JP2000034543A - Piston ring for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a piston ring excellent in wear resistance and free from adherence to a piston ring groove at a low cost by composing the main body of a piston ring to be mounted on a piston ring groove of a piston made of an Al-Si series aluminum alloy of steel contg. specified amounts of C, Si and Mn. SOLUTION: The main body of a piston ring to be mounted on a piston ring groove of a piston made of an Al-Si series aluminum alloy is composed of steel contg., by weight, 0.59 to 0.76% C, 0.15 to 0.35% Si, <=0.60% Mn, preferably >=0.4% Mn, and the balance Fe with inevitable impurities. Moreover, in the case it is used for a pressure ring, when at least the side face is subjected to chemical conversion treatment to impact about 1 to 10 μm thickness and about 2 to 5 μm roughness with manganese phosphate or the like, the initial adherence of the aluminum alloy can be suppressed. Moreover, in the case it is used for a primary pressure ring, at least the outer circumferential sliding face is coated with a hard chromium plating film excellent in wear resistance at a thickness of about 70 to 80 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piston ring for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, piston rings for internal combustion engines are often used with two pressure rings and one oil ring. The pressure ring seals high-temperature combustion gas in the internal combustion engine and also radiates heat of the piston heated to a high temperature by combustion to the cylinder. Therefore, the pressure ring is made of steel such as cast iron, Si-Cr steel or high chrome martensitic steel, and if necessary,
In order to improve the sliding properties such as wear resistance, seizure resistance, adhesion resistance and friction coefficient of these base materials, a hard chrome plating film by electroplating on the outer peripheral surface or a nitriding layer by nitriding treatment is applied. And have been used. Among these materials, cast iron has a high Si content of 2% or more, and Si-Cr steel has a high Si content of 1% or more to obtain high yield strength.

[0003] Pistons made of Al-Si based aluminum alloys such as AC8A, AC8B, AC8C or alloys of which composition is changed are often used in internal combustion engines. The piston ring attached to the piston ring groove of the piston adheres between the Al-Si based aluminum alloy groove surface of the piston and the side surface of the piston ring due to the high output and high speed of the internal combustion engine. This causes problems such as wear of the piston ring groove and sticking of the piston ring. As a countermeasure against these problems, measures such as providing a resin film containing a solid lubricant on the side surface of the piston ring (Japanese Patent Laid-Open No. 7-63266) and providing an alumite film on the side surface of the piston ring groove have been taken. Its use was limited due to cost.

[0004]

SUMMARY OF THE INVENTION The present invention provides a low-cost piston which has excellent wear resistance on the outer peripheral sliding surface and the upper and lower surfaces of the piston ring and does not adhere to the piston ring groove of an aluminum alloy piston. The purpose is to provide a ring.

[0005]

The inventor of the present invention has conducted intensive studies on the occurrence of adhesion between an Al-Si based aluminum alloy piston and a piston ring material. The present inventors have found that it is related to the Si content of the material, and have reached the present invention. The present invention contains only the minimum amount of Si necessary for maintaining the function as a piston ring, and has a C content of 0.59 to 0.76% and a Si content of 0.15% by weight.
An object of the present invention is to provide a piston ring mainly containing a steel material containing 0.35% or less and Mn of 0.60% or less, the balance being Fe and unavoidable impurities. The outer peripheral sliding surface of the piston ring main body has a hard chromium plating film if necessary, and the side surface has a base material as it is or has a chemical conversion treatment film.
The chemical conversion coating applied to the side surface of the piston ring has an effect of preventing adhesion in the early stage of use, and may be applied.

The piston ring of the present invention contains only a necessary minimum amount of Si component and does not impair the function as a piston ring. 76%, Si 0.15
A steel material containing 0.35% and Mn of 0.60% or less, the balance being Fe and inevitable impurities is used as a base material or a main body. Next, reasons for limiting each component of the piston ring base material will be described.

C is an element that forms a solid solution in Fe and contributes to the strength, and is an important element that contributes to the wear resistance by reducing the amount of ferrite while forming carbides. % Is needed. However, C is an element which forms an interstitial solid solution in Fe like N, so that a large amount of addition causes a decrease in elongation and drawing during processing, and a large amount of carbide formation, especially generation of proeutectoid carbide, is caused by the counterpart material. Therefore, the upper limit is set to 0.76% because the groove surface of the Al-Si-based aluminum alloy piston is worn.

[0008] Si is an element that suppresses the decrease in tension by improving the heat resistance by forming a solid solution in Fe, so that at least 0.15% is necessary. However, a large amount of Si
Since the addition lowers the thermal conductivity, the heat dissipation of the piston ring decreases, and the temperature rise of the Al-Si-based aluminum alloy piston is promoted. Therefore, not only does the seizure resistance of the piston ring groove surface be impaired, but it also reacts with primary crystals or eutectic Si of the Al-Si-based aluminum alloy piston to cause sticking of the piston ring and cohesive wear of the piston ring groove. Therefore, the upper limit is set to 0.35%.

Mn is an element added as a deoxidizing agent at the time of producing an ingot. Note that Mn is added as an essential component because it is necessary to form a solid solution in Fe without oxidizing Si in order to exert the effect of Si with a small addition amount. However, addition of a large amount lowers hot workability, so that 0.6
0% was made the upper limit. Preferably, 0.4% or more of Mn is added.

When the above-described piston ring main body is used as a pressure ring, a chemical conversion coating is applied on at least the side surfaces, thereby suppressing initial adhesion with an Al-Si aluminum alloy. The chemical conversion treatment is performed by a phosphate chemical conversion treatment such as manganese phosphate, zinc phosphate, etc., to a thickness of 1 to 10
It is preferable to form a coating having a roughness of 2 to 5 μm. When the above-described piston ring body is used as the first pressure ring, it is preferable to apply a hard chrome plating film having excellent wear resistance to at least the outer peripheral sliding surface. The hard chromium plating film preferably has a thickness of 70 to 80 μm. Hereinafter, the present invention will be described in detail with reference to examples.

[0011]

EXAMPLES Example 1 The piston rings shown in Table 1 were manufactured and subjected to an actual machine test using an actual engine.

[0012]

[Table 1]

Table 1 shows the chemical components of the piston ring material used in this experiment, the hardness of the core, and the surface treatment.
Test material No. in the table. Nos. 1 to 3 are steels of the present invention, and the tempered state was a state in which quenching and tempering were performed after deformed drawing. Next, N
o. Nos. 4 to 6 are materials currently used as piston rings. 4 is Si-Cr steel (SWOSC-
V), No. 5 is spheroidal graphite cast iron (equivalent to FCD700),
No. Reference numeral 6 denotes flaky graphite cast iron (equivalent to FC250). Hard chrome plating applied to the outer peripheral sliding surface has a thickness of 70 to 80
It was a μm film. The zinc phosphate film applied to the side surface was a film having a thickness of 2 to 4 μm.

Using these materials, a 2nd ring of φ86 × 1.5 × 3.3 mm was manufactured by ordinary piston ring processing, and an actual engine test under the following conditions was performed. Engine test conditions and results are as described.

1. Engine test conditions Engine used Water-cooled 6-cylinder 2,500cc engine (piston ring
2nd ring: φ86 × 1.5 × 3.3) Piston: Piston made of Al—Si aluminum alloy (equivalent to AC8A) 6,000 rpm × 4/4 (load) × 100 hours This condition is 100 hours of test time. The inside is set so that the zinc phosphate film partially disappears and the piston ring base material and the piston contact and slide.

[0016]

[Table 2]

The following is clear from the engine test results. (1) Since the piston ring 1 of the present invention has a small amount of Si, it does not adhere to the piston groove, and the wear amount on the upper and lower surfaces of the ring and the wear amount of the Al piston groove are also small. However, since the amount of Si is small, the tension reduction rate is higher than that of the working material ring, but is 5% or less, which is not a practical problem. The wear of the outer peripheral sliding surface of the piston ring is small due to the effect of the hard chrome plating. (2) The piston rings 2 and 3 of the present invention had the same piston ring groove wear and adhesion as the piston ring 1 of the present invention. However, since the wear resistance of the base material was inferior to that of the hard chrome plating, the wear of the outer peripheral sliding surface of the piston ring was larger than that of the current material ring, but was 5.0 μm or less, and there was no practical problem. (3) Since the current piston ring materials 1 to 3 contain a large amount of Si, they adhere to the piston grooves, and the wear amount of the piston ring Al piston grooves increases. However, the current piston ring material 1 has a higher base metal hardness than 2 and 3, so the amount of wear on the upper and lower surfaces of the ring is small, and 2 has a lower thermal conductivity than 1 and 3, so that the amount of wear on the Al piston groove is smaller. In many cases, 3 has a lower base material hardness than 1.2, so that the amount of wear on the upper and lower surfaces of the ring is large. (4) Under the present test conditions, the wear amount of the upper and lower surfaces of the ring and the wear amount of the Al piston groove do not pose a practical problem if both are 5 μm or less. Therefore, only the piston ring of the present invention and the current piston ring material 3 are subjected to the test conditions. Applicable. However, the current piston ring materials 1 and 2 require some countermeasures against ring upper and lower surface wear and Al piston groove wear.

[0018]

According to the piston ring body of the present invention, the amount of Si is suppressed to be much smaller than in the prior art, so that the wear of the piston made of the aluminum alloy containing Si is reduced. Further, in order not to impair the function as a piston ring, the amount of carbon was determined in a hypoeutectoid or eutectoid range, and a minimum amount of Si was added. Therefore, the piston ring of the present invention is made of Al-Si
Extremely suitable for use in combination with a series aluminum composite piston.

Claims (3)

[Claims] 1. A piston ring mounted in a piston ring groove of a piston made of an Al—Si-based aluminum alloy, wherein the piston ring main body has a C content of 0.59 to 0.5% by weight.
0.76%, Si 0.15 to 0.35%, Mn 0.60
%, And a steel ring comprising the balance of Fe and unavoidable impurities. 2. The piston ring for an internal combustion engine according to claim 1, wherein the piston ring is a pressure ring in which a chemical conversion coating is applied to at least a side surface of the piston ring body. 3. The piston ring for an internal combustion engine according to claim 1, wherein said piston ring is a first pressure ring having a hard chromium plating film applied to at least an outer peripheral sliding surface of said piston ring main body.