Abstract:
Disclosed is a planetary gear train ( 8 ) comprising an internal gear ( 24 ), a sun gear ( 52 ), a planet carrier ( 10 ) which is provided with planet shafts ( 18 ) and on which at least one planetary gear ( 20 ) is mounted, and a shifting device with a sliding sleeve ( 66 ). Said shifting device allows for a direct connection between a shaft ( 44 ) driving the planetary gear train ( 8 ) and an output shaft ( 12 ) of the planetary gear train ( 8 ) in one shifting position while making it possible to modify the rotational speed between the driving shaft ( 44 ) and the output shaft ( 12 ) of the planetary gear train ( 8 ) in another shifting position. The planet shaft ( 18 ) is disposed inside the planet carrier ( 10 ) so as to be rotatable within a bearing ( 22, 80 ).

Description:
This application is a national stage completion of PCT/EP2004/005329 filed May 18, 2004 which claims priority from German Application Serial No. 103 23 254.0 filed May 23, 2003. 
   FIELD OF THE INVENTION 
   The invention concerns a planetary gear. 
   BACKGROUND OF THE INVENTION 
   Commercial vehicles with a large number of gear ratios frequently exhibit a speed range gear which is connected to the principal gear with its gear ratios. By means of a speed range gear, the overall multiplication factor of the principal gear can be increased, because all of the gear ratios of the principal gear can be used together with each gear ratio of the speed range gear, and in at least one gear ratio of the speed range gear, the multiplication factor of the gear ratios of the principal gear can be reduced and/or increased. 
   A speed range gear for automobiles has been disclosed, by way of example, in DE 41 21 709 A1. A planetary gear of this type, installed downstream of the principal gear, provides the possibility of operating the automobile in two different speed ranges for each of the gear ratios of its principal gear. In a first slowed-down gear ratio level of the speed range gear, the annulus of the planetary gear is coupled to the gearbox by means of a switching clutch, so that the output shaft of the speed range gear exhibits a lower revolution speed than the output shaft of the principal gear. In a second gear ratio level, direct transmission takes place from the output shaft of the principal gear to the output shaft of the speed range gear, whereby the direct connection between the output shaft of the principal gear and the output shaft of the speed range [gear] is created by means of a switching clutch. The switching device is extremely complex. 
   DE 198 51 895 A1 describes an additional speed range gear in the form of a planetary gear. In that publication, the annulus of the planetary gear is connected in a torque-proof manner to the gearbox. The sun gear of the planetary gear is arranged coaxially to the output shaft of the main gear and is freely rotatable relative to the output shaft of the principal gear. In order to create a reduction ratio between the output shaft of the principal gear at the output shaft of the speed range gear, the sun gear can be connected in a torque-proof manner to the output shaft of the principal gear. This planetary gear is also complex and problematic for the mounting of individual components. 
   The invention is based on the task of improving a planetary gear and especially the component mounting. 
   SUMMARY OF THE INVENTION 
   A planetary gear which includes an annulus, a sun gear and a planet gear carrier with planet wheel axle, on which at least one planet wheel is mounted, exhibits a switching device with a sliding collar, which, in one switching position, enables a direct connection between the shaft, which drives the planetary gear and an output shaft of the planetary gear and, in another switching position, enables modification of the revolution speed between the driving shaft and the output shaft of the planetary gear. To improve the mounting and reduce friction losses, the planet wheel axle is arranged rotatably in a bearing assembly in the planet gear carrier. 
   In an especially advantageous embodiment, the planet wheel is arranged rotatably in a bearing assembly on the rotatable planet wheel axle. 
   Preferably, the mounting of the planet wheel axle in the planet gear carrier represents a different type of bearing assembly than the mounting of the planet wheel on the planet wheel axle. In this regard, in a preferred embodiment, the planet wheel axle is mounted in the planet gear carrier by means of a friction bearing assembly, and the planet wheel is mounted on the planet wheel axle by means of a roller bearing assembly. In another, also preferred embodiment, the planet wheel axle is mounted in the planet gear carrier by means of a roller bearing assembly, and the planet wheel is mounted on the planet wheel axle by means of a friction bearing assembly. In this context, the planet wheel axle may exhibit oil supply devices which are connected to a gear oil supply. 
   It is advantageous to have a device which is exhibited by the planet gear carrier and which prevents axial displacement of the planet wheel axle in the planet gear carrier. 
   In a specific embodiment, the switching device exhibits a neutral position which lies between the two switching positions and in which the output shaft of the planetary gear is not driven. 
   Both the annulus and the sun gear may exhibit pressure pads which rest against the planet wheel. Preferably, the roller bearing assembly includes a multiple row bearing. 
