JP2007185073A - Bearing mechanism, motor, and recording disc drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a deterioration in performance of a bearing mechanism caused by a fixing screw in the bearing mechanism where a shaft is secured to a plate by using the fixing screws. <P>SOLUTION: The bearing mechanism 10 of a motor 1 comprises a fixed shaft 22 on which a flange portion 221 is formed, a lock member 23 fixed to the step portion of the fixed shaft 22, a sleeve member 31 which has a hub, and a fixing screw 26 for fixing the fixed shaft 22 to a base plate 21a, wherein a radial dynamic pressure bearing mechanism 410 is interposed between the inner side face of the sleeve member 31, and the fixed shaft 22 and a thrust dynamic pressure bearing mechanism 420 between the flange portion 221 and the lower end face 311 of the sleeve member 31. Since rigidity of the bearing mechanism 10 is enhanced by providing the flange portion 221 integrally with the fixed shaft 22, a deterioration in performance of the thrust dynamic pressure bearing mechanism 420 caused by tightening the fixing screw 26 can be prevented. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric motor and a bearing mechanism using fluid dynamic pressure provided in the motor.

  2. Description of the Related Art Conventionally, a recording disk drive device such as a hard disk device has been provided with a spindle motor (hereinafter referred to as “motor”) that rotationally drives the recording disk, and uses fluid dynamic pressure as one of the motor bearing mechanisms. A bearing mechanism is adopted. In such a bearing mechanism using fluid dynamic pressure, in many cases, a thrust dynamic pressure bearing mechanism and a radial dynamic pressure bearing mechanism are configured between a shaft or a portion connected to the shaft and a sleeve into which the shaft is inserted. Is done.

  Patent Document 1 discloses a bearing mechanism in which a shaft is inserted into a sleeve in which an inner sleeve and an outer sleeve are combined, and a radial bearing is formed between the outer peripheral surface of the shaft and the inner peripheral surface of the inner sleeve. Thrust bearings are respectively formed on the upper end surface and the lower end surface of the inner sleeve. Further, a flow path that communicates vertically is provided between the inner sleeve and the outer sleeve, and a shaft that faces the upper end surface of the inner sleeve and the outer sleeve, and a shaft that faces the lower end surface of the inner sleeve. An annular taper seal is formed between the flange portion and the outer sleeve. Patent Document 2 discloses a structure in which the inner rotor and the outer rotor of Patent Document 1 are integrated.

On the other hand, in Patent Document 3, a flange member is provided at both ends of the shaft, a radial dynamic pressure generator is provided between the shaft and the hub, and a thrust dynamic pressure generator is provided between the lower flange member and the hub. A bearing mechanism is disclosed.
JP 2005-48890 A JP 2002-70849 A JP 2005-339716 A

  In recent years, recording disk drive devices are also mounted on mobile phones, portable music players, etc., and there is a demand for small and thin recording disk drive devices. Therefore, the same applies to motors that are drive sources of recording disk drive devices. Further downsizing and thinning are required. In the case of a motor used in a recording disk drive apparatus of 1 inch or less, a moment acts on the rotor due to a load caused by a reaction force from the head suspension when the head enters. When contact occurs between the members constituting the bearing mechanism due to the moment, abnormal vibration due to contact occurs, and reading / writing becomes impossible. For this reason, contact within the bearing is not caused by the moment, and it is also required to reduce power loss by reducing the loss of the bearing mechanism.

  By the way, as in Patent Document 1, in order to provide the thrust dynamic pressure bearing mechanism at two locations on the upper and lower sides of the sleeve, it is necessary to strictly manage the dimension between the upper and lower surfaces of the sleeve. However, when the motor is extremely reduced in size and thickness, such highly accurate processing and assembly becomes difficult. In addition, when two thrust dynamic pressure bearing mechanisms are provided, energy loss due to the entire bearing mechanism also increases. Furthermore, in the motor of Patent Document 1, it is also necessary to strictly control the position adjustment of this member when attaching the retaining member to the shaft.

  On the other hand, when thinning a motor, it is required to make the shaft as short as possible, and it becomes difficult to attach the shaft to a thin plate-like member by press fitting, and other work such as welding becomes complicated. . In Patent Document 3, in order to avoid such a problem, both ends of the shaft are easily fixed to the top and bottom of the housing by fixing screws.

  However, when the upper and lower parts of the shaft and the housing are fixed with fixing screws, stress due to the fixing screws is generated inside the shaft, so that the shaft and the flange member are likely to be distorted, and the thrust movement between the flange member and the hub occurs. There is a risk that unacceptable distortion may occur in the pressure bearing mechanism.

  The present invention has been made in view of the above problems, and is a bearing mechanism employed in a small and thin motor, in which a shaft is attached to a plate using a fixing screw. It aims at preventing the performance deterioration of (especially a thrust dynamic pressure bearing mechanism).

