JPH04171210A - Filter recycling device for internal combustion engine - Google Patents

Abstract

PURPOSE:To promote improvement in temperature rise property or enlargement of a burning area and assurance of high recycling performance by providing a microwave producing means to produce microwaves which are fed into a heating room installed in an exhaust pipe in an internal combustion engine and a specific filter to capture particulates. CONSTITUTION:A heating room 13 installed in an exhaust pipe 12, a magnetron 14 as a microwave producing means and a filter 16 to capture particulates existing in exhaust gas are provided. The filter is constructed of a structure with the opening ratio of 60% or more. A preset amount or more of particulates per cell in the filter can be captured to enhance heating capacity in microwave heating per cell and increase temperature promptly to a temperature zone where particulates can be burned. In addition, a high heating capacity of each cell allows prompt thermal diffusion to an adjacent cell and temperature rise in a temperature zone where particulates can be burned over a wide area inside the filter. It is thus possible to recycle the filter in a short time and at a high efficiency.

Description

[Detailed Description of the Invention] Industrial Application Field - The present invention relates to a regeneration device for an internal combustion engine filter that collects particulate matter contained in exhaust gas discharged from a diesel engine. .

Conventional Technology The high economic growth of so-called developed countries such as Europe, America and Japan has greatly contributed to civilization on earth.

However, the waste of fossil fuel energy centered on economic growth in developed countries has polluted the earth's atmosphere.

In terms of global environmental conservation, countermeasures against global warming, that is, measures to reduce CO2 emissions, are currently receiving a lot of attention, but countermeasures against acid rain, which can lead to deforestation, cannot be ignored.

Acid rain is a natural phenomenon caused by air pollutants such as sulfur oxides and nitrogen oxides, and in recent years many countries around the world have introduced regulations on the emission of air pollutants from fixed sources such as co-generation systems and automobiles. It is in the movement to be strengthened against mobile sources such as. In particular, regulations regarding automobile exhaust gas have been shifted from conventional concentration regulations to total volume regulations, and the regulatory values themselves have been significantly reduced.

Among automobiles, diesel vehicles are subject to stricter emission regulations for particulates as well as nitrogen oxides. It is considered impossible to achieve exhaust gas control values using conventional measures to reduce pollutants in exhaust gas by improving combustion such as delaying fuel injection timing, and it is currently essential to install an exhaust gas after-treatment device. .

This post-processing device has a filter that collects particulates.

However, if particulates continue to be collected, the filter becomes clogged and its collection ability is significantly reduced, and the flow of exhaust gas becomes poor, resulting in a reduction in engine output or engine stoppage.

Therefore, technological development to regenerate the collection ability of filters is currently underway all over the world, but it has not yet been put to practical use.

It is known that particulates burn at temperatures of about 600°C. As means for generating a heat source to raise the temperature of the particulates to this high temperature range, combustion methods, one-way electric heaters, microwave methods, and the like are being considered.

Combustion-based devices heat particulates by blowing combustion heat through a filter. Furthermore, a single electric heater type device has a configuration in which the heater is provided close to the input end face of the filter, and the particulates are heated by the radiant heat of the heater. Further, a microwave type device heats the particulates by feeding microwaves to a heating chamber housing the filter and utilizing the dielectric loss of the particulates.

Although each of these devices uses a different heating means, the basic system configuration regarding filter regeneration is almost the same. The configuration of a conventional device will be explained using a microwave system as a representative example. A microwave-based filter regeneration device is proposed in, for example, Japanese Patent Laid-Open No. 1-290910. The device disclosed in the publication is shown in FIG. In the figure, 1 is an engine, 2.3 is a cylindrical heating chamber in which T M o t p mode is excited, 4 is a microwave radiation antenna, 5 is a waveguide, 6 is a microwave generation means, and 7 is a Filter 8 is a switching valve for exhaust gas flow.

In such a configuration, the filter is disposed approximately at the center of the heating chamber in the tube axis direction, and a space '9.10 is created between both end surfaces of the heating chamber in the tube axis direction and the end surfaces of the filter. The microwave generated by the microwave generating means 6 passes through the waveguide 5 and is fed to the heating chamber 2 or 3 from the radiation antenna 4 which projects into the spaces 9 and 1o. The particulates collected in the filter 7 are dielectrically heated by the supplied microwaves and heated to 600° C. or higher. On the other hand, the particulates heated by the air supplied in an appropriate amount are combusted and regeneration of the filter progresses.

Problems to be Solved by the Invention However, conventional microwave-based regenerators do not have a detailed study of the filter structure, and forcibly heat a suitable filter. Met. For this reason, there has been insufficient consideration of the compatibility between the microwave heating method used as a regenerator and the filter structure, and the means to improve regeneration performance have focused on improving the microwave generation means and heating chamber configuration. Overall performance improvement could not be achieved.

