JP5553519B2 - Exhaust purification device - Google Patents

Description

  The present invention relates to an exhaust emission control device.

  Particulate matter (particulate matter) discharged from diesel engines is mainly composed of carbonaceous soot and SOF (Soluble Organic Fraction) consisting of high-boiling hydrocarbon components. Furthermore, the composition contains a small amount of sulfate (mist-like sulfuric acid component). As a measure to reduce this type of particulates, a particulate filter is installed in the middle of the exhaust pipe through which the exhaust gas flows. Has been performed conventionally.

  The particulate filter has a porous honeycomb structure made of a ceramic such as cordierite, and the inlets of the respective channels partitioned in a lattice shape are alternately sealed, and the channels are not sealed. The outlet is sealed, and only the exhaust gas that has permeated through the porous thin wall that defines each flow path is discharged downstream.

  Then, the particulates in the exhaust gas are collected and deposited on the inner surface of the porous thin wall, so that the particulates are appropriately burned and removed before the exhaust resistance increases due to clogging. It is necessary to regenerate, but in normal diesel engine operation conditions, there are few opportunities to obtain exhaust temperatures that are high enough for particulates to self-combust, so a catalyst regeneration type that integrally supports an oxidation catalyst. Adoption of a particulate filter is being studied.

  That is, if such a catalyst regeneration type particulate filter is employed, the oxidation reaction of the collected particulates is promoted to lower the ignition temperature, and the particulates can be burned and removed even at an exhaust temperature lower than the conventional one. It becomes possible.

  However, even when such a catalyst regeneration type particulate filter is used, the trapped amount exceeds the particulate processing amount in the operation region where the exhaust temperature is low, so such a low exhaust gas. If the operation state at the temperature continues, there is a possibility that the particulate filter will fall into an over trapped state without the regeneration of the particulate filter proceeding well.

  Therefore, a flow-through type oxidation catalyst is separately arranged in front of the particulate filter, and fuel is added to the exhaust gas upstream of the oxidation catalyst at the stage where the amount of particulate accumulation has increased. It is considered to perform forced regeneration.

  That is, the fuel (HC) added on the upstream side of the particulate filter undergoes an oxidation reaction while passing through the preceding oxidation catalyst, and the catalyst bed of the particulate filter immediately after the inflow of exhaust gas heated by the reaction heat. The temperature is raised, the particulates are burned out, and the particulate filter is regenerated.

  As a specific means for executing this kind of fuel addition, post-injection is added at the timing of non-ignition later than the compression top dead center following the main injection of fuel performed near the compression top dead center. What is necessary is just to add a fuel in gas.

  As shown in FIG. 4, when such a particulate filter 1 is installed in the middle of the exhaust pipe 3 together with the oxidation catalyst 2 in the previous stage, the previous stage is provided in the casing 4 interposed in the middle of the exhaust pipe 3. The oxidation catalyst 2 and the particulate filter 1 are arranged and accommodated in series, and a disk-shaped dispersion plate 5 having a large number of air diffusion holes 5a is placed on the inlet side of the oxidation catalyst 2 at a right angle to the introduction direction of the exhaust gas 6. I try to arrange it.

  An inlet pipe 7 for introducing exhaust gas 6 from the upstream exhaust pipe 3 is inserted into the casing 4 and extended to a position where it hits the central portion of the dispersion plate 5. A large number of air diffusion holes 7 a are opened at the portion of the casing 7 that has entered the casing 4, and the exhaust gas 6 introduced from the upstream exhaust pipe 3 passes through the air diffusion holes 7 a of the inlet pipe 7 and the dispersion plate 5. The gas is diffused through each air diffusion hole 5 a and guided to the inlet side end face of the oxidation catalyst 2.

  In addition, as prior art document information that technically discloses the arrangement state of the oxidation catalyst 2 and the particulate filter 1 in the preceding stage, there is, for example, the following Patent Document 1 by the same applicant as the present invention.

JP 2009-13793 A

  However, in such a conventional structure, the pressure increases at the downstream side where the flow of the exhaust gas 6 passing through the inlet pipe 7 hits the dispersion plate 5, and most of the exhaust gas 6 passes through the diffuser hole 7 a on the downstream side. 7, the flow of the exhaust gas 6 exiting from the upstream air diffuser 7a spreads in a bell mouth shape due to the influence of the exhaust gas 6 ejected here (see FIG. 5). As a result of the flow of the exhaust gas 6 being obliquely blown against the entry side end face of the oxidation catalyst 2, there was a problem that soot would easily adhere to the entry side end face of the oxidation catalyst 2.

  That is, as shown in the schematic cross-sectional view of the vicinity of the inlet side end surface of the oxidation catalyst 2 in FIG. There is a problem that a vortex s is generated, and a site where the vortex s is generated becomes a substantial stagnation place of the flow of the exhaust gas 6, and clogging is likely to occur due to deposition and deposition of soot here.

