JP2003156035A - Dynamic pressure fluid bearing device, and spindle motor using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dynamic pressure fluid bearing device with improved pumping effect. SOLUTION: In the dynamic pressure fluid bearing device comprising a stationary member 3 having a radial bearing surface and a thrust bearing surface, a rotary member 2 which is supported by these bearing surfaces and rotatable around the axis relatively to the stationary member 3, and a lubricating fluid 8 held between the rotary member and the bearing surfaces, forming a plurality of grooves 9 for generating the dynamic pressure which have returning points, are asymmetric in the direction of the rotary shaft, and regularly repeated in the rotational direction in the radial bearing surface, and forming a plurality of grooves 10 for generating the dynamic pressure which have returning points, are asymmetric in the radial direction, and regularly repeated in the rotational direction in the thrust bearing surface, the grooves 9 are formed more densely on a moving origin side passage 9c than on a moving destination side passage 9b of the lubricating fluid with the returning point as the boundary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrodynamic bearing device and a spindle motor using the same, and can be suitably used for a mechanism such as a recording disk driving motor, which requires high speed rotation.

[0002]

2. Description of the Related Art In a mechanism such as a motor for driving a recording disk, which requires high-speed rotation, grooves such as V-shape, U-shape, and herringbone shape are formed on a bearing surface and / or the surface of a rotating member facing the bearing surface. In addition, the lubricating fluid is retained between the rotating member and the bearing surface, and the rotating member and the bearing surface are kept in non-contact with each other by the pressure generated by the pumping action of the groove during rotation, that is, the dynamic pressure. A hydrodynamic bearing device that enables the above is used.

Among such hydrodynamic bearing devices, in a hydrodynamic bearing device in which a radial bearing surface for receiving a load in the radial direction and a thrust bearing surface for receiving a load in the thrust direction are respectively provided on a stationary member to support a rotating member. In some cases, air bubbles may stay near the boundary between the radial bearing surface and the thrust bearing surface. The accumulated bubbles cause the lubricating fluid to be pushed out of the bearing device by thermal expansion at high temperature of the motor,
This is an unfavorable existence because it hinders writing / reproducing on a recording disk.

Therefore, in order to prevent air bubbles from accumulating, the dynamic pressure generating groove of the radial bearing surface has a herringbone shape which is asymmetric in the axial direction, that is, a path far from the thrust bearing surface with the folding point of the herringbone as a boundary. Has a long and short path on the near side, and has an unbalanced herringbone shape.The grooves for generating dynamic pressure on the thrust bearing surface have a spiral shape.The radial bearing part and thrust bearing part are directly connected to each other, and the floating force of the rotating member is increased. Has been proposed (Japanese Patent Laid-open No. 2000-21).
5589). With this configuration, dynamic pressure is generated so that both the lubricating fluid held on the radial bearing surface and the lubricating fluid held on the thrust bearing surface move toward the vicinity of the boundary, so that the retention of bubbles is prevented. It

[0005]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention Aside from the fact that the dynamic pressure generating groove of the conventional bearing device is bent in a V shape, a U shape, a herringbone shape, a spiral shape, etc. One groove having a constant gradient and depth from the movement source side (the side far from the thrust bearing surface) of the lubricating fluid to the movement destination side (the side close to the thrust bearing surface),
On the thrust bearing surface, only one groove having a continuous gradient and a constant depth was repeatedly formed in the rotational direction. However, since the size of the motor has been large in the related art, a sufficient pumping force can be obtained by enlarging the dynamic pressure generating groove in the configuration described in JP-A-2000-215589, and no trouble occurs.

However, with the demand for downsizing of the motor size, it has become necessary to design a dynamic pressure generating groove which produces a large pumping force in a limited bearing area.

Therefore, the object of the present invention is to solve the above-mentioned problems in Japanese Patent Laid-Open No.
It is another object of the present invention to provide a hydrodynamic bearing device having an improved pumping action as compared with the configuration described in 00-215589.

