JP2000291648A - Dynamic pressure-type bearing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy (perpendicularity) between a shaft and a flange part. SOLUTION: In a dynamic pressure-type bearing unit comprising a shaft member 2 consisting of a shaft 2a and a flange part 2b, a radial bearing part 10 radially supporting the shaft member 2, and a thrust bearing part 11 for supporting the flange part 2b of the shaft member 2 in the thrust direction, and capable of supporting the shaft member 2 by the radial bearing part 10 and the thrust bearing part 11 by their dynamic pressure action in a non-contact state, the shaft 2a and the flange part 2b are integrated. On this occasion, a dynamic pressure groove of the thrust bearing part 11 is formed on an upper surface of a thrust supporting part 13 opposite to an end surface of a bearing 7 and the flange part 2b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dynamic pressure type bearing unit. This bearing unit is used especially for information equipment, for example, a magnetic disk device such as HDD and FDD, a CD-RO
It is suitable for supporting a spindle motor such as an optical disk device such as an M or DVD-ROM, a magneto-optical disk device such as an MD or MO, or a spindle scanner motor such as a laser beam printer (LBP) polygon scanner motor.

[0002]

2. Description of the Related Art Spindle motors for various information devices are required to have high rotational accuracy, high speed, low cost, low noise, and the like. One of the components that determine these required performances is a bearing that supports the spindle of the motor.In recent years, as this type of bearing, the use of a dynamic pressure bearing having characteristics excellent in the required performance has been studied. Or they are actually used.

FIG. 5 shows an example of this type of spindle motor. A shaft member 22 rotatably supported by a bearing unit 21 is shown in FIG.
(Consisting of a shaft 22a and a thrust disk 22b that becomes a flange when mounted on the shaft 22a) is generated between the motor stator 4 fixed to the bearing member 27 and the motor rotor 5 mounted on the shaft member 22. This is a structure that is driven to rotate by an exciting force. The bearing unit 21 is provided with a radial bearing portion 30 for supporting the shaft member 22 in the radial direction and a thrust bearing portion 31 for supporting the thrust disk 22b in the thrust direction. A dynamic pressure bearing having a groove for generating dynamic pressure (dynamic pressure groove). The dynamic pressure grooves of the radial bearing portion 30 are formed on the inner peripheral surface of the bearing member 27, and the dynamic pressure grooves of the thrust bearing portion 31 are formed on both end surfaces of the thrust disk 22b fixed to the lower end of the shaft member 22. . At the bottom of the bearing member 27, a step is formed by adding the width of the thrust bearing gap (t = about 10 to 20 μm) to the thickness of the thrust disk 22b. Thrust bearing gaps Cs1 and Cs2 having the above-mentioned predetermined width are formed on both axial sides of the disk 22b.
+ Cs2).

In this bearing unit 21, after a thrust disk 22b and a back metal 33 are assembled in a bearing member 27, a shaft 22a having a diameter smaller than the inner diameter by an amount corresponding to a radial bearing gap Cr is inserted into the inner diameter of the bearing member 27. Further, the shaft 22a is assembled by pressing the tip of the shaft 22a into the inner diameter of the thrust disk 22b.

[0005]

In the bearing unit 21, if the accuracy of the perpendicularity between the shaft 22a and the thrust disk 22b is poor, the thrust disk in the thrust bearing gaps Cs1, Cs2.
22b may come into contact with the facing surface and deteriorate the bearing performance. Therefore, in the assembling process, it is necessary to press-fit the shaft 22a into the thrust disk 22b with high accuracy. Further, even if it is attempted to measure the perpendicularity, since the shaft 22a and the thrust disk 22b are already incorporated in the unit, it is generally difficult to measure and confirm the accuracy of the shaft 22a and the thrust disk 22b. This leads to an increase in assembly costs.

Accordingly, an object of the present invention is to provide a dynamic pressure bearing unit which can improve the accuracy (squareness and the like) between a shaft and a thrust disk at low cost.

[0007]

In order to achieve the above object,
The dynamic pressure bearing unit according to the present invention includes a shaft member including a shaft and a flange portion, a radial bearing portion that supports the shaft member in the radial direction, and a thrust bearing portion that supports the flange portion of the shaft member in the thrust direction. The radial bearing and the thrust bearing each support the shaft member in a non-contact manner by a dynamic pressure action, and the shaft and the flange are integrally formed.

[0008] When the shaft member is formed as an integral structure as described above, the accuracy of the perpendicularity between the shaft and the flange portion can be easily secured, and the perpendicularity can be measured before assembling into the bearing unit. In addition, accuracy measurement and its confirmation work are also easy.

In the radial bearing of this dynamic pressure type bearing unit, a bearing member is arranged on the outer peripheral side of a shaft member, and a radial bearing gap of a radial bearing portion is formed between the outer peripheral surface of the shaft member and the bearing member facing the shaft member. It is constituted by doing.

[0010] The thrust bearing portion is provided on both sides of the flange portion.
It has three thrust bearing gaps. in this case,
One (first) thrust bearing gap of the thrust bearing portion can be constituted by one end surface of the flange portion and a bearing member (for example, the end surface) opposed thereto. Also,
A thrust support portion is provided to face the other end surface of the flange portion, and the other (second) thrust bearing gap can be formed by the thrust support portion and the other end surface of the flange portion.

The dynamic pressure groove of the thrust bearing is desirably provided on one of the bearing member and the thrust support (determined by the direction of the thrust load) or on both.

One end of the bearing member is preferably sealed with a seal member.

[0013]

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

FIG. 1 is a sectional view of a spindle motor for information equipment provided with a dynamic pressure type bearing unit 1 according to the present invention.
As an example, an HDD (hard disk drive) spindle motor is shown. The spindle motor includes a bearing unit 1 that rotatably supports a shaft member 2 and a shaft member 2.
And a disk hub 3 holding one or more magnetic disks D, and a motor stator 4 and a motor rotor 5 opposed to each other via a radial gap. The stator 4 is attached to a cylindrical outer peripheral portion of a casing 9 that holds the bearing unit 1, and the rotor 5 is attached to an inner peripheral surface of the disk hub 3. When the stator 4 is energized, the rotor 5 rotates by the exciting force between the stator 4 and the rotor 5, and the disk hub 3 and the shaft member 2 rotate.

As shown in FIGS. 1 and 2, the bearing unit 1 includes a shaft member 2, a so-called bag-shaped housing 6 having a bottomed cylindrical shape, and a thick-walled cylindrical shape fixed to the inner peripheral surface of the housing 6. Bearing member 7 and one end of bearing member 7 (housing 6
And a sealing member 8 such as a seal washer for sealing the main member. The shaft member 2 includes a shaft 2a and a shaft.
And a flange 2b provided at the lower end of the housing 2a. The shaft 2a is arranged on the inner periphery of the bearing member 7, and the flange 2b is accommodated between the bearing member 7 and the bottom of the housing 6. .

The bearing member 7 is made of, for example, a soft metal such as copper or brass. A radial bearing surface 10 a having a dynamic pressure groove is formed on the inner peripheral surface of the bearing member 7.
At the time of rotation), a dynamic pressure is generated in the radial bearing gap Cr between the radial bearing surface 10a and the outer peripheral surface of the shaft 2a, and the radial bearing portion 10 that supports the shaft 2a in a non-contact manner in the radial direction is configured. . The width of the radial bearing gap Cr in the figure is exaggerated (the same applies to thrust bearing gaps Cs1 and Cs2 described later).

The bearing member 7 can be formed not only of a soft metal or the like but also of, for example, a sintered metal. In this case, the dynamic pressure groove is compression-molded, that is, a concave / convex groove shape corresponding to the dynamic pressure groove shape of the radial bearing surface 10a (see FIG. 3A) is formed on the outer peripheral surface of the core rod. By supplying the sintered metal and pressing the sintered metal, and transferring the dynamic pressure groove corresponding to the groove shape to the inner peripheral portion of the sintered metal, the molding can be performed at low cost and with high precision. In this case, the release of the sintered metal can be easily performed using the springback of the sintered metal by releasing the pressing force. When a sintered metal is used as the material of the bearing member 7 as described above, the bearing member 7 can be used as a dynamic pressure type oil-impregnated bearing in which lubricating oil or lubricating grease is impregnated.

Thrust bearing gaps Cs1 and Cs2, which are gaps in the axial direction, are provided on both axial sides of the flange portion 2b.
The thrust bearing gap Cs1 is formed between the upper end face 2b1 of the flange 2b and the end face of the bearing member 7 facing the same, and the other thrust bearing gap Cs2 is formed at the lower end face 2 of the flange 2b.
It is formed between b2 and the upper surface of the thrust support portion 13 opposed thereto. This embodiment exemplifies a structure in which the thrust support portion 13 is formed integrally with the housing 6 and the thrust support portion 13 is a bottom portion that seals the opening at the other end of the housing 6. Thrust bearing surfaces 11a and 11b each having a dynamic pressure groove are formed on the lower end surface of the bearing member 7 facing one thrust bearing clearance Cs1 and the upper surface of the thrust support portion 13 facing the other thrust bearing clearance Cs2. Further, at the time of the rotation, a dynamic pressure is generated in the thrust bearing gaps Cs1 and Cs2, and the thrust bearing portion 11 that non-contactly supports the flange portion 2b from both sides in the thrust direction is configured.

The shape of the hydrodynamic grooves of the radial bearing surface 10a and the thrust bearing surfaces 11a and 11b can be arbitrarily selected, and may be any of well-known herringbone type, spiral type, step type, multi-arc type and the like. They can be selected or used in appropriate combination. 3A and 3B show a herringbone type as an example of a dynamic pressure groove shape. FIG. 3A shows a radial bearing surface 10a, and FIG. 3B shows a thrust bearing surface 11b provided on a thrust support portion 13. Is shown. As shown in the figure, the radial bearing surface 10a has a first groove region m1 having a hydrodynamic groove 14 inclined on one side, and a first groove region m1.
A second groove region m2 in which the dynamic pressure grooves 14 inclined in the other direction are arranged in the axial direction, and an annular smooth portion n located between the two groove regions m1 and m2. n and the back part 15 between the dynamic pressure grooves 13 are at the same level. Thrust bearing surface 11b
The dynamic pressure groove 16 has a substantially V-shape having a bent portion substantially at the center in the radial direction.

In the bearing unit 1, the shaft member 2 is inserted into the housing 6 with the flange portion 2b facing down, and the thrust bearing gaps Cs1, Cs of a predetermined width (about 10 to 20 μm) are further inserted.
The bearing member 7 is assembled by press-fitting or bonding it to a predetermined position on the inner peripheral portion of the housing 6 so that s2 is formed. Then, this bearing unit 1 is
Is press-fitted or adhered to the cylindrical inner peripheral portion of
The spindle motor shown in FIG. 1 is assembled by press-fitting an assembly (motor rotor) including the disk hub 3 into the upper end of the shaft 2a.

In the present invention, the shaft 2a of the shaft member 2 and the flange portion
2b are integrally formed by, for example, forging or machining. When the shaft member 2 has an integral structure as described above, the shaft
Accuracy such as the perpendicularity between the flange 2a and the flange portion 2b can be easily increased, and the perpendicularity can be measured before assembling into the bearing unit, so that precision measurement and confirmation thereof can be easily performed. In addition, since the motor rotor can be mounted last, lubrication to the bearing unit 1 becomes easy, and further, handling as a spindle unit becomes possible, and there is an advantage that handling becomes easy. The shaft member 2 is a shaft
It is also possible to manufacture by integrating the 2a and the flange portion 2b by welding and then finishing them to predetermined accuracy.

As described above, since the motor rotor is press-fitted into the shaft 2a, the material of the shaft member 2 is desirably formed of a high-hardness iron-based material. On the other hand, in the case of an iron-based material, it is difficult to form a dynamic pressure groove on the end face of the flange portion 2b by plastic working or machining as in the conventional case, so that the processing cost rises. If the pressure grooves are provided not on the flange portion 2b but on the end face of the bearing member 7 or the thrust support portion 13, this kind of problem can be solved. That is, the bearing member 7 and the thrust support portion 13 can be formed of a soft metal or a sintered metal (a material that is easy to perform plastic working or machining), and the working cost can be reduced. For example, when a soft metal is used, press working is performed.When a sintered metal is used, a radial bearing surface 10 is used.
By the same compression molding as in a, the thrust bearing surfaces 11a and 11b with the dynamic pressure grooves 16 can be formed. If the processing cost is not a problem, the thrust bearing surfaces 11a and 11b can be formed on both end surfaces of the flange portion 2b.

FIG. 4 shows another embodiment of the present invention. This bearing unit 1 corresponds to the configuration shown in FIG.
The housing 6 and the bearing member 7 of FIG. 1 are integrated into a single bearing member 7 ′, and the bottom opening of the bearing member 7 ′ is closed by a separate thrust support 13 (for example, a back metal 33 similar to the conventional one). The following shows the structure. Other substantial configurations are the same as those in FIGS. Also in this case, the shaft member 2 has an integral structure, and the thrust bearing surfaces 11a and 11b can be provided on the end surface of the bearing member 7 'and the thrust support portion 13, respectively.

[0024]

As described above, in the present invention, since the shaft member has an integral structure, the accuracy such as the perpendicularity between the shaft and the flange portion can be easily increased, and the accuracy can be easily measured and confirmed. . Therefore, a high-precision and inexpensive bearing unit suitable for use in a spindle motor for information equipment can be provided.

Further, if the dynamic pressure groove of the thrust bearing portion is provided in one or both of the bearing member and the thrust support portion, even if the shaft member is formed of a hard material such as iron, By forming the member and the thrust support portion with a soft metal, a sintered metal, or the like in which the dynamic pressure grooves are easily processed, the processing cost of the thrust bearing surface can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a spindle motor for information equipment having a dynamic pressure bearing unit according to the present invention.

FIG. 2 is an enlarged sectional view of a main part of FIG.

3A is a sectional view of a bearing member, and FIG. 3B is a plan view of a thrust bearing portion.

FIG. 4 is a cross-sectional view showing another embodiment of the present invention.

FIG. 5 is a sectional view of a conventional spindle motor for information equipment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing unit 2 Shaft member 2a Shaft 2b Flange part 7 Bearing member 7 'Bearing member 8 Seal member 10 Radial bearing part 10a Radial bearing surface 11 Thrust bearing part 11a Thrust bearing surface 11b Thrust bearing surface 13 Thrust support part 14 Dynamic pressure Groove 16 Dynamic pressure groove Cr Radial bearing clearance Cs1 Thrust bearing clearance Cs2 Thrust bearing clearance

Claims (8)

[Claims] 1. A shaft member comprising a shaft and a flange portion,
It has a radial bearing part that supports the shaft member in the radial direction, and a thrust bearing part that supports the flange part of the shaft member in the thrust direction. The radial bearing part and the thrust bearing part do not contact the shaft member by dynamic pressure action. A dynamic pressure bearing unit, wherein a shaft and a flange portion are integrally formed. 2. The dynamic bearing according to claim 1, wherein a bearing member is disposed on an outer peripheral side of the shaft member, and a radial bearing gap of the radial bearing portion is formed between the outer peripheral surface of the shaft member and the bearing member facing the bearing member. Pressure bearing unit. 3. The dynamic pressure type bearing unit according to claim 1, wherein the thrust bearing portion has two thrust bearing gaps on both sides of the flange portion. 4. The dynamic pressure type bearing unit according to claim 1, wherein one end face of the flange portion and a bearing member facing the flange portion constitute one thrust bearing gap of the thrust bearing portion. 5. A thrust support portion is provided to face the other end surface of the flange portion, and the thrust support portion and the other end surface of the flange portion constitute the other thrust bearing gap of the thrust bearing portion. Or the dynamic pressure bearing unit according to 4. 6. The dynamic pressure bearing unit according to claim 4, wherein a dynamic pressure groove of the thrust bearing portion is provided in the bearing member. 7. The dynamic pressure bearing unit according to claim 4, wherein a dynamic pressure groove of the thrust bearing portion is provided in the thrust support portion. 8. The dynamic pressure bearing unit according to claim 2, wherein one end of the bearing member is sealed with a seal member.