JPH11264409A - Dynamic pressure fluid bearing device and motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To preventing a device from breaking down shortly which is caused by a shortage of lubricant for a thrust bearing part or a radial bearing part, and prevent the amount of lubricant which lubricates the thrust bearing part from decreasing extremely which is caused by too much lubricant which is stored in the thrust bearing part transferring to the radial bearing part in a rotating sleeve body rotating. SOLUTION: A communicating ejected bar part along a radius direction is provided to two places at both ends in an angle of 180 degree at a lower inside part 12b1 of a fixed thrust plate 12b. A slit part is provided between an inside end face of the communicating protruded stripe part and a peripheral face of a fixed axis member 12a. A communicating path along the radius direction is provided between the communicating ejected bar part and a lower face of a thrust groove part 20. A lubricant 44 is held in the communicating path by surface tension, and an upper end of the lubricant 44 which is held in space between the fixed axis member 12a and a sleeve part 18a1 communicates with an inside part of the lubricant 44 which is held in a lower thrust bearing part 42.

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 in which a rotating sleeve body is rotatably supported via a lubricating liquid with respect to a fixed shaft body having a thrust portion protruding from a shaft portion. The motor provided with the hydrodynamic bearing device, in particular, only one of the thrust bearing portion and the radial bearing portion can be prevented from inconvenience such as shortage of lubricating fluid and shortening of the life of the device, and can be held in the thrust bearing portion. The present invention relates to a hydrodynamic bearing device that prevents excessive amount of lubricating fluid from moving excessively to a radial bearing portion and lubricating the thrust bearing portion, and an electric motor including the hydrodynamic bearing device. .

[0002]

2. Description of the Related Art FIG.
Is a hydrodynamic bearing in which a rotating sleeve body d as a rotor is rotatably supported via a lubricating oil e (lubricating liquid) with respect to a vertically fixed shaft body c having a thrust plate part b projecting from a shaft part a. FIG. 10 is a cross-sectional view of a conventional example of a spindle motor (electric motor) for driving a hard disk including the device.

The fixed shaft c has a lower end (base end) having a base f.
The upper end (tip) is fixed to a lid or the like of a hard disk drive. The sleeve portion d1 of the rotating sleeve member d is sleeve-fitted to a portion of the shaft portion a of the fixed shaft member c closer to the base end than the thrust plate portion b, and the annular thrust groove portion g opens radially inward. And the thrust plate b
Is fitted outside.

In a spindle motor provided with such a conventional hydrodynamic bearing device, a lubricating oil e of a thrust bearing k formed in a gap between a thrust plate b and a thrust groove g, a sleeve d1 and a shaft. When the lubricating oil e of the radial bearing portion i formed in the gap a is continuous with the lubricating oil of the radial bearing portion i due to factors such as tolerance, assembly, and thermal deformation during rotation of the rotary sleeve body d. When e moves downward (toward the base end), the lubricating oil e of the thrust bearing portion k which follows it also moves. Therefore, if the moving amount increases, the lubricating oil e of the thrust bearing portion k becomes insufficient, and Inconveniences such as a decrease in accuracy and a shortened life of the bearing device, that is, the spindle motor occur.

On the other hand, an annular gas portion m is formed in the inner peripheral portion of the gap between the base end surface of the thrust plate portion b and the base end surface of the thrust groove portion g. e and the lubricating oil e of the radial bearing part i are separated, the lubricating oil e
When the number of shafts decreases, there is a problem that rotation accuracy is reduced due to insufficient lubricating oil generated in only one of the bearing portions, and that the entire bearing device, that is, the entire spindle motor is shortened in life.

When the lubricating oil e of the radial bearing portion i moves excessively (toward the tip) due to factors such as tolerance, assembly, and thermal deformation during the rotation of the rotary sleeve member d, the lubrication of the radial bearing portion i is prevented. Insufficient oil e can occur.

Further, during rotation of the rotary sleeve member d, air bubbles tend to collect near the outer peripheral portion of the gap between the thrust groove portion g and the thrust plate portion b, and the air bubbles are hardly released to the outside.
Such air bubbles expand by heat and cause the lubricating oil e to leak outside.

The present invention has been made in view of the above-mentioned problems in the prior art, and a first object of the present invention is to provide a lubricating fluid shortage in only one of a thrust bearing and a radial bearing. In addition to preventing the occurrence of inconveniences such as shortening the life of the device, the lubricating fluid retained in the thrust bearing moves excessively to the radial bearing when the rotating sleeve rotates and lubricates the thrust bearing An object of the present invention is to provide a hydrodynamic bearing device and an electric motor that can prevent the amount of liquid from becoming too small.

A second object is to reduce the amount of lubricating liquid moving toward the distal end of the radial bearing portion due to the lubricating liquid moving pressure directed toward the distal end when the rotary sleeve rotates, and the lack of lubricating fluid in the radial bearing portion can be prevented. An object of the present invention is to provide a hydrodynamic bearing device and an electric motor that can be prevented.

A third object of the present invention is to provide a hydrodynamic bearing device and an electric motor capable of releasing bubbles near the outer peripheral portion of the gap between the thrust groove and the thrust plate to the outside.

[0011]

Means for Solving the Problems (1) A hydrodynamic bearing device according to the present invention is directed to a fixed shaft having a shaft portion and a thrust portion projecting radially outward from the shaft portion. A sleeve portion fitted to a portion of the shaft portion closer to the base end than the thrust portion, and a rotary thrust surface opposed to a base end surface of the thrust portion on a base end side in the axial direction. The rotating sleeve body is mainly composed of a radial bearing portion in which the shaft portion and the sleeve portion face each other and a thrust in which the rotating thrust surface and the thrust portion face each other via the lubricating liquid filled in the gap between the fixed shaft body and the rotating sleeve body. A hydrodynamic bearing device rotatably supported in a bearing portion, wherein the bearing portion has a base-side thrust bearing portion at a portion where a base-side surface of the thrust portion and a rotary thrust surface face each other. , The thrust surface on the proximal side and the rotating thrust The proximal axial thrust bearing portion has a larger proximal axial thrust gap than the proximal thrust bearing portion, and a part of the proximal axial thrust enlarged portion has a lubricating liquid. The gap in the axial direction is narrow enough to be held by surface tension, and the held lubricating fluid is held in the inner peripheral portion of the lubricating fluid held in the proximal thrust bearing portion and in the gap between the shaft portion and the sleeve portion. Having a communication path that can be continuous with the distal end of the lubricating liquid, at least the inner peripheral part of the part other than the communication path of the base end side axial gap expanding part is a gas part, and the gas A breathing hole communicating the portion and the outside is provided in the fixed shaft body, and a communication path is provided when the lubricating fluid held by the radial bearing portion and the distal side faces the base-side axial gap enlarged portion moves in the proximal direction. The continuity of the lubricating fluid due to is interrupted (claim 1).

