JP2001050274A - Manufacture of bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a bearing of two-point support structure where sintered body is incorporated into a housing, efficiently in a relatively simple manner to give appreciable bearing performance. SOLUTION: A housing 21 is fitted in a die 31 wherein its diametrally external surface is restrained, and a raw material 1A is inserted in the housing 21. With a core rod 32 of a uniform outside diameter pressed in the raw material 1A, the raw material 1A is axially compacted with inner punches 33B and 34B of an upper and a lower punch 33 and 34, so that the diametrally external surface of the raw material 1A is bonded under compression to the diametrally internal surface of the housing 21 while the diametrally internal surface thereof is pressed at both axial ends against the core rod 32 to form shaft supporting surface 12 with an intermediate recess 13 in between. The raw material 1A is formed under deformation into a bearing body 10A, which is compression-bonded to the housing 21 to finish a bearing 20A.

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 compressing 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 compressing 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 relates to a method for manufacturing a bearing in which a cylindrical bearing main body is incorporated in a cylindrical housing, wherein a cylindrical material molded into the bearing main body is provided in the housing. By inserting the core rod with a uniform outer diameter into the material and compressing the material in the axial direction, the outer diameter surface of the material is pressed against the inner diameter surface of the housing, while the inner diameter surfaces of both ends in the axial direction of the material are compressed. Are pressed against the core rod to form on a bearing surface that supports the rotating shaft, and a middle relief portion that does not contact the rotating shaft is formed between these bearing surfaces. 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 material having a uniform outer diameter is inserted into a housing whose outer diameter is restricted by being fitted into a molding hole of a molding die, and a diameter is formed between the material and the inner diameter of the material. A molding method is employed in which only the material is axially compressed by a punch from a state in which the core rod having the material is inserted into the material. The outer surface of the material bulges and is pressed against the inner surface of the housing. In addition, the inner diameter surfaces of both ends in the axial direction of the material bulge toward the inner diameter side and are pressed against the core rod to be formed on the bearing surface, and a middle relief portion is formed between the bearing surfaces.
The material is thus plastically deformed and formed into a bearing body, and the outer diameter surface is pressed against the housing inner diameter surface to be integrated with the housing. The present invention employs a combination of a material and a housing and a molding die in which such a deformation mode is appropriately made, so that the bearing main body is incorporated in the housing, and the clearance amount is relatively small. A bearing having a two-point support structure having a large middle clearance can be efficiently manufactured by a relatively simple method.

Further, since the bearing surface formed on the bearing body 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 precision. Further, since the density of the bearing surface can be increased, the wear resistance is improved. On the other hand, it is possible to make the density of the inner diameter surface where the middle relief portion is formed lower than that of the bearing surface, and it is possible to form the diameter of the middle relief portion relatively large, so that the lubricating oil content and the oil retention amount are reduced. It can be increased, and the lubricity is improved. As a result, a bearing having a high level of bearing performance can be manufactured.

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 an axial direction of a 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 can be further stabilized.

[0010]

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.
They are shown in the order of (f). In the first embodiment, the housing 21 is fitted to the molding apparatus, and the material 1A fitted in the housing 21 is compressed in the axial direction to obtain the bearing 20A. The molding apparatus includes a die 31 having a fitting hole 30 into which the housing 21 fits, a core rod 32, and upper and lower punches 33 and 34. The fitting hole 30 of the die 31 has a shape corresponding to the housing 21, and as shown in FIG. 1 (a), is provided on the entrance side (upper side) of the cylindrical main part 30a via a horizontal step part 30d. An opening 30c having an inner diameter larger than that of the main portion 30a is formed.

As shown in FIG. 1 (b), the upper punch 33 is slidably inserted into the opening 30c of the fitting hole 30 and is slidably inserted into the outer punch 33A. And an inner punch 33B. As shown in FIG. 1A, the lower punch 34 includes an outer punch 3 slidably inserted into the main portion 30a of the fitting hole 30.
4A and an inner punch 34B slidably inserted into the outer punch 34A. Upper and lower punches 3
The outer diameters of the inner punches 33B and 34B of the third and the third are the same. The core rod 32 includes upper and lower inner punches 33B, 34.
B is slidably inserted into B.

As shown in FIG. 1 (a), the housing 21 is a cylindrical one having a uniform inner diameter and a flange 23 formed at one end of a main cylindrical portion 22.
The cylindrical portion 22 is fitted to the main portion 30a of the fitting hole 30, and the outer diameter of the flange 23 is fitted to the opening 30c in an intermediate fitting state. As for the length (height) in the axial direction, the cylindrical portion 22 has a main portion 30 a of the fitting hole 30.
And the flange 23 is set shorter than the opening 30c. Further, the inner diameter of the housing 21 is set to a size in which the inner punches 33B, 34B of the upper and lower punches 33, 34 are slidably inserted. Housing 2
Although the material of 1 is arbitrary, for example, a sintered material is used in addition to bronze, brass, an aluminum alloy, and steel. 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 raw material 1A is formed by sizing a sintered body or a sintered body, and has a simple cylindrical shape having uniform outer and inner diameters. The length of the material 1A in the axial direction is substantially the same as that of the housing 21, the outer diameter is a dimension fitted in the housing 21, and the inner diameter is a gap between the inner diameter surface and the core rod 32. The dimensions are set respectively.

Next, a procedure for manufacturing a bearing by a molding apparatus will be described. [Step 1-Fitting of Housing] As shown in FIG. 1A, the upper end of the lower punch 34 inserted into the main portion 30a of the fitting hole 30 of the die 31 is held at the same level as the step portion 30d. The core rod 32 is protruded from the upper surface of the die 31 by a predetermined length. The housing 21 with the flange 23 facing up is coaxially fitted into the core rod 32, and is placed and set on the outer punch 34A of the lower punch 34. As a setting state of the housing 21, the lower punch 34 may be slightly lowered from the step portion 30d, and the lower end portion of the cylindrical portion 22 may be fitted to the main portion 30a. Next, as shown in FIG.
Is lowered, and the housing 21 is pushed into the fitting hole 30 by the outer punch 33A of the upper punch 33 to be fitted. The lower punch 34 is lowered together with the housing 21. The housing 21 is in a state where the outer diameter surface is restrained by the die 31.

[Step 2—Compression of Material] The upper punch 33 is raised and retracted once, and the material 1A is fitted on the core rod 32 and set on the housing 21 as shown in FIG. Next, the upper punch 33 is lowered again as shown in FIG.
The material 1A is pushed into the housing 21 to be fitted. At this time, the core rod 32 is moved down following the material 1A. Next, as shown in FIG. 1E, the inner punches 33B and 34B of the upper and lower punches 33 and 34 are put into the material 1 respectively.
A is moved to the A side, and only the material 1A is compressed in the axial direction.

The compressed material 1A is subjected to the action of expanding the outer diameter surface, and the outer diameter surface is pressed against the inner diameter surface of the housing 21. Also, the inner diameter surfaces of both ends in the axial direction of the material 1 </ b> A bulge toward the inner diameter side and are pressed against the core rod 32 to be formed on the shaft support surface 12. Further, a gap between the shaft support surface 12 and the core rod 32 remains on the inner diameter surface, and the middle escape portion 13 is formed. On the other hand, the housing 21
Is pressed from the material 1A to the outer diameter side, and the outer diameter surface is pressed against the inner diameter surface of the fitting hole 30. The material 1A is plastically deformed as described above to be formed into the bearing main body 10A, and the bearing main body 10A is press-bonded to the inner diameter surface of the housing 21 to form a bearing 20A in which both are integrated.

[Step 3-Demolding of bearing] The upper punch 33 is raised and retracted, and as shown in FIG. 1 (f), the lower punch 34 is raised together with the core rod 32 to take out the bearing 20 A from the die 31. Demold. Thereafter, the core rod 32 is lowered to obtain the bearing 20A.

According to the first embodiment, the housing 21 is fitted to the die 31 of the molding apparatus.
A bearing 20A having a two-point support structure in which a bearing main body 10A made of a sintered body is incorporated in a housing 21 by a simple method of fitting the raw material 1A therein and then compressing only the raw material 1A in the axial direction. It can be manufactured efficiently.

Since the bearing surface 12 of the bearing 20A is formed by strongly pressing the inner diameter surface of the material 1A against the core rod 32, the inner diameter and the coaxiality match with high precision, and the density is further increased. Excellent in abrasion resistance and rotating shaft support force. On the other hand, since the middle relief portion 13 does not press against the core rod 32, the density is lower than that of the bearing surface 12, and the middle relief amount can be made relatively large. The amount can be increased and lubricity is improved. As a result, the bearing 20A exhibits excellent bearing performance. Further, since the degree of compression of both the bearing surfaces 12 is substantially equal, the porosity of the bearing surfaces 12 is equalized. Therefore, the hydraulic pressure generated on the bearing surfaces 12 is also equalized and the rotating shaft is well balanced. Can be supported.

In the above-described embodiment, the outer diameter of the material 1A is a dimension fitted into the housing 21 (a dimension inserted while sliding). The dimension may be such that a small gap is formed, or the dimension may be such that the inner diameter of the raw material 1A itself is not so large that it is press-fitted into the housing 21. Further, the outer diameter of the housing 21 is a dimension that is fitted in the fitting hole 30 of the die 31 in the middle, but may be a dimension that is press-fitted into the fitting hole 30. If the outer diameter of the housing 21 is such that there is a gap between the outer diameter surface and the fitting hole 30, the material 1
It is not preferable because the diameter of the housing 21 may be increased at the time of compression of A.
That is not the case.

(2) Second Embodiment—FIG. 2 Next, a second embodiment of the present invention will be described. In the second embodiment, as shown in FIG. 2A, the material 1A is previously fitted to the housing 21 by an appropriate device other than the molding device. Next, as shown in FIG. 2B, the material 1A and the housing 21 are fitted and set on the core rod 32. From this state, the housing 2 is
1 is fitted into the fitting hole 30 of the die 31 (the state shown in FIG. 1D), and thereafter, the material 1A is compressed as in the first embodiment.

(3) Third Embodiment—FIGS. 3 and 4 In the third embodiment, as shown in FIG.
The material 1A is compression-molded by applying the core rod 32A for forming a dynamic pressure groove in place of 2 to the first embodiment or the second embodiment to form a bearing in which the dynamic pressure groove is formed on the shaft support surface 12. Here is an example. The core rod 32A is shown in FIG.
As shown in the figure, a plurality of V-shaped convex portions 32a 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 the inner diameter surfaces at both ends. The protrusion 32a can be formed by means such as cutting or plating of the core rod 32A, and has a height of about several μm.

In the third embodiment, as shown in FIG. 3A, the procedure of the first embodiment or the second embodiment is as follows.
The material 1A and the housing 21 are inserted into the fitting holes 30 of the die 31.
And set the inner diameter surfaces of both ends of the material 1A to the core rod 3
It is made to correspond to the portion where the convex portion 32a of 2A is formed. From this state, the upper and lower punches 33,
The inner punches 33B and 34B of 34 are moved to the material 1A side, and only the material 1A is compressed in the axial direction.

The material 1A is plastically deformed as in the first embodiment, and is formed into a bearing body 10C. As shown in FIG. 4 (b) (the housing 21 is omitted), a herringbone-shaped dynamic pressure groove 14 is formed on the bearing surface 12C of the bearing main body 10C by a convex portion 32a of a core rod 32A. Is established. The bearing body 10C is pressed against the inner diameter surface of the housing 21 to form a bearing 20C.
The mold is released as shown in FIG. Demolded bearing 20C
In this case, since the outer diameter surface is restrained by the die 31 and spring back occurs in which the entire diameter slightly increases, it is possible to remove the bearing 20C from the core rod 32A without abrading the convex portion between the dynamic pressure grooves 14. it can.

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 by using the core rods 32A for forming the dynamic pressure grooves as in the third embodiment can be applied to the first and second embodiments. .

The shape of the dynamic pressure groove shown in the third embodiment is arbitrary, and the number thereof is appropriately selected. However, from the viewpoint of more stably supporting the rotating shaft, a plurality of grooves are formed on the shaft supporting 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.

The rough shape is a groove extending along the axial direction. When the rotating shaft rotates only in 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 32a formed on the core rod 32A, 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.

[0030]

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 is low, the content of lubricating oil and the amount of retained oil are 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 (f).

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

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 of the present invention. is there.

[Explanation of symbols]

 1A: Material 10A, 10C: Bearing body 12: Bearing surface 13: Middle relief 20A, 20C: Bearing 21: Housing 32, 32A: Core rod 32a: Convex part for forming a dynamic pressure groove

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3J011 BA02 CA01 CA02 DA02 LA01 SB19 4K018 CA13 CA15 FA02 FA46 HA03 JA34 KA03 KA22

Claims (2)

[Claims] 1. A method of manufacturing a bearing, comprising a cylindrical bearing main body incorporated in a cylindrical housing, wherein a cylindrical material molded into the bearing main body is inserted into the housing, and The outer diameter surface of the material is pressed against the inner diameter surface of the housing by compressing the material in the axial direction from the state where the core rod with a uniform outer diameter is inserted inside, while the inner diameter surface of both ends in the axial direction of the material is attached to the core rod. A method of manufacturing a bearing, comprising: forming on a bearing surface for supporting a rotary shaft by pressing, and forming a middle relief portion not in contact with the rotary shaft between the bearing surfaces. 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.