Abstract:
The invention relates to a gear shifting device ( 118 ) for connecting parts of a transmission ( 102 ) rotation at different rotational speeds with at least one auxiliary unit, the gear shifting device ( 118 ) being-actuated by a control fluid. For each auxiliary unit one unit is provided in which valves ( 4, 5, 6, 7 ), shift cylinder ( 1 ), piston ( 2 ) and gear shift elements ( 2 A) are comprised. The gear shifting device ( 118 ) is actuated by electrically controlled, pulsed 2/2-way valves ( 4, 5, 6, 7 ) and is connected to a displacement measuring device ( 3 ) whose signals can be transmitted to the 2/2-way valves ( 4, 5, 6, 7 ). The signals are used to control the 2/2-way valves ( 4, 5, 6, 7 ) according to the position of the piston ( 2 ) which is detected by the displacement measuring device ( 3 ) with respect to the shift cylinder ( 1 ).

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a gear shifting device for a multi-ratio gear-changing transmission. 
     The problem on which this invention is based is to provide a gear shifting device which makes variable synchronizing times and short gear shifting times possible. 
     The problem is solved with a gear shifting device with the disclosed of claim  1 . 
     SUMMARY OF THE INVENTION 
     For each auxiliary unit of the gear-changing transmission, it is proposed that the unit be comprised of valves, shift cylinders, pistons and gear-shifting elements. Pulsed 2/2-way valves are used as release valves. At the same time, a displacement measuring device is used which indicates the actual position of the piston in relation to the shift cylinder. 
     When engaging the gear wheels in a torque-transmitting connection, it is possible to adapt shift force with the shift time. The adaptation preferably consists of the valves being loaded at a higher frequency when engaging the connection than when disengaging. 
     In another advantageous development, the pulse frequency of the 2/2-way valves provided when shifting gear on level ground is different from the pulse frequency when shifting gear on non-level ground, i.e. on uphill and downhill gradients. The pulse frequency when shifting gear on level ground is advantageously lower than on a non-level road. 
     In another advantageous development, the pulsed valve is operated with a voltage which amounts to a multiple of the standard voltage. 
     The displacement measuring device is preferably situated within the shift cylinder, but it can also be provided in a position outside the shift cylinder where it is connected with the movable part of the unit. 
     In another advantageous development, the piston of the auxiliary unit is placed upon a piston rod upon which it is axially movable. Upon the piston rod is provided the pistons of the gear shift units of several auxiliary units without hindering each other. The units are preferably disposed in one row for the auxiliary unit concerned. 
     In another advantageous development, several gear shift units, of which each gear shift unit belongs to an auxiliary unit, are comprised in one part. The part can be assembled separately from the transmission and then adapted and attached to the transmission as a unit. This also makes separate production possible, and testing of a complete gear shifting device independent of the transmission type involved. 
     In another advantageous development, the shift units have stops which dampen the impact of the piston on the edges of the shift cylinders. The stops can be provided within the shift cylinder or also outside on a part of the shift units connected with the piston. 
     Contrary to already known gear shifting devices, this whole gear shifting device sits in the immediate proximity of the auxiliary unit. An auxiliary unit is preferably formed of two gear wheels which are disposed side by side in the transmission and can be alternately engaged in the torque transmission. An auxiliary unit, however, can also consist of only one gear wheel engageable in the torque transmission when, e.g. two opposite gear wheels do not have to be engaged when shifting gear to a reverse gear ratio. 
     By virtue of a compact unit arrangement, it is also possible to eliminate connecting elements between gear shift elements, preferably formed of shift forks or shift levers, and the shift cylinders and shift pistons. As already mentioned, in such connecting elements shift rods are essentially made of steel which to a great extent contributes to the total weight of the transmission. The reaction times between a command to trigger a gear shift and the movement of the shift element is clearly abbreviated by the elimination of the bulky shift rods to be moved. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is explained in detail with reference to drawings which show: 
     FIG. 1 is transmission with gear shifting devices; 
     FIG. 2 is an arrangement of gear shifting devices in a row; and 
     FIG. 3 is a representation of a gear shifting device. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a diagrammatic representation of a transmission  102  in a vehicle (not shown here). The transmission  102  has a clutch bell housing  104 , a main gear  106  and an auxiliary gear  108 , in addition, an input shaft  110  and an output shaft  112  with output flange  114 . A component  116  is provided on the main gear  106 . In the arrangement (shown here) the component  116  has three separate gear shifting devices  118 ,  120  and  122 . The gear shifting device  118 , shown by way of example, engages with a shift fork  124  in a sliding sleeve  126  which is axially displaceable along a shaft  128  and non-rotatably connected with the shaft  128 . As a result of a displacement, the sliding sleeve  126  can be connected either with the gear wheel  130  or the gear wheel  132  to form a torque transmission. The gear shifting devices  118 ,  120  and  122  are connected, via electric lines  134 , with a control device  136  such as an electronic transmission computer or vehicle master. The gear shifting devices  118 ,  120  and  122  are likewise connected, via lines  140 , with a supply device  138  for an actuation fluid. 
     FIG. 2 shows a segment of the housing of transmission  102 , where in one part  116 , the gear shifting devices  118 ,  120  and  122 , are comprised. The component  116  is fastened on the transmission  102  by means of connecting elements  144 . Line  140  for feeding the actuation fluid and electric lines  134  for connection with the control device  136  lead to the gear shifting devices  118 ,  120  and  122 . 
     FIG. 3 shows a basic representation of a gear shifting device  118  for an automatic transmission in vehicles, with a displacement measuring device and pulse sensitive directional valves in the longitudinal section, which has a shift cylinder  1 , formed by two cylinder parts  1 A and  1 B, and one piston  2 . 
     By virtue of the configuration of the shift cylinder  1  with two separate cylinder parts  1 A and  1 B, the weight moved can be considerably reduced. 
     In the embodiment shown, piston  2 , designed as a shift element, moves between the fixed cylinder parts  1 A and  1 B. 
     The piston  2  is designed in one piece with a shift fork  2 A so connecting elements between the piston  2  and another shift element, such as shift fork  2 A or a possible shift lever, are not needed. The connection between piston  2  and shift fork  2 A is thus sturdy and formed with the shortest path. 
     In the same manner in another embodiment (not shown), it is possible that cylinder parts  1 A and  1 B be connected with the shift fork  2 A, such that cylinder parts  1 A and  1 B move relative to shift piston  2 . 
     As a result of the structurally advantageous design of shift cylinder  1 , namely, a design divided in two parts  1 A and  1 B, the parts  1 A and  1 B thus can also serve as shift elements whereby a variable transmission configuration is possible. 
