Electromagnetic coupling apparatus

An electromagnetic coupling apparatus comprising:

• an armature hub fixed to a rotating shaft of a device, said armature hub having a flange unit;
• a leaf spring having a proximal end portion fixed to said flange unit of said armature hub;
• a stopper plate coupled to said flange unit of said armature hub together with said leaf spring, said stopper plate having a plurality of flange portions each extending in a radial direction and formed with a through hole;
• an armature to which a free end portion of said leaf spring is fixed and which is biased in a decoupling direction;
• a rubber stopper disposed between said flange unit of said stopper plate and said armature;
• a fixing member fixed to said armature, said fixing member having a trunk portion extending through a through hole formed in each of said flange portions of said stopper plate and a head portion projecting from each of said flange portions of said stopper plate to a side opposite said armature and formed with an annular projecting ridge portion on a peripheral portion thereof;
• a rubber vibration insulator disposed between a side surface of said flange unit of said armature hub and said head portion of said fixing member, said rubber vibration insulator being constituted by a cylindrical portion which is sandwiched between said side surface of each of said flange portions of said stopper plate and said head portion of said fixing member and which has an outer circumferential surface fitted with said projecting ridge portion of said fixing member, and a disk portion formed in said cylindrical portion to be integral therewith and having a through hole to fit on said trunk portion of said fixing member;
• a rotor opposing said armature through a first gap of a predetermined size;
• an electromagnetic coil for generating a magnetic flux in order to cause said rotor to magnetically attract said armature against a biasing force of said leaf spring;
• and
• a field core fixed to said unit to accommodate said electromagnetic coil,
• wherein a second gap larger than the first gap is formed between a distal end of said projecting ridge portion of said fixing member and said flange portion of said stopper plate, and a third gap is formed between one side surface of said disk portion of said rubber vibration insulator and said side surface of each of said flange portions of said stopper plate.