JPH05256191A - Exhaust passage of combustion device - Google Patents

Abstract

(57) [Summary] [Purpose] The toughness, heat resistance and heat insulation of the exhaust passage liner are further improved to prevent cracks or breakage due to thermal stress or mechanical stress, and to reduce combustion exhaust gas. Provided is an exhaust passage of a combustion device capable of maintaining a high temperature. [Structure] Silicon Carbide (SiC) and Alumina (Al ₂ O
₃ ) and an exhaust passage liner 8 mainly composed of aluminum (Al), and the exhaust passage liner 8 has a mullite layer on the surface of the exhaust passage line 8 on the side of the exhaust passage to form a mullite exhaust passage 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust passage of a combustion device used in an exhaust system of various combustion devices such as an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as an exhaust passage communicating with an exhaust valve of an internal combustion engine, one provided in a water-cooled cylinder head has been widely used. Preventing temperature drop as much as possible, for example, improving the initial conversion efficiency of exhaust gas purification catalysts,
In order to improve the initial response characteristics of the oxygen sensor element and improve the operating efficiency of the turbine type turbocharger, it is also possible to consider lining the exhaust passage wall provided in the cylinder head. Has been.

As such an exhaust passage with improved heat insulation performance, a layer made of inorganic fibers is provided on the wall surface of the exhaust passage forming portion of the cylinder head, and a layer made of ceramics is provided on the inner surface of the layer made of inorganic fibers. Structures provided (Japanese Patent Laid-Open Nos. 59-175693 and 60-18)
No. 0659, Jitsukai Sho 60-149853), or a tubular ceramic body is provided on the wall surface of the exhaust passage forming portion of the cylinder head, and at least a part is made of zirconia or the like in order to secure the fixing of the ceramic body. A structure having a reinforcing body (Japanese Patent Laid-Open No. 60-1696).
55), and a structure in which a ceramic sprayed layer is provided on the wall surface of the exhaust passage provided in the cylinder head (JP-A-58-99180 and JP-A-62-40232).

[0004]

However, in such a conventional exhaust passage, the ceramics may be damaged by cracks or the like due to thermal stress or mechanical stress, and the exhaust passage may be orthogonal to the exhaust direction. There is a problem that the temperature of the combustion exhaust gas may be lowered due to the large amount of heat that escapes. Further, there is a problem that even if the ceramic sprayed layer is provided, peeling may occur due to thermal stress or mechanical stress, and it has been a problem to solve these problems. ..

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and further improves the toughness, heat resistance and heat insulation of the exhaust passage liner, and improves the toughness, heat resistance and heat insulation of the exhaust passage liner. It is possible to prevent cracks or damage from occurring, and the heat transfer in the exhaust direction is much better than the heat escape in the direction orthogonal to the exhaust direction, which reduces the temperature of the combustion exhaust gas. It is possible to prevent as much as possible. For example, when applied to the exhaust passage of an internal combustion engine, the initial conversion efficiency of the exhaust gas purifying catalyst is improved, the initial response characteristics of the oxygen sensor element are improved, and the operation of the turbine supercharger is improved. It is an object of the present invention to provide an exhaust passage of a combustion device which has good heat resistance and good heat insulation properties, which can improve efficiency.

[0006]

The exhaust passage of the combustion apparatus according to the present invention comprises silicon carbide (SiC) and alumina (A).
1 ₂ O ₃ ) and an exhaust passage liner mainly composed of aluminum (Al), and a surface of the exhaust passage liner on the exhaust passage side is made of mullite (3Al ₂ O ₃ .2SiO ₂ ) material. Therefore, the structure of the invention relating to the exhaust passage of such a combustion device is used as means for solving the above-mentioned conventional problems.

The exhaust passage liner used in the exhaust passage of the combustion apparatus according to the present invention is made of silicon carbide (Si).
C), alumina (Al ₂ O ₃ ) and aluminum (Al)
Is mainly used, for example, SiC: 30 to 55
% By weight, Al ₂ O ₃ : 67 to 30% by weight, Al: 3-1
It is desirable to have a composition of 5% by weight.

In this case, since silicon carbide (SiC) is effective for improving the strength and toughness of the exhaust passage liner, it is preferable to set it to 30 to 55% by weight.
l ₂ O ₃ ) has a high melting point and a low thermal conductivity and is therefore effective in improving the heat resistance and heat insulating properties of the exhaust passage liner. Al) remains in the ceramic grain boundary layer mainly composed of silicon carbide and alumina to improve the strength and toughness value of the ceramics main body, and Al by casting and Al in the exhaust passage liner are melt-bonded to each other to form Al. Since it is effective in increasing the bonding strength to the cylinder block or the like, it is preferably 3 to 15% by weight.

Further, when the surface of the exhaust passage liner on the exhaust passage side is made of mullite (3Al ₂ O ₃ .2SiO ₂ ) material, a thermal spraying method for performing plasma spraying using mullite powder, vapor deposition such as ion plating, etc. It is possible to employ a firing method in which a paste is applied and then fired.

In this case, when a mullite layer is provided to make the surface of the exhaust passage liner on the exhaust passage side to have a mullite quality, the layer thickness is preferably about 5 to 10 μm, and if it is too thin. The effect as the heat-resistant layer and the heat-insulating layer decreases, and if it is too thick, cracks and the like are likely to occur, which is not preferable.

In addition to the heat resistance of the raw material itself, the mullite layer is made to have an appropriate layer thickness as described above and to be porous having pores,
Further improvement in thermal shock resistance and further improvement in heat insulation due to low thermal conductivity will be brought about.

[0012]

In the exhaust passage of the combustion apparatus according to the present invention, the exhaust passage liner mainly composed of silicon carbide, alumina and aluminum is provided, and the surface of the exhaust passage liner on the exhaust passage side is made of mullite. So
The surface of the exhaust passage is made of mullite with a high melting point and low thermal conductivity that is excellent in thermal shock resistance, heat resistance and heat insulation, so that the toughness, heat resistance and heat insulation of the exhaust passage liner are further improved. It is improved, and it is less likely to be damaged by cracks, etc., and of the heat of combustion exhaust gas, the amount of heat transferred in the exhaust direction is large and the amount of heat transferred in the direction orthogonal to the exhaust direction is small. Then, the temperature of the combustion exhaust gas will be exhausted to the downstream side without significantly lowering, and the temperature of the combustion exhaust gas will be higher than before, so that, for example, when applied to the exhaust passage of an internal combustion engine, Further improvement of the initial conversion efficiency of the exhaust gas purifying catalyst, further improvement of the initial response characteristics of the oxygen sensor element, operating efficiency of the turbocharger More it becomes the like further improvement is achieved.

[0013]

1 shows an exhaust passage of a combustion apparatus according to an embodiment of the present invention, in which the combustion apparatus is an internal combustion engine.

In FIG. 1, 1 is a cylinder head, 2 is a cooling water passage provided in the cylinder head 1, 3 is a combustion chamber, and 4 is a combustion chamber.
Is a valve seat, 5 is an exhaust valve, 6 is a valve stem guide, 7 is an exhaust passage, and 8 is an exhaust passage liner provided on the wall surface of the exhaust passage 7.
In order to make the surface of the exhaust passage liner main body 8a on the exhaust passage side have a mullite quality, the mullite layer 8b is formed by a vapor deposition method (CVD method).

In this embodiment, the exhaust passage liner 8
In manufacturing, silicon carbide (SiC): 50
A cylindrical exhaust passage liner main body 8a having a composition of 40% by weight of alumina (Al ₂ O ₃ ) and 10% by weight of aluminum (Al) is manufactured according to the shape of the exhaust passage 7, and then, The tubular exhaust passage liner main body 8
Mullite (3Al ₂ O ₃ · 2SiO ₂ ) on the inner surface of a
A mullite layer 8b having a thickness of 8 μm was formed by a vapor deposition method (CVD method) using, and thereby an exhaust passage liner 8 having a mullite surface on the exhaust passage side surface was obtained.

Next, the exhaust passage liner 8 thus produced is set in a cylinder block casting mold of an internal combustion engine, and a molten aluminum alloy is cast into the exhaust passage liner 8, which is shown in FIG. A cylinder head 1 made of such an aluminum alloy was obtained.

Therefore, in the aluminum alloy cylinder head 1 manufactured as described above, the surface of the exhaust passage 7 is formed of the mullite layer 8b having a high melting point and a low thermal conductivity which is excellent in thermal shock resistance, heat resistance and heat insulation. In addition, the exhaust passage liner main body 8a is a composite of ceramics and metal (Al) mainly composed of silicon carbide (SiC) and alumina (Al ₂ O ₃ ). Al in 8a is welded, and the exhaust passage liner 8 is firmly bonded to the exhaust passage 7 side of the cylinder head 1.

Since the mullite ceramics forming the exhaust passage side surface of the exhaust passage liner 8 is excellent in thermal shock resistance, it sufficiently withstands thermal shock due to rise and fall of exhaust temperature which varies depending on increase and decrease in engine speed. In addition to being able to do so, it also has the characteristics of heat resistance and heat insulation (low thermal conductivity), which are one of the characteristics of ceramics, so it is difficult to convey the exhaust temperature in the direction of the water-cooled core (direction orthogonal to the exhaust direction). It has the function of discharging toward the outlet while keeping the temperature high.

Therefore, it is possible to effectively prevent a decrease in the temperature of the combustion exhaust gas and to raise the exhaust gas temperature.

The mullite layer 8b also has a large number of holes, and the holes also improve impact resistance and contribute to the improvement of heat resistance and heat insulation by providing low thermal conductivity. ..

Further, the exhaust passage liner main body 8a
Has a composition of ceramics (SiC, Al ₂ O ₃ ): 90% by weight, and metal (Al): 10% by weight.
Since the ceramics are completely bonded and the metal remains in the grain boundary layer, the strength and toughness of the ceramics body is high, and it is used as an engineon component with significant mechanical vibration and thermal shock. It can withstand the use of. If the mullite layer 8b is not present on the surface, the metal Al content is eluted and the structure is easily destroyed.

Next, the cylinder head 1 shown in FIG. 1 according to the embodiment of the present invention was assembled to each engine, and a bench test and a go-stop durability test under full load were performed.
After 0 hours, no damage was observed around the exhaust port liner, and no trouble occurred.

Further, the exhaust temperature is about 150 ° C. at the exhaust port outlet as compared with the case of a normal aluminum alloy engine.
Was observed.

Further, since the exhaust passage liner main body 8a, which is a composite of silicon carbide (SiC) and alumina (Al ₂ O ₃ ) and has an excellent fracture toughness, is used, the exhaust port due to the vibration which was initially a concern. Since the high temperature combustion exhaust gas can be sent to the downstream O ₂ sensor system, the exhaust gas purification catalyst system, the turbine type supercharger system, etc. without causing any damage, it is possible to effectively utilize this heat. Thus, it was confirmed that the startup characteristics of the O ₂ sensor could be improved, the initial conversion efficiency of the exhaust gas purifying catalyst could be improved, and the supercharging efficiency of the turbine type supercharger could be improved.

[0025]

The exhaust passage of the combustion apparatus according to the present invention is provided with an exhaust passage liner mainly composed of silicon carbide, alumina and aluminum, and the exhaust passage liner surface on the exhaust passage side is made of mullite. Therefore, it is possible to further improve the toughness, heat resistance and heat insulation of the exhaust passage liner, and make it difficult for cracks or damage due to thermal stress or mechanical stress to occur. In addition to being possible, it is possible to reduce the escape of heat of the combustion exhaust gas in the direction orthogonal to the exhaust direction to increase the heat transfer in the exhaust direction, and to prevent the temperature of the combustion exhaust gas from decreasing as much as possible. Since it becomes possible to flow the combustion exhaust gas to the downstream side, for example, in the case of an O ₂ sensor used for air-fuel ratio control in a combustion device, It has a remarkably excellent effect that the start-up characteristics are improved, the initial conversion efficiency of the exhaust gas purifying catalyst is improved, and the supercharging efficiency of the turbine type supercharger is improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view of a cylinder head portion of an internal combustion engine showing an embodiment of an exhaust passage of a combustion device according to the present invention.

[Explanation of symbols]

 7 Exhaust passage 8 Exhaust passage liner 8a Exhaust passage liner mainly 8b Mullite layer

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[Procedure amendment]

[Submission date] March 17, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

Therefore, in the aluminum alloy cylinder head 1 manufactured as described above , the surface of the exhaust passage 7 has a high melting point and low thermal conductivity excellent in heat shock resistance, heat resistance and heat insulation as shown in FIG. And the exhaust passage liner main body 8a is a composite of ceramics and a metal (Al) mainly composed of silicon carbide (SiC) and alumina (Al ₂ O ₃ ). And Al in the exhaust passage liner main body 8a are welded together, and the exhaust passage liner 8 is firmly connected to the exhaust passage 7 side of the cylinder head 1.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

The mullite layer 8b is shown in FIG.
As described above, there are a large number of holes , and the holes also improve impact resistance and contribute to the improvement of heat resistance and heat insulation by providing low thermal conductivity.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 2

[Correction method] Added

[Correction content]

FIG. 2 is a micrograph (× 933 times) showing a cross-sectional structure of an exhaust passage liner in an embodiment of an exhaust passage of a combustion apparatus according to the present invention.

[Procedure amendment 4]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Added

[Correction content]

[Fig. 2]

Claims (1)

[Claims] 1. An exhaust passage of a combustion apparatus, comprising an exhaust passage liner mainly composed of silicon carbide, alumina and aluminum, and the surface of the exhaust passage liner on the exhaust passage side is made of mullite.