CN101203685A

CN101203685A - Fluid dynamic bearing apparatus

Info

Publication number: CN101203685A
Application number: CNA2006800172872A
Authority: CN
Inventors: 森夏比古; 山下信好; 大熊真史; 三谷健一; 里路文规; 古森功; 水谷敏幸
Original assignee: NTN Corp
Current assignee: NTN Corp
Priority date: 2005-05-18
Filing date: 2006-05-15
Publication date: 2008-06-18
Anticipated expiration: 2026-05-15
Also published as: JP4987248B2; CN101203685B; JP2006322511A

Abstract

The purpose of the invention is a bearing member comprising highly accurate dynamic pressure generating portions and stably manufacturable at low cost. Dynamic pressure grooves (8a1) and (8a2) as the dynamic pressure generating portions are formed in the inner peripheral surface of an electroformed part (10) by electroforming, and the electroformed part (10) is inserted and the bearing member (8) is injection-molded with a resin. A shaft member (2) is inserted to the inner periphery of the bearing member.

Description

Fluid dynamic bearing apparatus

Technical field

The present invention relates to be used for be used for the bearing means of rotatably mounted shaft component by the hydrodynamic pressure that produces in the bearing play.Such bearing means is called " fluid dynamic bearing apparatus ", and be suitable for using in the spindle motor that is installed in the information apparatus (for example such as disk devices such as HDD and FDD, such as optical disk unit such as CD-ROM/RAM or such as MD/MO equimagnetic optical disk unit), be installed in the polygon scanner motor in laser beam printer (LBP) or its analog or be installed in the small motor in the electronic equipment (as axial fan).

Background technique

In fluid dynamic bearing apparatus, the shaft component dynamic pressure effect by the fluid that in the radial bearing gap, produces and diametrically to be supported usually with the non-contacting mode of bearing components.In order in the radial bearing gap, to produce the dynamic pressure effect of fluid, in any one surperficial presumptive area at least in the inner circumferential surface of the external peripheral surface of shaft component respect to one another and bearing components, form the dynamic pressure groove of for example arranging, produce part as dynamic pressure with the chevron structure.

Simultaneously,, require extra high running accuracy, therefore, must form dynamic pressure groove with very high degree of precision for the fluid dynamic bearing apparatus that is used for information apparatus above-mentioned.As the method that forms this class dynamic pressure groove on the inner circumferential surface of bearing components, the shaping roll-in is known (for example, seeing JP10-196640A).

In the invention of in above-mentioned JP10-196640A, describing, roll-in machinery with a plurality of projections is inserted in the inner circumference of bearing components, allow roll-in machinery alternately to advance to wherein in the axial direction with counterclockwise going up when rotating in the clockwise direction then, thereby in the inner circumference of bearing components, form the dynamic pressure groove.Forming by above-mentioned shaping roll-in in the method for dynamic pressure groove,, be difficult to stably produce high-precision groove in batches with low cost owing to the characteristic of this method causes the shape of groove to be easy to change.

In addition, in the bearing means of use above-mentioned in information apparatus, to running accuracy require much higher.Therefore, the gap (play) that is provided with between the external peripheral surface of the inner circumferential surface of bearing components respect to one another and shaft component with highi degree of accuracy is important.

Summary of the invention

Thus, an object of the present invention is for a kind of fluid dynamic bearing apparatus with high running accuracy is provided.

To achieve these goals, fluid dynamic bearing apparatus according to the present invention comprises: bearing components; And shaft component, described shaft component is inserted in the inner circumference of described bearing components; It is characterized in that, the injection molding that partly inserts in wherein by electroforming forms described bearing components, and any in the external peripheral surface of the inner circumferential surface of electroforming part and the shaft component relative with the inner circumferential surface of described electroforming part is equipped with dynamic pressure formed thereon and produces part.

Form the electroforming part by making metal ion be deposited on the electroforming process that forms metal layer on the main surface.Also can be by using and the similar method and carry out the formation of such metal layer of electroless-plating (electroless plating) with the similar method of metallide.Under situation about dynamic pressure generating unit branch being formed on the electroforming part, the cross section of shaped portion is formed the corresponding non-perfect circle of shape that produces part with dynamic pressure, under situation about dynamic pressure generating unit branch being formed on the shaft portion, the cross section of shaped portion is formed perfect circle.Because the characteristic of electroforming process, the shaped portion of main shaft is changed into the electroforming part with highi degree of accuracy, and the surface that shaped portion is converted to has the surface accuracy of the surface accuracy of following main shaft.Therefore, if improve the surface accuracy (particularly, the surface accuracy of the shaped portion of main shaft) of main shaft in advance, then can be with the inner circumferential surface of the molded bearing components of highi degree of accuracy, thereby make and can the bearing play be set with highi degree of accuracy.

For example, assign to improve in advance the precision of the shaped portion of main shaft by on the inner circumferential surface of electroforming part, forming the dynamic pressure generating unit, thereby make that can form dynamic pressure with highi degree of accuracy produces part.Bearing components can be by following step manufacturing: make and have the main shaft (main shaft manufacturing step) that produces the corresponding shaped portion of shape of part with the dynamic pressure on the excircle of main shaft; On the excircle of the main shaft that comprises shaped portion, form electroforming part (electroforming step); Carry out injection molding (molded step) when after forming the electroforming part, inserting the electroforming part; And after injection molding, main shaft and electroforming partly be separated from each other (division step).

In the division step after above-mentioned injection molding, main shaft and electroforming partly are separated from each other.For example, can so that expanding, the inner circumference of electroforming part carry out such separating on diameter by making the internal stress on the radial expansion direction that accumulates in the electroforming part owing to the execution electroforming process discharge.By the diameter expansion amount of above-mentioned operation electroforming part when insufficient, main shaft and electroforming partly are heated or cooled so that the thermal expansion amount difference between main shaft and the electroforming partly when only.Thereby, can from the inner circumference of bearing components, extract main shaft out smoothly, do not produce part and do not damage the dynamic pressure that is formed on the electroforming part.

The main shaft that uses during molded electroforming part can be directly as the shaft component of bearing means, and the separating member that separates with main shaft also can be as the shaft component of bearing means.Under latter event, the main shaft that separates can be used in the electroforming process repeatedly.Therefore, can stably produce the high-precision bearing member in batches.

Produce example partly as dynamic pressure, can a plurality of dynamic pressure grooves that wait layout with chevron structure be shown example.The dynamic pressure groove pattern-like shape that comprises the dynamic pressure groove becomes extremely complicated shape.Even in this case,, then accurately shift the shape of shaped portion by electroforming process if in the main shaft manufacturing step, on the excircle of main shaft, form the shaped portion that has with the corresponding part of dynamic pressure groove pattern in advance.Therefore, can easily form Dynamic High-accuracy pressure tank pattern with low cost.Notice that for example, the dynamic pressure that is formed on the electroforming part produces partly and can be formed by a plurality of arc-shaped surface and above-mentioned dynamic pressure groove.

In molded step, when being inserted into mold, carries out by the main shaft that will carry out electroforming process injection molding (inserted mode system), thus the molded integratedly bearing components that partly constitutes by mould portion and electroforming.In inserted mode system, only partly come molded integratedly high precision part by the precision of raising mold with the hi-Fix electroforming.Therefore, if afterwards electroforming part and main shaft are separated from each other, then the moulded parts of gained can directly be used as the bearing components of bearing means.Because the characteristic of electroforming process, the external peripheral surface of electroforming part is formed has coarse surface.Therefore, when carrying out inserted mode system as described above, the injection molding material enters the external peripheral surface of electroforming part, makes bonding force between them because anchor effect and grow.

Preferably, on the electroforming part, forming flange before the molded step.By forming flange, prevent that flange and mould portion break away from or relative to each other rotation each other after injection molding.Therefore, between electroforming part and mould portion, can obtain higher adhesive force.Particularly, form non-perfect circle, can obtain better to prevent the effect of above-mentioned rotation by external peripheral surface with flange.Flange also comprises from the axle center along the flange (with reference to Fig. 7) of the direction extension of tilting and along the flange (with reference to Fig. 6) that extends perpendicular to the direction in axle center.

Can form the flange of electroforming part by making the plastic deformation of electroforming part.For example, if electroforming part form the tight end surfaces that contacts pressurized in the axial direction with the excircle of main shaft, then because the part of pressurized can not be deformed into the internal side diameter that closely contacts with main shaft, thus electroforming end partly by plastic deformation to its radial outside.Therefore, can easily form outside flange.Particularly, coming by injection molding under the situation of molded electroforming part, if the clamping by metal mold makes the plastic deformation of electroforming part partly, after forming flange, the electroforming that is formed in wherein in the maintenance flange-shape partly is injected into resin or metal in the cavity in the former state, thereby makes and can form bearing by inserted mode system.Therefore, can make bearing with low cost, and not need to form the special process of flange.Note, because the external peripheral surface of the flange of plastic deformation is generally non-perfect circle, thus can form the flange that external peripheral surface is non-perfect circle, and do not add other step especially.

If form the flange that forms by plastic deformation on an end of electroforming part or on two end, then plastic deformation becomes littler to the influence of the axial portions of bearing surface.Therefore, can prevent to reduce for the performance of bearing bearing surface precision important, on the axial portions of bearing surface.

By the way, if it is too big to be applied to the pressure of electroforming part under the situation that forms flange by plastic deformation, then worry is, because impact at that time, the inner circumferential surface that forms the tight electroforming part that contacts with main shaft can be peeled off from the external peripheral surface of main shaft.In order to prevent this situation, expectation be, with before the plastic deformation and the variation of the axial length of the part of the electroforming afterwards be arranged on electroforming part after the plastic deformation axial length 50% in.Particularly, when the electroforming part axial length before the flange plastic deformation is L2, when the axial length of electroforming part after the flange plastic deformation is L1, expectation be that L1 and L2 are arranged to satisfy following expression:

0＜A/L1≤0.5 (here, A=L2-L1)

Material as carry out injection molding in molded step can use metallic material, pottery etc. and resin material.Using under the situation of metallic material, for example can use low melting metal (such as magnesium alloy) injection molding, be used for metallic dust and tackiness agent are carried out mutual injection molding so-called MIM molded, then carry out degreasing and sintering etc.Under the situation of using pottery, for example can use the so-called CIM that is used for ceramic powder and tackiness agent are carried out mutual injection molding molded, then carry out degreasing and sintering.Usually, under the situation of using resin material, the object of gained is good in the feature aspect plasticity and the light weight.Under the situation of using metallic material, the object of gained is good in the feature aspect rigidity, electric conductivity and the heat resistance.In addition, under the situation of using pottery, the weight ratio metallic material of the object of gained lighter, and the feature at aspects such as rigidity, heat resistances is good.

