Assembled driveshaft

The invention relates to an assembled driveshaft in the case of which individual driving elements, especially gears, are non-rotatingly connected to a hollow shaft, with the connection between the hollow shaft and the driving elements essentially being achieved by a force or friction locking connection between the plastically expanded hollow shaft and the elastically pretensioned driving elements. For improving the bending and torsional stiffness of the driveshaft, at least one driving element has been produced to comprise at least two toothed discs with different diameters connected to each other by a sleeve, with the sleeve either being positioned directly on the shaft to form a basis for the connection or radially spaced from the shaft between the discs.

BACKGROUND OF THE INVENTION 
The invention relates to an assembled driveshaft in the case of which 
individual driving elements, especially gears, are non-rotatingly attached 
to a hollow shaft, with the connection between the hollow shaft and the 
driving elements essentially being achieved by force or friction locking 
between the plastically expanded hollow shaft and the elastically 
pretensioned driving element. 
An assembled driveshaft in which a hollow shaft is expanded in a die in 
such a way that due to a polygonous cross-section of the hollow shaft, a 
form-fitting engagement occurs in the region of the gears, is known from 
DE 34 25 600. Assembled driveshafts where the connection between the 
hollow shaft and the driving elements is essentially achieved by friction 
locking between the plastically expanded hollow shaft and the elastically 
pretensioned driving elements are described in DE 38 03 684. Such shafts, 
especially, are composed of individual sleeves and tubular portions. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to increase the bending stiffness 
of shafts of the above type while at the same time simplifying their 
production process. The objective is achieved in that at least one driving 
element is produced to be integral with at least two toothed discs having 
different diameters and connected to each other via a sleeve. The 
production-technical advantages of such a design being that the total 
number of components is reduced in that for example two gears may be 
produced as one single relatively uncomplicated casting and connected to 
the shaft jointly. These advantages in respect of shaft strength are the 
result of the double wall of the shaft in accordance with the invention, 
which considerably increased both the bending strength and the torsional 
strength of the shaft. Those gear rings located in the region of highest 
bending and/or torsional loads on the shaft are preferably combined to 
form one driving element connected by a sleeve. It is particularly 
advantageous to combine those gears positioned in the region of direct 
force flow across the shaft. 
A first advantageous embodiment of the invention is characterized in that 
between the toothed discs, of which there are at least two, there is 
provided a sleeve adjoining their hubs and attached to the hollow shaft 
via a friction locking connection. This achieves a further 
production-technical advantage in that by expanding one single continuous 
axial region of the hollow shaft it is possible to simultaneously attach 
several driving elements, i.e. preferably two gears, while using one 
simply designed probe with one single sealing region. Depending on the 
material selected, most of the bending and torsional forces acting on the 
shaft may be accommodated by the sleeve connecting the toothed discs. 
In a second advantageous embodiment it is proposed that between the toothed 
discs, of which there are at least two, there is provided a sleeve 
starting in the vicinity of the teeth and being at a radial distance from 
the hollow shaft. In this case, the friction locking connection of the 
driving element has to be produced in the region of the hubs of the 
toothed discs or in their direct vicinity, with two individual portions of 
the hollow shaft having to be plastically expanded in the axial direction. 
As a result of the considerably larger diameter of the sleeve connecting 
the toothed discs, bending strength and torsional strength are again 
increased considerably, with possibly less material being used. To 
increase the strength of the shaft further, longitudinally extending 
reinforcing ribs whose cross-section extends radially relative to the 
shaft axis may be drawn in between the toothed discs. 
To achieve a friction locking connection between the driving elements and 
the hollow shaft as described with reference to the latter embodiment, it 
is possible to associate the toothed discs with symmetrical sleeve 
attachments or sleeve attachments unilaterally extending inwardly or 
outwardly, with the inwardly extending sleeve advantageously shortening 
the component length. By using outwardly extending sleeve attachments it 
is possible to increase the strength of the connection with the hollow 
shaft in that on the outside further tubular pieces are slid on which, 
following the plastic deformation of the hollow shaft, remain elastically 
pretensioned relative to the sleeve attachments. This achieves a radial 
clamping-in effect which is particularly advantageous if the driving 
element with the two toothed discs is made of a less elastic material, 
i.e. a cast material, with malleable cast iron, especially GTS 65 being 
particularly suitable. 
The tubular pieces slid on to the sleeve attachments of the driving 
elements may extend so as to be axially stepped and additionally, they may 
enter a direct friction locking connection with a basic tube of the hollow 
shaft. Their outer surface may serve as a running face for roller 
bearings, one reason in favor of this solution being that the material for 
these tubular pieces in any case has to have a higher yield point than 
that of the hollow shaft and the driving elements. A bearing material such 
as 100 CR 6 is particularly suitable whereas the material for the 
continuous hollow shaft may be ST 35, for example. 
Two preferred embodiments are illustrated in the attached drawings and 
described below.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 illustrates a driveshaft comprised of a hollow shaft 1. At its ends 
there have been inserted tubular pieces 2, 3 with a tubular piece 4 having 
been slid on to cover the latter. A driving element 6 has been slid on to 
the hollow shaft formed in this way and attached in a force or friction 
locking way through internal plastic deformation of the hollow shaft. The 
driving element 6 consists of two toothed discs 9, 10 connected to each 
other by a sleeve 11 which adjoins their hubs. The sleeve 11 being 
directly located on the hollow shaft 1. Circumferentially distributed 
reinforcing ribs 5 are indicated by way of example on the toothed disc 10. 
Furthermore, tubular pieces 12, 13 have been slid on to the tubular shaft 
1. These pieces 12, 13 consist of a bearing material and serve as a track 
for a roller bearing. The tubular piece 4 being inserted into the latter 
and clamping in the end of the tubular shaft 1 together with the tubular 
piece 3. 
FIG. 2 shows an essentially continuous hollow shaft 21, with tubular pieces 
22, 23 having been inserted at the ends. A driving element comprising two 
toothed discs, 29, 30 connected via a sleeve 31 radially spaced from 
hollow shaft 21 and starting in the vicinity of the teeth has been slid on 
to the hollow shaft 21. In the region of the hubs, the toothed discs are 
followed by axially outwardly extending sleeve attachments 14, 15 which 
directly produce the force and friction locking connection with the hollow 
shaft 21. The sleeve attachments can also be axially inwardly extending as 
shown by dashed lines in FIG. 2. The upper half of the figure shows a 
circumferentially extending annular reinforcing rib 7 and as an 
alternative, the lower half of the figure illustrates circumferentially 
distributed longitudinally extending reinforcing ribs 8. Tubular pieces 
32, 33 made of a bearing material are slid on to the sleeve attachments 
14, 15 and continue in a stepped way and in the region following the 
sleeve attachments they are in direct friction locking contact with the 
hollow shaft 21. 
While the invention has been illustrated and described as embodied in an 
assembled crankshaft, it is not intended to be limited to the details 
shown, since various modifications and structural changes may be made 
without departing in any way from the spirit of the present invention. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of this invention.