a partition part provided with a through hole configured to communicate the first and second spaces. The casing is divided into a cylindrical first case portion integrally formed with the partition part, a second case section being connected to one end of the first casing in the axial direction and covering the second space, and a third case portion connected to the other end of the first case portion in the axial direction and covering the first space. This motor drive device for vehicles includes: a sensor disposed within the casing; a signal cable extending from the sensor to an external connector provided in the second case portion or the third case portion and which is passed through the through hole of the partition part; and an anchoring unit. The anchoring unit anchors the signal cable to the first case portion in the vicinity of the through hole of the partition part. 
     Preferably, the external connector or a cable fixing member provided in the second case portion or the third case portion is disposed at a position facing the through hole of the partition part in the axial direction. 
     Preferably, the signal cable has a first cable extending from the external connector, and a second cable extending from the sensor side and being connected to the first cable. In this case, the first cable and the second cable are connected by an internal connector, and the anchoring unit preferably includes a connector fixing member that fixes the internal connector in the vicinity of the through hole of the partition part. 
     Preferably, the external connector is provided in the third case portion. In this case, the external connector or the cable fixing member to a tip of the internal connector preferably has a length in the axial direction not less than a length in the axial direction from the external connector or the cable fixing member to an end plane of the partition part on the second space side. 
     Preferably, the anchoring unit includes a play retaining member configured to retain a playing part of the first cable or the second cable in the vicinity of the through hole of the partition part. 
     Preferably, the first cable is connected to the sensor that is fixed to the first case portion. 
     The signal cable may extend along the axial direction between an internal connector to which the sensor is integrally provided and the external connector. In this case also, the anchoring unit preferably includes a connector fixing member configured to fix the internal connector in the vicinity of the through hole of the partition part. 
     Preferably, an oil tank configured to store lubricating oil is provided lower of the second space, and the through hole is an opening for returning lubricating oil from the first space to the oil tank in the second space. 
     The motor drive device for vehicles further includes a reducer unit configured to reduce rotation of the motor rotating shaft, which is positioned in the second space. The reducer unit includes an input shaft coupled with one end of the motor rotating shaft in the axial direction and an output shaft disposed parallel to the input shaft. In this case, the through hole of the partition part is preferably provided at a position below shaft centers of the input shaft and the output shaft of the reducer unit. 
     The motor drive device for vehicles is preferably an in-wheel motor drive device in which the casing is disposed in an inner hollow region of the wheel. In this case, the one side of the motor rotating shaft in the axial direction is an outer side in a vehicle width direction, and the other side of the motor rotating shaft in the axial direction is an inner side in the vehicle width direction. 
     Advantageous Effects of Invention 
     According to the present invention, the wired state of the signal cables within the casing can be directly confirmed in the assembling process of the motor drive device for vehicles. Therefore, according to the present invention, it is possible to improve the reliability of the wired state of the signal cable within the casing. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a longitudinal section view cutting the in-wheel motor drive device according to an embodiment of the present invention at a predefined plane, and illustrating this in a developed manner. 
         FIG. 2  is a cross sectional view illustrating an inner structure of a reducer unit of the in-wheel motor drive device according to an embodiment of the present invention, and schematically represents a state viewed from an outer side in a vehicle width direction. 
         FIG. 3  is a cross sectional view schematically illustrating a wiring structure of a signal cable in an embodiment of the present invention. 
         FIG. 4  is a view conceptually illustrating a positional relationship in an axial direction of a partition part and an internal connector, in an embodiment of the present invention. 
         FIG. 5  is a view conceptually illustrating an anchored state of the internal connector, viewing the first case portion from the outer side in the vehicle width direction, in an embodiment of the present invention. 
         FIG. 6  is a view conceptually illustrating a position of the external connector, viewing the third case portion from an outer side in the vehicle width direction, in Modification 1 of an embodiment of the present invention. 
         FIG. 7  is a view schematically illustrating another arrangement example of a rotary angle sensor. 
         FIG. 8  is a view schematically illustrating another example of a connected position of the signal cable. 
         FIG. 9  is a view schematically illustrating another arrangement example of the external connector. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of the present invention is described in detail with reference to the drawings. Identical or equivalent portions within the drawings will be provided with identical reference symbols, and their descriptions will not be repeated. 
     Basic Configuration Example of In-Wheel Drive Device 
     First described with reference to  FIG. 1  and  FIG. 2  is an example of a basic configuration of an in-wheel motor drive device  1  according to an embodiment of the present invention. The in-wheel motor drive device  1  is installed in passenger cars such as electric automobiles and hybrid vehicles. 
       FIG. 1  is a longitudinal section view cutting the in-wheel motor drive device  1  according to an embodiment of the present invention at a predefined plane, and illustrating this in a developed manner.  FIG. 2  is a cross sectional view illustrating an inner structure of a reducer unit  31  of the in-wheel motor drive device  1 , and schematically represents a state viewed from an outer side in a vehicle width direction. The predefined plane illustrated in  FIG. 1  is a developed plan view connecting a plan view including an axis M and an axis N shown in  FIG. 2 , and a plan view including the axis N and an axis O, in this order. A left side of printed  FIG. 1  represents an outer side (outboard side) in the vehicle width direction, and a right side of printed  FIG. 1  represents an inner side (inboard side) in the vehicle width direction. In  FIG. 2 , each gear within the reducer unit  31  is represented by an addendum circle, and each individual tooth is omitted in the drawing. 
     The in-wheel motor drive device  1  includes a wheel hub bearing unit  11  provided at the center of a wheel W, a motor unit  21  that drives the wheels, and a reducer unit  31  that reduces the rotation of the motor unit  21  and transmits this to the wheel hub bearing unit  11 . 
