JP2007170574A - Fluid bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid bearing device wherein a bearing sleeve is positioned and fixed to a housing with high precision. <P>SOLUTION: A first bearing sleeve 8 and a second bearing sleeve 9 are fixed at the inner periphery of the housing 7 by being separated from each other in the axial direction. A resin-made spacer 10 is arranged between the bearing sleeves 8 and 9. The rigidity in the axial direction of the spacer 10 is lower than the rigidity of the first and second bearing sleeves 8, 9. In such a state that the first and second bearing sleeves 8, 9 are positioned and fixed in the housing 7, therefore, the spacer 10 is greatly compressed in the axial direction compared with the bearing sleeves 8, 9. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device.

  A hydrodynamic bearing device supports a shaft member in a relatively rotatable manner with a lubricating film of fluid generated in a bearing gap, and recently, for example, an HDD utilizing its excellent rotational accuracy, high-speed rotational performance, quietness, etc. Starting with bearings for spindle motors mounted on information devices such as magnetic disk devices such as CD-ROM, CD-R / RW, DVD-ROM / RAM, etc., and magneto-optical disk devices such as MD, MO, etc. As a bearing for a small motor such as a polygon scanner motor of a laser beam printer (LBP), a color wheel motor of a projector, or a fan motor.

  For example, in a hydrodynamic bearing device incorporated in a spindle motor for HDD, both a radial bearing portion that supports a shaft member in a radial direction or a thrust bearing portion that supports a shaft direction in a thrust direction exerts a dynamic pressure action on the lubricating fluid in the bearing gap. A configuration including a dynamic pressure bearing provided with a dynamic pressure generating portion for generating the pressure is known. In this case, a dynamic pressure groove as a dynamic pressure generating portion is formed on either the inner peripheral surface of the bearing sleeve or the outer peripheral surface of the shaft member facing the bearing sleeve, and the radial bearing is disposed in the radial bearing gap between both surfaces. The part is often formed. In addition, a dynamic pressure groove is formed on one end surface of the flange portion provided on the shaft member and an end surface of the bearing sleeve facing the flange portion, and a thrust bearing portion is formed in the thrust bearing gap between both surfaces. (See, for example, Patent Document 1).

Usually, this type of bearing sleeve is fixed at a predetermined position on the inner periphery of the housing. At this time, the bearing sleeve fixed to the housing is, for example, one in which a plurality of hydrodynamic groove forming regions are provided in the inner periphery of one bearing sleeve and separated in the axial direction (see Patent Document 1). In addition, for the purpose of making the bearing span of the radial bearing portion longer, there is known one in which a plurality of bearing sleeves are arranged apart from each other in the axial direction. In this case, a member such as a spacer (also referred to as a spacer) is often interposed between the plurality of bearing sleeves (see, for example, Patent Document 2).
JP 2003-239951 A Japanese Patent No. 3602707

  As described above, when a plurality of bearing sleeves are used, the positional accuracy (such as coaxiality) between the bearing sleeves and the assembly accuracy of the bearing sleeve with respect to the housing become problems. For example, when a thrust bearing gap is formed between an end surface of the bearing sleeve and a surface (such as an end surface of the flange portion) facing the end surface, it is necessary to accurately determine the axial position of the bearing sleeve relative to the housing. It is not easy to accurately perform this kind of positioning and fixing in a hydrodynamic bearing device having a configuration in which a spacer is interposed between bearing sleeves.

  That is, since there is a dimensional tolerance for each of the bearing sleeve and spacer, if they are fixed to the inner periphery of the housing in a state where they are in contact with each other in the axial direction, they are affected by variations in the axial dimension of each part. Thus, the fixing position of the bearing sleeve with respect to the housing may be shifted in the axial direction from a predetermined position. Thrust bearing clearance is usually on the order of several μm to several tens of μm. When the sum of the dimensional tolerances of the above parts exceeds the required width of the thrust bearing clearance, the thrust bearing clearance is managed with high accuracy. Difficult to do.

  An object of the present invention is to provide a hydrodynamic bearing device in which positioning and fixing of a bearing sleeve with respect to a housing is performed with high accuracy.

  In order to solve the above-described problems, the present invention provides a housing, a plurality of bearing sleeves that are axially spaced on the inner periphery of the housing, a spacer that is disposed between the bearing sleeves, and an inner bearing sleeve. A shaft member inserted into the periphery, and a radial bearing portion that supports the shaft member in a relatively rotatable manner with a lubricating film of fluid generated in a radial bearing gap between the outer peripheral surface of the shaft member and the inner peripheral surface of the bearing sleeve. Further, there is provided a hydrodynamic bearing device in which a bearing sleeve is fixed to a housing with compressive deformation in the axial direction of a spacer. Here, the compressive deformation of the spacer includes not only elastic deformation but also plastic deformation.

