JP2002061650A - Method for manufacturing sintered bearing with dynamic pressure groove - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form surely and efficiently a dynamic pressure groove, even when a bearing member has a small spring back amount or hardly has it. SOLUTION: A core rod 20A provided with a groove 21 and a projection 22 on an outer peripheral surface is inserted in a cylindrical bearing member 15. The bearing member 15 is compressed in a die hole 5a, so that the bearing member 15 is pressed on the core rod 20A to transfer a bearing surface 11a and a dynamic pressure groove 12 on the inner peripheral surface of the bearing member 15. Then, an outer peripheral surface of the bearing member 15 is released from the die, and the core rod 20A is drawn out while both of end surfaces of the bearing member 15 are pressed by upper and lower punches. Since an enlarging diameter amount of the bearing member 15 increases by pressurization in addition to spring back, draw of the core rod becomes possible and easy. As a result, a dynamic pressure groove can be surely formed.

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.

[0003] As a technique for solving these problems, there is a method described in Japanese Patent Application Laid-Open No. 10-306827. In this method, a core rod having a pattern corresponding to the dynamic pressure groove to be formed on the outer peripheral surface is inserted into a bearing material, and the bearing material is compressed to bring the inner peripheral surface into close contact with the outer peripheral surface of the core rod. By transferring the unevenness of the core rod to the inner peripheral surface of the bearing material, the bearing material is released from the compressed state, and then the bearing material is removed from the core rod using spring back generated in the bearing material. is there.

[0004]

In the above conventional method,
The inner diameter of the bearing material is sufficiently expanded by springback to remove the bearing material with the dynamic pressure groove from the core rod, so that the irregularities on both the outer peripheral surface of the core rod and the inner peripheral surface of the bearing material do not interfere with each other without meshing Is required. For this reason, it is desirable that the material generate springback as large as possible. However,
The springback (the ratio of the amount of expansion of the inner diameter of the bearing material when the compression to the outer diameter of the core rod is released) of the general sintered alloy for plain bearings is at most about 0.2%. The maximum step of the unevenness that can be formed on the peripheral surface is 1/2 of the amount of springback that occurs (the amount of radial springback). Also, some sintered bearings made of relatively low-density sintered alloys and relatively soft and plastically deformable sintered alloys, such as copper-based sintered alloys, hardly cause springback. It is difficult to form a dynamic pressure groove in a simple bearing material.

Therefore, according to the present invention, a dynamic pressure groove can be reliably formed even with a bearing material having a small or little springback amount (for example, made of a copper-based sintered alloy or the like), and 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.

[0006]

SUMMARY OF THE INVENTION The present invention is a method of manufacturing a cylindrical sintered bearing having a dynamic pressure groove formed on a bearing surface, wherein the groove for forming the bearing surface and the dynamic pressure groove are formed. The core rod having the ridges formed thereon formed on the outer peripheral surface is inserted into a bearing material made of a cylindrical sintered body, and then the bearing material is compressed in a die hole to convert the bearing material into a core rod. The bearing surface and the dynamic pressure groove are transferred to the inner peripheral surface of the bearing material by pressure contact.After that, the outer peripheral surface of the bearing material is released from the die, and both ends of the bearing material are pressurized. It is characterized in that the core rod is relatively extracted from the material.

According to the present invention, in the step of relatively extracting the core rod from the bearing material, springback occurs in the bearing material by releasing the outer peripheral surface of the bearing material from the die. Since both end faces are pressurized, the inner and outer diameters of the bearing material are expanded. That is, the inner diameter of the bearing material is further increased by pressurizing both end surfaces in addition to the springback. Therefore, it is possible or easy to extract the core rod, and as a result,
The dynamic pressure groove can be reliably formed, and a deeper dynamic pressure groove can be formed.

In the present invention, the depth of the groove of the core rod is caused by the amount of radial springback of the bearing surface generated when the outer peripheral surface of the bearing material is released from the die and by the pressing of both end surfaces of the bearing material. The amount is set to be larger than the sum of the expansion amount of the radius of the bearing surface and the preferable method. It is preferable that the bearing surface is sized or shaved with the ridge of the core rod while the core rod is being extracted from the bearing material.

In this method, the depth of the groove of the core rod is larger than １ ／ of the sum of the amount of springback and the amount of diameter expansion caused by pressing both end faces of the bearing material. For this reason, the unevenness of the outer peripheral surface of the core rod slightly interferes with the unevenness formed on the bearing surface, but the interference portion is sized or shaved by the ridge of the core rod. Therefore, a dynamic pressure groove can be formed reliably and efficiently in a bearing material having a small or almost no springback amount. Further, since the formed bearing surface is sized or shaved, the bearing surface is dense and has excellent dimensional accuracy. Further, as described above, the bearing material expands its diameter by pressurizing both end faces of the bearing material, so that the bearing material loosens greatly with respect to the core rod, and therefore, it is possible to smoothly advance the initial stage of extracting the core rod. it can.

