JPH05149127A - Exhaust emission control device for diesel engine - Google Patents

Abstract

PURPOSE:To scavenge particulates in exhaust gas of a diesel engine with a filter and to efficiently burn them with an electric heater. CONSTITUTION:A plural number of filter traps 3, 4 are connected to an exhaust pipe 1 through a switch valve 2, and exhaust gas is let to flow to the filter traps 3, 4 to burn particulates through the switch valve 2 of 20-150liters/min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for efficiently purifying soot, that is, particulates in exhaust gas discharged from a diesel engine so as to purify the exhaust gas.

[0002]

2. Description of the Related Art Attempts have been made to purify exhaust gas by collecting and burning particulates in exhaust gas from a diesel engine. For example, Japanese Utility Model Laid-Open No. 61-55115 shows an example thereof. The apparatus disclosed in the publication has a structure in which a heat radiating member extending in the axial direction is provided in the honeycomb filter, and an electric heater is arranged in front of the honeycomb filter. In this known example, the exhaust gas entering from the inlet side of the honeycomb filter passes between the cells constituting the honeycomb filter and flows to the outlet side. During such exhaust gas flow, particulates in the exhaust gas are collected by the filter.

Since the flow resistance of the exhaust gas increases as the amount of collected particulates increases, when the resistance exceeds a predetermined value, the electric heater is energized to burn the particulates. However, it is not preferable to forcibly combust the particulates in a part of the exhaust pipe that is being used while the vehicle is traveling, and the engine is stopped.

Since the combustion of particulates requires a high temperature of 600 ° C. or higher, energization of the electric heater is not sufficient for the battery mounted on the vehicle with the engine stopped, and a separate power source is required.

The need for a separate power source means that if a considerable amount of particulates are trapped in the filter and the flow resistance of the exhaust gas increases, a vehicle equipped with a diesel engine must be carried into the facility equipped with the power source. , Has become one of the practical inconveniences.

Therefore, an attempt has been made to connect a generator directly connected to a diesel engine to an electric heater so as to secure a necessary amount of electricity. This attempt is quite useful, but the increase in exhaust gas flow resistance due to the particulates trapped in the filter has already put a heavy burden on the diesel engine. It is not the best measure to impose on.

[0007] An improvement to this attempt is to connect a pair of filter traps to the exhaust pipe and stop the flow of exhaust gas to the other filter trap by a switching valve while passing the exhaust gas to one filter trap. The particulates collected in the filter trap are burned by an electric heater. This improvement plan allows the exhaust gas to flow to another filter trap by the switching valve before the exhaust gas flow resistance due to the trapped particulates significantly increases, and the particulates can be burned. There are few.

However, this improvement is also difficult if the heat of the electric heater is not easily transferred to the filter, and the temperature rise in the filter cannot be expected quickly due to the influence of the outside temperature, and the particulate combustion efficiency is poor. There are some drawbacks.

[0009]

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to solve the above-mentioned problems of the prior art.

[0010]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention basically connects a plurality of filter traps to an exhaust pipe through a switching valve, and putty collected in the filter. When burning the curate with an electric heater, a technical means of flowing an exhaust gas of 20 to 150 l / min through a switching valve is used.

Specifically, the present invention relates to a plurality of filter traps connected to an exhaust pipe connected to a diesel engine via a switching valve, and the switching valve includes at least 20 to 20% of the filter traps. 150 liters /
Provided is an exhaust gas purifying apparatus for a diesel engine, which has a flow rate of min of exhaust gas and further has a filter arranged in the filter trap and an electric heater arranged upstream of the filter. Preferably, the filter carries a low temperature combustion catalyst.

[0012]

According to the present invention, during the burning of particulates,
Since a part of the exhaust gas is supplied, the temperature of the exhaust gas near 200 ° C assists a part of heat generation of the electric heater and accelerates combustion of particulates. A high temperature atmosphere near the heater is poured into the filter to accelerate the temperature rise of the filter.
Thus, the burden on the battery and generator can be reduced.
Further, the catalyst works to burn the particulates at a low temperature, which is effective in reducing the amount of electric power.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a pair of filter traps 3 and 4 are connected to an exhaust pipe 1 connected to a diesel engine (not shown) via a switching valve 2. A muffler (not shown) is attached to the downstream side of the filter traps 3 and 4.

As shown in FIG. 2, each of the filter traps 3 and 4 has a casing 5 having a large-diameter portion bulged outward, and a sealing material 6 stretched on the inner peripheral side of the casing 5. It has a filter 7 which is housed in the sealing material 6 and is made of a foamable ceramic body, and three electric heaters 8 located in front of the filter 7. The electric heater 8 is connected to a battery or a generator using a lead wire 9.

Exhaust gas entering from the inlets 10 of the filter traps 3 and 4 passes between the electric heaters 8 and enters the filter 7 to collect soot, that is, particulates in the filter and to the outlet 11 in a purified form. Head over.

The low temperature combustion catalyst carried on the filter 7 is an alkali metal such as Cs or K, Cu, Co, Mn, V, La or Ce.
Or a combination of two or more kinds. For example, Cu-
A catalyst consisting of a combination of La-Cs-V can be used.

As shown in FIG. 3, the electric heaters 8 are, for example, spiral-shaped ones separated from each other (three in the illustrated example) so as not to obstruct the flow of exhaust gas.

The switching valve 2 is 20 to 150 when the main part of the exhaust gas is flowing to one of the filter traps 3 or 4.
It functions to flow liter / min of exhaust gas into the other filter trap (4 or 3). Generally, the exhaust gas is 20
Since it has a temperature of around 0 ° C., the temperature of around 200 ° C. can be maintained by flowing 20 to 150 liter / min of exhaust gas in the other filter trap (4 or 3). In the example shown in FIG. 1, when a large amount of particulates are trapped in the filter trap 4 and it becomes necessary to burn the particulates, the switching valve 2 causes the main part of the exhaust gas to flow into the filter trap 3, At the same time that 20-150 liters / min of exhaust gas is passed through the trap 4,
The electric heater 8 is energized. The energization heats and burns the particulates collected by the filter 7 through the exhaust gas. That is, the exhaust gas at around 200 ° C. is heated to around 600 ° C. by the electric heater 8 and burns the particulates. This is more efficient than transferring the heat of the electric heater directly to the particulates. The use of a low temperature catalyst can further lower the combustion temperature of particulates.

[0019]

[Effect] In the present invention, since the exhaust gas is heated by the electric heater and the particulates are burned by the high temperature exhaust gas, the particulates in the filter can be efficiently burned.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an example of the present invention.

FIG. 2 is an enlarged sectional view of a filter trap.

FIG. 3 is a front view of an electric heater.

[Explanation of symbols]

 1 Exhaust pipe 2 Switching valve 3, 4 Filter trap 7 Filter 8 Heater

Claims (2)

[Claims] 1. A plurality of filter traps connected via a switching valve to an exhaust pipe connected to a diesel engine, and at least one of the filter traps having an exhaust gas of 20 to 150 liters / min. And an electric heater disposed upstream of the filter, and an exhaust gas purifying apparatus for a diesel engine. 2. The filter carries a catalyst for low temperature combustion,
The exhaust gas purifying apparatus according to claim 1, wherein a plurality of electric heaters are used.