     To detect the position of piston  2  in shift cylinder  1  or between the cylinder parts  1 A and  1 B, according to FIG. 3, in parallel with the displacement axis of piston  2 , a displacement measuring device  3  is attached, e.g. inductive path sensors connected with a control device  36 , which, depending on the position of piston  2 , detected by the inductive path sensors, relay electronic control signals to pulse-sensitive valves  4 ,  5 ,  6  and  7 . 
     The piston  2  has a guide shoulder  2 B by which it is guided in a recess  8  formed on each of the cylinder parts  1 A and  1 B. Both cylinder parts  1 A and  1 B and the piston  2  are arranged around a rail  9  which extends axially through the cylinder parts  1 A and  1 B and the piston  2 , in the direction of movement of piston  2 . 
     The arrangement of the cylinder parts  1 A and  1 B and of the piston  2  upon the rail  9  is beneficial mainly in the sense that a series of shift cylinders can thereby be easily arranged in a small space, the reduced number of parts and the easy assembly result in a decisive cost advantage. In principle, the controls for all the gear shifting devices of a transmission can be fitted upon rail  9 . 
     Referring to FIG. 3, the cylinder parts  1 A and  1 B are fitted firmly, pre-assembled upon rail  9 , but they obviously can be fixed in assembled state, depending on the tolerances of the transmission. 
     To shift piston  2  in shift cylinder  1 , a pneumatic or hydraulic pressure is fed to the gear shifting device from an external source  138 , via the pressure lines  10  and  11 . In each pressure line  10  and  11 , two electromagnetic 2/2-way valves, respectively  4 ,  5  and  6 ,  7 , are interposed, which control the through flow of the pressure medium through pressure lines  10  and  11  in such a manner that the piston  2  moves at a speed corresponding to an optimal speed found empirically or via simulation of the path position. The control mode of the valves can be adapted specifically to the transmission depending on the weights to be shifted. 
     The pulse-sensitive valves  4 ,  5 ,  6  and  7  are designed for continuous operation at 4 volts, but are operated here by 24 volt pulses. By controlling the pulse valves  4 ,  5 ,  6  and  7  with strong current pulses, they react very quickly. The pulse valves  4 ,  5 ,  6  and  7  are controlled in shift cylinder  1 , depending on the position of piston  2 , which has been detected by the displacement measurement device  3  via the control device  136 . According to the position of piston  2 , different electric pulses are delivered to the pulse valves  4 ,  5 ,  6  and  7 , the pulse valves opening with a predefined low pulse frequency. Thus the through flow of pressure medium changes during a gear shifting operation in shift cylinder  1 , which sets piston  2  in shift cylinder  1  in motion and thus also changes the speed of piston  2 . The control of the pulse valves  4 ,  5 ,  6  and  7  is designed so that all pulse-sensitive valves can be controlled separately, against each other, or jointly, thereby resulting in different piston speeds and also different dynamic forces. 
     In this manner, the piston speed of each two pulse-sensitive 2/2-way valves is changed so that the piston is moved with as full a pressure force as possible during the shift stroke, up to the beginning of transmission synchronization, and after termination of the synchronization phase is brought to its low speed end position. 
     To illustrate the operation of the gear shifting device, a gear shifting cycle is described below in principle. 
     In one gear shifting operation, if pressure medium is fed through line  10  of the gear shifting device, pulse valve  5 , which has the function of a feed valve, opens, while pulse valve  4 , designed as a drain valve, is closed. Thus, the pressure medium reaches line  10  through cylinder part  1 A into the working chamber  12  of piston  2  and moves piston  2  from one stop surface  13  on cylinder part  1 A in the direction of stop surface  14  in the cylinder part  1 B lying opposite stop surface  13 . 
     At the start of the transmission synchronization phase, shortly before striking the stop surface  14 , piston  2  remains in its locked position wherein the pressure load of piston  2  considerably increases by further feeding of pressure medium through line  10 . 
     The part of piston working chamber  12 , lying in the direction of motion of piston  2 , is relaxed during the whole gear shifting operation, via pressure line  11 , and the open pulse valve  6 , which is designed as a drain valve. The same time. 
     At the termination of the synchronization operation, piston  2  is unlocked whereby it is again set in motion in the direction of its end position on stop surface  14 , which it does at higher speed due to the high pressure load during the synchronization operation. At the same time, the existing position of piston  2  is detected by the displacement measuring device  3  which controls the pulse valves  6  and  7 , via electric pulses, in a manner such that the pulse valve  6 , serving as a vent, is closed which results in a so-called cushion of pressure medium drastically reducing the movement of piston  2  on the last portion of the short path toward stop surface  14 . The pressure supply via pulse valve  5  to pressure line  10  has already been adjusted during or toward the end of the brief stoppage of piston  2  during the synchronization phase of the transmission, by the closing of feed valve  5 . In order to bring piston  2  to its end position, in spite of the pressure medium cushion between piston  2  and stop surface  14 , the pulse valve  6  is shifted to an open position by the displacement measuring device  3  immediately before the piston  2  strikes stop surface  14  so that the pressure medium located between piston  2  and stop surface  14  can escape via the pressure line  11  and piston  2 , will not spring back when striking stop surface  14 . 
     When reversing, the same shift sequence is in the same inverse direction wherein pulse valves  5  and  6  are closed, the gear shifting device is pressure loaded via the pressure line  11  and open pulse valve  7 , and relaxed via open pulse valve  4  and pressure line  10 . 
     In the gear shifting device proposed, a variation of the synchronization times is possible by the electronically controlling the pulsed valves. Thus, different synchronization processes for gear shifts can be carried out on level ground, in downhill gradients and in uphill gradients. During gear shifts on level ground, the synchronization devices can be operated with maximum care. In downhill gradients, the synchronization devices can be loaded with a high pulse frequency and can be utilized up to a maximum load, which can lead to brief safer shifting times. Because of the variability of shifting or synchronizing forces, shifting speeds can be optimized. If the vehicle is also provided with a calculated vehicle weight, the results of the calculation can be included in the control of the pulse frequency. Thus, the synchronization time can be adapted according to the vehicle weight and a further optimization of shift time and careful treatment of the synchronization can be achieved. 
     To prevent gear shifts in a tooth-on-tooth position of the connecting gears, a monitor of such a position can be provided. When such a case is detected, the synchronization force is minimized in order to obtain a drag torque in the synchronization whereby the tooth-on-tooth position is removed. 
     When controlling the valves, care must be taken that they are not overloaded. An overload could be generated due to a continuous pulse or to short pauses between the pulses. 
     
