JP2002310144A - Bearing mechanism, driving motor using the same, hard disk driving mechanism and polygon mirror drive mechanism using the driving motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing mechanism for raising radial dynamic pressure and for realizing the rotation with less whirling using the high radial dynamic pressure, by rationally arranging shapes of a thrust and a thrust dynamic pressure generating groove. SOLUTION: Any one of thrust surfaces of two first member side thrust surfaces 22a, 23a, and two second member side thrust surfaces 31c, 31d is provided with the spiral thrust dynamic pressure generating groove for generating the thrust dynamic pressure to form thrust bearing clearances GS1 and GS2. Any one of the outer peripheral surface 21a of a shaft part 21 and the inner peripheral surface 31a of a cylindrical part 31 is provided with a formation radial bearing clearance part GR along the circumferential direction of a herring bone-shape radial dynamic pressure generating groove for generating the radial dynamic pressure. A hydraulic fluid is led through the thrust bearing clearances GS1 and GS2, and flows into the radial bearing clearance GR to generate the radial dynamic pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing mechanism, a drive motor using the bearing mechanism, a hard disk drive mechanism using the drive motor, and a polygon mirror drive mechanism.

[0002]

2. Description of the Related Art Conventionally, in a bearing mechanism used for a hard disk drive mechanism of a storage device or a polygon mirror drive mechanism of a copier or a laser printer, etc., a dynamic pressure is required to realize high-speed rotation with little whirling. Bearings may be employed. For example, JP-A-10-24
FIG. 8 of Japanese Patent No. 9464 discloses the following as an example of a dynamic pressure bearing mechanism in which a shaft is inserted and held in a sleeve (bearing body) so as to be relatively rotatable around its axis.

[0003] That is, two flanges (axial thrust surfaces) formed on the shaft in a direction substantially perpendicular to the axis at a predetermined distance in the axial direction, and formed on the sleeve so as to be opposed to the flanges. A thrust bearing gap is formed between each of the two end surfaces (sleeve-side thrust surface). Further, a radial bearing gap is formed between the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve disposed opposite to the shaft. A herringbone-shaped thrust dynamic pressure generating groove that generates a thrust dynamic pressure by introducing a lubricant (working fluid) with the relative rotation of the shaft and the sleeve,
The sleeve is formed on both end faces along the circumferential direction. Further, a herringbone-shaped radial dynamic pressure generating groove for generating a radial dynamic pressure by introducing a lubricant is formed along the circumferential direction on the outer peripheral surface of the shaft.

In such a structure, when the shaft is relatively rotated at a high speed of, for example, 10,000 to 20,000 revolutions per minute inside the sleeve,
The radial dynamic pressure is generated in the radial bearing gap by the pumping action of the lubricant on the radial dynamic pressure generating groove. Therefore, for example, when a radial force acts on the rotation axis due to vibration or other disturbance, the dynamic pressure acts as a restoring force, realizing stable rotation with less whirling compared to a sliding bearing due to friction. Will be able to That is, as the radial dynamic pressure becomes higher, the load capacity of the dynamic pressure bearing increases and the whirling decreases.

[0005]

However, in the bearing mechanism disclosed in the above-mentioned publications, since the shape of the thrust dynamic pressure generating groove and the radial dynamic pressure generating groove and the positional relationship between them are not considered, the radial dynamic pressure is not considered. However, it was difficult to say that a sufficiently high pressure was not obtained and that stable rotation with little whirling was still sufficiently realized. In addition, a dynamic pressure bearing that generates radial and thrust dynamic pressure in the form of air pressure without using lubricating oil as a working fluid has also been proposed, but in the case of using air pressure, according to the study of the present inventors, In order to generate sufficient radial and thrust dynamic pressure, a high speed of 40,000 to 50,000 revolutions per minute or more is required, and whirling tends to occur more and more.

SUMMARY OF THE INVENTION An object of the present invention is to increase the radial dynamic pressure, and particularly to increase the radial dynamic pressure, by devising the shapes of the thrust dynamic pressure generating groove and the radial dynamic pressure generating groove and arranging them both rationally and effectively. An object of the present invention is to provide a bearing mechanism capable of achieving stable rotation with little whirling, a drive motor using the bearing mechanism, and a hard disk drive mechanism and a polygon mirror drive mechanism using the drive motor.

[0007]

In order to solve the above-mentioned problems, a bearing mechanism of the present invention comprises a shaft member of a first member which is rotatable relative to an axis of a second member. A bearing mechanism inserted and held in a cylindrical portion, wherein a first member-side thrust surface formed in the first member in a direction substantially orthogonal to the axis, and disposed opposite to the first member-side thrust surface. A thrust bearing gap forming a single or a series of flow paths is disposed at a predetermined distance in the axial direction between the second member-side thrust surface formed in the second member and the second member-side thrust surface. Between the outer peripheral surface of the shaft portion of one member and the inner peripheral surface of the cylindrical portion of the second member disposed opposite thereto, both ends are individually communicated with the thrust bearing gap, A radial bearing gap is arranged, and the first member and the second member The first member-side thrust surface in which spiral thrust dynamic pressure generating grooves for introducing a working fluid separately from the inlet side of the thrust bearing gap to generate a thrust dynamic pressure with the relative rotation are disposed opposite to each other. And either one of the second member-side thrust surface and the working fluid formed along the circumferential direction, and each of the working fluids flowing out separately from the outlet side of the thrust bearing gap to both ends of the radial bearing gap. A herringbone-shaped radial dynamic pressure generating groove for introducing and generating a radial dynamic pressure is formed along one of the outer peripheral surface of the shaft portion and the inner peripheral surface of the cylindrical portion along the circumferential direction. It is characterized by that.

In the present invention, a thrust bearing gap forming a single or a series of flow paths is disposed at a predetermined distance in the axial direction between the first member-side thrust surface and the second member-side thrust surface. On the other hand, a radial bearing gap is arranged between the outer peripheral surface of the shaft portion and the inner peripheral surface of the cylindrical portion in such a manner that both ends are individually communicated with the thrust bearing clearance. As a result, when viewed in a cross section including the axis, the thrust bearing gap and the radial bearing gap have a U-shape or a crank shape as a whole, and a bearing gap through which the working fluid smoothly flows is formed.

A spiral thrust dynamic pressure, which generates a thrust dynamic pressure by introducing a working fluid separately from the inlet side of the two thrust bearing gaps with the relative rotation of the first member and the second member. The generation groove is formed in one of the first member-side thrust surface and the second member-side thrust surface along the circumferential direction. Further, a herringbone-shaped radial dynamic pressure generating groove for introducing the working fluid flowing out from the outlet side of the thrust bearing gap to both ends of the radial bearing gap to generate radial dynamic pressure is provided on the outer peripheral surface of the shaft portion. And the inner peripheral surface of the cylindrical portion is formed along the circumferential direction. That is, the outlet side of each thrust bearing gap and the inlet side of both ends of the radial bearing gap are separately communicated at the shortest distance, and the thrust dynamic pressure is sufficiently increased at the terminal end (outlet) of the spiral thrust dynamic pressure generating groove. Since the working fluid flows directly into both ends (entrances) of the herringbone-shaped radial dynamic pressure generating grooves, pressure loss and fluid leakage hardly occur. In addition, the working fluid that has flowed in separately from both sides of the herringbone-shaped radial dynamic pressure generating grooves is further increased in radial dynamic pressure by the ridges on both sides constituting the herringbone-shaped mountain shape, and the ridges on both sides are further increased. Since the highest radial dynamic pressure is generated at the intersection where the two meet, the energy loss during this period is also small.

