JPH0159360B2 - - Google Patents

Description

[Detailed Description of the Invention] <Object of the Invention> Industrial Field of Application The present invention relates to plain bearings, and more specifically, to the rise in temperature of lubricating oil due to the increase in output of internal combustion engines in recent years, and the oxidation of lubricating oil at high temperatures. Therefore, the present invention relates to a plain bearing that exhibits sufficient performance under conditions such as an increase in the amount of organic acids generated.

BACKGROUND ART Bearing metals conventionally used in internal combustion engines have a half-shaped or cylindrical steel backing metal, and a multilayered copper-based or aluminum-based bearing alloy. These copper-lead bearing alloys, bronze bearing alloys, aluminum bearing alloys, etc. developed as bearings for high loads have excellent load-bearing properties, but they have other properties required for bearing alloys, such as seizure resistance and embedment resistance. There are problems with compatibility, etc., and in order to solve this problem, it is necessary to overlay a metal with embeddability and compatibility on the bearing alloy. For example, in conventional automobile bearings, a copper or aluminum alloy is adhered as an intermediate layer on a back metal by sintering, casting, pressure welding, etc.;
On top of that, an overlay layer with a thickness of 10 to 30 μm was applied.
Layer bearings are used. This overlay layer has the effect of improving the bearing's wear resistance, conformability, and foreign matter embedding ability. Conventionally, the composition of the overlay layer is Pb-Sn, Pb-Sn-Sb, Pb-Sn-Cu.
system, Pb-Sn-In system, etc. are known, and in particular, the US patent
85-90% lead, 8% tin as disclosed by No. 2605149
Pb-Sn-Cu based overlays with ~12% copper and 2-3% copper are most commonly used. The lead in this overlay improves the compatibility between the bearing and the journal and the embedding of foreign matter in the lubricating oil, and the tin improves corrosion resistance.
Copper plays a role in improving fatigue resistance.

However, in recent years, the output of internal combustion engines has increased,
As the temperature of the lubricating oil increases, the overlay tends to soften and wear resistance deteriorates, and high temperatures also promote oxidation of the lubricating oil, producing corrosive products such as organic acids. The problem of corroding overlays has created a need for the development of these improved overlays.

Problems to be Solved by the Invention The present invention aims to solve these problems, and specifically improves corrosion resistance and wear resistance by increasing the tin content of the conventional Pb-Sn-Cu overlay. The object of the present invention is to provide an overlay with improved fatigue resistance by adding antimony to the overlay.

<Structure of the Invention> Means for Solving the Problems and Their Effects The present invention provides a flat bearing for use in an internal combustion engine, in which the surface of the base body contains 15 to 30% tin and 1.0 to 5.0% copper, and the remainder is substantially It is characterized in that an overlay layer made of lead or an overlay layer further added with 0.1 to 5.0% antimony is formed.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIGS. 1a and 1b are a perspective view and a sectional view taken along arrow A-A, respectively, showing an example of the plain bearing of the present invention.

In FIG. 1, reference numeral 1 indicates a backing metal, 2 a copper or aluminum alloy layer, 3 a nickel plating layer, and 4 an overlay layer.

Tin in conventional overlays is in solid solution with lead;
Some exist as a matrix, and some exist as a copper-tin intermetallic compound in this matrix, and the remaining tin forms fine tin crystals and is scattered throughout the matrix. . During operation of the internal combustion engine, this copper-tin intermetallic compound combines with the fine tin crystals or tin dissolved in the matrix, and gradually transforms into a copper-tin intermetallic compound with a high tin content. . As a result, the amount of solid solution tin and interspersed tin in the matrix is reduced, reducing the corrosion and abrasion resistance of the overlay.

Furthermore, tin in the overlay that is present near the nickel plating layer forms an intermetallic compound with the nickel and gradually migrates into the nickel layer. In this case as well, as with the copper-tin intermetallic compound mentioned above, the tin content gradually shifts to a tin-nickel intermetallic compound with a higher tin content during operation of the internal combustion engine, so the tin content in the overlay near the nickel plating layer increases significantly. The wear resistance and corrosion resistance in this area are greatly reduced.

Based on the observation of the behavior of tin as described above, the present invention increases the tin content in the overlay to 15-30%,
Furthermore, by adding antimony in an amount of 0.1 to 5.0%, the above-mentioned problems of wear resistance and corrosion resistance are solved, and fatigue resistance is further improved.

Next, to explain the role and addition amount of each element in the overlay of the present invention, tin improves the corrosion resistance and wear resistance of lead. Below 15%, the amount of tin interspersed in the matrix is reduced for the reasons mentioned above, and the overlay corrosion and abrasion resistance is greatly reduced. Furthermore, if the tin content exceeds 30%, fatigue resistance and conformability will deteriorate. Therefore, the optimal tin content is 15-30%.

Furthermore, when antimony is added to a conventional overlay, it combines with the tin in the overlay, and as an intermetallic compound interspersed with fine crystals in the lead-tin matrix, this compound is hard and improves the wear resistance of the overlay. But its content is 0.1~5.0
% is optimal; anything higher than that will result in poor compatibility with the journal.

