CN101018955A

CN101018955A - Fluid bearing device and motor having the same

Info

Publication number: CN101018955A
Application number: CN200680000852.4A
Authority: CN
Inventors: 古森功
Original assignee: NTN Corp
Current assignee: NTN Corp
Priority date: 2005-06-27
Filing date: 2006-06-21
Publication date: 2007-08-15
Anticipated expiration: 2026-06-21
Also published as: CN101018955B; JP4794922B2; JP2007002966A

Abstract

A fluid bearing device having high bearing performance and high durable lifetime and manufacturable at low cost. The fluid bearing device (1) comprises, as major components, a shaft member (2) and a bearing member (7) having a cylindrical radial bearing face (A) facing the outer peripheral surface (2a) of the shaft member (2). The bearing member (7) is injection-molded with an electrocast part (10) inserted therein, and the radial bearing face (A) is formed on the electrocast part (10). Furthermore, a thrust bearing face (B) is formed on the upper end surface (7b) of the bearing member (7), and the shaft member (2) is supported on the bearing member in a thrust direction by the dynamic pressure action of a lubricating fluid produced in the clearance of a thrust bearing facing the thrust bearing face (B).

Description

The motor of fluid dynamic-pressure bearing device and outfit fluid dynamic-pressure bearing device

Technical field

The present invention relates to the motor of fluid dynamic-pressure bearing device and outfit fluid dynamic-pressure bearing device.

Background technique

The fluid film that utilization forms in the bearing play, fluid dynamic-pressure bearing device are rotatably supporting spindle unit.This fluid dynamic-pressure bearing device roughly is divided into: dispose the bearing (so-called hydraulic bearing) that is used for producing the dynamic pressure generating section of dynamic pressure in the lubricating fluid of bearing play; Do not dispose the bearing of dynamic pressure generating section.All showed remarkable feature at aspects such as high speed rotating, high running accuracy, low noises for two types.Consider those characteristics, except that mounted fan motor in personal computer (PC) etc., fluid dynamic-pressure bearing device is widely applicable for: the small motor that information apparatus is used, for example be installed in disk set such as HDD and FDD, such as CD-ROM, the compact disk equipment of CD-R/RW and DVD-ROM/RAM, with such as the spindle motor in the magneto-optical disk apparatus of MD and MO be installed in polygon mirror scanner (polygon scanner) motor in laser beam printer (LBP) or the analogue.

For example, the fluid dynamic-pressure bearing device that is used for fan electromotor in above-mentioned multiple motor, the motor with blade is by radial bearing portion radial support, so that rotatable.In addition, the reaction force (thrust) of the air blast action that is produced by blade is by the axial component support of the magnetic force that produces between stator coil and the rotor magnet, and since the thrust load of the difference between magnetic force and the thrust supported by thrust bearing portion.In many cases, in the bearing means that fan electromotor is used, hydraulic bearing is used does radial bearing portion, and wherein the axle head of running shaft keeps and holds the so-called pivot bearing that parts contact and be used the thrust bearing portion that does (for example referring to JP2000-46057A).

The example of the fluid dynamic-pressure bearing device of using as spindle motor, the structure shown in Figure 25 is known.In this fluid dynamic-pressure bearing device, be provided with radial bearing portion 400 at the outer surface of spindle unit 100 with between the interior perimeter surface of the intermediary in radial bearing gap, the bearing part 200 relative with non-contact mode radial support spindle unit 100 with it.In addition, at the end face of the lip part 110 that is provided with on the spindle unit 100 with between the intermediary in the thrust bearing gap parts relative (bearing part 200 and cover 300), be provided with the thrust bearing portion 500 of non-contact mode along thrust direction shaft member with it.

In recent years, particularly in disk set adding information apparatus wherein,, also be intended to reduce size and thickness along with the quick improvement of performance; And the size of convection cell Hydrodynamic bearing apparatus reduces to exist the demand of continuous strictness.Yet in fluid dynamic-pressure bearing device as shown in figure 25, wherein: radial bearing portion and two thrust bearing portions radially are stacked on together the aspect, and the radial dimension of bearing means is bigger usually, has limited reducing of size.

Consider this point, for example disclose the wherein structure of spindle unit formation frusto-conical structure, wherein: the bearing part of sintering metal is disposed in its periphery; It is big and in the little bearing play of its diameter of another axial side (inclination bearing play) to be formed on its diameter of axial side between spindle unit and bearing part; And the thrust bearing gap is formed between the end face and the packaged unit relative with it of spindle unit.Utilize this structure, need not to provide the lip part 110 of the spindle unit 100 shown in Figure 25, can make the axial dimension of bearing means littler like this (for example with reference to JP2002-276649A).

In JP2000-46057A, in the disclosed fluid dynamic-pressure bearing device, be used for forming simultaneously at the groove (dynamic pressure generating section) of radial bearing gap generation hydrodynamic and the formation of bearing part.Yet, in this system, be difficult to guarantee the sufficient accuracy class of dynamic pressure generating section.In addition, because thrust bearing portion is formed by pivot bearing,, and there is the worry of this wearing and tearing negative effect running accuracy because the long-term wearing and tearing of using of bearing means are inevitably.In addition, from guaranteeing essential load capacity (instantaneous rigidity) viewpoint with respect to momentary load, what pivot bearing neither be sharp.

In JP2002-276649A, in the disclosed fluid dynamic-pressure bearing device,, the outer surface of spindle unit and the interior perimeter surface of bearing part need be formed conical surface in order to form the inclination bearing play.Yet, accurately and effectively do not form conical surface easily by machining at all.Compare with outer surface especially, utilize perimeter surface in the more difficult formation of current techniques state, so be difficult to highi degree of accuracy and finish the interior perimeter surface of circular cone of bearing part at low cost; Therefore, self-evident, when the dynamic pressure generating section that provides in the perimeter surface in the circular cone at bearing part such as the dynamic pressure groove, be difficult to guarantee the essential precision of dynamic pressure generating section.The bearing performance that comprises the fluid dynamic-pressure bearing device of running accuracy greatly depends on the validity of bearing play.Therefore, can not obtain highly accurate bearing play, so can not obtain satisfied bearing performance according to design condition etc. with stable manner.

Summary of the invention

First purpose of the present invention is to provide at low cost the high bearing performance of performance and long-life fluid dynamic-pressure bearing device.

Second purpose of the present invention is to provide at low cost the fluid dynamic-pressure bearing device that disposes high-precision inclination bearing play and show high bearing performance.

In order to realize first purpose, according to the present invention, provide fluid dynamic-pressure bearing device, comprising: spindle unit; The cylinder radial bearing surface relative with the outer surface of spindle unit; By the bearing part that forms by injection moulding under the situation of inserting electroforming portion (electroformed poriotn), this electroforming portion has the radial bearing surface; With thrust bearing portion, it disposes thrust bearing surface that forms and the thrust bearing gap of facing the thrust bearing surface on the end face of bearing part, wherein: the dynamic pressure effect that utilizes the lubricating fluid that produces in the thrust bearing gap is along thrust direction shaft member.The surperficial presentation surface of radial bearing described herein surface and thrust bearing is to the surface in bearing play and thrust bearing gap radially.Whether be formed in those surfaces such as the dynamic pressure generating section of dynamic pressure groove is inessential.

In said structure, this bearing part forms by injection moulding under the situation of inserting electroforming portion, so, to compare by the situation that bonding grade is fixed together with two or more parts (for example sleeve pipe and shell) wherein, assembling process is simplified and has been realized reducing of cost; In addition, can realize the raising of precision.

In addition, when as in the present invention, when thrust bearing portion is formed by hydraulic bearing, can avoid because the deterioration of running accuracy of wearing and tearing, this is the problem that relates to when being formed by pivot bearing.In addition, in hydraulic bearing, thrust bearing portion realizes is not that point as the situation of pivot bearing supports but face supports, thus can enlarge the Area of bearing of thrust bearing portion, and can on the outside of radial bearing portion, form thrust bearing portion.Therefore, can realize the raising of bearing rigidity and instantaneous rigidity.

This electroforming portion is the metal layer that deposits on the surface of grand master pattern (master) through electroforming; The method that it can plate (plating) or electroless plating (chemical plating) based on electrolysis forms.Because the feature of electroforming, the surface accuracy of electroforming portion, the surface accuracy that particularly begins the side that deposits is such: obtained the compact surfaces that the surface structure of the grand master pattern that is used to form electroforming portion is accurately shifted with micron order.Therefore, by improving the surface accuracy of grand master pattern, the surface of fine finishing electroforming portion accurately.In the present invention, above-mentioned feature is used to the radial bearing surface of bearing part is formed electroforming portion, thus can be especially with the running accuracy of High Accuracy Control radial bearing portion.

The thrust bearing gap for example is formed between the end face and thrust bearing surface of the lip part that is provided with on the spindle unit.Examples of components corresponding to this lip part comprises the parts with rotor magnet assembly department.These parts are also referred to as rotor, and the indispensable parts of formation motor, so with wherein for forming the thrust bearing gap, the situation that separating component is added in the bearing means is compared, by these parts being used to form the parts in thrust bearing gap, can obtain the number of components and the minimizing of installation steps quantity and reducing of cost.

