JPS61215415A - Exhaust manifold of internal-combustion engine - Google Patents

Abstract

PURPOSE:To provide constructive strength for an internal ceramic-fiber pipe on the outside of which an external pipe made of light alloy is formed, by having ceramic particles stick to the internal peripheral surface of the ceramic fiber. CONSTITUTION:An exhaust manifold 1 is made up in such a manner that an internal pipe 2 shaped in the specified manifold form is integrally cast in an external pipe 3 made of aluminum alloy. The internal pipe 3 is mainly made of ceramic fiber and the internal peripheral face 5 which is a face exposed to exhaust gas is provided with higher structual strength by sintering ceramic particles 6 to the crossing parts of and the spacings of the ceramic fiber 4. When an engine is operated, the internal peripheral face 5 of the internal pipe 2 is kept exposed to high-temperature exhaust gas, however, the internal peripheral face 5 has high structual strength as mentioned above so that the ceramic fiber 4 can be prevented from separation and detachment from said face due to thermal stress, pulsated pressure of exhaust gas and vibration.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to improvements in exhaust manifolds for internal combustion engines.

(Prior Art) Some exhaust manifolds for internal combustion engines are constructed using ceramic materials as shown in FIGS. 10 to 12 (Japanese Patent Application No. 189472).

That is, the main body 1 of the exhaust manifold has a double structure consisting of an inner pipe body 2 and an outer pipe body 3, and the inner pipe body 2 is formed into a manifold shape from ceramic 5iW1, while the outer pipe body 3
The inner mw body 2 is integrally cast with aluminum alloy or the like.

In this case, the ceramic inner tube 2 can be formed by a paper lamination method in which thin ceramic fiber vapor impregnated with a binder such as a silica-based aqueous solution is laminated, or by a wire mesh mold in a solution in which ceramic fibers are suspended. It can be made in half or as a single piece using the vacuum forming method, in which the product is placed in a container and formed using suction.

The exhaust manifold 1 having such a configuration is characterized by being lightweight and having excellent heat insulation properties because it is a combination of ceramic material and aluminum alloy.

(Problem to be Solved by the Invention) However, in the case of the above-mentioned exhaust manifold 1, the density of the ceramic fibers constituting the inner tube body 2 is smaller than that of metal or solid ceramic, and the inner circumferential surface is not directly exposed to the exhaust gas. Since it is exposed to gas, if it is used for a long time, the ceramic fibers on the surface in contact with the exhaust gas may peel or fall off due to repeated thermal stress, pulsating pressure of exhaust gas, vibration, etc. The surrounding surface was in a disadvantageous environment compared to other parts in terms of durability.

In order to increase the durability of the inner tubular body 2, it is possible to increase the density of the ceramic fibers and create a structure that makes the inner peripheral surface difficult to peel off, but this has been difficult with conventional ceramic molding methods.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an exhaust manifold in which the inner circumferential surface of the inner pipe body, which is susceptible to damage, is structurally reinforced.

(Means for Solving the Problems) The present invention provides an exhaust manifold in which an outer tube made of a light alloy is formed on the outside of an inner tube made of ceramic fibers. It combines ceramic particles.

Also, the inner tube of this exhaust manifold is made of ceramic fiber! It is obtained by sucking and impregnating a ceramic particle suspension from the inner surface of material I and sintering it.

(Function) By impregnating the ceramic fibers, mainly the inner circumferential surface, with ceramic particles and sintering, the ceramic particles bond to the intersections and gaps of the ceramic l1F4, forming a strong skeletal structure, so that the inner surface of the exhaust manifold is This strengthens the structure and makes it less susceptible to damage such as fiber delamination caused by exhaust gas.

(Example) Embodiments of the present invention are shown in FIGS. 1 to 9.

In FIG. 1, 1 is an exhaust manifold according to the present invention, and its cross section is constructed as shown in FIGS. 2 and 3.

That is, an inner tube 2 formed into a predetermined manifold shape is integrally cast with an outer tube 3 made of aluminum alloy. The inner tube body 3 is composed of ceramic II fibers 4 as a base material,
Ceramic particles 6 are sintered at the intersections and gaps of the ceramic fibers N4 on the inner circumferential surface 5, which is the exhaust gas surface.
A strong skeletal structure as shown in FIG. 4 is formed. The density of the ceramic particles 6 occupying the inner tubular body 2 is higher as it is closer to the inner peripheral surface 5 and lower as it is farther away, and as shown in FIG.

The above-mentioned inner tube body 2 is manufactured using a molding apparatus 10 shown in FIG. The molded IIF 10 is formed into a double cylinder shape that can be divided along the axis, and the inner cylinder 11 is provided with an injection hole 12, and the outer cylinder 13 is provided with a drainage hole 14 connected to a suction pump (not shown). In addition, the inner cylinder 11 and the outer cylinder 13
is communicated with through a large number of pores 16 through a filter 15, and is formed! ! :! A vibration mechanism 17 is connected to the outside of the device 10.

