JP2002295472A - Dynamic pressure fluid bearing device and motor provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dynamic pressure fluid bearing device capable of reducing the influence of a centrifugal force acting on lubrication liquid. SOLUTION: This dynamic pressure fluid bearing device is provided with a shaft body 104, a sleeve body 106 having a sleeve part 122 sleeve-fitted in a shaft part 108 of the shaft body 104 and a thrust support part 128 fitted externally in a thrust plate part 110, radial bearing parts 136, 138 for supporting the shaft part 108 and the sleeve part 122 so as to rotate relatively and freely, thrust bearing parts 144, 146 for supporting the thrust plate part 110 and the thrust support part 128 so as to rotate relatively and freely, and lubrication liquid filled into these bearing parts. The sleeve body 106 is provided with a second ventilation hole 158 for communicating with the outside, and a second enlarged clearance part 162 on an inner peripheral face of the thrust support part 128 communicates with the second ventilation hole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrodynamic bearing device having a shaft and a sleeve which are relatively rotatable via a lubricating liquid, and a motor having the same.

[0002]

2. Description of the Related Art As a conventional hydrodynamic bearing device, for example, one having a structure shown in FIG. 6 is known. This known hydrodynamic bearing device includes a rotating shaft 2 and a sleeve 4 fitted with the rotating shaft 2, and a lubricating liquid (lubricating oil) is provided between the rotating shaft 2 and the sleeve 4. Is filled. The rotary shaft body 2 has a shaft portion 6 and a thrust plate portion 8 provided at one end of the shaft portion 6.
And a thrust support portion 12 provided on one end side of the sleeve portion 10. The shaft portion 6 is fitted to the sleeve portion 10, and the thrust plate portion 8 is fitted to the thrust support portion 12 outside.

[0003] Between the sleeve portion 10 and the shaft portion 6,
A pair of radial bearings 14, 1 spaced apart in the axial direction
The radial dynamic pressure bearings 14 and 16 have a herringbone groove for generating dynamic pressure, and an enlarged gap 18 is provided between the pair of radial bearings 14 and 16.
The enlarged gap portion 18 communicates with the outside via a ventilation hole 20 provided in the sleeve body 4.

Further, a thrust support portion 8 and a thrust plate portion 8
A pair of thrust bearing portions 22 and 24 are provided on both sides of the thrust plate portion 8 between the thrust bearing portions 22 and 24.
24 has a herringbone groove. The shaft portion 6 of the shaft body 2 is provided with an axial ventilation hole 26 extending in the axial direction. The axial ventilation hole 26 and the enlarged gap portion 18 are connected via a radial ventilation hole 28. An axial breathing hole 30 is provided at a connection portion between the thrust plate portion 8 and the shaft portion 6 so as to penetrate the thrust plate portion 8 in the axial direction, and the thrust plate portion 8 is provided with the axial breathing hole 30. A radial breathing hole 32 communicating with the outer peripheral surface of the thrust plate 8 is provided in the radial direction.

In the hydrodynamic bearing device having such a configuration, the radial bearing portion 14 (upper one in FIG. 6) is used.
The air bubbles which can be mixed in the lubricating liquid can be released to the outside from the upper end between the upper end of the sleeve portion 10 and the shaft portion 6 and to the lower portion through the enlarged gap portion 18 and the vent hole 20. Bubbles that can be mixed in the lubricating liquid in the other radial bearing portion 16 (the lower one in FIG. 6) pass through the enlarged gap portion 18 and the ventilation hole 20 in the upper portion and the axial breathing hole 3 in the lower portion.
0, each can be released to the outside through the axial vent 26, the radial vent 32, the enlarged gap 18 and the vent 20. Bubbles that can be mixed in the lubricating fluid in each of the thrust bearing portions 22 and 24 include an axial respiratory hole 30, an axial vent 26, a radial vent 28,
The radial breathing hole 32, the axial breathing hole 30,
Axial vent 26, radial vent 28, enlarged gap 18
And can be released to the outside through the vent hole 20. In this manner, both ends of the radial bearings 14 and 16 in the axial direction and both ends of the thrust bearings 22 and 24 in the radial direction, that is, portions where the lubricating fluid pressure is low in the dynamic pressure generating grooves are communicated with the outside air. By communicating like this,
In those portions, bubbles separated from the lubricating liquid are released to the outside, thus preventing the outflow / dissipation of the lubricating liquid due to bubble expansion when the temperature rises or the air pressure drops.

[0006]

In recent years, a hard disk drive has been incorporated in portable equipment such as a notebook personal computer, and a spindle motor using a hydrodynamic bearing device has been adopted in this hard disk drive.
In the field of such portable devices, there is a strong demand for reducing the current for driving the spindle motor in order to extend the operation time without charging by the built-in battery as much as possible. However, in the spindle motor provided with the conventional hydrodynamic bearing device as described above, a relatively large drive current is required due to a relatively large loss in each bearing portion, and the portable device can be operated for a long time by the built-in battery. It is one of the factors that hinders.

In the field of hard disk drives, the recording density has been increasing in recent years.
In order to satisfy the demand for higher density, it is necessary to stably rotate the rotor hub on which the recording disk is mounted. However, in a spindle motor equipped with a hydrodynamic bearing device, the rotor hub is rotatably supported via the lubricating liquid. Therefore, when the rotation speed of the rotor hub increases and the centrifugal force increases, the lubricating liquid is affected by the centrifugal force. As a result, when the influence is increased, it becomes difficult to stably support the rotor hub.

