JP2011074951A - Fluid dynamic bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve run-out accuracy of a rotor fixed on a housing of an axis fix type fluid dynamic bearing device easily at low cost. <P>SOLUTION: An outer circumference surface 7b (fixing surface 7b1) of the housing 7 is formed as a cutting surface on a basis of an inner circumference surface 8a of a bearing sleeve 8. Dimension error (uneven wall thickness) of the bearing sleeve 8 and the housing 7, and assembly error of the bearing sleeve 8 and the housing 7 are canceled by cutting of the housing 7 thereby. Consequently, run-out accuracy of the outer circumference surface 7b of the housing 7 to the inner circumference surface 8a of the bearing sleeve 8 is improved without increasing machining accuracy of the bearing sleeve 8 and the housing 7 and fixing accuracy of both more than necessary. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fluid dynamic pressure bearing device for supporting a rotary member in a radial direction by a dynamic pressure action of a fluid film generated in a radial bearing gap between an outer peripheral surface of a shaft member and an inner peripheral surface of a bearing sleeve. In particular, the present invention relates to a fixed shaft type hydrodynamic bearing device having a shaft member as a fixed side and a bearing sleeve and a housing as a rotation side.

  Due to its high rotational accuracy and quietness, the fluid dynamic pressure bearing device is driven by a magnetic disk drive for information equipment (for example, HDD), an optical disk drive such as a CD / DVD / Blu-ray disc, or a magneto-optical disk drive such as an MD / MO. It is suitably used as a spindle motor for devices and the like.

  For example, HDD disk drive devices tend to increase the number of disks mounted as HDD capacity increases. As the number of mounted disks increases, the weight increases, so that the vibration of the disk hub on which the disks are mounted increases, and the rotation accuracy of the disk and thus the reading accuracy of the disk may be reduced. Under such circumstances, there is a need for a fluid dynamic bearing device that can be stably supported even when the weight increases due to an increase in the number of mounted disks.

  FIG. 10 shows a case where a shaft rotation type fluid dynamic pressure bearing device 100 (see, for example, Patent Document 1) with the shaft member 102 as a rotation side is applied to a spindle motor of an HDD disk drive device. The fluid dynamic pressure bearing device 100 includes a shaft member 102, a bearing sleeve 108 with the shaft member 102 inserted into the inner periphery, and a housing 107 with the bearing sleeve 108 fixed on the inner peripheral surface. When the shaft member 102 rotates, a dynamic pressure action is generated in the fluid film in the radial bearing gap between the shaft member 102 and the bearing sleeve 108, thereby forming a radial bearing portion R that rotatably supports the shaft member 102. . The housing 107 is fixed to the base 106 on the fixed side, and the disk hub 103 is fixed to the upper end portion of the shaft member 102. In such a shaft rotation type fluid dynamic bearing device 100, the radial bearing portion R supports the lower region of the shaft member 102 than the fixed portion (upper end portion) to the disk hub 103 with the radial bearing portion R. Thus, the shaft member 102 is cantilevered. For this reason, the support of the shaft member 2 by the radial bearing portion R becomes unstable, and when the number of mounted disks increases and the weight increases, the vibration of the disk hub 103 may increase.

  On the other hand, FIG. 1 shows a case where a shaft fixed type fluid dynamic bearing device 1 (see, for example, Patent Document 2) with the shaft member 2 as a fixed side is applied to a spindle motor of an HDD disk drive device. The fluid dynamic pressure bearing device 1 includes a shaft member 2, a bearing sleeve 8 in which the shaft member 2 is inserted on the inner periphery, and a housing 7 in which the bearing sleeve 8 is fixed on an inner peripheral surface. When the bearing sleeve 8 and the housing 7 rotate, a dynamic pressure action is generated in the fluid film in the radial bearing gap between the shaft member 2 and the bearing sleeve 8, and thereby the radial bearing that rotatably supports the bearing sleeve 8 and the housing 7. Part R is configured. Both end portions of the shaft member 2 are fixed to the base 6 a and the cover 6 b on the fixed side, and the disc hub 3 is fixed to the outer peripheral surface of the housing 7. As described above, in the shaft-fixed type fluid dynamic bearing device 1, since the fixed portion between the housing 7 and the disk hub 3 is arranged on the outer periphery of the radial bearing portion R, the fixed portion is arranged in the axial direction of the radial bearing portion R. Designs can be arranged within the area. For this reason, even when the number of mounted disks increases, the support of the bearing sleeve 8 and the housing 7 by the radial bearing portion R can be stabilized and the vibration of the disk hub 3 can be suppressed.