  The invention according to claim 1 is a bearing mechanism using a fluid dynamic pressure used in an electric motor, wherein a fixed shaft integrally having a flange portion extending outward from the central axis at one end, and the central axis And a fixing screw that fixes the one end of the fixing shaft to the plate by being screwed to the one end of the fixing shaft, and a sleeve that is inserted into the fixing shaft and that has one end face facing the flange portion. A radial dynamic pressure bearing mechanism formed between the member, the fixed shaft and the inner peripheral surface of the sleeve member, and a thrust dynamic pressure formed between the one end surface of the sleeve member and the flange portion A bearing mechanism.

  A second aspect of the present invention is the bearing mechanism according to the first aspect, wherein the other end of the fixed shaft is screwed into the other end of the fixed shaft along the central axis. Another fixing screw for fixing to one plate is further provided.

  Invention of Claim 3 is a bearing mechanism of Claim 1 or 2, Comprising: The said fixed shaft has a step part which reduced the diameter in the said other end, and the said bearing mechanism is the said fixed An annular retaining member that is attached to the step portion of the shaft and faces the other end surface of the sleeve member opposite to the one end surface is further provided.

  The invention according to claim 4 is the bearing mechanism according to any one of claims 1 to 3, wherein the sleeve member is the other end face opposite to the one end face or the radial dynamic pressure bearing mechanism. By connecting the other end face side portion of the first end face with the one end face, a circulation path in which lubricating oil is continuously filled together with the gap of the radial dynamic pressure bearing mechanism and the gap of the thrust dynamic pressure bearing mechanism is provided. A communication hole to be formed is provided.

  The invention according to claim 5 is the bearing mechanism according to any one of claims 1 to 4, wherein the sleeve member projects an annular projecting portion that projects from the one end surface and covers an outer peripheral surface of the flange portion. And a tapered gap that gradually increases as the distance from the one end surface of the sleeve member increases between the flange portion and the annular projecting portion, and the lubricating oil that continues from the thrust dynamic pressure bearing mechanism in the tapered gap. Thus, a taper seal is formed.

  A sixth aspect of the present invention is the bearing mechanism according to any one of the first to fifth aspects, wherein in the radial dynamic pressure bearing mechanism, there is only one position where the dynamic pressure is maximum in the central axis direction. It is.

  A seventh aspect of the present invention is the bearing mechanism according to any one of the first to sixth aspects, wherein the dynamic pressure bearing mechanism that receives the force in the thrust direction is only the thrust dynamic pressure bearing mechanism.

  An invention according to an eighth aspect is an electric motor, wherein the bearing mechanism according to any one of the first to seventh aspects, a plate on which the one end of the fixed shaft is fixed by the fixing screw, an electric machine, And a field magnet that is attached to the sleeve member and generates a torque about a predetermined central axis between the armature and the armature.

  The invention according to claim 9 is a recording disk drive device, wherein the recording disk records information, the motor according to claim 8 that rotates the recording disk, and reading and / or information from the recording disk. A head unit that performs writing; and a head unit moving mechanism that moves the head unit relative to the recording disk and the motor.

  In the present invention, the rigidity of the fixed shaft can be improved by integrally providing the flange portion on the fixed shaft, and even if the fixed shaft is fixed to the plate with a fixing screw, the performance degradation of the thrust dynamic pressure bearing mechanism is prevented. can do.

  In the invention of claim 2, the height of the fixed shaft can be kept low to make the motor thinner, and in the invention of claim 3, the retaining member can be easily attached to the fixed shaft.

  In the invention of claim 4, bubbles are prevented from staying in the radial dynamic pressure bearing mechanism and the thrust dynamic pressure bearing mechanism, and in the invention of claim 5, the bubbles generated in the lubricating oil can be discharged.

  FIG. 1 is a diagram showing an internal configuration of a recording disk drive device 60 including an electric spindle motor 1 (hereinafter referred to as “motor 1”) according to an embodiment of the present invention. The recording disk drive device 60 is a so-called hard disk device, and rotates while holding a disk-shaped recording disk 62 for recording information, an access unit 63 for reading and / or writing information to the recording disk 62, and the recording disk 62. An electric motor 1 and a housing 61 for housing the recording disk 62, the access unit 63, and the motor 1 in the internal space 110 are provided.

  As shown in FIG. 1, the housing 61 has an opening in the upper part and an opening of the first housing member 611 having a lidless box shape to which the motor 1 and the access unit 63 are attached to the inner bottom surface, and the opening of the first housing member 611. A plate-like second housing member 612 that forms the internal space 110 by covering the plate is provided. In the recording disk drive device 60, the second housing member 612 is joined to the first housing member 611 to form the housing 61, and the internal space 110 is a clean space that is extremely free of dust and dirt.

  The recording disk 62 is placed on the upper side of the motor 1 and is fixed to the motor 1 by the clamper 621. The access unit 63 includes a head 631 close to the recording disk 62 and an arm 632 that supports the head 631 as a head unit, and reading and / or writing of information is magnetically performed by the head unit. The access unit 63 includes a head unit moving mechanism 633 that moves the head 631 relative to the recording disk 62 and the motor 1 by moving the arm 632. With these configurations, the head 631 accesses a required position of the recording disk 62 in the state of being close to the rotating recording disk 62, and reads and / or writes information.

