JP3818626B2 - Method for producing sintered oil-impregnated bearing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a manufacturing method of the oil-impregnated sintered bearings used in the bearing of various motors.
[0002]
[Prior art]
Sintered oil-impregnated bearings are compacted and sintered after compacting metal powder, adjusting the shape and dimensions, adjusting the surface pores such as sliding surfaces, and impregnating the internal pores with lubricating oil for various rotations. Used in equipment. The operating feature is that when a rotating shaft is attached to a sintered oil-impregnated bearing and rotated, the lubricating oil stored in the bearing pores oozes out between the rotating shaft and forms an oil film on the sliding surface, thereby causing sliding friction. In the part where the hydraulic pressure on the sliding surface is high, the lubricating oil returns to the inside of the bearing hole and oozes out again with the rotating shaft. By this repetition, the lubricating performance of the sliding surface of the shaft support part is maintained. . In this case, the excess lubricating oil that has oozed out may flow near the end face of the bearing and scatter on the rotating shaft. The splashing of the lubricating oil may contaminate the periphery of the bearing element or shorten the bearing life due to the loss of the lubricating oil.
[0003]
A technique for preventing such leakage and scattering of the lubricating oil is disclosed in, for example, Japanese Utility Model Publication No. 47-36736 and Japanese Patent Publication No. 8-19941. There is a method in which a tapered portion whose diameter is gradually enlarged toward the end portion is provided, and the inner wall surface of the tapered portion is formed more coarsely than the shaft support portion. What is formed in this way is that oil is accumulated in the wedge-shaped space formed between the tapered portion of the bearing bore and the rotating shaft by surface tension, and an oil film is continuously formed to facilitate the driving, and the oil is It absorbs easily and prevents external leakage.
[0004]
Further, as disclosed in Japanese Utility Model Publication No. 8-9450, there is a structure in which a member such as a porous sintered body is in contact with both ends of an oil-impregnated bearing press-fitted into a housing. This porous member has pores that can absorb oil that oozes out from the oil-impregnated bearing during operation, and a gap is formed between the porous shaft and the oil that oozes out from the oil-impregnated bearing. It is sucked and stored, and oil is retained in the gap to prevent leakage. If the oil-impregnated bearing has insufficient oil, the oil in the porous member can be sucked, so that the service life is prolonged.
[0005]
[Problems to be solved by the invention]
In the sintered oil-impregnated bearing as described above, the former has a shape in which the chamfer of the inner hole is expanded, and the chamfered portion is formed on the porous surface, so that it is easy to manufacture and prevents oil leakage. In the latter case, the members have to be manufactured separately, but the oil moves within the bearing element and there is no external leakage, and each is excellent. By the way, recently, the rotating shaft is often rotated at a higher speed, and even in that case, a sintered oil-impregnated bearing that can reliably maintain the oil leakage preventing effect and has an excellent bearing life is expected. Therefore, an object of the present invention is to realize a sintered oil-impregnated bearing that can be manufactured by a normal manufacturing process and that has less oil leakage.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the manufacturing method of the present invention has a shaft support portion (10a) at a portion including the middle in the shaft hole direction as a bearing material as illustrated in FIG. After manufacturing a sintered body (10A) having a large inner hole portion (10b) having an inner diameter larger than the shaft support portion at both ends, the shaft support portion (10a) is formed into a mold by sizing the sintered body. While correcting with the core, at least the end surface on the side where the large inner hole portion (10b) is formed is compressed with the upper and lower punches, and the hole portion near the end surface is reduced in diameter in the large inner hole portion. The main part is to form the inner hole small portion (1c) having a larger diameter than the inner diameter of the rear shaft support portion (1a).