JP 2006-112614 A JP 2006-220307 A

  Further, in order to increase the shake accuracy of the rotating body (reduce the shake), it is important to improve the shake accuracy of the mounting surface of the rotating body in the fluid dynamic pressure bearing device.

  For example, in the case of a shaft rotation type fluid dynamic bearing device 100 as shown in FIG. 10, the disk hub 103 is attached to the outer peripheral surface of the shaft member 102, and the shaft center of the shaft member 102 is the center of rotation. For this reason, by processing the shaft member 102 with high accuracy, the deflection accuracy of the mounting surface of the disk hub 103 (the outer peripheral surface of the shaft member 102) can be increased.

  On the other hand, in the case of the shaft fixed type fluid dynamic bearing device 1 as shown in FIG. 1, the mounting surface of the disk hub 3 is provided on the outer peripheral surface of the housing 7, and the shaft center of the inner peripheral surface of the bearing sleeve 8 is It becomes the center of rotation. Therefore, the deflection accuracy of the mounting surface of the disk hub 3 (the outer peripheral surface of the housing 7) is affected by the dimensional accuracy of the housing 7, the fixing accuracy between the housing 7 and the bearing sleeve 8, and the dimensional accuracy of the bearing sleeve 8. . In this way, the fixed shaft type fluid dynamic bearing device has many points that require increased machining accuracy and fixed accuracy in order to increase the runout accuracy of the mounting surface of the rotating body compared to the rotating shaft type, which increases costs. And this leads to a decrease in productivity.

  The problem to be solved by the present invention is to increase the deflection accuracy of the outer peripheral surface of the housing simply and at low cost in a shaft-fixed type fluid dynamic bearing device.

  In order to solve the above-described problems, the present invention provides a shaft member, a bearing sleeve in which the shaft member is inserted on the inner periphery, a cylindrical housing in which the bearing sleeve is fixed on the inner periphery, and an outer peripheral surface of the shaft member. And a radial bearing portion that rotatably supports the bearing sleeve and the housing with respect to the shaft member on the fixed side by the dynamic pressure action of the fluid film generated in the radial bearing gap between the inner sleeve and the inner peripheral surface of the bearing sleeve In the shaft fixed type fluid dynamic pressure bearing device, the outer peripheral surface of the housing is a surface cut with reference to the inner peripheral surface of the bearing sleeve fixed to the inner peripheral surface.

  In this way, by cutting the outer peripheral surface of the housing with the inner peripheral surface of the bearing sleeve as a reference, the dimensional error of the bearing sleeve and the housing and the assembly error between them can be offset by the cutting of the housing. Thereby, the runout accuracy of the outer peripheral surface of the housing (the mounting surface of the rotating body) with respect to the inner peripheral surface of the bearing sleeve can be increased without unnecessarily increasing the processing accuracy of the bearing sleeve and the housing and the fixing accuracy of both.

  In particular, in fluid dynamic pressure bearing devices used for spindle motors of various disk drive devices, there is an increasing demand for improvement in disk rotation accuracy, and the deflection accuracy of the outer peripheral surface of the housing relative to the inner peripheral surface of the bearing sleeve is increased. For example, it is required to be suppressed to 5 μm or less. According to the present invention, by cutting the outer peripheral surface of the housing on the basis of the inner peripheral surface of the bearing sleeve, the above requirement can be satisfied easily and at low cost.

  In the fluid dynamic bearing device of the present invention, since the dimensional error of the bearing sleeve and the housing and the assembly error between the bearing sleeve and the housing are offset by the cutting of the housing, the dimensional tolerance of the single housing after the cutting becomes large. There is. When the dimensional tolerance of such a single housing becomes large, the weight balance of the rotating member may be lost, and the rotational accuracy may be reduced. Therefore, it is preferable that the dimensional tolerance of the housing, particularly the dimensional tolerance of the thickness in the radial direction, be as small as possible, and specifically, be suppressed to 40 μm or less.

