JP2002097503A - Method of manufacturing sintered bearing with dynamic pressure groove - Google Patents

Abstract

PROBLEM TO BE SOLVED: To securely and efficiently form dynamic pressure grooves on a bearing material even if it has no or less spring-back. SOLUTION: A core rod 20A having a groove 21 and convex projection 22 side by side on its outer circumferential surface is inserted into the cylindrical bearing material 15. Subsequent compression of the bearing material 15 in a die opening 5a results in pressure bonding of the material 15 to the core rod 20A. A bearing surface 11a and the groove 12 are transfered on to the inner circumferential surface of the material 15. The material 15 is released from die 5, and the core rod 20A is removed from the material 15. The depth of the groove 21 is set to be larger than a half of the amount of spring-back exhibited by the inner diameter of the bearing surface 11a when the outer circumferential surface of the material 15 is released from die 5. The bearing surface 11a is sized or shaved by convex projection 22 of core rod 20a during the removal of the core rod 20A from the material 15.

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 sintered bearing having a cylindrical surface and a dynamic pressure groove formed on a bearing surface for supporting a rotating shaft.

[0002]

2. Description of the Related Art In a sintered bearing, as a lubricating oil impregnated in a sintered body exudes to a bearing surface and an oil film is formed between the bearing surface and a rotating shaft, frictional resistance is reduced and noise is reduced. And characteristics that vibration is suppressed. In recent years, in such sintered bearings, there are widely provided those in which a dynamic pressure groove formed on a bearing surface can obtain a dynamic pressure effect, that is, an improved bearing force due to a high pressure of lubricating oil flowing into the dynamic pressure groove. Have been. Conventionally, rolling and etching using a photomask have been proposed to form a dynamic pressure groove in a sintered bearing, but it is difficult to apply to a bearing having a relatively small diameter, and mass production is poor. there were.

Japanese Patent Laid-Open Publication No. Hei 3-20112 discloses that the inner peripheral surface of a bearing material is pressed against the outer peripheral surface of a grooved core rod at one or more locations in the circumferential direction. The groove of the core rod is transferred to the inner peripheral surface, and thereafter, the bearing material is separated from the core rod by dividing the bearing material at the dividing surface,
A method of mounting a divided bearing material in a housing to form a bearing is described. In this method, since the core rod and the bearing material are engaged in the mold, the bearing is divided in advance, the groove of the core rod is transferred to the bearing material in the mold, and the bearing material is extracted from the die together with the core rod. By separating the split pieces of the bearing from the core rod, it is possible to form a dynamic pressure groove on the bearing surface.

In the method described in Japanese Patent Application Laid-Open No. Hei 10-306827, the core rod has a surface on which the dynamic pressure grooves are formed on the bearing surface and a surface on which the other region is formed, similarly to the above. And Then, after inserting the core rod into the bearing material, compressing the outer peripheral surface of the bearing material and transferring the outer peripheral surface shape of the core rod to the inner peripheral surface of the bearing material, the core rod and the bearing material are removed from the die without being shifted in the axial direction. Extract and release from the compressed state. Then
Since spring back (elastic return) occurs in the bearing material and the hole expands in diameter, the completed bearing is extracted from the core rod using this. In this method, the bearing material is compressed to form a dynamic pressure groove, and the bearing is extracted from the core rod using springback generated when the compressed state applied to the outer peripheral surface of the bearing material is released. There is an advantage that a cylindrical one can be used.

A technique for releasing a bearing from a core rod using such a springback is disclosed in Japanese Unexamined Patent Publication No. Hei.
As described in Japanese Patent Publication No. 107705, the present invention is also applicable to the production of a sintered bearing having a bearing surface at both ends of a bearing and an inner portion having a middle clearance larger than the diameter of the shaft. It is possible. Specifically, the core rod has a small-diameter portion forming a portion of the bearing surface and a large-diameter portion forming a middle relief portion, and the core rod is inserted into a bearing material, and the large-diameter portion is disposed at an intermediate portion in the axial direction. From the state, the outer peripheral surface of the core rod is transferred to the inner peripheral surface of the bearing material by pressing the bearing material against the core rod in the mold. Thereafter, the core rod and the bearing material are pulled out of the die without being displaced in the axial direction to release the compressive force, the inner diameter of the bearing material is increased by the generated springback, and the bearing material is pulled out of the core rod.

