JP2006300178A - Fluid bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid bearing device capable of preventing pressure difference of lubricating oil in the fluid bearing device. <P>SOLUTION: A housing 7 is formed by injection molding of resin while a bearing sleeve 8 and a thrust member 9 retained at a relative position with respect to the bearing sleeve 8 along the axial direction are used as insert members. At this time, the housing 7 is a sealed structure except for a seal space S. An inside diameter side of a thrust bearing space of a thrust bearing part T1 is communicated with the seal space through a radial bearing space, and an outside diameter side thereof is communicated with the seal space through a circulation passage 10. The circulation passage 10 is formed by melting a circulation passage forming material after injection molding of the housing 7 in the sate that the soluble circulation passage forming material is supplied to a surface of the bearing sleeve 8. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device in which a shaft member is supported in a non-contact manner in a radial direction by an oil film formed in a radial bearing gap.

  A hydrodynamic bearing device which is a kind of the above-described hydrodynamic bearing device generates pressure by the hydrodynamic action of fluid generated in the bearing gap due to relative rotation between the bearing sleeve and a shaft member inserted in the inner periphery of the bearing sleeve. The bearing device supports the shaft member in a non-contact manner by pressure. This hydrodynamic bearing device has features such as high-speed rotation, high rotation accuracy, and low noise. Information equipment such as magnetic disk devices such as HDD, CD-ROM, CD-R / RW, DVD-ROM / For small motors such as optical disk devices such as RAM, spindle motors for disk drives in magneto-optical disk devices such as MD and MO, polygon scanner motors for laser beam printers (LBP), color wheel motors for projectors, and axial fans It is suitable as a bearing device.

As this type of hydrodynamic bearing device, a structure in which a bearing part such as a bearing sleeve is enclosed in a resin housing formed by outsert molding is known (Patent Document 1).
Japanese Patent Laid-Open No. 2003-130043

  By the way, in the hydrodynamic bearing device described in the above publication, the oil filled in the radial bearing gap flows downward during the operation of the bearing due to the existence of processing errors and the like, and the thrust bearing gap provided at the bottom of the housing In some cases, the oil pressure at the tank becomes extremely large. Under such circumstances, the pressure difference between the oil pressure in the thrust bearing gap and the oil pressure (atmospheric pressure) in the seal space becomes large, which may cause local negative pressure in the lubricating oil. The generation of the negative pressure causes the generation of bubbles in the lubricating oil, which may adversely affect the bearing performance. In addition, when the oil pressure in the thrust bearing gap decreases, the shaft member is pressed against the thrust member and slides, so that abnormal wear may occur at the sliding portion.

  Accordingly, an object of the present invention is to prevent the occurrence of a pressure difference of lubricating oil in a hydrodynamic bearing device.

  In order to achieve the above object, a hydrodynamic bearing device of the present invention includes a shaft member, a bearing sleeve having a shaft member inserted into an inner periphery thereof, a housing in which the bearing sleeve is inserted and injection-molded, and a seal having an oil level. A radial bearing portion that supports the shaft member in the radial direction with an oil film formed in a radial bearing gap between the space, the outer peripheral surface of the shaft member and the inner peripheral surface of the bearing sleeve, and communicates with the seal space via the radial bearing gap And a clearance filled with lubricating oil, and a circulation path that passes between the inner peripheral surface of the housing and the outer peripheral surface of the bearing sleeve and communicates the clearance and the seal space. It is.

  As described above, in the hydrodynamic bearing device having the gap portion communicating with the seal space through the radial bearing gap, and the circulation path communicating with the gap portion and the seal space, the radial bearing gap to the gap portion, and further A lubricating oil circulation path is formed through the circulation path to the seal space. Therefore, for example, even when the lubricating oil pressure in the gap increases due to the inflow of the lubricating oil from the radial bearing gap, the lubricating oil flows into the seal space through the circulation path. Thus, the generation of bubbles due to local negative pressure generated in the lubricating oil can be prevented. On the contrary, when the pressure of the lubricating oil decreases in the gap, the pressure difference is eliminated by the flow of the lubricating oil through the circulation path.

