KR20050109311A - Regenerative diesel particulate filter system comprising microwave heater - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel engine soot filter system mounted on an exhaust pipe and regenerating the filter at an appropriate time by monitoring and combusting soot accumulated in the filter during operation of a vehicle or the like. The present invention includes a catalyst carrying porous filter, an inlet and an outlet of an exhaust gas, and a conductive housing accommodating the catalyst carrying porous filter, a microwave generating means for generating microwaves, and microwaves generated by the microwave generating means. A diesel particulate filter comprising microwave transmission means for transmitting to the apparatus, detection means mounted to the housing for detecting a state of exhaust gas, and electronic control means for controlling the operation of the microwave generating means based on a detection signal of the detection means. Provide a system. According to the present invention, it is possible to provide a diesel particulate filter system which minimizes power consumption and is free of breakage or melting.

Description

Diesel particulate filter system with microwave heating device {REGENERATIVE DIESEL PARTICULATE FILTER SYSTEM COMPRISING MICROWAVE HEATER}

The present invention relates to a diesel engine soot filter system for filtering soot generated from a diesel engine. More specifically, the present invention relates to a diesel engine soot filter system. A regenerative diesel engine particulate filter system.

As used in the description of the present invention, the term 'soot' refers to the fine particles generated by the combustion of fuel, which in the art is referred to as particulate material (PM), soot or fine dust. It is also called.

A diesel particulate filter (DPF) system is a device installed between an engine such as a diesel vehicle and a muffler to capture and burn soot in the exhaust gas generated from a diesel engine and release it to the atmosphere.

An example of such a device is US Pat. No. 6,709,489. The device of the patent uses a honeycomb filter made of cordierite (2MgO-2Al ₂ O ₃ -5SiO ₂ ) as a filter. The filter is composed of a plurality of channels parallel to the traveling direction of the exhaust gas, and has a structure in which open and closed channels are alternately planarly formed on the inlet side of the exhaust gas. Exhaust gas entering the open channel of the filter accumulates soot near the end of the open channel or on the channel wall, and the remaining exhaust gas is discharged out of the filter through a so-called wall-flow through the channel wall.

In such a soot filter system, since the channel wall is blocked by particulate matter accumulated in the filter, a process of regenerating the filter by removing it is necessary. The patent uses microwaves as an energy source for the regeneration of filters. The microwaves generated by the microwave generating means are transmitted to the filter to dielectrically heat the filter, and the smoke accumulated in the filter by the heating of the filter is burned and removed.

In the conventional diesel particulate filter system, a high temperature of 650 ° C. or higher is required for combustion of the soot accumulated in the filter. Therefore, excessive battery power is consumed for high temperature heating, and it is practically difficult to apply this system to a vehicle. Moreover, the amount of heat generated in the combustion process of soot may occur when the temperature of the filter exceeds 1000 ° C., which may cause the filter to melt and form a local temperature gradient, resulting in breakage of the filter.

On the other hand, there have been attempts to lower the regeneration temperature of the filter by supporting or coating the catalyst on the filter. This technique regenerates the filter by burning or oxidizing the catalyst material on the ceramic carrier constituting the filter to burn or oxidize the soot collected in the filter at a temperature of at least about 250 ° C, preferably at least about 350 ° C. However, when the temperature of the engine exhaust gas is low, for example, immediately after start-up or at low speeds such as idling or running at low speeds, smooth regeneration cannot be performed because the temperature of the exhaust gas is lower than the catalyst active temperature. If this condition persists for a long time, a significant amount of soot accumulates in the filter of the system. Accumulated soot blocks the pores of the filter and increases the back pressure of the engine, which in turn can adversely affect engine performance and even cause the engine to shut down. Furthermore, when the exhaust gas of high temperature flows in at high speed, the accumulated soot is rapidly burned, and the filter is brought to a high temperature of 1000 ° C. or higher to locally melt the filter or to form a temperature gradient inside the filter to damage the filter.

As described above, the conventional soot filter system of the microwave regeneration method and the catalyst regeneration method exhibits a problem of melting and breakage of the filter. 1A to 1B are photographs photographing melted and broken states of a filter generated in a conventional soot filter system, respectively.

In addition, the soot filter system of the conventional microwave regeneration method and the catalyst regeneration method may have a fatal adverse effect on the performance of the diesel engine by the sintering of the soot during regeneration.

Engine exhaust gases contain Ca, Zn and Mg oxides in the engine oil additives or Fe, Cu, Cr oxides due to engine wear and a variety of oxides due to corrosion of the engine exhaust pipes. These metal oxides are used to filter the soot filter system. Captured as it passes. The trapped metal oxide particles are sintered by a high temperature superheat phenomenon of 1000 ° C. or more often occurring in the above-described catalyst regeneration method and microwave regeneration method, thereby adhering to the filter or forming coarse particles. The ash of the sintered soot blocks the open pores of the filter, which in turn raises the engine back pressure and lowers the efficiency of the engine.

