JP2002153015A - Oil dynamic-pressure bearing motor and motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil dynamic-pressure bearing and a motor, using a material with high machinability as a material for a disc retaining member and capable of preventing hydrogen sulphide gas from being produced, even if the disc-retaining member comes into contact with oil as lubricating fluid. SOLUTION: This oil dynamic-pressure bearing motor comprises a relative rotating bearing member 5 and a disc-retaining member 11, where oil is included as the lubricating fluid between the bearing member 5 and the disc-retaining member 11, and dynamic pressure is generated in the oil, when the bearing member 5 and the disc-retaining member 11 is rotated relatively. The bearing member 5 and the disc-retaining member 11 comes into contact with the oil through a micro clearance. The disc-retaining member 11 is formed out of stainless steel containing lead and has coating for inhibiting making contact with the lead, on a surface which comes into contact with the oil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil dynamic bearing motor and a motor having a shaft and a bearing member, wherein the shaft and the bearing member can rotate relative to each other without contacting each other. It can be used as a motor for driving a disk or the like, or as a motor for various devices requiring high rotational accuracy.

[0002]

2. Description of the Related Art As a motor for various devices requiring high rotational accuracy, a motor using a dynamic pressure bearing in a bearing portion is used. For example, in a hard disk drive, the recording density of a hard disk increases with the date and time, and accordingly, the rotational speed and rotational accuracy of the disk have become higher. In order to meet the demand for higher rotation speed and higher rotation accuracy of the disk, it is suitable to use a hydrodynamic bearing motor.

The structure of a conventional dynamic bearing motor for a disk drive is as follows. Insert the above-mentioned shaft member of the hub set, in which one end of the shaft member is joined and fixed to the center portion of the hub on which the disc is mounted, into the sleeve which has been subjected to the groove processing for radial dynamic pressure generation, The grooved thrust plate is fixed to the other end of the shaft member, the thrust plate is sandwiched between the counter plate and the sleeve, the counter plate is fixed to the sleeve, and a gap between the counter plate and the sleeve is formed. Sealing with an adhesive or the like forms a bearing set. Next, lubricating fluid is filled into the radial dynamic pressure bearing portion between the shaft member and the sleeve and the thrust dynamic pressure bearing portion between the thrust plate, the counter plate, and the sleeve, and the rotor is provided on the inner peripheral surface side of the peripheral wall of the hub. A magnet is fixed to form a rotor set. Furthermore, a base set in which insulating paper and a flexible wiring board are adhered to a base frame, and a core winding set in which a conductive wire is wound around a laminated core coated with insulating paint and used as a drive coil, is used as the base set. Assemble to form a stator set. By assembling the rotor assembly with the stator assembly, a disk drive fluid dynamic pressure motor is obtained.

In recent years, various devices using hydrodynamic bearing motors,
For example, in a disk drive motor, demands for high-speed rotation and high rotation accuracy and a demand for thinning have become severe, and accordingly, a dynamic bearing motor has also been required to be thin. Further, it is necessary to install a seal device for preventing leakage of the lubricating fluid at an axial end of the hydrodynamic bearing motor. For example, in the case of a capillary seal, it is necessary to secure a sufficient amount of lubricating fluid by increasing the depth dimension of the capillary seal in order to solve the problem caused by the evaporation of the lubricating fluid and improve reliability. However, increasing the depth dimension of the capillary seal becomes a hindrance factor for reducing the thickness of the hydrodynamic bearing motor.

[0005] The applicant of the present invention has assured the joint strength and bending strength and the rigidity of the dynamic pressure bearing by securing a sufficiently long joint length between the constituent members while reducing the overall thickness. A patent application was previously filed for a hydrodynamic bearing device capable of doing this. The invention described in the specification and drawings of Japanese Patent Application No. 11-239140 is one of them. Its structural feature is that it has a shaft member and a sleeve that rotate relative to each other, and a radial dynamic pressure bearing portion and a thrust dynamic pressure bearing portion are formed between the shaft member and the sleeve. The sleeve has a cylindrical portion for forming a radial dynamic pressure bearing portion and a projection for forming a thrust dynamic pressure bearing portion formed on the outer peripheral side of the cylindrical portion. The shaft member has a central shaft inserted into the cylindrical portion of the sleeve and an outer peripheral portion surrounding the projecting portion of the sleeve, and a radial member is provided between the outer peripheral surface of the central shaft and the inner peripheral surface of the cylindrical portion of the sleeve. A dynamic pressure bearing portion is formed, and a thrust dynamic pressure bearing portion is formed between an axially facing surface of the protrusion of the sleeve and a shaft member.

