Patent Publication Number: US-2005115345-A1

Title: Transmission with particular transmission shafts

Description:
According to the preamble of claim  1 , the invention relates to a transmission for a motor vehicle.  
      The pre-published German patent application DE 103 05 241 A1 shows a dual-clutch transmission  30  ( FIG. 3 ) where the input sides of both clutches K 1 , K 2  of the dual-clutch are connected with a drive shaft  2  of a prime mover (not shown).  
      The output sides of the two clutches K 1 , K 2  are non-rotatably connected with two transmission input shafts of which one input shaft  3  is designed as hollow shaft and in which the second input shaft  4  is coaxially accommodated and rotatably supported.  
      To form transmission speeds, upon the two input shafts  3 ,  4  fixed gear wheels  11 ,  13 ,  14 ,  44 ,  37  are situated, which are rotatably supported with idler gears  7 ,  9 ,  10 ,  35  on a first countershaft  5  and with idler gears  16 ,  17 ,  34 ,  36  upon a second countershaft  6 .  
      A reverse gear shaft having one reverse gear wheel (not shown), which for reversal of direction or rotation meshes with the fixed gear  14  and the reverse gear idler gear  10 .  
      The transmission  30  further has available upon both paraxial countershafts  5 ,  6 , so-called shifting sets  23 ,  25 ,  31 ,  32  with synchronizer rings and sliding sleeves which, by actuation devices (not shown), are axially displaceable upon the countershafts  5 ,  6  for non-rotatable connection of the latter with the idler gears.  
      Besides, one output gear wheel  18 ,  19  is fastened on each one of the two countershafts  5 ,  6  and meshes with a toothing  20  on a differential transmission  21 .  
      This dual-clutch transmission  30  further has available one other coupling device  38  by means of which the two transmission input shafts  5 ,  6  can be optionally non-rotatably interconnected.  
      Finally the gear sequence in the dual-clutch transmission  30 , starting from the two clutches K 1  and K 2  of the dual clutch, is as follows: reverse gear RG and second gear G 2 ; fourth gear G 4  and sixth gear G 6 ; fifth gear G 5  and seventh gear G 7 ; first gear G 1  and third gear G 3 .  
      A transmission  30 . 1  is derived from this dual-clutch transmission shown in  FIG. 4 , having only one starting gear clutch K 1 , which is not known from the pre-published German patent application DE 103 05 242 A1. As shown by a comparison between the two transmissions according to  FIGS. 3 and 4 , both are, to a great extent, identically designed so that considerable savings in cost are possible in the development, production and storage of transmission parts both of the dual-clutch transmission and of the transmission.  
      Let it be only marginally observed that the transmission  30 . 1 , according to  FIG. 4 , despite the immediately adjacent arrangement of each two non consecutive transmission gears in an H-gate, can be shifted without problem when using a conversion device for the purpose, such as disclosed in the unpublished DE 102 31 547 A1.  
      As shown by the comparison between the two transmissions of  FIG. 3  and  FIG. 4 , the essential difference between them is that the dual-clutch transmission  30  has two input shafts  3 ,  4  available, while the transmission  30 . 1  of  FIG. 4  has only one transmission input shaft  4 . 1  connected with the output side of the clutch K 1  and upon which are fastened all input-side fixed gears  11 ,  13 ,  14 ,  33 ,  37  of the transmission  30 . 1 . For this reason, the transmission input shaft  4 . 1  has to be separately laid out, produced and stored as a single part of the two transmissions  30 ,  30 . 1 , which increases the development, production and storage costs.  
      Against this background, the problem on which the invention is based is to introduce a technical solution, especially for the described mechanical assembly, a principle for production of a dual-clutch transmission and of a transmission having only one starting and gear clutch by which further savings in cost can be obtained regarding the different transmission input shafts.  
      The solution of the problem results from the features of the main claim while advantageous developments and embodiments of the invention can be understood from the sub-claims.  
      The invention departs from a transmission having one starting and/or gear clutch, the input side of which is connected with one drive shaft of a prime mover and the output side with one transmission input shaft upon which fixed gears are fastened. The transmission has further available at least one countershaft upon which are rotatably supported or fastened gear wheels designed as idler gears or as fixed gears situated and designed as fixed gears or rotatably supported and designed as idler gears, and shifting sets which, for connecting the idler gears with the respectively coordinated shaft, are non-rotatably and axially moveably supported on the shaft and are there axially movable by way of setting devices.  
