JPH055411A - Exhaust emission control system for diesel engine - Google Patents

Abstract

PURPOSE:To collect soot in exhaust gas by one filter trap, to regenerate the filter trap and to prevent the generation of the thermal distortion of the filter trap. CONSTITUTION:An exhaust emission control system is provided with a filter trap 3 disposed in an exhaust system, a first branch exhaust pipe 6 and a second branch exhaust pipe 7 branching from an exhaust pipe 5 of a diesel engine 4, a heating pipe 8 connected to the branch position of the first and second branch exhaust pipes 6, 7, a burner 9 connected to the heating pipe 8 and change-over valve 11 for changing over the passages of the first and second branch exhaust pipes 6, 7 and the heating pipe 8. The filter trap 3 is divided into two regions of a central part X and a peripheral part Y in ventilation by a sealing member 3b. To the central part X, the first branch exhaust pipe 6 is connected. To the peripheral part Y, the second branch exhaust pipe 7 is connected. Thus, the central part X and the peripheral part Y of the filter trap 3 are alternately regenerated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel engine exhaust gas purification system in which a filter trap is provided to remove soot such as carbon in exhaust gas from a diesel engine, and the soot collected by the filter trap is burned. Regarding the device.

[0002]

2. Description of the Related Art In a diesel engine, reduction of nitrogen oxides and soot is an important issue, but in a method of improving the combustion method of the engine, soot is increased when the amount of nitrogen oxides is reduced, and soot is increased. There is a contradictory problem that the amount of nitrogen oxides increases when it is attempted to decrease, and it is extremely difficult to reduce both at the same time. Therefore, various methods of removing soot by a filter trap have been proposed.

In order to remove the soot contained in the exhaust gas, it is general to pass the exhaust gas through a filter trap made of ceramics and burn the collected soot. As the combustion method, a catalyst is applied to the surface of the filter trap and fired to burn at the exhaust gas temperature, a method of burning with an electric heater or burner, a method of heating the filter trap with an electric heater to burn, There is a method of burning the soot by heating the filter trap with a burner using a part of it.

However, in the above-mentioned method, the manufacturing cost of the filter trap becomes high, and in the diesel engine, the catalyst is poisoned by the sulfur compound in the fuel, and further, when only the exhaust gas is used as the heat source. Has a problem that this is not always possible depending on the engine state, and the above-mentioned method has a problem that the electric heater consumes a large amount of power and is not suitable for a battery-powered vehicle. In order to solve the problem, the above-mentioned method is drawing attention.

FIG. 4 shows a conventional example, in which branch exhaust pipes 52 and 53 are connected in parallel to an exhaust pipe 51, and branch exhaust pipes 52 and 5 are connected.
3, the filter traps 54 and 55 are respectively arranged in
A switching valve 56 is provided at the inlet of the branch exhaust pipe 53, and a heating pipe 57, is provided on the upstream side of the filter traps 54, 55.
58 is connected to the burner 60 via the switching valve 59. The exhaust gas of the engine flows into either one of the branch exhaust pipes 52 and 53 by switching the switching valve 56, and soot is collected by the filter trap 54 or 55. The regeneration of the filter trap is performed by switching the switching valve 59 to the dormant filter trap from the burner 60 to the heating pipes 57, 5
The high temperature air is sent via 8 to burn the soot collected in the filter trap.

[0006]

However, the conventional filter trap described above has a problem in that it requires two filter traps, a switching valve, etc., and the device becomes large. Further, when the soot is burned by the burner, the temperature of the central part of the filter trap becomes high and the temperature difference between the central part of the filter trap and the outer peripheral part becomes large. ing.

The present invention solves the above-mentioned problems, and enables one filter trap to collect soot in exhaust gas and to regenerate the filter trap, while preventing the occurrence of thermal strain in the filter trap. An object of the present invention is to provide an exhaust gas purifying device for a diesel engine.

