Abstract:
A front-axle output of an automatic transmission having situated in a sealed housing ( 15 ) a front-axle spur pinion ( 1 ) which is operatively connected via an intermediate gear ( 4 ) with a driving gear. The output spur gear ( 1 ) is also connected for transmitting a torque to a differential ( 5 ) with a co-axially positioned pinion shaft ( 3 A) which has one pinion engaged with the differential ( 5 ). The output spur gear ( 1 ) is designed as one piece with a side shaft ( 2 ) which is connected with the pinion shaft ( 3 A) in an area of low bending stress between a support ( 10 ) of the pinion ( 3 ) and the pinion shaft ( 3 A) and an output spur gear support ( 8 ).

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a front-axle output of an automatic transmission. 
     A front-axle transmission according to the preamble, the Applicant&#39;s 4 HP 18, has been disclosed, e.g. in the book “Automatische Fahrzeuggetriebe” by H. J. Forster, Springer Verlag 1991, page 473. This known transmission has a front-axle output configurated in a manner such that torque is transmitted, via an intermediate gear from a front-axle spur pinion, having an input gear to an output gear; each input, intermediate and output gear is designed as a spur gears. In the hub of the output gear is supported, with a positive fit, a pinion shaft of a pinion that engages a differential and is a bevel drive. Next to the support in the output-gear hub, the pinion shaft is supported in an area adjoining the pinion. 
     The output spur gear is supported on each side of the gear by a tapered roller bearing with an adjusting spacer. The tapered roller bearing situated upon the side remote from the differential is adapted and supported by its outer rollway body in a cover of the front-axle output housing. The outer rollway body of the other tapered roller bearing is supported in an intermediate plate disposed between the lid and the front-axle output housing, the housing being sealed with the intermediate plate. 
     On the side of the output gear, facing the differential or the pinion, is attached a spacer sleeve with a cup spring set and a parking interlock gear, said parts being guided via the pinion shaft. The parking interlock gear lies with an end remote from the output gear on a shaft shoulder of the pinion shaft and with its other end on the cup spring set which Is supported by the spacer sleeve on the output gear. 
     A disadvantage of this known solution is the great multiplicity of parts and a correspondingly high assembly expense from which high costs result from production and eventual repair works. 
     Therefore, the problem on which this invention is based is to provide a front-axle output of an automatic transmission which has a small number of parts, is easy and economical to assemble and has the lightest possible weight. 
     SUMMARY OF THE INVENTION 
     By virtue of the inventive development of the output spur gear with an axial extension as a side shaft, the connecting point between the pinion shaft and the output spur gear or the side shaft can be transferred to an area of low bending stress along the pinion support, it being possible to use the support already available in the area of the pinion support. 
     The side shaft, as well as the pinion shaft, can be dimensioned in this area with a smaller diameter or with less wall thickness than In the area of the output spur gear support and of the pinion support, since these can have a lesser bending resistance torque on the connecting point due to the transfer of their connecting point from the area of highest introduction of force and bending stress to the output spur gear support. Therefrom results the advantage of economy in material and weight, since the side shaft can be designed resistant to bending on the area adjoining the output spur gear. 
     Besides, the multiplicity of parts can be clearly reduced with the inventive solution, since in the support of the side shaft with the output spur gear, it is possible to omit a support on both sides of the output spur gear whereby it is possible, e.g. to spare on the side of the pinion a roller bearing with corresponding support in an intermediate plate provided precisely therefor with additional sealing points. 
     The considerable simplification of the construction offers the added advantage of reducing assembly and manufacturing costs. 
     Another simplification of the front-axle output configuration results when the side shaft is designed forming a single piece with the parking interlock gear. Thereby can be advantageously spared additional fastening elements for the parking interlock gear and the assembly thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING(S) 
     The invention will now be described, by way of example, with reference to the accompanying drawings in which: 
     FIG. 1 is a diagrammatic cross-section of an output spur gear of a front-axle, output pinion with a side shaft connected with a pinion shaft; 
     FIG. 2 is an enlarged representation of the connecting point between the side shaft and the pinion shaft with a spacer ring situated therebetween according to FIG. 1 before the fastening with a fastening element; 
     FIG. 3 is an enlarged representation of the connecting point between the pinion shaft and the side shaft with a spacer ring situated therebetween according to FIG. 1 including the assembly of a fastening element; and 
     FIG. 4 is a planar view of the ring spacer. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1 is shown an output spur gear  1  of a front-axle output of an all-wheel automatic transmission designed forming a single piece with a side shaft  2  connected with a pinion shaft  3 A. 
     The output spur gear  1  engages with its teeth in an intermediate gear connected by teeth with an input gear of a transmission output shaft (not shown in detail) and transmits an output torque of the output shaft to a differential  5  via the pinion shaft  3 A and a pinion  3  designed as tapered pinion. 
     In the instant embodiment, the output spur gear  1  with the side shaft  2  is designed as a hollow shaft and has a parking interlock gear  6 , said parking interlock gear  6  and the side shaft  2  being designed forming a single piece. 
     Between the output spur gear  1  and the pinion shaft  3 A, the connection  7  has circumferentially a positive connection  17  and axially movable connecting element  22 . The connection  7  is situated in an area of low bending stress between an output spur gear support  8 , which has a cylinder roller bearing  9  and a support  10  of the pinion shaft  3 A, the connection  7  lying in an area adjoining the support  10 . The support  10  of the pinion shaft  3 A is designed, as known per se, with two tapered roller bearings  11 ,  12 . The cylinder roller bearing  9  of the output spur gear support  8  is located upon the side of the output spur gear  1  remote from the pinion shaft  3 A, the outer rollway body  13  of the cylinder roller bearing  9  being supported in a cover  14  of a sealed housing  15 . 
