PATENT ABSTRACT
The present invention provides a drive gear device that can easily be made compact and lightweight with a simple configuration, and that has little friction loss. Among externally toothed sun gear members ( 12   a,    12   b ) and ring gear members ( 16, 17 ) of first and second planetary gear mechanisms ( 11   a,    11   b ), one pair, which are first paired members ( 12   a,    12   b ), are coupled to a coupling member ( 12 ) for equalizing the rotational speeds and rotational directions of the first paired members ( 12   a,    12   b ), and the other pair, which are second paired members ( 16, 17 ) are coupled to opposite rotation members ( 18, 19 ) for making the second paired members ( 16, 17 ) rotate in opposite directions. Rotational torque inputted to the coupling member ( 12 ) is distributed to the first planetary gear mechanism ( 11   a ) and the second planetary gear mechanism ( 11   b ), and is outputted from planetary carriers ( 15   a,    15   b ).

PATENT DESCRIPTION
TECHNICAL FIELD 
       [0001]    The present invention relates to a drive gear unit, and particularly to a drive gear unit adopted to transmit a rotary motion or a motive power (torque) in two paths. 
       BACKGROUND ART 
       [0002]    Conventionally, various types of devices have been proposed which are used for control of a torque or rotational speed to be distributed to a drive wheel of an automobile. 
         [0003]    For example, Patent Document 1 discloses a differential gear unit  510  as illustrated in a configuration diagram of  FIG. 25 . The differential gear unit  510  includes two sets of pinion gear units  520   a  and  520   b , and sun gears as external gears  523   a  and  523   b  of the pinion gear units  520   a  and  520   b  and are connected to each other via an inner connection member  522 . Outer connection members  527   a  and  527   b  are connected respectively to internal gears  526   a  and  526   b  of the pinion gear units  520   a  and  520   b , and gears  528   a  and  528   b  meshed with a gear member  529  are formed at shaft-perpendicular end surfaces of the outer connection members  527   a  and  527   b . When a driving force is input to the inner connection member  522 , the driving force is output from the carriers  525   a  and  525   b . It is possible to control distribution of the driving force and rotational speed by rotation or stop of the gear member  529 . 
         [0004]    Patent Document 2 discloses a spur gear differential unit as illustrated in a perspective view of  FIG. 26 . This spur gear differential unit includes first and second sun gears  603  and  605  and first and second pinion gears  607  and  609  which are engaged with each other. The first pinion gear  607  is engaged only with the first sun gear  603 , and the second pinion gear  609  is engaged only with the second sun gear  605 . The first and second sun gears  603  and  605  have the same number of teeth, and different addendum circle diameters. One of the first and second sun gears  603  and  605  is subjected to positive profile shifting, and the other is subjected to negative profile shifting. 
         [0005]    Patent Document 3 discloses a transmission device illustrated in a configuration diagram of  FIG. 27 . This transmission device includes pinion gear sets  718  and  719 , connected respectively to output shafts  716  and  717 , and a shifting mechanism  722  between the output shafts  716  and  717 . The shifting mechanism  722  can be switched between shift positions S 1  and S 2  so as to allow the right and left shafts to correspond to braking and driving by rotation in the same direction at the shift position S 1  or to be reversely rotated at the shift position S 2 . 
       CITATION LIST 
     Patent Literature 
       [0006]    Patent Document 1: JP 2006-214530 A 
         [0007]    Patent Document 2: US 2011/0245012 
         [0008]    Patent Document 3: US 2010/0323838 
       SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
       [0009]    The differential gear unit  510  of  FIG. 25  has the gear member  529  arranged in non-parallel with respect to central axes of the pinion gear units  520   a  and  520   b , and thus, a structure thereof is complicated, manufacturing cost thereof increases, and further, a frictional loss is caused by the engagement between the gear member  529  and the gears  528   a  and  528   b  of the outer connection members  527   a  and  527   b . In addition, the gear member  529  is arranged in a radial direction with respect to the central axes of the pinion gear units  520   a  and  520   b , and a torsional torque acts on the outer connection members  527   a  and  527   b , and thus, it is difficult to reduce a size and weight thereof. 
         [0010]    The spur gear differential unit of  FIG. 26  is a stepped pinion gear unit to operate as a simple differential gear which allows a rotational difference between right and left wheels of a vehicle. Accordingly, there is a need for rotating a carrier that rotatably supports the first pinion gear  607  and the second pinion gear  609  in order to change torque distribution or cause a difference in the rotational speed. In such a case, a configuration for the rotation of the carrier becomes complicated and large, and further the frictional loss is also caused. 
         [0011]    A transmission unit of  FIG. 27  is configured to be bilaterally asymmetrical and complicated with first and second pinion gear sets  718  and  719  having different configurations, and thus, the frictional loss is large. 
         [0012]    The present invention has been made in view of such circumstances, and aims to provide a drive gear unit which allows easy reduction in size and weight with a simple configuration, and has a small frictional loss. 
       Solution to Problem 
       [0013]    The present invention provides a drive gear unit configured as follows in order to solve the problems described above. 
         [0014]    A drive gear unit includes: (a) a housing; (b) first and second pinion gear units each of which includes a sun gear as an external gear in which an external sun gear is formed, a pinion gear in which a pinion gear to be engaged with the external sun gear is formed, an internal gear in which inner teeth to be engaged with the pinion gear are formed, and a carrier which supports the pinion gear while allowing to rotate and revolve around the external sun gear, and in which the sun gear as external gear, the internal gear and the carrier are rotatable; (c) a connection member to which any one first pair between the sun gears as external gears of the first and second pinion gear units and the internal gears of the first and second pinion gear units is fixed and which causes each rotational speed and each rotation direction of the first pair to be the same; and (d) a reverse rotation member to which another second pair between the sun gears as external gears of the first and second pinion gear units and the internal gears of the first and second pinion gear units is fixed and which causes each rotation direction of the second pair to reverse each other. A rotational torque input to the connection member is distributed into the first pinion gear unit and the second pinion gear unit, and is output from the carrier. 
         [0015]    In the above-described configuration, the internal gears of the first and second pinion gear units rotate in the reverse directions by the reverse rotation member in a case in which the sun gears as external gears of the first and second pinion gear units are engaged with the connection member, and thus, it is possible to evenly distribute a rotational torque input to the connection member into the carriers of the first and second pinion gear units. Since the sun gears as external gears of the first and second pinion gear units rotate in the reverse directions in the case of the internal gears of the first and second pinion gear units are connected to the connection member, it is possible to evenly distribute the rotational torque input to the connection member into the carriers of the first and second pinion gear units. 