The shaft portion and the thrust portion constituting the fixed shaft body are
They may be formed integrally or may be formed by combining separate components.

The thrust bearing portion and the radial bearing portion include:
It is desirable to have a groove for generating dynamic pressure.

The radial bearing portion (the distal-side radial bearing portion in the case where the radial bearing portion is divided into the distal-side radial bearing portion and the proximal-side radial bearing portion) has a dynamic pressure of the lubricating fluid that is slightly increased toward the distal end within a tolerance range. It can be designed to create a balance.

As the lubricating liquid, various lubricating oils such as spindle oil can be used.

At least the inner peripheral portion of the base-side axial-gap enlarged portion is provided with a lubricating fluid at an axial gap between the base-side surface of the thrust portion and the rotating thrust surface. It is preferable that it is large enough not to hold.

The communication path may be formed, for example, on a part of the proximal-side axial gap enlarged portion, on one or both surfaces of the thrust portion on the proximal side and the rotating thrust surface, preferably on the thrust portion. A substantially radially continuous projection (e.g., approximately a projection) is formed on the proximal surface so as to project in the axial direction so that the axial clearance on both surfaces is narrower than the other portion of the enlarged proximal axial clearance. (Protrusions in the radial direction). This projection can be provided on one of the surfaces to provide a communication path with the other surface, and the both surfaces can be provided with projections opposed in the axial direction to connect the two projections. It can be a road. The number of communication paths extending radially inward from the proximal thrust bearing portion may be one, or may be two or more.

The lubricating fluid held in the communication path is between the inner peripheral portion of the lubricating fluid held in the proximal thrust bearing and the tip of the lubricating fluid held in the gap between the shaft and the sleeve. To continue. If the lubricating fluid in one of the proximal thrust bearing or the radial bearing decreases due to evaporation or dropping due to impact, etc., the lubricating fluid from the other bearing with a reduced lubricating fluid through the communication path Is replenished. For this reason, it is possible to prevent the shortage of the lubricating fluid in only one of the bearings, thereby shortening the service life of the device.

During rotation of the rotating sleeve, tolerance, assembly,
Due to factors such as thermal deformation, a pressure is generated in the lubricating fluid that is held in the gap between the shaft and the sleeve and moves toward the proximal end from the distal end toward the enlarged axially-distal portion on the proximal end side. It can move end-to-end. In that case, when the proximal movement pressure exceeds the limit, the centrifugal force and the surface tension of the lubricating fluid in the communication path also act together, and the inner peripheral portion of the lubricating fluid held by the proximal thrust bearing portion, The continuation of the lubricating fluid through the communication path between the shaft portion and the tip of the lubricating fluid held in the gap between the sleeve portion is interrupted. This prevents the amount of the lubricating fluid retained in the proximal thrust bearing from excessively moving to the radial bearing and causing the amount of the lubricating fluid that lubricates the proximal thrust bearing to be reduced. Further, if the lubricating fluid is interrupted and gas is introduced into the radial bearing portion from the distal end in this way, the lubricating fluid moving pressure in the proximal direction decreases and becomes balanced, so that the Movement to the side is suppressed.

[0020] If the base-side moving pressure of the lubricating liquid held in the gap between the shaft portion and the sleeve portion as described above is eliminated during rotation or by rotation stop, the lubrication held by the base-side thrust bearing portion. The continuity of the lubricating liquid through the communication path between the inner peripheral part of the liquid and the tip of the lubricating liquid held in the gap between the shaft part and the sleeve part can be restored.

With the expansion or contraction of the gas portion of the proximal-side axial gap expansion portion, the gas moves through the breathing hole.

The breathing hole has a cross-sectional size large enough to prevent the lubricating liquid from being retained in the breathing hole by surface tension (capillary action) when the inside of the breathing hole is closed. Is preferred. In this case, the lubricating fluid is prevented from being retained in the breathing hole by surface tension in a state where the inside of the breathing hole is closed, so that the movement of gas through the breathing hole is performed with high reliability, and the lubricating fluid is also prevented from being moved. Release of the mixed air bubbles and the like to the outside through the breathing hole can be performed with high reliability.

In the hydrodynamic bearing device, the outer peripheral surface of the shaft portion is provided with a radially outer opening in a circumferential portion where the communication path does not exist at a position facing the distal end of the sleeve portion. It may have a side arc-shaped groove.

The front-side interface of the lubricating liquid held by the radial bearing portion is provided on the surface of the circumferentially-arc-shaped enlarged radial gap formed between the front-side arc-shaped groove portion and the inner peripheral surface of the sleeve portion. The lubricating fluid, which is located due to the tension and is held in the radial direction, is prevented from flowing into the gap between the base end surface of the thrust portion and the rotary thrust surface in the circumferential bearing portion.

During rotation of the rotating sleeve, tolerances, assembly,
Due to factors such as thermal deformation, a pressure is generated in the lubricating fluid that is held in the gap between the shaft portion and the sleeve portion, and moves toward the proximal end in the lubricating fluid whose front end faces the enlarged portion in the axial direction at the proximal end, and the base moves toward the base. When the pressure exceeds the limit, when the continuity of the lubricating fluid through the communication path is interrupted, the gas is easily introduced into the radial bearing portion from the distal end side through the circumferentially extending arc-shaped radial gap expansion portion. Movement to the proximal end side is more reliably suppressed.

In this hydrodynamic bearing device, the rotary sleeve body has an annular thrust groove having a radially inward opening externally fitted to a thrust portion (for example, an annular thrust plate portion). The surface on the side and the surface on the distal side are rotational thrust surfaces, respectively. Thrust bearing portions may be provided in both of the portions where the surfaces face each other. In that case, the lubricating fluid of the distal-side thrust bearing portion and the proximal-side thrust bearing portion can be continuous through the lubricating fluid between the outer periphery of the thrust portion and the outer periphery of the thrust groove portion. In addition, a radially inward interface of the distal-side thrust bearing has a distal interface of the lubricating fluid, and the distal interface faces radially inward, and a proximal interface of the lubricating fluid is located on the proximal side of the radial bearing. The base interface can face the base side, and in this case, both ends of the fixed shaft can be fixed.

