JPH1162969A - Sintered oil retaining bearing and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a dynamic pressure generating recessed part, easy to generate a high dynamic pressure, at a low cost. SOLUTION: A protrusion 11 axially protruded is formed on the inner peripheral sides of the two end faces of a cylindrical sintered body 10, and a plurality of axially extending groove-form recessed parts 13 are formed at equal intervals throughout a portion extending between the two end faces of the protrusion 11. The sintered body 10 is arranged in the cavity 6 of a mold 1, and axially compressed by upper and lower punches 3 and 4 to produce a bearing 10A. Through plastic flow generated by compressing the protrusion 11, the upper and lower end parts of the groove-form recessed part 13 disappear, and a central part is expanded to form a dynamic pressure generating recessed part 14.

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 suitable for supporting a shaft rotating at a relatively high speed, such as a spindle motor bearing, with high precision.

[0002]

2. Description of the Related Art In the above-described sintered oil-impregnated bearing, the lubricating oil contained therein exudes to an inner peripheral surface which is a sliding surface with a shaft to form an oil film. Is suppressed. Further, as a further improved effect of suppressing vibration and noise, there is a sintered oil-impregnated bearing in which a groove or a concave portion is formed on an inner peripheral surface to reduce frictional resistance. In such a bearing, the lubricating oil supplied to the groove and the concave portion flows with the rotation of the shaft together with the reduction of the frictional resistance, so that the pressure of the lubricating oil increases and a dynamic pressure is generated. It also has the effect of supporting part of the shaft load by dynamic pressure.

[0003]

As for the dynamic pressure, the higher the pressure is, the more preferable the rigidity of the bearing is. Therefore, in a sintered oil-impregnated bearing, the lubricating oil leaks due to its porosity. There was such a characteristic that the dynamic pressure was hard to increase and a large dynamic pressure was hardly obtained. Therefore, in order to secure the dynamic pressure, for example, the shape of the groove is V-shaped, and the bent portion is directed in the rotation direction of the shaft, or the depth of the groove becomes shallower toward the rotation direction of the shaft, There is one in which flowing lubricating oil is concentrated on the end side of the groove to obtain a large dynamic pressure. However, since the degree of leakage of the lubricating oil does not change, the obtained dynamic pressure is limited. In addition, since it is difficult to form such grooves by die molding, the sintered body is formed by performing post-processing by cutting or rolling, resulting in an increase in manufacturing cost. . Therefore, the present invention provides a sintered oil-impregnated bearing and a method for producing the same, in which dynamic pressure is easily generated and the dynamic pressure becomes large to improve rigidity of the bearing and increase in production cost is suppressed. It is intended to provide.

[0004]

According to a first aspect of the present invention, there is provided a sintered oil-impregnated bearing having at least one of an axial length, a depth and a density of a dynamic pressure generating recess formed on an inner peripheral surface. One of the characteristics is that it changes when viewed along the circumferential direction.

[0005] Specifically, in the case of a shape, if it is formed in a polygonal shape, a rectangular shape or a circular shape, the axial length changes when viewed along the circumferential direction. The longitudinal cross-sectional area along the axial direction decreases toward the end in the circumferential direction. In the case of depth,
If the bottom is formed to have an inclined shape that becomes shallower toward the end in the circumferential direction, the cross-sectional area along the circumferential direction becomes smaller as it goes toward the circumferential direction. As described above, if the longitudinal cross-sectional area or the cross-sectional area is reduced toward the end in the circumferential direction, the end becomes a wedge-shaped gap and dynamic pressure is easily generated. If the shaft supported by the bearing rotates in one direction, at least the end in the rotation direction may be formed as described above. In the case of density, if the density of the transition portion from the edge of the dynamic pressure generating recess to the inner peripheral surface is higher than that of the other portion (that is, the porosity is lower), the transition portion becomes the shaft. Since the lubricating oil flowing along with the rotation is most concentrated and the dynamic pressure is increased, the dynamic pressure is easily generated and the leak of the dynamic pressure is suppressed. In addition, if the density of the bottom of the dynamic pressure generating concave portion is lower than the density of other portions, the dynamic pressure generating concave portion can be rich in lubricating oil. As a result, the rigidity of the bearing is improved, and the shaft can be supported with high accuracy.

