Abstract:
it is an object of the present invention to provide a differential limiting apparatus increasing the capacity of the clutch to obtain the enough large differential limiting force. 
     The differential limiting apparatus comprising a housing  2  rotated by driving force of a driving source, a differential mechanism  3  having one pair of output gears  3 A,  3 B to distribute said driving force to one pair of output shafts differentially, a clutch  4  disposed directly between the one pair of output gears  3 A,  3 B and having the inner clutch plate  4 A and the outer clutch plate  4 B as an annular frictional plate to restrict a differential movement of the differential mechanism  3 , and an output mechanism  5  driving said clutch  4 , the output mechanism  5  includes a first cam  52 C moved along an axial direction, and a pushing pin  35  as a transmitting member transmitting the axial movement of said first cam  52 C to the clutch  4.

Description:
INCORPORATION BY REFERENCE 
       [0001]    The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2007-254286, filed on Sep. 28, 2007. The content of the application is incorporated herein by reference in their entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a differential limiting apparatus, and more particularly relates to the differential limiting apparatus having a clutch restricting a differential movement of a differential mechanism. 
         [0004]    2. Description of the Prior Art 
         [0005]    It is well known for a prior differential limiting apparatus to restrict a differential movement of the differential apparatus by connecting between an input shaft and one output shaft of a pair of output shafts as disclosed in a published patent document; Tokkai 2007-138983. 
         [0006]    This conventional differential limiting apparatus includes a housing rotated with an input shaft, a differential mechanism distributing differentially a rotating force from the housing, a clutch restricting a differential movement of the differential mechanism and a driving mechanism driving the clutch. 
         [0007]    The housing includes a front housing being a hollow cylindrical body having a bottom and opening to one direction, a rear housing being an annular cylindrical body equipped on the opening of the front housing. The housing is connected to the input shaft and constructed to rotate by receiving a driving force from a driving source such as an engine of a vehicle. 
         [0008]    The differential mechanism includes a ring gear as a pair of output gears respectively connected to the pair of output shafts, a sun gear, planetary gears engaged in mesh with the ring gear and the sun gear. The differential mechanism is accommodated in the housing and constructed to distribute a rotational force from the housing to a pair of the output shafts differentially. 
         [0009]    The clutch includes a plurality of outer clutch plates and a plurality of inner clutch plates and the clutch is disposed between an inner surface of the housing and an outer surface of the ring gear. The clutch is constructed to connect the input shaft and the one output shaft in order to restrict the differential movement of the differential mechanism when the plural outer clutch plates and the plural inner clutch plates are engaged in friction. The plural outer clutch plates are engaged in mesh of spline engagement with the inner surface of the front housing and the plural inner clutch plates are engaged in mesh of spline engagement with the outer surface of the ring gear. Each of the plural outer clutch plates and each of the plural inner clutch plates are disposed alternatively each other. 
         [0010]    The driving mechanism includes an electro magnetic clutch, a pilot clutch driven by receiving an electro magnetic force from the electro magnetic clutch, and a cam mechanism transforming a rotational force from the housing to a pushing force toward a main clutch by driving the pilot clutch. The driving mechanism is disposed around peripheries of a pair of output shafts inside the housing. The pushing force is transmitted via a cylindrical portion to a bottom portion of a cylindrical output transmitting member having the bottom portion and a cylindrical portion, and after that transmitted via the cylindrical portion of the output transmitting member to the main clutch in order to connect the outer clutch plates and the inner clutch plates by friction. 
         [0011]    In the above-mentioned construction of the prior art, when the driving force from an engine is input into the housing through the input shaft, the housing is rotated around the rotational axis. Upon the rotation of the housing, the rotational force is transmitted to the planetary gear, and after that from the planetary gear to the ring gear and the sun gear. Since the ring gear and the sun gear are respectively connected to each of the output shafts, the driving force from the engine is distributed differentially according to a state of the driving of the vehicle and the torque differentially distributed is transmitted to the right and left output shaft. 
