JP2007263166A - Dynamic pressure bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dynamic pressure generating device which can suppress deterioration in bearing performance caused by the occurrence of contamination as much as possible. <P>SOLUTION: A dynamic pressure generating part A is disposed on a radial bearing face out of the inner peripheral face 8a of a sleeve 8 as a porous member. The dynamic pressure generating part A comprises: a first inclined groove group A1 constituted of a plurality of first inclined grooves A11 arranged in a circumferential direction; and a second inclined groove group A2 constituted of a plurality of second inclined grooves A21 different in inclination direction from the first inclined grooves A11 and arranged in the circumferential direction. In the first inclined groove group A1 of the dynamic pressure generating part A, a hill A12 is formed between the first inclined grooves A11, A11 adjacent to each other in the circumferential direction. In the second inclined groove group A2, a hill A22 is formed between the adjacent second inclined grooves A21, A21. A smooth surface A3 is formed between the first inclined groove group A1 and the second inclined groove group A2 around the whole circumference of the inner peripheral face 8a. Here, a surface opening hole ratio of the inner peripheral face 8a is maximized at a smooth surface A3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a hydrodynamic bearing device.

  The dynamic pressure bearing device supports a rotary member such as a shaft member in a non-contact manner in a freely rotatable manner by a dynamic pressure action of a fluid generated in a bearing gap. This type of bearing device has features such as high-speed rotation, high rotation accuracy, and low noise, and more specifically as a bearing device for motors installed in various electrical equipment including information equipment. As a bearing device for a spindle motor of a disk drive in an optical disk device such as a magnetic disk device such as CD-ROM, CD-R / RW, DVD-ROM / RAM, or a magneto-optical disk device such as MD or MO, or a laser It is preferably used as a bearing device for a motor such as a polygon scanner motor of a beam printer (LBP), a color wheel motor of a projector, or a fan motor.

  For example, in a hydrodynamic bearing device incorporated in an HDD spindle motor, one or both of a radial bearing portion that supports a shaft member in a radial direction and a thrust bearing portion that supports the shaft member in a thrust direction are configured by a hydrodynamic bearing. Things are known. In this case, a dynamic pressure groove that forms a dynamic pressure generating portion is formed on either the inner peripheral surface of the bearing sleeve or the outer peripheral surface of the shaft member facing the bearing sleeve, and the radial bearing gap between the two surfaces is radial. A bearing part is often formed. In addition, a dynamic pressure groove is formed on one end surface of the flange portion provided on the shaft member and an end surface of the bearing sleeve facing the flange portion, and a thrust bearing portion is formed in the thrust bearing gap between both surfaces. (See, for example, Patent Document 1).

As a shape of the dynamic pressure generating portion, for example, as shown in FIG. 8, a pair of inclined grooves (dynamic pressure grooves) 105 and 106 having different inclination directions are arranged in a herringbone shape is known (for example, Patent Documents). 2). In this case, one inclined groove group 107 formed by arranging a plurality of inclined grooves 105 inclined in one direction in the circumferential direction and a plurality of inclined grooves 106 inclined in the other direction are arranged in the circumferential direction. An annular smooth portion 109 is often provided between the other inclined groove group 108. In such a configuration, as the shaft member rotates, the fluid in the bearing gap passes through the inclined grooves 105 and 106 in the axial center of the dynamic pressure generating unit 104 (one inclined groove group 107 and the other inclined groove group 108 and To the smoothing portion 109 located between the smoothing portion 109 and a high-pressure oil film.
JP 2003-239951 A JP 2003-336636 A

  By the way, in the hydrodynamic bearing device mounted on the information device, the shaft member and the bearing sleeve are mainly in contact at the time of starting and stopping, and the contact region (dynamic pressure groove forming region or The area facing this is worn. In particular, recently, for the purpose of increasing the capacity of information devices represented by HDDs, for example, in disk drive devices such as HDDs, the number of disks mounted on the shaft member side tends to increase. Therefore, in the disk drive device (dynamic pressure bearing device) as described above, the rotating body weight of the dynamic pressure bearing device including the disk increases, and there is a concern that the amount of wear in the contact surface area increases. In this case, the generated abrasion powder is mixed into the lubricating oil as contamination, and there is a possibility that the lubrication performance is lowered and the bearing performance is lowered. In addition, contamination such as abrasion powder accumulates in the bearing gap, which may cause the rotating body to be locked (rotation stopped), and there is a concern that reliability for long-term use may be reduced.

  The subject of this invention is providing the dynamic-pressure generator which can suppress the fall of the bearing performance resulting from generation | occurrence | production of contamination as much as possible.

  In order to solve the above-described problems, the present invention provides a radial bearing gap, a porous member having a radial bearing surface facing the radial bearing gap, and a radial bearing surface, and generates a fluid dynamic pressure action in the radial bearing gap. A first inclined groove group including a plurality of first inclined grooves arranged in a circumferential direction, and the first inclined groove has a different inclination direction and a circular shape. The second inclined groove group is composed of a plurality of second inclined grooves arranged in the circumferential direction, and the first inclined groove group and the second inclined groove group are interposed via the first inclined groove and the second inclined groove. In a dynamic pressure generating device in which a fluid flows between, a smooth surface is provided between both the inclined groove groups, and the surface opening ratio of the radial bearing surface is maximized on the smooth surface. Providing equipment. Here, the surface opening ratio refers to the ratio of the total area (total area) of each opening, which occupies per unit area.

