Abstract:
A transmission shift device for a transmission having a range group transmission and a shift lever with a superimposed H-shaped shift pattern in which a shift and selector shaft is operatively connected at one end with the shift lever and at the other end with a shift mechanism. A blocking device, which is actuated by, prevents or makes inadvertent transmission gear shifts in a range group detectable to the driver so that the shift and selector shaft is independently shiftable from a first shift gate to a shift gate of the next two lower gears. The transmission shift device prevents undesired incorrect gearshifts in a range group shift as well as making it possible to downshift across several gearsets by making the force of displacing the shift and selector shaft changeable over the regulated distance to the shift gear of the next lower gears.

Description:
This application is a national stage completion of PCT/EP2006/009905 filed Oct. 13, 2006, which claims priority from German Application Serial No. 10 2005 051 377.8 filed Oct. 27, 2005. 
     FIELD OF THE INVENTION 
     The invention concerns a transmission shift device. 
     BACKGROUND OF THE INVENTION 
     Transmissions of large industrial vehicles are usually divided into a main transmission, a splitter group transmission and a range transmission. At the same time, these transmissions have a shifting device supported by pneumatic circuit conducts pneumatic gearshifts in the splitter group transmission and in the range transmission while, at the same time, the gearshifts in the main transmission are manually carried out by the driver being supported by the pneumatic circuit in the force to be exerted. 
     Electronic devices are used to a greater extent for control of motor vehicle transmissions used today. These arrangements serve, together with other ends, also prevent, in the transmission, gearshifts that are not admissible due to other conditions, in particular to high vehicle speeds calculated on the gear intended to be shifted. 
     Such a pneumatic shift device with mechanisms for protecting against incorrect actuation has become known from DE-OS 24 47 860. The described device has different elements dispersed throughout the whole transmission so that, between the individual pneumatic elements, complicated branching air pressure lines are needed and a multiplicity of electric lines of individual elements for the electronic control device have to be laid. The parts comprise a main shut-off valve for the pneumatics and a gate blocking cylinder. 
     The pneumatic switch of a group transmission is triggered by a pneumatic valve on the shift lever. In certain cases, the result of this is that the driver, despite an activated gate block, can select the incorrect gate since the pressure build up in the gate block cylinder occurs too slowly due to the line lengths. 
     Besides, German patent applications DE 100 29 497 A1 and DE 100 29 527 A1 have disclosed an electro-pneumatic shift unit for a vehicle transmission having a pneumatically shifted range group transmission whose gearshifts can be preselected manually on a shift lever by the driver. The shift unit comprises a blocking device for mechanically preventing the manual gearshift of inadmissible gear ratios of the vehicle transmission and a device for preventing the pneumatic gearshift of inadmissible gear ratios of the vehicle transmission. The blocking device for mechanically preventing the manual gearshift and the device for preventing the pneumatic gearshift are controlled by a common control device. 
     The shift unit is now designed so as to result in preventing an undesired direct change from the shift gate for the gears five and six of the gear group of high gears to the shift gate lying in the same location for the gears one and two of the gear group of lower gears. For the purpose, in a preselected change from the gear group for higher gears to the gear group for lower gears, the shift shaft is then automatically moved by the blocking device by way of a recoil force produced in the shift gate of the gears three and four when the transmission shift lever, after the range group change preselection, has been brought to its neutral position. 
     A ramp built in the shift shaft and axially extending there with constant axial gradient services, during interaction with a pin of the blocking device engaging there, for the purpose that in the operating situation described, the shift shaft is autonomously pushed with constant force to the gate for the third and fourth gears. The blocking device and particularly the ramp in the shift shaft are constructed and synchronized with each other so that the driver, when needed, can overpress the recoil force applied by the blocking device together with the ramp. Thereby a downshift is determined by need with gear group change, for example, from the fifth gear to the second gear. 
     Although the already known electro-pneumatic shift unit has a few advantages, it is of comparatively complex construction. Besides, the shift unit is associated with a technical problem that the blocking force with which the shift shaft is held in the gate for the third and fourth gears must be relatively great in order that the driver, via the increased control force to be applied by him in a shift lever actuation, is reliably signalized that a group change has taken place when an incorrect gearshift is to be prevented. 
