JP4080229B2 - Hydrodynamic bearing, spindle motor, and recording disk drive - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a dynamic pressure bearing using an oil-impregnated sintered body, a spindle motor employing the dynamic pressure bearing, and a recording disk drive device.
[0002]
[Prior art]
  A recording disk drive device such as a hard disk has a spindle motor for rotational driving arranged concentrically with the recording disk. The spindle motor mainly includes a stationary member to which a stator having an armature coil is fixed, a rotating member to which a rotor magnet facing the stator is fixed, and a bearing mechanism that rotatably supports the rotating member on the stationary member; It is composed of
[0003]
  As the performance of the apparatus increases, a dynamic pressure bearing is adopted as the bearing mechanism for the purpose of improving accuracy. The hydrodynamic bearing is composed of, for example, a shaft having a shaft main body and a plate portion extending radially outward from the outer peripheral surface thereof, and a hollow cylindrical member that can rotate relative to the shaft, and one of them is a rotating member. Is a stationary member. The hollow cylindrical member has a radial inner peripheral surface that faces the outer peripheral surface of the shaft body in the radial direction via a minute gap, and a thrust surface that faces the plate portion in the axial direction through a minute gap. Each minute gap is filled with lubricating oil such as oil to constitute a radial bearing portion and a thrust bearing portion. When one of the shaft and the hollow cylindrical member starts rotating with respect to the other, dynamic pressure is generated in each bearing portion, and the rotating side member is rotatably supported in a non-contact manner with respect to the stationary side member. The
[0004]
  Such a dynamic pressure bearing needs to process each member with high accuracy, and generally increases the cost. Therefore, an oil-containing sintered body may be used for the hollow cylindrical member for the purpose of processing at a low cost. The oil-impregnated sintered body is impregnated with oil used as a lubricating fluid obtained by solidifying metal powder with a mold and sintering the powder. In this case, dynamic pressure generating grooves are respectively formed on the radial inner peripheral surface and the thrust surface of the hollow cylindrical member. Since the dynamic pressure generating groove is integrally formed by pressing with a mold, the hollow cylindrical member is made of a normal metal body, and the hollow cylinder is compared with the case where the dynamic pressure generating groove is electrolytically processed or rolled. The manufacturing of the shaped member becomes easy and the cost can be reduced.
[0005]
[Problems to be solved by the invention]
  However, when an oil-containing sintered body is used for the hollow cylindrical member, the following problems occur due to processing restrictions on the dynamic pressure generating groove. First, when trying to obtain a sufficient depth of the dynamic pressure generating groove on the radial inner peripheral surface of the hollow cylindrical member, the outer diameter relative to the inner diameter is reduced so that the thickness of the hollow cylindrical member is reduced. Is set. For this reason, the area of the thrust surface of the hollow cylindrical member is reduced, while a thrust bearing portion of a desired size cannot be secured, and the bearing rigidity of the thrust bearing portion is sacrificed. Conversely, if the area of the thrust surface is increased so that the thrust bearing portion is sufficiently large, the thickness of the hollow cylindrical member increases accordingly, and the depth of the dynamic pressure generating groove on the inner peripheral surface becomes sufficiently deep. become unable. That is, when the oil-impregnated sintered body is used for the hollow cylindrical member, the performance required for each of the radial bearing portion and the thrust bearing portion is such that if one is realized, the other is difficult to be realized. Thus, when the member which comprises a dynamic pressure bearing is comprised with an oil-impregnated sintered compact, sufficient performance as a dynamic pressure bearing may not be obtained.
[0006]
  An object of the present invention is to obtain sufficient performance as a hydrodynamic bearing in a hydrodynamic bearing using an oil-containing sintered body.
[0007]
[Means for Solving the Problems]
  The hydrodynamic bearing according to claim 1 includes a first member and a second member.
  The first member includes a shaft main body and a plate portion extending radially outward from the outer peripheral surface of the shaft main body. The second member is disposed so as to be rotatable relative to the first member, and includes a hollow cylindrical member and a thrust member.
  The hollow cylindrical member has a radial inner peripheral surface that is opposed to the outer peripheral surface of the shaft body in the radial direction via a minute gap, and a plate portion side facing surface that is opposed to the plate portion in the axial direction via a minute gap. .
  The thrust member has a hollow cylindrical member and a thrust surface that faces the plate portion in the axial direction through a minute gap.
  The hollow cylindrical member is composed of an oil-containing sintered body. The thrust member is a separate member from the hollow cylindrical member and is made of an alloy or an oil-containing sintered body.
  The thrust member is attached radially outward of the hollow cylindrical member.
  A radial bearing is provided in the minute gap between the outer circumferential surface of the shaft body and the radial inner circumferential surface of the hollow cylindrical member, and fluid dynamic pressure is applied to the lubricating oil held in the minute gap during relative rotation. A radial dynamic pressure generating groove formed on the radial inner peripheral surface of the hollow cylindrical member to be induced is provided.