  According to such a configuration, the fluid that oozes from the surface of the porous member during the relative rotation of the member (for example, the shaft member) that faces the porous member via the radial bearing gap constitutes each inclined groove group. It flows toward the smooth surface located between the first inclined groove group and the second inclined groove group via the inclined groove and the second inclined groove. Thereby, the fluid is collected on the smooth surface, and the pressure in the region is increased. At the same time, the surface open area ratio of the smooth surface is the largest among the radial bearing surfaces on which the dynamic pressure generating portion is provided, so that contamination such as abrasion powder mixed in the fluid is collected along with the fluid collected on the smooth surface. It becomes easier to flow into the porous member than in other places. On the other hand, since the area of the radial bearing surface other than the smooth surface is smaller than that of the smooth surface, the contamination once entering the porous member through the smooth surface is removed from the outside of the porous member. Without being allowed to flow out into the porous member. Therefore, it is possible to eliminate as much contamination as possible from the fluid circulating inside the bearing, thereby avoiding the above-mentioned problems caused by contamination.

  In order to solve the above problems, the present invention provides a thrust bearing gap, a porous member having a thrust bearing surface facing the thrust bearing gap, a thrust bearing surface, and a hydrodynamic action of fluid on the thrust bearing gap. The first inclined groove group is composed of a plurality of first inclined grooves arranged in the circumferential direction, and the inclined direction is different from the first inclined groove. And a second inclined groove group composed of a plurality of second inclined grooves arranged in the circumferential direction, and the first inclined groove group and the second inclined groove group via the first inclined groove and the second inclined groove. In the hydrodynamic bearing device in which fluid flows between the two, the smooth surface is provided between the two inclined groove groups, and the surface opening ratio of the thrust bearing surface is maximized on the smooth surface. A pressure bearing device is provided.

  As described above, the present invention can be applied not only to the dynamic pressure generating portion provided on the radial bearing surface of the porous member but also to the dynamic pressure generating portion provided on the thrust bearing surface of the porous member. it can. Therefore, as described above, contamination such as wear powder mixed in the fluid together with the fluid collected in the area on the smooth surface is more likely to flow into the porous member than in other places, and also through the smooth surface. Thus, the contamination that has entered the inside of the porous member can be captured inside the porous member without escaping to the outside. Accordingly, it is possible to eliminate as much contamination as possible from the fluid circulating inside the bearing, thereby avoiding the above-described problems caused by the occurrence of contamination.

  In any of the above cases, the position where the smooth surface is formed with respect to the inclined groove is determined so that a recess having the smooth surface as a bottom surface is formed between the first inclined groove group and the second inclined groove group. Good. According to such a configuration, the contamination that has flowed through the surface opening of the smooth surface together with the fluid is captured inside the porous sleeve, while the contamination is stored in the recess formed between the two inclined groove groups. . Therefore, it is possible to avoid as much as possible such a situation in which such contamination returns to the bearing gap and the like together with the fluid. Therefore, contamination is captured inside the porous member, and contamination is captured by the concave portion formed by the smooth surface, so that the ability to eliminate such contamination can be further enhanced.

  The porous member having the above configuration can be formed of, for example, a sintered metal. In this case, it is possible to create a difference in surface area ratio by, for example, sizing the surface other than the smooth surface by making the processing process after sintering different between the smooth surface and the other surface region. .

  In addition, the porous member having the above-described configuration includes, for example, a first porous resin portion and a second porous resin portion having different internal porosity, and the first porosity having a relatively high internal porosity. The quality resin part may have a smooth surface. In this case, the surface aperture ratio of the smooth surface and the surface aperture ratio of the region other than the smooth surface can be adjusted relatively easily.

  As described above, according to the present invention, it is possible to provide a dynamic pressure generating device capable of suppressing as much as possible a decrease in bearing performance due to the occurrence of contamination.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. The “up and down” direction in the following description merely indicates the up and down direction in each drawing for the sake of convenience, and does not specify the installation direction, usage mode, or the like of the hydrodynamic bearing device.

  FIG. 1 conceptually shows a configuration example of a spindle motor provided with a fluid dynamic bearing device 1 according to an embodiment of the present invention. This spindle motor is used, for example, for an HDD equipped with a magnetic disk, and includes a hydrodynamic bearing device 1 that supports a rotary member 3 having a shaft member 2 and a hub portion 11 in a non-contact manner in the radial direction, A drive unit 4 including a stator coil 4a and a rotor magnet 4b opposed to each other through a gap and a bracket 5 are provided. The stator coil 4a is fixed to the bracket 5, and the rotor magnet 4b is fixed to the rotating member 3 (hub portion 11). The housing part 7 of the fluid dynamic bearing device 1 is fixed to the inner periphery of the bracket 5. Further, as shown in the figure, the hub 6 holds disks 6 (two in FIG. 1). In the spindle motor configured as described above, when the stator coil 4a is energized, the rotor magnet 4b is rotated by the exciting force generated between the stator coil 4a and the rotor magnet 4b. The disk 6 fixed to the portion 11 rotates integrally with the shaft member 2.

