JP2000179543A - Dynamic pressure bearing device and spindle motor using this dynamic pressure bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To take sufficient countermeasures against a lubricating fluid leak by providing a lubricating fluid outflow preventing groove in a rotary/fixed member side in the end part of an end part side cylinder part in a radial dynamic pressure bearing, and forming the preventing groove of fixed member side in a fixed position and the preventing groove of rotary member side helically in an axial direction. SOLUTION: Lubricating fluid outflow preventing grooves 4, 5 are accumulation spaces for holing a lubricating fluid 3. The lubricating fluid 3 leaking out downward from a radial dynamic pressure bearing part is impeded from flowing out by surface tension of the lubricating fluid first in a position increasing a clearance between a rotary member 2 and a fixed member 1, that is, in a position of the lubricating fluid outflow preventing groove 5. When the lubricating fluid is placed in a condition near full in the lubricating fluid outflow preventing groove 5 by damaging a seal in a position thereof, action of centrifugal force and surface tension is operated in the lubricating fluid by tapered first end edge and another end edge of the one more lubricating fluid outflow preventing groove 4, and an outflow of the lubricating fluid is impeded by generating a seal effect of centrifugal force and surface tension.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure bearing device incorporating a measure for preventing lubricating fluid leakage in a dynamic pressure bearing device for driving an OA device such as a magnetic disk device, an optical disk device, a magneto-optical disk device, and a polygon mirror drive device. And a spindle motor using the same.

[0002]

2. Description of the Related Art Recently, media based on digital data such as the Internet, intranets, and video-on-demand have appeared. Although such media is suitable for handling on a PC, a large-capacity and high-speed storage is indispensable. As a demand for such storage, increasing the capacity of an HDD (magnetic disk device) is a very important achievement item. A device that records and reproduces a large amount of information with multimedia in mind is DV
Development of large capacity D-ROM devices, DVD-RAM devices, and the like has become important.

[0003] Methods of increasing the capacity of the HDD include increasing the size of the disk, increasing the number of disks, and improving the areal recording density. However, the increase in the size and number of disks is contrary to compactness, power saving, and cost reduction, and is not an effective solution except for specific fields such as workstations and servers. Therefore, a method of improving the areal recording density has been adopted. MR (Magnet Re
This is a head technology that can be substituted for sistive) or GMR (Giant MR). As the recording density increases, the change in the magnetic field decreases, the current becomes weak, and data cannot be read. MR
In the head, a change in the magnetic field appears as a change in the electric resistance value.
This is a head that performs reproduction using an MR element utilizing the R effect, and has higher sensitivity than a conventional thin film head. The GMR head uses a GMR element exhibiting a giant magnetoresistance effect, and the data of the reproduction output is several times higher in sensitivity than the MR head. Using these magnetic heads, recently 1000
HDDs from 0 tpi (Track per inch) to 20,000 tpi are being developed. For example, 20000 tpi
Indicates that the distance between the tracks is 1.27 μm, the radial run-out of the spindle motor of such an apparatus is not more than about 1.27 μm, and the non-repetitive run-out is 0.1
Those having a size of about 3 μm or less are required. For such non-repetitive runout, the limit of the ball bearing is reached, and in the case of higher recording density, a spindle motor of a fluid bearing is required.

In a DVD-RAM device of an optical disk, the track pitch of the disk is 0.74 μm, which is smaller than that of an HDD device. Due to the evolution of the optical pick servo technology, the rotation accuracy required for the spindle motor used for HDD is not required.
VD-RAM device and OAW (Optically Assisted Win
Magneto-optical disk drive and NFR (Nea
(R Field Recording) technology requires a spindle motor using a hydrodynamic bearing device.

[0005] That is, as the capacity increases, the spindle motor for driving a disk or the like is required to have high rotational accuracy, and the movement of using a hydrodynamic bearing for such a spindle motor is rapidly spreading. Particularly in the case of a magneto-optical disk device based on the OAW technology or a magneto-optical disk device based on the NFR technology, the hydrodynamic bearing device is becoming indispensable.

The reasons for using a hydrodynamic bearing for a spindle motor are as follows. (1) Irregular shaft runout can be suppressed. In a ball bearing, not all steel balls can be machined into a uniform shape, which causes sudden shaft runout during rotation.
When the shaft deflection is reduced, the positioning error of the magnetic head can be reduced in the magnetic disk device, and the positioning error of the beam spot can be reduced in the DVD device, and it is easy to cope with the improvement of the recording density. (2) Impact resistance is improved. This is because the fluid film plays a role of buffer. (3) Noise generated in the bearing is reduced. (4) Long fatigue life until the bearing is broken by metal fatigue.

In the case of a spindle motor for reading and writing by floating a magnetic head or the like on the rotatingly driven recording medium surface in the order of microns or submicrons, the thrust direction of the rotor is improved in order to improve reliability such as impact. Displacement must be kept small and 1000G
It is necessary to improve the fastening strength of the members so that the motor members are not deformed by a large impact.

In particular, when a fluid bearing is used, there is a problem that the lubricating fluid is insufficient due to scattering or the like, and the dynamic pressure characteristics are deteriorated.

[0009] In order to prevent the lubricating fluid of the hydrodynamic bearing from scattering and contaminating the recording medium and the like, it is necessary to take measures for retaining and scattering the lubricating fluid. Therefore, Japanese Patent Application Laid-Open No. Hei 6-3
As described in JP-A-11695 and JP-A-7-46810, a method of providing a lubricating fluid outflow prevention groove of a bearing device is generally used.

As described in JP-A-8-163821 and JP-A-8-163820, a circulation passage is provided in a fluid bearing device to take measures against a partial shortage of oil.

[0011]

The impact resistance of a fluid bearing is improved. However, when a magnetic disk device or a CD-ROM device is mounted on a notebook personal computer, a portable terminal, or the like, the impact resistance of a hydrodynamic bearing spindle motor is required. Also 1000G
It is becoming. The dynamic pressure bearing is characterized in that when the bearing rotates, it floats up due to dynamic pressure and becomes in a non-contact state, so that the bearing portion is allowed to move about the floating amount. Therefore, when an impact is applied, the rotating member moves. If there is nothing to restrict the movement, the rotating member comes off the bearing. Therefore, the motor is provided with a retaining member to prevent the rotor from coming off. However, there is a phenomenon in which the lubricating fluid leaks out when the bearing portion makes a large movement in the thrust direction, and it is necessary to take measures against this.

Also, measures must be taken to retain and scatter the lubricating fluid so that the lubricating fluid of the fluid bearing does not scatter and contaminate the recording medium or the like. . As a countermeasure against this, Japanese Patent Application Laid-Open
The measures described in JP-A-3111695 and JP-A-7-46810 in which a groove for preventing lubricating fluid outflow of a bearing device is provided are insufficient, and measures for the sealing are devised and a labyrinth is provided on the outer peripheral portion of the bearing through-hole. It is necessary to provide a configuration.

As described in JP-A-8-163821 and JP-A-1-63820, a circulating passage is provided in a hydrodynamic bearing device to take measures against a partial shortage of oil. A structure suitable for a small spindle motor using a hydrodynamic bearing device is required, for example, the bearing becomes large and the bearing becomes large and can be adopted only for a large spindle motor.

However, in the conventional bearing device and the like as described above, a special seal mechanism as a measure against lubricating fluid leakage, such as one provided in a lubricating fluid outflow preventing groove simply in a gap between bearing portions or one circulating lubricating fluid, is provided. Provisions and the like have been proposed.

In these prior art examples, for example, in the case of a dynamic pressure bearing, when the amount of the lubricating fluid is small, there is a problem that the lubricating fluid is held in the circulation path and a sufficient lubricating fluid is not supplied to the lubricating function part. On the other hand, if the amount of the lubricating fluid is too large, there is a problem that the lubricating fluid leaks, and the bearing seal device is not sufficient to prevent the lubricating fluid from leaking.

[0016]

SUMMARY OF THE INVENTION The present invention provides the following advantages over the prior art bearing sealing device: (1) Even if the amount of lubricating fluid injected changes or moves slightly, it can be absorbed. A structure in which the dynamic pressure bearing has a space and the lubricating fluid in the space is stably held. (2) The bearing structure must be able to withstand external force so that the lubricating fluid does not scatter outside the bearing even when subjected to external force. (3) The lubricating fluid surface on the outlet end side of the open end of the dynamic pressure bearing portion is in a stable wet state and hardly leaks.

In view of the above conditions, in order to solve the problem, the present invention provides a mechanism for holding a lubricating fluid of a dynamic pressure bearing device. (1) An end portion of an end side cylindrical portion of a radial dynamic pressure bearing There is a lubricating fluid outflow preventing groove on the rotating member side and the fixed member side, the lubricating fluid outflow preventing groove on the fixed member side is formed at a fixed position, and the lubricating fluid outflow preventing groove on the rotating member side is formed spirally in the axial direction. I do. (2) A lubricating fluid outflow prevention groove is formed at the end of the cylindrical portion at the end of the radial dynamic pressure bearing on the rotating member side and the fixed member side at a partially opposed position. (3) Both the lubricating fluid outflow prevention grooves on the rotating member side and the fixed member side are grooves having a shape in which the gap decreases as approaching the open end of the end side cylindrical portion of the radial dynamic pressure bearing. Set the tilt angle within the specified range. (4) The lubricating fluid outflow preventing groove on the rotating member side is formed so that the end side cylindrical portion of the radial dynamic pressure bearing has a groove surface having a shape in which the gap decreases toward the open end, and the groove on the fixed member side. The lubricating fluid outflow preventing groove is formed so that the end side cylindrical portion of the radial dynamic pressure bearing has a groove surface having a shape in which a gap increases toward the open end, and the inclination angle of the groove is set within a specified range. (5) The lubricating fluid outflow preventing groove on the rotating member side is formed so that the end side cylindrical portion of the radial dynamic pressure bearing has a groove surface in which a gap increases toward the open end, and the groove on the fixed member side. The lubricating fluid outflow prevention groove is formed so that the end side cylindrical portion of the radial dynamic pressure bearing has a groove surface having a shape in which the gap decreases toward the open end, and the inclination angles of the grooves are set within a specified range. (6) In the case of a radial dynamic pressure bearing having an eccentricity of 5% or more, a lubricating fluid outflow preventing groove is formed on the rotating member side and the fixed member side at the end of the end side cylindrical portion of the radial dynamic pressure bearing. (7) The lubricating fluid outflow prevention groove on the side of the spiral rotating member is set to have several cycles. (8) The dynamic pressure bearing of the above means is used for a bearing of a spindle motor.

[0018]

According to the first aspect of the present invention, there is provided a dynamic pressure bearing portion comprising a radial dynamic pressure fluid bearing and a thrust dynamic pressure fluid bearing for rotatably supporting a rotating body with respect to a fixed member. In the hydrodynamic bearing device, the hydrodynamic bearing is filled with a lubricating fluid, and both ends in the axial direction of the hydrodynamic bearing for rotating the rotating member in a non-contact manner with respect to the fixed member are open ends. A lubricating fluid outflow preventing groove is provided on both the fixed member side and the rotating body side at the end of the cylindrical portion on the end side of the bearing. The position of the lubricating fluid outflow preventing groove on the fixed member side is fixed, and the lubricating fluid outflow groove on the rotating member side is fixed. The position of the preventing groove periodically changes along the axial distance, and the lubricating fluid outflow preventing groove on the fixed member side and the lubricating fluid outflow preventing groove on the rotating member side are configured to partially face each other. A hydrodynamic bearing device characterized by having The lubricating fluid outflow preventing groove is provided on the rotating member side and the fixed member side at the end of the open end side cylindrical portion of the radial dynamic pressure bearing, so that the surface tension of the lubricating fluid outflow preventing groove on the fixed member side is increased. The lubricating fluid is held by the lubricating fluid, and the lubricating fluid outflow prevention groove on the rotating member side holds the lubricating fluid by centrifugal force and surface tension, thereby preventing the lubricating fluid of the radial dynamic bearing from flowing out of the rotating member. Is done. Further, the position of the lubricating fluid outflow preventing groove on the fixed member side of the two lubricating fluid outflow preventing grooves is at a fixed position, but the position of the lubricating fluid outflow preventing groove on the rotating member side periodically changes vertically. In addition, when the relative position of the two grooves changes with the rotation, the dynamic pressure generating portion can be replenished by itself. Even if a shock is applied,
Due to the self-replenishment function, the holding capacity of the lubricating fluid outflow preventing groove is enhanced so that the lubricating fluid that has begun to leak returns to the lubricating fluid outflow preventing groove, and further returns to the dynamic pressure generating portion, thereby providing a highly reliable bearing device. It has the action of:

According to a second aspect of the present invention, the lubricating fluid outflow prevention grooves provided on both the rotating member side and the fixed member side are formed on the end side cylindrical portion of the radial dynamic pressure bearing toward the open end. 2. The hydrodynamic bearing device according to claim 1, wherein a groove surface for reducing the gap is formed, wherein the lubricating fluid is held by the surface tension in the lubricating fluid outflow preventing groove on the fixed member side. In addition, the lubricating fluid outflow prevention groove on the rotating member side has an effect that the lubricating fluid is held by centrifugal force and surface tension, so that an effective seal can be performed. In addition, the groove is provided on the fixed member side and the rotating member side. The edges of the lubricating fluid outflow prevention grooves are different from each other,
The dynamic pressure generating section can be self-replenished.

According to a third aspect of the present invention, the lubricating fluid outflow preventing grooves provided on both the rotating member side and the fixed member side are formed on the end side cylindrical portion of the radial dynamic pressure bearing toward the open end. There is a groove surface with a reduced gap, and each of the groove surfaces is formed at an inclination angle α, β from the axial direction, and the inclination angles α, β have a relationship of (Equation 4). Item 2. The dynamic bearing device according to Item 2.

