JP4738831B2 - Hydrodynamic bearing device - Google Patents

Description

The present invention relates to a hydrodynamic bearing device . The hydrodynamic bearing device including the housing is an information device, for example, a magnetic disk device such as an HDD, an optical disk device such as a CD-ROM, CD-R / RW, or DVD-ROM / RAM, or a magneto-optical disk device such as an MD or MO. It is suitable for a spindle motor such as a laser scanner, a polygon scanner motor of a laser beam printer (LBP), and other small motors.

  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. In recent years, the use of a fluid bearing having characteristics excellent in the required performance has been studied or actually used. .

  This type of hydrodynamic bearing includes a hydrodynamic bearing provided with dynamic pressure generating means for generating dynamic pressure in a fluid (for example, lubricating oil) in a bearing gap, and a so-called circular bearing (not provided with dynamic pressure generating means). The bearing surface is roughly divided into a bearing having a perfect circular shape.

  For example, in a hydrodynamic bearing device incorporated in a spindle motor of a disk drive device such as an HDD, both a radial bearing portion that supports a rotating member in the radial direction and a thrust bearing portion that supports the thrust direction in the thrust direction may be configured by dynamic pressure bearings. is there. As a thrust bearing portion in this type of hydrodynamic bearing device (dynamic pressure bearing device), for example, both end surfaces of a flange portion of a shaft portion provided on a rotating member, and surfaces facing these (end surface of a bearing sleeve, bottom surface of a housing) It is known that a dynamic pressure groove as a dynamic pressure generating portion is formed on either one of the upper end surface or a thrust member fixed to the housing or an end surface of a lid member, and a thrust bearing gap is formed between both surfaces. (For example, see Patent Document 1).

Also, for purposes such as maintaining the fluid pressure properly (maintaining the pressure balance with other locations) in areas away from the atmosphere opening side such as the seal space (for example, the thrust bearing located inside the anti-seal space side of the housing) Thus, there is known one in which an axial groove (communication groove) through which fluid flows is provided on the outer peripheral surface of the bearing sleeve (see, for example, Patent Document 2).
JP 2003-239951 A JP 2003-307212 A

  This type of bearing device is composed of various parts including a housing, a bearing sleeve, and a shaft member. In order to ensure the high bearing performance required for the higher performance of information equipment, Efforts are being made to improve the processing accuracy and assembly accuracy. On the other hand, with the trend of lowering the price and downsizing of information equipment, there is an increasing demand for cost reduction and downsizing of this type of bearing device.

  In particular, in order to meet the demands for downsizing due to the recent portability of information equipment, it has been studied to reduce the size of each component of the bearing device. For example, in order to reduce the size of a cylindrical bearing sleeve, it is indispensable to reduce the thickness. However, if a communication groove is provided on the outer periphery of the bearing sleeve, the following adverse effects may occur.

  The bearing sleeve is usually made of sintered metal, and a dynamic pressure generating portion such as a dynamic pressure groove is formed on the inner periphery by sizing after sintering. After sizing, the bearing sleeve removed from the die or the like generates a springback, and its outer periphery is displaced (expanded) to the outer diameter side. However, during sizing, the communication groove area on the outer peripheral surface is not in contact with the die or the like. Since it is not compressed to the inner diameter side, the amount of spring back is smaller than that of other places. By adjusting the number of communication grooves (for example, three locations), the bias of the springback amount can be reduced to some extent. However, as the thickness is reduced as described above, the bias of the springback amount becomes more significant. In this case, the inner peripheral surface and the outer peripheral surface of the bearing sleeve after sizing are not a perfect circle but an ellipse or a substantially polygonal cross-sectional shape having a small diameter near the communication groove. For this reason, there is a possibility that the radial bearing gap with the shaft member has a large variation in the circumferential direction, and stable bearing rigidity cannot be obtained.

  The subject of this invention is providing the low-cost hydrodynamic bearing apparatus which can exhibit high bearing performance stably.

