JP4435848B1 - Shaft fixed type fluid dynamic pressure bearing device, spindle motor and recording disk device having the same - Google Patents

Abstract

Provided are a fluid dynamic pressure bearing device that adjusts oil pressure inside a bearing and has excellent reliability, a spindle motor equipped with the fluid dynamic pressure bearing device, and a recording disk device.
The upper and lower thrust bearings are constituted by dynamic pressure generating grooves provided on the thrust plate (upper) and the thrust plate (lower) facing the upper and lower surfaces of the rotating sleeve, and the inner peripheral surface of the rotating sleeve A radial bearing is formed by a dynamic pressure generating groove provided on the outer peripheral surface of the shaft. The vertical thrust bearing gap and radial bearing gap are connected and filled with oil, and the vertical thrust dynamic pressure groove is spiral, Acts to push oil into the bearing, and on the radially outer side facing the sleeve of the upper and lower thrust plates, there is a stepped portion made of a cut surface having a gap larger than the thrust gap, and this stepped portion and the sleeve The oil reservoir created on the surface is connected by a reflux hole provided between the outer periphery of the sleeve and the inner periphery of the hub. Shaft fixing type fluid dynamic pressure bearing device is characterized in that to balance the difference.
[Selection] Figure 1

Description

  The present invention relates to a highly reliable shaft-fixed fluid dynamic pressure bearing device capable of effectively adjusting the pressure of lubricating oil inside a bearing, and a spindle motor and a recording disk device including the same.

  Conventionally, as a spindle motor bearing for rotationally driving a recording medium such as a magnetic disk, an optical disk, or a magneto-optical disk, an oil or the like is provided between the shaft and the sleeve in order to support the shaft and the sleeve so as to be relatively rotatable. Various hydrodynamic bearing devices that use lubricating oil and utilize oil pressure have been proposed (see, for example, Patent Documents 1 and 2).

  This type of known example relates to a so-called shaft rotation type fluid dynamic pressure bearing device (in the industry terminology, referred to as a single bag structure bearing device).

  On the other hand, the present inventors have conducted original research and development on a shaft-fixed fluid dynamic bearing device. That is, a sleeve having a through hole at its center is rotatably inserted into a shaft that is a fixed shaft, and a minute radial gap is formed between the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve. A dynamic bearing groove is formed on at least one of the peripheral surfaces to form a radial bearing portion, and a flange-like thrust plate (lower) larger than the shaft outer diameter is fixed to the lower end portion of the shaft. The bottom surface of the sleeve and the bottom surface of the sleeve are opposed to each other via a small thrust gap (bottom), and a dynamic pressure generating groove is formed on at least one of the top surface of the thrust plate (bottom) and the bottom surface of the sleeve, and the thrust bearing ( (Lower).

  A flange-shaped thrust plate (upper) larger than the outer diameter of the shaft is fixed to the upper end of the shaft. The lower surface of the thrust plate (upper) and the upper surface of the sleeve are opposed to each other via a minute thrust gap (upper). , A dynamic pressure generating groove is formed in at least one of the lower surface of the thrust plate (upper) and the upper surface of the sleeve to form a thrust bearing (upper), and there is a step on the radially outer side of the thrust plate (lower), An oil sump (lower) is formed between the lower surface of the sleeve.

  Furthermore, there is a step on the radially outer side of the thrust plate (upper), and an oil reservoir (upper) is formed between the upper surface of the sleeve.

  In addition, the sleeve has an outer periphery that is fitted and fixed to a first inner peripheral surface of a hub that rotates by mounting a recording medium, and the outer peripheral surface of the thrust plate (upper) that is the fixed side and the rotating side. There is a gap between the second inner peripheral surfaces of a certain hub, and a capillary seal portion (upper) [opening portion (upper)] is formed. There is a gap between the outer peripheral surface of the thrust plate (lower) on the fixed side and the inner peripheral surface under the spacer attached to the lower side of the first inner peripheral surface of the hub on the rotating side, and the capillary seal portion ( Bottom) [Opening (bottom)].

  The thrust gap (lower), radial gap, and thrust gap (upper) are connected and filled with a lubricating fluid such as oil. The fixed thrust plate (upper and lower) has a fixed shaft structure, and the end of the series of minute gaps has a fixed shaft structure (both ends open) in contact with the atmosphere at the upper and lower capillary seals.