As described above, the spiral groove is used as the thrust dynamic pressure generating groove, the herringbone-shaped groove is used as the radial dynamic pressure generating groove, and both are rationally and effectively arranged, so that a higher-pressure radial is formed. Dynamic pressure can be obtained, and as a result, the load capacity of the dynamic pressure bearing increases, and stable rotation with little whirling can be realized. In the herringbone shape, when the radial dynamic pressure generating groove itself does not have an intersection where the ridges on both sides merge, it means an intersection obtained when the ridges on both sides are extended.

In the present invention, if the depth of the thrust dynamic pressure generating groove in the axial direction is formed so as to decrease continuously or stepwise from the inlet side to the outlet side of the working fluid in the thrust bearing gap, the inlet is formed. Since the working fluid (for example, air) sufficiently taken in on the side is compressed toward the outlet side and the thrust dynamic pressure is increased, the thrust load capacity can be further increased.

The maximum depth D1 of the thrust dynamic pressure generating groove
Is set to be less than 2.5 times the minimum depth D2, the working fluid (for example, air) is sufficiently compressed in the thrust dynamic pressure generating groove to increase the thrust dynamic pressure and also suppress the decrease in bearing rigidity. can do.

Further, the width of the thrust dynamic pressure generating groove is reduced continuously or stepwise along the longitudinal direction of the thrust dynamic pressure generating groove as it goes from the inlet side to the outlet side of the working fluid in the thrust bearing gap. In this case, the thrust load capacity can be further increased. If the maximum width W1 of the thrust dynamic pressure generating groove is set to be within 2.5 times the minimum width W2, the thrust dynamic pressure is increased and the reduction in bearing stiffness is reduced as in the case of the groove depth. Can be suppressed.

By the way, in a section along the longitudinal direction of the thrust dynamic pressure generating groove, when a wall having a predetermined thickness toward the inlet side is formed at the end of the thrust dynamic pressure generating groove on the outlet side of the working fluid. Therefore, the bearing rigidity at the outlet side of the working fluid having a high thrust dynamic pressure is increased.
Therefore, the thrust load capacity can be increased by increasing the depth of the thrust dynamic pressure generating groove sufficiently to increase the inflow amount of the working fluid. In this case, if the front end surface (inner wall surface) of the wall is made to protrude beyond the radial bearing gap toward the fluid inlet, the bearing rigidity on the fluid outlet side is further increased.

Next, a plurality of radials exhibiting a herringbone shape passing through the intersection of the ridges on both sides constituting the chevron shape and having a reference line dividing an angle formed by the ridges directed in a direction substantially orthogonal to the axis. The dynamic pressure generating grooves are arranged in such a manner that the reference lines are arranged in two groove rows that are separated by a predetermined distance in the axial direction. The radial dynamic pressure generating grooves are arranged along the two reference lines, and the whirling of the rotating body is determined at two intersections separated by a predetermined distance in the axial direction (or two reference lines connecting the intersections). ), So that stable rotation with little whirling is possible.

The greater the distance between the reference lines, the higher the effect of preventing whirling, so that more stable rotation is possible. Specifically, a method of making the axial separation distance (groove widening width) of both end portions of the mountain-shaped ridge portion different between the two groove rows, and a method of expanding the mountain-shaped ridge portion from the reference line A method may be adopted in which the separation distance in the axial direction to each end is different on both sides of the reference line. In the latter case, the axial separation distance (inner spread width) between the reference line and the expanded end of the ridge (inner ridge) on the side opposite to the other groove row is equal to the reference line and the other groove row. It may be set to be larger than the separation distance (outside expansion width) in the axial direction between the ridge portion (outside ridge portion) on the side that does not face and the expansion end. In addition,
In order to reduce the whirling sufficiently, for example, the distance between the reference lines may be set to １ ／ or more of the radial bearing length when viewed in the axial direction.

When air, which is a compressive fluid, is used as the working fluid, there is no fear of running out of oil or oil leakage due to high-speed rotation when using a liquid (eg, lubricating oil). High-speed rotation becomes possible, and the load capacity of the dynamic pressure bearing portion can be increased.

According to another aspect of the present invention, there is provided a drive motor including the above-mentioned bearing mechanism, wherein one of the first member and the second member of the bearing mechanism is provided with a stator. The rotor is disposed on the other rotating side member.

According to such a drive motor, stable rotation with little whirling can be realized from low-speed rotation to high-speed rotation, and it can be adapted to a wide range of rotational load.

In this drive motor, a fixed portion to the motor base portion is formed at one end side of the fixed side member in the axial direction, and the radial bearing gap passes through the intersection of the ridges on both sides constituting the mountain shape. A plurality of radial dynamic pressure generating grooves exhibiting a herringbone shape in which a reference line dividing an angle formed by these ridge portions is oriented in a direction substantially orthogonal to the axis, and two grooves whose reference lines are separated by a predetermined distance in the axial direction. The groove width of the groove row located on the side away from the fixed portion of the two rows is formed to be larger than the groove width of the other groove row. . As a result, a large radial dynamic pressure is generated on the side of the radial dynamic pressure generating groove where the groove expansion width is large. In other words, a large radial dynamic pressure acts on the side remote from the fixed portion, that is, on the side far from the fixed portion and in which whirling tends to increase, and stable rotation with little whirling can be performed.

Next, a hard disk drive mechanism according to the present invention includes the drive motor described above, and a hard disk attached to the rotating member and rotating integrally therewith.

Further, in the polygon mirror driving mechanism of the present invention, a plurality of reflection surfaces are formed in a polyhedral shape so as to be integrated with the driving motor and the rotation side member and surround the periphery of the rotation axis. And a polygon mirror.

According to such a hard disk drive mechanism or polygon mirror drive mechanism, stable rotation with little whirling can be realized from low-speed rotation to high-speed rotation.
It can adapt to a wide range of rotating loads.

[0024]

Embodiments of the present invention will be described below with reference to embodiments shown in the drawings. (Embodiment 1) FIG. 1 shows a first embodiment of a hard disk drive mechanism using the bearing mechanism of the present invention. The hard disk drive mechanism 100 is configured to
A first member 2 (fixed side member) attached by bolts 9 so as to stand up from one side thereof, and a second member 3 (rotary side member) rotatably disposed outside the first member 2. The second member 3 constitutes the radial dynamic pressure bearing 20 and the thrust dynamic pressure bearing 30 of the bearing mechanism 1. In the following description, the side closer to the motor base 8 (that is, the fixed portion F side of the bearing mechanism 1 and the motor base 8) is lower (lower) and the far side is upper with respect to the axial direction of the bolt 9. (Upper).