     The motor unit  21  and reducer unit  31  are disposed offset of the axis O of the wheel hub bearing unit  11 . The axis O extends in the vehicle width direction, and is coaxial to the axle. In the present embodiment, the one side in the axis O direction is the outer side in the vehicle width direction, and the other side in the axis O direction is the inner side in the vehicle width direction. 
     In regards to positions in the axis O direction, the wheel hub bearing unit  11  is disposed on one side of the in-wheel motor drive device  1  in the axis direction, the motor unit  21  is disposed on the other side of the in-wheel motor drive device  1  in the axis direction, the reducer unit  31  is disposed on the one side in the axis direction of the motor unit  21 , and the position in the axis direction of the reducer unit  31  overlaps with the position in the axis direction of the wheel hub bearing unit  11 . 
     The in-wheel motor drive device  1  is a motor drive device for vehicles to drive wheels of an electric motor vehicle. The in-wheel motor drive device  1  is connected to a vehicle body not illustrated. The in-wheel motor drive device  1  can make the electric motor vehicle run at a speed of 0 to 180 km/h. 
     The in-wheel motor drive device  1  includes a casing  10  that defines its enclosure. In the description of the casing  10 , a direction along an axis M direction of the motor unit  21  (axis O direction of the reducer unit  31 ) is also called an axial direction. Moreover, a direction orthogonal to the axis M direction is called a radial direction. 
     The casing  10  includes a partition part  54  that partitions in the axial direction a first space S 1  in which the motor unit  21  is disposed and a second space S 2  in which the reducer unit  31  is disposed. The partition part  54  extends in the radial direction, and has an insertion hole  54   a  through which one end of the motor rotating shaft  22  in the axis M direction is inserted. The casing  10  is divided into three case portions  51 ,  52 , and  53  along the axial direction. 
     The first case portion  51  is a cylindrical case portion with the partition part  54  in an integrated manner. The first case portion  51  has a part  51   a  located on the other side in the axial direction (inner side of the vehicle width direction) of the partition part  54  and a part  51   b  located on the one side in the axial direction (outer side of the vehicle width direction) of the partition part  54 . The partition part  54  is disposed offset to one side in the axial direction from a center position of the first case portion  51  in the axial direction. Therefore, the first case portion  51  mainly functions as a motor casing that surrounds the first space S 1 . In the following description, among the first case portion  51 , the part  51   a  surrounding the first space S 1  side is called body part  51   a,  and the part  51   b  surrounding the first space S 1  side is called protruding part  51   b.    
     The second case portion  52  is connected to the one end of the first case portion  51  in the axial direction and covers the second space S 2 . The second case portion  52  includes a cylindrical portion  52   t  that abuts an end plane of the protruding part  51   b  of the first case portion  51 , and a wall portion  52   f  of a plate form that closes the one end of the cylindrical portion  52   t  in the axial direction. As such, the second case portion  52  mainly functions as a reducer unit casing that surrounds the second space S 2 . 
     The third case portion  53  is connected to the other end of the first case portion  51  in the axial direction, and covers the first space S 1 . The third case portion  53  is a lid of the first case portion  51 , and functions as a rear cover (motor casing cover). The third case portion  53  is shaped as a bowl for example, and includes a cylindrical portion  53   t  that abuts an end plane of the body part  51   a  of the first case portion  51 , and a wall portion  53   r  of a plate shape that closes the other end of the cylindrical portion  53   t  in the axial direction. 
     In this case, the motor unit  21  is covered from the one side in the axial direction by the partition part  54 , and is covered from the other side in the axial direction by the wall portion  53   r.  The reducer unit  31  is covered from the one side in the axial direction by the wall portion  52   f  of the second case portion  52 , and is covered from the other side in the axial direction by the partition part  54 . The wall portion  52   f  of the second case portion  52  defines an outer side end plane of the casing  10  in the vehicle width direction, and the wall portion  53   r  of the third case portion  53  defines an inner side end plane of the casing  10  in the vehicle width direction. 
     As such, in the present embodiment, the first space S 1  including a motor chamber is divided by a cylindrical portion defined by the body part  51   a  of the first case portion  51  and the cylindrical portion  53   t  of the third case portion  53 , and by the partition part  54  and the wall portion  53   r  that intersect with this cylindrical portion. The second space S 2  including a reducer chamber is divided by a cylindrical portion defined by the cylindrical portion  52   t  of the second case portion  52  and the protruding part  51   b  of the first case portion  51 , and by the partition part  54  and the wall portion  53   f  that intersect with this cylindrical portion. 
     The wheel hub bearing unit  11  is deemed as a rotating inner ring/stationary outer ring, and has an inner ring  12  as a rotating ring (hub ring) that couples with the wheel W, an outer ring  13  as a stationary ring disposed coaxially to an outside diameter side of the inner ring  12 , and a plurality of rolling elements  14  disposed in an annular space between the inner ring  12  and the outer ring  13 . The center of rotation of the inner ring  12  matches with the axis O passing through the center of the wheel hub bearing unit  11 . 
     The outer ring  13  penetrates through the wall portion  52   f  of the casing  10  (second case portion  52 ), and is connected and fixed to this wall portion  52   f.  For example, a plurality of outer ring protrusions that protrude in an outer radial direction are provided upright at various positions in a circumferential direction on an outer peripheral surface of the outer ring  13 , and bolts are passed through from the one side in the axis O direction to the through holes provided to each of the outer ring protrusions. Shank portions of the bolts screw together with a female screw drilled in the wall portion  52   f  of the casing  10 . 
