Rotary shafts – gudgeons – housings – and flexible couplings for ro – Coupling accommodates drive between members having... – Coupling transmits torque via radially spaced ball
Reexamination Certificate
2000-09-11
2002-08-13
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Coupling accommodates drive between members having...
Coupling transmits torque via radially spaced ball
96
Reexamination Certificate
active
06431988
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a fixed type constant velocity joint used in power transmission systems for automobiles and various industrial machines and adapted to tolerate only an operating angular displacement between two shafts on the driving and driven sides, and it also relates to an assembling method therefor.
For example, there is a fixed type constant velocity joint in the form of a UF (undercut free) type shown in FIG.
15
. This constant velocity joint comprises an outer ring
5
that has a mouth portion
4
and whose inner spherical surface
1
is formed with a plurality of track grooves
2
disposed at circumferentially equispaced intervals to extend axially toward an open end
3
, an inner ring
8
whose outer spherical surface
6
is formed with a plurality of track grooves
7
paired with the track grooves
2
of the outer ring
5
and disposed at circumferentially equispaced intervals to extend axially, a plurality of balls
9
interposed between the track grooves
2
and
7
of the outer and inner rings
5
and
8
for torque transmission, and a cage
10
interposed between the inner spherical surface
1
of the outer ring
5
and the outer spherical surface
6
of the inner ring
8
for holding the balls
9
. The plurality of balls
9
are received in pockets
13
formed in the cage
10
and disposed at circumferentially equispaced intervals.
A stem portion (not shown) integrally extending from the mouth portion
4
of the outer ring
5
has, for example, a rotatable shaft on the driven side connected thereto, while the inner ring
8
has a rotatable shaft on the driving side joined thereto as by serrations. This results in a construction that allows torque transmission while tolerating operating angular displacement between the two rotatable shafts.
FIG. 15
shows the state in which the operating angle &thgr; is 0° and
FIG. 16
shows the state in which the operating angle &thgr; is at its maximum (50°). The operating angle &thgr; shall mean an angle formed between the rotatable shaft X of the outer ring
5
and the rotatable shaft Y of the inner ring
8
. Further, when the rotatable shafts X and Y of the outer and inner rings
5
and
8
take an operating angle &thgr; other than 0°, the plane perpendicular to the bisector of the angle &thgr; between the two rotatable shafts X and Y is referred to as the joint center plane P′. If all of the balls
9
are in the joint center plane P when an operating angle &thgr; is taken, the distances from the ball center to the two rotatable axes X and Y are equal; therefore, transmission of rotary motion at constant velocity is performed between the two rotatable shafts X and Y. The intersection between the joint center plane P′ and the rotatable shaft X, Y is referred to as the joint center O′. In this constant velocity joint, the joint center O′ is fixed without regard to the operating angle &thgr;.
Each track groove
2
in the outer ring
5
is formed to predetermined depths from the inner spherical surface
1
of the outer ring
5
, its depth gradually varying axially. This track groove
2
has an arcuate bottom
2
a
in the innermost region of the mouth portion
4
, and a straight bottom
2
b
parallel to the rotatable shaft X on the open side of the mouth portion
4
. Each track groove
7
of the inner ring
8
is formed to predetermined depths from the outer spherical surface
6
of the inner ring
8
, its depth gradually varying axially. This track groove
7
has an arcuate bottom
7
a
on the open side of the mouth portion
4
, and a straight bottom
7
b
parallel to the rotatable shaft Y in the innermost region of the mouth portion
4
.
In recent years, there have been needs for reduction of the minimum radius of rotation of automobiles (particularly, light-weight cars and small-sized cars) and the increase of the operating angle as the degree of freedom of geometrical design is increased for better automobile steerability. However, with conventional constant velocity joints, an operating angle &thgr; max=50° is the upper limit. And realizing the increase of the operating angle requires increasing the outer diameter of the mouth portion
4
of the outer ring
5
. Therefore, at present a design that is counter to light weight and compact design cannot but be resorted to.
In this constant velocity joint, in order to provide a construction capable of taking large operating angles, the center of curvature, O
1
′, of the track groove
2
of the outer ring
5
is axially offset by an distance F′ with respect to the center of curvature, O
4
′, of the inner spherical surface
1
of the outer ring
5
, that is the outer spherical surface
12
of the cage
10
, and the center of curvature, O
2
′, of the track groove
7
of the inner ring
8
is axially offset by an distance F′ in axially opposite directions of the outer ring-side with respect to the center of curvature, O
3
′, of the outer spherical surface
6
of the inner ring
8
, that is the inner spherical surface
11
of the cage
10
(track offset). Similarly, the center of curvature, O
3
′, of the inner spherical surface
11
of the cage
10
and the center of curvature, O
4
′, of the outer spherical surface
12
are axially offset with respect to the joint center plane P′ in opposite directions by an equal distance f′ (cage offset).
As a result, a pair of track grooves
2
and
7
form a wedge-shaped track whose spacing gradually varies axially in one direction. Each ball
9
is rollably incorporated between a pair of track grooves
2
and
7
and is subjected to the action of an axial tension that causes the ball to move toward wider spacings in the wedge-shaped track when torque is transmitted with the outer and inner rings
5
and
8
taking an operating angle &thgr;.
Further, in this constant velocity joint, the ratio of the cage offset quantity f′ to the total offset quantity (f′+F′) (the sum of the cage offset quantity f′ and the track offset quantity F′) is set such that f′/(f′+F′)=0-0.11. Since optimum ranges of the cage offset quantity f′ and the total offset quantity (f′+F′) vary according to the size of the joint, they have to be determined in relation to the fundamental size indicating the joint size.
Therefore, the ratio, f′/PCR′, of the cage offset quantity f′ to the length PCR′ of a line connecting the center of curvature, O
2
′, of the track groove
7
of the inner ring
8
(or the center of curvature, O
1
′, of the track groove
2
of the outer ring
5
) and the center of the ball
9
, is used, and, in conventional cases, the optimum range of the cage offset quantity f′ is so set as to satisfy the relation f′/PCR′=0-0.017. Further, the ratio of the cage offset quantity f′ to the total offset quantity (f′+F′) is so set as to satisfy the following conditions:
when (
f′+F′
)
/PCR′
=0.14,
f′
/(
f′+F′
)=0,
and
when (
f′+F′
)
/PCR′
=0.15,
f′
/(
f′+F′
)=0.11.
In this connection, the conventional constant velocity joint has been designed to have a size and shape that satisfy the conditions that include f′/(f′+F′)=0-0.11 and f′/PCR′=0-0.017. Therefore, the joint-making assembling of the inner ring
8
, cage
10
and outer ring
5
has been performed in the following manner.
In incorporating the inner ring
8
into the cage
10
, the inner ring
8
is positioned relative to the cage
10
at right angles to the axis of the cage
10
, as shown in
FIG. 17
, and the spherical projection
14
positioned between the track grooves
7
of the inner ring
8
is dropped into one of the pockets
13
of the cage
10
; in this state, the inner ring
8
is inserted into the cage
10
. When the center O
5
&prime
Arent Fox Kintner & Plotkin & Kahn, PLLC
NTN Corporation
Thompson Kenn
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