Patent Abstract:
A shifting device for the shifting of a transmission with a shifting shaft ( 2 ), having a multiplicity of shifting forks or shifting levers ( 8, 10, 12, 14 ) placed in an axial slidable manner for the carrying out of a shifting procedure with a selection apparatus ( 28, 30, 32, 42, 44, 46 ) for the choice of a shifting fork ( 8, 10, 12, 14 ) from the multiplicity of shifting forks for the carrying out of the shifting procedure and with blocking disk ( 52 ) for the prevention of the movement of non-chosen shifting forks ( 8, 10, 12, 14 ). The elements ( 2, 8, 10, 12, 14, 20, 22 ) for the carrying out of the shifting procedure are made from a material of high structural strength and the elements of the selection apparatus ( 28, 30, 32, 42, 44, 46 ) and the blocking apparatus ( 52 ) are constructed from a material of lesser structural strength.

Full Description:
This application is a national stage completion of PCT/EP2004/010296 filed Sep. 15, 2004 which claims priority from German Application Serial No. 103 47 492.7 filed Oct. 13, 2003. 
   FIELD OF THE INVENTION 
   The invention concerns a shifting device. 
   BACKGROUND OF THE INVENTION 
   For the shifting of a transmission, especially where vehicles are concerned, a shifting device is provided in the transmission with the aid of which the individual gear stages can be engaged. As this is done, it is possible that parts of the shifting device can be moved manually by the vehicle driver or, alternating, this function may be carried out by actuators which are energized by at least one auxiliary power medium to execute the necessary movements required by the shifting mechanism. 
   Customarily, the expended forces which are sufficient for the selection of the individual gear stages are less than those forces to be exerted upon the shifting of the selected gear stage, which has a result that the elements of the selection apparatus on the shifting device can be otherwise dimensioned than are those of the necessary components, which are intended for the execution of the shifting. 
   The costs for a shifting device of this kind for a transmission are essentially dependent upon the complexity of the employed installed components, upon the materials thereof, upon the required expense for the mechanical working of the components and further upon manufacturing costs for the machining, shaping and heat treatment. 
   DE A1 198 43 584 makes known a shifting apparatus for a multistage shifting transmission wherein, on a single shifting shaft, a multiplicity of shifting forks are placed. A selection mechanism enables the choice of one of the shifting forks by way of the turning of a shifting shaft. Alternately, if the shifting shaft is axially displaced, then the respectively selected shifting fork is activated to carry out the intended shifting action. A blocking shaft, placed parallel to the shifting shaft, is likewise rotated upon the turning of the shifting shaft and thereby, employing, in its function as a blocking shaft, the movement of such shifting forks which were not chosen as indicated above. The components for this construction must be manufactured in a complex manner and at high cost. Following the assembly of the components, the co-action of the functioning parts generates noise and frequently leads to critical noise problems. 
   EP-B1 0 633 412 teaches of an actuator for a sliding collar enclosed in a shifting transmission, having a shifting rod located and slidable in the direction of its longitudinal axis on which a shifting fork, as well as a ring-shaped engagement unit, are rigidly affixed. The actuation apparatus is constructed as a combined plastic-metal component, where a metal part, which serves as the ring-shaped engagement unit as well as a core for the shifting rod, is sprayed with a plastic material and the shifting fork consists exclusively of plastic. In this assembly, simply a combination of plastic and metal must be created as a component, in order to assure the required stability of a component necessary for the shifting of a gear stage. 
   The purpose of the invention is to demonstrate a shifting device, which can be economically manufactured and can operate at a low noise level without containing a complex binding construction. 
   SUMMARY OF THE INVENTION 
   According to the invention, a shifting device for the shifting of a transmission possesses a shifting shaft upon which a multiplicity of shifting forks or shifting rockers (hereinafter referred to as “shifting forks”) are placed in an axial, slidable alignment for the execution of shifting procedures. Provided are: a) a selection apparatus for the choice of one of the shifting forks out of the multiplicity of shifting forks and b) blocking disks for the prevention of an axial motion of the non-chosen shifting forks. For the carrying out of shifting procedures, these elements are being constructed of a material of greater structural strength while, contrarily, the elements of the selection apparatus are being made from a material of lower grade. 
   In an advantageous embodiment, the elements of the selection apparatus make use of ring-shaped engagement units, specifically for each shifting fork. The ring-shaped engagement units are axially affixed and slidable along the shifting shaft to enable the execution of the shifting procedure. The ring-shaped engagement units are rotatable about the shifting shaft for the selection of one of the shifting forks and possess elements of a come-along apparatus, which enable an axial sliding of the ring-shaped engagement unit because of the axial motion of the shifting shaft in the shifting procedure. 
   Another advantageous embodiment demonstrates, that the ring-shaped engagement units on the shaping fork, coact with a blocking means for prevention of axial motion of non-chosen shifting forks on the shifting shaft. 
   In a particularly advantageous embodiment, elements of the blocking means incorporate rotatable blocking disks, the circumferences of which extend into an axial movement area of the ring-shaped engagement units. The contour of a blocking disk is designed in such a manner that the eliminated zone of the blocking disks, which is in segmental shape, allow an axial movement of the ring-shaped engagement units on the shifting shaft, while other areas of the blocking disks are appropriate for preventing an axial movement of the ring-shaped engagement units. 
   Advantageously, recesses are present on the ring-shaped engagement units, which recesses co-act with projections on the shifting shaft. The projections penetrate the recesses, if the associated shifting forks are not engaged and further the projections slide the ring-shaped engagement units axially if the selected shifting fork is in a displaced position in order to change the gear stage. 
   The elements of the selection apparatus exhibit advantageously, exhibit complementary toothings which mesh and enable a rotation of the elements of the selection apparatus in relation to one another. In this operation, due to their formation, only parts of the ring-shaped engagement unit possess toothing. 
   Representing one embodiment, an area of a section in the blocking disks can exhibit a toothing, which can mesh into the toothing of a ring-shaped engagement unit. 
   An inventive embodiment would be especially advantageous, if the elements for the carrying out shifting procedure were made of steel or aluminum, while the elements of the selection apparatus and of the blocking disks are constructed of aluminum or plastic or, again, from a combined compounding. 
   In the case of a particularly advantageous design of the invention, an actuator can be provided for the axial displacement of the shifting shaft, while an additional actuator governs the elements of the selection apparatus as well as those of the of the blocking disks. In this way, a transmission becomes available for ratio control of rotation of the shifting shaft actuator in an axial movement thereof. 
   Advantageously, at least one actuator is provided, which is designed to operate electromechanically, pneumatically or hydraulically. 

   
     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 first shifting device with individual elements, and 
       FIG. 2  is a second presentation of detailed elements of a second embodiment of the shifting device. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   According to  FIG. 1 , four shifting forks, namely  8 ,  10 ,  12  and  14  are placed on a shifting shaft  2 . Shifting shaft  2  is axially slidably supported in bearings  4  and  6  which, in turn, are affixed in a housing (not shown) of the shifting transmission. The shifting forks are installed so as to be moveable in relation to the shifting shaft  2 . For the purposes of clarity of illustration and better understanding, not all possible shifting forks are shown on the shaft  2 . Further, individual elements of the shifting device are presented in a somewhat exploded view separate from the shifting shaft. In a completed assembly, however, all shifting forks are located in a manner similar to that of shifting fork  12 , which is shown on the shifting shaft  2 . Presented in  FIG. 1  is an arrangement of the three shifting forks  8 ,  10  and  12  of the shifting shaft  2 , while the shifting fork  14  is placed underneath the shifting shaft  2  in this arrangement. The following components, described here, serve analogously for every shifting fork, if these also can be described and explained by a single typical shifting fork, because of their common characteristics. 
   The shifting shaft  2  possesses projections in the form of two pins  16 ,  18  on the shifting fork  10 , which enclose the shifting fork  10  between them. Between pins  16  and  18  and the shifting fork  10  is to be found at each side of the shifting fork  10 , one sheet metal, contoured disk  20 ,  22 . The contoured disks  20 ,  22  are bounded on their inner circumference, similar openings  24  through which, respectively, the pins  16  and  18  can be axially inserted. The remaining area between each of the openings  24 , bounded by the inner circumference of a contoured disk  20  and  22  is able, by a mutual turning of a contoured disk  20  and  22  on the shifting shaft  2 , with the aid of the pins  16  and  18 , to make a mutual overlap. Thereby, in a case of an axial movement of the shifting shaft  2  over the pin  16  and  18  and the contoured disk  20  and  22  even the shifting fork  10  is axially displaced and a gear stage can be engaged in the transmission. 
   In order to turn the contoured disk  20  and  22  on the shifting shaft  2 , the contoured disk  20  and  22  possesses a contoured surface (hereinafter “contour  26 ”) on its outer circumference, which co-acts with a complementary contour on a ring-shaped engagement unit  28  and/or  30  and forms a turn-fast connection between the contoured disk  20  and  22  and the ring-shaped engagement unit  28  and  30  ( FIG. 2 ). 
   Such a device, basically including a ring-shaped engagement unit  32  is pictured in its location on the shifting fork  12 , wherein currently two single, ring-shaped engagement units are combined to form one component. In order to enable a rotation of the ring-shaped engagement unit  32  on the shifting shaft  2 , without interfering with the arms of the shifting fork  12 , the ring-shaped engagement unit  32  is furnished with a recess  34 . On the outer circumference of the ring-shaped engagement units  28 ,  30 ,  32  is provided a toothing  36 , which can stand in engagement with corresponding toothing  38 ,  40  on gears  42  and  44 . This is correspondingly valid for all shifting forks  8 ,  10 ,  12  and  14 . The gears  42  and  44  are turn-fast affixed on a shaft  46 , which is essentially aligned parallel to shifting shaft  2 . The shaft is rotated by an actuator  48  such as, for example, an electric motor through a ratio train with a toothing  50 . The arrangement however, can also be so designed that the actuator  48  is directly bound to the shaft  46  without the ratio train. Laterally located to the gears  42  and  44  is respectively a blocking disk  52  of a blocking apparatus, which does not possess a complete, circular circumference, but has a recess in the form of a circular segment  54 . 
   The blocking disks  52  of the differing shifting forks  8 ,  10 ,  12 ,  14  also exhibit such segmental cutoffs at various positions on their circumferences, so that the two blocking disks  52  always present the same cutoffs to one shifting fork, while otherwise, the cutoffs on the blocking disks  52  of the other shifting forks are provided for rotation about the axis of the common shaft  46 . The blocking disks  52  act together with the ring-shaped engagement units  28 ,  30 ,  32  for the formation of the blocking apparatus, for example by the edges of the toothings of the ring-shaped engagement unit  28 ,  30 ,  32 . In this way, the blocking disks  52  hold the ring-shaped engagement units  28 ,  30   32  and therewith also hold the shifting forks in their axial position on the shifting shaft  2  and only permit an axial movement of the currently selected shifting fork in the area of the segment  54  on the blocking disk  52 . 
   The shifting shaft  2  is connected to an actuator  60  by way of a transfer block  56  with a ball-joint drive  58  which is, in turn, connected to an actuator  60 , for instance, an electric motor. Instead of the ball drive  58 , this power transfer can be accomplished by a gear drive (not shown). The illustrated actuators  48  and  60  are shown in  FIG. 1  as being co-axial or axis parallel to the shaft  2  and  46  which is to be placed in motion. By way of an appropriate directive gear drive, the possibility exists that an assembly, which stands at an angle to the shaft, may also be installed at a right angle, for instance. 
