Abstract:
An object of the present invention is to remove adverse effects on an in-wheel motor driving apparatus due to the existence of moisture in the apparatus. There is provided an in-wheel motor driving apparatus in which a driving apparatus for generating driving force of a wheel having a wheel hub bearing section is provided in the wheel, the in-wheel motor driving apparatus, wherein a portion of the driving apparatus, except the wheel hub bearing section, is housed in a case having a sealed structure and thereby the inside of the driving apparatus is blocked from outside air, and air in the case is replaced with inert gas as required. As a result, dew condensation is prevented in the case, and adverse effects due to the existence of moisture in the case are removed.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates to an in-wheel motor driving apparatus. 
       BACKGROUND ART 
       [0002]    A conventional in-wheel motor driving apparatus  101  is disclosed in, for example, Japanese Patent Laid-Open No. 2005-324722 (Patent Literature 1). 
         [0003]    The in-wheel motor driving apparatus  101  shown in  FIG. 7  includes a motor section  103  which rotationally drives a motor-side rotation member  106 , a speed reduction section  105  which reduces the rotational speed of the motor-side rotation member  106  and transmits the rotation to a wheel-side rotation member  108 , and a wheel hub bearing section  104  having a wheel hub  109  which is fixedly connected to the wheel-side rotation member  108 . 
         [0004]    In the motor section  103  of the in-wheel motor driving apparatus  101  configured as described above, a breather apparatus  110  is installed in order to maintain a constant pressure in the in-wheel motor driving apparatus  101 . 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         Patent Literature 1: Japanese Patent Laid-Open No. 2005-324722 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0006]    Meanwhile, the breather apparatus  110  is installed at a case  107  of the motor section  103  and hence may be damaged by a flying stone, and the like. 
         [0007]    The breather apparatus  110  is ventilation means between the inside of the in-wheel motor driving apparatus  101  and the outside. Therefore, when the breather apparatus  110  is damaged, water may enter the inside of the in-wheel motor driving apparatus  101  from the breather apparatus  110 , so as to cause a short-circuit in the motor section  103 , or so as to form rust in a member configuring the speed reduction section  105 . 
         [0008]    Further, when moisture exists in the in-wheel motor driving apparatus  101 , the moisture may condense in the apparatus to cause water to accumulate in the apparatus. 
         [0009]    When water accumulates in the in-wheel motor driving apparatus  101 , the lubrication performance of the circulating lubricating oil may be deteriorated, so as to cause, in the long run, a failure of a gear tooth surface and a bearing section which configure the speed reduction section  105 . 
         [0010]    Accordingly, an object of the present invention is to remove the adverse effects due to the existence of moisture in the in-wheel motor driving apparatus. 
       Solution to Problem 
       [0011]    In order to solve the above-described problems, the present invention is characterized by an in-wheel motor driving apparatus in which a driving apparatus for generating driving force of a wheel having a wheel hub bearing section is provided in the wheel, wherein a portion of the driving apparatus, except the wheel hub bearing section, is housed in a case having a sealed structure. 
         [0012]    When the case covering the driving apparatus is configured as the sealed structure in this way, the inside of the driving apparatus is blocked from outside air, and hence dew condensation in the case can be prevented, so that adverse effects due to the existence of moisture in the case can be removed. 
         [0013]    It is more preferred to replace air in the case with inert gas. 
         [0014]    As the inert gas, it is possible to use nitrogen gas and argon gas. 
         [0015]    When the case is composed of a case main body and a lid member, the case can be configured as a sealed structure by arranging a sealing member between the case main body and the lid member. 
         [0016]    As the sealing member, it is possible to use one or both of a gasket, such as an O-ring, and a liquid gasket. 
         [0017]    As the driving apparatus, it is possible to use a driving apparatus including a motor section which rotationally drives a motor-side rotation member, a speed reduction section which reduces the rotational speed of the motor-side rotation member and transmits the rotation to a wheel-side rotation member, and a wheel hub bearing section which has a wheel hub fixedly connected to the wheel-side rotation member. In this case, the inside of the driving apparatus is configured as a sealed structure by arranging a sealing member between the wheel hub bearing section, and the case covering the motor section and the speed reduction section. 