[0007]
Specifically, the metal powder is compacted, and the shaft support portion (10a) is formed in a portion including the middle in the shaft hole direction, and the inner diameter is larger than the shaft support portion on one end side or both end sides of the shaft support portion. For the green compact (10) having a large portion (10b), the step of sintering the green compact, and the sintered body (10A), the shaft support (10a) is made of gold. While correcting with the mold core, at least the end surface on the side forming the large inner hole portion (10b) is compressed with the upper and lower punches, and the inner hole portion in the vicinity of the end surface of the large inner hole portion is reduced in diameter. A sizing step for forming the inner hole small portion (1c) having a diameter larger than the inner diameter of the shaft support portion (1a) after the correction, and a step for impregnating the sizing body (1) obtained in the sizing step with a lubricating oil; It goes through.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing four examples of sintered oil-impregnated bearings to which the present invention is applied, each in a vertical cross-sectional shape. FIG. 1A shows a cylindrical shape in which a large inner hole and a small inner hole are formed on both ends of the shaft support in the bearing inner hole, and FIG. 1B shows a large inner hole and a small inner hole. Is formed only on one end side of the shaft support, (c) is a flanged shape with respect to (a), (d) is a spherical outer shape with a large inner hole and a small inner hole Are formed on both ends of the shaft support. In these structural descriptions, the same or similar members or parts that are operatively the same are denoted by the same reference numerals, and redundant descriptions are omitted.
[0009]
In FIG. 1 (a), the sintered oil-impregnated bearing 1 has a shaft support portion 1a at the middle portion of the bearing inner hole, and the surface thereof is relatively densely formed by sizing. At both ends of the shaft support 1a, an inner diameter large portion 1b having an inner diameter larger than that of the shaft support 1a adjacent to the shaft support 1a, and an inner hole size larger than the shaft support 1a adjacent to the inner diameter large portion 1b, A small inner hole portion 1c smaller than the large hole portion 1b is provided. Each large inner hole portion 1b is connected via a slope (tapered slope) whose inner diameter is gradually enlarged from the corresponding portion of the shaft support portion 1a. This slope may be a convex or concave slope. The inner diameter large portion 1b and the surface of the inclined surface are rough surfaces having more pores than the shaft support portion 1a. On the other hand, the small inner hole portion 1c is located near the end surface and is connected via a slope (tapered slope) whose inner diameter is gradually reduced from the corresponding portion of the large inner diameter portion 1b toward the opening on the end surface side. . The inner hole small portion 1c is denser on the surface and in the vicinity around the surface of the large inner diameter portion 1b.
[0010]
The sintered oil-impregnated bearing 1 in FIG. 1B has a structure in which the large inner diameter portion 1b and the small inner hole portion 1c of FIG. 1A are formed only on one end side of the shaft support portion 1a. This is suitable for a bearing element that is used so that the side on which the portion 1b and the small inner hole portion 1c are formed becomes the open side of the bearing. Further, the sintered oil-impregnated bearing 1 in FIG. 1C has a structure in which a flange 1d is formed on one end side of the outer periphery of the bearing in FIG. 1A. As an example of use, the flange 1d can be used as an attachment element. It is. The sintered oil-impregnated bearing 1 in FIG. 1 (d) is a self-aligning bearing in which the outer peripheral shape of the bearing is formed as a spherical surface 1e, and the inner hole structure is the same as described above although the outer shape is different.
[0011]
In addition, each sintered oil-impregnated bearing 1 in FIGS. 1A to 1D is provided with a chamfer along the end surface, which is a conventional technique of this type of bearing, and an oil groove or a dynamic pressure groove is provided on the shaft support portion 1a. Providing the intermediate portion of the shaft support portion 1a which is a sliding surface as a middle relief shape which is a large diameter portion which is not in contact with the rotating shaft, both ends of the sintered oil-impregnated bearing as described in Japanese Utility Model Publication No. 8-9450 It is possible to add a configuration such as contacting a porous member to the surface.
[0012]
Next, the manufacturing method of the above-described sintered oil-impregnated bearing will be described with reference to a manufacturing example of the sintered oil-impregnated bearing 1 shown in FIG. The sintered oil-impregnated bearing 1 shown in FIGS. 1B to 1D is inferred from the explanation of FIG. 1A because the outer shape of the bearing is shaped by the same method as the conventional one. FIG. 2 is a schematic cross-sectional view illustrating a powder molding procedure.
