JPH02217667A - Fiber-reinforced piston ring for internal combustion engine - Google Patents

Abstract

PURPOSE:To make a piston ring light in weight and with excellent high temp. strength by forming it from Al alloy matrix having a tensile strength at 300 deg.C over a specified value and ceramic fibers, whose fiber volume fraction shall be specified percentile, and thereby giving a specified value of tensile strength at 300 deg.C. CONSTITUTION:A piston ring is made of a composite material consisting of Al alloy matrix having a tensile strength at 300 deg.C over 10kg/mm<2> and ceramic fibers whose fiber volume fraction is between 3-25%, and it shall have a tensile strength at 300 deg.C over 20kg/mm<2>. This fiber-reinforced piston ring 1 is light, excellent in high temp. strength, and good in producibility with hot extrusion process etc.

Description

[Detailed description of the invention] A9 Purpose of the invention (1) Industrial application fields The present invention relates to a fiber-reinforced piston ring for internal combustion engines.

(2) Prior Art Conventionally, piston rings of this type have been made of iron-based materials such as cast iron, spring steel, and stainless steel (see, for example, "Piston Rings" published by Nikkan Kogyo Shimbun).

(3) Problems to be Solved by the Invention In recent years, internal combustion engines have tended to have higher rotation speeds and higher outputs, and correspondingly, piston rings are required to be lighter.

An example of a material that has a lower specific gravity than the iron-based material is an aluminum alloy, but currently the high-temperature strength of the aluminum alloy is low, so if the piston ring is constructed using that alloy, it will not be able to withstand high temperatures during engine operation. For example, at 200 to 300'C, the tensile strength of the piston ring decreases significantly, resulting in problems such as an increase in the amount of blow-by gas and oil consumption.

An object of the present invention is to provide a fiber-reinforced piston ring that is lightweight and has excellent high-temperature strength, which can solve the above problems.

B1 Structure of the invention (1) Means for solving the problem The present invention has a tensile strength of 10 kg/r at 300°C.
Consisting of an aluminum alloy matrix with a diameter of 3 to 25% and a ceramic fiber with a fiber volume ratio of 3 to 25%,
It is characterized by having a tensile strength at 00°C of 20 kg/+nm" or more.

(2) Function The fiber-reinforced piston ring made of the aluminum alloy matrix and ceramic fibers is lightweight and has excellent high-temperature strength, and also has good productivity through hot extrusion processing and the like.

However, if the tensile strength of the matrix at 300 "C" is less than 10 kg/mm, the strength of the piston ring itself cannot be improved even if ceramic fibers are combined.

Furthermore, if the fiber volume fraction (Vf) of the ceramic fiber is less than 3%, the high-temperature strength improvement effect cannot be obtained, while if it exceeds 25%, it is difficult to obtain a green compact by applying the powder metallurgy method. The moldability deteriorates, the processability also becomes poor, and the manufacturing cost increases.

Further, if the tensile strength of the piston ring at 300'C is less than 20 kg/m'', the high temperature strength decreases and the tension decreases, resulting in an increase in the amount of blow-by gas and oil consumption.

(3) Example 1. A fiber-reinforced piston ring 1 for an internal combustion engine shown in FIG. 2 is composed of an aluminum alloy matrix and ceramic fibers. As a matrix, 300'
J Is whose tensile strength in C is 11 kg/mouth 2
2024 (AI!, -Cu-based high-strength aluminum alloy) is used, and SiC whiskers are used as the ceramic fiber.

Next, an example of manufacturing the piston ring will be described.

(a) Using the molten aluminum alloy, a cooling rate of 102 to 106" (:/
Aluminum alloy powder was produced under conditions of sec.

b) The alloy powder was classified to obtain an alloy powder with an average diameter of 20 μm.

(C) Alloy powder and SiC whiskers were mixed by adding acetone as a solvent, and then the mixture was subjected to a drying treatment for 10 hours to remove acetone.

(d) Using the mixture, apply CIP (cold isostatic pressing method) under conditions of a pressing force of 4000 kg/cd and a pressing time of 1 minute to a diameter of 160 mm, a length of 200 mm, and a density of 85%. A powder was obtained.

(e) The green compact was heated to 500°C in an Ar gas atmosphere and hot extruded under conditions of an extrusion ratio of 10 or more to obtain a sintered bar with a diameter of 50 mm and a length of 1800 Ifil. Ta.

([) The sintered body is cut in a direction perpendicular to the extrusion direction to obtain a disc-shaped material, and the material is machined to produce a ring-shaped material having abutment 2 (Fig. 1). Obtained.

(g) A fiber-reinforced piston ring was obtained by performing finishing processing such as polishing on the ring-shaped material.

Table 1 shows the relationship between the fiber volume fraction of SiC whiskers and the tensile strength at 300''C for piston rings A1 to A4 obtained by the method using the matrix. Tensile strength at °C 8 kg/am2
JIS 6061 (/lMg-33 series corrosion-resistant aluminum alloy) is used.

Table I As is clear from Table 1, piston rings A2 and A are made of an aluminum alloy matrix with a tensile strength of 10 kg/7 or more at 300°C and a fiber volume percentage of 3 to 25%.
It is composed of SiC whiskers of 300
The tensile strength at 'C is 20 kg/mm2 or more.

Piston ring A4 has a high fiber volume percentage of SiC whiskers of 30%, which causes the above-mentioned problems. Furthermore, piston ring B has low tensile strength at high temperatures due to insufficient strength of the matrix.

FIG. 3 shows a piston ring A according to the present invention! And the results of an actual machine durability test when a comparative example piston ring is used as a top ring are shown. This test runs the engine at 6 rpm.
Blow-by gas Wk (f/1Ilin) during engine operation after 100 hours of continuous operation at 00Orpm
) was done by asking for. In addition, the air supply pressure P
Il was -500 mmHg.

In Fig. 3, line a indicates piston ring A2, and line a indicates aluminum alloy (AA standard A390) as a comparative example.
．． Tensile strength at 300℃ 11kg/ff111”)
Furthermore, the line C corresponds to the steel piston ring as a comparative example.

As is clear from the line a, in the case of the piston ring A2 according to the present invention, the amount of blow-by gas is small even in the high rotation range of the engine of 6000 rpm or more, as in the low rotation range. This is because the piston ring A2 is lightweight 1 and has high high temperature strength.

In the case of the steel piston ring shown by line C, the sealing performance deteriorates due to the inertia force in the high engine speed range, and the amount of blow-by gas increases.

In the case of the aluminum alloy piston ring shown by the line, the high-temperature strength is low, so the amount of blow-by gas increases as the engine speed increases.

FIG. 4 shows the behavior of the piston ring 10 in the top ring movement 4 of the piston 3, with FIG. 4(a) showing the compression process and FIG. 4(b) showing the explosion process. 5 is the inner peripheral surface of the cylinder bore of the cylinder block 6.

In this way, during the compression process, the piston ring 10 assumes a posture such that its center line X-X has a predetermined inclination with respect to the cylinder bore center line Y-Y, but during the explosion process, it is Piston ring 1° is its center 1x-x
The position is such that it approximately coincides with the cylinder bore center line Y-Y.

Since the piston ring 1° has a pair of end surfaces 1a1b facing the opposing inner surfaces 4a and 4b of the top ring groove 4, both end surfaces 1a are used in the explosion process.

One of the two lbs 1b on the crankcase side strongly abuts one opposing inner surface 4b. As this abutment is repeated, the end face 1b tends to be hit and worn, and a recess 7 is formed as shown in FIG. 4(C).

The piston ring 1 according to the present invention is manufactured using a disk-shaped material obtained by hot extrusion processing in the manufacturing process and cutting processing in a direction perpendicular to the extrusion direction, so that the piston ring 1 shown in FIG. As shown in FIG. 2, the aluminum alloy powder is elongated in the extrusion direction d, and the SiC whiskers are present at the grain boundaries, so that both end surfaces 1a1 facing the opposing inner surfaces 4a and 4b of the top ring groove 4 are formed.
In b, a substantially minute circular fiber group f made of SiC whiskers
, are dispersed innumerably, and on the sliding surface 1c that slides in contact with the cylinder bore inner circumferential surface 5, there are substantially minute oval fiber groups [2] made of SiC whiskers and whose longitudinal direction is oriented in the cylinder bore center line direction Y-Y. are scattered in countless numbers.

