JP2001041244A - Manufacture of bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To high-efficiently manufacture a two-point support structure bearing having a middle run-off through a comparatively simple method as bearing performance is improved. SOLUTION: A core rod 22 is inserted in a uniform outside diameter material (a sintered substance) 1A provided at one end part in an axial direction with the small part 3 of an inside diameter, and the material 1A is pressed in the cavity of a molding hole 20 by an upper punch 23 and axially compressed. The outside diameter surface of one end part in an axial direction of the material 1A is compressed toward the inside diameter side to decrease an outside diameter and meanwhile, the outside diameter surface of the other end part in an axial direction is expanded to increase an outside diameter. Along with this deformation, the inside diameter surfaces of two end parts in an axial direction are brought into pressure contact with the core rod 22 to form a pivotal support surface 12 to support a rotary shaft. A middle run-off 13 which has an inside diameter layer than that of the pivotal support surface 12 and with which the rotary shaft makes no contact is formed between the pivotal support surfaces 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a bearing suitable for supporting a shaft rotating at a relatively high speed, such as a drive shaft of a spindle motor built in precision equipment, with high precision. The present invention is a technique for obtaining a bearing having a desired shape by causing plastic deformation by compressing a material, and as a material, mainly, a sintered body obtained by sintering a green compact or a sintered body A cylindrical porous body subjected to sizing (recompression) is used. Further, the bearing manufactured according to the present invention is impregnated with lubricating oil and is suitably used as a sintered oil-impregnated bearing.

[0002]

2. Description of the Related Art In a sintered oil-impregnated bearing, the lubricating oil impregnated in a sintered body seeps into an inner diameter surface, and an oil film is formed between the inner diameter surface and a rotating shaft, thereby reducing frictional resistance. It has the characteristic that noise and vibration are suppressed. In addition, as a sintered oil-impregnated bearing with further enhanced vibration and noise suppression effects,
A gap (hereinafter, referred to as a middle relief portion) having an inner diameter slightly larger than the outer diameter of the rotating shaft and not in contact with the rotating shaft is formed on the inner diameter surface at the central portion in the axial direction. As a two-point support structure limited to a surface, there is a structure in which the effect of reducing frictional resistance and the support force of the rotating shaft are further stabilized.

[0003] Sintered oil-impregnated bearings are usually manufactured mainly by the steps of sintering a cylindrical green compact obtained by compression-molding a raw metal powder, sizing the sintered body and finishing it into a final shape. Have been. By the way, when manufacturing a bearing having the above-mentioned middle relief, if the middle relief is formed by machining a sintered body, pores exposed on the inner diameter surface are crushed, which hinders the circulation operation of the lubricating oil. Will be. For this reason, in the sizing process of the sintered body,
Alternatively, a method in which the sintered body is compressed once again after sizing to independently form the middle relief portion is preferable. In either case, the inner diameter surfaces at both axial ends protrude radially inward,
By generating plastic deformation in the sintered body as a material, in which the central portion in the axial direction swells outward in the radial direction, two spaced apart bearing surfaces and a relief portion between them are formed simultaneously on the inner diameter surface. Is done.

[0004]

In the bearing having the above-mentioned two-point support structure, in order to enhance the bearing performance such as the reduction of the frictional resistance and the improvement of the support force of the rotary shaft, the inner diameter of the two separated shaft supporting surfaces and It is required that the coaxiality match with high accuracy. It is also important that a sufficient amount of lubricating oil be supplied to the bearing surface. However, although various methods have been proposed for plastic deformation of a sintered body,
At present, there has not been found a certain manufacturing method which is relatively simple and sufficiently satisfies the requirements for improving bearing performance.

Accordingly, the present invention has a middle clearance portion in which the rotating shaft does not contact the inner diameter surface at the axial center portion, and furthermore, the inner clearance amount of the middle clearance portion is relatively large, and the inner diameter surfaces at both axial end portions are small. A bearing having a two-point support structure that functions as a bearing surface for supporting a rotating shaft can be efficiently manufactured by a relatively simple method, and its bearing performance (identical inner diameter of the two bearing surfaces, coaxial It is an object of the present invention to provide a method of manufacturing a bearing that can also achieve improvements in the bearing strength, lubricity, wear resistance, and the like of the rotating shaft with increasing degrees.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a porous material having a cylindrical shape, having at least one small-diameter inner diameter portion at one end in the axial direction and having a uniform outer diameter or a large-diameter outer portion at a part of the outer diameter surface. With the core rod inserted, the material consisting of the body is pressed into the forming hole of the mold and compressed in the axial direction, so that the outer diameter surface at one axial end of the material is compressed to the inner diameter side and While reducing the diameter, the outer diameter surface at the other end in the axial direction is expanded to increase the outer diameter. With this deformation, the inner diameter surfaces at both ends in the axial direction are pressed against the core rod to support the rotating shaft. It is formed on a shaft support surface, and is characterized in that a middle clearance portion is formed between the shaft support surfaces and has a larger inner diameter than the shaft support surface and does not contact the rotating shaft. As the material according to the present invention, a sintered body or a porous body obtained by sizing the sintered body as described above is used, and after production, the sintered body is impregnated with a lubricating oil and is suitably used as a sintered oil-impregnated bearing.

In the present invention, for example, a cylindrical material having a uniform outer diameter is press-fitted by a punch and axially compressed while a core rod is inserted into a cylindrical forming hole formed in a die. A molding method is adopted.
In this case, the inner diameter of the material is set to a size that forms a gap between the inner diameter surface and the core rod. Also, the forming hole,
The portion on the inlet side is larger than the outer diameter of the material, and the inner part is a hole whose diameter is smaller than the outer diameter of the material through a step.

When a material is pressed into such a molding hole,
One end on the front end side in the press-fitting direction and the central portion following this are press-fitted into the reduced diameter portion of the molding hole, and the outer diameter surface is compressed to the inner diameter side,
Outer diameter shrinks. On the other hand, the other end on the rear end side in the press-fitting direction is compressed in the axial direction, so that the outer diameter surface expands until it comes into pressure contact with the inner diameter surface of the large-diameter portion on the inlet side of the forming hole, and the outer diameter increases. I do. Also, by compressing the material in the axial direction,
The inner diameter surfaces at both ends in the axial direction swell toward the inner diameter side and are pressed against the core rod to form on the bearing surface, and the inner diameter surface between these bearing surfaces has a clearance between the core rod and the inner escape surface. Department. The present invention adopts a combination of a material and a mold in which such a deformation mode is appropriately performed, and thereby a bearing of a two-point support structure having a middle relief portion having a relatively large middle clearance amount can be provided by a relatively simple method. And can be manufactured efficiently.

According to the present invention, since the shaft supporting surface for supporting the rotating shaft is formed by strongly pressing the inner diameter surface of the material against the core rod, the inner diameter and the coaxiality match with high accuracy. Further, since the density of the bearing surface can be increased, the wear resistance is improved. On the other hand, the density of the inner diameter surface where the middle relief portion is formed can be made lower than that of the bearing surface, and the diameter of the middle relief portion can be formed relatively large, so that the lubricating oil content is increased. And lubricity is improved. As a result, a bearing having a high level of bearing performance can be manufactured.

As the material of the present invention, those having the following shapes are particularly used. It has a uniform outer diameter and a small inner diameter portion at one axial end. It has a small inner diameter portion at one end in the axial direction and a large outer diameter portion at the other end. It has an inner small diameter portion at both axial ends and an outer large diameter portion at one axial end. It has a small inner diameter part and a large outer diameter part at one axial end.

Further, the present invention is characterized in that a convex portion or a concave portion for forming a dynamic pressure groove is formed on an outer diameter surface of a core rod to which inner diameter surfaces of both ends in the axial direction of the material are pressed. According to this, in the case of the former convex portion, a dynamic pressure groove corresponding to the shape of the convex portion is formed on the bearing surface. In the case of the latter concave portion, a bearing surface engraved according to the shape of the concave portion and a dynamic pressure groove between the bearing surfaces are simultaneously formed. When the dynamic pressure grooves are formed on the bearing surface, the dynamic pressure effect generated in the dynamic pressure grooves (the lubricating oil flowing into the dynamic pressure grooves) Increased rigidity with higher pressure)
Accordingly, the supporting force of the rotating shaft is synergistically increased, and the supporting force of the rotating shaft is more stabilized.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. (1) First Embodiment-FIG . 1 Reference numeral 1A in FIG. 1A is a sintered body or a material obtained by sizing a sintered body. It should be noted that the materials of all the embodiments described later are also the same sintered bodies. The material 1A is a cylindrical material having a uniform outer diameter and a small inner diameter portion 3 formed at one axial end.

A forming apparatus shown in FIG. 1 includes a die 21 having a forming hole 20, a core rod 22, upper and lower punches 23,
24. The forming hole 20 is formed in a stepped shape whose inner diameter is reduced by two steps from the inlet side (upper side) toward the inner part. That is, the forming hole 20 has a cylindrical main portion 20a at a central portion in the axial direction, a squeezed portion 20b at a deeper portion having a smaller diameter than the main portion 20a, and an opening 20c on the inlet side having a larger diameter than the main portion 20a. It is composed of Each transition from the opening 20c to the main part 20a and from the main part 20a to the aperture forming part 20b is formed in a gentle taper shape. Upper punch 2
3 is inserted into the opening 20c, and the lower punch 24 is inserted into the aperture forming portion 20b.

The outer diameter of the raw material 1A is the same as that of the main part 20 of the molding hole 20.
a is larger than the inner diameter of the opening a
The size is set such that a gap is formed between the inner diameter surface of c and the inner diameter surface. The inner diameter of the inner diameter small diameter portion 3 is the same as that of the core rod 22.
Is set smaller than the diameter of the inner diameter, and the inner diameter other than the inner diameter small diameter portion 3 is set to a size where a gap is formed between the inner diameter surface and the core rod 22.

In order to compression-mold the material 1A by the above-mentioned molding apparatus, first, as shown in FIG.
The cavity is formed in the molding hole 20 while the core rod 22 is held at a position protruding from the upper surface of the die 21 by a predetermined length. Next, the material 1 </ b> A is fitted into the core rod 22 with the small inner diameter portion 3 facing upward, and the lower end thereof is inserted into the opening 20 c of the forming hole 20. From this state, as shown in FIG. 1B, the core rod 22 and the upper punch 23 are lowered, and the raw material 1A is pressed into the cavity of the forming hole 20 by the upper punch 23 and is compressed in the axial direction. The core rod 22 and the upper punch 23 are lowered while synchronizing until the upper end of the core rod 22 is lowered to the same level as the upper surface of the die 21. Thereafter, the core rod 22 is held at that position, and only the upper punch 23 is moved to the lower end. Is slightly lowered into the opening 20c. In addition, the material 1A was inserted into the molding hole 20.
The positions of the core rod 22 and the lower punch 24 at the time of press-fitting are not limited to the positions shown in FIG. 1A, and for example, the upper end of the core rod 22 may be flush with the upper surface of the die 21. The upper surface of the lower punch 24 is
Or the opening 20 of the forming hole 20.
The state may be raised to the region c.

By this operation, the lower end of the material 1A is press-fitted from the main portion 20a of the forming hole 20 into the squeezing portion 20b, the center portion is press-fitted into the main portion 20a, and the outer diameter surface of these portions is compressed toward the inner diameter side. And the outer diameter is reduced. In particular, the lower end portion is formed into a narrowed portion 11 having a smaller diameter than the central portion by being press-fitted into the drawn portion 20b. The lower end face of the material 1 </ b> A is restrained by the lower punch 24 and is compressed in the axial direction by the upper punch 23. The upper end portion of the material 1A plastically flows toward the outer diameter side in response to the compression of the core rod 22 pressed into the small inner diameter portion 3 in addition to the compression in the axial direction, and the outer diameter surface is pressed against the inner diameter surface of the opening 20c. Swells to the outside diameter until the outside diameter increases,
The outer large diameter portion 17 is newly formed. Further, the inner diameter surfaces of both ends in the axial direction of the material 1A are the core rods 22 on the upper end side.
At the lower end side, swells toward the inner diameter side by the compression action, and presses against the core rod 22 to form on the shaft support surface 12. Further, on the inner diameter surface between the bearing surfaces 12, a gap with the core rod 22 remains, and the middle escape portion 1
It is set to 3. In this way, the material 1A is plastically deformed, and the bearing 10A is formed. The bearing 10 </ b> A is obtained by lifting the upper punch 23 and raising the lower punch 24 and removing the die from the die 21.

According to the first embodiment, the material 1A having the relatively large middle clearance 13 is formed by a simple method of press-fitting the material 1A into the forming hole 20 of the die 21 and compressing the material 1A in the axial direction. The bearing 10A having the point support structure can be manufactured efficiently.

The bearing surface 12 of the bearing 10A is formed by strongly pressing the inner diameter surface of the material 1A against the core rod 22, so that the inner diameter and the coaxiality match with high precision, and the density is further increased. Excellent in abrasion resistance. on the other hand,
Since the middle relief portion 13 does not press against the core rod 22, the density is lower than that of the shaft supporting surface 12, so that the lubricating oil content can be increased and lubricity is improved. As a result, the bearing 10A exhibits excellent bearing performance. In addition, since the degree of compression toward the inner diameter side of both ends is substantially equal, the porosity of the bearing surfaces 12 at both ends is equalized, and the hydraulic pressure generated on the bearing surfaces 12 at both ends is also equalized. The rotating shaft can be supported in a well-balanced manner.

(2) Second Embodiment—FIG. 2 The molding apparatus according to the second embodiment is a die 2 of the first embodiment.
A die 21A is used instead of 1. Forming hole 2 of die 21A
Reference numeral 0 does not have the aperture forming portion 20b, and includes a main portion 20a penetrating to the lower end and an opening 20c. The periphery of the opening 20c on the entrance side is chamfered in a tapered shape.

The material of the second embodiment shown by reference numeral 1B in FIG. 2A has a cylindrical shape having an outer diameter large diameter portion 2 formed at one axial end and an inner diameter small diameter portion 3 formed at the other end. belongs to. The outer diameter of the outer diameter large diameter portion 2 is set to be larger than the inner diameter of the opening 20c of the forming hole 20, and the outer diameter other than the outer diameter large diameter portion 2 is larger than the inner diameter of the main portion 20a. The size is set such that a gap is formed between the outer diameter surface and the inner diameter surface of the opening 20c. Also, the inner diameter of the small-diameter portion 3 is set smaller than the diameter of the core rod 22, and the inner diameter of the portions other than the small-diameter portion 3 is set to a size where a gap is formed between the inner surface and the core rod 22. I have.

FIG. 2A shows the compression molding of the material 1B.
As shown in FIG. 3, the material 1B is fitted into the core rod 22 with the small-diameter inner portion 3 facing upward, and the edge of the lower large-diameter portion 2 on the lower side is brought into contact with the chamfered portion of the opening 20c. As in the embodiment, the core rod 22 and the upper punch 23 are lowered, and the material 1B is pressed into the cavity of the forming hole 20 by the upper punch 23 and is compressed in the axial direction. Material 1
In B, the outer diameter surface at the lower end and the central portion is compressed to the inner diameter side following the inner diameter surface of the main portion 20a of the molding hole 20, and the outer diameter large diameter portion 2 at the lower end disappears. Further, the outer diameter surface at the upper end portion bulges to the outer diameter side until the outer diameter surface is pressed against the inner diameter surface of the opening 20c, and the outer diameter is enlarged, so that the outer diameter large diameter portion 17 is newly formed. on the other hand,
The inner diameter surface has a bearing surface 12 at both ends, and a middle relief 13 between the bearing surfaces 12. In this way, the material 1B is plastically deformed, and the bearing 10B shown in FIG. 2B is formed.

(3) Third Embodiment—FIG. 3 In the third embodiment, as shown in FIG. 3, a raw material 1C is formed using the same forming apparatus as the second embodiment. Material 1C
As shown in FIG. 3 (a), is a cylindrical shape having an outer diameter large diameter portion 2 formed at one axial end and an inner diameter small diameter portion 3 formed at both ends. The outer diameter of the outer diameter large-diameter portion 2 is set to such a size that its outer diameter surface is formed with the opening 20 c of the molding hole 20. Main part 2
It is set larger than the inner diameter of 0a. In addition, the inner diameter of the small-diameter portion 3 is set to such a size that a gap is formed between the inner diameter surface and the core rod 22. The diameter difference between the outer diameter surface and the inner diameter surface is about several μm to several tens μm.

FIG. 3A shows the compression molding of the material 1C.
As shown in the figure, the material 1C is fitted into the core rod 22 with the outer diameter large diameter portion 2 facing upward, and the lower end is formed in the opening 2 of the forming hole 20.
0c, the core rod 22 and the upper punch 23 are lowered in the same manner as in the first embodiment.
As a result, the material 1C is pressed into the cavity of the molding hole 20 and is compressed in the axial direction. The material 1C is plastically deformed similarly to the second embodiment, and as shown in FIG.
The outer diameter large diameter portion 2 at the upper end is formed into a bearing 10C having an outer diameter large diameter portion 2A formed by expanding the diameter.

(4) Fourth Embodiment—FIG. 4 In a fourth embodiment, as shown in FIG. 4, a raw material 1D is formed using the same forming apparatus as in the first embodiment. Material 1D
As shown in FIG. 4 (a), is a cylindrical shape having an outer diameter large diameter portion 2 and an inner diameter small diameter portion 3 formed at one end in the axial direction. Outer diameter large diameter part 2 and outer diameter large diameter part 2 in material 1D
Outside diameters are set smaller than the opening 20c of the forming hole 20 and larger than the main part 20a. The inner diameter of the small-diameter portion 3 is set to be smaller than the diameter of the core rod 22.
The size is set such that a gap is formed between the inner diameter surface and the core rod 22. The diameter difference between the outer diameter surface and the inner diameter surface is about several μm to several tens μm.

FIG. 4 (a) shows the compression molding of the material 1D.
As shown in the figure, the material 1D is fitted into the core rod 22 with the large-diameter outer portion 2 facing upward, and the lower end is formed in the opening 2 of the forming hole 20.
0c, the core rod 22 and the upper punch 23 are lowered in the same manner as in the first embodiment.
The material 1D is pressed into the cavity of the molding hole 20 by pressing.
The material 1D is plastically deformed as in the first embodiment,
As shown in FIG. 4B, the outer diameter large diameter portion 2 at the upper end is formed into a bearing 10D having an outer diameter large diameter portion 2A formed by expanding the diameter.

Next, fifth and sixth embodiments for manufacturing a bearing having a flange and a dynamic pressure groove formed on a shaft support surface will be described. (5) Fifth Embodiment-FIGS. 5 and 6 Reference numeral 1E in FIG . 5A is a material used in the fifth embodiment. This material 1E has a flange 5 (outside large diameter portion) and an inside small diameter portion 3 having a larger diameter than the large outside diameter portion 2 of the material 1B or the like of the second embodiment at one end in the axial direction. It is cylindrical. The flange 5 remains after the compression molding and is used as a fixing means or a positioning means.

A molding apparatus for compression molding the material 1E is shown in FIG.
As shown in the figure, a die 31 having a forming hole 30 and a material 1
E, the core rod 22A and the upper and lower punches 3
3, 34. The forming hole 30 of the die 31 is formed in a stepped shape whose inner diameter is reduced by two steps from the entrance side (upper side) toward the inner part. That is, the forming hole 30 is a cylindrical main portion 30a at the center in the axial direction, a narrowing forming portion 30b at a deeper portion having a smaller diameter than the main portion 30a, and a portion forming a flange with a larger diameter than the main portion 30a. An opening 30c on the entrance side
It is composed of The transition from the opening 30c to the main portion 30a is formed in a horizontal step portion 30d, and the transition from the main portion 30c to the aperture forming portion 30b is formed in a gentle taper shape. The upper punch 33 is the opening 3 of the forming hole 30.
0c, and the lower punch 34 is inserted into the squeeze forming section 30b.

The outer diameter of the flange 5 of the material 1E is set to such a size that a gap is formed between the outer diameter surface and the opening 30c of the forming hole 30, and the outer diameter of the material 1E other than the flange 5 is , Are set slightly larger than the inner diameter of the main portion 30a. Further, the inner diameter of the inner diameter small diameter portion 3 is set to a size such that a gap is formed between the inner diameter surface and the core rod 22A.

The material 1E is compressed in the axial direction, so that the inner diameter surfaces at both ends in the axial direction are pressed against the core rod 22A as in the above embodiments.
6A, as shown in FIG. 6A, a plurality of V-shaped convex portions 22a are formed on the outer diameter surface of the material 1E which is pressed against the inner diameter surfaces at both ends.
Are formed in a herringbone shape at equal intervals in the circumferential direction. The protrusion 22a can be formed by means such as cutting or plating of the core rod 22A, and the height thereof is set to about several μm.

In order to compression-mold the material 1E by the above-mentioned molding apparatus, first, as shown in FIG.
The core rod 22A is held at a position protruding a predetermined length from the upper surface of the die 31 to form a cavity in the forming hole 30. Next, the material 1E is fitted into the core rod 22A with the flange 5 facing upward, and the lower end thereof is inserted into the opening 30c of the forming hole 30 and the portion where the convex portion 22a is formed is fitted to the inner diameter surfaces of both ends of the material 1E. Make it correspond. From this state, as shown in FIG.
At the same time, the upper punch 33 is lowered, and the material 1E is pressed into the cavity of the molding hole 30 by the upper punch 33 and is compressed in the axial direction.

By this operation, the lower end of the material 1E is press-fitted from the main portion 30a of the forming hole 30 into the squeezing portion 30b, the center portion is press-fitted into the main portion 30a, and the outer diameter surface of these portions is compressed toward the inner diameter side. And the outer diameter is reduced. In particular, the lower end portion is formed into the narrowed portion 11 having a smaller diameter than the central portion by being press-fitted into the narrowed portion 30b. The flange 5, which is the upper end of the material 1E, is constrained by the step 30d of the forming hole 30, is compressed in the axial direction by the upper punch 33, and flows plastically to the outer diameter side, and its outer diameter surface is the inner diameter surface of the opening 30c. Until it comes into contact with the flange 5A, and is formed on the flange 5A having an enlarged outer diameter.

Further, by being compressed in the axial direction, the inner diameter surfaces of both ends in the axial direction of the material 1A bulge toward the inner diameter side, and are pressed against the core rod 22A to form the bearing surface 12, and at the same time, the shaft 1 As shown in FIG. 6B, a herringbone-shaped dynamic pressure groove 14 is formed on the support surface 12 by a convex portion 22a. Further, in the inner diameter surface between the bearing surfaces 12, a gap with the core rod 22 </ b> A remains, and the clearance portion 13 is formed. In this way, the material 1E is plastically deformed, and the bearing 10E is formed.

The bearing 10E raises the upper punch 33,
It is obtained by lifting the lower punch 34 together with the core rod 22A and removing it from the die 31. In the demolded bearing 10E, the restraint of the outer diameter surface by the die 31 is released, and spring back occurs in which the entire diameter is slightly increased. Therefore, the protrusion between the dynamic pressure grooves 14 is not worn away from the core rod 22A. The bearing 10E can be removed.

Bearing 10 manufactured according to the fifth embodiment
According to E, in addition to the two-point support structure for supporting the rotating shaft on the shaft supporting surface 12, the dynamic pressure effect generated in the dynamic pressure groove 14 (improvement in rigidity due to increasing the pressure of the lubricating oil flowing into the dynamic pressure groove). The supporting force of the rotating shaft increases synergistically, and the supporting force of the rotating shaft becomes more stable. In addition, from the viewpoint that the effect that the lubricating oil concentrates on a part of the dynamic pressure groove 14 and the dynamic pressure increases is expected, the bearing 10
E is preferably set such that the rotation direction of the rotating shaft is oriented in the direction of the V-shaped tip of the dynamic pressure groove 14 (the direction of arrow R in FIG. 6B).

(6) Sixth Embodiment—FIG. 7 The fifth embodiment is a method of manufacturing a bearing provided with a flange at one end in the axial direction. This is an example of forming a bearing provided with a flange.

The molding apparatus shown in FIG. 7 includes a die 31, a core rod 22A and a lower punch 34 similar to the molding apparatus of the fifth embodiment, and an upper punch 33A replacing the upper punch 33. In this case, the main portion 30a of the forming hole 30 of the die 31 is set shorter than the main portion 30a of the fifth embodiment in accordance with the shape of the material 1F. Upper punch 33A
Has a cylindrical concave portion 33a formed on the punch surface.
The inner diameter of the concave portion 33a is set to be the same as the inner diameter of the main portion 30a of the forming hole 30 of the die 31.

Material 1F of the sixth embodiment shown in FIG.
Is formed with a flange 5 at a central portion in the axial direction. The outer diameter of one end (upper side in the figure) of the flange 5 is smaller than the outer diameter of the other end, and the outer diameter small-diameter portion 9 and the outer diameter, respectively. Large diameter part 2
It has been. Also, on the outer diameter small diameter portion 9 side, there is an inner diameter small diameter portion 3.
Are formed. The outer diameter of the flange 5 is set to be larger than the inner diameter of the opening 30 c of the forming hole 30 of the die 31. In addition, a gap is formed between the outer diameter surface of the outer diameter small-diameter portion 9 and the inner diameter surface of the concave portion 33a of the upper punch 33A, and the outer diameter of the outer diameter large-diameter portion 2 corresponds to the outer diameter surface. The size is such that a gap is formed between the diaphragm forming portion 30a and the inner diameter surface of the main portion 30a, and is larger than the inner diameter of the throttle forming portion 30b.

FIG. 7A shows the compression molding of the material 1F.
As shown in FIG. 5, the material 1F is fitted into the core rod 22A with the outer diameter small diameter portion 9 facing upward, the lower end of the outer diameter large diameter portion 2 is inserted into the main portion 30a of the forming hole 30, and the convex portion 22a is formed. The corresponding portions correspond to the inner diameter surfaces of both ends. From this state, as shown in FIG. 7B, the upper punch 33A is lowered together with the core rod 22A, and the material 1F is pressed into the cavity of the molding hole 30 by the upper punch 33A and is compressed in the axial direction.

By this operation, the outer diameter large diameter portion 2 of the material 1F
Is formed from the main portion 30a of the forming hole 30 to the drawing forming portion 30b.
The outer diameter is reduced by press-fitting, and the outer diameter large diameter part 2 is formed in the narrowed part 11, and the upper part of the outer diameter large diameter part 2 swells to the outer diameter side and is pressed against the inner diameter surface of the main part 30 a. Further, the flange 5 at the central portion in the axial direction is press-fitted into the opening 30c to reduce the outer diameter, and is formed on the flange 5A. Also, by being compressed in the axial direction, the inner diameter surfaces of both ends in the axial direction of the material 1F swell toward the inner diameter side, and are pressed against the core rod 22A to form the bearing surface 12, and at the same time, the bearing surface 12 FIG.
A herringbone-shaped dynamic pressure groove similar to that shown in FIG. Further, in the inner diameter surface between the bearing surfaces 12, a gap with the core rod 22 </ b> A remains, and the clearance portion 13 is formed. In this way, the material 1F is plastically deformed, and the bearing 10F is formed. The bearing 10F is
It is obtained by raising the upper punch 33A, raising the lower punch 34 together with the core rod 22A, and removing the die from the die 31.

The form in which the dynamic pressure grooves are formed on the shaft supporting surface by using the core rods 22A for forming the dynamic pressure grooves as in the fifth and sixth embodiments is of course applicable to the first to fourth embodiments. can do.

(7) Other Embodiments The present invention is not limited to the above-described first to sixth embodiments. For example, the shape of a material, the shape of a manufactured bearing, or the shape of a dynamic pressure groove may vary. It can be changed to a different form. Hereinafter, other embodiments will be described. In each drawing, the same components as those in the above-described embodiment are denoted by the same reference numerals.

A. FIG. 8A shows a material having a flange 5 at one end in the axial direction and a small inner diameter portion 3 at the other end. The position of the flange 5 is arbitrary, and may be formed at the center in the axial direction, for example, like the material 1F of the sixth embodiment (see FIG. 7A). Further, as in the sixth embodiment, it is also possible to use a cylindrical material in which the outside diameter of the portion other than the flange is different.

FIGS. 8B to 8E show a material in which a counterbore-shaped tapered surface 6 is formed on the periphery of the opening of the shaft hole. An outer diameter large diameter portion 2 and an inner diameter small diameter portion 3 are appropriately formed on each material. In these, an annular convex portion 7 whose outer peripheral surface is gentle is formed on one end surface of the materials (c) to (e). In the material shown in FIG. 8 (f), a small-diameter inner diameter portion 3 is formed at one end in the axial direction, and an outer diameter surface of the same end is formed as a tapered small-diameter portion 8 that gradually decreases in diameter toward the end. ing.

In any case including the above embodiments, the boundary between the small inner diameter portion 3 and the other portion on the inner diameter surface is clear (transitions at a right angle), but the boundary between the two. The portion may be formed on a slope. FIG. 8 (g) is a material obtained by arranging the material of FIG. 8 (b) in such a manner.
Further, as shown in FIG. 8 (h), the outer peripheral surface may have a chamfered peripheral edge.

B. The shape of the bearing will be described a modification of the bearing. 9 (a) shows a bearing having a uniform outer diameter, and FIG. 9 (b) shows a bearing in which a throttle portion 11 is formed at one end in the axial direction. FIGS. 9 (c) and 9 (d).
The tapered surface 16 is formed on the periphery of the opening of the shaft hole of these bearings. The bearing shown in FIG. 9E is obtained by chamfering the outer peripheral surface of the bearing shown in FIG. 9C. FIG.
The bearing shown in (f) has a flange 5A formed at one end. The mode in which the tapered surface is formed on the periphery of the opening of the shaft hole can be applied to a bearing having a flange. The bearing shown in FIG. 9G has a spherical shape as a whole, a flat end face in the axial direction, and a cylindrical side face. The bearing shown in FIG. 9H is obtained by forming a throttle 11 at one end of the bearing shown in FIG. 9G.

C. Shape of Dynamic Pressure Groove The shape of the dynamic pressure groove described in the fifth and sixth embodiments is arbitrary, and the number thereof is appropriately selected. However, from the viewpoint of more stably supporting the rotating shaft, a plurality of It is preferable that they are arranged at equal intervals along the circumferential direction of the support surface. In each of the above embodiments, the effect of increasing the dynamic pressure is obtained according to the herringbone shape, that is, the shape, but the effect can also be obtained by the cross-sectional shape of the depth.

In order to achieve this, the general shape is a groove extending along the axial direction. When the rotating shaft rotates in only one direction, the end of the rotating shaft in the direction opposite to the rotating direction is the deepest portion. From the section to the direction of rotation of the rotating shaft. When the rotating shaft rotates in both the forward and reverse directions, the middle part in the circumferential direction is set as the deepest part, and the inclination is made so as to gradually become shallower from the deepest part toward both ends in the circumferential direction. The thus formed dynamic pressure groove has a wedge-shaped gap in which the cross-section (cross-section when cut into a circle) becomes shallower in the direction of rotation of the rotary shaft, and the lubricating oil concentrates on the shallow tip of the groove. A wedge effect can be obtained.

D. The core rod for forming the dynamic pressure groove The dynamic pressure groove 14 shown in the fifth and sixth embodiments is formed by the convex portion 22a formed on the core rod 22A.
Instead of such a convex part, a dynamic pressure groove can be formed by a concave part. That is, the engraving pattern is opposite to that of the fifth and sixth embodiments, and when the inner diameter surface of the inner diameter small diameter portion of the material is pressed against the core rod, it is introduced into the recess formed in the core rod and the projection is projected. The inner diameter surface of the projection functions as a bearing surface, and the groove between the projections functions as a dynamic pressure groove. In this case, by further projecting the convex portion, a bearing having a large amount of middle clearance by its height can be obtained. The concave portion formed in the core rod can be formed by means such as electric discharge machining or electrolytic corrosion.

[0049]

As described above, according to the present invention,
A two-point support structure bearing with a relatively large middle relief
It can be efficiently manufactured by a relatively simple method. In the bearing manufactured by the present invention, the inner diameter and the coaxiality of the bearing surfaces at both ends in the axial direction are matched with high accuracy, and the density is increased to improve wear resistance.
On the other hand, in the central portion in the axial direction where the middle relief portion is formed,
Since the density is low, the content of the lubricating oil is sufficiently ensured. As a result, excellent bearing performance is exhibited.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing steps of a method for manufacturing a bearing according to a first embodiment of the present invention in the order of (a) and (b).

FIG. 2 is a longitudinal sectional view showing steps of a method for manufacturing a bearing according to a second embodiment of the present invention in the order of (a) and (b).

FIG. 3 is a longitudinal sectional view showing steps of a method for manufacturing a bearing according to a third embodiment of the present invention in the order of (a) and (b).

FIG. 4 is a longitudinal sectional view showing steps of a method for manufacturing a bearing according to a fourth embodiment of the present invention in the order of (a) and (b).

FIG. 5 is a longitudinal sectional view showing steps of a method for manufacturing a bearing according to a fifth embodiment of the present invention in the order of (a) and (b).

FIG. 6A is a partial perspective view of a core rod used in a fifth embodiment of the present invention, and FIG. 6B is a vertical perspective view showing a part of a bearing manufactured in the fifth embodiment of the present invention. is there.

FIGS. 7A and 7B are longitudinal sectional views showing steps of a method for manufacturing a bearing according to a sixth embodiment of the present invention in the order of FIGS.

FIG. 8 is a longitudinal sectional view showing another embodiment of the bearing material used in the present invention.

FIG. 9 is a longitudinal sectional view showing another embodiment of the bearing manufactured by the present invention.

[Explanation of symbols]

 1A to 1F: Material 2: Large outer diameter part 3: Small inner diameter part 5: Flange of material (large outer diameter part) 10A to 10F: Bearing 12: Bearing surface 13: Middle relief part 14: Dynamic pressure groove 20 , 30: forming hole 22, 22A: core rod 22a: convex portion for forming dynamic pressure groove

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3J011 AA04 BA02 CA01 CA02 DA02 JA02 LA01 SB19 4K018 CA13 CA13 FA15 FA46 HA03 KA03 KA22

Claims (6)

[Claims] A core rod is made of a cylindrical material having a small inner diameter portion at least at one end in the axial direction and having a uniform outer diameter or a large outer diameter portion at a part of the outer diameter surface. In the inserted state, the material is pressed into the forming hole of the mold and compressed in the axial direction, so that the outer diameter surface of one end in the axial direction of the material is compressed to the inner diameter side to reduce the outer diameter while the axial direction is reduced. By expanding the outer diameter surface of the other end to increase the outer diameter, along with this deformation, the inner diameter surfaces of both ends in the axial direction are pressed against the core rod to form a bearing surface for supporting the rotating shaft, A method for manufacturing a bearing, comprising: forming between a shaft support surface a middle relief portion having an inner diameter larger than that of the shaft support surface and not contacting a rotating shaft. 2. The method according to claim 1, wherein the material has a uniform outer diameter and a shape having a small inner diameter portion at one axial end. 3. The material according to claim 1, wherein the material has a small-diameter inner diameter portion at one axial end and a large-diameter outer diameter portion at the other axial end. Manufacturing method of bearing. 4. The bearing according to claim 1, wherein the material has a shape having a small inner diameter portion at both ends in the axial direction and a large outer diameter portion at one end in the axial direction. Manufacturing method. 5. The method for manufacturing a bearing according to claim 1, wherein the material has a shape having a small inner diameter portion and a larger outer diameter portion at one end in the axial direction. 6. A convex or concave portion for forming a dynamic pressure groove is formed on an outer diameter surface of the core rod to which inner diameter surfaces of both ends in the axial direction of the material are pressed. The method for producing a bearing according to any one of claims 1 to 5.