JP4468781B2 - Copper alloy plain bearing - Google Patents

Description

  The present invention relates to a copper alloy-based slide bearing, and more particularly to a slide bearing with a Bi-based overlay, and more particularly to a slide bearing used for a main bearing, a connecting rod bearing, etc. of an internal combustion engine. . JIS KJ3, KJ4, SAE48, SAE49, etc. are used for the copper alloys of these plain bearings. Moreover, in order to improve the conformability, these copper alloys are overlaid with a soft metal such as Pb and Sn.

Pb-free Cu alloy-based sliding material containing 0.1 to 5% Ag and 0.001 to 1% S as essential components proposed by Patent Document 1 (Japanese Patent Laid-Open No. 7-150273) is in direct contact with the mating shaft. An Ag-S concentrated layer is formed on the surface to be coated, and this concentrated layer improves seizure resistance. As a method of using this sliding material, a so-called overlay bearing having a resin coating is also mentioned (paragraph number 0019).
In the bearing with the resin overlay of Patent Document 1, when the resin overlay is worn out and the Cu—Sn—Ag alloy is exposed, Ag contained in the Cu—Sn—Ag alloy reacts with S in the oil to cause a bearing alloy. Ag ₂ S with excellent sliding properties is formed on the outermost surface. On the other hand, when the resin overlay layer remains, Ag ₂ S having excellent sliding characteristics is not generated.

  In Patent Document 2 (Japanese Patent Laid-Open No. 7-166182), an Ag-S concentrated layer is formed on the surface of a cooling compressor bearing material in which pores of a sintered Cu alloy containing 0.1 to 5% Ag are impregnated with a resin. As a method for forming an Ag-S concentrated layer, methods such as impregnating pores with S-containing solid lubricant and adding S compound to pore-impregnated oil are proposed. ing.

Conventionally, Pb alloy system was mainly used as overlay, but Pb is an environmental pollutant although Pb is excellent in compatibility. Yes.
Patent Document 3 (Japanese Patent Laid-Open No. 11-50296) discloses a Bi-based alloy in which Sn, In, and / or Ag is added to an overlay deposited on the surface of a semi-circular Cu-Sn alloy layer via a Ni intermediate layer. Propose to improve sliding performance.

  Patent Document 4 (Japanese Patent Laid-Open No. 11-257355) describes a Bi-based alloy containing Sn, In and / or Ag as an overlay deposited on the surface of a semi-circular Cu-Sn alloy layer via a Ni intermediate layer. Propose to do.

Patent Document 5 (Japanese Patent Application Laid-Open No. 2003-156045) discloses a Bi-phase precipitate particle density of 50 to 300 / μm ² in order to reduce the brittle nature of Bi and enable Bi to be used for the overlay. Propose to do.
Patent Document 6 (Japanese Patent Application Laid-Open No. 2003-156046) proposes adding hard materials such as Si ₃ N ₄ and Al ₂ O ₃ to a Bi-based overlay to improve wear resistance.
JP-A-7-150273 JP-A-7-166182 Japanese Patent Laid-Open No. 11-50296 JP-A-11-257355 Japanese Patent Laid-Open No. 2003-156045 Japanese Patent Laid-Open No. 2003-156046

In general, the conformability is considered to be related to the hardness of the material. By the way, indentation hardness expressed in kg / mm ² , Bi reaches several times Pb, and Cu indentation hardness is one digit higher than Bi and Pb. It can be explained that the reason why the compatibility of the Bi-based overlay is inferior to that of the Pb-based overlay corresponds to the difference in the hardness characteristics.
The achievements of the additive element proposed in Patent Document 4, the adjustment of the plating precipitation density proposed in Patent Document 5, and the addition of hard materials proposed in Patent Document 6 are compared with the conventional Pb-based overlay. Not done. Therefore, considering the above-mentioned level of the prior art, it can be said that there is a great need for development to make the compatibility of the Bi-type overlay equal to or higher than that of the Pb-type overlay.

The Ag-S concentration layer and Ag ₂ S proposed in Patent Documents 1 and ₂ impart compatibility and seizure resistance to the Cu alloy, but use with Bi or Bi alloy that has better compatibility than the Cu alloy Does not mention or consider.

The inventors of the present invention have been diligently researching and developing the Bi-based overlay, and found that the surface layer in which Bi and Ag ₂ S coexist realizes the performance of the conventional Pb-based overlay, thereby completing the present invention.

According to the present invention, in a slide bearing in which a Bi-based overlay is attached to the sliding surface side of a lining made of a copper-based bearing alloy, the Bi-based overlay is a Bi-Ag system, and at least a surface that contacts a mating shaft is 1 The present invention provides a plain bearing characterized in that Ag ₂ S of not less than mass% is precipitated. The present invention will be described below.

Either Bi or Ag ₂ S alone is less than the performance of Pb overlay, but the reason why the result of exceeding the performance of Pb overlay can be considered as follows.
Bi, which is the main component of the overlay, is worn by the surface irregularities of the mating shaft at the initial stage of sliding, and conforms to the mating shaft, so that a lubricating oil film is easily formed on the sliding surface. However, the conforming surface is inferior to the Pb-based overlay, and Ag ₂ S has no conforming action, so the ratio of the bearing surface in solid contact with the mating shaft is higher than the proportion of the Pb-based overlay in contact with the mating shaft. Become. A part of the bearing surface where Ag ₂ S and Bi coexist is in direct contact with the mating shaft, but the contact ratio of Ag ₂ S increases as the Bi surface is worn by the mating shaft. Therefore, when the familiar surface is formed to some extent, the excellent sliding characteristics of Ag ₂ S suppress the occurrence of seizure.
Subsequently, the thickness, composition, preparation method and the like of the overlay of the present invention will be described.

The Bi-based overlay is a Bi—Ag binary system, and the content of Ag including those existing as Ag ₂ S is preferably 0.1 to 10% by mass. Bi-Ag binary overlays are proposed by adding a less than 10% by mass of In and Sn proposed in Patent Document ₄ , and Si ₃ N ₄ and Al ₂ O ₃ proposed in Patent Document 6. A hard particle such as 0.05 to 25% by volume may be added.
Note that Ag ₂ S precipitated in the overlay of the present invention is low-temperature type (β-type, monoclinic) silver sulfide.

FIG. 1 shows a longitudinal section of a plain bearing, wherein 1 is a back metal plate such as SPCC, 2 is a bearing alloy layer (so-called lining) such as Cu—Sn alloy, 2 ′ is a Ni intermediate plating layer, 3 is An overlay (sometimes referred to as a “break-in layer”), both of which are known. As the overlay 3, a Bi-based overlay having a thickness in the range of 5 to 12 μm is used.
Generally, it is said that the initial wear amount of the overlay is about 1 to 2 μm. Therefore, it is sufficient that the above Ag ₂ S is generated in a region extending from the surface of the overlay to this thickness range (hereinafter referred to as “surface layer portion”), and as a result, in the deep portion, Bi-Ag binary system, pure Bi, etc. Various compositions may be employed, and a lining may be provided immediately below the surface layer portion.
S added to the Bi-Ag binary composition described above combines with Ag and precipitates as Ag ₂ S.

Silver sulfide (Ag ₂ S) is produced when hydrogen sulfide gas is passed through a silver nitrate solution. Since Ag ₂ S produced in this way is soluble in a normal Bi plating solution, Ag ₂ S-dispersed Bi plating is not practical. Therefore, the present inventors have intensively studied a method for forming Ag ₂ S on the surface layer of Bi-based overlay without sulfiding Bi. As a result, the Ag in the Bi-Ag overlay is overlaid by heat treatment in oil containing S, such as ZnDTP, which is a sulfur additive, or in gas containing S, such as SO ₃ and SO _2. It was found that Ag ₂ S can be precipitated by diffusing to the outermost surface. The heat treatment temperature is preferably 120 ° C. to 180 ° C., and the heat treatment time is preferably 30 min to 120 min.
Even if Ag ₂ S deposited on the surface of the overlay wears out, Ag in the Bi overlay reacts with S in the oil due to the thermal load during sliding, and Ag ₂ S with excellent sliding characteristics is formed on the outermost surface of the overlay. Precipitate.

As a method for preparing a Bi-Ag overlay (ie, an overlay before Ag ₂ S precipitation), there are the following methods:
(a) Bi-Ag alloy plating.
(b) After Bi plating, Ag flash plating is applied and Ag is diffused in the overlay by heat treatment.
(c) Bi is plated on Cu-Sn-Ag alloy (lining). Ag is diffused from the base material into the overlay by heat treatment.
(d) Bi is plated through an intermediate Ag plating layer. Ag is diffused from the intermediate layer into the overlay by heat treatment.

As conditions for Bi- (Ag) plating, for example, the following are preferable.
a) Methanesulfonic acid: 50-250ml / l
Methanesulfonic acid Bi: 50-250ml / l
Methanesulfonic acid Ag: 10-100ml / l
β-naphthol: 0.5-50g / l
Bath temperature: 25 ° C
Current density: 0.5-5A / dm ²

b) Methanesulfonic acid: 50-120ml / l
Methanesulfonic acid Bi: 50-250ml / l
(Methanesulfonic acid Ag: 10-100 ml / l)
Polyoxyethylene nonylphenyl ether: 0.5-50g / l
Bath temperature: 25 ° C
Current density: 0.5-5A / dm ²

c) Sulfuric acid: 50-120ml / l
Nitric acid Bi: 5-30g / l
(Nitrate Ag: 5-50ml / l)
Polyoxyethylene nonylphenyl ether: 0.5-50g / l
Bath temperature: 25 ° C
Current density: 0.5-5A / dm ²

