JP4340211B2 - Diesel particulate filter - Google Patents

Description

  The present invention relates to a diesel particulate filter used for removing fine particles (particulates) contained in a large amount in exhaust gas of a diesel engine.

  Diesel engine exhaust gas contains a large amount of fine particles (particulates) mainly composed of carbon. When this particulate is released into the atmosphere, it causes environmental pollution. Therefore, a diesel particulate filter (hereinafter sometimes referred to as “DPF”) for collecting the particulate is disposed in the exhaust system of the diesel engine. The particulate matter in the exhaust gas is removed before being released to the atmosphere.

  Conventionally used DPF uses a porous honeycomb structure having a large number of flow holes (cells) penetrating in the axial direction partitioned by partition walls, and the adjacent flow is such that its end face has a checkered pattern. It has a structure in which holes are sealed at one end opposite to each other (see, for example, Patent Document 1).

  Then, when exhaust gas of the diesel engine is ventilated from one end face of the honeycomb structure, the exhaust gas containing particulates flows into the structure through a circulation hole whose end on the one end face side is not sealed, and is porous The other end of the structure is passed through the other partition hole where the end of the other end surface is not sealed. And when passing through this partition, the particulates in the exhaust gas are captured by the partition, and the purified exhaust gas from which the particulates have been removed is discharged from the other end surface of the structure.

By the way, such a DPF having a conventional structure can be obtained by producing a honeycomb structure that constitutes a main part thereof by extrusion molding and filling end portions of predetermined cells of the obtained honeycomb structure with a plugging material. However, when extruding a thin-walled structure such as a honeycomb structure, there are many restrictions on the material composition such as having to use a material with high fluidity in order to ensure moldability. It was not manufactured using a material having a suitable composition.
JP 2001-269585 A

  The present invention has been made in view of such conventional circumstances, and the object of the present invention is to limit the material composition for ensuring formability as compared with the case of extrusion molding a honeycomb structure. An object of the present invention is to provide a DPF having a novel structure capable of producing its constituent members by a manufacturing method such as press molding with a small amount.

  According to the present invention, a plurality of inner layer flat plates each having a first through hole and a second through hole, each of which is porous and formed of at least one through hole, and a gas inflow through hole formed of at least one through hole are provided. One uppermost flat plate and one lowermost flat plate having a gas outflow through-hole composed of at least one through-hole, and the plurality of inner-layer flat plates include the uppermost flat plate and It is laminated with a predetermined interval between the lowermost flat plate and every other one, the first through hole of the other inner flat plate adjacent to the upper side or the uppermost layer The gas inflow through hole of the other lower layer flat plate or the gas outflow through hole of the lowermost layer flat plate connected to the gas inflow through hole of the flat plate by the annular member. Connected by an annular member and further laminated. Layer flat plates, the entire outer periphery of the inner flat plates and the flat for the lowermost layer is a diesel particulate filter having a covered structure by the outer peripheral wall, it is provided.

  Since the DPF of the present invention can be manufactured by a manufacturing method in which the constituent members are less restricted in material composition such as press molding, compared to the case where the honeycomb structure is manufactured by extrusion molding like a conventional DPF. Thus, the degree of freedom in selecting the material composition is high, and it can be manufactured using a material composition more suitable as a DPF.

  FIG. 1 is an explanatory diagram showing an example of an embodiment of a DPF according to the present invention. As shown in FIG. 2, the DPF of the present invention includes a plurality of inner layer flat plates 1 each having a first through hole 4 and a second through hole 5 that are porous and each include at least one through hole. As shown in FIG. 4, one uppermost flat plate 2 having a gas inflow through hole 6 made of at least one through hole and a gas outflow through hole 7 made of at least one through hole as shown in FIG. And a single lowermost flat plate 3.

  As shown in FIG. 1, a plurality of inner layer flat plates 1 are laminated at a predetermined interval between an uppermost layer flat plate 2 and a lowermost layer flat plate 3. Then, the plurality of laminated inner layer flat plates 1 are alternately arranged on the first through hole 4 of the other inner layer flat plate 1 or the uppermost layer flat plate 2 whose first through hole 4 is adjacent to the upper side. Gas inflow through of the second through hole 5 of the other inner layer flat plate 1 or the lower layer flat plate 3 which is connected to the gas inflow through hole 6 by the annular member 8 and the second through hole 5 is adjacent to the lower side. The hole 7 and the annular member 9 are connected. Furthermore, the entire outer peripheral portion of the laminated uppermost layer flat plate 2, inner layer flat plate 1 and lowermost layer flat plate 3 is covered with an outer peripheral wall 10.

