JPH06241022A - Exhaust gas purifier - Google Patents

Abstract

PURPOSE:To improve the regeneration rate of a filter upstream of regenerating gas at the time of filter regeneration by heating particulates by means of microwave, and make it difficult to thermally deteriorate a filter itself. CONSTITUTION:This exhaust gas purifier is provided with a coating layer 19 consisting of high dielectric constant material at a filter surface which is easy to cool with regenerating gas and easy to leave unburnt parts. At the time of filter regeneration, particulates and a coating layer 19 are heated by a microwave from a microwave oscillator 15 for ignition and combustion of particulates. The particulates are easy to be ignited by the coating layer, and the filter 2 itself is not heated. It is thus possible to improve the durability of the filter 2 itself.

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 filter regeneration method as described above, a method using an electromagnetic wave (microwave) used in a microwave oven or the like is already known as a particulate ignition means, and further, it is further disclosed in JP-A-3-245809. In the publication, there is a drawback of filter regeneration by electromagnetic waves, that is, a large amount of unburned particulate remains near the filter end face on the upstream side of the filter regeneration gas (the temperature of the particulate near the end face due to the cooling action of the regeneration gas Disclosed is an exhaust gas purifying device which aims to improve the filter regeneration rate on the upstream side of regeneration by configuring the partition wall forming the filter and the plug material itself with a high dielectric constant material that easily absorbs electromagnetic waves in order to eliminate Has been done.

[0004]

However, in the above-described exhaust gas purification device, the plug material and the filter partition wall themselves are heated by the electromagnetic wave as described above, and the ignition of the particulates that are heated by the electromagnetic wave is assisted. In addition, there is a possibility that the filter itself may be thermally deteriorated and the durability may be deteriorated as the usage period is extended.

In view of the problem of such an exhaust emission control device, the present invention aims to improve the regeneration rate of the filter portion on the upstream side of the regeneration gas and to prevent the filter itself from being thermally deteriorated.

[0006]

To achieve the above object, according to the present invention, a filter for collecting particulates in exhaust gas is provided in an exhaust passage of an internal combustion engine, and when the filter is regenerated, an electromagnetic wave is applied to the filter. In the exhaust gas purification device for supplying the regeneration gas for particulate combustion and burning the particulates collected in the filter,
There is provided an exhaust emission control device characterized in that the filter portion of the filter on the upstream side of the regeneration gas flow is coated with a material that easily absorbs the electromagnetic waves.

[0007]

[Function] The filter itself is not used as a heat source, but a portion that constitutes the filter is coated with a material that easily absorbs electromagnetic waves, and this coating layer absorbs electromagnetic waves and generates heat. The temperature is lower than that of the heat generation type of the filter, and it is less prone to thermal degradation.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings by taking an exhaust purification device having a basic structure in which a single filter is provided in an exhaust passage as an example. With reference to FIG. 1 showing a schematic configuration of an exhaust emission control device according to the present invention, reference numeral 1 is an exhaust pipe that guides exhaust gas from a diesel engine main body E to a filter 2.

Since the filter 2 collects particulates in the exhaust gas, it is constructed as a honeycomb structure in which plugs 4 are alternately arranged at the ends of a large number of cells 3. When collecting particulates, the exhaust gas is exhausted. Enters from the cell 3a having an open end on the upstream side in the exhaust gas flow direction, passes through the partition wall 5, and then exits outside the filter from the cell 3b having an open end on the exhaust gas flow side.

In order to divert the exhaust gas from the filter 2 during filter regeneration, a bypass pipe 6 is connected to the upstream and downstream sides of the filter 2, and the upstream side connecting portion a and the downstream side connecting portion b are connected.
At the time of filter regeneration, the first exhaust control valve 7 is operated at the position indicated by the dotted line in the figure to guide the exhaust gas from the engine E to the bypass pipe 6.
And a second exhaust control valve 8 are provided respectively. Filter 2
Is housed in a cylindrical trap container 10 whose periphery is covered with a heat insulating cushion material 9.
When the filter is regenerated, the electric air pump 11 is installed in the exhaust pipe portion on the exhaust downstream side of 0 and upstream of the second exhaust control valve 8.
The air pipe 12 that supplies the secondary air from the downstream side to the upstream side of the filter is opened, and the air pipe 12 is provided with a first opening / closing valve 14 that opens and closes the pipe in response to a signal from a control circuit (ECU) 13.

The ECU 13 is supplied with various parameters representing the operating state of a vehicle equipped with the present apparatus, and also with a characteristic representing the amount of particulate collection in the filter 2 (for example, filter pressure loss value). Has become
On the other hand, it outputs a signal that also controls the opening and closing of the exhaust control valves 7 and 8. A waveguide 16 connected to a microwave oscillator 15 is opened in a portion of the trap container 10 on the exhaust downstream side of the filter 2, and the operation of the microwave oscillator 15 is also controlled by the ECU 13. It has become so.