  FIG. 2 is a longitudinal sectional view showing a configuration of the motor 1 used for rotating the recording disk 62 (see FIG. 1). In FIG. 2, although the longitudinal cross section in the surface containing the central axis J1 of the motor 1 is shown, also about the structure located in the back | inner side rather than a cut surface, the part is drawn with the broken line. As shown in FIG. 2, the motor 1 includes a stator portion 2 that is a fixed assembly and a rotor portion 3 that is a rotating assembly, and the rotor portion 3 is a bearing that uses fluid dynamic pressure by lubricating oil. Via a mechanism 10 (a fixing shaft 22, a sleeve member 31, a retaining member 23, and fixing screws 26 and 27, which will be described later, are main parts), the stator part 2 is supported rotatably around a central axis J1. The In the following description, for convenience, the rotor part 3 side is described as the upper side and the stator part 2 side is the lower side along the central axis J1, but the central axis J1 does not necessarily coincide with the direction of gravity.

  The stator part 2 includes a base plate 21a that is a base part for holding each part of the stator part 2, a fixed shaft 22 having a step part 222 having one end fixed at a predetermined mounting position of the base plate 21a and the other end having a reduced diameter. An annular retaining member 23 attached to the step 222 of the fixed shaft 22, a fixing screw 26 for fixing the fixed shaft 22 to the base plate 21a, an armature 24 attached to the base plate 21a, and an electric machine disposed above the armature 24 A thin plate-like magnetic shield plate 25 that blocks electromagnetic noise from the child 24 is provided. The base plate 21a is a part of the first housing member 611 (see FIG. 1), and the first housing member 611 is pressed by pressing a plate-like member made of aluminum, an aluminum alloy, or a magnetic or nonmagnetic iron-based metal. It is formed integrally with other parts.

  The fixed shaft 22 further includes a flange portion 221 that extends outward from the central axis J1 at one end (lower end) on the side fixed to the base plate 21a, and a screw hole 223 that penetrates along the central axis J1 is formed in the fixed shaft 22. Is formed. The fixing screw 26 is screwed to the lower end of the fixing shaft 22 along the central axis J1, and the base plate 21a is sandwiched between the head of the fixing screw 26 and the lower surface of the flange portion 221, so that the lower end of the fixing shaft 22 becomes the base plate. 21a is fixed. In addition, although the protrusion which protrudes below is provided in the lower end center of the fixed shaft 22 in order to fix to the base plate 21a, if the flange part 221 is provided substantially in the lower end of the fixed shaft 22, it is a strict meaning. It is not necessary that the lower end of the flange and the lower surface of the flange portion 221 coincide.

  On the other hand, the bearing mechanism 10 includes another fixing screw 27 that is screwed onto the upper end of the fixed shaft 22 along the central axis J1, and a portion of the second housing member 612 in the vicinity of the fixed shaft 22 (hereinafter referred to as “upper plate”). 21b ") is sandwiched between the head of the fixing screw 27 and the upper end of the fixing shaft 22, whereby the upper end of the fixing shaft 22 is fixed to the upper plate 21b. Note that the fixed shaft 22 and the retaining member 23 are made of stainless steel, free-cutting stainless steel, or the like.

  In the motor 1, the flange portion 221 is integrally provided on the fixed shaft 22 as a part of the fixed shaft 22. Thereby, compared with the case where a shaft and a flange part are formed with another member, a highly accurate squareness can be given between the upper surface of the flange part 221 and the central axis J1, and also the flange part 221 is fixed. A strong fastening strength can be obtained between the main portion of the shaft 22. Further, the bearing mechanism 10 and the motor 1 can be made thin with respect to the direction of the central axis J1. The fixed shaft 22 integrally having the flange portion 221 may be manufactured by cutting from one original member, or may be manufactured by a molding process including sintering.

  The armature 24 is attached to the base plate 21a from above by press-fitting or bonding, and includes a core 241 formed by laminating a plurality of (in this embodiment, five) core plates formed of thin silicon steel plates. The core 241 supports a plurality of teeth 243 radially arranged around the central axis J1 and the plurality of teeth 243 from the outside (that is, connects the ends of the teeth 243 far from the central axis J1). A ring-shaped core back. The thickness of each of the core plates forming the core 241 is 0.1 to 0.35 mm, and preferably 0.2 mm. In each core plate, the portions corresponding to each of the plurality of teeth 243 and the core back are integrally formed, so that the plurality of teeth 243 and the core back are magnetically connected.

  The armature 24 includes a plurality of coils 242 formed by winding a conductive wire having a diameter of 0.05 to 0.3 mm (more preferably 0.1 mm) around each of the plurality of teeth 243 of the core 241 in multiple layers. Further prepare.

  The rotor portion 3 is inserted into the fixed shaft 22 of the stator portion 2 with a slight gap and is a part of a bearing mechanism 10 that rotatably supports the rotor portion 3, and a substantially cylindrical sleeve member 31; A field magnet 32 is provided which is attached to the sleeve member 31 and arranged around the central axis J1. The sleeve member 31 is made of stainless steel, free-cutting stainless steel, aluminum, aluminum alloy, copper, phosphor bronze, or the like, and is formed in a substantially cylindrical shape centered on the central axis J1, and serves as a sleeve. One end face (hereinafter referred to as “lower end face”) 311 is opposed to the flange portion 221 of the fixed shaft 22 and the other end face (hereinafter referred to as “upper end face”) 312 serving as a sleeve. It faces the retaining member 23. The field magnet 32 generates torque (that is, rotational force) centered on the central axis J <b> 1 with the armature 24.