The first member 2 has a cylindrical fixed shaft 21 (shaft portion) having an axis substantially coincident with the axis of the bolt 9, and an outer peripheral surface of an upper end portion and a lower end portion of the fixed shaft 21 attached to the outer peripheral surface with an adhesive or the like. It has an annular upper thrust plate 22 and a lower thrust plate 23 which are respectively fixed. On the other hand, the second member 3 has a cylindrical sleeve 31 (cylindrical portion) having an axial insertion hole 31h, and a stepped cylindrical hub 32 fixed to the sleeve 31 from the outside. . The fixed shaft 21 is inserted into the insertion hole 31h of the sleeve 31 along the direction of the axis O, and the inner peripheral surface of the cylindrical portion of the second member 3, that is, the insertion hole 3h.
1 h (sleeve 31) and the outer peripheral surface of the shaft portion of the first member 2, that is, the outer peripheral surface 21 a of the fixed shaft 21, the radial bearing gap G of the radial dynamic pressure bearing portion 20.
R is formed. The radial bearing gap GR is filled with air (that is, gas), and the second member 3 is held rotatably around the axis O.

In the second member 3, the cylindrical portion 3 of the hub 32
The inner peripheral surface 32b of 2a and the outer peripheral surface 31b of the sleeve 31 are integrally connected (specifically, fitted by a tapered surface and / or tightly fitted) in direct contact over the entire circumference. Then, the tip of the skirt portion 32c extending downward in connection with the cylindrical portion 32a of the hub 32 enters the horizontal motor base portion 8 from the upper side to the inside, and the hub 3
Reference numeral 2 denotes a motor-less base 8 which is covered with a bowl without a bottom.

The upper end surface 31c (the second member side thrust surface) of the sleeve 31 fixed to the hub 32 in this manner is
An upper thrust bearing gap GS1 that is arranged opposite to a lower end surface 22a (first member side thrust surface) of an upper thrust plate 22 fixed to an upper end portion of the fixed shaft 21, and is filled with air between both surfaces 31c and 22a. (Thrust bearing gap) is formed. Similarly, the lower end surface 31d (the second member-side thrust surface) of the sleeve 31 is disposed so as to face the upper end surface 23a (the first member-side thrust surface) of the lower thrust plate 23, and between the two surfaces 31d, 23a. A lower thrust bearing gap GS2 (thrust bearing gap) filled with air is formed. The radial bearing gap GR is connected at both ends to an outlet of the upper thrust bearing gap GS1 and an outlet of the lower thrust bearing gap GS2.

As described above, the radial bearing gap GR of the radial dynamic pressure bearing section 20, the upper thrust bearing gap GS1 and the lower thrust bearing gap GS2 of the thrust dynamic pressure bearing section 30 are provided.
Is a radial bearing clearance G when viewed in a half section including the axis.
R is located radially inward with respect to the thrust bearing gaps GS1 and GS2, and is formed so as to have a crank shape or a U-shape bent at a right angle and communicate with each other. In addition, 4
Is an upper air inlet formed in an annular shape between the inner peripheral surface of the upper end portion of the hub 32 and the outer peripheral surface of the upper thrust plate 22 for guiding external air to the upper thrust bearing gap GS1; Inner peripheral surface of lower end of hub 32 and lower thrust plate 2
3 is a lower air inlet for guiding outside air to the lower thrust bearing gap GS2.

Next, a ring-shaped stator core 11a,
A coil unit 11 comprising a plurality of coils 11b wound around the core 11a at predetermined intervals in the circumferential direction.
(Stator portion) is fixedly fitted into the motor base portion 8. The coil unit 11 is positioned so as to protrude into an annular space 8 a formed on the upper surface of the motor base 8.

The skirt portion 32c of the hub 32 covers the coil unit 11 in the axial direction of the fixed shaft 21, and extends in a skirt shape to a position where its tip reaches the space 8a. A spacer 6 is provided on the outer peripheral surface of the cylindrical portion 32a.
A plurality of data recording hard disks 6 are attached via a. Further, on the inner peripheral surface side of the skirt portion 32c, a ring-shaped permanent magnet 12 (rotor portion) is arranged in the space portion 8a at a position facing the coil unit 11 at predetermined intervals in the circumferential direction. It is attached in the form to make it. The permanent magnet 12 is connected to the coil unit 11
Together with the drive motor 40 (drive unit), and the second member 3 (that is, the hub 32 and the sleeve 31 attached thereto) and the hard disk 6 are connected to the first member 2 (that is, the fixed shaft 21 and the upper and lower thrust plates 22, 23). ) Plays a role to rotate integrally around the axis O. in this way,
The bearing mechanism 1 is supported in a cantilever manner with respect to the motor base 8 (bolt 9).

On the other hand, the fixed shaft 2
1 and the coil unit 11 are integrated. At this time, the coil unit 11 and the permanent magnet 12 are arranged below the radial dynamic pressure bearing portion 20 (radial bearing gap GR), the inner diameter 2r2 of the sleeve 31 is increased, and the load of the radial dynamic pressure bearing portion 20 is increased. The capacity is increasing.

Next, the inner diameter of the insertion hole 31h (the inner peripheral surface 31a) of the sleeve 31 is set to 2r2, and the insertion hole 31h of the fixed shaft 21 is set.
Assuming that the outer diameter of a portion inserted into the inside is 2r1, the size R = r2-r1 of the radial bearing gap GR is 0.2 to 20.
μm (preferably 1 to 10 μm; for example, 3 μm). The size S1 of the upper thrust bearing gap GS1 and the size S2 of the lower thrust bearing gap GS2 are:
Both are adjusted to 0.1 to 10 μm (preferably 1 to 5 μm; for example, 3 μm).

In the bearing mechanism 1 of this embodiment, the upper end surface 31c of the sleeve 31 and the lower end surface 2 of the upper thrust plate 22
2a, an upper thrust dynamic pressure generating groove (thrust dynamic pressure generating groove) is formed. In addition, sleeve 3
1 and the upper end surface 23a of the lower thrust plate 23
A lower thrust dynamic pressure generating groove (thrust dynamic pressure generating groove) is formed in either one of them.

FIG. 2 shows the lower thrust dynamic pressure generating groove 23 formed on the upper end surface 23a of the lower thrust plate 23.
b shows an example. On the upper end surface 23a of the lower thrust plate 23, a plurality (3 in this embodiment)
(Three) lower thrust dynamic pressure generating grooves 23b. Specifically, as shown in FIG. 2A, each groove 23b is formed in a spiral (also referred to as a spiral or spiral) groove pattern engraved on the lower thrust plate 23. Here, the spiral lower thrust dynamic pressure generating groove 23b has a logarithmic spiral () in which an introduction guide angle equal to the inlet angle α is obtained at all points on the center line CL of the groove (see FIG. 2B). logarithmic spiral), and is used as a so-called pump IN type in which a working fluid is introduced from the radial outside to the inside of the lower thrust bearing gap GS2. Therefore, the air introduced from the outside (the lower air introduction port 5) flows in from the inlet side located on the radially outer side, is introduced along the spiral groove 23b, and flows in from the outlet side located on the radially inner side. (Lower thrust bearing gap GS2 or radial bearing gap GR).

In FIG. 2C, the ratio of the depth D of the lower thrust dynamic pressure generating groove 23b to the size S2 of the lower thrust bearing gap GS2 in the direction of the axis O (see FIG. 1) is 1.
It is adjusted to be within the range of 0 to 2.5. As a result, the depth D of the lower thrust dynamic pressure generating groove 23b is relatively increased to increase the inflow amount of the working fluid, and the size S2 of the lower thrust bearing gap GS2 is relatively reduced, so that the lower thrust dynamic pressure is reduced. Increase. As a result, a sufficient thrust load capacity can be secured without reducing the rigidity of the bearing mechanism.

