JPH079050B2 - Connecting rod for internal combustion engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a connecting rod for an internal combustion engine,
In particular, the present invention relates to a connecting rod for an internal combustion engine that includes a connecting rod body having a rod portion and a cap fastened to the connecting rod body by a bolt.

[0002]

2. Description of the Related Art Heretofore, as this type of connecting rod, one made of a high-strength aluminum alloy to which a large amount of Si, Fe, Mn or the like has been added by applying a powder metallurgy method is known.

[0003]

However, the conventional high-strength aluminum alloy for connecting rod (hereinafter referred to as a known alloy) has the following problems. (A) Since the known alloy has a fine metal structure and therefore is excellent in strength, it has poor creep characteristics. Therefore, at the bolt fastening portion of the cap that is constantly subjected to compressive stress at high temperatures, creep occurs with long-term use. The shrinkage increases, and as a result, the bolt fastening force may be reduced, or in extreme cases, the bolt fastening portion may be broken. (B) The known alloy aims to lower the coefficient of thermal expansion and improve the Young's modulus by adding a large amount of Si, Fe, Mn, etc. However, considering the productivity and toughness as an industrial material, the coefficient of thermal expansion is about 18 ×. 10 ^-6 / ℃, Young's modulus is about 1
The limit is 0000 kg / mm ² .

When a connecting rod is made of aluminum alloy and is combined with a steel crankshaft, the coefficient of thermal expansion of the aluminum alloy should be close to that of steel when determining the clearance between them and the press-fitting margin. Although the degree of freedom in design increases, the known alloy cannot meet such requirements. Therefore, the clearance between the crankpin hole of the connecting rod and the crankpin of the crankshaft greatly increases as the temperature rises.

The Young's modulus is an important factor that influences the displacement and strain of the connecting rod in the elastic region when a load is applied, and it is necessary to sufficiently increase the Young's modulus in order to downsize the connecting rod. However, known alloys cannot meet such requirements. (C) Known alloys include primary crystal Si and eutectic S that precipitate on the alloy.
Since i and intermetallic compounds are extremely fine, there is a relatively large amount of sliding wear, and as a result, there is a problem that durability is poor under high surface pressure and high-speed sliding. is not.

An object of the present invention is to provide a connecting rod for an internal combustion engine which can solve the above problems.

[0007]

The present invention provides a connecting rod for an internal combustion engine comprising a connecting rod body having a rod portion and a cap fastened to the connecting rod body by a bolt, wherein the connecting rod body has a weight of 12.0. % ≤ Si ≤ 28.0 wt%, 0.8 wt% ≤ Cu ≤ 5.0 wt%, 0.3 wt% ≤ Mg ≤ 3.5 wt%, 2.0 wt% ≤ Fe ≤ 10.0 wt% %, 0.5 wt% ≤ Mn ≤ 2.9 wt% and the balance Al containing unavoidable impurities, and is composed of a high strength aluminum alloy using a rapidly solidified aluminum alloy powder, and the cap is the rapidly solidified aluminum alloy powder. 1. In a high-strength aluminum alloy matrix using 1., at least one hard particle selected from Al ₂ O ₃ particles, SiC particles, Si ₃ N ₄ particles, and metallic Si particles. It is characterized by being composed of a composite material in which 5% by weight or more and 15.0% by weight or less are dispersed.

[0008]

When the composition of the rapidly solidified aluminum alloy powder is specified as described above, it has excellent high-temperature strength, wear resistance and Young's modulus, and also has a low thermal expansion coefficient and improved stress corrosion cracking resistance. High strength aluminum alloy,
Therefore, the matrix of the connecting rod body and the cap can be constructed.

Further, the rapidly solidified aluminum alloy is generally difficult to work, but by specifying the content of each chemical component as described above, hot plastic workability such as hot extrusion workability and hot forging workability is obtained. It is possible to improve productivity and improve productivity of the connecting rod body and the cap.

The reasons for containing each chemical component and the hard particles and the reasons for limiting the content are as follows. (A) About Si Si has the effects of improving the wear resistance, Young's modulus and thermal conductivity of the matrix of the connecting rod body and cap formed from the rapidly solidified aluminum alloy powder, and reducing the coefficient of thermal expansion. However, if it is less than 12.0% by weight, the above effect cannot be obtained, while 2
If it exceeds 8.0% by weight, the formability is deteriorated in the hot extrusion process and the hot forging process, and the connecting rod body or the like is likely to be cracked. (B) Regarding Cu Cu has the effect of strengthening the connecting rod body and the like during heat treatment. However, if less than 0.8% by weight, the above effect cannot be obtained, while if more than 5.0% by weight,
Hot forgeability deteriorates and stress corrosion cracking resistance of the connecting rod body deteriorates. (C) About Mg Like Mg, Mg has the effect of strengthening the connecting rod body and the like during heat treatment. However, if it is less than 0.3% by weight, the above effect cannot be obtained, while if it is 3.5% by weight.
If it exceeds the range, the hot forgeability deteriorates and the stress corrosion cracking resistance of the connecting rod body and the like deteriorates. (D) About Fe Fe has the effect of improving the high temperature strength and Young's modulus of the connecting rod body and the like. However, if it is less than 2.0% by weight, improvement in high temperature strength in the connecting rod body or the like cannot be expected, while if it exceeds 10.0% by weight, high speed hot forging becomes practically impossible. (E) About Mn Mn has the effect of improving hot forgeability and improving high-temperature strength and stress corrosion cracking resistance of the connecting rod body and the like, particularly in the range of Fe ≧ 4 wt%. However, if it is less than 0.5% by weight, the above effect cannot be obtained, while if it exceeds 2.9% by weight, adverse effects such as deterioration of hot forgeability rather occur. (F) Hard Particles The four kinds of hard particles specified as described above are dispersed in the cap matrix to fix crystal dislocations, improve the creep characteristics of the cap at high temperature, and increase the thermal expansion coefficient. And also has the effect of improving Young's modulus and wear resistance. However, when the content of the hard particles in the rapidly solidified aluminum alloy powder is less than 1.5% by weight, the wear resistance of the cap is not improved, and the Young's modulus is improved and the coefficient of thermal expansion is also decreased. If it exceeds 15.0% by weight, the hot forgeability is deteriorated, and the fatigue strength and machinability of the cap are remarkably deteriorated.

[0011]

1 shows a connecting rod 1 for an internal combustion engine, which connecting rod 1 has a connecting rod body 3 having a rod portion 2,
The connecting rod body 3 is provided with a cap 5 that is fastened with bolts 4.

The content of each chemical component in the rapidly solidified aluminum alloy powder is limited to the following in the matrix of the connecting rod body 3 and the cap 5 in order to particularly improve stress corrosion cracking resistance and hot forgeability. To be done.

14.0 wt% ≦ Si ≦ 18.0 wt% 2.0 wt% ≦ Cu ≦ 5.0 wt% 0.3 wt% ≦ Mg ≦ 1.5 wt% 3.0 wt% ≦ Fe ≦ 6.0% by weight 0.5% by weight ≦ Mn ≦ 2.5% by weight When the cap 5 to be thermally affected is composed of the composite material, the cap 5 has Young's modulus, coefficient of thermal expansion, creep characteristics and mechanical properties. Since workability is a problem,
The content of the hard particles is preferably 9.0% by weight or more and 13.0% by weight or less. The reason is that if it is less than 9.0% by weight, the creep property improving effect tends to decrease, while
This is because if it exceeds 13.0% by weight, the machinability tends to decrease.

When sliding wear with a steel crankshaft poses a problem, the content of hard particles should be 2.0% by weight or more and 4.0% by weight or less, depending on the type of the steel. preferable. The reason is that if it is less than 2.0% by weight, the amount of wear of the cap 5 tends to increase, while if it exceeds 4.0% by weight, the amount of wear of the crankshaft tends to increase.

When the cap 5 is manufactured, for example, rapidly solidified aluminum alloy powder and hard particles are mixed to obtain a mixed powder, and then the cold isostatic pressing method (CIP method) or the like is applied to the mixed powder. To obtain a green compact, and then subject the green compact to hot extrusion processing.

In this case, the particle size of the rapidly solidified aluminum alloy powder is not less than 325 mesh and not less than 45% by weight and not more than 70% by weight. The reason is that if the powder having the above particle size is less than 45% by weight, the fatigue strength decreases, while
This is because if it exceeds 0% by weight, the creep characteristics deteriorate.