         [0012]    In this stage, when the electro magnetic clutch is energized, the pilot clutch is started to be driven by an electro magnetic force of the electro magnetic clutch. At this time, the rotational force of the housing is transformed to the pushing force by the cam when the rotational force from the housing is received by the cam at the driving stage of the pilot clutch. The pushing force is exerted from the output member to the main clutch through the output transmitting member. Then the outer clutch plates and the inner clutch plates are relatively approached to be contacted in friction, and by the frictional contact the housing and the ring gear are connected, that is to say the input shaft and the output shaft corresponding to the ring gear are connected to be able to transmit the rotational force so that the differential movement is restricted. 
         [0013]    However, in the differential limiting apparatus of the published patent document of Tokkai 2007-138983 as the prior art, it is necessary for the conventional differential limiting apparatus to increase a number of the clutch plates in order to obtain the larger differential limiting force, resulting to make a bigger longitudinal size of the whole apparatus if a longitudinal length of the main clutch is longer than a longitudinal length of the planetary gear and a longitudinal length of the flange portion of the ring gear. As a result, a number of the outer clutch plates and the inner clutch plates are limited so that a capacity of the clutch is limited to make an obstruction to obtain an enough large differential limiting force. 
       SUMMARY OF THE INVENTION 
       [0014]    In view of the previously mentioned circumstances, it is an object of the present invention to provide a differential limiting apparatus increasing the capacity of the clutch to obtain the enough large differential limiting force. Particularly, the differential limiting apparatus has mainly a clutch for restricting the differential movement and installing the clutch between a pair of output shafts to increase the capacity of the clutch to obtain the enough large differential limiting force. 
         [0015]    In order to achieve the above and other objects, one aspect of the present invention having mainly a housing rotated by driving force of a driving source, a differential mechanism having one pair of output gears to distribute the driving force to one pair of output shafts differentially, a clutch disposed directly between the one pair of output gears and having an annular frictional plate to restrict a differential movement of the differential mechanism, and an output mechanism driving the clutch. Thereby, the clutch of the present invention is constructed to connect directly the one pair of output gears to transmit the rotational force of the housing so that it is for the present invention to increase double a differential restricting force of the differential mechanism created by the clutch, compared to the conventional differential limiting apparatus having the clutch installed between the input shaft and one of output gears. Namely, the differential rotation of the output gears is restricted double by two ways of restrictions based on next two operations; one is that torque of the other of output gears transmitted to the one of output gears through the clutch restricts a rotation of the one of output gears and the other is that torque of the one of output gears transmitted to the other of output gears through the clutch restricts a rotation of the other of output gears because the clutch is installed directly between the one pair of output gears. 
         [0016]    Second aspect of the present invention according to the one aspect of the present invention provides a differential limiting apparatus mainly having the clutch installed directly and circumferentially on the one pair of output gears. Thereby, the differential limiting apparatus can reduce a total longitudinal length of the apparatus itself because the clutch is installed in a radial direction of the one pair of output gears. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    Various other objects, features and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description of the preferred embodiments when considered in connection with the accompanying drawings, in which: 
           [0018]      FIG. 1  is a partially cut oblique perspective diagram explaining a differential limiting apparatus according to one embodiment of the present invention; 
           [0019]      FIG. 2  is a cross sectional diagram explaining a differential limiting apparatus according to one embodiment of the present invention; 
           [0020]      FIG. 3  is a cross sectional diagram viewed from A-A arrow in the  FIG. 2 ; 
           [0021]      FIG. 4  is a cross sectional diagram viewed from B-B arrow in the  FIG. 2 ; 
           [0022]      FIG. 5  is a cross sectional diagram viewed from C-C arrow of the  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     [Whole Construction of the Differential Device for the Vehicle] 
       [0023]    In  FIG. 1  and  FIG. 2 , a numeral  1  shows the differential limiting apparatus according to one embodiment of the present invention. The differential limiting apparatus  1  mainly consists of a housing  2  rotated by receiving torque from an engine, a differential mechanism  3  distributing differentially rotational force from the housing  2  to one pair of unillustrated tire shafts, a clutch  4  limiting a differential operation of the differential mechanism  3 , and an output mechanism  5  operating the clutch  4 . 