[0006] In addition to the invention according to the above-mentioned application, Japanese Patent Application No. Hei 11 (1999) -197, as an invention in which the overall thickness of the hydrodynamic bearing motor is reduced.
There is an invention described in the specification and drawings of Japanese Patent No. 272647. In short, these inventions provide a sufficient amount of lubricating fluid by moving the sealing device for preventing leakage of the lubricating fluid toward the outer periphery in the radial direction with respect to the shaft member, instead of providing the seal device at both ends of the shaft member. While ensuring the overall thickness.

Incidentally, the material of the hub holding the recording disk is preferably a material having a linear expansion coefficient substantially equal to the material of the recording disk mounted on the hub. For example, in the case of mounting a magnetic disk made of glass, Is
Ferrite stainless steel is generally used as a material for the hub. On the other hand, a hard disk drive (HDD) has become widespread as an external storage device of a computer or an image recording device for digital broadcasting, and demand for cost reduction has been required in accordance with a further increase in demand. However, further cost reductions must break through many technical barriers. In particular, stainless steel hubs
Not only good dimensional accuracy, but also good surface roughness is required, so high-precision CNC lathes are used to perform high-precision cutting, resulting in high parts costs and reduced motor costs. The proportion of parts cost occupied is quite high.

[0008] Therefore, in order to enhance the machining efficiency of a stainless steel hub or the like, stainless steel excellent in machinability (free-cutting property) is employed. In order to improve the machinability of steel materials such as stainless steel, sulfur (S), lead (P
The composition of the material is devised by adding a small amount of b), thermium (Te), selenium (Se), or reducing the content of carbon (C) and chromium (Cr).

However, lead added for improving the machinability of steel materials such as stainless steel is used as a lubricating fluid for a dynamic pressure bearing, for example, an ester type, a mineral oil type, or a polyalphaolefin (PAO) type. Due to the catalytic action of gelling the oil, under environmental conditions of long-term use at high temperatures, the viscosity of the oil gradually increases due to gelation, and the current value increases due to an increase in bearing resistance. Is
There was a problem that rotation performance deteriorated. In addition, the gelation further progresses to form a jelly-like shape, and the reliability of the bearing is remarkably reduced, for example, the bearing is seized.

[0010] In steel materials such as stainless steel, manganese (Mn) is usually added in order to improve the rollability or elongation during production and to improve the deep drawability during processing. In addition, sulfur (S) is added to improve machinability, and the sulfur combines with manganese and exists in the material as manganese sulfite (MnS). This manganese sulfite is easily decomposed, and water (H ₂ O)
Reacts with to generate hydrogen sulfide gas (H ₂ S). If the hydrogen sulfide gas adheres to the surface of the recording disk, it may cause a problem in recording and reproducing information. Particularly, in the case of a magnetic disk, the metal magnetic film formed on the disk surface and the magnetic film of the magnetic head are eroded, and the recording / reproducing performance is deteriorated.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. Oil is interposed between a relatively rotating bearing member and a disk holding member as lubricating fluid. In a motor that generates dynamic pressure between the bearing member and the disk holding member by the relative rotation of the bearing member and the disk holding member, the material of the disk holding member is made of a material having good machinability,
It is an object of the present invention to provide an oil dynamic pressure bearing motor and a motor in which the oil does not gel and the hydrogen sulfide gas is not generated even when the disk holding member comes into contact with oil as a lubricating fluid.

[0012]

According to the first aspect of the present invention,
It has a bearing member and a disk holding member that rotate relative to each other, and oil is interposed between the bearing member and the disk holding member as lubricating fluid, and a dynamic pressure is generated in the oil when the bearing member and the disk holding member rotate relative to each other. In the oil dynamic pressure bearing motor, the bearing member and the disk holding member are in contact with oil through a minute gap, and the disk holding member is made of lead-containing stainless steel.
It is characterized by having a coating for preventing contact with the contained lead.

