JP2014129887A - Fluid dynamic pressure bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow easy formation of a hub, and to prevent oil leakage by setting the capacity of a seal space with high accuracy while preventing the deformation of a seal surface when pressing and fixing the hub into the outer peripheral face of a shaft member.SOLUTION: A fluid dynamic pressure bearing device includes a hub 3 protruded from the outer peripheral face of a shaft member 2 to the outer diameter and mounted with a rotating body D, a seal member 9 formed separately from the hub 3, and having a disc part 9a fixed to the outer peripheral face of a shaft part 2a and covering the upper end opening of a housing 7, and a cylindrical part 9b protruded downward from the outer diameter end of the disc part 9a, and the seal space formed between the outer peripheral face of the lateral part of the housing 7 and the inner peripheral face of the cylindrical part 9b of the seal member 9. An axial clearance between the disc part 9a of the seal member 9 and an upper side end face 7a3 of the lateral part 7a of the housing 7 and an axial clearance between the disc part 9a of the seal member 9 and an upper side end face 8c of a bearing sleeve 8 are each set to be a greater value than a total amount δ of thrust bearing clearances from a first thrust bearing part T1 and a second thrust bearing part T2.

Description

  The present invention relates to a fluid dynamic pressure bearing device that rotatably supports a shaft member with an oil film generated in a bearing gap between the shaft member and the bearing member.

  Due to its high rotational accuracy and quietness, the fluid dynamic pressure bearing device has various disk drive devices (for example, magnetic disk drive devices such as HDDs, optical disk drive devices such as CDs, DVDs, and Blu-ray discs, or magneto-optical devices such as MD and MO). It is preferably used for a spindle motor of a disk drive device, a polygon scanner motor of a laser beam printer, a color wheel motor of a projector, a cooling fan motor of an electronic device, or the like.

  As such a fluid dynamic pressure bearing, for example, Patent Document 1 discloses a bearing member (a bearing sleeve and a housing), a shaft member inserted into the inner periphery of the bearing member, and an outer diameter projecting from an end of the shaft member. A configuration with a provided disk hub is shown. A seal space is formed between the inner peripheral surface of the disk hub and the outer peripheral surface of the bearing member, and this seal space prevents leakage of the lubricating oil filled in the bearing member to the outside. Thus, by forming the seal space on the outer periphery of the bearing member, for example, the seal space is increased in diameter and the volume is increased as compared with the case where the seal space is formed on the inner periphery of the bearing member. Accordingly, the axial dimension of the seal space can be reduced while maintaining the volume of the seal space, and the axial dimension of the bearing device can be reduced.

JP 2006-207787 A

  The disk hub provided in the fluid dynamic pressure bearing device of Patent Document 1 includes a disk portion protruding from the outer peripheral surface of the shaft member to the outer diameter, a cylindrical portion protruding in the axial direction from the disk portion, and an outer portion from the cylindrical portion. It integrally has a flange projecting in diameter. A disk mounting surface on which a magnetic disk or the like is mounted is provided on the upper surface of the flange portion, and a seal surface that forms a seal space between the outer peripheral surface of the bearing member is formed on the inner peripheral surface of the cylindrical portion. . Thus, by forming both the disk mounting surface and the seal surface on the disk hub, the disk hub has a complicated shape having a bifurcated portion including a flange portion and a cylindrical portion. For this reason, it becomes difficult to form a disk hub, and there is a possibility that the processing accuracy of the disk mounting surface and the seal surface may be lowered. In particular, it is extremely difficult to form a disk hub having the above-mentioned bifurcated portion by metal pressing.

  Further, when the disk hub is press-fitted and fixed to the outer peripheral surface of the shaft member, the disk hub may be deformed due to resistance during press-fitting. In this case, the seal surface formed on the disk hub may be deformed, the accuracy of the volume of the seal space may be reduced, and oil leakage may occur.

  The problems as described above occur not only when the disk hub is used, but also when the sealing surface is formed on the hub on which the rotating body is mounted. For example, when the seal surface is formed on a hub of a polygon scanner motor on which a polygon mirror is mounted or on a hub of a color wheel motor on which a color wheel is mounted, the same problem as described above occurs.