  FIG. 3 is a longitudinal sectional view showing the sleeve member 31, and FIG. 4 is a bottom view showing only the lower end surface 311 of the sleeve member 31. 2 and 3, the sleeve member 31 protrudes from the lower end surface 311 and covers the outer peripheral surface of the flange portion 221 of the fixed shaft 22. The sleeve member 31 protrudes from the upper end surface 312 and protrudes from the upper end surface 312. As shown in FIGS. 3 and 4, the second annular protrusion 314 that covers the outer peripheral surface, and two communication holes 318 that communicate the lower end surface 311 and the upper end surface 312 are provided.

  As shown in FIG. 3, the sleeve member 31 further includes a disk portion 315 to which a field magnet 32 (see FIG. 2) is attached, forming a so-called hub. When the members constituting the bearing mechanism 10 are extremely small, if the sleeve and the hub are formed as separate members, the sleeve inner peripheral surface may be distorted when the sleeve is press-fitted into the hub. By forming each of the sleeve and the hub as an integral member, the number of parts can be reduced and the coaxiality between the sleeve and the hub can be improved. Thus, the structure of the motor 1 is particularly suitable for downsizing.

  Next, the bearing mechanism 10 using the fluid dynamic pressure that supports the rotor portion 3 of the motor 1 to be rotatable with respect to the stator portion 2 will be described. FIG. A is a longitudinal sectional view showing a part of the motor 1 (the right half in FIG. 2) in an enlarged manner. In addition, FIG. In A, parallel oblique lines indicating a cross section of the sleeve member 31 are omitted, and two herringbone grooves 316 and 317 described later formed in the sleeve member 31 are indicated by a symbol of a chevron pattern on the sleeve member 31 side. (The same applies to FIGS. 8 and 9).

  FIG. As shown in A, in the motor 1, between the outer peripheral surface of the fixed shaft 22 and the inner peripheral surface of the sleeve member 31, between the lower end surface 311 of the sleeve member 31 and the flange portion 221 of the fixed shaft 22, and the sleeve A minute gap is provided between the upper end surface 312 of the member 31 and the retaining member 23. Hereinafter, these gaps are referred to as “side gap 41”, “lower gap 42”, and “upper gap 43”, respectively.

  The outer peripheral surface of the flange portion 221 is an inclined surface whose outer diameter gradually decreases toward the lower side, and gradually increases as the distance from the lower end surface 311 of the sleeve member 31 increases between the flange portion 221 and the first annular projecting portion 313. An expanding first taper gap 44 is formed. On the other hand, the outer peripheral surface of the retaining member 23 is an inclined surface whose outer diameter gradually decreases toward the upper side, and is separated from the upper end surface 312 of the sleeve member 31 between the retaining member 23 and the second annular projecting portion 314. A second taper gap 45 that gradually increases is formed.

  In the motor 1, the communication hole 318 and the plurality of gaps (hereinafter referred to as “filling gaps”) are continuously filled with lubricating oil, which is a working fluid, to form a so-called full-fill bearing mechanism. The taper seal is formed between the first taper gap 44 and the second taper gap 45, and the interface of the lubricating oil continuing from the lower gap 42 (thrust dynamic pressure bearing mechanism 420) and the upper gap 43 becomes meniscus due to capillary action and surface tension. Thus, the first taper gap 44 and the second taper gap 45 serve as an oil buffer to prevent the lubricant from flowing out. In the motor 1, since the oil buffer has a visible structure, the lubricating oil can be easily injected and inspected.

  On the inner circumferential surface of the sleeve member 31, pressure (indicated by an arrow 52) generated at a portion on the upper end surface 312 side during rotation of the rotor portion 3 (pressure 51) generated at a portion on the lower end surface 311 side. And a dynamic pressure groove for generating a higher dynamic pressure in the lubricating oil, and a radial dynamic pressure bearing mechanism 410 is formed in the side gap 41. Further, on the lower end surface 311 of the sleeve member 31, pressure (indicated by an arrow 54) generated at the site on the first annular projecting portion 313 side when the rotor unit 3 rotates is generated at the site on the fixed shaft 22 side. Is provided with a dynamic pressure groove for generating a dynamic pressure higher than the pressure (indicated by an arrow 53) in the lubricating oil, and a thrust dynamic pressure bearing mechanism 420 including the dynamic pressure groove is formed in the lower gap. . The width of the gap of the radial dynamic pressure bearing mechanism 410 (namely, the width of the side gap 41), the width of the gap of the thrust dynamic pressure bearing mechanism 420 (namely, the width of the lower gap 42), the thrust dynamic pressure of the sleeve member 31. Of the width of the upper gap 43 on the side opposite to the bearing mechanism 420, the radial dynamic pressure bearing mechanism 410 has the smallest gap width and the upper gap 43 has the largest width. Specifically, the gap width of the radial dynamic pressure bearing mechanism 410 is 2 to 4 μm, the gap width of the thrust dynamic pressure bearing mechanism 420 is 5 to 8 μm, and the width of the upper gap 43 is 20 to 32 μm. The

  In the motor 1, in order to reduce the thickness, the radial dynamic pressure bearing mechanism 410 has only one position where the dynamic pressure is maximized in the direction of the central axis J <b> 1.