The disk holding member is made of lead-containing free-cutting stainless steel, so that the disk holding member can be finished with high precision. Further, since the disc holding member prevents the contained lead from contacting with the oil by the film, it is possible to prevent the gelation of the oil due to the reaction between the oil and the lead and the generation of hydrogen sulfide gas.

According to a second aspect of the present invention, in the first aspect of the present invention, the film is formed by subjecting the disk holding member to a base treatment in a wood bath and then performing electroplating or electroless plating. It is characterized by having.
Although it is generally difficult to plate stainless steel, plating can be performed relatively easily by applying electroplating or electroless plating after a base treatment in a wood bath.

According to a third aspect of the present invention, in the first aspect, the coating contains a solid lubricant or a wear-resistant material. When the film contains a solid lubricant or a wear-resistant material, the wear resistance and slidability of the disk holding member are improved.

According to a fourth aspect of the present invention, in the first aspect, the film is formed of a resin material. A film made of a resin material can be formed at a relatively low cost. It is even better to form the film with a resin having good oil resistance.

According to a fifth aspect of the present invention, in the first aspect of the invention, a thrust dynamic pressure bearing is formed between the disk holding member and an end surface of the bearing member. The disk holding member can also be used as a component of the thrust dynamic pressure bearing, so that cost reduction and thinning of the oil dynamic pressure bearing motor can be achieved.

According to a sixth aspect of the present invention, in the first aspect of the present invention, a capillary seal for preventing oil from scattering is formed between the disk holding member and the end face of the bearing member. . The oil storage space for the oil, which is the lubricating fluid of the oil dynamic pressure bearing, is expanded to the space between the disk holding member and the end surface of the bearing member. Thus, the reliability of the dynamic pressure bearing can be ensured.

According to a seventh aspect of the present invention, in the first aspect of the present invention, a capillary seal for preventing oil from scattering is formed between the ring-shaped projection of the disk holding member and the peripheral surface of the bearing member. It is characterized by being. The storage space for the oil, which is the lubricating fluid of the oil dynamic pressure bearing, is expanded between the ring-shaped projection of the disk holding member and the peripheral surface of the bearing member, while suppressing the expansion of the oil dynamic pressure bearing motor in the axial direction. It is possible to secure a sufficient amount of oil to secure the reliability of the dynamic pressure bearing.

According to an eighth aspect of the present invention, a rotor hub having a disk holding portion for holding at least one magnetic disk, the rotor hub is rotatably supported, and the rotor hub is rotated by an electromagnetic force generated between the rotor hub and the rotor hub. The rotor hub or the stator is made of stainless steel containing manganese sulfite, and the rotor hub or the stator is formed with a film for preventing contact between the manganese sulfite and moisture in the air. It is characterized by the following.

The rotor hub or the stator is made of stainless steel containing free-cutting manganese sulfite,
A highly accurate rotor hub or stator can be obtained. Stainless steel containing manganese sulphite generates hydrogen sulfide gas when it comes into contact with moisture, but a film is formed to prevent contact with moisture in the air, thus suppressing the generation of hydrogen sulfide gas can do.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an oil dynamic bearing motor and a motor according to the present invention will be described with reference to the drawings. Each of the illustrated embodiments is an example of an oil dynamic pressure spindle motor for a hard disk drive.

1 and 2, a motor frame 1 has a cylindrical portion 2 extending upward from a central portion, and a stator core 3 is fitted and fixed to the outer peripheral side of the cylindrical portion 2. The stator core 3 has a plurality of salient poles radially, and a driving coil 4 is wound around each salient pole. An insulating sheet 17 is laid on the upper surface of the motor frame 1 at a position facing the drive coil 4. A flexible circuit board 18 is provided in a concave portion formed on the lower surface side of the motor frame 1.
Is fixed, and an end line of the drive coil 4 is connected to the flexible circuit board 18 through a hole of the motor frame 1.