Therefore, since the fiber area ratio is high on both end faces 1a and Lb, the above-mentioned beating and wear is prevented, and on the other hand, on the sliding face 1c, the fiber area ratio is lower than that on the end faces 1a and lb, so the cylinder bore inner circumference Abrasion of the surface 5 is suppressed, and the abrasion resistance of the sliding surface 1c is also improved due to a predetermined fiber volume ratio.

In this case, if only the end face 1b on the crankcase side, where wear occurs due to beating, has a high fiber area ratio, the intended purpose can be achieved.

In addition, in the method for manufacturing the piston ring 1, the ring-shaped material may be subjected to hot forging at a heating temperature of 450° C. after the step (e). When this process is applied, in the piston ring 1, the fiber area ratio of both end surfaces 1a11b and the fiber area ratio of the sliding surface 1c change, and the fiber area ratio of both end surfaces 1a, lbO is higher than that of the sliding surface IC. There is a tendency to In this case, of both end surfaces 1a and lb, only the end surface lb on the crankcase side needs to have a high fiber area ratio.

The maximum diameter of precipitates and crystallized substances in the aluminum alloy matrix is preferably 50 μm or less.

In this case, if the maximum diameter exceeds 507/m, the strength of the piston ring will decrease and uniform quality will be hindered.

In addition, in order to improve the sliding properties, carbon particles, BN particles and MoS7 are added to the piston rings as solid lubricants.
At least one selected from particles is preferably contained in an amount of 0.5 to 10% by volume. In this case, if the solid lubricant content is less than 0.5% by volume, the lubricating effect will be small;
If it exceeds 10% by volume, the strength of the piston ring will decrease.

C1 Effects of the Invention According to the present invention, by using a specific aluminum alloy matrix and ceramic fibers as described above, fibers for internal combustion engines are produced which are lightweight, have excellent high-temperature strength, and have good productivity. Reinforced piston rings can be provided.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which Fig. 1 is a plan view of a fiber-reinforced piston ring, Fig. 2 is a sectional view taken along the line ■-n in Fig. 1,
Figure 3 is a graph showing the relationship between engine speed and blow-by gas amount, Figure 4 is an explanatory diagram showing the behavior of the piston ring during engine operation, and Figure 5 is an explanatory diagram showing the structure of the fiber-reinforced piston ring. be. DESCRIPTION OF SYMBOLS 1... Fiber reinforced piston ring, la, lb... End face, IC... Sliding surface, 3... Piston, 4... Top ring groove, 4a, 4b... Opposing inner surface, 5 ...
Cylinder bore inner peripheral surface, f...substantially minute circular fiber group,
f2...Substantially minute elliptical fiber group, Y-Y...Cylinder bore center line Figure 1. 5. Prison procedure amendment (llI4Q) Indication of the case of May 20, 1990 Patent application 1990. Name of invention No. 37940 Relationship to the case of a person who corrects fiber-reinforced piston rings for internal combustion engines Patent applicant

Claims (5)

[Claims] (1) Tensile strength at 300℃ is 10kg/mm^2
or more aluminum alloy matrix and fiber volume ratio 3
A fiber-reinforced piston ring for an internal combustion engine, comprising ~25% ceramic fiber and having a tensile strength at 300°C of 20 kg/mm^2 or more. (2) The maximum diameter of precipitates and crystallized substances in the aluminum alloy matrix is 50 μm or less,
1) Fiber-reinforced piston ring for internal combustion engines as described in item 1). (3) As a solid lubricant, at least one selected from carbon particles, BN particles, and MoS_2 particles is used as a solid lubricant.
．． The fiber-reinforced piston ring for an internal combustion engine according to item (1) or item (2), containing 5 to 10% by volume. (4) On the end surface of the piston that faces the opposing inner surface of the ring groove, countless substantially minute circular fiber groups made of the ceramic fibers are dispersed, and on the sliding surface that slides against the inner circumferential surface of the cylinder bore, the ceramic fibers are dispersed. The fiber for an internal combustion engine according to item (1), item (2), or item (3), wherein countless groups of substantially minute oval fibers are dispersed, the longitudinal direction of which is oriented toward the center line of the cylinder bore. Reinforced piston ring. (5) The (1), (2) or The fiber-reinforced piston ring for an internal combustion engine according to item (3).