  A thrust bearing portion is formed in the minute gap between the thrust surface of the thrust member and the thrust member side facing surface of the plate portion facing the thrust surface in the axial direction, and the lubricating oil held in the minute gap at the time of relative rotation On the other hand, a thrust dynamic pressure generating groove formed on a thrust surface of a thrust member for inducing fluid dynamic pressure is provided.
[0008]
  In this dynamic pressure bearing, a hollow cylindrical member having a radial inner peripheral surface for constituting a radial bearing portion and a thrust member having a thrust surface for constituting a thrust bearing portion are separate members, and both At least one of the members is made of an oil-containing sintered body. For this reason, compared with the case where both the radial bearing part and the dynamic pressure generating groove of the thrust bearing part are formed in a hollow cylindrical member made of a conventional oil-containing sintered body, the bearing performance is improved. Because it is only necessary to mold either the dynamic bearing generating groove for the radial bearing or the thrust bearing for the member made of the oil-impregnated sintered body. It is because it is released from the restrictions on processing. As a specific example of improving the bearing performance, when forming a member made of an oil-impregnated sintered body, the dynamic pressure generating groove of one bearing part is sufficiently deep regardless of the other bearing part, The area can be made sufficiently large. In addition, by using an oil-containing sintered body, it can be formed at a lower cost.
[0009]
  The hydrodynamic bearing according to claim 2 has a so-called full-fill structure in which the lubricating oil of the radial bearing portion and the thrust bearing portion of claim 1 is continuously held so as to be able to flow mutually, and a meniscus is formed only at one place. Eggplant.
  According to a third aspect of the present invention, in the dynamic pressure bearing, the pumping pressure at which the radial bearing portion of the second aspect pushes lubricating oil into the thrust bearing portion side during steady rotation, and the thrust bearing portion pushes into the radial bearing portion side. It may be configured to act larger than the pumping pressure.
[0010]
  According to a fourth aspect of the present invention, there is provided a spindle motor according to any one of the first to third aspects, a stator fixed to one of the first member and the second member, and a first facing the stator. A rotor magnet fixed to the other of the member and the second member and for generating a rotating magnetic field in cooperation with the stator. In this spindle motor, since the dynamic pressure bearing according to any one of claims 1 to 3 is employed, the performance of the dynamic pressure bearing is improved and high-speed rotation is possible.
[0011]
  According to a fifth aspect of the present invention, there is provided a recording disk drive device comprising: a housing; the spindle motor according to the fourth aspect fixed in the housing; and a circle capable of recording information fixed to the other of the first member and the second member. A plate-shaped recording medium and information access means for writing or reading information at a required position of the recording medium are provided. Since this recording disk drive apparatus employs the spindle motor according to the fourth aspect, high-speed rotation is possible, and information writing and reading speeds are improved.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
  [First Embodiment]
  (1) Configuration of spindle motor
  FIG. 1 is a longitudinal sectional view schematically showing a schematic configuration of a spindle motor 1 as an embodiment of the present invention. The spindle motor 1 is a recording disk driving spindle motor and constitutes a part of a recording disk device such as a hard disk. Further, the hydrodynamic bearing 4 as one embodiment of the present invention is configured as a bearing mechanism of the spindle motor 1. Note that OO shown in FIG. 1 is the rotation axis of the spindle motor 1. In the description of the present embodiment, the vertical direction in FIG. 1 is referred to as the “axis vertical direction” for convenience, but the direction in the actual mounting state of the spindle motor 1 is not limited.
[0013]
  In FIG. 1, the spindle motor 1 mainly includes a stationary member 2, a rotating member 3, and a dynamic pressure bearing 4 for rotatably supporting the rotating member 3 on the stationary member 2. The spindle motor 1 further includes a stator 6 composed of a stator core fixed to the stationary member 2 and a coil wound around the stator core, and a rotor magnet 7 fixed to the rotating member 3. A magnetic circuit unit for applying a rotational force to the rotating member 3 is configured.
[0014]
  Stationary member
  The stationary member 2 includes a bracket 10 and a sleeve 11 fixed in the central opening of the bracket 10. More specifically, the bracket 10 is made of aluminum, and a cylindrical opening 10a extending upward in the axial direction is formed at the center opening edge of the bracket 10, and the outer peripheral surface of the sleeve 11 is fitted to the inner peripheral surface thereof. ing. A stator 6 is fixed to the outer peripheral surface of the cylindrical portion 10a.
