Patent Publication Number: US-2010120575-A1

Title: Transmission

Description:
This application is a National Stage completion of PCT/EP2008/050103 filed Jan. 8, 2008, which claims priority from German patent application serial no. 10 2007 006 228.3 filed Feb. 8, 2007. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a transmission of the type explained. 
     BACKGROUND OF THE INVENTION 
     A transmission with a housing is known from the patent document DE 195 02 560 A1 in which two relatively rotatable gearwheels are arranged. The two gearwheels engage, whereby the respective shafts of the gearwheels are mounted with one end in an output-side bearing bracket and the other end in an output-side bearing bracket. The two bearing brackets are separated from the transmission housing by means of an elastic spring ring. 
     A similar embodiment is also known from the patent document GB 814,724. In this embodiment as well, the shafts which are provided with gearwheels are also mounted respectively in bearing brackets, wherein decoupling of the shaft ends is provided for by means of ring-shaped rubber elements. 
     It has been demonstrated that in the known transmissions the provided means for decoupling is not sufficient to reduce sound or, as the case may be, noise and vibration transmission. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is therefore to propose a transmission of the type initially described by means of which a complete elimination of sound and vibration transmission to the transmission housing can be realized. 
     Accordingly, a transmission with a housing is proposed in which at least two shafts for adjusting a desired gear ratio can be coupled to each other, wherein the shafts are mounted in the housing by means of bearing brackets, and wherein the bearing brackets are mounted on the housing by means of at least one damping element for damping sound and vibration. Inventively, a shifting device adjusting the gear ratio is affixed to at least one of the bearing brackets. 
     In this way, the noise and vibration produced by the shifting device, for example by the gearwheel sets, is not transmitted to the housing either, because the shifting device, independently of its design in any given instance, is affixed to or, as the case may be, supported by the already decoupled bearing brackets. 
     In a particularly advantageous embodiment of the invention with a shifting device that incorporates an actuating rod for operating shift forks, each end of the actuating rod is movably mounted on the respectively associated bearing bracket. Consequently, the gear ratio desired at any given time can be achieved through actuation of the shift forks without transmitting the resulting noise and vibration to the housing. Furthermore, the effects of thermal expansion can be prevented because of the same thermal expansion coefficients with respect to the position of the main shaft in the shifting device. 
     In another embodiment of the shifting device in which the shifting device comprises a plurality of selector rails for actuating shift levers, each end of the shift rails can be displaceably mounted on the assigned bearing bracket. Therefore, here too, there is decoupling from the housing via the bearing brackets. 
     In order to also advantageously absorb axial forces by means of the two bearing brackets, the two bearing brackets can be connected to the shafts in an axial direction via at least one connecting element or similar device. In this way longitudinal extension between the shafts made of steel and the aluminum housing can be prevented, in particular, in the case of housings comprised of aluminum compounds. As a result, different primary tensions on the bearings of the shafts can be avoided. In addition, due to the elastic coupling between the bearings of the shafts and the housing, load alternation in all axial directions which can lead to axial displacement can be prevented. Round rods or discs, or similar elements, can be used as connecting elements. 
     It has been demonstrated that with a shifting device having shift rails and shift levers, it is an advantage if the bearing brackets are connected via a disc. In this way, the levers of the shifting device can be displaceably mounted on the disc, so that they can also be decoupled from the housing. The levers can preferably be mounted by means of a bolt that is provided as a swiveling axis which is connected to the disc. The bolt used can preferably be designed as a hexagon screw or something similar, which is screwed into a corresponding threaded hole of the disc that forms the connecting element. Other types of fastening means can, however, also be used, such as welds, rivets, or similar, so the connection specified is only an example. 
     In order to adjust the shaft bearing, for example, in order to allow for a tapered roller bearing, it is particularly advantageous if the selected connecting elements can be longitudinally adjusted. When round rods are used as connecting elements, they can be attached with their respective ends inside recesses of the housing that are lined with the damping element or similar. Other types of attachment are also conceivable. 
     One possible example of this invention can be designed as a countershaft transmission. The countershaft transmission has a transmission input shaft, a countershaft, and a main shaft, as well as a transmission output shaft, which are coupled to each other via a gearwheel set. The transmission input shafts, the countershaft, and the main shaft, along with the associated shifting device, are mounted above the decoupled bearing bracket inside the housing. In addition, the shifting device which is normally adjacent to the transmission input shaft and the main shaft is attached in to one end of the two bearing brackets respectively, in order to realize the previously described complete decoupling between the gearwheel set of the countershaft transmission and the housing. Other applications are also conceivable, as, for example, in transmissions that are differently configured. 
