JP2015113728A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device which is compactified by achieving the arrangement of a sensor while keeping a high detection accuracy without separately retaining a space necessary for installing the sensor such as a temperature sensor.SOLUTION: A casing 4 holding an oxidation catalyst 2 (an exhaust emission control catalyst) is equipped, within a range from an entrance end to a dispersion plate 5, with a temperature sensor 9 (a sensor), and an insertion port is formed in the uppermost stream part at a site which enters the inside of the casing 4, of an inlet pipe 7, so that the sensor of the temperature sensor 9 is arranged through the insertion port in the main flow of an exhaust gas 6 in the inlet pipe.

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 done in the past.

  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. 2, when installing such a particulate filter 1 in the middle of the exhaust pipe 3 together with the oxidation catalyst 2 in the previous stage, the front stage is placed in a 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 diffuser holes 7 a are opened in a portion 8 that enters the casing 4 of the exhaust gas 7. The exhaust gas 6 introduced from the exhaust pipe 3 on the upstream side passes through the diffuser 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 led to the inlet side end of the oxidation catalyst 2.

  Further, the inlet pipe 7 projecting in front of the casing 4 is provided with a temperature sensor 9 for detecting the temperature by inserting a detector 9a into the exhaust gas 6 stably flowing in the inlet pipe 7. The regeneration control of the particulate filter 1 is executed based on the temperature detected by the temperature sensor 9.

  On the other hand, FIG. 3 shows another arrangement example of the temperature sensor 9. In the case of the example shown here, the temperature sensor is disposed between the dispersion plate 5 in the casing 4 and the inlet side end of the oxidation catalyst 2. 9 and a detector 9a is inserted into the exhaust gas 6 stabilized after passing through the dispersion plate 5, and temperature detection is performed.

  In short, in the range from the inlet side end to the dispersion plate 5 in the casing 4, the exhaust gas 6 flowing in the inlet pipe 7 hits the dispersion plate 5 and blows out from the air diffuser holes 5 a, and the flow of the exhaust gas 6 is disturbed. Since it is in a diffusion state and it is difficult to detect the temperature with high accuracy, the actual situation is that the temperature sensor 9 is arranged to avoid this range.

  In addition, as prior art document information regarding the arrangement of the temperature sensor in this type of exhaust purification apparatus, there is the following Patent Document 1 by the same applicant as the present invention.

JP 2004-225657 A

  However, in the arrangement of the temperature sensor 9 as shown in FIG. 2, the sensor boss 10 for inserting and supporting the temperature sensor 9 needs to be welded all around, and the arrangement space and welding cost of the sensor boss 10 itself, and its welding are required. A work space that does not hinder the work must be ensured. Also in the arrangement of the temperature sensor 9 as shown in FIG. 3, the sensor boss 10 avoids spot welding (not shown) on the outer periphery of the dispersion plate 5. Of the dispersion plate 5 and the oxidation catalyst 2 so that the arrangement of the temperature sensor 9 that is shifted to the oxidation catalyst 2 side does not prevent the smooth flow of the exhaust gas 6 into the oxidation catalyst 2. Since the space between the side ends had to be wide, there was a problem that such an arrangement of the temperature sensor 9 was one factor that hindered the downsizing of the exhaust purification device.

  In particular, in recent years, not only the particulate filter 1 that collects particulates in the exhaust gas 6 is provided in the middle of the exhaust pipe 3, but also NOx is selectively removed downstream of the particulate filter 1 even in the presence of oxygen. It has also been proposed that a selective reduction catalyst capable of reacting with ammonia is provided, and urea water is added as a reducing agent between the selective reduction catalyst and the particulate filter 1 to simultaneously reduce particulates and NOx. Therefore, downsizing of the exhaust purification device is an important issue.

  Here, the temperature sensor 9 is described as an example, but in various sensors other than the temperature sensor 9 used for grasping the NOx amount, the particulate amount, etc. in the exhaust gas 6 on the entry side of the oxidation catalyst 2. Of course, the situation is the same.

  The present invention has been made in view of the above-described circumstances, and does not secure a separate space necessary for installation of a sensor such as a temperature sensor, and realizes the arrangement of the sensor while maintaining high detection accuracy, thereby exhaust purifying apparatus. The purpose is to make the system compact.

  In the present invention, an exhaust purification catalyst is held by a casing and installed in the middle of an exhaust pipe, and an inlet pipe for introducing exhaust gas from the exhaust pipe is inserted into the inlet side of the casing, and the inlet pipe is connected to the exhaust pipe. It extends to a position facing the inlet side end of the purification catalyst with a required interval, and opens a large number of air diffusion holes in the part that enters the casing, and the inside of the casing is partitioned at the tip position of the inlet pipe. An exhaust gas purification apparatus comprising a dispersion plate that opens a large number of air diffusion holes and diffuses exhaust gas, and is equipped with a sensor in a range from the inlet side end to the dispersion plate in the casing, and the inlet pipe An insertion port is drilled in a portion that enters the casing, and the detector of the sensor is arranged in the main stream of the exhaust gas in the inlet pipe through the insertion port. It is an feature.

  Thus, in this way, even if the sensor is arranged in the range from the inlet side end of the casing to the dispersion plate where the arrangement of the sensor has been avoided until now, the detector of the sensor is inserted through the insertion port. Since it is arranged in the main flow of exhaust gas in the pipe, it is possible to perform highly accurate detection of exhaust gas with a stable flow, and it is not necessary to separately secure a space necessary for installing the sensor. It will be.

