JP2622906B2 - Flexible disk drive - Google Patents

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, in a flexible disk drive of this kind, information is recorded and reproduced by rotating a rotating shaft of a recording medium with a ball bearing or an oil-impregnated metal bearing. In the above bearings, each bearing supports the radial direction, and the thrust direction is fixed and supported by bonding the shaft and the inner race of the ball bearing. Similarly, in the oil-impregnated metal bearing, the rotating shaft can be supported by inserting a plurality of washers between the hub fixed to the shaft and the oil-impregnated metal.

Further, the rotating shaft of the recording medium is changed to Japanese Patent Publication No. Sho 63-50564.
In the case of supporting with a hydrodynamic bearing device known in
Shaft (recording medium rotating shaft), an outer cylinder having a bottom wall at one end,
The bearing can be supported by a dynamic pressure bearing 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 drive, if the bearing length for supporting the rotating shaft is reduced due to the clearance between the rotating shaft and the inner diameter of the bearing or the radial clearance of the bearing, The rotation axis oscillates and the track centering accuracy of the recording medium decreases, and the function as the device is not satisfied. For this reason,
There is a problem that the device cannot be made thin.

Further, since the flexible disk drive has a lower rotation speed than that of a VTR or the like, when the thrust force of the rotating shaft is received by a hydrodynamic thrust bearing,
Since the bearing does not float due to low bearing rigidity, it is necessary to make the area of the shaft end of the rotary shaft larger than the cross section of the shaft or to form a tapered surface, which complicates the structure. Further, for the same reason, grease having high viscosity different from the lubricant of the radial bearing portion must be used for the thrust bearing, and two types of lubricants are used, which causes a problem in assemblability. .

SUMMARY OF THE INVENTION The present invention solves such a conventional problem. A flexible disk drive which can rotate a rotary shaft with high accuracy even if a bearing portion is short, and has a simple structure and good assemblability. The purpose is to provide.

[0007]

In order to achieve the above object, a flexible disk drive according to the present invention comprises a rotating shaft for rotating a disk-shaped magnetic recording medium for recording / reproducing.
In a flexible disk drive in which a helical groove provided on an inner surface of a sleeve holds a lubricant in a radial direction by a dynamic pressure type radial fluid bearing and a thrust member supports a shaft end in a thrust direction, the thrust member is made of a cermet. The thrust member is provided with a ventilation hole for ventilating the inside and outside of the sleeve.

In addition, the end of the rotating shaft that comes into contact with the thrust member is formed into a spherical surface, and the edge of the boundary between the outer peripheral surface of the rotating shaft and the spherical surface of the rotating shaft end is formed on the inner surface of the sleeve so as not to contact the inner surface of the sleeve. Provide a relief part.

[0009]

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

By providing a vent hole in the thrust member, the pressure of the lubricating oil held in the helical groove on the inner peripheral surface of the sleeve is prevented from changing, the shaft runout (oil whirl) of the rotating shaft is eliminated, and a stable pumping pressure is generated. By doing so, the rotating shaft rotates with high accuracy. The ventilation holes release the pushing pressure during assembly of the rotating shaft, and facilitate assembly.

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

[0012]

FIG. 1 shows a cross section of a motor section of a flexible disk drive including a medium rotating shaft and a bearing according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a medium rotation axis.
(Hereinafter, referred to as a rotating shaft), which is fixed to the inner peripheral portion of the hub 5 by press-fitting or the like.
Is tightly fixed by tightening, so that the rotating shaft 1 and the rotor 6 are integrated via the hub 5 and are rotatable. A magnet 9 is attached to the inner surface of the outer peripheral portion of the rotor 6 by bonding or the like, and forms a rotor of the motor unit. On the other hand, a plurality of coils 8 wound on the stator 7 are arranged for each polarization, and constitute a stator of a motor unit. When the winding coil 8 is energized, the magnet 9 receives rotational force,
The rotor 6 rotates.

The sleeve 2 constituting the bearing is fixed to the substrate 51 with screws 52. The stator 7 is supported by a flange portion of the sleeve 2 and is 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 rotating shaft 1. And sleeve 2
Is provided with a herringbone type helical groove 4 on its inner peripheral surface, and lubricating oil is injected. The magnet 9 and the stator 7 are configured such that the end of the rotating shaft 1 abuts on the thrust member 3 with the height direction being slightly shifted in order to generate a magnetic thrust force.

FIG. 2 shows details of the bearing portion. The sleeve 2 is positioned around the inner peripheral hole of the stator 7 and, as shown in FIG.
Then, the lower surface is screwed to the substrate 51, respectively. As shown in FIG. 2 (b), a counterbore portion 22 and a throttle portion 23 are provided at the bottom of the sleeve 2. After the thrust member 3 is inserted into the counterbore portion 22, the throttle portion is crushed and the thrust member is thrust. The member 3 is held and fixed.

The end of the rotating shaft 1 is a spherical surface 11 whose radius of curvature is machined to 0.75 to 2 times the shaft diameter. Spherical 11
Is in contact with and supported by the thrust receiving surface 31 of the thrust member 3. The edge 12 at the boundary between the outer peripheral surface of the rotating shaft 1 and the spherical surface 11 is slightly separated 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, on the inner surface of the bearing portion, there are provided two herringbone type helical grooves 4 in upper and lower stages, and 6 to 12 helical grooves are formed respectively. The angle θ is 10 to 20 °. The upper and lower helical grooves 4a and 4b have different widths in the axial direction, respectively, and hold the lubricating oil to support the rotary shaft 1 in the radial direction.

On the inner surface of the bearing portion, an upper relief portion 24,
A relief portion 25 between the upper and lower helical grooves 4a, 4b;
A bottom relief portion 26 is provided. This is for facilitating the escape of the tool and the insertion of the rotary shaft 1 during the assembling of the herringbone type helical groove 4. The relief portion 25 between the helical grooves 4a and 4b is processed sufficiently deeper than 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 clearance processing portion 28 from the thrust receiving surface 31 of the thrust member 3 is determined by the rotation shaft. The inner surface of the bearing portion is not in contact with the edge portion 12 because the inner surface of the bearing portion is slightly higher than the edge portion 12 of the spherical surface 11.

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

Next, the operation of the above embodiment will be described. When power is supplied to the winding coil 8, the rotor 6 rotates. Therefore, the rotating shaft 1 fixed to the rotor 6 rotates. The clearance between the rotating shaft 1 and the inner surface of the bearing portion is set to several μm, and the herringbone type helical groove 4 having two upper and lower stages on the inner surface of the bearing portion.
Holds lubricating oil, and by the rotation of the rotating shaft 1,
Pressure is applied to the lubricating oil, and the oil film allows the rotating shaft 1 to be supported with high accuracy without contact with the inner surface of the bearing portion. Furthermore, as in the present embodiment, the distribution of the hydraulic pressure is optimized by changing the number of the helical grooves, the angle θ, and the ratio of the width up and down, so that the bearing rigidity can be increased.

A thrust member 3 made of cermet
Is fixed to the bottom of the sleeve 2 by squeezing, and the thrust receiving surface 31 comes into contact with the end spherical surface 11 of the rotating shaft 1 to support the thrust. 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, a fluorine-based synthetic oil).
By the combination of the finishing work described above and the spherical surface 11 of the rotating shaft 1, the thrust can be supported with low friction and the durability can be enhanced.

Further, the ventilation hole 32 of the thrust member 3 prevents a change in pressure inside the bearing during rotation of the shaft, obtains smooth rotation, and at the same time, releases pressure when the rotating shaft 1 is assembled, thereby facilitating assembly.

As described above, according to the above embodiment, the radial direction of the rotating shaft 1 is supported via the oil film of the lubricating oil held by the two-stage herringbone type helical groove 4 provided on the inner surface of the bearing. The rotating shaft 1 has the advantages that it is not in contact with the sleeve 2, has small shaft runout, is supported with high precision, and has excellent durability. Further, 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, the thrust member 3 can be fixed to the bottom of the sleeve 2 by squeezing, so that the bearing can be made thinner. Furthermore, the high hardness of the cermet, the optimal finishing of the thrust receiving surface 31 and the spherical surface 11 at the end of the rotating shaft 1 allow the use of the same lubricating oil as that of the helical groove 4 and the thrust support with low friction. Has the effect of increasing durability.

In addition, the relief portion on the inner surface of the bearing portion and the ventilation hole of the thrust member 3 stabilize the pressure of the lubricating oil during rotation, and at the same time, quickly eliminate bubbles in the oil to suppress shaft runout and smoothly. This has the effect of obtaining a proper rotation. Furthermore, the pressure at the time of assembling the rotating shaft 1 is released, and there is an effect that the assembling is facilitated.

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

[0027]

According to the present invention, as is apparent from the above embodiment, the medium rotating shaft for rotating the disk-shaped magnetic recording medium is supported by a dynamic pressure type fluid radial bearing, and the end of the rotating shaft is made spherical. The radial bearing part and the thrust receiving part are lubricated with the same lubricating oil to support the thrust.Thus, the rotation accuracy of the medium rotating shaft is improved, and the structure is simple and short. It was made feasible.

The provision of the vent hole in the thrust member stabilizes the pressure in the bearing portion to obtain smooth rotation, and has the effect that the pressure can be released at the time of assembling the shaft to facilitate the assembly. .

Further, since a cermet is used for the thrust member and the end spherical surface of the medium rotating shaft is thrust-supported, the thrust can be received with low friction and the durability can be improved. Since the bearing can be fixed to the bottom by tightening, there is an effect that the bearing portion can be made thin.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a motor unit including a medium rotating 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 illustrating the medium rotating shaft, a bearing, and a herringbone type helical groove of the bearing.

FIG. 3 is a cross-sectional view of another embodiment of a relief portion at the bottom of a 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 ... Spherical surface of shaft end, 12 ... Edge part, 28 ... Escape part, 32 ... Ventilation hole.

Claims (4)

(57) [Claims] 1. A rotating shaft for rotating a disk-shaped magnetic recording medium for recording / reproducing is radially supported by a dynamic pressure type radial fluid bearing in which a helical groove provided on an inner surface of a sleeve holds a lubricant. In a flexible disk device in which a shaft end is thrust-supported by a thrust member, the thrust member is made of cermet, and the thrust member is provided with a ventilation hole for ventilating the inside and outside of the sleeve. Flexible disk device. 2. An end of a rotating shaft abutting on a thrust member has a spherical surface, and the radius of the spherical surface is 0.75 to 0.75 of the shaft diameter of the rotating shaft.
2. The flexible disk drive according to claim 1, wherein the number is twice as large. 3. A relief processing portion is provided on an inner surface of the sleeve so that an edge of a boundary between an outer peripheral surface of the rotary shaft and a spherical surface at an end of the rotary shaft does not contact the inner surface of the sleeve. Item 3. The flexible disk device according to Item 2. 4. The flexible disk device according to claim 2, wherein the same lubricating oil as the lubricating oil used for the radial bearing portion is used for the thrust receiving portion.