Printed coil unit for small size actuator

A flat brushless motor of a small size comprising a printed coil unit composed of a lamination of a plurality of disc-shaped printed coil sheets each having a plurality of spiral conductor patterns, said lamination constituting a stator;

• a magnetic yoke member for supporting said printed coil unit disposed thereon;
• a disc-shaped magnet disposed in opposition to said coil unit with a small cap between said magnet and said conductor pattern, said magnet being uniformly magnetized with alternating poles in the circumferential direction and serving as a rotor;
• and a rotatable supporting shaft for supporting said magnet and said yoke member at respective centers,
• wherein said magnet has n paired magnetic poles arrayed in the circumferential direction and has an inner diameter r.sub.1 and an outer diameter r.sub.2, each of said printed coil sheets being provided with a row of 2n spiral conductor patterns disposed circumferentially, at least one of said printed coil sheets having opposed planar disc surfaces and a magnetic sensor element disposed in said printed coil sheet with a magneto-sensitive portion of said sensor element located in opposition to said magnet at a position within a region lying outside of said spiral conductor patterns at a distance R given by the range r.sub.1 .ltoreq.R.ltoreq.r.sub.2 .times.1.1 from the center of said magnet, said magnetic sensor element being enclosed within a notch formed in said one printed coil sheet, said sensor element being confined between the planes determined by the opposed surfaces of said one printed coil sheet.