JP2006342975A - Dynamic pressure type bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and accurately set a thrust bearing clearance in a thrust bearing part. <P>SOLUTION: A rotary shaft 2 is inserted into a housing 7, and the lower end face 2b2 of a thrust plate 2b is brought into contact with the inner bottom face 7c1 of the housing 7. Thereafter, when a bearing member 8 is pushed along the inner peripheral face 7a of the housing 7 till it abuts on the upper end face 2b1 of the thrust plate 2b, the fixing position of the bearing member 8 is determined relative to the housing 7. After fixing the bearing member 8 at this position, a solvent is supplied into the housing 7 to dissolve a resin layer 19 for elimination. When the resin layer 19 is eliminated, a thrust bearing clearance having a width equal to thickness δ of the resin layer 19 is formed between the lower end face 8b of the bearing member 8 and the inner bottom face 7c1 of the housing 7. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device. This bearing device is especially a spindle motor such as an information device, for example, a magnetic disk device such as HDD or FDD, an optical disk device such as CD-ROM or DVD-ROM, a magneto-optical disk device such as MD or MO, or a laser beam printer ( It is suitable for supporting a spindle such as a polygon scanner motor of LBP).

  In addition to high rotational accuracy, spindle motors of the various information devices are required to have high speed, low cost, low noise, and the like. One of the components that determine the required performance is a bearing that supports the spindle of the motor.In recent years, the use of a hydrodynamic bearing having characteristics excellent in the required performance has been studied as this type of bearing. Or it is actually used.

FIG. 7 shows a configuration example of a hydrodynamic bearing device incorporated in a spindle motor of a disk device such as an HDD (see, for example, Patent Document 1). The hydrodynamic bearing device includes a radial bearing portion 21 that supports a rotary shaft 20 as a shaft member in a non-contact manner so as to be rotatable in a radial direction, and a thrust bearing portion 22 that supports the rotary shaft 20 in a non-contact manner so as to be rotatable in a thrust direction. These bearing portions 21 and 22 are both dynamic pressure bearings having a dynamic pressure generating groove (dynamic pressure groove) on the bearing surface. The dynamic pressure groove of the radial bearing portion 21 is formed on the inner peripheral surface (radial bearing surface) 23 a of the housing 23 or the outer peripheral surface of the rotary shaft 20, and the dynamic pressure groove of the thrust bearing portion 22 is provided at the lower end of the rotary shaft 20. The thrust plate 20b is formed on both end surfaces 20b1 and 20b2 or on the opposite surfaces (thrust bearing surfaces). A step portion 23c having a width dimension obtained by adding the size of the thrust bearing gap (approximately 10 to 20 μm on both sides) to the width dimension of the thrust plate 20b is provided at a lower portion of the side portion 23b of the housing 23. By incorporating the bottom (back metal) 23e into the following spigot 23d, thrust bearing gaps S1, S2 having predetermined values are formed on both axial sides of the thrust plate 20b.
Japanese Patent Laid-Open No. 10-269691

  In the above bearing device, in order to set the thrust bearing gaps S1 and S2 to predetermined values, it is necessary to accurately manage the width dimension (axial dimension) of the step portion 23c of the housing 23 and the width dimension of the thrust plate 20b. Managing the width dimension of the step portion 23c with high accuracy contributes to an increase in the number of manufacturing steps and manufacturing cost of the housing 23.

  Therefore, the present invention provides a configuration capable of easily and accurately setting the thrust bearing gap of the thrust bearing portion, thereby ensuring the excellent bearing performance of this type of hydrodynamic bearing device, and manufacturing cost. It aims at further reducing.