[0015]
  The sleeve 11 is a cylindrical member, and a through hole 51 penetrating in the axial direction is formed at the center thereof. The inner peripheral surface of the through-hole 51 has a radial inner peripheral surface 53 having the smallest diameter, an upper inner peripheral surface 52a having a larger diameter than the radial inner peripheral surface 53 at the upper end opening, and a larger diameter than the radial inner peripheral surface 53 at the lower end opening. The first lower inner peripheral surface 54 and a second lower inner peripheral surface having a larger diameter than the first lower inner peripheral surface 54. A plane perpendicular to the axial direction is formed between the radial inner peripheral surface 53 and the upper inner peripheral surface 52a, and a seal member described later is fixed. A plane perpendicular to the axial direction is formed between the radial inner peripheral surface 53 and the first lower inner peripheral surface 54, and acts as a thrust surface of a thrust bearing portion described later. A plane perpendicular to the axial direction is formed between the first lower inner peripheral surface 54 and the second lower inner peripheral surface, and the thrust cover 12 is fixed to close the lower end opening of the through hole 51. Since the upper surface of the thrust cover 12 acts as another thrust surface of a thrust bearing portion to be described later, a plane between the first lower inner peripheral surface 54 and the second lower inner peripheral surface is formed with high accuracy, and the thrust cover 12 Is fixed to the sleeve 11 with high accuracy.
[0016]
  Rotating member
  The rotating member 3 is a member that is rotatably supported with respect to the sleeve 11 via the dynamic pressure bearing 4. The rotating member 3 includes a rotor hub 14 on which a recording disk (not shown) is placed on the outer periphery, and an inner portion of the rotor hub 14. A shaft 15 is provided on the circumferential side and is pivotally supported by the sleeve 11 via the hydrodynamic bearing 4.
[0017]
  The rotor hub 14 is made of stainless steel having magnetism, and has a cup shape having a central hole that covers the sleeve 11 and the stator 6 close to the upper portion thereof. The inner peripheral surface of the boss portion to which the rotor magnet 7 is fixed and the inner diameter is small is opposed to the upper outer peripheral surface of the sleeve 11 with a minute gap. A recording disk is fitted on the outer peripheral surface of the boss portion, placed on the enlarged diameter portion below the boss portion, and fixed by recording disk fixing means attached to the upper end surface of the boss portion. The rotor magnet 7 faces the stator 6 with a small gap in the radial direction. Then, by energizing the coil of the stator 6, electromagnetic interaction between the stator 6 and the rotor magnet 7 occurs, and torque acts on the rotating member 3.
[0018]
  The shaft 15 is made of stainless steel having substantially the same quality as the rotor hub 14, and the upper end in the axial direction is fitted in the center hole of the rotor hub 14. A thrust flange 46 is integrally formed at the lower end of the shaft 15. That is, the shaft 15 is composed of a cylindrical shaft main body 45 and a thrust flange 46 (corresponding to a plate portion).
[0019]
  The thrust flange 46 is an annular and disk-shaped portion that extends radially outward from the outer peripheral surface of the lower end of the shaft body 45 of the shaft 15 to a position where a minute gap is formed with respect to the first lower inner peripheral surface 54 of the sleeve 11. is there. The thrust flange 46 has an upper thrust surface 47 on the shaft body 45 side and a lower thrust surface 48 on the opposite side.
[0020]
  (2) Configuration of bearing mechanism
  FIG. 2 is a view showing the vicinity of the dynamic pressure bearing 4 of the spindle motor 1 and is a partially enlarged view of FIG. The hydrodynamic bearing 4 is a hydrodynamic bearing for rotatably supporting the rotating member 3 with respect to the stationary member 2, more specifically, the rotor hub 14 and the shaft 15 with respect to the sleeve 11 via the lubricating oil 8. It is. The hydrodynamic bearing 4 has first and second radial bearing portions 21 and 22 and first and second thrust bearing portions 23 and 24. Hereinafter, the structure of each bearing part 21-24 is demonstrated, touching the structure of the sleeve 11, the thrust cover 12, and the shaft 15. FIG.
[0021]
  Radial bearing
  The sleeve 11 includes a hollow cylindrical sleeve main body 16, a sliding cylindrical portion 17 fitted to the inner peripheral surface of the sleeve main body 16, and an annular seal member 18 provided on the upper portion of the sliding cylindrical portion 17. It consists of and. The sliding cylindrical portion 17 is a hollow cylindrical member that is opposed to the outer peripheral surface of the shaft main body 45 in the radial direction via a minute gap. A central hole of the sliding cylindrical portion 17 is a through hole 51, and an inner peripheral surface thereof is a radial inner peripheral surface 53. The sliding cylindrical portion 17 is a member made of an oil-containing sintered body. Here, the oil-impregnated sintered body is a material obtained by impregnating oil into a material obtained by sintering a metal mold, a metal compound powder, or a non-metal powder that has been pressure-molded with a molding die. There are fine continuous pores formed inside. For example, as a raw material, what has a copper-type material (For example, Cu-Fe, Cu-Sn, Cu-Sn-Pb etc.) as a main component is used. For this reason, the sliding cylindrical part 17 can hold | maintain the lubricating oil 8 in the continuous void | hole formed in the inside.
