JP2016107236A - Honeycomb structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a honeycomb structure in which the early activation of the catalyst is possible and the purification capability can be improved.SOLUTION: The honeycomb structure 1 includes a plurality of cell walls 2, and a plurality of cell holes 3 surrounded by the plurality of cell walls 2, and is configured so as the exhaust gas discharged from an internal combustion engine to be passed through the plurality of cell holes 3. In 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 X of the honeycomb structure 1. The protrusion portion 4 is formed so as the heat capacity per unit volume to be smaller than the cell wall 2, and between the central part 11 of the whole length in axial direction X and an upstream side end part 12 which is the exhaust gas inflowing side end part, at least one is formed.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 A structure 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.

  An example of such a honeycomb structure is disclosed in Patent Document 1. The honeycomb structure of Patent Document 1 has a cell wall made of a ceramic material and a cell hole surrounded by the cell wall. On the cell wall, pores communicating between the cell holes are formed, and on the inner peripheral surface of the cell hole, a protrusion protruding to the inside of the cell hole is formed.

JP 2009-154148 A

However, the honeycomb structure of Patent Document 1 has the following problems.
In the honeycomb structure of Patent Document 1, both the cell walls and the protrusions are formed of the same material. Therefore, by forming the protrusions, the heat capacity in the honeycomb structure increases, and it takes time to raise the temperature of the honeycomb structure to the activation temperature. Thereby, the temperature rise of the honeycomb structure is delayed.

  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 early activation of a catalyst and improving purification performance.

One aspect of the present invention is a honeycomb structure having a plurality of cell walls and a plurality of cell holes surrounded by the plurality of cell walls, and through which the exhaust gas discharged from the internal combustion engine flows. Because
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,
It is formed so that the heat capacity per unit volume of the protrusion is equal to or less than the heat capacity per unit volume of the cell wall, and is a central part of the entire length in the axial direction and an end part on the side where exhaust gas flows. At least one honeycomb structure is formed between the upstream end and the upstream end.

The honeycomb structure includes the protrusions inside the cell holes. Therefore, early activation of the catalyst in the honeycomb structure is possible, and purification performance can be improved.
That is, in a honeycomb structure having no protrusion, when exhaust gas flows through the inside of the cell hole, a boundary layer in which the flow rate of the exhaust gas decreases on the surface of the cell wall forming the cell hole due to the influence of the viscosity of the exhaust gas. Is formed. 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. For this reason, the amount of heat received from the exhaust gas in the honeycomb structure is reduced, and the activation delay of the catalyst and the purification performance are reduced.

  In the honeycomb structure, by forming the protrusions inside the cell holes, the flow direction of the exhaust gas flowing through the cell holes can be changed, and a turbulent flow can be formed around the protrusions. . This turbulent flow destroys the boundary layer, thereby recovering the mass transfer rate of the exhaust gas in the cell hole and improving the contact efficiency between the exhaust gas and the honeycomb structure. As a result, early activation of the catalyst is enabled, exhaust gas is efficiently purified by the catalyst, and purification performance in the honeycomb structure can be improved.

  In addition, the contact efficiency between the exhaust gas and the honeycomb structure can be particularly greatly improved by the turbulent flow around the protrusions. For this reason, the catalyst disposed around the protrusions is activated by heating at an early stage, and the entire honeycomb structure can be activated quickly by utilizing reaction heat generated by the activation. it can.

  Moreover, the heat capacity per unit volume in the protrusion is smaller than the heat capacity per unit volume in the cell wall. Therefore, the amount of heat received at the protrusion can be reduced, and the temperature of the catalyst layer and the cell wall can be increased efficiently. Thereby, the said catalyst layer can be activated at an early stage.

  In addition, in the honeycomb structure, by providing the protrusions, the honeycomb structure has a special shape, for example, a structure that reduces the flow resistance by partially eliminating cell walls, and the like. Early activation and improvement in purification performance are possible. Therefore, a reduction in the surface area of the honeycomb structure can be suppressed, and an effective amount of catalyst for purification can be ensured. Therefore, the maximum purification performance in the honeycomb structure can be improved.