         [0018]    Further, since the inside of the wheel hub bearing section is configured as a sealed structure, lubricating oil can be shared among insides of the wheel hub bearing section, the motor section, and the speed reduction section. 
         [0019]    The power supply cable of the stator of the motor section needs to be connected to an external inverter. Therefore, in order to prevent outside air from entering through the power supply cable, it is preferred to provide a terminal block hermetically fixed to the case, and dispose the distal end of the power supply cable from the stator on the outside of the case via the terminal block in such a manner that outside air is prevented from entering the case. 
         [0020]    Further, it is also possible to provide the terminal block in a sealed terminal box provided on the outer surface of the case of the motor section, connect the wiring cable connected to the inverter to the terminal block in the terminal box, and applying a coating between the core wire and the sheath of the wiring cable in such a manner that moisture is prevented from entering the inverter. 
       Advantageous Effects of Invention 
       [0021]    As described above, according to the present invention, the case covering the driving apparatus is configured as the sealed structure, and thereby the inside of the driving apparatus is blocked from outside air, as a result of which dew condensation in the case can be prevented, and adverse effects due to the existence of moisture in the case can be removed. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0022]      FIG. 1  is a schematic sectional view of an in-wheel motor driving apparatus according to an embodiment of the present invention. 
           [0023]      FIG. 2  is a schematic sectional view of an in-wheel motor driving apparatus according to an embodiment of the present invention. 
           [0024]      FIG. 3  is a partial detailed view showing an example of drawing a power supply cable. 
           [0025]      FIG. 4  is a schematic plan view of an electric vehicle provided which includes the in-wheel motor driving apparatus. 
           [0026]      FIG. 5  is a rear view of the electric vehicle in  FIG. 4 . 
           [0027]      FIG. 6  is a schematic longitudinal sectional view of the speed reduction section of the embodiment shown in  FIG. 1 . 
           [0028]      FIG. 7  is a schematic sectional view of a conventional in-wheel motor driving apparatus. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0029]    Hereinafter, embodiments of the present invention will be described based on the attached drawings. 
         [0030]    As shown in  FIG. 4 , an electric vehicle  11  provided with an in-wheel motor driving apparatus according to an embodiment of the present invention includes a chassis  12 , front wheels  13  as steering wheels, rear wheels  14  as driving wheels, and in-wheel motor driving apparatuses  21  which transmit driving force to the right and left rear wheels  14 , respectively. As shown in  FIG. 5 , the rear wheels  14  are housed in wheel housings  12   a  of the chassis  12 , and are fixed to a lower portion of the chassis  12  via a suspension system (suspension)  12   b.    
         [0031]    The suspension  12   b  includes suspension arms extending rightward and leftward therefrom to support the rear wheels  14 , and struts including coil springs and shock absorbers to reduce vibration of the chassis  12  by absorbing vibrations that the rear wheels  14  receive from the ground. Further, the left and right suspension arms have stabilizers at their joints to reduce the vehicle body&#39;s inclination during turning. Note that it is desirable that the suspension  12   b  is an independent suspension system capable of moving the left and right wheels upward and downward separately to improve ground following capability and to efficiently transmit driving force of the driving wheels to the road surface even if the road surface has some irregularities. 
         [0032]    Since the in-wheel motor driving apparatuses  21  provided in the electric vehicle  11  respectively drive the left and right rear wheels  14  and are mounted inside the wheel housings  12   a , the electric vehicle  11  does not need to have the motor, drive shafts, differential gear mechanism and other components on the chassis  12 . Therefore, the electric vehicle  11  has advantages that a sufficient passenger room can be secured and that the rotation of the left and right driving wheels can be individually controlled. 
