JP2618161B2 - Metal honeycomb catalytic converter 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 metal honeycomb catalytic converter provided for an internal combustion engine of a vehicle and a method of manufacturing the same .

[0002]

2. Description of the Related Art As one of catalytic converters interposed in the middle of an exhaust pipe to prevent exhaust gas from automobiles, there is a metal honeycomb catalytic converter as shown in FIG. 5 (for example, JP-A-54-13462). Gazette).

[0003] To explain this, the case 5 is interposed in the middle of the exhaust pipe of the engine and oxidizes harmful components such as HC and CO by passing exhaust gas through the metal honeycomb catalyst 3. .

As shown in FIGS. 8 and 9, a metal honeycomb catalyst 3 is formed by superposing and winding a flat metal foil 1 and a corrugated metal foil 2 to form a plurality of passages 3a formed by the polymerization. The catalyst is carried on the entire surface.

The case 5 for holding the metal honeycomb catalyst 3 has an upper and lower two-part structure of an upper part 5a and a lower part 5b. Inelastic with 5b
The metal honeycomb catalyst 3 is fixed by welding the cap 4 from the outside of the case 5 as shown in FIG.

[0006]

However, in such a conventional catalytic converter, there is a problem that the metal honeycomb catalyst 3 is damaged due to a temperature difference between the case 5 and the case.

This is because the metal honeycomb catalyst 3, which passes the high-temperature exhaust gas and generates the heat of oxidation reaction, is very unlike the case 5 in which the case 5 that comes into contact with the outside air is kept in a vehicle mounted state. In spite of the high temperature, the periphery of the end portion is inelastically held by the cap 4 so that FIG.
This is because the expansion in the radial direction is restricted as shown in FIG. The thermal stress at this time acts as a compressive force on the metal foil 1, and this acts repeatedly.
As shown in FIG. 2, the metal foil 1 is cracked.

[0008] The present invention has been made in view of such a conventional problem , and harmful thermal stress at the end of the metal honeycomb.
To avoid damage to the catalytic converter due to the occurrence of high
It is intended and this <br/> to provide a metal honeycomb catalytic converter showing the durability.

[0009]

According to the present invention for this [Means for Solving the Problems]
The metal honeycomb catalytic converter is a flat metal foil and a corrugated metal foil is formed by polymerization and winding to form a plurality of passages, and a catalyst is supported on the passages to form a metal honeycomb catalyst,
Cap the metal honeycomb catalyst around its front and rear ends.
In the catalytic converter and held in a non-elastically case via, also provided a non-reaction region in which the catalyst is not exposed from the front end over a predetermined length of the metal honeycomb catalyst
And

[0010] In addition, the metal honeycomb catalytic converter according to the present invention.
A method of manufacturing a barter is to apply a water-repellent masking agent over a predetermined length to a front end portion of a metal honeycomb carrier formed by polymerizing and winding a flat metal foil and a corrugated metal foil, and then coating the carrier with a coating liquid. , And impregnated with the catalyst metal in the coating layer formed by drying and firing this,
A non-reactive region is provided over a predetermined length from the front end.

[0011]

When the exhaust gas containing unburned components such as HC passes through the catalytic converter, the highest temperature is at the portion in contact with the exhaust gas having a high unburned component concentration, that is, at the front end of the metal honeycomb catalyst. is there.

[0012] The metal honeycomb catalytic converter according to the present invention.
In the method, the front end of the honeycomb catalyst is constituted by a non-reaction area where the catalyst is not exposed, so that the temperature of the non-reaction area due to the reaction heat of the catalyst can be suppressed. Therefore, no excessive thermal stress is generated even in a state of being held by the surrounding cap or case with high rigidity, and therefore, there is no possibility of cracking the metal foil constituting the honeycomb.

The non-reactive region is located behind the metal honeycomb support.
Although it may be provided at the end, the rear end of the catalyst has a much smaller thermal load than the front end because exhaust gas that has been treated with unburned components passes through it. Hateful.

[0014]

Next, an embodiment of the present invention will be described with reference to the drawings. However, the same portions as those in FIG. 7 and the following portions are denoted by the same reference numerals.

In FIG. 1 or FIG. 2, 4 is a cap,
5 is a two-part case composed of an upper part 5a and a lower part 5b,
6 is a metal honeycomb catalyst. The metal honeycomb catalyst 6
As in FIG. 7, it is held inelastically inside the case 5 via caps 4 fitted at both front and rear ends.

The shape of the metal honeycomb catalyst 6 is the same as that of FIG. 7, and the flat metal foil 1 and the corrugated metal foil 2 are wound while being polymerized by welding or nickel brazing. It is finished in an elliptical cross-sectional shape having a number of passages 6a (see FIGS. 3 and 4). However, as shown in FIG. 1, FIG. 3, FIG. 4, and FIG. 5, the catalyst layer 7 on the surface is coated only on the areas E and F except for the area D having a predetermined length from the front end. Thus, the region D is a non-reaction region, and the regions E and F are reaction regions.

Next, the production of such a metal honeycomb catalyst 6 is described.
An example of the fabrication method will be described .

First, activated alumina powder and a cerium nitrate solution are mixed and impregnated with cerium, and then dried and fired to obtain a cerium-supported alumina powder. on the other hand,
Alumina sol produced by mixing and dispersing boehmite alumina with nitric acid and water to form a sol and ceria (cerium oxide) are ball-milled together with the cerium-supported alumina powder to obtain a coating solution.

Next, the metal honeycomb carrier manufactured as described above is immersed in the coating solution, and the excess solution is removed by air blow, followed by drying at 150 ° C. for 1 hour in air.
Then, it is fired in air at 650 ° C. for 2 hours. A metal such as platinum or palladium serving as a catalyst is impregnated after this calcination treatment, or is supported by being charged in the ball milling step. Then, the metal honeycomb supporting the catalyst is subjected to microwave drying and firing treatments for finishing to obtain a finished catalyst.

In order to produce a metal honeycomb catalyst having a non-reactive region D as in the present invention, a water repellent masking agent such as varnish is applied to the front end of the metal honeycomb before the above-mentioned coating step, and a coating solution There we clause so as not to adhere. When the catalyst metal is impregnated after firing the coated carrier, a masking agent may be applied before the impregnation. This masking agent is later separated from the honeycomb catalyst by a solvent or calcination.

In general, since the end of the metal honeycomb catalyst has a cutting section of a metal foil, when a large force acts due to thermal stress or the like, a crack is easily generated from a small scratch or the like as a starting point. For this reason, as described above, when the high-temperature exhaust gas containing the unburned component passes, there is a possibility that the metal honeycomb catalyst 6 may be damaged at the front end where the thermal load becomes large. Since there is a non-reaction region D over a predetermined length from the portion, the reaction heat of the catalyst is not generated at the front end, and therefore, the magnitude of the thermal stress generated due to the difference in thermal expansion with the case 5 is also small. Only smaller.
For this reason, cracks are less likely to occur at the front end of the catalyst.

FIGS. 3, 4 and 5 show embodiments in which a non-reactive region having no catalyst is provided only at the front end of the metal honeycomb catalyst 6. This non-reactive region is also shown in FIG. May be provided in the region F at the rear end in addition to the region D at the front end. As described above, the thermal stress is sufficiently smaller on the rear end side than on the front end side where the oxidation reaction actively occurs. Although it is possible to reduce the risk, if the exhaust gas temperature and the reaction temperature are expected to be extremely high due to the relationship between the air-fuel ratio and the exhaust gas composition, the non-reaction region should be provided at the rear end as well. However, it is more certain from the viewpoint of damage prevention.

[0023]

As described above, the metal according to the present invention is
In the honeycomb catalytic converter, a non-reactive area is provided at the front end of the catalyst where large thermal stress is likely to occur, and excessive force due to reaction heat acts on the front end of the metal foil forming the metal honeycomb
Therefore , it is possible to obtain an effect of reliably preventing cracks from being generated from the portion and improving the durability and reliability of the metal honeycomb catalytic converter.

[Brief description of the drawings]

FIG. 1 is a half sectional side view of an embodiment of the present invention.

FIG. 2 is a plan half sectional view of the same.

FIG. 3 is a schematic view of a GG section of FIG. 1;

FIG. 4 is a schematic view of an HH section in FIG. 1;

FIG. 5 is a schematic view of a II section of FIG. 2;

FIG. 6 is a schematic sectional view corresponding to FIG. 5 of another embodiment of the present invention.

FIG. 7 is a side half sectional view of a conventional example.

FIG. 8 is a sectional view taken along line AA of FIG. 7;

FIG. 9 is a detailed view of a portion B in FIG. 8;

FIG. 10 is a vertical sectional view of a portion C in FIG. 7;

FIG. 11 is a schematic cross-sectional view showing a state of action of a compressive force on a metal honeycomb catalyst.

FIG. 12 is an enlarged view of a main part of an end face of a metal honeycomb catalyst showing a state in which a crack is generated based on the compressive force.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flat metal foil 2 Corrugated metal foil 4 Cap 5 Case 6 Metal honeycomb catalyst 7 Catalyst layer D Non-reaction area E Reaction area

Claims (2)

(57) [Claims] 1. A metal honeycomb formed by polymerizing and winding a flat metal foil and a corrugated metal foil to form a plurality of passages, supporting a catalyst facing the passages to form a metal honeycomb catalyst, Inelastic catalyst through cap around its front and rear ends
In the catalytic converter and held in the case, the metal honeycomb catalytic converter catalyst over a predetermined length from the front end portion of the metal honeycomb catalyst is characterized in that a non-reaction zone is not exposed. 2. A method in which a flat metal foil and a corrugated metal foil are polymerized.
The front end of the metal honeycomb carrier
After applying the water repellent masking agent over the length,
Immerse the body in the coating solution, dry and bake it
The formed coating layer is impregnated with catalytic metal,
To provide a non-reactive area over a predetermined length from
A method for manufacturing a metal honeycomb catalytic converter.