JP3195113B2 - 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 provides 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 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 sliding bearing by specifying a boundary layer between an intermediate layer and an overlay.

[0002]

2. Description of the Related Art An attempt to improve the performance of a sliding bearing from the same viewpoint as described above has been made by paying attention to the metal structure of a boundary layer between a Ni barrier and a Pb-Sn-In ternary overlay.
In this case, it is proposed that the boundary layer be made of a Sn-In solid solution containing 52% or more of Sn. In the present invention, it is described that the solid solution structure of the boundary layer has good adhesion to the surface layer (overlay).

[0003]

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, the temperature of lubricating oil is 120-140 °
It is assumed to be about C, and since this temperature is much lower than the melting point of the 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, a melt-solidification distinct from a plating structure (a particle dispersion structure in which Pb, Sn, In, etc. are hardly distinguished-traces of thermal diffusion are also partially observed). Organization (Pb
(A structure in which Sn or the like is dispersed in the matrix).

The present inventor has proposed that Pb in a laboratory and a test vehicle be used.
When the performance of a sliding bearing provided with a -Sn-In ternary overlay was examined, the bearing was subjected to a thermal load, and Sn and In in the overlay diffused to the Ni plating layer interface, and various compounds were formed in the compound layer. Compound exists, among which InS
It was found that when the ratio of n4 was large, the melting point of the overlay interface was lowered, and the low melting point phase was melted out due to the heat generated during sliding, leading to melting and peeling to seizure.

Accordingly, the present invention aims to improve the seizure resistance of the sliding bearing which has been subjected to Pb-Sn-In ternary overlay by reducing the formation of InSn ₄ compound.

[0007]

The first aspect of the sliding bearing of the present invention that achieves the above objects is to provide a lining and an N bearing.
In a plain bearing including an i-based intermediate layer and a Pb-Sn-In alloy surface layer, a Ni-based intermediate layer and a Pb-Sn-
The thickness is 0.1 to 5 μm between the In alloy layer and
The composition is 20 to 73% by weight of In, 8% or less of Sn (including 0), and the balance is substantially Ni.
A sliding bearing is characterized in that a boundary layer made of an i-In-based intermetallic compound is formed.
In a plain bearing including an alloy surface layer, the thickness between the Ni-based intermediate layer and the Pb-Sn-In alloy layer is 0.1
-5 μm and the composition is 10% by weight or less of In (including 0), 20-74% by weight of Sn, and the balance is substantially Ni.
And a boundary layer mainly formed of a Ni—Sn-based intermetallic compound.

Hereinafter, the configuration of the present invention will be described. In the present invention, the boundary layer is a layer that exists between the overlay and an intermediate layer such as a Ni barrier, is identified by an optical microscope, and is made of an intermetallic compound. In the present invention, the composition of the boundary layer is determined as described above because, in this range, the low melting point compound InSn ₄ is not formed or the amount thereof is very small.

A first aspect of the present invention is a plain bearing having a high In content in the boundary layer, and this boundary layer is formed when the In content in the overlay is high. Here, when the In content of the boundary layer is less than 20% by weight, the relative amount of Sn in the compound layer increases, and InSn ₄ is easily formed. On the other hand, when the In content of the boundary layer exceeds 73% by weight, pure In which does not form a compound is generated, and the possibility that an InSn ₄ compound is generated increases. Next, Sn in the boundary layer
If the amount is zero, the InSn ₄ compound is not generated, so the amount of Sn in the boundary layer may be zero. On the other hand, S
If the n content exceeds 8%, the possibility of forming an InSn ₄ compound increases.

When the thickness of the boundary layer exceeds 5 μm,
Fatigue peeling is likely to occur in the boundary layer, and 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. In this case, InSn ₄ is very easily generated, which is not preferable.

A second aspect of the present invention is a plain bearing having a high Sn content in the boundary layer. This boundary layer is formed when the Sn content in the overlay is high. Here, when the Sn content of the boundary layer is less than 20% by weight, the relative I
The amount of n increases, and InSn ₄ is easily formed. On the other hand, when the Sn content of the boundary layer exceeds 74% by weight, pure Sn that does not form a compound is generated, and InSn ₄ is easily formed. Next, if the amount of In in the boundary layer is zero, no InSn ₄ compound is generated, so that
The amount of n may be zero. On the other hand, the In content is 10%
If it exceeds 300, there is a high possibility that an InSn ₄ compound will be produced.

In the present invention, the boundary layer is made of Ni ₃ Ni, NiIn,
_{Ni 2 In 3, Ni 3 Sn} , composed of intermetallic compounds such as _{Ni 3 Sn 2, Ni 3 Sn} 4. When Ni ₂ In ₃ exceeds 10%, In—Sn
The tendency to form InSn _4, known as the γ phase in the system 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. However, by limiting the composition of the boundary layer as described above, the generation of a large amount of this InSn ₄ compound can be avoided.