[0021]

(Equation 4)

In the lubricating fluid outflow preventing groove on the fixed member side, the lubricating fluid is retained by surface tension, and in the rotating member side lubricating fluid outflow preventing groove, the lubricating fluid is retained by centrifugal force and surface tension. Is performed, and by setting the inclination angle of the lubricating fluid outflow prevention groove within a predetermined range, an effective seal can be achieved.

According to a fourth aspect of the present invention, the lubricating fluid outflow preventing groove provided on the rotating member side has a groove surface on the end side cylindrical portion of the radial dynamic pressure bearing whose gap increases toward the open end. The lubricating fluid outflow prevention groove formed on the fixed member side is formed so as to have a groove surface on the end side cylindrical portion of the radial dynamic pressure bearing in which the gap decreases toward the open end. The lubricating fluid bearing device according to claim 1, wherein the lubricating fluid outflow preventing grooves provided on the fixed member side and the rotating member side are less likely to be stepped from each other. In addition to being able to replenish the pressure generating part by itself, the lubricating fluid is held by the surface tension in the lubricating fluid outflow preventing groove on the fixed member side, and the lubricating fluid by the surface tension is held in the lubricating fluid outflow preventing groove on the rotating member side. Holding is done It has an effect of effective seal is possible by.

According to a fifth aspect of the present invention, the lubricating fluid outflow prevention groove provided on the rotating member side has a groove surface on the end side cylindrical portion of the radial dynamic pressure bearing whose gap increases toward the open end. The lubricating fluid outflow prevention groove formed on the fixed member side is formed so as to have a groove surface on the end side cylindrical portion of the radial dynamic pressure bearing in which the gap decreases toward the open end. The groove surface of each of the lubricating fluid outflow prevention grooves has an inclination angle γ, δ from the axial direction, and the inclination angles γ, δ have a relationship of (Equation 5). Dynamic bearing device.

[0025]

(Equation 5)

In the lubricating fluid outflow preventing groove on the fixed member side, the lubricating fluid is held by the surface tension, and in the rotating member side lubricating fluid outflow preventing groove, the lubricating fluid is held by the surface tension. By setting the inclination angle of the lubricating fluid outflow prevention groove within a predetermined range, an effective seal can be achieved.

According to a sixth aspect of the present invention, the lubricating fluid outflow preventing groove provided on the rotating member side has a groove surface on the end side cylindrical portion of the radial dynamic pressure bearing whose gap decreases toward the open end. The lubricating fluid outflow prevention groove formed on the fixed member side is formed so as to have a groove surface on the end side cylindrical portion of the radial dynamic pressure bearing whose gap increases toward the open end. 2. A lubricating fluid bearing device according to claim 1, wherein the lubricating fluid is held by the surface tension in the lubricating fluid outflow preventing groove on the fixed member side, and the lubricating fluid outflow on the rotating member side is performed. The prevention groove has a function of enabling effective sealing by holding the lubricating fluid by centrifugal force and surface tension, and has an end of the lubricating fluid outflow prevention groove provided on the fixed member side and the rotating member side. The edges are stepped to each other Have staggered There may be self-replenishing in dynamic pressure generator.

According to a seventh aspect of the present invention, the lubricating fluid outflow preventing groove provided on the rotating member side has a groove surface on the end side cylindrical portion of the radial dynamic pressure bearing whose gap decreases toward the open end. The lubricating fluid outflow prevention groove formed on the fixed member side is formed so as to have a groove surface on the end side cylindrical portion of the radial dynamic pressure bearing whose gap increases toward the open end. The groove surface of each lubricating fluid outflow prevention groove has an inclination angle γ, δ from the axial direction, and the inclination angles γ, δ have a relationship of (Equation 6). Dynamic bearing device.

[0029]

(Equation 6)

In the lubricating fluid outflow preventing groove on the fixed member side, the lubricating fluid is held by surface tension, and in the rotating member side lubricating fluid outflow preventing groove, the lubricating fluid is held by centrifugal force and surface tension. Is performed, and by setting the inclination angle of the lubricating fluid outflow prevention groove within a predetermined range, an effective seal can be achieved.

According to an eighth aspect of the present invention, the lubricating fluid outflow prevention grooves provided on both the rotating member side and the fixed member side are formed in the end side cylindrical portion of the radial dynamic pressure bearing, and The lubricating fluid outflow preventing groove is formed at a fixed height, and the lowermost point of the lower end of the lubricating fluid outflow preventing groove on the rotating member is located below the lubricating fluid outflow preventing groove on the fixed member. The upper end of the lubricating fluid outflow preventing groove on the fixed member is located at the uppermost position of the lower end of the lubricating fluid outflow preventing groove on the rotating member side. The uppermost end of the lubricating fluid outflow preventing groove on the rotating member side is located at the upper end of the lubricating fluid outflow preventing groove on the fixed member side. Located above (opposite to the open end) the upper end of the upper end of the lubricating fluid outflow prevention groove on the rotating member side. 8. The hydrodynamic bearing device according to claim 1, wherein the position is located on the upper side (opposite of the open end) of the lubricating fluid outflow preventing groove on the fixed member side. The edges of the lubricating fluid outflow prevention grooves provided on the rotating member side and the fixed member side are different from each other, and are unlikely to be stepped. Since the lubricating fluid outflow preventing groove is formed so as to change periodically in the axial direction, a sealing effect is generated in various places, and the outflow is prevented by the action of the centrifugal force and surface tension of the lubricating fluid in the gap. In addition, since the position of the lubricating fluid outflow prevention groove is different, the holding capacity of the lubricating fluid outflow prevention groove is strengthened so that the lubricating fluid returns to the dynamic pressure generating part, and an effect that a highly reliable bearing device can be produced. Have.

According to the ninth aspect of the present invention, the lubricating fluid outflow prevention grooves provided on both the rotating member side and the fixed member side are formed in the end side cylindrical portion of the radial dynamic pressure bearing. The lubricating fluid outflow preventing groove is formed at a fixed height, and the lowermost point of the lower end of the lubricating fluid outflow preventing groove on the rotating member is located below the lubricating fluid outflow preventing groove on the fixed member. The upper end of the lubricating fluid outflow preventing groove on the fixed member is located at the uppermost position of the lower end of the lubricating fluid outflow preventing groove on the rotating member side. The lowermost point position of the upper end of the lubricating fluid outflow preventing groove on the rotating member side is lower than the position of the upper end portion of the lubricating fluid outflow preventing groove on the fixed member side. The uppermost point of the upper end of the lubricating fluid outflow prevention groove on the rotating member, which is located on the upper side (opposite of the open end) 8. The hydrodynamic bearing device according to claim 1, wherein the upper end is located on the upper side (opposite to the open end) of the upper end of the lubricating fluid outflow prevention groove on the fixed member side. The edge of the lubricating fluid outflow prevention groove provided on the rotating member side and the fixed member side is unlikely to be stepped from each other, and is located at a certain position of the lubricating fluid outflow prevention groove on the fixing member side, Since the lubricating fluid outflow preventing groove is formed so as to change periodically in the axial direction, a sealing effect is generated in various places, and the outflow is prevented by the action of the centrifugal force and surface tension of the lubricating fluid in the gap. In addition, since the position of the lubricating fluid outflow prevention groove is different, the holding capacity of the lubricating fluid outflow prevention groove is strengthened so that the lubricating fluid returns to the dynamic pressure generating part, and an effect that a highly reliable bearing device can be produced. Have.

According to a tenth aspect of the present invention, the lubricating fluid outflow prevention grooves provided on both the rotating member side and the fixed member side are formed in the end side cylindrical portion of the radial dynamic pressure bearing. The lubricating fluid outflow preventing groove is formed at a fixed height, and the lowermost point of the lower end of the lubricating fluid outflow preventing groove on the rotating member is located below the lubricating fluid outflow preventing groove on the fixed member. The uppermost position of the lower end of the lubricating fluid outflow preventing groove on the rotating member side is located at the upper end position of the lubricating fluid outflow preventing groove on the fixed member side. It is located on the lower (open end) side and above the lower end of the lubricating fluid outflow preventing groove on the fixed member side (opposite to the open end), and on the rotating member side on the lubricating fluid outflow preventing groove. The lowermost point of the end is closer to the upper end of the lubricating fluid outflow prevention groove on the fixed member side. The upper end of the lubricating fluid outflow preventing groove on the rotating member side, which is located on the upper portion (open end) side and the upper side (opposite of the open end) of the lower end of the lubricating fluid outflow preventing groove on the fixed member side. The uppermost position of the portion is located on the upper side (opposite to the open end) side of the upper end of the lubricating fluid outflow preventing groove on the fixed member side.
The lubricating fluid outflow prevention groove provided on the rotating member side and the fixed member side is different from the edge of the lubricating fluid outflow prevention groove, and the lubricating fluid outflow prevention groove on the fixed member side is fixed. Position, and the lubricating fluid outflow prevention groove on the rotating member side is formed so as to periodically change in the axial direction, so that a sealing effect occurs at various places, and the centrifugal force and surface tension of the lubricating fluid in the gap are reduced. In addition to blocking the outflow by the action,
Since the positions of the lubricating fluid outflow preventing grooves are different from each other, the holding capacity of the lubricating fluid outflow preventing grooves is enhanced so that the lubricating fluid returns to the dynamic pressure generating portion, and an effect that a highly reliable bearing device can be obtained.

According to an eleventh aspect of the present invention, the lubricating fluid outflow prevention grooves provided on both the rotating member side and the fixed member side are formed in the end side cylindrical portion of the radial dynamic pressure bearing, and The lubricating fluid outflow preventing groove is formed at a fixed height, and the lowermost point of the lower end of the lubricating fluid outflow preventing groove on the rotating member is located below the lubricating fluid outflow preventing groove on the fixed member. It is located on the lower side (open end) side of the end position, and the uppermost position of the lower end of the lubricating fluid outflow preventing groove on the rotating member side is the position of the lower end of the lubricating fluid outflow preventing groove on the fixed member side. The lowermost point position of the upper end of the lubricating fluid outflow preventing groove on the rotating member side is located lower (open end) side than the upper end position of the lubricating fluid outflow preventing groove on the fixed member side ( (Open end) side and above the lower end of the lubricating fluid outflow prevention groove on the fixed member side The uppermost position of the upper end of the lubricating fluid outflow preventing groove on the rotating member side is lower than the upper end position of the lubricating fluid outflow preventing groove on the fixed member side (open end). The hydrodynamic bearing device according to any one of claims 1 to 7, wherein the lubricating fluid outflow prevention grooves provided on the rotating member side and the fixed member side are opposite to each other. The lubricating fluid outflow prevention groove on the fixed member is located at a fixed position, and the lubricating fluid outflow prevention groove on the rotating member is formed so that it changes periodically in the axial direction. The effect is generated, the lubricating fluid is prevented from flowing out by the action of the centrifugal force and surface tension of the lubricating fluid in the gap, and the lubricating fluid returns to the dynamic pressure generating part by displacing the position of the lubricating fluid outflow preventing groove The retention capacity of the lubricating fluid outflow prevention groove is enhanced It has the effect that reliability can be higher bearing device.

According to a twelfth aspect of the present invention, the lubricating fluid outflow prevention grooves provided on both the rotating member side and the fixed member side are formed in the end side cylindrical portion of the radial dynamic pressure bearing. The lubricating fluid outflow preventing groove is formed at a fixed height, and the lowermost point of the lower end of the lubricating fluid outflow preventing groove on the rotating member is located below the lubricating fluid outflow preventing groove on the fixed member. It is located on the lower side (open end) side of the end position, and the uppermost position of the lower end of the lubricating fluid outflow preventing groove on the rotating member side is the position of the lower end of the lubricating fluid outflow preventing groove on the fixed member side. The lowermost point position of the upper end of the lubricating fluid outflow preventing groove on the rotating member side is located lower (open end) side than the lower end position of the lubricating fluid outflow preventing groove on the fixed member side ( (Open end) side, the uppermost point of the upper end of the lubricating fluid outflow prevention groove on the rotating member side The lower (open end) side of the upper end of the lubricating fluid outflow preventing groove on the fixed member side and the upper (opposite to the open end) side of the lower end of the lubricating fluid outflow preventing groove on the fixing member side 8. The hydrodynamic bearing device according to claim 1, wherein the lubricating fluid outflow preventing grooves provided on the rotating member side and the fixed member side are hardly stepped with each other. In contrast, the lubricating fluid outflow preventing groove on the fixed member side is located at a fixed position, and the lubricating fluid outflow preventing groove on the rotating member side is formed so as to periodically change in the axial direction. The lubricating fluid is prevented from flowing out by the action of the centrifugal force and surface tension of the lubricating fluid in the gap, and the lubricating fluid returns to the dynamic pressure generating part by displacing the position of the lubricating fluid outflow preventing groove. The holding capacity of the lubricating fluid outflow prevention groove has been enhanced. It has the effect that reliability can be higher bearing device.

According to a thirteenth aspect of the present invention, the lubricating fluid outflow preventing grooves provided on both the rotating member side and the fixed member side are formed in the end side cylindrical portion of the radial dynamic pressure bearing. The lubricating fluid outflow preventing groove is formed at a fixed height, and the lubricating fluid outflow preventing groove on the rotating member side is spirally formed in the axial direction when developed in the circumferential direction, and the spiral lubricating fluid outflow groove is formed. 13. The hydrodynamic bearing device according to claim 1, wherein when the axial distance of the prevention groove is set as a displacement, n cycles are performed in one development (n is a positive integer of 1 or more). The position of the lubricating fluid outflow prevention groove is displaced more than once, increasing the chances of lubricating fluid returning to the dynamic pressure generating part, enhancing the holding capacity as a dynamic pressure bearing, and providing a highly reliable bearing. It has the effect that the device can be made.

