Tripod constant velocity joint

Details Tripod constant velocity joint Tripod constant velocity joint

1998-12-07

2001-01-23

Knight, Anthony (Department: 3629)

Rotary shafts, gudgeons, housings, and flexible couplings for ro

Coupling accommodates drive between members having...

Tripod coupling

C464S132000, C464S905000

Reexamination Certificate

active

06176787

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tripod type constant velocity joint mounted to drive axles of a car for transmitting power to drive wheels, and more particularly, the present invention relates to a tripod type constant velocity joint which can reduce frictional resistance generated between a tripod housing and a cylindrical roller which are in contact with each other.
2. Description of the Prior Art
Generally, a constant velocity joint is mounted to drive axles connected to a final reduction gear in a front wheel drive car or a four wheel drive car and functions to transmit power to drive wheels. The constant velocity joint can transmit power due to the fact that a contact point between a drive shaft and a driven shaft exists on a line which bisects an angle between them.
A constant velocity joint consists of a sliding joint, a shaft and a fixed joint. The sliding joint is used for absorbing displacements in X and Y directions in a car, and examples of the sliding joint include a tripod type joint, a double offset type joint, a cross groove type joint, etc. The fixed joint is used for absorbing a steering angle of the car, and examples of the fixed joint include a Rzeppa type joint, a Birfield type joint, etc.
The present invention is concerned with a tripod type constant velocity joint, and therefore, a construction of a tripod type constant velocity joint of the prior art will be described hereinafter with reference to
FIGS. 1 through 5
.
A tripod type constant velocity joint mounted to drive axles connected to a final reduction gear in a car for transmitting power to drive wheels, as shown in
FIGS. 1 through 3
, includes a tripod housing
20
which defines an opening. The tripod housing
20
is formed with three track grooves
21
which are communicated with the opening and are uniformly spaced apart from one another in a circumferential direction. Each track groove
21
has a contact groove
22
formed in a side wall section thereof. The contact groove
22
has a bottom wall portion which defines a pair of guide surfaces P and Q which are parallel to each other. A spider
23
is disposed in the opening of the tripod housing
20
and has three trunnions
24
which project from an outer surface thereof to be inserted into the three track grooves
21
, respectively. Three pairs of a needle roller
25
, a spherical roller
26
and a cylindrical roller
27
are sequentially and diametrically fitted around the three trunnions
24
of the spider
23
, respectively. By this, the cylindrical roller
27
is engaged into the contact groove
22
. A striker-out
28
and a retainer ring
29
are locked to a threaded portion of each trunnion
24
above the needle roller
25
. The striker-out
28
and the retainer ring
29
prevent the cylindrical roller
27
from being released.
In the tripod type constant velocity joint constructed as mentioned above, when the joint is rotated at a certain joint angle, the cylindrical roller
27
engaged into the contact groove
22
defined in the track groove
21
of the tripod housing
20
is rolled on the pair of guide surfaces P and Q of the contact groove
22
, and at the same time, the spherical roller
26
absorbs an aligning movement of the cylindrical roller
27
.
On the other hand, the cylindrical roller
27
is moved along the pair of guide surfaces P and Q of the contact groove
22
of the tripod housing
20
upon rolling as described above. According to this, as shown in
FIG. 4
, it is possible to control a direction over a specified angle &bgr;.
However, the tripod type constant velocity joint of the prior art suffers from defects in that since an upper end surface and a lower end surface of the cylindrical roller
27
are in contact with all of a left lower end contact point A
1
, a right lower end contact point A
2
, a right upper end contact point A
3
and a left upper end contact point A
4
formed in the contact groove
22
of the tripod housing
20
while performing a direction control over the specified angle &bgr;, a great deal of frictional resistance is generated between the cylindrical roller
27
and the tripod housing
20
.
In other words, in the tripod type constant velocity joint as shown in
FIG. 5
, when assuming that F
1
, F
2
, F
3
, and F
4
are frictional resistance at the contact points A
1
, A
2
, A
3
and A
4
, respectively, and l
1
, l
2
, l
3
, and l
4
are distances from a center of the cylindrical roller
27
to the contact points A
1
, A
2
, A
3
and A
4
, respectively, since the upper end surface and the lower end surface of the cylindrical roller
27
are in contact with all contact points A
1
, A
2
, A
3
and A
4
formed in the contact groove
22
, rotational friction moment M
4
of the cylindrical roller
27
is described by M
4
=F
1
l
1
+F
2
l
2
+F
3
l
3
+F
4
l
4
, whereby the frictional resistance cannot but be increased.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made in an effort to solve the problems occurring in the prior art, and an object of the present invention is to provide a tripod type constant velocity joint which can reduce frictional resistance generated between a cylindrical roller and a contact groove of a tripod housing while the cylindrical roller is rolled over, thereby to be reliably operated.
In order to achieve the above object, according to the present invention, an extended portion is formed at a contact groove, or an inclined portion or a projected portion is formed on a cylindrical roller, such that the cylindrical roller comes into contact with the contact groove only at two contact points.


REFERENCES:
patent: 4786270 (1988-11-01), Iwasaki
patent: 5474500 (1995-12-01), Girguis

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