JP4615328B2 - Hydrodynamic bearing device - Google Patents

Description

  The present invention relates to a hydrodynamic bearing device. The hydrodynamic bearing device here is an information device, for example, a magnetic disk device such as HDD or FDD, an optical disk device such as CD-ROM, CD-R / RW, or DVD-ROM / RAM, or a magneto-optical disk such as MD or MO. It is suitable as a bearing device for a spindle motor such as a device, a polygon scanner motor of a laser beam printer (LBP), a color wheel of a projector, or a small motor such as an electric device such as an axial fan.

  In addition to high rotational accuracy, the various motors are required to have high speed, low cost, low noise, and the like. One of the components that determine the required performance is a bearing that supports the spindle of the motor, and in recent years, as this type of bearing, the use of a hydrodynamic bearing having characteristics excellent in the required performance has been studied. Or it is actually used.

As an example of the above-mentioned dynamic pressure bearing, for example, a shaft bearing having a shaft portion and a flange portion is provided with a radial bearing portion that non-contact supports the shaft member in the radial direction, and a thrust bearing portion that non-contact supports the shaft member in the thrust direction It is known (see, for example, Patent Document 1). In this type of dynamic pressure bearing device, a dynamic pressure groove as a dynamic pressure generating means is provided on the inner peripheral surface of the bearing member constituting the radial bearing portion or the outer peripheral surface of the shaft portion. In addition, dynamic pressure grooves are provided on both end surfaces of the flange portion constituting the thrust bearing portion or on the end surface of the bearing member facing these.
JP 2002-061637 A

  The hydrodynamic bearing device having the above-described configuration is composed of components such as a bearing member and a shaft member, and each component is processed in order to ensure high rotational performance required for rapid performance improvement of information equipment. Efforts are being made to increase accuracy and assembly accuracy.

  By the way, the axial width of the thrust bearing gap changes during operation of the hydrodynamic bearing device due to temperature changes depending on the operating conditions. For example, when a shaft member having a flange portion is made of stainless steel in consideration of wear resistance and a bearing member is made of brass in consideration of workability, the linear expansion coefficient of brass is made of stainless steel and brass. Therefore, the amount of thermal expansion in the axial direction at the time of temperature rise is greater in the case of the bearing member made of brass than in the flange portion made of stainless steel. At this time, the thrust bearing gap width increases. In general, in a hydrodynamic bearing device, the viscosity of a fluid (for example, lubricating oil) decreases at a high temperature, and thus a decrease in bearing rigidity, particularly in the thrust direction, becomes a problem. If it is too large, the thrust bearing gap width increases at high temperatures, so that the bearing rigidity in the thrust direction further decreases. On the other hand, when the temperature is low, the motor torque increases due to an increase in the viscosity of the lubricating oil, but the difference in the linear expansion coefficient acts in the direction of increasing this torque. In such a structure, there is a problem in that the difference in thermal expansion between the flange portion and the bearing member acts in a direction that promotes each defect at both high temperature and low sound.

  In the present invention, in view of such a situation, a dynamic pressure bearing device capable of improving the rigidity of a thrust bearing at a high temperature and reducing the torque at a low sound is provided.

In order to achieve the above object, in the present invention, a bearing member, a shaft member that is inserted into the inner periphery of the bearing member, a shaft member that includes a flange portion that projects to the outer diameter side of the shaft portion, and one end opening of the bearing member A lid portion that seals the shaft portion, a radial bearing portion that supports the shaft member in a non-contact manner in the radial direction by the dynamic pressure action of lubricating oil generated in a radial bearing gap between the bearing member and the shaft portion, a bearing member and a flange portion, A first thrust bearing portion that supports the shaft member in a non-contact manner in one thrust direction by a dynamic pressure action of lubricating oil generated in a first thrust bearing gap between the second thrust bearing portion and a second thrust portion between the lid portion and the flange portion In a hydrodynamic bearing device comprising a second thrust bearing portion that non-contact-supports the shaft member in the other thrust direction by the hydrodynamic action of lubricating oil generated in the bearing gap, the bearing further faces the outer peripheral surface of the flange portion, and the bearing the end surface of the member and abutting, A clearance defining portion that defines the sum of the widths of the first thrust bearing clearance and the second thrust bearing clearance is provided. The clearance defining portion is provided separately from the bearing member, and the axial linear expansion coefficient of the flange portion is determined by the clearance defining portion. And the bearing member is formed of sintered metal, and the gap defining portion and the flange portion of the shaft member are both formed of stainless steel. A bearing device is provided.