  As described above, according to the honeycomb structure, the catalyst can be activated at an early stage and the purification performance can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 3 is an explanatory view showing a honeycomb structure in Example 1. III-III arrow sectional drawing in FIG. IV-IV arrow sectional drawing in FIG. The graph which shows the change of the mass transfer rate in a honeycomb structure. FIG. 6 is an enlarged cross-sectional view showing a first shape example of a protrusion in Example 2. FIG. 9 is an enlarged cross-sectional view illustrating a second shape example of a protrusion in Example 2. FIG. 9 is an enlarged cross-sectional view showing a third shape example of the protrusion in Example 2. FIG. 9 is an enlarged cross-sectional view showing a fourth shape example of the protrusion in Example 2. FIG. 9 is an enlarged cross-sectional view illustrating a fifth shape example of a protrusion in Example 2. Explanatory drawing of the projection part in FIG. FIG. 10 is an enlarged cross-sectional view illustrating a sixth shape example of a protrusion in Example 2. FIG. 9 is an enlarged cross-sectional view showing a seventh shape example of the protrusion in Example 2. FIG. 10 is an enlarged cross-sectional view illustrating an eighth shape example of a protrusion in Example 2. In Example 3, (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 3, (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. Sectional drawing which shows the 1st example of a shape of the honeycomb structure in Example 4. FIG. Sectional drawing which shows the 2nd example of a shape of a honeycomb structure in Example 4. FIG. Sectional drawing which shows the 3rd example of a shape of a honeycomb structure in Example 4. FIG. FIG. 10 is an explanatory view showing an example of the shape of a protrusion in Example 4.

  In the honeycomb structure, the protrusion is preferably formed of a hydrocarbon adsorbing material. In this case, hydrocarbons can be adsorbed by the protrusions, and emissions during warming can be further reduced.

  Moreover, it is preferable that the catalyst layer is formed in the surface of the said projection part. In this case, the formation range of the catalyst layer in the honeycomb structure can be expanded to increase the supported amount of catalyst, or to reduce the thickness of the catalyst while maintaining the supported amount of catalyst. Thereby, the purification performance in the honeycomb structure can be improved.

  Moreover, it is preferable that the distance of the said projection part and the said upstream edge part is 2 mm-30 mm. In this case, before the boundary layer is fully developed in the cell hole, a turbulent flow can be formed by the protrusions, and the boundary layer can be destroyed. Thereby, the fall of the mass transfer rate in exhaust gas can be suppressed effectively, and the contact efficiency of exhaust gas and the said honeycomb structure can be improved more.

  In each of the cell holes, it is preferable that the protrusion protrudes from more than half of the cell walls among the plurality of cell walls surrounding the cell hole. In this case, the boundary layer formed on the surface of each cell wall surrounding the cell hole in which the projection is formed can be efficiently destroyed. Thereby, the fall of the mass transfer rate in exhaust gas can be suppressed effectively, and the contact efficiency of exhaust gas and a honeycomb structure can be improved more.

  Further, in each of the cell holes, it is preferable that the protrusion protrudes from more than half of the vertices formed at the intersections of the plurality of cell walls surrounding the cell hole. In this case, the boundary layer formed on the surface of each cell wall surrounding the cell hole in which the projection is formed can be efficiently destroyed. Thereby, the fall of the mass transfer rate in exhaust gas can be suppressed effectively, and the contact efficiency of exhaust gas and a honeycomb structure can be improved more.

  Moreover, it is preferable that the plurality of protrusions have the cell holes formed at positions shifted in the axial direction. In this case, it is possible to prevent the boundary layer from being formed again on the downstream side of the protrusion after the boundary layer is destroyed at the protrusion formed on the upstream side of the honeycomb structure. Thereby, the contact efficiency between the exhaust gas and the honeycomb structure can be improved in a wider range.

