JP6139961B2 - Honeycomb structure - Google Patents

Description

  For example, the present invention allows exhaust gas exhausted from an exhaust port of an engine, burner, combustion device, etc. to pass through a honeycomb body to eliminate and remove harmful substances contained in the exhaust gas by oxidation / reduction reactions. The present invention relates to a honeycomb structure comprising purifying gas.

Conventionally, diesel engines are often used for trucks, ships, etc. because of their high thermal efficiency. In recent years, they have been reconsidered as prime movers with low CO ₂ emissions, and the use of passenger cars continues to increase. However, diesel engines are the compression ignition type, NO _X is most generated no particulate matter in the gasoline engine (referred to PM) is contained in the exhaust gas as well. In addition, it is effective to increase the contact area with the exhaust gas for the metal honeycomb. However, the exhaust gas flowing through the gas passage composed of the honeycomb cells is disturbed, and the exhaust gas is positively applied to the catalyst. The structure of making it contact is proposed. This honeycomb structure is a loss in terms of increasing the surface area by forming a thin plate with a perforated structure, but it generates turbulent flow in the gas passage and positively contacts exhaust gas due to the turbulence with the catalyst. .

  In addition, it is known that an exhaust gas purifying metal honeycomb body has improved durability against deformation or breakage due to thermal expansion or thermal stress. The exhaust gas purifying metal honeycomb body has a large number of mesh-shaped vent holes in the axial direction in which two different corrugated strips made of thin metal plates are alternately abutted, and the exhaust gas purifying A catalyst is supported. The two types of corrugated strips are composed of strips having a triangular waveform having a structure in which substantially equilateral triangles are connected in the longitudinal direction and strips having a substantially sine wave (see, for example, Patent Document 1).

Further, an exhaust gas purifying device for an internal combustion engine using a metal honeycomb is known. The exhaust gas purifying apparatus for an internal combustion engine performs HC purification using a lean NO _x catalyst using a metal substrate, and in the exhaust passage of the internal combustion engine along the exhaust gas flow direction, nitrogen oxidation of the exhaust gas column is performed. A lean NO _x catalyst in which a catalyst layer for purifying substances in an oxygen-excess atmosphere is supported on a metal honeycomb (metal substrate), and a reaction catalyst (oxidation catalyst) for performing an oxidation reaction of at least hydrocarbon (HC) in the exhaust gas column, (For example, refer to Patent Document 2).

  An exhaust gas purification device using a metal honeycomb is known. The exhaust gas purifying device effectively absorbs microwaves at the time of cold start of the internal combustion engine, rapidly brings the temperature of the catalyst to the catalyst operating temperature, and purifies harmful exhaust gas discharged at the time of cold start And one of the reflection ends of the cavity resonator is constituted by a surface of the metal absorber coated with a catalyst material such as Pt / Rh or Pd / Rh on the microwave absorber side, and the metal honeycomb and the cavity are interposed through the casing. The resonator is electrically connected to the resonator (see, for example, Patent Document 3).

JP-A-8-24670 JP 2003-206733 A JP 2000-104540 A

  By the way, the metal honeycomb is obtained by alternately winding and winding the corrugated thin plates and the flat thin plates, and joining the corrugated thin plates and the flat thin plates with a brazing material. The metal honeycomb is covered with an outer case and bonded to each other by a brazing material to form a metal honeycomb structure. The metal honeycomb structure has a very strong structure as described above, and has extremely high durability even when the exhaust gas is at a high temperature and / or at a high vibration acceleration, and has a low pressure loss. For this reason, it is mounted on motorcycles for exhaust gas purification. However, the metal honeycomb structure has a high strength as described above, but the metal thin plate is in close contact with the metal outer case so that the heat conduction is good, and the inside of the metal honeycomb is improved. There was a problem that the temperature was easily transmitted to the outer case, and the outer case became hot.

  In order to solve the above problems, an object of the present invention is to form a thermal barrier layer made of air or heat insulating material that does not allow exhaust gas to flow between the outer case and the honeycomb body made of metal or ceramics. The high temperature inside the body is difficult to be transmitted to the outer case, the temperature of the outer case is kept lower than the exhaust gas temperature to improve safety, and the exhaust gas temperature flowing through the honeycomb body is properly maintained. To provide a honeycomb structure comprising oxidizing and reducing harmful substances contained in exhaust gas to eliminate and remove harmful substances and purifying exhaust gas.

