WO2012043575A1

WO2012043575A1 - Fluid dynamic bearing device and assembly method thereof

Info

Publication number: WO2012043575A1
Application number: PCT/JP2011/072101
Authority: WO
Inventors: 古森　功; 哲弥栗村
Original assignee: Ntn株式会社
Priority date: 2010-09-28
Filing date: 2011-09-27
Publication date: 2012-04-05

Abstract

Disclosed is a fluid dynamic bearing device which operates quietly, has high precision, high support stiffness and low-cost manufacturability, and easily replaces rolling bearings; also disclosed is an assembly method thereof. The fluid dynamic bearing device comprises: an outside member (20) provided with a radial bearing surface (29R) and thrust bearing surfaces (22T, 23T) formed on both ends of said radial bearing surface; and an inside member (10) disposed inside said outside member (20) and provided with a radial bearing surface (11R) and thrust bearing surfaces (12T, 13T) opposed to the radial bearing surface (29R) and thrust bearing surfaces (22T, 23T), respectively. A radial bearing gap (R) is formed between the radial bearing surfaces (29R, 11R) of the outside member (20) and the inside member (10), a thrust bearing gap (T) is formed between the thrust bearing surfaces (22T, 23T, 12T, 13T), and a lubricant is interposed between said bearing gaps (R, T). The outside member (20) comprises two members, an outer outside member (20a) and an inner outside member (20b). Each of said two outside members (20a, 20b) comprises a cylindrical part (20a₁, 20b₁) and a radial part (20a₂, 20b₂) formed integrally from a material, and said two outside members (20a, 20b) are fixed by fitting together the aforementioned cylindrical parts (20a₁, 20b₁). Dynamic pressure grooves (11a₁, 11a₂, 29a₁, 29a₂) are formed in multiple rows on the radial bearing surfaces (29R, 11R) of either the outside member (20) or the inside member (10).

Description

Fluid dynamic bearing device and assembly method thereof

The present invention relates to a fluid dynamic bearing device that rotatably supports a rotating body by a dynamic pressure action of lubricating oil generated in a bearing gap between an inner member and an outer member.

A fan motor mounted on a personal computer or OA equipment has a built-in bearing, and the rotating shaft to which the fan is attached is rotatably supported by this bearing. In this type of application, a so-called rolling bearing is generally used that includes a plurality of rolling elements between an outer ring and an inner ring and includes a cage that holds the rolling elements (for example, Patent Documents). 1).

On the other hand, as a fluid dynamic pressure bearing device, fluid dynamics having a structure comprising a cylindrical bearing ring, an outer member composed of a bearing plate fitted to both ends thereof, and an inner bearing plate member disposed inside the outer member. There is a pressure bearing device (Patent Document 2).

JP 2000-249142 A JP 2008-275159 A

By the way, since fan motors and the like mounted on personal computers and OA devices are continuously operated for a long time, quietness and high reliability are required in recent years. However, rolling bearings avoid the generation of so-called cage noise caused by collision between the cage pocket and rolling elements during operation, and friction noise caused by rolling of the rolling elements on the raceway surface of the inner and outer rings. Since it is not possible, it is difficult to meet the demand for further improvement in quietness.

Regarding this problem, the present inventors paid attention to a fluid dynamic pressure bearing device. As an example, a fluid dynamic pressure bearing device disclosed in Patent Document 2 includes a first bearing ring (12) and a pair of first bearing plates that protrude from the first bearing ring (12) to the inner diameter side. (16, 20) constitute an outer member (first bearing member), and a cylindrical second bearing ring (14) attached to the rotary shaft and an outer periphery of the second bearing ring (14) An inner member (second bearing member) is constituted by the second bearing plate (18) fixed to the surface. When the inner member rotates, a radial bearing gap is formed between the inner peripheral surface of the first bearing ring (12) and the second bearing plate (18), and the pair of first bearing plates (16 20) and a second bearing plate (18), a thrust bearing gap is formed. When the pair of first bearing plates (16, 20) and the second bearing plate (18) are engaged in the axial direction, the withdrawal of the inner member from the inner periphery of the outer member is restricted, and the fluid movement Since the pressure bearing device can be integrated, it can be easily assembled to a fan motor or the like.

However, in the fluid dynamic pressure bearing device described above, since the outer member is composed of many parts, the processing cost of each part and the assembly cost of these parts increase, making it difficult to reduce the cost. In addition, it is difficult to process a dynamic pressure groove with high accuracy.

Also, in the above-described fan motor and the like, switching from a rolling bearing to a fluid dynamic pressure bearing is difficult to replace as it is because of differences in its usage and bearing dimensions. That is, in many cases, two rolling bearings are incorporated as a bearing usage method for such applications. Compared to conventional rolling bearings, fluid dynamic pressure bearings can support rotating bodies without contact, so they are superior in terms of quietness and reliability, while fluid dynamic pressure bearings are similar to rolling bearings. Even if a device is proposed, when using two fluid dynamic bearing devices, it is difficult to maintain good concentricity and alignment between the two, and measures such as increasing the bearing clearance are required. there were. When the bearing clearance is increased, the support rigidity is lowered, and there is a problem in performance.

An object of the present invention is to provide a fluid dynamic pressure bearing device that is excellent in quietness, highly accurate, has high support rigidity, can be manufactured at low cost, and can be easily replaced from a rolling bearing, and an assembly method thereof. It is in.

As a result of various studies to solve the above-described problems, the present inventor has found that a fluid dynamic pressure bearing unit having high radial support rigidity that fits into the space of two incorporated rolling bearings in order to replace the rolling bearings. It came to a new idea that it was effective.

The present invention includes a radial bearing surface, an outer member having a thrust bearing surface formed at both ends thereof, and a radial bearing surface disposed inside the outer member and opposed to each of the radial bearing surface and the thrust bearing surface. And an inner member having a thrust bearing surface, a radial bearing gap is formed between the radial bearing surfaces of the outer member and the inner member, and a thrust bearing gap is formed between the thrust bearing surfaces. In a fluid dynamic pressure bearing device in which lubricating oil is interposed in a bearing gap, the outer member is composed of two members, an outer member on the outside and an outer member on the inside, and the two outer members are both cylindrical. And the radial portion are formed of an integral material, and the cylindrical portion is fitted and fixed, and a plurality of rows are arranged on the radial bearing surface of either the outer member or the inner member. The formation of dynamic pressure grooves The one in which the features.

As described above, the outer member includes two members, that is, an outer member on the outer side and an outer member on the inner side. Both of the two outer members are formed of a single portion of a cylindrical portion and a radial direction portion. The cylindrical part is fitted and fixed, and multiple rows of dynamic pressure grooves are formed on the radial bearing surface of either the outer member or the inner member. In addition, it can be manufactured at low cost and has excellent quietness. In addition, it is possible to realize a fluid dynamic pressure bearing device that fits the space of the incorporated rolling bearing and has high support rigidity, and is suitable for replacement from the rolling bearing. More specifically, since the fitting portions of the outer and inner outer members have a sufficient length, stable fitting and fixing can be obtained, the outer member has high rigidity, and the bearing clearance is increased. The accuracy can be set. Further, when the outer member is formed by pressing a plate material, the radial bearing surface and the thrust bearing surface are formed with high accuracy by this pressing, and the outer member can be manufactured at low cost.

Since the inner member is made of sintered metal, when a plurality of dynamic pressure grooves are formed in the axial direction on the radial bearing surface of the inner member, the plastic flow when the dynamic pressure grooves are rolled is affected by the inside of the sintered metal. It can be absorbed by the pores, and therefore, the rise of the surface due to plastic flow is suppressed, and the dynamic pressure groove can be formed with high accuracy. Further, when the dynamic pressure groove is formed on the thrust bearing surface of the inner member, it can be molded at the same time as pressing or sizing of the inner member, so that it can be manufactured with high accuracy and at low cost.

Specifically, the material of the sintered metal forming the bearing surface is made of copper-iron, and the blending ratio of copper is 10 to 80%. If the blending ratio of copper is less than 10%, there will be a problem with the formability and lubricity of the dynamic pressure grooves, while if the blending ratio of copper exceeds 80%, it is difficult to ensure wear resistance. Accordingly, the blending ratio of copper is desirably 10 to 80%.

The surface opening ratio of the radial bearing surface of sintered metal is 2 to 20%. When the surface opening ratio is less than 2%, the circulation of the lubricating oil is not sufficient, and when the surface opening ratio exceeds 20%, a pressure drop generated in the lubricating oil occurs. Therefore, the surface porosity is preferably 2 to 20%.

A plurality of rows of dynamic pressure grooves are formed on the radial bearing surface of the inner member, and dynamic pressure grooves are formed on the thrust bearing surface of the inner member. As a result, when the inner member is made of sintered metal, the dynamic pressure grooves can be manufactured with high accuracy and low cost by rolling, pressing, or molding during sizing, and fluid with high radial support rigidity. It becomes a hydrodynamic bearing device.

A plurality of rows of dynamic pressure grooves are formed on the radial bearing surface of the inner member, and dynamic pressure grooves are formed on the thrust bearing surface of the outer member. The dynamic pressure groove on the radial bearing surface of the inner member is formed by the rolling process described above, and the dynamic pressure groove on the thrust bearing surface of the outer member is formed by pressing, so it can be manufactured accurately and at low cost. This is a fluid dynamic bearing device with high radial support rigidity.

A plurality of rows of dynamic pressure grooves are formed on the radial bearing surface of the outer member, and dynamic pressure grooves are formed on the thrust bearing surface of the outer member. In this case, the dynamic pressure grooves on both the radial bearing surface and the thrust bearing surface are formed at the time of pressing the outer member, so that it can be manufactured with high accuracy and at low cost.