  Since the outer peripheral surface of the housing serves as a mounting surface for the rotating body, it is preferable to reduce the surface roughness as much as possible. Specifically, the surface roughness is preferably set to Ra 0.8 μm or less.

  When the inner peripheral surface of the housing and the outer peripheral surface of the bearing sleeve are fitted with a gap between them and an adhesive is interposed in the gap, so-called gap bonding is difficult, it is difficult to increase the fixing accuracy of both, and there is an assembly error. Therefore, the present invention is particularly preferably applied.

  It is desirable to secure a removal force of the rotating body attached to the outer peripheral surface of the housing of 1500 N or more. The rotating body and the housing can be fixed by press-fitting, for example.

  In the fluid dynamic pressure bearing device, a fixed surface that is press-fitted into the outer peripheral surface of the housing and an flank that is provided in an axial region of the radial bearing portion and has a smaller diameter than the fixed surface. Can be formed. As a result, the housing and the rotating body are not press-fitted (or the pressure input is reduced) in the axial direction region of the radial bearing portion. Therefore, in this region, deformation of the housing and the bearing sleeve, particularly the radial bearing surface (supported by the radial bearing portion). Deformation of the surface, the same applies to the following), and a reduction in the supporting force in the radial direction can be prevented.

  As described above, according to the present invention, in the fluid dynamic bearing device of the fixed shaft type, the deflection accuracy of the outer peripheral surface of the housing can be easily increased at low cost.

It is a sectional view of a spindle motor incorporating a fixed shaft type fluid dynamic bearing device. It is an axial sectional view of a fixed shaft type fluid dynamic bearing device. It is an axial sectional view of a bearing sleeve. It is a top view of a bearing sleeve. It is a bottom view of a bearing sleeve. It is radial direction sectional drawing of a housing and a bearing sleeve. (A)-(c) is sectional drawing which shows the machine which cuts the outer peripheral surface of a housing. It is a device for measuring the deflection accuracy of the outer peripheral surface of the housing with respect to the inner peripheral surface of the bearing sleeve, (a) is a YY sectional view of (b) figure, (b) is (a) figure from the X direction. FIG. It is an axial direction sectional view showing other examples of a shaft fixed type fluid dynamic pressure bearing device. It is sectional drawing of the spindle motor incorporating the shaft rotation type fluid dynamic pressure bearing apparatus.

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

  FIG. 1 is a sectional view of a spindle motor for information equipment incorporating a fluid dynamic bearing device 1 according to the present invention. The spindle motor is used for a disk drive device such as an HDD, and includes a stator coil 4 provided on the fixed side (base 6a) and a rotor magnet 5 provided on the rotation side (disk hub 3). . The fluid dynamic pressure bearing device 1 is a so-called fixed shaft type in which the shaft member 2 is on the fixed side and the housing 7 and the bearing sleeve 8 are on the rotation side. In the present embodiment, the lower end portion of the shaft member 2 is fixed to the base 6 a and the upper end portion is fixed to the cover 6 b, and the disc hub 3 as a rotating body is fixed to the outer peripheral surface of the housing 7. A predetermined number (two in FIG. 1) of disks D are held on the disk hub 3. In the spindle motor configured as described above, when the stator coil 4 is energized, the rotor magnet 5 rotates, and accordingly, the disk hub 3, the disk D, the housing 7, and the bearing sleeve 8 rotate together.

  As shown in FIG. 2, the fluid dynamic bearing device 1 includes a shaft member 2, a bearing sleeve 8 in which the shaft member 2 is inserted on the inner periphery, and a cylindrical housing 7 in which the bearing sleeve 8 is fixed to the inner peripheral surface 7 a. And a sealing member 10 that is fixed to the shaft member 2 and prevents leakage of the lubricating oil to the outside. In the present embodiment, the housing 7 is formed in a cylindrical shape having both ends in the axial direction, and one seal member 10 is provided at each end opening of the housing 7. In the following, for convenience of explanation, in the axial direction, the side where the shaft member 2 protrudes greatly from the housing 7 is defined as the lower side, and the opposite side is defined as the upper side.

