JP2013061025A - Fluid dynamic bearing device and motor equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a cost in a fluid dynamic bearing device where an opening part at one end of a cylindrical member is sealed by a cover member while securing required bearing performance.SOLUTION: In the fluid dynamic bearing device 1, a lower end opening of a housing 7 which is the cylindrical member is sealed by the disc-shaped cover member 10. The cover member 10 is formed by punching a metal plate and has a burr 10f at one edge of an outer circumferential surface 10c. After being formed in the punching process, the cover member 10 is fitted into the space in the lower end opening of the housing 7 with the burr 10f facing outward. The cover member 10 is fixed to the lower end of the housing 7 and the lower end opening of the housing 7 is sealed by plastically deforming the lower end of the housing 7 toward the inner diameter while enfolding the burr 10f.

Description

  The present invention relates to an improvement in a fluid dynamic bearing device and a motor including the same.

  The fluid dynamic pressure bearing device is a bearing device that supports a shaft member in a non-contact manner so as to be relatively rotatable with respect to the bearing member by a fluid lubricating film (oil film) formed in a radial bearing gap. This fluid dynamic pressure bearing device has characteristics such as high-speed rotation, high rotation accuracy, and low noise. Recently, a disk drive device (for example, a magnetic disk drive device such as an HDD or the like, a CD) In addition, it is suitably used as a motor bearing device such as a spindle motor of an optical disc driving apparatus such as a DVD or a Blu-ray disc, a polygon scanner motor of a laser beam printer (LBP), or a fan motor of an electric device.

  As one configuration example of the fluid dynamic bearing device, for example, as described in Patent Document 1 below, a shaft member, a housing as a cylindrical member having both ends opened and the shaft member inserted into the inner periphery, And a lid member that seals the opening at one end of the housing, and the shaft member is supported in the radial direction by a fluid lubricating film (oil film) formed in a radial bearing gap facing the outer peripheral surface of the shaft member. . In this fluid dynamic pressure bearing device, the lid member is formed in a disk shape from a metal material such as stainless steel, copper alloy, aluminum alloy, etc., and is fixed to the inner periphery of one end opening of the housing by an appropriate means such as adhesion or press-fitting. Has been.

Japanese Patent Laid-Open No. 2004-144205

  For the purpose of reducing the cost of the fluid dynamic bearing device having the above-described configuration, attempts have been made to use a lid member as a metal punched product (press-cut product). When a metal plate is punched by intruding a cutting blade in the thickness direction of the metal plate, thereby obtaining a disc-shaped lid member 100, the outer peripheral surface of the lid member 100 is directed from the punching start side to the end side. Thus, there are a case where the shearing portion 101, the fracture portion 102 and the burr 103 are formed in order [see FIG. 7A], and a case where the shearing portion 101 and the burr 103 are formed [see FIG. 7B]. . That is, when the disc-shaped lid member 100 is formed by punching a metal plate, the burr 103 is formed at one end portion of the outer peripheral surface of the lid member 100 (one outer peripheral edge portion of the lid member 100). The shearing portion 101 is a plastically deformed surface formed by sliding the side surface of the cutting blade with respect to the metal plate, and is generally formed on a smooth surface without unevenness. On the other hand, the fracture portion 102 is formed on a rough surface having minute irregularities, and the burr 103 is a protrusion projecting from one outer peripheral edge on the punching end side. Therefore, if the lid member obtained by punching the metal plate is fixed as it is to the inner periphery of the opening portion of the housing by a widely adopted fixing means such as press fitting, adhesion, welding, etc., various problems may occur.

  That is, when a lid member having a burr on the outer peripheral surface (one outer peripheral edge) is press-fitted into the inner periphery of the opening of the housing, a part or all of the burr will fall off due to a press-fitting resistance, and the shape of the housing In some cases, the accuracy of the attitude of the lid member relative to the housing is adversely affected. If the posture accuracy of the lid member with respect to the housing is not ensured, particularly when the shaft member is supported in one thrust direction on the inner bottom surface of the lid member, the rotational accuracy of the shaft member in one thrust direction is adversely affected. In addition, even if the lid member is bonded and fixed to the inner periphery of the opening of the housing, it is difficult to completely cover the burr with an adhesive, and the burr may fall off during operation of the fluid dynamic bearing device, etc., resulting in contamination. is there. For example, it is possible to cover the entire burr by applying a large amount of adhesive, but the excess adhesive may solidify on the end surface of the lid member, which may adversely affect the bearing performance. Further, even if the lid member is fixed to the inner periphery of the opening of the housing by welding, the presence of the burr becomes an obstacle to securing a predetermined welding accuracy and welding strength. For this reason, the one end opening of the housing cannot be sealed in a predetermined manner, which may cause a fatal problem such as external leakage of fluid.

  The various problems described above can be solved by subjecting the outer peripheral surface of the lid member formed by punching to a finishing process such as grinding and polishing, and smoothing the outer peripheral surface of the lid member. However, if this is done, the cost merit resulting from the use of the metal punching product as the lid member is lost as the number of steps increases.

  In view of such circumstances, an object of the present invention is to reduce the cost while ensuring the required bearing performance in a fluid dynamic pressure bearing device in which one end opening of a cylindrical member is sealed with a lid member. It is in.