         [0033]    On the other hand, for further improvement of driving stability of the electric vehicle  11 , unsprung weight needs to be reduced. Further, the size and weight of the in-wheel motor driving apparatus  21  need to be further reduced to provide a still larger passenger room. 
         [0034]    As shown in  FIG. 1 , the in-wheel motor driving apparatus  21  includes a motor section A which generates driving force; a speed reduction section B which reduces the rotational speed of the motor section A and outputs the rotating force; and a wheel hub bearing section C which transmits the output from the speed reduction section B to the driving wheel  14 . The motor section A and the speed reduction section B are housed in a sealed case  22 . As shown in  FIG. 5 , the in-wheel motor driving apparatus  21  is attached inside the wheel housing  12   a  of the electric vehicle  11 . 
         [0035]    Unlike the conventional case, the case  22  is not provided with the breather apparatus, and is formed to have a sealed structure so that the inside of the case  22  is blocked from outside air to prevent dew condensation in the case  22 . The air in the case  22  may be replaced with inert gas, such as nitrogen gas and argon gas. 
         [0036]    In order to seal the inside of the case  22 , an O-ring  22   c  is provided between the case  22   a  of the motor section A and the case  22   b  of the speed reduction section B to provide sealing therebetween. 
         [0037]    Further, an O-ring  22   d  is also provided on the outer side end surface of the case  22   b  of the speed reduction section B, on which end surface a fixing flange  33   a  of the wheel hub bearing section C is mounted. Thereby, the airtightness between the case  22   b  of the speed reduction section B and the wheel hub bearing section C is also maintained. 
         [0038]    The case  22   a  of the motor section is composed of a case main body  22   aa  covering the outer peripheral surface of the motor section A, and a lid member  22   ab . An O-ring  22   e  is also provided between the case main body  22   aa  and the lid member  22   ab  to provide sealing therebetween. 
         [0039]    Further, the central portion of the lid member  22   ab  is composed of a lid member  22   ac  which is separated from the lid member  22   ab . An O-ring  22   d  is also provided between the lid member  22   ab  and the separate lid member  22   ac  to provide sealing therebetween. 
         [0040]    A stator  23  of the motor section A is connected to a wiring  61  of an external inverter by a power supply cable  62 . However, it is desirable to adopt a wiring structure as shown in  FIG. 3 , in order to prevent moisture from entering the case  22   a  of the motor section A through a gap between a core wire  62   a  and a sheath  62   b  of the power supply cable  62 . 
         [0041]    In the wiring structure shown in  FIG. 3 , a terminal block  64  is hermetically fixed to the case  22   a  with a sealing material  63 , and the distal end of the power supply cable  62  from the stator  23  is drawn to the outside of the case  22   a  via the terminal block  64  in such a manner that outside air is prevented from entering the case  22   a  through the gap between the core wire  62   a  and the sheath  62   b  of the power supply cable  62  disposed outside the case  22   a.    
         [0042]    Further, the terminal block  64  is drawn into a terminal box  65  having a sealed structure and provided on the outer surface of the case  22   a  of the motor section A, a terminal  66  of the power supply cable  62  connected to the inverter is connected to the terminal block  64  in the terminal box  65 , and a coating  67  is applied to fill the gap between the core wire  62   a  and the sheath  62   b  of the power supply cable in such a manner that moisture is prevented from entering the inverter. 
         [0043]    The wiring from the terminal box  65  to the outside is provided via a connector  68  having a sealed structure. 
         [0044]    The motor section A is a radial gap motor including the stator  23  fixed to the case  22   a  of the motor section A, a rotor  24  disposed so as to face the inner side of the stator  23  with a radial gap therebetween, and a motor-side rotation member  24   b  fixedly connected to the inner side of the rotor  24  to rotate together with the rotor  24 . The motor-side rotation member  24   b  is supported by roller bearings  36   a  and  36   b  rotatably with respect to the case  22   a  of the motor section A. 
         [0045]    The motor-side rotation member  24   b  is disposed across the motor section A and the speed reduction section B to transmit the driving force of the motor section A to the speed reduction section B. The motor-side rotation member  24   b  has a hollow structure into which an input shaft  25  of the speed reduction section is fitted and fixed. The two eccentric sections  25   a  and  25   b  are disposed at a 180-degree phase difference so that their centrifugal forces due to their eccentric movement are cancelled each other. 
         [0046]    The speed reduction section B includes curved plates  26   a  and  26   b  which serve as revolution members and which are rotatably held by the eccentric sections  25   a  and  25   b ; a plurality of outer pins  27  which are held at fixed locations on the speed reduction section housing  22   b  and serving as outer circumferential engager for engagement with the outer circumferential portion of the cycloid discs  26   a  and  26   b ; a motion conversion mechanism which transmits the rotational movement of the curved plates  26   a  and  26   b  to a wheel-side rotation member  28 ; and counterweights  29  disposed adjacently to the eccentric sections  25   a  and  25   b . Further, the speed reduction section B is provided with a speed reduction section lubrication mechanism which supplies lubricating oil to the speed reduction section B. 
         [0047]    The wheel-side rotation member  28  includes a flange section  28   a  and a shaft section  28   b . The flange section  28   a  has its end surface formed with holes at an equidistant interval on a circle centering on a rotational center of the wheel-side rotation member  28 , for fixing the inner pins  31 . Further, the shaft section  28   b  is fitted and fixed to a hub ring  32  so as to transmit the output of the speed reduction section B to the wheel  14 . The flange section  28   a  of the wheel-side rotation member  28  and the input shaft  25  are rotatably supported by roller bearings  36   c.    
         [0048]    As shown in  FIG. 6  each of the curved plates  26   a  and  26   b  has, along the outer peripheral portion thereof, a plurality of waveforms in the form of trochoid curves, such as epitrochoid curves, and has a plurality of through holes  30   a  penetrating from one end surface to the other end surface. The through holes  30   a  are made equidistantly on a circle centering on the rotational center of the cycloid discs  26   a  and  26   b , and accommodate inner pins  31  which will be described later. Further, a through hole  30   b  is formed at the center of the curved plates  26   a  and  26   b , so as to be fitted with the eccentric sections  25   a  and  25   b.    
         [0049]    The curved plates  26   a  and  26   b  are supported by a roller bearing  41  rotatably with respect to the eccentric sections  25   a  and  25   b . The roller bearing  41  is a cylindrical roller bearing including an inner ring member which fits the outer diameter surface of each of the eccentric sections  25   a  and  25   b , on the outer diameter surface of which an inside raceway surface is formed, an outside raceway surface which is directly formed on the inner diameter surface of the through hole  30   b  of each of the curved plates  26   a  and  26   b , a plurality of cylindrical rollers  44  disposed between the inside raceway surface and the outside raceway surface, and a retainer (not shown) which retains the interval between the adjacent cylindrical rollers  44 . 
         [0050]    The outer pins  27  are equidistantly provided along a circumferential track centered about the rotational axis of the input shaft  25 . When the curved plates  26   a  and  26   b  make orbital motion, the curved waveforms engage with the outer pins  27  to cause the curved plates  26   a  and  26   b  to make axial rotation. Here, the outer pin  27  is rotatably supported by a needle roller bearing with respect to the speed reduction section housing  22   b . Thereby, the contact resistance between the outer pins  27  and the curved plates  26   a  and  26   b  can be reduced. 
         [0051]    The counter weights  29  are disks each having an off-center through hole in which the input shaft  25  fits, and are disposed adjacently to the eccentric sections  25   a  and  25   b  respectively, at a 180-degree phase difference therefrom in order to cancel unbalanced inertia couple caused by the rotation of the cycloid discs  26   a  and  26   b.    
         [0052]    The motion conversion mechanism includes the plurality of inner pins  31  held by the wheel-side rotation member  28 , and the through holes  30   a  formed in the curved plates  26   a  and  26   b . The inner pins  31  are equidistantly provided on a circumferential track about the rotational axis of the wheel-side rotation member  28 , and one axial direction end portion thereof is fixed to the wheel-side rotation member  28 . In addition, in order to reduce frictional resistance with the curved plates  26   a  and  26   b , needle roller bearings are provided at places of contact with the inner wall surface of the through holes  30   a  of the curved plates  26   a  and  26   b.    
         [0053]    The through holes  30   a  are provided at positions respectively corresponding to the plurality of inner pins  31 . In addition, the inner diameter of the through holes  30   a  is set so as to be larger by a predetermined size than the outer diameter of the inner pins  31  (the outer diameter indicating “the maximum outer diameter including the needle roller bearing”, and the same is applied hereinafter). 
         [0054]    The speed reduction section lubrication mechanism is configured to supply lubricating oil to the speed reduction section B, and includes a lubricating oil passage  52 , a lubricating oil supply port  53 , a lubricating oil discharge port  54 , a lubricating oil reservoir  55 , a rotary pump  51 , and a circulation oil passage  56 . 
         [0055]    The lubricating oil passage  52  axially extends inside the input shaft  25 . Further, the lubricating oil supply port  53  is provided at the eccentric sections  25   a  and  25   b.    
         [0056]    The lubricating oil discharge port  54  for discharging the lubricating oil in the speed reduction section B is provided at least one place of the case  22   b  at the position of the speed reduction section B. 
         [0057]    Further, the circulation oil passage  57  connecting the lubricating oil discharge port  54  to the lubricating oil passage  52  is provided in the case  22   a  of the motor section A. The lubricating oil discharged from the lubricating oil discharge port  54  is refluxed to the lubricating oil passage  52  via the circulation oil passage  57 . 
         [0058]    The wheel-hub bearing section C includes the hub ring  32  which is fixedly connected to the wheel-side rotation member  28  and to which the wheel  14  is attached, and a fixed ring  33  which holds the hub ring  32  rotatably with respect to the case  22   b  of the speed reduction section B. The hub ring  32  includes a cylindrical hollow section  32   a  and a flange section  32   b . The flange section  32   b  is fixedly connected to the wheel  14  with bolts  32   c . A spline and a male screw are formed on the outer diameter surface of the shaft section  28   b  of the wheel-side rotation member  28 . Further, a spline hole is formed on the inner diameter surface of the hollow section  32   a  of the hub ring  32 . The wheel-side rotation member  28  is screwed to the inner diameter surface of the hub ring  32 , and the distal end of the wheel-side rotation member  28  is then secured with a nut  32   d  to fasten the hub ring  32  and the wheel-side rotation member  28  to each other. 
         [0059]    The hub ring  32  has a wheel fitting flange section  32   b  integrally formed on the outer surface of the hollow section  32   a  thereof. An outer raceway surface is integrally formed on the vehicle-outer-side outer diameter surface of the hollow section  32   a . An inner ring  32   e  having an inner raceway surface on the outer surface thereof is fitted to the vehicle-inner-side outer diameter surface of the hollow section  32   a.    
         [0060]    The fixed ring  33  has, on the inner peripheral surface thereof, an outer raceway surface and an inner raceway surface respectively facing the outer raceway surface and the inner raceway surface of the hub ring  32 , and has the fixing flange  33   a  on the outer peripheral surface thereof. 
         [0061]    The hub ring  32  and the fixing ring  33  are opposed to each other with their respective outer raceway surfaces and inner raceway surfaces, and a plurality of rows of balls  34  are placed between these two surfaces. 
         [0062]    The fixing flange  33   a  of the fixed ring  33  and the case  22   b  of the speed reduction section B are fastened to each other with bolts  71 . Further, the case  22   b  of the speed reduction section B and the case  22   a  of the motor section A are fastened to each other with bolts  72 . 
