JP2003139129A - Dynamic pressure bearing, spindle motor using the bearing, and disc drive device having the spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reinforce a seal strength, to stabilize a feed of oil to a thrust bearing part, and to hold a sufficient amount of oil by increasing a volume of the interior of a taper seal part. SOLUTION: A taper seal part 28 where a gap which is inclined from the external side in a radial direction to the internal side and the gap size of which is gradually increased as it is spaced away from the thrust bearing part 22 is formed between a conical surface 14a of a thrust plate 14 and an inclined surface 25a, opposed in a radial direction to the conical surface, of a ring-form member 25. The interface of lubrication oil 8 held at the thrust bearing part 22 is formed in the taper seal part 28.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure bearing, a spindle motor using the same, and a disk drive equipped with this spindle motor.

[0002]

2. Description of the Related Art As a bearing means for rotatably supporting a rotor of a spindle motor, for example, JP-A-8-1
As disclosed in Japanese Patent Application Laid-Open No. 05445, a pair of thrust plates are arranged at upper and lower portions in the axial direction of a fixed shaft, and an outer peripheral surface of a fixed shaft located between the pair of thrust plates and a rotor radially opposed thereto. A dynamic pressure that holds the lubricating oil (oil) with the inner peripheral surface and moves the lubricating oil in a predetermined direction by the rotation of the rotor to generate a supporting pressure for supporting the radial load applied to the rotor. A radial bearing is formed by forming a groove for pressure generation, and lubricating oil is retained between the axial inner surfaces of the thrust plates facing each other and the axial axial surfaces of the rotor axially opposed to each other. Then, the rotation of the rotor moves the lubricating oil in a predetermined direction to form a dynamic pressure generating groove for generating a supporting pressure for supporting the load in the thrust direction applied to the rotor. And a pair of thrust bearing portions, and first and second taper seal portions having varying axial and radial intervals between the thrust plate and the opposing rotor and seal cap. Some have a structure in which the first and second taper seal portions prevent the lubricating oil from leaking to the outside of the bearing.

In such a structure, since the structure of the bearing portion is symmetrical and the same characteristic is given to any posture, it is easy to obtain stable rotation of the spindle motor.
Further, since it is sufficient to form the dynamic pressure generating groove only on one surface side of the thrust plate, there is an advantage that the yield of member processing is improved.

[0004]

In the oil seal structure in the above-mentioned conventional example, the first and second taper seal portions are continuously formed, and the interface position of the oil in the normal state is the outer circumference of the thrust plate. The first dimension in which the size of the radial gap formed between the surface and the inner peripheral surface of the rotor changes
In the second taper seal part where the axial dimension formed between the upper surface of the thrust plate and the lower surface of the seal cap changes due to the action of centrifugal force during steady rotation. By intruding and increasing the volume of the seal part, and directing the oil interface inward in the radial direction, centrifugal force is used to press the oil interface toward the thrust bearing part side and prevent oil from flowing out. It has a structure.

The taper seal portion gradually expands the gap size of the gap formed in the seal portion as it is separated from the bearing portion, thereby causing a gap in the capillary force depending on the position where the oil interface is formed, and holding it by the bearing portion. When the amount of oil decreases, it has the function of supplying oil from the taper seal part, and when the volume of oil held in the bearing part increases due to temperature rise etc., the increased amount is accommodated. ing.

However, when the rotation speed of the spindle motor is further increased, the influence of centrifugal force on the oil is increased, so that the inflow amount of the oil from the first taper seal portion to the second taper seal portion is increased. . At this time,
Due to dimensional restrictions, when the second taper seal portion is provided in the direction orthogonal to the rotary shaft core, a sufficient volume cannot be secured, and there is a concern that oil will flow out of the bearing.

Further, due to the increase in the influence of centrifugal force due to the increase in speed, the oil is peeled off from the outer peripheral surface of the thrust plate in the first taper seal portion and sticks to the inner peripheral surface of the rotor.

At the time of high speed rotation, in the thrust bearing portion,
The centrifugal force causes the oil to move outward in the radial direction, and the amount of oil retained is reduced. As described above, the taper seal part has a function of supplying oil when the amount of oil retained in the bearing part decreases,
When the oil is stuck to the inner peripheral surface of the rotor due to the action of the centrifugal force, the continuity of the oil is lost and the oil is insufficiently supplied to the bearing portion. Therefore, in the thrust bearing portion, not only the amount of oil held becomes insufficient, the bearing rigidity decreases and the rotation support becomes unstable, but also contact sliding between the thrust plate and the rotor occurs and seizure occurs. .