  The shaft member 2 is made of, for example, stainless steel and has a substantially cylindrical shape. The outer peripheral surface 2 a of the shaft member 2 includes a cylindrical bearing surface 2 a 1 radially opposed to a radial bearing surface (indicated by a dotted line in FIG. 2) of the inner peripheral surface 8 a of the bearing sleeve 8, and the shaft of the shaft member 2. An escape portion 2a2 is formed which is formed at a substantially central portion in the direction and is slightly smaller in diameter than the support surface 2a1. When applied to a spindle motor of an HDD disk drive device as in this embodiment, the diameter of the shaft member 2 (particularly the diameter of the support surface 2a1) is in the range of 2 to 4 mm. The upper and lower ends of the shaft member 2 are fixed to fixed members (base 6a and cover 6b). In this embodiment, the lower end portion of the shaft member 2 is provided with a press-fit portion 2a3 that protrudes downward from the lower opening of the housing 7 and has a slightly smaller diameter than the support surface 2a1, and the press-fit portion 2a3 is a fixing hole of the base 6a. It is press-fitted and fixed to 6a1. An axial screw hole 2b is formed at the upper end of the shaft member 2, and a bolt or the like (not shown) is fixed to the screw hole 2b via a fixing hole 6b1 provided in the cover 6b. 2 is fixed to the cover 6b.

The bearing sleeve 8 is formed of a metal material or a resin material in a substantially cylindrical shape, and is formed of a sintered metal, particularly copper, iron, or a sintered metal using copper and iron-based metal powder in this embodiment. On the inner peripheral surface 8a of the bearing sleeve 8, a radial dynamic pressure generating portion that generates a dynamic pressure action on a fluid film (for example, an oil film) in the radial bearing gap is formed. It becomes. In this embodiment, as shown in FIG. 3, herringbone-shaped dynamic pressure grooves 8a1 and 8a2 are formed in two regions separated in the axial direction as radial dynamic pressure generating portions. Specifically, herringbone-shaped hill portions 8a10 and 8a20 (shown by cross-hatching in FIG. 4) slightly projecting to the inner diameter are formed in two regions separated in the axial direction of the inner peripheral surface 8a of the bearing sleeve 8. It is formed. The hill portions 8a10 and 8a20 are composed of annular portions 8a11 and 8a21 formed at the substantially central portions in the axial direction, and inclined portions 8a12 and 8a22 extending from the annular portions 8a11 and 8a21 in the axial direction. Dynamic pressure grooves 8a1 and 8a2 are formed between the radial directions of 8a22. The top surfaces of the hill portions 8a10 and 8a20 have a smooth cylindrical surface shape. The groove depth of the dynamic pressure grooves 8a1 and 8a2 (that is, the radial height of the hill portions 8a10 and 8a20) is set in the range of 2.5 to 5 μm, for example. In the present embodiment, the upper dynamic pressure groove 8a1 is formed asymmetrically in the axial direction for the purpose of intentionally creating a circulation of lubricating oil inside the bearing. Specifically, of the dynamic pressure grooves 8a1, the axial dimension X ₁ of the upper region the annular portion 8a11 of the hill portion 8a10 is formed to be larger than the axial dimension X ₂ of the lower region. On the other hand, the lower dynamic pressure groove 8a2 is formed in an axially symmetrical shape.

  The upper end surface 8b and the lower end surface 8c of the bearing sleeve 8 are each formed with a thrust dynamic pressure generating portion that generates a dynamic pressure action on the fluid film in the thrust bearing gap, and the formation region of the thrust dynamic pressure generating portion is a thrust bearing surface. It becomes. In this embodiment, a spiral-shaped dynamic pressure groove 8b1 is formed as a thrust dynamic pressure generating portion on the upper end surface 8b of the bearing sleeve 8 (see FIG. 4), and a spiral-shaped dynamic pressure groove 8c1 is similarly formed on the lower end surface 8c. Formed (see FIG. 5). These dynamic pressure grooves 8b1 and 8c1 are so-called pump-in type dynamic pressure grooves that are formed between the spiral-shaped hill portions 8b10 and 8c10 and push the lubricating oil into the inner diameter side as the shaft member 2 rotates. .

  A predetermined number of axial grooves 8d1 extending in the axial direction are formed on the outer peripheral surface 8d of the bearing sleeve 8. In the present embodiment, for example, three axial grooves 8d1 are formed at equal intervals in the circumferential direction. In the assembled state of the fluid dynamic pressure bearing device 1, as shown in FIG. 2, a circulation path for circulating lubricating oil inside the bearing by the axial groove 8 d 1 of the bearing sleeve 8 and the inner peripheral surface 7 a of the housing 7 is provided. Part is composed.

  The housing 7 is formed in a cylindrical shape with a metal material or a resin material. In this embodiment, the housing 7 is formed in a cylindrical shape having both axial ends opened by brass (see FIG. 2). The outer peripheral surface 8d of the bearing sleeve 8 is fixed to the inner peripheral surface 7a of the housing 7 by, for example, gap adhesion. The method for fixing the housing 7 and the bearing sleeve 8 is not limited to this, and for example, means such as press-fitting, press-fitting with an adhesive, or welding (including ultrasonic welding and laser welding) can be employed.

  The outer peripheral surface 7b of the housing 7 is a surface that is cut with reference to the inner peripheral surface 8a of the bearing sleeve 8 (specifically, the top surfaces of the hill portions 8a10 and 8a20 formed on the inner peripheral surface 8a). Specifically, of the outer peripheral surface 7b of the housing 7, at least a cylindrical fixed surface 7b1 to which the disk hub 3 is press-fitted and fixed (a region excluding the tapered surface 7b2 at the upper end) is the cutting surface. Yes. By this cutting process, the fixed surface 7b1 of the outer peripheral surface 7b of the housing 7 has a deflection accuracy with respect to the inner peripheral surface 8a of the bearing sleeve 8 of 5 μm or less and a surface roughness of Ra 0.8 μm or less. The housing 7 after cutting has a dimensional tolerance of a radial thickness on the fixed surface 7b1 of 40 μm or less. Further, the removal force of the disc hub 3 (see FIG. 1) with respect to the fixed surface 7b1 of the housing 7 is set to 1500 N or more. When both are press-fitted and fixed as in this embodiment, the outer diameter dimension of the fixing surface 7b1 of the housing 7 is set so that the removal force of the disk hub 3 is 1500 N or more.

  The seal member 10 is formed in a ring shape with a metal material or a resin material, and is fixed to the outer peripheral surface 2a of the shaft member 2 by any means such as press fitting, adhesion, welding, welding, and caulking. In the present embodiment, one seal member 10 is arranged on each side of the bearing sleeve 8 in the axial direction, and the end surface 10b on the bearing inner side of each seal member 10 is a thrust bearing surface of the end surfaces 8b and 8c of the bearing sleeve 8 (see FIG. 2 (indicated by a dotted line). The outer peripheral surface 10a of the seal member 10 has a tapered surface shape whose diameter is gradually increased toward the axial center, and a shaft is formed between the tapered outer peripheral surface 10a and the cylindrical inner peripheral surface 7a of the housing 7. A wedge-shaped seal space S is formed in which the radial width gradually decreases toward the center in the direction. In a state in which the lubricating oil is filled in the fluid dynamic pressure bearing device 1, the inner space of the bearing sealed by the seal space S is filled with the lubricating oil including the inner pores of the bearing sleeve 8, and the oil level of the lubricating oil is It is always maintained inside the seal space S.

  In the fluid dynamic pressure bearing device 1 having the above configuration, when the disk hub 3, the housing 7, and the bearing sleeve 8 rotate together, the inner surface 8 a of the bearing sleeve 8 and the outer surface 2 a of the shaft member 2 are interposed. A radial bearing gap is formed. Then, the pressure of the oil film in the radial bearing gap is increased by the dynamic pressure action of the dynamic pressure grooves 8a1 and 8a2 generated along with the rotation of the shaft member 2, and the rotary side member including the bearing sleeve 8 is radialized by this dynamic pressure action. Radial bearing portions R1 and R2 that are supported in a non-contact manner in the direction are formed at two locations separated in the axial direction.

