JPH07111028A - Rotational driving device - Google Patents

Abstract

PURPOSE:To improve sealability and to prevent splashing of bearing fluid by increasing the joint strength of a stopper member and lessening the temp. rise of a magnetic fluid sealing part while maintaining the reduction in the thickness of the device. CONSTITUTION:The rotational driving device for a rotating body which has a metal 5 disposed via the bearing fluid 12 with a central shaft 4 and the magnetic fluid seal 16 spatially arranged axially outward from this metal 5 to prevent the leakage of the bearing fluid 12 and is constituted to drive the rotating body by generating a dynamic pressure is provided. The outer peripheral surface of the central shaft 4 is provided with the stepped annular stopper member 35 which consists of a magnetic material and is composed of a large-outside diameter part 35A and small-outside diameter part 35B. The outer peripheral surface 35a of the large-outside diameter part 35A is formed larger than the inner peripheral surface 5a of the metal and the inner peripheral surface 16c of the magnetic pole piece of the magnetic fluid seal 16. In addition, the large-outside diameter part 35A is arranged between the metal 5 and the magnetic fluid seal 16 in an axial direction and the small-outside diameter part 35b is disposed to face the inner peripheral surface 16c of the magnetic pole piece of the magnetic fluid seal 16 in a circumferential direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary drive device.

[0002]

2. Description of the Related Art Conventionally, a spindle motor for driving a disk as shown in FIG. 4 is known as a drive device for a rotary body configured to generate a dynamic pressure to drive the rotary body. This spindle motor is a so-called fixed center shaft type, and only the right half of the center line is shown in order to avoid complication of the drawing.

In the figure, reference numeral 1 indicates a frame. A through hole is formed in the center of the frame 1, and a groove having a constant width is formed on one surface (the upper surface in the drawing) along the circumference. ing. A stator core 2 is fixed to the inner peripheral surface 1a of the groove, and a coil 3 is wound around the stator core 2. A center fixed shaft 4 made of a magnetic material is fitted and fixed in the through hole.
A plurality of herringbone-shaped dynamic pressure generating grooves 4a serving as a dynamic pressure generating means are formed at appropriate positions on the outer peripheral surface of the.

A metal 5 as a radial slide bearing is loosely fitted and arranged on the outer periphery of the center fixed shaft 4.
A hub 6 shaped so as to cover the stator core 2, the coil 3 and the like is fitted and fixed to the outer periphery of, by, for example, press fitting. A protrusion 6 a protruding upward is formed on the upper surface of the hub 6, and the upper surface 6 b inside the protrusion 6 a of the hub 6 is formed.
And the upper surface 5b of the metal 5 are flush with each other.

A ring-shaped retaining member 15 is fitted and fixed to the outer periphery of the central fixed shaft 4 above the upper surface 5b of the metal 5. The outer peripheral surface of the retaining member 15 is larger than the outer peripheral surface of the metal 5, and the metal 5 and the hub 6
It is intended to prevent the (rotating body) from coming out of the device.

A protrusion 6a above the retaining member 15
A magnetic fluid seal 16 is arranged on the inner circumference. The magnetic fluid seal 16 includes a magnet 16b and a magnet 16b.
And pole pieces 16a, 16a, which are magnetic pole pieces that are provided so as to sandwich the pole piece in the axial direction, and which form the magnetic path. Between the magnetic fluid 17,17
Can be retained. Therefore, the magnetic fluid seal 16 prevents the lubricating oil (bearing fluid) 12 such as the oil filled in the sliding portion from leaking from the bearing portion to the outside, and the dust from the outside to the inside of the bearing portion. It is intended to prevent such intrusion.

A spacer 19 is provided on the outer peripheral surface of the hub 6.
The magnetic disks 18 and 18 are mounted in the axial direction with the drive magnets 7 fixed to the inner circumference of the stator core 2 at opposite positions. Above coil 3
A terminal wire 8 is led out from the terminal, and the terminal wire 8 is soldered to a predetermined position (solder land portion) of a flexible substrate 9 having a conductor pattern formed on the upper surface. One end of the flexible lead wire 10 is connected to the end of the conductor pattern of the flexible substrate 9, and the other end of the flexible lead wire 10 extends outside the motor and is connected to the power supply means 11.

Then, by applying a predetermined driving voltage to the coil 3 from the power supply means 11 outside the motor through the flexible lead wire 10, the conductor pattern and the terminal wire 8,
The hub 6 mounted with the magnetic disks 18, 18 is adapted to rotate.

Reference numeral 20 indicates a disk retainer, and reference numeral 21 indicates a magnetic fluid seal provided in the middle of the passage 13 communicating with the outside from below.

