Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
1999-11-09
2004-08-03
La Villa, Michael (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C428S674000, C428S457000, C428S473500, C428S474400, C428S418000, C428S699000, C384S014000, C384S276000, C384S280000, C384S283000, C508S100000
Reexamination Certificate
active
06770381
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a sliding bearing for an internal combustion engine, and more particularly to a sliding bearing consisting of a copper-based bearing alloy, on which an overlay is applied.
BACKGROUND TECHNIQUE
The present applicant proposed in (1) Japanese Unexamined Patent Publication No. 9-249,924 and (2) European patent publication No. 0795693A2 a copper alloy, which has a particular structure considerably exceeding the properties of the kelmet used heretofore as the sliding-bearing alloy of an internal combustion engine. The alloy proposed in publication (1) is a copper alloy, which contains As; Sn, Sb, In, Mn, Fe, Bi, Zn, Ni and/or Cr as the solute element(s) of a Cu matrix and, further, essentially no secondary phase consisting of or containing these elements is formed. Likewise, the surface layer of the sliding-bearing alloy proposed in (2) is exposed when an overlay is locally worn out during the initial breaking-in of the overlay. At least a portion of the exposed surface layer consists of a copper alloy in which the above-mentioned elements such as Ag and the like are concentrated. At least the boundary of the bulk portion contiguous to the copper-alloy surface and its vicinity contain the above-mentioned elements such as Ag and the like in the solid solution and consists of such solid solution is essentially free from a secondary phase consisting of or containing these elements.
The sliding bearing proposed in the above-mentioned publication (2) consists of a copper alloy, which contains Ag, Sn, Sb, In, Al, Mg and/or Cd, and Cu essentially in balance, and which is bonded to the backing metal. Ag and the like are solid-dissolved in the Cu matrix at least in the vicinity of the sliding surface. Essentially no secondary phase, such as an Ag phase, is formed. A phase, which contains a hexagonal compound of Ag and the like with one another or Ag and the like with Cu, a compound of the Ag and the like with sulfur and oxygen, or an eutectic, is formed on the surface caused to slide with an opposing shaft.
An overlay is unnecessary or an extremely thin overlay is sufficient for the sliding bearings proposed in these publications (1) and (2), because the seizure resistance of the copper alloys in these publication is improved.
Incidentally, when a sliding bearing is used under high surface pressure, the shaft deflects by a few microns, with the result that the localized surface pressure of the bearing becomes so high that seizure is liable to occur at such portions. The life of a sliding is therefore limited from the aspect of surface pressure. In the most general kelmet bearing (thickness of lining=0.2 mm, Ni barrier=2 &mgr;m, Pb-based overlay=20 &mgr;m) the life of such kelmet is a million km under surface pressure of 7 MPa. Surface pressure of 70 MPa corresponds to an engine with 4000-8000 cc of displacement, equipped with a turbo-charger.
It is expected that the sliding-bearing alloys proposed in the above-mentioned publications (1) and (2) exceed the surface pressure mentioned above. However, the above mentioned publications (1) and (2) give no consideration as to which overlay is optimum for a sliding bearing used under high surface pressure. The present inventors tested, therefore, various overlays and carried out research for the purpose of providing a sliding bearing for an internal combustion engine capable of being used under higher load than heretofore.
DISCLOSURE OF INVENTION
The sliding bearing of an internal combustion engine according to the present invention is characterized in that: a copper alloy contains from 0.1 to 2% by weight of Ag and from 1 to 10% by weight of Sn as the essential elements, the balance essentially consisting of Cu, is bonded to a backing metal, and has on its side opposite to the backing metal a roughened surface of approximately 0.5 to approximately 10 &mgr;m of roughness (Rz); the roughened surface is coated with at least one thermo-setting resin, which is selected from the group consisting of polyimide resin, polyamide-imide resin, epoxy resin and phenol resin, and which contains from 55 to 95% by weight of MoS
2
; Ag and Sn are solid-dissolved in the Cu matrix of the copper alloy in at least the vicinity of the sliding surface where essentially no secondary phase of these elements is formed; and, a concentrated layer of said Ag and Sn, a hexagonal compound of these Ag and Sn with one another, a hexagonal compound of Cu and these elements, or a eutectic of Ag and Sn or Cu and these elements, is formed as a sub-layer of at least a portion of the sliding layer, which portion is brought into direct contact with an opposing shaft.
In addition, according to an embodiment of the sliding bearing, there is provided a sliding bearing for an internal combustion engine: wherein its copper alloy contains 10% by weight or less of at least one additive element selected from the group consisting of Ab, In, Al, Mg and Cd; the essential elements and the additive elements are solid-dissolved in the Cu matrix of the copper alloy in at least the vicinity of the sliding surface where essentially no secondary phase of these elements is formed; and, a concentrated layer of said essential and additive elements, a hexagonal compound of these elements with one another, a hexagonal compound of Cu and these elements, or a eutectic of said essential elements and additive elements or Cu and these elements, is formed as a sub-layer of at least a portion of the sliding layer, which portion is brought into direct contact with an opposing shaft.
The present invention is described hereinafter in detail.
First, the copper alloy used in the present invention is explained. This copper alloy is based on the publications (1) and (2) by the present applicant mentioned above. Specifically, the following points are utilized. The particular additive elements, which are solid-dissolved in the Cu matrix, move to the lining surface, while friction heat generates and the structure of the lining surface changes. The particular additive elements then locally form a concentrated layer. A hexagonal compound or a eutectic composition, which is formed as the concentration progresses to some extent, has excellent solid-lubrication effect and excellent sliding performance under high surface pressure.
In basic experiments the seizure resistance of various compounds was investigated. The results are hereinafter explained.
A metal sheet or an alloy sheet, the composition of which is shown in Table 1, was cast or rolled and heat-treated to form a hexagonal compound shown in the equilibrium phase-diagram. However, the heat treatment was not carried out for No. 3 having a eutectic composition. The sheet was then worked in the form of a specimen (1 cm
2
of the surface area, 1.0-1.5 &mgr;m of roughness Rz). The specimens were subjected to a test of seizure resistance under the following conditions.
Tester: a pin-on disc tester shown in
FIG. 2
Sliding Speed: 15 m/s
Load: Gradual increase of load (step mode), 500N/10 min
Kind of oil: 10 w-30
Temperature of oil: room temperature
Opposed material: hardened S55C (Hv 550-650),
roughness—0.5-0.8 &mgr;m Rz
In FIG.
2
:
5
—oil-feeding pad;
6
—hydraulic cylinder;
7
—a test piece;
8
—disc;
9
—balance weight; and
10
—a load cell.
The results are shown in Table 1.
TABLE 1
Seizure
Composition (wt %)
Load
Material
No.
Cu
Au
Sn
Others
(kg/mm
2
)
Structure
1
—
72
28
—
860
h-Ag
3
Sn(&egr;)
2
—
85
15
—
840
h-Ag—Sn(&zgr;)
3
—
3
97
—
900
Ag—Sn eutectic
4
—
25
—
Cd = 75
800
h-Ag—Cd(&egr;)
5
—
73
—
In = 27
880
h-Ag
3
In(&zgr;′)
6
—
60
—
Mg = 40
800
h-Mg
3
Ag(&egr;)
7
—
73
—
Sb = 27
820
h-Ag
3
Sb(&egr;)
8
—
85
—
Sb = 15
840
h-Ag—Sb(&zgr;)
9
—
87
—
Al = 13
900
h-Ag—Al(&zgr;)
10
1
—
99
—
760
h-Cu—Sn eutectic
11
15
—
—
Cd = 85
800
h-Cd
3
Cu(&egr;)
12
52
—
—
Cd = 48
780
h-CdCu
2
13
67
—
—
Sb = 33
800
h-Cu
4.5
Sb(&egr;)
14
—
—
95
Cd = 5
820
h-Cd—Sn(&bgr;)
15
—
—
79
In = 21
880
h-InSn
4
(&ggr;)
16
100
—
—
—
400
Kamiya Soji
Kanayama Hiroshi
Kawakami Shinya
Tomikawa Takashi
Armstrong Kratz Quintos Hanson & Brooks, LLP
La Villa Michael
Taiho Kogyo Co. Ltd.
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