  As described above, by making the axial linear expansion coefficient of the flange portion the same as or larger than the axial expansion coefficient of the gap defining portion, the thrust bearing gap is increased by the thermal expansion of the flange portion at high temperatures. It becomes small, and it becomes possible to suppress the fall of the bearing rigidity of the thrust direction at the time of high temperature. On the contrary, when the temperature is low, the thrust bearing gap becomes large due to the difference in the thermal expansion in the axial direction, so that it is possible to suppress an increase in motor torque at the low temperature.

  The gap defining portion may be in any form as long as it is formed on a member that can define the thrust bearing gap. That is, when forming separately from a bearing member and a cover part, when forming integrally with a cover part, the case where forming with a bearing member is considered.

  By providing the gap defining portion as described above, the thrust bearing gap width can be managed with high accuracy, and a thrust bearing gap with a predetermined dimension can be easily formed. It is most preferable that the gap defining portion has an axial width that is equal to the sum of the first thrust bearing gap, the second thrust bearing gap, and the axial width of the flange portion.

  Further, in the above configuration, the radial bearing portion includes a hydrodynamic bearing provided with a hydrodynamic groove having a shape inclined in the axial direction, such as a herringbone shape and a spiral shape, and a plurality of axial groove-shaped hydrodynamic grooves. A dynamic pressure bearing (step bearing) provided at a predetermined interval in the direction and a dynamic pressure bearing (multi-arc bearing) in which a radial bearing surface is configured by a multi-arc surface can be used.

  The above-described dynamic pressure bearing device can be provided as a motor for a disk device or the like including the dynamic pressure bearing device, a rotor magnet, and a stator coil, and has high thrust bearing rigidity at high temperatures, low temperature With low torque.

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

  FIG. 1 conceptually shows a configuration example of a spindle motor for information equipment incorporating a dynamic pressure bearing device (fluid dynamic pressure bearing device) 1. This spindle motor for information equipment is used for a disk drive device such as an HDD, and is a dynamic pressure bearing device 1 and a rotor (hereinafter referred to as a disk hub 3) attached to a shaft member 2 of the dynamic pressure bearing device 1. ), A stator coil 4 and a rotor magnet 5 and a bracket 6 which are opposed to each other with a gap in the radial direction, for example. The stator coil 4 is attached to the outer periphery of the bracket 6, and the rotor magnet 5 is attached to the inner periphery of the disk hub 3. The disk hub 3 holds one or more disks D such as magnetic disks on the outer periphery thereof. A housing 7 is attached to the inner periphery of the bracket 6. When the stator coil 4 is energized, the rotor magnet 5 is rotated by electromagnetic force generated between the stator coil 4 and the rotor magnet 5, and the disk hub 3 and the shaft member 2 are rotated accordingly.

  FIG. 2 shows an example of the hydrodynamic bearing device 1 used in the spindle motor. The hydrodynamic bearing device 1 includes a bearing member 20 having a sleeve-like portion and a shaft member 2 inserted in the inner periphery of the bearing member 20 as main constituent members. In the present embodiment, the bearing member 20 includes: A sleeve-shaped bearing sleeve 8 and a cylindrical housing 7 having a bearing sleeve 8 fixed to the inner periphery are configured. A lid portion 7 c that seals the opening is fixed to one end opening of the housing 7, and a seal member 9 is fixed to the other end opening 7 a of the housing 7. For convenience of explanation, the description will proceed with the opening 7a side of the housing 7 as the upward direction and the side sealed by the lid portion 7c of the housing 7 as the lower side.

