JP2010048309A - Fluid bearing device and motor equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid bearing device with high adhesive strength of a bearing sleeve to a housing and stably exerting predetermined bearing performance. <P>SOLUTION: The fluid bearing device 1 is equipped with the bottomed cylindrical housing 7 with one end opened and the other end blocked, the bearing sleeve 8 adhering to be fixed to an inner periphery of the housing 7, and a shaft member 2 inserted into an inner periphery of the bearing sleeve 8 as main components. A lower-end outer periphery of the bearing sleeve 8 is provided with a step part 13 which forms a first space 15 as an adhesive reservoir between itself and a first inner peripheral surface 7a1 of a small diameter part 7a composing the housing 7. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device and a motor including the same.

  The hydrodynamic bearing device is a bearing device that rotatably supports a shaft member with an oil film formed in a bearing gap. This hydrodynamic bearing device has characteristics such as high-speed rotation, high rotation accuracy, and low noise. In recent years, the hydrodynamic bearing device has been utilized as a motor bearing device for motors mounted on various electrical devices including information devices. More specifically, magnetic disk devices such as HDD, optical disk devices such as CD-R / RW and DVD-R / RW, spindle motors such as magneto-optical disk devices such as MD and MO, laser beam printer (LBP) It is suitably used as a bearing device for motors such as polygon scanner motors and fan motors.

Among the various motors described above, as a hydrodynamic bearing device incorporated in a spindle motor such as a disk device, for example, as described in Patent Document 1, a bottomed cylindrical housing having one end opened and the other end closed, A shaft member made of a bearing sleeve fixed to the inner periphery, a shaft member inserted in the inner periphery of the bearing sleeve, and an oil film formed in a radial bearing gap between the inner peripheral surface of the bearing sleeve and the outer peripheral surface of the shaft member It is well-known what is provided with the radial bearing part which supports this to a radial direction. Adhesion, press-fitting, press-fitting, laser welding, etc. can be used as means for fixing the bearing sleeve to the bottomed cylindrical housing, but considering cost effectiveness, an adhesive such as gluing, press-fitting, etc. was used. In many cases, fixing means are employed.
JP 2003-239974 A

  Recently, the number of disks mounted on a motor tends to increase as the capacity of a disk device increases. This increase in weight causes an increase in impact load. Therefore, in order to stably maintain the desired bearing performance, it is required to further increase the fixing strength of the bearing sleeve to the housing.

  Usually, the bearing sleeve is fixed to the bottomed cylindrical housing at a predetermined position on the inner periphery of the housing in a state where an adhesive is applied in advance to at least one of the inner peripheral surface of the housing and the outer peripheral surface of the bearing sleeve. After the bearing sleeve is inserted, the adhesive is solidified. However, since the diameter difference (dimension difference) between the inner peripheral surface of the housing and the outer peripheral surface of the bearing sleeve fixed to each other is extremely small, the insertion side of the bearing sleeve in the insertion direction front side ( In some cases, the adhesive is scraped to the closed side of the housing, and the adhesive wraps around one end surface of the bearing sleeve. When such a situation occurs, not only the amount of adhesive to be interposed between the housing and the bearing sleeve is insufficient, but the required adhesive strength is not satisfied, but the wraparound adhesive is not removed from one end surface of the bearing sleeve. May adhere to the shaft member and the like and adversely affect the bearing performance.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to provide a hydrodynamic bearing device that has high adhesive strength between the housing and the bearing sleeve and can stably exhibit the desired bearing performance. It is to provide.

  In order to solve the above problems, in the present invention, a housing having one end opened and the other end closed, a bearing sleeve bonded and fixed to the inner periphery of the housing, a shaft member inserted into the inner periphery of the bearing sleeve, A hydrodynamic bearing device including a radial bearing portion that supports a shaft member in a radial direction with an oil film formed in a radial bearing gap between an inner peripheral surface of the bearing sleeve and an outer peripheral surface of the shaft member. A hydrodynamic bearing device is provided in which a step portion for forming an adhesive reservoir with a housing is provided on the outer periphery of the end portion of the housing.

  As described above, if a step portion that forms an adhesive reservoir with the housing is provided on the outer periphery of the end portion on the housing closing side of the bearing sleeve, when the bearing sleeve is inserted, the front side in the insertion direction (the housing closing state). The volume of adhesive that can be held on the side) can be increased. Therefore, the adhesive is scraped with the insertion of the bearing sleeve, and it is possible to effectively suppress or prevent the scraped adhesive from going around to the end face side of the bearing sleeve. Further, since the adhesive scraping is effectively suppressed and an adhesive pool is formed between the housing and the housing, the space between the inner peripheral surface of the housing and the outer peripheral surface of the bearing sleeve fixed to each other is increased. Many adhesives can be retained. Therefore, the adhesive strength of the bearing sleeve to the housing can be increased without deteriorating the bearing performance, and the reliability of the hydrodynamic bearing device can be increased. Further, since the adhesive holding capacity can be increased, it is possible to allow variations in the amount of adhesive applied, so that the assembly process of the bearing sleeve to the housing can be simplified.