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 corners of the ridges of the core rod and the corners of the grooves are chamfered in an arc-shaped cross section, since the ridges on the bearing side are 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 increasing from one end to the other end, or the center portion is the deepest, and from there, the depth increases toward both ends. 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 a 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, the upper and lower punches 3, 4 press the bearing material 15 in the axial direction and compress it. The pressure of this pressurization is set to be an initial stage of the elastic deformation region or the plastic deformation region of the bearing material 15, and therefore, the overall length (height) of the bearing material 15 is slightly reduced. Next, as shown in FIG. 3D, the core rod 20A is lifted and pulled out of the bearing material 15 while maintaining the state where the bearing material 15 is pressed by the upper and lower punches 3 and 4. When the upper punch 3 is lifted and unloaded after the core rod 20A is extracted, the bearing material 15 is elastically restored and both the inner and outer diameters are reduced. As described above, the bearing surface 11a and the dynamic pressure groove 1 are formed on the inner peripheral surface.
2 is obtained. FIG. 4 (a) shows a half section of the obtained bearing 10A, which is used, for example, by mounting one or two bearings 10A in a housing.

FIG. 4B shows a bearing 10B manufactured in the same manner as described above using the core rod 20B shown in FIG.
The bearing 10B has bearing surfaces 1 at both ends.
1a and a dynamic pressure groove 12 are respectively 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. 3C, the bearing material 15 is engaged with the core rod 20A in one of the following states.

As shown in FIG. 5A, almost no springback occurs in the bearing material 15 and the core rod 20A
Groove 21 and ridge 22 of bearing, and bearing surface 11 of bearing material 15
a and the dynamic pressure groove 12 are almost completely engaged with each other without any gap. If the bearing material 15 is made of a soft material such as a copper alloy, has a relatively low density, and has a small inner diameter of, for example, 5 mm or less, such a state is likely to occur.

Next, as shown in FIG. 5C, springback occurs in the bearing material 15, but the amount of springback is smaller than the depth of the groove 21 of the core rod 20A. Reference numeral 22 denotes a state in which it engages with the dynamic pressure groove 12 of the bearing material 15. 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. Further, the groove 2 of the core rod 20A is larger than the radial expansion amount of the bearing surface 11a due to the spring back of the bearing material 15.
A similar situation occurs when the depth of 1 is large.

Next, as shown in FIG. 5B, springback occurs in the bearing material 15 and the inner diameter of the bearing surface 11a of the bearing material 15 is larger than the outer diameter of the ridge 22 of the core rod 20A, or It is the same state. In such a form, the amount of springback of the bearing material 15 and the depth of the groove 21 of the core rod 20A are substantially the same, and the core rod 20A and the bearing material 15 do not engage with each other.
The core rod 20 can be extracted from the fifth rod 5. Conventional methods make use of this configuration.

Then, as shown in FIG. 3 (c), after the bearing material 15 is released from the die 5, the inner and outer diameters of the bearing material 15 are reduced by pressing the bearing material 15 with the upper and lower punches 3, 4. When the entire length is reduced while expanding, the depth corresponding to 1/2 of the diameter expansion amount can be obtained, so that the dynamic pressure groove 12 can be formed deeper. That is, the bearing material 15 is removed from the die 5 and the bearing material 15 is removed.
5A, when the groove 21 of the core rod 20A and the ridge 11 of the bearing material 15 are substantially engaged with each other as shown in FIG. Although there is a difference depending on the characteristics of the bearing material 15, the state shown in FIG. 5C or FIG. 5B may be obtained. If the bearing material 15 is pressurized from the state shown in FIG. 5C, the state shown in FIG.

Next, from the bearing material 15 to the core rod 20A
A mode for extracting the sword will be described. FIG. 5 (a) or FIG.
As shown in (c), the state in which the ridge 22 of the core rod 20A interferes with the ridge 11 of the bearing material 15 is changed from the state shown in FIG.
When the ridge 22 of the core rod 20A is pressed, the ridges 11 of the core rod 20A are pressed against the side surfaces of the ridges 11 of the bearing material 15 to apply a shearing force to the ridges 11, but when the side surfaces are slightly deformed, the bearing material 15 is expanded. A pushing force is generated. FIG. 6A shows the state of the process. Thereby, the bearing material 15
A gap is formed between the inner peripheral surface of the core rod 20A and the core rod 20A, or the gap is enlarged. From here the core rod 20
When A is extracted, the following two forms occur depending on the characteristics of the bearing material 15.