By the way, when electroforming partly is formed when cylindrical, after electroforming partly forms, think that the residual stress on the diameter expansion direction is applied to the internal component of electroforming part.Simultaneously, using under the situation of resin as the injection molding material, the cylindrical resin mould portion shrinks owing to being cured.Therefore, after electroforming part resin molded, the inner circumferential surface of the external peripheral surface of electroforming part and resin cast part is by mutual extrusion.In addition, when the inner circumferential surface of electroforming part became the corresponding smooth surface of external peripheral surface with main shaft, the external peripheral surface of electroforming part became rough surface generally.Therefore, after resin molded, resin enters the irregular part on the surface of electroforming part, and produces anchor effect.Because above-mentioned compound action can obtain the strong bonding force between electroforming part and resin cast part.

Practical for above-mentioned electrocast bearing is dropped into as industrial products, guarantee that stably the stronger bonding force between electroforming part and the mould portion is necessary.Simultaneously, even obtained strong bonding force,, then also can hinder electrocast bearing and drop into practical if other bearing characteristics (as the bearing surface precision) is degenerated.

Thus, in the present invention, resin is as the injection molding material of bearing components, and the molded contraction of resin is set at more than or equal to 0.02% to smaller or equal in 2.0% the scope.Be arranged on 0.02% or bigger by the molded contraction with resin, the contractile force that produces in the resin cast part when the resin of fusing is cured increases.Therefore, can guarantee required bonding force between electroforming part and mould portion.Simultaneously, when the molded contraction of resin was too big, the contractile force of mould portion was excessive, and the worry that causes is that electroforming partly can be owing to the contractile force transmission is out of shape.Yet the upper limit of molded contraction is set as 2.0%, thereby makes and can avoid this class adverse effect.

According to the present invention, what expect is, dynamic pressure produces the cross section that partly has diametrically, wherein, with the radius r 1 of the imaginary circle that connects in the inner circumferential surface of electroforming part greater than with the radius r 2 of the external imaginary circle of the external peripheral surface of shaft component, and wherein the circularity sum of the external peripheral surface of the circularity of the bearing surface of electroforming part and shaft component is 4 μ m or littler.

As mentioned above, be configured to r1＞r2 with the radius of a circle r1 that connects in the bearing surface of electroforming part with the radius r 2 of the external peripheral surface of shaft component, thereby can guarantee minimum play between the external peripheral surface of the bearing surface of bearing components and shaft component, thereby make and when shaft component and bearing components relative to each other rotate, to avoid contact and slip between shaft component and the bearing components as much as possible, to obtain the stable rotation bearing state as much as possible.Simultaneously, even when having guaranteed above-mentioned minimum play, if the circularity of the external peripheral surface of the bearing surface of bearing components and shaft component is too high, then the bearing play also is uneven in a circumferential direction.Therefore, comprising such as the running accuracy of precision such as circular runout of axle reduces, and the life-span that also has a bearing is owing to the worry of all wearing and tearing and reducing on such contact and the surface on the sliding parts.According to the checking of the present inventor, have been found that circularity sum when the external peripheral surface of the circularity of the bearing surface of electroforming part and shaft component is 4 μ m or more hour can avoids above-mentioned harmful effect based on this viewpoint.

In this case, the main shaft that uses in electroforming process can directly be used as shaft component.The surface configuration of main shaft is accurately transferred to micron order on the inner circumferential surface as the electroforming of bearing surface part.Therefore, when the circularity sum of the external peripheral surface of the circularity of the bearing surface that limits the electroforming part as described above and shaft component, be only about half of (the 2 μ m) of above-mentioned sum as the circularity of the external peripheral surface of the shaft component of main shaft.Therefore, handle, make that circularity is above-mentioned numerical value or littler, then running accuracy that can stably obtain and long bearing life if in advance main surface is carried out fine finishing.

Separate member and the main shaft made with main shaft and also can be used as shaft component.In addition in this case, if the surface of member by fine finishing make its circularity be above-mentioned numerical value (for above-mentioned and half) or littler, the running accuracy that can stably obtain then.

Note, on public cross section radially, measuring radius r 1 and r2 and circularity.Necessary is along axially (desirably, three or more equal at interval points) intercepts along cross section radially in some arbitrfary points, and to satisfy above-mentioned condition in each position of extracting like this.Notice that " circularity " mentioned refers to two concentrically ringed following two how much concentric radius of a circles poor (with reference to Figure 36) of minimum situation that are spaced apart when circular body is clamped by two how much concentric circles here.

Be used for to be formed on the electroforming part on the thrust bearing surface of the end of thrust direction upper support shaft component.In this case, needn't be attached in the main body by the member (thrust plate etc.) that will constitute the thrust bearing surface as press fit and bonding mode.Therefore, reduced the number of step and the number of parts, thereby the cost that makes it possible to achieve bearing means reduces.

As the thrust bearing part, can also use dynamic pressure effect by fluid (this effect results from the end surfaces and the thrust bearing gap between the thrust bearing surface relative with end surfaces of shaft component) on the thrust direction with the dynamic bearing of non-contacting mode supporting axle member and be used for the way of contact shaft component being bearing in the lip-deep pivot bearing of thrust bearing along the thrust direction.For example, can construct dynamic bearing by forming a plurality of dynamic pressure grooves in the end surfaces of thrust bearing surface and the shaft component relative any with the thrust bearing surface.

Form by dynamic bearing and the dynamic pressure groove is formed under the lip-deep situation of thrust bearing in thrust bearing part, have and the corresponding erose thrust bearing shaping surface part of the shape of dynamic pressure groove if on the axle head of main shaft, form in advance, then can form the dynamic pressure groove on thrust bearing surface with highi degree of accuracy by electroforming process.On the other hand, be formed at the dynamic pressure groove under the situation on the end surfaces of shaft component, carry out electroforming process by main shaft, wherein, axle head forms plat surface, and the thrust bearing surface forms and do not have dynamic pressure to produce the flat-surface shapes of part.Then, after electroforming part and main shaft were separated from each other, the shaft component that the dynamic pressure groove is formed in another step on the end surfaces in advance was inserted in the inner circumference of shaft component, thereby constructs dynamic bearing.

Using under the situation of main shaft as shaft component, also can on the other end of main shaft, form another thrust bearing surface and the shaped portion that on an end of main shaft, is formed for forming the thrust bearing surface.In this case, if assign to form the thrust bearing surface by forming section, and after main shaft and electroforming partly are separated from each other, then with main shaft counter-rotating and be inserted in the inner circumference of bearing components, the thrust bearing part can be configured between the thrust bearing surface of the bearing construction part of main shaft and electroforming part.For the bearing construction part of main shaft, for example, consider that a plurality of dynamic pressure grooves are formed on the structure on the end surfaces, structure or the axle head that end surfaces is formed plat surface is formed spherical structure.Under the situation of preceding two kinds of structures, dynamic bearing is made of the bearing construction part and the thrust bearing surface of main shaft, and under the situation of a kind of structure in back, pivot bearing is made of bearing construction part and thrust bearing surface.

Bearing means with above-mentioned structure can be preferably used for motor, for example, is used for the spindle motor such as dish devices such as HDD.This motor is characterised in that not expensive, in addition, and running accuracy and durability height.

Foregoing description shows in the external peripheral surface of the inner circumferential surface of electroforming part and the shaft component relative with this inner circumferential surface any and forms the situation that dynamic pressure produces part.Yet, above-mentioned various structures also can similarly be applied to such situation (perfectly round bearing): any in the external peripheral surface of the inner circumferential surface of electroforming part and the shaft component relative with this inner circumferential surface has perfect circular cross section, and do not have dynamic pressure to produce part.In this case, the cross section of main shaft forms perfect circle.Therefore, the radial bearing surface of bearing components (inner circumferential surface of electroforming part) is formed perfect circle.Therefore, after main shaft and electroforming partly are separated from each other, have perfect circular shaft component and be inserted in the inner circumference of bearing components, thereby the radial bearing gap with perfect circle is formed between the external peripheral surface of surperficial and relative with this radial bearing surface shaft component with perfect circular cross section of the radial bearing with perfect circle.

According to the present invention, can obtain following effect.

(1) can the bearing play be set with highi degree of accuracy, thereby can improve the bearing performance of bearing means.

(2) can stably provide bearing components with low cost with Dynamic High-accuracy pressure generation part.In addition, when forming the dynamic pressure groove, do not produce the powder that can produce, can avoid the generation of polluting by cutting.

(3) by flange portion, can prevent the electroforming part and mould portion breaks away from mutually or relative to each other rotation, therefore, can further improve electroforming partly and the bonding force between the mould portion.

(4) bearing means can show bearing performance steady in a long-term, and number can reduce part count and rigger the time, reduces thereby make it possible to achieve cost.

(5) between electroforming part and mould portion, can stably obtain strong bonding force.Simultaneously, electroforming part can be limited because the distortion that the contraction of mold causes, thereby feasiblely higher bearing performance can be obtained.

(6) can improve the rigidity, heat resistance, electric conductivity etc. of bearing.Therefore, even electrocast bearing also can use under rugged environment such as high capacity, high temperature, thereby the feasible purposes that can help enlarging electrocast bearing.

Description of drawings

In the accompanying drawing:

Fig. 1 is the perspective view that illustrates according to bearing components of the present invention;

Fig. 2 A is the perspective view of main shaft, and Fig. 2 B illustrates the perspective view of main shaft being carried out the state of sheltering, and Fig. 2 C is the perspective view that the electroforming axle is shown;

Fig. 3 is the just sectional view after inserted mode system of bearing components;

Fig. 4 is the sectional view of injection molding metal mold;

Fig. 5 is the sectional view of injection molding metal mold;

Fig. 6 is the sectional view of bearing means;

Fig. 7 is the sectional view that the electroforming step is shown;

Fig. 8 is the sectional view of bearing components;

Fig. 9 is the sectional view that the embodiment of fluid dynamic bearing apparatus is shown;

Figure 10 is the sectional view that the example of the spindle motor that uses fluid dynamic bearing apparatus of the present invention is shown;

Figure 11 is the sectional view that another example of the spindle motor that uses fluid dynamic bearing apparatus of the present invention is shown;

Figure 12 is the sectional view that another embodiment of fluid dynamic bearing apparatus is shown;

Figure 13 is the sectional view that another embodiment of fluid dynamic bearing apparatus is shown;

Figure 14 is the sectional view that another embodiment of fluid dynamic bearing apparatus is shown;

Figure 15 is the sectional view that another embodiment of fluid dynamic bearing apparatus is shown;

Figure 16 is the sectional view that another embodiment of fluid dynamic bearing apparatus is shown;

Figure 17 is the sectional view that an embodiment of radial bearing part is shown;

Figure 18 is the sectional view that another embodiment of radial bearing part is shown;

Figure 19 is the sectional view that another embodiment of radial bearing part is shown;

Figure 20 is the sectional view that another embodiment of radial bearing part is shown;

Figure 21 is the perspective view according to bearing components of the present invention;

Figure 22 A is the perspective view of main shaft, and Figure 22 B illustrates the perspective view of main shaft being carried out the state of sheltering, and Figure 22 C is the perspective view that the electroforming axle is shown;

Figure 23 is the planimetric map that the axle head of main shaft is shown;

Figure 24 is the bearing components sectional view after inserted mode system just;

Figure 25 is the sectional view that molded step is shown;

Figure 26 is the sectional view that the example of the spindle motor that uses fluid dynamic bearing apparatus of the present invention is shown;

Figure 27 is the sectional view that the embodiment of fluid dynamic bearing apparatus is shown;

Figure 28 is the local amplification view of bearing components;

Figure 29 is the sectional view of bearing components;

Figure 30 is the sectional view that another embodiment of fluid dynamic bearing apparatus is shown;

Figure 31 is the sectional view that another embodiment of fluid dynamic bearing apparatus is shown;

Figure 32 will be used as the front view of the main shaft of shaft component;

Figure 33 is the perspective view of main shaft;

Figure 34 is the perspective view that illustrates through the main shaft of sheltering;

Figure 35 is the perspective view of electroforming axle; And

Figure 36 is the sectional view of bearing means on radial direction, and the zoomed-in view of bearing means.