A plurality of rows of dynamic pressure grooves are formed on the radial bearing surface of the outer member, and dynamic pressure grooves are formed on the thrust bearing surface of the inner member. Also in this case, it can be manufactured with high accuracy and at low cost by the above-described press working or mold forming during sizing.

When the plurality of rows of dynamic pressure grooves formed on the radial bearing surface of either the outer member or the inner member are formed in a herringbone shape, a good dynamic pressure action can be generated, and high support rigidity can be obtained. it can. As an example of forming a plurality of rows of dynamic pressure grooves in the axial direction on the radial bearing surface, two rows are desirable.

The outer member is composed of two members, an outer member on the outside and an outer member on the inside. Specifically, both the outer outer member and the inner outer member are substantially L-shaped in cross section, and a radial bearing surface is formed on the inner peripheral surface of the cylindrical portion of the inner outer member, and the radial direction A thrust bearing surface is formed on the inner side surface of the portion, and a thrust bearing surface is formed on the inner side surface of the radially outer portion of the outer member. And the cylindrical part outer peripheral surface of an inner side outer member is fitted by the cylindrical part inner peripheral surface of an outer side outer member. Both the outer and inner outer members can be easily manufactured by pressing the plate material, and the fitting portions of the outer and inner outer members have a sufficient length, so that stable fitting, Fixation is obtained. Further, the rigidity of the outer member is high, and the bearing gap can be set with high accuracy.

Furthermore, a convex portion for temporary fixing is provided on at least one of the inner circumferential surface of the cylindrical portion of the outer member on the outer side and the outer circumferential surface of the cylindrical portion of the inner outer member, and the convex portions are provided at three or more locations in the circumferential direction. By providing, the thrust bearing clearance between the outer member and the inner member can be temporarily fixed. Therefore, the subsequent bonding work can be performed efficiently.

By providing a display to identify the rotational direction on the outer surface of the fluid dynamic bearing device, the assembly can be efficiently performed without erroneous assembly of the rotational direction, and the rotational direction in the finished product can be easily achieved. It can be known and can be efficiently incorporated into the device. As a suitable example of the display for identifying the rotation direction, an identification groove formed on the end face of the inner member can be used.

It is desirable that at least the end face of the inner member is subjected to a sealing treatment or an oil repellent agent to prevent the lubricating oil from seeping out.

In the above fluid dynamic pressure bearing device, it is desirable to adjust the oil amount at a temperature exceeding the operating temperature range after the lubricating oil is put inside. Thereby, at the time of use, it can prevent that lubricating oil leaks out by thermal expansion.

Further, as a result of various studies, the present inventors have corrected the pressure of the lubricating oil interposed in the space between the radial bearing gap and the thrust bearing gap in order to prevent deterioration of the bearing performance of the fluid dynamic bearing device. It came to a new idea of keeping pressure.

That is, at least a portion of the inner member that forms the radial bearing surface and the thrust bearing surface is formed of sintered metal, and the space between the radial bearing gap and the thrust bearing gap is maintained at a positive pressure.

As described above, at least the radial bearing surface and the thrust bearing surface forming part of the inner member are made of sintered metal, so that it can be manufactured with high accuracy, excellent quietness and low cost, and the radial bearing gap Since the space between the thrust bearing gap and the thrust bearing gap is maintained at a positive pressure, deterioration of the bearing performance can be prevented. Here, the positive pressure means a pressure higher than the atmospheric pressure.

Radial dynamic pressure grooves and thrust dynamic pressure grooves are formed on the radial bearing surface and the thrust bearing surface of the inner member, respectively. Thereby, the dynamic pressure groove of the inner member made of sintered metal can be manufactured with high accuracy and low cost by rolling, pressing, or molding at the time of sizing.

Since the thrust dynamic pressure groove is a pump-out type, the lubricating oil is sent to the outer diameter side, and the pressure of the lubricating oil existing in the space between the radial bearing gap and the thrust bearing gap is maintained at a positive pressure. Therefore, deterioration of bearing performance can be prevented. Herringbone shape is preferable as the pump-out type thrust dynamic pressure groove.

The surface opening of the inner member is provided by providing a region having a surface opening ratio larger than that of each bearing surface in the outer surface portion of the inner member located in the space between the radial bearing gap and the thrust bearing gap. The internal lubricating oil is guided to the outer surface portion having a large rate, and the pressure of the lubricating oil in this portion is maintained at a positive pressure. Thereby, deterioration of bearing performance can be prevented.

If at least one of the radial dynamic pressure groove and the thrust dynamic pressure groove of the inner member is formed by press working, the region where the surface open area ratio of the outer surface portion of the inner member is large is processed by the above press working. By not using a surface, it can be easily formed without additional processing.

If at least one of the radial dynamic pressure groove and the thrust dynamic pressure groove of the inner member is formed by rolling processing, the region where the surface open area ratio of the outer surface portion of the inner member is large is the rolling processing described above. By not using the processed surface, it can be easily formed without additional processing.

少なくとも At least one of the radial bearing surface and the thrust bearing surface of the inner member is sealed. Thereby, the pressure drop of lubricating oil can be suppressed.

As described above, since the fluid dynamic bearing device is an integral type, it can be easily assembled and a silent fan motor can be realized.

As a method of assembling the fluid dynamic pressure bearing device of the present invention, an inner member and an inner outer member are inserted into an outer member, and thrust bearing surfaces on both sides of the inner member are placed outward. After contacting the thrust bearing surface of the member and the thrust bearing surface of the inner outer member, the inner member is separated from the outer outer member by the total amount of the thrust bearing gap, so that a thrust bearing gap is formed. It is set and temporarily fixed in that state. With such an assembling method, the thrust bearing gap can be easily set with high accuracy.

The fluid dynamic bearing device temporarily fixed with the thrust bearing gap set, in the next step, injects an adhesive into the fitting portions of the outer and inner outer members and hardens them. Since the bonding work is performed in such a temporarily fixed state, the workability is extremely good.

According to the present invention, the outer member is composed of two members, that is, an outer member on the outer side and an outer member on the inner side, and the two outer members are both formed of an integral material including a cylindrical portion and a radial portion. In addition, since a plurality of rows of dynamic pressure grooves are formed on the radial bearing surface of one of the outer member and the inner member, the number of parts is small, and high-precision and low-cost manufacturing is possible. Excellent quietness. More specifically, since the fitting portions of the outer and inner outer members have a sufficient length, stable fitting and fixing can be obtained, the outer member has high rigidity, and the bearing clearance is increased. The accuracy can be set. In addition, it is possible to realize a fluid dynamic pressure bearing device that fits the space of a rolling bearing incorporated in a fan motor or the like and has high radial support rigidity, and is suitable for replacement from a rolling bearing.

Also, since the convex portion for temporary fixing is provided, the fluid dynamic pressure bearing device is easy to set and assemble the thrust bearing gap. The accuracy of the outer member on the outside and the accuracy of the outer member on the inner side can be press-fitted without any loss, and it is suitable for continuously injecting and bonding an adhesive. Further, since the display for identifying the rotation direction is provided, the fluid dynamic pressure bearing device can be efficiently assembled and assembled to the equipment used, and is particularly suitable as a fluid bearing device for a fan motor.

Further, the inner member is accommodated in the outer member on the outside and the outer member on the inner side, the outer outer member and the outer member on the inner side are fitted, and the thrust bearing gap is set and the convex portion is set. By means of an assembling method in which the thrust bearing gap is temporarily fixed, and then an adhesive is injected and cured, setting and assembling of the thrust bearing gap is easy, and assembling workability can be improved.

It is a longitudinal cross-sectional view of the fluid dynamic pressure bearing apparatus concerning this invention. It is a side view which shows the dynamic pressure groove formed in the inner member. It is a front view which shows the dynamic pressure groove formed in the inner member. It is a side view which shows the dynamic pressure groove formed in the inner member. It is the longitudinal cross-sectional view which expanded the fluid dynamic pressure bearing apparatus partially. It is a right side view of a fluid dynamic bearing device. It is a longitudinal cross-sectional view of the fan motor incorporating the fluid dynamic pressure bearing device. It is a longitudinal cross-sectional view which shows the modification of a fluid dynamic pressure bearing apparatus. It is a longitudinal cross-sectional view which shows the modification of a fluid dynamic pressure bearing apparatus. It is a longitudinal cross-sectional view which shows the modification of a fluid dynamic pressure bearing apparatus. It is a longitudinal cross-sectional view of the fluid dynamic pressure bearing apparatus concerning this invention. FIG. 9b is a cross-sectional view taken along line AA in FIG. 9a. It is a side view which shows the dynamic pressure groove formed in the inner member. It is a front view which shows the dynamic pressure groove formed in the inner member. It is a side view which shows the dynamic pressure groove formed in the inner member. It is a longitudinal cross-sectional view which shows an assembly method. It is a longitudinal cross-sectional view which shows an assembly method. It is a cross-sectional view which shows the state which inject | pours an adhesive agent into the fitting part of an outward member. It is a longitudinal cross-sectional view of a fluid dynamic pressure bearing device. It is a side view which shows the dynamic pressure groove formed in the inner member. It is a front view which shows the dynamic pressure groove formed in the inner member. It is a side view which shows the dynamic pressure groove formed in the inner member. It is the longitudinal cross-sectional view which expanded the fluid dynamic pressure bearing apparatus partially. It is a longitudinal cross-sectional view of the fan motor incorporating the fluid dynamic pressure bearing device. It is a longitudinal cross-sectional view which shows the modification of a fluid dynamic pressure bearing apparatus. It is a longitudinal cross-sectional view of a fluid dynamic pressure bearing device. It is a right view of a fluid dynamic pressure bearing device. FIG. 20 is a transverse sectional view taken along line BB in FIG. It is a longitudinal cross-sectional view which shows an assembly method. It is a longitudinal cross-sectional view which shows an assembly method. It is a cross-sectional view which shows the state which inject | pours an adhesive agent into the fitting part of an outward member.

