JPH01232152A - Fiber reinforced aluminum alloy made piston internal combustion engine - Google Patents

Abstract

PURPOSE:To improve high temperature wear resistance and agglutination resistance by finely dispersing in a matrix of Al alloy an intermetallic compound of Al and a predetermined metal in a part partitioning the bottom surface of a top ring groove of fiber reinforced aluminum material. CONSTITUTION:A top ring groove 30 partitions its bottom surface by a compound material 32 with an aluminum alloy as the matrix and short fiber or whisker serving as the reinforcing member. An intermetallic compound with at least one kind of metal element, selected from a group of Al and Fe, Ni, Co, Cr, Cu, Ma, Mo, V, W, Ta, Nb, Ti, Zn, is fine dispersed in the matrix of the compound material 32. The reinforcing member in the compound material 32 sets its volume percentage of 3% or more, and the intermetallic compound sets its volume percentage of 10 to 50%, obtaining the total volume percentage of 60% or less by the reinforcing member and the intermetallic compound. In this way, wear resistance and agglutination resistance are improved in the time of high temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a piston for an internal combustion engine, and more particularly to a piston for an internal combustion engine made of a fiber-reinforced aluminum alloy.

Conventional Technology Pistons for internal combustion engines made of aluminum alloy are prone to wear in their top ring grooves, so pistons whose surrounding areas of the top ring grooves are compositely reinforced with various reinforcing materials have been developed. This has been proposed and implemented in the past.

For example, JP-A No. 58-9386, filed by the same applicant as the present applicant, describes that the area around the top ring groove is compositely reinforced with ceramic fibers. Publication No. 218341 and JP-A-61-
Publication No. 132260 describes a piston in which the portion around the top ring groove is compositely reinforced with a foamed metal body and cast iron fibers.

Problems to be Solved by the Invention According to the above-mentioned piston in which the area around the top ring groove is compositely reinforced with a reinforcing material, the top ring groove is stronger than in the case where the entire piston is made of only aluminum alloy. This improves the wear resistance of the wall surface of the piston, thereby improving the durability of the piston. However, when these pistons are used under relatively high temperature conditions in order to improve the performance of internal combustion engines, the wear of the walls of the top ring groove becomes large, and the temperature of the walls of the top ring groove increases. When the temperature exceeds 250° C., wear resistance that is almost the same as that of a piston made only of aluminum alloy can be obtained.

The inventors of the present application conducted various experimental studies on conventional aluminum alloy pistons as described above, and found that
When conventional pistons are used under severe thermal conditions where the wall surface of the top ring groove exceeds 250°C, rapid wear occurs due to the transfer of the matrix aluminum alloy to the top ring. That is, it was found that adhesive wear is likely to occur on the lower surface of the top ring groove. In addition, this adhesive wear is caused by reinforcing materials that prevent the matrix from coming into direct contact with the top ring under normal conditions.
This is caused by the fact that the aluminum alloy softens when heated to high temperatures, so that the reinforcement on the surface of the composite is no longer properly retained by the matrix, and the softened aluminum alloy comes into direct contact with the top ring. I understand.

Therefore, in the conventional piston as described above, it is necessary to maintain the temperature reached around the top ring groove at least 220°C or less, preferably 200°C or less during operation of the internal combustion engine. For example, the position of the top ring groove, the dimensions of each part of the piston, the formation of the oil channel, etc. are factors that restrict the degree of freedom in piston design.

Furthermore, in order to reduce the amount of wear on the top ring groove wall surface in the high temperature range of around 250°C, the inventors of the present application have found that the composite material itself has high wear resistance even in this temperature range, and the material used To achieve this, (a) the reinforcing material must have sufficient rigidity to support the top ring even at high temperatures, and (b) the matrix must have sufficient rigidity to support the top ring even at high temperatures. Two important points are that it has sufficient heat resistance to maintain the reinforcing material in an appropriate state without causing plastic deformation.
The composite material of JP-A-59-218341 and the composite material of JP-A-61-132260 lack the characteristic (b).
It was determined that the characteristics of b) were lacking.

In view of the above problems, the inventors of the present application conducted further experimental research and found that at least the bottom surface of the top ring groove is made of a composite material with an aluminum alloy as a matrix and short fibers or whiskers as a reinforcing material. A defined piston in which an intermetallic compound of Al and a specific metal element is finely dispersed in an aluminum alloy as a matrix, and each of the reinforcing material, the intermetallic compound, the sum of the reinforcing material and the intermetallic compound A piston with a volume ratio set to a predetermined value can greatly improve the wear resistance and adhesion resistance of the bottom surface of the top ring groove without increasing the amount of wear on the top ring. It has been found that weight reduction and high output can be achieved.

In other words, in conventional research and development of aluminum alloy-based composite materials, the dominant idea is that the matrix is a carrier responsible for transmitting stress between reinforcing materials, and the matrix must have relatively high toughness. has been considered. Therefore, efforts have been made to suppress the precipitation of intermetallic compounds that cause matrix embrittlement as much as possible. However, as a result of various experimental studies, in order to improve the adhesion resistance of aluminum alloy composite materials at high temperatures of 250°C or higher, it has been found that intermetallic compounds, which have been thought to be the cause of embrittlement, must be added to the matrix. By appropriately setting the type and amount of the intermetallic compound in relation to the amount of reinforcing material, the wear resistance and adhesion resistance of the top ring groove can be improved. It was found that excellent pistons can be obtained.

In addition, the above-mentioned Japanese Patent Application Laid-Open No. 59-218341 and Japanese Patent Application Laid-open No. 61
As described in Japanese Patent No. 13226.0, a composite material in which an intermetallic compound is formed in an aluminum alloy matrix and a piston in which such a composite material is incorporated into a top ring groove are already known. However, in these composite materials, the intermetallic compounds are formed in the areas around the network structure and the areas around the cast iron fibers, and in the cells of the network structure (voids in the network structure). Therefore, in the cell part of the network structure and the matrix between the cast iron fibers, there are only parts of aluminum alloy with low heat resistance, and therefore, the composite material does not form intermetallic compounds. Even if wear resistance can be improved, it is not possible to avoid adhesion at high temperatures of 250° C. or higher.

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 is based on the knowledge that the top ring groove wall surface has excellent wear resistance and adhesion resistance. It is an object of the present invention to provide a piston for an internal combustion engine that does not increase the amount of wear and therefore has a large degree of freedom in design, thereby making it possible to reduce the weight and increase the output of the internal combustion engine.

Means for Solving A8 According to the present invention, at least the bottom surface of the top ring groove is defined by a composite material having an aluminum alloy as a matrix and short fibers or whiskers as a reinforcing material. , AI and F in the matrix of the composite material
e SN I SCos Cr5Cu, Mn, Mo
, V, W, Ta5NbSTi, and an intermetallic compound with at least one metal element selected from the group consisting of Zr is finely dispersed, and the volume percentage of the reinforcing material in the composite material is 3% or more. Yes, the volume fraction of the intermetallic compound is 10
~50%, and the total volume fraction of the reinforcing material and the intermetallic compound is 60% or less, which is achieved by a piston for an internal combustion engine made of a fiber reinforced aluminum alloy.

Effects and Effects of the Invention According to the present invention, intermetallic compounds of Al and other predetermined metal elements are finely formed in the aluminum alloy as a matrix, at least in the portion defining the bottom surface of the top ring groove. The intermetallic compound strengthens, or consolidates, the matrix between the reinforcements, which holds the reinforcements in place even at high temperatures and allows the matrix to contact the top ring directly. The wear resistance and adhesion resistance of the top ring groove wall can be improved compared to the case of conventional pistons, and the amount of reinforcing material and intermetallic compounds can be set to a predetermined value. Therefore, an increase in the amount of wear on the top ring can be avoided.

According to the results of experimental research conducted by the inventors, if the volume fraction of the reinforcing material is too low, the wear resistance and adhesion resistance of the bottom surface of the top ring groove cannot be sufficiently improved. .

On the other hand, if the volume fraction of the reinforcing material is too high, the amount of wear of the top ring as a mating material increases, and it becomes difficult to form the top ring groove by machining. According to one detailed feature of the invention, therefore, the volume fraction of the reinforcement is between 3 and 409
6, especially set at 3-30%.

Also, according to the results of experimental research conducted by the inventors of the present application,
The intermetallic compound may be any intermetallic compound of Al and the above-mentioned metal elements, but among the intermetallic compounds, AI and F
It is preferable that the ratio of the intermetallic compound with at least one metal element in e s Co SN i is 50% or more, and in particular, the volume fraction of such specific intermetallic compound is 1096
It is preferable that it is above. Therefore, according to yet another detailed feature of the present invention, the ratio of the intermetallic compound between AI and at least one metal element of F 6 s CONNi is set to 50% or more, and the composite The volume fraction of such specific intermetallic compound in the material is set to 10% or more.

Also, according to the results of experimental research conducted by the inventors of the present application,
It is preferable that the intermetallic compounds are dispersed as uniformly as possible, and the average value of the shortest distance between the intermetallic compounds is 100
The average value of the shortest distance between intermetallic compounds is preferably 3 μm or more, particularly 5 μm or more in order to avoid embrittlement of the matrix. According to yet another detailed feature of the invention, therefore, the average value of the shortest distances between the intermetallic compounds is set between 3 and 100 μm, particularly between 5 and 50 μm.

Furthermore, according to the results of experimental research conducted by the inventors of the present application,
When the intermetallic compound is granular, its maximum particle size is 50
It is preferably 30 μm or less, especially 30 μm or less, and when the intermetallic compound is acicular, the maximum length is 100 μm or less.
It is preferably 50 μm or less, particularly 50 μm or less.

Note that the reinforcing material in the composite material of the present invention may be any material that has been conventionally used in the production of composite materials, but the reinforcing material may be any material that is excellent in improving wear resistance, high temperature stability, etc. Preferably, the material is made of ceramic.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be explained in detail below by way of example embodiments with reference to the accompanying figures.

Example 1 Short alumina fibers (95% AI!! 03.5% S102, manufactured by ICI "Safil RFJ") with an average fiber diameter of 2.8 μm, fiber length of 2 to 3 cm, and Ni powder (purity 99%) with an average particle diameter of 5 μm %) in water and then suction molding to obtain an outer diameter of 90+n as shown in Figure 1.
m, inner diameter 70mff1. Four cylindrical molded bodies 10 having a height of 20) were formed. In this case, the volume percentages of alumina short fibers and Ni powder in each compact are 7% and 5%, respectively, with 12 alumina short fibers and 11% Ni powder.
4 were in a substantially uniformly mixed state, and in particular, the alumina short fibers were oriented in a two-dimensional random manner along the cylindrical surface of the molded body.

Next, each molded body was preheated to 300° C. for 20 minutes in the atmosphere, and then each molded body 10 was heated as shown in FIG.
The knockout plunger 2 is placed in the mold cavity 20 of the mold 1.8 of the high-pressure casting device 16 for piston casting.
A molten metal 24 of aluminum alloy (JIs standard AC8A) at 780°C is poured into the mold cavity, and the molten metal is pressurized to a pressure of 1000 kg/c by a pressurizing plunger 26 that fits into the mold. The pressurized state was maintained until the eluate was completely solidified, thereby forming four piston rough materials. Next, each piston rough material was subjected to heat treatment TVs, that is, heated to 490'C for 4 hours, water cooled, then heated to 220'C for 6 hours, and then cooled in a furnace.

Next, one of the piston rough materials formed as described above was cut and the structure of the part compositely reinforced with alumina short fibers was investigated. The short fibers are dispersed, and in the region between each alumina short fiber, the intermetallic compound Al3Ni, which is formed by Ni powder reacting and diffusing with Al in the aluminum alloy, is finely dispersed. It existed. The volume fraction of this Al3Ni is approximately 2
It was 7%. In addition, the composition of the area other than the composite reinforced part of the piston rough material is the original aluminum alloy (JIS standard AC8A
) was observed to remain the same.

[Abrasion test] From the composite part of the piston rough material cut as described above, lO
Wear specimens for friction and wear testing were prepared having dimensions of 15×6IIIn. In this case, test pieces were cut out such that the test surface, which had dimensions of 15 x 6 mm, was perpendicular to the axis of the piston blank.

Then outer diameter 35IIlff11 inner diameter 30III11
Gas nitrocarburized stainless steel (JI) with a width of 10 mm
A wear test piece was brought into contact with the outer peripheral surface of a cylindrical test piece made of S standard 5US440B) at room temperature, and a contact surface pressure of 60 kg/mm', sliding speed 0°3m
A wear test was conducted by rotating a cylindrical test piece for 1 hour at /see. The results of this wear test are shown in FIG. In Figure 3, the upper half shows the wear amount of the wear test piece (wear scar depth μm).
), and the lower half represents the amount of wear (wear area Q rag ) of the cylindrical test piece that is the mating material.

From Figure 3, the depth of the wear scar on the wear test piece is 6 μm,
The amount of wear on the cylindrical test piece was 0.4 mg, which indicates that the composite material formed in the composite reinforced portion of the piston rough material described above has extremely excellent friction and wear characteristics at room temperature.

[Manufacturing of pistons] From the piston rough material formed as described above, as shown in FIG. A composite material in which an area 17 mm from the end surface 28a including the top ring groove 30 is reinforced with alumina short fibers over an area of 7°5Il111 from the cylindrical outer peripheral surface, and intermetallic compounds are finely dispersed in the matrix. A piston consisting of 32 pieces was formed by machining. In addition, in Figure 4, 34.3
6.38.40 respectively indicate the top land, second land, third land, and skirt part, and 42.4
4 indicates a second ring groove and an oil ring groove, respectively, and 46 indicates a piston pin hole. In this case, in order to set the thermal conditions of the bottom surface 30a of the top ring groove to various conditions, three types of pistons 1 to 2 were formed in which the distance from the end surface 28 to the bottom surface 30a was 15 mms 12+111111.8 mm.

Next, the pistons ■ to ■ were assembled into a 4-cylinder 2000CC diesel engine with a turbocharger, and a full-load continuous operation durability test was conducted for 300 hours under the following conditions. After the test, the maximum wear depth and The maximum wear depth on the bottom surface of the top ring was measured. These measurement results are shown in Table 1 below as composite material No. 1. The top ring is made of gas nitrocarburized stainless steel.
It was formed in accordance with IS standard 1sUs440B).

Table 1 Rotation speed: 4500 rpm+ Cooling water temperature: 105±5℃ Oil temperature: 125±5℃ Exhaust temperature: 850℃ Output/torque: 106PS/26.4kgm From Table 2, regardless of the top ring groove position, the top ring groove The amount of wear on the bottom surface of the bottom surface of the top ring and the bottom surface of the top ring is a small, almost constant value, and no abnormal wear such as adhesion has occurred. It can be seen that the piston having the above-described structure has excellent wear resistance and adhesion resistance at high temperatures.

Example 2 Co powder (purity 9) with an average particle size of 12 μm was used instead of Ni powder.
9%) and Fe powder with an average particle size of 10 μm (99% purity)
Using the same method as in Example 1, four piston rough materials each containing composite materials No. 2 and No. 3 were formed. The volume percentages of Co powder and Fe powder in the compact were 4% and 5%, respectively.

Next, we investigated the structure of the cross section of each piston rough material, and found that
In composite material No. 2, the volume ratio in the matrix was 30.
% intermetallic compound Al9CO! ! was finely dispersed, and in composite material No. 3, Al3Fe with a volume percentage of 28% was finely dispersed in the matrix.

In addition, wear test pieces were cut out from each composite material in the same manner as in Example 1, and each test piece was subjected to an abrasion test at room temperature under the same manner and conditions as in Example 1. The results of this wear test are shown in FIG. From FIG. 3, it can be seen that composite materials No. 002 and No. 3 have excellent friction and wear characteristics similar to composite materials No. 1.

Furthermore, from each of the remaining piston raw materials, pistons with the same dimensions as in Example 1 were prepared in the same manner as in Example 1.
A durability test was conducted on each piston in the same manner and under the same conditions as in Example 1. The results of these tests are shown in Table 2.

From Table 2, the amount of wear on the lower surface of the top ring groove and the lower surface of the top ring is small regardless of whether the composite material defining the lower surface of the top ring groove is Composite Material No. 2 or Composite Material No. 3. Therefore, it can be seen that these pistons, like the piston of Example 1, have excellent wear resistance and adhesion resistance at high temperatures.

Comparative Example A molded body Al having the same dimensions and shape as the molded body 10 formed in Actual Gun Example 1 described above, which does not contain Nl powder and is made only of short alumina fibers with a volume fraction of 7%. Cast iron short fibers (JI
A three-dimensional network structure made of B1 nickel (porosity 90%, cell size approximately 1'
The volume ratio formed by processing mm) is approximately 10%.
In the case of Example 1, the molded body C and the molded body E made of NIO powder (average particle size 2 μm 1 purity 99%) with a volume ratio of about 8% and alumina short fibers with a volume ratio of 796 were used instead of the Ni powder, respectively. Piston rough material A- in the same manner and under the same conditions as
C and E were formed.

Next, when we investigated the structure of the cross section of composite materials A-C and E of each piston raw material, we found that in composite material A, there were no intermetallic compounds in the matrix, and in composite materials B and C, there were no intermetallic compounds in the matrix. and intermetallic compounds Al 3 Fe and AI 3. around the cast iron fibers and the network structure, respectively. Ni
was found to be generated. In addition, in the composite material E, due to the reaction between the matrix Al and the NiO powder, the intermetallic compound Al3Ni with a volume fraction of about 27% and AI with a volume fraction of about 7% are formed. ! 03 was generated, and their size was about 100 to 150 μm.

Next, wear test pieces A-C were cut out from these composite materials, and aluminum alloy (JIS
Abrasion test pieces were cut out from a portion consisting only of the standard AC8A), and the wear test pieces were subjected to an abrasion test at room temperature in the same manner and under the same conditions as in Example 1.

The results of these wear tests are shown in FIG.

From Figure 3, Composite Materials A-C of Comparative Examples have better friction and wear characteristics than the matrix-only case (D). It can be seen that the friction and wear characteristics are far superior to other materials. In addition, in composite material E, both the wear test piece and the cylindrical test piece had relatively high wear values, and it can be seen that it is not suitable as a material for defining the lower surface of the top ring groove.

It is presumed that this is because Al 203 falls off from the matrix when the wear test piece and the cylindrical test piece slide against each other, and wear is accelerated by the fallen particles. In addition, in the case of this composite material, the formation ratio of the intermetallic compound Al3N1 and the oxide A+ = 03 is constant due to the chemical reaction, so in order to ensure a certain level of wear resistance, it is necessary to It is necessary to reduce the amount of NiO powder contained in the. Although not shown as experimental results, it was found that fairly good wear resistance was ensured when the volume fraction of Al3Ni was 1% or less. However, in that case, the volume fraction of the intermetallic compound Al3Ni is 4
It was found that adhesive wear easily occurs in pistons in which the lower surface of the top ring groove is defined by the composite material.

[Temperature Measurement] As shown in FIG. 5, in the pistons ① to ② subjected to the durability test in Example 1, a temperature was measured at a position 0.2 mIn inside from the bottom wall 30b of the top ring groove. A thermocouple 48 with a diameter of 0.1n++++ was installed so that the tip was located, and the diesel engine was operated for 30 minutes under the same conditions as the durability test in Example 1, thereby measuring the temperature near the top ring groove. The average value was calculated. As a result, the temperature near the top ring groove is 210°C in the case of piston ■.
It was found that the temperature was 250°C in the case of the piston (2) and 270°C in the case of the piston (3).

The following is clear from these temperature measurement results and the results of the above-mentioned wear tests and durability tests.

(1) In the temperature range of about 210° C. or lower, both the conventional composite materials A-C and the composite material of the present invention have fairly good friction and wear properties. Further, even if only aluminum alloy (D) is used, the amount of wear itself becomes high, but no adhesion occurs.

(2) In the temperature range of 250°C or higher, the composite material of the present invention has almost the same wear resistance as that of 210°C or lower, whereas the conventional composite material A-C Both cause extreme adhesive wear and, in the worst case, ring stick. These conventional composite materials result in abnormal wear that is almost the same as in the case of aluminum alloy alone.

(3) Composite material E is similar to the composite material in the present invention25
Adhesion does not occur even at temperatures above 0°C, but the amount of wear is extremely high. In this composite material, intermetallic compounds that are effective in preventing adhesion and AI = 03 particles that cause wear are generated at a certain ratio, so it is possible to achieve both friction and wear properties and adhesion properties. is virtually impossible.

Example 3 Instead of the alumina short fibers in Example 1, silicon carbide long fibers (
α-5i C99%, average fiber diameter 20μm) with length 2~
3. Chopped fibers, silicon nitride whiskers (α
-513N 499%, average fiber diameter 1 μm, average fiber length 1
Composite materials N, o, 4 and No.
, 5, the lower surface of the top ring groove was defined, and the position of the top ring groove formed a piston that was the same as the piston (2) of Example 1. Similarly, instead of the alumina short fibers of Example 1, cast iron short fibers (with an average fiber diameter of 20 μm and an average fiber length of 3 cm) (
By using JIS standard FC23) at a volume ratio of 20%, the lower surface of the top ring groove is defined by composite material No. 6, and the position of the top ring groove is the same as the piston ■ of Example 1. It was formed in the same manner and under the same conditions as in Example 1.

These pistons were then subjected to a durability test in the same manner and under the same conditions as in Example 1.

The results of this test are shown in Table 3.

Table 3 shows that when the reinforcing material is cast iron short fibers, the amount of wear on the bottom surface of the top ring groove and the bottom surface of the top ring is relatively high, and adhesive wear occurs, whereas the reinforcing material is silicon carbide fibers. When the reinforcing material is silicon carbide fibers or silicon nitride whiskers, the amount of wear on both the bottom surface of the top ring groove and the bottom surface of the top ring is small, and no adhesion occurs. It can be seen that good abrasion resistance and adhesion resistance can also be ensured. Although not shown in the experimental results, the reinforcing materials were alumina-silica short fibers (52% Al25i03.48% SiO, average fiber length 3III111, average fiber diameter 3μ11), silicon carbide whiskers (99% β-8IC). .

Average fiber length 50μ11 average fiber diameter 0.1μa+), mineral short fibers (45% SlO!, 40%CaO110%Al!)
! 03, balance MgO1 average fiber length 2Il1m1 average fiber diameter 5μmM), glass fiber (64%5IO2125%
It was found that good abrasion resistance and adhesion resistance could be ensured even when the composition was 203 (Al: 203, balance Mg O1, average fiber length: 510 G%, average fiber diameter: 10 μm).

Example 4 The type of powder mixed into the compact was the same Ni powder as the Ni powder used in Example 1, and the same Co powder as the Co powder and Fe powder used in Example 2. and Fe
By setting the amount of each powder to various values as shown in Table 4 below, the volume fraction of the intermetallic compound in the composite material to be formed is substantially 0%, 596 ．．
Molded bodies were formed so that the proportions were 10%, 20%, 30%, 40%, 50%, and 60%, and the top ring groove was formed using these molded bodies in the same manner and under the same conditions as in Example 1. Forms a piston whose position is the same as piston ① of Example 1,
A durability test was conducted on each piston in the same manner and under the same conditions as in Example 1.

The results of these tests are shown in Table 5.

From Table 5, regardless of the type of intermetallic compound, adhesion occurs when the volume fraction is 5% or less, and conversely, adhesion occurs when the volume fraction is 60%.
It can be seen that in the above cases, the land portion of the piston is damaged due to the matrix of the composite material becoming too brittle. Therefore, it can be seen that the volume fraction of the intermetallic compound is preferably 10 to 50%.

Example 5 The volume fraction of alumina short fibers contained in the molded body was set to 296.
3%, 5%, 10%, 20%, 30%, and 40%, and by setting the volume fraction of Ni powder to the values shown in Table 4 of Example 4, 56 types of compacts were produced. Using each molded body, form a piston having the same dimensions as piston ① in the same manner and under the same conditions as in Example 1,
A durability test was conducted on each piston in the same manner and under the same conditions as in Example 1. The results of these tests
As shown in the figure. In Fig. 6, 0 means that no adhesion occurs and the amount of wear on the bottom surface of the top ring groove is extremely small, and Δ means that no adhesion occurs but the bottom surface of the top ring groove wears very little. This indicates that the amount of wear exceeded 15 μm, × indicates that adhesive wear occurred, and + indicates that the land portion of the piston was damaged.

From Figure 6, in order to ensure good abrasion resistance and adhesion resistance on the bottom surface of the top ring groove, the volume percentage of the alumina short fibers should be 3% or more, and the volume percentage of the intermetallic compound Al3N1 should be 3% or more. is 10-50%, alumina short fibers and intermetallic compound A
It can be seen that the total volume fraction of 13NI is preferably 60% or less.

The same tests as in this example were conducted on the silicon carbide fibers and silicon nitride whiskers used in Example 3 as reinforcing materials, and on the Co particles used in Example 2 as the reinforcing material. The same results as those shown in FIG. 6 were obtained when the powder and Fe powder were also used.

Example 6 In place of the N1 powder in Example 1, alloy powders and pure metal powders shown in Table 6 below were used, and as shown in Table 7 below, the alloy powders were Volume ratio 5%
, and the overall volume fraction for pure metal powder is 5.
% to form molded bodies, and each molded body was used to form two piston rough materials in the same manner and under the same conditions as in Example 1. Next, the type of intermetallic compound dispersed in the matrix was determined by examining the cross-sectional structure of the composite part of one piston rough material of each set. The results are shown in Table 7 below.

In addition, pistons having the same dimensions as piston (2) of Example 1 were formed from the remaining piston raw materials, and a durability test was conducted on each piston in the same manner and under the same conditions as in Example 1. As a result, it was found that no abnormality such as adhesion occurred on the lower surface of the top ring groove in any of the pistons, and the amount of wear was extremely small.

In addition, we investigated in detail whether or not adhesion would occur by changing the volume fraction of the various powders in the compact shown in Table 7 below and the mixing ratio of the mixed powder, and found that (1) The total amount of compounds is 10% or more in terms of volume percentage. (2) The intermetallic compound of at least one of AI, Fe s Co, and N1 is 50% or more of the total amount of intermetallic compounds. In this case, it was found that the wear resistance and adhesion resistance of the bottom surface of the top ring groove of the piston were extremely good. In addition, if the above two conditions (1) and (2) are satisfied, Fe s Co s
N! Metal elements other than Cr, Mo sV, W, N
Similarly good results were obtained in the case of Ta. Furthermore, if an intermetallic compound other than the intermetallic compound of AI and Fe5Co or Ni is included, the
It has been found that particularly good results can be obtained when the volume fraction of the 5Co1Ni intermetallic compound is 10% or more.

Table 2 0...No adhesion occurred X...Adhesion completed; Table 6 Powder type Purity (%) Average particle size (μff1) Nl
-50%Fe 99 12Ni-50%C
o 99 12Fe-50%Co
99 1ON l-30%Cu 99
10Fe-20%Mn 99. 10C
u 99 15 Mn 99 10 Ti 99 10 Several embodiments of the present invention have been described above in detail along with the results of various experimental studies conducted by the inventors of the present application. It will be obvious to those skilled in the art that the invention is not limited to the examples and that various other embodiments are possible within the scope of the invention.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing a cylindrical molded body made of short alumina fibers and N1 powder, and Figure 2 is a piston rough material formed by high-pressure casting using the molded body shown in Figure 1. Figure 3 is a graph showing the results of wear tests conducted on the composite materials of Example 1.2 and Comparative Example;
The figure is a sectional view showing one embodiment of the piston according to the present invention, FIG. 5 is an illustration showing the manner in which the thermal lightning pair is arranged inside the piston, and FIG. It is a graph showing the results. 10... Molded object, 12... Alumina short fiber, 14.
...Ni powder, 16...High pressure casting device, 18... Mold, 20... Mold cavity, 22... Knockout plunger, 24... Molten aluminum alloy, 26... Pressure plunger, 28...Head part, 2
8a... End face, 30... Top ring groove, 32...
・Composite material, 34...Top land, 36...Second land, 38...Third land, 40...Skirt portion, 42...Second ring groove, 44...Oil ring groove, 46... ...Piston pin hole, 48...Thermocouple patent applicant: Toyota Motor Corporation representative
Patent attorney Masa Akashi
Tsuyoshi Figure 1 Figure 2 Figure 3 Figure 4 Figure 30... Top ring groove Figure 5

Claims (1)

[Claims] At least the bottom surface of the top ring groove is defined by a composite material having an aluminum alloy as a matrix and short fibers or whiskers as a reinforcing material, and the matrix of the composite material contains Al, Fe, Ni, Co, Cr, and Cu. ,Mn,
An intermetallic compound with at least one metal element selected from the group consisting of Mo, V, W, Ta, Nb, Ti, and Zr is finely dispersed, and the volume percentage of the reinforcing material in the composite material is is 3% or more, the volume percentage of the intermetallic compound is 10 to 50%, and the total volume percentage of the reinforcing material and the intermetallic compound is 60% or less, a piston for an internal combustion engine made of a fiber-reinforced aluminum alloy. .