JPH0543777U - Brushless DC motor - Google Patents

Abstract

(57) [Abstract] [Purpose] The purpose of this is to suppress the increase in the number of parts and the heat generated by vortices when a shield plate is provided on the disk device side. In a brushless DC motor incorporated in a spindle 2 of a disk device, a rotor yoke 3 fixed to the spindle 2 is bent toward the disk device to form a shield part 3a, and the shield part 3a covers a rotor magnet. ing.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a shield of a brushless DC motor, for example, in a magnetic disk device of a computer and having a motor incorporated in its spindle.

[0002]

[Prior Art]

 In recent years, the so-called light, thin, short, and small sizes of magnetic disk devices used in computers have increased in order to increase storage capacity and speed, and disks have also changed from medium-diameter disks to small-diameter disks. The so-called spindle motor, which is an integrated brushless DC motor, is required to be more compact, higher in performance and lower in cost.

FIG. 2 shows an outer rotor type brushless DC motor. A rotor yoke 3 is integrally fixed to an end portion of a spindle 2 of a disc device 1 which is a main body, and a rotor magnet 4 is attached to a tip of the rotor yoke 3. Supported and fixed. On the other hand, inside the rotor magnet 4 and on the disk device 1 side, a stator core 5 and a stator coil 6 are provided, and a Hall element 7 for position detection is arranged.

FIG. 3 shows an inner rotor type brushless DC motor in which a stator core 5 and a stator coil 6 are arranged outside a rotor yoke 3 and a rotor magnet 4 fixed to a spindle 2.

[0005]

[Problems to be solved by the device]

 In the brushless DC motor shown in FIGS. 2 and 3, the rotor magnet 4 rotates at a high speed at a position very close to the disk device 1 which is mainly made of an aluminum material, and the leakage flux from the rotor magnet 4 is generated. Has a problem in that it passes through an aluminum material, which is a non-magnetic material, and has an adverse effect on the disk portion.Also, in the aluminum material, eddy current loss occurs due to this leakage flux, and heat is generated. Accuracy is getting worse.

For this reason, in order to eliminate the influence of the leakage magnetic flux on the aluminum material, a thin magnetic shield plate 8 such as a silicon steel plate or permalloy is arranged on the side of the magnet rotor of the disk device 1. However, the number of parts is increased, which is disadvantageous in cost reduction, and although the eddy current loss is smaller than before, eddy current is still generated in the magnetic shield plate 8 and heat is generated.

The present invention provides a brushless DC motor that has few parts and has no effect of heat, except that the number of parts is increased by providing a magnetic shield plate and the disk device is exposed to magnetic flux and heated by eddy current. For the purpose of provision.

[0008]

[Means for Solving the Problems]

 According to the present invention, which achieves the above-mentioned object, in a brushless DC motor in which a rotor magnet is arranged to face a stator via a rotor yoke fixed to a spindle of a disk device, the tip of the rotor yoke that supports the rotor magnet is It is characterized by being molded into a shield part that covers the end surface of the rotor magnet on the disk device side.

[0009]

[Action]

 By forming the shield part on the rotor yoke itself, a separate shield plate is not required, and the number of parts is reduced.At the same time, the rotor yoke is a rotor, the relative position does not change, eddy current loss does not occur, and leakage does not occur. The magnetic path length of the magnetic flux is shortened, and the magnetic flux acting on the aluminum member of the disk device is drastically reduced.

[0010]

【Example】

 An embodiment of the present invention will now be described with reference to FIG. In FIG. 1, the same parts as those in FIGS. 2 and 3 are designated by the same reference numerals. In FIG. 1, a rotor including a rotor yoke 3 and a rotor magnet 4 is attached to an end portion of a spindle 2 of the disk device 1, and a stator core 5 and a stator are provided on the disk device 1 side so as to face the rotor magnet 4. The coil 6 is arranged.

The rotor yoke 3 has a base end fixed to the spindle 2 and a front end forming a bent shield portion 3 a on the disk device 1 side. The shield portion 3a is formed so as to cover the end surface of the rotor magnet 4 on the disk device 1 side. In this case, the shield portion 3a that covers the disk device 1 side of the rotor magnet 4 is covered to such an extent that it does not hinder the operation of the motor. The rotor yoke 3 is formed of a magnetic material such as a silicon steel plate because the shield portion 3a is formed at the tip of the rotor yoke 3, and is manufactured by a steel plate press in the same manner as in the conventional case. Further, since the rotor magnet 4 is bonded by the adhesive at the tip of the rotor yoke including the bent shield portion 3a, the bonding area becomes large and the bonding becomes strong.

[0012]

[Effect of the device]

 As described above, the present invention has the following effects. (1) Since the rotor yoke is fixed to the rotor magnet, the relative position does not change, so no eddy current loss occurs in the shield part of this yoke. (2) Since the magnetic path length of the leakage flux is shortened, the magnetic flux applied to the aluminum part of the disk device is drastically reduced. (3) Since the shield part is formed at the same time when the steel plate is pressed, the number of parts does not increase and there is little cost increase. (4) When fixing the magnet and the yoke with adhesive, it is not necessary to pay attention to the protrusion of the adhesive, and since the adhesive effect can be expected between the shield part and the magnet end face, the adhesive strength is improved. Reliability is increased. (5) Since this shield part functions as a part of the yoke, it is possible to reduce the thickness of the steel plate. (6) An effect of reinforcing the cup-shaped yoke against centrifugal force during high-speed rotation can be expected.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional outer rotor type.

FIG. 3 is a configuration diagram of a conventional inner rotor type.

[Explanation of symbols]

 1 disk device 2 spindle 3 rotor yoke 3a shield part 4 rotor magnet

Claims (1)

[Scope of utility model registration request] 1. In a brushless DC motor in which a rotor magnet is arranged to face a stator via a rotor yoke fixed to a spindle of a disk device, a tip of the rotor yoke supporting the rotor magnet is
A brushless D formed by forming a shield portion so as to cover the end surface of the rotor magnet on the disk device side.
C motor.