Embodiments of the present invention will be described below with reference to the drawings.

A fluid dynamic bearing device according to a first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the fluid dynamic pressure bearing device 4 includes an inner member 10 and an outer member 20 that rotatably supports the inner member 10. The inner member 10 is attached to a rotating shaft (not shown), and the outer member 20 is attached to a housing (not shown). Lubricating oil is interposed between the surfaces of the inner member 10 and the outer member 20 that face each other in the axial direction and the radial direction (the radial bearing gap R and the thrust bearing gap T).

The inner member 10 includes a protruding portion 10a and a sleeve portion 10b, and is formed of a sintered metal. The protrusion 10a has outer

peripheral surfaces

11 ₁ and 11 ₂ and both side surfaces 12 and 13, the outer

peripheral surfaces

11 ₁ and 11 ₂ form radial bearing surfaces 11R ₁ and 11R ₂ , and both side surfaces 12 and 13 are thrust bearings.

Surfaces

12T and 13T are formed. The outer

peripheral surfaces

11 ₁ and 11 ₂ have a cylindrical surface shape and are in contact with the lubricating oil filled in the radial bearing gap R. In order to show the details of the filled state of this lubricating oil, FIG. 3 shows an enlarged partial vertical section of the left end of the fluid dynamic bearing device 4 of FIG. Lubricating oil, the radial bearing gap R, is filled to an intermediate position of the thrust bearing gap T and the seal space S _1.

Dynamic pressure grooves

11a ₁ and 11a ₂ are formed in a plurality of rows in the axial direction on the outer

peripheral surfaces

11 ₁ and 11 ₂ of the protruding portion 10a. Specifically, as shown in FIG. 2b,

dynamic pressure grooves

11a ₁ and 11a ₂ formed on the entire outer

peripheral surfaces

11 ₁ and 11 ₂ and bent in a V shape, and

hill portions

11b ₁ and 11b partitioning the

dynamic pressure grooves

11a ₁ and 11a ₂ are formed. ₂ (indicated by cross-hatching in the figure) and a herringbone shape alternately arranged in the circumferential direction. A small diameter portion 11c is formed between the radial bearing surfaces 11R ₁ and 11R ₂ . The

dynamic pressure grooves

11a ₁ and 11a ₂ are formed by rolling, for example. In this embodiment, since the inner member 10 is formed of a sintered metal, the plastic flow of the outer

peripheral surfaces

11 ₁ and 11 ₂ of the protruding portion 10a due to the compression of the rolling process can be absorbed by the internal pores of the sintered metal. For this reason, the swelling of the surface of the protrusion part 10a by plastic flow is suppressed, and the

dynamic pressure grooves

11a ₁ and 11a ₂ and the

hill parts

11b ₁ and 11b ₂ can be formed with high accuracy. If the small diameter portion 11c is simultaneously processed when the

dynamic pressure grooves

11a ₁ and 11a ₂ are rolled, the clearance depth between the radial bearing surfaces 11R ₁ and 11R ₂ and the small diameter portion 11c can be processed with high accuracy, and the circumference The above variation can also be reduced.

As shown in FIG. 1, both side surfaces 12 and 13 of the protruding portion 10 a of the inner member 10 form a radial flat surface perpendicular to the axis H, and contact with the lubricating oil filled in the thrust bearing gap T. Yes.

Dynamic pressure grooves

12a and 13a are formed on both side surfaces 12 and 13 of the protruding portion 10a. Details are shown in FIGS. 2a and 2c. 2a shows the left side 12 of the protrusion 10a, and FIG. 2c shows the right side 13 of the protrusion 10a. As shown in the figure,

dynamic pressure grooves

12a and 13a formed on the entire surfaces of both side surfaces 12 and 13 and bent in a V shape, and

hill portions

12b and 13b (indicated by cross-hatching in the figure) partitioning the grooves, It exhibits a herringbone shape that is alternately arranged in the circumferential direction. Since the inner member 10 is formed of a sintered metal, the

dynamic pressure grooves

12a and 13a on the both side surfaces 12 and 13 can be formed with high accuracy by pressing. In addition, the

dynamic pressure grooves

12a and 13a can be molded simultaneously with the sizing of the protruding portion 10a.

As shown in FIG. 1, the sleeve portion 10b is formed longer than the width between both side surfaces 12, 13 of the protruding portion 10a, and protrudes in the axial direction from both side surfaces 12, 13. Chamfered portions 10d are provided at both axial ends of the cylindrical inner peripheral surface 10c of the sleeve portion 10b. The inner member 10 is formed by, for example, press-fitting (light press-fitting) the inner peripheral surface 10c into the outer peripheral surface of the rotating shaft (not shown) or interposing an adhesive between the inner peripheral surface 10c and the outer peripheral surface of the rotating shaft. By this, it is fixed to the rotating shaft.

The material of the sintered metal that forms the inner member 10 is copper iron-based, and the blending ratio of copper is 10 to 80%. If the copper blending ratio is less than 10%, there will be a problem with the formability and lubricity of the dynamic pressure grooves, while if the copper blending ratio exceeds 80%, it is difficult to ensure wear resistance. In consideration of lubricity, copper iron is preferable, but other materials such as iron, copper, and stainless steel can be used. However, in any case, the surface area ratio needs to be 2 to 20%. When the surface opening ratio is less than 2%, the circulation of the lubricating oil is not sufficient, and when the surface opening ratio exceeds 20%, the pressure generated in the lubricating oil decreases. Further, the density of the copper-iron-based sintered member is set to 6 to 8 g / cm ³ in order to maintain the lubricity and plastic workability.

Next, the outer member 20 will be described. As shown in FIG. 1, the outer member 20 includes two members, an outer member 20a on the outside and an outer member 20b on the inner side. The outer member 20a on the outer side includes a cylindrical portion 20a ₁ and a radial portion 20a ₂ . Is formed of an integral material, and the inner side outer member 20b is also formed of an integral material of a cylindrical portion 20b ₁ and a radial direction portion 20b ₂ . The outer outer member 20a and the inner outer member 20b are both formed in a substantially L-shaped longitudinal section. The outer outer member 20a has a cylindrical portion 20a ₁ and a radial portion 20a ₂ formed at one end of the cylindrical portion 20a ₁ . The inner outer member 20b has a cylindrical portion 20b ₁ and a radial portion 20b ₂ formed at one end of the cylindrical portion 20b ₁ . The outer peripheral surface 27 of the cylindrical portion 20b ₁ of the inner of the outer member 20b is lightly press-fitted to the inner peripheral surface 21 of the cylindrical portion 20a1 of the outer of the outer member 20a, and is fixed by interposing an adhesive 45.

Since the chamfered portion 28 is provided on the inner periphery of the end surface of the cylindrical portion 20a ₁ of the outer member 20a on the outer side, the adhesive 45 can be easily injected. Both the outer outer member 20a and the inner outer member 20b are formed in a substantially L shape by pressing a plate material. Specifically, the plate material is a stainless steel plate, a cold rolled steel plate, or the like, and the plate thickness is about 0.1 to 1 mm.

In this embodiment, the inner peripheral surface 29 of the cylindrical portion 20b ₁ of the inner outer member 20b forms a radial bearing surface 29R. The inner side surface 22 of the radial direction portion 20a ₂ of the outer side outer member 20a and the inner side surface 23 of the radial direction portion 20b ₂ of the inner side outer member 20b form thrust

bearing surfaces

22T and 23T. The inner peripheral surface 29 and the inner side surfaces 22 and 23 are all formed as smooth surfaces without irregularities, and the

dynamic pressure grooves

11a ₁ , 11a ₂ , 12a and 13a are the outer peripheral surface 11 ₁ of the protruding portion 10a of the inner member 10. , 11 ₂ and both side surfaces 12, 13.

A small-diameter inner peripheral surface 24 at the inner diameter side end of the radial direction portion 20a ₂ of the outer outer member 20a and a small-diameter inner peripheral surface 25 at the inner diameter side end of the radial direction portion 20b ₂ of the inner outer member 20b are It is formed in a tapered surface shape whose diameter increases toward the outside. Seal spaces S ₁ and S ₂ are formed between the small-diameter inner

peripheral surfaces

24 and 25 and the end outer

peripheral surfaces

41 and 42 of the sleeve portion 10b of the inner member 10 to further prevent leakage of the lubricating oil. can do. In this structure, since the fitting length between the inner peripheral surface 21 of the cylindrical portion 20a ₁ of the outer member 20a on the outer side and the outer peripheral surface 27 of the cylindrical portion 20b ₁ of the inner outer member 20b is large, it is stable. Assembly and adhesive fixing can be realized.

In this embodiment, the

dynamic pressure grooves

11a ₁ , 11a ₂ , 12a and 13a have a herringbone shape and are for one-way rotation. In order to identify the direction of rotation, the following display is provided. An identification groove 44 is formed in the right end face 43 of the sleeve portion 10b from which the inner member 10 protrudes. When the end portion of the sleeve portion 10b having the identification groove 44 is arranged on the right side as shown in the figure, it can be seen that the rotation direction of the inner member 10 is the left direction (counterclockwise direction). In the above description, when the identification display is arranged on the right side, the rotation direction is set to the left direction. On the contrary, the rotation direction may be set to the right direction (clockwise direction).

FIG. 4 shows details of the identification groove 44. 4 is a right side view of the fluid dynamic bearing device 4. FIG. The inner outer member 20b is fitted to the outer outer member 20a, and the fitting portion is bonded and fixed. An identification groove 44 is formed in the end face 43 of the sleeve portion 10b of the inner member 10. The identification grooves 44 are formed at two locations on the diameter, and the identification grooves 44 are formed by a powder forming process or a sizing process of the inner member 10 made of sintered metal. Therefore, since the identification groove is formed in the manufacturing process of the inner member 10, the cost is not increased. The identification groove 44 is not limited to the groove having the above shape, and may be, for example, an arrow-shaped identification groove that directly indicates the rotation direction. In addition to the above, the display for identifying the rotation direction is, for example, a display indicating the rotation direction on the outer surface of the outer member 20, or the hues of the outer outer member 20a and the inner outer member 20b being different. It may be formed on the surface. For this purpose, materials of different hues are used or surface treatment is performed.