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a housing portion 7, a sleeve portion 8 fixed to the inner periphery of the housing portion 7, a lid member 9 that closes one end of the housing portion 7, and the housing portion 7 and the sleeve portion 8. The shaft member 2 that relatively rotates and the seal portion 10 are mainly provided.

  The shaft member 2 is formed of, for example, a metal material such as SUS steel, and includes a shaft portion 2a and a flange portion 2b provided integrally or separately at the lower end of the shaft portion 2a. In this embodiment, on the outer peripheral surface 2a1 of the shaft portion 2a, there are provided large-diameter surfaces 2a2, 2a2 that form radial bearing gaps of the radial bearing portions R1, R2 between the inner peripheral surface 8a of the sleeve portion 8 described later. It is done.

  The housing part 7 is formed in a cylindrical shape with a metal material such as brass or a resin material, for example, and has a form in which both axial ends thereof are opened. A fixing surface 7 a for fixing a lid member 9 to be described later is formed on the inner periphery of the lower end of the housing part 7. Further, the outer peripheral surface 8c of the sleeve portion 8 is bonded to the inner peripheral surface 7b of the housing portion 7 located above the fixed surface 7a by, for example, bonding (including loose bonding or press-fitting bonding), press-fitting, welding (ultrasonic welding, (Including laser welding).

  The sleeve portion 8 is a porous body and is formed in a cylindrical shape. In this embodiment, the sleeve portion 8 is formed in a cylindrical shape from a sintered metal porous body mainly composed of copper. Of course, the sleeve portion 8 can be formed of a material other than metal, such as resin or ceramics.

  A dynamic pressure generating portion A is provided on the entire or partial region of the inner peripheral surface 8a of the sleeve portion 8. In this embodiment, the dynamic pressure generating parts A are formed at two locations apart in the axial direction, and each dynamic pressure generating part A has a plurality of first inclined grooves arranged in the circumferential direction as shown in FIG. A first inclined groove group A1 composed of A11 and a second inclined groove group A2 composed of a plurality of second inclined grooves A21 that are different in inclination direction and arranged in the circumferential direction from the first inclined groove A11. Consists of. These dynamic pressure generating portions A and A face the outer peripheral surface 2a1 (large diameter surface 2a2 in this embodiment) of the shaft portion 2a as a radial bearing surface when the shaft portion 2a is inserted into the inner periphery of the sleeve portion 8. When the shaft portion 2a (rotating member 3) rotates, radial bearing gaps of first and second radial bearing portions R1 and R2 described later are formed between the outer peripheral surface 2a1 of the opposing shaft portion 2a (FIG. 2). See).

  More specifically, in the first inclined groove group A1 of the dynamic pressure generating part A, as shown in FIG. 3, a plurality of first inclined grooves A11 inclined in one axial direction of the sleeve part 8 are arranged in the circumferential direction. A hill portion A12 (a region indicated by fine cross-hatching in FIG. 3) is formed between the first inclined grooves A11 and A11 that are formed over the circumferential direction and close to each other. In the second inclined groove group A2, a plurality of second inclined grooves A21 inclined in the other axial direction are formed in the circumferential direction, and between the adjacent second inclined grooves A21 and A21. Hill part A22 (area shown by fine cross-hatching in FIG. 3) is formed. Between the first inclined groove group A1 and the second inclined groove group A2 having the above-described configuration, a smooth surface A3 (a region indicated by cross-hatching in FIG. 3) extends over the entire circumference of the inner peripheral surface 8a. It is formed.

  Here, the surface open area ratio of the inner peripheral surface 8a having the dynamic pressure generating portions A and A becomes maximum at the smooth surface A3. That is, the surface area ratio of the smooth surface A3 is at least larger than that of the first and second inclined grooves A11 and A21 (bottom surfaces thereof) and larger than that of the hill portions A12 and A22 (top surface). Therefore, in this embodiment, the sleeve portion 8 corresponds to the porous member.

  In this embodiment, the first and second inclined grooves A11, A21 are on the same plane as the region excluding the dynamic pressure generating portion A on the inner peripheral surface 8a as shown in FIG. Is on a cylindrical surface having a larger diameter than the inclined grooves A11 and A21. Further, the hill portions A12, A22 are on the same surface having a smaller diameter than the inclined grooves A11, A12. With respect to the dynamic pressure generating portion A located on the lower side in the axial direction of the inner peripheral surface 8a, the inclined grooves A11 and A21 and the inclined groove groups A1 and A2 and the smooth surface A3 having the same configuration as described above are formed.

  A dynamic pressure generating portion B composed of a plurality of inclined grooves arranged in a predetermined shape is formed on the entire lower surface 8b of the sleeve portion 8 or a partial annular region. In this embodiment, for example, as shown in FIG. 5, a plurality of inclined grooves B1 are arranged in a spiral shape, and the hill portion is provided between the plurality of inclined grooves B1 and the inclined grooves B1 and B1 adjacent to each other in the line circumferential direction. The dynamic pressure generating part B is formed with B2. This dynamic pressure generating portion B is opposed to the upper end surface 2b1 of the flange portion 2b as a thrust bearing surface, and a thrust bearing gap of a first thrust bearing portion T1 to be described later is formed between the upper end surface 2b1 and the opposite end surface 2b1 when the shaft portion 2a rotates. (See FIG. 2).

