Abstract: A rotation detecting device for a brushless motor having: a stator core on which a coil is wound; a driving magnetic pole portion which opposes the stator core, which comprises a plurality of magnetic poles, and which is rotated; an FG magnetized portion which is rotated together with the driving magnetic pole portion and which comprises a plurality of magnetic poles; and an FG pattern which opposes the FG magnetized portion. In the device, relative positions of the stator core, the driving magnet pole portion, the FG magnetized portion, and the FG pattern in the circumferential direction are set so that the minimum point c of a torque ripple of the brushless motor does not coincide with points a and b of an output signal from the FG pattern which function as a trigger for rotation control.

Abstract: In a brushless motor (1), a stator base board (10) has three grooves (14) which are cut radially of a mounting hole (103). A core holder (32) holding a stator core (31) has three protrusions (33) which extend downwardly in the direction of the axis of the motor (1). Each of the protrusions (33) has a first engaging portion (331) having a width which is substantially equal to a width of the grooves (14), and a second engaging portion (332) which is semi-circularly protruded from the outer cylindrical surface of the first engaging portion (331). When each of the protrusions (33) is fitted in the respective cut portions (14), two gaps (34) are formed between the outer surfaces of the second engaging portion (332) and the inner surfaces of the cut portions (14). Through the gaps (34), coil terminals (351) are extended from the upper surface (102) of the stator base board (10) to the lower surface, and are then soldered to lands (43) of the wiring pattern.

Abstract: In a motor speed controller (which, in accordance with rotations of a rotor having a drive magnet, detects an induced voltage in each of drive coils in m phases less than the number of drive magnets wound around a stator, generates speed signals which includes m square wave pulses at every 360.degree.

Abstract: A rotary cylinder device has a stationary cylinder with a stationary shaft; a rotary cylinder rotatably mounted on the stationary shaft, the rotary cylinder having an opening on one side thereof which is opposite to the other side where the rotary cylinder confronts with the stationary cylinder; a signal recording and reproducing magnetic head provided on the periphery of the rotary cylinder; an electric motor including: a rotor member of the electric motor, which is provided in the opening of the rotary cylinder and secured to the rotary cylinder; a stator member of the electric motor, which is confronted with the rotor member; and a first magnetic shielding member arranged to cover the opening of the rotary cylinder.

Abstract: A device for detecting the speed of a plural-phase motor in which a speed deviation occurring every m periods is eliminated, to provide a speed detection signal high in accuracy at low cost. The motor speed detecting device in which, among drive signals driving a plural-phase motor, m-phase drive signals (where m is a natural number which is not less than two (2) and equal to or smaller than the number of phases of said motor) are detected, and combined to form a signal, comprises a frequency divider adapted to subject the signal thus formed to 1/(m.times.n) frequency division (where n is a natural number).

Abstract: A signal of one pulse per turn of a motor is obtained by using an m-phase driving coil (L) to be reciprocally electrified in positive and negative directions; a driving magnet which faces the driving coil (L), whose driving magnetic poles S and N are alternately polarized, and which rotates together with a rotary shaft; homopolar position detecting magnetic element (N+) formed on at least one of the driving magnetic poles (N and S); magnetic detectors arranged so as to face the driving magnet to detect the magnetic fields of both the driving magnetic poles (N and S) and the position detecting magnetic element (N+); a brushless-motor driving circuit for supplying a driving current to the driving coil (L) in accordance with signals provided from magnetic detectors; and a synthesizing element for synthesizing a rotational position signal from signals provided from the magnetic detectors, a counter electromotive voltage waveform of the driving coil (L), and a reference voltage (COM).

Abstract: A magnetic detector, such as is used in a frequency generator, for detecting the rotational rate of a motor includes magnetic resistance elements and an operational amplifier. The magnetic resistance elements have a predetermined resistance ratio and are connected serially between a power source and ground. The common node between the two magnetic resistance elements serves as an output terminal for providing an output voltage. The output voltage from the output terminal being supplied to one of the two input terminals of the amplifier. The voltage from a resistance voltage divider disposed between the power source and ground is supplied to the other input terminal of the amplifier. A change of the resistance ratio between the two magnetic resistance elements is effected by a resistor disposed in series with the elements or in parallel with one of the elements.