     The outer ring  13  has a carrier member  61  connected and fixed thereto. On the outer peripheral surface of the outer ring  13 , a plurality of outer ring protrusions  13   g  are provided that protrude in the outer radial direction at various locations in the circumferential direction. The carrier member  61  is positioned on the other side of the outer ring protrusion  13   g  in the axis O direction, and from the one side in the axis O direction, a bolt  62  is passed through a through hole of the outer ring protrusion  13   g  and a female screw hole of the carrier member  61 . The carrier member  61  is fixed to the outer periphery of the second case portion  52  of the casing  10  by a bolt  63  passed through from the other side in the axis O direction. 
     The inner ring  12  is of a cylindrical form longer than the outer ring  13 , and is passed through a center hole of the outer ring  13 . On one end of the inner ring  12  in the axis O direction that protrudes externally (outer side in the vehicle width direction) from the outer ring  13 , a coupling portion  12   f  is formed. The coupling portion  12   f  is a flange, and configures a coupling unit for coaxially coupling a brake rotor and the wheel. The inner ring  12  couples with the wheel W at the coupling portion  12   f,  and rotates integrally with the wheel W. 
     Plural rows of rolling elements  14  are disposed in the annular space between the inner ring  12  and the outer ring  13 . The outer peripheral surface of the inner ring  12  at a middle portion in the axis O direction configures an inner race surface of the plurality of rolling elements  14  disposed in a first row. An inner race wheel  12   r  fits with the outer peripheral surface on the other end of the inner ring  12  in the axis O direction. An outer peripheral surface of the inner race wheel  12   r  configures an inner race surface of the plurality of the rolling elements  14  disposed in a second row. The inner peripheral surface of the outer ring  13  on the one end in the axis O direction configures an outer race surface of the rolling elements  14  in the first row. The inner peripheral surface of the outer ring  13  on the other end in the axis O direction configures an outer race surface of the rolling elements  14  in the second row. In the annular space between the inner ring  12  and the outer ring  13 , a sealing material  16  also intervenes. The sealing material  16  seals both ends of the annular space, and prevents intrusion of dust and contaminants. In the center hole of the other end of the inner ring  12  in the axis O direction, an output shaft  38  of the reducer unit  31  is inserted and is spline fitted. 
     The motor unit  21  has a motor rotating shaft  22 , a rotor  23 , and a stator  24 , and these are disposed successively in this order from the axis M of the motor unit  21  radially towards the outside. The stator  24  includes a cylindrical core portion (hereinafter, called “stator core”)  25 , and a coil  26  wound around the stator core  25 . The stator core  25  has steel plates of a ring form stacked in the axis M direction. The motor unit  21  is a radial gap motor with an inner rotor and outer stator form, however this may be of another form. For example, although not illustrated, the motor unit  21  may be an axial gap motor. 
     Both ends of the motor rotating shaft  22  are rotatably supported to the partition part  54  of the first case portion  51  and the wall portion  53   r  of the third case portion  52  and via the rolling-element bearings  27 ,  28 . The rolling-element bearing  27  is positioned on the outer side in the vehicle width direction of the rolling-element bearing  28 . Accordingly, the one end of the motor rotating shaft  22  in the axis M direction is supported by the rolling-element bearing  27 , and the other end of the motor rotating shaft  22  in the axis M direction is supported by the rolling-element bearing  28 . 
     The axis M serving as the center of rotation of the motor rotating shaft  22  and the rotor  23  extends parallel to the axis O of the wheel hub bearing unit  11 . Namely, the motor unit  21  is disposed offset, to be away from the axis O of the wheel hub bearing unit  11 . For example, as illustrated in  FIG. 2 , the axis M of the motor unit  21  is disposed offset in a vehicle front-rear direction from the axis O, more specifically on a vehicle front side than the axis O. 
     The reducer unit  31  has an input shaft  32  that couples coaxially with the motor rotating shaft  22  of the motor unit  21 , an input gear  33  provided coaxially with the outer peripheral surface of the input shaft  32 , a plurality of intermediate gears  34 ,  36 , an intermediate shaft  35  coupled with the centers of these intermediate gears  34 ,  36 , the output shaft  38  coupled coaxially to the inner ring  12  of the wheel hub bearing unit  11 , and an output gear  37  provided coaxially to the outer peripheral surface of the output shaft  38 . 
     The input gear  33  is an external helical gear. The input shaft  32  is of a hollow structure, and one end  22   e  in the axis direction of the motor rotating shaft  22  is inserted into a hollow portion  32   h  of the input shaft  32 . Accordingly, the motor rotating shaft  22  spline fits (or serration fits) in a relatively non-rotatable manner against the input shaft  32 . 
     The input shaft  32  is supported freely rotatable on both ends of the input gear  33  to the wall portion  52   f  of the second case portion  52  and the partition part  54  of the first case portion  51 , via the rolling-element bearings  32   a,    32   b.  The rolling-element bearing  32   a  is positioned on the outer side in the vehicle width direction of the rolling-element bearing  32   b.  Accordingly, the one end of the input shaft  32  in the axis M direction is supported by the rolling-element bearing  32   a,  and the other end of the input shaft  32  in the axis M direction is supported by the rolling-element bearing  32   b.    
     The axis N serving as the center of rotation for the intermediate shaft  35  of the reducer unit  31  extends parallel to the axis O. Both ends of the intermediate shaft  35  are supported freely rotatable by the wall portion  52   f  of the second case portion  52  and the partition part  54  of the first case portion  52  via rolling-element bearings  35   a,    35   b.  At the middle portion of the intermediate shaft  35 , the first intermediate gear  34  and the second intermediate gear  36  are provided coaxially to the axis N of the intermediate shaft  35 . The first intermediate gear  34  and the second intermediate gear  36  are external helical gears, and the diameter of the first intermediate gear  34  is greater than the diameter of the second intermediate gear  36 . The first intermediate gear  34  a the larger diameter is disposed on the other side in the axis N direction of the second intermediate gear  36 , and meshes with the input gear  33  with a smaller diameter. The second intermediate gear  36  with a smaller diameter is disposed on the one side in the axis N direction of the first intermediate gear  34 , and meshes with the output gear  37  with a greater diameter. 