As described above, the conventional diesel particulate filter systems have problems of melting and breaking of the filter due to overheating of the filter and increasing the engine back pressure due to the sintering of the fumes, so that diesel vehicles and industrial fields requiring high reliability are required. It is difficult to apply.

The present invention is to solve the above problems, by burning the soot trapped in the filter at an appropriate time irrespective of the state of the exhaust gas, the combustion of the soot does not cause breakage or melting of the filter and the sintering of the soot An object of the present invention is to provide a diesel particulate filter system in which the problem of increase in engine back pressure does not occur.

In addition, an object of the present invention is to provide a diesel particulate filter system that can minimize the power consumption of the system required for the regeneration of the filter.

In order to achieve the above technical problem, the present invention provides a catalyst-supported porous filter, an inlet and an outlet of the exhaust gas, and a conductive housing for accommodating the catalyst-supported porous filter, microwave generating means for generating microwaves, and the microwave generating means. Microwave transmission means for transmitting the microwaves to the porous filter inside the conductive housing, detection means mounted on the housing to detect a state of the exhaust gas, and controlling the operation of the microwave generation means based on a detection signal of the detection means. It provides a diesel particulate filter system comprising an electronic control means.

In the present invention, the porous filter may further include a microwave absorbing material, wherein the catalyst particles are preferably applied on the micro absorbing material.

In the present invention, the catalyst supported on the filter may be a noble metal or a transition metal catalyst.

According to an embodiment of the present invention, the detecting means includes a temperature sensor, and the electronic control means operates the microwave generating means when the temperature of the exhaust gas flowing into the porous filter is equal to or less than the active temperature of the catalyst, When the temperature of the exhaust gas is higher than the catalyst active temperature, the function of stopping the operation of the microwave generating means. Alternatively, the detecting means includes a pressure sensor, and the electronic control means operates the microwave generating means when the pressure of the exhaust gas flowing into the porous filter is greater than or equal to a predetermined pressure, and the pressure of the exhaust gas is less than or equal to a predetermined pressure. In this case, the function of stopping the operation of the microwave generating means may be performed. In addition, in the present invention, the detecting means includes two pressure sensors, and the electronic control means may be configured by the difference between the pressure of the exhaust gas flowing into the filter and the pressure of the exhaust gas flowing out of the filter. The operation may be controlled, which may be implemented by a pressure difference sensor for measuring the pressure difference between the inlet and outlet sides of the filter.

In the present invention may further comprise a heat insulating means for blocking the flow of exhaust gas between the porous filter and the housing and insulates the filter.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram schematically showing the configuration of a diesel particulate filter system according to an embodiment of the present invention.

2, the filter system of the present invention includes a filter assembly 200 attached to an exhaust pipe of a diesel engine. The filter assembly 200 includes a porous filter 210 and a housing 224 for receiving and supporting the porous filter 210 and is inserted into an exhaust pipe of a diesel engine. The region inside the housing 224 forms a microwave heating chamber by the supply energy of the microwave generating means 120. The housing is preferably made of a non-electrical material, preferably a conductive metal so as to trap the microwaves inside the microwave heating chamber.

The porous filter 210 is formed of a ceramic material such as cordierite, alumina, silicon carbide, zirconia (ZrO ₂ ), titania (TiO ₂ ), zeolite, activated carbon, or silica. In the present invention, the structure of the filter 210 may be any type of honeycomb monolith, pleated fiber, or foam filter. In addition, filters of any structure regardless of the flow type of the exhaust gas, that is, the wall-flow type or the channel-flow type, may be used as the filter of the present invention.

3A and 3B are front views of a part of the filter 210 of FIG. 1 as viewed from the inlet side of the exhaust gas.

Referring to FIG. 3A, the filter 210 includes a plurality of channels 212 and 214 which are divided by a plurality of lattice walls 216 forming a support and are parallel to the inflow direction of the exhaust gas. As shown, the channels can be divided into an open channel 212 and a closed channel 214 with respect to the inlet gas, wherein the open channel 212 and the closed channel 214 are formed alternately with each other in plan view. It is.

3B is a cross-sectional view of the filter of FIG. 3A taken along line AA ′. Referring to FIG. 3B, the outlet end 218 of the open channel 212 of the filter 210 is closed. Accordingly, the exhaust gas introduced into the open channel 212 of the filter 210 is blocked by the closed outlet end 218 and discharged through the porous wall 216 (see arrow). Accordingly, the particulate matter contained in the exhaust gas is collected at the outlet end of the open channel 212 and the porous wall 216, and the concentration of the particulate matter contained in the exhaust gas is reduced.

3A and 3B are only examples of filter structures usable in the present invention, and filters of other structures described above may also be used. For example, a pleated fibrous filter manufactured by adhering a sheet pleated with ceramic fibers and a flat sheet may be used. In the pleated fibrous filter, the inner space defined by the pleated sheet and the flat sheet serves as a passage channel for the exhaust gas, similar to the open channel 212 of FIGS. 3A-3B described above.

In the present invention, the filter 210 carries a catalyst that activates combustion of soot. The catalyst promotes oxidation of soot and lowers the combustion temperature. The catalyst preferably includes a noble metal catalyst or a transition metal catalyst such as Pt, Pd, Rh, Ir, Os, Ni, Co, Au, Ag, and the like. The catalyst is activated at a temperature of about 250-400 ° C. to promote combustion of the soot. Further, in the present invention, as the catalyst, a catalyst in the form of a combination of the listed metal catalysts and other oxide catalysts, such as Pt / BaO, may also be used. The catalyst may be applied to the filter surface or doped inside the filter by conventional application means such as dipping. The catalyst particles are preferably dispersed in the filter on a nano scale, that is, a particle size of several to several hundred nm.

In addition, in the present invention, the filter 210 may further include a microwave absorbing material. The microwave absorbing material is particularly useful when a material having a low microwave absorbing performance such as cordierite is used as a support of the filter 210. The microwave absorbing material absorbs and heats microwaves generated and transmitted by the microwave generating means. As the microwave absorbing material, a dielectric material having high dielectric constant and heat resistance such as SiC and metal oxide is used. The microwave absorbing material is applied to the surface of the filter or doped therein during manufacture of the filter support. When a microwave absorbing material is applied to the filter surface, the application process of the catalyst is preferably carried out after the application of the microwave absorbing material so that the catalyst can be exposed outside the microwave absorbing material.

Referring back to FIG. 1, a heat insulation means 240 is inserted between the filter 210 and the housing 222. The thermal insulation means 240 prevents exhaust gas from flowing between the filter and the housing 222 and insulates the filter 210.

As shown, the assembly 200 of the present invention may be equipped with one or more sensors. The sensor detects state information of the exhaust gas, such as temperature and / or pressure. The temperature and / or pressure information detected by the sensor is used as driving information of the microwave generating means 120. In the present invention, a temperature sensor 242 may be a conventional temperature sensor such as a thermistor, and the pressure sensors 244 and 246 may be a diaphragm type pressure sensor or a semiconductor pressure sensor.

The microwave controller 110 controls the operation of the microwave generating means 120 based on the detection information of the sensor. In the present invention, the microwave controller 110 may be implemented by a separate microcontroller, but may be integrated into an electronic control unit (hereinafter, referred to as "ECU") mounted on a vehicle.

 The microwave controller 110 receives the temperature of the exhaust gas from a sensor, for example, a temperature sensor 242, mounted in the assembly 200, and operates the microwave generating means 120 when the temperature of the exhaust gas is lower than the catalytically active temperature. Let's do it. The microwaves generated by the microwave generating means 120 are guided to the microwave heating chamber by a transmission means 122 such as a waveguide or coaxial cable to collect the dielectric material, the microwave absorbing material, and / or the soot trapped in the filter. Heat directly. The microwave energy supplied keeps the temperature of the filter at a temperature suitable for the activity of the catalyst at about 250 ° C. or higher, preferably about 350 ° C. or higher, to burn the soot collected in the filter 210.

When the temperature of the exhaust gas is higher than the catalyst active temperature, the microwave controller 110 stops the operation of the microwave generating means 120. At this time, since the catalyst is sufficiently activated by the temperature of the exhaust gas itself, the filter can be regenerated without the microwave generator 120.

Thus, in the filter system of the present invention, the filter is regenerated at an appropriate time regardless of the operating state of the engine, that is, the temperature of the exhaust gas. Therefore, according to the present invention, the collected soot does not accumulate in the filter, and there is no fear that the filter is overheated and melted or broken due to the rapid combustion of the collected soot.

On the other hand, the control of the microwave controller 110 of the present invention may be performed based on the pressure of the exhaust gas. For example, the microcontroller 110 operates the microwave generating means when the back pressure measured by the pressure sensor 244 mounted on the inflow side of the exhaust gas is higher than or equal to a predetermined pressure, and when the pressure is lower than the predetermined pressure, the operation of the microwave generating means. Can be stopped. Here, since the back pressure, which is a reference of whether the microwave generating means is operated, can be easily selected or specified by those skilled in the art to which the present invention pertains based on a normal engine back pressure, a detailed description thereof will be omitted.

In addition, operation control of the microwave generating means 120 may be performed based on the pressure difference between the exhaust gas inlet side and the outlet side of the filter. The pressure difference between the inlet and outlet of the filter is determined by providing pressure sensors 244 and 246 on the inlet and outlet sides of the filter, respectively, or by installing a pressure difference sensor (not shown). It may be performed by operating the microwave controller 110 when it exceeds.

Although not described separately, of course, the microwave controller 110 of the present invention may control the microwave generating means 120 by considering both the above-described temperature and pressure as variables. In addition, the control of the microwave controller 110 in the present invention may be performed according to the travel distance information as well as the state information of the exhaust gas. For example, the microwave controller 110 periodically operates the microwave generating means 120 at every predetermined driving distance (for example, 100 km) based on the output of the traveling distance sensor (not shown) of the vehicle or the traveling distance information of the ECU. Soot can also be burned.

The above-described embodiments of the present invention are merely illustrative of embodiments of the present invention. Those skilled in the art to which the present invention pertains can make various modifications and modifications to the above-described embodiments, the modifications and modifications to the extent that does not depart from the scope of the technical spirit of the present invention the scope of the present invention Will belong to.

The diesel particulate filter system of the present invention can perform the regeneration operation of the filter at an appropriate regeneration time regardless of the temperature of the exhaust gas. In addition, the diesel particulate filter system of the present invention uses a metal catalyst to perform regeneration of the filter in a low temperature state. Accordingly, by burning the soot continuously collected at a low temperature, the abnormal high temperature phenomenon and the sintering phenomenon of the soot, which are found in the conventional system, do not occur. As a result, the filter system of the present invention has a significantly lower risk of breakage, melting, and increased engine back pressure than in the prior art, and improves the reliability of the product. In addition, according to the present invention, by selectively performing the microwave regeneration and catalyst regeneration according to the engine condition it is possible to minimize the power consumed by the diesel engine filter system.

1A and 1B are photographs of the filter melted and broken due to overheating or temperature non-uniformity of the filter in the conventional diesel particulate filter system, respectively.

2 is a view schematically showing the configuration of a diesel particulate filter system according to an embodiment of the present invention.

3A and 3B schematically illustrate the front and cross-sectional structures of the wall flow honeycomb monolithic filter used in the diesel particulate filter system of FIG. 2, respectively.

<Short description of the symbols in the drawings>

110: microwave controller 120: microwave generating means

122: microwave transmission means 200: filter assembly

210: filter 212: open channel

214: closed channel 216: porous wall

218: outlet 224: housing

240: heat insulation means 242: temperature sensor

244, 246: pressure sensor

Claims (10)

Catalytically supported porous filters; A conductive housing having an inlet and an outlet of the exhaust gas and containing the catalyst carrying porous filter; Microwave generating means for generating microwaves; Microwave transmitting means for transmitting microwaves generated by the microwave generating means to the porous filter inside the conductive housing; Detection means mounted to the housing to detect a state of the exhaust gas; And And an electronic control means for controlling the operation of the microwave generating means based on the detection signal of the detection means. The method of claim 1, And said porous filter further comprises a microwave absorbing material. The method of claim 1, Wherein said catalyst comprises a noble metal catalyst or a transition metal catalyst. The method of claim 1, The detecting means comprises a temperature sensor, The electronic control means operates the microwave generating means when the temperature of the exhaust gas flowing into the porous filter is less than or equal to the active temperature of the catalyst, and operates the microwave generating means when the temperature of the exhaust gas is greater than or equal to the catalyst active temperature. Diesel soot filter system, characterized in that the stop. The method of claim 1, The detecting means comprises a pressure sensor, The electronic control means operates the microwave generating means when the pressure of the exhaust gas flowing into the porous filter is greater than or equal to a predetermined pressure, and stops the operation of the microwave generating means when the pressure of the exhaust gas is less than or equal to the predetermined pressure. Diesel soot filter system. The method of claim 1, The detecting means comprises two pressure sensors, And said electronic control means controls the operation of said microwave generating means by the difference between the pressure of the exhaust gas flowing into said filter and the pressure of the exhaust gas flowing out of said filter. The method of claim 1, The detecting means includes a pressure difference sensor for measuring the pressure difference between the inlet side and the outlet side of the filter, And said electronic control means controls the operation of said microwave generating means in accordance with the output of said pressure differential sensor. The method of claim 1, And a heat insulating means for preventing the flow of exhaust gas between the porous filter and the housing and having a heat insulating function. Noble or transition metal catalyst supported porous filters; A conductive housing having an inlet and an outlet of the exhaust gas and containing the metal catalyst-carrying porous filter; Microwave generating means for generating microwaves; And And a microwave transmission means for transmitting the microwaves generated by the microwave generation means to the porous filter inside the conductive housing. The method of claim 9, And electronic control means for controlling the operation of the microwave generating means, And said electronic control means controls the operation of said microwave generating means for every predetermined travel distance based on the travel distance information of the vehicle on which said system is mounted.