JPH0525685A - 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 the vertex (a) is directed to the side of the sliding face 4a. The concn. of alloy elements in a corner area (c)1 formed by the adjacent both slants (b) of the crystals 6 is higher than that of alloy elements in a flat area (d)1 excluding the corner area (c)1. In such a manner, the surface area of the sliding face 4a is expanded, by which the surface layer 4 has sufficient oil presenving properties, and furthermore, by preferentially wearing the side of the vertex (a) of the pyramidal crystals 6, its initial fitness can be improved. Moreover, in accordance with the increase of its hardness in the corner are (c)1, the parts having high hardness are dotted on the sliding face 4a, so that 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 Heretofore, as a sliding member of this kind, a sliding bearing in which the surface layer is made of a Pb-Sn alloy has been known (see JP-A-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 the retention property, that is, the oil retaining property is not sufficient, the initial conformability is poor, and the seizure resistance is poor because the 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 the high hardness portion is scattered on the sliding surface to improve 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,
In order to form the sliding surface, the surface layer has at least one of a plurality of pyramid-shaped projections with vertices facing the sliding surface and a plurality of truncated pyramidal projections with an upper bottom surface facing the sliding surface. It is characterized in that the alloy element concentration of a corner region having a protrusion and formed by both slopes adjacent to the protrusion is higher than the alloy element concentration of a flat region of the slope excluding the corner region.

[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 for mating with the mating member x. And an alloy surface layer 4. A Cu plating layer is provided between the backing metal 2 and the lining layer 3, and a Ni plating barrier layer is provided between the lining layer 3 and the surface layer 4, if necessary.

The back metal 2 is made of a rolled steel plate, and its thickness is determined by the set thickness of the slide 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 the function of softening the surface layer 4 to improve the 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. 3 and 4, the surface layer 4
Is an aggregate of columnar crystals 5 of Pb alloy extending from the lining layer 3, and has a plurality of pyramidal protrusions with the apex a directed toward the sliding surface 4a to form the sliding surface 4a. Has a quadrangular pyramidal crystal 6. The quadrangular pyramidal crystals 6 form the tips of the columnar crystals 5.

[0014] In the quadrangular pyramid-shaped crystals 6, the alloy element concentration in the corner regions c _1, which is formed by phase Tonariru both slope b (Cu, Sn concentration), the slope b excluding the corner region c ₁
Is higher than the alloying element concentration in the plane region d ₁ of.
Similarly, the alloy element concentrations of the corner regions c ₂ formed by the adjacent side surfaces e of the columnar crystal body 7 and the corner regions c ₃ formed by the adjacent slopes b and side surfaces e are the same as those of the plane regions d ₁ and It is higher than the alloying element concentration in the plane area d ₂ of the side surface e.

Such a concentration distribution of the alloying element has a corner area c due to the end effect produced during the electroplating process.
_It is considered that the current densities of _{1 to} c ₃ are higher than those of the plane regions d ₁ and d ₂ , and Sn is segregated in the corner regions c _{1 to} c ₃ respectively.

As a result, in each of the corner regions c _{1 to} c ₃ , the metal structure becomes dense, so that the hardness is increased,
Thereby, the seizure resistance of the quadrangular pyramidal crystal 6 and the columnar crystal body 7 can be improved.

FIG. 5 is an X-ray diffraction pattern 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 defined as 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 on 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 on the crystal axes a, b, 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 the seizure resistance thereof is improved.

FIG. 6 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.
And a surface layer formed of a Cu alloy lining layer by electroplating, and is applied to a journal portion of a crankshaft for an engine.

FIG. 7 is an X-ray diffraction diagram of Pb alloy crystals in the surface layer of the conventional example. From this figure, the orientation to a specific crystal plane is not recognized. Table 2 shows the integrated intensity Ihkl and the orientation index Oe on various (hkl) planes.

[0024]

[Table 2] As is clear from FIG. 6 and Table 2, the crystal shape of the conventional Pb alloy is an indefinite shape in which the crystal planes are randomly oriented. Due to this, the hardness of the Pb alloy becomes lower than that of the Pb alloy having the (h00) plane orientation.

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. 6) in the conventional example, and its crystal shape is indefinite.

FIG. 8 shows the seizure test results of the present inventions (1) to (4) and comparative examples (1) and (2).

The seizure test was conducted by rubbing each slide bearing on the rotary shaft and gradually increasing the load applied to the slide bearing. FIG. 8 shows the surface pressure when seizure occurs on the surface layer of each slide 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. 8, the 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 since the Pb alloy crystal forming the sliding surface 4a is the quadrangular pyramidal crystal 5, the apex a side thereof is preferentially worn and the surface layer 4 is formed.
It is because the initial familiarity of can be improved,
Also, the surface area of the sliding surface 4a is expanded by the quadrangular pyramidal crystals 6 so that the surface layer 4 has sufficient oil retaining property.
In addition to these, as the hardness of the corner region c ₁ increases,
Since high-hardness portions are scattered on the sliding surface 4a, the same sliding characteristics as those obtained by dispersion strengthening can be obtained, which is also a factor in improving the seizure-occurring surface pressure. There is.

In the quadrangular pyramidal crystal 5, when the preferential wear on the apex side ends at the initial stage of sliding to form a flat surface (corresponding to the top and bottom surfaces of the truncated pyramid), An oil film always exists between the mating member and the corner area c.
_{Since the} wear resistance improving effect is obtained by the scattered point distribution of the high hardness portion due to _{1, the} wear of the sliding surface 4a thereafter is performed very slowly.

As shown in FIG. 9 (a), in the present invention, the surface layer 4 forms the sliding surface 4a on the upper bottom surface f so as to form the sliding surface 4a.
Plural quadrangular pyramidal crystals (pyramidal protrusions) 8 facing a
The case of having only the pyramidal crystals and the case of having the quadrangular pyramidal crystals 6 and the quadrangular pyramid crystals 8 are also included. The same figure (b)
[FIG. 4] is an electron micrograph (10,000 times) showing the crystal structure of the Pb alloy on the sliding surface 4a. In this case, sliding surface 4a
Since at least a part of the above is formed from the upper bottom surface f of the quadrangular truncated pyramid crystal 8, an oil film is formed between the mating member and the upper bottom surface f from the beginning of sliding, and the wear resistance of the high hardness portion is increased. It is possible to obtain the effect of improving the property to improve the initial conformability and to stabilize it.

In the truncated pyramidal crystal 8, the alloy element concentration in the corner region c ₄ formed by the adjacent upper bottom face f and slope b is higher than that in the flat region d ₃ of the upper bottom face f. ..

The present invention also includes a crystal in which the quadrangular pyramidal crystals 6 and / or the quadrangular pyramid crystals 8 form a part of the sliding surface 4a. In this case, the area ratio of the pyramidal crystals 6 and the like on the sliding surface 4a is set to 50% or more.

As described above, in order to obtain excellent sliding characteristics, the inclination of the quadrangular pyramidal crystals 6 and the truncated quadrangular pyramid crystals 8 poses a problem.

Therefore, as shown in FIGS. 4 and 10, 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 a 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 becomes θ> 30 °, the oil retaining property of the surface layer 4 and the preferential wear property on the apex side are deteriorated.

The tilt angle θ in the case of the truncated pyramidal crystal 8 is, as shown in FIGS. 9 (a) and 11, the straight line r passing through the upper bottom central portion n and the lower bottom central portion p and the lower bottom central portion p. Is defined as an angle formed by a reference line m passing through and 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.

[0039]

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.

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 on a sliding surface.

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

FIG. 5 is an X-ray diffraction diagram of a Pb alloy crystal in the first example of the surface layer.

FIG. 6 is a micrograph showing a crystal structure of a Pb alloy on a sliding surface of a conventional example.

FIG. 7 is an X-ray diffraction diagram of a Pb alloy crystal in a surface layer of a conventional example.

FIG. 8 is a graph showing a result of a burn-in test.

FIG. 9A is a schematic perspective view of a main part showing a second example of the surface layer, and FIG. 9B is a micrograph showing a crystal structure of a Pb alloy corresponding to FIG.

FIG. 10 is an explanatory diagram showing a method for measuring a tilt angle of a pyramidal crystal.

FIG. 11 is an explanatory diagram showing a method of measuring a tilt angle of a truncated pyramidal crystal.

[Explanation of symbols]

1 sliding bearing (sliding member) 4 surface layer 4a sliding surface 6 quadrangular pyramidal crystal (pyramidal protrusion) 8 quadrangular truncated pyramid crystal (pyramidal pyramid protrusion) a vertex b slope c ₁ corner region d ₁ plane Area f Top bottom

Claims (1)

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 In order to form the sliding surface (4a), a plurality of pyramidal protrusions (6) with the apex (a) facing the sliding surface (4a) side and the upper bottom surface (f) toward the sliding surface (4a) side. A corner region (c ₁ ) formed by at least one projection (6, 8) of the plurality of truncated pyramid-shaped projections (8) facing each other and both slopes (b) adjacent to each other. The alloy element concentration of) is a slope (b) excluding its corner region (c ₁ ).
Is higher than the alloying element concentration in the plane region (d ₁ ) of the above.