JP4588561B2 - Hydrodynamic bearing device - Google Patents

Description

  The present invention relates to a hydrodynamic bearing device that supports a shaft member in a non-contact manner by a hydrodynamic action of a fluid generated in a bearing gap. This hydrodynamic bearing device is a spindle of information equipment, for example, a magnetic disk device such as an HDD, an optical disk device such as a CD-ROM, CD-R / RW, DVD-ROM / RAM, or a magneto-optical disk device such as an MD or MO. It is suitable for motors, polygon scanner motors of laser beam printers (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 hydrodynamic bearing having characteristics excellent in the required performance has been studied or actually used. Yes.

  For example, in a hydrodynamic bearing device incorporated in a spindle motor of a disk drive device such as an HDD, both the radial bearing portion that supports the shaft member in the radial direction and the thrust bearing portion that supports the axial direction are configured by the hydrodynamic bearing. There is. As a thrust bearing portion in this type of dynamic pressure bearing device, for example, a dynamic pressure groove as a dynamic pressure generating portion is formed on an end surface of the bearing sleeve, and an end surface of the bearing sleeve and an end surface of the flange portion opposed to the end surface A thrust bearing gap is formed between the two (see, for example, Patent Document 1).

  In addition, an axial groove is formed on the outer peripheral surface of the bearing sleeve for the purpose of circulating a fluid such as lubricating oil between both end faces of the bearing sleeve and maintaining the pressure balance inside the bearing including the thrust bearing gap. Is known (see, for example, Patent Document 2).

On the other hand, for the purpose of appropriately controlling the thrust bearing gap and obtaining a stable thrust support force, there is known one provided with a step portion on the inner periphery of a housing for fixing the bearing sleeve. According to this, when the bearing sleeve is fixed to the inner periphery of the housing by means of, for example, press-fitting or bonding, the bearing sleeve is moved until the one end surface of the bearing sleeve comes into contact with the contact surface provided in the housing in the axial direction. By pushing into the inner periphery, the axial positioning of the bearing sleeve with respect to the housing is performed accurately and simply (see, for example, Patent Document 3).
JP 2003-239951 A JP 2003-232353 A JP 2002-061637 A

  By the way, in the hydrodynamic bearing device provided with this kind of contact surface, a dynamic pressure generating portion provided on one end surface of the bearing sleeve that contacts the contact surface, for example, a plurality of dynamic pressure grooves arranged in a predetermined shape is provided. The thrust bearing gap between the one end surface of the bearing sleeve provided with the dynamic pressure generating portion and the end surface of the flange portion facing the bearing sleeve communicates with the fluid flow path.

  However, as described above, since the axial positioning of the bearing sleeve is usually performed with some pressure input (pushing force), the abutment surface is elastically deformed depending on the pushing force, In some cases, the dynamic pressure groove on the end surface of the bearing sleeve that abuts against this is blocked.

  In this case, even if axial flow is ensured in the fluid flow path, the fluid pressure groove portion is blocked, so that, for example, radial fluid flow is provided between the thrust bearing gap and the fluid flow path. There is a risk that the smooth flow of the fluid inside the bearing may be hindered. This type of problem is particularly noticeable when the contact surface is formed of a soft material, such as a resin material, as compared with a metal bearing sleeve.

  An object of the present invention is to provide a fluid dynamic bearing device capable of ensuring fluid flow inside the bearing and stably exhibiting high bearing performance.

In order to solve the above problems, the present invention provides a housing, a bearing sleeve fixed to the inner periphery of the housing and provided with a dynamic pressure generating portion on one end surface, a shaft member that rotates relative to the housing and the bearing sleeve, A thrust bearing portion for supporting the shaft member in a thrust non-contact manner by a dynamic pressure action of a fluid generated in a thrust bearing gap between the one end surface of the bearing sleeve and the shaft member opposed thereto; an inner periphery of the housing; and a bearing sleeve A plurality of dynamic pressure grooves as a dynamic pressure generating portion are arranged on one end face of the bearing sleeve , provided with a fluid flow path that is provided between the outer circumference and allows fluid to flow between both end faces of the bearing sleeve. is the region forming the housing is formed in a shape having a bottom integrally with a resin material, the bearing sleeve is fixed in press-fit or press-bonded to the inner peripheral surface of the housing, the housing, the shaft Abutment surface is provided for by contact with one end surface of the sleeve for positioning in the axial direction of the bearing sleeve relative to the housing, by pushing towards the bearing sleeve on the bottom side of the housing, one end face of the bearing sleeve and those The abutting contact surface is elastically deformed, and the thrust bearing gap and the fluid flow path are communicated with the abutting surface , and a radial groove having a groove depth larger than the dynamic pressure groove is provided. Provided is a hydrodynamic bearing device characterized by being formed.

  As described above, in the present invention, the radial groove that communicates between the thrust bearing gap and the fluid flow path is formed on the contact surface of the housing. According to this, as described above, the dynamic pressure groove (dynamic pressure generating portion) on the end surface of the bearing sleeve is prevented from being blocked by the contact surface that is elastically deformed due to the pushing force, and the fluid inside the bearing is smooth. Secure distribution. Therefore, the pressure balance of the fluid inside the bearing is properly maintained, and stable bearing performance can be exhibited over a long period of time.

  Also, this type of radial groove can be formed integrally with the housing, for example, by resin or metal injection molding. Thereby, the radial groove can be formed with high accuracy and at low cost. In addition, after molding the housing body, it eliminates the need for machining such as cutting and avoids the generation of chips, simplifying the cleaning work after molding, improving the work efficiency and preventing the occurrence of contamination. Can be achieved.

  The radial groove is particularly effective when a dynamic pressure generating portion provided on one end surface of the bearing sleeve is composed of a plurality of dynamic pressure grooves arranged in a predetermined shape. In other words, the dynamic pressure groove formed as the dynamic pressure generating portion is not so deep as several μm to several tens of μm, and may be easily blocked by the contact surface that has undergone elastic deformation. . On the other hand, if the radial groove is formed on the contact surface of the housing as in the present invention, the groove depth can be made larger than that of the dynamic pressure groove. Therefore, it is possible to reliably avoid the situation where the dynamic pressure groove is blocked by the elastic deformation of the contact surface, and appropriately set the size of the radial groove (groove depth) according to the fluid flow rate inside the bearing. can do.

  The fluid flow path formed between the inner periphery of the housing and the outer periphery of the bearing sleeve can be constituted by, for example, an axial groove formed on the outer periphery of the bearing sleeve, and the shaft formed on the inner periphery of the housing It can also consist of directional grooves. In the latter case, both the axial groove and the radial groove are molded integrally with the housing, thereby simplifying the machining process and further reducing the cost. In addition, by making the formation position of these axial grooves and the formation position of the radial grooves coincide with each other in the circumferential direction, a situation in which the fluid flow path of the fluid is blocked or detoured is avoided, and the fluid is more efficiently flowed. Can be distributed.

  The fluid dynamic bearing device having the above-described configuration can also be provided as a spindle motor of a disk device including the fluid dynamic bearing device.

  As described above, according to the present invention, it is possible to provide a fluid dynamic bearing device capable of ensuring fluid flow inside the bearing and stably exhibiting high bearing performance at low cost.

  Hereinafter, an 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 fluid dynamic bearing device 1 according to an embodiment of the present invention. This spindle motor is used in a disk drive device such as an HDD, and is opposed to the hydrodynamic bearing device 1 that rotatably supports the shaft member 2 to which the disk hub 3 is attached via a radial gap, 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 disk hub 3. The housing 7 of the hydrodynamic bearing device 1 is fixed to the inner periphery of the motor bracket 6. The disk hub 3 holds one or a plurality of disk-shaped information recording media (hereinafter simply referred to as disks) D 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 D held by the hub 3 rotates integrally with the shaft member 2.

