JP2003307212A - Fluid lubricated bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the leakage of lubricating oil. <P>SOLUTION: The inside space of a housing 2 sealed with a seal member 5 as well as an internal pore (a pore in a porous structure) of a bearing member 3 is filled with the lubricating oil without the presence of air. The oil surface of the lubricating oil exists within a seal space S1. Under a reduced pressure of 100 Torr, the lubricating oil does not leak outside the housing 2 even when a fluid bearing device 1 is put in an optional attitude such as normal, inverted, sideways turning or inclined attitude. <P>COPYRIGHT: (C)2004,JPO

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 for supporting a rotating member in a non-contact manner by an oil film of lubricating oil generated in a radial bearing gap. This bearing device is used for information equipment,
For example, magnetic disk devices such as HDD and FDD, CD-R
Optical disk devices such as OM, CD-R / RW and DVD-ROM / RAM, spindle motors such as magneto-optical disk devices such as MD and MO, copiers, laser beam printers (LBP), scanner motors such as bar code readers,
Alternatively, it is suitable for electric appliances, for example, small motors such as axial fans.

[0002]

2. Description of the Related Art In addition to high rotation accuracy,
Higher speed, lower cost and lower noise are required.
One of the components that determines the required performance is a bearing that supports the spindle of the motor, and in recent years, the use of a fluid bearing having the characteristics excellent in the required performance has been studied or actually used. . This type of fluid dynamic bearing includes a so-called fluid dynamic pressure bearing having dynamic pressure generating means for generating dynamic pressure in the lubricating oil in the bearing gap, and a so-called fluid perfect circular bearing having no dynamic pressure generating means (bearing surface is Bearings that have a perfect circular shape).

FIG. 7 shows an example of the configuration of a spindle motor for information equipment in which a fluid dynamic bearing device 11 is incorporated. This spindle motor is used in a disk drive device such as a DVD-ROM, and is mounted on the shaft member 12 and a fluid bearing device 11 that rotatably supports the shaft member 12, and supports, for example, an optical disk 13 that is a drive target. And a supporting member 14 (a turntable in the illustrated example), and a motor stator 15 and a motor rotor 16 that are opposed to each other via a radial gap.

The hydrodynamic bearing device 11 includes a housing 21 having an opening at one end and a bottom at the other end, and the housing 21.
The cylindrical bearing member 22 fixed to the inner peripheral surface of the shaft 21, the shaft member 12 inserted through the inner peripheral surface of the bearing member 22, the thrust plate 23 provided at the bottom of the housing 21, and the opening of the housing 21. And a seal member 24 attached to the main component. A groove (dynamic pressure groove) for generating dynamic pressure is provided on the inner peripheral surface of the bearing member 22 or the outer peripheral surface of the shaft member 12. Lubricating oil is injected into the internal space of the housing 21.

The stator 15 is attached to the outer periphery of the housing 21 of the hydrodynamic bearing device 11, and the rotor 16 is attached to the support member 1.
It is attached to 4. When the stator 15 is energized, the rotor 16 is rotated by the exciting force between the stator 15 and the rotor 16, whereby the support member 14 and the shaft member 12 are integrally rotated.

The rotation of the shaft member 12 causes a dynamic pressure action of the lubricating oil by the dynamic pressure groove in the radial bearing gap between the inner peripheral surface of the bearing member 22 and the outer peripheral surface of the shaft member 12, so that the shaft member 12 is rotated.
The outer peripheral surface of the is supported in a non-contact manner in the radial direction. Further, the other end side (lower side in FIG. 7) of the shaft member 12 is supported by the thrust plate 23 in the thrust direction.

[0007]

[Patent Document 1] Japanese Patent Laid-Open No. 11-191943

[0008]

Lubrication of the lubricating oil into the internal space of the housing 21 is usually performed with the shaft member 12 not mounted when the spindle motor is assembled, and the shaft member 12 is mounted after the lubrication. There is. Therefore, the housing 2
It is unavoidable that air mixes into the internal space of No. 1 and the thermal expansion and contraction of the air in the internal space of the housing due to changes in the ambient temperature, heat generation of the motor, and changes in atmospheric pressure during use at high altitude or during air transportation The lubricating oil causes the sealing member 2
4 may be pushed out of the seal space between the inner peripheral surface of the shaft member 4 and the outer peripheral surface of the shaft member 12 and leak to the outside. In particular, when the motor is used in an upright position (a position in which the opening side of the housing 21 faces downward) or a horizontal position (a position in which the opening side of the housing 21 faces in the horizontal direction), the lubricating oil flows. Since the oil easily collects on the side of the opening, the lubricating oil easily leaks.

From the above circumstances, the conventional hydrodynamic bearing device 11
The motor with the built-in was worried about its use in an inverted posture or a sideways posture, and there were restrictions on its posture.

In the hydrodynamic bearing device 11 having the above-mentioned structure, the thrust bearing portion supports the end surface of the shaft member 12 on the other end side by the thrust plate 23.
By being pressed against the thrust plate 23 by the magnetic force between the stator 15 and the rotor 16, axial movement to one end side (upper side in FIG. 7) is restricted. However, when a shock load or the like that exceeds the above magnetic force is applied to the motor, or when the motor is used in an inverted posture or a sideways posture, the shaft member 12 moves axially toward one end side with respect to the housing 21, The housing 21 may come off.

The object of the present invention is to prevent the lubricating oil from leaking to the outside due to the expansion and contraction of the air remaining in the internal space of the housing under a high temperature / low temperature environment, a high altitude use, and a reduced pressure environment during air transportation. Another object of the present invention is to provide a hydrodynamic bearing device capable of stable operation and transportation in any posture, and a motor incorporating the hydrodynamic bearing device.

Another object of the present invention is to prevent the shaft member from coming off the housing by restricting the axial relative movement of the shaft member toward the one end side with respect to the housing.

[0013]

In order to solve the above problems, the present invention provides a housing having an opening at one end and a bottom at the other end, a shaft member and a bearing member housed in the housing, and a bearing member. Is provided between the inner peripheral surface of the shaft member and the outer peripheral surface of the shaft member, and is disposed at the opening of the housing and the radial bearing portion that supports the shaft member in the radial direction in a non-contact manner with the oil film of the lubricating oil generated in the radial bearing gap. In a hydrodynamic bearing device equipped with a seal member, the internal space of the housing is filled with lubricating oil to a level where the lubricating oil does not leak outside even if the air remaining in the internal space of the housing expands or contracts under a depressurized environment. Provided configuration.
Here, the atmospheric pressure in the reduced pressure environment is, for example, from atmospheric pressure to 100.
Torr.

