Magnetorheological fluid devices and process of controlling force in exercise equipment utilizing same

A magnetorheological fluid device, comprising:

• (a) a shaft for attaching to a first member;
• (b) a rotor having a first rotor surface and a second rotor surface which are outwardly facing and generally radially extending, said rotor having an outer radius Ro defining an outer periphery, said rotor connected to said shaft such that relative rotation is restrained;
• (c) a housing for attaching to a second member, said housing including a hollowed out cavity formed therein defined partially by a flux member which provides a magnetic flux path, said flux member including an inner radius Ri forming an innermost periphery and having a recess formed therein including a first inner surface and second inner surface which face each other, said recess receiving a portion of said rotor and forming a first gap between said first inner surface and said first rotor surface, and a second gap between said second inner surface and said second rotor surface;
• (d) a magnetorheological fluid comprised of ferromagnetic particles disbursed in a viscous fluid contained within and at least partially filling said cavity and substantially filling said first and second gaps;
• (e) a coil adjacent said first and second gaps for creating a standing magnetic field in said magnetic flux path which causes said magnetorheological fluid to change rheology and cause a change in a restraining force exerted upon said rotor;
• and
• (f) spring means for center biasing said rotor relative to said housing such that said first and said second gaps maintain a constant thickness due to said center biasing.

A magnetorheological fluid device, comprising:

• (a) a shaft for attaching to a first member;
• (b) a rotor having a first rotor surface and a second rotor surface which are outwardly facing and generally radially extending, said rotor having an outer radius Ro defining an outer periphery, said rotor member connected to said shaft member such that relative rotation is restrained;
• (c) a housing for attaching to a second member, said housing including a hollowed out cavity formed therein defined partially by a flux member which provides a magnetic flux path, said flux member including an inner radius Ri forming an innermost periphery and having a recess formed therein including a first inner surface and second inner surface which face each other, said recess receiving a portion of said rotor and forming a first gap between said first inner surface and said first rotor surface, and a second gap between said second inner surface and said second rotor surface, said inner radius Ri of said flux member and said outer radius Ro of said rotor sized in the ratio of Ri/Ro such that Ri/Ro ratio is between 0.70 and 0.99 such that a minimum amount of steel is required;
• (d) a magnetorheological fluid comprised of ferromagnetic particles disbursed in a viscous fluid contained within and at least partially filling said cavity and substantially filling said first and second gaps;
• (e) a coil adjacent said first and second gaps for creating a standing magnetic field in said magnetic flux path which causes said magnetorheological fluid to change rheology and cause a change in restraining force exerted upon said rotor;
• and
• (f) spring means for center biasing said rotor relative to said housing such that said first and said second gaps maintain a constant thickness due to said center biasing.

A process of controlling a force between a first member and second member which are relatively moveable and are included within a piece of exercise equipment, comprising the steps of:

• (I) attaching between said first member and said second member of said piece of exercise equipment a rotary acting magnetorheological fluid device having a shaft for connection to said first member, a housing for attachment to said second member, said housing including a flux member providing a magnetic flux path, said flux member further including an inner radius Ri, a rotor having an outer radius Ro rotatably secured to said shaft, said rotor being received within a recess formed in said flux member and forming a working section located between said inner radius Ri and outer radius Ro, a magnetorheological fluid containing ferromagnetic particles disbursed within a viscous fluid contained within said working section, a coil adjacent to said working section for generating a magnetic field therein upon electrical energization of said coil thereby causing a change in rheology of said magnetorheological fluid wherein a ratio of Ri/Ro is between 0.7 and 0.99, and
• (II) controlling a force exerted by said magnetorheological fluid device between said first member and said second member in accordance with a magnetic field applied to said magnetorheological fluid by electrical energization of said coil which causes a rheology change of said magnetorheological fluid.

A process of controlling a force between two relatively moving first and second members included within a piece of exercise equipment, comprising the steps of:

• (I) attaching a rotary-acting magnetorheological fluid device containing a magnetorheological fluid between said first member and said second member, and
• (II) controlling a force exerted by said rotary-acting magnetorheological fluid device between said moving members in accordance with a magnetic field applied to said magnetorheological fluid, wherein said rotary-acting magnetorheological fluid device further comprises:
• (a) a shaft for attaching to a first member;
• (b) a rotor having a first rotor surface and a second rotor surface which are outwardly facing and generally radially extending, said rotor having an outer radius Ro defining an outer periphery, said rotor connected to said shaft such that relative rotation is restrained;
• (c) a housing for attaching to a second member, said housing including a hollowed out cavity formed therein defined partially by a flux member which provides a magnetic flux path, said flux member including an inner radius Ri forming an innermost periphery and having a recess formed therein including a first inner surface and second inner surface which face each other, said recess receiving a portion of said rotor and forming a first gap between said first inner surface and said first rotor surface, and a second gap between said second inner surface and said second rotor surface, said inner radius Ri of said flux member and said outer radius Ro of said rotor sized in the ratio of Ri/Ro such that Ri/Ro ratio is between 0.70 and 0.99 such that a minimum amount of steel is required;
• (d) a magnetorheological fluid comprised of ferromagnetic particles disbursed in a viscous fluid contained within and at least partially filling said cavity and substantially filling said first and second gaps;
• (e) a coil adjacent said first and second gaps for creating a standing magnetic field in said magnetic flux path which causes said magnetorheological fluid to change rheology and cause a change in restraining force exerted upon said rotor;
• and
• (f) spring means for center biasing said rotor relative to said housing such that said first and said second gaps maintain a constant thickness due to said center biasing.

A process of controlling a torque between two relatively moving first and second members included within a piece of exercise equipment, comprising the steps of:

• (I) attaching a rotary acting magnetorheological fluid device between said two relatively moving first and second members wherein said rotary acting magnetorheological fluid device is further comprised of;
• (a) a shaft for connection to said first member,
• (b) a rotor having a first rotor surface and a second rotor surface which are outwardly facing and generally radially extending, said rotor having an outer radius Ro defining an outer periphery, said rotor connected to said shaft such that relative rotation is restrained,
• (c) a housing for connection to said second member, said housing including a hollowed out cavity formed therein defined partially by a flux member which provides a magnetic flux path, said flux member including an inner radius Ri forming an innermost periphery and having a recess formed therein including a first inner surface and second inner surface which face each other, said recess receiving a portion of said rotor and forming a first gap between said first inner surface and said first rotor surface, and a second gap between said second inner surface and said second rotor surface, said inner radius Ri of said flux member and said outer radius Ro of said rotor sized in the ratio of Ri/Ro such that Ri/Ro ratio is between 0.70 and 0.99 such that a minimum amount of steel is required,
• (d) a magnetorheological fluid comprised of ferromagnetic particles disbursed in a viscous fluid contained within and at least partially filling said cavity and substantially filling said first and second gaps, and
• (e) a coil adjacent said first and second gaps for creating a standing magnetic field in said magnetic flux path which causes said magnetorheological fluid to change rheology, and
• (II) controlling a force exerted by said rotary acting magnetorheological fluid device between two relatively moving first and second members via electrically energizing said coil.

A rotary acting magnetorheological fluid apparatus included in a piece of exercise equipment, comprising:

• (a) a shaft;
• (b) a rotor which is rotatably connected to said shaft;
• (c) a flux member providing a flux path and having a recess formed therein for receiving a portion of said rotor thus forming a first gap and a second gap adjacent said rotor;
• (d) a magnetorheological fluid comprised of ferromagnetic particles disbursed in a viscous fluid contained within said first gap and said second gap;
• (e) a coil adjacent said first gap and said second gap for creating a magnetic field within said flux path which causes said magnetorheological fluid in said first gap and said second gap to change rheology and exert a force upon said rotor;
• and
• (f) a flywheel interconnected to said shaft.