US20120230618A1 - Fluid dynamic bearing device - Google Patents

Fluid dynamic bearing device Download PDF

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Publication number
US20120230618A1
US20120230618A1 US13/509,910 US201013509910A US2012230618A1 US 20120230618 A1 US20120230618 A1 US 20120230618A1 US 201013509910 A US201013509910 A US 201013509910A US 2012230618 A1 US2012230618 A1 US 2012230618A1
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US
United States
Prior art keywords
sealing member
peripheral surface
bearing sleeve
axial
outer peripheral
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US13/509,910
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English (en)
Inventor
Kouyou Suzuki
Hiroshi Niwa
Fuminori Satoji
Kimihiko Bito
Yoshiharu Inazuka
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NTN Corp
Original Assignee
NTN Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP2009292554A external-priority patent/JP2011133023A/ja
Priority claimed from JP2010029638A external-priority patent/JP5670061B2/ja
Application filed by NTN Corp filed Critical NTN Corp
Assigned to NTN CORPORATION reassignment NTN CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: SATOJI, FUMINORI, BITO, KIMIHIKO, INAZUKA, YOSHIHARU, NIWA, HIROSHI, SUZUKI, KOUYOU
Publication of US20120230618A1 publication Critical patent/US20120230618A1/en
Abandoned legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C32/00—Bearings not otherwise provided for
    • F16C32/06—Bearings not otherwise provided for with moving member supported by a fluid cushion formed, at least to a large extent, otherwise than by movement of the shaft, e.g. hydrostatic air-cushion bearings
    • F16C32/0629—Bearings not otherwise provided for with moving member supported by a fluid cushion formed, at least to a large extent, otherwise than by movement of the shaft, e.g. hydrostatic air-cushion bearings supported by a liquid cushion, e.g. oil cushion
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C17/00—Sliding-contact bearings for exclusively rotary movement
    • F16C17/10—Sliding-contact bearings for exclusively rotary movement for both radial and axial load
    • F16C17/102—Sliding-contact bearings for exclusively rotary movement for both radial and axial load with grooves in the bearing surface to generate hydrodynamic pressure
    • F16C17/107—Sliding-contact bearings for exclusively rotary movement for both radial and axial load with grooves in the bearing surface to generate hydrodynamic pressure with at least one surface for radial load and at least one surface for axial load
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/02—Parts of sliding-contact bearings
    • F16C33/04—Brasses; Bushes; Linings
    • F16C33/06—Sliding surface mainly made of metal
    • F16C33/10—Construction relative to lubrication
    • F16C33/1025—Construction relative to lubrication with liquid, e.g. oil, as lubricant
    • F16C33/106—Details of distribution or circulation inside the bearings, e.g. details of the bearing surfaces to affect flow or pressure of the liquid
    • F16C33/1085—Channels or passages to recirculate the liquid in the bearing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/72—Sealings
    • F16C33/74—Sealings of sliding-contact bearings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/72—Sealings
    • F16C33/74—Sealings of sliding-contact bearings
    • F16C33/741—Sealings of sliding-contact bearings by means of a fluid
    • F16C33/743—Sealings of sliding-contact bearings by means of a fluid retained in the sealing gap
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/72—Sealings
    • F16C33/74—Sealings of sliding-contact bearings
    • F16C33/741—Sealings of sliding-contact bearings by means of a fluid
    • F16C33/743—Sealings of sliding-contact bearings by means of a fluid retained in the sealing gap
    • F16C33/745—Sealings of sliding-contact bearings by means of a fluid retained in the sealing gap by capillary action
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2220/00—Shaping
    • F16C2220/02—Shaping by casting
    • F16C2220/04—Shaping by casting by injection-moulding

Definitions

  • the present invention relates to a fluid dynamic bearing device in which a shaft member is supported to be relatively freely rotatable by a dynamic pressure action of a lubricating oil, which is to be generated in bearing gaps.
  • a bearing sleeve made of a sintered metal is fixed to an inner periphery of a bottomed cylindrical housing, and a shaft member is inserted along an inner periphery of the bearing sleeve.
  • the shaft member is supported by a dynamic pressure action of a lubricating oil, which is to be generated in radial bearing gaps formed between an outer peripheral surface of the shaft member and an inner peripheral surface of the bearing sleeve.
  • a sealing member is fixed to an end portion of the bearing sleeve, and the lubricating oil filling an inside of the housing is sealed by this sealing member.
  • the sealing member comprises an integral piece of a disk-like first sealing portion to abut against an end surface of the bearing sleeve and a cylindrical second sealing portion to abut against an outer peripheral surface of the bearing sleeve.
  • a first seal space is formed between an inner peripheral surface of the first sealing portion and the outer peripheral surface of the shaft member, and a second seal space is formed between an outer peripheral surface of the second sealing portion and an inner peripheral surface of the housing.
  • the above-mentioned sealing member is formed, for example, by injection molding of a resin.
  • a fluid dynamic bearing device disclosed in Patent Literature 2 comprises: a shaft member; a bearing member having an inner periphery along which the shaft member is inserted; and a sealing member provided at an opening portion of the bearing member so as to seal a lubricating oil filling an inside of the bearing member.
  • the sealing member of this fluid dynamic bearing device is formed by injection molding of a resin.
  • a shape of the outer peripheral surface of the sealing member can be conformed to a shape of the outer peripheral surface of the bearing sleeve.
  • accuracy of the outer peripheral surface of the sealing member itself is low, by conforming the shape of the sealing member to the shape of the outer peripheral surface of the bearing sleeve that has been processed with high accuracy, the accuracy of the outer peripheral surface of the sealing member can be increased.
  • the sealing member is press-fitted to the bearing sleeve in this way, a high load is applied to the sealing member, which leads to a risk that the sealing member is subjected to damage such as cracking.
  • a weld line may be formed at a merging portion of the resin that has been injected into a cavity.
  • Such a portion formed a weld-line is more fragile than other regions, and hence the damage to be caused by press-fitting as described above is liable to start from this portion.
  • the communication paths for communicating the first seal space and the second seal space to each other are formed of axial grooves formed in an inner peripheral surface of the sealing member, a thickness of the sealing member is reduced by an amount of the axial grooves thus formed. As a result, strength of the sealing member is reduced.
  • the fragile portion with the weld line is formed in such a thin portion, strength of this part is locally markedly reduced, which leads to a higher risk that the damage as described above is caused by press-fitting.
  • a countermeasure for example, when a thickness of the sealing member is generally increased to enhance the strength, the damage to be caused by press-fitting is prevented.
  • a countermeasure causes higher material cost and an increase in dimension of the fluid dynamic bearing device in general, and hence is not preferred.
  • the sealing member is formed by injection molding in a manner that the weld line is not formed, the strength can be increased.
  • FIG. 10 a when a pin gate 103 is provided at a center of a bottom portion 102 of a bottomed cylindrical cavity 101 and a molten resin is injected from the pin gate 103 , the molten resin flows in all circumferential directions without being divided (refer to FIG. 10 b ). Thus, the weld line is not formed.
  • FIG. 11 it is necessary to perform a step of removing a central part 120 of a bottom portion 111 of a bottomed cylindrical molded product 110 , and hence processing becomes more troublesome.
  • the weld line is not formed also when an annular film gate is provided to a die set for molding the sealing member (not shown).
  • an annular gate mark is formed on the molded product, and hence an operation of removing the gate mark is required, which is troublesome.
  • Patent Literature 2 above discloses a method of forming a sealing member 200 by injecting, as illustrated in FIG. 27 a , a molten resin Q from a gate 202 (film gate) provided at a position corresponding to an outer peripheral edge portion of an outer end surface 201 (end surface on an atmosphere contact side) of the sealing member 200 .
  • a gate cutting mark 203 projected from the outer end surface 201 of the sealing member 200 is formed, and hence there is a risk that the gate cutting mark 203 comes into contact with other members such as a disk hub.
  • the gate portion of the resin-molded product is cut off by being plucked simultaneously with opening the die set, and hence the resin of the gate portion is stretched before being perfectly cured.
  • it is difficult to control a projecting amount of the gate mark which leads to a higher risk that the gate cutting mark 203 projects from the outer end surface 201 of the sealing member 200 and comes in contact with members on a rotary side (disk hub and the like).
  • the sealing member 200 is taken out of the die set, it is necessary to perform a post-treatment process on the gate cutting mark 203 (removal process along the line X in FIG. 27 b ).
  • man-hours increase, with the result that higher processing cost is required.
