Abstract:
A drive force transmission device includes a clutch operatively interposed between a hub member and a drum member to selectively transmit drive power therebetween. A first rotating shaft member is coupled to the hub member to rotate with the hub member. A second rotating shaft member is coupled to a separating wall part of the drum member to rotate with the drum member. A support member rotatably supports the second rotating shaft member via a bearing. The support member includes a restriction part that restricts axial movement of an outer race of the bearing. A bottom portion of the separating wall part is a radially offset towards the bearing space with respect to a top portion of the separating wall so that the bottom portion radial overlaps with the restriction part as viewed perpendicular to a rotational axis of the drum member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. National stage application of International Application No. PCT/JP2012/078588, filed Nov. 5, 2012, which claims priority to Japanese Patent Application No. 2011-244331 filed in Japan on Nov. 8, 2011, the contents of which are hereby incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a drive force transmission device that is suitable for drive systems in hybrid vehicles. 
         [0004]    2. Background Information 
         [0005]    In the past, hybrid drive force transmission devices have been known in which a dry clutch that transmits drive power and disconnects drive power from the engine is disposed in the drum interior space of a clutch drum. This conventional device has a clutch hub shaft that is linked integrally with a clutch hub, a clutch drum shaft that is linked integrally with the clutch drum, and a unit housing that rotatably supports the clutch drum shaft via a pair of bearings, which are provided around the dry multi-plate clutch (e.g., Japanese Laid-Open Patent Application No. 2010-151313). 
       SUMMARY 
       [0006]    However, this conventional hybrid drive force transmission device has a structure in which the separating wall part of the clutch drum is disposed offset towards the clutch space so as to circumvent a restriction part that restricts axial movement of the bearing outer race. For this reason, when the constituent elements at the periphery of the clutch are laid out in a predetermined space in the axial direction, there has been the problem that the clutch space is decreased due to the separating wall part that is disposed offset towards the clutch space relative to the restriction part. 
         [0007]    The present invention focuses on the above problem, it being an object of the invention to provide a drive force transmission device whereby it is possible to increase the size of the clutch space in which the first rotating shaft member and hub member that are coupled together are disposed when laying out the constituent elements at the periphery of the clutch within a predetermined space in the axial direction. 
         [0008]    In order to achieve the above objective, a drive force transmission device is provide that basically comprises a hub member, a drum member, a clutch, a first rotating shaft member, a second rotating shaft member and a support member. The drum member has a cylindrical part and a separating wall part extending radially inward from the cylindrical part to partition a drum interior space into a bearing space and a clutch space. The clutch is operatively interposed between the hub member and the drum member to transmit drive power upon engagement and cease to transmit drive power upon disengagement. The clutch has a plate member supported by the cylindrical part of the drum. The first rotating shaft member is coupled to the hub member to rotate integrally with the hub member. The second rotating shaft member is coupled to the separating wall part of the drum member to rotate integrally with the drum member. The support member is disposed at an outer circumferential position on the second rotating shaft member and rotatably supports the second rotating shaft member via a bearing. The support member includes a restriction part that restricts axial movement of an outer race of the bearing. The restriction part is provided at an end position of the support member towards the separating wall part. The separating wall part has a bottom portion being partially disposed at an inner circumferential position with respect to the restriction part. The bottom portion of the separating wall part has a radially extending centerline that is offset by a bearing-side offset amount towards the bearing space with respect to a radially extending centerline of a top portion of the separating wall part so that the separating wall part radial overlaps with the restriction part as viewed perpendicular to a rotational axis of the drum member. 
         [0009]    Thus, the separating wall part of the drum member is disposed at a position towards the inner circumference of the restriction part for restricting axial movement of the bearing outer race, offset towards the bearing space so as to overlap with the restriction part in the radial direction. Specifically, the separating wall part that partitions the drum interior space of the drum member is disposed so as to have been moved in the axial direction towards the first bearing from an offset position that lies towards the clutch space to an offset position that lies towards the bearing space. For this reason, when the drum interior space is a space having the same predetermined volume, disposing the separating wall part offset towards the bearing space will increase the clutch space correspondingly in accordance with the reduction in the bearing space. As a result, when the constituent elements of the clutch periphery are laid out in the predetermined space in the axial direction, it is possible to increase the size of the clutch space in which the first rotating shaft member and hub member that are coupled together are disposed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Referring now to the attached drawings which form a part of this original disclosure. 
           [0011]      FIG. 1  is a schematic overview of the hybrid drive force transmission device of Embodiment 1 (example of a drive force transmission device). 
           [0012]      FIG. 2  is a sectional view showing the peripheral configuration of the dry multi-plate clutch in the hybrid drive force transmission device of Embodiment 1. 
           [0013]      FIG. 3  is a perspective view showing the piston arm of the dry multi-plate clutch of Embodiment 1. 
           [0014]      FIG. 4  is a sectional view across line  4 - 4  in  FIG. 3  showing the piston arm of the dry multi-plate clutch of Embodiment 1. 
