JPH11253814A - Metal carrier for electric heating type catalytic device - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To eliminate a center electrode and a supporting pin of a honeycomb body, reduce air flow resistance, uniform heat generation, have good thermal efficiency, and have an insulating film having excellent durability and brazing that can be brazed. I will provide a. SOLUTION: A corrugated sheet material 1 and a flat sheet material 2 are overlapped to form a layer 4, and a sheet material of a central portion 5 of the layer 4 is formed into a flat plate shape, the same corrugated plate shape, or It is formed into corrugated sheets of different shapes and stacked. At least one plate in the layer 4 is coated with an insulating film, wound around a central portion 5 in the longitudinal direction of the layer 4 to form a honeycomb body 3, and divided into two winding end portions 3a and 3b of the outer plate. Outer cylinder portions 6a, 6
The EHC 10a is formed by providing the electrode portions 7a and 7b containing b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal carrier for a catalyst device constituting a honeycomb body used for an exhaust gas purifying device of an internal combustion engine, and more particularly to a metal carrier for an electrically heated catalyst device.

[0002]

2. Description of the Related Art Exhaust gas regulations for automobiles have been strengthened year by year in the United States, countries in Europe, Taiwan, and also in Japan. In particular, the California regulations in the United States have strict HC regulations, and it is necessary to keep HC low in almost all areas from the start of the engine to the high speed range. HC is an unburned fuel component mainly due to incomplete combustion, but especially when the engine is started, the A / F (air-fuel ratio) is intentionally made rich (a lot of fuel), so that the amount of HC emission is large.
Further, since the inner wall of the cylinder is cooled, unburned HC is easily discharged in the vicinity of the wall without ignition.
As a measure to reduce this HC, each manufacturer uses an engine. That is, tumble, swirl, GDI (fuel direct injection), etc.
Further, as an improvement measure for increasing the oxygen concentration, the A / F is made lean (low fuel), and as an improvement measure for increasing the exhaust gas temperature, a timing retard (retarding the ignition timing) is performed.

[0003] However, it is difficult to clear the regulation value of the California regulations only by improving the engine, and at present it is necessary to rely on post-processing. It is said that in a test run in California emission measurement mode, about 50% of the total emission of HC is emitted in the first minute, and it is important how exhaust emission control immediately after engine start is important. I understand. Therefore, as a countermeasure when starting the engine, a metal carrier (hereinafter referred to as E
HC), HC absorber, burner-heated catalyst carrier (B
HC) and the like are considered promising.

A metal carrier for a catalyst device used in a conventional exhaust gas purifying device is a metal carrier for a catalyst device, in which a brazing material is interposed between a thin metal flat plate and a corrugated plate, and the flat plate and the corrugated plate are stacked and rolled from the center. The honeycomb body was formed into a honeycomb shape, and the brazing material was melted using a high-vacuum furnace, and bonding was performed at the contact portions of the plate materials. Ni-based brazing material is used for the brazing material,
Further, a ferrite stainless steel material was used for the flat plate material and the corrugated plate material. A structure in which the honeycomb body thus formed is accommodated in a metal outer cylinder is known as a metal carrier for a catalyst device. (For example, JP-A-56-4373).

[0005] A catalyst supporting layer is formed on the surface of the honeycomb passage of the honeycomb body, and the noble metal catalyst is supported on the catalyst supporting layer to serve as an exhaust gas purifying catalyst. And it is disposed in an exhaust passage of an internal combustion engine in the exhaust gas HC, CO, NO _x
Purify and so on. Since it is necessary to secure as many honeycomb passage areas as possible in a limited volume, the thicknesses of the flat plate and the corrugated plate are made as thin as possible within a range where strength can be maintained.

The noble metal catalyst supported on the catalyst support layer promotes a catalytic reaction under a certain high-temperature environment. Therefore, the catalytic device is required to be exposed to a high-temperature exhaust gas of the internal combustion engine as much as possible. It is provided near the exhaust valve.