  • a gate mark 302 is formed in a spot-facing portion (sunk part with respect to an end surface) 303 provided in an end surface 301 of a sealing member 300 , the gate mark 302 is prevented from projecting from the end surface 301 of the sealing member.
  • a die set for molding the sealing member 300 has to have more complicated shape, which leads to an increase in processing cost.
  • an oil-repellent agent is applied to the end surface 301 , there is a risk that the oil-repellent agent pools in the spot-facing portion 303 and more of the oil-repellent agent is wasted.
  • the outer peripheral surface 304 of the sealing member 300 serves as a bonding fixation surface with respect to other members and the oil-repellent agent flows down to the bonding fixation surface, there is a risk that an adhesive cannot be uniformly applied and the sealing member 300 is less firmly fixed.
  • Patent Literature 2 above discloses an example in which, as illustrated in FIG. 29 , gates 402 (pin gates) are provided at positions corresponding to an inner end surface 401 (end surface on an oil contact side) of a sealing member 400 (the sealing member 400 illustrated in FIG. 29 is upside-down with respect to the sealing member 200 illustrated in FIG. 27 a ).
  • gate cutting marks are formed on the inner end surface 401 of the sealing member 400 , and fine resin remnants are formed on the gate cutting marks.
  • the gate cutting marks come into contact with the lubricating oil, there is a risk that the resin remnants are mixed as contaminants into the lubricating oil.
  • the present invention provides a fluid dynamic bearing device, comprising: a shaft member; a bearing sleeve having an inner periphery along which the shaft member is inserted; a housing having an inner periphery by which the bearing sleeve is held; a sealing member comprising an injection-molded product of a resin and having: a large-diameter inner peripheral surface which is fixed to an outer peripheral surface of an end portion of the bearing sleeve by press-fitting; and a small-diameter inner peripheral surface; a radial bearing portion for generating a dynamic pressure action of a lubricating oil in a radial bearing gap between an outer peripheral surface of the shaft member and an inner peripheral surface of the bearing sleeve so as to support the shaft member in a radial direction; a first seal space formed between the small-diameter inner peripheral surface of the sealing member and the outer peripheral surface of the shaft member so as to seal the lubricating oil
  • the sealing member when the weld line as a result of injection molding of the sealing member is formed at the circumferential position out of the deepest portion of the axial groove, which forms a thinned portion of the sealing member, the sealing member is prevented from being provided with parts having locally low strength, and hence damage to be caused by press-fitting is prevented.
  • the axial groove formed in the large-diameter inner peripheral surface of the sealing member comprises a plurality of axial grooves
  • the weld line be formed at a circumferential position out of a deepest portion of the radial groove.
  • a fluid dynamic bearing device to be used in a disk drive device for HDDs which has a shaft member whose diameter ranges from 2 mm to 4 mm
  • the press-fitting margin of the sealing member and the bearing sleeve difference in diameter between the sealing member and the bearing sleeve
  • the outer peripheral surface of the sealing member can be conformed to the shape of the bearing sleeve. Note that, press-fitting operation is difficult when the press-fitting margin is excessively large.
  • the lubricating oil filling the inside of the housing comprises an ester-based lubricating oil.
  • strength of a portion formed a weld-line is influenced by a curing speed of a molten resin charged in the cavity. Specifically, strength of the portion tends to decrease when the resin is quickly cured, and the strength of the portion tends to increase when the resin is slowly cured.
  • the sealing member is constantly held in contact with the lubricating oil (in particular, ester-based lubricating oil) filling the inside of the housing, and hence, when a resin for the sealing member is poor in oil resistance, there is a risk that strength of the sealing member decreases or stress cracks occur.
  • the resin for the sealing member be slowly cured and excellent in oil resistance.
  • examples of such a resin comprise crystalline resins, in particular, a crystalline resin selected from a group consisting of PPS, ETFE, PEEK, PA66, PA46, PA6T, and PA9T.
  • the communication path can be formed, for example, of an axial groove formed in an outer peripheral surface of the bearing sleeve and the above-mentioned axial groove of the sealing member.
  • the weld line can be provided at the circumferential position out of the deepest portion of the odd number of axial grooves.
  • the present invention provides a fluid dynamic bearing device comprising: a shaft member; a bearing member having an inner periphery along which the shaft member is inserted; a sealing member fixed to an opening portion of the bearing member so as to seal a lubricating oil filling an inside of the bearing member; and a radial bearing portion for generating a dynamic pressure action of a lubricating oil in a radial bearing gap between an outer peripheral surface of the shaft member and an inner peripheral surface of the bearing sleeve so as to support the shaft member in a radial direction; wherein the sealing member comprises an injection-molded product formed by injecting a resin from a side gate, and wherein a gate mark with respect to the side gate is formed at a position lower than an axial position of an outer end surface of the sealing member.
  • the sealing member is formed by injection of a resin from what is called a side gate formed in a die opening surface of a die set, a gate portion of a resin-molded product is not plucked off by die opening, and hence the gate mark is not stretched.
  • the gate mark to be formed on an outer peripheral surface of the sealing member can be provided at a position lower than the axial position of the outer end surface of the sealing member.
  • the “position out of contact with the lubricating oil” means a position out of contact with the lubricating oil inside the bearing member sealed by the sealing member, and hence does not exclude a position at which a lubricating oil having leaked from the inside of the bearing member may come into contact with the gate mark.
  • a seal space is formed of the outer peripheral surface of the sealing member, it suffices that, on the outer peripheral surface of the sealing member, the gate mark is formed on the atmosphere side with respect to an oil surface within the seal space.
  • the gate mark is formed at a position out of an inner end portion of a fixation surface with respect to the bearing member.
  • the gate mark projects to an outer-diameter side from the fixation surface provided with respect to the bearing member, there is a fear in that fixation to the bearing member is disturbed, and hence it is preferred that the gate mark be formed on an inner-gate side with respect to the fixation surface provided with respect to the bearing member.
  • the gate mark can be formed, for example, on a chamfered portion formed at an upper end of the outer peripheral surface of the sealing member.
  • the outer end surface of the sealing member can be flattened.
  • an oil-repellent agent is applied to this end surface, there occurs no problem such as an increase in amount of wasted oil-repellent agent or flowing of the oil-repellent agent down to the outer peripheral surface of the sealing member unlike the case where the spot-facing portion is provided in the end surface (refer to FIG. 17 ).
  • the sealing member as described above can be manufactured by the steps of: injecting a molten resin from a runner into a cavity through a side gate formed in a molding surface for molding the outer peripheral surface of the sealing member; taking out, after the resin has been cured, a resin-molded product formed of an integral piece of a runner resin portion cured in a runner and the sealing member from a die set; and separating the runner resin portion and the sealing member from each other.
  • the gate mark is not stretched simultaneously with die opening, and the gate mark is prevented from projecting from the end surface of the sealing member.
  • the runner resin portion and the sealing member of the resin-molded product taken out of the die set are separated from each other by bending a boundary portion between the runner resin portion and the sealing member, a situation in which the gate mark is stretched is reliably prevented.
  • the sealing member is prevented from being damaged by press-fitting to the bearing sleeve.
  • the present invention without causing an increase in processing cost or entry of contaminants into the lubricating oil, it is possible to reliably prevent a situation that the gate mark of the sealing member, which is an injection-molded product of a resin, comes into contact with other members such as the disk hub.
  • FIG. 1 A sectional view of a spindle motor of a disk drive device for HDDs.
  • FIG. 2 A sectional view of a fluid dynamic bearing device.
  • FIG. 3 A sectional view of a bearing sleeve.
  • FIG. 4 A sectional view taken along the line A-A ( FIG. 5 ) of a sealing member.
  • FIG. 5 A plan view of the sealing member viewed in a direction of the arrow B of FIG. 4 .
  • FIG. 6 A sectional view of a die set for forming the sealing member by injection molding.
  • FIG. 7 A sectional view taken along the line X-X of the die set of FIG. 6 .
  • FIG. 8 A sectional view illustrating a state in which the bearing sleeve and the sealing member are fixed to each other by press-fitting.
  • FIG. 9 A sectional view illustrating Example.
  • FIG. 10 a A sectional view illustrating Reference Example of the die set for forming the sealing member by injection molding.
  • FIG. 10 b A sectional view taken along the line Y-Y of the die set of FIG. 10 a.
  • FIG. 11 A sectional view illustrating a method of forming the sealing member according to Reference Example.
