JP2016107239A - Honeycomb structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a honeycomb structure in which the decrease in purification capability resulting from poisoning substances is suppressed and the purification capability can be improved.SOLUTION: The honeycomb structure 1 includes a plurality of cell walls 2, a plurality of cell holes 3 surrounded by the plurality of cell walls 2, and a catalyst layer 5 covering the surface of the cell walls 2, and passes an exhaust gas exhausted from an internal combustion engine through the plurality of cell holes 3 for purification. In at least a portion of the plurality of cell holes 3, there is formed a protrusion portion 4 protruding toward the center side of the cell hole 3 from the cell wall 2 as viewed from the axial direction of the honeycomb structure 1. At least a portion of the protrusion portion 4 is a trap protrusion portion 41 having a surface roughness larger than the surface roughness on the cell walls 2.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a honeycomb structure used in a catalyst device for purifying exhaust gas discharged from an internal combustion engine.

  As a catalytic device for purifying exhaust gas of an internal combustion engine such as an automobile, a cell wall provided in a lattice shape and a plurality of cell holes formed surrounded by the cell wall inside an exhaust pipe through which the exhaust gas flows (Patent Document 1) is known in which a honeycomb structure including: The catalyst device circulates high-temperature exhaust gas through the cell holes of the honeycomb structure, thereby heating the catalyst supported on the honeycomb structure to an activation temperature or higher to purify the exhaust gas.

JP 2009-154148 A

However, the honeycomb structure disclosed in Patent Document 1 has the following problems.
The exhaust gas discharged from the internal combustion engine contains poisonous substances such as phosphorus, sulfur, and manganese. When these poisoning substances adhere to the catalyst, the activity of the catalyst is lost and the purification performance of the catalyst is lowered.

  The present invention has been made in view of such a background, and an object of the present invention is to provide a honeycomb structure capable of improving purification performance by suppressing reduction in purification performance due to poisoning substances.

One embodiment of the present invention includes a plurality of cell walls, a plurality of cell holes surrounded by the plurality of cell walls, and a catalyst layer covering the surface of the cell walls, and exhaust gas discharged from an internal combustion engine A honeycomb structure for purifying by flowing through the plurality of cell holes,
At least a part of the plurality of cell holes is formed with a protrusion protruding from the cell wall toward the center side of the cell hole when viewed from the axial direction of the honeycomb structure,
At least a part of the protrusions is a trap protrusion having a surface roughness larger than the surface roughness of the cell wall.

The honeycomb structure includes the trap protrusion formed inside the cell hole. The trap protrusion protrudes to the inside of the cell hole and thus easily comes into contact with a poisoning substance contained in the exhaust gas. Further, the trap protrusion changes the flow direction of the exhaust gas flowing through the cell hole, and a turbulent flow is formed around the trap protrusion. Thereby, the mass transfer rate around the trap protrusion can be improved, and the poisoning substance can be efficiently collected by the trap protrusion.
Further, by making the surface roughness of the trap protrusion larger than the surface roughness of the cell wall, minute irregularities are formed on the surface of the trap protrusion. By forming the unevenness, the poisonous substance contained in the exhaust gas easily adheres to the trap protrusion, and the poisoning substance can be easily collected by the trap protrusion. Thereby, it can suppress that the purification performance of the said catalyst layer falls by poisoning substance.

  In addition, when exhaust gas flows through the cell holes of the honeycomb structure that does not have the protrusions, a boundary layer is formed on the surface of the cell wall forming the cell holes due to the influence of the viscosity of the exhaust gas. In this boundary layer, since the heat transfer rate and the mass transfer rate are lowered, the contact efficiency between the exhaust gas and the honeycomb structure is lowered. Therefore, in the honeycomb structure, the amount of heat received from the exhaust gas is reduced, and activation delay in the catalyst and purification performance are reduced.

