JP2001059106A - Manufacture of bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently manufacture a bearing of two-point support structure with a sintered body built in a housing and having excellent bearing performance in a relatively simple method. SOLUTION: This manufacturing method comprises a disposing process in which housing 21 is disposed in a forming hole 30 and a press-fitting process in which a core rod 32 having a large diameter part 32b for forming a dynamic pressure groove is inserted into the stock 1A, the large diameter part 32b is held in a condition corresponding to the inside diameter surface of a center part in the axial direction of the stock 1A and the stock 1A is press-fitted in the housing 21. In the press-fitting process, the outside diameter surface of the stock 1A is pressed against the inside diameter surface of the housing 21, the inside diameter surface of the stock 1A is pressed against the core rod 32, and an inner relief part 13 and a pivotably supported surface 12 are formed by the large diameter part 32b and the core rod body part 32a of the core rod 32, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing suitable for use in 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 relates to a method of manufacturing a bearing of a type in which a bearing body having a middle relief portion that does not contact a rotating shaft is incorporated in a housing. The bearing body is formed by molding a material made of a sintered body or a porous body obtained by sizing the sintered body, 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. However, as a bearing, there is a type in which a sintered body is incorporated in a housing in addition to a sintered body alone. By the way, in the case where the above-mentioned middle relief portion is formed, if the middle relief portion is formed by machining the sintered body, the pores exposed on the inner diameter surface are crushed, which hinders the circulation operation of the lubricating oil. Become. For this reason, it is preferable to form the middle relief portion at the same time in the sizing step of the sintered body, or to form the middle relief portion by deforming the sintered body again after sizing. In any case, the two inner shafts are separated from each other by causing plastic deformation in the sintered body such that the inner diameter surfaces at both ends in the axial direction project radially inward or the central portion in the axial direction swells radially outward. The supporting surface and the clearance between them are formed on the inner diameter surface at the same time.

[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 and that the supply amount of the lubricating oil to the bearing surface be sufficient. However, although various methods of plastically deforming a sintered body have been conventionally proposed, a certain manufacturing method that is relatively simple and does not sufficiently satisfy requirements for improving bearing performance has been found at present. there were. Also, in a bearing of a type in which a sintered body is incorporated in a housing, even if the bearing is formed into a housing after forming a bearing surface and an intermediate relief portion, the sintered body is deformed due to deformation. In many cases, the inner diameter of the surface is different or the coaxiality is impaired, and it is extremely difficult to size the sintered body after the assembly to form the bearing surface and the middle relief.

Therefore, the present invention provides a bearing having a two-point support structure in which a sintered body is incorporated in a housing, by a relatively simple method, efficiently and with excellent bearing performance (the inner diameter of two bearing surfaces, It is an object of the present invention to provide a method capable of manufacturing a rotating shaft having a coaxiality having the same bearing capacity, lubricating property, and wear resistance.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to a cylindrical member having a central relief portion in which the rotating shaft does not come into contact with an inner diameter surface at a central portion in the axial direction, and rotating at both axial ends on both sides of the central relief portion. A method for manufacturing a bearing in which a bearing main body having a shaft supporting surface for supporting a shaft is incorporated in a cylindrical housing, comprising: an arranging step of arranging the housing in a molding hole; A press-fitting step of press-fitting the material coaxially into a housing arranged in the molding hole while maintaining a state in which the core rod having the diameter portion is inserted into the material to be molded into the bearing body. The outer diameter surface of the raw material is pressed against the inner diameter surface of the housing, while the inner diameter surface of the raw material is pressed against the core rod to form a middle relief portion and a bearing surface on the inner diameter surface. 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 arrangement step, for example, the housing is pressed into the molding hole. In this case, the outer diameter of the housing is larger than the inner diameter of the forming hole, and the housing is tightly fitted in the forming hole. In order to dispose the housing in the molding hole, an intermediate fitting in which the housing is simply inserted into the molding hole and fitted thereto, or a loose fit in which a gap is formed between the outer diameter surface of the housing and the inner diameter surface of the molding hole, may be used. Form.

