JPH0520782A - Flexible disk device - Google Patents

Abstract

PURPOSE:To obtain a flexible disk device which excels in the assembling performance with a simple structure by attaining the highly accurate revolution of a rotary shaft of a recording medium despite a shortened baring part. CONSTITUTION:In regard to a flexible disk device, a rotary shaft 1 which revolves a magnetic recording medium is supported in the radial direction by a dynamic pressure type radial fluid bearing which holds a lubricant through a helical groove 4 provided on the inner surface of a sleeve 2. Then the axis end part is supported by a thrust member 3. This member 3 is made of cermet and contains a venting hole 32 which secures the ventilation between the inside and the outside of the sleeve 2. Furthermore the end part of the rotary shaft which has a contact with the member 5 is formed into a sphere 11. Then a relief machining part is formed on the inner surface of the sleeve 2 so that a contact is inhibited between an edge part 12 of the sphere 11 and the inner surface of the sleeve 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible disk device used for an external storage device such as a computer.

[0002]

2. Description of the Related Art Conventionally, a flexible disk device of this type records and reproduces information by supporting and rotating a rotary shaft of a recording medium with a ball bearing or an oil-impregnated metal bearing. In the bearing, each bearing is supported in the radial direction, and in the thrust direction, the shaft and the ball bearing inner ring are fixed by being adhered and supported. Similarly, in the oil-impregnated metal bearing, the rotary shaft can be supported by inserting a plurality of washers between the hub fixed to the shaft and the oil-impregnated metal.

In addition, the rotary shaft of the recording medium is changed to Japanese Patent Publication No. 63-50564.
When supported by a dynamic pressure type hydrodynamic bearing device known in Japanese Patent Publication, etc.,
The shaft (recording medium rotation shaft), an outer cylinder having a bottom wall at one end,
A dynamic pressure bearing portion can be supported between the end of the shaft and the bottom wall of the outer cylinder, and between the outer peripheral surface of the shaft and the inner peripheral surface of the outer cylinder.

[0004]

However, in the above-mentioned conventional flexible disk device, when the bearing length for supporting the rotary shaft is shortened due to the clearance between the inner diameters of the rotary shaft and the bearing and the radial clearance of the bearing, The rotation axis swings and the track centering accuracy of the recording medium deteriorates, and the function of the device is no longer fulfilled. For this reason,
There is a problem that the device cannot be thinned.

Further, since the flexible disk device has a lower rotation speed than that of a VTR device or the like, when the thrust force of the rotating shaft is received by the dynamic pressure type fluid thrust bearing,
Since the bearing rigidity decreases and the bearing does not float, it is necessary to make the area of the shaft end of the rotary shaft larger than the shaft cross section or to make it a tapered surface, which complicates the structure. Further, for the same reason, it is necessary to use high-viscosity grease or the like different from the lubricant of the radial bearing portion in the thrust bearing, and two types of lubricants are used, which causes a problem in assembling. .

The present invention solves the above-mentioned problems of the prior art. A flexible disk device that can rotate a rotary shaft with high precision even if the bearing portion is short, has a simple structure, and is easy to assemble. The purpose is to provide.

[0007]

In order to achieve the above object, the flexible disk device of the present invention comprises a rotary shaft for rotating a disk-shaped magnetic recording medium for recording / reproducing,
In a flexible disk device in which a radial groove is supported by a dynamic pressure type radial fluid bearing holding a lubricant in a helical groove provided on the inner surface of the sleeve, and a shaft end portion is thrust supported by a thrust member, the thrust member is a cermet and The thrust member is provided with a vent hole for ventilating the inside and the outside of the sleeve.

Further, the end of the rotary shaft that abuts on the thrust member is formed into a spherical surface, and further, the inner surface of the sleeve is attached to the inner surface of the sleeve so that the edge of the boundary between the outer peripheral surface of the rotary shaft and the spherical surface of the end of the rotary shaft does not contact the inner surface of the sleeve. Provide a relief processing part.

[0009]

According to the above construction, by using a cermet having a large hardness and a high mechanical strength for the thrust member, it is possible to provide excellent durability even if it is made thin.
A so-called pivot bearing can be configured by bringing the end of the rotating shaft, which has been subjected to spherical processing, into contact with the thrust member, and thrust can be supported with low friction.

By providing a ventilation hole in the thrust member, the pressure of the lubricating oil retained in the helical groove on the inner peripheral surface of the sleeve is prevented, and the shaft runout of the rotary shaft (oil whirl) is prevented.
And the stable pumping pressure is generated, the rotary shaft rotates with high accuracy. The vent hole releases the pushing pressure when assembling the rotary shaft and facilitates the assembly.

Further, by providing a relief portion on the inner surface of the sleeve so that the spherical edge portion at the end of the rotary shaft does not contact the inner surface of the sleeve, finishing of the edge portion can be omitted and durability can be improved.

