JP2997900B2 - Ceramic exhaust manifold and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic exhaust manifold and a method of manufacturing the same, and more particularly, to an exhaust manifold made of a composite of ceramic and metal with minimal heat dissipation and a method of manufacturing the same.

[0002]

2. Description of the Related Art Fine ceramic technology has recently attracted attention, and various components have been manufactured using ceramics manufactured by this technology. For example, many ceramic components have been used in internal combustion engines for automobiles. .

[0003] The types of ceramics are extremely large, and each has its own characteristic feature as physical properties. However, when configuring a component that must have many features, such as a component of an internal combustion engine, for example,
Since it is not feasible with different types of ceramics, a ceramic composite structure that meets the required characteristics will be devised by combining several types of ceramics having different characteristics or by combining ceramics and metal.

An example of a component using such a ceramic composite is an exhaust manifold of an internal combustion engine.

A conventional exhaust manifold using a ceramic composite uses a ceramic composite in which a cylindrical tubular body made of aluminum titanate is cast around a metal such as aluminum or cast iron. It has been known.

[0006]

The above-described conventional exhaust manifold has good heat insulating properties, but has a low strength level of aluminum titanate.
It has a disadvantage that it is easily broken due to stress generated by shrinkage, thermal stress generated during operation, and many other causes.

SUMMARY OF THE INVENTION The object of the present invention is to eliminate the above-mentioned disadvantages of the prior art. It is an object of the present invention to provide an exhaust manifold made of a composite of ceramics and metal, which can withstand severe thermal cycling and is easy to manufacture. Accordingly, an object of the present invention is to provide a low-cost ceramic exhaust manifold and a method of manufacturing the same.

[0008]

In order to solve the above-mentioned problems, the present invention relates to all elements of silicon (Si), nitrogen (N) and oxygen (O) and titanium (Ti) and zirconium (Zr). , Hafnium (Hf), yttrium (Y), boron (B), and aluminum (Al).
%, And one port is divided into a plurality and has a flange connected to an exhaust port communicating with an exhaust port of each cylinder. Connected to the flanges,
The present invention provides a ceramic exhaust manifold characterized in that a cast-in metal is disposed on its outer surface, and further comprises silicon (Si) as a main component, and nitrogen (N) and oxygen (O) all. And a mixed powder containing at least one element selected from the group consisting of titanium (Ti), zirconium (Zr), hafnium (Hf), yttrium (Y), boron (B) and aluminum (Al). And the step of forming the inner cylinder shape of the exhaust manifold using the mixed powder, and the step of sintering the inner cylinder shape in a nitrogen atmosphere to nitride and sinter each element contained, A step of heating in an atmosphere containing oxygen after the nitriding sintering step to change a part of the nitride to an oxide;
A step of immersing the inner cylinder of the exhaust manifold, which is a sintered part formed through the above-described steps, in a molten metal and depositing the metal around the inner cylinder; And a step of processing into a ceramic exhaust manifold.

[0009]

Embodiments of the present invention will be described below in detail. First, an exhaust manifold for an internal combustion engine according to the present invention will be described.

FIG. 1 is a partial side view showing an exhaust system of an internal combustion engine. In FIG. 1, reference numeral 1 denotes a cylinder head of the internal combustion engine, and an exhaust port 2 is provided above the cylinder head. Although only one exhaust port is shown in FIG. 1, in the case of a multi-cylinder internal combustion engine, the exhaust port is derived from each of the plurality of cylinders. Reference numeral 3 denotes an exhaust valve rod. Reference numeral 4 denotes an exhaust manifold, one port of which is divided into a plurality and has a flange 10 which is connected to a flange provided at an exhaust port of each cylinder, and the other port is gathered in one place to form one flange 12 It is connected to the. An inner cylinder 5 made of ceramics according to the present invention is provided on the inner side, and a metal outer cylinder 6 is provided on the outer side. The exhaust manifold 4 is connected between the exhaust port 2 and the exhaust turbine port 8 of the supercharger 7. In FIG. 1, a circular hole 14 drawn inside the exhaust manifold 4 is an exhaust hole connected to another cylinder.

The exhaust manifold 4 is obtained by forming an inner cylinder 5 made of ceramics by a method described later, and then casting the inner cylinder 5 with a metal such as aluminum or cast iron to form an outer cylinder 6.

The inner cylinder 5 of the exhaust manifold 4 is manufactured as follows. 5 parts by weight of metal titanium (Ti) powder is added to 100 parts by weight of silicon (Si) powder, a predetermined amount of oil is added thereto, and the mixture is kneaded with a pressure kneader to prepare a plastic composition. I do.

Separately, a mold for manufacturing an inner cylinder is prepared, and the above composition is filled in the mold. Thereafter, the molded composition is taken out of the mold after being pressed by a press at a pressure of about 0.4 ton / cm @ 2. Note that the exhaust manifold 4 has one port branched like a deer's horn, and the other port has one port.
Because of the complicated shape that is integrated into one, it is not possible to produce a cylindrical molded product by one press working.
Therefore, first, two gutter-shaped molded articles made of the above-described composition in which the inner cylinder is vertically divided are made, and these are bonded together with an adhesive to form a cylindrical inner cylinder, which is put into a furnace and placed in a nitrogen atmosphere. Degreasing up to 500 ° C, up to 1400 in the same nitrogen atmosphere
Bake at ℃. By this calcination, the above composition is completely nitrided, and has a volume near 15% inside,
In addition, uniformly dispersed pores are formed.

Next, this was subjected to a heat treatment in the air at 1000 ° C. According to the dimension measurement after the heat treatment, the dimension of the inner cylinder is almost the same as the dimension at the time of molding with the mold. The outer periphery of the inner cylinder thus made is cast in a metal such as aluminum or cast iron to produce an exhaust manifold for a diesel engine. As one method of casting metal around the inner cylinder, after closing both sides of the inner cylinder, it is immersed in molten metal, then pulled up and covered with metal around the inner cylinder. After that, the metal is cut and finished to a desired shape. In addition, the thermal conductivity, strength, coefficient of thermal expansion of the inner cylinder after sintering in the above atmosphere,
The results of product identification by X-rays are shown in the charts of FIGS. 2 and 3.

The ceramic inner cylinder 5 manufactured by the above-described manufacturing method has the same thermal characteristics as the conventional inner cylinder manufactured by aluminum titanate.
It can be seen from the chart that the strength is greatly superior.

The exhaust manifold was not damaged when the inner cylinder was manufactured or when the outer cylinder was cast in the inner cylinder. The exhaust manifold was connected to the exhaust port of a diesel engine equipped with an exhaust energy recovery device, and a bench test was performed. As a result, there was no problem in durability. Although it is a problem outside the gist of the present invention, it was also found that since the exhaust energy did not escape from the exhaust manifold to the outside, the fuel consumption rate was improved by about 2.9% as compared with the related art.

In addition to the above examples, in the present invention, the percentage of the metal powder to be mixed with the silicon Si powder is changed, the type thereof is changed, and the percentage of the ceramic powder is changed. Was changed, and the same inner cylinder made of ceramics as in the above example was prepared. In the charts of FIGS. 2 and 3, examples of Example Nos. 2 to 13 are such.

In the next embodiment, the inner cylinder of the first embodiment, in which sintering in the atmosphere was completed, was immersed in a polycarbosilane solution or an organosilicon polymer solution to impregnate it into the internal pores. Thereafter, a heat treatment was performed under predetermined conditions in the air or in an ammonia atmosphere, and this portion was converted into a thin nitride film. Thereafter, an exhaust manifold was manufactured in the same manner as in the above-described example. The exhaust manifold thus configured has a somewhat increased strength compared to that of the first embodiment.

Further, in the next embodiment, the polycarbosilane paste or the organic silicon polymer paste having a higher viscosity than the polycarbosilane solution or the organic silicon polymer solution used in the above embodiment is completed until the above-mentioned sintering in the atmosphere. After coating on the surface of the inner cylinder of Example 1 described above, baking was performed under the same conditions as above to form a thin nitride film on the surface of the inner cylinder. Thereafter, an exhaust manifold was manufactured in the same manner as in the above-described example. In the exhaust manifold configured as described above, since the inner wall of the inner cylinder in contact with the exhaust gas is covered with the thin nitride film, the heat insulating property is improved as compared with that of the first embodiment.

[0020]

According to the present invention, there is provided an exhaust manifold comprising a composite of ceramic and metal, wherein an oxide composite reaction sintered ceramic is used in place of aluminum titanate which is a ceramic constituting the tubular body. Since the thermal conductivity is the same as that of the conventional type, the strength is three times that of the conventional type, and the reliability of parts used in a portion where the thermal cycle is severe is improved. In addition, since the dimensional change rate during sintering is small and the variation in the change rate is small, the mold design becomes easy. Further, for the same reason, the amount of processing after sintering is reduced, which leads to low cost of parts.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view of a ceramic exhaust manifold.

FIG. 2 is a diagram.

FIG. 3 is another chart.

[Explanation of symbols]

 1 ... Cylinder head 2 ... Exhaust port 3 ... Rod 4 ... Exhaust manifold 5 ... Inner cylinder 6 ... Outer cylinder 7 ... ... Supercharger 8 ... Exhaust turbine port

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F01N 7/16 F01N 7/10 F01N 7/18

Claims (8)

(57) [Claims] (1) silicon (Si), nitrogen (N), oxygen (O),
All elements and titanium (Ti), zirconium (Z
r), hafnium (Hf), yttrium (Y), boron (B), aluminum (Al), and is formed in a tubular shape from a ceramic containing at least 12% of pores. , One port is divided into a plurality and each has a flange connected to an exhaust port communicating with the exhaust port of each cylinder, and the other port is gathered in one place and connected to one flange, and its outer surface has A ceramic exhaust manifold in which a cast-in metal is arranged. 2. The ceramic exhaust manifold according to claim 1, wherein an amorphous ceramic is formed inside the pores. 3. The ceramic exhaust manifold according to claim 1, wherein a dense ceramic thin film is formed on an inner surface of said ceramics containing 12% or more of pores and not in contact with metal. 4. The exhaust manifold according to claim 1, wherein the metal on the outer surface is aluminum. 5. The exhaust manifold according to claim 1, wherein the metal on the outer surface is cast iron. 6. Silicon (Si) as a main component, which contains all elements of nitrogen (N) and oxygen (O), titanium (Ti), zirconium (Zr) and hafnium (H
f) forming a mixed powder containing at least one element from the group of elements of yttrium (Y), boron (B) and aluminum (Al), and using the mixed powder to form the inner cylinder of the exhaust manifold. Forming, sintering the inner cylindrical shape in a nitrogen atmosphere, nitriding and sintering each of the contained elements, and heating in an atmosphere containing oxygen after the nitriding sintering step. Converting a part of the nitride into an oxide, and immersing the inner cylinder of the exhaust manifold, which is a sintered part formed through the above-described steps, in a molten metal, and forming a metal around the inner cylinder. And a step of processing the deposited metal into a desired shape. A method for manufacturing a ceramic exhaust manifold, comprising: 7. After the step of heating a part of the inner cylinder in an atmosphere containing oxygen, the inner cylinder is immersed in a polycarbosilane or organic silicon polymer solution and then heated to form a thin nitride film on the surface of the pores. 7. The method for manufacturing a ceramic exhaust manifold according to claim 6, further comprising a forming step. 8. After the step of heating a part of the inner cylinder in an atmosphere containing oxygen, a polycarbosilane or an organosilicon polymer paste is applied to the inner side surface of the inner cylinder, and then heat-treated. 7. The method for manufacturing a ceramic exhaust manifold according to claim 6, further comprising a step of forming a thin nitride film on a side surface.