[0008]

In order to solve the above-mentioned problems, a hydrodynamic bearing device of the present invention has a stationary member having a radial bearing surface and a thrust bearing surface, and a stationary member supported by these bearing surfaces. On the other hand, a rotary member that is relatively rotatable about the axis and a lubricating fluid that is retained between the rotary member and the bearing surface are provided, and the radial bearing surface and / or the surface of the rotary member that faces the radial bearing surface is lubricated. A plurality of grooves for dynamic pressure generation that are regularly repeated in the rotational direction are formed so that a dynamic pressure that moves the fluid toward the thrust bearing surface is generated, and a thrust bearing surface and / or a rotating member that faces the thrust bearing surface. In the hydrodynamic bearing device, a plurality of grooves for dynamic pressure generation that are regularly repeated in the rotational direction are formed on the surface of so as to generate dynamic pressure that moves the lubricating fluid toward the rotation axis core, The groove Characterized in that the better the migration source side path are densely formed than in the target-side path of the lubricating fluid.

In the bearing device of the present invention, the conventional fixed idea is removed, and the groove density is made different between the moving destination side path and the moving source side path of the lubricating fluid, and the grooves are densely formed on the moving source side. As a result, the dynamic pressure generating groove becomes asymmetric in the direction in which the lubricating fluid is moved, and the pumping action occurs so that the lubricating fluid moves in the predetermined direction. Moreover, since it is only necessary to change the density at the turning point, the desired pumping force can be obtained even with a limited bearing area.

The first means for making the movement-source-side path relatively dense is a herringbone shape in which the groove on the radial bearing surface extends a predetermined length longer in the movement-source-side path than in the movement-destination-side path. The second groove is formed between the adjacent grooves of the extended portion. By forming one second groove between the grooves of the extended portion, the density of the grooves of the extended portion is doubled, and when two grooves are formed, the density is tripled, and the pumping power is improved.

A second means for making the movement-source-side path relatively dense is to form a groove on the radial bearing surface into a herringbone shape, and form a second groove between adjacent grooves in the movement-source-side path. That is. In this case, the herringbone shape before forming the second groove may be axially symmetrical,
It may be asymmetric in which the movement source side route is extended by a predetermined length. In any case, by forming one second groove, the density of the grooves in the entire movement source side path is doubled, and when two grooves are formed, the density is tripled and the pumping power is improved.

A third means for making the movement-source-side path relatively dense is a herringbone shape in which the groove on the radial bearing surface extends a predetermined length longer in the movement-source-side path than in the movement-destination-side path. , The angle of the extension with respect to the circumference is smaller than that of the non-extension. As a result, compared with the case where the movement source side path is extended with the same gradient, the interval between the grooves is narrowed even if the axial length of the extended portion is the same, and the density of the grooves can be increased.

A fourth means for making the movement-source side path relatively dense is a herringbone shape in which the groove on the radial bearing surface extends a predetermined length longer in the movement-source-side path than in the movement-destination-side path. , The depth of the extension is deeper than that of the non-extension. Although the plane area of the groove does not change, doubling the depth can be expected to improve the pumping force similar to the case where one second groove having the same depth is formed.

On the other hand, one means for making the moving-source-side path relatively dense on the thrust bearing surface is to make the groove on the thrust-bearing surface spiral, and to provide a second groove between adjacent grooves of the moving-source side path. Forming a groove. Although it depends on the curvature of the spiral and the length of the second groove, it is certain that the density of the grooves increases with the number of the second grooves.

Similarly, another means is to make the groove of the thrust bearing surface into a herringbone shape, and to form a second groove between the adjacent grooves of the movement source side path. Like the spiral, it depends on the curvature of the herringbone and the length of the second groove, but it is certain that the density of the grooves increases with the number of the second grooves.

A spindle motor having the above-mentioned hydrodynamic bearing device, a magnet fixed to its rotating member, and a stator provided on a stationary member so as to be energized so as to generate a rotational force in cooperation with the magnet, It becomes a driving source of high-speed rotation that does not leak the lubricating fluid.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1 An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an axial sectional view showing a spindle motor for driving a recording disk to which a hydrodynamic bearing device of the present invention is applied, FIG. 2 is a front view showing a main part of a radial bearing surface of the motor of FIG. 1, and FIG. It is a front view which shows the groove | channel of the radial bearing surface of embodiment. In FIG. 3, the filled area is a groove and the white area is a hill between the grooves.