  The present invention devised to achieve the above object includes a shaft member, a cylindrical member having both ends opened and a shaft member inserted into the inner periphery, and a lid member for sealing one end opening of the cylindrical member, The fluid motion is such that the shaft member is supported in the radial direction by the fluid lubrication film formed in the radial bearing gap facing the outer peripheral surface of the shaft member, and the shaft member is supported in one thrust direction on the inner bottom surface of the lid member. In the pressure bearing device, the lid member is formed by punching a metal plate and has a burr at one end portion of the outer peripheral surface, and the one end opening of the cylindrical member with the burr member facing the burr outward The lid member is fixed to the cylindrical member by being plastically deformed to the inner diameter side while winding the burr by caulking.

  In the fluid dynamic pressure bearing device according to the present invention, a lid member formed by punching a metal plate and having a burr on one end portion (one outer peripheral edge portion) of the outer peripheral surface is a cylindrical member with the burr facing outward. One end is fitted into the opening. For this reason, contact between the tubular member and the burr is avoided at the stage where the lid member is fitted (arranged) to the one end opening of the tubular member. The deterioration of bearing performance due to is prevented as much as possible. In addition, in the present invention, the lid member is fixed to the cylindrical member by plastically deforming one end of the cylindrical member toward the inner diameter side while winding the burr of the lid member by caulking. In this way, the crimping portion formed on the cylindrical member can be covered while pressing the burr of the lid member against the outer bottom surface of the lid member, so that the occurrence of contamination due to the fall off of the burr can be prevented. . From the above, according to the present invention, even when the punched lid member (press cutting) is used as it is, the occurrence of contamination can be prevented as much as possible. Accordingly, the cost of the fluid dynamic bearing device can be reduced while ensuring the required bearing performance.

  In the above configuration, a space may be formed between the caulking portion and the outer bottom surface of the lid member, and the burr may be covered with an adhesive filled in the space. In this way, the fixing force of the lid member with respect to the cylindrical member can be improved, and the burr can be more effectively prevented from falling off. The caulking portion may be formed partially (particularly in the portion where the burr exists) in the circumferential direction of the tubular member, or may be formed over the entire circumference of the tubular member. Further, the space width of the space may be gradually reduced toward the proximal end side of the crimped portion. This is because the capillary force pulling action acts on the adhesive filled in the space, and the adhesive can be appropriately held in the space.

  The lid member is fitted into the opening at one end of the cylindrical member, and the radial gap between the inner circumferential surface of the cylindrical member and the outer circumferential surface of the lid member facing each other is filled with adhesive (filling / filling). It may be solidified). In this way, in addition to increasing the fixing strength of the lid member with respect to the cylindrical member, the sealing performance of the one end opening of the cylindrical member is enhanced, so that external leakage of the lubricating fluid is effectively prevented, and fluid movement is prevented. The reliability of the pressure bearing device can be increased. Further, even if there is an uneven surface-like fractured portion on the outer peripheral surface of the punched lid member [see FIG. 7 (a)], if the lid member is fitted with a gap, the lid is attached to one end opening of the cylindrical member. At the stage of fitting the members, it is possible to prevent as much contamination as possible from sliding between the tubular member and the broken portion of the lid member. In addition, when the fracture | rupture part exists in the outer peripheral surface of a cover member, since the contact area of the cover member with respect to an adhesive agent (adhesive layer) increases, it becomes advantageous when raising the adhesive strength of the cover member with respect to a cylindrical member.

  A step surface can be provided on the cylindrical member, and the inner bottom surface of the lid member can be brought into contact with the step surface. In this way, the axial relative position of the lid member with respect to the cylindrical member can be accurately determined. For example, when the thrust bearing portion is configured on the inner bottom surface of the lid member, the thrust bearing portion The bearing performance can be easily secured. Moreover, since the lid member can be clamped from both sides in the axial direction by the stepped surface and the crimping portion of the cylindrical member, the fixing strength of the lid member with respect to the cylindrical member is further improved.

  If a thrust bearing gap is formed between the end surfaces of the shaft members facing each other and the inner bottom surface of the lid member, a thrust bearing portion composed of a so-called dynamic pressure bearing can be formed, so that the thrust direction (one thrust direction) It is advantageous in increasing the support ability and quietness. In this case, a thrust dynamic pressure generating part that generates fluid dynamic pressure in the thrust bearing gap can be provided on the inner bottom surface of the lid member that is one surface forming the thrust bearing gap. The lid member can be formed on the inner bottom surface of the lid member simultaneously with the formation of the lid member by punching the metal plate. In this way, it is possible to save the trouble of forming the thrust dynamic pressure generating portion in a separate process, and thus it is possible to configure the thrust bearing portion including the dynamic pressure bearing at low cost.

  In the above configuration, a bearing sleeve that forms a radial bearing gap with the outer peripheral surface of the shaft member can be fixed to the inner periphery of the cylindrical member. In this way, it becomes easy to optimize the required characteristics required for each part of the fluid dynamic bearing device. It is also possible to use a member (bearing member) in which a cylindrical member and a bearing sleeve are provided integrally. This is advantageous in reducing the cost of the fluid dynamic bearing device by reducing the number of parts and the number of assembly steps.

