JP3675550B2 - Full circle sintered oil impregnated bearing and compression molding jig for the bearing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sintered oil-impregnated bearing, and more particularly to a perfect circle sintered oil-impregnated bearing used as a motor bearing and a compression molding jig for the bearing.
[0002]
[Prior art]
In a conventional round-sintered oil-impregnated bearing, the pores are increased and the oil is soaked in a volume ratio of 20% to 25%, and the oil soaked in the pores is easily generated by the self-lubricating action of the true-circle sintered oil-impregnated bearing. Thus, the pores are enlarged, and for this purpose, a perfect circle sintered oil-impregnated bearing is molded at a low density.
[0003]
[Problems to be solved by the invention]
In the conventional round-sintered oil-impregnated bearings, the amount of oil that is molded and soaked at low density is increased, and the oil that comes out of many pores can be lubricated by self-lubricating action, but it is low density. There was a problem in the service life due to bearing wear. Further, when the clearance between the true circle sintered oil-impregnated bearing and the shaft was reduced to about 4 μm, smooth lubrication could not be achieved only by the self-lubricating action of the true circle sintered oil-impregnated bearing.
[0004]
The present invention has been made in view of the above-mentioned problems of the prior art, and can be used for lubrication and a long-life, completely-sintered oil-impregnated bearing and compression molding of the bearing. The purpose is to provide a jig.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 of the present invention is a perfectly circular sintered oil-impregnated bearing that supports a shaft loosely inserted into an axial hole. A bearing is formed by forming a perfect circle part, forming at least two recesses in the true circle part, and forming a full circumference perfect circle part having a higher density than the perfect circle part on both sides in the axial direction of the true circle part. The oil exuded by the self-oiling action is held in the recess.
[0006]
The invention according to claim 2 is characterized in that at least a part of the concave portion is formed in a wedge shape in the rotational direction of the shaft to generate a dynamic pressure, thereby enhancing a lubricating effect .
[0007]
Furthermore, the invention described in claim 3 is characterized in that the concave portion is inclined at a predetermined angle with respect to the shaft center to generate a dynamic pressure to enhance a lubricating effect .
[0008]
The invention described in claim 4 is a method of manufacturing a perfect circle sintered oil-impregnated bearing having an axial hole into which a shaft is loosely inserted, and (a) a large diameter portion integrally formed in the axial direction and an intermediate portion A convex portion and a concave portion are formed at equal intervals in the circumferential direction, and the outer diameter of the convex portion is set smaller than the outer diameter of the large diameter portion. On the other hand, a jig in which the outer diameter of the concave portion is set larger than the outer diameter of the small diameter portion is disposed concentrically with a die having a cylindrical inner surface, and (b) between the jig and the die. (C) The molded powder material is compression-molded to produce a compression-molded body having a predetermined shape, (d) the compression-molded body is sintered, and (e) the cylindrical core rod has a small diameter. It is arranged concentrically with a die having an inner diameter portion and a larger diameter inner diameter portion, and the compression molded body after sintering is inserted into the core rod and repressurized. Thus, a perfect circle is formed at the axial center and the vicinity thereof, and at least two recesses are formed in the true circle, and at the both sides in the axial direction of the true circle, the whole circumference true circle is denser than the true circle. It is characterized by forming a circular part .
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIGS. 1 and 2, a perfect circle sintered oil-impregnated bearing 2 (hereinafter simply referred to as a bearing) according to the first embodiment of the present invention includes a shaft 4 of a motor (not shown), for example. The upper end 6, the lower end 8, and the central portion 10 sandwiched between the upper end 6 and the lower end 8 are provided.
[0013]
The upper end portion 6 and the lower end portion 8 are formed so that the inner diameter is a perfect circle over the entire circumference, while the central portion 10 has at least two (six in FIG. 2) axially extending recesses 12. It is formed at equal intervals in the circumferential direction. The recess 12 has a depth of about 5 μm to 100 μm, and is set so that the sum of the volumes of the recess 12 is 10% or less of the volume of oil that has soaked into the bearing 2. Note that the inner diameter of the portion 14 other than the concave portion 12 of the central portion 10 is formed to be a perfect circle.
