JPS61170271A - Brushless motor - Google Patents

Abstract

PURPOSE:To reduce a torque ripple and a cogging by forming pole teeth of different phases on a stator core with respect to irregular pole teeth of a rotor, detecting the position of the pole teeth of the rotor to switch a current, thereby increasing a generated torque. CONSTITUTION:A rotor core 5 formed with teeth at the same angle pitches on the inner periphery is mounted on a shaft 8 together with an outer frame 6, and rotatably supported by a bearing unit mounted on a stator core 1. A coil 4 is wound on the core 1, a permanent magnet 2 and a yoke 3 are mounted, and secured to an inner frame 11 together with a bearing unit 9. Further, a position detector 7 is disposed on the circular arc of the outer periphery of the core 1, and mounted in the frame 11. The detector 7 detects the irregular surface of the rotor pole teeth, and delivers an energization command to each phase coil. The core 1 has 6 pole teeth groups of different phases with respect to the pole teeth of the core 5 as basic units.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a brushless motor used as a head actuator of a hard disk drive.

BACKGROUND OF THE INVENTION As personal computers have become popular as office equipment, floppy disk devices, hard disk devices, and optical disk devices have also become popular as external storage devices. Among these devices, demand is increasing for hard disk devices with short access times and large capacities.

A hard disk device consists of a spindle motor, a disk,
It consists of a bed actuator, magnetic head, disk enclosure, breathing filter, position control circuit, and recording/reproducing circuit. Among these, the head actuator is an important mechanism for positioning the magnetic head with high precision and high speed.

Conventionally, voice coil motors and stepping motors have been mainly used as the head actuator motors of hard disk drives. FIG. 6 shows a configuration using a voice coil motor. In Figure 6, (24) is the yoke, (2
5) is a permanent magnet attached to the yoke (24), (26)
is a coil, and (27) is an arm, which is directly connected to the coil (26) and has a magnetic head attached to its tip. (28
) is the shaft, and (23) is the support stand. York (24
) and a permanent magnet (25) creates a static magnetic field in the air gap containing the coil (26). When the coil is energized, thrust is generated according to Fleming's left-hand rule, and the magnetic head disposed opposite the coil (26) can be moved.

As described above, this method using a voice coil motor has the advantage of making it easy to perform accurate position control because there is no cogging, but on the other hand, it requires a large volume to obtain the desired driving force and consumes power. It also has the disadvantage of being large.

Next, FIG. 7 shows an actuator using a stepping motor. (33) is a magnetic head, (31) is an arm, (32) is a shaft serving as the rotation center of arm (31), (30) is a pulley, and (29) is a stepping motor. A metal band is wrapped around the outer periphery of the pulley (30), and one end is fixed to the arm. This results in
When the stepping motor (29) rotates, the arm (31)
) rotates around the shaft (32), and the magnetic head (33) moves. Since the stepping motor (29) is driven in an open loop, it has the advantage that the drive circuit is simpler and the volumetric efficiency of the driving force is better than that of the voice coil motor, but there is a limit to the miniaturization of the step angle and precision It has the disadvantage that it is not suitable for precise position control.

Problems to be Solved by the Invention As described above, the conventional head actuator using a voice coil motor has the drawbacks of large volume and high power consumption, and an actuator with fine positioning performance and high 1-lux performance is available for stepping motors. It wasn't.

An object of the present invention is to provide a brushless motor for an actuator that has minute position controllability and high torque performance.

Means for Solving the Problems The brushless motor of the present invention includes a rotor core made of a magnetic material having a plurality of concave and convex magnetic pole teeth arranged at a constant angle of 3° on the inner periphery, and a rotor core with a slight air gap between the rotor core and the rotor core. a stator core made of a magnetic material and having a plurality of magnetic pole tooth groups facing each other while maintaining the same angular pitch as the rotor magnetic pole teeth, and a permanent magnet attached to the stator core; a plurality of multiphase coils attached to the stator core; a bearing device that maintains a constant gap between the rotor core and the stator core and rotatably supports the rotor; and an outer periphery of the stator. It is equipped with a non-contact sensor that is composed of a plurality of sensor elements arranged at pitches with different phases on the top or near the outer circumference, detects the rotor magnetic pole teeth, and outputs multiphase electrical signals with different phases. Features.

Function: With this configuration, the torque is generated based on the change in the roughness similar to that of a stepping motor, and a large torque can be generated with a relatively small amount of electric power. Furthermore, since the cogging is small, it is suitable for minute positioning, and by detecting the position of the magnetic pole teeth of the rotor and switching the current -4=, smooth movement without torque ripple can be obtained.

EXAMPLE Hereinafter, a brushless motor according to an example of the present invention will be described with reference to the drawings.

Figure 4 shows the principle diagram. This figure shows the motor of the present invention developed in a straight line. The stator core has magnetic pole tooth groups A and B.
, a core (12) with C and A, ■.

It consists of a core (13) with C. (14) is a rotor core, and (15) is a magnet. Magnetic pole tooth groups A, B, C
When , the permeance change of each magnetic pole tooth group can be treated as a sine wave by devising the tooth shape.
It can be expressed as the following formula.

(Left below) P^=Po+Paogθ P K= P
a P cog 0PB=Pn0Pcog(θ-12
0°) PII=Po P cog(θ-120°
) Pc=P, +Pcog(θ-240°) p5==
pIIPaog(θ-240°)P,. : Permian PII when teeth are facing, in: Permeance θ = 2 when teeth are not facing
π・(-) Also, the magnetic flux created by the permanent magnet is: 3Φm=average magnetic flux created by the permanent magnet (blank below) Next, a coil current is caused to flow as follows.

