JP3232029B2 - Cylinder block - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder block for an automobile engine, and more particularly, to a cylinder block manufactured by die casting of an Al alloy, and a cylinder block manufactured by casting a cylinder liner portion. .

[0002]

2. Description of the Related Art A cylinder block in which a cylinder liner is cast from an Al alloy is manufactured first by, for example, F
Place a C cast iron cylinder liner in the given mold,
It has been manufactured by casting a molten metal of an Al alloy in a mold and then polishing the inner peripheral surface of the cylinder liner to form a sliding surface of a piston.

[0003] In recent years, the following method has begun to be used for manufacturing Al alloy cylinder blocks. That is, first, a cylinder having a porous structure, which has the shape of a cylinder liner and is made of, for example, alumina fiber, carbon fiber, or alumina powder or silicon carbide powder as a bone component, is manufactured. This cylindrical body is usually called a preform.

Then, for example, when manufacturing a cylinder block of a four-cylinder engine, four preforms are placed in a predetermined mold, and then A
The molten alloy is cast and the whole is cooled. In this process,
The melt impregnates the voids of the preform. As a result, the preform is converted into a composite material composed of an Al alloy and the bone component to become a cylinder liner, and at the same time, the entire A is formed.
It is cast in an alloy.

[0005] Therefore, in the case of this cylinder block, the sliding surface of the cylinder liner with the piston is composed of a composite material surface in which bone components are exposed in an Al alloy as a matrix. As a method for producing the preform having the porous structure described above, a suction dehydration molding method, an extrusion molding method, a press molding method, and the like are known. The suction dehydration molding method will be described as a typical example.

In this method, first, the bone component such as alumina fiber, carbon fiber, alumina powder and silicon carbide powder is mixed with water, and if necessary, various organic binders and inorganic binders are added. To prepare a slurry. On the other hand, as shown in FIG. 3, a cylindrical mold 2 having a water-permeable wall surface is prepared, the lower end opening thereof is sealed with a plate 2a, and the upper end opening is provided with a plate 2c having a suction port 2b. The cylindrical mold 2 is immersed in the slurry 1 described above. Then, a vacuum is drawn from the suction port 2b to bring the internal space of the cylindrical mold 2 into a negative pressure state.

The air in the internal space of the cylindrical mold 2 is drawn out,
Then, the water of the slurry 1 passes through the wall of the cylindrical mold 2 and is drawn into the cylindrical mold 2.
It is being removed. As a result, the bone components dispersed in the slurry 1 adhere to the outer peripheral surface of the cylindrical mold 2 while being entangled with each other and bonded to each other by the binder to form the cylindrical body 3 having a desired thickness. .

Next, the whole is taken out of the slurry 1 and
After removing the plates 2a and 2b, they are dried and
Is removed from the mold to form a dried cylinder, and finally, the dried cylinder is fired at a predetermined temperature. As a result, as shown in FIG.
The whole shape is a cylindrical shape, and the wall surface 4a has a preform having a three-dimensional porous structure in which bone components in the slurry are bound by a binder, and there are voids communicating with each other between the bone components. Can be

In the case of the extrusion molding method, a screw 5b is provided in a cylinder 5a as shown in FIG.
A bone component and a binder component are charged from a hopper 5d of an extruder 5 having a die 5c of a predetermined shape mounted on the tip, and extruded from the die 5c while kneading the whole by rotating a screw 5b. The preform 4 is formed.

[0010]

When the preform manufactured as described above is used as the base of the cylinder liner, the following problems arise. First,
Considering that the molten aluminum alloy is press-fitted into the mold and the gap of this preform is impregnated with the molten aluminum alloy to form a cylinder liner, it depends on the casting method and the casting conditions. Reforms should not be too tight. This is because it becomes difficult for the molten metal to impregnate the voids.

However, when the preform is excessively rough, the casting of the molten metal into the voids becomes easy, but on the other hand, the mechanical strength of the preform becomes small, and the pressure during the casting of the molten metal is reduced. When the shape is collapsed or compressed, the shape becomes dense and impregnation of the molten metal may not occur. Therefore, it is necessary that the manufactured preform has a porous structure with an appropriate porosity.

Further, the cylinder liner manufactured as a composite material of the preform and an Al alloy as a matrix is required to have excellent wear resistance. In consideration of the above-mentioned problems at the time of casting the molten metal of the Al alloy and the problem of wear resistance of the manufactured cylinder liner, the porosity of the preform, in other words, the volume ratio of the bone composition in the preform is appropriate. Will be decided.

For example, Japanese Patent Application Laid-Open No. 6-322459 discloses a sliding member made of an aluminum alloy using a suction dehydration molding method for producing a preform in which bone components are alumina short fibers and mullite particles. ing. In this case, the volume fraction of each of the alumina short fibers and the mullite particles in the manufactured aluminum alloy sliding member is 2%.
The volume fractions of these bone components in the preform are selected so as to be １２12% and ２５25%.

Japanese Patent Publication No. 3-8867 discloses a sliding member made of an aluminum alloy in which the volume content of alumina fiber is 8.0 to 20.0%. Also in this case, the volume ratio of the alumina fiber in the preform is selected so that the volume ratio of the alumina fiber in the aluminum alloy sliding member to be manufactured has the above-described value.

For this purpose, for example, in the case of the suction dehydration molding method, the type, shape, or compounding amount of the bone component is appropriately selected at the time of preparing the slurry. For example, when using inorganic fiber such as alumina fiber, its length,
Volume ratio is adjusted by factors such as aspect ratio and blending amount,
When using an inorganic powder such as mullite particles,
The volume ratio is adjusted by the particle size, the amount of the compound, and the like.

By the way, among various casting methods, the die casting method is known as a method in which a molten metal is press-fitted at a high temperature to produce a large amount of castings with high precision and smooth and beautiful casting surface in a short time. In the case of this die casting method, the rate of molten metal at the time of casting is high, and the cooling rate is also very high, so that it is suitable as a method for producing a thin casting with high productivity.

Therefore, the preform described above is
When manufacturing cylinder blocks by casting with alloy,
By applying this die casting method, the productivity in manufacturing the cylinder block can be increased. In general,
In order not to disintegrate the preform during die casting of an Al alloy, the volume ratio of the bone component of the preform should be 50%.
It is necessary to be about%.

However, the volume fraction of the bone composition is 50%.
When die casting of an Al alloy is performed on a preform of a certain degree, there is a problem that the preform is not impregnated with a molten metal of the Al alloy, and it is difficult to manufacture a cylinder liner as a composite material. In order to manufacture a cylinder block made of Al alloy under high productivity by casting the preform with a molten metal of Al alloy in this way, and therefore inexpensively,
Although the application of the die-casting method is considered to be optimal, the above-mentioned problems occur, so that it has not been industrially adopted so far.

Therefore, when manufacturing a cylinder block using a preform, a molten metal casting method in which a molten aluminum alloy is impregnated without disintegrating the preform is generally applied. However, the molten metal casting method has a problem that the equipment is larger and the productivity is lower than that of the die casting method.

As a preform using a balloon, there is one described in Japanese Patent Application Laid-Open No. Hei 3-177532. However, this aims at preventing the collapse of the balloon during casting by selecting the particle size and the spheroidization ratio of the balloon. That is, although the overall weight can be reduced, nothing is described about the wear resistance.

[0021] The present invention solves the above-mentioned problems in manufacturing an Al alloy cylinder block by applying a die casting method to a preform, and develops a preform that enables die casting. The purpose of the present invention is to provide an aluminum alloy cylinder block manufactured by using an aluminum alloy cylinder block whose wear resistance of the cylinder liner portion is not inferior to that of the conventional FC cast iron. I do.

[0022]

Means for Solving the Problems In the course of intensive studies to achieve the above object, the present inventors have selected two kinds of bone components, alumina / silica fiber and alumina particles, and used them. To produce various preforms having different volume fractions of bone components,
We tried die casting of molten alloy and investigated the depth of impregnation of preform with molten metal.

As a result, in the case of a preform in which the volume fraction of the bone composition is 18% or less, Al
It has been found that the impregnation depth of the molten alloy is 2 mm or more. Therefore, considering that the thickness of the cylinder liner portion in the cylinder block is generally set to about 2 mm, the use of a preform in which the volume fraction of the bone composition is 18% or less can be sufficiently achieved by die casting. It has been found that a cylinder block can be manufactured.

For the purpose of producing a preform at low cost, the amount of inorganic fibers such as alumina fibers, which are relatively expensive, was reduced, and other bone components to be used instead were examined. As a result, they found that the inorganic balloon described below is inexpensive and can function sufficiently as a bone component of the preform. The present invention is a cylinder block manufactured by a die casting method by using a preform developed based on the above findings.

That is, before the die casting, the inorganic balloon is hollow, and the apparent volume ratio is about 50% due to the addition of the binder and the like. In addition, as the casting proceeds, the molten aluminum alloy penetrates into the hollow portion of the inorganic balloon to lower the overall volume ratio, thereby obtaining a cylinder liner favorably impregnated with the Al alloy.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A cylinder block according to the present invention has the same structure as that of a conventional cylinder block except that a cylinder liner portion is made of a composite material of a preform and an Al alloy described later.
It is no different from an alloy cylinder block. In the above-described composite material, the matrix is an Al alloy, and the bone component is composed of at least an inorganic balloon.
The feature is that the inner space of the inorganic balloon is also filled with the Al alloy at the time of die casting.

In this composite material, the bone component may be only an inorganic balloon, but other bone components include alumina fiber, carbon fiber and carbon fiber which have been conventionally used.
It is preferable to include inorganic fibers such as ceramic fibers, mullite fibers, asbestos, and rock wool, and inorganic powders such as alumina powder and carbon silicon powder, because the strength and wear resistance of the composite material are improved.

In any case, these bone components are deformed by, for example, thermal decomposition, melting or the flow of the molten metal during die casting of the molten Al alloy, which will be described later, so that the situation that the original shape is not maintained does not occur. You need to be there. This composite material has an A to a preform in which the mineral balloon is at least bone constituent.
1 is formed by die casting.

The inorganic balloon is a minute hollow body having a thin crust.
When the alloy is die-cast, the reason is not clear, but the shell of the inorganic balloon is formed with micropores in its spherical shape, from which a molten aluminum alloy is press-fitted. As a result, in the process of die-casting, It is considered that the inner space of the inorganic balloon is also filled with the Al alloy.

Therefore, in the case of this composite material, the volume ratio of the inorganic balloon, which is a bone component, is not the volume ratio of the hollow body but the volume ratio occupied only by the shell portion of the balloon. However, in the preform which is a precursor of this composite material, the apparent volume fraction of the bone composition is a volume fraction as a hollow body,
The value is much larger than the volume fraction substantially occupied by the shell portion of the inorganic balloon in the composite material.

That is, the volume ratio of the inorganic balloon changes from an apparently large value in the preform to a substantially small value by filling the internal space of the inorganic balloon with the molten metal in the process of die casting. is there. The cylinder block is manufactured as follows. First, the above-mentioned suction dehydration molding method, extrusion molding method,
The preform is formed by a press forming method or the like.

As the inorganic balloon to be used, for example,
Glass balloon, shirasu balloon, carbon balloon,
Alumina balloons and the like can be given. The size of the balloon is preferably about 20 to 120 μm. A balloon that is too small has a high shell strength, so that the molten metal of the Al alloy does not fill the interior space of the balloon during die casting, the composite material as described above is not formed, and conversely, the balloon is too large. When it becomes, it ruptures at the time of die casting
This is because they are dispersed in the alloy, and the strength characteristics and wear resistance of the composite material are impaired.

At the time of molding the preform, a binder component is blended. As the binder component used,
Organic binders such as methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, polyvinyl alcohol, hydroxyethylcellulose, and phenolic resin; powdery binders such as frit; and inorganic binders such as sol-like binders such as colloidal silica and alumina sol. it can.

A preform may be formed by simultaneously blending various inorganic fibers and inorganic powders conventionally used. At this time, the mixing ratio of the above-described bone composition is
The sum of the substantial volume fraction of the balloon and the volume fraction of other bone components in the composite material after die casting is 18
%.

In this case, since the apparent volume ratio of the balloon in the preform becomes a large value, the amount of relatively expensive inorganic fibers used can be reduced. The preform thus formed is set in a die-casting machine, a molten metal of an Al alloy is cast, and the preform is made into a composite material with the Al alloy, and the whole is cast.

After the casting, the surface of the formed composite material is subjected to, for example, cutting and honing to form a sliding surface, thereby obtaining the cylinder block of the present invention.

[0037]

Example: Glass balloon (20-120 μm in diameter),
Alumina / silica fiber (fiber diameter 2.5μm, length 50 ~
150 μm, aspect ratio 20 to 60), mullite particles (350 mesh), and a frit as an inorganic binder are mixed, and the mixture is put into a hopper of an extruder shown in FIG. 5, and extruded at a cylinder temperature of 0 ° C. Then, a cylindrical preform having a length of 138 mm, an outer diameter of 95.1 mm and a wall thickness of 3.8 mm was produced.

In this preform, the apparent volume ratio of the glass balloon is 40%, the volume ratio of the alumina / silica fiber is 1.5%, the volume ratio of the mullite particles is 3.5%, and the volume ratio of the inorganic binder is 5%. 0.0%. Conversely, the porosity of this preform is 50%. The apparent volume ratio of the glass balloon was 40.
%, But the substantial volume ratio occupied by the shell portion is 6%.
%.

Accordingly, the substantial volume ratio of the bone component in the preform is 16%.
Then, the preform was set in a die casting machine having a mold clamping force of 300 ton, and was die cast under the conditions of an injection speed of 1.0 m / sec, a casting pressure of 500 kg / cm ² , a gate speed of 30 m / sec, and a filling time of 0.17 sec. . The thickness of the resulting composite was reduced to 1.8 mm. Then, after cutting the surface of the composite material, honing was performed. At that time, a micrograph (100-fold magnification) of the metal structure is shown in FIG. 1 as a substitute drawing.

In FIG. 1, a white portion indicates an Al alloy, and a black portion indicates a void or a bone composition. As is clear from FIG. 1, the shell of the glass balloon is dispersed in the Al alloy while maintaining the spherical shape, and the inside is also filled with the Al alloy. Next, the wear resistance of the composite material was evaluated according to the following specifications.

A pin-shaped piston ring material to be described later was pressed against the surface of the composite material with a load of 50 kg, and 1 ml of lubricating oil was added thereto.
/ Min while supplying the composite material at a stroke of 50 mm,
It was reciprocated for 2 hours at a speed of 200 cpm, and the abrasion amount at that time was measured. The test was performed for a Cr-plated ring material and a nitride-plated ring material.

For comparison, abrasion resistance was also evaluated for FC250, a high silicon aluminum alloy, which has been used as a conventional cylinder liner. The result is shown in FIG. In the figure, the white frame shows the case where the piston ring material is a Cr-plated ring material, and the black frame shows the case where the piston ring material is a nitride ring material.

As is apparent from FIG. 2, the composite material of the present invention has a superbly superior abrasion resistance as compared with the high silicon aluminum alloy, and also has a higher abrasion resistance than the conventional cylinder liner material FC250. There is no inferiority in practical use.

[0044]

As is apparent from the above description, the aluminum alloy cylinder block of the present invention has a wear resistance which is practically comparable to that of FC cast iron whose cylinder liner portion is conventionally used frequently. Is showing. Since the cylinder block of the present invention can be manufactured by a die-casting method, productivity is increased, and lower cost production can be realized as compared with the related art. In addition, since inexpensive inorganic balloons are used in place of relatively expensive inorganic fibers as bone components, cost reduction is realized in terms of materials.

[Brief description of the drawings]

FIG. 1 is a micrograph showing a metallographic structure of a cylinder liner portion of the present invention.

FIG. 2 is a graph showing the results of a wear resistance test.

FIG. 3 is a schematic view showing a method of forming a preform by a suction dehydration forming method.

FIG. 4 is a sectional view showing a preform.

FIG. 5 is a schematic view showing an extruder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Slurry 2 Cylindrical type 2a, 2c plate 2b Suction port 3 Cylindrical body 4 Preform 4a Preform 4 wall 5 Extruder 5a Cylinder 5b Screw 5c Dice 5d Hopper

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenichi Asano 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Koichi Kimura 1-8-1, Shintoda, Hamamatsu-shi, Shizuoka No. 1 Nichias Co., Ltd. in Hamamatsu Research Institute (72) Inventor Koji Iwata 1-8-1, Shintoda, Hamamatsu-shi, Shizuoka Prefecture Nichias Co., Ltd. in Hamamatsu Research Institute (56) References JP-A-48-29604 (JP, A) JP-A-57-177874 (JP, A) JP-A-6-322459 (JP, A) JP-A-10-314914 (JP, A) JP-A-9-14045 (JP, A) JP-A-4- 251658 (JP, A) JP-A-3-177532 (JP, A) JP-A-57-43952 (JP, A) JP-B-3-8867 (JP, B2) (58) Fields investigated (Int. ⁷ , DB name) B22D 19/08 B22D 19/14 F02F 1/00

Claims (1)

(57) [Claims] 1. A cylinder block, wherein a cylinder liner portion is made of a composite material of an Al alloy and at least an inorganic balloon, and an inner space of the inorganic balloon is also filled with the Al alloy.