JP2021099134A - Sintered oil-impregnated bearing and manufacturing method of the same - Google Patents

Abstract

To provide a sintered oil-impregnated bearing which can suppress the generation of a squeeze in a low-temperature environment.SOLUTION: There is employed a sintered oil-impregnated bearing in which a composition includes copper at 10% or higher and 59% or lower, and tin at 0.5% or higher and 3.0% or lower as a whole at a mass ratio, a remaining part is a ferrous sintered alloy composed of iron and inevitable impurities, a porous area rate of an internal peripheral face of the bearing is 20% or higher and 50% or lower, the total number of pores is 800-pieces/mm2 or larger, and in a porous distribution, the number of pores of larger than 100 μm at a circle equivalent diameter is at higher than 0.5% and 1.0% or lower of the total number of the pores, the number of pores of larger than 80 μm and 100 μm or smaller at the circle equivalent diameter is at 1.5% or lower of the total number of the pores, the number of pores of larger than 60 μm and 80 μm or smaller at the circle equivalent diameter is at 1.0% or lower of the total number of the pores, the number of pores of larger than 40 μm and 60 μm or smaller at the circle equivalent diameter is at 3.0% or lower of the total number of the pores, and the number of pores of 40 μm or smaller at the circle equivalent diameter is a remaining part of the total number of the pores.SELECTED DRAWING: None

Description

An embodiment of the present invention relates to a sintered oil-impregnated bearing and a method for manufacturing the same, and more particularly to a sintered oil-impregnated bearing for an electric motor electrically mounted on an automobile or the like and a method for manufacturing the same.

The sintered oil-impregnated bearing has a bearing body formed of a porous sintered body and impregnated with lubricating oil in the pores of the sintered body, and has an advantage that it can be used for a long time without lubrication. Due to this advantage, sintered oil-impregnated bearings are applied to various bearing devices, and are also being applied to bearings of various electrical motors in the field of automobile manufacturing. Since these electrical motors are arranged in the interior of an automobile, noise generated when the shaft and the inner peripheral surface of the bearing come into contact with metal and slide, that is, so-called squealing noise, is jarring and therefore squeaking noise is generated. Various means for prevention are being studied.

Patent Documents 1 and 2 provide sintered oil-impregnated bearings that do not generate squealing noise even when used in a cold region environment such as 20 ° C. below zero or 30 ° C. below zero, and have a high effective porosity. By imparting the contradictory characteristics of low air permeability to the sintered oil-impregnated bearing, the generation of squealing noise is prevented. That is, the air permeability affects the exudability of the lubricating oil and the oil pressure of the sliding surface, and those having a high air permeability are likely to generate a squealing noise when sliding in a cold region environment. On the other hand, if the density of the sintered oil-impregnated bearing is increased in order to increase the air permeability, the number of pores decreases, and as a result, the effective porosity decreases, and the oil-containing capacity decreases accordingly. Therefore, increasing the effective porosity to increase the oil-containing capacity increases the air permeability. As described above, the air permeability and the effective porosity are in a trade-off relationship, and it is difficult to increase the effective porosity (oil-containing capacity) and decrease the air permeability.

In response to the above problems, in Patent Documents 1 and 2, by using porous reduced porosity as the iron powder, a large number of fine pores are arranged in the iron phase of the sintered oil-impregnated bearing to increase the effective porosity. By increasing the effective porosity while keeping the air permeability low, we solve the conflicting problems of air permeability and effective porosity, and provide sintered oil-impregnated bearings that do not generate squealing noise even when used in cold climates. ing.

However, when the sintered oil-impregnated bearing is used as a bearing for a power window motor for opening and closing windows of an automobile, there is a problem that squealing noise is generated even in a normal temperature environment. Since the power window operates only for a short time and is operated intermittently, a sufficient amount of lubricating oil is supplied and a strong oil film is formed between the shaft and the inner peripheral surface of the bearing. There is a problem that the operation is stopped before the operation is performed, so that the oil film formation between the shaft and the inner peripheral surface of the bearing is always insufficient. In the technique disclosed in Patent Document 3, the air permeability of the sintered oil-impregnated bearing is suppressed to be small by arranging medium pores and suppressing the number of large interparticle pores in the interparticle pores of the sintered oil-impregnated bearing. As it is, pores for supplying lubricating oil are arranged, and as a result, a sufficient amount of lubricating oil is supplied from the start of operation, and a strong oil film is formed between the shaft and the inner peripheral surface of the sintered oil-impregnated bearing. be able to.

Japanese Unexamined Patent Publication No. 2003-12674 Japanese Unexamined Patent Publication No. 2005-082867 Japanese Patent No. 6011805

However, when used as a bearing for a power window motor for opening and closing windows of an automobile, the sintered oil-impregnated bearing of Patent Document 3 can suppress the generation of squealing noise due to use in a normal temperature environment, but in cold regions. When used in a low temperature environment such as an environment, it may not be possible to sufficiently suppress the generation of squealing noise.

An object of the present invention is to provide a sintered oil-impregnated bearing in which the generation of squealing noise is suppressed, and a method for manufacturing such a sintered oil-impregnated bearing.