[0006]

In the former method (Japanese Patent Laid-Open No. Hei 3-20112), the bearing material must be divided, and the sizing must be performed when the bearing material is mounted in the housing. Since it is necessary to combine the divided pieces of the bearing, there is a disadvantage that it is complicated and inefficient. On the other hand, the latter method (JP-A-10-3068)
No. 27, JP-A-2-107705) presupposes that the bearing material causes springback. Therefore, as in the case where the bearing material has a relatively low density or is easily deformed plastically like a copper-based sintered alloy, springback hardly occurs, or even if it occurs, the diameter of the bearing material is 0%. In the case where only about .1% occurs, the smaller the diameter of the bearing, the smaller the dynamic pressure groove can be manufactured. For this reason,
The dynamic pressure effect as expected cannot be obtained.

Therefore, according to the present invention, a dynamic pressure groove can be reliably formed even with a bearing material having a small or almost no springback amount (for example, made of a copper-based sintered alloy or the like). It is an object of the present invention to provide a manufacturing method capable of efficiently manufacturing a sintered bearing with a dynamic pressure groove having a dense bearing surface and excellent dimensional accuracy.

[0008]

SUMMARY OF THE INVENTION The present invention is a method of manufacturing a cylindrical sintered bearing having a dynamic pressure groove inclined with respect to a circumferential direction on a bearing surface, wherein the bearing surface is formed. Insert a core rod in which a groove for forming and a ridge for forming a dynamic pressure groove on the outer peripheral surface is inserted into a cylindrical bearing material,
By compressing the bearing material in the die hole, the bearing material is pressed against the core rod to transfer the bearing surface and the dynamic pressure groove to the inner peripheral surface of the bearing material, and then the outer peripheral surface of the bearing material is released from the die A step of relatively extracting the core rod from the bearing material in a state in which the outer peripheral surface of the bearing material is released from the die, and the depth of the groove of the core rod is 1/1 / spring amount of the inner diameter of the bearing surface generated when the outer peripheral surface of the bearing material is released from the die. It is larger than 2 and is characterized in that the bearing surface is sized or shaved with the ridges of the core rod during the extraction of the core rod from the bearing material.

According to the present invention, the amount of springback generated when the outer peripheral surface of the bearing material is released from the die is smaller than the depth of the groove of the core rod, and the depth of the groove is smaller than 1/2 of the amount of springback. When the core rod is large, the ridges of the core rod sizing or shaving the bearing surface formed on the bearing while extracting the core rod from the bearing material. Therefore, the amount of springback is small or
Alternatively, it is possible to form the dynamic pressure groove reliably and efficiently in a bearing material having little. Since the formed bearing surface is sized or shaved, it is dense and has excellent dimensional accuracy.

In the present invention, the groove of the core rod is transferred to form a ridge on the inner peripheral surface of the bearing, and the protruding end surface of the ridge serves as the bearing surface. Here, it is preferable that the protruding edge of the protruding ridge of the core rod and the inner corner of the groove be chamfered in an arcuate cross-section because the protruding ridge on the bearing side is less susceptible to shear fracture when the core rod is extracted.

Further, when viewed in the axial direction of the core rod, the depth of the groove of the core rod is gradually deeper from one end to the other end, or the central portion is the deepest, and the depth from the center toward the both ends is increased. It can take any form, gradually becoming shallower. According to these embodiments, the ridges of the bearing material are less susceptible to shear fracture, and sizing or shaving is performed smoothly.

Further, the present invention includes that the portions where the grooves and the ridges are formed on the core rod are arranged at two separated positions corresponding to both ends of the bearing. A bearing surface and a dynamic pressure groove are formed at both ends of an inner peripheral surface of a bearing manufactured using this core rod, and a middle relief portion having a diameter larger than that of the bearing surface is formed between these.

Further, as the bearing material used in the present invention, it is preferable that at least the inner peripheral surface of the sintered body is sized from the viewpoint of improving the dimensional accuracy.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a core rod 20A according to the embodiment, and a plurality of substantially V-shaped grooves 21 converging in the circumferential direction are formed in a herringbone pattern on the outer peripheral surface of the core rod 20A. The depth of each groove 21 is uniform and formed at equal intervals, and between each groove 21 there is a ridge 22 whose outer diameter is equal to the outer diameter of the core rod 20A.
The groove 21 is a portion forming the bearing surface of the inner peripheral surface of the bearing, and the ridge 22 is a portion forming the dynamic pressure groove.

FIG. 2 shows another embodiment of the core rod. In this core rod 20B, the portions where the grooves 21 and the ridges 22 shown in FIG. 1 are formed are provided at two separated places corresponding to both ends of the bearing. The part between the two forms a middle relief part having a larger diameter than the bearing surface.

The core rods 20A and 20B are formed, for example, by masking a portion to be the groove 21 on the outer peripheral surface of a hard steel rod polished to an outer diameter corresponding to the bottom surface of the groove 21.
Next, a hard alloy plating is applied to the surface of the steel bar, and thereafter, the masking is removed and the plated surface can be polished and finished to a predetermined size. In addition, a groove 21 is formed by etching a steel rod having an outer diameter of the core rods 20A and 20B by providing a photomask of a photocurable resin on a portion to be the protruding ridge 22, and thereafter forming the groove. It can also be manufactured by finishing.

Next, a method of manufacturing a sintered bearing with a dynamic pressure groove by combining the core rod 20A shown in FIG. 1 with a mold will be described with reference to FIG. First, as shown in FIG. 3A, a mold for molding the bearing material 15 includes a die 5 having a die hole 5a forming an outer peripheral surface of a bearing, and an upper and lower slidably inserted into the die hole 5a. And punches 3 and 4. The upper and lower punches 3, 4 are cylindrical, and a core rod 20A is slidably inserted into these holes. In the illustrated example, the core rod 20A inserted into the upper punch 3 is configured to descend from above. However, the configuration of the mold may be such that the core rod 20A is elevated from the lower punch 4 side. Alternatively, a die in which the die 5 is movable in the axial direction (vertical direction in FIG. 3) or a die in which the axial direction is entirely horizontal can be used. Further, a means for cleaning the core rod 20A with air or a brush may be added.

As the bearing material 15, a sintered body formed into a cylindrical shape or a sintered body subjected to sizing is used. The latter can provide higher dimensional accuracy.

Now, as a manufacturing process, first, FIG.
As shown in (a), the bearing material 15 is set coaxially above the die hole 5a, and the core rod 20A is connected to the bearing material 15A.
And the portions where the dynamic pressure grooves are formed, that is, the portions where the grooves 21 and the ridges 22 are formed, correspond to the entire inner peripheral surface of the bearing material 15. Next, the upper punch 3 and the core rod 20A brought into contact with the bearing material 15 are lowered at the same speed, that is, while maintaining the positional relationship between the bearing material 15 and the core rod 20A, and the bearing material 15 is inserted into the die hole 5a. The bearing material 15 is sandwiched between the upper and lower punches 3 and 4.

Next, the bearing blank 15 is compressed in the axial direction at a predetermined pressure by the upper and lower punches 3 and 4. The bearing material 15 is compressed while its outer peripheral surface is constrained by the inner peripheral surface of the die hole 5a.
1 and the inner peripheral surface of the bearing material 15 is pressed against the outer peripheral surface of the core rod 20A. This allows
As shown in FIG. 3B, the groove 21 and the ridge 22 of the core rod 20 </ b> A are transferred to the inner peripheral surface of the bearing material 15, and the ridge 11 and the dynamic pressure groove 12, each having a protruding end surface as the bearing surface 11 a. Are respectively formed.

Next, as shown in FIG. 3 (c), the upper and lower punches 3, 4 and the core rod 20A are raised to release the bearing material 15 from the die 5 and release it from the compressed state.
The lift speeds of the upper and lower punches 3 and 4 and the core rod 20A are the same, and the bearing material 15 and the core rod 20A are raised while maintaining the positional relationship. Next, as shown in FIG. 3D, the core rod 20 </ b> A is lifted while the upper punch 3 is kept in contact with the bearing material 15, and
Extract from 5. Thus, a bearing 10A in which the bearing surface 11a and the dynamic pressure groove 12 are formed on the inner peripheral surface is obtained. FIG.
(A) shows a longitudinal section obtained by dividing the obtained bearing 10A in half.
One or two are mounted and used.

FIG. 4B shows a bearing 10B manufactured using the core rod 20B shown in FIG. 2. The bearing 10B has a bearing surface 11a and a dynamic pressure groove 12 at both ends. Each of them is formed, and a middle relief portion 14 having a diameter larger than that of the bearing surface 11a and having the same diameter as the dynamic pressure groove 12 is formed therebetween.

In the present embodiment, in the state shown in FIG. 3 (c), the bearing material 15 is in contact with the core rod 20A in one of the following two forms (A) and (B). Is engaged.

(A) The amount of diameter expansion caused by springback caused by removal from the mold is extremely small, and the groove 21 of the core rod 20A and the ridge 11 of the bearing material 15 are almost completely meshed and engaged. The bearing material 15 is made of a soft material such as a copper-based alloy, has a relatively low density,
If the inner diameter is small, for example, 5 mm or less, such a state is likely to occur.

(B) As shown in FIG. 5, springback occurs in the bearing material 15, but the springback amount Sb is smaller than the depth of the groove 21 of the core rod 20A.
For this reason, the protrusion 22 of the core rod 20A is
3 is engaged with the dynamic pressure groove 12. Here, the depth of the groove 21 of the core rod 20A is larger than １ ／ of the springback amount Sb of the inner diameter of the bearing surface 11a. Such a state is likely to occur when the bearing material 15 has a relatively high density and a relatively large inner diameter because the bearing material 15 is made of a relatively hard alloy or is sized in advance.

In the case where the bearing material 15 has the characteristics described in the above (A), if the core rod 20A is to be pulled out from the state of FIG. Is pressed to apply a shearing force to the ridge 11, but if the side is slightly deformed, a pushing force for expanding the diameter of the bearing material 15 is generated. As a result, FIG.
A gap corresponding to the springback amount Sb is formed between them, and the outer diameter increases. When the core rod 20A is further extracted from this, the following two forms are generated depending on the characteristics of the bearing material 15.

One is that the diameter of the bearing material 15 is further increased,
The ridge 22 of the core rod 20A is the bearing surface 1 of the bearing material 15
It is sized by sliding and pressing on 1a.
The other is that the elastic restoring force (force for reducing the diameter) of the inner peripheral surface of the bearing material 15 and the pushing and expanding force of the core rod 20A are balanced, and the bearing is formed by the portion near the protruding end on the side surface of the ridge 22 of the core rod 20A. Shaving is performed so as to shear the surface layer of the surface 11a. In any case, after the core rod 20A is extracted from the bearing material 15, the bearing 1
The inner peripheral surface of 0A is elastically restored and its diameter is reduced. Also, bearing surface 1
1a becomes a smoother surface than the state of the sintered body because the pores decrease due to the abrasion.

By setting the depth of the groove 21 of the core rod 20A based on an experimental value or the like so that these behaviors can occur, the bearing material 15 hardly or rarely causes springback. Also, the dynamic pressure groove 12 can be secured even after the core rod 20A is extracted. In addition, from the viewpoint of avoiding the ridge 11 of the bearing material 15 from being sheared and broken when the core rod 20A is extracted from the bearing material 15, as shown in FIG. Preferably, the inner corner 21a of the groove 21 is chamfered in a smooth arc-shaped cross section. Further, the side surface of the ridge 22 of the core rod 20A may be gently inclined, or the groove 21 of the core rod 20A may be inclined.
Is set to an appropriate width, shear fracture can be more reliably avoided, and the dynamic pressure groove 12 can be made deeper.