According to the present invention, the seal strength can be strengthened and the oil supply to the thrust bearing portion can be stabilized, and the volume in the taper seal portion can be increased to correspond to a further high speed rotation, and a sufficient amount can be obtained. It is an object of the present invention to provide a dynamic pressure bearing capable of holding the oil, a spindle motor using the dynamic pressure bearing, and a disk drive device including the spindle motor.

[0010]

In order to solve the above problems, a dynamic pressure bearing of the present invention comprises a shaft, an annular thrust plate projecting radially outward from an outer peripheral surface of the shaft, and A hollow formed with a step portion facing the outer peripheral surface of the thrust plate and one surface in the axial direction, and a radial inner peripheral surface continuous to the step portion and radially opposed to the outer peripheral surface of the shaft with a minute gap therebetween. A dynamic pressure bearing having a cylindrical sleeve, wherein lubricating oil is retained between an outer peripheral surface of the shaft and a radial inner peripheral surface of the sleeve,
A radial bearing portion is configured by providing a dynamic pressure generating groove for inducing a dynamic pressure in the lubricating oil, and the lubricating oil is held between one surface in the axial direction of the thrust plate and the step portion. A thrust bearing portion is configured by providing a dynamic pressure generating groove for inducing dynamic pressure in the lubricating oil,
The thrust plate has a substantially conical shape formed in an inclined surface shape so that the outer diameter thereof is reduced as at least a part of the outer peripheral surface thereof is distant from one surface in the axial direction,
On the inner peripheral surface of the stepped portion facing the inclined outer peripheral surface of the thrust plate, an inner peripheral surface is formed in an inclined surface shape so that the inner diameter expands from the radially inner side to the outer side. A ring-shaped member is mounted, and between the ring-shaped member and the substantially conical thrust plate, the thrust is inclined from the outer side toward the inner side in the radial direction with respect to the axis of rotation. It is characterized in that a tapered seal portion is formed in which the size of the gap gradually increases as the distance from the bearing portion increases, and an interface of the lubricating oil held by the thrust bearing portion is formed in the tapered seal portion ( Claim 1).

As described above, according to the present invention, in the dynamic pressure bearing which utilizes lubricating oil such as oil as the working fluid, the taper seal on the thrust bearing portion side has a shape inclined with respect to the rotation axis so that the rotation can be improved. Compared to the case where the taper seal part is configured in the direction parallel or orthogonal to the axis, the volume inside the taper seal part increases, and the lubricating oil does not split due to centrifugal force even during high speed rotation. A structure that allows stable supply of lubricating oil from the bearing to the thrust bearing is adopted.

With this structure, the lubricating oil is not peeled off from the outer peripheral surface of the thrust plate by centrifugal force even during high speed rotation, and the continuity of the lubricating oil is not lost at the outer peripheral portion of the thrust plate. . Further, since the interface of the lubricating oil is oriented in the direction inclined with respect to the axis of rotation, the centrifugal force acts in the direction of pressing down the interface of the lubricating oil, so that the seal strength is maintained high.

Further, in the dynamic pressure bearing of the present invention, a pair of thrust plates are disposed adjacent to both ends of the radial inner peripheral surface, and the stepped portion on which the ring-shaped member is mounted is also of the pair. One pair is formed on the sleeve corresponding to the thrust plate (claim 2).

A thrust plate and a step portion for accommodating the thrust plate are arranged adjacent to each other at both ends of the radial inner peripheral surface of the radial bearing portion so that the thrust plate is thrust from both end sides of the radial bearing portion. The bearing forces of the bearing portions act in opposite directions, and the load support in the axial direction is stabilized.

Further, in the dynamic pressure bearing of the present invention, the stepped portion is provided with an annular flat plate-shaped member having a central opening on the axially outer side of the ring-shaped member. An inner peripheral surface of the shaft faces the outer peripheral surface of the shaft with a minute gap therebetween, and the taper seal portion is defined between the inner peripheral surface of the flat plate-shaped member and the outer peripheral surface of the shaft. It is characterized in that it is opened to the outside through a minute gap (claim 3).

By setting the radial dimension of the gap between the outer peripheral surface of the shaft and the inner peripheral surface of the flat plate-shaped member to be as small as possible, the vapor generated by the vaporization of the lubricating oil is exposed to the outside. Since the outflow resistance can be increased and the vapor pressure near the interface of the lubricating oil can be kept high, further evaporation of the lubricating oil can be effectively prevented.