     The axis N of the intermediate shaft  35  is disposed above the axis O and axis M, as illustrated in  FIG. 1 . Moreover, the axis N of the intermediate shaft  35  is disposed in the vehicle anterior of the axis O and in the vehicle posterior of the axis M. The reducer unit  31  is a parallel-shaft gear reducer with three shafts disposed spaced out in a vehicle front-rear direction, having respective axes O, N, M extending parallel to each other. In the present embodiment, a cylindrical portion positioned on the outer side in the vehicle width direction (one side in the axial direction) of the partition part  54 , namely the cylindrical portion  52   t  of the second case portion  52 , and the protruding part  51   b  of the first case portion  51  are disposed to surround the axes O, N, M (a plurality of shafts  32 ,  35 ,  38 ). 
     The output gear  37  is an external helical gear, and is provided coaxially to a middle portion of the output shaft  38 . The output shaft  38  extends along the axis O. One end of the output shaft  38  in the axis O direction is inserted into the center hole of the inner ring  12 , and is fitted in a relatively non-rotatable manner. Such fitting is spline fitting or serration fitting. The middle portion of the output shaft  38  in the axis O direction (one end side) is supported by the wall portion  52   f  of the second case portion  52  via the rolling-element bearing  38   a.  The other end of the output shaft  38  in the axis O direction (other end side) is supported freely rotatable by the partition part  54  of the first case portion  51  via the rolling-element bearing  38   b.    
     The reducer unit  31  reduces the rotation of the input shaft  32  and transmits it to the output shaft  38  by meshing a driving gear of a smaller diameter and a driven gear of a larger diameter, namely meshing the input gear  33  with the first intermediate gear  34 , and meshing the second intermediate gear  36  with the output gear  37 . Rotating elements from the input shaft  32  to the output shaft  38  of the reducer unit  31  define a drive transmitting path that transmits the rotation of the motor unit  21  to the inner ring  12 . The input shaft  32 , the intermediate shaft  35 , and the output shaft  38  are supported by both ends by the rolling-element bearings described above. These rolling-element bearings  32   a,    35   a,    38   a,    32   b,    35   b,    38   b  are radial bearings. 
     In the present embodiment, as illustrated in  FIG. 2 , an oil tank  40  is provided lower of the second space S 2 . The casing  10  protrudes downwards at a position below the input shaft  32 , and the oil tank  40  is formed in that protruding part. The oil tank  40  stores lubricating oil. As such, the casing  10  encapsulates lubricating oil, and the lubricating oil circulates within the casing  10 . 
     The lubricating oil lubricates the motor unit  21  and the rotating elements of the reducer unit  31 , as well as been used to cool the stator  24  that is a heat generating element of the motor unit  21 . The in-wheel motor drive device  1  includes an oil pump (not illustrated) that pumps up the lubricating oil from the oil tank  40 , and an oil passage that guides the lubricating oil pumped up by the oil pump to the motor unit  21  and the reducer unit  31 . 
     The oil pump is for example coupled coaxially to the output shaft  38 , and is driven by the output shaft  38 . More specifically, the other end of the output shaft  38  in the axis O direction extends upon penetrating through the partition part  54 , and the oil pump may couple with the other end of the output shaft  38  in the axis O direction that protrudes from this partition part  54 . 
     When electric power is supplied to the stator  24  of the motor unit  21  via a three-phase power cable (not illustrated) from the outside of the in-wheel motor drive device  1 , the rotor  23  of the motor unit  21  rotates, and the rotation is outputted from the motor rotating shaft  22  to the reducer unit  31 . The reducer unit  31  reduces the rotation inputted from the motor unit  21  to the input shaft  32 , and outputs the rotation from the output shaft  38  to the wheel hub bearing unit  11 . The inner ring  12  of the wheel hub bearing unit  11  rotates at the same rotational speed as the output shaft  38 , and drives the wheel (not illustrated) that is attached and fixed to the inner ring  12 . 
     A power cable is drawn into the first space S 1  from a terminal box (not illustrated) provided in the casing  10 . The terminal box is, for example, provided upper of the first case portion  51  or the third case portion  53 . 
     Here, a plurality of sensors including a rotary angle sensor (resolver)  28  is disposed within the casing  10 , and detected signals of the sensors are transmitted externally (vehicle body side) via signal cables. Therefore, signal cables are arranged for each sensor, within the casing  10 . 
     In the present embodiment, the signal cables are drawn out externally from locations different from the power cables. The signal cables are not drawn externally through the terminal box, but is drawn externally from the wall portion  53   r  of the third case portion  52  of the casing  10 . The wiring structure of the signal cables according to the present embodiment is described in details below. 
     Wiring Structure of Signal Cables 
     Described with reference to  FIG. 3  is the wiring structure of the signal cables according to the present embodiment.  FIG. 3  is a cross-sectional view schematically illustrating the wiring structure of the signal cables in the present embodiment. In  FIG. 3 , illustration of the reducer unit  31  has been omitted. 
     As illustrated in  FIG. 3 , a signal line outlet  53   b  is provided in the wall portion  53   r  of the third case portion  53 . The signal line outlet  53   b  is disposed on an outer side in a radial direction of the position of the outer peripheral surface of the stator  24 , when viewing the casing  10  from the inner side in the vehicle width direction along the axis direction. More specifically, the first space S 1  has a motor chamber S 11  and a wire housing chamber S 12  positioned below the motor chamber S 11 , and the signal line outlet  53   b  is provided at a region facing the wire housing chamber S 12  among the wall portion  53   r  of the third case portion  53 . 
