JP5726687B2 - Fluid dynamic bearing device - Google Patents

Description

  The present invention relates to a fluid dynamic bearing device.

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

  For example, in Patent Document 1, 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 opening on one end side of the housing are closed. A fluid dynamic bearing device with a bottom is shown. When the shaft member rotates, a radial bearing gap is formed between the outer peripheral surface of the shaft member and the inner peripheral surface of the bearing sleeve, and the shaft member is supported in a non-contact manner so as to be relatively rotatable by a fluid film generated in the radial bearing gap. .

  In the above fluid dynamic bearing device, a communication path is provided between the outer peripheral surface of the bearing sleeve and the inner peripheral surface of the housing in order to maintain the pressure balance of the space on the closed side of the housing. Specifically, an axial groove is provided on the outer peripheral surface of the bearing sleeve, and a communication path is formed by the axial groove and the cylindrical inner peripheral surface of the housing. By this communication path, the space on the closed side of the housing communicates with the space on the open side of the housing, and the space on the closed side of the housing can be maintained at atmospheric pressure.

  Further, in the fluid dynamic pressure bearing device disclosed in the same document, the herringbone-shaped dynamic pressure groove formed on the inner peripheral surface of the bearing sleeve has an axially asymmetric shape. As a result, as the shaft member rotates, the lubricating oil in the radial bearing gap is pushed into the closed side of the housing, moves to the housing opening side through the communication path, and is supplied again to the radial bearing gap. By forcibly circulating the lubricating oil in this way, it is possible to more reliably prevent the generation of a local negative pressure in the internal space of the bearing device.

JP 2011-58542 A

  However, depending on the structure of the fluid dynamic bearing device, it may be difficult to provide the communication path as described above. For example, when a bearing sleeve having an axial groove formed on the outer peripheral surface is used as an insert part and the housing is injection molded with resin, the injected resin fills the axial groove on the outer peripheral surface of the bearing sleeve. Can not form.

  In a fluid dynamic pressure bearing device in which no communication passage is provided, when the axially asymmetric herringbone-shaped dynamic pressure groove is provided as described above and the lubricating oil in the radial bearing gap is pushed toward the closing side of the housing, the housing There is a possibility that the pressure in the space on the closed side will increase excessively and the shaft member will float up (that is, the supporting force on the housing opening side will be excessive).

  For example, if the unbalance of the herringbone-shaped dynamic pressure groove is reduced and the force (pumping force) that pushes the lubricating oil in the radial bearing gap into the housing closing side is reduced, the shaft member can be prevented from overlifting. There is a possibility that the generation of negative pressure in the space on the housing closing side cannot be reliably prevented.

  As described above, when the communication path cannot be provided, it has been difficult to prevent both over-levitation of the shaft member and generation of negative pressure.

  The problem to be solved by the present invention is that in a fluid dynamic pressure bearing device in which a communication path cannot be provided, the pressure in the space on the closed side of the housing is properly maintained, and the shaft member is prevented from over-levitation and generation of negative pressure. There is.

  The present invention made to solve the above-mentioned problems includes a shaft member, a sintered metal sleeve having a shaft member inserted into the inner periphery, a cylindrical housing holding the sleeve on the inner periphery, and a shaft of the housing. Generates a hydrodynamic action on the bottom that closes the opening at one end in the direction, the radial bearing gap formed between the outer peripheral surface of the shaft member and the inner peripheral surface of the sleeve, and the lubricating fluid filled in the radial bearing clearance A fluid dynamic pressure bearing device in which a fixed portion between the sleeve and the housing is not provided with a communication path that communicates both axial ends of the fixed portion. The dynamic pressure groove is a radial bearing. A first inclined groove for pushing the lubricating fluid in the gap toward one axial end side (housing side of the housing), and a second inclined for pushing the lubricating fluid in the radial bearing gap toward the other axial end side (opening side of the housing) Herringbone with grooves When the axial dimension of the first inclined groove is L1, the axial dimension of the second inclined groove is L2, and the axial dimension of the entire dynamic pressure groove is L, L1> L2 and 5 ≦ (L3 / L4) × 100 ≦ 20 (where L3 = L1−L2, L4 = L−L3).

