In a variety of mechanical devices, including the powertrains of vehicle automatic transmissions, overrunning clutches are used to produce a one-way driving connection between an input and an output race of the overrunning clutch. Specifically, the clutch is capable of transmitting torque when the rotation of one race with respect to the other is in one direction, and the clutch overruns, or freewheels, when the rotational direction of one race with respect to the other is reversed.
The shape and orientation of the input and output races with respect to each other may vary depending on design. Some one-way clutches have input and output races that are oriented radially concentric with respect to each other. In another design, the confronting faces of the input and output races are planar.
The mechanical means used to lock a one-way clutch are varied, but commonly consist of rollers, sprags, rockers, or strut types of torque transmitting elements positioned between an input and an output race. Depending on the particular type of one-way clutch and the direction of rotation, each of the races contains unique surface features that engage one or more of the torque transmitting elements.
The operating modes of a basic one-way clutch are a locked mode in one given direction, and a freewheel mode in the opposite direction. In this type of one-way clutch, the operating mode of the clutch is determined only by the direction of torque being applied to the input race.
The increased complexity of power transmitting mechanisms has led to a class of selectable one-way clutches, henceforth referred to as SOWC's. A SOWC is similar to a one-way clutch in basic operation as described above. However, as the name implies, SOWC's are capable of producing a driving connection between an input and output race in one or both rotational directions and/or are also able to freewheel in one or both rotational directions.
In a SOWC, a moveable selector ring or plate, henceforth to be called a selector plate, is commonly employed to restrict the free movement of one or more of the torque transmitting elements to achieve the various operating modes. For example, but not limited to the following, in a first position of a selector plate in a SOWC, the torque transmitting elements may have movement that is unrestricted by the selector plate, while in a second position of the selector plate, some or all of the elements may be either held in contact with the confronting face, or kept from contacting the confronting face.