In the above press-fitting step, the material is inserted into the core rod penetrating the housing, and the material is inserted into the housing while maintaining a state in which the large-diameter portion of the core rod corresponds to the inner diameter surface at the axial center portion of the material. Press in and press-fit. In the present invention, the shapes and dimensions of the housing and the material are set such that the following relationship can occur. That is, when the material is press-fitted into the housing, the material pressed against the inner diameter surface of the housing is reduced in diameter and both are pressed against each other,
The inner diameter surface of the material is pressed against the core rod, and a large relief portion is formed on the inner diameter surface by the large diameter portion of the core rod, and bearing surfaces are formed on both sides of the middle relief portion. Preferably, the material and the housing have the same axial length.

According to the present invention, by adopting a combination of a material and a housing in which the above-described modification is appropriately made, the bearing main body is incorporated in the housing, and the amount of clearance is reduced. A bearing having a two-point support structure having a relatively large middle relief can be efficiently manufactured by a relatively simple method. In addition, since the middle relief portion is formed by being pressed against the large diameter portion of the core rod, by forming the large diameter portion accurately, the middle relief portion can be reliably and accurately formed in the desired shape and dimensions. Can be formed.

Further, since the bearing surface formed on the bearing body is formed by pressing the inner diameter surface of the material strongly 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 middle relief portion can have a lower density than the bearing surface, so that the lubricating oil content increases and the lubrication of the bearing surface can be improved. As a result, a bearing having a high level of bearing performance can be manufactured.

In a preferred embodiment of the present invention, a convex portion or a concave portion for forming a dynamic pressure groove is formed on the outer diameter surface of the core rod to which the 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. Also,
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) The support force of the rotating shaft is synergistically increased by the improvement of the rigidity accompanying the high pressure, and the supporting force of the rotating shaft can be further stabilized.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. (1) First Embodiment-FIG. 1 FIGS . 1A to 1C show a bearing forming process according to a first embodiment.
These are shown in the order of (d). In the present embodiment, the housing 21 is arranged in the die 31 of the molding apparatus, and then the material 1A is press-fitted into the housing 21 to manufacture a bearing.

As shown in FIG. 1, the molding apparatus includes a die 31 having a molding hole 30 into which the housing 21 is press-fitted, a core rod 32, and upper and lower punches 33 and 34. The forming hole 30 of the die 31 has a shape corresponding to the housing 21. As shown in FIG. 1A, the forming hole 30 is provided on the inlet side (upper side) of the cylindrical main portion 30a via a horizontal step portion 30d. An opening 30c having a larger diameter than the main portion 30a is formed.

As shown in FIG. 1A, the core rod 32
In the vicinity of the upper end portion, a large-diameter portion 32b having a larger diameter than the other main portion (herein referred to as the main body portion 32a).
Are formed coaxially with the main body 32a. The large-diameter portion 32b forms a middle relief portion on the inner diameter surface of the material 1A, and has a step of about several μm from the main body portion 32a. The length of the large diameter portion 32b is, for example, about half of the length of the material 1A. FIG. 1 (c)
As shown in the figure, the length of the main body portion 32a above the large-diameter portion 32b is set to such a size that the upper end thereof can slightly protrude from the material 1A in a state where the large-diameter portion 32b is arranged in the axial center of the material 1A. Is set.

As shown in FIG. 1B, the upper punch 33
The lower punch 34 is slidably inserted into the opening 30 c of the forming hole 30, and the lower punch 34 is slidably inserted into the main portion 30 a of the forming hole 30.
The lower punch 34 has a large diameter portion 32 of the core rod 32.
The main body portion 32a lower than b is slidably inserted. And the main body part 32a above the large diameter part 32b
Are slidably inserted into the upper punch 33.

As shown in FIG. 1 (a), the housing 21 has a uniform inner diameter, and has a cylindrical shape in which a flange 23 is formed at one end of a cylindrical portion 22 which forms a main body. Cylindrical part 2
The outer diameter of 2 is larger than the inner diameter of the main part 30a of the forming hole 30, and the outer diameter of the flange 23 is set to be larger than the inner diameter of the opening 30c. Further, with respect to the axial length (height), the cylindrical portion 22 is set shorter than the main portion 30a of the forming hole 30, and the flange 23 is set shorter than the opening 30c. The housing 21 is made of a material that can be press-fit into the forming hole 30 while being plastically deformed. For example, bronze, brass,
Sintered materials are used in addition to aluminum alloys and steels. In the case of using a sintered material, if a material having pores larger than the material 1A is used, the oil impregnated in the housing 21 is effectively supplied to the bearing main body side by capillary force, so that the bearing life can be extended. preferable.

The material 1A shown in FIG. 1C is a sintered body or a cylindrical porous body formed by sizing the sintered body. The outer diameter surface of the material 1A is mainly composed of an outer diameter small diameter portion 4a having an outer diameter larger than the inner diameter of the housing 21, and an outer diameter large diameter portion 4b having a diameter larger than the outer diameter small diameter portion 4a at one end. Is formed. The other end of the inner diameter surface of the material 1A (the end opposite to the outer diameter large diameter portion 4b) is provided with an inner diameter small diameter portion 3.
a is formed. The inner diameter of the small-diameter portion 3a can be inserted into the large-diameter portion 32b of the core rod 32 while sliding, and a small gap is formed between the inner diameter surface and the main body 32a of the core rod 32. Dimensions are set. The inner diameter of the large-diameter portion 3b other than the small-diameter portion 3a is naturally set to be larger than the small-diameter portion 3a. The axial length of the material 1A is set equal to that of the housing 21.

Next, a procedure for manufacturing a bearing by a molding apparatus will be described. [Step 1-Housing Arrangement] As shown in FIG. 1A, the upper end of the lower punch 34 inserted into the main portion 30a of the forming hole 30 of the die 31 is held at the same level as the step portion 30d, while the core rod 32 is held. From the upper surface of the die 31 for a predetermined length. Next, the housing 21 with the flange 23 facing up
Is coaxially fitted into the core rod 32 to form a lower punch 34.
Set on top. Next, as shown in FIG. 1B, the upper punch 33 and the core rod 32 are both lowered, and the upper punch 33 pushes the housing 21 into the forming hole 30. The lower punch 34 is lowered together with the housing 21. The housing 21 includes a cylindrical portion 22 having a main portion 30 a of a molding hole 30.
Then, the flanges 23 are press-fitted into the openings 30 c, respectively, so that the outer diameter surface is restrained by the die 31.

[Step 2—Press-fitting of Material] After the upper punch 33 is lifted and retracted once, as shown in FIG.
A state in which the material 1A is fitted on the core rod 32 with the outer diameter large diameter portion 4b facing upward and placed on the housing 21, and the large diameter portion 32b of the core rod 32 corresponds to the axial center of the inner diameter surface of the material 1A. And Next, as shown in FIG. 1D, the upper punch 33 is lowered again, and the material 1A is pushed into the housing 21 by the upper punch 33 and press-fitted.
At this time, the core rod 32 is lowered integrally with the material 1A.

When the material 1A is pressed into the housing 21, its outer diameter surface is plastically deformed in accordance with the inner diameter surface of the housing 21, and its diameter is reduced over its entire length. The diameter surface becomes straight, and the outer diameter surface is pressed against the inner diameter surface of the housing 21. On the other hand, the inner diameter surface of the raw material 1 </ b> A is plastically deformed following the core rod 32, and is pressed against the core rod 32 to form the shaft support surface 12 and the middle relief 13. That is, the small-diameter portion 3a at the lower end of the material 1A protrudes toward the inner diameter side, and the inner diameter surface is formed on the shaft support surface 12 that presses against the main body portion 32a of the core rod 32 and supports the rotary shaft. Also, the outer diameter large diameter portion 4 which has disappeared
b flows plastically to the inner diameter side, and the inner diameter surface presses against the main body portion 32a of the core rod 32, and the other bearing surface 1
2 is formed. Further, a large-diameter portion 3 at the central portion in the axial direction.
b is weakly pressed against the large-diameter portion 32b of the core rod 32 and is formed in the middle escape portion 13 where the rotating shaft does not contact.

As a result of the plastic deformation of the material 1A, the material 1A is formed into the bearing body 10A, and the bearing 20A in which the bearing body 10A and the housing 21 are integrated is formed. The bearing 20A raises and retracts the upper punch 33 and, together with the core rod 32, lower punch 3
4 is lifted and the mold is released from the die 31. Thereafter, the core rod 32 is lowered to obtain the bearing 20A. In the demolded bearing 20A, since the outer diameter surface is restrained by the die 31 and spring back is generated, the core rod 32 is pulled out of the bearing 20A without being hindered by the large diameter portion 32b. Can be.

According to the first embodiment, the housing 2
1 is press-fitted into the die 31 and then the raw material 1A is press-fitted into the housing 21 by a simple method such that the bearing body 10A made of a sintered body is incorporated in the housing 21. The bearing 20A can be manufactured efficiently. Also, since the middle relief portion 13 is formed by being pressed against the large diameter portion 32b of the core rod 32, by forming the large diameter portion 32b accurately, the middle relief portion 13 can be formed into a desired shape and dimensions. It can be formed reliably and with high precision.

Since the bearing surface 12 of the bearing 20A is formed by pressing the inner diameter surface of the material 1A strongly against the core rod 32, the inner diameter and the coaxiality match with high precision, and the density is increased. Excellent in abrasion resistance and rotating shaft support force. On the other hand, since the middle relief portion 13 can be pressed against the core rod 32 weakly, the density is lower than that of the bearing surface 12, and therefore, the content of the lubricating oil can be increased, and the lubrication of the bearing surface 12 can be increased. The performance is improved. As a result, the bearing 20A exhibits excellent bearing performance.
Also, since the degree of compression of both the bearing surfaces 12 can be made substantially equal, the porosity of the bearing surfaces 12 is equalized, so that the hydraulic pressure generated on the bearing surfaces 12 is also equalized, and Can be supported in a well-balanced manner.

In the above embodiment, the housing 21
The outer diameter of the hole is a size that is pressed into the forming hole 30 to be tightly fitted. However, the outer diameter is a size that is fitted into the forming hole 30 in the middle, or a slight gap is formed between the outer diameter of the forming hole 30 and the inner diameter surface. The dimensions may be such that the loose fit is formed. If the outer diameter of the housing 21 is such that there is a gap between the outer diameter surface of the housing 21 and the fitting hole 30, the housing 21 is press-fitted when the material 1A is pressed.
Although it is not preferable because there is a possibility that the diameter of the housing 21 may be increased, it is not limited as long as the housing 21 has a high rigidity and expands in an elastic deformation region, that is, does not plastically deform.

(2) Second Embodiment FIG. 2 Next, a second embodiment of the present invention will be described. The forming apparatus according to the second embodiment is obtained by changing the forming hole 30 and the lower punch 34 of the die 31 used in the first embodiment. The molding hole 30 in this case is, as shown in FIG.
A small-diameter portion 30b having a smaller diameter than the main portion 30a is formed in a deeper portion (lower portion) of the lower portion 3a.
4 is inserted. In the second embodiment, a housing 21 similar to that of the first embodiment, and FIG.
A bearing is manufactured from the material indicated by reference numeral 1B in (c).

In this case, the outer diameter of the cylindrical portion 22 of the housing 21 is larger than the inner diameter of the small-diameter portion 30b and slightly smaller than the inner diameter of the main portion 30a of the forming hole 30. Reference numeral 22 is set to a size that fits in the state of intermediate fitting. The outer diameter of the flange 23 is set to be larger than the inner diameter of the opening 30c as in the first embodiment.

The material 1B has a uniform outer diameter, and the outer diameter is set larger than the inner diameter of the housing 21. An inner diameter small diameter portion 3a is formed at one axial end of the inner diameter surface. The inner diameter of the inner diameter small diameter portion 3a is larger than the outer diameter of the main body portion 32a of the core rod 32 and smaller than the outer diameter of the large diameter portion 32b, so that a small gap is formed between the inner diameter surface and the main body portion 32a. It is set to the size to be formed. The inner diameter of the large-diameter portion 3b other than the small-diameter portion 3a is set to such a size that a minute gap is formed between the inner diameter surface and the large-diameter portion 32b of the core rod 32.