     In a transmission shift device, between the shift lever and the connecting means of the transmission, since there are some parts to be moved, their bearing friction on other parts caused by motion, the same as the gate blocking force, take care in the extreme case that despite the control force of the driver on the shift lever, the gate blocking described cannot be overpressed. 
     Therefore, the instant invention is based on the problem of providing a shift device for a generic transmission which is of simple construction and reliably prevents incorrect gearshifts between ratio groups of the range group transmission by way of a blocking device, the same as makes possible an emergency downshift across the range group of the transmission from a very high gear to a very low gear. 
     SUMMARY OF THE INVENTION 
     Accordingly, the invention relates to a shift device for a range group transmission and a shift lever having a superimposed H-shaped shift pattern in which a shift and selector shaft is operatively connected at one end with the shift lever and at the other end with a transmission-side shift mechanism, such as shift rails and/or shift rockers. In addition, the transmission shift device has a blocking device which is actuatable by a pressure medium and prevents, or at least makes noticeable, the unintended activation of transmission gears in a range group change so that the shift and selector shaft in a range group change independently, i.e., without influence by the driver and is displaceable from one shift gate to the shift gate of the next two lower gears. 
     This transmission shift device is additionally constructed for preventing undesired incorrect gearshifts in a range group change, as well as for making it possible in an emergency to downshift across several gear steps so that the shift and selector shaft is displaceable from a shift gate with a force variable over the regulating distance to the shift gate of the next lower gears. 
     This transmission device is associated with several advantages. In the first place, it effectively prevents that, in case of a range group change in the transmission preselected by the driver, triggering inadvertent downshifts which undesiredly surpass several, in any case more than three, gear steps. This occurs by the fact that the shift and selector shaft, after the range group change preselected by the driver and after reaching the neutral position of the shift and selector lever without the driver&#39;s influence and controlled by the actuator, is led to the shift gate of the immediately next lower gears. The controlling force with which the shift and selector lever or the shift lever is pushed to the shift gate is initially great and decreases in direction to the last mentioned shift gate. Thereby the adjusting motion occurs at the start quicker than at the end whereby the danger area for an undesired gearshift is quickly abandoned. 
     On the other hand, in emergency situations, the driver still can effect a downshift across several gears, for example, from the sixth gear to the first gear, should he deem this convenient. To do so, he has to overcome only the adjusting force of the blocking device. At first, this is easy and increasingly becomes more difficult on account of the opposite set direction. Thereby the driver is unmistakably signaled that he will carry out an at least unusual downshift. 
     it is provided, according to a preferred embodiment of the invention, that the variable forces F 1  to F 2 , automatically acting on the shift and selector shaft, consist of a static basic force F K  produced by a piston-cylinder arrangement and which, changed by a lever system regarding its amount and its effective direction, is transmitted to the shift and selector shaft. 
     To produce the static basic force F K , it is preferably provided that the piston-cylinder arrangement comprises one cylinder and one axially slideable locking piston located therein. The cylinder has also a bore for conducting gas as pressure means. The pressure chamber of the cylinder is loaded, via a bore, with the unmodulated main pressure of a related pressure means system which, during operation of the vehicle, is steady and unregulated. 
     In one other embodiment of the invention, the blocking piston has an adjusting bolt projecting out of the cylinder and a front side acting upon a stop pawl that is supported to rotate about a rotation point. The stop pawl serves for the deflection and variation according to magnitude of the static basic force produced by the piston-cylinder arrangement in the variable controlling force across the regulating distance of the shift and selector shaft. 
     To solve this problem, a lock pawl is provided that has a first lever arm and a second lever arm. The first lever arm is in contact with the shift and selector shaft and the second lever arm interacts with the front side of the adjusting bolt of the blocking piston. 
     To be able to implement a mechanically reliable contact between the lock pawl and the shift and selector shaft, it is preferably provided that the shift and selector shaft has in the contact area with the first lever arm of the lock pawl a shift collar on which the first lever arm axially engages. 
     Upon the shift and selector shaft, to produce the desired control force variable over the regulated distance, in addition, it is provided that the second lever arm has a special arm geometry on its side facing the blocking piston which, during axial displacement of the blocking piston or a deviation of the lock pawl, produces lever arm lengths of different effectiveness. 
