Abstract:
A transmission having a first input shaft, a second input shaft, an output shaft, a first clutch, and a second clutch, wherein each one of the input shafts in connectible to the crankshaft of a drive motor by one of the clutches, wherein each one of the input shafts is connectible to the output shaft by means of gearwheel pairs to transmit torque, wherein a respective actuatable selector fork is provided to connect respective groups of two gearwheel pairs to the input shaft to transmit torque, wherein every gearwheel pair is assigned a transmission ratio, wherein a number of transmission ratios that are gradational relative to one another is provided, wherein the two transmission ratios of a group of gearwheel pairs are a first transmission ratio (N) and the one after the next (N+2), with N an integer number, in particular N=1, 2, 3, 4 or 5.

Description:
[0001]    The invention relates to a transmission, in particular for motor vehicles. 
       BACKGROUND 
       [0002]    Many types of transmissions for motor vehicles are known in the art. For instance, in what are known as manual transmissions, a clutch may connect the transmission input shaft to a crankshaft of a drive motor, and an output shaft is provided. Between the input shaft and the output shaft, there is a plurality of gearwheel pairs that may be selected by means of a shift lever. In these gearwheel pairs, one of the gearwheels is generally a fixed gearwheel that is firmly connected to the shaft whereas the other gearwheel is a loose gearwheel that is free to rotate on the shaft but connectible for co-rotation therewith by means of a locking mechanism. This may occur by means of the shift lever, a process which is also referred to as engaging a transmission ratio. In this process, the clutch is usually engaged and disengaged by a foot-operated pedal. 
         [0003]    Auto shift gearboxes in which the transmission is actuated as described above by means of an actuator in an automated way have also become known in the art. In such a system, the clutch is also actuated in an automated way by means of an actuator. 
         [0004]    A disadvantage of these transmissions is that when the transmission ratio is changed, there is a period of time in which no transmission ratio is engaged and consequently no driving torque is applied. Thus shifting operations without interrupting the tractive force are impossible. 
         [0005]    For this reason, what are known as double clutch transmissions have become known, which allow transmission ratio changes without interrupting the tractive force. Such transmissions may be actuated by actuators that allow the transmission ratio to be selected and engaged or disengaged as well as the clutch to be operated. These transmissions have two transmission input shafts, which are connectible to a crankshaft of a drive motor by means of two clutches. These transmissions also have an output shaft and a plurality of gearwheel pairs disposed between the two input shafts and the output shaft, allowing a transmission ratio to be engaged simultaneously for each input shaft unless both clutches are engaged at the same time. When the transmission ratio is changed, it is only necessary to disengage one clutch and to engage the other clutch at essentially the same time. 
         [0006]    An advantageous actuating device is known, for instance, from the older German Patent Application DE 10 2013 221 058 of the same applicant. This document discloses an actuating device having two roller assemblies, wherein the transmission ratios are actuated by means of selector forks with contacting elements. The contacting elements engage in grooves of the roller assemblies. A change from one groove to another groove is implemented in a direction-of-rotation-dependent way. 
       SUMMARY OF THE INVENTION 
       [0007]    Prior art transmissions have been found to have different shifting speeds for shifting into higher and lower gears. This results in different shifting times, which may be considered rather inadequate for dynamic shifting cycles, whereas shifting cycles for selected transmission ratio changes are fast if the dynamic aspect seems less important. 
         [0008]    An object of the invention is to provide an improved transmission compared to the prior art, in particular in terms of transmission ratio change dynamics. 
