JP2011220238A - Exhaust emission control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control system 1 whose handling workability such as maintenance of an engine 70 or the like can be improved while being capable of improving exhaust emission control performance of the engine 70.SOLUTION: The exhaust emission purifying system 1 includes two gas controlling bodies 2, 3 for purifying exhaust emissions emitted by the engine 70; inside cases 4, 20 incorporating the gas controlling bodies, 2, 3; and outside cases 5, 21 incorporating the inside cases 4, 20. The outside cases 5, 21 are apposed in the moving direction of the exhaust emissions to be coupled together. The inside cases 4, 20 adjacent to each other are formed into a double structure where one inside case is inserted into the other. A loosely fitting gap 23 is made between an inside surface of the one inside case 4 (20) and an outside surface of the other inside case 20 (4).

Description

  The present invention relates to an exhaust gas purification device mounted on a diesel engine or the like, and more particularly to an exhaust gas purification device that removes particulate matter (soot, particulates) and the like contained in exhaust gas. .

  2. Description of the Related Art Conventionally, there has been known a technology in which a diesel particulate filter (hereinafter referred to as DPF) is provided as an exhaust gas purification device in an exhaust path of a diesel engine (hereinafter referred to as engine), and exhaust gas from the engine is purified by DPF. (See, for example, Patent Document 1). In the DPF, a technique in which an inner case is provided in a double structure inside the outer case and an oxidation catalyst or a soot filter is built in the inner case is also known (see, for example, Patent Document 2). In the DPF, a technique is also known in which a case containing an oxidation catalyst and a case containing a soot filter are detachably connected via a bolt-fastened flange (see, for example, Patent Documents 3 and 4).

  In the DPF described in Patent Document 4, the upstream case and the downstream case have the same diameter when connecting the upstream case with a single structure containing an oxidation catalyst and the downstream case with a single structure containing a soot filter. The oxidation catalyst and the soot filter are arranged close to each other by closely fitting the other case to the enlarged diameter portion provided in one case. By adopting such a configuration, the region between the oxidation catalyst and the soot filter in the case is narrowed (the heat dissipation area is narrowed), so that the exhaust gas temperature can be prevented from lowering between the oxidation catalyst and the soot filter. There is an advantage that you can.

JP 2004-263593 A JP 2005-194949 A JP 2009-228516 A JP 2009-91982 A

  However, in the configuration of Patent Document 4, a single-structure upstream case containing an oxidation catalyst and a single-structure downstream case containing a soot filter are connected to each other, and a diameter-enlarged portion provided in one case is connected. Since the other case is tightly fitted to each other, the two cases (tightly fitted portions) may be integrated due to rust and the like and may not be easily separated. Further, since the outer surface of each case becomes hot due to the passage of exhaust gas, there is a problem that it is difficult to improve handling workability because it is necessary to perform maintenance work and the like of the DPF while each case is sufficiently cooled. .

  Therefore, the present invention has a technical problem to provide an exhaust gas purifying apparatus that has been improved by examining the above problems.

  The invention of claim 1 includes two gas purifying bodies for purifying exhaust gas discharged from the engine, an inner case in which the gas purifying bodies are incorporated, and an outer case in which the inner cases are incorporated, Each of the outer cases is an exhaust gas purifying device connected side by side in the exhaust gas movement direction, and the inner cases adjacent to each other have a double structure in which one is inserted into the other. A loose fitting gap is provided between the inner side surface and the outer side surface of the other inner case.

  According to a second aspect of the present invention, in the exhaust gas purifying apparatus according to the first aspect, the outer surface of the inner case is provided with a joint flange protruding outward in the radial direction, and is formed on the joint flange. One end portion of the outer case in the exhaust gas movement direction is fixed to the stepped portion, and the adjacent joining flanges are overlapped and detachably connected.

  According to a third aspect of the present invention, in the exhaust gas purifying apparatus according to the second aspect, due to the presence of the joining flange, the inner case is supported without being in direct contact with the outer case.

  According to a fourth aspect of the present invention, in the exhaust gas purifying apparatus according to any one of the first to third aspects, a sensor boss body for supporting an exhaust gas sensor is provided on one outer surface of the adjacent inner cases. The sensor boss body protrudes radially outward from a boss body through hole formed in the outer case, and the outer surface of the one inner case surrounds the sensor boss body and the boss body through hole The collar that closes the door is fixed.

  According to a fifth aspect of the present invention, in the exhaust gas purifying apparatus according to the fourth aspect, a pipe of a differential pressure sensor as the exhaust gas sensor is connected to the sensor boss body, and the pipe is disposed along the outer surface of the outer case. It is to let you.

  According to the first aspect of the present invention, there are provided two gas purifying bodies for purifying exhaust gas discharged from the engine, an inner case in which the gas purifying bodies are incorporated, and an outer case in which the inner cases are incorporated. The exhaust gas purifying apparatus in which the outer cases are connected side by side in the exhaust gas movement direction, and the inner cases adjacent to each other have a double structure in which one of the inner cases is inserted into the other. Since there is a loose clearance gap between the inner side surface of the first inner case and the outer side surface of the second inner case, the second inner case is separated from the first inner case, so that A certain gas purification body can be largely exposed to the outside. For this reason, there exists an effect that the workability | operativity of the maintenance operation | work (separation of each said gas purification body etc.) performed by isolate | separating each said outer case can be improved. Further, the inner cases can be easily attached and detached by the existence of the loose fitting gap between the inner cases. That is, for example, in the conventional configuration in which the inner cases are closely fitted to prevent leakage of exhaust gas, the inner cases are integrated with each other due to rust and cannot be easily separated. Compared to this, the invention of claim 1 makes it extremely easy to separate the two inner cases, and in this respect as well, there is an advantage that the maintainability and the exchange workability of each gas purifier can be improved.

  According to a second aspect of the present invention, in the exhaust gas purifying apparatus according to the first aspect, the outer surface of the inner case is provided with a joint flange protruding outward in the radial direction, and is formed on the joint flange. One end portion of the outer case in the exhaust gas movement direction is fixed to the stepped portion, and the adjacent joining flanges are overlapped and detachably connected to each other. The case can be easily positioned with respect to the joint flange. Further, when the outer case and the joining flange are fixed, it is possible to prevent the outer peripheral side of the joining flange from interfering with a fixing jig such as a welding torch and a welding rod. Can be improved.

  According to a third aspect of the present invention, in the exhaust gas purifying apparatus according to the second aspect, the inner case is supported by the outer flange without being in direct contact with the outer flange due to the presence of the joining flange. Mechanical vibration and deformation force applied to the outer case are difficult to reach the inner case, and the inner case itself and the gas purifying body in the inner case itself are damaged or the gas purifying body is displaced. Can be prevented. Moreover, since the said outer case is covered over the outer periphery whole region of the said inner case, a heat insulation layer (heat insulation area | region) can be ensured in the outer periphery whole region of the said inner case. For this reason, the fall of the exhaust gas temperature in the said inner side case can be suppressed reliably. Furthermore, an increase in the surface temperature of the outer case can also be suppressed.

  According to a fourth aspect of the present invention, in the exhaust gas purifying apparatus according to any one of the first to third aspects, a sensor boss body for supporting an exhaust gas sensor is provided on one outer surface of the adjacent inner cases. The sensor boss body projects radially outward from a boss body through hole formed in the outer case, and the outer surface of the one inner case surrounds the sensor boss body and penetrates the boss body. Since the collar which closes the hole is fixed, the presence of the collar can improve the connection strength between the outer case and the inner case. Further, it is possible to easily and reliably prevent the exhaust gas in the inner case from leaking from the boss body through hole.