[0014]
In the above configuration, when the shaft 4 rotates, the oil 18 is supplied to the clearance portion 16 between the shaft 4 and the bearing 2 by the self-oiling action of the bearing 2. Since many pores are formed in the recess 12, oil supply is promoted and oil 18 is accumulated in the recess 12. However, the recess 12 is formed only in the central portion 10, and the upper and lower end portions 6, 8 are all around the periphery. Since it is a perfect circle part, the oil 18 collected in the recess 12 is securely held in the recess 12 and smooth lubrication becomes possible.
[0015]
FIG. 3 shows a true circular dynamic pressure sintered oil-impregnated bearing, which is a modification of the perfect circle sintered oil-impregnated bearing 2, and a plurality of (at least two) wedge-shaped recesses 12 a are formed at equal intervals in the central true circle portion 14. It is what.
[0016]
The recesses 12 shown in FIGS. 1 and 2 have substantially the same depth in the circumferential direction, but the wedge-shaped recesses 12a in FIG. 3 gradually decrease in depth along the rotation direction of the shaft 4. In addition, the depth of the deepest part from the perfect circle part 14 is set to about 5 μm to 50 μm, and the sum of the volumes of the recesses 12 a is set to be 10% or less of the volume of the oil soaked in the bearing 2. Yes.
[0017]
In the above configuration, with the rotation of the shaft 4, the oil 18 is held in the recess 12 a and the recess 12 a is formed in a wedge shape with respect to the rotation direction. Due to the rotational force, the oil is supplied to the round part 14 having a clearance of about 4 μm as small as 4 μm and smooth lubrication is possible.
[0018]
4, 5 and 6 show still another modification of the above-mentioned perfectly circular dynamic pressure sintered oil-impregnated bearing.
The recess 12b shown in FIG. 4 is formed in a wedge shape like the recess 12a shown in FIG. 3, but the recess 12a in FIG. 3 has a flat bottom surface, whereas the recess 12b in FIG. The bottom surface is formed in an arc shape along the rotation direction of the shaft 4. 5 has a trapezoidal cross section, and a part of the recess 12c is formed in a wedge shape along the rotation direction of the shaft 4. As shown in FIG. Furthermore, the recess 12d shown in FIG. 6 has an isosceles triangular cross-sectional shape, and both sides of the recess 12d are formed in a wedge shape, so that the shaft 4 can rotate in any direction.
[0019]
7 and 8 show a true circular dynamic pressure sintered oil-impregnated bearing 20 according to the second embodiment of the present invention.
The bearing 20 has a substantially cylindrical shaft hole 20a into which the shaft 4 of a motor (not shown), for example, is loosely inserted, and a plurality of (at least two) inclined inner surfaces of the shaft hole 20a at a predetermined angle with respect to the shaft center. ) Recesses 22 are formed at equal intervals, and the inner diameter of the portion 24 other than the recesses 22 is formed to be a perfect circle.
[0020]
The concave portion 22 has a depth of about 5 μm to 100 μm, and is set so that the sum of the volume of the concave portion 22 is 10% or less of the volume of oil that has soaked into the bearing 20.
[0021]
In the above configuration, the oil is held in the recess 22 as the shaft 4 rotates, and the recess 22 is formed at a certain angle with respect to the rotation direction or in a twisted shape. Is generated by the rotational force of the shaft 4, and oil is supplied to the round part 24 having a clearance of about 4 μm as small as 4 μm to enable smooth lubrication.
[0022]
As a matter of course, as shown in FIG. 9, the recess 22 can be inclined in a direction opposite to the inclination direction of FIGS. 7 and 8.
[0023]
Next, the manufacturing process of the perfect circle sintered oil-impregnated bearing according to the present invention will be described taking the bearing 2 of FIG. 1 as an example.
