JP6454067B2 - 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, it has a composition containing a small amount of sulfate (mist-like sulfuric acid component). As a measure for reducing this type of particulates, a particulate filter is installed in the middle of the exhaust system passage through which exhaust gas flows. It has been done 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 defining each flow path is discharged to the downstream side.

  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.

  When such a particulate filter is installed in the exhaust system path together with the preceding stage oxidation catalyst, as shown in FIG. And the particulate filter 2 are arranged and accommodated in series, and a disc-like dispersion plate 3 having a large number of air diffusion holes 3a is provided on the outlet side of the particulate filter 2 in the flow of the exhaust gas 4. It is arranged at a right angle to mute the sound.

  Further, the outlet side of the casing 1 has a cone shape that gradually decreases in diameter from the rear side to the downstream side of the dispersion plate 3, and an outlet pipe 5 is connected to the outlet side end of the casing 1. Although the exhaust gas 4 is converged, a temperature sensor 6 for detecting the temperature by inserting a detector 6 a into the exhaust gas 4 stably flowing in the outlet pipe 5 is provided in the outlet pipe 5. The regeneration control of the particulate filter 2 is executed based on the temperature detected by the temperature sensor 6.

  On the other hand, FIG. 4 shows another arrangement example of the temperature sensor 6. In the case of the example shown here, the temperature sensor is provided immediately before the outlet pipe 5 in the cone-shaped portion on the outlet side of the casing 1. 6, a detector 6a is inserted into the flow of the exhaust gas 4 converged by the cone shape on the outlet side of the casing 1, and temperature detection is performed.

  In short, in order to accurately detect the exhaust gas temperature, it is important to induce a certain amount of the exhaust gas 4 to the detector 6a of the temperature sensor 6, and until now, inevitably in the middle of the outlet pipe 5 (see FIG. 3) or just before (see FIG. 4), the actual situation is that the temperature sensor 6 must be arranged.

  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 such a situation where the degree of freedom in layout of the temperature sensor 6 is low, interference between the temperature sensor 6 and surrounding structures is likely to occur, and this is one factor that deteriorates the mountability of the exhaust purification device. There was a problem of becoming.

  In particular, in recent years, not only the particulate filter 2 that collects the particulates in the exhaust gas 4 is provided in the middle of the exhaust system path, but also NOx is selectively removed downstream of the particulate filter 2 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 2 to simultaneously reduce particulates and NOx. Therefore, improvement of the mountability of the exhaust gas purification device is an important issue.

  Here, the temperature sensor 6 is described as an example, but various sensors other than the temperature sensor 6 used for grasping the NOx amount, the particulate amount and the like in the exhaust gas 4 on the outlet side of the particulate filter 2. Of course, the situation is the same.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to improve the mountability of an exhaust emission control device by increasing the degree of freedom in layout of sensors such as a temperature sensor.

The present invention includes an exhaust purification catalyst held by a casing and is provided in the middle of an exhaust system path, and an outlet pipe for extracting exhaust gas from the exhaust system path is connected to the outlet side of the casing. An exhaust purification device comprising a dispersion plate having a large number of air diffusion holes between the outlet side end of the exhaust purification catalyst,
The outlet side of the casing has a cone shape that gradually decreases in diameter toward the downstream side from the rear of the dispersion plate to the outlet pipe,
Equipped with a sensor in the range from the outlet side end to the dispersion plate in the casing, and forming an air inlet larger than the air diffusion holes in the dispersion plate so as to guide the flow of exhaust gas toward the detector of the sensor,
The sensor, in combination with pre Kishirubefuguchi, is characterized in that it has been configured to be placed in selected positions in a cone of the casing.

  Thus, in this way, even if the sensor is arranged by selecting an arbitrary position in the range from the outlet side end to the dispersion plate in the casing, the exhaust gas having the flow rate and flow velocity necessary for accurate detection can be obtained. The gas flow can be directly guided to the sensor detector through the air guide port of the dispersion plate, so that it is not necessary to place the sensor in a limited place such as in the middle or immediately before the outlet pipe. The degree of freedom is significantly increased.

  In the present invention, it is preferable that a guide pipe for guiding the flow of exhaust gas passing through the air guide port to a position just before the sensor detector is provided on the outlet side of the air guide port of the dispersion plate. By doing so, it becomes possible to more reliably guide the flow of exhaust gas at the flow rate / velocity required for accurate detection to the sensor detector by the induction pipe, and to improve the detection accuracy of the sensor detector. This can be further enhanced.

  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, the degree of freedom in sensor layout can be significantly increased, so that the sensor can be placed at an arbitrary position within the range from the outlet end to the dispersion plate in the casing. It is possible to easily avoid the interference between the sensor and the surrounding structure, and the mountability of the exhaust emission control device can be greatly improved as compared with the prior art.