[0022]
  The sleeve body 16 is made of a general metal made of a copper-based alloy (the general metal here is not porous like a sintered body). Therefore, the thermal expansion coefficients of the sliding cylindrical portion 17 and the sleeve main body 16 are substantially equal, and there is almost no distortion or the like due to thermal expansion between both members. On the radial inner peripheral surface 53, herringbone-like dynamic pressure generating grooves 25 and 26 for generating dynamic pressure in the lubricating oil 8 are formed side by side in the axial direction. The dynamic pressure generating grooves 25 and 26 are formed by arranging a plurality of substantially “<”-shaped grooves formed by connecting a pair of spiral grooves inclined in directions opposite to the rotation direction. is there. The axial dimension of the dynamic pressure generating groove 25 is such that the spiral groove on the upper side in the axial direction is formed larger than the lower side, and the pumping pressure by the upper spiral groove is generated larger than the lower side. On the other hand, the axial dimension of the dynamic pressure generating groove 26 is substantially the same in the upper and lower spiral grooves in the axial direction, and both pumping pressures are generated equally.
[0023]
  The seal member 18 is press-fitted and fixed in a recess formed in the upper inner peripheral surface 52 a of the sleeve 11, and the inner peripheral surface of the seal member 18 faces the annular groove 30 provided on the outer peripheral surface of the shaft 15 in the radial direction. Yes. The material of the seal member 18 is made of the same copper alloy as that of the sleeve body 16. Thus, the first and second radial bearing portions 21 and 22 are aligned in the axial direction by the radial inner peripheral surface 53 of the sleeve 11, the outer peripheral surface 37 of the shaft main body 45 of the shaft 15, and the lubricating oil 8 therebetween. It consists of
[0024]
  Thrust bearing
  The first lower inner peripheral surface 54 of the sleeve body 16 forms a stepped portion 52 at the lower end of the through hole 51. The step portion 52 is an annular recess or space for accommodating the thrust flange 46 of the shaft 15. The stepped portion 52 has a larger diameter than the radial inner peripheral surface 53, and has a thrust surface 56 and a first lower inner peripheral surface 54 around the through hole 51 and facing the lower side in the axial direction, and each surface is a thrust flange. 46 is opposed to the upper thrust surface 47 and the outer peripheral surface. Here, the sliding cylindrical portion 17 extends to a position facing the upper thrust surface 47 of the thrust flange 46. For this reason, the thrust surface 56 is formed only at a position corresponding to the radially outer peripheral side of the upper thrust surface 47.
[0025]
  A spiral dynamic pressure generating groove 27 for generating dynamic pressure in the lubricating oil 8 as the shaft 15 rotates is formed on the thrust surface 56 of the sleeve body 16. The dynamic pressure generating groove 27 is composed of a plurality of spiral grooves that are inclined with respect to the rotation direction and arranged in the rotation direction, and the pumping pressure acts so that the lubricating oil 8 is directed radially inward. Thus, the first thrust bearing portion 23 is formed by the thrust surface 56 of the sleeve 11, the upper thrust surface 47 of the thrust flange 46, and the lubricating oil 8 therebetween.
[0026]
  A thrust surface 12 a is formed at a portion facing the lower thrust surface 48 of the thrust flange 46 on the upper end surface in the axial direction of the thrust cover 12. A spiral dynamic pressure generating groove 28 for generating dynamic pressure in the lubricating oil 8 as the shaft 15 rotates is formed on the thrust surface 12a. The dynamic pressure generating groove 28 includes a plurality of spiral grooves that are inclined in the rotation direction and are arranged in the rotation direction, and the pumping pressure is generated so that the lubricating oil 8 is directed radially inward. Thus, the second thrust bearing portion 24 is formed by the lower thrust surface 48 of the thrust flange 46, the thrust surface 12a of the thrust cover 12, and the lubricating oil 8 therebetween.
[0027]
  The surface tension seal portion 29 is a structure for preventing leakage of the lubricating oil 8 from the first radial bearing portion 21, and the inner peripheral surface of the seal member 18 at the outer end in the axial direction of the first radial bearing portion 21. And the outer peripheral surface of the shaft 15. Specifically, in the axial direction of the outer peripheral surface of the shaft 15, the gap between the inner peripheral surface of the sleeve 11 and the inner peripheral surface of the sleeve 11 expands toward the outer side in the axial direction. An inclined surface 30 is formed. The surface tension of the lubricating oil 8 held on the bearing portion and the air pressure of the outside air are balanced, and the meniscus of the lubricating oil 8 is located on the inclined surface 30. As a result, if the lubricating oil 8 tries to move further outward, the curvature of the liquid level tends to increase, and this acts as a resistance to prevent the lubricating oil 8 from moving outside the bearing.
[0028]
  As described above, the hydrodynamic bearing 4 includes the radial bearing portions 21 and 22 and the thrust bearing portions 23 and 24, and the lubricating oil 8 is continuously filled in the bearing portions. Further, the lubricating oil 8 in each bearing portion is sealed by a surface tension seal portion 29 formed in the upper portion in the axial direction of the gap between the outer peripheral surface of the shaft 15 and the inner peripheral surface of the sleeve 11. Further, the gaps constituting the bearing portions 21 to 24 are completely filled with the lubricating oil 8 (does not have a portion blocked by air), so that only the surface tension seal portion 29 leads to the outside air. It has a full fill structure.