  • FIG. 12 A sectional view of a spindle motor of a disk drive device for HDDs.
  • FIG. 13 A sectional view of a fluid dynamic bearing device.
  • FIG. 14 A sectional view of a bearing sleeve.
  • FIG. 15 A sectional view illustrating a state in which the bearing sleeve and the sealing member are fixed to each other by press-fitting.
  • FIG. 16 A sectional view taken along the line A-A ( FIG. 17 ) of the sealing member.
  • FIG. 17 A plan view of the sealing member viewed in a direction of the arrow B of FIG. 16 .
  • FIG. 18 An enlarged sectional view illustrating a vicinity of a gate mark of the sealing member.
  • FIG. 19 A sectional view of a die set for forming the sealing member by injection molding.
  • FIG. 20 An enlarged sectional view illustrating a vicinity of a gate of the die set of FIG. 19 .
  • FIG. 21 A sectional view taken along the line X-X of the die set of FIG. 19 .
  • FIG. 22 a A side view illustrating a step of separating a resin cured in a runner and the sealing member from each other.
  • FIG. 22 b Another side view illustrating the step of separating the resin cured in the runner and the sealing member from each other.
  • FIG. 22 c Still another side view illustrating the step of separating the resin cured in the runner and the sealing member from each other.
  • FIG. 23 An enlarged sectional view of a boundary portion of an integrally-molded product of the resin cured in the runner and the sealing member.
  • FIG. 24 A sectional view of a fluid dynamic bearing device according to another embodiment.
  • FIG. 25 An enlarged sectional view of the fluid dynamic bearing device of FIG. 24 .
  • FIG. 26 An enlarged sectional view of a sealing member of FIG. 24 .
  • FIG. 27 a A sectional view illustrating a step of molding a conventional sealing member.
  • FIG. 27 b An enlarged view of a part A of the sealing member of FIG. 27 a , from which a gate portion has been cut off.
  • FIG. 28 a A top view of a sealing member according to Reference Example.
  • FIG. 28 b A sectional view of the sealing member of FIG. 28 a.
  • FIG. 29 A sectional view illustrating a step of molding a conventional sealing member.
  • FIG. 1 illustrates a spindle motor for information apparatus, which incorporates a fluid dynamic bearing device 1 according to the embodiment of the present invention.
  • This spindle motor is used for disk drive devices for, for example, HDDs, and comprises the fluid dynamic bearing device 1 for rotatably supporting a shaft member 2 having a diameter in range from 2 mm to 4 mm, a disk hub 3 mounted to the shaft member 2 , and stator coils 4 and rotor magnets 5 facing each other across a radial gap, for example.
  • the stator coils 4 are fixed to an outer peripheral surface of a bracket 6
  • the rotor magnets 5 are fixed to an inner peripheral surface of the disk hub 3 .
  • the fluid dynamic bearing device 1 is mounted to an inner periphery of the bracket 6 .
  • the disk hub 3 holds a predetermined number of disks D (two disks in FIG. 1 ) such as a magnetic disk.
  • the stator coils 4 When the stator coils 4 are energized, the rotor magnets 5 are rotated by an electromagnetic force between the stator coils 4 and the rotor magnets 5 . With this, the disk hub 3 and the shaft member 2 are rotated integrally with each other.
  • the fluid dynamic bearing device 1 illustrated in FIG. 2 comprises, as main components, the shaft member 2 , a bottomed-cylindrical housing 7 opened at one end and closed at another end, a bearing sleeve 8 fixed to an inner peripheral surface of the housing 7 and having an inner periphery along which the shaft member 2 is inserted, and a sealing member 9 for sealing the opening portion of the housing 7 .
  • the opening side of the housing 7 is referred to as an upper side
  • the opposite side is referred to as a lower side.
  • the shaft member 2 is made of, for example, a metal material such as a stainless steel, and comprises a shaft portion 2 a , and a flange portion 2 b provided at a lower end of the shaft portion 2 a integrally or as a separate member.
  • the shaft member 2 may be entirely made of a metal material, or may have a hybrid structure of a metal and a resin, which is obtained, for example, by forming a part (for example, both end surfaces) or the entirety of the flange portion 2 b with a resin.
  • the bearing sleeve 8 is obtained by forming a sintered metal containing, for example, copper (or copper and iron) as a main component into a cylindrical shape.
  • the bearing sleeve 8 may be formed of a soft metal such as brass.
  • an inner peripheral surface 8 a of the bearing sleeve 8 there are provided upper and lower regions (dotted line parts of FIG. 2 ) to serve as respective radial bearing surfaces of a first radial bearing portion R 1 and a second radial bearing portion R 2 in a manner that the first radial bearing portion R 1 and the second radial bearing portion R 2 are axially spaced apart from each other.
  • the dynamic pressure generating grooves 8 a 1 on the upper side are formed asymmetrically in the axial direction with respect to a belt-like part at an axially central portion of hill portions (indicated by cross-hatching in FIG. 3 ). Specifically, an axial dimension X 1 of an upper region with respect to the belt-like part is larger than an axial dimension X 2 of a lower region with respect to the belt-like part.
  • a region (dotted line parts of FIG. 2 ) to serve as a thrust bearing surface of a first thrust bearing portion T 1 .
  • this region although not shown, there are formed dynamic pressure generating grooves arranged, for example, in a spiral pattern.
  • an axial groove 8 d 1 for communicating both end surfaces 8 b and 8 c to each other.
  • the axial groove 8 d 1 comprises three equiangularly arranged axial grooves 8 d 1 (refer to FIG. 8 ).
  • the housing 7 is formed of a cylindrical small diameter portion 7 a , a cylindrical large diameter portion 7 b arranged on the small diameter portion 7 a , and a bottom portion 7 c sealing the opening portion at the lower end of the small diameter portion 7 a .
  • the small diameter portion 7 a , the large diameter portion 7 b , and the bottom portion 7 c are formed integrally with each other.
  • An inner peripheral surface of the small diameter portion 7 a and an inner peripheral surface 7 b 1 of the large diameter portion 7 b are continuous with each other through intermediation of a stepped surface 7 d formed as a flat surface extending in a direction orthogonal to the axial direction.
  • a region (dotted line parts of FIG. 2 ) to serve as a thrust bearing surface of a second thrust bearing portion T 2 .
  • this region there are formed dynamic pressure grooves (not shown) arranged, for example, in a spiral pattern.
  • the housing 7 structured as described above is formed by injection molding of a resin.
  • the small diameter portion 7 a , the large diameter portion 7 b , and the bottom portion 7 c of the housing 7 are formed to have thicknesses substantially equal to each other.
  • the resin forming the housing 7 is mainly formed of a thermoplastic resin, and examples of the resin that can be used comprise amorphous resins such as polysulfone (PSU), polyethersulfone (PES), polyphenylsulfone (PPSU), and polyetherimide (PEI), and crystalline resins such as liquid crystal polymer (LCP), polyetheretherketone (PEEK), polybutyrene terephthalate (PBT), polyphenylene sulfide (PPS), and polyamide (PA).
  • amorphous resins such as polysulfone (PSU), polyethersulfone (PES), polyphenylsulfone (PPSU), and polyetherimide (PEI)
  • crystalline resins such as liquid crystal polymer (LCP), polyetheretherketone (PEEK), polybutyrene terephthalate (PBT), polyphenylene sulfide (PPS), and polyamide (PA).
  • filler examples include fibrous filler such as glass fiber, whisker-like filler such as potassium titanate, scale-like filler such as mica, and fibrous or powdered conductive filler such as carbon fiber, carbon black, graphite, carbon nanomaterial, and metal powder. Such filler may be used singly or in a combination of two or more kinds of filler.
  • the sealing member 9 is formed into an L-shape in cross-section comprising a disk-like first sealing portion 9 a and a cylindrical second sealing portion 9 b projecting downward from an outer-diameter end of the first sealing portion 9 a .
  • An inner peripheral surface 9 a 2 of the first sealing portion 9 a forms a small-diameter inner peripheral surface of the sealing member 9
  • an inner peripheral surface 9 b 2 of the second sealing portion 9 b forms a large-diameter inner peripheral surface of the sealing member 9 .
  • an inner end surface (lower end surface 9 a 1 ) of the first sealing portion 9 a there are formed a predetermined number of radial grooves 9 a 10 horizontally extending in a radial direction across the lower end surface 9 a 1 .
  • a predetermined number of axial grooves 9 b 20 vertically extending in the axial direction across the inner peripheral surface 9 b 2 at the same circumferential positions as those of the radial grooves 9 a 10 .
