Abstract:
A torque transmission device for the transmission of torque between a first component and a second component which are mounted such that they can rotate about a common rotational axis. The torque transmission device includes a clutch configured to actuate in the axial direction and an actuation unit with a converter device and an actuating device. The converter device includes at least one axially movable first converter element and a second converter element assigned to the second component. The converter elements are configured such that relative rotation between the first and the second converter elements is converted into an axial movement of the first converter element to actuate the clutch. The actuating device is configured to generate selective coupling action between the first converter element and a structural element of the clutch.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a National Stage application of PCT International Application No. PCT/EP2011/004332 (filed on Aug. 29, 2011), under 35 U.S.C. §371, which claims priority to German Patent Application No. DE 10 2010 045 721.3 (filed on Sep. 16, 2010), which are each hereby incorporated by reference in their complete respective entireties. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a torque transmission device for the transmission of torque between a first and a second component which are mounted such that they can rotate about a common rotational axis. 
       BACKGROUND 
       [0003]    Torque transmission devices of this type often have a clutch which can be actuated in the axial direction and an actuation unit with a converter device and an actuating device. Here, the converter device serves to convert a movement which is produced by the actuating device into a movement which is suitable for actuating the clutch. It is of great significance in torque transmission devices that they have a reliable and efficient method of operation and, in particular, that the required torque can be transmitted to the desired extent. Moreover, they have to be compact and simple to cool. 
       SUMMARY 
       [0004]    It is therefore an object of the present invention to provide a torque transmission device of the abovementioned type which satisfies the abovementioned requirements and which is at the same time inexpensive. 
         [0005]    This object is achieved by a torque transmission device for the transmission of torque between a first component and a second component which are mounted such that they can rotate about a common rotational axis, comprising a clutch which can be actuated in the axial direction and an actuation unit with a converter device and an actuating device, the converter device comprising at least one axially movable first converter element and a second converter element which is assigned to the second component, which converter elements are arranged such that they can be rotated relative to one another and are configured in such a way that a relative rotation between the first and the second converter element can be converted into an axial movement of the first converter element for actuating the clutch, the actuating device being configured in such a way that a coupling action can be generated selectively between the first converter element and a structural element of the clutch, which structural element is connected fixedly to the first component so as to rotate with it, in order to bring about a relative rotation of the converter elements with respect to one another. 
         [0006]    According to the invention, the converter device of the actuation unit comprises at least one axially movable first converter element and a second converter element which is assigned to the second component. The converter elements are arranged such that they can be rotated relative to one another and are configured in such a way that a relative rotation between the first and the second converter element can be converted into an axial movement of the first converter element for actuating the clutch. The actuating device is configured in such a way that a coupling action can be generated selectively between the first converter element and a structural element of the clutch, which structural element is connected fixedly to the first component so as to rotate with it, in order to bring about a relative rotation of the converter elements with respect to one another. 
         [0007]    In other words, it is provided that the converter device utilizes a relative rotation of the two converter elements, in order to drive the first converter element to perform an axial movement which serves to actuate the clutch. The actuating device produces a coupling action between a structural element which is connected to the first component and the first converter element. Upon actuation of the actuating device, a part of the converter device is therefore ultimately coupled to the first component, in order to utilize a rotational speed difference, present in a non-actuated state of the torque transmission device, between the first and the second component to actuate the converter device. As a result of the coupling action, a rotationally fixed connection does not necessarily have to be produced. In many cases, it is sufficient and even preferred if merely a “slipping” coupling action is produced between the structural element and the first converter element by the actuating device. 
         [0008]    For example, in the case of a rotation of the first component and a second component which is at rest, the first converter element is accelerated, upon activation of the actuating device, by way of the coupling action with the structural element which is connected fixedly to the first component so as to rotate with it, whereas the second converter element which is assigned to the second component does not perform a rotational movement. On account of the coupling action with the first component via the structural element, the first converter element rotates relative to the second converter element, as a result of which an axial movement of the first converter element is generated, which axial movement actuates the clutch. 
         [0009]    It goes without saying that the torque transmission device operates in an analogous way if the first component does not move initially and the second component rotates or if the two components rotate at different rotational speeds. It is essential merely that there is any rotational speed difference at all between the two components. However, this situation exists as a rule if an actuation of the torque transmission device is requested, since no torque transmission is required if the rotational speeds of the two components are identical. 
         [0010]    The utilization of the rotational speed difference which is present in any case before coupling of the components to generate the axial actuating force of the clutch makes high efficiency of the torque transmission device possible. For example, the converter device can be designed in such a way that the characteristic of the axial movement of the first converter element is a function of the rotational speed difference between the first and the second component. Furthermore, it is advantageous that, in addition to the actuating device and the converter device, no further structural units are necessary to produce the functional capability of the actuation unit. The latter can therefore be of compact and robust design and can be produced inexpensively. In addition, the compact overall design simplifies the dissipation of the waste heat which is generated during operation of the torque transmission device. 
         [0011]    In accordance with one advantageous embodiment, the actuating device comprises an electromagnet which is configured and arranged in such a way that a magnetic coupling action can be generated between the first converter element and the structural element which is connected fixedly to the first component so as to rotate with it. An electromagnet is a robust and inexpensive component which in addition reacts rapidly to corresponding request signals, with the result that the torque transmission device can be actuated rapidly overall. Moreover, electromagnets can be controlled in a simple way, with the result that the torque which is transmitted via the torque transmission device can also be controlled satisfactorily. 
         [0012]    The electromagnet preferably comprises a coil which is arranged coaxially with respect to the first and the second structural element. 
         [0013]    A robust and structurally simple embodiment of the torque transmission device provides that the second converter element is connected to the second component such that it is fixed axially and fixed so as to rotate with the latter. The second converter element can therefore serve as axial support for the axial movement of the first converter element. Since the second converter element is connected fixedly to the second component so as to rotate with it, it is already sufficient for the generation of a relative rotation of the two converter elements, moreover, to couple the first converter element selectively to the structural element. 
         [0014]    The first converter element can be arranged such that it can be rotated relative to the first component and to the second component. The rotation, which is possible at least within defined limits, of the first converter element relative to the two components ensures satisfactory decoupling of the two components in a non-actuated state of the torque transmission device, which leads to improvements in efficiency. 
         [0015]    The converter elements preferably form a ramp mechanism which comprises, in particular, at least one rolling body which is arranged between the converter elements. The converter elements can in each case have at least one V-shaped or U-shaped groove, in which the rolling body is arranged, in order to guide the latter reliably. A converter device which is provided with a ramp mechanism ensures a reliable conversion of a relative rotational movement of the two components into an axial movement. 
         [0016]    If the coupling action between the structural element and the first converter element is generated, for example, by virtue of the fact that the two stated components are pressed against one another, a reinforcement of the initially provided pressing force can be brought about with a suitable refinement of the ramp mechanism. As a result of the initially, for example, comparatively weak coupling action between the structural element and the first converter element, a first rotation of the first converter element relative to the second converter element is generated, as has already been described in the preceding text. The ramp mechanism converts this rotation into an axial movement which, in the case of a suitable relative arrangement and design of the structural element and of the first converter element, leads to boosting of the coupling action which acts between them. This boosting coupling action in turn brings about more pronounced “driving” of the first converter element by the structural element which is connected fixedly to the first component so as to rotate with it. As a result, the relative rotation between the first and the second converter element is increased, which in turn leads to a further axial movement of the first converter element and therefore to boosting of the above-described coupling action. The automatic boosting of the initially applied actuation force by way of a suitable design of the actuation unit is called self-energizing. 
         [0017]    More efficient heat dissipation and a more compact overall design are achieved if the first component surrounds the converter device and/or the actuating device at least partially and, in particular, covers the actuating device completely in the axial direction. An additional housing to protect the converter device and/or the actuating device is then not necessary. 
         [0018]    As an alternative or in addition, it can be provided that the first converter element has a recess which receives the actuating device at least partially, in particular completely, in order to protect it and also in order to achieve an efficient method of operation of the actuation unit on account of the compact overall design. 
         [0019]    The clutch can be an, in particular dry-running, multiple disk clutch. 
         [0020]    In accordance with one embodiment, the structural element comprises a first frictional face which interacts with the first converter element and a second frictional face which lies opposite and interacts with a multiple disk assembly of the multiple disk clutch, in order to improve the coupling action between the structural element and the first converter element upon actuation of the torque transmission device. 
         [0021]    The structural element which is connected fixedly to the first component so as to rotate with it is preferably a disk of the multiple disk clutch, that is to say a coupling action is produced between a disk of the multiple disk clutch and the first converter element in order to actuate the torque transmission device. The structural element is, in particular, a “pilot disk” which is configured to be somewhat more robust than the remaining disks of the multiple disk assembly, forms a type of link between the first converter element and the multiple disk assembly, and which is configured to be correspondingly more stable in order to absorb the actuation forces which act on it. If a magnetic coupling action is provided between the pilot disk and the first converter element, it proves advantageous to produce the pilot disk and/or the first converter element from highly magnetically permeable material. This facilitates the routing of magnetic flux lines through the stated components and therefore improves the coupling action which acts between them upon actuation of the torque transmission device. Improved field flux routing is also assisted by a design of the stated components which is comparatively stable in cross section. 
         [0022]    The first component is preferably a clutch basket of the clutch. 
         [0023]    Further embodiments of the invention are specified in the description, the subclaims and the drawings. 
     
    
     
       DRAWINGS 
         [0024]    In the following text, the invention will be explained using advantageous embodiments purely by way of example with reference to the appended drawings, in which: 
           [0025]      FIG. 1  illustrates a cross section through a diagrammatically illustrated embodiment of the torque transmission device in accordance with the invention. 
           [0026]      FIG. 2  illustrates the embodiment which is illustrated in  FIG. 1 , in an actuated state. 
           [0027]      FIG. 3  illustrates an outline sketch for the method of operation of the ramp mechanism of the converter device, and 
           [0028]      FIG. 4  illustrates a sectional view of one embodiment of the torque transmission device in accordance with the invention with a wet-running multiple disk clutch. 
       
    
    
     DESCRIPTION 
       [0029]      FIG. 1  illustrates a torque transmission device  10  which comprises a multiple disk clutch  12  for the transmission of a torque from a shaft  14  to a flange  16 , and vice versa. 
         [0030]    The flange  16  is configured in one piece with a clutch basket section  18   a  of a clutch basket  18 . Outer disks  20  which can be displaced axially with the aid of a spline system  24  in relation to a rotational axis R which is common to the flange  16  and the shaft  14  and are connected fixedly to the clutch basket section  18   a  so as to rotate with it are arranged on the clutch basket section  18   a . The outer disks  20  are arranged in an alternating manner with inner disks  22  which are in turn connected by means of a spline system  24 ′ to the shaft  14  such that they can be displaced axially but are fixed to said shaft  14  so as to rotate with it. 
         [0031]    A coupling action can be produced between the shaft  14  and the flange  16  in a manner which is known per se, by a multiple disk assembly which is formed from the disks  20 ,  22  being pressed together. On account of the frictional forces which then act between the disks  20 ,  22 , a torque transmission takes place between the rotating components  14 ,  16 , which torque transmission is dependent, inter alia, on the force which loads the multiple disk assembly. 
         [0032]    In order to actuate the multiple disk clutch  12 , an actuation unit  26  is provided with a converter device  28  which converts a rotational speed difference between the shaft  14  and the flange  16  into an axial movement which loads the multiple disk assembly. The converter device  28  comprises a converter element  30  which is connected to the shaft  14  such that it is fixed axially and fixed so as to rotate with the latter. Said converter element  30  interacts via a plurality of rolling bodies  32  with a further converter element  34  which, however, in contrast to the converter element  30 , is arranged such that it can be rotated and moved axially in relation to the shaft  14 . Furthermore, the converter element  34  is also rotatable and axially movable in relation to the flange  16  and the clutch basket section  18   a  which is configured integrally with it. 
         [0033]    Together with the rolling bodies  32  which are arranged distributed around the shaft  14  in the circumferential direction and in V-shaped grooves  32   a  for guidance, the converter elements  30 ,  34  form a ramp mechanism of a type which is known per se, which ramp mechanism will also be explained in detail in the following text using  FIG. 3 . A relative rotation of the converter element  34  with respect to the converter element  30  leads to the converter element  34  being pressed to the left against a pilot disk  36  which, like the outer disks  20 , is connected to the clutch basket section  18   a  in an axially displaceable and fixed manner so as to rotate with the latter. The axial loading of the pilot disk  36  by the converter element  34  leads to the multiple disk assembly being pressed together, which leads in the above-described way to a torque transmission between the shaft  14  and the flange  16 . It goes without saying that the pilot disk  36  which is of more stable configuration than the outer disks  20  can in principle be structurally identical with the outer disks  20  if the performance requirements of the torque transmission device  10  allow. 
         [0034]    A relative rotation of the converter elements  30 ,  34  is generated by a coupling action being produced between the converter element  34  and the pilot disk  36 , as a result of which the converter element  34  is ultimately coupled to the clutch basket  18  in a manner which is effective for drive purposes but is not necessarily fixed so that they rotate together, and said converter element  34  is therefore activated to perform a rotational movement. Since a coupling action between the flange  16 , which is connected, for example, to a further shaft (not shown), and the shaft  14  is then required merely if there is a rotational speed difference between the two stated components, this means that a coupling action of the converter element  34  with the clutch basket  18  leads to a movement of the converter element  34  relative to the converter element  30  which is connected fixedly to the shaft  14  so as to rotate with it. On account of the ramp mechanism, this rotation leads to an axial movement of the converter element  34  which is pressed more strongly against the pilot disk  36  as a result and therefore compresses the multiple disk assembly of the clutch  12  more strongly, which multiple disk assembly is supported axially on the flange  16 . The stronger pressing force of the converter element  34  leads to an increased friction between the converter element  34  and the pilot disk  36 , which in turn leads to a stronger coupling of the converter element  34  to the rotational movement of the clutch basket  18 . In order to reinforce this effect, the coupling action between the converter element  34  and the pilot disk  36  can be improved by way of corresponding friction linings. As a result of the boosted coupling of the converter element  34  to the rotational movement of the clutch basket  18 , the converter element  34  is rotated further with respect to the converter element  30 , which in turn leads to a boosted pressing force. 
         [0035]    In other words, a self-energizing action is generated by the utilization of the rotational speed difference between the flange  16  and the shaft  14  in order to generate the force which loads the multiple disk assembly with the aid of the ramp mechanism, which self-energizing action exceeds the force which was initially applied for the coupling action between the converter element  34  and the pilot disk  36 . 
         [0036]    The actuation force which is required at the beginning of the actuation of the clutch  12  is provided by an electromagnet  38  which is arranged coaxially with respect to the shaft  14 , the flange  16  and the converter elements  30 ,  34  and the disks  20 ,  22 . If current is applied to the electromagnet  38 , a magnetization is induced in the converter element  34 , which magnetization, together with a corresponding induced magnetization of the pilot disk  36 , generates a magnetic coupling action which is sufficient to couple the converter element  34  to the pilot disk  36  so strongly that a relative rotation with respect to the converter element  30  is brought about, which relative rotation initiates the above-described self-energizing action. It goes without saying that the converter element  34  and/or the pilot disk  36  are manufactured from highly magnetically permeable material in order to produce an efficient coupling action, since a comparatively great magnetization is induced by a given magnetic field in the case of materials of this type. 
         [0037]    A magnetic flux F which is generated by the induced magnetization and penetrates the converter element  34  and the pilot disk  36  is illustrated qualitatively in  FIG. 2 . In order to prevent a magnetic “short circuit” which would weaken a coupling action between the pilot disk  36  and the converter element  34 , recesses  40  are provided in the converter element  34 , which recesses  40  force the magnetic flux F to exit the converter element  34  and enter the pilot disk  30 . 
         [0038]    In order to protect the actuation unit  26 , the clutch basket  18  has a housing section  18   b  which is connected fixedly to the section  18   a  so as to rotate with it and surrounds the actuation unit  26  substantially completely. Independently of this, but likewise assisting the compactness and robustness of the torque transmission device  10  is the aspect that the electromagnet  38  is arranged in a recess  34 ′ of the converter element  34 . As a result of the spatial closeness of the electromagnet  38  to the converter element  34  and the pilot disk  36 , the magnetic field which is generated by the electromagnet  38  can act particularly efficiently on the converter element  34  and the pilot disk  36 . 
         [0039]      FIG. 3  outlines the embodiment of a ramp mechanism  41  of the converter device  28  in diagrammatic form, the lower wedge corresponding to the converter element  30  and the upper wedge symbolizing the converter element  34 . The rolling body  32 , a ball here, is arranged between the converter elements  30 ,  34 . Since the converter element  30  is arranged fixedly, a relative movement of the converter element  34  to the right, which corresponds to a relative rotation of the two converter elements  30 ,  34 , leads to an axial movement of the converter element  34  (corresponds to a movement upward in  FIG. 3 ). The initial movement of the converter element  34  to the right is brought about by the above-described magnetic coupling action which is generated by the electromagnet  38 . Here, the converter element  34  is “carried along” with the pilot disk  36  which is rotating more rapidly, as a result of which the above-described self-energizing action is initiated. It goes without saying that the self-energizing action is, inter alia, a function of a coefficient of friction between the pilot disk  36  and the converter element  34  and the gradient α of the ramp mechanism  41 . The greater the stated coefficient of friction and/or the smaller the gradient α, the greater the self-energizing effect of the actuation unit  26 . 
         [0040]      FIG. 4  illustrates a torque transmission device  10 ′ with wet-running disks  20 ,  22 . In the case of a “wet” clutch  12  of this type, the coefficients of friction which are active in its interior are relatively constant on account of comparatively low wear. Moreover, the dissipation of the frictional heat which occurs during operation is ensured by a lubricant which fills the interior of the torque transmission device  10 ′. The dissipation of heat is assisted by the advantageously compact embodiment of the clutch basket  18  which, as described, encloses essential parts of the torque transmission device  10 ′ in the manner of a housing. 
         [0041]    In order to prevent a discharge of lubricant from the region of the clutch  12  and the actuation unit  26 , a sealing element  42  is provided. Moreover, a bearing  19   a  between the housing section  18   b  and a flange  44  which carries the electromagnet  38  is configured as a bearing which is sealed on one side. 
         [0042]    It goes without saying that the functional principle, described in detail multiple times in the preceding text, of the torque transmission device  10 ,  10 ′ can also be readily realized with a “dry” clutch. A bearing  19   b  which mounts the shaft  14  in the flange  16  would then be configured as a sealed, grease-lubricated bearing. The same applies to the bearing  19   a . In return, the sealing element  42  could be dispensed with. A dedicated lubrication means is not obligatory for the actuation unit  26 , since the relative movements which occur between the converter elements  30 ,  34  are comparatively low. The advantage of a “dry” clutch lies in the greater utilization of coefficient of friction and therefore in the usually lower frictional coefficient in comparison with “wet” clutches. Moreover, the basic torque behavior of “dry” clutches is usually better, since “dry” clutches can be ventilated completely. Basic torque is to be understood as the torque which is also transmitted in the non-actuated state of the torque transmission device. In the case of “wet” clutches, a certain transmission of torque takes place solely as a result of hydrodynamic effects on account of the movement of the lubricant. 
         [0000]    
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 LIST OF REFERENCE SIGNS 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 10, 10′ 
                 Torque transmission device 
               
