JPH0779540B2 - Brushless motor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat-opposed brushless motor.

2. Description of the Related Art In recent years, electronic devices such as magnetic recording devices have been reduced in size and weight. Along with that, the motors used are also smaller and lighter.

Hereinafter, a conventional brushless motor will be described with reference to the drawings. FIG. 3 is a sectional view of a conventional brushless motor. Reference numeral 1 is a rotor magnet, which is fixed to a drive shaft 4 held by a chassis 2 via a bearing 3. A stator coil 5 is fixed to a back yoke 6 made of a silicon steel plate, and the back yoke 6 is fixed to the chassis 2.

The brushless motor configured as described above is one in which a current is sequentially passed through the stator coil 5 to generate a magnetic flux, and the rotor magnet 1 is rotated by the attractive force / repulsive force with the magnetic field generated by the rotor magnet 1. is there.

Problems to be Solved by the Invention However, in the above-mentioned configuration, due to the directionality of the magnetic permeability generated when the silicon steel plate 6 of the back yoke 6 that converges the magnetic flux of the rotor magnet 1 is rolled, when the rotor magnet 1 rotates. There is a problem in that the suction force and the repulsion force become stronger and weaker, resulting in cogging and uneven rotation.

Further, in the above-mentioned configuration, when the electric current is sequentially passed through the stator coil 5, the attraction force and the repulsion force between the rotor magnet 1 and the stator coil 5 change with the change of the magnetic flux generated by the stator coil 5. Then, vertical vibration is induced in the stator coil 5, and the back yoke 6
There is a problem that the magnetic recording head, the magnetic reproducing head, etc. (not shown) provided on the chassis 2 are vibrated by being transmitted to the chassis 2 via the to cause wow flutter and jitter.

In view of the above problems, the present invention provides a brushless motor capable of reducing rotation unevenness due to cogging during rotation of a rotor magnet and reducing vibration transmission to a chassis.

Means for Solving the Problems In order to solve the above problems, a brushless motor according to the present invention has a stator coil fixed to a flexible plate-like body in which a magnetic fluid is sealed, and the plate-like body is used as a rotor magnet. The stator coil is fixed to the chassis so that the stator coil is located at a position separated by a predetermined distance.

Action According to the above configuration, as the rotor magnet rotates,
Since the magnetic fluid in the plate-like body also moves, cogging due to the magnetic permeability directionality of the back yoke does not occur and uneven rotation can be reduced.

Further, with the above configuration, the vibration generated in the stator coil when the brushless motor rotates is attenuated by the flexibility of the plate and the viscosity of the magnetic fluid enclosed in the plate, and the vibration to the chassis is generated. Can be reduced.

Embodiment A brushless motor according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a brushless motor according to an embodiment of the present invention. In FIG. 1, 1 is a rotor magnet, 2 is a chassis, 3 is a bearing, 4 is a drive shaft,
Reference numeral 5 is a stator coil, and the above is the same as the conventional configuration. FIG. 2 is a cross-sectional view of a plate-like body used for the back yoke, 8 is a magnetic fluid, 9 is a sealed container of the magnetic fluid 8 made of a resin molded product, and the magnetic fluid 8 can freely flow inside the sealed container 9. It is possible to move. The feature of this embodiment is that
This back yoke is arranged in place of the conventional back yoke 6 made of a silicon steel plate.

In the above structure, when the rotor magnet 1 is rotated by the magnetic flux generated by applying an intermittent current to the stator coil, the magnetic fluid 8 in the back yoke 7 is stored in the sealed container 9 according to the magnetic flux generated by the rotating rotor magnet 1. To move. Therefore, cogging does not occur and smooth rotation can be obtained.

Further, when the brushless motor rotates, the vibration of the stator coil 5 generated by the change in magnetic flux is transmitted to the back yoke 7, but is damped by the flexibility of the enclosure 8 and the viscosity of the enclosed magnetic flux 9. Therefore, the transmission of vibration to the chassis 2 is reduced.

EFFECTS OF THE INVENTION As described above, according to the present invention, the stator coil is fixed to the plate-like body in which the magnetic fluid is sealed, and the plate-like body is predetermined with respect to the rotor magnet rotatably provided on the chassis. By fixing the stator coil to the chassis so that the stator coil is located at a position separated by a certain distance, it is possible to improve the uneven rotation of the rotor magnet and to prevent the vibration generated by the stator coil when the brushless motor rotates. Transmission to the chassis can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a brushless motor according to an embodiment of the present invention, FIG. 2 is a sectional view of its back yoke, and FIG. 3 is a sectional view of a conventional brushless motor. 1 ... Rotor magnet, 2 ... Chassis, 3 ... Bearing, 4 ... Drive shaft, 5 ... Stator coil, 7 ... Back yoke, 8 ... Magnetic fluid, 9 ... Encapsulation container.

Claims (1)

[Claims] 1. A stator coil is fixed to a plate-like body in which a magnetic fluid is sealed, and the plate-like body is placed at a predetermined distance from a rotor magnet rotatably provided on a chassis. A brushless motor fixed to the chassis so that the stator coil is positioned.