The internal space of the fluid dynamic bearing device 4 having the above configuration is filled with lubricating oil including the internal pores of the sintered metal inner member 10. As shown in FIGS. 1 and 3, the lubricating oil is filled up to the radial bearing gap R, the thrust bearing gap T, and the seal spaces S ₁ and S ₂ . The lubricating oil is drawn to the outer diameter side (radial bearing gap R side) by the capillary force of the bearing gap. The oil level of the lubricating oil is held in the seal spaces S ₁ and S ₂ . Note that the lubricating oil is pushed into the outer diameter side (the radial bearing gap R side) by the centrifugal force or the pushing force by the dynamic pressure groove acting on the lubricating oil in the thrust bearing gap T as the rotary shaft rotates. Since the centrifugal force, the pushing force, and the capillary force due to the bearing gap can prevent the lubricating oil from leaking out, a design without providing the seal spaces S ₁ and S ₂ is also possible.

In order to prevent the lubricating oil from seeping out from the end portion of the sleeve portion 10b of the inner member 10, it is desirable to seal the end surface 43 ₁ , the end outer

peripheral surfaces

41 and 42, and the chamfered portion 10d. Further, as another method for preventing the lubricant from seeping out, an oil repellent may be applied to the end of the sleeve portion 10b. Furthermore, the effect can be further enhanced by combining these.

In the present embodiment, the radial direction portion 20a ₂ of the outer member 20a on the outer side, the radial direction portion 20b ₂ of the outer member 20b on the inner side, and the side surfaces 12 and 13 of the inner member 10 opposite to this are Although the one formed at a right angle is shown, the present invention is not limited to this, and the radial direction portion 20a ₂ , the radial direction portion 20b ₂ and the side surfaces 12 and 13 facing the radial direction portion 20a ₂ can also be formed to be inclined in a conical shape.

FIG. 5 shows a fan motor 1 incorporating the fluid dynamic bearing device 4 of the present embodiment. This fan motor 1 is used for discharging heat generated inside a personal computer, OA equipment, etc. to the outside and cooling the inside, and is a fluid dynamic bearing that rotatably supports the rotary shaft 2 in a non-contact manner. The apparatus 4, the fan 3 attached to the rotary shaft 2, a stator coil 50 and a rotor magnet 51 that are opposed to each other via a radial gap, and a case 52 are provided. The stator coil 50 is attached to the outer periphery of the housing portion 53 of the case 52, and the rotor magnet 51 is attached to the inner periphery of the fan 3. The fluid dynamic bearing device 4 is incorporated in the housing portion 53 of the case 52. In the fan motor 1 configured as described above, when the stator coil 50 is energized, the rotor magnet 51 is rotated by the magnetic force between the stator coil 50 and the rotor magnet 51, and accordingly, the fan 3 is connected to the rotating shaft 2. Rotates together.

In the fluid dynamic pressure bearing device 4, the inner member 10 is provided between the

inner surfaces

22 and 23 of the outer member 20 in the axial direction, so that the

inner surfaces

22 and 23 of the outer member 20 and the inner member 10 When the both side surfaces 12 and 13 are engaged in the axial direction, the inner member 10 is prevented from coming off from the inner periphery of the outer member 20 (see FIG. 1). Thereby, since separation of the inner member 10 and the outer member 20 can be prevented and the fluid dynamic bearing device 4 can be handled integrally, attachment to the rotating shaft 2 and the housing part 53 becomes easy.

Next, a modification of the first embodiment is shown in FIG. Parts having the same functions as those of the first embodiment described above are denoted by the same reference numerals, and redundant description is omitted. The same applies to the following modifications and embodiments.

In this modification, the thrust direction of the

dynamic pressure grooves

22a, 23a is, on the outside of the outer member 20a of the radial portion 20a ₂ of the inner surface 22 and the inner outer inner surfaces 23 of the radial portion 20b ₂ of the member 20b , Each is formed. And the both side surfaces 12 and 13 of the protrusion part 10a of the inward member 10 are formed in the smooth surface without an unevenness | corrugation. The

dynamic pressure grooves

22a and 23a in the thrust direction are formed by pressing, for example, when the outer member 20a on the outside and the outer member 20b on the inner side are formed from a plate material by pressing. Therefore, the

dynamic pressure grooves

22a and 23a can be formed with high accuracy. The shapes of the

dynamic pressure grooves

12a and 13a are the same as those shown in FIGS. 2a and 2c. Other parts are the same as those in the first embodiment.

Next, a second modification of the first embodiment is shown in FIG. In this modification, a plurality of rows of dynamic pressure grooves 29a ₁ and 29a ₂ in the radial direction are formed on the radial bearing surface 29R of the inner outer member 20b. Then, the radial bearing surface 11R _1, 11R ₂ of the projecting portion 10a of the inner member 10 is formed with no smooth surface irregularities. The radial dynamic pressure grooves 29a ₁ and 29a ₂ are formed, for example, by pressing when the inner outer member 20b is formed from a plate material by pressing. Therefore, the dynamic pressure grooves 29a ₁ and 29a ₂ can be formed with high accuracy. The shapes of the dynamic pressure grooves 29a ₁ and 29a ₂ are the same as those shown in FIG. 2b. Other parts are the same as those in the first embodiment.

FIG. 8 shows a third modification of the first embodiment. In this modification, a plurality of rows of dynamic pressure grooves 29 a ₁ and 29 a _{2 in} the radial direction and

dynamic pressure grooves

22 a and 23 a in the thrust direction are both formed in the outer member 20. The radial bearing surfaces 11R ₁ and 11R ₂ and the

thrust bearing surfaces

12T and 13T of the protruding portion 10a of the inner member 10 are all formed as smooth surfaces without irregularities. The radial dynamic pressure grooves 29a ₁ and 29a ₂ and the thrust

dynamic pressure grooves

22a and 23a are both formed, for example, by pressing the outer member 20a on the outer side and the outer member 20b on the inner side by pressing from a plate material. And formed by press working. Therefore, the

dynamic pressure grooves

29a ₁ , 29a ₂ , 22a and 23a can be formed with high accuracy. The shapes of the

dynamic pressure grooves

29a ₁ , 29a ₂ , 22a and 23a are the same as those shown in FIGS. 2a, 2b and 2c. Other parts are the same as those in the first embodiment.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 9a is a longitudinal sectional view of the fluid dynamic bearing device 4 of this embodiment, and FIG. 9b is a transverse sectional view taken along line AA of FIG. 9a. As shown in FIG. 9a, a convex portion 27a is provided at the open end of the outer peripheral surface 27 of the cylindrical portion 20b ₁ of the inner outer member 20b. As shown in FIG. 9b, the convex portions 27a are formed on the outer peripheral surface 27 of the cylindrical portion 20b ₁ of the inner outer member 20b at eight locations in the circumferential direction. This convex portion 27a is press-fitted into the inner peripheral surface 21 of the cylindrical portion 20a ₁ of the outer member 20a on the outside. And it is temporarily fixed by the convex part 27a in a state where a thrust bearing gap is set, and is fixed with an adhesive 45 interposed. Since a state where the convex portion 27a is partially press-fitted to the inner peripheral surface 21 of the cylindrical portion 20a ₁ of the outer of the outer member 20a, the accuracy of the outer of the outer member 20a and the inner of the outer member 20b is impaired Absent.

Incidentally, the convex portion 27a is formed eight on the outer peripheral surface 27 of the cylindrical portion 20b ₁ of the inner of the outer member 20b, the number of the projections 27a is if three or more, can be a number of appropriate The shape of the convex portion 27a is not limited to a round protrusion, and may be a shape extending in the axial direction. Further, the convex portion can also be formed on the inner peripheral surface 21 of the cylindrical portion 20a ₁ of the outer member 20a on the outside. In short, the convex portion can be press-fitted within a range that does not impair the accuracy of the outer member 20a on the outer side and the outer member 20b on the inner side, and is temporarily fixed by the convex portion with a thrust bearing gap set. Any form is acceptable. Other parts are the same as those in the first embodiment. Further, the form of formation of the dynamic pressure grooves is not limited to that of the present embodiment, and may be any form of the first to third modifications of the first embodiment described above.

Next, a third embodiment of the hydrodynamic bearing device of the present invention will be described with reference to FIGS. 10 (a) to 10 (b). 10a shows the left side surface 12 of the protruding portion 10a, and FIG. 10c shows the right side surface 13 of the protruding portion 10a.

In the hydrodynamic bearing device of the first embodiment shown in FIGS. 1 to 8, the supply of lubricating oil is insufficient in the

spaces

30a and 30b between the radial bearing gap and the thrust bearing gap, and this portion becomes negative pressure. In such a case, performance deterioration of the bearing portion may occur, and problems such as contact between the inner member 10 and the outer member 20 may occur. In the third embodiment, the following two configurations (1) and (2) are adopted in order to keep the

spaces

30a and 30b at a positive pressure.

