Direct current dynamo electric machine

A direct current dynamo electric machine comprising:

• (a) a non-magnetic cylindrical rotor comprising (i) a rotor shaft, (ii) a small diameter sleeve-like insulating cylinder secured to the rotor shaft, (iii) a winding structure with a high-density winding disposed around the outer periphery of the insulating cylinder to occupy a substantial portion of the volume of the rotor between the outer periphery of the insulating cylinder and the outer diameter of the rotor, and (iv) means for disposing of and shaping a large number of coil ends of the winding;
• and
• (b) a stator for rotatably supporting the rotor and comprising (i) a yoke, (ii) a pair of main magnets disposed in opposing relation to each other in the yoke, the main magnets being rectangular in cross-section and larger in width than the outer diameter of the rotor in a direction perpendicular to a magnetic field established by the main magnets, (iii) thin trapezoidal pole shoes mounted on the opposing surfaces of the main magnets along substantial portions of the entire areas of the surfaces thereof and wherein each pole shoe has a rotor-opposing surface corresponding to the diameter of the rotor and the pair of pole shoes define therebetween a large working air gap to form a double-pole magnetic field corresponding to the outside portion of the rotor, and (iv) a pair of blocking permanent magnets disposed in opposing relation to each other on opposite sides of the rotor between the main magnets with air gaps formed at both ends of each blocking permanent magnet, for equalizing leakage magnetic fields occurring on both sides of the rotor between those surface portions of the main magnets and the pole shoes not facing the rotor with a reverse magnetic field of the blocking permanent magnets, thereby to converge magnetic fluxes on the rotor.