In such a hydrodynamic bearing device,
In order to release air bubbles that may be mixed in the lubricating liquid to the outside, the axial ventilation holes 26, the radial ventilation holes 28, the axial ventilation holes 30, and the radial ventilation holes 32 are required. The large number of holes complicates the structure of the bearing device itself and increases the manufacturing cost. SUMMARY OF THE INVENTION It is an object of the present invention to provide a hydrodynamic bearing device which can open air bubbles in a lubricating fluid to the outside as required by a vent having a relatively simple structure.

Another object of the present invention is to provide a hydrodynamic bearing device which can reduce the influence of centrifugal force acting on a lubricating liquid. Further, the object of the present invention is
An object of the present invention is to provide a motor capable of stably and rotatably supporting a rotor by reducing the influence of a centrifugal force acting on a lubricating liquid.

[0010]

SUMMARY OF THE INVENTION The present invention provides a shaft having a shaft portion and a thrust plate projecting radially outward from the shaft portion, and a sleeve fitted to the shaft portion of the shaft body. A sleeve body having a portion and a thrust support portion externally fitted to the thrust plate portion, a pair of radial bearing portions for rotatably supporting the shaft portion and the sleeve portion, and the thrust plate portion. A pair of thrust bearings for supporting the thrust support relatively rotatably,
A lubricating fluid filled between the shaft body and the sleeve body, wherein the annular first enlarged gap is provided between the pair of radial bearings; The sleeve body is provided with a first ventilation hole for communicating the first enlarged gap portion to the outside, and an adjacent radial bearing portion adjacent to the adjacent thrust plate portion is directed in a direction toward the thrust plate portion. A herringbone groove for generating a dynamic pressure that is unbalanced in the axial direction so as to pump the lubricating liquid, and an adjacent thrust bearing adjacent to the adjacent radial bearing is provided with the lubricating liquid radially inward. Having a dynamic pressure generating spiral groove for pumping the lubricating liquid, wherein the separated thrust bearing apart from the thrust bearing has a dynamic pressure generating spiral groove for pumping the lubricating liquid radially inward. The radially inner side of the separated thrust bearing portion is substantially sealed from the outside, and the sleeve body further includes the thrust plate portion of the shaft body and the thrust support portion of the sleeve body. A second vent is provided for communicating an annular space between the thrust support with the outside, and a second enlarged gap is provided in a part of the inner peripheral surface of the thrust support corresponding to the second vent. The second enlarged gap portion extends in the axial direction toward the second ventilation hole.

According to the present invention, a pair of radial bearings are provided between the shaft of the shaft and the sleeve of the sleeve, and a pair of thrust bearings are provided between the thrust plate and the thrust support. Is provided. The herringbone for generating dynamic pressure of the adjacent radial bearing portion adjacent to the thrust plate portion pumps the lubricating liquid in the direction toward the thrust plate portion, and generates the dynamic pressure of the adjacent thrust bearing portion adjacent to the adjacent radial bearing portion. Since the spiral groove for pumping the lubricating liquid radially inward, dynamic pressure is generated in the lubricating liquid in the adjacent radial bearing and the adjacent thrust bearing. Also,
Since the spiral groove for generating dynamic pressure of the separated thrust bearing part, which is separated from the adjacent thrust bearing part, pumps the lubricating liquid to the radially inner side which is substantially sealed to the outside, the lubricating liquid of the separated thrust bearing part is also used. Dynamic pressure is generated. Since the dynamic pressure is generated in this manner, the shaft portion of the shaft body and the sleeve portion of the sleeve body are rotatably supported via the lubricating liquid of the pair of radial bearing portions, and the thrust plate portion of the shaft body and the sleeve The thrust support of the body is rotatably supported via the lubricating liquid of the pair of thrust bearings.

The spiral groove portions used in the pair of thrust bearing portions have a high dynamic pressure generation efficiency and have a lower viscous resistance of the lubricating liquid than the herringbone grooves. Can be reduced. In addition, since the dynamic pressure generation efficiency is high, it is possible to reduce the diameter of the thrust plate portion of the shaft body. By reducing the diameter in such a manner, the thrust bearing portion which tends to be proportional to the peripheral speed of the thrust plate portion is used. Loss can be further reduced. As a result, the loss can be reduced, and as a result, the current value of the drive current of the motor including the hydrodynamic bearing device can be reduced as much as possible. still,
The shaft portion and the thrust plate portion constituting the shaft body may be integrally formed, or may be formed by combining separate components.

In such a hydrodynamic bearing device, the dynamic pressure of the lubricating fluid in the adjacent radial bearing portion is the lowest on the side of the remote radial bearing portion, and the dynamic pressure of the lubricating fluid in the remote radial bearing portion is low on both sides. (Adjacent radial bearing portion side and the opposite side), and the dynamic pressure of the lubricating liquid of the pair of thrust bearing portions is lowest on the radially outward side.
For this reason, the first radial bearing is located between the pair of radial bearings.
An enlarged gap portion is provided, the first enlarged gap portion is communicated with the outside through the first ventilation hole, and a second enlarged gap portion is provided in an annular space between the thrust support portion and the thrust plate portion. The second enlarged gap portion communicates with the outside via the second ventilation hole. Therefore, bubbles that can be mixed in the lubricating fluid of the pair of radial bearings are opened to the outside through the first enlarged gap and the first ventilation hole, and bubbles that can be mixed in the lubricating fluid of the pair of thrust bearings are: Air bubbles that can be mixed with the lubricating fluid of the pair of radial bearing portions and the pair of thrust bearing portions are opened to the outside through the first enlarged gap portion and the second ventilation hole, and thus, are released to the outside with a relatively simple ventilation hole structure. The hydrodynamic bearing device can be opened, whereby the manufacturing cost of the hydrodynamic bearing device can be reduced.

Further, since the second enlarged gap provided between the thrust plate and the thrust support extends in the axial direction toward the second ventilation hole, the lubricating liquid in the second enlarged gap is provided. Is formed so as to expand in the radial direction.
Therefore, for example, even when the shaft body rotates at a high speed with respect to the sleeve body, almost no centrifugal force acts on the interface of the lubricating liquid in the second enlarged gap, and therefore, the lubricating liquid in the pair of thrust bearings is The shaft is hardly affected by the centrifugal force and, for example, can stably and rotatably be supported.

In the present invention, the second enlarged gap portion is formed by providing an arc-shaped concave portion extending in the axial direction on an inner peripheral surface of the thrust support portion of the sleeve body. According to the present invention, since the second enlarged gap is formed by providing the arc-shaped concave portion on the inner peripheral surface of the thrust support, the second enlarged gap can be formed relatively easily. Further, in the second enlarged gap portion having such a configuration, the interface of the lubricating liquid is formed so as to extend in the radial direction from the inner surface of the concave portion to the outer peripheral surface of the thrust plate portion so as to face each other. Centrifugal force hardly acts on the interface of the lubricating liquid.

Further, according to the present invention, a shaft having a shaft portion and a thrust plate protruding radially outward from the shaft portion;
A sleeve body having a sleeve portion fitted to the shaft portion of the shaft body and a thrust support portion fitted externally to the thrust plate portion; and a rotatably supporting the shaft portion and the sleeve relative to each other. A pair of radial bearings, a pair of thrust bearings for rotatably supporting the thrust plate and the sleeve, and a lubricating fluid filled between the shaft and the sleeve And an annular first enlarged gap portion is provided between the pair of radial bearing portions, and the sleeve body communicates the first enlarged gap portion to the outside. And a radial bearing adjacent to the adjacent thrust plate is unbalanced in the axial direction so as to pump the lubricating liquid in a direction toward the thrust plate. Dynamic pressure The thrust bearing has a raw herringbone groove, and an adjacent thrust bearing adjacent to the adjacent radial bearing has a dynamic pressure generating spiral groove for pumping the lubricating fluid radially inward. The spaced apart thrust bearing part has a spiral groove for generating dynamic pressure for pumping the lubricating liquid radially inward, and the radially inner side of the spaced apart thrust bearing is substantially sealed from the outside. The sleeve body further includes a second portion for communicating a gap between the thrust plate portion of the shaft body and the thrust support portion of the sleeve body to the outside between the pair of thrust bearing portions. A vent is provided, and one end of the second vent is used to hold the lubricant filled in a gap between the thrust plate portion and the thrust support portion by surface tension. Over path holding portion is provided, the tapered retaining portion, characterized in that it extends in the axial direction.

According to the present invention, since the basic structure is substantially the same as the above-described hydrodynamic bearing device, the shaft body and the sleeve body are relatively rotatable via the lubricating liquid as described above. And air bubbles that can be mixed in the lubricating liquid of the pair of radial bearings and the pair of thrust bearings can be released to the outside. Further, a tapered holding portion is provided at one end side of the second ventilation hole, and since the tapered holding portion extends in the axial direction, the interface of the lubricating liquid in the tapered holding portion is formed so as to expand in the radial direction. You. Therefore, for example, the shaft body rotates at a high speed with respect to the sleeve body, and almost no centrifugal force acts on the interface of the lubricating liquid in the tapered holding portion, and the shaft body can be stably rotatably supported.

Further, in the present invention, the one end side of the second ventilation hole is disposed radially outward of the thrust plate portion of the shaft body, and is provided on an inner peripheral surface of the thrust support portion of the sleeve body. A ring member is mounted so as to cover the one end side of the second ventilation hole, a tapered surface is formed on an inner peripheral surface of one end of the ring member, and the tapered surface of the ring member is The taper holding portion is formed at the one end side of the pore.

According to the present invention, since the ring member is mounted on the inner peripheral surface of the thrust support portion so as to cover the second air hole, the taper surface of the ring member is held at one end side of the second air hole by the ring member. The desired tapered holding portion can be formed with a relatively simple configuration. Furthermore, the present invention includes the hydrodynamic bearing device according to any one of claims 1 to 4, wherein one of the shaft body and the sleeve body is mounted on the rotor, and the other is mounted on the housing. A motor characterized in that:

According to the present invention, the shaft is mounted on the rotor,
The present invention can be applied to a shaft rotation type motor by mounting a sleeve body on a housing, and can be applied to a fixed shaft type motor by mounting a shaft body on a housing and mounting a sleeve body on a rotor. The above-described operation can be achieved in such a motor.

This motor includes a magnetic disk such as a hard disk, a magneto-optical disk, a CD-ROM, a CD-R,
It can be used as a spindle motor for driving a recording medium such as an optical disc such as a D-RW, a DVD-ROM, and a DVD-RAM, in particular, a disc-shaped recording medium, and various other motors.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a hydrodynamic bearing device according to the present invention and a motor provided with the same will be described below with reference to FIGS. First Embodiment of Hydrodynamic Bearing Device First, a first embodiment of a hydrodynamic bearing device according to the present invention will be described with reference to FIGS. FIG.
FIG. 2 is a cross-sectional view illustrating the hydrodynamic bearing device of the first embodiment, and FIG. 2 is a partially enlarged plan view illustrating a second enlarged gap portion and its vicinity in the hydrodynamic bearing device of FIG. 1 in an enlarged manner. .

