JPH04178163A - Brushless motor - Google Patents

Abstract

PURPOSE:To reduce a motor current so as to get a brushless motor small in shaft deflection by magnetizing one part each of the magnetization faces of, at least, the two magnetic poles of the rotor magnets, which are magnetized in a plurality of poles supported freely in rotation in opposition to driving winding, into the pole reverse to the magnetic pole in question at the positions different in radius. CONSTITUTION:PG 6 is magnetized with magnetism reverse to the main magnetic pole, at one part of the magnetic pole of the rotor magnet 1 in opposition to the magnetism detection means of a stator. Furthermore, the reverse magnetization to the main magnetic pole is performed in the position, which forms an angle of 180 deg. with PG6 so as to provide PG balance magnetization 11. This magnetization is performed as far as to the inside periphery of the magnet. And the quantity equivalent to the amount that the magnetization suction force of PG6 is weak is provided by Pg balance magnetization 11 so as to balance the suction force. Hereby, precession can be prevented, and the motor current can be reduced, and the shaft deflection can be made small.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a brushless motor for rotationally driving a disk such as a floppy disk.

BACKGROUND ART FIG. 4 is a plan view of a rotor (magnet side) of a conventional brush motor, and FIG. 5 is a plan view of a stator (coil side). Moreover, FIG. 6 shows a side view of the motor.

As shown in FIG. 6, the rotor magnet 1 has a drive winding 2
It has a structure in which it is arranged opposite to and can rotate via a bearing 3. As shown in FIG. 5, the pulse generator shown in FIG. From the pole 6 (hereinafter referred to as PG), a signal waveform as shown in FIG. 8a is obtained by the magnetic detection means 5a. The signal waveform and other magnetic detection means 5b, 5
The device calculates the signal waveform obtained from c and generates one pulse per one rotation of the rotor as shown in FIG. It is.

Problems to be Solved by the Invention However, in a conventional brushless motor, when the rotor 7 rotates, the PG magnetized part is polarized opposite to the main magnetic pole, so the boundary between them becomes zero or a weakly magnetized part, and the stator yoke 9 Since the magnetic attraction force with this magnetic pole is weaker than with other poles, the magnetic pole portion including the PG rotates while maintaining a position far from the stator yoke 9. A so-called grinding motion shown in FIG. 7 is performed. For this reason, the bearing has disadvantages in that the pressure on the bearing increases, the motor current increases, and the shaft runout increases.

The present invention solves the above problems and aims to provide a brushless motor with reduced motor current and reduced shaft runout.

Means for Solving the Problems In order to achieve the above object, the present invention provides a stator yoke, an electrical connection means provided above the stator yoke, and a plurality of drive windings arranged in a plane on the electrical connection means. A portion of a magnetized surface of at least two magnetic poles of a bearing disposed at the center and a multi-pole magnetized rotor magnet that is tightly coupled to the bearing and rotatably supported opposite the drive winding. This is achieved by the fact that the magnetic poles are magnetized at positions with different radii and opposite polarities to the magnetic poles.

Effects The present invention has the above-described configuration, and the attraction force with the stator yoke 9 is reduced by the fact that parts of the magnetized surfaces of the two magnetic poles are magnetized at positions with different radii and opposite polarities to the magnetic poles. The unbalance of the shaft is alleviated, the grinding motion is suppressed, the motor current is reduced, and the shaft runout can be reduced.

Embodiment FIG. 1 shows an embodiment of the present invention, and shows a magnetization pattern of a rotor magnet. As shown in the figure, a PG 6 is magnetized to a part of the magnetic pole of the rotor magnet 1 facing the magnetic detection means 5 of the stator with a polarity opposite to that of the main magnetic pole. Further P
Magnetization with opposite polarity to the main magnetic pole is also performed at a position making a 180 degree angle with G6 (hereinafter, this will be referred to as PG balance magnetization 11).
).