■8” IO' ginθ IK=
L' 111110IB=IO-□. (θ−1
20°) IW=-Io'n1n(θ-120°)I
(!= In-11111 (θ-240°) IC=-I
. -,, (θ-240°) The magnetic flux created by the coil is Φ. ^=-N-P^・ ■8 Φ. N=-N-P
K-INΦ. B=-N-P[I・In Φ. Edit=-
N-PII-I [Φ. (j= N-Pc" Ia
Φa6=NP(!-IσN Number of coil turns of the knee pole tooth group The magnetic flux of each phase is the sum of Φ and Φ., and the following is obtained.

RA=Ro-ro. , θ RK” R6+ r
aomθRB:R(1rcog(θ-120°)
RI=RO+raog(θ-120°)Rc=R,
-r 66, (θ-240') Rty'= Ro
+ r cog (θ-240″′) R, : Magnetic resistance when the teeth are not opposed, R,...: Magnetic resistance when the teeth are opposed, Each phase thrust is: Flux density, S: Cross-sectional area of permanent magnet) Theoretically, it is possible to move without cogging or torque ripple.

The theoretical absence of cogging and torque ripple leads to improved positional accuracy. That is, external disturbances that impair positioning are reduced, there is no need to increase the gain of the control loop, the mechanical resonance point can be lowered, and the structure and assembly can be simplified.

2(a) and 2(b) are external views of this embodiment, FIG. 1 is a cross-sectional view, and FIG. 3 is a cross-sectional view taken along line AA' in FIG. 1. A rotor core (5
) is attached to the shaft (8) together with the outer frame (6), and rotatably supported by a bearing device attached to the stator core (1).

On the other hand, a coil (4) is wound around the stator core (1), a permanent magnet (2) and a yoke (3) are attached, and the inner frame (11) is attached to the stator core (1) along with a bearing device (9). Fixed. Further, a position detector (7) is arranged on the outer circumferential arc of the stator core ( ) and attached to the inner frame (11). This position detector (7) detects the irregularities of the rotor magnetic pole teeth in a non-contact manner, and uses a magnetoresistive element, optical detection means, or the like. Since an energization command is given to each phase coil based on the output signal of the position detector (7), the optimum phase coil is always selected and energized, resulting in a highly efficient motor. As shown in the third cross-sectional view, the basic unit of the stator core (1) is six groups of magnetic pole teeth having different phases with respect to the magnetic pole teeth of the rotor core (5). Of course the same stator core (1)
A plurality of basic units of magnetic pole tooth groups may be arranged within. This embodiment consists of two basic units of magnetic pole tooth groups.

Figure 5 shows the arrangement of permanent magnets. In FIG. 5(,), a magnetic circuit is constructed by connecting two magnets with a yoke using the arrangement method adopted in this embodiment. (15) is the stator core,
(16) is a magnet, and (17) is a yoke.

In addition, a fifth
There are the method shown in FIG. (b) and the method shown in FIG. Figure 5(b) shows the difference? (18) is the stator core, (19) is the magnet, Fig. 5 ((20) in (7)
(21) is a stator core, and (22) is a magnet.

In addition, although the example showed the example of three phases, it goes without saying that two phases or other multiphases may be used.

Effects of the Invention - As shown in the jZ, the brushless motor of the present invention has a rotor core having uneven teeth at a constant angular pitch on the inner circumference, and a stator consisting of magnetic pole teeth having a different phase with respect to the rotor magnetic pole teeth. Since a position detector is provided to detect the position of the recess I''1 of the rotor core, which is placed on the outer periphery of the core and the stator core, it is possible to obtain a motor that generates a large torque and has small torque ripple and cogging. can.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of one embodiment of the brushless motor of the present invention, Fig. 2 is an explanatory diagram of the stator and magnet attachment of the brushless motor of Fig. 1, and Figs. It is an explanatory view of an actuator. (1)...Fixed r-core, (2)...Permanent magnet, (3
) yoke, (4)...coil, (5)...rotation f-
Core, (6)...Outer frame, (7)...Position detector, (8)...-Shirt 1~, (11)...Inner frame agent Yoshihiro Morimoto No. 1 cause 7-44 Yamiko Core 2...-Eisougi 6-...! Tsukasa @J-Core 7-family enemy has the first volume tll, Shi\7toq--Ischix instigation! 2nd evil figure 3rd cause 5th (tail 2 1ri (lI)) q 6th evil figure 7th cause

Claims (1)

[Claims] 1. A rotor core made of a magnetic material having a plurality of concave and convex magnetic pole teeth at a constant angular pitch on the inner circumference, and a rotor core that faces the rotor core with a slight air gap and has the same angular pitch as the rotor magnetic pole teeth. a stator core made of a magnetic material having a plurality of magnetic pole tooth groups including a plurality of magnetic pole teeth; a permanent magnet attached to the stator core; and a plurality of multiphase coils attached to the stator core. and a bearing device that maintains a constant gap between the rotor core and the stator core and rotatably supports the rotor;
A non-contact sensor that is composed of a plurality of sensor elements arranged on or near the outer circumference of the stator at pitches of mutually different phases, detects rotor magnetic pole teeth, and outputs multiphase electric signals having mutually different phases. Brushless motor with.