  The housing 7 is configured integrally or separately with a cylindrical side portion 7b and a lid portion 7c that seals one end opening of the side portion 7b. The side portion 7b and the lid portion 7c are formed of a metal material such as stainless steel or brass, or a resin material such as PPS (polyphenylene sulfide), LCP (liquid crystal polymer), or PEEK (polyether ether ketone). In this embodiment, the side part 7b and the cover part 7c are integrally formed of brass. Although not shown in the figure, a part of the annular region serving as the thrust bearing surface of the upper end surface 7c1 of the lid portion 7c has dynamic pressure grooves arranged in a spiral shape or a herringbone shape, for example. Yes. At that time, the dynamic pressure groove provided on the upper end surface 7c1 can be molded simultaneously with the molding of the housing composed of the side portion 7b and the lid portion 7c, thereby eliminating the trouble of separately forming the dynamic pressure groove in the lid portion 7c. It can be omitted.

  The bearing sleeve 8 is formed in a cylindrical shape, and is fixed to the inner peripheral surface 7 b 1 of the side portion 7 b of the housing 7. The shaft member 2 is rotatably inserted into the inner peripheral surface 8 a of the bearing sleeve 8. The bearing sleeve 8 is made of, for example, a soft metal material such as brass or aluminum (aluminum alloy), or a sintered metal material. In this embodiment, the bearing sleeve 8 is formed of a porous body made of sintered metal, particularly a sintered metal porous body mainly composed of copper or iron. A dynamic pressure generating means is provided in a region of the inner peripheral surface 8a of the bearing sleeve 8 serving as a radial bearing surface. In this embodiment, for example, a herringbone-shaped or spiral-shaped dynamic pressure groove is provided as the dynamic pressure generating means. Is formed. Specifically, as shown in FIG. 3, for example, herringbone-shaped dynamic pressure grooves 8a1 and 8a2 are formed in regions that are two radial bearing surfaces that are separated from each other in the axial direction. The groove 8a1 is formed to be axially asymmetric with respect to the axial center m. At this time, the axial dimension X1 of the upper region from the axial center m is larger than the axial dimension X2 of the lower region. Therefore, when the shaft member 2 rotates, the pulling force (pumping force) of the fluid (for example, lubricating oil) by the dynamic pressure groove 8a1 becomes relatively larger than that of the lower symmetrical dynamic pressure groove 8a2. In addition, the area | region used as a radial bearing surface can form arbitrary numbers, and can also form in one place or three or more places of an axial direction.

  The outer peripheral surface 8b of the bearing sleeve 8 is provided with one or a plurality of circulation grooves 8b1 opened at both end surfaces 8c and 8d. In this embodiment, three circulation grooves 8b1 are formed at equal intervals in the circumferential direction. During the operation of the hydrodynamic bearing device, the lubricating oil pushed downward as a whole is returned upward by the circulation groove 8b1. The circulation groove can also be formed on the inner peripheral surface 7b1 of the side portion 7b of the housing 7.

  Further, in this embodiment, although not shown in the figure, a partial annular region serving as a thrust bearing surface of the lower end surface 8c of the bearing sleeve 8 is arranged in a spiral shape or a herringbone shape as dynamic pressure generating means. A dynamic pressure groove is formed.

  A seal member 9 made of a metal material or a resin material is fixed to the upper end opening 7a of the housing 7 by means such as press-fitting or bonding. In this embodiment, the seal member 9 has an annular shape and is formed separately from the housing 7. The inner peripheral surface 9a of the seal member 9 gradually increases in diameter toward the upper side, and opposes the outer peripheral surface 2a1 of the shaft portion 2a via a seal space S having a predetermined volume. Further, the lower end surface 9 b of the seal member 9 is in contact with the upper end surface 8 d of the bearing sleeve 8. Lubricating oil is filled in the internal space of the hydrodynamic bearing device 1 sealed with the seal member 9, and the oil level of the lubricating oil is maintained within the range of the sealing space S in this state. Note that the seal member 9 can be formed integrally with the housing 7 in order to reduce the number of parts and the number of assembly steps. Alternatively, the upper end side region of the inner peripheral surface 8a of the bearing sleeve 8 is formed to have a slightly larger diameter than the region serving as the radial bearing surface, and a seal space having a predetermined volume is formed on the inner diameter side of the region formed to have the large diameter. You may be made to do.