The illustrated hydrodynamic bearing device 102 includes a shaft 1
04, and a sleeve body 104 fitted to the shaft body 104. A space between the shaft body 102 and the sleeve body 106 is filled with a lubricating liquid (lubricating oil) such as spindle oil. The shaft body 104 is in the axial direction (vertical direction in FIG. 1).
1 and one end of the shaft 108 (FIG. 1).
And a thrust plate portion 110 provided at a lower end portion thereof, which are integrally formed. The thrust plate portion 110 has a disk shape and protrudes radially outward coaxially with the shaft portion 108. An annular arc-shaped concave portion 112 having an arc-shaped cross section is provided at an axially intermediate portion of the shaft portion 108. The other end of the shaft 108 is the other end (the upper end in FIG. 1)
The diameter of the small diameter portion 11 is gradually reduced toward
The diameter is reduced to 4. The shaft 108 is provided with a female screw 116 extending in the axial direction from the other end.

The sleeve body 106 is formed of the sleeve forming body 11
8 and a fixed thrust plate 120. The sleeve portion 122 of the sleeve forming body 118 is
4, the shaft portion 108, more specifically, the thrust plate portion 110
And a small-diameter portion 114 is sleeve-fitted.
The inside diameter of one end (lower end in FIG. 1) of the sleeve portion 122 in the sleeve forming body 118 is gradually increased toward the one end to the middle inside diameter portion 124 and the large inside diameter portion 126. The disk-shaped fixed thrust plate 120 is internally fitted and fixed to the large inner diameter portion 126, so that the shaft body 104 is fixed.
A thrust support portion 128 which is fitted to the thrust plate portion 110 in the radial direction and in the axial direction excluding the shaft portion 108 is formed.

An arcuate concave portion 11 of the shaft portion 108 is provided at an axially intermediate portion of the inner peripheral surface of the sleeve portion 122 of the sleeve body 106.
An annular recess 130 is provided opposite to the annular recess 2, and the bottom surface of the annular recess 130 is formed flat. Sleeve part 12
The second annular concave portion 130 and the annular circular concave portion 112 of the shaft portion 108.
Defines the first enlarged gap 132. The sleeve portion 122 is provided with a first ventilation hole 134 extending in a radial direction. One end of the first ventilation hole 134 communicates with the first enlarged gap portion 132, and the other end is open to the outer peripheral surface of the sleeve 122. .

A pair of radial bearings 136 and 138 are provided on both sides of the first enlarged gap 132 between the sleeve portion 122 of the sleeve body 106 and the shaft portion 108 of the shaft body 104 at an interval in the axial direction. Have been. Thrust plate 11
The center of the radial bearing portion 136 (the upper radial bearing portion in FIG. 1) (the bent position of the groove) is located at the center of the radial bearing portion 136 in the axial direction, and is vertically symmetrical in FIG. In this embodiment, the herringbone groove 140 is formed on the inner peripheral surface of the sleeve 122. When the shaft body 104 and the sleeve body 106 rotate relatively, the herringbone groove 140
As a result, a dynamic pressure is generated in the lubricating liquid filled in the spaced radial bearing portion 136 so that the pressure is balanced in the axial direction toward the center in the axial direction and the pressure increases, and the pressure of the lubricating liquid is the highest at both ends in the axial direction. Becomes lower.

An adjacent radial bearing portion 138 (the lower thrust bearing portion in FIG. 1) adjacent to the thrust plate portion 110 has its center (the bent position of the groove) at the center.
A herringbone groove 142 for generating dynamic pressure, which is biased to the side (downward in FIG. 1) and is unbalanced in the axial direction so as to pump the lubricating liquid toward the thrust plate 110, has Like the spaced radial bearing 136, the herringbone groove 142 is formed in the sleeve 12.
2 is formed on the inner peripheral surface. When the shaft body 104 and the sleeve body 106 rotate relative to each other, the dynamic pressure generated in the lubricating oil filled in the adjacent radial bearing portion 138 by the herringbone groove 142 causes the adjacent radial bearing portion 138
Of the thrust plate portion 110 side is increased toward a position near the end,
It becomes the lowest at the end of the adjacent radial bearing portion 138 on the first enlarged gap 132 side. In this embodiment, the herringbone grooves 140, 14 of the radial bearings 136, 138 are used.
Although 2 is provided on the inner peripheral surface of the sleeve body 106, it may be provided on the outer peripheral surface of the shaft portion 108 of the shaft body 104 instead of or in addition to this.

Thrust support portion 128 of sleeve body 106
A pair of thrust bearings 144 and 146 are provided between the shaft member 104 and the thrust plate 110 of the shaft body 104. In this embodiment, both inner end surfaces of the thrust support portion 110 gradually incline to both outer sides (up and down directions in FIG. 1) at radially outward directions from the inner peripheral portions formed substantially in parallel to inner and outer intermediate positions. After being separated from each other, the pair of thrust bearing portions 144 and 146 are substantially parallel to each other. It is provided between. The thrust bearing portions 144 and 146 are respectively
Pump-in type spiral groove 148,1 for generating dynamic pressure
The spiral groove portions 148 and 150 are formed on both end surfaces (the upper end surface and the lower end surface in FIG. 1) of the thrust plate portion 110. Shaft 104 and sleeve 10
6 rotates relative to the spiral groove 148,
150, the adjacent thrust bearing 144 and the adjacent radial bearing 13 adjacent to the adjacent radial bearing 138
A dynamic pressure is generated in the lubricating fluid filled in the separate thrust bearing portions 146 spaced apart from the inner surface 8 so that the pressure increases radially inward, and the dynamic pressure of the lubricating oil is increased by the adjacent thrust bearing portion 144 and the separated thrust. It becomes lowest on the radially outer peripheral side of the bearing portion 146. In this embodiment, the spiral grooves 148 and 150 of the thrust bearing portions 144 and 146 are provided in the thrust plate portion 110. However, the spiral grooves 148 and 150 may be provided in the thrust support portion 128 instead or in addition to this. .

