Abstract:
In an auxiliary range transmission comprising a main group having a main transmission shaft and two main countershafts capable of rotating in relation to two auxiliary countershafts of a range or an auxiliary transmission group, a gearshift element is provided, which, in a first position, rotationally engages a loose gear of the main group and, in a second position, rotationally locks a loose gear of the range or auxiliary group with the main shaft. In an alternative embodiment, a splitter group may also be arranged in front of the main group in place of the range or auxiliary transmission group.

Description:
This is a Continuation-In-Part application of pending international patent application PCT/EP2007/007236 filed Aug. 16, 2007 and claiming the priority of German patent application 10 2006 038 194.7 filed Aug. 16, 2006. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to an auxiliary range transmission with two main countershafts and two auxiliary countershafts in a main and, respectively, an auxiliary transmission part. 
     U.S. Pat. No. 4,876,924 discloses an auxiliary range transmission, in which a main group and a range group are each provided with two independent countershafts. Three gearshift elements are provided in the main transmission. Two of these three gearshift elements are displaceable in both axial directions. The third gearshift element is displaceable in only one axial direction. Here the third gearshift element, in a merely schematic representation, is shown on the side facing the range group. In the detailed drawing associated with this schematic drawing, on the other hand, the third gearshift element is arranged on the side remote from the range group. Multiple spring-loaded clutches are further provided, which serve to couple loose gears of the range group to the associated main shaft. 
     U.S. Pat. No. 5,447,082 likewise discloses an auxiliary range transmission having a main group, a range group and parallel offset countershafts. The auxiliary range transmission here only has bilaterally acting gearshift elements. No gearshift element is provided between the loose gear of the main group and the loose gear of the range group 
     U.S. Pat. No. 6,257,082 B1 likewise discloses an auxiliary range transmission having a main group, a range group and parallel offset countershafts. In this case a gearshift clutch is provided between the main group and the range group. 
     The main object of the invention is to provide a cost-effective auxiliary range transmission, which, in spite of being compact in construction, has a large number of gears. 
     SUMMARY OF THE INVENTION 
     In an auxiliary range transmission comprising a main group having two main countershafts capable of rotating in relation to two auxiliary countershafts of a range group, a gearshift element is provided, which, in a first position, rotationally locks a loose gear of the main group and, in a second position, rotationally locks a loose gear of the range group to a main shaft, wherein, in an alternative embodiment, a splitter group may also be arranged in front of the main group in place of the range group. 
     A single gearshift clutch can advantageously be used to shift both a loose gear of the main group and alternatively a loose gear of the auxiliary shift group. This auxiliary shift group may, in particular, be a range group on the output side of the main group. Alternatively or in addition, however, the auxiliary shift group may also be a splitter group arranged axially in front of the main group. 
     The auxiliary shaft range may provide three different transmission ratios, so that the total number of gears of the auxiliary range transmission is obtained as the number of gears in the main group multiplied by the number of gears in the auxiliary shift group. 
     The auxiliary shift group may in particular have two gearshift elements for providing the three transmission ratios. Each of these two gearshift elements can be brought into two positions. These positions may take the form of limit positions, a central neutral position being provided between these positions. 
     Use of the gear in the main group, which is actuated by the gearshift element also assigned to the auxiliary shift group, is forcibly prevented in those transmission states of the auxiliary shift group in which the loose gear of the adjacent gearwheel plane of the auxiliary shift group lies in the transmission path. For this reason it is particularly advantageous if a gearwheel plane of the main group, which is not necessarily needed in all shift states of the auxiliary shift group, can be arranged adjacent to the range group. 
     The invention will become more readily apparent from the following description of exemplary embodiments thereof with reference to the accompanying drawings: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1 . shows a first embodiment of an auxiliary range transmission having a range group and gearshift elements, 
         FIG. 2 . shows the transmission paths in the gears of the auxiliary range transmission according to  FIG. 1 , 
         FIG. 3 . shows a table with the positions of the gearshift elements according to  FIG. 1  for providing three transmission ratios in the range group, 
         FIG. 4 . shows a second embodiment of an auxiliary range transmission having a range group and gearshift elements, and 
         FIG. 5 . shows the transmission paths in the gears of the auxiliary range transmission according to  FIG. 4   
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       FIG. 1  shows a first embodiment of an auxiliary range transmission  23  having a range group and gearshift elements. This auxiliary range transmission  23  is used in a commercial vehicle. 