Spindle unit can also be formed have two kinds of various outer diameters as one spindle unit, and between the thrust bearing surface of the ledge surface of two outer surfaces that connect two various outer diameters and bearing part, form the thrust bearing gap.In this case, the ledge surface of outer surface and spindle unit is respectively in the face of radial bearing gap and thrust bearing gap, so can be easily and control perpendicularity between radial bearing gap and the thrust bearing gap accurately, thereby make it possible to achieve the raising of running accuracy.In addition, in this case, can also be for example between the outer surface of spindle unit and bearing part, seal space be set, be used to prevent the leakage of lubricating fluid of the inside of filled bearing.

On the thrust bearing surface of bearing part, can be formed in the thrust bearing gap, producing the dynamic pressure generating section of hydrodynamic pressure.In this case, with the injection moulding of bearing part simultaneously, can form dynamic pressure generating section by molded, thus can save time and the effort that forms dynamic pressure generating section discretely, thereby realize further the reducing of cost of fluid dynamic-pressure bearing device.

Can also not only form electroforming portion with the radial bearing surface but also with the thrust bearing surface.In this case, electroforming portion comprises: the radially electroforming portion with radial bearing surface; With become whole with electroforming portion radially or separate and have the thrust electroforming portion on thrust bearing surface.By also the thrust bearing surface being formed electroforming portion, because the above-mentioned feature of electroforming also can obtain high running accuracy in thrust bearing portion.

In addition,,, provide fluid dynamic-pressure bearing device, having comprised: spindle unit according to the present invention in order to realize second purpose; Spindle unit is inserted into the bearing part in week in it; With the inclination bearing play, it is formed between the interior perimeter surface of the outer surface of spindle unit and bearing part and axioversion, spindle unit is tilted the fluid film that forms in the bearing play and rotatably supports, wherein: bearing part disposes the electroforming portion in the face of the inclination bearing play, and forms by injection moulding under the situation of inserting electroforming portion.

As mentioned above, because the feature of electroforming, it is the compact surfaces that the surface structure of grand master pattern is accurately translated into micron order that the deposition of electroforming portion begins side surface.Therefore, when the outer surface of grand master pattern forms conical surface corresponding to the interior perimeter surface structure of electroforming portion, and when carrying out meticulous fine finishing (finishing) thereon with its precision of abundant raising, can obtain perimeter surface in the circular cone accurately, this is difficult to be formed by the traditional mechanical processing method.Compare with interior perimeter surface, outer surface is formed by machining usually easily accurately, so fine finishing is also not really difficult as the outer surface of the grand master pattern of conical surface accurately.Therefore, by forming electroforming portion with in the face of the inclination bearing play, can highi degree of accuracy and to obtain its diameter at low cost big and in the little inclination bearing play of another axial side an axial side.

Because bearing part can form by injection moulding (insert molding), can simplify reduce the raising with precision of assembling process with the realization cost under the situation of inserting above-mentioned electroforming portion.

In said structure, on one in the electroforming portion of the outer surface of spindle unit or bearing part, form the dynamic pressure generating section relative with the inclination bearing play, can in the inclination bearing play, produce hydrodynamic to obtain the raising of bearing rigidity.When forming dynamic pressure generating section in the electroforming portion at bearing part, because the characteristic of electroforming, by in grand master pattern, forming pattern corresponding to the structure of dynamic pressure generating section, can highi degree of accuracy and make dynamic pressure generating section at low cost.On the other hand, when forming dynamic pressure generating section on the outer surface at spindle unit, the outer surface of grand master pattern forms the smooth surface of no concave-convex surface.This electroforming portion forms by using this grand master pattern, and after electroforming portion was separated from grand master pattern, the spindle unit that forms dynamic pressure generating section on its outer surface in advance was inserted into the interior week of electroforming portion, thereby bearing means is assembled.

As long as can produce hydrodynamic in (radial bearing gap, thrust bearing interval and inclination bearing play) in the bearing play, above-mentioned dynamic pressure generating section can adopt multiple known form.The example that produces the dynamic pressure production department of hydrodynamic in radial bearing gap and inclination bearing play comprises: a plurality of dynamic pressure grooves that adopt herringbone structure, helix structure etc. to arrange; With the axial groove that equates that the circle spacing is provided with; Along the circumferential direction a plurality of arcuate surface of She Zhiing, harmonic forms surface etc.The example that produces the dynamic pressure production department of hydrodynamic in the thrust bearing gap comprises: a plurality of dynamic pressure grooves that adopt herringbone structure, helix structure or radially be provided with.

Gou Zao fluid dynamic-pressure bearing device can suitably be used for having the motor of rotor magnet and stator coil as mentioned above.Especially, has above-mentioned feature for obtaining the fluid dynamic-pressure bearing device of the present invention that first purpose obtains, so it is suitable as the bearing that fan electromotor is used.In this case, it for example can adopt following structure, wherein: the reaction force (thrust) and the rightabout vertically magnetic force of the blasting action that is produced by blade are caused being applied between stator coil and the rotor magnet, and since the thrust load of the difference between magnetic force and the reaction force supported by thrust bearing portion.The magnetic attraction that produces between back yoke that is provided with on the outside of rotor magnet (back yoke) (magnet assembly) and rotor magnet also can provide edge and the rightabout magnetic force of thrust.

For realizing that the fluid dynamic-pressure bearing device of the present invention that second purpose obtains is suitable as the particularly bearing in the motor that an urgent demand size reduces, for example, the spindle motor that information apparatus is used.

As mentioned above, according to the present invention, reducing of the number by part count and number of assembling steps can obtain the reduction of fluid dynamic-pressure bearing device cost.In addition, can provide and have high bearing performance and long-life fluid dynamic-pressure bearing device.

According to the present invention, can provide the fluid dynamic-pressure bearing device that disposes highi degree of accuracy inclination bearing play and have high bearing performance at low cost.

Description of drawings

Fig. 1 is the sectional view of example that has wherein added the fan electromotor of the fluid dynamic-pressure bearing device that helps to obtain first purpose of the present invention;

Fig. 2 is first embodiment's the sectional view that helps to obtain the fluid dynamic-pressure bearing device of first purpose of the present invention;

Fig. 3 A is the figure that shows the end face of bearing part;

Fig. 3 B is the longitudinal section of bearing part;

Fig. 4 A is the perspective view of grand master pattern (master);

Fig. 4 B realizes sheltering or the perspective view of the grand master pattern of mask thereon;

Fig. 4 C is the perspective view of electroformed parts;

Fig. 5 is the sectional view of the bearing part behind insert molding (insert molding) just in time;

Fig. 6 is second embodiment's the sectional view that helps to obtain the fluid dynamic-pressure bearing device of first purpose of the present invention;

Fig. 7 is the perspective view of another form of electroformed parts;

Fig. 8 is the 3rd embodiment's the sectional view that helps to obtain the fluid dynamic-pressure bearing device of first purpose of the present invention;

Fig. 9 is the sectional view of the radial bearing portion that formed by the multi sphere bearing;

Figure 10 is another sectional view of the radial bearing portion that formed by the multi sphere bearing;

Figure 11 is another sectional view of the radial bearing portion that formed by the multi sphere bearing;

Figure 12 is the sectional view of the radial bearing portion that formed by step bearing;

Figure 13 is the sectional view of the radial bearing portion that formed by non-cylindrical bearing;

Figure 14 is the sectional view that fluid dynamic-pressure bearing device adds the example of the spindle motor that information apparatus wherein uses;

Figure 15 is the sectional view that has wherein added the example of the spindle motor that the information apparatus of the fluid dynamic-pressure bearing device that helps to obtain second purpose of the present invention uses;

Figure 16 is the amplification view of main portion of the fluid dynamic-pressure bearing device of Figure 15;

Figure 17 is the sectional view of the upper end face of cover;

Figure 18 is the schematic representation that shows the dynamic pressure effect in the inclination bearing play;

Figure 19 A is the perspective view of grand master pattern;

Figure 19 B realizes sheltering or the perspective view of the grand master pattern of mask thereon;

Figure 20 is the perspective view of electroformed parts;

Figure 21 is the schematic representation that electroformed parts is installed in injection molding mould wherein;

Figure 22 A is the sectional view that shows the step that adopts when forming the dynamic pressure groove by some other methods to 22D;

Figure 23 A is second embodiment's the sectional view that helps to obtain the fluid dynamic-pressure bearing device of second purpose of the present invention;

Figure 23 B is the 3rd embodiment's the sectional view that helps to obtain the fluid dynamic-pressure bearing device of second purpose of the present invention;

Figure 24 is the sectional view that the peripheral passage is arranged on the fluid dynamic-pressure bearing device shown in wherein Figure 23 A; With

Figure 25 is the schematic representation of the structure of traditional fluid dynamic-pressure bearing device;

Embodiment

Hereinafter, embodiments of the invention are described with reference to the accompanying drawings.

Fig. 1 is the concept map that shows according to fluid dynamic-pressure bearing device of the present invention, more particularly, has added the example of structure of the fan electromotor of the fluid dynamic-pressure bearing device 1 that helps to realize first purpose of the present invention.This fan electromotor disposes: with the non-contact mode fluid dynamic-pressure bearing device 1 of shaft member 2 rotatably; Blade with spindle unit 2 rotations; Be fixed to the rotor (lip part) 9 of spindle unit 2; With through the media of radial clearance stator coil 4 respect to one another and rotor magnet 5; The so-called radial clearance type of this fan electromotor fan electromotor.This stator coil 4 is installed to the bearing part 7 of fluid dynamic-pressure bearing device 1, and rotor magnet 5 is installed to rotor 9.When stator coil 4 was powered, blade utilized the electromagnetic force rotation between stator coil 4 and the rotary magnet 5.Fan electromotor also can be so-called axial gap fan electromotor (not shown), and wherein: stator coil 4 and rotor magnet 5 are through the intermediary of axial clearance toward each other.

