Electric machine

An electric drive motor for signal processing equipment comprising a stator and a rotor together forming a cylindrical radial air gap, a stationary motor housing of generally cylindrical configuration, said motor housing being made of soft magnetic material and serving as part of the magnetic circuit of the motor, brush means located between one axial end of said motor housing and said rotor;

• a separate flux guide member of generally cylindrical configuration mounted in the interior of the motor housing between the other axial end thereof and said rotor coaxial with the rotation axis of the latter, and having a diameter slightly smaller than the diameter of the motor housing and being of a magnetically soft material;
• rpm-signal generating means located in the flux guide member part to be shielded at least from electromagnetic interference originating exteriorly of the motor housing;
• the rpm-signal generating means including a relatively thin ferromagnetic rotor disk connected to the rotor coaxially with the axis of rotation thereof and having a plurality of teeth on its circumference, a stationary ring surrounding said rotor disk and being formed with a number of permanent magnetic pole pairs of opposite pole polarity and corresponding to the number of teeth on the rotor disk, and a stationary inductive coil arranged coaxially with the axis of rotation of said rotor in proximity to the path of movement of the teeth of the rotor disk to generate rpm signals.