JPH03242868A - Spindle motor - Google Patents

Abstract

PURPOSE:To absorb thermal deformation due to the difference of the thermal expansion coefficients of a hub member and a yoke member by fixing the end parts of the hub member and the yoke member to each other, and providing clearance between the other parts of both the members except fixed end parts extending over whole circumference practically. CONSTITUTION:The hub member 6 is formed of aluminum or aluminum alloy, and the yoke member 8 is formed of iron, and the thermal expansion coefficient of the hub member 6 is larger than the thermal expansion coefficient of the yoke member 8. Then, the hub member 6 and the yoke member 8 are fixed to each other at their end parts by shrinkage fitting, and the clearance is provided between the other parts except fixed end parts of both extending over the whole circumference practically. Accordingly, the inner circumferential surface of the thick wall part 16 of the hub member 6 and the outer circumferential surface of the end part of the yoke member 8 corresponding to it are brought into direct contact and fixed, and both the members never come into contact directly with each other excepting the fixed parts. Thus, the thermal deformation caused by the difference of the thermal expansion coefficients of the hub member 6 and the yoke member 8 can be absorbed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a spindle motor, and more particularly to a spindle motor in which a hub member and a yoke member are formed from materials having different coefficients of thermal expansion.

[Prior art and its drawbacks]

Generally, a spindle motor that rotationally drives a recording member such as a magnetic disk includes a mounting bracket, a hub member that is rotatable relative to the mounting bracket, a rotor magnet attached to the hub member, and a hub member. It includes a yoke member interposed between rotor magnets and a stator disposed inside the rotor magnets,
The recording member is attached to the outer peripheral surface of the hub member. In this type of spindle motor, the hub member is made of aluminum or an aluminum alloy, and the yoke member is made of iron, and the hub member and the yoke member have different coefficients of thermal expansion.

If the hub member and the yoke member are fixed together over substantially their entire length by means such as shrink fitting, the following problem occurs.

That is, since the coefficients of thermal expansion of the hub member and the yoke member are different, when the ambient temperature rises or falls, there will be a difference in the degree of expansion or contraction between the hub member and the yoke member, and if this difference becomes large, the recording member will deform. This can cause waviness, noise, etc. during rotation.

Therefore, in order to solve this problem, for example, as disclosed in U.S. Pat. No. 4,717.977, a method such as shrink fitting the hub member and the yoke member at the center in the longitudinal direction is taken. A spindle motor has also been proposed in which the motor is fixed by a screwdriver and a gap is provided between the two ends.

In such a spindle motor, since a gap exists at both ends of the hub member and the yoke member, thermal deformation caused by the difference in coefficient of thermal expansion between the two can be absorbed by the gap, thereby significantly reducing the deformation of the recording member. It can be suppressed.

However, in this spindle motor, since the space between both ends of the hub member and yoke member is open, dust etc. that adhere to the inner circumferential surface of the hub member and/or the outer circumferential surface of the yoke member during assembly etc. It flows into the storage chamber (the chamber in which the recording member is stored) through the gap, causing contamination.

[Purpose of the invention]

The present invention has been made in view of the above facts, and its main purpose is to absorb thermal deformation caused by the difference in coefficient of thermal expansion between the hub member and the yoke member, and also to suppress the occurrence of contouring. An object of the present invention is to provide an improved spindle motor that can be used.

[Summary of the invention]

According to the present invention, there is provided a mounting bracket, a hub member rotatable relative to the mounting bracket, a rotor magnet disposed inside the hub member, and a space between the hub member and the rotor magnet. a yoke member interposed in the
a stator disposed inside the rotor magnet, and wherein the hub member and the yoke are made of materials with different coefficients of thermal expansion, one end of the hub member and the yoke. are fixed to each other, a gap is provided between them at substantially the entire circumference except for the one end, and an elastic sealing means is interposed between the other ends. Provided is a spindle motor characterized by the following.

〔Concrete example〕

Hereinafter, a specific example of a spindle motor according to the present invention will be described with reference to the accompanying drawings.

In FIG. 1, the illustrated spindle motor includes a mounting bracket 2, a shaft member 4, and a hub member 6. The mounting bracket 2 has a substantially disk shape, and a boss portion 2a is provided at the center bracket. This mounting bracket 2
is attached to the drive frame (not shown).

The shaft member 4 is fixed to the mounting bracket 2, and the shaft member 4
A hub member 6 is rotatably attached to. In the specific example, the lower end portion of the shaft member 4 is fixed to the boss bracket 2a of the mounting bracket 2 by means such as press fitting. The hub member 6 has a substantially cylindrical shape, and the inner diameter of one end (upper end) thereof is smaller than the inner diameter of the other portion. This hub member 6
A yoke member 8 is disposed on the inner circumferential surface of the yoke member 8 over substantially its entire length, and an annular rotor magnet 10 is attached to the inner circumferential surface of the yoke member 8 at a substantially central portion in the longitudinal direction.

The manner in which the hub member 6 and yoke member 8 are fixed will be described in detail later.

The hub member 6 is rotatably supported by the shaft member 4 via a pair of bearing members 12 and 14.

In the specific example, as shown in the figure, the hub member 6 is rotatably supported by a bearing member 12 via a yoke member 8 at one end (the one end is a thick portion 16), and at the other end. It is rotatably supported by the other bearing member 14 via the yoke member 8 and a bushing member 18 attached to the inner peripheral surface of the yoke member 8 . Magnetic fluid seal mechanisms 20 and 22 are disposed on the outside of the bearing members 12 and 14. One of the magnetic fluid seal mechanisms 20 has an annular bushing member 24 fixed to one end of the shaft member 4 on the outside of the bearing member 12, and an annular magnet 26 and a pair of pole pieces 28 are attached to this bushing member 24. A magnetic fluid is filled between the pole piece 28 and the yoke member 8. Further, the other magnetic fluid sealing mechanism 22 has an annular bushing member 30 fixed to the shaft member 4 on the outside of the bearing member 14, and an annular magnet 32 and a pair of pole pieces 34 are attached to this bushing member 30. , pole piece 3
4 and the bushing member 18 are filled with magnetic fluid. A plate-shaped spring member 38 is disposed between the bushing member 24 of the magnetic fluid sealing mechanism 20 and the inner ring 36 of the bearing member 12.
is interposed, and the spring member 38 applies a preload to the bearing members 12 and 14.

A stator 40 is disposed inside the rotor magnet 10, and the stator 40 is fixed to an intermediate portion of the shaft member 4 (a portion between the pair of bearing members 12 and 14). A hub member 6 is provided between the stator 40 and the annular protrusion 42 of the shaft member 4.
A circuit board 44 is provided for controlling the rotation of.

In such a spindle motor, as shown by the dashed line in FIG. Lower recording disk 46
is placed on the flange portion 50 of the hub member 6. and,
The hub member 6 (together with the yoke member 8 and rotor magnet 10) and the recording disk 46 are rotationally driven in a predetermined direction with respect to the mounting bracket 2, shaft member 4, and stator 40.

Next, the manner in which the hub member 6 and the yoke member 8 are fixed will be described with reference to FIG. 2 as well as FIG. 1.

In a specific example, the hub member 6 is formed from aluminum or an aluminum alloy, the yoke member 8 is formed from iron, and the coefficient of thermal expansion of the hub member 6 is greater than the coefficient of thermal expansion of the yoke member 8. Generally, when the ambient temperature rises or falls, thermal deformation occurs due to the difference in thermal expansion or contraction between the two.
In the specific example, the above-mentioned thermal deformation is absorbed as required. That is, one end of the hub member 6 and the yoke member 8 are fixed by a means such as shrink fitting, and a gap is provided between the two over substantially the entire circumference except for the one end. ing. Instead of shrink fitting, one end of both can be fixed by means such as press fitting or adhesive. Therefore, the inner circumferential surface of the thick part 16 of the hub member 6 and the corresponding outer circumferential surface of one end of the yoke member 8 (which has a smaller diameter than the other parts) are directly contacted and fixed, and other than the above-mentioned fixed part There is no substantial contact between the two. In the specific example, an annular groove 52 having a rectangular cross section is further formed on the inner circumferential surface of the other end of the hub member 6 . This annular groove 52 has an elastically deformable O which can be made of synthetic rubber, for example.
- a ring 54 (constituting an elastic sealing means) is housed;
This O-ring 54 is pressed against the outer peripheral surface of the yoke member 8. In the specific example, an annular protrusion 8a (see FIG. 2) is provided on the outer peripheral surface of the other end of the yoke member 8, and this annular protrusion 8a acts on the O-ring 54. Therefore, as can be easily understood from FIG. 1, when the hub member 6 is moved downward relative to the yoke member 8 in FIG. 1 and the two are fixed, the positional relationship shown in FIG. Until this point, the O-ring 54 does not act relatively strongly on the outer circumferential surface of the yoke member 8, and relative movement between the two is achieved smoothly. On the other hand, when the positional relationship shown in FIG. Due to this, the O-ring 54 acts strongly on the outer peripheral surface of the yoke member 8, and the Q-IJ song 4
Thus, the space between the yoke member 8 and the hub member 6 is reliably sealed. Further, the other end of the hub member 6 is reliably supported by the yoke member 8 via this O-ring 54, and the rotation of the hub member 6 and therefore the recording disk 46 is stabilized.

The spindle motor described above has the following features.

First, the hub member 6 and yoke member 8 are fixed only at one end, and there is a gap between them at the middle and other ends, so they expand or contract due to changes in ambient temperature. However, the thermal deformation caused by the difference in expansion or contraction between the two is absorbed by the gap between the two, so that the recording disk 46 is prevented from waviness caused by the deformation of the hub member 6. In particular, when the thick portion 16 is provided at one end of the hub member 6 and fixed to the yoke member 8 as in the specific example, the portion where thermal deformation is likely to occur,
That is, the deformation at one end becomes uniform in the circumferential direction, thereby making it possible to further suppress the occurrence of waviness or the like in the recording disk 46.

Second, since the hub member 6 is supported directly by the yoke member 8 at one end and by the yoke member 8 via the O-ring 54 at the other end, the hub member 6 is reliably supported by the shaft member 4 via the yoke member 8, and the hub member 6 and therefore the recording disk 46 are stably rotated.

Thirdly, at one end of the hub member 6, the hub member 6 and the yoke member 8 are directly fixed to form a seal, and at the other end, an O-ring 54 seals the space between the two. A disk chamber (a chamber in which the recording disk 46 is housed) that is sealed and removes dust and the like that adheres to the outer circumferential surface of the yoke member 8 and/or the inner circumferential surface of the hub member 6 during assembly work, etc.
It is possible to reliably prevent intrusion into the environment and suppress the occurrence of contamination.

In the specific example shown in FIGS. 1 and 2, one O-ring 54 is interposed between the hub member 6 and the yoke member 8. For sealing, a plurality of grooves may be formed in the inner peripheral surface of the hub member 6, and O-rings may be accommodated in the guide grooves.

In the specific example shown in FIGS. 1 and 2, an O-ring 54 is interposed, but instead of the O-ring 54, an adhesive layer may be interposed.

In the following description, the same members as those shown in FIGS. 1 and 2 are designated by the same numbers.

In FIG. 3 showing the first modification, an annular recess 60 is formed in the inner peripheral edge of the lower end of the hub member 6'' in FIG. 3, while a lower end of the yoke member 8'' in FIG. An annular protrusion 62 is formed that protrudes radially outward. The tip of the annular protrusion 62 projects somewhat into the recess 60 of the hub member 6'', and defines a housing space with a rectangular cross section that is open downward by the annular protrusion 62 of the hub member 6'' and yoke member 8''. .

After the hub member 6' and the yoke member 8 are fixed in the same manner as in the above-described specific example, the housing space is filled with, for example, a rubber adhesive over its entire circumference.

Even in such a modification, the lower end of the hub member 6'' is reliably supported via the adhesive layer 64 (which acts as an elastic sealing means), and the adhesive layer 64 connects the hub member 6'' and the yoke. It is ensured that the space between the members 8' is sealed, so that the first
Effects similar to those of the embodiment shown in FIGS. 2 and 2 are achieved.

FIG. 4 shows a second variant, in which O
- the ring is attached to the yoke member;

In FIG. 4, an annular groove 66 having a rectangular cross section is formed on the outer peripheral surface of the lower end of the yoke member 8''.
An O-ring 68 is housed within the tank 6 and serves as an elastic sealing means at the bottom of the tank. The O-ring 68 protrudes from the groove 66 and acts elastically on the inner peripheral surface of the hub member 6'', supporting the hub member 6'' and sealing between the hub member 6'' and the yoke member 8''. It will be easily understood that the same effects as the specific example shown in FIGS. 1 and 2 can be achieved in this second modification as well.

Although specific examples of the spindle motor according to the present invention have been described below, the present invention is not limited to such specific examples, and various modifications to the deformation angle are possible without departing from the scope of the present invention.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a specific example of a spindle motor according to the present invention. FIG. 2 is an enlarged cross-sectional view of a part of the spindle motor shown in FIG. 1. FIG. 3 is an enlarged cross-sectional view of a part of the first modification of the spindle motor. FIG. 4 is an enlarged cross-sectional view of a part of a second modification of the spindle motor. 2... Mounting bracket 5 6 - Shaft members 6' and 6''... Hub members 8' and 8''... Yoke member 0... Rotor magnet 0... Stator 6... Recording disk 4 and 68... O-ring 4... Adhesive layer

Claims (1)

[Claims] 1. A mounting bracket, a hub member that is rotatable relative to the mounting bracket, a rotor magnet disposed inside the hub member, and the hub member and the rotor magnet. A spindle motor comprising a yoke member interposed between the rotor magnet and a stator disposed inside the rotor magnet, the hub member and the yoke portion being made of materials having different coefficients of thermal expansion, the hub member and one end of the yoke portion are fixed to each other;
A gap is provided between the two at substantially the entire circumference except for the one end, and an elastic sealing means is interposed between the other end. spindle motor.