     In the connection  7  between pinion shaft  3 A and side shaft  2 , there is an overlapping area  16  in which the positive connection  17  is designed such that the pinion shaft  3 A has a multi-groove spline which extends partly into the side shaft  2 . In the overlapping area  16 , a splined shaft  17  is provided, in this embodiment, as a multi-groove spline on the outer side of the pinion shaft  3 A and inside shaft  2 , by which the pinion shaft  3 A and the side shaft  2  are non-rotatably interconnected in a telescopic state. 
     Since the force Is introduced in the area of the output spur gear  1 , the strongest bending stress is here. For this reason, the side shaft  2  with the output spur gear  1  are given in larger dimensions in this area than in those areas situated between the output spur gear support  8  and the connection  7  with the pinion shaft  3 A, the diameter and wall thickness of the side shaft  2  always further tapering downward from the output spur gear support  8  to the connecting point  7 . 
     For axial fastening of the pinion shaft  3 A on the side shaft  2 , a fastening element  18  is provided which in the instant embodiment is designed as a bolt. The bolt  18  is passed through a constriction  19  which is formed in the interior of the side shaft  2  and screwed centrally into the pinion shaft  3 A. The constriction serves as a stop for a head of the bolt  18  in the side shaft  2 . When screwing in the bolt  18 , the side shaft  2  is pressed on a step  20  of the pinion shaft  3 A. 
     The removable axial fastening of the side shaft  2  on the pinion shaft  3 A by means of the bolt  18  makes it possible, in a simple manner, to assemble the side shaft  2  with the output spur gear  1  and to be easily changed in case of subsequent damage. 
     At the connection  7 , between the step  20  and the front face  21  of the side shaft  2 , a spacer ring  22  is disposed which makes possible a centering for alignment or the pinion shaft  3 A and the side shaft  2  even in case of manufacturing imprecisions. 
     As a result of manufacturing tolerances, there is at first, prior to tightening of the bolt  18 , only a line contact between the front face  21 , the spacer ring  22  and the step  20  of the pinion shaft  3 A. 
     In FIGS. 2 and 3 is shown an enlarged segment of the connection  7  with the spacer ring  22  according to FIG.  1 . In FIG. 2 the connection  7  is shown prior to fastening of the side shaft  2  on the pinion shaft  3 A by means of the bolt  18 . FIG. 3 shows the position of the spacer ring  22  after fastening of the side shaft  2  on the pinion shaft  3 A by the bolt  18 . 
     The inner diameter of the spacer ring  22  is here designed in such a manner that the spacer ring  22  can be guided via the overlapping area  16  of the pinion shaft  3 A up to the step  20 . In the overlapping area  16 , the outer diameter of the spacer ring  22  is designed larger than the outer diameter of the side shaft  2  in order that the front face  21  of the side shaft  2  abuts on a side face or flank  23  of the spacer ring  22 . 
     During the assembly, due to the screwing of the bolt  18  into the pinion shaft pinion shaft  3 A in such a manner that the front face  21  presses on the side surface  23  of the spacer ring  22 , and the spacer ring  22  abuts on the step  20  by its side surface  24  lying opposite to the side surface  23 . 
     The spacer ring  22  has in its cross-section a trapezoidal shape, the side surfaces  23 ,  24  forming an angle α, e.g. of 40°. The angle is dependent on the friction ratio and the admissible tensile strength of the spacer ring. The axial width of the spacer ring  22  here diminishes starting from its outer diameter toward its inner diameter. 
     Due to the tightening of the bolt  18 , if the output spur gear  1  is more strongly pressed against the spacer ring  22 , there originates, because of the inclined or conical side surfaces  23 ,  24  and as result of the non-parallel position of the front face  21  relative to the step  20 , a radial force F r  on the spacer ring  22  resulting from the axial screwing force. As long as the radial force F r  is stronger than the static friction force F h  of the front surface  21  on the side surface  23  and of the step  20  on the front surface  24 , the spacer ring  22  is radially moved from its center until a balance of forces appears and the spacer ring  22  forms on both sides of the side surfaces  23 ,  24  a linear contact or contact line with the step  20  and the front surface  21 . If the spacer ring  22  remains in this position, the bolt  18  can be screwed into a pre-defined tightening torque. 
     The pinion shaft  3 A and the side shaft  2  with the output spur gear  1  are finally disposed aligned on a central axis, which ensures very quiet running during operation and thus a small load of the teeth and of the supports. 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Reference numerals 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                  1 
                 output spur gear 
               
               
                   
                  2 
                 side shaft 
               
               
                   
                  3A 
                 pinion 
               
               
                   
                  4 
                 pinion shaft 
               
               
                   
                  5 
                 differential 
               
               
                   
                  6 
                 parking interlock gear 
               
               
                   
                  7 
                 connection 
               
               
                   
                  8 
                 output spur gear support 
               
               
                   
                  9 
                 cylinder roller bearing 
               
               
                   
                 10 
                 support of the pinion shaft 
               
               
                   
                 11 
                 tapered roller bearing 
               
               
                   
                 12 
                 tapered roller bearing 
               
               
                   
                 13 
                 rollway body 
               
               
                   
                 14 
                 cover 
               
               
                   
                 15 
                 housing 
               
               
                   
                 16 
                 overlapping area 
               
               
                   
                 17 
                 splined shaft 
               
               
                   
                 18 
                 fastening element 
               
               
                   
                 19 
                 constriction 
               
               
                   
                 20 
                 step 
               
               
                   
                 21 
                 front face of the side shaft 
               
               
                   
                 22 
                 spacer ring 
               
               
                   
                 23 
                 side surface of the spacer ring 
               
               
                   
                 24 
                 side surface of the spacer ring