In order to solve the above-described problems, the present invention provides a bearing sleeve formed of sintered metal, a housing having a cylindrical shape and a fixing surface for fixing the outer peripheral surface of the bearing sleeve to the inner periphery, and a bearing sleeve. Rotating member having a shaft portion inserted in the inner periphery and rotating with respect to the bearing sleeve and the housing, and a lubricating film for fluid generated in a radial bearing gap between the outer peripheral surface of the shaft portion and the inner peripheral surface of the bearing sleeve In the hydrodynamic bearing device having the radial bearing portion that supports the rotating member in the radial direction in a non-contact manner, the outer peripheral surface of the bearing sleeve is a smooth cylindrical surface having no communication groove, and the entire surface is formed by sizing. The housing has a shape in which one end in the axial direction is opened, and an axial communication groove is formed on the inner periphery of the housing so as to communicate between both end surfaces of the bearing sleeve and allow fluid to flow . C Axial end of Managing opening side, is open in the axial direction, the fixed surface and communicating groove is, the fluid bearing apparatus characterized in that it is constituted by a plastically worked surface by both forged provide.

  In this way, by providing axial communication grooves on the inner periphery of the housing to communicate between both axial ends of the bearing sleeve, the amount of spring back after sizing the bearing sleeve is made uniform over the entire circumference. Is done. Therefore, the roundness of the inner peripheral surface or outer peripheral surface of the bearing sleeve can be maintained with high accuracy, and for example, the radial bearing gap between the inner peripheral surface and the rotating member can be properly managed. In addition, when an axial communication groove is provided on the outer peripheral surface of the bearing sleeve, the communication groove is formed at the same time as the molding of the green compact. Therefore, the die and punch of the compacting mold are compatible with the communication groove. However, by providing it on the housing side as in the present invention, the mold can be simplified and the cost can be reduced.

  As a method of forming the axial communication groove on the inner periphery of the housing, for example, cutting is conceivable, but this is a processing step different from the processing (turning) for forming the fixed surface of the housing inner periphery. Is required, leading to high costs. Further, in the cutting process, generation of chips is unavoidable, and this may be mixed in the fluid as contamination. In order to prevent this, a complicated cleaning process is required, for example, a separate cleaning process for the housing is performed after cutting, resulting in an increase in cost.

  On the other hand, if both the communication groove and the fixed surface are formed by forging as in the present invention, the communication groove and the fixed surface can be formed by the same processing method. Compared to the case, the cost can be reduced. In addition, since the forging process generally has a shorter cycle time than cutting or the like, the production efficiency (mass productivity) can be improved. In addition, in the forging process, chips are not generated unlike the cutting process, and the generation of burrs is suppressed as compared with the case where the housing is formed of resin. Therefore, the cleaning operation can be simplified, and the cost of deburring can be saved, thereby further reducing the cost.

In order to solve the above problems, the present invention includes a bearing sleeve formed of a sintered metal, a tubular shape, fixing surface that fixes the outer peripheral surface of the bearing sleeve on the inner circumference is formed a housing, a bearing A shaft member inserted into the inner periphery of the sleeve, and a rotating member that rotates relative to the bearing sleeve and the housing, and a fluid generated in a radial bearing gap between the outer peripheral surface of the shaft portion and the inner peripheral surface of the bearing sleeve. A radial bearing portion for supporting the rotating member in the radial direction in a non-contact manner with a lubricating film, and the outer peripheral surface of the bearing sleeve is a smooth cylindrical surface having no communication groove, and the entire surface is a surface formed by sizing. , the inner periphery of the housing, upon between both end faces of the bearing sleeve and communicating the fluid molding in forging a housing for use in a fluid bearing device communicating groove is formed in the distribution can be axially, the forging mold This The groove forming portion extending parallel to the stroke direction of the mold is provided, the fluid bearing apparatus for a housing, which comprises forging the communication groove by causing stroke forging mold provided with the groove forming portion in the axial direction A manufacturing method is provided.

As described above, by forging a communication groove on the inner peripheral surface of the housing by forging the die for forging provided with a groove forming portion extending parallel to the stroke direction of the die in the axial direction, An axial communication groove is accurately and easily formed on the inner periphery.

  In addition, a forging die provided with a groove forming portion is provided with a surface forming portion for forming a fixed surface, and the groove forming portion and the surface forming portion simultaneously forge the fixed surface with the communication groove, In one forging press operation (one stroke), the fixed surface of the housing and the communication groove are formed simultaneously. Thereby, the cycle time can be further shortened and further mass productivity can be improved.

  The housing configured as described above is generated in, for example, the housing, a bearing sleeve fixed to the fixed surface of the housing, a rotating member that rotates with respect to the bearing sleeve and the housing, and a radial bearing gap between the rotating member and the bearing sleeve. The present invention can be provided as a hydrodynamic bearing device including a radial bearing portion that supports a rotating member in a radial direction in a non-contact manner with a fluid lubricant film, and a seal space that is provided on one end opening side of the housing and is open to the atmosphere side.

