Abstract:
The invention relates to a system of structural shapes to build a line of products having gears of different total ratio or a different number of ratio steps. Transmissions ( 2 ) of vehicles consisting of three successively disposed partial gears ( 10, 22 40 ), a main gear part ( 22 ), a multi-gear split gear part ( 40 ) and a multi-gear group transmission ( 10 ) have for the split gear part ( 40 ) and the group transmission part ( 10 ) and the gear steps of each main gear part ( 22 ) in all structural shapes on all gear wheels ( 28, 32, 36 ) the same number of teeth with at least those gear wheel pairs ( 28 - 52 - 54, 32 - 50, 36 - 48 ) corresponding to the gear wheel pairs of the structural shape of the transmission ( 2 ) having the least number of gear steps.

Description:
FIELD OF THE INVENTION 
     The invention relates to a system of structural shapes for transmissions of vehicles. 
     BACKGROUND OF THE INVENTION 
     The heavy costs compel manufacturers of transmissions to implement the necessary variants of a range of products with a minimum of different structural parts. Not only the variable cost of products is decisive, but also the complexity of costs resulting from the multiplicity of parts. 
     Changes in the internal combustion engines due to the introduction of the electronic injection techniques and the need of optimal solutions regarding costs for the different operation requirements of the vehicles always leads to different products. For example, in the class of medium and heavy trucks the gear range desired works with the following requirements: 
     12 gears, finely stepped in the upper gears; 
     optionally direct speed or high speed; 
     the same or similar conditions of the different gears; 
     10 gears with less fine grading; 
     broad torque ranges from about 1000 Nm to about 3000 Nm; 
     all products manually shifted, alternatively partly and/or fully automated. 
     A solution known already for use of similar parts in different transmissions is shown in the Applicant&#39;s ECOSPLIT-16-gear transmission disclosed, e.g. in the publication Johannes Looman&#39;s  Zahnradgetrieb , third edition, Springer Publishing House, Berlin Heidelberg 1996 on pages 264 ff in different shapes. The same transmission with different wheel widths leads to transmission of torques of different magnitude. Different ratio series result in designs for direct-speed of high-speed versions. Adaptations can be made by changing the lengths of the wheels, shafts, housing gear selection, etc. Additional aggregates like can result in a change of the housing and of the driving teeth. The multiplicity of products used leads to undesirably high logistic costs and costs of adaptation to the respective individual situations. DE 41 29 290 A1 has disclosed a transmission line of products in a multi-gear transmission for reducing the multiplicity of parts for different admissible input torques. But here are provided only transmissions having the same number of ratio steps. The transmission lines of products do not concern any transmission with a different number of gears. 
     The transmissions often have versions with two different ratio series. This is offered by transmission manufacturers so that the vehicle manufacturers have available transmissions of equal structure which are adaptable to different utilizations of the vehicles. Thus, transmission in high-speed and direct-speed versions, e.g. can be built which are used in the cross-country or on the road. 
     The problem on which this invention is based is to overcome the existing problems and high costs and to show a system of structural parts for equivalent uses which are interchangeable for different transmissions having different numbers of gears. 
     SUMMARY OF THE INVENTION 
     It is proposed to provide a line of products of transmissions in a manner such that, departing from a basic variant which has a specific arrangement of gear wheel pairs, one other variant can be produced by changing or adding in the form of a modular system only one gear wheel pair. Thereby can be obtained a modified total ratio of the transmission either by maintaining the former number of ratio steps or by a higher number of ratio steps. In all cases, the gear wheels of the group transmission remain unchanged. All gear wheel pairs of the variant with the smallest number of reduction steps are kept in all variants. 
     The whole transmission consists of a multi-gear split gear part, a multi-gear main gear part and a multi-gear group transmission which are successively disposed in one line. The inventive system can be used both for transmissions having one countershaft and in transmissions having a load distribution over several, preferably two, countershafts. The group transmission preferably consists of a planetary transmission whose sun gear is driven by the main shaft of the transmission and whose planet carrier constitutes the output shaft of the transmission and whose planet carrier constitutes the output shaft of the transmission. The ring gear of the planetary transmission can optionally be coupled with the transmission housing or with the planet carrier to form different ratio steps. The basic variant is preferably formed by 8-gear variants. According to the inventive system, on the basis of the latter designs of 10-gear variants and 12-gear variants are advantageously formed. 