This magnetization position is placed as close to the inner circumference of the magnet as possible to prevent a decrease in the torque generated by the motor.

In the above configuration, since the PG magnetized portion and the main magnetic pole have opposite polarities, there is a portion where the magnetization is zero or weakly magnetized at the boundary portion, and the pole including the PG has a weak attraction force with the stator yoke. Further, the PG balance magnetization 11 is also opposite to the main magnetic pole.

In other words, the amount corresponding to the weak magnetization attraction force of the PG part is
Balanced magnetization 11 is provided to prevent grinding motion by balancing the attractive forces, thereby reducing motor current and reducing shaft runout.

As a result, the motor current value becomes almost the same as in the case without PC magnetization.

FIG. 2 shows a magnetization pattern of a magnet in a second embodiment of the present invention. On both adjacent poles of the pole forming an angle of 180 degrees with PG magnetization 6, PC balance magnetization 11 with opposite polarity to the main pole.
a,llb is implemented. The poles of the magnet that are 180 degrees opposite each other (hereinafter referred to as counter poles) are responsible for generating torque of the motor. In the first embodiment, since both the opposite electrodes have opposite polarity magnetization, this opposite electrode causes a decrease in torque, so-called torque ripple. In the second embodiment, since only 11 locations of opposite poles facing each other by 180 degrees have reverse polarization, the torque ripple is improved more than in the first embodiment.

FIG. 3 shows a magnetization pattern of a magnet according to a third embodiment of the present invention. 1st. In the second embodiment, since the numbers of PG, PG balance magnetized polarity, N, and S magnetized in the magnetic poles are not the same, the leakage magnetic flux toward the upper side of the stator yoke is unidirectionally S bonded.

It is biased toward the N system, and as a result, the value of leakage magnetic flux becomes large.

On the other hand, in this embodiment, since the N and S magnets are magnetized in the same number, the balance is maintained, and the above-mentioned drawbacks are improved. Note that even if the rotor magnet has magnetized poles other than those described above, such as multi-pole magnetization for speed control (not shown), or even if all the magnetized polarities are opposite to those in the example, the actual This does not impair the effectiveness of the invention.

Effects of the Invention As is clear from the above embodiments, by having balanced magnetization, there is no unbalance of magnetic attraction force (no grinding motion, motor current is reduced, and a brushless motor with small shaft runout can be provided. .

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the magnetization pattern of the rotor magnet in the first embodiment of the present invention, and FIG.
FIG. 3 is a plan view showing the magnetization pattern of the rotor magnet in the embodiment of the present invention, FIG. 3 is a plan view showing the third embodiment of the present invention, and FIG. 4 is a plan view showing the magnetization pattern of the rotor magnet in the conventional embodiment. Figure 5 is a plan view of the stator;
Figure 6 is a partial sectional view of the side surface of the spindle motor, Figure 7 is a sectional view of the bearing that performs precession motion, and Figure 8 is a sectional view of the PG.
FIG. 3 is a diagram showing signal waveforms. DESCRIPTION OF SYMBOLS 1... Rotor magnet, 2... Drive winding, 3... Bearing, 4... Circuit board, 5... Magnetic detection means ,6...PG,
7... Rotor, 8... Spindle hub, 9... Stator yoke, 10... Stator, 11... PG balance magnetization, 12...
····shaft. Name of agent: Patent attorney Haruaki Koba and two others Figure 1 Figure 2. Figure 3 1c Figure 4 Figure 5 2 Figure 7

Claims (1)

[Claims] A stator yoke and an electrical connection means provided above the stator yoke,
a plurality of drive windings disposed in a plane on the electrical connection means, a bearing disposed at the center thereof, and a plurality of poles engaged with the bearings and rotatably supported opposite the rotor winding; A brushless motor characterized in that parts of the magnetized surfaces of at least two magnetic poles of a magnetized rotor magnet are magnetized at positions with different radii and opposite polarities to the magnetic poles.