JP2740743B2 - Manufacturing method of sintered oil-impregnated bearing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a sintered oil-impregnated bearing in which a porous portion is impregnated with a lubricating oil so that lubrication with a rotating shaft can be suitably performed.

[0002]

2. Description of the Related Art Sintered oil-impregnated bearings formed of a porous sintered alloy and used by impregnating with lubricating oil can be used for a long time without lubrication. Have been.

In this type of oil-impregnated sintered bearing, a pump having a smaller diameter than the bearing hole is inserted into a bearing hole formed in a bearing body formed of a porous sintered alloy, and the pump is rotated by the rotation of the rotating shaft. The lubricating oil absorbed from the numerous fine oil-impregnated holes (voids) of the bearing body by the action and the lubricating oil leached out due to expansion due to frictional heat form an oil film on the sliding surface with the rotating shaft, The oil film is configured to support the rotating shaft without trouble such as burning.

[0004]

By the way, the inventors of the present invention have conducted further studies to make the above-mentioned sintered oil-impregnated bearing have a low porosity on a part of the inner peripheral surface of the bearing hole, so that the rotating shaft and the rotating shaft can be easily connected to each other. It has been found that it is possible to suitably lubricate the lubricating oil between the sliding surface of the bearing. Then, as shown in FIG. 8, a sintered oil-impregnated bearing 13 having a sliding surface portion 12 with a reduced porosity on a part of the inner peripheral surface 11 of the bearing hole 10 in the circumferential direction is produced, and the rotating shaft 14 of the bearing 13 Is the sliding range θ where the sliding surface 15 and the rotating shaft 14 are closest to each other during the rotation of the rotating shaft 15 (this θ is determined by the dimensions of the bearing and the rotating shaft).
It can be expressed by the sum of 0 and Δθ that fluctuates depending on the rotation speed of the shaft body and the load condition. ) And the friction coefficient, it was found that the friction coefficient was reduced in a specific range of θ as shown in FIG.

Accordingly, in the bearing 13 having the above structure, the effect of reducing the friction coefficient can be obtained by suppressing the fluctuation of θ within a certain range. However, if the fluctuation is large, the above effect cannot be obtained sufficiently. There was a problem. In other words, when the fluctuation of θ becomes large under severe operating conditions or environmental conditions, the bearing and the rotating shaft may instantaneously come into metallic contact, and the frictional force increases, It was found that the life of the bearing was shortened due to unpleasant vibration and the original function of the bearing with reduced porosity could not be exhibited.

The fluctuation of θ is caused by the fluctuation of Δθ. The fluctuation of Δθ is caused by the fact that when the rotating shaft 14 rotates and fluid lubrication occurs between the rotating shaft 14 and the sliding surface 15 of the bearing 13, the oil pressure of the lubricating oil becomes unbalanced, thereby causing rotation. This is mainly due to the fact that the shaft 14 receives a force. As a result of examining the influence of the porosity of the inner peripheral surface on the variation of Δθ, as shown in FIG. 10, when the porosity of the inner peripheral surface of the bearing hole is reduced, Δ
We have found that θ increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to reduce the variation in the coefficient of friction by suppressing the variation in the sliding range between the sliding surface and the rotating shaft, thereby achieving a longer life. It is an object of the present invention to provide a method for producing a sintered oil-impregnated bearing that can be used.

[0008]

A method of manufacturing a sintered oil-impregnated bearing according to the present invention comprises a sintered body in which a bearing hole through which a rotary shaft is inserted is formed in a bearing body formed of a porous sintered alloy. A method of manufacturing an oil-impregnated bearing, comprising compressing metal powder between a die and a core rod disposed inside thereof and having an ironing portion formed on a part of an outer peripheral surface over the entire circumference. By forming the powder and moving the core rod out of the green compact by relative movement, the inner peripheral surface of the bearing hole is axially pushed by an ironing portion, and a hole is formed over at least one end in the axial direction over the entire circumferential direction. Is characterized in that a sliding surface formed by crushing is partially provided, and then the green compact is sintered.

[0009]

According to the method of manufacturing a sintered oil-impregnated bearing according to the present invention, when the core rod is pulled out from the green compact pressed between the die and the core rod, the ironed portion formed on the core rod and the green compact are pressed. The inner peripheral surface of the green compact is squeezed by the relative movement with respect to the inner peripheral surface of the body, and fragments of the metal powder constituting the green compact and small pieces thereof are opened in the inner peripheral surface of the bearing hole. By entering the hole, the hole is crushed. In this case, by appropriately setting the position of the ironing portion with respect to the inner peripheral surface of the green compact, a burning surface in which the sliding surface formed by crushing the holes is formed at at least one end in the axial direction of the inner peripheral surface. An oil-impregnated bearing is formed.

