A direct current motor used, for example, in a machine tool, comprising an armature (1), a plurality of main magnetic poles disposed around the armature having field windings (2) wound thereon, and a plurality of E-shaped interpoles (8) disposed at the intermediate position along the outer circumference of said armature between the adjacent main magnetic poles, each of the E-shaped interpoles consisting of a center pole (81) to which an interpole winding (10) is wound and two side poles (82, 83), and the width of the gap between the outer circumference of the armature and the end surface of each of the side poles increases from the portion of the gap which is remote from the center pole to the portion of the gap which is adjacent to the center poles.
In the DC motor according to the present invention, the linearity of the magnetic flux used for commutation is ensured in a wide range of the armature current, and, therefore, commutating characteristics of the E-shaped interpoles is improved.