On the inner peripheral side of the cylindrical portion 2 of the motor frame 1, a cylindrical bearing member 5 is press-fitted and fixed. The shaft 8 is inserted on the inner peripheral side of the bearing member 5 with a small gap. A ring-shaped thrust plate 9 is integrally fixed to an outer periphery of a lower end portion of the shaft 8, and the thrust plate 9 is fitted with a gap in a large-diameter portion formed on an inner peripheral side of a lower end portion of the bearing member 5. . A counter plate 7 is fixed to the bearing member 5 at the lower end of the bearing member 5 by means such as caulking. The counter plate 7 is in close contact with the bearing member 5 so that the oil described below does not leak. There are minute gaps between the lower surface of the thrust plate 9 and the upper surface of the counter plate 7 opposed thereto, and between the upper surface of the thrust plate 9 and the ceiling surface of the large diameter portion of the bearing member 5 opposed thereto. . These minute gaps and the minute gap between the bearing member 5 and the shaft 8 communicating therewith are filled with oil as a lubricating fluid.

The inner peripheral surface of the bearing member 5 and the shaft 8 opposed thereto
A herringbone-shaped or spiral-shaped dynamic pressure groove is formed on at least one of the outer peripheral surfaces of the outer peripheral surface, and radial dynamic pressure bearings 10 and 20 are formed above and below, respectively. When the shaft 8 rotates relative to the bearing member 5, a radial dynamic pressure is generated in the oil at the radial dynamic pressure bearings 10 and 20, and the shaft 8 is supported in the radial direction without contacting the bearing member 5. You. Further, at least one of the lower surface of the thrust plate 9 and the upper surface of the counter plate 7 opposed thereto, and at least one of the upper surface of the thrust plate 9 and the ceiling surface of the large diameter portion of the bearing member 5 opposed thereto are herring. Bone-shaped or spiral-shaped dynamic pressure grooves are formed, and thrust bearings 15 and 16 are formed above and below the thrust plate 9. When the shaft 8 is relatively rotated with respect to the bearing member 5, a thrust dynamic pressure is generated in the oil in the thrust bearings 15 and 16, and the shaft 8 is supported in the thrust direction without contact with the bearing member 5 and the counter plate 7. You.

The upper end of the shaft 8 protrudes upward from the upper end surface of the bearing member 5, and the center hole of the rotor hub 11, which is a disk holding member, is pressed into the outer periphery of the protruding end, so that the shaft 8 and the rotor hub 11 are integrated. I have. The rotor hub 11 has a shape in which a flat cup is turned down, and a flange-shaped disk holding portion 12 is formed at a lower end on the outer peripheral side of the outer peripheral wall. At least one magnetic disk is held in the disk holding unit 12, and the magnetic disk is integrally attached to the rotor hub 11 by an appropriate clamp. Rotor hub 11
A rotor magnet 13 is fixed to the inner peripheral surface side of the outer peripheral wall of the rotor. The rotor magnet 13 has an N pole and an S pole alternately in the circumferential direction, and the energization of the drive coil 4 is controlled in accordance with the rotational position of the rotor magnet 13, so that the rotor magnet 13 is located between the rotor magnet 13 and the stator core 3. An electromagnetic force is generated, and the rotor hub 11 integrated with the rotor magnet 13, the shaft 8, and a magnetic disk (not shown) mounted on the rotor hub 11 are driven to rotate.

The outer peripheral portion of the upper end of the bearing member 5 has a small diameter, and the outer peripheral surface of the small diameter portion is a tapered surface 6 whose diameter continuously decreases from the upper side to the lower side in the axial direction. The upper end surface of the bearing member 5 and the lower surface of the rotor hub 11 face each other with a minute gap therebetween. The minute gap communicates with the radial dynamic pressure bearing 10 and the like. Oil is full. The tapered surface 6 is surrounded by a ring-shaped protrusion 14 integrally formed on the lower surface of the rotor hub 11, and a gap continuously extending from the top to the bottom between the tapered surface 6 and the ring-shaped protrusion 14. Are formed. This gap serves as a capillary seal for preventing the scattering of oil, and the oil is interrupted in this gap, and the end face of the oil is dented by surface tension. The surface tension acts to prevent the oil from leaking.

The magnetic disk mounted on the rotor hub 11 tends to use a glass disk in order to increase the recording density and improve the impact resistance. Glass discs have the advantage of better smoothness compared to aluminum discs. If the recording wavelength is shortened by floating the magnetic head with a gap of 0.02 μm or less from the disk surface, the surface recording density of the disk can be increased. For that purpose, it is essential to improve the smoothness of the disk surface. Also, even if the head comes into contact with the disk due to the application of an impact force or the like, the glass disk has the advantage that it is hard to be damaged due to its high hardness and recording and reproducing errors are hardly generated.