During blade rotation, among the figure along the thrust of the direction of arrow Y on spindle unit 2, as reaction force to blasting action.Between stator coil 4 and rotor magnet 5, be applied with the magnetic force (repulsive force) that is directed to offset this thrust, and the T of thrust bearing portion of fluid dynamic-pressure bearing device 1 supports because the thrust load that the difference between thrust and the magnetic force produces.The R1 of radial bearing portion and the R2 of fluid dynamic-pressure bearing device 1 are supporting the radial load that acts on the spindle unit 2.

Fig. 2 is the amplification view of the main portion of the fluid dynamic-pressure bearing device 1 shown in Fig. 1.This fluid dynamic-pressure bearing device 1 comprises that mainly spindle unit 2 and spindle unit 2 are inserted into the bearing part 7 in week in it.

This bearing part 7 is the moulded resin products that form by injection moulding under the situation of inserting electroforming portion 10; Its molded 11 of being formed by electroforming portion 10 and resin material forms.

As long as base resin allows injection moulding, the base resin that is configured for forming molded 11 resin material is noncrystal or crystal unimportant.The example of noncrystal resin comprises: polysulfones (PSU); Polyether sulfone (polyether sulfone, PES); Polyphenylene Sulfone (polyphenyl sulfone, PPSU); And Polyetherimide (PEI); The example of crystal resin comprises: liquid-crystalline polymer (LCP); Polyether-ether-ketone (polyetheretherketone, PEEK); Polybutylene terephthalate (polybutyrene terephthalate, PBT); And polyphenylene sulfide (PPS).As required, one or both that select from the multiple packing such as reinforcing material (adopting forms such as fiber, powder), oiling agent and conductive material or polytype packing mix with above-mentioned base resin.

Also can form for molded 11 by metallic material.The example of the metallic material that can be used comprises the low melting point metal material such as magnesium alloy and aluminum alloy.In this case, compare with the situation of wherein using resin material, it can obtain improvement at aspects such as intensity, thermal resistance, electric conductivity.In addition, molded 11 also can be by the molded formation of so-called MIM, wherein: after the mixture injection moulding of using metallic dust and tackiness agent, realize degreasing and sintering.In addition, also can use for molded 11 stupalith to form by injection moulding.

This molded 11 comprises: adopt the sleeve part 11a of band round-ended cylinder form, sleeve part 11a has electroforming portion 10 in week within it; Bottom 11b from the outward extending essence disc-shape in the bottom of sleeve part 11a; With from the upwardly extending cylindrical part 11c of the peripheral end of bottom 11b, the 11a of this forms the integral unit with interface to 11c.The assembly department 11d of stator coil 4 usefulness is set on the outer surface of sleeve part 11a; Stator coil 4 utilizes tackiness agent or analogue to be mounted to assembly department 11d.Except the opening of locating in the top, this molded 11 is sealed, and also with the shell that acts on the parts that hold fan electromotor.This base portion 11b forms the bottom of fan electromotor, and cylindrical part 11c constitutes the sidepiece of fan electromotor.

This electroforming portion 10 has the radial bearing surfaces A in the face of the radial bearing gap.Shown in Fig. 3 B, in this embodiment, the radial bearing surfaces A has for example to become the herringbone pattern setting and be formed on a plurality of dynamic pressure groove Aa1 and Aa2 in isolated two zones that are perpendicular to one another, as dynamic pressure generating section.This top dynamic pressure groove Aa1 in axial direction asymmetricly forms with respect to axial centre (axial centre between the tipper zone, upper and lower), and the axial dimension X1 in the zone on the upside of axial centre m is greater than the axial dimension X2 in the zone of its downside.On the other hand, bottom dynamic pressure groove Aa2 in axial direction forms symmetrically, and the axial dimension in its zone, upper and lower is identical with above-mentioned axial dimension X2.In this case, during the rotation of spindle unit 2, it is relatively large that the lubricating fluid in top dynamic pressure groove Aa1 is drawn into the power of force rate in the dynamic pressure groove Aa2 of bottom symmetry of (pump power).

In addition, the thrust bearing surface B in the face of the thrust bearing gap is formed in the annular region of all or part upper end face 7b that constitutes bearing part 7 (molded 11); And a plurality of dynamic pressure groove Ba that arrange with spiral pattern are formed among the B of thrust bearing surface as shown in Figure 3A.

For example, this spindle unit 2 forms the solid shaft that forms by such as stainless metallic material.The outer surface 2a of this spindle unit 2 forms the circular cross section structure that does not have projection and depression.The rear surface of this spindle unit 2 forms no shaggy plat surface.

As lip part, the rotor 9 that for example has blade on its outer surface is fixed to the upper end of spindle unit 2.This rotor magnet 5 is attached to the interior perimeter surface of the cylindrical part 9b of rotor 9.For example pass through the resin injection moulding under the situation of inserting spindle unit 2, this rotor 9 can form with spindle unit 2 integral body.As long as rotor 9 can with the whole rotation of spindle unit 2, the structure of rotor 9, installation method etc. are had no particular limits; For example, it can also be fixed to spindle unit 2 by bonding or press fit.In addition, rotor 9 can also be formed by metallic material.

In the rear surface of the round plate 9a that forms rotor 9, within it the part radial zone on the side have with the upper end face 7b that is arranged on bearing part 7 on the axial relative thrust receiving surface 9a1 of thrust bearing surface B.During the rotation of spindle unit 2, the thrust bearing gap of the T1 of thrust bearing portion that describes below is formed between thrust bearing surface B and the thrust receiving surface 9a1.

The structure of this fluid dynamic-pressure bearing device 1 as mentioned above, and the lubricant oil as lubricating fluid is for example being filled in the inner space of bearing part 7.

In above-mentioned fluid dynamic-pressure bearing device 1, when spindle unit 2 rotations, the intermediary through the radial bearing gap, the radial bearing surfaces A that forms in the electroforming portion 10 that constitutes spindle unit 7 is relative with the outer surface 2a of spindle unit 2.When spindle unit 2 rotation, the dynamic pressure that in the radial bearing gap, produces lubricant oil, and the oil film rigidity is improved the result by pressure: spindle unit in the non-contact mode by radial support.As a result, form with non-contact mode radially and rotatably first R1 of radial bearing portion and second R2 of radial bearing portion of shaft member 2.

In addition, when spindle unit 2 rotations, the intermediary through the thrust bearing gap, B is relative with the thrust receiving surface 9a1 of rotor 9 on the thrust bearing that forms on the upper end face 7b of bearing part 7 surface.When spindle unit 2 rotations, the dynamic pressure that in the thrust bearing gap, also produces lubricant oil, and the oil film rigidity is improved the result by this pressure: spindle unit 2 is rotatably supported along the thrust direction in non-contacting mode.Therefore, form in the non-contact mode along the thrust direction T of thrust bearing portion of shaft member 2 rotatably.

As mentioned above, in the present invention, the T of thrust bearing portion is formed by hydraulic bearing, the deterioration of running accuracy of wearing and tearing so it can be avoided, and this is the problem that the T of thrust bearing portion relates to when being formed by pivot bearing.In addition, when the T of thrust bearing portion is formed by hydraulic bearing, the T of thrust bearing portion realizes is not that the point of the situation of pivot bearing supports but face supports, so that the Area of bearing of the T of thrust bearing portion becomes is big, and can form the T of thrust bearing portion on the outside of R1 of radial bearing portion and R2.Therefore, can improve bearing rigidity with respect to momentary load.

Then, describe the manufacture process of above-mentioned fluid dynamic-pressure bearing device 1 with reference to the accompanying drawings, emphasis is the manufacture process of bearing part 7.

Fig. 4 A has partly shown the manufacture process of the bearing part 7 that is used to constitute above-mentioned fluid dynamic-pressure bearing device 1 to 4C and Fig. 5.More particularly, Fig. 4 A has shown the step (grand master pattern production stage) of producing grand master pattern 12; Fig. 4 B has shown the step (mask step) of carrying out mask on the part of the grand master pattern 12 that needs mask; Shown the step (electroforming step) that forms electroformed parts 14 by electroforming with Fig. 4 C.After those steps, carried out the step of the electroforming portion 10 that utilizes molded of resin material electroformed parts 14; With electroforming portion 10 and grand master pattern 12 is separated from one another to produce the step of bearing part 7.

In the grand master pattern production stage shown in Fig. 4 A, adopt the grand master pattern 12 of solid shaft form to form by conductive material such as quenching stainless steel, nickel chrome steel, some other nickel alloys and evanohm.Except those metallic material, grand master pattern 12 can conduct electricity the nonmetallic material such as stupalith of (by for example forming conductive film in its surface) by becoming and form.

In a part of outer surface of grand master pattern 12, be formed with forming section N, be used to form the electroforming portion 10 of bearing part 7.In forming section N, the outstanding recess patterns of the interior perimeter surface of electroforming portion 10 is reversed; At its two-part place in axial direction, there be depression 12a1 and the 12a2 that forms on the circumference that forms the spine between dynamic pressure groove Aa1 and the Aa2 respectively.Certainly, according to the structure of dynamic pressure generating section, depression 12a1 and 12a2 also can form helix structure etc.

In the mask step shown in Fig. 4 B, except forming section N, mask 13 (by the indication of the dot pattern among the figure) is set on the outer surface of grand master pattern 12.As the cladding material of mask 13, suitably select and use to have the electrical insulation attribute and with respect to the existing product of the corrosion resistance of Electrolytic solution.