  In the motor 1, FIG. 3 and FIG. As shown in A, the dynamic pressure groove of the radial dynamic pressure bearing mechanism 410 provided on the inner peripheral surface of the sleeve member 31 is a herringbone groove 316 formed in a V shape that opens in the rotation direction of the sleeve member 31. And the herringbone groove 316 has a shape in which the part above the bent part 3161 is longer than the part below the bent part 3161 so that the rotor part 3 is slightly below the center of the side gap 41 when the rotor part 3 rotates. Thus, the lubricating oil is pushed downward in the central axis J1 direction (that is, in the direction of the arrow 52) as much as the pressure generated in the lubricating oil becomes maximum and is biased. 4 and 5. As shown in A, the dynamic pressure groove of the thrust dynamic pressure bearing mechanism 420 is a herringbone groove 317 formed in a V shape that opens toward the rotation direction 71 of the sleeve member 31 (that is, the rotation direction of the rotor portion 3). Since the herringbone groove 317 is formed in a deviated shape in which the portion outside the bent portion 3171 is longer than the inside portion, the rotor portion 3 is slightly inside from the approximate center of the lower gap 42 when rotating. The lubricating oil is pushed inward in the radial direction (that is, in the direction of the arrow 54) by the amount that the pressure generated in the lubricating oil becomes maximum and is biased.

  These dynamic pressure bearing mechanisms can suppress the occurrence of local negative pressure of the lubricating oil in the region on the fixed shaft 22 side of the thrust dynamic pressure bearing mechanism 420 when the rotor portion 3 is rotated by the bearing mechanism. It is possible to prevent the generation of bubbles due to the bubbles, and further to prevent abnormal vibration and image sticking due to the bubbles.

  As described above, in the motor 1, the filling gap formed between the fixed shaft 22, the retaining member 23 and the sleeve member 31 (that is, the side gap 41, the lower gap 42, the upper gap 43, the first taper gap 44, and the first taper gap 44). 2 taper gap 45) and the two communicating holes 318 formed in the sleeve member 31 are continuously filled with lubricating oil, and the rotor portion 3 utilizes fluid dynamic pressure due to the lubricating oil when the rotor portion 3 rotates. Is supported. Then, the recording disk 62 (see FIG. 1) attached to the rotor unit 3 rotates as the rotor unit 3 rotates with respect to the stator unit 2 about the central axis J1.

  In the bearing mechanism 10, in order to reduce the thickness of the motor 1, only the thrust dynamic pressure bearing mechanism 420 in the lower gap 42 is the dynamic pressure bearing mechanism that receives the thrust force. Therefore, the base plate 21 a and the field magnet 32 are used. The sleeve member 31 is urged toward the flange portion 221 in a non-contact manner by a magnetic action generated between the sleeve portion 31 and the flange portion 221. That is, the field magnet 32 and the base plate 21 a also serve as a biasing mechanism that biases the sleeve member 31. Thereby, when the rotor part 3 rotates, the rotor part 3 is stably supported in the thrust direction in cooperation with the levitation force and the magnetic action of the thrust dynamic pressure bearing mechanism 420. When the base plate 21a is formed of a non-magnetic material, the magnetic material is disposed at a position facing the field magnet 32 of the base plate 21a. As another example of the urging mechanism, the magnetic center in the direction of the central axis J1 of the armature 24 (see FIG. 2) is shifted magnetically to the base plate 21a side from the magnetic center of the field magnet 32. It may be one that generates an action.

  FIG. B is shown in FIG. A region C1 on the outer peripheral side of the upper gap 43 shown in A and region C2 on the inner peripheral side of the upper gap 43 relative to the region C6 on the outer peripheral side of the lower gap 42, a region C3 facing the bent portion 3161 of the side gap 41, and the lower gap 42 is a diagram showing the relative level of pressure generated in the lubricating oil in each region of a region C4 on the inner peripheral side of 42 and a region C5 facing the bent portion 3171 of the lower gap 42. FIG. In the motor 1, FIG. A and FIG. As shown in B, the pressure generated in the lubricating oil in the region C3 is higher than the pressure in the region C5, and the lubricating oil pushed downward in the central axis J1 direction (that is, in the direction of the arrow 52) in the side gap 41 is The lower gap 42, the communication hole 318, and the upper gap 43 are returned to the side gap 41 to form a lubricating oil circulation path indicated by an arrow 55. In other words, the communication hole 318 that guides the lubricating oil from the outer peripheral side of the flange portion 221 to the outer peripheral side of the retaining member 23, together with the clearance of the radial dynamic pressure bearing mechanism 410, the clearance of the thrust dynamic pressure bearing mechanism 420, and the upper clearance 43. A circulation path 55 that is continuously filled with lubricating oil is formed. As a result, the pressure difference of the lubricating oil at both end faces of the sleeve member 31 is suppressed, and even if bubbles are generated in the lubricating oil, the radial dynamic pressure bearing mechanism 410 and the thrust dynamic pressure bearing mechanism 420 It is possible to prevent the bubbles from staying in the bearing mechanism and to discharge the generated bubbles to the outside of the bearing mechanism through the taper seals of the first taper gap 44 and the second taper gap 45.