However, since the temperature of the exhaust gas is low at the time of starting the internal combustion engine, the catalytic reaction is not sufficiently performed even in such a catalytic device, so that the HC, C
O, the insufficient ability to purify and NO _x. EHC is generally used to eliminate this disadvantage.

FIG. 7 shows an example of a conventionally used EHC. In FIG. 7, (A) is a front view, (B) is a schematic diagram of an axial cross section of (A), (C) is a perspective view showing a process of a honeycomb body forming an EHC, and (D) is a plate material configuration. FIG.

To form the honeycomb body 33, FIG.
As shown in (D), a plurality of layers in which the flat plate member 32 and the corrugated plate member 31 are overlapped are further laminated, a brazing material 34 is interposed between the plate members, and at least one of the plate members is interposed.
(C) With one end of the superposed layer 33a as the center,
As shown in FIG.

The honeycomb body 33 thus formed is inserted into the outer cylinder 35, and the center electrode 3 is placed at the center of the honeycomb body 33.
6. The outer peripheral electrode 37 is provided on the outer peripheral portion to form the EHC 30, and the honeycomb body 3 is formed by applying a current in the direction of winding the plate material.
3 is heated. Adjustment of the resistance value of the EHC 30 is performed by the number of superposed layers.

In another embodiment of the EHC shown in FIG. 8, three layers of a stainless steel plate member 51 and a corrugated plate member 52 are further laminated, and wound from the central portion to form a honeycomb having a cross section in the shape of a tom. The body 53 is formed, and the outside is formed by an electrically insulating layer 54.
And conductor connection portions A and B which are housed in the outer cylinder 55, penetrate the outer cylinder 55 and the insulating layer 54, and are electrically connected to both ends of the plate material are provided. A gap 56 for insulation is provided in a portion overlapping each other. In order to maintain the gap 56, a bar-shaped support (pin) 57 projecting from a main metal carrier 58 provided downstream is provided in each layer forming the honeycomb body.
When the conductor connection portions A and B are connected to a power supply (not shown), the honeycomb body 53 thus formed forms a heating element having an entire length of the plate member as an electric resistor, and is thus heated by Joule heat. Therefore, when the low-temperature exhaust gas discharged at the time of starting the engine passes through the honeycomb body 53, the catalytic reaction is easily promoted by the heated catalyst supporting layer. The electric resistance value of the honeycomb body 53 can be adjusted by the number of layers formed by overlapping the flat plate member 51 and the corrugated plate member 52 one by one.

[0012]

Among the above-mentioned EHCs, the one shown in FIG. 7 has the following problems. (1) Since the electrode 36 is located at the center of the honeycomb body 33, the exhaust resistance increases.
(2) In the vicinity of the center electrode 36, the heat generated by the EHC is taken away by the electrodes, so that the heat is not uniformly generated.
Is usually ferritic stainless steel such as SUS430, but since it does not contain Al, its oxidation resistance is inferior to the material of the honeycomb body 33.
There is a drawback that durability is low in the use environment of EHC which is constantly exposed to the above temperature range.

Further, the EHC having the structure shown in FIG.
The honeycomb body 53 is supported on the main metal carrier 58 by the support body 57.
(2) Support 5
7 deprives the EHC of heat generation, so that the heat generation of the honeycomb body 53 is not uniform, (3) the pressure loss is large because the support body 57 has ventilation resistance, and (4) the number of parts is large, and the production is difficult, so the cost is high. (5) Since the space 56 for insulation is provided, the area of the heater is reduced, so that there is a disadvantage that the thermal efficiency is low.