           [0015]      FIG. 5  is an enlarged sectional view showing the layout configuration of the constituent elements of the clutch periphery in the hybrid drive force transmission device of Embodiment 1. 
           [0016]      FIG. 6  is an enlarged view showing the layout configuration of the constituent elements of the clutch periphery in the hybrid drive force transmission device of a comparative example. 
           [0017]      FIG. 7  is an enlarged sectional view showing the layout configuration of the constituent elements of the clutch periphery in the hybrid drive force transmission device of Embodiment 2. 
           [0018]      FIG. 8  is an enlarged sectional view showing the locations requiring special processing in the layout configuration of the constituent elements of the clutch periphery in the hybrid drive force transmission device of Embodiment 1. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0019]    A preferred embodiment of the drive force transmission device of the present invention is described below based on Embodiment 1 and Embodiment 2 shown in the drawings. 
       Embodiment 1 
       [0020]    First, the configuration will be described. The configuration of the hybrid drive force transmission device of Embodiment 1 (an example of a drive force transmission device) is described below under the headings: General system configuration, Dry multi-plate clutch peripheral configuration, and Clutch periphery constituent element layout configuration. 
         [0021]    General System Configuration 
         [0022]      FIG. 1  is a general schematic diagram showing the hybrid drive force transmission device of Embodiment 1. The general system configuration of the device is described below with reference to  FIG. 1 . 
         [0023]    The hybrid drive force transmission device of Embodiment 1, as shown in  FIG. 1 , comprises an engine Eng, a motor and clutch unit M/C, and a transmission unit T/M. The motor and clutch unit M/C that is coupled to the engine output shaft  1  of the engine Eng has a clutch hub shaft  2 , a clutch hub  3 , a clutch drum shaft  4 , a transmission input shaft  5 , a clutch drum  6 , a dry multi-plate clutch  7 , and a slave cylinder  8 . 
         [0024]    With the hybrid drive force transmission device of Embodiment 1, when the dry multi-plate clutch  7  that is normally open has disengaged, the motor/generator  9  and the transmission input shaft  5  are linked via the clutch drum  6  and the clutch drum shaft  4 , producing an electric drive mode. When the dry multi-plate clutch  7  is made to engage under hydraulic pressure by the slave cylinder  8 , the engine Eng and the motor/generator  9  are linked via the engaged dry multi-plate clutch  7 , producing a hybrid drive mode. The engine output shaft  1  and the clutch hub shaft  2  are linked via a damper  21 . 
         [0025]    The motor and clutch unit M/C (shaded cross-sectional region in  FIG. 1 ) has the dry multi-plate clutch  7 , the slave cylinder  8 , and the motor/generator  9 . The dry multi-plate clutch  7  is engaged by linkage with the engine Eng and interrupts transmission of drive power from the engine Eng. The slave cylinder  8  carries out hydraulic control of engagement and disengagement of the dry multi-plate clutch  7 . The motor/generator  9  is disposed at an outer circumferential position on the clutch drum  6  of the dry multi-plate clutch  7  and transmits power to the transmission input shaft  5 . In this motor and clutch unit M/C, a unit housing  81  having a first clutch hydraulic path  85  to the slave cylinder  8  is provided while preserving sealing with an O-ring  10 . 
         [0026]    The motor/generator  9  is a synchronous alternating current motor having a rotor support frame  91  that is integrally formed with the clutch drum  6  and a motor rotor  92  that is supported by and fixed on the rotor support frame  91  and that contains an embedded a permanent magnet. There also is a motor stator  94  that is fixed on the unit housing  81  and is disposed at the motor rotor  92  with an air gap  93  interposed, and a stator coil  95  that is wound onto the motor stator  94 . A water jacket  96  that allows flow of cooling water is formed in the unit housing  81 . 
         [0027]    The transmission unit TIM is linked and connected to the motor and clutch unit M/C and has a transmission housing  41 , a V-belt stepless transmission mechanism  42 , and an oil pump O/P. The V-belt stepless transmission mechanism  42  is housed in the transmission housing  41 , with the V-belt suspended between two pulleys, providing a stepless variable gear ratio by varying the belt contact diameter. The oil pump O/P is a hydraulic oil source that provides hydraulic pressure to the required components. With the oil pump pressure as the source pressure, hydraulic pressure is conducted to the required components from a control valve (not shown) that modulates the pressure, e.g., the transmission hydraulic pressure, that is provided to the pulley chamber or the clutch/brake hydraulic pressure. This transmission unit T/M also has a forward/reverse switching mechanism  43 , an oil tank  44 , an end plate  45 , and a clutch unit case  46 . The clutch unit case  46  is fixed integrally on the transmission housing  41 . The end plate  45  has a second clutch hydraulic path  47 . 
         [0028]    The oil pump O/P is driven as a result of transfer of rotational drive torque from the transmission input shaft  5  via a chain drive mechanism. The chain drive mechanism has a drive-side sprocket  51  that rotates along with rotational drive of the transmission input shaft  5 , a driven-side sprocket  52  that rotationally drives a pump shaft  57 , and a chain  53  that is suspended on both sprockets  51 ,  52 . The drive-side sprocket  51  is mounted between the transmission input shaft  5  and an end plate  45  and is rotatably supported via a brush  55  on a stator shaft  54  that is fixed to the transmission housing  41 . Thus, splined joining occurs with the transmission input shaft  5 , and rotational drive torque from the transmission input shaft  5  is transmitted via a first adaptor  56  that fits via teeth on the drive-side sprocket  51 . 
         [0029]    Dry Multi-Plate Clutch Periphery Configuration 
         [0030]      FIG. 2  is a sectional view showing the configuration of the periphery of the dry multi-plate clutch in the hybrid drive force transmission device of Embodiment 1.  FIG. 3  is an oblique view showing the piston arm of the dry multi-plate clutch.  FIG. 4  is a sectional view across line A-A in  FIG. 3  showing the piston arm. The configuration of the periphery of the dry multi-plate clutch  7  is descried below based on  FIGS. 2 to 4 . 
         [0031]    The clutch hub  3  is integrally coupled to the clutch hub shaft  2  that is fixed on the engine output shaft  1  of the engine Eng. As shown in  FIG. 2 , drive plates  71  of the dry multi-plate clutch  7  are held on the clutch hub  3  by splined joining. 
         [0032]    The clutch drum  6  is integrally coupled to the transmission input shaft  5  of the /transmission unit T/M. As shown in  FIG. 2 , driven plates  72  (plate members) of the dry multi-plate clutch  7  are held on this clutch drum  6  by splined joining. 
         [0033]    With the dry multi-plate clutch  7 , the drive plates  71  and the driven plates  72  are interposed alternately between the clutch hub  3  and the clutch drum  6  so that they are aligned in multiple plates. In other words, by engagement of the dry multi-plate clutch  7 , torque transfer between the clutch hub  3  and the clutch drum  6  is enabled, and by disengagement of the dry multi-plate clutch  7 , torque transfer between the clutch hub  3  and the clutch drum  6  is disconnected. 
         [0034]    The slave cylinder  8  is a hydraulic pressure actuator that controls engagement and disengagement of the dry multi-plate clutch  7  and is disposed at a location that is between the transmission unit TIM and the clutch drum  6 . As shown in  FIG. 2 , the slave cylinder  8  has a piston  82  that is slidably provided in a cylinder hole  80  of the unit housing  81 , a first clutch hydraulic path  85  that is formed in the cylinder housing  81  and conducts clutch pressure output by the transmission unit T/M, and a cylinder oil housing  86  that communicates with the first clutch hydraulic path  85 . In addition to a piston arm  83 , as shown in  FIG. 2 , a needle bearing  87 , a return spring  84 , and a hydraulic plate  88  are interposed between the piston  82  and the dry multi-plate clutch  7 . 
         [0035]    The piston arm  83  generates press force for the dry multi-plate clutch  7  as a result of the press force from the slave cylinder  8 , and the piston arm is slidably provided in a through-hole  61  formed in the clutch drum  6 . The return spring  84  is interposed between the piston arm  83  and the clutch drum  6  and is constituted by an assembly of a plurality of disc springs. The needle bearing  87  is interposed between the piston  82  and the piston arm  83 , and the piston  82  inhibits induction of rotation that occurs along with rotation of the piston arm  83 . The press plate  88  is provided integrally with an elastic support plate  89  and is elastically supported on the clutch drum  6 . This press plate  88  and elastic support plate  89  constitute a partitioning elastic member that blocks leak oil from the sliding part of the piston arm  83  from flowing into the dry multi-plate clutch  7 . In other words, the elastic support plate  89  and the press plate  88  that are sealed and fixed at the piston arm attachment location of the clutch drum  6  have a partitioning function that produces a wet space in which the slave cylinder  8  is disposed and a dry space in which the dry multi-plate clutch  7  is disposed. 
         [0036]    The piston arm  83 , as shown in  FIGS. 3 and 4 , is constituted by an arm body  83   a  that is formed in the shape of a ring, arm pins  83   b  that multiply protrude into the arm body  83   a , and a snap ring  83   c  that fixes the arm pins  83   b  to the arm body  83   a . When assembling the piston arm  83 , the pin shoulders  83   e  of the arm pins  83   b  are inserted into the multiple pin holes  83   d  that are formed in the arm body  83   a , producing a state in which the ring fitting grooves  83   f  that are formed on the pin shoulders  83   e  are directed into central locations in the arm body  83   a . Next, force is applied to the snap ring  83   c  to carry out insertion from the inner surface side in a compressed state, whereupon the force applied to the snap ring  83   c  is released, allowing diameter expansion to occur as a result of the elastic restitution force. As a result, the snap ring  83   c  is fitted into the ring fitting groove  83   f , and all of the arm pins  83   b  are simultaneously fixed in the arm body  83   a.    
         [0037]    The leak oil recovery path in Embodiment 1, as shown in  FIG. 2 , comprises a first bearing  12 , a first oil seal  31 , a leak oil path  32 , a first recovery oil path  33 , and a second recovery oil path  34 . Specifically, the path is a circuit whereby leak oil from the sliding part of the piston  82  passes through the first recovery oil path  33  and the second recovery oil path  34  that are sealed by the first oil seal  31  and then returns to the transmission unit T/M. In addition, the path is a circuit whereby leak oil from the sliding part of the piston arm  83  passes through the leak oil path  32  that is sealed by the partitioning elastic members (press plate  88 , elastic support plate  89 ) and the first recovery oil path  33  and second recovery oil path  34  that are sealed by the first oil seal  31  and then returns to the transmission unit TIM. 
         [0038]    The first bearing  12  rotatably supports the clutch drum shaft  4  on the unit housing  81 . In order to prevent shaft displacement of the clutch drum  6  with respect to the unit housing  81 , no interposing elements other than the first bearing  12  are provided between the unit housing  81  and the clutch drum  6 . 
         [0039]    The first oil seal  31 , as shown in  FIG. 2 , is disposed at a location that is downstream in the leak oil flow direction from the partitioning elastic members (press plate  88 , elastic support plate  89 ), providing a seal between the opposing surfaces of the unit housing  81  and the clutch drum  6 . This first oil seal  31  has a lip-seal structure in which a seal is formed as a result of the seal elastic force, and reliable sealing performance is ensured as a result of restriction of shaft core displacement of the clutch drum  6  by the first bearings  12 ,  12 . 
         [0040]    The leak oil path  32 , as shown in  FIG. 2 , passes through the clutch drum  6  and is formed as a result of communication of the first recovery oil path  33  and the sealing blocking space produced by the partitioning elastic members (press plate  88 , elastic support plate  89 ). 
         [0041]    The first recovery oil path  33 , as shown in  FIG. 2 , is formed by a gap resulting from opposition of the unit housing  81  and the clutch drum  6 . The first oil seal  31  and the second recovery oil path  34  are disposed at a position that is radially outward from the sliding part of the piston arm  83  and the piston  82 . As a result, the second recovery oil path  34  serves as an oil path that extends from the sliding part of the piston arm  83  and the piston  82  in a radially outward direction. 
         [0042]    The second recovery oil path  34 , as shown in  FIG. 2 , is formed as a short oil path that is downstream from the first oil seal  31  of the unit housing  81 . A long oil path upstream from the first oil seal  31  serves as the first recovery oil path  33  due to the gap resulting from opposition of the unit housing  81  and the clutch drum  6 . 
         [0043]    The bearing lubricating oil path of Embodiment 1, as shown in  FIG. 2 , comprises a needle bearing  20 , a second oil seal  14 , a first shaft core oil path  19 , a second shaft core oil path  18 , and a lubricating oil path  16 . This bearing lubricating oil path effects bearing lubrication through a route whereby the bearing lubricating oil from the transmission unit T/M passes through the needle bearing  20 , the first bearings  12 ,  12  that rotatably support the clutch drum  6  on the unit housing  81 , and the needle bearing  87  that is interposed between the piston  82  and the piston arm  83 , before returning to the transmission unit T/M. 
         [0044]    The needle bearing  20 , as shown in  FIG. 2 , is set between the opposing surfaces of the clutch hub  3  and the clutch drum  6  that are opposite each other in the axial direction. As a result of this needle bearing  20 , recursive movement of the clutch hub  3  and the clutch drum  6  in the axial direction is restricted, ensuring relative rotation between the clutch hub  3  and the clutch drum  6 . 
         [0045]    The second oil seal  14 , as shown in  FIG. 2 , is interposed between the clutch hub shaft  2  and the clutch drum  6 . This second sealing member  14  seals inflow of bearing lubrication oil from the wet space in which the slave cylinder  8  is disposed to the dry space in which the dry multi-plate clutch  7  is disposed. 
         [0046]    The first shaft core oil path  19  is formed in the shaft core position of the transmission input shaft  5 . The second shaft core oil path  18  is formed on the clutch drum  6  and communicates with the first shaft core oil path  19 . The lubricating oil path  16  is formed in the clutch drum  6  and communicates with the second shaft core oil path  18  via the needle bearing  20  and a gap  17  with the clutch hub shaft  2 . 
         [0047]    Clutch Periphery Constituent Element Layout Configuration 
         [0048]      FIG. 5  is an enlarged sectional view showing the layout configuration of the clutch periphery constituent elements in the hybrid drive force transmission device of Embodiment 1. The layout configuration of the constituent elements at the clutch periphery is described below with reference to  FIGS. 2 and 5 . 
         [0049]    As shown in  FIG. 5 , constituent elements at the clutch periphery of the dry multi-plate clutch  7  (clutch) are the clutch hub shaft  2  (first rotating shaft member), the clutch hub  3  (hub member), the clutch drum shaft  4  (second rotating shaft member), the clutch drum  6  (drum member), the unit housing  81  (support member), the second oil seal  14  (oil seal), and the needle bearing  20  (thrust bearing). 
         [0050]    The clutch hub shaft  2 , as shown in  FIG. 5 , is coupled to the clutch hub  3  by serrated joining and rotates integrally with the clutch hub  3 . In the serrated joining part  21 , in which the clutch hub shaft  2  and the clutch hub  3  fit together via grooves, the clutch hub shaft  2  is inserted while cuttings are produced, and the accumulation thereof is used to prevent axial movement. 
         [0051]    The clutch drum shaft  4 , as shown in  FIG. 5 , is coupled to the clutch drum  6  by welded joining and rotates integrally with the clutch drum  6 . The welded joining part  22  between the clutch drum shaft  4  and the clutch drum  6  forms a step where abutment occurs between the two in the axial direction. Of the surfaces that abut in the circumferential direction formed on both sides with the step surface interposed, the surface abutting on the bearing side is used for serrated joining, whereas the surface abutting on the clutch side is joined by welding. 
         [0052]    The unit housing  81 , as shown in  FIG. 5 , is provided at a location on the outer circumference of the clutch drum shaft  4  and is a static member whereby the clutch drum shaft  4  is rotatably supported via a first bearing  12  (bearing). The first bearing  12  serves as an integrated bearing in which two sets of balls  12   c ,  12   d  (rolling bodies) are interposed between an inner race  12   a  and an outer race  12   b . Movement in the axial direction of the inner race  12   a  of the first bearing  12  is restricted by a snap ring  15  that is provided on a ring groove  4   a  of the clutch drum shaft  4 . 
         [0053]    The clutch drum  6 , as shown in  FIGS. 2 and 5 , has a cylindrical part  6   a  on which the driven plates  72  (plate member) of the dry multi-plate clutch  7  are provided, and a separating wall part  6   b  that extends in a radially inward direction from the cylindrical part  6   a  and links with the clutch drum shaft  4 , partitioning the drum inner space onto a bearing space Sb and clutch space Sc. 
         [0054]    As shown in  FIG. 5 , a restriction part  81   a  that restricts motion of the outer race  12   b  of the first bearing  12  in the axial direction is provided at an end position of the unit housing  81  towards the separating wall part  6   b . The separating wall part  6   b  is disposed at a position towards the inner circumference of the restriction part  81   a , offset towards the bearing space Sb so as to overlap with the restriction part  81   a  in the radial direction. When the separating wall part  6   b  is disposed offset at a location towards the inner circumference of the restriction part  81   a , the bearing outer diameter R of the integrated first bearing  12  is made larger than the bearing outer diameter R′ when a pair of bearings is provided, each with one set of rolling bodies interposed between an inner race and outer race (refer to  FIG. 6 ). As a result, a wider space is ensured in the radial direction towards the inner circumference of the restriction part  81   a , and the separating wall part  6   b  is disposed offset in this space. Specifically, the gap in the axial direction between a centerline CL′ in an axial direction towards the bottom of the separating wall part  6   b  and the centerline CL in the axial direction towards the top of the separating wall part  6   b  is taken as the bearing-side offset amount EOFF. 
         [0055]    The second oil seal  14  is interposed between the two opposing surfaces in the radial direction of the outer circumferential surface  2   a  of the clutch hub shaft  2  and the inner circumferential surface  62   a  of the ring-shaped protrusion  62  formed on the separating wall part  6   b , thereby inhibiting ingress of oil from the bearing space Sb to the clutch space Sc in which the dry multi-plate clutch  7  is disposed. In this second oil seal  14 , the outer circumferential surface  2   a  of the clutch hub shaft  2  is the pressed-upon surface, and the inner circumferential surface  62   a  of the ring-shaped protrusion  62  formed on the separating wall part  6   b  is the seal surface. 
         [0056]    The needle bearing  20  is interposed between opposing surfaces in the radial direction of the step surface  4   b  of the clutch drum shaft  4  and the end surface  2   b  of the clutch hub shaft  2 . With this needle bearing  20 , the step surface  4   b  of the clutch drum shaft  4  is the setting surface for the ring-shaped bearing member, and the end surface  2   b  of the clutch hub shaft  2  serves as the needle rolling surface. In other words, with the needle bearing  20 , because the ring-shaped bearing member has an integrated structure, positioning (centering) can be carried out using one surface as a reference, and the only location that requires special processing such as carburizing to increase material hardness is thus the end surface  2   b  of the clutch hub shaft  2 . In  FIG. 5 , a second bearing  13  that is rotatably supported on the unit housing  81  is interposed in the clutch hub shaft  2 . 
         [0057]    The operation of the device is described below. A comparative example will first be described under the heading Comparative example, and the operation of the hybrid drive force transmission device of Embodiment 1 will then be discussed under the heading Clutch periphery constituent element layout operation. 
       COMPARATIVE EXAMPLE 
       [0058]      FIG. 6  is an enlarged sectional view showing the layout configuration of the clutch periphery constituent components in the hybrid drive force transmission device of a comparative example. The layout configuration of the constituent elements at the clutch periphery in the comparative example will be described below with reference to  FIG. 6 . 
         [0059]    The comparative example is a hybrid drive force transmission device wherein the rotor of a motor/generator is supported on a clutch drum, and a dry multi-plate clutch that transmits drive and disconnects drive from an engine is disposed in a drum interior space of the clutch drum. This device has, disposed around the dry multi-plate clutch, a clutch hub shaft that is integrally linked with a clutch hub, a clutch drum shaft that is integrally linked with the clutch drum, and a unit housing that rotatably supports the clutch drum shaft via a pair of ball bearings. The clutch drum is coupled to the clutch drum shaft by a separating wall part that partitions the drum interior space into a bearing space Sb′ and a clutch space Sc′. A restriction part that restricts motion of the outer race of the bearing in the axial direction is provided at an end location of the unit housing towards the separating wall part, and the separating wall part is disposed at an outer location of the restriction part offset towards the clutch space so that the restriction part is circumvented. Specifically, the comparative example is one in which the gap in the axial direction between the centerline CL′ in the axial direction towards the bottom of the separating wall part and the centerline CL in the axial direction towards the top of the separating wall part is taken as the clutch-side offset amount ΔOFF′. 
         [0060]    In the comparative example, the dividing wall part of the clutch drum has a structure in which the separating wall part of the clutch drum is offset towards the clutch space Sc′ so that the restriction part that restricts movement of the outer race of the bearing in the axial direction is circumvented. For this reason, when the constituent elements at the clutch periphery are laid out in the predetermined space S in the axial direction, the clutch space Sc′ is narrowed by the separating wall part that has been offset towards the clutch space relative to the restriction part. 
         [0061]    As a result of narrowing of the clutch space Sc′, it is impossible to avoid narrowing of the linkage width wh in the axial direction between the clutch hub shaft and the clutch hub. Consequently, linkage of the clutch hub shaft and the clutch hub, as shown in  FIG. 6 , is achieved by a weld connection that can ensure the desired linage strength while providing a narrow linkage width wh in the axial direction. With this welding connection, it is necessary to carry out a finishing process whereby the welded portion is finished by grinding after carrying out the welding operation. For this reason, productivity decreases and costs increase. 
         [0062]    Clutch Periphery Constituent Element Layout Operation 
         [0063]    In solving the problems with the comparative example, it is necessary to focus not only on the clutch hub and the clutch hub shaft on the upstream side of the clutch, but also on resolving problems with layout of the constituent elements on the downstream side of the clutch. The layout operation of the clutch periphery constituent elements reflecting this issue is described below. 
         [0064]    First, the bearing is changed to an integrated first bearing  12  in which the ball diameter in the two ball bearings of the comparative example is increased, thereby increasing the transmission capacity and the size in the radial direction. As a result, the bearing outer diameter R of the first bearing  12  is larger than the bearing outer diameter R′ of the two ball bearings of the comparative example, and a large space is ensured in the radial direction. At this time, the dimensions of the bearing outer diameter R of the first bearing  12  are set in consideration of both maintaining the oil chamber volume of the cylinder oil chamber  86  and providing piston control. 
         [0065]    The separating wall part  6   b  of the clutch drum  6  is disposed offset towards the inner circumference of the restriction part  81   a  in the space that has been ensured by using the integrated first bearing  12  in which the size has been increased in the radial direction. This offsetting, as shown in  FIG. 5 , involves offsetting towards the bearing space Sb (bearing-side offset amount DOFF) at a position that is towards the inner circumference of the restriction part  81   a , so that the restriction part  81   a  and the separating wall part  6   b  overlap in the radial direction. 
         [0066]    Specifically, the separating wall part  6   b  that partitions the drum interior space of the clutch drum  6  is disposed so as to have been moved in the axial direction towards the first bearing  12  from an offset position that lies towards the clutch space Sc′ ( FIG. 6 ) to an offset position that lies towards the bearing space Sb ( FIG. 5 ). For this reason, as shown in  FIG. 5 , assuming the drum interior space is a space S having the same predetermined volume, by disposing the separating wall part  6   b  offset towards the bearing space Sb, the clutch space Sc can be correspondingly increased in accordance with the reduction in the bearing space Sb. 
         [0067]    Consequently when laying out the constituent elements at the clutch periphery in the predetermined space in the axial direction, it is possible to increase the clutch space Sc in which the clutch hub  3  and the clutch hub shaft  2  that are coupled together are disposed. As a result, the linkage width Wh (&gt;wh) in the axial direction of the clutch hub  3  and the clutch hub shaft  2  can be ensured to be larger than in the comparative example, and serration joining is suitable for use as the linkage configuration for the clutch hub shaft  2  and the clutch hub  3 . This serrated joining is carried out only by a step in which the clutch hub shaft  2  is inserted while cuttings are produced, and the accumulation thereof is used to prevent axial movement. For this reason, finish processing is not required as with the comparative example, and a reduction in cost as well as an increase in productivity can be achieved. 
