Koyo Seiko Company, Ltd.

Jtekt Corporation

Hirohide Inayama

Atsushi Ishihara

Sadaaki Mori

Tomofumi Takahashi

Minoru Kitabayashi

Tetsuo Horie

Hideki Jonokuchi

Naotake Kanda

Noboru Niguchi

Masaru Horikawa

An electric motor includes an annular stator core having a pair of ends opposed to each other in an axial direction, and a coil wound around the stator core. The stator core includes a pair of powder magnetic cores each arranged at the pair of ends and a laminated steel plate arranged between the paired powder magnetic cores. Each of the paired powder magnetic cores includes a section arranged outside the coil in the axial direction.

Electric motor

A brushless motor includes an annular stator and a rotor which has a plurality of permanent magnets alternately arranged in circumferential direction on the rotor to form poles and which is disposed within the stator to be rotatable with respect to the stator. The stator includes a cylindrical yoke and a plurality of teeth which are same in size one another, are connected to the yoke to extend therefrom toward the rotor, and are disposed at even interval in the circumferential direction. Width of each of the teeth in the circumferential direction is set to be greater than or at a vicinity of the value which is obtained by dividing outer diameter of the rotor by the number of the teeth and multiplying the result of dividing by &#x3c0;/2.

Brushless motor and electric power steering apparatus incorporating the same

A bridge () in conformity with a tooth opening angle of the stator () is provided between a permanent magnet () and a permanent magnet () in a rotor (), so that a magnetic flux for a reluctance torque is made to pass an inner side of the permanent magnet (). An opening angle of each of ribs () on both sides of the permanent magnet () is set to be equal to or smaller than the teeth interval opening angle and equal to or larger than a half thereof. Thereby, reluctance of the rib () against a magnetic flux in a circumferential direction is increased and leakage of the magnetic flux of the permanent magnet () is prevented.

Brushless DC motor

The power steering apparatus comprises a torque sensor for detecting a steering torque applied to a steering wheel and a steering assist motor which is driven to rotate based on the detected steering torque. The motor is driven under field weakening control in a high-speed rotation area. The motor is a brushless motor comprising a rotor having a plurality of permanent magnets which are respectively fixed in a plurality of recesses provided in a rotor core. With the electric power steering apparatus, a steer-assisting force can be obtained in high-speed steering.

Electric power steering apparatus

A brushless DC motor including a stator having plural slots; and a rotor which has plural permanent magnets and is divided into three rotor blocks in a rotation axis direction, the three rotor blocks being layered so that the arrangement angles of the rotor blocks differ from each other by an amount of a mechanical angle in a rotary direction that is equivalent to one third of a pulsation period of cogging torque generated by the rotor and stator. A brushless DC motor including a rotor having plural magnetic poles provided at an equal pitch in a circumferential direction by mounting permanent magnets in magnet mounting holes; and a stator having plural slots arranged at an equal pitch in a circumferential direction. The magnetic poles of the rotor include magnetic poles whose magnet deviation angle formed by the central line of an effective polar opening angle and the central line of the magnet mounting hole is the first angle; and magnetic poles whose magnet deviation angle is the second angle different from the first angle.

Brushless DC motor and method of manufacturing brushless DC motor

In a brushless DC motor constructed by a rotor to which a permanent magnet is attached; and a stator having a plurality of slots, when an effective opening angle of magnetic pole of the rotor that was set to a predetermined opening angle whose base is the rotation axis of the rotor is &thgr;2 and a salient area opening angle of magnetic pole formed within the effective opening angle &thgr;2 of magnetic pole is &thgr;3, the opening angles &thgr;2 and &thgr;3 are set so that cogging torque generated by the effective opening angle &thgr;2 of magnetic pole and cogging torque generated by the salient area opening angle &thgr;3 of magnetic pole are mutually in antiphase. Accordingly, a brushless DC motor capable of reducing cogging torque is realized.

An electric power steering apparatus being provided with: a torque sensor for detecting a steering torque applied to a steering wheel (not shown); and a steering assisting motor driven by a drive circuit to which the voltage of a mounted battery P is applied, in which the drive circuit rotates the motor in accordance with a motor current instruction value determined based on the steering torque detected by the torque sensor , is further provided with: judging means for judging whether the motor current instruction value is higher than a first threshold value or not; boosting instruction outputting means for, when the judging means judges that the motor current instruction value is higher, outputting a boosting instruction for boosting the voltage of the mounted battery P; and a boosting circuit for boosting the voltage of the mounted battery in response to the outputted boosting instruction. Even when the voltage of the mounted battery P fluctuates, a voltage from which a stable steering assisting force is always obtained can be supplied to the steering assisting motor, so that the steering assisting motor can be reduced in size.

Growing community of inventors

Nara, Japan

Hirohide Inayama