[0029]
  Shaft support method
  In accordance with the rotation of the spindle motor 1, the pumping pressure by the first and second radial bearing portions 21 and 22 is increased to generate a supporting pressure necessary for supporting a load in the radial direction (radial direction), and at the same time, lubricating oil The pumping pressure acts so as to push 8 downward in the axial direction. In addition, since the pumping pressure from the first and second radial bearing portions 21 and 22 is larger than the pumping pressure acting on the radially inner peripheral side of the first thrust bearing portion 23 during steady rotation, the pumping pressure is somewhat offset. It acts to push the lubricating flow 8 radially outward. The first thrust bearing portion 23 is a load in the thrust direction (axial direction) due to the interaction between the radially inner pumping pressure generated here and the pumping pressure from the first and second radial bearing portions 21 and 22. Support. Further, the pumping pressure propagates to the second thrust bearing portion 24 through a minute gap formed on the outer peripheral surface of the thrust flange 46, and the pumping pressure and the first and second radials on the radially inner peripheral side of the bearing portion. The pushing pressure from the bearing portions 21 and 22 interacts. As a result, the center of the second thrust bearing portion 24 becomes a high pressure and supports the load in the thrust direction.
[0030]
  In this way, the dynamic pressure bearing 4 supports the rotating member 3 in a non-contact manner with respect to the stationary member 2 so as to be rotatable. The retained amount of the minute gap lubricating oil 8 is appropriately changed depending on the rotational operation of the spindle motor, the temperature, and the like. However, since the gap that forms the surface tension seal portion 29 acts as an oil reservoir, there is such a change. However, the lubricating oil 8 does not run out or leak.
[0031]
  (4) Configuration of hard disk device
  Next, a hard disk device as a recording disk driving device provided with the spindle motor 1 will be described as an example. FIG. 3 shows a schematic diagram of an internal configuration of a general hard disk device 80. The interior of the housing 81 forms a clean space that is extremely free of dust, dust, and the like, and the spindle motor 1 on which a disk-shaped recording disk 83 that stores information is mounted is installed. In addition, a magnetic head moving mechanism 87 that reads and writes information from and to the recording disk 83 is disposed inside the housing 81. The magnetic head moving mechanism 87 includes a head 86 that reads and writes information on the recording disk, and the head. The supporting arm 85 and the actuator unit 84 that moves the head and the arm to required positions on the disk are configured.
[0032]
  (5) Features of the hydrodynamic bearing of this embodiment
  BookThe dynamic pressure bearing of the embodiment has the following characteristics.
  In the hydrodynamic bearing 4 of this embodiment, the sleeve main body 16 having the sliding cylindrical portion 17 having the radial inner peripheral surface 53 for constituting the radial bearing portions 21 and 22 and the thrust surface 56 constituting the thrust bearing portion 23. Are separate members, and the sliding cylindrical portion 17 is made of an oil-containing sintered body. For this reason, compared with the case where the member which has both the radial inner peripheral surface 53 and the thrust surface 56 like the past is comprised with an oil-containing sintered compact, the outer diameter at the time of shape | molding the sliding cylindrical part 17 is made small. Therefore, the dynamic pressure generating grooves 25 and 26 having a desired depth can be obtained. That is, the processing of the dynamic pressure generating grooves 25 and 26 of the first and second radial bearing portions 21 and 22 can be freely set in a shape such as a depth regardless of the configuration of the first thrust bearing portion 23. Similarly, the first and second thrust bearing portions 23 and 24 can be freely set in shape such as their outer dimensions regardless of the configuration of the sliding cylindrical portion 17. Therefore, since the radial bearing parts 21 and 22 and the thrust bearing parts 23 and 24 can be freely set in shape without being constrained by each other's configuration, the advantages of using the oil-impregnated sintered body are enjoyed to the maximum. be able to.
[0033]
  MaIn addition, the volume occupied by the oil-impregnated sintered body is small and the oil content can be reduced as compared with the conventional case where the member having the radial inner peripheral surface 53 and the thrust surface 56 is constituted by the oil-impregnated sintered body. Therefore, the change in the interface position of the lubricating oil 8 of the surface tension seal portion 29 during thermal expansion is reduced. Therefore, the volume of the space | gap of the surface tension seal | sticker part 29 can be reduced, for example, the height of a motor can be suppressed by making the sealing member 18 thin.
[0034]
  [First reference example]
  This first reference exampleThe basic configuration of the spindle motor 101 is the same as that of the spindle motor 1 of the first embodiment, and only the configuration of the sleeve 111 constituting the dynamic pressure bearing 104 is different. Hereinafter, this difference will be described. As shown in FIG. 4, the sleeve 111 constituting the hydrodynamic bearing 104 includes a hollow cylindrical sleeve main body 116, a sliding cylindrical portion 117 fitted to the inner peripheral surface of the sleeve main body 116, and a sliding cylinder. The annular seal member 118 provided at the upper part of the cylindrical part 117 and the annular sliding annular part 119 provided at the lower part of the sliding cylindrical part 117 are different, and the configuration of the sliding annular part 119 is different. To do.