  The hydrodynamic bearing device having the above-described configuration can be configured, for example, to perform fluid flow between the inside of the other end of the housing and the seal space. According to this, the pressure balance of the fluid inside the bearing is properly maintained. Stable bearing performance is exhibited over a long period of time.

  The hydrodynamic bearing device having the above configuration can also be provided as a spindle motor of a disk device having the hydrodynamic bearing device.

  Thus, according to the present invention, a hydrodynamic bearing device that can stably exhibit high bearing performance can be provided at low cost.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 conceptually shows a configuration example of a spindle motor for information equipment incorporating a hydrodynamic bearing device 1 according to a first embodiment of the present invention. This spindle motor is used in a disk drive device such as an HDD, and is opposed to a hydrodynamic bearing device 1 that rotatably supports a rotating member 3 having a shaft portion 2 through a gap in the radial direction, for example. The stator coil 4 and the rotor magnet 5 and the motor bracket 6 are provided. The stator coil 4 is attached to the outer periphery of the motor bracket 6, and the rotor magnet 5 is attached to the outer periphery of the rotating member 3. The housing 7 of the hydrodynamic bearing device 1 is fixed to the inner periphery of the motor bracket 6. Although not shown, the rotating member 3 holds one or more disk-shaped information recording media (hereinafter simply referred to as disks) such as magnetic disks. In the spindle motor configured as described above, when the stator coil 4 is energized, the rotor magnet 5 is rotated by the electromagnetic force generated between the stator coil 4 and the rotor magnet 5. The disk held by the member 3 rotates integrally with the shaft portion 2.

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a housing 7, a bearing sleeve 8 fixed to the housing 7, and a rotating member 3 that rotates relative to the housing 7 and the bearing sleeve 8 as main components. For convenience of explanation, in the housing 7 openings formed at both ends in the axial direction, the side sealed by the lid member 11 is the lower side, and the side opposite to the sealing side is the upper side.

  The rotating member 3 includes, for example, a hub portion 9 disposed on the opening side of the housing 7 and a shaft portion 2 that is inserted into the inner periphery of the bearing sleeve 8.

  The hub portion 9 includes a disc portion 9a that covers the opening side (upper side) of the housing 7, a cylindrical portion 9b that extends axially downward from the outer peripheral portion of the disc portion 9a, and a disk that is provided on the outer periphery of the cylindrical portion 9b. A mounting surface 9c and a flange 9d are provided. A disc (not shown) is fitted on the outer periphery of the disk portion 9a and placed on the disc mounting surface 9c. Then, the disc is held on the hub portion 9 by appropriate holding means (such as a clamper) not shown.

  The shaft portion 2 is formed integrally with the hub portion 9 from resin or metal, and includes a flange portion 10 as a separate member at the lower end thereof. The flange portion 10 is made of metal and is fixed to the shaft portion 2 by means such as screw connection. The shaft portion 2 can also be formed separately from the hub portion 9. At this time, the shaft portion 2 can be made of metal and the hub portion 9 can be made of resin, or the reverse combination.

  The bearing sleeve 8 is formed in a cylindrical shape with a porous body made of, for example, a metal non-porous body or sintered metal. In this embodiment, a sintered metal porous body mainly composed of copper is formed in a cylindrical shape.

  A dynamic pressure groove as a radial dynamic pressure generating portion is formed on the entire inner surface 8a of the bearing sleeve 8 or a partial cylindrical region. In this embodiment, for example, as shown in FIG. 3, two regions where a plurality of dynamic pressure grooves 8a1 and 8a2 are arranged in a herringbone shape are formed apart from each other in the axial direction. In the formation region of the upper dynamic pressure groove 8a1, the dynamic pressure groove 8a1 is formed to be axially asymmetric with respect to the axial center m (the axial center of the upper and lower inclined groove regions). The axial dimension X1 of the upper region is larger than the axial dimension X2 of the lower region.

  For example, although not shown in the drawing, a region in which a plurality of dynamic pressure grooves are arranged in a spiral shape is formed on the entire lower surface 8c of the bearing sleeve 8 or a partial annular region. This dynamic pressure groove forming region is opposed to the upper end surface 10a of the flange portion 10 as a thrust bearing surface, and a second thrust bearing portion T2 described later between the shaft portion 2 (rotating member 3) and the upper end surface 10a when rotating. (See FIG. 2).