[0012]

1 is a cross-sectional view of a motor portion of a flexible disk device including a medium rotating shaft and a bearing portion according to an embodiment of the present invention. In FIG. 1, 1 is a medium rotation axis
(Hereinafter referred to as a rotary shaft) is fixed to the inner peripheral portion of the hub 5 by press fitting, etc.
The peripheral edge of the aperture is fixed by tightening, so that the rotary shaft 1 and the rotor 6 are integrated via the hub 5 and can rotate. A magnet 9 is attached to the inner surface of the outer peripheral portion of the rotor 6 by adhesion or the like, and constitutes the rotor of the motor unit. On the other hand, a plurality of wound coils 8 are arranged on the stator 7 for each polarization to form a stator of the motor unit. When the winding coil 8 is energized, the magnet 9 receives a rotational force,
The rotor 6 rotates.

The sleeve 2 constituting the bearing portion is fixed to the base plate 51 with screws 52. The stator 7 is supported by the flange portion of the sleeve 2 and fixed by screws 50.
The thrust member 3 is fixed to the bottom of the sleeve 2 by squeezing and supports the end of the rotary shaft 1. And sleeve 2
A herringbone type helical groove 4 is provided on the inner peripheral surface of, and lubricating oil is applied. Further, in order to generate a magnetic thrust force, the magnet 9 and the stator 7 are arranged such that the end of the rotary shaft 1 abuts on the thrust member 3 in a state where the height direction is slightly shifted.

FIG. 2 shows details of the bearing portion. The sleeve 2 is positioned around the inner peripheral hole of the stator 7, and the stator 7 is positioned on the upper surface of the flange portion 21 as shown in FIG.
, And the board 51 is screwed to the lower surface. As shown in FIG. 2 (b), the bottom of the sleeve 2 is provided with a spot facing portion 22 and a narrowing portion 23. After inserting the thrust member 3 into the spot facing portion 22, the narrowing portion is crushed to thrust. The member 3 is held and fixed.

The end of the rotary shaft 1 is a spherical surface 11 whose radius of curvature is 0.75 to 2 times the shaft diameter. Sphere 11
The tip of the abuts against the thrust receiving surface 31 of the thrust member 3 and is supported. The edge portion 12 at the boundary between the outer peripheral surface of the rotating shaft 1 and the spherical surface 11 is slightly apart from the thrust receiving surface 31. The thrust member 3 is provided with a ventilation hole 32 at a position separated from the spherical surface 11 of the rotating shaft 1.

As shown in FIG. 2B, a herringbone type helical groove 4 which is vertically arranged in two stages is provided on the inner surface of the bearing portion, and 6 to 12 helical grooves are formed respectively. The angle θ is 10 to 20 °. Further, the upper and lower helical grooves 4a and 4b are provided with different axial widths, and each retains lubricating oil and supports the rotary shaft 1 in the radial direction.

On the inner surface of the bearing portion, a relief processing portion 24 on the upper side,
The relief processing portion 25 between the upper and lower helical grooves 4a and 4b,
A bottom relief processing portion 26 is provided. This is for facilitating the escape of the tool and the insertion of the rotary shaft 1 when assembling the herringbone type helical groove 4. Further, the relief processing portion 25 between the helical grooves 4a and 4b is machined sufficiently deeper than the depth of the helical groove to stabilize the pressure of the lubricating oil held in the helical groove 4.

FIG. 3 shows another embodiment of the relief processing portion at the bottom of the inner surface of the bearing portion. The height of the relief processing portion 28 from the thrust receiving surface 31 of the thrust member 3 is determined by Since it is slightly higher than the edge portion 12 of the spherical surface 11, the inner surface of the bearing portion does not come into contact with the edge portion 12.

FIG. 4 shows the thrust member 3.
The material is cermet (for example, TC50 manufactured by Kyocera), and the ventilation hole 32 is opened by the mold at the time of molding. At least the thrust receiving surface 31 is surface-finished by lapping or fluid polishing. Thrust member 3
The thickness of this example is as thin as approximately 0.4 mm in this embodiment, but since it is a cermet, it has sufficient strength against fixation by squeezing and drop impact force.

Next, the operation of the above embodiment will be described. When the winding coil 8 is energized, the rotor 6 rotates. Therefore, the rotary shaft 1 fixed to the rotor 6 rotates. The clearance between the rotating shaft 1 and the inner surface of the bearing is set to a few μm, and the herringbone type hollow groove 4 in two stages above and below the inner surface of the bearing is used.
The lubricating oil is retained in the
Pressure is applied to the lubricating oil, and the oil film can support the rotary shaft 1 with high accuracy without contact with the inner surface of the bearing portion. Further, as in this embodiment, the distribution of hydraulic pressure is optimized by changing the ratio of the number of helical grooves, the angle θ, and the width to the upper and lower sides, so that the bearing rigidity can be increased.