  In order to achieve the above object, the present invention provides a bottomed cylindrical housing having a cylindrical inner peripheral surface, a bearing member fixed to the inner peripheral surface of the housing, and an inner peripheral surface of the bearing member. A shaft member having a shaft portion, a thrust plate provided on the shaft portion, an inner peripheral surface of the bearing member, and an outer peripheral surface of the shaft portion of the shaft member, the relative relationship between the shaft member and the bearing member. A radial bearing portion that supports the shaft portion in a non-contact manner so that the shaft portion can rotate in the radial direction by a dynamic pressure action generated during rotation, and between the both end surfaces of the thrust plate of the shaft member, the lower end surface of the bearing member, and the inner bottom surface of the housing, respectively A dynamic pressure type bearing device provided with a thrust bearing portion that is provided in a non-contact manner to support the thrust plate so as to be rotatable in the thrust direction by a dynamic pressure effect generated at the time of relative rotation between the shaft member and the bearing member. When assembling the bearing device, the inner bottom of the housing And a lower end surface of the thrust plate, and between the lower end surface of the bearing member and the upper end surface of the thrust plate, a resin layer having a predetermined thickness is interposed in at least one portion, thereby A structure is provided in which the thrust bearing gap is set to a predetermined value by adjusting the fixing position and then dissolving and removing the resin layer with a solvent.

  By interposing the resin layer in the above-mentioned part, the bearing member is fixed at a position where the thickness of the resin layer is added in the housing. Therefore, when the resin layer is removed, a gap equal to the thickness of the resin layer is formed between both end faces of the thrust plate and the inner bottom face of the housing and the lower end face of the bearing member, and this gap becomes the thrust bearing gap. Also with this configuration, the thrust bearing gap can be set to a predetermined value easily and accurately.

  In the above configuration, the resin layer can be formed on the lower end surface of the thrust plate. In this case, the resin layer is made to flow by the centrifugal force accompanying the rotation of the shaft member with the resin liquid dropped on the lower end surface of the thrust plate. After forming a layer of thickness, it can be dried and solidified. Thereby, a resin layer having a predetermined thickness can be easily and accurately formed. Further, by providing a discharge portion for discharging the resin layer solution at the bottom of the housing, the discharge operation of the solution is facilitated.

  In the above configuration, the bearing member is preferably formed of a porous body, more preferably formed of sintered metal. This facilitates processing when the dynamic pressure groove is formed in the bearing member, and also impregnates the pores of the bearing member with lubricating oil or lubricating grease to make a dynamic pressure type oil-impregnated bearing, or as a dynamic pressure type gas bearing, The bearing performance can be improved.

  According to the present invention, the thrust bearing gap of the thrust bearing portion can be set easily and accurately, thereby further reducing the manufacturing cost while ensuring the excellent bearing performance of this type of hydrodynamic bearing device. be able to.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 shows a configuration example of a spindle motor for information equipment incorporating a hydrodynamic bearing device 1 according to an embodiment of the present invention. This spindle motor is used in a disk drive device such as an HDD, and includes a hydrodynamic bearing device 1 that rotatably supports a rotating shaft 2 as a shaft member in a non-contact manner, and a disk hub 3 mounted on the rotating shaft 2. The motor stator 4 and the motor rotor 5 are provided to face each other via a radial gap. The stator 4 is attached to the outer periphery of the casing 6, and the rotor 5 is attached to the inner periphery of the disk hub 3. The housing 7 of the hydrodynamic bearing device 1 is mounted on the inner periphery of the casing 6. The disk hub 3 holds one or more disks D such as magnetic disks. When the stator 4 is energized, the rotor 5 is rotated by the exciting force between the stator 4 and the rotor 5, whereby the disk hub 3 and the rotating shaft 2 are rotated together.

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a bottomed cylindrical housing 7 having a cylindrical inner peripheral surface 7a, a cylindrical bearing member 8 fixed to the inner peripheral surface 7a of the housing 7, and a rotating shaft as a shaft member. 2 and the seal member 10 that seals the upper end surface side (opening side of the housing 7) of the bearing member 8 are main components.