      To solve the stated problem it is provided in this transmission that the input shaft be comprised of at least two non-rotatably interconnected part shafts.  
      In development of this inventive basic principle, it can be provided that the part shafts be interconnected with positive fit or frictional engagement by shaft couplings, heat shrinking or thermal jointing process.  
      In a special embodiment of the invention, the part shafts can be designed as full shafts joined to each other by their respective front sides.  
      Another alternative of the non-rotatable connection between the part shafts can determine that the part shafts be interconnected by means of axial or radial plug-in toothings.  
      According to another development of the invention, one of the part shafts can be designed as a full shaft and another part shaft as a hollow shaft with the full shaft being non-rotatably accommodated in the hollow shaft. In addition, the hollow shaft used construction can also be used in building a dual-clutch transmission.  
      In this connection, it is deemed convenient that the idler and fixed gears, as well as the coupling devices, situated on the part shafts have the same design and be arranged in the same sequence in the transmission as in a dual-clutch transmission.  
      For using at least one full shaft of the transmission also in a dual-clutch transmission, it is preferably provided that in its end facing the clutch, the shaft is made shorter in comparison with the full shaft of the dual-clutch transmission.  
      In addition, compared to the hollow shaft of the dual-clutch transmission, it is advantageous that the hollow shaft of the transmission has a reduced internal diameter and/or a plug-in toothing so that the full shaft can be accommodated therein in force-locking and/or positive fit manner.  
      In addition, it can be provided that at least one full shaft has axial and/or radial bores available to reduce the weight and/or to design pressure medium lines.  
      The inventive construction principle is not basically limited to transmissions having two countershafts. On the contrary, the design can also be used in transmissions having only one countershaft preferably paraxial with the transmission input shaft. 
    
    
      For better understanding of the invention, the description is accompanied by one drawing which shows:  
       FIG. 1  is a diagrammatic representation of a seven-speed transmission;  
       FIG. 2  is an alternative to the transmission according to  FIG. 1 ;  
       FIG. 3  is an already known dual-clutch transmission; and  
       FIG. 4  is a seven-speed transmission according to the prior art. 
    
    
      For better orientation in the above mentioned Figures, in prior art transmissions and in the inventive transmissions, the same reference numerals have been given to the same parts of the transmission. The features of the transmission, according to the prior art already explained above ( FIG. 3  and  FIG. 4 ), will not be repeated herebelow but will be referred to.  
      As can now be understood from  FIG. 1 , the shaft arrangement and speed sequence of an inventively designed transmission  1  are quite similar to the design of the already known transmission of  FIG. 3  and  FIG. 4 . The latter, thus has in the first place, one starting and gear clutch AK the input side of which is connected width a drive shaft  2  of a prime mover.  
      In this embodiment, an output side  8  of the clutch AK is connected via a short section with a transmission input shaft  22 ,  24  paraxially with which two countershafts  5 ,  6  are disposed. But the transmission input shaft  24  can also be directly and non-rotatably connected with the output side of the clutch AK  
      Upon the two countershafts  5 ,  6  are rotatably supported idler gears  7 ,  9 ,  10 ,  16 ,  17 ,  34 ,  35 ,  36  of the seven forward speeds and of the reverse speed, which can be driven by the gear wheels (fixed gears)  11 ,  13 ,  14 ,  33 ,  37  fastened on the transmission input shaft  22 ,  24 .  
      On the ends pointing to the clutch AK of the two countershafts  5 ,  6 , output gear wheels  18 ,  19  are fastened, which are meshed with a toothing  20  of an axle-differential transmission  21  so that the latter can be driven by the two countershafts  5 ,  6 .  
      The arrangement or distribution of the idler and fixed gears on the transmission shafts is not critical for utilization of the advantages resulting from the invention.  
      In comparison with the known vehicle transmission, it is possible to achieve a development, production and storage of parts of more favorable cost. According to the core idea of the invention, it is provided, that the single transmission input shaft consists of two non-rotatably interconnected part shafts  22  and  24  which, with regard to the arrangement and design of said fixed gears  11 ,  13 ,  14 ,  33 ,  37 , could be likewise used in a dual-clutch transmission  30  ( FIG. 3 ) with only slight changes.  