  FIG. 6 is a bottom view showing the retaining member 23. As shown in FIG. 6, the retaining member 23 includes four agitation grooves 231 that agitate the lubricating oil on a surface facing the upper end surface 312 of the sleeve member 31 (that is, the lower surface of the retaining member 23). The stirring groove 231 is a spiral groove that faces the outer side in the radial direction and goes in a direction opposite to the rotation direction 71 of the sleeve member 31. As a result, the lubricating oil is pushed inward in the radial direction of the upper gap 43 (see FIG. 5A) by the pressure generated by the stirring groove 231 when the rotor portion 3 rotates, and in the region of the upper gap 43 on the fixed shaft 22 side. Generation of negative pressure can be prevented.

  FIG. 7 is an enlarged longitudinal sectional view showing the upper gap 43. On the upper end surface 312 of the sleeve member 31, as shown in FIG. 7, a tapered portion 3121 is formed in which the gap (that is, the upper gap 43) with the retaining member 23 gradually increases toward the outside in the radial direction. By lowering the pressure outside the radially inner side of the upper gap 43, the bubbles existing in the upper gap 43 or the bubbles moving to the upper opening of the communication hole 318 are passed through the taper seal in the second taper gap 45. It becomes easy to be discharged outside the bearing. Further, the sleeve member 31 includes a protruding portion 3122 that protrudes toward the retaining member 23 with respect to the tapered portion 3121 around the fixed shaft 22 on the upper end surface 312. Even if the sleeve member 31 is lifted upward, the protruding portion 3122 is a part that abuts against the retaining member 23 and prevents the sleeve member 31 from moving, and the dimension between the lower end surface 311 and the protruding portion 3122 is highly accurate. Is done. Thereby, the attachment position of the central axis J1 direction of the sleeve member 31 can be determined with high accuracy.

  Although the motor 1 has been described above, in the bearing mechanism 10 of the motor 1, since the flange portion 221 is integrally provided on the fixed shaft 22, the shaft and the flange portion are formed as separate members as described above. Compared to the case, the squareness with high accuracy can be given between the upper surface of the flange portion 221 and the central axis J1, and the connection strength of the flange portion 221 on the fixed shaft 22 is extremely high.

  Here, in the bearing mechanism 10, the lower end portion of the fixed shaft 22 is fixed to the base plate 21 a by the fixing screw 26, and a large internal stress is generated at the lower end portion of the fixed shaft 22 by fixing the fixed shaft 22. When the shaft and the flange portion are separate members, the distortion of the shaft appears as it is as the inclination of the thrust dynamic pressure surface of the flange portion, but in the bearing mechanism 10, a part of the fixed shaft 22 in which the flange portion 221 is formed as one member. Therefore, the rigidity of the lower end portion of the fixed shaft 22 is high, and distortion due to the screwing of the fixing screw 26 can be suppressed to a low level. As a result, the performance degradation of the thrust dynamic pressure bearing mechanism 420 can be prevented.

  In particular, in the thin motor 1 in which the dynamic pressure is only one position in the radial dynamic pressure bearing mechanism 410 with respect to the central axis J1 direction, the fixing screw 26 is screwed to the position of the flange portion 221. Forming the portion 221 as a part of the fixed shaft 22 is particularly suitable for such a thinned motor. In addition, the fixed shaft 22 with the integral flange portion 221 is preferably used for an outer peripheral surface having a diameter of 2.7 mm or less that constitutes a part of the radial dynamic pressure bearing mechanism 410. More preferably, it is used for a thickness of 5 mm or less. As a result, the rigidity of the small-diameter fixed shaft 22 is increased, and an unacceptable deformation on the outer peripheral surface due to tightening of the fixing screw 26 is prevented.

  In the bearing mechanism 10, the fixed shaft 22 is fixed to the upper plate 21b by the upper fixing screw 27. However, the thrust gap is not formed in the upper gap 43, and the upper gap is somewhat large. Even if the shaft 22 and the retaining member 23 are separate members, the performance of the bearing mechanism 10 does not deteriorate due to the fastening of the upper fixing screw 27.

  In addition, since the upper end of the fixed shaft 22 is fixed to the upper plate 21b by the fixing screw 27, the upper and lower ends of the fixed shaft 22 can be easily attached to the plate despite the small size, and the fixed shaft 22 Therefore, the motor 1 can be made thin.

  Further, in the motor 1, the stepped portion 222 is formed on the fixed shaft 22, and the positioning of the retaining member 23 is completed simply by abutting against the stepped portion 222. Therefore, the retaining member 23 can be easily attached to the fixed shaft 22. Furthermore, the bearing mechanism 10 can be easily assembled by simply inserting the sleeve member 31 and the retaining member 23 in this order from above the fixed shaft 22.