[0010]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 1 (a) and 1 (b) show a first example of a sintered oil-impregnated bearing manufactured by the manufacturing method according to the present invention. In FIG. Reference numeral 2 denotes a rotation axis.

A sintered oil-impregnated bearing 1 shown in FIGS. 1 (a) and 1 (b) is a bearing body 3 made of a porous sintered alloy.
In addition, a cylindrical integrally molded bearing in which a bearing hole 4 into which the rotating shaft 2 is inserted is formed. The inner peripheral surface 5 of the bearing hole 4 is crushed over the entire area in the circumferential direction from the central portion in the axial direction to one end of the opening to reduce the porosity.
A sliding surface 6 is formed, and a second sliding surface (multi-porosity portion) having a high porosity is continuously formed toward the other open end.
7 are formed.

[0012] Here, the production of oil-impregnated sintered bearing according to the present invention
An example of the method will be described. The sintered oil-impregnated bearing 1
Is prepared by mixing powders of several kinds of metals or the like as raw material powder, and filling the raw material powder into a predetermined mold D (see FIGS. 2 (a) and 2 (b)) to form a bearing molding M. It can be manufactured by molding and firing this at a predetermined temperature to obtain a sintered body, further performing predetermined sizing on the sintered body, and finally impregnating with a lubricating oil.

As shown in FIGS. 2 (a) and 2 (b), the mold D for filling the raw material powder at the time of molding the bearing molded body M has a cylindrical die 8 and a die 8 inside. The cylindrical upper and lower punches 9 and 10 inserted and disposed and the core rod 11 inserted and disposed in the upper and lower punches 9 and 10 form a cylindrical filling chamber R. The surfaces corresponding to the outer peripheral surface, the upper end surface, the lower end surface, and the inner peripheral surface of the sintered oil-impregnated bearing 1 are respectively formed. An ironing portion is formed in an intermediate portion of the core rod 11. Fig. 2
In the example shown in (a), the concave streak 11a is used.
A part of 1a is assembled so as to constitute a wall of the filling chamber R.

When the metal powder is formed into a predetermined bearing molding M by using the die D, after filling the raw material powder into the filling chamber R of the die D, a predetermined pressure is applied by the upper punch 9. The bearing is pressed and molded, and the lower punch 10 is punched upward to form a cylindrical bearing molding M. At the time of punching of the lower punch 10, the upper step forming the concave streak 11 a of the core rod 11 squeezes the raw material powder filled in the filling chamber R, thereby forming the inside of the formed bearing molded body M. The holes P on the peripheral surface are crushed.

[0015] That is, as shown in FIG. 3, concave 11a
In the inner peripheral surface of the bearing molding M squeezed by the upper step, the metal powder constituting the inner peripheral surface is scraped or moved by the step of the concave streak 11a. As a result, the shards of the metal powder that have been shaved and the small pieces m of the metal powder that has been moved are embedded in the holes P that are to be opened in the inner peripheral surface 5 of the bearing hole 4. As a result, the first sliding surface 6 in which the holes P are crushed is formed on the inner peripheral surface 5 of the bearing hole 4 in the portion where the step of the concave streak 11a is slid.

In the sintered oil-impregnated bearing 1 manufactured by the manufacturing method according to the present embodiment, a hole is formed in a part of the inner peripheral surface 5 of the bearing hole 4 in the axial direction over the entire circumferential direction. Crush P first
Since the sliding surface 6 is formed, the coefficient of friction between the rotating shaft 2 and the rotating shaft 2 at the time of rotation of the rotating shaft 2 is suppressed to be low, and the second sliding surface 7 formed continuously on this portion Since the lubricating oil is supplied, the oil pressure balance of the lubricating oil during rotation of the rotating shaft 2 is kept constant.

[0017] In this way, the production method according to an embodiment of the present invention
According to the sintered oil-impregnated bearing 1 manufactured as described above, the hole P is formed in a part of the inner peripheral surface 5 of the bearing hole 4 in the axial direction over the entire circumferential direction.
By forming the first sliding surface 6 in which the pressure is reduced, the friction coefficient between the rotating shaft 2 and the first sliding surface 6 is kept low, and the second sliding surface 7 having a high porosity is continuously formed in this portion to lubricate. By supplying the oil, the oil pressure balance of the lubricating oil at the time of rotation of the rotating shaft 2 is kept constant.
The fluctuation of the coefficient of friction during the rotation can be suppressed low, and the life of the sintered oil-impregnated bearing 1 can be prolonged.

FIG . 4 is a cross- sectional view showing a manufacturing method according to the present invention.
Shows a second example of the oil-impregnated sintered bearing is. This second
In the sintered oil-impregnated bearing 1 according to the example , the inner peripheral surface 5 of the bearing hole 4 is crushed from the axial central portion to one opening end side over the entire circumferential direction to reduce the porosity. A first sliding surface 6 is formed. In addition, a second sliding surface 7 having a tapered multi-porosity and having a diameter gradually increasing toward the other end of the opening is formed continuously from the first sliding surface 6.

[0019] In the oil-impregnated sintered bearing 1 having such a configuration, the coefficient of friction with suppressed low in the first sliding surface 6, the rotary shaft 2 by the lubricating oil is supplied from the second sliding surface 7 Fluctuation of the friction coefficient during rotation can be suppressed low, and similarly, the life of the sintered oil-impregnated bearing 1 can be extended. In this case, the mold D (FIG. 2)
), And sintering it at a predetermined temperature to give a predetermined sizing to the sintered body to form the second sliding surface 7, whereby a desired bearing can be obtained.

FIG . 5 is a view showing a structure manufactured by the manufacturing method according to the present invention.
Shows a third example of oil-impregnated sintered bearing is. In this example , a first sliding surface 6 having a reduced porosity is formed on the inner peripheral surface 5 of the bearing hole 4 with a predetermined width from both ends of the opening and over the entire area in the circumferential direction. ing.

Between these first sliding surfaces 6, a second sliding surface 7 having a high porosity is formed at an intermediate portion in the axial direction continuous with the first sliding surfaces 6. In this case, the coefficient of friction can be kept low, and by supplying lubricating oil from the second sliding surface 7, the fluctuation of the friction coefficient when the rotating shaft 2 rotates can be kept low. Therefore, as in the first example, the life of the sintered oil-impregnated bearing 1 can be extended. In this case, the core rod 11 of the mold D (see FIG. 2) is provided with two concave streaks 11a at predetermined intervals in the axial direction so as to correspond to the first sliding surface. A desired bearing can be formed.

The fourth to third example, and later from the first
In the example , the first sliding surface 6 that mainly receives the load from the rotating shaft 2 is provided at an axial end of the bearing hole 4. In particular, in the third example , two first sliding surfaces 6 are provided at both ends of the bearing hole 4.

The ends of the axial direction of the bearing hole 4, i.e., the end portion in the axial direction of the bearing moldings M, since the upper punch 9 or lower punch 10 is close to the pressure surface to be pressurized, molded With the pressure distribution at the time, the density of the metal powder is higher than the vicinity of the center of the bearing formed body M in the axial direction. Therefore, if the first sliding surface 6 is provided in this portion, the mechanical rigidity of the first sliding surface 6 can be improved, and a sintered oil-impregnated bearing having high load bearing performance can be configured. .

Further , as described above, since the density of the metal powder at both ends in the axial direction of the bearing formed body M increases, the porosity at that portion decreases. Leakage of the lubricating oil from both end surfaces is prevented, and the lubricity of the lubricating oil can be improved.

FIG . 6 is a view showing a method of manufacturing according to the present invention.
And shows a fourth example of the oil-impregnated sintered bearing which is, in this example, the entire circumference from the center of the axial direction on the inner peripheral surface 5 of the bearing hole 4 to the one opening end portion side The first sliding surface 6 having a reduced porosity by being crushed over the entire surface is formed, and the boundary line is continuously formed into a corrugated shape so that lubricating oil can be suitably supplied. A second sliding surface 7 having a porosity is formed toward the other open end.

Also in this sintered oil-impregnated bearing 1, the friction coefficient of the first sliding surface 6 can be kept low,
By supplying the lubricating oil from the sliding surface 7, fluctuations in the friction coefficient during rotation of the rotating shaft can be suppressed to a low level, and similarly, the life of the sintered oil-impregnated bearing 1 can be extended. In this case, the mold D (see FIG. 2)
The shape of the concave streak 11a formed on the core rod 11 of the first
A desired bearing can be formed by forming a wave shape corresponding to the sliding surface 6.

In the manufacturing method according to the above embodiment , a recess 11a is provided in the core rod 11 as an ironing portion for forming the first sliding surface 6, and the stepped portion of the recess 11a is used to form a bearing molding. Although the inner peripheral surface 5 of M is hardened, a roughened portion having a higher surface roughness than other portions may be provided on a part of the outer circumferential surface of the core rod 11 instead. In this case, the core rod 11
When the roughened portion is extracted, the roughened portion is slid on the inner circumferential surface 5 of the bearing molded body M on which the roughened portion is arranged, and the inner circumferential surface 5 is formed similarly to the concave streak 11a. In addition, the first sliding surface 6 can be formed.

Further , in the manufacturing method, the inner peripheral surface 5 of the bearing molding M is ironed by an ironing portion in the state of the green compact formed by pressing, and the first sliding surface 6 is formed. However, instead of this, the first sliding surface 6 may be formed by squeezing the inner peripheral surface 5 in the state of the sintered body or the sintered body. In these cases, particularly in the case of a sintered body, the movement of the metal powder as shown in FIG. 3 is not performed, and as shown in FIG. By being deformed, it is formed like an eave and closes each hole P. Thereby, the holes P in the inner peripheral surface 5 can be crushed in the same manner as described above.

[0029] However, it was carried out blinding in the state of powder compact can be blinding by small force, and since fill the pores P by piece m fine metal powder, to reliably reduce the porosity This is preferable in that it can be performed and a crushing step can be included in the molding step, and there is no need to provide a new step after sintering.

[0030]

The method for manufacturing a sintered oil-impregnated bearing according to the present invention is characterized in that a die is disposed between a die and a core rod having an ironed portion formed on the entire circumference on a part of an outer peripheral surface thereof. By compressing the metal powder to form a green compact, and by relative movement when extracting the core rod from the green compact, the inner peripheral surface of the bearing hole is axially squeezed by an ironing portion, and a circumferential direction is applied to at least one end in the axial direction. Since the sliding surface formed by crushing the holes is partially provided over the entire area, and thereafter the compact is sintered, the sliding surface is emptied by small pieces of metal powder which are scraped or moved by the ironing portion. By filling the holes, the pores on the sliding surface can be easily and reliably crushed, and it is not necessary to newly provide a step of crushing the pores on the sliding surface after sintering, thereby shortening the manufacturing process, Product cost can be reduced An effect.

[Brief description of the drawings]

FIG. 1 is a view showing a first example of a sintered oil-impregnated bearing manufactured by a manufacturing method according to the present invention, wherein FIG.
(B) is a side sectional view.

FIGS. 2A and 2B are views showing a setting state of a mold when manufacturing the sintered oil-impregnated bearing according to the first example , wherein FIG. 2A is a side sectional view, and FIG.

FIG. 3 is an enlarged sectional view showing a sliding surface of a sintered oil-impregnated bearing manufactured by the manufacturing method according to the present invention.

FIG. 4 is a plan sectional view showing a second example of the sintered oil-impregnated bearing manufactured by the manufacturing method according to the present invention.

FIG. 5 is a plan sectional view showing a third example of the sintered oil-impregnated bearing manufactured by the manufacturing method according to the present invention.

FIG. 6 is a plan sectional view showing a fourth example of the sintered oil-impregnated bearing manufactured by the manufacturing method according to the present invention.

FIG. 7 is an enlarged sectional view showing a sliding surface of a sintered oil-impregnated bearing formed by another manufacturing method different from the manufacturing method according to the present invention.

FIG. 8 is a schematic side view showing a sliding range of a sliding surface between a conventional oil-impregnated sintered bearing and a rotating shaft.

FIG. 9 shows the variation of the sliding range between the sliding surface of the bearing and the rotating shaft,
It is a figure showing the relation with a coefficient of friction.

FIG. 10 is a diagram showing a relationship between a change in a sliding range between a sliding surface of a bearing and a rotating shaft and a porosity of an inner peripheral surface of the bearing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sintered oil-impregnated bearing 2 Rotating shaft 3 Bearing main body 4 Bearing hole 5 Inner peripheral surface 6 Sliding surface

Continuing from the front page (72) Tomoyuki Kikuta, Inventor 390 Umeda, Kosai-shi, Shizuoka Prefecture Asmo Co., Ltd. (72) Inventor Daisuke 390 Umeda, Kosai-shi, Shizuoka Prefecture Asmo Co., Ltd. 219108 (JP, A) JP-A-4-307112 (JP, A) Jikken 47-73636 (JP, Y1) Jikken 49-42414 (JP, Y1)

Claims (1)

(57) [Claims] 1. A method for producing a sintered oil-impregnated bearing having a bearing body formed of a porous sintered alloy and having a bearing hole through which a rotating shaft is inserted, comprising: a die; The relative movement when the metal powder is compressed to form a green compact between the core rod and a core rod having an ironing portion formed all around the part of the outer peripheral surface, and the core rod is extracted from the green compact. Thus, a sliding surface formed by squeezing the inner peripheral surface of the bearing hole in the axial direction with the ironing portion and crushing the hole over the entire circumferential direction at least at one end in the axial direction is partially provided. A method for producing a sintered oil-impregnated bearing, characterized by sintering a body.