[0013]
The molding die apparatus used is mainly a die 4 forming a die hole 4a. A cylindrical lower punch 8 and a lower core 5 are provided below the die hole 4a, and the die hole 4a. The upper punch 7 and the upper core 6 are disposed above the upper part. A difference from a general powder molding die for obtaining a bearing material shape is that the core is divided into upper and lower parts. As can be seen from FIGS. 2 (a) and 2 (b), the lower core 5 has a thickness for forming the large inner hole portion 10b or 1b of the bearing inner hole, and the upper end portion is a tapered portion 5a. . The upper core 6 has the same upper portion as the thickness of the lower core 5, and the lower portion is an upper core small diameter portion 6b for forming the shaft support portion 10a or 1a of the bearing via the taper portion 6a. .
[0014]
FIG. 2A shows a state in which the powder 2 is filled in the cavity formed by the lower core 5 and the lower punch 8 in the die hole 4a of the die 4 by a normal method. The powder 2 is a copper-based or iron-based alloy powder, or a normal mixed powder for forming an alloy. FIG. 2B shows a state in which the upper core 6 is lowered and the upper core small diameter portion 6 b is brought into contact with the upper end surface of the lower core 5. From this state, as the device drive, the upper core 6 and the lower core 5 are lowered and the upper core 6 and the lower core 5 are lowered so that the upper core small diameter portion 6b comes to the upper and lower intermediate portions of the powder 2 as shown in FIG. The punch 7 is also lowered. FIG. 2 (c) shows a state in which the powder 2 is compressed to a predetermined density and size by the upper punch 7 and the lower punch 8 and manufactured into a green compact (molded body) 10. Thereafter, the upper punch 7 and the upper core 6 are raised, and the green compact (molded body) 10 is pushed up and released by the lower punch 5 as shown in FIG. In this case, the lower core 5 is similarly raised. The inner hole of the produced green compact (molded body) 10 includes a shaft support portion 10 a formed by the upper core small diameter portion 6 b, an inner diameter large portion 10 b formed by the upper core 6 and the lower core 5, and the upper core 6. It has a shape having a tapered inner hole surface 10 c formed corresponding to the tapered portion 6 a and the tapered portion 5 a of the lower core 5.
[0015]
(Sizing) The green compact (molded body) 10 is sintered by a normal method in the next step. The sintered body 10A is sized using a mold as shown in FIG. The sizing mold has a normal structure including a die 14, a lower punch 18, an upper punch 17 and a core 19. FIG. 3A shows a state in which a sintered body 10A, which is a bearing material, is inserted into a mold. In this case, whether to adopt negative sizing or positive sizing is appropriately determined depending on the density of the obtained sintered bearing 1 and the desired surface condition. FIG. 3 (b) shows a state in which the sintered body 10 </ b> A is compressed by the upper and lower punches 17 and 18. The sintered body 10A is shaped into a design shape by this sizing and becomes a sintered bearing (sizing body) 1, which is pushed up by the lower punch 18 and released. The sintered bearing (sizing body) 1 is formed as a small inner hole portion 1c having a large diameter reduced at the end face side of the large inner hole portion 10b of the sintered body 10A. Not touching. Further, the vicinity of the small inner hole portion 1c is denser than the portion remaining as the large inner hole portion 1b.
[0016]
In the illustrated sizing example, in the case where a normal chamfer is provided at the inner hole opening of the sintered bearing (sizing body) 1, the chamfered portion is compressed together with the end surface of the sintered body 10A which is a bearing material. Further, the core rod 19 has a simple columnar shape, but, similarly to the core structure of the powder molding die shown in FIG. 2, using the lower core 5 and the upper core 6 having the small diameter portion 6b, The shaft support portion 10a may be sized by the core small-diameter portion 6b to be the shaft support portion 1a, and the lower core 5 and the upper core 6 may be brought into contact with the small inner hole diameter 1c reduced in size by sizing. According to this method, the accuracy of the inner diameter of the inner hole small portion 1c is stabilized, and the amount of surface pores of the inner hole small portion 1c can be reduced.