  A radial dynamic pressure generating portion that generates fluid dynamic pressure in the radial bearing gap can be provided on the outer peripheral surface of the shaft member. The radial dynamic pressure generating portion can be formed on a surface (for example, the inner peripheral surface of the bearing sleeve) facing the outer peripheral surface of the shaft member through the radial bearing gap, but the radial dynamic pressure generating portion is minute. In many cases, a plurality of dynamic pressure grooves are provided in the circumferential direction, and if this type of dynamic pressure groove is formed on the inner peripheral surface of the bearing sleeve with high accuracy, there is a high possibility that the manufacturing cost will increase. On the other hand, when the radial dynamic pressure generating portion is provided on the outer peripheral surface of the shaft member, a minute dynamic pressure groove can be accurately formed by combining relatively simple means such as rolling and grinding. Therefore, it is advantageous in reducing the manufacturing cost.

  The fluid dynamic pressure bearing device according to the present invention described above can be suitably used by being incorporated in a motor provided with a stator coil and a rotor magnet, for example, a spindle motor for a disk drive device.

  As described above, according to the present invention, in a fluid dynamic pressure bearing device in which one end opening of a cylindrical member is sealed with a lid member, the required bearing performance is secured and the cost is reduced. be able to.

It is sectional drawing which shows notionally an example of the spindle motor for information equipment with which the fluid dynamic pressure bearing apparatus was integrated. 1 is a cross-sectional view including a shaft of a fluid dynamic bearing device according to a first embodiment of the present invention. (A) is a sectional view of the bearing sleeve, and (b) is a diagram showing a lower end surface of the bearing sleeve. It is a figure which shows the inner bottom face of a cover member. (A)-(c) figure is a principal part expanded sectional view which shows the fixing process of the cover member with respect to a housing in steps. It is a shaft-containing sectional view of a fluid dynamic bearing device according to a second embodiment of the present invention. (A) (b) Both figures are figures which show typically the principal part of the cover member formed by punching.

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

  FIG. 1 conceptually shows a configuration example of a spindle motor for information equipment in which a fluid dynamic pressure bearing device is incorporated. The spindle motor is used in a disk drive device such as an HDD, and includes a fluid dynamic bearing device 1 that rotatably supports a shaft member 2, a disk hub 3 fixed to the shaft member 2, and a radial direction, for example. The stator coil 4 and the rotor magnet 5 that are opposed to each other through the gap, and the motor base 6 are provided. The stator coil 4 is attached to the outer periphery of the motor base 6, and the rotor magnet 5 is attached to the inner periphery of the disk hub 3. The bearing member 9 of the fluid dynamic bearing device 1 is fixed to the inner periphery of the motor base 6. The disk hub 3 holds one or a plurality of disks D (two in the illustrated example). In the above configuration, when the stator coil 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 disk D held by the disk hub 3 are rotated. It rotates integrally with the shaft member 2.

  FIG. 2 shows a fluid dynamic bearing device 1 according to the first embodiment of the present invention. The fluid dynamic pressure bearing device 1 includes a shaft member 2, a bearing member 9 in which the shaft member 2 is inserted on the inner periphery, and a lid member 10 that seals one end opening of the bearing member 9 as constituent members. The space is filled with lubricating oil (indicated by dense scattered dot hatching) as a fluid. In the present embodiment, a bearing member 9 is constituted by a cylindrical bearing sleeve 8 disposed on the outer periphery of the shaft member 2 and a cylindrical housing 7 having both ends opened and the bearing sleeve 8 fixed to the inner periphery. The lid member 10 is fixed to the inner periphery of one end opening of the housing 7. Therefore, in the present embodiment, the housing 7 corresponds to the cylindrical member referred to in the present invention. Hereinafter, for convenience of explanation, the side on which the lid member 10 is provided is referred to as the lower side, and the opposite side in the axial direction is referred to as the upper side.

  The bearing sleeve 8 is formed of a sintered metal porous body in a cylindrical shape. An annular groove 8c1 and a radial groove 8c2 having an outer diameter end connected to the annular groove 8c1 are formed on the upper end surface 8c of the bearing sleeve 8, and a circumferential direction 8d of the bearing sleeve 8 is provided in the circumferential direction. The axial direction groove | channel 8d1 is formed in the one or several places (In this embodiment, three places of the circumferential direction. Refer FIG.3 (b)). The bearing sleeve 8 can also be formed of other porous bodies represented by porous resin, soft metals such as brass.

  On the inner peripheral surface 8 a of the bearing sleeve 8, a cylindrical region serving as a radial bearing surface that forms a radial bearing gap with the outer peripheral surface 21 a of the opposed shaft portion 21 is provided at two positions in the axial direction. ing. As shown in FIG. 3, radial cylindrical pressure regions A1 and A2 each having a plurality of dynamic pressure grooves Aa inclined in the axial direction are arranged in a herringbone shape in each cylindrical region serving as a radial bearing surface. Each is formed. In the upper radial dynamic pressure generating portion A1, the axial dimension X1 of the dynamic pressure groove Aa in the upper region is larger than the axial dimension X2 of the dynamic pressure groove Aa in the lower region. On the other hand, in the lower radial dynamic pressure generating portion A2, the axial dimensions of the upper region dynamic pressure groove Aa and the lower region dynamic pressure groove Aa are equal to the axial dimension X2. The dynamic pressure grooves Aa are not limited to the herringbone shape but can be formed (arranged) in a spiral shape.

  The lower end surface 8b of the bearing sleeve 8 is provided with an annular region serving as a thrust bearing surface that forms a thrust bearing gap of the first thrust bearing portion T1 with the upper end surface 22a of the opposing flange portion 22. In this annular region, as shown in FIG. 3B, a thrust dynamic pressure generating portion B is formed by arranging a plurality of spiral-shaped dynamic pressure grooves Ba in the circumferential direction. The dynamic pressure groove Ba can also be formed in a herringbone shape. The thrust dynamic pressure generating part B can also be formed on the upper end surface 22a of the opposing flange part 22.

  The shaft member 2 includes a shaft portion 21 and a flange portion 22 provided integrally or separately at the lower end of the shaft portion 21. Here, the shaft portion 21 is made of a highly rigid melted material (for example, stainless steel such as SUS420J2). And the flange portion 22 are integrally formed. Of the outer peripheral surface 21 a of the shaft portion 21, a region facing the region between the radial bearing surfaces (radial dynamic pressure generating portions A 1, A 2) of the inner peripheral surface 8 a of the bearing sleeve 8 has a cylindrical shape that is retracted toward the inner diameter side. An escape portion 23 is provided. By providing such an intermediate escape portion 23 on the outer peripheral surface 21 a of the shaft portion 21, a radial is provided between the inner peripheral surface 8 a of the bearing sleeve 8 formed on a cylindrical surface having a substantially constant diameter and the intermediate escape portion 23. A radial gap having a larger gap width than the bearing gap is formed. Since this radial gap can function as a lubricating oil reservoir, it is possible to fill two radial bearing gaps adjacent in the axial direction with abundant lubricating oil during bearing operation. This stabilizes the rotational accuracy in the radial direction. Further, since the gap width of the radial gap is ensured to be larger than that of the radial bearing gap, the loss torque can be reduced, which contributes to lower power consumption of the motor.

  The housing 7 as a cylindrical member is formed in a substantially cylindrical shape with both ends in the axial direction being made of a molten material (for example, a solid metal material such as brass or stainless steel), and a cylindrical side portion 7a; A ring-shaped seal portion 7b extending from the upper end of the side portion 7a to the inner diameter side is integrally provided. The side portion 7a is provided with a relatively small-diameter small-diameter inner peripheral surface 7a1 and a relatively large-diameter large-diameter inner peripheral surface 7a2, and the small-diameter inner peripheral surface 7a1 and the large-diameter inner peripheral surface 7a2 Are connected via a step surface 7a3 extending in a direction orthogonal to the axial direction. A bearing sleeve 8 is fixed to the inner periphery of the small-diameter inner peripheral surface 7a1 by appropriate means such as adhesion, press-fitting, press-fitting adhesion (combination of press-fitting and adhesion), and welding. On the other hand, the lid member 10 is fixed to the inner periphery of the large-diameter inner peripheral surface 7a2 in a state where the outer diameter side region of the inner bottom surface 10a is in contact with the stepped surface 7a3. The axial relative position of the lid member 10 with respect to the bearing member 9) is determined, and the gap width of the thrust bearing gap between the thrust bearing portions T1 and T2 is managed to a specified value.

  The inner peripheral surface 7b1 of the seal portion 7b is formed in a tapered surface shape that is gradually reduced in diameter downward, and the radial dimension is gradually reduced downward between the outer peripheral surface 21a of the opposing shaft portion 21. A wedge-shaped seal space S is formed. The upper end surface 8c of the bearing sleeve 8 is in contact with the inner diameter side region of the lower end surface 7b2 of the seal portion 7b, and the bearing sleeve 8 is positioned relative to the housing 7 in the axial direction. The outer diameter side region of the lower end surface 7b2 of the seal portion 7b is gradually retracted upward toward the outer diameter side, and an annular gap is formed between the upper end surface 8c of the bearing sleeve 8 and the upper outer peripheral chamfer. ing. An inner diameter end portion of the annular gap is connected to an annular groove 8 c 1 on the upper end surface 8 c of the bearing sleeve 8.

  The lid member 10 is fixed to the inner periphery of the large-diameter inner peripheral surface 7 a 2 of the housing 7 and seals the lower end opening of the housing 7. This lid member 10 is a punched product (press-cut product) formed into a disk shape by punching a metal plate such as stainless steel, copper alloy, aluminum alloy, etc., and is directly applied without any special post-processing after punching. It is used. In the illustrated example, the outer peripheral surface 10c of the lid member 10 includes a shearing portion 10d, a fracture portion 10e, and a burr 10f that are formed in accordance with the punching process. As described above, the shearing portion 10e is a smooth surface formed by sliding the side surface of the cutting blade with respect to the metal plate. Moreover, the fracture | rupture part 102 is a rough surface (uneven surface) where the minute unevenness | corrugation continued. Further, the burr 10f is originally a protrusion projecting from the outer peripheral edge of one end on the punching end side, but is formed in the housing 7 in the fluid dynamic bearing device 1 as a finished product shown in FIG. The crimped portion 12 is plastically deformed toward the inner diameter side.

  The inner bottom surface (upper end surface) 10a of the lid member 10 is provided with an annular region serving as a thrust bearing surface that forms a thrust bearing gap of the second thrust bearing portion T2 between the lower end surface 22b of the opposing flange portion 22. It has been. As shown in FIG. 4, a thrust dynamic pressure generating portion C formed by arranging a plurality of dynamic pressure grooves Ca in a spiral shape is formed in the annular region serving as the thrust bearing surface. The thrust dynamic pressure generating portion C is molded at the same time as the lid member 10 is formed by punching a metal plate. The thrust dynamic pressure generating portion C can also be formed on the lower end surface 22b of the opposing flange portion 22.

  Here, the manner of fixing the lid member 10 to the housing 7 will be described in detail. As shown in the enlarged view of FIG. 2, the lower end portion of the housing 7 (side portion 7 a) has a caulking portion 12 that is inclined with respect to the axial direction so that the distal end portion is located on the inner diameter side of the base end portion. However, it is provided integrally with the side portion 7a so as to wind the burr 10f of the lid member 10 (so that the burr 10f of the lid member 10 is pressed against the outer end surface 10b of the lid member 10). As a result, the lid member 10 is urged upward in the axial direction, and the inner surface of the large-diameter inner peripheral surface 7a2 of the housing 7 is brought into contact with the stepped surface 7a3 of the side portion 7a. It is fixed on the circumference. The front end portion of the crimping portion 12 is positioned on the inner diameter side of the burr 10 f of the lid member 10 and constitutes the lowermost end portion of the fluid dynamic pressure bearing device 1.

  The caulking portion 12 is provided over the entire circumference of the housing 7, and forms an annular space 13 between the outer bottom surface 10 b of the lid member 10. The annular space 13 is solidified by being filled with an adhesive 14, and the burr 10 f of the lid member 10 is covered (captured) with the adhesive 14. As described above, the caulking portion 12 is inclined with respect to the axial direction so that the distal end portion is positioned relatively on the inner diameter side. Therefore, the caulking portion 12 and the outer bottom surface 10b of the lid member 10 The annular space 13 formed between the two has a tapered shape (wedge shape) in which the space width is gradually reduced toward the proximal end side of the caulking portion 12. Further, the lid member 10 of the present embodiment has an outer diameter dimension set smaller than an inner diameter dimension of the large-diameter inner peripheral surface 7a2 of the housing 7, and is fitted into the inner periphery of the large-diameter inner peripheral surface 7a2. Therefore, a minute radial gap 15 is formed over the entire circumference between the outer peripheral surface 10c of the lid member 10 and the large-diameter inner peripheral surface 7a2 of the housing 7 facing each other. Is filled with an adhesive 14 and solidified.

  The fixing structure of the lid member 10 to the housing 7 shown above can be obtained as follows. First, as shown in FIG. 5 (a), the lid member 10 formed into a disk shape by punching a metal plate is left on the large-diameter inner peripheral surface 7a2 of the housing 7 without any special post-processing. Fit a gap on the inner circumference. At this time, the lid member 10 has a large-diameter inner peripheral surface in a state in which the burr 10f projecting from one end portion (one outer peripheral edge portion) of the outer peripheral surface 10c with the punching process is directed (arranged) to the bearing outer side. A gap is fitted to the inner periphery of 7a2. At the lower end (upper end in FIG. 5 (a)) of the side portion 7a of the housing 7, an annular convex portion 7c that becomes the crimped portion 12 is integrally formed by undergoing plastic deformation upon being crimped.

  Next, the lower end portion of the housing 7 is plastically deformed toward the inner diameter side while winding the burr 10d by caulking to form the caulking portion 12. Here, as shown in FIG. 5B, pressure is applied to the annular projection 7c provided at the lower end of the housing 7, and the annular projection 7c has an inner diameter so as to wind (cover) the burr 10d. The caulking portion 12 is formed over the entire circumference of the housing 7 by being plastically deformed (tilted) to the side. By forming such a caulking portion 12, the burr 10 f of the lid member 10 is pressurized and plastically deformed toward the inside of the bearing, and further, the inner bottom surface 10 a of the lid member 10 is pressed against the step surface 7 a 3 of the housing 7. It is done. As a result, the lid member 10 is positioned relative to the housing 7 in the axial direction, and the stepped surface 7a3 of the side portion 7a of the housing 7 and the crimping portion 12 formed on the lower end portion of the housing 7 Thus, it is fixed by caulking to the inner periphery of the large-diameter inner peripheral surface 7a2 of the housing 7 so as to be sandwiched from both sides in the axial direction.

  And as shown in FIG.5 (c), the adhesive 14 is filled and solidified in the annular space 13 formed between the crimping part 12 and the outer bottom face 10b of the lid member 10, and the burr 10f of the lid member 10 is solidified. Is coated with an adhesive 14. The minute radial gap 15 formed between the outer peripheral surface 10 c of the lid member 10 and the large-diameter inner peripheral surface 7 a 2 of the housing 7 is also filled with the adhesive 14 and solidified. Thereby, the lid member 10 is bonded and fixed to the inner periphery of the large-diameter inner peripheral surface 7a2 of the housing 7, and the lower end opening of the housing 7 is sealed. In order to fill the adhesive 14 in the radial gap 15, for example, the adhesive 14 is filled in the radial gap 15 before the caulking part 12 is formed. In the middle of forming, a method of filling the adhesive 14 in the radial gap 15 can be employed.

  In the fluid dynamic pressure bearing device 1 having the above-described configuration, a radial bearing surface formed at two positions on the upper and lower sides of the inner peripheral surface 8a of the bearing sleeve 8 and an outer peripheral surface 21a of the shaft portion 21 facing the radial bearing surface are respectively provided. A radial bearing gap is formed. As the shaft member 2 rotates, the pressure of the oil film formed in both radial bearing gaps is increased by the dynamic pressure action of the dynamic pressure groove Aa, and as a result, the radial bearing portion that supports the shaft member 2 in the radial direction in a non-contact manner. R1 and R2 are spaced apart from each other in two axial directions. At the same time, between the upper end surface 22a of the flange portion 22 and the thrust bearing surface provided on the lower end surface 8b of the bearing sleeve 8 facing this, and the lower end surface 22b of the flange portion 22 and the lid facing this. A thrust bearing gap is formed between each of the thrust bearing surfaces provided on the upper end surface 10a of the member 10. As the shaft member 2 rotates, the pressure of the oil film formed in the thrust bearing gaps is increased by the dynamic pressure action of the dynamic pressure grooves Ba and Ca. As a result, the shaft member 2 is not moved in the thrust direction. A first thrust bearing T1 that supports the contact and a second thrust bearing T2 that supports the shaft member 2 in the thrust other direction are formed.

  Further, since the seal space S has a wedge shape in which the radial dimension is gradually reduced toward the inner side of the housing 7, the lubricating oil in the seal space S is pulled into the inner side of the housing 7 by a pulling action due to capillary force. It is drawn toward. Further, the seal space S has a buffer function for absorbing the volume change amount accompanying the temperature change of the lubricating oil filled in the internal space of the housing 7, and the oil surface of the lubricating oil is kept within the range of the assumed temperature change. It is always held in the seal space S. Therefore, lubricating oil leakage from the inside of the housing 7 is effectively prevented.

  Further, due to the axial dimensional difference between the upper and lower dynamic pressure grooves Aa constituting the radial dynamic pressure generating portion A1, the pumping force of the lubricating oil interposed in the radial bearing gap during the rotation of the shaft member 2 causes the upper region to move to the lower region. It becomes relatively large compared. Therefore, when the shaft member 2 rotates, the lubricating oil interposed in the gap between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 21a1 of the shaft portion 21 flows downward, and the thrust bearing of the first thrust bearing portion T1. Clearance → Axial fluid passage 11 formed by the axial groove 8d1 of the bearing sleeve 8 → annular space formed by the upper outer chamfer of the bearing sleeve 8, etc. → formed by the annular groove 8c1 and the radial groove 8c2 of the bearing sleeve 8 The fluid passage is circulated and is drawn again into the radial bearing gap of the radial bearing portion R1.

  By adopting such a configuration, the pressure balance of the lubricating oil is maintained, and at the same time, the generation of bubbles accompanying the generation of local negative pressure, the occurrence of lubricant leakage and vibration due to the generation of bubbles, etc. The problem can be solved. Since the sealing space S communicates with the above circulation path, even if bubbles are mixed in the lubricating oil for some reason, when the bubbles circulate with the lubricating oil, the lubricating oil in the sealing space S It is discharged from the oil surface (gas-liquid interface) to the outside air. Therefore, adverse effects due to bubbles can be prevented more effectively.

  As described above, in the fluid dynamic pressure bearing device 1 according to the present invention, the lid member 10 formed by punching a metal plate and having the burr 10f on one end portion (one end outer peripheral portion) of the outer circumferential surface 10c is burred. It is fitted to the large-diameter inner peripheral surface 7a2 (lower end opening) of the housing 7 with 10f facing outward. Therefore, contact between the housing 7 and the burr 10f is avoided at the stage where the lid member 10 is fitted (arranged) to the lower end opening of the housing 7, so that the burr 10f falls off due to contact with the housing 7, and thus contamination occurs. The deterioration of bearing performance due to is prevented as much as possible. Further, since the lid member 10 is fitted to the housing 7 in the above-described manner, the burr 10f of the lid member 10 does not contact the stepped surface 7a3 of the housing 7, so that the accuracy of fixing the lid member 10 to the housing 7 is not ensured. A situation can be prevented as much as possible. In addition, in the present invention, the lid member 10 is fixed to the housing 7 by plastically deforming the lower end portion (annular convex portion 7c) of the housing 7 to the inner diameter side while winding the burr 10f of the lid member 10 by caulking. . In this way, the caulking portion 12 formed in the housing 7 can cover the burr 10f of the lid member 10 while pressing the burr 10f against the outer bottom surface 10b of the lid member 10. Therefore, the occurrence of contamination due to the fall off of the burr 10f is prevented. Can be prevented. From the above, according to the present invention, even if the punched lid member 10 is used as it is, the occurrence of contamination can be prevented as much as possible. Therefore, the cost of the fluid dynamic bearing device 1 can be reduced while ensuring the required bearing performance.

  Further, the crimping portion 12 is formed over the entire circumference of the housing 7, and the lid member 10 is formed with the adhesive 14 filled in the annular space 13 formed between the crimping portion 12 and the outer bottom surface 10 b of the lid member 10. Nokaeri 10f was coated. As a result, the fixing force of the lid member 10 to the housing 7 can be improved, and the burr 10f can be more effectively prevented from falling off. In particular, since the space width of the annular space 13 is gradually reduced toward the proximal end side of the caulking portion 12, a capillary force pulling action acts on the adhesive 14 filled in the annular space 13. Therefore, the adhesive 14 can be appropriately held in the annular space 13, that is, the burr 10f can be appropriately covered.

  Furthermore, in this embodiment, the lid member 10 is fitted into the large-diameter inner circumferential surface 7a2 (lower end opening) of the housing 7 with a gap, and the large-diameter inner circumferential surface 7a2 of the housing 7 and the outer circumferential surface 10c of the lid member 10 facing each other. Since the adhesive 14 is filled in the gaps 15 in the radial direction and solidified, the fixing force of the lid member 10 to the housing 7 is further enhanced, and the sealing performance of the lower end opening of the housing 7 is further enhanced. Further, the lid member 10 of the present embodiment has an uneven surface-like fractured portion 10e on the outer peripheral surface 10c. However, if the lid member 10 is fitted into the gap, the lid member 10 is attached to the lower end opening of the housing 7. At the stage of fitting (arrangement), the occurrence of contamination due to sliding between the large-diameter inner peripheral surface 7a2 of the housing 7 and the broken portion 10e of the outer peripheral surface 10c of the lid member 10, and by extension, the dropping of the broken portion 10e is prevented as much as possible. can do. In addition, since the uneven | corrugated surface-shaped fracture | rupture part 10e exists in the outer peripheral surface 10c of the cover member 10, the contact area of the cover member 10 with respect to the adhesive agent 14 with which the radial direction clearance 15 was filled increases. Thereby, the adhesive strength of the lid member 10 to the housing 7 can be increased.

  The fluid dynamic bearing device 1 according to the embodiment of the present invention has been described above, but the present invention is not limited to the fluid dynamic bearing device 1 according to the embodiment described above. Hereinafter, a fluid dynamic bearing device 1 according to another embodiment to which the present invention is applicable will be described with reference to the drawings. In the other embodiments described below, from the viewpoint of simplifying the description, the same reference numerals are given to substantially the same configurations as those of the above-described embodiments, and the duplicate description will be omitted.

  FIG. 6 is an axial cross-sectional view of the fluid dynamic bearing device 1 according to the second embodiment of the present invention. The main difference of the fluid dynamic pressure bearing device 1 shown in FIG. 2 from that shown in FIG. 2 is that the radial dynamic pressure generators A1, A2 generate fluid dynamic pressure in the radial bearing gaps of the radial bearing portions R1, R2. 6, the dynamic pressure grooves Aa) indicated by cross-hatching are formed on the outer peripheral surface 21 a of the shaft portion 21 facing the inner peripheral surface 8 a of the bearing sleeve 8 via the radial bearing gap.

  Here, a widely adopted technique for forming the dynamic pressure groove Aa on the inner peripheral surface 8a of the bearing sleeve 8 made of sintered metal is the outer periphery of the sintered body formed in a cylindrical shape. By inserting a core rod having a groove mold part corresponding to the dynamic pressure groove shape on the surface, and applying a pressing force to the sintered body from both sides in the axial direction in this state, the inner peripheral surface of the sintered body becomes the outer peripheral surface of the core rod. The shape of the groove part is transferred to the inner peripheral surface of the sintered body, and then the core rod is pulled out from the inner periphery of the sintered body using the spring back of the sintered body that is generated by releasing the compression force. That's it. However, if the axial dimension of the bearing sleeve 8 increases, it is necessary to apply a considerably large pressing force to the sintered body when the dynamic pressure groove Aa is processed. For this reason, there is a limit in processing accuracy, such as a large variation in internal density and a deterioration in accuracy in each part of the bearing sleeve 8.

  On the other hand, when the dynamic pressure groove Aa is provided on the outer peripheral surface 21a of the shaft portion 21, it is easy to form the minute dynamic pressure groove Aa with high accuracy by combining relatively simple means such as rolling and grinding. In addition, the inner peripheral surface 8a of the bearing sleeve 8 can be formed into a smooth cylindrical surface having no irregularities. Therefore, in this case, the manufacturing process of the bearing sleeve 8 made of sintered metal is completed by performing a correction process (sizing) on the inner peripheral surface and the outer peripheral surface of the sintered body, and the inner peripheral surface as described above. There is no need to provide a step of molding the dynamic pressure groove. Therefore, the accuracy of the bearing can be ensured through simplification of the shape of the bearing sleeve 8, and the characteristics of the bearing sleeve 8, and consequently the fluid dynamic pressure bearing device 1 as a whole, can be ensured.

  In addition, when forming the dynamic pressure groove Aa by rolling on the outer peripheral surface of the shaft portion 21 (shaft material) made of melted material, it is desirable to subject the outer peripheral surface of the shaft material after heat treatment to rolling. The amount of swell of meat produced by rolling can be reduced compared to the case of rolling the unheat-treated shaft material, so that the subsequent finishing process can be simplified or the finishing process can be omitted. Because you can.

  In the above embodiment, the caulking portion 12 is formed by plastic deformation of the annular convex portion 7c integrally provided at the lower end of the housing 7 toward the inner diameter side. It is not necessary to provide the convex portion 7c. For example, the caulking portion 12 can be formed by plastically deforming the flat lower end surface of the housing 7. Further, the caulking portion 12 is not necessarily formed over the entire circumference of the housing 7, and may be formed only in a circumferential region where the burr 10f exists.

  In the above embodiment, the lid member 10 is fitted into the lower end opening of the housing 7 due to the use of the lid member 10 having the fracture portion 10e on the outer peripheral surface 10c. In some cases, the concavo-convex fracture portion 10e is not formed on the outer peripheral surface 10c of the lid member 10 (see FIG. 7B). When such a lid member 10 is used, the outer peripheral surface 10 c of the lid member 10 slides with respect to the large-diameter inner peripheral surface 7 a 2 of the housing 7 when the lid member 10 is fitted into the lower end opening of the housing 7. Even if compared with the case where the fractured portion 10e is formed on the outer peripheral surface 10c, the probability of occurrence of contamination is greatly reduced. Therefore, the fitting of the lid member 10 to the lower end opening of the housing 7 is not necessarily performed. There is no need to do this with a gap fit.

  Moreover, in the above embodiment, the seal part 7b which forms the seal space S between the housing 7 and the outer peripheral surface 21a of the shaft part 21 is integrally provided, but the seal part 7b may be a separate member. It is possible (not shown). Further, in the above embodiment, the bearing member 9 is constituted by the housing 7 as a cylindrical member and the bearing sleeve 8 fixed to the inner periphery of the housing 7, but the bearing member 9 corresponds to the bearing sleeve 8. It is also possible that the part and the part corresponding to the housing 8 are provided integrally (not shown).

  Further, in the above embodiment, the radial bearing portions R1 and R2 including the dynamic pressure bearing are configured by providing the radial dynamic pressure generating portion in which a plurality of the dynamic pressure grooves Aa having a herringbone shape or the like are arranged in the circumferential direction. The radial bearing portions R1 and R2 made of a hydrodynamic bearing form a step surface having a plurality of axial grooves in the circumferential direction or a multi-arc surface on one of two surfaces facing each other through a radial bearing gap. It can also be configured. Further, either one or both of the radial bearing portions R1 and R2 can be constituted by a so-called perfect circle bearing.

  Further, in the above embodiment, the thrust dynamic pressure generating portions B and C are configured by the spiral or herringbone-shaped dynamic pressure grooves Ba and Ca, but either one or both of the thrust dynamic pressure generating portions B and C are used. Can be configured by arranging a plurality of radial dynamic pressure grooves extending in the radial direction in the circumferential direction. In addition, the thrust bearing portion may be a pivot bearing in which one end (lower end) of the shaft member 2 is in contact with and supported by the inner bottom surface 10a of the lid member 10 instead of the dynamic pressure bearing described above.

  In the above embodiment, the lubricating oil is used as the lubricating fluid that fills the internal space of the fluid dynamic bearing device 1, but the fluid dynamics using a lubricating grease, a magnetic fluid, or a gas such as air as the lubricating fluid. The present invention can also be preferably applied to the pressure bearing device 1.

  In the above description, the case where the present invention is applied to the fluid dynamic bearing device 1 in which the shaft member 2 is the rotating side and the bearing member 9 is the stationary side has been described. The present invention can be preferably applied to the fluid dynamic bearing device 1 having the stationary side and the bearing member 9 as the rotation side.

DESCRIPTION OF SYMBOLS 1 Fluid dynamic pressure bearing apparatus 2 Shaft member 7 Housing 8 Bearing sleeve 9 Bearing member 10 Lid member 10c Outer peripheral surface 10d Shear part 10e Breaking part 10f Burl 12 Clamping part 13 Annular space 14 Adhesive 15 Radial gap A1, A2 Radial movement Pressure generating part B Thrust dynamic pressure generating part C Thrust dynamic pressure generating part R1, R2 Radial bearing part T1 First thrust bearing part T2 Second thrust bearing part

Claims (8)

A radial member gap facing the outer peripheral surface of the shaft member includes a shaft member, a cylindrical member having both ends opened and a shaft member inserted into the inner periphery, and a lid member for sealing one end opening of the cylindrical member. In the fluid dynamic bearing device in which the shaft member is supported in the radial direction by the formed lubricating film of fluid,
The lid member is formed by punching a metal plate, and has a burr at one end of the outer peripheral surface,
The lid member after punching is fitted into one end opening of the cylindrical member with the burr facing outward, and one end of the cylindrical member is plastically deformed to the inner diameter side while winding the burr by caulking. The fluid dynamic pressure bearing device is characterized in that the lid member is fixed to the cylindrical member.   2. The fluid dynamic bearing device according to claim 1, wherein a space is formed between the crimping portion and the outer bottom surface of the lid member, and the burr is covered with an adhesive filled in the space. The lid member is fitted into the opening at one end of the cylindrical member,
The fluid dynamic pressure bearing device according to claim 1, wherein an adhesive is filled in a radial gap between the outer peripheral surface of the lid member and the inner peripheral surface of the cylindrical member facing each other.   The fluid dynamic pressure bearing device according to claim 1, wherein a stepped surface is provided on the cylindrical member, and an inner bottom surface of the lid member is brought into contact with the stepped surface. A thrust bearing gap is formed between the end surfaces of the shaft members facing each other and the inner bottom surface of the lid member,
The fluid dynamic pressure according to claim 1, wherein the thrust dynamic pressure generating portion that generates fluid dynamic pressure in the thrust bearing gap is formed on the inner bottom surface of the lid member at the same time as the lid member is formed by punching a metal plate. Bearing device.   The fluid dynamic pressure bearing device according to claim 1, wherein a bearing sleeve that forms the radial bearing gap is fixed to an inner periphery of the cylindrical member with an outer peripheral surface of the shaft member.   The fluid dynamic pressure bearing device according to claim 1, wherein a radial dynamic pressure generating portion that generates fluid dynamic pressure in a radial bearing gap is formed on an outer peripheral surface of the shaft member.   A motor comprising the fluid dynamic bearing device according to any one of claims 1 to 7, a stator coil, and a rotor magnet.

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