Subsequently, the Ag concentration of the overlay obtained by the various production methods (a) to (d) described in paragraph 0015 is as follows.
Production method (a): Uniform in the thickness direction of the surface layer (hereinafter referred to as “structure A”).
Production method (b): high Ag concentration on the surface side and low Ag concentration on the substrate side (hereinafter referred to as “structure b”).
Production method (c), (d): low Ag concentration on the surface side and high Ag concentration on the substrate side (hereinafter referred to as “structure c”).
Structure A can also be made by diffusing Ag into Bi over a sufficient period of time during the heat treatment in production method (b). Structures B and C can also be made by controlling the current density during the plating process (a).
Regarding structure C, even if Ag in the surface layer of the Bi overlay is depleted, Ag is supplied to the surface layer sequentially from the Cu-Sn-Ag alloy or intermediate Ag plating layer by the thermal load during sliding, and the top surface of the overlay Stably forms Ag ₂ S.

Example A copper alloy bearing having a thickness of 0.2 mm shown in Table 1 was pressure-welded to a back metal plate (thickness: 1.3 mm, SPCC). Copper alloy bearing (lining) was Cu-Sn (Cu: 94.5%, Sn: 5%); Cu-Sn-Ag (Cu: 0.4%, Sn: 5%, Ag: 1%)) . Furthermore, an intermediate layer was formed by Ag and Ni plating for some materials. The bimetallic material thus prepared was subjected to overlay plating in the step shown in FIG. 2 to deposit an overlay having a thickness of 8 μm.
For Bi plating, the metasulfonic acid bath described in Paragraph 0016 was used.
The heat treatment was performed in oil.
As comparative examples, Pb overlay (Pb-Sn-Cu) and resin overlay (PAI + MoS ₂ ) were used.

The methods for preparing the overlays of Nos. 1 to 8 in Table 1 were as follows.
No. 1 to 4: The heat treatment of FIG. 2 was performed in a lubricating oil at 150 ° C. for 60 minutes.
No. 5 to 8: The heat treatment in FIG. 2 was not performed.
No. 5: Ag was not added to the Bi overlay.

The following tests were conducted on the slide bearing samples prepared as described above.
Seizure resistance testing machine <br/> Testing machine: Static load seizure testing machine Sliding speed: 2.86m / sec. (1300rpm)
Bearing dimensions: φ42mm x w17mm
Bearing surface pressure: Load gradually increasing shaft material: S55C (quenched)
Lubricating oil type: 5W-30 SL
Lubrication temperature: 140 ℃

Test per piece <br/> Testing machine: Reciprocating load testing machine Sliding speed: 6.6m / sec. (3000rpm)
Bearing dimensions: φ42mm x w17mm
Bearing surface pressure: Load gradually increasing shaft material: S55C (quenched)
Lubricating oil type: 10W-30 CF4,
Lubrication temperature: 140 ℃

  Table 2 shows the result of EPMA analysis of the bearing surface before and after the seizure test. In addition, the analysis after a test analyzed places other than the structure | tissue flow part by baking.

In the seizure resistance test, when the seizure occurred, the base lining was not exposed when the surface pressure was 80 MPa or less, and the base lining was exposed when the surface pressure was 80 MPa or more.
As shown in FIGS. 2 and 3, in the present embodiment (Nos. 1 to 4), the seizure surface pressure and seizure load are higher than those of the conventional Pb overlay (No. 7) and resin overlay (No. 8). It is high.
In addition, before and after the seizure test, those having 1.0% by mass or more of Ag ₂ S on the surface layer tended to have a high seizure load.

  As described above, the overlay developed by the present invention can be replaced with a conventional Pb overlay in terms of sliding performance.

It is sectional drawing of the example of a sliding bearing. It is process drawing which shows an overlay plating process. It is a graph which shows the result of a printing test. It is a graph which shows the result of a one-piece test.

Explanation of symbols

1 Back metal plate 2 Bearing alloy layer 2 'Ni intermediate plating layer 3 Overlay

Claims (5)

In a slide bearing in which a Bi-based overlay is deposited on the sliding surface side of a lining made of a copper-based bearing alloy, the Bi-based overlay is a Bi-Ag system, and at least 1% by mass of Ag is formed on the surface in contact with the mating shaft. ₂ Copper alloy plain bearing characterized by the precipitation of S. 2. The copper alloy plain bearing according to claim 1, wherein the Bi-based overlay contains 0.1 to 10% by mass of Ag. 3. The copper alloy slide bearing according to claim 2, wherein the Ag concentration is substantially uniform in the thickness direction in the Bi overlay. The copper alloy slide bearing according to claim 2, wherein the Ag concentration is relatively low in the thickness direction in the Bi-based overlay and on the side near the lining. 3. The copper alloy plain bearing according to claim 2, wherein an Ag concentration is relatively high in a lining vicinity side in a thickness direction in the Bi-based overlay.

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