JPH0741784A - Porous sliding bearing filled with grease - Google Patents

Abstract

PURPOSE:To efficiently produce a porous sliding bearing filled with a grease which is free from the outflow and spattering of grease and excellent in the retention of grease so that it suffers little decrease in the amount of lubricating oil even when a shaft is turned at high speed for a long time. CONSTITUTION:A porous sliding bearing made of a sintered metal or a porous synthetic resin is impregnated with a mixture of 5-99wt.% lubricating grease and 95-1wt.% powder of an ultra-high-molecular-weight polyolefin of an average molecular weight of 1X10<6> to 5X10<6> in a state in which the mixture is liquefied by heating at a temperature above the gel point of the polyolefin and below the dropping point of the grease. The mixture is then solidified by cooling to give the objective bearing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grease-filled porous bearing having a porous bearing impregnated with lubricating grease, and a method for producing the same.

[0002]

2. Description of the Related Art Generally, an oil-impregnated bearing in which a lubricating oil or grease is impregnated and held in a porous bearing material in which metal, ceramic, or synthetic resin is sintered or foamed at a temperature not higher than the melting temperature thereof to form an interconnecting hole is formed. Are known.

As a grease to be impregnated into the porous bearing material, a grease containing alkali metal soap, alkaline earth metal soap or polyurea as a thickener is generally used.

The lubrication state of such a grease-filled porous plain bearing filled with grease will be described with reference to FIG. 1. In the rotating state of the shaft 1, capillary action and temperature rise due to friction with the shaft 1 occur, and The lubricating oil 3 is supplied to the sliding surface by the leaching of the lubricating oil 3 due to the difference in expansion coefficient between the quality bearing 2 and the grease impregnated therein. Further, when the rotation of the shaft 1 is stopped, the lubricating oil 3 is sucked into the porous bearing 2 again due to the temperature drop. And such a porous bearing 2
The housing 4 is externally fitted to prevent the lubricating oil 3 from scattering.

[0005]

However, in the grease-filled porous plain bearing described above, the lubricating oil flows out of the housing along the rotating shaft over the housing during the rotation of the shaft, or when the lubricating oil leaks out of the shaft. Even after the rotation is stopped, it is not absorbed by the bearing material and evaporates or scatters, which causes a shortage of lubricating oil when the shaft rotates, resulting in deterioration of the sliding characteristics of the bearing device and
There is a problem of causing a burn-in phenomenon.

In view of the above, the present invention solves the above-described problems, and the grease-filled porous plain bearing does not leak or scatter the lubricating oil, and even if the shaft is rotated at a high speed for a long time, the amount of lubricating oil is increased. It is an object of the present invention to reduce the amount of decrease in the amount of grease and to have excellent grease retention, and to efficiently manufacture such a grease-filled porous plain bearing.

[0007]

In order to solve the above problems, in the present invention, a structure in which a porous plain bearing is impregnated with the following solid grease is adopted.

The lubricating grease of 5 to 99% by weight has an average molecular weight of 1 × 10 ^6.
~ 5 x 10 ⁶ ultra high molecular weight polyolefin powder 95 ~
A solid grease obtained by dispersing 1% by weight at a temperature not lower than the gelling point of the ultrahigh molecular weight polyolefin and not higher than the dropping point of the lubricating grease to be solidified by cooling.

Further, the grease-filled porous plain bearings described above are formed by adding 5 to 99% by weight of lubricating grease to the porous plain bearings.
And a mixture of 95 to 1% by weight of ultra-high molecular weight polyolefin powder having an average molecular weight of 1 × 10 ^{6 to} 5 × 10 ⁶ at a temperature not lower than the gel point of the ultra-high molecular weight polyolefin and not higher than the dropping point of the lubricating grease. It can be produced by solidifying the mixture by impregnating it in a state of being heated and then cooling.

The details will be described below.

The molding material for the porous bearing used in the present invention is not particularly limited, and powder metallurgy, cast iron,
A well-known molded body made of a synthetic resin or the like and having continuous ventilation holes by sintering or foam molding can be adopted. The continuous vent is
Although the size is not particularly limited, if the diameter is at least 30 μm or more, the mixture of the lubricating grease and the ultrahigh molecular weight polyolefin described later can be easily impregnated.

The ultrahigh molecular weight polyolefin powder in the present invention may be a powder composed of polyethylene, polypropylene, polybutene or a copolymer thereof, or a mixed powder prepared by mixing individual powders, and the molecular weight of each powder is determined by a viscosity method. The average molecular weight measured by
It is 0 ^{6 to} 5 × 10 ⁶ . Polyolefins having such an average molecular weight range are superior to low molecular weight polyolefins in rigidity and oil retention, and hardly flow even when heated to a high temperature. The blending ratio of such ultra-high molecular weight polyolefin in the lubricating composition is 95 to 1% by weight, and the amount thereof depends on the desired oil separation degree, tenacity and hardness of the composition. Therefore, the higher the amount of the ultra-high molecular weight polyolefin compounded, the higher the hardness of the gel after being dispersed and held at a predetermined temperature.

The lubricating grease used in the present invention is
The lubricating grease thickened with soap or non-soap is not particularly limited, and includes lithium soap-diester type, lithium soap-mineral oil type, sodium soap-mineral oil type, aluminum soap-mineral oil type, lithium soap-
Examples of greases include diester mineral oil-based, non-soap-diester-based, non-soap-mineral oil-based, non-soap-polyol ester-based and lithium soap-polyol ester-based greases.

The melting point of the above-mentioned ultra-high molecular weight polyolefin varies depending on the above-mentioned average molecular weight, and therefore is not constant. For example, the melting point of the one having an average molecular weight of 2 × 10 ⁶ by the viscosity method is 136 ° C. As a commercial product having the same average molecular weight, Mitsui Petrochemical Co., Ltd .: Miperon (registered trademark)
XM-220 and the like.

Therefore, in order to disperse and retain the ultra-high molecular weight polyolefin in the above-mentioned lubricating grease, after mixing the above-mentioned materials, the ultra-high-molecular-weight polyolefin is heated to a temperature above the gelling temperature and lower than the dropping point of the lubricating grease. Heat to a temperature, for example 150-200 ° C.

In the present invention, the porous grease is impregnated with the lubricating grease in such a state that the ultra-high molecular weight polyolefin is melted and dispersed. The impregnation method in that case is impregnation under normal pressure or under pressure. May be Especially 1kgf /
Good results have been obtained by high pressure impregnation at cm ² or higher.
After such impregnation, it is cooled to at least room temperature and solidified to form an oily surface, that is, a surface through which oil oozes out, on the surface of the porous bearing.

[0017]

In the grease-filled porous sliding bearing according to the present invention, the communicating hole of the porous bearing is impregnated with the mixed solution of the lubricating grease and the polyolefin having the predetermined molecular weight, and the mixture is cooled and solidified, whereby It will be filled with solid grease. The surface of such a bearing is an oily surface on which lubricating oil gradually exudes from solid polyolefin, and there is no excess lubricating oil that scatters even when subjected to centrifugal force. Therefore, a proper amount of lubricating oil is always supplied to the sliding surface, and stable lubrication characteristics are given to the bearing.

Example 1 As a porous bearing material, a polyvinyl formal porous body (Kanebo Co., Ltd .: Kanebo Sponge Cygnus, pore diameter> 30 μm) was molded into a cylindrical sliding bearing shape shown in FIG. And ultra-high molecular weight polyolefin (Mitsui Petrochemical Industry Co., Ltd .: Miperon) 20
A mixture of 6 parts by weight of a solid wax containing a low molecular weight polyolefin (manufactured by Mitsui Kasei Co., Ltd .: sun wax) and 74 parts by weight of a lubricating grease (lithium soap-mineral oil type) was placed in a high temperature tank at 150 to 180 ° C. The porous plain bearing was impregnated with this mixture at a high pressure of 10 kgf / cm ² .

Next, this is heated in the high temperature tank at 150-
After heating at 180 ° C. for 30 minutes, it was cooled to room temperature to produce a solid grease-filled porous plain bearing.

In order to check the grease retention of the obtained bearing, this bearing was used at an ambient temperature of 100 ° C. and a rotation speed of 3600.
A continuous operation test was performed under the conditions of rpm and a radial load of 200 g, and the relationship between the operation time and the grease reduction amount (% by weight) was examined. The results are shown in the graph of FIG.

[Comparative Example 1] A sintered bearing made of cast iron (pore diameter> 30 μm) was used as a porous bearing material, and a synthetic lubricating oil poly-α-olefin (Floyl 947P manufactured by Kanto Kasei Kogyo Co., Ltd.) was used as a liquid. Decompression condition (10 ^-4 Tor at temperature 60 °
It was impregnated with r).

In order to investigate the grease retention of the obtained bearing, the grease retention of the bearing was examined in exactly the same manner as in Example 1, and the results are also shown in FIG.

As is clear from the results shown in FIG. 2, the bearing of Comparative Example 1 lost 16% by weight of grease due to outflow or evaporation after 400 hours of continuous operation. It can be seen that the lubricating grease retainability is excellent because the reduction is only 10% by weight.

[0024]

As described above, the present invention provides a grease-filled porous plain bearing which is obtained by impregnating a porous plain bearing with a mixture of lubricating grease and a predetermined ultra-high molecular weight polyolefin and cooling and solidifying the mixture through predetermined heat treatment. Therefore, there is an advantage that the lubricating oil does not flow out or scatter, and even if the shaft is rotated at a high speed for a long time, the amount of reduction of the lubricating oil is small and the grease holding property is excellent. Further, such a grease-filled porous plain bearing has an advantage that it can be efficiently manufactured by a relatively simple method of impregnation.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a usage state of a grease-filled porous plain bearing.

FIG. 2 is a chart showing the relationship between the running time and the grease reduction amount in the example.

[Explanation of symbols]

 1 Shaft 2 Porous bearing 3 Lubricating oil 4 Housing

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Claims (2)

[Claims] 1. A grease-filled porous plain bearing obtained by impregnating a porous plain bearing with the following solid grease. Note: Lubrication grease 5 to 99% by weight, average molecular weight 1 × 10 ⁶
~ 5 x 10 ⁶ ultra high molecular weight polyolefin powder 95 ~
A solid grease obtained by dispersing 1% by weight at a temperature not lower than the gelling point of the ultrahigh molecular weight polyolefin and not higher than the dropping point of the lubricating grease to be solidified by cooling. 2. Lubricating grease 5-9 for the porous plain bearing
A mixture of 9% by weight and 95 to 1% by weight of an ultrahigh molecular weight polyolefin powder having an average molecular weight of 1 × 10 ^{6 to} 5 × 10 ⁶ is added to the gel point of the ultrahigh molecular weight polyolefin or more and the dropping point of the lubricating grease. A method for producing a grease-filled porous plain bearing, which comprises impregnating the mixture under heating at the following temperature and then cooling to solidify the mixture.