  The housing 7 includes a cylindrical side portion 7b and a bottom portion 7c, and the inner peripheral surface 7a of the side portion 7b is formed to have the same inner diameter from the upper end to the lower end. The bottom portion 7c of the housing 7 is provided with a discharge portion 7d, and this discharge portion 7d is sealed by a suitable plug, for example, a ball plug 7d1 as shown in FIG. In this embodiment, the side portion 7b and the bottom portion 7c of the housing 7 are integrated, but both may be separate structures.

  The rotating shaft 2 includes a shaft portion 2a and a thrust plate 2b provided integrally with or separately from the shaft portion 2a. The width dimension of the thrust plate 2b is W1. The shaft portion 2a is inserted into the inner peripheral surface 8a of the bearing member 8 with a predetermined radial bearing gap S5, and the thrust plate 2b is located in the space between the lower end surface 8b of the bearing member 8 and the inner bottom surface 7c1 of the housing 7. Be contained. The thrust plate 2b has a predetermined size between the upper end surface 2b1 and the lower end surface 8b of the bearing member 8, and between the lower end surface 2b2 of the thrust plate 2b and the inner bottom surface 7c1 of the housing 7. Thrust bearing gaps S3 and S4 are provided.

  The bearing member 8 is formed of, for example, a porous material, particularly a sintered metal, and an oil-impregnated bearing is formed by impregnating the inside pores with lubricating oil or lubricating grease. A dynamic pressure groove is formed in a region of the inner peripheral surface 8a of the bearing member 8 that serves as a radial bearing surface. This dynamic pressure groove is compression-molded, for example, a groove mold having an uneven pattern corresponding to the dynamic pressure groove shape of the radial bearing surface (see FIG. 3A) is formed on the outer peripheral surface of the core rod, and sintered on the outer periphery of the core rod. By supplying a metal, pressing the sintered metal, and transferring a dynamic pressure groove corresponding to the groove shape to the inner peripheral portion of the sintered metal, the metal can be formed at low cost and with high accuracy. When the rotary shaft 2 rotates, a dynamic pressure action is generated in the radial bearing gap S5, and the shaft portion 2a of the rotary shaft 2 is supported in a non-contact manner so as to be rotatable in the radial direction by an oil film of lubricating oil formed in the radial bearing gap S5. Is done. Thereby, the radial bearing part 11 which non-contact supports the rotating shaft 2 rotatably in the radial direction is configured. The bearing member 8 may be formed of a soft metal or an alloy (for example, copper, brass, etc.) in addition to the sintered metal. Further, the dynamic pressure groove on the radial bearing surface may be formed on the outer peripheral surface of the shaft portion 2 a of the rotating shaft 2.

  Dynamic pressure grooves are respectively formed in the upper end surface 2b1 of the thrust plate 2b or the lower end surface 8b of the bearing member 8 and the lower end surface 2b2 of the thrust plate 2b or the inner bottom surface 7c1 of the housing 7 that serve as the thrust bearing surface. The When the rotary shaft 2 rotates, a dynamic pressure action is generated in the thrust bearing gaps S3 and S4, and the thrust plate 2b of the rotary shaft 2 is rotatable in the thrust direction by the oil film of the lubricating oil formed in the thrust bearing gaps S3 and S4. Is supported in a non-contact manner. Thereby, the thrust bearing part 12 which non-contact-supports the rotating shaft 2 rotatably in a thrust direction is comprised.

  The dynamic pressure groove shape of the radial bearing surface and the thrust bearing surface can be arbitrarily selected, and a known herringbone type, spiral type, step type, multi-arc type or the like is selected, or these are appropriately combined. Can be used together. 3A and 3B show a herringbone type as an example, and FIG. 3A shows an example in which the dynamic pressure groove 14 is provided on the radial bearing surface 8a1 of the inner peripheral surface 8a of the bearing member 8. FIG. 3B shows an example in which the dynamic pressure groove 16 is provided on the thrust bearing surface 2b21 on the lower end surface 2b2 of the thrust plate 2b. For example, two radial bearing surfaces 8a1 are provided on the inner peripheral surface 8a of the bearing member 8 so as to be separated from each other in the axial direction. The dynamic pressure groove 16 of the thrust bearing surface 2b1 has a substantially V shape having a bent portion at a substantially central portion in the radial direction.