     If, for example, the transmission features an additional range group on the transmission output shaft, as is common in so-called range transmissions, it can be provided, in accordance with another advantageous embodiment of the invention, for the transmission output shaft with the coupled range group to be decoupled from the housing by means of at least one additional damping member or similar component for the purpose of damping noise and vibration. 
     In this way, not only noise transmission from the gearwheel set of the countershaft transmission is decoupled, but also noise transmission from the range group, i.e. from the planetary transmission to the housing, is prevented. In this way, an overall concept for noise reduction for a transmission is attainable. 
     In the context of an additional embodiment of the invention, a support point for the so-called GP reaction of the range group and a bearing carrier of the transmission output shaft can be attached to a damping element on the housing for the purpose of decoupling the range group. As a support point, a clutch body of the GP reaction is provided which, together with the bearing carrier, can be affixed in the simplest possible manner via a retaining bolt inside a recess of the housing. For example, the recess can be lined with the damping element. Other means of attaching the clutch body and the bearing carrier to the housing are also conceivable for the purpose of decoupling. In employing them, however, it is essential that the damping element be interposed in some manner along the transmission path, in order to realize complete decoupling of the transmission output shaft with the range group and the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
       The invention will be explained in more below on the basis of the drawings. 
       They show: 
         FIG. 1  A schematic, cross-sectional, partial view of the housing of an inventive transmission with a shifting device comprising shift forks which is arranged inside the housing in such a way as to reduce noise and vibration; 
         FIG. 2  A schematic, cross-sectional partial view of an inventive transmission with a shifting device comprising shift rails which is arranged inside the housing in such a way as to reduce noise and vibration; and 
         FIG. 3  A schematic, partially cross-sectional view of an output-side bearing of the inventive transmission with a range group that is arranged in such as way as to reduce noise and vibration. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     In each of  FIGS. 1 and 2 , a transmission with a countershaft transmission is schematically as an example. The countershaft transmission features a transmission input shaft  1  that is coupled to a main shaft  2 . A countershaft  3  is arranged parallel to the transmission input shaft  1  and the main shaft  2 . The countershaft  3  is coupled via two constant wheels  4  to the transmission input shaft. In addition, the countershaft  3  comprises a gearwheel set  5  with a plurality of gearwheels, in order to realize the desired gear ratios between the transmission input shaft  1  and the main shaft  2  or, as the case may be, the transmission output shaft. 
     The transmission input shaft  1 , the main shaft  2 , and the countershaft  3  are each mounted on an input-side bearing bracket  7  and an output-side bearing bracket  8 . For this purpose, the two bearing brackets  7 ,  8  are each constructed in the region of the respective bearing positions as bearing carriers for the bearings of the shaft. 
     In  FIG. 1  the mounting of the countershaft  3  is realized by means of a tapered roller bearing  12 ,  12 ′. In contrast to the transmission depicted in  FIG. 2 , an actuation rod  9  with a shift fork  10  attached to it is provided as the shifting device in the case of the transmission depicted in  FIG. 1 . The actuation rod  9  is movably mounted in the corresponding collets  11 ,  11 ′ of the two bearing brackets  7 ,  8 . As a result of the fact that the bearings of the transmission input shaft  1 , the main shaft  2 , and the countershaft  3  are provided in separate bearing brackets  7 ,  8 , the axial distance between the two bearings is retained. The bearing brackets  7 ,  8  are received in an elastic manner by the corresponding recesses  15 ,  15 ′,  16 ,  16 ′ of the housing components  13 ,  13 ′ on the input side and the output side of the countershaft transmission. For this purpose, the recesses  15 ,  15 ′,  16 ,  16 ′ are lined with a damping element  17  that is composed, for example, of elastic material. 
     In order to absorb the axial force of the transmission input shaft  1 , the main shaft  2 , and the countershaft  3 , the two bearing brackets  7 ,  8  are connected via connecting elements. In  FIG. 1  round rods  14 ,  14 ′ are used as connecting elements. These are connected in each case to an upper and a lower end of the previously described recesses  15 ,  15 ′;  16 ,  16 ′ in the wall of the housing sections  13 ,  13 ′. Via the recesses  15 ,  15 ′;  16 ,  16 ′ which are each lined with the damping element  17 , both the bearing brackets  7 ,  8  and the ends of the round rods  14 ,  14 ′ are decoupled from the housing sections  13 ,  13 ′. Because the shifting element with its actuation rod  9  is also held by the bearing brackets  7 ,  8 , the shifting device is also decoupled from the housing sections  13 ,  13 ′. An elastic material with damping characteristics is used as a damping element  17 . 
     In addition, not only is there a prevention of longitudinal expansion between the housing sections  13 ,  13 ′ which are made, for example, of aluminum and the shafts  1 ,  2 ,  3  which are made of steel, but also, due to the elastic mounting in all three axial directions, the load alternation that can lead to axial displacement is also dampened. The round rods  14 ,  14 ′ can be adjustable for length, in order to adjust the bearing position of the mountings of the transmission input shaft  1 , the main shaft  2 , and the countershaft. 
     In this way complete decoupling of the transmission prevents noise and vibration of the gearwheel set  5  from the countershaft transmission to the housing sections  13 ,  13 ′ via the bearings and the shifting device. 
     In contrast to  FIG. 1 ,  FIG. 2  depicts another shifting device. The shifting device depicted in  FIG. 2  comprises shift rails  18  that are actuated by shift levers in a known manner, in order to realize desired gear ratios in the transmission. The ends of the shift rails  18  are displaceably mounted on the bearing brackets  7 ,  8 . Sliding guides  20 ,  20 ′ are provided for this purpose. The shift levers  19  are retained by the connecting element for the connection of the two bearing brackets  7 ,  8 . A plate  21  is used as a connecting element in the embodiment shown in  FIG. 2 . The shift levers  19  are rotatably mounted by means of hexagon bolts  22  which are screwed into the plate  21  so that the hexagon bolts  22  form the pivotal point for the levers  19 . 
     The two bearing brackets  7 ,  8  are curved at the ends so that the curved ends are held respectively in the recesses  15 ,  15 ′;  16 ,  16 ′ in the wall of the housing  13 . For this purpose, the recesses  15 ,  15 ′;  16 ,  16 ′ also contain the damping element  17 . In order to center the bearing arrangement in the housing  13 , the bearing bracket  8  is fixed inside the recess  16 ′ of the housing  13  by means of a riveted bolt  24 . 
       FIG. 3  is a partial view of an output-side bearing of a so-called range transmission. With this arrangement the main shaft  2  is coupled to a range group as a planetary gear train. For this purpose the sun gear  25  is connected to the main shaft  2 . The spider shaft or, as the case may be, the planet carrier is formed by the transmission output shaft  6 . 
     In order to realize a gear ratio from the transmission input shaft  1  to the transmission output shaft  6 , the ring gear  26  is connected to the housing  33 . The ring gear  26  engages the planet gears  32 . In order to support this so-called GP reaction on the housing  33 , a coupling body  27  is provided as a support point. In the inventive transmission the coupling body  27  is connected with the housing  33  by means of a bearing carrier  28  of the transmission output shaft via an additional damping element  29 . 
     For this purpose, the bearing carrier  28  of the roller bearing  30  of the transmission output shaft  6  is attached to the coupling body  27  of the GP reaction by means of retaining bolts  31 ,  31 ′ in the associated retaining collet  23 ,  23 ′ of the housing  33 . Each retaining collet  23 ,  23 ′ is lined with the additional damping element  29 , in order to enable complete decoupling of the output-side bearing of the transmission output shaft  6 , as well as the range group that is also coupled to the main shaft  2 . The damping element  29  is also made of an elastic material or similar. 
     REFERENCE CHARACTERS 
     
         
           1  Transmission input shaft 
           2  Main shaft 
           3  Countershaft 
           4  Constant wheels 
           5  Gearwheel set 
           6  Transmission output shaft 
           7  Input-side bearing bracket 
           8  Output-side bearing bracket 
           9  Actuating rod 
           10  Shift fork 
           11 ,  11 ′ Collet 
           12 ,  12 ′ Tapered roller bearing 
           13 ,  13 ′ Housing, housing section 
           14 ,  14 ′ Round rod 
           15 ,  15 ′ Recess 
           16 ,  16 ′ Recess 
           17  Damping element 
           18  Shift rail 
           19  Shift lever 
           20 ,  20 ′ Sliding guide 
           21  Plate 
           22  Hexagon bolt 
           23 ,  23 ′ Retaining collet 
           24  Bolt 
           25  Sun gear 
           26  Ring gear 
           27  Coupling body 
           28  Bearing carrier 
           29  Additional damping element 
           30  Roller bearing 
           31 ,  31 ′ Retaining bolt 
           32  Planet gears 
           33  Housing