In carrying out electroforming, grand master pattern 12 is dipped in the Electrolytic solution that comprises such as the metal ion of nickel or copper ion, and then, to grand master pattern 12 power supplies, so that go up the deposition (electro-deposition) that realizes the expectation metal in the zone (being forming section N) except that the place that mask 13 is set.This Electrolytic solution can comprise as required such as the sliding material of carbon or such as the stress lightening material of asccharin.According to required chemical attribute, suitably select the type of electrodeposit metals such as the bearing surface of the physical attribute of hardness and fatigue strength and hydraulic bearing.

By above-mentioned steps, formed the electroformed parts 14 of the electroforming portion 10 of the forming section N that comprises grand master pattern 12 and cover grand master pattern 12.In this case, depression 12a1 that forms in forming section N and the structure of 12a2 are passed to the interior perimeter surface of electroforming portion 10, and a plurality of dynamic pressure groove Aa1 and Aa2 shown in Fig. 3 B are formed so that axially spaced from one another.When electroforming portion 10 was too thick, its release property of grand master pattern 12 worsened relatively, and when electroforming portion 10 was too thin, the serviceability of electroforming portion 10 reduced, so according to essential bearing attribute, bearing size, its purposes etc., electroforming portion 10 is set to optimum thickness.

Except the said method based on the electrolysis plating, electroforming portion 10 can also be formed by the method based on electroless plating.In this case, the insulation attribute of the electric conductivity of grand master pattern 12 and mask 13 is just optional; Instead, they need show corrosion resistance.

The electroformed parts 14 that is formed by above-mentioned steps is transferred to molded step.Though not shown, in molded step, electroformed parts 14 is set in the predetermined mold as insertion parts, and then by using above-mentioned resin material to carry out injection moulding (insert molding).After injecting resin material, resin material solidifies and opens mould; Then, obtained molded product, wherein: as shown in Figure 5, comprise that the electroformed parts 14 of grand master pattern 12 and electroforming portion 10 is whole with molded 11 one-tenth.At this moment, with injection moulding simultaneously, a plurality of dynamic pressure groove Ba with the spiral pattern setting as shown in Figure 3A are formed in molded 11 the upper end face (the upper end face 7b of bearing part 7).

After this, this molded product is transferred to separating step, and wherein: it is separated into integral unit and the grand master pattern 12 that comprises electroforming portion 10 and molded 11 (bearing part 7).In this separating step, the internal stress of accumulation is released in electroforming portion 10, thereby: the diameter of the interior perimeter surface of electroforming portion 10 increases, and is discharged by the outer surface 12a from grand master pattern 12.For example by electroformed parts 14 or bearing part 7 are applied impact, or the interface between the outer surface 12a of the interior perimeter surface of electroforming portion 10 and grand master pattern 12 applied axial pressing force, realized the release of internal stress.By discharging internal stress, the diameter of electroforming portion radially increases, and between the outer surface of the interior perimeter surface of electroforming portion 10 and grand master pattern 12, form the gap (preferably being not less than the degree of depth of dynamic pressure groove) that is fit to size, thereby can in axial direction extract grand master pattern 12 reposefully from the interior perimeter surface of electroforming portion 10, avoid the dynamic pressure groove and the excessive interference between the forming section N that forms on the outer surface 12a of grand master pattern 12 (depression 12a1 and 12a2) that in the interior perimeter surface of electroforming portion 10, form simultaneously.As a result, molded product can be divided into bearing part 7 and the grand master pattern 12 that comprises electroforming portion 10 and molded 11.For example, can control the increasing diameter dosage of electroforming portion 10 by changing the thickness of electroforming portion 10.

When only when impacting the diameter in the interior week that can not increase electroforming portion 10 fully, thereby produce the difference of thermal expansion amount therebetween, molded product can be divided into grand master pattern 12 and bearing part 7 by heating or cooling electroforming portion 10 and grand master pattern 12.

Be inserted into the bearing part 7 that separates from grand master pattern 12 as mentioned above with the spindle unit 2 of grand master pattern 12 separation of produced, and the inner space packing lubrication oil of bearing part 7, thereby fluid dynamic-pressure bearing device 1 as shown in Figure 2 finished.Because the grand master pattern 12 that separates can repeatedly be used for electroforming, can be with stable manner and produce high-precision bearing parts 7 at low cost in enormous quantities.The grand master pattern 12 that separates also can be used as spindle unit 2 same as before.

As mentioned above, in the present invention, can form bearing part 7 by injection moulding under the situation of inserting electroforming portion 10, therefore with wherein as in the prior art, by bonding etc., sleeve pipe is fixed to the situation in the interior week of shell and compares, and can simplify assembling process and realize reducing of cost.

In addition, in the present invention, bearing part 7 configured in one piece are useful on the assembly department 11d of stator coil 4, and also with acting on the shell of the parts that hold motor, so need not to provide with the be in place support of usefulness of bearing means and stator coil.Therefore, by reducing number of components and reducing the number of assembling steps number, can realize reducing of motor cost.

In addition, because the feature of electroforming, the surface of electroforming portion, particularly begin the side that deposits, be the compact surfaces of the surface accuracy of the grand master pattern 12 that is transferred with micron order, so, by forming the particularly forming section N of the outer surface of grand master pattern 12 accurately, can form electroforming portion 10 accurately, i.e. the radial bearing surfaces A.Therefore, according to structure of the present invention, can control running accuracy, the particularly running accuracy of radial bearing portion accurately.In addition, because thrust bearing surface B and the side by side molded formation of insert molding can save the time and the effort that form thrust bearing surface B discretely, thus further the reducing of the cost of realization fluid dynamic-pressure bearing device 1.

In addition, because the feature of electroforming, the outer surface of electroforming portion 10 forms rough surface, so during insert molding, form in the trickle convex-concave of outer surface that molded 11 resin material enters electroforming portion 10, thereby the exasperate anchoring effect occurs.Therefore, strong retention force between electroforming portion 10 and molded 11, occurs, and between electroforming portion 10 and molded 11, realized preventing rotation and break away from.Therefore, can provide the high strength of HI high impact resistance to hit bearing part 7.

Fig. 6 has shown the fluid dynamic-pressure bearing device according to second embodiment for realizing that first purpose of the present invention is made.Fluid dynamic-pressure bearing device shown in the figure is different from above-mentioned fluid dynamic-pressure bearing device part and is: electroforming portion 10 comprise the radially electroforming 10a of portion and with the whole thrust electroforming 10b of portion that forms and have thrust bearing surface B of the 10a of electroforming portion radially.Because the above-mentioned feature of electroforming by also so form thrust bearing surface B in electroforming portion 10, also can obtain high running accuracy in the T of thrust bearing portion.In addition, the parts of this fluid dynamic-pressure bearing device and function are identical with the parts and the function of fluid dynamic-pressure bearing device 1 shown in Figure 2, so same parts by identical label representative, and will be omitted its unnecessary description.

Bearing part 7 shown in Fig. 6 can form by for example grand master pattern shown in Fig. 7 22.This grand master pattern 22 comprise axial region 2 2a and be fixed to the round plate 22b of axial region 22a.Mask 13 is set on the outer surface of axial region 22a, except with the rear surface of the continuous section axial of the rear surface of round plate 22b zone and round plate 22b.When carrying out electroforming by use grand master pattern 22, can obtain electroformed parts 14, wherein: radially 10a of electroforming portion and the thrust electroforming 10b of portion are formed by integral body.By using this electroformed parts to carry out insert molding, formed bearing part 7 as shown in Figure 6.

Though in Fig. 6, radially 10a of electroforming portion and the thrust electroforming 10b of portion are whole each other, they also can be used as separating part and form.When forming them as separating part, for example formation zone of mask 13 is changed.

Fig. 8 has shown the fluid dynamic-pressure bearing device for realizing that above-mentioned first purpose of the present invention is made according to the 3rd embodiment.The main distinction of embodiment shown in fluid dynamic-pressure bearing device shown in the figure and Fig. 6 is: the outer surface of spindle unit 32 is divided into minor diameter outer surface 32a and major diameter outer surface 32b; And the thrust bearing gap is set between the upper end face 7b (thrust bearing surface B) of the ledge surface 32c that connects two outer surfaces and the bearing part 7 relative with it.Utilize this structure, the minor diameter outer surface 32a of spindle unit 32 and the ledge surface 32c of spindle unit 32 are respectively in the face of radial bearing gap and thrust bearing gap.Therefore, being set at the lip part (rotor 9) that separates with spindle unit with thrust bearing gap wherein compares with the said structure between the bearing part, can be easily and control perpendicularity between radial bearing gap and the thrust bearing gap accurately, thus make it possible to achieve the further raising of running accuracy.

In addition, in this embodiment, molded 11 configured in one piece forming bearing part 7 has: from the outboard shafts of the upper end of sleeve part 11a to the sealed department 11e that projects upwards; And the seal space S of predetermined volumes is formed between the major diameter outer surface 32b of the interior perimeter surface of sealed department 11e and spindle unit 32.The sealing space S has enough big capacity to absorb the thermal expansion amount of lubricant oil owing to temperature variation, so oil level is consistently in seal space S.In this embodiment, the interior perimeter surface of sealed department 11e forms the conical surface that the diameter that axially makes progress increases gradually.Or rather, seal space S is the cone structure that reduces gradually to the inside of bearing part 7, and utilizes the seal space of filling lubricant oil, because the suction power of capillary attraction to bearing inside is applied to lubricant oil.As a result, the leakage of lubricant oil prevented reliably, thereby the structure in the motor of being suitable for that wherein will avoid lubricant pollution is provided.

