Apparatus and method for controlling the engagement of a gap-type electromagnetic coupling and for alleviating engagement noise

An electromagnetic coupling apparatus responsive to a stimulating signal, said apparatus comprising:

• a multiple-turn winding;
• first and second members normally separated by an air gap and rotatable relative to one another, said members being movable into engagement by closure of said gap;
• holding means for holding said members separated by said gap and disengaged when said winding is de-energized;
• magnetically permeable flux path means for producing, when the winding is excited, magnetic flux threading through said members and said gap to attract said members into torque-transmitting engagement;
• said first member having a disk-shaped portion composed of magnetic material for engaging with said second member, said disk-shaped portion including non-magnetic areas circumferentially and asymmetrically spaced in said disk-shaped portion;
• first means responsive to said stimulating signal for exciting said winding to create an average m.m.f. in said flux path means sufficient to attract said members into engagement by relative motion which closes said gap;
• second means for sensing the closure of said gap between said first and second members;
• third means responsive to said second means for reducing the m.m.f. in said flux path means to a level at which said members are retained in touching engagement but with a sufficiently low force that such members may rotatively slip without transmitting from one to the other the full torque for which the coupling is rated;
• and
• fourth means after said third means have acted for gradually increasing the average m.m.f. in said flux path upwardly from its reduced value to a predetermined value which causes said members to be magnetically attracted so as to produce rated torque transmission without relative slippage.

An armature for engaging a rotor in an electromagnetic clutch comprising:

• a magnetic disk for rotation about an axis perpendicular to the plane of said planar face;
• a series of non-magnetic areas in said disk of said armature forming a flux gap in said disk;
• and
• means for reducing the audible noise resulting from the vibration of said armature upon engagement with said rotor including segments and bridge areas defined by said non-magnetic areas wherein neither all of said segments or all of said bridge areas have the same resonant frequency.

An apparatus for energizing the multiple-turn winding of an electromagnetic coupling having an armature and a rotor separated by an air gap, said apparatus comprising:

• a current control means for controlling the average current energizing said winding;
• a first means responsive to an actuation signal for controlling said current control means to allow unrestricted current energization of said winding;
• a second means for sensing the closure or said air gap between said armature and said rotor;
• a third means responsive to said second means for controlling said current control means so as to reduce the average current energization said winding;
• and
• a fourth means responsive to said second means for controlling said current control means so as to gradually increase the average current energizing said winding from the reduced average current set by said third means to full current.

A method for energizing a multiple-turn winding of an electromagnetic clutch or brake, wherein the armature and rotor of the clutch or brake are separated by an air gap, said method comprising the steps of:

• energizing said winding so as to cause said armature to move across said gap and into contact with said rotor;
• sensing the armature closing into contact with the rotor;
• reducing the energization of said winding in response to the closure of said gap between said armature and rotor so as to decrease the torque coupling and increase the slippage between said armature and said rotor;
• and
• gradually increasing the energization of said winding to full energization, full torque coupling and no-slip contact between said armature and said rotor.

An apparatus for controlling the energization of the multiple-turn winding of an electromagnetic coupling having first and second engaging members separated by a air gap, said apparatus comprising:

• energization means for energizing said winding;
• first means for sensing the closure of the air gap between said first and second members in response to the energization of said winding;
• and
• second means responsive to the detection of gap closure by said first means for adjusting the energization of said winding by said energization means.

A control unit to a stimulating signal for causing an electromagnetic coupling to engage, said coupling having:

• first and second members normally separated by an air gap and rotatable relative to one another, said members being movable into engagement by closure of the gap,
• spring means for normally holding said members separated by said gap and disengaged, and
• a multiple-turn winding and magnetically permeable flux path means for producing, when the winding is excited, magnetic flux threading through said members and gap to attract said members into torque-transmitting engagement,
• said control circuit comprising, in combination:
• (1) means responsive to said stimulating signal for exciting said winding to create an average m.m.f. in said flux path means sufficient to attract said members into engagement by relative motion which closes said gap,
• (2) means for sensing the closure of said gap between said first and second members,
• (3) means responsive to said means (2) for reducing the average m.m.f. in said flux path means to a level at which said members are retained in touching engagement but with a sufficiently low force that such members may rotatively slip without transmitting from one to the other the full torque for which the coupling is rated, and
• (4) means operative after said means (3) have acted for gradually increasing the average m.m.f. in said flux path upwardly from its reduced value to a predetermined value which causes said members to be magnetically attracted so as to produce rated torque transmission without relative slippage.