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This paper describes a new two-way, over-running mechanical clutch and electronic control for four wheel drive systems. This package is called the “Lock On Demand” (LOD) system. The LOD system is composed of a two-way over-running roller clutch, an electronic controller, and sensors. The controller actuates the roller clutch mechanism, putting the vehicle in 2WD or 4WD based on the information from sensors which measure speed, throttle position, brake activity, etc. The two way roller clutch is composed of a cammed inner race, a cylindrical outer race, rollers and retainer. An electro-magnetic coil is used as the activating trigger for the mechanical clutch. In this paper, the LOD system is introduced, and details are given for the operation of the roller clutch and controller. In addition, the results from a finite element analysis (FEA) are included.

A one-way pulley for automotive accessory drive belt applications has been developed which incorporates a wrap-spring overrunning clutch in a compact package with high torque capacity. Belt “chirp” during large speed changes and flap at resonance are eliminated and belt life is improved by decoupling torque transmission in one direction. The equations and relationships between maximum torque capacity and slip of the wrap spring clutch are detailed. Test results at different operating conditions describe the performance of the pulley for automotive alternator applications. This over-running pulley design offers a cost effective direct replacement for standard alternator pulleys.