JPH06241021A - Exhaust gas purifier - Google Patents

Abstract

PURPOSE:To prevent a filter from being melted by overheat at the time of filter regeneration by heating particulates by means of microwave. CONSTITUTION:This exhaust gas purifier is provided with a coating layer 19 consisting of high dielectric constant material at a filter outer periphery part 2a 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 microwave from a microwave oscillator 15 for ignition and combustion of particulates. The particulates are easy to burn by the coating layer, and the filter 2 itself is not heated, so it is possible to improve the durability of the filter. Its outer periphery may be heated by an electric heater or a microwave absorber in place of coating.

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.

In the filter regeneration method described above, a method using electromagnetic waves (microwaves) used in microwave ovens, etc. is already known as a particulate ignition means, and further, it is further disclosed in Japanese Patent Laid-Open No. 3-275110. In this type of exhaust emission control device, the outer peripheral portion of the filter is made of a high dielectric constant material that easily absorbs electromagnetic waves for the purpose of preventing the generation of unburned particulates in the outer peripheral portion of the filter. An exhaust emission control device that attempts to improve the regeneration rate is disclosed.

[0004]

However, in the above-described exhaust gas purifying apparatus, since the outer peripheral portion of the filter itself is heated by electromagnetic waves as described above, when the particulate regenerates and burns, the temperature becomes higher than that of the central portion of the filter. There is a risk that the filter material will be melted and damaged in this portion, and the original particulate collection function of the filter may be impaired.

The present invention has been made in view of the above problems of the exhaust gas purification device, and it is an object of the present invention to make the outer peripheral portion of the filter less susceptible to melting loss.

[0006]

In order to achieve the above object, according to the present invention as set forth in claim 1, a filter is provided in an exhaust passage of an internal combustion engine to collect particulates in exhaust gas, and a filter is regenerated. At this time, in an exhaust emission control device that supplies electromagnetic waves to the filter to burn particulates collected by the filter, the outer peripheral portion of the filter is coated with a material that easily absorbs the electromagnetic waves.

Further, according to the invention as set forth in claim 2, a filter for collecting particulates in the exhaust gas is provided in the exhaust passage of the internal combustion engine, and when the filter is regenerated, electromagnetic waves are supplied to the filter to collect it. In the exhaust gas purification device that burns the collected particulates, a heater is provided on the outer periphery of the filter. Further, in the invention according to claim 3, a filter for collecting particulates in the exhaust gas is provided in the exhaust passage of the internal combustion engine, and when the filter is regenerated, electromagnetic waves are supplied to the filter to collect the particulates. In the exhaust gas purifying apparatus that burns curate, a holding material made of a material that easily absorbs the electromagnetic waves is provided on the outer periphery of the filter.

[0008]

In the invention described in claim 1, since the filter itself does not serve as a heat source, but the coating layer provided on the outer peripheral portion of the filter absorbs electromagnetic waves and generates heat, the temperature of the filter temperature is relatively low, Melting loss is unlikely to occur. Also, in the invention described in claim 2, the filter itself does not generate heat, and the heater disposed on the outer periphery generates heat, so that the filter temperature is lower than that of the filter heat generating type.

Further, according to the third aspect of the invention as well, the holding material provided on the outer periphery of the filter absorbs electromagnetic waves to generate heat and heats the outer peripheral portion of the filter, so that the amount of heat received by the filter is greater than that directly generated by the filter. Less is.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the inventions described in each claim will be described with reference to the drawings by taking an exhaust emission control 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 as a first embodiment, 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, and the exhaust gas is collected when collecting the particulates. 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 bypass 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 to connect the upstream side connecting portion a and the downstream side connecting portion b.
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 holding material 9.
An air pump 12 that supplies secondary air from the filter downstream side to the upstream side by an electric air pump 11 is opened at the exhaust pipe portion on the exhaust downstream side and on the upstream side of the second exhaust control valve 8 when the filter is regenerated. The 12 is provided with a first opening / closing valve 14 for opening and closing the pipe in response to a signal from a control circuit (ECU) 13.

The ECU 13 receives various parameters representing the operating state of a vehicle equipped with the present apparatus, and also receives a characteristic representing the amount of particulates trapped in the filter 2 (for example, a 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 is supposed to be done.

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, the exhaust gas does not flow into the bypass pipe 6.

Next, when the filter is regenerated, the exhaust control valves 7 and 8 are moved 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 shown 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, the illustrated device is a so-called backflow regeneration type exhaust gas purification device in which the flow direction of the regeneration gas in the filter at the time of filter regeneration is opposite to the flow direction of the exhaust gas in the filter at the time of collecting particulates. Of course, the present invention is not limited to this reproduction method. According to the first embodiment of the exhaust emission control device configured as described above,
For example, silicon carbide, titanium oxide, zinc oxide, nickel oxide, or the like may be formed on the partition wall surface in the vicinity of the filter (which will be referred to as the filter outer peripheral portion 2a) including the filter outer peripheral surface that contacts the holding material 9 described above. A 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 the filter outer peripheral portion 2a coated with a high dielectric constant material, and the filter outer peripheral surface 2b and the surfaces of the partition walls 5 defining the cells 3a and 3b are also made of the high dielectric constant material. A coating layer 19 made of is formed. According to this embodiment, however, by coating the coating layer 19 on the filter outer peripheral portion 2a as described above, the electromagnetic wave from the microwave oscillator 15 causes the coating layer 19 on the filter to generate heat during filter regeneration. The particulates collected on the filter outer peripheral portion 2a are heated.

As described above, since the coating layer 19 is provided on the outer peripheral portion 2a of the filter where the temperature of the filter 2 is not likely to rise due to heat radiation from the filter 2, the particulates are effectively heated and ignited at this portion. , The reproduction rate of this part can be improved. In addition, since the filter 2 itself is not directly heated as described above, the temperature of the filter itself is lower than that of a filter using the filter as a heat source, and therefore the possibility of melting loss is low, and long-term use is not possible. However, the thermal damage of the filter 2 can be suppressed to a low level.

Next, a second embodiment of the present invention will be described. still,
With respect to each of the embodiments described below, constituent elements of the apparatus, which are similar to those of the apparatus of the preceding embodiment, are designated by the same reference numerals, and description of the operation thereof will be omitted. Referring to FIG. 3 showing a schematic configuration of the apparatus of the second embodiment, in this embodiment, the outer peripheral portion 2a of the filter 2 is not provided with the coating layer as described above, and the outer peripheral surface 2b is surrounded by the coating layer. Therefore, the electric heater 20 is arranged on the upstream side of the regeneration, and the heat insulating material 21 is provided outside the electric heater 20 along the inner wall surface of the trap container 10.

This electric heater 20, like the microwave oscillator 15 and the electric air pump 11, is energized by the ECU 1.
According to the present embodiment, when the filter is regenerated, the power is supplied only during the first half of the filter regeneration period according to the operating condition as shown in FIG. 4, for example. still,
A ring-shaped seal member 22 is mounted downstream of the heat insulating material 21 on the downstream side of the regeneration gas so that the regeneration gas and the exhaust gas do not flow through the gap.

With respect to the operation of the electric heater 20 arranged as described above, the coating layer 1 in the previous embodiment is used.
9 (FIG. 1), the electric heater 20 generates heat instead of the coating layer generating heat, so that the filter outer peripheral portion 2a is secured while ensuring the regeneration rate of the filter outer peripheral portion 2a.
Is prevented from melting. In this embodiment, if the electric heater 20 itself is made of a material that easily absorbs electromagnetic waves, heat can be generated corresponding to the operation of the microwave oscillator 15 even when the heater is not energized, and the filter 2 can be heated. It will be possible.

The first and second embodiments of the present invention described above are directed to a backflow regeneration type exhaust purification device in which the regeneration gas flow direction during filter regeneration is opposite to the exhaust gas flow direction during particulate collection. It is an example to which the present invention is applied, but the present invention is, of course, a so-called forward flow regeneration type exhaust purification device in which the exhaust gas flow direction during particulate collection and the regeneration gas flow direction during filter regeneration are the same. Is similarly applicable.

FIG. 5 shows a third embodiment in which the present invention is applied to an exhaust gas purification apparatus of a forward flow regeneration system and further has a heat generation form different from the previous embodiment. Also in this embodiment, the same components as those in the previous embodiment are designated by the same reference numerals. Microwave absorber 2 arranged as described above
3 is made of a high-dielectric material as described above, and its function is exactly the same as that of the coating layer 19 (FIG. 1) and the electric heater 20 in the previous embodiment.
The absorbing material 23 generates heat by absorbing the microwave from the microwave oscillator 15, and the particulates are burned by the heating of the filter that does not melt.

Although the first, second and third embodiments of the present invention have been described above, in common with each of these embodiments, the temperature difference in the radial direction during filter regeneration causes heat generation in the vicinity of the filter outer peripheral portion. Compared to the conventional type of exhaust purification system that has no source,
It can be significantly reduced, and in this respect, thermal deterioration of the filter can be prevented and durability can be 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.

[0025]

As described above, according to the invention of claim 1, the filter itself does not become a heat source,
Since the coating layer provided on the outer peripheral portion of the filter absorbs electromagnetic waves and generates heat, the temperature of the filter temperature is relatively low and the filter durability is improved. Also, in the invention described in claim 2, the filter itself does not generate heat, and the heater disposed on the outer periphery generates heat, so that the filter temperature is lower than that of the filter heat generating type.

Further, according to the third aspect of the invention as well, the holding material provided on the outer periphery of the filter absorbs electromagnetic waves to generate heat and heats the outer peripheral portion of the filter, so that the amount of heat received by the filter is greater than that directly generated by the filter. Less and its durability is improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an exhaust gas purification apparatus of a reverse flow regeneration system as a first embodiment according to the present invention.

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

FIG. 3 is a schematic device configuration diagram of an exhaust emission control device as a second embodiment according to the present invention.

FIG. 4 is a timing chart showing operating conditions of each filter regeneration means of the apparatus of FIG.

FIG. 5 is a schematic device configuration diagram of an exhaust emission control device as a third embodiment according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Exhaust pipe 2 ... Filter 11 ... Electric air pump 15 ... Microwave oscillator 19 ... Coating layer 20 ... Electric heater 23 ... Microwave absorber

Claims (3)

[Claims] 1. An exhaust gas purification device, wherein 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, electromagnetic waves are supplied to the filter to burn the particulates collected in the filter. In the device, an exhaust emission control device, wherein an outer peripheral portion of the filter is coated with a material that easily absorbs the electromagnetic wave. 2. An exhaust gas purification system, wherein 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, electromagnetic waves are supplied to the filter to burn the particulates collected in the filter. In the device, an exhaust emission control device is characterized in that a heater is provided on the outer periphery of the filter. 3. An exhaust gas purification system, wherein 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, electromagnetic waves are supplied to the filter to burn the particulates collected in the filter. In the device, an exhaust gas purification device, wherein a holding material made of a material that easily absorbs the electromagnetic wave is provided on the outer periphery of the filter.