On the other hand, when the bearing material 15 has the characteristics described in the above (B), springback occurs in the bearing material 15, so that the dynamic pressure groove 12 becomes deeper.
When extracting the core rod 20A from the bearing material 15,
The sizing or the shaving is applied to the bearing surface 11a of the bearing material 15. In order to perform such processing on the bearing surface 11a, as described above, the depth of the groove 21 of the core rod 20A is set to be larger than 1/2 of the springback amount of the inner diameter of the bearing surface 11a.

For example, a cylindrical sintered body having a density of 6.6 cm ³ , an inner diameter of 4 mm and an outer diameter of 8 mm made of a bronze-based sintered alloy containing 8% by weight of Sn is used as a bearing material. When the bearing is compressed by the method shown in FIG. 3, the inner diameter is the same as the outer diameter of the core rod, and no springback is observed. On the other hand, a bearing similarly manufactured from a sintered material of the same material having an inner diameter of 10 mm and a thickness of 2.5 mm has an inner diameter that is about 4 μm larger than the outer diameter of the core rod. That is, the radius springback amount in this case is 2
At μm, this means that 0.4% of springback has occurred relative to the outer diameter of the core rod. Therefore, when applying a manufacturing method of extracting a core rod using a springback using a sintered material of such a material, a dynamic pressure groove cannot be formed in the bearing material 15 having an inner diameter of 4 mm. 2μ depth for bearing material 15 with inner diameter 10mm
Thus, m dynamic pressure grooves can be formed.

Next, referring to FIG. 6, another example of the dynamic pressure groove forming portion formed by the groove of the core rod and the ridge is illustrated. The grooves and the ridges in the illustrated example are basically formed in a herringbone pattern, similarly to those shown in FIG.

The core rod 20C shown in FIG.
Is along the outer peripheral surface of the core rod 20C, and the ridge 22 is formed so as to protrude from the outer peripheral surface of the core rod 20C. In order to manufacture such a core rod 20C by an etching method, a steel bar having a portion serving as a ridge 22 larger than other main portions is used as a material, and a portion serving as a groove 21 is masked in this steel bar, followed by etching. Process. Further, in order to manufacture by plating, masking and plating are performed while leaving portions that become the ridges 22.

The core rod 20D shown in FIG.
When viewed in the axial direction of the core rod 20D, the depth of the groove 21 becomes gradually smaller from one end to the other end (from the lower end, which is the distal end side of the core rod 20D in the figure, to the upper end), and the groove 21 is formed on the shallow side. The end of 22 smoothly continues to the outer peripheral surface of the core rod 20D. Such a core rod 20D is, for example, a core rod 20C shown in FIG.
Can be obtained by polishing the ridges 22 to be conical. According to the core rod 20D, one end of the dynamic pressure groove formed in the bearing is deepest when viewed in the axial direction, and becomes gradually shallower toward the other end. When the core rod 20D is pulled out from the bearing material 15, the height of the ridge 22 gradually increases from the tip side in the withdrawal direction, that is, from the upper end in the drawing direction. There is an advantage that sizing or shaving is performed smoothly. In addition, the sizing amount or the shaving amount can be increased as the height of the ridge 22 increases.

The core rod 20E shown in FIG.
When viewed in the axial direction of the core rod 20E, the center portion is the deepest, and gradually becomes shallower toward both ends from there, and both ends of the ridge 22 smoothly continue to the outer peripheral surface of the core rod 20E. ing. Such a core rod 20E can be obtained, for example, by polishing the ridge 22 of the core rod 20C shown in FIG.
According to such a core rod 20E, the dynamic pressure groove formed in the bearing is deepest at the axial center, and gradually becomes shallower toward both ends. And FIG.
As in the case of the core rod 20D of (b), there are advantages that the ridges of the bearing material are not susceptible to shearing and that sizing or shaving is performed smoothly.

Next, another embodiment of the dynamic pressure groove formed in the bearing will be described with reference to FIG. A plurality of fine V-shaped ridges 11 converging in the circumferential direction are formed on the inner peripheral surface of the bearing 10C in FIG. 7A, and the inner peripheral surface of these ridges 11 is the bearing surface 11a. is there. The groove between the ridges 11 is a dynamic pressure groove 12. A spiral ridge 11 is formed over the entire inner surface of the bearing 10D shown in FIG. 7B, and the inner surface of the ridge 11 is a bearing surface 11a. The spiral groove between the ridges 11 is a dynamic pressure groove 12.

