JPH05240251A - Sintered oil retaining bearing - Google Patents

Abstract

PURPOSE:To stabilize lubricating characteristics and extend a life by impregnating a sintered bearing molding with perfluoro polyether oil. CONSTITUTION:A bearing molding, which is obtained by molding a metal material successively through required processes of compression molding, baking, and compression molding, may be any bearing having uniformly distributed pares and a form such as flat surface bearing, thrust bearing, journal bearing or the like in which a shaft makes fact contact with the bearing, and a slippage is caused by the rotation of the bearing. Perfluoro polyether oil is a perfect fluorinated oil having an ether bonding of -CF2-O-CF2-in the main chain, and it has a low glass transition temperature under low pressure condition because of its large molecular bending property, a wide liquid temperature range, and excellent heat resistance, chemical resistance, and oxidation resistance, and also shows an extremely low vapor pressure from low temperature to high temperature because of its large molecular weight and low pour point. Further, it has also characteristics such as satisfactory lubricating characteristic, low friction coefficient, and high load property.

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 obtained by impregnating a sintered bearing molded product with lubricating oil, and more particularly to a sintered oil-impregnated bearing used under low pressure conditions.

[0002]

2. Description of the Related Art In general, a sintered oil-impregnated bearing has a structure in which the lubricating oil is impregnated and held in the pores of a sintered bearing molded product, and the lubricating oil is exuded to the sliding surface during its use to ensure stable sliding for a long time. It is intended to obtain friction characteristics.

Molded products of such sintered bearings are usually
Fine powder particles made of iron, copper, zinc, tin, graphite, nickel, lead, etc. or alloys combining these are mixed, compression molded,
It is obtained by subjecting it to treatments such as firing and sizing, and it has a uniform porous structure.

On the other hand, a synthetic lubricating oil such as mineral oil or diester oil has been used as the lubricating oil impregnated into the sintered bearing molded product.

However, the sintered oil-impregnated bearing described above has a low vacuum (atmospheric pressure of 10 ² Pa) or a medium vacuum (10 ² to 10 Pa).
^If it is used under the condition of ( ^-1 Pa), the lubricating oil may evaporate and the torque may increase. Therefore, bearings used in aircraft equipment and artificial hygiene equipment, etc., which are subject to low pressure use conditions, have their sliding surfaces molded or coated with a self-lubricating polymer material such as tetrafluoroethylene resin or polyimide, or A solid lubricant such as gold, silver or molybdenum disulfide was coated to improve lubricity.

[0006]

However, a bearing using the above-mentioned self-lubricating polymer material or solid lubricant is
Its lubrication characteristics easily change according to the shape of the solid surface,
Also, in terms of durability of the lubricating film, there is a problem that the life of the lubricating film is inferior to that of the fluid lubricated bearing.

In view of the above, the present invention solves the above-mentioned problems and allows a bearing used under a low pressure condition to be lubricated by fluid lubrication in which its sliding surface is completely separated by an oil film. It is an object to stabilize the lubrication characteristics of the bearing under such conditions and to extend the life of the bearing.

[0008]

In order to solve the above problems, the present invention employs a structure in which a sintered bearing molded article is impregnated with perfluoropolyether oil.

[0009]

The sintered oil-impregnated bearing according to the present invention can be obtained by adding mineral oil, various ester oils, poly-α, and the like, which have been conventionally used, to a sintered bearing compact.
Since it is impregnated with perfluoropolyether oil whose vapor pressure is significantly lower than that of olefin oil,
Even when used under low pressure conditions such as × 10 ⁵ to 1 × 10 ^-1 Pa below atmospheric pressure, the lubricating oil exuded on the sliding surface hardly evaporates, and exhibits stable lubricating characteristics for a long period of time.

[0010]

EXAMPLE The sintered bearing molded product used in the present invention is not particularly limited in its material, and a desired metal material is subjected to a compression molding step, a firing step and a compression molding (sizing) as in the conventional case. It may be one that is formed through successive steps, and usually has pores of 50 μm or less (the majority of pores have a diameter of 10
(μm or less) is evenly distributed.

Also, the shape of the bearing molded product is not particularly limited, and the shaft and the bearing such as a flat bearing, a thrust bearing, and a journal bearing are mechanically in surface contact with each other, and the bearing is rotated. Any bearing may be used as long as it causes slippage. The bearing here mainly refers to a sliding bearing, but when a porous sintering agent is used for the cage of the rolling bearing, a bearing subjected to the same treatment as the above sliding bearing may be used.

Further, the perfluoropolyether oil used in the present invention is a completely fluorinated oil having an ether bond of --CF ₂ --O--CF ₂ --in its main chain, and is shown by the following [Chemical formula 1]. It may be of such a structure.

[0013]

[Chemical 1]

The above-mentioned perfluoropolyether is 2,
2,3,3-Tetrafluorooxetane was subjected to ring-opening polymerization with a fluorine ion catalyst, and the resulting oligomer was directly fluorinated with fluorine gas to be converted into a perfluoro body. It is a polyether having a repeating unit of.

Since such a perfluoropolyether oil has a large number of ether bonds in the main chain and has a large molecular flexibility, it exhibits the following excellent lubricating characteristics under low pressure conditions. That is, the glass transition temperature is low, and therefore the liquid temperature range (freezing point to boiling point) is extremely wide. On the other hand, chemically, due to the electric attraction effect of fluorine, it does not show the original ether property, and has excellent heat resistance, chemical resistance, and oxidation resistance. The viscosity index is 150 to 210, which is considerably superior to that of mineral oil and the like, and because of its large molecular weight and low pour point, it exhibits a very low vapor pressure from low temperature to high temperature.
In addition, it has good lubrication characteristics, such as a low coefficient of friction and high load resistance compared to general lubricating oils.

In order to impregnate a sintered bearing molded product with the perfluoropolyether oil, it is preferable to impregnate this with the bearing molded product alone in order to achieve the intended object of the present invention. From an economical point of view, it is also possible to impregnate a mixed oil blended with another lubricating oil. In this case, examples of the other lubricating oil blended with the perfluoropolyether oil include diester oil, polyol ester oil, poly α-olefin oil and the like.

In addition, as long as the effect of the present invention is not impaired, antioxidants such as hindered phenols and aromatic amines, polyalkylmethacrylates, and styrene can be added to perfluoropolyether oils or mixed oils with other lubricating oils. Needless to say, a viscosity index improver such as a hydride of a diene copolymer, a higher fatty acid (oleic acid, stearic acid, etc.), a higher alcohol (oleyl alcohol, etc.) or another oiliness improver may be added.

[Experimental Example] Perfluoropolyether oil (Fomblin Z manufactured by Montefloss) was used, and the pore size was 1 to 1.
A 0 μm sintered copper alloy bush-shaped sliding bearing compact was immersed, and perfluoropolyether oil was impregnated into the communicating holes of the bearing compact under reduced pressure. Then, excess oil adhering to the surface of the molded bearing was removed with a clean cloth to obtain a sintered oil-impregnated bearing.

A home electric motor equipped with the obtained bearing was used in an atmosphere of medium vacuum, but the amount of loss due to evaporation was very small, stable friction characteristics and long life were obtained.

[0020]

As described above, according to the present invention, since the sintered oil-impregnated bearing is impregnated with perfluoropolyether oil having a very low vapor pressure, the sliding surface is completely separated by the oil film even under a low pressure condition. There is an advantage that stable lubrication can be achieved by fluid lubrication, and that a sintered oil-impregnated bearing used in a vacuum motor or the like can be stably provided with excellent lubrication characteristics and a long life can be achieved.

Claims (1)

[Claims] 1. A sintered oil-impregnated bearing obtained by impregnating a sintered bearing molded product with perfluoropolyether oil.