JP2709613B2 - piston ring - Google Patents

Description

The present invention relates to a piston ring for an internal combustion engine having a double structure of a hard chromium plating layer and a composite dispersion plating layer on a sliding surface, and particularly relates to a cylinder ring. The present invention relates to a piston ring having good initial conformability and excellent wear resistance.

[Conventional technology]

In recent years, along with performance improvements such as smaller and lighter engines and higher output, the conditions required for piston rings have become increasingly severe, and not only wear resistance, seizure resistance, breakage resistance, etc. Improvements have been made from various perspectives.

In general, in an engine immediately after assembly, it is unavoidable that an error occurs in the size of the piston ring and the cylinder due to the restriction on the accuracy of part production, and a gap is generated between the two. If the engine is operated in a state in which the gap remains, the airtightness of the combustion chamber is broken, and gas blows through the crank chamber (compression leakage). The gas blow-through breaks the lubricating oil film that uniformly covers the inner surface of the cylinder, causing abnormal wear between the piston ring and the cylinder and causing scuffing. At the same time, the lubricating oil enters the combustion chamber through this gap, and the oil consumption increases.

Therefore, in the initial operation immediately after the assembly of the engine, which is called the familiar operation, it is necessary to eliminate the gap between the piston ring and the cylinder in a short period of time by performing the sliding of the piston ring and the cylinder, and to allow the two to be quickly adapted.

Generally, a piston ring having excellent wear resistance has a sliding surface with high hardness, and thus the period of the running-in operation tends to be long. For this reason, a method of providing a soft coating layer such as tin plating on the outer peripheral sliding surface of the piston ring or a method of processing the cross section of the ring on a taper has been adopted as a device to adapt the piston ring and the cylinder in a short time. ing.

[Problems to be solved by the invention]

However, in this method of applying tin plating, under conditions of high temperature and high load, the tin plating layer is too soft, so that it is easily worn out at an early stage of startup, and the effect of adaptation is almost eliminated. The method of forming a taper on the outer peripheral sliding surface of the ring has a problem that the angle of the taper affects the airtightness of the combustion chamber and the oil retaining property of the inner peripheral surface of the cylinder.

Therefore, an object of the present invention is to provide a piston ring that has good initial conformability even under high temperature and high load conditions, does not generate scuffing, completes conforming operation in a relatively short time, and has excellent wear resistance. That is.

[Means for solving the problem]

The present inventor has conducted intensive studies to achieve the above object, and as a result, by forming a composite dispersed plating layer having an appropriate hardness on a hard chromium plating layer having excellent wear resistance,
It has been discovered that a piston ring having good initial conformability and excellent wear resistance can be provided, and the present invention has been completed.

That is, the piston ring for an internal combustion engine of the present invention has at least on its outer peripheral sliding surface an internal combustion layer having a double structure layer composed of a hard chromium plating layer and a composite plating layer formed on the hard chromium plating layer. In an engine piston ring, the composite plating layer is composed of 10 to 40% by weight of cobalt, 1 to 10% by weight of phosphorus, and a nickel-cobalt-phosphorous alloy base composed of the balance of nickel. -30% by volume, and the hardness of the composite plating layer is 600-750 by Micro Vickers.

[Action]

In the piston ring coating of the dual structure of the present invention,
The upper (second) silicon nitride particle-dispersed composite plating film is
Since the material is somewhat softer than the lower (first layer) hard chromium plating layer, it is well-adapted to the cylinder in the early stage of engine start, and does not wear rapidly. Also, the lower (first layer) hard chromium plating layer has a high hardness, so it can be used for a long time (even after the upper layer is worn).
Good abrasion resistance can be maintained.

〔Example〕

The present invention will be described in detail by the following examples with reference to the accompanying drawings.

FIG. 1 is a sectional view of a piston ring for an internal combustion engine according to one embodiment of the present invention. In the present embodiment, a hard chromium plating layer 2 and a nickel-cobalt-phosphorus alloy composite plating layer 3 dispersed with silicon nitride particles are formed on the outer peripheral sliding surface of the piston ring 1 so as to have a double structure.

The first hard chromium plating layer can be obtained by electroplating using a plating bath mainly composed of chromic acid. As such a plating bath, a Sargent bath or a silicon fluoride bath which is a kind of a fluoride bath can be used. The hard chromium plating layer has high hardness and high abrasion resistance. Therefore, the heat of the hard chrome plating layer is 80 ~ 200μm
If so, it is good.

The hard chromium plating layer is inferior in initial conformability because the hardness is too high. To compensate for this disadvantage, a nickel-cobalt-phosphorus alloy composite plating film in which silicon nitride particles are dispersed is formed on the first layer as a second layer. .

Phosphorus contained in the composite coating increases the hardness of the coating, exhibits excellent effects on abrasion resistance and seizure resistance, and also improves the corrosion resistance of the matrix. Since the hardness of the plating film containing phosphorus is improved by heat treatment, the hardness suitable for obtaining good initial conformability (HMV6
00 to 750). However, when the amount of phosphorus is 1% by weight or less, the hardness does not become HMV600 or more even when heat treatment is performed, and the effects of wear resistance and scuff resistance are small. If it exceeds 10% by weight, the hardness increases but becomes brittle, and the impact strength also decreases. Therefore, the amount of phosphorus is preferably 1 to 10% by weight. A more preferable phosphorus content is 4 to 7% by weight.

Cobalt improves the heat resistance and corrosion resistance of the plating alloy base and also improves the crush fatigue strength of the coating. If the amount of cobalt in the alloy matrix is less than 10% by weight, the above effect cannot be obtained remarkably, and if it exceeds 40% by weight, the effect is not remarkably changed. . A more preferable cobalt content is 20 to 30% by weight.

The silicon nitride particles exhibit an excellent effect of improving the wear resistance of the film together with phosphorus. Further, since silicon nitride has low wettability with metals, it also contributes to improvement of seizure resistance and scuff resistance. The amount of silicon nitride is 5 to 30% by volume, and the average particle size is 0.5 to 5%.
μm is good. If the capacity is less than 5% or the particle size is less than 0.5 μm, the area of silicon nitride occupying the base surface is small, and the effect of improving wear resistance and scuff resistance is small. In addition, capacity is 30
% Or the particle size exceeds 5 μm, the abrasion of the mating material increases, and the strength of the composite film also decreases. More preferably, the average particle size of the silicon nitride particles is 0.8 to
At 1.2 μm, the content is 15-25% by volume.

In forming the composite plating film, a material obtained by dispersing silicon nitride particles 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 described above is used. Sulfate, sulfamate and the like are used as the nickel compound and the cobalt compound, and phosphoric acid, phosphorous acid and the like are used as the phosphorus compound.

The obtained composite plating film is washed with water, dried, and then heat-treated as necessary. The heat treatment temperature is about 200-300 ° C., and the time is 30-60 minutes. The heat treatment cures the base of the composite coating and provides a composite coating having a hardness suitable for obtaining good initial conformability.

 The present invention is described in more detail by the following examples.

Example 1 A first step of forming a hard chromium plating layer as a first layer on an outer peripheral sliding surface of a piston ring, and a first step of forming a second layer as a first layer
A second step of forming a composite dispersed plating layer on the layer, and a third step of subjecting the obtained double-structured layer to a heat treatment,
A film was formed.

First, in the first step, nominal diameter x width x thickness is 77mm x 1.5m
A plurality of piston rings of SKD-61 material of mx 3.1 mm were collectively used as a base material, and hard chrome plating was performed under the conditions shown in Table 2 using a plating bath having a bath composition shown in Table 1.

The thickness of the hard chromium plating layer obtained in the first step was 100 μm.

As a second step, the piston ring having the hard chromium plating layer obtained in the first step on the surface is immersed in a plating bath having the composition shown in Table 3, and the plating bath temperature is 60 ° C., the pH is 4, and the current density is in 10A / dm ² by flowing a 5 minute current,
Electroplating was performed.

The heat of the composite plating film of the second layer obtained in the second step was 7 μm, and the composition was 30% by weight of cobalt, 6.5% by weight of phosphorus, and 20% by volume of silicon nitride.

Next, as a third step, the obtained double-layered film is subjected to 250
Heat treatment was performed at 1 ° C. for 1 hour to cure the film. At this time, the hardness of the hard chromium plating layer as the first layer was 980 by Micro Vickers, and the hardness of the composite plating film layer of the second layer was 750 by Micro Vickers.

Actual test Cast iron (FC-) for 4 cycle water-cooled 4-cylinder 1300cc engine
25) Assemble the above piston ring into the engine cylinder and conduct a 100 hour bench test at 7500 rpm full load.
Oil consumption was measured.

Comparative Example 1 For comparison, an actual machine test was performed in the same manner as in Example 1 using a piston ring in which only a hard chrome plating layer was formed on the outer peripheral sliding surface of the piston ring, and oil consumption was measured.

 The test results are shown in FIG.

As is clear from FIG. 2, the piston ring of the present invention has a smaller oil consumption from the initial point in time than the piston ring having only the hard chromium plating layer on the sliding surface. This is because the gap between the piston ring and the cylinder disappears in a short time, that is, the initial conformability is good.

In the examples, no scuffing was observed.

〔The invention's effect〕

As described in detail above, the piston ring of the present invention having the hard chromium plating layer and the nickel-cobalt-phosphorus alloy composite plating layer dispersed with silicon nitride particles on the outer peripheral sliding surface has an initial conformability and a scuff resistance due to the composite dispersed plating film. Excellent in nature,
The hard chromium plating layer provides excellent long-term wear resistance.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a piston ring according to one embodiment of the present invention, and FIG. 2 is a graph showing the relationship between test time and oil consumption in the piston rings of Example 1 and Comparative Example 1. 1 ... Piston ring base material 2 ... Hard chrome plating layer 3 ... Silicon nitride particle dispersed nickel-cobalt-phosphorus alloy composite plating film

Claims (2)

(57) [Claims] 1. A piston ring for an internal combustion engine having a double-layered structure comprising a hard chromium plating layer and a composite plating layer formed on the hard chromium plating layer at least on its outer peripheral sliding surface. The composite plating layer has an average particle size of 0.5 in a nickel-cobalt-phosphorus alloy matrix comprising 10 to 40% by weight of cobalt, 1 to 10% by weight of phosphorus and the balance of nickel.
5 to 30% by volume of silicon nitride particles of 5 to 5 μm are dispersed, and the hardness of the composite plating layer is
A piston ring for an internal combustion engine, wherein the number is from 0 to 750. 2. The piston ring for an internal combustion engine according to claim 1, wherein the composite plating layer has a temperature of 200 to 300 ° C.
A piston ring for an internal combustion engine, which is heat-treated for 30 to 60 minutes.