Further, at the end of the lower thrust dynamic pressure generating groove 23b at the end of the working fluid at the outlet side of the working fluid, the tip projects toward the fluid inlet side from the radial bearing gap GR.
A wall portion (land portion) 23c is formed. Land part 2
By providing 3c, the bearing stiffness on the outlet side of the working fluid having a high thrust dynamic pressure is increased.

As shown in FIG. 2C, the depth of the lower thrust dynamic pressure generating groove 23b in the direction of the axis O is from the inlet side (ie, radially outer side) to the outlet side (ie, radially inner side) of the groove. , It decreases linearly along the longitudinal direction. In other words, the air sufficiently taken in on the outside is compressed toward the inside, and the lower thrust dynamic pressure is increased, thereby increasing the thrust load capacity. In such a case, the depth D of the lower thrust dynamic pressure generating groove 23b is determined by using an average value of the maximum depth D1 on the longitudinal entrance side and the minimum depth D2 on the longitudinal exit side. I do.

Further, as shown in FIG. 2 (b), the width of the lower thrust dynamic pressure generating groove 23b also increases from the inlet side (ie, radially outer side) to the outlet side (ie, radially inner side) of the groove. It decreases along the longitudinal direction. That is,
The air sufficiently taken in on the outside is compressed toward the inside, and the thrust dynamic pressure is increased, thereby increasing the thrust load capacity. The width of the lower thrust dynamic pressure generating groove 23b is measured in a direction perpendicular to the groove center line CL, and continuously decreases from the maximum width W1 on the inlet side to the minimum width W2 on the outlet side.

Here, specific examples in FIGS. 2B and 2C are shown below. -Depth D (average value) of lower thrust dynamic pressure generating groove 23b:
0.1 to 25 μm (preferably 1 to 12.5 μm; for example, 2.5 μm) Ratio of groove depth D to size S2 of lower thrust bearing gap GS2: 1.0 to 2.5 (preferably 1.2.5 μm). 3 to 1.8; for example 1.5) Ratio of maximum depth D1 to minimum depth D2: 1.0 to 2.5
(Desirably 1.5 to 2.0; e.g. 1.75) ratio of maximum width W1 to minimum width W2: 1.0 to 2.5 (desirably 1.5 to 2.0; e.g. 1.75) )

FIG. 2 also applies to the case where an upper thrust dynamic pressure generating groove 22b (not shown) is formed on one of the upper end surface 31c of the sleeve 31 and the lower end surface 22a of the upper thrust plate 22. it can.

Next, as shown in FIG. 3, one of the outer peripheral surface 21a of the fixed shaft 21 and the inner peripheral surface 31a of the sleeve 31 (in this embodiment, the outer peripheral surface 21a of the fixed shaft 21)
A radial dynamic pressure generating groove 21b is formed. The radial dynamic pressure generating groove 21b passes through the intersection 21b0 of the center lines CL and CL of the both side ridges 21b1 and 21b2 constituting the mountain-shaped (or boomerang-shaped) pattern, and these ridges 21
A herringbone shape in which a reference line BL that divides an angle formed by the center lines CL of CL b1 and 21b2 (that is, a groove forming angle θ) is directed in a direction substantially orthogonal to the axis O (almost horizontal in this embodiment). Present. Therefore, the air introduced from the outlet side located radially inward of the upper thrust bearing gap GS1 is ridged on both sides 21b with the reference line BL interposed therebetween.
The fluid flows in from both ends of the expanded portion 21b2 and generates the maximum radial dynamic pressure near the intersection 21b0.

The plurality of radial dynamic pressure generating grooves 21b
Are formed over the entire outer peripheral surface 21a of the fixed shaft 21 at a predetermined pitch interval, and the two radial dynamic pressure generating groove rows in which the reference line BL is separated in the axis O direction by a predetermined interval (that is, the reference line distance L). (Hereinafter, also simply referred to as a groove row) 2
1U, 21L. The radial dynamic pressure generating grooves 21b are arranged in alignment along the two reference lines BL, BL. As a result, the whirling of the second member 3 is caused by the two reference lines BL, The shape is supported by BL, and whirling is reduced.

The separation distance (ie, groove expansion width H) between the expanded ends of these ridge portions 21b1, 21b2 in the direction of the axis O is different for each of the radial dynamic pressure generating groove rows 21U, 21L. In the example, the groove row 2 located on the lower side, that is, on the side of the fixing portion F of the bolt 9 to the motor base portion 8
The groove expansion width HU of the groove row 21U located on the upper side, that is, on the side separated from the fixing portion F, is set to be larger than the groove expansion width HL of 1L. A large radial dynamic pressure is generated by increasing the groove expansion width HU of the upper groove row 21U where the whirling tends to increase, and the whirling of the second member 3 is suppressed by increasing the load capacity.

Further, the reference line B of each groove row 21U, 21L
Regarding the separation distance in the direction of the axis O from L to each of the expanded ends of the ridge portions 21b1 and 21b2 on both sides, the ridge portion on the side facing the reference line BL and the other groove row (that is, the inner ridge portion).
Separation distances (ie, inner widening widths) HU2 and HL2 in the direction of the axis O from the expanding end of 21b2 are the expanding ends of the ridges (ie, outer ridges) 21b1 on the side not facing the reference line BL and the other groove row. The separation distances (that is, the outside expansion widths) HU1 and HL1 in the direction of the axis O with respect to the section are each set to be larger than HU1 and HL1. By setting these dimensions, the distance L between the reference lines becomes relatively large, and the whirling of the second member 3 is further reduced. Specifically, when viewed in the direction of the axis O, the distance L between the reference lines is preferably equal to or more than の of the radial bearing length. However, the inside expansion width of one of the groove rows 21U and 21L may be set to be larger than the corresponding outside expansion width.

Here, the specific shape of the radial dynamic pressure generating groove 21b will be described with reference to the explanatory diagram of FIG. FIG. 4 illustrates a single radial dynamic pressure generating groove 21b for simplicity of description, and omits the groove width to form an outer ridge 21b1 and an inner ridge 21b2 with a center line CL (see FIG. 3). Is displayed.

As shown in FIG. 4A, the outer ridge 21
The angle between the b1 and the reference line BL (ie, the outside forming angle) θ1
Is equal to the angle θ2 between the inner ridge 21b2 and the reference line BL (ie, the inner forming angle) θ2, and the circumferential length (ie, outer circumferential length) C1 of the outer ridge 21b1 is equal to the inner ridge 2
When it is equal to the circumferential length 1b2 (that is, the inner circumferential length) C2, the outer expanded width H1 and the inner expanded width H2 are set equal.

In FIG. 4A, assuming that the inner circumference C2 is larger than the outer circumference C1, as shown in FIG.
The inner expansion width H2 is larger than the outer expansion width H1. Also,
In FIG. 4A or FIG. 4B, assuming that the inner forming angle θ2 is larger than the outer forming angle θ1, as shown in FIG. 4C, the inner expanding width H2 is smaller than the outer expanding width H1. Is also great.
When the inner widening width H2 is set to be larger than the outer widening width H1 in this way, the reference line distance L can be increased without increasing the radial bearing length when viewed in the axis O direction, This is effective in suppressing whirling of the second member 3.