When a glass disk having the above advantages is used, a material having a linear expansion coefficient substantially equal to that of the glass disk is selected as the material of the rotor hub 11. By doing so, deformation of the disk due to temperature fluctuations in the use environment is eliminated, and troubles such as track deviation can be avoided. Ferritic stainless steel is a material that has almost the same linear expansion coefficient as that of a glass disk.
A ferritic stainless steel is used as the material of No. 1. FIG. 7 shows the composition of SUS430, which is a typical ferritic stainless steel, and sulfur free-cutting stainless steel SUS430 to which sulfur (S) is added to improve machinability.
3 shows the composition and properties of lead-free-cutting stainless steel obtained by adding lead (Pb) to SUS430F.

As is apparent from FIG. 7, the workability of a material obtained by adding sulfur and lead to stainless steel is better than that of a material obtained by adding only sulfur. Therefore, in order to increase the recording density, the material of the rotor hub 11 as the disk holding member is a free-cutting material obtained by adding sulfur and lead to stainless steel, and the rotor hub 11 is precisely machined. However, as described above, lead has a catalytic action to gel the ester-based, mineral-oil-based, and polyalphaolefin-based oils, which are the lubricating fluids for hydrodynamic bearings. It is necessary to avoid contact.

Therefore, in the embodiment shown in FIGS. 1 and 2,
On the surface of the rotor hub 11, which is the disk holding member, that comes into contact with the oil as the lubricating fluid, a coating is formed to prevent the lead contained in the rotor hub 11 from coming into contact with the oil. More specifically, an oil passage communicating from the radial dynamic pressure bearings 10 and 20 formed between the shaft 8 and the bearing member 5 to the capillary seal formed between the bearing member 5 and the rotor hub 11. And at least a portion of the rotor hub 11 facing the oil passage,
In order to prevent contact between the lead contained in the rotor hub 11 and the oil, a coating is formed so that the lead is not exposed.

The above-mentioned film can be formed by subjecting the rotor hub 11 to a surface treatment. There is plating treatment as an inexpensive surface treatment method. Stainless steel is a material that is hardly activated because its surface is covered with a passive film. Therefore, even if the plating treatment is directly performed, the plating is not performed well. Therefore, a base treatment is performed using a wood bath (nickel chloride + ammonium chloride) to form a base treatment layer. Electroplating or electroless nickel plating is performed thereon.

Sulfur is combined with manganese and exists as manganese sulfate (MnS). Manganese sulfate is easily decomposed and reacts with water to generate hydrogen sulfide gas. The hydrogen sulfide gas erodes the metal magnetic film formed on the surface of the magnetic disk and the magnetic film of the magnetic head, and deteriorates the recording / reproducing performance. As shown in FIG. 7, it is understood that a material having a higher ratio of manganese to sulfur (Mn / S) has a larger amount of gas generation. This has nothing to do with the amount of lead.

Therefore, it is necessary to reduce the area where manganese sulfate is exposed from the surface of the rotor hub 11 in order to reduce the gas emitted from the surface of the rotor hub 11 as the disk holding member. For this purpose, the surface of the rotor hub 11 is covered by the surface treatment such as plating as described above. Although the surface treatment is desirably performed on the entire surface of the rotor hub 11, a part of the surface of the rotor hub 11 may be surface-treated within a range that can satisfy the standard of the gas generation amount.

According to the above-described embodiment, the rotor hub 11 can be used as a lubricating fluid while improving the recording density of the disk by enabling precision machining by using a material having good machinability for the rotor hub 11. Even if it comes into contact with oil, it can prevent gelation of the oil,
Generation of hydrogen sulfide gas can be suppressed.

Next, different embodiments of the present invention will be described. In the embodiment shown in FIG. 3, a dynamic pressure groove is formed on at least one of the upper end surface of the bearing member 5 and the ceiling surface of the rotor hub 11 as a disk holding member opposed thereto, and the thrust dynamic bearing 21 is formed here. It is formed. A thrust dynamic pressure bearing 15 is also formed between the upper surface of the thrust plate 9 fixed to the lower end of the shaft 8 and the step of the bearing member 5 opposed thereto. As described above, since there are two thrust dynamic pressure bearings 21 and 15, the thrust plate 9 formed in the embodiment shown in FIGS.
Thrust dynamic bearing 16 between the bearing and the counter plate 7
Has been omitted. Other configurations are the same as those of the embodiment shown in FIGS.