Further, if the dynamic pressure generating concave portion is closed on the inner peripheral surface, the dynamic pressure generating concave portion is always secured in the dynamic pressure generating concave portion of the lubricating oil, and the leakage of the dynamic pressure is suppressed. Conversely, when the dynamic pressure generating concave portion is opened on the end face of the bearing, although the dynamic pressure leaks to some extent, lubricating oil can be supplied from the opening to the dynamic pressure generating concave portion, so A stable dynamic pressure can be obtained even with the amount of lubricating oil.

A second invention of the present invention is a method suitable for manufacturing the above-described sintered oil-impregnated bearing, wherein a cylindrical sintered body arranged in a cavity of a mold is axially moved by a punch. To form a dynamic pressure generating recess on the inner peripheral surface thereof, a groove-like concave portion extending substantially in the axial direction is formed on the inner peripheral surface of the sintered body, and at least grooves on both end surfaces of the sintered body are formed. At least one of a position corresponding to the groove-shaped concave portion and a position corresponding to at least a groove-shaped concave portion of an end surface of the punch that is in contact with both end surfaces of the sintered body, provided with a convex portion protruding in the axial direction, The width of both ends of the groove is reduced by compressing the sintered body in the axial direction by the punch and causing the protrusion to plastically flow around the groove in the inner peripheral surface of the sintered body by the protrusion. Or, by making it disappear, the concave part becomes a dynamic pressure generating concave part. It is characterized by the formation Te.

According to this manufacturing method, plastic flow is formed around both ends of the groove-shaped concave portion by the convex portions formed on at least one of the both end surfaces of the sintered body and the end surface of the punch contacting the sintered body. Greatly occurs. For this reason, the groove-shaped concave portion is deformed, and a dynamic pressure generating concave portion corresponding to the shape and the depth of the groove-shaped concave portion is formed. It is optional whether or not the groove-shaped concave portions are open at both end surfaces of the sintered body. The width (circumferential length) of the dynamic pressure generating concave portion increases from both ends in the axial direction toward the center by reducing or eliminating the width of both ends of the groove-shaped concave portion due to the plastic flow. Such a shape (for example, a rhombus shape or a circular shape). The desired shape and cross-sectional shape of the dynamic pressure generating concave portion itself can be obtained by appropriately controlling the amount of compression processing in accordance with the convex portion and the groove-shaped concave portion. In addition, since the dynamic pressure generating concave portion can be formed at the same time as the sintered body is compressed, an increase in manufacturing cost is suppressed as compared with the case of forming by performing post-processing by cutting or rolling.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a cylindrical sintered body 10 as a raw material.
2A is a vertical perspective view of a sintered body 10, and FIG. 2B is a vertical view of a sintered oil-impregnated bearing (hereinafter simply referred to as a bearing) 10 </ b> A manufactured from the sintered body 10. Perspective view, FIG. 3
(A), (b) is a longitudinal cross-sectional view of the metal mold 1 showing the steps of the manufacturing method. The die 1 shown in FIGS. 3A and 3B has a die 2 having a hole 2a having a circular cross section, an upper punch 3 fitted in the hole 2a of the die 2 and movable vertically. A lower punch 4 and a columnar core 5 that can be fitted into the hollow portions of the upper and lower punches 3 and 4 are provided. The sintered body 10 is compressed by the mold 1 to obtain the bearing 10A shown in FIG.

As shown in FIG. 1 and FIG. 2 (a), on the inner peripheral side of the upper and lower end faces of the sintered body 10, ridges (convex portions) 11 of the same height protruding in the axial direction are entirely provided. It is formed over the circumference. As shown in FIG. 1, the holes of the sintered body 10 have a regular polygonal cross section (a regular pentagonal shape in the illustrated example). The two-dot chain line 12 in FIGS. 1 and 2 (a) is a circular inner circumferential surface (sliding surface with the shaft) formed in close contact with the core 5 of the mold 1 when the bearing 10A is manufactured. Is shown. In this case, a plurality of corners of the hole that protrude outside the inner peripheral surface 12 are formed as groove-shaped recesses 13 extending in the axial direction. These groove-shaped recesses 13 are formed at equal intervals in the circumferential direction, and pass through the upper and lower ridges 11 and open to the end surfaces of the ridges 11.