         [0009]    An exemplary embodiment of the invention relates to a transmission having a first input shaft, a second input shaft, an output shaft, a first clutch, and a second clutch, wherein each one of the input shafts is connectible to the crankshaft of a drive motor by one of the clutches, wherein each one of the input shafts is connectible to the output shaft by means of gearwheel pairs to transmit torque, wherein a respective actuatable selector fork is provided to connect respective groups of two gearwheel pairs to the output shaft to transmit torque, wherein every gearwheel pair is assigned a transmission ratio, wherein a number of transmission ratios that are gradational relative to one another are provided, wherein the two transmission ratios of a group of gearwheel pairs are a first transmission ratio (N) and the one after the next (N+2), with N an integer number, in particular N=1, 2, 3, 4 or 5 etc. As a consequence, to shift down two transmission ratios, i.e. from transmission ratio  3  to transmission ratio  1  and/or from transmission ratio  4  to transmission ratio  2  and/or from transmission ratio  5  to transmission ratio  3  and/or from transmission ratio  6  to transmission ratio  4  and/or from transmission ratio  7  to transmission ratio  5 , no complex shifting cycles need to be carried out because the down-shifting is actuated by a selector fork. Thus a short shifting time is achieved in particular for dynamically relevant shifting cycles. 
         [0010]    In this context, it is particularly advantageous if the transmission ratios of an input shaft have two groups of gearwheel pairs that comprise the transmission ratios N, N+2, N+4, and N+6, with N an integer, in particular N=1, 2, or 3. This allows even downshifting from transmission ratio N to transmission ratio N−4 to be implemented in a particularly fast way. 
         [0011]    In this context, it is advantageous if the transmission ratios of an input shaft have two groups of gearwheel pairs and if these gearwheel pairs comprise transmission ratios  1 ,  3 ,  5 , and  7 . 
         [0012]    It is further expedient if the transmission ratios of a first input shaft have two groups of gearwheel pairs, with one group of gearwheel pairs comprising transmission ratios  1  and  3  and another group of transmission ratios comprising transmission ratios  5  and  7 . 
         [0013]    It is particularly advantageous if the transmission ratios of a first input shaft have two groups of gearwheel pairs and if these gearwheel pairs comprise transmission ratios  2 ,  4 , and  6 . 
         [0014]    In this context, it is further advantageous if the transmission ratios of the reverse gear R are assigned to one of the gearwheel pairs. 
         [0015]    It is particularly advantageous if the transmission ratios of a second input shaft have two groups of gearwheel pairs and if a first group of gearwheel pairs comprises transmission ratios R and  2  and another group of gearwheel pairs comprises transmission ratios  4  and  6 . 
         [0016]    In accordance with a particularly advantageous aspect, transmission ratios  3 ,  5  and  2 ,  4 , respectively, of the individual groups may be disposed adjacent to one another on the respective input shaft in the arrangements described above. In this way, shifting cycles from  4  to  2  and from  5  to  3  likewise have correspondingly short shifting times. 
         [0017]    In this context, it is advantageous if the gearwheel pairs of at least one of the input shafts or of all input shafts are actuated in pairs by a selector fork, with the selector forks of an input shaft actuated by a respective controller drum. 
         [0018]    In accordance with the invention it is likewise advantageous if a respective controller drum is provided to actuate the gearwheel pairs of an input shaft, i.e. if two controller drums are provided to actuate the transmission in the case of two input shafts and the associated gearwheel pairs thereof. 
         [0019]    In this context, it is particularly advantageous if each one of the controller drums is driven by a respective electric motor. This allows the transmission to be actuated in a particularly quick and energy-efficient way. 
         [0020]    The present invention will be explained in more detail below based on preferred exemplary embodiments in connection with the associated figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a schematic representation of a transmission of the prior art. 
           [0022]      FIG. 2  is a schematic representation of a transmission of the invention. 
