Bearing assembly for the cross member of a universal joint

The invention relates to a bearing assembly for a cross member. To avoid negative influences of axial forces which occur during the operation of the universal joint and which make it necessary to provide axial support for the rolling members, there have been provided supporting discs which are supported directly, via a bore, on a step of the arm. The seal which is located axially in the direction of the open end of the bearing bush is not subjected to any axial forces, as a result of which disadvantageous influences on the sealing effect of the seal are avoided. Furthermore, there is no need for any special fixing arrangement for the seal, with the exception of providing a seat which permits a defined association with the bearing bush.

BACKGROUND OF THE INVENTION 
The invention relates to a bearing assembly for supporting the arms of a 
cross member of a universal joint in associated joint yokes, with axially 
fixed bearing bushes which are received in the bores thereof and in each 
of which an arm is received with rolling members arranged therebetween. 
The end faces of the arms are supported relative to the base of the 
bearing bushes and the annular space towards the open end of the bearing 
bush containing a supporting disc holding the rolling members as well as a 
seal for sealing the bearing space between the inner wall of the bearing 
bush and the outer face of the arm. 
With prior art assemblies of this type, the supporting disc is directly 
supported as a separate component on the seal fixed in the bearing bush or 
on the arm, for example. 
There are other prior art solutions where the supporting disc for the 
rolling members is inserted into the seal by vulcanization measures, for 
example DE GM No. 8416023.3. 
The disadvantage of the two above-mentioned designs is that the supporting 
forces have to be received via the seal. This has an adverse effect on the 
sealing effect because the supporting forces cause the seal to be 
deformed, which in turn affects the contact between the sealing lips and 
the associated sealing faces. Such deformation has an additional 
disadvantage in that it is possible for the rolling members to carry out a 
limited axial movement and there is a risk of them taking up an inclined 
position. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a bearing 
assembly in which the seal itself or even the holding means for the seal 
are free from axial forces exerted by the bearing members, i.e., they are 
not subjected to any loads exerted by them. 
Pursuant to this object, and others which will become apparent hereafter, 
one aspect of the present invention resides in the supporting disc 
provided with a bore being supported on a step of the associated arm of 
the cross member in the direction of its axis of rotation. Additionally, 
in the region adjoining the supporting disc, in the direction of the open 
end of the bearing bush, the seal is inserted into the annular space and 
firmly associated, especially with the bearing bush. 
The advantage of this design is that the rolling members are supported 
axially, i.e., in the direction of the axis of rotation of the cross 
member, directly on a separate supporting disc which in turn is firmly 
axially supported on the step of the associated arm. The axially following 
seal inserted into the annular space is free from any axial forces, i.e., 
it does not even have to be fixed to the associated receiving means 
relative to which it should be arranged in a non-rotating way. As a rule, 
a friction locking connection is sufficient. In a preferred embodiment the 
seal is firmly associated with the bearing bush, i.e., it is firmly 
supported on the inner wall of the bearing bush to create a friction 
locking effect, with the fixing means or the friction locking connection 
being dimensioned in such a way that the seal is pressed out of its seat 
as a result of the pressure of the lubricant pressed therein. As the 
arrangement of the supporting disc ensures a sufficiently large number of 
throttle gaps, the pressure during the course of lubrication is reduced to 
such an extent that no worthwhile pressing-out forces occur. Furthermore, 
as a rule, the sealing lips are arranged in such a way that they open 
under the lubrication pressure so that lubricant can escape. 
In a preferred embodiment, the step is designed as a face conically 
increasing towards the open end of the bearing bush and the supporting 
disc is provided with a corresponding conical bore. This design permits 
the arm of the cross member to be shaped in such a way that it does not 
change its diameter stepwise, i.e., a good transition is achieved without 
there being any strength-reducing notches. 
To facilitate through-lubrication, the supporting disc, in its region 
adjoining the bore, is provided with circumferentially distributed 
recesses for forming through-channels. These end in the region of the 
sealing lips so that the ejected lubricant may lift these off their seat 
in the direction of flow. To prevent any pressure from building up, the 
sum of the passage cross-sections of the through-channels is greater than 
that of the lubricating grooves in the end disc. 
In a further embodiment, in order to increase the supporting force for the 
supporting disc in its region adjoining the step, the disc comprises an 
axially projecting reinforcing collar in which the bore is positioned. 
Finally, it is proposed to manufacture the supporting disc from polyamide. 
On the one hand, this material has a sufficiently high strength for 
effectively supporting the rolling members and, on the other hand, if 
paired with the cross member made of steel, it exhibits good sliding 
properties so that the supporting disc is able to move on the step without 
generating a high friction effect or wear symptoms if the axial forces 
transmitted by the rolling members increase. 