  Here, it is noted that a diffuser hole 5a having a small number of holes is formed in the central portion of the dispersion plate 5 against which the inlet pipe 7 abuts to avoid an excessive increase in pressure loss. From the viewpoint of encouraging the exhaust gas 6 to blow out from the air diffuser holes 7a in FIG. 7, the tip of the inlet pipe 7 needs to be sufficiently blocked so as not to cause an excessive increase in pressure loss.

  If the distance L (see FIG. 4) from the dispersion plate 5 to the inlet side end surface of the oxidation catalyst 2 is sufficiently long, the exhaust gas 6 can easily form a flow along the axial direction of the oxidation catalyst 2. Securing the distance L long prevents the casing 4 from being made compact, and significantly deteriorates the mountability on the vehicle. Therefore, the flow of the exhaust gas 6 is maintained while keeping the casing 4 compact. Improvement is desired.

  The present invention has been made in view of the above circumstances, and prevents the clogging of the exhaust purification catalyst by improving the flow of exhaust gas introduced into the exhaust purification catalyst such as an oxidation catalyst while keeping the casing compact. The purpose is that.

The present invention provides an exhaust purification catalyst for purifying exhaust gas by passing it through a casing and is provided in the middle of the exhaust pipe, and an inlet pipe for introducing exhaust gas from the exhaust pipe to the inlet side of the casing. The inlet pipe is inserted into the axial direction of the catalyst, and the inlet pipe is extended to a position facing the inlet side end surface of the exhaust purification catalyst with a predetermined interval, and a large number of portions are inserted into the casing. An exhaust purification device having an air diffusion hole opened and a front end closed with a lid, wherein the casing is partitioned at the front end position of the inlet pipe, and a dispersion plate that opens a large number of air diffusion holes to diffuse exhaust gas the lid of the inlet pipe, the shape of the hole number of diffusing pores of the inlet pipe area decreases gradually allowed and diverging pores from the upstream side to the downstream side is opened in a triangular shape tapering toward the downstream side In addition, a non-hole region extending in the axial direction of the inlet pipe without opening a diffuser hole is formed in a triangular shape that becomes wider toward the downstream side, and is secured at a plurality of locations in the circumferential direction on the downstream side. It is what.

  In this way, the exhaust gas ejected from the air diffuser on the upstream side of the inlet pipe avoids the part where the exhaust gas is ejected from the air diffuser on the downstream side, and enters the non-porous region on the downstream side where the resistance to flow is low. In addition, a sufficient distance to the inlet end surface of the exhaust purification catalyst is secured by blowing out from the air diffuser on the upstream side of the inlet pipe, so that it is easy to form a flow along the axial direction of the oxidation catalyst. In the entire exhaust gas flow, the flow component in the axial direction of the exhaust purification catalyst is greatly increased as compared with the conventional one.

  When exhaust gas is introduced from the axial direction to the inlet end surface of the exhaust purification catalyst, no vortex is generated at the inlet of each flow path of the exhaust purification catalyst, so that no soot deposits occur here. However, even if temporarily attached, the exhaust gas flow is blown away immediately, and as described above, the flow component toward the axial direction of the exhaust purification catalyst is much larger than the conventional exhaust gas flow. When the number is increased, problems such as growth of clogs deposited and accumulated at the inlets of the respective channels and clogging can be avoided.

  According to the above-described exhaust purification device of the present invention, the exhaust gas flows along the axial direction of the exhaust purification catalyst without securing a long distance between the lid that closes the tip of the inlet pipe and the exhaust purification catalyst. Thus, the exhaust gas purification catalyst can be introduced into the inlet end surface of the exhaust gas purification catalyst, so that the exhaust gas flow introduced into the exhaust gas purification catalyst can be improved while keeping the casing compact to prevent the exhaust gas purification catalyst from being clogged. It is possible to achieve an excellent effect of being able to.

It is sectional drawing which shows an example of the form which implements this invention. FIG. 2 is a development view of the inlet pipe of FIG. 1. It is a perspective view which shows the blowing condition of the exhaust gas from the inlet pipe of FIG. It is sectional drawing which shows a prior art example. It is a perspective view which shows the blowing condition of the exhaust gas from the inlet pipe of FIG. It is an enlarged view which shows typically the entrance side end surface vicinity of the oxidation catalyst of FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIGS. 1 to 3 show an example of an embodiment for carrying out the present invention. In the same manner as described above with reference to FIGS. 4 to 6, the casing 4 disposed in the middle of the exhaust pipe 3 has a front stage. The oxidation catalyst 2 (exhaust purification catalyst for purifying by passing exhaust gas) and the particulate filter 1 are arranged in series, and the exhaust gas 6 from the upstream exhaust pipe 3 is placed on the inlet side of the oxidation catalyst 2. An inlet pipe 7 to be introduced is inserted, and the inlet pipe 7 is extended to a position facing the inlet side end face of the oxidation catalyst 2 with a predetermined interval, and a large number of air diffusion holes are introduced into the casing 4. 7a is opened and the tip is closed with a dispersion plate 5 (lid), the number of diffuser holes 7a of the inlet pipe 7 is decreased on the downstream side relative to the upstream side, and the downstream circumferential direction The entrance pie without opening the diffuser holes 7a at a plurality of locations. Thereby ensuring the imperforate region 8 extending in the axial direction of 7.

  In particular, in the present embodiment, as shown in a development view in FIG. 2, the number of the diffuser holes 7a of the inlet pipe 7 gradually decreases from the upstream side to the downstream side, and each non-porous region 8 becomes downstream from the upstream side. As shown by a two-dot chain line in FIG. 2, the region where the air diffusion holes 7a are open is formed in a triangular shape that tapers toward the downstream side. The non-porous region 8 extending in the axial direction of the inlet pipe 7 without opening the air diffusion hole 7a is formed in a triangular shape that becomes wider toward the downstream side.

  Thus, with this configuration, as shown in FIG. 1 and FIG. 3, the exhaust gas 6 ejected from the upstream air diffuser 7a of the inlet pipe 7 and the exhaust gas 6 ejected from the downstream air diffuser 7a. It flows along the non-porous region 8 on the downstream side with little resistance to flow, and is sufficiently discharged to the inlet side end surface of the oxidation catalyst 2 by being ejected from the air diffusion hole 7a on the upstream side of the inlet pipe 7. Therefore, it is easy to form a flow along the axial direction of the oxidation catalyst 2, and the flow component toward the axial direction of the oxidation catalyst 2 out of the entire flow of the exhaust gas 6 is significantly larger than the conventional one. Will be increased.

  Then, when the exhaust gas 6 is introduced from the axial direction with respect to the inlet side end face of the oxidation catalyst 2, the vortex s (see FIG. 6) does not occur at the inlet of each flow path of the oxidation catalyst 2. Soot deposition does not occur, and even if it temporarily adheres, it is immediately blown off by the flow of the exhaust gas 6, so that the axial direction of the oxidation catalyst 2 in the entire flow of the exhaust gas 6 as described above. When the flow component toward is greatly increased as compared with the prior art, defects such as clogging that accumulates at the inlet of each flow path and causing clogging can be avoided.

  Therefore, according to the above-described embodiment, the exhaust gas 6 is supplied to the oxidation catalyst without securing a long distance L (see FIG. 1) between the dispersion plate 5 closing the tip of the inlet pipe 7 and the oxidation catalyst 2. 2 can be introduced into the inlet end surface of the oxidation catalyst 2 in a flow along the axial direction of the oxidation catalyst 2, so that the flow of the exhaust gas 6 introduced into the oxidation catalyst 2 can be improved while keeping the casing 4 compact. Clogging of the oxidation catalyst 2 can be prevented.

  Note that the exhaust purification apparatus of the present invention is not limited to the above-described embodiment, and the exhaust purification catalyst housed in the casing in the middle of the exhaust pipe is not necessarily oxidized in the front stage of the particulate filter. The catalyst is not limited to the catalyst, and may be an oxidation catalyst using the particulate filter itself as a carrier, or may be various catalysts such as a NOx occlusion reduction catalyst, a selective reduction catalyst, and a three-way catalyst. Also, the lid that closes the tip of the inlet pipe does not necessarily have to be made of a dispersion plate. If sufficient improvement in exhaust gas flow can be achieved with only the inlet pipe, the dispersion plate is simply abolished. Of course, a lid having only a function of closing the tip of the inlet pipe may be used, and various modifications can be made without departing from the scope of the present invention.

1 Particulate filter 2 Oxidation catalyst (exhaust gas purification catalyst)
3 Exhaust pipe 4 Casing 5 Dispersion plate (lid)
5a Air diffuser 6 Exhaust gas 7 Inlet pipe 7a Air diffuser 8 Non-porous region

Claims (1)

An exhaust purification catalyst for purifying exhaust gas by passing through it is held by a casing and is provided in the middle of the exhaust pipe, and an inlet pipe for introducing exhaust gas from the exhaust pipe to the inlet side of the casing is provided at the axial center of the exhaust purification catalyst. The inlet pipe is extended to a position facing the inlet side end face of the exhaust purification catalyst with a required interval, and a large number of air diffusion holes are opened in the part that enters the casing. An exhaust purification device having a front end closed with a lid , and a dispersion plate that partitions the inside of the casing at the front end position of the inlet pipe and opens a large number of air diffusion holes to diffuse exhaust gas. co when the body, the decreased gradually allowed and diverging pores toward the downstream side hole number of diffusing pores from the upstream side of the inlet pipe is formed in a triangular shape that tapers toward a region which is open to the downstream side The non-hole region extending in the axial direction of the inlet pipe without opening the air diffusion holes is formed in a triangular shape that becomes wider toward the downstream side, and is secured at a plurality of locations in the circumferential direction on the downstream side. Exhaust purification device.

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