JPH11181504A - Core rod for forming bearing surface of dynamic pressure type porous oil impregnated bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the precise formation of a bearing surface having dynamic pressure grooves on the inner peripheral surface of a cylindrical sintered metallic base stock formed into the bearing body of a dynamic pressure type porous oil impregnated bearing with a small man-hour. SOLUTION: On the outer peripheral surface 1a of a core rod 1 made of a cemented carbide, a forming part 1b having a first range 1b1 for forming the dynamic pressure groove on the bearing surface and a second range 1b2 for forming the range except the dynamic pressure groove, is arranged. The forming part 1b is formed by an etching. This core rod 1 is inserted into the inner diameter part of the sintered metallic base stock and the pressing force is applied on the sintered metallic base stock and the inner peripheral surface is pressurized to the forming part 1b of the core rod 1 to form the bearing surface having the shape corresponding to the forming part 1b on the inner peripheral surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core rod for forming a bearing surface having a dynamic pressure groove inclined in an axial direction on an inner peripheral surface of a cylindrical bearing body made of a sintered alloy.

[0002]

2. Description of the Related Art Smaller spindle motors related to information equipment are required to have further improved rotational performance and lower cost. As a means for achieving this, the bearings of spindles are replaced with rolling oil bearings instead of rolling bearings. Is being considered. However, since a porous oil-impregnated bearing is a kind of a perfect circular bearing, unstable vibration is likely to occur where the eccentricity of the shaft is small, and so-called whirling occurs at half the rotational speed. Cheap. Therefore, a herringbone type or spiral type dynamic pressure groove is provided on the bearing surface, and a dynamic pressure oil film is formed in the bearing gap by the dynamic pressure effect accompanying the rotation of the shaft to support the shaft floating and prevent unstable vibration. Has been attempted in the past.

[0003]

Conventionally, as a method of forming a dynamic pressure groove in a bearing surface, a shaft-shaped jig in which a plurality of balls harder than a bearing material are arranged and arranged at equal circumferential intervals is made of brass or aluminum. A method of plastically forming a dynamic pressure groove by inserting a ball into the inner peripheral surface of a bearing material made of a soft metal such as an alloy and applying a spiral motion to the ball by rotating and feeding the jig while pressing the ball against the inner peripheral surface of the material. It is known (Patent No. 2541208)
However, in this method, the material rises in the area adjacent to the dynamic pressure groove at the time of molding, and it is necessary to remove the material with a lathe or a reamer (Japanese Patent Laid-Open No. Hei 8-232958), which increases the man-hour. is there.

SUMMARY OF THE INVENTION The present invention is directed to a molded portion that can accurately mold the bearing surface of a hydrodynamic porous oil-impregnated bearing made of sintered metal with a small number of man-hours, has excellent durability, and has a shape corresponding to the shape of the bearing surface. It is to provide a core rod that can be easily processed.

[0005]

According to the present invention, a core rod for forming a bearing surface is provided on an inner peripheral surface of a cylindrical sintered metal material serving as a bearing body of a hydrodynamic porous oil-impregnated bearing. A core rod for forming a bearing surface having a pressure groove, comprising a cemented carbide, forming a first region for forming a dynamic pressure groove forming region on the bearing surface, and a region other than the dynamic pressure groove. A molded portion having a second region for performing the process is provided on the outer peripheral surface.

When a cylindrical sintered metal material is supplied to the outer diameter portion of the core rod and a pressing force is applied to the sintered metal material, the inner peripheral surface thereof is pressed against the core rod forming portion, causing plastic flow. Bites into the molded part. As a result, the shape of the molded portion is transferred to the inner peripheral surface of the sintered metal material, and the bearing surface having the dynamic pressure groove inclined in the axial direction is formed. The formation region of the dynamic pressure groove on the bearing surface is formed simultaneously by the first region of the forming portion, and the region other than the dynamic pressure groove is formed by the second region of the forming portion at the same time. This eliminates the need for conventional post-processing of the bearing surface (processing to remove material bumps),
The number of steps can be reduced, and the molding accuracy of the bearing surface can be increased. After forming the bearing surface, the core rod can be released from the inner diameter of the sintered metal material without breaking the dynamic pressure groove by utilizing the springback of the sintered metal material by removing the pressing force. .

By the way, the molding portion of the core rod receives a large force from the material when molding the bearing surface, and the core rod is used repeatedly. Therefore, in order to maintain the molding accuracy of the bearing surface, the core rod is load-resistant,
It is desirable that the material has excellent wear resistance. Therefore,
In the present invention, the core rod is formed of a cemented carbide having excellent load deformation resistance and wear resistance. In a dynamic pressure bearing of a type in which a dynamic pressure groove is formed on the shaft side, S is used as a material for the shaft in order to enable etching of the dynamic pressure groove and enhance workability.
It is common to use a US-based material (such as SUS420J2), but the SUS-based material does not provide the above properties required for the present invention.

