Structural Dynamics of a Dual Clutch Offset Compound Gear Transmission with Electro-Magnetically Actuated Engagement

This paper describes a structural dynamic analysis of a dual clutch Offset Compound Gear (OCG) transmission for application in a two-speed rotorcraft transmission with Electro-Magnetically Actuated (EMA) clutch engagement. This model includes the nonlinear axial contact dynamics between clutch plates. The applied electro-magnetic engagement force is proportional to the magnetic flux traveling axially through the clutch pack. Since the magnetic reluctance is inversely related to the dynamic air gaps between clutch plates, the engagement force rapidly increases as the plates come into contact. Due to the momentum and inertia of the clutch plates, the impacting plates generate an impulsive axial spike in clutch pressures. Since the friction torque transmitted by the clutch is proportional to the instantaneous clutch pressure, the axial plate contact dynamics can be a significant source of shock torque loads delivered to the driveline during shifting. The simulation results capture this phenomena and demonstrate the magnitude of the effect. To the authors’ knowledge, axial clutch plate contact dynamics have not been previously considered or accounted for in the literature on clutch dynamics.