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a housing 7 having a bottom portion 7b, a bearing sleeve 8 fixed to the housing 7, and a shaft member 2 that rotates relative to the housing 7 and the bearing sleeve 8 as main components. Is done. For convenience of explanation, the bottom 7b side of the housing 7 will be described below, and the side opposite to the bottom 7b will be described as the upper side.

  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 addition, the shaft member 2 can also have a hybrid structure of a metal material and a resin material. In this case, the sheath portion including at least the outer peripheral surface 2a1 of the shaft portion 2a is formed of the metal, and the remaining portion (for example, the shaft portion) The core part of the part 2a and the flange part 2b) are formed of resin. In order to secure the strength of the flange portion 2b, the flange portion 2b can be made of a resin / metal hybrid structure, and the core portion of the flange portion 2b can be made of metal together with the sheath portion of the shaft portion 2a.

  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. Of course, the bearing sleeve 8 can be formed of a material other than metal, such as resin or ceramic, regardless of whether it is non-porous or porous.

  As shown in FIG. 3A, for example, as shown in FIG. 3A, a plurality of dynamic pressure grooves 8a1 and 8a2 are arranged in a herringbone shape on the entire inner surface 8a of the bearing sleeve 8 or a partial cylindrical region. The two regions are formed at two positions apart in the axial direction. The formation region of the dynamic pressure grooves 8a1 and 8a2 is a radial bearing surface that faces the outer peripheral surface 2a1 of the shaft portion 2a, and when the shaft member 2 rotates, between the outer peripheral surface 2a1 and radial bearing portions R1 and R2 described later. A radial bearing gap is formed (see FIG. 2). In the formation region of the upper dynamic pressure groove 8a1, the dynamic pressure groove 8a1 is formed 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 area above m is larger than the axial dimension X2 of the lower area.

  On the outer peripheral surface 8b of the bearing sleeve 8, one or more grooves 10b extending in the axial direction are formed over the entire length in the axial direction. In this embodiment, three axial grooves 10b are formed at equal intervals in the circumferential direction. These axial grooves 10b constitute a fluid flow path for lubricating oil between the bearing sleeve 8 and the inner peripheral surface 7c of the opposing housing 7 in a state where the bearing sleeve 8 is fixed to the inner periphery of the housing 7 (see FIG. 2). . Further, these axial grooves 10b are provided simultaneously with the green compacting of the bearing sleeve 8 main body by providing a portion corresponding to the axial groove 10b in advance in a green compact forming die forming the main body of the bearing sleeve 8 for example. Can be molded.

  As shown in FIG. 3B, a region where a plurality of dynamic pressure grooves 8c1 are arranged in a spiral shape is formed as a thrust dynamic pressure generating portion on the entire lower surface 8c of the bearing sleeve 8 or a partial annular region. The The formation region of the dynamic pressure groove 8c1 is a thrust bearing surface that faces the upper end surface 2b1 of the flange portion 2b, and a thrust bearing of a second thrust bearing portion T2, which will be described later, between the upper end surface 2b1 when the shaft member 2 rotates. A gap is formed (see FIG. 2).

  As shown in FIG. 3A, a circumferential groove 8d1 having a V-shaped cross section is formed over the entire circumference of the upper end surface 8d of the bearing sleeve 8 at a substantially central portion in the radial direction. One or a plurality of radial grooves 8d2 are formed in the inner diameter side region of the upper end surface 8d defined by the circumferential groove 8d1. As shown in FIG. 2, the radial groove 8 d 2 communicates between the circumferential groove 8 d 1 and the upper end of the inner peripheral surface 8 a of the bearing sleeve 8 when the seal portion 9 is in contact with the bearing sleeve 8.