Also in the embodiment shown in FIG. 3, the rotor hub 11 is provided with a coating for preventing contact with lead contained in the material of the rotor hub 11 on a surface of the dynamic pressure bearing which comes into contact with oil as a lubricating fluid. Therefore, the same effects as those of the embodiment shown in FIGS. 1 and 2 can be obtained.

In the embodiment shown in FIG. 4, the upper end face 22 of the bearing member 5 is inclined continuously downward toward the outside in the radial direction, and the inclined upper end face 22 and the disk holding member facing the inclined upper end face 22 are provided. A capillary seal 23 is provided between the rotor hub 11 and the ceiling surface to prevent oil, which is a lubricating fluid for a dynamic pressure bearing, from scattering. Other configurations are the same as those of the embodiment shown in FIGS. 1 and 2, and the same effects as those obtained by the embodiment shown in FIGS. 1 and 2 can be obtained.

In the embodiments described so far, the shaft rotates together with the rotor. In the embodiment shown in FIG. 5, the rotor rotates about a fixed shaft.
In FIG. 5, a shaft 38 is press-fitted and fixed in a hole at the center of the motor frame 31, and a bearing member 35 is rotatably fitted on the outer peripheral side of the shaft 38. Between the outer circumference of the shaft 38 and the inner circumference of the bearing member 35, there are radial dynamic pressure bearings 40, 5.
0 is formed. A thrust plate 39 is fixed to the outer periphery of the upper end of the shaft 38, and the thrust plate 39 is accommodated in a large diameter portion of the bearing member 35. A counter plate 37 is fixed to the upper end of the bearing member 35, and the upper end of the shaft 38 and the thrust plate 39 are sealed.
Upper surface of thrust plate 39 and counter plate 37
, A thrust dynamic pressure bearing 46 is formed between the lower surface of the thrust plate 39 and the step of the bearing member 35.

The motor frame 31 integrally has a cylindrical portion 32 so as to be positioned radially outward of the bearing member 35, and a stator core 33 is fitted and fixed to the outer peripheral side of the cylindrical portion 3. A drive coil 34 is wound around each of the plurality of salient poles of the stator core 33. The motor frame 31 has a step portion 48 formed radially inward of the cylindrical portion 32. The lower end of the bearing member 35 is a tapered portion 36 whose diameter becomes smaller and the diameter continuously increases from top to bottom. The tapered portion 36 fits inside the step portion 48, and the dynamic pressure bearing is formed. And a capillary seal 47 for preventing scattering of oil forming the lubricating fluid.

The outer periphery of the upper end of the bearing member 35 is
2, a rotor hub 41 as a disk holding member is press-fitted and fixed to the outer periphery of the upper end. A flange-shaped disk holding portion 42 is formed on the outer peripheral side of the peripheral wall of the rotor hub 41. A rotor magnet 43 is fixed to the inner peripheral side of the peripheral wall of the rotor hub 41.
The inner peripheral surface of the rotor magnet 43 and the outer peripheral surface of the stator core 33 face each other with an appropriate gap. By controlling the energization of the drive coil 34 according to the rotational position of the rotor magnet 43, the electromagnetic force generated between the rotor magnet 43 and the stator core 33 causes the rotor magnet 4 to rotate.
3. The rotating body including the rotor hub 41, the bearing member 35, and the counter plate 37 rotates integrally. The rotating body rotates in a non-contact manner by the radial dynamic pressure bearings 40 and 50 and the thrust dynamic pressure bearings 45 and 46.

According to the embodiment shown in FIG. 5, the rotor hub 41 does not directly contact the oil which is the lubricating fluid of the dynamic pressure bearing. However, it is desired that the rotor hub 41 be precisely machined by precision machining as described above. Therefore, as a material of the rotor hub 41, a free-cutting stainless steel containing manganese sulfite as described above is used. Is selected. However, the rotor hub 4
When the manganese sulfite contained in the material 1 is exposed, the manganese sulfite contacts the water in the air and reacts to generate hydrogen sulfide gas. The hydrogen sulfide gas causes the recording / reproducing performance to deteriorate as described above.