  In this embodiment, the thrust bearing gaps S3 and S4 are set in the following procedure, for example.

  First, the resin layer 19 having a predetermined thickness δ is formed on the lower end surface 2b2 of the thrust plate 2b of the rotating shaft 2 in the manner shown in FIG. A synthetic resin material that forms the resin layer 19 is dissolved with a solvent to form a resin liquid L, and a predetermined amount of the resin liquid L is dropped onto the lower end surface 2b2 of the thrust plate 2b. Thereafter, the rotating shaft 2 is rotated at a predetermined speed. Then, the dropped resin liquid L flows to the outer diameter side by centrifugal force and spreads on the lower end surface 2b2 of the thrust plate 2b with a uniform thickness. Thereafter, when the resin liquid L is dried and solidified, a resin layer 19 having a predetermined thickness δ is formed on the lower end surface 2b2 of the thrust plate 2b. According to this method, the resin layer 19 having a uniform thickness can be formed with high accuracy. The thickness δ of the resin layer 19 is managed so as to be a value (δ = S3 + S4) obtained by adding the set values of the thrust bearing gaps S3 and S4 (about 10 to 20 μm).

  Next, as shown in FIG. 5, the rotary shaft 2 is inserted into the housing 7, and the lower end surface 2 b 2 of the thrust plate 2 b is brought into contact with the inner bottom surface 7 c 1 of the housing 7 through the resin layer 19. Thereafter, when the bearing member 8 is pushed in along the inner peripheral surface 7a of the housing 7 until it comes into contact with the upper end surface 2b1 of the thrust plate 2b, the fixing position of the bearing member 8 with respect to the housing 7 is determined. That is, the distance (axial dimension) between the lower end surface 8b of the bearing member 8 and the inner bottom surface 7c1 of the housing 7 is determined by the width dimension W1 of the thrust plate 2b and the thickness δ of the resin layer 19 (W1 + δ). . In this state, the bearing member 8 is fixed to the inner peripheral surface 7 a of the housing 7. Examples of the fixing method include press-fitting and adhesion. Alternatively, the rotary shaft 2 and the bearing member 8 may be assembled in advance, and both may be inserted into the housing 7 together.

  After the fixing position of the bearing member 8 is determined as described above, a solvent is supplied into the housing 7 to dissolve the resin layer 19. This dissolved solution is discharged from a discharge portion 7 d provided on the bottom portion 7 c of the housing 7. After discharging the solution, the discharge portion 7d is sealed with an appropriate stopper, for example, a ball stopper 7d1 as shown in FIG.

  When the resin layer 19 is removed in the above-described manner, as shown in FIG. 2, the resin layer is interposed between the both end faces 2b1, 2b2 of the thrust plate 2b and the lower end face 8b of the bearing member 8 and the inner bottom face 7c1 of the housing 7. Thrust bearing gaps S3 and S4 (δ = S3 + S4) having a size equal to 19 thickness δ are formed. Then, when the upper surface side of the bearing member 8 is sealed with the seal member 10 and the inside of the housing 7 is filled with lubricating oil, the hydrodynamic bearing device 1 shown in FIG. 2 is obtained.

  According to this embodiment, since the total value of the thrust bearing gaps S3 and S4 is equal to the thickness δ of the resin layer 19 (δ = S3 + S4), if the thickness δ of the resin layer 19 is accurately managed, the thrust plate Even when there is some dimensional error in the width dimension W1 of 2b, the thrust bearing gaps S3 and S4 can be set with high accuracy.

  It is desirable to form an axial groove 8c for supplying a solvent on the outer peripheral surface of the bearing member 8 so that the supplied solvent can reach the resin layer 19 smoothly.

  In this embodiment, the resin layer 19 is interposed between the lower end surface 2b2 of the thrust plate 2b and the inner bottom surface 7c1 of the housing 7 in the step of setting the thrust bearing gaps S3 and S4. 19 may be interposed between the upper end surface 2b1 of the thrust plate 2b and the lower end surface 8b of the bearing member 8, or may be interposed simultaneously in these two parts.

  The combination of the synthetic resin material and the solvent for forming the resin layer 19 can be arbitrarily selected as long as the resin layer 19 can be reliably dissolved, but excludes chlorinated resins, chlorinated solvents, and corrosive solvents. Is preferred. As a specific combination of the resin material and the solvent, for example, the one indicated by a circle in FIG.

1 is a cross-sectional view of a spindle motor having a hydrodynamic bearing device according to an embodiment of the present invention. 1 is a cross-sectional view of a hydrodynamic bearing device according to an embodiment of the present invention. It is sectional drawing {FIG. 3 (a)} of a bearing member, and top view (FIG. 3 (b)) which shows the upper end surface of a thrust board. It is a conceptual diagram which shows the formation process of a resin layer. It is a figure explaining the setting process of a thrust bearing clearance gap. It is a figure which shows the combination of the resin material and solvent which can be applied in embodiment. It is sectional drawing which shows the conventional dynamic pressure type bearing apparatus.

Explanation of symbols

1 Hydrodynamic bearing device 2 Rotating shaft
2a Shaft
2b Thrust plate 2b1 Upper end surface 2b2 Lower end surface 7 Housing 7a Inner peripheral surface 7a1 Stepped portion 7c Bottom portion 7c1 Inner bottom surface 7d Discharge portion 8 Bearing member 8b Lower end surface 11 Radial bearing portion 12 Thrust bearing portion 19 Resin layer S3 Thrust bearing gap S4 Thrust bearing Clearance S5 Radial bearing clearance

Claims (6)

A bottomed cylindrical housing having a cylindrical inner peripheral surface;
A bearing member fixed to the inner peripheral surface of the housing;
A shaft member having a shaft portion inserted into the inner peripheral surface of the bearing member, and a thrust plate provided on the shaft portion;
Provided between the inner peripheral surface of the bearing member and the outer peripheral surface of the shaft portion of the shaft member, the shaft portion can be freely rotated in the radial direction by a dynamic pressure action generated during relative rotation between the shaft member and the bearing member. A non-contact radial bearing portion,
The thrust plate is provided between both end surfaces of the thrust plate of the shaft member, a lower end surface of the bearing member, and an inner bottom surface of the housing, and is caused by a dynamic pressure action generated during relative rotation between the shaft member and the bearing member. A hydrodynamic bearing device provided with a thrust bearing portion that supports non-contact in a thrust direction so as to be freely rotatable,
At the time of assembling the dynamic pressure type bearing device, at least one portion is provided between the inner bottom surface of the housing and the lower end surface of the thrust plate, and between the lower end surface of the bearing member and the upper end surface of the thrust plate. The thrust bearing gap is set to a predetermined value by adjusting the fixing position of the bearing member with respect to the housing by interposing a resin layer having a predetermined thickness, and then dissolving and removing the resin layer with a solvent. A hydrodynamic bearing device characterized by that.   The hydrodynamic bearing device according to claim 1, wherein the resin layer is formed on a lower end surface of the thrust plate.   The resin layer is formed by allowing the resin liquid dropped on the lower end surface of the thrust plate to flow with a centrifugal force accompanying the rotation of the shaft member to form a layer with a predetermined thickness, and then drying and solidifying it. The hydrodynamic bearing device according to claim 2.   The hydrodynamic bearing device according to claim 1, wherein a discharge portion for discharging the solution of the resin layer is provided at a bottom portion of the housing.   The hydrodynamic bearing device according to claim 1, wherein the bearing member is formed of a porous body.   The hydrodynamic bearing device according to claim 5, wherein the porous body is a sintered metal.

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