Abstract:
A dual clutch device having an input side, a first output side, and a second output side, which are arranged rotatably about an axis of rotation, and having a first, radially outer friction clutch for producing frictional engagement between the input side and the first output side and a second, radially inner friction clutch for producing frictional engagement between the input side and the second output side. Each friction clutch has a first friction element, which engages in the input side in a torque-transmitting manner, a second friction element, which engages in the associated output side in a torque-transmitting manner, a control element for providing an axially pressing force on the friction elements, and a leaf spring element, which is spirally wound around the axis of rotation and which is arranged axially between the control element and the friction elements.

Description:
BACKGROUND 
       [0001]    The invention relates to a dual clutch. In particular the invention relates to a dual clutch for the use in a motorcycle. 
         [0002]    A dual clutch is used in connection with a dual clutch transmission in order to perform a change in gears between successive gears in a rapid and precise fashion. Here, a drive engine acts upon an input side of the dual clutch and two friction clutches that can be controlled independent from each other can each generate a frictional engagement to an allocated transmission input shaft. A pair of toothed wheels may be active at each transmission input shaft, with the pairs of toothed wheels of the different transmission input shafts usually acting upon the same output shaft. When the first clutch is opened and the second one is closed, a predetermined gear is engaged. In order to change gears, the first clutch is opened and the second one is closed. 
         [0003]    In order to transfer the technology of the dual clutch and/or the dual clutch transmission from a motor vehicle to a motorcycle some framework conditions must be observed. For example an actuating force must be applied manually for the two friction clutches, commonly by the rider of the motorcycle. If the torque to be transferred is strong, the rider can be overwhelmed over an extended period of time. In order to reduce the clutch forces to be applied manually it is known to use manually operated auxiliary clutches and a main clutch that can be operated by the auxiliary clutch. WO 2011/050772 A1 and WO 2011/050775 A1 show exemplary embodiments for such devices, also called power clutches. 
         [0004]    Power clutches may however require a relatively large structural space and are associated with certain complexity. For example, for a dual clutch with two power clutches a total of four clutches must be designed, with their cooperation being subject to precise controlling. Such a complex dual clutch can lead to increased costs for development and production. 
       SUMMARY 
       [0005]    The objective of the present invention is to provide an improved dual clutch, particularly for the use in a motorcycle. The invention attains this objective via a dual clutch device comprising one or more features of the invention. Preferred exemplary embodiments are discussed below. 
         [0006]    A dual clutch device comprises an input side, a first output side, and a second output side, which are arranged rotationally about an axis of rotation, further a first, radially outer friction clutch for generating a frictional engagement between the input side and the first output side and a second radial inner friction clutch for generating a frictional engagement between the input side and the second output side. Here, each friction clutch comprises a first friction element, which engages the input side in a torque-proof fashion, a second friction element which engages the corresponding output side in a torque-proof fashion, a control element for providing an axial compression upon the friction elements, and a leaf spring element, which is arranged axially between the control element and the friction elements. 
         [0007]    The leaf spring element may provide an amplification of the compression depending on a distortion of its ends. By the use of the principle of spring elements an actuating force for clutches can be reduced so that an actuating system for the friction clutches can be designed in a simplified fashion or sized smaller. The stress of an auxiliary energy source provided for actuation, for example a hydraulic pump or an electric system, can be kept low thereby. The overall weight of a surrounding vehicle, particularly a motorcycle, can be kept low. In case of manual operation of the frictional clutches a low force to be applied by the driver can be realized such that relaxed driving can be supported with gear shifting that is hardly strenuous. Additionally, the use of the radially offset flat spring—clutches can contribute to saving axial structural space of the dual clutch device. This way the unit comprising the dual clutch device and a drive engine or a transmission can be designed narrower so that a diagonally positioned angle of the motorcycle can be large in which the dual clutch device is installed. 
         [0008]    The flat spring element can particularly be positioned at an angle about the axis of rotation or wound spirally. A spiral or helical line is a curve which extends about a point or an axis and, depending on the perspective of the observer, increases or decreases the distance thereto. An angular element forms an acute angle with the axis of rotation; however it extends straight and extends not about the axis of rotation. This angular or spirally wound leaf spring element can be designed in a particularly compact fashion in the axial direction and implement particularly well the desired amplification of the axial compression upon the friction elements. 
         [0009]    Preferably an axially extending section of the input side is implemented for the purpose of engaging the first friction element of the first friction clutch radially at the outside in a form-fitting fashion and the first friction element of the second friction clutch radially at the inside in a form-fitting fashion. 
         [0010]    By arranging the friction clutches on different radial sides of a common element, namely the axial section of the input side, a radially compact design of the dual clutch device can be yielded. The number of the components required for the dual clutch device can be reduced. This way production costs can be lowered. 
         [0011]    The section can be produced in one piece from sheet metal. This way production costs can be reduced. Additionally, engagement structures that can be used for the transmission of force can be used radially inside and radially outside in reference to the first friction element, can be formed easily and cost-effectively. 
         [0012]    Several friction elements may be provided at each friction clutch. This way multi-disc clutches result which can be used advantageously, particularly for the application in a motorcycle. 
         [0013]    The dual clutch device can be implemented for the purpose to run in an oil bath. This embodiment is also called wet or wet-running, and can facilitate cooling, lubrication, or cleaning of elements of the dual clutch device. Additionally a response behavior by slide friction of friction elements engaging each other can be controlled easier. Any integration with a transmission, also running in an oil bath, can be facilitated here. 
         [0014]    Here, an axial actuating element may be included, which acts upon the leaf spring element of a friction clutch, with the leaf spring element being embodied, when an axial compression force is missing, to compress the friction elements upon the actuating element so that the friction clutch closes. This embodiment is also called “normally closed”. 
         [0015]    In another embodiment an axial actuating element is provided which acts upon the leaf spring element of a friction clutch, with the leaf spring element being embodied to press the friction elements apart when an axial operating force upon the actuating element is missing, so that the friction clutch opens. This embodiment is also called “normally open”. 
         [0016]    The two latter embodiments can be combined with each other, by one friction clutch being opened upon activation and the other one being closed upon activation. This way advantages develop when providing actuating forces. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The invention is now explained in greater detail with reference to the attached figures. Here it shows in detail: 
           [0018]      FIG. 1  a longitudinal section through a dual clutch device; 
           [0019]      FIGS. 2 and 3  details of the dual clutch device of  FIG. 1 ; 
           [0020]      FIG. 4  variants of the embodiment of the dual clutch device of  FIGS. 1 to 3 ; and 
           [0021]      FIG. 5  a section of a friction clutch of the dual clutch device of the previous figures. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]      FIG. 1  shows a longitudinal section through a dual clutch device  100 . An input side  110  for connecting to a drive engine, a first output side  115  for connecting to a first transmission input shaft  120 , and a second output shaft  125  for connecting to a second transmission input shaft  130  are arranged about an axis of rotation  105 . The transmission input shafts  120  and  130  are preferably embodied coaxially in reference to the axis of rotation  105 . 
         [0023]    A first friction clutch  135  for the production of a friction-fitting engagement between the input side  110  and the first output side  115  and a second friction clutch  140  for generating a friction-fitting engagement between the input side  110  and the second output side  125  are arranged radially offset in reference to each other. In one embodiment, selected as an example, the first friction clutch  135  is opened without actuation (“normally open”) and the second friction clutch  140  is closed without actuation (“normally closed”). In  FIG. 1  the first friction clutch  135  is opened because it is not actuated, and the second friction clutch  140  is opened because it is actuated. 