The present invention is intended to solve such conventional problems, and its basic purpose is to provide a device configuration that improves the overall performance of a filter regeneration device using a microwave heating method.

Means for Solving the Problems In order to solve the above problems, a filter regeneration device for an internal combustion engine according to the present invention includes a heating chamber provided in an exhaust pipe of an internal combustion engine;
A configuration that includes a microwave generating means that generates microwaves to supply power to the heating chamber, and a fill ladder that is housed in the heating chamber and is made of a structure with a porosity of 60% or more that collects particulates in the exhaust gas. Consisting of

Furthermore, the filter is composed of a structure with a cell count of 200 cells/inch' or less.

Effect of the Invention With the above-described configuration, the present invention collects a predetermined amount or more of particulates in each cell of the filter. This increases the heat generation capacity of each cell by microwave heating and allows the temperature to be quickly raised to a temperature range where particulates are combusted. Further, the high heat generation capacity of each cell promotes heat diffusion to adjacent cells, and the temperature within the filter can be raised to a temperature range where particulates are combusted over a wide area. Therefore, particulate combustion can be promoted in the entire area of the filter, and filter regeneration can be performed in a short time and with high efficiency.

Example Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, 11 is an engine (internal combustion engine), 12
13 is an exhaust pipe, 13 is a heating chamber provided in the exhaust pipe, 14 is a magnetron that is a microwave generating means, 15 is a waveguide that transmits the microwave generated by the magnetron to the heating chamber,
I6 is a filter that collects particulates in exhaust gas, and 17 is an exhaust gas bypass pipe that bypasses engine exhaust gas during filter regeneration.

The filter 16 is configured in a honeycomb shape using a polyhard ceramic such as mullite or cordierite as a carrier. This filter is composed of a structure with a porosity of 60% or more or a structure with a cell count of 200 cells/inch" or less.

The heating chamber 13 has predetermined openings in the shape of a honeycomb or punching to form a flow path for exhaust gas, and both end wall surfaces are limited by metal members 18 and 19 having a radio wave shielding function. Further, a heat insulating material 20 is provided between the filter and the wall surface of the heating chamber.

Reference numerals 21 and 22 indicate valves which are means for opening and closing the exhaust gas flow path, and the figure shows a state in which the exhaust gas is introduced to the filter 16. 23 and 24 are pressure detection means, which detect the pressure inside the exhaust pipe on the exhaust gas inflow side of the filter and on the exhaust gas outflow side of the filter. 25 is a temperature detecting means, which detects the exhaust gas temperature on the exhaust gas outflow side of the filter. 26 is a drive power source for the magnetron 14, and 27 is a control unit that controls the valves 21, 22 and the drive power source 26 based on the detected pressure signal and temperature signal to execute filter regeneration.

In the filter regeneration device having such a configuration, the flow of exhaust gas, the particulate collection process, and the regeneration process will be described below.

Exhaust gas from the internal combustion engine is normally guided to the filter 16 through the exhaust pipe 12 because the valve 21 is open and the valve 22 is closed. Particulates are removed while flowing through this filter. The purified exhaust gas is released into the atmosphere.

If the filter continues to collect particulates, it will become clogged, so the filter must be regenerated at an appropriate time. This timing is determined at the timing when the differential pressure value of the outputs of the pressure detection means 23 and 24 provided in the exhaust pipe reaches a preset pressure value.

At this appropriate time, the valves 21 and 22 are controlled and the exhaust gas is guided to the exhaust bypass pipe 17. Thereafter, the filter 16 begins to regenerate. In response to a regeneration start instruction from the control section 27, the drive power source 26 is activated to operate the magnetron 14. The microwave generated by the magnetron 14 is transmitted through a waveguide 15 and a coupling hole 28 provided on the outer peripheral side wall of the metal pipe body.
Power is supplied to the heating chamber through the heating chamber. The particulates collected by the filter 16 are dielectrically heated by the microwaves, and the temperature rises to become red-hot.

By the way, since this coupling position is biased toward one end surface of the filter 16, the particulates present in the region on the exhaust gas inlet side are dielectrically heated more strongly than in other regions, and the temperature rises quickly and becomes red-hot.

Air is required for red-hot particulates to burn, but preheat the particulates for 5-10 minutes before introducing the air to the filter. Thereafter, the valve 21 is controlled and a portion of the exhaust gas is guided to the filter 16. The particulates, heated by this air, quickly move into a combustion state. This combustion state is accompanied by microwave heating and moves downstream of the exhaust gas from the filter. During this time,
The temperature detection means 25 detects the exhaust gas temperature downstream of the filter.