  In this DPF, a gas inflow passage 11 is formed by the gas inflow through hole 6 of the uppermost layer flat plate 2 and the first through hole 4 of each inner layer flat plate 1. Similarly, a gas outflow passage 12 is formed by the gas outflow through hole 7 of the lowermost layer flat plate 3 and the second through hole 5 of each inner layer flat plate 1. The gas inflow passage 11 includes a gap 13 between adjacent inner layer flat plates 1 in which the second through holes 5 are connected to each other by an annular member 9, and an inner layer adjacent to the lowermost layer flat plate 3 and the lowermost layer flat plate 3. The gas outflow passage 12 communicates with the gap 15 between the inner flat plate 1 and the adjacent inner layer flat plate 1 in which the first through holes 4 are connected to each other by the annular member 8. , And the gap 16 between the uppermost flat plate 2 and the inner flat plate 1 adjacent to the uppermost flat plate 2.

  In the DPF having such a structure, when exhaust gas containing fine particles (particulates) is caused to flow into the gas outflow passage 11 from the gas inflow through hole 6 of the uppermost plate 2, the exhaust gas is first gas. Adjacent to the gap 13 between the adjacent inner-layer flat plates 1 connected to each other through the inflow passage 11 and connected to each other by the annular member 9 or the lowermost-layer flat plate 3 and the lowermost-layer flat plate 3. After entering the gap 15 between the inner layer flat plate 1 and passing through the inside (pores) of the inner layer flat plate 1 above and / or below the gap, the first through holes 4 are mutually annular. The gap 14 between the adjacent inner layer flat plates 1 connected by the member 8 or the gap 16 between the uppermost layer flat plate 2 and the inner layer flat plate 1 adjacent to the uppermost layer flat plate 2 is further removed. Gas outflow passage 1 communicating with 16 Go to be finally discharged from the gas outflow through holes 7 of the lowermost flat plate 3 to the outside. When the exhaust gas circulating in the DPF passes through the inside (pores) of the porous inner layer flat plate 1, the fine particles contained in the exhaust gas are captured on the surface of the inner layer flat plate 1, and the fine particles are In the removed state, it is discharged to the outside of the DPF.

  In the present invention, the uppermost-layer flat plate 2 and the lowermost-layer flat plate 3 may be dense so that there are almost no pores, or may be porous like the inner-layer flat plate 1. May be. When the uppermost layer flat plate 2 and the lowermost layer flat plate 3 are dense, there is an advantage that high strength can be obtained as compared with the case of being porous. On the other hand, when the uppermost layer flat plate 2 and the lowermost layer flat plate 3 are porous, not only the gas inflow through hole 6 and the gas outflow through hole 7 but also the uppermost layer flat plate 2 and the lowermost layer flat plate 3. The gas inside and outside the DPF also flows through the pores. That is, in addition to the gas flow as described above, the gas that enters the gap 16 from the outside of the DPF through the pores of the uppermost plate 2, passes through the gas outlet passage 12, and is discharged to the outside from the gas outlet through hole 7. A flow and a gas flow that enters the gap 15 from the gas inflow through hole 6 through the gas inflow passage 11 and is discharged to the portion through the pores of the lowermost layer flat plate 3 are generated. In this case, since the uppermost layer flat plate 2 and the lowermost layer flat plate 3 also act as a filtration layer in the same manner as the inner layer flat plate 1, there is an advantage that the efficiency of the filter is improved.

FIG. 5 is an explanatory diagram showing another example of the embodiment of the DPF according to the present invention. In this embodiment, the distance D ₁ of the gap 14 between the adjacent inner layer flat plates 1 in which the first through holes 4 are connected to each other by the annular member 8, and the mutual second through holes 5 are connected to each other by the annular member 9. It is configured so as to be narrower than the distance D ₂ of the gap 13 between the connected adjacent inner layer flat plates 1.

  As can be seen from the fine particle removal mechanism described above, the gap 13 between the adjacent inner layer flat plates 1 in which the second through holes 5 are connected by the annular member 9 enters the exhaust gas before the fine particles are removed. Since the gap is on the front side of the filtration membrane, the filtered fine particles gradually accumulate as the usage time elapses. Therefore, it is necessary to set a wide interval with a certain margin so that the pressure loss of the DPF does not increase or the filtering ability is not lowered by the fine particles accumulated in the gap 13 within a short period of time.

  In contrast, the gap 14 between the adjacent inner layer flat plates 1 in which the first through holes 4 are connected to each other by the annular member 8 contains fine particles captured on the surface of the inner layer flat plate 1. Only the exhaust gas from which the fine particles have already been removed flows. Therefore, the gap 14 does not need to consider the influence of the deposition of fine particles, and can perform a necessary function even at a narrow interval.

Therefore, as shown in FIG. 5, the interval D ₁ of the gap 14 between the adjacent inner layer flat plates 1 in which the first through holes 4 are connected to each other by the annular member 8 is set to the second penetration by the annular member 9. if configured to be narrower than the distance D ₂ of the gap 13 between the inner flat plate 1 adjacent to the hole 5 to each other are connected, while the number of inner flat plate 1 and the same, i.e., the same filtration capacity A small DPF with a smaller volume can be obtained while keeping it.

  FIG. 6 is an explanatory view showing still another example of the embodiment of the DPF according to the present invention. In this embodiment, two first through-holes 4 and 4 ′ having different dimensions and arrangement are provided in a part of the inner-layer flat plate 1 ′ located in the upper layer, and the uppermost flat-plate 2 is substantially the same as the first through-holes. Two gas inflow through holes 6 and 6 'are provided with the same size and arrangement. The structure of the remaining inner layer flat plate 1 and lowermost layer flat plate 3 is the same as that of the embodiment shown in FIG.

  In the DPF of the present invention, as in the embodiment shown in FIG. 1 described above, it is not necessary to form all the first through holes and second through holes of each inner layer flat plate with the same number, size and arrangement. The number, size, and arrangement of the first through holes and the second through holes are changed for some of the inner layer flat plates, and the gas inflow through holes in the uppermost plate and the gas outflow through holes in the lowermost plate are correspondingly changed. The number, size, and arrangement may be selected as appropriate. In the example of FIG. 6, in addition to the gas inflow passage 11, the gas inflow through hole 6 ′ of the uppermost layer flat plate 2 and the first through hole 4 ′ of the inner layer flat plate 1 ′ communicate with the vicinity of the center of the DPF. One gas inflow passage 11 ′ is formed so that the gas can easily flow into the DPF. In addition, as an example other than the embodiment described here, for example, the hole diameter of the first through hole of each inner layer flat plate is decreased as it goes to the lower layer, or the hole diameter of the second through hole is increased as it goes to the lower layer. By doing so, it is also possible to improve the pressure loss of the DPF.

  For example, as shown in FIG. 7, the DPF of the present invention is arranged such that the uppermost layer flat plate 2 and the lowermost layer flat plate 3 are positioned in the uppermost layer and the lowermost layer, respectively, and the inner layer flat plate 1 and the outer periphery between them. The members 17 and the annular members 8 or 9 can be alternately stacked and integrated. The outer peripheral member 17 has an outer periphery having the same size and shape as the outer periphery of a flat plate such as the inner layer flat plate 1 and the like, and an annular member having the same height (thickness) as the gap between the flat plates to be obtained. After the integration, the outer peripheral wall is configured together with the outer edge portion of the flat plate such as the inner layer flat plate 1. Further, the annular members 8 and 9 are annular members having a height equivalent to the gap between the flat plates to be obtained, and the first through holes 4 and the second through holes 5 of the adjacent inner layer flat plates 1. Any of the first through hole 4 of the inner layer flat plate 1 and the gas inflow through hole 6 of the uppermost layer flat plate 2, and the second through hole 5 of the inner layer flat plate 1 and the gas outflow through hole 7 of the lowermost layer flat plate 3. It is the member which connects these.

  In addition, a columnar spacer having a height equivalent to the gap between the flat plates to be obtained is sandwiched between the flat plates as needed together with the outer peripheral member 17 and the annular members 8 and 9 as required. You may make it improve. In that case, the dimensions and arrangement of the spacer are not particularly limited, but it is preferable to set the dimensions and arrangement so as not to hinder the flow of exhaust gas in the DPF as much as possible.

  Also, as shown in FIGS. 8 (a) and 8 (b), a member in which the outer peripheral member 17 and the annular member 8 or 9 are integrally formed on the inner layer flat plate 1 in advance is produced by press molding or the like, and these are alternately The DPF according to the present invention can be more easily produced by laminating the layers. When the spacer as described above is provided, it is preferable that the spacer is also formed integrally.

  The DPF of the present invention can be produced using a flat plate having a through hole, a thin annular member, or the like as described above, but these members are compared with the case of extrusion molding a honeycomb structure. Since it can be produced by a manufacturing method such as press molding with a high degree of freedom in selecting a material composition, it can be produced using a material composition more suitable as a DPF.

  For example, when a honeycomb structure is extrusion-molded as in the production of a conventional DPF, it is necessary to add a relatively large amount of a binder such as methylcellulose to the material in order to ensure moldability. If it contains a large amount, it tends to cause overcombustion in the firing process, causing problems such as product failure. In the production of the DPF of the present invention, even if a binder is used, only a small amount is required, so that such a problem does not occur. Moreover, since binders, such as methylcellulose, are expensive, if the usage-amount can be restrained, it is advantageous also at the point of manufacturing cost.

  In the present invention, a plurality of first through holes, second through holes, exhaust gas inflow through holes, and exhaust gas outflow through holes may be provided as necessary. Furthermore, the material of each flat plate, the porosity, the pore diameter, the size and shape of the through-hole, the number of inner layer flat plates to be used, etc. are not particularly limited, and are appropriately determined according to the use form and required filtration performance. You can choose.

  Further, in the present invention, for convenience of explanation, the names of members representing the vertical arrangement such as the uppermost flat plate and the lowermost flat plate are used, but this indicates the arrangement direction when using an actual DPF. It is not limited. That is, the DPF of the present invention is not only used in such an arrangement that the uppermost flat plate is positioned at the uppermost position and the lowermost layer flat plate is positioned at the lowermost position. The upper layer flat plate and the lowermost layer flat plate can be used by being arranged in an arbitrary direction, for example, so as to be positioned forward and backward, respectively.

  The present invention can be suitably used as a diesel particulate filter for removing fine particles contained in a large amount in exhaust gas of a diesel engine.

It is explanatory drawing which shows an example of embodiment of the diesel particulate filter which concerns on this invention. It is explanatory drawing which shows an example of the structure of the flat plate for inner layers. It is explanatory drawing which shows an example of the structure of the flat plate for uppermost layers. It is explanatory drawing which shows an example of the structure of the flat plate for lowermost layers. It is explanatory drawing which shows another example of embodiment of the diesel particulate filter which concerns on this invention. It is explanatory drawing which shows another example of embodiment of the diesel particulate filter which concerns on this invention. It is explanatory drawing which shows an example of the manufacturing method of the diesel particulate filter which concerns on this invention. It is explanatory drawing which shows an example of the member used for manufacture of the diesel particulate filter which concerns on this invention. It is explanatory drawing which shows an example of the member used for manufacture of the diesel particulate filter which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Inner layer flat plate, 2 ... Uppermost layer flat plate, 3 ... Bottom layer flat plate, 4 ... 1st through-hole, 5 ... 2nd through-hole, 6 ... Gas inflow through-hole, 7 ... Gas outflow through-hole, 8 ... annular body, 9 ... annular body, 10 ... outer peripheral wall, 11 ... gas inflow passage, 12 ... gas outflow passage, 13 ... gap, 14 ... gap, 15 ... gap, 16 ... gap, 17 ... outer periphery member.

Claims (2)

A plurality of inner-layer flat plates each having at least one first through-hole and second through-hole, and one upper-layer flat plate having a gas inflow through-hole comprising at least one through-hole; A lowermost flat plate having at least one through hole for gas outflow, and the plurality of inner layer flat plates are predetermined between the uppermost flat plate and the lowermost flat plate. The first through hole of the other inner layer flat plate adjacent to the upper one or the gas inflow through hole of the uppermost layer flat plate is annularly formed every other sheet. The second through hole is connected by a member, and the second through hole of the other inner layer flat plate adjacent to the lower side or the gas outflow through hole of the lowermost layer flat plate is connected by an annular member and further laminated. The uppermost layer flat plate, the inner layer flat plate and the front Diesel particulate filter having a whole outer peripheral portion of the lowermost flat plates is covered by the outer peripheral wall structure.   The interval between the adjacent inner layer flat plates in which the first through holes are connected to each other by the annular member is between the adjacent inner layer flat plates in which the second through holes are connected to each other by the annular member. The diesel particulate filter of Claim 1 narrower than the space | interval of.

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