  In the present invention, since the housing is injection molded by inserting the bearing sleeve (including both insert molding and outsert molding), for example, the housing is inserted in a state where a groove for the circulation path is formed in advance on the surface of the bearing sleeve. Even if it molds, since a slot is filled up with molten resin supplied at the time of injection molding, a circulation way cannot be formed. Therefore, in the present invention, after the housing is injection molded in a state where a soluble circulation path forming material is supplied to the surface of the bearing sleeve, the circulation path forming material is dissolved.

  As the soluble circuit forming material, any water-soluble or organic solvent-soluble material can be used. The supply of the circulation path forming material to the surface of the bearing sleeve can be performed by, for example, applying the circulation path forming material to the formation area of the circulation path on the surface of the bearing sleeve and curing the same. As the circulation path forming material, it is necessary to use a material that does not lose its shape due to the injection pressure during the injection molding or does not peel off from the bearing sleeve.

  After the injection molding of the housing, a solvent (water or an organic solvent) for dissolving the circulation path forming material is supplied to the inner space of the molded housing to dissolve the circulation path forming material. Thereby, a circulation path can be formed in the contact portion between the housing and the bearing sleeve. In particular, when a seal space is formed on the outer periphery of the shaft member and the housing has a sealed structure except for this seal space, groove forming by post-processing after injection molding becomes difficult because of the hermeticity of the housing. The procedure is particularly compatible with bearing devices having this type of housing.

  This hydrodynamic bearing device can be provided with a thrust bearing portion that supports the shaft member in the thrust direction by the dynamic pressure action of the lubricating oil generated in the gap portion. The thrust bearing portion is configured, for example, by providing a flange portion on the shaft member and forming the gap portion between one end surface of the flange portion and the end surface of the bearing sleeve (first thrust bearing portion). .

  In addition to the first thrust bearing portion, a second thrust bearing portion that supports the shaft member in a non-contact manner in the reverse thrust direction can be provided. For example, the second thrust bearing portion is provided with a thrust member that is opposed to the bearing sleeve with the flange portion interposed therebetween and in which the axial relative position with respect to the bearing sleeve is held on the bearing device, and the other end surface of the flange portion. And the end face of the thrust member can be formed by forming the gap portion. In this case, the housing can be injection-molded by inserting the bearing sleeve and the thrust member, whereby the assembly process of the hydrodynamic bearing device can be simplified by omitting the assembly process of the bearing sleeve and the thrust member.

  In the above description, the case where the dynamic pressure bearing that supports the shaft member in a non-contact manner by the dynamic pressure action of the fluid generated in the thrust bearing gap is exemplified as the thrust bearing portion. It can also be constituted by a pivot bearing which is in contact with and supported by the shaft.

  In this pivot bearing, the shaft end to be contacted and supported is formed in a spherical shape, and a space (gap portion) communicating with the seal space is formed around the spherical shaft end through a radial bearing gap. If this gap portion communicates with the seal space via the circulation path, it is possible to prevent problems such as lifting of the shaft member due to an increase in the pressure of the lubricating oil in the thrust bearing portion.

  The hydrodynamic bearing device having the above configuration can be preferably used for a motor having the bracket, the rotor magnet, and the stator coil, for example, a spindle motor for HDD.

  As described above, according to the present invention, the pressure balance of the lubricating oil in the bearing device can be properly maintained, so that bubbles are generated due to the generation of local negative pressure, and further, vibration and abnormal wear occur. Can be prevented, and the bearing performance can be further improved.

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

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

  FIG. 2 shows a first embodiment of the hydrodynamic bearing device 1 used in the spindle motor. The hydrodynamic bearing device 1 includes a shaft member 2, a housing 7, a bearing sleeve 8, and a thrust member 9 as main components. In the following description, for convenience of description, the description will be made with the side having the seal space S as the upper side and the opposite side in the axial direction as the lower side.

  In this hydrodynamic bearing device 1, the first radial bearing portion R 1 and the second radial bearing portion R 2 are separated in the axial direction between the inner peripheral surface 8 a of the bearing sleeve 8 and the outer peripheral surface of the shaft portion 2 a of the shaft member 2. Is provided. A first thrust bearing portion T1 is provided between the lower end surface 8d of the bearing sleeve 8 and the upper end surface 2b1 of the flange portion 2b of the shaft member 2, and the inner bottom surface 9a (end surface) of the thrust member 9 and the flange portion 2b. A second thrust bearing portion T2 is provided between the lower end surface 2b2 and the second thrust bearing portion T2.