  • each of the radial grooves 9 a 10 of the first sealing portion 9 a is formed into a rectangular shape in cross-section (not shown), and each of the axial grooves 9 b 20 of the second sealing portion 9 b is formed into a circular-arc shape in cross-section (refer to FIG. 5 ).
  • the radial groove 9 a 10 and the axial groove 9 b 20 respectively comprise three radial grooves 9 a 10 and three axial grooves 9 b 20 , which are equiangularly arranged.
  • a chamfered portion 9 c (refer to FIG. 4 ).
  • a gate mark 24 ′ is formed at a circumferential position corresponding to a deepest portion R of one of the axial grooves 9 b 20 (refer to FIG. 5 ).
  • a weld line W is formed at a position on the opposite side of the gate mark 24 ′ with respect to an axial center. The weld line W is formed so as to horizontally extend in the radial direction across the first sealing portion 9 a and vertically extend in the axial direction across the second sealing portion 9 b .
  • the weld line W of the second sealing portion 9 b is formed at a circumferential position out of the deepest portions R of the axial grooves 9 b 20 .
  • the weld line W of the second sealing portion 9 b is formed in a region of a cylindrical surface 9 b 21 between the axial grooves 9 b 20 in the circumferential direction.
  • the weld line W of the first sealing portion 9 a is formed at a circumferential position out of deepest portions of the radial grooves 9 a 10 .
  • the weld line W of the first sealing portion 9 a is formed in a region of a flat surface 9 a 11 between the radial grooves 9 a 10 in the circumferential direction.
  • the weld line W is formed at the positions out of thin portions of the sealing member 9 .
  • the sealing member 9 structured as described above is formed by injection molding of a resin. It is preferred to select, as the resin for the sealing member 9 , a material which is relatively slowly cured and is excellent in oil resistance. For example, it is possible to suitably use crystalline resins, specifically, a crystalline resin selected from a group consisting of PPS, ETFE, PEEK, PA66, PA46, PA6T, and PA9T. More specifically, the following can be used.
  • PPS cross-linked PPS RG-40JA and linear PPS RE-04 manufactured by AGC MATEX CO., LTD.;
  • ETFE Neoflon EP-521 and EP-541 manufactured by DAIKIN INDUSTRIES, ltd.;
  • PEEK PEEK 150GL15, PEEK 150GL30, PEEK 450GL15, and PEEK 450GL30 manufactured by Victrex plc.;
  • PA66 A3HG5 manufactured by BASF SE
  • PA46 TW300 manufactured by DSM N.V.;
  • PA6T ARLEN RA230NK manufactured by Mitsui Chemicals, Inc.
  • PA9T Genestar GR2300 manufactured by KURARAY CO., LTD. It can be said that, of those crystalline resins, PA6T is an optimum material for the sealing member because PAT6 exhibits most excellent properties, specifically, provides highest strength to portions at which the weld line W is to be formed and highest oil resistance against an ester-based lubricating oil. Note that, those crystalline resins may be used singly or in a combination of a plurality of types of those crystalline resins. Alternatively, it is possible to add the filler referred to in the above description of the material for the housing 7 .
  • a die set used for injection molding of the sealing member 9 is formed of a fixed die 21 and a movable die 22 as illustrated in FIG. 6 , and a cavity 23 and a gate 24 are formed in a clamped state.
  • the gate 24 is what is called a side gate provided in a clamping surface of the fixed die 21 and the movable die 22 .
  • the gate 24 is provided in a tapered surface 25 provided to form the chamfered portion 9 c , and is arranged to come to a circumferential position of one of molding portions 26 provided to form the axial grooves 9 b 20 of the second sealing portion 9 b (refer to FIG. 7 ).
  • the weld line W is formed at the circumferential central portion between the other axial grooves 9 b 20 .
  • the sealing member 9 formed as described above is fixed to an upper end of an outer periphery of the bearing sleeve 8 by press-fitting.
  • the inner peripheral surface 9 b 2 of the second sealing portion 9 b of the sealing member 9 is press-fitted to the outer peripheral surface 8 d of the bearing sleeve 8 from above.
  • a press-fitting margin of the sealing member 9 and the bearing sleeve 8 is set within a range of from 40 ⁇ m to 60 ⁇ m.
  • the outer peripheral surface 9 b 1 of the second sealing portion 9 b deforms in conformity with the outer peripheral surface 8 d of the bearing sleeve 8 , and hence dimensional accuracy is increased.
  • the fragile weld line W is formed at the position out of thin portions of the sealing member 9 (the deepest portion of the radial groove 9 a 10 of the first sealing portion 9 a and the deepest portion of the axial groove 9 b 20 of the second sealing portion 9 b ).
  • the sealing member 9 is prevented from being provided with parts having locally markedly low strength, and hence damage to be caused by press-fitting is prevented.
  • a first seal space S 1 having a predetermined capacity is formed between the inner peripheral surface 9 a 2 of the first sealing portion 9 a and an outer peripheral surface 2 a 1 of the shaft portion 2 a
  • a second seal space S 2 having a predetermined capacity is formed between the outer peripheral surface 9 b 1 of the second sealing portion 9 b and the inner peripheral surface 7 b 1 of the large diameter portion 7 b of the housing 7
  • the inner peripheral surface 9 a 2 of the first sealing portion 9 a and the inner peripheral surface 7 b 1 of the large diameter portion 7 b of the housing 7 are each formed as a tapered surface increased upward in diameter. Accordingly, the first seal space S 1 and the second seal space S 2 each exhibit a tapered shape gradually diminished downward.
  • each of the radial grooves 9 a 10 formed in the lower end surface 9 a 1 of the first sealing portion 9 a and the upper end surface 8 c of the bearing sleeve 8 form a radial communication path 12 a
  • each of the axial grooves 9 b 20 formed in the inner peripheral surface 9 b 2 of the second sealing portion 9 b and corresponding one of the axial grooves 8 d 1 formed in the outer peripheral surface 8 d of the bearing sleeve 8 form an axial communication path 12 b (refer to FIG. 8 ).
  • the communication paths 12 need to have a predetermined flow-path area or more.
  • a cross-sectional area of the axial grooves 9 b 20 formed in the second sealing portion 9 b is increased, the second sealing portion 9 b is partially thinned, with the result that strength decreases.
  • the second sealing portion 9 b receives high load by being press-fitted to the bearing sleeve 8 , and hence it is necessary to secure strength as high as possible.
  • the following structure may be employed.
  • the axial communication paths 12 b may be formed with cooperation of the axial grooves 9 b 20 of the second sealing portion 9 b and the axial grooves 8 d 1 of the bearing sleeve 8 , thereby securing the flow-path area of the axial communication paths 12 b while downsizing the axial grooves 9 b 20 of the second sealing portion 9 b and securing strength of the sealing member 9 .
  • the interior space of the housing 7 which is sealed with the sealing member 9 and comprises inner pores of the bearing sleeve 8 , is filled with a lubricating oil (for example, ester-based lubricating oil), and thus the fluid dynamic bearing device 1 as illustrated in FIG. 2 is completed.
  • a lubricating oil for example, ester-based lubricating oil
  • radial bearing gaps are formed between the radial bearing surfaces of the inner peripheral surface 8 a of the bearing sleeve 8 and the outer peripheral surface 2 a 1 of the shaft portion 2 a .
  • thrust bearing gaps are formed respectively between the thrust bearing surface of the lower end surface 8 b of the bearing sleeve 8 and an upper end surface 2 b 1 of the flange portion 2 b and between the thrust bearing surface of the inner bottom surface 7 c 1 of the housing 7 and a lower end surface 2 b 2 of the flange portion 2 b .
  • a dynamic pressure of a lubricating oil is generated in the radial bearing gaps due to the dynamic pressure generating grooves 8 a 1 and 8 a 2 of the radial bearing surfaces, and the shaft portion 2 a of the shaft member 2 is rotatably supported in the radial direction in a non-contact manner through a lubricating oil film formed within the radial bearing gaps.
  • the first radial bearing portion R 1 and the second radial bearing portion R 2 for rotatably supporting the shaft member 2 in the radial direction in a non-contact manner.
  • a dynamic pressure of a lubricating oil is generated in the thrust bearing gaps due to the dynamic pressure generating grooves of the thrust bearing surfaces, and the shaft member 2 is rotatably supported in the thrust direction in a non-contact manner through a lubricating oil film formed in the thrust bearing gaps.