According to a fourteenth aspect of the present invention, the lubricating fluid outflow preventing grooves provided on both the rotating member side and the fixed member side are formed in the end side cylindrical portion of the radial dynamic pressure bearing. When the clearance with the fixed member is constant, the two lubricating fluid outflow prevention grooves are formed at a fixed height, and the radial dynamic pressure bearing is used with an eccentricity of 5% or more. Even if one of the two opposed lubricating fluid outflow prevention grooves is not a spiral groove,
When the eccentricity is 5% or more, the eccentricity exerts an effect as a spiral lubricating fluid outflow prevention groove, and has an effect of effectively preventing leakage of the lubricating fluid.

According to a fifteenth aspect of the present invention, a housing, a stator core fixed directly or indirectly to the housing, a shaft fixed to the housing, a retaining plate fixed to the shaft, A bearing sleeve that is rotatable relative to the shaft via a bearing, and a rotor that is fixed directly or indirectly to an outer peripheral portion of the sleeve, and the shaft comprises the shaft and the sleeve. A herringbone groove is formed, and a retaining plate is sandwiched between a radial dynamic pressure bearing, a thrust retaining plate, and a sleeve via a lubricating fluid in a gap, and a dynamic pressure groove is provided in one of the retaining plate and the thrust retaining plate. It is a thrust hydrodynamic fluid bearing with a lubricating fluid in the gap by forming a hydrodynamic groove in either the retaining plate or the sleeve. The lubricating fluid outflow preventing groove is provided on both the shaft side and the bearing sleeve side at the end of the end side cylindrical portion, and the position of the lubricating fluid outflow preventing groove on the shaft side is constant, and the lubricating fluid outflow preventing groove on the sleeve side is provided. The position of the groove is periodically changed along the axial distance, and the groove for preventing lubricating fluid outflow on the shaft side and the groove for preventing lubricating fluid outflow on the sleeve side are connected to one of the bearings.
According to another aspect of the present invention, there is provided a spindle motor using a hydrodynamic bearing device, which has a lubricating fluid outflow prevention groove configured to be partially opposed by rotation. Lubricating fluid outflow prevention grooves are provided on the rotating member side and the fixed member side at the end of the cylindrical portion at the open end side of the radial dynamic pressure bearing. The lubricating fluid is retained by the centrifugal force and the surface tension in the lubricating fluid outflow preventing groove on the rotating member side, thereby preventing the lubricating fluid of the radial dynamic pressure bearing from flowing out of the sleeve. Furthermore, the edges of the lubricating fluid outflow preventing grooves provided on the sleeve side and the shaft side are unlikely to be stepped from each other, and when the lubricating fluid outflow preventing grooves on the sleeve side are lower, they extend over many steps. When the sealing effect is exhibited and the lubricating fluid outflow prevention groove on the sleeve side is higher, the sealing effect can be exerted over several stages and the position of the lubricating fluid outflow prevention groove on the shaft side Is at a fixed position, but the position of the lubricating fluid outflow prevention groove on the sleeve side changes periodically up and down, so that the relative position of the two grooves changes with rotation, Can be self-replenishing. Furthermore, even when an impact is applied, the self-replenishing function returns the lubricating fluid that has begun to return to the lubricating fluid outflow prevention groove, and further enhances the holding capacity of the lubricating fluid outflow prevention groove so as to return to the dynamic pressure generating portion. This has the effect of providing a highly reliable bearing device.

According to a sixteenth aspect of the present invention, there is provided a spindle motor using the hydrodynamic bearing device according to the first to fourteenth aspects, wherein the position of the lubricating fluid outflow preventing groove on the shaft side is fixed. Since the position of the lubricating fluid outflow prevention groove on the sleeve side periodically changes vertically, the relative position of the two grooves changes with rotation, so that the dynamic pressure generating portion can be self-replenished. Has an action.

[0040]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows a hydrodynamic bearing device as an embodiment of the present invention. In FIG. 1, 1 is a fixed member, 2 is a rotating member, 3 is a lubricating fluid, 4 is a lubricating fluid outflow preventing groove, 5 is a lubricating fluid outflow preventing groove, 6 is a thrust plate, 7 is an open end opening gap, and 8 is This is a fluid holding groove.

Before describing the bearing of the first embodiment, the conventional bearing will be described a little here. Considering a general fluid dynamic pressure radial bearing as shown in FIG. 19 in the mechanism for holding the lubricating fluid in the bearing, the hydrodynamic bearing of FIG. 19 has a structure in which two open ends 100 and 101 are provided. Considering this, first, the lubricating fluid is held at a balance of the capillary suction pressure at the two open ends 100 and 101, and the surface position of the lubricating fluid at the open end is balanced by the two pressures acting on the surface. is there. That is, assuming that the capillary suction pressures at the two open ends are P1 and P2, roughly, P1 = P
2 is in equilibrium.

When some pressure is applied to one open end,
The lubricating fluid moves to a position where the pressure is balanced. That is, for example, assuming that the external pressure is P3, P1 = P2
The state changes to a state where the equilibrium is maintained at + P3.

In such a structure in which the open ends are at both ends of the bearing, the position of the lubricating fluid in the bearing is determined by the pressure balance, so that when an external force is applied, the lubricating fluid always moves. Along with this movement, leakage of the lubricating fluid occurs in the conventional bearing.

In the present invention, in order to prevent the leakage even when the lubricating fluid 3 moves, the lubricating fluid outflow preventing grooves 4 and 5 are provided as shown in FIG. The lubricating fluid outflow prevention grooves 4 and 5 are storage spaces for holding the lubricating fluid 3.

Since the holding pressure of the lubricating fluid due to the capillary action is inversely proportional to the gap distance, if the lubricating fluid outflow prevention grooves 4 and 5 hold a large amount of the lubricating fluid 3 even during normal rotation, the lubricating fluid is generated in the dynamic pressure generating portion. One of the lubricating fluid outflow prevention grooves 4 and 5 is formed as a spiral groove so that 3 can be supplied by itself.

When this spiral groove is represented by a development view of two lubricating fluid outflow preventing grooves of the dynamic pressure bearing of the motor as shown in FIG. 2, the lubricating fluid outflow preventing groove 5 on the fixed member side is shown by a solid line. The lubricating fluid outflow preventing groove 4 on the rotating member side is developed so as to have a wavy position as shown by a broken line. That is, the broken line of the lubricating fluid outflow prevention groove 4 on the rotating member side periodically changes in the axial direction distance as described in the claims. FIG. 2 also shows the rotational angle position of the development, and the cycle is one cycle per revolution in the axial distance of the lubricating fluid outflow prevention groove 4 on the rotating member side.

The mechanism will be described below. Near the position facing the lubricating fluid outflow preventing groove 4 on the rotating member 2 side, a lubricating fluid outflow preventing groove 5 whose gap decreases toward the lower side is also formed on the surface on the fixed member 1 side. FIG. 3 is an enlarged view of this portion, and shows a state near the rotation angle of 0 degrees in FIG. The positional relationship between the lubricating fluid outflow preventing groove 4 on the rotating member 2 and the lubricating fluid outflow preventing groove 5 on the fixing member 1 is slightly different from that of the lubricating fluid outflow preventing groove 5 on the fixing member 1.
Is located above.

The lubricating fluid 3 which has leaked downward from the radial dynamic pressure bearing portion flows out at the position where the gap between the rotating member 2 and the fixed member 1 becomes large, that is, at the lubricating fluid outflow preventing groove 5 due to the surface tension of the lubricating fluid. Is blocked. This state is referred to as a first-stage seal. In order to express the sealing state, FIG. 3 shows a first-stage sealing state of the lubricating fluid.

When the seal at the lubricating fluid outflow preventing groove 5 is damaged and the lubricating fluid outflow preventing groove 5 is almost full of the lubricating fluid, the first end of the other lubricating fluid outflow preventing groove 4 is opened. Due to the taper at the edge and the other edge, the action of centrifugal force and surface tension acts on the lubricating fluid, creating a centrifugal force and surface tension sealing effect and preventing the outflow of the lubricating fluid. This state is referred to as a second-stage seal. When the lubricating fluid is almost full in the two lubricating fluid outflow preventing grooves until the centrifugal force and the surface tension sealing effect alone are insufficient, the lubricating fluid outflow preventing groove 4 has an edge on the open end side of the rotating member 2. The outflow is prevented by the action of the centrifugal force and the surface tension of the lubricating fluid in the wedge-shaped gap between the lubricating fluid and the fixing member 1. This state is referred to as a third-stage seal. Since the position of the lubricating fluid outflow prevention groove is different, a sealing effect can be provided over many stages.

FIG. 4 is an enlarged view of the configuration of the two lubricating fluid outflow preventing grooves, and shows a state at a rotation angle of about 180 degrees in FIG. As for the positional relationship between the lubricating fluid outflow preventing groove 4 on the rotating member 2 side and the lubricating fluid outflow preventing groove 5 on the fixing member 1 side, the lubricating fluid outflow preventing groove 5 on the fixing member 1 side is located slightly lower.

The sealing effect in FIG. 4 will be described. The lubricating fluid that has leaked downward from the radial dynamic pressure bearing portion is prevented from flowing out by the surface tension at the position where the gap between the rotating member 2 and the fixed member 1 becomes large, that is, at the lubricating fluid outflow preventing groove 4 on the rotating member side. Is done. This state is referred to as a first-stage seal. The effect of retaining the surface tension at that point is slight, and the leaked lubricating fluid adheres to the lubricating fluid outflow preventing groove 4 at a large radial position on the upper edge side by rotational centrifugal force. Next, the action of the centrifugal force and the surface tension acts on the lubricating fluid due to the taper at the first edge of the lubricating fluid outflow preventing groove 4 and the edge of the lubricating fluid outflow preventing groove 5 on the other fixing member 1 side. The outflow of the lubricating fluid is prevented by generating a centrifugal force and a surface tension sealing effect. This state is the second
It is a step seal. When the lubricating fluid outflow preventing groove 4 on the rotating member 2 side is insufficiently sealed in the second stage, the inclined surface of the lower edge of the lubricating fluid outflow preventing groove 5 on the other stationary member 1 side and the rotating member Outflow is prevented by the action of the surface tension of the lubricating fluid in the wedge-shaped gap between the inner surface of the lubricating fluid and the inner surface of the lubricating fluid. This state is referred to as a third-stage seal. Since the position of the lubricating fluid outflow prevention groove is different, a sealing effect can be provided over many stages.

The sealing effect as shown in FIGS. 3 and 4 occurs everywhere in the deployed position as shown in FIG.
The lubricating fluid returns to the hydrodynamic bearing part automatically by forming the position of the lubricating fluid outflow prevention groove in a spiral so that the sealing effect at that position changes in the lubricating fluid that has been sealed and held. Would.

This self-replenishment mechanism is made possible by changing the position of the lubricating fluid outflow preventing groove in a spiral shape and by changing the position of the lubricating fluid outflow preventing groove.

Next, the leakage of the lubricating fluid to the outside is divided into a phenomenon in which the lubricating fluid rises on the boundary surface with rotation and a phenomenon in which the lubricating fluid is scattered by centrifugal force. This complicates sealing measures for the hydrodynamic bearing. This rising phenomenon is also called diffusion wetting, and it is important to prevent it at least in part. The phenomena will be explained including the countermeasures.

Considering the interface in the form of a combination of gas, liquid and solid phase, there are five types of gas / liquid, gas / solid, liquid / liquid, liquid / solid and solid / solid.
Although the type may be considered, the free energy for forming the interface must be positive for an interface to exist between the two phases. Capillary phenomenon is a phenomenon related to a movable interface among the above interfaces, and the interface has a certain shape and area when reaching an equilibrium state. The gas / liquid and gas / solid interfaces are particularly referred to as surfaces, and the sealing of the bearing is a problem of the gas / liquid surface, where surface tension and surface free energy are related.

First, the surface free energy will be briefly described. FIG. 5 is a diagram for explaining surface free energy.

In FIG. 5, when the movable bar BC having no resistance is moved in the direction of the arrow in the tank filled with liquid, the liquid AB is moved.
The surface area of the CD increases. Move the bar by dx and B '
In order to move to the position C ′, work must be performed against the cohesive force in the liquid. When this operation is reversibly diffused, the energy of the work is stored on the liquid surface, and when the surface is shrunk, the energy is used again. Assuming that work W is performed when a new area BB′C′C is formed, the specific surface energy is expressed by W / (f · dx). If the coefficient is γ, then

[0059]

(Equation 7)

Since fdx is an increase in surface area, if it is dA,

[0061]

(Equation 8)

DG is the increase in free energy. Therefore, the coefficient γ is dG / dA, which is the surface free energy per unit area. That is, this γ is equal to the surface tension.

In a bearing in which both ends of a dynamic pressure bearing are open ends, free surface energy or surface tension is involved in the seal portion.

The basic equation of the capillary phenomenon is as shown in (Equation 9).

[0065]

(Equation 9)

The basic equation of the capillary phenomenon is also called the Young-Laplace equation. Deriving from the explanatory diagram of FIG.
If the two radii of curvature are R1 and R2, and if the area of the curved surface is made sufficiently small as shown in the figure, R1 and R2 can be regarded as constant. Assuming now that the curved surface is moved outward by a small distance, the increase ΔA of the area associated therewith can be approximated by (Equation 10).

[0067]

(Equation 10)

The area increase ΔA and the added work W
Relationship with

[0069]

[Equation 11]

Is satisfied. On the other hand, the internal pressure must be reduced by ΔP to be balanced. Therefore, since the work W ′ = − ΔP · xydz of the gas accompanying the movement of this surface is in mechanical equilibrium, the basic equation of the capillary phenomenon can be derived from the relation of W + W ′ = 0.