The motor 1 has a rotor 2 as a rotating member for rotating the recording disk D and a bracket 3 as a stationary member. The rotor 2 is composed of a rotating shaft 4 and a disk-shaped hub 5 fixed to one end of the rotating shaft 4. A wall extending in the same direction as the rotating shaft 4, that is, downward in the drawing is formed on the peripheral edge of the hub 5. The magnet 6 is attached inside.

The bracket 3 includes a bracket main body 31 having a through hole concentric with the rotary shaft 4, a cylindrical support member 32 fitted between the bracket main body 31 and the rotary shaft 4, and a support. The disk-shaped cover 33 is fixed to the open end surface of the member 32 and faces the end surface of the rotary shaft 4 opposite to the hub 5 side. A cylindrical wall extending toward the hub 5 is formed on the periphery of the through hole in the bracket body 31, and the stator 7 is fixed to the outer peripheral surface of the wall. The stator 7 is connected to unillustrated leads and can be energized from the outside.

An annular notch is formed at the free end of the rotary shaft 4, and a ring 41 protruding radially outward from the outer peripheral surface of the rotary shaft 4 is fixed to the notch, and the ring 41 is fixed to the ring 41. An annular recess 42 is formed on the inner peripheral surface of the opposing support member 32, and the ring 41 and the recess 42 are fitted together to prevent the rotary shaft 4 from coming off.

The inner peripheral surface of the support member 32 serves as a radial bearing surface 34, and the lubricating fluid 8 is retained between the radial bearing surface 34 and the outer peripheral surface of the rotary shaft 4 facing the radial bearing surface 34. The end surface of the support member 32 on the hub 5 side becomes a thrust bearing surface 35, and the lubricating fluid 8 is held between the thrust bearing surface 35 and the upper surface of the support member 32 facing the thrust bearing surface 35. The lubricating fluid on the radial bearing surface 34 side and the lubricating fluid on the thrust bearing surface 35 side are continuous. Predetermined dynamic pressure generating grooves 9 and 10 are formed on the bearing surfaces 34 and 35, or on the surface facing the rotating member, which faces the bearing surfaces 34 and 35, respectively. Due to these dynamic pressure generating grooves, a radial load supporting pressure is generated in the lubricating fluid held between the radial bearing surface 34 and the outer peripheral surface of the rotary shaft 4 during rotation, whereby a radial dynamic pressure bearing portion is constituted, Further, a thrust load supporting pressure is generated in the lubricating fluid held between the thrust bearing surface 35 and the lower surface of the hub 5, whereby a thrust dynamic pressure bearing portion is constituted, and the rotating member is in a non-contact state with the stationary member. Is kept.