The "pores" of a sintered oil-impregnated bearing consist of the following two types of pores. That is, the pores formed as gaps between powder particles (hereinafter referred to as "interparticle pores") possessed by a general sintered alloy and the iron phase of the sintered alloy formed by spongy porous iron powder. Fine pores (hereinafter referred to as "fine pores") dispersed in (iron part). The interparticle pores are relatively large pores and have a large effect on the air permeability of the sintered oil-impregnated bearing. On the other hand, although some of the fine pores communicate with each other, many of them do not communicate with each other, and the influence on the air permeability of the sintered oil-impregnated bearing is small.

In order to suppress the generation of squealing noise, it is necessary to keep the shaft and the inner peripheral surface of the bearing on which the shaft slides in a good sliding state without metal contact. Therefore, the shaft and the inner peripheral surface of the bearing must be in a good sliding state. It is necessary to form an appropriate oil film between the two, hold the shaft with the pressure of the oil film, and suppress metal contact. Generally, in order to supply lubricating oil, it is necessary to increase the air permeability to smoothly supply the lubricating oil, but from the viewpoint of forming an oil film between the shaft and the inner peripheral surface of the bearing, the bearing If the air permeability of the bearing is high, the lubricating oil leaks and an appropriate oil film cannot be formed.

In addition, since the viscosity of the lubricating oil increases in a low temperature environment, the lubricating oil between the shaft and the inner peripheral surface of the bearing decreases, an appropriate oil film is not formed, and the shaft and the inner peripheral surface of the bearing come into metal contact. Sometimes.

Therefore, the present inventor pays attention to the size of the interparticle pores so that an appropriate oil film is formed even in a low temperature environment, and if the interparticle pores having an appropriate size are arranged, the bearing can be used even in a low temperature environment. We have conducted extensive research based on the prediction that a good oil film can be formed from the start of operation by supplying insufficient lubricating oil at the start of operation while keeping the air permeability small, and at the same time, a large size including fine pores and interparticle pores. As a result of repeated studies on the number of pores in the above, the present invention is completed.

In one embodiment of the present invention, as large pores in a sintered oil-impregnated bearing, the number of interparticle pores having a pore diameter of more than 100 μm, which is equivalent to a circle, is more than 0.5% of the total number of pores and 1.0% or less. The number of interparticle pores whose pore diameter is more than 80 μm and 100 μm or less (hereinafter, may be referred to as “80 to 100 μm”) as a medium-sized pore with a certain arrangement. The number of interparticle pores is 1.5% or less of the total number of pores, and the pore diameter is more than 60 μm and 80 μm or less (hereinafter, may be referred to as “60 to 80 μm”) in the equivalent circle diameter. The number of interparticle pores, which is 0% or less and the pore diameter is more than 40 μm and 60 μm or less (hereinafter, may be referred to as “40 to 60 μm”), is adjusted to 3.0% or less of the total number of pores. .. By arranging large pores including interparticle pores at a predetermined ratio and suppressing the number of medium-sized interparticle pores in this way, the air permeability of the bearing is kept small even in a low temperature environment. Pore for supplying lubricating oil is arranged, and as a result, a sufficient amount of lubricating oil is supplied from the start of operation, and a strong oil film can be formed between the shaft and the inner peripheral surface of the bearing.

Examples of embodiments of the present invention are given below. The present invention is not limited to the following embodiments.

<1> An iron-based sintered alloy in which the overall composition contains copper: 10% or more and 59% or less and tin: 0.5% or more and 3.0% or less in terms of mass ratio, and the balance is iron and unavoidable impurities. The pore area ratio of the inner peripheral surface of the bearing is 20% or more and 50% or less, the total number of pores is 800 / mm ² or more, and the pore distribution is the number of pores exceeding 100 μm in the equivalent circle diameter. The number of pores exceeding 0.5% and 1.0% or less of the total number, and the number of pores having a circle equivalent diameter of more than 80 μm and 100 μm or less is 1.5% or less of the total number of pores, and the number of pores having a circle equivalent diameter of more than 60 μm and 80 μm or less. The number of pores is 1.0% or less of the total number of pores, the number of pores with a circle-equivalent diameter of more than 40 μm and 60 μm or less is 3.0% or less of the total number of pores, and the number of pores with a circle-equivalent diameter of 40 μm or less is the balance of the total number of pores. Is a sintered oil-impregnated bearing.

<2> The sintered oil-impregnated bearing according to <1>, wherein the overall composition contains at least 5% by mass or less of at least one selected from the group consisting of zinc and nickel.

<3> At least one solid lubricant component selected from the group consisting of graphite, molybdenum disulfide, manganese sulfide, and calcium fluoride is 0.2 parts by mass with respect to 100 parts by mass of the iron-based sintered alloy. The sintered oil-impregnated bearing according to <1> or <2>, which is 2 parts by mass or less and is dispersed in the pores of the iron-based sintered alloy.

<4> Using a raw material powder obtained by mixing copper powder and at least one powder selected from the group consisting of tin powder and copper-tin alloy powder with iron powder, the raw material powder is compression-molded to have a density of 5. A method for producing a sintered oil-impregnated bearing in which a molded body in the range of .5 Mg / m ³ or more and 6.8 Mg / m ^{3 or less is molded and the obtained molded body is sintered.} By mass ratio, it contains copper: 10% or more and 59% or less, tin: 0.5% or more and 3.0% or less, and the balance is composed of iron and unavoidable impurities. As the iron powder, fine pores are formed from the surface to the inside. It is spongy and has a specific surface area of 110 m ² / kg or more and 500 m ² / kg or less by the gas adsorption method, and the powder on the 140 mesh sieve is 14% or more and 29% or less, and the powder under the 140 mesh sieve and on the 325 mesh sieve. Is 45% or more and 64% or less, and the porous iron powder A having a particle size distribution in which the powder under the 325 mesh sieve is the balance, and the hollow shape having pores inside, and the specific surface area by the gas adsorption method is 80 m ² / kg or more. 110 m ² / kg or less, powder on 90 mesh sinter is more than 5% and less than 10%, powder under 90 mesh sinter and on 140 mesh sinter is 20% or more and 35% or less, powder under 140 mesh sinter is the balance The powder having a particle size distribution of 50 μm or more inside the powder on the 90 mesh sieve is contained in an amount of 50% or more and less than 80% with respect to the powder, and is under the 90 mesh sieve and 140 mesh sieve. The powder having pores of 40 μm or more and 60 μm or less inside the above powder is a porous powder composed of porous iron powder B containing 50% or more and less than 80% with respect to the powder, and the porous iron powder A is Using an iron powder having a proportion of 80% or more and 95% or less in the porous iron powder, the powder under a 325 mesh sieve is used as at least one powder selected from the group consisting of the tin powder and the copper-tin alloy powder. As a copper powder other than copper by the copper-tin alloy powder, a foil-like copper powder under a 100-mesh sieve or a foil-like copper powder under a 100-mesh sieve in an amount of 2% by mass or more based on the total amount of the raw material powder is used. A method for manufacturing a sintered oil-impregnated bearing, in which electrolytic copper powder under a 200-mesh sieve is used and the sintering temperature in the sintering is 760 ° C. or higher and 810 ° C. or lower.

<5> For the raw material powder, at least one selected from the group consisting of zinc and nickel, and at least one selected from the group consisting of copper-zinc alloy powder and copper-nickel alloy powder so as to be 5% by mass or less. The method for manufacturing a sintered oil-impregnated bearing according to <4>, which is added.

<6> At least one selected from the group consisting of graphite powder of 0.2 parts by mass or more and 2 parts by mass or less, molybdenum disulfide powder, manganese sulfide powder, and calcium fluoride powder with respect to 100 parts by mass of the raw material powder. The method for producing a sintered oil-impregnated bearing according to <4> or <5>, wherein the solid lubricant component powder of the above is added.

In the present specification and the like, the powder under the nnn mesh sieve means a powder having a size of passing through the sieve of the nnn mesh, and the powder on the mmm mesh sieve means a sieve having an opening of mmm mesh. It means a powder of a size that does not pass through. For example, the powder under the 140-mesh sieve and on the 325-mesh sieve means a powder having a size of the mesh that passes through the sieve with a mesh size of 140 mesh and does not pass through the sieve with a mesh size of 325 mesh.

According to the embodiment of the present invention, it is possible to provide a sintered oil-impregnated bearing in which the generation of squealing noise is suppressed even in a low temperature environment.

(1) Sintered oil-impregnated bearing (1-1) Composition of sintered alloy The overall composition of the sintered alloy constituting the sintered oil-impregnated bearing is copper: 10% or more and 59% or less, tin: 0 in terms of mass ratio. A metallographic structure consisting of an iron phase, a copper alloy (Cu—Sn alloy) phase, and pores (interparticle pores and fine pores), which contains 5.5% or more and 3.0% or less, and the balance is composed of iron and unavoidable impurities. The iron-copper-based sintered alloy to be presented is used.

Iron is applied in the form of porous iron powder, which will be described later, and forms an iron phase to contribute to the improvement of bearing strength, and the fine porosity dispersed in the iron phase increases the effective porosity to increase the oil-containing capacity. To do.

Copper forms a soft copper-based alloy (Cu—Sn) phase, which contributes to improvement of compatibility with the shaft and suppression of seizure. When the amount of copper in the total composition is 10% by mass or more, the above-mentioned effect is obtained, and when the amount of copper in the total composition is 59% by mass or less, fine pores dispersed in the iron phase can be sufficiently secured. .. As a result, the effective porosity can be increased and the oil-containing capacity can be sufficiently secured. From these facts, the amount of copper in the total composition is set to 10% by mass or more and 59% by mass or less.

Tin has an action of generating a eutectic liquid phase with copper to promote sintering, and an action of alloying with copper to strengthen the copper-based alloy phase and improving the wear resistance of the copper-based alloy phase. If the amount of tin in the total composition is less than 0.5% by mass, the above-mentioned action is poor. On the other hand, if the amount of tin in the overall composition exceeds 3.0% by mass, the hardness of the copper-based alloy phase increases too much and the compatibility with the shaft is impaired. From these facts, the amount of tin in the total composition is set to 0.5% by mass or more and 3.0% by mass or less.

Since zinc and nickel have an action of strengthening the copper alloy phase and contributing to the improvement of wear resistance of the copper alloy phase, at least one of zinc and nickel may be contained as a component of the sintered alloy. However, if the amount of these elements is excessive, the wear of the shaft tends to increase. Therefore, when at least one of zinc and nickel is contained as a component, the total amount of zinc and nickel is 5% by mass or less of the total composition.

(1-2) Pore area ratio The pore area ratio of the inner peripheral surface of the bearing shall be 20% or more and 50% or less. If the pore area ratio of the inner peripheral surface of the bearing is less than 20%, the number of pores is small and a sufficient lubrication effect cannot be obtained. On the other hand, when the pore area ratio of the inner peripheral surface of the bearing exceeds 50%, the strength of the sintered oil-impregnated bearing is significantly reduced.

(1-3) Total number of pores If the total number of pores (interparticle pores and fine pores) exposed on the inner peripheral surface of the sintered oil-impregnated bearing is poor, the effective porosity will be low and the oil-containing capacity will be poor, and the lubricating oil will be poor. Since the supply capacity becomes poor, the total number of pores is set to 800 / mm ² or more.

(1-4) Pore distribution Most of the total number of pores exposed on the inner peripheral surface of the sintered oil-impregnated bearing are fine pores, and the effective porosity is increased by these fine pores to increase the oil-containing capacity. On the other hand, if the interparticle pores are made too small to reduce the air permeability, the lubricating oil supply capacity is lowered and a sufficient amount of lubricating oil cannot be supplied, and the formation of an appropriate oil film is impaired. For this reason, by arranging large pores at a predetermined ratio and suppressing the number of medium-sized interparticle pores, the lubricating oil supply capacity is improved while suppressing the increase in air permeability, and in a low temperature environment. It is also possible to suppress the generation of squealing noise.

As the large pores, the number of interparticle pores having a diameter equivalent to a circle and exceeding 100 μm is arranged so as to be more than 0.5% and 1.0% or less of the total number of pores. In the present specification and the like, the "circle equivalent diameter" means the diameter of a circle when the area of one pore is the area of one circle having the same area. If the number of interparticle pores having a diameter equivalent to a circle and exceeding 100 μm is 0.5% or less of the total number of pores, the number of large pores is small and the lubricating oil supply capacity cannot be improved in a low temperature environment. On the other hand, when the number of interparticle pores having a diameter equivalent to a circle exceeding 100 μm exceeds 1.0% of the total number of pores, the number of communicating pores increases and the air permeability of the sintered oil-impregnated bearing increases, and in a low temperature environment. Lubricating oil leaks and the noise level increases.

Further, even if large pores are arranged as described above, if medium-sized pores are present, the air permeability of the sintered oil-impregnated bearing increases excessively, so that particles having a diameter equivalent to a circle of 80 to 100 μm. The number of interstitial pores is 1.5% or less of the total number of pores, and the number of interparticle pores having a circle-equivalent diameter of 60 to 80 μm is 1.0% or less of the total number of pores, and the circle-equivalent diameter is 40 to 60 μm. The number of interparticle pores shall be 3.0% or less of the total number of pores.

The interparticle pores having a circle-equivalent diameter of 40 μm or less are formed as the above-mentioned balance of the total number of pores, and contribute to the oil-containing capacity of the sintered oil-impregnated bearing.

(1-5) Air permeability The air permeability of the sintered oil-impregnated bearing is closely related to the sliding noise, and the relationship between the air permeability and the noise level is close to a quadratic function. It gets higher. Therefore, the air permeability of the sintered oil-impregnated bearing ^{is preferably 30 × 10-11} cm ² or less. On the other hand, the air permeability of the sintered oil-impregnated bearing affects the supply capacity of the lubricating oil, and if the air permeability is ^{less than 1 × 10-11} cm ² , the supply of the lubricating oil is hindered and good sliding characteristics are exhibited. become unable. From these facts, it is preferable that the air permeability of the sintered oil-impregnated bearing is 1 × ^10-11 cm ² or more and 30 × ^10-11 cm ^{2 or less.}

(2) Method for manufacturing sintered oil-impregnated bearing (2-1) Raw material powder The raw material powder is a spongy porous iron powder having a large number of micropores, copper powder, and tin powder and copper-tin alloy powder. A mixed powder in which at least one kind of powder is added and mixed is used.

(2-2) Porous iron powder A
The iron powder is used by mixing two types of iron powder. One of them is, for example, a spongy iron powder having a large number of micropores from the surface to the inside and having a specific surface area of 110 m ² / kg or more and 500 m ² / kg or less by a gas adsorption method (BET method-ISO 9277). A can be used. The fine pores of the porous iron powder A form fine pores of the sintered oil-impregnated bearing. Here, the iron powder having a specific surface area ^{of less than 110 m 2} / kg by the gas adsorption method has few fine pores, and the fine pores of the iron phase of the sintered alloy obtained by the iron powder are reduced, so that the sintered oil-impregnated bearing is oil-impregnated. The ability is significantly reduced. On the other hand, ^{iron powder having a specific surface area of more than 500 m 2} / kg tends to have a large amount of fine powder, and interparticle pores are likely to be formed as closed pores, resulting in a significant decrease in lubricating oil supply capacity. Examples of the porous iron powder A that can be used in the embodiment of the present invention include a product name LD80 (specific surface area of about 200 m ² / kg) and a product name P100 (specific surface area of about 175 m ² / kg) manufactured by Heganes. , And trade name R12 (specific surface area is about 225 m ² / kg) and the like.

If the porous iron powder A is only a fine powder, it becomes difficult to effectively form fine pores in the iron phase. On the other hand, if only coarse powders are used, the coarse powders cause bridging, which forms large interparticle pores, which leads to an increase in air permeability of the sintered oil-impregnated bearing. Therefore, the porous iron powder A needs to have a particle size distribution including an appropriate amount of the porous iron powder A having a certain size. From this point of view, the particle size distribution of the porous iron powder A is as follows: powder on 140 mesh sieve is 14% or more and 29% or less, powder under 140 mesh sieve and on 325 mesh sieve is 45% or more and 64% or less, 325 mesh sieve. The particle size distribution is such that the powder below is the balance. If any of these particle size distributions deviates, it becomes difficult to obtain the above-mentioned fine pores. As described above, since the coarse powder causes bridging, the powder on the 80 mesh sieve is preferably less than 1%.

(2-3) Porous iron powder B
Since the coarse powders bridge each other to form large interparticle pores, the particle size distribution of the powder on the 90-mesh sieve is more than 5% and less than 10%, so that the equivalent circle diameter exceeds 100 μm. The number of interparticle pores is adjusted to more than 0.5% and 1.0% or less of the total number of pores.

Further, when only the above-mentioned porous iron powder A is used as the iron powder, the medium pores are only the interparticle pores formed after sintering the gaps between the raw material powders when the raw material powder is molded. The number of medium pores is small, the air permeability is low, and the lubricating oil supply capacity is reduced. Therefore, a porous iron powder B having a hollow shape having pores of a certain size inside and having a specific surface area of 80 m ² / kg or more and 110 m ² / kg or less by the gas adsorption method is used, and the porous iron powder B is used. The pores of a certain size existing inside form medium-sized pores of the sintered oil-impregnated bearing.

When the specific surface area of the porous iron powder B by the gas adsorption method ^{is less than 80 m 2} / kg, the iron powder has few pores of a certain size, and the medium pores of the sintered alloy obtained by this iron powder The number is reduced and the air permeability is reduced. Further, when the specific surface area of the porous iron powder B ^{exceeds 110 m 2} / kg, the number of fine pores increases, the number of pores having a certain size decreases, and the air permeability decreases. The pores having a certain size inside the porous iron powder B are partially formed as open pores communicating with the surface of the porous iron powder B. Examples of the porous iron powder B that can be used in the embodiment of the present invention include DHC-250 (specific surface area of about 100 m ² / kg) manufactured by DOWA IP Creation Co., Ltd.

Since it is necessary for the porous iron powder B to form medium-sized pores by the pores having a certain size inside, if only fine powder is used, medium-sized pores are formed. Becomes difficult. On the other hand, if only coarse powders are used, the coarse powders cause bridging, which forms coarse interparticle pores and causes an increase in air permeability of the sintered oil-impregnated bearing. Therefore, it is necessary for the porous iron powder B to have a particle size distribution that includes an appropriate amount of the porous iron powder B having a certain size.

Therefore, in the porous iron powder B, the powder on the 90 mesh sieve is more than 5% and 10% or less, the powder under the 90 mesh sieve and the powder on the 140 mesh sieve is 20% or more and 35% or less, and the powder under the 140 mesh sieve is. It is constructed as the remaining particle size distribution. Further, the powder on the 90 mesh sieve has 50% or more and less than 80% of the powder having pores of 50 μm or more inside, and the powder under the 90 mesh sieve and on the 140 mesh sieve has pores of 40 μm or more and 60 μm or less inside. The powder should be contained in an amount of 50% or more and less than 80%. By constructing the porous iron powder B in this manner, it is possible to adjust the large pores and the medium pores of the sintered alloy obtained after sintering to the above range. If any of these particle size distributions and the size of the pores contained in the powder deviates, it becomes difficult to obtain large pores and medium pores having the above particle size distribution.

As with the porous iron powder A, in the porous iron powder B, a coarse powder such as a powder on an 80 mesh sieve causes bridging, so that the powder on the 80 mesh sieve is less than 1%. Is preferable.

(2-4) Ratio of Porous Iron Powder A and Porous Iron Powder B The ratio of the porous iron powder A to the total iron powder (total amount of the porous iron powder A and the porous iron powder B) is the mass ratio. When it is 80% or more, a sufficient number of fine pores can be secured and the oil-containing capacity is improved. Further, when the ratio of the porous iron powder A to the total iron powder is 95% or less in terms of mass ratio, a sufficient number of pores having a medium size can be sufficiently secured, and the air permeability is improved. As a result, the lubricating oil supply capacity is improved. Therefore, the ratio of the porous iron powder A to the total iron powder is 80% or more and 95% or less in terms of mass ratio, and the iron powder to which the porous iron powder A and the porous iron powder B are added is used as the iron powder. ..

(2-5) Copper powder The amount of copper in the composition of the raw material powder is 10% by mass or more and 59% by mass or less for the reason described above. The amount of copper in the raw material powder is given as the copper powder except for the copper produced by the copper-tin alloy powder when the copper-tin alloy powder described later is used.

The entire amount of the copper powder can be applied as a foil-like copper powder. When copper powder is applied in the form of foil-like copper powder, the foil-like copper powder is arranged so as to wrap around the porous iron powder, so that the amount of copper exposed on the inner peripheral surface of the bearing is increased for the amount of addition. Alternatively, the air permeability can be reduced by blocking the communication holes inside the porous powder, which is present in a small amount. On the other hand, since foil-shaped copper powder is more expensive than the commonly used electrolytic copper powder, it is costly to add a part of the copper powder in the form of electrolytic copper powder when the amount of copper powder added is large. Above preferred. However, even in this case, since the above effect can be obtained by using the foil-shaped copper powder, it is preferable to use at least 2% by mass or more of the amount of the foil-shaped copper powder added with respect to the entire raw material powder.

A part of the copper powder generates a tin and Cu—Sn eutectic liquid phase to promote sintering, but if a large copper powder is used, coarse outflow holes are formed and the air permeability is increased. There is a risk. Therefore, in the case of foil-like copper powder, it is preferable to use one having a particle size under a sieve of 100 mesh, and when using electrolytic copper powder, it is preferable to use one having a particle size under a sieve of 200 mesh.

(2-6) At least one powder of tin powder and copper-tin alloy powder Tin is provided in the form of at least one powder of tin powder and copper-tin alloy powder. Since the amount of tin in the overall composition is 0.5% by mass or more and 3% by mass or less as described above, at least one of the tin powder and the copper-tin alloy powder is the amount of tin in the composition of the raw material powder. Is added so as to be 0.5% by mass or more and 3% by mass or less.

Tin has the effect of generating a Cu—Sn eutectic liquid phase to promote sintering, and the effect of alloying with copper to strengthen the copper-based alloy phase and improve the wear resistance of the copper-based alloy phase. In order to exert these actions uniformly on the sintered alloy, it is preferable to use a fine powder under a 325 mesh sieve as the powder of at least one of the tin powder and the copper-tin alloy powder. Further, in the embodiment of the present invention, the copper-tin alloy powder forms medium-sized interparticle pores, but at least one of the tin powder and the copper-tin alloy powder is used as a powder having a certain size. Then, since interparticle pores having a medium size are formed as outflow pores from these powders, it becomes difficult to control the pore distribution. From this point as well, as described above, it is preferable to use a fine powder under a 325 mesh sieve as the powder of at least one of the tin powder and the copper-tin alloy powder.

When a copper-tin alloy powder is used, it is necessary to generate a liquid phase at the sintering temperature. Therefore, it is preferable to use a copper-tin alloy powder having a tin content of 50% by mass or more as the copper-tin alloy powder. ..

When at least one of zinc and nickel is added as a component of the sintered alloy, if zinc is added in the form of a simple powder, it easily volatilizes during sintering, and if nickel is added in the form of a simple powder, it becomes a copper alloy phase. Hard to spread. Therefore, when at least one of zinc and nickel is applied, it is preferable to apply in the form of copper alloy powder in either case. As described above, when at least one of zinc and nickel is added, the amount (total amount) of at least one of zinc and nickel is 5% by mass or less, and therefore at least one of the copper-zinc alloy powder and the copper-nickel alloy powder. The seed powder is added so that the amount (total amount) of at least one of zinc and nickel is 5% by mass or less in the composition of the raw material powder. When these copper alloy powders are used, it is necessary to adjust the amount of the copper powder added according to the amount of copper contained in the copper alloy powders.

(2-7) Molding The raw material powder described above forms a die having a mold hole for forming the outer peripheral shape of the molded body and the shape of the lower end surface of the molded body, as in the case of manufacturing a normal sintered oil-impregnated bearing. The die cavity formed by the lower punch and the core rod that forms the inner peripheral shape of the molded body is filled, and the upper punch that forms the upper end surface shape of the molded body and the lower punch are compression-molded to form a substantially cylindrical shape. It is molded into a molded body. At this time, the molded body density is formed in the range of ^{5.5 Mg / m 3} or more and 6.8 Mg / m ³ or less, which is the same as the molded body density of a normal sintered oil-impregnated bearing. However, in the raw material powder that can be used in the embodiment of the present invention, the above-mentioned porous iron powder is used as the iron powder, and the apparent density is lower than that of the ordinary atomized iron powder. The gap between the powder particles is formed smaller than that of the molded body of the oil-impregnated bearing.

(2-8) Sintering The obtained molded product may be heated and sintered in a non-oxidizing atmosphere in the same manner as in the case of manufacturing a normal sintered oil-impregnated bearing. If the sintering temperature is less than 760 ° C., sintering does not proceed and the strength of the sintered body decreases. On the other hand, when the sintering temperature exceeds 810 ° C., the amount of Cu—Sn eutectic liquid phase generated becomes excessive, and the Cu—Sn eutectic liquid phase exudes into the interparticle pores formed by the copper-tin alloy powder. , It becomes difficult to obtain the desired pore distribution. Therefore, the sintering temperature in sintering is set to 760 ° C. or higher and 810 ° C. or lower.

(3) Other Embodiments In the above-mentioned sintered oil-impregnated bearing, at least one solid lubricant component of graphite, molybdenum disulfide, manganese sulfide, and calcium fluoride is added as in the case of the conventional sintered oil-impregnated bearing. You may. By using these solid lubricant components, the coefficient of friction when sliding with the shaft can be reduced. These solid lubricant components do not react with the iron phase or copper alloy phase of the sintered alloy and are dispersed inside the interparticle pores. When these solid lubricant components are used, the effect is poor if the amount is less than 0.2 parts by mass with respect to 100 parts by mass of the iron-based sintered alloy, and if it exceeds 2 parts by mass, the strength of the bearing is significantly reduced. Therefore, when the solid lubricant component is used, the total amount of the solid lubricant component is in the range of 0.2 parts by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the iron-based sintered alloy. When such a solid lubricant component is used, the powder of the solid lubricant component of 0.2 parts by mass or more and 2 parts by mass or less may be added to 100 parts by mass of the above-mentioned raw material powder.

In the method for manufacturing a sintered oil-impregnated bearing described above, similarly to the conventional sintered oil-impregnated bearing, the sintered body after sintering can be recompressed by sizing or the like forcing the dimensions of the bearing. Further, the recompression process for applying a taper to the inner peripheral surface of the bearing as described in Japanese Patent Publication No. 63-067047 can also be performed.

The following powders (1) to (5) were prepared as raw material powders.
(1) Porous iron powder A: Specific surface area: 200 m ² / kg, 140 mesh sieve: 19.2%, 140 mesh sieve and 325 mesh sieve: 54.7%, and 325 mesh sieve: 26. 1% particle size distribution (2) Porous iron powder B
(B-1): Specific surface area: 100 m ² / kg, 90 mesh sieve: 5.5%, 90 mesh sieve and 140 mesh sieve: 32.0%, and 140 mesh sieve: 62.5%. Particle size distribution, ratio of powder having pores of 50 μm or more inside the powder on the 90 mesh sieve to the powder: 70%, having pores of 40 μm or more and less than 60 μm inside the powder under the 90 mesh sieve and on the 140 mesh sieve. Ratio of powder to the powder: 70%
(3) Electrolytic copper powder: 90% by mass of powder under a 200 mesh sieve
(4) Foil-like copper powder: 90% by mass of powder under 100 mesh sieve
(5) Tin powder: under a 325 mesh sieve

The ratio (mass%) of the above-mentioned porous iron powder A and the above-mentioned porous iron powder B is set to porous iron powder A: porous iron powder B = 90:10, and the above-mentioned electrolytic copper powder is added to the above-mentioned electrolytic copper powder by 5% by mass. , 6% by mass of foil-like copper powder, and 1% by mass of tin powder are added, and 0.5 parts by mass of zinc stearate powder, which is a molding lubricant, is added to a total of 100 parts by mass of these powders and mixed. The powder was prepared.

Using the obtained raw material powder, a molded product sample having a molded product density of 6.6 Mg / m ³ was prepared, and the obtained molded product sample was heated to 790 ° C. in a decomposed ammonia gas atmosphere to be sintered, and then outside. After preparing a cylindrical sintered body sample having a diameter of 10.30 mm, an inner diameter of 7.31 mm and a height of 6.63 mm, the obtained cylindrical sintered body sample was used in the same re-pressing die and at the same pressure. It was recompressed and processed to an outer diameter of 10.22 mm, an inner diameter of 7.32 mm, and a height of 6.50 mm to prepare a sintered sample of sample number 1.

Further, a sintered sample of sample number 2-6 was prepared by the same operation as the sintered sample of sample number 01 except that the ratios shown in Table 1 were used. The porous iron powder B (b-2) shown in Table 1, which is not used in Sample No. 1, is represented below.
(B-2): Specific surface area: 100 m ² / kg, ratio of powder having pores of 50 μm or more inside powder on 90 mesh sieve to the powder: 80%, powder under 90 mesh sieve and on 140 mesh sieve Ratio of powder having pores of 40 μm or more and less than 60 μm inside the sieve to the powder: 65%

These sintered body samples are cut in the axial direction, the inner peripheral surface is observed with an optical microscope, and the area of pores and the total number of pores are measured using image analysis software (Quick Grain Standard Video manufactured by Innotek Co., Ltd.). , And the equivalent circle diameter of each pore and its distribution were investigated, and the ratio of the number of pores belonging to the range of each pore distribution to the total number of pores was investigated. These results are also shown in Table 1.

Further, these sintered body samples are vacuum-impregnated with the trade name Anderol 465 (manufactured by Anderol Japan) as lubricating oil to prepare a sintered oil-impregnated bearing sample, which is mounted as a bearing of a motor shaft of an electric motor to lower the temperature of the electric motor. The friction coefficient when operated at (−45 ° C.) was measured. The results of this friction coefficient measurement are also shown in Table 1. The motor has a shaft having a diameter of 7.29 mm, a sliding speed of 101 m / min, and a PV value of 110 MPa · m / min.

In Table 1, "-# nnn" means the powder under the nnn mesh sieve, and "+ # mmm" means the powder on the mmm mesh sieve.

From the results of sample numbers 1-6 in Table 1, the number of interparticle pores having a circular equivalent diameter of more than 100 μm exceeds 0.5% of the total number of pores and is 1.0% or less in Samples 1 and 2 at low temperatures. It was confirmed that the coefficient of friction of was reduced. Further, 90 of the porous iron powder B (b-1) containing 50% or more and less than 80% of the powder having pores of 50 μm or more inside the powder on the 90 mesh sieve as the raw material powder. It was confirmed that the friction coefficient at low temperature was small in Sample 1 and Sample 2 in which the powder on the mesh sieve was more than 5% and less than 10%.

The sintered oil-impregnated bearing of the embodiment of the present invention is suitable for bearings of electric motors that are used intermittently and for a short time, such as bearings of motors for power windows of automobiles even in a low temperature environment.

Claims (6)

An iron-based sintered alloy containing copper: 10% or more and 59% or less and tin: 0.5% or more and 3.0% or less in terms of mass ratio, and the balance being iron and unavoidable impurities.
The pore area ratio of the inner peripheral surface of the bearing is 20% or more and 50% or less.
The total number of pores is 800 / mm ² or more, and the pore distribution is
The number of pores with a diameter equivalent to a circle exceeding 100 μm exceeds 0.5% of the total number of pores and 1.0% or less.
The number of pores with a diameter equivalent to a circle exceeding 80 μm and 100 μm or less is 1.5% or less of the total number of pores.
The number of pores with a diameter equivalent to a circle exceeding 60 μm and 80 μm or less is 1.0% or less of the total number of pores.
A sintered oil-impregnated bearing in which the number of pores having a circle-equivalent diameter of more than 40 μm and 60 μm or less is 3.0% or less of the total number of pores, and the pores having a circle-equivalent diameter of 40 μm or less are the remainder of the total number of pores. The sintered oil-impregnated bearing according to claim 1, wherein the overall composition contains at least 5% by mass or less of at least one selected from the group consisting of zinc and nickel. At least one solid lubricant component selected from the group consisting of graphite, molybdenum disulfide, manganese sulfide, and calcium fluoride is 0.2 parts by mass or more and 2 parts by mass with respect to 100 parts by mass of the iron-based sintered alloy. The sintered oil-impregnated bearing according to claim 1 or 2, which is less than or equal to a portion and is dispersed in the pores of the iron-based sintered alloy. Using a raw material powder obtained by mixing copper powder with iron powder and at least one powder selected from the group consisting of tin powder and copper-tin alloy powder, the raw material powder is compression-molded to have a density of 5.5 Mg / molding the m ³ or more 6.8 mg / m ³ or less of the range moldings, a process for the preparation of oil-impregnated sintered bearings of sintering the resulting molded body,
The composition of the raw material powder contains copper: 10% or more and 59% or less, tin: 0.5% or more and 3.0% or less in terms of mass ratio, and the balance is composed of iron and unavoidable impurities.
As the iron powder
It is spongy with fine pores from the surface to the inside, has a specific surface area of 110 m ² / kg or more and 500 m ² / kg or less by the gas adsorption method, and the powder on the 140 mesh sieve is 14% or more and 29% or less, under the 140 mesh sieve. And the porous iron powder A having a particle size distribution in which the powder on the 325 mesh sieve is 45% or more and 64% or less and the powder under the 325 mesh sieve is the balance.
Hollow with pores inside, specific surface area by gas adsorption method is 80 m ² / kg or more and 110 m ² / kg or less, powder on 90 mesh sieve is more than 5% and less than 10%, under 90 mesh sieve and 140 The powder on the mesh sieve has a particle size distribution of 20% or more and 35% or less, the powder under the 140 mesh sieve is the balance, and the powder having pores of 50 μm or more inside the powder on the 90 mesh sieve is the powder. On the other hand, 50% or more and less than 80% of the powder is contained, and 50% or more and less than 80% of the powder having pores of 40 μm or more and 60 μm or less is contained inside the powder under the 90 mesh sieve and on the 140 mesh sieve. It is a porous powder composed of a porous iron powder B, and is
Using an iron powder in which the ratio of the porous iron powder A to the porous iron powder is 80% or more and 95% or less.
A powder under a 325 mesh sieve was used as at least one powder selected from the group consisting of the tin powder and the copper-tin alloy powder.
As the copper powder other than copper by the copper-tin alloy powder, the foil-like copper powder under a 100-mesh sieve or the foil-like copper powder under a 100-mesh sieve in an amount of 2% by mass or more based on the total amount of the raw material powder is contained and the balance is Using electrolytic copper powder under a 200 mesh sieve,
A method for manufacturing a sintered oil-impregnated bearing, wherein the sintering temperature in the sintering is 760 ° C. or higher and 810 ° C. or lower. At least one selected from the group consisting of zinc and nickel is added to the raw material powder, and at least one selected from the group consisting of copper zinc alloy powder and copper nickel alloy powder is added so as to be 5% by mass or less. The method for manufacturing a sintered oil-impregnated bearing according to claim 4. At least one solid lubricant selected from the group consisting of graphite powder of 0.2 parts by mass or more and 2 parts by mass or less, molybdenum disulfide powder, manganese sulfide powder, and calcium fluoride powder with respect to 100 parts by mass of the raw material powder. The method for producing a sintered oil-impregnated bearing according to claim 4 or 5, wherein the agent component powder is added.