  The shaft member 2 is formed of a metal material such as stainless 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 to forming the entire shaft member 2 from metal, for example, by forming the entire flange portion 2b or a part thereof (for example, both end surfaces) from resin, a hybrid structure of metal and resin can be obtained.

  The bearing sleeve 8 is formed in a cylindrical shape with a porous body made of a sintered alloy, for example, a sintered metal mainly composed of copper. The sintered metal is impregnated with lubricating oil. In addition, the bearing sleeve 8 can be formed of a solid metal material, for example, a soft metal such as brass.

  On the inner peripheral surface 8a of the bearing sleeve 8, two upper and lower regions serving as radial bearing surfaces of the first radial bearing portion R1 and the second radial bearing portion R2 are provided apart in the axial direction. In these two regions, a plurality of dynamic pressure grooves G arranged in a herringbone shape, for example, are formed as dynamic pressure generating portions. The upper dynamic pressure groove G corresponding to the first radial bearing portion R1 is formed asymmetrically in the axial direction, and the axial length X of the upper dynamic pressure groove is the lower dynamic pressure groove in the region. Is slightly larger than the axial length Y (X> Y). On the other hand, the dynamic pressure grooves G in the lower region corresponding to the second radial bearing portion R2 are formed symmetrically in the axial direction, and the axial lengths of the upper and lower dynamic pressure grooves G are equal in the region. The region serving as the radial bearing surface can also be formed on the outer peripheral surface of the shaft portion 2 a of the shaft member 2.

  A region serving as a thrust bearing surface of the first thrust bearing portion T1 is formed on the lower end surface 8d of the bearing sleeve 8. In this region, a plurality of dynamic pressure grooves arranged in a spiral shape, for example, are formed as dynamic pressure generating portions (not shown).

  The thrust member 9 is integrally formed into a bottomed cylindrical shape including a bottom portion 14 and a cylindrical gap defining portion 15 protruding above the outer diameter portion of the bottom portion 14 using a soft metal material such as brass or other metal materials. Is done. A region serving as a thrust bearing surface of the second thrust bearing portion T2 is formed on the inner bottom surface 9a of the thrust member 9, and a plurality of dynamic pressure grooves arranged in a spiral shape, for example, as a dynamic pressure generating portion are formed in this region. It is formed (not shown).

  The housing 7 is formed by resin injection molding using the bearing sleeve 8 and the thrust member 9 as insert parts (insert molding). In this insert molding, the shaft member 2 is inserted into the inner periphery of the bearing sleeve 8, the flange portion 2 b of the shaft member 2 is accommodated in the inner periphery of the gap defining portion 15 of the thrust member 9, and This is performed in a state where the end surface is in contact with the lower end surface 8d of the bearing sleeve 8. The relative axial position between the thrust member 9 and the bearing sleeve 8 is maintained by the contact between the upper end surface of the gap defining portion 15 and the lower end surface 8d of the bearing sleeve 8, thereby the first thrust bearing portion. Each thrust bearing gap between T1 and the second thrust bearing portion T2 is set to a specified width.

  The resin forming the housing 7 is mainly a thermoplastic resin. For example, as the amorphous resin, polysulfone (PSF), polyethersulfone (PES), polyphenylsulfone (PPSU), polyetherimide (PEI) As the crystalline resin, liquid crystal polymer (LCP), polyether ether ketone (PEEK), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), or the like can be used. The type of filler to be filled in the resin is not particularly limited. For example, as the filler, fibrous filler such as glass fiber, whisker-like filler such as potassium titanate, and scaly filler such as mica. A fibrous or powdery conductive filler such as carbon fiber, carbon black, graphite, carbon nanomaterial, or metal powder can be used. These fillers may be used alone or in combination of two or more. In this embodiment, as a material for forming the housing 7, a resin material in which 2 to 8 wt% of a carbon fiber or a carbon nanotube as a conductive filler is mixed with a liquid crystal polymer (LCP) as a crystalline resin is used.

