Motor/encoder assembly for tape drives
A magnetic/encoder assembly has a compact design and combines the features of motor, encoder and chuck locating feature within a single motor housing. The motor/encoder includes a DC brushless motor with an inner magnetic rotor. The motor windings and the commutation electronics are mounted towards the bottom side of a printed circuit board. The rotor of the motor is extended above the surface of the printed circuit board. The extended rotor provides a precision seat for the magnetic wheel with multiple poles. The top surface of the printed circuit board mounts the sensor for the encoder. The extension of the rotor provides the precision mounting surface of the cartridge driving chuck.
1. A motor/encoder assembly for a tape drive comprising:
a motor housing;
a DC motor mounted in the housing, the DC motor having a rotor, a field magnet attached to the rotor, and laminations and windings;
a code wheel mounted on the rotor within the motor housing;
a code wheel sensor fixedly mounted within the motor housing;
a chuck mounting element on the rotor; and
a printed circuit board mounted in the motor housing, the rotor extending axially through the printed circuit board, wherein the field magnet, the motor laminations and the windings are positioned in the motor housing axially below the printed circuit board; the code wheel is positioned on the rotor axially above the printed circuit board, and the code wheel sensor is mounted on a top surface of the printed circuit board.
2. The assembly of claim 1 , wherein the code wheel is a magnetic code wheel comprising a magnet-ring holder attached to the rotor, and a magnet-ring mounted to a surface of the magnet-ring holder.
3. The assembly of claim 2 , wherein the magnet-ring is axially magnetized and has alternating north and south poles around the circumference of the magnet-ring.
4. The assembly of claim 1 , wherein the code wheel is an optical code wheel, and the code wheel sensor includes a U-shaped module with a light source and a sensor portion, positioned on the printed circuit board such that the optical code wheel passes between the light source and the sensor portion.