JPH108101A - Manufacture of oil-containing bearing integrally sintered - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an integrally sintered oil- containing bearing, by which number of the manufacturing processes is reduced and an oil groove and an air groove or a recessed groove, etc., improving the lubricating effect can easily be formed. SOLUTION: Powder is filed up into a gap between a die 24 having the recessed part in the inner surface and a core rod having a step part with both a small diameter part and a large diameter part. The powder is compressed to compact a green compact having the bearing part 24 at one end and a projecting part 32 on the outer surface. Successively, the core rod is shifted in the axial direction and the small diameter part in the core rod is extended over the whole length of an inner hole of the green compact. The green compact incorporated in the recessed part of the die is converged so as to form one more bearing part 26 at the other end of the green compact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered oil-impregnated bearing and, more particularly, to a relief portion for reducing the rotational load of a shaft at the center of an inner hole, and the shaft is supported at both ends. The present invention relates to a method for manufacturing an integrated sintered oil-impregnated bearing.

[0002]

2. Description of the Related Art Conventionally, sintered oil-impregnated bearings have been widely used as bearings for motors used in OA equipment, audio equipment, home electric appliances and the like.

FIG. 32 shows a conventional assembly in which two cylindrical bearings 100, 100 are press-fitted into a cylindrical housing 102, and FIG. 33 shows a conventional assembly in which two cylindrical bearings 100, 100 are press-fitted into a flanged housing 104. An assembly is shown.

In the above-mentioned conventional assembly, the eccentricity of the two cylindrical bearings 100 and 100 is inevitable. In addition, in order to reduce the cost, recently, an integrated sintered oil-impregnated bearing combining the two cylindrical bearings is widely used. It is used.

In a conventional integrated sintered oil-impregnated bearing, as shown in FIG. 34, a cylindrical sintered body 106 is first manufactured as shown in FIG. First, a processed product 110 that is produced by machining the central portion 108 of the inner hole 106 and a cylindrical sintered body 112 having a stepped inner hole as shown in FIG. Die 11 having body 112 with stepped bore
There is known a plastic worked product 120 or the like which is formed into a product by forming a small outer diameter portion 118 by recompressing using the sizing core 116 and the sizing core 116.

As shown in FIG. 36, a compact 122 is manufactured using a predetermined mold (not shown), and after removing the compact 122 from the mold, another compact 12 is formed.
A recompressed product 126 which is recompressed and commercialized in step 4 is also known.

[0007]

Among the conventional methods for manufacturing an integrated sintered oil-impregnated bearing, the one shown in FIG. 34 requires a machining step, and the plastic work piece 120 shown in FIG.
Requires a step of reducing the outer diameter of the re-pressing section 118 and a step of re-pressing, and the re-compressed product 126 shown in FIG. 36 requires a step of re-compressing. There was a problem that increases.

Further, there is a problem that not only is it difficult to form an oil groove or an air vent groove having a deep penetration of, for example, 0.05 mm or more, but it is also difficult to form a wedge-shaped concave groove for enhancing a lubricating effect.

The present invention has been made in view of the above-mentioned problems of the prior art, and reduces the number of manufacturing steps and easily forms oil grooves and air grooves, or concave grooves for enhancing a lubricating effect. It is an object of the present invention to provide a method for manufacturing an integrated sintered oil-impregnated bearing that can be used.

[0010]

Means for Solving the Problems To achieve the above object, the invention according to claim 1 of the present invention has a relief portion at a central portion of an inner hole for reducing a rotational load of a shaft. A method for producing an integrated sintered oil-impregnated bearing that supports a shaft at both ends, wherein a powder is filled between a die having a concave portion on the inner surface and a stepped core rod having a small-diameter portion and a large-diameter portion, By compressing the powder, a compact having a bearing at one end and having a protruding portion on the outer surface is formed, and the core rod is moved in the axial direction so that the small diameter portion of the core rod extends over the entire length of the inner hole of the compact. And another compact is formed at the other end of the green compact by narrowing down the green compact contained in the concave portion of the die to the inner diameter of the die.

Further, the invention according to claim 2 is characterized in that the volume of the concave portion of the die is set to approximately twice the volume of the green compact squeezed out to the small diameter portion of the core rod. .

Further, the invention according to claim 3 is characterized in that a portion of the inner surface of the die other than the concave portion is formed in a cylindrical shape, and an outer surface of the integrated sintered oil-impregnated bearing is formed in a cylindrical shape.

According to a fourth aspect of the present invention, there is provided the first punch having an inner surface near one end of the die having a stepped shape, the first punch having an outer diameter substantially equal to the inner diameter of the opening of the stepped shape, and the stepped portion. A brim is formed on the outer surface of the green compact according to the shape, and one end of the green compact is formed by a second punch having an inner diameter substantially equal to the outer diameter of the small diameter portion of the core rod.

According to a fifth aspect of the present invention, the core rod has a plurality of convex portions extending in an axial direction on an outer surface of the small diameter portion and an outer surface of the large diameter portion. A plurality of penetrating oil grooves and air vent grooves are formed on the inner surface of the sintered oil-impregnated bearing.

According to a sixth aspect of the present invention, the core rod has a plurality of projections extending in an axial direction on an outer surface of the small diameter portion, and the projections of the integrated sintered oil-impregnated bearing are formed by the projections. A plurality of grooves for enhancing the lubricating effect are formed on the inner surface of the bearing at both ends.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. The integrated sintered oil-impregnated bearing according to the present invention performs compaction drawing in the step of compressing the powder as described below, and a relief portion is provided at the center of the inner hole of the integrated sintered oil-impregnated bearing without increasing the number of steps. Is provided.

FIG. 1 shows a straight or cylindrical integrated sintered oil-impregnated bearing 2 according to the present invention, in which a relief portion 4 is formed at the center of the inner hole, and FIG. The integrated sintered oil-impregnated bearing 6 is shown, and a relief 8 is formed in the center of the inner hole.

FIG. 3 shows an oil groove and an air release groove 10 having a sectional shape shown in FIG. 4 on the inner surface of the integrated sintered oil-impregnated bearing 2 of FIG.
5 is an integrated sintered oil-impregnated bearing 2A. FIG. 5 shows an integrated sintered oil-impregnated bearing 6 in FIG. It is an oil-impregnated bearing 6A.

FIG. 6 shows an integrated sintered oil-impregnated bearing 2B in which a concave groove 14 for enhancing the lubricating effect is formed on the inner surface of the integrated sintered oil-impregnated bearing 2 of FIG. Yes,
FIG. 8 shows an inner surface of the integrated sintered oil-impregnated bearing 6 of FIG.
An integrated sintered oil-impregnated bearing 6B having the same cross-sectional shape as that of FIG.

The grooves 14 and 16 are not limited to the cross-sectional shape shown in FIG.
(C), grooves (d) having various cross-sectional shapes such as (d),
14b and 14c are conceivable. In addition, FIG.
In (b), (c), and (d), reference numeral 18 denotes a contact portion between the shaft and the bearing.

Here, in the integrated sintered oil-impregnated bearings 2, 2A and 2B shown in FIGS. 1, 3 and 6, the length of the relief portion 4 is the same as that of the conventional assembly shown in FIGS. The distance between the two bearings 100, 100 can be set substantially the same.

In the integrated sintered oil-impregnated bearings 2A and 6A shown in FIGS. 3 and 5, two or more, for example, six piercing oil grooves and air vent grooves 10,
12 promotes the circulating action of the oil exuded by the self-lubricating action, and in FIGS. 6 and 8, two or more, for example, six concave grooves 14, 16 provided in the bearing inner hole are provided with the shaft. Due to the rotational force generated by the rotation, the concave grooves 14, 16
The oil accumulated in the shaft is supplied to the contact portion between the shaft and the bearing to enhance the lubrication effect, thereby reducing the rotational load of the shaft.

Next, a method of manufacturing the straight type integrated sintered oil-impregnated bearing 2 shown in FIG. 1 will be described with reference to FIG. First, in the press forming step of compressing the metal powder together with a small amount of binder, the upper bearing portion 20 is formed at the time of pressurizing up to FIG. 9 (e), and at the time of extraction of FIG. While holding down the upper punch 22 by air pressure, the die 24 is lowered and the lower bearing portion 26 is drawn down by hold-down to form the lower bearing portion 26, and a relief portion 4 is provided at the center of the inner hole to form a relief. The contact length of the bearing has been reduced.

FIG. 10 shows a mold used in the above-mentioned powder compacting step, and includes a small-diameter portion 28a and a large-diameter portion 28b.
The inner diameter of the bearing is determined by the stepped core rod 28 having the following formula, and the outer diameter of the bearing is determined by the die 24. Die 2
4 has an annular recess 24a for squeezing out the green compact.
Are formed, and the inner surface of the die 24 except for the concave portion 24a is formed in a cylindrical shape. The upper and lower end surfaces of the bearing are determined by the upper punch 22 and the lower punch 30, respectively. The upper punch 22 has an inner diameter substantially equal to the outer diameter of the small diameter portion 28a of the core rod 28, while the lower punch 30 has a larger diameter of the core rod 28. The outer diameter of the upper punch 22 and the lower punch 30 are both set substantially equal to the inner diameter of the die 24.

Hereinafter, the compressed state of the powder will be described in detail for each step. The molding method is based on a non-simultaneous three-time pressing method.