When the bearing 2 is manufactured, a powder material is compression molded to produce a molded body having a predetermined shape. FIGS. 10 and 11 show a core rod 26 that determines the inner diameter of the bearing 2 in this powder compression molding.
[0024]
The core rod 26 includes a large-diameter portion 26a formed integrally in the axial direction, an intermediate portion 26b formed with a plurality of irregularities, and a small-diameter portion 26c, and the intermediate portion 26b includes the recess 12 of the bearing 2. And a recess 26e corresponding to the central perfect circle part 14 of the bearing 2 are formed at equal intervals in the circumferential direction. The outer diameter of the convex portion 26d is set to be slightly smaller than the outer diameter of the large diameter portion 26a, while the outer diameter of the concave portion 26e is set to be about 5 μm to 20 μm larger than the outer diameter of the small diameter portion 26c.
[0025]
As shown in FIG. 12, the core rod 26 is arranged concentrically with a die 28 having a cylindrical inner surface, and a powder 34 of a predetermined material is filled between the upper and lower punches 30 and 32, and then compression molding is performed. Thus, the compression molded body 36 shown in FIGS. 13 and 14 is manufactured.
[0026]
The compression molded body 36 manufactured in this way has a small circular part 36a at the upper part, a concave part 36b for retaining oil at the central part, a convex part 36c larger than the upper diameter by 5 μm to 20 μm, and a central concave part 36b at the lower part. It has a larger perfect circle part 36d.
[0027]
Next, after the compression-molded body 36 is sintered, it is re-pressurized as shown in FIG. As shown in FIG. 15, the die 38 that determines the outer diameter of the bearing 2 in this re-pressurization step is manufactured such that the inner diameter of the lower portion 38a is 0.1 mm to 0.3 mm smaller than the inner diameter of the upper portion 38b. At the center of the die 38 in the axial direction, a cylindrical repressurizing core rod 40 (concentrated in a perfect circle) is concentrically disposed, and a compression molded body 36 is inserted into the core rod 40 and re-engaged by upper and lower punches 42 and 44. Pressurize.
[0028]
FIGS. 16 and 17 show the re-pressurized body 46 obtained in the above process. The upper perfect circle part 46a and the lower true circle part 46b have high density and fewer pores, while the central convex part 46c Although it has the same diameter as the perfect circle portions 46a and 46b, it has a larger number of pores than the upper and lower perfect circle portions 46a and 46b because it is formed larger by 5 to 20 μm during powder compression molding. Moreover, since the recessed part 46d is not press-contacted to the repressurization core rod 40 at the time of repressurization, the surface of the sintered body is maintained as it is and there are many pores.
[0029]
Thereafter, the re-pressurizing body 46 is immersed in oil and soaked in the pores to obtain a product (bearing 2 in FIG. 1).
[0030]
In addition, the recessed part formed in a bearing center part is set so that the volume may be 10% or less of the volume of the oil which has soaked into the bearing.
[0031]
As described above, the perfect circle sintered oil-impregnated bearing according to the present invention is formed by molding the upper and lower perfect circle portions at a standard density or higher density so that the number of pores is smaller than conventional and the oil has a volume ratio of 20% to Even if the pores are small and it is difficult for oil to come out, smooth lubrication is maintained by retaining the oil that has exuded by self-lubricating action in two or more recesses provided in the center of the bearing, resulting in low density. The resulting bearing wear can be improved.
[0032]
Furthermore, the clearance between the bearing and the shaft is reduced to about 4 μm, and the problem that smooth lubrication cannot be achieved only by the self-lubricating action of the true circle sintered oil-impregnated bearing is provided in the center of the true circle sintered oil-impregnated bearing. In addition, dynamic pressure was generated by inclining two or more concave portions at a predetermined angle with respect to the wedge shape or the shaft center, and the lubrication effect was enhanced as a true circular dynamic pressure sintered oil-impregnated bearing.
[0033]
18, 19 and 20 show a conventional perfect circle sintered oil impregnated bearing, a conventional perfect circle sintered oil impregnated bearing having a plurality of convex portions on the inner surface thereof, It is a graph which shows the result of having manufactured the several sample with respect to each of an oil impregnation bearing, and having investigated the axial loss change rate (change rate of a friction coefficient).
[0034]
As can be seen from this graph, in the conventional perfect circular bearing or the conventional perfect circular bearing having a plurality of convex portions on the inner surface of the bearing, the rate of change in shaft loss increases rapidly after 4000 hours or 10,000 hours, respectively. On the other hand, in the perfect circle bearing having a plurality of recesses according to the present invention, the rate of change in shaft loss did not fluctuate much even after 30000 hours, and a good lubricating effect was obtained.
[0035]
【The invention's effect】
The present invention is implemented in the form as described above, and has the following effects.
According to the first aspect of the present invention, since at least two concave portions are formed in the perfect circle portion provided in the vicinity of the axial center of the bearing, the oil exuded by the self-lubricating action of the bearing is Even if the clearance between the bearing and the shaft is as small as about 4 μm, smooth lubrication is possible.
[0037]
In addition, since the entire circumference of the perfect circle is formed on both sides in the axial direction of the perfect circle, the oil flow that has accumulated in the recess is prevented from flowing out in the circumference of the circumference and the wear resistance is improved. It is possible to provide a bearing having an improved and long life. Further, even if the rotation of the shaft stops, the oil is not washed away and is absorbed into the original pores of the bearing by the capillary action, so that smooth lubrication is performed without any loss of oil.
[0038]
Further, according to the invention described in claim 2, since at least a part of the upper Symbol recess formed in a wedge shape in the rotational direction of the shaft, the oil of the recess is moved to a true circle portion from the recess by the rotational force of the shaft, Hydraulic pressure is generated by the wedge shape of the recess, and dynamic pressure is generated by the rotational force of the shaft. As a result, since the oil is lubricated to a small round part having a clearance of about 4 μm, the lubrication effect can be enhanced as a true circular dynamic pressure sintered oil-impregnated bearing.
[0039]
According to the invention described in claim 3 , since at least two concave portions inclined at a predetermined angle with respect to the shaft center are formed in the perfect circle portion provided in the vicinity of the axial center of the bearing, the self-lubricating action of the bearing The exuded oil is held in the recess, and the held oil moves from the recess to the perfect circle by the rotational force of the shaft, and hydraulic pressure is generated by the twisted shape of the recess and becomes dynamic pressure by the rotational force of the shaft. . As a result, since the oil is lubricated to a small round part having a clearance of about 4 μm, the lubrication effect can be enhanced as a true circular dynamic pressure sintered oil-impregnated bearing as in the second aspect of the invention.
[0041]
According to the invention described in claim 4 , it has a large-diameter portion, an intermediate portion, and a small-diameter portion that are integrally formed in the axial direction, and the convex portion and the concave portion are arranged in the circumferential direction in the intermediate portion. A jig that is formed at equal intervals and whose outer diameter of the convex portion is set smaller than the outer diameter of the large diameter portion, while the outer diameter of the concave portion is set larger than the outer diameter of the small diameter portion, is a cylindrical inner surface. It is arranged concentrically with a die having a diameter, filled with a powder material between a jig and a die, and compression molded to produce a compression molded body of a predetermined shape. Can be easily determined.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a perfect circle sintered oil impregnated bearing according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along line II-II in FIG.
3 is a cross-sectional view similar to FIG. 2 of a perfectly dynamic pressure sintered oil-impregnated bearing, which is a modification of the bearing of FIG. 1, and particularly shows a wedge-shaped recess.
4 is a cross-sectional view showing another modification of the true circular dynamic pressure sintered oil-impregnated bearing of FIG. 3. FIG.
5 is a cross-sectional view showing still another modified example of the true circular dynamic pressure sintered oil-impregnated bearing of FIG. 3. FIG.
6 is a cross-sectional view showing still another modified example of the true circular dynamic pressure sintered oil-impregnated bearing of FIG. 3. FIG.
7 is a cross-sectional view similar to FIG. 2 of a true circular dynamic pressure sintered oil-impregnated bearing, which is a modification of the bearing of FIG. 1, and particularly shows a recess having a twisted shape.
8 is a cross-sectional view taken along line VIII-VIII in FIG.
9 is a cross-sectional view similar to FIG. 8, showing a modification of the bearing of FIG.
10 is a front view of a core rod used in powder compression molding of the bearing of FIG. 1. FIG.
11 is a plan view of the core rod of FIG.
FIG. 12 is a longitudinal sectional view showing a powder compression molding process.
FIG. 13 is a longitudinal sectional view of a molded body obtained in a powder compression molding process.
14 is a bottom view of the molded body of FIG. 13;
FIG. 15 is a longitudinal sectional view showing a re-pressurization step.
FIG. 16 is a longitudinal sectional view of a repressurized body obtained in a repressurization step.
17 is a cross-sectional view taken along line XVII-XVII in FIG.
FIG. 18 is a graph showing an axial loss change rate of a conventional perfect circle bearing.
FIG. 19 is a graph showing an axial loss change rate of a conventional perfect circle bearing having a plurality of convex portions on the inner surface thereof.
FIG. 20 is a graph showing the rate of change of shaft loss of a perfect circle bearing according to the present invention.
[Explanation of symbols]
2,20 Perfectly round sintered oil-impregnated bearing 4 Shaft 6 Upper end 8 Lower end 10 Central part 12, 22 Recess 14, 24 Central perfect part 16 Clearance part 26, 40 Core rod 28, 38 Die 30, 42 Upper punch 32, 44 Lower punch 34 Material powder 36 Compression molded body 46 Repressurized body

Claims (4)

In the perfect circle sintered oil-impregnated bearing that supports the shaft loosely inserted in the shaft hole,
A perfect circle portion is formed at and near the axial center of the bearing, and at least two concave portions are formed in the true circle portion. A true-circle sintered oil-impregnated bearing characterized in that the oil exuded by the self-lubricating action of the bearing is held in the concave portion by forming a circular portion . 2. The true circle sintered oil-impregnated bearing according to claim 1, wherein a lubricating effect is enhanced by forming a dynamic pressure by forming at least a part of the recess in a wedge shape in the rotation direction of the shaft . 2. The true circle sintered oil-impregnated bearing according to claim 1, wherein the concave portion is inclined at a predetermined angle with respect to the shaft center to generate a dynamic pressure to enhance a lubricating effect . A method for producing a perfect circle sintered oil-impregnated bearing having a shaft hole into which a shaft is loosely inserted,
(A) having a large-diameter portion, an intermediate portion, and a small-diameter portion that are integrally formed in the axial direction, wherein the convex portion and the concave portion are formed at equal intervals in the circumferential direction; and A jig in which the outer diameter of the convex portion is set smaller than the outer diameter of the large-diameter portion while the outer diameter of the concave portion is set larger than the outer diameter of the small-diameter portion is concentric with a die having a cylindrical inner surface Arranged in a shape,
(B) filling a powder material between the jig and the die;
(C) compression-molding the filled powder material to produce a compression-molded body having a predetermined shape;
(D) sintering the compression molded body,
(E) By placing a cylindrical core rod concentrically with a die having a small-diameter inner diameter portion and a large-diameter inner diameter portion and inserting the sintered compact into the core rod and repressurizing,
A perfect circle part is formed in the axial center and the vicinity thereof, and at least two concave parts are formed in the true circle part, and an entire circumference perfect circle part having a higher density than the true circle part on both sides in the axial direction of the true circle part A method of manufacturing a perfect circle sintered oil-impregnated bearing, wherein

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