In order to manufacture a bearing 10A from the sintered body 10, first, as shown in FIG. 3A, the sintered body 10 is placed in a cavity 6 formed by a die 2, a lower punch 4 and a core 5. Then, as shown in FIG. 3B, the upper punch 3 is lowered to compress the sintered body 10 in the axial direction. Then, the upper and lower ridges 11 are compressed to generate a plastic flow, so that the upper and lower ends of the groove-shaped recess 13 disappear, and protrude toward the core 5 to be pressed by the core 5, and the inner peripheral surface having a circular cross section 12 are formed. Although the central portion of the groove-shaped concave portion 13 remains, the shape thereof is affected by the plastic flow and the shape thereof is changed as shown in FIG.
A rhombus shape as shown in FIG. This remaining recess is
It is a dynamic pressure generating recess 14. This dynamic pressure generating recess 14 is
Corresponding to the number of the groove-shaped recesses 13, they are formed at equal intervals in the circumferential direction at a substantially central portion in the axial direction of the inner peripheral surface 12.

The dynamic pressure generating recess 14 of the bearing 10A manufactured as described above is formed in a rhombus shape.
When viewed along the circumferential direction, the length in the axial direction varies such that the central portion is the longest and converges in a tapered shape toward both ends. FIG. 4A,
2B shows an AA ′ cross section along the circumferential direction and a BB ′ cross section along the axial direction in FIG. 2B, respectively. As shown in these figures, the bottom of the dynamic pressure generating concave portion 14 has the deepest center portion, and the inner peripheral surface 1 extends from the center portion.
It is inclined to become gradually shallower toward 2. Therefore, the lubricating oil flowing with the rotation of the shaft is concentrated at the corners in the circumferential direction, and dynamic pressure is easily generated.

Further, the periphery of the dynamic pressure generating concave portion 14 is particularly strongly compressed due to the influence of the plastic flow of the upper and lower ridges 11 and has a high workability. And the density at the bottom of the dynamic pressure generating concave portion (ie, the porosity is low). The portion where the density is high is indicated by dots in FIG. As shown in FIG. 4A, particularly in the case of looking at a cross section in the circumferential direction, the density of the transition portion 15 extending from the edge portion 14a of the dynamic pressure generating concave portion 14 to the inner peripheral surface 12 is high, while the edge portion 14a The density of the bottom portion 14b other than that is low. The transition portion 15 having a high density is a portion where the lubricating oil flowing with the rotation of the shaft 16 is concentrated most and the dynamic pressure is increased. Since the density of the transition portion 15 is high, the dynamic pressure is easily generated, And the leak of the dynamic pressure is suppressed. Also, the dynamic pressure generating recess 14
Since the density of the bottom portion 14b is lower than the surrounding density, the lubricating oil can be contained abundantly. As a result, the rigidity of the bearing is improved, and the shaft can be supported with high accuracy. Furthermore, since the dynamic pressure generating recess 14 can be formed at the same time as the sintered body 10 is compressed, an increase in manufacturing cost is suppressed as compared with the case where the sintered body 10 is formed by performing post-processing by cutting or rolling.

The shape, size, depth, and the like of the dynamic pressure generating recess formed as described above are determined by the shape, thickness, and thickness of the compressed protrusion (the protrusion 11 in the first embodiment). By appropriately controlling the height and the like, the shape, the length and the width of the groove-shaped concave portion, a desired one can be obtained. In other words, the amount of compression processing according to the convex portions and groove-shaped concave portions formed on the sintered body may be appropriately set so that a desired dynamic pressure generating concave portion is formed. For example, as shown in FIG. 5, the width of the upper and lower ends of the triangular dynamic pressure generating concave portion 17 and the groove-shaped concave portion is reduced and left, and the portion is formed as a groove 18a opening to the end face of the bearing. It is also possible to form the dynamic pressure generating recess 18 and the like.

