Rotary constant velocity universal joint

A universal joint wherein torque-transmitting balls are engaged between complementary grooves formed in an inner and outer joint member, with the balls being supported by a supporting element which is arranged in a jaw-like opening formed on one side of the universal joint through which the balls may be inserted in operative engagement within the joint. The invention is directed toward the curvature of the grooves which are arranged in such a way that a connecting line extending between the center of the radius of curvature of the grooves and the center of the torque-transmitting balls forms an angle relative to the central axis of rotation of the joint which is smaller than or equal to 85.degree., the angle being taken in accordance with the arcsine of the projection of the center of the radius of curvature of the grooves and the ball center onto a vertical plane extending perpendicularly relative to the axis of rotation of the joint, divided by the length of the radius of curvature.

The present invention relates generally to a rotary constant velocity 
universal joint and more particularly to a joint which includes an outer 
hollow joint member having an inner wall provided with grooves, an inner 
joint member which is arranged in the outer joint member having an outer 
wall provided with a number of grooves corresponding to the number of 
grooves in the outer joint member, with the centerlines of the grooves of 
the inner joint member being curved and with one groove of each of the 
outer and inner joint member forming a jaw-like opening for directing 
torque-transmitting balls into the angle bisecting plane and jointly 
receiving a ball for torque transmitting purposes. 
Joints of the type to which the present invention relates are known in the 
prior art for example from U.S. Pat. No. 1,975,758 wherein the 
torque-transmitting balls are controlled by a wedge-like cooperation 
between two grooves and wherein the jaw-shaped opening of the grooves in 
the extended joint occurs toward the joint interior. However, even with a 
small articulation angle of less than 30.degree., the jaw-like opening 
will open toward the end opposite the joint interior. As a result, the 
torque-transmitting balls are jammed in or will even fall out so that at 
the same time the joint is destroyed. With such a joint, a supporting 
system with a cage is required which prevents the balls from being pressed 
outwardly since otherwise only small angles of articulation would be 
possible due to the offset of the centers of the ball grooves of the inner 
and outer joint members relative to the joint center. Since this offset 
will be unfavorably small, it will not enable the joint to be adapted to 
the contact between the ball and the groove. The latter dependence can be 
shown theoretically. 
Other joints are known in the prior art, for example from U.S. Pat. No. 
4,116,020, wherein the grooves serving to receive the balls extend 
relative to each other in such a manner that the grooves of the inner and 
outer joint member not only require a cage but, in addition, a supporting 
element which holds the cage in position when the joint is articulated. 
The present invention is directed toward provision of a joint structure 
which will simplify the structural arrangement of the joint while 
maintaining favorable production or manufacturing conditions. Furthermore, 
the invention is directed toward a system which will simplify the guidance 
system for the torque-transmitting balls and will increase the angle of 
articulation of the joint. 
Additionally, the invention is directed toward achievement of easy axial 
assembly of the joint without requiring axial clearance or axial play 
while permitting a type of assembly which will subsequently allow the 
components to be connected in a manner wherein they cannot be unfastened 
from each other. 
SUMMARY OF THE INVENTION 
Briefly, the present invention may be described as a universal joint 
assembly including an inner joint member and an outer joint member with 
torque-transmitting balls arranged in torque-transmitting engagement 
therebetween wherein the balls in the joint interior, at one end, are 
supported by a supporting element arranged at jaw-like openings at one end 
of the curved grooves and wherein the curved grooves of the inner and 
outer joint members are arranged in such a way that a connecting line 
extending between the center of the radius of curvature of the grooves and 
the ball center forms an angle .omega. relative to the axis of rotation of 
the respective joint member, with the angle .omega. being smaller than or 
equal to 85.degree.. This type of arrangement, taking into account the 
respective effective contacts between the ball and the ball groove, 
prevents a reversal of the jaw-like opening. 