[0013] Further, since the amount of In solid solution in the Pb-based overlay is large, the formation of an In precipitation phase can hardly occur on the phase diagram, but it is sufficiently possible that In exists in the metal form in the plating structure. Therefore, in the boundary layer, there is a possibility that In is enriched by diffusion and an In precipitation phase is formed to form a eutectic having a low melting point with InSn4. Therefore, in the present invention, In
The composition of the boundary layer was determined as described above so that the melting phenomenon due to Sn4 did not occur.

[0014]

The preferred composition of the Pb-based overlay alloy used in the present invention will be described below. Sn is an element that improves the conformability, corrosion resistance, fatigue resistance, wear resistance, and the like of the overlay. When the Sn content is less than 2%, these effects are not obtained. On the other hand, when Sn becomes 10% or more, Sn diffuses into the Ni plating layer deposited 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 Sn content is 10% or more, the melting point of the Pb alloy is lowered, the melting is likely to occur, and seizure under high-speed operation is likely 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 produced by plating. The preferred amount of Sn is 3 to 8%.

In is an element that improves the conformability and corrosion resistance of the overlay. When the amount of In is less than 0.05%, these effects are not obtained. On the other hand, when the amount of In exceeds 10%, the melting point of the overlay is lowered, and the above-mentioned undesired phenomenon occurs. Therefore, in the present invention, the content of In is 0.0
It needs to be 5 to 10%, preferably 0.5 to 10%.
-8%, more preferably 7-8%.

In the present invention, in order to separately form the first and second boundary layers, Sn and In in the overlay are used.
The amount and the temperature and time of the heat treatment may be controlled.

In the method for producing the overlay alloy according to the present invention, the overlay alloy is prepared by ternary plating on the lining. Preferably, plating is performed by adjusting the plating time using a known plating bath of 150 to 200 g / l of lead borofluoride, 5 to 15 g / l of Sn borofluoride, about 2 g / l of gelatin, and about 2 g / l of hydroquinone. And Pb-Sn ternary alloy plating can be obtained. Similarly, In plating is performed by a known flash plating or alkali cyanide bath, and finally, diffusion between the In layer and the Pb—Sn binary alloy plating layer is performed. The overlay plating thickness is preferably 3 to 25 μm.

Thereafter, a heat treatment is further performed under such a condition that Ni-Sn or Ni-In based intermetallic compound is preferentially formed. For this purpose, it is necessary to perform the heat treatment at a holding temperature of 120 to 180 ° C., a rate of temperature rise to the holding temperature of 10 to 100 ° C./min, and a cooling rate from the holding temperature of 1 to 100 ° 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.
The high-speed running or high-speed rotation referred to in the present invention is 60 rpm.
It means 00 rpm or more or peripheral speed 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 Ni plating of 1 to 3 .mu.m according to the following plating bath compositions and conditions. However, sample N
o. 3 is an example of plating on an aluminum alloy. Pb-Sn plating composition and conditions Pb (BF ₄ ) ₂ : 50 to 200 g / l Sn (BF ₄ ) ₂ : 5 to 30 g / l HBF ₄ : 50 to 200 g / l 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: 100-200 g / l Na sulfamate: 100-200 g / l Sulfamic acid: 10-50 g / l NaCl: 20-80 g / l Glucose: 5-11 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 Lubrication method: Pad lubrication

The rapid rise of the friction torque of each sample was judged to be seizure, and the overlay surface was observed by an electron microscope to confirm the occurrence of melt-peeling. Table 1 shows the results.

[0025]

[Table 1]

FIG. 1 shows the X-ray diffraction peak profile of Sample 13 after the heat treatment. Here, in addition to the peaks of Cu and Pb of Kelmet and the peak of Ni from the Ni barrier, the peaks appear from the boundary layer appearing first by the heat treatment. It is clear that most of this peak is Ni3Sn4 and InSn4 is not detected.

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).

[0028]

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 Sample 13.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-168295 (JP, A) JP-A-4-26731 (JP, A) JP-A-62-20915 (JP, A) (58) Investigation Field (Int.Cl. ⁷ , DB name) C25D 7/10 F16C 33/12

Claims (2)

(57) [Claims] 1. A lining, a Ni-based intermediate layer, and Pb-
In a plain bearing including a Sn—In alloy surface layer, a thickness between the Ni-based intermediate layer and the Pb—Sn—In alloy layer is 0.1 to 5 μm and a composition is In 2.
A plain bearing comprising 0 to 73% by weight, Sn 8% or less (including 0) and the balance substantially Ni, and further comprising a boundary layer mainly formed of a Ni-In intermetallic compound. 2. A lining, a Ni-based intermediate layer, and Pb-
In a sliding bearing material including a Sn—In alloy surface layer, a thickness between the Ni-based intermediate layer and the Pb—Sn—In alloy layer is 0.1 to 5 μm and a composition is I
n 10% by weight or less (including 0), Sn 20 to 74% by weight
And the balance is substantially Ni, and mainly Ni-
A sliding bearing, wherein a boundary layer made of a Sn-based intermetallic compound is formed.