  An annular first chamfered portion 8 a 1 is formed between the inner peripheral surface 8 a and the lower end surface 8 b of the sleeve portion 8. An annular second chamfered portion 8a2 is also formed between the inner peripheral surface 8a and the upper end surface 8d.

  The lid member 9 that closes the lower end side of the housing portion 7 is formed of, for example, a metal material or a resin material, and is fixed to a fixing surface 7 a provided at the inner peripheral lower end of the housing portion 7.

  On the entire upper surface 9a of the lid member 9 or a partial annular region, for example, a dynamic pressure generating portion C having the same arrangement mode as in FIG. 5 (the direction of the spiral is reversed) is formed. This dynamic pressure generating portion C is opposed to the lower end surface 2b2 of the flange portion 2b as a thrust bearing surface, and forms a thrust bearing gap of the second thrust bearing portion T2 described later between the lower end surface 2b2 and the shaft portion 2a when rotating. (See FIG. 2).

  The seal part 10 as a sealing means is formed of a metal material or a resin material separately from the housing part 7 and is fixed to the inner periphery of the upper end of the housing part 7 by means such as press fitting, adhesion, welding, welding or the like. In this embodiment, the sealing portion 10 is fixed in a state where the lower end surface 10b of the sealing portion 10 is in contact with the upper end surface 8d of the sleeve portion 8 (see FIG. 2).

  A seal surface 10a is formed on the inner periphery of the seal portion 10, and a seal space S is formed between the seal surface 10a and the outer peripheral surface 2a1 of the shaft portion 2a facing the seal surface 10a. In a state where lubricating oil, which will be described later, is filled inside the hydrodynamic bearing device 1, the oil level of the lubricating oil is always maintained within the range of the seal space S.

  As the lubricating oil filled in the hydrodynamic bearing device 1, various types of lubricating oil can be used, but the lubricating oil provided to the hydrodynamic bearing device for a disk drive device such as an HDD may be used at the time of use or Considering temperature changes during transportation, ester-based lubricating oils excellent in low evaporation rate and low viscosity, such as dioctyl sebacate (DOS), dioctyl azelate (DOZ) and the like can be suitably used.

  In the dynamic pressure bearing device 1 having the above-described configuration, when the shaft member 2 rotates, the dynamic pressure generating portion A (same for both upper and lower sides) formed on the inner peripheral surface 8a of the sleeve portion 8 serves as a radial bearing surface and faces the opposite shaft portion 2a. A radial bearing gap is formed between the outer peripheral surface 2a1 (in this embodiment, the large-diameter surfaces 2a2 and 2a2). Then, along with the rotation of the shaft portion 2a, the lubricating oil flows into the inclined grooves A11 and A21 from both ends of the dynamic pressure generating portion A, and further flows onto the smooth surface A3 so as to merge from the vertical direction. In this case, the pressure of the oil film formed on the smooth surface A3 is increased by the dynamic pressure action of the lubricating oil generated by the inclined grooves A11 and A21. In this way, the first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft member 2 in a non-contact manner in the radial direction are configured by the dynamic pressure action of the lubricating oil generated by the respective dynamic pressure generating portions A and A. Is done.

  At the same time, a thrust bearing gap formed between the dynamic pressure generating portion B formed on the lower end surface 8b of the sleeve portion 8 and the upper end surface 2b1 of the flange portion 2b opposed thereto, and formed on the upper end surface 9a of the lid member 9 is formed. The pressure of the lubricating oil film formed in the thrust bearing gap between the generated dynamic pressure portion C and the lower end surface 2b2 of the flange portion 2b opposed thereto is increased by the dynamic pressure action of the inclined groove B1 and the like. The first thrust bearing portion T1 and the second thrust bearing portion T2 that support the rotating member 3 (hub portion 11) in a non-contact manner in the thrust direction are configured by the pressure of these oil films.

  In this case, the area of the inner peripheral surface 8a in which the dynamic pressure generating portions A and A are provided, that is, the surface opening ratio of the radial bearing surface is maximum at the smooth surface A3. That is, the surface area ratio of the smooth surface A3 is at least larger than that of the first and second inclined grooves A11 and A21 (bottom surfaces thereof) and larger than that of the hill portions A12 and A22 (top edge surfaces thereof). Accordingly, contamination such as wear powder mixed in the lubricating oil together with the fluid collected on the smooth surface A3 is more likely to flow into the sleeve portion 8 (porous member) than in other places. On the other hand, since the area of the inner peripheral surface 8a other than the smooth surface A3 is smaller than that of the smooth surface A3, the contamination that has entered the sleeve portion 8 via the smooth surface A3 is reduced. It is possible to capture the inside of the portion 8 without losing it as much as possible. Therefore, when the hydrodynamic bearing device 1 is used, for example, the wear powder generated by repeated sliding contact at the time of starting and stopping is contaminated with the lubricating oil circulating in the bearing internal space (for example, a region indicated by a dotted pattern in FIG. 2). As a result, it is possible to eliminate as much contamination as possible from the lubricating oil, thereby suppressing the deterioration in bearing performance due to contamination as much as possible.