As shown in FIG.
First, powder is filled in a mold formed by the core rod 28 and the lower punch 30. Next, as shown in FIG. 9B, after lowering the upper punch 22 to seal the powder inside the die 24, the core rod 28 is raised, and the first upper pressing is started. In FIG. 9C, the upper punch 22 is further lowered to perform a first upper pressurization, and the die 24 and the upper punch 22 are both lowered by the withdrawal of FIG. Perform pressure. After the lower pressurization is completed, the upper punch 22 is further lowered as shown in FIG. 9E, and the final pressurization by the upper punch 22 is completed. At this point, the compression of the upper bearing portion 20 is substantially completed, and the lower end surface of the green compact is made to substantially coincide with the lower end of the annular concave portion 24a of the die 24.

Next, referring to FIG.
After the small-diameter portion 8 is lowered in the axial direction to extend the small-diameter portion 28a of the core rod 28 over the entire length of the inner hole of the green compact, the green compact drawing is started, and in FIG. While holding the die 30 at the current position, the die 24 and the core rod 28 are simultaneously lowered at least by a distance corresponding to the axial length of the concave portion 24a of the die 24, and the green compact stored in the concave portion 24a of the die 24 is removed. The compacting is completed by drawing out. Thereafter, as shown in FIG. 9 (h), the upper punch 22 is raised and at the same time the die 24 is lowered to start withdrawing the green compact, and as shown in FIG. To complete the extraction of the green compact.

That is, the compression molding of the powder is completed by FIG. 9 (e), and the drawing and extraction of the green compact are completed by FIGS. 9 (e) to 9 (i).

When the pressurization in FIG. 9E is completed, the inner diameter of the green compact becomes small only in the upper part 20 and the other part becomes a large-diameter stepped hole. The outer diameter of the green compact is increased by an amount corresponding to the depth of the die concave portion 24a at the lower portion of the green compact. Is drawn down to the inner diameter of the die 24. At this time, the upper punch 22 is held at the pressure completion position so as not to break the green compact, and the green compact is clamped by air pressure.

The clamping force is stronger than the force that the green compact tends to extend upward by drawing and does not break the green compact.
It is set to 0 kg / cm ² or less. If the clamping force is weak, cracks occur in the drawn portion, and if it is strong, the compact is deformed. The squeezing amount is approximately twice the volume of the green compact squeezed out to the small-diameter portion 28a of the core rod 28 as the squeezing volume of the outer diameter (the volume of the recess 24a). This is because about half of the contracted volume of the outer diameter is absorbed by the elastic deformation of the green compact particles.

Cracks may occur if the sectional shape of the constricted portion (recess 24a) is not appropriate. In addition to the shape shown in FIG. 10, (a), (b), (c), and (c) of FIG.
The squeezed portions 24b, 24 having a sectional shape as shown in FIG.
c, 24d, 24e, etc. can also be adopted.

9 (e) to 9 (i), the movable core rod 28 is lowered after the completion of the pressurization shown in FIG. 9 (e). ) 28
b enters the lower punch 30 and the first stage (small diameter portion) 2
8a guides the upper part of the inner diameter of the green compact. Movable core rod 2
8 is completed, the die 24 is lowered and the green compact is drawn out with a drawing output for extracting the green compact. The core rod 28 is lowered synchronously with the die 24 until the drawing is completed. Pressing under the inner diameter due to wall friction is performed on the drawn portion.
After the drawing is completed, the core rod 28 is separated from the movement of the die 24, and is held together with the green compact at the drawing end position by air pressure, and the core rod 28 is lowered upon completion of the drawing in FIG. 9 (i). Thereafter, the green compact is discharged from the molding position by a feeder (not shown), and the die 24, the core rod 28 and the upper punch 22 return to the filling position.

The green compact thus obtained is then sintered,
After being subjected to an oil impregnation process, it is commercialized as an integrated sintered oil impregnated bearing, but there are also products that are manufactured by performing a sizing finish for the purpose of correcting the dimensions of the inner and outer diameters according to the required accuracy.

Next, a method of manufacturing the integrated sintered oil-impregnated bearing 6 with a flange shown in FIG. 2 will be described with reference to FIG. 12. Since this manufacturing method is substantially the same as the above-mentioned straight type,
Only the differences will be described.

In the press molding step of compressing the powder,
The upper bearing part 34 is formed at the time of pressurizing up to FIG. 12 (e), and the lower bearing part 36 is drawn at the time of drawing out of FIG. 12 (i).
In FIG. 12 (e) and thereafter, the upper first punch 40 of the brim portion performs the green compact drawing by synchronizing with the upper ram 42 to escape, and the relief portion 8 is provided at the center of the inner diameter to form the shaft with the shaft. The contact length of the bearing has been reduced.