  The housing 7 is injection-molded with a resin composition based on a crystalline resin such as LCP, PPS, or PEEK, or an amorphous resin such as PSU, PES, or PEI. For example, as shown in FIG. 7a and a bottom portion 7b formed integrally with the lower end of the side portion 7a. Examples of the resin composition forming the housing 7 include fibrous fillers such as glass fibers, whisker-like fillers such as potassium titanate, scaly fillers such as mica, carbon fibers, carbon black, graphite, carbon A material in which an appropriate amount of a fibrous or powdery conductive filler such as nanomaterials or various metal powders is blended with the base resin according to the purpose can be used.

  As shown in FIG. 4, for example, as shown in FIG. 4, a region where a plurality of dynamic pressure grooves 7b11 are arranged in a spiral shape is formed on the entire upper surface 7b1 of the bottom portion 7b or a partial annular region. The formation region of the dynamic pressure groove 7b11 is a thrust bearing surface that faces the lower end surface 2b2 of the flange portion 2b, and a thrust bearing of a second thrust bearing portion T2, which will be described later, between the lower end surface 2b2 when the shaft member 2 rotates. A gap is formed (see FIG. 2).

  The outer peripheral surface 8b of the bearing sleeve 8 is fixed to the inner peripheral surface 7c of the housing 7 by appropriate means such as bonding (including loose bonding and press-fitting bonding), press-fitting, and welding.

  A small diameter portion 7d having a smaller diameter than the side portion 7a is formed at the lower end of the inner peripheral surface 7c. In this embodiment, the step between the inner peripheral surface 7d1 of the small diameter portion 7d and the inner peripheral surface 7c of the side portion 7a is in contact with the lower end surface 8c provided with the dynamic pressure generating portion of the bearing sleeve 8. It becomes. Thereby, the axial dimension of the small diameter portion 7d is the axial direction from the lower end surface 8c of the bearing sleeve 8 to the upper end surface 7b1 of the bottom portion 7b when the lower end surface 8c of the bearing sleeve 8 is in contact with the contact surface 7e. Match the width.

  One or a plurality of radial grooves 10a extending radially are formed on the contact surface 7e serving as the upper end surface of the small diameter portion 7d. In this embodiment, three radial grooves 10a are provided at equal intervals in the circumferential direction as shown in FIG. These radial grooves 10a communicate with the upper end surface 8d of the bearing sleeve 8 through the axial groove 10b when the lower end surface 8c of the bearing sleeve 8 is in contact with the contact surface 7e. Further, the inner diameter end of the radial groove 10a has an axial gap (first gap) between the lower end surface 8c of the bearing sleeve 8 and the upper end surface 2b1 of the flange portion 2b via the radial gap between the small diameter portion 7d and the flange portion 2b. It also communicates with a thrust bearing gap of the thrust bearing portion T1 (see FIG. 2 for both). These radial grooves 10a, for example, together with the dynamic pressure grooves 7b11 on the upper end surface 7b1 of the bottom portion 7b, are formed on the required portions of the mold for forming the housing 7 (the portions for forming the contact surface 7e and the upper end surface 7b1). By processing the groove mold for forming the 10 a and the dynamic pressure groove 7 b 11, the mold can be formed simultaneously with the housing 7.

  With the bearing sleeve 8 inserted into the inner periphery of the housing 7 in which the small-diameter portion 7d and the contact surface 7e having the above structure are formed, and with the shaft member 2 inserted into the inner periphery thereof, the inner periphery of the housing 7 is provided with a predetermined press-fitting allowance. Then, when the lower end surface 8c of the bearing sleeve 8 comes into contact with the upper end surface of the small diameter portion 7d, that is, the contact surface 7e, the axial position of the bearing sleeve 8 with respect to the housing 7 is determined. Thereafter, for example, the outer peripheral surface 8 b of the bearing sleeve 8 is bonded and fixed to the inner peripheral surface 7 c of the housing 7 by solidifying an adhesive previously applied to the inner peripheral surface 7 c of the housing 7. At this time, even if the resin contact surface 7e is elastically deformed as the bearing sleeve 8 is pushed downward, and the dynamic pressure groove 8c1 provided on the lower end surface 8c is closed, the contact surface The radial groove 10a provided on the 7e side ensures a communication state between the axial groove 10b and the region serving as the thrust bearing gap. For the above-described reason, the dynamic pressure groove 8c1 positioned at the contact portion of the lower end surface 8c of the bearing sleeve 8 with the contact surface 7e can be omitted.

