JP2015218680A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device including a casing mounted in the middle of an exhaust system while embracing an exhaust emission control catalyst, and a plurality of sensors installed on at least one of the inlet and outlet sides thereof, for actualizing the mounting of the sensors at optimum positions and thus improving the detecting accuracy.SOLUTION: The exhaust emission control device includes a casing 4 mounted in the middle of the exhaust system while embracing an oxidation catalyst 2 (the exhaust emission control catalyst), and a plurality of sensors 9 installed on at least one of the inlet and outlet sides of the casing 4. A sensor boss 12 is integrated therewith for supporting the sensors 9 fitted therethrough. The sensor boss 12 is commonly used for the sensors 9 to be mounted on the casing 4.

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. 3, 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 preceding 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 sensor 9 for detecting the temperature by inserting a detector 9a into the exhaust gas 6 flowing stably in the inlet pipe 7, Based on the temperature detected by the sensor 9, regeneration control of the particulate filter 1 is executed.

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

  Incidentally, as prior art document information relating to the mounting of sensors in this type of exhaust gas purification apparatus, there is the following Patent Document 1 and the like.

JP 2011-208572 A

  However, in order to appropriately control the exhaust gas purification apparatus in recent years, not only the temperature of the exhaust gas 6 but also various information such as NOx concentration, PM concentration, oxygen concentration, etc. have become necessary. However, it is necessary to weld the cylindrical sensor boss 10 around the circumference in order to insert and support the sensor 9, and the arrangement of the sensor boss 10 itself is required. It is necessary to secure space, welding allowance, working space where all-around welding work is possible.

  For this reason, when the plurality of sensor bosses 10 are attached, the sensor bosses 10 need to be spaced apart from each other by a sufficient distance in the circumferential direction of the inlet pipe 7 or the casing 4, but the circumferential direction of the small-diameter inlet pipe 7 It is difficult to dispose the plurality of sensor bosses 10 at a sufficient distance apart from each other, and as shown in FIG. 5, the plurality of sensor bosses 10 are disposed at a sufficient distance in the circumferential direction of the casing 4. However, the degree of freedom of layout of each sensor 9 is greatly reduced, and the problem of interference with surrounding structures is likely to occur. By setting one sensor 9 to the optimum position, the remaining sensors 9 can be moved from the optimum position. There is a possibility that some sensors 9 may be deteriorated in detection accuracy because they must be attached to the shifted positions.

  In this example, the particulate filter 1 and the preceding oxidation catalyst 2 are held by the casing 4. However, various catalysts such as a NOx occlusion reduction catalyst, a selective reduction catalyst, a three-way catalyst, etc. Needless to say, the same problem also occurs when a plurality of sensors are installed on the entry side or the exit side of the casing holding the handle.

  The present invention has been made in view of the above circumstances, and a plurality of sensors are provided on at least one of an inlet side and an outlet side of a casing that is interposed in the middle of an exhaust system by holding an exhaust purification catalyst. It is an object of the present invention to improve detection accuracy by mounting each sensor at an optimal position.

  The present invention is an exhaust gas purification apparatus that includes an exhaust purification catalyst in the middle of an exhaust system by a casing and is equipped with a plurality of sensors on at least one of the inlet side and the outlet side of the casing, A sensor boss for inserting and supporting the sensors is integrated, and the sensors are attached to the casing in common with the sensor boss.

  Thus, in this case, when mounting a plurality of sensors on at least one of the entry side and the exit side of the casing, it is not necessary to attach each sensor individually via the sensor boss. There is no need to dispose the sensor boss at a sufficient distance in the circumferential direction of the casing.

  That is, by sharing the same sensor boss, it becomes possible to arrange a plurality of sensors close to each other and mount them in a compact manner, thereby greatly improving the degree of freedom of layout of each sensor and making it difficult to cause interference with surrounding structures. Therefore, it is possible to realize the attachment of each sensor to the optimum position.

  Further, in the present invention, at least one of the entry side and the exit side of the casing is provided with a recess portion consisting of two planes that abut at a substantially right angle, and is fitted to the recess portion and welded all around the two planes. It is preferable to employ a sensor boss having an L-shaped cross section.