  In the honeycomb structure, by forming a turbulent flow around the protrusions, the boundary layer can be broken and the heat transfer rate and mass transfer rate of the exhaust gas in the cell holes can be recovered. Thereby, the contact efficiency of exhaust gas and the said honeycomb structure can be improved. Therefore, the purification performance of the catalyst can be sufficiently exerted, and the purification performance of the honeycomb structure can be improved.

  As described above, according to the present invention, it is possible to provide a honeycomb structure that can improve purification performance by suppressing reduction in purification performance due to poisoning substances.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 3 is an explanatory view showing a honeycomb structure in Example 1. The III-III arrow directional cross-sectional view of the honeycomb structure in FIG. 2 is an enlarged cross-sectional view of a honeycomb structure in Example 1. FIG. Sectional drawing of the projection part in Example 1. FIG. FIG. 6 is an explanatory view showing a honeycomb structure in Example 2. Sectional drawing of the projection part in Example 2. FIG. FIG. 9 is an enlarged cross-sectional view illustrating a first shape example of a protrusion in Example 3. FIG. 9 is an enlarged cross-sectional view showing a second shape example of the protrusion in Example 3. FIG. 9 is an enlarged cross-sectional view illustrating a third shape example of a protrusion in Example 3. FIG. 9 is an enlarged cross-sectional view showing a fourth shape example of the protrusion in Example 3. FIG. 10 is an enlarged cross-sectional view showing a fifth shape example of the protrusion in Example 3. Explanatory drawing of a projection part in FIG. FIG. 12 is an enlarged cross-sectional view illustrating a sixth shape example of a protrusion in Example 3. FIG. 9 is an enlarged cross-sectional view illustrating a seventh shape example of a protrusion in Example 3. FIG. 10 is an enlarged cross-sectional view illustrating an eighth shape example of a protrusion in Example 3. In Example 4, (a) a sectional view showing a first shape example of the protruding portion, (b) a sectional view showing a second shape example of the protruding portion, and (c) a third shape example of the protruding portion. Sectional drawing. In Example 4, (a) a sectional view showing a fourth shape example of the protruding portion, (b) a sectional view showing a fifth shape example of the protruding portion, and (c) a sixth shape example of the protruding portion. Sectional drawing.

  In the honeycomb structure, it is preferable that the surface roughness of the trap protrusion is larger than the surface roughness of the catalyst layer. In this case, the poisoning substance can be collected more efficiently by increasing the unevenness formed on the surface of the trap protrusion.

  Moreover, the said trap protrusion part is formed with the porous material, and it is preferable that the average hole diameter of a pore is 10 nm-1000 nm. The average particle diameter of the Mn oxide particles contained in the exhaust gas is about 10 nm to 80 nm. Therefore, the Mn oxide particles can be efficiently collected by setting the average pore diameter in the trap protrusion to a size suitable for collecting Mn oxide particles contained in the exhaust gas.

  Moreover, it is preferable that the distance between the upstream end part in the axial direction of the honeycomb structure and the trap protrusion is 2 mm to 30 mm. The honeycomb structure is easily affected by poisonous substances in a range from 2 mm to 30 mm from the upstream end. Therefore, by forming the trap protrusion in this range, poisonous substances contained in the exhaust gas can be efficiently collected.

  Moreover, it is preferable that the said trap protrusion part is formed with the material provided with the property to adsorb | suck phosphorus and sulfur. In this case, an adsorption effect of phosphorus and sulfur can be imparted to the trap protrusion, and the phosphorus and sulfur collection performance of the trap protrusion can be improved.

  The catalyst layer is preferably not formed on the surface of the trap protrusion and the surface of the trap protrusion is exposed. In this case, the surface roughness of the trap protrusion can be appropriately set without being affected by the surface roughness of the catalyst layer. Therefore, the surface roughness of the trap protrusion can be made suitable for the usage environment. Further, since the catalyst layer is not formed on the trap protrusion, the amount of catalyst used can be reduced and the cost can be reduced.