The dynamic pressure generating groove 9 formed on the radial bearing surface 34 has a herringbone shape which is asymmetric in the axial direction as shown in FIG. Although only the herringbone-shaped groove is shown in FIG. 2 in order to explain the pumping action of the present embodiment in an easy-to-understand manner, the second groove is actually formed as will be described later with FIG. 3). The lubricating fluid facing the radial bearing surface 34 tends to go from the upper and lower end portions toward the turning point at the central portion by the pumping action of the groove 9, but in this embodiment, the turning point 9a serves as a boundary and is lower than the upper path 9b. Route 9
Since c has an asymmetrical shape elongated by a predetermined length, the lower pumping action prevails and the lubricating fluid tends to move upward in the drawing, that is, toward the thrust bearing surface 35. Therefore, in this embodiment, the lower route 9c is the source side and the upper route 9b is the destination side. On the other hand, on the lower surface of the hub 5 (the surface facing the thrust bearing surface 35), a spiral dynamic pressure generating groove (broken line in FIG. 1) that generates a moving pressure of the lubricating fluid from the outside in the radial direction toward the shaft core. ) 10 is formed. As a result, when the rotor 2 rotates, a dynamic pressure is generated that directs the lubricating fluid 8 radially inward, that is, toward the radial bearing portion. The lubricating fluid of the radial dynamic pressure bearing portion and the lubricating fluid of the thrust dynamic pressure bearing portion are continuous, and both bearing portions are directly connected, so that the pump action and the dynamic pressure generating groove by the dynamic pressure generating groove 9 are formed. Due to the pumping action of 10, the pressure of the lubricating fluid filled over both bearing portions is increased, and a radial load supporting pressure and a thrust load supporting pressure are generated. Here, the pump pressure to the thrust dynamic pressure bearing portion generated by the unbalanced herringbone dynamic pressure generating groove 9 is applied to the radial dynamic pressure bearing portion generated by the spiral dynamic pressure generating groove 10 at the initial stage of rotation. It is set higher than the pump pressure of. Therefore, when the rotor rotates twice, the force for pumping the lubricating fluid in the radial dynamic pressure bearing portion to the thrust side exceeds the force for pumping the lubricating fluid in the thrust dynamic pressure bearing portion to the radial side, and both bearing portions are continuously filled. A moving pressure to the thrust side is generated in the lubricating fluid. With the movement of the lubricating fluid, as the gas-liquid interface 8a (FIG. 1) on the moving side of the radial dynamic pressure bearing portion moves in the dynamic pressure generating groove 9, the dynamic pressure generating groove 9 moves to the thrust side. Since the moving pressure decreases, the pump pressure from the thrust side and the pump pressure from the radial side gradually balance, and eventually the movement of the lubricating fluid stops and this state is maintained. The equilibrium position of the gas-liquid interface 8a is automatically adjusted depending on the temperature, the load, the attitude of the motor, and the like.

Further, in this embodiment, as shown in FIG. 3, when the circumference P connecting the turning points 9a is centered,
In the extension area E of the lower path 9c excluding the symmetrical area C, second grooves 9d are formed in parallel with the lower path 9c at equal intervals with respect to one lower path 9c. As a result, the pumping action of the entire movement source side path is further improved. In this respect, it is remarkable that the conventionally known dynamic pressure generating groove is formed only in the symmetrical area C, or even if the extended area E is formed, the second groove is not formed. Be different.

As described above, the gas-liquid interface on the moving source side of the lubricating fluid in the radial dynamic pressure bearing portion is settled at the position of the lower path 9c of the dynamic pressure generating groove 9 when the rotor 2 rotates. Then, as the rotor 2 rotates, the hills and grooves of the dynamic pressure generating groove 9 are continuously repeated at this gas-liquid interface, and a narrow and wide gap between the radial bearing surface 34 and the outer peripheral surface of the rotary shaft 4 is created. I will repeat. Therefore, the gas-liquid interface undulates so as to pulsate. When the number of dynamic pressure generating grooves at the gas-liquid interface is small, the number of waves is small and the amplitude is large, and the waves at the gas-liquid interface are likely to entrain bubbles. In the present embodiment, as described with reference to FIG. 3, the second groove 9d is formed in the extension region of the dynamic pressure generating groove 9 where the gas-liquid interface is located, and the number of grooves in this portion is increased. The structure has a structure in which the wave amplitude at the gas-liquid interface is reduced and air bubbles are less likely to be involved.

The depth of the second groove 9d is determined by the lower path 9c.
Does not have to be the same as the depth of the above, and may be formed deeper than the lower passage 9c to further improve the pumping action. Further, the groove for generating dynamic pressure may be formed on the outer peripheral surface of the rotary shaft 4 facing the radial bearing surface 34. Thrust bearing surface 35
The dynamic pressure generating grooves on the side are the fourth and fifth embodiments.
See in detail.

-Second Embodiment- A second embodiment of the present invention will be described with reference to FIG.
FIG. 4 is a front view showing a groove on the radial bearing surface. In this embodiment as well, the groove 19 has a herringbone shape, but unlike the first embodiment, there is no extension region E. Lower path 1 instead
A second groove 19d is formed between 9c and parallel to the lower path 19c. Also in this case, the depth of the groove 19d may be the same as that of the groove 19 or may be deeper than the groove 19. Other configurations are the same as those in the first embodiment.