               
                   
                 12 
                 Multiple disk clutch 
               
               
                   
                 14 
                 Shaft 
               
               
                   
                 16 
                 Flange 
               
               
                   
                 18 
                 Clutch basket 
               
               
                   
                 18a 
                 Clutch basket section 
               
               
                   
                 18b 
                 Housing section 
               
               
                   
                 19a, 19b 
                 Bearing 
               
               
                   
                 20 
                 Outer disk 
               
               
                   
                 22 
                 Inner disk 
               
               
                   
                 24, 24′ 
                 Spline system 
               
               
                   
                 26 
                 Actuation unit 
               
               
                   
                 28 
                 Converter device 
               
               
                   
                 30, 34 
                 Converter element 
               
               
                   
                 34′ 
                 Recess 
               
               
                   
                 32 
                 Rolling body 
               
               
                   
                 32a 
                 Groove 
               
               
                   
                 36 
                 Pilot disk 
               
               
                   
                 38 
                 Electromagnet 
               
               
                   
                 40 
                 Recess 
               
               
                   
                 41 
                 Ramp mechanism 
               
               
                   
                 42 
                 Sealing element 
               
               
                   
                 44 
                 Flange 
               
               
                   
                 R 
                 Rotational axis 
               
               
                   
                 F 
                 Magnetic flux 
               
               
                   
                 α 
                 Gradient