         [0068]    In addition, by increasing the size of the clutch space Sc to provide additional space allowance, the linking width Wd (&gt;wd) in the axial direction between the clutch drum shaft  4  and the separating wall part  6   b  of the clutch drum  6  can be ensured to be longer than in the comparative example. As a result, an improvement in linkage strength between the separating wall part  6   b  and the clutch drum shaft  4  is achieved. 
         [0069]    Next, the reason for switching to the integrated first bearing  12  in Embodiment 1 rather than using the two ball bearings of the comparative example is described below. When the two ball bearings are switched to an integrated first bearing  12 , the number of parts can be decreased, but there is an attendant decrease in the bearing yield strength. However, by increasing the ball diameter of the integrated first bearing  12  the transmission capacity is increased, and the size in the radial direction is increased, preventing a decrease in the bearing yield strength. In addition, sufficient space in which the separating wall part  6   b  of the clutch drum  6  can be offset can be ensured in accordance with the increase in the bearing outer diameter R. In other words, a decrease in the number of parts can be achieved without needlessly increasing the bearing outer diameter. 
         [0070]    The effects are described below. With the hybrid drive force transmission device of Embodiment 1, the listed below can be obtained. 
         [0071]    (1) The drive force transmission device has a clutch (dry multi-plate clutch  7 ) that is interposed between a hub member (clutch hub  3 ) and a drum member (clutch drum  6 ), the clutch transmitting drive power by engaging and ceasing transmitting of drive power by disengaging, a first rotating shaft member (clutch hub shaft  2 ) that links to the hub member (clutch hub  3 ) and rotates integrally with the hub member (clutch hub  3 ), a second rotating shaft member (clutch drum shaft  4 ) that is coupled to the drum member (clutch drum  6 ) and rotates integrally with the drum member (clutch drum  6 ), and a support member (unit housing  81 ) that is provided at an outer circumferential position on the second rotating shaft member (clutch drum shaft  4 ) and rotatably supports the second rotating shaft member (clutch drum shaft  4 ) via a bearing (first bearing  12 ); the drum member (clutch drum  6 ) having a cylindrical part  6   a  on which a plate member (driven plate  72 ) of the clutch (dry multi-plate clutch  7 ) is provided, and a separating wall part  6   b  that extends from the cylindrical part  6   a  radially inward and links with the second rotating shaft member (clutch drum shaft  4 ), partitioning the drum interior space into a bearing space Sb and a clutch space Sc, and a restriction part  81   a  that restricts movement of the outer race  12   b  of the bearing (first bearing  12 ) in the axial direction being provided at an end position of the support member (unit housing  81 ) towards the separating wall part  6   b , the separating wall part  6   b  being disposed at an inner circumferential position on the restriction part  81   a , offset towards the bearing space Sb so that there is overlap in the radial direction with the restriction part  81   a . For this reason, the size of the clutch space Sc in which the first rotating shaft member (clutch hub shaft  2 ) and the hub member (clutch hub  3 ) that are coupled together are disposed can be increased when the constituent elements at the clutch periphery are laid out in the predetermined space in the axial direction. 
         [0072]    (2) The bearing referred to above is an integrated bearing (first bearing  12 ) in which two sets of rolling bodies (balls  12   c ) are interposed between an inner race  12   a  and outer race  12   b , and the outer diameter (bearing outer diameter R) of the integrated bearing (first bearing  12 ) is set larger than the outer diameter R′ when a pair of bearings is used, each with one set of rolling bodies interposed between an inner race and an outer race. For this reason, in addition to the effect of (1), the number of parts is decreased, and a decrease in the bearing yield strength is prevented, while ensuring that there is sufficient space for offsetting the separating wall part  6   b  of the drum member (clutch drum  6 ). 
       Embodiment 2 
       [0073]    Embodiment 2 is an example in which the seal surface and pressed-upon surface of the second oil seal  14  are different from in Embodiment 1. 
         [0074]    The configuration will be described first.  FIG. 7  is an enlarged sectional view showing the layout configuration of the constituent elements at the clutch periphery in the hybrid drive force transmission device of Embodiment 2. The layout configuration of the constituent elements at the clutch periphery will be described below with reference to  FIG. 7 . 
         [0075]    The constituent elements at the clutch periphery in the dry multi-plate clutch  7  (clutch), as shown in  FIG. 7 , are a clutch hub shaft  2  (first rotating shaft member), a clutch hub  3  (hub member), a clutch drum shaft  4  (second rotating shaft member), a clutch drum  6  (drum member), a unit housing  81  (support member), a second oil seal  14  (oil seal), and a needle bearing  20  (thrust bearing). 
         [0076]    A second oil seal  14  is interposed between opposing surfaces in the radial direction of an outer circumferential surface  2   a  of the clutch hub shaft  2  and an inner circumferential surface  62   a  of the ring-shaped protrusion  62  formed in the separating wall part  6   b , suppressing ingress of oil from the bearing space Sb to the clutch space Sc in which the dry multi-plate clutch  7  is disposed. With the second oil seal  14 , the inner circumferential surface  62   a  of the ring-shaped protrusion  62  formed on the separating wall part  6   b  is the pressed-upon surface, and the outer circumferential surface  2   a  of the clutch hub shaft  2  is the seal surface. The remainder of the configuration is similar to Embodiment 1. The same designations are provided for corresponding configuration elements, and descriptions of them are omitted. 