     According to another alternative, this active principle is reversed so that the front side of the adjusting bolt has a geometry which, when interacting with the second lever arm of the lock pawl during an axial displacement of the blocking piston or a deviation of the lock pawl produces lever arm lengths of different effect. 
     The lever arm lengths of different effect modulate or change the static basic force F K  produced by the piston-cylinder arrangement into a controlling force F 1  to F 2  changeable via the angle of avertence or the regulating distance of the shift and selector shaft. At the same time, at the beginning of the control movement there acts a relatively strong control force F 1  which, in direction to the shift gate, to be autonomously moved along as desired, diminishes to a control force F 2 . 
     A specially compact construction of this transmission shift device provides that the shift and selector shaft be located in a housing; that the shift collar of the shift and selector shaft be built in the area of a chamber of the housing; that the lock pawl be tiltably located on the housing in the area of the chamber; that the control bolt of the blocking piston projects axially into the chamber, and that the cylinder be a component part of the housing or be fastened thereon. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described, by way of example, with reference to the accompanying drawings in which: 
         FIG. 1  is a diagrammatic representation of a drivetrain of an industrial vehicle; 
         FIG. 2  is a shift lever of the transmission shift device, according to  FIG. 1 ; 
         FIG. 3  is a shift diagram for the shift lever, according to  FIG. 2 ; 
         FIG. 4  is a diagrammatic cross-sectional view of an inventive transmission shift device with a blocking device in a first actuation position, and 
         FIG. 5  is a transmission shift device, according to  FIG. 3 , in a second actuation position. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Accordingly,  FIG. 1  shows a motor vehicle  2  with a prime mover  4 , a transmission  6  and a clutch  8  situated therebetween. The transmission  6  has a main transmission  10 , a splitter group transmission  12  and a range group transmission  14 . The main transmission  10  is manually shifted by the driver, via a shift lever  16 . For this purpose, the shift lever  16  is operatively connected via a shift and selector shaft  32  and a transmission shift device  30  with a transmission-side gearshift mechanism (not shown). The transmission shift device  30  also comprises blocking means which prevents undesired gearshift operations and/or make them detectable to the driver at least during a shift lever side gearshift operation. The shift lever  16  can also be connected with the transmission shift device  30 , via pneumatic lines (not shown). As a whole, the transmission  6  is connected with an electronic control device  20 , via electric connecting lines  18 , and the shift lever, via electric connecting lines  26 . 
       FIG. 2  shows an enlarged representation of the shift  16  for the transmission  6 , according to  FIG. 1 , which is actuatable in conformity with a shift pattern  28 , according to  FIG. 3 . The shift pattern  28  is designated as a “superimposed H” since the terminal positions of the respective H-legs of two H-shift diagrams in an H-shift diagram GP-L the slow gear positions and in an H-shift diagram GP-S the quick gear positions of the shift lever are superimposed. Thereby the gearshift positions G 1  and G 5  for the first gear (the same as for the fifth gear); G 2  and G 6  for the second gear (the same as for the sixth gear); G 3  and G 7  for the third gear (the same as for the seventh gear), and G 4  and G 8  for the fourth gear and the eighth gear, respectively, on the same place of a shift lever deflection. 
     Laterally, a toggle switch  22  is located on the shift lever  16  for preselecting or for triggering the gearshift of the splitter group transmission  12 . On the front side of the shift lever  16  is one other toggle switch  24  by way of which the range group transmission  14  is preselected or switched. Both toggle switches  22  and  24  are electric switches connected to the control device  20 , via at least one electric connecting line  26 . 
     In a gearshift of the shift lever  16 , according to the shift pattern  28 , as explained regarding the forward gears, two ratio steps are coordinated with each terminal position of the shift lever  16 , which differ by the ratio jump of the range group transmission  14 . In the “slow” position of the toggle switch  24 , the shift positions G 1  and G 4  of the H-shift diagram GP-L, as well as the downshift gear RG can be obtained by the driver for manually disengagement and/or carrying out of shift operations. In the “quick” toggle switch position, these are the gears G 5  to G 8  of the H-shift diagram GP-S. In this embodiment, a neutral position N of the shift lever  16  is in the shift gate position G 1 / 2  between the shift positions for gears G 1  and G 2 . 