     This auxiliary range transmission  23  comprises a constant input E 1 , a main group  7  and a range group  12 . This range group  12  comprises three gearwheel planes N 1 , N 2 , N 3  and two gearshift elements S 3 , S 4 . According to  FIG. 3  these two gearshift elements S 3 , S 4  can be used to obtain three different transmission ratios i 1 , i 2 , i 3  in the range group  12 . 
     Next to the engine crankshaft (not represented in further detail) in the power transmission path is a drive-away clutch K, which is followed by the auxiliary range transmission  23 . 
     The engine can be frictionally coupled by means of the drive-away clutch K to a transmission input shaft  1 . This transmission input shaft  1  has a fixed gear  2 , which meshes with two fixed gears  3   a ,  3   b , which are arranged diametrically opposite one another about a main axis  24  and are in each case arranged at the front end of two main countershafts  4   a ,  4   b . These two fixed gears  3   a ,  3   b  together with the aforementioned fixed gear  2  therefore form a constant input E 1 . Their fixed gears  3   a ,  3   b  are each succeeded by two further fixed gears  5   a ,  6   a ,  5   b ,  6   b  of diminishing diameter. Two gearwheel planes H 3 , H 2  of the main group  7  are assigned to the latter fixed gears  5   a ,  6   a ,  5   b ,  6   b . Only forward gears are assigned to these two gearwheel planes H 3 , H 2 . For this purpose the two fixed gears  5   a ,  6   a ,  5   b ,  6   b  of these two gearwheel planes H 3 , H 2  mesh with loose gears  8 ,  9 , which are arranged coaxially so that they can rotate about a main shaft  10 . The front end of the main shaft  10  is here supported in a blind hole in the rear end of the transmission input shaft  1 . 
     A first gearshift element S 1 , which in a forward position serves to rotationally lock the transmission input shaft  1  to the main shaft  10 , so that a direct through-drive is established to the range group  12 , is arranged between the fixed gear  2  on the transmission input shaft  1  and the foremost loose gear  8  on the main shaft  10 . In a rear position the foremost loose gear  8  on the main shaft  10  can be rotationally locked to the latter. The neutral position of the first gearshift element S 1  lies between the forward position and the rear position. 
     Situated behind each of the two small fixed gears  6   a ,  6   b  on the front main countershafts  4   a ,  4   b  is a fixed gear  11   a  and  11   b  respectively, which is of smaller diameter but wider. These wide fixed gears  11   a ,  11   b  mesh with a loose gear  25 , which is rotatably arranged coaxially with the main shaft  10 . A gearwheel plane H 1 , which among other things is assigned to the first forward gear I, is thereby formed. These other fixed gears  11   a ,  11   b  furthermore each mesh by way of an intermediate gear  12   a ,  12   b  with a loose gear  13  on the main shaft  10 , so that a gearwheel plane HR is formed by two reverse gears R 1  and R 2 . A second gearshift element S 2  is arranged coaxially on the main shaft  10  between the gearwheel plane H 1  of the first forward gear I and the gearwheel plane H 2  of a second forward gear II situated in front of it. The loose gear  9  or the loose gear  25  can therefore alternatively be coupled to the main shaft  10  by means of the second gearshift element S 2 . A neutral position of the second gearshift element S 2  is situated between the relative positions of the second gearshift element S 2 . 
     The main shaft  10  continues partially in the succeeding range group  12 . Thus at the front end of the range group  12  a loose gear  14  is coaxially supported so that it can rotate on the main shaft  10 . This loose gear  14  meshes with two medium-sized fixed gears  16   a ,  16   b , which are each arranged, rotationally fixed, on one of two rear auxiliary countershafts  15   a ,  15   b . These two auxiliary countershafts  15   a ,  15   b  are arranged diametrically opposite one another about the main axis  24 . The loose gear  14  with the two medium-sized fixed gears  16   a ,  16   b  here forms the foremost and first gearwheel plane N 1  of the range group  12 . The fixed gears  16   a ,  16   b  are followed on the auxiliary countershafts  15   a ,  15   b  by large fixed gears  17   a ,  17   b . These fixed gears  17   a ,  17   b  mesh with a loose gear  19 , which is again arranged coaxially so that it can rotate on the mains shaft  10 . The loose gear  19  with the two large fixed gears  17   a ,  17   b  therefore forms the second gearwheel plane N 2  of the range group  12 . 
     The foremost loose gear  14  of the range group  12  can be rotationally locked to the main shaft  10  by means of the third gearshift element S 3  shifted into a rear position h 3 . This third gearshift element S 3  is on the other hand shifted into the forward position v 3  in order to couple the rearmost loose gear  13  of the main group  7  to the main shaft  10 . 
     Behind the second gearwheel plane N 2  of the range group  12  the transmission output shaft  22  is arranged in alignment with the main shaft  10 . This transmission output shaft  22  is rotationally locked to a fixed gear  20 , which meshes with two fixed gears  21   a ,  21   b , which are each rotationally locked to one of the two auxiliary countershafts  15   a ,  15   b . The three rearmost fixed gears  20 ,  21   a ,  21   b  thereby form the third gearwheel plane N 3  of the range group  12 . 
     The transmission output shaft  22  can be rotationally locked to the main shaft  10  by means of the fourth gearshift element S 4  shifted into a rear position h 4 . If the fourth gearshift element S 4  is shifted into the forward position v 4 , on the other hand, it establishes a rotationally fixed connection between the loose gear  19  situated in front and the main shaft  10 . Like the first two gearshift elements S 1 , S 2 , the third and the fourth gearshift elements S 3 , S 4  also each have a middle neutral position n 3  and n 4  respectively. 
     It is thereby impossible for the loose gears  13 ,  14  in the gearwheel plane HR of the reverse gear and the first gearwheel plane of the range group to be rotationally locked to the main shaft  10  simultaneously, since both gearwheels  13 ,  14  are actuated by means of the same, that is to say the third sliding sleeve S 3 . The middle transmission ratio i 2  assigned to the first gearwheel plane N 1  of the range group cannot therefore be combined with the reverse gear. The size ratios of the gearwheels in the range group  12  do not allow their first gearwheel plane N 1  to be involved in forming the highest—that is to say the shortest—transmission ratio i 3 . This affords a quick reverse gear, which is important in drive-off and tight maneuvering operations. 
       FIG. 2  shows the transmission path in the auxiliary range transmission  23  according to  FIG. 1 , whilst  FIG. 3  relating to the range group  12  shows 
     the possible shift positions v 3 , n 3 , h 3  of the third gearshift element S 3  and 
     the possible shift positions v 4 , n 4 , h 4  of the fourth gearshift element S 4 . Here this auxiliary range transmission  23  is designed in such a way that the range group  12  has four range areas, so that a total of twelve forward gears I to XII and two reverse gears R 1  and R 2  are formed. 
     In the first forward gear I 
     the first gearshift element S 1  is in the neutral position, 
     the second gearshift element S 2  is in the rear position, 
     the third gearshift element S 3  is in the neutral position n 3  and 
     the fourth gearshift element S 4  is in the forward position v 4 . 
     The power transmission path runs via the constant input E 1 , the first gearwheel plane H 1 , and in the range group via the second gearwheel plane N 2  and the third gearwheel plane N 3 . 
     In the second forward gear II 
     the first gearshift element S 1  is in the neutral position, 
     the second gearshift element S 2  is in the forward position, 
     the third gearshift element S 3  is in the neutral position n 3  and 
     the fourth gearshift element S 4  is in the forward position v 4 . 
     The power transmission path runs via the constant input E 1 , the second gearwheel plane H 2 , and in the range group via the second gearwheel plane N 2  and the third gearwheel plane N 3 . 
     In the third forward gear III 
     the first gearshift element S 1  is in the rear position, 
     the second gearshift element S 2  is in the neutral position, 
     the third gearshift element S 3  is in the neutral position n 3  and 
     the fourth gearshift element S 4  is in the forward position v 4 . 
     The power transmission path runs via the constant input E 1 , the third gearwheel plane H 3 , and in the range group via the second gearwheel plane N 2  and the third gearwheel plane N 3 . 