       
         
               
             
               
               
               
               
             
           
               
                   
               
               
                 Reference numerals 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                  1 
                 shift cylinder 
                 106 
                 main gear 
               
               
                  1A 
                 cylinder part 
                 108 
                 auxiliary gear 
               
               
                  1B 
                 cylinder part 
                 110 
                 input shaft 
               
               
                  2 
                 piston 
                 112 
                 output shaft 
               
               
                  2A 
                 shift fork 
                 114 
                 output flange 
               
               
                  2B 
                 guide shoulder 
                 116 
                 gear shifting device 
               
               
                  3 
                 displacement measuring device 
                 118 
                 gear shifting device 
               
               
                  4 
                 pulse-sensitive valve 
                 120 
                 gear shifting device 
               
               
                  5 
                 pulse-sensitive valve 
                 122 
                 gear shifting device 
               
               
                  6 
                 pulse-sensitive valve 
                 124 
                 shift fork 
               
               
                  7 
                 pulse-sensitive valve 
                 126 
                 sliding sleeve 
               
               
                  8 
                 recess 
                 128 
                 shaft 
               
               
                  9 
                 guide rail 
                 130 
                 gear wheel 
               
               
                  10 
                 pressure line 
                 132 
                 gear wheel 
               
               
                  11 
                 pressure line 
                 134 
                 line 
               
               
                  12 
                 working chamber of the piston 
                 136 
                 control device 
               
               
                  13 
                 stop surface 
                 138 
                 pressure source 
               
               
                  14 
                 stop surface 
                 140 
                 line 
               
               
                 102 
                 transmission 
                 144 
                 connecting element 
               
               
                 104 
                 clutch bell