JPH01253553A - Combination of cylinder sleeve and piston of internal combustion engine - Google Patents

Abstract

PURPOSE:To obtain an internal combustion engine excellent in durability by providing a cylinder sleeve made of a sintered aluminum alloy having specific composition excellent in heat resistance and wear and abrasion resistance and a piston made of aluminum alloy comprising the external peripheral surface of the skirt thereof coated with specific heat resistant resin. CONSTITUTION:The cylinder sleeve fittedly secured to the cylinder block of an internal combustion engine shall be made of a sintered aluminum alloy. This aluminum alloy is made by press-molding powder comprising aluminum alloy powder composed of primary Si whose grain diameter is 20mum or less, Si, Cu, Mg, and Fe compounded at a specific rate respectively, aluminum and inevitable impurity mixed with aluminum oxide powder of 1 through 5 weight % composed of spherical particles of 1 through 10mum in average particle diameter uniformly and then sintering or hot working it. On the other hand, the piston made of an aluminum alloy and fittedly secured to this sleeve is constituted with the external peripheral surface coated with heat resistant resin in which at least one kind of powder out of MoS2 powder, thermosetting fluorocarbon resin and others dispersedly added.

Description

[Detailed Description of the Invention] The present invention relates to a combination of a cylinder sleeve and a piston for an internal combustion engine, and particularly relates to a combination of a cylinder sleeve and a piston for an internal combustion engine, and particularly to a combination of a sintered AfJ with good heat resistance and wear resistance.
This relates to a combination of an alloy cylinder sleeve and an Al alloy piston whose outer peripheral surface is covered with heat-resistant resin.

The cylinder block of an internal combustion engine is the basic part of the Isoseki main body, and its lifespan determines the lifespan of the entire internal combustion engine.

Cylinder block is wear resistant.

This is often made of cast iron because it has good corrosion resistance, is easy to machine, and is inexpensive.
In recent years, in order to reduce the weight of the vehicle and improve thermal conductivity, those made of A, 11 alloy have also been adopted.

Cylinder blocks made of AfJ alloy include: (1) one in which a cast iron sleeve is fitted into the inner wall of the cylinder (e.g., Japanese Patent Application Laid-open No. 142352/1983), and (2) the entire cylinder block including the inner wall is made of He1 alloy. There is something that was done (
For example, Japanese Patent Application Laid-Open No. 61-14451q).

However, in the first type, which uses a cast iron sleeve, the sleeve facing the combustion chamber is made of cast iron, which has poor thermal conductivity. In addition, since the coefficient of thermal expansion of He-1 alloy is approximately twice that of cast iron, when the temperature rises, the relationship between the cast iron sleeve and the AfJ alloy cylinder block body surrounding it will deteriorate. There is a tendency for gaps to form between the two.

The second type of all-Δg alloy cylinder block has
In order to ensure the heat resistance and wear resistance of the cylinder inner wall portion, a K sleeve made of a high Si-containing Al alloy called Alsil is used, but it has the following drawbacks. ■First crystal S
The grain size of i is large (30 to 100 μTrL), and machinability after vj formation is poor. ■The distance between Si particles is large,
It is necessary to perform an edging treatment in order to expose the SL powder particles, which are hard particles, to the inner wall surface of the cylinder, which requires wear resistance. The hardness of 082 particles is not very large (HV
1200), the wear resistance is insufficient when a large load is applied. (2) In particular, when the humidity on the inner wall of the cylinder reaches 200°C to 300°C in J3 air-cooled engines, the hardness of the base material decreases rapidly and the wear resistance of the blades at high temperatures deteriorates. ■Also, general A, l! Regarding the alloy sleeve, in relation to the above item (2), hard Or plating, SiC dispersed N
Surface treatment such as lambda plating must be applied to impart wear resistance, which increases processing costs.

Based on the above, it is desired to develop an Al alloy material with excellent heat resistance and wear resistance that can be used as a cylinder sleeve material.

On the other hand, since the piston of an internal combustion engine thermally expands during operation of the engine, in anticipation of this expansion, a gap is provided between the piston and the inner wall of the cylinder to the extent that it can be maintained at room temperature. This gap is called piston clearance, and is expressed as the difference between the cylinder inner diameter and the piston maximum outer diameter. If the piston clearance is too small, seizure will occur between the inner walls of the cylinder, and if the piston clearance is too large, the compression pressure will drop.

This can cause blow pie, oil build-up, dilution (dilution of engine oil with gasoline), and can also cause piston slap.

The piston skirt, which is in contact with the inner wall of the cylinder, receives side thrust (side pressure) caused by the inclination of the connecting rod, and functions to maintain the correct linear motion of the piston.
Because of the piston clearance, the reciprocating piston impacts the cylinder wall when changing its direction of motion. This is piston slap. If the piston slap is severe, problems such as accelerated wear of the screw cylinder and ring name and increased engine oil consumption will occur, so the minimum piston clearance must be set to the extent that such phenomena do not occur. It won't happen.

However, since the △p alloy piston, which is suitable for Ua and high-speed rotation, has a large coefficient of thermal expansion, when used in combination with the inner wall of a cast iron cylinder, the piston clearance, especially at the top of the head, must be increased. Various improvements have been made to the shape of the skirt portion to keep the piston clearance small in the skirt portion where the temperature range is small.

In contrast, we adopted a Hep alloy piston, and the entire cylinder block, including the inner wall of the cylinder, was
) In an engine made of an alloy, it is possible to set a smaller piston clearance than in the combination of the above-mentioned He1 alloy and cast iron.

In this way, when using an Al alloy piston, special measures are taken to keep the piston clearance as small as possible, but in that case, care must be taken to prevent wear of the screws and skirts. . Particularly, in a cylinder using a sleeve made of a high S-containing AfJ alloy such as Alsil, problems such as "galling" and cracking are likely to occur at the skirt portion.

Conventionally, this problem has been dealt with by applying iron plating, heat-resistant resin coating, etc. to the outer peripheral surface of the skirt.

However, when iron plating is applied, there is a problem of wear of the AJ alloy sleeve, and there is also the drawback that the cost of the piston is high.

The present invention was devised against this technical background, and its main purpose is to reduce as much as possible the wear of the A1 alloy sleeve and the A9 alloy piston that comes into sliding contact with the A1 alloy sleeve. It is.

Another object of the present invention is to improve the wear characteristics of a heat-resistant resin coating, which can be coated at a lower cost than plating, and to apply the improved heat-resistant resin coating to a piston made of A1 alloy. By applying it to the outer periphery, the wear of the piston can be further reduced, and the cost of manufacturing the piston can be reduced.

This purpose is to increase the particle size of primary SL contained in the structure to 20u.
m or less, 5L11-30%, CU0.8-5%
, MO0.3 to 3.5%, Fe2 to 10% (all numbers are weight ω%), balance...8g and inevitable impurities, 1 alloy powder contains spherical particles with an average particle size of 1 to 10 μm. After compacting a mixed powder made by uniformly mixing 1 to 5 weight 1 B% of Al203 powder, the temperature was 400 to 550°C.
Sintered by sintering or hot working in '7 A, l)
A cylinder sleeve is formed with the alloy, and the outer periphery of the piston made of alloy 1 is covered with a heat-resistant resin in which at least one of M(+82 powder, polydetrafluoroethylene resin powder, boron nitride powder, and graphite powder) is added and dispersed. (by)

In cast products made of A1 alloy containing S= of many ω, such as Alsil, coarse primary crystals sL crystallize and the necessary strength cannot be obtained, so improvement treatment (for example, adding Na to the molten metal) ) to refine the primary crystal S layer. However, since there is a limit to its miniaturization effect,
The particle size of primary sL is suppressed to 20 μm or less by producing i-alloy powder with high SL content containing Fe exceeding the solid solubility limit by the atomizing method, and the compacted powder is hot-extruded to produce high-strength A method for obtaining a sintered AfJ alloy member has been proposed.

The cylinder sleeve made of A1 alloy of the present invention was obtained according to this method, but in order to further improve the wear resistance at room temperature and high temperature, AfJ203 made of spherical particles with an average particle size of 1 to 10 μm was used. Powder is added. AN
The amount of 20s powder added is 1 to 5 per 1 alloy powder to the raw stone.
% by weight is appropriate; if it is less than 1% by weight, the effect of improving wear resistance will not be achieved, and if it exceeds 5% by weight, the effect on the mating sliding member will be large, and as the amount added increases, the compacted product will not improve. Hot workability decreases. In addition, the reason why spherical He1203 particles are used is to alleviate the aggressiveness of AfJzOs, whose hardness reaches Hv2500, and the reason why the particle size is set to 1 to 10 μm is that if the particle size is less than 1 μm, the raw material Aj20s In addition to poor handling of the powder, the necessary wear resistance is difficult to achieve.If the diameter exceeds 10 μm, the machinability of the fired crystal deteriorates, and particles tend to fall off from the alloy matrix, causing damage to the sliding surface of itself and its counterpart. This is because this results in accelerated wear of the piston, which is a member.