         [0024]    As shown, it is preferred that an axially extending section  142  of the input side  110  is used equally for the torque-proof engagement of the first friction clutch  135  and the second friction clutch  140 . This section  142  is combined with a radially extending section in an exemplary fashion; in other embodiments here a one-piece implementation of the two sections may be given as well. The section  142  is preferably implemented to embody torque-proof counter supports both for the friction elements of the outer first friction clutch  135  as well as the inner second friction clutch  140 . As illustrated, the friction elements of both friction clutches  135 ,  140  may engage in a form-fitting fashion and preferably also in a manner axially displaceable in the section  142 . For this purpose, the section  142  may carry outer gear teeth engaged by the friction elements of the first friction clutch  135 , and an interior gear teeth engaged by the friction elements of the second friction clutch  140 . In another embodiment the section  142  comprises a strip of circumferential material with constant thickness about the axis of rotation  105 , which is formed such that alternating it extends at two different radii about the axis of rotation so that exterior gear teeth and interior gear teeth develop. 
         [0025]    A first actuating device  145  and a first leaf spring element  150  are allocated to the first friction clutch  135 , a second actuating device  155  and a second leaf spring element  160  to the second friction clutch  140 . The leaf spring elements  150  and  160  act oppositely the actuating devices  145  and  155  in the axial direction. In the embodiment shown the leaf spring elements  150  and  160  each cause the closing of the friction clutches  135  and  140 , while any actuation via the activation device  145  and  155  respectively cause an opening of the friction clutches  135  and  140 . This constellation is also called “normally closed”; equivalently a “normally open” arrangement is also possible, in which the respective actuating device  145 ,  155  is used for closing and the respective leaf spring element  150 ,  160  for opening the allocated friction clutch  135 ,  140 . Further, in the embodiment shown a “sliding” motion of the friction clutches  135 ,  140  is provided, with an axially acting compression force acting upon the activation devices  145 ,  155  in order to operate them. In one alternative embodiment a “tensile” activation of the devices  145 ,  155  may occur as well. The activation of the devices  145 ,  155  may for example occur via an electric or hydraulic actuator. 
         [0026]    The friction clutches  135  and  140  respectively comprise a plurality of blades  165  and friction disks  170 , which are provided alternating as axially arranged stacks. Blades  165  engage in a torque-proof fashion at the input side  110  and the friction disks  170  at the corresponding output sides  115 ,  125 . In other embodiments blades  165  and friction disks  170  can also be inversed or exclusively blades  165  or exclusively friction disks  170  may be used. Preferably another friction coating is provided between axially contacting elements  165 ,  170 . 
         [0027]      FIG. 2  shows in detail the dual clutch device  100  in the proximity of the first friction clutch  135 . The output side  115  comprises a radially circumferential section, engaged by the friction disks  170  in a torque-proof fashion, and an optional axially extending section for the torque-proof connection to the first transmission input shaft  120 . These two sections are connected to each other in a torque-proof fashion. The first actuating device  145  comprises a control element  205 , which is connected to the first output side  115 . The embodiment shown represents a one-piece connection to the radial section of the output side  115 . The control element  205  extends radially inwardly, with the first leaf spring element  150  being arranged between the control element and one end of the stack of blades  165  and friction disks  170 . The leaf spring element  150  extends in a preferred embodiment spirally about the axis of rotation  105  or is angular with regards to the axis of rotation  105 , and preferably further exhibits a strong spring-stiffness in order to transfer even a minor axial motion of the control element  205  to the stack of blades  165  and friction disks  170 . This way a friction-fitting connection can be generated between the input side  110  and the output side  115  so that torque can be transmitted by the friction clutch  135 . The relative rotation of the input side  110  in reference to the first output side  115  subjects the leaf spring element  150  to compression strain. This way, the leaf spring element  150  can get wedged slightly between the control element  205  and the end of the stack of blades  165  and friction disks  170  so that an axial expansion force develops which increases the compression force acting axially upon the blades  165  and the friction disks  170 . The closing force upon the friction clutch  135  is in this case increased by a portion of the torque transmitted via the friction clutch  135 . The compression force acting upon the blades  165  and the friction disks  170  can therefore be greater by many times than an originally caused compression force of the control element  205 , before a friction-fitting engagement occurs between the blades  165  and the friction disks  170 . The engagement of the friction clutch  135  can therefore occur with lower force than upon the blades  165  and the friction disks  170  so that for example via manual actuation strong torque can be coupled or decoupled securely via the friction clutch  135 . 