  Further, with respect to the protrusion formed in the cell hole provided at the radially inner position on the central axis side of the honeycomb structure, the protrusion is provided at a position radially outside the cell hole. It is preferable that the protrusion formed in the cell hole is formed on the upstream side in the axial direction. In the honeycomb structure, the flow rate of the exhaust gas in the cell hole provided at the radially outer position tends to be lower than the flow rate of the exhaust gas in the cell hole provided at the radially inner position. For this reason, in the cell hole provided at the radially outer position, a boundary layer is likely to be formed at the upstream position, and forming a protrusion at the upstream position suppresses the formation of the boundary layer. It is effective. Therefore, as described above, the formation of the boundary layer in each of the cell holes can be suppressed by adjusting the position of the protrusion in consideration of the radial position of the honeycomb structure. Thereby, the early activation and purification performance in the honeycomb structure can be further improved.

  Further, when viewed from the axial direction, it is preferable that at least one of the corners of the protrusions and the corners formed between the protrusions and the cell walls is formed by a curved surface. In this case, the flow resistance due to the formation of the protrusions can be reduced. Thereby, the early activation and purification performance in the honeycomb structure can be improved.

  Further, the protruding portion has an upstream inclined surface formed such that the protruding amount gradually increases from the upstream end portion of the protruding portion toward the downstream side, or the downstream end portion of the protruding portion. It is preferable that at least one of the downstream inclined surfaces formed so that the protruding amount gradually increases from the first side toward the upstream side is formed. In this case, an increase in flow resistance due to the formation of the protrusions can be suppressed, and pressure loss can be reduced. In addition, it is possible to suppress the exhaust gas from staying around the projection and effectively use the catalyst around the projection.

  Further, the flow resistance in the cell hole provided at a position radially outside the cell hole than the flow resistance in the cell hole provided in the radial inner position on the central axis side of the honeycomb structure. It is preferable that the protrusion is formed so as to be small. In this case, variation in the flow rate of the exhaust gas between the cell holes on the radially outer side of the honeycomb structure and the cell holes on the radially inner side can be reduced and made uniform. As a result, the honeycomb structure can be activated at an early stage and the purification performance can be improved.

Example 1
Examples of the honeycomb structure will be described with reference to FIGS.
As shown in FIGS. 1 and 2, the honeycomb structure 1 includes a plurality of cell walls 2 and a plurality of cell holes 3 surrounded by the plurality of cell walls 2. It is configured to distribute the exhausted exhaust gas.
As shown in FIGS. 3 and 4, the plurality of cell holes 3 are formed with protrusions 4 protruding from the cell walls 2 toward the center of the cell holes 3 when viewed from the axial direction X of the honeycomb structure 1. Has been. It is formed so that the heat capacity per unit volume of the protrusion 4 is equal to or less than the heat capacity per unit volume of the cell wall 2, and the center part 11 of the entire length in the axial direction X and the end part on the side where the exhaust gas flows in At least one upstream end portion 12 is formed.

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 7.
The exhaust pipe 6 includes an arrangement pipe 61 that contains the honeycomb structure 1, an upstream pipe 62 provided on the upstream side of the arrangement pipe 61, and a downstream pipe 63 provided on the downstream side.

  As shown in FIG. 2 to FIG. 4, the honeycomb structure 1 includes a cylindrical ceramic carrier formed by cell walls 2 arranged in a lattice shape, and a catalyst for purifying exhaust gas supported on the surface of the ceramic carrier. Layer 5. The cell wall 2 is made of a ceramic material, and in this example, cordierite having a porosity of 30% to 40% 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. Further, 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. 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 adopted, the honeycomb structure excellent in purification performance and productivity can be easily obtained. Can get to.