  In this embodiment, the first and second chamfered portions 8a1 and 8a2 are provided between the inner peripheral surface 8a and the upper end surface 8d of the sleeve portion 8 and between the inner peripheral surface 8a and the lower end surface 8b, respectively. ing. These chamfered portions 8a1 and 8a2 are usually formed for the purpose of taking in as much lubricating oil as possible to escape out of the radial bearing gap into the sleeve portion 8 and supplying as much lubricating oil as possible to the radial bearing gap. Therefore, it is preferable that the surface open area ratio of the chamfered portions 8a1 and 8a2 is larger than the surface open area area of the inner peripheral surface 8a excluding the smooth surface A3 and smaller than the surface open area ratio of the smooth surface A3. With this configuration, the amount of lubricating oil returning to the radial bearing gap is ensured as much as possible, and the contamination once flowing into the sleeve portion 8 together with the lubricating oil is first chamfered portion 8a1 (or second chamfered portion 8a2). It is possible to avoid returning to the radial bearing gap through the bearing as much as possible. Therefore, the contamination capturing ability of the sleeve portion 8 by providing the smooth surface A3 can be further enhanced.

  In some cases, the length of the first inclined groove A11 on the upper side in the axial direction (in order to further improve the circulation of the lubricating oil in the bearing internal space or to avoid the occurrence of a local negative pressure state as much as possible ( For example, as shown in FIG. 8, a configuration in which the axial length lower dimension is larger than the groove length (axial width dimension) of the second inclined groove A21 on the lower side in the axial direction is conceivable. As described above, by increasing the surface hole area ratio of the smooth surface A3 to be larger than the surface hole area ratios of the chamfered portions 8a1 and 8a2, it is possible to increase the lubricating oil circulation capability and to increase the contamination capturing capability of the sleeve portion 8. it can.

  Further, in this embodiment, the smooth surface A3 with respect to each of the inclined grooves A11, A12 is formed between the inclined groove groups A1, A2 of the dynamic pressure generating part A so that a recess having the smooth surface A3 as a bottom surface is formed. A radial position was defined. According to such a configuration, in addition to the contamination that has entered the inside of the sleeve portion 8 through the surface opening of the smooth surface A3 together with the lubricating oil being captured inside the sleeve portion 8, the contamination is in both the inclined grooves. It is stored in a recess formed between the groups A1 and A2. For this reason, it is possible to avoid as much as possible such a situation in which such contaminants return to the radial bearing gap together with the lubricating oil. Accordingly, it is possible to further improve the contamination eliminating capability and more reliably prevent the deterioration of the bearing performance caused by the contamination.

  Further, when the sleeve portion 8 is formed of a sintered metal as in this embodiment, the porous member (sleeve portion 8) having the smooth surface A3 can be formed through the following steps, for example. . First, the raw material powder containing the metal powder as a main raw material is compression-molded into a predetermined shape (for example, the shape shown in FIG. 3). At this time, the region corresponding to, for example, the smooth surface A3 of the green compact is formed in another portion of the dynamic pressure generating portion A (inclined grooves A11, A21, hill portions A12, A22, etc.) as shown in FIG. Compared to a larger diameter. Then, after passing through the sintering step, size sizing is performed on the sleeve portion 8 (sintered product) to correct the sleeve portion 8 including the inner peripheral surface 8a and the lower end surfaces 8b and 8d. Thereafter, groove sizing is mainly applied to the inner peripheral surface 8a. Specifically, a molding die having a shape following the dynamic pressure generating portion A shown in FIGS. 3 and 4 is pressed against the inner peripheral surface 8a of the sleeve portion 8, and the inner peripheral surface 8a is deformed following the die. The dynamic pressure generating part A is formed. In the dimension sizing and groove sizing, the sizing of the inner peripheral surface 8a including the dynamic pressure generating portion A is performed using a sizing pin. However, as described above, the smooth surface A3 is formed to have a larger diameter than other portions. Therefore, at the time of each sizing, only the region excluding the smooth surface A3 having a large diameter can be sized in the inner peripheral surface 8a. Therefore, about the smooth surface A3, the surface opening rate at the time of compacting can be maintained, and, thereby, a larger surface opening rate can be obtained compared to other places. Before the groove sizing, the inner peripheral surface 8a can be subjected to a sealing process by rotational sizing or the like. By passing through this process, the dynamic pressure action and the contamination capturing ability of the sleeve portion 8 can be further enhanced.

  When the smooth surface A3 is formed by the above method, the inner peripheral surface 8a (inclined grooves A11, A21) is taken into account the amount of springback after compression so that the mold removal after the compacting is performed smoothly. It is preferable to determine the inner diameter dimension of the smooth surface A3 with respect to (). Moreover, if the inner diameter dimension of the smooth surface A3 is excessively increased, the width dimension of the radial bearing gap formed between the smooth surface A3 and the surface facing this (the large diameter surface 2a2 of the shaft member 2) becomes excessive. There is a possibility that sufficient oil film forming ability may not be obtained. Therefore, it is preferable to set the inner diameter dimension of the smooth surface A3 from the viewpoint of bearing rigidity together with moldability.

  Further, most of the contamination mixed in the lubricating oil is wear powder generated during use. Therefore, it is preferable to determine the size (hole diameter) of the hole that opens on the surface of the smooth surface A3 in accordance with the size of the generated abrasion powder. When the porous member is formed of sintered metal as described above, the size of the surface opening diameter can be appropriately set by adjusting the size of the raw material powder (metal powder) to be used, for example. .