The hydrodynamic bearing device having the above structure can be obtained, for example, by evacuating the inner space of the housing to atmospheric pressure and then replacing the inner space of the housing with lubricating oil (vacuum impregnation). ). Specifically, after assembling the hydrodynamic bearing device in an unlubricated state (for example, the form shown in FIGS. 1 to 4), the hydrodynamic bearing device is entirely or partially (at least an opening portion with respect to the outside of the hydrodynamic bearing device). It can be obtained by immersing in a lubricating oil in a vacuum tank, evacuating the air in the internal space of the housing in that state, and then opening it to atmospheric pressure to fill the internal space of the housing with the lubricating oil.

However, depending on the degree of vacuum in the vacuum chamber, a small amount of air remains inside the housing after the atmospheric pressure is released. If there is a large amount of residual air, the lubricating oil may be pushed out of the housing due to the expansion and contraction of the residual air that accompanies changes in the ambient temperature, and the lubricating oil may leak. In particular, when the motor is used in an inverted posture or a sideways posture, the lubricating oil flows in the internal space of the housing and tends to collect on the side of the opening, so that the above-mentioned lubricating oil leakage easily occurs.
Even if the residual air is small, the residual air may expand and push the lubricating oil to the outside of the housing under a depressurized environment due to use at high altitude or by air transportation, causing a lubricating oil leak.

The factors of the thermal expansion of air include temperature and atmospheric pressure. However, when the expansion and contraction amount of air is calculated within the range of temperature and atmospheric pressure assumed as the use environment, the effect of atmospheric pressure is greater. Recognize.

The use and storage environment of a small spindle motor incorporating the hydrodynamic bearing device of the present invention is generally as follows. Temperature: Operating temperature 0 to 60 ° C Storage temperature -40 to 90 °
C atmospheric pressure: atmospheric pressure during transportation ~ 0.3 atm (altitude about 1000
0m) When the expansion ratio is calculated from the equation of state of gas, PV = nRT P: Pressure V: Volume n, R: Constant determined by gas T: Absolute temperature, so that the temperature is -40 to 90 ° C at a constant pressure. When changed, V ₉₀ / V _-40 = 363/233 = 1.56 times When the pressure is changed from atmospheric pressure to 0.3 atm at a constant temperature, V ₉₀ / V _-40 = 1 / 0.3 = 3 .33 times, in order to suppress the leakage of lubricating oil due to the expansion of air, consider a change in atmospheric pressure that has a greater effect under the environment of the above standard, and design a structure that does not cause leakage of lubricating oil. It is desirable to do.

For example, the altitude in air transportation is 10,000 m.
Assuming that, the atmospheric pressure in that case is about 230 Torr
Since it is (0.3 atm), it is necessary to inject the lubricating oil under the reduced pressure environment of 230 Torr so that the lubricating oil does not leak. In the inspection at the time of manufacturing the bearing device, allow 1
It is desirable to confirm that there is no lubricating oil leak at 00 Torr.

As described above, the hydrodynamic bearing device of the present invention and the motor equipped with the hydrodynamic bearing device are capable of expanding and contracting the air remaining in the inner space of the housing under high temperature and low temperature environments, under high pressure environment and under reduced pressure environment such as air transportation. Also, the lubricating oil does not leak to the outside, and stable operation and transportation are possible regardless of the posture of the motor.

Since the hydrodynamic bearing device in which the inner space of the housing is filled with the lubricating oil as described above has a structure like a syringe with a plug at the tip, the shaft member moves in the axial direction due to vibration during transportation. This also has the effect of suppressing the shaft member from coming off the housing to some extent.

In order to solve the above problems, the present invention provides a housing having an opening at one end and a bottom at the other end, a shaft member and a bearing member housed in the housing,
Provided between the inner peripheral surface of the bearing member and the outer peripheral surface of the shaft member,
A radial bearing part that supports the shaft member in the radial direction in a non-contact manner with an oil film of lubricating oil generated in the radial bearing gap, and a thrust bearing part that is provided at the bottom of the housing and supports the end face of the other end side of the shaft member in the thrust direction. A hydrodynamic bearing device including a seal member arranged in an opening of the housing, the shaft member having a protrusion that comes into contact with the seal member and restricts relative axial movement of the shaft member toward one end of the housing. Provide a configuration.

Here, the "protruding portion" can be formed integrally with the shaft member, or by fixing a member separate from the shaft member to the shaft member. Further, the shape of the “protruding portion” is not particularly limited, and any shape such as a ring shape, a partial ring shape, a dot shape, or a pin shape can be adopted. When the shaft member receives an external force or gravity and moves relative to the housing in the one end side in the axial direction, the protruding portion comes into contact with the seal member to restrict further relative movement of the shaft member in the axial direction. As a result, the shaft member is held in the housing and is prevented from coming off the housing.

In addition to the above construction, the interior space of the housing is filled with lubricating oil, and the expansion and contraction of the air remaining in the interior space of the housing under a reduced pressure environment from atmospheric pressure to 100 Torr lubricates the interior of the housing. It is possible to have a configuration in which there is no oil leakage.

In the above structure, an axial gap of 0.05 mm to 0.5 mm can be provided between the protrusion and the seal member. The value of the axial gap is a value when the end surface on the other end side of the shaft member is in contact with the thrust bearing portion.

In order to avoid contact between the protruding portion and the seal member during steady operation (when the end surface on the other end side of the shaft member is rotating in a state where the end surface of the shaft member is in contact with and supported by the thrust bearing portion), a contact between the protruding portion and the seal member is avoided. Must have a constant axial clearance. This axial clearance needs to be 0.05 mm or more in consideration of the dimensional tolerance of each component and the assembly error.

On the other hand, when the bearing device is repeatedly subjected to vibration, impact load, or the like during operation or transportation due to the existence of the axial gap, the shaft member is axially moved with respect to the housing within the axial gap. Relative movement is possible. Therefore, if the axial gap is too large, the relative movement of the shaft member in the axial direction allows the external air to pass through the seal space (the space between the inner peripheral surface of the seal member and the outer peripheral surface of the shaft member). There is a possibility that the oil may flow into the inside or the lubricating oil inside the housing may be pushed out of the seal space and leak to the outside. In addition, as the value of the axial clearance increases, the amount of lubricating oil that fills the internal space of the housing increases, and the amount of change in volume of lubricating oil due to thermal expansion / contraction increases, so the amount of change in volume is absorbed. In order to prevent the lubricating oil from leaking to the outside, it is necessary to increase the volume of the seal space. However, it is often difficult to increase the axial dimension of the seal member due to space constraints, and increasing the inner diameter dimension of the seal member may lead to deterioration of the sealing function (decrease in capillary force). Therefore, it is not preferable.