  Moreover, compared with the conventional structure in which the inner case is provided with an enlarged diameter portion in order to closely fit both inner cases, there is no influence on the pipe allowance of the inner case, the radius of the sensor boss body, the welding allowance, etc. The distance between the end face of the gas purifier and the mounting position of the exhaust gas sensor can be set to the shortest dimension (zero or arbitrary dimension). As a result, the overall length of the exhaust gas purification device can be shortened, and the exhaust gas purification device can be easily mounted on various devices. Since the exhaust gas sensor can be brought close to the end face of the gas purification body, it can contribute to improvement of control performance such as automatic regeneration of the exhaust gas purification device.

  According to the invention of claim 5, in the exhaust gas purifying apparatus according to claim 4, a pipe of a differential pressure sensor as the exhaust gas sensor is connected to the sensor boss body, and the pipe is connected to an outer surface of the outer case. Therefore, the pipe is close to the outer surface of the outer case. For this reason, for example, when the exhaust gas purification device is assembled to the engine, the piping is unlikely to become an obstacle, and the exhaust gas purification device is easy to handle and mount. Therefore, it is easy to mount and assemble the exhaust gas purification device.

It is a section explanatory view of DPF. It is an external appearance perspective view of DPF. It is an external appearance top view of DPF. It is an external appearance bottom view of DPF. It is an external appearance front view of DPF. It is an external appearance side view of DPF. It is a cross-sectional side view of the upstream of DPF. It is a cross-sectional side view of the downstream of DPF. It is decomposition | disassembly cross-section explanatory drawing of DPF. It is a separation side view of a clamping flange (semi-arc body). (A) is an expanded side sectional view of a catalyst side joining flange, (b) is an enlarged side sectional view showing a welding mode. It is sectional drawing which shows the attachment part of the sensor boss body with respect to a gas temperature sensor. It is a top view of the diesel engine which provided DPF. It is sectional drawing which shows the attachment part of the sensor boss body with respect to a differential pressure sensor. It is an expanded sectional view which shows the attachment part of the sensor boss body with respect to a gas temperature sensor. It is sectional explanatory drawing of the DPF modification which is a structure which does not insert adjacent inner cases. It is sectional explanatory drawing of the DPF modification which is a structure which abbreviate | omitted the heat shielding case.

  Hereinafter, an exhaust gas purification apparatus embodying the present invention will be described with reference to the drawings. In the following description, the exhaust gas inlet 12 side of the diesel particulate filter 1 is the left side, and the silencer 30 side is the right side. Such terms indicating specific directions and positions are used for convenience of explanation, and do not limit the technical scope of the present invention.

(1). Schematic structure of DPF First, the schematic structure of the exhaust gas purification device will be described. As shown in FIGS. 1, 6 and 13, a continuous regeneration type diesel particulate filter 1 (hereinafter referred to as DPF 1) as an exhaust gas purification device is provided. The DPF 1 reduces carbon monoxide (CO) and hydrocarbons (HC) in the exhaust gas of the diesel engine 70 in addition to removing particulate matter (PM) in the exhaust gas discharged from the diesel engine 70. It is composed. The DPF 1 is for collecting particulate matter (PM) and the like in the exhaust gas. The DPF 1 is configured in a substantially cylindrical shape extending long in the left-right direction intersecting the output shaft (crankshaft) of the diesel engine 70 in plan view. The DPF 1 is disposed on the flywheel housing 78 of the diesel engine 70. An exhaust gas inlet pipe 16 (exhaust gas intake side) and an exhaust gas outlet pipe 34 (exhaust gas discharge side) are provided on the left and right sides (one end side and the other end side in the exhaust gas movement direction) of the DPF 1. They are distributed to the left and right. The exhaust gas inlet pipe 16 on the exhaust gas intake side of the DPF 1 is bolted to the exhaust manifold 71 of the diesel engine 70 so as to be detachable. An exhaust pipe 48 is connected to the exhaust gas outlet pipe 34 on the exhaust gas discharge side of the DPF 1.

  As shown in FIGS. 1 to 6, the DPF 1 is composed of a diesel oxidation catalyst 2 such as platinum and a soot filter 3 having a honeycomb structure through a cylindrical inner case 4 and 20 on a DPF casing 60 made of a heat-resistant metal material. It is structured to be accommodated in series. The DPF 1 is attached to the flywheel housing 78 via a flange side bracket leg 61 and a casing side bracket leg 62 as a support. In this case, one end of the flange side bracket leg 61 is detachably bolted to the outer peripheral side of the DPF casing 60 via a joint flange 26 (details will be described later). One end side of the casing side bracket leg 62 is integrally fixed to the outer peripheral surface of the DPF casing 60 by welding.

  On the other hand, as shown in FIGS. 1 to 6 and FIG. 13, the other end side of the flange side bracket leg 61 is detachably fastened to the upper surface (DPF attachment portion) of the flywheel housing 78 with two retrofitting bolts 88. The The other end side of the casing side bracket leg 62 is detachably fastened to the upper surface (DPF attachment portion) of the flywheel housing 78 with a front bolt 87 and a rear bolt 88. On the other end side of the casing side bracket leg 62, a notch hole 89 for engaging the attaching bolt 87 is formed.

  That is, when the DPF 1 is assembled to the diesel engine 70, first, the leading bolt 87 is incompletely screwed onto the upper surface of the flywheel housing 78. Then, the operator lifts the DPF 1 with both hands, and the casing-side bracket leg 62 is locked to the leading bolt 87 through the notch hole 89 to temporarily fix the DPF 1 to the diesel engine 70. In this state, the operator can release both hands from the DPF 1. Thereafter, the inlet flange body 17 is fastened to the exhaust manifold 71, and the exhaust gas inlet pipe 16 is fixed to the exhaust manifold 71.

  On the other hand, the flange side bracket leg 61 and the casing side bracket leg 62 are fastened to the upper surface of the flywheel housing 78 by three retrofitting bolts 88. Further, the front bolt 87 is also completely fastened, and the DPF 1 is detachably fixed to the upper surface of the flywheel housing 78. The DPF 1 can be removed in the reverse procedure. As a result, the DPF 1 is stably connected and supported to the rear part of the diesel engine 70 by the bracket legs 61 and 62 and the exhaust manifold 71 at the upper part of the flywheel housing 78 that is a highly rigid member. Moreover, the attachment or detachment operation | work of DPF1 to the diesel engine 70 can be performed by one operator.

  In the above configuration, the exhaust gas of the diesel engine 70 flows from the exhaust manifold 71 of the diesel engine 70 to the diesel oxidation catalyst 2 side in the DPF casing 60 and moves from the diesel oxidation catalyst 2 to the soot filter 3 side for purification. It is processed. Particulate matter in the exhaust gas cannot pass through the porous partition walls between the cells in the soot filter 3. That is, the particulate matter in the exhaust gas is collected by the soot filter 3. Thereafter, exhaust gas that has passed through the diesel oxidation catalyst 2 and the soot filter 3 is discharged to the exhaust pipe 48.

When the exhaust gas passes through the diesel oxidation catalyst 2 and the soot filter 3, if the temperature of the exhaust gas exceeds a renewable temperature (for example, about 300 ° C.), NO (nitrogen monoxide) is oxidized to unstable NO ₂ (nitrogen dioxide). The particulate matter collected by the soot filter 3 is oxidized and removed by O (oxygen) released when NO ₂ returns to NO. In addition, when particulate matter accumulates on the soot filter 3, the particulate matter is oxidized and removed by maintaining the temperature of the exhaust gas at a temperature higher than the regenerative temperature. Is recovered (the soot filter 3 is regenerated).