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said form.

  Although the case where the sleeve part 8 as a porous member was formed with a sintered metal was demonstrated in the said embodiment, it is not restricted to this, For example, the sleeve part 8 can also be formed with porous resin. Specifically, for example, as shown in FIG. 6, a sleeve portion 8 as a porous member is composed of a first porous resin portion 12 and a second porous resin portion 13 having different internal porosity. The smooth surface A3 may be formed by the first porous resin portion 12 that is configured and has a relatively high internal porosity.

  In this case, each of the porous resin portions 12 and 13 is formed by, for example, molding a resin composition containing a pore forming material into a predetermined shape (such as injection molding), and then removing the pore forming material with a solvent such as water or alcohol. It is formed by doing. Speaking of the porous member (sleeve portion 8) having the above configuration, for example, the first porous resin portion 12 formed in a ring shape in advance is used as an insert part, and the remaining portion of the sleeve portion 8, that is, the second porous resin. It can be formed by molding the portion 13. With such a configuration, the smooth surface A3 and the other regions of the inner peripheral surface 8a can be formed by separate members, so that the surface area ratio of the smooth surface A3 and other regions can be relatively high. It can be easily adjusted. Further, the inner diameter dimension of the smooth surface A3 can be set separately from the inclined groove A11 and the like.

  The base resin used for the porous resin parts 12 and 13 may be any thermoplastic resin or thermosetting resin as long as it can be injection-molded and satisfies the required heat resistance, oil resistance, mechanical strength, and the like. For example, one or a plurality of materials selected from the material group exemplified below can be used. One or more kinds of various fillers such as a reinforcing material, a lubricant, and a conductive material can be blended with the base resin. When the sleeve portion 8 made of porous resin is formed as described above, the base resin of the first porous resin portion 12 has a melting point higher than that of the base resin used for the second porous resin portion 13. Higher ones are used.

  Here, as resin materials that can be used as the base resin, for example, polyphenylene sulfide (PPS), polyether ketone (PEK), polyether ether ketone (PEEK), polyether imide (PEI), polyether sulfone (PES) , Polyamideimide (PAI), thermoplastic polyimide (TPI), thermosetting polyimide, polyamide (PA), polyamide 6T, polyamide 9T, and other aromatic polyamides, tetrafluoroethylene / hexafluoropropylene copolymer (PFA), ethylene -Fluorine-based copolymer resins such as tetrafluoroethylene copolymer (ETFE).

  Resin composition used for molding porous resin portions 12 and 13 by mixing pore forming material and filler with the above base resin by a kneading method generally used for resin mixing such as dry blending and melt kneading. Things are obtained. As the pore-forming material, in order to prevent melting at the time of molding, after having a melting point higher than the melting temperature of the selected base resin, and blended with the base resin to mold the porous resin parts 12, 13, Those that can be removed using a solvent that is insoluble in the base resin can be used. Among these, in particular, weak alkaline substances that can be easily removed after molding (for example, water-soluble) and can be used as a rust preventive agent can be suitably used.

  As the pore-forming material, organic alkali metal salts represented by sodium benzoate, sodium acetate, sodium sebacate, sodium succinate, or sodium stearate, potassium carbonate, sodium molybdate, potassium molybdate, sodium tungstate, Inorganic alkali metal salts such as sodium triphosphate and sodium pyrophosphate can be used. Among these, sodium benzoate, sodium acetate, and sodium sebacate are particularly preferable because they have a high melting point, increase the degree of freedom in selecting a base resin, and exhibit excellent water solubility. These metal salts may be used alone or in combination of two or more. The average particle diameter of the pore forming material used is preferably 0.1 to 500 μm, although it depends on the size of the wear powder to be considered as described above. When the particle diameter of the pore forming material, that is, the hole diameter formed in the sleeve portion 8 is 0.1 μm or less, the lubricating oil is not smoothly supplied to the bearing gap due to the surface tension of the lubricating oil, and the hole diameter is 500 μm or more. This is because the surface area becomes small and the desired bearing rigidity cannot be obtained.

  The mixing ratio of the pore forming material is preferably 10 vol% to 90 vol% with respect to the total amount including the base resin, the pore forming material, the filler, and the like. This is because if the amount is less than 10 vol%, a sufficient amount of pores cannot be secured, and if it exceeds 90 vol%, the desired mechanical strength cannot be obtained. If the entire bearing internal space is filled with lubricating oil and the amount of oil inside the bearing needs to be minimized as in the above embodiment, the above blending ratio is used for the purpose of reducing the oil content of the sleeve portion 8. Is preferably 10 vol% to 30 vol%. Alternatively, when used in applications where durability is important, the blending ratio is particularly preferably 40 vol% to 60 vol% for the purpose of increasing the oil content.

  In the above description, the dynamic pressure generating portion A is provided on the inner peripheral surface 8a (radial bearing surface) of the sleeve portion 8 facing the radial bearing gap, and the first and second inclined grooves constituting the dynamic pressure generating portion A are provided. Although the case where the smooth surface A3 having the above-described configuration is provided between the groups A1 and A2 has been described, such a smooth surface can be provided, for example, in a dynamic pressure generating portion provided on the end surface of the sleeve portion 8.