  • the first thrust bearing portion T 1 and the second thrust bearing portion T 2 for rotatably supporting the shaft member 2 in both the thrust directions in a non-contact manner.
  • the first and second seal spaces S 1 and S 2 each exhibit a tapered shape gradually diminished toward the inside of the housing 7 as described above. Therefore, owing to drawing-in action caused by a capillary force, a lubricating oil in both the seal spaces S 1 and S 2 is drawn in a direction in which the seal spaces are narrowed, that is, drawn toward the inside of the housing 7 . As a result, it is possible to effectively prevent leakage of the lubricating oil from the inside of the housing 7 . Further, the seal spaces S 1 and S 2 each have a buffering function with which the volume amount varied in accordance with the variation in temperature of the lubricating oil filling the interior spaces of the housing 7 is absorbed. Within the expected range of the variation in temperature, the oil surfaces of the lubricating oil are constantly formed in the seal spaces S 1 and S 2 .
  • the dynamic pressure generating grooves 8 a 1 on the upper side are formed asymmetrically in the axial direction (refer to FIG. 3 ).
  • the force thus generated circulates the lubricating oil through the path formed of the thrust bearing gap of the first thrust bearing portion T 1 , the fluid paths formed of the axial grooves 8 d 1 of the bearing sleeve 8 , and the communication paths 12 between the sealing member 9 and the bearing sleeve 8 in the stated order.
  • the first seal space S 1 communicates to the above-mentioned circulation path, and the second seal space S 2 communicates thereto via the axial gap 11 .
  • the present invention is not limited to the above-mentioned embodiment.
  • the gate 24 used at the time of forming the sealing member 9 by injection molding is provided at one point, but the present invention is not limited thereto.
  • the gate may comprise gates provided at a plurality of points.
  • the inner peripheral surface 9 a 2 of the first sealing portion 9 a is formed into a tapered shape, but the present invention is not limited thereto.
  • the inner peripheral surface 9 a 2 of the first sealing portion 9 a may be formed as a cylindrical surface, and the outer peripheral surface of the shaft portion 2 a opposed thereto may be formed as a tapered surface.
  • the inner peripheral surface 7 b 1 of the large diameter portion 7 b of the housing 7 is formed as a tapered surface.
  • the inner peripheral surface 7 b 1 may be formed as a cylindrical surface, and the outer peripheral surface 9 b 1 of the second sealing portion 9 b opposed thereto may be formed as a tapered surface.
  • the bearing sleeve 8 is provided with the dynamic pressure generating portions formed of the herringbone or spiral dynamic pressure generating grooves, but the present invention is not limited thereto.
  • the dynamic pressure generating portions may be formed as follows: forming dynamic pressure generating grooves having other shapes; or forming the inner peripheral surface 8 a of the bearing sleeve 8 into a multi-arc shape obtained by combining a plurality of circular arcs.
  • the dynamic pressure generating portions may be provided not to the inner peripheral surface 8 a and the lower end surface 8 b of the bearing sleeve 8 and to the inner bottom surface 7 c 1 of the housing 7 , but to a member facing those surfaces across the bearing gaps (outer peripheral surface 2 a 1 of the shaft portion 2 a and both the end surfaces 2 b 1 and 2 b 2 of the flange portion 2 b of the shaft member 2 ).
  • a cylindrical bearing may be formed, in which both the inner peripheral surface 8 a of the bearing sleeve 8 and the outer peripheral surface 2 a 1 of the shaft portion 2 a of the shaft member 2 are formed as cylindrical surfaces.
  • the dynamic pressure generating portions for actively generating the dynamic pressure action are not formed, but still the dynamic pressure action is generated by slight centrifugal whirling of the shaft portion 2 a.
  • a sleeve test sample 130 having the same structure as that of the bearing sleeve 8 according to the above-mentioned embodiment was press-fitted to an inner periphery of a seal test sample 140 having the same structure as that of the above-mentioned sealing member 9 , and whether or not the seal test sample 140 was damaged was observed.
  • the seal test sample 140 there were prepared example seal test samples 140 each having a weld line formed at a circumferential intermediate portion between axial grooves (refer to FIG.
  • comparison-example seal test samples 140 each having a weld line formed at a circumferential position corresponding to a deepest portion of one of axial grooves (not shown).
  • the sleeve test sample 130 was made of a metal (brass), and the seal test samples 140 were made of a resin (PA6T).
  • an inner diameter of the cylindrical portion 141 was set to approximately 7.5 mm, and an outer diameter of the cylindrical portion 141 was set to 9 mm.
  • An axial length of a press-fitting portion of the sleeve test sample 130 and the seal test sample 140 was set to 2.45 mm.
  • Example breakage occurred only in example seal test samples 140 having a press-fitting margin of 90 ⁇ m or more
  • Comparison Example breakage occurred only in comparison-example test samples 140 having a press-fitting margin of 50 ⁇ m or more. From this fact, it was confirmed that the seal test samples according to Example are higher in strength with respect to press-fitting of the sleeve test sample than the seal test samples according to Comparison Example.
  • Example Comparative Example 10 No breakage No breakage 20 ⁇ ⁇ 30 ⁇ ⁇ 40 ⁇ ⁇ 50 ⁇ Breakage occurred 60 ⁇ 70 ⁇ 80 ⁇ 90 Breakage occurred
  • the sleeve test samples 130 and the seal test samples 140 as described above each have a size suited to fluid dynamic bearing devices which have a shaft member ranged a diameter from 2 mm to 4 mm and which are to be incorporated, for example, into a disk drive device for HDDs.
  • fluid dynamic bearing devices it is necessary to secure a press-fitting margin of approximately 40 ⁇ m between the sleeve and the seal.
  • breakage occurred only in seal test samples having a press-fitting margin of 50 ⁇ m or more. Thus, in consideration of safety factor, it is difficult to use those seal test samples as actual products.
  • the seal test samples according to Example each have a strength sufficient to withstand press-fitting with a press-fitting margin of up to 80 ⁇ m, and hence can be satisfactorily used even under a condition that a press-fitting margin is 40 ⁇ m or more.
  • FIG. 12 illustrates a spindle motor for information apparatus, which incorporates a fluid dynamic bearing device 1 according to the embodiment of the present invention.
  • This spindle motor is used for disk drive devices for, for example, HDDs, and comprises the fluid dynamic bearing device 1 for rotatably supporting a shaft member 2 , a disk hub 3 mounted to the shaft member 2 , and stator coils 4 and rotor magnets 5 facing each other across a radial gap, for example.
  • the stator coils 4 are fixed to an outer peripheral surface of a bracket 6
  • the rotor magnets 5 are fixed to an inner peripheral surface of the disk hub 3 .
  • the fluid dynamic bearing device 1 is mounted to an inner periphery of the bracket 6 .
  • the disk hub 3 holds a predetermined number of disks D (two disks in FIG. 12 ) such as a magnetic disk.
  • the stator coils 4 When the stator coils 4 are energized, the rotor magnets 5 are rotated by an electromagnetic force between the stator coils 4 and the rotor magnets 5 . With this, the disk hub 3 and the shaft member 2 are rotated integrally with each other.
  • the fluid dynamic bearing device 1 illustrated in FIG. 13 comprises, as main components, the shaft member 2 , a bearing member C having an inner periphery along which the shaft member 2 is inserted, and a sealing member 9 provided at an opening portion of the bearing member C.
  • the bearing member C comprises a bottomed-cylindrical housing 7 opened at one end and closed at another end, and a bearing sleeve 8 fixed to an inner peripheral surface of the housing 7 and having an inner periphery along which the shaft member 2 is inserted.
  • the opening side of the housing 7 is referred to as an upper side
  • the opposite side is referred to as a lower side.
  • the shaft member 2 is made of, for example, a metal material such as a stainless steel, and comprises a shaft portion 2 a , and a flange portion 2 b provided at a lower end of the shaft portion 2 a integrally or as a separate member.
  • the shaft member 2 may be entirely made of a metal material, or may have a hybrid structure of a metal and a resin, which is obtained, for example, by forming a part (for example, both end surfaces) or the entirety of the flange portion 2 b with a resin.
  • the bearing sleeve 8 is obtained by forming a sintered metal containing, for example, copper (or copper and iron) as a main component into a cylindrical shape.
  • the bearing sleeve 8 may be formed of a soft metal such as brass.