In the hydrodynamic bearing device 102, the lubricating oil is filled in the spaced radial bearing portion 136, and the adjacent radial bearing portion 138 to the adjacent thrust bearing portion 144, the outer peripheral surface of the thrust plate portion 110, and the spaced apart thrust bearing portion. 14
It is substantially continuously filled up to its radially inward over 6 and is substantially separated and filled in two places. Since the lubricating liquid is filled in this manner, the separated radial bearing 1
On the outer side of 36 (upper side in FIG. 1), the shaft 10
8 is gradually reduced in diameter, and a taper portion 152 is provided in which a gap with the sleeve portion 122 expands in a taper shape. The outer interface of the lubricating liquid filled in the separated radial bearing portion 136 is formed on the taper portion 152 by surface tension. To position. Also, inside the radial bearing portion 136 (lower side in FIG. 1), the sleeve portion 1 is connected to one end of the first enlarged gap portion 132.
A tapered portion 154 that expands in a tapered manner between the shaft portion 22 and the shaft portion 108 is provided, and the interface of the separated radial bearing portion 136 inside the lubricating liquid is located in the tapered portion 154 due to surface tension. Also, the inside of the adjacent radial bearing portion 148 (FIG. 1)
(Upper side), a tapered portion 156 is provided at the other end of the first enlarged gap portion 132 so that the space between the sleeve portion 122 and the shaft portion 108 expands in a tapered shape, and the lubricating liquid of the adjacent radial bearing portion 138 is provided. The inner interface is located at the tapered portion 156 due to surface tension.

Referring also to FIG. 2, in this embodiment, the sleeve body 106 is further provided with a second ventilation hole 158. The second ventilation hole 158 extends linearly in the axial direction (the vertical direction in FIG. 1 and the direction perpendicular to the paper surface in FIG. 2), and one end 160 of the second ventilation hole 158 is formed in the thrust support portion 128 facing the outer peripheral portion of the thrust plate portion 110. It opens to the end face, and the other end communicates with the first ventilation hole 134. The thrust plate portion 110 of the shaft body 104 corresponds to the second communication hole 158.
A second enlarged gap portion 162 is provided between the outer peripheral surface of the sleeve member 106 and the inner peripheral surface of the thrust support portion 128 of the sleeve body 106.
It communicates with the ventilation hole 134.

In this embodiment, an arc-shaped concave portion 164 is formed on the inner peripheral surface of the thrust support portion 128, so that a second enlarged gap portion 162 extending in the axial direction toward the second ventilation hole 158 is formed. Thus, the second enlarged gap 16
By providing 2, a gap is formed in the continuous lubricating liquid from the adjacent thrust bearing 144 to the separated thrust bearing 146, and the gap is communicated with the second communication hole 158. In the second enlarged gap 162, at both ends of the arc-shaped concave portion 164, the gap between the radially opposed outer peripheral surface of the thrust plate portion 110 is small, and the arc-shaped concave portion 164 is formed.
Since the gap with the outer peripheral surface of the thrust plate portion 110 gradually increases toward the center portion of the fourth portion 4, both end portions of the second enlarged gap portion 162 function as taper holding portions that hold the lubricating liquid by using surface tension. As shown in FIG. 2, the lubricating liquid existing in the annular space between the inner peripheral surface of the thrust support portion 128 and the outer peripheral surface of the thrust plate portion 110 removes the lubricating liquid from the second enlarged gap 16.
2, one interface 166 of the lubricating liquid is located at one end (lower end in FIG. 2) of the second enlarged gap 162 by surface tension, and the other interface 168 is
Due to the surface tension, the other end of the second enlarged gap 162 (FIG. 2)
At the upper end), these interfaces 166, 16
8 is held so as to face in the radial direction, in other words, to expand in the radial direction. Since the lubricating liquid is retained, sufficient lubricating liquid can be retained at both ends of the second enlarged gap 162, and the lubricating liquid can be replenished to the thrust bearings 144 and 146 as required. it can.

Applying the hydrodynamic bearing device of the first embodiment
Embodiments of the motor will, with reference to FIG. 3, the hydrodynamic bearing device described above 10
2 is applied to a spindle motor as an example of a motor. FIG. 3 shows a hydrodynamic bearing device 102.
FIG. 2 is a cross-sectional view showing a spindle motor provided with a spindle motor. 3, in the illustrated spindle motor 170, one end (the lower end in FIGS. 1 and 3) of the sleeve body 106 is coaxially fitted and fixed to the inner annular wall 174 of the housing 172, and A cup-shaped rotor hub 176 is fitted and fixed to the small diameter portion 114 of the shaft portion 108, and the sleeve body 1
The motor is mounted as a shaft rotation type motor in which the shaft body 104 rotates with respect to 06. The stator 178 is externally fitted and fixed to the inner annular wall portion 174 of the housing 172, the rotor magnet 181 is internally fitted and fixed to the outer peripheral wall portion 180 of the rotor hub 176, and the rotor magnet 181 is fixed to the stator 178.
Are located facing radially outward. Further, the other end of the first ventilation hole 134 opened on the outer peripheral surface of the sleeve body 106 communicates with the internal space of the spindle motor 170 above the inner annular wall portion 174 of the housing 172, and the communication between the housing 172 and the rotor hub 176. It is open to the outside through a gap 182 therebetween. With this configuration, the first and second enlarged gaps 13 of the hydrodynamic bearing device 102 are provided.
2, 162 are opened to the outside through the inside of the spindle motor 170. A hard disk (not shown) as a recording medium is externally fitted to the rotor hub 176 and fixed by a clamp member (not shown) screwed to the female screw portion 116.