The thrust member 3 made of cermet
Is fixed to the bottom of the sleeve 2 by tightening, and the thrust receiving surface 31 contacts the end spherical surface 11 of the rotary shaft 1 to support the thrust. Since the thrust receiving surface 31 and the spherical surface 11 are substantially in point contact with each other and are lubricated with the same oil as the lubricating oil of the helical groove 4 (for example, fluorine-based synthetic oil), the thrust receiving surface 31
By combining the finishing process of 1) with the spherical surface 11 of the rotary shaft 1, thrust can be supported with low friction and, at the same time, durability can be improved.

Further, the vent holes 32 of the thrust member 3 prevent pressure changes inside the bearing during shaft rotation, obtain smooth rotation, and at the same time release pressure when the rotary shaft 1 is assembled, facilitating assembly.

As described above, according to the above-described embodiment, the radial direction of the rotary shaft 1 is supported by the two-stage herringbone type helical groove 4 provided on the inner surface of the bearing through the oil film of the lubricating oil held therein. The rotary shaft 1 does not come into contact with the sleeve 2, has a small shaft runout, is supported with high accuracy, and has the advantage of being excellent in durability. Furthermore, since there is no contact, there is an effect that noise during rotation can be reduced.

Further, by using a cermet for the thrust member 3, there is an effect that the thrust member 3 can be fixed to the bottom portion of the sleeve 2 by tightening, and the bearing portion can be made thinner. Furthermore, due to the high hardness of the cermet, the optimal finish of the thrust receiving surface 31, and the spherical surface 11 at the end of the rotary shaft 1, the same lubricating oil as that of the helical groove 4 can be used, and thrust is supported with low friction. Has the effect of increasing durability.

Further, the relief processing portion on the inner surface of the bearing portion and the vent hole of the thrust member 3 stabilize the pressure of the lubricating oil during rotation, and at the same time, quickly eliminate air bubbles in the oil to suppress shaft runout and smooth it. It has the effect of obtaining proper rotation. Further, the pressure at the time of assembling the rotary shaft 1 is also released, which has the effect of facilitating the assembly.

When the bearing length is short, the bearing rigidity can be adjusted by appropriately selecting the clearance between the rotating shaft 1 and the inner surface of the bearing and the viscosity of the lubricating oil, and the flexible disk device can be made thinner. It has the effect of being able to.

[0027]

As is apparent from the above embodiment, the present invention supports a medium rotating shaft for rotating a disk-shaped magnetic recording medium by a dynamic pressure type fluid radial bearing, and makes the end portion of the rotating shaft spherical. Thrust bearing by abutting against the thrust member and lubricating the radial bearing part and the thrust receiving part with the same lubricating oil to improve thrust accuracy of the medium rotating shaft, and with a simple and short bearing. It was made feasible.

Further, by providing the vent member in the thrust member, it is possible to stabilize the pressure in the bearing portion and obtain smooth rotation, and to relieve the pressure when assembling the shaft to facilitate the assembly. .

Further, since a cermet is used as the thrust member and the end spherical surface of the medium rotating shaft is thrust-supported, the thrust bearing can be received with low friction and the durability can be enhanced, and the thrust member can be made into a sleeve. Since it can be fixed to the bottom portion by squeezing, there is an effect that the bearing portion can be thinned.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a motor unit including a medium rotation shaft and a bearing unit of a flexible disk device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the medium rotation shaft, a bearing portion, and a herringbone type helical groove of the bearing portion.

FIG. 3 is a cross-sectional view of another embodiment of the relief processing portion at the bottom of the bearing portion.

FIG. 4 is a plan view and a sectional view of a thrust member.

[Explanation of symbols]

1 ... Rotating shaft, 2 ... Sleeve, 3 ... Thrust member,
4 ... Herringbone type helical groove, 11 ... Shaft end spherical surface, 12 ... Edge portion, 28 ... Relief processing portion, 32 ... Vent hole.

Claims (4)

[Claims] 1. A rotary shaft for rotating a disk-shaped magnetic recording medium for recording / reproducing is supported in a radial direction by a dynamic pressure type radial fluid bearing in which a lubricant is held in a helical groove provided on an inner surface of a sleeve, In a flexible disk device in which a shaft end portion is thrust-supported by a thrust member, the thrust member is made of cermet, and the thrust member is provided with a vent hole for ventilating the inside and the outside of the sleeve. Flexible disk device. 2. The end of the rotary shaft that comes into contact with the thrust member is spherical, and the radius of the spherical surface is 0.75 to the axial diameter of the rotary shaft.
The flexible disk device according to claim 1, wherein the flexible disk device is doubled in number. 3. A relief processing portion is provided on the inner surface of the sleeve so that the edge portion of the boundary between the outer peripheral surface of the rotation shaft and the spherical surface of the end portion of the rotation shaft does not contact the inner surface of the sleeve. Item 2. The flexible disk device according to item 2. 4. The flexible disk device according to claim 2, wherein the same thrust oil as that used for the radial bearing portion is used for the thrust receiving portion.