FIG. 13 shows a mold used for manufacturing the integrated sintered oil-impregnated bearing 6. 13, a core rod 28 for determining the inner diameter of the bearing and a lower punch 30 for determining the lower end face of the bearing are the same as those shown in FIG.
The die 44 is used as a mold for determining the outer diameter of the bearing. The die 44 has a stepped shape having at least two stepped portions 44b and 44c on the inner surface near the upper end thereof in order to form a flange. It has become. The dies that determine the upper end surface of the bearing are two punches, an upper first punch 40 for forming a brim portion and an upper second punch 38 for forming a boss portion. The upper first punch 40 has an outer diameter substantially equal to the inner diameter of the stepped opening and an inner diameter equal to the inner diameter below the die recess 44a, while the upper second punch 38 has an inner diameter substantially equal to the inner diameter of the upper first punch 40. Equal outer diameter and small diameter portion 28a of core rod 28
Has an inner diameter substantially equal to the outer diameter of

The difference in the powder compression molding is that the upper pressing amount L1 is small and the lower pressing amount L2 of the withdrawal is large.
Is to escape from the green compact in synchronization with the upper ram 42.

The die 44 has an annular concave portion 44a formed as a narrowed portion. The cross-sectional shape may be the same as that shown in FIG.

FIG. 14 shows a method for manufacturing the integrated sintered oil-impregnated bearing 2A having the straight oil groove and the air vent groove shown in FIG.

Since the two or more through-grooves 10 provided in the bearing inner hole are formed in the compact, they have a structure having many pores so that oil can easily flow in and out by a self-lubricating action. Excess oil at the contact portion between the shaft and the bearing is absorbed by the concave groove portion 10 and exudes again by the self-lubricating action, so that the circulation action is promoted. Further, the depth of the piercing groove 10 is 0.0.
5 mm or more and the width is 0.2 mm or more. The core rod can be made shallow, deep, wide or narrow as required by the core rod. Further, since the concave groove 10 penetrates, air interposed between the bearing and the shaft can be released.

The green compact drawing of FIG. 14 is substantially the same as the green compact drawing of FIG. 9, but differs in the mold used.

FIG. 15 shows a mold used in the green compact drawing of FIG. 14. The core rod 46 for determining the inner diameter of the bearing is, as shown in FIG. ) 46a and a second step (large-diameter part) 46b. The first step 46a forms upper and lower inner diameters of the green compact, while the second step 46b defines a central relief part 4.
Is formed, and the lower punch 48 is guided. Since the oil groove and the air release groove 10 are formed over the entire length in the axial direction of the bearing, the convex portions 46c forming the oil groove and the air release groove 10 are formed in both the first step 46a and the second step 46b in the axial direction. Have been.

The die 24 for determining the outer diameter of the bearing is shown in FIG.
The same ones as shown in Table 1 are used. The inner hole of the upper punch 50 that determines the upper end surface of the bearing has a plurality of recesses 5 corresponding to the cross-sectional shape of the first stage 46a of the core rod 46.
In the inner hole of the lower punch 48 that determines the lower end surface of the bearing, a plurality of concave portions corresponding to the cross-sectional shape of the second stage 46b of the core rod 46 are formed.

The unevenness of the core rod 46 for forming the oil groove and the air vent groove 10 is manufactured by contour transfer processing using an NC electric discharge machine.

FIG. 17 shows a method of manufacturing the integrated sintered oil-impregnated bearing 6A with a collar and an oil groove shown in FIG. The green compact drawing by this method is substantially the same as the green compact drawing of FIG. 12, and differs in the mold used.

FIG. 18 shows a die used in the green compact drawing of FIG. 17. The core rod 52 for determining the inner diameter of the bearing is similar to the core rod 46 of FIG. ) 52a and a second step (large diameter portion) 52b are formed in a stepped shape, and the projections 52c forming the oil groove and the air vent groove 12 are formed in both the first step 52a and the second step 52b. Have been. Die 44 for determining outer diameter of bearing
The same die as that shown in FIG. 13 is used. Also, the upper first punch 40 for determining the flange portion of the bearing is shown in FIG.
The same as the first punch shown in 3 is used,
A plurality of recesses 54a corresponding to the cross-sectional shape of the first stage 52a of the core rod 52 are formed in the inner hole of the upper second punch 54 that determines the boss portion. A plurality of recesses corresponding to the cross-sectional shape of the second stage 52b of the core rod 52 are formed in the hole. The core rod 52 is manufactured in the same manner as the core rod 46 in FIG.

