JPH1162948A - Dynamic pressure air bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost bearing of high accuracy by forming the bearing of a sintered alloy, providing a bearing face opposed to the outer peripheral surface of a shaft through a clearance, and inclined dynamic pressure grooves formed on the bearing face, and levitating to support the shaft by dynamic pressure action of air in the clearance. SOLUTION: A bearing face 4 opposed to the outer peripheral surface of a shaft through a bearing clearance is formed on the inner peripheral surface of a bearing body 1 formed of a sintered alloy into porous cylindrical shape. The bearing face 4 has a first dynamic pressure generating area m1 with a plurality of dynamic pressure grooves 5 inclined in one direction in relation to an axial direction and arranged in a circumferential direction, a second dynamic pressure generating area M2 axially separated from the first area M1 and having a plurality of dynamic pressure grooves inclined in the other direction in relation to the axial direction and arranged in the circumferential direction, and an annular smooth part (n) formed between both areas M1, m2. Air is collected to the smooth part (n) by the relative rotation of the shaft and bearing body 1, and dynamic pressure at this part is heightened. Bearing rigidity is increased because of no dynamic pressure groove in the smooth part (m). The grooves 5 can be formed by compression molding so as to reduce cost, and thermal deformation is small because of the sintered alloy so as to be able to maintain high accuracy even under high temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure generating device which forms a dynamic pressure groove by forming a dynamic pressure groove in an inner peripheral surface of a sintered alloy made of a porous body, thereby generating a dynamic pressure by a relative motion between the shaft and the shaft. The present invention relates to a dynamic pressure air bearing configured to support a rotating shaft.

[0002]

2. Description of the Related Art A dynamic pressure bearing can suppress unstable vibration called so-called whirling, in which a shaft oscillates at half the rotational speed. For example, a polygon mirror motor of a laser beam printer or a magnetic disk drive is used. It is suitable as a bearing for equipment that requires high rotational accuracy at high speeds, such as a spindle motor for motors.

In this type of dynamic pressure bearing, a dynamic pressure groove for generating a dynamic pressure may be formed on the bearing surface. In such a case, a method of forming the dynamic pressure groove is to etch the outer peripheral surface of the shaft. Is the most common method.

[0004]

However, while etching has the advantage of being capable of high-precision processing, it has the disadvantage of being unsuitable for mass production due to many chemical processing steps and high production costs.

As another processing method, for example, Japanese Patent Publication No. 5-316
There is a method described in JP-A-81. In this method, a metal outer cylinder having an adhesive applied to an inner peripheral surface thereof is fitted on the inner peripheral surface of the outer die, and ridges corresponding to the shape of the dynamic pressure groove are arranged on the outer peripheral surface of the inner die. Then, molten synthetic resin is injected into the annular space between the inner mold and the outer cylinder, and the inner cylinder molded by solidification of the resin is fixed to the outer cylinder to produce a bearing. This method is more suitable for mass production than etching, but has a limit in reducing production costs, such as the need to apply an adhesive to the inner peripheral surface of a metal outer cylinder every time. Also,
Although the resin portion is thin, the deformation due to heat is larger than that of metal, so that it becomes difficult to secure an appropriate bearing clearance with a change in the ambient temperature.

Accordingly, an object of the present invention is to provide a low-cost and highly accurate dynamic pressure air bearing.

[0007]

Means for Solving the Problems To achieve the above objects,
According to the present invention, a bearing surface made of a sintered alloy and opposed to an outer peripheral surface of a shaft to be supported via a bearing gap, and an inclined dynamic pressure groove formed on the bearing surface are provided. The shaft is floated and supported by the dynamic pressure action of the air in the bearing gap that sometimes occurs.

[0008] In this case, it is desirable to form a dynamic pressure groove after performing sealing processing on at least the bearing surface.

The sealing treatment may be performed by any one of shot blasting, sand blasting, barrel polishing, tumbling, and rotary sizing, or by heat impregnating or anaerobic curing organic impregnation in the pores of the sintered alloy. It can be carried out by impregnating an agent.

Further, at least the bearing surface may be coated with a resin after the formation of the dynamic pressure grooves.

In this case, any one of the above-mentioned sealing treatments (shot blasting, sand blasting, barrel polishing, tumbler treatment, rotation sizing, or heat impregnating or anaerobic curable organic impregnation of the bearing body) is performed. It is desirable to coat at least the bearing surface with a resin after forming the dynamic pressure groove.

