JP2000291646A - Bearing mechanism, and hard disc driving mechanism and polygon mirror driving mechanism using the bearing mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing mechanism capable of generating the sufficient radial dynamic pressure even in a zone of a comparatively low speed, and easily and inexpensively executing the surface working to generate the radial dynamic pressure. SOLUTION: The dot-like fine irregularity is dispersedly formed on at least one of an outer peripheral surface 2a of a first member and an inner peripheral surface 3a of a second member (herein after a roughed surface), opposite to one another through a bearing clearance G filled with the liquid to rough the surface, and its central line average roughness Ra is adjusted within a range of 0.1-1.0 μm. According to this construction, as the sufficient radial dynamic pressure can be generated at a comparatively low speed of rotation, a time of the dynamic pressure insufficient condition in the starting or stopping of a rotating mechanism can be shortened, and the components in the bearing part are hardly abraded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a bearing mechanism, a hard disk drive mechanism and a polygon mirror drive mechanism using the same.

[0002]

2. Description of the Related Art Conventionally, dynamic pressure bearings have been employed in hard disk drive mechanisms of storage devices, polygon mirror drive mechanisms of copiers, laser printers, and the like in order to realize rotation with little whirling. There is. As such a dynamic pressure bearing, for example, Japanese Unexamined Patent Publication No.
As disclosed in Japanese Patent No. 15128, a rotating shaft is inserted inside a cylindrical bearing body, and a herringbone-shaped dynamic pressure generating groove is formed in the outer circumferential surface of the rotating shaft in the circumferential direction. Things are known. In this structure, when the rotating shaft is rotated at a high speed inside the bearing body, a radial dynamic pressure is generated in a gap between the rotating shaft and the bearing body due to a pumping action of the fluid to the dynamic pressure generating groove, for example, vibration or other disturbance. Therefore, when a radial force acts on the rotation axis, the dynamic pressure acts as a restoring force, so that stable rotation with little whirling can be realized.

[0003]

However, the mechanism using the herringbone-shaped dynamic pressure generating grooves employed in the above-mentioned conventional dynamic pressure bearings is not sufficient unless the high-speed rotation of 10,000 to 20,000 rotations is normally performed. Radial dynamic pressure does not occur,
Problems such as running out of oil due to high-speed operation are more likely to occur. In addition, in a low-speed rotation state when the rotation mechanism is started or stopped, the bearing portion and the rotating shaft come into contact with each other due to insufficient dynamic pressure, which is likely to cause wear. Although a hydrodynamic bearing that generates radial dynamic pressure in the form of air pressure without using lubricating oil has also been proposed, in the case of using air pressure, according to the study of the present inventors, sufficient radial dynamic pressure has been proposed. In order to generate the pressure, a higher speed of 40,000 to 50,000 revolutions or more is required, and the above problem is further promoted.

An object of the present invention is to provide a bearing mechanism which can generate a sufficient radial dynamic pressure even in a relatively low-speed region, and which can be easily manufactured at a low cost with easy surface processing for generating the radial dynamic pressure. It is to provide a hard disk drive mechanism and a polygon mirror drive mechanism.

[0005]

In order to solve the above-mentioned problems, a bearing mechanism according to the present invention has a shaft-shaped first member and an insertion hole through which the first member is inserted. A predetermined amount of liquid-filled bearing gap between the inner surface of the insertion hole and the outer peripheral surface of the first member in a state where relative rotation of the first member around the axis in the insertion hole is allowed. A second member forming a, at least one of the outer peripheral surface of the first member and the inner peripheral surface of the second member opposed thereto,
By scattering and forming minute irregularities in the form of dots, the center line average roughness Ra is set to 0.1 μm to 1.0 μm.
m, the first member and the second member are relatively rotated to generate a radial dynamic pressure around the first member in the bearing gap. I do. In the present invention, the center line average roughness Ra means a value measured by a method defined in Japanese Industrial Standard B0601.

Further, the hard disk drive mechanism of the present invention provides a bearing mechanism as described above, and one of the first member and the second member of the bearing mechanism as a fixed side and the other as a rotating side. (Hereinafter, referred to as a rotating member), and a recording hard disk attached to the rotating member and rotating integrally therewith.

Further, a polygon mirror driving mechanism according to the present invention is a member which is on the rotating side with one of the first and second members of the bearing mechanism being the fixed side and the other being the rotating side. (Hereinafter, referred to as a rotating member) and a driving unit for rotating the driving member, and the driving member is integrated with the rotating member.
A polygon mirror in which a plurality of reflection surfaces are formed in a polyhedral shape so as to surround the rotation axis.

In the present invention, scattered minute irregularities are dispersedly formed on at least one of the outer peripheral surface of the first member and the inner peripheral surface of the second member opposed to each other with the bearing gap therebetween (hereinafter referred to as a roughened surface). By adjusting the center line average roughness Ra in the range of 0.1 μm to 1.0 μm, a sufficient radial dynamic pressure can be generated even in a relatively low-speed region. In addition, since sufficient radial dynamic pressure can be generated at a lower rotation speed compared to a conventional bearing mechanism using a conventional dynamic pressure generation groove, the time during which the dynamic mechanism becomes inadequate when starting or stopping the rotation mechanism. Can be shortened, and the member is less likely to be worn on the bearing portion.

