JP2607991B2 - Sliding member - Google Patents

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 a surface layer having a sliding surface with a mating member.

[0002]

2. Description of the Related Art Conventionally, as this kind of sliding member, there has been known a sliding bearing in which the surface layer is made of a Pb-Sn alloy (see Japanese Patent Application Laid-Open No. 56-96088).

[0003]

Problems to be Solved by the Invention This type of plain bearing is
It is applied to the journal part of the crankshaft, the large end of the connecting rod, etc. in the engine. However, in the current situation where the engine tends to be high-speed and high-power, the surface layer of the conventional plain bearing is oil There is a problem that the retention property, that is, the oil retention property is not sufficient, and the seizure resistance is poor due to poor initial conformability.

[0004] In view of the above, the present invention provides the surface layer with sufficient oil retention by specifying the structure of the surface layer.
It is another object of the present invention to provide the sliding member in which the initial conformability of the surface layer is improved and thereby the seizure resistance of the surface layer is improved.

[0005]

According to the present invention, there is provided a sliding member having a surface layer having a sliding surface with a mating member, wherein the surface layer has a plurality of ridges adjacent to a plurality of ridges on the surface. Between the clubs
Grown with the crystal plane orientation so that
Of a plating layer with multiple crystals, followed by a surface
It is formed through processing, and has a plurality of chevron projections forming the sliding surface, the chevron projections have a plurality of ridges extending from the top toward the hem and are adjacent to each other. It is characterized in that it is formed in a substantially star shape in which the slope between the ridges is depressed.

[0006]

1 and 2, a sliding bearing 1 as a sliding member is applied to a journal portion of a crankshaft, a large end portion of a connecting rod and the like in an engine.
The first and second halves ₁ 1, consisting of 1 _2. Both halves 1 ₁ ,
1 ₂ has the same structure, and has a back metal 2, a lining layer 3 formed on the inner peripheral surface of the back metal 2, and a sliding surface 4 a formed on the surface of the lining layer 3 and mating with the member x. And a surface layer 4. A Cu plating layer is provided between the back metal 2 and the lining layer 3, and a lining layer 3 and a surface layer 4 are provided.
A Ni plating barrier layer is provided between the layers as needed.

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, Cu-based alloy, Al, Al-based alloy, etc., and has a thickness of 50 to 500 μm, usually 300 μm.
m. The surface layer 4 is made of a Pb alloy and has a thickness of 5 to 50 μm, usually about 20 μm.

The Pb alloy constituting the surface layer 4 is 80 to 9
It contains 0% by weight of Pb and 3 to 20% by weight of Sn, and optionally contains Cu, In, Ag, Tl, Nb, Sb, and N.
At least one selected from i, Cd, Te, Bi, Mn, Ca, and Ba is contained in an amount of 10% by weight or less.

Although Cu, Ni and Mn have a function of improving the hardness of the surface layer 4, if the content exceeds 10% by weight, the hardness becomes too high and the initial conformability decreases.
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 and improving the initial conformability, but when the content exceeds 10% by weight, the strength of the surface layer 4 decreases. When adding In or the like, it is desirable to adjust the content so that the hardness Hmv of the surface layer 4 is 8 to 15.

The surface layer 4 is formed by electroplating,
It is formed through an electric etching process on the surface . In the electroplating process, the plating solution was 40 to 180 g of Pb ²⁺ per liter, and 1.5 to 35 g per liter.
A fluorinated plating solution containing g of Sn ²⁺ and, if necessary, 15 g or less of Cu ²⁺ per liter is used. The temperature of the plating solution is 10 to 35 ° C, and the cathode current density is 3 to
It is set to 15 A / dm ² respectively. In the electric etching process, an aqueous solution containing 20 to 100 g of borofluoric acid per liter of water is used as an etching solution, and the plating layer is connected to the (+) side.

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

As shown in FIG. 3 and FIG.
The crystal plane sharp apex a on so that toward the slide surface 4a side
Has a plurality of quadrangular pyramidal crystals 6 grown with the following orientation . Each quadrangular pyramid-shaped crystal 6 forms the tip of each columnar crystal 7 extending from the lining layer 3, and thus the plating layer 5 is composed of an aggregate of columnar crystals 7.

FIG. 5 is a graph showing the relationship between P and P on the sliding surface 4 a of the surface layer 4.
5 is an electron micrograph (× 10,000) showing the crystal structure of the alloy b, and the sliding surface 4a is formed by subjecting the surface of the plating layer 5 to an electric etching process. Surface layer 4
Has a plurality of angled projections 8 forming a sliding surface 4a as shown in FIG.
Are formed in a substantially star shape having a plurality of, e.g., four ridges d in the illustrated example, and a concave slope e between the adjacent ridges d. In this example, the area ratio of the chevron 8 on the sliding surface 4a is 100%.

The reason for obtaining the above-mentioned shape is as follows. That is, in the quadrangular pyramid-shaped crystal 6 with the orientation of the crystal plane, the alloy element concentration (Cu, Sn concentration) of each ridge line portion f is:
It is higher than the alloying element concentration of the slope g between the adjacent ridge lines f. Such a concentration distribution of the alloy element is obtained when the current density of each ridge line portion f becomes higher than that of each slope portion g due to the edge effect generated during the electroplating process.

As a result, at each ridge f, the metal structure becomes denser and its hardness is increased, so that in the above-mentioned electric etching process, the amount of dissolution of each ridge f is extremely small. g has a concave shape due to its increased amount of dissolution. Therefore, in the chevron 8,
The hardness of the top portion b and each ridge line portion d is higher than the hardness of each slope portion e.

As described above, when the sliding surface 4a is formed by a plurality of angled projections 8, the top b side of each angled projection 8 is maintained at an appropriate hardness, and the top b side is preferentially preferential. And the initial conformability of the surface layer 4 can be improved. Further, the surface area of the sliding surface 4a is increased due to the fact that each chevron projection 8 has a substantially star shape in which the slope e is recessed,
Thereby, the surface layer 4 can have sufficient oil retaining properties.

When the preferential wear on the top b side is completed at the beginning of the sliding operation and a flat surface (corresponding to the upper bottom surface of the truncated pyramid) is formed, a gap is formed between the flat surface and the mating member. Since the oil film is always present, the subsequent sliding surface 4a wears very slowly.

FIG. 7 is an X-ray diffraction diagram of the Pb alloy crystal in the surface layer 4, where only the diffraction peaks of the (200) plane and the (400) plane are recognized by the Miller index.

Here, an orientation index Oe is shown as an index indicating the orientation of the crystal plane, (However, hkl is Miller index, Ihkl is (hkl)
Defined as the integrated intensity of the plane, ΣIhkl is the sum of Ihkl), in the (hkl) plane, its orientation index Oe is 1
The closer to 00%, the more crystal planes oriented in the direction perpendicular to the (hkl) plane.

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

[0022]

[Table 1]

According to Table 1, the orientation index Oe of the (h00) plane of the Pb alloy is 100%.
The alloy crystal has crystal planes oriented in the respective axial directions at crystal axes a, b, and c, that is, (h00) plane.

As described above, when the crystal plane is oriented in a direction orthogonal to the (h00) plane, the crystal structure of the Pb alloy is a face-centered cubic structure. 4 increases in its seizure resistance and abrasion resistance.

FIG. 8 is a graph showing P on the sliding surface of the conventional surface layer.
5 is an electron micrograph (× 10,000) showing the crystal structure of alloy b. This surface layer comprises 8% by weight of Sn and 2% by weight of Cu.
The surface layer is formed on a Cu alloy lining layer by electroplating, and is applied to the journal portion of an engine crankshaft.

FIG. 9 is an X-ray diffraction diagram of a Pb alloy crystal in the surface layer of the conventional example. From this figure, no orientation to a specific crystal plane is recognized. Table 2 shows the integrated intensity Ihkl and the orientation index Oe in various (hkl) planes.

[0027]

[Table 2]

As is clear from FIGS. 8 and 9 and Table 2, the crystal shape of the conventional Pb alloy is an irregular shape in which crystal planes are randomly oriented, and the surface layer is composed of aggregates of granular crystals. . Due to this, the hardness of the surface layer is (h0
0) It is lower than that of a surface layer having a plane orientation.

FIG. 10 shows the relationship between the area ratio of the angled projections on the sliding surface and the surface pressure at which seizure occurs in the surface layer of various slide bearings. In this figure, the one having an area ratio of 100% corresponds to the sliding surface in the present invention shown in FIG. 5, and the one having an area ratio of 0% corresponds to the sliding surface in the conventional example shown in FIG. If the area ratio is less than 100%,
In addition to the chevron 8, a pyramidal crystal 6, a granular crystal, and the like are included.

The seizure test was carried out by rubbing each of the sliding bearings on the rotating shaft and gradually increasing the load applied to the sliding bearings. The values in FIG. 10 are obtained by determining the surface pressure when the surface layer of each slide bearing is seized.

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

As is apparent from FIG. 10, the seizure resistance of the surface layer 4 is improved with an increase in the area ratio of the chevron projections 8, and this is remarkable when the area ratio is 50% or more. Angle projection 8
Is preferably 80% or more.

FIGS. 11A and 11B show that the plating layer 5 is
So that toward the upper bottom surface k to the sliding surface 4a side is a flat top
2 shows a case where only a plurality of truncated pyramidal crystals 9 of a plurality of Pb alloys grown with the orientation of the crystal planes are provided . FIG. 4B is an electron micrograph (× 10,000) showing the crystal structure of the Pb alloy.
Which corresponds to FIG. From such a crystal 9, a chevron-shaped projection 10 having a flat top k is obtained as shown in FIG. The same sliding characteristics as described above can be obtained by the sliding surface 4a having the angled projection 10 or the hybrid structure of the angled projection 10 and the angled projection 8. In this case, at least a part of the sliding surface 4a is formed by the flat top portion k of the chevron projection 10, so that an oil film is formed between the mating member and the top portion k from the beginning of the sliding to improve the initial conformability. Good and stable.

The present invention also includes a case where the angled protrusion 10 or the two angled protrusions 8 and 10 form a part of the sliding surface 4a. In this case, the area ratio of the chevron projections 10 and the like on the sliding surface 4a is desirably 50% or more.

In order to obtain excellent sliding characteristics as described above, the inclination of the chevron-shaped projections 8 and 10 and thus the quadrangular pyramid-shaped crystal 6 and the truncated quadrangular-pyramidal crystal 9 becomes a problem.

Therefore, as shown in FIGS. 4 and 13, on the bottom side of the quadrangular pyramid crystal 6, the crystal 6 is projected to define an imaginary plane L along the sliding surface 4a. The inclination angle between a straight line n passing through the vertex a of the crystal 6 and the bottom center part m and a reference line p passing through the bottom center part m and perpendicular to the virtual plane L is θ.
Is defined, the inclination angle θ of the pyramidal crystal 6 is 0 ° ≦ θ.
≦ 30 ° is set. When the inclination angle θ is θ> 30 °, the oil retaining property of the surface layer 4 and the preferential wear property on the vertex a side decrease.

The tilt angle θ in the case of the truncated quadrangular pyramidal crystal 9 is, as shown in FIGS. 11A and 14, a straight line t passing through the upper bottom center r and the lower bottom center s and a lower bottom center s. , And is defined as an angle formed by a reference line p perpendicular to the virtual plane L. Also in this case, the inclination angle θ is set to 0 ° ≦ θ ≦ 30 °.

[0038] The hitting the formation of such quadrangular pyramid-shaped crystals 6, the electric plating key processing instead of the sense, it is possible to use PVD, ion plating, CVD, vapor phase plating such as sputtering.

The present invention is not limited to a plain bearing, but is applicable to other sliding members.

[0040]

According to the present invention, by specifying the structure of the surface layer as described above, a sliding member with improved seizure resistance of the surface layer can be provided.

[Brief description of the drawings]

FIG. 1 is an exploded plan view of a sliding 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 on a plating layer surface.

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

FIG. 5 is a micrograph showing a crystal structure of a Pb alloy in a first example of a sliding surface.

FIG. 6 is a schematic plan view of a main part showing a first example of a sliding surface.

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

FIG. 8 is a micrograph showing a crystal structure of a Pb alloy on a sliding surface of a conventional example.

FIG. 9 is an X-ray diffraction diagram of a Pb alloy crystal in a conventional example surface layer.

FIG. 10 is a graph showing the relationship between the area ratio of the chevron on the sliding surface and the surface pressure at which seizure occurs.

FIG. 11A is a schematic perspective view of a principal part showing a second example of a plating layer, and FIG. 11B is a micrograph showing the crystal structure of a Pb alloy, corresponding to FIG.

FIG. 12 is a schematic plan view of a main part showing a second example of the sliding surface.

FIG. 13 is an explanatory view showing a method of measuring the inclination angle of a pyramidal crystal.

FIG. 14 is an explanatory diagram showing a method of measuring the inclination angle of a truncated quadrangular pyramid crystal.

[Explanation of symbols]

1 sliding bearing (sliding member) 4 surface layer 4a sliding surface 5 plating layer 6 quadrangular pyramid-shaped crystals (crystals) 8,10 Yamagata projections 9 quadrangular pyramid-shaped crystals (crystals) b, k top c skirt d, f ridgeline e , g slope x partner

Claims (2)

(57) [Claims] 1. A sliding member having a surface layer (4) having a sliding surface (4a) with a mating member (x), wherein the surface layer (4) has a plurality of ridge portions (f ) on its surface. ) And adjacent ridge lines
Of the crystal plane so as to have a slope part (g) existing between the parts (f).
Has multiple crystals (6, 9) grown with orientation
Formation of plating layer (5), followed by surface treatment
Be one that is, a plurality of chevron projections (8, 10) forming the sliding surface (4a), said angled protrusion (8,
10) has a plurality of ridges (d) extending from the tops (b, k) toward the hem (c), and has a concave slope (e) between adjacent ridges (d). A sliding member having a substantially star shape. 2. The area ratio of the angled projections (8, 10) on the sliding surface (4a) is 50% or more.
The sliding member as described in the above.