[0010]

However, the above-mentioned rotary drive device has the following problems. That is, since the retaining area of the retaining member 15 with the central fixed shaft 4 is small, the retaining strength is insufficient for impact and external force, and there is a fear of detaching from the device.

Here, as shown in FIG. 5 (a), it is conceivable to simply increase the thickness of the retaining member 25 by the length L in the axial direction to increase the joint strength. The device is lengthened by L in the axial direction, which runs counter to the recent demand for thinning.

Further, as shown in FIG. 5 (b), the wall thickness of the retaining member 25 is increased in the axial direction to increase the joint strength, and the inner peripheral surface of the pole piece 26a of the magnetic fluid seal 26 is conventionally formed. It is conceivable to make the magnetic fluid seal larger by making it larger with the outer peripheral surface of the retaining member 25 so as not to change the overall length in the axial direction. Since it is proportional to the third power and to the square of the rotation speed, the larger the shaft diameter of the seal portion and the higher the rotation speed, the more the heat generation amount increases at this ratio. There is a fear that reliability will decrease.

Therefore, according to the present invention, the strength of the joining of the retaining member is increased while maintaining the thinness of the device, the temperature rise of the magnetic fluid seal portion is small, and the sealing property is good, and the bearing fluid is prevented from scattering. An object is to provide a possible rotary drive device.

[0014]

In order to achieve the above object, a rotary drive device of the present invention is provided with a radial slide bearing disposed between a central shaft and a bearing fluid, and a center of the radial slide bearing. And a magnetic fluid seal portion that is arranged outwardly in the axial direction of the shaft to prevent the bearing fluid from leaking to the outside, and is configured to generate dynamic pressure to drive the rotor. The stepped ring-shaped retaining member made of a magnetic material and having a large outer diameter portion and a small outer diameter portion is provided on the outer peripheral surface of the central shaft, and the outer periphery of the large outer diameter portion of the retaining member is A surface larger than the inner peripheral surface of the radial slide bearing and the inner peripheral surface of the magnetic pole piece of the magnetic fluid seal portion, and the large outer diameter portion is arranged in the axial direction between the radial slide bearing and the magnetic fluid seal portion. The side of the small outer diameter part It is characterized in that is opposed in the circumferential direction to the pole piece inner peripheral surface of the seal.

[0015]

According to the rotary drive device having such means, the large outer diameter portion having a diameter larger than the inner peripheral surface of the radial slide bearing and the inner peripheral surface of the magnetic pole piece of the magnetic fluid seal portion functions as a retaining member for the rotating body. At the same time, a labyrinth seal shape is formed between the opposing member and the bearing fluid, and scattering of the bearing fluid is prevented. Further, the joining area of the retaining member can be made larger than that of the conventional one, and the joining strength is increased, but since the outer peripheral surface has a step shape, the magnetic fluid seal portion can be arranged at the same position in the conventional axial direction. Thinning is maintained. Also, since the outer peripheral surface of the retaining member has a stepped shape, the inner peripheral surface of the magnetic pole piece of the magnetic fluid seal can be made smaller than when the retaining member is simply thickened, and the temperature of the seal portion rises. Can be suppressed.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an enlarged cross-sectional view of a main part of a center axis fixed type disk drive motor showing a first embodiment of the present invention, that is, a retaining member and a magnetic fluid seal part. The same components and those having the same function are designated by the same reference numerals, and the description thereof will be omitted here to avoid duplication.

The difference between the rotary drive device of this embodiment and that of the prior art is that the retaining member 35 disposed above the metal 5 has a stepped ring shape consisting of a large outer diameter portion 35A and a small outer diameter portion 35B. It is a point that is a member.

Here, the retaining member 35 is made of a magnetic material and is externally fitted and fixed to the outer peripheral surface of the central fixed shaft 4.
Further, the outer peripheral surface 35 of the large outer diameter portion 35A of the retaining member 35
a is larger than the inner peripheral surface 5a of the metal 5 and the inner peripheral surface 16c of the pole piece 16a which is a magnetic pole piece of the magnetic fluid seal 16, and the large outer diameter portion 35A is located between the metal 5 and the magnetic fluid seal 16 in the axial direction. Placed on the other hand, while the small outer diameter part 3
The side surface (outer peripheral surface) 35b of 5B faces the inner peripheral surface 16c of the pole piece 16a of the magnetic fluid seal 16 in the circumferential direction.

Accordingly, the inner peripheral surfaces 16c, 16c of the pole pieces 16a, 16a and the retaining member 35 made of a magnetic material.
Between the small outer diameter portion 35B and the side surface 35b of the magnetic fluid 17,
17 can be held, and the magnetic fluid sealing function can be exerted as in the conventional case.