JP 2008-185179 A JP 2003-314536 A

  However, several problems have been found in the fluid dynamic pressure bearing having the shaft fixed (both ends opening) structure developed by the present inventors.

  That is, when the sleeve starts to rotate, oil is drawn toward the center of the herringbone groove of each radial bearing portion and the upper and lower thrust bearing portions by pumping by the dynamic pressure generating groove, but the bearing is caused by the unbalance of the dynamic pressure generating groove. A pressure difference occurs in the oil in the gap, and the oil filled in the bearing flows from a higher pressure to a lower pressure. For example, a herringbone dynamic pressure groove of a radial bearing cannot realistically be made to have the same length (width) of grooves facing in opposite directions. The same applies to the thrust bearing.

  Another example of the pressure difference inside the bearing is that if the cylindrical (radial) gap formed by the sleeve shaft hole and the shaft inserted into the sleeve is not uniform, for example, the sleeve shaft hole is If the sleeve is slightly tapered, when the sleeve starts to rotate, the pressure on the side with the smaller gap becomes higher than the side with the larger gap, and pressure is applied to the oil filled between the sleeve shaft hole and the shaft outer diameter. Make a difference.

  In this way, when a pressure difference is generated in the oil filled in a series of connected gaps, the oil tries to cancel the pressure difference, so that the flow generally flows from the high pressure side to the low pressure side. In the fluid dynamic pressure bearing having a shaft fixed (opening at both ends) structure, oil is extruded into one opening, and air enters the bearing from the other opening. The intruded air becomes bubbles in the bearing, and the bubbles expand due to a temperature rise, a low pressure environment, etc., and the oil is pushed out of the bearing to form a so-called non-full-fill structure, causing problems in durability and reliability of the spindle motor.

  Furthermore, when the sleeve starts to rotate, oil is drawn toward the center of the herringbone groove of each radial bearing portion and the upper and lower thrust bearing portions by pumping by the dynamic pressure generating groove, and the fluid dynamic pressure at the center of the herringbone groove However, at both ends of the herringbone groove, the oil pressure decreases and negative pressure is generated. The gas (air) dissolved in the oil by the negative pressure becomes bubbles in the bearing. Even when subjected to severe vibration or impact, the oil in the bearing is exposed to a rapid pressure drop, and bubbles are generated in the oil. Even if the generated bubbles are very small, they are increased by repeated severe vibrations and shocks. The bubbles expand due to temperature rise, low pressure environment, etc., and the oil is pushed out of the bearing. Problems arise in the durability and reliability of the motor.

  The present invention has been made paying attention to the above points, and the bearing function of oil as lubricating oil interposed between a shaft fixed shaft and a rotating sleeve can be applied to fluctuations in pressure, vibration and impact. It is an object of the present invention to provide a novel shaft-fixed fluid dynamic pressure bearing device, a spindle motor equipped with this device, and a recording disk device which can always perform a lubricating function stably.

  The present invention can solve the above problems by providing the following configuration.

(1) A sleeve having a through hole at the center is inserted into a shaft serving as a fixed shaft so as to be relatively rotatable, and a small radial bearing gap is formed between the shaft outer peripheral surface and the sleeve inner peripheral surface, A dynamic pressure generating groove is formed on at least one of the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve to form a radial bearing portion,
A flange-like thrust plate (lower) larger than the outer diameter of the shaft is fixed to the lower end portion of the shaft, and the upper surface of the thrust plate (lower) and the lower surface of the sleeve are interposed through a minute thrust bearing gap (lower). A thrust bearing (lower) is formed by forming a dynamic pressure generating groove on at least one of the upper surface of the thrust plate (lower) and the lower surface of the sleeve,
A flange-like thrust plate (upper) larger than the outer diameter of the shaft is fixed to the upper end portion of the shaft, and the lower surface of the thrust plate (upper) and the upper surface of the sleeve are interposed through a minute thrust bearing gap (upper). And a dynamic pressure generating groove is formed on at least one of the lower surface of the thrust plate (upper) and the upper surface of the sleeve to constitute a thrust bearing (upper),
There is a step on the radially outer side of the thrust plate (lower), and an oil sump (lower) communicating with the step is formed between the lower surface of the sleeve,
There is a step on the radially outer side of the thrust plate (upper), and an oil sump (upper) communicating with the step is formed between the upper surface of the sleeve,
In the sleeve, the outer periphery of the sleeve is fitted and fixed to the first inner peripheral surface of a hub that rotates with a recording medium mounted thereon,
There is a gap between the outer peripheral surface of the thrust plate (upper) on the fixed side and the second inner peripheral surface of the hub on the rotating side, forming a capillary seal (upper), and the fixed side There is a gap between the outer peripheral surface of the thrust plate (lower) and the inner peripheral surface under the spacer attached to the lower side of the first inner peripheral surface of the hub on the rotating side. )
Near the outer periphery of the sleeve, a linear notch or small hole is provided along the axial direction, and a reflux hole is formed between a part of the first inner peripheral surface of the hub,
The opening (upper) of the reflux hole is connected to the oil reservoir (upper), and the other opening (lower) is connected to the oil reservoir (lower).
The thrust gap (lower), the radial gap, and the thrust gap (upper) are connected and filled with oil without interruption, and have a full-fill structure.
The oil reservoir (upper) (lower) is connected to the reflux hole and the thrust gap (upper) (lower) and is filled with oil. When the sleeve rotates, the oil flows through the reflux hole. A fixed shaft type fluid dynamic bearing device characterized by flowing.