  The problem to be solved by the present invention is that, in a fluid dynamic pressure bearing device in which a seal space is formed on the outer periphery of a bearing member, by simplifying the shape of the hub and facilitating the formation, the mounting surface of the rotating body and the lubricating oil This is to improve the processing accuracy of the sealing surface.

  Another problem to be solved by the present invention is that even when the hub is press-fitted and fixed to the outer peripheral surface of the shaft member, deformation of the seal surface is prevented, the volume of the seal space is set with high accuracy, and oil leakage is prevented. There is to do.

  In order to solve the above problems, the present invention provides a shaft member having a shaft portion and a flange portion, a bearing sleeve in which the shaft portion is inserted in an inner periphery, and a cylindrical shape in which the bearing sleeve is fixed on an inner peripheral surface. A housing having a bottom portion that closes one side axial opening, a hub that protrudes from the outer peripheral surface of the shaft member to an outer diameter, and on which the rotating body is mounted, the shaft A disk part fixed to the outer peripheral surface of the part and covering the other axial opening of the side part of the housing, and a cylindrical part protruding from the outer diameter end of the disk part to the other axial direction, Leakage of the lubricating oil formed between the seal member formed separately, and the outer peripheral surface of the side portion of the housing and the inner peripheral surface of the cylindrical portion of the seal member, is filled in the housing. A seal space to be prevented, an outer peripheral surface of the shaft portion, and the bearing sleeve. A radial bearing portion that supports the shaft member in the radial direction by a dynamic pressure action generated in an oil film in a radial bearing gap between the inner peripheral surface of the hub, one end surface in the axial direction of the bearing sleeve, and the flange that opposes the radial bearing portion A first thrust bearing portion that supports the shaft member in one thrust direction by a dynamic pressure action generated in an oil film in a thrust bearing gap between the end surface of the housing portion, an end surface of the bottom portion of the housing, and a flange portion that faces the first thrust bearing portion. A fluid dynamic pressure bearing device including a second thrust bearing portion that supports the shaft member in the other thrust direction by a dynamic pressure action generated in an oil film in a thrust bearing gap between the end surface and the disk portion of the seal member And the axial clearance between the other axial end surface of the side portion of the housing and the axial clearance between the disc portion of the seal member and the other axial end surface of the bearing sleeve. To provide a fluid dynamic pressure bearing device which is set to a value greater than the total amount of the thrust bearing gap of the first thrust bearing portion and the second thrust bearing portion.

  Thus, in the fluid dynamic pressure bearing device of the present invention, the seal member is formed separately from the hub on which the rotating body is mounted, and the seal space is formed between the inner peripheral surface of the seal member and the outer peripheral surface of the bearing member. Is formed. That is, a mounting surface on which the rotating body is mounted is formed on the hub, and a sealing surface that forms a seal space is formed on the seal member. Thus, by forming the mounting surface and the seal surface as separate members, it is not necessary to form a bifurcated portion in the hub, and the shape of the hub can be simplified. Therefore, formation of the hub is facilitated, the manufacturing cost can be reduced, and the processing accuracy of the hub is increased. Further, since the sealing surface is not a complicated shape member having a bifurcated portion but a simple shape sealing member, the processing accuracy of the sealing surface is improved.

  By simplifying the shape of the hub as described above, the hub can be formed by, for example, metal press molding.

  In addition, by forming the hub and the seal member separately as described above, for example, even when the hub is press-fitted and fixed to the outer peripheral surface of the shaft member, the influence of the hub press-fitting may affect the seal member. Therefore, the deformation of the seal surface formed on the seal member can be prevented.

  If the inner peripheral surface of the seal member and the outer peripheral surface of the shaft member are fitted via a gap, the seal surface can be reliably prevented from being deformed when the seal member is fixed to the shaft member. In this case, the seal member can be thinned, and cost and weight can be reduced.

  If the shaft member is provided with a locking portion that comes into contact with the end face of the seal member, the seal member can be easily positioned with respect to the shaft member. In this case, the seal member can be clamped and fixed from both sides in the axial direction by the locking portion of the shaft member and the hub.

  For example, a magnetic disk, which is a storage medium of an HDD, can be mounted on the hub as a rotating body.

