Brushless motor
AssigneeHitachi, Ltd.
InventorsTadashi Takahashi, Kazuo Onishi
Life of this patent
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Abstract
A brushless motor with a permanent magnet as a rotor is disclosed in which the rotational position of the rotor is detected by Hall elements thereby to control a transistor, which in turn is used to control the current flowing in the stator winding.
Claims14
A brushless motor comprising a rotor with a permanent magnet, a stator with stator windings disposed around the rotor at spaced intervals, a plurality of first control means each associated with respective ones of said stator windings for producing an output in accordance with the rotational position of the rotor, and an electric control circuit for controlling a current flowing through each of the stator windings in accordance with the output of said first control means, wherein said electric control circuit comprises a plurality of transistors connected in series with respective stator windings, the control terminals of said transistors being connected with the output of respective ones of said first control means, voltage comparator means for comparing a reference voltage and the voltage induced in each of said stator windings in accordance with the rotation of said rotor, second control means for controlling said first control means in response to the output of said voltage comparator means, and bypass circuit means connected in parallel with each of said stator windings for allowing a current due to a voltage induced in each of the stator windings to flow back to the stator windings, said bypass circuit comprising a constant voltage element to eliminate a voltage level higher than the level of said voltage induced in accordance with the rotation of the rotor.
A brushless motor comprising a totor having a permanent magnet, a stator including a plurality of cores disposed about said rotor at spaced intervals and a stator winding disposed on each core, a plurality of transistors each connected in series with one of said stator windings and each having a control terminal, a plurality of control means each associated with a respective one of said stator windings for applying to the control terminal of the transistor connected to the associated stator winding an output in accordance with the rotational position of said rotor, and bypass circuit means connected in parallel with each stator winding for short-circuiting said stator winding in response to induction in said stator winding of a voltage above a predetermined level.
Dependencies are inferred from the claim text.