(1) As shown in FIGS. 10 (a) to 10 (c), the

dynamic pressure grooves

12a and 13a of the

thrust bearing surfaces

12T and 13T formed on the both side surfaces 12 and 13 of the inner member are rotated by the outer diameter. Use a pump-out specification that sends lubricant to the side. In general, dynamic pressure grooves 12a of the herringbone pattern, in 13a, but the folded portion P is provided, and the radius _{r h} of the folded portion P, the dynamic pressure grooves 12a, an outer radius _{r 1} of 13a, the inner radius _{r 2} When r _h ² = (r ₁ ² + r ₂ ² ) / 2 holds, the fluid pressure in the pump-in direction generated on the outer diameter side from the folded portion P and the inner diameter side from the folded portion P are generated. The fluid pressure in the pump-out direction becomes equal. For example, when the diameter is φ2, the outer diameter is φ4, and the diameter (2r _h ) of the folded portion P is φ3.16, the fluid pressure is equal on the inner diameter side and the outer diameter side. At this time, the radius r _h of the folded portion P is larger than an intermediate point between the outer radius r ₁ and the inner radius r ₂ . On the other hand, in the present embodiment, the radius r of the folded portion is made larger than r _h [= (r ₁ ² + r ₂ ² ) ^1/2 / 2 ^1/2 ] obtained by the above formula (r > R _h ). In this case, since the fluid pressure in the pump-out direction generated on the inner diameter side of the folded portion P becomes more dominant than the fluid pressure in the pump-in direction, the lubricating oil flows in the pump-out direction on the entire

thrust bearing surfaces

12T and 13T. The lubricating oil is supplied to the space between the radial bearing gap and the thrust bearing gap.

(2) The chamfered portion 10e provided on the outer diameter side of the both side surfaces 12 and 13 of the inner member 10 is not subjected to post-processing such as rolling, pressing, or sizing, and is molded in a powder molding process. Leave as a face. Thereby, the surface aperture ratio of the chamfered portion 10e becomes larger than the surface aperture ratio of the radial bearing surface or the thrust bearing surface of the inner member 10. Therefore, even when the

space

30a, 30b between the radial bearing gap and the thrust bearing gap, which the chamfered portion 10e faces, tries to become negative pressure for some reason, the inside of the inner member 10 via the chamfered portion 10c. Lubricating oil can be supplied to the

spaces

30a and 30b to keep the

spaces

30a and 30b in a positive pressure state.

By adopting the configurations (1) and (2) described above, the generation of negative pressure in the

spaces

30a and 30b between the radial bearing gap and the thrust bearing gap is prevented, and the

spaces

30a and 30b are made positive. Pressure can be maintained. This effect can be obtained only by adopting one of configurations (1) and (2) depending on the bearing size and use conditions. Regarding the configuration of (1), the case of pumping out by the herringbone-shaped

dynamic pressure grooves

12a and 13a has been illustrated, but it is also possible to pump out by the spiral-shaped dynamic pressure grooves. Furthermore, in the third embodiment described above, the case where the configurations (1) and (2) are applied to the first embodiment shown in FIGS. 1 to 8 is illustrated, but the same configuration (1 ) And (2) can be applied to the second embodiment shown in FIG.

Next, a method for assembling the fluid dynamic bearing device of the present invention will be described with reference to FIGS. In this assembling method, the fluid dynamic pressure bearing device of the second embodiment is shown, but the first embodiment, the third embodiment, and their modifications are similarly applicable.

The gap setting device shown in FIG. 11 includes a fixing jig F and a moving jig G that is arranged inside the fixing jig F and is movable in the vertical direction. The fixing jig F has an inner peripheral surface 35 that is slidably fitted to the mounting surface 30, the guide surface 34, and the moving jig G. The moving jig G has an outer peripheral surface 38 slidably fitted to the shoulder surface 36, the guide surface 37 and the fixing jig F. Outside this gap setting device, the inner member 10 is accommodated in the outer member 20a on the outer side and the outer member 20b on the inner side, and the outer member 20b on the inner side is moved to the outer side until there is no thrust bearing gap T. It pushes in relative to the direction member 20a. A set of the outer member 20a on the outer side, the outer member 20b on the inner side, and the inner member 10 in this state is placed on the fixing jig F and the moving jig G as shown in FIG. That is, after the inner peripheral surface 10c of the sleeve portion 10b of the inner member 10 is fitted to the guide surface 37 of the moving jig G, the outer member 20a on the outer side, the outer member 20b on the inner side, and the inner member 10 The set is inserted downward, fitted to the guide surface 34 of the fixing jig F, and further inserted downward, and the outer surface of the radial direction portion 20a ₂ of the outer member 20a on the outside contacts the mounting surface 30. To install. At this time, the moving jig G is retracted downward.

Thereafter, the moving jig G is raised and moved to the lower end surface of the sleeve portion 10b of the inner member 10 where the thrust bearing gap T is zero between the outer member 20a on the outer side and the outer member 20b on the inner side. The shoulder surface 36 of the tool G is brought into contact. With this position as the reference position, as shown in FIG. 12, the moving jig G is further raised to move the inner member 10 upward, and from the outer outer member 20a press-fitted through the convex portion 27a. The inner outer member 20b is separated. The clearance between the inner side surface 22 of the outer member 20a on the outer side and the protruding portion 10a of the inner member 10 is stopped at a position where the total amount Δ of the thrust bearing clearances T on both sides is reached, and the clearance setting is completed.

In this assembling method, the outer member 20a on the outer side, the outer member 20b on the inner side, and the inner member 10 can be set and temporarily fixed outside the gap setting device including the fixing jig F and the moving jig G. . Since the gap setting device including the fixing jig F and the moving jig G performs only the gap setting, the workability is good.

As described above, with the thrust bearing gap T set and the outer member 20a on the outer side and the outer member 20b on the inner side being temporarily fixed, as shown in FIG. The outer member 20a and the inner outer member 20b are injected into the fitting portion. Since the chamfered portion 28 is provided on the inner peripheral surface 21 of the end surface of the cylindrical portion 20a1 of the outer member 20a on the outer side, it is easy to inject adhesive. Thereafter, the adhesive is solidified by baking. An adhesive that can omit firing, such as an anaerobic adhesive, may be used. Alternatively, the thrust bearing gap T may be set after first applying an adhesive. In any case, since the outer member 20a on the outer side and the outer member 20b on the inner side are temporarily fixed, a special jig for maintaining the set thrust bearing gap T is unnecessary, and workability is improved. Will improve.

Lubricating oil is injected between the assembled inner member 10 and outer member 20 including the internal pores of the sintered metal inner member 10. Thereafter, the oil is heated to a set temperature exceeding the maximum temperature (upper limit) assumed in the usage environment of the fluid dynamic pressure bearing device 4, and the lubricating oil overflowing from the inner diameter side end portion of the thrust bearing gap T due to thermal expansion at this time Wipe off. Thereafter, by cooling to room temperature, the lubricating oil contracts, the oil surface moves backward to the bearing inner side (outer diameter side), and is held in the seal spaces S ₁ and S ₂ . Thereby, if it is in the assumed temperature range, lubricating oil will not leak by thermal expansion. Thus, the fluid dynamic bearing device 4 is completed.

In the above embodiment, the

dynamic pressure grooves

11a ₁ , 11a ₂ , 12a, 13a, 22a, 23a, 29a ₁ , and 29a ₂ are formed in a herringbone shape, but appropriate dynamic pressures such as a spiral shape, a step shape, and an arc shape are used. It can be composed of grooves. Further, as an example in which the

dynamic pressure grooves

11a ₁ , 11a ₂ , and 29a ₁ , 29a ₂ are formed in a plurality of rows in the axial direction on the radial bearing surface, two rows are shown, but three rows in the axial direction or You may form with the above row | line | column.

14 to 24, another configuration example of the fluid dynamic bearing device will be described. As shown in FIG. 14, the fluid dynamic bearing device 10 includes an inner member 11 and an outer member 20 that rotatably supports the inner member 11. The inner member 11 is attached to a rotating shaft (not shown), and the outer member 20 is attached to a housing (not shown). Lubricating oil is interposed between the surfaces of the inner member 11 and the outer member 20 facing each other in the axial direction and the radial direction (radial bearing gap R and thrust bearing gap T).

The inner member 11 is made of sintered metal. The inner member 11 has an outer peripheral surface 12 and both side surfaces 13 and 13, the outer peripheral surface 12 forms a radial bearing surface 12R, and both side surfaces 13 and 13 form

thrust bearing surfaces

13T and 13T. The outer peripheral surface 12 has a cylindrical shape, and both side surfaces 13 and 13 are flat surfaces in the radial direction perpendicular to the axis A. A radial bearing gap R is formed between the radial bearing surface 12R of the inner member 11 and the radial bearing surface 29R of the outer member 20, and the thrust bearing surfaces 13T, 13T of the inner member 11 and the thrust bearing of the outer member 20 are formed. Thrust bearing gaps T and T are formed between the

surfaces

23T and 24T.

Chamfered portions

11 b and 11 c are formed at both ends of the outer peripheral surface 12 of the inner member 11, and

spaces

30 a and 30 b are formed between the outer member 20 and the outer member 20. The radial bearing gap R, the thrust bearing gaps T and T, and the

spaces

30a and 30b are filled with lubricating oil. In order to show the details of the state of filling with this lubricating oil, FIG. 16 shows a partial vertical cross-section in which the upper half of the fluid dynamic bearing device 10 of FIG. Lubricating oil is filled in the radial bearing gap R, the thrust bearing gaps T and T, and the

spaces

30a and 30b located between the radial bearing gap R and the thrust bearing gaps T and T.

A dynamic pressure groove 12 a is formed on the outer peripheral surface 12 of the heel inner member 11. Specifically, as shown in FIG. 15 (b), a dynamic pressure groove 12a formed on the entire outer peripheral surface 12 and bent in a V shape, and a hill portion 12b partitioning the dynamic pressure groove 12a (shown by cross hatching in the figure) And a herringbone shape alternately arranged in the circumferential direction.

