192 clutches and power-stop control – Clutches – Automatic
Reexamination Certificate
1999-10-21
2001-04-24
Bonck, Rodney H. (Department: 3681)
192 clutches and power-stop control
Clutches
Automatic
C192S04100R
Reexamination Certificate
active
06220414
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a one-way clutch disposed, for example, in a torque transmission path for transmitting torque of a crank shaft of a vehicle engine rotating together with slight variations in angular velocity to an input shaft of auxiliary equipment (an auxiliary equipment shaft) through a power transmission belt, and particularly relates to measures for preventing a locking failure of the clutch due to high-frequency slight variations in angular velocity of the crank shaft or the like and measures for improving the ability of sprags to follow increase in angular velocity of the crank shaft or the like.
DESCRIPTION OF THE PRIOR ART
For example, as disclosed in Japanese Patent Application Laid-Open Gazette No. 61-228153, there is know a technique for reducing a load of a power transmission belt by disposing a one-way clutch in a torque transmission path for transmitting torque of a crank shaft of a vehicle engine to an auxiliary equipment shaft through the power transmission belt to absorb slight variations in angular velocity of torque, resulting from an explosion stroke of the engine, in the one-way clutch. In particular, if the auxiliary equipment is an alternator, its rotor has large inertial torque and therefore the effect of reducing a belt load is significant.
In this case, high-frequency slight variations in angular velocity of the crank shaft within the high engine speed range (e.g., at 5000 rpm) fall within a range to be sufficiently absorbable by elasticity of the power transmission belt, since the amplitude of variations is small. Therefore, the power transmission belt takes a light load. On the contrary, low-frequency slight variations in angular velocity of the crank shaft within the low engine speed range have a large amplitude, and therefore a heavy load is placed on the power transmission belt. As can be seen from these circumstances, the emphasis for the role of the one-way clutch is laid on absorbing, especially, low-frequency slight variations in angular velocity of the crank shaft within the low engine speed range.
Now, description will be made about the structure of a conventional one-way clutch disposed in the torque transmission path. As shown in
FIG. 5
, this one-way clutch includes an inner ring a, an outer ring b, and sprags c, c, . . . each disposed between the inner and outer rings a, b for rocking motion in a plane orthogonal to an axis of rotation of the inner and outer rings a, b. Each of the sprags c tilts in a direction to wedge between the inner and outer rings a, b (clockwise direction in
FIG. 5
) to transmit torque therebetween, and tilts in a direction to come into sliding contact with the inner and outer rings a, b (counter-clockwise direction in
FIG. 5
) to cut off transmission of torque between the inner and outer rings a, b. The sprags c, c, . . . are each normally urged to tilt in the above wedging direction while being guided slidably on each corresponding riding land f of a cage e by a pressing force F
1
of each corresponding leaf spring d.
More specifically, in the plane where the sprag c rocks, a contact point Q at which the sprag C contacts the corresponding riding land f is positioned closer to the outer periphery of the clutch than a line (dot-dash line in
FIG. 5
) extending from a pressing point P, at which the sprag c takes a pressing force F
1
of the leaf spring d, along the direction of the pressing force F
1
. Thus, the pressing force F
1
is converted into a tilting force F
2
that acts tangentially on the contact point Q of the sprag c to tilt the sprag c in the wedging direction.
In the above configuration, for example, when torque of the crank shaft is input to the outer ring b, for the period of increase in angular velocity of the crank shaft during slight variations in angular velocity thereof, each sprag c tilts in the wedging direction while shifting its contact point Q with rising land f toward the outer ring b by relative rotation of the outer ring b in a locking direction together with a pressing force F
1
from the leaf spring d, thereby transmitting torque between the inner and outer rings a, b. On the other hand, for the period of decrease in angular velocity of the crank shaft during slight variations in angular velocity thereof, each sprag c tilts in the direction to slidingly contact the inner and outer rings a, b while shifting the contact point Q toward the inner ring a against the pressing force F
1
of the leaf spring d by relative rotation of the outer ring b in an unlocking direction, thereby cutting off transmission of torque between the inner and outer rings a, b.
However, the above-mentioned conventional one-way clutch has the following problems. First, this one-way clutch readily causes a locking failure due to high-frequency (e.g., 160-Hz) slight variations in angular velocity within the high engine speed range. The reason for this seems as follows: When the sprag c tilts in the direction to slidingly contact the inner and outer rings a, b by relative rotation of the outer ring b in its unlocking direction, the sprag c wedges between the leaf spring d and the riding land f to produce a frictional force between the sprag c and the riding land f. This frictional force suppresses the tilting motion of the sprag c in the direction of wedging between the inner and outer rings a, b at the time of relative rotation of the outer ring b in its locking direction. This readily causes the above-mentioned locking failure in association with a deteriorated ability of the sprag c to follow slight variations in angular velocity as the engine speed increases.
Second, in the conventional one-way clutch, each sprag c cannot sufficiently follow high-frequency (e.g., 160-through 170-Hz) slight variations in angular velocity within the high engine speed range. Therefore, slips readily occur between each sprag c and respective inner and outer rings a, b. More specifically, the slight variations in angular velocity cause each sprag c to produce vibrations that may be accompanied with slips over the inner and outer rings a, b. This makes it inadequate for each sprag c to tilt in the direction to wedge between the inner and outer rings a, b for the period of increase in angular velocity during slight variations in angular velocity.
To cope with this, it can be considered that the pressing force F
1
against each sprag c is increased by increasing the thickness of each leaf spring d so that vibrations of each sprag c are suppressed so as to securely tilt the sprag c in the wedging direction.
However, if the thickness of the leaf spring d is increased, a stress generated in the leaf spring d is also increased correspondingly. This results in another problem that the leaf spring d may readily be broken. Accordingly, in actuality, it is difficult to increase a pressing force F
1
of each leaf spring d.
A first object of the present invention is to avoid a one-way clutch, disposed in a torque transmission path for transmitting torque accompanied with slight variations in angular velocity, from causing a locking failure for the period of increase in angular velocity during slight variations in angular velocity within the high engine speed range of a vehicle engine or the like by allowing each sprag to tilt in the wedging direction regardless of a frictional force between the sprag and a corresponding riding land.
A second object of the present invention is to improve the ability of each sprag, guided on a corresponding riding land of a cage in the same one-way clutch, to follow increase in angular velocity during high-frequency slight variations in angular velocity within the high engine speed range by enabling increase in a force that tilts the sprag in a direction of wedging between inner and outer rings without the necessity for increasing a pressing force of a pressing mechanism such as a leaf spring that normally urges the sprag into tilting motion in the wedging direction.
SUMMARY OF THE INVENTION
To attain the above first object, in the present invention, a contact point of each spr
Domoto Masakazu
Miyata Hirofumi
Nagaya Shuichi
Nishikawa Shinichiro
Satoda Masahiko
Bando Chemical Industries Ltd.
Bonck Rodney H.
Cole Thomas W.
Nixon & Peabody LLP
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