Planar commutator, rotor and direct current electric motor

A planar commutator for a direct current electric motor, comprising:

• a plurality of segment pieces that are generally planar and are arranged one after another in a circumferential direction about a rotational axis of the planar commutator, wherein a slidably engaging surface of each segment piece, which is slidably engageable with a plurality of brushes of the direct current electric motor, extends in a plane that is generally perpendicular to the rotational axis, and each segment piece includes a radially inner engaging portion at a radially inner end part of the segment piece;
• and
• a plurality of conductive lines, each of which extends along a corresponding straight line and electrically interconnects between the radially inner engaging portions of corresponding two of the plurality of segment pieces to implement the same electric potential in the corresponding two of the plurality of segment pieces, wherein the plurality of conductive lines is held under tension and defines a generally circular space at a location radially inward of the plurality of conductive lines, and the generally circular space is adapted to receive a rotatable shaft therethrough while leaving an empty radial gap between the rotatable shaft and the plurality of conductive lines all around the rotatable shaft.