[0035]
  Similar to the sliding cylindrical portion 17 of the first embodiment, the sliding cylindrical portion 117 is an oil-impregnated sintered body that is opposed to the outer peripheral surface of the shaft main body 145 of the shaft 115 in the radial direction via a minute gap. This is a hollow cylindrical member. A central hole of the sliding cylindrical portion 117 is a through hole 151, and an inner peripheral surface thereof is a radial inner peripheral surface 153. The sliding annular portion 119 provided at the lower portion of the sleeve main body 116 is made of a copper-based alloy and made of a general metal and annular member, and has an inner peripheral surface that is the same inner diameter as the radial inner peripheral surface 153 and a lower end of the through hole 151. A step portion 152 is formed together with a lower inner peripheral surface 154 of the sleeve body 116. The step portion 152 has a thrust surface 156 formed in the sliding annular portion 119 and facing the lower side in the axial direction around the through hole 151, and a lower inner peripheral surface 154, and each surface is a first flange of the thrust flange 146. The thrust surface 147 and the outer peripheral surface are opposed to each other. Here, the sliding annular portion 119 is provided along the entire surface of the first thrust surface 147 of the thrust flange 146, and accordingly, an area of a thrust bearing portion described later is secured wider than that of the first embodiment. be able to.
[0036]
  This first reference exampleIn the hydrodynamic bearing 104, the thrust bearing portion 123 extends radially inward to the position of the outer peripheral surface 137 of the shaft body 145, so that a sufficient capacity can be secured against the thrust load. . Accordingly, the outer diameter of the hydrodynamic bearing 104 is limited, and the diameter cannot be increased beyond a certain level. Further, in order to ensure the bearing characteristics, the thrust bearing portion 123 with respect to the first and second radial bearing portions and the other thrust bearing portion. The hydrodynamic bearing 104 is particularly effective when a larger support pressure is required.
[0037]
  Further, if the sliding annular portion 119 is formed as an integral member with the sleeve main body 116, the number of parts can be reduced.
    [Second Reference Example]
  This second reference exampleThe basic configuration of the spindle motor 201 is the same as that of the spindle motor 1 of the first embodiment, and only the configuration of the sleeve 211 constituting the dynamic pressure bearing 204 is different. Hereinafter, this difference will be described.
[0038]
  As shown in FIG. 5, the sleeve 211 constituting the hydrodynamic bearing 204 is provided in a hollow cylindrical sleeve main body 216, an annular seal member 218 provided on the upper portion of the sleeve main body 216, and a lower portion of the sleeve main body 216. It is comprised from the cyclic | annular sliding annular part 219 which consists of an obtained oil-containing sintered compact. That is, in 1st Embodiment, although the oil-impregnated sintered compact is employ | adopted for the sliding cylindrical part 17 which is a member which comprises the radial bearing parts 21 and 22,This second reference exampleThen, the sliding annular portion 219 which is a member constituting the thrust bearing portion 223 is made an oil-impregnated sintered body, and the first and second radial bearing portions 221 and 222 are radially reduced by reducing the inner peripheral surface of the sleeve body 16. The difference is that the inner peripheral surface 253 is made of a general metal.
[0039]
  BookSecond reference exampleIn the hydrodynamic bearing 204, since there are no restrictions on the dimensions of the members when the sliding annular portion 219 and the sleeve main body 216 are formed, the thrust bearing portion 223 having the desired size, the first and second radial bearing portions 221, 222 can be obtained. Moreover, in this dynamic pressure bearing 204, the proportion of the oil-containing sintered body is smaller than that of the first embodiment, and the lubricating oil 8 held by the dynamic pressure bearing is also reduced. The accompanying volume change can be made small.
[0040]
  [Third reference example]
  This third reference exampleAs shown in FIG. 6, the dynamic pressure bearing 304 of the spindle motor 301 includes a sleeve body 316 having a radial inner peripheral surface 353 constituting the radial bearing portions 321 and 322 and a thrust surface 356 constituting the thrust bearing portion 323. The sliding annular part 319 is a separate memberSecond reference example204 except that the sliding annular portion 319 is arranged only on the outer peripheral side in the radial direction. ThisSecond reference exampleThe radial inner peripheral surface 353 can be secured longer than the above.
[0041]
  [Second embodiment]
  As shown in FIG. 7, the dynamic pressure bearing 404 of the spindle motor 401 according to the present embodiment includes a hollow cylindrical sleeve body 416 and a sliding body made of an oil-containing sintered body fitted to the inner peripheral surface of the sleeve body 416. An annular sliding ring composed of a moving cylindrical part 417, an annular seal member 418 provided at the upper part of the sliding cylindrical part 417, and an oil-containing sintered body provided at the lower part of the sliding cylindrical part 417 Part 419. That is, the present embodiment is different from the first embodiment in that the radial bearing portions 421 and 422 and the thrust bearing portion 423 are each composed of a separate oil-impregnated sintered body.
[0042]
  In the hydrodynamic bearing 404 of the present embodiment, a sliding cylindrical portion 417 made of an oil-containing sintered body having a radial inner peripheral surface 453 constituting the radial bearing portions 421 and 422, and a thrust surface constituting the thrust bearing portion 423. And the sliding annular portion 419 made of an oil-impregnated sintered body having 456. Therefore, compared with the case where the member having the radial inner peripheral surface 353 and the thrust surface 356 is made of an oil-impregnated sintered body, There are no dimensional restrictions when molding the members 417 and 419.
[0043]
  [Third embodiment]
  FIG. 8 illustrates the present invention.Third embodiment2 is a longitudinal sectional view schematically showing a schematic configuration of a spindle motor 501 of FIG. This spindle motor 501 is also for recording disk drive as described above, but the structure of the hydrodynamic bearing is different. In the dynamic pressure bearing 504, the thrust bearing portion 23 of the spindle motor 1 of the first embodiment is provided at the lower portion of the shaft 15, whereas the thrust bearing portion 523 is on the upper side of the shaft 515 and the rotor hub 514. The main difference is that it is provided on the back side of the.
[0044]
  That is, a sliding cylindrical portion 517 made of an oil-containing sintered body is disposed on the sleeve body 516 so as to face the outer peripheral surface of the shaft 515, and the thrust surface 556 is formed on the upper surface of the sleeve body 516 on the back surface of the rotor hub 514. They are formed to face each other. Thus, the first and second radial bearing portions 521 and 522 are formed above and below the sliding cylindrical portion 517 in the axial direction, and the thrust bearing portion 523 is formed on the upper side on the first radial bearing portion 521 side. The first radial bearing portion 521 has a dynamic pressure generating groove so that the lubricating oil 8 is pushed upward in the axial direction, and the thrust bearing portion 523 moves so that the lubricating oil 8 is pushed radially inward. A pressure generating groove is formed, and the lubricating oil 8 in both bearing portions is continuously held to interact with each other to support loads in the radial direction and the thrust direction, respectively. In the second radial bearing portion 522, the lubricating oil 8 supports the radial load independently of the first radial bearing portion 521 (the lubricating oil 8 is not continuous) by the air vent 561. The minute gap on the radially outer circumferential side of the thrust bearing portion 523 forms a surface tension seal portion on the outer circumferential surface of the sleeve body 516, and the minute gaps on the lower and upper axial directions of the first and second radial bearing portions 521 and 522 are formed. The gap forms a surface tension seal part in a part of the air vent part 561, and the minute gap on the lower side in the axial direction of the second radial bearing part 522 forms a surface tension seal part with the enlarged diameter part at the lower end of the shaft. The lubricant oil 8 is held so as not to leak. The air vent 561 communicates with the outside of the bearing through a lateral through-hole extending in the radial direction in the sleeve main body 516, a vertical through-hole formed by a vertical groove on the inner peripheral surface of the cylindrical portion 510a of the bracket 510 and an outer peripheral surface of the sleeve main body 516. Yes. The lower side of the second radial bearing portion 522 communicates with the outside of the bearing through the lower end of the vertical through hole. A dynamic pressure bearing such as the dynamic pressure bearing 504 having a plurality of parts communicating with the outside air may be referred to as a partial fill structure with respect to the full fill structure because the lubricating oil is partially retained.
[0045]
  Such a dynamic pressure bearing 504 of the spindle motor 501 also has the same effect as the dynamic pressure bearing 4 of the first embodiment.
  [Other Embodiments]
  As mentioned above, although embodiment of the hydrodynamic bearing of this invention was described, this invention is not limited to the said embodiment, It can change in the range which does not deviate from the summary of this invention.
[0046]
  For example, in the illustrated embodiment, the shaft is fixed to the rotor hub and the rotating member is configured as a so-called shaft rotation type spindle motor. However, the shaft is a part of the stationary member. The present invention can also be applied to a fixed spindle motor. Further, the type of the dynamic pressure generating groove constituting the bearing portion is not limited to the above embodiment. That is, it may be a herringbone, spiral, or other shape groove.
[0047]
  In addition to the hard disk recording device, the spindle motor according to the present invention can be employed in other recording disk driving devices, polygon mirror driving devices of laser beam printers, and color wheel driving devices used in projectors.
[0048]
【The invention's effect】
  In the hydrodynamic bearing according to claim 1, a hollow cylindrical member having a radial inner peripheral surface for constituting a radial bearing portion and a thrust member having a thrust surface for constituting a thrust bearing portion are separate members. In addition, at least one of both members is made of an oil-containing sintered body. For this reason, compared with the case where both the radial bearing part and the dynamic pressure generating groove of the thrust bearing part are formed in a hollow cylindrical member made of a conventional oil-containing sintered body, the bearing performance is improved. Because it is only necessary to mold either the dynamic bearing generating groove for the radial bearing or the thrust bearing for the member made of the oil-impregnated sintered body. It is because it is released from the restrictions on processing. As a specific example of improving the bearing performance, the dynamic pressure generating groove can be made sufficiently deep or the area of the bearing portion can be made sufficiently large when a member made of an oil-containing sintered body is molded.