Further, a gas exhaust pipe 17 for exhausting regenerated combustion gas from the filter 2 at the time of filter regeneration at an exhaust pipe portion on the exhaust upstream side of the filter 2 and on the exhaust downstream side of the first exhaust control valve 7. Is opened and opened / closed by a second opening / closing valve 18 controlled by the ECU 13. At the time of collecting particulates, the exhaust gas from the engine E flows into the filter 2 as it is, as shown by the solid line arrow in the figure, and in the process of passing through the filter 2, the particulates in the exhaust gas are contained in the cells 3 (particularly the cells). 3a)). At this time, since the bypass pipe 6 is closed by the exhaust control valves 7 and 8, exhaust gas does not flow into the bypass pipe 6.

Next, when the filter is regenerated, the exhaust control valves 7 and 8 move to the dotted line positions as described above, and as a result, the exhaust gas from the engine E enters the bypass pipe 6 as indicated by the dotted arrow. It flows in, bypasses the filter 2, and flows to the downstream side. Then, at substantially the same time, the microwave oscillator 15 and the electric air pump 11 are operated, and the first opening / closing valve 14 and the second opening / closing valve 18 also open their respective passages,
As described above, the secondary air for regeneration is supplied to the filter 2 from the downstream side thereof, and the microwave oscillator 15
The particulates in the filter 2 are heated by the electromagnetic waves from the. Therefore, in the illustrated exhaust gas purification apparatus, the flow direction of the regeneration gas in the filter at the time of filter regeneration (dotted arrow) is opposite to the exhaust gas flow direction in the filter at the time of particulate collection, that is, so-called reverse flow regeneration It becomes a device.

According to the present embodiment, in the exhaust gas purifying apparatus constructed as above, the filter outer surface of the filter portion including the filter end surface 2a on the upstream side in the regenerating gas flow direction described above (see FIG. For example, silicon carbide (SiC) or aluminum nitride (Al
N), or titanium oxide, zinc oxide whiskers, or other material that easily absorbs electromagnetic waves (high dielectric constant material) is coated by, for example, a wash coat.

FIG. 2 shows an enlarged cross section of a filter portion coated with a high dielectric constant material. In the drawing, not only the surface of the plug 4 on the filter end face 2a side but also each cell 3a,
On the surface of the partition wall 5 defining 3b, a coating layer 19 made of a high dielectric constant material is formed over a predetermined region from the filter end surface 2a to the regeneration gas downstream side. According to this embodiment, however, since the coating layer 19 is formed on the upstream side of the regeneration gas as described above, not only the particulates inside the cell 3a but also the coating layer 19 is heated by electromagnetic waves during regeneration of the filter. , It will heat up the particulates near this.

As described above, the coating layer 19 is intensively coated on the filter portion, which is normally strongly affected by the cooling action from the regenerating gas and is likely to cause the particulate unburned residue. The particulates can be effectively heated and ignited to improve the regeneration rate of this part. In addition, since the filter 2 itself is not directly heated, thermal damage to the filter 2 will not occur even if it is used for a long period of time. It can be kept at a low level.

Further, due to the exhaust gas flow state during particulate collection as shown by the solid arrow in FIG. 2, the device of this embodiment has a structure in which a large amount of particulates are deposited in the vicinity of the filter end face 2a. When the coating layer 19 is formed on this portion, it is natural that the particulates are easily ignited and the filter regeneration time is shortened.

Although the present invention has been described by taking the exhaust gas purification apparatus of the reverse flow regeneration system as an example, the present invention is as shown in FIG.
The present invention is also applicable to an exhaust gas purification apparatus of a forward flow regeneration system in which the exhaust gas flow direction during particulate collection is the same as the regeneration gas flow direction during filter regeneration (with reference to FIG. 3, the embodiment of FIG. 1). The same numbers are attached to the same components as).

In this case, the filter portion coated with the high dielectric constant material becomes a portion in the vicinity of the filter end surface 2b on the upstream side of the regeneration gas, depending on the regeneration gas flow direction, and the regeneration described in this embodiment as well. The regeneration rate of the gas supply side is improved. Further, although each of the above-described embodiments is a single filter type exhaust emission control device, the present invention is naturally applicable to a dual filter type forward flow / backflow regeneration type device in which filters are arranged in parallel.

[0020]

As described above, according to the present invention, a material that easily absorbs electromagnetic waves is coated on the regeneration gas upstream side portion of the filter, which is originally easily cooled by the regeneration gas, during regeneration. Since this coating layer absorbs electromagnetic waves and generates heat, the regeneration rate of this portion is improved and the durability of the filter itself is improved because the filter is not configured to directly generate heat.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a backflow regeneration type exhaust emission control device according to the present invention.

FIG. 2 is a partially enlarged cross-sectional view of the filter shown in FIG.

FIG. 3 is an apparatus configuration diagram in which the present invention is applied to a forward-flow regeneration type exhaust purification apparatus.

[Explanation of symbols]

 1 ... Exhaust pipe 2 ... Filter 11 ... Electric air pump 15 ... Microwave oscillator 19 ... Coating layer

Claims (1)

[Claims] 1. An exhaust passage of an internal combustion engine is provided with a filter for collecting particulates in exhaust gas, and when the filter is regenerated, electromagnetic waves and regeneration gas for particulate combustion are supplied to the filter. An exhaust emission control device for burning particulate matter trapped in a filter, characterized in that the filter portion on the upstream side of the regeneration gas flow of the filter is coated with a material that easily absorbs the electromagnetic waves.