[0012]

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

As shown in FIG. 1, the bearing body (1) is formed of a sintered alloy into a porous cylindrical shape. Bearing body (1)
A bearing surface (4) is formed on an inner peripheral surface of the shaft, which faces an outer peripheral surface of a shaft (not shown) via a bearing gap. The bearing surface (4) has an axially inclined, for example, herringbone type ( A plurality of spiral pressure dynamic grooves (5) may be provided. The dynamic pressure groove (5) generates dynamic pressure in the bearing gap during relative rotation with the shaft, and the dynamic pressure action causes the shaft to float and be supported on the bearing body (1).

A first surface in which a plurality of dynamic pressure grooves (5) inclined to one side with respect to the axial direction are arranged in the circumferential direction on the bearing surface (4).
A dynamic pressure generating region (m1) and a second dynamic pressure in which a plurality of dynamic pressure grooves (5) which are axially separated from the first region (m1) and inclined to the other side with respect to the axial direction are arranged in the circumferential direction. Generation area (m2)
And an annular smooth portion (n) located between the first region (m1) and the second region (m2). Both areas (m1) (m
The dynamic pressure groove (5) in (2) is partitioned by a part of the bearing surface (smooth portion n) therebetween and is discontinuous, and is formed symmetrically about the center line (L) in the bearing width direction. Have been. The back portion (6) of the dynamic pressure groove (5) and the smooth portion (n) are formed continuously.

As described above, the two dynamic pressure generating regions (the first region m1 and the second region m2) separating the dynamic pressure groove (5) in the axial direction.
Are formed in the opposite directions. When relative rotation occurs between the shaft and the bearing body (1), the air is collected in the smooth portion (n) by the dynamic pressure grooves formed in the opposite direction. Since the dynamic pressure in this part increases and there is no dynamic pressure groove in the smooth part, the rigidity of the bearing is higher than when the dynamic pressure groove is continuous in the axial direction. This is because uniformity can be avoided.

The above-mentioned dynamic pressure groove (5) can be compression molded by the following procedure. That is, in a sizing process after sintering, etc., a molded portion formed of irregularities inclined in the axial direction is formed on the outer peripheral surface of the core rod (sizing pin), and a cylindrical shape obtained by sintering is formed on the outer peripheral surface of the core rod. A porous body (bearing body material) is supplied, and a pressing force is applied to the porous body to press the inner diameter portion thereof against the core rod forming portion, and a dynamic pressure groove having a shape corresponding to the core rod forming portion is formed on the inner diameter portion. It is transcribed. After the formation of the dynamic pressure groove, if the spring back of the porous body by removing the compression force is used, the core rod can be connected to the porous body (bearing body) without breaking the dynamic pressure groove.
Can be released from the inner diameter portion of the mold.

In addition, a similar molded portion is formed on the outer peripheral surface of a hollow and elastically contractible shaft member, and a core member is inserted into the inner diameter portion of the shaft member to hold the shaft member at a constant diameter. At the same time, the porous body is supplied to the shaping portion of the shaft member, and in this state, a pressing force is applied to the porous body to press the inner diameter portion of the porous body against the forming portion, so that the inner diameter portion is formed into the forming portion. After forming a dynamic pressure groove having a corresponding shape, the core member can be removed from the inner diameter portion of the shaft member so that the shaft member can be reduced in diameter, and then the porous body can be formed by releasing the shaft member from the shaft member. it can.

In either method, the bearing body (1) can be manufactured at low cost because it can be dealt with by only slightly improving the conventional sizing device.
Further, since it is a sintered alloy, thermal deformation is smaller than that of resin, and high accuracy can be maintained even at high temperatures.

By the way, on the bearing surface of the bearing body (1),
Since there are openings (portions where the pores forming the porous structure of the bearing body are open to the outer surface), depending on the conditions of use of the bearing, the amount of air escape may increase and the dynamic pressure effect may become insufficient. It can happen. Therefore, in such a case, the outer surface of the bearing body (1), particularly the bearing surface (4) is subjected to sealing treatment,
The surface porosity on the bearing surface (4) is 10% or less, preferably 5% or less.
% Is desirable.