       [Construction of the Housing  2 ] 
       [0024]    The housing  2  is a hollow construction driven rotatably around a rotational axis O as a whole and consists of a front housing  20  being hollow cylindrical with a bottom and a rear housing  21  being almost circularly annular, as shown in  FIGS. 1 ,  2 . The front housing  20  includes a parts inserting inlet  20 A opened to one direction along the rotational axis O to the tire shafts. The rear housing  21  covers the parts inserting inlet  20 A of the front housing  20 . 
         [0025]    The front housing  20  is equipped with an accommodating space  20 B, a tire shaft inserted hole  20 C, first gear accommodating spaces  20 D, and second gear accommodating spaces  20 E, as shown in  FIG. 2 . The accommodating space  20 B is communicated with the parts inserting inlet  20 A in order to accommodate the differential mechanism  3 , the clutch  4  and most of the output mechanism  5 . The tire shaft inserted hole  20 C is communicated with the accommodating space  20 B. A number of the first gear accommodating spaces  20 D and the second gear accommodating spaces  20 E is respectively five in the one embodiment. In the front housing  20  are formed plural first torque transmitting faces  200 D, plural first pinion gear supporting surfaces  201 D, plural second torque transmitting faces  200 E, plural second pinion gear supporting surfaces  201 E. Each of these first torque transmitting faces  200 D and first pinion gear supporting surfaces  201 D defines each of a plurality of the first gear accommodating spaces  20 D, and each of these second torque transmitting faces  200 E and second pinion gear supporting surfaces  201 E defines each of the second gear accommodating spaces  20 E. 
         [0026]    The tire shaft inserted hole  20 C provides an approximately uniform inner diameter and constructs a step penetrating hole into which the unillustrated left tire shaft is inserted. The first gear accommodating spaces  20 D and the second gear accommodating spaces  20 E are respectively communicated with each other as shown in  FIG. 3  and are placed in parallel in a same predetermined distance around the rotational axis O of the tire shaft inserted hole  20 C shown in  FIG. 2 . 
         [0027]    On a left end portion of the front housing  20  along the rotational axis O is mounted an annular ring gear mounting flange  20 F projecting from an outer surface of the front housing  20 . The ring gear mounting flange  20 F has a plurality of penetrating holes  20   f  positioned in parallel with each other at a predetermined distance in circumferential direction. 
         [0028]    On an inner surface of the front housing  20  is equipped an annular stepped surface  20 G faced to an inner end face of the rear housing  21 . On the inner surface of the front housing  20  is also screwed a ring spacer  22  positioned between the stepped surface  20 G and the inner end face of the rear housing  21 . The ring spacer  22  is made of a non-magnetic material and opened along the rotational axis O. 
         [0029]    In a bottom portion of the front housing  20  are formed plural through holes  20 H positioned at places corresponding to the second gear accommodating spaces  20 E and positioned in parallel with each other at predetermined interval around the rotational axis O. The number of the plural through holes  20 H is five in the one embodiment. A plurality of filling caps  23  having oil holes  23 A cover respectively the plural through holes  20 H. A first supporting portion  201  for a right output gear  3 B is mounted on the bottom of the front housing  20 . The first supporting portion  201  for the right output gear  3 B supports slidably a gear portion of a right output gear  3 B of the one pair of right and left output gears  3 B,  3 A. 
         [0030]    On the other hand, the rear housing  21  consists of a cylindrical first element  21 A, an annular second element  21 B and a connecting ring  21 C, and is screwed into the front housing  20  in a side of the parts inserting inlet as shown in  FIG. 2 . The second element  21 B includes an inner circumferential surface faced to an outer circumferential surface of the first element  21 A through an annular space  25 . The connecting ring  21 C is placed between the first element  21 A and the second element  21 B. The first element  21 A and the second element  21 B are respectively made of a magnetic material such as soft iron etc. and the connecting ring  21 C is made of a non-magnetic material such as stainless steel etc. 