When the core rod is formed of a cemented carbide, there is a problem in a method of processing the formed portion. In other words, cemented carbide has a high hardness, so it is difficult to machine with normal machining,
Also, there is no processing accuracy. Further, in general, cemented carbide materials often contain additives for improving corrosion resistance, and in many cases etching cannot be performed. Although there is an example in which a core rod for forming a bearing surface is formed of a cemented carbide, it is for forming a bearing surface (a perfect circular bearing) having no dynamic pressure grooves.

Therefore, in the present invention, the workability of the formed part is improved by forming the core rod from a cemented carbide containing no additive for improving the corrosion resistance and processing the formed part by etching. And

[0010]

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

FIG. 1 shows a core rod 1 for forming a bearing surface according to the present invention.

At two locations on the outer peripheral surface 1a of the core rod 1, a forming portion 1b for forming the bearing surface 2b on the inner peripheral surface 2a of the bearing body (2: see FIG. 4) of the hydrodynamic porous oil-impregnated bearing is provided. It is formed to be spaced apart in the direction. As shown in FIG. 2, the forming portion 1b includes a first region 1b1 for forming a formation region of the dynamic pressure groove 2b1 on the bearing surface 2b, and a region other than the dynamic pressure groove 2b1 on the bearing surface 2b, that is, a dynamic pressure groove 2b1. Back part 2b2 between and bearing surface
The second region 1b2 (shown by cross-hatching in FIG. 1) forms the annular smooth portion 2b3 at the axially intermediate portion of 2b. The first region 1b1 is formed so as to correspond to the dynamic pressure groove pattern of the bearing surface 2b, and the drawing illustrates a case where the first region 1b1 corresponds to the so-called herringbone type dynamic pressure groove 2b1. The second region 1b2 is recessed by a predetermined amount with respect to the first region 1b1, and the recess amount is substantially equal to the depth of the dynamic pressure groove 2b1, for example, 2 to 4 μm.
m. The shape of the dynamic pressure groove 2b1 is arbitrary as long as it is inclined with respect to the axial direction. When another inclined groove such as a spiral type is used, the first region 1b1 has a shape corresponding to the groove shape. Form. In FIG. 2, the irregularities of the molded portion 1b are drawn in an exaggerated manner.

The core rod 1 is formed of a cemented carbide (for example, K20 class) having excellent load deformation resistance and wear resistance. As the cemented carbide, an alloy containing no additive for improving corrosion resistance, for example, G20 manufactured by Tokyo Tungsten Co., Ltd., is used in order to enable an etching process described later.

The molded part 1b can be formed by the following procedure (etching).

A photomask of the bearing surface 2b is manufactured based on the drawings (production of a photomask).

The cemented carbide core rod 1 is degreased and coated with a commercially available resist (resist coating).

After the resist is dried, a photomask is wound around the core rod 1 made of cemented carbide, and thereafter, a portion other than the second region 1b1 (corresponding to the first region 1b1) which is irradiated with ultraviolet rays and is shielded from light by the photomask. The resist is cured (baked).

Using a developing solution, the uncured resist, that is, the resist corresponding to the second region 1b2 is dissolved and removed (development).

The base material surface of the second region 1b2 is immersed in an etching solution such as caustic soda for a predetermined period of time (usually 1 to 10 minutes) to dissolve and remove it, thereby forming the second region 1b2. At this time, the etching solution may be energized to perform electrolytic etching (etching).

The remaining hardened resist is stripped off using an organic solvent or the like, and the first region 1b1 is exposed (resist stripping).

FIG. 5 shows the bus shape in the axial direction of the core rod 1 manufactured by the above-mentioned etching process. As shown in FIG. 5, the depth of the second region 1b2 does not vary, and is therefore etched uniformly in the axial direction.
It can be understood that the boundary between the region 1b2) and the non-etched portion (the first region 1b1) is formed at an acute angle.

6 to 9 show circumferential shapes (ad, X to Z) of the core rod 1 manufactured by etching.
Is shown. As shown in FIG. 1, a to d represent shapes in four circumferential regions including the first region 1b1. In addition, Y represents the shape of the unetched portion (roundness), and X and Z represent the shape of the etched portion (roundness). The circumferential shape (ad) and the roundness (X to Z) were all measured with a Talylond (roundness measuring device).

FIGS. 6 to 9 show circumferential shapes (a to d).
Thus, the first region 1b1 is precisely evenly distributed in the circumferential direction (8 equally distributed).
It can be understood that the variation in the depth of the second region 1b2 is small. It can also be understood from the comparison between X, Z and Y that the difference in roundness between the etched portion and the non-etched portion is small. Therefore, it is determined that the core rod 1 is uniformly etched in the circumferential direction.

