Clean pump

DETAILED DESCRIPTION A principal object of the present invention is therefore to provide a clean pump allowing a current consumed by a controllable bearing to be reduced, a radial rigidity to be increased and a necessary driving force to be obtained.
In short, the present invention relates to a clean pump provided with a ring-shaped rotary impeller disposed in a case member, and a rotor provided at one side of the impeller, with the case member provided therebetween.
The rotor and the impeller are radially supported by a passive radial magnetic bearing.
Provided at the other side of the impeller is an active magnetic bearing formed of a combined electromagnet including a permanent magnet and an electromagnet, the active magnetic bearing being zero-power-controlled by a control circuit.
According to the present invention, therefore, zero-power-control of the combined electromagnet achieves a necessary driving force, increases a radial rigidity and reduces power consumption.
According to a preferred embodiment of the present invention, a permanent magnet is provided at a part of a yoke where a combined magnet is formed with a first coil wound for increasing a magnetomotive force of the combined magnet including a magnetomotive force of the permanent magnet and a second coil wound for reducing the magnetomotive force.
According to another preferred embodiment of the present invention, a plurality of position sensors are provided between a plurality of combined electromagnets and sensor outputs are applied as first feedback signals to a control circuit.
The control circuit includes a comparing circuit for comparing an externally applied position setting signal and the first feedback signals and second feedback signals, a PID control circuit for controlling a phase and a gain of an output signal of the comparing circuit, an integration circuit for integrating an output signal of the PID control circuit and applies the integrated output signal as a second feedback signal to the comparing circuit, a first amplifying circuit for amplifying only a positive signal component extracted from the output signal of the PID control circuit to drive a first coil, and a second amplifying circuit for amplifying only a negative signal component from the output signal of the PID control circuit to drive a second coil