Bearings – Rotary bearing – Plain bearing
Reexamination Certificate
1999-12-09
2001-10-23
Hannon, Thomas R. (Department: 3682)
Bearings
Rotary bearing
Plain bearing
C384S300000, C384S907000, C384S908000
Reexamination Certificate
active
06305847
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a sliding bearing, particularly to a sliding bearing in which a bearing metal layer is covered with a coating layer.
Sliding bearings in which a layer of a bearing metal such as copper alloy, aluminum alloy or the like is covered with a coating layer comprising a resin as the base are disclosed in, for example, JP-A 58(1983)-108,299. In this publication, the coating layer to be applied to the layer of a bearing metal such as aluminum alloy or the like is formed by incorporating a solid lubricant such as graphite, molybdenum disulfide or the like into a thermosetting resin such as a phenolic resin, an epoxy resin or the like, with the intention of improving the anti-seizure property of the coating layer.
Moreover, JP-A 4(1992)-83,914 discloses an improvement of the lubricity of the coating layer by adding a polyimide resin as a binding material to a solid lubricant such as molybdenum disulfide or the like. Furthermore, an example is shown in which hard particles such as chromium oxide particles, aluminum oxide particles or the like are added to improve the wear resistance.
In addition, JP-A 10(1998)-37,962 describes that the wear resistance is improved by allowing the: hard particles added to the resin and the solid lubricant having a spherical shape.
Recently owing to the high power and high revolution speed of internal combustion engine, the sliding bearings have become used under severer conditions, so that sliding bearings having a higher quality have been desired.
As shown in the above-mentioned conventional techniques, in the case of the coating layer in which a solid lubricant is added to a thermosetting resin used as the base resin, the coefficient of friction has been improved, but the wear resistance has rather become low. Further, in the case of the coating layer in which hard particles are added to the thermosetting resin, wear resistance has been improved, but anti-seizure property have become low. Thus, it has been impossible to make the coating layer excellent in all of coefficient of friction, wear resistance and anti-seizure property which are required for sliding bearings, so that sliding bearings in which a balance has been maintained among these properties have been prepared. Moreover, there has been a limit in improving these properties by only controlling the composition of the solid lubricant and the hard particles.
SUMMARY OF THE INVENTION
The present inventors have found that coefficient of friction, wear resistance and anti-seizure property can be more greatly improved by using a coating layer comprising a thermosetting resin added thereto soft metal particles and have accomplished this invention.
According to the first aspect of this invention, there is provided a sliding bearing in which a bearing metal layer is covered with a coating layer, wherein the coating layer comprises a thermosetting resin as a base resin and soft metal particles dispersed in the base resin in an amount of 0.1 to 10% by volume based on the volume of the coating layer.
DETAILED DESCRIPTION OF THE INVENTION
In the bearing metal layer, there can be used known bearing metals such as copper alloy, aluminum alloy and the like, and these can be appropriately selected depending upon purposes such as load carrying capacity, wear resistance and the like.
As the base resin in the coating layer, there are used thermosetting resins such as polyimide resins, epoxy resins, phenolic resins and the like because they have a great bonding force to the soft metals and can be cured by heating in the course of production of the bearing.
The polyimide resins include polyamide-imide, polyamino-bismaleimide, diiosyanate-denatured resins thereof, BPDA-denatured resins thereof, sulfone-denatured resins thereof and the like. In particular, desirable are those resins having high fatigue resistance such as polyamide-imide (referred to hereinafter as PAI), and the like. This PAI means a polymer having alternately amide bond and imide bond in the main chain, and includes denatured polyamide-imide resins, too.
The soft metal referred to herein means a soft metal which is harder than the base resin but has a hardness Hv of 60 or less. These soft metals are high in thermal conductivity and include not only pure metals, but also alloys. The wear resistance is improved by adding soft metal particles harder than the base resin and the anti-seizure property are improved by the high heatdissipation property. Specifically, the soft metal includes copper, silver, gold, aluminum, tin, zinc, indium and the like and alloys thereof. Hard metals, which have a hardness Hv exceeding 60, for example, molybdenum, nickel, iron and the like are not adequate because when these metals are used, the wear resistance is improved but the anti-seizure property is deteriorated and the attacking property against the counter member becomes high.
Moreover, it is preferable that the soft metal particles are of an easily sulfurizable metal such as copper, silver, tin, zinc or the like (referred to hereinafter as the second aspect of this invention). Among the soft metal particles, the easily sulfurizable metal particles are used, this metal reacts with sulfur contained in a lubricating oil to form a thin sulfide film excellent in lubricity on the surfaces of the particles, whereby the coefficient of friction is made smaller.
The soft metal particles are required to be dispersed in the coating layer which is in the form of a thin film and hence the diameters of the particles are preferably 5 &mgr;m or less, and particles having diameters of 0.05 to 3 &mgr;m are more preferable because they are easy to handle.
The amount of the soft metal particles added should be 0.1 to 10% by volume based on the volume of the coating layer. When the amount is less than 0.1% by volume, no sufficient addition effect is obtained. Moreover, when the amount exceeds 10% by volume, the forming of the coating layer becomes difficult. The amount is particularly preferably 0.5 to 5% by volume.
Furthermore, a solid lubricant can be contained in the coating layer in an amount of not more than 80% by volume based on the volume of the coating layer (referred to hereinafter as the third aspect of this invention). When the solid lubricant is contained, the coefficient of friction becomes smaller.
As the solid lubricant, there can be used at least one member selected from the group consisting of resins such as polytetrafluoroethylene (PTFE) and the like; graphite (Gr); and metal sulfides such as molybdenum disulfide (MoS
2
), copper sulfide (CuS), tin sulfide (SnS) and the like. When the content thereof exceeds 80% by volume, the wear resistance is deteriorated.
The wear resistance can be improved by adding hard particles to the coating layer in an amount of not more than 5% by volume based on the volume of the coating layer (referred to hereinafter as the fourth aspect of this invention).
As the hard particles, there can be used at least one material having a high hardness, for example, oxides (Al
2
O
3
, CoO—Al
2
O
3
, etc.), nitrides (TiN, Si
3
N
4
, etc.), carbides (SiC, TiC, WC, etc.), fluorides (CaF
2
, NaF, etc.), hard metals (Ni, Mo, Fe, etc.), and the like. When the amount exceeds 5% by volume, the anti-seizure property is deteriorated and attacking property against the counter member becomes high.
As these hard particles, there are used those having particle diameters of about 0.05 to 5 &mgr;m; however, the particles are desirably contained in the uniformly dispersion state in the coating layer which is in the form of a thin film, and it is preferable to use the particles in the form of fine particles having particle diameters of 0.1 to 3 &mgr;m.
Incidentally, the total content of the soft metal, the solid lubricant and the hard particles should preferably be not more than 90% by volume because when they are contained excessively, the coating layer becomes brittle and easy to peel.
The thickness of the coating layer having the above-mentioned composition is preferably about 2 to 30 &mgr;m. When the thickness
Hiramatsu Nobutaka
Ono Akira
Shibayama Takayuki
Tanaka Takuya
Yamamoto Koichi
Browdy and Neimark
Daido Metal Company Ltd.
Hannon Thomas R.
LandOfFree
Sliding 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 Sliding bearing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Sliding bearing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2552137