The advantage of the invention is that when producing the two-part outer 
joint member, for example, the part containing the grooves may be 
manufactured as a standard part whereas the connecting part may be 
produced for different connecting dimensions. In this way, the amount of 
material required for producing the joint and the storage costs thereof 
are reduced. Additionally, the invention is such that it enables the 
application of cold forming production techniques in a particularly 
favorable manner. 
A further advantage of the invention consists in the fact that it is 
possible to use a particularly simple form for the supporting part which 
ensures functioning of the conventional cage. Because of the direction of 
the groove, it is ensured that at any angle of articulation the 
torque-transmitting balls will be pressed against the supporting element. 
Even with large articulation angles exceeding 40.degree., appropriate 
support will still be provided so that from this point of view there are 
no restrictions on the joint insofar as such an embodiment is concerned. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its use, reference 
should be had to the accompanying drawings and descriptive matter in which 
there are illustrated and described preferred embodiments of the invention 
.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings, and more particularly to FIG. 1, there is 
shown a rotary constant velocity universal joint embodying the present 
invention which essentially consists of an outer joint member 1 formed in 
two parts. The two parts of the outer joint member 1 are denoted part 1a 
and 1b and are surrounded by a sleeve 2 in a form-fitted manner so that 
the sleeve 2 may be welded to the part 1b in order to be formed as one 
unit during production of the assembly. 
Part 1a of the outer joint member is provided with grooves 3 which receive 
therein torque-transmitting balls 4. 
The outer joint member 1 forms a hollow space wherein there is accommodated 
an inner joint member 5 which is also formed with grooves 6 in which the 
torque-transmitting balls 4 are engaged or guided. The grooves 3 and 6 
extend in such a manner that they are formed undercut-free and so that 
they form a jaw-like opening extending toward the joint interior. As a 
result of the reduction in the cross-section of the grooves 3 and 6 toward 
the end face of the outer joint member, the balls 4 are constantly pushed 
toward the jaw-like open end of the grooves. In order to prevent the balls 
from falling out of the joint interior, there is provided a supporting 
element 7 which secures the balls in place within the joint assembly. 
The part 1b of the outer joint member is formed with a connecting pin 8 
which may be adapted to different connecting dimensions. At the opposite 
end, provision is made for splines 9 in the inner joint member 5 in order 
to enable it to receive therein a drive shaft (not shown). 
In the operation of the joint assembly, the balls 4 are constantly pushed 
against the supporting element 7 at any angle of articulation of the 
joint. The balls 4 comprise ball centers 10 which form a plane 11 which 
extends through the joint center 12, with the radius of curvature 
intersecting the center 13 of the radius of curvature 14 and the axis of 
rotation 15 of the respective joint member 1 or 5 at an angle .omega. 
which is smaller than or equal to 85.degree.. 
FIG. 2 shows the joint illustrated in FIG. 1 in an articulated condition. 
Again, the drawing of FIG. 2 shows the plane 11 which extends through the 
joint center 12 even when the joint is articulated, with the centers of 
curvature 13, relative to the joint axis of rotation 15 of the respective 
joint member 1 and 5, forming an angle .omega. which is smaller than or 
equal to 85.degree.. 
FIG. 3 illustrates the theoretical considerations related to the embodiment 
of the invention wherein the outer joint member 1 and the corresponding 
inner joint member 5 having the grooves 3 and 6 accommodate the 
torque-transmitting balls 4. The supporting element 7 is indicated 
schematically and the grooves 6 and 3 of the inner joint member 5 and the 
outer joint member 1 extend in such a manner that the center 13 of the 
radius of curvature is positioned on a line 22 or 14, respectively, which 
forms an angle .omega. with the axis of rotation 15 of the joint. The 
angle .omega. should always be smaller than 85.degree.. Furthermore, FIG. 
3 shows that under these conditions it is irrelevant whether the center 13 
of the radius of curvature is arranged on the side of the joint center 12 
facing or away from the grooves 3, 6. 
