Abstract:
A powershift transmission of a flexible design for a working machine. The powershift transmission has at least six transmission shafts ( 2, 8, 15, 17, 22, 27, 30 ) arranged spaced apart from one another. A loose wheel ( 25 ), connected to the clutch ( 26 ) for the third gear, meshes with a fixed wheel ( 29 ) which is connected to the drive output shaft ( 30 ) in a rotationally fixed manner.

Description:
[0001]    This application claims priority from German patent application serial no. 10 2016 203 502.9 filed Mar. 3, 2016. 
       FIELD OF THE INVENTION 
       [0002]    The invention concerns a powershift transmission for working machines. 
       BACKGROUND OF THE INVENTION 
       [0003]    To drive the vehicle wheels, working machines such as construction machines and in particular backhoe loaders and telehandlers, have to have a powershift transmission with transmission shafts parallel to one another and a distance apart, in order to leave some distance between the drive input shaft and the drive output shaft. 
         [0004]    DE 10330159A1 discloses a powershift transmission for construction machines of the type defined in more detail below. The disadvantage of this system is that the options for possible gearwheel pairings are very limited, since the loose wheel on the transmission shaft carrying the clutch for the third gear meshes with the fixed wheel on the transmission shaft carrying the clutch for the second gear. Since the transmission ratios for forward driving should be almost the same as the transmission ratios for driving in reverse, there is little freedom for varying the overall transmission ratio in this transmission system. 
       SUMMARY OF THE INVENTION 
       [0005]    The purpose of the present invention is to provide a powershift transmission for construction machines, in which the design of the axle separation is more flexible and the options for gearwheel pairing, in particular the possible diameters of the gearwheels, are improved. 
         [0006]    This objective is achieved by a powershift transmission of the type concerned which also embodies the characteristics specified in the principal claim. 
         [0007]    According to the invention, the transmission shaft for the drive input of the front wheels is decoupled from the transmission shaft with the clutch for the second gear. Thus, the transmission shaft with the clutch for the second gear drives either only the rear wheels of the vehicle, or is only used as a transmission shaft without a drive output shaft for the front wheels or the rear wheels. In this way either the transmission shaft for driving the front wheels can be made as a separate transmission shaft provided with a cut-off clutch, or the separate transmission shaft for driving the rear wheels is at the same time used as the transmission shaft for driving the front wheels. This provides much more freedom for designing the transmission ratios. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Further characteristics emerge from the description of the figures, which show: 
           [0009]      FIG. 1 : A powershift transmission according to the invention, with six forward gears and three reversing gears and a transmission shaft, which acts at the same time as the drive output shaft for driving the front wheels and as the device shaft for driving the rear wheels; 
           [0010]      FIG. 2 : An arrangement of the wheels of the powershift transmission shown in  FIG. 1 ; 
           [0011]      FIG. 3 : A powershift transmission with six forward gears and three reverse gears, with a transmission shaft that acts as the drive output shaft for driving the front wheels, and with a cut-off clutch; 
           [0012]      FIG. 4 : An arrangement of the wheels of the powershift transmission shown in  FIG. 3 ; 
           [0013]      FIG. 5 : A powershift transmission with three forward gears and three reverse gears, with a transmission shaft that acts as the drive output shaft for the front wheels and for the rear wheels; 
           [0014]      FIG. 6 : The arrangement of the wheels of the powershift transmission shown in  FIG. 5 ; 
           [0015]      FIG. 7 : A powershift transmission with three forward gears and three reverse gears, with a transmission shaft for driving the front wheels, and with a cut-off clutch; and 
           [0016]      FIG. 8 : The arrangement of the wheels of the powershift transmission shown in  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]      FIG. 1 : 
         [0018]    By way of the hydrodynamic torque converter  1  a drive motor (not shown), for example a Diesel engine, drives the transmission shaft  2 , which is also referred to as the input shaft. The transmission shaft  2  is connected to the fixed wheels  3 , “fixed wheel” meaning that the gearwheel is connected to the shaft in a rotationally fixed manner. The loose wheel  4  can be connected to the transmission shaft  2  by means of the clutch  5  for driving in reverse. “Loose wheel” means that the gearwheel is mounted and able to rotate on the transmission shaft. The auxiliary power take-off shaft  6  passes through the transmission shaft  2  and is not referred to as a transmission shaft. The power take-off shaft  6  is provided for driving an auxiliary drive output, for example a hydraulic pump, and is connected directly to the drive motor. The fixed wheel  3  meshes with the fixed wheel  7 , which is connected in a rotationally fixed manner to the transmission shaft  8 . The loose wheel  9  can be connected to the transmission shaft  8  by means of the clutch for forward driving. The loose wheel  9  meshes with the fixed wheel  11  and the fixed wheel  12  meshes with the loose wheel  13 . The fixed wheel  12  is connected rotationally fixed to the transmission shaft  8  and the loose wheel  13  can be connected to the transmission shaft  15  by means of the clutch  14  for the fourth gear. The fixed wheel  11  is connected rotationally fixed to the transmission shaft  15 . The fixed wheel  16  meshes with the fixed wheel  11  and is connected rotationally fixed to the transmission shaft  17 . By means of the clutch  18  for the first gear the loose wheel  19  can be connected to the transmission shaft  17 . By means of the clutch  20  for the second gear the loose wheel  21  can be connected to the transmission shaft  22 . The loose wheel  21  meshes with the fixed wheel  16  and the fixed wheel  23  meshes with the loose wheel  19 . The fixed wheel  23  is connected in a rotationally fixed manner to the transmission shaft  22  and the fixed wheel  24  is also connected in a rotationally fixed manner to the transmission shaft  22 . The fixed wheel  24  meshes with the loose wheel  25 , and the loose wheel  25  can be connected by means of the clutch  26  for the third gear to the transmission shaft  27 . The fixed wheel  28  is connected rotationally fixed to the transmission shaft  27  and meshes with the loose wheel  21 . The loose wheel  25  meshes with the fixed wheel  29 , the fixed wheel  29  being connected rotationally fixed to the transmission shaft  30  which forms on the one hand the drive output for the rear wheel  31  and at the same time also the drive output for the front wheel  32 . 
         [0019]      FIG. 2 : 
         [0020]    By virtue of the arrangement of the transmission shafts, the fixed wheel  29  can rotate about the loose wheel  25  and the loose wheel  25  can rotate about the fixed wheel  24 . In this way the axial distance can be maintained even if the gearwheels have different diameters. With the arrangement shown in  FIGS. 1 and 2 , six gears in the forward travel direction and three gears in the reversing travel direction can be engaged. 
         [0021]      FIG. 3 : 
         [0022]    The structure of the powershift transmission in  FIG. 3  is identical to the structure of the powershift transmission according to  FIG. 1 , as far as the drive output to the rear wheel  31 , which is not arranged on the transmission shaft  30  but instead on the transmission shaft  22 . It is true that the drive output to the front wheel  32  is arranged on the transmission shaft  30 , but the loose wheel  25  meshes with a loose wheel  33  which can be connected to the transmission shaft  30  by means of the cut-off clutch  34 . With this arrangement six gears in the forward travel direction and three gears in the reversing direction can again be obtained. 
         [0023]      FIG. 4 : 
         [0024]    The arrangement of the wheels shown in  FIG. 4  is identical to the wheel arrangement shown in  FIG. 2 . 
         [0025]      FIG. 5 : 
         [0026]    The arrangement shown in  FIG. 5  is identical to that shown in  FIG. 1 , except that in  FIG. 5  the clutch  14  for the fourth gear and the loose wheel  13  are not present. As a result, in this powershift transmission three gears in the forward direction and three reversing gears can be engaged. 
         [0027]    
       FIG. 6 
     
