Variable stiffness torsional coupling and machine using same

A machine comprising:

• an engine with a drive shaft;
• a driven device with an work shaft;
• the drive shaft being torsionally coupled to the work shaft by a variable stiffness torsional coupling;
• the variable stiffness torsional coupling including a first coupler attached to rotate with the drive shaft, and a second coupler attached to rotate with the work shaft, and the second coupler being oriented to rotate with respect to the first coupler about an axis through a continuum of negative, neutral and positive torque orientations, and one of the first coupler and the second coupler including a plurality of piston and barrel combinations in contact with an other of the first coupler and the second coupler, and each of the piston and barrel combinations defining a variable volume chamber fluidly connected to a fluid transfer passage, and a piston moves with respect to a barrel of each piston and barrel combination responsive to rotation of the first coupler relative to the second coupler to change a volume of the variable volume chamber, and further including a pressure control device for controlling a pressure of a fluid in the fluid transfer passage;
• an electronic controller in control communication with the pressure control device and configured to execute a resonance avoidance algorithm to generate pressure control signals for the pressure control device;
• and
• wherein a rotational stiffness of the first coupler relative to the second coupler increases and decreases responsive to an increase and a decrease, respectively, of the pressure of the fluid.

A method of driving rotation of a work shaft, comprising the steps of:

• applying a torque from a drive shaft of an engine to the work shaft of a driven device through a variable stiffness torsional coupling;
• the applying step includes rotating a first coupler relative to a second coupler away from a neutral torque orientation;
• increasing engine speed from zero toward an operational speed during an engine start up;
• and
• reducing a torsional resonance vibration during the engine start up by reducing a rotational stiffness of the variable stiffness torsional coupling responsive to an engine speed.