Clutches are used in the transmission of power in a wide variety of mechanical devices, including automobiles, trucks, motorcycles, aircraft, mining equipment, construction equipment, industrial equipment, agricultural equipment, and the like. In any case, a clutch is used in the transmission of power from one component of a mechanical device to another component of the device. The clutch typically transfers power from one component of the clutch (a driving member) to another component of the clutch (a driven member) when the clutch is engaged, but does not transfer power when the clutch is not engaged. For instance, the clutch can be designed to transfer power from a cam plate to a rocker plate which are contained within the clutch.
Simple one-way clutches of conventional designs can be used to provide a one-way drive connection between inner and outer races. Clutches of this type typically include sprags or rollers which can connect the races in a manner whereby power is transferred between the races when the clutch is engaged, but which can be disengaged at times or under conditions when power transmission is not desired. Such clutches are commonly used in the powertrain or driveline of various automotive vehicles, including automobiles and trucks.
Conventional one-way clutch assemblies have at least one sprag or roller which driveably locks two notched or pocketed races together mutually in one rotary direction and allows the races to rotate freely in the other direction. Rocker and sprag type one-way clutch assemblies can increase the torque capacity for a given package size compared to those of a roller-type clutch, but they are generally limited in torque transmitting capacity by the magnitude of the contact or bearing stresses caused by contact of the rockers or sprags with the races.
The clutch described in U.S. Pat. No. 5,070,978 is reported to overcome the limitation of torque transmitting capacity as well as having additional benefits. The one-way overrunning clutch described in U.S. Pat. No. 5,070,978 includes a drive member and a driven member, which are mounted for clockwise and counterclockwise rotation about a common axis. The drive member includes a planar drive face, normal to the common axis, which connects with a source of power for rotating the planar drive face either clockwise or counterclockwise. The driven member includes a planar driven face, positioned in close proximity to and in confronting relationship with the drive face. The drive and driven members are coupled to one another through a series of pockets in one of the drive faces, and a plurality of cooperating struts carried by the other face, such that when the drive member is driven counterclockwise, it drives the driven member with it. When the drive member is driven clockwise, it does not drive the driven member, but rotates freely relative to the driven member. Column stability of the strut, which transmits the torsion load between the races, is an importance factor in the design.
U.S. Pat. No. 5,954,174 discloses a ratchet one-way clutch assembly having an inner race with notches, an outer race with pockets, and rockers located in the pockets to engage the notches. The rockers of these clutches have a pivot ridge which mates with a peak or recess in the pockets in the outer race to position the rocker in the pocket. The center of mass of each rocker is located such that the rocker tends to engage or disengage a notch in the inner race. The teachings of U.S. Pat. No. 5,954,174 disclose the utilization of a spring to provide a tilting force on each rocker directed to produce engagement of the rocker with a notch of the inner race.
U.S. Pat. No. 5,806,643 discloses a generally L shaped strut that is used in a one-way drive device. This one-way drive device is comprised of (1) a first member rotatable about an axis and including a first generally planar face normal to the axis, the first face including a first recess defining a first shoulder; (2) a second member rotatable about the axis and including a second generally planar face which is positioned in close proximity to and in confronting relationship with the first planar surface, the second face including a second recess defining a second shoulder; and (3) a coupling arrangement operatively extending between the first face and the second face, the coupling arrangement including a strut having a first end surface for engagement with the first shoulder and a second end surface opposite the first end surface for engagement with the second shoulder, wherein a first contact area is achieved upon engagement of the first end surface with the first shoulder and a second contact area is achieved upon engagement of the second end with the second shoulder, the first contact area being substantially larger than the second contact area.
U.S. Pat. No. 7,100,756, U.S. Pat. No. 7,223,198, U.S. Pat. No. 7,383,930, U.S. Pat. No. 7,488,481, U.S. Pat. No. 7,451,862, U.S. Pat. No. 7,455,156, and U.S. Pat. No. 7,455,157 disclose the use of rockers in ratcheting one-way clutch devices. For instance, U.S. Pat. No. 7,455,157 discloses an overrunning clutch including a cam plate formed with cams angularly spaced about a central axis, and a rocker plate that includes pockets angularly spaced about the central axis. Each pocket includes a first concave surface having a center located within the pocket and through which a pivot axis passes. In the design disclosed each pocket contains a rocker that includes a first convex surface complementary to and at least partially surrounded by the first concave surface. Springs, supported on the rocker plate, each urge a rocker to pivot about the pivot axis toward the cam plate.
The some application it is desirable to employ a two-way clutch which can optionally produces a drive connection between components when their relative rotation is in a first direction or a second direction (clockwise or counterclockwise), but which overruns when the relative rotation is in the opposite direction. In some applications, it is also desirable for such a two-way clutch to have a neutral position which does not produce a drive connection in either direction and which operates with virtually no drag while in the neutral position. Conventional two-way clutches typically employ a first/reverse clutch pack which increases the size, cost, and complexity of the clutch assembly. Additionally, such two-way clutches typically utilize hydraulic components which are too slow to be useful in many applications. For instance, hydraulic parts can take up to 0.5 seconds to act with some application demanding an activation time of 20 milliseconds or less. Another drawback associated with conventional two-way clutches is that they cause some degree of drag and the inefficiency associated therewith. In other words, conventional two-way clutches are not typically energy efficient. Conventional two-way clutches also typically lock-up in the case of clutch failure which can lead to a catastrophic condition.
There is a need for an improved two-way clutch which can operate in a neutral position with virtually no drag for high efficiency operation. It would also be highly desirable for such a two-way clutch to be capable of fitting into the envelope of conventional two-way clutches and to be capable of being engaged or disengages in short activation times of 20 milliseconds or less. Such a two-way clutch should also be highly durable, highly reliable, and provide a long trouble-free service life, but to revert to a free-wheeling state on failure to avoid catastrophic damage from occurring. It would also be highly desirable for such a two-way clutch to be of a relatively simple design which is capable of fitting into the envelope of conventional two-way clutches. As always, it would also be desirable for such a two-way clutch to be capable of being produces at a relatively low cost as compared to conventional two-way clutches.