In the inner space of such fluid dynamic-pressure bearing device, local negative pressure can be in bearing operation period generation.The generation of this negative pressure causes generating bubble, and the leakage of lubricant oil and generation vibration thus.Consider this, in this embodiment, the lower end of bearing part 7 (sleeve part 11a) opens wide, and 15 sealings of opening tegmentum parts, and the bottom gap between sleeve part 11a and the cover 15 is provided; In addition, provide the peripheral passage (through hole) 16 that bottom gap and seal space S between be communicated with of opening to atmosphere.Utilize this structure, formed the continuous peripheral passage that thrust bearing gap, radial bearing gap, bottom gap and peripheral passage 16 are formed.In bearing operation period, the peripheral passage is passed in the circulation of flowing of the lubricant oil of filled bearing inside, thereby has kept the essential pressure of lubricant oil steady, and can prevent the problems referred to above.Behind bearing part 7 molded, for example utilize machining etc. to form peripheral passage 16; In addition, when molded bearing part 7 (molded 11),, can also provide the molded mould that utilizes the molded peripheral passage 16 of pin, thereby form the peripheral passage with molded 11 molded while.Otherwise those of the parts essence of this fluid dynamic-pressure bearing device and above-mentioned fluid dynamic-pressure bearing device are identical, so same parts is indicated by same numeral, and its unnecessary description will be left in the basket.

Though in the above-described embodiments, when hydrodynamic was produced by the dynamic pressure groove of herringbone structure among R1 of radial bearing portion and the R2 or helix structure, this should not explain on being limited property ground.For example, can also adopt multi sphere bearing, step bearing or the non-cylindrical bearing that is used for R1 of radial bearing portion and R2.In those bearings, a plurality of arcuate surface, axial groove and harmonic forms generate the surface and constitute dynamic pressure generating section respectively.As in the above-described embodiments, this dynamic pressure generating section can be formed in the electroforming portion 10 of bearing part 7; The method of relevant formation dynamic pressure generating section, it is based on the step that is used to form the dynamic pressure groove, so will omit its detailed description.

Fig. 9 has shown that multi sphere bearing wherein forms one or two the structure example among radial bearing R1 of portion and the R2.In this example, the zone of the interior perimeter surface of the bearing part 7 (electroforming portion 10) of formation radial bearing surfaces A is made up of three arcuate surface 33 (so-called three arc bearings).Each centre of curvature of three arcuate surface 33 is from the identical distance of axial centre O skew of bearing part 7.In each zone of being determined by three arcuate surface 33, the radial bearing gap is the wedge gap 35 that reduces gradually with the wedge shape form along two circumferencial directions.Therefore, when carrying out relative the rotation, the lubricant oil in the radial bearing gap is forced into the minimum clearance of wedge gap 35 with spindle unit 2 (comprising the spindle unit 32 shown in Fig. 8) when bearing part 7, and its pressure increases.Utilize this dynamic pressure effect of lubricant oil, bearing part 7 and spindle unit 2 are supported in non-contacting mode.It is dark and be called the axial groove of separating vessel to form a step (or a section (step)) in the boundary portion between three arcuate surface 33.

Figure 10 shown the wherein R1 of radial bearing portion and R2 in one or two another structure example that forms by the multi sphere bearing.In this example, the zone of the interior perimeter surface of bearing part 7 is made up of three arcuate surface 33 (so-called three arc bearings) equally; In each zone of being determined by three arcuate surface 33, the radial bearing gap is the wedge gap 35 that reduces gradually along a circumferencial direction with the wedge shape form.The multi sphere bearing of this structure is also referred to as conical bearing.It is dark and be called the axial groove of separating vessel 34 to be formed with a step (or a section (step)) in the boundary portion between three arcuate surface 33.Therefore, when bearing part 7 and spindle unit 2 when predetermined direction carries out relative the rotation, the lubricant oil in the radial bearing gap is forced into the minimum clearance of wedge gap 35, and its pressure increases.Utilize this dynamic pressure effect of lubricant oil, bearing part 7 and spindle unit 2 are supported in non-contacting mode.

Figure 11 has shown one or two another structure example that is formed by the multi sphere bearing among the wherein R1 of radial bearing portion and R2.In this example, the structure shown in Figure 10 be modified so that: the presumptive area θ in the minimum clearance side of three arcuate surface 33 is formed the concentric arcs surface that its radian center is the axle center O of bearing part 7 (spindle unit 2).Therefore, each presumptive area θ has shown fixed radial bearing play (minimum clearance).The multi sphere bearing of this structure is also referred to as the taper plane bearing.

Figure 12 has shown one or two structure example that is formed by step bearing among the wherein R1 of radial bearing portion and R2.In this example, adopt a plurality of dynamic pressure grooves 36 of axial groove form to be disposed on predetermined circle in the zone of interior perimeter surface of the bearing part 7 (electroforming portion 10) of forming the radial bearing surfaces A.

Figure 13 has shown one or two structure example that is formed by non-cylindrical bearing among the wherein R1 of radial bearing portion and R2.In this example, the zone that constitutes the bearing part 7 (electroforming portion 10) of radial bearing surfaces A is made up of three harmonic wave forms surfaces 37.In each zone of being determined by three harmonic wave forms surfaces 37, the radial bearing gap is the wedge gap 38 that reduces gradually with the wedge shape form along two circumferencial directions.Therefore, when bearing part 2 carries out relative the rotation with bearing part 7, according to counterrotating direction, be filled in the minimum clearance side that lubricant oil in the radial bearing gap is forced into wedge gap 38, and its pressure increases.Utilize this dynamic pressure effect of lubricant oil, spindle unit 2 and bearing part 7 are supported in non-contacting mode.When not having eccentricity (, when the axle center is axle center O), the minimum width h of wedge gap 38 can utilize following equation to be similar to and draw:

h＝c+aw·cos(Nw·θ)

Wherein: c, aw and Nw are constants, c is average bearing radial gap; Aw is a wave amplitude; θ is a phase place along the circumferential direction; With Nw be wave number order (Nw 〉=2; In this embodiment, Nw=3).Though in the example shown, spindle unit 2 and bearing part 7 are homocentric, the common shaft center O, the center of spindle unit 2 also can be displaced to a center O '.

Though in said structure, as in the situation of R1 of radial bearing portion and R2, two radial bearing portions are axially spaced from one another, also can be provided in the single radial bearing portion of extending on the vertical area of interior perimeter surface of bearing part 7, or three or more radial bearing portions.In addition, though Fig. 9 is so-called three arc bearings to multi sphere bearing shown in Figure 11, this should not understand on being limited property ground; Also can adopt so-called four arc bearings, five arc bearings or by six or the multi sphere bearing that forms of a plurality of arcuate surface.In addition, though when the non-cylindrical bearing shown in Figure 13 was formed by three harmonic wave forms surface, as in the situation of multi sphere bearing, it also can adopt by four or the surperficial non-cylindrical bearing that forms of a plurality of harmonic wave forms.

In addition, though in the above-described embodiments, dynamic pressure generating section is formed in the radial bearing surfaces A of the electroforming portion 10 that constitutes bearing part 7, also can provide dynamic pressure generating section in the outer surface 2a of the spindle unit 2 relative with the radial bearing surfaces A.In this case, the radial bearing surfaces A of electroforming portion 10 forms the periphery with concave-convex surface.

In addition, though in above-mentioned situation, dynamic pressure generating section is set in the radial bearing surfaces A of electroforming portion 10 or among the outer surface 2a of spindle unit, and dynamic pressure is generated by dynamic pressure portion in the radial bearing gap, thereby form R1 of radial bearing portion and R2 by hydraulic bearing, form periphery by radial bearing surfaces A with concave-convex surface with electroforming portion 10, and the surface with the outer surface 2a of spindle unit 2 forms the circular cross section structure with concave-convex surface also can form R1 of radial bearing portion and R2.

In addition, though in the said structure example, the T of thrust bearing portion is generated the dynamic pressure effect of lubricant oil by the dynamic pressure groove of helix structure, the T of thrust bearing portion also can be formed by so-called step bearing, so-called corrugated bearing (not shown) such as (having the ripple stepped form), wherein: adopt a plurality of dynamic pressure grooves of radial groove form to be set at interval in the zone that constitutes thrust bearing surface B with predetermined circle.In addition, as in the situation of R1 of radial bearing portion and R2, in the T of thrust bearing portion, hydraulic bearing portion can be formed on the thrust receiving surface 9a1 of the rotor 9 relative with thrust bearing surface B or the ledge surface 32c of spindle unit 32.

Above-mentioned fluid dynamic-pressure bearing device 1 can be added in the motor except that fan electromotor.Figure 14 has shown the example of this application, and it has conceptually shown the information apparatus spindle motor that is used for such as the disk set of HDD.In this information apparatus spindle motor, the lip part that is installed to the spindle unit 2 of fluid dynamic-pressure bearing device 1 is formed by the dish hub 19 that keeps one or more disks.Utilize this electric machine structure, molded 11 is only formed by the sleeve part 11a of the assembly department 11d with stator coil 5 usefulness, and above-mentioned bottom 11b and cylindrical part 11c are separated from one another.The modes of installing according to stator coil 4 and rotor magnet 5 etc. also can wholely as mentioned above form each several part.In addition, the parts of this example and effect are identical with above-mentioned those, so same parts is indicated by same numeral, and its unnecessary description will be left in the basket.