In the case of a dynamic pressure bearing, a lubricating fluid reservoir groove is provided on one or both of the fixed member and the rotating member. As a result of experiments conducted by the present inventors, the inclination angle of the groove is as follows. Experimental results as described were obtained.

FIG. 7 shows a groove 1 for holding and flowing out the lubricating fluid on the rotating member near the boundary between the fixed member 9 and the rotating member 10.
FIG. 3 is a schematic view in which 1 is formed. The angle ε between the inclined surface of the outflow prevention groove and the surface of the fixing member is defined. Let the complementary angle of the angle ε be the angle κ. In FIG. 7, the liquid level of the lubricating fluid held in the outflow prevention groove is defined as h.

From FIG.

[0074]

(Equation 12)

Further,

[0076]

(Equation 13)

Since the area of the liquid is triangular, the pressure Δ
P is represented by (Equation 14).

[0078]

[Equation 14]

Applying these relationships to the equation of capillary action,

[0080]

(Equation 15)

Therefore, since the lubricating fluid to be used is known, the right side of (Equation 16) is constant. for that reason,
(Equation 16) is a function of h and κ.

[0082]

(Equation 16)

Therefore, from the relationship between κ and ε,

[0084]

[Equation 17]

Here, C is a constant. The relationship between the liquid surface height h of the lubricating fluid and the angle ε is shown in FIG.
It can be seen that h is large in the range of 10 degrees. In FIG. 8, C =
It is calculated by 1.

Further, a change rate (dh / dε) of the liquid level height h with respect to the angle ε is obtained.

[0087]

(Equation 18)

(Equation 18) The relationship between the rate of change of the liquid level and the angle ε is shown in FIG. In the figure, C = 1 is calculated. From FIG. 9, the rate of change of the liquid level is minimum when the angle ε is close to about 60 degrees, and the rate of change increases as the angle ε approaches both sides. At a large angle of 60 degrees or more in relation to FIG. 8, the height of h decreases,
The angle ε is 6 because the holding capacity is reduced.
It must be within the range of 0 degrees or less. When ε is 10 degrees or less, h is large in FIG. 8 and the rate of change of the height is large in FIG. 9. Not the angle of inclination. Therefore, the preferred angle ε is (Equation 1)
9).

[0089]

[Equation 19]

Based on this, it is preferable that the angle αβ shown in FIGS. 3 and 4 be as shown in (Equation 20).

[0091]

(Equation 20)

Since the two lubricating fluid outflow prevention grooves often face at the same time, the maximum value of the angles α and β is 60
The angle was set at half the degree. In addition, since the two lubricating fluid outflow prevention grooves are often individually formed at the angles of the tips, the minimum angles of the angles α and β are set to the minimum values of (Equation 19).

(Embodiment 2) FIG. 10 shows a fluid dynamic pressure bearing according to Embodiment 2. The parts analogous to those in the first embodiment use the same part numbers, and description thereof is omitted. FIGS. 11 and 12 are enlarged explanatory views of the open end of the radial bearing.

The second embodiment is different from the first embodiment in FIG. 1 in that the lubricating fluid outflow preventing groove provided on the rotating member side has a gap in the cylindrical portion on the end side of the radial dynamic pressure bearing toward the open end. Is formed so that there is a groove surface that increases
The lubricating fluid outflow prevention groove provided on the fixed member side is formed so that the end side cylindrical portion of the radial dynamic pressure bearing has a groove surface such that the gap decreases toward the open end. is there.

The second embodiment will be described. In FIG. 10, 1 is a fixed member, 2 is a rotating member, 3 is a lubricating fluid,
Reference numeral 6 denotes a thrust plate, 7 denotes an open end opening gap, 8 denotes a fluid holding groove, 11 denotes a lubricating fluid outflow preventing groove, and 12 denotes a lubricating fluid outflow preventing groove.

The lubricating fluid outflow preventing groove 11 on the rotating member side is spirally formed in the developing axial direction. When the axial distance of the outflow prevention groove 11 is set as a displacement, n cycles are performed in one development (n is a positive integer).

The mechanism will be described below. Further, a lubricating fluid outflow preventing groove 12 is formed near the position facing the lubricating fluid outflow preventing groove 11 on the rotating member 2 side, and the gap decreases as it goes downward on the surface on the fixing member 1 side. FIG. 11 is an enlarged view of this portion. The positional relationship between the lubricating fluid outflow preventing groove 11 on the rotating member 2 side and the lubricating fluid outflow preventing groove 12 on the fixing member 1 is slightly different from that of the lubricating fluid outflow preventing on the fixing member 1 side. The groove 12 is located above.

The lubricating fluid that has leaked downward from the radial dynamic pressure bearing portion is first supplied to the rotating member 2 and the second inclined surface 1 of the fixed member 1.
The outflow is blocked by the surface tension of the lubricating fluid at a position where the gap formed by the lubricating fluid 6 becomes large, that is, at the second inclined surface 16 of the lubricating fluid outflow preventing groove 12. This is a first-stage seal.

The first-stage seal at the lubricating-fluid outflow preventing groove 12 is damaged, and the lubricating-fluid outflow preventing groove 1 is damaged.
When the lubricating fluid fills the first inclined surface 15 of the second lubricating fluid and the lubricating fluid in the lubricating fluid outflow preventing groove 12 is almost full, the first inclined surface 13 of the other lubricating fluid outflow preventing groove 11,
The first inclined surface 13 includes a portion where the gap (gap formed by the angle γ in FIG. 11) increases as going downward, and a second inclined surface 14 where the gap decreases. Due to the space between the first inclined surface 13 of the lubricating fluid outflow preventing groove 11 and the space of the lubricating fluid outflow preventing groove 12, the action of the surface tension acts on the lubricating fluid, and a surface tension sealing effect is generated to prevent the outflow of the lubricating fluid. You. This is the second-stage seal. Further, when the lubricating fluid becomes almost full in the two lubricating fluid outflow preventing grooves to the extent that the surface tension sealing effect alone is not sufficient,
The second end of the lubricating fluid outflow prevention groove 11 on the open end side of the rotating member 2
The outflow is prevented by the action of the centrifugal force and the surface tension of the lubricating fluid in the wedge-shaped gap between the inclined surface 14 and the fixing member 1. This is the third stage seal. Since the position of the lubricating fluid outflow prevention groove is different, a sealing effect can be provided over many stages.

FIG. 12 is an enlarged view of the structure of the two lubricating fluid outflow preventing grooves. The positional relationship between the lubricating fluid outflow preventing groove 11 on the rotating member 2 side and the lubricating fluid outflow preventing groove 12 on the fixed member 1 side is as follows. The lubricating fluid outflow prevention groove 12 on the fixing member 1 side is located slightly below.

The sealing effect in FIG. 12 will be described.
The lubricating fluid that has leaked downward from the radial dynamic pressure bearing portion is initially at a position where the gap between the rotating member 2 and the fixed member 1 is large, that is, the first inclined surface 13 of the lubricating fluid outflow prevention groove 11 on the rotating member side. The outflow is prevented by the surface tension at the gap with the fixing member. This is a first-stage seal. The effect of retaining the surface tension at that point appears as a slight effect due to the centrifugal force. Further, the leaked lubricating fluid acts so as to adhere to a large radial position of the first inclined surface 13 of the lubricating fluid outflow prevention groove 11 by the rotational centrifugal force. If the lubricating fluid leaks to an extent that the first seal is not sufficient, the first inclined surface 1
3 and the lubricating fluid outflow prevention groove 12 on the other fixing member 1 side
And the second inclined surface 16 holds the lubricating fluid. This is the second stage seal. Further, the lubricating fluid outflow prevention groove 1
Due to the first first inclined surface 13 and the first inclined surface 15 of the lubricating fluid outflow prevention groove 12 on the other fixed member 1 side, the action of centrifugal force and surface tension acts on the lubricating fluid, and the surface tension sealing effect And the outflow of the lubricating fluid is prevented. This is the third-stage seal. Furthermore, the slippery fluid outflow prevention groove 11
Due to the second inclined surface 14 and the first inclined surface 15 of the lubricating fluid outflow preventing groove 12 on the other fixed member 1 side, the action of the centrifugal force and the surface tension is sealed with the lubricating fluid. This is the fourth stage seal. When the lubricating fluid outflow prevention groove 11 on the rotating member 2 side is insufficiently sealed at the fourth stage,
The wedge-shaped gap between the first inclined surface 15 of the lubricating fluid outflow preventing groove 12 on the other fixed member 1 side and the inner surface of the rotating member 2 prevents the outflow by the action of the surface tension of the lubricating fluid. This is the fifth stage seal. Since the position of the lubricating fluid outflow prevention groove is different, a sealing effect can be provided over many stages.

Since the seal is different in each part due to the rotation in this state, the leaked lubricating fluid returns to the dynamic pressure generating part with the rotation.
By making one of the grooves 1 and 12 a spiral groove, the leaked lubricating fluid acts to supply the lubricating fluid 3 to the dynamic pressure generating unit by itself.

Each of the lubricating fluid outflow preventing grooves 11 and 12 has two inclined surfaces. The first inclined surface and the second inclined surface are such that the first inclined surface has a longer inclined surface, and the longer inclined surface is the inclined surface of the lubricating fluid outflow prevention groove.

The angle of inclination of the inclined surface of the groove for preventing lubricating fluid outflow is set to an angle γ on the rotating member side, and set to an angle δ on the fixed member side.

The inclination angles γ and δ are within a certain range for the same reason as in the first embodiment, which has a sealing effect. Therefore, it is preferable to design them within the range. The condition is represented by (Equation 21).

[0106]

(Equation 21)

Although the two lubricating fluid outflow prevention grooves face each other at the same time, since the inclination angle is not axially symmetric with respect to the axis, it is considered that the maximum value of the angles γ and δ should be 60 degrees. In the case of Example 2, the experimental result was such that the space was slightly too large at 60 degrees, and the result was that a small angle up to 55 degrees was suitable. In addition, since the two lubricating fluid outflow prevention grooves are often individually formed at the angles of the tips, the minimum angles of the angles γ and δ were set to the minimum values of (Equation 19).

Embodiment 3 FIG. 13 shows a fluid dynamic pressure bearing according to Embodiment 3. The analogous parts to the first and second embodiments use the same part numbers, and the description is omitted. FIGS. 14 and 15 are enlarged explanatory views of the open end of the radial bearing.

The third embodiment is different from the first embodiment in FIG. 1 in that the lubricating fluid outflow preventing groove provided on the rotating member side has a gap in the cylindrical portion on the end side of the radial dynamic pressure bearing toward the open end. Is formed so that there is a groove surface that reduces
The lubricating fluid outflow prevention groove provided on the fixed member side is formed such that a groove surface is formed in the end side cylindrical portion of the radial dynamic pressure bearing so that a gap increases toward the open end. is there.

Embodiment 3 will be described. In FIG. 10, 1 is a fixed member, 2 is a rotating member, 3 is a lubricating fluid,
Reference numeral 6 denotes a thrust plate, 7 denotes an open end opening gap, 8 denotes a fluid holding groove, 17 denotes a lubricating fluid outflow preventing groove, and 18 denotes a lubricating fluid outflow preventing groove.

The lubricating fluid outflow preventing groove 17 on the rotating member side is spirally formed in the developing axial direction. When the axial distance of the outflow prevention groove 17 is set as a displacement, n cycles are performed in one development (n is a positive integer).

The mechanism will be described below. In addition, a lubricating fluid outflow preventing groove 18 is formed near the position facing the lubricating fluid outflow preventing groove 17 on the rotating member 2 side, and the clearance increases as it goes downward on the surface on the fixed member 1 side. FIG. 15 is an enlarged view of this portion, and the positional relationship between the lubricating fluid outflow preventing groove 17 on the rotating member 2 side and the lubricating fluid outflow preventing groove 18 on the fixing member 1 side is slightly different. The groove 17 is located above.

The lubricating fluid that has leaked downward from the radial dynamic pressure bearing portion is first supplied to the rotating member 2 and the first inclined surface 2 of the fixed member 1.
1, that is, at the first inclined surface 21 of the lubricating fluid outflow preventing groove 18, the outflow is prevented by the surface tension of the lubricating fluid. This is a first-stage seal.

The first-stage sealing effect at the lubricating-fluid outflow preventing groove 18 is impaired, and the lubricating-fluid outflow preventing groove 18 is filled with the lubricating fluid also on the second inclined surface 20 of the lubricating-fluid outflow preventing groove 18. When the lubricating fluid 18 is almost full, the second inclined surface 20 of the other lubricating fluid outflow preventing groove 17 has a gap (as indicated by the angle γ in FIG. There is a portion where the configured gap is small, and a first inclined surface 19 where the gap is reduced. Due to the space between the second inclined surface 20 of the lubricating fluid outflow preventing groove 17 and the space of the lubricating fluid outflow preventing groove 20, the action of the surface tension acts on the lubricating fluid, and a surface tension sealing effect is generated to prevent the outflow of the lubricating fluid. You. This is the second-stage seal. Further, when the lubricating fluid is almost full in the two lubricating fluid outflow preventing grooves until the surface tension sealing effect alone is not sufficient, the first lubricating fluid outflow preventing groove 17 on the open end side of the rotating member 2 in the first direction. The lubricating fluid is held in a space defined by the inclined surface 19 and the first inclined surface of the lubricating fluid outflow prevention groove 18 of the fixed member 1. This is the third-stage seal. If the lubricating fluid leaks insufficiently even with the third stage seal, the lubricating fluid outflow prevention groove 1
7, the first inclined surface 19 and the second
The lubricating fluid is held in a wedge-shaped gap between the lubricating fluid and the inclined surface 22. This is the fourth stage seal. Furthermore, the outflow is prevented by the action of the centrifugal force and the surface tension of the lubricating fluid in the wedge-shaped gap between the first inclined surface 19 of the lubricating fluid outflow preventing groove 17 and the fixing member 1. This is the fifth stage seal. By matching the position of the lubricating fluid outflow prevention groove,
A sealing effect can be provided over many stages.

