Patent ID: 6740996
Filing Date: 2004-05-25
Classification: H02K

Abstract:
A motor drive comprising:a DC motor, said DC motor having a casing at one side and a worm fixedly mounted on an output shaft thereof and fastened pivotally with said casing; a speed reducing mechanism, said speed reducing mechanism comprising a main shaft fastened pivotally with said casing, and a worm gear mounted on said main shaft for free rotation relative to said main shaft and meshed with said worn, said worm gear having a plurality of radial engagement blocks equiangularly located on one side thereof; a clutch mounted inside said casing, said clutch comprising a clutch gear, said clutch gear axially movably mounted on said main shaft of said speed reducing mechanism, an annular flange protruded from an opposite side thereof, and a locating groove extended around the periphery of said annular flange, said clutch gear being axially movable along said main shaft relative to said worm gear between a first position where said clutch gear is forced into engagement with the radial engagement blocks of said worm gear for enabling synchronously rotation with said worm gear, and a second position where said clutch gear is disengaged from the radial engagement blocks of said worm gear for enabling idle running, a spring member adapted to force said clutch gear into engagement with said worm gear, a lever coupled to the locating groove of said clutch gear, and a locking plate coupled to said lever for operation by the user to drive said lever to move said clutch gear away from said worm gear for enabling said main shaft to run idle; a mechanical step counter adapted to control forward/backward rotation of said DC motor, said mechanical step counter comprising a limit switch, a first reducing gear set coupled to said main shaft for synchronous rotation and adapted to drive said limit switch to control forward rotation of said DC motor, and a second reducing gear set coupled to said main shaft for synchronous rotation and adapted to drive said limit switch to control backward rotation of said DC motor, said first reducing gear set and said second reducing gear set each having a last reducing gear, said last reducing gear having a gear shaft extending out of one sidewall of said casing, and a protruding block mounted on said gear shaft of said last reducing gear and adapted to trigger a respective contact of said limit switch; and an electronic step counter, said electronic step counter comprising a control IC, a multi-magnet member mounted on one end of said worm for synchronous rotation, and an inductor fixedly mounted in said casing and facing said multi-magnet member and adapted to detect the pulse of said DC motor and output a signal to said control IC subject to the pulse of said DC motor, enabling said control IC to calculate the time to control forward/backward rotation of said DC motor.