JPH0647617U - Exhaust gas purification device - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] Exhaust gas purification device for removing particulates contained in exhaust gas discharged from an internal combustion engine such as a diesel engine, especially in the inside of a filter. Provided is an exhaust gas purifying apparatus which does not cause a large temperature difference and therefore does not generate a crack in a filter. An exhaust gas purifying apparatus comprising a combination of a plurality of honeycomb structures, wherein a honeycomb structure forming a central portion of the exhaust gas purifying apparatus has a structure as compared with a honeycomb structure forming an outer peripheral portion thereof. The exhaust gas purifying apparatus is characterized by having a structure in which the amount of collected particulates per unit volume is small.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an exhaust gas purifying apparatus for removing particulates contained in exhaust gas discharged from an internal combustion engine such as a diesel engine.

[0002]

[Prior art]

 Conventionally, as this type of exhaust gas purifying apparatus, for example, one integrally formed by a porous silicon carbide sintered body or a divided honeycomb is provided in a casing provided with a passage communicating with the exhaust gas side of an internal combustion engine. A filter having a structure is provided, and a heat source such as a burner is used in the passage to collect a predetermined amount of particulates, and then the particulates in the filter are burned and removed by the heat source for regeneration. To be done.

However, the above-mentioned conventional technique has the following problems. Not only in the integrated type, but also in the split type, the temperature difference between the outer peripheral portion and the central portion increases as the size increases, and the central portion becomes a higher temperature than the outer peripheral portion. It has the drawback that deterioration progresses from one side. As a method of solving such a defect, a method of making the center part hollow, providing a device for inserting cold air, sealing the end face of the center part to prevent particulates from adhering, etc. have been submitted. ing. In such a conventional method, not only the filtration efficiency is deteriorated, but also the temperature distribution inside the filter causes an extreme difference, and as a result, the filter is cracked.

[0004]

[Problems to be solved by the device]

 The present inventor has completed the present invention as a result of various studies to improve the above-mentioned drawbacks, and the purpose of the present invention is not to cause an extreme temperature difference inside the filter, so that no crack is generated in the filter. The exhaust gas purifying apparatus is provided.

[0005]

[Means for Solving the Problems]

 The gist of the present invention is an exhaust gas purification apparatus that is configured by combining a plurality of honeycomb structures, and the honeycomb structure that constitutes the central portion of the exhaust gas purification apparatus is the honeycomb structure that constitutes the outer peripheral portion. The exhaust gas purifying device is characterized by having a structure in which the amount of collected particulates per unit volume is smaller than that of the above.

That is, in the present invention, since the amount of collected particulates is proportional to the filtration area, the central area has a smaller filtration area per unit volume than the outer circumference, and as a result, the central area has a smaller filtration area than the outer circumference. The part has a smaller number of cells per unit area, and the cell wall thickness is the same as or thicker than the outer peripheral part, whereby the particulate collection amount is reduced.

When the filter that collects the particulates is heated to burn the particulates, the temperature of the filter rises in proportion to the calorific value of combustion of the particulates / time / volume, but the particulates in the central portion are heated. -Since the amount of collected heat is smaller than that of the outer peripheral part, the combustion heat generation amount of the particulates can be suppressed, and since the amount of heat released in the outer peripheral part is larger than that in the central part, the filter near Is difficult to heat up, but the temperature of the filter in the central part is small because the amount of heat radiation is small, so it tends to accumulate heat and rise in temperature. Moreover, this inclination becomes more remarkable as the filter capacity increases. Therefore, as in the present invention, the cell density of the honeycomb structure is lower in the central part, and the heat capacity increases when the cell wall thickness increases, and the synergistic effect of reducing the filtration area reduces the regeneration filter. The temperature of the filter can be made uniform.

Next, the drawings will be described. FIG. 1 is an explanatory view for explaining an installation state of an exhaust gas purifying apparatus according to the present invention, and FIG. 2 is a front view of the exhaust gas purifying apparatus according to the present invention. In FIG. 1, the exhaust gas discharged from the engine room E passes through an exhaust pipe E'and is discharged. The exhaust gas purification device 1 is installed on the way. The exhaust gas purifying device 1 is provided with a metallic casing 2, and a passage 2a of the casing 2 is connected to an exhaust pipe Ea of the internal combustion engine E.

As shown in FIG. 2, the exhaust gas purifying apparatus 1 has a honeycomb structure a, a ,. ． ． , And the honeycomb structures b, b ,. ． ． , C, c ,. ． ． Place. Then, the honeycomb structure d having the smallest cell density is arranged in the central portion thereof.

The cross-sectional area of each honeycomb structure is 6 square cm to 40 square cm, and the length is 100 L to 300 L, and it depends on the amount of gas discharged from the engine to be purified. It can be changed appropriately. Regarding the cell wall thickness and cell density, the cell wall thickness is in the range of 0.1 to 1.0 mm, and the cell density is in the range of 50 cells / square inch to 400 cells / inch 2. It is possible to select the combination freely with increasing density and decreasing sequentially as it goes inside. Both honeycomb structures are porous and made of ceramic such as SiC. The porosity is 30 to 70%, and the average pore diameter can be arbitrarily selected within the range of 1 μm to 50 μm.

Since the filter according to the present invention facilitates reproduction, the conventional method has a plurality of reproduction systems and lacks in practicality. However, the present invention has a simple reproduction system and is highly practical.

[0012]

【Example】

 Next, the present invention will be described more specifically with reference to Examples. Example 1 An exhaust gas purifying apparatus for a 12-liter diesel engine will be described in detail. The filter used in the exhaust gas purifying apparatus is a split type of a porous silicon carbide honeycomb structure. The size of each of the divided filter parts of the honeycomb structure is 30 mm in length, 30 mm in width, and 150 mm in length, and a combination of 49 of them forms a filter. The shape of the divided filter parts is not limited to the above, and various shapes such as 50 × 50 × 100 L may be used. The 24 outermost cells have a cell wall thickness of 0.3 mm and a cell density of 300 cells / square inch, and the next 16 cells have a cell wall thickness of 0.43 mm and a cell density of 170 cells / square inch. It is an inch, and the center 9 have a cell wall thickness of 0.43 mm and a cell density of 100 cells / square inch. Further, since the corner portion of the outermost peripheral portion has a particularly large amount of heat radiation, it is preferable for the four cells to have a cell wall thickness of 0.2 mm and a cell density of 300 cells / square inch. The porosity of each filter part was 40%, and the average pore diameter was 20 μm.

[0013]

[Effect of device]

 As described above, in the present invention, the honeycomb structure forming the central portion of the exhaust gas purification device has a particulate collection amount per unit volume as compared with the honeycomb structure forming the outer peripheral portion. The small structure suppresses the amount of heat generated in the central part and reduces the temperature difference between the central part and the outer peripheral part. Although it could not be completely combusted, in the present invention, it becomes easier to completely combust, and this has the effect of extending the filter life.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining an installation state of an exhaust gas purification device.

FIG. 2 is a front view of an exhaust gas purifying apparatus according to the present invention.

[Explanation of symbols]

1 Exhaust Gas Purification Device E Engine Room 2 Casing E'Exhaust Pipe 3 Filter a, a. ． , Honeycomb structure 4 filter holding member b, b. ． , 5 〃 c, c. ． ，

Claims (1)

[Scope of utility model registration request] 1. An exhaust gas purification apparatus configured by combining a plurality of honeycomb structures, wherein a honeycomb structure forming a central portion of the exhaust gas purification apparatus is a honeycomb structure forming an outer peripheral portion. An exhaust gas purifying device having a structure in which the amount of collected particulates per unit volume is smaller than that of the exhaust gas purifying device.