   In order to shift the gear stage, it is necessary that the shifting forks  8 ,  10 ,  12  or  14  be pushed axially. The shifting forks  8 ,  10 ,  12  and  14  are freely supported on the shifting shaft  2  and for engagement, these must be axially shape-fit with the shifting shaft  2  by the pins  16 ,  18  and the contoured disk  20 ,  22 . The toothed ring-shaped engagement units  28 ,  30 ,  32  are rotated by the shaft  46 , which shaft is provided with gears  42 ,  44 . The shifting shaft  2  moves itself for the engagement of the gear stages only in the axial direction. The selective preliminary choice of the gear stage to be shifted is carried out in that the contoured disk  20 ,  22  are rotated by the ring-shaped engagement units  28 ,  30 ,  32  which encompass them and thereupon close a discrete angle. Analogous to this angle, the cutouts  24  in the contoured disks  20 ,  22  are provided which, by way of the non-shifted gear stages, as soon as the shifting shaft moves itself, lead to an engagement of the pins  16  and/or  18  and thereby to no correspondingly movement contoured disk of the corresponding shifting fork. In the case of the fork to be shifted which is in this position, its necessary contoured disk  20  and  22  lacks an internal opening  24 , so that the fork undergoes an axial movement and the desired gear stage is engaged. In each of the different selection positions, there is always one contoured pair  20 ,  22  without internal cutouts  24  in overlap with the rods  16 ,  18  so that an action can be initiated. All of the rest of the ring-shaped engagement units are coinciding with the internal cutouts  24  with the appropriate rods  16 ,  18  and no axial motion can occur. 
     FIG. 2  shows a shifting device in accord with  FIG. 1  in a partially released condition. In this case, the segments  54  on the blocking disks  52  are provided with a toothing, so that the blocking disks in the non-blocking angular position can mesh into the outer toothing of the appropriate ring-shaped engagement unit  28 ,  30 . The ring shaped engagement units  28 ,  30  are designed here as separate components so that the necessity of the formation of toothing  36 , as is required with the ring-shaped engagement unit  32 , is eliminated. 
   Since the elements taking part in the selection of the shifting fork to be shifted are exposed only to comparatively small forces, the design of these elements finds that a construction material of a lesser structural strength will suffice. Such a material would be plastic or a metal other than steel, but possibly including aluminum. Aluminum, in comparison to steel, is a low strength metal and plastic, both in comparison to steel and aluminum, in turn, is a material of lesser strength. 
   Appropriate for a plastic construction, in the present embodiment, is the ratio determining stage with the toothing  50  to which can be added the shaft  46  and all gears  42 ,  44  and blocking disks  52  which are on the shaft  46 . Likewise, the ring-shaped engagement units  28 ,  30 ,  32  can be made of plastic both in the assembled state as well as in the separate part versions. The elements of plastic can be pre-manufactured and require no or only minuscule reworking. This is essentially cheaper than the construction materials for systems built of greater structural strength. A further advantage can be found with elements made of plastic producing a lesser generation of noise, since plastic possesses, essentially, a noise dampening function. Known at the present time and generally criticized noise problems, such as rattling in the transmission and scraping of gears, can be avoided by the above system. 
   REFERENCE NUMERALS 
   
       
         2  shifting shaft 
         4  bearing 
         6  bearing 
         8  shifting fork 
         10  shifting fork 
         12  shifting fork 
         14  shifting fork 
         16  pin 
         18  pin 
         20  contoured disck (externally) 
         22  contoured disk (externally) 
         24  internal opening of  20 ,  22   
         26  contour at outer circumference 
         28  rich-shaped engagement unit 
         30  ring-shaped engagement unit 
         32  ring-shaped engagement unit 
         34  cutout 
         36  toothing 
         38  toothing 
         40  toothing 
         42  gear 
         44  gear 
         46  shaft 
         48  actuator 
         50  toothing 
         52  blocking disk 
         54  segment 
         56  transfer block 
         58  universal ball joint 
         60  actuator

Technology Classification (CPC): 5