Protrusions 4 are provided in all the cell holes 3 constituting the honeycomb structure 1 of this example.
The protrusion 4 is made of zeolite which is a hydrocarbon adsorbing material, and the porosity thereof is 45% to 65%. Therefore, the protrusion 4 is formed with a porosity larger than the porosity of cordierite forming the cell wall 2. Thereby, even if the difference in specific heat of the material is taken into consideration, the heat capacity per unit volume in the protrusion 4 is smaller than that of the cell wall 2. In this example, the protrusions 4 are provided in all the cell holes 3 of the honeycomb structure 1, but the protrusions 4 may be provided only in some of the cell holes 3. Moreover, the protrusion part 4 may be formed so that it may become hollow other than a porous material.

  As shown in FIG. 3, a pair of protrusions 4 are formed in one cell hole 3. When viewed from the axial direction X, each protrusion 4 is disposed on each of the pair of cell walls 2 facing each other and the pair of cell walls 2 among the six cell walls 2 forming the cell hole 3. It is formed along the cell wall 2. Each of the pair of protrusions 4 has the same shape, and is arranged so as to be symmetric with respect to an imaginary 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. Moreover, the corner | angular part 41 in the external shape of the projection part 4 is formed by the smooth curved surface. In FIG. 3, the corner 44 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. 4, the protrusion 4 has a semi-elliptical cross-sectional shape. Therefore, the protrusion 4 is smoothly connected to the curved upstream-side inclined surface 42 and the upstream-side inclined surface 42 formed so that the protruding amount increases toward the downstream side from the upstream end 12, and the downstream side. And a curved downstream inclined surface 43 formed so that the amount of protrusion increases from the side end toward the upstream side. The protruding direction Z of the protrusion 4 is the normal direction of the cell wall 2 on which the protrusion 4 is formed. When the protrusion 4 is formed across the plurality of cell walls 2, each cell wall 2 in the normal direction.

The protrusion 4 is formed at a position upstream of the central portion 11 in the axial direction X of the honeycomb structure 1 and at a position where the distance S between the upstream end 12 and the protrusion 4 is 20 mm. . In this example, the arrangement positions of the protrusions 4 in the axial direction X are the same in all the cell holes 3.
The entire surface of the protrusion 4 is covered with the catalyst layer 5.

Next, the function and effect of this example will be described.
In the honeycomb structure 1, the flow direction of the exhaust gas flowing through the cell holes 3 can be changed to form a turbulent flow around the protrusion 4. This turbulent flow destroys the boundary layer, thereby recovering the mass transfer rate of the exhaust gas in the cell hole 3 and improving the contact efficiency between the exhaust gas and the honeycomb structure 1. As a result, the catalyst layer 5 can be activated early, and the exhaust gas can be efficiently purified by the catalyst layer 5 to improve the purification performance in the honeycomb structure 1.

  In particular, the contact efficiency between the honeycomb structure 1 and the exhaust gas can be greatly improved by forming a turbulent flow around the protrusion 4. Therefore, heat exchange between the honeycomb structure 1 and the cell wall 2 is performed particularly efficiently around the protrusion 4, and the catalyst layer 5 around the protrusion 4 can be activated early. And the whole honeycomb structure 1 can be activated rapidly using the reaction heat of the activated catalyst layer 5.

  Further, the heat capacity per unit volume in the protrusion 4 is smaller than the heat capacity per unit volume in the cell wall 2. Therefore, the amount of heat received at the protrusion 4 can be reduced, and the catalyst layer 5 can be activated efficiently.

  Moreover, in the honeycomb structure 1, by providing the protrusions 4, the honeycomb structure 1 has a special shape, for example, a catalyst layer without using a structure that partially eliminates cell walls and reduces flow resistance. 5 can be activated early and purification performance can be improved. Therefore, a decrease in the surface area of the honeycomb structure 1 can be suppressed, and the supported amount of the catalyst layer 3 in the honeycomb structure 1 can be ensured. Therefore, the maximum purification performance in the honeycomb structure 1 can be improved.

  Further, the protrusion 4 is made of a hydrocarbon adsorbing material. For this reason, hydrocarbons can be adsorbed by the protrusions 4, and emissions during warming can be further reduced.

  A catalyst layer 5 is formed on the surface of the protrusion 4. Therefore, the formation range of the catalyst layer 5 in the honeycomb structure 1 can be expanded, and the thickness of the catalyst layer 5 can be reduced. Furthermore, the speed in the space inside the protrusion 4 is reduced, and the desorption rate of hydrocarbons adsorbed on the protrusion 4 made of zeolite can be reduced. Therefore, the amount of hydrocarbons desorbed after the catalyst reaches its activity can be increased, and improvement in purification performance can be expected. Thereby, the purification performance in the honeycomb structure 1 can be improved.

Further, the distance between the protrusion 4 and the upstream end 12 is 20 mm. FIG. 5 is a graph showing a change in mass transfer rate in the vicinity of the surface of the cell wall 2 forming the cell hole 3, where the vertical axis is the mass transfer rate and the horizontal axis is from the upstream end 12 in the honeycomb structure 1 Distance S. Further, in solid lines G1 to G5, the formation density of the cell holes 3 in the honeycomb structure 1 is changed. The formation density is 1.86 pieces / mm ^{2 for} the solid line G1, 1.16 pieces / mm ^{2 for} the solid line G2, 0.93 pieces / mm ^{2 for} the solid line G3, and 0.62 pieces for the solid line G4. / Mm ² and the solid line G5 are 0.31 pieces / mm ² . As shown in FIG. 5, in any of the solid lines G <b> 1 to G <b> 5, the mass transfer rate is greatly reduced when the distance S between the protrusion 4 and the upstream end 12 is in the range of 2 mm to 30 mm. In other words, the boundary layer is developed within this range. Therefore, by forming the protrusion 4 within the range where the distance S between the protrusion 4 and the upstream end 12 is 2 mm to 30 mm, before the boundary layer is fully developed in the cell hole 3, the protrusion 4 Turbulence can be created and the boundary layer can be destroyed. It is possible to effectively suppress a decrease in mass transfer rate in the exhaust gas, and to further improve the contact efficiency between the exhaust gas and the honeycomb structure 1.

  Further, in each cell hole 3, the protruding portion 4 protrudes from more than half of the plurality of cell walls 2 surrounding the cell hole 3. Therefore, the boundary layer formed on the surface of each cell wall 2 surrounding the cell hole 3 in which the protrusion 4 is formed can be efficiently destroyed. Thereby, the fall of the heat transfer rate and substance transfer rate in exhaust gas can be suppressed effectively, and the contact efficiency of exhaust gas and honeycomb structure 1 can be improved more.

  Further, in each cell hole 3, the protrusion 4 protrudes from more than half of the vertices 21 formed at the intersections of the plurality of cell walls 2 surrounding the cell hole 3. Therefore, the boundary layer formed on the surface of each cell wall 2 surrounding the cell hole 3 in which the protrusion 4 is formed can be efficiently destroyed. Thereby, the fall of the mass transfer rate in exhaust gas can be suppressed effectively, and the contact efficiency of exhaust gas and honeycomb structure 1 can be improved more.

  Further, when viewed from the axial direction X, the corner 41 of the protrusion 4 is formed by a curved surface. Therefore, the flow resistance due to the formation of the protrusions 4 can be reduced. As a result, an increase in pressure loss in the honeycomb structure 1 can be suppressed and early activation and purification performance can be improved.

  Further, the protruding portion 4 includes an upstream inclined surface 42 formed so that the protruding amount gradually increases from the upstream end portion of the protruding portion 4 toward the downstream side, and the downstream end of the protruding portion 4. A downstream inclined surface 43 is formed so that the amount of protrusion gradually increases from the portion toward the upstream side. Therefore, it is possible to suppress an increase in flow resistance due to the formation of the protrusions 4 and to reduce pressure loss. Moreover, the stay of the exhaust gas around the protrusion 4 can be suppressed, and the mass transfer rate of the exhaust gas can be improved.

  As described above, according to the honeycomb structure 1 of the present example, it is possible to activate the catalyst early while suppressing an increase in pressure loss, and it is possible to improve the purification performance.

(Example 2)
This example shows an example of the shape of the protrusions in the honeycomb structure viewed from the axial direction X.
The protrusions 4 of the honeycomb structure 1 shown in FIG. 6 are formed in a substantially rectangular shape along the three cell walls 2 out of 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 120 ° point-symmetric with respect to the center point P of the cell hole.

The protrusions 4 of the honeycomb structure 1 shown in FIG. 7 have a substantially fan shape, and are formed on all of the six vertices 21 formed by the six cell walls 2.
The protrusions 4 of the honeycomb structure 1 shown in FIG. 8 are formed at three vertices 21 arranged by skipping one of the six vertices 21 formed by the cell walls 2. That is, the three protrusions 4 are arranged so as to be 120 ° point-symmetric with respect to the center point P of the cell hole 3.

  The protrusions 4 of the honeycomb structure 1 shown in FIG. 9 are formed on four of the six apexes 21 formed by the cell walls 2. The protrusions 4 are formed in two of the three pairs of vertices 21 facing each other, and have a line-symmetric shape with respect to a virtual line L connecting the vertices 21 where the protrusions 4 are not formed. Note that the same shape can be obtained when the protrusions 4 are arranged so as to be 180 ° symmetrical with respect to the center point P.

  The protrusions 4 of the honeycomb structure 1 shown in FIGS. 10 and 11 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 12 toward the downstream side. In the cell hole 3, three corners 41 where the protrusions 4 are formed and three corners 41 where the protrusions 4 are not formed are alternately arranged. That is, the three protrusions 4 are arranged so as to be 120 ° point-symmetric with respect to the center point P of the cell hole 3.

  The protrusions 4 of the honeycomb structure 1 shown in FIG. 12 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 120 ° symmetrical with respect to the center point P of the cell hole 3.

Here, a method for forming the protrusions 4 in the honeycomb structure 1 shown in FIGS. 10 to 12 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. 13 are formed in an annular shape so as to protrude from the entire circumference 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. 14 is a modification of the honeycomb structure 1 shown in FIG. 14 has a hexagonal shape similar to that of the honeycomb structure 1 shown in FIG. 13, 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 shown in FIGS. 10-12, 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 3)
This example shows an example of the shape of the protrusions in the honeycomb structure 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. 15A has a rectangular shape formed along the cell wall 2.
The protrusion 4 of the honeycomb structure 1 shown in FIG. 15B is formed by forming a corner 41 on the tip side of the protrusion 4 of FIG. 15A in an arc shape. The upstream corner portion of the protrusion 4 is a curved upstream inclined surface 42 formed so that the protrusion amount increases from the upstream end portion 12 toward the downstream side. Further, the downstream corner portion of the protrusion 4 is a curved downstream inclined surface 43 formed so that the amount of protrusion increases from the downstream end toward the upstream side.
The protrusion 4 of the honeycomb structure 1 shown in FIG. 15C includes an upstream inclined surface 42 that is inclined so that the protrusion amount increases from the upstream end of the protrusion 4 toward the downstream. . The downstream side of the downstream side end portion of the upstream inclined surface 42 is formed along the cell wall 2.

