One-way clutch

Details One-way clutch One-way clutch

2002-07-12

2004-05-11

Rodriguez, Saul (Department: 3681)

192 clutches and power-stop control

Clutches

Automatic

C192S04100R

Reexamination Certificate

active

06732843

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a one-way clutch, and more particularly, to a one-way clutch which prevents sprags from sinking into pockets of a retainer and achieves a stable engagement characteristic, by means of a protuberance formed at an edge of each pocket of a retainer so as to protrude in a radially outward direction.
As shown in
FIG. 12
, a one-way clutch employed in an automatic power transmission system of an automobile usually comprises a retainer
13
, a spring
14
, and sprags
15
. The one-way clutch is disposed in an annular space
20
defined between an outer ring
11
and an inner ring
12
. By means of relative rotation arising between the outer ring
11
and the inner ring
12
, the inner and outer rings are subjected to repeated rotation and locking. Specifically, when the sprags
15
are rotated in one direction, the sprags
15
act as wedges, whereby the outer ring
11
and the inner ring
12
rotate in an integrated fashion (locked state), thus transmitting power. When the sprags
15
are rotated in the opposite direction, the sprags
15
perform idle running, thus interrupting power transmission (i.e., an unlocked state). The one-way clutch which repeatedly performs transmission and interruption of power requires synchronism between sprags' operations and appropriate engagement at all times. For this reason, considerable thought has been put into measures for preventing another member from hindering operations of the sprags. Further, the one-way clutch of sprag type can achieve a stable engagement characteristic for the sprags even when variations attributed to misalignment have arisen between inner and outer bearing rings.
In such a one-way clutch of sprag type, the spring
14
is guided along the inner radius side of the retainer
13
, thereby accurately positioning, in a radial direction, the sprags
15
held by the retainer
13
and the spring
14
. Tongue-like flaps
14
t
of the spring
14
usually impart pre-stress (force) to the sprags
15
in a direction in which the sprags
15
are to be locked, thus contributing to an engagement characteristic. As mentioned, in relation to the one-way clutch, every time idle running and engagement of the sprags
15
are repeated, an outer peripheral cam surface
15
a
of each sprag
15
rotates over an inner peripheral surface (raceway surface)
11
a
of the outer ring
11
, and an inner peripheral cam surface
15
b
rotates over an outer peripheral surface (raceway surface)
12
a
of the inner ring
12
.
In some cases, a one-way clutch of sprag type experiences slippage for reasons of misalignment, vibration, or decentering between the outer and inner rings during the course of pivotal movement in which sprags shift from a free rotation state to a locked state and vice versa, As shown
FIG. 11
, when slippage has arisen, torque is imparted to each sprag
15
while an edge Q of each pocket
13
p
of the retainer
13
is taken as a fulcrum. At this time, a recess
5
c
of the sprag
15
overlaps the edge Q of the pocket
13
p
of the retainer
13
. The sprag
15
rotates in the direction of arrow Z while the point Q is taken as a fulcrum. If the pocket
13
p
of the retainer
13
is large, there arises a problem or a protuberance id formed at an upper edge of the sprag
15
sinking in toward the inner radius side of the pocket
13
p
. If such a sinking phenomenon arises, ensuring synchronism between sprags becomes difficult, thereby adversely affecting engagement performance of the clutch. However, each of the pockets
13
p
of the retainer
13
must have a predetermined minimum length for ensuring smooth action of the sprag
15
.
The one-way clutch such as that shown in
FIG. 12
is constituted of a retainer
23
, a spring
14
guided by the retainer, and sprags
15
fitted into pockets
13
p
of the retainer
13
and pockets
14
p
of the spring
14
. The one-way clutch is placed in an annular space defined between an unillustrated outer ring and an unillustrated inner ring. In such a one-way clutch, tongue-like flaps
14
t
of the spring
14
usually impart pre-stress (force) to the sprags
15
toward a direction in which the sprags
15
are to be locked, thus contributing to an engagement characteristic, and support the respective sprags
15
at all times. The one-way clutch is conveyed or transported while the retainer
13
, the spring
14
, and the sprags
15
are built together. The one-way clutch is incorporated into a space between an outer ring and an inner ring at a location where an automatic power transmission system is to be built.
As mentioned above, before being incorporated into a space between an outer ring and an inner ring, the one-way clutch is transported while a retainer, a spring, and sprags are built together. The sprags are merely held by tongue-like flaps formed in a spring guided along an inner radius side of the retainer. Retaining force (supporting force) of the tongue-like flaps of the spring substantially fails to act on the sprags before the clutch is incorporated into a space between an outer ring and an inner ring. In other words, the sprags are in a so-called free state. Accordingly, there has been a problem of sprags readily dropping from pockets of a spring (or pockets of a retainer) when subjected to slight external force during, e.g., transport.
Every time idle running and engagement of the sprags
15
are repeated, an outer peripheral cam surface
15
a
of each sprag
15
rotates over an inner peripheral surface (raceway surface)
11
a
of the outer ring
11
, and an inner peripheral cam surface
15
b
rotates over an outer peripheral surface (raceway surface)
12
a
of the inner ring
12
. Such a one-way clutch which repeatedly performs transmission and interruption of power requires synchronous actions and appropriate engagement of sprags at all times. Hence, considerable thought is put into preventing another member from hindering the actions of the sprags.
In some cases, a one-way clutch of sprag type experiences slippage for reasons of misalignment, vibration, or decentering between outer and inner rings during the course of a pivotal movement process in which sprags shift from a free rotation state to a locked state and vice versa. As shown
FIG. 11
, when slippage has arisen, torque is imparted to each sprag
15
while an edge Q of each pocket
3
p
of the retainer
13
is taken as a fulcrum. At this time, a recess
15
c
of the sprag
14
overlaps the edge Q of the pocket
13
p
of the retainer
13
. The sprag
15
rotates in the direction of arrow Z while the point Q is taken as a fulcrum. If the pocket
13
p
of the retainer
13
is large, there arises a problem of a protuberance
15
d
formed at an upper edge of the sprag
15
sinking (falling) in toward the inner radius side of the pocket
13
p
, as designated by a chain double-dashed line. If such a sinking phenomenon arises, the sprag fails to return to its original engagement position, thus failing to ensure synchronism and adversely affecting engagement performance of the clutch. Alternatively, the retainer
3
may be damaged. However, each of the pockets
13
p
of the retainer
13
is required to have a predetermined length for ensuring smooth action of the sprag
15
.
SUMMARY OF THE INVENTION
The invention has been conceived to solve the problem and object of the present invention is to provide one-way clutch which prevents dropping of sprags from pockets even when subjected to external force during transport and which involves a simple assembly operation.
Another object of the invention is to provide a one-way clutch which ensures a required length for pockets of a retainer and prevents an upper end of each sprag from sinking into a corresponding pocket even when the sprag has experienced slippage and torque.
Another object of the invention is to provide a one-way clutch in which an upper end of a sprag does not sink into a corresponding pocket of a retainer even when the sprag experiences slippage, to thereby generate torque.
In order to solve the aforesaid object, the i

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