JPH07111024A - Spindle motor - Google Patents

Abstract

PURPOSE:To obtain a high precision gap and hence to effectively improve seal effect by utilizing an outer race of a ball bearing supporting a rotor hub and providing a labyrinth gap between the outer circumferential surface of this outer race and the inner circumferential surface of a base supporting cylinder. CONSTITUTION:A base 1 to be a fixed member is formed with an annular recessed part 2 in an appropriate place, and a boss part 3 is provided to be projected in the center of this part 2, and a fixed shaft 5 is forcibly fitted and fixed in this center hole 4, and then the rotor hub 8 is freely rotatably supported via the upper and lower ball bearings 6 and 7 by the shaft 5. A short supporting cylinder 13 is projectingly provided on the upper surface of the boss part 3, and this outer circumference is fitted into a stator 14, to which a rotary magnet 12 fixed via a slight gap to the hub 8 is opposed. The inner circumference of the supporting cylinder 13 is made to be a some small diameter and this is regared as a labyrinth gap surface 13a, which is opposed to the outer race of the ball bearing 7 via a gap G1 so as to make the labyrinth effect sufficient. Then, the level of the lower end of an inner circumferential part of the hub 8 supported by the ball bearings 6 and 7 is raised to be positioned in the middle part of the ball bearing 7, so that the seal length is secured enough.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor mainly used for rotating a recording disk such as a magnetic disk.

[0002]

2. Description of the Related Art Conventionally, this kind of spindle motor is constructed as shown in FIG. 4, for example. That is, the annular recess 2 is formed at an appropriate position of the base 1 serving as the fixing member, the boss 3 is provided at the center of the annular recess 2, and the boss 3 is formed.
A fixed shaft 5 is press-fitted and fixed in the center hole 4 of the rotor hub 8, and a rotor hub 8 is rotatably supported on the fixed shaft 5 thus erected on the base 1 via an upper ball bearing 6 and a lower ball bearing 7. .

The rotor hub 8 is made of a non-magnetic material such as aluminum, and a magnetic disk is placed on an annular projecting portion 9 formed on the outer periphery of the lower portion and fixed with a screw hole 10. By sandwiching the magnetic disk between them, the magnetic disk can be rotated integrally with the rotor hub 8. A rotor magnet 12 is mounted on the inner peripheral surface of the annular overhanging portion 9 of the rotor hub 8 via a yoke 11.

A short support cylinder 13 is provided on the upper surface of the boss portion 3 of the base 1, and a stator 14 is externally fitted and fixed to the outer circumference of the support cylinder 13, and a slight gap is provided on the outer circumference of the stator 14. The rotor magnets 12 face each other.

An annular wall 15 is provided on the upper surface of the rotor hub 8 so as to protrude toward the inner periphery, and a cap 17 for closing the upper surface is fixed to the inside of the annular wall 15 by, for example, an ultraviolet curable adhesive 18. Grease and the like from the bearings 6 and 7 are prevented from scattering from the upper surface of the rotor hub 8 into the disk chamber. An annular lid seal 19 hermetically closes the screw hole 10 on the inner surface of the rotor hub 8.

[0006]

However, in the above spindle motor, although the cap 17 can prevent grease and the like from being scattered from the upper surface of the motor, it is possible to prevent the grease from being scattered from the lower surface (outer peripheral portion) of the rotor hub 8. Does not give very good results.

That is, with respect to the scattering of grease and the like from the outer periphery of the lower portion of the rotor hub 8, the inner peripheral surface of the annular recessed portion 2 of the base 1 and the outer peripheral surface of the stator 14 and the inner peripheral surface of the lower portion of the rotor hub 8 are prevented. This is prevented by configuring a labyrinth seal, but it is very difficult to control the gap between the fixed part and the rotating part, that is, the accuracy of the gap is difficult to obtain, and the labyrinth effect does not always work effectively. It was hard to say that

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a spindle motor capable of maintaining a highly accurate labyrinth gap and enhancing a sealing effect. To provide.

