JPS60187712A - Exhaust manifold for internal-combustion engine - Google Patents

Abstract

PURPOSE:To simplify manufacture, and to lighten the weight of the titled exhaust manifold by forming an external pipe body unified by casting an internal pipe body consisting of an inner layer made of hard ceramic fiber and an outer layer made of soft ceramic fiber from the outside by aluminum and using the external pipe body as the exhaust manifold. CONSTITUTION:An inner layer 11A for an internal pipe body 11 in an exhaust manifold proper 10 is formed by hard ceramic fiber and an external layer 11B by soft ceramic fiber, and an external pipe body 12 made of aluminum is cast to the outside of the internal pipe body and unified, thus manufacturing the exhaust manifold proper. Accordingly, the melting point on casting lowers, excessive thermal stress is not applied to the internal pipe body 11, the external layer 11B absorbs heat shrinkage and expansion difference with the external pipe body 12 and prevents the generation of excessive thermal stress because the external layer 11B is soft, and the exhaust manifold can be lightened because an aluminum material is used.

Description

[Detailed Description of the Invention] (Technical Field) This invention is based on l! i lj3 is related to the exhaust manifolds 1 to 1.

(Background and Prior Art) It is generally well known that in multi-cylinder internal combustion engines for automobiles, a 471 air manifold (exhaust manifold) is installed connected to the exhaust port of each cylinder. It is well known that various improvements have been made to the structure of exhaust manifolds in order to avoid adverse thermal effects during casting and engine operation, and to reduce weight.

Examples of such conventional exhaust manifolds include those disclosed in Japanese Utility Model Publication No. 56-37047M and Japanese Utility Model Publication No. 57-47713.
The latter is shown in FIGS. 1 (Δ) and (B).

This is made by molding the air manifold main body 1 into a predetermined manifold shape using solid ceramic +A, and the inner tube body 2 is integrally cast. vJ', which has a substantially similar shape to the inner tube body 2 which is cast by
It is formed into a two-car tube structure consisting of an iron outer tube body 3, and is divided into three parts A, B, and CL in the cylinder row direction to form 4iS.

According to this, by using the above-mentioned ceramic material, it is possible to significantly reduce the heavy vi-ridge polishing material portion, and the weight of the exhaust manifold main body 1 can be reduced.

On the other hand, the thermal shock applied to the inner pipe body 2 during casting of the exhaust manifold main body 1, the thermal stress, vibrations, etc. accompanying the operation and stop of the engine are absorbed by the three-part structure described above. The inner tubular body 2 is made of inflexible solid ceramic material, and the outer tubular body 3 is made of cast iron with a high melting point (the molten metal temperature during casting is 1.5 mm).
500 to 1 to 600 degrees Celsius), thermal shock during the manufacture of the exhaust manifold body 1, and thermal stress caused by the difference in the coefficient of thermal expansion between the two tubes 2 and 3 during engine operation, etc. This is to prevent the flute body 2 from being damaged.

However, in conventional exhaust manifolds for internal combustion engines, the exhaust manifold main body 1 is divided into three parts in the longitudinal direction in order to avoid the above-mentioned adverse thermal effects, resulting in an increase in the number of parts. However, there is a problem in that the number of man-hours for manufacturing and assembly increases, leading to an increase in costs.

In addition, since the solid ceramic material forming the inner tube 2 has a low porosity and does not have sufficient heat insulation, the temperature of the outer tube 3 may become high. It has become essential to use materials such as these, and this has become a factor that hinders further weight reduction of exhaust manifolds.

(Purpose of the Invention) This invention was made by focusing on these conventional problems, and aims to completely reduce the weight of the exhaust manifold by using an integrated structure and aluminum material, while improving its durability. cover with the purpose of making it happen.

(Disclosure of the Invention) In this invention, in the exhaust manifold of a multi-cylinder internal combustion engine for automobiles as shown in (a) above, the inner pipe body is formed into a predetermined manifold shape, and the inner side that is exposed to exhaust gas is molded with hard ceramic fibers. The outer tube is coated with soft ceramic fiber, and this inner tube is integrally cast from the outside. This forms an exhaust manifold body having a two-vehicle tube structure.

According to this, the high-temperature exhaust heat is insulated by the ceramic fiber inner tube with low thermal conductivity, making it possible to use aluminum with a low melting point for the outer tube, which is significantly more effective than refined steel. Overlapping is reduced.

The outer layer of the inner tube made of ceramic fiber is much more flexible than solid ceramic, while aluminum has a much lower melting point than cast iron (the temperature of the molten metal during casting is around 700°C), as mentioned above. As a result, the thermal stress generated in the inner casing during casting is minimal, and the thermal stress caused by engine operation and stoppage can be sufficiently absorbed, making it possible to form an integrated fS1 exhaust manifold. Cost reduction can be achieved. The inner layer of the inner tube is made of hard ceramic fiber, so it won't get crushed by exhaust gas and has sufficient durability.

(Example) Hereinafter, one embodiment of the present invention will be described based on the drawings.

As shown in FIGS. 2(A), (B), and (C), the exhaust manifold main body 10 consists of 4 cylinders (6 cylinders).
It is formed of 4 structures.

This exhaust manifold main body 10 is formed of a double pipe structure including an inner pipe body 11 and an outer pipe body 12, and further includes an inner pipe body 11 and an outer pipe body 12.
is formed of two layers: an inner layer 11A and an outer layer 11B.