Figure 15 is the concept map that shows the structure example of information apparatus spindle motor, has wherein added according to fluid dynamic-pressure bearing device 51 of the present invention, more particularly, has added the fluid dynamic-pressure bearing device that helps to realize above-mentioned second purpose.This information apparatus spindle motor is used for the magnetic disk drive such as HDD, and disposes: the fluid dynamic-pressure bearing device 51 of shaft member 52 rotatably; Be installed to disc pack 52 and keep the dish hub 59 of one or more disk D; Through the intermediary of radial clearance, stator coil 54 that faces with each other and rotor magnet 55; With support 56.This stator coil 54 is installed to the periphery of support 56, and rotor magnet 55 is installed to the interior week of dish hub 59.When stator coil 54 is powered, the electromagnetic force rotation that rotor magnet 55 is produced between stator coil 54 and the rotor magnet 55, and utilize it, spindle unit 52 and dish hub 59 rotate as an integral unit (rotary component 53).

When fluid dynamic-pressure bearing device shown in Figure 15 51 is used in some out of Memory device spindle motors, such as the spindle motor that optical disk unit or magnetooptic disc device are used, the rotating disk of supporting disk is fixed to spindle unit 52; When fluid dynamic-pressure bearing device 51 was used for prism scanner (polygon scanner) motor of laser beam printer (LBP), prism (polygon mirror) was installed to spindle unit 52; And when fluid dynamic-pressure bearing device 51 was used in the fan electromotor of personal computer (PC), fan was fixed to spindle unit 52 (those examples are all not shown).

This fluid dynamic-pressure bearing device 51 mainly comprises: spindle unit 52; The bearing part 57 that in the periphery of spindle unit 52, is provided with; Cover 58 with the opening at an end place that is enclosed in bearing part 57.Hereinafter, for convenience of description, these cover 58 sides will be called downside, and will be called upside with its axially relative side.

This spindle unit 52 is by forming such as the stainless metallic material of desired stiffness and wearability that provides.This spindle unit 52 comprises: Frusto-conical conus portion 52a, and its diameter is in an axial side little (upside in the example shown) and big in another side (downside in the example illustrated); With cylinder base portion 52b, it is set at and becomes whole on the top of conus portion 52a and with conus portion 52a.Outer surface 52a1 and the rear surface 52a2 of conus portion 52a form the smooth surface with concave-convex surface.

This dish hub 59 is by being fixed to the base portion 52b of spindle unit 52 such as press fit or press fit/bonding suitable mode, and spindle unit 52 is whole to form rotary component 53 with 59 one-tenth of dish hubs.Can also under the situation of inserting spindle unit 52, form rotary component 53 by injection molded trays hub 59.

This bearing part 57 comprises: perimeter surface forms the electroforming portion 60 of conical surface in it; With molded 61 of the periphery that covers electroforming portion 60.As described below, molded 61 forms by injection moulding under the situation of inserting electroforming portion 60.

The interior perimeter surface 57a of bearing part 57 forms conical surface, corresponding to the structure of the outer surface of the conus portion 52a of spindle unit 52.Each bus of the outer surface 52a1 of the interior perimeter surface 57a of bearing part 57 and the conus portion 52a of spindle unit 52 is parallel to each other, and such two surperficial 57a and 52a1 can become the surface that contacts with each other.As described below, when spindle unit 52 rotations, between the outer surface 52a1 of the conus portion 52a of the interior perimeter surface 57a of bearing part 57 and spindle unit 52, form isolated two the inclination bearing clearance C 1 that are perpendicular to one another, so as its diameter in the axial direction on the side little and on axial downside diameter big.Though in the example shown, the gap width of inclination bearing clearance C 1 is exaggerated so that conveniently understand structure, and the actual a few approximately μ m of the size in gap are to tens μ m.

As shown in figure 16, on the interior perimeter surface of electroforming portion 60, form isolated two the inclination bearing surface C that are perpendicular to one another; During spindle unit 52 rotations, in relative with inclination bearing surface C respectively zone, be formed with inclination bearing clearance C 1.In each inclination bearing surface C,, be formed with a plurality of dynamic pressure groove Ca that for example arrange with herringbone structure as dynamic pressure generating section.Though in the example shown, two inclination bearing surface C are formed on the interior circumferential surface of identical electroforming portion 60, also can form inclination bearing surface C independently in two or more electroforming portion 60.As dynamic pressure groove structure, except the herringbone structure shown in the figure, can also adopt helix structure etc.

This cover 58 forms the structure of plate-like by the metallic material such as stainless steel or brass, and is fixed to the stepped part that forms by tackiness agent or analogue in the opening of the larger diameter side of bearing part 57.Thrust bearing surface D is formed on the upper end face 58a of cover 58; During the rotation of spindle unit 52, thrust bearing clearance C 2 is formed in the zone relative with thrust bearing surface D.In the thrust bearing surface,, a plurality of dynamic pressure groove Ca that for example adopt helix structure as shown in figure 17 to arrange have been formed as the thrust dynamic pressure generating section that is used for producing dynamic pressures in thrust bearing clearance C 2.Except that the helix structure shown in the figure, also can adopt herringbone structure, radial structure etc. as dynamic pressure groove layout.In addition, the thrust bearing surface D that has such as the dynamic pressure generating section of dynamic pressure groove also can be formed among the rear surface 52a2 of spindle unit 52.

Though not shown, can form the seal space between the outer surface 52a1 of the upper end of interior perimeter surface of bearing part 57 and the spindle unit 52 relative with it.This seal space is formed for example at the narrower cone space of bearing means private side.Adopt this tapered configuration, utilize capillary attraction, lubricant oil is sucked by the inboard towards bearing means, leaks into the outside of bearing means so can prevent lubricating fluid.The sealing space has the capacity that is enough to absorb owing to the thermal expansion amount of temperature variation lubricating fluid, and lubricant oil remains in the seal space consistently like this.The sealed member that separates with bearing part can also be fixed to the interior perimeter surface of the upper end portion of bearing part 57, and form the seal space between the outer surface of the interior perimeter surface of sealed member and the spindle unit relative with it.

In said structure, the oil that slides is for example being filled as lubricating fluid in the inner space of bearing means.When in this state, spindle unit 52 is caused carrying out relative the rotation (in this embodiment with bearing part 57, spindle unit 52 rotations), by the intermediary effect of two inclination bearing clearance C 1, the inclination bearing surface C on the interior perimeter surface of bearing part 57 is relative with the outer surface 52a1 of spindle unit 52.When spindle unit 52 rotation, the dynamic pressure that produces lubricant oil in each inclination bearing clearance C 1, and has as shown in figure 18 applied level (radially) component Fr and component Ft (along the thrust direction) vertically downward on spindle unit 52.Therefore, formed radially and in the non-contact mode along a thrust the direction rotatably first inclination bearing K1 of portion and the second inclination bearing K2 of portion of shaft member 52.

When spindle unit 52 rotations, by the intermediary of thrust bearing clearance C 2, the thrust bearing surface D that forms on the upper end face 58a of cover 58 is relative with the rear surface 52a2 of spindle unit 52.When spindle unit 52 rotations, in thrust bearing clearance C 2, produce the dynamic pressure of lubricant oil, and the rigidity of the oil film of the lubricant oil that forms in thrust bearing clearance C 2 is improved by pressure, and spindle unit 2 in the non-contact mode along the thrust direction by rotatably to upper support.As a result, formed in the non-contact mode along another thrust direction T of thrust bearing portion of shaft member 52 rotatably.

Next, will process that make bearing part 57 be described.

Figure 19 A has shown the step of the bearing part 57 that is used to make above-mentioned bearing means to Figure 21.More particularly, Figure 19 A has shown the step (grand master pattern production stage) that is used to make grand master pattern 62; Figure 19 B has shown the step (mask step) that is used for realizing mask on the part of the grand master pattern 62 that needs the mask place; Figure 20 has shown the step (electroforming step) that is used to form electroformed parts 64 by electroforming; Shown the step (molded step) of the electroforming portion 60 that utilizes resin or the molded electroformed parts 64 of analogue with Figure 21.After those steps, this bearing part 57 is by being used for the step manufacturing that electroforming portion 60 and grand master pattern 62 is separated from one another.

In the grand master pattern manufacturing step shown in Figure 19 A, grand master pattern 62 is formed by the conductive material such as the stainless steel of accepting to quench, nickel chrome steel, some other nickel alloys or evanohm.Except that those metallic material, grand master pattern 62 also can be formed by nonmetallic material, such as being conducted electricity the stupalith (for example, forming conductive film in its surface) of giving processing.Grand master pattern 62 disposes frusto-conical portion 62a and forms and from the axially extended columnar portion 62b in the lower end of frusto-conical portion 62a with frusto-conical portion 62a is whole.Consistent with the structure of the interior perimeter surface of bearing part 57, the outer surface of frusto-conical portion 62a forms tapered surface, so that little and big at another side diameter at an axle side diameter.

In a part of axial region of the outer surface of the frusto-conical portion 62a that constitutes grand master pattern 62, be formed with the forming section N1 of the electroforming portion 60 that is used to form bearing part 57.This forming section N1 is the structure that the convex-concave pattern of the interior perimeter surface of wherein electroforming portion 60 is reversed; And in two axial positions, the depression Ka that is formed for formation spine between dynamic pressure groove Ca circumferentially is capable.Certainly, depression Ka also can form the helix structure consistent with dynamic pressure groove pattern etc.