  At the same time, thrust bearing gaps are formed between both end faces 8b and 8c of the bearing sleeve 8 and the end faces 10b of the seal members 10, respectively. Then, the pressure of the oil film in both thrust bearing gaps is increased by the dynamic pressure action of the dynamic pressure grooves 8b1 and 8c1 generated with the rotation of the shaft member 2, and the rotation side member including the bearing sleeve 8 is moved by this dynamic pressure action. Thrust bearing portions T1 and T2 that are supported in a non-contact manner in both thrust directions are formed.

  Hereinafter, the finish cutting process of the outer peripheral surface 7b of the housing 7 will be described. This finishing cutting process is performed by fixing the bearing sleeve 8 and the housing 7 and then cutting (turning) the outer peripheral surface 7b of the housing 7 with the inner peripheral surface 8a of the bearing sleeve 8 as a reference.

First, the outer peripheral surface 8d of the bearing sleeve 8 is fixed to the inner peripheral surface 7a of the housing 7 to constitute a sub-assembly product A as shown in FIG. In this embodiment, both are fixed by gap adhesion. The housing 7 and the bearing sleeve 8 have a shape that is uneven in the circumferential direction because it is practically impossible to form a complete cylindrical shape. Specifically, a thick portion C _max and a thin portion C _min are formed in the housing 7, and a thick portion D _max and a thin portion D _min are formed in the bearing sleeve 8. In addition, it is practically impossible to make the gap between the housing 7 and the bearing sleeve 8 uniform, and the large gap B _max and the small gap B _min are formed. Therefore, the deflection accuracy of the outer peripheral surface 7b ′ of the housing 7 with respect to the inner peripheral surface 8a of the bearing sleeve 8 is affected by the dimensional accuracy and fixing accuracy of the housing 7 and the bearing sleeve 8 before the finish cutting.

  Cutting (turning) is performed on the subassemblies A of the housing 7 and the bearing sleeve 8 fixed as described above. Specifically, first, as shown in FIG. 7A, a cylindrical shaft material 22 ′ is fixed to a rotating device 21 of a cutting machine (not shown), and the rotating device 21 and the shaft material 22 ′ are integrated. Rotate. In this state, the rotating shaft 22 is formed by cutting the outer peripheral surface of the shaft material 22 '(see the dotted line in FIG. 7A). As shown in FIG. 7B, the rotary shaft 22 includes a small-diameter outer peripheral surface 22a that supports the inner peripheral surface 8a of the bearing sleeve 8, and a large-diameter outer peripheral surface 22b provided on the proximal end side of the small-diameter outer peripheral surface 22a. And a radial shoulder surface 22c formed between the small-diameter outer peripheral surface 22a and the large-diameter outer peripheral surface 22b. Thus, by processing the outer peripheral surface of the rotating shaft 22 in a state where the shaft material 22 ′ is rotated together with the rotating device 21, the rotation center of the rotating device 21 and the outer peripheral surface of the rotating shaft 22 (particularly the small-diameter outer peripheral surface 22 a). And the outer peripheral surface of the rotating shaft 22 can be rotated with very good runout accuracy.

  Next, the bearing sleeve 8 and the sub assembly A of the housing 7 are mounted on the rotary shaft 22. At this time, after the outer peripheral surface of the shaft material 22 ′ is cut to form the rotating shaft 22 as described above, the sub-assembly product A is mounted on the rotating shaft 22 without removing the rotating shaft 22 from the rotating device 21. Thus, the sub assembly A can be mounted in a state in which the excellent deflection accuracy of the small-diameter outer peripheral surface 22a of the rotating shaft 22 is maintained. Specifically, the small-diameter outer peripheral surface 22a of the rotary shaft 22 is fitted to the inner peripheral surface 8a of the bearing sleeve 8 (specifically, the top surfaces of the hill portions 8a10 and 8a20 formed on the inner peripheral surface 8a, see FIG. 3). As a result, the inner peripheral surface 8a of the bearing sleeve 8 becomes the reference surface for the finish cutting of the outer peripheral surface 7b of the housing 7.

