JP2006187135A - Motor and method for injecting conductive fluid to earthing means - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form labyrinth structures at axial upper and lower sides of a fluid seal of an earthing means, to prevent the evaporation and the dispersion of the fluid seal, and to enable the long term use of the labyrinth structures. <P>SOLUTION: A bush 200 and a rotor hub 300 are made to face the protrusion 110 of an axial body 100 with gaps formed outside the radial direction. A conductive fluid is filled into a fluid seal holder formed of the protrusion 110 of the axial body 100, the bush 200 and the rotor hub 300. Gaps 111, 112, 211 and 310 formed at axial upper and lower sides of the fluid seal holder are formed so as to be slightly smaller than the radial gaps of the fluid seal holder. Compatibility is eliminated between the fluid seal holder and the radial gaps, thus preventing the evaporation and the dispersion of the fluid seal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fluid seal as a grounding means for conducting electrical continuity between a stationary part and a rotating part, a hard disk spindle motor using a gas dynamic pressure bearing having this fluid seal, and the spindle motor The present invention relates to an adopted recording disk drive device.

  For example, a hard disk drive device as a recording disk drive device is a device housing constituting a storage chamber, a spindle motor mounted in the device housing, a magnetic recording disk mounted on the spindle motor, and writing recording information on the recording disk. And / or a magnetic head for reading recorded information. In recent years, the amount of programs, data, etc. handled by this hard disk drive has increased, and the storage capacity of the hard disk drive has been increased and the speed of writing and reading of recorded information has been increasingly demanded. The accuracy of spindle motors is increasing. With this increase in accuracy, the bearing means for rotatably supporting the spindle motor is also replacing the ball bearings with the dynamic pressure bearings. In a hydrodynamic bearing, a minute gap is formed between relatively rotating parts, and the lubricating fluid held in the gap is hydrodynamically pressed by a hydrodynamic groove formed on the bearing surface by the relative rotation of these parts. And the other part (rotating part) is rotatably supported in a non-contact manner with respect to one part (stationary part). Generally, liquid or gas is used, and the radial part of the rotating part is used. It comprises a radial bearing portion that supports the direction and a thrust bearing portion that supports the thrust direction of the rotating portion. When such a dynamic pressure bearing is adopted, it can rotate with lower noise and higher accuracy than a ball bearing.

  However, in the near future, it is expected that the amount of programs, the amount of data, etc. will further increase, and accordingly, the rotation speed of the spindle motor is required to be high speed rotation of 20000 rpm or more. At such high speed rotation, when oil is used as the lubricating fluid, the axial loss during rotation increases due to the viscous resistance of the oil, making it difficult to cope with high speed rotation of 20000 rpm or more. In addition, since the viscosity characteristic of oil has a characteristic that greatly changes depending on the temperature, it is difficult to stably and freely support the rotating part in an environment where the ambient temperature changes greatly.

  Therefore, in order to cope with further high speed rotation, it is considered to employ a gas dynamic pressure bearing using air as a lubricating fluid. When gas is used as the lubricating fluid, the viscosity resistance is very small compared to oil (the viscosity resistance of gas is about 1/1000 of the viscosity resistance of oil), so the axial loss during rotation is small, and the temperature Even if the viscosity changes, the viscosity characteristics do not change greatly, and the rotating part can be stably supported at high speed.

  However, when a gas dynamic pressure bearing is employed as the bearing means, the rotating part to which the magnetic disk is attached is supported via the compressed gas layer, and the following problem is newly generated. Generally, when a magnetic disk rotates at high speed, static electricity is generated in the rotating disk due to friction with air in the apparatus housing. When static electricity is generated in this way, the rotating part is supported via the compressed gas layer during rotation, so that the generated static electricity does not flow from the magnetic disk to the apparatus housing but is stored in the magnetic disk. In this way, when the accumulated static electricity is discharged, the information recorded on the magnetic disk (magnetically recorded) may be damaged.

  Such a problem of static electricity also occurs when the magnetic head of the hard disk drive is composed of an MR head. That is, the MR head is not durable against static electricity, and therefore, the MR head may be damaged if static electricity accumulates on the magnetic disk. For this reason, when an air dynamic pressure bearing is employed, a grounding means for electrically connecting the rotating portion and the stationary portion is required. A fluid seal is generally used as the grounding means. (See Patent Document 1 for a fluid seal of such a conventional spindle motor).

JP 2000-240811 A

  FIG. 10 shows an example of a fluid seal structure diagram as a conventional grounding means.

  The fluid seal Z is formed by filling a conductive fluid between the outer peripheral surface of the protrusion of the shaft body D and the inner peripheral surface of the bush F fitted in the rotor hub E.