[0008]

To this end, an exhaust gas purifying apparatus for a diesel engine according to the present invention has a first branch branched from a filter trap 3 arranged in an exhaust system and an exhaust pipe 5 of a diesel engine 4. An exhaust pipe 6 and a second branch exhaust pipe 7, a heating pipe 8 connected to the branch positions of the first and second branch exhaust pipes 6, 7, a burner 9 connected to the heating pipe 8, and a first And a switching valve 11 for switching the passages of the second branch exhaust pipes 6 and 7 and the heating pipe 8,
The filter trap 3 has a central portion X by the sealing member 3b.
And a peripheral portion Y are divided into two regions in a ventilated manner, the first branch exhaust pipe 6 is connected to the central portion X, the second branch exhaust pipe 7 is connected to the outer peripheral portion Y, and the filter trap The central part X and the outer peripheral part Y of 3 are alternately reproduced. The numbers added to the above-mentioned configurations are for comparison with the drawings, and the configurations of the present invention are not limited thereby.

[0009]

In the present invention, for example, as shown in FIG.
The filter trap 3 has a central portion X by the sealing member 3b.
And a peripheral portion Y are divided into two regions in a ventilated manner, the first branch exhaust pipe 6 is connected to the central portion X, the second branch exhaust pipe 7 is connected to the outer peripheral portion Y, and the filter trap Since the central part X and the outer peripheral part Y of 3 are alternately regenerated, one filter trap 3 can collect soot in the exhaust gas and regenerate the filter trap, thus downsizing the device. And cost can be reduced. Further, when the outer peripheral portion Y of the filter trap 3 is burned and regenerated, the exhaust gas flows to the central portion X to carry away the heat accompanying combustion, and when the central portion X of the filter trap 3 is burned and regenerated. Since the exhaust gas flows and is kept warm in the outer peripheral portion Y, the temperature gradient in the filter trap 3 becomes gentle, and the occurrence of thermal strain in the filter trap 3 can be prevented.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of an exhaust gas purifying apparatus for a diesel engine of the present invention.

The exhaust gas purifying apparatus 1 comprises a filter trap 3 made of ceramics disposed in a housing 2, an exhaust pipe 5 of a diesel engine 4, a first branch exhaust pipe 6 branched from the exhaust pipe 5, and A second branch exhaust pipe 7,
A heating pipe 8 connected to the branch positions of the first and second branch exhaust pipes 6, 7; a burner 9 connected to the heating pipe 8; and a fan 10 for supplying combustion air to the burner 9. It is composed of first and second branch exhaust pipes 6 and 7 and a switching valve 11 for switching the passages of the heating pipe 8. The filter trap 3 is ventilated into two regions, a central portion X and an outer peripheral portion Y, by a sealing member 3b, and a first branch exhaust pipe 6 is connected to the central portion X and is connected to the outer peripheral portion Y. Is connected to the second branch exhaust pipe 7.

2 and 3 show an embodiment of the filter trap 3 according to the present invention. FIG. 2 shows the exhaust inflow side 6
FIG. 3A is an enlarged cross-sectional view, and FIG. 3B is an enlarged plan view.

The filter trap 3 is made of a cordierite ceramic filter as a whole and has a large number of cells 3a formed in a honeycomb shape inside. On the exhaust gas inflow side of the filter trap 3, an annular band sealed by the sealing member 3b is formed, and is divided into two regions, a central part X and an outer peripheral part Y, in an air-permeable manner. Then, in the central portion X and the outer peripheral portion Y,
A checkered pattern, that is, each cell 3a is alternately plugged vertically and horizontally by a sealing member 3c (only a part is shown in the figure). Further, as shown in FIG. 3A, the exhaust gas discharge side R of the filter trap 3 has a pattern opposite to the inflow side L, that is, the cells 3a opened on the inflow side.
Are sealed by the sealing member 3c.

In the filter trap constructed as described above, the exhaust gas flows into each cell 3a opened from the inflow side L, and as shown in FIG. 3, passes through the walls 3d in four vertical and horizontal directions. Then, it flows into the cells 3a that are plugged by the sealing member 3c, soot in the exhaust gas is collected and discharged from the discharge side R.

Next, the operation of the present invention will be described. First, assuming that the switching valve 11 is in the position shown by the solid line in FIG. 1, the exhaust gas of the engine is exhausted through the exhaust pipe 5, the first branch exhaust pipe 6, and the central portion X of the filter trap 3, and the soot in the exhaust gas is removed. , Trapped in the central portion X of the filter trap 3.
When the amount of soot trapped in the central portion X of the filter trap 3 increases and the pressure difference between the inlet side and the outlet side of the filter trap 3 reaches or exceeds a predetermined value, the switching valve 11 is operated by the electronic control unit (not shown) so that The exhaust gas is discharged via the second branch exhaust pipe 7 and the outer peripheral portion Y of the filter trap 3, and the soot in the exhaust gas is captured by the outer peripheral portion Y of the filter trap 3. Burner 9 at the same time
Is operated, hot air is sent to the central portion X of the filter trap 3 through the heating pipe 8 and the first branch exhaust pipe 6,
The soot captured by the filter trap 3 is burned to regenerate the central portion X of the filter trap 3.

When the amount of soot trapped on the outer peripheral portion Y of the filter trap 3 increases, the switching valve 11 is switched to the position indicated by the solid line, and the exhaust gas contains the first branch exhaust pipe 6 and the central portion X of the filter trap 3. The soot contained in the exhaust gas is captured by the central portion X of the filter trap 3.
At the same time, the burner 9 is operated, high temperature air is sent to the outer peripheral portion Y of the filter trap 3 through the heating pipe 8 and the second branch exhaust pipe 7, and the soot trapped in the filter trap 3 is burnt to burn the soot. The outer peripheral portion Y of No. 3 is reproduced. Hereinafter, by switching the switching valve 11, the central portion X and the outer peripheral portion Y of the filter trap are alternately burned and regenerated.

[0017]

As is apparent from the above description, according to the present invention, it is possible to collect the soot in the exhaust gas and regenerate the filter trap with one filter trap.
It is possible to reduce the size of the device and reduce the cost.
Furthermore, when burning and regenerating the outer peripheral portion of the filter trap, exhaust gas flows to the central portion to carry away heat accompanying combustion, and when burning and regenerating the central portion of the filter trap, exhaust gas is exhausted to the outer peripheral portion. Since the gas flows and is kept warm, the temperature gradient in the filter trap becomes gentle, and the occurrence of thermal strain in the filter trap can be prevented.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an exhaust gas purifying apparatus for a diesel engine of the present invention.

FIG. 2 is a plan view showing an exhaust gas inflow side of a filter trap according to the present invention.

3 is an enlarged sectional view of FIG. 2, and FIG. 3B is an enlarged plan view of FIG.

FIG. 4 is a configuration diagram showing an example of a conventional diesel engine exhaust gas purification device.

[Explanation of symbols]

1 ... Exhaust gas purifying device, 3 ... Filter trap, 3a ...
Cell 3b, 3c ... Sealing member, 4 ... Diesel engine, 5 ...
Exhaust pipe 6 ... First branch exhaust pipe, 7 ... Second branch exhaust pipe, 8 ... Heating pipe, 9 ... Burner 11 ... Switching valve, X ... Central part, Y ... Outer peripheral part

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Junichi Nishimura 1-3-1 Nishitsurugaoka, Oi-cho, Iruma-gun, Saitama Tonen Research Institute

Claims (1)

Claim: What is claimed is: 1. A filter trap disposed in an exhaust system,
A first branch exhaust pipe and a second branch exhaust pipe branched from an exhaust pipe of a diesel engine, a heating pipe connected to branch positions of the first and second branch exhaust pipes, and a heating pipe connected to the heating pipe. A burner and a switching valve for switching the passages of the first and second branch exhaust pipes and the heating pipe, and the filter trap is divided into two regions, a central part and an outer peripheral part, by a sealing member. The first branch exhaust pipe is connected to the central portion, and the second branch exhaust pipe is connected to the outer peripheral portion, and the central portion and the outer peripheral portion of the filter trap are alternately regenerated. An exhaust gas purification device for a diesel engine, which is characterized by: