JPH07116490B2 - Manufacturing method of sintered bearing material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION “Object of the Invention” The present invention relates to a method for manufacturing a sintered bearing material, which has an accurate non-contact area in the middle portion of the inner diameter of the sintered bearing material, and has straight outer surfaces on both end sides. An object of the present invention is to obtain a method capable of properly manufacturing a product capable of forming a stable and appropriate mounting relationship with a housing.

(Industrial field of application) A sintered bearing material that has a non-contact area in the middle of the inner diameter surface to reduce friction and is always properly mounted on the housing.

(Prior Art) It has been practiced to use a sintered metal material such as an oil-impregnated bearing. However, a typical sintered metal bearing material of the related art has a straight inner diameter surface in the axial direction. Is. That is, since the inner diameter surface is formed by the sizing core upon sizing after compacting and sintering, it is natural that the inner surface is straight along the sizing core surface.

When the conventional general sintered metal is used and the rotary shaft is supported at two places, the length of each bearing may be short, but the concentricity between the two bearings is provided. Is difficult. If an attempt is made to receive the shaft with a single piece of sintered metal in order to eliminate the above-mentioned concentricity, the axial length of the bearing material becomes large. The contact area is large and the friction is large. Further, since the temperature rise of the bearing body during the continuous operation is large, the relief which does not contact the shaft material is formed in the intermediate portion of the inner diameter surface of the bearing material as described above. That is, the method is as follows.

Mechanical drilling As in Japanese Patent Laid-Open No. 58-84222, the cylindrical sintered body is compressed with both upper and lower end surfaces and outer diameter both ends constrained to bulge the outer diameter central portion and the inner diameter central portion. A method of expanding to form a non-contact area.

(Problems to be solved by the invention) Conventional powder compacted sintered bearing materials having a straight inner diameter surface have large surface friction with the shaft material, and in particular suppress runout during rotation of the shaft material. Such a bearing material having a long bearing length has a large friction and a high temperature rise during continuous rotation.

In order to avoid this disadvantage, according to the above item, it is difficult to perform the drilling process on the inner surface, the man-hour is increased, and the cost is inevitably increased.

The one according to the preceding paragraph can be said to eliminate the disadvantages in the above case, but since it utilizes the phenomenon of bulging during compression operation, there is a tendency that an accurate shape structure cannot be secured, and strength is also insufficient. Since it is easy to become, it requires a certain thickness and is relatively short. Furthermore, the outer surface of both ends of this product has a small diameter part, that is, only the middle part is bulged as described above. Even if a substantially solid setting can be obtained by leaving a space on each side of the housing, or by assuming a special configuration in which one side of the housing has a size and shape that matches the outer diameter size of one end of the bearing body. At the other end of the bearing body, there is no choice but to leave a gap between the bearing body and the housing, and it is difficult to obtain a stable set state.

"Structure of the Invention" (Means for Solving the Problem) A powder compacting step of forming a raw material powder charged between a core and a mold into a cylindrical body, and a compaction tube After sintering the body, insert the middle part of the molding area between the sizing core and the sizing die, which are in a large diameter state, and sizing by the upper and lower punches, and the large diameter part of the middle portion of the sizing core described above. By forming a diameter expansion region in the intermediate portion of the inner hole of the molded cylindrical sintered body by, then extruding the sizing body together with the sizing core from the mold, after that the sizing core is removed by spring back of the sizing body. Manufacturing method of sintered bearing material.

(Function) The compacted and sintered sintered tubular body is charged between the sizing die and the sizing core, which has a large diameter in the middle part of the molding area, and is sized so that the inner part of the inner hole has the large diameter part. An enlarged sizing body is obtained.

After this sizing, a spring back is obtained in the sizing body by removing the sizing body together with the core from the mold, and the core large diameter is generally 10 μm or less due to the taper at the boundary with the large diameter portion of the sizing core. The part can be pulled out easily.

The inner and outer surfaces of the product after sizing are both formed as a powder compact or a compression-molded layer, which uniformly stabilizes the structure and dimensions and also appropriately obtains strength.

Therefore, even a relatively thin product or a relatively long product having a length larger than the outer diameter can be appropriately manufactured. Since the sliding surfaces for the shaft members on both end sides each have an appropriate size and structure formed by die molding, an effective bearing action can be obtained. Moreover, the inner diameter of the product including both ends is uniform and straight, so that no special work is required for the housing mounting portion, and moreover, it is possible to always mount the housing in a solid state.

(Example) A concrete embodiment of the present invention as described above will be described with reference to the accompanying drawings. In the present invention, powder compaction is performed by an operation method as shown in FIG.
Next, the sizing after sintering the green compact is carried out by the method shown in steps in FIG.

That is, the powder compaction shown in FIG. 1 is exactly the same as that which has been generally performed conventionally, in which the raw material powder is charged between the core 1 and the die 2, and then the upper and lower punches 3, 3a is operated along the core 1 to perform powder compacting, and the inner and outer surfaces are both formed as straight compacts.

The powder compact obtained by the method of FIG. 1 as described above is then subjected to a sintering treatment to obtain a sintered body 4 as shown in FIG. 1 (B).

The sintered body obtained as described above is then subjected to a sizing treatment through the steps as shown in FIG. 2, and in this sizing, the sizing in which the middle portion of the sizing region is made the large diameter portion 11a Core 11, upper and lower punches 12, 13 and mold
Use 15.

That is, first, as shown in FIG. 3A, the above-mentioned sintered body 4 is set with the upper end of the sizing core 11 aligned with the upper surface of the die 15, and the upper punch 12 is pressed down to obtain the sintered body 4. Is the upper end side straight portion 11b of the sizing core 11 as described above.
Is pressed into the gap 14 between the mold and the inner surface of the mold, and then the large diameter portion 11
It is press-fitted between a and the mold 15. In order to effectively reduce the friction of the large diameter portion 11a with respect to the outer diameter of the sizing core 11 as a product bearing, about 5 to 10 μm is generally sufficient. It is relatively easily press-fitted between the diameter portion 11a and the inner surface of the die 15 to be in the state of FIG.
Compression sizing is performed as shown in FIG.

In the case of compression sizing as shown in FIG. 2 (C), the lower punch 13 and the sizing core 11 are both pushed up from the die 15 to knock out the sizing material 6 as shown in FIG. 2 (D). It As shown in FIG. 2D, the sizing material 6 that has been compressed at the time of sizing springs back due to such knockout, and a certain amount of gap is generated between the inner hole and the molding region of the sizing core 11. When the sizing core 11 is appropriately pulled out together with the lower punch 13 in this state, only the sizing material 6 remains on the die 15 as shown in FIG. 2 (E). That is, the sizing material 6 remaining on the mold 15 as shown in FIG. 2 (E) is discharged out of the molding area as shown in FIG.
Returning to the state of FIG. (A), the sizing similar to the above is repeated for the new sintered material 4.

Regarding the above-described sizing treatment, the details of the spring-back of the sizing material as shown in FIG. 2D will be described in practice. The sizing was performed by compressing the upper and lower punches 12 and 13 between the core and the die. It was confirmed by the study of the present inventors that when the sizing material 6 is pulled out from the mold 15 later, the diameter is increased by about +0.1 to + 0.2% from the mold size in any of the inner and outer diameters. There is. That is, even if there is some variation due to material, structure, etc., the above-mentioned springback amount is obtained under general sizing conditions, and the size of the large diameter portion 11a in the sizing core is set within this springback amount range. By increasing the diameter, the sizing core 11 having such a large diameter portion 11a can be pulled out substantially appropriately. At the time of this withdrawal, elastic deformation of the sizing material 6 is also obtained, so that it is substantially easy. For example, when the inner diameter of the sizing material 6 is 8 mm, many products in which the inner diameter of the expanded portion of the sizing material 6 is 8.005 to 8.010 mm have been studied, but there is no problem and smooth sizing is performed. Moreover, the expanded portion can sufficiently reduce the friction with respect to the shaft material.

The thus-obtained one according to the present invention has a straight outer diameter, so that there is nothing to be troubled when mounting it on the housing, and moreover, the middle portion of the inner hole is accurately formed into a central relief shape. The friction resistance between the shaft and the shaft is small, and since it is integrated, the coaxiality is also accurate.

[Advantages of the Invention] According to the present invention as described above, it is possible to form an appropriate non-contact surface for the shaft member on the inner diameter surface, thereby effectively reducing the friction at the time of bearing action, and moreover the whole is effective. It is clear that since it is formed by compaction molding or compression molding, it is excellent in strength, and it can be obtained as an accurate product in terms of dimensions, and it is possible to set a high degree of coaxiality because it is an integrally molded material. Moreover, since the outer surface can be mass-produced with a straight surface, there is nothing to worry about when mounting on the housing, and it is possible to provide a bearing material that can always make stable and accurate setting easily at low cost. It is an invention that is industrially highly effective.

[Brief description of drawings]

The drawings show the technical contents of the present invention. FIG. 1 is a cross-sectional view of a powder compacting mechanism in the method of the present invention, and FIG. 2 shows each step of a sizing mechanism for the compacted sintered body. It is sectional explanatory drawing shown in steps. Therefore, in these drawings, 1 is a core, 2 is a mold,
3 and 3a are punches, 4 is a sintered body, 6 is a sizing material, 10 is a housing, 11 is a sizing core, 11a is its large diameter portion, 1
1b is a straight part, 12 is an upper punch, 13 is a lower punch, 14 is a gap, and 15 is a sizing die.

Claims (1)

[Claims] 1. A powder compacting step of compacting a raw material powder charged between a core and a die into a cylindrical body, and a compacting zone after sintering the compacted cylindrical body. The intermediate portion is charged between the sizing core and the sizing die in a large diameter state, and sizing is performed by the upper and lower punches, and the formed tubular sintered body is formed by the large diameter portion in the intermediate portion of the sizing core molding region. A method for producing a sintered bearing material, characterized in that an expanded diameter region is formed in an intermediate portion of an inner hole, a sizing body is then extruded from a mold together with a sizing core, and then the sizing core is extracted by spring back of the sizing body. .