         [0031]    In the first element  21 A of the rear housing  21  is equipped a tire shaft inserted hole  210 A communicated to the accommodating space  20 B of the front housing  20  and opened to a direction of the rotating axis O of the tire shaft inserted hole  20 C. The tire shaft inserted hole  210 A has an approximately uniform inner diameter and is constructed as a stepped penetrating hole penetrated by an unillustrated right tire shaft. A second supporting portion  210 B for the right output gear  3 B supports slidably a boss portion of the right output gear  3 B of the one pair of right and left output gears  3 B,  3 A on the stepped surface of the tire shaft inserted hole  210 A. 
       [Construction of the Differential Mechanism  3 ] 
       [0032]    The differential mechanism  3  provides the one pair of right and left output gears  3 B,  3 A, a plurality of first pinion gears  3 C and a plurality of second pinion gears  3 D, and is accommodated in the accommodating space  20 B of the housing  2  as shown in  FIG. 1 ,  FIG. 2 . A gear member  31 A of the left output gear  3 A and a gear member  32 B of the right output gear  3 B are respectively constructed with a helical gear and also the plural first pinion gears  3 C and the plural second pinion gears  3 D are respectively constructed with a helical gear. The first pinion gears  3 C are engaged in mesh with the gear member  31 A of the left output gear  3 A in condition that gear axes of the pinion gears  3 C are parallel with a gear axis of the left output gear  3 A. On the other hand, the second pinion gears  3 D are engaged in mesh with these first pinion gears  3 C respectively as shown in  FIG. 3  and also the gear member  32 B of the right output gear  3 B in condition that gear axes of the pinion gears  3 D are parallel with a gear axis of the right output gear  3 B. 
         [0033]    The output gear  3 A includes a boss member  30 A as a first boss portion and the gear member  31 A as a first cylindrical portion, and arranged rotatably on the rotational axis O of the housing  2  as shown in  FIG. 2 . As shown in  FIG. 3 , it is set that a gear diameter ratio between an engaging portion of the gear member  31 A of the output gear  3 A with the first pinion gears  3 C and an engaging portion of the gear member  32 B of the output gear  3 B with the second pinion gears  3 D is equal to a gear diameter ratio between the first pinion gears  3 C and the second pinion gears  3 D so that a velocity ratio of the output gears  3 A,  3 B can be set as an equal ratio, that is to say 1 vs. 1. Each of the gear diameters is a pitch circle diameter. 
         [0034]    The boss member  30 A consists of a hollow cylindrical member having an annular flange  300 A at an approximately center portion of the boss member  30 A along its axial direction. The flange  300 A is mounted slidably against a flange  300 B of the output gear  3 B and an inner surface of the front housing  20  through a washer  27  and a washer  28  respectively. An inner gear portion on an internal surface of the boss member  30 A engages in mesh with a left output shaft of the one pair of unillustrated right and left output shafts in a way of a spline engagement after the left output shaft is inserted into the tire shaft inserted hole  20 C. 
         [0035]    The gear member  31 A consists of an internal gear, like a ring gear, having an internal peripheral surface faced to an outer peripheral surface of the boss member  30 A through a first annular space  29  and the gear member  31 A is a cylindrical body having a part of bottom. The internal gear of the gear member  31 A engages in mesh with the outer surface portion of the flange  300 A of the boss member  30 A in spline engagement. The end of the gear member  31 A is slidably mounted on a gear member  32 B of the output gear  3 B through a washer  34  and the bottom of the gear member  31 A is slidably mounted on the flange  300 B through the washer  27 . 
         [0036]    The output gear  3 B includes a boss member  30 B as a second boss portion, an intermediate member  31 B as a hollow second cylindrical portion and the gear member  32 B, as shown in  FIG. 2 . The output gear  3 B is slidably mounted at an axis of the output gear  3 A in a state that a part of the boss member  30 A is inserted into the output gear  3 B. 
