Abstract:
A dual-clutch for a motor vehicle includes an input, first and second outputs, friction plates for producing a drive connection between the input and the first and second outputs alternately, a housing including an inlet and an outlet, containing at least a portion of the friction plates, and a cooling system including a fan impeller rotating with the input and producing an air stream flowing through the housing from the inlet to the outlet.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to a dual-clutch transmission for motor vehicles, having two transmission subsections, a dry dual clutch, which transmits the torque from the engine to one or the other of the two transmission subsections, and a cooling system having a fan impeller for cooling the dual clutch. 
         [0003]    2. Description of the Prior Art 
         [0004]    Dual clutch transmissions are automatic shift transmissions, which allow a fully automatic gear change without an interruption in power by means of two transmission subsections. The transmission controller chooses the gears automatically or according to driver requirements within the permitted engine speed ranges. Torque is transmitted via one of the two clutches, which connect the two transmission subsections to the engine. While one clutch is closing, the other opens. 
         [0005]    Dry dual clutches of this kind often may have inadequate cooling and are susceptible to overheating particularly in the case of small engines, where there is a need for frequent gear changes and the clutch disks are subject to high slip loading, especially when starting off or in stop-and-go mode. In parallel with the overheating, troublesome clutch odor can occur in the passenger compartment when using specific friction linings. 
         [0006]    A dual clutch transmission with active air cooling is already known from DE 10 2010 007 198 A1. To generate the cooling air stream, use is made of a fan impeller, which is seated on one of the output shafts of the dual clutch or on one of the transmission input shafts. In this known version, only the starting clutch is cooled. With a cooling system of this kind, the required cooling capacity cannot be provided at high slip speeds. 
       SUMMARY OF THE INVENTION 
       [0007]    A dual-clutch for a motor vehicle includes an input, first and second outputs, friction plates for producing a drive connection between the input and the first and second outputs alternately, a housing including an inlet and an outlet, containing at least a portion of the friction plates, and a cooling system including a fan impeller rotating with the input and producing an air stream flowing through the housing from the inlet to the outlet. 
         [0008]    The cooling system for the dry dual clutch adequately cools all the functional components of the dual clutch. The fan impeller rotates with the input shaft driven by an engine, and the cooling air stream generated by the fan impeller can pass through the entire housing of the dual clutch. 
         [0009]    Continuous intensive cooling is possible and, due to the fact that the fan impeller rotates with the input shaft of the clutch, that is to say preferably with an engine crankshaft, cooling in accordance with the engine speed is automatically possible. 
         [0010]    The fan impeller preferably rotates at the same speed as the shaft coming from the engine, which is synchronized with the input shafts of the dual clutch in accordance with the gear selected. This combination of features can be achieved by particularly simple technical means since the fan impeller need merely be mounted on the engine output shaft or directly coupled thereto. 
         [0011]    The fan impeller can be mounted as a separate component on the driving disk, seated on the engine output shaft, of the dual clutch. Alternatively, it is also possible for the fan impeller to be integrated directly into the driving disk, or the fan impeller to be accommodated in the central disk of the clutch. 
         [0012]    In either case, however, the driving disk, the central disk and the clutch system may have passage openings for the cooling air, depending on where the fan impeller is seated. 
         [0013]    The fan impeller draws in the cooling air from the outside of the clutch housing. The inlet zone for the cooling air into the clutch housing would preferably be located ahead of the fan impeller in the direction of flow. 
         [0014]    Since the cooling air stream should reach the entire housing of the dual clutch, the outlet zone for the cooling air preferably lies at the opposite end of the clutch housing from the inlet zone. 
         [0015]    In order to ensure that the cooling air is at a sufficiently low temperature, the inlet and outlet zones for the cooling air can be connected by a conduit system to the front radiator of the vehicle. This also ensures that the cooling air is as far as possible dry since it is absolutely essential that the air drawn in should contain no water. 