  (II) According to the invention described in claim 2 of the present invention, the flow of exhaust gas having a flow rate and flow velocity necessary for accurate detection can be more reliably guided to the sensor detector by the induction pipe. The detection of the exhaust gas by the detector of the sensor can be performed with higher accuracy.

It is sectional drawing which shows an example of the form which implements this invention. It is sectional drawing which shows another example of a form of 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 for carrying out the present invention. In substantially the same manner as described above with reference to FIGS. 3 and 4, the particulate filter 2 (exhaust gas purification catalyst) is placed together with the preceding oxidation catalyst in a casing. 1 is mounted in the middle of the exhaust system path, and an outlet pipe 5 for extracting exhaust gas 4 from the exhaust system path is connected to the outlet side of the casing 1, and the outlet pipe 5 and the particulate filter 2 are connected. The exhaust gas purification apparatus provided with a dispersion plate having a large number of air diffusion holes 3a between the discharge side end and the temperature sensor 6 is provided in a range from the exit side end to the dispersion plate 3 in the casing 1, and the temperature A large air inlet 8 larger than the air diffusion hole 3a is formed in the dispersion plate 3 so as to guide the flow of the exhaust gas 4 toward the detector 6a of the sensor 6.

  That is, the air inlet 8 is opened at an appropriate position of the dispersion plate 3 so as to face the detector 6 a of the temperature sensor 6 in the axial direction of the particulate filter 2. The flow of the gas 4 is blown directly onto the detector 6a of the temperature sensor 6.

  Thus, in this way, even if an arbitrary position is selected in the range from the outlet side end to the dispersion plate 3 in the casing 1 and the temperature sensor 6 is arranged, the flow rate necessary for accurate detection is obtained. The flow rate of the exhaust gas 4 at a flow rate can be directly guided to the detector 6a of the temperature sensor 6 through the air guide port 8 of the dispersion plate 3, and the temperature sensor 6 can be provided at a limited place such as in the middle or immediately before the outlet pipe 5. Therefore, the degree of freedom in layout of the temperature sensor 6 is remarkably increased.

  Therefore, according to the above embodiment, the degree of freedom in layout of the temperature sensor 6 can be remarkably increased. Therefore, the temperature sensor 6 is arranged at an arbitrary position in the range from the outlet end to the dispersion plate 3 in the casing 1. Thus, the interference between the temperature sensor 6 and the surrounding structure can be easily avoided, and the mountability of the exhaust emission control device can be greatly improved as compared with the prior art.

  FIG. 2 shows another embodiment of the present invention. In the example shown here, the exhaust gas 4 passing through the air guide port 8 is disposed on the outlet side of the air guide port 8 of the dispersion plate 3. A guide pipe 9 for guiding the flow to a position just before the detector 6a of the temperature sensor 6 is provided so as to project the exhaust gas 4 having a flow rate and a flow rate necessary for accurate detection. The flow can be more reliably guided to the detector 6a of the temperature sensor 6 by the induction pipe 9, and the accuracy of detection by the detector 6a of the temperature sensor 6 can be further improved.

  The exhaust purification apparatus of the present invention is not limited to the above-described embodiment. The exhaust purification catalyst housed in the casing in the middle of the exhaust system path is not necessarily a particulate filter (particulate filter itself). The catalyst is not limited to an oxidation catalyst as a carrier), and may be various catalysts such as a NOx storage reduction catalyst, a selective reduction catalyst, a three-way catalyst, and the sensor is not necessarily limited to a temperature sensor. Of course, 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.

1 Casing 2 Particulate filter (exhaust gas purification catalyst)
3 Dispersing plate 3a Aeration hole 4 Exhaust gas 5 Outlet pipe 6 Temperature sensor (sensor)
6a Detector 8 Air guide 9 Guide pipe

Claims (2)

An exhaust purification catalyst is held by a casing and installed in the middle of the exhaust system path, and an outlet pipe for extracting exhaust gas from the exhaust system path is connected to the outlet side of the casing, and the outlet pipe and the exhaust purification catalyst are connected to each other. An exhaust purification device comprising a dispersion plate having a large number of air diffusion holes between the outlet side end,
The outlet side of the casing has a cone shape that gradually decreases in diameter toward the downstream side from the rear of the dispersion plate to the outlet pipe,
Equipped with a sensor in the range from the outlet side end to the dispersion plate in the casing, and forming an air inlet larger than the air diffusion holes in the dispersion plate so as to guide the flow of exhaust gas toward the detector of the sensor,
The sensor before by the combination of the Kishirubefuguchi, exhaust gas purification apparatus characterized by being configured to be disposed selects the position cone of the casing.   2. The exhaust gas purification according to claim 1, wherein a guide pipe for guiding the flow of the exhaust gas passing through the air guide port to a position immediately before the detector of the sensor is provided on the outlet side of the air guide port of the dispersion plate. apparatus.

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