         [0037]    The boss member  30 B consists of a cylindrical member having the flange  300 B faced to the flange  300 A of the output gear  3 A. The boss member  30 B is slidably disposed at a second supporting portion  210 B for the right output gear through a washer  26 . An inner gear portion on an internal surface of the boss member  30 B engages in mesh with a right output shaft of the one pair of unillustrated right and left output shafts in a way of a spline engagement after the right output shaft is inserted into the tire shaft inserted hole  210 A. 
         [0038]    The intermediate member  31 B consists of a cylindrical member having an inner peripheral surface faced to an outer peripheral surface of the gear member  31 A of the output gear  3 A through a second annular space  30 . The intermediate member  31 B is constructed as a function of a single body with the flange  300 B of the boss member  30 B. In the intermediate member  31 B are formed a plurality of pin through holes  310 B penetrated movably and respectively by plural push pins  35  as an output transmitting member along a direction parallel to the rotating axis O. The plural pin through holes  310 B are formed in a predetermined interval each other in the peripheral direction of the intermediate member  31 B. 
         [0039]    The gear member  32 B consists of an annular internal gear, like a ring gear, positioned at a side of the left tire shaft in the second annular space  30  as shown in  FIG. 2  and  FIG. 4 . The gear member  32 B is slidably mounted on a first supporting member  201  for the right output gear through a washer  24  and engaged in mesh with a gear portion of an internal surface of the intermediate member  31 B in a way of a spline engagement. Therefore, the output gear  3 B is engaged in mesh with the second pinion gear  3 D through the boss member  30 B and the gear member  32 B engaged with the boss member  30 B in the spline engagement. 
         [0040]    The plurality of first pinion gears  3 C are rotatably accommodated in plural first gear accommodating spaces  20 D respectively as shown in  FIG. 3  and  FIG. 5 . Each peripheral surface of the first pinion gears  3 C is slidably mounted on each of a plurality of first torque transmitting surfaces  200 D. Each one side of the first pinion gears  3 C in a side of left tire shaft is slidably supported by each of the first pinion gear supporting surfaces  201 D respectively. 
         [0041]    The plurality of second pinion gears  3 D are rotatably accommodated in plural second gear accommodating spaces  20 E respectively as shown in  FIG. 3  and  FIG. 4 . Each peripheral surface of the first pinion gears  3 C is slidably mounted on each of a plurality of second torque transmitting surfaces  200 E. Each one side of the second pinion gears  3 D in a side of right tire shaft is slidably supported by each of second pinion gear supporting surface  201 E respectively. 
         [0000]    [Construction of the clutch  4 ] 
         [0042]    As shown in  FIG. 2 , the clutch  4  is a friction type main clutch consisting of a plurality of inner clutch plates  4 A as a first clutch plate and a plurality of outer clutch plates  4 B as a second clutch plate. The clutch  4  is installed directly between the output gear  3 A and the output gear  3 B, in detail circumferentially out of the output gear  3 A and circumferentially inside the output gear  3 B in the second annular space  30 . The clutch  4  connect and disconnect directly the output shaft  4 A and the output shaft  4 B in order to construct to restrict a differential movement of the differential mechanism  3 . By the above construction, the differential restricting force is doubled compared to the conventional apparatus. 
         [0043]    Each of the plural inner clutch plates  4 A and each of the outer clutch plate  4 B are disposed alternatively in a potion facing each other along the rotational axis O and consist of an annular frictional plate. The inner clutch plates  4 A are engaged in mesh with an outer peripheral portion of the gear member  31 A of the output gear  3 A in a way of a spline engagement and the outer clutch plates  4 B are engaged in mesh with an inner peripheral portion of the intermediate member  31 B of the output gear  3 B in a way of a spline engagement. One outer clutch plate  4   b  at a far right end of the plural clutch plates  4 B performs function to be an input portion into the clutch  4  so that it is constructed to connect the output gear  3 A and the output gear  3 B in order to transmit a rotational force of the housing  2  by frictionally engaging the outer clutch plates  4 A and the inner clutch plates  4 B by a movement of the one clutch plate  4   b  to a pushing direction when the one clutch plate  4   b  receives a pushing force to a direction of the left tire shaft from a cam member, detailed later, of the output mechanism  5  through the plurality of the pushing pins  35 . The plural pushing pins  35  are urged to original position by a spring etc. 