Therefore, even in the embodiment shown in FIG. 5, a film for preventing the contact between the contained manganese sulfite and the moisture in the air is formed on the entire surface or a part of the rotor hub 41. . In addition, as long as the material contains manganese sulfite, not only the rotor hub 41 but also the stator core 33, the bearing member 35, etc.
Since there is a possibility that hydrogen sulfide gas is generated upon contact with moisture in the air, a film for preventing contact between manganese sulfite and moisture in the air is formed on the surfaces of the stator core 33, the bearing member 35, and the like. Good.

As a method of forming a film, a method in which a stainless steel surface is subjected to a wood bath followed by nickel electroplating or electroless plating has been described above. However, a structure in which a portion between a rotor hub and a bearing member is used as a bearing is described. MoS ₂ containing molybdenum disulfide as a solid lubricant
-In some cases, self-lubricating properties are imparted by incorporating Ni plating or a fluororesin. Further, in order to improve abrasion resistance and slidability, SiC, TiC, WC, Al ₂ O ₃ , B
It is also effective to apply wear-resistant composite nickel plating containing hard fine particles such as N.

As a film forming method other than plating, a vapor deposition method (PVD), a chemical vapor deposition method (CVD), a thermal spraying method, or the like can be used. The vapor deposition method is also called a physical vapor deposition method, and includes vacuum deposition, sputtering, ion plating and the like. Thermal CVD, plasma C
VD, laser CVD and the like. According to these film forming methods, various films such as molybdenum disulfide, DLC, and SiO ₂ can be easily formed.

The coating formed on the rotor hub and other parts is not limited to a metal coating or a coating made of a ceramic material, but may be a resin coating. It is preferable to coat the oil contact portion with a resin such as epoxy or liquid crystal polymer having good oil resistance. For forming the resin film, a spray method, an injection method, or the like can be used.

The above description has been made on the assumption that a film is formed on the surface of the rotor hub and other parts in order to prevent contact between lead contained in stainless steel and oil or contact between manganese sulfite and moisture in the air. But
In some cases, another member may be added to the stainless steel material to prevent contact with oil or moisture in the air. That is the embodiment shown in FIG. The embodiment shown in FIG. 6 is basically the same as the embodiment shown in FIGS.
1 has a L-shaped cross section from the contact surface of the dynamic pressure bearing with oil which is a lubricating fluid, specifically, from the surface facing the upper end surface of the bearing member 5 to the surface facing the tapered surface 6 of the bearing member 5. This is a mold in which a ring-shaped press part 51 is bonded as a whole. The pressed part 51 is made of a material that does not contain lead or manganese sulfite. With such a configuration, the intended purpose can be achieved.

The present invention can, of course, achieve a predetermined effect by being applied to a motor having an oil dynamic pressure bearing. However, as described above, the rotor hub or the stator or the like contains stainless steel containing manganese sulfite. When steel is used, even if it does not have an oil dynamic pressure bearing, manganese sulfite reacts with moisture in the air to generate gas. In addition, it is effective to form a film that prevents contact with moisture in the air.

[0049]

According to the first to sixth aspects of the present invention, in the oil dynamic bearing motor, since the disk holding member is formed of lead-containing stainless steel, it has a lead free cutting property. Effects can be obtained.・ High-precision finishing of disc holding members.・ Reduction of tool cost due to extension of tool life.・ With the extension of tool life, the frequency of setup change is reduced and the operating rate of machining equipment is improved.・ Reduced capital investment due to improved occupancy rates.・ Improve productivity by reducing processing time.

The free-cutting stainless steel as described above gels the oil when the oil of the dynamic pressure bearing comes in contact with the lead contained therein. Since a film is formed on the contact surface with the oil and the contact with the oil is prevented,
The oil gelation rate is suppressed, the life of the dynamic pressure bearing is extended, and a highly reliable oil dynamic pressure bearing motor can be obtained.

According to the sixth and seventh aspects of the present invention, the capillary seal for preventing oil scattering is provided between the disk holding member and the end face of the bearing member, or between the ring-shaped projection of the disk holding member and the bearing. By forming it between the peripheral surface of the member and the oil dynamic pressure bearing, the space for storing the oil, which is the lubricating fluid, is expanded, and the oil dynamic pressure bearing motor can be expanded in the axial direction, and the oil storage capacity can be sufficiently increased. And the reliability of the dynamic pressure bearing can be ensured.