Further, for example, there is an imbalance in the rotating shaft inserted into the inside of the cylindrical bearing body, or external disturbance such as external force or vibration occurs in the radial direction, so that the rotating shaft is periodically and non-performing. Periodic whirling occurs. If all of the whirling motions are periodic whirling motions, the position shifted by the whirling motions can be grasped in a fixed manner, and the rotation axis can be corrected. However, for the whirling that occurs aperiodically, the timing and the position are random, so that it is impossible to correct the whirling. However, in the bearing mechanism of the present invention as described above, the eccentricity of the aperiodic runout around the axis of the first member in the insertion hole can be kept within a small range of 20% or less.

[0010] The same effects as those of the present invention can be achieved in exactly the same manner when the fluid filled in the bearing gap is replaced with a gas such as air instead of a liquid. An equivalent invention can be expressed as follows: a shaft-shaped first member, and an insertion hole through which the first member is inserted, and the relative rotation of the first member around the axis in the insertion hole. In the allowed state, between the inner surface of the insertion hole and the outer peripheral surface of the first member,
A second member forming a predetermined amount of bearing gap filled with gas, and at least one of an outer peripheral surface of the first member and an inner peripheral surface of the second member opposed to the first member has a dotted shape. The surface roughness of the first member and the second member is adjusted by adjusting the center line average roughness Ra in a range of 0.1 μm to 1.0 μm by dispersing and forming the minute irregularities. The bearing mechanism generates a radial dynamic pressure around the first member in the bearing gap. Also in such a bearing mechanism, the range of the eccentricity of the aperiodic runout can be reduced to a range of 20% or less.

On the roughened surface facing the bearing gap, for example, as conceptually shown in FIG. 2 (in this case, reference numeral 2a indicates a roughened surface), scattered small irregularities are almost two-dimensionally formed. It is desirable that they are uniformly dispersed in order to generate a uniform radial dynamic pressure. Specifically, for example, when the center line average roughness Ra is measured along an arbitrary direction on a rough surface, for example, along any two directions orthogonal to each other,
The measured values are defined as Ra1 and Ra2, and the average value (Ra1 + Ra2) of the absolute value | Ra1−Ra2 |
2) / 2 ratio (2 × | Ra1-Ra2 | / (Ra1
+ Ra2)) is preferably within 30%.

In the present invention, it is desirable that the relative rotation speed between the outer peripheral surface of the first member and the inner peripheral surface of the second member for generating a sufficient radial dynamic pressure is adjusted to approximately 2000 rpm or more. . When the rotational speed is less than 2000 rpm, the generated dynamic pressure is insufficient, and the member is easily worn due to an increase in contact friction. Further, in the bearing mechanism of the present invention, as described above, a sufficient dynamic pressure can be generated even in a low-speed rotation range (for example, about 2000 to 20000 rpm, or a still lower speed of about 2000 to 15000 rpm) than the conventional bearing mechanism. Has features. However, the present invention is not limited to the range of the number of rotations, and can be sufficiently applied to, for example, a bearing portion that rotates at a high speed at or above the above speed. It is possible to achieve a specific effect that the life is extended.

In the present invention, the reason why the dynamic pressure can be generated at a lower speed as compared with the conventional bearing mechanism using the dynamic pressure generating groove is that the outer peripheral surface of the first member and the inner peripheral surface of the second member opposed thereto are generated. The liquid existing in the bearing gap between the outer peripheral surface of the first member and the inner peripheral surface of the second member is led to the gap narrowed by the convex portion by dispersing and forming the above-mentioned minute unevenness on at least one of the above. It is considered that the wedge film effect that occurs when this occurs is contributed. The wedge film effect is caused by the local narrowing of the gap when the first member and the second member are relatively eccentric, so to speak, by a macroscopic factor. The effect works synergistically,
It is considered that the dynamic pressure generating effect is further enhanced. In addition, since the irregularities are formed in a much finer dispersion than the conventional dynamic pressure generating grooves, a more uniform and high-level wedge film effect can be expected.

On the other hand, with respect to the improvement of the sealing property, a minute labyrinth effect is generated when the liquid passes between the irregularities of the bearing gap because minute irregularities are dispersedly formed on the facing surface of the bearing gap. It is considered that the sealing property between the outer peripheral surface of the first member and the inner peripheral surface of the second member is improved.
The effect of improving the sealing performance becomes more remarkable by adjusting the center line average roughness Ra in the range of 0.15 μm to 0.2 μm. Thus, for example, even when high-speed rotation is required, the radial dynamic pressure is less likely to be insufficient, and rotation that is smooth and has less whirling can be realized. In addition, as a specific configuration for allowing the radial dynamic pressure to be used as a restoring force of the rotation axis, the first member is provided in a form in contact with a supported portion formed on the second member side. A mode in which a rotation support portion that rotatably supports the second member while allowing the second member to move in the radial direction within the range of the bearing gap can be exemplified.