  Moreover, it is preferable that the said catalyst layer arrange | positioned upstream from the said trap protrusion part does not contain platinum and palladium but contains rhodium. On the upstream side of the trap protrusion, the amount of poisonous substances contained in the exhaust gas is larger than that on the downstream side. Therefore, by using the above catalyst layer containing rhodium that does not contain platinum and palladium that are easily affected by poisoning substances and is not easily affected by poisoning substances, it is possible to suppress a reduction in purification performance.

  Moreover, it is preferable that the catalyst layer containing at least one of platinum, palladium, and rhodium is formed outside the range of 1.5 mm from the downstream end of the protrusion to the downstream side. In the range of 1.5 mm from the downstream end of the projection to the downstream side, the purification action by the catalyst layer is difficult to work due to the retention of exhaust gas. Therefore, in addition to this range, by forming the catalyst layer containing platinum and palladium, the amount of the catalyst layer used can be reduced and the cost can be reduced.

  Moreover, it is preferable that the catalyst layer containing at least one of platinum, palladium, and rhodium is formed outside the range of 1.0 mm from the upstream end of the protrusion to the upstream side. In the range of 1.0 mm from the upstream end of the protrusion to the upstream side, the purification action by the catalyst layer is difficult to work due to the retention of exhaust gas. Therefore, in addition to this range, by forming the catalyst layer containing platinum and palladium, the amount of the catalyst layer used can be reduced and the cost can be reduced.

Example 1
Examples of the honeycomb structure will be described with reference to FIGS.
As shown in FIGS. 1 to 5, the honeycomb structure 1 includes a plurality of cell walls 2, a plurality of cell holes 3 surrounded by the plurality of cell walls 2, and a catalyst layer 5 that covers the surface of the cell walls 2. The exhaust gas discharged from the internal combustion engine is circulated through the plurality of cell holes 3 to be purified.
At least a part of the plurality of cell holes 3 is formed with a protrusion 4 protruding from the cell wall 2 toward the center side of the cell hole 3 when viewed from the axial direction X of the honeycomb structure 1.
At least a part of the protrusion 4 is a trap protrusion 41 having a surface roughness larger than that of the cell wall 2.

This will be described in more detail below.
As shown in FIG. 1, the honeycomb structure 1 of this example is for purifying exhaust gas generated in an automobile engine. The honeycomb structure 1 is disposed inside an exhaust pipe 6 through which exhaust gas flows, and the honeycomb structure 1 and the exhaust pipe 6 form a catalyst device 100.
The exhaust pipe 6 includes an arrangement pipe 62 that includes the honeycomb structure 1, an upstream pipe 61 provided on the upstream side of the arrangement pipe 62, and a downstream pipe 63 provided on the downstream side. The upstream pipe 61, the arrangement pipe 62, and the downstream pipe 63 are formed so as to be coaxial with the central axis O of the honeycomb structure 1. Note that the central axes of the upstream pipe 61 and the downstream pipe 63 may be shifted from the central axis O of the honeycomb structure 1.

  As shown in FIGS. 4 and 5, the honeycomb structure 1 includes a columnar ceramic carrier formed by cell walls 2 arranged in a lattice shape, and a catalyst that is carried on the surface of the ceramic carrier and purifies exhaust gas. Layer 5. 1 to 3 are diagrams in which the catalyst layer 5 is omitted (the same applies to FIGS. 8 to 18 described later). The cell wall 2 is made of a ceramic material having a porosity of 30% to 40%. In this example, cordierite having a porosity of 33% is used. A plurality of cell holes 3 partitioned by cell walls 2 are formed in the honeycomb structure 1, and the cross-sectional shape of each cell hole 3 is a hexagon. The cross-sectional shape of the cell hole 3 may be various polygonal shapes or circular shapes other than the hexagonal shape. However, when the rectangular shape or the hexagonal shape is used, the honeycomb structure 1 having excellent purification performance and productivity can be obtained. Can be obtained.

As shown in FIGS. 1 and 2, when viewed from the axial direction X of the honeycomb structure 1, the formation density indicating the number of formed cell holes 3 per unit area is uniform.
As shown in FIGS. 3 to 5, trap projections 41 are provided in all the cell holes 3 constituting the honeycomb structure 1 of this example, and a pair of trap projections 41 is provided in one cell hole 3. Is formed. In this example, the trap protrusions 41 are provided in all the cell holes 3 of the honeycomb structure 1, but the trap protrusions 41 may be provided only in some of the cell holes 3. Further, the number of trap protrusions 41 can be changed as appropriate.

  As shown in FIG. 4, when viewed from the axial direction X, the trap projection 41 has a pair of cell walls 2 and a pair of cell walls 2 that are opposed to each other among the six cell walls 2 that form the cell holes 3. It is formed along the cell walls 2 arranged on both sides. Each of the pair of trap protrusions 41 has the same shape, and is symmetrical with respect to a virtual line L passing through the center point P of the cell hole 3 and parallel to the pair of opposing cell walls 2. Has been placed. Moreover, the corner | angular part in the external shape of the trap protrusion 41 is formed by the smooth curved surface. In FIG. 4, the corner formed by the cell wall 2 and the protrusion 4 is not a curved surface, but may be formed by a curved surface.

As shown in FIG. 5, the protrusion 4 has a semi-elliptical cross-sectional shape. Therefore, the protrusion 4 smoothly connects the curved upstream-side inclined surface 43 formed so that the amount of protrusion increases from the upstream end toward the downstream side, and the upstream-side inclined surface 43, and the downstream side. And a curved downstream inclined surface 44 formed so that the amount of protrusion increases from the side end toward the upstream side. The protruding direction of the protruding portion 4 is the normal direction of the cell wall 2 on which the protruding portion 4 is formed. When the protruding portion 4 is formed across a plurality of cell walls 2, each cell wall 2 The normal direction at.
In the axial direction X of the honeycomb structure 1, the trap protrusion 41 is formed at a position upstream of the central portion 12 and at a position where the distance S from the upstream end 11 is 20 mm. .

  The trap protrusion 41 is formed by mixing an additive having the property of adsorbing phosphorus and sulfur with cordierite, which is a porous material. As this additive, for example, barium, strontium, calcium, magnesium, lanthanum, cerium, praseodymium and the like can be used. Moreover, the porosity of the trap protrusion 41 of this example was 65%, and the surface roughness was 15 μm in terms of arithmetic average roughness. Moreover, the average hole diameter in the trap protrusion 41 is 10 nm to 1000 nm. In addition, it is preferable that the surface roughness in the trap protrusion 41 is in the range of 6 μm to 20 μm in arithmetic average roughness. In this case, the performance of collecting poisonous substances in the trap protrusion 41 can be improved.

As shown in FIGS. 4 and 5, the catalyst layer 5 includes a first catalyst layer 51 made of a catalyst containing rhodium without containing platinum and palladium, and a catalyst made of a catalyst containing at least one of platinum, palladium, and rhodium. Two catalyst layers 52 are formed.
The first catalyst layer 51 is formed on the upstream side of the upstream end portion of the trap protrusion 41, and the arithmetic average roughness of the first catalyst layer 51 is 4 μm. The second catalyst layer 52 is formed downstream of the downstream end of the first catalyst layer 51, and the arithmetic average roughness of the second catalyst layer 52 is 4 μm. It should be noted that the catalyst layer 5 is present on the surface of the trap projection 41, in a range from the upstream end of the trap projection 41 to 1.0 mm, and in a range from the downstream end of the trap projection 41 to 1.5 mm. Is not formed, and the catalyst layer 5 is formed outside these ranges.

Next, the function and effect of this example will be described.
The honeycomb structure 1 includes a trap projection 41 formed inside the cell hole 3. Since the trap protrusion 41 is formed so as to protrude inside the cell hole 3, it easily comes into contact with a poisoning substance contained in the exhaust gas. Furthermore, the trap protrusion 41 changes the flow direction of the exhaust gas flowing through the cell hole 3, and a turbulent flow is formed around the trap protrusion 41. Thereby, the substance transfer rate around the trap protrusion 41 can be improved, and the trap protrusion 41 can efficiently collect poisonous substances.
Further, by making the surface roughness of the trap projection 41 larger than the surface roughness of the cell wall 3, minute irregularities are formed on the surface of the trap projection 41. By forming the unevenness, the poisonous substance contained in the exhaust gas easily adheres to the trap projection 41, and the trap projection 41 can easily collect the poisonous substance. Thereby, it can suppress that the purification performance of the catalyst layer 5 falls by poisoning substance.

  Further, as described above, the turbulent flow is formed around the trap projection 41, thereby destroying the boundary layer formed inside the cell hole 3 and restoring the mass transfer rate of the exhaust gas in the cell hole 3. Can do. Thereby, the contact efficiency between the exhaust gas and the honeycomb structure 1 can be improved. Therefore, the purification performance of the catalyst can be sufficiently exerted, and the purification performance of the honeycomb structure 1 can be improved.

  Further, the surface roughness of the trap protrusion 41 is larger than the surface roughness of the catalyst layer 5. Therefore, the poisoning substance can be collected more efficiently by increasing the surface roughness of the trap protrusion 41.

  Moreover, the trap protrusion 41 is made of a porous material, and the average pore diameter of the pores is 10 nm to 1000 nm. Therefore, the average pore size is set to a size suitable for collecting Mn oxide particles contained in the exhaust gas, and Mn oxide particles can be efficiently collected.

  Further, the distance between the upstream end 11 in the axial direction of the honeycomb structure 1 and the trap protrusion 41 is 20 mm. The honeycomb structure 1 is easily affected by poisoning substances in the range of 2 mm to 30 mm from the upstream end portion 11. Therefore, by forming the trap protrusion 41 within this range, poisonous substances contained in the exhaust gas can be efficiently collected.

  The trap protrusion 41 is formed of a material having a property of adsorbing phosphorus and sulfur. Therefore, the trap protrusion 41 can be provided with an adsorption effect of phosphorus and sulfur, and the trapping performance of phosphorus and sulfur in the trap protrusion 41 can be improved.

  Further, the catalyst layer 5 is not formed on the surface of the trap protrusion 41 and the surface of the trap protrusion 41 is exposed. Therefore, the surface roughness of the trap protrusion 41 can be appropriately set without being affected by the surface roughness of the catalyst layer 5. Therefore, the surface roughness of the trap protrusion 41 can be set to a size suitable for the usage environment.

  Further, the catalyst layer 5 disposed on the upstream side of the trap protrusion 41 does not contain platinum and palladium but contains rhodium. In the honeycomb structure 1, the upstream side of the trap protrusion 41 has a larger amount of poisonous substances contained in the exhaust gas than the downstream side. Therefore, by using the catalyst layer 5 containing rhodium which does not contain platinum and palladium which are easily affected by poisoning substances and which is not easily affected by poisoning substances, it is possible to suppress a reduction in purification performance.

  Moreover, the catalyst layer 5 containing at least one of platinum, palladium, and rhodium is formed outside the range of 1.5 mm from the downstream end of the protrusion 4 to the downstream side. In the range from the downstream end of the protrusion 4 to 1.5 mm downstream, the purification action by the catalyst layer 5 is difficult to work due to the retention of exhaust gas. In this example, the catalyst layer is within this range. Not formed. Therefore, by forming the catalyst layer 5 containing at least one of platinum, palladium, and rhodium other than this range, the usage amount of the catalyst layer 5 can be reduced and the cost can be reduced.

  Further, a catalyst layer 5 including at least one of platinum, palladium, and rhodium is formed outside the range of 1.0 mm from the upstream end of the protrusion 4 to the upstream side. In the range of 1.0 mm from the upstream end of the protrusion 4 to the upstream side, the purification action by the catalyst layer 5 is difficult to work due to the retention of exhaust gas. Therefore, by forming the catalyst layer 5 containing rhodium outside this range, the amount of the catalyst layer 5 used can be reduced and the cost can be reduced.