  • an inner peripheral surface 8 a of the bearing sleeve 8 there are provided two upper and lower regions (dotted line parts of FIG. 13 ) to serve as respective radial bearing surfaces of a first radial bearing portion R 1 and a second radial bearing portion R 2 in a manner that the first radial bearing portion R 1 and the second radial bearing portion R 2 are axially spaced apart from each other.
  • the dynamic pressure generating grooves 8 a 1 on the upper side are formed asymmetrically in the axial direction with respect to a belt-like part at an axially central portion of hill portions (indicated by cross-hatching in FIG. 14 ). Specifically, an axial dimension X 1 of an upper region with respect to the belt-like part is larger than an axial dimension X 2 of a lower region with respect to the belt-like part.
  • a region (dotted line parts of FIG. 13 ) to serve as a thrust bearing surface of a first thrust bearing portion T 1 .
  • this region although not shown, there are formed dynamic pressure generating grooves arranged, for example, in a spiral pattern.
  • an axial groove 8 d 1 for communicating both end surfaces 8 b and 8 c to each other.
  • the axial groove 8 d 1 comprises three equiangularly arranged axial grooves 8 d 1 (refer to FIG. 15 ).
  • the housing 7 is formed of a cylindrical small diameter portion 7 a , a cylindrical large diameter portion 7 b arranged on the small diameter portion 7 a , and a bottom portion 7 c sealing the opening portion at the lower end of the small diameter portion 7 a .
  • the small diameter portion 7 a , the large diameter portion 7 b , and the bottom portion 7 c are formed integrally with each other.
  • An inner peripheral surface of the small diameter portion 7 a and an inner peripheral surface 7 b 1 of the large diameter portion 7 b are continuous with each other through intermediation of a stepped surface 7 d formed as a flat surface extending in a direction orthogonal to the axial direction.
  • a region (dotted line parts of FIG. 13 ) to serve as a thrust bearing surface of a second thrust bearing portion T 2 .
  • dynamic pressure grooves (not shown) arranged, for example, in a spiral pattern.
  • the housing 7 is formed of, for example, a resin.
  • the small diameter portion 7 a , the large diameter portion 7 b , and the bottom portion 7 c of the housing 7 are formed to have thicknesses substantially equal to each other.
  • the sealing member 9 is formed into an L-shape in cross-section comprising a disk-like first sealing portion 9 a and a cylindrical second sealing portion 9 b projecting downward from an outer-diameter end of the first sealing portion 9 a .
  • a lower end surface 9 a 1 of the first sealing portion 9 a there are formed a predetermined number of radial grooves 9 a 10 horizontally extending in the radial direction across the lower end surface 9 a 1 .
  • an inner peripheral surface 9 b 2 of the second sealing portion 9 b there are formed a predetermined number of axial grooves 9 b 20 vertically extending in the axial direction across the inner peripheral surface 9 b 2 at the same circumferential positions as those of the radial grooves 9 a 10 .
  • the radial groove 9 a 10 and the axial groove 9 b 20 respectively comprise three radial grooves 9 a 10 and three axial grooves 9 b 20 , which are equiangularly arranged (refer to FIG. 17 ).
  • a gate mark 24 ′ is formed at an upper end portion of an outer peripheral surface 9 b 1 of the second sealing portion 9 b .
  • the gate mark 24 ′ is formed at a position lower than an axial position X of an outer end surface of the sealing member 9 (upper end surface 9 a 3 of the first sealing portion 9 a in FIG. 18 ).
  • the gate mark 24 ′ is positioned so as not to be held in contact with the lubricating oil filling the inside of the housing 7 , specifically, provided on the atmosphere side with respect to an oil surface maintained in a second seal space S 2 to be formed between the outer peripheral surface 9 b 1 of the sealing member 9 and the inner peripheral surface 7 b 1 of the housing 7 (upper side in FIG. 18 ).
  • a position of the oil surface in the second seal space S 2 fluctuates owing to volumetric expansion and shrinkage of the lubricating oil in accordance with a variation in temperature.
  • the gate mark 24 ′ is provided on the atmosphere side with respect to an upper end position S 0 of the oil surface.
  • a chamfered portion 9 c is formed on the upper end portion of the outer peripheral surface 9 b 1 of the second sealing portion 9 b , and the gate mark 24 ′ is formed at the chamfered portion 9 c.
  • the gate mark 24 ′ is formed at a circumferential position of one of the axial grooves 9 b 20 , and a weld line W is formed at a position on the opposite side of the gate mark 24 ′ with respect to an axial center.
  • the weld line W is formed so as to horizontally extend in the radial direction across the first sealing portion 9 a and vertically extend in the axial direction across the second sealing portion 9 b .
  • the weld line W of the second sealing portion 9 b is formed in a region of a cylindrical surface 9 b 21 between the axial grooves 9 b 20 in the circumferential direction
  • the weld line W of the first sealing portion 9 a is formed in a region of a flat surface 9 a 11 between the radial grooves 9 a 10 in the circumferential direction.
  • the weld line W is formed at the position out of the thin portions of the sealing member 9 so that reduction in strength of the sealing member 9 is prevented.
  • the sealing member 9 structured as described above is formed by injection molding of a resin. It is preferred to select, as the resin for the sealing member 9 , a material which is relatively slowly cured and is excellent in oil resistance. For example, it is possible to suitably use crystalline resins, specifically, a crystalline resin selected from a group consisting of PPS, ETFE, PEEK, PA66, PA46, PA6T, and PA9T. More specifically, the following can be used.
  • PPS cross-linked PPS RG-40JA and linear PPS RE-04 manufactured by AGC MATEX CO., LTD.;
  • ETFE Neoflon EP-521 and EP-541 manufactured by DAIKIN INDUSTRIES, ltd.;
  • PEEK PEEK 150GL15, PEEK 150GL30, PEEK 450GL15, and PEEK 450GL30 manufactured by Victrex plc.;
  • PA66 A3HG5 manufactured by BASF SE
  • PA46 TW300 manufactured by DSM N.V.;
  • PA6T ARLEN RA230NK manufactured by Mitsui Chemicals, Inc.
  • PA9T Genestar GR2300 manufactured by KURARAY CO., LTD. It can be said that, of those crystalline resins, PA6T is an optimum material for the sealing member because PAT6 exhibits most excellent properties, specifically, provides highest strength to portions at which the weld line W is to be formed and highest oil resistance against an ester-based lubricating oil. Note that, those crystalline resins may be used singly or in a combination of a plurality of types of those crystalline resins.
  • a die set used for injection molding of the sealing member 9 is formed of a fixed die 21 and a movable die 22 as illustrated in FIG. 19 , and a cavity 23 and a gate 24 are formed in a clamped state.
  • the gate 24 is what is called a side gate provided in a clamping surface of the fixed die 21 and the movable die 22 .
  • the gate 24 is provided in a tapered molding surface 25 provided to form the chamfered portion 9 c of the sealing member 9 , and is arranged to come to a circumferential position of one of molding portions 26 provided to form the axial grooves 9 b 20 of the second sealing portion 9 b .
  • the gate 24 is formed into a horizontally-long rectangular shape in which a circumferential dimension L 2 (refer to FIG. 21 ) is larger than an axial dimension L 1 (refer to FIG. 20 ).
  • a circumferential dimension L 2 (refer to FIG. 21 ) is larger than an axial dimension L 1 (refer to FIG. 20 ).
  • each of the axial grooves 9 b 20 with respect to the axial center corresponds to a circumferential central portion between the other two axial grooves 9 b 20 . Therefore, when the gate 24 is arranged at a circumferential position corresponding to one of the axial grooves 9 b 20 , the weld line W is formed at the circumferential central portion between the other two axial grooves 9 b 20 .
  • this resin-molded product is taken out of the die set. As illustrated in FIG. 22 , this resin-molded product is an integral piece of a runner resin portion 28 cured in a runner and the sealing member 9 . As illustrated in FIG. 23 , at a boundary portion of the runner resin portion 28 and the sealing member 9 of the resin-molded product (that is, gate portion P), there are formed V grooves 29 a and 29 b .
  • the V groove 29 a is formed of an inclined portion 28 b provided at an end portion on the sealing member 9 side of an upper surface 28 a of the runner resin portion 28 , and the chamfered portion 9 c formed at an upper end of the outer peripheral surface 9 b 1 of the sealing member 9 .
  • the V groove 29 b is formed of an inclined portion 28 c provided at a lower surface of the runner resin portion 28 and the outer peripheral surface 9 b 1 of the sealing member 9 .