  As described above, the mounting surface of the rotating body is formed on the hub and the seal surface is formed on the seal member, so that the shape of the hub can be simplified and the formation can be facilitated. Thereby, the processing accuracy of the mounting surface is increased and the rotation accuracy of the rotating body is improved, and the processing accuracy of the seal surface is increased and the sealing performance is improved.

  Further, by fitting the seal member to the shaft member via a gap, it is possible to prevent the seal member from being deformed and to prevent the seal performance from being lowered.

It is sectional drawing of the spindle motor incorporating the fluid dynamic pressure bearing apparatus which concerns on one Embodiment of this invention. It is sectional drawing of a fluid dynamic pressure bearing apparatus. It is sectional drawing of a bearing sleeve. It is a bottom view of a bearing sleeve. It is a top view of a housing. (A)-(d) is sectional drawing which shows the assembly process of a fluid dynamic pressure bearing apparatus. It is sectional drawing which expands and shows the fixed part periphery of a sealing member and a shaft member. It is sectional drawing of the housing which concerns on other embodiment. It is sectional drawing which expands and shows the fixing | fixed part of the housing and bearing sleeve of FIG.

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

  FIG. 1 shows a motor in which a fluid dynamic bearing device 1 according to an embodiment of the present invention is incorporated. This motor is a spindle motor used in, for example, a 2.5-inch HDD disk drive device, and includes a fluid dynamic bearing device 1 that rotatably supports the shaft member 2 and a hub 3 (disk that is fixed to the shaft member 2. Hub), a bracket 6 to which the fluid dynamic bearing device 1 is attached, and a stator coil 4 and a rotor magnet 5 that are opposed to each other through a gap in the radial direction. The stator coil 4 is attached to the bracket 6, and the rotor magnet 5 is attached to the hub 3. A rotating body is mounted on the hub 3, and in the present embodiment, a predetermined number (two in the illustrated example) of magnetic disks D as HDD storage media are mounted. When the stator coil 4 is energized, the rotor magnet 5 is rotated by the electromagnetic force between the stator coil 4 and the rotor magnet 5, whereby the hub 3, the disk D, and the shaft member 2 are rotated together.

  As shown in FIG. 2, the fluid dynamic bearing device 1 includes a shaft member 2, a bearing member A in which the shaft member 2 is inserted on the inner periphery, a hub 3 fixed to an end of the shaft member 2, and a bearing member. And a seal member 9 for sealing the opening of A. In the present embodiment, the bearing member A includes a bottomed cylindrical housing 7 and a bearing sleeve 8 fixed to the inner peripheral surface 7 a 1 of the housing 7. In the following description, in the axial direction, the opening side (sealing member 9 side) of the housing 7 is the upper side, and the closing side (bottom 7b side) is the lower side.

  The shaft member 2 includes a shaft portion 2a and a flange portion 2b provided at the lower end of the shaft portion 2a. The shaft portion 2a includes a large diameter portion 2a1, a small diameter portion 2a2 extending upward from the large diameter portion 2a1, and a shoulder surface 2a3 formed between the large diameter portion 2a1 and the small diameter portion 2a2. The shoulder surface 2a3 functions as a locking portion that comes into contact with the seal member 9 from below. The outer peripheral surface 2a11 of the large-diameter portion 2a1 is formed in a smooth cylindrical surface shape, and a relief portion 2a12 having a slightly smaller diameter than the other regions is formed in the intermediate portion in the axial direction. The flange portion 2b has a disk shape protruding from the lower end portion of the shaft portion 2a to the outer diameter. Both end surfaces 2b1 and 2b2 of the flange portion 2b are formed flat and face the lower end surface 8b of the bearing sleeve 8 and the upper end surface 7b1 of the bottom portion 7b of the housing 7 in the axial direction. The flange portion 2b functions as a retaining member for the shaft member 2 from the bearing member A (the housing 7 and the bearing sleeve 8) by engaging with the lower end surface 8b of the bearing sleeve 8 in the axial direction. The shaft member 2 is formed of a metal such as stainless steel, for example, and the shaft portion 2a and the flange portion 2b are integrally formed by cutting. In addition, after the shaft portion 2a and the flange portion 2b are formed separately from each other by metal, they are joined together by welding or the like, or the shaft portion 2a is formed by metal and the flange portion 2b is formed by resin. You can also.