     The wire housing chamber S 12  is divided in the axial direction by the partition part  54  and the wall portion  53   r,  as with the motor chamber S 11 . At a boundary position between the motor chamber S 11  and the wire housing chamber S 12 , a boundary wall  55  disposed on the outer periphery of the stator  24  is disposed. The boundary wall  55  extends from the partition part  54  to the inner side in the vehicle width direction. 
     An external connector  81  is inserted through the signal line outlet  53   b  in the axial direction. Namely, the external connector  81  is fixed to a region facing the wire housing chamber  812  among the wall portion  53   r  of the third case portion  53 . The external connector  81  is a connecting member for collecting the plurality of signal cables within the casing  10  and connecting them to external signal cables (not illustrated). 
     In the present embodiment, a rotary angle sensor  71 , an oil temperature thermistor  72 , and a motor thermistor  73  are disposed inside the casing  10 . The rotary angle sensor  71  is a sensor that detects angle of rotation of the motor rotating shaft  22 . The oil temperature thermistor  72  is a sensor that detects the temperature of the lubricating oil circulating within the casing  10 . The motor thermistor  73  is a sensor that detects the temperature of the coil  26  of the motor unit  21 . 
     The rotary angle sensor  71  is attached on the other end side of the motor rotating shaft  22  in the axis M direction, and is housed in a sensor chamber S 3  provided on the wall portion  53   r  of the third case portion  53 . The wall portion  53   r  has a cylindrical opening  53   a  that communicates the motor chamber S 11  of the first space S 1  with the sensor chamber S 3 . The rotary angle sensor  71  is disposed in an annular space between the other end of the motor rotating shaft  22  in the axis M direction passed through this opening  53   a  and the cylindrical plane of the opening  53   a.  The sensor chamber S 3  is closed by a lid portion  56  connected to the third case portion  53 . 
     A signal cable  71   c  extending from the rotary angle sensor  71  is arranged to the external connector  81  along an inner end plane of the third case portion  53 . A wire connection exists in a middle position of the signal cable  71   c.  For example, a cable  71   a  extending from the external connector  81  and a cable  71   b  extending from the rotary angle sensor  71  are connected by an internal connector  88 . 
     The signal cable  71   c  is arranged from the motor chamber S 11  to the wire housing chamber S 12  by passing through a gap in the axial direction between the wall portion  53   r  of the third case portion  53  and the boundary wall  55  that retains the stator  24 . Play of the signal cable  71   c  is retained by a clamp member  84 , and is fixed to the wall portion  53   r  of the third case portion  53 . The clamp member  84  is a play retaining member that retains the play of the signal cable  71   c.  This allows for preventing the signal cable  71   c  from interfering with the motor unit  21 . 
     As such, since the rotary angle sensor  71  is fixed to the third case portion  53  provided with the external connector  81 , the wire connection of the signal cable  71   c  of the rotary angle sensor  71  and the connection to the external connector  81  concludes within the third case portion  53 . 
     On the other hand, the oil temperature thermistor  72  and the motor thermistor  73  are disposed independently of the third case portion  53 , different from the rotary angle sensor  71 . More specifically, the oil temperature thermistor  72  is, for example, disposed within the oil tank  40  in the second space S 2  as illustrated in  FIG. 2 . The motor thermistor  73  is, for example, provided to a coil (coil end)  26   a  positioned on one side in the axis M direction of the stator core  25 , as illustrated in  FIG. 3 . 
     Therefore, the signal cable  72   c  of the oil temperature thermistor  72  is drawn into the wire housing chamber S 12  of the first space S 1  through the through hole  54   c  of the partition part  54 . The signal cable  72   c  has the cable  72   b  extending from the oil temperature thermistor  72  and the cable  72   a  extending from the external connector  81  side, and these cables  72   a,    72   b  are connected in the vicinity of the through hole  54   c.    FIG. 2  schematically illustrates a state in which the cable  72   a  whose one end is connected to the oil temperature thermistor  72  is arranged to the through hole  54   c.    
     The partition part  54  has, in addition to the insertion hole  54   a  described above, two through holes  54   b,    54   c.  The signal cable  73   c  of the motor thermistor  73 , after being drawn out to the second space S 2  side once passed through one of the through holes,  54   b,  is drawn into the other through hole  54   c  to the wire housing chamber S 12 . As illustrated in  FIGS. 2 and 3 , the through hole  54   c  is positioned relatively outer in the radial direction and below the through hole  54   b.    
     That is to say, the signal cable  73   c  of the motor thermistor  73  disposed in the motor chamber S 11  of the first space S 1  is drawn into the wire housing chamber S 12  via the through holes  54   b,    54   c  and detouring to the second space S 2  (reducer chamber) side. The through holes  54   b,    54   c  provided in the partition part  54  are oil return paths (opening) to return the lubricating oil from the motor chamber S 11  in the first space S 1  to the oil tank  40  in the second space S 2 . In the present embodiment, two through holes  54   b,    54   c  are provided as the oil return paths, however the oil return path may be accomplished as one through hole. 
     The signal cable  73   c  includes the cable  73   b  extending from the motor thermistor  73  and the cable  73   a  extending from the external connector  81  side, and these cables  73   a,    73   b  are also connected in the vicinity of the through hole  54   c.    FIG. 2  schematically illustrates a state in which the cable  73   c  whose one end is connected to the motor thermistor  73  is arranged to the through hole  54   c  via the through hole  54   b.    
     The external connector  81  is disposed at a position facing the through hole  54   c  in the axial direction, through which the signal cables  72   c,    73   c  are passed. Therefore, it is possible to arrange the two connector side cables  72   a,    73   a  whose one end is connected to the external connector  81 , linearly along the axial direction. 