One is that, as shown in FIG. 6B, the diameter of the bearing material 15 is further increased, and the ridges 22 of the core rod 20A are formed.
Is slid by pressing against the bearing surface 11a of the bearing material 15. The other is, as shown in FIG. 6 (c), when the elastic return force (force for reducing the diameter) of the inner peripheral surface of the bearing material 15 and the pushing force by the core rod 20A are balanced, and the convexity of the core rod 20A is increased. Shaving is performed so as to shear the surface layer of the bearing surface 11a by a portion near the corner on the side surface of the ridge 22. In any case, after the core rod 20A is extracted from the bearing material 15 and the upper punch 3 is retracted to remove the pressurization, the inner peripheral surface of the bearing 10A is elastically restored and the diameter is reduced. Further, the bearing surface 11a becomes smoother than the sintered body because the pores decrease due to wear.

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 has little or no springback. Also, the core rod 20A can be extracted, and the dynamic pressure groove 12 can be secured. Further, the dynamic pressure groove 12 can be made deeper.

As shown in FIG. 5, from the viewpoint of preventing the projection 11 of the bearing material 15 from being sheared and broken when the core rod 20A is pulled out from the bearing material 15, as shown in FIG. 22a and corner 21 of groove 21
It is preferable that a be squared into a smooth arc-shaped cross section. In addition, if the side surface of the ridge 22 of the core rod 20A is gently inclined, or if the groove 21 of the core rod 20A is set to an appropriate width, shear breakage can be more reliably avoided, and the dynamic pressure groove 12 can be more securely formed. It can be deep.

Next, referring to FIG. 7, 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. There is an advantage that sizing or shaving is smoothly performed. 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 ridges 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 becomes gradually 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 of FIG. 8A, 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 of FIG. 8B, 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.

[0037]

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 one embodiment of the present invention in the order of (a) to (d).

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

FIGS. 5A to 5C are longitudinal sectional views schematically showing various forms of a relationship between a core rod and a bearing material in a state where an outer peripheral surface of the bearing material is released from a die.

FIGS. 6A to 6C are longitudinal sectional views schematically showing various forms of a relationship between the core rod and the bearing material when the core rod is extracted from the bearing material.

FIG. 7 is a side view showing various modifications of grooves and ridges formed in a core rod.

8A and 8B are half sectional views showing various modifications of a bearing surface and a dynamic pressure groove formed on a bearing.

[Explanation of symbols]

5 die, 5a die hole, 10A, 10B, 10C, 1
0D: bearing, 11a: bearing surface, 12: dynamic pressure groove, 15: bearing material, 20A, 20B: core rod, 21: groove, 21
a ... corner, 22 ... ridge, 22a ... corner.

 ──────────────────────────────────────────────────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-company (72) Inventor Go Yanase 520 Minoridai, Matsudo-shi, Chiba F-term (reference) 3J011 AA04 BA02 CA03 DA02 LA01 SB19

Claims (6)

[Claims] 1. A method for manufacturing a cylindrical sintered bearing having a dynamic pressure groove formed on a bearing surface, comprising: a groove for forming the bearing surface; and a ridge for forming the dynamic pressure groove. The core rod formed on the outer peripheral surface is inserted into a bearing material made of a cylindrical sintered body, and then the bearing material is compressed in a die hole, thereby pressing the bearing material against the core rod to form a bearing material. Transfer the bearing surface and the dynamic pressure groove to the inner peripheral surface, then release the outer peripheral surface of the bearing material from the die,
A method of manufacturing a sintered bearing with a dynamic pressure groove, wherein a core rod is relatively extracted from a bearing material while both end surfaces of the bearing material are pressurized. 2. The depth of the groove of the core rod is such that a radial springback amount of the bearing surface generated when the outer peripheral surface of the bearing material is released from the die, and both end surfaces of the bearing material are pressurized. It is set to be larger than the sum of the amount of expansion of the radius of the bearing surface caused by this, and during the extraction of the core rod from the bearing material, the bearing surface is sized or shaved with the ridge of the core rod. The method for producing a sintered bearing with a dynamic pressure groove according to claim 1. 3. The sintered bearing with dynamic pressure grooves according to claim 1, wherein the corners of the ridges and the corners of the grooves in the core rod are chamfered in an arc-shaped cross section. Manufacturing method. 4. The core rod according to claim 1, wherein a depth of the groove is gradually reduced from one end to the other end when viewed in the axial direction of the core rod.
The method for producing a sintered bearing with a dynamic pressure groove according to any one of the above. 5. The depth of the groove of the core rod, when viewed in the axial direction of the core rod, is the deepest at a central portion and gradually becomes shallower toward both ends from the central portion. 4. The method of manufacturing a sintered bearing with a dynamic pressure groove according to any one of claims 1 to 3. 6. The core rod according to claim 1, wherein the groove and the projection are formed at two separated positions corresponding to both ends of the bearing. Of manufacturing sintered bearings with dynamic pressure grooves.