     In the fourth forward gear IV 
     the first gearshift element S 1  is in the forward position, 
     the second gearshift element S 2  is in the neutral position, 
     the third gearshift element S 3  is in the neutral position n 3  and 
     the fourth gearshift element S 4  is in the forward position v 4 . 
     The power transmission path runs directly via the main shaft  10 , and in the range group via the second gearwheel plane N 2  and the third gearwheel plane N 3 . 
     In the fifth forward gear V 
     the first gearshift element S 1  is in the neutral position, 
     the second gearshift element S 2  is in the rear position, 
     the third gearshift element S 3  is in the rear position h 3  and 
     the fourth gearshift element S 4  is in the neutral position n 4 . 
     The power transmission path runs via the constant input E 1 , the first gearwheel plane H 1 , and in the range group via the first gearwheel plane N 1  and the third gearwheel plane N 3 . 
     In the sixth forward gear VI 
     the first gearshift element S 1  is in the neutral position, 
     the second gearshift element S 2  is in the forward position, 
     the third gearshift element S 3  is in the rear position h 3  and 
     the fourth gearshift element S 4  is in the neutral position n 4 . 
     The power transmission path runs via the constant input E 1 , the second gearwheel plane H 2 , and in the range group via the first gearwheel plane N 1  and the third gearwheel plane N 3 . 
     In the seventh forward gear VII 
     the first gearshift element S 1  is in the rear position, 
     the second gearshift element S 2  is in the neutral position, 
     the third gearshift element S 3  is in the rear position h 3  and 
     the fourth gearshift element S 4  is in the neutral position n 4 . 
     The power transmission path runs via the constant input E 1 , the third gearwheel plane H 3 , and in the range group via the first gearwheel plane N 1  and the third gearwheel plane N 3 . 
     In the eighth forward gear VIII 
     the first gearshift element S 1  is in the forward position, 
     the second gearshift element S 2  is in the neutral position, 
     the third gearshift element S 3  is in the rear position h 3  and 
     the fourth gearshift element S 4  is in the neutral position n 4 . 
     The power transmission path runs directly via the main shaft  10 , and in the range group via the first gearwheel plane N 1  and the third gearwheel plane N 3 . 
     In the ninth forward gear IX 
     the first gearshift element S 1  is in the neutral position, 
     the second gearshift element S 2  is in the rear position, 
     the third gearshift element S 3  is in the neutral position n 3  and 
     the fourth gearshift element S 4  is in the rear position h 4 . 
     The power transmission path runs via the constant input E 1 , the first gearwheel plane H 1  and directly from the main shaft  10  to the transmission output shaft  22 . 
     In the tenth forward gear X 
     the first gearshift element S 1  is in the neutral position, 
     the second gearshift element S 2  is in the forward position, 
     the third gearshift element S 3  is in the neutral position n 3  and 
     the fourth gearshift element S 4  is in the rear position h 4 . 
     The power transmission path runs via the constant input E 1 , the second gearwheel plane H 2  and directly from the main shaft  10  to the transmission output shaft  22 . 
     In the eleventh forward gear XI 
     the first gearshift element S 1  is in the rear position, 
     the second gearshift element S 2  is in the neutral position, 
     the third gearshift element S 3  is in the neutral position n 3  and 
     the fourth gearshift element S 4  is in the rear position h 4 . 
     The power transmission path runs via the constant input E 1 , the third gearwheel plane H 3  and directly from the main shaft  10  to the transmission output shaft  22 . 
     In the twelfth forward gear XII 
     the first gearshift element S 1  is in the forward position, 
     the second gearshift element S 2  is in the neutral position, 
     the third gearshift element S 3  is in the neutral position n 3  and 
     the fourth gearshift element S 4  is in the rear position h 4 . 
     Accordingly in this twelfth forward gear XII both the main group  7  and the range group  12  are connected to direct through-drive, so that in the auxiliary range transmission  23  the direct gear is engaged. 
     In the first reverse gear R 1   
     the first gearshift element S 1  is in the neutral position, 
     the second gearshift element S 2  is in the neutral position, 
     the third gearshift element S 3  is in the forward position v 3  and 
     the fourth gearshift element S 4  is in the forward position v 4 . 
     The power transmission path runs via the constant input E 1 , the second gearwheel plane HR of the reverse gear, and in the range group via the second gearwheel plane N 2  and the third gearwheel plane N 3 . 
     In the second reverse gear R 2   
     the first gearshift element S 1  is in the neutral position, 
     the second gearshift element S 2  is in the rear position, 
     the third gearshift element S 3  is in the forward position v 3  and 
     the fourth gearshift element S 4  is in the rear position h 4 . 
     The power transmission path runs via the constant input E 1 , the second gearwheel plane HR of the reverse gear directly to the transmission output shaft  22 . 
     Here one of the three transmission ratios i 1  to i 3  is the direct through-drive. The auxiliary range transmission is preferably designed in such a way that the direct through-drive represents the highest, that is to say the fastest transmission ratio i 3 . Alternative configurations are also feasible, however. Thus the auxiliary range transmission  23  can in principle be configured in three different ways:
         a) embodiment with three different transmission ranges, that is range groups   b) embodiment with three split transmissions, which is not represented in the drawing here, and   c) embodiment with two split transmissions and one range transmission, which may be the direct through-drive, for example.
 
Whilst the configuration a) is represented in  FIG. 1  to  FIG. 2 , the configuration  3 ) is represented in  FIG. 4  and  FIG. 5  below.
       

     It can be seen from this that instead of the gearwheel plane HR of the reverse gear, one of the gearwheel planes H 1  to H 3  may also be arranged at the rearmost point of the main group  107 , so that its loose gear  113  can be coupled to the main shaft  110  by means of the third gearshift element S 3 . Such a configuration lends itself, in particular, to a crawler gear combined with the third gearshift element S 3 , which can then be used only in combination with the shortest transmission ratio i 3 . 
     According to  FIG. 4  the first gearwheel plane H 1  and the gearwheel plane HR of the reverse gear are transposed compared to the preceding exemplary embodiment. The transmission ratios are furthermore somewhat modified in practice. Instead of the gearwheel plane HR of the reverse gear, therefore, the first gearwheel plane H 1  of a forward gear is adjacent to the range group  112 . This first gearwheel plane H 1  of the forward gear has the highest transmission ratio—that is to say the shortest transmission—so that this first gearwheel plane H 1  forms a crawler gear I. Here this crawler gear I is engaged by the gearshift element S 3 , which is also assigned to the foremost loose gear  119  of the range group  112 . The range group  112  is used to form two split transmissions and one range transmission. 
     In the crawler gear I 
     the first gearshift element S 1  is in the neutral position, 
     the second gearshift element S 2  is in the neutral position, 
     the third gearshift element S 3  is in the forward position and 
     the fourth gearshift element S 4  is in the rear position. 
     The power transmission path runs via the constant input E 1 , the first gearwheel plane H 1 , and in the range group via the second gearwheel plane N 2  and the third gearwheel plane N 3 . 
     In the second forward gear II 
     the first gearshift element S 1  is in the neutral position, 
     the second gearshift element S 2  is in the forward position, 
     the third gearshift element S 3  is in the neutral position and 
     the fourth gearshift element S 4  is in the forward position. 
     The power transmission path runs via the constant input E 1 , the second gearwheel plane H 2 , and in the range group via the second gearwheel plane N 2  and the third gearwheel plane N 3 . 
     In the third forward gear III 
     the first gearshift element S 1  is in the neutral position, 
     the second gearshift element S 2  is in the forward position, 
     the third gearshift element S 3  is in the rear position and 
     the fourth gearshift element S 4  is in the neutral position. 
     The power transmission path runs via the constant input E 1 , the second gearwheel plane H 2 , and in the range group via the first gearwheel plane N 1  and the third gearwheel plane N 3 . 
     In the fourth forward gear IV 
     the first gearshift element S 1  is in the forward position, 
     the second gearshift element S 2  is in the neutral position, 
     the third gearshift element S 3  is in the neutral position and 
     the fourth gearshift element S 4  is in the forward position. 
     The power transmission path runs directly to the range group and thence via the second gearwheel plane N 2  and the third gearwheel plane N 3 . 
     In the fifth forward gear V 
     the first gearshift element S 1  is in the forward position, 
     the second gearshift element S 2  is in the neutral position, 
     the third gearshift element S 3  is in the rear position and 
     the fourth gearshift element S 4  is in the neutral position. 