  The shaft member 2 is made of, for example, a metal material such as stainless steel, and includes a shaft portion 2a and a flange portion 2b provided at one end of the shaft portion 2a. Or it is set as the hybrid structure (For example, the axial part 2a is formed with a metal material, and the flange part 2b is formed with a resin material) which consists of a metal part and a resin part. In the present embodiment, the shaft portion 2a and the flange portion 2b are integrally formed of stainless steel. The outer peripheral surface 2a1 of the shaft portion 2a is opposed to two upper and lower regions that are radial bearing surfaces of the inner peripheral surface 8a of the bearing sleeve 8. In the present embodiment, the upper end surface 2b1 and the lower end surface 2b2 of the flange portion 2b are formed as flat smooth surfaces.

  In this embodiment, on the inner peripheral side of the boundary portion between the side portion 7b and the lid portion 7c of the housing 7, the gap defining portion Y that defines the sum of the widths of the first thrust bearing gap and the second thrust bearing gap is provided. An annular spacer member 10 is provided. The spacer member 10 is made of, for example, a metal material such as stainless steel or brass, or a resin material. In the present embodiment, the spacer member 10 is made of stainless steel. The spacer member 10 is fixed to the inner peripheral surface 7b1 and the like of the housing 7 separately from the side portion 7b and the lid portion 7c of the housing 7, and the inner peripheral surface of the spacer member 10 is the same as the outer peripheral surface 2b3 of the flange portion 2b. Opposing through a minute gap. As a method of fixing the spacer member 10 to the housing 7, in addition to adhesion, press-fitting, or welding, for example, the spacer member 10 is used as an insert part, the housing 7 is insert-molded, and the bottom surface 10b of the spacer member 10 is attached to the lid portion 7c. Alternatively, the outer diameter surface 10c can be fixed in a state of being partially embedded in the side portion 7b.

  The bottom surface 10b of the spacer member 10 is in contact with the upper end surface 7c1 of the lid portion 7c, and the upper end surface 10a is in contact with the lower end surface 8c of the bearing sleeve 8, whereby the fixing position of the bearing sleeve 8 with respect to the housing 7 is determined. That is, when the bearing sleeve 8 is pushed in along the inner peripheral surface 7b1 of the housing 7 until it contacts the spacer member 10, the position of the lower end surface 8c of the bearing sleeve 8 relative to the upper end surface 7c1 of the lid portion 7c of the housing 7 is The bearing sleeve 8 is fixed to the inner peripheral surface 7b1 of the housing 7 with an adhesive or the like in this state.

  In the hydrodynamic bearing device 1 having the above-described configuration, when the shaft member 2 rotates, the outer peripheral surface 2a1 of the shaft portion 2a is a region that becomes a radial bearing surface spaced apart at two locations above and below the inner peripheral surface 8a of the bearing sleeve 8. Opposes through radial bearing gap. As the shaft member 2 and the bearing sleeve 8 rotate relative to each other, the lubricating oil filled in the radial bearing gap generates a dynamic pressure action, and the shaft member 2 is supported in a non-contact manner in the radial direction by the pressure. . As a result, the first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft member 2 in a non-contact manner so as to be rotatable in the radial direction are formed.

  Further, the upper end surface 2b1 of the flange portion 2b of the shaft member 2 is opposed to a region serving as a thrust bearing surface formed on the lower end surface 8b of the bearing sleeve 8 via the first thrust bearing gap, and the flange portion 2b The lower end surface 2b2 is opposed to a region serving as a thrust bearing surface formed on the upper end surface 7c1 of the lid portion 7c of the housing 7 via a second thrust bearing gap. As the shaft member 2 and the bearing sleeve 8 rotate relative to each other, the lubricating oil filled in the thrust bearing gaps generates a dynamic pressure action, and the shaft member 2 is supported in a non-contact manner so as to be rotatable in the thrust direction by the pressure. . Thereby, the first thrust bearing portion T1 and the second thrust bearing portion T2 that support the shaft member 2 in a non-contact manner so as to be rotatable in both directions of the thrust are formed.

