Clutch having a variable viscosity fluid

A clutch for transferring torque, said clutch comprising:

• a cam which is rotatable about the axis and has a camming surface which surrounds the axis, there being multiple lobes along the camming surface;
• a rotor located around the axis and also being rotatable about the axis, the rotor enclosing a fluid chamber and further having piston cavities which open toward the camming surface on the cam;
• a rheological fluid in the fluid chamber, whereby viscosity of the fluid is variable;
• pistons located in the piston cavities where they are exposed to the rheological fluid in the fluid chamber, the pistons projecting from the piston cavities toward the camming surface of the cam which they contact;
• the configuration of the camming surface on the cam and the location and number of the pistons in the rotor being such that the volume of the fluid chamber remains essentially constant irrespective of the angular position of the cam relative to the rotor, whereby the rheological fluid holds the pistons against the camming surface;
• an electrical device for controlling the viscosity of the rheological fluid and thus controlling the slippage between the cam and rotor.

A process for transmitting torque between first and second members that are capable of rotation about a common axis, said process comprising:

• providing a camming surface on the first member, with the camming surface having lobes;
• providing a second member with piston cavities that open out of the second member toward the camming surface on the first member and also with a fluid chamber to which the piston cavities are exposed;
• providing pistons in the piston cavities of the second member, with the pistons extending to and contacting the camming surface on the first member;
• providing a rheological fluid that fills the fluid chamber;
• applying torque to one of the members;
• and
• controlling the viscosity of the rheological fluid to render it viscous enough that the pistons grip the camming surface of the first member sufficiently to enable torque to be transferred between the members.