  The bearing sleeve 8 is formed in a cylindrical shape with a sintered metal mainly composed of copper, for example. In addition, the bearing sleeve 8 can be formed of a soft metal such as brass.

  On the inner peripheral surface 8a of the bearing sleeve 8, there is formed a radial dynamic pressure generating portion that generates a dynamic pressure action on the lubricating oil in the radial bearing gap. In the present embodiment, radial dynamic pressure generating portions are formed in two regions separated in the axial direction of the inner peripheral surface 8a of the bearing sleeve 8 (shown by dotted lines in FIG. 2). For example, as shown in FIG. 3, the radial dynamic pressure generating portion includes herringbone-shaped dynamic pressure grooves 8 a 1 and 8 a 2. The upper dynamic pressure groove 8a1 is formed to be axially asymmetric. Specifically, the axial dimension X1 of the upper region from the cylindrical portion of the central portion in the axial direction of the hill (shown by cross-hatching in FIG. 3) It is larger than the axial dimension X2 of the lower region (X1> X2). The lower dynamic pressure groove 8a2 is formed symmetrically in the axial direction.

  A thrust dynamic pressure generating portion that generates a dynamic pressure action on the lubricating oil in the thrust bearing gap is formed on the lower end surface 8b of the bearing sleeve 8 (indicated by a dotted line in FIG. 2). In the present embodiment, a pump-in type spiral-shaped dynamic pressure groove 8b1 as shown in FIG. 4 is formed as the thrust dynamic pressure generating portion. An axial groove 8d1 is formed over the entire length in the axial direction on the outer peripheral surface 8d of the bearing sleeve 8. In this embodiment, for example, three axial grooves 8d1 are equally arranged in the circumferential direction.

  The housing 7 is formed into a bottomed cylindrical shape by, for example, resin injection molding. In this embodiment, the housing 7 is comprised by the cylindrical side part 7a and the bottom part 7b which obstruct | occludes the lower end opening part of the side part 7a, as shown in FIG. The inner peripheral surface 7a1 of the housing 7 is formed in a cylindrical surface shape, and the outer peripheral surface 8d of the bearing sleeve 8 is fixed by gap bonding, press-fitting, press-fitting with an adhesive interposed therebetween, or the like. At the upper end of the outer peripheral surface 7a2 of the housing 7, a tapered surface 7a21 having a diameter reduced downward is provided, and a cylindrical surface 7a22 is provided below the tapered surface 7a21. The taper surface 7 a 21 forms a seal space S between the inner peripheral surface of the seal member 9. The inner peripheral surface of the bracket 6 (see FIG. 1) is fixed to the cylindrical surface 7a22 by appropriate means such as press-fitting or adhesion.

  On the upper end surface 7b1 of the bottom portion 7b of the housing 7, a thrust dynamic pressure generating portion that generates a dynamic pressure action on the lubricating oil in the thrust bearing gap is formed (indicated by a dotted line in FIG. 2). In this embodiment, a pump-in type spiral-shaped dynamic pressure groove 7b10 as shown in FIG. 5, for example, is formed as the thrust dynamic pressure generating portion.

  The seal member 9 is formed separately from the hub 3 and is fixed to the shaft member 2. In the present embodiment, as shown in FIG. 2, the seal member 9 includes a disk portion 9 a that covers the upper end opening of the housing 7 and a cylindrical portion 9 b that protrudes downward from the outer diameter end of the disk portion 9 a. The disk portion 9a and the cylindrical portion 9b are integrally formed by, for example, metal press molding or resin injection molding.

  The disk portion 9 a is fixed to the shaft portion 2 a of the shaft member 2. Specifically, the inner peripheral surface 9a1 of the disk portion 9a and the outer peripheral surface 2a21 of the small diameter portion 2a2 of the shaft portion 2a are fitted via a gap, and in this state, the disk portion 9a is connected to the shoulder surface 2a3 ( The locking part) and the lower end surface 3a2 of the hub 3 are clamped and fixed from above and below. The lower end surface 9a2 of the disk portion 9a faces the upper end surface 7a3 of the side portion 7a of the housing 7 and the upper end surface 8c of the bearing sleeve 8 with an axial gap δ therebetween. This axial gap δ is filled with lubricating oil and has a value larger than the total amount of thrust bearing gaps of a first thrust bearing portion T1 and a second thrust bearing portion T2, which will be described later. That is, the size of the axial gap δ is set so that the disk portion 9 a does not contact the housing 7 or the bearing sleeve 8 even when the shaft member 2 contacts the bottom portion 7 b of the housing 7.

