JP3195118B2 - Plain bearing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding bearing used for a journal portion of a crankshaft and a large end portion of a connecting rod in an internal combustion engine. In particular, the present invention relates to a bearing alloy layer such as a kelmet or aluminum bearing alloy, commonly referred to as a lining, an intermediate layer such as Ni plating, and a Pb-Sn-In-Cu alloy surface layer (commonly referred to as an "overlay"). The present invention relates to a technique for improving the seizure resistance and fatigue resistance of a plain bearing comprising the above-mentioned method by specifying a boundary layer between an intermediate layer and an overlay.

[0002]

2. Description of the Related Art The present applicant has already filed an application for the following lead alloy for a sliding bearing. JP-B-60-41695: An alloy containing 5 to 20% of tin, 0.05 to 10% of indium, and 0.05 to 5% of copper, with the balance being lead and unavoidable compound lead. Prior to this application, Pb alloys for ternary overlays mainly lacked wear resistance. Therefore, the addition of copper or the like as a quaternary component improves wear resistance and enhances the overall performance of the overlay. It is declared in the gazette.

Japanese Patent Publication No. 3-72692: Lead containing 2 to 20% of tin, more than 10% to 15% of indium, and 0.05 to 5% of copper, with the balance being lead and unavoidable impurities. alloy. This alloy has a higher indium content than that of the alloy, thereby reducing the wetting angle of the lubricating oil on the overlay surface, simultaneously improving wear resistance and conformability, and enhancing the overall performance of the overlay.

JP-B-2-39572: 2 to 20% of tin, 0.05 to 15% of indium,
An alloy containing 0.01 to less than 0.05% of copper, the balance being lead and unavoidable impurities. This alloy has a P
The gazette states that by making the copper content smaller than that of the alloy b, the plating structure is made denser, the wear resistance is improved, and the overall performance of the overlay is increased. As can be seen from the above prior arts, the conventional overlay has been improved from the aspect of composition.

As an improvement from a viewpoint different from the above viewpoint, an attempt to improve the performance of a plain bearing focusing on the metal structure of a boundary layer between a Ni barrier and a Pb-Sn-In ternary overlay has been made in Japanese Patent Application Laid-Open No. HEI 9-163191. In Japanese Patent Application Laid-Open No. 4-168295, it is proposed that the boundary layer be made of a Sn-In solid solution containing 52% or more of Sn.

[0006]

In recent years, in some high-speed running automobiles, seizure of slide bearings has occurred, and it has been pointed out that the performance of the bearings is insufficient. Observation of the bearing where trouble occurred showed that melting occurred due to local temperature rise in the overlay where seizure occurred, and that peeling of the overlay occurred in the fused part.

Conventionally, it has been assumed that the temperature of the lubricating oil is about 140 ° C. (publication, column 8, line 27) or about 120 ° C. (publication, column 7, line 39). Since this temperature is much lower than the melting point of Pb alloy,
It was not expected that the overlay would melt. On the other hand, in a bearing seized in a high-speed running vehicle, the melting structure is clearly different from the plating structure (a particle dispersion structure in which Pb, Sn, In, Cu, etc. are hardly distinguished-traces of thermal diffusion are also partially observed). -A coagulated structure (a structure in which Sn or the like is dispersed in a Pb matrix) was observed. In the prior art, the solid solution structure of the boundary layer is formed on the surface layer (overlay).
The evaluation of the organization has been made from the viewpoint of good adhesiveness with the tissue.

The inventor has proposed that Pb in a laboratory and a test vehicle be used.
When the performance of a sliding bearing provided with a quaternary overlay of -Sn-In-Cu was examined, the bearing was subjected to a thermal load, and Sn, In, and Cu in the overlay diffused to the Ni overlay interface to form a compound layer. Various compounds are present in the
It was found that when the proportion of InSn ₄ was large, the melting point at the interface of the overlay was lowered, and the low-melting-point phase was melted out by the heat generated during sliding, leading to melting and peeling to seizure.

Therefore, the present invention is to reduce the amount of InSn ₄ compound generated by reducing the amount of Pb-Sn-In-Cu
An object of the present invention is to improve the seizure resistance of a slide bearing provided with a quaternary overlay.

[0010]

The sliding bearing material of the present invention that achieves the above object has a lining and a Ni bearing.
A plain bearing comprising a Pb-Sn-In-Cu alloy surface layer, wherein the Ni-based intermediate layer and the P
a thickness of 0.1 to 5 μm between the b-Sn—In—Cu alloy layer and 30 to 70% by weight of Cu ₆ Sn ₅ , 1
A boundary layer containing 0 wt% or less (including 0) of In ₃ Ni ₂ and a balance of Ni ₃ Sn ₂ identified by X-ray diffraction is formed.

