JP2005321089A - Dynamic pressure bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the axial dimension of a seal space. <P>SOLUTION: This dynamic pressure bearing device comprises a seal member 9 fixed to a specified position on an outer peripheral surface 2a1 of a shaft portion 2a. During the rotation of a shaft member 2, a lower end surface 9b of the seal member 9 is opposite an upper end surface 8b of a bearing sleeve 8 with a specified thrust bearing clearance in between to form a second thrust bearing clearance T2. Further, an outer peripheral surface 9a on the seal member 9 forms a seal space S with a specified volume between itself and an upper end section inner peripheral surface 7a1 of a housing 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydrodynamic bearing device that supports a rotating member in a non-contact manner by a hydrodynamic action of a fluid (lubricating fluid) generated in a bearing gap. This bearing device is a spindle of information equipment such as magnetic disk devices such as HDD and FDD, optical disk devices such as CD-ROM, CD-R / RW and DVD-ROM / RAM, and magneto-optical disk devices such as MD and MO. It is suitable for a motor, a polygon scanner motor of a laser beam printer (LBP), or an electric device such as a small motor such as an axial fan.

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

  For example, in a hydrodynamic bearing device incorporated in a spindle motor of a disk drive device such as an HDD, a radial bearing portion that supports a shaft member in a non-contact manner in the radial direction, and a thrust bearing portion that supports the shaft member in a non-contact manner in a thrust direction. As the radial bearing portion, a dynamic pressure bearing in which a groove for generating dynamic pressure (dynamic pressure groove) is provided on the inner peripheral surface of the bearing sleeve or the outer peripheral surface of the shaft member is used. As the thrust bearing portion, for example, a motion in which dynamic pressure grooves are provided on both end surfaces of the flange portion of the shaft member, or surfaces facing the flange portion (the end surface of the bearing sleeve, the end surface of the thrust member fixed to the housing, etc.). A pressure bearing is used (for example, refer to Patent Documents 1 and 2).

Usually, the bearing sleeve is fixed at a predetermined position on the inner periphery of the housing, and a seal member is provided at the opening of the housing in order to prevent fluid (for example, lubricating oil) injected into the inner space of the housing from leaking outside. Is often provided. The inner peripheral surface of the seal member forms a seal space between the outer peripheral surface of the shaft member, and the volume of the seal space is determined by the thermal expansion of the lubricating oil filled in the inner space of the housing within the operating temperature range. It is set to be larger than the amount of volume change due to the contraction. Therefore, even when there is a change in the volume of the lubricating oil accompanying a change in temperature, the oil level of the lubricating oil is always maintained in the seal space (see Patent Document 1).
JP 2003-65324 A JP 2003-336636 A

  As described above, in the conventional hydrodynamic bearing device, the seal space is formed between the inner peripheral surface of the seal member fixed to the opening of the housing and the outer peripheral surface of the shaft member. In order to provide a function of absorbing the volume change amount of the lubricating oil accompanying the temperature change, it is necessary to ensure a relatively large axial dimension of the seal space (seal member). Therefore, it is necessary to lower the axial center position of the bearing sleeve relative to the bottom side of the housing in the interior of the housing by design, so that the separation distance between the bearing center of the radial bearing portion and the center of gravity of the rotating body is reduced. Depending on the use conditions, the load capacity for moment load may be insufficient. Further, in the configuration in which the thrust bearing portions are provided on both sides of the flange portion of the shaft member, the axial distance between the thrust bearing portions is relatively small, and accordingly, the load capacity of the moment load by the thrust bearing portion is reduced accordingly. Tend. In particular, in the case of a hydrodynamic bearing device used in a disk drive device, a relatively large moment load acts on the shaft member as the rotor (rotor mounted with a rotor hub, rotor magnet, disk, clamper, etc.) rotates. Moment load resistance is an important characteristic.

  Further, in this type of hydrodynamic bearing device, the thrust bearing gap of the thrust bearing portion is affected by component accuracy, assembly accuracy, etc., so that it is difficult to manage to a desired value, and therefore complicated assembly work is strong. It is the reality.

  An object of the present invention is to make it possible to reduce the axial dimension of the seal space in this type of hydrodynamic bearing device, thereby increasing the load capacity against the moment load of the hydrodynamic bearing device, or It is to make the axial dimension of the pressure bearing device compact.

  Another object of the present invention is to increase the load capacity of the moment load by the thrust bearing portion.

  A further object of the present invention is to provide a method capable of easily and accurately setting a thrust bearing gap in this type of hydrodynamic bearing device.

  In order to solve the above-described problems, the present invention provides a housing, a bearing sleeve fixed inside the housing, a shaft member that rotates relative to the housing and the bearing sleeve, and a seal member that is positioned on one end of the housing. And a radial bearing unit that supports the shaft member in a radial contactless manner by a fluid dynamic pressure action generated in a radial bearing gap between the bearing sleeve and the shaft member. It has a shaft portion inserted into the inner peripheral surface of the sleeve and a flange portion provided in the shaft portion, the seal member is fixed to the shaft member, a seal space is formed on the outer peripheral surface side of the seal member, and the seal A first thrust bearing portion is provided between one end surface of the member and one end surface of the bearing sleeve facing the member, and the first thrust bearing portion is sealed by a dynamic pressure action of fluid generated in the thrust bearing gap. The shaft member is supported in a non-contact manner in the thrust direction, and a second thrust bearing portion is provided between one end surface of the flange portion and the other end surface of the bearing sleeve facing the flange portion, and the second thrust bearing portion is provided in the thrust bearing gap. Provided is a configuration in which a shaft member is supported in a non-contact manner in a thrust direction by a dynamic pressure action of a generated fluid.

  Here, as the fluid (lubricating fluid), a liquid such as lubricating oil (or lubricating grease) or a magnetic fluid, or a gas such as air can be used.

  According to the above configuration, since the seal space is provided on the outer peripheral surface side of the seal member provided in the shaft portion, the volume capable of absorbing the volume change amount accompanying the temperature change of the fluid filled in the internal space of the housing. In the sealing space, it is possible to make the axial dimension of the sealing space (seal member) smaller than the conventional one. Therefore, in the housing, the axial center position of the bearing sleeve can be set relatively closer to one end of the housing than before (the bearing sleeve is closer to one end of the housing than before). Or the axial dimension of the bearing sleeve is made larger than before.) This reduces the distance between the bearing center of the radial bearing and the center of gravity of the rotating body, and increases the load capacity for moment load. Can do. In addition, when the bearing sleeve is disposed closer to the one end side of the housing than in the past, the axial dimension of the hydrodynamic bearing device can be made smaller than in the past.

  In addition, since the first thrust bearing portion and the second thrust bearing portion are provided so as to sandwich the bearing sleeve from both sides in the axial direction, both thrusts are compared with the configuration in which the thrust bearing portions are provided on both sides of the flange portion. The axial separation distance between the bearing portions increases, and the load capacity of the moment load by the thrust bearing portion increases accordingly.

  Although the width (radial dimension) of the seal space may be uniform in the axial direction, it is preferable that the seal space has a tapered shape that gradually decreases toward the inside of the housing from the viewpoint of improving the sealing performance. . That is, when the seal space has the above tapered shape, the fluid in the seal space is drawn by the capillary force toward the direction in which the seal space becomes narrower (inner direction of the housing). Therefore, the leakage of fluid from the inside of the housing to the outside is effectively prevented. As a means for realizing such a configuration, a means for forming a tapered surface gradually reducing in diameter toward the outside of the housing on the outer peripheral surface of the seal member, a surface facing the outer peripheral surface of the seal member through the seal space, For example, there is a means for forming a tapered surface that gradually increases in diameter toward the outside of the housing on the inner peripheral surface of one end of the housing. In particular, according to the former means, since the seal member rotates together with the shaft member, in addition to the pull-in action by the capillary force described above, the pull-in action by the centrifugal force during rotation can be obtained (so-called centrifugal force seal) ), Leakage of fluid from the inside of the housing to the outside is more effectively prevented.

  The seal member can be fixed to the shaft member by an appropriate fixing means such as adhesion, combined use of adhesion and press-fitting, and welding (ultrasonic welding). When bonding (or a combination of bonding and press-fitting) is employed as the fixing means, at least one bonding site of the seal member and the shaft member may be provided with a recess filled with an adhesive. The recess may be provided in the form of a circumferential groove, or may be provided in the form of a depression at one place or a plurality of places in the circumferential direction. The adhesive is also filled in the concave portion of the adhesion site and solidifies, whereby the fixing strength of the seal member to the shaft member is improved.

  In order to solve the above problems, the present invention is located on the housing, a bearing sleeve fixed inside the housing, a shaft member that rotates relative to the housing and the bearing sleeve, and one end of the housing. In a hydrodynamic bearing device including a seal member and a radial bearing portion that supports the shaft member in a radial direction by a hydrodynamic action of fluid generated in a radial bearing gap between the bearing sleeve and the shaft member, the seal member is Provided on the shaft member, one end surface of the seal member is opposed to one end surface of the bearing sleeve via a thrust bearing gap, and the outer peripheral surface of the seal member is gradually reduced in diameter toward the outside of the housing, and A configuration having a tapered surface facing the seal space is provided.

  In the hydrodynamic bearing device having the above-described configuration, the radial bearing portion includes a hydrodynamic groove provided with a hydrodynamic groove having a shape inclined in the axial direction, such as a herringbone shape or a spiral shape, and a radial bearing gap in one of the circumferential directions. Alternatively, it can be composed of a dynamic pressure bearing (multi-arc bearing) reduced in a wedge shape on both sides, or a dynamic pressure bearing (step bearing) in which a plurality of axial groove-shaped dynamic pressure grooves are provided at predetermined intervals in the circumferential direction. .

  The fluid dynamic bearing device having the above configuration can be preferably used as a fluid dynamic bearing device for a spindle motor used in information equipment, for example, a disk device or the like.

  In order to solve the above problems, the present invention provides a housing, a bearing sleeve fixed inside the housing, a shaft portion inserted into the inner peripheral surface of the bearing sleeve, and a flange portion provided in the shaft portion. The shaft member in the radial direction due to the hydrodynamic action of fluid generated in the radial bearing gap between the inner peripheral surface of the bearing sleeve and the outer peripheral surface of the shaft member. A non-contact supporting radial bearing portion and a first member that non-contact supports the seal member and the shaft member in the thrust direction by a dynamic pressure action of a fluid generated in a thrust bearing gap between one end surface of the seal member and one end surface of the bearing sleeve. A thrust bearing portion, and a second thrust bearing portion for supporting the shaft member in a thrust direction in a thrust direction by a dynamic pressure action of a fluid generated in a thrust bearing gap between the one end surface of the flange portion and the other end surface of the bearing sleeve. In addition, the shaft portion of the shaft member is inserted into the inner peripheral surface of the bearing sleeve, and the seal member is attached to the shaft portion, whereby the bearing sleeve is connected to one end surface of the seal member. A step of interposing between one end surface of the flange portion, and after the step, adjusting the axial relative position of the shaft portion and the seal member to adjust one end surface of the bearing sleeve and the seal member and one end surface of the flange portion; A step of forming a gap corresponding to the total amount of the thrust bearing gaps of the first thrust bearing portion and the second thrust bearing portion, and a step of fixing the seal member to the shaft portion after the step; And a step of housing the assembly including the bearing sleeve, the shaft member, and the seal member assembled in the above-described process inside the housing.

  According to the above configuration, since the thrust bearing gap is set at the stage where the bearing sleeve, the shaft member, and the seal member are assembled in advance, the thrust bearing gap can be set easily and accurately. After setting the thrust bearing clearance, the assembly work including the bearing sleeve, shaft member, and seal member is accommodated inside the housing, so that the assembly work between the members is completed, and the assembly work is simplified. Is done.

  ADVANTAGE OF THE INVENTION According to this invention, the load capability with respect to the moment load of a dynamic pressure bearing apparatus can be improved, or the axial direction dimension of a dynamic pressure bearing apparatus can be made compact. Accordingly, it is possible to reduce the size of a spindle motor used in an information device including the dynamic pressure bearing device, for example, a disk device.

  Further, according to the present invention, the load capacity of moment load by the thrust bearing portion can be enhanced.

  Furthermore, according to the present invention, the thrust bearing gap in this type of hydrodynamic bearing device can be set easily and accurately.

  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 according to this embodiment. This spindle motor is used in a disk drive device such as an HDD, and includes a hydrodynamic bearing device 1 that rotatably supports the shaft member 2 in a non-contact manner, a rotor (disk hub) 3 mounted on the shaft member 2, For example, a stator coil 4 and a rotor magnet 5 are provided to face each other with a gap in the radial direction. The stator coil 4 is attached to the outer periphery of the bracket 6, and the rotor magnet 5 is attached to the inner periphery of the disk hub 3. The housing 7 of the hydrodynamic bearing device 1 is attached to the inner periphery of the bracket 6. The disk hub 3 holds one or more disks D such as magnetic disks. When the stator 4 is energized, the rotor magnet 5 is rotated by the electromagnetic force between the stator coil 4 and the rotor magnet 5, whereby the disk hub 3 and the shaft member 2 are rotated together.

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 is configured by constituting a housing 7, a bearing sleeve 8 fixed to the housing 7, a shaft member 2, and a seal member 9 fixed to the shaft member 2.

  Between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft portion 2a of the shaft member 2, the first radial bearing portion R1 and the second radial bearing portion R2 are provided apart from each other in the axial direction. A first thrust bearing portion T1 is provided between the upper end surface 8b of the bearing sleeve 8 and the lower end surface 9b of the seal member 9, and the lower end surface 8c of the bearing sleeve 8 and the upper side of the flange portion 2b of the shaft member 2 are provided. A second thrust bearing portion T2 is provided between the end surface 2b1. For convenience of explanation, the description will proceed with the bottom 7b side of the housing 7 as the lower side and the opening side of the housing 7 (the side opposite to the bottom 7b) as the upper side.

  For example, the housing 7 is formed into a bottomed cylindrical shape by injection molding of a resin material, and includes a cylindrical side portion 7a and a bottom portion 7b provided integrally with a lower end of the side portion 7a. Further, a stepped portion 7d is integrally formed at a position separated from the inner bottom surface of the bottom portion 7b by a predetermined dimension in the axially upper direction.

  The resin forming the housing is mainly a thermoplastic resin. For example, as an amorphous resin, polysulfone (PSF), polyethersulfone (PES), polyphenylsulfone (PPSU), polyetherimide (PEI), etc. 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.