  In this fluid dynamic pressure bearing device, the axial dimension difference between the first inclined groove and the second inclined groove of the herringbone-shaped dynamic pressure groove, that is, the unbalance amount L3 (= L1-L2) of the dynamic pressure groove is determined by the dynamic pressure. It is set to 5% or more of the axial dimension L4 (= L−L3) of the axially symmetric region of the groove. Thereby, even when the communication path is not provided in the fixing portion between the housing and the sleeve, the lubricating oil is sufficiently supplied to the space on the closing side of the housing, and generation of negative pressure in this space can be prevented. Further, by setting the unbalance amount L3 of the dynamic pressure groove to 20% or less of the axial dimension L4 of the axially symmetric region of the dynamic pressure groove, even when the communication path is not provided in the fixing portion between the housing and the sleeve. Further, it is possible to prevent the pressure in the space on the closed side of the housing 7 from becoming excessive, and to prevent the shaft member from excessively floating. At this time, a part of the lubricating oil supplied to the space on the closed side of the housing escapes from the surface opening on the lower end surface of the sleeve to the inside of the sleeve. It is possible to surely prevent the member from overlifting.

  According to the fluid dynamic pressure bearing device described above, the pressure in the space on the closed side of the housing is properly maintained even when the communication path cannot be formed by, for example, molding the housing with resin using the sleeve as an insert part. can do.

  The dynamic pressure groove may have a shape in which, for example, the inclination angle of the first inclined groove with respect to the circumferential direction is equal to the inclination angle of the second inclined groove with respect to the circumferential direction.

  In addition, the dynamic pressure groove includes an annular hill portion between the first inclined groove and the second inclined groove, or the first inclined groove and the second inclined groove are continuous in the axial direction. can do.

  In the above fluid dynamic pressure bearing device, an annular seal portion is provided in the opening on the other axial end side of the housing, and the lubricating fluid leaks between the inner peripheral surface of the seal portion and the outer peripheral surface of the shaft member. A sealing space to prevent can be formed. At this time, the space closer to the housing than the seal space is filled with the lubricating fluid, and the interface between the atmosphere and the lubricating fluid is maintained inside the seal space.

  The housing can be integrally formed with the seal portion or integrally formed with the bottom portion, for example.

  The above-described sleeve can be formed of, for example, a copper iron-based sintered metal.

  The fluid dynamic bearing device described above can be suitably used for a spindle motor of an HDD disk drive device, for example.

  As described above, according to the present invention, in the fluid dynamic pressure bearing device in which the communication path cannot be provided, the pressure in the space on the closed side of the housing is properly maintained, and the shaft member is excessively floated and negative pressure is generated. Can be prevented.

It is sectional drawing of the spindle motor of the disk drive device of HDD incorporating the fluid dynamic pressure bearing apparatus which concerns on embodiment of this invention. It is sectional drawing of the said fluid dynamic pressure bearing apparatus. It is sectional drawing of the sleeve of the said fluid dynamic pressure bearing apparatus. It is a bottom view of the sleeve of the fluid dynamic bearing device. It is a top view of the bottom part of the fluid dynamic bearing device. It is sectional drawing of the sleeve of the fluid dynamic pressure bearing apparatus which concerns on other embodiment. It is sectional drawing of the fluid dynamic pressure bearing apparatus which concerns on other embodiment.

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

  The spindle motor shown in FIG. 1 is used, for example, in an HDD disk drive device. The spindle motor is opposed to the fluid dynamic pressure bearing device 1 according to an embodiment of the present invention and the disk hub 3 fixed to the shaft member 2 of the fluid dynamic pressure bearing device 1 via, for example, a radial gap. In addition, a drive unit 4 including a stator coil 4a and a rotor magnet 4b and a bracket 5 are provided. The stator coil 4 a is fixed to the bracket 5, and the rotor magnet 4 b is fixed to the disk hub 3. The fluid dynamic bearing device 1 is fixed to the inner periphery of the bracket 5. The disk hub 3 holds one or a plurality of disks 6 (two in FIG. 1). In the spindle motor configured as described above, when the stator coil 4a is energized, the rotor magnet 4b rotates, and accordingly, the disk 6 held by the disk hub 3 rotates integrally with the shaft member 2.

  As shown in FIG. 2, the fluid dynamic bearing device 1 includes a shaft member 2, a sleeve 8 made of sintered metal having the shaft member 2 inserted into the inner periphery, and a cylinder having the sleeve 8 fixed to the inner periphery. The housing 7 mainly includes a bottom portion 9 that closes an opening portion on one axial end side of the housing 7, and a seal portion 10 that is disposed on the opening portion on the other axial end side of the housing 7. In this embodiment, the case where the housing 7 and the seal part 10 are integrally formed is shown.

  The shaft member 2 is formed of a metal material such as stainless steel, for example, and includes a shaft portion 2a and a flange portion 2b provided integrally or separately at the lower end of the shaft portion 2a. The outer peripheral surface 2a1 of the shaft portion 2a is a smooth cylindrical surface without irregularities. A clearance portion 2a2 having a slightly smaller diameter than the outer peripheral surface 2a1 is provided at a substantially central portion in the axial direction of the outer peripheral surface 2a1. The flange portion 2b has a disk shape. The upper end surface 2b1 and the lower end surface 2b2 of the flange portion 2b are flat surfaces without unevenness.

  The sleeve 8 is formed of a sintered metal, for example, a copper-based sintered metal mainly composed of copper, an iron-based sintered metal mainly composed of iron, or copper mainly composed of copper and iron. It is made of iron-based sintered metal.

  On the inner peripheral surface 8a of the sleeve 8, radial bearing surfaces 8a1 and 8a2 are provided in two regions separated in the axial direction. Herringbone-shaped dynamic pressure grooves G and F as shown in FIG. 3 are formed on the radial bearing surfaces 8a1 and 8a2.

  The dynamic pressure groove G has an axially asymmetric herringbone shape. Specifically, the dynamic pressure groove G is inclined downward toward the rotation direction leading side (left side in FIG. 3) of the shaft member 2 and a plurality of first inclined grooves G1 arranged side by side in the circumferential direction, The shaft member 2 has a plurality of second inclined grooves G2 which are inclined upward toward the rotational direction leading side and are arranged side by side in the circumferential direction. When the shaft member 2 rotates, the first inclined groove G1 pushes the lubricating oil in the radial bearing gap downward, and the second inclined groove G2 pushes the lubricating oil in the radial bearing gap upward. At this time, the first inclined groove G1 and the second inclined groove G2 have the same inclination angle with respect to the circumferential direction, and the axial dimension L1 of the first inclined groove G1 is the axial dimension L2 of the second inclined groove G2. (L1> L2). For this reason, the downward pumping force by the first inclined groove G1 exceeds the upward pumping force by the second inclined groove G2, and the pumping force that causes the lubricating oil in the radial bearing gap to flow downward is generated as the whole dynamic pressure groove G. . The difference in axial dimension between the first inclined groove G1 and the second inclined groove G2 is set within a predetermined range. Specifically, when the axial dimension of the entire dynamic pressure groove G is L, the unbalanced amount L3 (= L1-L2) of the dynamic pressure groove G and the axially symmetric region of the dynamic pressure groove G The ratio L3 / L4 to the axial dimension L4 (= L−L3) is set in the range of 5% or more and 20% or less (5 ≦ (L3 / L4) × 100 ≦ 20).