Chamfered portions

11 b and 11 c are formed at both ends of the outer peripheral surface 12. The dynamic pressure groove 12a is formed by rolling, for example. Since the inner member 11 is formed of sintered metal, the plastic flow of the outer peripheral surface 12 of the inner member 11 due to the compression of the rolling process can be absorbed by the internal pores of the sintered metal. For this reason, the rise of the surface of the inner member 11 due to plastic flow is suppressed, and the dynamic pressure groove 12a and the hill portion 12b can be formed with high accuracy. When the dynamic pressure groove 12a is rolled, the chamfered

portions

11b and 11c at both ends of the outer peripheral surface 12 are not rolled. That is, the chamfered

portions

11 b and 11 c are only formed by a powder forming step of a sintered metal that constitutes the inner member 11. Therefore, the surface open area ratio of the chamfered

portions

11b and 11c is larger than that of the radial bearing surface.

As shown in FIG. 14, both side surfaces 13 and 13 of the inner member 11 form a flat surface in the radial direction perpendicular to the axis A, and

dynamic pressure grooves

13 a and 13 a are formed on both side surfaces 13 and 13. . Details are shown in FIGS. 15A and 15C. FIG. 15A shows the left side surface 13 of the inner member 11, and FIG. 15C shows the right side surface 13 of the inner member 11. As shown in the figure,

dynamic pressure grooves

13a, 13a formed on the entire surfaces of both side surfaces 13, 13 and bent in a V shape, and

hill portions

13b, 13b (indicated by cross-hatching in the figure) partitioning the grooves, It exhibits a herringbone shape that is alternately arranged in the circumferential direction. The herringbone shape of the

dynamic pressure grooves

13a and 13a for thrust is a pump-out specification in which lubricating oil is sent to the outer diameter side by rotation, as in FIGS. 10 (a) to 10 (c). Thereby, the lubricating oil is sent to the outer diameter side, and the pressure of the lubricating oil in the

spaces

30a and 30b (see FIG. 16) is kept at a positive pressure. Thereby, deterioration of bearing performance can be prevented.

Since the inner member 11 is made of sintered metal, the

dynamic pressure grooves

13a and 13a on the side surfaces 13 and 13 are formed by rolling, for example. Also in the rolling process of the

dynamic pressure grooves

13a and 13a on the both side surfaces 13 and 13, the plastic flow of the both side surfaces 13 and 13 due to the compression of the rolling process is burned in the same manner as the rolling process of the dynamic pressure grooves 12a on the outer peripheral surface 12. Can be absorbed by the internal pores of the metal. For this reason, the rise of the surface of the inner member 11 due to plastic flow is suppressed, and the dynamic pressure groove 13a and the hill portion 13b can be formed with high accuracy. Further, the chamfered

portions

11b and 11c are not rolled when the dynamic pressure groove 13a is rolled. Therefore, the surface opening ratio of the chamfered

portions

11b and 11c is larger than the surface opening efficiency of the thrust bearing surface 13T, similarly to the relationship with the radial bearing surface 12R described above. The

chamfered portions

11b and 11c correspond to regions where the surface area ratio is larger than that of each bearing surface provided on the outer surface portion of the inner member 11.

As shown in FIG. 16, the internal space of the fluid dynamic bearing device 10 in which the outer member 20 and the inner member 11 are assembled is filled with lubricating oil including the inner pores of the inner member 11 made of sintered metal. Therefore, in addition to the lubricating oil being sent to the outer diameter side by the pump-out specification of the thrust

dynamic pressure grooves

13a and 13a described above, the chamfered

portions

11b and 11c having a large surface opening ratio are In combination with the fact that the lubricating oil inside the member 11 is guided, the pressure of the lubricating oil in the

spaces

30a, 30b is maintained at a positive pressure more reliably. Thereby, deterioration of bearing performance can be prevented.

The radial dynamic pressure groove 12a and the thrust

dynamic pressure grooves

13a and 13a of the inner member 11 can be molded by press working as another processing method. In this case, since it is press working with a mold, it can be formed with high accuracy. Further, the radial dynamic pressure groove 12a and the thrust

dynamic pressure grooves

13a, 13a can be molded simultaneously with the sizing of the inner member 11. The radial dynamic pressure groove 12a formed on the outer peripheral surface 12 of the inner member 11 can be taken out from the mold using a spring back after molding. Even when the radial dynamic pressure groove 12a and the thrust

dynamic pressure grooves

13a and 13a are pressed, the chamfered

portions

11b and 11c are not pressed. Therefore, as in the case of the rolling process described above, the surface open area ratio of the chamfered

portions

11b and 11c is larger than both the bearing surfaces of the radial bearing surface 12R and the thrust bearing surface 13T. The

chamfered portions

As shown in FIGS. 14 and 16, chamfered

portions

11d and 11d are provided at both axial ends of the cylindrical inner peripheral surface 11a of the inner member 11. The inner member 11 is formed by, for example, press-fitting (light press-fitting) the inner peripheral surface 11a into the outer peripheral surface of the rotating shaft (not shown) or interposing an adhesive between the inner peripheral surface 11a and the outer peripheral surface of the rotating shaft. As a result, the rotation shaft is fixed. The inner peripheral surface 11a corresponds to a fixed surface with the shaft.

The material of the sintered metal that forms the inner member 11 is copper-iron based, and the blending ratio of copper is 10 to 80%. If the copper blending ratio is less than 10%, there will be a problem with the formability and lubricity of the dynamic pressure grooves, while if the copper blending ratio exceeds 80%, it is difficult to ensure wear resistance. In consideration of lubricity, copper iron is preferable, but other materials such as iron, copper, and stainless steel can be used. In any case, the surface open area ratio can take any value as long as it is within the range in which the circulation property and dynamic pressure effect of the lubricating oil can be obtained, but the range of 2 to 20% is desirable. When the surface opening ratio is less than 2%, the circulation of the lubricating oil is not sufficient, and when the surface opening ratio exceeds 20%, the pressure generated in the lubricating oil decreases. Further, as long as the oil circulation is not hindered, at least one of the radial bearing surface 12R and the thrust bearing surface 13T of the inner member 11 can be sealed. Thereby, the pressure drop of lubricating oil can be suppressed. The density of the copper-iron-based sintered member is set to 6 to 8 g / cm ³ in order to maintain the lubricity and plastic workability.

Next, the outer member 20 will be described. As shown in FIG. 1, the outer member 20 is composed of two members, an inner outer member 20a and an outer outer member 20b. The inner outer member 20a has a cylindrical portion 20a1 and a radial direction portion 20a2. The outer outer member 20b is also formed of an integral material with the cylindrical portion 20b1 and the radial direction portion 20b2. The inner outer member 20a and the outer outer member 20b are both formed in a substantially L-shaped longitudinal section. The outer peripheral surface 21 of the cylindrical portion 20a1 of the inner outer member 20a is lightly press-fitted into the inner peripheral surface 22 of the cylindrical portion 20b1 of the outer outer member 20b and fixed with an adhesive 45 interposed therebetween.

Since the chamfered portion 28 (see FIG. 16) is provided on the inner periphery of the end surface of the cylindrical portion 20b1 of the outer member 20b on the outer side, the adhesive 45 can be easily injected. Both the inner outer member 20a and the outer outer member 20b are formed in a substantially L shape by pressing a plate material. Specifically, the plate material is a stainless steel plate, a cold rolled steel plate, or the like, and the plate thickness is about 0.1 to 1 mm.

In this configuration, the inner peripheral surface 29 of the cylindrical portion 20a1 of the inner outer member 20a forms a radial bearing surface 29R. The inner side surface 23 of the radial direction portion 20a2 of the inner outer member 20a and the inner side surface 24 of the radial direction portion 20b2 of the outer outer member 20b form thrust

bearing surfaces

23T and 24T, respectively. Both the inner peripheral surface 29 and the inner side surfaces 23 and 24 are formed as smooth surfaces without irregularities, and the

dynamic pressure grooves

12 a and 13 a are formed in the outer peripheral surface 12 and the both side surfaces 13 and 13 of the inner member 11. . A small-diameter inner peripheral surface 26 is formed at the inner diameter side end of the radial direction portion 20b2 of the outer outer member 20b, and a small-diameter inner peripheral surface 25 is formed at the inner diameter side end of the radial direction portion 20a2 of the inner outer member 20a. Has been. In this structure, since the fitting portion between the inner peripheral surface 22 of the cylindrical portion 20b1 of the outer member 20b on the outer side and the outer peripheral surface 21 of the cylindrical portion 20a1 of the inner outer member 20a has a sufficient length, Stable assembly and adhesive fixing can be realized.

Lubricating oil is filled in the internal space of the fluid dynamic bearing device 10 having the above structure including the internal pores of the sintered metal inner member 11. As shown in FIG. 16, the lubricating oil is filled in the radial bearing gap R, the thrust bearing gaps T and T, and the

spaces

30a and 30b. Lubricating oil inside the inner member 11 is guided to the chamfered

portions

11b and 11c having a large surface opening ratio, and the pressure of the lubricating oil in the

spaces

30a and 30b is maintained at a positive pressure. In addition to this, the herringbone shape of the thrust

dynamic pressure grooves

13a, 13a has a pump-out specification in which the lubricating oil is sent to the outer diameter side by rotation, so that the lubricating oil is sent to the outer diameter side, and the space The pressures of the

lubricating oils

30a and 30b are more reliably maintained at a positive pressure. Thereby, deterioration of bearing performance can be prevented.

On the sealing surface, the lubricating oil is drawn to the outer diameter side (radial bearing gap R side) by the capillary force of the bearing gap. Further, as the rotating shaft rotates, the lubricating oil in the thrust bearing gap T is subjected to a centrifugal force or a pushing force by the dynamic pressure groove, whereby the lubricating oil is pushed into the outer diameter side (radial bearing gap R side). Leakage of the lubricating oil can be prevented by the centrifugal force, the pushing force, and the capillary force due to the bearing gap.