  In this way, a recess is provided at an optimal position on at least one of the inlet side and the outlet side of the casing, and the sensor boss having an L-shaped cross section is fitted into the recess to completely cover the two planes of the recess. By circumferential welding, it is possible to easily attach the sensor boss and easily realize the attachment of each sensor to the optimum position.

  In addition, when the sensor boss is mounted, the sensor boss and each sensor are accommodated in the recess so that each sensor does not protrude greatly outside the outer shape of the casing. The flexibility of layout is further improved.

  Further, when mounting each sensor via such a depression, the depression is a first plane substantially perpendicular to the axial direction of the casing and a second plane along the axial direction of the casing. It is preferable that each sensor is inserted at a substantially right angle with respect to the second plane.

  In this way, the detection of each sensor is inserted into the main flow of exhaust gas passing through the center of the exhaust purification catalyst, and the detection is performed more than when the detector is inserted from the outer peripheral surface of the conventional casing. The child can be shortened, and a special long sensor need not be manufactured.

  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, a plurality of sensors are provided on at least one of the inlet side and the outlet side of the casing that is interposed in the middle of the exhaust system by holding the exhaust purification catalyst. By using the same sensor boss, multiple sensors can be placed close together and mounted compactly, which greatly improves the layout freedom of each sensor and causes interference with surrounding structures. Therefore, it is possible to improve the detection accuracy by mounting each sensor at an optimal position.

  (II) According to the invention described in claim 2 of the present invention, it is possible to easily realize the attachment of each sensor to the optimum position by using the depressions, and at the time of the attachment, The sensor boss and each sensor can be housed to prevent the sensor from projecting outward from the outer shape of the casing, thereby further avoiding interference with the surrounding structure and further improving the freedom of layout of each sensor. it can.

  (III) According to the invention described in claim 3 of the present invention, when performing detection by inserting the detector of each sensor into the main flow of exhaust gas passing through the center of the exhaust purification catalyst, the outer peripheral surface of the conventional casing The detector can be shortened as compared with the case where the detector is inserted, and the production of a special long sensor can be eliminated, and the cost can be reduced by making it easy to adopt a general-purpose sensor. be able to.

It is sectional drawing which shows an example of the form which implements this invention. It is the perspective view which looked at the hollow part and sensor boss | hub of FIG. 1 from diagonally upward. 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. It is sectional drawing which shows the example of arrangement | positioning of the several conventional sensor boss | hub.

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

  FIG. 1 and FIG. 2 show an example of an embodiment for carrying out the present invention. In the example shown here, the particulate filter 1 is arranged in the preceding stage in substantially the same manner as described above with reference to FIG. 3 and FIG. Is mounted in the middle of the exhaust pipe 3 together with the oxidation catalyst 2 (exhaust gas purification catalyst) and an inlet pipe 7 for introducing the exhaust gas 6 from the exhaust pipe 3 is fitted on the inlet side of the casing 4 In addition, the inlet pipe 7 is extended to a position facing the inlet side end of the oxidation catalyst 2 at a required interval, and a large number of air holes 7a are opened in a portion 8 that enters the casing 4; The exhaust gas purification apparatus includes a dispersion plate 5 that divides the inside of the casing 4 at the front end position of the inlet pipe 7 and opens a large number of air diffusion holes 5 a to diffuse the exhaust gas 6. Minutes from the entry side In the range extending to the plate 5, a hollow portion comprising a plane 11 a (first plane) substantially orthogonal to the axial direction of the casing 4 and a plane 11 b (second plane) extending along the axial direction of the casing 4. 11 is provided, and a sensor boss 12 having an L-shaped cross section is fitted into the recess 11 and welded all around the two planes 11a and 11b, and a plane 11b along the axial direction of the casing 4 is provided. Each of the sensors 9 is inserted at a substantially right angle.

  Here, each sensor 9 is attached to the sensor boss 12 by means such as screwing, and an opening portion on the casing 4 side through which each sensor 9 is passed is covered with the sensor boss 12. Thus, the sensor boss 12 is welded all around so that the airtightness is maintained.