The large outer diameter portion 35A of the retaining member 35
The outer peripheral surface 35a of the metal 5 and the inner peripheral surface 16 of the pole piece 16a, which is a magnetic pole piece of the magnetic fluid seal 16.
Since it is larger than c, the large outer diameter portion 35A is capable of exerting a retaining function of the rotating body, and its opposing member has a labyrinth seal shape as shown in the drawing. 12 scattering prevention is also possible.

Further, as shown in the drawing, the joint area (relative to the center fixed shaft) of the retaining member 35 can be made about twice or more larger than the conventional one, and the joint strength can be enhanced. Since the outer peripheral surface has a stepped shape, the magnetic fluid seal portion 16 can be arranged at the same position in the conventional axial direction, and therefore the retaining member can be maintained while keeping the device thin. It is possible to increase the bonding strength of No. 35.

Further, as described above, since the outer peripheral surface of the retaining member 35 has a step shape, the magnetic fluid seal 1 is formed.
The inner peripheral surface 16c of the pole piece 16a of No. 6 can be made smaller than when the retaining member is simply thickened [see FIG. 5 (b)], so that the temperature rise of the seal portion 16 can be suppressed. It is possible to maintain good sealing performance.

FIG. 2 is an enlarged cross-sectional view of a retaining member and a magnetic fluid seal portion of a central axis fixed type disk drive motor according to a second embodiment of the present invention, which has been described in the previous embodiment. The same reference numerals are attached to the same components and those having the same functions.

The difference between the rotary drive device of the second embodiment and that of the first embodiment is that the upper end portion of the central fixed shaft 14 has a smaller diameter than the other shaft portions, and the first portion is attached to this small diameter portion. The retaining member 55 that has the same structure as that of the embodiment and is reduced in the circumferential direction.
This is the point where is fitted and fixed.

Here, the inner peripheral surface 36c of the pole piece 36a of the magnetic fluid seal 36 further extends toward the axial center as compared with the first embodiment because the central fixed shaft 14 has a smaller diameter.

It goes without saying that the same effects as those of the first embodiment can be obtained even with this structure.
In addition, as described above, the inner peripheral surface 3 of the pole piece 36a
Since 6c extends from the first embodiment toward the axial center, the rotational speed of the seal portion decreases and the heat generation amount of the seal portion decreases, so that the effect of further increasing the seal pressure resistance can be expected. .

FIG. 3 is an enlarged cross-sectional view of essential parts (a retaining member, a magnetic fluid seal part, and a hub) of a center shaft rotating type disk drive motor showing a third embodiment of the present invention. The same components as those described in the embodiments and those having the same functions are designated by the same reference numerals.

In the rotary drive device of the third embodiment, since the central shaft is a rotary type, a hub having a magnetic disk (not shown) mounted on the upper end portion of the central rotary shaft 24. 30 is fitted and fixed, and the central rotary shaft 24 is fitted with a metal 5 which is fitted and fixed to a bearing holder 31 on the frame side.
Is supported via a bearing fluid 12.

The retaining member 45 has a shape in which a part of the upper surface of the large outer diameter portion 35A of the retaining member 35 shown in the first embodiment is projected upward, and the hub 30 and the center thereof are provided. When the rotating body such as the rotating shaft 24 tries to separate from the device, the protruding portion 45C of the large outer diameter portion 45A comes into contact with the lower pole piece 16a (fixed side) to prevent the separation. There is.

By the way, the shape of the retaining member 45 is exactly the same as that of the first embodiment except that the protruding portion 45C is formed, and the connection with surrounding parts is also the same as that of the first embodiment. Therefore, it goes without saying that the same effect as that of the first embodiment can be obtained.

Further, the apparatus of this embodiment is modified and applied as in the second embodiment, that is, the upper end portion of the central rotary shaft 24 has a smaller diameter than the other shaft portions, and this small diameter portion has this embodiment. Of course, it is also possible to reduce the retaining member 55 of the example in the circumferential direction with the same structure and fit and fix it.

Regarding the detailed drawing numbers in the retaining members 45 and 55 shown in FIGS. 2 and 3, as described above, the structure thereof is approximately the same as that of the first embodiment.
The numbers in the drawing numbers of the first embodiment are changed and the alphabetical parts are not changed.

The invention made by the present inventor has been specifically described based on the embodiments, but the invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say, for example, in each of the above-described embodiments, an example in which a herringbone-shaped dynamic pressure generating groove is formed on the shaft as the dynamic pressure generating means is described. It may be formed on the inner peripheral surface, and as the dynamic pressure generating groove, for example, Japanese Patent Publication No. 63-
It may be a spiral groove as described in Japanese Patent No. 60247.

Further, the dynamic pressure generating means is not limited to these grooves, but is disclosed in, for example, JP-A-3-107612.
As described in Japanese Laid-Open Patent Publication No. 3-96426 and Japanese Utility Model Laid-Open No. 3-96426, a protrusion for supporting a rotating body is provided on either the rotating body or the non-rotating body, and a wedge-shaped gap is formed between the protruding portion and the moving body. It may be one that is adapted to generate a pressure effect.

Further, in each of the above embodiments, an example of application to a spindle motor for driving a magnetic disk is described, but it goes without saying that the same can be applied to other rotary drive devices. .

[0036]

As described above, according to the rotary drive device of the present invention, a stepped ring shape made of a magnetic material and having a large outer diameter portion and a small outer diameter portion is formed on the outer peripheral surface of the central shaft. Of the retaining member, the outer peripheral surface of the large outer diameter portion of the retaining member is made larger than the inner peripheral surface of the radial slide bearing and the magnetic pole piece of the magnetic fluid seal portion, and the large outer diameter portion is in the axial direction. Is placed between the radial plain bearing and the magnetic fluid seal part at
Since the side surface of the small outer diameter portion was made to face the inner peripheral surface of the magnetic pole piece of the magnetic fluid seal in the circumferential direction, the large outer diameter portion having a diameter larger than the inner peripheral surface of the radial slide bearing and the magnetic pole piece of the magnetic fluid seal portion , Which functions as a retaining member for the rotating body, and has a labyrinth seal shape between the opposing member and the opposing member, which makes it possible to prevent the bearing fluid from scattering. In addition, the joining area of the retaining member can be made larger than before and the joining strength is increased.
On the other hand, since the outer peripheral surface has a stepped shape, it is possible to arrange the magnetic fluid seal portion at the same position in the conventional axial direction. Therefore, while keeping the device thin, the retaining member is joined. It is possible to increase the strength. Further, as described above, since the outer peripheral surface of the retaining member has a step shape, the inner peripheral surface of the magnetic pole piece of the magnetic fluid seal can be made smaller than when the retaining member is simply thickened, and It is possible to suppress the temperature rise of the seal portion and maintain good sealability.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a retaining member and a magnetic fluid seal portion of a central shaft fixed type rotary drive device according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a retaining member and a magnetic fluid seal portion of a central shaft fixed type rotary drive device according to a second embodiment of the present invention.

FIG. 3 is an enlarged cross-sectional view of a retaining member, a magnetic fluid seal portion, and a hub of a central shaft rotation type rotary drive device according to a third embodiment of the present invention.

FIG. 4 is a transverse cross-sectional view of a center shaft fixed type rotary drive device showing a conventional technique.

5 is a cross-sectional view of a main part for pointing out a problem when the device shown in FIG. 4 is simply improved. FIG.

[Explanation of symbols]

 4,14,24 Central shaft 5 Radial slide bearing 5a Radial slide bearing inner peripheral surface 12 Bearing fluid 16,36 Magnetic fluid seal part 16a, 36a Magnetic fluid seal magnetic pole piece 16c, 36c Magnetic pole piece inner peripheral surface 35, 45, 55 Stopping member 35A, 45A, 55A Large outer diameter portion 35a, 45a, 55a Outer peripheral surface of large outer diameter portion 35B, 45B, 55B Small outer diameter portion 35b, 45b, 55b Small outer diameter portion side surface

Claims (1)

[Claims] 1. A radial slide bearing arranged between the central shaft and a bearing fluid via a bearing fluid, and a radial slide bearing spaced apart from the radial slide bearing outward in the axial direction of the central shaft, to the outside of the bearing fluid. With a magnetic fluid seal part that prevents leakage,
A rotary body driving device configured to generate a dynamic pressure to drive a rotary body, wherein a stepped ring made of a magnetic body and having a large outer diameter portion and a small outer diameter portion is provided on an outer peripheral surface of the central shaft. A retaining member having a large diameter, the outer peripheral surface of the large outer diameter portion of the retaining member being larger than the inner peripheral surface of the radial slide bearing and the inner peripheral surface of the magnetic pole piece of the magnetic fluid seal portion, and the large outer diameter portion. Is disposed between the radial slide bearing and the magnetic fluid seal portion in the axial direction, and the side surface of the small outer diameter portion is circumferentially opposed to the magnetic pole piece inner peripheral surface of the magnetic fluid seal. Drive.