  • the integral piece as described above of the runner resin portion 28 and the sealing member 9 is cut at the gate portion P to be separated. Specifically, under a state in which the runner resin portion 28 is fixed, downward load is applied to the sealing member 9 (refer to FIG. 22 a ), and then the gate portion P is bent (refer to FIG. 22 b ). In this way, the gate portion P is cut and the runner resin portion 28 and the sealing member 9 are separated from each other (refer to FIG. 22 c ). In this case, the V groove 29 a is formed at the upper end portion of the gate portion P, in other words, formed on a side to which the integral piece is stretched when the gate portion P is bent. Thus, the gate portion P is cut from the V groove 29 a .
  • the integral piece of the runner resin portion 28 and the sealing member 9 can be accurately cut at the gate portion P.
  • the V groove 29 b is formed also at the lower end portion of the gate portion P, in other words, formed also on a side to which the integral piece is compressed when the gate portion P is bent.
  • the gate portion P is bent from the V groove 29 b .
  • the above-mentioned integral piece can be more accurately cut at the gate portion P.
  • the gate mark 24 ′ as a result of cutting the gate portion P is formed (refer to FIG. 18 ).
  • the gate mark 24 ′ is not stretched unlike, for example, a case where the gate portion P is plucked off simultaneously with opening the die set.
  • the gate portion P can be cut under a state in which the resin is perfectly cured.
  • a situation in which the gate mark 24 ′ is stretched is more reliably prevented. In this way, the integral piece can be accurately cut at the gate portion P.
  • the gate mark 24 ′ projects upward with respect to an outer end surface (upper end surface 9 a 3 ) of the sealing member 9 is avoided, with the result that the gate mark 24 ′ and the disk hub 3 are prevented from interfering with each other.
  • the gate mark 24 ′ may be subjected to the post-treatment process. In this case, the gate mark 24 ′ that has undergone the post-treatment process is left on the outer peripheral surface 9 b 1 (chamfered portion 9 c ) of the sealing member 9 .
  • the sealing member 9 formed as described above is fixed to the upper end of the outer periphery of the bearing sleeve 8 by press-fitting. Specifically, the inner peripheral surface 9 b 2 of the second sealing portion 9 b of the sealing member 9 is press-fitted to the outer peripheral surface 8 d of the bearing sleeve 8 from above. With this, the outer peripheral surface 9 b 1 of the second sealing portion 9 b , around which the second seal space S 2 is formed, can be conformed to the outer peripheral surface 8 d of the bearing sleeve 8 .
  • the outer peripheral surface 8 d of the bearing sleeve 8 is formed with high accuracy, a dimensional accuracy of the outer peripheral surface 9 b 1 of the sealing member 9 can be increased in accordance therewith. With this, a capacity of the second seal space S 2 can be set with high accuracy.
  • the fragile weld line W is formed at the position out of thin portions of the sealing member 9 (the radial groove 9 a 10 of the first sealing portion 9 a and the axial groove 9 b 20 of the second sealing portion 9 b ).
  • the sealing member 9 is prevented from being provided with parts having locally markedly low strength, and hence damage to be caused by press-fitting is prevented.
  • a first seal space S 1 having a predetermined capacity is formed between the inner peripheral surface 9 a 2 of the first sealing portion 9 a and an outer peripheral surface 2 a 1 of the shaft portion 2 a
  • the second seal space S 2 having a predetermined capacity is formed between the outer peripheral surface 9 b 1 of the second sealing portion 9 b and an inner peripheral surface 7 b 1 of the large diameter portion 7 b of the housing 7
  • the inner peripheral surface 9 a 2 of the first sealing portion 9 a and the inner peripheral surface 7 b 1 of the large diameter portion 7 b of the housing 7 are each formed as a tapered surface increased upward in diameter. Accordingly, the first seal space S 1 and the second seal space S 2 each exhibit a tapered shape gradually diminished downward.
  • each of the radial grooves 9 a 10 formed in the lower end surface 9 a 1 of the first sealing portion 9 a and the upper end surface 8 c of the bearing sleeve 8 form a radial communication path 12 a (refer to FIG.
  • each of the axial grooves 9 b 20 formed in the inner peripheral surface 9 b 2 of the second sealing portion 9 b and corresponding one of the axial grooves 8 d 1 formed in the outer peripheral surface 8 d of the bearing sleeve 8 form an axial communication path 12 b (refer to FIG. 15 ).
  • the communication paths 12 need to have a predetermined flow-path area or more.
  • the axial grooves 9 b 20 are formed along the second sealing portion 9 b as described above, there is a risk that the second sealing portion 9 b is partially thinned and strength decreases.
  • the size of the axial grooves 9 b 20 (depth and circumferential width) cannot be unnecessarily increased.
  • the second sealing portion 9 b receives high load by being press-fitted to the bearing sleeve 8 , and hence it is necessary to secure strength as high as possible.
  • the axial communication paths 12 b may be formed with cooperation of the axial grooves 9 b 20 of the second sealing portion 9 b and the axial grooves 8 d 1 of the bearing sleeve 8 , thereby securing the flow-path area of the axial communication paths 12 b while downsizing the axial grooves 9 b 20 of the second sealing portion 9 b and securing strength of the sealing member 9 .
  • the interior space of the housing 7 which is sealed with the sealing member 9 and comprises inner pores of the bearing sleeve 8 , is filled with a lubricating oil (for example, ester-based lubricating oil), and thus the fluid dynamic bearing device 1 as illustrated in FIG. 13 is completed.
  • a lubricating oil for example, ester-based lubricating oil
  • radial bearing gaps are formed between the radial bearing surfaces of the inner peripheral surface 8 a of the bearing sleeve 8 and the outer peripheral surface 2 a 1 of the shaft portion 2 a .
  • thrust bearing gaps are formed respectively between the thrust bearing surface of the lower end surface 8 b of the bearing sleeve 8 and an upper end surface 2 b 1 of the flange portion 2 b and between the thrust bearing surface of the inner bottom surface 7 c 1 of the housing 7 and a lower end surface 2 b 2 of the flange portion 2 b .
  • a dynamic pressure of a lubricating oil is generated in the radial bearing gaps due to the dynamic pressure generating grooves 8 a 1 and 8 a 2 of the radial bearing surfaces, and the shaft portion 2 a of the shaft member 2 is rotatably supported in the radial direction in a non-contact manner through a lubricating oil film formed within the radial bearing gaps.
  • the first radial bearing portion R 1 and the second radial bearing portion R 2 for rotatably supporting the shaft member 2 in the radial direction in a non-contact manner.
  • a dynamic pressure of a lubricating oil is generated in the thrust bearing gaps due to the dynamic pressure generating grooves of the thrust bearing surfaces, and the shaft member 2 is rotatably supported in the thrust direction in a non-contact manner through a lubricating oil film formed in the thrust bearing gaps.
  • the first thrust bearing portion T 1 and the second thrust bearing portion T 2 for rotatably supporting the shaft member 2 in both the thrust directions in a non-contact manner.
  • the first and second seal spaces S 1 and S 2 each exhibit a tapered shape gradually diminished toward the inside of the housing 7 as described above. Therefore, owing to drawing-in action caused by a capillary force, a lubricating oil in both the seal spaces S 1 and S 2 is drawn in a direction in which the seal spaces are narrowed, that is, drawn toward the inside of the housing 7 . As a result, it is possible to effectively prevent leakage of the lubricating oil from the inside of the housing 7 . Further, the seal spaces S 1 and S 2 each have a buffering function with which the volume amount varied in accordance with the variation in temperature of the lubricating oil filling the interior spaces of the housing 7 is absorbed. Within the expected range of the variation in temperature, the oil surfaces of the lubricating oil are constantly formed in the seal spaces S 1 and S 2 .
  • the dynamic pressure generating grooves 8 a 1 on the upper side are formed asymmetrically in the axial direction (refer to FIG. 14 ).
  • the force thus generated circulates the lubricating oil through the path formed of the thrust bearing gap of the first thrust bearing portion T 1 , the fluid paths formed of the axial grooves 8 d 1 of the bearing sleeve 8 , and the communication paths 12 between the sealing member 9 and the bearing sleeve 8 in the stated order.
  • the pressure balance of the lubricating oil can be maintained, and it is possible to solve problems such as generation of bubbles due to local generation of a negative pressure, and leakage of the lubricating oil and occurrence of vibration caused by the generation of bubbles.
  • the first seal space S 1 communicates to the above-mentioned circulation path, and the second seal space S 2 communicates thereto via the axial gap 11 .