In the herringbone shape,
When the ridge portions 21b1 and 21b2 on both sides have no intersection,
Alternatively, the ridge portions 21b1, 21b on both sides at the top of the mountain shape
When b2 is connected in a curved shape, both edge portions 21b
An intersection obtained by extending the center line CL of 1, 21b2 toward the top of the chevron is used. Further, in order to obtain a large radial dynamic pressure, the groove forming angle θ = θ1 + θ2 is desirably 40 to 60 °.

In FIG. 3C, the ratio of the depth d of the radial dynamic pressure generating groove 21b to the size R of the radial bearing gap GR in the radial direction (see FIG. 1) is 0.75 to 1.
5 is adjusted. This allows
As the depth d of the radial dynamic pressure generating groove 21b relatively increases, the inflow amount of the working fluid increases, and the radial bearing clearance G
The magnitude R of R relatively decreases and the radial dynamic pressure increases. Therefore, a sufficient radial load capacity can be secured without lowering the rigidity of the bearing mechanism 1.

As shown in FIG. 3 (c), the depth of the radial dynamic pressure generating groove 21b in the radial direction is determined on the inlet side of the groove (FIG. 3).
(a), ridges 21b1, 21b on both sides of the reference line BL
3 (a) to the intersection 2 in FIG. 3 (a).
1b0), it decreases linearly along the longitudinal direction. In other words, the air sufficiently taken in at both ends of the ridges 21b1 and 21b2 at the spread ends is the intersection 2
The radial load is increased by being compressed toward 1b0 and increasing the radial dynamic pressure.
In such a case, the depth d of the radial dynamic pressure generating groove 21b is equal to the maximum depth d on the longitudinal entrance side.
An average value of 1 and the minimum depth d2 on the outlet side in the longitudinal direction is used.

Further, as shown in FIG. 3 (b), the width of the radial dynamic pressure generating groove 21b decreases along the longitudinal direction of the groove from the inlet side to the outlet side of the groove. In other words, the air taken in on the inlet side of the groove is compressed toward the outlet side, and the radial dynamic pressure is increased, thereby increasing the radial load capacity. The width of the radial dynamic pressure generating groove 21b is measured in a direction perpendicular to the groove center line CL, and continuously decreases from the maximum width w1 on the inlet side to the minimum width w2 on the outlet side. However, the maximum width w1 is defined by the entrance width w11 of the outer ridge 21b1 and the inner ridge 2
The larger value of the entrance width w12 of 1b2 is used. As the minimum width w2, the groove width at the intersection 21b0 between the groove center lines CL of the side edge portions 21b1 and 21b2 is used.

Here, specific examples in FIGS. 3B and 3C are shown below. The depth d (average value) of the radial dynamic pressure generating groove 21b: 0.
1 to 15 μm (preferably 1 to 7.5 μm; for example, 3 μm
m) ・ Ratio between groove depth d and size R of radial bearing gap GR:
0.75 to 1.5 (desirably 0.9 to 1.25; for example, 1.0)-Ratio of the maximum depth d1 to the minimum depth d2: 1.0 to 1.5
(Preferably 1.0 to 1.25; for example, 1.1) A ratio of the maximum width w1 to the minimum width w2: 1.0 to 1.5 (preferably 1.0 to 1.25; for example, 1.1) )

In the hard disk drive mechanism 100 configured as described above, by driving the drive motor 40 by supplying a current to the coil 11b of the coil unit 11 in FIG.
Rotate at a rotation speed of rpm. At this time, the working fluid whose thrust dynamic pressure has been sufficiently increased at the end portions (outlets) of the spiral thrust dynamic pressure generating grooves 22b and 23b (see FIG. 2) is directly converted into a herringbone-shaped radial dynamic pressure generating groove 21b. (See FIG. 3)
Pressure loss and fluid leakage hardly occur. In addition, the working fluid is further increased in radial dynamic pressure by the ridges 21b1 and 21b2 on both sides constituting the herringbone-shaped mountain shape, and reaches the intersection 21b0 where the ridges 21b1 and 21b2 on both sides meet to provide the highest radial pressure. A dynamic pressure is generated, and energy loss during this period is small.

(Embodiment 2) FIG. 5 shows a second embodiment of a hard disk drive mechanism using the bearing mechanism of the present invention. Since the drive motor 40 (drive unit) used in the hard disk drive mechanism 200 has the same structure as that of the first embodiment (FIG. 1), the same parts as those in FIG. Is omitted.

The hard disk drive mechanism 200 includes a first member 220 (rotating side member) supported by the motor base portion 8 and rotatably arranged, and a second member 230 fixedly attached to the motor base portion 8. (Fixed side member), and the first member 220 and the second member 230 are
The radial dynamic pressure bearing portion 20 and the thrust dynamic pressure bearing portion 30 of the bearing mechanism 1 are configured.

The first member 220 of the hard disk drive mechanism 200 is secured by bolts 29 whose axes are oriented vertically.
Cylindrical rotating shaft 221 (shaft portion) and axial insertion hole 2
A stepped cylindrical hub 222 having a height of 22 h
9 is fixed in a form having an axis substantially coincident with the axis. On the other hand, the second member 230 has the insertion hole 23 in the axial direction.
1h, a cylindrical sleeve 231 (cylindrical portion) having an annular upper thrust plate 23 fixed to an upper end and a lower end of the sleeve 231 with an adhesive or the like.
2 and a lower thrust plate 233.

With respect to the insertion hole 231h of the sleeve 231,
The rotating shaft 221 is inserted along the direction of the axis O, and the inner peripheral surface of the cylindrical portion of the second member 230, that is, the inner peripheral surface 231a of the insertion hole 231h (sleeve 231), and the outer periphery of the axial portion of the first member 220. A radial bearing gap GR of the radial dynamic pressure bearing portion 20 is formed between the surface, that is, the outer peripheral surface 221 a of the rotating shaft 221. The radial bearing gap GR is filled with air (that is, gas), and the first member 22 is filled with air.
0 is held rotatably about the axis O. And
The hub 222 constituting the first member 220 has a cylindrical portion 2
The tip of the skirt portion 222c extending downward in connection with 22a enters the upper portion of the horizontal motor base portion 8 from above, whereby the hub 222 lowers the bottomed bowl with respect to the motor base portion 8. Is covered.

The upper end surface 221c (the first member-side thrust surface) of the rotating shaft 221 faces the lower end surface 232a (the second member-side thrust surface) of the upper thrust plate 232 fixed to the upper end of the sleeve 231. And both sides 221c, 23
Upper thrust bearing gap GS filled with air between 2a
21 (thrust bearing gap) is formed. Similarly, the lower end surface 221d (first member-side thrust surface) of the rotating shaft 221 is disposed so as to face the upper end surface 233a (second member-side thrust surface) of the lower thrust plate 233.
A lower thrust bearing gap GS22 (thrust bearing gap) filled with air is formed between d and 233a. And the radial bearing gap GR has
The upper thrust bearing gap GS21 communicates with the outlet side of the lower thrust bearing gap GS22. The shaft end 29a of the bolt 29 is formed in a spherical pivot shape, and supports the own weight (thrust load) of the first member 220 by contacting the upper surface of the motor base portion 8 when the drive motor 40 is stopped and when rotating at low speed. I do.

As described above, the radial bearing gap GR of the radial dynamic pressure bearing section 20, the upper thrust bearing gap GS21 and the lower thrust bearing gap GS of the thrust dynamic pressure bearing section 30 are provided.
22 is a crank shape or a U-shape bent at a right angle in a form in which the radial bearing gap GR is located radially outward with respect to the two thrust bearing gaps GS21 and GS22 when viewed in a half section including the axis. Presenting and communicating. In addition,
Reference numeral 24 denotes an upper air inlet formed in an annular shape between the outer peripheral surface of the upper end portion of the rotating shaft 221 and the inner peripheral surface of the upper thrust plate 232 to guide external air to the upper thrust bearing gap GS21. Reference numeral 25 denotes a lower air inlet formed in an annular shape between the outer peripheral surface of the lower end portion of the rotating shaft 221 and the inner peripheral surface of the lower thrust plate 233 for guiding external air to the lower thrust bearing gap GS22. Further, between the inner peripheral surface 222a of the insertion hole 222h (the hub 222) and the outer peripheral surface 231b of the sleeve 231 and between the inner bottom surface of the hub 222 and the upper end surfaces of the sleeve 231 and the upper thrust plate 232,
An air introduction passage (gap) 26 for guiding outside air to the upper air inlet 24 is formed.

In the bearing mechanism 1 shown in FIG.
An upper thrust dynamic pressure generating groove (thrust dynamic pressure generating groove) is formed in one of the upper end surface 221c of the first thrust plate 1 and the lower end surface 232a of the upper thrust plate 232. Further, the lower end surface 221 d of the rotating shaft 221 and the lower thrust plate 233
A lower thrust dynamic pressure generating groove (thrust dynamic pressure generating groove) is formed on one of the upper end surface 233a and the upper surface 233a.

FIG. 6 shows the lower thrust plate 233
The figure shows an example of a lower thrust dynamic pressure generating groove 233b formed on the upper end surface 233a of the upper surface. This lower thrust plate 23
A plurality of lower thrust dynamic pressure generating grooves 233b (30 in this embodiment) are formed along the circumferential direction on the upper end surface 233a. Specifically, each groove 233b is formed as shown in FIG.
As in (a), it is formed in a spiral groove pattern. However, the pump OUT in which the working fluid is introduced from the radially inner side to the outer side of the lower thrust bearing gap GS22.
Used by type (entrance angle β). Therefore, the air introduced from the outside (the lower air inlet 25) flows in from the inlet side located on the radially inner side, and the spiral groove 233b is formed.
And flows into the inside (the lower thrust bearing gap GS22 or the radial bearing gap GR) from the outlet side located radially outward.

In the hard disk drive mechanism 200 configured as described above, the current is supplied to the coil 11b of the coil unit 11 in FIG.
Rotate at a rotation speed of 00 rpm. At this time, the working fluid whose thrust dynamic pressure has been sufficiently increased at the end portions (outlets) of the spiral thrust dynamic pressure generating grooves 232b and 233b (see FIG. 6) is directly converted into a herringbone shape as in the first embodiment. Flows into the both ends (inlets) of the radial dynamic pressure generating groove 21b (see FIG. 3), and pressure loss and fluid leakage hardly occur.

(Embodiment 3) FIG. 7 shows an example of a polygon mirror driving mechanism using the bearing mechanism of the present invention. The drive motor 40 (drive unit) used in the polygon mirror drive mechanism 300 also has the same structure as that of the first embodiment (FIG. 1). Description is omitted.

The polygon mirror driving mechanism 300 is disposed on the motor base portion 8 with a first member 320 (fixed side member) attached by bolts 9 so as to stand up from one side thereof, and is rotatably disposed outside the first member 320. Second member 3
30 (rotary side member), and the first member 320 and the second member 330 constitute the radial dynamic pressure bearing portion 20 and the thrust dynamic pressure bearing portion 30 of the bearing mechanism 1.

As shown in FIG. 8, the main part is enlarged, and the first member 320 includes a cylindrical fixed shaft 321 (shaft portion) having an axis substantially coincident with the axis of the bolt 9, and a fixed shaft 321.
And an annular upper thrust plate 322 and a lower thrust plate 323, which are fixed to the outer peripheral surfaces of the upper end and lower end, respectively, with an adhesive or the like. On the other hand, the second member 330 includes a cylindrical sleeve 331 (cylindrical portion) having an axial insertion hole 331h, a stepped cylindrical hub 332 fixed to the sleeve 331 from the outside, and a hub 332. 332 has an annular upper closing plate 333 and a lower closing plate 334, which are fixed to the inner peripheral surfaces of the upper end portion and the lower end portion with an adhesive or the like, respectively.

With respect to the insertion hole 331h of the sleeve 331,
The fixed shaft 321 is inserted along the direction of the axis O, and the inner peripheral surface of the cylindrical portion of the second member 330, that is, the inner peripheral surface 331 a of the insertion hole 331 h (sleeve 331) and the outer periphery of the axial portion of the first member 320. A radial bearing gap GR of the radial dynamic pressure bearing portion 20 is formed between the surface, that is, the outer peripheral surface 321 a of the fixed shaft 321. The radial bearing gap GR is filled with air (that is, gas) and the second member 33
0 is held rotatably about the axis O.

The upper end surface 322a (first member side thrust surface) of the upper thrust plate 322 fixed to the outer peripheral surface of the upper end portion of the fixed shaft 321 and the lower end surface 322b (first member side thrust surface) are closed at the top. The lower end surface 333a (second member side thrust surface) of the plate 333 and the upper end surface 331c of the sleeve 331
(The second member-side thrust surface).
A first upper thrust bearing gap GS311 (thrust bearing gap) and a second upper thrust bearing gap GS312 (thrust bearing gap) are formed. Similarly, the fixed shaft 321
A lower end surface 323a (first member side thrust surface) of a lower thrust plate 323 fixed to an outer peripheral surface of a lower end portion of the upper end surface 32
3b (first member-side thrust surface) faces the upper end surface 334a (second member-side thrust surface) of the lower closing plate 334 and the lower end surface 331d (second member-side thrust surface) of the sleeve 331, respectively. Disposed, the first lower thrust bearing gap GS
321 (thrust bearing gap) and a second lower thrust bearing gap GS322 (thrust bearing gap) are formed.

Further, the first upper thrust bearing gap GS31
The first and second upper thrust bearing gaps GS312 form a series of flow paths in which air seeing these gaps flows continuously from the first upper thrust bearing gap GS311 to the second upper thrust bearing gap GS312. . That is, both gaps GS31
1, GS312 constitutes an upper thrust bearing gap GS31 (thrust bearing gap) connected in series. Similarly,
The first lower thrust bearing gap GS321 and the second lower thrust bearing gap GS322 constitute a lower thrust bearing gap GS31 (thrust bearing gap) connected in series. The radial bearing gap GR is communicated at both ends thereof with the outlet side of the upper thrust bearing gap GS31 and the outlet side of the lower thrust bearing gap GS32.