In the spindle motor 170, when the rotor hub 176 rotates in a predetermined direction, the lubricating fluid in the separated radial bearing portion 136 is balanced toward the center in the axial direction and the pressure increases, so that the lubricating fluid is mixed in the lubricating fluid. The resulting air bubbles are separated at the tapered portion 152 and then opened to the outside through the inside of the motor.
After being separated in the above, it is opened to the outside through the first enlarged gap 132, the first ventilation hole 134 and the inside of the motor.

Further, in the lubricating liquid in the adjacent radial bearing portion 138, a dynamic pressure is generated by the herringbone groove portion 142 so that the pressure is biased to a position closer to the end of the adjacent radial bearing portion 138 near the thrust plate 110 side. At the same time, a dynamic pressure is generated in the lubricating fluid in the adjacent thrust bearing portion 144 by the spiral groove portion 148 so that the pressure increases radially inward, so that the dynamic pressure necessary for alignment in the adjacent radial bearing portion 138 is increased. A dynamic pressure is generated in the lubricating fluid, and the lubricating fluid in the adjacent thrust bearing 144 generates a dynamic pressure capable of supporting the load in the axial direction. At the same time, the radially inward side of the spaced-apart thrust bearing portion 146 defines a closed space that is substantially sealed from the outside by the fixed thrust plate 120, so that the spaced-apart thrust bearing portion 1
A dynamic pressure is generated in the lubricating fluid at 46 that can support the axial load. Adjacent and remote thrust bearings 144, 14
6 is composed of the pump-in type spiral grooves 148 and 150, so that the dynamic pressure generation efficiency is high, the viscosity resistance of the lubricating fluid is smaller than that of the herringbone groove, and thus the adjacent and separated thrust bearings 144 are provided. , 146 can be reduced as much as possible, and the thrust plate 11 can be reduced as compared with the case where the herringbone groove is used.
0 can be reduced in diameter, whereby the loss due to rotation can be further reduced.

The dynamic pressure generated in the lubricating fluid of the adjacent radial bearing 138 is lowest on the first enlarged gap 132 side of the adjacent radial bearing 138, and the dynamic pressure generated in the lubricating fluid of the adjacent thrust bearing 144 is , On the outer peripheral side of the adjacent thrust bearing portion 144. Bubbles that can be mixed in the lubricating liquid in the adjacent radial bearing portion 138 and / or the adjacent thrust bearing portion 144 are on the side where the lubricating liquid has a low pressure,
That is, the tapered portion 156 of the adjacent radial bearing portion 138
And / or radially outward of the adjacent thrust bearing portion 144 to both ends of the second enlarged gap portion 162 (a portion functioning as a taper holding portion). Then, the first enlarged gap 1
The air bubbles separated from the lubricating liquid by the tapered portion 156 of the thirty-two are opened to the outside through the first enlarged gap 132, the first ventilation hole 134 and the inside of the motor, and are lubricated at both ends of the second enlarged gap 162. The bubbles separated from the liquid are opened to the outside through the second enlarged gap 162, the second vent 158, the first vent 134, and the inside of the motor.
Further, the dynamic pressure generated in the lubricating fluid of the separated thrust bearing 146 is lowest on the outer peripheral side of the separated thrust bearing 146, and the bubbles that can be mixed in the lubricating fluid in the separated thrust bearing 146 are low pressure lubricating fluid. On one side, that is, radially outward of the separated thrust bearing 146, the second enlarged gap 1
The air bubbles that have moved to both ends of the lubricating liquid at both ends of the second enlarged gap 162 are released to the outside in the same manner as described above.

The hydrodynamic bearing device 102 further has the following features. Since the tapered portions 152 and 154 where the interface of the lubricating liquid of the separated radial bearing portion 136 is located extend in the axial direction of the hydrodynamic bearing device, in other words, in the axial direction of the spindle motor 170, the interface of the lubricating liquid is
As understood from FIGS. 1 and 3, the tapered portion 152 is formed so as to expand in the radial direction (in other words, in the tapered portion 152, the interface surface faces upward and the tapered portion 1 is formed).
At 54, the interface surface is formed to face down). Therefore, even if the rotor hub 176 rotates at a high speed in a predetermined direction integrally with the shaft body 104, such a tapered portion 1
The centrifugal force hardly acts on the interface between the lubricating liquids 52 and 154, and therefore the lubricating liquid in the separated radial bearing portion 136 is hardly affected by the centrifugal force. Since the tapered portion 156 where the interface of the lubricating liquid of the adjacent radial bearing portion 138 is located also extends in the axial direction of the hydrodynamic bearing device, the interface of the lubricating liquid is similar to the lubricating liquid of the separated radial bearing portion 136. Is formed so as to expand in the radial direction. Therefore, even if the rotor hub 176 rotates at a high speed in a predetermined direction, almost no centrifugal force acts on the interface of the lubricating liquid in the tapered portion 156. Further, the adjacent and spaced thrust bearing portions 14
Second enlarged gap 1 in which the interface of the lubricating liquids 4,146 is located
As shown in FIG. 2, both ends of the thrust plate 11
Since the annular space between the zero and the thrust support 128 extends substantially tangentially, the interface of the lubricating liquid at both ends of the second enlarged gap 162 is formed so as to expand in the radial direction. Therefore, even if the rotor hub 176 rotates at a high speed in a predetermined direction, almost no centrifugal force acts on the interface of the lubricating liquid at both ends of the second enlarged gap 162, and therefore, the adjacent and separated thrust bearings 144, 146 Is hardly affected by the centrifugal force. As described above, the lubricating fluid in the radial bearing portions 136, 138 and the thrust bearing portions 144, 146 is hardly affected by the centrifugal force.
4 (the rotor hub 176 rotating integrally therewith) can be stably supported in rotation.