(2). Assembly Structure of Diesel Oxidation Catalyst With reference to FIGS. 1 and 9, a structure for assembling a diesel oxidation catalyst 2 that is an example of an exhaust gas purifier (filter) that purifies exhaust gas discharged from the diesel engine 70 will be described. . The diesel oxidation catalyst 2 is provided in a substantially cylindrical catalyst inner case 4 made of a heat-resistant metal material. The catalyst inner case 4 is formed in a substantially cylindrical catalyst outer case 5 made of a heat-resistant metal material. That is, the catalyst inner case 4 is fitted on the outside of the diesel oxidation catalyst 2 via the ceramic heat insulating material 6 made of ceramic fiber. The diesel oxidation catalyst 2 is protected by press-fitting the catalyst heat insulating material 6 between the diesel oxidation catalyst 2 and the catalyst inner case 4.

  The catalyst outer case 5 is fitted on the outside of the catalyst inner case 4 via a thin plate support 7 having an L-shaped cross section. The catalyst outer case 5 is one of the elements that constitute the DPF casing 60 described above. Note that the diesel oxidation catalyst 2 is protected by the catalyst heat insulating material 6. The stress (mechanical vibration, deformation force) of the catalyst outer case 5 transmitted to the catalyst inner case 4 is reduced by the thin plate support 7.

  As shown in FIGS. 1 and 9, a disk-like side lid 8 is fixed to one end of the catalyst inner case 4 and the catalyst outer case 5 by welding. An outer lid body 9 is fastened to the outer surface side of the side lid body 8 with bolts and nuts. The gas inflow side end face 2a of the diesel oxidation catalyst 2 and the side lid 8 are separated by a certain distance L1 (gas inflow space 11). An exhaust gas inflow space 11 is formed between the gas inflow side end surface 2 a of the diesel oxidation catalyst 2 and the side lid 8. An exhaust gas inlet 12 facing the exhaust gas inflow space 11 is opened in the catalyst inner case 4 and the catalyst outer case 5. A closing ring body 15 is fixed between the opening edge of the catalyst inner case 4 and the opening edge of the catalyst outer case 5 in a sandwiched manner. Since the clearance between the opening edge of the catalyst inner case 4 and the opening edge of the catalyst outer case 5 is closed by the closing ring body 15, the exhaust gas flows between the catalyst inner case 4 and the catalyst outer case 5. Can be prevented.

  As shown in FIGS. 1 to 6 and 9, an exhaust gas inlet pipe 16 is disposed on the outer peripheral surface of the catalyst outer case 5 in which the exhaust gas inlet 12 is formed. An inlet flange body 17 is welded and fixed to one open end of the exhaust gas inlet pipe 16. The inlet flange body 17 is detachably bolted to the exhaust manifold 71 of the diesel engine 70. One end of the exhaust gas inlet pipe 16 communicates with the exhaust manifold 71. The other open end of the exhaust gas inlet pipe 16 is welded to the outer peripheral surface of the catalyst outer case 5 so as to cover the exhaust gas inlet 12 from the outside. A pair of reinforcing bracket bodies 18 are fixed by welding between the outer peripheral surface of the catalyst outer case 5 and the side edges of the inlet flange body 17. The presence of both the reinforcing bracket bodies 18 ensures the connection strength between the exhaust manifold 71 and the exhaust gas inlet pipe 16.

With the above configuration, the exhaust gas of the diesel engine 70 flows into the exhaust gas inlet pipe 16 from the exhaust manifold 71 and enters the exhaust gas inflow space 11 from the exhaust gas inlet pipe 16 through the exhaust gas inlet 12. Then, the exhaust gas that has reached the exhaust gas inflow space 11 is supplied to the diesel oxidation catalyst 2 from the left gas inflow side end surface 2a. Nitrogen dioxide (NO ₂ ) is generated by the oxidation action of the diesel oxidation catalyst 2.

(3). Assembling Structure of Soot Filter A structure for assembling a soot filter 3 as an example of an exhaust gas purifying body (filter) that purifies exhaust gas discharged from the diesel engine 70 will be described with reference to FIGS. 1 and 9. The soot filter 3 is provided in a substantially cylindrical filter inner case 20 made of a heat-resistant metal material. The filter inner case 20 is provided in a substantially cylindrical filter outer case 21 made of a heat-resistant metal material. That is, the filter inner case 20 is fitted on the outside of the soot filter 3 through the mat-shaped filter heat insulating material 22 made of ceramic fiber. The filter outer case 21 is one of the elements constituting the DPF casing 60 described above together with the catalyst outer case 5. The soot filter 3 is protected by press-fitting a filter heat insulating material 22 between the soot filter 3 and the filter inner case 20.

  As shown in FIGS. 1 and 9, the catalyst inner case 4 formed in a cylindrical shape with a straight ridge line is a downstream side into which an upstream side cylinder portion 4 a for accommodating the diesel oxidation catalyst 2 and a filter inner case 20 described later are inserted. It is comprised by the side cylinder part 4b. In addition, the upstream side cylinder part 4a and the downstream side cylinder part 4b are cylinders of substantially the same diameter and are integrally formed. The catalyst inner case 4 and the filter inner case 20 are formed in a cylindrical shape having substantially the same diameter. That is, the catalyst inner case 4 and the filter inner case 20 have a cylindrical shape with a straight ridge line and the diameters at both ends are equal.

  On the outer peripheral surface of the downstream cylindrical portion 4b in the catalyst inner case 4, a heat shield case 190 extending to the exhaust downstream side is provided. The heat shielding case 190 is one of the elements constituting the catalyst inner case 4. The upstream side of the heat shield case 190 is formed in a cylindrical shape having a smaller diameter than the downstream side. The upstream end 190a of the heat shield case 190 is fitted and fixed to the outer peripheral surface of the downstream cylindrical portion 4b of the catalyst inner case 4 by welding. In this case, the upstream end 190a of the heat shield case 190 is located on the exhaust upstream side of the exhaust downstream end surface of the catalyst inner case 4 (open end surface corresponding to the gas outflow side end surface 2b of the diesel oxidation catalyst 2). Yes. Therefore, an upstream gap 23 a is formed between the outer peripheral surface of the downstream cylindrical portion 4 b in the catalyst inner case 4 and the inner surface of the heat shield case 190.

  The outer diameter of the diesel oxidation catalyst 2 and the outer diameter of the soot filter 3 are formed to be equal. The thickness of the catalyst heat insulating material 6 and the thickness of the filter heat insulating material 22 are also similar. The catalyst inner case 4 and the filter inner case 20 are formed of a material having the same plate thickness. The exhaust upstream side (exhaust gas intake side) of the filter inner case 20 is inserted into the heat shield case 190. That is, the adjacent catalyst inner case 4 and filter inner case 20 have a double structure in which the filter inner case 20 is inserted into the catalyst inner case 4. The double structure may be one in which the catalyst inner case 4 is inserted into the filter inner case 20. In this case, the heat shield case 190 is provided on the filter inner case 20 side so as to extend toward the exhaust upstream side.

  In the embodiment, the outer diameter of the filter inner case is made smaller than the inner diameter of the heat shielding case 190 on the exhaust downstream side. For this reason, in the state where the exhaust upstream side of the filter inner case 20 is inserted into the heat shield case 190, the downstream gap 23 as a loose fitting gap is provided between the inner surface of the heat shield case 190 and the filter inner case 20. Is formed. The clearance gap of the downstream gap 23 is formed to have a dimension (for example, 2 mm) larger than the plate thickness (for example, 1.5 mm) of each inner case 4, 20. For example, even if each inner case 4, 20 is rusted or thermally deformed, the exhaust upstream side of the filter inner case 20 can be easily put in and out of the heat shield case 190.

  Further, a thin plate-shaped ring-shaped catalyst side joint flange 25 that is welded and fixed to the outer periphery of the catalyst inner case 4 (in the embodiment, the heat shielding case 190), and a thin ring-shaped ring-shaped filter side that is welded and fixed to the outer periphery of the filter inner case 20 And a joining flange 26. The catalyst side joining flange 25 and the filter side joining flange 26 are formed in a donut shape having a substantially L-shaped cross section. The inner peripheral side of the catalyst side joining flange 25 is welded and fixed to the exhaust downstream side of the outer periphery of the heat shield case 190. The outer peripheral side of the catalyst side joining flange 25 is projected (protruded) toward the outer peripheral side (radial direction, radially outer side) of the catalyst outer case 5. A stepped step portion 25 a is formed at the bent corner portion of the catalyst side joining flange 25. An end portion on the exhaust gas downstream side of the catalyst outer case 5 is fixed to the step portion 25a by welding. The inner peripheral side of the filter-side joining flange 26 is welded and fixed to a longitudinally middle part (middle part in the exhaust gas movement direction) of the outer periphery of the filter inner case 20. The outer peripheral side of the filter side joining flange 26 is projected (protruded) toward the outer peripheral side (radial direction, radially outer side) of the filter outer case 21. A stepped step portion 26 a is formed at the bent corner portion of the filter side joining flange 26. The exhaust upstream end of the filter outer case 21 is fixed to the step 26a by welding.

  As shown in FIGS. 1 to 5, 9, and 12, the catalyst-side joining flange 25 and the filter-side joining flange 26 are abutted with each other through the gasket 24. The joint flanges 25 and 26 are sandwiched from both sides in the exhaust gas movement direction by a pair of thick plate-like central clamping flanges 51 and 52 surrounding the outer peripheral sides of the outer cases 5 and 21. The catalyst outer case 5 and the filter outer case 21 are detachably connected by fastening the center holding flanges 51 and 52 with the bolts 27 and nuts 28 and holding the joint flanges 25 and 26.

  As shown in FIGS. 1 and 12, the exhaust upstream end of the filter outer case 21 is connected to the exhaust downstream end of the catalyst outer case 5 via the center clamping flanges 51 and 52 and the joint flanges 25 and 26. In a state where the two are connected, a catalyst downstream space 29 is formed between the diesel oxidation catalyst 2 and the soot filter 3. That is, the gas outflow side end surface 2b of the diesel oxidation catalyst 2 (catalyst inner case 4) and the intake side end surface 3a of the soot filter 3 (filter inner case 20) face each other with a distance L2 for sensor attachment.

  As shown in FIGS. 1 and 9, the cylindrical length L4 of the catalyst outer case 5 in the exhaust gas movement direction is formed longer than the cylindrical length L3 of the upstream cylinder portion 4a in the catalyst inner case 4 in the exhaust gas movement direction. . The cylindrical length L6 of the filter outer case 21 in the exhaust gas movement direction is formed shorter than the cylindrical length L5 of the filter inner case 20 in the exhaust gas movement direction. A length (L2 + L3 + L5) obtained by adding the sensor mounting interval L2 in the catalyst downstream space 29, the cylinder length L3 of the upstream cylinder portion 4a in the catalyst inner case 4, and the cylinder length L5 of the filter inner case 20 is It is configured to be substantially equal to a length (L4 + L6) obtained by adding the cylindrical length L4 of the catalyst outer case 5 and the cylindrical length L6 of the filter outer case 21.

  Further, the exhaust upstream end of the filter inner case 20 protrudes from the exhaust upstream end of the filter outer case 21 by a difference in length between the cases 20 and 21 (L7≈L5−L6). For this reason, in the state where the filter outer case 21 is connected to the catalyst outer case 5, the exhaust downstream side of the catalyst outer case 5 (the catalyst inner case 4 The exhaust upstream end of the filter inner case 20 is inserted into the downstream cylindrical portion 4b). That is, the exhaust upstream side of the filter inner case 20 is inserted into the downstream cylinder portion 4b (catalyst downstream space 29) so as to be removable.

In the above configuration, nitrogen dioxide (NO ₂ ) generated by the oxidation action of the diesel oxidation catalyst 2 is supplied from the intake side end face 3 a into the soot filter 3. Particulate matter (PM) contained in the exhaust gas of the diesel engine 70 is collected by the soot filter 3 and continuously oxidized and removed by nitrogen dioxide (NO ₂ ). In addition to the removal of particulate matter (PM) in the exhaust gas of the diesel engine 70, the content of carbon monoxide (CO) and hydrocarbon (HC) in the exhaust gas of the diesel engine 70 is reduced.

(4). The structure of the silencer 30 Next, the structure of the silencer 30 that attenuates the exhaust gas sound discharged from the diesel engine 70 will be described with reference to FIGS. 1, 8 and 9. As shown in FIG. 1, FIG. 8 and FIG. 9, the silencer 30 includes a substantially cylindrical silencer inner case 31 made of a heat resistant metal material, a substantially cylindrical silencer outer case 32 made of a heat resistant metal material, and a silencer outer case. 32 and a disc-shaped side lid 33 fixed to the side end portion of the downstream side by welding. A silencer inner case 31 is provided in the silencer outer case 32. The muffler outer case 32 and the catalyst outer case 5 and the filter outer case 21 constitute the DPF casing 60 described above. The diameter of the cylindrical silencing outer case 32 is substantially the same as the diameter of the cylindrical catalyst outer case 5 and the diameter of the cylindrical filter outer case 21.

  Disc-shaped inner lid bodies 36 and 37 are fixed to both ends of the muffler inner case 31 in the exhaust gas movement direction by welding. A pair of exhaust gas introduction pipes 38 is provided between the inner lid bodies 36 and 37. The exhaust upstream side end of each exhaust gas introduction pipe 38 penetrates the upstream inner lid 36. An end portion of each exhaust gas introduction pipe 38 on the exhaust downstream side is closed by a downstream inner lid body 37. A plurality of communication holes 39 are formed in the middle of each exhaust gas introduction pipe 38. An expansion chamber 45 is communicated with each exhaust gas introduction pipe 38 through a communication hole 39. The expansion chamber 45 is formed inside the silencer inner case 31 (between the inner lids 36 and 37).

  Exhaust gas outlet pipes 34 arranged between the exhaust gas introduction pipes 38 are passed through the silencer inner case 31 and the silencer outer case 32. One end side of the exhaust gas outlet pipe 34 is closed by an outlet lid 35. A large number of exhaust holes 46 are formed in the entire exhaust gas outlet pipe 34 in the silencer inner case 31. Each exhaust gas introduction pipe 38 communicates with the exhaust gas outlet pipe 34 via a plurality of communication holes 39, an expansion chamber 45, and a number of exhaust holes 46. An exhaust pipe 48 is connected to the other end side of the exhaust gas outlet pipe 34. In the above configuration, the exhaust gas that has entered the both exhaust gas introduction pipes 38 of the silencer inner case 31 passes through the exhaust gas outlet pipe 34 via the plurality of communication holes 39, the expansion chamber 45, and the numerous exhaust holes 46. The exhaust pipe 48 is then discharged out of the silencer 30.

  As shown in FIG. 1 and FIG. 9, the inner diameter side of the filter outlet side joining flange 40 having a thin ring shape is welded and fixed to the exhaust downstream end of the filter inner case 20. The outer diameter side of the filter outlet side joining flange 40 is projected toward the outer peripheral side (radially outer side, radial direction) of the filter outer case 21. A stepped step 40 a is formed at the bent corner of the filter outlet side joining flange 40. An end portion on the exhaust downstream side of the filter outer case 21 is fixed by welding to a step portion 40 a of the filter outlet side joining flange 40. A thin-plate-like silencer-side joining flange 41 protruding from the outer peripheral side (radially outward) of the silencer outer case 32 is welded and fixed to the exhaust upstream end of the silencer inner case 31. Note that the exhaust upstream side of the silencer inner case 31 protrudes by a predetermined cylindrical dimension L10 toward the exhaust upstream side from the silencer side joining flange 41. The exhaust upstream end of the silencer outer case 32 is welded and fixed to the exhaust downstream side of the silencer side joining flange 41 on the outer peripheral surface of the silencer inner case 31.

  As shown in FIG. 1 and FIG. 7 to FIG. 10, a pair of thick plates that butt the filter outlet side joining flange 40 and the muffler side joining flange 41 through the gasket 24 and surround the outer peripheral sides of the outer cases 21 and 32. The outlet flanges 53 and 54 sandwich the joint flanges 40 and 41 from both sides in the exhaust gas movement direction. Then, the filter outer case 21 and the silencer outer case 32 are detachably connected by fastening the outlet clamping flanges 53 and 54 with the bolts 42 and the nuts 43 and clamping the joint flanges 40 and 41. .

  As shown in FIGS. 1 and 9, the cylindrical length L9 of the muffler outer case 32 in the exhaust gas movement direction is formed shorter than the cylinder length L8 of the muffler inner case 31 in the exhaust gas movement direction. The exhaust upstream end of the silencer inner case 31 protrudes from the exhaust upstream end (joining flange 41) of the silencer outer case 32 by a difference in length between the cases 31 and 32 (L10≈L8−L9). ing. In other words, in the state where the silencer outer case 32 is connected to the filter outer case 21, the exhaust downstream side end (filter outlet side joint) of the filter outer case 21 is only the dimension L10 where the upstream end of the silencer inner case 31 protrudes. The exhaust upstream end of the silencer inner case 31 is inserted into the filter downstream space 49 formed in the flange 40).

(5). Next, the connection structure of the adjacent outer cases 5, 21, 32 will be described with reference to FIGS. 1 and 7 to 10. FIG. As shown in FIGS. 1 and 7 to 10, the thick plate-like central clamping flange 51 (52) is divided into a plurality (two in the embodiment) in the circumferential direction of the catalyst outer case 5 (filter outer case 21). The semicircular arc bodies 51a and 51b (52a and 52b) are used. Each semi-arc body 51a, 51b (52a, 52b) is formed in an arc shape (substantially semicircular horseshoe shape). In a state where the filter outer case 21 is connected to the catalyst outer case 5, the ends of the semicircular arc bodies 51a and 51b (52a and 52b) abut each other along the circumferential direction (contact). That is, the outer peripheral side of the catalyst outer case 5 (filter outer case 21) is annularly surrounded by the semicircular arcs 51a and 51b (52a and 52b).

  The center clamping flange 51 (52) is provided with a plurality of bolt fastening portions 55 with through holes at equal intervals along the circumferential direction. In the embodiment, eight bolt fastening portions 55 are provided on one set of central clamping flanges 51. When viewed in units of the semicircular arc bodies 51a and 51b (52a and 52b), the bolt fastening portions 55 are provided at four locations at equal intervals along the circumferential direction. On the other hand, bolt holes 56 corresponding to the respective bolt fastening portions 55 of the center clamping flange 51 (52) are formed through the catalyst side joining flange 25 and the filter side joining flange 26.

  When connecting the catalyst outer case 5 and the filter outer case 21, the outer peripheral side of the catalyst outer case 5 is surrounded by the catalyst-side semicircular arcs 51 a and 51 b, and the outer peripheral side of the filter outer case 21 is both on the filter side. The catalyst side joining flange 25 and the filter side joining flange 26, which are enclosed by the semicircular arc bodies 52a, 52b and sandwich the gasket 24, are exhausted by the semicircular arc bodies 51a, 51b, 52a, 52b (central clamping flanges 51, 52). Clamp from both sides in the gas movement direction. Next, the bolts 27 are inserted into the bolt fastening portions 55 of the center clamping flanges 51 and 52 on both sides and the bolt holes 56 of the joint flanges 25 and 26 and tightened with the nuts 28. As a result, the joint flanges 25 and 26 are sandwiched and fixed by the center sandwiching flanges 51 and 52, and the connection between the catalyst outer case 5 and the filter outer case 21 is completed. Here, the abutting portions of the end portions of the catalyst-side semicircular arc bodies 51a and 51b and the filter-side semicircular arc bodies 52a and 52b are configured to be positioned with a phase shift of 72 ° from each other.

  As shown in FIGS. 1 and 7 to 10, the thick plate-shaped outlet pinching flange 53 (54) is divided into a plurality (two in the embodiment) in the circumferential direction of the filter outer case 21 (silencer outer case 32). The semicircular arc bodies 53a and 53b (54a and 54b) are used. The semicircular arc bodies 53a, 53b (54a, 54b) of the embodiment have basically the same form as the semicircular arc bodies 51a, 51b (52a, 52b) of the center clamping flange 51 (52). The outlet clamping flange 53 (54) is also provided with a plurality of bolt fastening portions 57 with through holes at equal intervals along the circumferential direction. On the other hand, bolt holes 58 corresponding to the respective bolt fastening portions 57 of the outlet clamping flange 53 (54) are formed through the filter outlet side joining flange 40 and the silencer side joining flange 41.

  When connecting the filter outer case 21 and the silencer outer case 32, the outer periphery side of the filter outer case 21 is surrounded by both semicircular arcs 53 a and 53 b on the filter outlet side, and the outer periphery side of the silencer outer case 32 is the silencer side. The filter outlet side joining flange 40 and the silencer side joining flange 41, which are enclosed by both the semicircular arc bodies 54a and 54b and sandwich the gasket 24, are formed into a group of semicircular arc bodies 53a, 53b, 54a and 54b (exit clamping flanges 53 and 54). And hold it from both sides in the exhaust gas movement direction. Next, the bolts 42 are inserted into the bolt fastening portions 57 of the outlet clamping flanges 53 and 54 on both sides and the bolt holes 58 of the joint flanges 40 and 41 and tightened with the nuts 43. As a result, both the joining flanges 40 and 41 are sandwiched and fixed by the both outlet sandwiching flanges 53 and 54, and the connection between the filter outer case 21 and the muffler outer case 32 is completed. Here, the abutting portions of the end portions of the semicircular arc bodies 53a and 53b on the filter outlet side and the semicircular arc bodies 54a and 54b on the silencing side are configured to be positioned with a phase shift of 72 °.

  As shown in FIGS. 1 and 7 to 10, a flange side bracket as a support for supporting a DPF casing 60 (outer cases 5, 21, 32) on a diesel engine 70 on at least one of the sandwiching flanges 51 to 54. A leg 61 is attached. In the embodiment, a support fastening portion 59 with a through hole is integrally formed at two locations located between adjacent bolt fastening portions 57 in one semicircular arc member 53a of the outlet holding flange 53 on the filter outlet side. ing. On the other hand, an attachment boss portion 86 corresponding to the support body fastening portion 59 is integrally formed on the flange side bracket leg 61.

  In the above configuration, the mounting boss portion 86 of the flange side bracket leg 61 is bolted to the support fastening portion 59 of one semicircular arc member 53a on the filter outlet side, whereby the outlet clamping flange 53 on the filter outlet side is secured. The flange side bracket leg 61 is detachably fixed. One end side of the casing side bracket leg 62 is welded and fixed to the outer peripheral side of the DPF casing 60 (catalyst outer case 5), and the other end side of both bracket legs 61 and 62 is bolted to the upper surface (DPF attachment portion) of the flywheel housing 78. This is as described above.

  As shown in FIGS. 1 and 7 to 10, two gas purification bodies 2 and 3 (diesel oxidation catalyst 2 and soot filter 3) for purifying exhaust gas discharged from the engine 70, and each gas purification body 2 and 3 are provided. Each of the inner cases 4, 20, 31 is built in, and the outer cases 5, 21, 32 in which the inner cases 4, 20, 31 are built. The inner cases 4, 20, 31 are connected to the outer cases 5, 21, 32 via joint flanges 25, 26, 40, 41 that protrude from the outer peripheral side of the outer cases 5, 21, 32. A plurality of combinations of the gas purifiers 2 and 3, the inner cases 4, 20, 31 and the outer cases 5, 21, 32 are provided, and the joining flanges 25, 26 (40, 41) are paired with a pair of sandwiching flanges 51, 52. The plurality of outer cases 5, 21, 32 are connected by being clamped and fixed at (53, 54).

  If comprised in this way, the adjacent joining flanges 25 and 26 (40, 41) can be pinched from both sides by each clamping flange 51, 52 (53, 54), and can be press-contacted (contact | adhered). In addition, since the sandwiching flanges 51 to 54 are configured separately without being welded to the outer cases 5, 21, 32, the stress caused by welding in the relationship between the sandwiching flanges 51 to 54 and the outer cases 5, 21, 32. There is no risk of concentration or distortion problems. Therefore, a substantially uniform pressure contact force can be applied to the entire joining flanges 25 and 26 (40, 41), and the surface pressure of the sealing surfaces (clamping surfaces) of the clamping flanges 51 to 54 can be maintained at a high level. As a result, it is possible to reliably prevent exhaust gas leakage from between the joint flanges 25 and 26 (40 and 41).

  As shown in FIG. 1 and FIGS. 7 to 10, the sandwiching flanges 51 to 54 are formed of horseshoe-shaped semicircular arcs 51 a and 51 b (52 a, 52 b and 53 a) which are divided into a plurality in the circumferential direction of the outer cases 5, 21 and 32. 53b, 54a, 54b), and is configured to surround the outer peripheral side of the outer cases 5, 21, 32 by a plurality of semicircular arc members 51a, 51b (52a, 52b, 53a, 53b, 54a, 54b). Yes. Therefore, although it is the clamping flanges 51-54 comprised by several semi-arc body 51a, 51b (52a, 52b, 53a, 53b, 54a, 54b), it can be set in the same assembly state as an integrated object. For this reason, it is easy to assemble the clamping flanges 51 to 54 as compared with the ring-shaped flange, and the assembling workability can be improved. Moreover, DPF1 with high sealing performance can be comprised, suppressing processing cost and assembly | attachment cost.

(6). Detailed Structure of Joining Flange Next, the detailed structure of each joining flange 25, 26, 40 will be described with reference to FIGS. 11 (a) and 11 (b). Since each of the joining flanges 25, 26, 40 has basically the same structure, the catalyst side joining flange 25 that is welded and fixed to the catalyst inner case 4 and the catalyst outer case 5 will be described as a representative example. As shown in FIGS. 11 (a) and 11 (b), a stepped step portion 25 a is formed at the bent corner portion of the catalyst side joining flange 25. The end portion on the exhaust downstream side of the catalyst outer case 5 is fitted on the step portion 25 a, and the step portion 25 a is welded and fixed to the end portion on the exhaust downstream side of the catalyst outer case 5.

  In this case, the end portion on the exhaust downstream side of the catalyst outer case 5 is abutted against the step portion 25a of the catalyst side joining flange 25, so that the catalyst outer case 5 is made to the catalyst side joining flange 25 by the presence of the step portion 25a. Easy positioning. Further, the welding of the catalyst outer case 5 and the stepped portion 25a is a butt weld, not a fillet weld that is overlapped. Then, the welding torch 192 and the welding rod 193 (see FIG. 11 (b)) are tilted away from the outer peripheral side of the catalyst side joining flange 25 or set up vertically so that the catalyst outer case 5 and the step portion 25a Can be welded close to the butt. Therefore, when the catalyst outer case 5 and the catalyst side joining flange 25 are welded, it is possible to prevent the outer peripheral side of the catalyst side joining flange 25 from interfering with the welding torch 192 and the welding rod 193, and the catalyst outer case 5 and the catalyst side joining flange 25. Welding workability (working workability) can be improved. Even if the length of the catalyst side joining flange 25 in the exhaust gas movement direction is short, the catalyst outer case 5 and the catalyst side joining flange 25 can be welded due to the presence of the stepped portion 25a. In this case, it is possible to reduce the area directly touching the outside air. For this reason, it contributes also to suppressing the fall of the exhaust gas temperature in the catalyst inner case 4 and the filter inner case 20.

  On the other hand, an L-shaped inner diameter side end 25b of the catalyst side joining flange 25 is extended along the exhaust gas movement direction of the catalyst inner case 4 (catalyst outer case 5). In this case, the inner diameter side end portion 25b extends toward the exhaust upstream side. The inner diameter side end 25b is fitted on the exhaust gas downstream end of the catalyst inner case 4, and the inner diameter side end 25b is welded and fixed to the outer peripheral surface of the catalyst inner case 4 (fillet welding). On the other hand, an L-shaped outer diameter side end portion 25c (outer peripheral side) of the catalyst side joining flange 25 is extended from the outer periphery of the catalyst outer case 5 in the radial direction (radially outward). The high rigidity of the catalyst side joining flange 25 is ensured by the stepped shape of the cross section of the catalyst side joining flange 25.

  As can be seen from the above description and FIGS. 1 and 9, the catalyst inner case 4 is supported without being in direct contact with the catalyst outer case 5 by interposing the catalyst side joining flange 25. For this reason, mechanical vibration and deformation force applied to the catalyst outer case 5 from the outside hardly reach the catalyst inner case 4, and the catalyst inner case 4 itself and the diesel oxidation catalyst 2 therein are damaged, or the diesel oxidation catalyst. 2 can be prevented from being displaced. Moreover, since the catalyst outer case 5 is covered over the entire outer periphery of the catalyst inner case 4, a heat insulating layer (heat insulating region) can be secured in the entire outer periphery of the catalyst inner case 4. For this reason, the fall of the exhaust gas temperature in the catalyst inner side case 4 can be suppressed reliably. Furthermore, an increase in the surface temperature of the catalyst outer case 5 can also be suppressed.

  In addition, the clamping flanges 51 and 52 and the joining flanges 25 and 26 are fastened by screwing the nuts 28 into the bolts 27 penetrating the bolt holes 56 of the sandwiching flanges 51 and 52 and the joining flanges 25 and 26. As described above, the outer diameter side end portion 25c of the catalyst side joining flange 25 is sandwiched by the sandwiching flanges 51 and 52.

(7). Gas Temperature Sensor Mounting Structure Next, the upstream gas temperature sensor 109 (downstream gas temperature sensor 112) attached to the DPF 1 will be described with reference to FIG. 1, FIG. 12, and FIG. A sensor boss body 110 for supporting a gas temperature sensor 109 (112), which is an example of an exhaust gas sensor, is provided on the outer peripheral surface of the adjacent inner cases 4 and 20 that are radially outward. In the embodiment, one end side of the cylindrical sensor boss body 110 is fixed by welding to a portion corresponding to the catalyst downstream space 29 in the outer peripheral surface of the catalyst inner case 4 (more specifically, the heat shield case 190). The other end side of the sensor boss body 110 is extended from a boss body through-hole 5a formed in the catalyst outer case 5 in a radial direction (radially outward) toward the outside of the catalyst outer case 5. A sensor mounting bolt 111 is screwed to the other end side of the sensor boss body 110. For example, a thermistor-type upstream gas temperature sensor 109 is passed through the sensor mounting bolt 111, and the upstream gas temperature sensor 109 is supported by the sensor boss body 110 via the sensor mounting bolt 111. A detection portion of the upstream gas temperature sensor 109 is inserted into the catalyst downstream space 29.