Next, a procedure for manufacturing a bearing by a molding apparatus will be described. [Step 1-Housing Arrangement] As shown in FIG. 2A, the housing 21 with the flange 23 facing upward is set in a molding apparatus, and then, as shown in FIG. Into the forming hole 30. In the housing 21, the lower end of the cylindrical portion 22 is press-fitted into the small diameter portion 30b of the forming hole 30, the narrowed portion 25 is formed, and the flange 23 is press-fitted into the opening 30c. Housing 21
Is in a state where the outer diameter surface is restricted by the die 31.

[Step 2—Press-fitting of Material] After the upper punch 33 is lifted and retracted once, as shown in FIG.
The material 1B is fitted on the core rod 32 with the small-diameter inner diameter portion 3a facing upward and placed on the housing 21, and the large-diameter portion 32b of the core rod 32 is made to correspond to the axial center of the inner diameter surface of the raw material 1B. . Next, as shown in FIG. 2D, the material 1B is pushed into the housing 21 by the upper punch 33 and press-fitted. At this time, the core rod 32 is lowered integrally with the material 1B.

When the material 1B is press-fitted into the housing 21, its outer diameter surface is plastically deformed to follow the inner diameter surface of the housing 21, and its diameter is reduced over its entire length. Thus, the squeezed portion 11 is formed, and the outer diameter surface is pressed against the inner diameter surface of the housing 21. On the other hand, the inner diameter surface of the material 1 </ b> B is plastically deformed following the core rod 32, and is pressed against the core rod 32 to form the shaft support surface 12 and the middle relief portion 13. That is,
The inner diameter surface of the throttle unit 11 is formed on the shaft support surface 12 that presses against the main body 32a of the core rod 32 and supports the rotating shaft. The large-diameter portion 3b at the upper end of the material 1B protrudes toward the inside diameter, and the inside surface is pressed against the main body portion 32a of the core rod 32 and is formed on the other shaft support surface 12. Furthermore, the large-diameter large-diameter portion 3b at the central portion in the axial direction is
2b is formed in the middle escape portion 13 in pressure contact with the rotating shaft without contact.

By plastically deforming the material 1B, the material 1B is formed into the bearing body 10B, and the bearing 20B in which the bearing body 10B and the housing 21 are integrated is formed. The bearing 20B raises and retracts the upper punch 33, and moves the lower punch 3 together with the core rod 32.
4 can be removed from the die 31 by raising it, and then the core rod 32 can be taken out by lowering.

(3) Third Embodiment—FIGS. 3 and 4 In the third embodiment, as shown in FIG.
2. The core rod 42 for forming a dynamic pressure groove instead of
This is an example in which a material 1A is formed by applying to the embodiment, and a bearing in which a dynamic pressure groove is formed on a shaft support surface 12 is formed. The core rod 42 has a main body 42a similar to the core rod 32.
And a large-diameter portion 42b.
As shown in FIG. 5, a plurality of V-shaped convex portions 43 are formed in a herringbone shape at equal intervals in the circumferential direction on an outer diameter surface of the material 1A which is pressed against inner diameter surfaces at both ends. The protrusion 43 can be formed by means such as cutting or plating of the core rod 42, and its height is several μm.
m.

In order to form the bearing, the housing 21 is press-fitted into the forming hole 30 in the same manner as in the first embodiment, and then, as shown in FIG. The portions of the core rod 42 where the protrusions 43 are formed correspond to the inner diameter surfaces of both ends of the material 1A. From this state,
As shown in FIG. 3B, the material 1A is pressed into the housing 21 by the upper punch 33 while the core rod 42 is lowered, and the bearing 20C in which the bearing body 10C is incorporated in the housing 21 is obtained.

The bearing surface 12 of the bearing body 10C has a structure shown in FIG.
As shown in (b) (the housing 21 is omitted in the figure), a herringbone-shaped dynamic pressure groove 14 is formed by the projection 43 of the core rod 42. Demolded bearing 20
In C, since the outer diameter surface is restrained by the die 31 to be released and the whole diameter slightly expands, spring back occurs. Therefore, it is necessary to remove the bearing 20C from the core rod 42 without abrading the convex portion between the dynamic pressure grooves 14. Can be.

Bearing 20 manufactured according to the third embodiment
According to C, in addition to the two-point support structure that supports the rotating shaft on the shaft supporting surface 12, due to the dynamic pressure effect generated in the dynamic pressure groove 14 (improved rigidity due to the high 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. From the viewpoint that the effect that the lubricating oil concentrates on a part of the dynamic pressure groove 14 and the dynamic pressure rises is sufficiently expected, the bearing 20
C is preferably set so 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. 4B).

The form in which the dynamic pressure grooves are formed on the shaft supporting surface using the core rods 42 for forming the dynamic pressure grooves as in the third embodiment can be applied to the second embodiment.

The shape of the dynamic pressure groove shown in the third embodiment is arbitrary, and the number thereof is also selected as appropriate. However, from the viewpoint of more stably supporting the rotating shaft, a plurality of grooves are formed on the bearing surface. It is preferable that they are arranged at equal intervals along the circumferential direction. In the third embodiment, the effect of increasing the dynamic pressure is obtained as a herringbone shape, that is, depending on the shape.
The effect can also be obtained depending on 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.

The dynamic pressure groove 14 shown in the third embodiment
Is formed by the convex portion 43 formed on the core rod 42, but a dynamic pressure groove can be formed by a concave portion instead of such a convex portion. That is, the pattern of the engraving is opposite to that of the third embodiment, and when the inner diameter surface of the inner diameter small diameter portion of the material 1A is pressed against the core rod, it is introduced into the concave portion formed in the core rod, and the convex portion protrudes. The inner diameter surface of the convex portion functions as a bearing surface, and the groove between the convex portions 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.

[0040]

As described above, according to the present invention,
The bearing body is configured to be incorporated in the housing,
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 can be reduced, the lubricating oil content can be sufficiently ensured. As a result, excellent bearing performance is exhibited.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a manufacturing process of a bearing according to a first embodiment of the present invention in the order of (a) to (d).

FIG. 2 is a longitudinal sectional view showing a manufacturing process of a bearing according to a second embodiment of the present invention in the order of (a) to (d).

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

FIG. 4A is a partial perspective view of a core rod used in a third embodiment of the present invention, and FIG. 4B is a vertical perspective view showing a part of a bearing manufactured in the third embodiment.

[Explanation of symbols]

 1A, 1B: Material 10A, 10B, 10C: Bearing body 12: Bearing surface 13: Middle relief portion 14: Dynamic pressure groove 20A, 20B, 20C: Bearing 21: Housing 30: Forming hole 32, 42: Core rod 32b, 42b … Large diameter part of core rod 43… Protrusion for forming dynamic pressure groove

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3J011 AA07 AA20 BA02 CA01 CA02 DA02 JA02 LA01 MA02 4K018 AA04 CA15 FA03 FA43 HA03 KA03

Claims (2)

[Claims] An inner surface of a cylindrical, central portion in the axial direction, which has a central relief portion in which the rotary shaft does not contact, and a shaft supporting surface for supporting the rotary shaft at both axial ends on both sides of the central relief portion. A method of manufacturing a bearing, wherein a bearing body having a large diameter portion capable of forming the middle relief portion is provided. A press-fitting step of press-fitting the material coaxially into a housing arranged in the molding hole while maintaining a state of being inserted into the material to be molded into the bearing body, wherein in the press-fitting step, an outer diameter surface of the material is provided. A method for manufacturing a bearing, comprising: pressing an inner diameter surface of a raw material against a core rod while pressing the inner diameter surface of the material against a core rod, and forming the middle relief portion and the bearing surface on the inner diameter surface. 2. A convex portion or a 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. 3. The method for producing a bearing according to item 1.