       [Construction of the Output Mechanism  5 ] 
       [0044]    The output mechanism  5  includes an electro magnetic clutch  5 A, pilot clutch  5 B driven by the electro magnetic clutch  5 A, and the cam mechanism  5 C connectable to the housing  2  by the pilot clutch  5 B. The output mechanism  5  is placed at a right side of the clutch  4 . 
         [0045]    The electro magnetic clutch  5 A has an electromagnet  50 A and an armature  51 A and is disposed at an outer peripheral area of the boss member  30 B of the output gear  4 B. The electromagnet  50 A is disposed in the annular space  25  of the rear housing  21  and supported rotatably by an outer peripheral surface of the first element  21 A through a ball bearing  32 . The armature  51 A is disposed at a side of the left tire shaft of the pilot clutch  5 B and engaged in mesh with an inner surface of the ring spacer  22  in a spline engagement. The armature  51 A is constructed to move to a direction to approach an internal end face of the rear housing  21  by the electromagnetic force of the electromagnet  50 A. 
         [0046]    The pilot clutch  5 B is a frictional sub-clutch having a plurality of inner clutch plates  50 B and a plurality of outer clutch plates  51 B and is disposed between the armature  51 A and the rear housing  21 . The pilot clutch  5 B is constructed such that it connects and disconnects the housing  2  and a cam mechanism  5 C of a cam member  50 C described later in detail and transmits the rotational force of the housing  2  to the cam member  50 C. 
         [0047]    Each of the plural inner clutch plates  50 B and each of the plural outer clutch plates  51 B are alternatively disposed at a position faced each other along the rotational axis O and are made of annular frictional plates. The plural inner clutch plates  50 B are engaged with an outer peripheral surface of the cam  50 C in a way of a spline engagement and the plural outer clutch plates  51 B are engaged with an inner peripheral surface of a ring spacer  22  in a way of a spline engagement. 
         [0048]    The cam mechanism  5 C includes a second cam member  50 C rotated by receiving the rotational force from the housing  2 , a cam follower  51 C creating the pushing force by rotation of the cam member  50 C, a first cam member  52 C outputting by receiving the pushing force of the cam follower  51 C, and the plurality of the pushing pins  35  transmitting the pushing force from the cam member  52 C to the clutch  4 . The cam mechanism  5 C is accommodated between an inner peripheral surface of the ring spacer  22  and an outer peripheral surface of the boss member  30 B of the output gear  3 B. 
         [0049]    The cam member  50 C equips an unillustrated annular cam groove opened to a side of cam follower and is disposed at a peripheral area of the boss member  30 B of the output gear  3 B. The cam member  50 C is rotatably supported by an inner end face of the first element  21 A, that is to say an inner opening peripheral edge of the tire shaft inserted hole  210 A, through a needle bearing  33 . 
         [0050]    The cam follower  51 C is inserted between a groove bottom of the cam groove of the cam member  50 C and a cam side end face of the cam member  52 C and constructed as a spherical ball as a whole. The cam follower  51 C is constructed to transmit the pushing force generated by rotation of the cam member  50 C to the cam member  52 C. 
         [0051]    The cam member  52 C consists of an annular member having a pushing face  520 C faced to pushing force receiving faces  35 A of the plural pushing pins  35  and the one outer clutch plate  4   b . The cam member  52 C is accommodated between a flange  300 B of the output gear  3 B and the armature  51 A of the electro magnet clutch  5 A and is engaged in mesh with an outer peripheral portion of the boss member  30 B of the output gear  3 B in spline engagement. The cam member  52 C is constructed such that it generates the output by receiving the pushing force from the cam follower  51 C to exert it on the pushing force receiving faces  35 A of the plural pushing pins  35  from the pushing surface  520 C. 
         [0052]    The pushing pins  35  are disposed between the outer clutch plate  4   b  of the input portion of the clutch  4  and the output portion of the cam member  52 C and are movably inserted in pin inserted holes  310 B of the flange  300 B of the output gear  3 B along the rotational axis O. The pushing pins  35  are constructed to receive the pushing force from the cam member  52 C to transmit it to the one outer clutch plate  4   b  of the clutch  4 . 
       [Operation of the Differential Limiting Device  1 ] 
       [0053]    When the torque from the engine of the vehicle is input into housing  2  through a driving pinion and a ring gear, the housing  2  is rotated around the rotational axis O. Upon the rotation of the housing  2 , the rotational force is transmitted to the first pinion gears  3 C and the second pinion gears  3 D and further transmitted to the output gear  3 A and the output gear  3 B through the first pinion gears  3 C and the second pinion gears  3 D. Since each of right and left tire shafts is engaged in mesh with each of the output shafts  3 B and  3 A in spline engagement, the torque from the engine is transmitted to each of the right and left tire shafts through the driving pinion, the ring gear, the housing  2 , the first pinion gears  3 C, the second pinion gears  3 D, the output gears  3 A,  3 B. 
         [0054]    Where the vehicle is driven in straight line and there is no slip between the road and each tire on the right and left tire shafts, the first pinion gears  3 C and the second pinion gears  3 D are revolved without self-rotation around the center axis of the output gears  3 A,  3 B upon the transmission of the torque from the engine to the housing. The first and the second pinion gears  3 C,  3 D and the output gears  3 A,  3 B are rotated as a body with the housing  2  so that torque from the engine is transmitted equally to right and left tire shafts to rotate each tire at same rotational speed. 
         [0055]    Where the right wheel drops into a muddy ground to occur a slip, the first pinion gears  3 C and the second pinion gears  3 D are rotated around its own axis as the self-rotation with intermeshing with the output gears  3 A,  3 B so that torque from the engine is distributed differently to the right and left tires. In actual, the left tire is rotated at lower speed than the speed of the housing  2  and the right tire is rotated at higher speed than the speed of the differential case  2 . 
         [0056]    In this one embodiment of the present invention, the differential rotation of the output gears  3 A,  3 B is restricted based on the operation described in next  1  and  2  items at the stage that the torque is input from the engine into the housing  2 . 
         [0000]    1 When the first pinion gears  3 C and the second pinion gears  3 D are rotated, each gear edge surface of the first pinion gears  3 C and the second pinion gears  3 D slides on the first torque transmitting surface  200 D and the second torque transmitting surface  200 E of the internal surface defining the first gear accommodating space  20 D and the second gear accommodating space  20 E so that it generates frictional resistance between them to restrict the differential rotation of the output gears  3 A,  3 B by the frictional resistance. 
         [0057]    On the other hand, upon the rotation of the first pinion gears  3 C and the second pinion gears  3 D, thrust force along the rotational axis is generated to each of the first pinion gears  3 C, the second pinion gears  3 D and the output gears  3 A,  3 B at the intermeshing surface between the pinion gears  3 C,  3 D and the output gears  3 A,  3 B because of a helical intermeshing engagement. The thrust force generated at the output gears  3 A,  3 B tend to separate the gear member  31 A of the output gear  3 A and the gear member  32 B of the output gear  3 B each other to push the output gear  3 A and the output gear  3 B to the washer  27  and the washer  24  so that frictional resistance is occurred between the output gear  3 A and the washer  27  and between the output gear  3 B and the washer  24  to restrict also the differential rotation of the output gears  3 A,  3 B by this frictional resistance. 