           [0023]      FIG. 3  is a view of a detail of a transmission of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]      FIG. 1  is a schematic representation of a transmission  1  of the prior art. The transmission  1  includes a first input shaft  2 , a second input shaft  3 , and clutches  4 ,  5  for connecting the input shafts  2 ,  3  to a non-illustrated crankshaft of a drive motor. The clutches  4 ,  5  are disposed in a clutch housing  6 , which is connectible to the crankshaft. Actuation devices  7 ,  8  are provided to actuate the clutches  4 ,  5 . The actuation devices  7 ,  8  are actuatable by a control unit to be able to actuate the one clutch  4  and/or the other clutch  5 . The input shafts  2 ,  3  are disposed to be at least coaxial with one another at least in sections, and the actuating devices  7 ,  8  are preferably likewise disposed to be coaxial with one another. Gearwheels  9 ,  10 ,  11 ,  12 ,  13 ,  14 ,  15 ,  16  of gearwheel pairs  9 / 17 ;  10 / 18 ;  11 / 19 ;  12 / 20 ;  13 / 21 ;  14 / 22 ;  15 / 23 , and  16 / 24  are fixed for co-rotation to the two input shafts  2 ,  3 . Gears  9 ,  10 ,  11 , and  12  are fixed for co-rotation to shaft  3  and gears  13 ,  14 ,  15 , and  16  are fixed for co-rotation to shaft  2 . 
         [0025]    Gears  17 ,  18 ,  19 ,  20 ,  21 ,  22 ,  23 ,  24  are connectible to the output shaft  25 , which is disposed to be parallel to the input shafts  2 ,  3 , by selector sleeves  26 ,  27 ,  28 , and  29 . For this purpose, the selector sleeves  26 ,  27 ,  28 , and  29  are axially movable by selector forks  30 ,  31 ,  32 , and  33 , which are to be moved in one direction or in the other direction in this process. The displacement of the selector forks  30 ,  31 ,  32 , and  33  is implemented by means of the roller elements  34 ,  35 ,  36 , and  37 , which may be rotated by drive motors  38 ,  39 . 
         [0026]    Also, pistons  40 ,  41  of piston/cylinder units  42 ,  43  may be actuated by the drive motors  38 ,  39  to be able to actuate the clutches  4 ,  5 . 
         [0027]    The transmission ratios Ü are arranged as follows: 
         [0028]    gearwheel pair  13 / 21  is assigned to the first transmission ratio Ü 1 , 
         [0029]    gearwheel pair  11 / 19  is assigned to the second transmission ratio Ü 2 , 
         [0030]    gearwheel pair  15 / 23  is assigned to the third transmission ratio Ü 3 , 
         [0031]    gearwheel pair  10 / 18  is assigned to the fourth transmission ratio Ü 4 , 
         [0032]    gearwheel pair  14 / 22  is assigned to the fifth transmission ratio Ü 5 , 
         [0033]    gearwheel pair  12 / 20  is assigned to the sixth transmission ratio Ü 6 , 
         [0034]    gearwheel pair  16 / 24  is assigned to the seventh transmission ratio Ü 7 , and 
         [0035]    gearwheel pair  9 / 17  with an intermediate gearwheel  44  is assigned to the transmission ratio of the reverse gear ÜR. In this context, the transmission ratios Ü 1  to Ü 7  and ÜR correspond to the known transmission ratios  1  to  7  and R of a transmission, which are also referred to as gears. 
         [0036]    It can be seen that the transmission ratios of a group of gearwheel pairs  13 / 21 ,  14 / 22  and  15 / 23 ,  16 / 24 , and  11 / 19 ,  12 / 20 , respectively, i.e. Ü 1 , Ü 5  and Ü 3 , Ü 7  and Ü 2 , Ü 6 , respectively, have a transmission ratio leap of 4, i.e. N and N+4. Thus to shift down from N to N−2, two groups of gearwheel pairs need to be involved. For instance, to shift down from Ü 3  to Ü 1 , the group of gearwheel pairs  13 / 21  and  14 / 22  as well as the group of gearwheel pairs  15 / 23  and  16 / 24  need to be involved; in this process, the selector sleeve of gearwheel pair  15 / 23  is actuated in a disengaging way and the selector sleeve of gearwheel pair  13 / 21  is actuated in an engaging way. To shift down from Ü 7  to Ü 5 , both gearwheel pair groups  13 / 21  and  14 / 22  as well as  15 / 23  and  16 / 24  are involved. 
         [0037]      FIG. 2  is a diagrammatic representation of a transmission  101  of the invention. The transmission  101  has a first input shaft  102 , a second input shaft  103 , and clutches  104 ,  105  for connecting the first and second input shafts  101 ,  102  to a non-illustrated crankshaft of a drive motor. The clutches  104 ,  105  are disposed in a clutch housing  106 , which is connectible to the crankshaft. To operate the clutches  104 ,  105 , actuating devices  107 ,  108  are provided. The actuating devices  107 ,  108  are controllable by a control unit to actuate one clutch  104  and/or the other clutch  105 . 
         [0038]    The input shafts  102 ,  103  are disposed to be coaxial with one another at least in sections, and the actuating devices  107 ,  108  are preferably likewise disposed to be coaxial with one another. Gearwheels  109 ,  110 ,  111 ,  112 ,  113 ,  114 ,  115 ,  116  of gearwheel pairs  109 / 117 ;  110 / 118 ;  111 / 119 ;  112 / 120 ;  113 / 121 ;  114 / 122 ;  115 / 123  and  116 / 124  are fixed for co-rotation to the two input shafts  102 ,  103 . Gearwheels  109 ,  110 ,  111 , and  112  are fixed for co-rotation to shaft  103  and gearwheels  113 ,  114 ,  115 , and  116  are fixed for co-rotation to shaft  102 . 
         [0039]    Gearwheels  117 ,  118 ,  119 ,  120 ,  121 ,  122 ,  123 ,  124  are connectible to the output shaft  125 , which is disposed to be parallel to the input shafts  102 ,  103 , by means of selector sleeves  126 ,  127 ,  128 , and  129 . For this purpose, the selector sleeves  126 ,  127 ,  128 , and  129  are axially movable by selector forks  130 ,  131 ,  132 , and  133 , which are to be moved in one direction or in the other direction in this process. The displacement of the selector forks  130 ,  131 ,  132 , and  133  is implemented by the roller elements  134 ,  135 ,  136 , and  137 , which may be rotated by drive motors  138 ,  139 , for instance electric or hydraulic motors. Roller elements  134 ,  135  and  136 ,  137 , respectively, may be combined to form a respective controller drum. 
         [0040]    Also, pistons  140 ,  141  of piston/cylinder units  142 ,  143  may be actuated by the drive motors  138 ,  139  to be able to actuate the clutches  104 ,  105 . 
         [0041]    The transmission ratios Ü are arranged as follows: 
         [0042]    gearwheel pair  113 / 121  is assigned to the first transmission ratio Ü 1 , 
         [0043]    gearwheel pair  110 / 118  is assigned to the second transmission ratio Ü 2 , 
         [0044]    gearwheel pair  114 / 122  is assigned to the third transmission ratio Ü 3 , 
         [0045]    gearwheel pair  111 / 119  is assigned to the fourth transmission ratio Ü 4 , 
         [0046]    gearwheel pair  115 / 123  is assigned to the fifth transmission ratio Ü 5 , 
         [0047]    gearwheel pair  112 / 120  is assigned to the sixth transmission ratio Ü 6 , 
         [0048]    gearwheel pair  116 / 124  is assigned to the seventh transmission ratio Ü 7 , and 
         [0049]    gearwheel pair  109 / 117  with an intermediate gearwheel  144  is assigned to the transmission ratio of the reverse gear ÜR. In this context, the transmission ratios Ü 1  to Ü 7  and ÜR correspond to the known transmission ratios  1  to  7  and R of a transmission, which are also referred to as gears. 
         [0050]    It can be seen in  FIG. 2  that the transmission ratios of a group of gearwheel pairs  113 / 121 ,  114 / 122  and  115 / 123 ,  116 / 124 , and  111 / 119 ,  112 / 120 , respectively, i.e. Ü 1 , Ü 3  and Ü 5 , Ü 7  and Ü 4 , Ü 6 , respectively, have a transmission ratio leap of only two, i.e. N and N+2. Thus to shift down from N to N−2, only one gearwheel pair group is involved. This accelerates the shifting cycle, in particular if roller elements are used for actuation. For instance, to shift down from Ü 3  to Ü 1 , only the group of gearwheel pairs  113 / 121  and  114 / 122  is involved; to shift down from Ü 7  to Ü 5 , only the group of gearwheels  115 / 123  and  116 / 124  is involved. 
         [0051]    A respective freewheel  45 ,  145  is provided between the respective drive motor  38 ,  39  and  138 ,  139 , respectively, and the piston. 
         [0052]      FIG. 3  is a sectional view of the arrangement of two roller elements  202  with a gearwheel  224  for driving purposes via a drive unit  225 , wherein the contact elements  210 ,  211  of the selector forks  212 ,  213  engage in the guide tracks  203 ,  204  and are movable in the guide tracks by rotating the roller elements  202 . 
         [0053]    Thus the gearwheel pairs of at least one of the input shafts or of all input shafts may be actuated in pairs by means of one of the selector forks  212 ,  213 . The selector forks  212 ,  213  of an input shaft may be actuated by a respective controller drum as the roller unit  202 . A respective controller drum as the roller element  202  is provided to actuate the gearwheel pairs of an input shaft, and for two input shafts and the associated gearwheel pairs, two controller drums as the roller elements  202  are provided to actuate the transmission. The controller drums as the roller elements  202  are preferably driven by one electric motor or by respective electric motors. 
         [0054]    In this respect and in particular in terms of the actuation of the clutch, reference is made to the older application DE 10 2013 221 058, whose disclosed content is hereby expressly incorporated in its entirety by reference herein. 
       LIST OF REFERENCE SYMBOLS 
       [0000]    
       
           1  transmission 
           2  input shaft 
           3  input shaft 
           4  clutch 
           5  clutch 
           6  clutch housing 
           7  actuating device 
           8  actuating device 
           9  gearwheel 
           10  gearwheel 
           11  gearwheel 
           12  gearwheel 
           13  gearwheel 
           14  gearwheel 
           15  gearwheel 
           16  gearwheel 
           17  gearwheel 
           18  gearwheel 
           19  gearwheel 
           20  gearwheel 
           21  gearwheel 
           22  gearwheel 
           23  gearwheel 
           24  gearwheel 
           25  output shaft 
           26  selector sleeve 
           27  selector sleeve 
           28  selector sleeve 
           29  selector sleeve 
           30  selector fork 
           31  selector fork 
           32  selector fork 
           33  selector fork 
           34  roller element 
           35  roller element 
           36  roller element 
           37  roller element 
           38  drive motor 
           39  drive motor 
           40  piston 
           41  piston 
           42  piston-cylinder unit 
           43  piston-cylinder unit 
           44  intermediate gearwheel 
           45  freewheel 
           101  transmission 
           102  input shaft 
           103  input shaft 
           104  clutch 
           105  clutch 
           106  clutch housing 
           107  actuating device 
           108  actuating device 
           109  gearwheel 
           110  gearwheel 
           111  gearwheel 
           112  gearwheel 
           113  gearwheel 
           114  gearwheel 
           115  gearwheel 
           116  gearwheel 
           117  gearwheel 
           118  gearwheel 
           119  gearwheel 
           120  gearwheel 
           121  gearwheel 
           122  gearwheel 
           123  gearwheel 
           124  gearwheel 
           125  output shaft 
           126  selector sleeve 
           127  selector sleeve 
           128  selector sleeve 
           129  selector sleeve 
           130  selector fork 
           131  selector fork 
           132  selector fork 
           133  selector fork 
           134  roller element 
           135  roller element 
           136  roller element 
           137  roller element 
           138  drive motor 
           139  drive motor 
           140  piston 
           141  piston 
           142  piston-cylinder unit 
           143  piston-cylinder unit 
           144  intermediate gearwheel 
           145  freewheel 
           202  roller element 
           203  guide track 
           204  guide track 
           210  contact element 
           211  contact element 
           212  selector fork 
           213  selector fork 
           224  gearwheel 
           225  driving stage