FIG. 17 shows the fan motor 1 incorporating the fluid dynamic bearing device 10. This fan motor 1 is used for discharging heat generated inside a personal computer, OA equipment, etc. to the outside and cooling the inside, and is a fluid dynamic bearing that rotatably supports the rotary shaft 2 in a non-contact manner. The apparatus 10 includes a fan 3 attached to the rotary shaft 2, a stator coil 50 and a rotor magnet 51 that are opposed to each other via a radial gap, and a case 52. The stator coil 50 is attached to the outer periphery of the housing portion 53 of the case 52, and the rotor magnet 51 is attached to the inner periphery of the fan 3. The fluid dynamic bearing device 10 is incorporated in the housing portion 53 of the case 52. In the fan motor 1 configured as described above, when the stator coil 50 is energized, the rotor magnet 51 is rotated by the magnetic force between the stator coil 50 and the rotor magnet 51, and accordingly, the fan 3 is connected to the rotating shaft 2. Rotates together.

As shown in FIG. 14, in the fluid dynamic bearing device 10, since the inner member 11 is provided between the axial directions of both inner side surfaces 23, 24 of the outer member 20, both inner side surfaces 23 of the

outer member

20, 24 and the both side surfaces 13 and 13 of the inner member 11 are engaged in the axial direction, so that the inner member 11 is prevented from coming off from the inner periphery of the outer member 20. Thereby, since separation of the inner member 11 and the outer member 20 can be prevented and the fluid dynamic bearing device 10 can be handled integrally, the attachment to the rotating shaft 2 and the housing part 53 becomes easy.

Next, a modification of the fluid dynamic bearing device 10 is shown in FIG. Parts having the same functions as those shown in FIGS. 14 to 17 described above are denoted by the same reference numerals, and redundant description is omitted. The same applies to the following embodiments.

In this modification, thrust

dynamic pressure grooves

23a, 24a are formed on the inner side surface 23 of the radial direction portion 20a2 of the inner outer member 20a and the inner side surface 24 of the radial direction portion 20b2 of the outer outer member 20b, respectively. Has been. And both the side surfaces 13 and 13 of the inward member 11 are formed by the smooth surface without an unevenness | corrugation. The

dynamic pressure grooves

23a and 24a for thrust are formed by press work when the inner outer member 20a and the outer outer member 20b are formed from a plate material by press work, for example. Therefore, the

dynamic pressure grooves

23a and 24a can be formed with high accuracy. The shapes of the thrust

dynamic pressure grooves

23a and 24a are the same as those shown in FIGS. 15 (a) and 15 (c). Other parts are the same as those shown in FIGS. In this modification, the radial dynamic pressure groove 12a is formed in the inner member 11. However, the radial dynamic pressure groove 12a can also be formed in the inner outer member 20a.

Another modification will be described with reference to FIG. In this modification,

sleeve portions

11e and 11f are formed so as to protrude from both ends of the inner member 11 in the axial direction. The outer diameter surfaces of the

sleeve portions

11e and 11f are formed at the inner diameter side end portion of the radial direction portion 20a2 of the inner outer member 20a at the inner diameter side end portion of the small diameter inner peripheral surface 25 and the radial direction portion 20b2 of the outer outer member 20b. It faces the small-diameter inner peripheral surface 26 with a seal gap. The small-diameter inner peripheral surface 25 and the small-diameter inner peripheral surface 26 are formed in a tapered shape that expands toward the outside of the bearing, and seal spaces S1, S2 are formed between the outer-

diameter surfaces

41, 42 of the

sleeve portions

11e, 11f. Is formed. The oil surface of the lubricating oil is held in the seal spaces S1 and S2.

In the configuration shown in FIGS. 14 to 18 and the modified example described above, the

dynamic pressure grooves

12a and 13a have a herringbone shape and are for one-way rotation. In this modification, the following display is provided to identify the rotation direction. As shown in FIG. 19, an identification groove 44 is formed on the end surface 43 of the sleeve portion 11 f on the right side of the inner member 11. When the end portion of the sleeve portion 11f having the identification groove 44 is arranged on the right side as shown in the figure, it can be seen that the rotation direction of the inner member 11 is the right direction (clockwise). In the above description, when the identification display is arranged on the right side, the rotation direction is set to the right direction. On the contrary, the rotation direction may be set to the left direction (counterclockwise direction).

FIG. 20 shows details of the identification groove 44. 3 is a right side view of the fluid dynamic bearing device 10. FIG. An identification groove 44 is formed on the end face 43 of the sleeve portion 11 f of the inner member 11. The identification grooves 44 are formed at two locations on the diameter, and the identification grooves 44 are formed by a powder forming process or a sizing process of the inner member 11 made of sintered metal. Therefore, since the identification groove is formed in the manufacturing process of the inner member 11, the cost does not increase. The identification groove 44 is not limited to the groove having the above shape, and may be, for example, an arrow-shaped identification groove that directly indicates the rotation direction. In addition to the above, the indication for identifying the rotation direction is, for example, a display indicating the rotation direction on the outer surface of the outer member 20, or the hues of the inner outer member 20a and the outer outer member 20b being different. It may be formed on the surface. For this purpose, materials of different hues are used or surface treatment is performed.

In this configuration, as shown in FIG. 19, a convex portion 21a is provided at the opening end of the outer peripheral surface 21 of the cylindrical portion 20a1 of the inner outer member 20a. FIG. 21 shows a cross section taken along line BB including the convex portion 21a. The convex portions 21a are formed on the outer peripheral surface 21 of the cylindrical portion 20a1 of the inner outer member 20a at eight locations in the circumferential direction. This convex portion 21a is press-fitted into the inner peripheral surface 22 of the cylindrical portion 20b1 of the outer member 20b on the outside. And it is temporarily fixed by the convex part 21a in the state which set the thrust bearing clearance gap, and it fixes with the adhesive agent 45 intervening. Since the convex portion 21a is partially pressed into the inner peripheral surface 22 of the cylindrical portion 20b1 of the outer member 20b, the accuracy of the inner member 20a and the outer member 20b is not impaired. .

In addition, although the convex part 21a was formed in eight places on the outer peripheral surface 21 of the cylindrical part 20a1 of the inner outer member 20a, if the number of the convex parts 21a is three or more, it can be an appropriate number. The shape of the convex portion 21a is not limited to a round protrusion, and may be a shape extending in the axial direction. Further, the convex portion can be formed on the inner peripheral surface 22 of the cylindrical portion 20b1 of the outer member 20b on the outside. In short, the convex portion can be press-fitted within a range in which the accuracy of the inner outer member 20a and the outer outer member 20b is not impaired, and is temporarily fixed by the convex portion with a thrust bearing gap set. Any form is acceptable. Other portions are the same as those of the first configuration shown in FIGS. Further, the formation form of the dynamic pressure groove is not limited to that of the present configuration, and may be the formation form of the configuration shown in FIGS.

In FIG. 19, in order to prevent the lubricating oil from seeping out from the end portions of the

sleeve portions

11e and 11f of the inner member 11, the end surfaces 43a and 44b, the end outer

peripheral surfaces

41 and 42, and the chamfered portion 11d are sealed. It is desirable to do. Further, as another method for preventing the lubricating oil from seeping out, an oil repellent may be applied to the end portions of the

sleeve portions

11e and 11f. Furthermore, the effect can be further enhanced by combining these.

In the configuration shown in FIGS. 14 to 17 and the present configuration, the radial direction portion 20a2 of the inner outer member 20a, the radial direction portion 20b2 of the outer outer member 20b, and the side surfaces 13, 13 of the inner member 11 opposite to the radial direction portion 20b2. However, the present invention is not limited to this, and the radial direction portion 20a2, the radial direction portion 20b2, and the side surfaces 13 and 13 facing the radial direction portion 20a2 may be formed in a conical shape. it can.

Next, a method for assembling the fluid dynamic bearing device of the present invention will be described with reference to FIGS. In this assembling method, the fluid dynamic bearing device shown in FIG. 19 is exemplified, but the structure shown in FIGS. 14 to 18 can be similarly applied.

The gap setting device shown in FIG. 22 includes a fixing jig F and a moving jig G that is arranged inside the fixing jig F and is movable in the vertical direction. The fixing jig F has an inner peripheral surface 35 that is slidably fitted to the mounting surface 30, the guide surface 34, and the moving jig G. The moving jig G has an outer peripheral surface 38 slidably fitted to the shoulder surface 36, the guide surface 37 and the fixing jig F. Outside this gap setting device, the inner member 11 is accommodated in the inner outer member 20a and the outer member 20b, and the inner outer member 20a is moved outside to the state where there is no thrust bearing gap T. It pushes in relative to the direction member 20b. A set of the outer member 20b on the outer side, the outer member 20a on the inner side, and the inner member 11 in this state is placed on the fixing jig F and the moving jig G as shown in FIG. That is, after the inner peripheral surface 11a of the inner member 11 is fitted to the guide surface 37 of the moving jig G, the outer outer member 20b, the inner outer member 20a, and the inner member 11 are set downward. It is inserted, fitted to the guide surface 34 of the fixing jig F, and further inserted downward, and the outer surface of the radial portion 20b2 of the outer member 20b on the outer side is placed in contact with the mounting surface 30. At this time, the moving jig G is retracted downward.

Thereafter, the moving jig G is raised and moved to the lower end surface of the sleeve portion 11f of the inner member 11 where the thrust bearing gap T is zero between the outer member 20b on the outer side and the outer member 20a on the inner side. The shoulder surface 36 of the tool G is brought into contact. With this position as a reference position, as shown in FIG. 23, the moving jig G is further raised to move the inner member 11 upward, and from the outer member 20b that has been press-fitted through the convex portion 21a. The inner outer member 20a is separated. The clearance between the inner side surface 24 of the outer member 20b on the outer side and the side surface 13 of the inner member 11 is stopped at a position where the total amount Δ of the thrust bearing clearances T on both sides is reached, and the clearance setting is completed.