         [0063]    In the embodiment shown in  FIG. 1 , an outer sealing member  74  and an inner sealing member  73  are respectively provided at the vehicle outer and inner sides of the space between the hub ring  32  and the fixed ring  33 , in which space the plurality of rows of balls  34  are accommodated. The space between the hub ring  32  and the fixed ring  33  is sealed by the outer sealing member  74  and the inner sealing member  73 , and grease for the balls  34  is filled in this sealed space. 
         [0064]    In an embodiment shown in  FIG. 2 , only the outer sealing member  74  is disposed, and the inner sealing member  73  is omitted. Thereby, the lubricating oil of the speed reduction section B is supplied between the hub ring  32  and the fixed ring  33 , so that the lubricating oil of the speed reduction section B is used for lubrication of the wheel hub bearing section C. 
         [0065]    Note that, in the present invention, the inside of the apparatus is sealed, but it is desirable that the amount of the lubricating oil filled in the inside of the apparatus is half or less of the inner volume of the apparatus. 
         [0066]    In the following, the operation principle of the in-wheel motor driving apparatus  21  will be described. In the motor section A, the rotor  24  composed of a permanent magnet or a magnetic body is rotated under the action of the electromagnetic force generated, for example, by supplying AC current to the coil of the stator  23 . When the input shaft  25  connected to the rotor  24  is rotated by the rotation of the rotor  24 , the curved plates  26   a  and  26   b  perform orbital motion about the rotational axis of the input shaft  25 . At this time, the outer pins  27  engage with the curved waveforms of the curved plates  26   a  and  26   b , to make the curved plates  26   a  and  26   b  rotate in the direction opposite to the rotation of the motor-side rotation member  25 . 
         [0067]    The inner pins  31  inserted into the through holes  30   a  are brought into contact with the inner wall surfaces of the through holes  30   a  according to the rotational movement of the curved plates  26   a  and  26   b . Thereby, the orbital motion of the curved plates  26   a  and  26   b  is not transmitted to the inner pins  31 , and only the rotational movement of the curved plates  26   a  and  26   b  is transmitted to the wheel hub bearing section C via the wheel-side rotation member  28 . 
         [0068]    At this time, the rotation of the input shaft  25  is reduced by the speed reduction section B and transmitted to the wheel-side rotation member  28 . Therefore, even when a motor section A of a low torque and high rotational speed type is adopted, necessary torque can be transmitted to the driving wheel  14 . 
         [0069]    Note that the reduction ratio of the speed reduction section B configured as described above is calculated by (ZA−ZB)/ZB, where ZA represents the number of the outer pins  27  and ZB represents the number of the waveforms of the curved plates  26   a ,  26   b . In the embodiment shown in  FIG. 1  where ZA=12 and ZB=11, the reduction ratio results in 1/11, which is a considerably high reduction ratio. 
         [0070]    In this way, when such speed reduction section B, which is capable of obtaining a high reduction ratio without multi-stage configuration, is adopted, it is possible to provide a compact in-wheel motor driving apparatus  21  with a high reduction ratio. Further, needle roller bearings are provided for the outer pins  27  and the inner pins  31 , and thereby the frictional resistance of the outer pins  27  and the inner pins  31  with respect to the curved plates  26   a  and  26   b  is reduced, so that the transmission efficiency of the speed reduction section B is improved. 
         [0071]    The unsprung weight can be suppressed by adopting the in-wheel motor driving apparatus  21  according to the above-described embodiments for the electric vehicle  11 . As a result, it is possible to obtain the electric vehicle  11  excellent in driving stability. 
         [0072]    Further, the above-described embodiments show examples in which the lubricating oil supply port  53  is provided at the eccentric sections  25   a  and  25   b , but the present invention is not limited to this. The lubricating oil supply port  53  can be provided at an arbitrary position of the input shaft  25 . However, from a viewpoint of stably supplying lubricating oil to the roller bearings  41 , it is desirable to provide the lubricating oil supply port  53  at the eccentric sections  25   a  and  25   b.    