         [0016]    According to the above-described configuration, the reverse rotation member does not transmit a driving force input to the connection member. In addition, there is no need of revolving the reverse rotation member. Thus, the drive gear unit can be simply configured, and easily reduced in size, and has a small frictional loss caused in the drive gear unit. 
         [0017]    Preferably, the drive gear unit further includes a control motor which rotates at least one of the second member of the first pinion gear unit, and the second member of the second pinion gear unit and the reverse rotation member. 
         [0018]    In this case, it is possible to rotate second members of the first and second pinion gear units in the reverse directions using the control motor, and control a difference in a rotational torque or rotational speed to be distributed to the carriers of the first and second pinion gear units. Since the part rotated to transmit the rotational torque and the part rotated by the control motor to distribute the rotational torque and control the difference in the rotational speed are completely separated from each other, the controllability is extremely favorable. Further, in a case in which an electrical system that drives the control motor or a unit that transmits the rotation of the control motor malfunctions, only the second members of the first and second pinion gear units are not rotated in the reverse directions, and the rotational torque is evenly distributed into the carriers of the first and second pinion gear units by the reverse rotation member, and the distribution of the rotational torque is hardly in an abnormal state. Thus, the unit is stable even when there is failure, and a mechanical operation of distributing the rotational torque is maintained. 
         [0019]    Preferably, the connection member is connected coaxially with the sun gears as external gears of the first and second pinion gear units which are the first pair. Outer teeth are formed in the internal gears of the first and second pinion gear units. The drive gear unit further includes: (a) a first auxiliary gear pair which has first outer teeth and second outer teeth to be engaged with the outer teeth of the internal gear of the first pinion gear unit coaxially formed, and is rotatably supported by the housing; and (b) a second auxiliary gear pair which has third outer teeth to be engaged with the second outer teeth of the first auxiliary gear pair and fourth outer teeth to be engaged with the outer teeth of the internal gear of the second pinion gear unit coaxially formed, and is rotatably supported by the housing. The first and second auxiliary gear pairs function as the reverse rotation members. 
         [0020]    In this case, the driving force is not transmitted to the first and second gears of the first and second auxiliary gear pairs and the frictional loss is small when the first and second auxiliary gear pairs are arranged in parallel to the rotation center axes of the sun gear as external gear of the first and second pinion gear units. In addition, there is no need that the first and second auxiliary gear pairs revolve around the internal gears of the first and second pinion gear units. Thus, the drive gear unit can be simply configured, and easily reduced in size. 
         [0021]    Preferably, outer teeth are formed in the internal gear of the first pinion gear unit. The drive gear unit further includes: (a) a dual concentric motor which includes an inner rotor arranged between the first pinion gear unit and the second pinion gear unit with both ends protruding to the first pinion gear unit side and the second pinion gear unit side and an outer rotor with both ends protruding the first pinion gear unit side and the second pinion gear unit side, and in which the sun gears as external gears of the first and second pinion gear units are connected coaxially at the both ends of the inner rotor and the second pinion gear unit side of the outer rotor is connected coaxially to the internal gear of the second pinion gear unit; (b) a third auxiliary gear pair which is connected coaxially to the first pinion gear unit side of the outer rotor and has inner teeth; and (c) a fourth auxiliary gear pair in which first outer teeth to be engaged with the outer teeth of the internal gear of the first pinion gear unit and second outer teeth to be engaged with the inner teeth of the third auxiliary gear pair are coaxially formed, and which is rotatably supported by the housing. The inner rotor of the dual concentric motor functions as the connection member. The outer rotor of the dual concentric motor and the third and fourth auxiliary gear pair function as the reverse rotation members. The dual concentric motor functions as the control motor and as a drive motor that drives the connection member to rotate. 
         [0022]    In this case, it is possible to easily reduce the size and weight of the drive gear unit. 
         [0023]    Preferably, outer teeth are formed in the internal gear of the first pinion gear unit. The drive gear unit further includes: (a) a fifth auxiliary gear pair which is connected coaxially to the first pinion gear unit side of the internal gear of the second pinion gear unit, and has inner teeth; (b) a sixth auxiliary gear pair in which first outer teeth to be engaged with the outer teeth of the internal gear of the first pinion gear unit and the second outer teeth to be engaged with the inner teeth of the fifth auxiliary gear pair are formed coaxially, and which is rotatably supported by the housing; and (c) a drive motor which is arranged between the first pinion gear unit and the second pinion gear unit and has an inner rotor with both ends protruding the first pinion gear unit side and the second pinion gear unit side, and in which the sun gears as external gears of the first and second pinion gear units are connected coaxially to the both ends of the inner rotor. The first pair is the sun gears as external gears of the first and second pinion gear units. The inner rotor of the drive motor functions as the connection member. The fifth and sixth auxiliary gear pairs functions as the reverse rotation members. 
         [0024]    In this case, it is possible to simplify the configuration by reducing the engagement points between the reverse rotation members. In addition, it is possible to decrease a dimension in the radial direction. 
         [0025]    Preferably, the connection member is connected coaxially with the sun gears as external gears of the first and second pinion gear units which are the first pair. Outer teeth are formed in the internal gears of the first and second pinion gear units. The drive gear unit further includes a reversing motor that has first and second output shafts, which are arranged coaxially, protrude to sides opposite to each other, and are driven to rotate in reverse directions, and in which first and the second external gears to be engaged with the outer teeth of the internal gears of the first and second pinion gear units are connected coaxially to the first and second output shafts. The reversing motor functions as the reverse rotation member and the control motor. 
         [0026]    In this case, the assembly of the reverse rotation member becomes easy. 
         [0027]    Preferably, the connection member is connected coaxially with the sun gears as external gears of the first and second pinion gear units which are the first pair. The inner teeth of the internal gear of the first pinion gear unit includes an inner teeth extension portion which is extended to the second pinion gear unit side. The inner teeth of the internal gear of the second pinion gear unit includes the inner teeth extension portion which is extended to the first pinion gear unit side. The drive gear unit further includes: (a) a first auxiliary gear pair which has a first gear and a second gear to be engaged with the inner teeth extension portion of the internal gear of the first pinion gear unit being formed coaxially, and is rotatably supported by the housing; and (b) a second auxiliary gear pair which has a third gear to be engaged with the second outer teeth of the first auxiliary gear pair and a fourth gear to be engaged with the inner teeth extension portion of the internal gear of the second pinion gear unit being formed coaxially, and is rotatably supported by the housing. The first and second auxiliary gear pairs function as the reverse rotation members. 