Next, the fine irregularities in the form of scattered spots formed on the roughened surface may be formed, for example, by using a bombardment particle having an average particle diameter adjusted in the range of 5 to 100 μm by forming the roughened surface portion (the above-described roughened surface forming surface). Part) at a speed of 50 m / sec to 300 m / sec. According to this method, it is possible to easily perform a surface roughening process in which minute irregularities in the form of dots are dispersedly formed, and it is possible to reduce the processing cost as compared with, for example, groove processing by photoetching or the like.

As the impact particles, by using particles harder than the material constituting the surface to be formed, it is possible to efficiently form unevenness. For example, when the material of the forming surface portion is an Fe-based material, as the material of the hard particles, ceramic particles such as silicon carbide, alumina, zirconia, silicon nitride, glass particles, high-speed tool steel, stainless steel (for example, high carbon Metal particles such as stainless steel) can be used. In addition, even when the impact particles which are not harder than the forming surface portion are used, the unevenness may be formed in some cases. For example, in the case where irregularities can be formed by using striking particles (for example, particles of high-speed tool steel or stainless steel) that are not harder than the forming surface portion, if they have a hardness of 50% or more of the forming surface portion hardness. There are many.

It is particularly desirable to use spherical particles as the shape of the impact particles in order to uniformly disperse and form fine irregularities. In this case, it is more advantageous to use spherical particles having a uniform size as much as possible because the impact force can be made uniform. Specifically, when the average particle size of the impact particles used is dm and the standard deviation of the particle size d is σd, σd / dm is preferably less than 0.05. In addition,
In order to generate a uniform radial dynamic pressure, it can be said that it is desirable to suppress variations in individual uneven shapes and dimensions.In this case, for example, by repeatedly projecting impact particles onto the It is effective to form.

Next, in the present invention, in order to sufficiently increase the radial dynamic pressure generating effect, the cylindrical outer peripheral surface radius of the first member is r1, and the cylindrical inner peripheral surface radius of the second member is r2. Then, it is desirable to adjust the value of r2-r1 in the range of 0.2 to 20 µm. r2-r1 is a parameter reflecting the size of the bearing clearance, which is 0.2 μm.
If it is less than m, the outer peripheral surface of the first member and the inner peripheral surface of the second member are likely to come into contact with each other, and the member may be easily worn due to increased friction. On the other hand, when r2-r1 exceeds 20 µm, the sealing performance of the gap is impaired, and the generated dynamic pressure may be insufficient. The value of r2-r1 is more preferably 4 μm
The thickness is preferably 10 to 10 μm. Note that when r1 and r2 are measured for the diameter D1 or D2 while changing the measurement position with respect to the outer peripheral surface or the inner peripheral surface, the maximum measured value of D1 is D1max, and the minimum measured value of D2 is D2min. It means the values calculated at D1max / 2 and D2min / 2, respectively.

Next, assuming that the outer peripheral radius of the first member is r1, the inner peripheral radius of the second member is r2, and the cylindricity of each surface is C, C ≦ (r2−r1) / 2 is satisfied. It is desirable to have. When C is larger than (r2-r1) / 2, the outer peripheral surface of the first member and the inner peripheral surface of the second member are likely to be in contact with each other, and the member may be easily worn due to increased friction. In the present invention, the cylindricity is based on Japanese Industrial Standard B0621.
Adopt the one defined in 5.4.

Next, the center line average roughness R peculiar to the present invention will be described.
The roughened surface having a can be formed very easily because, for example, the above-described processing by the hard particle projection is easily applied to the outer peripheral surface of the shaft-shaped first member. In this case, the inner peripheral surface of the second member has at least a center line average roughness Ra of 1.
It can be said that adjustment to 0 μm or less is desirable from the viewpoint of avoiding member wear due to increased friction. In order to further enhance the effect of preventing the rotational axis from whirling due to the generation of the radial dynamic pressure, it is more preferable that the inner peripheral surface of the second member be the same roughened surface.

In addition, at least one of the outer peripheral surface of the first member and the inner peripheral surface of the second member opposed to the first member has the above-mentioned scattered minute irregularities and a groove portion contributing to the generation of radial dynamic pressure. You can also. By adding such a groove, the effect of preventing whirling due to the generation of radial dynamic pressure can be further enhanced.

[0022]

Embodiments of the present invention will be described below with reference to embodiments shown in the drawings. (Embodiment 1) FIG. 1 shows an example of a hard disk drive mechanism using the bearing mechanism of the present invention. The hard disk drive mechanism 100 includes a fixed shaft 2 as a first member attached to a base 8 by bolts 9 in a form rising from one surface thereof, and a rotating member as a second member rotatably disposed outside the base. 3, and the fixed shaft 2 and the rotating member 3 constitute a main part of the bearing mechanism 1.