The particle size of the hard particles is preferably 5 μm or more and 74 μm or less in order to improve wear resistance without impairing fatigue strength and improve creep characteristics. The reason for this is that if the thickness is less than 5 μm, the handling becomes poor, while
This is because if it exceeds 4 μm, the fatigue strength tends to decrease.

The reason why the connecting rod body 3 is made of the above-mentioned high-strength aluminum alloy containing no hard particles is that the connecting rod body 3 is preferentially required to have fatigue strength, and therefore it is advantageous not to contain hard particles. is there. On the other hand, the cap 5 is less required to have fatigue strength than the connecting rod body 3, but the surface pressure of the bolt fastening portion is high and it is necessary to reduce creep shrinkage, so that the cap 5 is made of a composite material containing hard particles.

Next, a method of manufacturing the composite material forming the cap 5 and various test results of the composite material will be described.

As the rapidly solidified aluminum alloy powder, S
i 17.2% by weight, Cu 2.5% by weight, Mg 0.
A powder consisting of 6 wt%, Fe 4.3 wt%, Mn 1.8 wt% and the balance Al containing inevitable impurities was subjected to an atomizing method to cool at a rate of 10 ³ to 10 ⁴ ° C / sec.
Manufactured under the conditions of.

Various hard particles are added to the rapidly solidified aluminum alloy powder in the amounts shown in Table 1, and composite materials (1) to (12) are manufactured through the following steps.

That is, after the rapidly solidified aluminum alloy powder and each hard particle are mixed in a V-type blender, a cold isostatic pressing method (CIP method) or a die compression molding method is applied to each mixed powder. To obtain a green compact having a density ratio of 75%.

In the cold isostatic press molding method, the mixed powder is put in a rubber tube to obtain 1.5 to 3.0 ton /
Molding is carried out under hydrostatic pressure of about cm ² , and in the mold compression molding method, the mixed powder is put into the mold, and the mixture is allowed to stand at room temperature in air.
Molding is performed under a pressure of about 5 to 3.0 ton / cm ² . Each green compact is placed in a soaking furnace with a furnace temperature of 400 ° C and held for 4 hours, and then each green compact is subjected to hot extrusion processing to be formed into a round bar shape with a diameter of 18 mm and a length of 450 mm. The composite materials (1) to (12) are obtained.

The extrusion method in this case may be either direct extrusion (forward extrusion) or indirect extrusion (rear extrusion), but an extrusion ratio of 5 or more is required. When the extrusion ratio is 5 or less, variations in strength increase, which is not preferable.

[0025]

[Table 1] For comparison, comparative materials (1) to (3) shown in Table 2 are manufactured by the same method as described above.

[0026]

[Table 2] The comparative material (1) has the same composition as the matrix of the composite materials (1) to (12), the comparative material (2) corresponds to JIS AC8C which is a casting material, and the comparative material (3) is It is a composite material.

Table 3 shows the thermal expansion coefficients (× 10 ⁻⁶ , 20 to 2) of the composite materials (1) to (12) and the comparative materials (1) and (2).
00 ° C.) and Young's modulus (200 ° C., kg / mm ² ) are shown.

[0028]

[Table 3] As is clear from Table 3, the composite materials (1) to (12) have a lower coefficient of thermal expansion and a higher Young's modulus than the comparative materials (1) and (2). Al
_This is due to the dispersion of hard particles such as ₂ O ₃ .

Table 4 shows the stress corrosion cracking test (JIS H87) for the composite materials (1) to (12) and the comparative material (3).
The result when 11) is performed is shown.

The stress corrosion cracking test is 80 mm long and 10 m wide.
A test piece with a thickness of 2 mm and a load of σ _0.2 × 0.9 (where σ _0.2 is the composite material (1)
~ (12) and the 0.2% proof stress of the comparative material (3)), 2 in a NaCl solution with a liquid temperature of 30 ° C and a concentration of 3.5%.
It is carried out by immersing for 8 days, and the superiority or inferiority of the stress corrosion cracking resistance property is judged by the presence or absence of cracks in the test piece.

[0031]

[Table 4] As is clear from Table 4, the composite materials (1) to (12) are superior in stress corrosion cracking resistance property to the comparative material (3),
This is mainly due to the inclusion of Mn.

Table 5 shows the results when a sliding wear test was conducted on the composite materials (2), (5), (8) and the comparative material (1).

In the sliding wear test, a test piece having a length of 10 mm, a width of 10 mm and a thickness of 5 mm was applied to a JIS S50C disc having a diameter of 135 mm rotating at a speed of 2.5 m / sec and a pressure of 200.
It was performed over a sliding distance of 18 km by pressing with kg / cm ^{2 and} lubricating oil dropped under the condition of 5 cc / min, and the wear amount is the weight difference (g) before and after the test in the test piece. It is measured by

[0034]

[Table 5] As is clear from Table 5, composite materials (2), (5),
Compared with the comparative material (1), (8) has excellent wear resistance, which is due to Al ₂ O ₃ , SiC, S in the matrix.
This is because hard particles such as i ₃ N ₄ are dispersed.

Table 6 shows the results when the creep test was conducted on the composite materials (2), (5), (8) and the comparative material (1).

The creep test was carried out on a test piece having a diameter of 10 mm and a parallel portion length of 40 mm at 12 kg / mm ² at 170 ° C.
Is applied for 100 hours, and the amount of creep shrinkage is measured by determining the ratio (%) of the length of the test piece before and after the test.

[0037]

[Table 6] As is clear from Table 6, composite materials (2), (5),
The creep shrinkage of (8) is smaller than that of the comparative material (1). This is because Al ₂ O ₃ , SiC, and
This is because the dislocations of the crystal of the matrix are fixed due to the dispersion of hard particles such as Si ₃ N ₄ .

The creep shrinkage of the comparative material (2), which is a cast material, is 0.04%, and the composite materials (2), (5),
That of (8) is almost comparable to cast material.

Table 7 shows a diameter of the connecting rod 1 of 45 mm.
The relationship between the dimensional change of the crank pin hole 6 and the temperature is shown.

In the connecting rod 1 of the embodiment, the connecting rod body 3 is made of the matrix material, that is, the comparative material (1), and the cap 5 is made of the composite material (3). In the comparative connecting rod 1, the connecting rod body 3 and the cap 5 are made of the comparative material (1). In both connecting rods 1, the cap 5 is fastened to the connecting rod body 3 with bolts 4.

[0041]

[Table 7] As is clear from Table 7, the example connecting rod 1 provided with the cap 5 made of the composite material (3) has a higher crankshaft temperature than the comparative example connecting rod 1 made of the comparative material (1). The amount of change in the diameter of the hole 6 is small, so that the change in clearance between the crankpin and the crankpin hole 6 during engine operation can be suppressed.
This is because the coefficient of thermal expansion of the cap 5 is lowered by dispersing 10% by weight of Al ₂ O ₃ particles in the matrix.

[0042]

According to the present invention, by using the constituent materials specified as described above, it has excellent high temperature strength, wear resistance and Young's modulus, and also aims to reduce the coefficient of thermal expansion and stress resistance. It is possible to provide a connecting rod for an internal combustion engine, which includes a connecting rod main body and a cap with improved corrosion cracking characteristics and high productivity, and in particular, has improved creep characteristics of the cap at high temperatures.

[Brief description of drawings]

FIG. 1 is a fragmentary front view of a connecting rod for an internal combustion engine.

[Explanation of symbols]

 1 connecting rod, 2 rod part, 3 connecting rod body, 4 bolts, 5 cap

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-60-121250 (JP, A) JP-A-60-50138 (JP, A) JP-A-61-104043 (JP, A)

Claims (1)

[Claims] 1. A connecting rod body having a rod portion (2).
(3) and the bolt (4) on the connecting rod body (3)
A cap for internal combustion engine having a cap (5) tightened by
In the connecting rod body, the connecting rod body (3) has: 12.0 wt% ≦ Si ≦ 28.0 wt%, 0.8 wt% ≦ Cu ≦ 5.0 wt%, 0.3 wt% ≦ Mg ≦ 3.5 % By weight, 2.0% by weight ≤ Fe ≤ 10.0% by weight, 0.5% by weight ≤ Mn ≤ 2.9% by weight, and a rapid solidification alloy consisting of the balance Al containing unavoidable impurities.
A high-strength aluminum alloy made of aluminum alloy powder
The cap (5) is made up of
High strength aluminum alloy mat using minium alloy powder
Licks, Al ₂O₃Particles, SiC particles, Si₃N_Four
Particles and at least one selected from metallic Si particles
Hard particles of 1.5% by weight or more and 15.0% by weight or less
Characterized by being composed of dispersed composite materials
Connecting rod for fuel engine.