         [0016]    In order to keep the cooling air clean, air filters can be arranged in the cooling air stream in the inlet and outlet zones of the clutch housing. 
         [0017]    The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0018]    The invention is illustrated by way of example in the drawing and is described in detail below with reference to the drawing, in which: 
           [0019]      FIG. 1  shows a section through the upper part of a first illustrative embodiment of a dual clutch, 
           [0020]      FIG. 2  shows the same section through a second illustrative embodiment of a dual clutch, 
           [0021]      FIG. 3  shows the same section through a third illustrative embodiment of a dual clutch, 
           [0022]      FIG. 4  shows the same section through a second clutch system in which the illustrative embodiments in  FIGS. 1 to 3  can be used, 
           [0023]      FIG. 5  shows a schematic overview of one possibility for directing the cooling air stream, 
           [0024]      FIG. 6  shows a schematic overview of a second possibility for directing the cooling air stream, and 
           [0025]      FIG. 7  shows a schematic overview of a third possibility for directing the cooling air stream. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0026]    According to  FIG. 1  of the drawing, the dual clutch system  1  essentially consists of a driving disk  2 , a central disk  3  connected to the latter, pressure plates  4  and  5  provided on both sides of the central disk  3 , and friction disks  6  and  7  located between the central disk  3  and the pressure plates  4  and  5  and supported on hubs secured to output shafts  10  and  11 , respectively. 
         [0027]    The driving disk  2  is seated on the input shaft  8  of the dual clutch  1  for conjoint rotation and consequently rotates with the latter at the same speed. The input shaft  8  is normally the drive shaft or crankshaft of an engine (not shown in the drawing). 
         [0028]    The driving disk  2  is connected by way of a torsional damper  9  to the central disk  3 , that is to say the central disk  3  revolves at the same speed as the driving disk  2 . The pressure plates  4  and  5  arranged on both sides of the central disk  3  revolve with the central disk  3  but can be moved axially relative to the central disk  3 . In this arrangement, the central disk is guided radially and supported axially on a hollow shaft bearing  34  by way of a hollow shaft  11 . 
         [0029]    To initiate the coupling process, one of the pressure plates  4  or  5  is moved towards the central disk  3 , thereby pressing the respective friction disk  6  or  7  firmly against the central disk  3 . 
         [0030]    Because the respective friction disk  6  or  7  is coupled, it rotates with the central disk  3  and transmits the torque of the engine to the respective output shaft  10  or  11  of the dual clutch  1 . 
         [0031]    The output shaft  10 , which can be connected to the friction disk  6  illustrated on the left in the drawing, is designed as a solid shaft and projects into a transmission housing (not shown in the drawing), where it serves to drive a first transmission subsection. This transmission subsection operates gears  1 ,  3  and  5 , for example. 
         [0032]    The output shaft  11 , which can be connected to the friction disk  7  illustrated on the right in the drawing, is designed as a hollow shaft which surrounds the solid shaft  10 . The hollow shaft  11  likewise leads into the transmission housing (not shown in the drawing) and is used to drive a second transmission subsection, which is provided for gears  2 ,  4 ,  6  and R, for example. 
         [0033]    The entire dual clutch  1  shown in the drawing is surrounded by a clutch housing  12 . 
         [0034]    In the starting state, especially in stop-and-go mode, in which the respective friction disk  6  or  7  between the central disk  3  and the respective pressure plate  4  or  5  slips, a considerable amount of frictional heat arises, and this must be dissipated since, otherwise, there would be both severe wear on the friction disks  6  and  7  and the generation of smells. 
         [0035]    To cool the dual clutch  1 , the clutch housing  12  is provided with an air inlet  13  and an air outlet  14 . The air inlet  13  is arranged in the region of the input side of the dual transmission  1 , and the air outlet  14  is arranged on the output side of the dual transmission  1 . 
         [0036]    To generate an intensive air stream through the clutch housing  12 , a fan impeller  15  is provided, being integrated into the driving disk  2 , as illustrated in  FIG. 1 . The fan impeller  15  thus rotates with the driving disk  2  and hence also with the drive shaft  8  of the engine. 