An object of the present invention is to provide an EHC honeycomb body comprising:
Electrodes and supports do not increase ventilation resistance, generate uniform heat, are easy to manufacture and do not increase cost, are thermally efficient, have durable insulation film, and can be brazed. An object of the present invention is to provide an EHC having:

[0015]

The metal carrier (EHC) for an electrically heated catalyst device according to the present invention includes a corrugated sheet formed by bending a thin metal plate having a band shape to form continuous corrugations, and a flat plate. A flat plate made of a strip-shaped thin metal plate overlaps, and a layer configured to include at least one electric insulating plate in the plate is formed in a toe-like shape around a central portion in the longitudinal direction of the plate. A honeycomb body provided with a number of mesh-shaped air passages formed by winding; and an electrode portion including a two-part outer cylinder portion provided at each of the winding end portions of the plate material on the outer periphery of the honeycomb body. ing.

[0016] In the longitudinal center portion of the layer of the laminated sheet material, the corrugated sheet material is formed flat by a predetermined area required for winding and is flatly overlapped with the flat material, or the flat material is necessary for winding. Is formed into the same waveform as the corrugated sheet material by a predetermined area and the corrugated sheet material and the waveform are overlapped,
Alternatively, the flat plate material is formed into a waveform different from the waveform of the corrugated sheet material by a predetermined area required for winding, and is overlapped with the corrugated sheet material to form a central portion of the honeycomb body.

Therefore, no electrode is provided at the central portion of the honeycomb body, and since the conductive cross-sectional area of the central portion is the same as other portions of the honeycomb body, the current density of the entire honeycomb body can be made uniform. it can. In addition, since an insulating plate material for insulation is not used, and insulation by voids is not used, durability can be improved, pressure loss of the honeycomb body can be reduced, and a thermally advantageous EHC can be provided.

[0018]

Next, embodiments of the present invention will be described with reference to the drawings. 1A and 1B are diagrams of a first embodiment of an EHC of the present invention, in which FIG. 1A is a schematic partial cross-sectional view showing the configuration of a plate material, and FIG. 1B is a schematic view of a cross section perpendicular to the axis of the EHC. .

In FIG. 1A, a corrugated sheet material 1 is a sheet material formed by bending a strip-shaped thin metal plate to form a continuous corrugated unevenness, and a flat plate material 2 is a plate material formed of a flat band-shaped thin metal plate. is there. The layer 4 is formed by stacking a plurality of these plate members. The plate material constituting the layer 4 includes at least one sheet material for electric insulation having at least one surface subjected to electric insulation treatment.

The central portion 5 in the longitudinal direction of the corrugated sheet material 1 is shown in FIG.
As shown in FIG. 3A, a waveform is not formed for a predetermined length but is made flat.

When the layer 4 of the plate material thus configured is wound in a tom-like shape around the substantially central portion 5, a honeycomb body 3 as shown in FIG. 1B is formed.

At the end 3a, 3b of the layer 4 on the outer periphery of the honeycomb body 3, two outer cylinder portions 6a, 6
b is provided including the electrodes to form electrode portions 7a and 7b. In this manner, the main body portion 10a of the EHC is formed. However, in general, in order to protect the EHC main body and facilitate the installation, as shown in FIG.
The EHC 10 is formed by covering the a, 6b and the outside of the exposed portion of the outer periphery of the honeycomb body 3 with an outer cylinder 9 via an insulating material 8. As the insulating material 8, an insulating material such as an insulating foil or an insulating sheet is used.

FIGS. 3A and 3B are views of a second embodiment of the EHC according to the present invention, wherein FIG. 3A is a schematic partial cross-sectional view showing the configuration of a plate material, and FIG. 3B is a cross section perpendicular to the axis of the EHC. FIG.

The second embodiment is the same as the first embodiment shown in FIG. 1 except for the configuration of the central portion 5 of the plate, so that only the configuration of the central portion 5 of the plate will be described here. In FIG. 3A, a flat plate 2 constituting a plate layer 4 is formed in a central portion 5 to have the same waveform as the corrugated plate 1 by a predetermined length. Therefore, when the layers are formed by laminating the plate materials, all the plate materials can be closely adhered to each other at the central portion 5.