Second Embodiment of the Hydrodynamic Bearing Device Next, a second embodiment of the hydrodynamic bearing device will be described with reference to FIGS. FIG. 4 is a cross-sectional view showing the hydrodynamic bearing device of the second embodiment, and FIG. 5 is a partially enlarged cross-sectional view showing the ring member and its vicinity in the hydrodynamic bearing device of FIG. In the second embodiment, the same members as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

Referring to FIGS. 4 and 5, in the second embodiment, the thrust support portion 1 of the sleeve body 106A is provided.
The inner diameter of the middle inner diameter portion 124 of the sleeve body 106 of the first embodiment is formed to be somewhat larger than the middle inner diameter portion 124 of the sleeve body 106 of the first embodiment. An annular recess 192 is formed radially inward of the inner peripheral surface of the groove 124. Further, the sleeve body 106
One end of the second ventilation hole 158 provided in the
The thrust plate 110 is disposed radially outward of the thrust plate 110, and one end 160 of the thrust plate 110 is open at the bottom of the annular recess 192.

In this embodiment, the ring member 194 is fitted to the inner peripheral surface of the middle inner diameter portion 124 of the thrust support portion 128A, and one end (the upper end in FIG. 5) of the ring member 194 is located in the annular concave portion 192. Then, it is attached so as to cover one end opening 160 of the second ventilation hole 158. A tapered surface 196 is formed on the inner peripheral surface at one end of the ring member 194, and the tapered surface 196 extends linearly outward in the radial direction toward one end thereof. This ring member 19
4, the tapered surface 196 faces the inner side surface 198 of the annular concave portion 192, and the tapered surface 196 (ring member 194) and the inner side surface 198 (sleeve body 10).
6A) constitutes the tapered holding portion 200, and this tapered holding portion 200 extends in the axial direction of the hydrodynamic bearing device 102A, as shown in FIGS. Other configurations of the hydrodynamic bearing device 102A of the second embodiment are substantially the same as those of the first embodiment shown in FIGS.

Then, In the hydrodynamic bearing device 102A provided with the ring member 194, a part of the lubricating liquid existing from the adjacent thrust bearing portion 144 to the separated thrust bearing portion 146 flows toward the second ventilation hole 158, and the interface is tapered. Since it is located on the retaining portion 200 (defined by the tapered surface 196 of the ring member 194 and the inner side wall 198 of the annular concave portion 192), the annular tapered retaining portion 2
00 can hold a sufficient amount of the lubricating liquid, and the thrust bearing portions 144 and 146 can be sufficiently supplied with the lubricating liquid. Further, as described above, since the tapered holding portion 200 extends in the axial direction of the hydrodynamic bearing device 102A, the interface of the lubricating liquid is formed so as to expand in the radial direction as shown in FIG. And therefore the rotor hub 17
Even when the rotor 6 rotates at a high speed, the centrifugal force hardly acts on the interface of the lubricating liquid in the taper holding section 200, and the lubricating liquid in the adjacent and spaced thrust bearings 144 and 146 is almost affected by the centrifugal force. Therefore, the same effect as that of the first embodiment is achieved.

The embodiments of the hydrodynamic bearing device and the motor provided with the same according to the present invention have been described above. However, the present invention is not limited to such embodiments, and does not depart from the scope of the present invention. Various variations and modifications are possible.

[0042]

According to the hydrodynamic bearing device of the first aspect of the present invention, the second enlarged gap portion provided between the thrust plate portion of the shaft and the thrust support portion of the sleeve is formed by the second enlarged gap. Since the lubricating liquid extends in the axial direction toward the two ventilation holes, the interface of the lubricating liquid in the second enlarged gap portion is formed so as to expand in the radial direction. Therefore, even when the shaft body and the sleeve body rotate at a relatively high speed, the centrifugal force hardly acts on the interface of the lubricating liquid in the second enlarged gap portion. Is hardly affected by this centrifugal force.

According to the hydrodynamic bearing device of the second aspect of the present invention, since the second enlarged gap is formed by providing the arc-shaped concave portion on the inner peripheral surface of the thrust support portion, it is relatively simple. The second enlarged gap portion can be formed at the same time.

According to the hydrodynamic bearing device of the third aspect of the present invention, the tapered holding portion is provided at one end of the second ventilation hole, and the tapered holding portion extends in the axial direction. The interface of the lubricating liquid in the tapered holding portion is formed so as to expand in the radial direction. Therefore, even when the shaft body and the sleeve body rotate at a relatively high speed, the centrifugal force hardly acts on the interface of the lubricating liquid in the tapered holding portion. According to the hydrodynamic bearing device of claim 4 of the present invention, the ring member having the tapered surface is mounted on the inner peripheral surface of the thrust support so as to cover the second ventilation hole. At one end of the pore, a tapered holding portion is formed by the tapered surface of the ring member.

Further, according to the motor of the fifth aspect of the present invention, the rotor can be stably rotatably supported by being applied to the shaft rotation type motor and the fixed shaft type motor.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of a hydrodynamic bearing device according to the present invention.

FIG. 2 is a partially enlarged plan view showing a second enlarged gap portion and its vicinity in the hydrodynamic bearing device of FIG. 1 in an enlarged manner.