  As shown in FIGS. 12 and 15, a collar 194 surrounding the sensor boss body 110 is fixed to the outer peripheral surface of the catalyst inner case 4 (more specifically, the heat shielding case 190). The front end surface of the collar 194 is in close contact with the inner peripheral surface of the catalyst outer case 5, and closes the boss body through hole 5a through which the sensor boss body 110 passes from the inside. For this reason, the presence of the collar 194 can improve the connection strength (rigidity) between the catalyst outer case 5 and the catalyst inner case 4 (more specifically, the heat shield case 190). Further, it is possible to easily and reliably prevent the exhaust gas in the catalyst inner case 4 and the filter inner case 20 from leaking from the boss body through hole 5a.

  In the above configuration, when the exhaust gas is discharged from the gas outflow side end face 2 b of the diesel oxidation catalyst 2, the exhaust gas temperature is detected by the upstream gas temperature sensor 109. In this case, since it becomes possible to position a part of the sensor boss body 110 on the upstream side of the gas outflow side end surface 2b of the diesel oxidation catalyst 2, the gas until the gas oscillating end surface 2b of the diesel oxidation catalyst 2 comes into contact with the gas. The sensor boss body 110 can be disposed on the outer peripheral surface of the catalyst inner case 4 (heat shield case 190) so that the upstream gas temperature sensor 109 approaches the outflow side end surface 2b. Further, by increasing the thickness of each outer case 5, 21, the thickness of each inner case 4, 20 can be reduced, and the diesel oxidation catalyst 2 and the soot filter 3 can be maintained at a temperature higher than the recyclable temperature. However, the weight of the DPF 1 can be reduced. As shown in FIG. 1, for example, a thermistor-type downstream gas temperature sensor 112 is attached to the sensor boss body 110 via a sensor mounting bolt 111, and the temperature of the exhaust gas on the discharge side end face 3 b in the soot filter 3. Is detected by the downstream gas temperature sensor 112. In this case, the sensor boss body 110 passes through the boss body through hole 21 a of the filter outer case 21.

(8). Next, the differential pressure sensor 63 attached to the DPF 1 will be described with reference to FIGS. 13 and 14. The differential pressure sensor 63, which is an example of the exhaust gas sensor, is for detecting the pressure difference of the exhaust gas between the upstream and downstream sides of the DPF 1 with the soot filter 3 interposed therebetween. Based on the pressure difference, the amount of particulate matter deposited on the soot filter 3 is converted, and the clogged state in the DPF 1 can be grasped. That is, based on the pressure difference of the exhaust gas detected by the differential pressure sensor 63, the regeneration control of the soot filter 3 can be automatically executed by operating, for example, an accelerator control means or an intake throttle control means (not shown). It is configured.

  The sensor bracket 66 is bolted to the mute-side outlet clamping flange 54 described above, and the sensor bracket 66 is disposed on the upper surface side of the DPF casing 60. A detection main body 67 of the differential pressure sensor 63 is attached to the sensor bracket 66. An upstream pipe joint body 64 and a downstream pipe joint body 65 are connected to a detection main body 67 of the differential pressure sensor 63 via an upstream sensor pipe 68 and a downstream sensor pipe 69, respectively. Similar to the sensor boss body 110, the sensor boss body 113 is disposed in the DPF casing 60. The upstream side pipe joint body 64 (downstream side pipe joint body 65) is fastened to the sensor boss body 113 by the pipe joint bolt 114.

  As described above, the upstream gap 23 a is formed between the outer peripheral surface of the downstream cylindrical portion 4 b in the catalyst inner case 4 and the inner peripheral surface of the heat shield case 190. One end side of the cylindrical sensor boss body 113 is welded and fixed to the outer peripheral surface of the heat shield case 190 on the upstream side of the exhaust. The other end side of the sensor boss body 113 is extended from the boss body through-hole 5a formed in the catalyst outer case 5 in the radial direction (radially outward) toward the outside of the catalyst outer case 5, and the pipe joint bolt 114 The upstream pipe joint body 64 is fastened to the sensor boss body 113. A detection main body 67 of a differential pressure sensor 63 is connected to the upstream pipe joint body 64 via an upstream sensor pipe 68. A collar 194 surrounding the sensor boss body 113 is also fixed, and closes the boss body through-hole 5a from the inside.

  In this case, as can be seen from FIGS. 13 and 14, one end side of the upstream sensor pipe 68 is connected to the upstream side pipe joint body 64 fastened to the sensor boss body 113 from a direction intersecting the protruding direction of the sensor boss body 113. Yes. The upstream sensor pipe 68 itself extends along the outer peripheral surface of the catalyst outer case 5, and the other end side of the upstream sensor pipe 68 is connected to a detection main body 67 attached to the sensor bracket 66. With this configuration, since the upstream sensor pipe 68 is close to the DPF casing 60, for example, when the DPF 1 is assembled to the diesel engine 70, the upstream sensor pipe 68 is less likely to become an obstacle, and the handling and mounting of the DPF 1 Good sex. Therefore, the DPF 1 can be easily mounted and assembled.

  As shown in FIG. 14, a sensor opening 190b that allows the hollow portion of the sensor boss body 113 to communicate with the upstream gap 23a is formed. When exhaust gas is discharged from the gas outflow side end face 2b of the diesel oxidation catalyst 2 to the catalyst downstream space 29, a part of the exhaust gas in the catalyst downstream space 29 becomes an upstream gap 23a, a sensor opening 190b, a sensor boss. It is configured to move to the detection main body 67 side through the hollow portion of the body 113, the hollow portion of the upstream side pipe joint body 64, and the upstream side sensor pipe 68.

  In the above configuration, when the exhaust gas in the catalyst downstream space 29 moves in the direction of the sensor opening 190b, the particulate matter contained in the exhaust gas is removed from the end portion (corner corner portion) of the catalyst inner case 4 on the exhaust downstream side. ) And the heat shielding case 190. Therefore, the amount of particulate matter deposited on the sensor opening 190b itself (edge portion) can be remarkably reduced as compared with the structure in which the sensor opening 190b is directly opened toward the catalyst downstream space 29. Further, the exhaust gas inflow pressure of the sensor opening 190b can be maintained below a predetermined pressure.

  In particular, compared with the area of the sensor opening 190b, the area of the upstream gap 23a formed over the entire circumference between the catalyst inner case 4 and the heat shield case 190 can be formed larger. Even if particulate matter accumulates in a part of the upstream gap 23a between the sensor 190 and the exhaust gas, exhaust gas is supplied to the sensor opening 190b from the other part (the part where there is no accumulation in the upstream gap). That is, the diesel engine 70 is continuously operated for a long time until the particulate matter is deposited on the entire area of the upstream gap 23a formed over the entire circumference between the catalyst inner case 4 and the heat shielding case 190. Is possible. The maintenance operation time interval for removing the particulate matter deposited in the sensor opening 190b can be set long. While the diesel engine 70 can be continuously operated for a long time, the differential pressure sensor 63 can be maintained in a highly accurate state for a long time.