   The form of the invention is considered particularly advantageous when the planetary gear represents a speed range gear of a vehicle transmission, formed in such a way as to be connected, by means of a torque-transferring drive train, to a principal gear, so that the output shaft of the principal gear forms the drive shaft of the planetary gear. 
   The invention may be used in an equally advantageous manner with a principal gear which includes two secondary shafts and a principal shaft mounted in a floating manner between the secondary shafts, so that the principal shaft serves as the output shaft of the principal gear and forms the drive shaft of the planetary gear, and the end of the principal shaft is mounted in the sun wheel of the planetary gear. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example, with reference to the accompanying drawings in which: 
       FIG. 1  is a schematic arrangement of the planetary gear; 
       FIG. 2  is the planetary gear with a first switching device; 
       FIG. 3  is the planetary gear with a second switching device. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A manual transmission  2  for a vehicle exhibits, within a gearbox  4 , a principal gear  6  and a speed range gear in the form of a planetary gear  8 , connected to the principal gear  6 . The planetary gear  8  includes a planet gear carrier  10 , which is implemented as a common component with an output shaft  12  of the manual transmission  2 . An output flange  14  is fastened to the output shaft  12 , and the output shaft  12  is mounted in a bearing assembly  16  in the gearbox  4 . The planet gear carrier  10  exhibits a plurality of planet wheel axles  18 , distributed around the circumference thereof, whereby one of said planet wheel axles  18  is shown. A planet wheel  20  is mounted on the planet wheel axle  18  in a roller bearing assembly  22 . Typically, three or five planet wheels  20  are distributed around the circumference of the planet gear carrier  10 . The roller bearing assembly  22  consists of a two-row cylinder roller bearing or needle bearing. The planet wheel  20  is surrounded on the outside by an annulus  24 , which exhibits a tooth system  26 , which can engage with a tooth system  28  on the gearbox  4 . 
   The planet gear carrier  10 , on the side of the planetary gear  8  lying opposite the output shaft  12 , exhibits an extension  36 , on which the planet gear carrier  10  is mounted in the gearbox  4  by means of a roller bearing  38 . A secondary shaft  30  of the principal gear  6  is mounted by means of a bearing assembly  32 , and another secondary shaft  40  of the principal gear  6  is mounted by means of a bearing assembly  42 , in the gearbox  4 . A principal shaft  44  of the principal gear  6 , at the end thereof, bears a gear wheel  46  of the reverse gear ratio. The gear wheel  46  is located on the principal shaft  44  with a small degree of radial play, which is typical of a manual transmission with a power split on two secondary shafts. Provided at the end of the principal shaft  44  according to  FIG. 1  is a pivot  45 , which can also be formed with a slit profile. A sun wheel  52  is arranged on the pivot  45  of the principal shaft  44 , whereby, according to  FIG. 1 , the principal shaft  44  is supported in the sun wheel  52 . Arranged between the sun wheel  52  and the output shaft  12  and/or the planet gear carrier  10  is a sleeve  50 , which conducts the oil between the shafts. Also provided for oil conduction is a sleeve  54  between the principal shaft  44  and the sun wheel  52 . 
   Arranged on the sun wheel  52  are two pressure pads  56  and  58 , which prevent an axial movement of the planet wheel  20  relative to the sun wheel  52 , but allow the planet wheel  20  to rest on the pressure pads in order to take up an axially directed force which results from the oblique toothing of the planetary gear  8 . Two additional pressure pads  60  and  62  are arranged radially inside the annulus  24  and similarly allow the planet wheel  20  to rest against them. The two pressure pads  60  and  62  prevent an axial movement of the planet wheel  20  relative to the annulus  24 . 
   A sliding collar  66  exhibits a first internal tooth system as a switching tooth system  68 , which engages with a switching tooth system  70  on the sun wheel  52  and forms a torque-proof connection between the sliding collar  66  and the sun wheel  52  ( FIG. 2 ). In order to form a torque-proof connection between the sliding collar  66  and the principal shaft  44 , the sliding collar  66  exhibits a second internal tooth system  72 , which engages with an external tooth system  74  on the principal shaft  44 . 
   In order to create an optionally torque-proof connection between the principal shaft  44  and the planet gear carrier  10 , so as to form a direct connection between the principal gear  6  and the output shaft  12  without changing the revolution speed, the sliding collar  66  exhibits a switching tooth system  76 , which can engage with a switching tooth system  78  on the extension  36  of the planet gear carrier  10 . 
   The top half of the planetary gear  8  in both  FIG. 2  and  FIG. 3  shows the switching position of the sliding collar  66 , which enables a torque-proof connection, by means of the switching tooth systems  68  and  70 , between the principal shaft  44  and the sun wheel  52 . The respective bottom half of each Figure represents the switching position of the sliding collar  66 , which shows a direct connection, by means of the switching tooth systems  76  and  78 , between the principal shaft  44  and the planet gear carrier  10 . In this switching position, the planetary gear  8  runs load-free, because the entire torque is transferred via the planet gear carrier  10 . 
