COMMUTATORLESS DIRECT CURRENT MOTOR

• US 3,839,661 A
• Filed: 02/23/1973
• Issued: 10/01/1974
• Est. Priority Date: 02/26/1972
• Status: Expired due to Term

• Current Assignee: Kinzo Wada
• Original Assignee: Kinzo Wada
• Inventors: Wada, Kinzo
• Primary Examiner(s): Rubinson, G. Z.
• Application Number:
  US05/335,159
• Time in Patent Office: 585 Days
• Field of Search: 318/138,171,254
• US Class Current: 318/400.11
• CPC Class Codes: H02K 29/08 using magnetic effect devices, e.g. Hall-plates, magneto-resistors H02K29/12 takes precedence

Abstract

A commutatorless direct current (DC) motor comprises, essentially, a rotor comprising a permanent magnet magnetized to have a sinusoidal distribution of magnetic flux density in the circumferential direction about the rotor axis and a circuit operating in accordance with voltages led out from voltage terminals of Hall elements provided to confront the rotor to cause currents of half sinusoidal waveform to flow through stator coils. This circuit is adapted further to pass currents of rectangular waveform through the stator coils at the time of starting of the rotor and to pass sinusoidal-waveform currents therethrough at the time of high-speed rotation of the rotor.

Claims

1. A commutatorless direct current motor using Hall elements, said motor comprising:

rotor means magnetized in a manner such that the resulting distribution of the strength of magnetic flux density along the circumferential direction about the rotor axis is of sinusoidal waveform;

a stator having stator coils;

a plurality of Hall elements disposed in positions to confront said rotor;

amplifier means coupled to each one of said Hall elements and operatively responsive to the voltages derived from the voltage terminals thereof for causing passage of current through the stator windings to form a rotating magnetic field, each of said amplifier means having a negative feedback circuit;

generator means for generating a control voltage proportional to the rotational speed of said motor; and

switching means responsive to the level of said control voltage when below a predetermined level for disconnecting said negative feedback circuit from said amplifier means and responsive to the level of said control voltage when above said predetermined level for connecting said negative feedback circuit to said amplifier means, whereby said amplifier means with an increased degree of amplification causes passage of a starting current of rectangular waveform through said stator coils during commencement of rotation of said rotor and said amplifier means with a decreased degree of amplification causes passage of a driving current of sinusoidal half-waveform through said stator coils when the rotation of said rotor reaches a predetermined speed.

2. A commutatorless direct current motor as defined in claim 1 wherein said switching means comprises a plurality of first transistors, each of which is connected to the corresponding negative feedback circuit, and a second transistor connected between said first transistors and ground, said control voltage being applied to the base electrode of said second transistor, said second transistor being rendered into a cutoff state in response to the level of said control voltage which is below said predetermined level to disconnect said first transistors from ground so that said first transistors become inoperative, and being rendered into a conductive state in response to the level of said control voltage which is above said predetermined level to connect said first transistors to ground so that said first transistors become operative.

3. A commutatorless direct current motor as defined in claim 1 wherein said amplifier means includes an input circuit formed in a differential amplifier having two first transistors, the base electrodes of which are respectively connected to the voltage terminals of a respective one of said Hall elements, the emitter electrodes of which are connected with each other, and a series circuit of a first resistor, a second transistor and a second resistor being connected across a power source, the base electrodes of said two first transistors being connected to the base electrode of said second transistor through a third resistor and a fourth resistor respectively, the emitter electrodes of said two first transistors being connected to the emitter electrode of said second transistor through a fifth resistor.

4. A commutatorless direct current motor as defined in claim 3 wherein said third resistor and said fourth resistor have the same resistance value.