  The dynamic pressure groove F has an axially symmetrical herringbone shape. Specifically, the dynamic pressure groove F is inclined downward toward the rotational direction leading side of the shaft member 2, and a plurality of first inclined grooves F1 arranged side by side in the circumferential direction, and the rotational direction of the shaft member 2 A plurality of second inclined grooves F2 that are inclined upward toward the leading side and are arranged side by side in the circumferential direction. When the shaft member 2 rotates, the first inclined groove F1 pushes the lubricating oil in the radial bearing gap downward, and the second inclined groove F2 pushes the lubricating oil in the radial bearing gap upward. Since the first inclined groove F1 and the second inclined groove F2 have the same inclination angle with respect to the circumferential direction and the same axial dimension, the downward pumping force by the first inclined groove F1 and the second inclined groove F2 Therefore, the pumping force that causes the lubricating oil in the radial bearing gap to flow in the axial direction as the entire dynamic pressure groove F does not occur. However, in actuality, due to a processing error of the dynamic pressure groove F, a slight axial pumping force is generated by the dynamic pressure groove F.

  Inclined hill portions G3, G4, F3, and F4 are provided between the circumferential directions of the inclined grooves G1, G2, F1, and F2 of the dynamic pressure grooves G and F, respectively. Further, between the axial direction of the first inclined groove G1 and the second inclined groove G2 of the dynamic pressure groove G and between the axial direction of the first inclined groove F1 and the second inclined groove F2 of the dynamic pressure groove F, Annular hills G5 and F5 are provided. The inclined hill portions G3 and G4 and the annular hill portion G5, and the inclined hill portions F3 and F4 and the annular hill portion F5 (regions indicated by cross-hatching in FIG. 3) are respectively continuous on the same cylindrical surface.

  A cylindrical surface 8a3 is provided between the axial directions of the radial bearing surfaces 8a1 and 8a2. The cylindrical surface 8a3 is continuous on the same cylindrical surface as the second inclined groove G2 of the dynamic pressure groove G and the first inclined groove F1 of the dynamic pressure groove F. The upper end of the first inclined groove G1 of the dynamic pressure groove G reaches the inner peripheral chamfer of the upper end face 8d of the sleeve 8, and the lower end of the second inclined groove F2 of the dynamic pressure groove F is the lower end face 8b of the sleeve 8. Has reached the inner circumference Changfa.

  On the lower end surface 8b of the sleeve 8, a spiral-shaped dynamic pressure groove 8b1 as shown in FIG. 4 is formed. The outer peripheral surface 8c of the sleeve 8 is a smooth cylindrical surface without irregularities. The upper end surface 8d of the sleeve 8 is a flat surface without unevenness.

  The sleeve 8 is formed by compression-molding a mixed metal powder containing copper-based metal powder and iron-based metal powder to form a green compact, and then sintering the green compact to form a sintered body. Manufactured by sizing the body and shaping it to a predetermined dimension. During the sizing process, the dynamic pressure grooves G and F are press-molded on the inner peripheral surface 8 a of the sleeve 8, and the dynamic pressure groove 8 b 1 is press-molded on the lower end surface 8 b of the sleeve 8.

  The housing 7 has a cylindrical shape with both axial ends open (see FIG. 2). The inner peripheral surface 7a of the housing 7 is a smooth cylindrical surface having no irregularities. At the lower end of the inner peripheral surface 7 a of the housing 7, a fixing surface 7 b that is larger in diameter than the inner peripheral surface 7 a and that fixes the bottom 9 is provided. The housing 7 is formed by resin injection molding using the sleeve 8 as an insert member, and the inner peripheral surface 7a of the housing 7 and the outer peripheral surface 8c of the sleeve 8 are in close contact with each other. Accordingly, a communication path that communicates both ends in the axial direction of the fixed portion is not formed in the fixed portion between the inner peripheral surface 7 a of the housing 7 and the outer peripheral surface 8 c of the sleeve 8.

  The bottom 9 is formed in a disk shape from a metal material or a resin material. A spiral dynamic pressure groove 9a1 as shown in FIG. 5 is formed on the upper end surface 9a of the bottom portion 9. The outer peripheral surface 9b of the bottom portion 9 is fixed to the fixing surface 7b of the housing 7 by appropriate means such as bonding, press-fitting, press-fitting with an adhesive interposed, or a combination thereof.

  The seal portion 10 is provided at the upper end opening of the housing 7, and in this embodiment, the seal portion 10 and the housing 7 are integrally formed of resin. The inner peripheral surface 10a of the seal portion 10 has a tapered shape that gradually increases in diameter upward. Between the inner peripheral surface 10a of the seal portion 10 and the outer peripheral surface 2a1 of the shaft portion 2a is formed a wedge-shaped seal space S having a gradually narrowing radial width downward. The lower end surface 10 b of the seal portion 10 is in contact with the upper end surface 8 d of the sleeve 8.

  Lubricating oil is injected into the fluid dynamic bearing device 1 composed of the above components. As a result, the internal space of the fluid dynamic bearing device 1 including the radial bearing gap, the thrust bearing gap, and the internal holes of the sleeve 8 is filled with the lubricating oil. That is, the space on the closed side of the housing 7 with respect to the seal space S is filled with the lubricating oil without interruption, and the oil level is always maintained within the range of the seal space S.

  When the shaft member 2 rotates, a radial bearing gap is formed between the radial bearing surfaces 8a1 and 8a2 (dynamic pressure groove G and F formation region) of the inner peripheral surface 8a of the sleeve 8 and the outer peripheral surface 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 G and F, and by this dynamic pressure action, the first radial bearing portion R1 and the second radial bearing portion R2 that rotatably support the shaft portion 2a in a non-contact manner. Is configured.

  At the same time, between the upper end surface 2b1 of the flange portion 2b and the lower end surface 8b (dynamic pressure groove 8b1 formation region) of the sleeve 8, and the lower end surface 2b2 of the flange portion 2b and the upper end surface 9a of the bottom portion 9 (moving). Thrust bearing gaps are respectively formed between the pressure groove 9a1 formation region). Then, the pressure of the oil film in the thrust bearing gap is increased by the dynamic pressure grooves 8b1 and 9a1, and by this dynamic pressure action, the first thrust bearing portion T1 and the second thrust bearing portion T1 that support the flange portion 2b rotatably in both thrust directions are contacted. And a thrust bearing portion T2.

  At this time, due to the difference in dimensions between the first inclined groove G1 and the second inclined groove G2 of the dynamic pressure groove G, a pumping force that pushes the lubricating oil in the radial bearing gap downward is generated. As described above, when the unbalance amount L3 of the dynamic pressure groove G is set to 5% or more of the axial dimension L4 of the axially symmetric region of the dynamic pressure groove G, the lubricating oil is introduced into the closed space of the housing 7. Sufficiently supplied, and generation of negative pressure in this space can be prevented. Further, by setting the unbalance amount L3 of the dynamic pressure groove G to 20% or less of the axial dimension L4 of the axially symmetric region of the dynamic pressure groove G, the space on the closed side of the housing 7, particularly the flange of the shaft member 2 It is possible to prevent the pressure in the space facing the lower end surface 2b2 of the portion 2b from becoming excessive, and to prevent the shaft member 2 from being overlifted. At this time, part of the lubricating oil supplied to the space on the closed side of the housing 7 escapes from the surface opening of the lower end surface 8b of the sleeve 8 to the inside of the sleeve 8, so the pressure in the space on the closed side of the housing 7 is reduced. The shaft member 2 can be reliably prevented from over-levitation.

  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, the shape of the herringbone-shaped dynamic pressure groove G formed on the inner peripheral surface 8a of the sleeve 8 is not limited to the above. For example, the annular hill portions G5 and F5 shown in FIG. 3 are omitted, and the first inclined groove G1 and the second inclined groove G2 and the first inclined groove F1 and the second inclined groove F2 are respectively shown in FIG. It may be continuous in the axial direction.

  Further, in the above embodiment, the case where the seal portion 10 and the housing 7 are integrally formed is shown. However, the present invention is not limited to this. For example, as shown in FIG. On the other hand, the bottom 9 and the housing 7 may be integrally formed of resin. In this case, the seal portion 10 is formed in a ring shape with a metal material or a resin material, and is fixed to the upper end of the inner peripheral surface of the housing 7.

  In the above-described embodiment, the case where the outer peripheral surface 8c of the sleeve 8 is a smooth cylindrical surface has been described, but the present invention is not limited to this. For example, a recess (for example, an axial groove) may be formed on the outer peripheral surface 8 c of the sleeve 8. In this case, the resin of the housing 7 enters the concave portion, and the sleeve 8 can be prevented from rotating or coming off from the housing 7.

  In the above embodiment, the case where the housing 7 is injection-molded using the sleeve 8 as an insert part is shown. However, the present invention is not limited thereto, and the sleeve 8 and the housing 7 are formed separately and then bonded or press-fitted. You may fix by appropriate means, such as. In particular, in the configuration shown in FIG. 7, it is difficult to injection-mold the housing 7 having the bottom 9 integrally with the sleeve 8 and the shaft member 2 as insert parts. Therefore, after the sleeve 8 and the housing 7 are formed separately and the shaft member 2 is inserted into the inner periphery of the sleeve 8, the outer peripheral surface 8c of the sleeve 8 and the inner peripheral surface 7a of the housing 7 are fixed.

  In the above embodiment, the herringbone-shaped dynamic pressure grooves G and F are formed on the inner peripheral surface 8 a of the sleeve 8. However, the present invention is not limited to this, and the dynamic pressure grooves are formed on the outer peripheral surface 2 a 1 of the shaft member 2. It may be formed. In this case, a dynamic pressure groove can be formed on the outer peripheral surface 2a1 of the shaft member 2 by rolling, for example. In the above-described embodiment, the dynamic pressure grooves G and F (radial bearing surfaces 8a1 and 8a2) are formed at two locations separated in the axial direction of the inner peripheral surface 8a of the sleeve 8. However, the present invention is not limited to this. The groove F may be omitted or the dynamic pressure grooves G and F may be continuous in the axial direction.

  In the above embodiment, as shown in FIGS. 4 and 5, spiral-shaped dynamic pressure grooves 8 b 1 and 9 a 1 are formed on the lower end surface 8 b of the sleeve 8 and the upper end surface 9 a of the bottom portion 9. However, it is not limited to this. For example, although not shown, a herringbone-shaped dynamic pressure groove or a radial groove having a step shape or a wave shape in the circumferential direction can be formed. The pump-in type dynamic pressure groove is not limited to the pump-in type dynamic pressure groove. Further, these dynamic pressure grooves may be formed on the upper end surface 2b1 and the lower end surface 2b2 of the flange portion 2b. In this case, dynamic pressure grooves can be formed on the upper and lower end surfaces 2b1 and 2b2 of the flange portion 2b, for example, by pressing.

  In the above-described embodiment, a so-called shaft rotation type fluid dynamic bearing device in which the shaft member 2 is the rotation side and the sleeve 8 is the fixed side is shown, but not limited thereto, the shaft member 2 is the fixed side, The present invention can also be applied to a so-called shaft-fixed type fluid dynamic bearing device in which the sleeve 8 is the rotating side.

  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.

  In order to confirm the effectiveness of the present invention, a plurality of types of sleeves 8 having different lengths of the first inclined groove G1 of the dynamic pressure groove G are formed, and the fluid dynamic pressure bearing device 1 having each sleeve 8 (see FIG. 3). The shaft member 2 was rotated at 5000 to 8000 rpm, and in each case, the presence or absence of over-levitation of the shaft member 2 and the occurrence of negative pressure was examined.

  As a result, as shown in Table 1, when the unbalance amount L3 (= L1-L2) of the dynamic pressure groove G is 0.10, generation of negative pressure is confirmed, and the unbalance amount L3 of the dynamic pressure groove G is confirmed. Was 0.80 and 1.00, it was confirmed that the shaft member was overlifted. On the other hand, when the unbalance amount L3 of the dynamic pressure groove G was 0.15 and 0.60, neither the shaft member over-levitation nor the generation of negative pressure was confirmed. From this result, the ratio L3 / L4 between the unbalanced amount L3 of the dynamic pressure groove G and the axial dimension L4 of the axially symmetric region of the dynamic pressure groove G is set to 5% or more and 20% or less. It was confirmed that it was possible to prevent both over-levitation and negative pressure.

