JP2008111520A - Dynamic pressure bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dynamic pressure bearing device including a dynamic pressure generating part, which keeps the moldability of the dynamic pressure generating part and its resistance against wear enhanced. <P>SOLUTION: A flange 8b installed in a bearing component 8 is furnished with a thrust dynamic pressure generating part through a die shaping process. This enhances the moldability of the dynamic pressure generating part owing to an easy pressurization in the axial direction, compared with the case where such a pressure generation part is formed at the open side end face of a housing 7 made of metal. If the bearing component 8 is formed from a porous material, a fluid as the lubricant impregnating the component 8 is fed bit by bit in the gaps in the bearing, which enhances the lubricating performance and allows a suppression of the wear of the dynamic pressure generating part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device that rotatably supports a shaft member by a hydrodynamic action of a lubricating fluid generated in a bearing gap.

  Due to its high rotational accuracy and quietness, the hydrodynamic bearing device is an information device, for example, a magnetic disk drive device such as HDD, an optical disk drive device such as CD-ROM, CD-R / RW, DVD-ROM / RAM, MD, Suitable for spindle motors such as magneto-optical disk drive devices such as MOs, small motors such as fan motors used for laser beam printer (LBP) polygon scanner motors, projector color wheels, cooling fans for electrical equipment, etc. Can be used.

  For example, a hydrodynamic bearing device disclosed in Patent Document 1 includes a cup-shaped housing formed by pressing a metal material, a bearing sleeve held on the inner periphery of the housing, and a shaft inserted on the inner periphery of the bearing sleeve. A member, and a rotor hub fixed to the shaft member and covering an opening of the housing. A radial bearing gap is formed between the inner peripheral surface of the bearing sleeve and the outer peripheral surface of the shaft member, and a thrust bearing gap is formed between the opening side end surface of the housing and the end surface of the rotor hub.

JP 2006-90390 A

  Since the opening-side end surface of such a housing faces the thrust bearing gap, high-precision processing is required for this portion. As a processing method of the end face of the metal housing, for example, electrolytic processing or mold forming can be considered. However, when the end face of the housing is processed by electrolytic processing, the equipment becomes expensive and the management becomes complicated, resulting in high cost and long manufacturing time. On the other hand, when processing the end face of the housing by molding, it is necessary to pressurize the cylindrical side wall portion of the housing in the axial direction. Therefore, when the housing has a complicated shape, it is difficult to sufficiently pressurize. It is difficult to improve accuracy.

  In general, the metal housing does not have an internal hole through which the lubricating fluid filled in the bearing permeates, and cannot hold the lubricating fluid inside. Therefore, when this housing faces the thrust bearing gap, sufficient lubricating fluid is not supplied to the thrust bearing gap, the lubricity is insufficient, and the portion facing the thrust bearing gap may be worn.

  An object of the present invention is to improve the formability and wear resistance of the portion of the hydrodynamic bearing device that faces the thrust bearing gap, and to reduce the cost.

  In order to solve the above-mentioned problems, the present invention includes a first member having a shaft portion, and a second member having the shaft portion inserted into the inner periphery, having one end opened in the axial direction and the other end closed. In the hydrodynamic bearing device that supports the first member so as to be relatively rotatable in the thrust direction by the hydrodynamic action of the lubricating fluid generated in the thrust bearing gap between the opening-side end surface of the member and the first member, the second member includes: A bearing part and a metal housing holding the bearing part on the inner periphery, the bearing part having a cylindrical sleeve part and a flange part extending from one end of the sleeve part toward the outer diameter; The flange portion faces the thrust bearing gap.

  Thus, in the hydrodynamic bearing device of the present invention, the flange portion of the bearing component formed separately from the housing is configured to face the thrust bearing gap. Thereby, the moldability of the part which faces a thrust bearing gap can be improved. For example, when the flange portion is molded, by reducing the axial dimension of the flange portion and forming it in a simple shape, it becomes easier to press in the axial direction and the end face can be processed with high accuracy. . Further, since the end face of the housing does not face the thrust bearing gap, the processing accuracy of the housing can be relaxed, and the cost can be reduced.

