Slide type universal joint

In a slide type universal joint, a slider is slidably fitted around a trunnion of an inner member and a roller, which rolls in a transmission groove of an outer member, is carried rotatably on the slider via a needle bearing, the slider and the roller being coupled together against axial relative displacement by an axial coupling means. This makes the joint simple in structure and reduces frictional resistance.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The field of the present invention is slide type universal joints of a type 
used in a bent portion of a bendable wheel drive axle for a front-wheel 
drive automobile, for example, and particularly, such universal joints as 
comprising a tubular or hollow cylindrical outer member connected to one 
transmission shaft and formed at its inner peripheral surface with a 
plurality of circumferentially spaced, axially extending transmission 
grooves, an inner member connected to another transmission shaft and 
having a plurality of trunnions which extend radially so as to project 
into the plurality of transmission grooves, and rollers carried on 
respective trunnions and rollably engaged in the corresponding 
transmission grooves. 
2. Description of the Prior Art 
There are conventionally known joints of this type, such as shown in FIG. 
5, in which a roller e is rotatably and slidably fitted around an outer 
periphery of a trunnion d of an inner member b via a needle bearing f. 
This type of joint has a simple structure, however, there are demerits 
that when the inner member b and mating outer member a are rotated in a 
condition with their axes crossed at an angle, the roller e is caused to 
slide in transmission groove C while rotating relative to the trunnion d 
so that a frictional force acts on needles of the needle bearing f in the 
rotational and axial directions, tending to cause a skew (or declining) 
phenomenon that results in a power loss, heating, vibration and the like. 
Improved joints for eliminating the mentioned demerits are also known, such 
as disclosed in Japanese Patent Publications No. 47413/81 and No. 13211/82 
and U.S. Pat. No. 4,891,035, for example. 
In case of the improved joints, as shown in FIG. 6, an inner guide ring g 
is slidably fitted around a trunnion d and an outer guide ring h is fitted 
around the inner guide ring g with a spherical contact provided 
therebetween, a roller e being rotatably carried on the outer guide ring h 
via a needle bearing i, wherein the roller e is swingable relative to the 
trunnion d. Accordingly, this type of joint has an advantage that even 
when the outer member a and the inner member b rotate with their axes 
inclined with respect to each other, the roller e does not incline but can 
roll within the transmission groove c smoothly without causing a slip. 
This joint, however, has problems that the number of parts increases, the 
structure is complicated, the weight increases and the cost becomes 
relatively high. 
The present invention has been proposed in view of these circumstances and 
an object thereof is to provide a slide type universal joint of the 
afore-mentioned type which is simplified in structure and has excellent 
properties. 
SUMMARY OF THE INVENTION 
In order to achieve the above object, the invention provides a slide type 
universal joint having a roller rotatably carried on an outer periphery of 
a slider via a needle bearing, wherein the slider and the roller are 
axially coupled to each other by an axial coupling means thereby to form a 
slide roller assembly. 
With the above arrangement, when the trunnion inclines, the slider is 
caused to slide relative to the trunnion thereby to prevent a frictional 
force from acting on the bearing in the axial direction. As a result, the 
bearing can operate normally at all times and the roller can roll smoothly 
in a transmission groove so that generation of any vibration due to 
frictional resistance can be avoided. Moreover, since the roller assembly 
can be formed of a small number of parts so that the structure can be made 
simple and obtained at a low cost and the weight can be reduced. 
Further, in addition to the above arrangement, if chamfers are provided on 
inner peripheral edges of the slider at axial opposite ends thereof, an 
advantage is obtained in that generation of a pinching in the trunnion can 
be prevented even if the slider is formed short in the sliding direction. 
Use of a short slider contributes to making the roller assembly compact. 
Further, if said axial coupling means comprises washers opposed to and 
placed in contact with axial end surfaces of the roller, and retaining 
rings retained in annular grooves formed on an outer peripheral surface of 
the slider and abutted against outer side surfaces of the washers, the 
coupling means can be obtained easily at a low cost. Moreover, this means 
can be mounted by merely forming the slider slightly longer than the 
roller in the axial direction.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
One embodiment according to the present invention will be described 
hereinafter with reference to the accompanying drawings. 
Referring first to FIGS. 1 and 2, two transmission shafts 1 and 2 are 
connected to each other via a slide type universal joint J according to 
this embodiment. The joint J includes, as primary elements, a tubular or 
hollow cylindrical outer member 3 integrally connected to an end portion 
of one transmission shaft 1 and having an open fore end surface, and an 
inner member 4 connected to an end portion of the other transmission shaft 
2 and accommodated inside the outer member 3. The outer member 3 is 
provided at its inner peripheral surface with a plurality of (three in 
this embodiment) axially extending transmission grooves 5 which are 
circumferentially spaced from each other at equal intervals. Each 
transmission groove 5 comprises left and right inner side walls 5a, 5a 
having such arcuate surfaces that the center of the surfaces is located 
centrally between the side walls and coincides with the central axis 0 
extending parallel to the axis of the outer member 3, and a bottom surface 
5b formed as an arcuate surface having its center located on the axis of 
the outer member 3 (see also FIG. 3). 
On the other hand, the inner member 4 has a boss 7 and, integrally on an 
outer peripheral surface of the boss, a plurality of (three in the 
embodiment) trunnions 8 which project into the mentioned transmission 
grooves 5, respectively. A cylindrical slider 9 is fitted around an outer 
periphery of each trunnion 8 in an axially slidable manner. A roller 10 is 
carried on an outer periphery of the slider 9 via a needle bearing 11 and 
the roller 10 is held in rollable engagement with the corresponding 
transmission groove 5. More specifically, the needle bearing 11 is 
inserted between the slider 9 and roller 10 such that it is in contact 
with the outer peripheral surface of slider 9 and the inner peripheral 
surface of roller 10. An axial coupling means 12 is provided between the 
slider 9 and the roller 10 to couple those elements axially and prevent 
their axial relative displacement. 
The axial coupling means 12 comprises, as shown in FIG. 3, a pair of 
washers 13, 13 opposed to and placed in contact with axial opposite end 
surfaces of the slider 9 and roller 10 and a pair of retaining rings or 
cir-clips 14, 14 which abut against outer side surfaces of the washers 13, 
13, respectively. The cir-clips 14, 14 are retained in a pair of annular 
grooves 15, 15, respectively, which are formed on the outer peripheral 
surface of the slider 9 at its axial opposite end portions. The slider 9, 
roller 10 and needle bearing 11 thus together constitute a slide roller 
assembly 16. Accordingly, when the joint J is to be assembled, the slide 
roller assembly 16 is previously assembled as a unit and mounted on each 
trunnion 8. 
Referring further to FIG. 3, the roller 10 has an outer peripheral surface 
10a of a part spherical configuration with its center being located on the 
central axis 0 so that the roller 10 is capable of inclining around the 
central axis 0. The cylindrical slider 9 is provided with a chamfer 17 
defining a conical or bugle shape on its inner peripheral edge at each of 
axial opposite ends thereof. 
Incidentally, reference numeral 18 in FIG. 1 denotes a flexible boot 
extended over the outer member 3 and the transmission shaft 2 for covering 
the open end of the outer member 3. 
The operation of this embodiment will now be described. If rotational 
torque is applied to one transmission shaft 1, for example, the torque is 
transmitted from the outer member 3 to the inner member 4, in other words, 
from one inner side wall 5a of transmission groove 5 of the outer member 3 
through the roller 10, needle bearing 11 and slider 9 to the trunnion 8 of 
inner member 4 and then through the boss 7 to the other transmission shaft 
2. 
As particularly shown in FIG. 4, when the transmission of torque is 
conducted between both the transmission shafts 1, 2 in a bent state 
wherein their axes to cross each other at an angle, the trunnion 8 repeats 
its inclining movement following the rotations of transmission shafts 1, 2 
and hence the slide roller assembly 16 carried on the trunnion 8 inclines 
simultaneously. In this state, the center of inclination of the slide 
roller assembly 16 is forced to move along the central axis 0 of the 
transmission groove 5 due to the engagement between the part spherical 
outer surface 10a of roller 10 and the arcuate inner side walls 5a, 5a of 
transmission groove 5. Moreover, since in the slide roller assembly 16 any 
axial relative displacement between the slider 9 and roller 10 is 
prevented by the axial coupling means 12, the inclination of the trunnion 
8 and of the slide roller assembly 16 results in generation of a sliding 
displacement between the trunnion 8 and the slider 9, whereby any 
frictional force is prevented from acting on the needle bearing 11 between 
the slider 9 and roller 10 of the slide roller assembly 16 in the axial 
direction. Accordingly, the needle bearing 11 operates normally without 
allowing a skew phenomenon to occur in its needles and permits the roller 
10 to roll smoothly in the transmission groove 5. Owing to the smooth 
operations of the respective elements in this manner, any vibration due to 
frictional resistance does not occur, thus allowing an efficient torque 
transmission between both the transmission shafts 1, 2. 
Moreover, since the slide roller assembly 16 is formed of the slider 9, the 
roller 10 and the needle bearing 12 as main elements, the number of parts 
of the assembly can be relatively small, making the structure simple and 
relatively light-weighted. 
Furthermore, since the cylindrical slider 9 is provided with the chamfers 
17 on its inner peripheral edges at axial opposite ends, even if the 
slider 9 is formed of a short axial length, it can slide smoothly relative 
to the trunnion 8 without causing a pinching. The slider 9 can thus be 
formed extremely short thereby to make the slide roller assembly 16 
compact. 
Additionally, the axial coupling means 12 between the slider 9 and the 
roller 10 is formed of washers 13, 13 and cir-clips 14, 14 so that its 
structure can be simple and the slide roller assembly 16 can be mounted 
easily by merely forming the slider 9 slightly longer than the roller 10 
in the axial direction. 
It should be noted that various modifications in design may be made to the 
above-described embodiment without departing from the invention as defined 
in the claims. For example, though in the embodiment the joint J has been 
illustrated as a tripod type having three trunnions 8, it can instead be 
formed as a bipod type having two trunnions.