  As described above, according to this example, it is possible to provide the honeycomb structure 1 that can improve the purification performance by suppressing the deterioration of the purification performance due to the poisoning substance.

(Example 2)
As shown in FIG. 7, in this example, the structure of the honeycomb structure 1 in Example 1 is partially changed.
In the catalyst layer 5 of the honeycomb structure 1, the first catalyst layer 51 is within a range of 1.5 mm from the upstream end 11 of the honeycomb structure 1 to the downstream end of the trap protrusion 41 on the downstream side. Thus, only the trap projection 41 is exposed from the first catalyst layer 51. The second catalyst layer 52 is formed on the downstream side of the downstream end portion of the first catalyst layer 51.

The honeycomb structure 1 of the present example includes, as the projecting portion 4, a downstream projecting portion 42 formed at a position downstream of the central portion 12 in the axial direction X.
The downstream protrusion 42 has the same configuration as the trap protrusion 41 shown in the first embodiment.
Other configurations are the same as those of the first embodiment. Of the reference numerals used in this example or the drawings relating to this example, the same reference numerals as those used in the first embodiment represent the same components as in the first embodiment unless otherwise specified.

As shown in this example, by forming the plurality of protrusions 4 of the trap protrusion 41 and the downstream protrusion 42, it is possible to suppress the formation of the boundary layer in a wide range, which is more preferable. The numbers of the trap protrusions 41 and the downstream protrusions 42 can be changed as appropriate.
Also in this example, the same effects as those of the first embodiment can be obtained.

Note that, when the plurality of protrusions 4 are formed in one cell hole 3 as in the honeycomb structure 1 of Example 2, a part of the protrusions 4 may be used as the trap protrusions 41, or all of them may be used as the trap protrusions 41. Also good.
Further, the configuration of the protrusion 4 may be changed for each cell hole 3.

(Example 3)
As shown in FIGS. 8 to 16, this example shows an example of the shapes of the trap protrusion 41 and the downstream protrusion 42 in the honeycomb structure 1 as viewed from the axial direction X.
Hereinafter, the trap protrusion 41 and the downstream protrusion 42 will be collectively referred to as the protrusion 4 as appropriate.
As shown in FIG. 8, the protrusion 4 of the honeycomb structure 1 is formed in a substantially rectangular shape along the three cell walls 2 among the six cell walls 2 forming the cell holes 3. One protruding portion 4 is disposed on the six cell walls 2 without being adjacent to each other. That is, the three protrusions 4 are arranged so as to be point-symmetrical with respect to the center point P of the cell hole 3 by 120 °.

As shown in FIG. 9, the protrusions 4 of the honeycomb structure 1 have a substantially fan shape, and are formed on all of the six apexes formed by the six cell walls 2.
As shown in FIG. 10, the protrusion 4 of the honeycomb structure 1 is formed at three vertices arranged by skipping one of the six vertices formed by the cell walls 2. That is, the three protrusions 4 are arranged so as to be point-symmetrical with respect to the center point P of the cell hole 3 by 120 °.

  As shown in FIG. 11, the protrusions 4 of the honeycomb structure 1 are formed at four of the six vertices formed by the cell walls 2. The protrusions 4 are formed in two of the three pairs of vertices facing each other, and have a line-symmetric shape with respect to a virtual line L connecting the vertices where the protrusions 4 are not formed. In addition, the same shape can be obtained when the protrusion 4 is disposed so as to be point-symmetrical with respect to the center point P by 180 °.

  As shown in FIGS. 12 and 13, the protrusions 4 of the honeycomb structure 1 are formed on three cell walls 2 among the six cell walls 2 forming the cell holes 3. The protrusion 4 is substantially L-shaped when viewed from the axial direction X. The protrusion 4 has a curved surface formed so as to go toward the center point P of the cell hole 3 while the amount of protrusion gradually increases from the upstream end toward the downstream side. In the cell hole 3, three corners where the protrusions 4 are formed and three corners where the protrusions 4 are not formed are alternately arranged. That is, the three protrusions 4 are arranged so as to be point-symmetric with respect to the center point P of the cell hole 3 by 120 °.

  As shown in FIG. 14, the protrusions 4 of the honeycomb structure 1 are formed on all of the six cell walls 2 that form the cell holes 3. One protrusion 4 is formed across two adjacent cell walls 2, and the protrusion 4 gradually increases from the upstream side toward the downstream side, and the center point of the cell hole 3 is increased. It has a curved surface formed to face P. The three protrusions 4 are arranged so as to be point-symmetric with respect to the center point P of the cell hole 3 at 120 °.

Here, a method of forming the protrusions 4 in the honeycomb structure 1 shown in FIGS. 12 to 14 will be described.
For the formation of the protrusion 4, a protrusion forming apparatus provided with a discharge nozzle for discharging the material slurry is used. The discharge nozzle is formed with a molding groove having a shape corresponding to the shape of the protrusion 4 on the outer peripheral side surface and a discharge port opened in the molding groove.

  First, the discharge nozzle is inserted inside the cell hole 3 that forms the protrusion 4. At this time, when viewed from the axial direction X, the central axis of the cell hole 3 and the central axis of the discharge nozzle are matched. Further, in the axial direction X, the forming groove is opposed to the formation position of the protrusion 4.

  Then, the material slurry is discharged into the forming groove from the discharge port, and the material slurry is filled into the forming groove. After the material slurry is solidified in the forming groove, the discharge nozzle is retracted from the cell hole 3. When the discharge nozzle is retracted, if the inner peripheral surface of the molding groove that forms the protrusion 4 on the tip side of the discharge nozzle interferes with the protrusion 4, this portion can be accommodated. The discharge nozzle can be easily retracted.

  The protrusions 4 of the honeycomb structure 1 shown in FIG. 15 are formed in an annular shape so as to protrude from the entire periphery of the inner peripheral surface of the cell hole 3. Therefore, the outer peripheral shape of the protrusion 4 is a hexagon that is the same shape as the outer peripheral shape of the cell hole 3. Further, the inner peripheral shape of the protrusion 4 is a hexagonal shape similar to the inner peripheral shape of the cell hole 3.

  A protrusion 4 of the honeycomb structure 1 shown in FIG. 16 is a modification of the honeycomb structure 1 shown in FIG. The outer peripheral shape of the protrusion 4 of the honeycomb structure 1 in FIG. 16 is a hexagon similar to that of the honeycomb structure 1 shown in FIG. 15, and the inner peripheral shape is circular.

  In the honeycomb structure 1 in which each protrusion 4 described above is formed, the configuration other than the above is the same as that of the first embodiment. Of the reference numerals used in this example or the drawings relating to this example, the same reference numerals as those used in the first embodiment represent the same components as in the first embodiment unless otherwise specified.

In the honeycomb structure 1, the protrusions 4 are formed so as to be point symmetric with respect to the center point P of the cell hole 3 or to be symmetric with respect to an imaginary line L passing through the center point P. In this case, a turbulent flow can be efficiently generated inside the cell hole 3 by the protrusion 4.
Moreover, in the protrusion part 4 of FIGS. 12-14, a turbulent flow can be formed so that the inside of the cell hole 3 may be stirred.
Also in this example, the same effects as those of the first embodiment can be obtained.

Example 4
This example shows an example of the shape of the protrusion 4 when viewed from a direction orthogonal to both the axial direction X and the protruding direction.
The protrusion 4 of the honeycomb structure 1 shown in FIG. 17A has a rectangular shape formed along the cell wall 2.
The protrusion 4 of the honeycomb structure 1 shown in FIG. 17B is formed by forming a corner on the tip side of the protrusion 4 in an arc shape. A curved upstream-side inclined surface 43 is formed at the upstream corner of the protrusion 4 so that the amount of protrusion increases from the upstream side toward the downstream side. In addition, a curved downstream inclined surface 44 is formed at the corner on the downstream side of the protrusion 4 so that the protruding amount increases from the downstream end toward the upstream side.
The protrusion 4 of the honeycomb structure 1 shown in FIG. 17C includes an upstream inclined surface 43 that is inclined so that the amount of protrusion increases from the upstream end of the protrusion 4 toward the downstream. . A downstream side of the downstream end portion of the upstream inclined surface 43 is formed along the cell wall 2.

The protrusion 4 of the honeycomb structure 1 shown in FIG. 18A has a full length from the upstream end to the downstream end of the protrusion 4, and the protrusion amount increases from the upstream to the downstream. And an upstream inclined surface 43 that is inclined to each other.
The protruding portion 4 of the honeycomb structure 1 shown in FIG. 18B has an upstream inclined surface 43 inclined so that the protruding amount increases from the upstream end of the protruding portion 4 toward the central position in the axial direction X. It has. Further, the protrusion 4 includes a downstream inclined surface 44 that is inclined so that the protrusion amount increases from the downstream end of the protrusion 4 toward the center position in the axial direction X.
The protruding portion 4 of the honeycomb structure 1 shown in FIG. 18C is a curved upstream inclined surface 43 formed so that the protruding amount increases from the upstream end of the protruding portion 4 toward the downstream side. It is. The curved surface is formed in a concave shape toward the inner side of the protrusion 4.

In the honeycomb structure 1 in which each protrusion 4 described above is formed, the configuration other than the above is the same as that of the first embodiment. Of the reference numerals used in this example or the drawings relating to this example, the same reference numerals as those used in the first embodiment represent the same components as in the first embodiment unless otherwise specified.
Moreover, the shape of the protrusion part 4 shown in this example shows an example, and may be other than these shapes. Moreover, you may combine the projection part 4 from which a shape differs.
Also in this example, the same effects as those of the first embodiment can be obtained.

DESCRIPTION OF SYMBOLS 1 Honeycomb structure 2 Cell wall 3 Cell hole 4 Protrusion part 41 Trap protrusion part 5 Catalyst layer

Claims (9)

A plurality of cell walls (2), a plurality of cell holes (3) surrounded by the plurality of cell walls (2), and a catalyst layer (5) covering the surface of the cell walls (2). A honeycomb structure (1) for purifying exhaust gas discharged from an internal combustion engine by circulating it through the plurality of cell holes (3),
At least a part of the plurality of cell holes (3) protrudes from the cell wall (2) toward the center of the cell hole (3) when viewed from the axial direction of the honeycomb structure (1). Protruding protrusion (4) is formed,
At least a part of the protrusion (4) is a trap protrusion (41) having a surface roughness larger than the surface roughness of the cell wall (2).   The honeycomb structure (1) according to claim 1, wherein the surface roughness of the trap protrusion (41) is larger than the surface roughness of the catalyst layer (5).   The honeycomb structure (1) according to claim 1 or 2, wherein the trap protrusion (41) is made of a porous material and has an average pore diameter of 10 nm to 1000 nm.   The distance between the upstream end (11) in the axial direction of the honeycomb structure (1) and the trap protrusion (41) is 2 mm to 30 mm. The honeycomb structure (1) according to claim 1.   The honeycomb structure (1) according to any one of claims 1 to 4, wherein the trap protrusion (41) is formed of a material having a property of adsorbing phosphorus and sulfur.   The surface of the trap projection (41) is not formed with the catalyst layer (5), and the surface of the trap projection (41) is exposed. The honeycomb structure (1) according to any one of the above.   The catalyst layer (5) disposed on the upstream side of the trap protrusion (41) does not contain platinum and palladium but contains rhodium. The honeycomb structure (1) described in 1.   The catalyst layer (5) containing platinum and palladium is formed outside a range of 1.5 mm from the downstream end of the protrusion (4) to the downstream side. The honeycomb structure (1) according to any one of?   The catalyst layer (5) containing platinum and palladium is formed outside a range of 1.0 mm from the upstream end of the protrusion (4) to the upstream side. The honeycomb structure (1) according to any one of -8.

Images