As a result of a test described later, it has been confirmed that if the axial gap is 0.5 mm or less, it is possible to prevent the lubricating oil from leaking from the inside of the housing to the outside, and the appropriate range of the axial gap is 0. It is 0.05 mm to 0.5 mm, preferably 0.05 mm to 0.3 mm.

In the above structure, a tapered seal space that gradually expands toward the one end can be provided between the inner peripheral surface of the seal member and the outer peripheral surface of the shaft member facing the seal member. By forming the seal space in the tapered shape, the lubricating oil in the seal space is drawn in by the capillary force in the direction in which the seal space becomes narrower (inward direction of the housing). Therefore, leakage of lubricating oil from the inside of the housing to the outside is prevented.

The tapered seal space can be formed by providing a tapered surface on at least one of the inner peripheral surface of the seal member and the outer peripheral surface of the shaft member. In the configuration in which the tapered surface is provided on the outer peripheral surface of the shaft member, the lubricating oil in the seal space receives a centrifugal force when the shaft member rotates, and the seal space narrows along the tapered surface of the shaft member (inside the housing). Direction). Therefore,
In addition to the pulling action by the above-mentioned capillary force, there is also the pulling action by the centrifugal force, so that the effect of preventing leakage of lubricating oil is further enhanced.

In the hydrodynamic bearing device in which the shaft end portion of the shaft member is contacted and supported in the thrust direction by the thrust bearing portion provided at the bottom of the housing, the pressure of the lubricating oil increases in the space around the thrust bearing portion, and the sealing member A pressure difference may occur with the lubricating oil in the seal space between the inner peripheral surface and the outer peripheral surface of the shaft member. This pressure difference is due to a machining error (taper shape of the shaft member or the inner peripheral surface of the bearing member, even if the width of the dynamic pressure groove is formed asymmetrically in the axial direction in the radial bearing portion, or even if it is symmetrical in design. The same may occur when the dimensional accuracy of the dynamic pressure groove width is large).

When such a pressure difference is generated, a local negative pressure is generated in the lubricating oil in the internal space of the housing, and bubbles are generated in the lubricating oil, which causes leakage of the lubricating oil and vibration. It may cause such as. In addition, the pressure of the lubricating oil around the thrust bearing increases, causing the shaft member to rise, or conversely, the pressure on the thrust bearing side decreases and the shaft member is pressed against the receiving member such as the thrust plate. In some cases, abnormal wear of the member may be caused.

Such a problem can be solved by providing a communicating groove for communicating the thrust bearing portion and the seal space. That is, when a pressure difference of the lubricating oil occurs between the space around the thrust bearing portion and the seal space,
A flow of lubricating oil occurs between the two spaces through the communication groove, so that the hydraulic pressure in both spaces is kept constant.

The above-mentioned communication groove is, for example, a first radial groove formed between one end surface of the bearing member on the bottom side of the housing and the surface of the housing opposed thereto, and on the opening side of the housing. A second radial groove formed between the other end surface of the bearing member and the surface of the seal member facing the other end surface;
The bearing member may have an axial groove formed between the outer peripheral surface of the bearing member and the inner peripheral surface of the housing.

The "fluid bearing device" of the present invention includes a so-called fluid dynamic pressure bearing device provided with a dynamic pressure generating device for producing a dynamic pressure in the lubricating oil in the bearing gap, and a so-called fluid dynamic bearing device having no dynamic pressure generating device. A fluid perfect circular bearing device (a bearing device having a perfect circular bearing surface) is included, but a fluid dynamic bearing device having a more excellent shaft supporting function is preferable. In the case of a fluid dynamic bearing device, the above-mentioned “dynamic pressure generating means” may be a dynamic pressure groove on one of the inner peripheral surface of the bearing member and the outer peripheral surface of the shaft member that face each other with a radial bearing gap therebetween. With the configuration,
The above-mentioned one circumferential surface can be configured to have a non-circular shape, for example, a plurality of circular arcs such as two circular arcs, three circular arcs, and four circular arcs.
Also called. ). In the former case, as the shape of the dynamic pressure groove,
Adopting various known dynamic pressure groove shapes such as herringbone shape, spiral shape, plural axial groove shapes (a bearing having plural axial grooves on a radial bearing surface is also called a "step bearing"). You can Further, the thrust dynamic pressure bearing portion may be formed by forming a dynamic pressure groove having a herringbone shape or a spiral shape on one of the surfaces facing each other through the thrust bearing gap. Further, as the material of the bearing member, copper alloy, stainless steel, brass, aluminum alloy or the like can be used in addition to porous sintered metal.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

FIG. 1 shows a fluid dynamic bearing device 1 according to the first embodiment. This hydrodynamic bearing device 1 is incorporated in a spindle motor for information equipment as shown in FIG. 7, for example, and has an opening 2a at one end (upper side in FIG. 1) and a bottom part at the other end (lower side in FIG. 1). A bottomed cylindrical housing 2 having 2c, a cylindrical bearing member 3 fixed to the inner peripheral surface of the housing 2, a shaft member 4, and a seal member 5 fixed to the opening 2a of the housing 2. It is configured as a main component. As described later, the first radial bearing portion R1 is provided between the inner peripheral surface 3a of the bearing member 3 and the outer peripheral surface 4a of the shaft member 4.
And the second dynamic pressure bearing portion R2 are provided separately from each other in the axial direction. Further, a thrust bearing portion T is provided between the bottom portion 2c of the housing 2 and the lower end surface 4b of the shaft member 4.

The housing 2 is made of a soft metal material such as brass and has a cylindrical side portion 2b and a bottom portion 2c. A thrust plate 6 made of resin, for example, is arranged in a region that serves as a thrust bearing surface on the inner bottom surface of the bottom portion 2c. In this embodiment, the housing 2 has a side portion 2b and a bottom portion 2c that are integrally formed.
It is also possible that the b and the bottom portion 2c have a separate structure, and a lid-like member made of metal that serves as the bottom portion 2c is caulked to the opening on the other end side of the side portion 2b, and fixed and sealed by means such as adhesion. In this case, the thrust plate 6 is arranged on the upper surface of the lid-shaped member.

The shaft member 4 is made of, for example, stainless steel (SU
S420J2) or other metallic material, and the lower end surface 4 thereof
b is formed into a convex sphere.

The bearing member 3 is formed of, for example, a porous body made of a sintered metal, particularly a sintered metal porous body containing copper as a main component. Further, on the inner peripheral surface 3a of the bearing member 3, two upper and lower regions serving as radial bearing surfaces (radial bearing surfaces of the first radial bearing portion R1 and the second radial bearing portion R2) are provided axially separated from each other. ing. In these regions, dynamic pressure grooves, for example, herringbone dynamic pressure grooves 3a1,
3a2 is formed.

The outer peripheral surface 4a of the shaft member 4 is inserted into the inner peripheral surface 3a of the bearing member 3, and an area (two upper and lower areas) serving as a radial bearing surface of the inner peripheral surface 3a of the bearing member 3, respectively.
Opposing via a radial bearing gap. Further, the lower end surface 4 b of the shaft member 4 contacts the upper surface of the thrust plate 6.

The seal member 5 is an annular member and is fixed to the inner peripheral surface of the opening 2a of the housing 2 by means such as press fitting or adhesion. In this embodiment, the inner peripheral surface 5 of the seal member 5 is
a is formed in a cylindrical shape, and the lower end surface 5b of the seal member 5 contacts the upper end surface 3b of the bearing member 3.

The inner peripheral surface 5a of the seal member 5 opposes the outer peripheral surface 4a of the shaft member 4 with a predetermined gap therebetween, thereby forming a cylindrical seal space S1 therebetween. The internal space of the housing 2 sealed by the seal member 5, including the internal pores of the bearing member 3 (pores of porous tissue), is filled with lubricating oil without interposing air, and the lubricating oil surface is sealed. It is in the space S1. The volume of the seal space S1 is set to be larger than the volume change amount of the lubricating oil with which the internal space of the housing 2 is filled due to the temperature change within the operating temperature range. As a result, even if the volume of the lubricating oil changes due to the temperature change, the oil surface of the lubricating oil can be constantly maintained in the seal space S1.

Lubricating oil is injected into the internal space of the housing 2 in the following manner, for example. First, each component (housing 2, bearing member 3, shaft member 4, thrust plate 6,
Unlubricated hydrodynamic bearing device 1 by assembling the seal member 5)
And the unlubricated hydrodynamic bearing device 1 is immersed in lubricating oil in a vacuum chamber. The air in the internal space of the housing 2 is drawn and exhausted by the vacuum pressure in the vacuum chamber, and the air is not present in the internal space. After that, when it is opened to the atmospheric pressure, the internal space of the housing 2 is filled with the lubricating oil. After the lubrication is finished, the hydrodynamic bearing device 1 is taken out of the vacuum chamber and heated to the operating upper limit temperature of the hydrodynamic bearing device 1.
With this heating, the lubricating oil filled in the internal space of the housing 2 thermally expands, and the excess lubricating oil is discharged to the outside from the seal space S1. Thereby, even when the hydrodynamic bearing device 1 is operated at the operation upper limit temperature, the oil level of the lubricating oil is maintained in the seal space S1. After that, when heating is stopped,
The oil level of the lubricating oil decreases as the temperature decreases, and the seal space S
Settle to a proper level within 1.

In the above-mentioned lubrication process, air may remain slightly in the internal space of the housing 2 depending on the degree of vacuum in the vacuum chamber. However, the amount of air remains at a predetermined level, that is, the hydrodynamic bearing device 1 and Under the environmental conditions expected to be the use / transportation environment of the motor incorporating this, the lubricating oil is pushed out of the seal space S1 due to the expansion of the air remaining in the inner space of the housing 2 and does not leak to the outside of the housing 2. If it is regulated by. In this embodiment, under reduced pressure at 100 Torr, the hydrodynamic bearing device 1 is in a normal posture (a posture in which the side of the opening 2a of the housing 2 faces upward) and an inverted posture (a posture in which the side of the opening 2a of the housing 2 faces downward. ), A horizontal posture (a posture in which the opening 2a side of the housing 2 is oriented in the horizontal direction) and an inclined posture (a posture in which the opening 2a side of the housing 2 is oriented in the inclination direction) 2 so that it does not leak outside.

In the hydrodynamic bearing device 1 having the above structure, when the shaft member 4 rotates, dynamic pressure of lubricating oil is generated in the radial bearing gap, and the outer peripheral surface 4a of the shaft member 4 is formed in the radial bearing gap. An oil film of lubricating oil is supported in a non-contact manner so as to be rotatable in the radial direction. Thereby, the shaft member 4
A first radial bearing portion R1 and a second radial bearing portion R2 that rotatably support in a radial direction in a non-contact manner are configured. At the same time, the lower end surface 4b of the shaft member 4 is contact-supported by the thrust plate 6, thereby forming a thrust bearing portion T that rotatably supports the shaft member 4 in the thrust direction.

The hydrodynamic bearing device 1 of this embodiment is also capable of expanding or contracting the residual air in the internal space of the housing due to changes in ambient temperature, heat generation of the motor, or decompression environment such as high altitude use or air transportation. Lubricating oil does not leak from the inside of the housing 2 to the outside regardless of the posture of the motor, and stable operation and transportation are possible.

FIG. 2 shows a fluid dynamic bearing device 1'according to the second embodiment. The hydrodynamic bearing device 1 ′ of this embodiment is different from the above-described first embodiment in that a seal formed between the inner peripheral surface of the seal member 5 ′ and the outer peripheral surface of the shaft member 4 ′ facing the seal member 5 ′. The point is that the space S2 has a tapered shape that gradually expands to one end side (outward direction) of the housing 2. In this embodiment, the tapered seal space S2
In order to form the above, the inner peripheral surface of the seal member 5 ′ is a tapered surface 5a ′ having a shape in which the diameter is gradually increased toward one end side, and the outer peripheral surface of the shaft member 4 ′ facing the tapered surface 5a ′ is
Tapered surface 4a1 'having a shape in which the diameter gradually decreases toward one end side
Is provided. The tapered surface 5a 'and the tapered surface 4a1'
One of them may be a cylindrical surface.

As shown enlarged in the chain line circle in FIG. 2, the lubricating oil L in the seal space S2 has the oil level in the seal space S2, and the seal space S2 is separated by the capillary force. It is drawn in the narrowing direction (the other end side: the inner direction of the housing 2). Therefore, the housing 2
The leakage of the lubricating oil L from the inside to the outside is effectively prevented. Further, the tapered surface 4a is formed on the outer peripheral surface of the shaft member 4 '.
By providing 1 ', when the shaft member 4'rotates, the lubricating oil L in the seal space S2 receives a centrifugal force, and the seal space S2 narrows along the tapered surface 4a1' (in the housing 2). (Inward). Therefore,
In addition to the pulling action by the above-mentioned capillary force, there is also the pulling action by the centrifugal force. Therefore, the effect of preventing the lubricating oil L from leaking out is further enhanced as compared with the hydrodynamic bearing device 1'of the first embodiment described above.

FIG. 3 shows a fluid dynamic bearing device 1 according to the third embodiment. The hydrodynamic bearing device 1 is incorporated in a spindle motor for information equipment as shown in FIG. 7, for example, and has an opening 2a at one end (upper side in FIG. 3) and a bottom part at the other end (lower side in FIG. 3). A bottomed cylindrical housing 2 having 2c, a cylindrical bearing member 3 fixed to the inner peripheral surface of the housing 2, a shaft member 4, and a seal member 5 fixed to the opening 2a of the housing 2. It is configured as a main component. As described later, the first radial bearing portion R1 is provided between the inner peripheral surface 3a of the bearing member 3 and the outer peripheral surface 4a of the shaft member 4.
And the second dynamic pressure bearing portion R2 are provided separately from each other in the axial direction. Further, a thrust bearing portion T is provided between the bottom portion 2c of the housing 2 and the lower end surface 4b of the shaft member 4.

The housing 2 is made of a soft metal material such as brass and has a cylindrical side portion 2b and a bottom portion 2c. A thrust plate 6 made of resin, for example, is arranged in a region that serves as a thrust bearing surface on the inner bottom surface of the bottom portion 2c. In this embodiment, the housing 2 has a side portion 2b and a bottom portion 2c that are integrally formed.
It is also possible that the b and the bottom portion 2c have a separate structure, and a lid-like member made of metal that serves as the bottom portion 2c is caulked to the opening on the other end side of the side portion 2b and fixed and sealed by means such as adhesion. In this case, the thrust plate 6 is arranged on the upper surface of the lid-shaped member.

The shaft member 4 is made of, for example, stainless steel (SU
S420J2) or other metallic material, and the lower end surface 4 thereof
b is formed into a convex sphere. In addition, the outer peripheral surface 4a of the shaft member 4
A disk-shaped washer 7 as a projecting portion is fixed to this by an appropriate means such as press fitting or adhesion.

The bearing member 3 is formed of, for example, a porous body made of a sintered metal, particularly a sintered metal porous body containing copper as a main component. Further, on the inner peripheral surface 3a of the bearing member 3, two upper and lower regions serving as radial bearing surfaces (radial bearing surfaces of the first radial bearing portion R1 and the second radial bearing portion R2) are provided axially separated from each other. ing. In these regions, dynamic pressure grooves, for example, herringbone dynamic pressure grooves 3a1,
3a2 is formed.

The outer peripheral surface 4a of the shaft member 4 is inserted into the inner peripheral surface 3a of the bearing member 3, and an area (two upper and lower areas) serving as a radial bearing surface of the inner peripheral surface 3a of the bearing member 3, respectively.
Opposing via a radial bearing gap. Further, the lower end surface 4 b of the shaft member 4 contacts the upper surface of the thrust plate 6.

The seal member 5 is an annular member, and is fixed to the inner peripheral surface of the opening 2a of the housing 2 by means such as press fitting or adhesion. In this embodiment, the inner peripheral surface 5 of the seal member 5 is
a is formed in a cylindrical shape, and the lower end surface 5b of the seal member 5 faces the upper end surface 3b of the bearing member 3 with a predetermined axial gap X therebetween.

The washer 7 provided on the shaft member 4 is arranged in the axial interval X, and when the lower end surface 4b of the shaft member 4 is in contact with the upper surface of the thrust plate 6, the washer 7 and the upper end surface 7a of the washer 7 are provided. An axial gap X1 is provided between the lower end surface 5b of the seal member 5 and an axial gap X between the lower end surface 7b of the washer 7 and the upper end surface 3b of the bearing member 3.
Two are provided. The size of the axial gap X1 is 0.05 m
m to 0.5 mm, preferably 0.05 mm to 0.3 mm
Is. The axial gap X2 may be set to a size such that the lower end surface 7b of the washer 7 does not come into contact with the upper end surface 3b of the bearing member 3 when the shaft member 4 rotates. It is preferable that the thickness is 0.05 mm or more in consideration of the above. The size of the axial gap X2 may be the same as the axial gap X1 or may be larger or smaller than the axial gap X1.

The inner peripheral surface 5a of the seal member 5 opposes the outer peripheral surface 4a of the shaft member 4 with a predetermined gap therebetween, thereby forming a cylindrical seal space S1 therebetween. The internal space of the housing 2 sealed by the seal member 5, including the internal pores of the bearing member 3 (pores of porous tissue), is filled with lubricating oil without interposing air, and the lubricating oil surface is sealed. It is in the space S1. The volume of the seal space S1 is set to be larger than the volume change amount of the lubricating oil with which the internal space of the housing 2 is filled due to the temperature change within the operating temperature range. As a result, even if the volume of the lubricating oil changes due to the temperature change, the oil surface of the lubricating oil can be constantly maintained in the seal space S1.

To the inner space of the housing 2, for example, the first
Lubricating oil is injected in the same manner as in the embodiment of the present invention, and even if the air remaining in the housing internal space expands and contracts in a depressurized environment from atmospheric pressure to 100 Torr, it is lubricated from the inside of the housing 2 regardless of the posture of the motor. It has a structure that does not leak oil.

In this embodiment, when the shaft member 4 receives an external force or gravity and moves axially relative to the housing 2, the washer 7 provided on the shaft member 4 comes into contact with the seal member 5. , Further restricts the axial relative movement of the shaft member 4. Thereby, the shaft member 4 is always held in the housing 2 and prevented from coming off from the housing 2.

Furthermore, since the axial clearance X1 between the washer 7 and the seal member 5 is set within the range of 0.05 mm to 0.5 mm, during steady operation (the lower end surface 4b of the shaft member 4 is When rotating while being supported by the thrust plate 6 in contact therewith, there is no contact between the washer 7 and the seal member 5, and a stable operating state can be obtained. Even when the shaft member 4 moves in the axial gap X1 relative to each other in the axial direction, air may flow into the housing 2 or the lubricating oil filled in the housing 2 may flow from the seal space S1. There is no phenomenon of being pushed out and leaking to the outside.

Since other matters are the same as those in the first embodiment, duplicate description will be omitted.

FIG. 4 shows a hydrodynamic bearing device 1'according to the fourth embodiment. Hydrodynamic bearing device 1'of this embodiment
Is different from the above-described third embodiment in that the seal space S2 formed between the inner peripheral surface of the seal member 5 ′ and the outer peripheral surface of the shaft member 4 ′ facing the seal space S2 is disposed at one end side of the housing 2. The point is that the taper shape is gradually expanded in the (outward direction). In this embodiment, in order to form the taper-shaped seal space S2, the inner peripheral surface of the seal member 5'is formed into a taper surface 5a 'having a diameter gradually increasing toward one end, and
On the outer peripheral surface of the shaft member 4'which faces the tapered surface 5a ', a tapered surface 4a1' having a shape in which the diameter is gradually reduced toward one end side is provided. It should be noted that one of the tapered surface 5a 'and the tapered surface 4a1' may be a cylindrical surface.

As shown enlarged in the chain line circle in FIG. 4, the lubricating oil L in the seal space S2 has a surface of the lubricating oil L, so that the lubricating oil L in the seal space S2 is separated by the capillary force. It is drawn in the narrowing direction (the other end side: the inner direction of the housing 2). Therefore, the housing 2
The leakage of the lubricating oil L from the inside to the outside is effectively prevented. Further, the tapered surface 4a is formed on the outer peripheral surface of the shaft member 4 '.
By providing 1 ', when the shaft member 4'rotates, the lubricating oil L in the seal space S2 receives a centrifugal force, and the seal space S2 narrows along the tapered surface 4a1' (in the housing 2). (Inward). Therefore,
In addition to the pulling action by the above-mentioned capillary force, there is also the pulling action by the centrifugal force, so that the effect of preventing the leakage of the lubricating oil L is further enhanced as compared with the hydrodynamic bearing device 1 ′ of the third embodiment described above.

In the embodiment described above, the radial bearing surface (the first radial bearing portion R1 and the second radial bearing portion R) is used.
Herringbone shaped dynamic pressure groove 3a as a dynamic pressure generating means on the inner peripheral surface 3a of the bearing member 3 which is the radial bearing surface 2).
Although 1 and 3a2 are formed, a spiral dynamic pressure groove may be formed instead of the herringbone shape. Alternatively, as shown in FIG. 8, a plurality of axial groove-shaped dynamic pressure grooves 3a3 may be formed as the dynamic pressure generating means on the inner peripheral surface 3a of the bearing member 3 serving as a radial bearing surface (so-called "step bearing"). )).

Alternatively, as shown in FIGS. 9 to 11, inside the bearing member 3 serving as the dynamic pressure generating means, which is the radial bearing surface (the radial bearing surfaces of the first radial bearing portion R1 and the second radial bearing portion R2). The peripheral surface 3a may be formed in a non-circular shape, for example, a plurality of arcs (so-called "arc bearing"). In the example shown in FIG. 9, the inner peripheral surface 3a of the bearing member 3 has two circular arc surfaces (3
a4, 3a5). The center of curvature O1 of the arcuate surface 3a4 and the center of curvature O2 of the arcuate surface 3a5 are offset from the outer peripheral surface 4a (round shape) of the shaft member 4 by the same distance. In the example shown in FIG. 10, the inner peripheral surface 3a of the bearing member 3 is composed of three arc surfaces (3a6, 3a7, 3a8). Center of curvature O3 of arc surface 3a6, center of curvature O4 of arc surface 3a7, center of curvature O of arc surface 3a8
Reference numerals 5 are offset from the outer peripheral surface 4a (perfect circle shape) of the shaft member 4 by an equal distance. In the example shown in FIG. 11, the inner peripheral surface 3a of the bearing member 3 is formed into four circular arc surfaces (3a9, 3a1).
0, 3a11, 3a12). Center of curvature O6 of arc surface 3a9, center of curvature O of arc surface 3a10
7, the center of curvature O8 of the circular arc surface 3a11, and the center of curvature O9 of the circular arc surface 3a12 are equidistantly offset from the outer peripheral surface 4a (round shape) of the shaft member 4.

The above dynamic pressure generating means may be provided on the outer peripheral surface 4a of the shaft member 4.

Alternatively, as shown in FIG. 12, the first radial bearing portion R1 (second radial bearing portion R2) may be a "true circular bearing" that does not have a dynamic pressure generating means.

In the embodiment shown in FIG. 13, the thrust bearing portion T, the inner peripheral surface 5a of the seal member 5 and the outer peripheral surface 4 of the shaft member 4 are used.
The communication groove 10 in which the seal space S1 between the a and the a is arranged at one location or a plurality of locations (two locations in the illustrated example) in the circumferential direction.
It was communicated with.

The communication groove 10 is composed of first and second radial grooves 10a and 10c and an axial groove 10b, and has a structure in which both radial grooves 10a and 10c are connected to both ends of the axial groove 10b. . The first radial groove 10a is formed between the one end surface 3c (on the housing bottom 2c side) of the bearing member 3 and the surface of the housing 2 facing this, specifically, the inner surface 2c1 of the housing bottom 2c. To be done. Also,
The second radial groove 10c is provided between the other end surface 3b (on the housing opening 2a side) of the bearing member 3 and the surface of the seal member 5 that faces the end surface 3b, specifically, the inner surface 5b of the seal member 5. Is formed. The axial groove 10b is formed between the outer peripheral surface of the bearing member 3 and the inner peripheral surface of the side portion 2b of the housing 2.

In the embodiment shown in FIG. 13, both the first and second radial grooves 10a and 10c are formed on both end surfaces 3c and 3b of the bearing member 3, and the axial groove 10b is an outer peripheral surface of the bearing member 3. Is formed in. During rotation of the shaft member 4, for example, when the pressure of the lubricating oil increases in the space of the thrust bearing portion T (the space around the shaft end portion of the shaft member 4), the sealing space S1 is generated from the periphery of the thrust bearing portion T through the communication groove 10. A flow of the lubricating oil toward is generated, and the pressure of the lubricating oil around the thrust bearing portion T and around the seal space S1 is kept equal. Therefore, it is possible to prevent the generation of bubbles due to the local negative pressure generated in the lubricating oil, the leakage of the lubricating fluid, the generation of vibrations, and the like caused by the bubbles. In addition, the lifting of the shaft member 4 due to the increased pressure of the lubricating oil around the thrust bearing portion T is also prevented. On the contrary to the above, in the case where the pressure in the seal space S1 is increased, similarly,
By the communication groove 10, the periphery of the thrust bearing portion T and the seal space S1 are kept at an equal pressure, and the leakage of lubricating oil due to the generation of bubbles and the abnormal wear of the thrust plate 6 due to the shaft member 4 being pressed against the housing bottom portion 2c. Such an adverse effect can be avoided.