         [0058]    Further more, each one side face of the first pinion gears  3 C is pushed on each of the first pinion gear supporting surfaces  201 D and each of the second pinion gears  3 D is pushed on each of the second pinion gear supporting surfaces  201 E based on the thrust force generated on the first pinion gears  3 C and the second pinion gears  3 D so that frictional resistance is created against the each self-rotation of the first pinion gears  3 C and the second pinion gears  3 D. Therefore, the differential rotation of the output gears  3 A,  3 B is also restricted by this frictional resistance. 
         [0000]    2 When the electro magnetic clutch  5 A is excited, a magnetic circuit is constructed through the rear housing  21  and the armature  51 A to move the armature  51 A to a side of the pilot clutch or the rear housing by the magnetic force. The pilot clutch  5 B is pushed to a side of the rear housing by the movement of the armature  51 A so that the inner clutch plates  50 B and the outer clutch plates  51 B of the pilot clutch  5 B approach each other to be contacted in frictional engagement. 
         [0059]    Next, after the inner clutch plates  50 B and the outer clutch plates  51 B are contacted each other in frictional engagement, the housing  2  and the cam member  50 C of the cam mechanism  5 C are connected each other through the pilot clutch  4 . At the stage of the connection between the housing  2  and the cam member  50 C, when the rotational force from the housing  2  is received by the cam member  50 C, the rotational force is transformed to the pushing force by the cam member  50 C and the cam follower  51 C. The pushing force is output from the cam member  52 C to the one outer clutch plate  4   b  of the input portion of the clutch  4  through the pushing pins  35 . 
         [0060]    Then, the one outer clutch plate  4   b  of the clutch  4  is pushed to a side of the bottom of the front housing  20  so that the inner clutch plates  4 A and the outer clutch plates  4 B of the clutch  4  are respectively approached each other to be contacted in frictional engagement, therefore connecting between the gear member  31 A and the intermediate member  31 B, that is to say between the output gear  3 A and the output gear  3 B to be able to transmit the rotational force of the housing  2 . Therefore, the differential rotation of the differential mechanism  3  is restricted. 
         [0061]    The present invention described above by one embodiment can make a result. Namely, the clutch  4  is constructed to connect directly the one pair of output gears  3 A,  3 B to transmit the rotational force of the housing  2  so that it is for the present invention to increase double a differential restricting force of the differential mechanism  3  created by the clutch  4 , compared to the conventional differential limiting apparatus having the clutch installed between the input shaft and one of output gears. That is to say, since the output gear  3 A,  3 B are rotated reversely each other at the generation of the differential movement, the differential rotation of the output gears  3 A,  3 B is restricted double by two ways of restrictions based on next two operations; one is that torque of the output gear  3 B transmitted to the output gear  3 A through the clutch  4  restricts the rotation of the output gear  3 A and the other is that torque of the output gear  3 A transmitted to the output gear  3 B through the clutch  4  restricts a rotation of the output gear  3 B because the clutch is installed directly between the one pair of output gears. Thereby the differential restricting force of the differential mechanism  3  is increased double. 
         [0062]    While the differential limiting apparatus according to the present invention has been described in detail with reference to the preferred embodiment, it will be apparent to those skilled in the art that the invention is not limited to the present embodiment, and that the invention may be realized in various other embodiments within the scope of the claims, for example; 
         [0000]    1 In the one embodiment of the present invention, the gear diameter ratio between the engaging portion of the gear member  31 A of the output gear  3 A with the first pinion gears  3 C and the engaging portion of the gear member  32 B of the output gear  3 B with the second pinion gears  3 D is set to be equal to a gear diameter ratio between the first pinion gears  3 C and the second pinion gears  3 D so that a velocity ratio of the output gears  3 A,  3 B can be set as an equal ratio, that is to say 1 vs. 1, however, the invention is not restricted to the construction but it may be set at other different ratio.
 
2 In one embodiment of the present invention, a number of the pinion gears  3 C and the pinion gears  3 D engaged with the output gears  3 A,  3 B is respectively five in the housing  2 , however, the invention is not restricted to the construction but other number than five of the pinion gears  3 C and the pinion gears  3 D may be set in the housing  2 .