Victor Company of Japan, Limited

Ken Enami

Kinzo Wada

Toyotaka Machida

Yukimi Hirose

Eiichi Kotake

A rotation control apparatus for a motor comprises a motor for rotating or moving a recording medium, a circuit for generating first and second reference signals, a circuit for passing a signal which is obtained by comparing phases of the first reference signal and a synchronizing signal through a filter circuit thereof so as to produce a first error signal therefrom, a circuit for producing a second error signal which is obtained by comparing phases of the second reference signal and the rotation detection signal, and a control circuit for controlling first and second switching circuits. The control circuit supplies a specific signal having a level dependent on the level of the second error signal to a capacitor of the filter circuit through the second switching circuit and selectively passes the second error signal through the first switching circuit when the motor rotates at a rotational speed which is not near a steady state rotational speed. The control circuit blocks the supply of the specific signal to the capacitor by the first switching circuit and selectively passes the first error signal through the first switching circuit when the motor rotates at a rotational speed which is approximately equal to the steady state rotational speed.

Rotation control apparatus for a motor

A synchronism discriminating circuit comprises a phase comparator supplied with a reference signal having a reference frequency and a reference phase and with an input signal of which a synchronism with respect to the reference signal is to be discriminated, for comparing the phase of the reference signal with the phase of the input signal and for producing an output signal responsive to a phase difference between the two signals, where the reference signal is made up of a series of pulses, and a discriminating circuit supplied with the reference signal and with the output signal of the phase comparator, for counting the pulses in the reference signal during a period in which the phase difference is within a predetermined range and for producing a synchronism discrimation signal when a predetermined number or more pulses in the reference signal are continuously counted.

Synchronism discriminating circuit

A rotation control device causes a disc on which information and sync signals are recorded to rotate at a predetermined speed. The control device includes a generator for generating a signal whose frequency is identical with that of a rotation signal which will be output from a frequency generator while the disc rotates at the predetermined speed. A control loop is defined which compares a phase of an output of the signal generator and a rotation signal output from the frequency generator, thereby controlling the drive of the motor.

Rotation control device for information recording disc

A protective circuit for an electric motor comprises a frequency signal generating circuit for generating a frequency signal in accordance with the rotational speed of the motor, a switching circuit switched over to either permit or cut off supply of current to the motor, and a detecting circuit for detecting that the period of the generated frequency signal has become larger than a predetermined period due to a decrease in the rotational speed of the motor, and cutting off the supply of current to the motor by the switching circuit.

Protective circuit for an electric motor

A commutatorless electrical motor comprises a cylindrical magnetic rotor having main magnetic poles where N and S poles are alternately arranged in the circumferential direction, and an axis of N and S poles of each magnet extends radially, and a sub magnetic poles at one end of the cylindrical rotor. The sub magnetic poles are arranged such that N and S poles of each magnetized area extends axially. The magnetized area providing each sub magnetic pole has an arcuate extent of .pi./2 or less in an electrical angle. Each of the magnetized area providing each sub magnetic pole makes a given change in the magnetic flux density distribution in the vicinity of rotational position detecting elements so that the rotational position of the rotor can be accurately detected. As a result, current switching circuit for changing over armature currents will be controlled by the accurate information from the detecting elements, and thus each armature winding will be energized in a desirable manner, reducing undesirable torque ripple.

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Fujieda, Japan

Ken Enami