         [0028]    The arrangement of the wheels shown in  FIG. 6  is identical to the wheel arrangement shown in  FIG. 2 . 
         [0029]      FIG. 7 : 
         [0030]    The powershift transmission according to  FIG. 7  is identical to the powershift transmission shown in  FIG. 3 , except in that in the powershift transmission according to  FIG. 7  the clutch  14  for the fourth gear and the loose wheel  13  are not present. This gives a powershift transmission with three forward and three reversing gears. 
         [0031]      FIG. 8 : 
         [0032]    The arrangement of the wheels shown in  FIG. 8  is identical to the wheel arrangement shown in  FIG. 2 . 
       INDEXES 
       [0000]    
       
           1  Hydrodynamic torque converter 
           2  Transmission shaft 
           3  Fixed wheel 
           4  Loose wheel 
           5  Clutch for driving in reverse 
           6  Auxiliary power takeoff shaft 
           7  Fixed wheel 
           8  Transmission shaft 
           9  Loose wheel 
           10  Clutch for forward driving 
           11  Fixed wheel 
           12  Fixed wheel 
           13  Loose wheel 
           14  Clutch for the fourth gear 
           15  Transmission shaft 
           16  Fixed wheel 
           17  Transmission shaft 
           18  Clutch for the first gear 
           19  Loose wheel 
           20  Clutch for the second gear 
           21  Loose wheel 
           22  Transmission shaft 
           23  Fixed wheel 
           24  Fixed wheel 
           25  Loose wheel 
           26  Clutch for the third gear 
           27  Transmission shaft 
           28  Fixed wheel 
           29  Fixed wheel 
           30  Transmission shaft 
           31  Drive output to the rear wheel 
           32  Drive output to the front wheel 
           33  Loose wheel 
           34  Cut-off clutch