The present invention consists in purifying the exhaust gas by the harmful substances Ru contained in the exhaust gas through the exhaust gas into the honeycomb body to be applied by arranging the exhaust pipe abolished by oxidation and reduction reactions In the honeycomb structure,
The honeycomb body a number of passages extending in the longitudinal direction with multiple inlet and outlet are formed, and the exhaust gas covers the outer periphery of the entire surface of the honeycomb body to discharge the exhaust gas inflow opening for flowing exhaust A cylindrical outer case provided with an outlet, and a closing member that is disposed on the inner wall surface of the outer case and closes the inlet of the passage located on the outer peripheral portion of the honeycomb body,
Said passage said inlet of said passage are closed by the closure member, the honeycomb body is positioned in the outer peripheral portion communicating with the inlet closed by a closure member positioned in the outer peripheral portion of the honeycomb body There relates to a honeycomb structure characterized by being constituted in the first thermal barrier coating is formed by air layer in which the exhaust gas does not flow.

In this honeycomb structure, the closing member extends from the inlet side of the outer case to the inlet of the outer peripheral portion of the honeycomb body and is spaced apart from the inner wall surface of the outer case over the entire circumference. An inner cylinder disposed to form a heat shield layer, wherein the front end surface of the inner cylinder forms the heat shield layer between the outer case and the inner cylinder, and It is closed to the inflow port. Furthermore, the second thermal barrier coating between the outer casing and the inner tubular body, and an air layer or air layer and the heat insulating material.
Alternatively, the closing member is a ring-shaped plate that closes the inlet of the passage located in the outer peripheral portion of the honeycomb body, and the ring-shaped plate closes the inlet of the passage to The first heat shield layer is formed on the outer periphery.

  Further, in this honeycomb structure, the honeycomb body is a corrugated thin plate or corrugated sheet formed of a flat thin plate formed by flatly forming a metal thin plate and a ridge line extending in the longitudinal direction and a groove between the ridge lines. Constructed from columnar metal honeycombs rolled up alternately with metal mesh, or from ceramic honeycomb formed from cordierite, silicon carbide or aluminum titanate, between the outer case and the ceramic honeycomb The ceramic felt or ceramic fiber cushioning material is interposed between the two.

In this honeycomb structure, the outer casing is the main body tube portion which is disposed said honeycomb body, the inlet tube portion from the inlet at the front end of the main body tube portion extends into the main body tube portion, and the main body tube portion It is comprised from the exit cylinder part which converges from the said main body cylinder part to the said discharge port in the rear end side. A diffusion cylinder for dispersing the exhaust gas is fitted and fixed to the inlet cylinder of the outer case, and one end of the diffusion cylinder opens to form the inlet for the exhaust gas. , A baffle plate with a plurality of through holes is fixed to the other end of the diffusion cylinder, and a plurality of through holes for diffusing the exhaust gas around the diffusion cylinder located in the inlet cylinder of the outer case. Further, the inner cylinder extends along the inlet cylinder of the outer case so as to be spaced from the inner wall surface of the inlet cylinder, and the front end surface of the inner cylinder is It is fixed to the outer peripheral surface of the diffusion cylinder.

In this honeycomb structure, the catalyst supported on the honeycomb body is an oxidation catalyst, a three-way catalyst, and / or a NO _x reduction catalyst, and the NO _x reduction catalyst is a hydrocarbon fuel, ammonia and / or urea. Is made to function as a reducing agent. Further, in the honeycomb structure, the catalyst is not supported in a region that forms the passage where the exhaust gas does not flow and is located on the outer peripheral portion of the honeycomb structure.

  In this honeycomb structure, the ridgeline of the corrugated thin plate or the corrugated wire mesh extends straight or bent parallel to the axis of the columnar body. Further, the flat thin plate and the corrugated thin plate or the corrugated wire net constituting the metal honeycomb body are made of stainless steel or iron-chromium aluminum alloy. Further, the flat thin plate and the corrugated thin plate or the corrugated wire net constituting the metal honeycomb body are joined to each other with a brazing material at a predetermined predetermined portion.