The configuration of the present invention will be described below. In the present invention, Cu ₆ Sn ₅ is an intermetallic compound known as a γ or γ ′ phase in a Cu—Sn phase diagram, and its amount is 30%.
If it is less than 3, Sn not identified as the compound becomes In
An Sn ₄ compound is formed and its amount becomes extremely large. That is, a part of Sn is in a metal state, and the remaining Sn is combined with In to form a Sn-In intermetallic compound. At that time, a large amount of the latter compound is formed. Therefore, Cu ₆ S
it is necessary to make the amount of n ₅ more than a predetermined amount. Meanwhile C
If u ₆ Sn ₅ exceeds 70% by weight, significant Sn in the overlay will diffuse towards the Ni barrier,
Sn in the overlay is depleted and its performance, especially corrosion resistance, is degraded.

When In ₃ Sn ₂ exceeds 10%, In—S
The tendency to form InSn _4, known as the γ phase in the n-system phase diagram, also increases. It is known from the state diagram that InSn ₄ forms a eutectic having an extremely low melting point with the In solid solution. Since the amount of In solid solution in the Pb-based overlay is large,
The formation of n solid solution hardly occurs on the phase diagram, but in the plating structure, In can be sufficiently present in the form of metal. Therefore, in the boundary layer, In is enriched by diffusion to form In solid solution, and InSn is formed. There is a risk of forming a eutectic having a low melting point with ₄ . Therefore, in the present invention, the melting phenomenon is prevented from occurring by regulating the amount of InSn ₄ .

In addition to the above compounds, an overlay alloy or metal, an alloy of Ni and a solid solution, In ₃ Sn
₂ and Ni ₃ Sn ₂ are mixed in the boundary layer.

On the other hand, if the thickness of the boundary layer exceeds 5 μm, fatigue separation easily occurs in the boundary layer, and the fatigue resistance is reduced. When the thickness of the boundary layer is 0.1 μm or less, there is substantially no difference from the state of the boundary layer immediately after plating, and the added element in the overlay, ie, I
n and Sn diffuse into the Ni barrier and are enriched at the Ni barrier interface. This is not preferable because InSn4 is very easily generated.

The preferred composition of the Pb-based overlay alloy used in the present invention will be described below. Tin is familiar,
It is an element that enhances corrosion resistance, fatigue resistance, wear resistance, and the like. If the tin content is less than 2%, these effects are not obtained.
On the other hand, when the tin content is 10% or more, tin diffuses into the Ni plating layer applied as a boundary layer on the surface of kelmet or the like, so that the Ni-Sn compound is easily formed. When the compound layer is thick, the overlay is apt to peel off.

Further, when the content of tin is 10% or more, the melting point of the Pb alloy is lowered, the melting is liable to occur, and seizure under high-speed operation is liable to occur. Here, the melting point of the Pb alloy or the overlay is not the melting point of the ingot but the melting point of the overlay alloy formed by plating. The preferred amount of tin is 3 to 8%.

In the prior art, it has been described that if the content of tin is less than 5%, there is no effect of improving the corrosion resistance. However, with respect to the Pb alloy in this low tin composition range, the properties such as seizure resistance are not described and the examples are not described. Nor. In fact, when the alloy of the present invention (namely, a comparative alloy having less than 5% tin in the conventional alloy) is tested at a low rotation speed, poor corrosion resistance is observed, and superiority such as seizure resistance is not observed. From this, it can be said that the melting of the overlay, which does not occur at low speed rotation, occurs at high speed operation, and it is necessary to limit the tin amount to less than 5% as a countermeasure.

Indium is an element that improves conformability and corrosion resistance. When the amount of indium is less than 0.05%, these effects are not obtained. On the other hand, when the amount of indium exceeds 10%, the melting point of the overlay is lowered, and the above-mentioned undesirable phenomenon occurs. Therefore, in the present invention, the content of indium needs to be 0.05 to 10%, preferably 0.5 to 8%, more preferably 7 to 8%.

Copper is an element that improves fatigue resistance and corrosion resistance. If the amount of copper is less than 0.1%, these effects are not obtained.
On the other hand, if the content of copper exceeds 5%, the overlay becomes hard, the conformability is reduced, and the seizure is reduced. Therefore, in the present invention, the content of copper is preferably 0.1 to 5%, more preferably 0.3 to 3%, and particularly preferably 0.5 to 1.5%.

The method of manufacturing the overlay alloy according to the present invention is basically performed by quaternary plating on the lining in the same manner as described in the prior art. Preferably, a known lead borofluoride 150 to 200 g / l,
Tin borofluoride 5 to 15 g / l, copper borofluoride 1 to 3 g
/ L, gelatin about 2g / l, hydroquinone about 2g / l
Pb-Sn-Cu ternary alloy plating can be obtained by performing plating by adjusting the plating time using the above plating bath. Similarly, indium plating is performed using a known flash plating or alkali cyanide bath.
-Diffusion between Sn-Cu ternary alloy plating layers. The overlay plating thickness is preferably 3 to 25 μm.

Thereafter, a heat treatment is further performed under such a condition that the Cu6 Sn5 compound is preferentially formed. For this purpose, the holding temperature is 150 to 200 ° C., and the rate of temperature rise to the holding temperature is 1
0 to 100 ° C./min, cooling rate from the holding temperature is 1 to 10
It is necessary to perform a heat treatment at 0 ° C./min. A more preferred cooling rate is 10 to 50 ° C / min. The lead alloy for a sliding bearing of the present invention has both good seizure resistance and fatigue resistance under high-speed rotation and running conditions. High-speed running or high-speed rotation in the present invention means a rotation speed of 6000 rpm or more or a peripheral speed of 16 m / s or more. Hereinafter, the present invention will be described in more detail with reference to Examples.

[0022]

EXAMPLES Overlays having the compositions and thicknesses shown in Table 1 were plated on kelmets having a Ni plating of 1 to 3 .mu.m under the following plating bath compositions and conditions. However, sample N
o. Numeral 12 is an example of plating on an aluminum alloy. Pb-Sn-Cu plating composition and conditions _{Pb (BF 4) 2: 50~200} g / l Sn (BF 4) 2: 5~30 g / l Cu (BF 4) 2: 0.1~10 g / l HBF _4: 50~200 g / l H. Q. : 0.1 to 10 g / l Peptone: 0.1 to 10 g / l Gelatin: 0.1 to 10 g / l Current density: 1 to 10 A / dm ² Bath temperature: 20 to 30 ° C In plating bath composition and Conditions Sulfamic acid In: 100 to 200 g / l Na sulfamate: 100 to 200 g / l Sulfamic acid: 10 to 50 g / l NaCl: 20 to 80 g / l Glucose: 5 to 11 g / l Triethanolamine: 1.5-3.5 g / l Current density: 1-2 A / dm ² Bath temperature: 25-35 ° C

The seizure test conditions of the sliding bearing are as follows. Seizure test machine: Multi-area tester Rotation speed: 2400 rpm (20 m / s) Load load: 10 kg / cm ² / sec

The fatigue test conditions are as follows. Fatigue test machine: 3-axis rotating load test machine Rotation speed: 8000 rpm Load: 300 kg / cm ² / sec Oil temperature: 150 ° C. Oil type: 7.5 W-30 SE

Table 1 shows the peeling temperature (seizure resistance) and the number of repetitions (fatigue resistance) of each sample.

[0026]

[Table 1]

* In the table, the term "number of repetitions" means the number of repetitions when the fatigue area reaches 10% of the bearing area. In addition,
The amounts of Cu ₆ Sn ₅ and In ₃ Ni ₂ were quantified by etching the bearing surface to expose the boundary layer and analyzing by X-ray diffraction.

Table 2 shows components and diffusion temperatures of the samples in Table 1 before the heat treatment.

[0029]

Table 2 Overlay component (wt%) Heat treatment conditions Pb Sn In Cu 1 bal 782 No heat treatment (In diffusion annealing only) 2 ７ 782 200 ° C. × 20 min 3 ↑ 782 200 ° C. × 1 h 4 １０ 10 75 200 ° C × 2h 5 ↑ 12 885 200 ° C × 2h 6 ６612 3 200 ° C × 1h 7 ↑ 752 200 ° C × 1h8 ９955 200 ° C × 30min 9 ↑ 8-3 200 ° C × 1h 10 @ 7 8 2 200 ° C x 2h

FIG. 1 shows the X-ray diffraction peak profile of Sample 3 after the heat treatment. FIG. 2 shows the peak profile of the X-ray diffraction image of Sample 3 before the heat treatment. According to these figures, Cu ₆ Sn ₅
And In ₃ Ni ₂ are formed, and particularly, the formation amount of the Cu ₆ Sn ₅ compound is increased. In addition, FIG.
No Sn ₄ peak was observed, indicating that InSn ₄ was not formed. The overlay component of Sample 3 after the heat treatment was Sn 6.8%, In 7.5%, Cu
1.0%.

From the above test results, it is clear that the sample of the present invention exhibits excellent performance in both the peeling temperature (seizure resistance) and the number of repetitions (fatigue resistance).

[0032]

As described above, according to the present invention, by specifying the structure of the boundary phase between the overlay and the intermediate layer, the melting phenomenon under high-speed running can be prevented.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction profile of heat-treated sample 3.

FIG. 2 is an X-ray diffraction profile of Sample 3 before heat treatment.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C25D 7/10 F16C 33/12

Claims (1)

(57) [Claims] 1. A lining, a Ni-based intermediate layer, and Pb-
In a sliding bearing including a Sn-In-Cu alloy surface layer, the Ni-based intermediate layer and the Pb-Sn-In-
X-ray diffraction having a thickness of 0.1 to 5 μm and containing 30 to 70% by weight of Cu ₆ Sn ₅ and 10% by weight or less (including 0) of In ₃ Ni ₂ between the layer and the Cu alloy layer A sliding bearing characterized in that a boundary layer in which the balance identified by ( ₃₎ is Ni ₃ Sn ₂ is formed.