  The shaft member 2 is made of, for example, a metal material such as stainless steel, or has a hybrid structure of metal and resin, and is provided with a shaft portion 2a and a flange portion provided integrally or separately at the lower end of the shaft portion 2a. 2b. In this embodiment, a concave portion, for example, a circumferential groove 2a2 is formed at a predetermined position on the outer peripheral surface 2a1 of the shaft portion 2a to which the seal member 9 is fixed.

  The bearing sleeve 8 is formed in a cylindrical shape with a porous body made of sintered metal, particularly a sintered body of sintered metal mainly composed of copper, and is fixed to a predetermined position on the inner peripheral surface 7 c of the housing 7. Note that the bearing sleeve 8 can be formed of not only a sintered metal but also a metal material other than a porous body, for example, a soft metal such as brass.

  The inner peripheral surface 8a of the bearing sleeve 8 is provided with two upper and lower regions that are radial bearing surfaces of the first radial bearing portion R1 and the second radial bearing portion R2, and are separated from each other in the axial direction. For example, herringbone-shaped dynamic pressure grooves 8a1 and 8a2 as shown in FIG. 3 are formed. The upper 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), and the axial dimension X1 of the upper region is lower than the axial center m. It is larger than the axial dimension X2 of the side region. Further, one or a plurality of axial grooves 8d1 are formed on the outer peripheral surface 8d of the bearing sleeve 8 over the entire axial length. In this example, three axial grooves 8d1 are formed at equal intervals in the circumferential direction.

  For example, a spiral dynamic pressure groove 8b1 as shown in FIG. 3 is formed on the upper end surface 8b of the bearing sleeve 8 serving as a thrust bearing surface of the first thrust bearing portion T1. Similarly, a spiral-shaped dynamic pressure groove 8c1 as shown in FIG. 3, for example, is formed on the lower end surface 8c of the bearing sleeve 8 that becomes the thrust bearing surface of the second thrust bearing portion T2.

  The seal member 9 is formed in a ring shape from, for example, a soft metal material such as brass (brass), other metal materials, or a resin material, and is fixed to a predetermined position on the outer peripheral surface 2a1 of the shaft portion 2a with an adhesive, for example. Is done. When the shaft member 2 rotates, the lower end surface 9b of the seal member 9 faces the upper end surface 8b of the bearing sleeve 8 via a predetermined thrust bearing gap, thereby constituting a first thrust bearing portion T1. Further, the outer peripheral surface 9 a of the seal member 9 forms a seal space S having a predetermined volume with the upper end (opening) inner peripheral surface 7 a 1 of the housing 7. Since the seal space S is formed on the outer peripheral surface 9a side of the seal member 9, a volume capable of absorbing the volume change amount due to the temperature change of the fluid filled in the internal space of the housing 7 is secured in the seal space S. In this case, the axial dimension of the seal space S (seal member 9) can be made smaller than before. Therefore, for example, the axial length of the bearing sleeve 8 is made larger than before, and the axial center m of the dynamic pressure groove 8a1 of the first radial bearing portion R1 is shifted to the upper end face 8b side. Thus, the axial dimension of 8 can be reduced as compared with the conventional case. According to the former, since the axial separation distance between the axial center m of the dynamic pressure groove 8a1 of the first radial bearing portion R1 and the axial center of the dynamic pressure groove 8a2 of the second radial bearing portion R2 increases, the moment load It is possible to increase the load capacity. On the other hand, according to the latter, the axial dimension of the hydrodynamic bearing device can be made smaller than before.

  In this embodiment, the outer peripheral surface 9 a of the seal member 9 includes a tapered surface 9 a 1 that is gradually reduced in diameter toward the outside of the housing 7, so that the seal space S gradually increases toward the inside of the housing 7. Presents a reduced taper shape. When the shaft member 2 rotates, the fluid in the seal space S is drawn toward the direction in which the seal space S is narrowed (inner direction of the housing) due to the pull-in action due to the capillary force and the pull-in action due to the centrifugal force during the rotation. Thereby, the leakage of the lubricating oil from the inside of the housing 7 is effectively prevented.

  The hydrodynamic bearing device 1 of this embodiment is assembled by the following process, for example.

  First, the shaft member 2, the bearing sleeve 8, and the seal member 9 are assembled. For example, as shown in FIG. 4, the bearing sleeve 8 is attached to the shaft portion 2a of the shaft member 2 placed on the upper surface of the base 10, and the lower end surface 8c of the bearing sleeve 8 is brought into contact with the upper end surface 2b1 of the flange portion 2b. Make contact. Then, after applying an adhesive, for example, a thermosetting adhesive, to the shaft portion 2b, the seal member 9 is attached to the shaft portion 2a, and the lower end surface 9b of the seal member 9 is brought into contact with the upper end surface 8b of the bearing sleeve 8. Let As a result, the bearing sleeve 8 is interposed between the lower end surface 9b of the seal member 9 and the upper end surface 2b1 of the flange portion 2b.

  Next, a thrust bearing gap is set. The thrust bearing gap is set by adjusting the axial relative position between the shaft member 2 and the seal member 9. For example, in the above state, that is, the lower end surface 8c of the bearing sleeve 8 is brought into contact with the upper end surface 2b1 of the flange portion 2b, and the lower end surface 9b of the seal member 9 is brought into contact with the upper end surface 8b of the bearing sleeve 8 From this state (the state where the thrust bearing gap is zero), the shaft member 2 with respect to the bearing sleeve 8 and the seal member 9 has a thrust bearing gap (with a size of δ1) of the first thrust bearing portion T1. The axial movement is performed by an amount corresponding to the total amount δ (= δ1 + δ2) with the thrust bearing gap (the size is δ2) of the two thrust bearing portions T2.

  Specifically, for example, as shown in FIG. 5, the assembly body assembled in the above-described state is placed on the upper surface of the jig 11 provided with the step portion 11 a having the predetermined depth W <b> 2, and the bottom of the bearing sleeve 8. The side end face 8c comes into contact with the upper surface of the jig 11, and the flange portion 2b is accommodated in the step portion 11a. Then, in this state, the shaft member 2 is pressed from above and moved relative to the bearing sleeve 8 and the seal member 9 in the axial direction by a predetermined amount δ. In this case, if the depth W2 of the stepped portion 11a is accurately managed so that W2 = W1 + δ with respect to the axial dimension W1 of the flange portion 2b, the lower end surface 2b2 of the flange portion 2b becomes the stepped portion. The thrust bearing gap δ (= δ1 + δ2) can be set easily and accurately by simply pushing the shaft member 2 until it contacts the bottom surface 11a1 of 11a. Therefore, the work and apparatus for setting the thrust bearing gap are simplified. Alternatively, the thrust bearing gap δ (= δ1 + δ2) can be set by setting W2> W1 + δ and managing the amount of axial relative movement of the shaft member 2.

  Alternatively, the thrust bearing gap is set by bringing the lower end surface 8c of the bearing sleeve 8 into contact with the upper end surface 2b1 of the flange portion 2b, and the lower side of the seal member 9 with respect to the upper end surface 8b of the bearing sleeve 8 at this time. It can also be carried out by adjusting the axial position of the seal member 9 so that the end face 9b comes to a position separated from the upper end face 8b in the axial direction by an amount corresponding to the total amount δ (= δ1 + δ2). Such axial position adjustment of the seal member 9 is performed, for example, by using a spacer whose width dimension is accurately controlled to a dimension equal to the total amount δ, using an upper end face 8b of the bearing sleeve 8 and a lower end face 9b of the seal member 9. Can be performed easily and accurately.

  As described above, the axial relative position between the shaft portion 2 and the seal member 9 is adjusted to set the thrust bearing gap (δ), and then the seal member 9 is fixed to the shaft portion 2a at that position. In this embodiment, the seal member 9 is bonded and fixed to the shaft portion 2a by heat-treating (baking) the thermosetting adhesive applied to the shaft portion 2a. At this time, the adhesive applied to the shaft portion 2a is filled in the circumferential groove 2a2 of the outer peripheral surface 2a1 and solidified, whereby the adhesive strength of the seal member 9 to the shaft member 2 is improved.

  Next, as shown in FIG. 6, the assembly comprising the shaft member 2, the bearing sleeve 8, and the seal member 9 assembled by the above process is inserted into the inner peripheral surface 7 c of the housing 7. The lower end surface 8 c is brought into contact with the step 7 d of the housing 7, and the outer peripheral surface 8 d of the bearing sleeve 8 is fixed to the inner peripheral surface 7 c of the housing 7 in this state. The bearing sleeve 8 can be fixed to the housing 7 by an appropriate means such as adhesion, press-fitting, a combination of adhesion and press-fitting, or welding (ultrasonic welding or the like). In the figure, the magnitude of δ is shown in a considerably exaggerated manner.

  When the assembly is completed as described above, the shaft portion 2a of the shaft member 2 is inserted into the inner peripheral surface 8a of the bearing sleeve 8, and the flange portion 2b is inserted into the lower end surface 8c of the bearing sleeve 8 and the bottom portion 7b of the housing 7. It will be in the state accommodated in the space part between a bottom face. Further, a seal space S having a predetermined volume is formed between the outer peripheral surface 9 a of the seal member 9 and the inner peripheral surface 7 a 1 of the upper end portion of the housing 7. Thereafter, the internal space of the housing 7 sealed by the seal member 9 is filled with, for example, lubricating oil as a fluid including the internal pores of the bearing sleeve 8. The oil level of the lubricating oil is always maintained within the range of the seal space S.

  When the shaft member 2 rotates, the regions (two upper and lower regions) of the inner peripheral surface 8a of the bearing sleeve 8 are opposed to the outer peripheral surface 2a1 of the shaft portion 2a via the radial bearing gap. Further, the region serving as the thrust bearing surface of the upper end surface 8b of the bearing sleeve 8 is opposed to the lower end surface 9b of the seal member 9 through the thrust bearing gap, and becomes the thrust bearing surface of the lower end surface 8c of the bearing sleeve 8. The region faces the upper end surface 2b1 of the flange portion 2b through a thrust bearing gap. As the shaft member 2 rotates, the dynamic pressure of the lubricating oil is generated in the radial bearing gap, and the shaft portion 2a of the shaft member 2 is rotated in the radial direction by the lubricating oil film formed in the radial bearing gap. It is supported non-contact freely. 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 and the seal member 9 are supported in a non-contact manner so as to be rotatable in the thrust direction by the oil film of the lubricating oil formed in the thrust bearing gap. 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. Since the thrust bearing gap (δ1) of the first thrust bearing portion T1 and the thrust bearing gap (δ2) of the second thrust bearing portion T2 are accurately managed as δ = δ1 + δ2 in the above assembly process, stable thrust is achieved. Bearing function can be obtained.

  Further, as described above, the dynamic pressure groove 8a1 of the first radial bearing portion R1 is formed to be axially asymmetric with respect to the axial center m, and the axial dimension X1 in the region above the axial center m is lower. It is larger than the axial dimension X2 of the side region (see FIG. 3). Therefore, when the shaft member 2 rotates, 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 second thrust bearing portion T2 It circulates through the path of the thrust bearing gap → the axial groove 8d1 → the thrust bearing gap of the first thrust bearing portion T1, and is again drawn into the radial bearing gap of the first radial bearing portion R1. In this way, the structure in which the lubricating oil flows and circulates in the internal space of the housing 7 prevents a phenomenon in which the pressure of the lubricating oil in the internal space becomes a negative pressure locally, resulting in the generation of negative pressure. Problems such as generation of bubbles, leakage of lubricating oil and generation of vibration due to 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.

  Further, since the pulling force (pumping force) of the lubricating oil toward the inner diameter side by the dynamic pressure groove 8b1 of the first thrust bearing portion T1 also acts on the lubricating oil in the radial bearing gap of the first radial bearing portion R1, the first radial Even if the differential pressure of the pull-in force in the bearing portion R1 is relatively low, good fluid circulation of the lubricating oil is ensured. As a result, the axial asymmetry in the dynamic pressure groove 8a1 of the first radial bearing portion R1 can be made smaller than in the prior art. For example, the axial dimension X1 of the upper region of the dynamic pressure groove 8a1 can be made smaller than in the past, The axial center m of the dynamic pressure groove 8a1 can be shifted to the upper end face 8b side, or the axial dimension of the bearing sleeve 8 can be reduced. According to the former, since the axial separation distance between the axial center m of the dynamic pressure groove 8a1 of the first radial bearing portion R1 and the axial center of the dynamic pressure groove 8a2 of the second radial bearing portion R2 increases, the moment load It is possible to increase the load capacity. On the other hand, according to the latter, the axial dimension of the hydrodynamic bearing device can be made smaller than before.

  FIG. 7 shows a hydrodynamic bearing device (fluid hydrodynamic bearing device) 21 according to another embodiment. The hydrodynamic bearing device 21 of this embodiment is different from the hydrodynamic bearing device 1 of the above-described embodiment in that the bearing sleeve is composed of an upper bearing sleeve 81 and a lower bearing sleeve 82, and a spacer member 83 is provided therebetween. It is in the point where it intervenes. The spacer member 83 is formed in a ring shape from a soft metal material such as brass (brass), other metal materials, or a resin material, and has a porous structure such as the upper bearing sleeve 81 and the lower bearing sleeve 82. Not.

  A first radial bearing portion R1 is provided between the inner peripheral surface 81a of the upper bearing sleeve 81 and the outer peripheral surface 2a1 of the shaft portion 2a of the shaft member 2, and the inner peripheral surface 82a of the lower bearing sleeve 82 and the shaft portion 2a A second radial bearing portion R2 is provided between the outer peripheral surface 2a1. A first thrust bearing portion T1 is provided between the upper end surface 81b of the upper bearing sleeve 81 and the lower end surface 9b of the seal member 9, and the lower end surface 82c of the lower bearing sleeve 82 and the flange portion of the shaft member 2 are provided. A second thrust bearing portion T2 is provided between the upper end surface 2b1 of 2b. An annular groove (V-groove) is formed on the lower end surface of the upper bearing sleeve 81 for identification with the lower bearing sleeve 82. Further, one or more axial grooves 81d1, 82d1, and 83d are formed on the outer circumferential surface 81d of the upper bearing sleeve 81, the outer circumferential surface 82d of the lower bearing sleeve 82, and the outer circumferential surface of the spacer member 83, respectively. Formed. These axial grooves 81d1, 82d1, and 83d are formed with the phases in the circumferential direction aligned and communicate with each other in the axial direction.

  Since the spacer member 83 having no porous structure is interposed between the upper bearing sleeve 81 and the lower bearing sleeve 82, the housing 7 has a structure higher than that of the fluid dynamic bearing device 1 of the above-described embodiment. The total amount of lubricating oil filled in the internal space can be small (because the lubricating oil is not impregnated in the spacer member 83). On the other hand, the volume change amount due to the thermal expansion / contraction of the lubricating oil is proportional to the total amount of the lubricating oil filled in the internal space of the housing 7, so the volume of the seal space S is reduced by the amount of the total oil amount. Can be small. Therefore, the hydrodynamic bearing device 21 of this embodiment can further reduce the axial dimension of the seal space S (seal member 9). Since other matters are the same as those in the above-described embodiment, a duplicate description is omitted.

  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 dynamic pressure grooves having a herringbone shape or a spiral shape. Is not limited to this.

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

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

  FIG. 9 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 this example, the region that becomes the radial bearing surface of the inner peripheral surface 8a of the bearing sleeve 8 is configured by three arc surfaces 8a4, 8a5, and 8a6 (so-called three arc bearings). The centers of curvature of the three arcuate surfaces 8a4, 8a5, 8a6 are offset from the shaft center O of the bearing sleeve 8 (shaft portion 2a) by an equal distance. In each region defined by the three arcuate surfaces 8a4, 8a5, and 8a6, the radial bearing gap has a shape gradually reduced in a wedge shape in both circumferential directions. Therefore, when the bearing sleeve 8 and the shaft portion 2a rotate relative to each other, 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 sleeve 8 and the shaft portion 2a are supported in a non-contact manner by the dynamic pressure action of the lubricating oil. Note that a deeper axial groove called a separation groove may be formed at the boundary between the three arcuate surfaces 8a4, 8a5, 8a6.

  FIG. 10 shows another example in the case where one or both of the radial bearing portions R1 and R2 are configured by multi-arc bearings. In this example as well, the region that becomes the radial bearing surface of the inner peripheral surface 8a of the bearing sleeve 8 is configured by three arc surfaces 8a7, 8a8, and 8a9 (so-called three arc bearings), but the three arc surfaces 8a7, In each region partitioned by 8a8 and 8a9, the radial bearing gap has a shape gradually reduced in a wedge shape with respect to one direction in the circumferential direction. The multi-arc bearing having such a configuration may be referred to as a taper bearing. Further, deeper axial grooves 8a10, 8a11, and 8a12 called separation grooves are formed at boundaries between the three arcuate surfaces 8a7, 8a8, and 8a9. For this reason, when the bearing sleeve 8 and the shaft portion 2a are relatively rotated in a predetermined direction, the lubricating oil in the radial bearing gap is pushed into the minimum gap side reduced in a wedge shape, and the pressure rises. The bearing sleeve 8 and the shaft portion 2a are supported in a non-contact manner by the dynamic pressure action of the lubricating oil.

  FIG. 11 shows another example in the case where one or both of the radial bearing portions R1 and R2 are configured by multi-arc bearings. In this example, in the configuration shown in FIG. 10, the predetermined regions θ on the minimum gap side of the three arcuate surfaces 8a7, 8a8, 8a9 are concentric with the axis O of the bearing sleeve 8 (shaft portion 2a) as the center of curvature. It is composed of arcs. Therefore, in each predetermined area θ, the radial bearing gap (minimum gap) is constant. The multi-arc bearing having such a configuration may be referred to as a tapered flat bearing.

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

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

  In the above embodiment, the inside of the hydrodynamic bearing device 1 is filled, and the radial bearing gap between the bearing sleeve 8 and the shaft member 2 and the thrust bearing between the bearing sleeve 8 and the shaft member 2 and the seal member 9 are filled. Lubricating oil is exemplified as the fluid that generates the dynamic pressure in the gap, but other fluids that can generate the dynamic pressure in each bearing gap, for example, gas such as air, magnetic fluid, etc. may be used. it can.

  Further, in the above description, the case where the radial bearing surface is formed on the inner peripheral surface 8a of the bearing sleeve 8 is exemplified, but the radial bearing surface is formed on the surface facing the radial bearing gap, that is, the outer peripheral surface 2a1 of the shaft portion 2a. You can also. Furthermore, although the case where the thrust bearing surface is formed on both end surfaces 8b and 8c of the bearing sleeve is illustrated, the surfaces facing each other through the thrust bearing gap, that is, the lower end surface 9b of the seal member 9 and the flange portion 2b of the shaft member 2 are illustrated. It can also be formed on the upper end surface 2b1.

1 is a cross-sectional view of a spindle motor for information equipment incorporating a fluid dynamic bearing device according to an embodiment of the present invention. It is sectional drawing which shows the dynamic pressure bearing apparatus which concerns on embodiment of this invention. It is sectional drawing of a bearing sleeve, and is a figure which shows a lower side end surface and an upper side end surface. It is a figure which shows an assembly process. It is a figure which shows an assembly process. It is a figure which shows an assembly process. It is sectional drawing which shows the hydrodynamic bearing apparatus which concerns on other embodiment of this invention. It is sectional drawing which shows other embodiment of a radial bearing part. It is sectional drawing which shows other embodiment of a radial bearing part. It is sectional drawing which shows other embodiment of a radial bearing part. It is sectional drawing which shows other embodiment of a radial bearing part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing apparatus 2 Shaft member 2a Shaft part 2b Flange part 7 Housing 8 Bearing sleeve 8a Inner peripheral surface 8b Upper end surface 8c Lower end surface 9 Seal member 9a Outer peripheral surface 9a1 Tapered surface R1, R2 Radial bearing part T1, T2 Thrust bearing Part S Seal space

Claims (8)

A housing, a bearing sleeve fixed inside the housing, a shaft member rotating relative to the housing and the bearing sleeve, a seal member located on one end of the housing, the bearing sleeve and the shaft In a hydrodynamic bearing device comprising a radial bearing portion that supports the shaft member in a non-contact manner in a radial direction by a hydrodynamic action of a fluid generated in a radial bearing gap between the members,
The shaft member has a shaft portion inserted into the inner peripheral surface of the bearing sleeve, and a flange portion provided on the shaft portion,
The seal member is fixed to the shaft member, a seal space is formed on the outer peripheral surface side of the seal member,
A first thrust bearing portion is provided between one end surface of the seal member and one end surface of the bearing sleeve facing the seal member, and the first thrust bearing portion is formed by the dynamic pressure action of fluid generated in a thrust bearing gap. Non-contact support of the member and shaft member in the thrust direction,
A second thrust bearing portion is provided between one end surface of the flange portion and the other end surface of the bearing sleeve opposed to the flange portion, and the second thrust bearing portion is formed by the dynamic pressure action of fluid generated in a thrust bearing gap. A hydrodynamic bearing device characterized in that a member is supported in a non-contact manner in a thrust direction.   2. The hydrodynamic bearing device according to claim 1, wherein a taper surface that is gradually reduced in diameter toward the outside of the housing is formed on an outer peripheral surface of the seal member.   The seal member is fixed to the shaft member with an adhesive, and at least one of the seal member and the shaft member is provided with a recess filled with an adhesive. The hydrodynamic bearing device described. A housing, a bearing sleeve fixed inside the housing, a shaft member rotating relative to the housing and the bearing sleeve, a seal member located on one end of the housing, the bearing sleeve and the shaft In a hydrodynamic bearing device comprising a radial bearing portion that supports the shaft member in a non-contact manner in a radial direction by a hydrodynamic action of a fluid generated in a radial bearing gap between the members,
The seal member is provided on the shaft member;
One end surface of the seal member is opposed to one end surface of the bearing sleeve via a thrust bearing gap,
The outer peripheral surface of the seal member is provided with a tapered surface that gradually decreases in diameter toward the outside of the housing and faces the seal space.   The hydrodynamic bearing device according to claim 1, wherein the radial bearing portion includes a hydrodynamic groove as a hydrodynamic pressure generating unit.   The hydrodynamic bearing device according to any one of claims 1 to 4, wherein the radial bearing portion is a multi-arc bearing.   A spindle motor of a disk device comprising the fluid dynamic bearing device according to claim 1. A shaft member having a housing, a bearing sleeve fixed inside the housing, a shaft portion inserted into the inner peripheral surface of the bearing sleeve, and a flange portion provided on the shaft portion, and the shaft member And a radial bearing that supports the shaft member in a radial direction in a radial direction by a dynamic pressure action of a fluid generated in a radial bearing gap between an inner peripheral surface of the bearing sleeve and an outer peripheral surface of the shaft member And a first thrust bearing portion that non-contact supports the seal member and the shaft member in the thrust direction by a dynamic pressure action of a fluid generated in a thrust bearing gap between one end surface of the seal member and one end surface of the bearing sleeve And a second thrust bearing portion that non-contact supports the shaft member in a thrust direction by a dynamic pressure action of a fluid generated in a thrust bearing gap between one end surface of the flange portion and the other end surface of the bearing sleeve. A method of manufacturing a dynamic pressure bearing apparatus having,
The shaft portion of the shaft member is inserted into the inner peripheral surface of the bearing sleeve, and the seal member is attached to the shaft portion, whereby the bearing sleeve is attached to one end surface of the seal member and one end surface of the flange portion. A process of interposing with
After the step, the first thrust bearing portion is adjusted between the bearing sleeve and one end surface of the seal member and one end surface of the flange portion by adjusting an axial relative position between the shaft portion and the seal member. And forming a gap having an amount corresponding to the total amount of thrust bearing gaps of the second thrust bearing portion;
After the step, fixing the seal member to the shaft portion;
And a step of housing the assembly including the bearing sleeve, the shaft member, and the seal member assembled in the step in the housing.

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