DESCRIPTION OF SYMBOLS 1 Fluid dynamic pressure bearing apparatus 2 Shaft member 7 Housing 8 Sleeve 9 Bottom part 10 Sealing part G Dynamic pressure groove G1 First inclination groove G2 Second inclination groove G3, G4 Inclined hill part G5 Annular hill part F Dynamic pressure groove F1 First inclination Groove F2 Second inclined groove F3, F4 Inclined hill portion F5 Annular hill portion R1, R2 Radial bearing portion T1, T2 Thrust bearing portion S Seal space

Claims (10)

A shaft member having a shaft portion and a flange portion provided at one axial end of the shaft portion, a sintered metal sleeve having the shaft portion inserted into the inner periphery, and an outer peripheral surface of the sleeve on the inner peripheral surface A fixed cylindrical housing, a bottom portion that closes an opening on one axial end side of the housing, a radial bearing gap formed between an outer peripheral surface of the shaft portion and an inner peripheral surface of the sleeve; Between the first thrust bearing gap formed between the end surface of the sleeve and one end surface of the flange portion facing the sleeve, and the end surface of the bottom portion and the other end surface of the flange portion facing the first thrust bearing gap A second thrust bearing gap formed in the radial bearing, a radial dynamic pressure groove for generating a dynamic pressure action in the lubricating fluid filled in the radial bearing gap, and a dynamic pressure in the lubricating fluid filled in the first thrust bearing gap. Pump interface that generates action Comprises a first thrust dynamic pressure groove flop, and a second second pump-in type for generating a dynamic pressure action on the lubricating fluid filled in the thrust bearing gap of the thrust dynamic pressure groove, the said sleeve housing The fluid dynamic pressure bearing device is not provided with a communication passage communicating with both axial ends of the fixed portion in the fixed portion.
The radial dynamic pressure groove has a first inclined groove for pushing the lubricating fluid in the radial bearing gap toward one end in the axial direction, and a second inclined groove for pushing the lubricating fluid in the radial bearing gap toward the other end in the axial direction. Herringbone shape with
When the axial dimension of the first inclined groove is L1, the axial dimension of the second inclined groove is L2, and the axial dimension of the entire radial dynamic pressure groove is L,
L1> L2 and 5 ≦ (L3 / L4) × 100 ≦ 20
(However, L3 = L1-L2, L4 = L-L3)
A fluid dynamic bearing device characterized by satisfying   The fluid dynamic bearing device according to claim 1, wherein the sleeve is used as an insert part and the housing is injection-molded with resin.   The fluid dynamic bearing device according to claim 1 or 2, wherein a magnitude of an inclination angle with respect to a circumferential direction of the first inclined groove is equal to a magnitude of an inclination angle with respect to the circumferential direction of the second inclined groove.   The fluid dynamic bearing device according to claim 1, wherein an annular hill portion is provided between the first inclined groove and the second inclined groove in the axial direction.   The fluid dynamic bearing device according to any one of claims 1 to 3, wherein the first inclined groove and the second inclined groove are continuous in the axial direction.   An annular seal portion is provided at the opening on the other axial end side of the housing, and a seal space is formed between the inner peripheral surface of the seal portion and the outer peripheral surface of the shaft member to prevent leakage of the lubricating fluid. The fluid dynamic bearing device according to claim 1.   The fluid dynamic bearing device according to claim 6, wherein the seal portion and the housing are integrally formed.   The fluid dynamic bearing device according to claim 1, wherein the housing and the bottom are integrally formed.   The fluid dynamic bearing device according to claim 1, wherein the sleeve is made of a copper iron-based sintered metal.   The fluid dynamic bearing device according to claim 1, wherein the fluid dynamic bearing device is incorporated in a spindle motor of an HDD disk drive device.

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