  In addition, the housing 7 can be formed by injection molding or MIM molding of a low melting point metal such as an aluminum alloy.

  The housing 7 thus formed integrally has a cylindrical side portion 7a, a seal portion 7b extending from the upper end of the side portion 7a toward the inner diameter side, and a bottom portion 7c that closes the lower end of the side portion 7a. It has a sealed structure except for the seal space S. The outer peripheral surface of the housing 7 is a straight cylindrical surface, and this outer peripheral surface is fixed to the inner peripheral surface of the bracket 6 shown in FIG.

  The inner peripheral surface 7b1 of the seal portion 7b forms a seal space S having a predetermined volume with the outer peripheral surface of the shaft portion 2a. In this embodiment, the inner peripheral surface 7 b 1 of the seal portion 7 b is formed in a tapered surface shape that gradually increases in diameter toward the outside of the housing 7, and thus the seal space S is a taper that gradually decreases in the inner direction of the housing 7. Presents a shape. Accordingly, the lubricating oil in the seal space S is drawn in the direction in which the seal space S becomes narrow due to the pull-in action by the capillary force, whereby the upper end opening of the housing 7 is sealed. The internal space of the housing 7 sealed with the seal member 9 is filled with lubricating oil including the internal pores of the bearing sleeve 8. The seal space S also has a buffer function that absorbs the volume change amount accompanying the temperature change of the lubricating oil filled in the internal space of the bearing member 7, and the oil level is always in the seal space S.

  In addition, while the inner peripheral surface 7b1 of the seal portion 7b is a cylindrical surface, the outer peripheral surface of the shaft portion 2a opposite to the cylindrical surface may be formed into a tapered surface. In this case, a function as a centrifugal force seal is also obtained. Therefore, the sealing effect is further enhanced.

  When the shaft member 2 rotates, the two upper and lower regions of the inner peripheral surface 8a of the bearing sleeve 8 that are the radial bearing surfaces face the outer peripheral surface of the shaft portion 2a via a radial bearing gap. Further, the region that becomes the thrust bearing surface of the lower end surface 8d of the bearing sleeve 8 faces the upper end surface 2b1 of the flange portion 2b via a gap portion (thrust bearing gap) having a predetermined width, and the inner bottom surface 9a of the thrust member 9 is formed. The region serving as the thrust bearing surface is opposed to the lower end surface 2b2 of the flange portion 2b via a gap portion (thrust bearing gap) having a predetermined width. As the shaft member 2 rotates, dynamic pressure of the lubricating oil is generated in the radial bearing gap, and the shaft member 2 is supported in a non-contact manner so as to be rotatable in the radial direction by the oil film of the lubricating oil formed in the radial bearing gap. Is done. Thus, the first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft member 2 in a non-contact manner so as to be rotatable in the radial direction are configured. At the same time, the dynamic pressure of the lubricating oil is generated in the thrust bearing gap, and the shaft member 2 is supported in a non-contact manner so as to be rotatable in the thrust direction by the lubricating oil film formed in the two thrust bearing gaps. Thereby, the 1st thrust bearing part T1 and the 2nd thrust bearing part T2 which non-contact-support the shaft member 2 rotatably in a thrust direction are comprised. Between the thrust bearing gaps of the first and second thrust bearing gaps, the lubricating oil can flow through a space between the outer peripheral surface of the flange portion 2 b and the inner peripheral surface of the thrust member 9.

  The thrust bearing gap of the first thrust bearing portion T1 has an inner diameter side communicating with the seal space S via the radial bearing gap, and an outer diameter side communicating with the seal space S via the circulation path 10. The circulation path 10 passes between the inner peripheral surface 7 a 1 of the housing 7 and the outer peripheral surface of the bearing sleeve 8, and passes between the lower end surface 7 b 2 of the seal portion 7 b and the upper end surface 8 c of the bearing sleeve 8. The first radial direction portion 10b and the second radial direction portion 10c passing between the lower end surface 8d of the bearing sleeve 8 and the upper end surface of the gap defining portion 15 are configured.

  As described above, the dynamic pressure groove G of the first radial bearing portion R1 is formed to be axially asymmetric, and the axial dimension X of the upper region is larger than the axial dimension Y of the lower region. Therefore, when the shaft member 2 rotates, the pulling force (pumping force) of the lubricating oil by the dynamic pressure groove G is relatively larger in the upper region than in the lower region. 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 of the shaft portion 2a flows downward, and the thrust of the first thrust bearing portion T1 It circulates through the path of the bearing gap → the second radial direction part 10c of the circulation path 10 and the axial direction part 10a → the first radial direction part 10b, and is drawn again into the radial bearing gap of the first radial bearing part R1. In this way, the configuration in which the lubricating oil flows and circulates inside the housing 7 prevents a phenomenon in which the pressure of the lubricating oil filled in the housing 7 becomes a negative pressure locally. Problems such as generation of bubbles accompanying the generation, leakage of lubricating oil and generation of vibration due to the generation of bubbles can be solved. In addition, even if bubbles are mixed in the lubricating oil for some reason, when the bubbles circulate with the lubricating oil, it is discharged from the oil surface (gas-liquid interface) of the lubricating oil in the seal space S to the outside air. The adverse effects due to the bubbles are more effectively prevented.

  The circulation path 10 can be formed by the following procedure, for example.

  First, as shown in FIG. 3 (a), the axial portion 10a, the first radial direction portion 10b, and the second radial direction are provided at one or a plurality of locations (three locations in the drawing) in the circumferential direction on the surface of the bearing sleeve 3. A groove 12 having a shape corresponding to the portion 10c is formed. Next, as shown in FIG. 3 (b), each groove 12 is filled with a circulation path forming material 13 made of resin or the like, cured as necessary, and then inserted into the housing 7 as described above. Perform molding. After forming, if a solvent is supplied from the seal space S and the circulation path forming material 13 is dissolved, the circulation path 10 shown in FIG. 2 is formed.

  The combination of the circulation path forming material 13 and the solvent can be arbitrarily selected as long as the circulation path forming material 13 can be reliably dissolved, but excludes chlorine-containing resins, chlorinated solvents, and corrosive solvents. Is preferred. As the combination of the circulation path forming material 13 and the solvent, those indicated by a circle in FIG.

  As shown in FIG. 3, the groove 12 is formed on the surface of the bearing sleeve 8 and filled with the circulation path forming material 13, and the circulation path forming material 13 is formed on the surface of the bearing sleeve without forming the groove 12. You may apply | coat to a strip | belt shape and harden this as needed. In this case, after the injection molding of the housing 7, the axial portion 10a is formed on the inner peripheral surface 7a1 of the housing 7, and the first radial portion 10b is formed on the lower end surface 7b2 of the seal portion 7b. In addition, the second radial direction portion 10c fills the groove 12 formed on the lower end surface 8d of the bearing sleeve 8 with the circulation path forming material 13, and also forms a similar groove on the upper end surface of the gap defining portion 15 of the thrust member 9. It can also be formed by filling it with the circulation path forming material 13.

  FIG. 4 shows an embodiment in which the side portion 7a and the bottom portion 7c of the housing 7 are integrally formed of resin or the like, and the seal portion 7b is a separate member. After the side part 7a and the bottom part 7c are insert-molded, the seal part 7b is welded to the upper end opening of the side part 7a by means such as ultrasonic welding. Since the seal portion 7b after welding is integrated with the side portion 7a, the housing 7 having a sealed structure excluding the seal space S can be obtained as in the embodiment shown in FIG. The formation procedure of the circulation path 10 is in accordance with the method described in the embodiment shown in FIG. 2, but in this configuration, the solvent is supplied to the inside of the housing 7 before the seal portion 7b is welded to the side portion 7a. Since the path forming material 13 can be dissolved, the advantage that the circulation path forming material 13 can be smoothly dissolved is obtained.

  FIG. 5 shows the gap defining portion 15 as a separate member from the thrust member 9. The thrust bearing gaps of the thrust bearing portions T1, T2 are formed by insert molding the housing 7 in a state where the gap defining portion 15 is in contact with the lower end surface 8d of the bearing sleeve 8 and the inner bottom surface 9a of the thrust member 9, respectively. Can be set to a specified width. In this case, at the time of injection molding of the housing 7, in addition to the bearing sleeve 8 and the thrust member 9, the gap defining portion 15 is also an insert part.