FIG. 19 shows a method of manufacturing the integrated sintered oil-impregnated bearing 2B having the grooves 14 for enhancing the lubricating effect shown in FIG. The two or more piercing grooves 14 provided on the inner surface of the bearing have a cross-sectional shape as shown in FIGS. 7A to 7D, and the self-lubricating action of the sintered oil-impregnated bearing is caused by the rotation of the shaft. In addition to retaining the exuded oil, the lubricating effect is increased by supplying the oil to the contact portion between the shaft and the bearing by the rotational force generated by the rotation of the shaft.

The green compact drawing shown in FIG.
Is substantially the same as the green compact drawing and differs in the mold used.

FIG. 20 shows a mold used in the green compact drawing of FIG. 19, and the core rod 58 for determining the inner diameter of the bearing is the same as the core rod 46 of FIG. The first stage (small diameter portion) 58a that forms the portion, and the second stage (large diameter portion) that forms the central relief portion and guides the lower punch
58b, but the convex portion 58c forming the concave groove 14 for improving the lubricating effect is formed in the first step 58c.
a only (FIG. 21).

The same die as the die 24 and the lower punch 30 shown in FIG. 10 is used for the die for determining the outer diameter of the bearing and the lower punch for determining the lower end face of the bearing. The inner hole of the upper punch 60 that determines the upper end surface of the bearing is provided with the core rod 5.
8, a plurality of recesses 60 corresponding to the cross-sectional shape of the first stage 58a.
a is formed. The concave groove 14 for enhancing the lubricating effect is formed only in the upper and lower inner diameter portions of the bearing, and the central portion is the relief portion 4 determined by the second stage 58b of the core rod.
In addition, the core rod 5 which forms the concave groove 14 which enhances the lubrication effect
The concavo-convex processing of No. 8 is manufactured by contour transfer processing using an NC electric discharge machine.

The sectional shape of the concave groove 14, that is, the shape of the convex portion 58c of the first stage 58a of the core rod is shown in FIG.
The shape is not limited to the shape shown in FIG.
Various shapes as shown in FIGS. 2 (a), (b) and (c) can be adopted.

FIG. 23 shows a method for manufacturing the integral sintered oil-impregnated bearing 6B with a flange having the groove 16 for enhancing the lubricating effect shown in FIG. The green compact drawing shown in FIG. 23 is substantially the same as the green compact drawing of FIG.
It differs in the mold used.

FIG. 24 shows a mold used in the green compact drawing of FIG. 23. The core rod 62 for determining the inner diameter of the bearing is, like the core rod 58 of FIG. The first stage (small diameter portion) 62a that forms the portion, and the second stage (large diameter portion) that forms the central relief portion and guides the lower punch
62b, and has a stepped shape.
(A) or convex portions 6 forming concave grooves 16 for improving the lubricating effect as shown in FIGS. 22 (a), (b) and (c).
2c is formed only in the first stage 62a.

The die for determining the outer diameter of the bearing, the upper first punch for determining the flange of the upper end surface of the bearing, and the lower punch for determining the lower end surface of the bearing are a die 44 and an upper first punch 40 shown in FIG. And the lower punch 30, but a plurality of recesses 64a corresponding to the cross-sectional shape of the first stage 62a of the core rod are formed on the inner surface of the upper second punch 64 that determines the boss. The grooves 16 for improving the lubrication effect are provided only at the inner diameter portions at the top and bottom of the bearing, and the center portion is the second stage of the core rod 62b
Is the escape portion 8 determined by the above. The core rod 62 is manufactured in the same manner as the core rod 58 in FIG.

The core rod 58 and the core rod 62
If the cross-sectional shape of the plurality of protrusions 58c, 62c formed in the shape is rectangular, the oil groove and the air vent groove having a rectangular cross section only at both end bearing portions of the integrated sintered oil-impregnated bearing shown in FIGS. Can also be formed.

A life test was conducted on three integrated sintered oil-impregnated bearing samples obtained by the green compact drawing method of the present invention and two bearing sample samples obtained by a conventional method for comparison. FIG. 25 to FIG. 29 show that these bearing samples are incorporated in a motor, and 200 rpm to 3000 rpm at 80 ° C.
It is a graph which shows the change of the shaft loss (motor consumption current value) at the time of performing the life evaluation of a bearing for 10000 hours while changing to rotation.

FIG. 25 is a conventional product having no relief at the center of the bearing, FIG. 26 is a conventional product having a relief at the center of the bearing by machining, plastic working or recompression, and FIG. FIG. 28 shows an invention in which a relief portion is provided at the center of the bearing by powder drawing, FIG. 28 further shows an invention in which a plurality of oil grooves and air vent grooves are added to the inner surface of the bearing, and FIG. The result of the invention which added the groove | channel is shown.