The sealing treatment can be performed by subjecting the outer surface of the bearing body (1) to any one of shot blasting, sand blasting, barrel polishing, tumbler treatment, and rotational sizing, and the dynamic pressure is reduced by these treatments. It is possible to increase the rigidity of the bearing body (1). Alternatively, the pores of the sintered alloy may be sealed by impregnating the bearing body (1) with a heat-curable or anaerobic-curing organic impregnating agent, in which case the porosity is reduced to almost 0%. Therefore, the dynamic pressure and the rigidity of the bearing can be improved in the same manner as in the sealing treatment. The dynamic pressure groove (5) may be formed after these sealing processes are completed.

Further, as shown in FIG. 2, at least the bearing surface (4) of the bearing body (1) is coated with a highly lubricating resin (7) such as a fluororesin after the formation of the dynamic pressure groove (5). (FIG. 2 conceptually shows a cross section of the bearing surface, and the shape and dimensions of each part are different from actual ones). As a result, the surface porosity on the bearing surface (4) becomes substantially 0%, so that the dynamic pressure and the bearing rigidity can be similarly improved. Further, the friction and wear characteristics at the time of starting and stopping can be improved. If the above-mentioned sealing treatment (a treatment for impregnating with an organic impregnating agent such as shot blasting or a heat-curing type) is performed in advance on the portion to be coated before this resin coating, escape of the resin agent from the opening portion is prevented. Thus, a good coating film (7) without unevenness can be obtained.

[0022]

EXAMPLE As an example, a copper-iron-based powder material was formed into a predetermined shape (forming), and this was sintered (sintered) and shaped (sizing) to form a cylindrical porous body. Was impregnated with an anaerobic organic impregnating agent (Resinol 90C, manufactured by Nippon Loctite). In the impregnating step of the impregnating agent, first, driver vacuum and wet vacuum were performed, and then pressure, water washing, curing, and drying were performed. A dynamic pressure groove (5) is formed on the obtained porous body by the former method (a method using spring back) of the above two types of dynamic pressure groove forming methods, and then a fluororesin (Nippon Acheson Co., Ltd.) (Emuralon 352) was coated on the entire surface of the bearing body (1). The resin coating was performed by coating the surface of the porous body with a fluororesin by hand spraying and tumbler coating, followed by drying at a predetermined temperature for a predetermined time (in the case of Emuralon 352, at 180 ° C. for 15 minutes). In this embodiment, the inner diameter of the bearing body (1) was φ10, the outer diameter was φ15, and the width in the axial direction was 10 mm.

The dimensional accuracy and the shape accuracy of the inner diameter surface of the bearing body of this embodiment and the bearing body disclosed in Japanese Patent Publication No. 5-31681 were compared and evaluated. It was confirmed that the accuracy was high (see FIG. 3).

[0024]

As described above, according to the present invention, the production cost can be reduced because the production is performed by using the sintered alloy, and the thermal deformation is less than that by using the resin. Can be finished with high precision.

[Brief description of the drawings]

FIG. 1 is a sectional view of a dynamic pressure air bearing according to the present invention.

FIG. 2 is a view conceptually showing a cross section of a bearing surface.

FIG. 3 is a diagram showing a comparison result between a product of the present invention and a conventional product.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bearing main body 4 Bearing surface 5 Dynamic pressure groove 7 Coating film

Claims (6)

[Claims] A bearing surface formed of a sintered alloy and opposed to an outer peripheral surface of a shaft to be supported via a bearing gap; and an inclined dynamic pressure groove formed in the bearing surface. A dynamic pressure air bearing that floats and supports the shaft by the dynamic pressure effect of air in the bearing gap generated during rotation. 2. The dynamic pressure air bearing according to claim 1, wherein at least the bearing surface is subjected to a sealing treatment and the dynamic pressure groove is formed. 3. The dynamic pressure air bearing according to claim 2, wherein the sealing treatment is performed by any one of shot blasting, sand blasting, barrel polishing, tumbling treatment, and rotational sizing. 4. The dynamic pressure air bearing according to claim 2, wherein the pore sealing treatment is performed by impregnating the pores of the sintered alloy with a heat-curable or anaerobic-curable organic impregnating agent. 5. The dynamic pressure air bearing according to claim 1, wherein at least the bearing surface is coated with a resin after forming the dynamic pressure groove. 6. The sealing treatment according to claim 3 or 4,
A dynamic pressure air bearing in which at least the bearing surface is coated with a resin after forming the dynamic pressure groove.