The hydrodynamic bearing device of the present invention can be used for various types of machinery other than electric motors. (1-1) In the hydrodynamic bearing device of (1), the proximal-side axial gap increasing portion gradually increases the axial gap toward the radially inward side. The radially inward interface of the lubricating liquid held by the base-side thrust bearing portion may be located at the axial-gap enlarged portion (claim 2).

In this case, the lubricating liquid located at the enlarged portion in the proximal axial direction gap is reliably drawn to the radially outward direction, that is, to the proximal axial thrust bearing portion by the surface tension. In the enlarged portion, the lubricating liquid is prevented from separating into the proximal thrust bearing portion and the inner peripheral side. (2) The hydrodynamic bearing device according to (1) or (1-1), wherein the communication path is provided on the base end surface of the thrust portion and protrudes toward the base end, and is substantially continuous in the radial direction. A protrusion formed between the rotation thrust surface and a radially inner end of the protrusion has a slit that opens in both the circumferential direction and the base end in the axial direction, and can hold the lubricating liquid by surface tension. It is preferable to have (claim 3).

The slit portion may be formed in a wedge shape, for example, in which a radial gap gradually increases toward the base end opening.

During rotation of the rotating sleeve body, tolerance, assembly,
Due to factors such as thermal deformation, a pressure is generated in the lubricating fluid that is held in the gap between the shaft and the sleeve and moves toward the proximal end from the distal end toward the enlarged axially-distal portion on the proximal end side. When moving in the end direction, there is a communication path between the inner peripheral portion of the lubricating fluid held in the proximal thrust bearing portion and the distal end portion of the lubricating fluid held in the gap between the shaft portion and the sleeve portion. The discontinuity of the lubricating liquid is likely to start at the slit. Therefore, it is possible to more reliably prevent the amount of the lubricating liquid retained in the proximal thrust bearing portion from excessively moving to the radial bearing portion and causing the amount of the lubricating liquid for lubricating the proximal thrust bearing portion to become too small. (3) The hydrodynamic bearing device according to (1), (1-1) or (2), wherein the radial bearing portion has a distal end close to a gap between the base end surface of the thrust portion and the rotary thrust surface. Side radial bearing portion, and a proximal-side radial bearing portion located closer to the proximal side than the distal-side radial bearing portion, and a shaft portion between the distal-side radial bearing portion and the proximal-side radial bearing portion. A radial gap between the outer peripheral surface and the inner peripheral surface of the sleeve portion has an intermediate radial gap expanding portion that is larger than both radial bearing portions, and the intermediate radial gap expanding portion extends from the distal radial bearing portion to the proximal end. A first gap enlargement portion in which the radial gap gradually increases toward the side, and a second gap enlargement portion in which the radial gap gradually increases from the base-side radial bearing portion toward the distal end; An interface on the base end side of the lubricating liquid held by the bearing portion is provided in the first gap enlarging portion. Both have an interface on the distal end side of the lubricating liquid held by the proximal radial bearing portion in the second gap enlarging portion, and an intermediate portion between the first gap enlarging portion and the second gap enlarging portion in the intermediate radial gap enlarging portion. The fixed shaft may be provided with a ventilation hole that communicates the vicinity of the portion and the outside at least when the rotating sleeve body rotates.

The first gap enlarging section and the second gap enlarging section in the intermediate radial gap enlarging section are not necessarily required to be adjacent to each other. For example, a portion having a constant radial gap may be provided between the first gap expanding section and the second gap expanding section.

The first and second gap enlarging portions in the intermediate radial direction enlarging portion are formed such that the outer circumferential surface of the shaft portion is gradually reduced in diameter toward the base end side and the tip end side, so that the radial gap is gradually increased. It is preferable to enlarge it.

A lubricating liquid is stored in the first gap expanding section and the second gap expanding section. When the lubricating fluid in the distal radial bearing or the thrust bearing, or in the proximal radial bearing, decreases due to evaporation or dropping due to impact, the lubricating fluid stored in the first gap widening portion is removed from the distal radial bearing. The lubricating fluid stored in the bearing portion and in the second gap expanding portion is supplied to the proximal radial bearing portion. Along with the replenishment of the lubricating liquid, gas is introduced into the intermediate radial gap expansion portion through the vent hole.

In addition, extra air bubbles mixed in the lubricating liquid and expansion of air bubbles due to a rise in temperature or a decrease in air pressure can be released to the outside through the air holes.

The vent should have a cross-sectional size that prevents the lubricating liquid from being retained in the vent by surface tension (capillary action) with the interior of the vent closed. preferable. In this case, since the lubricating liquid is prevented from being held in the vent hole by surface tension in a state where the inside of the vent hole is closed, the gas is introduced with high reliability, and bubbles mixed in the lubricating liquid are removed. It can be reliably released to the outside through the ventilation hole.

The number of ventilation holes or the number of openings to the intermediate radial direction enlarged portion or the outside can be one or two or more, respectively. (3-1) In the hydrodynamic bearing device of (3), the radial gap between the shaft portion and the sleeve portion gradually increases toward the base end side of the base side radial bearing portion. It has an end radial direction gap widening portion, and in this base end radial direction gap widening portion, a non-rotating base end interface of the lubricating liquid held by the base side radial bearing portion can be located, Further, an interface retracting mechanism is provided for retracting the proximal interface toward the distal end with the rotation of the rotary sleeve body, and the external opening of the vent hole is provided near a boundary between the proximal radial bearing portion and the proximal radial gap expanding portion. It is preferable that the opening is opened in the lubricating liquid when the rotation sleeve is not rotating, and communicates with the outside air when the rotating sleeve body rotates.

When the rotating sleeve rotates, centrifugal force acts on the lubricating liquid filled in the gap between the fixed shaft and the rotating sleeve. Therefore, during non-rotation, the lubricating liquid held by surface tension so that the base interface is located at the base radial direction gap enlarged portion further leaks or leaks to the base side by the action of the centrifugal force. Or by falling off due to an impact. However, with the interface retraction mechanism, the base interface of the lubricating liquid is drawn from the position at the time of non-rotation to the distal side with the rotation of the rotating sleeve body, so that the lubricating liquid is dissipated or leaked by the action of centrifugal force, or Dissipation due to falling off due to impact hardly occurs.