  In this embodiment, the bearing sleeve 8 is fixed to the inner periphery of the housing 7 so that the positions of the radial groove 10a and the axial groove 10b coincide with each other in the circumferential direction. The circumferential direction positions of the grooves 10a are not necessarily matched, and may be shifted in the circumferential direction. In this case, the fluid (lubricating oil) between the radial groove 10a and the axial groove 10b flows through the chamfer 8e provided on the outer periphery of the lower end of the bearing sleeve 8, the contact surface 7e, and the inner periphery of the side portion 7a. This is done through a gap between the surface 7c (see FIG. 2).

  As shown in FIG. 2, the seal portion 9 as a sealing means is formed separately from the housing 7 with, for example, a metal material or a resin material, and is press-fitted, adhered, welded to the inner periphery of the upper end portion of the side portion 7a of the housing 7, It is fixed by means such as welding. In this embodiment, the seal portion 9 is fixed in a state where the lower end surface 9b of the seal portion 9 is in contact with the upper end surface 8d of the bearing sleeve 8 (see FIG. 2).

  A taper surface is formed on the inner peripheral surface 9a of the seal portion 9, and the radial dimension gradually increases between the taper surface and the outer peripheral surface 2a1 of the shaft portion 2a facing the taper surface. An expanding annular seal space S is formed. Lubricating oil is injected into the internal space of the housing 7 sealed by the seal portion 9, and the inside of the housing 7 is filled with the lubricating oil (a dotted area in FIG. 2). In this state, the oil level of the lubricating oil is maintained within the range of the seal space S.

  In the dynamic pressure bearing device 1 configured as described above, when the shaft member 2 rotates, the radial bearing surface of the bearing sleeve 8 (the dynamic pressure grooves 8a1 and 8a2 forming region of the inner peripheral surface 8a) is radially aligned with the outer peripheral surface 2a1 of the shaft portion 2a. Opposing through the bearing gap. As the shaft member 2 rotates, the lubricating oil in the radial bearing gap is pushed toward the axial center m of the dynamic pressure grooves 8a1 and 8a2, and the pressure rises. By such dynamic pressure action of the dynamic pressure grooves 8a1 and 8a2, 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.

  At the same time, the thrust bearing clearance between the thrust bearing surface of the bearing sleeve 8 (the dynamic pressure groove 8c1 formation region of the lower end surface 8c) and the upper end surface 2b1 of the flange portion 2b opposed thereto, and the thrust bearing surface of the housing 7 In the thrust bearing gap between the (lower region 2b2 formation region of the upper end surface 7b1) and the lower end surface 2b2 of the flange portion 2b facing this, an oil film of lubricating oil is formed by the dynamic pressure action of the dynamic pressure grooves 7b11, 8c1, respectively. It is formed. The pressure of these oil films forms a first thrust bearing portion T1 and a second thrust bearing portion T2 that support the shaft member 2 in a non-contact manner in the thrust direction. At this time, the thrust bearing gap (total) of the first and second thrust bearing portions T1, T2 is always set to a value obtained by subtracting the axial width of the flange portion 2b from the axial width of the small diameter portion 7d. Thereby, both thrust bearing clearances (total) are managed with high accuracy.

