JPH0457862B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piston ring used in an internal combustion engine, and particularly to an oil-scraped piston ring (hereinafter referred to as an oil-scraped ring).

In recent years, as the performance of internal combustion engines has improved and specification conditions have become more severe, the performance of oil scrubbing rings has become more important.

The main role of the oil scraper ring is to scrape off excess lubricant on the cylinder inner wall into the oil pan, prevent excess lubricant from entering the combustion chamber, and maintain an appropriate lubricant film on the cylinder inner wall. This prevents direct contact between the outer circumferential surface of the piston ring and the inner wall surface of the cylinder, thereby preventing abnormal wear.

As mentioned at the beginning, various improvements have been made to the oil scrubbing ring that plays this role in order to cope with the performance improvement of internal combustion engines and the increasingly severe operating conditions of internal combustion engines in recent years.

As a result, a combination oil scraper ring 3 consisting of a spacer expander 1 and a side rail 2 as shown in Fig. 1, which has been mainly used in gasoline engines and has been highly praised for its performance, can also be used in diesel engines with a high heat load. The second
It has come to be used in place of the oil scraper ring consisting of a cast iron oil scraper ring body 4 and a coil expander 5 as shown in the figure. As described above, the oil scraper ring has recently come into use, and a combination oil scraper ring consisting of a spacer expander and a side rail has come to be widely used.

Much research and development has been carried out on the side rails, which play a major role in the performance of this combination oil scraper ring, but the current situation is that no one has yet been developed that exhibits sufficient performance. There is a strong demand for the development of a combination oil scraper ring that can sufficiently handle the high performance and severe operating conditions of engines.

In view of this situation, the present invention aims to provide an excellent combination oil scraper ring side rail that solves the conventional defects.

A detailed description will be given below with reference to the accompanying drawings.

FIG. 3 is a front view showing one embodiment of the side rail 2 of the present invention, and FIG. 4 is a sectional view taken along the line AA in FIG. 3. The base material of this side rail is steel,
A nitrided layer 6 (including a soft nitrided layer, a sulfonitrided layer, and a carbonitrided layer) is provided on the outer peripheral surface 21. The inner peripheral surface 22 is provided with chrome plating 7.

With this structure, the nitrided layer gives the outer peripheral surface of the side rail an extremely high hardness of approximately HV1200, and exhibits excellent wear resistance. In particular, the outer peripheral surface 21 of the side rail 2 slides on the cylinder inner wall surface 8 at high speed, and the operating conditions are that combustion products are present in the lubricating oil, so it is necessary to exhibit excellent performance against abrasive wear. There is. The nitrided layer exhibits excellent performance against this abrasive wear, and the side rail outer peripheral surface exhibits sufficient wear resistance.

The inner peripheral surface 22 of the side rail 2 transmits the tension of the spacer expander 1 to the side rail 2 via the small protrusion 11 of the spacer expander, and presses the side rail 2 against the cylinder inner wall surface 8. Therefore, the inner circumferential surface 7 of the side rail and the small protrusion 11 are always in contact with each other under high surface pressure, and this contact surface moves slightly during operation. Therefore, the inner circumferential surface of the side rail must exhibit excellent performance, especially against fine movement wear (fretting wear). In the present invention, since the inner peripheral surface 22 of the side rail 2 is coated with chrome plating 7,
Demonstrates excellent fretting wear resistance.

In order to exhibit this excellent fretting wear resistance, the chrome plating must not peel off due to denting near the surface in contact with small protrusions due to the softness of the base material. The thickness is 5 μm or more to provide strength,
Even if the base material is soft, it is necessary to prevent the chrome plating from peeling off by making sure that it is not affected by it.

FIG. 5 shows another embodiment of the present invention, which differs from the previous embodiment in that the upper and lower surfaces 23 and 24 of the side rail 2 also have nitride layers 6.

In this way, not only the outer peripheral surface 21 but also the upper and lower surfaces 2
By applying a nitrided layer 6 to 3 and 24 as well, the wear resistance of the upper and lower surfaces is improved.

FIG. 6 shows yet another embodiment of the present invention, in which a nitride layer 6 is formed on the entire outer surface of the side rail 2.
The inner circumferential surface 22 is further provided with chromium plating 7 on the nitrided layer. By doing so, it is possible to efficiently produce a side rail having the same effect as that shown in FIG. 4.

In addition, the steel of the base material of the side rail of the present invention, in weight percent, contains C: 0.16 to 1.4%, Si: 1.0% or less,
Mn: 1.0 or less, Cr: 11.0 to 19.0%, and Mo, V,
It is desirable to use a material containing 0.5 to 5.0% of one or more of W and Ti and having a tempered martensite base. By using a base material of this material, sufficient performance can be exhibited even under high heat load conditions such as those in diesel engines.

The reasons for limiting the ingredients will be explained below.

If the amount of C is less than 0.16%, the amount of carbides produced will be small, and the wear resistance obtained by the presence of carbides will be poor. On the other hand, if it exceeds 1.4%, embrittlement occurs as the amount of carbides increases, making it impossible to plastically deform the wire into a piston ring shape under normal conditions.

Si is added as a deoxidizing agent, but if it exceeds 1.0%, it becomes a factor that causes embrittlement.

Mn is also added for deoxidation and desulfurization, but if it exceeds 1.0%, it deteriorates the oxidation resistance of the steel.

If Cr is less than 11%, the amount of Cr carbide that is highly hard and has excellent wear resistance will be reduced, and it will also have corrosion resistance and
Heat resistance also decreases. If it exceeds 19%, it will form a solid solution in the base.
The amount of Cr and carbide increases, and the strength (toughness) of the material increases.
This results in a decrease in

Mo, V, W, and Ti are carbide-forming elements and have the effect of preventing softening in the deep part of the material.
If it is less than 0.5%, this effect will not occur, and if it exceeds 5.0%, the base will become extremely brittle.

Note that there is no problem even if P and S are contained as impurities as long as they are less than 0.04%. Hardenability can also be improved by adding Ni.

Further, the base material of the side rail of the present invention has a tempered martensitic matrix structure, and fine carbides mainly composed of Cr are precipitated in this matrix. For this reason, a certain degree of wear resistance is maintained even on the worn and exposed base material surface.

Next, a fretting wear test was conducted to confirm the performance of the side rail of the present invention.

This fretting wear test was conducted using a reciprocating friction and wear tester.

First, the lower test piece (width 10 mm x thickness 10 mm x length 70 mm), which is assumed to be a spacer expander material, is
The lower test piece was made from JIS SUS201 material and was nitrided to form a 10 μm nitride layer on the surface.
I made a board.

On the other hand, upper test pieces (diameter 5 mm x length 30 mm), which were assumed to be side rail materials, were made from a material equivalent to JIS SUS440B, and samples 1 to 4 were prepared with the following surface treatments on the outer circumferential surface.

Sample 1...Chrome plating (thickness 10μm) Sample 2... (thickness 3μm) Sample 3...Nitride layer (thickness 30μm) Sample 4...No surface treatment The lower test piece manufactured in this way On the other hand, a fretting wear test was conducted by pressing the upper test piece and moving the lower test piece from side to side.

(Test conditions) Contact load: 10 kgf Amplitude applied to lower test piece: 150 μm Lubricating oil: None Test time: 30 minutes (Evaluation method) Upper test piece (side rail material): Evaluated by weight loss before and after the test.

Lower test piece (spacer expander material): Evaluated based on the maximum depth of the recess caused by wear.

The results of this test are as shown in FIG. 7, but for sample 2, peeling of the chrome plating occurred during the test and no data could be taken.

As is clear from this test result, sample 1 (invention) with 10 μm of chrome plating has better fretting wear on itself than sample 3 with nitrided layer, and also has significantly better wear on the mating material. Proven.

The reason why the mating material wears so well is thought to be that in the case of chromium plating, an oxide film is formed on the contact surface more quickly than a nitride layer, so metal contact does not occur. In comparison, it is difficult to form an oxide film on a nitrided layer, so when the oxide film is broken, metal contact occurs, which is thought to increase friction.

As described above, the side rail of the present invention takes into full consideration the sliding characteristics of the outer circumferential surface of the side rail and the characteristics of the inner circumferential surface of the side rail, and applies separate and most suitable treatments to the inner and outer circumferences of the side rail. As a result, we have obtained a side rail that exhibits excellent performance.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of main parts showing a conventional oil scraper ring consisting of a spacer expander and side rail installed in a ring groove and inserted into a cylinder. Figure 2 is a conventional cast iron oil scraper ring body and coil. FIG. 3 is a front view of a side rail showing an embodiment of the present invention; FIG. The AA enlarged cross-sectional view, FIG. 5, and FIG. 6 show other embodiments of the present invention, and the cross-sectional view corresponding to FIG. 4 and FIG.
The figure is a graph showing the test results. Explanation of symbols, 1...Spacer expander, 2
...Side rail, 21...Side rail outer peripheral surface, 2
2... Side rail inner peripheral surface, 23... Side rail upper surface, 24... Side rail lower surface, 6... Nitride layer, 7...
Chrome plating layer, 8... Cylinder inner wall surface.

Claims (1)

[Claims] 1. On the side rail of the combination oil scraper ring,
A side rail of a combination oil scraper ring characterized in that the base material is made of steel, at least the outer peripheral surface thereof has a nitrided layer, and the inner peripheral surface has chromium plating of 5 μm or more.