         [0037]    In this design, the cooling air stream  16  generated by the fan impeller  15  is matched to the speed of the input shaft  8 , that is to say that, at a relatively high engine speed, at which the friction disks  6  and  7  may also be subject to relatively severe thermal stress, the air stream is also intensified. 
         [0038]    By means of this optimum active air cooling of the dual clutch, the temperatures of the clutch system consisting of the central disk  3 , the pressure plates  4  and  5  and the friction disks  6  and  7  are reduced, thereby not only reducing wear on the individual clutch components but also stabilizing the friction coefficient of the friction disks  6  and  7 . Stabilizing the friction coefficient of the disks also makes it possible to transmit a more stable torque for the same contact force by the pressure plates  4  and  5 . Moreover, the generation of smells is significantly reduced. 
         [0039]    By virtue of the structural arrangement of the air inlet  13  and of the air outlet  14  at opposite ends of the clutch housing, very intensive air circulation through the entire dual clutch  1  is possible. By virtue of this extremely active air cooling, it may also be possible to reduce the volumes of the cast masses of the central disk  3  and of the pressure plates  4  and  5 , and therefore in this respect too savings are possible and clutch losses are reduced, thereby making it possible to compensate for the losses caused by the fan impeller. 
         [0040]    In order to be able to convey the cooling air stream  16  through the driving disk  2  at the same level as the fan impeller  15 , air passage openings  27  are provided, enabling the cooling air to be drawn out of the zone connected to the air inlet  13 , ahead of the driving disk  2 , and to be directed through the entire clutch to the air outlet  14 . 
         [0041]    In the case of the second illustrative embodiment of the dual clutch  1 , which is illustrated in  FIG. 2 , the same reference numerals are used for corresponding components as in the first illustrative embodiment illustrated in  FIG. 1 . 
         [0042]    In this second illustrative embodiment too, the dual clutch once again consists of the central disk  3 , the pressure plates  4  and  5  and the friction disks  6  and  7 , which transmit the torque of the engine to the respective output shaft  10  or  11  in the coupled state. 
         [0043]    As in the illustrative embodiment illustrated in  FIG. 1 , the driving disk  2 , which is connected to the central disk  3  by way of a torsional damper  9 , is seated on the input shaft  8 , which starts from the engine and projects into the clutch housing. 
         [0044]    In a manner similar to that in the illustrative embodiment illustrated in  FIG. 1 , a fan impeller  17  is provided, which rotates with the driving disk  2 . In this case, the fan impeller  17  is designed as a separate component and is arranged between the driving disk  2  and the coupling zone. Thus, the fan impeller  17  lies behind the driving disk  2  in the direction of flow of the cooling air stream  16 . By means of a holder  18 , the fan impeller  17  is connected in a substantially rigid manner to the driving disk  2  and therefore rotates at the same speed as the driving disk  2  and the engine shaft  8 . 
         [0045]    In order to direct the cooling air stream  16  through the driving disk  2 , air passage openings  19  and  27  are provided in the driving disk  2  and in the central disk  3  at the same level as the fan impeller  17 , cooling air being drawn in by the fan impeller  17  through said openings from the zone connected to the air inlet  13 , that ahead of the driving disk  2 , and directed by said impeller through the entire clutch to the air outlet  14 . For this second illustrative embodiment of the dual clutch  1 , the same advantages apply as for the illustrative embodiment shown in  FIG. 1 . 
         [0046]    In the third illustrative embodiment of the dual clutch  1 , which is illustrated in  FIG. 3 , the same reference numerals are used for corresponding components as in the first illustrative embodiment illustrated in  FIG. 1 . 
         [0047]    In this third illustrative embodiment too, the dual clutch once again consists of the central disk  3 , the pressure plates  4  and  5  and the friction disks  6  and  7 , which transmit the torque of the engine to the respective output shaft  10  or  11  in the coupled state. 