In addition to Aj) 203 powder, SL powder particles and other hard ceramic powders (eg, SLC) are also used.

Szs N4) can also be used, but its wear resistance (wear resistance of baked crystals) is slightly inferior to that when AN 20s powder is used. AJ) It is also effective to use powder of lubricating materials such as graphite, boride, sulfide, etc. together with 20ss ceramic powder, and in addition to dispersing hard ceramic particles in the sintered material, particles of lubricating + i material are also dispersed. The wear resistance can be improved by imparting self-lubricating properties. Also, in some cases, even if only a lubricating material powder is used without using ceramic powder, the self-lubricating properties of the sintered material may cause the sintered material to withstand 1? Improved wear resistance can be measured.

The reason for limiting the composition of the He1 alloy powder and the particle size of the primary crystal S= is as follows.

(1) Si (11 to 30,000 m%)...Si contributes to improving the wear resistance and Young's modulus of the fired crystal, suppresses the coefficient of thermal expansion, and can improve the thermal conductivity. However, S^bay m
If it is less than 11% by weight, the wear resistance and strength will be poor, and if it exceeds 30% by weight, the formability during hot extrusion or hot forging will be poor and the product will be prone to cracking.

In addition, to make the primary crystal SL powder particle size 20 μm or less,
If the grain size exceeds 20 μm, the machinability of the sintered crystal deteriorates, and it is likely to break due to large concentrated loads due to sliding contact with the piston, which is a mating moving member, and the crystal will fall off due to the breakage.
This is because one particle accelerates the wear of itself and the piston. For particles with a diameter of 20 μm or less, the molten AJ gold alloy is made to flow out from the pores, and an inert gas is injected into it using an atomization method, or a centrifugal spray method, etc., at a cooling rate of 102 to 10'C/sec from the molten state. Obtainable. Such a high cooling rate cannot be obtained when the sliding member (cylinder sleeve) is formed by a melting method.

(2) Cu (0.8~51ff1%>-CU is effective for strengthening the matrix by heat treatment. However, 0.
．． If it is less than 8% by weight, there is no effect of addition, and if it exceeds 5% by weight, hot workability decreases and the resistance to corrosion cracking properties deteriorates.

(3) Mg (0.3 to 3.5% by weight) - Like Cu, Mg is effective in strengthening the matrix by heat treatment.

However, if it is less than 0.3%, there is no addition effect, and 3.5%
If it exceeds ω%, hot workability decreases and the resistance to corrosion and cracking properties deteriorates.

(4) Fe (2-10 %)...Add FC to 4f
In this case, the hardness of the alloy is at a temperature of 200°C as shown in Figure 1.
It decreases rapidly when heated from ℃ to 300℃. On the other hand, 2
Such a rapid decrease in sand-sliding is not observed in the Hel alloy containing ~10 wt% FC. The amount of Fe added is preferably 2 to 10% by weight; if it is less than 2% by weight, no improvement in the high temperature strength of the fired crystal can be expected, and if it exceeds 10% by weight, high-speed hot working becomes impossible.

On the other hand, examples of heat-resistant resins applicable to Al alloy bis-bonds include polyimide resins and polyamide resins.

Polyimide amide resin (or polyamideimide resin)
is suitable. If a powder with good lubricity, such as Me 82 powder, polytetrafluoroethylene resin powder, Ta nitride powder, or graphite powder, is added to such heat-resistant resin, the wear resistance of the resin coating will be improved.

The upper limit of addition J when Mll 32 powder, polytetrafluoroethylene resin powder, boron nitride powder, and graphite powder are added alone is as follows based on the difference in their specific gravity.

The preferred thickness of the resin coating is 2 to 50 μm. Film thickness is 2
If it is less than μm, the adhesion to the piston skirt surface will be poor and the base material may be exposed, resulting in 50/
If the length exceeds 1 m, no improvement in sliding properties (seizure resistance, wear resistance) is observed.

Note that when a chemical conversion film is formed on the surface of the piston as a coating base layer for the resin film, the density of the resin film is improved. 1
As a chemical conversion coating treatment method for 1 alloy, ■Chromium! Using a mixture of salt and an alkali such as sodium carbonate, at a temperature of 70
MBV method, which is treated at ~100°C; ■ Allodein method, which uses a mixture of phosphoric acid, chromic acid, and fluoride (Atod
In particular, the coating obtained by the MBV method has a roughened surface to a certain extent, so that the resin coating has good texture.

Figure 2 shows a water-cooled motorcycle engine 1 as a side view with main parts cut away. The engine 1 employs a double overhead camshaft type valve mechanism, and a piston 4 (eg, made of JIS ACgA material) connected to a crank @8 is fitted into a cylinder 2.

The inner wall portion of the cylinder 2 is made of Δg alloy (e.g., JISADC
It is formed of a cylinder sleeve 3 that is integrated into a cylinder block body made of 12 materials by casting. and,
The outer peripheral surface of the skirt 5 of the piston 4 fitted into the cylinder sleeve 3 is covered with a polyimide amide resin coating 6 (FIG. 3).

MQ32 particles 7 are added and dispersed in the polyimide amide resin coating 6, and the polyimide amide resin coating 6 is made by mixing a polyimide amide resin and M a S 2 powder in hexadimethylpyrrolidone as a solvent. Spray on the outer peripheral surface of the skirt 5 (temperature 190
It is formed by applying heat baking treatment for 2 hours and 30 minutes at °C.

The cylinder sleeve 3 made of sintered crystal is manufactured as follows.

■YJ production of 1 alloy powder to original PI...Atomization method using inert gas by melting A1 alloy of specified composition.

Cooling rate 102-1 by centrifugal spray method, roll quenching method, etc.
Powder with a particle size of less than 105 μm is produced under conditions of 0.06° C.

■Powder mixing...AIJ alloy powder with an average particle size of 1 to 10
1 to 5% by weight of Al203 powder consisting of μm spherical particles is added and mixed uniformly.

■Powder compacting...The obtained powder is pressed to a pressure of 4.000 by the cold isostatic press method (CIP method) at 9f/cti.
The powder is compacted to obtain a cylindrical powder compact as a material for extrusion processing.

■Hot extrusion processing (sintering): Hot extrusion processing is performed on the extrusion processing material, which is a powder compact, at 4Ji 450°C to obtain the cylinder sleeve 3. Note that, in consideration of preventing oxidation of the molded product, it is preferable to perform hot extrusion processing in a non-oxidizing atmosphere.

The thus obtained cylinder sleeve 3 has good abrasion resistance and heat resistance, and the piston skirt 5, which is the mating sliding member, has a polyimide amide resin coating 6 on its outer peripheral surface. Therefore, excellent durability can be achieved by applying a surface treatment such as hard Cr plating to the sliding surface of the cylinder sleeve 3. Moreover, since the cylinder sleeve 3 has an initial normal temperature hardness even after being heated to a temperature of 200° C. to 300° C. (when returning to normal temperature), it can also be used for air-cooled engines. Furthermore, the cylinder sleeve 3 in which AfJ20s particles are dispersed has a characteristic that its hardness does not decrease even when it receives heat during integration with the cylinder block body by casting, and has a great practical effect.

On the other hand, the outer circumferential surface of the skirt of the piston 4, which is in sliding contact with the cylinder sleeve 3, is coated with M o S 2 particles 7 that provide lubricity.
A polyimide amide resin coating 6 is applied, which prevents the piston 4 from seizing and has good durability.

In manufacturing J3, cylinder sleeve 3, Af
0.5 to 5% by weight of a lubricating material (graphite, boride, sulfide, etc.) powder may be blended with the hep alloy powder together with the JzOs powder, in which case the cylinder/sleeve 3 will have self-lubricating properties. Therefore, it exhibits excellent seizure resistance in sliding contact with the piston 4 whose skirt 5 is covered with the polyimide amide resin coating 6 in which MoS2082 particles are dispersed.

As is clear from the above description, in the combination of the cylinder sleeve and piston of the internal combustion engine according to the present invention, the A1 alloy that is the base material of the cylinder sleeve has excellent wear resistance and heat resistance. In addition, it has high hardness AJ in the base material.
Because the zOs particles are dispersed, the cylinder sleeve exhibits excellent wear resistance in the temperature range from room temperature to high temperature without applying surface treatment such as hard Cr plating to the sliding surface.
The piston made of Alloy 1, whose outer periphery is covered with heat-resistant resin in which lubricating powder such as OS2 powder is dispersed, is also compatible with the fact that the highly hard Aj) 20s particles contained in the cylinder sleeve are spherical and less aggressive to the opponent.迟, burn-in, rf,
It is hard to wear and has good durability. Furthermore, the cost of coating the piston with a heat-resistant resin is lower than that of plating the piston, resulting in cost reduction.

[Brief explanation of the drawing]

Fig. 1 is a graph showing changes in hardness due to temperature of Alsil-based AJI alloy; Fig. 2 is a cutaway side view of main parts showing a water-cooled motorcycle engine employing a combination of a cylinder sleeve and a piston according to an example of the present invention; FIG. 3 is an enlarged view of the skirt portion of the piston. 1... Engine, 2... Cylinder, 3... Cylinder sleeve, 4... Piston, 5... Skirt, 6
... Polyimide amide resin coating, 7... MO32 particles, 8... Crank book. Representative: Patent attorney Nozomu Ehara, 3 other authors, Figure 1 Temperature ("C) Figure 2 Figure 3 Procedural amendments June 1, 1988 Director General of the Patent Office Kunio Ogawa 1, $ display 1988 Year Patent Application No. 78252 3 Relationship with the case of the person making the amendment Patent applicant 4, agent 8 Contents of the amendment (1) The scope of the patent claims is amended as shown in the attached sheet. (2) Page 8 The description in the 5th to 9th lines is “Temperature 400”
C・~550℃...Polytetrafluoroethylene resin powder,'' is corrected as follows. ``Cylinder sleeve is formed by sintering A1 alloy obtained by hot working by sintering at a predetermined temperature, MO32 powder, thermosetting fluororesin powder,'' Claims (1) In the structure The particle size of the initial product SL contained is 20 μm or less, 5L is 11 to 30%, and CuO is 8 to 5%. AN 20s powder 1 consisting of spherical particles with an average particle size of 1 to 10 μm in A1 alloy powder with a composition of 0.3 to 3.5% Mg, 2 to 10% Fe (all numbers are weight %), and the balance...Al and inevitable impurities. A cylinder sleeve formed of 0 metal-containing material is formed by compacting a mixed powder in which ~5% by weight is uniformly mixed, and then sintering it in a blood molding plate or hot working to sinter the powder to 1''7. A made by coating the outer peripheral surface with a heat-resistant resin in which at least one of the following powders is added and dispersed: 1m nitride powder, and graphite powder.
Combination of internal combustion 1m cylinder sleeve and piston, consisting of a 1-alloy piston. (2) The combination of a cylinder sleeve and a piston for an internal combustion engine as set forth in claim 1, wherein 0.5 to 5% by weight of graphite powder is mixed in the mixed powder. (3) The combination of a cylinder sleeve and a piston for an internal combustion engine according to claim 1, wherein the heat-resistant resin is a polyimide resin, a polyamide resin, or a polyimide amide resin.

Claims (3)

[Claims] (1) The particle size of primary Si contained in the structure is 20 μm or less, with Si 11-30%, Cu 0.8-5%, Mg
Al with a composition of 0.3 to 3.5%, Fe2 to 10% (all numbers are weight %), and the balance...Al and inevitable impurities.
A consisting of spherical particles with an average particle size of 1 to 10 μm in alloy powder
A cylinder sleeve formed of a sintered Al alloy obtained by sintering or hot working at a temperature of 400°C to 550°C after compacting a mixed powder in which 1 to 5% by weight of l_2O_3 powder is uniformly mixed, and MoS_2 It is composed of an Al alloy piston whose outer peripheral surface is coated with a heat-resistant resin in which at least one of powder, polytetrafluoroethylene resin powder, boron nitride powder, and graphite powder is added and dispersed. Combination of cylinder sleeve and piston for internal combustion engines. (2) The combination of a cylinder sleeve and a piston for an internal combustion engine as set forth in claim 1, wherein 0.5 to 5% by weight of graphite powder is mixed in the mixed powder. (3) The combination of a cylinder sleeve and a piston for an internal combustion engine according to claim 1, wherein the heat-resistant resin is a polyimide resin, a polyamide resin, or a polyimide amide resin.