[0017]
The manufactured sintered bearing (sizing body) 1 becomes a sintered oil-impregnated bearing of the present invention when impregnated with lubricating oil (impregnated with normal pressure oil, vacuum or reduced pressure oil) in the next step. FIG. 4 shows a use state in which the rotary shaft 3 is mounted on the sintered oil-impregnated bearing 1 after impregnation. The rotary shaft 3 is inserted through the inner hole of the sintered oil-impregnated bearing 1 and is pivotally supported by the pivotal support portion 1a. On both sides of the shaft support portion 1a, the large inner hole portion 1b is positioned on the shaft support portion 1a side, and the small inner hole portion 1c is positioned closer to the end face than the large inner hole portion 1b. A minute gap S1 for oil film formation is secured between the rotating shaft 3 and the shaft support 1a, and a large oil gap S2 is secured between the rotating shaft 3 and the large inner hole 1b. A gap S3 suitable for preventing oil leakage is secured between the small inner hole portions 1c. In other words, in the sintered oil-impregnated bearing 1, the inner hole dimensions are such that the inner hole large portion 1b> the inner hole small portion 1c> the shaft support portion 1a. The density of the bearing inner hole surface is such that the inner hole large portion 1b <the inner hole small portion 1c <the shaft support portion 1a.
[0018]
(Operation) In the above bearing structure, for example, when the sintered oil-impregnated bearing 1 is fixed and the rotary shaft 3 is rotated, the lubricating oil impregnated in the pores of the shaft support portion 1a oozes into the clearance S1 and becomes a sliding surface. An oil film is formed. This lubricating oil is heated by frictional heat or outside air, and an excessive amount is generated due to thermal expansion. The excess lubricating oil flows into the annular gap S2 of the large inner hole portion 1b, and the large inner hole portion 1b. And then try to scatter from the hole end opening to the outside. However, in this bearing structure, since the tapered inclined surface that continues from the inner hole large portion 1b and the shaft support portion 1a to the inner hole large portion 1b is a portion where the pore density is coarse, the lubricating oil is used as the inner hole. It is easy to be sucked into or ooze out into the pores of the large portion 1b, functions as an oil reservoir adjacent to the shaft support portion 1a, and has an effect of preventing lack of lubricating oil in the shaft support portion 1a. The lubricating oil circulation between them is also improved. Moreover, since the small inner diameter portion 1c is located on the end surface side of the shaft hole and is smaller than the inner diameter size of the large inner hole portion 1b, it functions as a dam that ensures the oil reservoir function of the large inner hole portion 1b. And function to structurally prevent external leakage of the lubricating oil. Further, the lubricating oil in the large inner hole portion 1b is such that the pores in the small inner diameter portion 1c are denser than the large inner hole portion 1b, and the large inner hole portion between the small inner hole portion 1c and the large inner hole portion 1b. Since the tapered slope gradually increases in diameter toward 1b, the rotation of the rotary shaft 3 pushes it toward the inner wall of the large inner bore 1b (in the direction of the shaft support 1a), and the external leakage of the lubricating oil also occurs due to its action. Is prevented.
[0019]
Here, the diameter and axial length of the large inner hole portion 1 b and the small inner hole portion 1 c are appropriately designed according to the size of the sintered oil-impregnated bearing 1. At this time, the small inner hole portion 1c is set to such a size that the dam action of the oil sump can be obtained without contacting even when the rotary shaft 3 is inclined by normal driving. The inner hole large portion 1b has a diameter of the shaft support portion 1a from the case where the difference from the diameter of the shaft support portion 1a is about several μm, for example, the diameter of the shaft support portion 1a is about 1 mm and the wall thickness is thin. In the case of about 10 mm, it is arbitrary such as about 0.1 to 1 mm, but in that case, it is designed in consideration of the formability of the small inner hole portion 1c by sizing. Further, in the case of a bearing shape in which the large inner hole portion 1b can be set large, an appropriate amount that does not leak during operation into the clearance S2, that is, the annular space between the rotary shaft 3 and the large inner hole portion 1b. It is also possible to employ a method of injecting the lubricating oil.
[0020]
5 and 6 are longitudinal sectional views showing the other two forms of the sintered oil-impregnated bearing 1 together with the sintered body before sizing. In this description, the same code | symbol is attached | subjected to the same or similar member or site | part as the above-mentioned form, and a change point is explained in full detail. 5 (b), (b-1) and FIG. 6 (b) show a sintered body 10A after the green compact 10 is sintered, and FIG. 5 (a), FIG. 6 (a) and FIG. 1) shows a sized body or sintered bearing 1 after sizing.