  When the dynamic pressure bearing device includes a dynamic pressure generating portion that generates a dynamic pressure action on the lubricating fluid in the thrust bearing gap, the dynamic pressure generating portion is formed on the end surface of the flange portion by molding or the like. The moldability of the generating part can be improved.

  Further, when the bearing part is formed of a porous material, the lubricating fluid impregnated inside the bearing part is sequentially supplied to the bearing gap, so that the lubricity in the thrust bearing gap is improved, and the portion of the portion facing the thrust bearing gap is improved. Wear can be suppressed.

  Further, in this hydrodynamic bearing device, an axial groove formed in one or both of the outer peripheral surface of the sleeve portion of the bearing component and the inner peripheral surface of the housing, and a shaft communicating with both ends of the interface between the outer peripheral surface and the inner peripheral surface In addition to forming a directional hole and forming a through hole in the bearing component having one end opened on the upper end surface of the bearing component and the other end communicating with the axial hole, the axial hole and the through hole allow Thus, the pressure balance of the lubricating fluid filled with the above can be maintained appropriately.

  As described above, in the hydrodynamic bearing device of the present invention, the formability of the portion facing the thrust bearing gap can be improved, so that the width accuracy of the thrust bearing gap is increased and the supporting force in the thrust direction is increased. . Further, the cost can be reduced by reducing the accuracy of the housing. Furthermore, the wear resistance is improved by improving the lubricity by making the bearing parts porous.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 conceptually shows a configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device 1 according to a first embodiment of the present invention. This spindle motor for information equipment is used in a disk drive device such as an HDD, and includes a hydrodynamic bearing device 1 and, for example, a stator coil 4 and a rotor magnet 5 that are opposed to each other with a gap in the radial direction. Yes. The stator coil 4 is attached to the outer peripheral side inner peripheral surface 6 a of the bracket 6, and the rotor magnet 5 is attached to the outer periphery of the disk hub 10 provided in the fluid dynamic bearing device 1. The disk hub 10 holds one or more disk-shaped information recording media (not shown) such as magnetic disks. A housing 7 of the hydrodynamic bearing device 1 is mounted on the inner periphery of the bracket 6. When the stator coil 4 is energized, the rotor magnet 5 is rotated by an exciting force generated between the stator coil 4 and the rotor magnet 5, and the disk hub 10 and the disk are rotated accordingly.

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a stationary member 2 as a second member and a rotating member 3 as a first member. The rotation side member 3 includes a shaft member 9 and a disk hub 10 provided so as to protrude from the shaft member 9 to the outer diameter. The fixed-side member 2 includes a bearing part 8 in which a shaft member 9 is inserted on the inner periphery, and a housing 7 that holds the bearing part 8 on the inner periphery, and is open at one end in the axial direction and closed at the other end. For convenience of explanation, the following explanation will be given with the opening side of the fixed member 2 being the upper side and the closing side being the lower side.

  As will be described in detail later, in this hydrodynamic bearing device 1, a radial bearing that supports the rotary member 3 in the radial direction between the outer peripheral surface of the shaft member 9 and the inner peripheral surface 8 a 1 of the sleeve portion 8 a of the bearing component 8. Thrust bearings that are formed with portions R1 and R2 and that support the rotary member 3 in the thrust direction between the lower end surface 10a1 of the base portion 10a of the disk hub 10 and the upper end surface 8b1 of the flange portion 8b of the bearing component 8. Part T is formed.

  The shaft member 9 is formed in a cylindrical shape by cutting or forging a metal material such as stainless steel. The outer peripheral surface 9a of the shaft member 9 faces the radial bearing gap of the radial bearing portions R1 and R2.