The method of processing the molded portion 1b is not limited to the above-mentioned etching (including electrolytic etching).
Other processing methods capable of performing precision processing on cemented carbide, such as laser processing and electric discharge processing, can also be employed.

The core rod 1 manufactured by the above procedure is
For example, it is used as a bearing surface forming die of the forming device shown in FIG. The bearing surface is formed by compacting metal powder mainly composed of copper or iron, and then inserting the core rod 1 into the inner diameter of a cylindrical sintered metal material 2 'obtained by firing. The pressing is performed by pressing the sintered metal material 2 ′ from both sides in the axial direction with the upper and lower punches 6 and 7 in a state where this is pressed into the die 5. When the upper punch 6 and the core rod 1 are lowered in conjunction with each other, a pressing force is applied to the sintered metal material 2 ′ from both the punches 6, 7 and the die 5, and the pressing force is applied to the sintered metal material 2 ′.
The upper and lower ends move toward the inner diameter side and are pressed against the opposing molded portions 1b. As a result, the shape of the molded portion 1b is transferred to the upper and lower ends of the inner peripheral surface of the sintered metal material 2 '. Molding part
A dynamic pressure groove 2b1 having a predetermined shape is formed in the first region 1b1 of the first region 1b, and a back portion 2b2 and a smooth portion 2b3 are formed in the second region 1b2 at the same time.

After that, the upper and lower punches 6 and 7 and the core rod 1 are raised in conjunction with each other, and the formed sintered metal material 2 ′ is extracted from the die 5. The sintered metal material 2 ′ is spring-backed at the same time as it is pulled out of the die 5, and its inner diameter surface is slightly enlarged. Therefore, even if the sintered metal material 2 ′ is pulled out from the core rod 1, the dynamic pressure groove 2 b 1 is formed. 1st area 1 of part 1b
It does not collide with b1.

As shown in FIG. 4, the inner peripheral surface 2a of the bearing body 2 thus obtained has an annular smooth portion 2b3 at the center and has opposing dynamic pressure grooves 2b1 on both sides. Bearing surfaces 2b are formed at two locations in the axial direction. After the bearing body 2 is washed and dried, it is impregnated with lubricating oil or lubricating grease to produce a hydrodynamic sintered oil-impregnated bearing having a hydrodynamic groove on the inner peripheral surface.

[0028]

As described above, according to the core rod of the present invention, it is possible to accurately form a bearing surface having a dynamic pressure groove with a small number of man-hours. If the core rod is made of a cemented carbide, it is possible to improve the wear resistance to enhance the durability, and also to improve the load deformability to improve the molding accuracy of the bearing surface. If the formed portion is formed by etching, a formed portion having a shape corresponding to the dynamic pressure groove pattern on the bearing surface can be easily formed, and it is possible to easily cope with a case where the dynamic pressure groove pattern is changed. In addition, the processing accuracy of the molded part is high.

[Brief description of the drawings]

FIG. 1 is a side view of a core rod for forming a bearing surface of a hydrodynamic porous oil-impregnated bearing according to the present invention.

FIG. 2 is a partially enlarged side view of the core rod.

FIG. 3 is a sectional view showing a sizing step using the core rod.

FIG. 4 is a cross-sectional view of a bearing main body formed using the core rod.

FIG. 5 is a diagram showing a generatrix shape in the axial direction of a core rod having a formed portion.

FIG. 6 is a diagram showing a shape in a circumferential direction of a core rod having a molded portion.

FIG. 7 is a view showing a shape in a circumferential direction of a core rod having a molded portion.

FIG. 8 is a view showing a shape in a circumferential direction of a core rod having a molded portion.

FIG. 9 is a diagram showing a shape in a circumferential direction of a core rod having a molded portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Core rod 1a Outer peripheral surface 1b Molded part 1b1 1st area 1b2 2nd area 2 Bearing body 2a Inner peripheral surface 2b Bearing surface 2b1 Dynamic pressure groove

Claims (2)

[Claims] 1. A core rod for forming a bearing surface having a dynamic pressure groove inclined in an axial direction on an inner peripheral surface of a cylindrical sintered metal material which is a bearing body of a dynamic pressure type porous oil-impregnated bearing. A molding portion made of cemented carbide and having a first region for molding a dynamic pressure groove forming region on the bearing surface and a second region for molding a region other than the dynamic pressure groove is provided on the outer peripheral surface; Core rod for forming the bearing surface of a hydrodynamic porous oil-impregnated bearing. 2. The core rod for forming a bearing surface of a hydrodynamic porous oil-impregnated bearing according to claim 1, wherein the formed portion is formed by etching.