JPH0352973Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to a diesel engine exhaust purification device that is installed in the exhaust system of a diesel engine and collects particulates such as carbon particles in the exhaust gas. .

[Prior art]

In order to remove particulates such as carbon particles from the exhaust gas of a diesel engine, a particulate trap filter is installed in the exhaust pipe to remove particulates from the exhaust gas.

FIG. 2 is a diagram showing a schematic structure of an exhaust gas purification device for a diesel engine equipped with the above-mentioned particulate trap filter. In the same figure, 1
Reference numeral 1 designates an exhaust pipe of a diesel engine, and a filter 13 is provided in the middle of the exhaust pipe 11 with a heat insulating material 12 interposed therebetween to collect particulates such as carbon particles in the exhaust gas.
A glow plug 14 and a light oil injection nozzle 1 are installed upstream of the
5. An air injection nozzle 16 is provided.

When regenerating the filter 13 to which particulate has adhered, a heating current is supplied from the battery 17 to the glow plug 14 to heat the glow plug 14, and at the same time, light oil and air are injected from the light oil injection nozzle 15 and the air injection nozzle 16. The filter 13 is regenerated by incinerating particulates such as carbon particles adhering to the filter 13 with the flame. Note that 17 and 18 in the figure are an oil pump and an air pump, respectively.

[Problem that the invention attempts to solve]

In the exhaust purification device having the above configuration, when the burner device consisting of the glow plug 14, the light oil injection nozzle 15, and the air injection nozzle 16 generates a flame to regenerate the filter 13, the filter 13
The temperature distribution inside is shown in Figure 3. That is, the temperature at the center of the filter 13 is high, but the temperature at the outer periphery is low. Therefore, even if the center of the filter 13 is raised to the particulate combustion temperature _T1 , the temperature of the outer peripheral part of the filter 13 remains below the particulate combustion temperature _T1 , and the particulate in the center is incinerated. There was a problem that the particulate on the outer periphery could not be incinerated. As a countermeasure to this, increasing the overall temperature will cause filter 1
The outer periphery of the filter 13 also reaches a particulate combustion temperature T1 _or higher, and the particulate in that part can also be incinerated, but the center of the filter 13 exceeds the filter usage limit temperature _T2 , so the center of the filter 13 will melt. A problem arises. In the end, there was a drawback that the regeneration efficiency of the filter 13 could not be improved.

The applicant has previously developed and filed an application for a particulate trap filter in which the outer periphery of the upstream end face of the filter is covered with a closing member, and the downstream side corresponding to the closing member is open. 59−
No. 194558). Although the particulate trap filter improves the regeneration efficiency of the filter, it has the disadvantage that the upstream outer peripheral portion of the filter does not collect particulate and the particulate trapping action, that is, the exhaust gas purification action is reduced. .

The present invention has been developed in view of the above points, and is a highly efficient filter regeneration system that can effectively burn particulates such as carbon particles attached to the outer periphery without melting and damaging the center of the filter. The purpose of the present invention is to provide an exhaust purification device for a diesel engine.

[Means for solving problems]

The present invention to solve the above problems is to provide a filter for collecting particulates in the exhaust gas at a predetermined position in the exhaust pipe of a diesel engine, and to collect particulates collected by the filter on the upstream side of the filter. In an exhaust purification system for a diesel engine that is equipped with a burner device that regenerates a filter by rate incineration, at least the upstream portion of the outer periphery of the filter is provided with a catalyst coating portion coated with a catalyst that lowers the combustion temperature of the particulate. It is characterized in that a non-catalyst coating part that is not coated with a catalyst is provided in the center part.

[Effect]

By configuring the particulate trap filter as described above, the particulate collected in the catalyst-coated area can be incinerated at a lower temperature than the particulate collected in the center, allowing the filter to be regenerated. In this case, the outer periphery can be regenerated without increasing the temperature of the center, and the regeneration efficiency can be improved without melting and damaging the filter.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a diagram showing the structure of a filter member of a particulate trap filter according to the present invention.
Figure a is a longitudinal cross-sectional view, and figure b is a cross-sectional view. As shown in the figure, the outer periphery 1a of a film 1 made of ceramic material is coated with a catalyst that lowers the combustion temperature of particulate, that is, a catalyst that lowers the activation energy of the reaction between carbon and oxygen.

FIG. 5 is a diagram showing the temperature distribution inside the filter 1 during regeneration of the particulate trap filter in which the outer periphery of the filter 1 is coated with a catalyst as described above. If the catalyst is coated,
Particulate combustion temperature _T3 is the particulate combustion temperature when no catalyst is coated.
Since the temperature of the filter 1 is lower than T ₁ , it is possible to incinerate the particulate collected by the filter 1 from the outer periphery to the center even if the temperature of the filter 1 is higher than the service limit temperature T ₂ of the filter 1. .

FIG. 4 is a diagram showing another filter structure of the particulate trap filter according to the present invention, in which FIG. 4A is a longitudinal cross-sectional view and FIG. 4B is a cross-sectional view. As shown in the figure, the filter 1 has a structure in which a catalyst is coated on the outer peripheral portion 1b of the upstream portion in a wedge shape. In the upstream part of the filter 1, the flame from the burner is concentrated in the center, and the temperature in the center becomes higher than the temperature in the outer circumference, but as it goes downstream, the flame spreads and the temperature distribution inside the filter 1 becomes relatively uniform. As described above, by coating the outer periphery of the upstream portion of the filter 1 with a large amount of catalyst, the particulate collected by the filter 1 from the outer periphery to the center of the filter 1 can be effectively incinerated. Therefore, if the filter 1 is configured as shown in FIG. 4, the amount of catalyst used for coating can be saved compared to the filter 1 having the structure shown in FIGS. 1a and 1b.

[Effect of idea]

As explained above, according to the present invention, at least the upstream portion of the outer periphery of the filter is coated with a catalyst that lowers the combustion temperature of the particulate collected by the filter, so it is important when regenerating the filter. The excellent effects of being able to regenerate the outer circumference without increasing the temperature of the filter and improving the regeneration efficiency without melting and damaging the filter are obtained.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the structure of a particulate trap filter according to the present invention, in which Figure a is a longitudinal sectional view, Figure b is a cross sectional view, and Figure 2 is a particulate trap filter structure. FIG. 3 is a diagram showing the temperature distribution in a conventional filter, and FIG. 4 is a diagram showing another filter structure of the particulate trap filter according to the present invention. In the diagram shown,
FIG. 5A is a longitudinal sectional view, FIG. 5B is a cross-sectional view, and FIG. 5 is a diagram showing the temperature distribution within the filter shown in FIG. 1. In the figure, 1...filter, 1a, 1b...catalyst coating portion.

Claims (1)

[Scope of Claim for Utility Model Registration] A filter for collecting particulates in the exhaust gas is provided at a predetermined position of the exhaust pipe of a diesel engine, and a filter for incinerating the particulates collected by the filter is provided on the upstream side of the filter. In the exhaust gas purification device for a diesel engine, which is equipped with a burner device for regenerating particulate matter, at least an upstream portion of the outer peripheral portion of the filter is provided with a catalyst coating portion coated with a catalyst that lowers the combustion temperature of the particulate, and at least a central portion of the filter An exhaust purification device for a diesel engine, characterized in that a non-catalytic coating portion is provided that is not coated with a catalyst.