   Between the two switching positions shown in each Figure, a neutral position is possible. 
   In  FIG. 2 , the planet wheel  20  is mounted on the planet wheel axle  18  in the roller bearing assembly  22 . Instead of a plurality of cylinder roller bearings as the roller bearing assembly  22 , it is also possible to consider a multiple row bearing, for example, a two-row needle bearing. The planet wheel axle  18  is rotatably mounted in the planet gear carrier  10  in a first friction bearing assembly  80  and a second friction bearing assembly  82 . By means of the friction bearing assembly  80 ,  82 , the planet wheel axle also becomes potentially axially displaceable, so that it must be axially immobilized. This is accomplished, on one hand, by means of a rim  84  on the extension  36  and, on the other hand, by means of a cup-shaped ring  86 , which is here clamped between the planet wheel axle  18  and the bearing assembly  16  in the gearbox  4 . 
   In the switching position of the sliding collar  66 , in which the switching tooth systems  68  and  70  engage with each other, the planetary gear  8  is subject to a high load. Through the use of two different kinds of bearing assemblies, according to the invention, this load can be reduced. The planet wheel  20 , which is driven by the sun wheel  52 , creates only a small amount of friction in the roller bearing assembly  22  in this switching position. In the friction bearing assembly  80 ,  82 , there is no difference in revolution speed between neighboring parts. 
   In the other switching position of the sliding collar  66 , in which the switching tooth systems  76  and  78  engage with each other, the planetary gear  8  is practically load-free. The roller bearing assembly  22  is subject to a high degree of friction, whereas the friction bearing assembly  80 ,  82  enables load-free gliding. 
     FIG. 3  shows a different embodiment of the sun wheel  52 . A running tooth system  64  of the sun wheel here exhibits a sleeve  48 , which is mounted in a torque-proof manner, whereby an internal tooth system  34  of said sleeve  48  engages with the running tooth system  64 . The sleeve  48  then exhibits the switching tooth system  70  as an external tooth system, for connection with the switching tooth system  68  of the sliding collar  66 . A friction bearing assembly  88  of the planet wheel  20  on the planet wheel axle  18  requires a supply of oil to this bearing assembly. To this end, boreholes  90 ,  92 , which open into a space  94  covered with a cap  96 , are provided in the planet wheel axle  18 . This space  94  is connected, by means of a line  98 , with the oil supply used elsewhere in the manual transmission  2 . The planet wheel axle  18  is mounted in the planet gear carrier  10  with the roller bearing assembly  22 , which, in this embodiment, consists of two individual cylinder roller bearings. 
   The arrangement according to the invention forms a claw-shaped switching device for a planetary gear which is arranged on the principal shaft of the gear. The switching of the rapid transmission ratio of the speed range gear, in direct connection, is practically load-free. Because the annulus is connected directly to the gearbox, there is no need for a support plate with a switching tooth system. Forces conducted by means of the output shaft can be borne in the annulus which is fastened to the gearbox, whereby an additional bearing assembly for the planet gear carrier can also be omitted. 
   Basically, the switching device according to the invention is suitable both for manual transmissions with one secondary shaft and for manual transmissions with a power split onto a plurality of secondary shafts. 
   REFERENCE NUMERALS 
   
       
         2  Manual transmission 
         4  Gearbox 
         6  Principal gear 
         8  Planetary gear 
         10  Planet gear carrier 
         12  Output shaft 
         14  Output flange 
         16  Bearing assembly 
         18  Planet wheel axle 
         20  Planet wheel 
         22  Roller bearing assembly 
         24  Annulus 
         26  Tooth system 
         28  Tooth system 
         30  Secondary shaft 
         32  Bearing assembly 
         34  Internal tooth system 
         36  Extension 
         38  Roller bearing 
         40  Secondary shaft 
         42  Bearing assembly 
         44  Principal shaft 
         45  Pivot 
         46  Gear wheel 
         48  Sleeve 
         50  Sleeve 
         52  Sun wheel 
         54  Sleeve 
         56  Pressure pad 
         58  Pressure pad 
         60  Pressure pad 
         62  Pressure pad 
         64  Running tooth system 
         66  Sliding collar 
         68  Switching tooth system 
         70  Switching tooth system 
         72  Internal tooth system 
         74  External tooth system 
         76  Switching tooth system 
         78  Switching tooth system 
         80  Friction bearing assembly 
         82  Friction bearing assembly 
         84  Rim 
         86  Ring 
         88  Friction bearing assembly 
         90  Borehole 
         92  Borehole 
         94  Space 
         96  Cap 
         98  Line