  The disk hub 10 is formed of, for example, a metal material, and is fixed to the upper end of the shaft member 9 by means such as bonding, press-fitting, or press-fitting (hereinafter referred to as press-fitting adhesion) with an adhesive. The disc hub 10 includes a base portion 10a having a substantially disk shape, a peripheral wall portion 10b extending axially downward from the outer peripheral portion of the base portion 10a, a flange portion 10c provided on the outer periphery of the peripheral wall portion 10b, and a disc mounting surface 10d. It has. The rotor magnet 5 is attached to the outer peripheral surface 10b1 of the peripheral wall 10b. A retaining member 11 is provided on the inner periphery of the peripheral wall portion 10b. The retaining member 11 is formed in a ring shape having a substantially L-shaped cross section by press molding of a metal material, for example, a soft metal such as brass, and is provided on a step portion 10e provided at the upper end portion of the inner peripheral surface of the peripheral wall portion 10b. It is fixed by appropriate means such as adhesion and welding. The retaining member 11 is engaged with a shoulder surface 7 d provided on the outer periphery of the upper portion of the housing 7 in the axial direction, thereby restricting the rotational side member 3 from being detached from the fixed side member 2.

  The housing 7 has a substantially cylindrical side portion 7a and a bottom portion 7b that closes the lower end opening of the side portion 7a, and is integrally formed by cutting or plastic working of a metal material (for example, brass forging). Is done. On the outer periphery of the side portion 7a, there are provided a shoulder surface 7d provided in the upper portion in the radial direction, a tapered surface 7f gradually reduced in diameter from the inner diameter end of the shoulder surface 7d, and a lower portion of the tapered surface 7f. A cylindrical surface 7g is formed. The tapered surface 7f forms an annular seal space S whose radial dimension is gradually reduced upward with the inner peripheral surface 11a of the retaining member 11 fixed to the disk hub 10. The seal space S communicates with an outer diameter side of a thrust bearing gap of a thrust bearing portion T described later. The bracket 6 is fixed to the cylindrical surface 7g by adhesion or the like. In the present embodiment, the side portion 7a and the bottom portion 7b are integrally formed, but they may be formed separately.

  The bearing component 8 integrally includes a sleeve portion 8a and a flange portion 8b extending from the upper end portion of the sleeve portion 8a toward the outer diameter. The bearing part 8 is fixed to the inner peripheral surface 7e of the housing 7 by appropriate means such as adhesion, press-fitting, press-fitting adhesion, welding, etc., and the lower end surface 8b2 of the flange portion 8b is formed on the inner periphery of the housing 7 By making contact with the surface 7c, the housing 7 is positioned in the axial direction. The porous material forming the bearing component 8 is not limited to a sintered metal, and for example, a porous resin can be used.

  Thus, by providing the flange portion 8b integrally with the cylindrical sleeve portion 8a, the rigidity in the radial direction of the bearing component 8 is increased, and the cross-sectional shape is prevented from being deformed when incorporated in the housing 7 or the like. it can. In particular, when the sleeve portion 8a is thinned, the rigidity improvement by the flange portion 8b is effective.

  On the inner peripheral surface 8a1 of the sleeve portion 8a, as shown in FIG. 3, dynamic pressure grooves 8a11 and 8a12 arranged in a herringbone shape are formed as radial dynamic pressure generating portions in two regions separated in the axial direction. Is done. Further, as shown in FIG. 4, dynamic pressure grooves 8b11 arranged in a spiral shape are formed on the upper end surface 8b1 of the flange portion 8b as a thrust dynamic pressure generating portion.

  One or a plurality of axial grooves 8a21 are formed on the outer peripheral surface 8a2 of the sleeve portion 8a. The axial groove 8a21 is formed between the outer peripheral surface 8a2 of the sleeve portion 8a and the inner peripheral surface 7e of the housing 7 between the inner peripheral surface 7e of the housing 7 when the bearing component 8 is fixed to the inner periphery of the housing 7. An axial hole 12a is formed that communicates both axial ends of the interface. In addition, one end of the bearing part 8 (the inner diameter end of the flange portion 8b) on the axial extension of the axial hole 12a is open to the upper end surface of the bearing part 8, and the other end communicates with the axial hole 12a. A through hole 8b3 is formed. The axial hole 12a and the through hole 12b form a communication hole 12 that communicates the space that the upper end surface of the bearing component 8 faces with the space that the lower end surface 8a3 faces. The axial groove that forms the axial hole 12 a may be formed on the inner peripheral surface 7 e of the housing 7. Alternatively, axial grooves may be formed on both the outer peripheral surface 8a2 of the sleeve portion 8a and the inner peripheral surface 7e of the housing 7.

