Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Patent
1990-10-26
1992-11-17
Van Balen, William J.
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
427294, 4283066, 4283084, 4283179, 4283202, 4283227, 428422, B32B 326
Patent
active
051642565
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a porous slide bearing made of a porous sintered compact impregnated with a lubricant and a method for manufacturing the same.
BACKGROUND ART
Porous slide bearings are mainly used in motors for household electric appliances, automotive motors and the like. A bearing of this type is made of a sintered compact having pores impregnated with a lubricating oil which oozes out onto the sliding surface during use, thus extending the bearing's working life.
A porous slide bearing is normally made of a sintered compact having a homogeneous porous structure obtained by subjecting the compact to such treatments as mixing, press molding, calcining or forming finely powdered grains of iron, copper, zinc, tin, graphite, nickel or an alloy thereof. Such a sintered compact usually has pores 50 microns or less in diameter (many of them are 10 microns or less).
In order to permit use of such a porous slide bearing for a prolonged period, its pores have to be impregnated with a sufficient amount of lubricating oil. However, since it is kept inside the pores of the sintered compact only by the action of surface tension and viscosity, a decrease in viscosity might happen together with an increase in volume due to frictional heat in the bearing or in a high-temperature environment, causing the lubricating oil to flow out of the bearing. Thus, the range of operating temperatures is restricted and the durability of the bearing can drop.
In order to solve these problems, with a bearing which is required to have a long life, it is necessary to provide an oil tank made of felt or wick and keep it in contact with the outer surface of the bearing.
But if such means is employed in applications where any oil stain is undesirable, it is necessary to provide a seal to prevent oil leakage. This will restrict the freedom of the design and increase the cost.
It is an object of this invention to provide an oil-containing bearing which can prevent the leakage of lubricant by use of simple means without using an oil tank.
SUMMARY OF THE INVENTION
In order to achieve the abovesaid object, the present invention consists of a porous slide bearing made of a porous sintered compact impregnated with a lubricating oil, characterized in that the sintered compact is impregnated with a first lubricant in the form of an oil or a grease containing a thickening agent at a concentration of less than 3 per cent by weight and with a second lubricant in the form of a grease containing a thickening agent at a concentration of 3 per cent by weight or more, the outer surface of the sintered compact being impregnated to a predetermined thickness with the second lubricant.
The lubricant held in the sintered compact flows onto the sliding surface, contributing to lubrication. The hard lubricant which has a comparatively high concentration of thickening agent serves to close the open ends of the pores, thus preventing the soft lubricant inside from leaking.
The present invention also encompasses in a method for producing a porous slide bearing including the steps of homogenizing a lubricant to make crystals contained therein into fine particles and to disperse them uniformly, and impregnating under vacuum the lubricant into pores in the porous slide bearing.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a vertical sectional front view of the pillow block in use; FIG. 2 is a vertical sectional side view of the same; FIG. 3 is an enlarged sectional view of the oil-containing bearing; FIG. 4 is a graph showing the relation between the shear rate and the apparent viscosity of grease; FIG. 5 is a flow chart showing the order of the manufacturing steps according to the present invention; and FIG. 6 is a vertical sectional view showing how the porous slide bearing according to this invention is used.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIGS. 1 and 2 show a pillow block having a porous slide bearing 1 supported by a steel housing 2. The bearing 1 has a bore 4 through which a shaft 3 is rotatably mounted. The in
REFERENCES:
patent: 2951721 (1960-09-01), Asp
patent: 4079170 (1978-03-01), Cluff
Ito Yoshinori
Nakanishi Kiyoshi
Sato Tasuku
NTN Corporation
Van Balen William J.
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