         [0077]    The operation of the invention is described below. In order to additionally reduce the cost of the clutch periphery configuration, it is necessary to reduce the number of rotational members that are to be subjected to thermal treatment (e.g., carburization) in order to increase material hardness. 
         [0078]    Specifically, with the clutch peripheral configuration of Embodiment 1, as shown in  FIG. 8 , because the needle bearing  20  is made to have an integrated structure with the ring-shaped bearing member, the only location B requiring special processing such as carburizing in order to increase material hardness is the end surface  2   b  of the clutch hub shaft  2 . However, with the second oil seal  14 , the outer circumferential surface  2   a  of the clutch hub shaft  2  is used as the pressed-upon surface, and the inner circumferential surface  62   a  of the ring-shaped protrusion  62  formed in the separating wall part  6   b  is used as the seal surface. For this reason, the inner circumferential surface  62   a  of the ring-shaped protrusion  62  formed in the separating wall part  6   b  is a location C requiring special processing such as carburizing in order to increase material hardness. Consequently, locations B, C requiring special processing span two members, the clutch hub shaft  2 , and the clutch drum  6 . 
         [0079]    In contrast, with the clutch periphery configuration in Embodiment 2, as shown in  FIG. 7 , because the needle bearing  20  is made to have an integrated structure together with the ring-shaped bearing member, locations requiring special processing such as carburizing to increase material hardness is limited only to the end surface  2   b  of the clutch hub shaft  2 . Thus, with the second oil seal  14 , the inner circumferential surface  62   a  of the ring-shaped protrusion  62  formed in the separating wall part  6   b  is the pressed-upon surface, and the outer circumferential surface  2   a  of the clutch hub shaft  2  is the seal surface. For this reason, the outer circumferential surface  2   a  of the clutch hub shaft  2  is a location requiring special processing such as carburizing in order to increase material hardness, and thus the location D requiring special processing is limited only to the clutch hub shaft  2 . 
         [0080]    Consequently, it is necessary only to subject the clutch hub shaft  2  to thermal treatment such as carburizing in order to increase material hardness, which additionally decreases the cost of the clutch periphery configuration. Otherwise, operation is similar to that of Embodiment 1, and descriptions are omitted. 
         [0081]    The effects are described below. With the hybrid drive force transmission device of Embodiment 2, the following effects can be obtained. 
         [0082]    (3) The aforementioned clutch is a dry multi-plate clutch  7 , where an oil seal (second oil seal  14 ) that suppresses ingress of oil from the bearing space Sb to the clutch space Sc in which the dry multi-plate clutch  7  is disposed between opposing surfaces in the radial direction of the outer circumferential surface  2   a  of the first rotating shaft member (clutch hub shaft  2 ) and the inner circumferential surface  62   a  of the ring-shaped protrusion  62  formed in the separating wall part  6   b , a thrust bearing (needle bearing  20 ) is disposed between axially opposing surfaces of a step surface  4   b  of the second rotating shaft member (clutch drum shaft  4 ) and an end surface  2   b  of the first rotating shaft member (clutch hub shaft  2 ), the step surface  4   b  being a setting surface on which a ring-shaped bearing member having an integrated structure is set, the oil seal (second oil seal  14 ) contacts a seal surface at the first rotating shaft member (clutch hub shaft  2 ) and a pressed-upon surface at the separating wall part  6   b . For this reason, in addition to the effects of (1) and (2) in Embodiment 1, by simply subjecting the first rotating shaft member (clutch hub shaft  2 ) to thermal treatment such as carburizing to improve material hardness, the cost of the clutch peripheral configuration can be additionally decreased. 
         [0083]    Although the drive force transmission device of the present invention was described above with reference to Embodiment 1 and Embodiment 2, the specific configuration is not restricted to these embodiments, and various design modifications and additions are permissible while remaining within the spirit of the invention as described in the claims. 
         [0084]    In Embodiments 1 and 2, a normal-open multi-plate dry clutch was presented as an example. However, in another example, the clutch may be a single-plate wet clutch, a multi-plate wet clutch, a single-plate dry clutch or some other type of hydraulically actuated clutch. Moreover, another example of the clutch is a normal-closed clutch that employs a diaphragm spring or the like. 
         [0085]    In Embodiments 1 and 2, a preferred example of a hybrid drive force transmission device for a hybrid vehicle was presented in which the engine and motor/generator were mounted, and the clutch was a drive-mode transition clutch. However, this is also suitable for engine drive force transmission devices in which only an engine is mounted as a drive source, and the clutch is used as a start clutch, as with engine automobiles. In addition, the invention also is suitable for use in motor drive force transmission devices in which only a motor/generator is mounted as a drive source, and the clutch is used as a start clutch, as with electric vehicles.