         [0028]    In this case, it is possible to connect the internal gears of the first and second pinion gear units so as to rotate in the reverse directions without forming the outer teeth in the internal gears of the first and second pinion gear units. 
         [0029]    Preferably, the connection member is connected coaxially with the sun gears as external gears of the first and second pinion gear units which are the first pair. The drive gear unit further includes an intermediate gear which is fixed to the connection member, and has outer teeth formed coaxially with the sun gears as external gears of the first and second pinion gear units. 
         [0030]    In this case, it is possible to input the driving force from a drive source arranged at outside of the drive gear unit to the intermediate gear, and distribute the output into the carriers of the first and second pinion gear units. 
         [0031]    Preferably, the first pair is the internal gears of the first and second pinion gear units. The drive gear unit further includes a reversing motor that has first and second output shafts, which are arranged between the first and second pinion gear units, protrude to sides opposite to each other coaxially and are driven to rotate in reverse directions, and in which the sun gears of the first and second pinion gear units are connected coaxially to the first and second output shafts. The reversing motor functions as the reverse rotation member and the control motor. 
         [0032]    In this case, the assembly of the reverse rotation member and the control motor becomes easy. 
       Effects of the Invention 
       [0033]    The drive gear unit of the present invention allows easy reduction in size and weight with the simple configuration, and has the small frictional loss. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0034]      FIG. 1  is a configuration diagram of a drive gear unit (First Embodiment). 
           [0035]      FIGS. 2( a ) to 2( c )  are perspective views illustrating engagement of gears of the drive gear unit (First Embodiment). 
           [0036]      FIG. 3  is a perspective view illustrating engagement of the gears of the drive gear unit (First Embodiment). 
           [0037]      FIG. 4  is a perspective view illustrating engagement of the gears of the drive gear unit (First Embodiment). 
           [0038]      FIGS. 5( a ) to 5( c )  are perspective views illustrating engagement of the gears of the drive gear unit (First Embodiment). 
           [0039]      FIGS. 6( a ) and 6( b )  are plan views illustrating engagement of the gears of the drive gear unit (First Embodiment). 
           [0040]      FIG. 7  is a configuration diagram of a drive gear unit (Second Embodiment). 
           [0041]      FIGS. 8( a ) and 8( b )  are plan views of engagement of gears of the drive gear unit (Second Embodiment). 
           [0042]      FIG. 9  is a configuration diagram of a main section of a drive gear unit (Third Embodiment). 
           [0043]      FIG. 10  is a cross-sectional view of the drive gear unit (Third Embodiment). 
           [0044]      FIG. 11  is a cross-sectional view of the drive gear unit (Third Embodiment). 
           [0045]      FIG. 12  is a cross-sectional view of the drive gear unit (Third Embodiment). 
           [0046]      FIG. 13  is a transparent view of gears of the drive gear unit (Third Embodiment). 
           [0047]      FIG. 14  is a configuration diagram of a main section of a drive gear unit (Fourth Embodiment). 
           [0048]      FIG. 15  is a configuration diagram of a main section of a drive gear unit (Fifth Embodiment). 
           [0049]      FIG. 16  is a configuration diagram of a main section of a drive gear unit (Sixth Embodiment). 
           [0050]      FIG. 17  is a configuration diagram of a biaxial motor unit (Sixth Embodiment). 
           [0051]      FIG. 18  is a configuration diagram of a main section of a drive gear unit (Seventh Embodiment). 
           [0052]      FIG. 19  is a configuration diagram of a main section of a drive gear unit (Eighth Embodiment). 
           [0053]      FIG. 20  is a configuration diagram of a main section of a drive gear unit (Ninth Embodiment). 
           [0054]      FIG. 21  is a cross-sectional view of the drive gear unit (Ninth Embodiment). 
           [0055]      FIG. 22  is a configuration diagram of a main section of a drive gear unit (Tenth Embodiment). 
           [0056]      FIGS. 23( a ) to 23( c )  are cross-sectional views of the drive gear unit (Tenth Embodiment). 
           [0057]      FIGS. 24( d ) and 24( e )  are cross-sectional views of the drive gear unit (Tenth Embodiment). 
           [0058]      FIG. 25  is a configuration diagram of a differential gear unit (Conventional Example 1). 
           [0059]      FIG. 26  is a perspective view of a spur gear differential unit (Conventional Example 2). 
           [0060]      FIG. 27  is a configuration diagram of a transmission unit (Conventional Example 3). 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0061]    Hereinafter, embodiments of the present invention will be described with reference to  FIGS. 1 to 24 . 
       First Embodiment 
       [0062]    A drive gear unit  10  of a first embodiment will be described with reference to  FIGS. 1 to 6 ( b ). 
         [0063]      FIG. 1  is an explanatory diagram schematically illustrating a configuration of the drive gear unit  10  by exemplifying drive of an automobile.  FIGS. 2( a ) to 5( c )  are perspective views illustrating engagement of gears of the drive gear unit  10 . Incidentally, although a spur gear is illustrated in order to allow easy understanding of the configuration of the present invention, a gear is not limited to the spur gear, and various types of gears such as a helical gear, a double helical gear, a bevel gear and a conical gear may be selected as appropriate. 
         [0064]    As illustrated in  FIGS. 1 to 2 ( c ), the drive gear unit  10  includes first and second pinion gear units  11   a  and  11   b , a connection shaft  12 , and first and second auxiliary gear pairs  18  and  19 . 
         [0065]    As illustrated in  FIGS. 1 and 2 ( b ), the first and second pinion gear units  11   a  and  11   b  includes (i) sun gears as external gears  12   a  and  12   b  in which external sun gears are formed, (ii) a plurality of pinion gears  14   a  and  14   b  in which pinion gears to be engaged with the external sun gear are formed, (iii) internal gears  16  and  17  in which inner teeth  16   a  and  17   a  to be engaged with the pinion gears are formed, and outer teeth  16   b  and  17   b  are formed on outer circumferential surfaces at radially outer sides than the inner teeth  16   a  and  17   a , and (iv) carriers  15   a  and  15   b  that supports the pinion gears  14   a  and  14   b  to be rotatable and revolvable. As illustrated in  FIGS. 2( a ) and 2( c ) , the pinion gears  14   a  and  14   b  are rotatably supported by support shafts  15   p  and  15   q  of the carriers  15   a  and  15   b , and each rotation of central shafts  15   s  and  15   t  of the carriers  15   a  and  15   b  is transmitted to each of right and left wheels  2   a  and  2   b . The internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b  are rotatably supported by a housing (not illustrated) of the drive gear unit  10 , and positions of rotation center axes of the internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b  are fixed with respect to the housing (not illustrated) of the drive gear unit  10 . Each of the sun gears as external gears  12   a  and  12   b , the internal gears  16  and  17 , and the carriers  15   a  and  15   b  of the first and second pinion gear units  11   a  and  11   b  is rotatable. 
         [0066]    As illustrated in  FIG. 3 , the sun gears as external gears  12   a  and  12   b  of the first and second pinion gear units  11   a  and  11   b  are fixed coaxially to the connection shaft  12 . In addition, an intermediate gear  13 , in which outer teeth to be engaged with an input gear  30  are formed, is fixed coaxially to the connection shaft  12  between the sun gears as external gears  12   a  and  12   b . The connection shaft  12  is a connection member. 