  In the present embodiment, the bearing component 8 is molded with a porous material (for example, a sintered metal containing copper as a main component). Specifically, the metal powder is compacted and heat-treated (sintered). Thereafter, the dimensional accuracy is increased by sizing (shaping) using a mold. The flange portion 8b is smaller in axial dimension than the housing 7 and has a simple shape, so that it is easy to pressurize in the axial direction. For this reason, an end surface can be processed with high precision by the above-mentioned mold forming (sizing). Therefore, since the moldability of the upper end face 8b1 of the flange portion facing the thrust bearing gap can be improved, the gap width of the thrust bearing gap is set with high accuracy and the supporting force in the thrust direction is increased.

  In addition, the dynamic pressure grooves 8a11, 8a12, and 8b11 can be formed simultaneously with the sizing of the bearing component 8. Specifically, a mold for forming the dynamic pressure grooves 8a11, 8a12, and 8b11 is formed on the mold used for the sizing, and the mold is pressed against the upper end surface 8b1 of the flange portion 8b simultaneously with the sizing. . Thereby, the shape of the molding die is transferred to the bearing component 8, and the dynamic pressure grooves 8a11, 8a12, and 8b11 are molded. As described above, since the flange portion 8b is easily pressurized in the axial direction, the dynamic pressure groove 8b11 can be molded with high accuracy. Further, since the radial dynamic pressure generating portion and the thrust dynamic pressure generating portion can be formed simultaneously with the molding of the bearing component 8, the number of processes is reduced, and the cost is reduced and the productivity is improved.

  The fluid dynamic bearing device 1 is completed by filling the internal space of the fluid dynamic bearing device 1 having the above configuration with, for example, lubricating oil as a lubricating fluid. In this state, the space inside the bearing relative to the seal space S is filled with lubricating oil, and the oil level is always held in the seal space S.

  When the shaft member 9 rotates, the dynamic pressure grooves 8a11 and 8a12 formed on the inner peripheral surface 8a1 of the bearing component 8 generate a dynamic pressure action on the lubricating oil in the radial bearing gap, thereby causing the shaft member 9 to move in the radial direction. Radial bearing portions R1 and R2 that are rotatably supported are formed. At the same time, the dynamic pressure groove 8b11 formed on the upper end surface 8b1 of the bearing component 8 generates a dynamic pressure action on the lubricating oil in the thrust bearing gap, thereby supporting the shaft member 9 rotatably in the thrust direction. A bearing portion T is formed.

  At this time, the lubricating oil that has oozed from the bearing component 8 formed of the porous material is sequentially supplied to the radial bearing gap and the thrust bearing gap, so that the lubricity between the members facing each other through each bearing gap is improved. improves. At the time of low speed rotation such as when the bearing device is started or stopped, the dynamic pressure action of the radial bearing portions R1, R2 and the thrust bearing portion T is not sufficiently expressed, and the radial dynamic pressure generating portion and the thrust dynamic pressure generating portion are not However, since the lubricity between these members is improved as described above, the wear of each dynamic pressure generating portion can be suppressed.

  Further, in the present embodiment, as shown in FIG. 2, the lower end surface 8a3 of the bearing component 8 and the inner bottom surface 7b1 of the housing 7 are formed by the communication hole 12 that communicates the upper end surface 8b1 and the lower end surface 8a3 of the bearing component 8. And a gap between the upper end surface of the bearing component 8 and the lower end surface 10a1 of the base portion 10a of the disk hub 10 (hereinafter referred to as a second gap). Therefore, the pressure balance in the internal space can be properly maintained. Further, as shown in FIG. 3, the dynamic pressure groove 8a11 of the inner peripheral surface 8a1 of the bearing component 8 is axially asymmetric with respect to the axial central portion m, specifically, in the region above the axial central portion m. Since the axial dimension X1 is larger than the axial dimension X2 of the lower region, when the shaft member 9 rotates, the pulling force (pumping force) of the lubricating oil by the dynamic pressure groove 8a11 is higher in the lower region. It becomes relatively large compared. Due to the differential pressure of the pulling force, the lubricating oil filled in the radial bearing gap of the first radial bearing portion R1 flows downward, flows through the first gap → the communication hole 12 → the second gap, and again the radial bearing gap. Return to. Thus, by forcibly circulating the lubricating oil in the radial bearing gap, it is possible to more effectively prevent the generation of a local negative pressure in the internal space of the bearing device. In addition, when it is not necessary to force the lubricating oil to flow through the radial bearing gap, the shape of the dynamic pressure groove 8a11 may be formed symmetrically with respect to the axial center part m.

  The present invention is not limited to the above embodiment. Hereinafter, other embodiments of the present invention will be described. In the following description, parts having the same configuration and function as those of the above embodiment are given the same reference numerals, and the description thereof is omitted.

  FIG. 5 shows a hydrodynamic bearing device 21 according to a second embodiment of the present invention. This hydrodynamic bearing device 21 is different from the above embodiment in that a disc-shaped retaining member 13 is fixed to the lower end of the shaft member 9. The upper end surface 13a of the retaining member 13 is opposed to the lower end surface 8a3 of the bearing component 8 through the thrust bearing gap. When the shaft member 9 rotates, a first thrust bearing portion T1 is formed between the upper end surface 8b1 of the bearing component 8 and the lower end surface 10a1 of the base portion 10a of the disk hub 10, and the lower end surface of the bearing component 8 The dynamic pressure generating portion formed in 8a3 generates a dynamic pressure action on the lubricating fluid in the thrust bearing gap, thereby forming a second thrust bearing portion T2 that supports the shaft member 9 rotatably in the thrust direction. As described above, the thrust bearing portions T1 and T2 are formed at two locations separated in the axial direction, so that the bearing rigidity, particularly the moment rigidity is enhanced.

  In the above embodiment, the disc hub 10 formed separately from the shaft member 9 is fixed. However, the present invention is not limited to this. For example, the disc hub 10 is formed by injection molding using the shaft member 9 as an insert part. The member 9 and the disk hub 10 may be integrally formed. Alternatively, the shaft member 9 and the disk hub 10 may be integrally injection-molded with the same material.

  Moreover, in the above embodiment, the sleeve part 8a and the flange part 8b which comprise the bearing component 8 are integrally formed, However, it is not restricted to this, For example, the sleeve part 8a and the flange part 8b which were formed separately are closely_contact | adhered. It may be fixed. Moreover, in the above embodiment, although the case where the bearing component 8 was formed with a porous material was shown, you may form not only this but other metal materials, for example. In this case, if the bearing component 8 is formed of a metal material having a hardness higher than that of the housing 7, the hardness of the portion facing the thrust bearing gap can be increased and the wear resistance can be improved. In this case, the dynamic pressure groove 8b11 as the thrust dynamic pressure generating portion does not necessarily have to be molded simultaneously with the formation of the bearing component 8. For example, after the formation of the bearing component 8, the dynamic pressure groove 8b11 is formed by pressing or machining. Also good.

  In the above embodiment, brass is used as the material of the housing 7, but the present invention is not limited to this, and other metal materials such as stainless steel can also be used. Moreover, although the case where the housing 7 was formed by a forging process was shown, it is not restricted to this, For example, it can also form by arbitrary methods, such as a press work.

  In the above embodiment, the communication hole 12 is configured by the axial groove 8a21 formed in the outer peripheral surface 8a2 of the sleeve portion 8a and the through hole 12b formed in the flange portion 8b. However, the present invention is not limited to this. . For example, although not shown, an axial groove 8a21 is formed on the outer peripheral surface 8a2 of the sleeve portion 8, a radial groove is formed on the lower end surface 8b2 of the flange portion 8b, and an axial groove is formed on the outer peripheral surface of the flange portion 8b. The hole formed by these grooves and the housing 7 can be communicated to form a communication hole. Through this communication hole, the outer diameter end of the thrust bearing gap of the thrust bearing portion T communicates with the space facing the lower end surface 8a3 of the sleeve portion 8a. Further, the axial grooves and the radial grooves can be formed not on the sleeve portion 8a side but on the housing 7 side.

  In the above, the herringbone-shaped dynamic pressure groove is formed as the radial dynamic pressure generating portion and the spiral-shaped dynamic pressure groove is formed as the thrust dynamic pressure generating portion, but this is not restrictive. For example, a spiral dynamic pressure groove, a multi-arc bearing, or a step bearing may be formed as the radial dynamic pressure generating portion. Further, as the thrust dynamic pressure generating portion, a herring vane-shaped dynamic pressure groove, a step bearing, or a wave bearing (a step bearing having a wave shape) may be formed.

  In the above description, the radial bearing portions R1 and R2 are spaced apart in the axial direction. However, the present invention is not limited thereto, and for example, they may be continuously formed in the axial direction. Alternatively, only one of the radial bearing portions R1 and R2 may be provided.

  In the above description, the first member having the shaft portion is the rotation side, and the second member having the bearing part is the fixed side. On the contrary, the first member is the fixed side, The structure by which two members become a rotation side may be sufficient.

  In the above, lubricating oil is used as the lubricating fluid, but other fluids that can generate a dynamic pressure action in each bearing gap, for example, gas such as air, magnetic fluid, or lubricating grease are used. You can also

  Further, the hydrodynamic bearing device of the present invention is not limited to the spindle motor used in the disk drive device such as the HDD as described above, but is used for information used under high-speed rotation, such as a spindle motor for driving a magneto-optical disk of an optical disk. It can also be suitably used as a fan motor for rotating shaft support in a small motor for equipment, a polygon scanner motor of a laser beam printer, or a cooling fan for electrical equipment.

It is sectional drawing which shows the spindle motor incorporating the dynamic pressure bearing apparatus. It is sectional drawing which shows the hydrodynamic bearing apparatus 1 which concerns on this invention. 3 is an axial sectional view of a bearing component 8. FIG. FIG. 6 is a top view of the bearing component 8. It is sectional drawing of the hydrodynamic bearing apparatus 21 which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing apparatus 2 Fixed side member (2nd member)
3 Rotating side member (first member)
4 Stator coil 5 Rotor magnet 6 Bracket 7 Housing 8 Bearing part 8a Sleeve part 8a21 Axial groove 8b Flange part 9 Shaft member 10 Disk hub 12 Communication hole 12a Axial hole 12b Through hole R1, R2 Radial bearing part T Thrust bearing part S Seal space

Claims (4)

A first member having a shaft portion; and a second member having the shaft portion inserted into the inner periphery and having one end opened in the axial direction and the other end closed, and is between the opening-side end surface of the second member and the first member In the hydrodynamic bearing device that supports the first member so as to be relatively rotatable in the thrust direction by the hydrodynamic action of the lubricating fluid generated in the thrust bearing gap of
The second member has a bearing part and a metal housing holding the bearing part on the inner periphery, and the bearing part extends from the one end of the sleeve part toward the outer diameter from the sleeve part. And the flange portion faces the thrust bearing gap.   The dynamic pressure bearing device according to claim 1, wherein a dynamic pressure generating portion that generates a dynamic pressure action on the lubricating fluid in the thrust bearing gap is formed on an end surface of the flange portion.   The hydrodynamic bearing device according to claim 1, wherein the bearing part is formed of a porous material.   An axial groove formed on one or both of the outer peripheral surface of the sleeve portion of the bearing component and the inner peripheral surface of the housing forms an axial hole that communicates both ends of the interface between the outer peripheral surface and the inner peripheral surface. The hydrodynamic bearing device according to claim 1, wherein one end is opened in an upper end surface of the bearing component, and the other end is formed with a through hole communicating with the axial hole.

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