JPH0649846Y2 - Honeycomb catalytic converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The honeycomb catalytic converter according to the present invention is provided in the middle of the exhaust system of an automobile to detoxify harmful components contained in the exhaust gas discharged from the engine. Used for.

(Prior art) In the middle of the exhaust system for exhausting the exhaust gas to the atmosphere in order to detoxify harmful components (NO _X , CO, HC, etc.) contained in the exhaust gas emitted from the automobile engine. It is widely practiced to provide a catalytic converter in the. As such a catalytic converter, various types of structures have been conventionally known. Among them, the one in which a catalyst such as platinum is attached to the surface of a honeycomb carrier formed of ceramic in a honeycomb shape is widely used because it has a high efficiency of purifying harmful substances and a small exhaust flow resistance. .

FIG. 4 has been widely used conventionally. An example of such a honeycomb catalytic converter is shown. This honeycomb catalytic converter accommodates the honeycomb catalyst carrier 2 in a casing 1 via buffer materials 3 and 4 in a buffer manner, and
Inner peripheral surface 1a of casing 1 and outer peripheral surface of honeycomb catalyst carrier 2
An air-impermeable mat 5 is provided between the mat 2a and 2a. And
The mat 5 prevents exhaust gas from passing through the honeycomb catalyst carrier 2 and bypassing between the peripheral surfaces 1a and 2a.

The casing 1 is formed by combining a pair of halves made by press-molding a metal plate in the middle. In this casing 1, an exhaust inlet 6 and an exhaust outlet 7 formed at both front and rear ends, and a cylindrical holding portion 8 formed in an intermediate portion are connected at steps 9 and 9. The inside diameter of the holding portion 8 is made sufficiently larger than the inside diameters of the exhaust inlet 6 and the exhaust outlet 7.

Among the cushioning materials 3 and 4 for cushioningly supporting the honeycomb catalyst carrier 2 in the casing 1 as described above, the cushioning material 3 wound around the outer peripheral surface of the catalyst carrier 2 is a braided stainless steel filament. Formed by corrugating the wire mesh. The cushioning material 3 cushions and supports the catalyst carrier 2 while being elastically compressed between the inner peripheral surface 1a of the casing 1 and the outer peripheral surface 2a of the honeycomb catalyst carrier 2.

Further, the cushioning materials 4 and 4 provided between the stepped portions 9 and 9 of the casing 1 and the corner portions of the honeycomb catalyst carrier 2 are formed by braiding fine filaments made of stainless steel in a string shape. The cushioning materials 4 and 4 prevent the corner portions of the brittle honeycomb catalyst carrier 2 from colliding with and damaging the inner surface of the casing 1.

Further, the air-impermeable mat 5 is disclosed in, for example, JP-A-51-69507.
As disclosed in the publication, it contains a substance having a thermal expansion property such as expandable mica. The mat 5 is filled in a thermally expanded state between the outer peripheral surface 2a of the honeycomb catalyst carrier 2 and the inner peripheral surface 1a of the holding portion 8 of the casing 1 to maintain airtightness between the peripheral surfaces 2a and 1a. Plan.

When the honeycomb catalytic converter configured as described above is used, exhaust gas containing harmful substances is sent from the exhaust gas inlet 6 into the casing 1, and the exhaust gas is passed through the honeycomb catalyst carrier 2 and then discharged from the exhaust gas outlet 7. Discharge. While passing through the honeycomb catalyst carrier 2, harmful components in the exhaust gas are oxidized by the action of the catalyst adhering to the surface of the catalyst carrier 2,
It is reduced and transformed into a harmless substance.

(Problems to be solved by the invention) Conventionally widely used honeycomb catalytic converters are constructed and operate as described above, and have practically sufficient performance in terms of purification of harmful components. Depending on the mode, the following inconvenience may occur.

That is, the temperature of the honeycomb catalyst carrier 2 at the time of use must be high (for example, 700 to 800 ° C.) so that the harmful substance can be effectively detoxified by oxidation and reduction. The energy for raising the temperature is obtained from the heat of the exhaust gas discharged from the engine and the reaction heat associated with the oxidation and reduction. However, the distance between the engine and the exhaust gas purifier tends to increase due to the shift to FF in automobiles. If this distance becomes extremely long, the temperature of the honeycomb catalyst carrier 2 cannot always be sufficiently raised and the sufficient oxidation, if the reaction heat is still small immediately after the start of use,
In some cases, the reduction reaction cannot be expected. Enclosing the periphery of the exhaust gas purifier with a heat insulating material causes an increase in manufacturing cost and an increase in weight, and thus cannot be practically adopted.