In this assembling method, the outer member 20b on the outer side, the outer member 20a on the inner side, and the inner member 11 can be set and temporarily fixed outside the gap setting device including the fixing jig F and the moving jig G. . Since the gap setting device including the fixing jig F and the moving jig G performs only the gap setting, the workability is good.

As described above, with the thrust bearing gap T set and the outer member 20b on the outer side and the outer member 20a on the inner side being temporarily fixed, as shown in FIG. The outer member 20b and the inner outer member 20a are injected into the fitting portion. Since the chamfered portion 28 is provided on the inner peripheral surface 22 of the end surface of the cylindrical portion 20b1 of the outer member 20b on the outer side, it is easy to inject adhesive. Thereafter, the adhesive is solidified by baking. An adhesive that can omit firing, such as an anaerobic adhesive, may be used. Alternatively, the thrust bearing gap T may be set after first applying an adhesive. In any case, since the outer member 20b on the outer side and the outer member 20a on the inner side are temporarily fixed, a special jig for maintaining the set thrust bearing gap T is unnecessary, and workability is improved. Will improve.

Lubricating oil is injected between the assembled inner member 11 and outer member 20 including the internal pores of the sintered metal inner member 11. After that, the fluid dynamic pressure bearing device 10 is heated to a set temperature exceeding the maximum temperature (upper limit) assumed in the usage environment, and the lubricating oil overflowing from the inner diameter side end portion of the thrust bearing gap T due to thermal expansion at this time Wipe off. Thereafter, by cooling to room temperature, the lubricating oil contracts, the oil surface moves backward to the bearing inner side (outer diameter side), and is held in the seal spaces S1 and S2. Thereby, if it is in the assumed temperature range, lubricating oil will not leak by thermal expansion. Thus, the fluid dynamic bearing device 10 is completed.

In the above description, the

dynamic pressure grooves

12a, 13a, 23a, and 24a are formed in a herringbone shape, but can be formed by appropriate dynamic pressure grooves such as a spiral shape, a step shape, and an arc shape. Further, the dynamic pressure grooves 12a may be formed in a plurality of rows in the axial direction on the radial bearing surface.

DESCRIPTION OF SYMBOLS 1 Fan motor 2 Rotating shaft 3 Fan 4 Fluid dynamic pressure bearing apparatus 10 Inner member 10a Protruding part 10b Sleeve part 11a1 Dynamic pressure groove 11a2 Dynamic pressure groove 11R1 Radial bearing surface 11R2 Radial bearing surface 12a Dynamic pressure groove 12T Thrust bearing surface 13a Dynamic Pressure groove 13T Thrust bearing surface 20 Outer member 20a Outer outer member 20b Inner outer member 21 Inner peripheral surface 22a Dynamic pressure groove 22T Thrust bearing surface 23a Dynamic pressure groove 23T Thrust bearing surface 27a Convex portion 29a1 Dynamic pressure groove 29a2 Dynamic pressure Groove 29R Radial bearing surface 40 Nozzle 44 Identification groove F Fixing jig G Moving jig H Axis R Radial bearing gap T Thrust bearing gap

Claims

An outer member having a radial bearing surface and thrust bearing surfaces formed at both ends thereof, and a radial bearing surface and a thrust bearing surface disposed inside the outer member and facing the radial bearing surface and the thrust bearing surface, respectively. A radial bearing gap is formed between the radial bearing surfaces of the outer member and the inner member, and a thrust bearing gap is formed between the thrust bearing surfaces, and the bearing gaps are lubricated. In the fluid dynamic bearing device with oil interposed,
The outer member is composed of two members, an outer member on the outside and an outer member on the inner side. Both of the two outer members are formed of an integral material of a cylindrical portion and a radial portion, A fluid dynamic bearing device, wherein a cylindrical portion is fitted and fixed, and a plurality of rows of dynamic pressure grooves are formed on a radial bearing surface of one of the outer member and the inner member. .
2. The fluid dynamic bearing device according to claim 1, wherein the outer member is formed by pressing a plate material.
The fluid dynamic bearing device according to claim 1 or 2, wherein the inner member is made of a sintered metal.
The fluid dynamic bearing device according to claim 3, wherein the sintered metal is made of copper-iron, and the compounding ratio of copper is 10 to 80%.
5. The fluid dynamic bearing device according to claim 3, wherein the sintered metal has a surface area ratio of at least 2 to 20% on a radial bearing surface.
6. The plurality of rows of dynamic pressure grooves are formed on a radial bearing surface of the inner member, and the dynamic pressure grooves are formed on a thrust bearing surface of the inner member. The fluid dynamic bearing device according to any one of the above.
The plurality of rows of dynamic pressure grooves are formed on the radial bearing surface of the inner member, and the dynamic pressure grooves are formed on the thrust bearing surface of the outer member. The fluid dynamic bearing device according to any one of the above.
6. The plurality of rows of dynamic pressure grooves are formed on a radial bearing surface of the outer member, and the dynamic pressure grooves are formed on a thrust bearing surface of the outer member. The fluid dynamic bearing device according to any one of the above.
6. The plurality of rows of dynamic pressure grooves are formed on a radial bearing surface of the outer member, and the dynamic pressure grooves are formed on a thrust bearing surface of the inner member. The fluid dynamic bearing device according to any one of the above.
10. The fluid dynamic bearing device according to claim 1, wherein the dynamic pressure grooves formed on the radial bearing surface have two rows.
11. The fluid dynamic bearing device according to claim 1, wherein the hydrodynamic groove has a herringbone shape.
Each of the outer outer member and the inner outer member has a substantially L-shaped longitudinal cross section, and a radial bearing surface is formed on the inner peripheral surface of the cylindrical portion of the inner outer member, and the inner surface of the radial portion. A thrust bearing surface is formed on the inner surface of the outer portion of the outer member in the radial direction, and the outer periphery of the cylindrical portion of the inner member of the outer member is formed on the inner peripheral surface of the outer member of the outer member. The fluid dynamic bearing device according to any one of claims 1 to 11, wherein the surfaces are fitted.
13. The fluid motion according to claim 12, wherein a convex portion for temporary fixing is provided on at least one of the inner peripheral surface of the cylindrical portion of the outer member on the outer side and the outer peripheral surface of the cylindrical portion of the inner outer member. Pressure bearing device.
14. The fluid dynamic bearing device according to claim 13, wherein convex portions for temporary fixing are provided in at least three locations in the circumferential direction.
The fluid dynamic bearing device according to any one of claims 1 to 14, wherein a display for identifying a rotation direction is provided on an outer surface of the fluid dynamic bearing device.
The fluid dynamic pressure bearing according to claim 15, wherein an indication for identifying a rotation direction provided on the outer surface is an identification groove formed on an end surface of an inner member of the fluid dynamic pressure bearing device. apparatus.
The fluid dynamic bearing device according to any one of claims 1 to 16, wherein the amount of oil is adjusted at a temperature exceeding the operating temperature range after the lubricating oil is put inside. Fluid dynamic bearing device.
The fluid dynamic bearing device according to any one of claims 3 to 5, wherein at least an end face of the inner member is sealed.
The fluid dynamic bearing device according to any one of claims 3 to 5, wherein at least one of a radial bearing surface and a thrust bearing surface of the inner member is sealed.
The fluid dynamic bearing device according to any one of claims 3 to 5, wherein an oil repellent is applied to at least an end face of the inner member.
The inner member has at least a portion forming a radial bearing surface and a thrust bearing surface made of sintered metal, and a space between the radial bearing gap and the thrust bearing gap is maintained at a positive pressure. The hydrodynamic bearing device according to any one of the above.
The fluid dynamic bearing device according to claim 21, wherein the thrust dynamic pressure groove is a pump-out type.
The fluid dynamic pressure bearing device according to claim 22, wherein the pump-out type thrust dynamic pressure groove has a herringbone shape.
The region having a larger surface opening ratio than each bearing surface is provided in an outer surface portion of the inner member located in a space between the radial bearing gap and a thrust bearing gap. The fluid dynamic bearing device according to claim 21.
25. The fluid according to claim 24, wherein at least one of a radial dynamic pressure groove and a thrust dynamic pressure groove of the inner member is formed by pressing, and the region is not a processing surface of the pressing process. Hydrodynamic bearing device.
25. At least one of a radial dynamic pressure groove and a thrust dynamic pressure groove of the inner member is formed by a rolling process, and the region is not a processed surface of the rolling process. Fluid dynamic bearing device.
A fan motor incorporating the fluid dynamic bearing device according to any one of claims 1 to 26.
The outer member is composed of two members, an outer member on the outside and an outer member on the inside. A radial bearing surface is formed on the inner peripheral surface of the cylindrical portion of the inner outer member, and a thrust bearing surface is formed on the inner surface of the radial portion. And a thrust bearing surface is formed on the inner side surface of the radial portion of the outer member on the outer side, and a radial bearing surface and a thrust bearing surface are provided on the inner side of the outer and inner outer members. An inner member is disposed, and a plurality of rows of dynamic pressure grooves are formed on the radial bearing surface of either the outer member or the inner member, and the inner circumferential surface of the cylindrical portion of the outer member is arranged on the inner side. An assembly method of a fluid dynamic pressure bearing device in which an outer peripheral surface of a cylindrical portion of an outer member is fitted, wherein an inner member and an inner outer member are inserted into the outer member, Thrust bearing of the outer member on the outer side of the thrust bearing surface on both sides of the inner member The inner bearing member is separated from the outer outer member by the total amount of the thrust bearing gap, and a thrust bearing gap is set. A method of assembling a fluid dynamic bearing device, characterized by being temporarily fixed by
29. The adhesive according to claim 28, wherein an adhesive is injected into a fitting portion of the outer member of the fluid dynamic pressure bearing device temporarily fixed with the thrust bearing gap set by the assembling method. Assembly method of fluid dynamic bearing device.