         [0048]    As in the illustrative embodiments illustrated in  FIGS. 1 and 2 , the driving disk  2 , which is connected to the central disk  3  by way of a torsional damper  9 , is seated on the input shaft  8 , which starts from the engine and projects into the clutch housing. 
         [0049]    In a manner similar to that in the illustrative embodiment illustrated in  FIG. 2 , a fan impeller  17  is provided, which rotates with the central disk  3 . In this case, the fan impeller  17  is designed as a separate component and is arranged between the driving disk  2  and the coupling zone. Thus, the fan impeller  17  lies behind the driving disk  2  in the direction of flow of the cooling air stream  16 . The central disk  3  is connected to the damper and therefore rotates at the same speed as the driving disk  2  and the engine shaft  8 . 
         [0050]    In order to direct the cooling air stream  16  through the central disk  3 , air passage openings  19  are provided in the driving disk  2  and in the central disk  3  at the same level as the fan impeller  17 , cooling air being drawn in by the fan impeller  17  through said openings from the zone connected to the air inlet  13 , that ahead of the driving disk  2 , and directed by said impeller through the entire clutch to the air outlet  14 . For this third illustrative embodiment of the dual clutch  1 , the same advantages apply as for the illustrative embodiment shown in  FIGS. 1 and 2 . 
         [0051]    According to  FIG. 4  of the drawing, the dual clutch  28  consists essentially of a driving disk  2 , a central disk  3  connected to the latter by an intermediate body  29 , pressure plates  4  and  5  provided on both sides of the central disk  3 , and friction disks  6   a  and  7   a  arranged between the central disk  3  and the pressure plates  4  and  5 . 
         [0052]    The driving disk  2  is seated on the input shaft  8  of the dual clutch  28  for conjoint rotation and consequently rotates with the latter at the same speed. The input shaft  8  is normally the drive shaft or crankshaft of an engine (not shown in the drawing). 
         [0053]    The driving disk  2  is connected by way of an intermediate body  29  to the central disk  3 , that is to say the central disk  3  revolves at the same speed as the driving disk  2 . The pressure plates  4  and  5  arranged on both sides of the central disk  3  revolve with the central disk  3  but can be moved axially relative to the central disk  3 . In this arrangement, the central disk  3  is guided radially by way of the intermediate body  29  with the connection to the driving disk  2 . Axial support is accomplished by way of the hollow shaft bearing  34  combined with an additional thrust washer  33 . 
         [0054]    To initiate the coupling process, one of the pressure plates  4  or  5  is moved towards the central disk  3 , thereby pressing the respective friction disk  6   a  or  7   a  firmly against the central disk  3 . 
         [0055]    Because the respective friction disk  6   a  or  7   a  is coupled, it rotates with the central disk  3  and transmits the torque of the engine to the respective output shaft  10  or  11  of the dual clutch  28 . 
         [0056]    The output shaft  10 , which can be connected to the friction disk  6  illustrated on the left in the drawing, is designed as a solid shaft and projects into a transmission housing (not shown in the drawing), where it serves to drive a first transmission subsection. This transmission subsection operates gears  1 ,  3  and  5 , for example. 
         [0057]    The output shaft  11 , which can be connected to the friction disk  7  illustrated on the right in the drawing, is designed as a hollow shaft which surrounds the solid shaft  10 . The hollow shaft  11  likewise leads into the transmission housing (not shown in the drawing) and is used to drive a second transmission subsection, which is provided for gears  2 ,  4 ,  6  and R, for example. 
         [0058]    The entire dual clutch  28  shown in the drawing is surrounded by a clutch housing  12 . 
         [0059]    In the starting state, especially in stop-and-go mode, in which the respective friction disk  6   a  or  7   a  between the central disk  3  and the respective pressure plate  4  or  5  slips, a considerable amount of frictional heat arises, and this must be dissipated since, otherwise, there would be both severe wear on the friction disks  6   a  and  7   a  and the generation of smells. 
         [0060]    To cool the dual clutches  1  and  28 , the clutch housing  12  is provided with an air inlet  13  and an air outlet  14 . The air inlet  13  is arranged in the region of the input side of the dual transmissions clutches  1  and  28 , and the air outlet  14  is arranged on the output side of the dual transmissions clutches  1  and  28 . 
         [0061]    To generate an intensive air stream through the clutch housing  12 , a fan impeller  17  is provided, being integrated either into the driving disk  2  or into the central disk  3 , as illustrated in  FIG. 1 . The fan impeller  17  thus rotates with the driving disk  2  and hence also with the drive shaft  8  of the engine, this being equivalent to the embodiments shown in  FIGS. 1 and 2 . 
         [0062]    In this design, the cooling air stream  16  generated by the fan impeller  17  is matched to the speed of the input shaft  8 , that is to say that, at a relatively high engine speed, at which the friction disks  6 / 6   a  and  7 / 7   a  may also be subject to relatively severe thermal stress, the air stream is also intensified. The friction disks  6   a  and  7   a  can optionally be embodied with a damper system  32 . 
         [0063]    An illustrative embodiment of one possibility for directing the cooling air stream is shown schematically in  FIG. 5 . The individual components are illustrated only schematically. 
         [0064]    A fan impeller  21  represented as a circle is driven by a motor  20 , likewise represented as a circle. This fan impeller  21  is arranged ahead of a dual clutch  22 . The cooling air stream  16  is passed through a conduit system  23 , which starts from the front radiator  24  and is introduced into the clutch housing  12  through an inlet filter  25  arranged in the air inlet of the clutch housing  12 . 
         [0065]    The fan impeller  21  driven by the motor  20  blows the cooling air through both clutch sections of the dual clutch  22 . The cooling air stream heated up therein then passes back to the front radiator  24  through the air outlet  14  and an outlet filter  26  arranged in the air outlet  14 . 
         [0066]    Routing the air in this way ensures that the cooling air is free of water. It is furthermore ensured that the cooling air flowing through the clutch components remains clean owing to the filters  25  and  26  arranged in the air inlet  13  and the air outlet  14  of the clutch housing  12 . 
         [0067]      FIG. 6  shows the same cooling circuit as in  FIG. 5  but without the main radiator. In this version, the heat from the clutch is exchanged with the environment at the front end  30  of the vehicle. 
         [0068]      FIG. 7  shows the same cooling circuit as in  FIG. 6  without the radiator, with heat exchange taking place in the region  31  of the engine. 
         [0069]    By means of the invention, therefore, an optimum active cooling system for a dry dual clutch is provided, thus increasing the performance thereof, reducing wear and possibly even enabling the cast masses of various clutch disks to be reduced and hence also reducing the generation of smells. 
       LIST OF REFERENCE SIGNS 
       [0000]    
       
           1  dual clutch/system  1   
           2  driving disk 
           3  central disk 
           4  pressure plate 
           5  pressure plate 
           6  friction disk 
           6   a  friction disk—with damper 
           7  friction disk 
           7   a  friction disk with damper 
           8  input shaft 
           9  torsional damper 
           10  output shaft (solid shaft) 
           11  output shaft (hollow shaft) 
           12  clutch housing 
           13  air inlet 
           14  air outlet 
           15  fan impeller 
           16  cooling air stream 
           17  fan impeller 
           18  holder 
           19  air passage opening 
           20  motor 
           21  fan impeller 
           22  dual clutch 
           23  conduit system 
           24  front radiator 
           25  inlet filter 
           26  outlet filter 
           27  air passage openings 
           28  dual clutch/system  2   
           29  intermediate body, dual clutch 
           30  front region of vehicle—no radiator 
           31  region of the engine—no radiator 
           32  damper 
           33  thrust washer 
           34  hollow shaft bearing 
       
     
         [0106]    In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that the alternate embodiments can be practiced otherwise than as specifically illustrated and described.