     As a basic condition, the ratio step i between all ratio steps is the same. The ratio step can also be provided as half ratio step φ 0.5 . The axial distances of the shafts in the transmissions are the same in all variants. 
     In an advantageous embodiment, the 12-gear variant has in comparison with the 10-gear variant an additional gear wheel pair shaped so that in the 12-gear transmission the ratio of the ninth gear is between the ratios of the gears 8 and 9 of the 10-gear transmission and the ratio of the eleventh gear is between the ratios of the gears 9 and 10 of the 10-gear transmission. 
     In another advantageous embodiment, it is proposed to build a high-speed variant of a transmission having the same number of ratios steps, to change one wheel pair of the main gear which does not constitute a constant wheel pair and to leave other wheel pairs of the transmission the same. 
     In one other advantageous embodiment, it is proposed to build a high-speed variant of a transmission having a number of ratio steps increased by two ratio steps, to add a wheel pair of the main gear and leave the same the other wheel pairs of the transmission. 
     Another advantageous embodiment comprises to build a high-speed variant of a transmission having a number of ratio steps increased by two ratio steps and formed from a direct-speed variant, the addition of a wheel pair to the main gear, the added wheel pair not constituting a wheel pair of a constant and the other wheel pairs of the transmission remaining the same. 
     In another advantageous embodiment, it is proposed to build a high-speed variant, to substitute for a wheel set of a constant a wheel set quicker by two ratio steps and to leave the same the other wheel pairs of the transmission. 
     One other advantageous embodiment proposes, in the manual gear shift of the transmission for changing the selector lever positions of a shift pattern, to dispose at least one gear wheel of the main gear upon the same shaft turned by 180 degrees around an imaginary axis. The imaginary axis is perpendicular to a longitudinal axis of the shaft. 
     In another advantageous embodiment, it is proposed that in a 12-gear transmission the ratio steps 1 to 8 and the reverse gear is manually shiftable and the ratio steps 9 to 12 automatedly shiftable and in the shift pattern of the transmission that a selector position is provided which marks the introduction of an automated gear shift mode. 
     A In another advantageous embodiment, it is proposed that in a 10-gear transmission the ratio steps 1 to 8 and the reverse gear is manually shiftable and the ratio steps 9 and 10 is automatedly shiftable and in the shift pattern of the transmission a selector lever position be provided which marks the introduction of an automated shift mode. 
     In still another advantageous embodiment, it is proposed that in a 10-gear transmission the ratio steps 1 to 6 and reverse gear is manually shiftable and the ratio steps 7 to 10 automatedly shiftable and in the shift pattern of the transmission a selector lever position is provided which marks the introduction of an automated gear shift mode. 
     For the above mentioned transmissions with automated shift mode, it is proposed as an advantageous design that the selector lever position for the automated shift mode be in an H- or HH-shift pattern in the outer right end of the selector gate. 
     Another advantageous shift pattern shows the selector lever position for the automated gear shift mode in an H- or HH-shift pattern at the end of an outer right shift gate. 
     Still another advantageous shift pattern shows the selector lever position for the automated gear shift mode in an H- or HH-shift pattern also in the outer right end of the selector gate, wherein to reach the selector lever position, there is provided in the selector gate a position in which is effected the gear shift of the range change group. 
     Still one other advantageous embodiment shows that the 12-gear variant, unlike the 10-gear variant, has an additional gear wheel pair which is shaped so that in the 12-gear transmission the ratio of the ninth gear is quicker by half a speed ratio change φ 0.5  than the ratio of the eighth gear of the 10-gear variant and the ratio of the eleventh gear is quicker by half a speed ratio change than the ratio of the 10-gear variant. 
     Still another advantageous embodiment shows that the 12-gear variant, unlike the 10-gear variant, has an additional gear wheel pair shaped so that in the 12-gear transmission the ratio of the tenth gear is half of a speed ratio change φ 0.5  quicker than the ratio of the ninth gear of the 10-gear variant and the ratio of the twelfth gear is quicker by half a speed ratio change than the ratio of the tenth gear of the 10-gear variant. Thereby the total spreading of the transmission is increased by one half φ 0.5  a speed ratio change. 
     In another advantageous embodiment, it is proposed that in the partial gears a different number of identical countershafts is respectively provided, the wheel pairs in transmissions with different capacities having the same tooth widths and the housing and gear shifts being equal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is explained in detail with reference to the drawings which show: 
     FIG. 1 is a transmission diagram for a direct-speed transmission with 8 gears; 
     FIG. 2 is a transmission diagram for a high-speed transmission with 8 gears; 
     FIG. 3 is a shift pattern for an 8-gear transmission; 
     FIG. 4 is a transmission diagram for a direct-speed transmission with 10 gears; 
     FIG. 5 is a transmission diagram for a high-speed transmission with 10 gears; 
     FIG. 6 is a shift pattern for a 10-gear transmission; 
     FIG. 7 is a transmission diagram for a direct-speed transmission with 10 gears; 
     FIG. 8 is another transmission diagram for a high-speed transmission with 10 gears; 
     FIG. 9 is another shift pattern for a 10-gear transmission; 
     FIG. 10 is a transmission diagram for a direct-speed transmission with 12 gears; 
     FIG. 11 is a transmission diagram for a high-speed transmission with 12 gears; 
     FIG. 12 is a shift pattern for a 12-gear transmission; 
     FIG. 13 is anothertransmission diagram for a high-speed transmission with 12 gears; 
     FIG. 14 is another transmission diagram for a high-speed transmission with 12 gears; 
     FIG. 15 is another shift pattern for a 12-gear transmission; 
     FIGS. 16 to  20  are shift patterns; and 
     FIGS. 21 to  24  are ratio series. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In all figures, the same part are provided with the same reference numerals. 
     FIG. 1 shows a transmission  2  in an 8-gear variant. An input shaft  4  is placed coaxially to a main shaft  6  of a main gear part  22 . At the end of the main shaft  6  is provided a sun gear  12  of a group transmission part  10  designed as planetary transmission. The sun gear  12  meshes with planetary gears  14  which are supported on a planet carrier  20 . The planetary gears  14  further mesh with a ring gear  16  which, via a shift device  24 , can be connected either with the housing  26  or with the output shaft  8  of the transmission  2 . The output shaft  8  is connected with the planet carrier  20 . Upon the main shaft  6  are further situated a reverse gear wheel  28  which can be non-rotatably connected, via a shifting device  30 , with the main shaft  6 . Upon the main shaft  6  is also situated a gear wheel  32  which can be non-rotatably connected, via a shift device  34 , with the main shaft  6 . One other gear wheel  36  upon the shaft  6  can be likewise connected, via the shift device  34 , with the shaft  6 . The gear wheel  36  can also be connected, via the shift device  38 , in the split gear part  40  with the input shaft  4 . The input shaft  4  carries a gear wheel  42  which is freely rotatable in relation to the input shaft and is engaged with a gear wheel  44  of the countershaft  46  of the main gear  42 . On its axial end, facing the main gear  22 , the input shaft  4  carries the shift device  38 , which makes possible for a torque transmission non-rotatably to connect the input shaft  4  either with the loosely turning gear wheel  42  or with the gear wheel  36  freely rotatably situated upon the main shaft  6  of the main gear  22 . The first gear wheel pair with the loose gear wheel  42  upon the input shaft  4  and the gear wheel  44  upon the countershaft  46  meshing therewith also are often designated as first constant or constant I while the second gear wheel pair consisting of the loose gearwheel  36  situated upon the main shaft  6  and the gear wheel  48  upon the countershaft meshing therewith are designated as second constant or constant II. With the aid of the shift device  38 , either the constant I or the constant II is engaged in the torque transmission. One other gear wheel  50  upon the countershaft  16  meshes with the gear wheel  32  and a gear wheel  52  upon the countershaft  26  meshes with a reverse gear  54  which, in turn, meshes with the gear wheel  28 . 
     FIG. 2 shows a high-speed variant of the 8-gear transmission of FIG.  1 . The gear wheel pair of the constant I consisting of the gear wheels  42  and  44  of FIG. 1 is exchanged for a gear wheel pair quicker by two ratio steps and consisting of the gear wheels  56  and  57 . All other parts remain the same as in FIG.  1 . 
     FIG. 3 shows a shift pattern  58  for 8-gear transmissions which applies to both variants of FIG.  1  and FIG.  2 . In the selector lever position, designated with R 1 / 2 , the shift device  30  of FIG. 1 is operated so that the gear wheel  28  for the reverse motion is non-rotatably connected with the main shaft  6 . The change over between first and second reverse motion results from the shift device  38  in the split gear part  40 , the selector lever position being retained in the position R 1 / 2 . When changing to the shift gate  68 , the shift device  30  is first disengaged from its torque transmission and then the selector lever position for either the gears ½ or ¾ is introduced in the shift gate  68  by actuating the shift device  34 . In the selector lever positions, the same as in all the correspondingly designated positions that follow, the shift device  38  also effects a change between gear  1  and  2  or  3  and  4 . A change in the shift gate  70  produces a change over of the shift device  24  from a slow ratio to a quick ratio. To this end in the selector gate  72  is overcome a position  75  which produces a predominantly pneumatically actuated change over of the shift device  24 . Then, during the shift in the shift gate  70 , the shift device  34  is again actuated to the right, according to FIG. 1 or  2 , to reach the selector lever position  5 / 6  and to the left to reach the position  7 / 8 . 
     The transmission variants of FIGS. 1 and 2 show the basic variants. The teeth of the parts used therein are provided in all variants that follow and remain equal for all variants. 
     FIG. 4 thus shows a 10-gear transmission which, unlike the transmission in FIG. 1, has an additional gear wheel pair. The additional gear wheel pair consists of the gear wheel  60  loosely rotatable on the main shaft  6  and the gear wheel  62  fixedly connected with the countershaft. A modified&#39;shift device  64  is provided for non-rotatable connection of the gear wheels  60  and  28  with the main shaft  6 . 
     FIG. 5 thus shows a 10-gear transmission in a high-speed variant which, unlike the transmission in FIG. 2, has an additional gear wheel pair. The additional gear wheel pair consists of the gear wheel  60  loosely rotatable on the main shaft  6  and the gear wheel  62  firmly connected with the countershaft  46 . To non-rotatably connect the gear wheels  60  and  62  with the main shaft  6 , a modified shift device  64  is again provided. Unlike the variant, such as shown in FIG. 4, the variant according to FIG. 5 has a changed constant I which here, the same as in FIG. 2, consists of a gear wheel pair which comprises the gear wheels  56  and  57 . All other teeth correspond to the teeth of the basic variant both in the direct-speed variant according to FIG.  1  and in the high-speed variant according to FIG.  2 . 
     FIG. 6 shows a shift pattern  66  for 10-gear transmissions which applies to both variants of FIG.  4  and FIG.  5 . In the selector lever position, designated with R 1 / 2 , the shift device  64  of FIG. 4 is operated so that the gear wheel  28  for the reverse gear is non-rotatably connected with the main shaft  6 . The change over between the first and second reverse gears results by the shift device  38  in the split transmission part  40 , wherein the selector lever position is maintained in the position R 1 / 2 . According to this shift pattern, the forward gears  1  and  2  are in the same shift gate  74  as the reverse gears. When changing in the shift gate  76 , the shift device  64  is first disengaged from its torque transmission and then the selector lever position for either the gears  5 / 6  or  3 / 4  is introduced in the shift gate  76  by actuating the shift device  34 . A change in the shift gate  78  produces a change over of the shift device  24  from a slow ratio to a quick ratio. To this end in the selector gate  80 , a position  82  is overcome which produces a predominantly pneumatically actuated. change over of the shift device  24 . 