  • the present invention is not limited to the above-mentioned embodiments.
  • still another embodiment of the present invention is described, but members having the same functions as those in the above-mentioned embodiments are denoted by the same reference symbols, and redundant description thereof is omitted.
  • the present invention is applicable also to a fluid dynamic bearing device 31 as illustrated in FIG. 24 .
  • a seal space S between an inner peripheral surface 39 a of a sealing member 39 and a tapered surface 2 a 2 formed on an outer peripheral surface of the shaft member 2 , and an outer peripheral surface 39 c of the sealing member 39 is fixed to an inner peripheral surface 7 a 1 of the housing 7 .
  • the outer peripheral surface 39 c of the sealing member 39 and the inner peripheral surface 7 a 1 of the housing 7 which are loosely fitted to each other across a gap, are fixed to each other by what is called gap-filling bonding performed by curing an adhesive G within the fitting gap (refer to FIG. 25 ).
  • a lower end surface 39 b of the sealing member 39 abuts against the upper end surface 8 c of the bearing sleeve 8 , and comes into contact with the lubricating oil filling the inside of the housing 7 .
  • the lower end surface 8 b of the bearing sleeve 8 abuts against a step portion 7 e formed at a lower end portion of the inner peripheral surface 7 a 1 of the housing 7 .
  • Radial grooves 8 c 1 are formed in the upper end surface 8 c of the bearing sleeve 8 , and those radial grooves 8 c 1 form communication paths for the lubricating oil.
  • the sealing member 39 is formed by injection molding with use of a side gate.
  • a gate mark 40 is formed on the outer peripheral surface 39 c .
  • the gate mark 40 is provided below the axial position X of an upper end surface 39 d of the sealing member 39 and on an inner-diameter side with respect to a radial position Y of the outer peripheral surface 39 c of the sealing member 39 .
  • the gate mark 40 is formed at a position at which the gate mark 40 is out of contact with the lubricating oil filling the inside of the housing 7 , specifically, at a position out of an inner end portion of a fixation surface with respect to the housing 7 on the outer peripheral surface 39 c of the sealing member 39 (lower end portion in FIG. 26 ).
  • the gate mark 40 is formed on a chamfered portion 39 e provided at an upper end portion of the outer peripheral surface 39 c of the sealing member 39 .
  • the bearing sleeve 8 is provided with the dynamic pressure generating portions formed of the herringbone or spiral dynamic pressure generating grooves, but the present invention is not limited thereto.
  • the dynamic pressure generating portions may be formed as follows: forming dynamic pressure generating grooves having other shapes; or forming the inner peripheral surface 8 a of the bearing sleeve 8 into a multi-arc shape obtained by combining a plurality of circular arcs.
  • the dynamic pressure generating portions may be provided not to the inner peripheral surface 8 a and the lower end surface 8 b of the bearing sleeve 8 and to the inner bottom surface 7 c 1 of the housing 7 , but to a member facing those surfaces across the bearing gaps (outer peripheral surface 2 a 1 of the shaft portion 2 a and both the end surfaces 2 b 1 and 2 b 2 of the flange portion 2 b of the shaft member 2 ).
  • a cylindrical bearing may be formed, in which both the inner peripheral surface 8 a of the bearing sleeve 8 and the outer peripheral surface 2 a 1 of the shaft portion 2 a of the shaft member 2 are formed as cylindrical surfaces.
  • the dynamic pressure generating portions for actively generating the dynamic pressure action are not formed, but still the dynamic pressure action is generated by slight centrifugal whirling of the shaft portion 2 a.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Sliding-Contact Bearings (AREA)
US13/509,910 2009-12-24 2010-11-24 Fluid dynamic bearing device Abandoned US20120230618A1 (en)

Applications Claiming Priority (5)

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JP2009292554A JP2011133023A (ja) 2009-12-24 2009-12-24 流体動圧軸受装置
JP2009-292554 2009-12-24
JP2010-029638 2010-02-15
JP2010029638A JP5670061B2 (ja) 2010-02-15 2010-02-15 流体動圧軸受装置及びその製造方法
PCT/JP2010/070861 WO2011077883A1 (ja) 2009-12-24 2010-11-24 流体動圧軸受装置

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20150192171A1 (en) * 2014-01-08 2015-07-09 Delta Electronics, Inc. Motor
US9196292B1 (en) * 2015-02-05 2015-11-24 Western Digital Technologies, Inc. Rotary spindle having a disk clamp bottom land facing and in contact with a shaft top land
EP2899417A4 (en) * 2012-09-18 2016-05-18 Ntn Toyo Bearing Co Ltd HYDRODYNAMIC BEARING DEVICE AND MOTOR THEREFOR

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104455007B (zh) * 2014-12-26 2017-04-26 东莞光洋信息科技有限公司 轴承结构及带有该轴承结构的主轴
DE112017004587T5 (de) * 2016-09-12 2019-06-13 Ntn Corp. Lagervorrichtung für ein fahrzeugrad

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070177831A1 (en) * 2003-08-18 2007-08-02 Katsuo Shibahara Fluid bearing device and manufacturing method thereof
US8267588B2 (en) * 2004-09-27 2012-09-18 Ntn Corporation Fluid lubrication bearing device and method of manufacturing the same
US8403565B2 (en) * 2006-03-20 2013-03-26 Ntn Corporation Fluid dynamic bearing device

Family Cites Families (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2962761A (en) * 1959-01-09 1960-12-06 Goshen Rubber Co Inc Apparatus for molding flashless rubber articles
JPH0648011B2 (ja) * 1985-10-22 1994-06-22 日本精工株式会社 転がり軸受用保持器
JP2005265119A (ja) 2004-03-19 2005-09-29 Ntn Corp 流体軸受装置及びその製造方法
US7798721B2 (en) 2004-03-30 2010-09-21 Ntn Corporation Fluid dynamic bearing device
JP2006077860A (ja) 2004-09-08 2006-03-23 Ntn Corp 流体軸受装置および流体軸受装置用のシール部材の製造方法
JP5095111B2 (ja) * 2006-03-20 2012-12-12 Ｎｔｎ株式会社 流体軸受装置
JP4994687B2 (ja) * 2006-03-23 2012-08-08 Ｎｔｎ株式会社 流体軸受装置
JP2008169944A (ja) * 2007-01-12 2008-07-24 Ntn Corp 流体軸受装置
WO2008143051A1 (ja) * 2007-05-10 2008-11-27 Nidec Corporation 流体動圧軸受、モータおよび記録ディスク駆動装置
JP5212690B2 (ja) 2007-05-10 2013-06-19 日本電産株式会社 流体動圧軸受機構、モータおよび記録ディスク駆動装置
CN101306569B (zh) * 2007-05-16 2011-03-23 鸿富锦精密工业（深圳）有限公司 模具装置和射出成型方法
JP2009103179A (ja) * 2007-10-22 2009-05-14 Ntn Corp 流体軸受装置
US7900967B2 (en) * 2008-09-16 2011-03-08 GM Global Technology Operations LLC Engine fitting and method of assembling vehicles

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070177831A1 (en) * 2003-08-18 2007-08-02 Katsuo Shibahara Fluid bearing device and manufacturing method thereof
US8267588B2 (en) * 2004-09-27 2012-09-18 Ntn Corporation Fluid lubrication bearing device and method of manufacturing the same
US8403565B2 (en) * 2006-03-20 2013-03-26 Ntn Corporation Fluid dynamic bearing device

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2899417A4 (en) * 2012-09-18 2016-05-18 Ntn Toyo Bearing Co Ltd HYDRODYNAMIC BEARING DEVICE AND MOTOR THEREFOR
US9476449B2 (en) 2012-09-18 2016-10-25 Ntn Corporation Fluid dynamic bearing device and motor with same
US20150192171A1 (en) * 2014-01-08 2015-07-09 Delta Electronics, Inc. Motor
US9903415B2 (en) * 2014-01-08 2018-02-27 Delta Electronics, Inc. Motor
US9196292B1 (en) * 2015-02-05 2015-11-24 Western Digital Technologies, Inc. Rotary spindle having a disk clamp bottom land facing and in contact with a shaft top land

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KR20120112547A (ko) 2012-10-11
KR101783730B1 (ko) 2017-10-10
US9512878B2 (en) 2016-12-06
CN102695888B (zh) 2015-09-30
CN102695888A (zh) 2012-09-26
US20140145366A1 (en) 2014-05-29

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