A preferred embodiment is described below in connection with the 
accompanying drawing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The universal joint shaft shown in FIG. 1 consists of two universal joints 
3 connected to each other by an intermediate shaft 4. The intermediate 
shaft 4 ensures a torque transmitting connection, but it also permits 
changes in length between the two universal joints 3. The two universal 
joints 3 each comprise two yokes 5, 23 containing bores in which the arms 
of a cross member 1 are received with bearing assemblies arranged 
therebetween. One of the yokes is designed as a driving yoke 5 and the 
other one as a flange yoke 23. The flange yokes 23, with their flanges, 
permit fixing to a driving or driven machine element. 
As can be seen from FIG. 2, the cross member 1 comprises two arms 2 
arranged at right angles relative to each other. Each arm 2 is received in 
a bearing bush 7 with rolling members 9 arranged therebetween. The bearing 
bush 7 has been inserted into the bore 6 of the associated driving yoke 5 
and flange yoke 23 and secured against axial displacement via a securing 
ring 8. Rolling members 9 are rollingly arranged on cylindrical outer 
faces 17 of the arms 2. The members 9 also roll on the inner wall 16 of 
the bearing bush 7. The arms 2 are supported on their end faces 10, for 
instance by providing an intermediate stop disc 26 at the base 11 of the 
bearing bush 7. However, in view of the types of material selected for 
pairing, it is also possible for the stop disc 26 to be eliminated and for 
the arm end face 10 to rest directly on the base 11 of the bearing bush 7. 
In the direction of the open end 13 of the bearing bush 7, the rolling 
members 9 arranged around the circumference of the arm outer face 17 are 
supported on a supporting disc 14. The supporting disc 14 comprises a 
conical bore 18 which, as can be seen in FIG. 3, is located in the region 
of the supporting disc provided with a reinforcing collar 22. By means of 
the conical bore 18, the supporting disc 14 is supported on a step 19 of 
the arm 2, which increases conically in the direction of the axis of 
rotation X and the open end 13 of the bearing bush 7, i.e., the supporting 
disc 14 is axially fixed relative to the arm 2 and accommodates the axial 
forces occurring during articulation and rotation of the universal joint 3 
and causes a displacement of the rolling members 9. The rolling members 9, 
with their end faces, are supported on the supporting disc 14. The axial 
force is introduced into the arm 2 via the supporting disc 14 and the stop 
19. 
In the axially adjoining region extending in the direction of the axis of 
rotation X and the open end 13 of the bearing bush 7, there is provided in 
the annular space 12 formed in this region between the inner wall 16 of 
the bearing bush 7 and the arm outer face 17 a seal 15 for sealing the 
bearing space. As can be seen in FIG. 3, the seal 15 is preferably firmly 
associated with the bearing bush 7. The seal 15 comprises a metallic 
reinforcing sleeve 25 to which the soft sealing part comprising the 
sealing lips 24 is vulcanized. As can also be seen in FIG. 3, the sealing 
lips 24 point in the direction of the open end 13 of the bearing bush 7. 
The seal 15 is inserted into the bearing bush 7 via friction locking only, 
there being no need for any special fixing means such as indentations or 
other connecting means. 
As can be seen in FIGS. 3 and 4 in particular, the supporting disc 14 has 
been provided with circumferentially distributed recesses 20 in the region 
of its conical bore 18. When the supporting disc 14 with its conical bore 
18 rests against the conical step 19 of the arm, these circumferentially 
distributed recesses 20 form through-channels 21 between the two. During 
lubrication, i.e., when pressing lubricant into the region of the rolling 
members 9 via lubricating bores provided for instance in the cross member 
and entering the arm end faces 10, these lubricating channels 21 ensure 
that the lubricant can reach the region of the sealing lips 24 which, due 
to being arranged so as to extend in the direction of the axis of rotation 
X, can lift off under the pressure of the lubricant, thereby permitting 
used lubricant to emerge. The arrangement of the lubricating channels 21 
and especially their cross-sectional shape, i.e., the gap effect caused by 
the through-channels 21, ensure that the lubricating pressure is reduced 
and that the seal 15, for example, cannot be pressed out of its seat in 
the bearing bush 7 due to the lubricating pressure. An essential advantage 
achieved by the selected arrangement and firm association of the seal 15 
with the bearing bush 7 is that it is possible to produce a preassembled 
unit consisting of the bearing bush 7, the end stop disc 26, the rolling 
members 9, the supporting disc 14, the seal 15 and possibly a further 
preseal. After fitting the cross member 1 in the bore 6 of the joint yoke 
5 and flange yoke 23, this unit as a whole may be inserted from the 
outside onto the arms 2. 
It is also conceivable for the seal to be firmly associated with the cross 
member. However, in such a case the fits have to be chosen to be such that 
when axial forces occur, it is possible for the supporting disc to rest 
against the stop 19, i.e., that the seal 15 can be displaced to such an 
extent that there is a sufficient clearance of movement. 
While the invention has been illustrated and described as embodied in a 
bearing assembly for the cross member of a universal joint, 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.