Bearing of an idler gear of an all-wheel transfer transmission

A bearing of an idler gear of an all-wheel transfer transmission that mates with a drive gear wheel and an output gear wheel to one vehicle axle is provided with a bush that is clamped in between two housing walls. The idler gear is disposed on tapered roller bearings which are disposed on the bush. A screw that passes centrally through the bush is tightened by a nut and as a result braces the inner races of the tapered roller bearings and places the tapered rollers without play against the running surfaces of the idler gear.

BACKGROUND AND SUMMARY OF THE INVENTION 
The present invention relates to the bearing of an idler gear in an 
all-wheel transfer transmission of a motor vehicle. The idler gear is 
disposed between first and second casing walls of a transmission case and 
mate with both a drive gear wheel originating from the locking system and 
an output gear driving one vehicle axle. 
In an all-wheel transfer transmission shown in German Published Unexamined 
Patent Application No. 3,604,143, the distance between the axes of the 
drive shaft originating from the all-wheel locking system and of the 
output shaft driving one vehicle axle must be relatively large in order to 
be able to laterally move this output shaft past the large-volume housing 
of the gear-shift transmission. If large gear wheels that mate with one 
another were used on the drive shaft and on the output shaft, the two 
vehicle axles would be driven in different rotating directions. A transfer 
transmission is therefore used that comprises a gear wheel of the drive 
shaft, an idler gear and a gear wheel on the output shaft. 
It is an objective of the invention to provide a bearing for the idler gear 
of such an arrangement that can be manufactured cost-effectively and in a 
simple manner ensures a bearing adjustment that is free from play, as well 
as the concentric running of the idler gear. 
This and other objectives are achieved in the present invention by 
providing a bearing for an idler gear which has a bush on which the idler 
gear is disposed. This bush has at least one side with a stop collar which 
rests against one casing wall. The other side of the bush is axially 
braced on the outside with respect to the other casing wall by means of a 
tightenable connection. 
If the idler gear is disposed on a bush that, by means of a screwed 
connection, axially braces the two casing walls of the transmission casing 
with one another, when the screwed connection is tightened, the axial play 
of the bearing clamped in between the two casing walls is made to equal 
zero. 
In an advantageous embodiment of the present invention, for the tightenable 
connection, a screwed connection is used with a screw that passes through 
the center of the bush and with its head, in the area of one casing wall, 
rests against the bush and that by means of a nut from the outside is 
braced with respect to the other casing side. In this embodiment, the bush 
that is fitted into a smooth through-bore of the transmission casing, with 
a stop collar, is placed against one side of the casing. The transmission 
casing which can be constructed of light metal and the casing walls of 
which are elastically bendable, is reinforced by the bush when the screwed 
connection is tightened and therefore causes less noise-generating sound 
radiation. 
When the idler gear is disposed on tapered roller bearings, the tightening 
of the tightenable connection ensures a precise concentricity. In an 
advantageous embodiment, the hub of the idler gear is a joint outer race 
of the tapered roller bearings and directly represents the running surface 
of the tapered roller bearings. Via the inner races of the tapered roller 
bearings that are clamped in between the two casing walls and the spacer 
that is disposed between them and in its length is precisely tolerated, 
the tapered rollers, when the tightenable connection is tightened, are 
placed against the idler gear so that the radial play of the bearing 
becomes zero. 
Other objects, advantages and novel features of the present invention will 
become apparent from the following detailed description of the invention 
when considered in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
The FIGURE shows a drive shaft 2 originating from an all-wheel differential 
transmission 1, on which a drive gear wheel 3 is torsionally fixed. This 
drive gear wheel 3, together with an idler gear 4 and an output gear wheel 
5 torsionally fixed on an output shaft 6, forms a transfer transmission 
for the drive of one vehicle axle that is enclosed by a transmission 
casing 8. One casing wall 7 of the transmission casing 8 is flanged onto 
the other casing wall 9 that in a preferred embodiment is cast of light 
metal in one piece with the overall transmission housing. 
A bush 10 is fitted into a smoothly penetrating bore through the two casing 
walls 7 and 9. This bush 10 has a stop collar 11 which rests against an 
outer lug 12 of one casing wall 7. A hexagon socket screw 13 passes 
centrally through the bush 10, the head 14 of this screw 13 being disposed 
in a hollowed-out space 15 of the bush 10. By means of a nut 16 that on 
the outside rests against the other casing wall 9, the two casing walls 7, 
9 are braced with respect to one another. As a result, the two casing 
walls 7, 9 at the same time also brace the inner races 17 and 18 of 
tapered roller bearings 19 and 20 located between them as well as a spacer 
21. By means of an adjusting disk 22 located between the inner race 17 and 
one casing wall 7, rough tolerance imprecisions are balanced by means of 
the selection of a certain disk thickness. Since one casing wall 7 is 
developed to be elastically bending, by the tightening of the screwed 
connection 13, 16, this casing wall 7 is deformable to such an extent that 
the axial play becomes zero and the inner races 17, 18 of the tapered 
roller bearings 19, 20 are braced between the casing walls 7, 9. At the 
same time, the rollers of the tapered roller bearings 19, 20 are placed 
against the conical running surfaces of the idler gear 4 and the radial 
play is eliminated. 
The nut 16 is secured against twisting in the illustrated preferred 
embodiment by a pin 23 fastened in the casing wall 9. The nut 16 therefore 
does not have to be held when the screw 13 is tightened. The splash oil 
that is thrown off by the gear wheels 3, 4, 5 into the transmission casing 
8 is sufficient for the lubrication of the tapered roller bearings 19, 20. 
In order to prevent a discharge of oil to the outside at the bush 10, an 
O-ring 24 is inserted between the stop collar 11 of the bush 10 and the 
lug 12 of one casing wall 7, and another O-ring 25 is inserted between the 
end face of the bush 10 and the nut 16. 
Although the present invention has been described and illustrated in 
detail, it is to be clearly understood that the same is by way of 
illustration and example only, and is not to be taken by way of 
limitation. The spirit and scope of the present invention are to be 
limited only by the terms of the appended claims.