         [0067]    It is preferable that an addendum circle diameter of the intermediate gear  13  fixed to the connection shaft  12  be smaller than each addendum circle diameter of the outer teeth  16   b  and  17   b  of the internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b . In this case, the intermediate gear  13  does not protrude, and thus, it is easy to configure the intermediate gear  13  not to interfere with the first and second auxiliary gear pairs  18  and  19 , and accordingly, it is possible to reduce a size of the drive gear unit  10 . In addition, it is possible to configure a drive source and the drive gear unit to be compact by bringing the rotation center axis of the input gear  30 , to be connected to the drive source, close to the drive gear unit. 
         [0068]    As illustrated in  FIG. 4 , a plurality of sets, for example, three sets of the first and second auxiliary gear pairs  18  and  19  are arranged at outer sides of the internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b  to be rotatable and parallel with the rotation center axis of the sun gears as external gears  12   a  and  12   b  of the first and second pinion gear units  11   a  and  11   b . The first auxiliary gear pair  18  includes a first gear  18   a  and a third gear  18   b  to be engaged with the outer teeth  16   b  of the internal gear  16  of the first pinion gear unit  11   a , and the first and third gear  18   a  and  18   b  are arranged coaxially. The second auxiliary gear pair  19  includes a second gear  19   a  and a fourth gear  19   b  to be engaged with the outer teeth  17   b  of the internal gear  17  of the second pinion gear unit  11   b , and the second and fourth gears  19   a  and  19   b  are arranged coaxially. The third gear  18   b  of the first auxiliary gear pair  18  and the fourth gear  19   b  of the second auxiliary gear pair  19  are engaged with each other. Incidentally, the inner teeth  16   a  and  17   a  of the internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b  are not illustrated in  FIG. 4 . The first and second auxiliary gear pairs  18  and  19  are rotatably supported by the housing (not illustrated) of the drive gear unit  10 , and positions of the rotation center axes of the first and second auxiliary gear pairs  18  and  19  are fixed with respect to the housing (not illustrated) of the drive gear unit  10 . 
         [0069]    Further, a control gear  5  fixed to a rotary shaft  4   a  of a control motor  4  is arranged at an outer side of the internal gear  17  of the second pinion gear unit  11   b . Outer teeth to be engaged with the outer teeth  17   b  of the internal gear  17  of the second pinion gear unit  11   b  are formed in the control gear  5 . The control gear  5  can be arranged to be engaged with any one of the first and second gears  18   a  and  19   a  of the first and second auxiliary gear pairs  18  and  19 , or arranged to be engaged with any one of the third and fourth gears  18   b  and  19   b  of the first and second auxiliary gear pairs  18  and  19 . 
         [0070]    Although not illustrated, the connection shaft  12 , the central shafts  15   s  and  15   t  of the carriers  15   a  and  15   b , and the first and second auxiliary gear pairs  18  and  19  are rotatably supported to a casing, for example, via a bearing, and the control motor  4  is fixed to the casing. 
         [0071]    Next, an operation of the drive gear unit  10  will be described. 
         [0072]    As illustrated in the perspective views of  FIGS. 5( a ) to 5( c ) , when a rotational torque is transmitted from the input gear  30  to the intermediate gear  13  in a case in which the first and second auxiliary gear pairs  18  and  19  and the control gear  5  are not provided, rotational torques Ta and Tb are distributed respectively to the central shafts  15   s  and  15   t  of the carriers  15   a  and  15   b  of the first and second pinion gear units  11   a  and  11   b . At this time, forces Fa and Fb proportional to the rotational torques Ta and Tb act in the same direction on the outer teeth  16   b  and  17   b  of the internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b.    
         [0073]    When the first and second gears  18   a  and  19   a  of the first and second auxiliary gear pairs  18  and  19  are engaged with the outer teeth  16   b  and  17   b  of the internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b , the forces Fa and Fb are transmitted from the outer teeth  16   b  and  17   b  of the internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b  to the first and second gears  18   b  and  19   b  of the first and second auxiliary gear pairs  18  and  19 . When the third and fourth gears  18   b  and  19   b  of the first and second auxiliary gear pairs  18  and  19  are engaged with each other, the rotational torques Ta and Tb are equal, and the forces Fa and Fb are balanced via the first and second auxiliary gear pairs  18  and  19  in the case of Fa=Fb, and the distribution of the rotational torques Ta and Tb is maintained. On the other hand, when there is a difference in rotational speed between the carriers  15   a  and  15   b , the difference in the rotational speed is transmitted from the outer teeth  16   b  and  17   b  of the internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b , that is, from one of the first and second auxiliary gear pairs  18  and  19  to the other, and the distribution of the rotational torques Ta and Tb does not changed without any difference between the forces Fa and Fb so that the rotational torques Ta and Tb are evenly distributed. 
         [0074]    In other words, the drive gear unit  10  includes the first and second auxiliary gear pairs  18  and  19 , and thus, can allow the rotational energy to be evenly distributed to the central shafts  15   s  and  15   t  of the carriers  15   a  and  15   b  of the first and second pinion gear units  11   a  and  11   b.    
         [0075]    Further, when a rotational torque Tc is added from the control gear  5  fixed to the rotary shaft  4   a  of the control motor  4 , the rotational torques Ta and Tb output from the central shafts  15   s  and  15   t  of the carriers  15   a  and  15   b  of the first and second pinion gear units  11   a  and  11   b  are distributed such that a torque corresponding to the rotational torque Tc is added to any one thereof, and is subtracted from the other one. Thus, it is possible to control the difference between the rotational torques Ta and Tb by adjusting the rotational torque Tc to be applied from the control gear  5 . 
         [0076]    In other words, the drive gear unit  10  includes the control gear  5  in addition to the first and second auxiliary gear pairs  18  and  19 , and thus, it is possible to control the distribution of the rotational energy with respect to the central shafts  15   s  and  15   t  of the carriers  15   a  and  15   b  of the first and second pinion gear units  11   a  and  11   b  by the control gear  5 . 
         [0077]    In this manner, the drive gear unit  10  can cause the rotational torques output from the central shafts  15   s  and  15   t  of the carriers  15   a  and  15   b  of the first and second pinion gear units  11   a  and  11   b  to be even, or control the difference between the rotational torques, and thus, can be used as the differential that distributes the rotational torque into right and left, and front and rear wheels. 
         [0078]    For example, it is configured such that the single input gear  30 , which transmits the driving force of an engine, is engaged with the intermediate gear  13  as illustrated in  FIG. 6( a )  in order to distribute a driving torque to the right and left wheels of an engine car. In the case of a hybrid type, it is configured such that an input gear  30   a  for driving the engine and an input gear  30   b  for driving a motor are engaged with the intermediate gear  13  as illustrated in  FIG. 6( b ) . Examples of the number of teeth of each gear in such cases are shown in the following Table 1. 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                   
                   
