Bearings – Rotary bearing – Plain bearing
Reexamination Certificate
2001-08-08
2003-07-29
Schwartz, Christopher P. (Department: 3683)
Bearings
Rotary bearing
Plain bearing
C384S902000
Reexamination Certificate
active
06599018
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an oil-impregnant sintered bearing in which a bearing main body is impregnated with lubricating oil for improving lubrication with a rotating axis member which runs through an internal diameter of the bearing, and manufacturing method thereof.
2. Related Art
An oil-impregnant sintered bearing is composed of a porous sintered metal, and is impregnated with lubricating oil prior to use. Consequently, the oil-impregnant sintered bearing can be used for a long period of time without being further oiled, has superior durability at high temperatures and low noise levels. For these reasons, it is widely used instead of a ball-bearing as a bearing for a rotating axis member.
This type of oil-impregnant sintered bearing comprises a cylindrical bearing main body of porous sintered metal, which an internal face is provided therein. A rotating axis member has a smaller diameter than the diameter of the internal face, and is inserted therein. Lubricating oil, which is sucked out from the great number of small pores which are buried in the bearing main body or opened in the surface of the internal face by the pump action accompanying the rotation of the rotating axis member, and a lubricating oil, which has been exuded by expansion caused by frictional heating, form an oil film at the section of the oil-impregnant sintered bearing which slides against the rotating axis member; this oil film supports the rotating axis member and protects it from damage such as burning.
However, in such an oil-impregnant sintered bearing, since even the sliding face, which the rotating axis member contacts while sliding, has a great number of pores which the lubricating oil is impregnated in, even when the oil film is formed between the rotating axis member and the sliding face, some of the lubricating oil leaks from the pores, reducing the oil pressure and allowing local contact between the rotating axis member and the sliding face. As a consequence, there are drawbacks that the frictional coefficient with the rotating axis member increases, and burns and the like may occur.
An oil-impregnant sintered bearing
101
shown in
FIG. 4
is a conventional proposal for dealing with these drawbacks. The oil-impregnant sintered bearing
101
having an internal diameter
104
, which is provide in a bearing main body
103
of porous sintered alloy having internal pores, and a rotating a is member
102
, which is inserted through the internal diameter
104
. A sliding face
105
is provided by closing pores in one region in the periphery direction on the inner peripheral face of the internal diameter
104
. This method for preserving the oil film stops the lubricating oil from leaking when the sliding face
105
contacts the rotating axis member
102
, and prevents the reduction in oil pressure mentioned above.
However, as for example disclosed in Japanese Patent Application, First Publication No. 4-307111, even when pores are closed in the inner peripheral face of a pressed powder body, obtained by pressure-forming of raw material powder, the pores sometimes re-open during sintering since tin and the like is included in the raw material powder. Consequently, oil seeps from the holes to the inside, and oil pressure decreases. Further, Japanese Patent Application, First Publication No. 5-180229 discloses technology for closing the pores in the inner peripheral face when plugging in a rod for forming the bearing at the time of post-sintering correction. However, this technology basically involves closing the pores which have appeared in the inner face, and cannot preserve the oil film since the surface layer may be broken by the oil pressure, allowing the oil to seep to the inside.
Further, Japanese Patent Application, First publication No. 8-28567 discloses technology which uses a welded material having no pores in one section of its inner peripheral face. However, since the welded material cannot contain lubricating oil, the capacity of lubricating oil which can be contained in the oil-impregnant sintered bearing is reduced.
SUMMARY OF THE INVENTION
The present invention has been realized in consideration of the above problems, and aims to provide an oil-impregnant sintered bearing which can reliably secure the oil film, formed on the sliding face, and a method for manufacturing the oil-impregnant sintered bearing.
A first aspect of the present invention provides an oil-impregnant sintered bearing comprising an internal diameter, which a rotating axis member is inserted through, provided in a bearing main body, formed by a porous sintered alloy having internal pores, and a sliding face, provided in one region of the inner peripheral face of the internal diameter. The sliding face is obtained by closing the pores which have been opened in the inner peripheral face. The density in a section preserving oil pressure, which extends from the sliding face of the bearing main body toward the outer side of the diameter, is higher than in other sections of the bearing main body.
According to this constitution, the density of the section preserving oil pressure, extending from the sliding face of the bearing main body to the outer side of the diameter, is higher than other sections of the bearing main body. Therefore, the pores in the internal area of the section preserving oil pressure are more greatly closed than the other section, with the result that oil does not seep from the sliding face to the inside, enabling the oil film to be secured over the sliding face.
A second aspect of the present invention provides a method for manufacturing the oil-impregnant sintered bearing, comprising the steps of pressure-forming a raw material powder to obtain a pressed powder body, sintering the pressed powder body, obtaining a bearing main body, formed by a porous sintered alloy having internal pores, and providing a sliding face in one region of the inner peripheral face of the internal diameter, the sliding face being provided by closing the pores which have been opened in the inner peripheral face; and making the density in a section preserving oil pressure, which extends from the sliding face of the bearing main body toward the outer side of the diameter, higher than in other sections of the bearing main body.
In this invention, the oil-impregnant sintered bearing is manufactured so that the density of the section preserving oil pressure, extending from the sliding face of the bearing main body to the outer side of the diameter, is higher than other sections of the bearing main body. Therefore, the pores in the internal area of the section preserving oil pressure are more greatly closed than the other section, with the result that oil does not seep from the sliding face to the inside, enabling the oil film to be secured over the sliding face.
According to a third aspect of the present invention, in the method of the second aspect, more raw material powder is filled in a part of a cavity for pressure-forming the pressed powder body where the section preserving oil pressure is to be provided than in other parts, and the compression rate of the raw material powder in the part during pressure-forming is made greater than in the other parts, thereby making the density in the section preserving oil pressure higher than in other sections of the bearing main body.
In this invention, in a cavity for pressure-forming a pressed powder body, more raw material powder is filled in a part where the section preserving oil pressure is to be provided than in other parts, and the compression rate of the raw material powder in the part during pressure-forming is greater than in the other parts. Therefore, when the pressed powder body is corrected after sintering to obtain the oil-impregnant sintered bearing, the density in the section preserving oil pressure can be made higher than in other sections of the bearing main body.
According to a fourth aspect of the present invention, in the method of the third aspect, the raw material powder is filled in a cavity comprised
Iguchi Junichi
Itoh Tooru
Maruyama Tsuneo
Nishio Kenji
Tanaka Takeshi
Kramer Devon
Mitsubishi Materials Corporation
Schwartz Christopher P.
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