  FIG. 7 shows an example thereof. The dynamic pressure generating portion B provided on the lower end surface 8b of the sleeve portion 8 is a first inclined groove group configured by a plurality of first inclined grooves B31 arranged in the circumferential direction. B3 and the first inclined groove B31 are composed of a second inclined groove group B4 including a plurality of second inclined grooves B41 having different inclination directions and arranged in the circumferential direction.

  More specifically, in the first inclined groove group B3 of the dynamic pressure generating part B forming the thrust bearing surface, as shown in FIG. 7, a plurality of first inclined grooves B31 inclined to one side in the radial direction of the sleeve part 8 are provided. Are formed in the circumferential direction, and a hill portion B32 (a region indicated by fine cross-hatching in FIG. 7) is formed in the first inclined grooves B31 and B31 that are close to each other in the circumferential direction. In the second inclined groove group B4, a plurality of second inclined grooves B41 inclined in the other radial direction are formed over the circumferential direction, and also between the adjacent second inclined grooves B41 and B41. Hill part B42 (region shown by fine cross-hatching in FIG. 7) is formed. Between the first inclined groove group B3 and the second inclined groove group B4 having the above-described configuration, an annular smooth surface B5 (a region indicated by rough cross-hatching in FIG. 7) extends over the entire periphery of the lower end surface 8b. Formed.

  Here, the surface opening ratio of the thrust bearing surface (here, the lower end surface 8b) having the dynamic pressure generating portion B is maximized on the smooth surface B5. That is, the surface area ratio of the smooth surface B5 is at least larger than that of the first and second inclined grooves B31 and B41 (bottom surfaces thereof) and larger than that of the hill portions B32 and B42 (of the top end surface). Therefore, also in this embodiment, the sleeve portion 8 corresponds to the porous member.

  Further, in this embodiment, the smooth surface B5 is on the same plane on the upper side in the axial direction (the central side in the axial direction of the sleeve portion 8) than the inclined grooves B31 and B41. Further, the hill portions B32 and B42 are on the same plane on the lower side in the axial direction (the lower end side in the axial direction of the sleeve portion 8) than the inclined grooves B31 and B41.

  The dynamic pressure generating part B having the above configuration forms a thrust bearing gap with the upper end surface 2b1 of the opposing flange part 2b when the shaft member 2 rotates. Then, along with the rotation of the shaft portion 2a, the lubricating oil flows into the inclined grooves B31 and B41 from both end sides (inner diameter side and outer diameter side) of the dynamic pressure generating part B, and further joins from the inner and outer diameter directions in a smooth surface. Flow onto B5. In this case, the pressure of the oil film formed on the smooth surface B5 is increased by the dynamic pressure action of the lubricating oil generated by the inclined grooves B31 and B41. Thus, the first thrust bearing portion T1 that supports the shaft member 2 in the thrust direction in a non-contact manner is configured by the dynamic pressure action of the lubricating oil generated by the dynamic pressure generating portion B.

  In this case, the surface area ratio of the lower end surface 8b having the dynamic pressure generating portion B is maximized on the smooth surface B5. That is, the surface area ratio of the smooth surface B5 is at least larger than that of the first and second inclined grooves B31 and B41 (bottom surfaces thereof) and larger than that of the hill portions B32 and B42 (of the top end surface). Accordingly, contamination such as wear powder mixed in the lubricating oil together with the fluid collected on the smooth surface B5 is more likely to flow into the sleeve portion 8 (porous member) than in other places. On the other hand, the area other than the smooth surface B5 in the lower end surface 8b has a smaller surface area ratio than that of the smooth surface B5. Therefore, the contamination that has entered the sleeve portion 8 through the smooth surface B5 is removed from the sleeve portion. 8 can be captured inside the 8 without losing as much as possible. Therefore, when the hydrodynamic bearing device 1 is used, for example, when wear powder generated due to repeated sliding contact at the time of starting and stopping is mixed into the lubricating oil as much as possible, it is possible to eliminate as much contamination as possible from the lubricating oil. As a result, it is possible to suppress the deterioration of the bearing performance due to contamination as much as possible.

  Of course, as described above, the smooth surface B5 of the dynamic pressure generating portion B provided on the lower end surface 8b is within the range that the smooth surface A3 of the dynamic pressure generating portion A provided on the inner peripheral surface 8a of the sleeve portion 8 can take. The same configuration (including material, formation method, etc.) is possible.

  In the above description, the sleeve portion 8 is exemplified as the porous member provided with the smooth surfaces A3 and B5. However, the present invention is not limited to this member. In other words, any porous member can be used as long as it is a porous member that faces a radial bearing gap or a thrust bearing gap and has a surface having a dynamic pressure generating portion that generates a dynamic pressure action of the lubricating oil in the bearing gap. is there. For example, in the case of the hydrodynamic bearing device 1 shown in FIG. 2, the shaft portion 2a, the flange portion 2b, or the lid member 9 of the shaft member 2 can be a porous member according to the present invention. In this case, from the viewpoint of oil leakage, only a part of each member is made a porous member (for example, a part facing each bearing gap is partially formed of porous resin), and a region facing the outside of the bearing is It can be used after being sealed to such an extent that oil leakage does not occur. Of course, the present invention is not limited to the form shown in FIG. 2 but can be applied to the hydrodynamic bearing apparatus 1 having any form as long as the hydrodynamic bearing apparatus 1 has a dynamic pressure generating portion.