As described above, the radial bearing gap GR of the radial dynamic pressure bearing section 20, the upper thrust bearing gap GS31 and the lower thrust bearing gap GS of the thrust dynamic pressure bearing section 30 are obtained.
32, when viewed in a half section including the axis, the radial bearing gap GR is located radially inward with respect to both thrust bearing gaps GS31 and GS32, and has a crank shape or a key shape bent at a right angle. Communication is formed. Note that 34
Is an upper air inlet formed in an annular shape between the inner peripheral surface of the upper closing plate 333 and the outer peripheral surface of the upper end of the rotating shaft 221 for guiding external air to the first upper thrust bearing gap GS311. , 35 are formed in an annular shape between the inner peripheral surface of the lower closing plate 334 and the outer peripheral surface of the lower end of the rotating shaft 221 to introduce lower air for guiding external air to the first lower thrust bearing gap GS321. Mouth.

In the bearing mechanism 1 shown in FIG. 8, one of the upper end surface 322a of the upper thrust plate 322 and the lower end surface 333a of the upper closing plate 333 has a spiral groove pattern similar to that shown in FIG. A first upper thrust dynamic pressure generating groove (thrust dynamic pressure generating groove) is formed and used in a pump OUT type in which a working fluid is introduced from the radial inside to the outside of the first upper thrust bearing gap GS311. ing. In addition, one of the lower end surface 322b of the upper thrust plate 322 and the upper end surface 331c of the sleeve 331,
It is formed in a spiral groove pattern similar to that shown in FIG.
Further, a second upper thrust dynamic pressure generating groove (thrust dynamic pressure generating groove) used in a pump IN type in which the working fluid is introduced from the radial outside to the second upper thrust bearing gap GS312 is formed.

Similarly, one of the lower end surface 323a of the lower thrust plate 323 and the upper end surface 334a of the lower closing plate 334 has a first lower thrust dynamic pressure generation groove (a pump OUT type spiral groove pattern). A thrust dynamic pressure generating groove) is formed. Further, the lower thrust plate 323
A second lower thrust dynamic pressure generating groove (thrust dynamic pressure generating groove) having a spiral groove pattern of a pump IN type is formed on one of the upper end surface 323b and the lower end surface 331d of the sleeve 331.

Therefore, the air introduced from the upper air inlet 34 (lower air inlet 35) flows into the first upper thrust bearing gap GS311 (first lower thrust bearing gap GS32).
1) flows from the radially inner side to the outer side, and then flows into the second upper thrust bearing gap GS312 (the second lower thrust bearing gap G).
The fluid flows from the outside in the radial direction of S322) to the inside, and further flows into the radial bearing gap GR.

The polygon mirror 53 has a plurality of reflection surfaces 53c formed in a polyhedral shape so as to surround the rotation axis, and is attached to the outer peripheral surface of the cylindrical portion 32a of the hub 32. A donut-shaped magnet plate 59 is also attached to the outer peripheral surface of the cylindrical portion 32a. A plurality of permanent magnets 57 are attached to a surface of the magnet plate 59 facing the polygon mirror 53 so as to surround the fixed shaft 21. The magnet 57 applies buoyancy to the polygon mirror 53 by the magnetic attraction, thereby preventing the polygon mirror 53 from bending under its own weight.

In the polygon mirror driving mechanism 300 constructed as described above, the electric current is supplied to the coil 11b of the coil unit 11 in FIG.
Rotate at a rotation speed of 000 rpm. At this time, the working fluid whose thrust dynamic pressure has been increased in two stages by the first and second upper thrust dynamic pressure generating grooves (first and second lower thrust dynamic pressure generating grooves) is different from those of the first and second embodiments. Similarly, it flows directly into both ends (entrances) of the herringbone-shaped radial dynamic pressure generating grooves (see FIG. 3), and almost no pressure loss or fluid leakage occurs.

(Embodiment 4) A method of machining the above-described dynamic pressure generating groove will be described. The upper and lower thrust dynamic pressure generating grooves 22b and 23b illustrated in FIG. 2 and the like, and the upper and lower thrust dynamic pressure generating grooves 232b and 23 illustrated in FIG. 6 and the like.
3b or the radial dynamic pressure generating groove 2 described in FIG.
The processing method 1b is appropriately selected from a method of chemically removing the material by etching or the like, a method of mechanically removing the material by impact particle projection, rolling, forging, coining, or the like.

FIG. 9A shows a case where the lower thrust dynamic pressure generating groove 23b (see FIG. 2) of the spiral groove pattern of the pump IN type is formed on the lower thrust plate 23 by projecting impact particles. . In this method, on the groove processing surface of the lower thrust plate 23, first, the groove scheduled portion 23b '
, And masking M is performed. Next, the striking particles B are projected from the injection nozzle N toward the planned groove portion 23b '. The impacting particles B used have an average particle diameter adjusted in a range of, for example, 5 to 100 μm, and the injection pressure from the nozzle N is adjusted so that the projection speed on the grooved surface is, for example, 50 to 300 m / sec. You.

As described above, the impact particles B
(A lower thrust dynamic pressure generating groove) 23b is processed, and the vicinity of the groove 23b is heated by the collision with the striking particles B to cause plastic deformation. As shown in FIG.
A raised portion E may be formed at the edge in the width direction of b. Since the bulging portion E sometimes becomes a burr to cause seizure of the bearing portion (the thrust dynamic pressure bearing portion) 30 (see FIG. 2C), for example, as shown in FIG. Polishing is performed along a substantially horizontal polished surface at 1 μm below the highest level of the bulge to remove the bulge E. The lower thrust plate 23 thus grooved is subjected to a predetermined assembling process, and the bearing mechanism 1 shown in FIG.
Incorporated in

The bulging portion E is a phenomenon that is observed not only in the projection of the impact particles but also in all mechanical removal processing methods such as rolling, forging, coining, and the like. It is desirable to remove by. Needless to say, it is desirable to apply the above-mentioned removal processing of the raised portion E also when processing a thrust dynamic pressure generating groove other than the pump IN type spiral groove pattern or a radial dynamic pressure generating groove.

Although air has been used as the working fluid in the embodiments described above, the present invention can be applied to other gases and liquids such as oil.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of a hard disk drive mechanism employing a bearing mechanism of the present invention.

FIG. 2 is a plan view of the lower thrust plate of FIG. 1, a partially enlarged view thereof, and a cross-sectional view showing the lower thrust dynamic pressure generating groove developed along the longitudinal direction thereof.

FIG. 3 is a developed side view of the fixed shaft of FIG. 1, a partially enlarged view thereof, and a cross-sectional view showing a radial dynamic pressure generating groove developed along a longitudinal direction thereof.

FIG. 4 is an explanatory diagram of a shape of a radial dynamic pressure generating groove of FIG. 3;

FIG. 5 is a longitudinal sectional view showing a second embodiment of a hard disk drive mechanism employing the bearing mechanism of the present invention.

FIG. 6 is a plan view of the lower thrust plate of FIG. 5, a partially enlarged view thereof, and a cross-sectional view showing the lower thrust dynamic pressure generating groove developed along its longitudinal direction.

FIG. 7 is a longitudinal sectional view showing an example of a polygon mirror driving mechanism employing the bearing mechanism of the present invention.

FIG. 8 is an enlarged half sectional view showing a main part of FIG. 7;

9A and 9B are an explanatory view and a cross-sectional view of a groove for processing a dynamic pressure generation groove in the lower thrust plate of FIG. 2;

[Explanation of symbols]

REFERENCE SIGNS LIST 1 bearing mechanism 2 first member (fixed side member) 21 fixed shaft (shaft portion) 21a outer peripheral surface 21b radial dynamic pressure generating groove 21b0 intersection 21b1 outer ridge 21b2 inner ridge 22 upper thrust plate 22a lower end (first member) Side thrust surface 22b Upper thrust dynamic pressure generating groove (thrust dynamic pressure generating groove) 23 Lower thrust plate 23a Upper end surface (first member side thrust surface) 23b Lower thrust dynamic pressure generating groove (thrust dynamic pressure generating groove) 23c Land portion (Wall portion) 3 Second member (rotating side member) 31 Sleeve (cylindrical portion) 31a Inner peripheral surface 31c Upper end surface (second member side thrust surface) 31d Lower end surface (second member side thrust surface) 31h Insertion hole 32 Hub 6 Hard disk 8 Motor base 11 Coil unit (stator) 12 Permanent magnet (rotor) 20 Radial dynamic pressure bearing 30 Last dynamic pressure bearing part 40 Drive motor (drive part) 53 Polygon mirror 100 Hard disk drive mechanism 300 Polygon mirror drive mechanism O Axis BL Reference line GR Radial bearing gap GS1 Upper thrust bearing gap (thrust bearing gap) GS2 Lower thrust bearing gap (thrust) Bearing clearance)

Continued on the front page (72) Inventor Kazunio Kato 2-30-30, Datong-cho, Minami-ku, Nagoya-shi, Aichi Prefecture Inside the Technology Development Laboratory of Daido Steel Co., Ltd. (72) Inventor Jun Jun Yatazawa 2-Datomo-cho, Minami-ku, Nagoya-shi, Aichi Prefecture 30-chome Daido Steel Co., Ltd. F-term (Technical Development Laboratory) 5H607 AA04 BB01 BB14 BB17 BB25 CC01 DD05 DD14 GG01 GG03 GG09 GG12 GG14 JJ03 JJ05 KK10 5H615 AA01 BB14 BB17 PP25 SS19 SS20 SS53

Claims (14)

[Claims] 1. A bearing mechanism in which a shaft portion of a first member is inserted and held in a cylindrical portion of a second member so as to be relatively rotatable around its axis, wherein the first member is substantially orthogonal to the axis. Between the first member-side thrust surface formed in the direction of the first member-side thrust surface and the second member-side thrust surface formed on the second member so as to face the first member-side thrust surface. While the thrust bearing gap forming the flow path of the first member is arranged at a predetermined distance in the axial direction, the outer peripheral surface of the shaft portion of the first member and the cylinder of the second member arranged to face the same. Between the inner peripheral surface of the shape portion, both ends are separately communicated with the thrust bearing gap,
A radial bearing gap is arranged, and a spiral thrust for generating a thrust dynamic pressure by introducing a working fluid separately from an inlet side of the thrust bearing gap with the relative rotation of the first member and the second member. Dynamic pressure generating grooves, either one of the first member-side thrust surface and the second member-side thrust surface arranged to face each other,
A herringbone-shaped radial motion that is formed along the circumferential direction and that introduces the working fluids separately flowing from the outlet side of the thrust bearing gap to both end sides of the radial bearing gap to generate radial dynamic pressure; A bearing mechanism, wherein a pressure generating groove is formed in one of an outer peripheral surface of the shaft portion and an inner peripheral surface of the cylindrical portion along a circumferential direction. 2. As the depth of the thrust dynamic pressure generating groove increases from the inlet side to the outlet side of the working fluid in the thrust bearing gap, the depth is continuously or stepwise along the longitudinal direction of the thrust dynamic pressure generating groove. The bearing mechanism according to claim 1, wherein the bearing mechanism is reduced in size. 3. The width of the thrust dynamic pressure generating groove is continuously or stepwise along the longitudinal direction of the thrust dynamic pressure generating groove as the width of the thrust dynamic pressure generating groove moves from the inlet side to the outlet side of the working fluid in the thrust bearing gap. The bearing mechanism according to claim 1 or 2, wherein the bearing mechanism is smaller. 4. In a cross section along a longitudinal direction of the thrust dynamic pressure generating groove, a wall portion having a predetermined thickness toward an inlet side is provided at an end of the thrust dynamic pressure generating groove on the outlet side of the working fluid. The bearing mechanism according to claim 1, wherein the bearing mechanism is formed. 5. A plurality of herringbone shapes passing through the intersection of the ridges on both sides constituting the chevron shape and exhibiting a herringbone shape in which a reference line dividing an angle formed by these ridges is directed in a direction substantially orthogonal to the axis. The bearing mechanism according to any one of claims 1 to 4, wherein the radial dynamic pressure generating grooves are arranged in such a manner that the reference lines are arranged in two groove rows that are separated by a predetermined distance in the axial direction. 6. The bearing mechanism according to claim 5, wherein distances in the axial direction between both ends of the ridge portion of the chevron shape in the axial direction are different between the two groove rows. 7. A distance (hereinafter, referred to as an inner widening width) in the axial direction between the reference line and an expanded end portion of a ridge portion (hereinafter, referred to as an inner ridge line portion) on a side facing the other groove row. Is the distance in the axial direction between the reference line and the expanded end of the other ridge line portion (hereinafter, referred to as an outer ridge line portion) not facing the groove row (hereinafter, referred to as an outer expanded width).
The bearing mechanism according to claim 5, wherein the bearing mechanism is set to be larger than the above. 8. The circumferential length of the inner ridge portion is set to be larger than the circumferential length of the outer ridge portion so that the inner spread width is larger than the outer spread width. The bearing mechanism according to claim 7, wherein the bearing mechanism is provided. 9. An angle formed between the inner ridge portion and the reference line so that the inner expanded width is larger than the outer expanded width. The bearing mechanism according to claim 7 or 8, wherein the bearing mechanism is set to be larger than the above. 10. The bearing mechanism according to claim 1, wherein the working fluid is air. 11. A bearing mechanism according to claim 1, wherein one of the first member and the second member of the bearing mechanism has a stator portion and the other has a rotating side. A drive motor, wherein rotor members are arranged on members. 12. A fixed portion to a motor base portion is formed at one end of the fixed side member in the axial direction, and the radial bearing gap passes through the intersection of the ridge portions on both sides forming a mountain shape. A plurality of the radial dynamic pressure generating grooves exhibiting a herringbone shape in which a reference line dividing an angle formed by the ridge line portion is oriented in a direction substantially orthogonal to the axis, and the reference lines are separated by a predetermined distance in the axial direction. In the groove row located on the side away from the fixed portion of the two rows, a separation distance (hereinafter, referred to as a groove) between both ends of the expanded ridge portion in the axial direction. 12. The drive motor according to claim 11, wherein the expansion width is formed larger than the groove expansion width of the other groove row. 13. A hard disk drive mechanism comprising: the drive motor according to claim 11; and a hard disk attached to the rotating member and rotating integrally therewith. 14. A drive motor according to claim 11 or 12, further comprising a polygon mirror integrated with said rotating member and having a plurality of reflecting surfaces formed in a polyhedral shape so as to surround a rotation axis thereof. A polygon mirror driving mechanism, comprising: