JPH0525686A - Sliding member - Google Patents

Abstract

PURPOSE:To provide a plain bearing provided with a surface layer excellent in seizing resistance. CONSTITUTION:A surface layer 4 is constituted of a Pb alloy, and its sliding face 4a is formed of plural pyramidal crystals 6 in which plural thin pieces having different area of flat faces (a) are laminated stepwise in such a manner that the area of the flat faces (a) is made smaller as it approaches to the opposing member. The concn. of the alloy elements in the peripheral area (d) of each flat face (a) is higher than that of the alloy elements in the inside area (d) of the flat face (a) excluding the peripheral area (c). In such a manner, the surface area of the sliding face 4a is expanded, by which the surface layer 4 has sufficient oil preserving properties, and furthermore, by preferentially wearing the side of the vertex (f) of the crystals 6, its initial fitness can be improved. Moreover, in accordance with the increase of the hardness of the peripheral area (c), the parts having high hardness are distributed in a dotted shape, the sliding properties similar to those in the case of strengthening dispersion can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding member, and more particularly to a sliding member having an alloy surface layer having a sliding surface with a mating member.

[0002]

2. Description of the Related Art Conventionally, as this type of sliding member, a slide bearing having the surface layer made of a Pb-Sn alloy has been known (see Japanese Patent Laid-Open No. 56-96088).

[0003]

This type of sliding bearing is
It is applied to the crank part of the crankshaft of the engine, the large end of the connecting rod, etc.However, under the current circumstances where the engine tends to be high speed and high output, the surface layer of the conventional slide bearing is made of the oil. There is a problem that retention property, that is, oil retaining property is not sufficient, initial conformability is poor, and seizure resistance is poor because hardness is relatively low.

In view of the above, the present invention specifies the structure of the surface layer so that the surface layer has sufficient oil retention,
Another object of the present invention is to provide the above-mentioned sliding member in which the initial conformability of the surface layer is improved and a high hardness portion is dispersed on the sliding surface, thereby improving the seizure resistance of the surface layer.

[0005]

SUMMARY OF THE INVENTION The present invention provides a sliding member having an alloy surface layer having a sliding surface with a mating member,
The surface layer is formed by stacking a plurality of thin pieces having different flat surface areas so as to form the sliding surface in a stepwise manner such that the flat surface area becomes smaller as the area is closer to the mating member. Of at least one of the pyramidal protrusions and the truncated pyramidal protrusions, and the alloy element concentration in the peripheral region of each flat surface is higher than the alloy element concentration in the inner region of the flat surface excluding the peripheral region. It is characterized by being

[0006]

1 and 2, a sliding bearing 1 as a sliding member is applied to a journal portion of a crankshaft in an engine, a large end portion of a connecting rod, and the like.
It consists of first and second halves 1 ₁ and 1 ₂ . Both halves 1 ₁ ,
1 and ₂ have the same structure and have a back metal 2, a lining layer 3 formed on the inner peripheral surface of the back metal 2, and a sliding surface 4a formed on the surface of the lining layer 3 with the mating member x. And a surface layer 4. A Cu plating layer is provided between the back metal 2 and the lining layer 3, and the lining layer 3 and the surface layer 4 are also provided.
A Ni-plated barrier layer is provided between them as required.

The back metal 2 is made of rolled steel plate, and its thickness is determined by the set thickness of the plain bearing 1. The lining layer 3 is made of Cu, a Cu-based alloy, Al, an Al-based alloy, or the like, and has a thickness of 50 to 500 μm, usually 300 μm.
It is about m. The surface layer 4 is composed of a Pb alloy and has a thickness of 5 to 50 μm, usually about 20 μm.

The Pb alloy forming the surface layer 4 is 80-9.
It contains 0% by weight of Pb and 3 to 20% by weight of Sn, and if necessary Cu, In, Ag, Tl, Nb, Sb, N.
10% by weight or less of at least one selected from i, Cd, Te, Bi, Mn, Ca and Ba.

Cu, Ni, and Mn have the function of improving the hardness of the surface layer 4, but if the content thereof exceeds 10% by weight, the hardness becomes too high and the initial conformability deteriorates.
When Cu or the like is added, the hardness Hmv of the surface layer 4 is 1
It is desirable to adjust the content so as to be 5 to 25.

In, Ag, Tl, Nb, Sb, Cd, T
e, Bi, Ca, and Ba have a function of softening the surface layer 4 to improve initial conformability, but when the content thereof exceeds 10% by weight, the strength of the surface layer 4 decreases. When In or the like is added, it is desirable to adjust the content so that the hardness Hmv of the surface layer 4 becomes 8 to 15.

The surface layer 4 is formed by an electroplating method, and the plating liquid is 40 to 1 per liter.
80 g Pb ²⁺ , 1.5-35 g Sn per liter
^2+, borofluoride based plating solution comprising the following Cu ²⁺ 15 g per liter, are used as occasion demands. The temperature of the plating solution is 10 to 35 ° C. and the cathode current density is 3 to 15 A / d.
m ² respectively.

FIG. 3 is an electron micrograph (× 10,000) showing the crystal structure of the Pb alloy on the sliding surface 4a. The surface layer 4 is made of a Pb alloy containing 8 wt% Sn and 2 wt% Cu. The surface layer 4 was formed on the Cu alloy lining layer 3, and the cathode current density in the electroplating process for forming the surface layer 4 was set to 6 A / dm ² .

As clearly shown in FIGS. 4 and 5, the surface layer 4
Is an aggregate of columnar crystals 5 of Pb alloy extending from the lining layer 3. A plurality of thin pieces b having different flat surface a areas are formed close to the mating member x in order to form the sliding surface 4a. It has a plurality of pyramidal protrusions, which are stacked in a stepwise manner so that the area of the flat surface a is as small as possible, in the illustrated example, a quadrangular pyramidal crystal 6. The quadrangular pyramidal crystals 6 form the tips of the columnar crystals 5.

The alloy element concentration (Cu, Sn concentration) in the peripheral region c of each flat surface a is higher than the alloy element concentration in the inner region d of the flat surface a excluding the peripheral region c.

With respect to the concentration distribution of such alloy elements, the current density in the peripheral region c becomes higher than that in the inner region d due to the end effect produced during the electroplating process, and Sn segregates in the peripheral region c. It seems to occur.

As a result, in the peripheral region c, the metal structure becomes denser, so that the hardness is increased, whereby good wear resistance of each thin piece b is obtained and the seizure resistance of the surface layer 4 is improved. .

FIG. 6 is an X-ray diffraction diagram of the Pb alloy crystal in the surface layer 4, and only the diffraction peaks of the (200) plane and the (400) plane are recognized by the Miller index.

Here, the orientation index Oe is used as an index representing the orientation of the crystal plane, (However, hkl is Miller index, Ihkl is (hkl)
The integrated intensity of the plane, ΣIhkl is the sum of Ihkl), and the closer the orientation index Oe is to 100% in the (hkl) plane, the more the crystal plane oriented in the direction orthogonal to the (hkl) plane. There will be many.

The (200) plane and (40) of the Pb alloy crystal
Table 1 shows the integrated intensity Ihkl and the orientation index Oe in the (0) plane.

[0020]

[Table 1] From Table 1, the orientation index Oe in the (h00) plane of the Pb alloy crystal is 100%, and therefore the Pb alloy crystal is
Crystal planes oriented in the respective axis directions of the crystal axes a, b, and c,
That is, it has a (h00) plane.

When the crystal plane is oriented in the direction orthogonal to the (h00) plane as described above, the crystal structure of the Pb alloy is a face-centered cubic structure, so that the atomic density in the orientation direction becomes high. The hardness of No. 4 is increased and its seizure resistance is improved.

FIG. 7 shows P on the sliding surface of the conventional surface layer.
It is an electron micrograph (10,000 times) which shows the crystal structure of b alloy. This surface layer consists of 8 wt% Sn and 2 wt% Cu.
The surface layer is made of a Pb alloy containing and is formed on a Cu alloy lining layer by electroplating, and is applied to a journal portion of an engine crankshaft.

FIG. 8 is an X-ray diffraction diagram of the Pb alloy crystal in the surface layer of the conventional example. Orientation to a specific crystal plane is not recognized from this figure. Table 2 shows the integrated intensity Ihkl and the orientation index Oe in various (hkl) planes.

[0024]

[Table 2] As is clear from FIGS. 7 and 8 and Table 2, the conventional example Pb
The crystal shape of the alloy is an indefinite shape in which the crystal planes are randomly oriented. Due to this, the hardness of the Pb alloy is (h0
It is lower than that of 0) plane-oriented Pb alloy.

Table 3 compares the composition, crystal structure, etc. of the surface layers of various slide bearings.

[0026]

[Table 3] The present invention (1) corresponds to the Pb alloy (FIG. 3) in the present invention. Comparative Example (1) corresponds to the Pb alloy (FIG. 7) in the conventional example, and its crystal shape is indefinite.

FIG. 9 shows the seizure test results of the present inventions (1) to (4) and comparative examples (1) and (2).

The seizure test was carried out by rubbing each sliding bearing on the rotary shaft and gradually increasing the load applied to the sliding bearing. FIG. 9 shows the surface pressure when seizure occurs on the surface layer of each plain bearing.

The test conditions are as follows. Rotating shaft material JIS S48C material with nitriding treatment, rotating shaft rotation speed 6000 rpm, lubrication temperature 120 ° C, lubrication pressure 3 kg / cm ² , load load 1 kg / sec.

As is apparent from FIG. 9, the present inventions (1) to (1) to
(4) has excellent seizure resistance as compared with Comparative Examples (1) and (2). The reason why such an effect is obtained is that the apex f side of the quadrangular pyramidal crystal 6 forming the sliding surface 4a can be preferentially worn to improve the initial conformability of the surface layer 4. And the surface area of the sliding surface 4a is a thin piece b
This is because the surface layer 4 is expanded by the quadrangular pyramidal crystals 6 that are stacked stepwise and has a sufficient oil retaining property. In addition to these, as the hardness of the peripheral region c increases, high hardness parts are distributed in a scattered manner on the sliding surface 4a, so that sliding characteristics similar to those in the case of dispersion strengthening are obtained. Can also be obtained
This is one of the reasons for improving the surface pressure at which seizure occurs.

In the quadrangular pyramidal crystal 6, when the preferential wear on the apex f side ends at the beginning of sliding and a flat surface a having a relatively large area appears, the flat surface a and the mating member are separated from each other. Since there is always an oil film on the surface, and the scattered resistance distribution of the high hardness portion by the peripheral region c provides the effect of improving wear resistance, the wear of the sliding surface 4a thereafter is extremely slow.

FIG. 10 shows a case where the sliding surface 4a is formed by a plurality of quadrangular truncated pyramid-shaped crystals (trapezoidal pyramidal protrusions) 8. In this case as well, sliding characteristics similar to the above can be obtained. FIG. 11 is a photomicrograph (10,000 times) showing the crystal structure of the Pb alloy on the sliding surface 4a. The same applies to the case where the quadrangular pyramidal crystals 6 and the quadrangular pyramid crystals 8 are mixed on the sliding surface 4a.

In these modifications, since at least a part of the sliding surface 4a is formed by the flat surface a having a relatively large area, an oil film is formed between the mating member and the flat surface a from the start of sliding. It is possible to improve the initial conformability and to stabilize the wear resistance by improving the wear resistance of the high hardness portion.

In FIG. 12, the tip end surface of each columnar crystal 5 is a flat surface a.
The surface layer 4 is formed on the sliding surface 4a.
Has a plurality of flat surfaces a.

According to this structure, as the hardness of the peripheral region c is increased, the high hardness portion is dispersed in the sliding surface 4a in a mesh shape, and the oil film forming effect is obtained in the same manner as described above. It is possible to obtain characteristics and improve seizure resistance.

The above-mentioned three types of columnar crystals 5 (FIG. 4, FIG. 10, FIG.
At least one of 2) forms a part of the sliding surface 4a, which is also included in the present invention. In this case, sliding surface 4a
The area ratio of at least one of the quadrangular-pyramidal crystal 6, the quadrangular-pyramidal-pyramidal crystal 8 and the flat surface a (FIG. 12) is set to 50% or more.

In order to obtain excellent sliding characteristics as described above, the quadrangular pyramidal crystal 6, the quadrangular pyramid pyramid crystal 8 and the flat surface a
The inclination of (FIG. 12) becomes a problem.

Therefore, as shown in FIGS. 4 and 13, on the bottom surface side of the quadrangular pyramidal crystal 6, the crystal 6 is projected to define an imaginary plane G along the sliding surface 4a. A straight line k passing through the apex f of the crystal 6 and the central portion h of the bottom surface forms an inclination angle θ with respect to a reference line m passing through the central portion h of the bottom surface and perpendicular to the virtual plane G.
, The inclination angle θ of the quadrangular pyramidal crystal 6 is 0 ° ≦ θ
It is set to ≦ 30 °. When the inclination angle θ is θ> 30 °, the oil retaining property of the surface layer 4a and the preferential wear property on the apex f side are deteriorated.

As shown in FIGS. 10 and 14, the tilt angle θ in the case of the truncated pyramid crystal 8 is a virtual line passing through the straight line r passing through the central portion n of the upper bottom surface and the central portion p of the lower bottom surface and the central portion p of the lower bottom surface. Surface G
Is defined as an angle formed by a reference line m perpendicular to. Also in this case, the inclination angle θ is set to 0 ° ≦ θ ≦ 30 °.

As shown in FIGS. 12 and 15, the inclination angle θ in the case of the flat surface a in FIG. 12 passes through the flat surface central portion s and is perpendicular to the flat surface a and the flat surface central portion s. Is defined as an angle formed by a reference line m passing through and being perpendicular to the virtual plane G.
Also in this case, the inclination angle θ is set to 0 ° ≦ θ ≦ 30 °.

The present invention is not limited to sliding bearings, but can be applied to other sliding members.

[0042]

According to the present invention, by specifying the structure of the surface layer as described above, it is possible to provide a sliding member having improved seizure resistance of the surface layer.

[Brief description of drawings]

FIG. 1 is an exploded plan view of a plain bearing.

FIG. 2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is a micrograph showing a crystal structure of a Pb alloy in a first example of a sliding surface.

FIG. 4 is a schematic perspective view of a main part showing a first example of a surface layer.

5 is a sectional view taken along line 5-5 of FIG.

FIG. 6 is an X-ray diffraction diagram of a Pb alloy crystal in the first example of the surface layer.

FIG. 7 is a micrograph showing a crystal structure of a Pb alloy on a sliding surface of a conventional example.

FIG. 8 is an X-ray diffraction diagram of a Pb alloy crystal in a surface layer of a conventional example.

FIG. 9 is a graph showing the results of a burn-in test.

FIG. 10 is a schematic perspective view of a main part showing a second example of the surface layer.

FIG. 11 is a micrograph showing a crystal structure of a Pb alloy in a second example of a sliding surface.

FIG. 12 is a schematic perspective view of a main part showing a third example of the surface layer.

FIG. 13 is an explanatory diagram showing a method for measuring a tilt angle of a quadrangular pyramidal crystal.

FIG. 14 is an explanatory diagram showing a method for measuring a tilt angle of a truncated pyramid crystal.

FIG. 15 is an explanatory diagram showing a method for measuring a tilt angle of a flat surface.

[Explanation of symbols]

1 Sliding bearing (sliding member) 4 surface layer 4a Sliding surface 6 Pyramidal crystals (pyramidal protrusions) 8 Pyramidal frustum crystals (frustum pyramidal protrusions) a flat surface b flakes c peripheral area d Inside area

Claims (2)

[Claims] 1. A sliding member comprising an alloy surface layer (4) having a sliding surface (4a) with a mating member (x), wherein the surface layer (4) is the sliding surface (4a). A plurality of thin pieces (b) having different areas of the flat surface (a) are formed in a stepwise manner such that the flat surface (a) has a smaller area as it is closer to the mating member (x). It has at least one of a plurality of stacked pyramidal protrusions (6) and a plurality of truncated pyramidal protrusions (8), and the alloy element concentration in the peripheral region (c) of each flat surface (a) is the peripheral region ( Flat surface excluding c) (a)
The sliding element is characterized in that the concentration is higher than the alloying element concentration in the inner region (d). 2. A sliding member comprising a surface layer (4) having a sliding surface (4a) with a mating member (x), wherein the surface layer (4) forms the sliding surface (4a). Having a plurality of flat surfaces (a), and the alloy element concentration in the peripheral area (c) of the flat surface (a) is in the inner area (d) of the flat surface (a) excluding the peripheral area (c). A sliding member having a higher concentration than the alloy element concentration.