  In this state, as shown in FIG. 7C, the fixing member 23 is fixed to the distal end portion of the rotating shaft 22, so that the sub assembly product A is positioned and fixed to the rotating shaft 22. The fixing member 23 includes a male screw portion 23a disposed on the shaft center and a contact portion 23b provided around the male screw portion 23a. The male screw portion 23a of the fixing member 23 is fixed to the screw hole 22d of the rotating shaft 22, and the abutting portion 23b is brought into contact with the end surface of the bearing sleeve 8, whereby the abutting portion 23b of the fixing member 23 and the rotating shaft 22 are brought into contact with each other. The bearing sleeve 8 is clamped and fixed from both sides in the axial direction by the shoulder surface 22c.

  Thereafter, the rotating shaft 22 and the sub-assembly A are rotated together, and the fixed surface 7b1 of the outer peripheral surface 7b of the housing 7 is cut in this state (FIG. 6 shows the outer peripheral surface 7b of the housing 7 after cutting by a dotted line. Show). Thus, by processing the outer peripheral surface 7b of the housing 7 with the inner peripheral surface 8a of the bearing sleeve 8 as a reference, even if the dimensional accuracy of each member and the fixing accuracy between the members are not so high, the bearing sleeve 8 The deflection accuracy of the outer peripheral surface 7b of the housing 7 with respect to the inner peripheral surface 8a can be increased. Specifically, the deflection accuracy can be suppressed to 5 μm or less. In other words, when the dimensional accuracy and fixing accuracy of the bearing sleeve 8 and the housing 7 are not set with high accuracy (for example, the radial thickness tolerance of the housing 7 is 5 μm or more, the radial thickness of the bearing sleeve 8 is The tolerance of the radial clearance between the housing 7 and the bearing sleeve 8 is 5 μm or more), and the deflection accuracy of the outer peripheral surface 7b of the housing 7 with respect to the inner peripheral surface 8a of the bearing sleeve 8 is 5 μm or less. If so, it can be estimated that the outer peripheral surface 7b of the housing 7 is cut with the inner peripheral surface 8a of the bearing sleeve 8 as a reference.

  The deflection accuracy of the outer peripheral surface (the outer peripheral surface 7b of the housing 7) of the sub-assembly product A between the bearing sleeve 8 and the housing 7 can be measured by, for example, the apparatus shown in FIG. The measuring device 30 used here includes a pin gauge 31, a base block 32 that fixes the pin gauge 31, and a measuring instrument 33 (for example, a dial gauge) that measures the deflection of the outer peripheral surface of the sub-assembly product A. The pin gauge 31 is fixed to a V-shaped groove 32a formed on the upper surface of the base block 32 by adhesion or the like. The outer diameter of the pin gauge 31 is set so that it can be inserted into the inner peripheral surface (the inner peripheral surface 8a of the bearing sleeve 8) of the sub assembly A and the fitting gap is as small as possible. For example, when the inner diameter of the bearing sleeve 8 is about 4 mm, the fitting gap between the bearing sleeve 8 and the pin gauge 31 is set to 2 μm or less. In a state where the sub assembly product A is extrapolated to the pin gauge 31, the sub assembly product A is rotated once around the pin gauge 31, and the deflection width of the outer peripheral surface of the sub assembly product A at this time is measured by the measuring device 33. In addition, if a measurement location is the fixed surface 7b1 of the outer peripheral surface 7b of the housing 7, a location will not be specifically limited. Moreover, the measurement location may be one point or a plurality of points may be measured.

  The present invention is not limited to the above embodiment. Hereinafter, although other embodiment of this invention is described, the same code | symbol is attached | subjected to the location which has the same structure and function as the said embodiment, and duplication description is abbreviate | omitted.

  For example, as shown in FIG. 9, a clearance surface 7b3 smaller in diameter than the fixed surface 7b1 may be formed in the axial direction region of the radial bearing portions R1 and R2 in the outer peripheral surface 7b of the housing 7. As a result, the housing 7 and the disk hub 3 are not press-fitted on the outer diameter side of the radial bearing portions R1 and R2 (or the pressure input is small). Therefore, in this region, the pressing force received by the housing 7 and the bearing sleeve 8 toward the inner diameter is increased. As a result, the radial bearing surface formed on the inner peripheral surface 8a of the bearing sleeve 8 can be reliably prevented from being deformed.