                   
                   
                 Reduction 
               
               
                   
                 Sun gear 
                 Planetary 
                 Inner teeth 
                 ratio 
               
               
                   
               
               
                 Number of 
                 20 
                 16 
                 52 
                 3.6 
               
               
                 teeth 
               
               
                   
               
             
          
           
               
                 Drive input 
                 Intermediate 
                 Reduction ratio 
               
               
                   
               
               
                 48 
                 12 
                 4 
               
               
                 40 
                 20 
                 2 
               
               
                   
               
             
          
         
       
     
         [0079]    The drive gear unit  10  can obtain an excellent action and effect as follows. 
         [0080]    Since the first and second auxiliary gear pairs  18  and  19  are arranged at the outer sides of the internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b , a force to act corresponding to the rotational torque decreases. Further, since the plurality of sets of the first and second auxiliary gear pairs  18  and  19  are arranged, the force that acts corresponding to the rotational torque can be shared among the respective sets. Thus, it is easy to secure strength for the gears of the first and second auxiliary gear pairs  18  and  19 . In addition, gear shafts inside the drive gear unit  10  are not misaligned due to the rotational torque. 
         [0081]    In addition, the first and second auxiliary gear pairs  18  and  19  are rotatably supported by the casing or the like, similar to the connection shaft  12  and the central shafts  15   s  and  15   t  of the carriers  15   a  and  15   b  to simply rotate, and do not revolve around the internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b  like the pinion gear. Furthermore, the first and second auxiliary gear pairs  18  and  19  are rotated only by the difference in the rotational speed between the central shafts  15   s  and  15   t  of the carriers  15   a  and  15   b  of the first and second pinion gear units  11   a  and  11   b , that is, the difference in the rotational speed between the wheels  2   a  and  2   b , and thus, each rotational speed thereof is low. 
         [0082]    From such points, the first and second auxiliary gear pairs  18  and  19  can be configured to be small. 
         [0083]    In addition, the first and second auxiliary gear pairs  18  and  19  and the rotation center axis of the control gear  5  are arranged in parallel with the rotation center axis of the first and third pinion gear units  11   a  and  11   b , and do not change in the axial direction in the drive gear unit  10 . Thus, it is possible to arrange the first and second auxiliary gear pairs  18  and  19  to be around the internal gears  16  and  17  of the first and third pinion gear units  11   a  and  11   b.    
         [0084]    Further, the first and second auxiliary gear pairs  18  and  19  and the rotation center axis of the control gear  5  are arranged in parallel with the rotation center axes of the first and third pinion gear units  11   a  and  11   b  and the rotary shafts thereof do not intersect each other. Thus, it is possible to manufacture the drive gear unit  10  with high performance and low cost using an existing technique, and further, a frictional loss of engagement is few. 
         [0085]    Accordingly, it is possible to allow the drive gear unit  10  to have a compact configuration, be reduced in size and weight, and be manufactured with high performance and low cost. 
         [0086]    The drive gear unit  10  can be formed to be bilaterally asymmetrical, and thus, it is easy to secure straight driving when being used in the automobile. 
         [0087]    In the drive gear unit  10 , the rotation for transmitting the rotational torque and the rotation for controlling the distribution of the rotational torque are completely separated. Since the total sum of the rotational torques output from the central shafts  15   s  and  15   t  of the carriers  15   a  and  15   b  of the first and second pinion gear units  11   a  and  11   b  does not change even when the control motor  4  is driven, the control motor  4  does not exert any influence on the rotation of the drive source such as the motor or the engine. Even when the rotation of the driving force generated by the drive source such as the motor or the engine is changed, there is no influence on the control of the difference in the rotational torque between the central shafts  15   s  and  15   t  of the carriers  15   a  and  15   b  of the first and second pinion gear units  11   a  and  11   b . Thus, the drive gear unit  10  allows an extremely favorable controllability with respect to the distribution of the rotational torque and the difference in the rotational speed. 
         [0088]    In addition, in a case in which the control motor  4  does not operate due to disconnection or the like, a function of equally distributing the rotational torque is maintained when the rotary shaft  4   a  of the control motor  4  freely rotates without any resistance. In a case in which the rotation of the rotary shaft  4   a  of the control motor  4  becomes a load, a difference of the rotational torque with respect to the load is caused, but the own function of distributing the rotational torque is maintained. In addition, the rotational torque to be distributed is restricted by such a load, and thus, it is expected to serve as a limited slip differential in which a control unit such as a friction brake or a viscous resistance is incorporated in an output shaft. In other words, the drive gear unit  10  is stable even in a case in which the control gear  5  does not function due to failure of the control motor  4 , and maintains the mechanical operation to distribute the rotational torque. 
       Second Embodiment 
       [0089]    A drive gear unit  10   a  of a second embodiment will be described with reference to  FIGS. 7 to 8 ( b ). The drive gear unit  10   a  of the second embodiment is configured in substantially the same manner as the drive gear unit  10  of the first embodiment. Hereinafter, the same reference numeral will be used for the same configuration part as the first embodiment, and a description will be given focusing on a different point from the first embodiment. 
         [0090]    As illustrated in  FIG. 7 , the drive gear unit  10   a  of the second embodiment includes the sun gears as external gears  12   a  and  12   b  of the first and second pinion gear units  11   a  and  11   b , the first and second auxiliary gear pairs  18  and  19 , and the control gear  5 , similar to the drive gear unit  10  of the first embodiment. 
         [0091]    The drive gear unit  10   a  of the second embodiment is different from the drive gear unit  10  of the first embodiment in terms of a configuration between the first and second pinion gear units  11   a  and  11   b . In other words, an electric motor  6  having a rotary shaft  8  protruding at both ends thereof is arranged between the first and second pinion gear units  11   a  and  11   b , and the sun gears as external gears  12   a  and  12   b  of the first and second pinion gear units  11   a  and  11   b  are fixed to both ends of the rotary shaft  8 . That is, the rotary shaft  8  of the electric motor  6  is a modification of the connection shaft  12  of the drive gear unit  10  of the first embodiment. In addition, the intermediate gear  13  is fixed to one side of the rotary shaft  8 . 
         [0092]    In addition, a transmission gear  31  to be engaged with the input gear  30  is rotated by the drive source, which is different from the drive gear unit  10  of the first embodiment. A set of the input gear  30  and the transmission gear  31  may be provided as illustrated in  FIG. 8( a ) , or two or more sets of the input gears  30   a  and  30   b  and transmission gears  31   a  and  31   b  may be provided as illustrated in  FIG. 8( b ) . It may be configured such that the transmission gear  31  is discarded as in the first embodiment, and a function thereof is realized by the input gear  30 , or that the intermediate gear  13  and the input gear  30  are non-parallel axes gears if dimensionally configurable. 
         [0093]    Similar to the drive gear unit  10  of the first embodiment, the drive gear unit  10   a  can distribute the rotational torque to be output to the central shafts  15   s  and  15   t  of the carriers  15   a  and  15   b  of the first and second pinion gear units  11   a  and  11   b , or control the a difference in the distribution of the rotational torque. 
         [0094]    A drive system is configured in an integrated manner by combining the electric motor, a deceleration unit, and the differential by incorporating the electric motor  6  in the drive gear unit  10   a  the electric motor  6 , and the drive gear unit  10   a  reduced in size is particularly suitable for the automobile driven by the motor. In other words, the pinion gear unit has the largest reduction ratio in a case in which the external sun gear is input, the carrier is output. Since a general automobile proceeds about 1.8 m to 2 m by a single rotation of a tire, and vehicle speed is about 160 Km/h, the output number of revolutions required for the carrier is about 1200 to 1500 rpm. The most efficient rotational speed for the motor is 5,000 rpm to 10,000 rpm. A reduction gear ratio of the pinion gear unit having the external sun gear as input and the carrier as output is generally about 3 to 8, and thus, it is possible to rotate the tire at the most efficient rotational speed of the motor. Accordingly, the drive gear unit  10   a  can realize a configuration of a motor drive system which is the most logical, and suitable for requests of vehicles. 
