Electromagnetic clutch and method for manufacturing same

An electromagnetic clutch comprising:

• a driving-side rotatable member that is made of a magnetic material and is rotated about a rotational axis upon receiving a rotational force from a rotational drive source;
• a driven-side rotatable member that is rotated about the rotational axis upon receiving the rotational force from the driving-side rotatable member;
• an electromagnetic coil that is shaped into an annular form, which is centered on the rotational axis, wherein the electromagnetic coil generates an electromagnetic attractive force upon energization of the electromagnetic coil;
• a coil housing that is fixed to a non-rotatable member and is made of a magnetic material, wherein the electromagnetic coil is received in and is fixed to the coil housing;
• an armature that is made of a magnetic material, wherein the armature is attracted to and attached to a friction surface of the driving-side rotatable member in an axial direction of the rotational axis by the electromagnetic attractive force generated from the electromagnetic coil;
• an elastic connector that joins between the driven-side rotatable member and the armature and is placed to rotate integrally with the driven-side rotatable member and the armature, wherein the elastic connector holds the armature at a location, which is spaced from the friction surface of the driving-side rotatable member, when the electromagnetic coil is not energized;
• and
• a thermal fuse that is fixed to the coil housing and is placed to receive frictional heat, which is generated by friction between the armature and the friction surface of the driving-side rotatable member, wherein the thermal fuse is melted and is opened to cut supply of an electric power to the electromagnetic coil when a temperature is equal to or higher than a predetermined temperature, and wherein the thermal fuse is placed on an inner side of an innermost part of the electromagnetic coil in a radial direction of the rotational axis, wherein
• the coil housing has an inner ring, which is shaped into an annular form and is placed on an inner side of the electromagnetic coil in the radial direction of the rotational axis,
• the inner ring has a cutout, which opens on an armature side in the axial direction,
• the thermal fuse is placed in the cutout in the radial direction,
• the cutout extends through the inner ring in the radial direction,
• the inner ring includes a cutout inner wall surface, which forms the cutout, and
• the cutout is placed between two circumferentially opposed surface sections of the cutout inner wall surface in a circumferential direction of the inner ring, while the two circumferentially opposed surface sections of the cutout inner wall surface radially inwardly extend from an outer peripheral surface of the inner ring and are opposed to each other in the circumferential direction.

An electromagnetic clutch comprising:

• a driving-side rotatable member that is made of a magnetic material and is rotated about a rotational axis upon receiving a rotational force from a rotational drive source;
• a driven-side rotatable member that is rotated about the rotational axis upon receiving the rotational force from the driving-side rotatable member;
• an electromagnetic coil that is shaped into an annular form, which is centered on the rotational axis, wherein the electromagnetic coil generates an electromagnetic attractive force upon energization of the electromagnetic coil;
• a coil housing that is fixed to a non-rotatable member and is made of a magnetic material, wherein the electromagnetic coil is received in and is fixed to the coil housing;
• an armature that is made of a magnetic material, wherein the armature is attracted to and attached to a friction surface of the driving-side rotatable member in an axial direction of the rotational axis by the electromagnetic attractive force generated from the electromagnetic coil;
• an elastic connector that joins between the driven-side rotatable member and the armature and is placed to rotate integrally with the driven-side rotatable member and the armature, wherein the elastic connector holds the armature at a location, which is spaced from the friction surface of the driving-side rotatable member, when the electromagnetic coil is not energized;
• and
• a thermal fuse that is fixed to the coil housing and is placed to receive frictional heat, which is generated by friction between the armature and the friction surface of the driving-side rotatable member, wherein the thermal fuse is melted and is opened to cut supply of an electric power to the electromagnetic coil when a temperature is equal to or higher than a predetermined temperature, and wherein the thermal fuse is placed on an inner side of an innermost part of the electromagnetic coil in a radial direction of the rotational axis, wherein
• the coil housing has an inner ring, which is shaped into an annular form and is placed on an inner side of the electromagnetic coil in the radial direction of the rotational axis,
• a cutout, which opens toward an armature side in the axial direction, is formed in the inner ring, and the inner ring has a closing portion, which closes the cutout on an inner side of the cutout in the radial direction,
• the thermal fuse is placed in the cutout on an outer side of the closing portion in the radial direction,
• the inner ring includes a cutout inner wall surface, which forms the cutout, and
• the cutout is placed between two circumferentially opposed surface sections of the cutout inner wall surface in a circumferential direction of the inner ring, while the two circumferentially opposed surface sections of the cutout inner wall surface radially inwardly extend from an outer peripheral surface of the inner ring and are opposed to each other in the circumferential direction.