FIG. 14 shows an embodiment in which the communication passage 10 'is formed in a member (housing 2 and seal member 5) facing the bearing member 3. That is, the first radial groove 10
a 'is formed on the inner side surface 2c1 of the housing bottom portion 2c, the second radial groove 10c' is formed on the inner side surface 5b 'of the seal member 5, and the axial groove 10b' is formed on the inner peripheral surface of the housing side portion 2b. With this communication groove 10 ', the same effect as that of the embodiment shown in FIG. 13 can be obtained.

In FIG. 13, the cylindrical seal space S1
14 shows the tapered seal space S2, the shape of the seal space is not particularly limited, and conversely, the tapered seal space S2 in the embodiment of FIG. It is also possible to use a cylindrical seal space S1 in the embodiment of FIG.

[0072]

EXAMPLE Lubricating oil was applied to the hydrodynamic bearing device 1 of the form shown in FIG. 1 in the above-described manner (vacuum impregnation), and the degree of vacuum in the vacuum chamber at that time was changed to release the housing 2 after the atmospheric pressure was released.
Five types of test bearing devices (Examples 1 and 2 and Comparative Examples 1 to 3) were produced in which the amount of air remaining in the inner space of was varied. It is difficult to measure the amount of air remaining in the internal space of the housing after vacuum impregnation, but for example, in a vacuum chamber at 380 Torr.
If the pressure is reduced to (1/2 of atmospheric pressure), it can be estimated that 50 vol% of air in the internal space volume remains inside the housing after the atmospheric pressure is released. Therefore, the residual air amount was estimated by this method.

Using each of the above test bearing devices, confirmation of the presence or absence of lubricating oil leakage when left in a depressurized environment (pressure reduction test), and incorporating each test bearing device into an actual machine motor, the operating posture was changed under atmospheric pressure. Then, the presence or absence of lubricating oil leakage was checked during ON-OFF operation (actual machine test). Table 1 shows the test results
(Decompression test) and Table 2 (implementation test). The test conditions are as follows. [Decompression test] Vacuum degree: 100 Torr [Actual machine test] Motor used: CD-ROM Actual machine motor rotation speed: 8000 rpm Atmosphere temperature: 60 ° C Motor attitude: Normal position, sideways, inverted operating condition: ON-OFF (30 seconds per cycle) Test time: 300,000 cycles

[0074]

[Table 1]

[0075]

[Table 2]

In the decompression test, the amount of air remaining in the housing internal space varies depending on the degree of vacuum in the vacuum chamber.
Even when vacuum impregnation was performed, there was a case where lubricating oil leak occurred under reduced pressure (Comparative Examples 1 to 3).

In the actual machine test, the ones to which the lubricating oil was drip-dried (Comparative Examples 2 and 3) were 5 to 5 in the lateral and inverted postures.
Lubricating oil leaked after 200,000 cycles. On the other hand, those subjected to vacuum impregnation (Example 1, Example 2, Comparative Example 1)
No lubricating oil leak occurred in all positions of 300,000 cycles.

Therefore, by performing the lubrication such that the lubricating oil does not leak even under the reduced pressure of 100 Torr as in the embodiment, it is possible to stably operate and transport under any assumed posture of use and environmental conditions. It is possible to provide a hydrodynamic bearing device that does not leak lubricating oil.

Further, in the structure shown in FIG. 3, the axial gap X1 between the washer 7 and the seal member 5 is 0.1 m.
Three types of hydrodynamic bearing devices 1 set to m, 0.3 mm, and 0.5 mm were produced (Examples 3 to 5), and each hydrodynamic bearing device 1 was manufactured.
A dummy disk 9 having a load equivalent to that of the actual machine was attached to the shaft member 4 of FIG. 5 (FIG. 5), and a 1000 G drop impact test was performed, and then the presence or absence of leakage of lubricating oil from the inside of the housing 2 was confirmed. The impact value of 1000 G was set with reference to the impact load resistance characteristics required for spindle motors used in recent portable youth equipment such as HDD devices for notebook computers. Further, the conventional hydrodynamic bearing device shown in FIG. 7 was tested under the same conditions as above (Comparative Example 4). The test results are shown in Table 3.

[0080]

[Table 3]

From the test results shown in Table 3, when an impact load of 1000 G was applied, the shaft member slipped out of the housing in Comparative Example 4 (shaft slippage), but shaft slippage did not occur in Examples 3-5. There was no lubricant leakage.

Further, the hydrodynamic bearing devices of Examples 3 to 5 and Comparative Example 4 were each incorporated into an actual machine motor (polygon scanner motor for laser beam printer), and after operating under the following conditions, the lubricating oil from the inside of the housing was used. The presence or absence of leakage was confirmed. The test results are shown in Table 4. [Operating conditions] Actual motor: Polygon scanner motor for LBP Rotation speed: 30000 rpm Heat cycle pattern: See Fig. 6 Test time: 20 cycles Motor posture: Lateral posture, inverted posture

[0083]

[Table 4] From the test results shown in Table 4, lubricating oil leakage was observed in Comparative Example 4 when operating under heat cycles, but in Examples 3 to 5, lubricating leakage was observed in any of the sideways posture and the inverted posture. I couldn't see it.

[0084]

The present invention has the following effects.

(1) Under reduced pressure environment, especially from atmospheric pressure to 100
Since the internal space of the housing is filled with the lubricating oil to the level where the lubricating oil does not leak outside even if the air remaining in the internal space of the housing expands or contracts under the environment of Torr, the high temperature / low temperature environment In any environment conditions that are assumed to be the use and transportation environment of the motor, such as use in high altitude or under reduced pressure such as during air transportation, even if you take any arbitrary posture such as normal posture, inverted posture, sideways posture, There is no leakage of lubricating oil from the inside of the housing to the outside, and stable operation and transportation are possible.

(2) By filling the internal space of the housing with the lubricating oil in a state where no air is interposed, it is possible to prevent the lubricating oil from leaking or cavitation due to the mixing of the air.

(3) The shaft member is always held in the housing by providing the shaft member with a protrusion that comes into contact with the seal member and restricts the axial relative movement of the shaft member toward one end side with respect to the housing. It is prevented from coming off.

