JP2009101344A - Exhaust gas cleaning filter and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas cleaning filter capable of suppressing an excessive temperature rise of the exhaust gas cleaning filter when collected PM is combusted and preventing thermal damages such as melt loss and cracks and a method for manufacturing the same. <P>SOLUTION: The exhaust gas cleaning filter 1 includes a cell 4 where a downstream end 202 is blocked by a plug section 6, an inflow side cell 41 that allows the exhaust gas G to flow in and an upstream end 201 are blocked by the section 6, an exhaust side cell 42 that exhausts the gas G and end 202 are blocked by the section 6, a hyperthermally capacious powder is filled in a portion upstream the section 6 and is calcined by sintering and has a thermally relaxing cell 43 where a thermally relaxing layer 431 is welded to a base material 2 and is formed thereby. The heat capacity of the layer 431 is bigger than those of the cell 41 and cell 42 and a difference in coefficient of thermal expansion between the layer 431 and material 2 is 2×10<SP>-6</SP>/°C or less. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification filter that collects particulates in exhaust gas discharged from an internal combustion engine and purifies the exhaust gas, and a method for manufacturing the same.

2. Description of the Related Art Conventionally, an exhaust gas purification filter that collects particulates (hereinafter simply referred to as PM) in exhaust gas discharged from an internal combustion engine and purifies the exhaust gas is known.
This exhaust gas purification filter has a honeycomb structure as a base material in which porous cell walls are arranged in a honeycomb shape and a large number of cells are provided. Of the above-mentioned cells, the downstream end of the inflow side cell for allowing exhaust gas to flow in and the upstream end of the exhaust side cell for discharging exhaust gas that has passed through the porous cell wall are generally blocked by a plug. It is.

When purifying exhaust gas using the exhaust gas purification filter, the exhaust gas flowing into the inflow side cell passes through the porous cell wall and moves to the exhaust side cell. At this time, PM in the exhaust gas is collected in a large number of pores existing on the cell wall, and the exhaust gas is purified. Thereafter, the purified exhaust gas is discharged from the discharge side cell.
The collected PM is periodically burned and removed. Thereby, the collecting function of the porous cell wall is regenerated. Various known methods have already been proposed as the combustion removal method. For example, there is a method in which the catalyst is supported on the surface of the cell wall, and the exhaust gas purification filter is heated by causing the catalyst reaction to generate heat to burn PM.

  By the way, when the PM collected by the exhaust gas purification filter is burned and removed, the generated heat of combustion may cause an excessive temperature rise, which may cause problems such as catalyst combustion and deterioration, and base material melting and cracking. was there. In particular, the greater the amount of PM collected, the greater the heat of combustion, which increases the risk of the above problems occurring.

Therefore, Patent Document 1 proposes an exhaust gas particulate purification filter that provides a non-capturing region in which PM is not collected by the cell wall between the central region and the outer peripheral region of the filter and suppresses thermal damage to the filter. Has been.
Further, Patent Document 2 proposes an exhaust gas purification apparatus for an internal combustion engine in which a heat absorption part having a larger heat capacity than other parts is provided at the downstream end of the filter to prevent catalyst deterioration and filter damage.

Patent Document 3 proposes a honeycomb structure in which a flow path separator, which is a layer in which exhaust gas does not substantially flow or significantly hinders the flow, is proposed.
Further, in Patent Document 4, in addition to the first sealing member, at least 0.2 with respect to the area of the cross section perpendicular to the central axis in the central portion of 2/3 from the central axis to the outer peripheral surface of the honeycomb structure. A honeycomb filter further comprising a second sealing member disposed so as to seal an opening corresponding to ˜2.5% and a manufacturing method thereof have been proposed.

Japanese Patent Laid-Open No. 5-44442 Japanese Patent Laying-Open No. 2005-2972 JP 2003-161136 A JP 2005-169308 A

However, Patent Document 1 can suppress the local excessive temperature rise of the filter by maintaining the low temperature in the non-collecting region. However, when the amount of accumulated PM is large, when the PM is burned, The non-collection region becomes a high temperature instantly, and the excessive temperature rise of the filter cannot be sufficiently suppressed.
In Patent Document 2, the heat capacity can be increased by providing the heat absorption part. However, when the PM is burned, the cell provided with the heat absorption part also becomes high temperature, and the excessive temperature rise of the filter is sufficiently increased. It cannot be suppressed.
Similarly, in Patent Document 3 and Patent Document 4, excessive temperature rise of the filter cannot be sufficiently suppressed.

  The present invention has been made in view of such conventional problems, and suppresses overheating of the exhaust gas purification filter when burning the collected PM, and prevents thermal damage such as melting and cracking. It is an object of the present invention to provide an exhaust gas purification filter that can perform the above-described process and a method for manufacturing the same.

A first invention includes a base material made of a ceramic honeycomb structure having an outer peripheral wall, a cell wall disposed in a honeycomb shape in the outer peripheral wall, and a large number of cells partitioned in the cell wall. Exhaust gas purification filter
The cell has an inflow side cell which becomes an inflow side passage through which the downstream end is closed by a plug portion and into which exhaust gas flows.
A discharge side cell which becomes an exhaust side passage for closing the upstream end with the plug portion and exhausting the exhaust gas passing through the cell wall from the inflow side cell;
Thermal relaxation formed by closing the downstream end with the plug portion, filling the portion upstream of the plug portion with high heat capacity powder, sintering by firing and welding to the base material A thermal relaxation cell provided with a layer,
The heat capacity of the heat relaxation layer is larger than the heat capacity of the inflow side cell and the discharge side cell, and the difference in thermal expansion coefficient between the heat relaxation layer and the base material is 2 × 10 ⁻⁶ / ° C. or less. The exhaust gas purification filter is characterized in that it exists (claim 1).