In the mask step shown in Figure 19 B, mask 63 (by the dot pattern indication) is set on the outer surface of grand master pattern 62, except forming section N1.As the cladding material of mask 63, show non-conductive and existing product corrosion resistance is suitably selected and used for electrolytic solution.

In carrying out electroforming, mask 62 is dipped in the electrolytic solution that comprises such as the metal ion of Ni or Cu; And then,, thereby the metallic filament lamp (electrolytic deposition) of expectation is not provided with therein the zone (forming section N1) of outer surface of the grand master pattern 62 of mask 63 to grand master pattern 62 power supply.As required, Electrolytic solution can comprise such as the sliding material of carbon or such as the stress lightening material of asccharin.According to the required hardness of the bearing surface of hydraulic bearing, such as the essential physical attribute of fatigue strength and essential chemical attribute, the metal types that electroforming is used is compatibly selected.

By above-mentioned steps, as shown in figure 20, be formed with electroformed parts 64, wherein the forming section N1 of grand master pattern 62 be covered with electroforming portion 60 and wherein electroforming portion 60 and grand master pattern 62 each other in integral body.In this case, the interior perimeter surface of electroforming portion 60 forms conical surface, and corresponding to the structure of the outer surface of the frusto-conical portion 62a of grand master pattern 62, and the convex-concave pattern of the forming section N1 that forms on grand master pattern 62 is transferred on it.As a result, as shown in figure 16, two inclination bearing surface C with a plurality of dynamic pressure groove Ca are formed on the interior perimeter surface of electroforming portion 60, so that it is spaced apart to be perpendicular to one another.When electroforming portion 60 was too thick, the deterioration with respect to its release property of grand master pattern 62 can appear; On the other hand, when it was too thin, electroforming portion 60 durability caused reducing.Therefore, it is set to optimum thickness according to required bearing performance, bearing size, purposes etc.

Except above-mentioned method based on the electrolysis plating, electroforming portion 60 can also be formed by the method based on electroless plating.In this case, the insulation attribute of the electric conductivity of grand master pattern 62 and mask 63 is unwanted; Instead, need corrosion resistance.

Next, the electroformed parts 64 that is formed by above-mentioned steps is transferred to the molded step that bearing part 57 is wherein formed by insert molding.

Figure 21 is the concept map that shows molded step; In molded step, electroformed parts 64 for example is supplied in the mould of being made up of patrix 65 and counterdie 66, its axial direction parallel with clamping direction (Vertical direction among the figure).In counterdie 66, be formed with the positioning hole 68 with the outer dia consistent size of the columnar portion 62b that forms grand master pattern 62, and the electroformed parts 64 that previous steps shifts is inserted into positioning hole 68 so that electroformed parts 64 is provided with in position.In patrix 65, the upper end portion that has formed grand master pattern 62 coaxially with positioning hole 68 can be fitted to bullport 70 wherein.

In above-mentioned mould, when movable mold (patrix 65 in this embodiment) made near fixed die (counterdie 66 in this embodiment), grand master pattern 62 was directed to precalculated position in the patrix 65 by bullport 70, and realizes then clamping.After finishing clamping, resin material is injected into cavity 67 to realize insert molding through door 69.As long as base resin allows insert molding, the base resin of forming the resin material of injection moulding is noncrystal or crystalline state inessential.The example of noncrystal resin comprises: polysulfones (PSU); Polyether sulfone (PES); Polyphenylene Sulfone (PPSU); And Polyetherimide (PEI); The example of crystal resin comprises: liquid-crystalline polymer (LCP); Polyether-ether-ketone (PEEK); Polybutylene terephthalate (PBT); And polyphenylene sulfide (PPS).As required, resin material can with mix from one or both or the polytype packing of selecting such as the multiple packing of reinforcing material (adopting any forms of fiber, powder etc.), oiling agent and conductive material.

Can also use metallic material as injected plastics material.The example of the metallic material that can use comprises the low melting point metal material such as magnesium alloy and aluminum alloy.In this case, compare, can obtain the improvement of relevant intensity, thermal resistance, electric conductivity etc. with the situation of wherein using resin material.In addition, can also adopt described MIM molded, wherein after the injection moulding of the mixture that uses metallic dust and tackiness agent, carry out degreasing and sintering.In addition, can also use stupalith as injected plastics material.

After finishing insert molding, mould is opened; Then, obtain molded product, wherein the electroformed parts of being made up of grand master pattern 62 and electroforming portion 60 64 and molded 61 are integral with one another.

After this, this molded product is transferred to separating step, and wherein: it is separated into electroforming portion 60 and molded 61 integral unit (bearing part 57) and the grand master pattern of forming 62.As in above-mentioned example, in this separating step, impact the separation that realizes two parts, with the diameter of the interior perimeter surface that increases electroforming portion 60 by for example applying to electroformed parts 64 (grand master pattern 62) or bearing part 57.This makes can in axial direction extract grand master pattern 62 out from the interior perimeter surface of electroforming portion 60 reposefully, avoids simultaneously in dynamic pressure groove pattern that forms on the interior perimeter surface of electroforming portion 60 and the excessive interference between the forming section N1 that forms on the outer surface of grand master pattern 62.When only when applying impact and can not fully increase the diameter in interior week of electroforming portion, as in above-mentioned example, thereby produce the poor of thermal expansion amount therebetween by heating or cooling electroforming portion 60 and grand master pattern 62, molded product can be divided into bearing part 57 and grand master pattern 62.

Because the feature of electroforming, the outer surface of electroforming portion 60 forms rough surface, so during insert molding, form the trickle coarse or convex-concave that molded 61 resin material enters the outer surface of electroforming portion 60, thereby because the exasperate anchoring effect is realized strong retention force.In addition, because electroforming portion 60 is formed to tilt with respect to axle direction, realize anti-the separation along a radial direction at least.Therefore, can provide displaying high-level impact-resistant high strength bearing part 57.

Then, separating the spindle unit of making 52 was inserted in the interior week of the bearing part 57 that is formed by above-mentioned steps; In addition, the inner space of bearing part 57 is filled with lubricant oil, and the larger diameter side opening tegmentum parts 58 of bearing part 57 seal, thereby obtains fluid dynamic-pressure bearing device 51 as shown in figure 15.The grand master pattern 62 that separates from electroforming portion 60 can be recycled and reused for production bearing part 57.

As mentioned above, in the present invention, bearing part 57 is by the electroforming portion 60 that faces inclination bearing clearance C 1 with under the situation that electroforming portion 60 inserts, by molded 61 formation of injection moulding formation.Because the feature of electroforming, the structure of the interior perimeter surface of electroforming portion 60 is consistent with the surface structure of grand master pattern 62, and the precision of the interior perimeter surface of electroforming portion 60 is consistent with the surface accuracy of grand master pattern 62.Therefore, by forming grand master pattern 62 with predetermined structure and predetermined accuracy, the interior perimeter surface of electroforming portion 60 forms with the highi degree of accuracy consistent with the structure of grand master pattern, so can highi degree of accuracy form perimeter surface in the circular cone with low cost, this is difficult to form accurately by conventional direction.Therefore, can improve the width accuracy of inclination bearing clearance C 1, thereby make the bearing performance that can improve fluid dynamic-pressure bearing device with such inclination bearing play.In addition, when as in this embodiment, the inclination bearing surface C with dynamic pressure groove Ca is formed by electroforming, because the feature of electroforming, can form high-precision dynamic pressure groove, so, can realize the raising of the bearing performance of fluid dynamic-pressure bearing device equally from this viewpoint.

Can adopt other method as the method that in the interior perimeter surface of electroforming portion 60, forms dynamic pressure groove Ca.Figure 22 A has shown the example to 22D, wherein: carry out electroforming, be formed on the lip-deep forming section N1 of grand master pattern 62 corresponding to the outstanding conductive film 72 of the structure of dynamic pressure groove Ca.Then, conductive film 72 is removed, thereby forms dynamic pressure groove Ca.

More particularly, at first, shown in Figure 22 A, forming section N1 is formed in the part area of outer surface of grand master pattern 62, and is formed on the forming section N1 corresponding to the outstanding conductive film 72 of dynamic pressure groove pattern.By for example utilizing electroconductive resin to realize jet printing on the surface of grand master pattern 62, conductive film 72 can form accurately.Then, shown in Figure 22 B, electroforming is undertaken by using grand master pattern 62, the electroforming portion 60 that the structure of formation forming section N1 is transferred.After electroforming finished, as in said process, molded 61 formed by injection moulding, and in addition, shown in Figure 22 C, grand master pattern 62 separates from molded product.In this process, conductive film 72 is with the surface isolation of electroforming portion 60 from grand master pattern 62.After this, shown in Figure 22 D, by the conductive film 72 on the interior perimeter surface of using solvent or analogue removal electroforming portion 60, obtain bearing part 57, wherein: dynamic pressure groove Ca is formed in the interior perimeter surface of electroforming portion 60.When adopting this mode to form bearing part 57, can use the grand master pattern 62 that separates from electroforming portion 60 same as before as spindle unit 52.By same as before grand master pattern 62 being used as spindle unit 52, compare with said structure, can more easily improve the width accuracy of inclination bearing clearance C 1.

Though in above-mentioned example, the inclination bearing surface C with dynamic pressure groove Ca is formed on the interior perimeter surface of electroforming portion 60, also can form the inclination bearing surface C with dynamic pressure groove Ca on the outer surface of spindle unit 52.Such fluid dynamic-pressure bearing device 51 can be assembled by following process: form the grand master pattern 62 of not concavo-convex smooth surface by using its outer surface, carry out electroforming; Form by molded step and separating step that perimeter surface is level and smooth bearing part 57 in it; In addition, formation has the inclination bearing surface C of dynamic pressure groove Ca on the outer surface of spindle unit 52; With the interior week that spindle unit 52 is inserted bearing part 57.In this case, the inclination bearing surface C on the outer surface of spindle unit 52 can be by such as forging or rolling plastic deformation or form by the method such as etching or jet printing.

Though in above-mentioned example, use for a short time and in the big inclination bearing clearance C 1 of downside diameter at the upside diameter, the inclination bearing play can also tilt along direction in opposite directions, or rather, tilt so that diameter is big and the downside diameter is little at upside.

Figure 23 A and 23B have shown another embodiment of the fluid dynamic-pressure bearing device that helps to realize second purpose of the present invention; This embodiment is corresponding to the structure shown in Figure 15, wherein: two fluid dynamic-pressure bearing devices 51 are in axial direction arranged side by side.

In each fluid dynamic-pressure bearing device 51, spindle unit 52 has two conus portion 52a each other in integral body, and bearing part 57 dispose with the outside of conus portion 52a two 60a of electroforming portion that outer surface is relative separately and 60b and with Unitarily molded molded 61 of the 60a of electroforming portion and 60b.During the rotation of spindle unit 52, the outer surface of two conus portion 52a and on the other side between perimeter surface 60a and the 60b, be formed with two types bearing play C11 and C12 tilting in opposite direction; And utilize the dynamic pressure effect of the lubricant oil produce in inclination bearing clearance C 11 and C12, bearing part 52 in the non-contact mode radially and supported along two thrust directions.Figure 23 A has shown that two types inclination bearing clearance C 11 of different true dip directions wherein and C12 are arranged with at the little example of they side diameters closer to each other; Shown wherein on the contrary that with Figure 23 B two kinds of inclination bearing playes are arranged with at the big example of they side diameters closer to each other.

In two fluid dynamic-pressure bearing devices 51, seal space is formed between the interior perimeter surface of upper and lower end of the outer surface of upper and lower conus portion 52a and bearing part 57, thereby has prevented the leakage (can also form the seal space of the sealed member that separates with bearing part 58) of lubricant oil.In this case, this cover 58 is optional.In addition, in two fluid dynamic-pressure bearing devices 51, utilize inclination bearing clearance C 11 and C12 to produce thrust support power along both direction, so (for example need not to provide any other thrust bearing gap, in the embodiment shown in fig. 15, the thrust bearing clearance C 2 that between the rear surface 52a2 of the upper end face 58a of cover 58 and the spindle unit 52 relative, forms) with it.

In two kinds of structures shown in Figure 23 A and the 23B, utilize based on the method for Figure 22 A to method shown in the 22D, the forming section N1 that is formed by conductive film 72 is formed on the outer surface of grand master pattern 62; And carry out electroforming step, molded step and separating step then, thereby can in the interior perimeter surface of 60a of electroforming portion and 60b, form dynamic pressure groove Ca.In this case, as in above-mentioned example, after grand master pattern 62 and the 60a of electroforming portion and 60b were separated from one another, grand master pattern 62 can be used as spindle unit 52 same as before.

In addition, by producing individually by each of bearing part 57 and spindle unit 52 is divided into two sub-units of obtaining, and then with the whole each other combination of sub-unit, can also ssembly drawing 23A and 23B shown in fluid dynamic-pressure bearing device 51.The possible example of the method that the sub-unit of spindle unit 52 is combined comprises bonding, and the example of the method that the sub-unit of bearing part 57 is combined comprises bonding and melting welding (ultrasonic welding etc.).

Figure 24 has shown modification, wherein: in the structure shown in Figure 23 A, for eliminate the imbalance of the pump amount produce in two inclination bearing clearance C 11 and C12, the curved part at the axial centre place of the annular space (inclination bearing play) between the interior perimeter surface of the outer surface of spindle unit 52 and bearing part 57 is allowed to through the peripheral passage 73 and the external communications of bearing part 57 especially.Though not shown, in the structure shown in Figure 23 B, peripheral passage 73 also can form in a similar fashion.

Though in the example of said structure, when hydrodynamic was produced by the dynamic pressure groove of herringbone structure that forms in the inclination bearing K1 of portion and K2 and the T of thrust bearing portion or helix structure, this should not explain on being limited property ground.For example, as inclination bearing K1 of portion and K2, can also adopt multi sphere bearing, step bearing or non-cylindrical bearing shown in Fig. 9 to 13.In those bearings, a plurality of arcuate surface, axial groove or harmonic wave forms surface are configured for producing the dynamic pressure generating section of dynamic pressure in the inclination bearing play.Certainly, those dynamic pressure generating sections can not only be formed in the interior perimeter surface of bearing part 57, and in the outer surface 52a1 of spindle unit 52.The formation method and structure of dynamic pressure production department is with above-mentioned those are identical, so will omit its detailed description.

When adopting the multi sphere bearing, can adopt three arc bearings, four arc bearings, five arc bearings and six or the multi sphere bearing that forms of multi sphere surface as each inclination bearing K1 of portion and K2.When adopting non-cylindrical bearing, can adopt non-cylindrical bearing by three or four or a plurality of harmonic wave forms surface compositions.

In the embodiment shown in Figure 15, when forming the inclination bearing by multi sphere bearing, step bearing or non-cylindrical bearing, except as in the situation of inclination bearing K1 of portion and K2, wherein two inclination bearing portions are provided so that the structure that is radially spaced each other, the structure of the single inclination bearing portion that can adopt that the vertical area of the outer surface of the vertical area of the interior perimeter surface that wherein is provided at bearing part 57 or spindle unit 2 extends.

In addition, can also form the T of thrust bearing portion by so-called step bearing, so-called corrugated bearing (having the ripple stepped form) etc., wherein: a plurality of dynamic pressure grooves that adopt the radial groove form are set at as (not shown) in the zone on thrust bearing surface at interval with predetermined circle.

Though in above-mentioned example, each of inclination bearing K1 of portion and K2 formed by hydraulic bearing, can also form it by the bearing of some other types.For example, though it is not shown, the interior perimeter surface of bearing part 57 (electroforming portion 60) can also be formed perimeter surface in the cylinder with dynamic pressure groove, arcuate surface etc., and will through the intermediary of inclination bearing play with this in the outer surface 52a1 of the relative spindle unit 52 of perimeter surface form the cylindrical periphery surface, thereby form so-called cylindrical bearing.When so forming inclination bearing K1 of portion and K2 by cylindrical bearing, the grand master pattern 62 that forms electroforming portion 60 usefulness is recycled and reused for electroforming; In addition, as forming in the situation of dynamic pressure groove Ca by removing conductive film 72 therein, grand master pattern 62 can be used as spindle unit 52 same as before.

Though in above-mentioned mobile

Hydrodynamic bearing apparatus

1 and 51, lubricant oil is used as the lubricating fluid that fill its inner space, can also use some other fluids that can produce dynamic pressure in each dynamic pressure groove, for example, magnetic fluid, or such as the gas of air.

Claims

1. fluid dynamic-pressure bearing device comprises:

Spindle unit;

The cylindrical shape radial bearing surface relative with the outer surface of spindle unit;

The bearing part that under the situation of inserting electroforming portion, forms by injection moulding, described electroforming portion has the radial bearing surface; With

Thrust bearing portion, it disposes thrust bearing surface that forms and the thrust bearing gap of facing the thrust bearing surface on the end face of bearing part,

Wherein: the dynamic pressure effect that utilizes the lubricating fluid that produces in the thrust bearing gap is along thrust direction shaft member.

2. fluid dynamic-pressure bearing device according to claim 1, wherein:

Described spindle unit disposes lip part; With

Described thrust bearing gap is formed between the end face and thrust bearing surface of lip part.

3. fluid dynamic-pressure bearing device according to claim 1, wherein:

Described spindle unit disposes ledge surface; With

Described thrust bearing gap is formed between ledge surface and the thrust bearing surface.

4. fluid dynamic-pressure bearing device according to claim 1, wherein: on the thrust bearing surface of bearing part, be formed with the dynamic pressure generating section that is used for producing hydrodynamic pressure in the thrust bearing gap.

5. fluid dynamic-pressure bearing device according to claim 1, wherein said electroforming portion comprises: the radially electroforming portion with radial bearing surface; With become with electroforming portion radially whole thrust electroforming portion and with electroforming part radially from thrust electroforming portion in a thrust electroforming portion, a described thrust electroforming portion has the thrust bearing surface.

6. fluid dynamic-pressure bearing device comprises:

Spindle unit;

Spindle unit inserts the bearing part in week in it; With

The inclination bearing play, it is formed between the interior perimeter surface of the outer surface of spindle unit and bearing part and axioversion, and spindle unit is rotatably supported by the fluid film that forms in the inclination bearing play,

Wherein: bearing part disposes the electroforming portion in the face of the inclination bearing play, and forms by injection moulding under the situation of inserting electroforming portion.

7. fluid dynamic-pressure bearing device according to claim 6, wherein: dynamic pressure generating section is formed among in the electroforming portion of the outer surface of spindle unit and bearing part one, so that dynamic pressure generating section is relative with the inclination bearing play.

8. motor comprises: according to each fluid dynamic-pressure bearing device of claim 1 to 7; Stator coil; And rotor magnet.