One-way clutch

192 clutches and power-stop control – Clutches – Automatic

Reexamination Certificate

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Details

C192S045100

Reexamination Certificate

active

06446775

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a one-way clutch that effects and blocks torque transmission between inner and outer rings by shifting intermediate members according to the direction of relative rotation between the inner and outer rings, and particularly relates to improvement of a spring member for pressing and urging each of the intermediate members into the shift in a direction to wedge between the inner and outer rings.
DESCRIPTION OF THE PRIOR ART
As for example disclosed in Japanese Unexamined Patent Publication No. 61-228153, it is known that in a belt type auxiliary equipment driving apparatus for a vehicle engine, a one-way clutch is disposed, in order to transmit torque of a crank shaft revolving with angular velocity variations due to an explosion stroke of the engine to input shafts of auxiliary equipment through a belt, in a torque transmission path so that for a period of increase in angular velocity during the angular velocity variations torque transmission is effected between the crank shaft and the input shafts of the auxiliary equipment to drive the input shafts into rotation, while for a period of decrease in angular velocity during the angular velocity variations the torque transmission is blocked to avoid torque due to moment of inertia of the input shafts from being transmitted to the crank shaft whereby load placed on the belt is reduced to provide elongated belt life.
Now, the operation of the above one-way clutch will be described. As shown in
FIG. 10
, each of intermediate members c is retained by a cage d between inner and outer rings a and b for clockwise and counterclockwise rocking motion in the figure and is normally pressed clockwise in the figure by a flat spring e as a spring member to wedge between the inner and outer rings a and b. For the period of increase in angular velocity, for example, when the outer ring b relatively rotates in its locking direction (clockwise in the figure) with respect to the inner ring a, the relative rotation causes each intermediate member c to wedge between the inner and outer rings a and b thereby effecting torque transmission between the inner and outer rings a and b. On the other hand, for the period of decrease in angular velocity, when the outer ring b relatively rotates in its idling direction, the relative rotation causes each intermediate member c to rock opposite to the direction to wedge between the rings against the pressing force of the flat spring e. This produces slippage between each intermediate member c and the inner and outer rings a, b thereby blocking torque transmission.
As the spring member, a coil spring is generally used apart from the above-mentioned flat spring e. A comparison of both the springs indicates that the coil spring is more suitable in durability. Here, description will also be made about the structure of the one-way clutch when the coil spring is used as the spring member. As shown in
FIGS. 11 and 12
, out of a pair of circumferentially opposed wall surfaces of each retaining hole g of the cage d, the wall surface on the opposite side to the wall surface of a protruding wall for supporting the intermediate member c to allow its rocking motion (left-hand side in
FIG. 12
) is formed with a recess h and the root end of the coil spring f (left end in
FIGS. 11 and 12
) is accommodated in the recess h. It is to be noted that the root end of the coil spring f is generally closely wound, though its illustration is omitted.
Meanwhile, in the one-way clutch, torque transmission is started not at a point in time when the angular velocities of the inner and outer rings a and b are coincident with each other for the period of increase in angular velocity but slightly behind the point in time. If this is described using the above case as an example, torque of the outer ring b is started to be transmitted to the inner ring a at a point in time when the outer ring b is further increased in angular velocity to relatively rotate by a certain angle with respect to the inner ring a after the angular velocity of the outer ring b has been increased for the period of increase in angular velocity until it matches the angular velocity of the inner ring a. The relative angle between the inner and outer rings a and b at the point in time is called “a delay angle”. If the delay angle is too large, excellent response to an angular velocity variation cannot be attained and therefore proper torque transmission cannot be provided.
The reasons for the occurrence of the delay angle are not only that each intermediate member c essentially requires a certain time to rock to wedge between the inner and outer rings a and b due to relative rotation of the inner and outer rings a and b in the locking direction but also that each intermediate member c vibrates due to angular velocity variations. Namely, when each intermediate member c vibrates, slippage occurs between the intermediate member c and each of the inner and outer rings a and b even if the inner and outer rings a and b relatively rotate in the locking direction, and therefore its wedging movement between the inner and outer rings a and b is further delayed so that the intermediate member c cannot follow an angular velocity variation.
Further, the frequency of angular velocity variations of the vehicle engine is low at low engine speeds and high at high engine speeds. For example, in a four-cycle four-cylinder engine involving two explosion strokes for one revolution of the crank shaft, the frequency of angular velocity variations reaches 100 to 200 Hz at high engine speeds where the speed of the crank shaft reaches 3000 to 6000 rpm.
Accordingly, in order to attain excellent response to angular velocity variations in the entire speed range of the vehicle engine, it is necessary to allow each intermediate member c to sufficiently follow high-frequency angular velocity variations at high engine speeds. To satisfy this requirement, the spring member must have a large spring constant enough to suppress variations of the intermediate member c due to such high-frequency angular velocity variations.
Problems to be Solved
However, the conventional one-way clutch using the coil springs f as the spring members generally has the disadvantage of a lower spring constant of the coil spring f as compared with the flat spring e of equal size in its operating direction. As can be seen from this point, the coil spring f is excellent in durability over the flat spring e, whereas the one-way clutch using the coil spring f has a problem of the difficulty in attaining excellent response to high-frequency variations as described above as compared with the one-way clutch using the flat spring e. In this case, if the spring constant is increased by increasing the size of each coil spring f in the operating direction, the one-way clutch will be greater. This causes a new problem of the difficulty in disposing the one-way clutch in an engine room of the vehicle.
Further, the conventional one-way clutch using the coil springs f has another problem. Specifically, as shown with exaggeration in
FIG. 13
, the root end of the coil spring f has a tendency to easily extrude from the recess h toward the outer ring b as a result of relative rotation between the inner and outer rings a and b. Further, if expansion and contraction of the coil spring f itself resulting from rocking motion of the intermediate member c is added to this tendency, the distal end (right end in
FIG. 14
) of the coil spring f is also displaced toward the outer ring b as shown with exaggeration in the figure. Furthermore, since the rotation of the coil spring f itself around the axis of the coil also concurs, these events results in easily providing an unstable pressing force on the intermediate member c. This also invites insufficient suppression of the above-mentioned vibrations of the intermediate member c.
The present invention has been made in view of the foregoing points and therefore a major object of the present invention is to obtain, in using coil springs as spring members for a one-w

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