     In the present embodiment, the sensor side cable  72   b  whose one end is connected to the oil temperature thermistor  72  and the connector side cable  72   a  whose one end is connected to the external connector  81  are connected by the internal connector  82  (internal connector  822  illustrated in  FIG. 4 ). Similarly, the sensor side cable  73   b  whose one end is connected to the motor thermistor  73  and the connector side cable  73   a  whose one end is connected to the external connector  81  are connected by the internal connector  82  (internal connector  823  illustrated in  FIG. 4 ). 
     As such, the connector side cables  72   a,    73   a  (first cable) and the sensor side cables  72   b,    73   b  (second cable) are connected by the internal connector  82 . The internal connector  82  is fixed to tips of the connector side cables  72   a,    73   a,  and at tip portions of the sensor side cables  72   b,    73   b,  a terminal portion (not illustrated) that engages with the internal connector  82  is provided. 
     Rough assembly procedures of the in-wheel motor drive device  1  is as follows. 
     Process P1: Assemble the motor unit  21  on the first space S 1  side of the first case portion  51 .
 
Process P2: Close the inner side plane of the first case portion  51  in the vehicle width direction with the third case portion  53  to which the external connector  81  and the rotary angle sensor  71  are fixed in advance.
 
Process P3: Connect the sensor side cables  72   b,    73   b  of the oil temperature thermistor  72  and the motor thermistor  73  and their connector side cables  72   a,    73   a,  with the internal connector  82 .
 
Process P4: Assemble the reducer unit  31  on the second space S 2  side of the first case portion  51 .
 
Process P5: Close the outer side plane of the first case portion  51  in the vehicle width direction with the second case portion  52 , to complete the casing  10 . Moreover, fix the wheel hub bearing unit  11  to the wall portion  52   f  of the second case portion  52 .
 
     As such, in the present embodiment, the wire connection work of the signal cables  72   c,    73   c  of the oil temperature thermistor  72  and the motor thermistor  73  is performed after connecting the first case portion  51  and the third case portion  53 . 
     Here, referring to the conceptual drawing of  FIG. 4 , a length in the axial direction from the external connector  81  attached to the third case portion  53  (or the inner end plane of the third case portion  53 ) to the position of the through hole  54   c  on the outer end plane of the partition part  54  in the vehicle width direction is represented by length L 1 . Moreover, a length in the axial direction from the external connector  81  attached to the third case portion  53  (or the inner end plane of the third case portion  53 ) to the tip position of the internal connector  82  is represented by length L 2 . 
     Under this condition, the length L 2  in the axial direction from the external connector  81  to the internal connector  82  is not less than the length L 1  in the axial direction from the external connector  81  to the partition part  54 . Accordingly, it is possible to expose the tip of the internal connector  82  to the second space S 2  side when coupling the third case portion  53  to the first case portion  51  in process P2. It is thus possible to easily perform the connecting work of the sensor side cables  72   b,    73   b  to the internal connector  82  in the second space S 2  side. 
     Moreover, in the present embodiment, in process P3, after the signal cables  72   c,    73   c  are connected, the internal connector  82  is anchored in the vicinity of the through hole  54   c  of the partition part  54 . Namely, the in-wheel motor drive device  1  includes an anchoring unit  83  to anchor the signal cables  72   c,    73   c  to the first case portion  51  in the vicinity of the through hole  54   c  of the partition part  54 . 
     The anchoring unit  83  includes, for example, a retaining member  86  that retains the internal connector  82 , and a bolt  87  for fixing the retaining member  86  to the partition part  54 . The retaining member  86  and the bolt  87  constitute a connector fixing member for fixing the internal connector  82  in the vicinity of the through hole  54   c  of the partition part  54 . 
     The retaining member  86  is formed in an L-shape for example, and has a first plate portion  86   a  fixed by the bolt  87  to an end plane of the partition part  54  on the second space S 2  side and extending in the radial direction, and a second plate portion  86   b  that intersects orthogonally to the first plate portion  86   a  and extends within the wire housing chamber S 12  towards the other side in the axial direction (inner side in the vehicle width direction). The internal connector  82  is retained by the second plate portion  86   b.    
       FIG. 5  conceptually illustrates a state in which the internal connector  82  ( 822 ,  823 ) is anchored by the partition part  54 .  FIG. 5  is a view looking at the first case portion  51  from the outer side in the vehicle width direction. The second plate portion  86   b  of the retaining member  86  has, for example, an engaged portion (not illustrated) to which an engaging portion provided in the internal connector  82  is engaged. The internal connector  82  may be fixed to the boundary wall  55  extending from the partition part  54  towards the inner side in the vehicle width direction. 
     As described above, the external connector  81  (signal line outlet  52   b ) is disposed at a position facing the through hole  54   c  of the partition part  54  in the axial direction. More specifically, as illustrated in the conceptual diagram of  FIG. 4 , in a case of viewing the partition part  54  from the outer side in the vehicle width direction, the through hole  54   c  and at least one part of the external connector  81  overlaps. This allows for visually confirming the state inside the wire housing chamber S 12 , and hence allows for confirming the wired state of the signal cables  72   c,    73   c  within the wire housing portion S 12 . 
     Namely, after completion of the wire connection work of the signal cables  72   c,    73   c  in process P3, it is possible to visually confirm the final wired state of the signal cables  72   c,    73   c  within the wire housing chamber S 12  before assembling the reducer unit  31  in process P4. That is to say, in the process of assembling the in-wheel motor drive device  1 , it is possible to confirm the wired state of the signal cables  72   c,    73   c  after assembly completion. 
