JP2015200339A - Slide member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve foreign object embedding performance of an overlay layer.SOLUTION: A slide member 1 includes: a lining layer 12; and an overlay layer 13 formed on the lining layer 12. The overlay layer 13 includes: a binder resin 131; graphite particles 132 dispersed in the binder resin 131; and soft metal particles 133 which are dispersed in the binder resin 131 and have an average particle diameter of 1 to 5 μm.

Description

  The present invention relates to a sliding member.

  In a plain bearing used for an automobile engine or the like, a technique of providing a resin overlay layer on a bearing alloy (lining layer) is known in order to improve initial conformability, seizure resistance, and wear resistance. The resin overlay layer includes a binder resin and a solid lubricant.

  The characteristics required for the sliding bearing are not only initial conformability, seizure resistance, and wear resistance, but also various other characteristics, one of which is foreign substance embeddability. A technique for improving the foreign substance burying property in the overlay layer is known (for example, Patent Documents 1 and 2). Patent document 1 is disclosing the coating layer which has a resin area | region and a soft metal area | region. Patent Document 2 discloses a coating layer in which a bulk soft material having an average particle size of 10 μm or more is mixed in a base resin.

JP 2007-239866 A JP 2007-239867 A

Patent Documents 1 and 2 both relate to a technique for improving the foreign matter burying property of a coating layer using mainly MoS ₂ and PTFE as a solid lubricant.

  On the other hand, the present invention provides a technique for improving the foreign matter burying property of the overlay layer.

  The present invention has a lining layer and an overlay layer formed on the lining layer, and the overlay layer is dispersed in a binder resin and the binder resin, and has an average particle size of 1 to 5 μm. Provided is a plain bearing having a soft metal.

  The soft metal may be Sn, Al, or Bi.

  The amount of the soft metal added may be 30 to 70% by volume.

  According to the present invention, the foreign substance burying property of the overlay layer can be improved.

The figure which shows the structure of the sliding member 1 which concerns on one Embodiment. FIG. 2 is a schematic view illustrating a cross-sectional structure of a sliding member 1.

1. Configuration FIG. 1 is a diagram illustrating a structure of a sliding member 1 according to an embodiment. The sliding member 1 is used as, for example, a sliding bearing between a crankshaft and a connecting rod of an internal combustion engine or a crankshaft and an engine block. In this example, the sliding member 1 is a half bearing, and when the two sliding members 1 are joined, a cylindrical bearing is obtained.

  The sliding member 1 has a backing metal 11, a lining (bearing alloy) layer 12, and an overlay layer 13. The backing metal 11 is a layer for reinforcing the mechanical strength of the lining layer 12. The back metal 11 is made of, for example, steel. The lining layer 12 is provided along the sliding surface of the bearing (the surface in contact with the shaft) and has characteristics as a bearing, for example, friction characteristics, seizure resistance, wear resistance, conformability, foreign matter embedment (foreign matter). This is a layer for imparting characteristics such as robustness and corrosion resistance. The lining layer 12 is made of a bearing alloy. In order to prevent adhesion with the shaft, the bearing alloy avoids becoming a so-called “toggle” with the shaft, and a material system different from the shaft is used. In this example, an aluminum alloy is used as a bearing alloy because it is used as a shaft bearing made of steel. In addition to an aluminum alloy, an alloy based on a metal other than aluminum, such as a copper alloy, may be used.

In the case of using an aluminum alloy, the composition is not particularly limited, but 10% by mass or less of Cr, Si, Mn, Sb, Sr, Fe, Ni, Mo, Ti, W, Zr, V, Cu, Mg, and Zn You may contain 1 or more types of elements and 1 or more types of elements among Sn, Pb, In, Tl, and Bi of 20 mass% or less. The former group of elements mainly imparts strength and wear resistance, and the latter group of elements mainly imparts conformability, and the bearing characteristics are adjusted by the type and amount of each additive element.

  When using a copper alloy, the composition is not particularly limited, but at least one of Pb and Bi of 25% by mass or less, Sn of 10% by mass or less, P, Ag, In, Ni of 2% by mass or less , Al or the like may be contained.

  Among these elements, soft metals such as Pb and Bi give conformability. Sn provides strength and wear resistance. Other components supplementarily improve the properties. In particular, P is effective for deoxygenation, promotion of sintering, strengthening and the like. Ag forms a compound effective for improving the sliding characteristics by reaction with the impurity component S in the lubricating oil or copper. In improves corrosion resistance and lubricating oil stagnation. Ni and Al strengthen copper.

  The overlay layer 13 is a layer for improving the characteristics of the lining layer 12 such as the coefficient of friction, conformability, corrosion resistance, and foreign material embedding property (foreign material robustness). The overlay layer 13 includes a binder resin, a solid lubricant, and a soft metal. The overlay layer 13 preferably contains 30 to 70% by volume of a solid lubricant.

  As the binder resin, for example, a known resin such as a thermosetting resin or a thermoplastic resin can be used. Specifically, the binder resin is at least one of a polyamide-imide (PAI) resin, a polyimide (PI) resin, a polyamide resin, a phenol resin, a polyacetal resin, a polyether catalyst ketone resin, a polyphenylene sulfide resin, and an epoxy resin. Including. Among these, PAI resin is preferable from the viewpoint of adhesive strength.

  The content of the binder resin in the overlay layer 13 is determined according to the amount of other additives, but is preferably 30 to 70% by volume, and more preferably 40 to 65% by volume.

  A solid lubricant is added to improve the friction characteristics. In this example, the solid lubricant includes at least graphite. Graphite improves wettability and initial conformability. The initial conformability is a property that improves the slidability when the sliding surface wears and becomes smooth when slidably contacting with the counterpart material after the start of sliding. When the slidability is improved by the expression of the initial conformability, the wear amount of the entire sliding layer is reduced.

  Graphite is a substance having a layered crystal structure in which the (002) planes are laminated, and has a property that the layers easily slip. This property reduces the coefficient of friction when the cleaved surface of graphite is oriented in the sliding direction. Therefore, the friction coefficient can be reduced by using graphite as the solid lubricant. From the viewpoint of reducing the starting torque, it is preferable that the degree of graphitization of graphite used as the solid lubricant is higher. For example, the degree of graphitization is preferably 90% or more.

  Graphite has a feature of high affinity with engine oil. Lubricating oil exists between the bearing and the mating shaft, and a film (oil film) is formed. There is a concern that oil leaks as the number of engine start-stops increases and the frequency of contact between the sliding member and the mating shaft increases. Since graphite has high affinity with engine oil, the contact angle between the overlay layer and engine oil is small. Therefore, the retention of engine oil is enhanced, leakage can be prevented, and sustainability is improved.

The solid lubricant may contain at least one of MoS ₂ , WS ₂ , polytetrafluoroethylene (PTFE), h-BN, and SB ₂ O ₃ in addition to or instead of graphite. For example, MoS ₂ gives good lubricity. Further, PTFE has an effect of reducing the friction coefficient because of its low intermolecular cohesion.

  A soft metal is added in order to improve foreign material burying property. The soft metal includes, for example, at least one of Sn, Al, and Bi. The content of the soft metal in the overlay layer 13 is preferably 30 to 70% by volume.

  FIG. 2 is a schematic view illustrating the cross-sectional structure of the sliding member 1. FIG. 2 shows an AA cross-sectional view of FIG. The thickness of the back metal 11 is, for example, 1.0 to 3.0 mm. The thickness of the lining layer 12 is, for example, 0.1 to 0.5 mm. The thickness of the overlay layer is, for example, 1 to 20 μm, and preferably 2 to 10 μm.

  The overlay layer 13 includes a binder resin 131, graphite particles 132, and soft metal particles 133. The graphite particles 132 and the soft metal particles 133 are dispersed in the binder resin 131.

The smaller the particle size, the smaller the surface roughness of the graphite particles 132, and the easier it is to form an oil film. That is, a low starting torque can be obtained. From this viewpoint, the average particle diameter of the graphite particles 132 is preferably 3 μm or less, and more preferably 2 μm or less. Here, the average particle size of the graphite particles 132, the median size d ₅₀ of the circle equivalent diameter is used. The average particle diameter is measured by a known method.

The soft metal particles 133 have a higher foreign substance burying property as the particle size is smaller. That is, seizure hardly occurs. From this viewpoint, the average particle diameter of the soft metal particles 133 is preferably 5 μm or less. Here, the average particle size of the soft metal particles 133, the median size d ₅₀ of the circle equivalent diameter is used. The average particle diameter is measured by a known method.

  The sliding member 1 is not limited to the slide bearing illustrated in FIG. For example, the present invention may be applied to piston skirts and compressor swash plates.

2. Manufacturing method The manufacturing method of the bearing which concerns on one Embodiment includes the process shown below.
(A) A step of preparing an overlay precursor containing a solid lubricant (graphite), a soft metal, and a binder resin (b) A step of molding a bearing base material (c) An overlay precursor is applied on the bearing base material Step (d) Step of drying the overlay precursor (e) Step of firing the overlay precursor

  In the preparation of the overlay precursor in the step (a), the method for mixing the solid lubricant, the soft metal, and the binder resin is not particularly limited, and a known method can be used. For example, the overlay precursor is adjusted by placing graphite and a binder resin in a kneader and mixing them under conditions of a shear rate of 0.1 to 2 m / s.

  In preparing the overlay precursor, the binder resin may be incompatible, but is preferably at least partially compatible from the viewpoint of practical use. The compatibility may be mechanically blended with high shear.

