JP2008208756A - Exhaust emission control device for diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent diesel particulate filters (DPF) for collecting and removing a particulate matter (PM) in exhaust emission from being clogged. <P>SOLUTION: A first DPF 16 and a second DPF 18 having different permeation hole diameters are respectively provided for an exhaust emission pipe 14 connected to an exhaust emission manifold 12 of the diesel engine 10 so that the permeation hole diameter becomes gradually smaller from upstream to downstream. With the large permeation hole diameter, the first DPF 16 has a function to collect only PMs of large particle size and facilitates low pressure loss. With the small permeation hole diameter, the second DPF 18 has a function to collect PMs of particle size larger than that of the second DPF. However, as the PMs of large particle size are removed by the first DPF 16, the second DPF 18 is not clogged in a relatively short period of time by the PMs of large particle size. Thus, it is possible to prevent clogging while suppressing rise in back pressure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification device that collects and removes particulate matter (PM) in exhaust gas by a diesel particulate filter (DPF) disposed in an exhaust passage.

For the purpose of purifying exhaust gas from a diesel engine, an exhaust gas purification device that collects and removes PM in exhaust gas using a DPF disposed in an exhaust pipe is known. In such an exhaust purification device, clogging of the DPF occurs due to PM collection, and therefore, regeneration processing for incinerating the collected PM as appropriate is indispensable. For this reason, as described in Japanese Patent Application Laid-Open No. 7-317529 (Patent Document 1), when the amount of collected PM estimated according to the engine operating state exceeds a predetermined value, the electric heater attached to the DPF is Techniques for operating and incinerating PM have been proposed.
JP 7-317529 A

However, in the conventionally proposed exhaust purification device, since PM of all particle diameters is collected by one DPF, the permeation hole diameter must be adapted to the PM of small particle diameter, and the PM of large particle diameter is required. As a result, clogging occurs in a relatively short time. For this reason, the regeneration interval of the DPF is shortened, and there is a possibility that the fuel consumption is reduced due to the operation of the electric heater.
Therefore, in view of the conventional problems as described above, the present invention provides a plurality of DPFs having different permeation hole diameters from the upstream side to the downstream side of the exhaust pipe so that the permeation hole diameters are gradually reduced. An object of the present invention is to provide an exhaust emission control device for a diesel engine in which clogging of DPF is difficult to occur.

For this reason, in the first aspect of the present invention, the plurality of diesel particulate filters having different permeation hole diameters are arranged from the upstream side to the downstream side of the exhaust pipe so that the permeation hole diameters are gradually reduced. Features.
According to a second aspect of the present invention, the diesel particulate filter located at the uppermost stream of the exhaust pipe is disposed in the vicinity of the outlet of the exhaust manifold.

  According to a third aspect of the present invention, the plurality of diesel particulate filters each carry an oxidation catalyst that oxidizes particulate matter.

  According to the first aspect of the present invention, the diesel engine exhaust pipe is provided with a plurality of diesel particulate filters having different permeation hole diameters so that the permeation hole diameter gradually decreases from the upstream side toward the downstream side. Is done. For this reason, since the diesel particulate filter located upstream of the exhaust pipe has a large permeation hole diameter, the diesel particulate filter exhibits a function of collecting only particulate matter having a large particle diameter, and can have a low pressure loss. . On the other hand, the diesel particulate filter located downstream of the exhaust pipe exhibits a function of collecting particulate matter having a diameter larger than its diameter because its permeation hole diameter is small, but the diesel particulate filter located upstream thereof. As a result, the particulate matter having a large particle diameter has been removed, so that the particulate matter having a large particle diameter does not cause clogging in a relatively short time. Therefore, it is possible to provide an exhaust purification device that is less likely to be clogged while suppressing an increase in back pressure.

Moreover, since the capacity | capacitance of the diesel particulate filter required for particulate matter removal in exhaust_gas | exhaustion is divided | segmented into plurality, size reduction can be achieved, reducing the thermal capacity of each diesel particulate filter. For this reason, the temperature of the diesel particulate filter can be increased in a short time, and an effect of facilitating on-vehicle layout can be expected.
According to the second aspect of the present invention, since the diesel particulate filter located in the uppermost stream of the exhaust pipe is disposed in the vicinity of the outlet of the exhaust manifold, the exhaust gas having a high temperature is introduced. For this reason, the oxidation of the particulate matter having a large particle diameter, in other words, the regeneration treatment can be promoted.

  According to the third aspect of the present invention, each diesel particulate filter carries an oxidation catalyst that oxidizes particulate matter. Therefore, it is possible to realize a continuously regenerative exhaust purification device that is less likely to be clogged. Can do.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows the overall configuration of an exhaust emission control device for a diesel engine according to the present invention.
The exhaust pipe 14 connected to the exhaust manifold 12 of the diesel engine 10 includes a first DPF 16 and a second DPF 18 having different permeation hole diameters so that the permeation hole diameter gradually decreases from the upstream side toward the downstream side. Each is arranged. The first DPF 16 and the second DPF 18 are formed with a number of cells extending substantially in parallel with the exhaust flow by partition walls made of a porous member such as ceramics, and the inlet and outlet of each cell are staggered alternately by a plugging material. It is formed by sealing in a child shape. Then, when the exhaust gas in the cell whose outlet is blocked flows into the adjacent cell whose inlet is blocked via the partition wall, PM in the exhaust gas is collected by the porous member of the partition wall, and the exhaust gas is discharged. Purified.

  Here, as shown in FIG. 2A, the first DPF 16 collects PM20 having a particle size of a predetermined value (for example, 50 nm) or more, while passing PM22 having a particle size of less than the predetermined value. The permeation hole diameter of the partition is set to a relatively large diameter. Further, in the second DPF 18, as shown in FIG. 5B, the partition hole has a relatively small permeation hole diameter so as to collect PM22 having a particle diameter less than a predetermined value.

  According to such an exhaust purification device, among the PM in the exhaust of the diesel engine 10, those having a particle size equal to or larger than a predetermined value are collected by the first DPF 16, while those having a particle size less than the predetermined value are second. Of DPF18. At this time, since the first DPF 16 located at the uppermost stream of the exhaust pipe 14 has a large permeation hole diameter, the first DPF 16 exhibits a function of collecting only a large particle size PM, and can have a low pressure loss. . On the other hand, the second DPF 18 located on the most downstream side of the exhaust pipe 14 has a function of collecting PM larger in diameter than the diameter because the diameter of the permeation hole is small, but the first DPF 16 has a large particle diameter. Since PM has been removed, clogging does not occur in a relatively short time due to the large particle size PM.

  Further, since the DPF capacity necessary for removing PM in the exhaust gas is divided into two, it is possible to reduce the size of the first DPF 16 and the second DPF 18 while reducing the heat capacities of the first DPF 16 and the second DPF 18. For this reason, it is possible to raise the temperature of the first DPF 16 and the second DPF 18 in a short time and to expect an effect that the in-vehicle layout becomes easy. The first DPF 16 located at the uppermost stream of the exhaust pipe 14 can be disposed in the vicinity of the outlet of the exhaust manifold 12 due to the downsizing thereof. The regeneration process of the diameter PM can be promoted. On the other hand, the second DPF 18 located on the most downstream side of the exhaust pipe 16 can promote the regeneration process because the PM has a small particle diameter even if the temperature of the exhaust gas introduced therein is slightly low.

Here, if each of the first DPF 16 and the second DPF 18 is loaded with an oxidation catalyst for oxidizing the collected PM, continuous regeneration is less likely to cause clogging due to a synergistic effect with the above-described action. An exhaust gas purification apparatus can be realized.
In the present embodiment, two DPFs are disposed in the exhaust pipe 14, but three or more DPFs may be disposed. In this way, when the PM in the exhaust gas passes through each DPF, the PM is sequentially collected in descending order of the particle size, so that it is possible to effectively suppress back pressure rise and clogging. .

1 is an overall configuration diagram of an exhaust emission control device for a diesel engine according to the present invention. The detail of the permeation | transmission hole diameter of DPF is shown, (A) is detailed sectional drawing of 1st DPF, (B) is detailed sectional drawing of 2nd DPF.

Explanation of symbols

10 Diesel engine 12 Exhaust manifold 14 Exhaust pipe 16 First DPF
18 Second DPF

Claims (3)

  An exhaust emission control device for a diesel engine, wherein a plurality of diesel particulate filters having different permeation hole diameters are arranged from the upstream side to the downstream side of the exhaust pipe so that the permeation hole diameters gradually decrease.   The diesel engine exhaust gas purification apparatus according to claim 1, wherein the diesel particulate filter located in the uppermost stream of the exhaust pipe is disposed in the vicinity of an outlet of the exhaust manifold.   The exhaust purification device for a diesel engine according to claim 1 or 2, wherein an oxidation catalyst for oxidizing the particulate matter is supported on each of the plurality of diesel particulate filters.

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