(2) In the fixed shaft type fluid dynamic bearing device according to (1),
The dynamic pressure generating groove of the thrust bearing (upper) and the dynamic pressure generating groove of the thrust bearing (lower) should have a spiral shape that acts in the direction of pushing oil into the bearing, and the pressure inside the bearing becomes atmospheric pressure or higher. Thus, the shaft-fixed fluid dynamic bearing device is provided with a function of preventing air from entering and discharging bubbles generated inside the bearing.

(3) In the fixed shaft type fluid dynamic bearing device according to (1),
The opening (upper) (lower) of the reflux hole is provided between the second inner peripheral surface of the hub and the inner peripheral surface under the spacer to the step of the thrust plate (upper) (lower). A shaft-fixed type fluid dynamic pressure bearing device.

  (4) A spindle motor comprising the shaft-fixed fluid dynamic bearing device according to any one of (1) to (3).

  (5) A recording disk device comprising the spindle motor according to (4).

  According to the present invention, even if a pressure difference occurs in the oil filled in the bearing by the rotation of the sleeve around the shaft, the opening end portion (outer periphery of the thrust plate) of the upper and lower thrust gaps is connected by the reflux hole. The oil flows through the reflux hole, the pressure is balanced, the oil is not pushed out from the capillary seal part (opening part), and the air enters from one capillary seal part (opening part). Nor.

  Furthermore, according to the present invention, a shaft, a sleeve, a radial bearing portion, a thrust bearing portion, a thrust plate (up and down), an oil reservoir, an upper and lower seal portion (upper and lower openings), a lubricating fluid, It has a reflux hole and always forms a stable oil closed circuit. The shaft is inserted into the shaft hole of the sleeve so as to be relatively rotatable, and a flange-like thrust plate (upper and lower) larger than the outer diameter of the shaft is fixed to both end surfaces of the shaft. The lubricating fluid is filled in a radial bearing gap formed between the sleeve and the shaft and a thrust bearing gap formed between the sleeve surface (upper and lower) and the thrust (upper and lower) surface. A radial dynamic pressure generating groove is formed on at least one of the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft, and the thrust dynamic pressure generating groove is formed on at least one of the upper and lower surfaces of the sleeve and the thrust (upper and lower) surface. Therefore, the lubricating performance of oil can be remarkably improved.

  In addition, according to the present invention, the dynamic pressure generating grooves of the thrust bearing (upper) and the thrust bearing (lower) are formed in a spiral shape so that the pressure in the bearing is greater than atmospheric pressure by acting in the direction of pushing oil into the bearing. Thus, air can be prevented from entering, and bubbles generated in the bearing can be effectively discharged.

Sectional drawing of the spindle motor containing the fluid dynamic pressure bearing apparatus which concerns on one Embodiment of this invention 1 is an enlarged view of the hydrodynamic bearing device included in FIG. 2 is a cross-sectional view of the half of FIG. 2 (filled with lubricating fluid) FIG. 2 is a half sectional view (a state where the lubricating fluid is filled (a) and a state where there is no lubricating fluid (b)). FIG. 2 is a cross-sectional view showing the positional relationship between a bearing portion, a bearing gap, a thrust surface, and a sleeve surface that cannot be fully explained in FIG. FIG. 2 is a perspective view showing a three-dimensional shape of a sleeve included in FIG. 1, in which a reflux hole is shown when (a) is a D-cut surface, and (b) is a hole. Sectional explanatory drawing which shows the structure of each internal peripheral surface of the hub contained in FIG. (A) is a cross-sectional plan view showing the opening of the reflux groove, (b) is an AOB line cross-sectional explanatory view of (a) (A) and (b) are two explanatory views about the pressure at the opening end of the thrust outer periphery. (A1) and (a2) are plan views of patterns formed in a spiral shape in which thrust dynamic pressure grooves according to the present invention are provided in different directions, and (b1) and (b2) are thrust dynamic pressures for comparison with the present invention. The top view of the pattern formed in the shape of the herringbone which provided the groove | channel in the different direction is shown, and each arrow mark shows the rotation direction of the sleeve arrange | positioned facing each other. (A) (b) is a development view of radial dynamic pressure groove (groove length imbalance), side pattern diagram Explanatory drawing which expands | deploys typically and shows the pressure vector of a bearing at the time of providing the upper and lower spiral thrust dynamic pressure grooves and the two-stage herringbone radial dynamic pressure grooves according to the present invention. Explanatory drawing schematically showing the pressure vector of a bearing in the case of having upper and lower herringbone thrust dynamic pressure grooves and two-stage herringbone radial dynamic pressure grooves for comparison with the present invention. Pressure distribution diagram schematically showing the pressure vector shown in FIG. Pressure distribution diagram schematically showing the pressure vector shown in FIG.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  A sleeve 102 having a through hole 102h at the center is inserted into a shaft 106 serving as a fixed shaft so as to be relatively rotatable.

  A minute radial bearing gap 52 is formed between the outer peripheral surface of the shaft 106 and the inner peripheral surface of the sleeve 102.

  A dynamic pressure generating groove G is formed on at least one of the outer peripheral surface of the shaft 106 and the inner peripheral surface of the sleeve 102 to form a radial bearing portion. That is, it is shown in the radial dynamic pressure groove 111.

  A flange-like thrust plate (lower) 104B larger than the outer diameter of the shaft 106 is fixed to the lower end portion of the shaft 106. The upper surface of the thrust plate (lower) 104B and the lower surface of the sleeve 102 are minute thrust. A thrust bearing (lower) is formed by forming a dynamic pressure generating groove G on at least one of the upper surface of the thrust plate (lower) 104B and the lower surface of the sleeve 102, facing each other via a bearing gap (lower) 103B. The That is, it is shown in the thrust dynamic pressure groove (lower) 105B.

  A flange-like thrust plate (upper) 104A larger than the outer diameter of the shaft 106 is fixed to the upper end portion of the shaft 106, and the lower surface of the thrust plate (upper) 104A and the upper surface of the sleeve 102 are minute thrusts. A thrust bearing (upper) is formed by forming a dynamic pressure generating groove G on at least one of the lower surface of the thrust plate (upper) 104A and the upper surface of the sleeve 102, facing each other through a bearing gap (upper) 103A. The That is, it is shown in the thrust dynamic pressure groove (upper) 105A.

  There is a step SB on the radially outer side of the thrust plate (lower) 104B, an oil reservoir (lower) 61B is formed between the lower surface of the sleeve 102, and on the radially outer side of the thrust plate (upper) 104A. There is a step SA, and an oil reservoir (upper) 61A is formed between the sleeve 102 and the upper surface of the sleeve 102. The sleeve 102 is mounted on the first inner peripheral surface 110A of the hub 110 that rotates by mounting a recording medium. The outer periphery of the sleeve 102 is fitted and fixed, and there is a gap between the outer peripheral surface of the thrust plate (upper) 104A on the fixed side and the second inner peripheral surface 110B of the hub 110 on the rotating side. This gap forms a capillary seal (upper). Further, there is a gap between the outer peripheral surface of the thrust plate (lower) 104B on the fixed side and the inner peripheral surface of the lower spacer 117 attached to the lower side of the third inner peripheral surface 110C of the hub 110 on the rotating side. There is a capillary seal part (bottom) (see FIG. 7).

  The sleeve 102 is provided with a cut surface (D cut surface) linearly cut in the axial direction on the outer periphery of the sleeve 102, and a reflux hole (communication hole) between a part of the first inner peripheral surface 110 </ b> A of the hub 110. ) 101, the opening of the reflux hole 101 is connected to the oil reservoir (upper) 61A, and the other opening is connected to the oil reservoir (lower) 61B (FIG. 6A). )reference).

  The thrust bearing gap (lower) 103B, the radial bearing gap 52, and the thrust gap (upper) 103A are connected and have a so-called full-fill structure filled with oil without interruption.

  Also, the oil reservoirs (upper) 61A, (lower) 61B and the reflux hole 101 and the thrust bearing gaps (upper) 103A, (lower) 103B are connected and filled with oil, and when the sleeve rotates, Oil flows (flows) through the reflux hole 101.

  The surface D, which is linearly cut in the axial direction of the outer periphery of the sleeve 102 described above, is provided at two symmetrical positions across the center line of the cylindrical sleeve 102 in the drawing, but three or more locations are provided as necessary. Can be formed on the outer circumference at regular intervals.

  As shown in FIG. 6B, the reflux holes 101 can also be provided as a pair of symmetrical left and right small holes sh parallel to the axial direction on the outer peripheral portion of the sleeve 102. In any case, if it is near the outer periphery of the sleeve 102, the configuration shape is not specified at all.

  If the left and right are not symmetrical, the rotating body including the sleeve 102 is unbalanced and causes vibration. However, if the vibration is small or within the standard conditions, the reflux hole may be provided at one location.

Further, the dynamic pressure generating groove G in the radial bearing portion formed on at least one of the outer periphery of the shaft 106 and the inner periphery of the sleeve 102 is arranged in two upper and lower stages in a herringbone shape as shown in FIG. It is. And preferably, the upper and lower groove intervals A1, B1 and A2, B2 are:
A1 + A2 = B1 + B2
It is ideal to keep this relationship.

  Further, the dynamic pressure generating grooves G formed in the thrust bearing gap (lower) 103B and the thrust bearing gap (upper) 103A have different spiral directions as shown in (a1) and (a2) of FIG. It can be formed in a spiral shape or a herringbone shape in different directions as shown in FIGS.

  It is obvious that the dynamic pressure generating groove G of any shape is formed in the direction in which the fluid pressure of the oil increases during rotation.

  Next, referring to FIG. 12 and FIG. 14, the pressure of the lubricating oil that is continuously filled in the thrust bearing gap (upper) 103A, the thrust bearing gap (lower) 103B, and the radial bearing gap 52 according to the present invention without interruption. The operation state of will be described.

  Referring to FIG. 12, the rotating lubricating oil first has a spiral shape as shown in FIG. 10 (a1) or (a2) in the upper and lower thrust bearing gaps (103A) (103B). The radial bearing gap 52 formed on the outer periphery of the shaft serves as a pumping vector uSs, lSs in the direction of the arrow toward the shaft 106, and is an arrow that pumps in the radial bearing at the top due to the two-stage herringbone configuration. Vectors uRi and uRo in the direction of the sign act so as to face each other, and in the lower part, vectors lRi and lRo in the direction of the arrow similarly pumped into the bearing act so as to face each other to maintain balance.

  If the pressure state of this lubricating oil is schematically developed, it will be shown in FIG. 14, and the pressure acting on the upper opening (upper) 51A and the lower opening (lower) 51B, and the thrust bearing gap (upper) The pumping vector uSs acting on 103A, the pumping vector uRi, uRo, lRo, lRi acting on the radial bearing gap 52, and the pumping vector lSs acting on the thrust bearing gap (lower) 103B are obtained. Both hold values higher than atmospheric pressure.

  Therefore, the air does not enter from the openings (upper) (lower) 51A, 51B in contact with the air during rotation, and bubbles generated in the bearing are also discharged.

  On the other hand, when the thrust bearing gap (upper) 103A and the thrust bearing gap (lower) 103B, which are different from the present invention, are formed in the herringbone shape shown in FIGS. 10 (b1) and (b2), the operating state of the lubricating oil pressure Will be discussed with reference to FIGS.

  In the thrust bearing gap (upper) 103A, vectors uSi and uSo pumping in the opposite directions from the outer circumference and the inner circumference of the gap (upper) 103A act by herringbone-like grooves in different oblique directions, and similarly. The vectors lSi and lSo pumping to the thrust bearing gap (bottom) 103B act, and the radial bearing gap 52 of the shaft 106 has a two-stage herringbone-like groove configuration as in FIG. Pumping vectors uRi, uRo, lRo, lRi work.

  If this vector relationship is shown as a schematic pressure distribution diagram, it can be expressed as FIG.

  That is, the pressure acting on the upper opening (upper) 51A and the lower opening (lower) 51B, the pumping vectors uSi and uSo acting on the thrust bearing gap (upper) 103A, and the pumping vector uRi acting on the radial bearing gap 52 , URo, lRo, lRi and the pumping vectors lSi and iSo acting on the thrust bearing gap (lower) 103B, it can be seen that the boundary points Pa1, Pb1, Pc1 of these vectors hold the same value as the atmospheric pressure.

  Therefore, when the dynamic pressure generating grooves G of the thrust bearing gaps (upper) (lower) 103A, 103B different from the present invention are herringbones, the thrust bearing gaps (upper) (lower) 103A, 103B and radial bearings are rotated during rotation. The effect of discharging bubbles in the gap 52 cannot be obtained.

  Further, the configuration and action of the reflux hole 101 will be described.

  The reflux hole 101 is shown as a straight cut surface D or a small hole sh near the outer periphery of the sleeve 102, and the opening (upper) 62A of the reflux hole 101 communicates with an oil reservoir (upper) 61A. Further, the opening (lower) 62B of the reflux hole 101 is communicated with the oil reservoir (lower) 61B.

  Moreover, the upper and lower oil reservoirs 61A, 61B are formed through steps SA, SB provided on the outer sides in the radial direction of the upper and lower thrust plates (upper) (lower) 104A, 104B.

  Therefore, in the lubricating oil filled in the upper and lower thrust bearing gaps 103A and 103B and the radial bearing gap 52, the pressures P1 and P2 of the upper and lower oil reservoirs 61A and 61B as shown in FIG. The upper and lower pressures P1 and P2 can always maintain the same state while always maintaining the state of FIG. 9B.

  Therefore, the oil is not pushed out from the openings (upper) (lower) 51A, 51B to the outside of the bearing. Moreover, intrusion of outside air can be completely prevented.

  In the figure, 71A is the sleeve surface (upper), 71B is the sleeve surface (lower), 72A is the upper thrust plate (lower surface), 72B is the lower thrust plate (upper surface), 73 is the inner peripheral surface of the sleeve, and 74 is the outer peripheral surface of the shaft. Surface, 107 is a clamp (screw top), 108 is a clamp (center axis top), 109 is a cover, 112 is a clamp (center axis), 113 is a fixture (stop ring), and 114 is a motor base. , 115 is a rotor magnet, 116 is a flange (magnetic shield), 117 is under a spacer, 118 is a core (stator), 119 is a coil (stator), and 120 is a shield plate (magnetic shield).

  In the above configuration, when rotating as a motor, the sleeve 102 rotates about the shaft 106, and the gap between the thrust plate (upper) 104 </ b> A and the thrust plate (lower) 104 </ b> B provided on the upper and lower sides of the shaft 106 and the sleeve 102. That is, the oil as the lubricating oil filled in the thrust bearing gap (upper) 103A, the thrust bearing gap (lower) 103B, and the radial bearing gap 52 is pumped by the dynamic pressure generating groove G, thereby enabling smooth rotation. To do.

  Even if an abnormal situation occurs during rotation as well as stationary due to an external factor such as an impact, the oil in the upper and lower oil reservoirs 61A and 61B is recirculated by the cut surface D of the sleeve 102. Enables supply to thrust bearing gap (upper) 103A and thrust bearing gap (lower) 103B via 101, preventing incomplete flow of oil, and maintaining a full-filled bearing state at all times to achieve high performance and reliable rotation Is obtained.

51A opening (top)
51B Opening (bottom)
52 Radial bearing clearance 61A Oil sump (top)
61B Oil reservoir (bottom)
62A Opening part of reflux hole (top)
62B Reflux hole opening (bottom)
71A Sleeve surface (top)
71B Sleeve surface (bottom)
72A On thrust plate (bottom surface)
72B Below thrust plate (upper surface)
73 inner peripheral surface of sleeve 74 outer peripheral surface of shaft 101 reflux hole (communication hole)
102 Sleeve 102h Through-hole 103A Thrust bearing clearance (upper)
103B Thrust bearing clearance (bottom)
104A Thrust board (top)
104B Thrust board (bottom)
105A Thrust dynamic pressure groove (top)
105B Thrust dynamic pressure groove (bottom)
106 Shaft 107 Fastening bracket (screw top)
108 Fastening bracket (top of central axis)
109 Cover 110 Hub 110A First inner peripheral surface 110B Second inner peripheral surface 110C Third inner peripheral surface 111 Radial dynamic pressure groove 112 Fastening bracket (central axis)
113 Fixing bracket (stop ring)
114 Motor base 115 Rotor magnet 116 Flange (magnetic shielding)
117 Spacer bottom 118 Core (stator)
119 Coil (stator)
120 Shield plate (magnetic shielding)
uSs, lSs, uRi, uRo, lRi, lRo, uSi, uSo, lSi, lSo Pumping vectors Pa, Pb, Pc, Pa1, Pb1, Pc1 Boundary point P1 Opening (upper) pressure P2 opening 51A (lower) 51B Pressure A1, B1, A2, B2 Herringbone groove spacing SA, SB Step sh Small hole D Cut surface G Dynamic pressure generating groove

Claims (5)

A sleeve having a through-hole at the center is inserted into a shaft serving as a fixed shaft so as to be relatively rotatable, and a minute radial bearing gap is formed between the shaft outer peripheral surface and the sleeve inner peripheral surface. And a dynamic pressure generating groove is formed in at least one of the sleeve inner peripheral surface to form a radial bearing portion,
A flange-like thrust plate (lower) larger than the outer diameter of the shaft is fixed to the lower end portion of the shaft, and the upper surface of the thrust plate (lower) and the lower surface of the sleeve are interposed through a minute thrust bearing gap (lower). A thrust bearing (lower) is formed by forming a dynamic pressure generating groove on at least one of the upper surface of the thrust plate (lower) and the lower surface of the sleeve,
A flange-like thrust plate (upper) larger than the outer diameter of the shaft is fixed to the upper end portion of the shaft, and the lower surface of the thrust plate (upper) and the upper surface of the sleeve are interposed through a minute thrust bearing gap (upper). And a dynamic pressure generating groove is formed on at least one of the lower surface of the thrust plate (upper) and the upper surface of the sleeve to constitute a thrust bearing (upper),
There is a step on the radially outer side of the thrust plate (lower), and an oil sump (lower) communicating with the step is formed between the lower surface of the sleeve,
There is a step on the radially outer side of the thrust plate (upper), and an oil sump (upper) communicating with the step is formed between the upper surface of the sleeve,
In the sleeve, the outer periphery of the sleeve is fitted and fixed to the first inner peripheral surface of a hub that rotates with a recording medium mounted thereon,
There is a gap between the outer peripheral surface of the thrust plate (upper) on the fixed side and the second inner peripheral surface of the hub on the rotating side, forming a capillary seal (upper), and the fixed side There is a gap between the outer peripheral surface of the thrust plate (lower) and the inner peripheral surface under the spacer attached to the lower side of the first inner peripheral surface of the hub on the rotating side. )
Near the outer periphery of the sleeve, a linear notch or small hole is provided along the axial direction, and a reflux hole is formed between a part of the first inner peripheral surface of the hub,
The opening (upper) of the reflux hole is connected to the oil reservoir (upper), and the other opening (lower) is connected to the oil reservoir (lower).
The thrust gap (lower), the radial gap, and the thrust gap (upper) are connected and filled with oil without interruption, and have a full-fill structure.
The oil reservoir (upper) (lower) is connected to the reflux hole and the thrust gap (upper) (lower) and is filled with oil. When the sleeve rotates, the oil flows through the reflux hole. A fixed shaft type fluid dynamic bearing device characterized by flowing. The fixed shaft type fluid dynamic bearing device according to claim 1,
The dynamic pressure generating groove of the thrust bearing (upper) and the dynamic pressure generating groove of the thrust bearing (lower) should have a spiral shape that acts in the direction of pushing oil into the bearing, and the pressure inside the bearing becomes atmospheric pressure or higher. Thus, the shaft-fixed fluid dynamic bearing device is provided with a function of preventing air from entering and discharging bubbles generated inside the bearing. The fixed shaft type fluid dynamic bearing device according to claim 1,
The opening (upper) (lower) of the reflux hole is provided between the second inner peripheral surface of the hub and the inner peripheral surface under the spacer to the step of the thrust plate (upper) (lower). A shaft-fixed type fluid dynamic pressure bearing device.   A spindle motor comprising the shaft-fixed fluid dynamic bearing device according to any one of claims 1 to 3.   A recording disk device comprising the spindle motor according to claim 4.

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