In addition, in the dynamic pressure bearing of the present invention, the dynamic pressure generating groove formed in the thrust bearing portion induces a dynamic pressure acting radially inward on the lubricating oil. As described above, the pump-in type spiral groove is formed, and the dynamic pressure generating groove formed in the radial bearing portion induces a dynamic pressure acting on the lubricating oil toward the thrust bearing portion side. As described above, a herringbone groove having an unbalanced shape in the axial direction is formed, and the lubricating oil is continuously retained between the thrust bearing portion and the radial bearing portion. (Claim 4).

By using a pump-in type spiral groove as the dynamic pressure generating groove of the thrust bearing portion, the outer diameter of the thrust plate can be reduced, and the peripheral speed can be reduced. Since the viscous resistance of the lubricating oil is smaller than that of the herringbone groove, it is possible to suppress the loss in the bearing portion and improve the efficiency.

Further, in the dynamic pressure bearing of the present invention, between the outer peripheral surface of the shaft and the radial inner peripheral surface, there is an air intervening portion communicating with the outside air at a substantially central portion in the axial direction of the radial inner peripheral surface. And a pair of the radial bearing portions are formed adjacent to both ends in the axial direction of the air intervening portion (claim 5).

By forming an air intervening portion between the outer peripheral surface of the shaft and the radial inner peripheral surface and forming a pair of radial bearing portions on both sides in the axial direction of the air interposing portion, the bearing span (bearing of the radial bearing portion (bearing (Interval distance) is expanded and the radial load is stabilized, so it is possible to quickly restore the normal state of the shaft tilting or touching that occurs when external vibration or shock is applied. Is possible.

Further, the spindle motor of the present invention includes a bracket for holding the stator, a rotor that rotates relative to the bracket, and a rotor magnet that is fixed to the rotor and that cooperates with the stator to generate a rotating magnetic field. And a dynamic pressure bearing for supporting the rotation of the rotor, wherein the dynamic pressure bearing is the dynamic pressure bearing according to any one of claims 1 to 5 (claim 6) ).

By using the above-mentioned dynamic pressure bearing as the bearing of the spindle motor, not only high-speed and high-accuracy rotational support is possible, but also seizure of the bearing is prevented, so that reliability and durability are improved. It becomes possible to make it excellent.

Further, the disk drive device of the present invention is a disk drive device in which a disc-shaped recording medium capable of recording information is mounted, and a housing and a spindle motor fixed inside the housing and rotating the recording medium. A disk drive device having an information access unit for writing or reading information at a required position on the recording medium, wherein the spindle motor is the spindle motor according to claim 6. Claim 7).

The spindle motor of the present invention not only enables high-speed and high-accuracy rotation support, but also has excellent reliability and durability, and therefore requires high rotation accuracy, durability and reliability. The present invention can be preferably used in a disk drive device that drives a hard disk, but is not limited to this, and also in a disk drive device that drives a fixed type recording medium such as a hard disk or a detachable recording medium such as a CD-ROM or DVD. It will be available as well.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a dynamic pressure bearing according to the present invention, a spindle motor using the dynamic pressure bearing, and a disk drive equipped with the spindle motor will be described below with reference to FIGS. Although described, the present invention is not limited to the examples described below.

The illustrated spindle motor includes a bracket 2
And a shaft 4 whose one end is fitted and fixed in the central opening 2a of the bracket 2, and a rotor 6 which is relatively rotatable with respect to the shaft 4. Rotor 6
A rotor hub 6a on which a recording disc (illustrated as a disc plate 53 in FIG. 3) is placed on the outer peripheral portion, and an axis on the shaft 4 via a minute gap which is located on the inner peripheral side of the rotor hub 6a and in which lubricating oil 8 is retained And a supported sleeve 6b. A rotor magnet 10 is fixed to the inner peripheral portion of the rotor hub 6a by means such as adhesion, and the bracket 2 is opposed to the rotor magnet 10 in the radial direction.
The stator 12 is attached to the.

A through hole 6c is formed in the sleeve 6b in the axial direction so that the inner peripheral surface forms a minute gap for retaining the lubricating oil 8 between the inner peripheral surface and the outer peripheral surface of the shaft 4 in the approximate center thereof. The upper and lower parts of the shaft 4 have a disk-shaped upper thrust plate 1 protruding outward in the radial direction.
4 and the lower thrust plate 16 are attached respectively.

Upper step portions 6d and lower step portions 6e having a diameter larger than the outer diameters of the upper and lower thrust plates 14 and 16 are formed at portions of the through hole 6c corresponding to the upper thrust plate 14 and the lower thrust plate 16. Has been done. The open side ends of the upper step 6d and the lower step 6e are closed by an upper seal cap 18 and a lower seal cap 20.