  In the step (b), the backing metal and the bearing alloy layer are pressed, for example, to form a bearing base material. Further, the bearing base is processed into a predetermined shape, for example, a cylindrical shape or a semicylindrical shape.

  In applying the overlay precursor (paint) on the bearing substrate in the step (c), it is preferable to use a diluent for uniform dispersion of the solid lubricant and the binder resin. Although it does not restrict | limit especially as a diluent, For example, N-methylpyrrolidone (NMP) is used. Moreover, the mixture ratio of a diluent is 30-70 volume% with respect to solid content, for example.

  When coating and depositing the overlay precursor on the bearing alloy layer, known methods such as pad printing, screen printing, air spray, airless spray, electrostatic coating, tumbling, squeeze method, roll method are used. It is done. Further, as common to all film forming methods, when the film thickness is insufficient, the overcoating may be performed a plurality of times instead of increasing the concentration of the overlay layer in the diluent.

  In step (d), the diluent is removed by drying the overlay precursor. Conditions such as drying time and drying temperature are not particularly limited as long as the diluent is dried. For example, drying is preferably performed at 50 to 150 ° C. for 5 minutes to 30 hours in the air. The drying time is more preferably 5 to 30 minutes.

  By firing in the step (e), a bearing having an overlay layer formed can be obtained. Specifically, for example, the bearing substrate after the step (d) is gradually heated to a firing temperature at a heating rate of 5 to 15 ° C./min, and is 150 to 300 ° C. and 0.2 to 1 in the atmosphere. Bake for 5 hours.

3. Examples Test pieces of sliding members were prepared under various conditions, and these test pieces were evaluated. As an evaluation item, seizure surface pressure was used.

3-1. Test piece preparation A 1.2 mm steel plate (SPCC (JIS)) is used as the back metal, and a 0.3 mm thick aluminum alloy (Al-89.5% Sn-7.0% si) is used as the lining layer (bearing alloy). -2.0% cu-1.O% cr-0.5%) was used. The bimetal which joined these was made into the base material.

  On the surface of the lining layer, an overlay precursor paint having an adjusted composition was applied by a roll method. During the application, NMP was used as a diluent. The ratio of overlay precursor to diluent was 50:50 (weight ratio). After application, it was dried at 100 ° C. for 15 minutes or 900 minutes. Then, it heated up to 180 degreeC with the temperature increase rate of 10 degree-C / min, and baked in air | atmosphere for 1 hour. Thus, a sliding member was produced. Note that the thickness of the overlay layer was 6 μm.

  The particle size of the soft metal was measured by particle size distribution measurement. Specifically, the particle size distribution measuring device LA-950V2 manufactured by HORIBA, Ltd. was used, and measurement was performed under wet conditions using water as a dispersion medium and an ultrasonic time of 5 minutes.

3-2. Seizure test A seizure test per piece was performed under the following conditions. In the seizure test, the surface pressure applied to each slide bearing was increased by 4.3 MPa every 3 minutes, and the surface pressure that resulted in seizure was measured as the seizure surface pressure. The seizure surface pressure was measured when no foreign matter was intentionally introduced and when the foreign matter was intentionally introduced. As the foreign matter, five pieces of iron having a particle diameter of 0.1 mm were used.

(Test conditions)
Test machine: Static load seizure test machine Sliding speed (rotational speed of the mating shaft): 20 m / sec (8000 rpm)
Bearing dimensions: φ48mm x axial length (w) 15.5mm
Bearing surface pressure: Gradually increasing load (4.3 MPa / 3 min)
Mating shaft material: S55C (quenched)
Axial roughness: 0.5 μm as surface roughness Rz
Lubricating oil type: 5W-30SM
Lubrication temperature: 80 ° C (continuous circulation)

3-3. Experimental result

  The test pieces (Examples 1 to 6) having an average particle diameter of soft metal particles of 1 to 5 μm are compared with test pieces (Comparative Examples 2 to 4) having an average particle diameter of soft metal particles of 6 μm or more. The seizure surface pressure at the time was high, and the seizure resistance was improved.

In addition, when compared with a test piece using MoS ₂ instead of a soft metal as an additive (Comparative Example 1), the test pieces using soft metal particles (Examples 1 to 6) have a seizure surface pressure at the time of introducing foreign matter. And seizure resistance was improved.

DESCRIPTION OF SYMBOLS 1 ... Sliding member, 11 ... Back metal, 12 ... Lining layer, 13 ... Overlay layer, 131 ... Binder resin, 132 ... Graphite particle, 133 ... Soft metal particle

Claims (3)

A lining layer,
An overlay layer formed on the lining layer,
The overlay layer is
A binder resin,
A sliding member having a soft metal dispersed in the binder resin and having an average particle diameter of 1 to 5 μm. The sliding member according to claim 1, wherein the soft metal is Sn, Al, or Bi. The sliding member according to claim 1 or 2, wherein the addition amount of the soft metal is 30 to 70% by volume.

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