FIG. 4 shows a more detailed cross-sectional view of the grooves 6 of the 
inner joint member 5 on an enlarged scale. As indicated in FIG. 4, the 
ball 4 is supported in a track base 41 and the contact angle between the 
track base 41 and the ball 4 is indicated by the angle .delta.. In 
accordance with the invention, the angle .delta. is smaller than 
50.degree.. A track flank 42 is shown which may extend tangentially or 
along a radius which is greater than the track base 41. 
FIGS. 5 and 6 depict in greater detail the grooves 3 of the outer joint 
member 1 wherein the ball 4 is illustrated. The grooves 3 are designed in 
such a manner that, as viewed in cross-section, they are undercut-free so 
that non-chip producing production techniques or formation processes may 
be applied without difficulty. Run-outs 44 of the track edge are shown 
which extend parallel and which open with an increasing distance from the 
groove base 40 even when the track edge angle exceeds 90.degree.. Freedom 
from undercuts is ensured in order to permit corresponding production 
processes for manufacturing of the outer joint member 1. 
FIG. 7 depicts a further embodiment of a joint in accordance with the 
invention wherein the supporting element 7 supports itself toward the 
joint interior on a supporting disc 24. A guiding face 30 which cooperates 
with a counter face of the supporting element 7 extends along the same 
radius as that of the supporting element 7 or it may have a line contact 
31. During assembly, a cylindrical hollow space 23 is used to fit the 
joint with a corresponding clearance or even so as to be clearance-free. A 
bore 32 is used during production for technical reasons so that external 
machining of the support element 7 is not necessary beyond the dead 
center. In addition, the bore 32 is provided to operate as a lubricant 
channel. A turned-out section or stepped configuration 36 permits 
freewheeling of the support element 7, with the diameter of the turned-out 
section 36 being smaller than the outer diameter of the supporting 
elements because the intermediate elements designed as fingers engage into 
the grooves 3 of the outer joint member 1. 
Referring now to FIGS. 8, 9, and 10, there is shown the various parts of a 
joint assembly with FIG. 10 illustrating the outer joint member 1b, FIG. 9 
showing the supporting element 7, and FIG. 8 showing the part 1a of the 
outer joint member. 
The outer joint member part 1b illustrated in FIG. 10 is formed together 
with the sleeve 2 in an arrangement adapted to be connected with the part 
1a of the outer joint member shown in FIG. 8. The joinder may be formed 
with a form-fitting engagement by means of a recess 16 and with 
longitudinal grooves 17. As shown in FIG. 8, first the inner joint member 
5 and the balls 4 are fitted into the outer joint member part 1a. 
Subsequently, the supporting element 7 depicted in FIG. 9 is introduced 
and thereafter the sleeve 2 together with the part 1b of the outer joint 
member 1 is pushed over the part 1a and the assembly is joined in a 
form-fitting manner with the recesses 16 and the grooves 17. 
FIGS. 11, 12, and 13 show an outer joint member and an inner joint member 
with the inner joint member being shown in FIG. 13 which is designed in 
such a manner that an increase in the angle of articulation can be 
achieved. The components are dimensioned such that the entire width 27 of 
the inner joint member 5 is wider than the length 28 of the outer joint 
member 1. However, it must be ensured that even under conditions of 
articulation the joint members 1 and 5 are permanently engaged. In order 
to permit a further increase in the angle of articulation, it is necessary 
for stays 29 remaining between the grooves 3 to be tapered toward the end 
facing the supporting element 7. In this manner, space is produced which 
is required for articulation of the inner joint member. 
FIG. 14 shows an embodiment of a rotary constant velocity joint which, in 
principle, corresponds to the joint illustrated in FIG. 1, the difference 
being that the supporting element 7 is designed as a ball socket section 
with a supporting end 25 extending over the entire circumference. In this 
embodiment, provision is also made for a cylindrical hollow space 23 which 
permits clearance-free assembly. 