The outer peripheral surface 2a of the fixed shaft 2 is a cylindrical surface,
The diameter of the base end portion is increased by a circumferential step surface 2c formed at an intermediate position in the axial direction. A bearing 7 is fitted on the outside of the fixed shaft 2a, and is supported by a step surface 2c. The rotating member 3 is provided with an insertion hole 3 in the axial direction.
The fixed shaft 2a is formed in a tubular shape having a, and the distal end side of the fixed shaft 2a is inserted into the insertion hole 3a, and one end surface is rotatably supported by a bearing 7. A bearing gap G is formed between the inner peripheral surface of the insertion hole 3a and the outer peripheral surface 2a of the fixed shaft 2. This bearing gap G is
It is in a state filled with lubricating oil, water and the like (that is, liquid). A male screw portion 2b protrudes from the tip end surface of the fixed shaft, and a ring-shaped stopper 13 having a screw hole 13a is screwed into the male screw portion 2b to prevent the rotation member 3 from being removed.

The bearing 7 supported on the stepped surface 2c of the fixed shaft 2 as the first member abuts on the end surface (supported portion) of the rotating member 3 as the second member, and the bearing gap of the rotating member 3 While allowing movement in the radial direction in the range of G, it functions as a rotation support portion that rotatably supports the movement.

Next, an annular fixing rib 8a protrudes from the center of the plate surface of the base portion 8, and the fixed shaft 2
Is fitted, and a cylindrical coil holder 10 is fitted on the outside of the fixing rib 8a. A coil unit 11 composed of a ring-shaped core 11a and a plurality of coils 11b wound around the core 11a at predetermined intervals in the circumferential direction is fixedly fitted further outside the coil holder 10. I have.

On the other hand, a cup-shaped disk holder 4 is attached to the rotating member 3 on the end face opposite to the side facing the bearing 7. The disk holder 4 has a top surface 4a formed flat, the tip of the fixed shaft 2 protruding at the center thereof, and is fixed to the rotating member 3 by bolts 5 at the top surface. The side wall portion 4b of the disk holder 4 extends in a skirt shape to a position covering the coil unit 11 in the axial direction of the fixed shaft 2, and a plurality of data recording hard disks 6 are mounted on the outer peripheral surface via spacers 6a. A plurality of permanent magnets 12 are mounted on the inner peripheral surface at predetermined positions in the circumferential direction at positions facing the coil unit 11.
These permanent magnets 12 constitute a drive motor section (drive section) together with the coil 11b attached to the coil unit 11, and the rotating member 3, the disk holder 4 and the hard disk 6 attached thereto are fixed to the fixed shaft 2 Plays a role to rotate integrally around.

Next, the inner peripheral surface of the insertion hole 3a of the rotating member 3 and the outer peripheral surface 2a of the fixed shaft 2 (for example, a portion facing the inner peripheral surface of the insertion hole 3a) are provided on at least one of them.
As schematically shown in FIG. 2 (a), fine irregularities Q
Are dispersed and the center line average roughness Ra is 0.1 μm.
To 1.0 μm, preferably 0.15 to 0.2 μm.

For example, as a method of roughening the outer peripheral surface 2a of the fixed shaft 2 as described above, a method of projecting impact particles B from an injection nozzle N as shown in FIG. In this embodiment, the injection nozzle N is moved forward and backward in the direction of the axis while rotating the fixed shaft 2 around the axis, so that the entire outer peripheral surface 2a is uniformly hit.

On the other hand, as shown in FIG. 5B, with respect to the inner peripheral surface of the insertion hole 3a, an injection nozzle N is inserted into the insertion hole 3 and the nozzle N is moved in the axial direction while ejecting the impact particles B. An example of a method of giving a blow by moving forward and backward can be exemplified. Further, as shown in FIG. 5 (c), the injection port of the injection nozzle N is positioned at one opening of the insertion hole 3a, and the impact particles B are sucked into the insertion hole 3a from the opening on the opposite side, and A method of injecting is also possible.

The impact particles B have an average particle diameter of 5 to 100 μm.
m is used, and the injection pressure from the nozzle N is adjusted so that the projection speed on the roughened surface (the uneven surface) is 50 m / sec to 300 m / sec. As described above, the shape of the impact particles B is preferably spherical, and it is desirable to use particles having a uniform diameter as much as possible. When the fixed shaft 2 or the rotating member 3 is made of alloy steel for machine structure (for example, Cr-Mo steel such as SCM440), the impact particles B are harder ceramic particles. For example, those configured as silicon carbide particles can be preferably used.

In this case, as shown in FIG. 2D, both the inner peripheral surface of the insertion hole 3a and the outer peripheral surface 2a of the fixed shaft 2 are
The surface may be roughened so as to satisfy 0.1 μm ≦ Ra ≦ 1.0 μm, or only one of the surfaces may be roughened as shown in FIG. However, the center line average roughness Ra of the other surface is desirably 1.0 μm or less.

Next, let the radius of the inner peripheral surface of the insertion hole 3a be r2,
The radius of the outer peripheral surface of a portion inserted into the insertion hole 3a of the fixed shaft 2 is defined as r1, and r2-r1 corresponding to the size of the bearing gap G.
Is adjusted to 0.2 to 20 μm (preferably 4 to 10 μm). The inner peripheral surface of the insertion hole 3a and the fixed shaft 2
When each cylindricity of the outer peripheral surface 2a is C, C ≦ (r2
−r1) / 2. In this embodiment, the specific dimensions of r2 and r1 are about 3 mm, and r2-r1 is 8 [mu] m. The axial length M of the insertion hole 3a is about 20 mm. The inner peripheral surface of the insertion hole 3a and the outer peripheral surface 2a of the fixed shaft 2 are each adjusted to have a center line average roughness Ra of about 0.19 μm.

In the hard disk drive mechanism 100 configured as described above, by operating the above-described drive motor section, for example, the rotating member 3 is moved from 4000 to 150
Rotate at a rotation speed of 00 rpm. Small irregularities as schematically shown in FIG. 2 are dispersedly formed on each of the surfaces 2a and 3a opposed to each other with the bearing gap G therebetween, and the center line average roughness Ra
Is adjusted to the above range, a dynamic pressure is generated in the bearing gap G in the radial direction of the fixed shaft 2, that is, in the radial direction. Then, even if a radial wobbling force acts on the rotating member 3 due to vibration or the like, the above-described radial dynamic pressure becomes a restoring force, and whirling hardly occurs. In the configuration of the present invention, since the rotation speed for generating a sufficient radial dynamic pressure is relatively low as described above, the fixed shaft 2 and the rotating member 3 are hardly worn. The mechanism is speculated as follows. That is, even if the above-mentioned run-out force acts, the bearing clearance G
It is considered that when the lubricating oil, water, and the like (ie, liquid) existing in the liquid crystal are introduced into the gap narrowed by the convex portions formed by dispersion, dynamic pressure is generated by a wedge film effect. Further, it is considered that when the liquid passes between the irregularities of the bearing gap, a labyrinth effect is generated, and the sealing property between the outer peripheral surface of the fixed shaft 2 and the inner peripheral surface of the rotating member 3 is improved.

FIG. 4 shows that the outer peripheral surface of the fixed shaft 2 constituted by the SCM 440 is firstly cut by a lathe, and
FIG. 3 shows an example in which the surface state after polishing in the circumferential direction with a diamond wheel of 000 is subjected to roughness analysis using an atomic force microscope, and the roughness distribution is three-dimensionally mapped. Since it is strongly rubbed and polished by the grinder rotating in one direction, it can be seen that a highly directional striped undulation is formed. With such a surface shape, generation of dynamic pressure becomes insufficient. On the other hand, FIG. 3 is a similar three-dimensional mapping showing the surface state after the spherical silicon carbide particles having an average particle diameter of 40 μm are projected at a projection speed of 200 m / s and roughened. It can be seen that the stripe-shaped undulations having directivity disappear, and instead, a large number of unevenness uniformly distributed two-dimensionally are formed. Note that the center line average roughness Ra of the surface after the treatment is 0.19 μm.

(Embodiment 2) FIG. 6 shows an example of a polygon mirror driving mechanism using the bearing mechanism of the present invention. The polygon mirror drive mechanism 200 includes a fixed shaft 50 having a base end buried in the base 58 so as to stand up from one surface thereof, a bearing member 52 non-rotatably integrated outside the base 58, and a bearing member 52a. And a polygon mirror 53 rotatably arranged outside the camera. The fixed shaft 50 and the bearing member 52a form a first member, and the polygon mirror 53 can be captured as an integrated second member (rotating member). The first member and the second member constitute a main part of the bearing mechanism 51.

The outer peripheral surface 52a of the bearing member 52 is a cylindrical surface, and thrust bearings 56, 56 having a diameter larger than that of the bearing member 52 are arranged on both axial sides thereof. The polygon mirror 53 has an insertion hole 53a in the axial direction, and a plurality of reflection surfaces 53c are formed in a polyhedral shape so as to surround the rotation axis O. Then, the bearing member 52 and the fixed shaft 50 are inserted into the insertion holes 3a, and the end faces on both sides are formed in the thrust bearings 56,5.
6 rotatably supported. And the insertion hole 5
A bearing gap G is formed between the inner peripheral surface of 3a and the outer peripheral surface 52a of the bearing member 52. This bearing gap G is
It is in a state filled with lubricating oil, water and the like (that is, liquid). The distal end of the fixed shaft 50 protrudes through the center of the disk-shaped magnet plate 59, and a male screw portion 52b is formed at the protruding portion, and a ring-shaped screw hole (not shown) is formed here. Are screwed. In addition, the thrust bearings 56, 56
In the same manner as described above, it functions as a rotation support unit for the polygon mirror 53.

Next, the fixed shaft 5 is provided on the plate surface of the base portion 58.
While a plurality of coils 54 are buried in a form surrounding 0, a plurality of permanent magnets 55 are attached to the end face of the polygon mirror 53 facing the same. These permanent magnets 55 constitute a drive motor section (drive section) together with the coil 54 on the base section 58 side, and play a role of integrally rotating and driving the polygon mirror 53 around the bearing member 5 (fixed shaft 50). Further, a plurality of permanent magnets 57 are attached to the plate surface of the magnet plate 57 facing the end surface on the opposite side of the polygon mirror 53 so as to surround the fixed shaft 50. The magnet 57 gives buoyancy due to the magnetic attraction to the polygon mirror 53, and serves to prevent the entire weight of the polygon mirror 53 from being applied to the thrust bearing 56.

The insertion hole 53 of the polygon mirror 53
As in the first embodiment, the inner peripheral surface of the inner peripheral surface a of FIG. 2A and the outer peripheral surface 52a of the bearing member 52 have minute irregularities Q in a scattered shape as schematically shown in FIG. Formed,
The surface is roughened so that the center line average roughness Ra is 0.1 μm to 1.0 μm, preferably 0.15 to 0.2 μm. The method of forming the roughened portion is exactly the same as that of the first embodiment, and thus a detailed description is omitted.

In the polygon mirror driving mechanism 200 configured as described above, the above-described driving motor section is operated, for example, to move the polygon mirror 53 to 1000
Rotate at a rotational speed of 0 to 40000 rpm. Since minute irregularities as schematically shown in FIG. 2 are dispersedly formed on each of the surfaces 52a and 53a opposed to each other with the bearing gap G interposed therebetween, and the center line average roughness Ra is adjusted to the above range. A dynamic pressure is generated in the bearing gap G in the radial direction of the fixed shaft 2, that is, in the radial direction. This radial dynamic pressure is applied to the polygon mirror 53.
To prevent whirling.

(Embodiment 3) In the bearing mechanism of the present invention, at least one of the outer peripheral surface of the first member and the inner peripheral surface of the second member opposed to the first member together with the scattered minute irregularities. Thus, a groove portion contributing to the generation of radial dynamic pressure can be formed. FIG. 7 shows an example. In the bearing mechanism 71, a bearing gap G is formed between the outer peripheral surface 72a of the fixed shaft 72 and the inner peripheral surface of the insertion hole 73a of the rotating member 73 disposed outside the fixed shaft 72. This fixed shaft 7
A row of grooves 72c for generating dynamic pressure is formed at a plurality of locations (two locations in this embodiment) in the axial direction on the outer peripheral surface of the workpiece 2. Each groove row is formed over the entire circumference at a predetermined interval so that the tip of the mountain-shaped (or boomerang-shaped) pattern of each groove 72c is located on the reference line BL in the circumferential direction of the fixed shaft 72. Yes (so-called herringbone form). A circumferential auxiliary groove 72d connecting one end of the groove 72c is formed for each row.

The entire outer peripheral surface 72a excluding the groove portions 72c and 72d includes a portion between adjacent grooves.
In the same manner as in the first or second embodiment, the above-described surface roughening process by dispersing and forming minute unevenness is performed. The method for forming the groove portions 72c, 72c is, for example, a method in which masking is performed on the outer peripheral surface 72d in such a manner that the groove pattern forming portion is exposed, etching is performed in that state, the groove pattern is cut, and then the masking is removed. Can be illustrated. On the other hand, a groove pattern may be carved by applying abrasion-resistant masking and performing shot blast grinding on an exposed portion. In any case, it is desirable that the roughening surface roughening process on the surface other than the groove is performed before the groove pattern is formed so that the formed groove pattern is not worn away.

[0042]

[Experimental Examples] In order to confirm the effects of the present invention, the following various experiments were performed. (Experimental Example 1) Using the apparatus shown in FIG. 8, the relationship between the surface roughness of both surfaces sandwiching the bearing gap and the bearing performance was examined under various conditions. First, the device 300 of FIG. 8 is provided on one end surface of a cylindrical shaft holder rotatably supported by a bearing.
Shaft 82 (first member) whose outer peripheral surface has been subjected to various surface roughening treatments
Are mounted so as to be integrally rotatable, and a cylindrical to-be-rotated body 83 having an insertion hole 83a, which has also been subjected to various surface roughening treatments, is mounted outside the shaft 82. The shaft 82
Are supported by bearings on both sides of the rotating body 83.

The rotating body 83 has an outer diameter of 30 mm, an insertion hole radius r2 of 3 mm, and an axial length of 2 in SCM440.
It is formed in a cylindrical shape of 0 mm. Also, the shaft 82 was adjusted by cutting so that its outer peripheral surface radius r1 had various values of r2-r1 (the size of the bearing gap G) of 0.19 to 21.0 [mu] m. The surface roughness of the cut surface is Ra = 0.
09 μm, Rmax = 1.2 μm, Rz = 0.9 μm. The inner peripheral surface of the insertion hole 83a and the outer peripheral surface 82a of the shaft 82 respectively have an average particle diameter of 40
~ 50μm spherical silicon carbide particles at a speed of 180m / sec ~
By projecting at 200 m / sec, the surface was roughened so that the center line average roughness Ra became various values of 0.07 to 1.5 μm. As a comparative example, the outer peripheral surface 82a of the shaft 8 is grind-polished in the circumferential direction (a diamond grindstone,
# 1000) A process was also prepared in which the inner peripheral surface of the insertion hole 83a was used as a drill cutting surface.