  In addition, since an annular taper seal is provided on the outer circumference of the thrust dynamic pressure bearing mechanism 420 (lower gap 42) and the outer circumference of the upper gap 43, in other words, on both end surfaces of the sleeve member 31, the center of the bearing mechanism 10 is provided. The height in the direction of the axis J1 can be kept low. In the motor 1 having such a structure, each of the fixed shaft 22, the retaining member 23, and the sleeve member 31 is formed as one member, that is, mainly one type of material (for example, an alloy, ceramics, or resin). The main part of the bearing mechanism 10 can be constituted by three members (and fixing screws 26 and 27), and the number of parts can be reduced. It can be reduced to facilitate assembly.

  Further, in the motor 1, since the thrust dynamic pressure bearing mechanism 420 is not formed in the upper gap 43, it is not necessary to strictly control the accuracy of the upper gap 43. Therefore, the bearing having the annular taper seals on both end faces of the sleeve member 31. The mechanism (especially the sleeve member 31) can be easily manufactured, and the defect rate at the time of manufacturing the motor 1 can be reduced. Furthermore, since the gap dimension is formed large in a wide range of the upper gap 43, energy loss in the bearing mechanism 10 due to an increase in pressure generated in the lubricating oil can be suppressed, and an increase in power consumption can be suppressed.

  In particular, the bearing mechanism 10 and the motor 1 can be easily manufactured even with a small and thin motor.

  FIG. 8 is a longitudinal sectional view showing a motor 1a according to another example. The motor 1a is shown in FIG. 5 except that the shape of the sleeve member 31 and the retaining member 23 is different from that of the motor 1 shown in FIG. The motor 1 has the same structure as that of the motor A, and the same components are denoted by the same reference numerals.

  In the motor 1 a, like the motor 1, a herringbone groove 316, which is a radial dynamic pressure groove, is formed on the inner peripheral surface of the sleeve member 31, and the outer peripheral surface of the fixed shaft 22 and the inner peripheral surface of the sleeve member 31 are formed. A radial dynamic pressure bearing mechanism 410 is formed in the side gap 41 therebetween. Further, a herringbone groove 317 that is a thrust dynamic pressure groove is formed in the lower end surface 311 of the sleeve member 31, and a thrust dynamic pressure bearing mechanism 420 is formed in the lower gap 42 between the lower end surface 311 and the flange portion 221. Is done.

  The communication hole 318 formed in the sleeve member 31 is not the upper end surface 312 opposite to the lower end surface 311, but the portion on the upper end surface 312 side (ie, the upper portion) of the radial dynamic pressure bearing mechanism 410, Inclined so as to communicate with the end surface 311. The communication hole 318 and the side gap 41 and the lower gap 42 form a circulation path that is continuously filled with lubricating oil. The dynamic pressure generated in the radial dynamic pressure bearing mechanism 410 and the thrust dynamic pressure bearing mechanism 420 is shown in FIG. In the motor 1a, the lubricating oil returns from the lower gap 42 to the lower gap 42 through the communication hole 318 and the side gap 41 in this order. Circulate. In other words, FIG. In the motor 1 shown in A, the upper gap 43 is a part of the lubricating oil circulation path, but the motor 1a in FIG. 8 has a structure in which the upper gap 43 is omitted from the circulation path.

  Also in the motor 1a, since the flange portion 221 is integrally provided on the fixed shaft 22, the rigidity of the lower end portion of the fixed shaft 22 is high, and distortion caused by the screwing of the fixing screw 26 is suppressed to a small level. Performance degradation can be prevented.

  In the motor 1a, the gap of the radial dynamic pressure bearing mechanism 410 out of the width of the radial dynamic pressure bearing mechanism 410, the width of the thrust dynamic pressure bearing mechanism 420, and the width (that is, the diameter) of the communication hole 318 is determined. The width is the narrowest, and the width of the communication hole 318 is the widest (the same applies to FIG. In order to realize a thin motor, the radial dynamic pressure bearing mechanism 410 has only one position where the dynamic pressure becomes maximum.

  Further, the shape of the communication hole 318 of the motor 1a is not limited to an inclined one, and as shown in FIG. 9, the hole extending horizontally from the upper portion of the radial dynamic pressure bearing mechanism 410 and the vertical direction from the thrust dynamic pressure bearing mechanism 420 are extended. What connected the hole may be used.

  As mentioned above, although embodiment of this invention has been described, this invention is not limited to the said embodiment, A various change is possible.

  For example, in the motors 1 and 1a, the dynamic pressure groove of the radial dynamic pressure bearing mechanism 410 provided on the inner peripheral surface of the sleeve member 31 has a shape in which the position of the bent portion of the herringbone groove is biased. Increase the number of grooves where high dynamic pressure is required without biasing the position, widen the groove width, or deepen the groove to reduce the dynamic pressure on both sides of the bent part (or position that can be regarded as a bent part). The strength may be different. Thereby, the same effect as the sleeve member 31 can be produced.

  Similarly, with respect to the dynamic pressure grooves of the thrust dynamic pressure bearing mechanism 420, the strength of the dynamic pressure on both sides of the bent portion (or the position that can be regarded as the bent portion) is changed by changing the number of grooves, the groove width, or the groove depth. May be different. In the case of the thrust dynamic pressure bearing mechanism 420, even if the outer and inner grooves of the herringbone groove are the same length, the flow of lubricating oil is faster on the outer side, so the generated pressure is higher on the outer side than on the inner side. And the generation of negative pressure on the inner peripheral side of the thrust dynamic pressure bearing mechanism 420 can be suppressed. Further, the dynamic pressure grooves of the radial dynamic pressure bearing mechanism 410 and the thrust dynamic pressure bearing mechanism 420 are not limited to herringbone grooves. For example, by providing double spiral dynamic pressure grooves of different directions, A dynamic pressure groove equivalent to the herringbone groove may be provided.

  Furthermore, in the motor 1, the number of the agitation grooves 231 provided on the lower surface of the retaining member 23 is four. However, the number is not limited thereto, and may be one or two or more.

  The recording disk drive device 60 having the motor according to the above embodiment is not limited to a hard disk device, and may be a disk drive device such as a removable disk device.

It is a figure which shows the internal structure of a recording disk drive device. It is a longitudinal cross-sectional view which shows the structure of a motor. It is a longitudinal cross-sectional view which shows a sleeve member. It is a bottom view which shows the lower end surface of a sleeve member. It is a longitudinal cross-sectional view which expands and shows a part of motor. It is a figure which shows the relative level of the pressure which arises in lubricating oil. It is a bottom view which shows a retaining member. It is a longitudinal cross-sectional view which expands and shows an upper gap | interval. It is a longitudinal cross-sectional view of another motor. It is a longitudinal cross-sectional view of another motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1a Motor 10 Bearing mechanism 21a Base plate 21b Upper plate 22 Fixed shaft 23 Stopping member 24 Armature 26, 27 Fixing screw 31 Sleeve member 32 Field magnet 44 First taper gap 60 Recording disk drive device 62 Recording disk 221 Flange 222 Step portion 311 Lower end surface 312 Upper end surface 313 First annular projecting portion 318 Communication hole 410 Radial dynamic pressure bearing mechanism 420 Thrust dynamic pressure bearing mechanism 631 Head 632 Arm 633 Head portion moving mechanism J1 Central axis

Claims (9)

A bearing mechanism using fluid dynamic pressure used in an electric motor,
A fixed shaft integrally having a flange portion extending outward from the central axis at one end;
A fixing screw for fixing the one end of the fixed shaft to the plate by being screwed to the one end of the fixed shaft along the central axis;
A sleeve member inserted into the fixed shaft and having one end surface facing the flange portion;
A radial dynamic pressure bearing mechanism formed between the fixed shaft and the inner peripheral surface of the sleeve member;
A thrust dynamic pressure bearing mechanism formed between the one end surface of the sleeve member and the flange portion;
A bearing mechanism comprising: The bearing mechanism according to claim 1,
A bearing mechanism further comprising another fixing screw for fixing the other end of the fixed shaft to another plate by being screwed to the other end of the fixed shaft along the central axis. . The bearing mechanism according to claim 1 or 2,
The fixed shaft has a stepped portion with a reduced diameter at the other end;
The bearing mechanism further includes an annular retaining member attached to the step portion of the fixed shaft and facing the other end surface opposite to the one end surface of the sleeve member. The bearing mechanism according to any one of claims 1 to 3,
The sleeve member communicates the one end surface with the other end surface opposite to the one end surface or the other end surface side portion of the radial dynamic pressure bearing mechanism, thereby the radial dynamic pressure bearing. A bearing mechanism comprising a communication hole that forms a circulation path that is continuously filled with lubricating oil together with a clearance of the mechanism and a clearance of the thrust hydrodynamic bearing mechanism. The bearing mechanism according to any one of claims 1 to 4,
The sleeve member further includes an annular projecting portion that projects from the one end surface and covers an outer peripheral surface of the flange portion,
A taper gap is formed between the flange portion and the annular projecting portion so as to gradually increase as the distance from the one end surface of the sleeve member increases, and a taper seal is formed in the taper gap by lubricating oil continuous from the thrust dynamic pressure bearing mechanism. A bearing mechanism characterized in that is formed. A bearing mechanism according to any one of claims 1 to 5,
In the radial dynamic pressure bearing mechanism, there is only one position where the dynamic pressure is maximized in the central axis direction. The bearing mechanism according to any one of claims 1 to 6,
A bearing mechanism characterized in that a dynamic pressure bearing mechanism receiving a force in a thrust direction is only the thrust dynamic pressure bearing mechanism. An electric motor,
A bearing mechanism according to any one of claims 1 to 7,
A plate on which the one end of the fixed shaft is fixed by the fixing screw;
Armature,
A field magnet that is attached to the sleeve member and generates a torque centered on a predetermined central axis with the armature;
A motor comprising: A recording disk drive device comprising:
A recording disk for recording information;
The motor according to claim 8, wherein the motor rotates the recording disk.
A head unit for reading and / or writing information on the recording disk;
A head part moving mechanism for moving the head part relative to the recording disk and the motor;
A recording disk drive device comprising:

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