To manufacture the inner tube body 2, first, a suspension in which ceramic fibers 4 are dispersed (starch and colloidal silicone added) is injected into the molding device 10 through the injection hole 12, the injection hole 12 is closed, and the vibration mechanism is injected. 17 is operated and water is drained from the drainage hole 14 by a suction pump (not shown), water in the suspension flows through the pores 16 and from the grooved hole 14, and the ceramic fibers 1114 in the suspension are absorbed into the filter 15. It is deposited on top and becomes the base material of the inner tube body 2.

Next, this base material is dried with hot air in the molding device 10, and then a suspension of ceramic particles 6 (added with starch) is injected through the injection hole 12 and sucked in the same process as for the base material. Then, the ceramic particles 6 impregnate the ms of the ceramic fibers 114, and the water in the suspension is discharged from the drainage holes 14.

At this time, as shown in FIG. 7, the volume fraction of the ceramic particles 6 is large near the inner circumferential surface 5 of the inner tube body 2, and decreases as it approaches the outer circumferential surface 7. can be controlled by the particle size of the ceramic particles 6 and the concentration of the ceramic particle suspension, as shown in Examples 1 and 2 in the table of FIG.

The base material impregnated with the ceramic particles 6 in this manner is taken out from the molding device 10 in parts and sintered at high temperature to obtain the inner tube body 2 as described above.

In the exhaust manifold 1 configured as described above, the inner circumferential surface 5 of the inner pipe body 2 is always exposed to high-temperature exhaust gas during engine operation. 6 is sintered to form a strong skeleton structure, the ceramic fibers 11t4 are unlikely to peel off or a12g due to thermal stress, pulsating pressure of exhaust gas, vibration, etc. The table in FIG. 9 shows the inner tube 2 in the table in FIG.
These are the results of a comparative test of the degree of damage by intermittent operation of the engine between Examples 1 and 2 and a conventional example of the inner tube body 2 made of ceramic. In this table, Examples 1 and 2 in which ceramic particles 6 were impregnated and sintered were the inner pipe body 2 made only of the conventional ceramic m fibers 4, or the similar inner pipe body 2 with alumina particles sprayed on the exhaust gas exposed surface 5. Both the depth and area of the damage are significantly smaller than the original.

In addition, since the inner tubular body 2 is impregnated with ceramic particles 6 from the inner circumferential surface 5, the portion near the outer circumferential surface 7 is filled with ceramic fibers [4].
It consists only of Therefore, due to the high heat insulation properties of the air in the gaps between the ceramic fibers 4, the inner circumferential surface 5 of the inner tube body 2
The high heat of the exhaust gas acting on the inner pipe body 2 is blocked and does not reach the outside of the inner pipe body 2.

On the other hand, since the outer tubular body 3 is made of aluminum alloy or gold casting, it is lightweight and has sufficient rigidity and strength.

(Effects of the Invention) As described above, the present invention provides an exhaust manifold in which an outer tube made of a light alloy is formed around an inner tube made of ceramic 5iei, which sucks ceramic particles from the inner peripheral surface of the inner tube. Because it is impregnated and sintered, a strong skeletal structure of ceramic fibers and ceramic particles is formed on the inner peripheral surface that is directly exposed to exhaust gas, making it difficult for the ceramic fibers to peel off or suffer II scratches due to exhaust gas. This improves the durability of the exhaust manifold.

In addition, ceramic particles are more distributed near the inner circumferential surface of the inner tube that is exposed to exhaust gas, and the area near the outer circumferential surface is composed only of ceramic fibers, so the light alloy casting that makes up the outer tube is It is possible to absorb the difference in heat shrinkage that occurs between the inner pipe body and the inner pipe body that is cast inside during casting, and therefore, the present invention has a lightweight and heat-insulating exhaust manifold that combines ceramic materials and light alloys. It has the effect that good castability can be maintained without affecting the advantage of being high.

[Brief explanation of the drawing]

Fig. 1 is a front view of an exhaust manifold showing an embodiment of the present invention, Fig. 2 is a sectional view of the same <A-A, and Fig. 3 is the same <B-
FIG. 4 is a detailed view of section C in FIG. 3, and FIG. 5 is a detailed view of section D in FIG. Further, FIG. 6 is a sectional view showing an embodiment of the method for manufacturing the inner tube constituting the exhaust manifold of the present invention, and FIG.
It is a detailed view of part E in the figure. Fig. 8 is a table comparing the two embodiments regarding the distribution of ceramic particles, and Fig. 9 is a comparison result of the damage test between the embodiment shown in Fig. 8 and the conventional inner fI4 tube made of ceramic 5IIl. This is a table showing FIG. 10 is a front view showing a conventional example of an exhaust manifold that combines an inner tube made of ceramic fiber and an outer tube made of aluminum alloy, No. 111i! ! 1 is the same <FF sectional view, and FIG. 12 is the same <GG sectional view. 1... Exhaust manifold, 2... Inner pipe body, 3...
- Outer tubular body, 4... Ceramic fiber, 5... Inner peripheral surface, 6... Ceramic particles.

Claims (1)

[Claims] An exhaust manifold comprising a light alloy outer tube formed on the outside of an inner tube made of ceramic fibers, characterized in that ceramic particles are bonded to the inner peripheral surface of the ceramic fibers of the inner tube. .