JPH06241020A - Exhaust gas purifier - Google Patents

Abstract

PURPOSE:To prevent microwave from leaking to the outside due to imperfect connection to an exhaust pipe such as improper filter setting at the time of filter regeneration by heating particulates by means of the microwave. CONSTITUTION:This exhaust gas purifier is provided with a case 7 which can be attached and removed to/from exhaust pipes 8, 9 by housing a filter 2. An electromagnetic wave shielding plate 17 is equipped between a connection part on the farther side from an electromagnetic wave oscillator 14 of both connection parts between the case and the exhaust pipe and the filter. The microwave which has passed through the filter 2 is reflected by the shielding plate before it reaches the connection part to the exhaust pipe to reduce outward leaking amount. At a connection part on the oscillator side, a clearance for electromagnetic wave reflection is formed by the contour of its flange.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification device provided in an internal combustion engine such as a diesel engine, and more particularly to an exhaust gas purification device provided with a filter for collecting particulates in exhaust gas in an exhaust system.

[0002]

2. Description of the Related Art Exhaust gas from an internal combustion engine typified by a diesel engine, for example, contains a large amount of exhaust particulates, that is, particulates. Therefore, the exhaust passage of the engine usually collects particulates. A filter is installed to do this. In addition, if the amount of particulates accumulated inside the filter increases due to use of this filter, the air permeability will gradually be impaired and engine performance will decline, so for example, use a gas burner or an electric heater. The filter is heated and a regeneration gas such as air is supplied, so that the particulates are ignited and burned to perform a filter regeneration process.

By the way, in the above-described filter regeneration method, electromagnetic wave (microwave) heating used in a microwave oven or the like is utilized as a particulate ignition means, and at the time of filter regeneration, a microwave from a microwave oscillator is used. An exhaust gas purification device is known in which the particulates themselves are heated and ignited and burned by transmission, and in JP-A-4-5412, an exhaust pipe on the side opposite to the side where the microwave oscillator of the filter is arranged. There is also disclosed a device in which a microwave shielding plate is arranged in the plate to prevent heating of a part other than the particulates by the microwave.

[0004]

By the way, in the exhaust gas purifying apparatus as described above, the filter is provided with a flange at its end in order to facilitate the attachment and detachment of the filter when the filter is replaced with a new one for a long period of use. It has a structure of being housed in a case and connected to an exhaust pipe, and a flange facing the flange of the case is provided on the piece and the exhaust pipe.

However, in the exhaust gas purifying apparatus in which the filter can be attached and detached as described above, since the connecting portion is located on the filter side of the microwave shielding plate, the flanges are exchanged when the filter is replaced. There is a possibility that microwaves may leak to the outside through the connection portion during filter regeneration due to inadequate connection of the connection or loosening due to vehicle vibration, and particulate ignition and combustion may not be effectively performed.

In view of the problem of the exhaust gas purifying apparatus, it is an object of the present invention to provide an exhaust gas purifying apparatus that reduces microwave leakage due to improper connection and enables effective filter regeneration processing.

[0007]

In order to achieve the above object, according to the present invention, a case accommodating a filter for trapping particulates in exhaust gas is detachably connected to an exhaust pipe of an internal combustion engine, In an exhaust emission control device that emits electromagnetic waves from one side of the filter to burn the collected particulates when the filter is regenerated, at least the side farther from the electromagnetic wave transmission side is connected to the case and the exhaust pipe. Electromagnetic wave shielding means is provided between the section and the filter.

[0008]

By providing the electromagnetic wave shielding means on the filter side of the connecting portion, even if the connecting portion is defective, the electromagnetic wave passing through the filter is shielded by the electromagnetic wave shielding means before reaching the connecting portion. Therefore, leakage of electromagnetic waves from the connecting portion to the outside is prevented, and the amount of leakage from the connecting portion is reduced as a whole.

[0009]

Embodiments of the present invention will be described with reference to the drawings. With reference to FIG. 1 showing a schematic configuration of an exhaust emission control device according to the present embodiment, 1 is an exhaust pipe for guiding exhaust gas from a diesel engine (not shown) to a filter 2, and 3 is exhaust gas from the filter 2 on a downstream side. It is an exhaust pipe leading to.

The filter 2 is provided with a filter holding material 4
It is housed inside a cylindrical case 7 having front and rear flanges 5 and 6, and the case 7 is connected to the exhaust pipes 1 and 3 via cone type exhaust pipes 8 and 9, respectively. Therefore, the cone type exhaust pipes 8 and 9 have flanges 1 at the front and rear ends thereof.
0, 11, 12, and 13 are formed respectively.

A waveguide 15 connected to a microwave oscillator 14 is opened in a cone-shaped exhaust pipe 9 arranged downstream of the filter 2 in the exhaust gas flow direction when collecting particulates. Therefore, when the filter is regenerated, the microwave emitted from the microwave oscillator 14 is guided to the inside of the cone type exhaust pipe 9. Further, according to the present embodiment, for example, punch metal for preventing microwave leakage from the downstream side of the opening of the waveguide 15 on the exhaust downstream side and in the vicinity of the connection portion with the exhaust pipe 3 is used. A small shielding plate 16 having innumerable small holes as described above is provided.

This utilizes the characteristic that microwaves cannot pass through a hole smaller than the wavelength (for example, a hole having a diameter of 50 mm or less), and such a small hole shielding plate 16 is arranged. Thus, microwaves are prevented from leaking to the exhaust gas downstream side of this, and the energy of the microwaves is provided for the purpose of being effectively used for particulate heating.

Further, according to the present embodiment, in order to prevent electromagnetic waves from leaking between the flange 11 of the cone type exhaust pipe 8 and the flange 5 of the case 7 which are matched with each other in the assembled state, the filter 2 is fitted through the flange 5 Inside the side case, an electromagnetic wave shielding plate 17 having a number of small holes and having the same structure as the shielding plate 16 is provided. That is, in this embodiment, since the electromagnetic wave shielding plate 17 is arranged on the exhaust upstream side of the filter 2 and on the filter side of the flanges 5, 11 for mounting the case, for example, temporarily, the cone type exhaust pipe 8,
Even when the connection between the flange 11 and the flange 5 is not complete due to the work of attaching and detaching the filter from the electromagnetic wave 9, the electromagnetic wave shielding plate 17 is provided before the microwave reaches the connection portion a.
Will be reflected and will be completely blocked here, and the leakage of microwaves through the connection part a will be prevented.

As described above, according to the present invention, since the shielding means is provided between the filter and the connecting portion on the side farther from the electromagnetic wave transmitting side in the connecting portion between the case housing the filter and the exhaust pipe, this side is provided. Compared with a conventional exhaust emission control device in which no shielding means is provided, the total amount of electromagnetic wave leakage is reduced, but in this embodiment, electromagnetic wave leakage countermeasures are also taken on the electromagnetic wave transmission side. To be done.

According to the present embodiment, however, the flanges 6 and 12 which serve as the connecting portion b between the case 7 and the cone type exhaust pipe 9.
2 is formed in a stepped shape as shown in FIG. 2, and has a depth of about a quarter wavelength (for example, about 3 cm) of the microwave transmitted at the entrance of the joint surface. A void 18 having is defined. This is to reduce the external leakage of microwaves by positively reflecting the microwaves that have entered at the connecting portion b to the inside of the exhaust pipe in this void space. Bolts and nuts 19 that connect both flanges at the time
Even if the tightening of the gasket is insufficient or the joining state between the gasket 20 and the flanges 6 and 12 changes due to use, microwaves are reflected by the inner wall surface 6a of the flange 6, effectively reducing external leakage. To be done.

Regarding the shape of the flange, as shown in FIG. 3, a large opening is not intentionally formed between the inner wall surfaces, but a ring-shaped space 18 'for microwave reflection is formed on the outside thereof. But good. Although the embodiment described above is intended to reduce the amount of microwave leakage to this side by providing a shield plate having a large number of holes as an electromagnetic wave shield means on the side opposite to the electromagnetic wave transmission side. A second embodiment of the present invention using other shielding means will be described below.

FIG. 4 shows a case in which the filter is accommodated, which is different from that of the previous embodiment. According to this embodiment,
The case 7'for housing the filter 2 is formed as if the cone type exhaust pipe 8 and the case 7 of the previous embodiment were integrated, and the connecting portion a to the exhaust pipe 1 on the side opposite to the electromagnetic wave transmitting side is formed. And the filter 2, a cone-shaped space 21 is defined.

According to this embodiment, however, the microwave is reflected by the inner wall surface 7a 'of the gradually converging space 21 in the process of going through the filter 2 toward the connecting portion, and the microwave at this time is reflected. Due to the deflection, the amount of microwaves that reach the connecting portion a ahead is reduced, and as a result, the leakage amount is reduced. In this embodiment also, the connection part b on the microwave transmission side is
As described above, the microwave reflection void 18 is formed,
The leakage amount as a whole is reduced.

Although the exhaust gas purifying apparatus according to the present invention has been described above based on the illustrated embodiments, these embodiments embody means for reducing the amount of microwave leakage to the outside. The flow direction and the number of filters are not limited to those shown in the figure, and for example, a so-called forward flow regeneration system in which a microwave oscillator is provided on the exhaust upstream side of the filter and a regeneration gas is supplied from the upstream side The same can be applied to an exhaust emission control device or a dual filter type exhaust emission control device in which filters are juxtaposed.

[0020]

As described above, according to the present invention, in the exhaust gas purifying device having the structure in which the filter is detachable,
By providing the electromagnetic wave shielding means at least on the filter side with respect to the connection part opposite to the transmission side of the electromagnetic wave, even if there is a defect in this connection part, the electromagnetic wave passing through the filter to the connection part is Since it is shielded by the electromagnetic wave shielding means before it reaches the portion, the amount of electromagnetic wave leakage from the connecting portion is reduced as a whole, and the filter regeneration efficiency is improved.

Further, along with this, the conventional leak inspection of the connecting portion can be simplified, which is advantageous in terms of maintenance.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an exhaust emission control device as a first embodiment according to the present invention.

FIG. 2 is a partially enlarged sectional view of a connection portion flange of FIG.

FIG. 3 is an enlarged sectional view of a flange as a modified example different from FIG.

FIG. 4 is a device configuration diagram of an exhaust emission control device as a second embodiment according to the present invention.

[Explanation of symbols]

 1, 3 ... Exhaust pipe 2 ... Filter 7, 7 '... Case 8, 9 ... Exhaust pipe (cone type) 14 ... Microwave oscillator 17 ... Electromagnetic wave shield plate 21 ... Space

Claims (1)

[Claims] 1. An exhaust pipe of an internal combustion engine is detachably connected to a case accommodating a filter for trapping particulates in exhaust gas, and at the time of filter regeneration, electromagnetic waves are transmitted from one side of the filter to the filter. In the exhaust gas purification device that burns the collected particulates, an electromagnetic wave shielding means is provided at least on the side farther from the electromagnetic wave transmission side, between the case and the exhaust pipe connecting portion and the filter. An exhaust emission control device characterized by the above.