JP2002030919A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device devised to reduce cost by eliminating a positive heating means such as an electric heater, etc., and to avoid blinding in a short period of time. SOLUTION: The exhaust emission control device of a diesel engine 1 (internal combustion engine) furnished with an accumulator fuel injection device 11 is constituted to inject proper quantity of fuel by high pressure in exhaust gas 3 from an injector 12 by providing a catalyst regeneration type particulate filter 5 furnished with an oxidating catalyst 7 on a front stage in the middle of an exhaust pipe 4 through which the exhaust gas 3 from the engine 1 flows, newly providing the injector 12 on an exhaust manifold 2 to be upstream from the particulate filter 5 and connecting the injector 12 to an accumulator 9 of the accumulator fuel injection device 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust emission control device.

[0002]

2. Description of the Related Art Particulate matter (particulate matter) emitted from a diesel engine is:
Soot composed of carbonaceous material and SO composed of high-boiling hydrocarbon component
F (Soluble Organic Fraction: Soluble Organic Component) and a small amount of sulfate (mist-like sulfuric acid component). Conventionally, a particulate filter is provided in the exhaust pipe through which gas flows.

[0003] This type of particulate filter has a porous honeycomb structure made of a ceramic such as cordierite, and the inlets of each of the flow paths partitioned in a lattice are alternately plugged, and the inlets are plugged. For outlets that are not done, their outlets are plugged,
Only the exhaust gas that has passed through the porous thin wall that defines each flow path is discharged downstream.

Since the particulates in the exhaust gas are collected and deposited on the inner surface of the porous thin wall, the particulates are appropriately burned and removed before the exhaust resistance increases due to clogging. Although it is necessary to regenerate the curated filter, in the normal operating state of the diesel engine, there are few opportunities to obtain a high exhaust temperature enough for the particulates to self-combust,
In general, it has been considered that active heating is performed by attaching an electric heater or the like.

[0005]

However, in the conventional means for attaching such an electric heater, an electric system for supplying power to the electric heater must be newly laid, and continuous electric particulates must be provided. In order to realize the trapping of particulates, it is necessary to provide a pair of particulate filters so as to alternately regenerate the particulate filters. This causes a problem that the system for regenerating the particulate filters becomes complicated and the cost increases. Yes, on the other hand,
If active heating by an electric heater or the like is not performed, there is a problem that the particulate filter is clogged in a short time.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made to reduce costs by eliminating the need for active heating means such as an electric heater and to avoid clogging in a short period of time. It is intended to provide an exhaust gas purification device.

[0007]

SUMMARY OF THE INVENTION The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine provided with a pressure accumulating type fuel injection device, wherein a catalyst regeneration type catalyst is provided in the exhaust passage through which exhaust gas from the internal combustion engine flows. A fuel injector, a new injector is provided at an appropriate position in an exhaust path upstream of the particulate filter, and the injector is connected to a pressure accumulating chamber of the pressure accumulating fuel injection device, and an appropriate amount of fuel is exhausted from the injector. It is characterized in that it is configured to be able to inject high pressure into gas.

Therefore, according to the present invention, when a large amount of particulates are trapped in the particulate filter and the tendency of the pressure loss to increase is increased, an appropriate amount of fuel is injected into the exhaust gas from the injector in the exhaust path at a high pressure. When the fuel is thermally decomposed in the relatively high temperature exhaust gas on the upstream side of the particulate filter, a large amount of HC is generated, and when this HC reaches the oxidation catalyst attached to the particulate filter, The oxidation reaction is promoted to burn, and the combustion of the HC greatly increases the temperature of the exhaust gas passing through the particulate filter, and the particulate collected by the particulate filter is burned and removed with the assistance of the oxidation catalyst. The high reaction temperatures required to achieve this are ensured.

[0009] In the case where the oxidation catalyst is separately provided in front of the particulate filter, the oxidation catalyst comes into contact with the exhaust gas, so that NO, HC, HC, and the like contained in the exhaust gas upstream of the particulate filter. The oxidation reaction of CO is promoted, NO ₂ is generated by oxidation of NO, and active oxygen is generated during the oxidation reaction of HC and CO,
The particulate filter of the particulate filter is efficiently burned and removed by the support of oxidation by the strong oxidizing NO ₂ and active oxygen, while the particulate filter integrally supports the oxidation catalyst. In this case, the oxidation reaction itself of the particulate matter collected by the particulate filter is directly promoted by the oxidation catalyst, and the particulate matter is efficiently burnt and removed.

[0010]

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

FIGS. 1 to 3 show an embodiment of the present invention. In an exhaust gas purifying apparatus of this embodiment, an exhaust gas 3 discharged from a diesel engine 1 through an exhaust manifold 2 flows. A catalyst regeneration type particulate filter 5 is provided in the casing 6 in the middle of the exhaust pipe 4.

The catalyst regeneration type particulate filter 5 is equipped with an oxidation catalyst 7 formed by adding an appropriate amount of a rare earth element such as cerium to alumina on which platinum is supported. In the example shown here, the case where the oxidation catalyst 7 is separately arranged in front of the particulate filter 5 is exemplified, but the oxidation catalyst 7 is integrally supported on the particulate filter 5. You may make it do.

The specific structure of the particulate filter 5 is as shown in FIG. 2. The particulate filter 5 has a porous honeycomb structure made of ceramic, and is divided into lattices. The inlets of the flow paths 5a are alternately plugged, and the inlets of the flow path 5a are not plugged.
As for a, the outlet thereof is plugged, and only the exhaust gas 3 that has passed through the porous thin wall 5b that divides each flow path 5a is discharged to the downstream side. The oxidation catalyst 7 disposed in front of the particulate filter 5 is formed as a flow-through type honeycomb structure as shown in FIG.

Further, in the diesel engine 1 shown in FIG. 1, fuel (light oil) in a fuel tank (not shown) is guided by a fuel pressure pump 8 through a common rail type pressure accumulating chamber 9 (substantial fuel injection device). Although a general pressure-accumulation type fuel injection device 11 that injects fuel into a cylinder by a (combustion injection nozzle) is provided, in the present embodiment, the exhaust manifold 2 upstream of the particulate filter 5 is also provided. An injector 12 is separately provided, and the injector 12 is connected to the pressure accumulating chamber 9 so that an appropriate amount of fuel can be injected from the injector 12 into the exhaust gas 3 of the exhaust manifold 2 at a high pressure.

However, the injector 12 may be installed at any position on the exhaust path upstream of the particulate filter 5, and may be installed in the exhaust pipe 4 upstream of the particulate filter 5. good.

In FIG. 1, reference numeral 13 denotes a pressure sensor for measuring the pressure of the exhaust gas 3 on the inlet side of the casing 6, and reference numeral 14 denotes a pressure sensor for measuring the pressure of the exhaust gas 3 on the outlet side of the casing 6. I have.

The pressure of the exhaust gas 3 on the inlet side and the outlet side of the casing 6 is measured by the pressure sensors 13 and 14, and the pressure on the inlet side is significantly larger than the pressure on the outlet side. When it is determined that a large amount of particulates are trapped in the particulate filter 5 and the tendency of the pressure loss to increase is increased, an appropriate amount of fuel is discharged from the injector 12 of the exhaust manifold 2 into the exhaust gas 3. When the fuel is injected at a high pressure, the fuel is thermally decomposed in the relatively high-temperature exhaust gas 3 upstream of the particulate filter 5 to generate a large amount of HC. When the gas reaches the temperature, the oxidation reaction is accelerated and burns, and the combustion of the HC greatly increases the temperature of the exhaust gas 3 passing through the particulate filter 5, High reaction temperatures required for the particulates trapped in the tee filter 5 is burned off while receiving assistance of the oxidation catalyst 7 (at least 300
℃ or more) is reliably obtained.

As shown in FIG. 1, in the case where the oxidation catalyst 7 is separately provided in front of the particulate filter 5, the oxidation catalyst 7 comes into contact with the exhaust gas 3 so that the An oxidation reaction of NO, HC, and CO in the exhaust gas 3 is promoted upstream of the curated filter 5, and NO ₂ is generated by oxidation of NO, and HC, C
Active oxygen is generated in the course of the oxidation reaction of O, and the particulates of the particulate filter 5 are efficiently burned and removed with the aid of oxidation by the strong oxidizing NO ₂ and active oxygen.

In the case where the oxidation catalyst 7 of the particulate filter 5 is integrally supported, the oxidation reaction itself of the particulates collected by the particulate filter 5 is directly promoted by the oxidation catalyst 7. Particulates are burned and removed efficiently.

Therefore, according to the above embodiment, the cost can be reduced by eliminating the need for a positive heating means such as an electric heater as in the prior art, and the exhaust gas temperature increases as the particulates self-burn. Even in an operating state where it cannot be obtained, the particulates can be appropriately burned and removed, so that clogging of the particulate filter in a short period can be reliably avoided.

Further, a newly installed injector 1 is provided in the exhaust manifold 2 by using a pressure accumulating fuel injection device 11 provided as a general equipment in the diesel engine 1.
Since high pressure injection of fuel into the exhaust gas 3 is realized only by connecting the pressure accumulator 9 to the pressure accumulator 9, the pressure of the existing pressure accumulator 9 can be used without providing a separate injection device. Fuel can be added to the exhaust gas 3 with good mixing properties,
In addition, the injection timing and injection pressure can be easily adjusted by applying the adjustment mechanism of the pressure accumulating fuel injection device 11 for the normal fuel injection into each cylinder.

It should be noted that the exhaust gas purifying apparatus of the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the gist of the present invention.

[0023]

According to the exhaust gas purifying apparatus of the present invention described above, the following various excellent effects can be obtained.

(I) In an operation state in which the cost can be reduced by eliminating the need for a positive heating means such as an electric heater as in the prior art, and the exhaust temperature cannot be obtained high enough to cause the particulates to self-burn. In addition, the particulates can be appropriately burned and removed, so that clogging of the particulate filter in a short period can be reliably avoided.

(II) Since a newly installed injector is connected to the pressure accumulating chamber of the accumulator type fuel injection device in the exhaust passage upstream of the particulate filter to realize high pressure injection of fuel, another injection is newly performed. The fuel can be added to the exhaust gas with good mixing properties by using the pressure of the existing accumulator without using a device, and the injection timing and injection pressure are also related to the normal fuel injection into each cylinder. The adjustment mechanism of the accumulator type fuel injection device can be easily applied by applying the same.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an embodiment for implementing the present invention.

FIG. 2 is a sectional view showing details of a particulate filter of FIG. 1;

FIG. 3 is a partially cutaway perspective view showing details of the oxidation catalyst of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diesel engine (internal combustion engine) 2 Exhaust manifold (exhaust path) 3 Exhaust gas 4 Exhaust pipe (exhaust path) 5 Particulate filter 7 Oxidation catalyst 9 Accumulation chamber 11 Accumulation type fuel injection device 12 Injector

Claims (3)

[Claims] An exhaust gas purifying apparatus for an internal combustion engine provided with an accumulator type fuel injection device, comprising a catalyst regeneration type particulate filter in an exhaust path through which exhaust gas from the internal combustion engine flows, wherein the particulate filter is provided. An injector is newly provided at an appropriate position in the exhaust path upstream of the curable filter, and the injector is connected to the accumulator of the accumulator type fuel injection device, so that the injector can inject an appropriate amount of fuel into the exhaust gas at high pressure. An exhaust gas purifying device characterized by comprising: 2. The apparatus according to claim 1, wherein an oxidation catalyst is separately provided in a stage preceding the particulate filter.
An exhaust gas purification device according to item 1. 3. The exhaust gas purifying apparatus according to claim 1, wherein an oxidation catalyst is integrally supported on the particulate filter.