Patent ID: 8459429

Claim:
A power transmission device for a water pump, comprising: a pulley ( 100 or 200 ) being rotated by a torque applied from an engine and having a magnetic flux generating means-mounting portion ( 108 ) formed on one side surface thereof and a disk assembly-mounting portion ( 102 or 202 ) formed on the opposite side surface thereof; a magnetic flux generating means ( 120 or 220 ) mounted on the magnetic flux generating means-mounting portion ( 108 ) of the pulley ( 100 or 200 ) to generate an attracting magnetic flux therefrom; a disk assembly ( 140 or 240 ) mounted on the disk assembly-mounting portion ( 102 or 202 ) of the pulley ( 100 or 200 ) and adapted to have frictional contact with a hub assembly ( 160 or 260 ); and the hub assembly ( 160 or 260 ) having a drive shaft mounted thereon and a frictional contact surface ( 170 or 262 ) adapted to have the frictional contact with the disk assembly ( 140 or 240 ), the drive shaft being rotated through the frictional contact with the disk assembly ( 140 or 240 ), wherein the disk assembly ( 140 or 240 ) comprises: a disk ( 146 or 246 ) made of a magnetizable material; a friction ring ( 142 or 242 ) frictionally contacting with the frictional contact surface ( 170 or 262 ) of the hub assembly ( 160 or 260 ); and a resilient ring ( 144 or 244 ) interposed between the disk ( 146 or 246 ) and the friction ring ( 142 or 242 ) in such a manner as to be fixed to the disk assembly-mounting portion ( 102 or 202 ) of the pulley ( 100 or 200 ) and adapted to resiliently pressurize the friction ring ( 142 or 242 ) toward the hub assembly ( 160 or 260 ), whereby when the attracting magnetic flux of the magnetic flux generating means ( 120 or 220 ) is not applied, the friction ring ( 142 or 242 ) makes frictional contact with the hub assembly ( 160 or 260 ) through the resilient pressurization of the resilient ring ( 144 or 244 ), whereas, when the attracting magnetic flux is applied, the disk ( 146 or 246 ) moves toward the pulley ( 100 or 200 ) to allow the frictional contact between the friction ring ( 142 or 242 ) and the hub assembly ( 160 or 260 ) to be released.