  The cylindrical portion 9 b is provided so as to surround the outer periphery of the housing 7. The inner peripheral surface 9b1 of the cylindrical portion 9b is opposed to the outer peripheral surface 7a2 of the housing 7 in the radial direction, and a seal space S is formed therebetween. Specifically, a wedge-shaped seal having a radial dimension gradually reduced upward between the cylindrical inner peripheral surface 9b1 of the cylindrical portion 9b and the tapered surface 7a21 of the outer peripheral surface 7a2 of the housing 7. A space S is formed. The seal space S prevents leakage of the lubricating oil filled in the housing 7 to the outside. Specifically, the lubricating oil held inside the seal space S is drawn upward (inside the bearing member A) by the capillary force of the seal space S. Further, by forming the seal space S with the tapered surface 7a21 of the outer peripheral surface 7a2 of the housing 7, a centrifugal force is applied to the lubricating oil in the seal space S when the shaft member 2 rotates, and the lubrication retained in the seal space S is achieved. Oil is drawn upwards. The volume of the seal space S is set to a size that can absorb the thermal expansion of the lubricating oil filled in the bearing member A.

  As shown in FIG. 1, the hub 3 is provided so as to protrude from the outer peripheral surface of the shaft member 2 to the outer diameter. Specifically, a disc portion 3a fixed to the shaft member 2, a cylindrical portion 3b extending downward from the outer diameter end of the disc portion 3a, and a protruding portion 3c protruding from the lower end of the cylindrical portion 3b to the outer diameter. Have. A flat disk mounting surface on which the disk D is mounted is provided on the upper surface 3c1 of the protruding part 3c, and a fixed surface of the rotor magnet 5 is provided on the inner peripheral surface 3b1 of the cylindrical part 3b. The inner peripheral surface 3a1 of the disk portion 3a is press-fitted and fixed to the outer peripheral surface 2a21 of the small diameter portion 2a2 of the shaft portion 2a (see FIG. 2). The lower end surface 3a2 of the disk portion 3a is in contact with the upper end surface 9a3 of the disk portion 9a of the seal member 9.

  As described above, the seal surface that forms the seal space S is formed on the seal member 9, and the disk mounting surface on which the disk D is mounted is formed on the hub 3. The shape of the hub 3 is simplified. Thereby, formation of the hub 3 is facilitated, and the hub 3 can be formed by, for example, metal press molding, the manufacturing cost of the hub 3 is reduced, and the processing accuracy of the disk mounting surface is increased. The rotational accuracy of D is increased. The hub 3 is not limited to metal press molding, and can be formed by, for example, metal machining (cutting or the like) or resin injection molding. Further, since the shape of the seal member 9 can be simplified, the processing accuracy of the seal surface can be increased, and the volume of the seal space S can be set with high accuracy to improve the seal performance.

  The fluid dynamic bearing device 1 is assembled as follows, for example. First, as shown in FIG. 6A, the shaft member 2 and the bearing sleeve 8 are inserted into the inner periphery of the housing 7. At this time, the lower end surface 8b of the bearing sleeve 8 and the upper end surface 7b1 of the bottom portion 7b of the housing 7 are brought into contact with both end surfaces 2b1, 2b2 of the flange portion 2b of the shaft member 2, respectively, and the thrust bearing gap is set to 0. To do. From this state, as shown in FIG. 6B, the shaft member 2 is lifted upward (housing opening side) with respect to the housing 7, and the thrust bearing gaps of the first thrust bearing portion T1 and the second thrust bearing portion T2 are increased. The bearing sleeve 8 is moved in the axial direction relative to the housing 7 by the total amount of the target value. By fixing the bearing sleeve 8 at this position, a thrust bearing gap (exaggerated in FIG. 6) is set.