These are incorporated into the apparatus 300 of FIG.
The shaft holder and the shaft 82 are rotationally driven at various values of 4000 rpm and 8000 rpm by a servo motor via a belt, and the rotation of the shaft 82
Was measured. If the dynamic pressure is satisfactorily generated and the friction of the bearing is reduced, the entrainment force is reduced. Conversely, if the friction is increased, the entrainment force is increased. Incidentally, the measurement of the entrainment force was performed by fixing one end of the extruded S to the outer peripheral surface of the rotated member 83, extending it to the side opposite to the entrained direction, and using a load meter (not shown) attached to the other end. The measurement was performed by measuring the tension generated in S.

The sealing state of the bearing gap G was evaluated as follows. That is, as shown in FIG.
A measurement hole 83h (with an inner diameter of about 1.9 mm) communicating with the insertion hole 83a is formed in the wall of the rotated member 83, and the measurement hole 83 is formed.
The pressure difference H between the pressure in the bearing gap G, which rises due to the generation of dynamic pressure, and the external pressure in the U-shaped tube attached to the
Was read. If the sealing state of the bearing gap G is poor, the generated dynamic pressure leaks out of the gap and the pressure drops, so that the pressure difference H decreases.

As described above, with respect to the state of occurrence of friction, assuming that the co-rotating force is F, “の も の” indicates that F <50 g, and 50 g ≦ F.
<100 g: “○”; 100 g ≦ F <150 g: “△”; F ≧ 150 g: “×”. ”,“ ○ ”for 50 KPa ≦ H <100 kPa,“ △ ”for 10 kPa ≦ H <50 kPa,
A sample with H <10 kPa was evaluated as “×”. The results are shown in Tables 1 and 2.

[0047]

[Table 1]

[0048]

[Table 2]

That is, from the results in Table 1, the insertion holes 83a
By adjusting the center line average roughness Ra of the inner peripheral surface of the shaft 82 and the outer peripheral surface 82a of the shaft 82 within the range of 0.1 μm to 1.0 μm, rotational friction is reduced, and sealing performance is improved. You can see that there is. In particular, Ra is 0.15 to 0.2 μm
Within this range, extremely good sealing properties are achieved even at low speed rotation (4000 rpm). In addition, number 1
According to the results of 0 and 11, the inner peripheral surface of the insertion hole 83a,
Even if only one of the outer peripheral surfaces 82a of the shaft 82 satisfies the above roughness condition, relatively good results can be obtained.
By comparing with the results of Nos. 2 to 8, it is clear that better results can be obtained when both conditions are satisfied. On the other hand, in the case of No. 29 in Table 2 in which fine irregularities are not dispersedly formed, the result is quite unsatisfactory even though the roughness range satisfies the above conditions.

On the other hand, according to the results shown in Table 2, by adjusting the value of r2-r1 in the range of 0.2 to 20 µm, the generated friction particularly during high-speed rotation (8000 rpm) is reduced. It can be seen that the pressure generation situation becomes better.

It should be noted that the center line average roughness R of the roughened surface obtained by projecting silicon carbide particles having various average particle diameters on the shaft 82 at various speeds for 0.2 minute per treatment is obtained.
Table 3 shows the measurement results of a, maximum height Rmax, and 10-point average roughness Rz.

[0052]

[Table 3]

When the impact particles having an average particle diameter adjusted in the range of 5 to 100 μm are projected at a speed of 50 m / sec to 300 m / sec, roughness suitable for the present invention is obtained. I understand.

(Experimental Example 2) Using the same material as in Example 1,
The rotated member 83 has an outer diameter of 20 mm and an insertion hole radius r2 of 3 m.
m, a cylindrical shape having an axial length of 20 mm. The outer diameter of the shaft 82 was adjusted such that r2-r1 (the size of the bearing gap G) was 8 m. The inner peripheral surface of the insertion hole 83a and the outer peripheral surface 82a of the shaft 82 have an average particle diameter of 40 to 50 μm as impact particles, respectively.
At a speed of 180 m / sec to 220 m /
By projecting in seconds, the surface was roughened so that the center line average roughness Ra became various values of 0.01 to 0.3 μm. Two shafts 82 each having been subjected to the surface roughening treatment were prepared for each condition, and a groove having the same form as that shown in FIG. 7 was formed in one of them with the dimensions shown in FIG. These were assembled in the apparatus 300 of FIG. 8, and the results of the evaluation of the state of occurrence of friction and the sealing performance were similarly performed. Table 4 shows the results.