     In the wire housing chamber S 12 , the signal cables  72   c,    73   c  (connector side cables  72   a,    73   a ) are preferably arranged linearly along the axial direction. Therefore, in a case in which there is play more than necessary in the connector side cables  72   a,    73   a,  it is preferable to anchor the playing part in the vicinity of the through hole  54   c  of the partition part  54 . In the present embodiment, as illustrated in  FIG. 3 , the anchoring unit  83  includes a clamp member  85  for retaining the playing part of the connector side cables  72   a,    73   a  in the vicinity of the through hole  54   c  of the partition part  54 . The clamp member  85  is fixed to the second plate portion  86   b  of the retaining member  86  together with the internal connector  82 . 
     Similarly for the sensor side cables  72   b,    73   b,  in the case in which there is play more than necessary, the anchoring unit  83  preferably includes a play retaining member (clamp member) that retains the playing part of the sensor side cables  72   b,    73   b  in the vicinity of the through hole  54   c  of the partition part  5 . 
     This thus allows for holding down unexpected movements of the signal cables  72   c,    73   c,  thereby preventing disconnection of the signal cables  72   c,    73   c.    
     As described above, according to the present embodiment, since the second case portion  52  is connected to the first case portion  51  after the fixing (anchoring) of the signal cables  72   c,    73   c  has completed, it is possible to improve the reliability of the wired state of the signal cables  72   c,    73   c  within the casing  10 . Therefore, it is possible to prevent defects such as disconnection of the signal cables  72   c,    73   c.    
     Moreover, since the fixed position of the signal cables  72   c,    73   c  does not extend over a plurality of case portions, it is easy to perform the wire connection work, and can minimize the play of the signal cables  72   c,    73   c.    
     Moreover, since the external connector  81  is fixed to the third case portion  53 , a wiring length from the external connector  81  to an inverter (not illustrated) installed on the vehicle body side may be minimized. 
     Moreover, since the external connector  81  is fixed to the third case portion  53  at a position facing the through hole  54   e  of the partition part  54 , it is possible to wire the cables  72   a,    73   a  extending from the external connector  81  linearly towards the through hole  54   c.  Therefore, it is possible to prevent any interference with peripheral components within the first space S 1  and the casing  10 . 
     Moreover, by having the length L 2  in the axial direction from the external connector  81  to the tip of the internal connector  82  be not less than the length L 1  in the axial direction from the external connector  81  to the partition part  54  in the state prior to performing the wire connection work of the signal cables  72   c,    73   c,  the internal connector  82  can be drawn out to the second space S 2  side in the assembly process. This thus facilitates the wire connection work. 
       FIG. 3  illustrates that the length L 2  in the axial direction prior to the play of the connector side cables  72   a,    73   a  being anchored is longer than a length L 2 ′ upon anchoring. The length L 2  in the case of not providing the internal connector  82  may be interpreted as the length in the axial direction from the external connector  81  to the tip positions of the cables  72   a,    73   a.    
     Modification 1 
     In the present embodiment, the external connector  81  is to be disposed at a position facing the through hole  54   c  of the partition part  54  in the axial direction, however it is not limited to this. As illustrated in the conceptual diagram of  FIG. 6 , a cable fixing member  89  that fixes the connector side cables  72   a,    73   a  to the third case portion  53  may be disposed at the position facing the through hole  54   c  in the axial direction. In this example also, it is possible to arrange the connector side cables  72   a,    73   a  linearly along the axial direction within the wire housing chamber S 12 . 
     Modification 2 
     In the present embodiment, the rotary angle sensor  71  is to be disposed on the other end side of the motor rotating shaft  22  in the axis M direction, however it is not limited to this. As illustrated in the schematic diagram of  FIG. 7 , the rotary angle sensor  71  may be disposed on the one end side of the motor rotating shaft  22  in the axis M direction. Namely, the rotary angle sensor  71  may be provided in the insertion hole  54   a  of the partition part  54 . 
     In this case, the signal cable  71   c  of the rotary angle sensor  71  may be arranged in the wire housing chamber S 1  upon passing through the through holes  54   b,    54   c  of the partition part  54 , as with the motor thermistor  73 . The sensor side cable  71   b  and the connector side cable  71   a  of the rotary angle sensor  71  are connected by the internal connector  82  anchored in the vicinity of the through hole  54   c.    
     Other Modifications 
     In the present embodiment, the internal connector  82  is to be anchored by the bolt  87  via the retaining member  86 , however it is not limited to this. For example, the internal connector  82  may be anchored to the partition part  54  by a cable tie, a clip, a hose band or the like. 
     Moreover, in the present embodiment, the through hole  54   c  that passes through the signal cables  72   c,    73   c  was to be the oil return path, however it is not limited to this. The through hole  54   c  provided in the partition part  54  may be, for example, a hole for inner pressure adjustment between the first space S 1  (motor chamber S 11 ) and the second space S 2  (reducer chamber), or alternatively a lightening hole for weight reduction or rigidity adjustment. The through hole  54   c  that passes through the signal cables  72   c,    73   c  is preferably provided below the shaft center of the input shaft  32  and the output shaft  38  of the reducer unit  31 , however the position of the through hole  54   c  is not particularly limited. 
     Regardless of the position of the through hole  54   c,  the play of the internal connector  82  and the signal cables  72   c,    73   c  is not to interfere with the rotor  23  and the stator  24  of the motor unit  21 , and is to be anchored in a range in which it does not interfere with the rotating elements (gear, bearing etc.) of the reducer unit  31 . Moreover, the play of the signal cables  72   c,    73   c  is anchored in a range not pinched between facing planes of the first case portion  51  and the second case portion  52  or the third case portion  53 . In a case in which the play of the signal cables  72   c,    73   c  is very small, and no contact may occur on to the rotating elements, heat generating elements, and facing surfaces, the signal cables  72   c,    73   c  do not need to be clamped. 
     Moreover, a plurality of sensors disposed within the casing  10  is to include the rotary angle sensor  71 , oil temperature thermistor  72 , and the motor thermistor  73 , however other types of sensors may be included. In the case in which the external connector  81  is provided to the third case portion  53  as in the present embodiment, the plurality of sensors disposed within the casing  10  is preferably fixed to components other than the second case portion  52  (first case portion  51  or third case portion  53 ). 
     Moreover, the wiring structure described above may be applied to the wiring structure of the sensor disposed outside the casing  10 . Such sensors include a wheel speed sensor (not illustrated). A wheel speed sensor is a rotary sensor typically used in ABS (anti-lock brake system). In this case, the wheel speed sensor is fixed to the outer peripheral portion of the first case portion  51 , and a sensor side cable of the wheel speed sensor is drawn into the first space S 1  or the second space S 2  from an inlet provided in the outer peripheral portion of the first case portion  51 . The inlet is provided with a sealing member. 
     Regardless of the type and the number of sensors disposed within the casing  10 , the signal cable passing through the through hole  54   c  of the partition part  54  may be one. 
     Moreover, in the present embodiment, the connector side cables  72   a,    73   a  and the sensor side cables  72   b,    73   b  are to be connected in the vicinity of the through hole  54   c  of the partition part  54 , however it is not limited to this. For example, as illustrated in the conceptual diagram of  FIG. 8 , the connected position of the signal cables  72   c,    73   c  may be a position on the inner side in the vehicle width direction of the first case portion  51 . Namely, the internal connector  82  may be provided at a position close to the external connector  81 . 
     In this case, the assembly processes P2 and P3 of the in-wheel motor drive device interchanges. Namely, after the wire connection work is performed for the signal cables  72   c,    73   c,  the inner end plane of the first case portion  51  in the vehicle width direction is closed with the third case portion  53 .  FIG. 8  illustrates a state in which the playing part of the sensor side cables  72   b,    73   b  is anchored in the vicinity of the through hole  54   c  in the outer end plane of the partition part  54  in the vehicle width direction. 
     Alternatively, in the present embodiment, the external connector  81  is to be fixed to the third case portion  53 , however this may be fixed to the second case portion  52 . Namely, a signal line outlet  52   b  may be provided in the second case portion  52 . In this case, as illustrated in the conceptual diagram of  FIG. 9 , the internal connector  82  may be anchored at a position on the inner side of the partition part  54  in the vehicle width direction. 
     The length in the axial direction of the sensor side cable between the sensor and the internal connector  82  may be 0. Namely, the sensor (for example the oil temperature thermistor  72 ) may be provided integrally with the internal connector  82 . In this case, at least one of the plurality of signal cables passed through the through hole  54   c  can have no sensor side cable. That is to say, a signal cable configured of a connector side cable may extend along the axial direction between the internal connector  82  to which the sensor is integrally provided and the external connector  81 . 
     In the embodiment described above, the reducer unit  31  is described as a four-shaft parallel-shaft type gear reducer, however this may be a three-shaft parallel-shaft type gear reducer. Alternatively, as long as it is a reducer mechanism with its final stage based on a parallel-shaft type gear, the reducer unit  31  may be a reducer combining a parallel-shaft type gear and a planetary gear. Moreover, the wheel hub bearing unit  11  is described as an inner ring rotating type, however this may be an outer ring rotating type. 
     Alternatively, the in-wheel motor drive device  1  is described as including the reducer unit  31 , however the in-wheel motor drive device  1  can include no reducer unit  31 . In this case, the second case portion  52  may be a simple lid that closes the through hole  54   c  of the partition part  54  of the first case portion  51 . 
     Alternatively, the present embodiment is described using an example of a motor drive device for vehicles whose casing  10  is disposed in the inner hollow region of the wheel, that is to say the in-wheel motor drive device, however it is not limited to this. That is to say, the wiring structure of the signal cable of the present embodiment may be applied to a motor drive device for vehicles including a casing that is divided into a cylindrical first case portion integrally formed with the partition part, a second case portion connected to one end of the first case portion in the axial direction and covering the second space, and a third case portion connected to the other end of the first case portion in the axial direction and covering the first space. 
     The embodiments disclosed in the present specification is only exemplary in all aspects, and should be considered not limitative. The scope of the present invention is shown not by the above descriptions but by the claims, and is intended to include meanings equivalent to the scope of the claims and all modifications within the scope. 
     REFERENCE SIGNS LIST 
     
         
           1  In-wheel motor drive device 
           10  Casing 
           11  Wheel hub bearing unit 
           21  Motor unit 
           22  Motor rotating shaft 
           24  Stator 
           26  Coil 
           31  Reducer unit 
           32  Input shaft 
           35  Intermediate shaft 
           38  Output shaft 
           40  Oil tank 
           51  First case portion 
           52  Second case portion 
           53  Third case portion 
           54  Partition part 
           54   b,    54   c  Through hole 
           71  Rotary angle sensor 
           72  Oil temperature thermistor 
           73  Motor thermistor 
           71   c,    72   c,    73   c  Signal cable 
           71   a,    72   a,    73   a  Connector side cable 
           71   b,    72   b,    73   b  Sensor side cable 
           81  External connector 
           82 ,  88 ,  822 ,  823  Internal connector 
           83  Anchoring unit 
           84 ,  85  Clamp member 
           86  Retaining member 
           89  Cable fixing member 
         S 1  First space 
         S 2  Second space 
         S 3  Sensor chamber 
         S 11  Motor chamber 
         S 12  Wire housing chamber 
         W Wheel