       Third Embodiment 
       [0095]    A drive gear unit  10   b  of a third embodiment will be described with reference to  FIGS. 9 to 13 .  FIG. 9  is a configuration diagram of a main section of the drive gear unit  10   b .  FIG. 10  is a cross-sectional view taken along line A-A of  FIG. 9 .  FIG. 11  is a cross-sectional view taken along line B-B of  FIG. 9 .  FIG. 12  is a cross-sectional view taken along line C-C of  FIG. 9 .  FIG. 13  is a transparent view of the gears taken along line D-D of  FIG. 9 . 
         [0096]    As illustrated in  FIG. 9 , the drive gear unit  10   b  is configured in substantially the same manner as that of the first embodiment. The drive gear unit  10   b  includes a dual concentric motor  100  arranged between the first and second pinion gear units  11   a  and  11   b , a third auxiliary gear pair  123 , and a fourth auxiliary gear pair  40  rotatably supported by a housing  10   k  of the drive gear unit  10   b , which is different from the first embodiment. In addition, outer teeth are not formed in an internal gear  17   p  of the second pinion gear unit  11   b.    
         [0097]    As illustrated in  FIG. 12 , the dual concentric motor  100  has two motors which are concentrically configured. In other words, an inner rotor to which a magnet  102  is fixed, that is, the connection shaft  12  is arranged at an inner side of a stator  110 , and an outer rotor  116  to which a magnet  104  is fixed is arranged at an outer side of the stator  110 . Coils  112  and  114  are provided in the stator  110  to oppose the magnets  102  and  104 , respectively. The stator  110  is fixed to a housing  10   k  of the drive gear unit  10   b  via a support member  150 . 
         [0098]    As illustrated in  FIG. 9 , the sun gears as external gears  12   a  and  12   b  of the first and second pinion gear units  11   a  and  11   b  are connected coaxially at both ends of the inner rotor of the dual concentric motor  100 , that is, the connection shaft  12  and rotate in an integrated manner. In other words, the inner rotor of the dual concentric motor  100 , that is, the connection shaft  12  functions as the connection member. 
         [0099]    As illustrated in  FIG. 9 , the third auxiliary gear pair  123  having inner teeth  122  is connected coaxially at the first pinion gear unit  11   a  side of the outer rotor  116  of the dual concentric motor  100 , and the third auxiliary gear pair  123  and the outer rotor  116  rotate in an integrated manner. The second pinion gear unit  11   b  of the outer rotor  116  of the dual concentric motor  100  is connected coaxially to the internal gear  17   p  of the second pinion gear unit  11   b , and the outer rotor  116  and the internal gear  17   p  rotate in an integrated manner. 
         [0100]    As illustrated in  FIGS. 9 and 10 , the outer teeth  16   b  are formed in the internal gear  16  of the first pinion gear unit  11   a  concentrically with the inner teeth  16   a.    
         [0101]    As illustrated in  FIGS. 9 to 11 , first and second gears  40   a  and  40   b  are formed coaxially at both sides of the fourth auxiliary gear pair  40 , first outer teeth  40   a  are engaged with the outer teeth  16   b  of the internal gear  16  of the first pinion gear unit  11   a , and second gear  40   b  are engaged with the inner teeth  122  of the third auxiliary gear pair  123 . 
         [0102]    When the outer rotor  116  of the dual concentric motor  100  rotates in a direction indicated by an arrow  180  in  FIG. 12 , for example, in a state in which the sun gears as external gears  12   a  and  12   b  of the first and second pinion gear units  11   a  and  11   b  and the carriers  15   a  and  15   b  are stationary, the second gear  40   b  of the fourth auxiliary gear pair  40  rotates in a direction indicated by an arrow  182  as illustrated in  FIG. 11 . Further, as illustrated in  FIG. 10 , the first external gear  40   a  of the fourth auxiliary gear pair  40  rotates in the direction indicated by the arrow  182 , and the internal gear  16  of the first pinion gear unit  11   a  rotates in a direction indicated by an arrow  184 . Meanwhile, the internal gear  17   p  of the second pinion gear unit  11   b  rotates in the same direction as the outer rotor  116  of the dual concentric motor  100 , that is, the direction indicated by the arrow  180  as illustrated in  FIG. 13 . Accordingly, the internal gears  16  and  17   p  of the first and second pinion gear units  11   a  and  11   b  rotate in the reverse directions, via the outer rotor  116  and the fourth auxiliary gear pair  40 . The outer rotor  116  of the dual concentric motor  100 , and the third and fourth auxiliary gear pairs  123  and  40  function as reverse rotation members. 
         [0103]    When the internal gears  16  and  17   p  of the first and second pinion gear units  11   a  and  11   b  rotate at the same rotational speed in the reverse directions, it becomes easy to control the torque distribution. An exemplary design to obtain such an effect is as follows. 
         [0104]    The number of teeth of the outer teeth  16   b  of the internal gear  16  of the first pinion gear unit  11   a : 120   
         [0105]    The number of teeth of the first gear  40   a  of the fourth auxiliary gear pair  40 : 12   
         [0106]    The number of teeth of the second gear  40   b  of the fourth auxiliary gear pair  40 : 16   
         [0107]    The number of teeth of the inner teeth  122  of the third auxiliary gear pair  123 : 160   
         [0108]    The number of arrangement of the fourth auxiliary gear pair  40 : 3   
         [0109]    When the inner rotor of the dual concentric motor  100 , that is, the connection shaft  12  rotates, a driving force (rotational torque) thereof is transmitted to the carriers  15   a  and  15   b  of the first and second pinion gear units  11   a  and  11   b  as similar to the first embodiment. At this time, when the outer rotor  116  of the dual concentric motor  100  is rotated, the torque distribution is changed. The drive gear unit  10   b  can control the driving by the inner rotor of the dual concentric motor  100 , and control the differential by the outer rotor, and thus, it is possible to perform the control of the driving force and the control of the torque distribution in an independent manner. 
         [0110]    The drive gear unit  10   b  uses the inner rotor of the dual concentric motor  100  for the driving, and uses the outer rotor of the dual concentric motor  100  for the control of the torque distribution. On the contrary, it is also possible to use the outer rotor of the dual concentric motor  100  for the driving, and the inner rotor for the control of the torque distribution, but it is possible to reduce the size and weight of the drive gear unit when using the inner rotor with not only a small size but also high output for the driving. 
         [0111]    It is easy to configure the drive gear unit  10   b  to have a small dimension in the axial direction, and be compact without any opening at an outer circumference thereof. In addition, the reverse rotation members are engaged at two points to be smaller than the three points of the first embodiment, and the outer rotor  116  of the drive motor  100  also serves as the reverse rotation member. Accordingly, it is possible to easily reduce the size and weight. 
       Fourth Embodiment 
       [0112]    A drive gear unit  10   c  of a fourth embodiment will be described with reference to  FIG. 14 . 
         [0113]      FIG. 14  is a configuration diagram of a main section of the drive gear unit  10   c . As illustrated in  FIG. 14 , the drive gear unit  10   c  has the intermediate gear  13  in addition to the drive gear unit  10   b  of the third embodiment. The intermediate gear  13  is fixed to the connection shaft  12 . The intermediate gear  13  is engaged with a transmission gear  32 . The intermediate gear  13  transmits a driving force via the transmission gear  32  from an outer side of a housing  10   m  of the drive gear unit  10   c . When the drive gear unit  10   c  of the fourth embodiment is used in, for example, a hybrid car, the driving force of the engine is input to the intermediate gear  13 . 
       Fifth Embodiment 
       [0114]    A drive gear unit  10   d  of a fifth embodiment will be described with reference to  FIG. 15 . 
         [0115]      FIG. 15  is a configuration diagram of a main section of the drive gear unit  10   d . As illustrated in  FIG. 15 , the drive gear unit  10   d  is arranged such that a drive motor  100   a  that drives the connection shaft  12  to rotate and a control motor  100   b  that drives the internal gear  17   p  of the second pinion gear unit  11   b  to rotate are arranged side by side in the axial direction. 
         [0116]    In the drive motor  100   a , a stator  110   a  surrounds the connection shaft  12  to which the magnet  102  is fixed, and a coil  112   a  is provided in the stator  110   a . The stator  110   a  is fixed to a housing  10   n  of the drive gear unit  10   d  via a support member  150   a.    
         [0117]    The internal gear  16  of the first pinion gear unit  11   a  and the internal gear  17   p  of the second pinion gear unit  11   b  are connected to each other so as to rotate in the reverse directions via a fifth auxiliary gear pair  121  and a sixth auxiliary gear pair  40  as substantially similar to the third embodiment. 
         [0118]    In other words, the fifth auxiliary gear pair  121  is a member that corresponds to the outer rotor  116  and the third auxiliary gear pair  123  of the drive motor  100  of the third embodiment, is connected coaxially to the internal gear  17  of the second pinion gear unit  11   b , and has inner teeth  122  at the first pinion gear unit  11   a  side. The sixth auxiliary gear pair  40  is rotatably supported by the housing  10   m  of the drive gear unit  10   d , and has the first and second gears  40   a  and  40   b  formed coaxially at both sides thereof. The first gear  40   a  of the sixth auxiliary gear pair  40  is engaged with the outer teeth  16   b  of the internal gear  16  of the first pinion gear unit  11   a , and the second gear  40   b  is engaged with the inner teeth  122  of the fifth auxiliary gear pair  121 . Accordingly, the internal gear  16  of the first pinion gear unit  11   a  and the internal gear  17   p  of the second pinion gear unit  11   b  rotate in the reverse directions as similar to the third embodiment. The fifth and sixth auxiliary gear pairs  123  and  40  functions as the reverse rotation members. 
         [0119]    Rotation of an output shaft  42  of the control motor  100   b  is transmitted to the internal gear  17  of the second pinion gear unit  11   b  via a planetary mechanism  43 . In other words, the external sun gear  45  of the planetary mechanism  43  is formed in the output shaft  42  of the control motor  100   b . An inner gear  46  of the planetary mechanism  43  is fixed to the housing  10   m  of the drive gear unit  10   d . A planetary shaft  119  that rotatably supports a pinion gear  44  of the planetary mechanism  43  is fixed to the internal gear  17  of the second pinion gear unit  11   b . Accordingly, the rotation of the output shaft  42  of the control motor  100   b  is transmitted to the internal gear  17  of the second pinion gear unit  11   b  via the planetary mechanism  43 . 
         [0120]    When the drive motor  100   a  rotates, a driving force (rotational torque) thereof is transmitted to the carriers  15   a  and  15   b  of the first and second pinion gear units  11   a  and  11   b . At this time, when the control motor  100   b  is rotated, the torque distribution is changed. The drive gear unit  10   c  can control the driving by the drive motor  100   a , and control the differential by the control motor  100   b , and thus, it is possible to perform the control of the driving force and the control of the torque distribution in an independent manner. 
         [0121]    It is possible to simplify the configuration of the drive gear unit  10   d  by reducing the engagement points between the reverse rotation members as similar to the drive gear unit  10   b  of the third embodiment. In addition, it is possible to decrease a dimension in the radial direction. 
       Sixth Embodiment 
       [0122]    A drive gear unit  10   e  of a sixth embodiment will be described with reference to  FIGS. 16 and 17 . 
         [0123]      FIG. 16  is a configuration diagram of a main section of the drive gear unit  10   e . As illustrated in  FIG. 16 , the drive gear unit  10   e  is arranged such that the drive motor  100   a  that drives the connection shaft  12  to rotate and the reversing motor  200  serving as the control motor are arranged side by side in the radial direction, which is different from the drive gear unit  10   d  of the fifth embodiment. 
         [0124]    The reversing motor  200  has first and second output shafts which are arranged coaxially, protrude to sides opposite to each other, and are driven to rotate in reverse directions. First and second gears  202  and  204  are fixed coaxially to output shafts  200   a  and  200   b  of the reversing motor  200 . The outer teeth  16   b  and  17   b  to be engaged with the first and second gears  202  and  204  are formed in the internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b.    
         [0125]      FIG. 17  is an explanatory diagram illustrating a configuration of the reversing motor  200 . As illustrated in  FIG. 17 , the reversing motor  200  has a motor  210  and a gear unit  220  being arranged coaxially inside a housing  201 . 
         [0126]    In the motor  210 , the output shaft  200   a  serving as the inner rotor is arranged inside a stator  214  fixed to the housing  201 , a magnet  212  is fixed to the output shaft  200   a , and a coil  216  is provided in the stator  214 . The output shaft  200   a  is rotatably supported by the housing  201 , and has one end portion thereof protruding from the housing  201  and the other end portion to which a gear  208  is fixed. 
         [0127]    The gear unit  220  includes a gear member  222  and a rotary member  224 . The gear member  222  is rotatably supported by the housing  201 , and has gears  222   a  and  222   b  at both ends thereof. The rotary member  224  is rotatably supported by the housing  201 , and inner teeth  226  are formed at one end portion thereof, and the output shaft  200   b  are formed coaxially at the other end portions side. The gear  222   a , one of the gear members  222 , is engaged with the gear  208  fixed to the output shaft  200   a , and the other gear  222   b  is engaged with the inner teeth  226  of the rotary member  224 . 
         [0128]    The reversing motor  200  preferably has the output shafts  200   a  and  200   b  rotating at the same rotational speed in the reverse directions in terms of easy design, but can be used even when the output shafts  200   a  and  200   b  have different rotational speed. 
         [0129]    When the reversing motor  200  rotates, the internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b  rotate in the reverse directions. The reversing motor  200  functions as the reverse rotation member and the control motor. Since the reversing motor  200  is unitized, it is easy to assemble. 
         [0130]    The drive gear unit  10   e  can control the driving force by the drive motor  100   a , and control the torque distribution by the reversing motor  200 . 
       Seventh Embodiment 
       [0131]    A drive gear unit  10   f  of a seventh embodiment will be described with reference to  FIG. 18 . 
         [0132]      FIG. 18  is a configuration diagram of a main section of the drive gear unit  10   f . As illustrated in  FIG. 18 , the intermediate gear  13  is fixed to the connection shaft  12  in the drive gear unit  10   f  instead of the drive motor  100   a  of the drive gear unit  10   d  of the sixth embodiment. The intermediate gear  13  is engaged with the transmission gear  32 , and rotation of, for example, an internal combustion engine or the motor is input via the transmission gear  32 . 
       Eighth Embodiment 
       [0133]    A drive gear unit  10   g  of an eighth embodiment will be described with reference to  FIG. 19 . 
         [0134]      FIG. 19  is a configuration diagram of a main section of the drive gear unit  10   g . As illustrated in  FIG. 19 , the drive gear unit  10   g  uses the reversing motor  200  instead of the connection shaft  12  of the first to seventh embodiments. In other words, the sun gears as external gears  12   a  and  12   b  of the first and second pinion gear units  11   a  and  11   b  are connected coaxially to the first and second output shafts  200   a  and  200   b  of the reversing motor  200 . 
         [0135]    The internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b  are connected so as to rotate at the same rotational speed in the same direction. In other words, the outer teeth  16   b  and  17   b  are formed in the internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b , and gears  52  and  54  formed at both sides of a gear member  50  are engaged with the outer teeth  16   b  and  17   b . The gear member  50  is rotatably supported by a casing (not illustrated) of the drive gear unit  10   g  via a bearing (not illustrated). The gear member  50  is the connection member. 
         [0136]    A transmission gear  34  is engaged with the outer teeth  16   b  of the internal gear  16  of the first pinion gear unit  11   a . When the rotation of the internal combustion engine or the motor is input to the internal gear  16  of the first pinion gear unit  11   a  via the transmission gear  34 , the internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b  rotate at the same rotational speed in the same direction. 
         [0137]    At this time, the sun gears as external gears  12   a  and  12   b  of the first and second pinion gear units  11   a  and  11   b  rotate in reverse directions in a case in which the reversing motor  200  is not driven, and thus, the torque is evenly distributed to the first pinion gear unit  11   a  side and the second pinion gear unit  11   b  side. In a case in which the reversing motor  200  is driven, and the sun gear as external gear  12   a  of the first pinion gear unit  11   a  and the sun gear as external gears  12   b  of the second pinion gear unit  11   b  rotate in the reverse directions, the distribution of the rotational torque into the first pinion gear unit  11   a  side and the second pinion gear unit  11   b  side is changed depending on such rotation in the reverse direction. Accordingly, it is possible to control the torque distribution by the reversing motor  200 . 
       Ninth Embodiment 
       [0138]    A drive gear unit  10   h  of a ninth embodiment will be described with reference to  FIGS. 20 and 21 .  FIG. 20  is a configuration diagram of a main section of the drive gear unit  10   h .  FIG. 21  is a cross-sectional view taken along line A-A of  FIG. 20 . 
         [0139]    As illustrated in  FIGS. 20 and 21 , the drive gear unit  10   h  of the ninth embodiment is configured in substantially the same manner as the drive gear unit  10  of the first embodiment. In other words, similar to the drive gear unit  10  of the first embodiment, the drive gear unit  10   h  includes the first and second pinion gear units  11   a  and  11   b , the connection shaft  12 , the first and second auxiliary gear pairs  18  and  19 , and the intermediate gear  13  fixed to the connection shaft  12 . 
         [0140]    As different from the first embodiment, the inner teeth  16   a  and  17   a  of the internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b  include inner teeth extension portions  16   c  and  17   c  which are extended to sides opposite to each other. 
         [0141]    The first and second auxiliary gear pairs  18  and  19  are arranged inwardly from the inner teeth  16   a  and  16   b  of the internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b , the first gear  18   a  of the first auxiliary gear pair  18  is engaged with the inner teeth extension portions  16   c  of the internal gear  16  of the first pinion gear unit  11   a , a second gear  18   b  of the first auxiliary gear pair  18  and a third gear  19   b  of the second auxiliary gear pair  19  are engaged with each other, and a fourth gear  19   a  of the second auxiliary gear pair  19  is engaged with an inner teeth extension portion  17   c  of the internal gear  17  of the second pinion gear unit  11   b.    
         [0142]    The first and second auxiliary gear pairs  18  and  19  is arranged between the pinion gears  14   a  and  14   b  of the first and second pinion gear units  11   a  and  11   b  so as not to interfere with the pinion gears  14   a  and  14   b  of the first and second pinion gear units  11   a  and  11   b  and the intermediate gear  13 . 
         [0143]    The first and second auxiliary gear pairs  18  and  19  is rotatably supported by a housing (not illustrated) of the drive gear unit  10   h , and a position of the rotation center axis of the first and second auxiliary gear pairs  18  and  19  is fixed with respect to the housing (not illustrated) of the drive gear unit  10   h.    
         [0144]    The internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b  are connected by the first and second auxiliary gear pairs  18  and  19  so as to rotate in the reverse directions, and thus, can evenly distribute the rotational torque input to the intermediate gear  13  into the first pinion gear unit  11   a  side and the second pinion gear unit  11   b  side. 
         [0145]    Incidentally, it is configured such that at least any one of the internal gear  16  of the first pinion gear unit  11   a , the internal gear  17  of the second pinion gear unit  11   b , the first auxiliary gear pair  18  and the second auxiliary gear pair  19  is rotated by the control motor in the case of controlling the torque distribution. 
       Tenth Embodiment 
       [0146]    A drive gear unit  10   i  of a tenth embodiment will be described with reference to  FIGS. 22 to 24 ( e ).  FIG. 22  is a configuration diagram of a main section of the drive gear unit  10   i .  FIG. 23( a )  is a cross-sectional view taken along line A-A of  FIG. 22 .  FIG. 23( b )  is a cross-sectional view taken along line B-B of  FIG. 22 .  FIG. 23( c )  is a cross-sectional view taken along line C-C of  FIG. 22 .  FIG. 24( d )  is a cross-sectional view taken along line D-D of  FIG. 22 .  FIG. 24( e )  is a cross-sectional view taken along line E-E of  FIG. 22 . 
         [0147]    As illustrated in  FIGS. 22 to 24 ( e ), the drive gear unit  10   i  is arranged such that the drive motor  100   a  that drives the connection shaft  12  to rotate and the control motor  100   b  that drives the internal gear  17  of the second pinion gear unit  11   b  to rotate are arranged side by side in the axial direction. 
         [0148]    Internal gears  16   q  and  17   q  of the first and second pinion gear units  11   a  and  11   b  are rotatably supported by the housing  10   n  of the drive gear unit  10   i  via a bearing, and are rotated in reverse directions by the first and second auxiliary gear pairs  18  and  19 . The inner teeth  16   a  and  17   a  of the internal gears  16   q  and  17   q  of the first and second pinion gear units  11   a  and  11   b  include the inner teeth extension portions  16   c  and  17   c  which are extended to the sides opposite to each other. The first and second auxiliary gear pairs  18  and  19  is rotatably supported by the housing  10   n  of the drive gear unit  10   i  via a bearing (not illustrated), and gears  18   a ,  18   b ,  19   a  and  19   b  are formed at both ends thereof in the axial direction. The second gear  18   b  of the first auxiliary gear pair  18  and the third gear  18   b  of the second auxiliary gear pair  19  are engaged with each other, the first gear  18   a  of the first auxiliary gear pair  18  is engaged with the inner teeth extension portion  16   c  of the internal gear  16   q  of the first pinion gear unit  11   a , and the fourth gear  19   a  of the second auxiliary gear pair  19  is engaged with inner teeth extension portion  17   c  of the internal gear  17  of the second pinion gear unit  11   b.    
         [0149]    An exemplary number of teeth of each gear is as follows. 
         [0150]    The number of teeth of the sun gears as external gears  12   a  and  12   b  of the first and second pinion gear units  11   a  and  11   b : 23   
         [0151]    The number of teeth of the pinion gears  14   a  and  14   b  of the first and second pinion gear units  11   a  and  11   b : 46   
         [0152]    The number of teeth of the inner teeth  16   a  and  17   a  of internal gears  16  and  17  of the first and second pinion gear units  11   a  and  11   b : 115   
         [0153]    The number of teeth of the first to fourth gears  18   a ,  18   b ,  19   a  and  19   b  of the first and second auxiliary gear pairs  18  and  19 : 13   
         [0154]    In this case, it is possible to arrange three sets of the first and second auxiliary gear pairs  18  and  19 , and set the number of each arrangement of the pinion gears  14   a  and  14   b  to be the same as three. 
         [0155]    The rotation of the output shaft  42  of the control motor  100   b  is transmitted to the internal gear  17   q  of the second pinion gear unit  11   b  via the planetary shaft  119  fixed to the internal gear  17   q  of the second pinion gear unit  11   b  as similar to the fifth embodiment. 
         [0156]    When the drive motor  100   a  rotates, a driving force (rotational torque) thereof is transmitted to the carriers  15   a  and  15   b  of the first and second pinion gear units  11   a  and  11   b . At this time, when the control motor  100   b  is rotated, the torque distribution is changed. Since the drive gear unit  10   i  can control the driving by the drive motor  100   a  and control the differential by the control motor  100   b , it is possible to perform the control of the driving force and the control of the torque distribution in an independent manner. 
       CONCLUSION 
       [0157]    As described above, the drive gear units  10  and  10   a  can be simply configured, easily reduced in the size and weight, and has the small frictional loss. 
         [0158]    Incidentally, the present invention is not limited to the embodiments described above, but can be implemented by being added with various types of modifications. 
         [0159]    For example, it may be configured such that the members illustrated in the embodiments are divided into a plurality of members to serve the same function. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           2   a ,  2   b  Wheel 
           4  Control Motor 
           4   a  Rotary Shaft 
           5  Control Gear 
           6  Electric Motor 
           8  Rotary Shaft (Connection Member) 
           10 ,  10   a  to  10   i  Drive Gear Unit 
           10   k ,  10   m ,  10   n  Housing 
           11   a  First Pinion gear Unit 
           11   b  Second Pinion gear Unit 
           12  Connection Shaft (Connection Member) 
           12   a  and  12   b  Sun Gear as External Gear 
           13  Intermediate Gear 
           14   a ,  14   b  pinion gear 
           15   a ,  15   b  Carrier 
           15   p ,  15   q  Support Shaft 
           15   s ,  15   t  Central Shaft 
           16 ,  17  Internal Gear 
           16   a ,  17   a  Inner Teeth 
           16   b ,  17   b  Outer Teeth 
           16   q ,  17   p ,  17   q  Internal Gear 
           18  First Auxiliary Gear Pair 
           18   a  First Gear 
           18   b  Second Gear 
           19  Second Auxiliary Gear Pair 
           19   a  Second Gear 
           19   b  Fourth Gear 
           30 ,  30   a ,  30   b  Input gear 
           31 ,  31   a ,  31   b  Transmission gear 
           40  Fourth Auxiliary Gear Pair, Sixth Auxiliary Gear Pair 
           50  Gear Member (Connection Member) 
           100  Dual Concentric Motor 
           100   a  Drive Motor 
           100   b  Control Motor 
           121  Fifth Auxiliary Gear Pair 
           123  Third Auxiliary Gear Pair 
           200  Reversing Motor 
           200   a ,  200   b  Output Shaft