[0049]
  In the hydrodynamic bearing according to the second and third aspects, the above-described effect can be obtained with a full-fill structure. In the spindle motor according to the fourth aspect, since the dynamic pressure bearing according to any one of the first to third aspects is employed, the performance of the dynamic pressure bearing is improved and high-speed rotation is possible. In the recording disk drive apparatus according to the fifth aspect, since the spindle motor according to the fourth aspect is employed, high-speed rotation is possible, and information writing and reading speed is improved.
[Brief description of the drawings]
FIG. 1 is a schematic vertical sectional view of a spindle motor according to a first embodiment of the present invention.
FIG. 2 is a view showing the vicinity of a bearing mechanism of the spindle motor according to the first embodiment, and is a partially enlarged view of FIG. 1;
FIG. 3 is a schematic configuration diagram of a general hard disk device.
[Fig. 4]First reference exampleFIG. 3 is a view showing the vicinity of a bearing mechanism of the spindle motor of FIG. 2 and corresponding to FIG. 2.
[Figure 5]Second reference exampleFIG. 3 is a view showing the vicinity of a bearing mechanism of the spindle motor of FIG. 2 and corresponding to FIG. 2.
[Fig. 6]Third reference exampleFIG. 3 is a view showing the vicinity of a bearing mechanism of the spindle motor of FIG. 2 and corresponding to FIG. 2.
[Fig. 7]Second embodimentFIG. 3 is a view showing the vicinity of a bearing mechanism of the spindle motor of FIG. 2 and corresponding to FIG. 2.
[Fig. 8] of the present inventionThird embodimentThe longitudinal cross-sectional schematic of the spindle motor of FIG.
[Explanation of symbols]
1, 101, 201, 301, 401, 501 Spindle motor
4, 104, 204, 304, 404, 504 Hydrodynamic bearing
11, 111, 211, 311, 411 Sleeve (second member)
15, 115, 215, 315, 415, 515 Shaft (first member)
16 Sleeve body (thrust member)
17, 117, 417, 517 Sliding cylindrical part (hollow cylindrical member)
45 Shaft body
46 Thrust flange (plate part)
119, 219, 319, 419 Sliding annular part (thrust member)
216, 316 Sleeve body (hollow cylindrical member)

Claims (5)

A first member having a shaft body and a plate portion extending radially outward from the outer peripheral surface of the shaft body;
A hollow cylindrical member having a radial inner circumferential surface opposed to the outer circumferential surface of the shaft main body in a radial direction via a minute gap, and a plate portion side facing surface opposed to the plate portion in the axial direction via a minute gap. A thrust member having a thrust surface facing in the axial direction through the plate portion and a minute gap, and a second member disposed to be rotatable relative to the first member;
With
The hollow cylindrical member is composed of an oil-containing sintered body,
The thrust member is a separate member from the hollow cylindrical member, and is composed of an alloy or an oil-containing sintered body, and is attached to the outer side in the radial direction of the hollow cylindrical member,
In the minute gap between the outer peripheral surface of the shaft main body and the radial inner peripheral surface of the hollow cylindrical member, fluid dynamic pressure is induced in the lubricating oil held in the minute gap during the relative rotation. A radial bearing portion including a radial dynamic pressure generating groove formed on the radial inner peripheral surface of the hollow cylindrical member is configured,
In the minute gap between the thrust surface of the thrust member and the thrust member side facing surface of the plate portion facing the thrust surface in the axial direction, the lubricating oil held in the minute gap is not affected by the relative rotation. A thrust bearing portion including a thrust dynamic pressure generating groove formed on the thrust surface of the thrust member that induces fluid dynamic pressure is configured.
A hydrodynamic bearing characterized by that.   The hydrodynamic bearing according to claim 1 is a hydrodynamic bearing in which the lubricating oil of the radial bearing portion and the thrust bearing portion is continuously held so as to be able to flow mutually, and a meniscus is formed only at one place.   In the dynamic pressure bearing according to claim 2, the pumping pressure at which the radial bearing portion pushes lubricating oil into the thrust bearing portion side during steady rotation is greater than the pumping pressure at which the thrust bearing portion pushes into the radial bearing portion side. A hydrodynamic bearing that also works greatly.   The hydrodynamic bearing according to claim 1, a stator fixed to one of the first member and the second member, and the other of the first member and the second member so as to face the stator. And a rotor magnet for generating a rotating magnetic field in cooperation with the stator.   5. A housing, a spindle motor according to claim 4 fixed inside the housing, a disc-shaped recording medium fixed to the other of the first member and the second member and capable of recording information, and the recording A recording disk drive comprising: information access means for writing or reading information at a required position on the medium.

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