  In this way, if the bearing sleeve is fixed to the housing with the axial deformation of the spacer, even if the axial dimensions of the individual bearing sleeves vary, the adverse effect of this variation can be attributed to the compressive deformation of the spacer. Can be reduced. Therefore, in the state of the assembly body in which the bearing sleeve is fixed to the housing, variation in the axial dimension can be suppressed, and the positioning and fixing of the bearing sleeve with respect to the housing can be performed with high accuracy.

  The spacer is preferably compressible and deformable according to the variation in the axial dimension of each bearing sleeve. Further, it is preferable that the compressive deformation is caused by a load such that a decrease in shape accuracy of the bearing sleeve is negligible. From the above viewpoint, the amount of compressive deformation is preferably adjusted by the axial rigidity and the axial dimension. For example, when the material is limited, the axial dimension of the spacer can be adjusted by adjusting the axial dimension. If the dimensions are limited, the material should be selected appropriately.

  Further, as the spacer, it is only necessary to satisfy the above conditions, and a spacer having a very high dimensional accuracy is not necessary. Moreover, it is not necessary to fix to the housing. Therefore, the molding cost of the spacer can be kept low, and the fixing operation of the bearing sleeve to the housing can be simplified. As a material that satisfies these conditions, for example, a material made of resin, rubber, or the like can be suitably used. A porous body, a porous resin, or the like can be used without any problem.

  Various methods such as press-fitting and bonding are conceivable as methods for fixing the bearing sleeve. Among them, fixing by bonding does not require so much accuracy in the radial dimension of the bearing sleeve (it can be manufactured to a certain extent), thus reducing the cost. Is possible and preferred.

  When the shaft member is provided with a flange portion that projects toward the outer diameter side, a thrust bearing gap can be formed between one end surface of the flange portion and the end surface of the bearing sleeve facing the flange portion. In particular, the flange portion is provided at two locations on the shaft member, and the end surfaces of the flange portions are respectively opposed to the end surfaces on the side opposite to the spacer of the bearing sleeve fixed in the axial direction, and a thrust is provided between the opposed surfaces. When providing a bearing gap, the thrust bearing gap can be managed with high accuracy, which is preferable.

  Moreover, when providing a flange part in a shaft member, the sealing space which prevents the outflow of the fluid inside a housing can also be formed between the outer peripheral surface of a flange part, and the surface facing this.

  As described above, according to the present invention, it is possible to provide a hydrodynamic bearing device in which the bearing sleeve is positioned and fixed with respect to the housing with high accuracy.

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

  FIG. 1 conceptually shows one configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device (dynamic pressure 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. The spindle motor is supported by a hydrodynamic bearing device 1 that rotatably supports a shaft member 2, a hub 3 fixed to the shaft member 2, and a radial gap, for example. And a stator coil 4 and a rotor magnet 5, and a bracket 6. 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 hub 3. The hydrodynamic bearing device 1 is fixed to the inner periphery of the bracket 6. The hub 3 holds one or a plurality (two in FIG. 1) of disks D as information storage media. In the spindle motor configured as described above, when the stator coil 4 is energized, the rotor magnet 5 is rotated by the exciting force generated between the stator coil 4 and the rotor magnet 5, thereby holding the hub 3 and the hub 3. The disc D thus rotated integrally with the shaft member 2.

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a housing 7, a first bearing sleeve 8 and a second bearing sleeve 9 fixed to the inner periphery of the housing 7, and a spacer 10 disposed between the bearing sleeves 8 and 9. The shaft member 2 is inserted into the inner periphery of the first bearing sleeve 8 and the second bearing sleeve 9 and is provided with the first flange portion 11 and the second flange portion 12 spaced apart in the axial direction. With. For convenience of explanation, the side from which the hub 3 fixed side end of the shaft member 2 protrudes from the hydrodynamic bearing device 1 will be described as the upper side, and the side opposite to the protruding side of the shaft member 2 will be described below.

  The housing 7 has a cylindrical shape with openings at both ends. For example, a metal (including an alloy) such as brass or aluminum is machined, or a crystalline resin such as LCP, PPS, or PEEK, or an amorphous material such as PPSU, PES, or PEI. It is formed by injection molding of a resin composition based on a resin. The inner peripheral surface 7a of the housing 7 is a straight cylindrical surface having a constant diameter in the axial direction, and the first bearing sleeve 8 and the second bearing sleeve 9 are separated from each other in the axial direction on the inner peripheral surface 7a. It is fixed in the state.

  The first bearing sleeve 8 and the second bearing sleeve 9 are formed in a cylindrical shape with, for example, a metal non-porous body or a porous body made of sintered metal. In this embodiment, the first bearing sleeve 8 and the second bearing sleeve 9 are formed in a cylindrical shape with a sintered metal porous body mainly composed of copper, and are formed on the inner peripheral surface 7a of the housing 7, for example, It is fixed by appropriate means such as adhesion (including loose adhesion), press-fitting (including press-fitting adhesion), and welding (including ultrasonic welding). Of course, these bearing sleeves 8 and 9 can be formed of a material other than metal such as ceramic. It does not matter whether the bearing sleeves 8 and 9 are porous bodies.

  A region where a plurality of dynamic pressure grooves are arranged as a radial dynamic pressure generating portion is formed on the entire inner surface or a part of the cylindrical region of the inner peripheral surface 8 a of the first bearing sleeve 8. In this embodiment, for example, as shown in FIG. 3A, a region in which a plurality of dynamic pressure grooves 8a1 are arranged in a herringbone shape is formed. Further, as shown in FIG. 4, a region where a plurality of dynamic pressure grooves 9 a 1 are similarly arranged in a herringbone shape is also formed on the inner peripheral surface 9 a of the second bearing sleeve 9. The formation regions of these dynamic pressure grooves 8a1 and 9a1 are opposed to the outer peripheral surface 2a of the shaft member 2 as radial bearing surfaces, respectively. Radial bearing gaps of the bearing portions R1 and R2 are respectively formed (see FIG. 2).

  As shown in FIG. 3B, for example, as shown in FIG. 3B, a plurality of dynamic pressure grooves 8b1 are arranged in a spiral shape on the entire upper surface 8b of the first bearing sleeve 8 or a part of the annular region. A region is formed. This dynamic pressure groove 8b1 formation region is opposed to the lower end surface 11a of the first flange portion 11 as a thrust bearing surface, and a first thrust bearing portion T1 described later is formed between the lower end surface 11a and the shaft member 2 when rotating. A thrust bearing gap is formed (see FIG. 2).

  As shown in FIG. 3C, for example, as shown in FIG. 3C, a plurality of dynamic pressure grooves 9b1 are arranged in a spiral shape on the entire lower surface 9b of the second bearing sleeve 9 or a partial annular region. A region is formed. This dynamic pressure groove 9b1 formation region is opposed to the upper end surface 12a of the second flange portion 12 as a thrust bearing surface, and a second thrust bearing portion T2 described later between the upper end surface 12a and the shaft member 2 when rotating. (See FIG. 2).

  One or a plurality of axial grooves 8c1 and 9c1 are formed on the outer peripheral surface 8c of the first bearing sleeve 8 and the outer peripheral surface 9c of the second bearing sleeve 9 fixed to the inner peripheral surface 7a of the housing 7, respectively. ing. In this embodiment, as shown in FIGS. 3B and 3C, three axial grooves 8c1 and 9c1 are formed, respectively.

  The spacer 10 has a cylindrical shape in this embodiment, and its upper end surface 10 a is in contact with the lower end surface 8 d of the first bearing sleeve 8, and the lower end surface 10 b is in contact with the upper end surface 9 d of the second bearing sleeve 9. In this state, the housing 7 is disposed at the substantially center in the axial direction of the inner periphery.

  The spacer 10 is made of a material having smaller axial rigidity than the first and second bearing sleeves 8 and 9, and is made of, for example, resin in this embodiment.

  The dimension (outer diameter dimension) of the outer peripheral surface 10c of the spacer 10 is slightly smaller than the inner diameter dimension of the housing 7 to be disposed. Further, one or a plurality of axial grooves 10c1 are formed on the outer peripheral surface 10c.

  Hereinafter, the process of fixing the bearing sleeves 8 and 9 to the housing 7 will be described with reference to FIGS. 4 and 5 as an example.

  FIG. 4 is a diagram conceptually showing a fixing process of the first bearing sleeve 8 and the second bearing sleeve 9 to the housing 7. In the figure, prior to fixing the first bearing sleeve 8, the second bearing sleeve 9 is positioned and fixed on the inner periphery of the housing 7 with the lower end surface 9 b as a reference surface. In this embodiment, the second bearing sleeve 9 is fixed to the housing 7 via an adhesive. The spacer 10 is placed on the second bearing sleeve 9 with its lower end surface 10 b in contact with the upper end surface 9 d of the second bearing sleeve 9.

  From this state, the first bearing sleeve 8 is introduced into the inner periphery of the housing 7 toward the position indicated by the one-dot chain line in FIG. Simultaneously with this introduction, the axial positioning with respect to the housing 7 is performed using the upper end surface 8b as a reference surface. At this time, when the sum of the axial dimensions of the bearing sleeves 8 and 9 and the spacer 10 is equal to or less than the sum of the required axial dimensions of the respective members, the axial direction of the bearing sleeves 8 and 9 is not particularly problematic. Can be accurately positioned.

  When the sum of the axial dimensions of the individual bearing sleeves 8 and 9 and the spacer 10 exceeds the sum of the required axial dimensions of the individual members, the first bearing sleeve 8 is inserted into the housing 7 as shown in FIG. The spacer 10 made of a material having a lower axial rigidity than the bearing sleeves 8 and 9 is compressed and deformed more than the bearing sleeves 8 and 9.

  Therefore, even when the variation of the axial dimension for each assembly component (the first and second bearing sleeves 8 and 9 and the spacer 10) from the predetermined dimension is large, the spacer 10 is greatly compressed and deformed. The first and second bearing sleeves 8, 8, avoiding a situation in which the fixing position of the first bearing sleeve 8 that performs positioning after the positioning and fixing of the second bearing sleeve 9 deviates greatly from the predetermined position in the axial direction. 9 can be reliably positioned and fixed with respect to the housing 7.

  In particular, in this embodiment, since the bearing sleeves 8 and 9 are made of a sintered metal porous body and the spacer 10 is made of resin, the amount of compressive deformation h (see FIG. 5) of the spacer 10 is the first. In a state where the bearing sleeve 8 is positioned at a predetermined position in the axial direction (pressed to the position indicated by a one-dot chain line in FIG. 4), the axial variation of each bearing sleeve 8 and 9 is summed up from the predetermined dimension. Almost equal. Therefore, positioning and fixing with respect to the housing 7 can be performed with high accuracy without lowering the surface accuracy of the inner peripheral surfaces 8a and 9a of the first and second bearing sleeves 8 and 9.

  Further, according to the above configuration, the lubricating oil in the radial bearing gap described later does not escape to the axial gap between the spacer 10 and the bearing sleeves 8 and 9. Therefore, the oil film pressure in the radial bearing gap can be reliably and well-balanced.

  Moreover, according to the said structure, since it is not necessary to perform the process for obtaining the axial direction dimension of each bearing sleeve 8 and 9 with high precision, the process cost for each component can be held down.

  In this embodiment, since the bearing sleeves 8 and 9 are fixed to the housing 7 by bonding, for example, the surface accuracy (roundness, cylindricity, etc.) of the inner peripheral surfaces 8a and 9a can be obtained with high accuracy. If so, the positioning and fixing can be performed with high accuracy without being affected by the surface accuracy of the outer peripheral surfaces 8c and 9c so much by positioning and fixing the inner peripheral surfaces 8a and 9a as the reference surface. Moreover, since the process for improving the surface accuracy of the outer peripheral surfaces 8c and 9c is not required, the processing cost is reduced accordingly.

  The shaft member 2 is formed of a metal material such as stainless steel, for example, and is inserted into the inner periphery of the first bearing sleeve 8 and the second bearing sleeve 9. The shaft member 2 as a whole has a shaft shape with substantially the same diameter, and a relief portion 2b formed in a smaller diameter than other places in an axially intermediate portion of the outer peripheral surface 2a (region facing the inner peripheral surface 10d of the spacer 10). Is formed. Further, in the outer peripheral surface 2 a of the shaft member 2, annular grooves 2 c as concave portions are formed in the fixing regions of the first flange portion 11 and the second flange portion 12, respectively. In this embodiment, the shaft member 2 is an integrally processed product made of metal. However, for example, a hybrid shaft made of metal and resin (the sheath portion is metal and the core portion is resin, etc.) can be used. .

  The first flange portion 11 and the second flange portion 12 are formed in an annular shape from a metal material such as a copper alloy such as brass, or a resin material such as LCP or PPS. The first flange portion 11 is fixed to the outer periphery of the shaft member 2 with its lower end surface 11 a facing the upper end surface 8 b of the first bearing sleeve 8. The second flange portion 12 is fixed to the outer periphery of the shaft member 2 with its upper end surface 12 a facing the lower end surface 9 b of the second bearing sleeve 9.

  Moreover, by fixing each flange part 11 and 12 to the shaft member 2, both surfaces 11a from the axial direction opposing space | interval of the lower end surface 11a of the 1st flange part 11, and the upper end surface 12a of the 2nd flange part 12. , 12a, the first bearing sleeve 8 and the second bearing sleeve 9, and the value obtained by subtracting the sum of the axial dimensions of the spacer 10 is a first thrust bearing portion T1, which will be described later. It is set as the sum total of the thrust bearing clearance of T2. Accordingly, as described above, by accurately determining the axial width from the upper end surface 8b of the first bearing sleeve 8 to the lower end surface 9b of the second bearing sleeve 9, the thrust bearing gaps of the thrust bearing portions T1 and T2 are determined. Can be managed with high accuracy.

  As shown in FIG. 2, an annular taper surface 11 b that gradually decreases in diameter toward the upper side in the axial direction is formed on the outer periphery of the first flange portion 11. Similarly, an annular tapered surface 12b that gradually decreases in diameter toward the lower side in the axial direction is also formed on the outer periphery of the second flange portion 12.

  Therefore, in the state where the first flange portion 11 is fixed to the shaft member 2, the radial dimension is between the outer peripheral surface including the tapered surface 11b and the upper end inner peripheral surface 7a1 of the housing 7 facing the outer peripheral surface. A tapered seal space S1 that gradually decreases toward the lower side in the axial direction (toward the bearing inner side) is formed.

  Similarly, in a state where the second flange portion 12 is fixed to the shaft member 2, the radial dimension between the outer peripheral surface including the tapered surface 12 b and the lower end inner peripheral surface 7 a 2 of the housing 7 facing the outer peripheral surface. Is formed into a tapered seal space S2 that gradually decreases toward the upper side in the axial direction (toward the bearing inner side).

  After assembly is performed as described above, lubricating oil is injected into the internal space of the housing 7. As a result, the hydrodynamic bearing device 1 in which the bearing inner space including the inner holes of the first bearing sleeve 8 and the second bearing sleeve 9 is filled with the lubricating oil is completed. At this time, the total sum of the volumes of the seal spaces S <b> 1 and S <b> 2 is larger than at least the volume change amount associated with the temperature change of the lubricating oil filled in the internal space of the hydrodynamic bearing device 1. Therefore, the oil level of the lubricating oil is always maintained in both the seal spaces S1 and S2.

  The seal spaces S1 and S2 are formed by the outer peripheral surfaces (tapered surfaces 11b and 12b) of the flange portions 11 and 12 projecting outward from the shaft member 2 and the inner peripheral surface 7a of the housing 7 (the upper and inner peripheral surfaces 7a1 and 7a1). And the peripheral surface 7a2). Therefore, the seal space can be formed on the outer diameter side as compared with the case where the seal space is formed between the seal portion fixed to the housing portion and the outer peripheral surface of the shaft member (see, for example, Patent Document 1). The seal volume can be increased. Thereby, it is possible to reduce the thickness of the flange portions 11 and 12 in the axial direction while securing the necessary volume of the seal space, and thus it is possible to reduce the thickness of the entire hydrodynamic bearing device 1.

  In the hydrodynamic bearing device 1 configured as described above, when the shaft member 2 rotates, the dynamic pressure groove 8a1 formation region of the first bearing sleeve 8 and the dynamic pressure groove 9a1 formation region of the second bearing sleeve 9 are opposed to each other. Radial bearing gaps are respectively formed between the outer peripheral surface 2a of the two. As the shaft member 2 rotates, the lubricating oil in the radial bearing gap is pushed toward the axial center of the dynamic pressure groove, and the pressure rises. As described above, the first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft member 2 in a non-contact manner in the radial direction are configured by the dynamic pressure action of the lubricating oil generated by the dynamic pressure grooves 8a1 and 9a1, respectively. (See FIG. 2).

  At the same time, a thrust bearing gap between the dynamic pressure groove 8b1 formation region formed in the upper end surface 8b of the first bearing sleeve 8 and the lower end surface 11a of the first flange portion 11 facing this, and the second The pressure of the lubricating oil film formed in the thrust bearing gap between the dynamic pressure groove 9b1 formation region formed in the lower end surface 9b of the bearing sleeve 9 and the upper end surface 12a of the second flange portion 12 opposite to the region is It is enhanced by the dynamic pressure action of the dynamic pressure grooves 8b1 and 9b1. Then, the first thrust bearing portion T1 and the second thrust bearing portion T2 that support the shaft member 2 in the thrust direction in a non-contact manner are configured by the pressure of these oil films (see FIG. 2).

  In this embodiment, as described above, the axial grooves 8c1, 9c1, 10c1 are formed on the outer peripheral surface 8c of the first bearing sleeve 8, the outer peripheral surface 9c of the second bearing sleeve 9, and the outer peripheral surface 10c of the spacer 10, respectively. By providing, an axial fluid flow path is formed between the inner peripheral surface 7a of the housing 7 which opposes. For this reason, when the shaft member 2 rotates, the thrust bearing gap of the first thrust bearing portion T1 and the thrust bearing of the second thrust bearing portion T2 that are formed apart from each other in the axial direction via the fluid flow path. The gap is in communication with the outer diameter side. According to this, the shaft member 2 is stabilized in the thrust direction by avoiding a situation in which the fluid (lubricating oil) pressure on either one of the thrust bearing portions T1 and T2 is excessively increased or decreased for some reason. Non-contact support. Of course, by providing the axial grooves 8c1, 9c1, and 10c1 on the inner peripheral surface 7a side of the opposing housing 7, a fluid flow path that communicates in the axial direction between thrust bearing gaps that are separated in the axial direction. Can also be configured.

  As described above, with the hydrodynamic bearing device 1 according to this embodiment, the runout rigidity of the shaft member 2 can be increased by taking a long bearing span and managing the thrust bearing gap with high accuracy. Therefore, it is possible to reduce sliding wear that occurs in a region other than the radial bearing surface or the thrust bearing surface, such as one-piece contact. Therefore, even under high-speed rotation exceeding 10,000 rpm, high bearing performance can be stably exhibited. Further, even when wear powder is generated, the wear powder is supplemented by the bearing sleeves 8 and 9 formed of a porous body, so that the hydrodynamic bearing device 1 can exhibit high bearing performance over a long period of time. Can be provided.

  Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment. Hereinafter, other configurations of the present invention will be described together with other configuration examples of the hydrodynamic bearing device to which the present invention is applicable.

  In the above-described embodiment, the case where the spacer 10 is formed of a resin whose axial rigidity is smaller than that of the bearing sleeves 8 and 9 has been described. However, the present invention is not limited to this. For example, it may be formed of an elastic body such as rubber, or may be formed of a sintered metal porous body that has a relatively large number of internal holes and is easily deformed in the axial direction. Alternatively, even if the spacer 10 is made of the same material as the bearing sleeves 8 and 9, the axial dimension thereof is larger than that of the bearing sleeves 8 and 9, and the axial alignment is performed as shown in FIG. As long as the bearing sleeves 8 and 9 are compressed and deformed in the axial direction, they can be used without any problem. Further, regarding the compressive deformation of the spacer 10 in the axial direction, only the amount of compressive deformation is important, and it does not matter whether the compressive deformation is caused only by elastic deformation or accompanied by plastic deformation.

  In the above embodiment, the case where the first bearing sleeve 8 is positioned and fixed in a state where the spacer 10 is placed on the second bearing sleeve 9 fixed to the inner periphery of the housing 7 has been described. It is not necessary to limit to a process. For example, the first bearing sleeve 8 is positioned in a state where an adhesive is applied in advance to the outer peripheral surface 10 c of the spacer 10 or a region facing the outer peripheral surface 10 c, and then the spacer 10 is attached to the housing 7 together with the first bearing sleeve 8. It is also possible to bond and fix. In this case, each of the bearing sleeves 8 and 9 is bonded and fixed to the housing 7, and the assembly body (fluid bearing device 1) in a state where the spacer 10 is bonded and fixed to the inner periphery of the housing 7 in a state of being compressed and deformed in the axial direction. Is obtained.

  In the above embodiment, the case where two bearing sleeves 8 and 9 and one spacer 10 provided between the bearing sleeves 8 and 9 are arranged on the inner periphery of the housing 7 has been described. The invention can also be applied to the case where three or more bearing sleeves are disposed on the inner periphery of the housing 7 and two or more spacers 10 are disposed between the bearing sleeves.

  For the purpose of enlarging the thrust bearing area and increasing the thrust support force, for example, the inner peripheral surface 7a of the housing 7 is omitted from illustration, but the small diameter portion and the large diameter portion formed on both axial sides of the small diameter portion are omitted. A thrust bearing comprising an axial end surface formed at the step portion of the large diameter portion and the small diameter portion and end surfaces 8b and 9b of the bearing sleeves 8 and 9 disposed at the same axial position as the end surface. A surface can also be constructed. According to this configuration, the thrust bearing area can be increased without increasing the area of the end faces 8b, 9b of the bearing sleeves 8, 9. Therefore, since the spacer 10 is compressed and deformed by a predetermined amount, it is not necessary to increase the axial load.

  Rather, when it is desired to ensure the amount of compressive deformation of the spacer 10 with a smaller axial load, the thickness of the bearing sleeves 8 and 9 is reduced, and the diameter of the end surface of the stepped portion of the housing 7 which becomes the thrust bearing surface correspondingly. The directional dimension can also be increased. Of course, the above configuration is also provided on the side of the second thrust bearing portion T2 formed between the lower end surface 9b of the second bearing sleeve 9 and the upper end surface 12a of the second flange portion 12 opposite to the lower end surface 9b. be able to.

  Moreover, in the said embodiment, although the two flange parts 11 and 12 were fixed to the shaft member 2, and the structure which seals the both-ends opening part of the housing 7 by this was illustrated respectively, this invention is a housing which closed one end. The hydrodynamic bearing device having a structure in which the other end opening is sealed between the outer peripheral surface of one flange portion fixed to the shaft member and the opposing surface thereof is also applicable. Alternatively, although not shown, one flange portion fixed to the shaft member 2 is disposed on the bottom side of the bottomed cylindrical housing, and both end surfaces of the flange portion and surfaces facing them (second bearing) The present invention can also be applied to a hydrodynamic bearing device having a structure in which a thrust bearing gap is formed between the sleeve 9 and the lower end surface 9b). Further, the flange portion does not necessarily need to form a seal space on the outer periphery thereof. For example, apart from the flange portion, a member on the bearing side (the housing 7 and the bearing sleeves 8 and 9 fixed to the housing 7). It is also possible to apply to a structure in which a seal portion is provided on the side) and a seal space is formed between the inner peripheral surface of the seal portion and the outer peripheral surface 2a of the shaft member 2 facing the seal portion.

  FIG. 6 shows an example of the above-described hydrodynamic bearing device, in which first and second bearing sleeves 8 and 9 and a spacer 10 are arranged on the inner periphery of a housing 27 having a bottomed cylindrical shape. In addition, a flange portion 22b provided at one end of the shaft member 22 is accommodated between the lower end surface 9b of the second bearing sleeve 9 and the upper end surface 7b1 of the bottom portion 7b of the housing 7 facing the second bearing sleeve 9. In this illustrated example, a step 27d is formed between the cylindrical portion 27a and the bottom 27b of the housing 27, and the lower end surface 9b of the second bearing sleeve 9 is brought into contact with the axial end surface 27d1 of the step 27d. Thus, the axial positioning of the bearing sleeve 9 with respect to the housing 27 is performed. An annular seal member 30 is fixed to the inner periphery of the upper end portion of the cylindrical portion 27 a of the housing 27 with the lower end surface 30 a in contact with the upper end surface 8 b of the first bearing sleeve 8. A seal space S3 is formed between the peripheral surface 30b and the outer peripheral surface 22a1 of the shaft member 22 facing the peripheral surface 30b. In this embodiment, instead of the upper end surface 8b of the first bearing sleeve 8, a dynamic pressure groove shown in FIG. 3B is formed on the upper end surface 27b1 of the bottom 27b of the housing 27. Since other configurations are the same as those in the above embodiment, description thereof is omitted.

  In the above configuration, when the shaft member 22 is relatively rotated, the dynamic pressure grooves 8a1 and 9a1 are opposed to these regions by the dynamic pressure grooves 8a1 and 9a1 provided on the inner peripheral surfaces 8a and 9a of the bearing sleeves 8 and 9, respectively. The dynamic pressure action of the lubricating oil is generated in the radial bearing gap between the outer peripheral surface 22a1 of the shaft portion 22a. The first radial bearing portion R11 and the second radial bearing portion R12 that support the shaft member 22 in a non-contact manner so as to be rotatable in the radial direction are constituted by the pressure of the oil film increased by the dynamic pressure action. (See FIG. 6).

  At the same time, the thrust bearing gap between the region where the dynamic pressure groove 9b1 is formed on the lower end surface 9b of the second bearing sleeve 8 and the lower end surface 11a of the flange portion 22b opposed to this, the upper end surface of the housing bottom portion 27b. The dynamic pressure action of the lubricating oil is generated in the thrust bearing gap between the dynamic pressure groove forming region 27b12 formed and the lower end surface 22b2 of the flange portion 22b facing the region. Then, the first thrust bearing portion T11 and the second thrust bearing portion T12 that support the shaft member 22 in a non-contact manner in the thrust direction are configured by the pressure of the oil film increased by the dynamic pressure action (FIG. 6). See).

  Also in this embodiment, for example, as shown in FIG. 5, the first bearing sleeve 8 is pushed into a predetermined position in the axial direction with respect to the housing 27, and the spacer 10 made of a material having a smaller axial rigidity than the bearing sleeves 8, 9 is provided. The first and second bearing sleeves 8 and 9 can be surely positioned and fixed with respect to the housing 27 by compressing and deforming larger than the bearing sleeves 8 and 9. At the same time, the axial width from the upper end surface 8b of the first bearing sleeve 8 to the lower end surface 9b of the second bearing sleeve 9 is accurately defined.

  In this embodiment, rather, the bearing sleeves 8 and 9 are positioned in the axial direction with respect to the housing 27 with high accuracy, so that the small-diameter surface 22a2 serving as a relief portion of the outer peripheral surface 22a1 of the opposing shaft member 22 is formed. By avoiding this, the large-diameter surface 22a3 serving as the radial bearing surface and the inner peripheral surfaces 8a and 9a can be accurately opposed to each other without being displaced in the axial direction. Thereby, the radial rigidity can be further improved.

  In the above embodiment, the dynamic pressure generating portion such as the dynamic pressure groove is provided on the inner peripheral surface 8a or upper end surface 8b of the first bearing sleeve 8, the lower end surface 9b side of the second bearing sleeve 9, or the housing. Although the case where it formed in the upper end surface 27b1 side of the bottom part 27b of 27 was demonstrated, it does not need to be restricted to this form. For example, the dynamic pressure generating portion can be formed on the outer peripheral surface 2a of the shaft member 2 facing these, the lower end surface 11a of the first flange portion 11, or the upper end surface 12a side of the second flange portion 12. . Further, the hub 3 is formed integrally with or separately from the shaft member 2, and the movement is performed on either one of the lower end surface of the hub 3 and the upper end surface 8 b of the housing 7 or the first bearing sleeve 8 facing the hub 3. It is also possible to form a pressure generating part. Similarly, the dynamic pressure generating portion of the form shown below can be formed on the side of the opposing shaft member 2.

  Moreover, in the above embodiment, the structure which generate | occur | produces the dynamic pressure effect | action of a lubricating fluid by herringbone shape or a spiral-shaped dynamic pressure groove is illustrated as radial bearing part R1, R2 and thrust bearing part T1, T2. However, the present invention is not limited to this. The same applies to the radial bearing portions R11 and R12 and the thrust bearing portions T11 and T12 shown in FIG.

  For example, although not shown as radial bearing portions R1 and R2, a so-called step-like dynamic pressure generating portion in which axial grooves are arranged at a plurality of locations in the circumferential direction, or a plurality of circular arc surfaces in the circumferential direction. A so-called multi-arc bearing in which wedge-shaped radial gaps (bearing gaps) are formed between the outer peripheral surfaces 2a of the opposing shaft members 2 may be employed.

  Alternatively, at least one of the inner peripheral surface 8a of the first bearing sleeve 8 and the inner peripheral surface 9a of the second bearing sleeve 9 is not provided with a dynamic pressure groove or an arc surface as a dynamic pressure generating portion. A so-called perfect circle bearing (fluid lubricated bearing) can be formed by a perfect outer peripheral surface 2a of the shaft member 2 facing the inner peripheral surface.

  One or both of the thrust bearing portions T1 and T2 are also 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 that becomes a thrust bearing surface. A step bearing or a corrugated bearing (the step mold is a corrugated one) can also be used.

  Besides, the thrust bearing portions T1 and T2 are configured so as to support the shaft member 2 in a non-contact manner by the dynamic pressure action of the dynamic pressure grooves. For example, the end portion of the shaft member 2 is formed in a spherical shape and faces this. It is also possible to configure a so-called pivot bearing that supports and supports the thrust bearing surface.

  In the first and second embodiments described above, the lubricating oil is exemplified as the fluid that fills the fluid bearing devices 1 and 21 and forms a lubricating film in the radial bearing gap and the thrust bearing gap. In addition, a fluid capable of causing a dynamic pressure action in each bearing gap, for example, a gas such as air, a fluid lubricant such as a magnetic fluid, or lubricating grease may be used.

It is sectional drawing of the spindle motor incorporating the hydrodynamic bearing apparatus which concerns on one Embodiment of this invention. It is sectional drawing of a hydrodynamic bearing apparatus. (A) is a sectional view of the first bearing sleeve, (b) is an upper end view of the first bearing sleeve viewed from the direction of arrow a, and (c) is a second bearing sleeve viewed from the direction of arrow b. FIG. It is a figure which shows notionally the fixing process to the housing of a bearing sleeve. It is the elements on larger scale which show conceptually the fixing process to the housing of a bearing sleeve. It is sectional drawing which shows the other structure of the hydrodynamic bearing apparatus which concerns on this invention.

Explanation of symbols

1, 21 Fluid bearing device 2, 22 Shaft member 3 Hub 4 Stator coil 5 Rotor magnet 7, 27 Housing 7a Inner circumferential surface 7a3 Small diameter portion 7a4, 7a5 Large diameter portion 8, 9 First bearing sleeve 8a Inner circumferential surface 8a1 Pressure groove 8b Upper end surface 8b1 Dynamic pressure groove 8c1 Axial groove 9 Second bearing sleeve 9a Inner peripheral surface 9a1 Dynamic pressure groove 9b Lower end surface 9b1 Dynamic pressure groove 9c1 Axial groove 10 Spacer 10a Upper end surface 10b Lower end surface 10c1 Axial groove 11 First flange portion 11a Lower end surface 12 Second flange portion 12a Upper end surface D Disc h Compression deformation amount S1, S2, S3 Seal spaces R1, R2, R11, R12 Radial bearing portions T1, T2, T11, T12 Thrust bearing Part

Claims (5)

A housing, a plurality of bearing sleeves that are spaced apart in the axial direction on the inner periphery of the housing, a spacer that is disposed between the bearing sleeves, and a shaft member that is inserted into the inner periphery of the bearing sleeve; And a hydrodynamic bearing device including a radial bearing portion that relatively rotatably supports the shaft member with a lubricating film of fluid generated in a radial bearing gap between an outer peripheral surface of the shaft member and an inner peripheral surface of the bearing sleeve. ,
The hydrodynamic bearing device, wherein the bearing sleeve is fixed to the housing along with compressive deformation of the spacer in the axial direction.   The hydrodynamic bearing device according to claim 1, wherein the spacer is made of resin.   The hydrodynamic bearing device according to claim 1, wherein the bearing sleeve is bonded and fixed to the housing.   The shaft member is provided with a flange portion projecting toward the outer diameter side, and a thrust bearing gap is formed between an axial end surface of the flange portion and an end surface of the bearing sleeve facing the flange portion. Item 2. The hydrodynamic bearing device according to Item 1. The hydrodynamic bearing device according to claim 4, wherein a seal space is formed between the outer peripheral surface of the flange portion and a surface facing the flange portion to prevent outflow of fluid inside the housing.

Images