  As described above, the axial grooves 10b serving as the fluid flow paths between the both end faces of the bearing sleeve 8 are provided on the outer periphery of the bearing sleeve 8, and the radial grooves 10a are provided on the contact surface 7e of the housing 7, whereby these axial directions are provided. Via the groove 10b and the radial groove 10a, the thrust bearing gaps of the thrust bearing portions T1 and T2 located inside the lower end of the housing 7 and the seal space S formed on the opening side of the housing 7 are in communication with each other. Become. According to this, for example, the shaft (2) is stably non-contacted in the thrust direction while avoiding a situation in which the fluid (lubricating oil) pressure on the thrust bearing portions T1, T2 side is excessively increased or decreased for some reason. It becomes possible to support.

  Further, 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 2a1 of the shaft portion 2a flows downward, and the first thrust bearing portion T1 Thrust bearing clearance → radial groove 10a → axial groove 10b → axial clearance between upper end face 8d and lower end face 9b outer diameter side region → circumferential groove 8d1 → radial groove 8d2 It is drawn again into the radial bearing gap of the one radial bearing portion R1. In this way, by configuring the lubricating oil to flow and circulate in the internal space of the housing 7, the pressure balance inside the bearings including the bearing gaps is properly maintained. 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.

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

  In the above-described embodiment, the case where the axial groove 10b is provided on the outer peripheral surface 8b of the bearing sleeve 8 has been described. However, the axial groove 10b serves as a fluid flow path between the inner periphery of the housing 7 and the outer periphery of the bearing sleeve 8. For example, as shown in FIG. 5, it may be formed on the inner peripheral surface 7 c of the housing 7. In this case, since both the radial groove 10a and the axial groove 10b for circulating and circulating the fluid inside the bearing can be formed on the housing 7 side, the axial direction is formed on the outer peripheral surface 8b of the bearing sleeve 8. The trouble of forming the groove 10b can be saved. In particular, when the bearing sleeve 8 is formed of sintered metal, this type of groove forming is performed simultaneously with the forming of the green compact, so that it corresponds to the axial groove 10b for the die or punch of the green mold. However, by providing it on the housing 7 side, the mold can be simplified and the cost can be reduced.

  In the above embodiment, the case where the contact surface 7e on which the radial groove 10a is formed is provided integrally with the housing 7 is described. However, the present invention is not particularly limited to this configuration. 7 can be provided separately. For example, FIG. 6 illustrates a case where the bottom 7b of the housing 7 is formed separately from the side 7a of the housing 7 and a contact surface 7e is provided on the bottom 7b. In the figure, the contact surface 7e constitutes the upper end surface of a cylindrical protruding portion 7f protruding from the outer periphery of a separate bottom portion 7b toward the bearing sleeve 8 (upward in the figure). The seal portion 9 is formed integrally with the housing 7 by, for example, resin injection molding.

  In this case, the bearing sleeve 8 is fixed to the inner periphery of the housing 7 in a state where the upper end surface 8d is in contact with the lower end surface 9b of the seal portion 9 formed integrally with the side portion 7a. Then, the bottom portion 7b as a separate body is pushed into the inner periphery of the housing 7, and the axial position of the bearing sleeve 8 relative to the housing 7 is determined when the lower end surface 8c of the bearing sleeve 8 abuts against the abutment surface 7e of the bottom portion 7b. decide. Then, for example, the bottom portion 7 b is bonded and fixed to the inner periphery of the housing 7 by solidifying an adhesive previously applied to the inner peripheral surface 7 c of the housing 7.

  As described above, even when the bottom portion 7b as a separate body is fixed to the housing 7, by providing the radial groove 10a on the contact surface 7e side, the dynamic pressure groove 8c1 is closed due to the pressing of the bottom portion 7b. Regardless of the presence or absence of this, it is possible to ensure the communication state between the axial groove 10b and the region serving as the thrust bearing gap. Therefore, the pressure balance inside the bearing can always be maintained and stable bearing performance can be exhibited.