  The hydrodynamic bearing device 1 having the above-described configuration is not limited to the above-described spindle motor for HDD, but also includes optical disk devices such as CD-ROM, CD-R / RW, DVD-ROM / RAM, and magneto-optical disks such as MD and MO. The present invention can be suitably applied as a bearing device for electrical equipment including information equipment such as a spindle motor mounted on information equipment such as equipment. In addition, as in the present invention, if the hydrodynamic bearing device is capable of removing contamination such as wear powder from the lubricating oil, the lock is generated due to the accumulation of wear powder during continuous operation. It can certainly be avoided. Therefore, it can be suitably provided as a bearing device having high reliability even for devices that require stable rotation performance (bearing performance) for a long period of time, such as a server HDD. Also for disk drives equipped with a plurality of disks 6 corresponding to the increase in capacity of information equipment, or for motors that require high rotational performance (bearing performance) under high-speed rotation. Thus, it is possible to provide a dynamic pressure bearing device that can exhibit stable bearing performance over a long period of time.

  In the above embodiment, the radial bearing portions R1 and R2 and the thrust bearing portions T1 and T2 are configured to generate the dynamic pressure action of the lubricating fluid by the herringbone shape or spiral shape dynamic pressure grooves. However, the present invention is not limited to this. That is, the dynamic pressure generating unit according to the present invention only needs to have the smooth surface A3 (or smooth surface B5) as described above, and may be any dynamic pressure generating unit that does not have the smooth surface A3 having the above-described configuration. A dynamic pressure generating portion (for example, a step bearing, a multi-arc bearing, etc.) having an arbitrary form can be configured.

  Further, in the above description, the lubricating oil is exemplified as the fluid that fills the inside of the hydrodynamic bearing device 1 and causes the hydrodynamic action in the radial bearing gap or the thrust bearing gap. A fluid capable of generating a dynamic pressure action, for example, a gas such as air, a fluid lubricant such as a magnetic fluid, or lubricating grease may be used.

1 is a cross-sectional view of a spindle motor provided with a fluid dynamic bearing device according to a first embodiment of the present invention. It is sectional drawing of a hydrodynamic bearing apparatus. It is a longitudinal cross-sectional view of a sleeve part. It is DD sectional drawing of the dynamic-pressure generation | occurrence | production part shown in FIG. It is a lower side view of a sleeve part. It is sectional drawing which shows the other structure of a sleeve part. It is a lower side view which shows the other structure of the lower end surface of a sleeve part. It is a longitudinal cross-sectional view of the sleeve part which shows the conventional dynamic pressure generating part shape.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing apparatus 8 Sleeve part 8b Lower end surface 8a Inner peripheral surface 12 1st porous resin part 13 2nd porous resin part A Dynamic pressure generating part (inner peripheral surface)
A1, A2 Inclined groove group A11, A21 Inclined groove A12, A22 Hill part A3 Smooth surface B Dynamic pressure generating part (lower end surface)
B3, B4 Inclined groove group B31, B41 Inclined groove B32, B42 Hill part B5 Smooth surface R1, R2 Radial bearing part T1, T2 Thrust bearing part S Seal space

Claims (5)

A radial bearing gap, a porous member having a radial bearing surface facing the radial bearing gap, and a dynamic pressure generating portion that is provided on the radial bearing surface and generates a dynamic pressure action of fluid in the radial bearing gap,
The dynamic pressure generating portion includes a first inclined groove group including a plurality of first inclined grooves arranged in a circumferential direction, and the first inclined groove has a different inclination direction and is arranged in a circumferential direction. A second inclined groove group composed of a plurality of second inclined grooves, and between the first inclined groove group and the second inclined groove group via the first inclined groove and the second inclined groove. In the hydrodynamic bearing device into which fluid flows,
A hydrodynamic bearing device, wherein a smooth surface is provided between the two inclined groove groups, and the surface opening ratio of the radial bearing surface is maximized on the smooth surface. A thrust bearing gap, a porous member having a thrust bearing surface facing the thrust bearing gap, and a dynamic pressure generating portion that is provided on the thrust bearing surface and generates a dynamic pressure action of fluid in the thrust bearing gap,
The dynamic pressure generating portion includes a first inclined groove group including a plurality of first inclined grooves arranged in a circumferential direction, and the first inclined groove has a different inclination direction and is arranged in a circumferential direction. A second inclined groove group composed of a plurality of second inclined grooves, and between the first inclined groove group and the second inclined groove group via the first inclined groove and the second inclined groove. In the hydrodynamic bearing device into which fluid flows,
A hydrodynamic bearing device characterized in that a smooth surface is provided between the two inclined groove groups, and the surface opening ratio of the thrust bearing surface is maximized on the smooth surface.   The hydrodynamic bearing device according to claim 1, wherein a recess having the smooth surface as a bottom surface is formed between the first inclined groove group and the second inclined groove group.   The hydrodynamic bearing device according to claim 1, wherein the porous member is formed of a sintered metal.   The porous member includes a first porous resin portion and a second porous resin portion having different internal porosity, and the first porous resin portion having a relatively high internal porosity is provided. The hydrodynamic bearing device according to claim 1, which has the smooth surface.

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