  In the conventional fluid seal structure as shown in FIG. 10, the circulating air flow A collides with the lower interface B of the fluid seal Z in the vicinity of the interface of the fluid seal Z. At this time, the intermolecular collision between the circulating air flow A and the fluid constituting the lower interface B is intense, the energy of the fluid constituting the lower interface B increases, and the fluid molecules near the lower interface B are liquid. The intermolecular force of the phase is shaken off. As a result, a state change (evaporation) from the liquid phase to the gas phase occurs at the lower interface B. In addition, when the fluid seal Z is exposed to the outside air C from the outside of the motor, the fluid molecules near the upper interface B cause evaporation. Since the outside air C is connected to the atmosphere, it does not saturate with the evaporated fluid molecules, and therefore evaporates permanently at the upper interface B. The circulating air stream A has higher kinetic energy than the outside air C, and the evaporation of the fluid near the lower interface B due to the collision between the circulating air stream A and the lower interface B is the kinetic energy of the air stream A. Due to the movement of the fluid near the lower interface B, the energy of the lower interface B increases, and the evaporation of the fluid near the lower interface B is further promoted. Therefore, the holding amount of the conductive fluid in the fluid seal Z is rapidly reduced, and it is impossible to secure a sufficient holding amount of the conductive fluid for a long period of time, thereby shortening the life of the fluid seal functioning.

  Usually, the surface tension (seal pressure resistance) of the upper interface B and the pressure of the outside air C are balanced. However, when a sudden pressure change occurs inside or outside the motor, this balanced state is lost, and when the pressure of the outside air C exceeds the seal pressure resistance, the conductive fluid filled as a fluid seal is scattered around. Even when the motor is started, the air inflow amount temporarily exceeds the air outflow amount, so that the pressure inside the motor increases. As a result, when the pressure inside the motor exceeds the seal pressure resistance of the fluid seal Z, the conductive fluid is scattered outside.

  The present invention has been made in view of the above problems of a spindle motor in a conventional disk drive device, and the object thereof is to have conductivity used when a gas dynamic pressure bearing is adopted. It is to suppress evaporation and scattering of the conductive fluid held in the fluid seal as the earthing means.

  Another object of the present invention is to provide a fluid seal, which is a grounding means for electrically connecting the motor rotating portion and the motor stationary portion, with the conductive fluid held by the fluid seal in a predetermined position. It is to provide a method for reliably injecting a fixed amount.

  According to a first aspect of the present invention, there is provided a spindle motor comprising: a gas dynamic pressure bearing that holds the motor rotating portion and the motor stationary portion so as to be rotatable around the rotation axis of the motor; the motor rotating portion; and the motor stationary portion. In a spindle motor comprising a grounding means for holding a conductive fluid for electrical continuity with each other, a part of the rotating part and one of the stationary parts are respectively located above and below the rotational axis of the grounding means. It has a labyrinth structure that is opposed to each other through a minute gap.

  According to claim 1 of the present invention, since the labyrinth structure portion is provided on the upper side and the lower side in the rotation axis direction of the grounding means, in the lower labyrinth structure portion, the fluid seal and the air circulated at the gas dynamic pressure Since a labyrinth portion with a very narrow space is provided between them, it serves to prevent the inflow of circulating air inside the motor. As a result, the circulating air cannot easily come into contact with the grounding means, and the evaporation of the conductive fluid in the grounding means can be suppressed. Similarly, the upper labyrinth structure portion cannot be easily contacted with outside air. Therefore, the air in the labyrinth structure is isolated from the outside. That is, it is not compatible with the outside air. For this reason, the air inside the labyrinth structure does not move to the outside, and is immediately saturated with respect to the evaporation of the conductive fluid. As a result, evaporation cannot be further promoted for the conductive fluid, and the conductive fluid does not evaporate. Moreover, since this labyrinth structure part also has a scattering prevention mechanism, scattering of the conductive fluid of the grounding means can be suppressed. In addition, even if the conductive fluid filled in the fluid seal scatters due to pressure changes such as external impacts, the amount of the conductive fluid decreases because this minute gap does not pass the conductive fluid that tries to scatter outside the fluid seal. Never do.

  A spindle motor according to a second aspect of the present invention is according to the first aspect, wherein the labyrinth structure portion is at least one of a part of the rotating part and a part of the stationary part that is opposed to the rotating radial direction via a minute gap. One of them is formed by having a protruding shape.

  According to claim 2 of the present invention, since the combination of the parts of the motor rotating part and the motor stationary part in the upper and lower labyrinth structure parts in the rotation axis direction is the same, the number of parts can be reduced and the cost can be reduced. Leads to.

  A spindle motor according to a third aspect of the present invention is according to the first aspect, wherein the two labyrinth structure portions are formed of two different members facing a part of the rotating portion via a minute gap in the rotational radius direction. And a stationary part.

  According to the third aspect of the present invention, since the combination of the parts of the motor rotating portion and the motor stationary portion in the upper and lower labyrinth structure portions in the rotation axis direction is different, the stationary portion is formed to form the labyrinth structure portion. The labyrinth structure portion can be formed by a combination of simple shapes without having to perform complicated machining on the rotating portion.

  In the spindle motor according to claim 4 of the present invention, the labyrinth structures on the upper side and the lower side in the direction of the rotation axis of the grounding means have a small annular disc on each of the upper side and the lower side in the direction of the rotation axis of the grounding means. It is formed by being narrowly attached with a gap.

  According to claim 4 of the present invention, in order to achieve the above-described effect 1 after charging more reliably, the longer the length of the labyrinth structure portion, the less the air circulation at both ends of the labyrinth structure portion. be able to. When the labyrinth structure portion is arranged in the axial direction of the motor, the height in the axial direction of the motor becomes large, and there is a limit in an environment where a smaller motor is required. Therefore, in the present invention, a gas dynamic pressure bearing spindle motor having a grounding means with a small size and a long life is realized by forming a labyrinth structure portion by utilizing a radial direction portion which is substantially unrelated to the size of the motor. ing.

  The spindle motor according to claim 5 of the present invention has a shaft included in the motor stationary part, the grounding means is constituted by a grounding means rotating part and a grounding means stationary part, and the grounding means stationary part fixed to the shaft. Has a projecting portion directed in the radial direction, and has a recess in the earthing means rotating portion facing the projecting portion, and holds the conductive fluid in the facing portion.

  A spindle motor according to a sixth aspect of the present invention has a shaft included in the motor rotating portion, and the grounding means includes an earthing means stationary portion and an earthing means rotating portion, and is fixed to the shaft. Has a protrusion in the radial direction, has a recess in the grounding means stationary part opposite the protrusion, and holds the conductive fluid in the opposite part.

  According to claim 5 and claim 6 of the present invention, it is possible to realize a grounding means having excellent resistance against centrifugal force due to high-speed rotation. That is, the centrifugal force is applied radially outward, but the conductive fluid is forced radially outward by the centrifugal force due to the concave portion facing inward in the radial direction and the projecting portion facing the same. As a result, they gather at the center of the grounding means, and at least at the time of rotation, this centrifugal force acts on the conductive fluid, so that it does not scatter outside the grounding means. Therefore, the higher the rotation speed of the motor, the stronger the flow of the conductive fluid toward the center of the grounding means, and a spindle motor having stable grounding performance can be realized even at high speed rotation.

  In the spindle motor according to claim 7 of the present invention, the radial gap of the facing portion becomes narrower as the facing surface formed by the projecting portion and the recessed portion forming the grounding means is closer to the center in the axial direction of the grounding means. A taper structure is formed.

  According to the seventh aspect of the present invention, since the facing surface between the projecting portion of the grounding means and the concave portion facing this has a taper seal structure, it can be held against an external impact when the motor is stationary. This taper seal portion prevents the conductive fluid that has been discharged from scattering outside. Further, even if a part of the conductive fluid is scattered, the scattered conductive fluid is collected in the concave portion due to the centrifugal force acting when the motor rotates, and the original normal state is restored. This prevents the conductive fluid from scattering both at rest and during rotation.

  A spindle motor according to an eighth aspect of the present invention includes a gas pressure bearing that holds the motor rotating portion and the motor stationary portion so as to be rotatable around the rotation axis of the motor, a motor rotating portion, and a motor stationary portion. The earthing means holding the conductive fluid to conduct the electrical continuity, and a part of the rotating part and a part of the stationary part via a minute gap on the upper and lower sides of the earthing means in the rotational axis direction, respectively. In the spindle motor having the labyrinth structure part that opposes, before assembling the motor rotation part and the motor stationary part to form the labyrinth structure part, an oil repellent agent is applied to the part corresponding to the labyrinth structure part of the motor rotation part and the motor stationary part. A step of applying, and a step of injecting a conductive magnetic fluid from the labyrinth structure portion to the grounding means after assembling the motor rotating portion and the motor stationary portion to form the labyrinth structure portion Characterized by a step of wiping the conductive magnetic fluid adhering to the labyrinth structure.

  In forming a fluid seal by injecting a conductive fluid into the grounding means according to claims 1 to 7, there are the following problems.

  FIG. 11 shows a scene in which a conductive fluid is injected into a grounding means portion having a labyrinth structure portion that is opposed to the upper side and the lower side in the rotation axis direction through a minute gap.

  A syringe needle a is used to inject the conductive fluid into the grounding means. And in order to inject a conductive fluid directly into the predetermined position b which forms the fluid seal which is an earthing means, it is desirable that the outer diameter of the syringe needle a is narrower than the gap e of the labyrinth part. On the other hand, in order for the labyrinth structure portion to exert a sufficient effect, the gap is preferably as narrow as possible, and usually about several tens of μm to 100 μm, and it is difficult to realize a syringe needle corresponding thereto.

  Since the gap e cannot be made larger than the diameter of the syringe needle a, if the conductive fluid is to be injected into the grounding means before the gap e is formed, the bush d and the rotor hub f are fitted before the bush d and the rotor hub f are fitted. A method of injecting a conductive fluid into the gap e1 between the shaft body c, that is, a method of injecting a conductive fluid into the gap between the rotor hub f and the shaft body c is conceivable. However, in the above method, since the grounding means portion is not completely formed, a predetermined amount of conductive fluid cannot be held. Furthermore, there is a possibility that the conductive fluid adheres to the portion g in which the bush d of the rotor hub f is fitted. When the adhesive is used for the inner fitting portion g to fix the bush d to the rotor hub f, the adhesive may not be cured because the conductive fluid adheres. There is a possibility that the conductive fluid may leak and fail to function as a fluid seal.

  On the other hand, according to claim 8 of the present invention, it is easy to apply an oil repellent in advance to the place where the labyrinth structure portion of the motor rotating portion and the motor stationary portion is formed before forming the labyrinth structure portion. An oil repellent agent can be applied to the labyrinth structure. In addition to the portion where the conductive fluid is injected into the grounding means, the conductive fluid adheres to the labyrinth structure portion, but by applying an oil repellent to the labyrinth structure portion, it can be easily wiped off, and the conductive fluid is conductive only at a predetermined position. Sexual fluid will be injected.

  The spindle motor according to claim 9 of the present invention is a method of measuring the weight of the motor before injecting the conductive fluid from the labyrinth structure portion to the grounding means, and injecting the conductive fluid into the grounding means in claim 8. And a step of confirming whether or not a predetermined amount of the conductive fluid has been injected by measuring the weight of the motor after performing the step and the step of wiping off the conductive fluid attached to the labyrinth structure. It is possible to do.

  According to claim 9 of the present invention, the grounding means is obtained by measuring the motor weight before injecting the conductive fluid and the motor weight after wiping off the conductive fluid adhering to other than the grounding means after injecting the conductive fluid. Since the amount of the conductive fluid injected into the gas can be grasped, a predetermined amount of oil can be accurately injected.

  A spindle motor according to a tenth aspect of the present invention is the method of injecting a conductive fluid according to the eighth aspect, wherein the grounding means includes the grounding portion connected to one of the upper and lower labyrinth structural portions. An annular injecting fluid holding portion that temporarily holds the injecting conductive fluid that is adjacent to the outside of the means is provided, and the step of injecting the conductive fluid includes a predetermined amount of the conducting fluid in the injecting fluid holding portion. And supplying a predetermined amount of air from outside the previous grounding means of the other labyrinth structure portion on the opposite side of the infusion fluid holding portion to the conductive fluid, thereby supplying the conductive fluid to the ground. Drawing in the central part in the axial direction of the means.

  According to the tenth aspect of the present invention, the conductive fluid can be accurately injected into the sealing means in the first to seventh aspects of the invention.

  ADVANTAGE OF THE INVENTION According to this invention, the evaporation and scattering of the electroconductive fluid hold | maintained at the fluid seal | sticker which is an electroconductive earth means used for a gas dynamic pressure bearing can be suppressed. Further, a predetermined amount of the conductive fluid held by the fluid seal can be reliably injected into a predetermined position.

  Hereinafter, an embodiment of a spindle motor according to the present invention and a recording medium driving device according to the present invention will be described. FIG. 1 is a cross-sectional view schematically showing an embodiment of a recording medium driving device according to the present invention, and FIG. 2 is a cross-sectional view showing an embodiment of a spindle motor according to the present invention.

  In FIG. 1, the recording medium driving device includes a rectangular parallelepiped device housing 2, and the device housing 2 includes a lower housing 4 and a cover member 6. The lower housing 4 has a base portion 8 and a side wall portion 10 extending upward from the side wall portion of the lower housing 4 of the base portion 8, and the cover member 6 covers the rectangular upper surface opening defined by the side wall portion 10. The housing 12 is attached to the lower housing 4 and the lower housing 4 and the cover member 6 are substantially sealed.

  In the housing chamber 12 of the apparatus housing 2, a magnetic disk 14 as a recording medium device, a spindle motor 16 for rotationally driving the magnetic disk 14, and writing and / or reading for writing and / or reading recorded information. A magnetic head 18 as means and a head moving mechanism 20 for moving the magnetic head 18 relative to the magnetic disk 14 as required are accommodated. The head moving mechanism 20 includes arm members 22 disposed above and below each magnetic disk 14, and a magnetic head 18 is attached to the tip of these arm members 22. The head moving mechanism 20 further includes an actuator 24 such as a voice coil motor, and the arm member 22 is rotated by the actuator 24 in a direction in which the arm member 22 approaches and separates from the magnetic disk 18.

  In such a recording medium driving apparatus, the magnetic disk 14 is rotationally driven in a predetermined direction by rotating the spindle motor 16 as described later. The actuator 24 rotates the arm member 22, and the magnetic head 18 mounted on the arm member 22 moves in the substantially radial direction of the corresponding magnetic disk 14, and the recording information to be recorded is magnetically applied to the magnetic disk 14 by the action of the magnetic head 18. The recorded information recorded on the magnetic disk 14 is read by the magnetic head 18.

  Next, the spindle motor 16 shown in the drawing will be described with reference to FIG. 2. The spindle motor 16 includes a substantially circular bracket 700, and the shaft body 100 is press-fitted in the axial direction at a substantially central portion of the bracket 700, for example. Is erected by. The bracket 700 and the shaft body 100 are made of a conductive and magnetic material such as iron or stainless steel. The bracket 700 and the shaft body 100 may be integrally formed. The shaft main body 102 extends substantially vertically from the bracket 700, and the tip shaft 101 extends from the upper end of the shaft main body 102. A lower annular member 810, a sleeve member 800, and an upper annular member 820 are mounted in this order from the lower end to the upper end (from bottom to top in FIG. 2) on the shaft main body portion 102 of the shaft body 100. The outer peripheral portions of the member 820 and the lower annular member 810 protrude radially outward from the sleeve member 800. The bracket 700 provided with the shaft body 100 is attached to the base portion 8 of the apparatus housing 2 of the recording medium driving device by an attaching screw (not shown) as shown in FIG. The bracket 700 may be omitted, and the shaft body 100 may be directly attached to the base portion 8 of the apparatus housing 2.

  A rotor hub 300 is rotatably supported on the shaft body 100. The rotor hub 300 has a hub body 301 having a cylindrical sleeve shape, and an annular flange 302 projecting radially outward is integrally provided at a lower portion of the hub body 301. The hub body 301 is made of a conductive material such as aluminum or an aluminum alloy. A plurality of (for example, three in this embodiment) magnetic disks 14 (see FIG. 1) are placed on the annular flange 302 via the annular spacer 303, and the clamp means 304 is attached to the rotor hub 300, so that these The magnetic disk 14 is fixed. The number of magnetic disks 14 attached to the rotor hub 300 can be set to an appropriate number of one, two, or four or more in relation to the storage capacity of the recording medium driving device.

  A bearing sleeve 830 corresponding to the sleeve member 800 of the shaft body 100 is attached to the inner peripheral surface of the hub body 300 by, for example, press fitting. As shown in FIG. 2, the inner peripheral surface of the bearing sleeve 830 is disposed to face the outer peripheral surface of the sleeve member 800, and the lower end surface thereof is disposed to face the outer peripheral portion of the inner peripheral end surface of the lower annular member 810. The upper end surface of the upper annular member 820 is disposed to face the outer peripheral portion of the inner peripheral end surface. The rotor hub 300 is rotatably supported by the shaft body 100 via a gas dynamic pressure bearing means. In this embodiment, the gas dynamic pressure bearing means includes a pair of radial gas dynamic pressure bearing portions 831 and 832 and a pair of thrust gas dynamic pressure bearing portions 811 and 821. The radial gas dynamic pressure bearing portions 831 and 832 for supporting the radial load acting on the rotor hub 300 are axially arranged between the outer peripheral portion of the sleeve member 800 of the shaft body 100 and the inner peripheral surface of the bearing sleeve 830 of the rotor hub 300. In this embodiment, the bearing grooves 833 and 834 are formed on the inner peripheral surface of the bearing sleeve 830. The bearing grooves 833 and 834 may be provided on the outer peripheral surface of the sleeve member 800 instead of or in addition to the inner peripheral surface of the bearing sleeve 830. Of the thrust gas bearing portions 811 and 821 for supporting the thrust load acting on the rotor hub 300, the upper bearing portion 821 is provided between the inner end surface of the upper annular member 820 and the upper end surface of the bearing sleeve 830. In this embodiment, the bearing ring 822 is formed on the inner end surface of the upper annular member 820. The lower bearing portion 811 is formed from a bearing groove 812 formed on the inner end surface of the lower annular member 810. The bearing grooves 812 and 822 may be provided on the upper end surface and the lower end surface of the bearing sleeve 830 instead of or in addition to the inner end surfaces of the upper annular member 820 and the lower annular member 810.

  An annular rotor magnet 350 is attached to the outer peripheral surface of the lower end portion of the rotor body 301. A stator 900 is disposed on the outer side in the radial direction so as to face the rotor magnet 350. The stator 900 includes a stator core 910 formed by stacking core plates, and a coil 920 wound around the stator core 910 as required. The stator core 910 is provided on the outer peripheral portion of the bracket body 700. 710 is attached to the inner peripheral surface.

  Since it is configured as described above, when a drive current is supplied to the coil 920, the stator core 910 is magnetized as required, and the rotor hub 300 and the magnet attached to the rotor hub 300 by the mutual magnetic action between the stator core 910 and the rotor magnet 350 are provided. The disk 14 (see FIG. 1) is rotationally driven in a predetermined direction. When the rotor hub 300 is rotationally driven as described above, in the pair of radial gas dynamic pressure bearing portions 831 and 832, the gas existing in the gap between the sleeve member 800 and the bearing sleeve 830 is compressed by the action of the bearing grooves 833 and 834. In the pair of thrust gas bearing portions 811 and 821, air existing in the gap between the bearing sleeve 830 and the upper annular member 820 and the lower annular member 810 is compressed by the action of the bearing grooves 812 and 822. As the pressure is increased, the hub body 301 is rotatably supported via the compressed air layer.

  In the spindle motor 16, a fluid seal as a grounding means is provided in order to ensure electrical continuity between the rotor hub 300 and the shaft body 100, and above and below the rotating shaft direction of the grounding means. The labyrinth structure part is formed. The labyrinth structure part will be described in detail below according to the embodiment.

1) First Embodiment of Labyrinth Structure Part of Fluid Seal FIG. 3 is a cross-sectional view of the first embodiment of the labyrinth structure part provided on the upper side and the lower side of the fluid seal of the present invention in the rotation axis direction.

  As shown in FIG. 3, the shaft body 100 is provided with an upper protrusion 110 and a lower protrusion 120, which are protrusions directed outward in the radial direction on the upper side and the lower side of the shaft body 100 in the rotation axis direction. The bush 200 facing the upper protrusion 110 of the shaft body 100 in the radial direction is fitted into the hub 300. The inner peripheral surface of the bush 200 is recessed with different lengths in the radial direction on the upper and lower sides in the rotational axis direction, and the upper end portion 220 of the inner peripheral surface forms a labyrinth structure portion facing the shaft body 100 with a minute gap. is doing. Further, a protrusion 230 is formed on the lower surface of the bush 200 in the axial direction, and a labyrinth structure portion is formed facing the lower protrusion 120 of the shaft body 100 with a slight gap. The inner peripheral diameter of the lower end 240 on the inner peripheral side of the bush 200 is larger than the diameter of the tip of the upper protrusion 110 of the shaft body 100. As a result, the bush 200 can be inserted into a predetermined position of the shaft body 100 and assembled.

2) Second Embodiment of Labyrinth Structure Part of Fluid Seal FIG. 4 is a sectional view of a second embodiment of the labyrinth structure part provided on the upper side and the lower side of the fluid seal of the present invention.

  As shown in FIG. 4, the shaft body 100 is provided with a protrusion 110 that extends radially outward. The bush 200 facing the upper side in the rotation axis direction of the protrusion 110 of the shaft body 100 in the radial direction is disposed substantially perpendicular to the rotation axis direction of the shaft body 100 and is fitted into the rotor hub 300. The inner peripheral surface portion 210 of the bush 200 has a so-called taper seal structure in which the shortest gap between the opposing surfaces gradually increases as the distance from the central axis of the protrusion 110 of the shaft body 100 in the rotational axis direction increases. Is provided. In the upper end portion 211 of the inner peripheral taper portion 210, an upper labyrinth structure portion is formed on the outer peripheral surface of the shaft body 100 so as to be opposed with a finer gap than the taper seal portion. Further, on the axially lower side of the central portion of the protrusion 110 of the shaft body 100, the rotor hub 300 is disposed to face the protrusion 110 of the shaft body 100 in the radial direction. In the inner peripheral taper part 310 of the rotor hub 300, as the inner peripheral taper part 210 of the bush 200 is separated from the center of the protrusion 110 of the shaft body 100 in the rotational axis direction as the center of symmetry, A so-called taper seal structure in which the shortest gap gradually increases is provided. At the lower end portion 311 of the inner peripheral surface portion 310, a lower labyrinth structure portion that is opposed to the outer peripheral surface of the shaft body 100 with a smaller gap than the taper seal structure portion is formed. In the taper seal structure portion of the bush 200 and the rotor hub 300, the conductive fluid 400 is held by forming a meniscus structure that is a gas-liquid interface as shown in FIG. With this structure, a stable surface tension acts on the fluid seal, prevents the fluid from scattering due to external impacts, etc., and the fluid is stably held in a quantitative manner for a long period of time. Then, the minute gap between the upper and lower labyrinth structure portions provided at the upper end portion 211 of the bush 200 and the lower end portion 311 of the rotor hub 300 can prevent the outside air from flowing into the fluid seal structure portion from the inside and outside of the motor. The evaporation of the conductive fluid can be prevented. Also, since the space surrounded by the upper and lower labyrinth structures is isolated from the outside, the air inside the space immediately saturates with respect to the evaporation of the conductive fluid, and the fluid seal evaporates further. Disappear. Therefore, evaporation of the conductive fluid can be suppressed, and a fluid seal that is stable for a long time can be formed. Even if the conductive fluid is scattered due to a pressure change such as an external impact, the labyrinth structure portion suppresses the outflow of the scattered fluid seal to the outside, so that the amount of the conductive fluid does not decrease. Further, in the fluid seal shape as shown in FIG. 3, since the fluid seal itself is formed long, the amount of conductive fluid that can be filled can be increased. Accordingly, an allowable amount of evaporation of the fluid seal, that is, an amount by which the conductive fluid may evaporate until the fluid seal stops functioning, and a stable fluid seal can be formed in the long term.

3) Third Embodiment in Labyrinth Structure of Fluid Seal FIG. 4 shows a cross-sectional view of a third embodiment in the labyrinth structure provided on the upper and lower sides in the axial direction of the fluid seal of the present invention.

  As shown in FIG. 5, the shaft body 100 is provided with a protrusion 110 that extends outward in the radial direction. The bush 500 is disposed so as to face the protrusion 110 of the shaft body 100 in the radial direction, and is fitted into the rotor hub 300. A fluid seal is formed in a gap formed between the inner peripheral surface 510 of the bush 500 and the outer peripheral surface of the protrusion 110 of the shaft body 100. Then, annular disks 600 and 610 are provided on the upper and lower sides of the bush 500 in the axial direction so as to sandwich the fluid seal. The gap formed by the annular discs 600 and 610 and the rotor hub 300 and the gap formed by the annular discs 600 and 610 and the bush 500 are very small, and try to enter the fluid seal from the inside and outside of the motor. It has the function of preventing air from coming into contact with the fluid seal. In this embodiment, the upper and lower sides of the fluid seal in the rotational axis direction are sandwiched between the annular discs 600 and 610. Therefore, the distance of the gap is long, and contact with external air is further prevented by that distance. Can do. Therefore, evaporation generated by contact between the fluid seal and air can be further prevented. Further, since the space surrounded by these gaps is isolated from the outside of the space, the circulation of air inside and outside the space is eliminated. That is, even if the air in the space is saturated, there is no place for scattering it. Therefore, the air in the space is always saturated, and the air in the space cannot promote the evaporation of the fluid seal beyond a certain level. Therefore, evaporation of the fluid seal can be suppressed, and a fluid seal that is stable for a long time can be formed. And even if the conductive fluid filled in the fluid seal scatters due to pressure changes such as external impact, the amount of the conductive fluid is reduced because the small gap does not pass the conductive fluid scattered outside the fluid seal. There is no.

  Next, a method for injecting a conductive fluid in a fluid seal portion having a labyrinth structure as in Embodiment 2, for example, will be described with reference to FIGS.

  First, the rotor hub 300 and the bush 200 are fitted inside. At that time, an adhesive is used for the portions 212 and 213 where the rotor hub 300 and the bush 200 are fitted in the radial direction and the axial direction, respectively, and the gap at the joint portion between the rotor hub 300 and the bush 200 is completely eliminated. To stick. This has an effect that oil can be sealed at the joints 212 and 213 between the rotor hub 300 and the bush 200 when the conductive fluid of the fluid seal is injected. Next, as shown in FIG. 6, an oil repellent is applied to the gaps 111, 112, 211, 310 between the rotor hub 300 and the bush 200 and the shaft body 100. Then, the rotor hub 300, the bush 200, and the shaft body 100 are assembled to form a labyrinth structure portion.

  Next, as shown in FIG. 7, the syringe needle is brought close to the labyrinth structure 410 on the upper side in the axial direction, and the conductive fluid is injected. The injected conductive fluid is first filled in the labyrinth structure 410. Further, by injecting the conductive fluid, the conductive fluid can be injected into a space in the labyrinth structure in which the protrusion 110 of the shaft body 100 is surrounded by the upper side and the lower side in the axial direction. In this state, the conductive fluid is divided into two portions, a labyrinth structure portion 410 and a space 420 in the labyrinth structure that surrounds the protrusion 110 of the shaft body 100 on the upper and lower sides in the axial direction. . However, since the labyrinth structure 410 is coated with an oil repellent, it can be easily wiped off. That is, as shown in FIG. 8, only the amount of conductive fluid injected into the space 420 in the labyrinth structure surrounding the protrusion 110 of the shaft body 100 on the upper and lower sides in the axial direction is obtained. Then, by taking the difference between the motor weight before injecting the conductive fluid shown in FIG. 6 and the motor weight after injecting the conductive fluid shown in FIG. 8, a predetermined amount of the conductive fluid can be accurately injected. it can. Further, by taking the difference between the motor weight before injecting the conductive fluid and the motor weight after injecting the conductive fluid, the amount of the conductive fluid injected into the labyrinth structure surrounded by the upper and lower sides in the rotation axis direction can be grasped. Therefore, it is easy to manage the amount of conductive fluid injected into a predetermined position.

  The method for injecting the conductive fluid into the fluid seal portion having the labyrinth structure portion can be performed in the same manner as in the first embodiment. With respect to the second embodiment, after injecting a conductive fluid into the fluid seal portion, the labyrinth structure portion may be formed by narrowing an annular disc on the upper side and the lower side in the rotation axis direction of the fluid seal.

  In addition, as shown in FIG. 9, injecting the conductive fluid in the case where an annular conductive fluid holding portion 430 to be injected is formed on the upper side in the axial direction of the labyrinth structure portion 410 formed by the shaft body 100 and the bush 200. Describe the method. Basically, it is the same as the above-described method for injecting a conductive fluid. Here, differences from the above injection method will be described. The holding portion 430 is formed by chamfering a part of the facing portion between the shaft body 100 and the bush 200. A predetermined amount of conductive fluid is injected into the holding portion 430. Then, by sucking air from the labyrinth structure portion 440 formed by the shaft body 100 and the rotor hub 300, the conductive fluid is surrounded by the protrusions 110 of the shaft body 100 on the upper and lower sides in the axial direction. Move to space 420.

  As described above, the labyrinth structure portion, the grounding means portion, the spindle motor, and the method of injecting the lubricating fluid into the labyrinth structure portion of the present invention have been described. However, the present invention is not limited to the embodiment and departs from the present invention. Various modifications or corrections can be made without this.

It is a figure which shows a recording medium drive device. It is sectional drawing which shows one Embodiment of the spindle motor of this invention. It is sectional drawing which shows 2nd embodiment of the labyrinth structure of the fluid seal | sticker of this invention. It is sectional drawing which shows 2nd embodiment of the labyrinth structure of the fluid seal | sticker of this invention. It is sectional drawing which shows 3rd embodiment of the labyrinth structure of the fluid seal | sticker of this invention. It is sectional drawing which shows before the oil injection of the oil injection method of this invention. It is sectional drawing which shows after oil injection of the oil injection method of this invention. It is sectional drawing which shows after oil wiping off of the oil injection method of this invention. It is sectional drawing which shows another form of the oil injection method of this invention. It is sectional drawing which shows the conventional fluid seal structure. It is sectional drawing which shows the oil injection | pouring of this invention.

Explanation of symbols

2 Apparatus housing 12 Accommodating chamber 16 Spindle motor 100 Shaft body 110 Shaft body protrusion 200, 500 Bush 210, 510 Bush inner peripheral part 300 Rotor hub 310 Rotor hub inner peripheral part 400 Fluid seal 410 Labyrinth structure part 600, 610 Labyrinth seal 700 Bracket 800 Sleeve member 810 Lower annular member 820 Upper annular member 830 Bearing sleeves 831 and 832 Radial gas dynamic pressure bearing portions 811 and 821 Thrust gas dynamic pressure bearing portions

Claims (11)

A gas dynamic pressure bearing that holds the motor rotating portion and the motor stationary portion so as to be rotatable around each other about the rotation axis of the motor, and a conductive material for electrical connection between the motor rotating portion and the motor stationary portion. In a spindle motor comprising a grounding means for holding a fluid,
A spindle motor characterized by having a labyrinth structure part which a part of the rotating part and a part of the stationary part oppose each other through a minute gap on the upper side and the lower side of the earthing means in the rotation axis direction.   The labyrinth structure part of the spindle motor according to claim 1, wherein at least one of the part of the rotating part and the part of the stationary part facing each other through a minute gap in the rotational radius direction has a protruding shape. A spindle motor characterized by being formed.   The two labyrinth structure portions of the spindle motor according to claim 1 are respectively formed by a part of the rotating portion and the stationary portions formed by two different members facing each other with a minute gap in the rotational radius direction. Spindle motor characterized by being made.   2. The spindle motor according to claim 1, wherein the labyrinth structures on the upper side and the lower side of the grounding means in the rotation axis direction are respectively provided with annular disks on the upper side and the lower side of the grounding means in the direction of the rotation axis. A spindle motor characterized in that it is formed by being narrowly attached.   5. The spindle motor according to claim 1, wherein the grounding means is constituted by a grounding means rotating part and a grounding means stationary part, and the grounding means stationary part has a projecting part extending in a radial direction. A spindle motor characterized by having a concave portion in the rotating portion of the grounding means so as to hold a conductive fluid in the facing portion.   5. The spindle motor according to claim 1, wherein the grounding means includes a grounding means stationary part and a grounding means rotating part, and the grounding means rotating part has the projecting part directed in a radial direction. A spindle motor characterized in that the grounding means stationary portion has a recess facing the surface, and a conductive fluid is held in the facing portion.   7. The spindle motor according to claim 5, wherein the projecting portion and the recessed portion forming the grounding means are narrower in a radial gap of the facing portion toward an axial center of the grounding means. A spindle motor characterized in that it forms a par structure. A gas dynamic pressure bearing that holds the motor rotating portion and the motor stationary portion so as to be rotatable around each other about the rotation axis of the motor, and a conductive material for electrical connection between the motor rotating portion and the motor stationary portion. A grounding means for holding a fluid, and a labyrinth structure part that is opposed to a part of the rotating part and a part of the stationary part through a minute gap on the upper side and the lower side of the grounding means in the rotational axis direction, respectively. In spindle motor
Before assembling the motor rotating portion and the motor stationary portion to form the labyrinth structure portion, applying an oil repellent agent to a portion corresponding to the labyrinth structure portion of the motor rotating portion and the motor stationary portion; and After assembling the motor rotating portion and the motor stationary portion to form the labyrinth structure portion, a step of injecting a conductive magnetic fluid from the labyrinth structure portion to the grounding means, and a conductive magnetic fluid attached to the labyrinth structure portion A method of injecting a conductive fluid, comprising: a step of wiping.   9. The method for injecting a conductive fluid according to claim 8, wherein a step of measuring a weight of a motor before injecting the conductive fluid from the labyrinth structure portion to the grounding means, and injecting the conductive fluid into the grounding means. Whether or not a predetermined amount of the conductive fluid was injected by comparing the motor weight with the step of measuring the motor weight after executing the step of wiping off the conductive fluid adhering to the labyrinth structure portion A method for injecting the conductive fluid into the grounding means, further comprising the step of confirming whether or not. 9. The method for injecting a conductive fluid according to claim 8, wherein the grounding means is temporarily supplied with an injecting conductive fluid adjacent to one labyrinth of the upper and lower labyrinth structure portions outside the grounding means. An annular infusion fluid holding part is provided to hold,
The step of injecting the conductive fluid includes a step of supplying a predetermined amount of conductive fluid to the injection fluid holding portion, and the grounding means of the other labyrinth on the side opposite to the injection fluid holding portion. And a step of drawing the conductive fluid into the central portion in the axial direction of the grounding means by sucking a predetermined amount of air from the outside. In a recording disk drive device to which a disk-shaped recording disk capable of recording information is mounted,
A recording disk drive device comprising a housing, a spindle motor fixed inside the housing and rotating the recording medium, and information access means for writing or reading information at a required position of the recording disk. ,
8. The recording disk drive device according to claim 1, wherein the spindle motor is a spindle motor according to any one of claims 1 to 7.

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