A small amount of lubricating oil 8 is retained between the flat portion extending from the inner peripheral portion of the through hole 6c to the inner peripheral surface of the upper step portion 6d and the lower surface (inner surface in the axial direction) of the upper thrust plate 14. A gap is formed, and a dynamic pressure generating groove 22 for generating a dynamic pressure in the lubricating oil 8 is formed in the plane portion of the upper stepped portion 6d, and the upper thrust bearing portion 24 is formed. Is configured.

Further, from the inner peripheral portion of the through hole 6c to the lower step portion 6e.
A minute gap for holding the lubricating oil 8 is formed between the flat surface portion reaching the inner peripheral surface of the lower thrust plate 16 and the upper surface (the inner surface in the axial direction) of the lower thrust plate 16, and the flat surface portion of the lower step portion 6e. The lower thrust bearing portion 26 is configured by forming a dynamic pressure generating groove 22 for generating a dynamic pressure in the lubricating oil 8 with the rotation of the rotor 6. These thrust bearing portions 24,
As the dynamic pressure generating groove 22 formed in 26, a pump-in type spiral groove is used so that the generated dynamic pressure pumps the lubricating oil 8 toward the shaft 4.
The dynamic pressure generating grooves are formed on the upper and lower thrust plates 1
4, 16 on the inner surface in the axial direction or the plane portions of the upper and lower step portions 6d and 6e and the upper and lower thrust plates 1
It is also possible to form both surfaces on the inner side surfaces in the axial direction of 4, 16.

As described above, when the dynamic pressure generating grooves 22 of the upper and lower thrust bearing portions 24 and 26 are spiral grooves, a herringbone groove formed by combining a pair of spiral grooves opposite to each other is used. Since the outer diameters of the upper and lower thrust plates 14 and 16 can be made smaller than those of the above, it is possible to reduce the influence of the lower thrust bearing portion 26 on the magnetic circuit portion including the rotor magnet 10 and the stator 12. It is possible to obtain a sufficient driving torque. Further, since the spiral groove has a smaller viscous resistance of the lubricating oil 8 generated when the spindle motor rotates as compared with the herringbone groove, the loss in the upper and lower thrust bearing portions 24 and 26 is reduced, and the electrical efficiency of the spindle motor is improved. It is possible to increase the power consumption and suppress the power consumption.

The outer peripheral surface of the upper thrust plate 14 extends from the outer peripheral end portion of the inner side surface in the axial direction substantially parallel to the axis of rotation as shown in a partially enlarged view in FIG. It is formed on the conical surface 14a that is inclined inward in the direction with respect to the axis of rotation. Further, on the inner peripheral surface of the upper step portion 6d, a small step portion 6d1 formed by cutting out a part of the inner peripheral surface has an inner peripheral surface radially opposed to the conical surface 14a of the upper thrust plate 14. The size of the gap formed between the conical surface 14a is the upper seal cap 18
An upper ring-shaped member 25 formed on the inclined surface 25a so as to gradually expand as it is separated from the side, that is, the upper thrust bearing portion 24, is fixed by means such as adhesion or press fitting.

The lubricating oil 8 held in the upper thrust bearing portion 24 passes through a gap substantially parallel to the axis of rotation formed between the upper thrust plate 14 and the inner peripheral surface of the upper step portion 6d, and then the upper portion. An interface is formed and held in a gap formed between the conical surface 14a of the thrust plate and the inclined surface 25a of the upper ring-shaped member 25, in which the size of the gap gradually increases toward the upper seal cap 18 side. ing. That is, the conical surface 14 of the upper thrust plate
The gap formed between a and the inclined surface 25 a of the upper ring-shaped member 25 functions as the upper taper seal portion 28.

In this case, the inclination angle of the conical surface 14a of the upper thrust plate 14 is set in the range of about 20 ° to 35 °, preferably about 26 ° to 33 ° with respect to the axis of rotation, and the upper ring shape is used. The inclination angle of the inclined surface 25a of the member 25 is set in the range of about 15 to 30 degrees, preferably about 20 to 27 degrees with respect to the axis of rotation. Further, the taper angle of the upper taper seal portion 28 formed between the conical surface 14a and the inclined surface 25a is about 2 degrees to 15 degrees.
And preferably in the range of about 5 to 10 degrees.

Although not shown in detail, the outer peripheral portion of the lower thrust plate 16 has the same space as the outer peripheral portion of the upper thrust plate 14 between the outer peripheral portion of the lower thrust plate 16 and the lower ring-shaped member 27 which faces the radial direction. A lower taper seal portion 30 is formed in the configuration.

At this time, the minimum gap size of the upper taper seal portion 28 is a gap formed between the outer peripheral surface of the upper thrust plate 14 and the inner peripheral surface of the upper step portion 6d and substantially parallel to the axis of the rotary shaft. Is set to be larger than the gap dimension of the upper thrust bearing portion 24, and the gap dimension of the gap of the upper thrust bearing portion 24 is set to the outer peripheral surface of the upper thrust plate 14 and the upper step portion 6d.
It is set to be smaller than the clearance dimension of the clearance formed between the inner peripheral surface and the substantially parallel to the axis of rotation.

That is, when the amount of the lubricating oil 8 retained in the upper thrust bearing portion 24 is reduced, the lubricating oil 8 retained in the upper taper seal portion 28 is reduced by the capillary force to the outer peripheral surface of the upper thrust plate 14. And upper step 6
It is supplied to the upper thrust bearing portion 24 through a gap formed between the inner peripheral surface of d and substantially parallel to the rotation axis.

Conversely, when the lubricating oil 8 held by the upper thrust bearing portion 24 expands in volume due to a temperature rise or the like, the interface of the lubricating oil 8 moves in a direction in which the clearance dimension of the upper taper seal portion 2 expands. By doing so, the increased amount of the lubricating oil 8 is accommodated in the upper taper seal portion 28.

Further, since the upper taper seal portion 28 is constructed so as to be inclined with respect to the axis of rotation, the interface of the lubricating oil 8 is also
The upper taper seal portion 28 is formed so as to face inward in the radial direction according to the inclination angle of the upper taper seal portion 28. Therefore, when the spindle motor rotates, the interface of the lubricating oil 8 is pressed against the upper thrust bearing portion 24 side by the centrifugal force, so that the seal strength is strengthened and the upper thrust plate 14 forming the upper taper seal portion 28 is formed. Since the conical surface 14 and the slanted surface 25a of the upper ring-shaped member 25 are mutually slanted with respect to the axis of rotation, the lubricating oil 8 is contaminated by the centrifugal force due to the centrifugal force.
It will not be peeled off and will not stick to the inclined surface 25a. Therefore, even in the spindle motor rotating at high speed, the lubricating oil 8 is prevented from flowing out from the seal portion, and the continuity of the lubricating oil 8 retained from the upper taper seal portion 28 to the upper thrust bearing portion 24 is lost, and the upper portion is lost. The supply of the lubricating oil 8 from the upper taper seal portion 28 to the thrust bearing portion 24 does not become insufficient.

In addition, by inclining the upper taper seal portion 28 with respect to the axis of rotation, the size of the seal portion can be increased as compared with the case where the taper seal portion is formed in a direction parallel or orthogonal to the axis of rotation. Can be made larger, thus increasing the volume.

Further, the upper and lower thrust bearing portions 24,
By forming the dynamic pressure generating grooves 22 of 26 as pump-in type spiral grooves in which the dynamic pressures generated respectively pump the lubricating oil 8 inward in the radial direction, the upper and lower thrust bearing portions 24, 26 are formed. The generated dynamic pressure has a pressure gradient that increases as it goes inward in the radial direction.
The bubbles generated in the lubricating oil 8 held in the upper and lower thrust bearing portions 24 and 26 during the filling of the air move from the radial inside of the bearing with high pressure to the radial outside of the pressure with low pressure. , The upper and lower tapered seal portions 2 having the largest gap size and the lowest pressure among the gaps in which the lubricating oil 8 is finally held.
8 and 30 move to the interface side of the lubricating oil 8 and are released into the air.

An annular recess 4a, which is a pair of inclined surfaces inclined inward in the axial direction, is formed in the substantially central portion of the outer peripheral surface of the shaft 4 so as to enlarge the gap between the inner peripheral surface of the through hole 6c. And the shaft 4 is formed in the recess 4a.
A communication hole 36 that communicates with the air formed therein opens.

The communicating hole 36 is formed in a vertical hole penetrating the shaft 4 in the axial direction, a first opening 36a opened in a recess 4a extending in the radial direction from the vertical hole, and a lower second taper seal portion 30. It is composed of a second opening 36b which is continuous and opens into a space communicating with the outside of the bearing through a minute gap defined between the inner peripheral surface of the lower seal cap 20 and the outer peripheral surface of the shaft 4. It should be noted that the vertical holes are sealed by sealing members 38 and 40 made of an elastic member such as rubber after the shaft 4 has been machined and cleaned so that both openings of the shaft 4 are opened. That is, the space on the inner side of the bearing with respect to the upper and lower seal caps 18 and 20 is air only through a minute gap formed between the inner peripheral surfaces of the upper and lower seal caps 18 and 20 and the outer peripheral surface of the shaft 4. Is in communication with.

The air taken into the communication hole 36 through the second opening 36b is a concave portion 4c opened by the first opening 36a.
And an inner peripheral surface of the through hole 6c, an annular gas interposition portion 42 is formed, and the gas interposition portion 42 holds in a minute gap between the outer peripheral surface of the shaft 4 and the inner peripheral surface of the through hole 6c. The lubricating oil 8 thus formed forms an interface between the lubricating oil 8 in a tapered gap formed between the pair of inclined surfaces of the concave portion 4a and the inner peripheral surface of the through hole 6c, and is divided vertically in the axial direction. It

The rotor 6 is provided on the inner peripheral surface of the through hole 6c at a portion corresponding to the lubricating oil 8 which is divided into upper and lower parts and held.
5, a dynamic pressure generating groove 44 for generating a dynamic pressure in the lubricating oil 8 is formed, and an upper radial bearing portion 46 and a lower radial bearing portion 48 are configured. The dynamic pressure generating grooves 44 formed in the upper and lower radial bearing portions 46, 48 are such that the dynamic pressures generated respectively cause the lubricating oil 8 to move axially outward, in other words, the adjacent upper and lower thrust bearing portions. So that it is pumped towards 24, 26,
A herringbone groove with an unbalanced shape in the axial direction is used.

By filling the dynamic pressure generating grooves 44 of the upper and lower radial bearing portions 46 and 48 with the lubricating oil 8 under pressure to the upper and lower thrust bearing portions 24 and 26, respectively, the lubricating oil 8 is filled. Air bubbles generated in the lubricating oil 8 held by the upper and lower radial bearing portions 46 and 48 at the time of movement move from the bearing portion having high pressure to the interface side with the gas interposed portion 42 having low pressure, and It is opened from 42 to the air outside the bearing through the communication hole 36.

In this structure, the dynamic pressure generating means 22 formed in the upper and lower thrust bearing portions 24 and 26 is a spiral groove, and a sufficient load supporting pressure cannot be generated by itself, but the adjacent upper and lower thrust bearing portions 24 and 26 cannot be generated. Radial bearing part 4
Since an unbalanced herringbone groove is formed in each of the shafts 6 and 48 as the dynamic pressure generating groove 44, the lubricating oil 8 faces each other by the spiral groove and the herringbone groove when the spindle motor rotates. Since the pressure is fed in the direction, the dynamic pressure required to support the load applied to the rotor 6 is generated and supported by the cooperation of both bearing portions.

The upper and lower thrust bearing portions 24,
26 and upper and lower radial bearing parts 4 adjacent to them
Since the lubricating oil 8 is continuously held in the bearings 6, 48, and the gas interposition portion 42 separating the upper and lower radial bearing portions 46, 48 communicates with the air through the communication hole 36, the upper and lower portions. Lubricating oil 8 for the upper and lower thrust bearing portions 24, 26 located in the taper seal portions 28, 30
Interface of the lubricating oil 8 of the upper and lower radial bearing portions 46, 48 located in the tapered gap defined between the interface between the upper surface and the lower surface of the recess 4a and the through hole 6c. Becomes

Therefore, for example, due to centrifugal force, external impact on the spindle motor, application of vibration, etc., the interface between the lubricating oil 8 in the upper and lower taper seal portions 28, 30 or the pair of concave portions 4a. When one of the interfaces of the lubricating oil 8 in the tapered gap defined between the inclined surface and the through hole 6c moves in a direction away from the bearing portion, the other interface also has a tapered gap in which each interface is located. By moving the inside to a position where the radii of curvature of the interface of the lubricating oil 8 become equal to each other, it is balanced, and is stably held without impairing the sealing effect.

The upper and lower radial bearing parts 46,
Reference numeral 48 designates adjacent upper and lower thrust bearing portions 24, 26.
That is, the lubricating oil 8 is continuous, and only one point maximizes the dynamic pressure from the interface of one lubricating oil 8 to the interface of the other lubricating oil 8, and there is no point that it minimizes. Therefore,
Even if bubbles are included in the lubricating oil 8, the pressure can be automatically removed from the interface located in the tapered gap into the air outside the bearing.

As described above, the bubbles generated in the lubricating oil 8 held in each bearing portion are gradually moved to the low pressure side and are released into the air from the interface of each lubricating oil 8. The lubricating oil 8 does not stay in the lubricating oil 8 held in the bearing portion, and the bubbles expand and increase in volume when the temperature of the spindle motor rises, whereby the lubricating oil 8 is prevented from leaking to the outside of the bearing. Moreover, since a special structure for discharging bubbles is not required, the structure of the spindle motor can be simplified.

By setting the radial dimension of the gap defined between the inner peripheral surfaces of the upper and lower seal caps 18 and 20 and the outer peripheral surface of the shaft 4 as small as possible, the upper and lower seal caps are rotated when the spindle motor rotates. Lower thrust plates 14, 16 and upper and lower seal caps 1
8 and 20, a radial gap defined by the rotor 6 and the radial gap defined by the outer peripheral surface of the shaft 4 and the upper and lower seal caps 18, 20 is generated in accordance with the rotation of the rotor 6. Differences occur in the velocity of the air stream. Therefore, the resistance of the steam (oil mist) generated by the vaporization of the lubricating oil 8 to the outside of the spindle motor is increased to keep the vapor pressure near the interface of the lubricating oil 8 high, so that further evaporation of the lubricating oil 8 occurs. Can be prevented.

If an oil repellent agent made of, for example, a fluorine-based material is applied to each of these surfaces, the lubricating oil 8 will not move due to an oil migration phenomenon when the spindle motor is stopped when centrifugal force does not act on the lubricating oil 8. It can be more effectively prevented from leaking to the outside.

FIG. 3 is a schematic diagram showing the internal structure of a general disk drive device 50. The inside of the housing 51 forms a clean space in which dust and the like are extremely small, and a disk-shaped disc plate 53 for storing information therein.
A spindle motor 52 mounted with is installed.
In addition, a head moving mechanism 57 for reading / writing information from / to the disk plate 53 is arranged inside the housing 51. The head moving mechanism 57 supports the head 56 for reading / writing information on the disk plate 53, and the head. The arm 55, the head 56, and the arm 55 are connected to the disk plate 53.
It is composed of an actuator unit 54 that moves it to a desired position above.

By using the spindle motor shown in FIG. 2 as the spindle motor 52 of the disk drive device 50, not only high-speed and high-accuracy rotation support is possible, but also reliability and durability are improved. Excellent one.

Although one embodiment of the dynamic pressure bearing according to the present invention, the spindle motor using the same, and the disk drive device equipped with this spindle motor has been described above, the present invention is not limited to this embodiment. Various changes and modifications can be made without departing from the scope of the present invention.

For example, the upper and lower thrust plates 1
The gaps formed between the inner peripheral surfaces of the upper and lower step portions 6d and 6e and the inner peripheral surfaces of the upper and lower step portions 6d and 6e are substantially parallel to the axis of rotation when the upper and lower thrust plates 14 and 16 are processed. Upper and lower thrust plates 1 for holding
It is provided because it is necessary to form a flat surface on the outer peripheral portion of the upper and lower thrust plates 14, 1 without providing this.
It is also possible to form a conical surface continuously at the outer peripheral end of the inner surface of 6 in the axial direction.

[0058]

According to the dynamic pressure bearing of the first aspect of the present invention, the volume of the taper seal portion is increased, and the lubricating oil is not divided by centrifugal force even during high speed rotation. Lubricating oil can be stably supplied from the taper seal portion to the thrust bearing portion.

According to the hydrodynamic bearing of the second aspect of the present invention, the supporting forces by the thrust bearing portions act in opposite directions from both ends of the radial bearing portion, so that the axial load is stabilized. It becomes possible to support.

According to the hydrodynamic bearing of the third aspect of the present invention, the radial dimension of the minute gap defined between the inner peripheral surface of the seal cap and the outer peripheral surface of the shaft is made as small as possible. By setting it, the outflow resistance of the steam generated by the evaporation of the lubricating oil to the outside can be increased and the steam pressure near the interface of the lubricating oil can be kept high, so that further evaporation of the lubricating oil can be effectively prevented. It will be possible.

According to the dynamic pressure bearing of the fourth aspect of the present invention, it is possible to suppress the loss in the bearing portion and improve the efficiency.

According to the hydrodynamic bearing of the fifth aspect of the present invention, the tilting or touching of the shaft, which occurs when external vibration or shock is applied, is restored to a normal state in a short time. It becomes possible.

According to the spindle motor of the sixth aspect of the present invention, not only the high-speed and high-accuracy rotation support is possible, but also seizure of the bearing portion is prevented, so that the reliability and durability are improved. It becomes possible to be excellent.

According to the disk drive apparatus of the seventh aspect of the present invention, the disk drive apparatus can be preferably used in a disk drive apparatus which requires high rotation accuracy, durability and reliability.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view schematically showing a schematic configuration of a spindle motor according to an embodiment of the present invention.

2 is a partially enlarged cross-sectional view schematically showing a schematic configuration near an upper thrust plate of the spindle motor shown in FIG.

FIG. 3 is a schematic diagram showing a schematic configuration of a disk drive device including the spindle motor shown in FIG.

[Explanation of symbols]

4 shafts 6b sleeve 8 Lubricating oil 14,16 Thrust plate 22,44 Dynamic pressure generation groove 24,26 Thrust bearing part 25,27 ring-shaped member 28,30 Taper seal part 46,48 Radial bearing

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) H02K 7/08 H02K 7/08 A 5H621 B 21/22 21/22 MF term (reference) 3J011 AA12 BA02 BA08 CA02 JA02 KA02 KA03 MA12 MA24 3J016 AA02 AA03 BB22 5D109 BB13 BB17 BB21 BB22 BB40 5H605 BB05 BB10 BB14 BB19 CC04 DD09 EB02 EB06 5H607 BB01 BB07 BB09 BB14 BB17 BB25 GG01 GG02 GG15H621 GA19H 621

Claims (7)

[Claims] 1. A shaft, an annular thrust plate projecting radially outward from an outer peripheral surface of the shaft, a step portion facing the outer peripheral surface of the thrust plate and one surface in the axial direction, and the step. A hollow cylindrical sleeve continuous with the outer peripheral surface of the shaft and radially inner peripheral surfaces facing each other in a radial direction with a minute gap, the outer peripheral surface of the shaft. Lubricating oil is retained between the inner peripheral surface of the sleeve and the radial inner peripheral surface of the sleeve, and a radial bearing portion is configured by providing a dynamic pressure generating groove for inducing dynamic pressure in the lubricating oil, and the axial line of the thrust plate. Lubricating oil is held between the one surface in the direction and the step portion, and a thrust bearing portion is configured by providing a dynamic pressure generating groove for inducing dynamic pressure in the lubricating oil, and the thrust plate is , Outside At least a part of the peripheral surface has a substantially conical shape formed in an inclined surface shape so that the outer diameter decreases as the distance from the one surface in the axial direction increases, and the inclined surface-shaped outer periphery of the thrust plate A ring-shaped member having an inclined inner peripheral surface is mounted on the inner peripheral surface of the step facing the surface so that the inner diameter expands from the radially inner side to the outer side. , A gap between the ring-shaped member and the substantially conical thrust plate that is inclined from the outer side to the inner side in the radial direction with respect to the rotation axis and further away from the thrust bearing portion. A dynamic pressure bearing characterized in that a taper seal portion whose size gradually increases is formed, and an interface of the lubricating oil held by the thrust bearing portion is formed in the taper seal portion. 2. The pair of thrust plates are disposed adjacent to both ends of the radial inner peripheral surface, and the stepped portion on which the ring-shaped member is mounted corresponds to the pair of thrust plates. The dynamic pressure bearing according to claim 1, characterized in that a pair is formed in the bearing. 3. The stepped portion is provided with an annular flat plate-shaped member having a central opening on the axially outer side of the ring-shaped member, and the inner peripheral surface of the flat plate-shaped member has the shaft portion. The taper seal portion is opened to the outside through a minute gap defined between the inner peripheral surface of the flat plate-shaped member and the outer peripheral surface of the shaft. The dynamic pressure bearing according to claim 1 or 2, characterized in that 4. A pump-in type spiral groove is formed in the dynamic pressure generating groove formed in the thrust bearing portion so that a dynamic pressure acting radially inward on the lubricating oil is induced. Further, the dynamic pressure generating groove formed in the radial bearing portion is unbalanced in the axial direction so that the dynamic pressure acting on the lubricating oil toward the thrust bearing portion side is induced. 4. A herringbone groove having a shape is formed, and the lubricating oil is continuously retained between the thrust bearing portion and the radial bearing portion. Dynamic pressure bearing described in. 5. An air intervening portion communicating with the outside air is formed between the outer peripheral surface of the shaft and the radial inner peripheral surface at a substantially central portion in the axial direction of the radial inner peripheral surface, and the radial bearing. 5. A pair of parts are formed adjacent to both ends in the axial direction of the air interposition part.
The dynamic pressure bearing according to any one of 1. 6. A bracket that holds a stator, a rotor that rotates relative to the bracket, a rotor magnet that is fixed to the rotor and that generates a rotating magnetic field in cooperation with the stator, and that supports the rotation of the rotor. In the spindle motor including a dynamic pressure bearing, the dynamic pressure bearing is the dynamic pressure bearing according to any one of claims 1 to 5. 7. A disk drive device in which a disc-shaped recording medium capable of recording information is mounted, a housing, a spindle motor fixed inside the housing to rotate the recording medium, and a required position of the recording medium. A disk drive device having an information access unit for writing or reading information to and from the disk drive device, wherein the spindle motor is the spindle motor according to claim 6.