  In the honeycomb structure according to the present invention, as described above, the first heat shield layer and / or the second heat shield layer is formed along the inner wall surface of the outer case. Hot exhaust gas does not flow in, the thermal energy of the exhaust gas is not conducted to the outer case where the honeycomb body is located, and the outer case is not heated to high temperature by the exhaust gas, so safety can be ensured. In addition, the honeycomb body is maintained at an appropriate temperature as the exhaust gas temperature, and can be made to disappear by reacting harmful substances such as HC contained in the exhaust gas with the aid of a catalyst. It is a simple structure in which only a closing member is provided, and the manufacturing cost is reduced.

It is sectional drawing which shows 1st Example of the honeycomb structure by this invention. Fig. 2 is a front view showing the honeycomb structure of Fig. 1. It is an expanded sectional view which shows the code | symbol A area | region of FIG. FIG. 2 is a perspective view for explaining a metal material composed of a flat thin plate and a corrugated thin plate constituting the honeycomb body in the honeycomb structure of FIG. 1. It is an end elevation which shows the state which piled up the metal flat thin plate of FIG. 4 and the wavelike thin plate. FIG. 2 is an end view showing the honeycomb structure of FIG. 1 which is a columnar body made by rolling a metal material of a flat thin plate and a corrugated wire mesh. FIG. 2 is a perspective view for explaining another metal material composed of a flat thin plate and a corrugated wire net constituting the honeycomb body in the honeycomb structure of FIG. 1. It is an end view which shows the state which piled up the metal flat thin plate of FIG. 7, and the corrugated metal mesh. It is sectional drawing which shows 2nd Example of the honeycomb structure by this invention. It is sectional drawing which shows 3rd Example of the honeycomb structure by this invention. It is an expanded sectional view which shows the code | symbol B area | region of 3rd Example shown in FIG. Test for comparison with the honeycomb structure of the present invention and the conventional honeycomb structure not provided with the inner cylinder at the portion corresponding to the line BB of the honeycomb structure in FIG. It is a graph which shows the measured temperature measurement. 6 is a graph showing low-temperature performance of a comparative test of the HC reduction rate between a honeycomb structure according to the present invention and a conventional honeycomb structure.

Hereinafter, embodiments of a honeycomb structure according to the present invention will be described with reference to the drawings. This honeycomb structure is applied by being disposed in the middle of an exhaust pipe (not shown). Exhaust gas G discharged from the exhaust port of an engine, burner, combustion device, flue, etc. to the exhaust pipe harmful substances HC, NO _X or the like contained in, using the catalyst supported on the honeycomb member 1 water, carbon dioxide, abolished by oxidation and reduction reactions to nitrogen, which purifies the exhaust gas G, wherein The honeycomb body 1 constitutes a carrier that does not have a function of collecting PM (particulate matter).

A first embodiment of a honeycomb structure according to the present invention will be described with reference to FIGS. The honeycomb structure, generally, the number exhaust gas G flows inlet 16 and outlet 26 and the honeycomb body 1 a number of passages 8,8N extending in the longitudinal direction are formed with a honeycomb body 1 outer circumferential side of the A cylindrical outer case 2 that covers the entire surface, and an inner cylindrical body 3 that is disposed so as to be spaced from the inner wall surface 20 on the front end side of the outer case 2 over the entire circumference to form a first heat shield layer 10. It is. In the first embodiment, the inner cylinder 3 functions as a closing member that does not allow the exhaust gas G to flow into the passages 8 and 8N of the outer peripheral portion 19 of the honeycomb body 1, and the first inner side wall 20 extends along the inner wall surface 20. It has a function of forming the heat shield layer 10. The outer case 2 has an inflow port 14 into which the exhaust gas G flows and an exhaust port 15 through which the exhaust gas G that flows in from the inflow port 14 passes through the honeycomb body 1 and is discharged to the exhaust gas passage. . The inner cylinder 3 is generally extended from the inlet 14 of the outer case 2 to the inlet 17 of the exhaust gas inflow end face of the honeycomb body 1, and the first heat shield layer 10 is formed between the inner case 3 and the outer case 2. Is formed. In addition, the rear end surface 17 of the inner cylinder 3 is positioned in contact with the inlet 16 on the upstream side of the honeycomb body 1, and the outer peripheral portion 19 of the honeycomb body 1 corresponding to the rear end surface 17 of the inner cylinder 3 is located. The second heat shield layer 24 into which the exhaust gas G does not flow is formed. Further, in this honeycomb structure, the first heat insulating layer 10 formed between the outer case 2 and the inner cylinder 3 and the second heat insulating layer 24 in the outer peripheral portion 19 of the honeycomb body 1 are an air layer and / Or it is comprised with the heat insulating material.