  Moreover, although the case where the circumferential direction groove | channel 8d1 and the radial direction groove | channel 8d2 were provided in the side of the bearing sleeve 8 was illustrated in the above embodiment, these grooves can also be provided in the side of the seal part 9 which opposes. According to this, since all the outer surfaces of the bearing sleeve 8 excluding the inner peripheral surface 8a and the lower end surface 8c can be made smooth, the molding die can be further simplified and the cost can be further reduced. be able to. Furthermore, by providing the dynamic pressure grooves 8a1, 8a2, 8c1 formed on the inner peripheral surface 8a and the lower end surface 8c on the side of the opposing shaft member 2, the outer surface of the bearing sleeve 8 is all made smooth. You can also.

  Moreover, although the radial direction groove | channel 10a formed in the housing 7 illustrated what made the cross-section V shape in the above embodiment, of course, it is also possible to set it as other groove shapes (groove cross-sectional shape). . Further, the number of the radial grooves 10a is not limited to three as shown in the figure, and two or four or more may be provided. Further, the location where the radial groove 10a is provided can be made of resin or metal, and as a molding method, for example, resin or metal injection molding, metal press molding, forging molding or the like can be adopted.

  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.

  For example, so-called step bearings or multi-arc bearings may be employed as the radial bearing portions R1 and R2. In addition, although the example shown below has illustrated the case where all provide the dynamic-pressure generation | occurrence | production part in the inner peripheral surface 8a of the bearing sleeve 8, as above-mentioned, these dynamic-pressure generation | occurrence | production parts are connected to the inner peripheral surface. You may provide in the outer peripheral surface 2a1 of the axial part 2a facing 8a.

  FIG. 7 shows an example of a case where one or both of the radial bearing portions R1 and R2 are constituted by multi-arc bearings. In the same figure, the area | region used as the radial bearing surface of the internal peripheral surface 8a of the bearing sleeve 8 is comprised by several arc surface 8a3 (this figure 3 arc surface). Each arc surface 8a3 is an eccentric arc surface centered at a point offset from the rotation axis O by an equal distance, and is formed at equal intervals in the circumferential direction. An axial separation groove 8a4 is formed between each eccentric arc surface 8a3.

  By inserting the shaft portion 2a of the shaft member 2 into the inner peripheral surface 8a of the bearing sleeve 8, the eccentric arc surface 8a3 and the separation groove 8a4 of the bearing sleeve 8 and the perfect circular outer peripheral surface 2a1 of the shaft portion 2a are interposed. The radial bearing gaps of the first and second radial bearing portions R1 and R2 are respectively formed. In the radial bearing gap, a region formed by the eccentric arc surface 8a3 and the perfect circular outer peripheral surface 2a1 is a wedge-shaped gap 8a5 in which the gap width is gradually reduced in the circumferential direction. The reduction direction of the wedge-shaped gap 8a5 coincides with the rotation direction of the shaft member 2.

  FIG. 8 shows another embodiment of the multi-arc bearing that constitutes the first and second radial bearing portions R1, R2. In this embodiment, in the configuration shown in FIG. 7, the predetermined area θ on the minimum gap side of each eccentric arc surface 8a3 is configured by a concentric arc centering around the rotation axis O. Accordingly, the radial bearing gap (minimum gap) 8a6 in each predetermined region θ is constant. The multi-arc bearing having such a configuration may be referred to as a tapered flat bearing.

  In FIG. 8, a region that is a radial bearing surface of the inner peripheral surface 8 a of the bearing sleeve 8 is formed by three arc surfaces 8 a 7, and the centers of the three arc surfaces 8 a 7 are offset from the rotation axis O by an equal distance. Yes. In each region defined by the three eccentric arc surfaces 8a7, the radial bearing gap 8a8 has a shape that is gradually reduced with respect to both circumferential directions.

  The multi-arc bearings of the first and second radial bearing portions R1 and R2 described above are all so-called three-arc bearings, but are not limited thereto, so-called four-arc bearings, five-arc bearings, and more than six arcs. You may employ | adopt the multi-arc bearing comprised by the several circular arc surface. Further, in addition to the configuration in which the two radial bearing portions are separated from each other in the axial direction as in the radial bearing portions R1 and R2, one radial bearing portion extends over the upper and lower regions of the inner peripheral surface 8a of the bearing sleeve 8. It is good also as a structure which provided.