The inner tube 11 is formed into a predetermined manifold shape using ceramic fiber, and the outer tube 12 is made of aluminum and is integrally cast with the inner tube 11 to have a substantially similar shape to the inner tube 11. Cast molded.

Silica/alumina fiber, alumina fiber, silica fiber, etc. are used as ceramic fibers for forming the inner tube body 11, but IH11A, which comes into contact with exhaust gas, has rigidity and hardness; The outer layer 11B is made of a soft material that shrinks easily.

An example of its properties is as follows.

The inner layer 11Δ is formed by a vapor lamination method in which a number of thin paper-like ceramic fibers impregnated with a binder such as a silica-based aqueous solution are laminated and molded, or by a wire mesh mold in an aqueous solution in which ceramic fibers are suspended. The product is then molded into a liquid and molded into halves or as a single piece using vacuum forming force.

When the vacuum forming method is used, the side that is in contact with the shape of the wire mesh, that is, the exhaust gas passage side, has a high density, which prevents fumes caused by exhaust gas. Durable against swelling of varnish, etc. On the other hand, the outer layer 11B is formed by splitting and molding Plankera 1-shaped ceramic fibers in half using a press or the like, and pasting them together with an adhesive such as silica sol on the outside of the inner layer 11A.

By the way, the exhaust manifold main body 10 (outer pipe body 12)
When casting, 'lB+f' is significantly lower than that of conventional cast iron.
Since molten aluminum with a low temperature of 700°C (near J) is used, the temperature drop in the inner tube 11 is reduced by approximately half, and the outer layer 1.1B in contact with the aluminum material is replaced with a conventional solid ceramic. Ceramic 7 is significantly more flexible
Since the molded body is made of 71 fibers, the thermal stress generated even on the relatively hard inner layer 11Δ is small, and it is possible to prevent the inner tube body 11 from breaking due to thermal shock during casting.

Furthermore, if the exhaust manifold main body 10 is made of a single-weight 14-piece structure for all cylinders, the number of manufacturing and assembly steps can be reduced due to the reduction in the number of parts, resulting in cost reduction. On the other hand, the outer layer 11B of the inner tubular body 11 undergoes heat shrinkage with the aluminum outer tubular body 12 due to repeated operation and stopping of the engine.
f. Easily absorbs clothing, reduces thermal stress, and can be expected to increase durability.

By the way, the critical temperature drop for failure due to thermal shock of typical solid heramics as well as ceramic fibers is shown below.

In addition, in this embodiment, since the inner tube body 11 is made of ceramic fiber, the thermal conductivity is lower than that of the conventional solid ceramic material, so that the exhaust gas is not cooled and the catalyst stagnation installed in the exhaust passage is not cooled. 1, while the outer capsule/body 12
This makes it possible to use aluminum 4Δ, which has a low melting point, for the outer tubular body 12 by reducing the temperature transfer to the outer tubular body 12.

Below are the thermal conductivities of ceramic and comparative air,
Exhaust gas temperature reaches 750°C/850°C during engine high-speed operation)
Indicates the temperature at the interface between the inner pipe body 11 and the outer pipe body 12 in the exhaust manifold main body 10 (1τ unit cal/cm-sec -°C) In this way, aluminum material can be used for the outer pipe body 12. As a result, -C exhaust manifold body 10 compared to the conventional example made of cast iron
The weight of the engine is significantly reduced, making the engine lighter.

<Effects of the Invention> According to the above-described invention, the inner tube body made of a ceramic molded body is made of a hard ceramic fiber for the inner layer that comes in contact with exhaust gas, and a soft ceramic fiber for the outer layer. Since the inner tube is integrally cast and the aluminum outer tube is cast on the outside, the melting point during casting is lowered, and excessive thermal stress is not applied to the inner tube, making it easier to exhaust air. The manifold body can be integrated with all cylinders (M construction), reducing manufacturing and installation man-hours and reducing costs.
The use of aluminum material has the effect of completely reducing weight.

In addition, since the inner layer of the inner pipe body is hard, it is difficult to contact any part of the exhaust gas.
3.The outer layer is soft and absorbs the difference in thermal contraction and expansion with the outer tube, preventing excessive thermal response and improving its durability. arise.

[Brief explanation of drawings]

Figure 1 (A> is a front view of the conventional example, and Figure 1 (B') is its ■
-r line sectional view. FIG. 2(A) is a front view of the first embodiment of the present invention;
B) is a cross-sectional view along the ■-■ line, and the same figure (, C) is the same figure (B)
It is a sectional view taken along the line ■-■. DESCRIPTION OF SYMBOLS 10... Exhaust manifold main body, 11... Inner pipe body, 12... Outer pipe body, 11A... Inner layer, 11B...
・Outer layer. Patent applicant Nissan Motor Co., Ltd. Figure 1 (A) Figure 1 (B) Figure 2 (A) Figure 2 (B) Figure 2 (C)

Claims (1)

[Claims] The exhaust manifold has a double pipe structure consisting of an inner tube body and an outer tube body formed in the shape of a manifold.The inner layer that is exposed to the exhaust gas is made of hard ceramic fiber, and the outer layer is covered with soft helical fiber. An exhaust manifold for an internal combustion engine, comprising a formed inner pipe body and an aluminum outer pipe body integrally formed by casting the inner pipe body from the outside.