Label declaration

1 fluid dynamic bearing apparatus

2 shaft components

3 dish hubs

4 stator coils

5 rotor magnets

7 housings

8 bearing components

8a1 dynamic pressure groove

8a2 dynamic pressure groove

10 electroforming parts

11 electroforming axles

12 main shafts

13 shelter

14 mould portions

20 flanges

A radial bearing surface

The N shaped portion

The R1 first radial bearing part

The R2 second radial bearing part

T thrust bearing part

The T1 first thrust bearing part

The T2 second thrust bearing part

Embodiment

To embodiments of the invention be described based on accompanying drawing.

Bearing components with structure of the present invention 8 shown in Figure 1 is by following step manufacturing: make main shaft (with reference to Fig. 2 A); Shelter the point (with reference to Fig. 2 B) that the needs of main shaft 12 are sheltered; By being carried out electroforming process, the unshielded part of main shaft 12 forms electroforming axle 11 (with reference to Fig. 2 C); Form bearing components 8 (with reference to Fig. 5) by electroforming part 10 with molded electroforming axles 11 such as resins; And electroforming part 10 and main shaft 12 be separated from each other.

By conductive metallic material, the stainless steel that has for example carried out Quenching Treatment forms at the main shaft 12 shown in Fig. 2 A.As a rule, as long as the plasticity of electroforming part 10 is good, also can use the metallic material except that stainless steel, for example nickel alloy, evanohm and analog.Even nonmetallic material, for example pottery also can be used as main shaft by carrying out conductive processing (for example, filming by forming conducting metal on its surface).Expectation be, in advance the surface of main shaft 12 is used to reduce the surface treatment of the frictional force between electroforming part 10 and the main shaft 12, for example carry out the fluororesin coating.Except that solid shaft, main shaft 12 can also form by hollow shaft or by the solid shaft that forms with resin filling hollow parts.

Shown in Fig. 2 A, go up to form in the zone (described zone is the part that will form electroforming part 10) of the external peripheral surface 12a of main shaft 12 and have and the corresponding erose shaped portion N of the shape of the radial bearing surfaces A of describing later.The each side of the irreqularity of shaped portion N and radial bearing surfaces A is antipodal each other, and the protruding part on radial bearing surface is corresponding with sunk part 12a1 and the 12a2 of shaped portion N.Example shown in the figure shows sunk part 12a1 and 12a2 and is formed situation with the humanoid corresponding structure of dynamic pressure groove pattern; Yet sunk part 12a1 and 12a2 also can be formed and the corresponding structure of spiral dynamic pressure groove pattern.

For example, by using process of surface treatment (as etching) and cutting process and process for machining (as pressing process) to form shaped portion N.The precision of external peripheral surface 12a that comprises the main shaft 12 of shaped portion N directly influences the molded precision that dynamic pressure produces part, and the result influences the bearing performance of dynamic bearing.Therefore, be necessary to improve in advance the precision of circularity, cylindricity, surface roughness etc., this function for bearing means is important.

In the masking steps shown in Fig. 2 B, shelter the 13 external peripheral surface 12a except that shaped portion N that are applied to main shaft 12.The existing article that can use nonconducting and anti-electrolytic solution corrosion are as the material of sheltering 13.

Electroforming process shown in the execution graph 2C by this way: make the main shaft 12 of sheltering processing immerse in the electrolytic solution, described electrolytic solution contains the metal ion of Ni, Cu etc., to make metal target deposit on the surface of main shaft 12 by electrolytic solution being applied electric power.In electrolytic solution, can also contain sliding material (for example carbon) or stress relieve material (for example asccharin) as required.Divide required physical property and chemical characteristics (for example hardness and fatigue strength) to select the suitable type of such electrodeposit metals according to the dynamic pressure generating unit.About the thickness of electroforming part 10, if electroforming part 10 is too thick, then its removeability from main shaft 12 descends, if electroforming part 10 is too thin, then its durability descends, or the like.Therefore, according to the size of required bearing performance, bearing, and further described thickness is set according to its purpose or the like optimization.For example, in shaft diameter is 1 to 6mm swivel bearing, preferably thickness is arranged in the scope of 10 to 200 μ m.

As mentioned above, form electroforming part 10 by using similar in appearance to the method for electrolysis plating.In addition, can also form electroforming part 10 by using similar in appearance to the method for electroless plating.

By above-mentioned step, shown in Fig. 2 C, formed electroforming axle 11, wherein, cylindrical electroforming part 10 invest main shaft 12 except that the zone of sheltering the external peripheral surface 12a 13 (shaped portion N).At this moment, on the irregularly shaped inner circumferential surface that is transferred to electroforming part 10 that is formed on shaped portion N on the external peripheral surface 12a of main shaft 12, thereby form a plurality of dynamic pressure grooves, produce part as dynamic pressure.Notice that when the coating material 3 that is used to shelter approached, in some cases, shown in the dotted line of Fig. 3, the two ends of electroforming part 4 were to coating material 3 lateral processes, and taper chamfered part 4a is formed on the inner circumferential surface of electroforming part.

Then, for example, electroforming axle 11 is sent to the molded step shown in Fig. 4, and by using electroforming axle 11 to carry out the injection molding (inserted mode system) that utilizes resin material as insertion parts.

In this molded step, electroforming axle 11 is provided to the metal mold that is made of trussell 15 and bottom mold 16, and wherein said electroforming axle 11 is in its state that axially parallels with the clamping direction (Vertical direction among Fig. 4) of metal mold.In bottom mold 16, form outside dimension corresponding positioning hole 18 with main shaft 12.Be inserted into the positioning hole 18 from the lower end of the rapid electroforming axle 11 that transmits of previous step, and realization is to the location of electroforming axle 11.In positioning states, the rear surface of electroforming part 10 engages with the molded surface of bottom mold 16 in the electroforming axle 11, and the upper end of electroforming part 10 from the joint line P.L. of metal mold towards second half mold (trussell 15 this embodiment) projection.The degree of depth L3 of positioning hole 18 is greater than (the L3＞L4) of the distance L 4 between the lower end of the lower end of main shaft 12 and electroforming part 10.Therefore, under the state before the die forging, the rear surface of main shaft 12 is floated from the bottom of positioning hole 18.By the adjusting amount of floating, can change the amount of plastic deformation of the flange on the lower end that is formed on electroforming part 10.

In above-mentioned trussell 15, guide hole 19 and positioning hole 18 coaxial formation.If the degree of depth L5 of guide hole 19 reaches the degree (noticing that the lower end of main shaft 12 arrives and contact the bottom of positioning hole 18) that the upper end of main shaft 12 during the forging shown in Fig. 5 did not arrive or contacted the bottom of guide hole 19, then the degree of depth L5 of guide hole 19 is enough.

In above-mentioned metal mold, when movable mold (trussell 15 among this embodiment) near fixing mold (bottom mold 16 among this embodiment) when carrying out die forging, at first, the upper end of main shaft 12 is inserted in the guide hole 19, and main shaft 12 carried out centering, the upper end face of electroforming part in addition, 10 adjoins on the molded surface of trussell 15.By making trussell 15 further near coming integrally to lower piezoelectric casting axle 11.Then, as shown in Figure 5, make the underpart of adjoining in the electroforming part 10 on the molded surface of bottom mold 16 distinguish plastic deformation to outside diameter, and on two axial end portions of electroforming part 10, form flange 20 with the upper end portion of adjoining the electroforming part 10 on the molded surface of trussell 15.By changing the structure of metal mold, can also only on an axial end of electroforming part 10, form flange 20.

After finishing clamping, by short tube 21, runner 22 and cast gate 23 resin material is injected in the chamber 17, and carries out inserted mode system.As resin material, the resin material of preferred mechanical intensity and oil resistant, function admirable such as heat-resisting.For example, can use the high-performance crystalline polymer, such as with liquid-crystalline polymer (LCP), polyphenylene sulfide (PPS) resin, polyoxymethylene (POM) resin and polyamide (PA) resin as resin material.As a rule, these are example, can select to be suitable for the resin material of the Environmental Conditions of purpose and bearing from various existing resin materials.As required, various fillers, for example strengthening agent (being any form that comprises fiber and powder) and oiling agent also can add in the resin material.

As resin material, in a kind of resin material of selecting, in the closed interval scope of molded shrinkage (predicted value after adding filler) 0.02% to 2.0% (preferably, in the closed interval scope 0.05% to 1.0%).According to the present inventor's checking, when molded shrinkage less than 0.02% the time, can not guarantee the enough adhesive forces between electroforming part 10 and the resin, cause worry to the bearing durability.On the other hand, have been found that when molded shrinkage surpasses 2.0% that the contractile force of resin part is excessive, this surface accuracy to bearing has adverse effect.

Note, also can use metallic material as injection material.The metal injection molding comprises deposite metal injection molding and metallic dust injection molding, and can adopt any among the present invention.The former is such technology: wherein, tinsel is considered to be worth doing and rod is melted or semi-molten, flows to then in the metal mold, then carries out molded.Specifically, when using low melting metal, for example when magnesium alloy or aluminum alloy, melting unit can miniaturization.The latter is such technology: wherein, metallic dust and Bond mix/knead together, and it is flow in the metal mold, from metal mold, take out then, and degrease and sintering.This technology is commonly referred to metal injection molding (MIM).Under the molded situation of this MIM, the metal that uses is not limited to for example low melting metal such as magnesium alloy or aluminum alloy, can select other metallic material widely according to the purpose of bearing, for example Cuprum alloy, ferro-alloy and copper-ferro-alloy.As mentioned above, use metal, thereby compare, can further improve intensity, heat resistance, electric conductivity etc. with the situation of using resin material as the injection molding material.