     The driver has to preselect a change between the two ratio or gear groups of the range group transmission  14  by way of the toggle switch  24  on the shift lever  16 . The change is carried out as soon as the shift lever  16  is manually adjusted to the neutral position N and this is also accomplished in the main transmission  10 . 
     The splitter group transmission  12  is preselected in position “L” or “S” with the toggle switch  22  on the side of the shift lever  16  and is shifted by actuating the clutch  8  (see the single arrow to the right, next to the shift lever  16 ). 
     As has already been said, the driver has to preselect the change of the range group transmission  14  by way of the toggle switch  24  on the shift lever  16 . The change is then carried out as soon as it has been manually shifted to the neutral position N in the main transmission  10 . Additional safeguarding steps must be found to prevent inadvertent gearshifts. A group blockage related to this therefore suppresses shifting of the range group transmission  14  to the slow ratio, thereby protecting both synchronization of the range group transmission  14  and synchronization of the main transmission  10 . 
       FIGS. 3 and 4  show the transmission shifting device  30  for the transmission  6  and the shift lever  16  with the superposed H-shift pattern  28  in diagrammatic sectional representations. The shift and selector shaft  32  are respectively to be detected which, in these representations, are connected at the left via an interface  34  with the transmission shift lever  16  and at their opposite end with the shift actuation on the transmission side. 
     The shift and selector shaft  32  is axially slidably supported in a housing  56  of the transmission shift device  20  which has a chamber  60 . In the area of the chamber  60 , the shift and selector shaft  32  has a radial shift collar  36  available which engages a lock pawl  38  tiltably supported around a rotation point  40  with a first lever arm  42 . The lock pawl  30  has a second lever arm  44  contiguous to the first lever arm  42 , which can be biased by an adjusting bolt  46  of a blocking piston  48  with a basic force F K . The blocking piston  48  is axially slidably located in a cylinder  50  of a piston-cylinder arrangement whose pressure space  54  can be pressurized with pressure means via a bore  52  in the cylinder  50 . 
     While the front side end of the adjusting bolt  46  of the blocking piston  48  is designed as a flat surface, the second lever arm  44  has a particular lever arm geometry  58  in the contact area with the adjusting bolt  46  which causes a lever arm length B, operative on the second lever arm  44 , to change, depending on the axial position of the blocking piston  48  or on the rotation angle of the lock pawl  38  around the point of rotation  40 . As a result of this constructional assembly, when the blocking piston  48  is actuated, the lock pawl  38 , with its first lever arm  42 , acts with controlling forces of a different magnitude F 1  to F 2  on the shift collar  36  of the shift and selector shaft  32 . 
     The invention also comprises structural alternatives in which the front side of the adjusting bolt  46  and/or the lever arm geometry  58  of the second lever arm  44  are designed of different shapes, but likewise exert adjusting forces of different magnitudes on the shift and selector shaft  32 , via the regulating distance. According to such an alternative given by way of example, both the second lever arm  44  and the front side of the adjusting bolt  46  have curved contact surfaces coordinated with each other. 
     In the examples shown in  FIGS. 4 and 5 , the lever arm geometry  58  of the second lever arm  44  is now selected so that in a first piston position ( FIG. 4 ) the force F 1 , acting upon the shift and selector shaft  32  in direction to the shift lever  16 , is comparatively great due to the effective lever length B on the second lever arm  44  and in another axial displacement of the blocking piston  48  in the cylinder  50  in direction to the lock pawl  38  decreases to a force F 2  to an effective lever arm length A ( FIG. 5 ). 
     By a skillful geometric design of the lock pawl  38  or of the lever arm lengths and contact geometries thereof, under the basic force F K , preset by the piston-cylinder arrangement  48 ,  50 , the forces F 1  to F 2 , acting on the shift and selector shaft  32 , can be adjusted in broad scopes, as needed. 
     The manner of operation of this transmission shift device  30  is explained in detail herebelow. 
     In an initial situation, according to  FIG. 4 , the sixth gear G 6  is activated in the transmission. The driver now intends a downshift to the third gear G 3 . Since the third gear G 3  can only be obtained via a range group change, the driver first actuates the toggle switch  24  on the shift lever  16  for preselecting the range group change. As soon as the shift lever  16  is shifted by the driver toward the neutral position N, which is mechanically accomplished in the main transmission  10 , the control device  20  produces, inside the transmission under actuator control, a range group change in the range group transmission  14  in which a first ratio step is disconnected and a second ratio step connected. 