[0036]

As described above, according to the present invention,
Even if the bearing material has little or no springback, the dynamic pressure groove can be formed reliably, and the bearing surface is dense and the dimensional accuracy is excellent. Can be manufactured.

[Brief description of the drawings]

FIG. 1 is a partial side view of a core rod according to an embodiment of the present invention.

FIG. 2 is a partial side view of a core rod according to another embodiment of the present invention.

FIG. 3 is a longitudinal sectional view showing a method of manufacturing a core rod according to an embodiment of the present invention in the order of (a) to (d).

FIG. 4A is a longitudinal sectional view of a bearing manufactured using a core rod according to one embodiment of the present invention, and FIG. 4B is a bearing manufactured using a core rod according to another embodiment of the present invention. FIG.

FIG. 5 is an enlarged view of a main part of FIG. 3 (c).

FIG. 6 is a side view showing various modified examples of grooves and ridges formed in a core rod.

FIG. 7 is a longitudinal sectional view showing various modifications of a bearing surface and a dynamic pressure groove formed on a bearing.

[Explanation of symbols]

 Reference Signs List 5: Die 5a: Die hole 10A, 10B, 10C, 10D: Bearing 11a: Bearing surface 12: Dynamic pressure groove 15: Bearing material 20A, 20B: Core rod 21: Groove 21a: Inner corner 22: Protrusion 22a: Protruding edge Part Sb: Springback amount

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Ichiemon Kano 5-12-22 Higashitaga, Hitachi City, Ibaraki Prefecture Inside Yawata Iron Works (72) Inventor Motohiro Miyasaka 520 Minordai, Matsudo City, Chiba Prefecture Hitachi Powder Metallurgy Co., Ltd. In-house (72) Inventor Go Yanase 520 Minordai, Matsudo-shi, Chiba F-term (reference) 3J011 AA20 BA02 CA02 DA01 DA02 KA02 LA01 MA21 PA02 SB19 4K018 FA02 FA05 HA04 HA06 KA03 KA03

Claims (6)

[Claims] 1. A method for manufacturing a cylindrical sintered bearing having a dynamic pressure groove inclined with respect to a circumferential direction on a bearing surface, comprising: a groove for forming the bearing surface; By inserting a core rod having a ridge for forming a groove and an outer peripheral surface formed on the outer peripheral surface into a bearing material made of a cylindrical sintered body, and then compressing the bearing material in a die hole, a bearing material is formed. Is pressed against the core rod to transfer the bearing surface and the dynamic pressure groove to the inner peripheral surface of the bearing material, and thereafter, the core rod is relatively extracted from the bearing material with the outer peripheral surface of the bearing material released from the die. The depth of the groove of the core rod is larger than １ ／ of the springback amount of the inner diameter of the bearing surface generated when the outer peripheral surface of the bearing material is released from a die; While extracting, the bearing surface is A method for producing a sintered bearing with a dynamic pressure groove, characterized in that sizing or shaving is carried out with the ridge of the core rod. 2. The sintered bearing with a dynamic pressure groove according to claim 1, wherein the protruding edge of the ridge and the inner corner of the groove in the core rod are chamfered in an arc-shaped cross section. Manufacturing method. 3. The core rod according to claim 1, wherein the depth of the groove of the core rod gradually decreases from one end to the other end when viewed in the axial direction of the core rod. Manufacturing method of sintered bearing with dynamic pressure groove. 4. The core rod according to claim 1, wherein the depth of the groove in the core rod is the deepest in the central part when viewed in the axial direction of the core rod, and gradually becomes shallower toward both ends from the central part. Or the manufacturing method of the sintered bearing with a dynamic pressure groove according to 2. 5. The core rod according to claim 1, wherein the groove and the ridge are formed at two separated positions corresponding to both ends of the bearing. Of manufacturing sintered bearings with dynamic pressure grooves. 6. The method according to claim 1, wherein the bearing material is obtained by sizing at least an inner peripheral surface of a sintered body. .