  Further, as shown in FIGS. 4 to 6, the honeycomb body 1 includes a flat thin plate 4 in which the metal thin plate is formed flat, a ridge line 6 in which the metal thin plate extends in the longitudinal direction, and a groove 7 between the ridge lines 6. The corrugated thin plate 5 formed in the shape of a corrugated plate is composed of columnar bodies 21 that are rolled up alternately and a path 8 is formed in each groove 7. Alternatively, as shown in FIGS. 7 and 8, the corrugated plate 4 is formed by a flat thin plate 4 in which a thin metal plate is formed, a ridge line 6N in which a metal wire net extends in the longitudinal direction, and a groove 7N between the ridge lines 6N. It is comprised from the columnar body similar to the columnar body 21 rounded by alternately superposing | stacking the waveform corrugated metal mesh 5N, and the channel | path 8N is each formed in each groove | channel 7N. In this honeycomb structure, the ridgeline 6 of the corrugated thin plate 5 or the ridgeline 6N of the corrugated wire mesh 5N is formed in a straight shape that is parallel to the axis of the columnar body 21 or a shape that extends by bending. The flat thin plate 4 and the corrugated thin plate 5 or corrugated wire mesh 5N constituting the honeycomb body 1 are made of stainless steel or iron-chromium aluminum alloy. Further, the flat thin plate 4 and the corrugated thin plate 5 or the corrugated wire net 5N constituting the honeycomb body 1 are joined to each other with a brazing material at a predetermined predetermined portion.

  In this honeycomb structure, the outer case 2 includes a main body cylinder portion 2M in which the honeycomb body 1 is disposed, an inlet cylinder portion 2F positioned on the exhaust gas G inflow side, and an outlet cylinder positioned on the exhaust gas G outflow side. The parts 2R are sequentially connected to form an integral structure. The inlet cylinder 2F is configured to expand from the exhaust pipe (not shown) for exhaust gas G to the main cylinder 2M on the front end side of the main cylinder 2M, and the outlet cylinder 2R includes the main cylinder 2R. On the rear end side of 2M, the main body cylinder portion 2M is configured to converge to an exhaust pipe (not shown). Further, in this honeycomb structure, the exhaust gas G is dispersed into the inlet 14 into which the exhaust gas G of the outer case 2 flows, and the honeycomb body is uniformly distributed from the entire surface of the inlet 17 that is the exhaust gas inflow end surface of the honeycomb body 1. The diffusion cylindrical body 9 is fitted and fixed so as to flow into 1. That is, the diffusion cylinder 9 is fitted and fixed to the inlet cylinder 2F of the outer case 2. An outlet cylinder 13 is fitted and fixed to the outlet cylinder 2R.

  The diffusion cylinder 9 constitutes an exhaust gas inlet 14 having one end opened, and a baffle plate 12 with a large number of through holes 11 is fixed to the other end. A plurality of through holes 11 for diffusing the exhaust gas G are formed around the diffusion cylinder 9 located in the inlet cylinder portion 2F of the outer case 2. Therefore, a part of the exhaust gas G flowing in from the inlet 14 of the diffusion cylinder 9 passes through the through holes 11 of the baffle plate 12, but diffuses through the through holes 11 around the diffusion cylinder 9 and enters the inlet. The exhaust gas G in the inner cylinder 3 is diffused and flows into the multiple inlets 16 of the honeycomb body 1 while flowing into the inner cylinder 3 in the cylinder portion 2F. Further, the inner cylinder 3 extends away from the inner wall surface 20 of the inlet cylinder 2F so as to form the first heat shield layer 10 along the inlet cylinder 2F of the outer case 2. The front end surface 22 of the body 3 is fixed to the outer peripheral surface 23 of the diffusion cylinder 9 by the fixing portion 18.

In this honeycomb structure, the catalyst supported on the honeycomb body 1, an oxidation catalyst, a three way catalyst, and / or NO _X reduction catalyst. Further, the NO _x reduction catalyst functions hydrocarbon fuel, ammonia and / or urea as a reducing agent. Further, in this honeycomb structure, a catalyst is not supported on the flat thin plate 4 and the corrugated thin plate 5 located on the outer peripheral portion 19 of the honeycomb body 1 corresponding to the space between the outer case 2 and the inner cylindrical body 3. Is. Further, alumina (Al ₂ O ₃ ), silica (SiO ₂ ), zirconia (ZrO ₂ ), ceria (CeO ₂ ), ceria (CeO ₂ ), so as to securely support the catalyst on the outer surface of the honeycomb body 1 on which the catalyst is supported. At least one ceramic of titania (TiO ₂ ) is coated. The catalyst supported on the honeycomb body 1 is specifically platinum (Pt), silver (Ag), potassium (K), palladium (Pd), iridium (Ir), iron (Fe), copper ( It is at least one oxidation / reduction catalyst of Cu), barium (Ba), ruthenium (Ru), and rhodium (Rh).

In order to test the effect of heat transfer to the outer peripheral surface of the honeycomb structure according to the present invention, a normal conventional honeycomb structure without an inner cylinder was prepared. The side surface temperature which is the outer peripheral surface of the outer case 2 at the position of line BB shown in FIG. 1 was measured for the honeycomb structure of the present invention and the conventional normal honeycomb structure.
As shown in FIG. 12, the measurement temperature was measured for the side surface temperature that is the outer peripheral surface of the outer case 2 with respect to the inlet temperature of the honeycomb body 1 of 200 ° C., 300 ° C., 400 ° C., and 500 ° C. The side surface temperature ◆ which is the outer peripheral surface of the outer case 1 of the honeycomb structure of the present invention may be lower by 15 ° C. to 50 ° C. than the side surface temperature ■ which is the outer peripheral surface of the outer case of the normal honeycomb structure. It could be confirmed. In the honeycomb structure of the present invention, the inner cylindrical body 3 is provided on the inlet side of the exhaust gas G of the honeycomb body 1, the first heat shield layer 10 is formed on the inlet side of the outer case 1, and the outer peripheral portion 19 of the honeycomb body 1. Since the second heat-insulating layer 24 is formed on the outer peripheral portion 19 of the honeycomb body 1 so that the exhaust gas G does not flow through the exhaust gas G, the heat-shielding effect on the outer case 1 with respect to the exhaust gas G compared to the conventional honeycomb structure. I found out that Further, even when the ring-shaped plate 25 of the second embodiment is provided, the second heat shielding layer 24 is formed on the outer peripheral portion 19 of the honeycomb body 1 as in the first embodiment. It has been confirmed that there is a heat shielding effect on.

  Referring to FIG. 13, for the honeycomb structure according to the present invention and the conventional normal honeycomb structure, the HC reduction rate at the inlet temperatures of 200 ° C., 300 ° C., 400 ° C., and 500 ° C. of the outer case 2 of the honeycomb body 1 Was measured respectively. As can be seen from the graph of FIG. 11, it was confirmed that the HC reduction rate ◆ of the honeycomb structure of the present invention was improved as compared with the HC reduction rate ■ of the normal honeycomb structure.

  next. A second embodiment of the honeycomb structure according to the present invention will be described with reference to FIG. The second embodiment does not include the inner cylinder 3 of the honeycomb structure of the first embodiment. Instead of the inner cylinder 3, a ring-shaped plate 25 is provided on the exhaust gas G inflow side of the honeycomb body 1. It is arranged. The ring-shaped plate 25 is fixed to the outer case 2 or the outer peripheral portion 19 of the honeycomb body 1 so as to close the inlet 16 of the outer peripheral portion 19 of the honeycomb body 1 and closes the inlet 16 of the passage 8N to exhaust into the passages 8 and 8N. It functions as a closing member that prevents the gas G from flowing in. When the ring-shaped plate 25 closes the inlet 16 of the outer peripheral portion 19 of the honeycomb body 1, the exhaust gas G cannot flow into the outer peripheral portion 19 of the honeycomb body 1, and the second heat shield layer 24 is formed. Is done. In the second embodiment, the inlet cylinder 2F of the outer case 2 is exposed to the exhaust gas G, and the first heat shield layer 10 as in the first embodiment is not formed. Is formed in the same manner as in the first embodiment.

  Further, a third embodiment of the honeycomb structure according to the present invention will be described with reference to FIGS. The honeycomb body 1 constituting the honeycomb structure according to the present invention can be formed of a ceramic honeycomb body 1C from a ceramic honeycomb formed of cordierite, silicon carbide, or aluminum titanate. As shown in FIGS. 10 and 11, the third embodiment is spaced from the inner wall surface 20 on the front end side of the outer case 2 over the entire circumference, like the first embodiment shown in FIGS. The configuration in which the inner cylindrical body 3 formed by forming the first heat shielding layer 10 is disposed is the same. In the case where the honeycomb body 1 is composed of the ceramic honeycomb body 1C, when the ceramic honeycomb body 1C is manufactured in a structure that accommodates the ceramic honeycomb body 1C in the outer case 2, the cordierite, silicon car constituting the ceramic honeycomb body 1C is produced. Since there is a possibility that a ceramic such as a bite or aluminum titanate is damaged due to impact or the like, in the third embodiment, a ceramic felt is formed at the boundary between the outer case 2 and the ceramic honeycomb body 1C in order to prevent the ceramic from being damaged. A buffer material 27 made of ceramic fiber or the like is interposed. Although the buffer material 27 has a function of a heat shield layer, a further heat shield effect can be secured by not flowing the exhaust gas G to the outer peripheral region of the ceramic honeycomb body 1C, or the buffer material is made thicker unnecessarily. There is no need to configure, and heat transfer to the outer case 2 is blocked, and overheating can be prevented. Furthermore, the heat insulation state of the ceramic honeycomb body 1C can be secured, the catalyst activation can be expected to be improved, the temperature rise of the peripheral device of the honeycomb structure or the outer periphery of the exhaust pipe can be prevented, and the heat damage can be expected to be prevented. Heat transfer to combustible materials can be prevented.

  Although not shown, a fourth embodiment of the honeycomb structure according to the present invention will be described. In the fourth embodiment, the inner cylindrical body 3 is disposed on the inner wall surface 20 of the outer case 2 in the third embodiment, but the configuration is not necessarily limited thereto. For example, as in the second embodiment shown in FIG. In addition, a ring-shaped plate that closes the outer peripheral portion may be disposed on the exhaust gas G inflow side of the ceramic honeycomb body 1C. Needless to say, the fourth embodiment can exhibit the same functions and effects as those of the third embodiment shown in FIGS.

  The honeycomb structure according to the present invention allows exhaust gas exhausted from exhaust ports of engines, burners, combustion devices, and the like to contact and pass through exhaust gas to eliminate and remove harmful substances contained in the exhaust gas through oxidation / reduction reactions. It is preferable to be applied as a carrier for purifying water.

DESCRIPTION OF SYMBOLS 1 Honeycomb body 1C Ceramic honeycomb body 2 Outer case 2F Inlet cylinder part 2M Main body cylinder part 2R Outlet cylinder part 3 Inner cylinder (closing member)
4 flat thin plate 5 corrugated thin plate 5N corrugated wire mesh 6, 6N ridge line 7, 7N groove 8, 8N passage 9 diffusion cylinder 10 second heat shield layer 11 through hole 12 baffle plate 14 inlet 15 outlet 16 inlet 19 outer periphery 20 Inner wall surface 21 Columnar body 22 Front end surface 23 Outer peripheral surface 24 First heat shield layer 25 Ring-shaped plate (closing member)
27 Buffer material G Exhaust gas

Claims (13)

In the honeycomb structure consists of a hazardous substance Ru contained in the exhaust gas through the exhaust gas into the honeycomb body to be applied by arranging the exhaust pipe is oxidation-reduction reaction abolished by purifying the exhaust gas ,
The honeycomb body a number of passages extending in the longitudinal direction with multiple inlet and outlet are formed, and the exhaust gas covers the outer periphery of the entire surface of the honeycomb body to discharge the exhaust gas inflow opening for flowing exhaust A cylindrical outer case provided with an outlet, and a closing member that is disposed on the inner wall surface of the outer case and closes the inlet of the passage located on the outer peripheral portion of the honeycomb body,
Said passage said inlet of said passage are closed by the closure member, the honeycomb body is positioned in the outer peripheral portion communicating with the inlet closed by a closure member positioned in the outer peripheral portion of the honeycomb body honeycomb structure but characterized by being composed in the first thermal barrier coating is formed by air layer in which the exhaust gas does not flow.   The closing member extends from the inlet side of the outer case to the inlet of the outer peripheral portion of the honeycomb body and is spaced from the inner wall surface of the outer case over the entire circumference to form a second heat shield layer. A front end surface of the inner cylinder is closed with respect to the inlet of the exhaust gas so as to form the heat shield layer between the outer case and the inner cylinder. The honeycomb structure according to claim 1, wherein the honeycomb structure is formed. The second thermal barrier layer, the honeycomb structure according to claim 2, characterized in that it is constituted by an air layer or air layer and the heat insulating material between the outer case and the inner tubular body.   The closing member is a ring-shaped plate that closes the inlet of the passage located at the outer peripheral portion of the honeycomb body, and the ring-shaped plate closes the inlet of the passage to close the outer peripheral portion of the honeycomb body. The honeycomb structure according to claim 1, wherein the first heat shielding layer is formed on the honeycomb structure.   The honeycomb body is rounded by alternately laminating a flat thin plate formed by flatly forming a metal thin plate and a corrugated thin plate or a corrugated wire mesh formed into a corrugated plate formed of a ridge line extending in the longitudinal direction and a groove between the ridge lines. A ceramic honeycomb made of cordierite, silicon carbide or aluminum titanate, and a ceramic felt or ceramic fiber between the outer case and the ceramic honeycomb. The honeycomb structure according to any one of claims 1 to 4, wherein a buffer material is interposed. The outer case includes a main body cylinder portion in which the honeycomb body is disposed, an inlet cylinder portion extending from the inlet to the main body cylinder portion on a front end side of the main body cylinder portion, and a rear end side of the main body cylinder portion. The honeycomb structure according to any one of claims 1 to 5, wherein the honeycomb structure includes an outlet tube portion that converges from the main tube portion to the discharge port.   A diffusion cylinder for dispersing the exhaust gas is fitted and fixed to the inlet cylinder portion of the outer case, and one end of the diffusion cylinder opens to form the inlet for the exhaust gas, A baffle plate with many through holes is fixed to the other end of the diffusion cylinder, and a plurality of through holes for diffusing the exhaust gas are formed around the diffusion cylinder located in the inlet cylinder of the outer case. The honeycomb structure according to claim 6, wherein the honeycomb structure is formed.   The inner cylinder extends from the inner wall surface of the inlet cylinder along the inlet cylinder of the outer case, and the front end surface of the inner cylinder is an outer peripheral surface of the diffusion cylinder. The honeycomb structure according to claim 7, wherein the honeycomb structure is fixed to the honeycomb structure. The catalyst supported on the honeycomb body is an oxidation catalyst, a three-way catalyst, and / or a NO _x reduction catalyst, and the NO _x reduction catalyst functions with hydrocarbon fuel, ammonia and / or urea as a reducing agent. The honeycomb structure according to any one of claims 1 to 8, wherein   The honeycomb structure according to claim 9, wherein the catalyst is not supported in a region forming the passage where the exhaust gas does not flow, which is located on the outer peripheral portion of the honeycomb body.   The honeycomb structure according to any one of claims 5 to 10, wherein the ridgeline of the corrugated thin plate or the corrugated wire mesh extends straight or bent parallel to the axis of the columnar body. body.   The flat thin plate and the corrugated thin plate or the corrugated wire mesh constituting the metal honeycomb body are made of stainless steel or iron chrome aluminum alloy, according to any one of claims 5 to 11. The honeycomb structure described.   The flat thin plate and the corrugated thin plate or the corrugated wire mesh constituting the metal honeycomb body are bonded to each other with a brazing material at a predetermined predetermined portion. A honeycomb structure according to claim 1.

Images