  Next, as shown in FIG. 6C, the seal member 9 is attached to the shaft portion 2a. At this time, the inner peripheral surface 9a1 of the disk portion 9a of the seal member 9 and the outer peripheral surface 2a21 of the small diameter portion 2a2 of the shaft portion 2a are fitted through a gap (exaggerated in FIG. 6). Thereby, when the seal member 9 is mounted on the shaft portion 2a, a large load is not applied to the disk portion 9a, and deformation of the seal member 9 can be prevented. The axial position of the seal member 9 relative to the shaft member 2 is determined by bringing the lower end surface 9a2 of the disk portion 9a into contact with the shoulder surface 2a3 of the shaft portion 2a.

  Thereafter, as shown in FIG. 6D, the hub 3 is mounted on the shaft portion 2a. The inner peripheral surface 3a1 of the disk portion 3a of the hub 3 has a slightly smaller diameter than the outer peripheral surface 2a21 of the small diameter portion 2a2 of the shaft portion 2a, whereby the hub 3 is press-fitted and fixed to the small diameter portion 2a2 of the shaft portion 2a. At this time, a large load is applied to the hub 3, but this load does not affect the seal member 9, and the accuracy of the seal space S is maintained. Thus, the lower end surface 3a2 of the disc portion 3a of the hub 3 press-fitted into the small diameter portion 2a2 of the shaft portion 2a is brought into contact with the upper end surface 9a3 of the disc portion 9a of the seal member 9. As a result, as shown in an enlarged view in FIG. 7, the disc portion 9 a of the seal member 9 is formed by the lower end surface 3 a 2 of the disc portion 3 a of the hub 3 and the shoulder surface 2 a 3 of the shaft portion 2 a of the shaft member 2. It is clamped from both directions.

  By the way, when the shaft portion 2a is press-fitted into the hub 3, the outer peripheral surface 2a21 of the small diameter portion 2a2 of the shaft portion 2a and the inner peripheral surface 3a1 of the disk portion 3a of the hub 3 slide through the press-fitting allowance. As a result, the surfaces of the shaft portion 2a and the hub 3 are scraped to generate shavings, which may be mixed into the lubricating oil filled in the bearing member A as contamination. At this time, as shown in FIG. 7, by fitting the inner peripheral surface 9a1 of the disk portion 9a of the seal member 9 and the outer peripheral surface 2a21 of the small diameter portion 2a2 of the shaft portion 2a through the gap C, The shavings G generated by press fitting with the small diameter portion 2a2 can be captured in the fitting gap C between the seal member 9 and the shaft portion 2a. In addition, the lower end surface 9a2 of the disk portion 9a of the seal member 9 and the shoulder surface 2a3 of the shaft portion 2a are brought into close contact with each other, so that the lubricating oil (scattering) filled in the fitting gap C and the bearing member A is filled. And the situation in which the shavings G captured in the fitting gap C are mixed into the lubricating oil can be reliably prevented.

  After assembling as described above, the fluid dynamic bearing device 1 shown in FIG. 2 is completed by filling the space inside the housing 7 including the internal pores of the bearing sleeve 8 with the lubricating oil. At this time, the oil level of the lubricating oil is held inside the seal space S.

  When the shaft member 2 rotates, a radial bearing gap is formed between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a11 of the large diameter portion 2a1 of the shaft portion 2a. Then, the pressure of the oil film in the radial bearing gap is increased by the dynamic pressure grooves 8a1 and 8a2, and the radial bearing portions R1 and R2 that support the shaft member 2 in a non-contact manner in the radial direction are configured by this pressure (dynamic pressure action). Is done.

  At the same time, between the lower end surface 8b of the bearing sleeve 8 and the upper end surface 2b1 of the flange portion 2b, and between the upper end surface 7b1 of the bottom portion 7b of the housing 7 and the lower end surface 2b2 of the flange portion 2b, respectively. A thrust bearing gap is formed. Then, the pressure of the oil film in the thrust bearing gap is increased by the dynamic pressure grooves 8b1 and 7b10, and the thrust bearing portions T1 and T2 for supporting the shaft member 2 in a non-contact manner so as to be rotatable in both thrust directions by this pressure (dynamic pressure action). Composed.

  At this time, the axial groove 8d1 formed in the outer peripheral surface 8d of the bearing sleeve 8 forms a communication path through which lubricating oil can flow. In this communication path, the closed side space (the space facing the bottom portion 7b) of the housing 7 and the open side space (the space facing the seal member 9) communicate with each other, and the lubricating oil filled in the bearing member A It is possible to prevent the occurrence of local negative pressure. In particular, in this embodiment, as shown in FIG. 3, the upper dynamic pressure groove 8a1 is formed in an axially asymmetric shape, so that the lubricating oil in the radial bearing gap is pushed downward as the shaft member 2 rotates. As a result, the lubricating oil is forcibly circulated through the communication path, and local negative pressure can be reliably prevented.

  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 function similar to said embodiment, and description is abbreviate | omitted.

  In the above embodiment, the seal member 9 is sandwiched and fixed between the shoulder surface 2a3 of the shaft portion 2a of the shaft member 2 and the lower end surface 3a2 of the disk portion 3a of the hub 3, but this is not restrictive. For example, an adhesive may be interposed between the outer peripheral surface 2a21 of the small diameter portion 2a2 of the shaft portion 2a and the inner peripheral surface 9a1 of the disk portion 9a of the seal member 9 to fix the shaft portion 2a. Or you may fix the axial part 2a and the sealing member 9 by means, such as welding and ultrasonic welding. In these cases, since the hub 3 is not involved in fixing the seal member 9 and the shaft portion 2a, the seal member 9 is fixed to the shaft portion 2a and the seal space S is formed before the hub 3 is attached to the shaft portion 2a. be able to. Therefore, it is possible to inject the lubricating oil into the bearing member A in a state where the hub 3 is not attached to the shaft portion 2a.

  In the above-described embodiment, the case where the HDD 3 is mounted with the HDD magnetic disk D as the rotating body is shown in the hub 3, but the present invention is not limited thereto. For example, the present invention can be applied to a hub 3 on which a polygon mirror of a polygon scanner motor or a color wheel of a color wheel motor is mounted.

  In the above embodiment, the case where the inner peripheral surface 7a1 of the housing 7 has a cylindrical surface shape (circular cross section) is shown. However, the present invention is not limited to this. For example, as shown in FIG. The inner peripheral surface 7a1 may be a non-circular shape (a regular decagon in the illustrated example). When the bearing sleeve 8 is lightly press-fitted into the inner peripheral surface 7 a 1 of the housing 7, the inner peripheral surface 7 a 1 of the housing 7 is brought into contact with the cylindrical sleeve outer peripheral surface 8 d of the bearing sleeve 8 in an elastically deformed state. Can do. Thereby, the processing accuracy of the inner peripheral surface 7a1 of the housing 7 is relaxed, and the manufacturing cost can be reduced. In this case, a gap P extending in the axial direction is formed between the inner peripheral surface 7a1 of the housing 7 and the outer peripheral surface 8d of the bearing sleeve 8 as shown in FIG. If this gap P is used as a communication path for lubricating oil, the axial groove 8d1 on the outer peripheral surface 8d of the bearing sleeve 8 as shown in FIG. 4 can be omitted, and the manufacturing cost of the bearing sleeve 8 is reduced. Since the cylindrical surface 7a22 of the outer peripheral surface 7a2 of the housing 7 is fixed to the inner peripheral surface of the bracket 6, it is preferable that at least the region where the bracket 6 is fixed has a cylindrical surface shape as shown in FIG.

  In the above embodiment, the bearing member A is constituted by a plurality of members (the housing 7 and the bearing sleeve 8). However, the present invention is not limited to this, and the bearing member A may be integrally formed, for example.

  Further, in the above embodiment, herringbone-shaped dynamic pressure grooves 8a1 and 8a2 as shown in FIG. 3 are formed as the radial dynamic pressure generating portion, but the present invention is not limited to this. For example, another shape of dynamic pressure grooves (such as a dynamic pressure groove extending in the axial direction) is formed on the inner peripheral surface 8a of the bearing sleeve 8, or the inner peripheral surface 8a is formed into a multi-arc shape by combining a plurality of cylindrical surfaces. Thus, a radial dynamic pressure generating unit may be configured. Or you may comprise what is called a perfect-circle bearing by making both the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a11 of the shaft member 2 which oppose through a radial bearing clearance into a smooth cylindrical surface shape. In this case, there is no radial dynamic pressure generating section that actively generates a dynamic pressure action on the oil film in the radial bearing gap, but the oil film pressure in the radial bearing gap increases due to the flow of the lubricating oil accompanying the rotation of the shaft member 2. It is done.

  In the above embodiment, spiral dynamic pressure grooves 8b1 and 7b10 as shown in FIGS. 4 and 5 are formed as thrust dynamic pressure generating portions that generate a dynamic pressure action on the lubricating oil in the thrust bearing gap. However, the present invention is not limited to this. For example, another shape of the dynamic pressure groove (such as a herringbone-shaped dynamic pressure groove) may be formed.

  Further, in the above embodiment, the radial dynamic pressure generating portion is formed on the inner peripheral surface of the bearing sleeve 8, but the radial dynamic pressure is applied to the outer peripheral surface 2a11 of the shaft member 2 facing this surface through the radial bearing gap. You may form a generation | occurrence | production part. Similarly, the thrust dynamic pressure generating portion may be formed on both end faces 2b1, 2b2 of the flange portion 2b of the shaft member 2.

DESCRIPTION OF SYMBOLS 1 Fluid dynamic pressure bearing apparatus 2 Shaft member 2a Shaft part 2a1 Large diameter part 2a2 Small diameter part 2a3 Shoulder surface 2b Flange part 3 Hub 3a Disk part 3b Cylindrical part 3b1 Inner peripheral surface 3c Protrusion part 3c1 Upper surface (disk mounting surface)
4 Stator coil 5 Rotor magnet 6 Bracket 7 Housing 7a Side 7b Bottom 7b10 Dynamic pressure groove 8 Bearing sleeve 8a1, 8a2 Dynamic pressure groove 8b1 Dynamic pressure groove 8d1 Axial groove 9 Seal member 9a Disk part 9b Cylindrical part 9b1 Inner circumferential surface ( Seal surface)
A Bearing member C Fitting gap D Disc G Shavings R1, R2 Radial bearing portion T1, T2 Thrust bearing portion S Seal space δ Axial clearance

Claims (2)

A shaft member having a shaft portion and a flange portion; a bearing sleeve having the shaft portion inserted into an inner periphery; a cylindrical side portion having the bearing sleeve fixed to an inner peripheral surface; and one axial direction of the side portion A housing having a bottom portion that closes the opening of the shaft, a hub that protrudes from the outer peripheral surface of the shaft member to an outer diameter, is mounted with a rotating body, and is fixed to the outer peripheral surface of the shaft portion. A sealing member formed separately from the hub, and having a disc portion covering the other axial opening of the disc portion, a cylindrical portion projecting from the outer diameter end of the disc portion to the other axial direction, and the housing A seal space that is formed between the outer peripheral surface of the side portion and the inner peripheral surface of the cylindrical portion of the seal member, and prevents leakage of lubricating oil filled in the housing; and the outer peripheral surface of the shaft portion Radial bearing gap between the bearing sleeve and the inner peripheral surface of the bearing sleeve An oil film in a thrust bearing gap between a radial bearing portion that supports the shaft member in a radial direction by a dynamic pressure action generated in the oil film, and one end surface in the axial direction of the bearing sleeve and an end surface of the flange portion that opposes the bearing sleeve. Movement generated in an oil film in a thrust bearing gap between the first thrust bearing portion that supports the shaft member in one thrust direction by the generated dynamic pressure action, and the end surface of the bottom portion of the housing and the end surface of the flange portion facing the first thrust bearing portion. A fluid dynamic pressure bearing device comprising a second thrust bearing portion that supports the shaft member in the other thrust direction by pressure action,
An axial gap between the disc portion of the seal member and the other axial end surface of the side portion of the housing, and an axial direction between the disc portion of the seal member and the other axial end surface of the bearing sleeve The fluid dynamic pressure bearing device in which the gap is set to a value larger than the total amount of thrust bearing gaps of the first thrust bearing portion and the second thrust bearing portion. The fluid dynamic bearing device according to claim 1, wherein the entire surface of the other end surface in the axial direction of the disk portion is in contact with the end surface of the hub.

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