As a result, the pumping action on the lower side is predominant due to the groove 19d, and the lubricating fluid tends to move upward in the drawing, that is, toward the thrust bearing surface. Since the pump pressure to the thrust side can be secured to the lubricating fluid in the radial bearing portion without securing the extension region E, it is useful for an ultra-thin motor with a short axial length. Further, also in the case of this embodiment, it is possible to reduce the inclusion of bubbles at the gas-liquid interface.

-Embodiment 3-A third embodiment of the present invention will be described with reference to FIG.
FIG. 5 is a front view showing a groove on the radial bearing surface. Also in this embodiment, the groove 29 has a herringbone shape, and the extension region E exists as in the first embodiment. However, the second groove is not formed between the lower path 29c, and instead, the angle with the circumferential line of the lower path 29c is smaller in the extension area E than in the symmetrical area C. Therefore, even if the area of the extension area E is 1/2 of the area of the symmetrical area C,
The length L1 in the extension region E of the lower path 29c is longer than L2. At this point, the gradient of the lower path is uniform and L1 and L2
Are different from the conventional asymmetric herringbone shape. Other configurations are the same as those in the first embodiment.

As a result, the lower pumping action prevails, and the lubricating fluid tends to move upward in the drawing, that is, toward the thrust bearing surface, and the pumping action is greater than that of the conventional configuration of L1 = L2.

Fourth Embodiment A fourth embodiment of the present invention will be described with reference to FIGS. 1 and 6. All of the above embodiments relate to improvements in grooves that generate radial load bearing pressure. On the other hand, this embodiment is an example of the groove for generating the thrust load supporting pressure.
FIG. 6 is a bottom view of the hub 5 of FIG.

A spiral dynamic pressure generating groove 10 (broken line in FIG. 1) is formed on the bottom surface of the hub 5 (the surface facing the thrust bearing surface 35), which concentrates from the outside in the radial direction toward the axis. ing. As a result, when the rotor rotates, a dynamic pressure is generated that directs the lubricating fluid 8 inward in the radial direction. Therefore, in this embodiment, the half of the entire length of the groove 10 on the axial center side is the destination side path and the outer half is the source side path. The second groove 10d is formed in the middle of the adjacent movement source side paths. Therefore, the pump action for directing the lubricating fluid 8 inward in the radial direction is improved as compared with the configuration in which the groove 10d is not formed. It should be noted that this embodiment may be used in combination with the first to third embodiments, or may be applied alone to a motor.

-Embodiment 5-A fifth embodiment of the present invention will be described with reference to FIG.
FIG. 7 shows another hub 15 applied to the motor of FIG.
FIG. Herringbone-shaped dynamic pressure generating grooves 20 are repeatedly formed in the bottom surface of the hub 15 in the circumferential direction. Both sides of the turning point of the herringbone may be symmetrical or asymmetrical to each other. However, the second groove 20d is formed between the adjacent grooves 20 on the outside of the turning point. This increases the pumping action of the lubricating fluid towards the shaft core. Moreover, the pump action can be further increased by increasing the number of the second grooves 20d without increasing the bottom area of the hub 15.

[0033]

As described above, according to the bearing device of the present invention, the dynamic pressure generating groove having the turning point for generating the load supporting pressure in the lubricating fluid at the time of rotation has the turning point as a boundary. By simply forming one side densely, the pump action for moving the lubricating fluid in the predetermined direction is improved. Therefore, the lubricating fluid can be stably held on the bearing surface without leaking, and a small bearing area is sufficient.

[Brief description of drawings]

FIG. 1 is an axial sectional view showing a spindle motor to which a hydrodynamic bearing device of the present invention is applied.

FIG. 2 is a front view showing a main part of the radial bearing surface of FIG.

FIG. 3 is a front view showing a groove on the radial bearing surface of the first embodiment.

FIG. 4 is a front view showing a groove on a radial bearing surface according to a second embodiment.

FIG. 5 is a front view showing a groove on a radial bearing surface according to a third embodiment.

FIG. 6 is a bottom view of the hub facing the thrust bearing surface of the fourth embodiment.

FIG. 7 is a bottom view of the hub facing the thrust bearing surface of the fifth embodiment.

[Explanation of symbols]

1 motor 2 rotors 3 brackets 4,14 rotation axis 5, 15 hubs 6 magnets 7 Stator 8 Lubricating fluid 32 Support member 34 Radial bearing surface 35 Thrust bearing surface 9, 19, 29, 10, 20 groove (for dynamic pressure generation) 9a, 19a, 29a Turning point 9b, 19b, 29b Route (destination side) 9c, 19c. 29c route (source side) 9d, 19d, 10d, 20d Second groove

[Procedure amendment]

[Submission date] April 1, 2002 (2002.4.1)

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3J011 AA07 BA02 BA08 CA03 JA02                       KA02 KA03                 5H605 BB05 BB10 BB14 BB19 EB02                       EB06                 5H607 BB01 BB07 BB09 BB14 BB17                       BB25 GG01 GG02 GG09 GG12                       GG15                 5H621 GA01 HH01 JK19

Claims (8)

[Claims] 1. A stationary member having a radial bearing surface and a thrust bearing surface, a rotating member supported by these bearing surfaces and rotatable about an axis relative to the stationary member, and the rotating member and the bearing surface. And a lubricating fluid retained between them. The radial bearing surface and / or the surface of the rotary member facing the radial bearing surface is regularly arranged in the rotating direction so that a dynamic pressure for moving the lubricating fluid toward the thrust bearing surface is generated. A plurality of grooves for dynamic pressure generation are repeatedly formed, and dynamic pressure for moving the lubricating fluid toward the radial bearing surface is generated on the surface of the thrust bearing surface and / or the rotating member facing the thrust bearing surface. In a hydrodynamic bearing device in which a plurality of grooves for generating a dynamic pressure are regularly formed in the rotation direction, the groove is formed in the movement source side path more than in the movement destination side path of the lubricating fluid. A hydrodynamic bearing device, which is densely formed. 2. A groove on the radial bearing surface has a herringbone shape in which the movement source side path extends a predetermined length longer than the movement destination side path, and a second groove is formed between adjacent grooves of the extended portion. The hydrodynamic bearing device according to claim 1, wherein the fluid pressure bearing device is dense in the movement source side path due to the formation of the. 3. A groove on the radial bearing surface has a herringbone shape, and a second groove is formed between adjacent grooves on the movement source side path, whereby the movement source side path is dense. The hydrodynamic bearing device according to claim 1. 4. The groove of the radial bearing surface has a herringbone shape in which the movement-source-side path extends a predetermined length longer than the movement-destination-side path, and the angle of the extended portion with respect to the circumferential line is not extended. 2. The hydrodynamic bearing device according to claim 1, wherein the fluid pressure bearing device is made denser by making the size smaller than that. 5. The groove of the radial bearing surface has a herringbone shape in which the movement source side path extends a predetermined length longer than the movement destination side path, and the depth of the extended portion is deeper than that of the non-extended portion. 2. The hydrodynamic bearing device according to claim 1, wherein the fluid pressure bearing device is dense in the movement source side path. 6. A groove on the thrust bearing surface is formed in a spiral shape, and a second groove is formed between adjacent grooves on the movement source side path, whereby the movement source side path is dense. Item 2. A hydrodynamic bearing device according to item 1. 7. A groove on the thrust bearing surface has a herringbone shape, and a second groove is formed between adjacent grooves on the movement source side path, whereby the movement source side path is dense. The hydrodynamic bearing device according to claim 1. 8. A hydrodynamic bearing device according to any one of claims 1 to 7, a magnet fixed to a rotating member of the hydrodynamic bearing device, and a stationary member that can be energized to generate a rotating force in cooperation with the magnet. A spindle motor comprising a stator provided.