Small-size motor

A small-size motor of a type comprising an upper motor case and a lower motor case which closes an opening of the upper case, said upper motor case comprising a cylinder shaped case having a top covering at one end and an opening at the other end in which a bearing for supporting a shaft is provided at the center of the top covering in a thrust direction, said lower motor case being attached to the opening of the upper motor case to close said opening, said upper and lower motor cases housing brushes and a commutator slidably engaged with the brushes, characterized in that the motor case interior defined by the upper and lower motor case is filled with an atmosphere containing vapor of at least one organic compound selected from the group consisting of paraffins, mono- or poly-hydric alcohols, ethers, cyclic ethers, esters, ketones, ether alcohols, ester alcohols, aminoalcohols, carboxylic acids, amides, primary, secondary and tertiary amines, imidazoles, imidazolines and monocyclic oxyterpenes.