  In the present invention, the linear expansion coefficient in the axial direction of the flange portion 2b is set to be equal to or larger than the linear expansion coefficient in the gap defining portion Y, here the spacer member 10. In this embodiment, both the flange portion 2b and the spacer member 10 are made of stainless steel. Specifically, the flange portion 2b is made of austenitic stainless steel in consideration of wear resistance. Considering the above conditions, the spacer member 10 can be formed of any one of austenitic, martensitic, and ferritic stainless steel (see FIG. 6). At this time, the linear expansion coefficient in the axial direction of the flange portion 2 b is equal to or greater than the linear expansion coefficient in the axial direction of the spacer member 10. That is, at the time of high temperature, the amount of thermal expansion in the axial direction of the flange portion 2b is equal to or larger than that of the spacer member 10, so that the thrust bearing gap is reduced. Therefore, it is possible to suppress a decrease in bearing rigidity in the thrust direction due to a decrease in the viscosity of the lubricating oil. On the other hand, since the thrust bearing gap becomes large due to the difference in the amount of thermal expansion in the axial direction at low temperatures, an increase in motor torque at low temperatures can be suppressed.

  Note that the gap defining portion Y, in this embodiment, the axial width W of the spacer member 10 is equal to the sum of the axial widths of the flange portion 2b, the first thrust bearing gap, and the second thrust bearing gap. The width of the thrust bearing gap and the second thrust bearing gap can be easily and accurately managed.

  The present invention can be similarly applied not only to the fluid dynamic bearing device shown in FIG. 2 but also to other fluid dynamic bearing devices exemplified below. In the following description, members and elements having basically the same functions as those in the embodiment shown in FIG.

  The hydrodynamic bearing device 1 shown in FIG. 4 has a side portion 7b of the housing 7 and a lid portion 7c as separate bodies, and a cylindrical portion 7ca as a gap defining portion Y is integrally provided on the outer diameter side upper portion of the lid portion 7c. The thrust bearing gap width is defined by bringing the upper end surface of the cylindrical portion 7 ca into contact with the lower end surface 8 c of the bearing sleeve 8. Also in this embodiment, the lid portion 7c is formed of any one of austenitic, ferritic, and martensitic stainless steel so that the relationship of the linear expansion coefficient is established.

  The hydrodynamic bearing device 1 shown in FIG. 5 differs from the first embodiment shown in FIG. 2 in that the gap defining portion Y is configured in a region indicated by the axial width W of the side portion 7b of the housing 7. In the illustrated example, the case where the bearing member 20 is constituted by two members of the housing 7 and the bearing sleeve 8 is illustrated, but the bearing member having a sleeve-like portion is constituted by one member, for example, a gap at the press molding stage. The axial width W of the defining portion Y may be defined. Also in this embodiment, the side part 7b of the housing 7 including the gap defining part Y is formed of any one of austenitic, ferritic, and martensitic stainless steel so that the above-described linear expansion coefficient relationship is established.

  In the above description, austenitic stainless steel is used as the material constituting the flange portion 2b, and austenitic, ferritic, and martensitic stainless steel is used as the material constituting the gap defining portion Y, and the axial direction of the flange portion 2b is set. Although the linear expansion coefficient is set to be equal to or larger than the linear expansion coefficient in the axial direction of the gap defining portion Y, the material options are not limited to this. FIG. 6 shows the magnitude relationship of the linear expansion coefficients of the main materials constituting each member. If the material constituting the flange portion 2b is the same as or higher than the material constituting the gap defining portion Y, the requirements of the present invention can be satisfied.

However, if the difference in the linear expansion coefficient between the two members is too large, there is a risk that a problem such as an excessively small thrust bearing gap width may occur, so care must be taken when selecting the material of the flange portion 2b. . In particular, when the flange portion 2b is formed of a resin material and the gap defining portion Y is formed of a metal material, the above problem occurs because the linear expansion coefficient of the resin material is generally much larger than that of the metal material. The fear of doing increases. Therefore, in this case, the flange portion 2b is preferably formed of a resin material having a linear expansion coefficient of 5 × 10 ⁻⁵ / ° C. or less.

When both the flange portion 2b and the gap defining portion Y are formed of a resin material, the linear expansion coefficient is 2 to 9 × 10 ⁻⁵ / ° C., and the difference between the linear expansion coefficients is 5 × 10 ⁻⁵ / ° C. or less. It is preferable to form with the resin materials which are.