The protrusion 4 of the honeycomb structure 1 shown in FIG. 16A 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. An upstream inclined surface 42 is provided.
The protrusion 4 of the honeycomb structure 1 shown in FIG. 16B has an upstream inclined surface 42 that is inclined so that the protrusion amount increases from the upstream end 12 of the protrusion 4 toward the central position in the axial direction X. It has. In addition, the protruding portion 4 includes a downstream inclined surface 43 that is inclined so that the protruding amount increases from the downstream end portion of the protruding portion 4 toward the center position in the axial direction X.
The protrusion 4 of the honeycomb structure 1 shown in FIG. 16C is a curved upstream inclined surface 42 formed so that the protrusion amount increases from the upstream end 12 to the downstream of the protrusion 4. 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.
Also in this example, the same effects as those of the first embodiment can be obtained.

Example 4
This example shows an example in which the position of the protrusion in the honeycomb structure is changed in the axial direction X.
A honeycomb structure 1 shown in FIG. 17 includes a pair of protrusions 4 disposed so as to face each other in each cell hole 3. Further, with respect to the protrusions 4 formed in the cell holes 3 provided in the radially inner position on the central axis O side of the honeycomb structure 1, the cells provided in the radially outer position than this. The protrusion 4 formed in the hole 3 is formed on the upstream side in the axial direction X. In the honeycomb structure 1, in the cell hole 3 provided at the radially outer position, a boundary layer is more easily formed at the upstream position than the radially inner cell hole 3, and the protrusion is formed at the upstream position. Formation of 4 is effective in suppressing the formation of the boundary layer. Therefore, as described above, the formation of the boundary layer in each cell hole 3 can be effectively suppressed by adjusting the position of the protrusion 4 in consideration of the radial position of the honeycomb structure 1. Thereby, the early activation and purification performance in the honeycomb structure 1 can be further improved.

  The honeycomb structure 1 shown in FIG. 18 includes a plurality of a pair of protrusions 4 arranged so as to face each other in each cell hole 3. In the central cell hole 30 formed at the center of the honeycomb structure 1, n pair of protrusions 4 are arranged in the axial direction X. And the number of a pair of protrusion parts 4 arrange | positioned downstream is decreased as it goes outside from the center cell hole 30 of the honeycomb structure 1. As shown in FIG. In this example, n-1 pairs of protrusions 4 are formed in the cell hole 3 surrounding the center cell hole 30, and the cell provided at a position radially outside the cell hole 3. In the hole 3, a pair of n−2 protrusions 4 is formed. That is, as it goes radially outward, the number of the pair of protrusions 4 in the cell hole 3 decreases by one from the number of the pair of protrusions 4 in the cell hole 3 provided on the inner side. Further, the protrusion 4 is not formed in the cell hole 3 formed on the outermost periphery of the honeycomb structure 1.

  In this case, the flow resistance in the cell holes 3 of the honeycomb structure 1 can be reduced from the central axis O side of the honeycomb structure 1 toward the radially outer side. This increases the flow rate of the exhaust gas in the radially outer cell holes 3 where the exhaust gas flow rate is likely to decrease, and between the radially outer cell holes 3 and the radially inner cell holes 3 of the honeycomb structure 1. The variation in the flow rate of the exhaust gas can be reduced and the flow rate can be made uniform. Therefore, the honeycomb structure 1 can be activated at an early stage and the purification performance can be improved.

  In addition, the arrangement positions in the axial direction X of the protrusions 4 arranged on the most upstream side in each cell hole 3 are all formed at the same position. Further, the protrusion 4 disposed on the downstream side of the protrusion 4 disposed on the most upstream side is disposed so as to be positioned upstream as it goes radially outward.

A honeycomb structure 1 shown in FIG. 19 is a modification of the honeycomb structure 1 shown in FIG.
In the axial direction X, the honeycomb structure 1 is also arranged so that the protrusions 4 arranged on the most upstream side in each cell hole 3 are arranged on the upstream side in the radial direction.

  When the plurality of protrusions 4 are formed in the axial direction X in one cell hole 3 as in the honeycomb structure 1 shown in FIGS. 17 to 19, when viewed from the axial direction X, the upstream side It is preferable that the formation positions of the protrusions 4 disposed on the side and the protrusions 4 disposed on the downstream side are different. For example, as shown in FIG. 20, the protrusion 402 disposed on the downstream side is symmetrical with respect to the center point P of the cell hole 3 with respect to the protrusion 401 disposed on the upstream side. It can arrange | position in the position which becomes. Moreover, the protrusion part 4 shown in FIGS. 6-10 in Example 2 can also be combined. In this case, the boundary layer on the surface of the cell wall 2 can be destroyed more efficiently.

  Further, by forming the plurality of protrusions 4 at positions shifted in the axial direction X, the protrusions 4 formed on the upstream side of the honeycomb structure 1 are formed again on the downstream side after breaking the boundary layer. This can be suppressed. Thereby, the contact efficiency between the exhaust gas and the honeycomb structure 1 can be improved in a wider range.

  In addition, the honeycomb structure 1 shown in Examples 1 to 4 shows an example, and can have various shapes other than these.

DESCRIPTION OF SYMBOLS 1 Honeycomb structure 2 Cell wall 3 Cell hole 4 Protrusion part

Claims (11)

It has a plurality of cell walls (2) and a plurality of cell holes (3) surrounded by the plurality of cell walls (2), and exhaust gas discharged from the internal combustion engine is put into the plurality of cell holes (3). A honeycomb structure (1) to be circulated and purified,
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,
The protrusion (4) is formed so that the heat capacity per unit volume is not more than the heat capacity per unit volume of the cell wall (2),
At least one is formed between the central part (11) of the full length in the axial direction of the honeycomb structure (1) and the upstream end part (12) which is the end part on the exhaust gas inflow side. A honeycomb structure (1) characterized by the above.   The honeycomb structure (1) according to claim 1, wherein the protrusion (4) is made of a hydrocarbon adsorbing material.   The honeycomb structure (1) according to claim 1 or 2, wherein a catalyst layer (5) is formed on a surface of the protrusion (4).   The honeycomb structure (1) according to any one of claims 1 to 3, wherein a distance between the protrusion (4) and the upstream end (12) is 2 mm to 30 mm.   In each cell hole (3), among the plurality of cell walls (2) surrounding the cell hole (3), the protrusion (4) protrudes from more than half of the cell walls (2). The honeycomb structure (1) according to any one of claims 1 to 4, characterized in that:   In each cell hole (3), the protrusion (4) protrudes from more than half of the vertices formed at the intersections of the plurality of cell walls (2) surrounding the cell hole (3). The honeycomb structure (1) according to any one of claims 1 to 5, wherein the honeycomb structure (1) is provided.   The honeycomb structure (1) according to any one of claims 1 to 6, wherein the plurality of protrusions (4) have the cell holes (3) formed at positions shifted in the axial direction. 1).   From the cell hole (3) to the protrusion (4) formed in the cell hole (3) provided at the radially inner position on the central axis side of the honeycomb structure (1). The protrusion (4) formed in the cell hole (3) provided at a position radially outside is also formed on the upstream side in the axial direction. The honeycomb structure (1) according to any one of the above.   When viewed from the axial direction, at least one of the corner (41) of the projection (4) and the corner (44) formed between the projection (4) and the cell wall (2). The honeycomb structure (1) according to any one of claims 1 to 8, wherein is formed by a curved surface.   The protrusion (4) has an upstream inclined surface (42) formed so that the protrusion amount gradually increases from the upstream end of the protrusion (4) toward the downstream side, or the protrusion The downstream inclined surface (43) formed so that the amount of protrusion gradually increases from the downstream end of the portion (4) toward the upstream side is formed. The honeycomb structure (1) according to any one of 1 to 9.   It is provided at a position radially outside the cell hole (3) with respect to the flow resistance in the cell hole (3) provided at a position on the radially inner side on the central axis side of the honeycomb structure (1). The honeycomb structure (1) according to any one of claims 1 to 10, wherein the protrusion (4) is formed so as to reduce a flow resistance in the cell hole (3). .

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