JPH083661A - Cylinder tube made of aluminum alloy and its production - Google Patents

Abstract

PURPOSE:To obtain sufficient strength in cylinder tube even if it is thin and to attain its lightening in weight and nonmagnetization. CONSTITUTION:This cylinder tube is constituted of an intermediate cylinder 3 made of heat resistant aluminum alloy for casting in which an internal layer 2 constituted of a fiber reinforced composite material is integrated and an external cylinder 4 made of a high strength aluminum alloy for working chilled and engaged with an intermediate cylinder 3, and this fiber reinforced composite material is the one in which a heat resistant aluminum allay for casting is blended with carbon fibers in the ratio of 15 to 50vol.% to the whole body of the fiber reinforced composite material, potassium titanate whiskers are blended in the ratio of 20 to 50vol.% to the carbon fibers, and they are compounded in such a manner that the total content of the carbon fibers and potassium titanate whiskers is regulated to the ratio of 18 to 60vol.% to the whole body of the fiber reinforced composite material. Thus, its specific wear amt., the coefficient of friction, hardness and logarithmic decrement are improved by the internal layer 2, and its strength to gaseous pressure is secured by the external cylinder body 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy cylinder tube for an internal combustion engine using an aluminum base fiber reinforced composite material and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, there has been a demand for a cylinder tube for an internal combustion engine to be lightweight and non-magnetic for measurement, and the applicant of the present invention has found that an aluminum-based fiber-reinforced composite material having a particularly high wear resistance, that is, an aluminum alloy. A composite material of carbon fiber and potassium titanate whiskers is composited on the inner surface of an aluminum alloy cylinder.
No. 60469 (Japanese Patent Laid-Open No. 3-24240).

[0003]

The aluminum-based fiber reinforced composite material and the aluminum alloy are compounded by a pressure casting method, and therefore the casting aluminum alloy does not deteriorate in strength by heating (for example, JIS standard,
AC8A) is used. However, since the aluminum alloy for casting has insufficient tensile strength, it is necessary to increase the wall thickness of the aluminum alloy, and when a plurality of cylinder tubes are arranged in parallel, the problem that the cylinder interval becomes large occurs. there were.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide an aluminum alloy cylinder tube which is thin and has sufficient strength, and which can realize weight reduction and demagnetization, and a method for manufacturing the same. And

[0005]

In order to solve the above problems, the aluminum alloy cylinder tube of the present invention is a heat resistant aluminum alloy for casting in which an inner surface layer made of a fiber reinforced composite material mainly containing carbon fibers is integrally formed. And an outer cylinder body made of a high-strength aluminum alloy that is externally fitted and fixed to the inner cylinder body.

Alternatively, in the above structure, the outer cylinder is made of a high-strength aluminum alloy for processing. Further, the fibers of the fiber-reinforced composite material having the above-mentioned structure are mainly composed of carbon fibers and are mixed with potassium titanate whiskers.

Furthermore, in the fiber-reinforced composite material having the above-mentioned constitution, carbon fibers are blended in a heat-resistant aluminum alloy for casting at a ratio of 15 to 50% by volume based on the whole fiber-reinforced composite material, and potassium titanate whiskers are added. 20 to 50% by volume with respect to the carbon fiber, and the total amount of carbon fiber and potassium titanate whiskers is compounded in the range of 18 to 60% by volume of the entire fiber reinforced composite material. Is.

In the method of manufacturing an aluminum alloy cylinder tube according to the present invention, when manufacturing the aluminum alloy cylinder tube, the inner surface layer preform is first molded, and then the precast body is formed by a pressure casting method. A reformed body is impregnated with a heat-resistant aluminum alloy for casting to form an inner cylinder body in which an inner surface layer made of a fiber-reinforced composite material is compounded on the inner surface, and further by cold fitting, the outer cylinder body is attached to the inner cylinder body. Is fitted and fixed.

In the above method, the preform body is molded by mixing carbon fibers and potassium titanate whiskers in a predetermined volume ratio, putting them in water, molding and then drying.

[0010]

According to the above structure, the inner surface layer made of the fiber reinforced composite material can ensure the specific wear amount, the friction coefficient and the hardness required for the cylinder tube, and can increase the logarithmic damping rate. The outer cylinder made of a high-strength aluminum alloy can ensure strength against gas pressure. Therefore, sufficient strength can be obtained with a thin wall thickness, weight reduction and demagnetization for measurement can be achieved, and abrasion resistance and attenuation rate can be improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an aluminum alloy cylinder tube and a method of manufacturing the same according to the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the cylinder tube 1 has a fiber reinforced composite material (hereinafter referred to as CFRM) on its inner surface.
A heat-resistant aluminum alloy for casting in which an inner surface layer 2 made of composite is integrated (for example, JIS standard, AC8A-
T6) made of an inner cylinder body 3 and an outer cylinder body 4 made of a high-strength aluminum alloy for processing (for example, JIS standard, A7075-T6), which is externally fitted and fixed to the inner cylinder body 3 by cold fitting. Has been done.

The CFRM forming the inner surface layer 2 is a composite of heat-resistant aluminum alloy for casting, which is a base material, and carbon fibers and potassium titanate whiskers.
As shown in the schematic view showing the microstructure of FRM, as a base material, a heat-resistant aluminum alloy for casting (for example, JI
S standard, AC8A) 11, carbon fiber 12 having a length of 0.1 to 10 mm, and potassium titanate whiskers (K
₂ O · 6TiO ₂ ) 13 is compounded, and the volume ratio of the carbon fibers 12 is 15 to 50 with respect to the entire CFRM.
20% to 50% of the potassium titanate whiskers are added to the carbon fibers 12 so that they are mixed in a volume ratio of 20%.
It is blended in a volume ratio (that is, the volume ratio of carbon fiber 12: potassium titanate whisker 13 is 5: 1 to 2:
1) and the total amount of the carbon fibers 12 and the potassium titanate whiskers 13 is 18 to 18 of the total CFRM.
It is in the range of 60% by volume.

The above materials can be compounded by using techniques such as pressure casting and powder metallurgy. When a cylinder tube is targeted, a preform of reinforced fiber can be manufactured and the casting can be performed by casting. The pressure casting method capable of die casting capable of obtaining a defect-free CFRM is most desirable. Next, the role of the carbon fiber 12 and the potassium titanate whisker 13 and the reason for determining the composite amount will be described.

First, the carbon fiber 12 plays a role of forming a composite, since the carbon fiber 12 has a specific gravity smaller than that of the base material of the aluminum alloy 11 and can reduce the weight of the CFRM.
Although it is possible to improve the wear resistance of the base material of the aluminum alloy 11 only by itself, potassium titanate whiskers 1
Coexistence with 3 can further improve wear resistance. The damping characteristics of the aluminum alloy 11 are improved.
That is, it is possible to increase the damping rate about twice that of mild steel. On the contrary, when the volume ratio of the carbon fibers 12 exceeds 50% by volume with respect to the entire CFRM, the addition amount of the potassium titanate whiskers 13 to be added to the carbon fibers 12 is 1
It is less than 20% by volume based on 2 (because the total amount of the carbon fibers 12 and the potassium titanate whiskers 13 is 60% by volume or less of the entire CFRM), which hinders the moldability of the preform body as described later. Because.

The role of compounding the potassium titanate whiskers 13 is that the carbon fiber 12 accounts for the proportion of the reinforcing fiber.
To 20 to 50% by volume, the wear resistance of the aluminum alloy 11 is remarkably improved, and the wear resistance is better than that of the carbon fiber alone or the potassium titanate whiskers 13 alone. Fiber 1
When mixed with 2, it functions as a binder that enables molding of the preform body and is stable with respect to the aluminum alloy 11 and the carbon fiber 12.

Next, the composite amount of both fibers 12, 13 is determined in consideration of the strength of the preform body, the permeability of the molten aluminum (depending on the fiber density), and the performance of the composite material. That is, since the preform having a fiber density, that is, a ratio (volume ratio) of reinforcing fibers to CFRM of more than 60% by volume has poor castability, the upper limit is set to 60% by volume. On the contrary, when the preform is pressure-cast, the fibers are entangled in the composite material to obtain a uniform dispersion.
8% by volume or more is desirable, and the lower limit is 18% by volume.

Next, if the amount of potassium titanate whiskers 13 in the reinforcing fibers is 20% by volume or less (that is, carbon fibers: potassium titanate whiskers = 5: 1), the strength of the preform is insufficient and molding cannot be performed. 50 on the contrary
Volume% (carbon fiber: potassium titanate whiskers = 2:
When it exceeds 1), aggregates of potassium titanate whiskers 13 are likely to be formed, and it is difficult to form a uniform composite material. Therefore, the amount of potassium titanate whiskers 13 in the reinforcing fiber is preferably in the range of 20 to 50% by volume. In particular, in the range where the carbon fiber 12 is more than the carbon fiber 12: potassium titanate whisker 13 = 3: 1 (33% by volume or less), the sliding property, that is, the wear resistance is excellent.

The base material of the aluminum alloy 11 provides the basic strength of the composite material, and forms the outer shell of the member when partially composited (in the case of the inner wall of the cylinder tube only). It is a thing. AC8A and the like are aluminum alloys having a strong age-hardening property and have good wettability with potassium titanate whiskers and carbon fibers, and are therefore preferable as the base alloy.

For example, as a more specific example, a single fiber is a carbon fiber 1 having a diameter of 5 to 15 μm and a length of 0.1 to 10 mm.
2 (true specific gravity 1.77 g / cm ³ ) and the diameter of single fiber is 0.4-
A press used for a metal mold after mixing with potassium titanate whiskers 13 (true specific gravity: 3.3 g / cm ³ ) having a volume of 1.5 μm and a length of 10 to 100 μm in a predetermined volume ratio and thoroughly stirring the mixture. A preform body P is manufactured by molding (pressure 20 kg f / cm ² ) into a cylindrical shape and drying.
The obtained preform P did not lose its shape and was easy to handle. And this preform body P
It compounded by the pressure casting method using the pressure casting apparatus 21 shown in FIG. That is, the preform body P is placed in the preheated forming portion 22a of the lower die 22, the upper die 23 is superposed and fixed on the lower die 22, and then the pressurizing cylinder device 24 is driven to drive the base metal melt M ( (Heat-resistant aluminum alloy for casting) is supplied to the forming portion 22a, and the preform body P has a volume ratio of 40%.
The inner cylindrical body 3 in which the inner surface layer 2 is integrated is molded by compounding so that At this time, the pouring temperature was 780 ° C., the pressure was 577 kgf / cm ² , the mold preheating temperature was 300 ° C., and the pressurizing time was 8 minutes. A heat-resistant aluminum alloy for casting having an inner surface layer 2 having a wall thickness of about 5 mm manufactured in this manner (for example, JIS standard, AC8A-T6)
The manufactured intermediate cylinder 3 could be manufactured.

Although carbon fibers generally have poor wettability with metals, they can be sufficiently brought into contact with each other by a pressure casting method, and they are solidified by pressure casting in a short time. No compound is generated and the material does not become extremely brittle. The applied pressure is preferably 300 kgf / cm ² or more.

Then, the inner cylindrical body 3 which is this composite is placed at 0.degree.
Cooled to a high strength aluminum alloy for processing (eg J
The outer cylinder 4 made of IS standard, 7075-T6) is heated to about 50 ° C. and subjected to cooling fitting to integrate the outer cylinder 4 with the composite of the inner cylinder 2 and the intermediate cylinder 3. Here, the reason why the inner cylindrical body 3 and the outer cylindrical body 4 are integrated with each other by cooling fitting is to avoid a decrease in strength of the outer cylindrical body 4 due to heating. It should be noted that the portion without the inner surface cylinder 2 is cut and separated for use.

Table 1 shows the material characteristics of the inner surface layer 2, the inner cylindrical body 3, and the outer cylindrical body 4 in the above structure.

[0024]

[Table 1]

As shown in Table 1, the inner cylinder 3 made of a heat-resistant aluminum alloy for casting and the outer cylinder 4 made of a high-strength aluminum alloy for processing have continuous physical characteristics from the inside to the outside, for example, the coefficient of thermal expansion. And shows thermal conductivity, and distortion due to a difference in thermal expansion does not occur during use. Further, the tensile strength of the outer cylinder 4 made of high-strength aluminum alloy for processing is remarkably high, and the cylinder tube 1 has high strength.

Next, Table 2 shows a comparison of various characteristics as a cylinder tube material. (Below margin)

[0027]

[Table 2]

As is clear from Table 2, a cylinder tube formed by externally fitting an outer cylinder 4 made of a high-strength aluminum alloy for processing onto an inner cylinder 3 having a composite inner layer 2 made of CFRM. 1 is also excellent in specific wear amount and friction coefficient,
In addition, it has an advantage that the logarithmic attenuation rate is large, and it is understood that it is suitable as a sliding material for the cylinder tube 1.

According to the above-mentioned embodiment, among the internal combustion engine parts, the heat resistance and wear resistance of the cylinder tube 1 which is required to have durability especially in a high temperature and wear environment are combined with the inner surface layer 2 made of CFRM. It was possible to improve the strength by using the inner cylinder 3 and to increase the strength to withstand a load such as gas pressure by forming a multilayer of the same kind of high-strength aluminum alloy for processing.
Further, although the inner cylinder 3 is not significantly improved in hardness, since the outer circumference is wrapped with the outer cylinder 4 made of a high-strength aluminum alloy for processing, there is no problem in strength as a cylinder tube.

Although a high strength aluminum alloy for processing is used for the outer cylinder 4 in the above embodiment, the strength is similarly high and the physical characteristics are continuous with the inner cylinder 3 made of the heat resistant aluminum alloy for casting. Other high-strength aluminum alloys may be used as long as they are such.

[0031]

As described above, according to the present invention, the inner surface layer made of the fiber reinforced composite material can secure the specific wear amount, the friction coefficient and the hardness required for the cylinder tube, and the logarithmic damping rate. The outer cylinder made of high-strength aluminum alloy for processing can secure the strength against gas pressure. Therefore, sufficient strength can be obtained with a thin wall thickness, weight reduction and demagnetization for measurement can be achieved, and abrasion resistance and attenuation rate can be improved.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of a cylinder tube according to the present invention.

FIG. 2 is a schematic diagram showing a microstructure of a fiber-reinforced composite material.

3 (a) and 3 (b) are explanatory views of a compounding operation of a preform body by a pressure casting device, respectively.

[Explanation of symbols]

 1 Cylinder Tube 2 Inner Cylinder 3 Intermediate Cylinder 4 Outer Cylinder 11 Aluminum Alloy 12 Carbon Fiber 13 Potassium Titanate Whisker 21 Pressure Casting Equipment

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Seiichi Kotake, 5-3 28 Nishikujo, Konohana-ku, Osaka City, Osaka Prefecture, Hitachi Shipbuilding Co., Ltd. (72) Ryuichi Hotta, Nishikujo, 5-cho, Osaka, Osaka 3-28 Hitachi Shipbuilding Co., Ltd. (72) Inventor Zhang Yibin 5-3-28 Nishikujo, Konohana-ku, Osaka City, Osaka Prefecture Hitachi Shipbuilding Co., Ltd.

Claims (6)

[Claims] 1. An inner cylinder made of a heat-resistant aluminum alloy for casting in which an inner surface layer made of a fiber-reinforced composite material mainly containing carbon fibers is integrally molded, and a high-strength aluminum alloy externally fitted and fixed to the inner cylinder. An aluminum alloy cylinder tube characterized by comprising an outer cylinder body made of aluminum. 2. The aluminum alloy cylinder tube according to claim 1, wherein the outer cylinder is made of a high-strength aluminum alloy for processing. 3. The aluminum alloy cylinder tube according to claim 1, wherein the fibers of the fiber-reinforced composite material are mainly composed of carbon fibers and potassium titanate whiskers are mixed therein. 4. A fiber-reinforced composite material comprising a heat-resistant aluminum alloy for casting, wherein carbon fibers are blended in a proportion of 15 to 50% by volume with respect to the entire fiber-reinforced composite material, and potassium titanate whiskers are added to said carbon fibers. 20 to 50% by volume, and the total amount of carbon fibers and potassium titanate whiskers was compounded at a rate of 18 to 60% by volume of the entire fiber reinforced composite material. The aluminum alloy cylinder tube according to claim 1 or 2. 5. When manufacturing the aluminum alloy cylinder tube according to claim 1, first, a preform body for an inner surface layer is formed, and then a heat resistant aluminum alloy for casting is applied to the preform body by a pressure casting method. It is impregnated to form an inner cylinder in which an inner surface layer made of a fiber-reinforced composite material is composited on the inner surface, and the outer cylinder is externally fitted and fixed to the inner cylinder by cooling fitting. Method for manufacturing aluminum alloy cylinder tube. 6. The preform body is molded by mixing carbon fibers and potassium titanate whiskers in a predetermined volume ratio, placing the mixture in water, molding and drying.
A method for manufacturing a cylinder tube made of the aluminum alloy described above.