[0055]

[Table 4]

That is, it can be seen that the seal formed and the state of occurrence of friction are good in the case where the groove is formed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an example of a hard disk drive mechanism employing a bearing mechanism of the present invention.

FIG. 2 is an explanatory view schematically showing the state of the rough surface.

FIG. 3 is a diagram showing an example of three-dimensional mapping of a rough surface formed by hard particle projection.

FIG. 4 is a diagram showing three-dimensional mapping of a roughened surface of a comparative example formed by grinder polishing.

FIG. 5 is a diagram schematically illustrating some examples of a surface roughening process by hard particle projection.

FIG. 6 is a longitudinal sectional view showing an example of a polygon mirror driving mechanism employing the bearing mechanism of the present invention.

FIG. 7 is an explanatory view showing an example in which a groove is formed together with minute irregularities on a roughened surface.

FIG. 8 is a schematic view of a frictional force evaluation device for a bearing gap used in Experimental Examples 1 and 2.

FIG. 9 is a view for explaining the principle of evaluating the sealing performance of a bearing gap.

FIG. 10 is a diagram showing dimensions of a groove formed on the shaft side in Experimental Example 2.

[Description of Signs] 1 Bearing mechanism 2 Shaft (first member) 2a Outer peripheral surface 2b Mounting screw part 3 Rotating body (second member) 3a Insertion hole 4 Rotating disk holder 6 Hard disk 7 Bearing (rotation supporting part) 11 Coil 12 Permanent Magnet B Impact particles 50 Shaft 51 Bearing mechanism 52 Bearing member (first member) 52a Outer peripheral surface 52b Mounting screw part 53 Polygon mirror 53a Insertion hole 54 Coil 55 Permanent magnet 100 Hard disk drive mechanism 200 Polygon mirror drive mechanism

Continuation of the front page (72) Inventor Kazuo Kato 354-3 Kameshinata, Kawagoe-machi, Mie-gun, Mie Prefecture F term (reference) 3J011 AA04 BA02 CA03 5D109 BB05 BB13 BB17 BB21 5H607 BB01 BB14 BB17 BB25 CC01 DD03 EE10 GG01 GG12 KK10

Claims (8)

[Claims] A first member having a shaft shape, and an insertion hole through which the first member is inserted, and the insertion member being inserted in a state where relative rotation of the first member around the axis of the first member is allowed. A second member forming a predetermined amount of a bearing gap filled with liquid between the inner surface of the hole and the outer peripheral surface of the first member, wherein the outer peripheral surface of the first member and the The center line average roughness Ra is adjusted in a range of 0.1 μm to 1.0 μm by forming scattered minute irregularities on at least one of the inner peripheral surfaces of the two members in a dispersed manner to roughen the surface. A bearing mechanism wherein relative dynamic rotation of the first member and the second member generates a radial dynamic pressure around the first member in the bearing gap. 2. The center line average roughness Ra of at least one of an outer peripheral surface of the first member and an inner peripheral surface of the second member opposed thereto is adjusted in a range of 0.15 μm to 0.2 μm. The bearing mechanism according to claim 1. 3. A cylindrical outer peripheral radius of the first member is r.
3. The bearing mechanism according to claim 1, wherein r2-r1 is adjusted in a range of 0.2 to 20 [mu] m, where r2 is a cylindrical inner peripheral surface radius of the second member. 4. When the radius of the outer peripheral surface of the first member is r1, the radius of the inner peripheral surface of the second member is r2, and the cylindricity of each surface is C, C ≦ (r2−r1) / 2 is satisfied. Claim 1 which is satisfied
4. The bearing mechanism according to any one of claims 3 to 3. 5. The scattered minute irregularities are obtained by adjusting the impact particles adjusted to have an average particle diameter in the range of 5 to 100 μm at a speed of 50 m / sec to 300 m / sec with respect to the surface on which the irregularities are formed. The bearing mechanism according to any one of claims 1 to 4, wherein the bearing mechanism is formed by projection. 6. A groove that contributes to the generation of the radial dynamic pressure, along with the scattered minute irregularities, on at least one of an outer peripheral surface of the first member and an inner peripheral surface of the second member opposed thereto. The bearing mechanism according to any one of claims 1 to 5, wherein the bearing mechanism is formed. 7. The bearing mechanism according to claim 1, wherein one of the first member and the second member of the bearing mechanism is a fixed side and the other is a rotating side. A hard disk drive mechanism comprising: a drive unit that rotationally drives a member (hereinafter, referred to as a rotating member); and a hard disk that is attached to the rotating member and rotates integrally therewith. 8. The bearing mechanism according to claim 1, wherein one of the first member and the second member of the bearing mechanism is a fixed side, and the other is a rotating side. A driving unit for rotating a member (hereinafter, referred to as a rotating member), and a polygon mirror integrated with the rotating member and having a plurality of reflecting surfaces formed in a polyhedral shape so as to surround the rotation axis. A polygon mirror driving mechanism, comprising: