Rotary shafts – gudgeons – housings – and flexible couplings for ro – Coupling accommodates drive between members having... – Tripod coupling
Reexamination Certificate
2002-04-24
2004-05-11
Browne, Lynne H. (Department: 3679)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Coupling accommodates drive between members having...
Tripod coupling
C384S505000, C464S905000
Reexamination Certificate
active
06733394
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a constant velocity joint, particularly a slide type tripod type constant velocity joint.
2. Brief Description of the Prior Art
Generally, a constant velocity joint is a kind of universal joint adapted to join two shafts, driving side and driven side, and capable of transmitting torque at constant velocity even if there is an angle between said two shafts. The slide type allows a relative axial displacement between two shafts by the plunging of the joint, while the tripod type comprises a tripod member having three radially projecting leg shaft and joined to one shaft, and a hollow cylindrical outer joint member having three axially extending track grooves and joined to the other shaft, the leg shafts of the tripod member being received in the track grooves of the outer joint member to effect torque transmission.
An example of a slide type tripod type constant velocity joint will now be described with reference to FIG.
14
. It comprises an outer joint member
1
having three axially extending track grooves
2
formed in the inner peripheral surface thereof, a tripod member
4
inserted in the outer joint member
1
and having three radially projecting leg shafts
5
having annular rollers
7
rotatably fitted on their columnar outer peripheral surfaces through a plurality of needle rollers
6
, said rollers
7
being inserted in the track grooves
2
. A pair of roller guide surfaces
3
opposed to each other in the circumferential direction of the track groove
2
are concave surface (partial cylindrical surfaces) parallel with the axis of the outer joint member
1
, while the outer peripheral surfaces of the rollers
7
fitted on the three leg shafts
5
are convex surfaces (partial sphere surfaces) suited for the roller guide surfaces
3
. Each roller
7
is engaged with the roller guide surfaces
3
of the corresponding track groove
2
and is capable of moving axially of the outer joint member
1
along the track groove
2
while rotating around the axis of the leg shaft
5
.
As shown in FIG.
14
(B), when torque is transmitted with the joint taking an operating angle &thgr;, the roller
7
and the roller guide surface
3
are in a mutually crossing relationship, as shown in FIG.
14
(C). In this case, whereas the roller
7
tends to make a rolling movement in the direction of arrow t shown in FIG.
14
(B), the roller
7
moves while being restrained by the roller guide surface
3
because the roller guide surfaces
3
are partial cylindrical surfaces parallel with the axis of the outer joint member
1
. As a result, sliding friction takes place between the roller guide surfaces
3
and the roller
7
, producing a slide resistance. Further, this sliding friction produces induced thrust in the axial direction. Such slide resistance and induced thrust cause vibrations and noise in a car body, influencing the NVH (noise, vibration and harshness) of automobiles, decreasing the freedom of the design of the suspension; thus, it is desired to minimize said slide resistance and induced thrust.
As for a slide type tripod type constant velocity joint that is designed to decrease such slide resistance and induced thrust, for example, one having the construction shown in
FIG. 15
is known. That is, as shown, the outer peripheral surface of the leg shaft
5
of the tripod member
4
is made a true spherical surface, and slidably fitted on this true spherical surface is the cylindrical inner peripheral surface of a cylindrical ring
8
. The ring
8
and roller
7
constitute a roller assembly which is relatively rotatable through needle rollers
6
. The needle rollers
6
are disposed in the so-called “all roller condition” between the cylindrical outer peripheral surface of the ring
8
and the cylindrical inner peripheral surface of the roller
7
and are prevented from slipping off by annular stop rings
9
. The roller
7
is received in the track groove
2
in the outer joint member
1
, and is capable of moving axially of the outer joint member
1
while rolling on the roller guide surfaces
3
of the track groove
2
.
The outer peripheral surface of the leg shaft
5
is a true spherical surface having a center of curvature on the axis of the leg shaft
5
, and the roller assembly (
7
,
8
,
9
) oscillates around said center of curvature. The roller assembly is oscillatable; therefore, when torque transmission is effected with the outer joint member
1
and the tripod member
4
taking an operating angle, the roller
7
is guided by roller guide surfaces
3
of the outer joint member
1
to keep a position parallel with the axis of the outer joint member
1
, and keeping this position, it correctly rolls on the roller guide surfaces
3
. Therefore, the sliding friction produced during torque transmission with the operating angle taken is reduced, suppressing the generation of slide resistance and induced thrust.
It is known to use a slide type tripod type constant velocity joint in order to transmit torque at constant velocity from an automobile engine to the wheels. The slide type tripod type constant velocity joint has barrel shaped rollers attached to the leg shafts of the tripod member and needle rollers are used as “cageless all roller type” to serve as rolling elements between the outer peripheral surface of the leg shaft and the inner peripheral surface of the barrel shaped roller. And, when torque is transmitted with an operating angle taken, induced thrust is produced by mutual friction between the inner parts during rotation, and slide resistance is produced even during stoppage if the joint is subjected to forceful axial expansion and contraction. The typical NVH phenomenon of automobiles in which such induced thrust and slide resistance take part includes the rolling of the car body during running, which is connected with the former, and a D-range idling vibration phenomenon in an AT car during stoppage, which is connected with the latter.
The key to solving the automobile NVH problem is to reducing the size of the induced thrust and slide resistance of the joint. Generally, the induced thrust and slide resistance of the joint tend to depend on the size of the operating angle. Therefore, applying the joint to the drive shaft of an automobile leads to a design restriction inhibiting the operating angle from being increased. Thus, in order to increase the freedom of the design of the suspension of automobiles, it has been a problem to reduce and stabilize the induced thrust and slide resistance.
However, since the rolling elements in the conventional slide type tripod type constant velocity joint are needle rollers of the all roller type, unbalanced loads, such as edge load, tend to act on the rolling element surfaces owing to the skewing or the like of the rollers during rotation. Further, the contact state does not become stabilized owing to factors associated with interior clearances and precision, resulting in the barrel shaped rollers being inclined to produce an edge load. Further, because of the construction, relative slip occurs between the ends of the barrel shaped roller, the leg shaft and the stop rings. Such phenomena as skew, edge load and relative slip are believed to govern the size of the frictional force in the joint.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to minimize the frictional force to further reduce the induced thrust and slide resistance and to improve stability.
An invention described in claim
1
is a constant velocity joint comprising an outer joint member having three track grooves each having circumferentially opposed roller guide surfaces, a tripod member having three radially projecting leg shafts, a roller inserted in each said track groove, and a ring fitted on each said leg shaft to rotatably support said roller, said roller being movable along said roller guide surfaces axially of the outer joint member, wherein said roller consists of a set of annular roller portions, the inner periphery of each said annular roller p
Kura Hisaaki
Kuroda Masayuki
Sugiyama Tatsuro
Arent & Fox PLLC
Browne Lynne H.
NTN Corporation
Thompson Kenn
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