JPH0820836A - Sintered oilless bearing and its production - Google Patents

Abstract

PURPOSE:To regulate porosity in a surface layer part and to develop a sintered oilless bearing excellent in fitness and wear resistance by forming a Cd-Zn alloy layer on the surface of an oilless bearing alloy prepared by sintering an iron powder having coppery plating film. CONSTITUTION:An iron powder, whose surface is plated with Cu or Cu alloy, or a powder mixture prepared by further mixing an Sn powder with the iron powder is compacted and then sintered in a Zn atmosphere, thus to produce a sintered compact in which Zn is adsorbed on the surface. At this time, a powder of solid lubricant, such as MoS2, graphite, and BN, is fixed on an adsorption layer composed essentially of Cu and Zn. The sintered oilless bearing, having >=18vol.% porosity in the overall sintered compact, >=25vol.% porosity in the inner layer part, and <=16vol.% porosity in the surface layer part, is produced. Because lubricating oil is contained by adsorption in the pores and also an alloy layer containing solid lubricant such as MoS2 is formed, the sintered oilless bearing, having <=1.5mum average wear amount per hour by the rotation under the conditions of 2000rpm number of revolution and 14kgf/cm<2> load and excellent in wear resistance and conformability, can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered oil-impregnated bearing and a method of manufacturing the same, and relates to a bearing for an electric motor and other bearings for a driving mechanism, and a bearing for a rotary shaft driven by the driving mechanism, which has friction from the start. The present invention aims to provide an oil-impregnated bearing having a small and constant state and good compatibility, and a preferable manufacturing method thereof.

[0002]

2. Description of the Related Art Bearings as members for supporting electric motors and other rotary shafts have been used in various ways, and in recent years, particularly, oil-impregnated bearings formed by compacting and sintering have been widely used. is there. In other words, this powder compacted and sintered bearing does not require man-hours such as drilling, cutting or assembling, and the target bearing can be obtained by a simple and mass-production molding, sintering or straightening process, and a low cost product can be obtained. It has a definite advantage that it can provide.

However, it is natural that it is preferable that such a bearing has low friction, and it has been previously announced that the material, the adoption of the lubricant, the structure, etc. have been announced by the present inventors. We have also made various proposals regarding the strength and familiarity of such sintered bearings. For example, in Japanese Examined Patent Publication No. 62-53580, it is proposed that brass powder and iron powder are mainly used, and that a mixture of bronze powder and this is compacted and then sintered.

In Japanese Patent Publication No. 63-46139, a green compact obtained by press-molding a mixture of bronze powder and iron powder is sintered at 700 to 1000 ° C. in a vaporized Zn gas atmosphere.
It has been proposed to form a gas atmosphere by arranging Zn or ZnO 2 on the upper layer of the green compact, or by putting them together in a container and heating them in a reducing or non-oxidizing atmosphere.

Further, in Japanese Patent Laid-Open No. 2-73947,
Any one or two of Fe, Cu, Sn and Pb or Sb, Bi
A powder compacted sintered body containing at least one kind, the surface of the sintered body being coated with an alloy layer mainly composed of Cu-Sn-Zn having a minimum thickness of 5 to 100 µm, and a sintered metal product thereof The manufacturing method has been announced.

[0006]

However, in spite of these various studies and improvement efforts, it has not always been possible to obtain a preferable product. That is, the first problem in such a conventional technique is familiarity, and even if the conventional bearing is excellent in familiarity, the familiarity time is about 10 minutes, and generally 20 to 30 minutes. Temperature, during which the bearing temperature rises with a drop in temperature after such familiarization. For example, the usage conditions of general household appliances are often not continuous operation, and intermittent operation (ON-OF
Under such an operating condition, the bearing having poor conformability is accompanied by an increase in temperature each time (even if it is reduced to some extent after conforming).

In the above-described powder compacted sintered oil-impregnated bearing, the impregnated oil seeps out from the oil hole of the bearing due to the difference in the coefficient of thermal expansion between the bearing material and the impregnated oil each time such temperature rise occurs.
When the temperature drops after running in (or after stopping), this exuded oil will be absorbed by the bearing, but it is difficult to absorb the entire amount of exuded oil, and some loss will occur.
In addition to causing pollution, a difference in temperature rise due to familiar slowdowns is accumulated as a difference in oil impregnation loss each time operation and stop are repeated, which causes a change in service life and reduces durability in any case.

Particularly in portable electric products, dry batteries or rechargeable power sources are used, and it is needless to say that it is preferable that the power consumption is smaller because the power capacity thereof is small. A bearing that is sufficient and has a large temperature rise at start-up consumes a large amount of power at start-up, which is not preferable in this respect either.

Further, as a general theory of conventional bearings, it is a matter of course that a bearing having excellent wear resistance is inferior in conformity, and an oil-impregnated bearing having favorable conformity is high in wear (large), It is impossible to satisfy both wear resistance and familiarity.

That is, even if it is confirmed that the above-mentioned prior arts have their respective merits such as strength, durability, and familiarity, the above-mentioned problems still remain unsolved. There is nothing that can provide a solution, and no technology that has specifically solved these problems.

[0011]

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, the present invention has made further practical and detailed investigations, and as a result, highly utilizes each characteristic of iron powder plated with copper or copper alloy, Moreover, by utilizing the characteristics or function of zinc in a specific state under the conditions of such a raw material powder, a unique constitutional relationship that cannot be obtained in the conventional technique is formed, and the above-mentioned problems are effectively solved and a special The present invention succeeds in obtaining a sintered oil-impregnated bearing having advantages, and is as follows.

(1) An alloy layer containing copper or a copper alloy and zinc as a main component is formed on the surface layer of a powder compacted sintered body of iron powder plated with copper or a copper alloy. Porosity is 18% by volume or more, inner layer porosity is 25% by volume or more, surface layer porosity is 16% by volume
A sintered oil-impregnated bearing characterized in that:

(2) A compacted and sintered body of iron powder plated with copper or a copper alloy, wherein the surface layer of the compacted and sintered body is copper or an alloy containing copper alloy and zinc as main components. A layer is formed, and by this copper or copper alloy and an alloy layer containing zinc as a main component, the pores of the microstructure due to the powder compaction sintering of the surface layer are miniaturized, and the friction coefficient continues for 30 minutes immediately after the start of rotation. A sintered oil-impregnated bearing characterized by being at the same level as when it was rotated above.

(3) The sintered oil-impregnated bearing as described in the above item (1) or (2), which has a porosity of 18 vol% or more and an air permeability of 30 Darcy or less.

(4) Rotation speed 2000 rpm, load: 14
Average amount of wear under 1 hour test condition with kgf / cm ²
The above (1)-
The sintered oil-impregnated bearing according to the item (3).

(5) Solid lubricant powder such as molybdenum disulfide, graphite or boron nitride is contained, and the solid lubricant powder is fixed on the surface layer by an alloy layer containing copper and zinc as main components. (1) characterized by
~ The sintered oil-impregnated bearing according to item (4).

(6) A compact formed by compacting iron powder plated with copper or a copper alloy is prepared, and the compact is compacted in a zinc atmosphere, and the porosity of the compact surface layer is adjusted. A method for producing a sintered oil-impregnated bearing, which comprises alloying by adsorbing zinc so as to reduce the porosity of the inner layer portion by 10% by volume or more.

(7) A powder compact formed by compacting an iron powder and a tin powder plated with copper or a copper alloy as a main material is prepared, and the powder compact is subjected to porosity in the surface layer in a zinc atmosphere. A method for producing a sintered oil-impregnated bearing, which comprises performing a sintering process for adsorbing zinc so as to reduce the porosity from the porosity of the inner layer portion by 10 vol% or less, and performing alloying with copper-zinc as a main component.

(8) The solid lubricant powder such as molybdenum disulfide, graphite or boron nitride is also used as a main material, and the solid lubricant powder is alloyed by adsorption of zinc to stabilize and fix the solid lubricant powder. The method for manufacturing a sintered oil-impregnated bearing according to the items (6) and (7).

(9) A method for producing a sintered oil-impregnated bearing as described in the above items (6) to (8), characterized in that iron powder coated with 30 to 60 wt% of copper or copper alloy is powder compacted. .

(10) The method for producing a sintered oil-impregnated bearing according to the above items (6) to (9), characterized in that copper or a copper alloy is melted and is sintered under a temperature condition in which iron is not melted. .

[0022]

[Function] By forming an alloy layer containing copper or a copper alloy and zinc as a main component on the surface layer portion of a powder compacted sintered body of iron powder plated with copper or a copper alloy It becomes a product in which the copper alloy is coated and bonded at the particle level, and the pore size of the compacted and sintered structure in the surface layer portion is made small, and the strength of the surface layer portion is increased.

The sintered body has a porosity of 18 vol% or more, an inner layer porosity of 25 vol% or more, and a surface layer porosity of 16 vol% or less. The amount of oil contained in the body is appropriately increased, and the outer peripheral surface layer has high density and low air permeability, and the amount of oil supplied from the surface layer pores to the sliding surface is controlled. The escape of the hydraulic pressure necessary for the fluid lubrication on the sliding surface is reduced to improve the lubrication performance and extend the life of the oil-impregnated bearing. That is, at the same oil content, the durability can be improved at least several times as much as the conventional one.

A compacted sintered body made of iron powder plated with copper or a copper alloy, wherein an alloy layer containing copper or a copper alloy and zinc as a main component is formed on the surface layer of the compacted sintered body. The copper or copper alloy and the alloy layer containing zinc as a main component refined the pores of the porous structure due to the powder compaction sintering of the surface layer, and the friction coefficient was continuously rotated for 30 minutes or more immediately after the rotation was started. Since the bearing is at the same level as that at the time, the bearing has good conformability immediately after the start of rotation and has a low friction coefficient.

Since the porosity is secured at 18% by volume or more and the air permeability is set at 30 darcy or less, the oil escape is properly controlled on the sliding surface while the bearing has an appropriate oil content. It is possible to obtain a bearing action that maintains sufficient lubricity.

Rotation speed 2000 rpm, load: 14 kgf / cm ²
The average amount of wear under test conditions for 1 hour was 1.5 μm
The following are advantageous bearings that cannot be obtained with conventional bearings, because the amount of wear is sufficiently reduced and the wear amount is limited to the minimum state particularly in the case of a good bearing whose conformability does not change from the start as described above. Show the characteristics.

A solid lubricant powder such as molybdenum disulfide, graphite or boron nitride is contained, and the solid lubricant powder is fixed in the surface layer portion by an alloy layer containing copper and zinc as a main component, so that liquid lubrication is achieved. The bearing has both performance and solid lubrication performance, and in particular, the solid lubricant serves as a stable functioning bearing, and particularly, the advantageous bearing action is maintained even during the action of the rotary bearing for a long continuous time. Even under the condition where the porosity of the surface layer portion is 14% by volume or less, a preferable bearing action under a low friction condition can be obtained. The preferable addition amount of the solid lubricant is about 0.5 to 8 parts with respect to 100 parts of the iron powder.

A compact formed by compacting iron powder plated with copper or a copper alloy is prepared, and the compact is sintered in a zinc atmosphere, and the porosity of the compact surface layer is adjusted to the inner layer porosity. By alloying so that zinc is adsorbed so as to be reduced by 10% by volume or more, the bearing having the above-mentioned constitutional relationship appropriately can be obtained accurately. In other words, alloying by adsorption of zinc is different from the case of simply mixing zinc, in which the surface layer part adsorbs and alloys zinc by sintering to reduce the area of the pores, and the inner part part has a density of compacted powder. As obtained, the iron powder particles in the surface layer remain as they are, but only the copper or copper alloy that binds this is alloyed with zinc to increase the volume and strength. Also, the characteristics of the present invention as described above can be effectively obtained.

A powder compact formed by compacting iron powder and tin powder plated with copper or a copper alloy as a main material is prepared, and the powder compact is subjected to a zinc atmosphere to adjust the porosity of the surface layer to the inner layer. By adsorbing zinc so as to reduce the porosity by less than 10% by volume, and performing a sintering treatment for alloying with copper-zinc as a main component, a product having an appropriate familiarity with tin content is obtained. To do. That is, the present invention obtained as described above can obtain a preferable structural relationship as a bearing under the condition that the skeleton structure by the iron powder is secured by the zinc adsorption, but the zinc content thus adsorbed has a friction coefficient It is recognized that seizure resistance is inferior to bronze-based bearing materials in spite of its low advantage, and such seizure resistance is covered by the addition of tin components, and bearings that are practically equipped with their respective advantages. And Although the amount of tin used for such a purpose is related to the amount of zinc adsorbed, it is generally about 2 to 10 wt% as a preferable range.

When a solid lubricant such as molybdenum disulfide, graphite or boron nitride is also used as a main material, the characteristics of the solid lubricant can be added to the above characteristics, and the alloying by zinc adsorption as described above is performed. The solid lubricant powder can also be fixed and stabilized, and a product having sufficient characteristics can be obtained.

By compacting iron powder coated with 30 to 60 wt% of copper or copper alloy, the amount of general iron powder is appropriately increased, and the skeletal structure is ensured by the iron powder. In addition, the plating coating with copper or a copper alloy can be effectively achieved, and preferable corrosion resistance can be achieved and the sintering mainly containing the copper component (copper or copper alloy) at the time of sintering can be appropriately achieved. Further, it is possible to appropriately obtain such zinc adsorption on the copper content and the above-mentioned characteristics associated therewith.

While effectively securing the bone nucleus structure obtained by the iron powder as described above by performing the sintering treatment under the temperature condition in which copper or copper alloy is melted and iron is not melted,
Moreover, a sintered integrated structure made of copper or a copper alloy can be appropriately formed. Further, it becomes possible to fully exhibit the unique function of the present invention as described above by utilizing the sintered integrated structure.

[0033]

EXAMPLES Specific examples of the present invention as described above will be shown, and the comparative examples will be described below. Example 1 100 wt parts of iron powder, 30 wt parts of copper was plated, and Cu-coated iron powder adhered on the surface was coated with tin powder (AT-Sn) and graphite powder or boron nitride powder (BN) by a spraying method of 325 mesh or less. ) Was blended in wt% as shown in Table 1 below.
4 kinds of materials are prepared and pressed into a constant state with a porosity of 20%.
It was sintered at 60 ° C. and was sintered in a normal atmosphere without Zn. That is, is an example of the present invention, and is a reference example.

[0034]

[Table 1]

Separately from the above, two kinds of bearings obtained by compacting two kinds of copper-tin based materials using copper powder by a conventional method to a porosity of 20% and respectively sintering the same at 760 ° C. are also referred to. Prepared as an example.

With respect to the examples of the present invention and comparative examples and comparative reference examples obtained as described above, the rotation speed is 2000 rpm,
The friction characteristic test with a load of 14 kgf / cm ² was carried out for 60 minutes, respectively, and the measurement and recording results are as shown in FIG.

That is, all of the following items have very low friction coefficients of about 0.01 to 0.02 immediately after the start of rotation, and there is almost no change in the friction coefficients even after 60 minutes. It was confirmed that it was very familiar and extremely excellent (there was a slight decrease in the value, but the fluctuation range was within 0.01 even after 60 minutes). The materials used for these are the same as the raw materials used, and only sintering in a Zn atmosphere is not performed, but the friction coefficient is 0 immediately after the start.
It is close to 14, and this value has dropped to near 0.07 after 60 minutes.

In the comparative reference example shown as above, a bronze alloy powder containing 9 wt% tin is used, and the friction coefficient is about 0.15 immediately after the start of rotation and about 0.12 even after 60 minutes. . In the comparative reference example, 5 wt% of tin powder was mixed with copper powder, which was similar to that at the start, but after 60 minutes, the friction coefficient was
Although it has decreased to nearly 0.10, all of these reference examples including the above also show a tendency for the friction coefficient to decrease even after 60 minutes, and it is clear that they are not always familiar. .

Further, the results of measuring the amount of wear of the products subjected to the above-mentioned tests are shown in Table 2 below.
AX) is 1.4 μm, and the minimum (MIN) and the average (AVE) are at least 1.
It is clear that a size of 5 μm or less can be secured. On the other hand, Comparative Examples 1 to 3 are at least 3 μm or more,
It was confirmed that the maximum value of the above-mentioned one reached about 15 μm, and it could be reduced to at least 1/10 or less by the present invention.

[0040]

[Table 2]

Especially, 0.5 wt% of boron nitride is used as a solid lubricant.
In the case of blending, the wear amount is MAX, MI
It was confirmed to be 0.4 μm including N, and the amount of wear was very small, showing excellent properties.

Example 2 The same as in Example 1, except that copper was plated and tin powder was added separately, and instead of being compacted, brass containing 5 wt% tin as a copper alloy was applied to iron powder. Using the same plated material as in Example 1, powder compacting and sintering were performed to manufacture a bearing having a porosity of 18% as a whole, a surface layer portion of 16%, and an inner layer portion of 25%.

The friction coefficient of this product was measured under the same test conditions as in Example 1, and the result was obtained immediately after the start.
It was about 0.03, which was substantially the same even after 60 minutes, and it was confirmed that it had a favorable conformability as in Example 1. Also, the wear amount after 60 minutes is 0.6 to 1.2.
It was confirmed to be at the same level as in Example 1 also in this point.

Example 3 As in Example 1, only Cu-plated iron powder was used, that is, tin powder was not used and Sn-free Cu-plated iron powder was used. As shown in Fig. 3, a product having changes in the whole, the surface layer portion and the inner layer portion was manufactured.

[0045]

[Table 3]

Each of the sintered oil-impregnated bearings 1 to 3 obtained as described above was tested and measured in the same manner as in Example 1. The result shows that the coefficient of friction was between 60 minutes after the start and 60 minutes after the start. 2 (A), those containing boron nitride are as shown in FIG. 2 (B), those without solid lubricant are as shown in FIG. 2 (C), and the amount of wear after 60 minutes is as shown in Table 4. The maximum value was 1.2 μm, which was considerably low, and the advantages of the present invention could be sufficiently confirmed.

[0047]

[Table 4]

Example 4 Copper-plated iron powder obtained by plating 50% of Cu with 50% by weight of iron powder was used. 2 parts of tin powder was added to 100 parts of this copper-plated iron powder.
Using the partially added raw material powder, a plurality of oil-impregnated bearings in which the overall porosity, surface layer porosity, and inner layer porosity were changed as shown in Table 5 below were manufactured.

[0049]

[Table 5]

The friction coefficient of each of the oil-impregnated bearings obtained as described above was measured in the same manner as in Examples 1 to 3 above.
The one in which boron nitride is mixed is shown in FIG. 3 (B), the one without such a solid lubricant is shown in FIG. 3 (C), and the result of measuring the amount of wear after the test for 60 minutes is as follows. As shown in Table 6, it was confirmed that all of the bearings had favorable compatibility and durability.

[0051]

[Table 6]

[0052]

As described above, according to the present invention, a sintered oil-impregnated bearing is excellent in productivity, can be manufactured simply and at low cost, and has excellent conformability and low wear characteristics. However, it is an invention that can produce a product having special characteristics that cannot be predicted in the prior art, and has a great effect industrially.

[Brief description of drawings]

FIG. 1 is a recording chart summarizing the friction coefficient measurement results of an inventive example, a comparative example, and a comparative reference example of Example 1 of the present invention.

FIG. 2 is a recording chart showing a friction coefficient measurement result for Example 3 of the present invention.

FIG. 3 is a recording chart showing a friction coefficient measurement result for Example 4 of the present invention.

Claims (10)

[Claims] 1. An alloy layer containing copper or a copper alloy and zinc as a main component is formed on a surface layer portion of a powder compact sintered body made of iron powder plated with copper or a copper alloy, and pores of the whole compact are formed. Porosity is 18% by volume or more and the porosity of the inner layer is 2
A sintered oil-impregnated bearing having a porosity of 5% by volume or more and a surface layer portion porosity of 16% by volume or less. 2. A powder compact sintered body made of iron powder plated with copper or a copper alloy, wherein an alloy layer mainly composed of copper or a copper alloy and zinc is provided on a surface layer portion of the powder compact sintered body. Is formed, and the pores of the microstructure due to the powder compaction sintering of the surface layer portion are refined by the alloy layer mainly composed of copper or copper alloy and zinc, and the friction coefficient is continuously 30 minutes or more even immediately after the start of rotation. Sintered oil-impregnated bearing characterized by being at the same level as when rotating. 3. The sintered oil-impregnated bearing according to claim 1, wherein the porosity is 18 vol% or more and the air permeability is 30 darcy or less. 4. The rotation speed is 2000 rpm, the load is 14 kgf / cm.
^The average amount of wear under the test conditions of 1 hour for ² is 1.5μ
The sintered oil-impregnated bearing according to claim 1, wherein the sintered oil-impregnated bearing has a diameter of m or less. 5. A solid lubricant powder such as molybdenum disulfide, graphite or boron nitride is contained, and the solid lubricant powder is fixed on the surface layer portion by an alloy layer containing copper and zinc as main components. The sintered oil-impregnated bearing according to claim 1, which is characterized. 6. A compact formed by compacting iron powder plated with copper or a copper alloy is prepared, and the compact is compacted in a zinc atmosphere, and the porosity of the compact surface layer is adjusted to the inner layer. A method for producing a sintered oil-impregnated bearing, which comprises alloying by adsorbing zinc so as to reduce the porosity by 10% by volume or more. 7. A powder compact formed by compacting iron powder and tin powder plated with copper or a copper alloy as a main material is prepared, and the powder compact has a porosity of a surface layer portion in a zinc atmosphere. A method for producing a sintered oil-impregnated bearing, which comprises performing a sintering process for adsorbing zinc so as to reduce the porosity by 10% or less from the porosity of the inner layer portion to achieve alloying with copper-zinc as a main component. 8. A solid lubricant powder such as molybdenum disulfide, graphite or boron nitride is also used as a main material, and the solid lubricant powder is alloyed by zinc adsorption to stabilize the fixing of the solid lubricant powder. The method for manufacturing a sintered oil-impregnated bearing according to claim 6 and claim 7. 9. The method for producing a sintered oil-impregnated bearing according to claim 6, wherein iron powder coated with 30 to 60 wt% of copper or copper alloy is powder compacted. 10. The method for producing a sintered oil-impregnated bearing according to claim 6, wherein copper or copper alloy is melted, and the sintering treatment is performed under a temperature condition in which iron is not melted.