[0009]

To achieve the above object, in a spindle motor of the present invention, a shaft erected on a fixed member and a rotor hub rotatably supported on this shaft via a ball bearing. A supporting cylinder protruding from a ball bearing of the fixing member, a stator externally fitted and fixed to the supporting cylinder, and a rotor magnet mounted on the rotor hub and facing the stator with a slight gap. A labyrinth gap having a labyrinth sealing function is formed between the outer peripheral surface of the outer ring of the ball bearing and the inner peripheral surface of the support cylinder.

In this case, it is desirable that a cylindrical boss portion into which the shaft is press-fitted is formed in the shaft supporting portion of the fixing member, and an annular member having a support cylinder formed on the outer periphery of the boss portion is externally fitted and fixed. .

[0011]

In the ball bearing that rotatably supports the rotor hub, since the surface accuracy and the roundness of the outer ring are formed with high accuracy, the support provided by the outer peripheral surface of a part of the outer ring of the ball bearing and the fixing member protruding. The labyrinth gap formed with the inner peripheral surface of the cylinder can be maintained with high precision and a minute gap, and can exhibit a high labyrinth sealing function.

[0012]

EXAMPLES Examples will be described in detail with reference to FIGS. It should be noted that the same reference numerals as in the related art indicate the same or corresponding ones.

FIG. 1 shows a first embodiment, in which an annular recess 2 is formed at an appropriate position of a base 1 which serves as a fixing member, a boss 3 is provided at the center of the annular recess 2, and the boss 3 is projected. Three
A fixed shaft 5 is press-fitted and fixed in the center hole 4 of the rotor hub 8, and a rotor hub 8 is rotatably supported by the fixed shaft 5 via an upper ball bearing 6 and a lower ball bearing 7.

A short supporting cylinder 13 is provided on the upper surface of the boss portion 3 of the base 1, and a stator 14 is externally fitted and fixed to the outer circumference of the supporting cylinder 13, and a slight gap is provided on the outer circumference of the stator 14. Rotor magnet 1 fixed to rotor hub 8
Two are facing each other.

The inner circumference of the support cylinder 13 is formed to have a slightly smaller diameter than that of the conventional one and serves as a labyrinth gap forming surface 13a. The labyrinth gap forming surface 13a faces the outer ring of the lower ball bearing 7 via a gap G1 (for example, 0.05 to 0.1 mm) capable of sufficiently exerting a labyrinth seal effect, and forms a labyrinth seal between the two.

Here, the rotor hub 8 supported by the ball bearings 6 and 7 is located at the central portion of the lower ball bearing 7 because the height of the lower end of the inner peripheral portion thereof is higher than that of the conventional one, and the boss portion 3 is correspondingly formed. Since the height of the support cylinder 13 is increased, the seal length of the labyrinth seal is sufficiently secured.

On the other hand, the outer peripheral surface of the annular overhanging portion 9 of the rotor hub 8 faces the inner peripheral surface of the annular concave portion 2, and a gap G2 (for example, 0.1) which can sufficiently exert the labyrinth sealing effect therebetween. ~ 0.2) has been formed.

In the spindle motor having such a structure, it is possible to greatly improve the scattering of grease and the like from the outer periphery of the lower portion of the rotor hub 8 which has been a problem by the labyrinth sealing effect of the gap G1. Particularly in the case of the embodiment, the labyrinth sealing effect is exhibited by the gap G2 between the rotor hub 8 and the base 1, and the scattering of grease or the like is reliably prevented.

Moreover, since the gap G1 is formed by using the outer ring of the ball bearing 7 in which a highly accurate roundness is ensured, the dimension control of the gap becomes easy, and the labyrinth seal is constructed relatively easily. can do.

2 and 3 show a second embodiment. A boss portion 3 is provided at the center of the annular recess 2 formed in the base 1, and the outer peripheral portion of the boss portion 3 is located at a position substantially corresponding to the outer periphery of the ball bearing 7 fixed to the shaft 5. It is a machined circumferential processed surface 20 and is arranged concentrically with the central hole 4 of the boss portion 3.

On the outer periphery of the boss portion 3, an annular stator holder 21 which is an annular member forming the support cylinder 13 is provided. In this stator holder 21, as shown in FIG.
1a has a labyrinth gap forming surface 21b facing the outer ring of the lower ball bearing 7 at the upper portion on the inner peripheral side, and a stator support surface 21c formed at the outer peripheral side together with a stator positioning step portion 21d, and has a mounting surface 21a. By externally fitting the circumferentially machined surface 20 of the boss 3, the stator holder 2
1 is fixed, and the supporting surface 21c of this stator holder 21
The stator 14 is externally fitted and fixed.

When the stator holder 21 is fixed, the labyrinth gap forming surface 21b faces the outer ring of the lower ball bearing 7 with a gap G1 (for example, 0.05 to 0.1 mm) capable of sufficiently exerting a labyrinth sealing effect therebetween. Constitutes a labyrinth seal.

Therefore, also in this embodiment, it is possible to greatly improve the scattering of grease and the like from the outer periphery of the lower portion of the rotor hub 8 by the labyrinth sealing effect of the gap G1, and further, between the rotor hub 8 and the base 1. The labyrinth sealing effect by the gap G2 is also exerted, and the scattering of grease or the like is reliably prevented.

Here, in the above-described embodiment, the base 1 is provided with the stator holder 21 as a separate member, and the gap G1 is formed by using this, but this is
The machining of the circumferentially machined surface 20 on the base 1 is relatively easy and highly accurate, and the machining of the inner and outer peripheral surfaces of the stator holder 21 as a separate member is relatively easily and highly accurately achieved, resulting in the labyrinth gap. This is because the forming surface 21b can be easily and highly accurately obtained.

The specific examples of the spindle motor according to the present invention have been described above, but the present invention is not limited to these specific examples, and various modifications and corrections can be made without departing from the scope of the present invention. .

[0026]

Since the present invention is constructed as described above, it has the following effects.

Since the labyrinth gap is formed between the outer peripheral surface of the ball bearing supporting the rotor hub and the inner peripheral surface of the support cylinder of the base, a highly accurate gap can be easily obtained. It is possible to enhance the labyrinth sealing effect.

Further, the inner peripheral surface of the support cylinder facing the outer ring of the ball bearing can be easily mounted by externally fitting and fixing the annular member having the support cylinder formed on the outer periphery of the boss portion formed on the shaft supporting portion of the fixing member. In addition, it is possible to obtain a highly precise labyrinth gap easily.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of a spindle motor according to the present invention.

FIG. 2 is a partial sectional view showing a second embodiment of the spindle motor according to the present invention.

FIG. 3 is a partial cross-sectional view showing the stator holder of FIG.

FIG. 4 is a sectional view showing a conventional spindle motor.

[Explanation of symbols]

 1 Base 2 Annular Recess 3 Boss 5 Shaft 6 and 7 Ball Bearing 8 Rotor Hub 12 Rotor Magnet 13 Support Tube 14 Stator 21 Stator Holder G1 Labyrinth Gap

Claims (2)

[Claims] 1. A shaft erected on a fixed member, a rotor hub rotatably supported on the shaft via a ball bearing, and a support cylinder projecting on a position outside the ball bearing of the fixed member. A stator magnet externally fitted and fixed to the support cylinder, and a rotor magnet that is mounted on the rotor hub and faces the stator with a slight gap, and the outer peripheral surface of the outer ring of the ball bearing and the inside of the support cylinder. A spindle motor characterized in that a labyrinth gap having a labyrinth sealing function is formed between the peripheral surface and the peripheral surface. 2. A cylindrical boss portion, into which the shaft is press-fitted and fixed, is formed in the shaft supporting portion of the fixing member, and an annular member having a support cylinder is externally fitted and fixed to the outer periphery of the boss portion. Item 1. The spindle motor according to item 1.