     To prevent an undesired gear being activated, the pressure means in the pressure space  54  of the cylinder  50  acts in the gate blocking device upon the blocking piston  48  in a manner such that its adjusting bolt  46  presses upon the second lever arm  44  of the lock pawl  38  with a basic force F K . On account of the lever length B, which is greatly operative in this position, to start an adjustment motion of the first lever arm  42  of the lock pawl  38  a relatively great shifting force F 1  is pressed upon the shift and selector shaft  32 . 
     From the shift position G 1 / 2 , which corresponds to the neutral position N in the shift gate for the first gear G 1  and the second gear G 2 , the shift and selector shaft  32  is pressed with a force diminishing over the regulated distance into the selector gate up to the shift position G 314 . The shift position G 3 / 4  corresponds to the neutral position of the shift gate for the gears G 3  and G 4 . Here only a shift force F 2  acts upon the shift and selector shaft  32  which, on account of the slight operative lever length A, is detectably less than the initial shift force F 1 . 
     If the driver now moves the shift lever  16  in the direction toward the position for the third gear G 3 , the third gear G 3  is also activated. An unintended downshift to the first gear G 1  is thereby reliably prevented. 
     So far as the driver really would wish to shift from the sixth gear G 6  to the first gear G 1 , this is absolutely possible. For this purpose, he has to move the shift and selector lever  32  by a related shift lever deflection, from shift position G 3 / 4  to shift position G 1 / 2  for which he only has to overcome the relatively low shift force F 2  at the start. On account of the non-linear arm geometry  58  of the second lever arm  44  of the lock pawl  38 , this control force rises non-linearly over the regulated distance of the shift and selector shaft  32  so that this increase of force up to the value of the shift force F 1  is clearly detected by the driver in the sense of a warning indication. As soon as the shift and selector shaft  32  has reached the shift position G 1 / 2 , shown in  FIG. 4 , the gear change the driver desires from the sixth gear G 6  to the first gear G 1  is possible. 
     Alternative to the electric connecting line  26  of the shift lever  16  and the electric toggle switch  22  with the control device  20 , a pneumatic valve arrangement in the shift lever  16  can also be provided which, via a pneumatic line, is connected with the transmission shift device  30  corresponding to the arrangement of DE-OS 24 47 860 and can trigger gearshifts in the splitter group transmission  12  and range group transmission  14 . 
     REFERENCE NUMERALS 
     
         
           2  motor vehicle 
           4  prime mover 
           6  transmission 
           8  clutch 
           10  main transmission 
           12  splitter group transmission 
           14  range group transmission 
           16  shift lever 
           18  connecting line 
           20  control device 
           22  toggle switch 
           24  toggle switch 
           26  connecting line 
           28  shift pattern 
           30  transmission shift device 
           32  shift and selector shaft 
           34  interface to shift lever 
           36  shift collar on the shift and selector shaft 
           38  lock pawl 
           40  rotation point of lock pawl 
           42  first lever arm 
           44  second lever arm 
           46  adjusting bolt 
           48  blocking piston 
           50  cylinder 
           52  bore in cylinder 
           54  pressure space 
           56  housing 
           58  lever arm geometry of lock pawl 
           60  chamber in housing  56   
         A operative lever length 
         B operative lever length 
         F 1  force of lock pawl on shift and selector shaft, pos. G 1 / 2   
         F 2  force of lock pawl on shift and selector shaft, pos. G 3 / 4   
         F K  basic force 
         G 1 / 2  shift position in the shift gate G 1 -G 2   
         G 314  shift position in the shift gate G 3 -G 4   
         G 5 / 6  shift position in the shift gate G 5 -G 6   
         G 718  shift position in the shift gate G 7 -G 8   
         G 1 -G 8  forward gears one to eight 
         GP-L H shift pattern for slow gear position 
         GP-S H shift pattern for quick gear positions 
         L shift position of the toggle switch  24   
         N neutral position 
         RG downshift gear 
         S shift position of the toggle switch  24