Sony Corporation

Konica Corporation

Mitsuo Uzuka

Tadayoshi Ikeda

Satoshi Sakamoto

Tadashi Miwa

Masahiro Makita

Hidehiro Kanda

In a rotation detection apparatus, a magnetism pattern section provided with plural magnetic poles and a FG (frequency generating) pattern section provided with plural toothed wire circuits are located so as to face each other. When either one of the magnetism pattern section and the FG pattern section is rotated together with a rotating member, plural wave signals are electrically induced in the plural toothed wire circuits. A signal processing cicuit synthesizes the plural wave signals so as to output a multiplication signal and detects the rotation of the rotating member based on the multiplication signal.

Rotation control device

Three-phase brushless motor having auxiliary magnetic pole on rotor

A brushless motor comprising a rotor assembly including a rotor magnet which is formed substantially as a hollow cylinder. In one embodiment, the rotor magnet is molded of synthetic resin and contains magnetic material. A rotor shaft is mechanically coupled to the rotor magnet. A stator assembly includes electromagnetic windings wound upon a core. The core has magnetic poles which are spaced from a surface of the cylindrical wall of the rotor magnet by an air gap. In one example, the rotor magnet is cup-shaped having an end wall which bridges the cylindrical wall so as to have the rotor shaft secured to such end wall. The stator assembly also may include a yoke member formed of magnetically permeable material and spaced from the opposite surface of the cylindrical wall of the rotor magnet, whereby the cylindrical wall of the rotor magnet rotates between the magnetic poles of the stator assembly and the yoke member.

Brushless motor

A brushless DC motor of the type including a rotor having a magnet for generating magnetic flux of alternating magnetic field polarities in a rotary path about its axis of rotation and a stator coaxial with the rotor and having a plurality of coils of respective phases in linking relation to the magnetic flux and adapted to be energized for the flow of current therethrough so as to produce a rotational torque, is provided with a control circuit in which switching transistors are connected with the coils of respective phases and are selectively turned ON in response to respective switching signals for energizing the respective coils, a switching signal generating circuit is normally responsive to the rotational position of the rotor for periodically changing its condition and thereby providing the switching signals to the switching transistors, and an additional switch device is connected to the switching signal generating circuit and is actuable to fix the condition of the latter so that only one of the switching transistors is continuously turned ON for energizing only the respective coil and thereby locking the rotor against rotation. Such locking of the rotor against rotation is particularly desirable in the case where the brushless DC motor is provided to directly drive a reel mount in a video tape recorder (VTR) or similar apparatus in which it is desired to prevent rotation of the reel mount during tape loading and unloading operations.

Control circuit of brushless DC motor

A driving circuit for a brushless DC motor is connected to energize the plurality of stator windings by detecting induced voltages in windings adjacent an energized winding, mixing these detected voltages in predetermined ratios, and comparing the mixed voltages with a reference level, in order to provide switch controlling signals fed to switches arranged between each of the plurality of stator windings and the energization source. Individual detectors to detect rotor position corresponding to the winding being energized are not required and delay circuits used to provide sequential pulses are also eliminated thereby promoting fabrication of the invention using integrated circuit technology.

Brushless DC motor driving circuit

A drive circuit for an alternate-phase brushless DC motor is arranged to minimize the torque ripple normally occurring with such motors. The motor has rotor magnets and at least two stator coils, and has a torque relationship in which the rotational torque for each coil extends over an electrical angle of more than 180 degrees and has gradual rising and falling portions intersecting with respective falling and rising portions of the torque of the other coil. The drive circuit includes a rotary position sensor, such as a Hall element, switching transistors for driving the stator coils, and switching signal forming circuitry responsive to the sensor to switch the switching transistors on and off alternately. In order to reduce the torque ripple, the drive circuit is made to energize the stator coils in the region of the intersections of the rotational torque, so that the coils are energized for more than 180 electrical degrees. In one preferred embodiment, a pair of additional switching transistors coupled to the stator coils are switched on by a circuit formed of a pair of differential amplifiers coupled to the Hall element and, through a logic gate, to the additional switching transistors.

Drive circuit for an alternate phase brushless DC motor

A drive circuit for a brushless DC motor assures that the stator coils of the motor do not generate unwanted electromagnetic noise, but does not sacrifice efficiency of the motor. The drive circuit can include an input circuit to which a rectangular switching signal is applied, a circuit including a drive transistor providing stator drive current in response to the input switching signal, and an RC smoothing circuit to impart sloping leading and trailing edges to the drive current so that the drive current assumes a somewhat sinusoidal shape and the electromagnetic noise is avoided. In order to prevent the motor efficiency from dropping under low-torque and high-speed conditions, the delay times for the leading and trailing edges are controlled to increase or decrease in dependence upon the load to the motor. In one embodiment, the collector-emitter voltage of the drive transistor is sensed and this voltage is furnished to a control transistor so that the latter adjusts the level of the input switching signal according to the sensed voltage level. Preferably, the base current applied to the drive transistor is kept near the saturation level.

Drive circuit for brushless DC motor

A brushless DC motor includes a rotor adapted to rotate about an axis and having a plurality of magnets for generating a magnetic flux; a stator having at least two coils through which an alternating signal is applied for rotating the rotor about its axis; and a reversible drive circuit for regulating the alternating signal through the coils and which includes first and second switching transistors for energizing the coils with the alternating signal, a rotational position sensing circuit for generating a position signal corresponding to the rotational position of the rotor, a rotational direction selecting circuit for producing a control signal corresponding to a desired rotational direction of the rotor, an NPN switch control transistor responsive to the position signal and control signal for alternately switching the first and second switching transistors so as to rotate the rotor in the forward direction, and a PNP switch control transistor in parallel with the NPN switch control transistor and responsive to the position signal, the control signal and an output from the NPN switch control transistor for alternately switching the first and second switching transistors so as to rotate the rotor in the reverse direction.

Reversible drive circuit for brushless DC motor

A DC motor having a rotor which rotates about an axis and a stator. The motor comprises at least two coils adapted to be energized for current to flow therethrough, each coil having a first current path portion through which current flows in a first direction and a second current path portion through which current flows in a second, opposite direction. A magnetic flux generator includes at least one pair of circumferentially disposed magnetic poles for generating flux of alternating magnetic field polarity in a rotary path about the axis, the magnetic flux linking each coil such that if a coil is energized throughout a region of magnetic flux of predetermined polarity, a rotational torque of predetermined direction is produced through a range having an electrical angle greater than 180.degree.. A circuit alternately energizes the coils for current to flow through each energized coil for a duration substantially equal to an electrical angle of 180.degree. when the energized coil is within the range of the torque of predetermined direction. In one embodiment, each coil is wound toroidally on a toroidal core, and the coils are separated by an electrical angle of 180.degree.. In this embodiment, one magnetic polarity of the magnetic flux is asymmetric with respect to the other magnetic polarity thereof. In another embodiment, the first and second current path portions are disposed on substantially the same cylindrical surface concentric about the axis, and the first and second current path portions are separated from each other by an electrical angle less than 180.degree..

DC motor

A driving circuit for a brushless motor of the type having a permanent magnet rotor and plural phase stator windings. The driving circuit includes position detectors for detecting the rotary position of the rotor. Switching devices are provided for supplying driving currents in sequence to the plural phases of the stator windings in accordance with the position of the rotor. The durations of the driving currents are controlled such that a portion of such currents flowing through adjacent phases are overlapped when the motor is started up; but the duration of each driving current is reduced as the motor approaches a normal speed so as to correspondingly reduce the overlapped portions. Preferably, the durations of the currents are reduced as the speed of the motor increases until such currents no longer have overlapped portions.

Growing community of inventors

Urawa, Japan

Mitsuo Uzuka