  In the above description, the radial bearing portions R1 and R2 and the thrust bearing portions T1 and T2 have exemplified the configuration in which the fluid dynamic pressure action is generated by the herringbone shape or spiral shape dynamic pressure grooves. Is not limited to this.

  For example, so-called step bearings or multi-arc bearings may be employed as the radial bearing portions R1 and R2.

  FIG. 7 shows an example in which one or both of the radial bearing portions R1 and R2 are configured by step bearings. In this example, a plurality of axial groove-shaped dynamic pressure grooves 8a3 are provided at predetermined intervals in the circumferential direction in a region that becomes a radial bearing surface of the inner peripheral surface 8a of the bearing sleeve 8.

  FIG. 8 shows an example of a case where one or both of the radial bearing portions R1 and R2 are configured by multi-arc bearings. In this example, the region that becomes the radial bearing surface of the inner peripheral surface 8a of the bearing sleeve 8 is configured by three arc surfaces 8a4, 8a5, and 8a6 (so-called three arc bearings). The centers of curvature of the three arcuate surfaces 8a4, 8a5, 8a6 are offset from the shaft center O of the bearing sleeve 8 (shaft portion 2a) by an equal distance. In each region defined by the three arcuate surfaces 8a4, 8a5, and 8a6, the radial bearing gap has a shape gradually reduced in a wedge shape in both circumferential directions. For this reason, when the bearing sleeve 8 and the shaft portion 2a rotate relative to each other, the lubricating fluid in the radial bearing gap is pushed into the minimum gap side reduced in a wedge shape in accordance with the direction of the relative rotation, and the pressure rises. The bearing sleeve 8 and the shaft portion 2a are supported in a non-contact manner by the dynamic pressure action of the lubricating fluid. Note that a deeper axial groove called a separation groove may be formed at the boundary between the three arcuate surfaces 8a4, 8a5, 8a6.

  FIG. 9 shows another example in the case where one or both of the radial bearing portions R1 and R2 are configured by multi-arc bearings. In this example as well, the region that becomes the radial bearing surface of the inner peripheral surface 8a of the bearing sleeve 8 is configured by three arc surfaces 8a7, 8a8, and 8a9 (so-called three arc bearings), but the three arc surfaces 8a7, In each region partitioned by 8a8 and 8a9, the radial bearing gap has a shape gradually reduced in a wedge shape with respect to one direction in the circumferential direction. The multi-arc bearing having such a configuration may be referred to as a taper bearing. Further, deeper axial grooves 8a10, 8a11, and 8a12 called separation grooves are formed at boundaries between the three arcuate surfaces 8a7, 8a8, and 8a9. Therefore, when the bearing sleeve 8 and the shaft portion 2a are relatively rotated in a predetermined direction, the lubricating fluid in the radial bearing gap is pushed into the minimum gap side reduced in a wedge shape, and the pressure rises. The bearing sleeve 8 and the shaft portion 2a are supported in a non-contact manner by the dynamic pressure action of the lubricating fluid.

  FIG. 10 shows another example in the case where one or both of the radial bearing portions R1 and R2 are configured by multi-arc bearings. In this example, in the configuration shown in FIG. 9, the predetermined regions θ on the minimum gap side of the three arcuate surfaces 8a7, 8a8, 8a9 are concentric with the axis O of the bearing sleeve 8 (shaft portion 2a) as the center of curvature. It is composed of arcs. Therefore, in each predetermined area θ, the radial bearing gap (minimum gap) is constant. The multi-arc bearing having such a configuration may be referred to as a tapered flat bearing.

  The multi-arc bearings in the above examples are so-called three-arc bearings, but are not limited to this, and so-called four-arc bearings, five-arc bearings, and multi-arc bearings composed of more than six arc surfaces are adopted. You may do it. Further, when the radial bearing portion is constituted by a step bearing or a multi-arc bearing, in addition to the configuration in which the two radial bearing portions are separated from each other in the axial direction as in the radial bearing portions R1 and R2, the bearing sleeve 8 It is good also as a structure which provided the one radial bearing part over the up-and-down area | region of the internal peripheral surface 8a.