      As made clear by a comparison of these two transmissions  1  and  30 , according to  FIG. 1  and  FIG. 3  and according to the principle on which the invention is based, it is not necessary to provide as separate, a transmission input shaft  4 . 1  like in the known transmission according to  FIG. 4 . On the contrary, the transmission  1 , according to  FIG. 1 , uses a hollow shaft  24  as a first transmission input shaft which, in the dual-clutch transmission  30 , is provided with the reference numeral  3 . Although in this embodiment, the section close to the clutch in the hollow shaft  24 , compared with the hollow shaft  3 , has been shortened by a portion for saving weight; the other construction and dimensions thereof are identical to a great extent.  
      In this hollow shaft  24 , the second transmission input shaft  22  is un-rotatably supported which, unlike the transmission input shaft  4  of the dual-clutch transmission  30 , has also been shortened by a portion close to the clutch which is indicated by a connecting means  12 ,  15 .  
      With regard to the arrangement and design of the speed fixed gears, the same as of its own design and other dimensions, the second transmission input shaft  22  preferably has the same design as the transmission input shaft  4  of the known dual-clutch transmission  30  according to  FIG. 3 .  
      The connection of the two transmission input shafts  22 ,  24  can be detachable even if for some cases an undetachable connection is preferred. This connection can also be a friction engaged or positive fit connection. In a detachable connection, for example, a plug-in toothing with axial or radial toothing means, is preferred.  
      In development of the invention, it can be convenient that the hollow shaft  24  has a smaller internal diameter when compared to the transmission input shaft  3  designed as a hollow shaft of the known dual-clutch transmission  30  according to  FIG. 3 .  
      The above mentioned shaft connection, together with the possibility of using the transmission input shafts used in the dual-clutch transmission  30 , has the added advantage that the bending torques acting upon one transmission inputs shaft, can mechanically and favorably be transferred to the other transmission input shaft.  
      Another alternative of the invention is shown in  FIG. 2 . A transmission  40  also uses the shaft arrangement and speed sequence of the known transmissions  30 ,  30 . 1 , according to  FIG. 3  and  FIG. 4 , but differs therefrom in that only one transmission input shaft is provided, which is composed of two part shafts  38 ,  39 .  
      While the first part shaft  38  is non-rotatably connected with the output side of the starting and gear clutch AK and to that extent corresponds to the first section of the single transmission input shaft  4 . 1  of the known transmission  30 . 1  ( FIG. 4 ), the second part shaft  39  consists of the second input shaft  4 , designed as full shaft of the known dual-clutch transmission  30  according to  FIG. 3 , which is only shortened by the section close to the clutch which in this dual-clutch transmission  30  is supported in the first transmission input shaft  3 .  
      The two part shafts  38 ,  39  are preferably designed as full shafts, the same as in positive fit and/or friction engagement manner interconnected respectively by one of their front sides by a shaft coupling, heat shrinking or thermal jointing process (welding, soldering, etc.). A connection  41  can also be designed as plug-in toothing. But finally one clutch can also be situated between the two part shafts  38 ,  39 .  
      Covered by the invention is the use of the construction principle thereof in transmissions having only one countershaft or more than two countershafts. In each case, the transmission input shaft consists of two part shafts which, even if with slight modifications, can also be used in the dual-clutch transmission  30  ( FIG. 3 ).  
      The comparison and embodiments used have made clear that by appropriate use of transmission parts of similar or different transmission types, it is possible to obtain clear advantages in cost in the development, production and storage of transmission parts.  
                               Reference Numerals                                                 1   transmission            2   drive shaft            3   transmission input shaft, hollow shaft            4   transmission input shaft, full shaft            4.1   transmission input shaft            5   first countershaft            6   second countershaft            7   idler gear            8   output side of the clutch AK            9   idler gear           10   reverse gear idler gear           11   fixed gear           12   connecting means           13   fixed gear           14   fixed gear           15   connecting means           16   idler gear           17   idler gear           18   output gear wheel           19   output gear wheel           20   toothing on differential transmission           21   differential transmission           22   transmission input shaft, full shaft           23   shifting set           24   transmission input shaft, hollow shaft           25   shifting set           30   dual-clutch transmission (prior art)           30.1   transmission (prior art)           31   shifting set           32   shifting set           33   fixed gear           34   idler gear           35   idler gear           36   idler gear           37   fixed gear           38   part shaft           39   part shaft           40   transmission           41   shaft connection           AK   starting and gear clutch           G1   first gear           G2   second gear           G3   third gear           G4   fourth gear           G5   fifth gear           G6   sixth gear           G7   seventh gear           RG   reverse gear           K1   clutch           K2   clutch