  Thus, when the plurality of sensors 9 are provided on at least one of the entry side and the exit side of the casing 4 (two in the illustrated example), the sensor boss 12 is individually provided for each sensor 9. Therefore, it is not necessary to install the sensor bosses 12 at a sufficient distance in the circumferential direction of the casing 4.

  That is, by sharing the same sensor boss 12, a plurality of sensors 9 can be arranged close to each other and can be compactly attached. This greatly improves the degree of freedom of layout of each sensor 9 and causes a problem of interference with surrounding structures. Since it is difficult to occur, it is possible to realize the attachment of each sensor 9 to the optimum position.

  In addition, a recess 11 is provided at an optimal position on at least one of the entrance side and the exit side of the casing 4, and a sensor boss 12 having an L-shaped cross section is fitted into the recess 11, so that two planes 11 a of the recess 11 are formed. , 11b, the sensor boss 12 can be attached without difficulty, and the attachment of each sensor 9 to the optimum position can be easily realized.

  In addition, when the sensor boss 12 and each sensor 9 are accommodated in the recess 11, the sensors 9 do not overhang outside the outer shape of the casing 4, so that interference with the surrounding structure is more reliably achieved. Thus, the degree of freedom of layout of each sensor 9 is further improved.

  Further, when detecting by inserting the detector 9a of each sensor 9 into the main flow of the exhaust gas 6 passing through the center of the oxidation catalyst 2, the detector 9a is inserted from the outer peripheral surface of the conventional casing 4 (FIG. 4). This makes it possible to shorten the detector 9a more than the reference), and it is not necessary to manufacture a special long sensor 9.

  Therefore, according to the above-described embodiment, when the plurality of sensors 9 are provided on at least one of the entry side and the exit side of the casing 4 that is interposed in the middle of the exhaust system by holding the oxidation catalyst 2, it is the same. By sharing the sensor boss 12, a plurality of sensors 9 can be arranged close to each other and can be compactly mounted. This greatly improves the degree of freedom of layout of each sensor 9 and makes it less likely to cause interference with surrounding structures. Therefore, the detection accuracy can be improved by mounting each sensor 9 at an optimum position.

  In addition, the use of the recess 11 makes it possible to easily realize the attachment of each sensor 9 to the optimum position. In addition, the sensor boss 12 and each sensor 9 are housed in the recess 11 when the casing 4 is attached. Thus, it is possible to prevent the sensors 9 from projecting outward from the outer shape, thereby more reliably avoiding interference with the surrounding structure and further improving the degree of freedom of layout of the sensors 9.

  Further, when detecting by inserting the detector 9a of each sensor 9 into the main flow of the exhaust gas 6 passing through the center of the oxidation catalyst 2, the detector 9a is inserted more than the case where the detector 9a is inserted from the outer peripheral surface of the conventional casing 4. The detector 9a can be shortened, the production of a special long sensor 9 can be eliminated, and the cost can be reduced by facilitating the adoption of the general-purpose sensor 9.

  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, various sensors such as a temperature sensor, NOx sensor, and PM sensor can be appropriately selected and adopted as the sensor, and further, the same applies to a case where a plurality of sensors are provided on the outlet side of the casing. Of course, various modifications can be made without departing from the scope of the present invention.

2 Oxidation catalyst (exhaust gas purification catalyst)
4 Casing 9 Sensor 11 Recess 11a Plane (first plane)
11b plane (second plane)
12 Sensor boss

Claims (3)

  An exhaust gas purification apparatus comprising an exhaust purification catalyst held by a casing in the middle of an exhaust system, and equipped with a plurality of sensors on at least one of an inlet side and an outlet side of the casing, wherein each sensor is An exhaust emission control device, wherein a sensor boss for inserting and supporting is integrated, and the sensors are attached to the casing in common with the sensor boss.   A sensor boss having an L-shaped cross section, which is provided with a recessed portion composed of two planes that strike substantially at right angles on at least one of the entrance side and the exit side of the casing, and can be fitted to the recess and welded all around the two planes. The exhaust emission control device according to claim 1, wherein:   The hollow portion is composed of a first plane substantially orthogonal to the axial direction of the casing and a second plane extending along the axial direction of the casing, and each sensor is fitted at a substantially right angle to the second plane. The exhaust emission control device according to claim 2, wherein the exhaust purification device is inserted.

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