  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. A step bearing or a corrugated bearing (the step mold is a corrugated one) can also be used.

  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 the dynamic pressure groove 8a1 or the circular arc surface 8a3 as a dynamic pressure generating portion, and the shaft portion opposed to the inner peripheral surface A so-called perfect circle bearing can be constituted by the perfect circular outer peripheral surface 2a1 of 2a.

  Further, in the above embodiment, 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. In addition, 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 for information equipment incorporating a fluid dynamic bearing device according to an embodiment of the present invention. It is sectional drawing of a hydrodynamic bearing apparatus. (A) is a longitudinal cross-sectional view of a bearing sleeve, (b) is a bottom end view. It is AA sectional drawing of a housing. It is a figure which shows the other structural example of a hydrodynamic bearing apparatus. It is a figure which shows the other structural example of a hydrodynamic bearing apparatus. It is a figure which shows the other structural example of a radial bearing part. It is a figure which shows the other structural example of a radial bearing part. It is a figure which shows the other structural example of a radial bearing part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing apparatus 2 Shaft member 2a Shaft part 2b Flange part 3 Disc hub 4 Stator coil 5 Rotor magnet 7 Housing 7a Side part 7b Bottom part 7c Inner peripheral surface 7d Small diameter part 7e Contact surface 8 Bearing sleeve 8a Inner peripheral surface 8a1, 8a2 Dynamic pressure grooves 8a3, 8a7 Eccentric arc surface 8b Outer peripheral surface 8c Lower end surface 8c1 Dynamic pressure groove 8d Upper end surface 8d1 Circumferential groove 8d2 Radial groove 9 Seal portion 10a Radial groove 10b Axial groove S Seal space R1, R2 Radial bearing T1, T2 Thrust bearing

Claims (7)

A housing, a bearing sleeve fixed to the inner periphery of the housing and provided with a dynamic pressure generating portion on one end face, a shaft member that rotates relative to the housing and the bearing sleeve, an end face of the bearing sleeve, and a shaft facing the shaft A thrust bearing portion that supports the shaft member in a non-contact manner in the thrust direction by the dynamic pressure action of the fluid generated in the thrust bearing gap between the member and the inner periphery of the housing and the outer periphery of the bearing sleeve. In what has a fluid flow path that allows fluid to flow between both end faces,
On one end face of the bearing sleeve, a region in which a plurality of dynamic pressure grooves as dynamic pressure generating portion is formed,
The housing is formed of a resin material in a shape having an integral bottom, and a bearing sleeve is fixed to the inner peripheral surface of the housing by press-fitting or press-fitting adhesion,
The housing, the abutment surface is provided for positioning in the axial direction of the bearing sleeve relative to the housing by contact with one end face in the axial direction of the bearing sleeve, by pushing towards the bearing sleeve on the bottom side of the housing, The abutting surface that abuts one end surface of the bearing sleeve is elastically deformed, and the thrust bearing gap and the fluid passage are communicated with the abutting surface , and the groove depth is larger than that of the dynamic pressure groove. A hydrodynamic bearing device characterized in that a large radial groove is formed.   The hydrodynamic bearing device according to claim 1, wherein the fluid flow path is configured by an axial groove formed on an outer periphery of the bearing sleeve.   The fluid dynamic bearing device according to claim 1, wherein the fluid flow path is configured by an axial groove formed in an inner periphery of the housing.   4. The hydrodynamic bearing device according to claim 2, wherein positions of the axial groove and the radial groove coincide with each other in the circumferential direction.   The hydrodynamic bearing device according to claim 1, wherein the radial groove is molded integrally with the housing.   The hydrodynamic bearing device according to claim 5, wherein the housing is formed by resin injection molding. A spindle motor of a disk device comprising the fluid dynamic bearing device according to any one of claims 1 to 6 .

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