FIG. 15 illustrates a further embodiment which, in principle, corresponds 
to the embodiment shown in FIG. 14, the difference being that the outer 
joint member 1 is formed as a unitary part. With such an embodiment, it is 
necessary for a shaft 33 and the inner joint member 5 to be formed as two 
individual components so that assembly of the joint may be achieved. 
FIG. 16 shows the individual components of the joint separately but 
arranged in the direction of assembly thereof and it will be seen that the 
joint components again comprise a part 1a of the outer joint member, the 
inner joint member 5, the torque-transmitting balls 4, and the supporting 
element 7. The part 1b of the outer joint member 1 is provided with a pin 
18, this pin being adaptable for connection with a device such as a motor 
vehicle. 
FIG. 17 shows a part 1b which incorporates a differently designed pin 18. 
In FIG. 18 there is illustrated a joint in accordance with the present 
invention shown in the assembled condition with the outer joint member 1 
accommodated in a holding device 19 and with the pin 18 and therefore the 
second part 1b of the outer joint member being held under a pretension by 
a further tool 20 which operates to permit the parts 1a and 1b to be 
welded together. 
Thus, it will be seen that in accordance with the present invention there 
is provided a structure which will enable simplification of a universal 
joint while maintaining favorable production conditions wherein apart from 
simplification of the ball guidance system and the support elements there 
occurs an increase in the angle of articulation. Additionally, the 
invention is directed toward achievement of easy axial assembly of the 
joint without axial clearance, with a type of assembly which permits the 
components to be secured to each other after assembly in such a manner 
that they cannot be unfastened. 
The objective of the invention is generally achieved in that the balls 4 in 
the joint interior, at one end, are supported by a supporting element 7 
arranged in a jaw-like opening and that the curved grooves of the inner 
joint member 5 and the grooves of the outer joint member 1 are arranged in 
such a way that a connecting line 22 which extends between the center 13 
of the radius of curvature and the ball center 10 forms, relative to the 
axis of rotation 15 of the joint, an angle .omega. which is smaller than 
or equal to 85.degree.. 
Various embodiments of the invention are shown and specific details of the 
structure of the grooves in the joint members are provided. For example, 
it will be seen that in accordance with an embodiment of the invention, 
the balls 4 may support themselves in the track base area 40, 41 of the 
grooves 3, 6 even during the torque-transmitting process. 
Furthermore, in accordance with an additional essential feature of the 
invention, the angle .omega. may have a value which is smaller than or 
equal to 80.degree. if the contact angle .delta. between the groove and 
the ball, measured from the groove base, is smaller than or equal to 
50.degree., the advantage of this embodiment being that the cost-effective 
production can be achieved by increasing tolerances and that joint angles 
of more than 45.degree. can be obtained without difficulty. 
Furthermore, it is possible for the center lines of the grooves of the 
outer joint member to consist of groove parts having different curvatures, 
with the groove parts having the more pronounced curvature being arranged 
at the end of the outer part away from the supporting element. 
Additionally, provision is made for the track flanks in the cross-section 
of the grooves, starting from the contact line or from the contact point 
between the groove and the ball, to extend tangentially or in a radius 
which is greater relative to the groove base. 
The modification of the contact point, when introducing the torque for a 
track flank with the tangent being 0 and for a radius greater than the 
groove base depending on the size of the radius as compared to other known 
groove designs becomes very restrictive. 
According to a further embodiment of the invention, when a track edge angle 
.delta..sub.K of the grooves is greater than 90.degree., the track flank 
run-out is undercut-free with the track flank run-outs of a groove 
extending parallel relative to each other or opening with an increasing 
distance from the groove base. 
Provision has further been made for the center of the radius of curvature 
to be arranged on the line in the region between the joint center and the 
ball center or in the area starting from the ball center and extending 
beyond the joint center. 
Provision has further been made for the groove to be undercut-free, the 
advantage being that even with an undercut-free groove design, the groove 
shape may be adapted to the respective production process, e.g., cold 
extruding, apart from the optimizing possibilities for the joint itself. 
According to a further feature of the invention, the outer joint member has 
been designed to form two parts and to comprise a groove-containing part 
and a connecting part, with a supporting disc being arranged between the 
parts, the advantage being that a connection cannot be provided until 
after assembly of the joint. 
The advantage of this embodiment is that by using standard parts the amount 
of material required as well as storage and production costs may be 
reduced for example, by larger batch sizes or larger numbers of parts. A 
further advantage consists in the economic production of the disc-shaped 
part of the outer joint member and of the inner joint member where the 
grooves for containing the balls extend in an undercut-free way and may be 
produced by cold or hot extrusion, precision forging and/or subsequent 
calibration. 
In accordance with a further feature of the invention, the connecting part 
and the outer joint member are connected to each other by welding or in a 
form-fitted manner by means of a sleeve surrounding the two parts. 
If the supporting disc is used, the connecting part does not need to be 
hardened. 
Between the connecting part and the sleeve or the supporting disc and the 
end face of the outer part facing the joint interior, provision has been 
made for a hollow space or at least a gap into which the connecting part 
may be pushed when the joint is assembled, thereby permitting compensation 
of axial play of the joint. 
Provision may also be made for the outer joint member to have a cylindrical 
hollow space or gap between the part or supporting disc respectively and 
the part as a free space for the compensation of the axial play of the 
joint. 
It is also advantageous that the inner diameter of the outer joint member, 
which serves as a guiding face for the inner joint member, is 
undercut-free. 
In order to achieve accurate assembly, without causing any distortion or 
deformation of the ball grooves, a further essential feature provides for 
the outer joint member to have a turned-out section for receiving an 
assembly tool. 
In order to ensure that grinding of the supporting element does not have to 
take place beyond the dead center, provision is made for the supporting 
element, in the area of the axis of symmetry, to have a bore whose 
diameter is greater than 0 but smaller than the outer diameter of the 
shaft. This bore also improves the supply of lubricant to the cooperating 
guiding faces. 
Furthermore, the end of the supporting element facing the balls has been 
designed across the entire circumference so as to be annular and as not 
having any recesses. 
A further important feature provides for the diameter of the supporting 
element to be greater than the turned-out section in the outer joint 
member. 
In order to achieve a large angle of articulation, the joint members must 
be permanently engaged. In order to ensure this, provision has been made 
for the entire width of the guiding face of the groove-containing inner 
joint member cooperating with the outer joint member to be at least 20% 
wider than the width of the guiding face of the outer joint member taking 
over the guidance of the inner joint member. 
A further way of increasing the angle of articulation is for the stays 
remaining between two adjoining grooves of the outer joint member to be 
tapered toward the end facing the supporting element. 
In accordance with a further essential feature, the connecting part for the 
supporting disc comprises a guiding face which cooperates with the 
supporting element, and there is a circumferentially extending line 
contact, with a radius R.sub.B being greater than a radius R.sub.K (see 
FIGS. 9 and 10). The radius R.sub.B may also be infinitely great, as a 
result of which a cone-shaped guiding face is produced. 
In addition, provision has been made for the guiding face to be formed by a 
supporting disc. 
The process for assembling a rotary constant velocity joint in accordance 
with the invention is characterized in that initially, in an initial 
direction, the connecting part, the supporting element, the balls, the 
inner joint member, and the groove-containing part of the outer joint 
member, one after the other, are joined upon impact and that subsequently, 
the connecting part and the outer joint member are connected in such a 
manner that they cannot be unfastened, or that initially the outer joint 
member and finally the connecting part are joined. 
The advantage of this design is that the assembly to the outer part can 
take place in the axial direction so that the parts are introduced into 
the outer joint member and that as a final step the pin of the outer joint 
member is pushed in and the play is offset by corresponding pressure in 
the joint. After introduction of the pin, a form-fitting connection of the 
two parts or welding may take place thereby giving the joint its final 
shape. 
Thus, it will be seen from the foregoing that the invention is particularly 
characterized in that the balls 4 in the joint interior, at one end, are 
supported by a supporting element 7 arranged at the jaw-like opening and 
that the curved grooves 6 of the inner joint member 5 and the grooves 3 of 
the outer joint member 1 are arranged in such a way that the connecting 
line 22 extends between the center 13 of the radius of curvature and the 
ball center 10 and forms an angle .omega. relative to the axis of rotation 
15 of the respective joint member 1, 5, with the angle .omega. being 
smaller than or equal to 85.degree.. 
With the joint in accordance with the present invention, even during the 
torque-transmitting process, the ball 4 supports itself in the track base 
area 40, 41 of the groove 3, 6. The angle .omega. will have a value 
smaller than or equal to 80.degree. if the contact angle .delta. between 
the groove 3, 6 and the ball 4 measured from the groove base is smaller 
than or equal to 50.degree.. 
The center lines of the grooves 3 of the outer joint member 1 consist of 
groove parts with different curvatures, with the groove parts having the 
most pronounced curvature being arranged at the end of the outer part away 
from the supporting element 7. The track flanks 42, 43 in the 
cross-section of the grooves 3, 6 starting from the contact line or from a 
contact point between groove 3, 6 and the ball 4, extend tangentially or 
in a radius which is greater relative to the groove base. 
As shown in the drawings, with a track edge angle .delta..sub.K (45) of the 
grooves 3, 6 greater than 90.degree., the track flank run-out 44 is 
undercut-free, and the track flank run-outs 44 of a groove 3, 6 extend 
parallel relative to each other or open with an increasing distance from 
the groove base 40, 41. 
The center 13 of the radius of curvature has been arranged on the line 22 
in the region between the joint center 12 and the ball center 10 or in the 
area starting from the ball center 10 and extending beyond the joint 
center 12. 
Furthermore, it will be seen that the inner diameter of the outer joint 
member 1, which serves as a guiding face 46 for the inner joint member 5, 
is undercut-free. The outer joint member 1 has a turned-out section 21 for 
receiving an assembly tool and in the area of the axis of symmetry the 
supporting element 7 has a bore 32 whose diameter is greater than 0 but 
smaller than the outer diameter of the shaft 33. 
The end 25 of the supporting element 7 facing the balls 4 has been designed 
across the entire circumference so as to be annular and without any 
recesses such as the recesses 26. 
The diameter 35 of the supporting element 7 is greater than the turned-out 
section 36 in the outer joint member and the entire width 27 of the 
guiding face 47 of the groove 6 containing the inner joint member 5 
cooperating with the outer joint member is at least 20% wider than the 
width 28 of the guiding face 46 of the outer joint member 1 taking over 
the guidance of the inner joint member 5. 
The stays 29 remaining between the two adjoining grooves 3 of the outer 
joint member 1 are tapered toward the end facing the supporting element 7 
and the connecting part 1b or the supporting disc 24 comprises a guiding 
face 30 which cooperates with the supporting element 7 and there is a 
circumferentially extending line contact 31, with the radius R.sub.B (39) 
being greater than the radius R.sub.K (38) as shown in FIGS. 9 and 10. 
Thus, it will be seen from the foregoing that the invention provides a 
joint assembly having a simpler structure than the prior art while 
maintaining favorable production characteristics wherein apart from the 
simplification of the ball guidance and the support there also is produced 
an increase in the angle of articulation. Additionally, the invention 
seeks to achieve easy axial assembly of the joint without axial clearance 
and a type of assembly which permits the components to be secured to each 
other after assembly in such a manner that they cannot be unfastened. 
While specific embodiments of the invention have been shown and described 
in detail to illustate the application of the inventive principles, it 
will be understood that the invention may be embodied otherwise without 
departing from such principles.