According to the eighth aspect of the present invention, there is provided a motor in which stainless steel whose machinability is improved by containing manganese sulfite is used as a material of a rotor hub having a disk holding portion. Alternatively, since the exposed area of manganese sulfite is reduced by coating a part thereof with a corrosion-resistant film, the reaction between water in the air and manganese sulfite can be suppressed, and the generation of hydrogen sulfide gas can be reduced. Therefore, when this motor is used as a disk drive motor, it is possible to reduce the erosion of the metal magnetic film formed on the disk surface or the magnetic film of the magnetic head, thereby preventing the deterioration of the recording / reproducing performance. .

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an oil dynamic bearing motor according to the present invention.

FIG. 2 is a sectional view showing a part of the embodiment in an enlarged manner.

FIG. 3 is a sectional view showing another embodiment of the oil dynamic bearing motor according to the present invention.

FIG. 4 is a sectional view showing still another embodiment of the oil dynamic bearing motor according to the present invention.

FIG. 5 is a sectional view showing still another embodiment of the oil dynamic bearing motor according to the present invention.

FIG. 6 is a sectional view showing still another embodiment of the oil dynamic bearing motor according to the present invention.

FIG. 7 is a diagram showing compositions and properties of various stainless steels that can be considered as a material of the disk holding member.

[Explanation of symbols]

 Reference Signs List 3 stator core 5 bearing member 8 shaft 9 thrust plate 10 radial dynamic pressure bearing 11 rotor hub as disk holding member 14 ring-shaped protrusion 15 thrust dynamic pressure bearing 16 thrust dynamic pressure bearing 20 radial dynamic pressure bearing 21 thrust dynamic pressure bearing 23 capillary seal

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H02K 5/16 H02K 5/16 Z 5/167 5/167 AB F Term (Reference) 3J011 AA07 AA20 BA02 BA08 CA02 CA05 JA02 KA02 KA03 MA24 QA03 QA05 SB02 SB05 SB12 SB15 SE04 5H605 AA05 BB05 BB14 BB19 CC03 CC04 DD03 DD05 EA06 EA07 EB08 EB09 EB16 EB26 EB28 EB33 FF03 GG10 5H607 AA04 BB01 BB14 GG17 GG01 GG16 GG01 GG25 DD01

Claims (8)

[Claims] A bearing member and a disk holding member which rotate relative to each other, wherein oil is interposed between the bearing member and the disk holding member as a lubricating fluid, and the bearing member and the disk holding member rotate relative to each other when the bearing member and the disk holding member rotate relative to each other. In an oil dynamic bearing motor in which dynamic pressure is generated in oil, the bearing member and the disk holding member are in contact with the oil via a minute gap, and the disk holding member is made of lead-containing stainless steel. An oil dynamic bearing motor comprising a film for preventing contact with lead contained in a contact surface with oil or a member separate from stainless steel. 2. The oil dynamic bearing motor according to claim 1, wherein the film is formed by subjecting the disk holding member to a base treatment in a wood bath and then performing electroplating or electroless plating. 3. The oil dynamic bearing motor according to claim 1, wherein the coating contains a solid lubricant or a wear-resistant material. 4. The oil dynamic bearing motor according to claim 1, wherein the film is formed of a resin material. 5. The oil dynamic bearing motor according to claim 1, wherein a thrust dynamic pressure bearing is formed between the disk holding member and an end surface of the bearing member. 6. The oil dynamic bearing motor according to claim 1, wherein a capillary seal for preventing oil from scattering is formed between the disk holding member and the end surface of the bearing member. 7. The oil dynamic bearing motor according to claim 1, wherein a capillary seal for preventing oil scattering is formed between the ring-shaped projection of the disk holding member and the peripheral surface of the bearing member. 8. A motor having a rotor hub having a disk holding part for holding at least one magnetic disk, and a stator rotatably supporting the rotor hub and rotating the rotor hub by an electromagnetic force generated between the rotor hub and the rotor hub. In the above, the rotor hub or the stator is made of stainless steel containing manganese sulfite, and the rotor hub or the stator is formed with a film for preventing contact between the manganese sulfite and moisture in the air. And the motor.