FIG. 3 is a sectional view showing an example in which the hydrodynamic bearing device of FIG. 1 is applied to a spindle motor.

FIG. 4 is a sectional view showing a second embodiment of the hydrodynamic bearing device according to the present invention.

FIG. 5 is a partially enlarged plan view showing the ring member and its vicinity in the hydrodynamic bearing device of FIG. 4 in an enlarged manner.

FIG. 6 is a sectional view showing an example of a conventional hydrodynamic bearing device.

[Explanation of symbols]

 Reference Signs List 102 hydrodynamic bearing device 104 shaft body 106, 106A sleeve body 108 shaft section 110 thrust plate section 122 sleeve section 128, 128A thrust support section 132 first enlarged gap section 134 first ventilation hole 136, 138 radial bearing section 144, 146 Thrust bearing part 158 Second ventilation hole 162 Second enlarged gap part 170 Spindle motor 176 Rotor hub 178 Stator 181 Rotor magnet 194 Ring member 200 Taper holding part

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3J011 AA07 BA06 CA02 JA02 KA04 MA24 5H605 AA04 BB05 BB09 BB19 CC04 EB03 EB16 5H607 AA00 AA04 BB01 BB04 BB07 BB09 BB17 CC01 GG03 GG12 GG15

Claims (5)

[Claims] A shaft having a shaft portion and a thrust plate protruding radially outward from the shaft portion; and a sleeve and a thrust plate fitted to the shaft portion of the shaft body. A sleeve body having a fitted thrust support portion, a pair of radial bearing portions for rotatably supporting the shaft portion and the sleeve portion, and the thrust plate portion and the thrust support portion. A hydrodynamic bearing device comprising: a pair of thrust bearing portions for rotatably supporting the bearing member; and a lubricating liquid filled between the shaft body and the sleeve body. An annular first enlarged gap portion is provided therebetween, and the sleeve body has a first ventilation hole for communicating the first enlarged gap portion to the outside, and is adjacent to the thrust plate portion. The adjacent radial bearing part An axially unbalanced dynamic pressure generating herringbone groove is formed so as to pump the lubricating liquid in a direction toward a thrust plate, and an adjacent thrust bearing adjacent to the adjacent radial bearing has a radial direction. It has a spiral groove for generating a dynamic pressure for pumping the lubricating liquid inward, and a separate thrust bearing part separated from the adjacent thrust bearing part is for generating a dynamic pressure for pumping the lubricating liquid radially inward. In addition to having a spiral groove, the radially inner side of the separated thrust bearing portion is substantially sealed from the outside, and the sleeve body further includes a thrust plate portion of the shaft body and the sleeve body. A second ventilation hole is provided for communicating an annular space between the thrust supporting portion and the outside to the outside. A second ventilation hole is provided on a part of the inner peripheral surface of the thrust supporting portion corresponding to the second ventilation hole. An enlarged gap portion is provided, and the second enlarged gap portion extends in the axial direction toward the second ventilation hole. 2. The second enlarged gap portion is formed by providing a circular arc-shaped concave portion extending in an axial direction on an inner peripheral surface of the thrust support portion of the sleeve body. A hydrodynamic bearing device according to any of the preceding claims. 3. A shaft body having a shaft portion and a thrust plate portion projecting radially outward from the shaft portion, and a shaft portion having a sleeve fitted to the shaft portion of the shaft body and a thrust plate portion. A sleeve body having a fitted thrust support portion, a pair of radial bearing portions for rotatably supporting the shaft portion and the sleeve portion, and the thrust plate portion and the thrust support portion. A hydrodynamic bearing device comprising: a pair of thrust bearing portions for rotatably supporting the bearing member; and a lubricating liquid filled between the shaft body and the sleeve body. An annular first enlarged gap portion is provided therebetween, and the sleeve body has a first ventilation hole for communicating the first enlarged gap portion to the outside, and is adjacent to the thrust plate portion. The adjacent radial bearing part An axially unbalanced dynamic pressure generating herringbone groove is formed so as to pump the lubricating liquid in a direction toward a thrust plate, and an adjacent thrust bearing adjacent to the adjacent radial bearing has a radial direction. It has a spiral groove for generating a dynamic pressure for pumping the lubricating liquid inward, and a separate thrust bearing part separated from the adjacent thrust bearing part is for generating a dynamic pressure for pumping the lubricating liquid radially inward. While having a spiral groove portion, the radially inner side of the separated thrust bearing portion is substantially sealed from the outside, and the sleeve body further includes a shaft member between the pair of thrust bearing portions. A second ventilation hole is provided for communicating a gap between the thrust plate portion and the thrust support portion of the sleeve body to the outside, and one end of the second ventilation hole has the thrust hole. A taper holding portion is provided for holding the lubricant filled in a gap between a strike plate portion and the thrust support portion by surface tension, and the taper holding portion extends in an axial direction. Hydraulic bearing device. 4. The one end side of the second ventilation hole is arranged radially outward of the thrust plate portion of the shaft body, and the inner peripheral surface of the thrust support portion of the sleeve body has the first end side. 2
A ring member is attached so as to cover the one end side of the ventilation hole, a tapered surface is formed on an inner peripheral surface of one end portion of the ring member, and the tapered surface of the ring member is connected to the one end side of the second ventilation hole. 4. The hydrodynamic bearing device according to claim 3, wherein the taper holding portion is formed. 5. A hydrodynamic bearing device according to claim 1, wherein one of the shaft body and the sleeve body is mounted on the rotor, and the other is mounted on the housing. A motor characterized in that: