JP2000290742A - Bearing device composed of cast iron shaft and aluminum bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the wear and seizure in a bearing device hard to occur by controlling the average grain diameter of Is grains in the contact and sliding face between a cast iron shaft and a bearing to the one higher than the specified magnification of the average thickness of a ferritic phase surrounding the spheroidal graphite grains of spheroidal graphite cast iron. SOLUTION: In the bearing device composed of a spheroidal graphite cast iron shaft having a bull's eye structure and an Al-Sn-Si aluminum alloy sliding bearing, in which Si grains of 5 to 40 μm grain diameter are present by >= 5 pieces per 3.56×10-2 mm2 in the aluminum alloy, the average grain size of the Si grains is made higher than the average thickness of the ferritic phase by >0.5 times. The structure of the aluminum alloy is controlled in such a manner that a ferritic phase 7 is formed around the spheroidal graphite 6, and the average grain diameter D of the Si grains 5 is made higher than the average thickness of the ferritic phase 7 by > 0.5 times. In the case of D=0.5, there is a boundary between the occurance of an attack on a mating bearing alloy by burrs 10 and the separation of the burrs 10 from the cast iron. A lapping action occurs in the initial stage of the using of the bearing, and, after that, lubricating oil sufficiently forms an oil film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing device including a cast iron shaft such as a connecting rod bearing and a main bearing of an internal combustion engine and an aluminum bearing. FIG. 1 is an assembly view of an engine crankshaft, a connecting rod, and a sliding bearing. In the sliding bearing, a pair of half-circle-shaped so-called metal members 1a and 1b are fixed to a large end of a connecting rod 3 by two bolts 2. It becomes. The inner surfaces of the metals 1a and 1b constitute sliding surfaces made of a sliding bearing alloy, and hold the crankshaft 4 rotatably.

[0002] Spheroidal graphite cast iron such as FCD700 is frequently used for the shaft of the bearing device, that is, the crankshaft 4. The aluminum alloy bearing of German Patent DE 3249133 C2 proposed by the present applicant as a bearing for such a spheroidal graphite cast iron shaft contains 0.5% to 11% of Si and has 3.56 × 10 Si particles having a particle size of 5 to 40 μm. -2mm
There are five or more particles per 2 and coarse Si particles lap the surface of the cast iron shaft to improve the bearing performance. Since the Si particles have a directionality extending in the rolling direction, the particle size varies depending on the measurement direction, but the particle size is measured in a large diameter, that is, in the rolling direction.

In recent years, as the capacity of an internal combustion engine has increased, the diameter of a cast iron shaft has also increased, and as a result, the solidification speed of cast iron has been decreasing. As a result, the structure becomes a so-called blue eye structure, a ferrite phase surrounding the periphery of the spherical graphite particles is generated, and the thickness thereof is also increased. 2 and 3 show the metal structure (magnification: 500 times) of such a cast iron shaft, and it can be seen that the thickness of the ferrite phase is 3 to 15 μm. Incidentally, the surface of the cast iron shaft generally has a roughness Rz of 0.5 to 1 μm.
m, but at the time of surface finishing, the ferrite peels off from the graphite particles and rises, and the height is 0.4 mm.
Edge burrs of about 0.5 μm are obtained. This burr is
It protrudes from the oil film interposed between the sliding contact surface of the cast iron shaft and the bearing and attacks the mating bearing alloy, causing wear and seizure.

[0004]

As described above, the lapping action of the conventional coarse-grained Si-aluminum alloy is not sufficient for the cast iron shaft on which burrs are generated as described above. That is, the conventional coarse-grained Si had a sufficient effect of wrapping cast iron having a pearlite + spheroidal graphite structure. Depending on the coarse-grained Si, it does not become sufficiently small, so that wear and seizure of the bearing device are likely to occur. Accordingly, it is an object of the present invention to reduce wear and seizure of a bearing device including a spheroidal graphite cast iron shaft having a blue-eye structure and an aluminum bearing.

[0005]

SUMMARY OF THE INVENTION The present invention provides a spheroidal graphite cast iron shaft having a blue-eye structure and an Al-Sn-Si based aluminum alloy plain bearing, wherein the aluminum alloy has Si particles having a particle size of 5 to 40 µm. 3.56 × 1
In a bearing device having 5 or more per 0-2 mm2,
The cast iron shaft and the aluminum bearing, wherein the average particle size of the Si particles on the sliding contact surface between the cast iron shaft and the bearing is larger than 0.5 times the average thickness of the ferrite phase surrounding the spherical graphite particles of the spheroidal graphite cast iron. It is intended to provide a bearing device comprising: Hereinafter, the present invention will be described in detail.

In the apparatus of the present invention, a shaft and a bearing made of a so-called half-split metal are well known, and are exemplified in FIG. These dimensions and structures are not particularly limited in the present invention. Spheroidal graphite cast iron having a blue-eye structure is also known, for example, C2.5% or more, Si
2.7% or less, Mn 0.4% or less, P 0.02% or less,
Contains 0.09% or less of Mg. For the bearing, an aluminum alloy containing Si generating coarse Si and containing Sn generating an Sn phase having excellent lubricity is used. A
l-Sn-Si aluminum alloy is 3 to 3% by weight.
It is preferable that the composition contains 5% Sn and 1 to 10% Si. Further, Cu, M as optional elements
g, Mn, etc., which form an intermetallic compound and precipitate harden 3% or less in total, and elements such as Zr, Cr, V, etc. which mainly precipitate and harden in metallic form, 2% or less, Pb , In, and Bi can be contained in a total amount of 10% or less of elements that form a soft phase and contribute to improvement in conformability.

FIGS. 2 and 3 show an example of a spherical cast iron structure having a blue-eye structure. FIG. 2 shows three coarse particles, in which ferrite (white) is formed around graphite particles on the surface of the cast iron. The edge formed on the polished surface becomes a burr. In FIG. 3, ferrite (white) is locally formed around two graphite particles present on the surface of the cast iron, and the polished edge of the surface becomes a burr. In the present invention, the average particle diameter (D) of Si particles at the sliding contact surface between the cast iron shaft and the bearing is larger than 0.5 times the average thickness (t) of the ferrite phase surrounding the spherical graphite particles of the spheroidal graphite cast iron ( The structure of the aluminum alloy is controlled so that D> 0.5t). That is, since the average thickness (t) of the ferrite phase having the blue-eye structure tends to necessarily increase as the diameter of the cast iron shaft increases, this must be given. Specifically, in the present cast iron shaft of an internal combustion engine, the average thickness of the ferrite phase is 5 μm or more and less than 100 μm, and is generally less than 5 to 15 μm. On the other hand, since the average particle diameter (D) of the Si particles of the aluminum alloy can be controlled relatively easily, the Si particles are coarsened so as to satisfy the relationship of D> 0.5t. If this relationship is satisfied, the ferrite burrs can be sufficiently removed by the Si particles on the sliding surface of the bearing device. More preferably, D> 0.7t. When the shape of the Si particles has directionality, a long particle size is measured.

In the present invention, in order to make the Si particles coarse so as to satisfy the relationship of D> 0.5t, basically, the production steps and conditions shown in the above-mentioned German Patent Publication, page 11, are used. In addition, the cooling rate especially after annealing is set to 100 ° C. /
It is preferable to perform super slow cooling for less than a time.

[0009]

The sliding contact surface of the bearing device shown in FIG.
Denotes Si particles, 6 denotes spherical graphite, and 7 denotes a ferrite phase.
D = 0.5t is a boundary between whether the burr 10 attacks the mating bearing alloy or whether the burr 10 is cut off from the cast iron. As for hardness (H), ferrite (Hf) has Hv ≒ 100 to 150, and Si particles (Hsi) have about Hv1000. The lapping action according to the present invention occurs in the early stage of use of the bearing, and thereafter, the lubricating oil sufficiently forms an oil film on the sliding contact surface, so that abrasion and seizing hardly occur. Hereinafter, the method of the present invention will be described in more detail with reference to examples.

[0010]

EXAMPLE Samples having various ferrite phase thicknesses were collected from a commercially available blue-eyed spheroidal graphite cast iron shaft, and the surface was wrapped to a roughness of Rz 0.8 μm. On the other hand, Sn
An Al alloy containing 2% and the following amount of Si was manufactured into a rolled plate by the method described in the above-mentioned German Patent, page 11. However, the cooling rate after annealing was set to less than 50 ° C./hour. The surface of the rolled plate was wrapped to have a roughness of Rz1 μm. Si content and S
The average size (μm) of the i-particle was as follows. Si (wt%) Si particle average size (μm) 2.8 2.5 2.8 3.5 3.5 5.2 5.2 3.5 7.3

The abrasion test was performed on the cast iron test material and the Al alloy rolled plate test material prepared as described above under the following conditions. Testing machine: Bush journal tester Load: 2.3 MPa (50 kgf) Shaft rotation: GO-STOP / 0-1000 rpm 5000
0 cycle lubrication: engine oil 10W30, 100 ° C Mating shaft: FCD700 equivalent (Hv280, 0.4 ~ 0.
6 μm Rz) Bearing dimensions: φ22 × 10 mm The test results are shown in the following table.

[0012]

As can be seen from Table 1, when D / t> 0.5, the amount of wear decreases.

The test for seizure resistance was performed under the following conditions. Table 2 shows the results. Testing machine: Journal type baking test machine Number of revolutions: 1300 rpm Lubricating oil: Engine oil SAE5W-30, 140 ° C Mating shaft: FCD700 equivalent (Hv280) Shaft surface roughness: 0.4 to 0.6 μm RZ Shaft diameter: 42 mm Load: Temporary Increase system 10MPa / 30min

[0015]

As can be seen from Table 1, when D / t> 0.5, seizure resistance is improved.

[0017]

As described above, according to the present invention, the structure of an aluminum-based sliding bearing alloy that slides on a spheroidal graphite cast iron shaft having a blue-eye structure is controlled in relation to the ferrite thickness of the blue-eye structure. Thereby, abrasion resistance and seizure resistance can be improved. Therefore,
The present invention can greatly contribute to improving the performance of an internal combustion engine having a large displacement.

[Brief description of the drawings]

FIG. 1 is a drawing showing an example of a bearing device.

FIG. 2 is a micrograph (magnification: 500 times) showing the metal structure of spheroidal graphite cast iron having a blue-eye structure.

FIG. 3 is a photograph similar to FIG.

FIG. 4 is a conceptual view of a bearing device sliding contact surface.

[Description of Signs] 1-Bearing 2-Bolt 3-Connecting Rod 4-Crankshaft 5-Si Particle 6-Spheroidal Graphite 7-Ferrite Phase 10-Burr

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C22C 9/10 C22C 9/10

Claims (3)

[Claims] 1. A spheroidal graphite cast iron shaft having a blue-eye structure,
An Al-Sn-Si-based aluminum alloy plain bearing, wherein the aluminum alloy has 5 or more Si particles having a particle size of 5 to 40 m per 3.56 x 10-2 mm2; Wherein the average particle size of the Si particles on the sliding contact surface is larger than 0.5 times the average thickness of the ferrite phase surrounding the spheroidal graphite particles of the spheroidal graphite cast iron, wherein the bearing device comprises a cast iron shaft and an aluminum bearing. . 2. The Al—Sn—Si based aluminum alloy contains 3 to 35% of Sn and 1 to 10% of Si by weight%.
A bearing device comprising the cast iron shaft according to claim 1 and an aluminum bearing. 3. The bearing device according to claim 1, wherein the average thickness of the ferrite phase is 5 μm or more and less than 100 μm.