When the layer 4 thus constructed is wound in a tom-like shape around the substantially central portion 5, a honeycomb body 13 as shown in FIG. 3B is formed.

Electrode portions 7a and 7b are formed by providing two-part outer cylinder portions 6a and 6b including electrodes on the end portions 3a and 3b of the layer 4 on the outer periphery of the honeycomb body 13a.
The main body portion 20a of the EHC is formed in this manner,
Normally, the outer side is further covered with an outer cylinder 9 via an insulating material 8, and E
The formation of HC is similar to the case shown in FIG.

FIGS. 4A and 4B are diagrams of a third embodiment of the EHC of the present invention, wherein FIG. 4A is a schematic partial cross-sectional view showing the structure of a plate material, and FIG. 4B is a cross section perpendicular to the axis of the EHC. FIG.

This third embodiment is the same as the first and second embodiments shown in FIGS. 1 and 3 except for the structure of the central portion 5 of the plate. Only the configuration will be described. In FIG. 4 (A), the flat plate material 2 forming the plate material layer 4 is formed into a corrugated shape by a predetermined length in the central portion 5, but the corrugated shape does not match the corrugated shape of the corrugated plate material 1. So that they are shaped differently.

For the shape of the waveform provided on the flat plate 2, for example, (1) the wave height is increased at the same pitch as the waveform of the corrugated plate 1.
(2) In addition to the shape in which the wave height is the same as the wave height of the corrugated sheet material 1 and only the pitch is changed, the shape of (1) or (2) can be provided separately for each flat material.

The substantially central portion 5 of the layer 4 thus constructed
Is wound around the center of the honeycomb body, a honeycomb body 23 as shown in FIG. 4B is formed.

At the end portions 3a and 3b of the layer 4 on the outer periphery of the honeycomb body 23, two divided outer cylinder portions 6a and 6b including electrodes are provided to form electrode portions 7a and 7b. The main body portion 30a of the EHC is formed in this way, but usually the outer side is further covered with an outer cylinder 9 via an insulating material 8, and the EH is formed.
Forming C is similar to the case shown in FIG.

In the honeycomb body formed by the plate material layer 4 having the central portion 5 thus formed,
Since the cross-sectional area of the conductor in the central portion is the same as the other portions, the current density of the entire honeycomb body is uniform. In addition, since an insulating plate is used for insulation and insulation by voids is not used, durability can be improved and pressure loss of the honeycomb body can be reduced to provide a thermally advantageous EHC.

Further, as shown in FIG. 5 (A), it is preferable that one electric insulating plate material disposed in the plate material layer 4 is disposed on the outer portion of the plurality of plate materials constituting the layer 4. is there. FIG. 5B shows a honeycomb body 33 formed by the layer 4 including the insulating corrugated sheet material 1a arranged as shown in FIG. 5A. If one insulating corrugated sheet material 1a forming the honeycomb body 33 is disposed outside the layer 4 composed of a plurality of sheet materials as described above, the electric resistance value of the entire length in the longitudinal direction of the sheet material forming the layer 4 is obtained. EHC effectively utilizing the above is obtained. In the above-described example, the corrugated plate is used as the insulating plate, but a flat plate may be used as the insulating plate. In addition, FIG.
The arrangement of the insulating corrugated sheet shown in FIG. 1 can be similarly applied to the first, second and third embodiments.

In order to set the electric resistance of the EHC to a predetermined value, the number of sets of the laminated corrugated sheet material and the flat sheet material constituting the layer, and the insulating plate material arranged in the layer as described above, Is determined by the position and the number of sheets, and the total length of the plate material. However, more detailed setting can be easily performed by further stacking the plate material.

Although the above-described EHC is used as an EHC alone, as shown in the side view of FIG. 6, it is connected in series with the metal carrier 11 or the ceramic carrier 12 provided downstream of the EHC 10a, 20a or 30a. Can be used.

There are the following methods of insulating treatment for forming the electric insulating layer of the electric insulating plate used in the EHC described above.

(1) PVD, CVD, ion plating
To the surface of the plate _Two O_Three Insulation such as
Or coating with Al etc.
And then changed to an insulating film by firing in air
(2) Stainless steel containing Al (for example, Fe-
20Cr-5Al) in air or equivalent
Firing in an atmosphere_Two O_ThreeFilm
Method of Precipitation (3) Immersion in molten Al
e to form an alloy layer of Al and Fe by interdiffusion of
After heating in air or an equivalent oxidizing atmosphere
By doing_Two O_Three Such as obtaining a film of
is there.

The method (1) has poor adhesion between the plate material and the coating and may easily peel off, and is suitable for forming a thin film, but is not suitable for a film having a thickness of 10 μm or more. There is a disadvantage that.

The method (2) is a simple method in which an insulating film of Al ₂ O ₃ can be easily obtained by baking in the air, and is a method which has been widely used.
Usually, the amount of Al contained in the base material is as small as 5%, and no matter how much precipitation occurs, a film having a thickness of 5 μm or more cannot be formed, and the insulation film itself has low durability against insulation. Most of the dissolved Al was consumed, and the oxidation resistance of the base material was significantly shortened.
High temperature of over ℃ is required, furnace cost, running cost, etc. are high, and it is difficult to form an insulating film on one side only by this method. It had to be removed because it had to be removed.

In the method (3), the Al content of the film is large, and the same Al ₂ O ₃ film as in the method (2) is obtained on the surface of the Fe—Al alloy layer by firing at about 1000 ° C. However, the alloy layer of Al and Fe is hard, and there is a problem in the durability of this part. Since a film of Al ₂ O ₃ is basically obtained by sintering in air, a thick film of 10 μm or more cannot be expected in this method, Therefore, there is a disadvantage that the durability of the insulating film to insulation is low.

In order to eliminate the above-mentioned disadvantages of the insulation treatment method, it is preferable to use the following method. That is, (4) The electric insulating layer of the electric insulating plate material has a two-layer structure of a base film and an insulating film, and each of the two layers is formed by thermal spraying. Ni-Cr or Ni-Al is used for the undercoat, to improve the adhesion between the base material and the insulating film and to reduce the difference in thermal expansion between the two to prevent peeling of the insulating film. It becomes possible. The insulating film is thermally sprayed with a material that can withstand repeated thermal cycles and is suitable for thermal spraying, for example, zirconia to a thickness of 10 to 200 μm.

By spraying such that the porosity of the insulating film becomes 5% or more, a film in which fine zirconia particles are intricately entangled can be formed. And a highly durable insulating film can be obtained.

(5) Further, a three-layer electric insulating layer in which a brazing film mainly containing Ni is applied by thermal spraying on the surface of the above-mentioned two-layer electric insulating layer formed by thermal spraying. Use the electrical insulating plate material. Therefore, the surface of the plate for electrical insulation on which the electrical insulation layer is
Since it is possible to braze to another plate material that comes into contact with the EHC, an EHC in which telescoping is prevented can be obtained.

[0044]

As described above, according to the present invention, a layer is formed by laminating a corrugated plate and a flat plate, and at least one plate in the layer is used as a plate for electrical insulation, and a central portion in the longitudinal direction of the layer is formed. To form a honeycomb body, an electrode is provided at the end of the outer periphery of the plate material, and the plate material at the center in the longitudinal direction of the layer to be wound is all formed into a flat plate shape or overlapped, or The center electrode is not required because it is molded and laminated on a corrugated sheet or formed on a corrugated sheet with a different shape, so the honeycomb body has less pressure loss and the central electrode does not lose heat. Heat generation of the body becomes uniform, and there is an effect that there is no reduction in durability due to rust caused by the material of the center electrode.Since the insulating plate material is used without providing a gap for insulation, the pin can hold the honeycomb body. Unnecessary and resistant In addition, heat dissipation is uniform because there is no heat dissipation due to pins, and pressure loss is small, and there is no extra void in the honeycomb body, so the entire honeycomb cross section becomes a heater, which is thermally advantageous. In addition, since the same manufacturing method as that of the conventional roll-shaped honeycomb body can be applied, there is an effect that the manufacturing cost is reduced.

[Brief description of the drawings]

FIG. 1 is a diagram of a first embodiment of an EHC of the present invention, in which (A) is a schematic partial cross-sectional schematic diagram showing a configuration of a plate material;
(B) is a schematic view of a cross section perpendicular to the axis of the EHC.

FIG. 2 is a schematic diagram of an axial section in which an outer cylinder is further provided in the EHC of FIG.

FIG. 3 is a view of a second embodiment of the EHC of the present invention, and is a view similar to FIG. 1;

FIG. 4 is a view of a third embodiment of the EHC of the present invention, and is a view similar to FIGS.

FIG. 5 is a diagram of another embodiment of the present invention, wherein FIG.
It is a figure similar to 3 and 4.

FIG. 6 is a diagram of another embodiment of the present invention.

FIG. 7 is a diagram of EHC according to the prior art, wherein (A)
Is a schematic view of a cross section perpendicular to the axis, (B) is a schematic cross sectional view in the axial direction,
(C) is an explanatory view in the middle of the process of the honeycomb body, and (D) is a schematic view showing the configuration of the plate material.

FIG. 8 is another EHC diagram according to the prior art,
(A) is a schematic view of a cross section perpendicular to the axis, and (B) is a schematic cross-sectional view in the axial direction.

[Explanation of symbols]

 1, 31, 52 Corrugated sheet material 1a, 31a Corrugated sheet material for electrical insulation 2, 32, 51 Flat sheet material 3, 13, 23, 33, 53 Honeycomb body 3a, 3b End of winding part 4 Layer of sheet material 5 Central part of sheet material 6a , 6b Two divided outer cylinder parts 7a, 7b Electrode part 8 Insulation material 9, 35, 55 Outer cylinder 10, 30 Electric heating type metal carrier (EHC) 10a, 20a, 30a Main body part of EHC 11 Metal carrier 12 Ceramic Carrier 34 brazing material 36 center electrode 37 outer electrode 54 electric insulating layer 56 void 57 support / pin

Claims (5)

[Claims] 1. A corrugated sheet formed by bending a strip-shaped thin metal plate to form continuous corrugations and a flat plate made of a flat strip-shaped thin metal plate are overlapped with each other and included in the plate. A layer including at least one sheet for electrical insulation, a honeycomb body having a large number of mesh-shaped air passages formed by being wound in a tomography around a central portion in the longitudinal direction of the plate; A metal support for an electrically heated catalyst device, comprising: an electrode portion including a two-part outer cylinder portion provided at each of the winding end portions of the plate material on the outer periphery of the honeycomb body. 2. The electrically heated catalytic device according to claim 1, wherein the corrugated sheet material is formed flat in an area necessary for the winding in a toroidal shape in the central portion in the longitudinal direction of the layer. Metal carrier. 3. The corrugated sheet material according to claim 1, wherein the flat plate material is formed in the longitudinal center portion of the layer to have the same waveform as that of the corrugated sheet material by an area required for winding in the shape of a tom. A metal carrier for an electrically heated catalyst device according to the above. 4. The corrugated sheet material according to claim 1, wherein the flat plate material is formed in a waveform different from the corrugated material of the corrugated sheet in an area necessary for winding in the shape of a tom in the longitudinal center portion of the layer. Metal carrier for electric heating type catalytic device. 5. The metal carrier for an electrically heated catalyst device according to claim 1, wherein the two divided outer cylinder portions are further inserted into one other outer cylinder via an insulating material.