  Further, in the present invention, it is preferable that the insertion port is formed in the most upstream portion in the portion of the inlet pipe that has entered the casing, and in this way, the most upstream portion in the portion of the inlet pipe that has entered the casing. As a result of the detection by the sensor, the detection is performed in a state where the flow rate is large in which most of the exhaust gas has not yet blown out from the air diffuser holes of the inlet pipe, and the detection accuracy for the exhaust gas is further improved.

  According to the exhaust emission control device of the present invention described above, various excellent effects as described below can be obtained.

  (I) According to the invention described in claim 1 of the present invention, it is possible to realize the arrangement of the sensor while maintaining high detection accuracy without separately securing a space necessary for the installation of the sensor. The exhaust emission control device can be greatly reduced in size and can be mounted on a vehicle more than before.

  (II) According to the invention described in claim 2 of the present invention, most of the exhaust gas is still scattered in each of the inlet pipes by performing detection by the sensor at the most upstream part in the portion of the inlet pipe that has entered the casing. The detection can be performed in a state where the flow rate is not blown out from the pores and the exhaust gas can be detected with higher accuracy.

It is sectional drawing which shows an example of the form which implements this invention. It is sectional drawing which shows an example of the conventional exhaust gas purification apparatus. It is sectional drawing which shows the other example of the conventional exhaust gas purification apparatus.

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

  FIG. 1 shows an example of an embodiment of the present invention. In the same manner as described above with reference to FIGS. 2 and 3, the particulate filter 1 is placed together with the preceding oxidation catalyst 2 (exhaust purification catalyst). It is held by the casing 4 and installed in the middle of the exhaust pipe 3. An inlet pipe 7 for introducing the exhaust gas 6 from the exhaust pipe 3 is inserted into the inlet side of the casing 4, and the inlet pipe 7 is connected to the oxidation catalyst 2. A large number of air diffusion holes 7a are opened in a portion 8 that extends into a position facing the inlet side end of the inlet pipe 7 and enters the casing 4, and the inside of the casing 4 is formed at the distal end position of the inlet pipe 7. And an exhaust purification device having a dispersion plate 5 that diffuses exhaust gas 6 by opening a large number of air diffusion holes 7a, and a temperature sensor 9 (sensor) in a range from the inlet side end to the dispersion plate 5 in the casing 4 ) It is equipped with a sensor boss 10 and an insertion port 11 is formed in the most upstream part of the inlet pipe 7 in the portion 8 that has entered the casing 4. Is arranged in the main stream of the exhaust gas 6 in the inlet pipe 7.

  Thus, in this way, even if the temperature sensor 9 is arranged in the range from the inlet side end of the casing 4 to the dispersion plate 5 where the arrangement of the temperature sensor 9 has been avoided so far, the temperature sensor 9 Since the detector 9a is arranged in the main flow of the exhaust gas 6 in the inlet pipe 7 through the insertion port 11, it is possible to detect the exhaust gas 6 with a stable flow with high accuracy, and the temperature. It is not necessary to secure a space necessary for installing the sensor 9 separately.

  In particular, in the present embodiment, as a result of detection by the temperature sensor 9 at the most upstream portion in the portion 8 that has entered the casing 4 of the inlet pipe 7, most of the exhaust gas 6 still has the air diffuser holes of the inlet pipe 7. The detection is performed in a state where the flow rate is not blown out from 7a, and the detection accuracy for the exhaust gas 6 is further increased.

  Therefore, according to the above embodiment, the arrangement of the temperature sensor 9 can be realized while maintaining a high detection accuracy without separately securing a space necessary for the installation of the temperature sensor 9. Significant downsizing can be achieved, and mounting on a vehicle can be improved as compared with the prior art. In particular, in the case of this embodiment, most of the exhaust gas 6 is still in the diffuser holes of the inlet pipe 7 by detecting the temperature sensor 9 at the most upstream part of the portion 8 that has entered the casing 4 of the inlet pipe 7. The detection can be performed in a state where the flow rate is not blown from 7a and the exhaust gas 6 can be detected with higher accuracy.

  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. In addition, the sensor is not necessarily limited to the temperature sensor, and various sensors such as a NOx sensor can be appropriately selected and employed, and various modifications can be made without departing from the scope of the present invention. Of course.

2 Oxidation catalyst (exhaust gas purification catalyst)
3 Exhaust pipe 4 Casing 5 Dispersion plate 5a Air diffuser hole 6 Exhaust gas 7 Inlet pipe 7a Air diffuser hole 8 Portion of the inlet pipe that enters the casing 9 Temperature sensor (sensor)
9a Detector 11 Insertion slot

Claims (2)

  An exhaust purification catalyst is held in the casing and installed in the middle of the exhaust pipe. An inlet pipe for introducing exhaust gas from the exhaust pipe is inserted into the inlet side of the casing, and the inlet pipe is inserted into the exhaust purification catalyst. It extends to a position facing the side end with a required interval, and opens a large number of air diffused holes at the site where it enters the casing, partitions the casing at the tip of the inlet pipe, and a large number of diffused holes. An exhaust emission control device comprising a dispersion plate that opens pores and diffuses exhaust gas, and is equipped with a sensor in a range from the inlet side end to the dispersion plate in the casing, and enters the casing of the inlet pipe. An insertion port is drilled in the slot, and the detector of the sensor is arranged in the main stream of the exhaust gas in the inlet pipe through the insertion port. Exhaust gas purification device.   2. The exhaust emission control device according to claim 1, wherein an insertion port is formed in a most upstream portion of a portion of the inlet pipe that enters the casing.

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