Patent Publication Number: US-2023140641-A1

Title: Powershift transmission of a motor vehicle

Description:
RELATED APPLICATIONS 
     This application claims the benefit of and right of priority under 35 U.S.C. § 119 to German Patent Application no. 10 2021 212 363.5, filed on 3 Nov. 2021, the contents of which are incorporated herein by reference in its entirety. 
     FIELD OF THE DISCLOSURE 
     The invention relates to a powershift transmission of a motor vehicle having a split group, which has a plurality of powershift stages, and whose input shaft can be rotatably driven by a drive shaft of a motorized drive, and transmits in a stepped-up manner to an output shaft of the split group a rotational movement corresponding to a selection of one of several powershiftable stage transmissions, wherein a synchromesh transmission group which has at least four gear stages can be rotatably driven by the output shaft of the split group via an intermediate group located therebetween and an axle transmission of the motor vehicle can be rotatably driven by the output shaft of the synchromesh transmission group, wherein the intermediate group has a first and a second switching element each having an output shaft, wherein the output shaft of the first switching element can be coupled in each case by means of a switchable coupling to a first idler, which has a higher number of teeth, of a high gear or a second idler, which has a lower number of teeth, of a low gear, and wherein the output shaft of the second switching element can be coupled in each case by means of a switchable coupling to a third idler, which has a higher number of teeth, of a high gear or to a fourth idler, which has a lower number of teeth, of a low gear, having a first output gear which is securely arranged on the output shaft of the synchromesh transmission group and in which the first idler and the third idler engage and having a second output gear which is arranged on the output shaft of the synchromesh transmission group and in which the second idler and the fourth idler engage. 
     BACKGROUND 
     In such a powershift transmission, it is known that the second idler and the fourth idler engage in the output gear, which is securely arranged on the output shaft of the synchromesh transmission group. If one of the switchable couplings of the first idler or the third idler is closed, the second idler and the fourth idler are also rotatably driven by means of the first output gear and the output shaft of the synchromesh transmission group and the second output gear. This leads in these second and fourth idlers to high speeds at the output shafts of the switching elements, on which they are supported, so as to be able to be freely rotated as a result of the open switchable couplings associated therewith. 
     This may lead to a rapid defect of the bearings of the second idler and the fourth idler on the output shafts of the intermediate transmission which are associated therewith in each case, and consequently to a failure of the powershift transmission. 
     SUMMARY 
     An object of the invention is therefore to provide a powershift transmission of a motor vehicle of the type mentioned in the introduction, which avoids this disadvantage and which with a simple structure has a high degree of resistance to defects. 
     This object is achieved according to the invention in that, when the second idler or the fourth idler is coupled, by means of a switching apparatus, the second output gear can be connected in a rotationally secure manner to the output shaft of the synchromesh transmission group and, when the first idler or third idler is coupled, the second output gear is decoupled by the switching apparatus from the output shaft of the synchromesh transmission group. 
     As a result of this solution, a free rotation of the second idler and the fourth idler on the output shafts of the intermediate transmission associated therewith, and consequently a failure of the powershift transmission, are prevented. 
     As a result of the powershift intermediate transmission, in a transmission of the type mentioned in the introduction, the number of powershiftable gears in the overall transmission in which all the gears can be switched without any interruption of tensile force is multiplied in a simple manner. 
     An internal combustion engine, such as a diesel engine, is suitable as a motorized drive. However, any other suitable motorized drive can also be used. 
     In this instance, the split group may have one or more powershiftable forward stage transmissions whose number is multiplied by the intermediate transmission. 
     The split group may also have one or more powershiftable reverse stage transmissions whose number is multiplied by the intermediate transmission. 
     The clutches and/or the switching apparatus may be able to be switched magnetically and/or switched electrohydraulically. 
     The clutches may be non-positive-locking clutches and/or frictionally engaging clutches. 
     The repeatedly powershiftable intermediate transmission may have a plurality of clutches which are each associated with a switching position of the repeatedly powershiftable intermediate transmission, wherein the clutches may be able to be switched, for example, in a manner operated in a manual or electrohydraulic manner. 
     The gear stages of the transmission are in this instance advantageously distributed in the manner of a dual-clutch transmission over the in particular two clutches so that a first clutch switches, for example, all the even gear stages and a second clutch switches, for example, all the odd gear stages. 
     In order to produce a hydraulic pressure for the electrohydraulic switchability, the input shaft may be able to be driven by means of a hydraulic pump by the drive shaft of the motorized drive so that no separate drive is required for the hydraulic pump. 
     A space-saving embodiment involves the clutches being dual-synchronous clutches which can be switched from a neutral position into a first clutch switching position and a second clutch switching position. 
     A long service-life is achieved when the second idler is rotatably supported by means of a roller bearing on the output shaft, which is associated therewith, of the intermediate group and/or the fourth idler is rotatably supported by means of a roller bearing on the output shaft, which is associated therewith, of the intermediate group. In an alternative preferred manner, the second idler may also be rotatably supported by means of a plain bearing on the output shaft, which is associated therewith, of the intermediate group. Similarly, the fourth idler may also be rotatably supported by means of a plain bearing on the output shaft, which is associated therewith, of the intermediate group. 
     In this instance, in order to reduce the required structural space, the roller bearing of the second idler and/or the roller bearing of the fourth idler may be a needle bearing. 
     The use of needle bearings is possible as a result of the decoupling according to the invention of the second output gear from the output shaft of the synchromesh subassembly since no overload of the needle bearings thus occurs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       One embodiment of the invention is illustrated in the drawings and is described in greater detail below. The single Figure of the drawing shows a schematic illustration of a powershift transmission for motor vehicles. 
     
