Abstract: When an armature plate is attracted to a rotor so that the turning force of the rotor is transmitted to the armature plate, the turning force of the armature plate is transmitted to a main shaft via a plate spring. An angle (hereinafter referred to as a slope angle) formed between the plate spring and the armature plate is set so as to be not smaller than 10° and not larger than 63°. Therefore, since the slope angle is larger than the slope angle (about 30) of the general electromagnetic clutch, the torque increase effect increases about 5 percent as compared with the general electromagnetic clutch, and also an excessive pressing force of the plate spring does not develop.

Abstract: An electromagnetic clutch (20) capable of connecting and disconnecting a driving power source and a rotary shaft (22) includes a rotor (25) rotated by the driving power source, and an armature (40) capable of being attracted to the rotor (25) by electromagnetic force to produce a transmission force transmitted from the rotor (25) to the rotary shaft (22). The electromagnetic clutch (20) further includes leaf springs (52) urging the armature (40) in such a direction as to separate the armature from the rotor (25). The leaf springs (52) each assume an orientation such that a boost force assisting the attractive force acting upon the armature (40) is produced based on the transmission force when the armature (40) is attracted to the rotor (40).

Abstract: An electromagnetic coil is energized to couple a rotor and an armature plate to each other. Each leaf spring extends in a direction so as to intersect at an obtuse angle with the rotating direction of the armature plate, and accordingly, when the power of the driving source is transmitted to the armature plate through the rotor, a compressive force acts upon the leaf spring. The leaf spring has an inclined portion, and the armature plate is pressed against the rotor by the compressive force. Each leaf spring has a first extended portion located between the first coupling portion and inclined portion thereof and a second extended portion located between the second coupling portion and inclined portion thereof. The compressive force applied per unit area can therefore be reduced by an amount corresponding to the increase in length of the leaf spring, making it unnecessary to thicken the leaf spring.

Abstract: An electromagnetic clutch for separably coupling a drive source and a rotary shaft has a rotor to be disposed in the outside of the rotary shaft concentrically therewith. The rotor is rotated by a drive source and accommodates an electromagnetic coil. The electromagnetic clutch has an armature plate that is attracted toward the rotor by an electromagnetic force generated by the electromagnetic coil so as to adhere to the rotor. Furthermore, the electromagnetic clutch has a coupler for coupling the armature plate and the rotary shaft to each other. The coupler includes a center part to be coupled to the rotary shaft and an elastically-deformable outer part for coupling the center part to the armature plate, the outer part being extended from the center part and elastically deformed when the armature plate is attracted to the rotor.