Plain bearing

Details Plain bearing Plain bearing

1998-10-14

2001-05-22

Footland, Lenard A. (Department: 3682)

Bearings

Rotary bearing

Plain bearing

C384S273000, C384S294000, C384S625000

Reexamination Certificate

active

06234678

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a plain bearing, and more particularly to a plain bearing for use with a shaft which bearing has a specified portion in a circumferential direction to which a shaft load is applied in a concentrated manner.
There is well known a plain bearing in which an overlay, composed of Pb, Sn, Al, or an alloy comprising one of these substances as a main component, is formed on a surface of a bearing alloy layer so as to enhance the conformability and foreign matter embeddability, thereby imparting an excellent anti-seizure property to the plain bearing. There has been proposed a technique in which hard particles are included in this overlay so as to enhance its wear resistance, and such a technique is disclosed, for example, in JP-A-3-219098 and JP-A-4-331817 filed by the Applicant of the present application.
JP-A-3-219098 discloses a plain bearing in which 0.3 to 25 vol. % of inorganic hard particles, having a particle diameter of not more than 15 &mgr;m, are added to an overlay of Pb base alloy, thereby imparting excellent wear resistance to the plain bearing.
JP-A-4-331817 discloses a plain bearing in which inorganic hard particles have a mean particle diameter of not more than 1.5 &mgr;m, and an overlay has surface roughness of not more than Rz 4 &mgr;m, and by doing so, an anti-seizure property and fatigue resistance are enhanced without adversely affecting wear resistance.
One of a major cause of a breakdown of a plain bearing, used in an internal combustion engine, is the inclusion or intrusion of solid foreign matters such as dirt and wear debris into lubricating oil, in which case abnormal wear develops in the plain bearing, thereby causing seizure.
Recently, there has been a demand for a plain bearing of the type which can exhibit excellent foreign matter embeddability even upon inclusion of solid foreign matters into lubricating oil. There is also known a plain bearing having an explosion load-receiving region to which a load is applied in a concentrated manner, and its representative example is a plain bearing used at a big end portion of a diesel engine.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a plain bearing in which in view of the difference in required properties between portions of the plain bearing disposed in a direction of a circumference thereof, that portion of the bearing for receiving or bearing an axial load is enhanced in wear resistance while the other portion is enhanced in foreign matter embeddability, so that the plain bearing can exhibit excellent wear resistance and foreign matter embeddability as a whole.
According to the feature of the present invention, 0.3 to 25 vol. % of hard particles, having a mean particle diameter of not more than 1.5 &mgr;m, are dispersed in a main load portion of an overlay, so that the main load portion is formed into a hard region harder than the other portion of the overlay.
Although Al alloy, Cu alloy or white metal can be used as a bearing alloy, Al alloy or Cu alloy is usually used particularly in the plain bearing for use in an internal combustion engine. Although bimetal, formed by bonding a bearing alloy to a backing metal, is extensively used, the plain bearing can be composed solely of a bearing alloy layer.
Soft metal, composed of Pb, Sn, Al, or an alloy comprising one of these substances as a main component, is used as the overlay, and one of these materials is suitably selected.
The thickness of the overlay is usually 10 to 30 &mgr;m in the case of the plain bearing for an automobile engine, and is 50 to 100 &mgr;m in the case of the plain bearing for an internal combustion engine of a ship, and this thickness is suitably selected according to use.
Examples of the hard particles include nitride (e.g. BN, TiN and Si
3
N
4
), carbide (e.g. SiC, TiC, B
4
C and TaC), fluoride (e.g. CF and CaF
2
), sulfide (e.g. MoS
2
and WS
2
) and the others. Preferably, the hard particles are harder than an overlay matrix, but the degree of hardness is not always restricted.
It is necessary that the hard particles should be dispersed in the overlay, and if the particle diameter of the hard particles is large, the fatigue resistance is lowered, and therefore the mean particle diameter thereof should be not more than 1.5 &mgr;m. For example, in a plain bearing used at a big end portion of a diesel engine, the thickness of the overlay is thin on the order of 10 to 30 &mgr;m, and therefore in order to obtain a low initial frictional coefficient, the mean particle diameter of the hard particles should preferably be not more than 1.5 &mgr;m.
The content of the hard particles in the hard region of the overlay should be 0.3 to 25 vol. %. If this content is less than 0.3 vol. %, the intended effect can not be obtained by the addition of the hard particles. In contrast, if this content is more than 25 vol. %, the fatigue resistance is lowered. The content of 0.5 to 20 vol. % is particularly preferred.
The term “main load portion” means that region which receives the axial load in a concentrated manner. This will be explained, for example, with reference to
FIG. 7
showing a big end portion of a diesel engine. A plain bearing
10
is mounted on a connecting rod
11
, and rotatably supports a shaft
12
. A cap
13
is fixedly secured by bolts
14
to a big end portion of the connecting rod
11
, and these portions jointly constitute a housing. In this example shown in
FIG. 7
, a large axial load or explosion load, is applied to an upper portion as indicated by arrow A. A main load portion M is disposed at an upper portion of the plain bearing. Thus, the plain bearing does not receive the axial load uniformly over the entire circumference thereof. The axial load is concentrated on a specified (localized) portion of the plain bearing, and is not applied to the other region or portion of the plain bearing. At the main load portion, the shaft and the overlay are partially brought into metal-to-metal contact with each other by the intermittent explosion load, so that wear of the contact portions proceeds. Therefore, the main load portion is formed into the hard region having excellent wear resistance.
The other portion is constituted by the overlay composed of soft metal, and therefore exhibits excellent foreign matter embeddability.
The hard region can be formed on the overlay by suitably using a plating method, a sputtering method or a pressure bonding method. For example, a plating method, disclosed in JP-A-3-219098, can be used. Using this method, a plating solution, having hard particles dispersed therein, is spouted toward the relevant portion to be formed into the hard region, thereby forming the hard region having the hard particles dispersed therein, whereas the content of the hard particles is low at the other portion.
As described above, according to the feature of the present invention, 0.3 to 25 vol. % of hard particles, having a mean particle diameter of not more than 1.5 &mgr;m, are dispersed in the main load portion of the overlay, so that the main load portion is formed into the hard region harder than the other portion, and by doing so, there can be provided the plain bearing having excellent wear resistance and excellent foreign matter embeddability.


REFERENCES:
patent: 4073550 (1978-02-01), Yahraus
patent: 3219098 (1991-09-01), None
patent: 4331817 (1992-11-01), None

Affiliated with

Also associated with

Rating

Plain bearing does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Plain bearing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Plain bearing will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2503438