    
    
     DETAILED DESCRIPTION 
     The illustrated powershift transmission has an internal combustion engine as a motorized drive  1 , by the drive shaft  2  of which an input shaft  4  of a split group  5  having a plurality of powershiftable stage transmissions is rotatably driven by means of a hydraulic pump  3 . 
     The input shaft  4  carries a first fixed gear  6  which meshes with an idler  8 , which is rotatably supported on an output shaft  7  of the split group  5 , of the split group  5 . 
     On the input shaft  4 , there is further arranged another idler  12  of the split group  5 , which idler meshes with another fixed gear  13  of the split group  5 , which gear is arranged in a rotationally secure manner on the output shaft  7  of the split group  5 . 
     The intermediate group  15  which has two switching elements  16  and  17  is rotatably driven via the output shaft  7  of the split group  5 , which forms an input shaft  14  of an intermediate group  15 . 
     The output shaft  18  of the first switching element  16  of the intermediate group  15  can be coupled by means of a first switchable clutch  20  to a first idler  21  which is arranged thereon with a higher number of teeth of a high gear of the synchromesh transmission group  19  or can be coupled by means of a second switchable clutch  22  to a second idler  23  which is arranged thereon with a lower number of teeth of a low gear of the synchromesh transmission group  19 . 
     The output shaft  24  of the second switching element  17  of the intermediate group  15  can be coupled by means of a third switchable clutch  25  to a third idler  26  which is arranged thereon with a higher number of teeth of a high gear of the synchromesh transmission group  19 , or the output shaft  24  can be coupled by means of a fourth switchable clutch  27  to a fourth idler  28  which is arranged thereon with a lower number of teeth of a low gear of the synchromesh transmission group  19 . 
     On an output shaft  29  of the synchromesh transmission group  19 , there is fixedly arranged a first output gear  30  of the synchronous transmission group  19 , in which output gear  30 , the first idler  21 , and the third idler  26  engage. 
     Via a switchable switching apparatus  31 , a second output gear  32  of the synchronous transmission group  19  can be coupled to the output shaft  29  of the synchronous transmission group  19 , in which output gear  32 , the second idler  23 , and the fourth idler  28  engage. In this case, the second output gear  32  has a substantially higher number of teeth than the first output gear  30 . 
     An axle  34  of the motor vehicle can be rotatably driven by the output shaft  29  of the synchromesh transmission group  19  via an axle transmission  33 . 
     Depending on the selection of the intermediate group  15  and the synchromesh transmission group  19 , as a result of a selected switching element  16 ,  17  of the intermediate group  15  in each case, a considerable increase of the forward gears and the reverse gears of the split group  5  can be achieved. 
     It is thus possible, for example, with another powershift transmission which is not illustrated and which has a split group of six forward gears, three reverse gears, a two-stage intermediate group, and a three-stage synchromesh transmission to achieve a number of thirty six forward gears and eighteen reverse gears in a simple manner. 
     When switching the first switchable clutch  20  or when switching the third switchable clutch  25 , via the first output gear  30 , the output shaft  29  of the synchromesh transmission group  19  is driven at a high speed via the first idler  21  or the third idler  26 . 
     If this is the case, the second output gear  32  is decoupled by the switching apparatus  31  from the output shaft  29  of the synchromesh transmission group  19 . Consequently, the high speed of the output shaft  29  of the synchromesh transmission group  19 , via the second output gear  32 , cannot rotatably drive the second idler  23  and the fourth idler  28  at a high speed and cannot overload the bearings on the output shafts  18  and  24 . 
     LIST OF REFERENCE NUMERALS 
     
         
           1  Motorized drive 
           2  Drive shaft 
           3  Hydraulic pump 
           4  Input shaft of split group 
           5  Split group 
           6  First fixed gear 
           7  Output shaft of split group 
           8  Idler of split group 
           12  Idler of split group 
           13  Fixed gear of split group 
           14  Input shaft of intermediate group 
           15  Intermediate group 
           16  First switching element 
           17  Second switching element 
           18  Output shaft of first switching element 
           19  Synchromesh transmission group 
           20  First switching clutch 
           21  First idler of synchromesh transmission group 
           22  Second switching clutch 
           23  Second idler of synchromesh transmission group 
           24  Output shaft of second switching element 
           25  Third switching clutch 
           26  Third idler of synchromesh transmission group 
           27  Fourth switching clutch 
           28  Fourth idler of synchromesh transmission group 
           29  Output shaft of synchromesh transmission group 
           30  First output gear of synchromesh transmission group 
           31  Switching apparatus 
           32  Second output gear of synchromesh transmission group 
           33  Axle transmission 
           34  Axle