Next, second to fourth embodiments of the present invention will be described. In the drawings referred to in the description of these embodiments, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

(2) Second Embodiment A second embodiment of the present invention will be described with reference to FIGS. 6 and 7A show a cylindrical sintered body 20 as a raw material. As shown in these figures, on the inner peripheral side of the upper and lower end surfaces of the sintered body 20, a ridge (convex portion) 21 having the same height and projecting in the axial direction is formed over the entire circumference. The hole of the sintered body 20 has a circular cross section as shown in FIG. 6, and a plurality of groove-shaped recesses 23 extending in the axial direction and opening on the end faces of the upper and lower ridges 21 are formed on the inner peripheral surface 22.
Are formed at equal intervals in the circumferential direction. These groove-shaped concave portions 23 have a two-stage configuration in which a small concave portion 23b having a rectangular cross section is formed at the bottom of a large concave portion 23a having an arc cross section.

FIG. 8 (b) shows a state in which the sintered body 20 is compressed in the axial direction by the same mold 1 as in the first embodiment to produce the bearing 20A. As shown in FIG. 7B, a dynamic pressure generating concave portion 24 corresponding to the groove-shaped concave portion 23 is formed on the inner peripheral surface 22 of the manufactured bearing 20A. The dynamic pressure generating concave portion 24 is composed of upper and lower groove portions 24b remaining after the width of the small concave portion 23b of the groove concave portion 23 is reduced, and a rhombic concave portion 23a between the groove concave portions 24b. In this case, the upper and lower ends of the large concave portion 23a of the groove-shaped concave portion 23 have disappeared due to the plastic flow generated by the compression of the ridge 21. The periphery of the dynamic pressure generating concave portion 24 has a higher density than the other portions due to a higher degree of processing, and the portion having the higher density is indicated by dots in FIG. .

According to the dynamic pressure generating recess 24 of the bearing 20A, the same operation and effect as those of the first embodiment can be obtained.
Since dynamic pressure can be obtained also by the grooves 24b opened in the upper and lower end surfaces, it is possible to support the shaft in a balanced manner over the entire length in the axial direction. Further, since lubricating oil can be supplied from the opening of the groove 24b, a stable dynamic pressure can be obtained even with a small amount of lubricating oil.

(3) Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 9 and FIG. 10A show a cylindrical sintered body 30 which is a raw material. As shown in these figures, a plurality of arc-shaped ridges (convex portions) of the same height protruding in the axial direction are provided on the inner peripheral side of the upper and lower end faces of the sintered body 30.
31 are formed at equal intervals in the circumferential direction. A notch 31a is formed at the center of each of the ridges 31.
The hole of the sintered body 30 has a circular cross section as shown in FIG. 9, and a plurality of groove-shaped recesses extending in the axial direction and opening on the end faces of the upper and lower ridges 31 are formed on the inner peripheral surface 32. 33 are formed at equal intervals in the circumferential direction. As shown in FIG. 10A, the width of the groove-shaped recess 33 is smaller than the width of the ridge 31, and is formed symmetrically about a line connecting the upper and lower cutouts 31a.

FIG. 11B shows a state in which the sintered body 30 is compressed in the axial direction by the same mold 1 as in the first embodiment to produce a bearing 30A. As shown in FIG. 10B, a groove-shaped recess 33 is formed on the inner peripheral surface 32 of the manufactured bearing 30A.
A hexagonal dynamic pressure generating concave portion 34 corresponding to the shape is formed. Although the upper and lower ends of the groove-shaped recess 33 have disappeared due to the plastic flow generated by the compression of the ridge 31, the notch 31a is formed in the center of the ridge 31, so that the dynamic pressure-generating recess is formed. The upper and lower ends of 34 extend in a triangular shape toward the end surface of the bearing 30A. The periphery of the upper and lower ends has a higher density than the other portions due to the higher degree of processing, and the portions having the higher density are indicated by dots in FIG. FIG. 12 (a),
10B shows an AA ′ cross section along the circumferential direction and a BB ′ cross section along the axial direction in FIG. 10B. As shown in FIGS. 12A and 12B, in this case, the dynamic pressure generating concave portion 34 has a substantially constant depth at the bottom in both the circumferential direction and the axial direction. The part is concavely curved.

In this bearing 30A, in addition to the same operation and effect as in the first embodiment, a ridge 31 is formed by dividing the end surface of the sintered body 30, and a notch 31a is formed in the center thereof. Therefore, the compression force of the upper and lower punches 3 and 4 applied to the ridges 31 is greater than that of the ridges over the entire circumference, which has an advantage that plastic flow is easily generated.

(4) Fourth Embodiment Next, a fourth embodiment of the present invention will be described with reference to FIGS. FIG. 13 and FIG. 14A show a cylindrical sintered body 40 which is a raw material. As shown in these figures, a plurality of groove-shaped recesses 43 extending in the axial direction and opening at upper and lower end surfaces are formed on the inner peripheral surface 42 of the sintered body 40.
Are formed at equal intervals in the circumferential direction. On the other hand, FIG.
As shown in FIG. 5, the groove-shaped recess 4 is located at a position corresponding to the groove-shaped recess 43 on the end face of the upper and lower punches 3A and 4A of the mold 1A.
A substantially U-shaped projection (projection) 41 is formed so as to surround the opening 3. FIG. 13 shows this ridge 41.
Only the two-dot chain line is shown. When the sintered body 40 is compressed as shown in FIG. 15B using the upper and lower punches 3A and 4A, a bearing 40A shown in FIG. 14B is manufactured. At the upper and lower end surfaces of the bearing 40A, a convex portion 41 is provided.
Is formed to form a substantially U-shaped concave portion 45, and a diamond-shaped dynamic pressure generating concave portion 44 corresponding to the groove-shaped concave portion 43 is formed on the inner peripheral surface 42.

In this bearing 40A, instead of forming ridges (projections) on the upper and lower end surfaces of the sintered body as in the first to third embodiments, ridges 41 are formed on the end surfaces of the upper and lower punches 3A and 4A. Thus, a plastic flow is generated around the upper and lower ends of the groove-shaped concave portion 43. Due to the plastic flow, the upper and lower end portions of the groove-shaped concave portion 43 disappear, and the periphery of the dynamic pressure generating concave portion 44 and the periphery of the concave portion 45 have a higher workability and a higher density than other portions. Thereby, an effect equivalent to that of the first embodiment is achieved. The portion where the density is high is indicated by dots in FIG.

The cross-sectional shape of the dynamic pressure generating recess shown in each of the above embodiments can be changed to various forms. FIGS. 16A to 16C show modified examples of the cross section in the circumferential direction of the dynamic pressure generating concave portion formed on the inner peripheral surface. In the figure, reference numeral 52 denotes an inner peripheral surface of the bearing, and reference numeral 54 denotes a dynamic pressure generating concave portion. As shown in FIG. 2B and FIG. 10B,
The upper and lower ends of the groove-shaped concave portion may be eliminated to completely close the inner peripheral surface, or as shown in FIG.
A configuration in which an opening is left only by reducing the width of the upper and lower ends of the groove-shaped concave portion may be employed. Thus, as described above, the shape and cross-sectional shape of the dynamic pressure generating concave portion itself are determined by the amount of compression processing corresponding to the convex portion formed on the sintered body (or the convex portion formed on the upper and lower punches) and the groove-shaped concave portion. By controlling appropriately, a desired product can be obtained.

[0025]

As described above, in the sintered oil-impregnated bearing of the present invention, the dynamic pressure generated in the dynamic pressure generating recess is large due to the shape and density of the dynamic pressure generating recess formed in the inner peripheral surface. And the leakage of the generated dynamic pressure is suppressed, and the bearing performance is improved. Further, according to the method for manufacturing a sintered oil-impregnated bearing of the present invention, it is possible to manufacture a dynamic pressure generating concave portion that generates an effective dynamic pressure without increasing the manufacturing cost.

[Brief description of the drawings]

FIG. 1 is a plan view of a sintered body according to a first embodiment of the present invention.

FIG. 2A is a vertical perspective view of a sintered body according to the first embodiment of the present invention, and FIG. 2B is a vertical perspective view of a bearing manufactured from the sintered body.

FIG. 3 is a cross-sectional view of a mold for explaining the manufacturing method according to the first embodiment of the present invention.

FIG. 4A is a sectional view taken along line AA ′ of FIG. 2B;
FIG. 2B is a sectional view taken along line BB ′ of FIG.

FIG. 5 is a vertical perspective view of a bearing according to a modified example of the first embodiment of the present invention.

FIG. 6 is a plan view of a sintered body according to a second embodiment of the present invention.

FIG. 7A is a vertical perspective view of a sintered body according to a second embodiment of the present invention, and FIG. 7B is a vertical perspective view of a bearing manufactured from the sintered body.

FIG. 8 is a cross-sectional view of a mold for explaining a manufacturing method according to a second embodiment of the present invention.

FIG. 9 is a plan view of a sintered body according to a third embodiment of the present invention.

10A is a vertical perspective view of a sintered body according to a third embodiment of the present invention, and FIG. 10B is a vertical perspective view of a bearing manufactured from the sintered body.

FIG. 11 is a cross-sectional view of a mold for explaining a manufacturing method according to a third embodiment of the present invention.

12A is a sectional view taken along line AA ′ of FIG.
FIG. 11B is a sectional view taken along line BB ′ of FIG.

FIG. 13 is a plan view of a sintered body according to a fourth embodiment of the present invention.

FIG. 14A is a vertical perspective view of a sintered body according to a fourth embodiment of the present invention, and FIG. 14B is a vertical perspective view of a bearing manufactured from the sintered body.

FIG. 15 is a sectional view of a metal mold for explaining a manufacturing method according to a fourth embodiment of the present invention.

FIG. 16 is a sectional view showing a modification of the sectional form of the dynamic pressure generating concave portion according to the present invention.

[Explanation of symbols]

1, 1A: die, 3, 3A: upper punch, 4, 4A: lower punch, 6: cavity, 10, 20, 30, 40: sintered body, 10A, 20A, 30A, 40A: sintered oil-impregnated bearing,
11, 21, 31, 41 ... ridges (projections), 12, 22,
32, 42, 52 ... inner peripheral surface, 13, 23, 33, 43 ...
Groove-shaped concave portions, 14, 24, 34, 44 ... dynamic pressure generating concave portions, 1
4a: rim, 15: transition.

Claims (6)

[Claims] 1. A sintered oil-impregnated bearing in which a dynamic pressure generating concave portion is formed on an inner peripheral surface of a cylindrical sintered body, wherein the dynamic pressure generating concave portion has an axial length, a depth and a density. A sintered oil-impregnated bearing characterized in that at least one of them changes when viewed along the circumferential direction. 2. The sintered oil-impregnated bearing according to claim 1, wherein the dynamic pressure generating recess is formed in a polygonal shape, a rectangular shape, a circular shape, or the like, and is closed on the inner peripheral surface. . 3. The sintered oil-impregnated bearing according to claim 1, wherein the dynamic pressure generating recess is formed in a polygonal shape, a rectangular shape, a circular shape, or the like, and is opened at an end face of the bearing. . 4. The density of a transition portion from the edge of the dynamic pressure generating recess to the inner peripheral surface is higher than the density of the other portion. 2. The sintered oil-impregnated bearing according to item 1. 5. The sintered oil-impregnated bearing according to claim 1, wherein a density of a bottom portion of the dynamic pressure generating concave portion is lower than a density of other portions. 6. A method for producing a sintered oil-impregnated bearing, wherein a cylindrical sintered body disposed in a cavity of a mold is axially compressed by a punch to form a dynamic pressure generating recess on an inner peripheral surface thereof. Forming a groove-shaped recess extending substantially in the axial direction on an inner peripheral surface of the sintered body; and positioning the sintering in the punch at a position corresponding to at least the groove-shaped recess on both end faces of the sintered body. At least one of the positions corresponding to the groove-shaped recesses on the end face that contacts both end faces of the body is provided with a protrusion that protrudes in the axial direction, and then the sintered body is axially moved by the punch. By causing the protrusions to plastically flow around the groove-shaped recesses on the inner peripheral surface of the sintered body by the protrusions, thereby reducing or eliminating the width of both ends of the groove-shaped recesses. Forming the recess as a dynamic pressure generating recess A method for producing a sintered oil-impregnated bearing.