  The housing 7 is formed in a cylindrical shape with a metal material such as stainless steel. The housing 7 has a shape in which both ends in the axial direction are opened, and one end side (lower end side) thereof is sealed with a lid member 11. A thrust bearing surface 7a is provided on the entire end surface (upper end surface) or a partial annular region on the opening side. In this embodiment, a region in which a plurality of dynamic pressure grooves 7a1 are arranged in a spiral shape is formed on the thrust bearing surface 7a as a thrust dynamic pressure generating portion, for example, as shown in FIG. The thrust bearing surface 7a (dynamic pressure groove 7a1 formation region) faces the lower end surface 9a1 of the disk portion 9a of the hub portion 9, and the first thrust bearing described later is formed between the thrust member surface 7a and the lower end surface 9a1 when the rotating member 3 rotates. A thrust bearing gap of the portion T1 is formed (see FIG. 2).

  The lid member 11 that seals the lower end side of the housing 7 is formed of a metal material or a resin material, and is fixed to a stepped portion 7 b provided on the inner peripheral side of the lower end of the housing 7. Here, the fixing means is not particularly limited, and for example, means such as adhesion (including loose adhesion, press-fit adhesion), press-fit, welding (for example, ultrasonic welding), welding (for example, laser welding), combinations of materials and requirements. It can be appropriately selected according to the assembly strength and sealing performance.

  A fixing surface 7 c for fixing the outer peripheral surface 8 b of the bearing sleeve 8 is formed on the inner periphery of the housing 7. The outer peripheral surface 8b of the bearing sleeve 8 is fixed to the fixing surface 7c by an appropriate means such as bonding (including loose bonding or press-fitting bonding), press-fitting, or welding.

  In addition to the fixed surface 7c, a communication groove 7d extending in the axial direction is formed on the inner periphery of the housing 7. In this embodiment, as shown in FIG. 4, the communication grooves 7 d are provided at three locations at equal intervals in the circumferential direction, and when the bearing sleeve 8 is fixed to the fixed surface 7 c, the lower end is the lower end surface of the bearing sleeve 8. The upper end of the bearing sleeve 8 communicates with the upper end surface 8 d of the bearing sleeve 8. Furthermore, the upper end of the communication groove 7d communicates with the thrust bearing gap of the first thrust bearing portion T1 (see FIG. 2 for both).

  On the outer periphery of the housing 7, a tapered surface 7e that gradually increases in diameter upward is formed. This tapered surface 7e forms an annular seal space S with the radial dimension gradually reduced upward from the sealing side of the housing 7 between the inner peripheral surface 9b1 of the cylindrical portion 9b. The seal space S communicates with the outer diameter side of the thrust bearing gap of the first thrust bearing portion T1 when the shaft portion 2 and the hub portion 9 are rotated.

  A cylindrical outer peripheral surface 7f having a constant diameter is formed at the lower end of the outer periphery of the housing 7. The cylindrical outer peripheral surface 7f is fixed to the inner peripheral surface 6a of the motor bracket 6 by means such as adhesion or press fitting, whereby the hydrodynamic bearing device 1 is incorporated into the motor.

  Hereinafter, an example of the manufacturing method of the housing 7 which comprises the hydrodynamic bearing apparatus 1 is demonstrated based on FIG. 5 and FIG.

  In this embodiment, the housing 7 is manufactured through three steps: an outer peripheral surface forming step (A), an inner peripheral surface forming step (B), and a thrust bearing surface forming step (C).

(A) Outer peripheral surface forming step First, after the wire is linearized, a cylindrical blank material cut to an appropriate size is cold forged (compressed) in a pair of molds (not shown), and the outer periphery of the housing 7 Surfaces (tapered surface 7e and cylindrical outer peripheral surface 7f) are formed. Note that the cold forging method is not limited to the above upsetting, and various forming methods such as forward extrusion or a combination of forward extrusion and upsetting can be used.

(B) Inner peripheral surface forming step Next, the inner peripheral surface (fixed surface 7c and communication groove 7d) of the housing 7 to be formed is formed by cold forging of the housing material 7 '. For example, as shown in FIG. 5, the die used is a die 16 that restrains the outer peripheral surface of the housing material 7 ′ and an upper punch that restrains the housing material 7 ′ in the axial direction from the thrust bearing surface 7a to be molded. 19 and a lower punch (rod) 18 having a molding surface 18a corresponding to the inner circumferential surface of the housing 7 to be molded. Here, as shown in FIG. 6, the molding surface 18a of the rod 18 forming the lower punch has a surface molding portion 18a1 corresponding to the fixed surface 7c and a convex groove molding portion 18a2 corresponding to the communication groove 7d. A plurality of locations (three locations at equal intervals in the circumferential direction in this example) are provided. The groove forming portion 18a2 is provided so as to extend in parallel with the stroke direction of the rod 18 (the vertical direction in FIG. 5).

As shown in FIG. 5, in a state where the housing material 7 ′ is constrained in the radial direction and the axial direction, the rod 18 is raised (in the direction of the arrow in the figure), and the inner peripheral portion of the housing material 7 ′ is moved from the lower end side to the upper end side. Punching toward. As a result, the housing material 7 ′ is opened at both axial ends, and the inner periphery thereof is formed into a shape that follows the surface forming portion 18 a 1 and the groove forming portion 18 a 2 (finished fixed surface 7 c and communication groove 7 d) of the forming surface 18 a. Is done. In this embodiment, by using the rod 18 having the step forming portion 18b corresponding to the step portion 7b in addition to the forming surface 18a, the fixed surface 7c of the finished product, the communication groove 7d, and the step portion 7b are simultaneously formed. The In this embodiment, the case has been described in which the inner peripheral portion of the housing material 7 ′ is punched from the lower side ( the side opposite to the thrust bearing surface 7a side) to the upper side (the thrust bearing surface 7a side). For example, if there is no part that specifies the punching direction, such as the stepped portion 7b, the punching may be performed from the top to the bottom.

(C) Thrust bearing surface forming step After the above steps (A) and (B), the thrust bearing surface 7a of the housing 7 to be formed is formed by cold forging of the housing material 7 '. For example, the die 16 and rod 18 shown in FIG. 5 and the lower end surface of the upper punch 19 shown in FIG. 5 are omitted in the mold used in this molding process, but the molding corresponding to the thrust bearing surface 7a of the housing 7 to be molded is omitted. It is composed of the surface. The upper punch 19 is lowered while the housing material 7 ′ is constrained in the radial direction by the die 16 and the rod 18, and a predetermined pressing force is applied to the upper end of the housing material 7 ′ with the molding surface of the upper punch 19 (not shown). Press. As a result, the upper end surface of the housing material 7 'is molded into a shape that follows the molding surface (the thrust bearing surface 7a of the finished product). Further, in this embodiment, although not shown in the figure, the housing material 7 ′ is obtained by using a groove die corresponding to the dynamic pressure groove 7a1 as the dynamic pressure generating portion formed in advance on the molding surface of the upper punch 19. At the same time as the thrust bearing surface 7a is formed, the shape of the dynamic pressure groove 7a1 is formed.

  The housing 7 (see FIG. 2) as a finished product is formed through the above steps (A) to (C).

  The hydrodynamic bearing device 1 is filled with lubricating oil including the internal pores of the bearing sleeve 8 (pores of the porous body tissue) (scattered region in FIG. 2). The oil level of the lubricating oil is always maintained in the seal space S.

  When the shaft portion 2 (rotating member 3) rotates, a region (a region where two dynamic pressure grooves 8a1 and 8a2 are formed) on the inner peripheral surface 8a of the bearing sleeve 8 is formed on the outer peripheral surface 2a of the shaft portion 2. And through a radial bearing gap. As the shaft portion 2 rotates, the lubricating oil in the radial bearing gap is pushed into the axial center m of the dynamic pressure grooves 8a1 and 8a2, and the pressure rises. The first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft portion 2 in a non-contact manner are configured by the dynamic pressure action of the dynamic pressure groove.

  At the same time, the thrust bearing clearance between the thrust bearing surface 7a (dynamic pressure groove 7a1 formation region) of the housing 7 and the lower end surface 9a1 of the hub portion 9 (disk portion 9a) opposite to the thrust bearing surface 7a and under the bearing sleeve 8 An oil film of lubricating oil is formed in the thrust bearing gap between the end surface 8c (dynamic pressure groove forming region) and the upper end surface 10a of the flange portion 10 facing the end surface 8c by the dynamic pressure action of the dynamic pressure groove. The pressure of these oil films forms a first thrust bearing portion T1 and a second thrust bearing portion T2 that support the rotating member 3 in a non-contact manner in the thrust direction.

  As described above, by providing the axial communication groove 7d on the inner periphery of the housing 7, the thrust bearing gap of the second thrust bearing portion T2 located inside the lower end of the housing 7 and the housing via the communication groove 7d. 7 is in communication with the seal space S formed on the opening side. According to this, for example, the fluid (lubricating oil) pressure on the second thrust bearing portion T2 side is excessively increased or decreased for some reason, and the rotating member 3 is stably contactless in the thrust direction. It becomes possible to support.

  In this embodiment, the dynamic pressure groove 8a1 of the first radial bearing portion R1 is formed to be axially asymmetric (X1> X2) with respect to the axial center m (see FIG. 3). At the time of rotation, the lubricating oil pulling force (pumping force) by the dynamic pressure groove 8a1 is relatively larger in the upper region than in the lower region. Then, due to the differential pressure of the pulling force, the lubricating oil filled in the gap between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a of the shaft portion 2 flows downward, and the second thrust bearing portion T2 It circulates through a path of thrust bearing clearance → communication groove 7d → axial clearance between the upper end surface 8d and the lower end surface 9a1, and is drawn again into the radial bearing clearance of the first radial bearing portion R1. Thus, by providing the axial communication groove 7d on the inner periphery of the housing 7 so that the lubricating oil flows and circulates in the inner space of the housing 7, the pressure balance inside the bearings including the bearing gaps is obtained. Is maintained properly. Also, an undesirable flow of the lubricating oil in the bearing internal space, for example, a phenomenon in which the pressure of the lubricating oil becomes a negative pressure locally is prevented, and bubbles are generated due to the generation of the negative pressure. Problems such as leakage and vibration can be solved.

  The first embodiment of the present invention has been described above, but the present invention is not limited to this embodiment and can be applied to other configurations.

  FIG. 7 shows a hydrodynamic bearing device 1 ′ according to the second embodiment. The hydrodynamic bearing device 1 ′ in the figure differs from the hydrodynamic bearing device 1 in the first embodiment in that the shaft portion 2 has a constant diameter shaft shape and the housing 7 has a bottomed cylindrical shape. . Thereby, the thrust bearing gap is formed only between the thrust bearing surface 7a provided on the side portion 7g of the housing 7 and the lower end surface 9a1 of the hub portion 9 facing the thrust bearing surface 7a. In addition, about the site | part and member which make the structure and operation | movement same as 1st Embodiment, the same reference number is attached | subjected below and this description is abbreviate | omitted.

  The housing 7 constituting the hydrodynamic bearing device 1 'includes a cylindrical side portion 7g provided with a thrust bearing surface 7a at the upper end, and a bottom portion 7h provided at the lower end of the side portion 7g, and the side portion 7g and the bottom portion. 7h is integrally forged.

  Also in this embodiment, the lubricating oil flows and circulates in the internal space of the housing 7 through the axial communication groove 7 d provided on the inner periphery of the housing 7. That is, the lubricating oil between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a of the shaft portion 2 flows downward, and the axial clearance between the lower end surface 8c of the bearing sleeve 8 and the upper end surface 7h1 of the bottom portion 7h → communication. It circulates through the path of the groove 7d → the axial clearance between the upper end surface 8d and the lower end surface 9a1, and is drawn again into the radial bearing clearance of the first radial bearing portion R1. Thereby, the pressure balance inside a bearing including each bearing clearance is maintained appropriately.

  FIG. 8 shows a hydrodynamic bearing device 21 according to the third embodiment. In this embodiment, the rotating member 22 includes a shaft portion 22a and a flange portion 22b provided integrally or separately at the lower end of the shaft portion 22a. A substantially cylindrical seal member 29 is fixed to the inner periphery of the upper end portion of the housing 27. The seal member 29 forms a seal space S 'whose radial dimension is gradually enlarged upward between the inner peripheral surface 29a and the outer peripheral surface 22a1 of the shaft portion 22a opposite to the inner peripheral surface 29a.

The housing 27 is a forged metal product, and includes a cylindrical side portion 27a and a bottom portion 27b that is integrated with the side portion 27a and is positioned at the lower end of the side portion 27a. On the upper end surface 27b1 of the bottom 27b of the housing 27, for example, a spiral dynamic pressure groove is formed as a thrust bearing surface, although not shown. The upper end surface 8d of the bearing sleeve 8 is formed with a circumferential groove 8d1 that divides the upper end surface 8d in the radial direction over the entire circumference, and a plurality of diameters are formed from the circumferential groove 8d1 toward the inner peripheral side. A direction groove 8d2 is formed.

  When the rotating member 22 rotates, a thrust bearing gap of the thrust bearing portion T11 is formed between the lower end surface 8c of the bearing sleeve 8 and the upper end surface 22b1 of the flange portion 22b, and the upper end surface 22b1 of the bottom portion 27b of the housing 27 and the flange portion. A thrust bearing gap of the thrust bearing portion T12 is formed between the lower end surface 22b2 of 22b.

  Also in this embodiment, the lubricating oil flows and circulates in the internal space of the housing 27 through the communication groove 27 d provided on the inner periphery of the housing 27. That is, the lubricating oil between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 22a1 of the shaft portion 22a flows downward, and the axial clearance between the lower end surface 8c of the bearing sleeve 8 and the upper end surface 27b1 of the bottom portion 27b → the bearing. The radial bearing gap of the first radial bearing portion R1 is circulated through the path of the dynamic pressure groove on the lower end surface 8c of the sleeve 8 → the communication groove 27d → the circumferential groove 8d1 and the radial groove 8d2 on the upper end surface 8d of the bearing sleeve 8. Will be drawn again. Thereby, the pressure balance inside a bearing including each bearing clearance is maintained appropriately.

  FIG. 9 shows a hydrodynamic bearing device 21 ′ according to the fourth embodiment. The hydrodynamic bearing device 21 ′ in the figure has a point that the seal member 29 is formed integrally with the side portion 27 a of the housing 27, and the bottom portion 27 b of the housing 27 is separated from the side portion 27 a, and this is inside the lower end of the side portion 27 a. The configuration is different from that of the hydrodynamic bearing device 1 according to the third embodiment in that it is fixed to the peripheral surface 27c1. In addition, about the site | part and member which has the same shape and effect | action as 3rd Embodiment, the same code | symbol is attached | subjected and this description is abbreviate | omitted.

  Also in this embodiment, the lubricating oil flows and circulates in the internal space of the housing 27 through the communication groove 27 d provided on the inner periphery of the housing 27. Therefore, the pressure balance inside the bearings including the bearing gaps can be maintained appropriately.

  Although not shown, the housing 27 is of a double-end open type, and the sealing member 29 and the bottom 27b are formed separately and fixed to the inner periphery of the upper end and the inner periphery of the lower end of the housing 27, respectively. The invention can be applied.

  In the above embodiments (first to fourth embodiments), the case where the housing 7 (27) is forged with a relatively hard metal such as stainless steel has been exemplified. The present invention can be similarly applied to the case of forging with a soft metal.

  In the above embodiment, the axial communication groove 7d (27d) formed on the inner periphery of the housing 7 (27) is exemplified as having a triangular cross section. Of course, other groove shapes (grooves) (Cross-sectional shape). This is because the inner periphery of the communication groove 7d (27d) formed by forging is a plastic working surface, and its surface roughness is good, so that there is a slight difference in the flowability of the lubricating oil due to the difference in cross-sectional shape. Even so, it is possible to ensure a smooth flow of the fluid in the communication groove 7d (27d). Further, the number of communication grooves 7d (27d) is not limited to three as shown in the figure, but may be two or four or more for the same reason.

  In the above embodiment, a dynamic pressure generating portion (for example, dynamic pressure grooves 8a1 and 8a2) for generating a fluid dynamic pressure action in each bearing gap is provided on the member side facing the rotating member 3 in each bearing gap. However, it can be provided on the rotating member 3 side. For example, the dynamic pressure groove 8a1, 8a2 formation region provided on the inner peripheral surface 8a of the bearing sleeve 8 and the dynamic pressure groove formation region provided on the lower end surface 8c are arranged on the outer peripheral surface 2a of the opposed shaft portion 2 (22a). It can also be provided on the upper end surface 10a of the flange portion 10 (22b). According to this, since the entire surface of the bearing sleeve 8 can be made smooth, it is not necessary to provide a molding site corresponding to the communication groove 7d, the dynamic pressure groove 8a1, etc. in the molding die. Further simplification and cost reduction can be achieved.

  Further, in the above embodiment, as the dynamic pressure bearings constituting the radial bearing portions R1 and R2 and the thrust bearing portions T1 and T2, for example, a dynamic pressure generating portion including a herringbone shape or a spiral shape dynamic pressure groove is used. Although the bearing is illustrated, the configuration of the dynamic pressure generating unit is not limited to this. As the radial bearing portions R1 and R2, for example, multi-arc bearings, step bearings, taper bearings, taper / flat bearings, and the like can be used.

  One or both of the thrust bearing portions T1 and T2, for example, are not shown in the figure, but 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 step bearing, a so-called corrugated bearing (the corrugated step mold) or the like.

  Moreover, although the radial bearing part R1 and R2 and the thrust bearing part T1 and T2 were comprised by the dynamic pressure bearing in the above embodiment, it can also comprise by bearings other than this. For example, the inner peripheral surface 8a of the bearing sleeve 8 serving as a radial bearing surface is a perfect circular inner peripheral surface not provided with dynamic pressure generating portions such as the dynamic pressure grooves 8a1 and 8a2, and the shaft portion 2 facing the inner peripheral surface is formed. A so-called perfect circle bearing can be constituted by the perfect circular outer peripheral surface 2a. Alternatively, the thrust bearing portions T1 and T2 can be constituted by pivot bearings. Of course, the structure concerning the above thrust bearing portions T1 and T2 can be similarly applied to the thrust bearing portions T11 and T12.

  In the above embodiment, the fluid bearing device 1 (21) is filled, and the radial bearing gap between the bearing sleeve 8 and the shaft portion 2, the bearing sleeve 8 and the shaft portion 2, or the housing is filled. As the fluid that forms the lubricating film in the thrust bearing gap between the rotary member 3 and the rotating member 3 (hub portion 9), the lubricating oil is exemplified, but other fluids that can form the lubricating film in the bearing gaps other than that, for example, It is also possible to use a fluid lubricant such as a gas such as air or a fluid such as a magnetic fluid, or lubricating grease.

It is sectional drawing of the spindle motor for information devices incorporating the hydrodynamic bearing apparatus which concerns on 1st Embodiment of this invention. It is sectional drawing of a hydrodynamic bearing apparatus. It is a longitudinal cross-sectional view of a bearing sleeve. It is a figure which shows the upper end surface of a housing. It is the schematic which shows an example of the manufacturing process of a housing. It is AA sectional drawing of the metal mold | die for forging. It is sectional drawing of the hydrodynamic bearing apparatus which concerns on 2nd Embodiment of this invention. It is sectional drawing of the hydrodynamic bearing apparatus which concerns on 3rd Embodiment of this invention. It is sectional drawing of the hydrodynamic bearing apparatus which concerns on 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1 'Fluid bearing apparatus 2 Shaft part 3 Rotating member 4 Stator coil 5 Rotor magnet 6 Motor bracket 7 Housing 7' Housing material 7a Thrust bearing surface 7a1 Dynamic pressure groove 7c Fixed surface 7d Communication groove 8 Bearing sleeve 8a1 Dynamic pressure groove 8d1 Circumferential groove 8d2 Radial groove 9 Hub portion 10 Flange portion 18a1 Surface forming portion 18a2 Groove forming portion 21, 21 ′ Fluid bearing device 22 Rotating member 22b Flange portion 27 Housing 27a Side portion 27b Bottom portion 27d Axial groove 29 Seal member S, S 'seal space R1, R2 radial bearing part T1, T2, T11, T12 thrust bearing part

Claims (5)

It has a bearing sleeve made of sintered metal, a housing having a cylindrical shape and a fixed surface for fixing the outer peripheral surface of the bearing sleeve on the inner periphery, and a shaft portion inserted into the inner periphery of the bearing sleeve. The rotating member that rotates relative to the bearing sleeve and the housing, and the lubricating film of fluid generated in the radial bearing gap between the outer peripheral surface of the shaft portion and the inner peripheral surface of the bearing sleeve support the rotating member in the radial direction in a non-contact manner. In a hydrodynamic bearing device including a radial bearing portion,
The outer peripheral surface of the bearing sleeve is a smooth cylindrical surface having no communication groove, and the entire surface is formed by sizing,
The housing has a shape with one axial end open,
An axial communication groove is formed in the inner periphery of the housing so as to communicate between both end faces of the bearing sleeve and allow the fluid to flow therethrough, and an axial end portion of the communication groove on the housing opening side faces in the axial direction. A hydrodynamic bearing device, characterized in that it is open and the fixed surface and the communication groove are both plastically processed by forging. 2. The hydrodynamic bearing device according to claim 1, wherein the housing does not have a portion that closes the axial end of the communication groove closer to the housing opening side than the axial end of the communication groove. The hydrodynamic bearing device according to claim 1, wherein the communication groove has a triangular cross section.   The fluid according to claim 1, further comprising a seal space provided on one end opening side of the housing and opened to the atmosphere side, wherein fluid is circulated between the inside of the other end of the housing and the seal space via the communication groove. Bearing device. A spindle motor of a disk device having the hydrodynamic bearing device according to any one of claims 1 to 4 .

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