         [0073]    Further, in the above-described embodiments, the two curved plates  26   a  and  26   b  of the speed reduction section B are provided to be 180 degrees out of phase with each other. However, the number of the curved plates can be arbitrarily set, and for example, when three curved plates are provided, the curved plates may be disposed to be 120 degrees out of phase with each other. 
         [0074]    Further, the above-described embodiments show an example of the motion conversion mechanism, which is composed of the inner pins  31  fixed to the wheel-side rotation member  28 , and the through holes  30   a  provided in the curved plates  26   a  and  26   b , but the present invention is not limited to this. As the motion conversion mechanism, it is possible to adopt an arbitrary form capable of transmitting the rotation of the speed reduction section B to the wheel hub  32 . For example, the motion conversion mechanism may be composed of inner pins fixed to the curved plates, and holes formed in the wheel-side rotation member. 
         [0075]    Note that the operation in the above-mentioned embodiments is described in view of the rotation of each of the members, but actually, power including torque is transmitted to the driving wheel from the motor section A. Therefore, the power reduced as described above is converted into power of high torque. 
         [0076]    Further, in the description of the operation in the above-described embodiments, electric power is supplied to the motor section A to drive the motor section A, and the power from the motor section A is transmitted to the driving wheel  14 . On the contrary, for example, in such a case where the vehicle decelerates or goes down a slope, power from the driving wheel  14  side may be converted to high-speed low-torque rotation by the speed reduction section B, so as to be transmitted to the motor section A for electric power generation. Further, the electric power generated by the motor section A may be stored in a battery so as to be used afterwards for driving the motor section A and may also be used for operating other electric apparatuses provided in the vehicle. 
         [0077]    Further, each of the above-described embodiments shows an example in which a radial gap motor is adopted in the motor section A, but the present invention is not limited to this. A motor having any configuration can be applied. For example, the motor may be an axial gap motor which is provided with a stator fixed to a housing, and a rotor disposed on the inner side of the stator so as to face the stator with an axial gap. 
         [0078]    Further, each of the above-described embodiments shows an example of the in-wheel motor driving apparatus  21  in which the cycloid speed reduction mechanism is adopted in the speed reduction section B, but the present invention is not limited to this. Any speed reduction mechanism can be adopted. For example, a planetary gear speed reduction mechanism, a parallel shaft gear speed reduction mechanism, and the like, can be adopted. 
         [0079]    Further, the present invention can also be applied to an in-wheel motor unit (motor direct drive) without speed reducer. 
         [0080]    Further, the electric vehicle  11  shown in  FIG. 4  is an example in which the rear wheels  14  are used as the driving wheels, but the present invention is not limited to this. The present invention may be applied for a vehicle in which the front wheels  13  are used as the driving wheels, or may be applied for a four-wheel drive vehicle. Note that it should be understood that, in this specification, “electric vehicle” is a concept including all the automobiles which obtain driving force from electric power, and includes, for example, hybrid car, and the like. 
         [0081]    Thus far, embodiments of the present invention have been described with reference to the drawings. However, the present invention is not limited to these illustrated embodiments. Any of these embodiments illustrated thus far may be modified or changed in many ways within the scope or within the equivalence of the present invention. Reference Signs List 
       REFERENCE SIGNS LIST 
       [0000]    
       
           21  In-wheel motor driving apparatus 
         A Motor section 
         B Speed reduction section 
         C Wheel hub bearing section 
         Case 
           22   a  Case 
           22   aa  Case main body 
           22   ab  Lid member 
           22   ac  Lid member 
           22   b  Case 
           22   c  O-ring 
           22   d  O-ring 
           22   e  O-ring 
           32  Hub ring 
           33  Fixed ring 
           62  Power supply cable 
           62   a  Core wire 
           62   b  Sheath 
           63  Sealing material 
           64  Terminal block 
           65  Terminal box 
           66  Sealing member 
           67  Coating 
           68  Connector