(9). Summary As is apparent from the above description and FIGS. 1, 9, and 12, the two gas purification bodies 2, 3 that purify the exhaust gas exhausted by the engine 70 and the gas purification bodies 2, 3 are incorporated. An exhaust gas purification apparatus comprising inner cases 4 and 20 and outer cases 5 and 21 incorporating the respective inner cases 4 and 20, wherein the respective outer cases 5 and 21 are connected side by side in the exhaust gas movement direction. The adjacent inner cases 4 and 20 have a double structure in which one is inserted into the other, and the inner side surface of the one inner case 4 (20) and the other inner case 20 (4 ) Is provided between the outer case and the inner case 20 (4) by separating the inner case 20 (4) from the inner case 4 (20). (4) Before being in The gas purifier 3 (2) can be largely exposed to the outside. For this reason, there is an effect that it is possible to improve the workability of maintenance work (cleaning of the gas purification bodies 2 and 3 etc.) performed by separating the outer cases 5 and 21. Further, due to the presence of the loose fitting gap 23 between the inner cases 4 and 20, the inner cases 4 and 20 can be easily attached and detached. That is, for example, in the conventional configuration in which the inner cases are closely fitted to prevent leakage of exhaust gas, the inner cases are integrated with each other due to rust and cannot be easily separated. Compared to this, in the embodiment, the separation of the inner cases 4 and 20 is extremely simple, and in this respect as well, there is an advantage that the maintenance performance and replacement workability of the gas purification bodies 2 and 3 can be improved.

  As apparent from the above description and FIGS. 1 and 9, the outer surfaces of the inner cases 4, 20 are provided with flanges 25, 26 projecting outward in the radial direction. One end of the outer cases 5 and 21 in the direction of moving the exhaust gas is fixed to the step portions 25a and 26a formed on the outer casing 26, and the adjacent joining flanges 25 and 26 are overlapped and detachably connected. Therefore, the outer cases 5 and 21 can be easily positioned with respect to the joint flanges 25 and 26 due to the presence of the step portions 25a and 26a. Further, when the outer cases 5 and 21 are fixed to the joining flanges 25 and 26, it is possible to prevent the outer peripheral side of the joining flanges 25 and 26 from interfering with a fixing jig such as a welding torch and a welding rod. The workability of the cases 5, 21 and the joint flanges 25, 26 can be improved.

  As is apparent from the above description and FIGS. 1 and 9, due to the presence of the joining flanges 25 and 26, the outer case 5 and 21 are supported by the inner case 4 and 02 without being in direct contact with each other. Therefore, mechanical vibration and deformation force applied to the outer cases 5 and 21 from the outside hardly reach the inner cases 4 and 20, and the inner cases 4 and 20 themselves and the gas purifiers 2 and 3 therein Can be prevented from being damaged, and the gas purifying bodies 2 and 3 from being displaced. Further, since the outer cases 5 and 21 are covered over the entire outer periphery of the inner cases 4 and 20, a heat insulating layer (heat insulating region) can be secured in the entire outer periphery of the inner cases 4 and 20. For this reason, the fall of the exhaust gas temperature in the said inner side cases 4 and 20 can be suppressed reliably. Furthermore, the surface temperature rise of the outer cases 5 and 21 can also be suppressed. Such an operational effect can be obtained similarly in the modified examples of the DPF 1 shown in FIGS. Here, the modification of FIG. 16 shows a DPF 1 in which adjacent flanges 25 and 26 (40 and 41) are overlapped and detachably connected without inserting adjacent inner cases 4 and 20 together. In the modification of FIG. 17, the heat shield case 190 is omitted, the inner diameter of the catalyst inner case 4 is set larger than the outer diameter of the filter inner case 20, and the exhaust gas upstream of the filter inner case is disposed downstream of the catalyst inner case 4. The DPF1 having a structure with the side inserted is shown.

  As shown in FIG. 1, FIG. 9, FIG. 12, and FIG. 14, the sensor boss body for supporting the exhaust gas sensors 109, 112, 63 is provided on the outer surface of one of the adjacent inner cases 4, 20 between the adjacent ones. 110, 113 are provided, and the sensor boss bodies 110, 113 project radially outward from boss body through holes 5a, 21a formed in the outer cases 5, 21, and the one inner case 4 , 20 is fixed with a collar 194 that surrounds the sensor boss bodies 110, 113 and closes the boss body through-holes 5a, 21a. The connection strength with the inner cases 4 and 20 can be improved. Further, it is possible to easily and reliably prevent the exhaust gas in the inner cases 4 and 20 from leaking from the boss body through holes 5a and 21a.

  In addition, compared with the conventional structure in which the inner case is provided with an enlarged diameter portion in order to closely fit the inner cases, the pipe expansion allowance of the inner cases 4 and 20, the radius and welding allowance of the sensor boss bodies 110 and 113, etc. The distance between the end surfaces of the gas purifying bodies 2 and 3 and the mounting positions of the exhaust gas sensors 109, 112, and 63 can be set to the shortest dimension (zero or arbitrary dimension). As a result, the total length of the DPF 1 can be shortened, and the DPF 1 can be easily mounted on various devices. Since the exhaust gas sensors 109, 112, and 63 can be brought close to each other until they come into contact with the end surfaces of the gas purification bodies 2 and 3, it is possible to contribute to improvement of control performance such as automatic regeneration of the DPF 1.

  As is clear from the above description and FIGS. 13 and 14, the piping 68 of the differential pressure sensor 63 as the exhaust gas sensor is connected to the sensor boss body 113, and the piping 68 is connected to the outside of the outer cases 5 and 21. Since it is along the side surface, the pipe 68 comes close to the outer surface of the outer cases 5 and 21. For this reason, for example, when the DPF 1 is assembled to the engine 70, the piping 68 is unlikely to be an obstacle, and the DPF 1 is easy to handle and mount. Therefore, the DPF 1 can be easily mounted and assembled.

  In addition, the structure of each part in this invention is not limited to embodiment of illustration, A various change is possible in the range which does not deviate from the meaning of this invention.

1 DPF (diesel particulate filter)
2 Diesel oxidation catalyst (gas purifier)
3 Soot filter (gas purifier)
4 catalyst inner case 5 catalyst outer case 5a, 21a boss body through hole 20 filter inner case 21 filter outer case 25 catalyst side joining flange 63 differential pressure sensor (exhaust gas sensor)
70 Diesel engine 109, 112 Gas temperature sensor (exhaust gas sensor)
110, 113 sensor boss body

Claims (5)

Two exhaust gas purifiers for purifying exhaust gas exhausted by the engine, an inner case in which the gas purifiers are incorporated, and an outer case in which the inner cases are incorporated. An exhaust gas purification device connected side by side in the moving direction,
The adjacent inner cases have a double structure in which one is inserted into the other, and there is a loose fit gap between the inner side surface of the one inner case and the outer side surface of the other inner case. ,
Exhaust gas purification device. A joining flange projecting radially outward is provided on the outer surface of the inner case, and one end of the outer case in the exhaust gas movement direction is fixed to a step formed on the joining flange. And the adjacent joining flanges are overlapped and detachably connected,
The exhaust gas purification apparatus according to claim 1. Due to the presence of the joining flange, the outer case is supported without being in direct contact with the inner case,
The exhaust gas purifier according to claim 2. A sensor boss body for supporting an exhaust gas sensor is provided on one outer surface of the adjacent inner cases, and the sensor boss body protrudes radially outward from a boss body through-hole formed in the outer case. A collar that surrounds the sensor boss body and closes the boss body through-hole is fixed to the outer surface of the one inner case.
The exhaust gas purification apparatus according to any one of claims 1 to 3. A pipe of a differential pressure sensor as the exhaust gas sensor is connected to the sensor boss body, and the pipe is along the outer surface of the outer case.
The exhaust gas purification apparatus according to claim 4.

Images