As shown in the above graph, the invention of FIG. 27 in which the relief portion is provided at the center of the bearing by the green compact drawing is larger than the conventional product of FIG. The loss is small and the rotational load on the shaft is reduced. Also, the product of the present invention shown in FIG. 27 has the same level as that of the conventional product in which a relief portion is provided at the center of the bearing by machining, plastic working or recompression working, although the manufacturing process is simplified. Axis loss. And FIG.
In the invention product having the oil groove and the air vent groove of No. 8, the change in the shaft loss is small even after more than 5000 hours, and a good lubricating effect is obtained.

Further, in the invention product in which a plurality of grooves for improving the lubricating effect are added, the change in the axial loss is small even after 10,000 hours, and a better lubricating effect is obtained.

Next, the strength of the straight compact drawing product will be described with reference to FIG.

In order to perform drawing on a green compact having low strength,
Although the cracks are likely to occur in the narrowed portion, the amount of reduction of the outer diameter that does not cause cracks from various tests is approximately twice the volume to be narrowed down to the inner diameter, and the cross-sectional shape of the narrowed portion is shown in FIGS.
As described above, the shape of (d) is good, but the strength test examples are shown in the table. The number of samples is 20, and the minimum and maximum values are entered. As can be seen from this table, the strength of the drawn portion is stronger than that of the normally formed upper bearing portion which is not drawn, regardless of whether it is a green compact or a sintered body, and there is no problem in strength.

Further, the accuracy of the sintered compact of the straight compact drawing will be described with reference to FIG.

The number of samples was 20 for the conventional product and the product of the present invention with respect to the dimensional variation of the outer diameter, inner diameter, and length, the roundness of the inner diameter, the coaxiality of the inner diameter, and the deflection of the outer diameter based on the inner diameter. In the table. As can be seen from this table, although there is almost no difference from the conventional product, there is a slight variation in the accuracy of the narrowed portion. This is an unavoidable variation, and there is no problem in use.

As described above, the present invention relates to a manufacturing method for forming an integrated sintered oil-impregnated bearing without increasing the number of steps by performing compacting and drawing in a step of compressing powder. is there. As a result, it is possible to manufacture a straight and flanged integrated sintered oil-impregnated bearing without performing the steps of post-processing, re-pressurization and re-compression.

Further, the oil groove and the air vent groove are difficult to be processed by post-processing, and when a deep groove processing of 0.05 mm or more is performed by re-pressing and re-compressing, the pores of the groove part become small, and the sintered oil-impregnated bearing is formed. Self-lubricating action is reduced and oil is less likely to come out. However, if compression molding is performed using a core rod 46 having a convex portion 46c shown in FIG. 16, an oil groove having a desired depth, width, and pores, and an air vent groove can be added.

Further, due to the rotational force generated by the rotation of the shaft, oil accumulated in the concave grooves 14, 14a, 14b, 14c as shown in FIGS. In the integrated sintered oil-impregnated bearing supplied with a high lubrication effect, it is difficult to perform post-processing of the concave groove portion 18, and pores become small in re-pressing and re-compressing, thereby reducing the self-lubricating effect. However, when compression molding is performed using a core rod 58 having a convex portion as shown in FIG. 21 or FIG. 22, a concave groove having a desired depth, width, and pores can be formed.

That is, by performing green compaction in the step of compressing the powder, it is possible to provide a relief portion for reducing the rotational load of the shaft at the center of the bearing bore without increasing the number of steps. Instead, it is possible to manufacture an integrated sintered oil-impregnated bearing having an oil groove, an air vent groove, a concave groove for enhancing a lubricating effect, and the like.

[0068]

The present invention is embodied in the form described above, and according to the first aspect of the present invention having the following effects, a bearing portion is provided at one end. First, a green compact having a projecting portion on the outer surface thereof is formed, and this projecting portion is narrowed down to the inner diameter of the die, so that another bearing portion is formed at the other end of the green compact. A relief part to reduce the rotational load of the shaft can be added at the center of the inner hole in the step of compressing the powder, and it is easy to manufacture an integrated sintered oil-impregnated bearing with bearings at both ends without increasing the manufacturing process can do.

According to the second aspect of the present invention, since the volume of the concave portion of the die is set to be approximately twice the volume of the green compact squeezed into the small diameter portion of the core rod, half of the volume of the squeezed is reduced. Even if the green compact particles are absorbed by the elastic deformation, a predetermined bearing portion can be formed at the other end of the green compact.

Further, according to the third aspect of the present invention, since the portion of the inner surface of the die other than the concave portion is formed in a cylindrical shape, a straight integrated sintered oil-impregnated bearing can be easily manufactured.

According to the fourth aspect of the present invention, the inner surface near one end of the die has a stepped shape, and the first punch having an outer diameter substantially equal to the inner diameter of the opening of the stepped shape and the stepped plate. A flange is formed on the outer surface of the green compact by the attached shape, and one end of the green compact is formed by the second punch having an inner diameter substantially equal to the outer diameter of the small diameter portion of the core rod. The oil-impregnated bearing can be easily manufactured.

According to the fifth aspect of the present invention, the core rod having a plurality of convex portions extending in the axial direction on the outer surface of the small diameter portion and the large diameter portion is used. An integrated sintered oil-impregnated bearing having a plurality of penetrating oil grooves and air vent grooves on the inner surface can be easily manufactured.

According to the sixth aspect of the present invention, the core rod having a plurality of convex portions extending in the axial direction on the outer surface of the small diameter portion is used. Thus, an integrated sintered oil-impregnated bearing having a plurality of concave grooves for enhancing the lubricating effect can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a straight type integrated sintered oil-impregnated bearing according to the present invention.

FIG. 2 is a longitudinal sectional view of a flanged integral sintered oil-impregnated bearing according to the present invention.

FIG. 3 is a longitudinal sectional view of an integrated sintered oil-impregnated bearing with a straight oil groove and an air vent groove according to the present invention.

FIG. 4 is a sectional view taken along line IV-IV in FIG. 3;

FIG. 5 is a longitudinal sectional view of an integral sintered oil-impregnated bearing with a flanged oil groove and an air vent groove according to the present invention.

FIG. 6 is a longitudinal sectional view of a straight type integrated oil-impregnated bearing with a concave groove according to the present invention.

7A is a cross-sectional view taken along line VII-VII in FIG. 6, FIG. 7B is a cross-sectional view showing a modified example thereof, and FIG.
FIG. 9 is a cross-sectional view showing another modified example, and FIG. 9D is a cross-sectional view showing still another modified example.

FIG. 8 is a longitudinal sectional view of an integral sintered oil-impregnated bearing with a groove having a flange according to the present invention.

FIG. 9 is a process chart showing a powder compression molding state of the straight type integrated sintered oil-impregnated bearing of FIG. 1;

10 is a longitudinal sectional view of a mold used for manufacturing the straight type integrated sintered oil-impregnated bearing of FIG.

11A is a cross-sectional view illustrating a modification of the throttle unit illustrated in FIG. 10, FIG. 11B is a cross-sectional view illustrating another modification, and FIG. 11C is a cross-sectional view illustrating another modification. FIG.
(D) is sectional drawing which shows another modification.

FIG. 12 is a process chart showing a powder compression molding state of the flanged integrated sintered oil-impregnated bearing of FIG. 2;

FIG. 13 is a longitudinal sectional view of a mold used for manufacturing the integrated sintered oil-impregnated bearing with a flange of FIG. 2;

FIG. 14 is a process diagram showing a powder compression molding state of the integrated sintered oil-impregnated bearing with the straight oil groove and the air vent groove of FIG. 3;

FIG. 15 is a longitudinal sectional view of a mold used for manufacturing the integrated sintered oil-impregnated bearing with the straight oil groove and the air vent groove shown in FIG. 3;

16 is a core rod shown in FIG. 15,
(A) is a plan view thereof, and (b) is a longitudinal sectional view thereof.

17 is a process diagram showing a powder compression molding state of the integrated oil-impregnated bearing with a flanged oil groove and an air vent groove of FIG. 5;

18 is a longitudinal sectional view of a mold used for manufacturing the integrated sintered oil-impregnated bearing with a flanged oil groove and an air vent groove of FIG. 5;

FIG. 19 is a process diagram showing a powder compression-molding state of the integrated sintered oil-impregnated bearing with the straight groove in FIG. 6;

FIG. 20 is a longitudinal sectional view of a mold used for manufacturing the integrated sintered oil-impregnated bearing with the straight groove in FIG. 6;

21 is a core rod shown in FIG. 20,
(A) is a plan view thereof, and (b) is a longitudinal sectional view thereof.

22A is a plan view showing a modification of the core rod of FIG. 21, FIG. 22B is a plan view showing another modification, and FIG. 22C is a plan view showing still another modification. It is.

FIG. 23 is a process diagram showing a powder compression molding state of the integrated sintered oil-impregnated bearing with a flanged concave groove of FIG. 8;

24 is a longitudinal sectional view of a mold used for manufacturing the integrated sintered oil-impregnated bearing with a flange and a concave groove shown in FIG. 8;

FIG. 25 is a graph showing the shaft loss of a conventional product having no relief at the center of the bearing.

FIG. 26 Plastic processing (re-pressing) of the relief at the center of the bearing
6 is a graph showing the shaft loss of the conventional product added in FIG.

