Rotary shafts – gudgeons – housings – and flexible couplings for ro – Coupling accommodates drive between members having... – Coupling transmits torque via radially spaced ball
Reexamination Certificate
2000-11-29
2003-01-14
Browne, Lynne H. (Department: 3679)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Coupling accommodates drive between members having...
Coupling transmits torque via radially spaced ball
C464S143000, C464S906000, C148S909000, C029S898020
Reexamination Certificate
active
06506121
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a cage for a stationary type constant-velocity joint (CVJ) comprising an outer ring and an inner ring, balls through which torque is transmitted between the outer and inner rings, and a cage for retaining the balls, and a method of manufacturing the cage, and a constant-velocity joint.
2. Description of the Related Art
FIG. 5
shows a conventional stationary type CVJ, which comprises an outer ring
50
formed with a plurality of curved track grooves
54
in its spherical inner surface
51
, an inner ring
52
formed with a plurality of curved track grooves
55
in its spherical outer surface
53
, radially opposite to the respective track grooves
54
, and balls
56
each received in a pair of radially opposed track grooves
54
and
55
.
The balls
56
are retained in pockets
60
of a cage
57
disposed between the inner and outer rings
52
,
50
with its outer spherical surface
58
guided by the inner spherical surface
51
of the outer ring
50
and its inner spherical surface
59
guided by the outer spherical surface
53
of the inner ring
52
.
The bottoms of the track grooves
54
and
55
are curved such that their respective centers of curvature Al and A
2
are spaced (or offset) equal distances from point O
0
in opposite directions along the axis of the rings. When torque is transmitted with the outer ring
50
and the inner ring
52
taking a working angle, the balls
56
are always in a plane perpendicular to the bisector of the working angle, so that the output ring can always rotate at a constant speed irrespective of the working angle.
The pockets
60
of the cage
57
are elongated in the circumferential direction of the cage as shown in
FIG. 6A
so that the balls
56
move in the circumferential direction in the pockets while sliding along the axially opposed side faces
61
as shown in
FIG. 6B
when the inner and outer rings are rotating with their axes inclined relative to each other. High wear resistance is therefore required for the side faces
61
.
To increase the wear resistance of the side edges
61
, a conventional CVJ cage
57
is manufactured following the next seven steps as shown in FIG.
7
:
Step 1: forming a short tubular member P
1
as shown at (A) by cutting a pipe;
Step 2: pressing the member P
1
from both ends to form a cage blank P
2
having outer and inner curved surfaces;
Step 3: turning the outer and inner surfaces into spherical outer and inner surfaces
58
,
59
(C);
Step 4: pressing the cage blank P
2
to form pockets
60
(D);
Step 5: shaving the perimeter of each pocket
60
to cut a pair of side faces
61
until the width between the side faces
61
becomes substantially equal to the diameter of the balls
56
(E);
Step 6: subjecting the cage blank P
2
to heat treatment such as carburizing to increase surface hardness; and
Step 7: grinding the cage blank P
2
(F) to finish spherical outer and inner surfaces
58
,
59
to form a cage
57
.
Because the cage blank is carburized after the pockets
60
have been formed, hardened layers
63
formed around the pockets
60
will have a uniform depth as shown in
FIGS. 6A
,
6
B. The side faces
61
as the ball rolling surfaces have a pretty high hardness of 58-63 HRC. The cage
57
is thus sufficiently wear resistant.
When torque is transmitted with the inner and outer rings forming a working angle, tensile and torsional forces act on the cage
57
. Thus, it is desirable to decrease the hardness to increase the toughness of the bridge portions
64
defined between the pockets
60
.
But since the cage blank is carburized after the pockets have been formed and their side faces
61
have been finished by shaving, the hardened layers formed around the pockets
60
have a uniform depth as shown in FIG.
6
B. The bridges
64
are thus high in hardness and low in toughness. Since the bridges
64
are formed by punching the pockets
60
, they naturally have a trapezoidal cross-section, which means that their width (circumferential dimension) at their inner side is smaller than at their outer side. Thus, if the number of balls and thus the number of pockets are increased to increase the load-bearing capacity of the joint without increasing its outer diameter, the width of the bridge portion on the radially inner side tends to be short.
Therefore there are several points to be improved to increase the strength of such a conventional cage.
Also, with such a conventional cage
57
, since the axially opposed side faces
61
of each cage
60
are finished by shaving, the width of the pockets
60
(or distances between the side faces
61
) tends to vary rather widely.
Thus, in assembling a constant-velocity joint, it is necessary to classify the cages
57
into ranks according to the width of the pockets
60
, classify the torque-transmitting balls into ranks according to the respective pocket widths, and adjust the gaps between the pockets
60
and the torque-transmitting balls
56
. If no suitable gaps are obtainable, there arises a necessity of grinding the side faces
61
of the pockets
60
. Thus, assembling is extremely troublesome and there remain points to be improved.
An object of the invention is to provide a cage for a constant-velocity joint that is high in mechanical strength, and a method of manufacturing such a cage, and a durable constant-velocity joint.
According to this invention, there is provided a cage of a stationary type constant-velocity joint having an outer ring and an inner ring. The cage has a cylindrical portion formed with a plurality of pockets at equal angular intervals to receive balls for transmitting a turning torque between the outer ring and the inner ring. The cage has a spherical outer surface kept in contact with and guided by a spherical inner surface of the outer ring and a spherical inner surface kept in contact with and guided by a spherical outer surface of the inner ring. The pockets each have a pair of end faces that are opposed to each other in a circumferential direction of the cage and a pair of side faces that are opposed to each other in an axial direction of the cage. Also, the pair of end faces are formed by cutting after hardening and have a lower surface hardness than the side faces.
The center of curvature of the spherical outer surface of the cylindrical portion may beat the same point as or spaced from the center of curvature of its spherical inner surface in an axial direction of the cylindrical portion.
By this arrangement, toughness is imparted to the bridge portions formed between the pockets and their tensile and torsional strengths are improved.
As a method for providing a lower surface hardness to a pair of the end faces of each pocket than a pair of the side faces, either of the following two methods may be adopted. One is to form the cylindrical portion of the cage with pockets from carburized case-hardened steel and cut the entire inner periphery of each pocket with the cutting depth deeper to form a smaller carburizing depth on the end faces than on the side faces, and the other is to cut only the end faces, thereby forming a smaller carburizing depth on the end faces than on the side faces.
The end faces of the pockets may be cut to inclined surfaces that incline so as to diverge radially outwardly.
On the constant-velocity joint comprising an outer ring, an inner ring and a cage mounted between the outer ring and the inner ring so that the center of curvature of the spherical outer surface of the cage is axially spaced from the center of curvature of the spherical inner surface of the cage, when torque is transmitted with the outer ring and the inner ring taking a working angle therebetween, the balls received in the pockets of the cage move along a path forming a figure “8” which is larger at its radially outer half than at its radially inner half. By forming the end faces of each pocket into inclined surfaces that incline so as to diverge radially outwardly, the width of each bridge portion at its inner side is increased. This increases the str
Katou Takuya
Kobayashi Masazumi
Maeda Takao
Tanio Masayuki
Browne Lynne H.
Dunwoody Aaron M
NTN Corporation
Wenderoth , Lind & Ponack, L.L.P.
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