When the temperature rise in the exhaust gas reaches saturation, it is determined that particulate combustion has been performed to the end of the filter, and it is determined that the filter regeneration has been completed. When the completion of combustion is confirmed, the valves 21 and 22 are controlled to their original states, that is, the valve 21 is opened and the valve 22 is closed, and the exhaust gas is guided to the filter I6 again. This completes a series of operations related to filter regeneration.

By the way, in order to complete filter regeneration by executing this regeneration process, it is necessary to effectively perform particulate combustion. A means for doing this is the filter structure of the present invention.

FIG. 2 illustrates the relationship between the amount of particulates collected in each cell and the number of cells using the aperture ratio as a parameter. The total amount of particulates collected throughout the filter is assumed to be constant.

FIG. 3 shows the relationship between the total amount of particulates collected by the filter and the filter regeneration rate, using the number of cells as a parameter. In regions where the total amount of filter capture was small, the regeneration rate decreased as the number of cells increased. The reason for this is thought to be that the amount of particulates trapped per each cell decreases as the number of cells increases, and therefore the heat generated by microwave heating per cell decreases. Note that when the total amount of trapped particles increases to a certain extent, the influence of the number of cells on the regeneration rate becomes almost unrecognizable. This is considered to be because the heat generation capacity of each cell is sufficient to diffuse heat to adjacent cells.

Maintaining a high regeneration rate over a wide range of trapped amounts is also important from the perspective of guaranteeing the system performance of the filter regeneration device. Therefore, in the present invention, in order to increase the amount of particulates collected per cell, the filter has a structure in which the porosity of the filter is 60% or more or the number of cells is 200 cells/inch or less.

FIG. 4 is a diagram comparing the filter regeneration process in the microwave heating method and the electric heater heating method. If the filter structure of the present invention is used, it can be expected to be effective even in a single electric heater type.

However, the temperature rise characteristics and combustion area near the end face of the filter are almost the same as shown in the figure;
The microwave method guarantees high performance as shown in the diagram in the progress of regeneration after the particulates present near the end face of the filter are eliminated by combustion. That is,
In the microwave method, almost the same temperature rise and combustion progress as near the end face is observed, but with the electric heater type, the area where particulates exist moves away from the heater source, so the heating temperature does not progress in the end face area and combustion progresses. The area tends to shrink, and eventually combustion disappears. Therefore, the filter structure of the present invention, which is optimized for compatibility with the microwave heating method, has a comprehensive improvement in the regeneration performance of the filter regeneration device.

Note that it is not necessary to continue the microwave power supply until the exhaust gas temperature reaches the maximum value, and the power supply can be stopped at an appropriate time before that. The stop timing and preheating time can be determined based on the amount of particulates collected.

Furthermore, although the above explanation describes a system in which part of the exhaust gas is used as combustion air, a dedicated air pump or the like may be added and the generated air may be used.

Furthermore, the content of control of each part related to heating and combustion of particulates can be determined comprehensively, including signals from each detection means provided in the regenerator and a signal indicating the operating state of the engine.

Effects of the Invention As described above, the filter regeneration device for an internal combustion engine of the present invention provides the following effects.

(11) By optimizing the structure of the filter, it is possible to increase the heat generation capacity, improve the temperature rise characteristics, or promote expansion of the combustion area through heat diffusion, thereby ensuring high regeneration performance.

(2) By providing an optimal filter structure for the microwave heating method, it is possible to improve the overall regeneration performance of the entire regeneration device.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a filter regeneration device for an internal combustion engine showing an embodiment of the present invention, Fig. 2 is a diagram showing the relationship between filter structure and particulate collection amount, and Fig. 3 is a diagram showing regeneration characteristics for the filter structure. 4 is a comparison diagram of regeneration progress between a microwave heating method and an electric heater heating method using the filter of the present invention, and FIG. 5 is a block diagram of a conventional filter regeneration device for an internal combustion engine. 11--Internal combustion engine, 13--Heating chamber, 14--Microwave generating means, 16--Filter. Name of agent Patent attorney Akira Kokiharu et al. 28 Akira 11♂ J'lt 剟°

Claims (2)

[Claims] (1) A heating chamber provided in an exhaust pipe of an internal combustion engine, a microwave generating means for generating microwaves to be supplied with electricity to the heating chamber, and a microwave generator housed in the heating chamber to collect particulates in the exhaust gas. A filter regeneration device for an internal combustion engine, comprising a filter made of a structure having a porosity of 60% or more. (2) A heating chamber provided in an exhaust pipe of an internal combustion engine, a microwave generating means for generating microwaves to be supplied with electricity to the heating chamber, and a microwave generator housed in the heating chamber to collect particulates in the exhaust gas. Number of cells is 200 cells/inch^2
A filter regeneration device for an internal combustion engine, comprising a filter consisting of the following structure.