Except resin material above-mentioned and metallic material, for example, can use pottery.Can use for example so-called CIM molded etc., wherein, it is molded that the mixture of ceramic powder and tackiness agent is injected into, then degrease and sintering.In this case, obtain such feature: the material of injection is lighter than metallic material, and rigidity and heat-resisting aspect more excellent than resin material.

After finishing inserted mode system, open mold.Then, obtain moulded parts as shown in Figure 3, wherein, the electroforming axle 11 that is made of main shaft 12 and electroforming part 10 combines with mould portion 14.

Then above-mentioned moulded parts is sent to division step, here, described moulded parts is separated into member (bearing components 8) and main shaft 12, and in described member (bearing components 8), electroforming part 10 and mould portion 14 combine.

In division step, bearing components 8 and main shaft 12 are separated from each other.Specifically, for example, by applying impact to electroforming axle 11 or bearing components 8, the residual stress that accumulates in the electroforming part 10 is eliminated, the inner circumferential surface 10a of electroforming part 10 expands diametrically, and between the external peripheral surface 12a of the inner circumferential surface 10a of bearing components 8 and main shaft 12, form the gap degree of depth of dynamic pressure groove (desirably, greater than).By forming described gap, cancellation be formed on the radial bearing surfaces A on the inner circumferential surface of bearing components 8 and be formed on axial engagement between the shaped portion N on the external peripheral surface of main shaft 12 with irreqularity.Therefore, by applying impact to electroforming axle 11 or bearing components 8, after the external peripheral surface 12a of main shaft 12 peeled off, main shaft 12 was extracted out from bearing components 8 in the axial direction in electroforming part 10, therefore can smoothly main shaft 12 and bearing components 8 be separated from each other, and not damage the radial bearing surfaces A.Note, for example,, the diameter expansion amount of electroforming part 10 can be controlled at 1 μ m in the scope of tens μ m by changing the thickness of electroforming part 10.

When only guaranteeing enough diameter expansion amounts on can not inner circumferential surface 10a in electroforming part 10 by eliminating stress, heating or cooling electroforming part 10 and main shaft 12, and it is poor to produce thermal expansion amount between them, thereby also main shaft 12 and bearing components 8 can be separated from each other.

In this case, if form main shaft 12 with metallic material or stupalith as mentioned above in advance, even then during the injection molding under the high temp/high pressure environment, also can avoid the distortion of main shaft 12.Therefore, can avoid the distortion of shaped portion N during the injection molding, therefore, can form the radial bearing surfaces A with highi degree of accuracy.In addition, the main shaft 12 that separates from electroforming part 10 can be used for the manufacturing of bearing components 8 repeatedly, and the radial bearing surfaces A is formed the corresponding shape of shape with the shaped portion N of main shaft 12.Therefore, can suppress the manufacture cost of main shaft 12, in addition, can stably produce the bearing components 8 that comprises dynamic pressure generation part in batches, wherein, precision is high and change less.

Note, because the characteristic of electroforming process causes the outer surface of electroforming part 10 to be formed rough surface.Therefore, during inserted mode system, the material of structure mould portion 14 presents micro irregularity on the outer surface of electroforming part, thereby owing to set effect (anchor effect) causes applying strong adhesive force.In addition, as mentioned above, in the present invention, flange 20 is formed on the electroforming part 10, also electroforming part 10 is carried out inserted mode system with the form that comprises flange 20.Therefore prevented separating and rotation between electroforming part 10 and the mould portion 14 effectively.Therefore, the adhesion between electroforming part 10 and the mould portion 14 increases, thereby the bearing components 8 with excellent durability and high reliability can be provided.Specifically, as shown in Figure 1, by 10 plastic deformations of electroforming part are formed under the situation of flange 20, the shape of the external peripheral surface 20a of flange 20 becomes and has the nonideal circle of erratic behavior at random in embodiment as shown in Figure 4 and Figure 5.As a result, obtain better anti-rotation effect.Note, in Fig. 1, for understandable purpose, the irreqularity of having drawn external peripheral surface 20a in exaggerative mode.

As mentioned above, forming by plastic deformation under the situation of flange 20, if it is too big to be applied to the pressurized energy from metal mold of electroforming part 10, then exist because the impact of this moment causes the risk peeled off from the external peripheral surface of main shaft 12 with the inner circumferential surface of the main shaft 12 tight electroforming parts 10 that contact.At this moment, when electroforming part 10 is peeled off, electroforming part 10 diameter expansion, and form gaps with main shaft 12.Therefore, during ensuing injection molding, the inner circumferential surface of electroforming part 10 shrinks randomly owing to injection pressure causes diameter, has the risk of the precision reduction that causes inner circumferential surface 10a.In order to prevent such situation, must make great efforts to prevent that electroforming part 10 from peeling off from main shaft 12 before injection molding, and think that the upper limit of amount of plastic deformation that can be by control electroforming part 10 realizes this.

According to check from above-mentioned viewpoint, the content below finding.In bearing components shown in Figure 68, the axial length (shown in broken lines among Fig. 5) of electroforming part 10 is L2 before plastic deformation, and when the axial length (illustrating with solid line among Fig. 6) of electroforming part 10 is L1 after the plastic deformation, if after the plastic deformation axial length of electroforming part 10 change A (=L2-L1) the axial length of electroforming part 10 50% in (being desirably in 20%), can prevent that then electroforming part 10 is owing to injection molding plastic deformation is before peeled off.On the other hand, if A equals 0, then can not form flange 20.Therefore, L1 and L2 are determined in expectation, to satisfy following expression:

0＜A/L1≤0.5

In the superincumbent description, shown the situation that forms flange 20 by plastic deformation; Yet, also can form flange 20 by other method except that plastic deformation.For example, as shown in Figure 7, if in advance main shaft 12 is formed axle shape with step difference, then when in the electroforming step, immersing main shaft 12 in the electrolytic solution, according to the electroforming condition can corner part 12a after electroforming finishes at main shaft 12 on formation inclined flange 20 as shown in Figure 7.Usually, this is because compare with the deposition of metal particle in other smooth of main shaft 12, increases at the deposition of the metal particle of corner part 12a.

Therefore, if after forming flange 20, form the electroforming part 10 that comprises flange 20, then can prevent the effect that electroforming part 10 is peeled off or rotated with top similarly acquisition by injection molding (shown in double dot dash line).

As shown in Figure 8, by a plurality of dynamic pressure groove 8a1 with 8a2 and be used to limit the vertical apart from each other main shaft 12 that is formed on of two radial bearing surfaces A that the protruding part of described dynamic pressure groove 8a1 and 8a2 constitutes from the inner circumferential surface (the inner circumferential surface 10a of electroforming part 10) of its bearing components that separates 8.This will be described later, and along with bearing components 8 is attached in the bearing means, the external peripheral surface of radial bearing surfaces A and shaft component 2 forms the radial bearing gap.

Then, figure 9 illustrates the example of the liquid dynamic bearing apparatus of making in the above-mentioned steps 1 that utilizes bearing components 8.As shown in Figure 9, except the bearing components 8 as the main composition parts, liquid dynamic bearing apparatus 1 comprises: housing 7, have the bottom 7c on the one end, and be used for bearing components 8 is fixed to its inner circumferential surface; Shaft component 2 is inserted in the inner circumference of bearing components 8; And sealing component 9.Notice that the convenience in order to describe below will be upsides and the axial opposite side of sealing component 9 sides is described when being downside in definition sealing component 9 sides.

Housing 7 forms by metallic material, for example the cylinder form of the end sealing of stainless steel or brass or resin material formation.Housing 7 comprises the open part 7a that is positioned at an end, and its other end seals.Housing 7 further comprises cylindrical lateral portion 7b and bottom 7c, and bottom 7c is on sidepiece 7b relative with open part 7a distolateral.In this embodiment, sidepiece 7b and bottom 7c form apart from each other, and bottom 7c is fixed to the following inner circumference of sidepiece 7b by methods such as for example bonding, press fit and welding.Though do not illustrate, form a plurality of dynamic pressure grooves that for example are arranged to helix structure or herringbone structure on the part annular zone on thrust bearing surface being used as of bottom 7c, produce part as dynamic pressure.Can be by pressing process etc. and side by side molded this class dynamic pressure groove of molded bottom 7c.In addition, sidepiece 7b and bottom 7c also can form.Notice that the material that is used to form sidepiece 7b and bottom 7c can be same to each other or different to each other, as long as described material can satisfy required performance.

Shaft component 2 is formed by for example metallic material (as stainless steel) dividually with above-mentioned main shaft 12.Shaft component is made of shaft portion 2a and flange portion 2b, and flange portion 2b is arranged on the end of shaft portion 2a integratedly or dividually.The cross section of the external peripheral surface of shaft portion 2a forms desirable circle, and it does not have dynamic pressure groove or analog.Shaft component 2 also can form the mixed construction that partly is made of metalwork and resin, perhaps only forms (for example, shaft portion 2a is formed by metallic material, and flange portion 2b is formed by resin material) by metallic material.The outside dimension of shaft portion 2a is slightly less than the internal diameter size of protruding part, limits and form dynamic pressure groove 8a1 and 8a2 in this radial bearing surfaces A on being formed on bearing components 8.Therefore, be similar in the radial bearing gap of 1 μ m in tens mu m ranges forming between the external peripheral surface of shaft portion 2a and two the radial bearing surfaces A.

By for example press fit and bonding method, will be fixed to the inner circumference of the open part 7a of housing 7 by the sealing component 9 that metallic material (as brass) or resin material form.In this embodiment, sealing component 9 forms annular shape, and forms dividually with housing 7.By having the seal space S of predetermined, the inner circumferential surface 9a of sealing component 9 is relative with the external peripheral surface of shaft portion 2a.The external peripheral surface of the shaft portion 2a relative with seal space S is formed along with extending upward the conical surface 2a2 that diameter reduces gradually, also is used as centrifugal seal when shaft component 2 rotations.After assembling fluid dynamic bearing apparatus 1, the inner space of being sealed ground sealed fluid flow dynamic bearing apparatus 1 by sealing component 9 is filled with the lubricant oil that for example is used as lubricating fluid, and under this state, the pasta of lubricant oil is maintained among the seal space S.Notice that in order to reduce the purpose of part count and assembling number in man-hour, sealing component 9 also can form with housing 7.

Bearing components 8 is fixed to the inner circumferential surface of the sidepiece 7b of housing 7.For the method that bearing components 8 is fixed to the housing inner circumference, select fixation method according to design condition, for example press fit, bonding, press fit and bonding combination and welding.Shaft component 2 rotatably is inserted in the inner circumference of bearing components 8.

As mentioned above, bearing components 8 has the composite structure that is made of mould portion 14 and electroforming part 10, and mould portion 14 is formed by resin material, and electroforming part 10 is fixing and be connected to the inner circumferential surface of mould portion 14, and bearing 8 forms cylinder form.Mould portion 14 and electroforming part 10 in the axial direction with the brute force on the whole length come fixed to one another be connected, the flange 20 of Yan Shening is formed on the upper end portion and underpart of electroforming part 10 diametrically, thereby has prevented effectively separating and rotation between mould portion 14 and the electroforming part 10.By above-mentioned electroforming process, on the radial bearing surfaces A of the inner circumferential surface 8a of bearing components 8, be individually formed lambdoid dynamic pressure groove 8a1 and 8a2.In this embodiment, axially be formed asymmetrically the dynamic pressure groove 8a1 in the zone with respect to axial centre m (passing the axial centre in the zone of valley and following valley), and dynamic pressure groove 8a1 on distinguish the axial dimension X2 greater than its inferior segment from the axial dimension X1 of axial centre m.Therefore, when shaft component 2 rotation, the feedback power (suction force) of the lubricant oil that produces by the dynamic pressure groove in last dynamic pressure groove 8a1 than in the dynamic pressure groove 8a2 of symmetry down greatly.

In addition, though do not illustrate, surface, the underpart of bearing components 8 8c as for example forming on the part annular zone on thrust bearing surface with a plurality of dynamic pressure grooves of helical arrangement, produce part as dynamic pressure.Can with form side by side molded this class dynamic pressure groove of bearing components 8, as long as on the zone of the bottom mold 16 relative, form flute profile in advance with rear surface 8c.In this case, bottom mold 16 is bottom mold of using in the molded step that forms above-mentioned bearing components 8.Molded by above-mentioned the time, can omit the work that on rear surface 8c, forms the dynamic pressure groove separately.

Construct fluid dynamic bearing apparatus 1 as described above, when shaft component 2 rotation, pass through the radial bearing gap external peripheral surface 2a1 with shaft portion 2a is relative respectively as go up zone and the lower area of the inner circumferential surface 8a of the bearing components 8 of radial bearing surfaces A.Then,, in above-mentioned radial bearing gap, produce the dynamic pressure of lubricant oil, and by described pressure, diametrically rotatably with the shaft portion 2a of the mode supporting axle member 2 that do not contact with bearing components 8 along with shaft component 2 rotation.Therefore, form the first radial bearing part R1 and the second radial bearing part R2, the described first radial bearing part R1 and the second radial bearing part R2 are with the rotatably mounted diametrically bearing components 2 of non-contacting mode.

In addition, zone as the rear surface 8c of the bearing components 8 on thrust bearing surface is relative with the upper end face 2b1 of flange portion 2b by the thrust bearing gap, and it is relative with the rear surface 2b2 of flange portion 2b to pass through the thrust bearing gap as the zone of the upper end face 7c1 of the bottom 7c on thrust bearing surface.Then, along with shaft component 2 rotations, in the thrust bearing gap, also produce the dynamic pressure of lubricant oil.By using described pressure, with housing 7 and on two thrust directions rotatable bearing components 8 with non-contacting mode supporting axle member 2.Therefore, formed the first thrust bearing fractional t1 and the second thrust bearing part T2 that is used on two thrust directions rotatably with so non-contacting mode supporting axle member 2.

Notice that in shaft component 2 rotations, lubricant oil is forced into the bottom side of housing 7.Therefore, if such state continuance, then the pressure of the lubricant oil in the thrust bearing gap of thrust bearing fractional t1 and T2 is increased to great degree, make and probably in lubricant oil, produce foam, thereby lubricant oil can leak, vibration perhaps can occur, all these may cause owing to the excessive increase of pressure.In this case, as Fig. 8 and shown in Figure 9, on the rear surface 9b of the external peripheral surface 8d of bearing components 8 and sealing component 9, circulating path 8d1 and 9b1 are set respectively, described circulating path 8d1 and 9b1 make thrust bearing gap (the thrust bearing gap of the first thrust bearing fractional t1 specifically) and seal space S communicate with each other.Thereby lubricant oil flows between thrust bearing gap and seal space S by circulating path 8d1 and 9b1, has discharged pressure difference in early days, can prevent above-described the sort of injurious effects.As example, Fig. 9 shows the situation that forms circulating path 8d1 on the external peripheral surface 8d of bearing components 8, and the situation that forms circulating path 9b1 on the rear surface 9b of sealing component 9.Yet circulating path 8d1 also can be formed on the inner circumferential surface of housing 7, and circulating path 9b1 also can be formed on the upper end face 8b of bearing components 8.

Figure 10 shows the structure example that the fluid dynamic bearing apparatus 1 shown in Fig. 9 is attached to the spindle motor that is used for information apparatus wherein.Described spindle motor is the motor that is used for disk drive device (as HDD), and comprises: fluid dynamic bearing apparatus 1 is used for the rotatably mounted shaft component 2 of non-contacting mode; Rotor (dish hub) 3 is connected to shaft component 2; And stator coil 4 and rotor magnet 5, the two all passes through radial clearance toward each other.Stator coil 4 is connected to the excircle of carriage 6, and rotor magnet 5 is connected to the inner circumference of dish hub 3.The housing 7 of fluid dynamic bearing apparatus 1 is connected to the inner circumference of carriage 6.One or more dish D, for example disk is maintained on the dish hub 3.When excitation stator coil 4, rotor magnet 5 rotates by the electromagnetic force between stator coil 4 and the rotor magnet 5, thereby dish hub 3 and shaft component 2 rotation integratedly each other.

Figure 11 shows the fluid dynamic bearing apparatus of the bearing components 8 that uses the embodiment shown in Fig. 6 and the structure example of motor.Motor has radial bearing part R that is used for rotatably mounted shaft component diametrically and the thrust bearing part T that is used for rotatably mounted shaft component on the thrust direction.By constructing radial bearing part R in the inner circumference that shaft component 2 is inserted into bearing components 8, by using the axle head of the protruding sphere of thrust plate 24 support shaft member 2 relative to construct radial bearing part T with the end surfaces of bearing components 8 in the mode of contact.

At disk drive device, for example among the HDD, existence dish D is by having the risk of static with air friction, with the static abrupt release to peripheral unit, magnetic head for example, thereby influence peripheral unit unfriendly.Specifically, when thrust plate 23 is formed from a resin, perhaps when thrust bearing part T is made of dynamic bearing, bring the trend of this adverse effect to become remarkable.On the other hand, when forming mould portion 14 by the injection molding metallic material, the static that is based upon on the dish D is discharged into ground rapidly by approach axes member 2 → electroforming part 4 → mould portion 14 → carriage 27.Therefore, can confinement plate D static electrification, and can prevent flashing between dish and peripheral unit.

Bearing components 8 above-mentioned not only can be used for fluid dynamic bearing apparatus shown in Figure 91, and can be widely used for having the fluid dynamic bearing apparatus of other structure.Fluid dynamic bearing apparatus to other structure is described below with reference to accompanying drawings.To come the function member identical of presentation function and structure and fluid dynamic bearing apparatus 1 shown in Figure 9 with common label, and omission will be repeated in this description with structure.

Fluid dynamic bearing apparatus shown in Figure 12 is such bearing means: wherein, thrust bearing part T is arranged on the open part 7a side of housing 7, and on a thrust direction with bearing components 8 non-contacting mode supporting axle members 2.Flange portion 2b is arranged on the lower end of shaft component 2, and the thrust bearing gap of thrust bearing part T is formed between the upper end face 8b of the rear surface 2b2 of flange portion 2b and bearing components 8.Sealing component 9 is connected to the inner circumference of the open part of housing 7, and seal space S is formed between the external peripheral surface of shaft portion 2a of the inner circumferential surface 9a of sealing component 9 and shaft component 2.The rear surface 9b of sealing component 9 is relative with the upper end face 2b1 of flange portion 2b by axial clearance between two parties.When shaft component 2 upward displacements, the upper end face 2b1 of flange portion 2b engages with the rear surface 9b of sealing component 9, thereby prevents shaft component 2 extractions.

Figure 13 is the diagrammatic sketch that another embodiment of fluid dynamic bearing apparatus 1 is shown.Fluid dynamic bearing apparatus 1 shown in Figure 13 mainly is different from fluid dynamic bearing apparatus shown in Figure 91 in the following areas.Specifically, in Figure 13, seal space S is formed on the outer radius portion of housing 7, and thrust bearing part T2 is formed between the rear surface 3a1 of plate portion 3a of the upper end face of housing 7 and formation dish hub 3.

Figure 15 is the diagrammatic sketch that another embodiment of fluid dynamic bearing apparatus 1 is shown.This embodiment and embodiment's main distinction shown in Figure 9 are: bearing components 28 forms with form and the housing 7 that comprises housing 7.For its structure, such in the bearing components 8 as shown in Figure 9, bearing components 28 also is made of mould portion 14 and electroforming part 10, described mould portion 14 is formed by resin material (being metallic material in some cases), and the inner circumferential surface of mould portion 14 is fixed and be connected to described electroforming part 10.For its shape, bearing components 28 is made of following part: the axle sleeve part 28a of shell-like can be inserted into shaft portion 2a in its inner circumference; Sealing and fixing part 28b extends upward from the outside diameter of axle sleeve part 28a, and sealing component 9 can be fixed to the inner circumference of standing part 28b self; And end standing part 28c, extend downwards from the outside diameter of axle sleeve part 28a, and the bottom can be divided 7c to be fixed to the inner circumference of end standing part 28c self.In axle sleeve part 28a, axial circulation path 29 is set, be used to make its upper end face 28a2 and rear surface 28a3 to communicate with each other.In this embodiment, in molded step shown in Figure 4, comprising as molded in the part of housing to bearing components 28.Therefore, reduced the number and the assembling number in man-hour of parts, thereby the cost that can realize fluid dynamic bearing apparatus 1 reduces.

Figure 16 is the diagrammatic sketch that another embodiment of fluid dynamic bearing apparatus 1 is shown.This embodiment and the embodiment's shown in Figure 13 main distinction is that embodiment as shown in Figure 15 is such, and bearing components 28 is to be included among Figure 13 to separately the form and the housing 7 of the housing 7 of body form.In addition in this embodiment, reduced the number and the assembling number in man-hour of parts, thereby can realize that the cost of fluid dynamic bearing apparatus 1 reduces.

As the structure of radial bearing part R1 and R2 and thrust bearing part T, T1 and T2, foregoing description shows the structure that produces hydrodynamic pressure by user's font and spirality dynamic pressure groove.Yet, the invention is not restricted to this.

For example, also can adopt so-called how protruding bearing and step bearing as radial bearing part R1 and R2.In those bearings, a plurality of arc-shaped surface (in how protruding bearing) and a plurality of axial groove (in the step bearing) produce part as dynamic pressure, and described dynamic pressure produces part and is used for producing dynamic pressure in the radial bearing gap.Those dynamic pressure generating unit branches are formed on the electroforming part 10 of bearing components 8, and its formation method is consistent with each step (with reference to Fig. 2 A to Fig. 2 C and Fig. 5) under the situation that forms the dynamic pressure groove.Therefore, with the descriptions thereof are omitted.

Figure 17 shows the example of one or two situation about being made of how protruding bearing among radial bearing part R1 and the R2.In this example, the zone as the inner circumferential surface 8a of the bearing components 8 on radial bearing surface constitutes (that is so-called three protruding bearings) by three arc-shaped surface 33.The centre of curvature of three arc-shaped surface 33 respectively departs from equal distance from the axle center O of bearing components 8 (bearing part 2a).In the zone that is limited by three arc-shaped surface 33, the radial bearing gap is a wedge gap 35, and each wedge gap 35 is reduced to wedge shape gradually on two circumferencial directions.Therefore, when bearing components 8 and shaft portion 2a relative to each other rotated, in response to the direction of this relative rotary motion, the lubricant oil in the radial bearing gap was pulled in minimum clearance one side of wedge gap 35, and its pressure rises.By the dynamic pressure effect of aforesaid lubricant oil, bearing components 8 and shaft portion 2a are supported in non-contacting mode.Notice that the darker axial groove that is called isolation channel also can be formed on three boundary parts between the arc-shaped surface 33.

Figure 18 shows another example of one or two situation about being made of how protruding bearing among radial bearing part R1 and the R2.In this example, constitute (that is so-called three protruding bearings) by three arc-shaped surface 33 as the zone of the inner circumferential surface 8a of the bearing components 8 of radial bearing surfaces A.Yet in the zone that is limited by three arc-shaped surface 33, the radial bearing gap is a wedge gap 35, and each wedge gap 35 is reduced to wedge shape gradually on a circumferencial direction.How protruding bearing with this structure is sometimes referred to as conical bearing.In addition, the darker axial groove that is called isolation channel 34 is formed on three boundary parts between the arc-shaped surface 33.Therefore, when bearing components 8 and shaft portion 2a relative to each other rotated with predetermined direction, the lubricant oil in the radial bearing gap was pulled to minimum clearance one side of wedge gap 35, and its pressure rises.By the dynamic pressure effect of aforesaid lubricant oil, bearing components 8 and shaft portion 2a are supported in non-contacting mode.

Figure 19 shows the another example of one or two situation about being made of how protruding bearing among radial bearing part R1 and the R2.In this example, in structure shown in Figure 180, each among the presumptive area θ on minimum clearance one side of three arc-shaped surface 33 by by with the axle center O of bearing components 8 (shaft portion 2a) as centre of curvature and the circular arc concentric with it constitutes.Therefore, in each predetermined zone θ, radial bearing gap (minimum bearing play) is constant.How protruding bearing with this structure is sometimes referred to as taper plane bearing (taper flat bearing).

Figure 20 shows the example of one or two situation about being made of the step bearing among radial bearing part R1 and the R2.In this example, in zone, with predetermined interval a plurality of axial flute profile dynamic pressure grooves 36 are set in a circumferential direction as the inner circumferential surface 8a of the bearing components 8 on radial bearing surface.

How protruding bearing in each example of mentioning in the above is so-called three protruding bearings.Yet, be not limited thereto the how protruding bearing that also can adopt so-called four protruding bearings, five protruding bearings and constitute by arc-shaped surface with six or more a plurality of circular arcs.In addition, when the radial bearing part is made of step bearing or how protruding bearing, can adopt single radial bearing partly to be set at the upper area of inner circumferential surface 8a of bearing components 8 and the structure on the lower area, and two radial bearings parts axially are set apart from each other, as the radial bearing part R1 structure the same with R2.Those dynamic pressures generation parts are formed by the electroforming part 10 of bearing components 8, and its formation method is consistent with each step (with reference to Fig. 2 A to Fig. 2 C) under the situation that forms the dynamic pressure groove.Therefore, will omit its description.

In addition, for the form of thrust bearing part T, T1, T2, shown the structure that produces the dynamic pressure effect of lubricant oil by spirality dynamic pressure groove.Yet, such thrust bearing part also can be by so-called step bearing (wherein, as a plurality of radially dynamic pressure grooves of flute profile that have being set in the zone on thrust bearing surface), so-called waveform bearing (wherein, stepped shape becomes waveform) and analog (not shown) constitute.

Embodiment above-mentioned shows fluid dynamic bearing apparatus 1 and is made of the dynamic bearing with non-contacting mode supporting axle member 2 on the thrust direction.Yet, constitute by the pivot bearing of mode supporting axle member 2 on the thrust direction with contact at the fluid dynamic bearing apparatus shown in Figure 14 1.In this case, the lower end 2a3 of the shaft portion 2a of shaft component 2 forms the sphere of projection, and lower end 2a3 supports in the mode that contacts by the upper end face 24a of thrust plate 24, and thrust plate 24 is by the upper end face 7c1 of the bottom 7c of the housing 7 that for example is adhesively fixed.

On electroforming part 10, not only can form the radial bearing surface but also can form the thrust bearing surface.The embodiment of this situation is described with reference to Figure 21 to 32 below.

At the bearing components with structure of the present invention 8 shown in Figure 21 by following step manufacturing: the step (with reference to Figure 22 A) of making main shaft 12; Shelter the step (with reference to Figure 22 B) of the point that the needs of main shaft 12 shelter; Carry out the step (with reference to Figure 22 C) that electroforming process forms electroforming axle 11 by unshielded part N to main shaft 12; Form the step (with reference to Figure 25) of bearing components 8 by electroforming part 10 with molded electroforming axles 11 such as resins; And with electroforming part 10 and main shaft 12 separated steps.

, therefore, will omit identical content below, and will mainly describe different contents with basic identical in the step above-mentioned shown in Figure 22 A to 22C in the step shown in Fig. 2 A to Fig. 2 C.

In the masking steps shown in Figure 22 B, shelter top and upper end face thereof that 13 (illustrating with the scatter diagram case) are applied to the external peripheral surface of main shaft 12.On these parts of being sheltered (masked portion M), electroforming metal and does not form electroforming part 10 not by electrolytic deposition in electroforming process (back description).Simultaneously, except masked portion M, shelter the external peripheral surface and the rear surface that are not applied to main shaft 12, these parts of not sheltered (not masked portion N) become and are used for forming the inner circumferential surface (radial bearing surfaces A) of electroforming part 10 and the shaped portion of inner bottom surface (thrust bearing surface B) thereof at electroforming process.

Shown in Figure 22 A and 22B, in the not masked portion N of main shaft 12, on the external peripheral surface of main shaft 12, formed and had and the corresponding erose radial bearing shaping surface part N1 of the dynamic pressure groove pattern of radial bearing surfaces A.The each side of the irreqularity of radial bearing surfaces A and radial bearing shaping surface part N1 is opposite each other fully, and the projection of radial bearing surfaces A is corresponding with sunk part 12a1 and the 12a2 of radial bearing shaping surface part N1.Shown example shows sunk part 12a1 and 12a2 and the corresponding situation of man type dynamic pressure groove pattern of radial bearing shaping surface part N1.Yet sunk part 12a1 and 12a2 also can form and the corresponding shape of spirality dynamic pressure groove pattern.

With with above-mentioned similar methods, in unshielded part N, on the part annular zone of the rear surface 12c of main shaft 12, as shown in figure 23, formed thrust bearing shaping surface part N2, this thrust bearing shaping surface part N2 has with the dynamic pressure groove pattern of thrust bearing described later surface B corresponding irregularly shaped.In addition, on thrust bearing shaping surface part N2, its irreqularity aspect is opposite fully with the irreqularity of thrust bearing surface B.Shown example shows thrust bearing shaping surface part N2 and the corresponding situation of spirality dynamic pressure groove pattern.Yet thrust bearing shaping surface part N2 also can form the corresponding shape of pattern with man type dynamic pressure groove.

Through step recited above, shown in Figure 22 C, formed electroforming axle 11, the cylindrical electroforming part 10 of its medial end portions sealing is coated on the not masking regional N of the external peripheral surface 12a of main shaft 12 and rear surface 12c.At this moment, as shown in figure 24, the shape of the radial bearing shaping surface part N1 of the external peripheral surface 12a of main shaft 12 is transferred on the inner circumferential surface 10a of electroforming part 10, and has the radial bearing surfaces A formation apart from each other in the axial direction of a plurality of dynamic pressure groove 8a1 and 8a2.In addition, the shape of the thrust bearing shaping surface part N2 of the rear surface 12c of main shaft 12 is transferred on the inner bottom surface 10c of electroforming part 10, and has formed the thrust bearing surface B (not shown) with a plurality of dynamic pressure grooves.

Then, electroforming part 11 is sent to molded step shown in Figure 25, and electroforming axle 11 is being carried out the injection molding (inserted mode system) that utilizes resin material in as insertion portion.

When opening mold after making resin material curing, as shown in figure 24, obtained moulded parts, wherein, the electroforming axle 11 and the mould portion 14 that are made of main shaft 12 and electroforming part 10 are integrated in together.

Then, above-mentioned moulded parts is sent to division step, and here, moulded parts is divided into electroforming part 10 and mould portion 14 and is integrated in together a member (bearing components 8) and main shaft 12.

As shown in figure 27, the bearing components 8 that separates from main shaft 12 forms the cylindrical of end sealing with the bottom 8c that integrates with bearing components 8 and sidepiece 8b.Particularly, in this embodiment, the upper end of electroforming part 10 also is coated with mould portion 14.Therefore, can prevent that electroforming part 10 from extracting out from its upper end.The inner circumferential surface of this coating part of mould portion 14 forms conical surface 14a, after bearing means is assembled, forms seal space between the external peripheral surface of shaft component 2 and conical surface 14a, and this will be described later.

As shown in figure 27, the shaft component of making dividually with main shaft 12 2 is inserted in the inner circumference of the shaft component 8 that separates with main shaft 12, thereby constructs fluid dynamic bearing apparatus (fluid dynamic bearing apparatus) 1.Shaft component 2 is by the good metallic material of abrasion resistance, and for example stainless steel forms, and the external peripheral surface 2a of shaft component 2 forms the perfect circle that does not have the dynamic pressure groove, and the rear surface 2b of shaft component 2 forms the flat-surface shapes that does not have the dynamic pressure groove.The outer diameter undersized of shaft component 2 is in the inner diameter size in the zone between the dynamic pressure groove of radial bearing surfaces A, and the zone between the dynamic pressure groove of described radial bearing surfaces A is the projection that limits the dynamic pressure groove.Therefore, forming greatly the radial bearing gap (not shown) in tens mu m ranges between the external peripheral surface of shaft component 2 and two the radial bearing surfaces A about 1 μ m.

In addition, by shaft component 2 being inserted in the inner circumference of bearing components 8, between the external peripheral surface 2a of the conical surface 14a of the upper end open part of mould portion 14 and shaft component 2, form the cone seal space S.After inserting shaft component 2, be closed at seal space S place the inner space of sealed fluid flow dynamic bearing apparatus 1 for example be filled with lubricant oil as lubricating fluid.In this state, the pasta of lubricant oil remains in the seal space S.Seal space S can be formed the cylindrical space that has same widths generally, and is formed the cone space that upper space wherein is expanded.In addition, the conical surface 14a that constitutes sealing also can be made of the member that separates with mould portion 14.

Construct fluid dynamic bearing apparatus 1 as described above.When shaft component 2 and bearing components 8 relative to each other rotate (for example, when shaft component 2 rotations), in above-mentioned radial bearing gap, produce the dynamic pressure of lubricant oil, and by its pressure, shaft component 2 is can be rotated to support in the radial direction with bearing components 8 non-contacting modes.Therefore, formed and be used in non-contacting mode at the first radial bearing part R1 and the second radial bearing part R2 of rotatably mounted bearing components 2 in the radial direction.

In addition, the thrust bearing of bearing components 8 surface B is relative with the rear surface 2b of shaft component 2 by the thrust bearing gap.Along with the rotation of shaft component 2, the dynamic pressure of lubricant oil also produces in the thrust bearing gap, and by its pressure, shaft component 2 by on the thrust direction rotatably to support with bearing components 8 non-contacting modes.Therefore, formed thrust bearing part T, be used on the thrust direction rotatably with non-contacting mode supporting axle member 2.

As mentioned above, in fluid dynamic bearing apparatus 1 of the present invention, radial bearing surfaces A and thrust bearing surface B are formed on the electroforming part 10, and bearing components 8 forms by the injection molding that each electroforming part 10 is inserted in wherein.Therefore, the structure of radial bearing part R1 and R2 and thrust bearing part T can be simplified, in addition, can reduce parts number and man-hour number, thereby the cost that makes it possible to achieve bearing means 1 reduces.In addition, because radial bearing surfaces A and thrust bearing surface B have carried out electroforming process, have high-precision dynamic pressure groove so can form, and can obtain high bearing performance.In addition, so do not produce the powder that can produce, also solved pollution problem by cutting because bearing surface A and B are molded.

In addition, once the main shaft 12 of Zhi Zaoing can be repeated to use, and radial bearing surfaces A and thrust bearing surface B form the corresponding shape of surface configuration with the shaped portion N1 and the N2 of main shaft after being molded.Therefore, can obtain the bearing components 8 that the precision of dynamic pressure groove does not each other almost have deviation, thereby make and stably to produce fluid dynamic bearing apparatus 1 in batches with high running accuracy.

Notice that the surperficial outer surface of electroforming part 10 is owing to the characteristic of electroforming process forms rough surface.Therefore, when inserted mode system, the resin material that constitutes mould portion 14 enters into the space that is caused by the atomic irreqularity on the outer surface of electroforming part 10, and applies anchor effect.Therefore, strong bonding force is applied between electroforming part 10 and the mould portion 14, and has prevented that reliably electroforming part 10 and mould portion 14 from relative to each other rotating and disengaging mutually.Therefore, can provide the strong bearing components of impact resistance 8.

When the effect that prevents this rotation and extraction was not enough, as shown in figure 28, flange 20 partly was formed on the electroforming part with electroforming, and is combined in the mould portion 14.Thereby, can further strengthen preventing the effect of rotating and extracting out.

In the example shown, flange 20 is formed on the corner part of radial bearing surfaces A and thrust bearing surface B in the mode that tilts, and can form this class flange 20 in electroforming process.Particularly, when the main shaft 12 of illustrated embodiment was dipped in the electrolytic solution, the deposition of the metal granule in the corner part 12d of the lower end of main shaft 12 was compared usually bigger with other parts.Therefore, in 20 growths of the inclined flange shown in Figure 28.Therefore, when in statu quo forming the electroforming axle 11 that is added with flange 20, can use flange 20 as the part that is used to prevent rotate and extract out by resin material.

Note, also can form flange 20 by making 10 plastic deformations of electroforming part.In this case, the formation position of concrete limit flange 20 for example, can not form flange 20 by upper end plastic deformation to the outer diameter side that makes electroforming part 10 yet.

Top description shows the situation that forms the dynamic pressure groove on radial bearing part R1 and R2 in the axial direction symmetrically.Yet the dynamic pressure groove also can be formed asymmetrically in the axial direction.Figure 29 shows the state that shaft component 2 is extracted out from bearing components 8, shows the example of above-mentioned asymmetric shaping here.In Figure 29, dynamic pressure groove 8a1 is formed asymmetrically with respect to its axle center (axle center in the updip skewed slot and the zone between the skewed slot that has a down dip) diametrically by top radial bearing part R1, and the upper area of dynamic pressure groove 8a1 is set to axial dimension X2 greater than lower region thereof from the axial dimension X1 of axle center m.On the radial bearing part R2 of bottom, dynamic pressure groove 8a2 forms in the axial direction symmetrically, and the upper area of dynamic pressure groove 8a2 and the axial dimension of lower area equal above-mentioned axial dimension X2 respectively.In this case, lubricant oil big by among the dynamic pressure groove 8a2 of the ratio of feedback power (suction force) in the dynamic pressure groove 8a1 of top in the bottom symmetry of dynamic pressure groove when shaft component 2 rotation.Therefore, in the radial bearing gap, produce flowing downward of lubricant oil, thereby make and lubricant oil can be supplied to fully thrust bearing part T.

In addition, top description shows the situation that forms radial bearing surfaces A and thrust bearing surface B on the electroforming part 10 that forms as single member.Yet, also can adopt such structure, wherein, electroforming part 10 is divided into two or more parts, and bearing surface A and B are individually formed on the electroforming part, thereby form dividually.

Then, describe the example of motor with reference to the accompanying drawings, wherein above-mentioned fluid dynamic bearing apparatus 1 is combined in the described motor.

Figure 26 shows the structure example of the spindle motor that is used for information apparatus.Spindle motor is to be used for disk drive, the motor of HDD for example, and comprise: fluid dynamic bearing apparatus 1, with the rotatably mounted shaft component 2 of non-contacting mode; Rotor (dish hub) 3 is connected to shaft component 2; Stator coil 4 and rotor magnet 5, both radial clearances by between two parties toward each other.Stator coil 4 is connected to the excircle of carriage 6, and rotor magnet 5 is connected to the inner circumference of dish hub 3.The bearing components 8 of fluid dynamic bearing apparatus 1 is connected to the inner circumference of carriage 6.One or more dish D, for example disk remains on the dish hub 3.When stator coil 4 was powered up, rotor magnet 5 rotated by the electromagnetic force between stator coil 4 and the rotor magnet 5, thereby dish hub 3 and shaft component 2 rotation integratedly each other.

Structure of the present invention not only can be used for above-mentioned fluid dynamic bearing apparatus 1, and the fluid dynamic bearing apparatus of the form shown in below being preferably used for having.The structure of fluid dynamic bearing apparatus is described below with reference to accompanying drawings.Identical label will be used to have and the structure of the fluid dynamic bearing apparatus 1 shown in Figure 27 and the member of function identical construction and function, and omission is repeated in this description.

Figure 30 is the view that another embodiment of fluid dynamic bearing apparatus 1 is shown.In fluid dynamic bearing apparatus 1, produce the dynamic pressure groove 8a1 of part and external peripheral surface 2a that 8a2 is formed on shaft component 2 goes up and the rear surface 2b of shaft component 2 upward (the dynamic pressure groove that is formed on the rear surface 2b does not illustrate) as dynamic pressure, the radial bearing surfaces A of bearing components 8 and thrust bearing surface B form cross section respectively and are perfect round-shaped and smooth surface configuration, and the both does not have the dynamic pressure groove.In this case, the external peripheral surface 12a of main shaft 12 and rear surface 12c are formed cross section respectively and are perfect round-shaped and smooth surface configuration, and the both does not have the dynamic pressure groove.Utilize main shaft 12 to carry out above-mentioned electroforming process and molded step.In addition, main shaft 12 separates with bearing components 8, to form radial bearing surfaces A and thrust bearing surface B.Then, shaft component 2 (being the member different with main shaft 12) is inserted in the inner circumference of bearing components 8.On the external peripheral surface 2a and rear surface 2b that the dynamic pressure groove is pre-formed at shaft component 2 by mechanical technology or etching.

Figure 31 is another embodiment's of fluid dynamic bearing apparatus 1 a view.In fluid dynamic bearing apparatus 1, be different from the embodiment shown in Figure 27 and Figure 29, thrust bearing part T is made of pivot bearing, and each among radial bearing part R1 and the R2 is made of the perfect round bearing that does not have dynamic pressure to produce part.The spherical surface 2c of projection is formed on the lower end of shaft component 2, and spherical surface 2c supports in the mode that contacts with spherical surface 2c by the thrust bearing surface portion B that has flat-surface shapes, thereby constructs the thrust bearing part T that is made of pivot bearing.In addition, the external peripheral surface 2a of shaft component 2 has the cross section that does not have the dynamic pressure groove and is perfectly circular shape, and perfectly round bearing is made of for perfectly circular external peripheral surface 2a and radial bearing surfaces A cross section.In this case, any among radial bearing part R1 and R2 and the thrust bearing part T also can be replaced by the dynamic bearing shown in Figure 27 or Figure 29.

Under embodiment's shown in Figure 31 situation, main shaft 12 self also can be used as shaft component 2, and the member that separates with main shaft 12 among the embodiment as shown in Figure 27 and Figure 29.In this case, shown in figure 32, the thrust bearing shaping surface part N2 that has flat-surface shapes that forms thrust bearing surface B is formed on the end (upper end among Figure 32) of main shaft 12, and the bearing construction part 2c that has protruding spherical form of structure thrust bearing part T is formed on the other end of main shaft 12.In electroforming process, electroforming part 10 is formed on the thrust bearing shaping surface part N2 of the main shaft 12 shown in Figure 32, simultaneously, shelters and is applied to bearing construction part 2c, thereby form electroforming axle 11.Then, electroforming axle 11 carries out inserted mode system, and bearing shaft member 8 and main shaft 12 are separated from each other.After this, with main shaft 12 counter-rotatings, spherical surface 2c partly is inserted in the inner circumference of bearing components 8 as bearing construction, and spherical surface 2c contacts with thrust bearing surface B then.Thereby, construct the thrust bearing part T that constitutes by pivot bearing.Therefore, can use main shaft 12 as the anchor clamps of molded electroforming part 10 and the element of bearing means 1 simultaneously.

This method also is applied in the embodiment shown in Figure 27 and Figure 29, thereby can directly main shaft 12 be used as shaft component 2.In this case, on an end surfaces of main shaft 12, form plat surface, on the other end surface, form dynamic pressure groove (or molding die of dynamic pressure groove).One of two end surfaces of main shaft 12 become the shaped portion of thrust bearing surface B, and another becomes the bearing construction part that is used to construct thrust bearing part T.

Show in the embodiment shown in Figure 27 and Figure 29 and to be used for producing the radial bearing part R1 of hydrodynamic pressure and the structure of R2 by man type and spirality dynamic pressure groove.Yet, the invention is not restricted to this, for example, also can be used as radial bearing part R1 and R2 at how protruding bearing shown in Figure 17 to Figure 20 and step bearing.

In addition, above-mentioned structure also can be applied to such situation: do not have dynamic pressure to produce the perfect round bearing of part as radial bearing part R1 and R2.

As shown in figure 33, except the external peripheral surface of main shaft 12 is not have the barrel surface shape of shaped portion N, perfectly the manufacturing step and the step shown in Fig. 2 A to Fig. 2 C of round bearing are basic identical.Particularly, perfectly round bearing by following step manufacturing: the step (with reference to Figure 34) of the area of application that the needs that apply main shafts 12 with masking material 13 are sheltered; By masked portion is not carried out the step (with reference to Figure 35) that electroforming process forms electroforming axle 11; Form the step (with reference to Fig. 5) of bearing components 8 by electroforming part 10 with molded electroforming axles 11 such as resins; And the step that electroforming part 10 and main shaft 12 are separated from each other.

When radial bearing part R1 and R2 were made of perfect round bearing, the size of the minimum play between the inner circumferential surface 10a (bearing surface) of electroforming part 10 and the external peripheral surface 2a of shaft component 2 greatly influenced bearing performance.As shown in figure 36, minimum play δ r by the imaginary circle P1 of the interior bearing surface 10a that is connected to electroforming part 10 radius r 1 and the difference r1-r2 of radius r 2 of imaginary circle P2 that is external in the external peripheral surface 2a of shaft component 2 represent.Minimum play δ r is arranged in hope: under shaft component shown in Figure 36 2 is inserted into state in the inner circumference of bearing components 8, and minimum play δ r 〉=0.

As mentioned above, by guaranteeing positive minimum play δ r, when shaft component 2 and bearing components 8 relative to each other rotate, can avoid occurring between them the contact condition do not expected, and can keep the stable rotation holding state.The size of minimum play δ r depends primarily on the diameter expansion amount of electroforming part 10 in division step.Therefore, the electroforming condition and the thickness of electroforming part 10 is set, to obtain the aforesaid numerical value that is used for minimum play δ r.

The circularity of the bearing surface 10a of electroforming part in this case, 10 (at the inscribed circle P1 of Figure 36 middle (center) bearing surface 10a and the semidiameter between the circumcircle P3 | r1-r3|) and the circularity of the external peripheral surface 2a of shaft component 2 (the inscribed circle P2 of external peripheral surface 2a and the semidiameter between the circumcircle P4 in Figure 36 | r2-r4|) sum is set to 4 μ m or littler.

As mentioned above, the circularity sum of the external peripheral surface 2a of the circularity of bearing surface 10a and shaft component on the other side 2 is restricted to 4 μ m or littler, therefore surperficial 10a and 2a bearing play between the two become more even on the whole circumference direction, and deviation is littler.Therefore, can obtain stable rotation bearing state more, in addition,

surperficial

10a and 2a both can form more level and smooth surface, thereby make can limit the wearing and tearing on two surfaces as much as possible when shaft component 2 and bearing components 8 relative to each other rotate.The external peripheral surface of main shaft 12 carries out fine-processing technique, to satisfy above-mentioned value conditions (δ r 〉=0, | r1-r3|+|r2-r4|≤4 μ m).

As example, shaft diameter  is that 1.5mm and circularity are that the main shaft of 0.5 μ m is made (SUS420F) by stainless steel, bathing (sulfamic acid nickel bath) by nickel sulfamic acid and carried out electroforming process two hours, is the electroforming part 10 of 0.1mm thereby form thickness.Thereby, have been found that the bearing means that can obtain to satisfy above-mentioned value conditions.

Note, when radial bearing part R1 and R2 are made of the dynamic bearing shown in Fig. 8, Fig. 9 etc., expectation be to satisfy above-mentioned value conditions.In this case, minimum play δ r by with the projection that limits and form the dynamic pressure groove in the imaginary circle that connects radius and represent with the difference of the radius of the external imaginary circle of the external peripheral surface 2a of shaft component 2.In addition, estimate the circularity of bearing surface 10a by the inner circumferential surface of projection.

Perfectly round bearing not only can be used as the swivel bearing device, and can be used as plain bearing arrangement, rotation/plain bearing arrangement and other oscillation bearing device, structure of the present invention can be applied to all kinds of bearing meanss of all that." swivel bearing device " refers to be used for the counterrotating device between supporting axle 2 and the bearing components 8, and " plain bearing arrangement " refers to be used for the device of the relative linear movement between supporting axle 2 and the bearing components 8." rotation/sliding bearing " refers to have simultaneously the device of the function of above-mentioned two kinds of bearing meanss, is used for rotatablely moving and linear motion between supporting axle 2 and the bearing components 8." oscillation bearing " refers to be used for the bearing of the oscillating motion between supporting axle 2 and the bearing components 8.Under any situation, bearing components 8 can be positioned on movable side or the fixed side, can problem not take place.In addition, also can pass through oiling agent, for example oil supplies to ground, bearing play and uses bearing means, and can not use bearing means to supply of lubricant ground, bearing play.

In the swivel bearing device, the cross section of main shaft 12 is formed circle basically.Yet under the situation of plain bearing arrangement, the cross section of main shaft 12 can be formed arbitrary shape, for example polygonal and non-perfect circle and circle.In addition, in plain bearing arrangement, it is constant that the shape of cross section of main shaft 12 is essentially in the axial direction.Yet, in swivel bearing device and rotation/plain bearing arrangement, adopt such form sometimes, wherein, shape of cross section is non-constant on the whole axis of axle.

In fluid dynamic bearing apparatus 1, use basically separate manufacturing with main shaft 12 and independent member that precision precision and main shaft 12 is similar to as shaft component 2.Yet in perfect round bearing, except above-mentioned, main shaft 7 can directly be used as shaft component 2.In this case, the surface accuracy of bearing surface 4 is corresponding with the precision of the external peripheral surface of main shaft 7.Therefore, can obtain to carry out afterwards the advantage of coupling work.

In above-mentioned description, lubricant oil has been shown as the lubricating fluid that is filled in the inside of fluid dynamic bearing apparatus.Yet, except above-mentioned, can also use the fluid that can in each bearing play, produce dynamic pressure, as air, and magnetic fluid.

Claims

1. fluid dynamic bearing apparatus comprises:

Bearing components; With

Shaft component, described shaft component are inserted in the inner circumference of described bearing components;

Wherein, the injection molding that partly inserts in wherein by electroforming forms described bearing components, and any in the external peripheral surface of the inner circumferential surface of electroforming part and the shaft component relative with the inner circumferential surface of described electroforming part is equipped with dynamic pressure formed thereon and produces part.

2. fluid dynamic bearing apparatus according to claim 1, wherein, described dynamic pressure generating unit branch is formed on the inner circumferential surface of described electroforming part.

3. fluid dynamic bearing apparatus according to claim 1, wherein, described dynamic pressure generating unit branch comprises a plurality of dynamic pressure grooves.

4. fluid dynamic bearing apparatus according to claim 1, wherein, described dynamic pressure generating unit branch comprises a plurality of arc-shaped surface.

5. fluid dynamic bearing apparatus according to claim 1, wherein, described electroforming partly is provided with flange.

6. fluid dynamic bearing apparatus according to claim 5, wherein, the external peripheral surface of described flange has non-perfect circle.

7. fluid dynamic bearing apparatus according to claim 5 wherein, forms described flange by described electroforming plastic deformation partly.

8. fluid dynamic bearing apparatus according to claim 5, wherein, described flange is formed on in two axial ends of bearing surface at least one.

9. fluid dynamic bearing apparatus according to claim 8, wherein, the axial length that described electroforming part had before the plastic deformation of flange is L2, the axial length that has after the plastic deformation of flange is L1, satisfy following relational expression: 0＜A/L1≤0.5, here A=L2-L1.

10. fluid dynamic bearing apparatus according to claim 1, wherein:

Described bearing components is formed by the resin as the injection molding material; And

The molded contraction factor of resin is set at more than or equal to 0.02% to smaller or equal in 2.0% the scope.

11. fluid dynamic bearing apparatus according to claim 1, wherein, described bearing components is formed by the metal as the injection molding material.

12. fluid dynamic bearing apparatus according to claim 1, wherein, described electroforming partly is provided with formation thrust bearing surface thereon, is used for the end at the described shaft component of thrust direction upper support.

13. fluid dynamic bearing apparatus according to claim 12, wherein, described thrust bearing surface contacts and supports described shaft component on the thrust direction.

14. fluid dynamic bearing apparatus according to claim 12, wherein, any in the end surfaces relative with described thrust bearing surface of described thrust bearing surface and described shaft component is provided with a plurality of dynamic pressure grooves formed thereon.

15. fluid dynamic bearing apparatus according to claim 1, wherein, described dynamic pressure produces the cross section that partly has diametrically, wherein, with the radius r 1 of the imaginary circle that connects in the inner circumferential surface of described electroforming part greater than with the radius r 2 of the external imaginary circle of the external peripheral surface of described shaft component, and the circularity sum of the external peripheral surface of the circularity of the inner circumferential surface of described electroforming part and described shaft component is 4 μ m or littler.

16. fluid dynamic bearing apparatus according to claim 1, wherein, described shaft component is the main shaft that uses when forming described electroforming part.

17. fluid dynamic bearing apparatus according to claim 1, wherein, described shaft component is the different member of main shaft that uses when forming described electroforming part.

18. fluid dynamic bearing apparatus according to claim 16 wherein, comprising: the thrust bearing surface is used for the end at the described shaft component of thrust direction upper support; Form the shaped portion on described thrust bearing surface, described shaped portion is on an end of described main shaft; And the thrust bearing surface, described thrust bearing surface is on the other end of described main shaft.

19. a motor, described motor comprises fluid dynamic bearing apparatus according to claim 1.

20. a method of making bearing components, described method comprises following step:

Manufacturing has the main shaft of shaped portion, and described shaped portion is corresponding with the dynamic pressure generation shape partly on the excircle of described main shaft;

On the excircle of the main shaft that comprises described shaped portion, form the electroforming part;

After forming described electroforming part, when inserting the electroforming part, carry out injection molding; And

After injection molding, described main shaft and described electroforming partly are separated from each other.

21. the method for manufacturing bearing components according to claim 20, wherein, described main shaft is different with the thermal expansion amount of described electroforming part partly to be separated from each other described main shaft and described electroforming by making.

22. the method for manufacturing bearing components according to claim 20 wherein, when carrying out injection molding when inserting the electroforming part, makes the plastic deformation of electroforming part by clamping metal mold, to form flange on the electroforming part.