In the interface retraction mechanism, a dynamic pressure generating groove is provided in the proximal radial bearing, and the dynamic pressure generated in the lubricating fluid by the dynamic pressure generating groove with the rotation of the rotary sleeve body is controlled by the proximal radial. The bearing portion may be biased toward the front end side to be higher. For this purpose, a structure in which the dynamic pressure generating groove is eccentric, for example, toward the front end in the axial direction of the base end radial bearing may be adopted. As the dynamic pressure generating groove of the dynamic pressure generating groove portion, for example, a herringbone groove or the like can be used. Also, the dynamic pressure generating groove is
It can be provided on either or both of the shaft portion and the sleeve portion.

The outer opening of the vent hole whose one opening is located near the intermediate portion between the first gap enlarging portion and the second gap enlarging portion in the intermediate radial direction enlarging portion is located at the proximal radial bearing portion and the proximal radial direction. It is located near the boundary of the gap expanding portion, and when the rotating sleeve body rotates, the base end interface is drawn into the base side radial bearing by the interface drawing mechanism, and the external opening is open to the outside air.

When the lubricating liquid held in the distal radial bearing portion or the proximal radial bearing portion is likely to seep through the inner surface of the ventilation hole to the outside opening of the ventilation hole, the rotation of the rotating sleeve body may occur. In some cases, the lubricating liquid is drawn into the lubricating liquid by the interfacial retraction mechanism, and the lubricating liquid is prevented from seeping out to the outside in any case, because the outer opening of the vent hole is opened in the lubricating liquid when not rotating. It is. (3-2) The hydrodynamic bearing device according to (3) or (3-1) is provided near the boundary between the base end side of the distal-side radial bearing portion and the first gap enlarged portion on the outer peripheral surface of the shaft portion. A radially outer opening has a circumferentially-sided base-side arc-shaped groove portion, and the base-side arc-shaped groove portion and the outside are provided at least in the fixed shaft body with a ventilation hole that communicates at the time of rotation of the rotary sleeve body. (Claim 4).

This air hole may have a common part with the air hole of (3). The preferred cross sectional size of the vent is as described in (3).

A circumferential base-side arc-shaped groove in the outer peripheral surface of the shaft near the boundary between the base end side of the front-end side radial bearing portion and the first gap enlarging portion and the outside are formed at least in the rotary sleeve body. It communicates with the vent when rotating. for that reason,
At the time of rotation of the rotary sleeve body, in the radial bearing portion on the distal end side, a pressure occurs at which the lubricating liquid moves toward the distal end due to factors such as tolerance, assembly, and thermal deformation, and when the lubricating liquid moves toward the distal end, Gas is introduced from the proximal end side into the distal-side radial bearing portion through the vent hole and the proximal-side arc-shaped groove. This gas is introduced into the distal-side radial bearing portion at a stage where the amount of movement of the lubricating liquid is relatively small, whereby the lubricating liquid moving pressure toward the distal end decreases and balances. The amount of movement to the side can be kept relatively small. (4) The hydrodynamic bearing device according to (1), (1-1), (2), (3) or (3-1) is an annular thrust groove having a radially inward opening externally fitted to the thrust portion. The rotation sleeve body has a base end side surface and a front end side surface of the thrust groove portion as a rotation thrust surface, respectively, and a portion where the front end surface of the thrust portion and the front end rotation thrust surface face each other, The thrust bearing portion is provided on both the surface on the proximal side of the portion and the portion where the rotational thrust surface on the proximal side is opposed, and the lubricating fluid of the distal side thrust bearing portion and the proximal side thrust bearing portion is supplied to the outer periphery of the thrust portion The lubricating fluid in each of the thrust bearings is continuous from the inner peripheral side to the outer peripheral with the rotation of the rotary sleeve body in each of the distal and proximal thrust bearings through the portion between the end face and the outer peripheral portion of the thrust groove. A dynamic pressure generating mechanism that generates a pressure distribution that moves to the side,
A distal interface of the lubricating liquid is provided radially inward of the distal-side thrust bearing portion, and an outer peripheral end surface of the thrust portion, and a distal-side and proximal-side thrust of a distal-side surface and a proximal-side surface of the thrust portion. A lubricating fluid circulation path that opens into the lubricating fluid filled in the gap between the thrust groove portion and the thrust portion may be provided in the thrust portion on the inner peripheral side portion of the bearing portion.

In the above dynamic pressure generating mechanism, a dynamic pressure generating groove is provided in each of the distal and proximal thrust bearings, and the dynamic pressure generated in the lubricating fluid by the dynamic pressure generating groove with the rotation of the rotary sleeve body. The height of the thrust bearing portions on the distal end side and the proximal end side can be increased toward the outer peripheral side. For this purpose, for example, when a herringbone groove is used as the dynamic pressure generating groove of the dynamic pressure generating groove, a structure in which the center of the dynamic pressure generating groove is eccentric to the outer peripheral side of the thrust bearing portion can be adopted. Further, the dynamic pressure generating groove portion can be provided in one or both of the thrust portion and the thrust groove portion.

When the rotating sleeve body rotates, the lubricating liquid in each thrust bearing moves from the inner peripheral side to the outer peripheral side,
Next, from the outer peripheral end surface of the thrust portion through the lubricating liquid circulation path in the thrust portion, to the inner peripheral side portion of the distal end side and the proximal end side thrust bearing portion of the distal side surface and the proximal side surface of the thrust portion. Flow and circulate. By circulating the lubricating liquid in this manner, bubbles in the lubricating liquid filled in the gap between the thrust groove portion and the thrust portion, particularly bubbles on the outer peripheral side of the thrust bearing portion, are formed radially inward of the distal thrust bearing portion. It is released from the interface of the lubricating liquid to the outside air.

The number of lubricating liquid circulation paths can be one or two or more.

It is preferable that the outer peripheral end face of the thrust portion has a circumferential introduction groove having a radially outward opening, and the opening of the lubricating liquid circulation path is located in the introduction groove.
This is because the lubricating liquid is easily introduced into the opening of the lubricating liquid circulation path together with bubbles. The introduction groove may extend over the entire circumference, but may have a part in the circumferential direction. (5) The electric motor of the present invention includes the above (1), (2), (3), (3-
The hydrodynamic bearing device according to (1) or (4) is provided, and the rotating sleeve body rotates as a rotor.

The electric motor may be a magnetic disk such as a hard disk, a magneto-optical disk, a CD-ROM,
The present invention can be used as various electric motors in addition to a spindle motor for driving a recording medium such as an optical disk such as a DR, a CD-RW, and a DVD, particularly a disk-shaped recording medium.

[0048]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a sectional view of a spindle motor (electric motor) for driving a hard disk provided with a hydrodynamic bearing device as an example of an embodiment of the present invention, and FIG. 2 is a dynamic fluid of the spindle motor. FIG. 3 is an enlarged view of the vicinity of the right side of the rotary thrust plate in FIG. 1. However, the rotary thrust plate in FIG. 1 and its peripheral portion are the I-O-
Corresponds to line I.

The lower end (base end) of the fixed shaft 12 is fitted and fixed in the fitting hole of the base 10 of the spindle motor, so that the fixed shaft 12 is erected and fixed. A holder 13 that holds a stator core 16 around which a stator coil 14 is wound is fixed on the outer peripheral side of the fixed shaft body 12 above the base 10.

The fixed shaft body 12 is provided with a vertically fixed shaft member 1.
2a (shaft portion) and an annular plate-shaped fixed thrust plate 12b (thrust plate portion) coaxially fitted and fixed on the upper portion of the fixed shaft member 12a. A rotating sleeve body 18 composed of a rotor hub 18a and a rotating thrust plate 18b is externally fitted to the fixed shaft body 12.

A hard disk is externally fitted and held on the cylindrical outer peripheral portion of the rotor hub 18a. A substantially lower half of the rotor hub 18a has a double tubular shape including an inner peripheral sleeve portion 18a1 and an outer peripheral rotor magnet holding portion 18a2. The sleeve portion 18a1 is sleeve-fitted to a portion of the fixed shaft member 12a between the fixed thrust plate 12b and the base 10. The inner diameter of the upper portion of the sleeve portion 18a1 is increased upward (toward the distal end) by the middle inner diameter portion 18a3 and the large inner diameter portion 18a.
The diameter is gradually increased to 4. The rotary thrust plate 18b is internally fitted and fixed to the lower end of the large inner diameter portion 18a4, so that an annular thrust groove 20 having a radially inward opening is formed on the inner peripheral side of the middle inner diameter portion 18a3.
Are externally fitted to the fixed thrust plate 12b. Large bore 18
Above the rotary thrust plate 18b at a4, an annular plate-shaped seal member 22 is fitted and fixed.

The fixed shaft body 12 can be fixed at the lower end to the base 10 and the upper end of the fixed shaft member 12a to the lid (not shown) of the hard disk drive. Rotation can be realized.

The rotor magnet holding portion 18a2 of the rotor hub 18a has a cylindrical rotor yoke 2 made of a ferromagnetic material.
The cylindrical rotor magnet 26 is internally fixed to the cylindrical rotor yoke 24 and is opposed to the stator core 16 with a radial gap therebetween. The rotor is
It comprises a rotating sleeve body 18, a cylindrical rotor yoke 24 and a rotor magnet 26.

The portion of the outer peripheral portion of the fixed shaft member 12a that faces the lower end of the sleeve portion 18a1 is tapered downward so that the gap between the fixed shaft member 12a and the inner peripheral surface of the sleeve portion 18a1 is reduced. Is formed at the lower end (base end) radial gap expanding portion 28 which gradually expands downward. The lower end of the inner peripheral surface of the sleeve portion 18a1 is subjected to an oil repellent treatment such as application of an oil repellent.

The lower inner peripheral side of the upper surface of the thrust groove 20 is inclined upward inward, and the fixed thrust plate 1
An upper (front end side) axial direction gap expanding portion 29 is formed between the upper surface of the upper surface 2b and the upper surface 2b. A fixed shaft member 12a is provided on the inner peripheral side of the upper axial gap widening portion 29.
An annular space portion 31 in which the gap is further enlarged in the axial direction and the radial direction is formed by the annular concave portion of the outer peripheral surface and the inner peripheral surface of the rotating thrust plate 18b opposed thereto. Above the annular space 31, an oil-repellent treatment such as application of an oil-repellent is applied to the inner peripheral surface of the rotary thrust plate 18 b and the outer peripheral surface of the fixed shaft member 12 a opposed thereto with a relatively narrow gap in the radial direction. It has been subjected.

The seal member 22 and the rotary thrust plate 1
An annular lubricating oil capturing groove 30 having a radially inward opening is formed between the fixed shaft members 8a and 8b, and the fixed shaft member 12a faces the inner peripheral surface of the seal member 22 and a relatively narrow gap (eg, 50 μm) in the radial direction. Is subjected to an oil repellent treatment such as application of an oil repellent.

The lower inner peripheral side portion 12 of the fixed thrust plate 12b
b <b> 1 is inclined upward inward, and a lower (proximal side) axial-direction gap enlarging portion 32 whose gap gradually increases is formed between the lower surface and the lower surface of the thrust groove 20.

The lower inner peripheral side portion 12 of the fixed thrust plate 12b
At two places separated by a 180-degree central angle in b1, radially extending connecting ridges 34 are provided. The lower surface of the connecting ridge portion 34 is the lower outer peripheral side portion 12b2 of the fixed thrust plate 12b.
, And both sides in the circumferential direction slightly expand upward. The inner end surface of the connecting ridge portion 34 is the lower inner peripheral side portion 12.
By inclining radially outward from the inner peripheral edge of b1 downward, the radial gap gradually increases downward between the inner peripheral edge of the fixed shaft member 12a and the wedge-shaped slit portion 36. Having. Connecting ridge 34 and thrust groove 2
A communication path 37 in the radial direction is formed between the lower side surface of the first and the lower side.

On the upper and lower surfaces of the fixed thrust plate 12b,
A herringbone groove 38 (a dynamic pressure generating groove other than the herringbone groove can also be used) for providing a dynamic pressure is provided, and an upper surface of the thrust groove 20 (a lower surface of the rotary thrust plate 18b) and a herringbone groove 38, respectively. Thrust groove 20
An upper (distal end) thrust bearing portion 40 and a lower (proximal end) thrust bearing portion 42 are formed between the lower thrust bearing portion 40 and the lower side surface.

A necessary portion of a gap between the fixed shaft body 12 and the rotary sleeve body 18 is filled with a lubricating oil 44. The upper interface and the lower interface of the lubricating oil 44 filled in the gap between the thrust groove 20 and the fixed thrust plate 12b are radially inward in the upper axial gap expanding section 29 and the lower axial gap expanding section 32, respectively. Turn to. Lower axial direction gap expanding portion 32
Since the gap gradually increases inward, the lubricating oil 44 located in the lower axial direction gap expanding portion 32 is drawn with high reliability to the radially outward direction, that is, the lower thrust bearing portion 42 side by the surface tension. The lubricating oil 44 is prevented from separating into the lower thrust bearing portion 42 and the inner peripheral side in the lower axial center gap expanding portion 32.

The portion other than the communication path 37 in the inner peripheral portion of the lower axial gap widening portion 32 is a gas portion 46. The lubricating oil 44 is held by the surface tension between the communication path 37, that is, between the communication ridge 34 and the lower surface of the thrust groove 20, whereby the fixed shaft member 12 a and the sleeve 18
The upper end portion of the lubricating oil 44 held in the gap with a1 and the inner peripheral portion of the lubricating oil 44 held in the lower thrust bearing portion 42 are continuous.

The herringbone groove 38 is provided so that the center of the dynamic pressure is eccentric to the outer peripheral side of the upper thrust bearing 40 and the lower thrust bearing 42, and the lubricating oil 44 in the upper and lower thrust bearings 40 and 42 is provided. A pressure distribution is generated that moves from the inner peripheral side to the outer peripheral side with the rotation of the rotating sleeve body 18.

An axial groove which forms a breathing hole 48 between the connecting ridge 34 and the outer peripheral surface of the fixed shaft member 12a at two positions separated by 90 degrees central angle on the inner peripheral surface of the fixed thrust plate 12b. 48a. The breathing hole 48 connects the gas portion 46 and the outside with the annular space 31 and the outer peripheral surface of the fixed shaft member 12a, the inner peripheral surface of the rotary thrust plate 18b, and the seal member 2.
2 through a gap with the inner peripheral surface.

At the outer peripheral end surface of the fixed thrust plate 12b and the inner peripheral side of the upper and lower thrust bearings 40 and 42 of the upper surface and the lower surface of the fixed thrust plate 12b,
The lubricating oil circulation passages 5 open into the lubricating oil 44 filled in the gap between the thrust groove 20 and the fixed thrust plate 12b.
0 in the fixed thrust plate 12b. An outer peripheral end surface of the fixed thrust plate 12b has an introduction groove 52 having an arc-shaped cross section with a radially outward opening over the entire circumference, and the opening of the lubricating oil circulation path 50 is located in the introduction groove 52.

When the rotary sleeve 18 rotates, the lubricating oil 44 in the upper and lower thrust bearings 40 and 42 moves from the inner peripheral side to the outer peripheral side, and then moves from the outer peripheral end face of the fixed thrust plate 12b to the inside of the fixed thrust plate 12b. Lubricating oil circulation path 5
After that, the fluid flows to the inner peripheral side of the upper and lower thrust bearings 40 and 42 of the upper surface and the lower surface of the fixed thrust plate 12b and circulates. By circulating the lubricating oil 44 in this manner, air bubbles in the lubricating oil 44 filled in the gap between the thrust groove portion 20 and the fixed thrust plate 12b, particularly air bubbles on the outer peripheral side of the upper and lower thrust bearing portions 40 and 42, become upper thrust. The lubricating oil 44 located radially inward of the bearing portion 40 is released to the outside from the interface.

The upper and lower inner peripheral surfaces of the sleeve portion 18a1 are respectively provided with herringbone grooves 54 for generating dynamic pressure.
55 (a dynamic pressure generating groove other than a herringbone groove can also be used) is provided, and an upper radial bearing portion 56 and a lower radial bearing portion 58 are formed between the fixed shaft member 12a and the outer peripheral surface thereof. Have been. Among them, the herringbone groove 55 for generating dynamic pressure of the lower radial bearing portion 58 reaches the upper part of the lower end radial gap enlarged portion 28, and the lubricating oil is formed by the herringbone groove 55 with the rotation of the rotating sleeve body 18. The center of the dynamic pressure generated in 44 in the axial direction is provided higher than the center of the lower radial bearing portion 58 in the axial direction. Sleeve part 1
The gap between the inner peripheral surface of the fixed shaft member 8a1 and the outer peripheral surface of the fixed shaft member 12a is usually several μm in the upper and lower radial bearing portions 56 and 58.
It is.

The sleeve portion 18 of the fixed shaft member 12a
Of the upper end of the portion opposed to a1, a quarter circumferential portion around the breathing hole 48 (the circumferential portion where the communication path 37 does not exist) has a substantially V-shaped cross-section outside the radial direction. It has a circumferentially upper arc-shaped groove portion 59 that opens to the side. The upper arc-shaped groove portion 59 is formed shallower than the depth of the annular concave portion 60.

The fixed shaft member 12a has an annular concave portion 60 having an arcuate cross section with a radially outward opening between the upper and lower radial bearing portions 56 and 58 on the outer peripheral surface. Its annular recess 6
An intermediate radial gap enlarged portion 62 is formed between the outer peripheral surface of the fixed shaft member 12a and the outer peripheral surface of the fixed shaft member 12a. Intermediate radial gap expansion section 62
The upper gap expanding portion (first gap expanding portion) in which the radial gap gradually increases downward from the upper radial bearing portion 56 constitutes the upper half thereof, and gradually increases upward from the lower radial bearing portion 58. The lower gap enlarging portion (second gap enlarging portion) in which the radial gap expands constitutes the lower half.

The upper radial bearing 5
6 has an interface on the lower end side of the lubricating oil 44 held therein, and the lower gap enlarged portion has an interface on the upper end side of the lubricating oil 44 held on the lower radial bearing portion 58.

The upper arcuate groove 59 and the sleeve 18a1
The lubricating oil 4 held by the upper radial bearing portion 56 is provided on the enlarged portion of the radially radial gap formed in the circumferential direction formed between the lubricating oil 4 and the inner peripheral surface.
4, the upper end interface of the circumferential portion corresponding to the upper arc-shaped groove portion 59 is located by surface tension, and the lubricating oil 44 held by the upper radial bearing portion 56 in the circumferential portion.
Is prevented from flowing into the lower axial direction gap widening portion 32.

Further, the lower end side interface of the lubricating oil 44 held by the lower radial bearing portion 58 is connected to the lower end radial gap enlarging portion 28.
Located in.

[0086] Near the boundary between the lower end of the upper radial bearing portion 56 on the outer peripheral surface of the fixed shaft member 12a and the upper gap enlarged portion of the intermediate radial gap enlarged portion 62, a radially outward portion having a substantially V-shaped cross section is formed. It has a circumferential lower arcuate groove 63 extending over a quarter circle that opens. The lower arc-shaped groove 63 is formed shallower than the depth of the annular concave portion 60.

In the fixed shaft member 12a, an outer opening 64a has a ventilation hole 64 located near the boundary between the lower radial bearing portion 58 and the lower end radial gap enlarged portion 28. The first internal opening 64b of the ventilation hole 64 opens near the middle between the upper gap expanding section and the lower gap expanding section in the intermediate radial gap expanding section 62. The second internal opening 64 c of the ventilation hole 64 opens to the lower arc-shaped groove 63.

When the rotary sleeve body 18 rotates, the lower end side interface of the lubricating oil 44 held by the lower radial bearing portion 58 is formed by the herringbone groove portion 55 of the lower radial bearing portion 58 so that the lower end radially enlarged gap portion 28 is formed. It is drawn upward or further upward, and the external opening 64a of the ventilation hole 64 opens to the outside air.

The lubricating oil 44 is stored in the upper gap expanding section and the lower gap expanding section in the intermediate radial gap expanding section 62.
In the upper radial bearing portion 56 or the lower radial bearing portion 58, when the lubricating oil 44 is reduced due to evaporation or dropping due to impact, the lubricating oil 44 stored in the upper radially enlarged portion of the intermediate radial gap enlarged portion 62 is The lubricating oil 44 stored in the lower radially enlarged portion of the intermediate radial direction enlarged portion 62 is supplied to the proximal radial bearing portion. With the replenishment of the lubricating oil 44, outside air is introduced into the intermediate radial gap expanding portion 62 through the ventilation hole 64.

The inner peripheral portion of the lubricating oil 44 held by the lower thrust bearing portion 42, the fixed shaft member 12a and the sleeve portion 18a
The space between the lubricating oil 44 held in the gap 1 and the leading end of the lubricating oil 44 is continued by the lubricating oil 44 held in the communication path 37. When the lubricating oil 44 decreases due to evaporation or dropping due to impact in one of the lower thrust bearing portion 42 and the upper radial bearing portion 56, the connection path 37 is formed from the other bearing portion to the bearing portion in which the lubricating oil 44 has decreased. The lubricating oil 44 is replenished via this.
Therefore, it is possible to prevent an inconvenience of shortage of lubricating oil in only one of the bearing portions and shortening of the life of the device.

The upper radial bearing portion 56 is designed so as to cause an imbalance in which the dynamic pressure of the lubricating oil 44 becomes slightly higher in the tolerance range.

At the time of rotation of the rotary sleeve member 18, due to factors such as tolerances, assembly, and thermal deformation, the upper end is held by the upper radial bearing portion 56 and the upper end thereof is directed downward to the lubricating oil 44 facing the lower axial direction gap enlarging portion 32. A moving pressure may be generated and the lubricating oil 44 may move downward. In this case, when the downward moving pressure exceeds the limit, the inner peripheral portion of the lubricating oil 44 held by the lower thrust bearing portion 42 also interacts with the centrifugal force and the surface tension of the lubricating oil 44 in the communication path 37, A communication path 37 between the fixed shaft member 12a and the tip of the lubricating oil 44 held in the gap between the sleeve portion 18a1.
As a result, the continuation of the lubricating oil 44 is interrupted. The slit portion 36 facilitates the start of such continuous interruption of the lubricating oil 44.

When the continuation of the lubricating oil 44 through the communication path 37 is interrupted, the lubricating oil 44 held in the lower thrust bearing portion 42 moves excessively to the upper radial bearing portion 56 to lubricate the lower thrust bearing portion 42. An excessive amount of the oil 44 is reliably prevented. Further, when the lubricating oil 44 is interrupted and gas such as air is introduced into the upper radial bearing portion 56 from the upper end side, the downward lubricating oil moving pressure is reduced and the lubricating oil 44 is balanced as described above. The downward movement of the oil 44 is suppressed. At this time, gas is easily introduced into the upper radial bearing portion 56 from the upper end side through the upper arc-shaped groove portion 59, so that the downward movement of the lubricating oil 44 is more reliably suppressed.

If the downward moving pressure on the lubricating oil 44 held in the gap between the fixed shaft member 12a and the sleeve portion 18a1 is eliminated during rotation or by rotation stop, the lower thrust bearing portion 42 holds the lubricating oil 44. A communication path 37 between the inner peripheral portion of the lubricating oil 44 and the tip of the lubricating oil 44 held in the gap between the fixed shaft member 12a and the sleeve portion 18a1.
Continuation of the lubricating oil 44 can be restored.

As the gas portion of the lower axial gap expanding portion 32 expands or contracts, the movement of gas such as air through the breathing hole 48 occurs.

When the rotary sleeve body 18 rotates, a pressure at which the lubricating oil 44 moves upward is generated in the upper radial bearing portion 56 due to factors such as tolerance, assembly, and thermal deformation. In this case, gas is introduced into the upper radial bearing portion 56 from the lower end through the vent hole 64 and the lower arc-shaped groove 63. This gas is introduced into the upper radial bearing portion 56 at a stage where the upward movement amount of the lubricating oil 44 is relatively small, whereby the upward lubricating oil moving pressure decreases and becomes balanced. The amount of upward movement of the head is relatively small.

Further, when the rotating sleeve body 18 rotates,
Centrifugal force acts on the lubricating oil 44 filled in the gap between the fixed shaft body 12 and the rotating sleeve body 18. Therefore, during non-rotation, the lubricating oil 44 held by surface tension so that the lower end interface is located at the lower end radial gap enlarged portion 28 is
The liquid is likely to dissipate by leaching or leaking further downward by the action of the centrifugal force or by falling off due to impact. However, the lower end side interface of the lubricating oil 44 held by the lower radial bearing portion 58 has a lower radial side. Since the herringbone groove 55 of the bearing portion 58 is drawn above or further above the lower end radial gap enlarging portion 28, the lubricating oil 44 is dissipated or leaked by the action of centrifugal force, or falls off by impact. Dissipation is less likely to occur.

The vertical positional relationship in the above description of the embodiment is merely for convenience of description based on the drawings, and does not limit the actual use state and the like.

[0086]

According to the hydrodynamic bearing device and the electric motor of the present invention, there is a disadvantage that the lubricating fluid is insufficient in only one of the base-side thrust bearing portion and the radial bearing portion and the device life is shortened. This prevents the lubricating fluid held in the proximal thrust bearing from excessively moving to the radial bearing, thereby preventing the amount of the lubricating fluid that lubricates the proximal thrust bearing from becoming too small.

According to the hydrodynamic bearing device of the fourth aspect and the electric motor provided with the same, the amount of movement of the lubricating fluid of the radial bearing portion at the distal end toward the distal end can be suppressed to a relatively small value.

According to the hydrodynamic bearing device of the fifth aspect and the electric motor having the hydrodynamic bearing device, bubbles in the lubricating liquid filled in the gap between the thrust groove and the thrust are released to the outside air.

[Brief description of the drawings]

FIG. 1 is a sectional view of a spindle motor for driving a hard disk.

FIG. 2 is a lower perspective view of a rotary thrust plate.

FIG. 3 is an enlarged view of the vicinity of a right side portion of the rotary thrust plate in FIG. 1;

FIG. 4 is a sectional view of a conventional example of a spindle motor for driving a hard disk.

[Explanation of symbols]

 12a Fixed shaft member 12b Fixed thrust plate 12b1 Lower inner peripheral side part 18a1 Sleeve part 20 Thrust groove part 34 Connecting ridge part 36 Slit part 37 Communication path 42 Lower thrust bearing part 44 Lubricating oil

Claims (6)

[Claims] A fixed shaft body having a shaft portion and a thrust portion projecting radially outward from the shaft portion is sleeve-fitted to a portion of the shaft portion closer to a base end side than the thrust portion. A rotating sleeve body having a combined sleeve portion and a rotating thrust surface that is opposed to a surface on the proximal end side of the thrust portion on the proximal end side in the axial direction is a gap between the fixed shaft body and the rotating sleeve body. A fluid dynamic bearing device rotatably supported mainly in a radial bearing portion in which a shaft portion and a sleeve portion face each other and in a thrust bearing portion in which a rotating thrust surface and a thrust portion face each other through a lubricating liquid filled in the bearing. The axial center of the thrust surface and the rotational thrust surface is provided on the inner peripheral side of the proximal thrust bearing portion at the portion where the proximal surface of the thrust portion and the rotational thrust surface are opposed to each other. Direction gap is the proximal thrust bearing part The base-side axial-gap enlarged portion has a large axial-gap, so that the lubricating liquid can be held by a part of the proximal-side axial-gap enlarged portion so that the lubricating liquid can be held by surface tension. A communication path through which the lubricating fluid can be continuous between the inner peripheral portion of the lubricating fluid held in the proximal thrust bearing portion and the tip end of the lubricating fluid held in the gap between the shaft portion and the sleeve portion. At least the inner peripheral portion of the portion other than the communication path of the proximal-side axial center gap expanding portion is a gas portion, and the fixed shaft body has a breathing hole communicating the gas portion and the outside. A hydrodynamic fluid bearing characterized in that, when the lubricating fluid held by the radial bearing portion and the distal end faces the enlarged portion in the axial direction of the proximal end moves in the proximal direction, the continuation of the lubricating fluid through the communication path is interrupted. apparatus. 2. The base-side axial-gap-enlarging portion, wherein the axial-direction gap gradually increases inward in the radial direction. 2. The hydrodynamic bearing device according to claim 1, wherein a radially inward interface of the lubricating liquid held by the thrust bearing portion is located. 3. The thrust portion is formed between a substantially radially continuous projection portion provided on the base end surface of the thrust portion and projecting toward the base end, and the rotation thrust surface. 3. The hydrodynamic bearing device according to claim 1, further comprising a slit at an inner end in a radial direction of the portion, the slit being opened in both a circumferential direction and a base end in an axial direction, and capable of holding a lubricating liquid by surface tension. 4. A radial bearing portion having a distal end close to a gap between a surface of a thrust portion on the proximal end side and a rotary thrust surface, and a radially-located proximal end of the radial bearing portion. Having a proximal-side radial bearing portion, between the distal-side radial bearing portion and the proximal-side radial bearing portion,
A radial gap between the outer peripheral surface of the shaft portion and the inner peripheral surface of the sleeve portion has an intermediate radial gap expansion portion that is larger than both radial bearing portions, and the intermediate radial gap expansion portion is the distal-side radial bearing portion. A first gap enlargement portion in which the radial gap gradually increases from the base end side, and a second gap enlargement portion in which the radial gap gradually increases from the base radial bearing portion toward the distal end, The first gap enlarging portion has an interface on the proximal end side of the lubricating liquid held by the distal radial bearing portion, and the interface on the distal end side of the lubricating liquid held by the proximal radial bearing portion is the second gap. The fixed shaft is provided with a ventilation hole which is provided in the enlarged portion, and which communicates at least the intermediate portion between the first gap enlarged portion and the second gap enlarged portion in the intermediate radial gap enlarged portion and the outside at the time of rotation of the rotary sleeve body. Radial shaft on the outer peripheral surface of the shaft Near the boundary between the base end side of the portion and the first gap enlarging portion, there is a circumferential base-side arc-shaped groove in the radially outward opening, and the base-side arc-shaped groove and the outside are at least 4. The hydrodynamic bearing device according to claim 1, wherein the fixed shaft is provided with a ventilation hole communicating with the rotating sleeve when the rotating sleeve is rotated. 5. A rotary sleeve body having an annular thrust groove having a radially inward opening externally fitted to the thrust portion, and a base-side surface and a front-end surface of the thrust groove are rotational thrust surfaces, respectively. The thrust portion has a thrust bearing portion at both the portion where the front-side surface and the front-side rotary thrust surface face each other, and the portion at which the base-side surface and the base-side rotary thrust surface face each other, The lubricating fluid of the distal-side thrust bearing portion and the proximal-side thrust bearing portion is continuous through a portion between the outer peripheral end surface of the thrust portion and the outer peripheral portion of the thrust groove portion, and is applied to the distal-side and proximal-side thrust bearing portions. Has a dynamic pressure generating mechanism that generates a pressure distribution in which the lubricating liquid in each thrust bearing moves from the inner peripheral side to the outer peripheral side with the rotation of the rotating sleeve body,
A distal interface of the lubricating liquid is provided radially inward of the distal-side thrust bearing portion, and an outer peripheral end surface of the thrust portion, and a distal-side and proximal-side thrust of a distal-side surface and a proximal-side surface of the thrust portion. 3. A thrust portion having a lubricating fluid circulation path which opens into a lubricating fluid filled in a gap between the thrust groove portion and the thrust portion in an inner peripheral side portion of the bearing portion.
5. The hydrodynamic bearing device according to 3 or 4. 6. An electric motor comprising the hydrodynamic bearing device according to claim 1, wherein the rotating sleeve body rotates as a rotor.