  In the above embodiment, the shaft member 2 protrudes from both sides of the cylindrical housing 7 in the axial direction. However, the present invention is not limited to this, and a lid (not shown) that closes one axial opening of the housing 7 is used. ) May be provided. This lid portion may be provided separately from the housing, or may be formed integrally with the housing. In this case, only one end of the shaft member 2 is fixed to the fixed side (base 6a).

  Further, the dynamic pressure generating portion formed in the bearing sleeve 8 is not limited to the above, but by forming a dynamic pressure groove of another shape or by making the inner peripheral surface 8a into a multi-arc shape combining a plurality of arcs, A dynamic pressure generating unit may be configured. Alternatively, instead of forming the dynamic pressure generating portion in the bearing sleeve 8, the dynamic pressure generating portion may be formed in the members (the shaft member 2 and the seal member 10) facing each other through the bearing gap. Furthermore, you may comprise what is called a perfect-circle bearing which made both the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a of the shaft member 2 cylindrical shape. In this case, a dynamic pressure generating portion that actively generates the dynamic pressure action is not formed, but the dynamic pressure action is generated by a slight swing of the bearing sleeve 8.

  In the above embodiment, an example in which the fluid dynamic pressure bearing device according to the present invention is incorporated in a spindle motor of an HDD disk drive device is shown. It can also be applied to a polygon scanner motor of a laser beam printer (LBP) or a color wheel motor of a projector.

DESCRIPTION OF SYMBOLS 1 Fluid dynamic pressure bearing apparatus 2 Shaft member 3 Disc hub 4 Stator coil 5 Rotor magnet 6a Base 6b Cover 7 Housing 8 Bearing sleeve 10 Seal member R1 / R2 Radial bearing part T1 / T2 Thrust bearing part S Seal space D Disk 21 Rotating device 22 'Shaft material 22 Rotating shaft 23 Fixed member 30 Measuring device 31 Pin gauge 32 Base block 33 Measuring instrument

Claims (8)

A shaft member, a bearing sleeve having the shaft member inserted into the inner periphery, a cylindrical housing having the bearing sleeve fixed to the inner periphery, and a radial between the outer periphery of the shaft member and the inner periphery of the bearing sleeve In a fixed shaft type fluid dynamic pressure bearing device including a radial bearing portion that rotatably supports a bearing sleeve and a housing with respect to a fixed shaft member by a dynamic pressure action of a fluid film generated in a bearing gap.
A hydrodynamic bearing device characterized in that the outer peripheral surface of the housing is a surface cut with reference to the inner peripheral surface of a bearing sleeve fixed to the inner peripheral surface thereof.   2. The fluid dynamic bearing device according to claim 1, wherein the deflection accuracy of the outer peripheral surface of the housing with respect to the inner peripheral surface of the bearing sleeve is 5 [mu] m or less.   The fluid dynamic bearing device according to claim 1 or 2, wherein a dimensional tolerance of a radial thickness of the housing is 40 µm or less.   The fluid dynamic bearing device according to claim 1, wherein a surface roughness of the outer peripheral surface of the housing is Ra 0.8 μm or less.   The fluid dynamic pressure bearing device according to any one of claims 1 to 4, wherein an inner peripheral surface of the housing and an outer peripheral surface of the bearing sleeve are fixed by gap adhesion.   The fluid dynamic bearing device according to any one of claims 1 to 5, wherein an extraction force of the rotating body fixed to the outer peripheral surface of the housing is 1500 N or more.   The fluid dynamic bearing device according to claim 1, wherein a rotating body is press-fitted and fixed to the outer peripheral surface of the housing.   The fixed surface press-fitted into the inner peripheral surface of the rotating body and the flank surface provided in an axial region of the radial bearing portion and having a smaller diameter than the fixed surface are formed on the outer peripheral surface of the housing. The fluid dynamic pressure bearing device according to any one of the above.

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