For this reason, as shown in FIG. 5, it is considered to omit the corrugated cushioning material 3 and instead provide the mat 5 having excellent heat retaining properties over substantially the entire length of the honeycomb catalyst carrier 2. That is, in this structure, by holding the catalyst carrier 2 inside the casing 1 by the mat 5, it is possible to sufficiently raise the temperature of the honeycomb catalyst carrier 2 after the start of use without using a heat insulating material. The time required can be shortened. However, the mat 5 is not supported by the catalyst carrier 2 as the catalytic converter is used.
Before the temperature rises and the volume expands, there is no action of holding the catalyst carrier 2. Therefore, if it is left as it is, the corner portion of the honeycomb catalyst carrier 2 is likely to be damaged before the catalytic converter is used.

If the string-shaped cushioning materials 4 and 4 as described above are provided between the corner portions of the catalyst carrier 2 and the step portions 9 of the casing 1, the catalyst carrier 2 is prevented from being damaged before use. You can do it. However, the cushioning material 4 formed by braiding stainless steel thin filaments in a string shape has a relatively high density, for example, a braid of thin filaments with a diameter of 0.1 mm and a bulk density of 1.3 g / cm ^3. Is formed. For this reason, the cushioning materials 4 and 4 are expensive to manufacture, and it is not preferable to provide the cushioning materials 4 and 4 because it is difficult to reduce the cost of the catalytic converter.

The honeycomb catalytic converter of the present invention eliminates the above-mentioned inconvenience by devising the structure of the cushioning material mounted between the corners of the catalyst carrier 2 and the stepped portions 9, 9 of the casing 1. is there.

(Means for Solving the Problem) In the honeycomb catalytic converter of the present invention, an exhaust inlet and an exhaust outlet each having a diameter smaller than that of the holding portion are continuously connected to the front and rear ends of a cylindrical holding portion formed in an intermediate portion by a step portion. A casing formed by the above, a honeycomb catalyst carrier supported inside the holding portion of the casing, and a material containing a thermally expansive substance, and the inner peripheral surface of the honeycomb catalyst carrier and the holding portion in a thermally expanded state. Between the peripheral surface and the front and rear ends of the honeycomb catalyst carrier, almost the entire length of the honeycomb catalyst carrier is filled to maintain airtightness between both peripheral surfaces, and a mat for supporting the honeycomb catalyst carrier inside the casing and elastic Between the step and the corner portion of the honeycomb catalyst carrier in a state where each ridge is elastically compressed and has a plurality of ridges extending in the axial direction and made of an annular wire mesh having flexibility and flexibility. Consisting of a cushioning material sandwiched between .

(Operation) In the case of the honeycomb catalyst converter of the present invention configured as described above, before use, the cushioning material collides with the corner portion of the honeycomb catalyst carrier and the inner surface of the casing, and the corner portion Effectively prevent the damage. That is, since a plurality of ridges provided in the cushioning material in the axial direction are elastically compressed, they are sandwiched between the step portion of the casing and the corner portion of the honeycomb catalyst carrier. The honeycomb catalyst carrier is bufferedly supported inside the casing. Therefore, as described above, damage to the corners of the honeycomb catalyst carrier can be prevented. In particular, since the protrusion provided in the axial direction surely intersects with the corner portion, all the protrusions effectively contribute to the buffer support of the corner portion. As a result, the cushioning material ensures the cushioning support of the honeycomb catalyst carrier.

Further, when the mat thermally expands as it is used, the mat keeps the honeycomb catalyst carrier warm, and at the same time, firmly holds the honeycomb catalyst carrier inside the casing. As a result, the time required for the temperature of the honeycomb catalyst carrier to rise sufficiently after the start of use can be shortened without providing a separate heat insulating material.

(Embodiment) FIGS. 1 to 3 show an embodiment of the honeycomb catalytic converter of the present invention. In the honeycomb catalytic converter of the present invention, the honeycomb catalyst carrier 2 is accommodated in the casing 1 in a buffer manner like the conventional catalytic converter described above. An air-impermeable mat 5 is provided between the inner peripheral surface 1a of the casing 1 and the outer peripheral surface 2a of the honeycomb catalyst carrier 2 except for the front and rear end parts (the left and right end parts in FIG. 1) of the catalyst carrier 2. It is provided over the entire length. By providing the air-impermeable mat 5 in this manner, the exhaust gas does not pass through the honeycomb catalyst carrier 2 and the both peripheral surfaces 1
Bypassing between a and 2a is prevented, and after the mat 5 is thermally expanded, the honeycomb catalyst carrier 2 can be firmly held inside the casing 1.

That is, the mat 5 wound around the catalyst carrier 2 so as to cover the outer peripheral surface 2a of the honeycomb catalyst carrier 2 excluding both front and rear ends thereof contains a material having a thermal expansion property such as expansive mica. I am letting you. This mat 5 irreversibly expands when the honeycomb catalyst carrier 2 becomes hot with use,
Inner peripheral surface 1a of casing 1 and outer peripheral surface of honeycomb catalyst carrier 2
Fills the gap between 2a. In the filled state, the bypass of the exhaust gas through this gap is prevented and the catalyst carrier 2 is firmly held to the casing 1.

Like the conventional catalytic converter, the casing 1 is formed by combining a pair of halves made by press-molding a metal plate in the middle. In this casing 1, an exhaust inlet 6 and an exhaust outlet 7 formed at both front and rear ends, and a cylindrical holding portion 8 formed in an intermediate portion are connected at steps 9 and 9. The inner diameter of the holding portion 8 is formed sufficiently larger than the inner diameters of the exhaust inlet 6 and the exhaust outlet 7.

Cushioning materials 10, 10 are sandwiched between the step portions 9, 9 of the casing 1 configured as described above and the corner portions of the honeycomb catalyst carrier 2. Even when the catalyst carrier 2 is moved in the axial direction (the left-right direction in FIG. 1) by these cushioning materials 10, 10, the corners of the catalyst carrier 2 collide with the step portions 9, 9. This prevents the corners from being damaged.

The cushioning materials 10 and 10 are different from the cushioning materials 4 and 4 (see FIG. 4) in the above-described conventional catalytic converter, and are different from those in the second to third embodiments.
It is configured as shown in detail in the figure. That is, it is formed by braiding stainless steel filaments, and is made by bending one end of a short cylindrical wire net having elasticity and flexibility toward the inside and forming an L-shaped cross section. In this way, the cushioning material 10 having an L-shaped cross section in which a part of the short cylindrical wire mesh is bent inward, has a plurality of axially extending directions (front and back directions in FIG. 2, left and right directions in FIG. 3). The ridges 11 and 11 are formed. Then, each of these ridges 11, 11 is projected from the outer peripheral surface and the end surface of the cushioning material 10.

In the assembled state of the honeycomb catalytic converter, these protrusions 10 and 10 are elastically compressed between the corner portions of the honeycomb catalyst carrier 2 and the step portions 9 and 9. Therefore, the honeycomb catalyst carrier 2 is buffered at the outer peripheral edges of both ends in the axial direction by the respective cushioning materials 10 and 10 inside the casing 1.

The exhaust gas purifying action of the honeycomb catalytic converter of the present invention configured as described above is the same as that of the conventional honeycomb catalytic converter described above. That is, at the time of use, exhaust gas containing harmful substances is sent from the exhaust gas inlet 6 into the casing 1, and the exhaust gas is passed through the honeycomb catalyst carrier 2 and then discharged from the exhaust gas outlet 7. As a result, the harmful components in the exhaust gas are oxidized and reduced by the action of the catalyst adhering to the surface of the catalyst carrier 2 while passing through the honeycomb catalyst carrier 2, and converted into harmless substances.

In particular, in the case of the honeycomb catalyst converter of the present invention, when the temperature of the honeycomb catalyst carrier 2 rises as it is used, the mat 5 wound around the outer peripheral surface 2a of the honeycomb catalyst carrier 2 for almost its entire length is irreversible. Thermally expands. The mat 5 fills the gap between the inner peripheral surface 1a of the casing 1 and the outer peripheral surface 2a of the honeycomb catalyst carrier 2. After the filling, the exhaust gas is prevented from bypassing through this gap, and at the same time, the honeycomb catalyst carrier 2 is provided inside the casing 1.
Hold firmly. At the same time, the heat insulation around the honeycomb catalyst carrier 2 is sufficiently kept by the mat 5.

In addition, before use and before the mat 5 thermally expands, the ring-shaped cushioning materials 10, 10 made of wire mesh collide with the corner portions of the honeycomb catalyst carrier 2 and the inner surface of the casing 1 and the corners Effectively prevent damage to the corners. That is, the cushioning materials 10, 10 are
The ridges 11, 11 are elastically compressed and sandwiched between the corners and the stepped portions 9, 9 of the casing 1. Therefore, when the mat 5 cannot be expected to hold the catalyst carrier 2 before thermal expansion of the mat 5, the honeycomb catalyst carrier 2 is prevented from moving in the axial direction, and The honeycomb catalyst carrier 2 is prevented from being damaged due to the collision with the step portions 9, 9.

After thermal expansion of the mat 5 due to use, the mat 5 firmly holds the honeycomb catalyst carrier 2 to the casing 1. Therefore, the cushioning action of the cushioning materials 10, 10 is sufficient only to prevent damage after assembling the catalytic converter and before use. That is, the vibration applied to the honeycomb catalytic converter before use is limited due to transportation, assembly and the like. Therefore, for example, the relatively simple cushioning material 10 formed by braiding filaments having a diameter of about 0.2 mm to have a bulk density of about 0.6 to 0.7 g / cm ³ is sufficient to prevent damage to the honeycomb catalyst carrier 2. Planned for. Therefore, the manufacturing cost of the cushioning materials 10 and 10 does not particularly increase. In addition, the ridges 11,
11 may be formed in a state of being slightly inclined with respect to the axial direction.

(Advantages of the Invention) Since the honeycomb catalytic converter of the present invention is configured and operates as described above, it is possible to shorten the time required until the temperature of the honeycomb catalyst carrier is sufficiently raised after the start of use. Further, the cushioning material in which a plurality of ridges extending in the axial direction are formed by braiding a wire mesh can be manufactured at low cost, but can reliably support the honeycomb catalyst carrier. Therefore, the production cost can be reduced without deteriorating the exhaust gas purification function and the honeycomb catalyst carrier damage prevention function.

[Brief description of drawings]

1 to 3 show an embodiment of a honeycomb catalytic converter of the present invention. FIG. 1 is a sectional view showing the entire structure, FIG. 2 is a front view of a cushioning material, and FIG. 3 is a partial cut of the cushioning material. Side view,
FIG. 4 is a sectional view showing an example of a conventional honeycomb catalytic converter, and FIG. 5 is a sectional view of a honeycomb catalytic converter using a mat as a cushioning material. 1: casing, 1a: inner peripheral surface, 2: honeycomb catalyst carrier, 2a: outer peripheral surface, 3, 4: buffer material, 5: mat, 6: exhaust inlet, 7: exhaust outlet, 8: holding portion, 9: step Part, 10: cushioning material, 11: ridge.

Claims (1)

[Scope of utility model registration request] 1. A casing formed by continuously connecting an exhaust inlet and an exhaust outlet having a diameter smaller than that of a holding portion formed in an intermediate portion to the front and rear ends of the holding portion, and a holding portion of the casing. The honeycomb catalyst carrier supported inside, and a material having a thermal expansion property, between the outer peripheral surface of the honeycomb catalyst carrier and the inner peripheral surface of the holding portion in a thermally expanded state, before and after the honeycomb catalyst carrier. Except for both ends, it is filled over almost its entire length to maintain airtightness between both peripheral surfaces, and a mat for supporting the honeycomb catalyst carrier inside the casing, and an annular wire mesh having elasticity and flexibility. A honeycomb catalyst having a plurality of ridges extending in the axial direction and comprising a cushioning material sandwiched between the step and the corner of the honeycomb catalyst carrier in a state where each ridge is elastically compressed. converter.