FIG. 27 is a graph showing the shaft loss of the product of the present invention in which a relief portion at the center of the bearing is added by green compact drawing.

FIG. 28 is a graph showing the shaft loss of the product of the present invention in which a relief portion at the center of the bearing is added by green compact drawing and further six oil grooves and air vent grooves are added.

FIG. 29 is a graph showing the shaft loss of the product of the present invention in which a relief at the center of the bearing was added by green compact drawing and six grooves were further added to enhance the lubrication effect.

FIG. 30 is a table showing the breaking strength of a green compact of a green compact and a sintered body.

FIG. 31 is a table showing the accuracy of a sintered body of a green compact drawn product.

FIG. 32 is a longitudinal sectional view of a conventional assembly into which two straight-type green compact drawing products are press-fitted.

FIG. 33 is a longitudinal cross-sectional view of a conventional flanged assembly into which two straight green compact drawn products are press-fitted.

FIG. 34 is a process chart showing a conventional method for forming a relief portion at the center of the inner hole of the integrated sintered oil-impregnated bearing by machining.

FIG. 35 is a process diagram showing another conventional method for forming a relief portion at the center of an inner hole of an integrated sintered oil-impregnated bearing by plastic working.

FIG. 36 is a process diagram showing still another conventional method for forming a relief portion at the center of the inner hole of the integrated sintered oil-impregnated bearing by recompression.

[Explanation of symbols]

2,2A, 2B, 6,6A, 6B Integrated sintered oil-impregnated bearings 4,8 Relief part 10,12 Oil groove and air vent groove 14,16 Concave groove for enhancing lubrication effect 20,34 Upper bearing part 22,50,60 Upper punch 24, 44 Die 24a, 24b, 24c, 24d, 24e, 44a Recess 26, 36 Lower bearing 28, 46, 52, 58, 62 Core rod 28a, 46a, 52a, 58a, 62a Small diameter portion 28b, 46b, 52b , 58b, 62b Large diameter portion 30, 48, 56 Lower punch 32 Projecting portion 38, 54, 64 Upper second punch 40 Upper first punch 52c, 58c, 62c Projection of core rod

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[Procedure amendment]

[Submission date] September 12, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG. 30 is a table showing the breaking strength of a green compact and a sintered body of a green compact.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG. 31 is a table showing the accuracy of a sintered compact of a green compact drawing product.

Claims (6)

[Claims] 1. A method for manufacturing an integrated sintered oil-impregnated bearing having a relief portion at a central portion of an inner hole and supporting a shaft at both ends thereof, the die having a concave portion on an inner surface. A powder is filled between a stepped core rod having a small diameter portion and a large diameter portion, and the powder is compressed to form a green compact having a bearing portion at one end and a projecting portion on the outer surface. By moving the core rod in the axial direction to extend the small-diameter portion of the core rod over the entire length of the inner hole of the green compact, and narrowing down the green compact contained in the concave portion of the die to the inner diameter of the die, A method of manufacturing an integrated sintered oil-impregnated bearing, wherein another bearing portion is formed at the other end of the green compact. 2. The method for manufacturing an integrated sintered oil-impregnated bearing according to claim 1, wherein the volume of the concave portion of the die is set to approximately twice the volume of the green compact squeezed into the small diameter portion of the core rod. . 3. The method for manufacturing an integrated sintered oil-impregnated bearing according to claim 1, wherein a portion of the inner surface of the die other than the concave portion is formed in a cylindrical shape, and an outer surface of the integrated sintered oil-impregnated bearing is formed in a cylindrical shape. . 4. An inner surface near one end of the die has a stepped shape, and a first punch having an outer diameter substantially equal to an inner diameter of an opening of the stepped shape, and an outer surface of the green compact formed by the stepped shape. 2. The method for manufacturing an integrated sintered oil-impregnated bearing according to claim 1, wherein a flange is formed, and one end of the green compact is formed by a second punch having an inner diameter substantially equal to the outer diameter of the small diameter portion of the core rod. 5. The core rod has a plurality of projections extending in the axial direction on the outer surface of the small diameter portion and the outer surface of the large diameter portion, and the projections form a plurality of projections on the inner surface of the integrated sintered oil-impregnated bearing. The method for manufacturing an integrated sintered oil-impregnated bearing according to claim 3 or 4, wherein the piercing oil groove and the air vent groove are formed. 6. The core rod has a plurality of protrusions extending in the axial direction on an outer surface of the small diameter portion, and the protrusions enhance a lubricating effect on inner surfaces of both end bearing portions of the integrated sintered oil-impregnated bearing. The method for manufacturing an integrated sintered oil-impregnated bearing according to claim 3 or 4, wherein a plurality of concave grooves are formed.