[0021]
In the structure of FIG. 5, an example in which the shape of the small inner hole portion 1c is devised at the stage of compacting, and the sintered body 10A obtained by sintering the compact 10 can be actively shaped by sizing. It is. In the sintered body 10A of FIG. 5B, a convex portion 10d is provided on the inner diameter side of the bearing end surface together with the shaft support portion 10a, the large inner diameter portion 10b, and the tapered inner hole surface 10c by compacting. In the sintered body 10A of FIG. 5B-1, the shape of the bearing end surface is changed to a tapered portion 10e that decreases from the inner diameter side toward the outer diameter side instead of the convex portion 10d of FIG. The convex part 10d and the taper part 10e are formed only by changing the end face shape of the upper and lower punches 7 and 8 in FIG. In the sizing, the convex portion 10d and the tapered portion 10e are compressed by a re-pressure punch (same as the upper and lower punches 17 and 18 in FIG. 3), which is effective in facilitating the formation of the small inner diameter portion 1c.
[0022]
On the other hand, the structure of FIG. 6 is an example in which the inner hole small portion 1c can be positively shaped by a corresponding punch shape when sizing the sintered body 10A. That is, the sintered body 10A in FIG. 6B is obtained by compacting and then sintering the same as in FIG. Then, in the sizing process, in the sintered bearing (sizing body) 1 in FIG. 6 (a), a recess 1f is additionally formed on the end face side from the small inner diameter portion 1c, and the sintered bearing (sizing body) in FIG. 6 (a-1). ) 1 is additionally formed with a tapered recess 1g on the end face side from the small inner diameter portion 1c. In order to facilitate the formation of the small inner diameter portion 1c, these are formed by simply providing corresponding convex portions or tapered convex portions on the end face of the re-pressure punch (upper and lower punches 17 and 18 in FIG. 3) in the sizing process. It becomes effective. As described above, the present invention only needs to include the technical elements specified in the claims, and the invention can be modified based on this as necessary in production.
[0023]
【The invention's effect】
As described above, the manufacturing method of the present invention can be formed by compacting and sizing by a normal sintered bearing manufacturing process. It can be mass-produced efficiently.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view schematically showing a shape example of a bearing of the present invention.
FIG. 2 is a longitudinal sectional view for explaining a powder compacting method when manufacturing the bearing.
FIG. 3 is a longitudinal sectional view for explaining a sizing method in manufacturing the bearing.
FIG. 4 is a vertical cross-sectional view for explaining a usage state of the bearing.
FIG. 5 is a view showing another embodiment of the bearing of the present invention together with a sintered body before sizing.
FIG. 6 is a view showing still another embodiment of the bearing of the present invention together with a sintered body.
[Explanation of symbols]
1 ... Sintered oil-impregnated bearing (sintered bearing)
DESCRIPTION OF SYMBOLS 1a ... Shaft support part 1b ... Large inner hole 1c ... Small inner hole 2 ... Powder 3 ... Rotating shaft 10 ... Green compact 10A ... Sintered body (sizing body or bearing material)

Claims (3)

As a bearing material, a sintered body having a shaft support portion in a portion including the middle in the shaft hole direction and having a large inner hole portion having an inner diameter larger than the shaft support portion at one end side or both end sides of the shaft support portion was manufactured. rear,
By sizing the sintered body, the shaft support portion is corrected with a mold core, and at least the end surface on the side forming the large inner hole portion is compressed with an upper and lower punch, and the end surface of the large inner hole portion A method for manufacturing a sintered oil-impregnated bearing, comprising reducing a diameter of a nearby hole portion to form a small inner hole portion having a diameter larger than the inner diameter dimension of the shaft support portion after the correction. The shape of the bearing end surface of the sintered body is a shape having a convex portion on the inner diameter side or a shape having a tapered portion that decreases from the inner diameter side toward the outer diameter side, and the convex portion or the tapered portion is compressed by an upper and lower punch. The method for producing a sintered oil-impregnated bearing according to claim 1. The method for manufacturing a sintered oil-impregnated bearing according to claim 1 or 2, wherein a punch having a convex portion or a tapered convex portion on an end face is used.

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