(4) 0.0 between the protrusion and the seal member
By providing an axial gap of 5 mm to 0.5 mm,
It is possible to avoid contact between the protruding part and the seal member and obtain a stable operating state, and at the same time, even if the shaft member relatively moves in the axial direction within the range of the axial gap, the air inflows into the housing. Moreover, it is possible to prevent the lubricating oil from leaking from the inside of the housing.

(5) By providing a tapered seal space that gradually expands toward the one end side between the inner peripheral surface of the seal member and the outer peripheral surface of the shaft member facing the seal member, the sealing performance is improved. Therefore, the leakage of lubricating oil can be prevented more effectively.

(6) By providing a communication groove for communicating the thrust bearing portion and the seal space, even when a pressure difference of the lubricating oil is generated between the thrust bearing portion and the seal space,
Both can be made equal pressure. Therefore, the generation of bubbles due to the pressure difference, the leakage of lubricating oil, the lifting of the shaft,
It is possible to prevent adverse effects such as abnormal wear of the thrust plate.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a fluid dynamic bearing device according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a fluid dynamic bearing device according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a fluid dynamic bearing device according to a third embodiment of the present invention.

FIG. 4 is a sectional view showing a fluid dynamic bearing device according to a fourth embodiment of the present invention.

FIG. 5 is a cross-sectional view of a hydrodynamic bearing device used in a test.

FIG. 6 is a diagram showing a heat cycle pattern.

FIG. 7 is a sectional view of a spindle motor incorporating a conventional hydrodynamic bearing device.

FIG. 8 is a cross-sectional view showing an example in which a plurality of axial groove-shaped dynamic pressure grooves are formed on the inner peripheral surface of the bearing member as the dynamic pressure generating means.

FIG. 9 is a cross-sectional view showing an example in which an inner peripheral surface of a bearing member is formed of a plurality of arcs as a dynamic pressure generating means.

FIG. 10 is a cross-sectional view showing an example in which an inner peripheral surface of a bearing member is formed of a plurality of arcs as a dynamic pressure generating means.

FIG. 11 is a cross-sectional view showing an example in which an inner peripheral surface of a bearing member is formed of a plurality of arcs as a dynamic pressure generating means.

FIG. 12 is a cross-sectional view showing an example in which the radial bearing portion is a perfect circular bearing without a dynamic pressure generating means.

FIG. 13 is a cross-sectional view showing an embodiment of a hydrodynamic bearing device having a communication groove.

FIG. 14 is a cross-sectional view showing another embodiment of a fluid dynamic bearing device having a communication groove.

[Explanation of symbols]

1, 1'fluid bearing device 2 housing 3 Bearing members 4,4 'shaft member 5 Seal member 7 Washer (projection) 10, 10 'communication groove 10a, 10a 'first radial groove 10b, 10b 'axial groove 10c, 10c 'second radial groove S1, S2 Sealed space R1, R2 radial bearing T thrust bearing

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3J011 AA07 BA04 BA10 CA01 CA02                       JA02 KA02 KA03 LA01 MA05                       SB01 SB19 SC01

Claims (10)

[Claims] 1. A housing having an opening at one end and a bottom at the other end, a shaft member and a bearing member housed in the housing, an inner peripheral surface of the bearing member and an outer peripheral surface of the shaft member. In a hydrodynamic bearing device provided between: a radial bearing portion for supporting the shaft member in a radial direction in a non-contact manner with an oil film of lubricating oil generated in a radial bearing gap; and a seal member arranged in an opening portion of the housing. The internal space of the housing is filled with the lubricating oil to a level at which the lubricating oil does not leak outside even when the air remaining in the internal space of the housing in a depressurized environment expands or contracts. Hydrodynamic bearing device. 2. The atmospheric pressure in the reduced pressure environment is from atmospheric pressure to 10
The hydrodynamic bearing device according to claim 1, wherein the hydrodynamic bearing device has a pressure of 0 Torr. 3. A housing having an opening at one end and a bottom at the other end, a shaft member and a bearing member housed in the housing, an inner peripheral surface of the bearing member and an outer peripheral surface of the shaft member. A radial bearing portion which is provided between the radial bearing portion and a radial bearing portion for supporting the shaft member in a radial direction in a non-contact manner with an oil film of lubricating oil, and which is provided at the bottom portion of the housing,
A hydrodynamic bearing device comprising: a thrust bearing portion that supports an end surface on the other end side of the shaft member in a thrust direction; and a seal member arranged in an opening portion of the housing, wherein the shaft is in contact with the seal member. A hydrodynamic bearing device, wherein the shaft member is provided with a protrusion that restricts axial relative movement of the member toward the one end side with respect to the housing. 4. The interior space of the housing is also lubricated by the expansion / contraction of air remaining in the interior space of the housing under a depressurized environment of atmospheric pressure to 100 Torr. 4. The hydrodynamic bearing device according to claim 3, wherein there is no oil leakage. 5. The hydrodynamic bearing device according to claim 3, wherein an axial gap of 0.05 mm to 0.5 mm is provided between the protrusion and the seal member. 6. The fluid according to claim 1, wherein the radial bearing portion is provided with a dynamic pressure generating means for generating a dynamic pressure in the lubricating oil in the radial bearing gap. Bearing device. 7. A tapered seal space that gradually expands toward one end side is provided between an inner peripheral surface of the seal member and an outer peripheral surface of the shaft member facing the seal member. 7. The hydrodynamic bearing device according to any one of 1 to 6. 8. A housing having an opening at one end and a bottom at the other end, a shaft member and a bearing member housed in the housing, an inner peripheral surface of the bearing member and an outer peripheral surface of the shaft member. A radial bearing portion that is provided between the radial bearing portion and a radial bearing portion that supports the shaft member in the radial direction in a non-contact manner with an oil film of lubricating oil, and a thrust bearing portion that supports the shaft end portion of the shaft member in the thrust direction. A hydrodynamic bearing device, which is disposed in an opening of a housing and includes a seal member that forms a seal space with the outer periphery of a shaft member, is characterized in that a communication groove is provided to connect the thrust bearing portion and the seal space. Hydrodynamic bearing device. 9. The first radial groove formed between the one end surface of the bearing member on the bottom side of the housing and the surface of the housing facing the communication groove, and the bearing on the opening side of the housing. A second radial groove formed between the other end surface of the member and the surface of the seal member facing the other end surface; and an axial groove formed between the outer peripheral surface of the bearing member and the inner peripheral surface of the housing. The fluid dynamic bearing device according to claim 8, further comprising: 10. A motor provided with the hydrodynamic bearing device according to claim 1.