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This paper discusses a new development in one way clutches (OWC), ratcheting OWC in torque converters (TC). While this has been tried before, and been successful in niche applications, it has not been introduced into mass production. Ford Motor Company has worked to develop a ratcheting OWC for use in TC. The efficiency of ratcheting OWC is better than friction type OWC. Ford Motor Company is working to implement ratcheting OWC into their torque converters, replacing friction type OWC.

This paper discusses new developments in the field of one-way clutches (OWC). These recent developments involve “Selectable OWC (SOWC)” actuating both hydraulically as well as electrically. The primary focus of this paper is a low-current consuming Electrical SOWC (eSOWC) used in hybrid transmission being designed and developed at Ford Motor Company. Other SOWCs currently being utilized across different applications at Ford are also discussed. Clutching devices represent significant cost, weight, size and drag-loss in automatic transmissions. However, implementation of SOWCs offers the potential to reduce transmission cost, size, weight, and spin loss; eSOWCs may also improve shift quality, reduce shift times, improve shift consistency and reduce OWC-related NVH. In Hybrid applications the electric motor(s) and SOWC create a system that is analogous to a manual transmission synchronizer.

This paper reviews ratcheting one way clutches (OWC). OWC represent a significant cost in a transmission. Optimizing the OWC type helps reduce cost and increase fuel efficiency, and is therefore worth studying. Although the ratcheting OWC design is the primary focus of this paper, some background on roller and sprag type OWC is given. The strengths and weaknesses of ratcheting OWC are discussed. Potential OWC failure modes are reviewed to help engineers perform a thorough design analysis. Formulae and other details useful for the design are also reviewed.