     FIG.  7  and FIG. 8 show two other variants of a 10-gear transmission with a modified arrangement of the gear wheel pairs so that in the outer shift gate  86  according to FIG. 9 there must be provided a reversal of shifting direction. FIG. 7 uses the same parts as the variant in FIG.  4 . The gear wheel  32  is disposed on the main shaft  6  rotated by 180° around an imaginary axis  88  which stands perpendicularly on the axis  90  formed by the longitudinal axis of the main shaft  6 . The gear wheels  28  and  60  are likewise turned by 180°. The shift device  92 ,  94  and  96  are correspondingly changed. The actuation to the right of the respective shift devices in each figure corresponds to the upward movement from the respective selector gate to a selector lever position in the appertaining shift pattern. FIG. 9 shows such a shift pattern  98  for 10-gear transmissions which applies to both variants according to FIG.  7  and FIG.  8 . In the selector lever position, designated with R 1 / 2 , the shift device  96  of FIG. 7 is operated so that the gear wheel  28  for the reverse gear be non-rotatably connected with the main shaft  6 . To that end, the shift device  96  is moved to the left in FIG.  7 . The shifting between the first and second reverse gears results by the shift device  38  in the split transmission part  40 , the selector lever position being retained in the position R 1 / 2 . According to this shift pattern, the forward gears  1  and  2  are in the same shift gate  100  as the gears  3  and  4  corresponding to the shift pattern  58  in FIG.  3 . When changing in the shift gate  100 , the shift device  96  is first switched off from its torque transmission and then, by actuating the shift device  94 , the selector lever position either for the gears ½ or for the gears ¾ is introduced in the shift gate  100 . A change in the shift gate  102  produces a change over of the shift device  24  from a slow ratio to a quick ratio. For that purpose, there is overcome in the selector gate  104  a position  82  which causes a change over of the predominantly pneumatically actuated shift device  24 . In the shift gate  102  are obtained the shift positions  5 / 6  and  7 / 8  for the corresponding gears  5 ,  6  and  7  and  8 . A further movement to the right in the shift pattern  98  leads to a shift gate  106  where lies the selector lever position for the gears  9  and  10 . If the selector lever in the shift gate  100  is guided from top to bottom, this corresponds to a shift movement of the shift device  94  from right to left in FIG.  7  and FIG. 8. A movement of the selector lever from the position  3 / 4  in the shift gate  100  to the position  5 / 6  in the shift gate  102  corresponds to a movement of the shift device  94  from left to right in FIGS. 7 and 8. Due to the fact that after overcoming the position  82 , a change over of the planetary transmission has occurred, the same transmission ratio as previously is not reached despite the engagement of the same gear wheel  60  in the torque transmission. Upon reaching the selector lever position  9 / 10  relative to the selector gate  104 , on one hand, a position opposite to the position R 1 / 2  is assumed but, on the other hand, the shift device  92  for connecting the gear wheel  36  with the main shaft must be moved to the left in FIGS. 7 and 8, a reversal of direction of movement of the selector lever in the shift gate  106  is required. But the same steps needed for this purpose are not object of this invention. 
     FIG. 8 shows the configuration corresponding to FIG. 7 for a high-speed variant of the 10-gear transmission according to FIG.  5 . 
     FIG. 10 shows a variant of a 12-gear transmission where, unlike the variant according to FIG. 7, one other gear wheel pair is added. The additional gear wheel pair comprises the gear  108  loosely rotatable on the main shaft  6  and the gear wheel  110  firmly connected with the countershaft  46 . A modified shift device  92  is provided for the non-rotatable connection of the gear wheels  108  and  36  with the main shaft  6 . 
     FIG. 11 shows a 12-gear transmission in a high-speed variant which unlike the transmission of FIG. 8 has an additional gear wheel pair. The additional wheel pair comprises the gear wheel  108  loosely rotatable on the main shaft  6  and the gear wheel  110  firmly connected with the countershaft  46 . A modified shift device  92  is again provided for nonrotatable connection of the gear wheels  108  and  36  with the main shaft  6 . Compared to the variant, such as shown in FIG. 10, the variant according to FIG. 11 has a changed constant I which like in FIG. 2 consists here of a gear wheel pair comprising the gear wheels  56  and  57 . All other teeth correspond to the teeth of the basic variant both in the direct-speed variant of FIG.  1  and in the high-speed variant of FIG. 2 
     FIG. 12 shows a shift pattern  114  for a 12-gear transmission. Compared to the shift pattern of FIG. 9, an additional shift position  10 / 12  is provided in the shift gate  106 . When the selector lever moves to this position, the shift device  92  of FIG. 10 or  11  moves to the left so that a connection is obtained between gear wheel  36  and main shaft  6 . The shift pattern  114  applies to both variants according to FIG.  10  and FIG.  11 . 
     FIG. 13 shows one other high-speed variant for a 12-gear transmission where, unlike the direct-speed variant of FIG. 10, not the gear wheel pair of the constant I consisting of the gear wheels  42  and  44 , but the two gear wheels  108  and  1   10  are replaced by the two gear wheels  116  and  117 . The wheel pair  116 - 117  is quicker by a whole ratio range than the original wheel pair. It is thereby possible, while maintaining constant I and constant  11 , to obtain from the direct-speed variant a high-speed variant having a total spread higher by a half ratio range. 
     FIG. 14 shows another high-speed variant for a 12-gear transmission having a changed constant I in comparison with FIG.  13 . Compared to the high-speed variant of FIG. 11, only the gear wheels  108  and  110  are here exchanged for the gear wheels  116  and  117  which have a total spread higher by half a ratio range. 
     In the shift pattern  114  of FIG. 12, when the highest shift position  10 / 12  is reached, the shift device  92  is moved to the left in FIG.  10  and FIG.  11 . However, in the shift pattern  118  of FIG. 15, which applies to the high-speed variants of FIG.  13  and FIG. 14, the shift device  92  must be moved to the right in FIG.  13  and FIG. 14, since the highest ratios are obtained when engaging the gear wheel  116 . If the arrangement of the shift positions from shift pattern  114  should also be kept in shift pattern  118 , similarly to FIG. 9 the shift direction must be reversed in the shift gate  106  in shift pattern  118 . But the steps needed to this end are not object of this invention. 
     FIG.  16  and FIG. 17 show two shift patterns  120  and  122  for a transmission having a partial automation of the gears above the sixth gear. The shift patterns  120  and  122  can be used for 10-gear variants. In the selector gate  80 , a position  82  is overcome during the selection and a gear shift position AUTO is obtained, which in the shift pattern  122  is at the right end of the selector gate  80 . In the shift pattern  120 , the shift position is on the upper end of the shift gate  78 . In the shift position AUTO, all gear shifts are no longer produced by changing the shift positions by means of selector levers, the higher gears being automatically engaged within admissible limits by a computer unit. 
     FIG.  18  and FIG. 19 show shift patterns  124  and  126  corresponding to the shift patterns  98 ,  114  and  118  of FIGS. 9,  12  and  15 . They apply to 10-gear and 12-gear variants with adequate arrangement of the shift positions AUTO in the shift gate  106  or at the end of the selector gate  104 . 
     FIG. 20 shows a shift pattern  128  corresponding to the shift pattern  66  of FIG.  6 . The shift pattern  128  applies to 10-gear variants, the gear shift position AUTO being situated in the shift gate  78 . 
     FIG. 21 shows by way of example a construction of the ratio line of a 12-gear transmission with a shift pattern  114  according to FIG. 12 and a transmission diagram according to FIG.  10 . It can be seen that for the first four gears of the group transmission part  10 , each is engaged in the slow ratio step. Starting from the fifth gear, the group transmission part  10  is  1 shifted to the quick ratio step and remains for the gears that follow in the shifted position which no more is changed. In each of the fifth to eighth gears the same gear wheels  32 ,  36 ,  42  and  60  are shifted as in the gears one to four only with the high-speed ratio step in the group transmission part  10 . In gears nine and eleven, either the gearwheel  42  of the constant I or the gear wheel  36  of the constant II are engaged, the same as the gear wheel  108  in the torque transmission. In the gears ten and twelve either the gear wheel  42  of the constant I and gear wheel  36  are engaged in the torque transmission or a direct connection of the input shaft  4  with the main shaft  6  is obtained. 
     FIG. 22 shows by way of example a construction of the ratio line of a 10-gear transmission with a shift pattern  98  according to FIG. 9 and a transmission diagram according to FIG.  7 . It can be seen that each of the first four gears of the group transmission part  10  is shifted to the slow ratio step. Starting from the fifth gear, the group transmission part  10  is shifted to the quick ratio step and for the gears that follow remains in this switched position which no more is changed. In each of the gears five to eight, the same gear wheel  32 ,  36 ,  42  and  60  are shifted as in gears one to four only with the quick ratio step in the group transmission part  10 . Compared to FIG. 10, the gearwheel  108  is missing in FIG. 7, Therefore, the ratio of the ninth gear corresponds to the ratio of the tenth gear of FIG.  21  and the ratio of the tenth gear to the ratio of the twelfth gear of FIG.  21 . It results herefrom that in the 12-gear variant of FIG. 21, the ratio of the ninth gear is between the ratios of the eighth and ninth gears of the 10-gear variant of FIG.  22  and the ratio of the eleventh gear of the 12-gear variant is between the ratios of the ninth and tenth gears of the 10-gear variant. In the gears nine and ten, either the gear heel  42  of the constant I and gear wheel  3  are engaged in the torque transmission or a direct connection of the input shaft  4  with the main shaft  6  is obtained with the shift devices  92  and  38 . 
     FIG. 23 shows by way of example one other construction of the ratio line of a 10-gear transmission with a shift pattern  66  according to FIG. 6 and a transmission diagram according to FIG.  4 . It can be seen that for each of the first six gears of the group transmission part  10 , the slow ratio step is shifted to. In the gears five and six either the gearwheel  42  of the constant I and the gear wheel  36  are engaged in the torque transmission or a direct connection of the input shaft  4  with the main shaft  6  is obtained with the shift device  34  and  38 . Starting from the seventh gear, the group transmission part  19  is shifted to the quick ratio step and for the gears that follow remains in this switched position which is changed no more. In the gears seven to ten, the same gear wheels  32 ,  36  and  42  are shifted as in the gears three to six only with the quick ratio step in the group transmission part  10 . Compared to FIG. 10, the gearwheel  108  is missing in FIG.  4 . Therefore, the ratio of the ninth gear corresponds to the ratio of the tenth gear of FIG.  21  and the ratio of the tenth gear to the ratio of the twelfth gear of FIG.  21 . It results herefrom that in the 12-gear variant of FIG. 21, the ratio of the ninth gear is between the ratios of the eighth and ninth gears of the 10-gear variant of FIG.  23  and the ratio of the eleventh gear of the 12-gear variant is between the ratios of the ninth and tenth gears of the 10-gear variant. 
     FIG. 24 shows by way of example a construction of the ratio line of an 8-gear transmission with a shift pattern  58  according to FIG. 3 and a transmission diagram according to FIG.  1 . It can be seen that for the first four gears of the group transmission part  10 , each is shifted to the slow ratio step. In the gears three and four either the gear wheel  42  of the constant I and the gear wheel  36  are engaged in the torque transmission or a direct connection of the input shaft  4  with the main shaft  6  is obtained with the shift devices  34  and  38 . Starting from the fifth gear, the group transmission part  10  is shifted to the quick ratio step and for the gears that follow remains in this shifted position which is no more changed. In each of the gears five to eight, the same gear wheels  32 ,  36 , and  42  are shifted as in the gears one to four only with the quick ratio step in the group transmission part  10 . 
     Reference Numerals 
       2  transmission 
       4  input shaft 
       6  main shaft 
       8  output shaft 
       10  group transmission part 
       12  sun gear 
       14  planetary gears 
       16  ring gear 
       20  planet carrier 
       22  main gear part 
       24  shift device 
       26  housing 
       28  reverse gear wheel 
       30  shift device 
       32  gear wheel 
       34  shift device 
       36  gear wheel 
       38  shift device 
       40  split gear part 
       42  gear wheel 
       44  gear wheel 
       46  countershaft 
       48  gear wheel 
       50  gear wheel 
       52  gear wheel 
       54  reverse gear wheel 
       56  gear wheel 
       57  gear wheel 
       58  shift pattern 
       60  gear wheel 
       62  gear wheel 
       64  shift device 
       66  shift pattern 
       68  shift gate 
       70  shift gate 
       72  selector gate 
       74  shift gate 
       75  position 
       76  shift gate 
       78  shift gate 
       80  selector gate 
       82  position 
       86  shift gate 
       88  axis 
       90  axis 
       92  shift device 
       94  shift device 
       95  shift device 
       98  shift pattern 
       100  shift gate 
       102  shift gate 
       104  selector gate 
       106  shift gate 
       108  gear wheel 
       110  gear wheel 
       114  shift pattern 
       116  gear wheel 
       117  gear wheel 
       118  shift pattern 
       120  shift pattern 
       122  shift pattern 
       124  shift pattern 
       126  shift pattern 
       128  shift pattern