  A chamfer (chamfering) can be provided on the outer peripheral edge of the bearing sleeve on the housing closing side, and at this time, the adhesive reservoir communicates with a space formed between the chamfer and the inner peripheral surface of the housing. It can be. In this way, the capacity of the adhesive pool can be further increased without providing a chamfer larger than necessary. Therefore, for example, when the thrust bearing portion (thrust bearing gap) is formed on one end face of the bearing sleeve, the above-mentioned merit can be more effectively enjoyed without reducing the bearing performance of the thrust bearing portion.

  The adhesive reservoir is composed only of a portion (hereinafter referred to as “axial portion”) having one end (end portion on the housing closing side) extending in the axial direction through the space, and an axial portion; A radial direction portion extending from the other end of the axial direction portion (an end portion on the housing opening side) to the outer diameter side may be provided. With the latter configuration, the adhesive reservoir can have a labyrinth structure, so that the adhesive retention capacity in the adhesive reservoir can be increased compared to the former configuration. In general, the tensile bond strength is larger than the shear bond strength. Therefore, if the latter configuration is adopted, the adhesive strength can be increased as compared with the case where the former configuration is adopted. Such a configuration can be obtained by providing the housing with a step portion that forms an axial portion and a radial portion between the step portion provided on the bearing sleeve.

  The hydrodynamic bearing device according to the present invention further includes a shaft member in one thrust direction by a dynamic pressure action of a fluid generated in a first thrust bearing gap between one end surface of the bearing sleeve and one end surface of the shaft member facing the bearing sleeve. The shaft member is supported in the other direction of the thrust by the dynamic pressure action of the lubricating fluid generated in the second thrust bearing gap between the first thrust bearing portion to be supported and the inner bottom surface of the housing and the other end surface of the shaft member opposed to the first thrust bearing portion. And a second thrust bearing portion. At this time, it is desirable to set the width (axial dimension) of the radial direction portion of the adhesive reservoir to be larger than the total amount of the gap widths of the first and second thrust bearing gaps. This is because if the width of the radial portion is smaller than the total amount of the gap widths of the thrust bearing gaps, there is a possibility that a thrust bearing gap having a predetermined width cannot be formed.

  When the adhesive reservoir has an axial part and a radial part, if the width of the radial part (axial dimension) is smaller than the width of the axial part (radial dimension), the adhesive is drawn by capillary force. By the action, it becomes possible to further increase the holding ability of the adhesive in the adhesive reservoir.

  The axial part of the adhesive reservoir may be axially constant with a constant width (cross-sectional area), but if the width is gradually reduced toward the other end side, the adhesive will be attracted by the pulling action by capillary force. The retention capacity of the agent is further increased.

  In this type of hydrodynamic bearing device, in order to prevent imbalance in internal pressure during bearing operation, a circulation path opened at both ends of the bearing sleeve is provided between the inner peripheral surface of the housing and the outer peripheral surface of the bearing sleeve. In some cases, the lubricating fluid inside the bearing is caused to flow and circulate through the circulation path. When such a circulation path is provided, it is desirable that the formation position of the circulation path and the formation position of the adhesive reservoir are different from each other in the circumferential direction. This is to prevent the adhesive from flowing into the circulation path when the bearing sleeve is bonded and fixed to the housing, so that the circulation path does not function normally.

  In this type of hydrodynamic bearing device, a seal member that seals one end of the housing is usually provided. Since the present invention contributes to improving the adhesive strength of the bearing sleeve to the housing, for example, the first seal space is formed on the inner peripheral side of the seal member, and the second seal space is formed on the outer peripheral side of the seal member. This is particularly suitable for a hydrodynamic bearing device in which the seal member is fixed to the bearing sleeve. For example, in the hydrodynamic bearing device having the configuration disclosed in Patent Document 1, since the bearing sleeve and the seal member are axially overlapped and fixed to the inner periphery of the housing, the seal member supplements the fixing strength of the bearing sleeve with respect to the housing. This is because such a complementary effect cannot be expected in the configuration in which the seal member is fixed to the bearing sleeve.

  The hydrodynamic bearing device having the above configuration can be suitably used by being incorporated in a motor having 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, it is possible to provide a hydrodynamic bearing device that has high adhesive strength between the housing and the bearing sleeve and can stably exhibit the desired bearing performance.

  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 incorporating a hydrodynamic bearing device according to the present invention. This spindle motor is used for a disk drive device such as an HDD, and has a hydrodynamic bearing device 1 that rotatably supports a shaft member 2, a disk hub 3 mounted on the shaft member 2, and a radial gap, for example. And a stator magnet 4 and a rotor magnet 5 which are opposed to each other. The stator coil 4 is attached to the outer periphery of the bracket 6, and the rotor magnet 5 is attached to the inner periphery of the disk hub 3. The housing 7 of the hydrodynamic bearing device 1 is attached to the inner periphery of the bracket 6. The disk hub 3 holds one or a plurality of disks D such as a magnetic disk (two in the illustrated example). 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 holding the disk D and the shaft member 2 are rotated together. .