Further, copper is added to improve the fatigue resistance of the overlay, but the best performance is achieved when the content is about 1.0 to 5.0%, and fatigue resistance decreases outside this range.

Example This will be further explained below using examples.

Example 1 First, a bearing alloy is degreased and pickled in the same manner as in general electroplating, and then nickel plated to a thickness of 1.0 to 2.0 μm. In the case of a copper-based bearing alloy, the role of this nickel plating is to prevent tin in the overlay from diffusing into the intermediate layer of copper alloy during operation of an internal combustion engine, thereby preventing the corrosion resistance of the overlay from deteriorating. This nickel plating is electroplated using a plating bath having the following bath composition (A) and current density.

Bath composition (A) Lead borofluoride (as lead metal)
60-120g/ 〃 Tin (as metal tin)
15～30 〃 〃 Copper (as metallic copper)
1 to 4 〃 Borofluoride hydrogen acid 40 to 50 〃 Resorcinol 1.0 to 5.0 〃 Gelatin 0.1 to 0.5 〃 Current density 1.0 to 3.0 A/dm ² After plating, the plain bearing has 4 layers: backing metal, bearing alloy, nickel, and new overlay. The composition of the new overlay is as follows.

Lead 66-84% Tin 15-30〃 Copper 1-4〃 Example 2 After nickel plating the bearing alloy in the same manner as in Example 1, the Pb-Sn-Cu based overlay plating solution of Example 1 was applied. Electroplating is carried out using the following bath composition (B) containing antimony chloride and current density.

Bath composition (B) Lead borofluoride (as metallic lead)
60-120g/ 〃 Tin (as metal tin)
15～30 〃 〃 Copper (as metallic copper)
1 to 4 Antimony (as metallic antimony) 0.1 to 5.0 Borohydrofluoric acid 40 to 50 Resorcinol 1.0 to 5.0 Gelatin 0.1 to 0.5 Current density 1.0 to 3.0 A/dm ² The composition of the overlay after plating is It is as follows.

Lead 61-83.9% Tin 15-30% Copper 1.0-5.0% Antimony 0.1-5.0% As mentioned above, the antimony in this new overlay combines with tin to form a tin-antimony intermetallic compound, which increases the Maintains hardness and improves wear resistance. In order to improve the conformability and embeddability of this new overlay, these properties can be further improved by softening annealing at a temperature of 100 to 150°C for about 2 hours after plating.

As explained in detail above, in order to measure the corrosion resistance of the new overlay, SAE10 without inhibitor was used.
1% oleic acid was added as a corrosive to engine oil, and the test piece was immersed therein at 121°C for 50 hours to measure the corrosion loss. As a result, the corrosion resistance of the new overlay was approximately five times that of the conventional overlay.

Furthermore, to measure the wear resistance of the new overlay, an underwood test was conducted at a load of 560 kg/cm ² , a rotation speed of 3500 rpm, an overlay thickness of 0.020 mm, a bearing back temperature of 175°C, a lubricant of SAE20W-40, and a test time of 100 hours. The weight loss of the bearing before and after the test was measured. As a result, the weight reduction of the new overlay was approximately one fifth of that of the conventional overlay. This is clearly determined to be an effect of the addition of tin and antimony.

<Effects of the invention> As explained in detail above, by increasing the tin content of the conventional overlay and further adding antimony, corrosion resistance, wear resistance, and fatigue strength have been greatly improved, and Increased output of internal combustion engines,
A plain bearing equipped with a new overlay layer that can sufficiently cope with the rise in temperature of lubricating oil and the increase in organic acids generated by oxidation of lubricating oil at high temperatures was obtained.

With regard to fatigue resistance and overlay plating based on Pb-Sn-In components containing approximately 10% indium, which is the conventional overlay plating with fatigue resistance,
A comparison test was conducted with the product of the present invention using an underwood tester under the same conditions as the wear resistance test described above until fatigue failure occurred in the overlay, and the results showed that both products had a durability time of 140 to 160 hours. It was confirmed that the components of the present invention have fatigue resistance. This new overlay was produced using Pb−Sn−Cu−Sb in the same plating bath.
4-component alloy plating is possible, and unlike overlays containing indium, multiple plating baths are not required, saving labor in the plating process. Heat treatment after plating is also unnecessary. Furthermore, each alloying element is generally easily available and has many advantages, such as being inexpensive.

[Brief explanation of drawings]

FIGS. 1a and 1b are a perspective view and a cross-sectional view taken along arrow A-A, showing an example of the plain bearing of the present invention. Reference numeral 1: backing metal, 2: copper or aluminum alloy layer, 3: nickel plating layer, 4: overlay layer.

Claims (1)

[Claims] 1. An overlay layer containing 15 to 30% tin and 1.0 to 5.0% copper, with the remainder being substantially lead, is formed on the surface of the base of a flat bearing used in an internal combustion engine. A plain bearing featuring: 2 15-30% tin, 1.0-5.0% copper, and 0.1-0.1% antimony on the surface of the base of plain bearings used in internal combustion engines.
A flat bearing characterized by forming an overlay layer containing 5.0% lead with the remainder being substantially lead.