FIG. 15 is an enlarged view of the structure of the two lubricating fluid outflow preventing grooves. The positional relationship between the lubricating fluid outflow preventing groove 17 on the rotating member 2 and the lubricating fluid outflow preventing groove 18 on the fixed member 1 is as follows. The lubricating fluid outflow prevention groove 18 on the fixed member 1 side is located slightly below.

The sealing effect in FIG. 15 will be described.
The lubricating fluid that has leaked downward from the radial dynamic pressure bearing portion is initially located at a position where the gap between the rotating member 2 and the fixed member 1 is large, that is, the second inclined surface 20 of the lubricating fluid outflow prevention groove 17 on the rotating member side. The outflow is prevented by the surface tension at the gap with the fixing member. This is a first-stage seal. The effect of retaining the surface tension at that point appears as a slight effect due to the centrifugal force. Further, the leaked lubricating fluid acts so as to adhere to a large radial position of the second inclined surface 20 of the lubricating fluid outflow prevention groove 17 by the rotational centrifugal force. If the lubricating fluid leaks to such an extent that the first stage seal is not sufficient, the lubricating fluid leaks from the second inclined surface 13 of the lubricating fluid outflow preventing groove 17 toward the first inclined surface 19, and the lubricating fluid flows out even on the fixed member side. It leaks into the prevention groove 18. Therefore, the lubricating fluid is held in a space defined by the first inclined surface 19 of the lubricating fluid outflow preventing groove 17 and the first inclined surface 21 of the lubricating fluid outflow preventing groove 18 on the fixing member 1 side.
This is the second stage seal. Further, the action of centrifugal force and surface tension is applied to the lubricating fluid by the first inclined surface 19 of the lubricating fluid outflow preventing groove 17 and the second inclined surface 22 of the lubricating fluid outflow preventing groove 18 on the other fixed member 1 side. It acts to create a surface tension sealing effect and prevents the outflow of lubricating fluid. This is the third-stage seal. Further, outflow is prevented by the action of the surface tension of the lubricating fluid in a wedge-shaped gap formed between the second inclined surface 14 of the slippery fluid outflow preventing groove 19 and the inner surface on the other rotating member 2 side. This is the fourth stage seal. Since the position of the lubricating fluid outflow prevention groove is different, a sealing effect can be provided over many stages.

Since the seal is different in each part due to the rotation in this state, the leaked lubricating fluid returns to the dynamic pressure generating part with the rotation.
By forming one of the grooves 7 and 18 into a spiral groove, the leaked lubricating fluid acts to supply the lubricating fluid 3 to the dynamic pressure generating unit by itself.

Further, each of the lubricating fluid outflow prevention grooves 17 and 18 has two inclined surfaces. As for the first inclined surface and the second inclined surface, the first inclined surface has a longer inclined surface, and the longer inclined surface is treated as the inclined surface of the lubricating fluid outflow prevention groove.

The angle of the inclined surface of the lubricating fluid outflow prevention groove is set to an angle γ on the rotating member side, and set to an angle δ on the fixed member side.

The inclination angles γ and δ are within a certain range for the same reason as in the first embodiment, and therefore, it is preferable to design the inclination angles γ and δ within the range. The condition is represented by (Equation 22).

[0121]

(Equation 22)

Although the two lubricating fluid outflow preventing grooves are simultaneously opposed to each other, since the inclination angle is not axially symmetric with respect to the axis, it is considered that the maximum value of the angles γ and δ should be 60 degrees. From experience, the value was smaller than 60 degrees in the case of Example 3. Also, since the two lubricating fluid outflow prevention grooves are often individually configured at the angle of the tip, the angles γ,
The minimum angle of δ was the minimum value of (Equation 19).

(Embodiment 4) In the above embodiment, the lubricating fluid outflow prevention groove on the rotating member side is a spiral groove. FIG. 2 is a detailed explanatory view showing the relationship between the spiral groove and the other lubricating fluid outflow preventing groove.

In fact, in the spiral groove according to the present invention,
There are several patterns of groove positions. Several embodiments will be described as a fourth embodiment. FIG. 16 is a developed view showing a positional relationship between the lubricating fluid outflow preventing groove on the fixed member side and the lubricating fluid outflow preventing groove on the rotating member side.

When this spiral groove is represented by a development view of two lubricating fluid outflow preventing grooves of the dynamic pressure bearing of the motor as shown in FIG. 16, the lubricating fluid outflow preventing groove 24 on the fixed member side is shown by a solid line. The lubricating fluid outflow prevention groove 23 on the rotating member side is developed so as to have a wavy position as shown by a broken line. That is, the broken line of the lubricating fluid outflow prevention groove 23 on the rotating member side periodically changes in the axial direction distance as described in the claims.
FIG. 16 also shows the rotational angle position of the development, and the period is 1 in the axial distance of the lubricating fluid outflow prevention groove 23 on the rotating member side.
16A, two cycles in FIG. 16A, two cycles in FIG. 16B, one cycle in FIG.
FIG. 16D shows two cycles, and FIG. 16E shows two cycles.

In the case of FIG. 16A, the lowermost point position 25 of the lower end of the lubricating fluid outflow preventing groove 23 on the rotating member side is relative to the lubricating fluid outflow preventing groove 24 on the fixed member side.
Is located on the upper side (opposite to the open end) of the lower end of the lubricating fluid outflow preventing groove 24 on the fixed member side, and is the uppermost position of the lower end of the lubricating fluid outflow preventing groove 23 on the rotating member side. 26
Is located on the upper side (opposite to the open end) of the upper end of the lubricating fluid outflow preventing groove 24 on the fixed member side, and is the lowest point of the upper end of the lubricating fluid outflow preventing groove 23 on the rotating member side. Position 27
Is located on the upper side (opposite to the open end) of the upper end of the lubricating fluid outflow preventing groove 24 on the fixed member side, and is located at the highest point of the upper end of the lubricating fluid outflow preventing groove 23 on the rotating member side. 28
Is located on the upper side (opposite to the open end) of the lubricating fluid outflow prevention groove 24 on the fixed member side.

In the case of FIG. 16B, the lowermost point position 25 of the lower end of the lubricating fluid outflow preventing groove 23 on the rotating member side is relative to the lubricating fluid outflow preventing groove 24 on the fixed member side.
Is located on the upper side (opposite to the open end) of the lower end of the lubricating fluid outflow preventing groove 24 on the fixed member side, and is the uppermost position of the lower end of the lubricating fluid outflow preventing groove 23 on the rotating member side. 26
Is located lower (open end) than the upper end of the lubricating fluid outflow preventing groove 24 on the fixed member side, and the lowest point position 27 of the upper end of the lubricating fluid outflow preventing groove 23 on the rotating member side. Is located on the upper side (opposite to the open end) of the upper end of the lubricating fluid outflow preventing groove 24 on the fixed member side, and is located at the highest point of the upper end of the lubricating fluid outflow preventing groove 23 on the rotating member side. Reference numeral 28 is located on the upper side (opposite to the open end) side of the upper end of the lubricating fluid outflow prevention groove 24 on the fixed member side.

In the case of FIG. 16C, the lowermost point position 25 of the lower end of the lubricating fluid outflow preventing groove 23 on the rotating member side is relative to the lubricating fluid outflow preventing groove 24 on the fixed member side.
Is located lower (open end) than the lower end of the lubricating fluid outflow preventing groove 24 on the fixed member side, and is located at the highest point position 26 of the lower end of the lubricating fluid outflow preventing groove 23 on the rotating member side. Is located lower (open end) than the upper end of the lubricating fluid outflow preventing groove 24 on the fixing member side and is higher (open end) than the lower end of the lubricating fluid outflow preventing groove 24 on the fixing member side. Of the lubricating fluid outflow prevention groove 2 on the rotating member side.
The lowermost point position 27 of the upper end portion 3 is located lower (open end) than the upper end portion of the lubricating fluid outflow preventing groove 24 on the fixed member side, and the lubricating fluid outflow preventing groove on the fixed member side. 2
4, the uppermost point 28 of the upper end of the lubricating fluid outflow preventing groove 23 on the rotating member side is located on the upper side (opposite of the open end) of the lubricating fluid outflow preventing groove 23 on the fixed member side. The groove 24 is located on the upper side (opposite of the open end) side of the upper end.

In the case of FIG. 16D, the lowermost point position 25 of the lower end of the lubricating fluid outflow preventing groove 23 on the rotating member side is relative to the lubricating fluid outflow preventing groove 24 on the fixed member side.
Is located lower (open end) than the lower end of the lubricating fluid outflow preventing groove 24 on the fixed member side, and is located at the highest point position 26 of the lower end of the lubricating fluid outflow preventing groove 23 on the rotating member side. Is located lower (open end) than the lower end of the lubricating fluid outflow preventing groove 24 on the fixed member side, and is located at the lowest point position 27 of the upper end of the lubricating fluid outflow preventing groove 23 on the rotating member side. The upper side is located lower (open end) than the upper end of the lubricating fluid outflow preventing groove 24 on the fixed member side and the upper side (open end) than the lower end of the lubricating fluid outflow preventing groove 24 on the fixing member side. Of the lubricating fluid outflow prevention groove 23 on the rotating member side.
The uppermost position 28 of the upper end of the groove is lower than the position of the upper end of the lubricating fluid outflow prevention groove 24 on the fixed member side (open end).
Located on the side.

In the case of FIG. 16E, the lowermost point position 25 of the lower end of the lubricating fluid outflow preventing groove 23 on the rotating member side is relative to the lubricating fluid outflow preventing groove 24 on the fixed member side.
Is located lower (open end) than the lower end of the lubricating fluid outflow preventing groove 24 on the fixed member side, and is located at the highest point position 26 of the lower end of the lubricating fluid outflow preventing groove 23 on the rotating member side. Is located lower (open end) than the lower end of the lubricating fluid outflow preventing groove 24 on the fixed member side, and is located at the lowest point position 27 of the upper end of the lubricating fluid outflow preventing groove 23 on the rotating member side. Is located lower (open end) than the position of the lower end of the lubricating fluid outflow preventing groove 24 on the fixed member side, and is closer to the uppermost point position 28 of the upper end of the lubricating fluid outflow preventing groove 23 on the rotating member side. Is located lower (open end) than the upper end of the lubricating fluid outflow preventing groove 24 on the fixed member side and is higher than the lower end (open end) of the lubricating fluid outflow preventing groove 24 on the fixing member side. On the opposite side.

Since the holding pressure of the lubricating fluid due to the capillary action is inversely proportional to the gap, the lubricating fluid outflow preventing grooves 23, 2
If the lubricating fluid is held even during normal rotation, the seal effect portion moves with the rotation, or the sealable holding space changes at the same position. This change is due to the fact that the positions of the lubricating fluid outflow preventing grooves 23 and 24 are different depending on the rotational position, and the difference is obtained by making the lubricating fluid outflow preventing grooves spiral. Also, since the sealable holding space changes at the same position, and the sealing effect changes with rotation,
A flow is generated in the lubricating fluid that has leaked due to the rotation position, and the flow works to supply the lubricating fluid to the dynamic pressure generating unit by itself. Since one of the lubricating fluid outflow preventing grooves is formed as a spiral groove, the leaked lubricating fluid or the initial surplus retained lubricating fluid can be supplied to the dynamic pressure generating unit by itself.

It is known that the cause of leakage of the lubricating fluid is greatly related to wettability. When a solid comes into contact with a liquid, a phenomenon of wetting appears. As a basic system of this wetting phenomenon, there is a system of a solid having a smooth surface, a liquid of a pure substance and a vapor thereof, and generally, wetting is roughly classified as follows.

(1) Adhesive wetting (2) Spreading wetting (3) Immersion wetting The level of the lubricating fluid in the bearing is a liquid / solid system, Wetting of the system occurs when the free energy of the system decreases due to wetting. The change W of the free energy due to the wetting is determined according to the shape of the wetting.
Then, assuming that the surface tensions of the liquid and the solid are γL, γS, and the interfacial tension γLS, Equation (23) is obtained.

[0134]

(Equation 23)

Each wetting occurs when W in (Equation 23) is negative. With respect to the wetting phenomenon, an important quantity is the contact angle θ. In FIG. 17, θ is the contact angle, which is the angle formed by the cut line drawn from the liquid-solid contact in the vertical plane of the solid surface.
There is a Young-Dupre equation between the contact angle θ and the tension,
It is also a conditional expression that keeps the solid surface and the liquid in equilibrium. The equation is (Equation 24).

[0136]

(Equation 24)

The equilibrium of (Equation 24) is determined by the balance of the three tensions of (Equation 24). (ΓLS) included in (Equation 23)
−γS) or (γS−γLS) is the point of (Equation 24).

By substituting (Equation 24) into (Equation 23),

[0139]

(Equation 25)

From (Equation 25), the adhesion wetting is always Wa <0.
So it always happens. Diffusion wetting occurs when cos θ ≧ 1, ie, only when cos θ = 1, ie, θ = 0. Immersion wetting occurs when cos θ> 0, ie, when θ <90 degrees.

Considering the problem that the lubricating fluid goes up on the shaft surface, it means that it is in a diffusion wet state.

When an external force is applied, or when the amount of surplus lubricating fluid is large, an oil path is likely to be formed, and the oil path may leak the lubricating fluid. It will be.

This diffusion wetting diffuses in the direction formed by the leakage and is negligible so that no tension acts. Therefore, the lubricating fluid outflow preventing groove is formed into a spiral groove, and the lubricating fluid outflow preventing groove is formed. As a result, the holding space that can be sealed changes at the same position, and the sealing effect changes with rotation, so that the lubricating fluid that leaks according to the rotation position is supplied to the dynamic pressure generation unit by itself. I will return.

The occurrence of the diffusion wetting in (Equation 23) is represented by Ws
<0, and γS> γLS + γL.
In order to prevent the occurrence, it is necessary to satisfy the relationship of γS <γLS + γL.

Considering the value of (γS−γLS) in (Equation 24), in the case of diffusion wetting, the solid surface is replaced with the solid-liquid interface, and the free energy is reduced. (1) (γS−γLS)> 0 (2) (γS−γLS) <0 (3) When (γS−γLS) = 0, in the cases of (2) and (3), Ws> 0 and the diffusion No leakage occurs. In the case of (1), there may be cases where Ws <0, and leakage occurs. As the value of (γS−γLS) increases, the possibility of leakage increases.

The problem that the lubricating fluid rises on the shaft surface depends on whether or not the condition of Ws <0 is satisfied. As measures for preventing diffusion wetting (rising phenomenon), (1) Ws> 0 ( That is, the condition γS <γLS + γL) is satisfied.

This is a method in which a metal surface is prevented from directly coming out of a solid surface, and the surface is protected with a material having a surface tension as low as possible, for example, a simulated oil or the like. (2) Maximize the substantial contact angle between the solid surface and the liquid as much as possible.

That is, the surface roughness of the solid surface is reduced, and the substantial contact angle between the solid surface and the liquid is increased as much as possible. (3) Use the seal holding force.

It is devised so that an external force acts in the direction of pulling back the phenomenon of diffusion leakage. In the present application, the seal holding force is changed in the same position by changing the lubricating fluid outflow preventing groove into a spiral groove and displacing the lubricating fluid outflow preventing groove at the same position. The lubricating fluid leaked by the rotational position is supplied to the dynamic pressure generating unit by itself and returned.

(Embodiment 5) Although a dynamic pressure bearing is generally supposed to be a bearing with a small eccentricity, it may not be neglected in practice because the unbalance amount of the motor is less than the shaft rigidity. In order to increase the shaft rigidity, the length of the bearing is increased. However, since the height of the motor is often determined, it is almost impossible to change the length. At this time, it is effective to reduce the bearing gap for the shaft rigidity. However, if the gap is reduced too much, there are problems such as a change in the temperature environment and an assembling workability. Actually, it is becoming impossible to reduce the eccentricity to zero. In the present application, measures are taken to prevent leakage of the lubricating fluid in consideration of the influence of the eccentricity.

In the case where the clearance is uniform, the bearing in which the lubricating fluid outflow prevention grooves of the fixed member and the rotating member are aligned at the same position and are opposed to each other. Is an uneven gap in the axial direction. When the lubricating fluid outflow preventing groove of the bearing at that time is developed, the lubricating fluid outflow preventing groove on the rotating member side has a cycle of one cycle in the axial direction with respect to the lubricating fluid outflow preventing groove on the fixed member side. Be expanded. This development is developed as shown in FIG.

Even if one of the two opposing grooves for preventing lubricating fluid outflow is not a spiral groove, when the eccentricity is 5% or more, the effect is exerted as a spiral lubricating fluid outflow preventing groove.
It effectively prevents leakage of lubricating fluid.

(Embodiment 6) FIG. 18 is a cross-sectional view of a spindle motor using a fluid dynamic pressure bearing device for driving a fixed shaft type recording medium as an embodiment of the present invention. Examples of the target recording medium include a magneto-optical disk, a fixed magnetic disk, and various other recording media.

The housing 29 has an upwardly projecting cylindrical portion 31 on the inner peripheral portion of the annular concave portion 30 at the upper opening, and forms a flange portion 32 on the outer peripheral side of the annular concave portion 30. A through hole 33 is provided at the center of the upwardly projecting cylindrical portion 31. The housing 29 can be formed integrally with the base of the fixed magnetic disk drive, for example.

The end of the shaft 35 is fitted and fixed in the through hole 33 of the housing 29. Upwardly projecting cylindrical part 3
An outer cylindrical portion 34 is provided on an outer peripheral portion of the first cylindrical portion 34. An inner lower portion of an inner peripheral portion of a stator core 36 made of a laminated silicon steel plate is adhesively fixed to an outer peripheral portion of the inner cylindrical portion 34. The stator core 36 is formed by stacking several silicon steel plates having a thickness of 0.2 mm, and packing the protrusions such as coining to prevent loosening. The surface is insulated by the impregnated epoxy electrodeposition coating film 37, and the coil 38 is wound on the stator core 36 in the insulated state. The terminal wire of the coil 38 is the concave portion 3 of the housing 29.
0 is soldered to the copper foil wire 39 deposited on the surface. The copper foil wire 39 passes through the inner surface of the housing 29 and is electrically connected to the chassis on the device side. The copper foil wire 39 and the housing 29 are electrically insulated by a polyimide-based insulating film. Since the copper foil wire 39 can use the housing 29 as a radiator, the temperature rise due to the resistance of the copper foil wire 39 is small and the resistance of the copper foil wire 39 can be kept low, so that a large amount of current can flow. This copper foil wire 3
9 is a housing 29 like a flexible printed circuit board.
Can be easily wired, so that wiring to irregularly shaped portions, which is impossible with a flexible printed board, is possible. Therefore, it can be used in places where wiring was impossible on a complicated component surface. HDD
In the apparatus, it is possible to reduce the weight by applying a copper foil wire to the suspension or arm of the magnetic head.

Since the copper foil wire 39 is placed on the surface of the housing 29, heat generated by the copper foil wire 39 is removed from the housing 2.
The heat is dissipated to 9 and the resistance of the coil 38 does not increase. Therefore, the resistance value of the motor as a whole is reduced, and the supply of the current amount is facilitated, so that the efficiency of the motor is improved,
Because it can be configured near the housing surface, the overall height of the motor can be reduced, and the heat generated by the motor coil can be suppressed.The temperature of the entire motor can be reduced, and the temperature of the bearings can be reduced. The width of the temperature change becomes smaller. As the temperature of the lubricating fluid increases, the viscosity decreases, so that the same clearance reduces the bearing stiffness. Since the bearing temperature rise can be suppressed by the copper foil wire 39, a decrease in bearing stiffness at high temperatures can be prevented, and the reliability of the bearing can be improved.

Since the spindle motor is driven without a sensor, no electronic parts are arranged inside the spindle motor, and only the connection lines of the coil wires are connected to the outside of the spindle motor. Copper wire 3
9 can be made thinner, so that the space for winding around the stator core 36 is further increased, and by winding many thick wires, the torque characteristics of the spindle motor can be improved.

The annular retaining plate 40 is fixed to the upper portion of the shaft 35 by a screw shaft 41 perpendicular to the shaft 35. The retaining plate 40 may be formed integrally with the shaft, or the screw shaft 41
It may be formed integrally with the one.

The sleeve 42 has an n-stage (n is an integer of 2 or more) cylindrical shape in which the outer diameter of the upper end is expanded, and the inner peripheral portion of the sleeve 42 facing the shaft 35 has a small diameter as a whole. A fluid reservoir 43 having an inner diameter slightly larger than the inner diameter of the small-diameter cylindrical portion is formed at the center thereof. Therefore, the small-diameter cylindrical portion is divided into upper and lower small-diameter cylindrical portions 44 and 45 with the fluid reservoir portion 43 interposed therebetween. Herringbone grooves are provided on the inner peripheral surfaces of the upper small-diameter cylindrical portion 44 and the lower small-diameter cylindrical portion 45, and a lubricating fluid is filled in the radial gap between the upper and lower herringbone grooves and the shaft 35. Have been. Radial load can be supported by the dynamic pressure generated by the herringbone groove with the rotation, thereby constituting a radial fluid dynamic pressure bearing. In particular, the load bearing pressure is increased by the up and down ring bone grooves. Note that such herringbone grooves may be provided on the radial surface of the fixed shaft 35.

Below the small-diameter cylindrical portion 45 below the radial bearing portion of the shaft 35, a lubricating-fluid outflow preventing groove 46 is formed in which the gap decreases as the oil-repellent treatment is performed on the inner surface. I have. Further, a lubricating fluid outflow preventing groove 47 is formed on the surface of the shaft 35 at a position facing the lubricating fluid outflow preventing groove 46 on the sleeve 42 side. In FIG. 18, the positional relationship between the lubricating fluid outflow preventing groove 46 on the sleeve 42 and the lubricating fluid outflow preventing groove 47 on the shaft 35 is such that the lubricating fluid outflow preventing groove 47 on the shaft 35 is slightly higher on the left side of the shaft 35. However, on the right side of the shaft 35, the lubricating fluid outflow prevention groove 47 on the shaft 35 side is located slightly lower.

The lubricating fluid outflow prevention grooves 46 and 47 are the same as those in the first embodiment.
As in the example of the above, the lubricating fluid outflow preventing groove 46 of the sleeve 42 on the rotating member side is formed as a spiral groove, and the positions of the lubricating fluid outflow preventing grooves are in a close positional relationship.

In the relationship of the lubricating fluid outflow prevention groove on the left side of the shaft 35 in FIG. 18, the lubricating fluid that has leaked downward from the radial dynamic pressure bearing portion firstly comes into contact with the sleeve 42 and the shaft 3.
The outflow is prevented by the surface tension of the lubricating fluid at the position where the gap of 5 becomes large, that is, at the lubricating fluid outflow preventing groove 47. This is a first-stage seal. When the seal at the lubricating fluid outflow preventing groove 47 is damaged and the lubricating fluid outflow preventing groove 47 is almost full of the lubricating fluid, the first edge of the other lubricating fluid outflow preventing groove 46 and the other end thereof are connected. Due to the taper at one edge, the action of the centrifugal force acts on the lubricating fluid, generating a centrifugal sealing effect and preventing the outflow of the lubricating fluid. This is the second-stage seal. If the lubricating fluid is almost full in the two lubricating fluid outflow preventing grooves until the centrifugal sealing effect alone is insufficient, the wedge between the end of the lubricating fluid outflow preventing groove 46 and the shaft 35 is formed on the sleeve open end side. The outflow is prevented by the action of the centrifugal force and the surface tension of the lubricating fluid in the gap. This is the third-stage seal. Since the position of the lubricating fluid outflow prevention groove is different, a sealing effect can be provided over many stages.

Further, in relation to the lubricating fluid outflow prevention groove on the right side of the shaft 35 in FIG. 18, the lubricating fluid that has leaked downward from the radial dynamic pressure bearing portion first becomes a position where the gap between the sleeve 42 and the shaft 35 becomes large. That is, the outflow is prevented by the surface tension at the lubricating fluid outflow prevention groove 46 on the sleeve side. This is a first-stage seal. The effect of retaining the surface tension at that point is slight, and the leaked lubricating fluid is removed by the rotational centrifugal force.
Adheres to a large radius position on the upper edge side of. Due to the taper at the first edge and the other edge of the lubricating fluid outflow preventing groove 46, centrifugal force acts on the lubricating fluid to generate a centrifugal sealing effect, thereby preventing the lubricating fluid from flowing out. This is the second-stage seal. When the lubricating fluid outflow preventing groove 46 on the sleeve 42 is almost full of the lubricating fluid, the other shaft 35 side has a lower edge of the lubricating fluid outflow preventing groove 47 and an inclined surface toward the other edge. In the wedge-shaped gap between the lubricating fluid and the inner surface of the sleeve 42, outflow is prevented by the action of the surface tension of the lubricating fluid. This is the third-stage seal. Since the position of the lubricating fluid outflow prevention groove is different, a sealing effect can be provided over many stages.

The sealing effect as shown in the figure occurs everywhere.
By forming the position of the lubricating fluid outflow prevention groove in a spiral shape so that the sealing effect at that position changes, the lubricating fluid returns to the dynamic pressure bearing part by itself.

This self-replenishment mechanism is made possible by spirally forming the lubricating fluid outflow preventing groove, changing the position of the lubricating fluid outflow preventing groove, and changing the mutual positional relationship.

The sleeve 42 above the shaft 35 is
The retaining plate 40 is formed in the small inner diameter portion 48 of the sleeve 42 with a slight radial gap from the outer peripheral portion of the retaining plate 40.
0 is press-fitted and fixed. The press-fitting of the thrust holding plate 50 restricts the sleeve 42 from moving up and down.
The movement restriction amount is a difference between the thickness of the small inner diameter portion 48 of the sleeve and the thickness of the retaining plate 40. The thrust movement regulation amount is regulated to 0.20 mm or less.

When the impact is applied, if the movement control amount is too large, the impact force acting on the retaining plate 40 becomes large, and further, the amount of movement of the magnetic disk mounted on the spindle motor becomes large, so that the impact is applied to the magnetic head. However, there is a possibility that the recording magnetic disk surface may be damaged, so that the movement restriction amount is suppressed more than necessary.

The thrust holding plate 50 is made of a heat-treated steel material having a micro Hickers hardness of 600 or more.
For example, SUS420J2 or SKD11 is used. On the thrust holding plate 50, a reinforcing plate 51 is further press-fitted into a large inner diameter portion 52 larger than the inner diameter of the middle inner diameter portion 49 to reinforce the strength in the thrust direction. The press-fitting of the thrust holding plate 50 was light press-fitting such that the deformation of the small inner diameter portion 48 of the sleeve did not occur, whereas the press-fitting of the reinforcing plate 51 was strongly press-fitted so as to withstand an impact. Further, the reinforcing plate 51 is coated with an ultraviolet curing adhesive 53.
The strength of the press-fitted part is strengthened. Further, bonding the press-fit portion of the adhesive 53 seals a path through which the lubricating fluid oozes out, and thus is useful for holding the lubricating fluid.

Since the retaining plate 40 is suppressed by the double structure of the thrust holding plate 50 and the reinforcing plate 51, there is no problem such as deformation or falling off due to a large impact. Since it has a double structure, it is possible to form a spiral groove or the like on the surface between the thrust holding plate 50 and the reinforcing plate 51 to provide a lubricating fluid holding area.

The rotor hub 54 has a substantially cup shape.
Inside the upper end portion of the cup cylindrical portion 55 of the rotor hub 54,
A central portion has a top surface portion 56 in a circular shape, and a lower end portion has an outwardly extending flange portion 57 outside. This rotor hub 54
The top surface 56 is externally fitted and fixed to the upper end of the sleeve 42. For this purpose, the rotor hub 54 is coaxial with the sleeve 42 and is assembled to the sleeve 42 such that the outer peripheral runout of the rotor hub 54 with respect to the small-diameter cylindrical portions 44 and 45 of the sleeve 42 is 5 μm or less.

A rotor yoke 58 made of a magnetic material having a cylindrical shape is fixedly fitted inside the inner peripheral portion of the cup cylindrical portion 55, and a drive magnet 59 is provided on the inner peripheral side thereof with a radial gap therebetween relative to the stator core 36. are doing. The gap is 0.15
mm to 0.3 mm.

The cup cylindrical portion 55 of the rotor hub 54 is an inner circumference regulating portion of the magnetic disk, and the flange 57 projecting outward at the lower end is a receiving surface portion on which the magnetic disk is mounted.

The upper surface of the retaining plate 40 and the thrust holding plate 5
0, a thrust dynamic pressure bearing portion is constituted by the lower surface of the retaining plate 40 and the thrust surface 60 of the sleeve 42, respectively. The upper surface of the retaining plate 40 and the thrust holding plate 50, and the lower surface of the retaining plate 40 and the thrust surface 60 of the sleeve 42 are parallel to each other, and a liquid lubricating fluid is interposed therebetween to regulate thrust movement. Separates the amount gap. A herringbone groove is provided over the entire upper and lower annular surfaces of the retaining plate 40. The herringbone-shaped groove generates a high pressure in the lubricating fluid interposed on the surface of the retaining plate 40 due to the forward rotation of the thrust surface 60 of the sleeve 42 and the thrust holding plate 50. Such a herringbone-shaped groove may be provided on the thrust surface 60 of the sleeve 42 or the surface of the thrust holding plate 50.

The inner peripheral portion of the reinforcing plate 51 has a tapered shape such that the gap between the reinforcing plate 51 and the screw shaft 41 increases as going downward. Further, the inner surface of the reinforcing plate 51 is subjected to an oil-repellent treatment.

The sleeve 42, the rotor hub 54, and the like are configured to freely rotate via the lubricating fluid with respect to the shaft 35, the stator core 36, and the like. By the radial dynamic pressure bearings of the small diameter cylindrical portions 44 and 45, the radial displacement of the sleeve 35 with respect to the shaft 35 during rotation can be sufficiently reduced, so that the deflection of the cup-shaped cylindrical portion 55 can be reduced. Since it is a hydrodynamic bearing, non-repetitive runout can be suppressed to 0.05 μm or less. The thrust bearings on the upper and lower surfaces of the retaining plate 40 allow the shaft 35 to rotate while the sleeve 42 is rotating.
Can be suppressed sufficiently small in the thrust direction.

When the sleeve 42 rotates relative to the shaft 35, the radial dynamic pressure bearings of the small upper and lower cylindrical portions 44 and 45 generate a load supporting pressure mainly in the radial direction in the lubricating fluid interposed therebetween. The thrust bearings on the upper and lower surfaces of the retaining plate 40 generate load supporting pressure mainly in the thrust direction in the lubricating fluid interposed therein. If the lubricating fluid leaks into the lubricating fluid outflow preventing groove 46 of the sleeve 42 or the lubricating fluid outflow preventing groove 47 of the shaft 35 adjacent to the lower small diameter cylindrical portion 45 in the rotation stopped state, the motor starts rotating. The lubricating fluid is supplied to the lower small cylindrical portion 17
Take in. Similarly, when the lubricating fluid is leaking to the inner peripheral portion of the reinforcing plate 51, when the spindle motor starts rotating, the lubricating fluid is taken into the retaining plate 40 as the thrust bearing.

When the rotation of the spindle motor stops and the relative movement between the shaft 35 and the sleeve 42 becomes zero, the gap between the shaft 35 and the sleeve 42 causes an inclination.
The lubricating fluid that cannot be held by the dynamic pressure bearing part leaks out to the lubricating fluid outflow prevention groove 47 provided in the shaft 35. When the spindle motor rotates, the lubricating fluid that has leaked into the lubricating fluid outflow preventing groove 47 enters the lower small-diameter cylindrical portion 45.

As described above, the lubricating fluid outflow preventing grooves 46, 4
In order for the leaked lubricating fluid in 7 to enter the small-diameter cylindrical portion, the inclination angle of the inclined surface of the lubricating fluid outflow prevention groove with respect to the axial direction of the shaft is determined experimentally in consideration of centrifugal force and surface tension. , (Equation 26).

[0179]

(Equation 26)

[0180]

According to the present invention as described above, claim 1
According to the invention described in the above, the lubricating fluid outflow preventing groove on the fixed member side is provided with the lubricating fluid outflow preventing groove on the rotating member side and the fixed member side at the end of the cylindrical portion on the open end side of the radial dynamic pressure bearing. The lubricating fluid is held by the tension and the lubricating fluid outflow prevention groove on the rotating member side holds the lubricating fluid by the centrifugal force and the surface tension. Is prevented.
Further, the position of the lubricating fluid outflow preventing groove on the fixed member side of the two lubricating fluid outflow preventing grooves is at a fixed position, but the position of the lubricating fluid outflow preventing groove on the rotating member side periodically changes vertically. In addition, when the relative position of the two grooves changes with the rotation, the dynamic pressure generating portion can be replenished by itself. Even when an impact is applied, the self-replenishing function returns the lubricating fluid that has begun to leak back to the lubricating fluid outflow prevention groove,
Furthermore, the holding ability of the lubricating fluid outflow prevention groove is enhanced so as to return to the dynamic pressure generating portion, and the advantageous effect that a highly reliable bearing device can be obtained is obtained.

According to the second aspect of the present invention, the lubricating fluid is held by the surface tension in the lubricating fluid outflow preventing groove on the fixed member side, and the centrifugal force and the surface tension in the lubricating fluid outflow preventing groove on the rotating member side. In addition to having the effect that effective sealing is enabled by holding the lubricating fluid,
The edges of the lubricating fluid outflow preventing grooves provided on the fixed member side and the rotating member side are unlikely to be stepped from each other, so that an advantageous effect that self-replenishment to the dynamic pressure generating portion can be obtained.

According to the third aspect of the present invention, the lubricating fluid is held by the surface tension in the lubricating fluid outflow preventing groove on the fixed member side, and the centrifugal force and the surface tension are applied to the lubricating fluid outflow preventing groove in the rotating member side. The lubricating fluid is held, and the lubricating fluid outflow preventing groove has an advantageous effect that the inclination angle of the groove is within a predetermined range, whereby effective sealing can be achieved.

According to the fourth aspect of the present invention, the edges of the lubricating fluid outflow preventing grooves provided on the fixed member side and the rotating member side are unlikely to be stepped from each other. In addition, the lubricating fluid is prevented by the surface tension in the lubricating fluid outflow preventing groove on the fixed member side, and the lubricating fluid is maintained by the surface tension in the lubricating fluid outflow preventing groove on the rotating member side. An advantageous effect that sealing can be achieved is obtained.

According to the fifth aspect of the present invention, the lubricating fluid is held by the surface tension in the lubricating fluid outflow preventing groove on the fixed member side, and the lubricating fluid is held in the lubricating fluid outflow preventing groove on the rotating member side by the surface tension. By holding the lubricating fluid and setting the inclination angle of the lubricating fluid outflow prevention groove within a predetermined range, an advantageous effect that an effective seal can be obtained is obtained.

According to the sixth aspect of the present invention, the lubricating fluid is held by the surface tension in the lubricating fluid outflow preventing groove on the fixed member side, and the centrifugal force and the surface tension cause the lubricating fluid outflow preventing groove in the rotating member side. In addition to having the effect that effective sealing is enabled by holding the lubricating fluid,
The edges of the lubricating fluid outflow preventing grooves provided on the fixed member side and the rotating member side are unlikely to be stepped from each other, so that an advantageous effect that self-replenishment to the dynamic pressure generating portion can be obtained.

According to the seventh aspect of the present invention, the lubricating fluid is held by the surface tension in the lubricating fluid outflow preventing groove on the fixed member side, and the centrifugal force and the surface tension are exerted in the lubricating fluid outflow preventing groove on the rotating member side. The lubricating fluid is held, and the lubricating fluid outflow preventing groove has an advantageous effect that the inclination angle of the groove is within a predetermined range, whereby effective sealing can be achieved.

According to the invention described in claims 8 to 13,
The edges of the lubricating fluid outflow prevention grooves provided on the rotating member side and the fixed member side are unlikely to be stepped from each other. Since the prevention groove is formed so as to periodically change in the axial direction, a sealing effect occurs at various places,
Outflow is prevented by the effect of centrifugal force and surface tension of the lubricating fluid in the gap, and the lubricating fluid flows out so that the lubricating fluid returns to the dynamic pressure generating part by making the position of the lubricating fluid outflow prevention groove different. The advantageous effect that the holding capacity of the prevention groove is enhanced and a highly reliable bearing device can be obtained is obtained.

According to the fourteenth aspect of the present invention, even if one of the two opposed lubricating fluid outflow preventing grooves is not a spiral groove, the spiral lubricating fluid outflow preventing groove is formed when the eccentricity is 5% or more. And the advantageous effect of effectively preventing the leakage of the lubricating fluid is obtained.

According to the fifteenth aspect of the present invention, the lubricating fluid outflow preventing grooves are provided at the end of the cylindrical portion at the open end of the radial dynamic pressure bearing on the side of the rotating member and the side of the fixed member. The lubricating fluid outflow prevention groove on the rotating member retains the lubricating fluid by the surface tension, and the lubricating fluid outflow preventing groove on the rotating member retains the lubricating fluid by the centrifugal force and the surface tension. Fluid escape from the sleeve is prevented. Furthermore, the edges of the lubricating fluid outflow preventing grooves provided on the sleeve side and the shaft side are unlikely to be stepped from each other, and when the lubricating fluid outflow preventing grooves on the sleeve side are lower, they extend over many steps. When the sealing effect is exhibited and the lubricating fluid outflow prevention groove on the sleeve side is higher, the sealing effect can be exerted over several stages and the position of the lubricating fluid outflow prevention groove on the shaft side Is at a fixed position, but the position of the lubricating fluid outflow prevention groove on the sleeve side changes periodically up and down, so that the relative position of the two grooves changes with rotation, Can be self-replenishing. Even when an impact is applied, the self-replenishing function returns the lubricating fluid that has begun to leak back to the lubricating fluid outflow prevention groove,
Furthermore, the holding ability of the lubricating fluid outflow prevention groove is enhanced so as to return to the dynamic pressure generating portion, and the advantageous effect that a highly reliable bearing device can be obtained is obtained.

According to the sixteenth aspect, the position of the lubricating fluid outflow preventing groove on the shaft side is at a fixed position, but the position of the lubricating fluid outflow preventing groove on the sleeve side periodically changes vertically. In addition, since the relative position of the two grooves changes with the rotation, the advantageous effect that the dynamic pressure generating portion can be self-replenished can be obtained.

Since the holding pressure of the lubricating fluid due to the capillary action is inversely proportional to the interval of the gap, the lubricating fluid is prevented from being supplied to the dynamic pressure generating portion by holding the lubricating fluid in the lubricating fluid outflow preventing groove in a large amount even during normal rotation. One of the grooves for preventing lubricating fluid outflow is formed as a spiral groove.

In the present application, a device is devised so that an external force acts in a direction to pull back the phenomenon of diffusion leakage. This ingenuity is achieved by making the lubricating fluid outflow prevention groove of this seal holding force into a spiral groove, and making it interfere with the lubricating fluid outflow prevention groove.
The holding space that can be sealed changes at the same position,
The sealing effect is changed with the rotation, and the lubricating fluid leaked according to the rotation position is supplied to the dynamic pressure generating unit by itself and returned.

Since the above method can prevent the leakage of the lubricating fluid, the reliability of the spindle motor is improved, and when applied to a magnetic disk drive, the influence of the magnetic head on the magnetic disk can be reduced. Therefore, an advantageous effect of improving the reliability of the entire apparatus can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram of a hydrodynamic bearing device according to an embodiment of the present invention.

FIG. 2 is a development view of two lubricating fluid outflow prevention grooves of the dynamic pressure bearing of the motor.

FIG. 3 is an enlarged view of a groove for preventing lubricating fluid from flowing out.

FIG. 4 is an enlarged view of a groove for preventing lubricating fluid from flowing out.

FIG. 5 is a diagram for explaining surface free energy.

FIG. 6 is a diagram for a basic equation of capillary action.

FIG. 7 is a schematic view in which a groove for holding and flowing out a lubricating fluid is formed.

FIG. 8 is a diagram showing the relationship between the angle ε and the liquid level height h of the lubricating fluid.

FIG. 9 is a graph showing the relationship between the angle ε and the rate of change of the liquid level height h of the lubricating fluid

FIG. 10 is a diagram of a fluid dynamic bearing according to the embodiment.

FIG. 11 is an enlarged view of a lubricating fluid outflow prevention groove.

FIG. 12 is an enlarged view of a lubricating fluid outflow prevention groove.

FIG. 13 is a view of a fluid dynamic bearing in the embodiment.

FIG. 14 is an enlarged view of a lubricating fluid outflow prevention groove.

FIG. 15 is an enlarged view of a lubricating fluid outflow prevention groove.

FIG. 16 is a developed view showing a positional relationship between the lubricating fluid outflow preventing groove on the fixed member side and the lubricating fluid outflow preventing groove on the rotating member side.

FIG. 17 is an explanatory diagram of a contact angle θ in a wetting phenomenon.

FIG. 18 is a cross-sectional view of a spindle motor using a fluid dynamic bearing device for driving a fixed shaft type recording medium as an embodiment.

FIG. 19 is a diagram of a fluid dynamic bearing in a conventional example.

[Explanation of symbols]

1, 9 fixing member 2, 10 rotating member 3 lubricating fluid 4, 5, 11, 12, 17, 18, 23, 24, 46,
47 Lubricating fluid outflow prevention groove 6 Thrust plate 7 Open end opening gap 8 Fluid holding groove 13, 15, 19, 21 First inclined surface 14, 16, 20, 22 Second inclined surface 25 Lubricating fluid on rotating member side The lowest point of the lower end of the outflow prevention groove 26 The highest point of the lower end of the lubricating fluid outflow prevention groove on the rotating member 27 The lowest point of the upper end of the lubricating fluid outflow preventing groove on the rotating member 28 The uppermost point of the upper end of the lubricating fluid outflow prevention groove on the rotating member side 35 Shaft 42 Sleeve 43 Fluid reservoir 44 Upper small diameter cylindrical part 45 Lower small diameter cylindrical part

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) H02K 21/22 H02K 21/22 MF term (Reference) 3J011 AA04 AA07 BA02 BA09 CA01 CA02 JA02 KA02 KA03 MA07 MA23 MA24 3J016 AA02 AA03 BB22 5H605 AA00 BB05 BB14 BB19 CC04 DD03 DD05 EA02 EB02 EB03 EB28 FF06 GG04 GG21 5H607 AA00 BB01 BB14 BB17 BB25 CC01 DD01 DD02 DD03 DD08 DD16 GG01 GG02 GG03 GG12 JJ05 J01H01K19H01

Claims (16)

[Claims] 1. A dynamic pressure bearing device provided with a dynamic pressure bearing portion comprising a radial dynamic pressure fluid bearing and a thrust dynamic pressure fluid bearing for rotatably supporting a rotating body with respect to a fixed member. The bearing is filled with lubricating fluid, and the rotating member is rotated in a non-contact manner with respect to the fixed member. Both ends in the axial direction of the dynamic pressure bearing are open ends, and the ends of the cylindrical portion on the end side of the radial dynamic pressure bearing are provided. The lubricating fluid outflow preventing grooves are provided on both the fixed member side and the rotating body side, and the position of the lubricating fluid outflow preventing groove on the fixed member side is fixed, and the position of the lubricating fluid outflow preventing groove on the rotating member side is periodically set at an axial distance. Wherein the lubricating fluid outflow preventing groove on the fixed member side and the lubricating fluid outflow preventing groove on the rotating member side have a lubricating fluid outflow preventing groove configured to partially face each other. . 2. A lubricating fluid outflow preventing groove provided on both the rotating member side and the fixed member side has a groove surface in which a gap decreases toward an open end in an end side cylindrical portion of the radial dynamic pressure bearing. The hydrodynamic bearing device according to claim 1, wherein: 3. A lubricating fluid outflow prevention groove provided on both the rotating member side and the fixed member side has a groove surface on the end side cylindrical portion of the radial dynamic pressure bearing whose gap decreases toward an open end. The hydrodynamic bearing device according to claim 2, wherein each of the groove surfaces is formed at an inclination angle α, β from the axial direction, and the inclination angles α, β have a relationship of (Equation 1). . (Equation 1) 4. The lubricating fluid outflow preventing groove provided on the rotating member side is formed such that a groove surface whose clearance increases toward an open end exists in an end side cylindrical portion of the radial dynamic pressure bearing, The lubricating fluid outflow prevention groove provided on the fixing member side is formed so that a groove surface whose gap decreases toward the open end exists in the end side cylindrical portion of the radial dynamic pressure bearing. The dynamic pressure bearing device according to claim 1. 5. The lubricating fluid outflow prevention groove provided on the rotating member side is formed such that a groove surface whose clearance increases toward the open end exists in the end side cylindrical portion of the radial dynamic pressure bearing, The lubricating fluid outflow preventing groove provided on the fixed member side is formed so that a groove surface whose gap decreases toward the open end exists in the end side cylindrical portion of the radial dynamic pressure bearing. 5. The hydrodynamic bearing device according to claim 4, wherein the groove surfaces of the preventing grooves have inclination angles [gamma] and [delta] from the axial direction, and the inclination angles [gamma] and [delta] have a relationship of (Equation 2). (Equation 2) 6. The lubricating fluid outflow prevention groove provided on the rotating member side is formed such that a groove surface whose clearance decreases toward an open end exists in an end side cylindrical portion of the radial dynamic pressure bearing, The lubricating fluid outflow prevention groove provided on the fixed member side is formed so that a groove surface whose clearance increases toward the open end exists in the end side cylindrical portion of the radial dynamic pressure bearing. The dynamic pressure bearing device according to claim 1. 7. The lubricating fluid outflow preventing groove provided on the rotating member side is formed such that a groove surface whose gap decreases toward an open end exists in an end-side cylindrical portion of the radial dynamic pressure bearing, The lubricating fluid outflow preventing groove provided on the fixing member side is formed so that the end cylindrical portion of the radial dynamic pressure bearing has a groove surface whose gap increases toward the open end. 7. The hydrodynamic bearing device according to claim 6, wherein the groove surfaces of the prevention grooves have inclination angles [gamma] and [delta] from the axial direction, and the inclination angles [gamma] and [delta] have a relationship of (Equation 3). (Equation 3) 8. A lubricating fluid outflow preventing groove provided on both the rotating member side and the fixed member side is formed in an end side cylindrical portion of the radial dynamic pressure bearing, and the lubricating fluid outflow preventing groove on the fixed member side is constant. The lowermost point position of the lower end of the lubricating fluid outflow preventing groove on the rotating member side is higher than the lower end position of the lubricating fluid outflow preventing groove on the fixed member side ( The uppermost position of the lower end of the lubricating fluid outflow preventing groove on the rotating member side is higher than the upper end position of the lubricating fluid outflow preventing groove on the fixed member side (open end). And the lowermost point of the upper end of the lubricating fluid outflow prevention groove on the rotating member side is higher than the position of the upper end of the lubricating fluid outflow prevention groove on the fixed member side (open end). And the uppermost point of the upper end of the lubricating fluid outflow prevention groove on the rotating member is located on the fixed member side. 8. The hydrodynamic bearing device according to claim 1, wherein the lubricating fluid outflow preventing groove is located on an upper side (opposite of an open end) side of an upper end. 9. A lubricating fluid outflow preventing groove provided on both the rotating member side and the fixed member side is formed in an end side cylindrical portion of the radial dynamic pressure bearing, and the lubricating fluid outflow preventing groove on the fixing member side is constant. The lowermost point position of the lower end of the lubricating fluid outflow preventing groove on the rotating member side is higher than the lower end position of the lubricating fluid outflow preventing groove on the fixed member side ( The uppermost position of the lower end of the lubricating fluid outflow preventing groove on the rotating member side is lower than the upper end position of the lubricating fluid outflow preventing groove on the fixed member side (open end). ) Side, the lowermost point position of the upper end of the lubricating fluid outflow preventing groove on the rotating member side is higher than the position of the upper end of the lubricating fluid outflow preventing groove on the fixed member side (the opposite of the open end). The uppermost point of the upper end of the lubricating fluid outflow prevention groove on the rotating member side is the lubrication on the fixed member side. 8. The hydrodynamic bearing device according to claim 1, wherein the fluid outflow prevention groove is located on an upper side (opposite of an open end) side of an upper end position. 10. A lubricating fluid outflow preventing groove provided on both the rotating member side and the fixed member side is formed in an end side cylindrical portion of the radial dynamic pressure bearing, and the lubricating fluid outflow preventing groove on the fixing member side is constant. The lowermost point position of the lower end of the lubricating fluid outflow preventing groove on the rotating member side is lower than the lower end position of the lubricating fluid outflow preventing groove on the fixed member side ( (Open end) side, and the uppermost position of the lower end of the lubricating fluid outflow prevention groove on the rotating member side is lower (open end) side than the upper end position of the lubricating fluid outflow prevention groove on the fixed member side. At the lower end of the upper end of the lubricating fluid outflow preventing groove on the rotating member, which is located above (the opposite of the open end) the lower end of the lubricating fluid outflow preventing groove on the fixed member side. Is located lower (open end) than the upper end of the lubricating fluid outflow prevention groove on the fixed member side. The upper end of the lubricating fluid outflow preventing groove on the rotating member is fixed to the uppermost position of the upper end of the lubricating fluid outflow preventing groove on the rotating member side. 8. The hydrodynamic bearing device according to claim 1, wherein the lubricating fluid outflow prevention groove on the member side is located on the upper side (opposite of the open end) of the upper end. 11. A lubricating fluid outflow preventing groove provided on both the rotating member side and the fixed member side is formed in an end side cylindrical portion of the radial dynamic pressure bearing, and the lubricating fluid outflow preventing groove on the fixing member side is constant. The lowermost point position of the lower end of the lubricating fluid outflow preventing groove on the rotating member side is lower than the lower end position of the lubricating fluid outflow preventing groove on the fixed member side ( (Open end) side, and the uppermost position of the lower end of the lubricating fluid outflow prevention groove on the rotating member side is lower (open end) side than the lower end position of the lubricating fluid outflow prevention groove on the fixed member side. And the lowermost point position of the upper end of the lubricating fluid outflow preventing groove on the rotating member side is located lower (open end) than the upper end position of the lubricating fluid outflow preventing groove on the fixed member side. And located above (at the opposite of the open end) the lower end of the lubricating fluid outflow prevention groove on the fixed member side. The uppermost position of the upper end of the lubricating fluid outflow preventing groove on the rotating member side is located lower (open end) than the upper end of the lubricating fluid outflow preventing groove on the fixed member side. The dynamic pressure bearing device according to claim 1, wherein: 12. A lubricating fluid outflow preventing groove provided on both the rotating member side and the fixed member side is formed in an end side cylindrical portion of the radial dynamic pressure bearing, and the lubricating fluid outflow preventing groove on the fixing member side is constant. The lowermost point position of the lower end of the lubricating fluid outflow preventing groove on the rotating member side is lower than the lower end position of the lubricating fluid outflow preventing groove on the fixed member side ( (Open end) side, and the uppermost position of the lower end of the lubricating fluid outflow prevention groove on the rotating member side is lower (open end) side than the lower end position of the lubricating fluid outflow prevention groove on the fixed member side. The lowermost point position of the upper end of the lubricating fluid outflow preventing groove on the rotating member side is located lower (open end) than the lower end position of the lubricating fluid outflow preventing groove on the fixed member side. The uppermost position of the upper end of the lubricating fluid outflow prevention groove on the rotating member side is the lubricating fluid flow on the fixed member side. The groove is located on the lower side (open end) side of the upper end of the protrusion prevention groove and is located on the upper side (opposite to the open end) side of the lower end of the lubricating fluid outflow prevention groove on the fixed member side. The dynamic pressure bearing device according to claim 1, wherein: 13. A lubricating fluid outflow preventing groove provided on both the rotating member side and the fixed member side is formed in an end side cylindrical portion of the radial dynamic pressure bearing, and the lubricating fluid outflow preventing groove on the fixed member side is fixed. The lubricating fluid outflow preventing groove on the rotating member side is spirally formed in the axial direction when it is developed in the circumferential direction, and the axial distance of the spiral lubricating fluid outflow preventing groove is increased. When the displacement is set, there are n cycles in one expansion (n
Is a positive integer of 1 or more).
2. The dynamic pressure bearing device according to 2. 14. A lubricating fluid outflow prevention groove provided on both the rotating member side and the fixed member side is formed in an end side cylindrical portion of the radial dynamic pressure bearing, and a gap between the rotating member and the fixed member is constant. In this case, the two lubricating fluid outflow prevention grooves are formed at a fixed height, and the eccentricity of the radial dynamic pressure bearing is 5%.
A hydrodynamic bearing device used as described above. 15. A housing, a stator core fixed directly or indirectly to the housing, a shaft fixed to the housing, a retaining plate fixed to the shaft, and a bearing for the fixed shaft. A bearing sleeve that is relatively rotatable through the rotor, and a rotor that is directly or indirectly fixed to an outer peripheral portion of the sleeve. The herringbone groove is formed in one of the shaft and the sleeve. The retaining plate is sandwiched between the radial dynamic pressure bearing, the thrust retaining plate, and the sleeve via the lubricating fluid in the gap, and a dynamic pressure groove is formed in one of the retaining plate and the thrust retaining plate. A dynamic pressure groove is formed in one of the sleeves to provide a thrust hydrodynamic bearing with lubricating fluid in the gap. The lubricating fluid outflow preventing grooves are on both the shaft side and the bearing sleeve side, the position of the lubricating fluid outflow preventing groove on the shaft side is constant, and the position of the lubricating fluid outflow preventing groove on the sleeve side is periodic at the axial distance. And the lubricating fluid outflow preventing groove on the shaft side and the lubricating fluid outflow preventing groove on the sleeve side have a lubricating fluid outflow preventing groove configured to be partially opposed to each other in one rotation of the bearing. A spindle motor using a hydrodynamic bearing device characterized by the following. 16. A spindle motor using the hydrodynamic bearing device according to claim 1.