  FIG. 6 shows an example in which the gap defining portion 15 is integrally formed with the bearing sleeve 8 made of sintered metal or the like. The housing 7 is insert-molded with the lower end surface of the gap defining portion 15 in contact with the inner bottom surface 9a of the thrust member 9, so that the thrust bearing portion T1 is similar to the bearing device shown in FIGS. , T2 thrust bearing clearance can be set to a specified width.

  FIG. 7 shows an embodiment in which the thrust bearing portion T is constituted by a pivot bearing. In this embodiment, the shaft end 2c of the shaft member 2 is formed in a spherical shape, and the shaft end 2c is in direct contact with the inner bottom surface 7c1 of the bottom portion 7c of the housing 7, so that the shaft member 2 is contact-supported in the thrust direction. Is done. Between the shaft end 2 c and the inner peripheral surface 7 a and the inner bottom surface 7 c 1 of the housing 7, a gap U is formed that communicates with the seal space S via a radial bearing gap. Since this clearance U communicates with the seal space S through the circulation path 10, during the operation of the bearing device, the radial bearing clearance and the clearance U from the seal space S are similar to the bearing device shown in FIG. Further, a lubricating oil circulation path that reaches the seal space S via the circulation path 10 is formed. Accordingly, it is possible to prevent adverse effects such as the generation of bubbles due to the unbalance of the lubricating oil pressure in the bearing device. The procedure for forming the circulation path 10 is in accordance with the method described in the first embodiment shown in FIG.

  FIG. 8 is an example in which the thrust bearing portion T is configured by bringing the shaft end 2 c into contact with the thrust member 11 in the embodiment shown in FIG. 7. In this case, the thrust member 11 and the bearing sleeve 8 are brought into contact with each other in the axial direction, and the insert molding of the housing 7 is performed in a state where the relative positions in the axial direction are defined. The procedure for forming the circulation path 10 is in accordance with the method described in the first embodiment shown in FIG.

  In the above description, the radial bearing portions R1 and R2 and the thrust bearing portions T1 and T2 are exemplified by the configuration in which the dynamic pressure action of the lubricating oil is generated by the herringbone-shaped or spiral-shaped dynamic pressure grooves. As the portions R1 and R2, so-called step bearings and multi-arc bearings may be employed. Furthermore, what is called a perfect circle bearing which does not have a dynamic-pressure generating part is also employable. Further, the thrust bearing portions T1 and T2 can be configured by so-called step bearings in which dynamic pressure grooves are radially arranged, so-called wave-type bearings (step-type wave-type bearings) or the like.

  9 and 10 show an example in which one or both of the radial bearing portions R1 and R2 are configured by multi-arc bearings. Among these, in the example shown in FIG. 9, the region that becomes the radial bearing surface of the inner peripheral surface 8 a of the bearing sleeve 8 is configured by three arc surfaces 8 a 1 as dynamic pressure generating portions (so-called three arc bearings). The centers of curvature of the three arcuate surfaces 8a1 are offset by the same distance from the shaft center O of the bearing member 7 (shaft member 2). In each region defined by the three circular arc surfaces 8a1, the radial bearing gap has a shape gradually reduced in a wedge shape with respect to both circumferential directions. Therefore, when the bearing sleeve 8 rotates relative to the bearing sleeve 8, the lubricating oil in the radial bearing gap is pushed into the minimum gap side reduced in a wedge shape in accordance with the direction of the relative rotation, and the pressure rises. The bearing member 7 and the shaft member 2 are supported in a non-contact manner by the dynamic pressure action of the lubricating oil. A deeper axial groove called a separation groove may be formed at the boundary between the three arcuate surfaces 8a1.

  FIG. 10 shows another example of the multi-arc bearing. In each region defined by the three arc surfaces 8a1, the radial bearing gap has a shape gradually reduced in a wedge shape with respect to one direction in the circumferential direction. Yes. The multi-arc bearing having such a configuration may be referred to as a taper bearing. Further, a deeper axial groove 8a3 called a separation groove is formed at the boundary between the three arcuate surfaces 8a1. In this configuration, although not shown, the predetermined regions on the minimum gap side of the three circular arc surfaces 8a1 may be configured by concentric circular arcs with the center O of the bearing sleeve 8 (the shaft member 2) as the center of curvature. Yes (sometimes called a tapered flat bearing).

  In the above description, the case where the dynamic pressure grooves of the first and second thrust bearing portions T1 and T2 are formed on the end surface 7c of the bearing member 7 and the inner bottom surface 8a1 of the lid member 8 is exemplified. A dynamic pressure groove as a dynamic pressure generating portion may be formed on one or both of both end faces 2b1 and 2b2.

It is sectional drawing which shows an example of the motor incorporating the hydrodynamic bearing apparatus. It is sectional drawing of embodiment of a hydrodynamic bearing apparatus. It is a perspective view which shows the formation process of a circulation path. It is sectional drawing which shows other embodiment of the hydrodynamic bearing apparatus. It is sectional drawing which shows other embodiment of the hydrodynamic bearing apparatus. It is sectional drawing which shows other embodiment of the hydrodynamic bearing apparatus. It is sectional drawing which shows other embodiment of the hydrodynamic bearing apparatus. It is sectional drawing which shows other embodiment of the hydrodynamic bearing apparatus. It is sectional drawing which shows other embodiment of a radial bearing part. It is sectional drawing which shows other embodiment of a radial bearing part. It is a table | surface which shows resin and solvent which can be used at the formation process of a circulation path.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing apparatus 2 Shaft member 2a Shaft part 2b Flange part 7 Housing 7a Side part 7b Seal part 7c Bottom part 8 Bearing sleeve 9 Thrust member 10 Circulation path 11 Thrust member 12 Groove 13 Circulation path formation material 15 Clearance definition part G Dynamic pressure Groove S Seal space R1 First radial bearing portion R2 Second radial bearing portion T1 First thrust bearing portion T2 Second thrust bearing portion T Thrust bearing portion

Claims (10)

A shaft member;
A bearing sleeve having a shaft member inserted on its inner periphery;
A housing that is injection molded with a bearing sleeve inserted;
A seal space having an oil level;
A radial bearing portion that supports the shaft member in the radial direction with an oil film formed in a radial bearing gap between the outer peripheral surface of the shaft member and the inner peripheral surface of the bearing sleeve;
A gap filled with lubricating oil, communicating with the seal space through a radial bearing gap;
A hydrodynamic bearing device comprising a circulation path that communicates between a gap portion and a seal space through an inner peripheral surface of a housing and an outer peripheral surface of a bearing sleeve.   The hydrodynamic bearing device according to claim 1, further comprising a thrust bearing portion that supports the shaft member in a thrust direction by a dynamic pressure action of lubricating oil generated in the gap portion.   The hydrodynamic bearing device according to claim 2, wherein a flange portion is provided on the shaft member, and the gap portion is formed between one end surface of the flange portion and the end surface of the bearing sleeve.   A thrust member facing the bearing sleeve across the flange portion and having an axial relative position with respect to the bearing sleeve is provided, and the gap portion is formed between the other end surface of the flange portion and the end surface of the thrust member. The hydrodynamic bearing device according to claim 3.   The hydrodynamic bearing device according to claim 4, wherein the housing is injection-molded by inserting a bearing sleeve and a thrust member.   The hydrodynamic bearing device according to claim 1, further comprising a thrust bearing portion that contacts and supports the shaft member in the thrust direction.   The hydrodynamic bearing device according to claim 6, wherein the gap is formed around a shaft end of the shaft member.   The hydrodynamic bearing device according to claim 1, wherein the seal space is formed on an outer periphery of the shaft member, and the housing is sealed except for the seal space.   2. The hydrodynamic bearing device according to claim 1, wherein the circulation path is formed by melting the circulation path forming material after injection molding the housing in a state where a soluble circulation path forming material is supplied to the surface of the bearing sleeve.   A motor comprising the hydrodynamic bearing device according to claim 1, a stator coil, and a rotor magnet.

Images