JPH05312269A - Combination of piston ring with cylinder - Google Patents

Abstract

PURPOSE:To provide a combination of a piston ring for internal combustion engine, on the sliding surface of which a coating layer excellent in wear- resistance and anti-seizure property, and less in affection from a mating material is provided, with a cylinder on which a coating layer excellent in wear- resistance. CONSTITUTION:A piston ring 4 on the sliding surface of which having a composite coating layer 6, in which chromium oxide particles of 0.5 to 10mum in mean particle diameter are dispersed in a base of Ni-Co-P alloy comprising P of 0.2 to 10wt.%, Co of 10 to 40wt.%, and the substantially remaining Ni within a range of 5 to 30% by volume ratio, is combined with a cylinder 1 on the sliding surface of which a hard chromium coating layer 3 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combination technique of a piston ring for an internal combustion engine having a composite plating layer having excellent wear resistance on a sliding surface and a cylinder having a hard chromium plating layer having excellent wear resistance. Regarding

[0002]

2. Description of the Related Art As a cylinder used in an internal combustion engine, a cast iron cylinder has been widely adopted. However, in recent years, as the weight of the internal combustion engine has decreased, aluminum alloy cylinders have been adopted. The transition is underway.

Since an aluminum alloy cylinder is more easily worn than a cast iron cylinder, a cast iron cylinder liner is attached to the cylinder bore which serves as a sliding surface. However, such a structure is not economically preferable because the weight increases and the manufacturing cost increases.

Therefore, there has been proposed a cylinder in which a hard chromium plating layer is formed on the inner peripheral surface of the aluminum alloy cylinder. A cylinder having such a hard chrome plating layer has improved wear resistance.

However, when a chromium-plated aluminum alloy cylinder and a piston ring having a generally used hard chrome plating on the outer peripheral sliding surface are combined, the sliding surface is kept in a short time. Cause shaving. It is also conceivable to form a composite dispersion-plated film in which silicon carbide particles are dispersed in nickel on the piston ring. In this case, although wear resistance is good, in the initial conditions of operation or under severe conditions at high speed and high load. However, there is a problem that baking is easily caused.

On the other hand, although the piston ring is usually made of cast iron or steel, the cast iron piston ring has a problem that it has sufficient seizure resistance but insufficient wear resistance. In the case of steel, for example, a high-chromium steel base material that has been subjected to a nitriding treatment to form a nitriding layer is used, but this has excellent wear resistance, but the initial scuff It occurs and there is a problem in terms of initial familiarity.

Therefore, it is an object of the present invention to provide wear resistance,
It is an object of the present invention to provide a combination of a piston ring for an internal combustion engine, which has a plating layer excellent in seizure resistance and less likely to attack the mating material on the sliding surface, and a cylinder having a plating layer excellent in wear resistance.

[0008]

As a result of earnest research in view of the above object, the present inventor has a composite plating layer in which chromium oxide particles are dispersed in a matrix of a nickel-cobalt-phosphorus alloy on a sliding surface. The present invention has been found out that the combination of a piston ring and a cylinder having a hard chrome plated layer on a sliding surface can reduce wear of the cylinder and the piston ring, and can significantly reduce seizure and scuffing. .

That is, the combination of the piston ring and the cylinder of the present invention is 0.2 to 10% by weight of phosphorus and 10 to 10% of cobalt.
Nickel consisting of 40% by weight, the balance consisting essentially of nickel
The base of the cobalt-phosphorus alloy has a composite plating layer in which chromium oxide particles having an average particle diameter of 0.5 to 10 μm are dispersed in a volume ratio of 5 to 30% on the sliding surface of the piston ring. It is characterized by having a plating layer on the sliding surface of the cylinder.

[0010]

In the present invention, a chromium oxide particle-dispersed nickel-cobalt-phosphorus composite plating layer having excellent wear resistance and seizure resistance, a small friction coefficient and good slidability is formed on the piston ring. By combining the piston ring with a cylinder that has a hard chrome plating layer that has excellent wear resistance but poor seizure resistance, both wear resistance is improved and seizure resistance between the cylinder and piston ring Scuffing resistance is greatly improved.

[0011]

The present invention will be described in detail below. FIG. 1 is a partial sectional view showing a sliding portion between a piston ring and a cylinder according to an embodiment of the present invention. Hard chrome plating layer 3 on aluminum alloy cylinder base material 2 of cylinder 1
Is formed on the outer peripheral surface of the piston ring base material 5 made of cast iron or steel.
A chromium oxide particle-dispersed nickel-cobalt-phosphorus composite plating layer 6 is formed.

The hard chromium plating layer 3 formed on the cylinder base material has a thickness of 30 to 200 μm, particularly 100 to 150 μm, and a micro Vickers hardness (H of about 800 to 950).
_MV ). Such a hard chrome plating layer 3 can be formed by a known method.

By the way, the hard chromium plating layer 3 itself has the following defects. That is, although the hard chrome plating layer has high hardness and excellent wear resistance, it has poor oil retention and the oil film is easily broken, so that it has poor seizure resistance. In particular, at the time of starting the operation or the initial operation, when the temperature is high, when using a supercharger, etc., metal contact with the mating material easily occurs, and seizure occurs. In particular, the wear resistance and the seizure resistance are contributed by the Cr oxide layer formed extremely thin on the surface of the hard chromium plating layer 3.
The r oxide layer disappears when the fuel is light oil or leaded gasoline. In addition, the passivation film on the surface of the hard chrome plating layer also disappears due to the reducing atmosphere. Therefore, contact between metal surfaces occurs. For this reason, it is necessary to provide a layer having particularly excellent seizure resistance on the sliding surface of the piston ring, which is the mating member.

In order to satisfy the above conditions, an aluminum alloy cylinder having a hard chromium plating layer 3 is combined with a piston ring having a chromium oxide particle-dispersed nickel-cobalt-phosphorus composite plating layer 6. As a result, seizure does not occur between the two, the wear resistance of the piston ring is maintained for a long time, and the hard chrome plating layer 3 of the cylinder is not attacked.

In the chromium oxide particle-dispersed nickel-cobalt-phosphorus composite plating layer 6 formed on the sliding surface of the piston ring, the phosphorus contained in the nickel-base alloy matrix increases the hardness of the film, wear resistance and wear resistance. It has an excellent effect on bakeability and also improves the corrosion resistance of the base. If the total amount of nickel + cobalt + phosphorus is 100% by weight, and the amount of phosphorus is less than 0.2% by weight, the hardness will not be high even if the heat curing treatment is performed and the effect of improving wear resistance will be small. On the other hand, if it exceeds 10% by weight, the hardness increases, but the plating film becomes rather brittle, the impact strength decreases, and the adhesion with the piston ring base material deteriorates. Therefore, the amount of phosphorus is 0.2-10% by weight. The preferred amount of phosphorus is 2 to 8% by weight.

Cobalt improves the heat resistance and corrosion resistance of the alloy base, and also improves the crush strength of the coating. If the total amount of nickel + cobalt + phosphorus is 100% by weight, and the amount of cobalt in the alloy base is less than 10% by weight, the above effect cannot be obtained remarkably, and even if it exceeds 40% by weight, the effect changes remarkably. There is no. Therefore, the amount of cobalt is 10-40
Weight% The preferred amount of cobalt is 10-35% by weight.

Nickel as a matrix is effective in increasing the toughness and corrosion resistance of the film and also increasing the hardness of the film. The amount of nickel is 50 to 89.8% by weight, preferably 57 to 88% by weight, based on 100% by weight of the total of nickel + cobalt + phosphorus.

The chromium oxide particles dispersed in the alloy matrix are
Along with phosphorus, it exerts an excellent effect in improving the wear resistance of the coating. Further, the coefficient of friction is small and the friction is reduced. Among the ceramics, chromium oxide has poor wettability with metals and is unlikely to be in a molten state, and therefore contributes to improvement in seizure resistance. The amount of chromium oxide is 5 to 30% by volume based on the entire composite plating layer, and the average particle size is 0.5 to 10%.
μm. When the volume occupancy of chromium oxide is less than 5% or the average particle diameter is less than 0.5 μm, the area of chromium oxide on the surface of the matrix is small and the effect of improving wear resistance is not sufficient. On the other hand, the volume ratio of chromium oxide exceeds 30%,
Alternatively, if the average particle size exceeds 10 μm, the wear of the mating material will be increased, and the film strength will also be reduced.

For the formation of the composite plating film, chromium oxide particles are dispersed in a plating bath in which a nickel compound, a cobalt compound and a phosphorus compound are dissolved so as to have the desired composition. Sulfate, sulfamate, etc. are used as the cobalt and nickel compounds, and hypophosphite, phosphite, etc. are used as the phosphorus compound.

Chromium oxide particle dispersed nickel-cobalt-
The thickness of the phosphorus composite plating layer 6 is preferably 20 to 200 μm, and particularly preferably 50 to 150 μm. The micro Vickers hardness (H _MV ) is about 800 to 900.

The composite plating film obtained is washed with water and dried,
The baking temperature is about 300 to 400 ° C., and the time is about 30 to 60 minutes. By this baking treatment, hydrogen occluded in the composite plating film and the base material is released, and a composite plating film having a hardness suitable for obtaining good initial conformability can be obtained.

By using the piston ring and the cylinder having the composite plating film as described above in combination, the wear resistance and the scuffing resistance between them are improved.

The present invention will be described in more detail with reference to the following specific examples. Example 1 Steel with nominal diameter x width x thickness of 86.0 mm x 2.0 mm x 3.6 mm (SKD-
61) Nitriding is applied to the entire surface of the piston ring made of
m nitride layer was formed.

A plurality of the piston rings were put together and a plating bath in which chromium oxide particles as a bath component shown in Table 1 were suspended was used to oxidize the sliding surface of the ring into a nickel-cobalt-phosphorus alloy matrix. A 100 μm thick composite plating layer in which chromium particles were dispersed was formed. The plating conditions are liquid temperature 55
C., pH 2.0, current density 5 A / dm ² .

Table 1 Plating bath components Nickel sulfate 250 g / liter Nickel chloride 30 g / liter Cobalt sulfate 50 g / liter Boric acid 30 g / liter Sodium hypophosphite 2 g / liter Chromium oxide particles (average particle size 1.5 μm, maximum particle size 5 μm ) 50 g / liter

The amount of phosphorus in the formed composite plating layer is 5.8.
The amount of wt% and cobalt was 40% by weight, and the amount of chromium oxide particles was 20% by volume.

Further, the piston ring was heated at 400 ° C. for 1 hour to carry out a heat curing treatment to cure the matrix. By this treatment, the micro Vickers hardness (H _MV ) became 890.

Actual Machine Test The actual piston test was carried out by mounting the piston ring obtained in Example 1 on a 4-cycle water-cooled 6-cylinder engine.

The cylinder was made of an aluminum alloy having a bore diameter of 85 mm, hard chrome plating was formed on its inner peripheral surface to a thickness of 150 μm, and the cylinder was heat-treated at 200 ° C. for 1 hour.
The surface roughness of this hard chrome plating layer is about 2.0.
The micro-Vickers hardness (H _MV ) was 890.

Rotation speed 7200rp using high lead gasoline as fuel
A bench test was performed at m and full load for 100 hours, and the wear amount of the outer peripheral sliding surface of the piston ring and the inner peripheral surface of the cylinder was measured. The results are shown in Figure 2. The surface conditions of the outer peripheral sliding surface of the piston ring and the inner peripheral surface of the cylinder were evaluated according to the following criteria.

◯: Scuffing is not observed. Δ: Light scuffing is recognized at 3 to 5 places. X: Scuffing is observed at 8 to 12 places. The results are shown in Table 2.

Comparative Examples 1 to 3 For comparison, the same steel piston ring as in Example 1 was provided with a composite plating layer in which 20% by volume of silicon carbide hard particles having an average particle size of 1.0 μm were dispersed in a nickel film. 80 μm (Comparative Example 1: Micro Vickers hardness (H _MV ) 410 after heat treatment), Hard chromium plating formed to 80 μm (Comparative example 2: Micro Vickers hardness after heat treatment)
(H _MV ) 950) and alloy steel SUS 440B (C: 0.75 to 0.95
% By weight, Si: 1.0% by weight or less, Mn: 1.0% by weight or less, P: 0.04% by weight or less, Ni: 0.6% by weight or less, C
r: 16.0 to 18.0 wt%, Mo: 0.75 wt% or less, balance F
A sample (comparative example 3) having a nitrided layer of 70 μm formed on the surface of e) by nitriding treatment was prepared.

With respect to the combination of each of the above piston rings and the cylinder used in Example 1, the wear amount of the outer peripheral sliding surface of the piston ring and the inner peripheral surface of the cylinder was measured in the same manner. The results are shown in Figure 2. The surface conditions of the outer peripheral sliding surface of the piston ring and the inner peripheral surface of the cylinder were evaluated in the same manner. The results are shown in Table 2.

FIG. 2 shows the amount of wear of the combination of the piston ring and the cylinder of Comparative Example 1 as 100, and the amount of wear of the piston ring and the cylinder of the other combinations as relative values.

[0035]

As is clear from FIG. 2 and Table 2, the combination of the piston ring and the cylinder of Example 1 was significantly better than the combinations of Comparative Examples 1 to 3 in terms of both wear amount and surface condition. ..

[0037]

As described above, according to the present invention,
Since the cylinder with the hard chrome plating on the inner peripheral surface and the piston ring having the chromium oxide particle dispersed nickel-cobalt-phosphorus composite plating layer on the sliding surface are combined, the compatibility between the cylinder and the piston ring is good, Wear on both sides is reduced, and seizure, scuffing, etc. are less likely to occur.

[Brief description of drawings]

FIG. 1 is a partial sectional view showing a sliding portion of a piston ring and a cylinder according to an embodiment of the present invention.

FIG. 2 is a graph showing wear amounts of piston rings and cylinders in actual machine tests of Examples and Comparative Examples.

[Explanation of symbols]

1 ... Cylinder 2 ... Cylinder base material 3 ... Hard chromium plating layer 4 ... Piston ring 5 ... Piston ring base material 6 ... Chromium oxide particle dispersed nickel-cobalt-phosphorus composite plating layer

Claims (1)

[Claims] 1. 0.2 to 10% by weight of phosphorus and 10 to 40 of cobalt
Composite plating layer in which chromium oxide particles having an average particle size of 0.5 to 10 μm are dispersed in a volume ratio of 5 to 30% in a matrix of nickel-cobalt-phosphorus alloy consisting of weight% and the remainder substantially consisting of nickel. A combination of a piston ring with a sliding surface and a cylinder with a hard chrome plating layer on the sliding surface.