JPS6047849A - Piston for internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent the generation of stick of rings by a method wherein the wall surface sections of piston ring grooves on the piston of aluminum alloy are strengthened by compounding with short fibers of alumina while the piston rings, fitted into these grooves, are made of martensite series stainless steel. CONSTITUTION:The piston main body 1 of aluminum alloy is provided on the outer peripheral surface 2 of the side section thereof with two ring grooves 7, 8, receiving the compression rings 5, 6, for preventing combustion gas from leaking into the side of crank chamber through a clearance between the piston main body 1 and the wall surface 4 of cylinder bore, and another ring groove 10, receiving an oil ring 9 for scraping down excessive oil. In this case, a part 13, from the head section 11 to the lower part of the lower wall 12 of the top ring groove 7 along the outer peripheral surface 2 of the side wall of the piston, is strengthened by compounding with the short fibers of alumina consisting of 80wt% or more of alumina and the balance of silica. On the other hand, the top ring 5 is made of martensite series stainless steel containing 0.55wt% or more of carbon.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to internal combustion engines, and more particularly to pistons thereof.

A piston of an internal combustion engine has a screw body that cooperates with a cylinder and a cylinder head to define a combustion chamber, and a plurality of piston rings fitted into piston ring grooves of the piston body. The piston body is generally made of aluminum alloy due to the need for weight reduction, and the piston ring is required to have excellent wear resistance, so special cast iron or spherical black '14 for piston rings is generally used. ) It is constructed of cast iron such as T7J iron.

With the recent increase in the output of internal combustion engines, pistons are being exposed to increasingly harsh conditions.
In order to improve the heat resistance and wear resistance of the screws, a part of the piston body, the side outer circumferential surface of the head part and the piston ring groove, which are subject to the severest heat load and are prone to wear, are Attempts have been made to compositely strengthen the wall surface of (1-Tubling!M) using reinforcement materials, and to reduce the cost to 1 and improve durability, the piston ring (compression ring) is made of steel. It has been attempted to do so. In this case, alumina 'JfiNu Iff, which has excellent adhesion to aluminum alloys and stability at high temperatures, is generally used as the reinforcement material.
The silling component material has heat resistance, abrasion resistance, and cost performance.
・5i-Cr steel is generally used.

However, when using a combination of a piston body whose wall surface of the piston cylinder groove is made of an aluminum alloy composite reinforced with alumina short fibers and a piston cylinder made of Si-crfJj4, internal combustion engines are particularly susceptible to harsh conditions. When operated under certain conditions (cooling water temperature of 100°C or higher, oil temperature of 130°C or higher), the so-called "ring" that adheres to the lower wall of the piston ring or piston cylinder groove (the wall on the opposite side of the cylinder head) Sticking may occur, and as a result, the function of the screw 1 ring may not be fully demonstrated, resulting in problems such as an increase in 70-by gas, a decrease in engine performance, and an increase in oil consumption. As a result of X-ray analysis, it was confirmed that aluminum alloy was attached to the bottom surface of the piston ring that caused the ring stick. Since the piston ring groove is strongly pressed against the lower surface of the piston ring groove by the high-pressure gas and heated to a high temperature, it is presumed that the joint plowing action of these causes the ring stick.

The inventors of the present application have developed a piston body 3i as a piston for an internal combustion engine, in which the wall surface of the piston ring groove is made of an aluminum alloy compositely reinforced with alumina short fibers 1.
- When used in combination with a piston ring made of Cr steel (in view of the various problems mentioned above,
Piston rings are made of various carbon steels and special steels, and the piston body is made of an aluminum alloy whose wall surface of the piston ring groove is compositely reinforced with alumina short fibers. i7] As a result of performing Kabuto,
It has been found that if the piston cylinder is made of Martenzium 1 stainless steel, especially Martenzium 1 to 100% stainless steel containing carbon of 1jj or more, ring stick can be prevented from occurring.

The present invention is based on the knowledge obtained as a result of various experimental studies conducted by the inventors of the present invention, and makes it possible to use an internal combustion engine in a normal operating state for a long period of time without causing ring stick. The purpose is to provide pistons that

According to the present invention, a piston for an internal combustion engine is provided, which is made of an aluminum alloy, and the wall surface of the piston ring groove is made of composite alumina short fibers consisting of 80 wt% or more of fluorumina and the balance of silica. This is achieved by a piston for an internal combustion engine having a reinforced piston body and a piston ring made of mardenzite stainless steel with a carbon content of 055 wt% or more and inserted into the piston ring groove.

According to the present invention, the heat resistance and abrasion resistance of the piston are improved by compositely reinforcing the wall surface of the piston ring groove with alumina short fibers, and the piston ring is made of martensitic stainless steel. As a result, its wear resistance is improved, so the durability of the piston can be improved, and although the reason is not clear, it is possible to reliably prevent the occurrence of ring stick due to adhesion of aluminum alloy. This makes it possible to use the internal combustion engine under normal operating conditions.

According to the results of experimental studies conducted by the inventors of the present application, when the bulk density of alumina short fibers is 0.08 g/cc or less, regardless of the fiber length or fiber diameter of the alumina short fibers, Heat resistance of the piston body - sufficiently improved wear resistance of the piston ring groove wall surface 1! Moreover, even if the bulk density of the alumina short fibers was increased to 0.3 a/ccu, the wear resistance of the bisto-silling full-walled surface did not improve much. 3 a/c
If it is higher than c, the amount of wear on the piston ring as a mating material will be small. d is large, and furthermore, the thermal expansion coefficient of aluminum alloy and aluminum alloy is 7. It has been confirmed that thermal fatigue cracks may occur at the boundary between the composite reinforced part and the non-composite reinforced part in G8 wire. Therefore, according to one detailed feature of the present invention, the bulk density of the alumina short fibers is 0.08 to 0.341/CC, preferably 0°0
It is set at 8 to 0.25 a/cc.

Furthermore, when producing short alumina fibers, the production method inevitably generates so-called non-fibrous particles that cannot completely take the form of fiber shoulder 1, and these non-fibrous particles are extremely hard < (Hv
<25 (1>=700 or more), and its size is extremely large, several tens to hundreds of microns, compared to fibers with a diameter of several microns. If the above non-fibrous particles are contained in a relatively large amount, it is extremely difficult to machine the piston ring groove, and the wear of the piston ring from other mating parts may increase. Furthermore, it has been experimentally confirmed that non-fibrous particles falling from the wax 71 may cause abnormal wear such as snobbing on the lower surface of the piston ring. According to one detailed feature, the amount of non-fibrous particles with a particle size of 150 μm or more contained in the alumina mechanical string aggregate used for composite reinforcement of the piston body is suppressed to 7 wt % or less.

In general, alumina has various crystal structures, and among these, alpha alumina is known to have the most stable structure and to have high hardness and elastic modulus.

For example, aluminum 9 is commercially available as a heat-resistant material. i74
In terms of heat resistance and dimensional stability, JA fibers have α-alumina content (α to heavy HH of total alumina in short alumina fibers).
In many cases, the weight ratio of alumina is (3Qwt% or more).From the properties of α-alumina and the alumina short fibers containing α-alumina, it is found that the alumina short fibers containing α-alumina are used in aluminum alloys. When a composite part is reinforced, the higher the α-alumina content, the better the mechanical strength and wear resistance of the composite part, but the wear of the mating part increases and the workability decreases. However, according to the results of experimental research conducted by the inventors of the present invention, contrary to the above expectations, the α-alumina content is 5 to 3 Qwt%, preferably 10 to 50 wt%.
%, it was found that the wear resistance and workability of the composite part could be improved by 1-1, and the wear of the mating member could be reduced. According to yet another detailed feature of the invention, therefore, the α-alumina content of the short alumina fibers is selected within the above-mentioned range.

Also, according to the results of experimental research conducted by the inventors of the present application,
If the piston ring is made of martensitic stainless steel, the occurrence of ring stick can be avoided, but even among martensitic stainless steels, the carbon content (■) is preferably 0.55 wt% or more, +J: 0,
It has been confirmed that ring stick cannot be effectively prevented unless the stainless steel contains 60 wt% or more of martensai-1. In addition, as the carbon content increases, carbon and chromium combine to form carbides, which corresponds to (). Furthermore, as the carbon content increases, the stainless steel becomes too hard, making it easy for the piston ring to break when it is assembled into the piston body (
turn into.

Therefore, according to yet another detailed feature of the invention, the martensitic stainless steel constituting the piston ring has a carbon content of 0.55 to 1.2 wt%, preferably 0.
．． j9 is set at 60 to 0.85 wt%. JIS is a martensitic stainless steel that meets these requirements.
Standards include SUS/120J2 (carbon content increased to the above range), 5US4.40B, 5US440Δ (carbon content increased to the above range), etc. In addition, piston rings made of these martensitic stainless steels have a fine martensitic base and a hardness of 1-1v (1kg) = 3 B O
~450 How hard is the heat treatment of quenching and tempering?
I! It is used after being i.

EXAMPLES Below, the present invention will be described in detail with reference to examples in connection with the results of various experimental studies conducted by the inventors of the present E1.

The wall surface of the piston ring vortex is made by combining the piston body made of aluminum alloy, which is compositely reinforced with aluminum small and short fiber version 1, and the piston ring made of 1j1tJ of various steels. When the Del-Zel engine was tested, it was found that if the piston ring was made of martensitic stainless steel (r4), ring stick may occur. Among them, it was recognized that ring stick occurs in some cases and not in others depending on the carbon content, so the first cylindrical test was carried out using various martensitic stainless steels with different carbon contents. This and a second cylindrical test piece containing aluminum reinforced with alumina short fibers were transferred to van der Borch 1 in a thickness abrasion tester and adhered. A mock test was conducted to see if this would occur.

J, the outer diameter lQmm of various martenzai 1-stainless steels shown in Table 1 below (however, AI is 5i-Crrll, which is a comparative example that has been used conventionally).
, a cylinder with a length of 15 mm is formed, and the cylinder is 105 mm long.
The first cylindrical specimen was heated to 0°C for 40 minutes, then quenched in air, then heated to 480 to 520°C for 2 hours, and tempered by water cooling. Created.

In addition, the average fiber diameter is 3.1μ, and the α-alumina content is 30wt%.
Alumina short fibers (95.5 wt% Al 20a, 4.
5wt%S! 02) with a bulk density of 0°15M
A cylindrical body with an outer diameter of 86111111, an inner diameter of 53 mm, and a width of 10Qnln+ was molded using silica as an inorganic binder. In this case, alumina 9. ii
The LIJ fl aggregate is treated so that the total amount of non-fibrous particles with a particle size of 150 μm or more is 0.8 wt%, and the alumina short fibers are Oriented in a dimensionally random manner. Next, the thus formed shoulder [after preheating the molded body to 600°C,
Placed in a mold (humidity: 270°C) of a high-pressure casting machine, pour molten aluminum alloy (JIS standard △C8A) (temperature: 750°C) into the mold, and pour the 8 molten metal at 1000 J/cm using a plunger. The molten metal was pressurized at 1f no. A second cylindrical test piece with an outer diameter of 83 mm and a length of 100 mm was created by taking out the solidified ff2 GA (inner cone-shaped solidified body and subjecting the solidified body to geometric machining). Then, the test piece was subjected to T7 heat treatment.

Next, the first and second cylindrical test pieces prepared as described above were set in a Fantairbolft friction testing machine so that their tl'ill lines were perpendicular to each other, and the first cylindrical test piece was 3.7'5k to the side of the second cylindrical specimen
Press with a pressing force of ( ), and apply room temperature il to the contact area.
'il sliding (guit twist motor Aile 5 W-30
An adhesion test was conducted in which a second cylindrical test piece was rotated for 20 minutes at a circumference of 1 degree Q and a speed of 9 m/Sec while supplying the same amount of water. The test results are shown in column 1 of Table 1 below.
“Development” refers to the appearance of the second cylindrical specimen, which is the pre-adhesion stage.
- This means that a phenomenon occurred in which aluminum in the matrix was transferred to the surface of the first cylindrical test piece.

II':::' in the specification (1'4'+7 unchanged)
In addition, (the wall surface of the tubling vortex is compositely reinforced by alumina The pistons were successively installed in a Deville engine and an adhesion test was conducted using an actual machine.

First, using the same alumina short fiber aggregate as the alumina short fiber aggregate used in the preparation of the second cylindrical test piece for the agglomerate test using the test piece described above, 1IIt was prepared using silica as a ta-based binder. Outer diameter 95mm, inner diameter 75Il+n
+, A circular 1+St-shaped fiber molded body with a height of 21 mm was created. In this case, the total amount of non-fibrous particles with a particle size of 150μ or more contained in one aggregate of alumina short fibers is Q, 8wt.
%, and the alumina short fibers were oriented in a substantially two-dimensional random pattern parallel to the cylindrical outer peripheral surface of the fiber molded body. Next, the fiber molded body was heated to 60. ．． After preheating to 0°C, it is placed in a mold (temperature 270'C) of a high-pressure casting machine, and a 71-rix metal of aluminum alloy (JIS standard AC8△) is placed in the TL mold. Easy temperature 7
50°C) and melted at 100°C with a plunger.
By pressurizing to a pressure of 0 k(+/'Lllll', melting is prevented from penetrating between the individual Flumina 9.n 05 dark blue,
The pressurized state of (a) is completely controlled by the stone height); after the fibers are pulsated until it hardens, the solidified body is taken out from the caster 511 and the solidified body is removed from the solidified body. - Composite reinforced with short fibers, lζ aluminum alloy J, outer diameter 93n1...
A cylindrical body with an inner diameter of 75 mm and a height of 2 ln1 m was cut out by machining. The cylindrical body is then placed in a piston casting mold, and an aluminum alloy (
△〉 to JIS standard 8C? 8. After pouring moisture (humidity measurement: 750°C) to form the piston body element (A), heat treating the piston body at T7, and then forming piston rings fl+'+ etc. by machining. and diameter 90Il+
A piston body with a length of 99 mm was formed. Furthermore, screws
Distance from the head to the bottom wall of the 1-tubing groove 61 (
is 18.5 mm, the minimum intermediate length of 1 to top ring iM is 2111 m, and the depth of the top ring groove is 4.5 mm.
mn+, and the inclination angle of the two walls of 1 to 7 degrees (1 to 7 degrees).

In addition, the outer diameter is 90 mm with Marten Rei 1~ series stainless steel A2~80 and 3i-Cr steel AI shown in Table 1.
, to form a C-shaped 1-Tublink cable moon with an inner diameter of 82.6 mm+, a maximum thickness of 2.2 mm, and an inclination angle of 7° on the upper surface, and after heating the moon to 1050'C for 20 to 30 seconds, it was placed in air. quenched and quenched, then heated to 580'C for 20~3
Tempering treatment (S
A half-geese stone was formed.

Fig. 1 is a partially cutaway perspective view of the piston shown in Fig. 1 is a partial vertical cross-sectional view showing an enlarged main part. In these figures, 1 indicates a piston body, and combustion gas is disposed on a side outer circumferential surface 2 of the body between the piston body 1 and the cylinder. Two ring grooves 7 and 8 that receive the combustion ring 5, and an oil ring that scrapes off excess oil In the illustrated embodiment, a ring groove 10 is formed in the side outer circumferential surface 2 from a part 11 of the spatula 1 to 1 below the lower wall 12 of the ring groove 7: That part is alumina'1.i78M
Compositely strengthened in navy blue. The composite reinforcing portion 13 defines the wall surface of the 1-twisting groove 7 that receives the 1-twisting ring 5, and also includes a top land 14 and a U-cantolan l'' at the portion where the side outer circumferential surface 2 is exposed. Note that the second ring 0 is made of cast iron for the piston link 1':i'jA, which has been conventionally used as a material for forming the piston link 4M.

The above-mentioned knowledge 414 is made and the Ic piston is sequentially moved to D L'
Tests: E (i
An adhesion test was conducted using an actual machine.

Table 2 Types used: 4-cylinder 4 cycle diesel (opening shilling bore diameter: 90 old 1st stroke: 86nv compression ratio + 21.5 total tillage: 218ε) CC fuel rating used: light oil engine rotation 1! 1: 4400 rpm Engine load: Full load Cooling water temperature: 105°C Test time: 50 hours The results of this adhesion test are shown in column (■) of Table 1.

In column (2) of Table 1, "occurrence" indicates that the top ring 5 stuck to the lower wall 12 of the top ring groove 7 and a ring stick f occurred.

From Columns I and ■ of Table 1, it is preferable to use martenleaitic stainless steel with a carbon content of 0.55 wt% or more, preferably 0.60 wt% or more, as the top ring material (47"). I understand.

In addition, the bulk density of alumina short fiber is 0.11! +/cc,
0. 21 (+/CC, 0, 26(]/CC) Adhesion test using test pieces and actual equipment conducted under the same conditions as each test in 71L above, except for the points modified to +/CC, 0, 26 (]/CC, average fiber diameter 3 as reinforcing fibers) Alumina short fiber Mt (95wt%A + 203.5wt%Si
Adhesion tests-1 and 7 on test pieces and actual equipment conducted under the same conditions as the above tests except that ○2) was used.
1~Rix metal JIS standard AC8P, AC4
, 0 was used in the test piece and practical adhesion tests conducted under the same conditions as the above-mentioned tests, the same results as those shown in Table 1 were obtained. ! '7.

As a result of the adhesion test using the above-mentioned test piece and actual machine, regardless of the specifications of J, Su, Alumina πj m Ift, the top ring constituent material was 0.55 wt% of carbon steel, and furthermore, Q, 60 wt%. % or more of martenyl-1-based stainless steel is preferred]. Therefore, cylindrical specimens were formed from martenzyl-based stainless steel that met the above requirements, and test specimens with various α-alumina contents were formed using martenzyl-based stainless steel that met the above requirements. Block specimens were formed from a composite reinforced aluminum alloy with alumina shortness id liF, and these test specimens were sequentially placed in a Van der Borft friction and wear tester to test the bottom surface of the top link and the bottom surface of the top link. A wear test was conducted to find out what range of α-alumina content of short alumina fibers is appropriate in order to minimize the wear m on the lower wall of Tubbling 1lrls.

First, a cylindrical body with an outer diameter of 35 nv, an inner diameter of 31 mm, and a length of 8.7 mm was formed from martenzite stainless steel △6 shown in Table 1 for final lifting, and the cylindrical body was subjected to the adhesion test using the test piece described above. A cylindrical test piece was prepared by performing the same heat treatment.

In addition, the α-alumina content is 2WL%, 8wt%, respectively.
2Qwt%, 34wt%, 43wt%, 61wt%,
61wt%, 93wt% average fiber shoulder [diameter 3.1μ]
1 2 03, 4.

Each aggregate of 5wt%Si○2) has a bulk density of 0.15(]
/QC, a rectangular parallelepiped of E'S OX 80 x 20 mm was molded using silica as an inorganic binder. In this case, the alumina short fiber aggregate was treated so that the total amount of non-fibrous particles with a particle size of 150μ or more contained therein was 0.6 wt%, and the alumina short fibers were oriented in a two-dimensional random manner along a plane of 80 x 80 mm. Ta. Next, the thus formed fiber shoulders (after preheating the molded body to 600°C,
The molten metal is placed in a mold (crystallinity 270°C) of a high-pressure casting device, and the molten metal is poured into the mold with an easily melted aluminum alloy (JIS standard 80) (d1^750°C). To Blancito”, 1000k! Due to the pressure of I/ω)■
Press the molten metal to +t1. The pressurized state was maintained at C until the molten metal was completely solidified. 10. After the molten metal has completely solidified, the solidified body is taken out from the mold, and a part made of aluminum 1X alloy reinforced with alumina short fibers is taken out for machine processing.10. 16X 15.7X6.35mm (7/
Lz Me J - short fibers are flat 1 curvature two-dimensional random orientation on a 15.7 x 6.35 mm surface) block test piece r3I ~
Create r3B and paste each block test piece.
' 7 heat treatment was performed.

Next, the cylindrical test piece and the block test piece prepared as in J-E above were sequentially put into a 1-FW friction and wear tester, the cylindrical test piece was brought into contact with the block test piece, and the contact area was heated at room temperature. Jun) 11 draw castle U-ta oil 5 W-
30> while applying a contact surface pressure of 20 k(+/m
A wear test was conducted in which the cylindrical test piece was rotated for 1 hour at a sliding speed of 0.3 mm/sec.

The results of this wear test are not shown in FIGS. 3 and 4.

In Figures 3 and 4, the upper half represents the wear of the block test piece (corrosion depth μ), and the lower half represents the wear amount (wear loss mq) of the cylindrical test piece. ing. Also the fourth
The figure is a graph showing the relationship between the α-alumina content of short alumina fibers and the abrasion penetration of a cylindrical test piece and a block test piece based on the test results shown in FIG.

3 and 4, and especially FIG. 4, it can be seen that when the α-alumina content is 5 wt% or more, especially when it is 10 to 70 wt%, the abrasion speed of the block test piece is small. On the other hand, when the α-alumina content of short alumina fibers is 5 to 60 wt%, the wear amount of the circular test piece is particularly 10 to 50 wt%.
In the case of the culm residence, it can be seen that it is small. Therefore, the alpha alumina content of the short alumina fibers that compositely strengthens the wall surface of the top ring groove of the piston body is 5~eowt%, especially 10~5Q.
Preferably, it is wt%.

Although the present invention has been described above with reference to several examples in relation to the results of various tests, the present invention is not limited to these examples, and there are many other examples within the scope of the present invention. It will be apparent to those skilled in the art that various embodiments are possible.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway perspective view of one embodiment of a piston for an internal combustion engine according to the present invention, and Fig. 2 is an enlarged longitudinal section of the main part of the embodiment shown in Fig. 1. 3 and 4 are graphs showing the results of friction and wear tests conducted using the α-alumina content of short alumina fibers as reinforcing fibers as a parameter. 1... Piston body, 2... Side outer peripheral surface, 3...
Schilling block, /l...Cylinder bore wall, 5.
...I-tubling, 6...second ring, 7...
・Top ring i: 4.8...Second ring groove, 9
...Oil ring. 10...Ring groove, 11...Head part, 12...
lower wall. 13... Composite Strengthening Department Patent Applicant 1 ~ Yota Automobile Co., Ltd. Agent Patent Attorney Masatake Akashi 1. Figure 2 (Method) (Voluntary) Procedural Amendment 11 October 11, 1958 1. Display of the case 1982 Patent Application No. 156115 2
, Name of the invention (internal combustion) Ikuseki Biston 3.7 IIi What is the relationship between the case and the case? Patent applicant address 1-1 Yota-cho, Wakita City, Aichi Prefecture Name (32
0) Toyota Motor Corporation 4, Agent Address: 104 Shinkawa 1-chome-5-19, Chuo-ku, Tokyo @ 3rd floor, Nagaoka Building, Kayabacho Telephone: 551-41716 Subject of amendment Page 14 of the specification

Claims (1)

[Scope of Claims] 1) A piston for an internal combustion engine, which is made of an aluminum alloy, and the wall surface of the piston ring groove is compositely reinforced with short alumina fibers made of 8Qwt% or more of alumina and the balance of silica. Piston body and carbon content is 0.5
A screw for an internal combustion engine that connects a piston ring which is made of Malden 1-noid stainless steel with a content of 5wt% or less and which is fitted into the piston ring groove. Internal liquid: A piston for an internal combustion engine, characterized in that the bisto sill groove is a 1-tubing groove, and the bisto sill is a top ring.