         [0028]      FIG. 3  shows a detail of the dual clutch  100  of  FIG. 1  in the proximity of the second friction clutch  140 . The second friction clutch  140  is opened by an axial actuating force upon the control element  205 . The actuating force compresses the second leaf spring element  160  in the axial direction. Just like the first leaf spring element  150  the second leaf spring element  160  preferably comprises an element, angular in reference to the axis of rotation  105  or in a spiral element, which extends about the axis of rotation  105 . If the axial actuation force of the control element  250  reduces in  FIG. 3  towards the left, the second leaf spring element  160  relaxes and pushes the stack of blades  165  and the friction disks  170  against the counter bearings  210  such that the stack is compressed and the blades  165  come into a friction-fitting engagement with the friction disks  170 . This way torque develops between the second output side  125  and the control element  205  so that the second leaf spring element  160  is compressed along its spiral direction of extension. The second leaf spring element  160  inverts the force of distortion so that an additional axial force develops. The stack of blades  165  and the friction disks  170  are therefore pressed more strongly towards the counter bearings  210  so that the friction-fitting engagement strengthens. 
         [0029]    In this variant as well a portion of the force transmitted via the second friction clutch  140  can be used to close the second friction clutch  140 . A self-enhancement of the applied actuating force develops upon the control element  205 . The second friction clutch  140  can therefore also be closed tightly while applying only minor actuating forces so that even a strong torque can be transmitted between the input side  110  and the output side  125 . 
         [0030]      FIG. 4  shows a schematic illustration of a helix  400 . A section of the helix  400 , which covers preferably less than 360° about an axis of rotation  105 , defines the preferred form of a leaf spring element  150  and  160  when it is embodied in a spiral shape. With regards to the preferred direction of transmission of torque by the dual clutch device  100  the direction of rotation of the helix  400  is selected such that the described claim for compression occurs along the direction of extension when the respective friction clutch  135 ,  140  shall be closed. In other words, by distorting the ends of a leaf spring element  150 ,  160  in the direction of compression about the axis of rotation  105  here an axial expansion force can be applied upon the ends of the spring leaf element  150 ,  160 . 
         [0031]    A spiral leaf spring element  150 ,  160  with the shape of the helix  400  shown in  FIG. 4  extends in one view upon the axis of rotation  105  clockwise away from the observer. When the end facing the observer is distorted clockwise in reference to the other end about the axis of rotation  105  here an axial expansion force develops upon the ends of the leaf spring element  150 ,  160  along the axis of rotation, which drives the ends axially apart. In one of the previous figures the distorting motion develops in one of the friction clutches  135 ,  140  by the leaf spring element  150 ,  160  being axially compressed to elements with different rotations. By the distorting effect the compression is strengthened so that minor compression and/or actuating force can be sufficient to trigger an opening and/or closing process of the corresponding friction clutch  135 ,  140 . A portion of the torque transmitted via the friction clutch  135 ,  140  is here used for providing the axial force upon the friction elements  165 ,  170 . 
         [0032]    In another embodiment one of the spiral leaf spring elements  150 ,  160  comprises several of the elements shown, which are screwed into each other. In a further embodiment one of the leaf spring elements  150 ,  160  is interrupted at the circumferential side. 
       LIST OF REFERENCE CHARACTERS 
       [0000]    
       
           100  Dual clutch device 
           105  Axis of rotation 
           110  Input side 
           115  First output side 
           120  First transmission input shaft 
           125  Second output side 
           130  Second transmission input shaft 
           135  First friction clutch 
           140  Second friction clutch 
           145  First actuating device 
           150  First leaf spring element 
           155  Second actuating element 
           160  Second leaf spring element 
           165  Blade 
           170  Friction disk 
           205  Control element 
           210  Counter bearing