  Further, one or both of the thrust bearing portions T1 and T2 are, for example, so-called step bearings, so-called wave bearings, in which a plurality of radial groove-shaped dynamic pressure grooves are provided at predetermined intervals in the circumferential direction in a region serving as a thrust bearing surface. It can also be constituted by a mold bearing (a step type having a wave shape) or the like.

  In the above embodiment, the inside of the hydrodynamic bearing device 1 is filled, and the radial bearing gap between the bearing sleeve 8 and the shaft member 2 and the thrust bearing gap between the bearing sleeve 8 and the housing 7 and the shaft member 2 are filled. Although the lubricant oil is exemplified as the fluid that generates the dynamic pressure, a fluid that can generate the dynamic pressure in each bearing gap, for example, a gas such as air, a magnetic fluid, or the like can also be used.

  Moreover, although the case where the thrust bearing surface is formed on the lower end surface 8c of the bearing sleeve 8 and the upper end surface 7c1 of the lid portion 7c is illustrated in the above embodiment, the flange portion 2b facing these via the thrust bearing gap. It can also be formed on the upper end surface 2b1 and the lower end surface 2b2.

1 is a cross-sectional view of a spindle motor for information equipment incorporating a fluid dynamic bearing device according to an embodiment of the present invention. It is sectional drawing which shows one Embodiment of the hydrodynamic bearing apparatus concerning this invention. It is sectional drawing of a bearing sleeve. It is sectional drawing which shows 2nd embodiment of the hydrodynamic bearing apparatus concerning this invention. It is sectional drawing which shows 3rd embodiment of the hydrodynamic bearing apparatus concerning this invention. It is a figure which shows the magnitude relationship of a linear expansion coefficient. It is sectional drawing which shows other embodiment of a radial bearing part. It is sectional drawing which shows other embodiment of a radial bearing part. It is sectional drawing which shows other embodiment of a radial bearing part. It is sectional drawing which shows other embodiment of a radial bearing part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing apparatus 2 Shaft member 2a Shaft part 2b Flange part 3 Disc hub (rotor)
4 Stator Coil 5 Rotor Magnet 7 Housing 8 Bearing Sleeve 9 Seal Member 10 Spacer Member 20 Bearing Member 7c Lid 8a1, 8a2 Dynamic Pressure Groove R1, R2 Radial Bearing T1, T2 Thrust Bearing S Seal Space Y

Claims (6)

A shaft member provided with a bearing member, a shaft portion inserted into the inner periphery of the bearing member, and a flange portion protruding to the outer diameter side of the shaft portion, a lid portion that seals one end opening of the bearing member, and a bearing member Lubricant generated in the first thrust bearing clearance between the bearing member and the flange portion, and the radial bearing portion that supports the shaft member in the radial direction without contact by the dynamic pressure action of the lubricating oil generated in the radial bearing clearance between the shaft portion and the shaft portion The first thrust bearing portion that non-contact supports the shaft member in one thrust direction by the dynamic pressure action of the oil, and the dynamic pressure action of the lubricating oil generated in the second thrust bearing gap between the lid portion and the flange portion. In a hydrodynamic bearing device comprising a second thrust bearing portion that non-contact supports the shaft member in the other thrust direction,
Furthermore, a clearance defining portion is provided which faces the outer peripheral surface of the flange portion and abuts with the end surface of the bearing member to define the sum of the widths of the first thrust bearing gap and the second thrust bearing gap. Provided separately from the member, the axial linear expansion coefficient of the flange portion is set to be greater than or equal to the axial linear expansion coefficient of the gap defining portion, the bearing member is formed of sintered metal, and the gap defining portion And the flange portion of the shaft member are both made of stainless steel.   The hydrodynamic bearing device according to claim 1, wherein the gap defining portion is formed integrally with the lid portion.   The hydrodynamic bearing device according to claim 1, wherein the gap defining portion is formed of a spacer member separate from the lid portion. 2. The radial bearing portion has a dynamic pressure groove as a dynamic pressure generating means.
The hydrodynamic bearing device according to any one of? The hydrodynamic bearing device according to any one of claims 1 to 3, wherein the radial bearing portion is a multi-arc bearing. A motor comprising the hydrodynamic bearing device according to any one of claims 1 to 5, a rotor magnet, and a stator coil.

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