  FIG. 2 shows an embodiment of the hydrodynamic bearing device 1 used in the spindle motor. The hydrodynamic bearing device 1 includes a shaft member 2, a bottomed cylindrical housing 7, a bearing sleeve 8 fixed to the inner periphery of the housing 7, and a seal member 9 that seals the opening of the housing 7. As a component. In the following description, for the sake of convenience of explanation, the description will be given with the side provided with the seal member 9 as the upper side and the opposite side in the axial direction as the lower side.

  The shaft member 2 is formed of, for example, a metal material such as stainless steel, and includes a shaft portion 2a and a flange portion 2b provided integrally or separately at the lower end of the shaft portion 2a. The shaft member 2 may be formed of a metal material as a whole, or may be a metal-resin hybrid structure in which, for example, the entire flange portion 2b or a part thereof (for example, both end surfaces) is formed of resin.

  The housing 7 has a bottomed cylindrical shape including a cylindrical side portion and a disc-shaped bottom portion 7c that is provided integrally with the side portion and closes the lower end opening of the side portion, and the side portion has a small diameter portion 7a. And a large-diameter portion 7b disposed on the upper side of the small-diameter portion 7a. The inner peripheral surface of the small diameter portion 7a includes a first inner peripheral surface 7a1 having a relatively small diameter located on the bottom side, and a second inner surface having a relatively large diameter located on the opening side from the first inner peripheral surface 7a1. And a peripheral surface 7a2. The inner peripheral surface (second inner peripheral surface 7a2) of the small diameter portion 7a and the inner peripheral surface 7b1 of the large diameter portion 7b are connected by a step surface 7e extending in a direction orthogonal to the axis. The housing 7 is an injection-molded product of resin, and the portions 7a to 7c are formed to have a substantially uniform thickness so as to prevent deformation due to a difference in shrinkage during molding shrinkage. The resin material used for molding the housing 7 is mainly a thermoplastic resin, and either a crystalline resin or an amorphous resin can be used. The housing 7 can be formed of a metal material in addition to the resin material.

  The inner bottom surface 7c1 of the housing 7 is provided with an annular region (blacked portion in FIG. 2) that becomes the thrust bearing surface of the second thrust bearing portion T2. A thrust dynamic pressure generating portion C formed by arranging the dynamic pressure grooves in a spiral shape is formed. The thrust dynamic pressure generating portion C is molded at the same time as the housing 7 is injection molded. The thrust dynamic pressure generating portion C can also be formed on the lower end surface 2b2 of the flange portion 2b of the shaft member 2.

  The seal member 9 is made of, for example, a soft metal material such as brass, another metal material, or a resin material, and has a disk-shaped first seal portion 9a and a cylindrical shape extending downward from the outer diameter side of the first seal portion 9a. The second seal portion 9b is integrally formed with an inverted L-shaped cross section. The seal member 9 is fixed to the outer periphery of the upper end of the bearing sleeve 8, and in the fixed state, an axial gap 11 is formed between the lower end surface of the second seal portion 9 b and the stepped surface 7 e of the housing 7. In the lower end surface 9a1 of the first seal portion 9a, one or a plurality of radial grooves 10 extending radially are formed.

  The inner peripheral surface 9a2 of the first seal portion 9a forms a first seal space S1 having a predetermined volume with the outer peripheral surface 2a1 of the shaft portion 2a. Further, the outer peripheral surface 9b1 of the second seal portion 9b forms a second seal space S2 having a predetermined volume with the inner peripheral surface 7b1 of the large diameter portion 7b of the housing 7. Since both the inner peripheral surface 9a2 of the first seal portion 9a and the inner peripheral surface 7b1 of the large-diameter portion 7b of the housing 7 are formed in a tapered surface shape whose inner diameter dimension is gradually increased upward, both seal spaces S <b> 1 and S <b> 2 exhibit a tapered shape that is gradually reduced in diameter downward (inside the housing 7).

  The bearing sleeve 8 is formed of a porous body made of a sintered metal, in particular, a sintered metal porous body mainly composed of copper, and is formed into a cylindrical shape and is press-fitted into the inner periphery of the small-diameter portion 7 a of the housing 7. Bonded and fixed (press-fit adhesion). The bearing sleeve 8 may be formed of a soft metal such as brass other than the sintered metal.

  On the inner peripheral surface 8a of the bearing sleeve 8, cylindrical regions (blacked portions in FIG. 2) that serve as the radial bearing surfaces of the first and second radial bearing portions R1 and R2 are provided separately in two axial directions. As shown in FIG. 3A, radial dynamic pressure generating portions A1 and A2 each having a plurality of dynamic pressure grooves Aa1 and Aa2 arranged in a herringbone shape are formed in the two regions, respectively. . The upper dynamic pressure groove Aa1 is formed axially asymmetric with respect to the axial center m (the axial center of the upper and lower inclined groove regions), and the axial dimension X1 of the upper region is lower than the axial center m. It is larger than the axial dimension X2 of the side region. On the other hand, the lower dynamic pressure groove Aa2 is formed symmetrically in the axial direction, and the axial dimension of the upper and lower regions thereof is equal to the axial dimension X2. The radial dynamic pressure generating portions A1 and A2 can be formed on the outer peripheral surface 2a1 of the shaft portion 2a, or a plurality of dynamic pressure grooves can be arranged in a spiral shape or the like.

  The lower end surface 8b of the bearing sleeve 8 is provided with an annular region (blacked portion in FIG. 2) that becomes the thrust bearing surface of the first thrust bearing portion T1, and this region is as shown in FIG. 3 (b). In addition, a thrust dynamic pressure generating portion B is formed by arranging a plurality of dynamic pressure grooves Ba in a spiral shape. The thrust dynamic pressure generating portion B can be formed on the upper end surface 2b1 of the flange portion 2b, or a plurality of dynamic pressure grooves can be arranged in a herringbone shape or the like.

  A plurality of locations (three locations in the present embodiment, see FIG. 3B) spaced apart in the circumferential direction on the outer periphery of the lower end of the bearing sleeve 8 are connected to the first inner peripheral surface 7a1 of the small diameter portion 7a constituting the housing 7. A step portion 13 that forms a first space 15 as an adhesive reservoir is provided therebetween. This step portion 13 is provided so as to connect the second chamfer 8g provided at the outer peripheral edge of the lower end of the bearing sleeve 8 and the large-diameter outer peripheral surface 8d, and a small-diameter outer peripheral surface 8e extending along the axis, and a small-diameter The step surface 8f extends from the upper end of the outer peripheral surface 8e to the outer diameter side so as to be orthogonal to the axis. More specifically, in the outer circumferential surface of the bearing sleeve 8, three regions spaced apart in the circumferential direction are provided with a tapered first chamfer 8 h, a large-diameter outer circumferential surface 8 d, and a tapered second chamfer 8 g in order from the top. On the other hand, in the three circumferential regions interposed between these regions, a first chamfer 8h, a large-diameter outer peripheral surface 8d, a small-diameter outer peripheral surface 8e, and a second chamfer 8g are provided in order from the top. The step portion 13 is molded at the same time as the bearing sleeve 8 is molded.

  The large-diameter outer peripheral surface 8d has a constant diameter over the entire length in the axial direction, has a predetermined amount larger in diameter than the first inner peripheral surface 7a1 of the small-diameter portion 7a of the housing 7, and slightly smaller in diameter than the second inner peripheral surface 7a2. Is done. The small-diameter outer peripheral surface 8e has a constant diameter over the entire length in the axial direction, and has a predetermined amount smaller than the first inner peripheral surface 7a1 of the small-diameter portion 7a. From the above, when the bearing sleeve 8 is fixed to the inner periphery of the housing 7 (small diameter portion 7a), the large diameter outer peripheral surface 8d and the first inner peripheral surface 7a1 are in close contact with each other, while the small diameter outer peripheral surface 8e and the first inner peripheral surface are in close contact with each other. A first space 15 having a constant gap width (cross-sectional area) is formed between the surface 7a1 as an adhesive reservoir. Further, a gap width (cross-sectional area) is formed between the second chamfer 8g of the bearing sleeve 8 and the first inner peripheral surface 7a1 of the small diameter portion 7a so as to communicate with the first space 15 as an adhesive reservoir. ) Is gradually enlarged to form a tapered second space 16.

  On the outer peripheral surface of the bearing sleeve 8, the circulation path 12 is formed between the inner peripheral surface of the small diameter portion 7 a of the housing 7 and the inner peripheral surface 9 b 1 of the second seal portion 9 b of the seal member 9. One or a plurality of axial grooves 8d1 are formed. More specifically, in this embodiment, as shown in FIG. 3B, one axial groove 8d1 is formed between each step 13 adjacent in the circumferential direction.

  In the hydrodynamic bearing device 1 having the above configuration, for example, after the shaft member 2 is disposed in the housing 7, the bearing sleeve 8 is bonded and fixed at a predetermined position on the inner periphery of the housing 7, and then the seal member 9 is attached to the bearing sleeve 8. Then, the inner space of the housing 7 is filled with lubricating oil as a lubricating fluid. An example of a specific procedure is shown below.

  First, an appropriate amount of adhesive G is applied to, for example, the step portion 13 of the bearing sleeve 8 (and may be applied to the inner peripheral surface of the small diameter portion 7a of the housing 7). Here, a thermosetting adhesive is used as the adhesive G. Next, with the shaft member 2 disposed on the inner periphery of the housing 7, the bearing sleeve 8 is inserted into the inner periphery of the small diameter portion 7 a of the housing 7 from the side where the adhesive G is applied (the lower end surface 8 b side) (strictly And the axial positioning of the bearing sleeve 8 relative to the housing 7, in other words, the clearance between both thrust bearing gaps is made. In the present embodiment, in a state where the lower end surface 2b2 of the flange portion 2b is in contact with the inner bottom surface 7c1 of the housing 7, the bearing sleeve 8 is moved until the lower end surface 8b contacts the upper end surface 2b1 of the flange portion 2b. Then, the shaft member 2 is lifted up by the total amount of the gap widths of the first and second thrust bearing gaps, and the gap is made.

  As the bearing sleeve 8 is inserted, the adhesive G applied to the step portion 13 is supplied between the large-diameter outer peripheral surface 8d of the bearing sleeve 8 and the inner peripheral surface of the small-diameter portion 7a. At this time, since the adhesive G functions as a lubricant, it is possible to smoothly push the bearing sleeve 8 in. Then, when the relative axial positioning of the bearing sleeve 8 with respect to the housing 7 is completed, the excess adhesive G that has not been supplied between the both surfaces 8d and 7a1 becomes the first space 15 as an adhesive reservoir, and further the second. It is held in the space 16. Note that after inserting the bearing sleeve 8 to a predetermined position, the adhesive G may be further filled between the large-diameter outer peripheral surface 8 d of the bearing sleeve 8 and the second inner peripheral surface 7 a 2 of the housing 7.

  After the relative positioning of the bearing sleeve 8 with respect to the housing 7 is completed, the assembly of the housing 7 and the bearing sleeve 8 is subjected to heat treatment (baking) to solidify the adhesive G, so that the inner diameter of the small diameter portion 7a of the housing 7 is increased. The bearing sleeve 8 is bonded and fixed around the periphery in a press-fit state (press-fit adhesion). After the assembly of the bearing sleeve 8 to the housing 7 is completed as described above, the seal member 9 is fixed to the outer periphery of the upper end of the bearing sleeve 8. After the sealing member 9 is fixed, the internal space of the housing 7 sealed with the sealing member 9 is filled with lubricating oil as a lubricating fluid including the internal pores of the bearing sleeve 8, whereby the hydrodynamic bearing device 1 shown in FIG. Complete.

  In the above description, the case where the bearing sleeve 8 is bonded and fixed to the inner periphery of the housing 7 by using the thermosetting adhesive G (thermosetting adhesive) has been described. It is also possible to bond and fix the both using an agent, for example, an anaerobic adhesive. Moreover, you may use the adhesive agent which has thermosetting and anaerobic property.

  When the shaft member 2 rotates in the hydrodynamic bearing device 1 having the above-described configuration and assembled as described above, the upper and lower two regions serving as the radial bearing surfaces of the inner peripheral surface 8a of the bearing sleeve 8 are respectively It faces the outer peripheral surface 2a1 of the shaft portion 2a via a radial bearing gap. As the shaft member 2 rotates, the oil film formed in the radial bearing gaps has its oil film rigidity increased by the dynamic pressure action of the dynamic pressure grooves Aa1 and Aa2, and the shaft member 2 can rotate in the radial direction by this pressure. Is supported in a non-contact manner. As a result, radial bearing portions R1 and R2 that support the shaft member 2 in a non-contact manner so as to be rotatable in the radial direction are spaced apart at two locations in the axial direction.

  At the same time, between the annular region serving as the thrust bearing surface of the lower end surface 8b of the bearing sleeve 8 and the upper end surface 2b1 of the flange portion 2b, and the annular region serving as the thrust bearing surface of the inner bottom surface 7c1 of the housing 7 First and second thrust bearing gaps are respectively formed between the lower end surface 2b2 of the flange portion 2b. As the shaft member 2 rotates, the oil film formed in the thrust bearing gaps has its oil film rigidity increased by the dynamic pressure action of the dynamic pressure groove, and the shaft member 2 can be rotated in both thrust directions by this pressure. Touch supported. As a result, a first thrust bearing portion T1 that supports the shaft member 2 in a non-contact manner so as to be rotatable in one thrust direction and a second thrust bearing portion T2 that supports the shaft member 2 in a non-contact manner so as to be rotatable in the other direction of the thrust are formed. Is done.

  Further, as described above, since the first and second seal spaces S1, S2 have a tapered shape that gradually decreases toward the inside of the housing 7, the lubricating oil in both the seal spaces S1, S2 is reduced. The seal space is pulled in the direction in which the seal space is narrowed by the pull-in action by the capillary force, that is, toward the inside of the housing 7. Thereby, the leakage of the lubricating oil from the inside of the housing 7 is effectively prevented. Further, the seal spaces S1 and S2 have a buffer function of absorbing a volume change amount accompanying a temperature change of the lubricating oil filled in the internal space of the housing 7, and within the range of the assumed temperature change, The oil level is always in the seal space S1, S2. In addition, while the inner peripheral surface 9a2 of the first seal portion 9a is a cylindrical surface, the outer peripheral surface of the shaft portion 2a facing this may be tapered. In this case, since the function as a centrifugal force seal can be further imparted to the first seal space S1, the sealing effect is further enhanced.

  Further, as described above, the upper dynamic pressure groove Aa1 has an axial dimension X1 in the upper region that is larger than the axial dimension X2 in the lower region than the axial center m. The pulling force of the lubricating oil by the dynamic pressure groove Aa1 is relatively larger in the upper region than in the lower region. Due to such differential pressure of the pulling force, the lubricating oil filled in the gap between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft portion 2a flows downward, and the first thrust bearing portion T1 The first radial bearing portion is circulated through the first thrust bearing clearance → the circulation path 12 formed by the axial groove 8d1 of the bearing sleeve 8 → the fluid passage formed by the radial groove 10 of the first seal portion 9a. It is drawn again into the radial bearing gap of 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. When the first seal space S1 communicates with the circulation path, and the second seal space S2 communicates with the axial clearance 11, the bubbles are mixed into the lubricating oil for some reason. However, when the bubbles circulate with the lubricating oil, the air is discharged from the oil surface (gas-liquid interface) of the lubricating oil in the seal spaces S1 and S2 to the outside air. Therefore, adverse effects due to bubbles can be prevented more effectively.

  As described above, if the step 13 forming the adhesive reservoir (first space 15) with the small diameter portion 7a of the housing 7 is provided on the outer periphery of the lower end of the bearing sleeve 8, the bearing sleeve 8 can be inserted when the bearing sleeve 8 is inserted. The capacity of the adhesive G that can be held on the front side in the insertion direction (the bottom 7c side of the housing 7) can be increased. Therefore, the adhesive G is scraped with the insertion of the bearing sleeve 8, and the scraped adhesive G is effectively suppressed or prevented from going around the lower end surface 8 b of the bearing sleeve 8. can do. As a result, it is possible to avoid adhesion of the adhesive to the thrust bearing surface provided on the lower end surface 8b of the bearing sleeve 8 and the flange portion 2b arranged in advance, and bearing performance, particularly the bearing of the first thrust bearing portion. It is possible to prevent performance degradation as much as possible.

  Further, since the sticking out of the adhesive G is suppressed or prevented, more adhesive G is provided between the inner peripheral surface of the housing 7 (small diameter portion 7a) and the outer peripheral surface of the bearing sleeve 8 fixed to each other. Can be held. Therefore, the adhesive strength of the bearing sleeve 8 with respect to the housing 7 can be enhanced without deteriorating the bearing performance, particularly the bearing performance of the first thrust bearing portion T1, and this can contribute to the improvement of the reliability of the fluid dynamic bearing device 1. .

  Further, the first space 15 as an adhesive reservoir is formed so as to communicate with a space (second space 16) formed between the second chamfer 8g and the first inner peripheral surface 7a1 of the small diameter portion 7a. Therefore, the capacity of the adhesive G that can be held can be further increased without taking the second chamfer 8g larger than necessary and reducing the area of the lower end surface 8b of the bearing sleeve 8. Therefore, the above effect can be enjoyed more effectively without deteriorating the bearing performance of the first thrust bearing portion T1.

  Further, as described above, since the dispersion capacity of the adhesive G can be allowed by the amount that the holding capacity of the adhesive G can be increased, the assembly of the bearing sleeve 8 to the housing 7 can be simplified. Can do.

  Moreover, the 1st space 15 as an adhesive reservoir was intermittently arrange | positioned in the circumferential direction so that the circulation path 12 and the circumferential direction position might differ. That is, in this embodiment, the adhesive sleeve G is applied to the stepped portion 13 provided intermittently in the circumferential direction so as to be different from the axial groove 8d1 forming the circulation path 12 in the circumferential direction. Since it is bonded and fixed to the housing 7, the adhesive G flows into the axial groove 8d1 as the bearing sleeve 8 is inserted, thereby effectively preventing the axial groove 8d1 (circulation path 12) from being filled. can do. Therefore, the lubricating oil flows and circulates smoothly in the inner space of the housing 7, and the desired bearing performance can be stably maintained.

  Instead of forming an axial groove on the outer peripheral surface of the bearing sleeve 8, a shaft is formed on the inner peripheral surface of the small-diameter portion 7a of the housing 7 (and the inner peripheral surface 9b1 of the second seal portion 9b of the seal member 9). It is also possible to form the circulation path 12 by forming a directional groove. In this case, in order to avoid the inflow of the adhesive G into the axial groove formed in the small diameter portion 7a, alignment is performed so that the circumferential position of the step portion 13 and the axial groove is different from each other. It is desirable to insert the bearing sleeve 8 into the inner periphery of the housing 7.

  The case where the first space 15 as the adhesive reservoir is configured by only a straight portion extending in the axial direction has been described above, but the lower end of the first space 15 has a second lower end as shown in FIG. The cross section has an inverted L shape having a portion that extends in the axial direction through the space 16 (hereinafter referred to as an axial portion 15a) and a radial portion 15b that extends from the upper end of the axial portion 15a to the outer diameter side. You can also. As shown in the figure, the first space 15 as an adhesive reservoir having such a structure has a step portion 14 that forms a radial gap and an axial gap of a predetermined width with the step portion 13 of the bearing sleeve 8. It can be obtained by providing it on the inner periphery of the housing 7 (small diameter portion 7a). The step portion 14 includes a third inner peripheral surface 7a3 having a smaller diameter than the first inner peripheral surface 7a1 provided below the first inner peripheral surface 7a1, and the third inner peripheral surface 7a3 and the first inner peripheral surface 7a1. It is comprised by the level | step difference surface 7a4 which connects.

  With such a configuration, the first space 15 functioning as an adhesive reservoir has a labyrinth structure, so that the holding ability of the adhesive G can be further enhanced. In general, the tensile bond strength is larger than the shear bond strength. Therefore, if the adhesive G is held also in the radial direction portion 15b of the first space 15 as an adhesive reservoir, compared to the case where the adhesive G is held in the first space 15 of the form shown in FIG. The adhesion strength of the bearing sleeve 8 to the housing 7 can be further increased.

  Note that the width (axial dimension) t of the radial direction portion 15b of the first space 15 is set larger by a predetermined amount than the total amount of the gap widths of the first and second thrust bearing gaps. This is because if the width t of the radial direction portion 15b is smaller than the total amount of the gap widths of the two thrust bearing gaps, the gaps of the two thrust bearing gaps cannot be formed in the above-described manner. Of course, when such an assembling procedure is not adopted, it is not necessary to adopt such a dimension setting.

  In the first space 15 having the above-described configuration, the width t of the radial direction portion 15b is set smaller than the width (radial dimension) d of the axial direction portion 15a. In this way, the adhesive G can be reliably held in the axial direction portion 15a of the first space 15 and in the second space 16 by the drawing-in action of the adhesive G by the capillary force. Therefore, it is possible to more effectively prevent the adhesive G from wrapping around the lower end surface 8b of the bearing sleeve 8 and the deterioration of the bearing performance due to this.

  In FIG. 4, the small-diameter outer peripheral surface 8e of the bearing sleeve 8 that forms the axial portion 15a of the first space 15 and the third inner peripheral surface 7a3 of the housing 7 are straight surfaces that are parallel to the axis over the entire length. Although the width d of the axial direction portion 15a is constant over the entire length, the width d of the axial direction portion 15a can be gradually reduced upward. If it does in this way, the retention capability of the adhesive G in the 1st space 15 can further be heightened by the drawing-in action of the adhesive G by capillary force. Such a configuration can be obtained by gradually expanding the small-diameter outer peripheral surface 8e of the bearing sleeve 8 upward as shown in FIG. 5A, or as shown in FIG. 5B. The third inner peripheral surface 7a3 of the housing 7 can also be obtained by gradually reducing the diameter upward. Although illustration is omitted, it can also be obtained by gradually expanding the small-diameter outer peripheral surface 8e of the bearing sleeve 8 upward and gradually reducing the diameter of the third inner peripheral surface 7a3 of the housing 7 upward. .

  Thus, when the width d of the axial direction portion 15a is gradually reduced upward, if the width t of the radial direction portion 15b is made smaller than the minimum width portion (upper end portion) of the axial direction portion 15a, the first The holding ability of the adhesive G in the space 15 can be further enhanced.

  Further, the case where the step portion 13 is formed only on one end side of the bearing sleeve 8 has been described above. However, the step portion 13 may be formed on the outer periphery of both ends of the bearing sleeve 8. With such a configuration, since the direction dependency when the dynamic pressure generating portion is formed on the inner peripheral surface 8a and the end surface of the bearing sleeve 8 is eliminated, the manufacturing process can be simplified.

  In the above description, the case where the large-diameter outer peripheral surface 8d of the bearing sleeve 8 is press-fitted and bonded to the first inner peripheral surface 7a1 of the housing 7 has been described, but the large-diameter outer peripheral surface 8d of the bearing sleeve 8 A gap may be adhered to the first inner peripheral surface 7a1.

  Although one embodiment of the hydrodynamic bearing device 1 to which the configuration of the present invention is applied has been described above, the configuration of the present invention described above is limited to the hydrodynamic bearing device 1 having the structure shown in FIG. Instead, for example, the present invention can be applied to the hydrodynamic bearing device 1 having the structure shown in FIG. The main difference of the hydrodynamic bearing device 1 shown in FIG. 2 from that shown in FIG. 2 is that the seal member 9 is formed in a ring shape and is fixed to the inner periphery of the opening of the housing 7. And the seal space S1 is formed only between the outer peripheral surface of the shaft portion 2a opposed to the shaft portion 2a. That is, the present invention is applied to a hydrodynamic bearing device having a configuration disclosed in Patent Document 1. In the illustrated example, the first space 15 as an adhesive reservoir has the same configuration as that shown in FIG. 2, but the width of the first space 15 can be gradually reduced upward, as shown in FIG. Alternatively, the configuration shown in FIG.

  In the above description, the radial bearing portions R1 and R2 and the thrust bearing portions T1 and T2 are exemplified by the configuration in which the dynamic pressure action of the lubricating oil is generated by the herringbone shape or spiral shape dynamic pressure grooves. So-called step bearings, multi-arc bearings, or non-circular bearings may be used as the portions R1 and R2, and so-called step bearings and wave bearings may be employed as the thrust bearing portions T1 and T2. Further, when the radial bearing portion is constituted by a step bearing or a multi-arc bearing, in addition to the configuration in which the two radial bearing portions are separated from each other in the axial direction as in the radial bearing portions R1 and R2, the bearing sleeve 8 It is good also as a structure which provided the one radial bearing part over the up-and-down area | region of the inner peripheral side. Furthermore, a so-called perfect circular bearing having no dynamic pressure generating portion may be used as the radial bearing portions R1 and R2, and a pivot bearing that contacts and supports one end of the shaft member may be employed as the thrust bearing portion.

It is sectional drawing of the spindle motor for information devices incorporating the hydrodynamic bearing apparatus. It is sectional drawing of the hydrodynamic bearing apparatus which concerns on one Embodiment of this invention. (A) is a sectional view of the bearing sleeve, and (b) is a plan view showing a lower end surface of the bearing sleeve. FIG. 3 is another configuration example of the part shown in the enlarged sectional view of FIG. 2. FIG. (A) (b) Both figures are the other structural examples of the part shown to the expanded sectional view of FIG. It is sectional drawing of the hydrodynamic bearing apparatus which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluid dynamic bearing apparatus 2 Shaft member 7 Housing 8 Bearing sleeve 9 Seal member 9a First seal part 9b Second seal part 13 Step part 15 First space (adhesive reservoir)
15a Axial direction portion 15b Radial direction portion 16 Second space G Adhesives R1, R2 Radial bearing portions T1, T2 Thrust bearing portions S1, S2 Seal space

Claims (10)

A housing with one end open and the other end closed, a bearing sleeve bonded and fixed to the inner periphery of the housing, a shaft member inserted into the inner periphery of the bearing sleeve, an inner peripheral surface of the bearing sleeve, and an outer periphery of the shaft member In a hydrodynamic bearing device comprising a radial bearing portion that supports a shaft member in a radial direction with an oil film formed in a radial bearing gap between the surface and
A hydrodynamic bearing device, characterized in that a step portion for forming an adhesive reservoir with a housing is provided on an outer periphery of an end portion of the bearing sleeve on the housing closing side.   2. The hydrodynamic bearing device according to claim 1, wherein the adhesive reservoir communicates with a space formed between a chamfer formed at an outer peripheral edge portion of the bearing sleeve on the housing closing side and an inner peripheral surface of the housing.   3. The hydrodynamic bearing according to claim 2, wherein the adhesive reservoir has an axial portion extending in the axial direction at one end through the space and a radial portion extending from the other end of the axial portion toward the outer diameter side. apparatus.   The hydrodynamic bearing device according to claim 3, wherein a step portion is provided in the housing, and an axial portion and a radial portion are formed between the step portion and the step portion of the bearing sleeve. And a first thrust bearing portion that supports the shaft member in one thrust direction by a dynamic pressure action of a lubricating fluid generated in a first thrust bearing gap between the one end surface of the bearing sleeve and the one end surface of the shaft member facing the bearing sleeve. A second thrust bearing portion for supporting the shaft member in a non-contact manner in the other direction of the thrust by the dynamic pressure action of the lubricating fluid generated in the second thrust bearing gap between the inner bottom surface of the housing and the other end surface of the shaft member facing the housing; With
The hydrodynamic bearing device according to claim 3, wherein the width of the radial portion is set to be larger than a total amount of gap widths of the first and second thrust bearing gaps.   The hydrodynamic bearing device according to claim 3, wherein a width of the radial portion is set smaller than a width of the axial portion.   The hydrodynamic bearing device according to claim 3, wherein the width of the axial portion is gradually reduced toward the other end side. Furthermore, it is formed between the inner peripheral surface of the housing and the outer peripheral surface of the bearing sleeve, and includes one or a plurality of circulation paths opened at both ends of the bearing sleeve,
The hydrodynamic bearing device according to claim 1, wherein the formation position of the circulation path and the formation position of the adhesive reservoir are different from each other in the circumferential direction.   2. A seal member for sealing one end of the housing, wherein a first seal space is formed on the inner peripheral side of the seal member, and a second seal space is formed on the outer peripheral side of the seal member. Fluid bearing device.   A motor comprising the hydrodynamic bearing device according to claim 1, a stator coil, and a rotor magnet.

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