     The power transmission path runs directly to the range group and thence via the first gearwheel plane N 1  and the third gearwheel plane N 3 . 
     In the sixth forward gear VI 
     the first gearshift element S 1  is in the rear position, 
     the second gearshift element S 2  is in the neutral position, 
     the third gearshift element S 3  is in the neutral position and 
     the fourth gearshift element S 4  is in the forward position. 
     The power transmission path runs via the constant input E 1 , the third gearwheel plane H 3 , and in the range group via the second gearwheel plane N 2  and the third gearwheel plane N 3 . 
     In the seventh forward gear VII 
     the first gearshift element S 1  is in the rear position, 
     the second gearshift element S 2  is in the neutral position, 
     the third gearshift element S 3  is in the rear position and 
     the fourth gearshift element S 4  is in the neutral position. 
     The power transmission path runs via the constant input E 1 , the third gearwheel plane H 3 , and in the range group via the first gearwheel plane N 1  and the third gearwheel plane N 3 . 
     In the eighth forward gear VIII 
     the first gearshift element S 1  is in the neutral position, 
     the second gearshift element S 2  is in the forward position, 
     the third gearshift element S 3  is in the neutral position and 
     the fourth gearshift element S 4  is in the rear position. 
     The power transmission path runs via the constant input E 1 , the second gearwheel plane H 2  and directly from the main shaft  110  to the transmission output shaft. 
     In the ninth forward gear IX 
     the first gearshift element S 1  is in the forward position, 
     the second gearshift element S 2  is in the neutral position, 
     the third gearshift element S 3  is in the neutral position and 
     the fourth gearshift element S 4  is in the rear position. 
     Accordingly in this ninth forward gear IX both the main group  107  and the range group  112  are connected to direct through-drive, so that in the auxiliary range transmission the direct gear is engaged. 
     In the tenth forward gear X 
     the first gearshift element S 1  is in the rear position, 
     the second gearshift element S 2  is in the neutral position, 
     the third gearshift element S 3  is in the neutral position and 
     the fourth gearshift element S 4  is in the rear position. 
     The power transmission path runs via the constant input E 1 , the third gearwheel plane H 3 , and directly from the main shaft  110  to the transmission output shaft. 
     Since in this exemplary embodiment the gearwheel plane HR of the reverse gear is connected to the second gearshift element S 2 —rather than the third gearshift element S 3 —there are, in contrast to the first exemplary embodiment, three available reverse gears R 1  to R 3 . 
     In the first reverse gear R 1   
     the first gearshift element S 1  is in the neutral position, 
     the second gearshift element S 2  is in the rear position, 
     the third gearshift element S 3  is in the rear position and 
     the fourth gearshift element S 4  is in the neutral position. 
     The transmission path runs via the constant input E 1 , the second gearwheel plane HR of the reverse gear, and in the range group via the first gearwheel plane N 1  and the third gearwheel plane N 3 . 
     In the second reverse gear R 2   
     the first gearshift element S 1  is in the neutral position, 
     the second gearshift element S 2  is in the neutral position, 
     the third gearshift element S 3  is in the forward position and 
     the fourth gearshift element S 4  is in the forward position. 
     The power transmission path runs via the constant input E 1 , the second gearwheel plane HR of the reverse gear, and in the range group via the second gearwheel plane N 2  and the third gearwheel plane N 3 . 
     In the third reverse gear R 3   
     the first gearshift element S 1  is in the neutral position, 
     the second gearshift element S 2  is in the neutral position, 
     the third gearshift element S 3  is in the neutral position and 
     the fourth gearshift element S 4  is in the rear position. 
     The power transmission path runs via the constant input E 1 , the second gearwheel plane HR of the reverse gear directly to the transmission output shaft  22 . 
     Instead of two main countershafts, it is also possible to provide three main countershafts. Alternatively or in addition it is also possible to provide three auxiliary countershafts instead of two auxiliary countershafts. The auxiliary countershafts and/or main countershafts may in particular be uniformly distributed around the periphery. 
     The embodiments described are only examples of configurations. It is also possible to combine the features described for different embodiments of the auxiliary range transmission. Further features, and in particular features not described, of the transmission parts pertaining to the invention are to be inferred from the gearwheel size ratios, that is to say in particular the transmission ratios, represented in the drawings.