  In the exhaust gas purification filter of the present invention, the cell includes an inflow side cell, an exhaust side cell, and a heat relaxation cell. The heat relaxation cell has a heat relaxation layer filled with a high heat capacity powder, and the heat capacity of the heat relaxation layer is larger than the heat capacities of the inflow side cell and the discharge side cell. Therefore, the combustion heat generated when the collected PM is burned and removed can be absorbed by the heat relaxation layer of the heat relaxation cell. Thereby, it can suppress that the said exhaust gas purification filter will be in an overheated state, and can prevent the thermal damages, such as a melting loss and a crack of the said base material.

Further, the heat relaxation layer is formed by filling the high heat capacity powder and sintering it by firing and welding it to the base material. That is, the heat relaxation layer is formed integrally with the base material. Therefore, even during use of the exhaust gas purification filter, the heat relaxation layer does not peel off or fall off from the base material, and sufficient seismic resistance can be ensured.
Further, the difference in thermal expansion coefficient between the heat relaxation layer and the substrate is as small as 2 × 10 ⁻⁶ / ° C. or less. Therefore, it is possible to suppress thermal stress between the heat relaxation layer and the base material, and to sufficiently secure thermal reliability such as thermal shock resistance in the exhaust gas purification filter.

  Moreover, the said heat relaxation cell is provided with the said plug part only in the downstream end. Since the heat relaxation layer is formed integrally with the base material, for example, in order to prevent the high heat capacity powder constituting the heat relaxation layer from leaking out of the heat relaxation cell, The plugs may not be provided at both ends of the heat relaxation cell. Therefore, when manufacturing the exhaust gas purification filter, it is possible to reduce the number of processes and reduce the manufacturing cost.

  Thus, according to the present invention, there is provided an exhaust gas purification filter capable of suppressing excessive temperature rise of the exhaust gas purification filter when burning the collected PM and preventing thermal damage such as melting and cracking. can do.

According to a second aspect of the present invention, in the method for producing the exhaust gas purification filter of the first aspect,
A molding step of extruding a ceramic material to produce the substrate made of a honeycomb structure; and
A drying step of drying the substrate;
A first firing step of firing the substrate;
Of the opening of the cell at the upstream end and the downstream end of the base material, a plugging step of disposing a plugging slurry in a portion forming the plug portion;
Among the cells in which the plugging slurry is disposed at the downstream end, a filling step of filling the high heat capacity powder on the upstream side of the plugging slurry in the cell to be the heat relaxation cell;
The base material filled with the high heat capacity powder is fired by firing the plugging slurry, and the plug portion is formed and the high heat capacity powder is sintered to be welded to the base material. And a second firing step for forming the heat relaxation layer. (Claim 7)

  As described above, the production method of the present invention performs the molding step, the drying step, the first firing step, the plugging step, the filling step, and the second firing step. Thus, the exhaust gas purification filter according to the first aspect of the present invention can be obtained, which can suppress excessive temperature rise of the exhaust gas purification filter when burning the collected PM and prevent thermal damage such as melting and cracking. Can do.

  Further, in the production method of the present invention, in the filling step, among the cells in which the plugging slurry is disposed at the downstream end, the plugging slurry in the cell serving as the heat relaxation cell is located upstream of the plugging slurry. After filling the high heat capacity powder, the plugging slurry is not disposed at the upstream end. In other words, the plugs are not provided at both ends of the cell serving as the heat relaxation cell, but are provided only at the downstream end.

  This is because, in the firing step (second firing step) after the filling step, the high heat capacity powder is sintered and welded to the base material to form the heat relaxation layer, and the heat relaxation This is because the layer and the substrate are integrally formed. For example, in order to prevent the high heat capacity powder constituting the heat relaxation layer from leaking out of the heat relaxation cell, the plug portions need not be provided at both ends of the heat relaxation cell. Therefore, the process can be reduced, and the manufacturing cost can be reduced.

  As described above, according to the manufacturing method of the present invention, the exhaust gas purification that can suppress the excessive temperature rise of the exhaust gas purification filter when burning the collected PM and prevent thermal damage such as melting and cracking can be prevented. A filter can be obtained. And the reduction of a process can be implement | achieved and manufacturing cost reduction can be aimed at.

According to a third aspect of the present invention, there is provided a method for producing the exhaust gas purification filter according to the first aspect of the present invention.
A molding step of extruding a ceramic material to produce the substrate made of a honeycomb structure; and
A drying step of drying the substrate;
Of the opening of the cell at the upstream end and the downstream end of the base material, a plugging step of disposing a plugging slurry in a portion forming the plug portion;
A first firing step for firing the base material on which the plugging slurry is disposed, and simultaneously forming the plug portion;
Among the cells in which the plug portion is formed at the downstream end, a filling step of filling the high heat capacity powder on the upstream side of the plug portion in the cell to be the heat relaxation cell,
A second firing step of firing the base material filled with the high heat capacity powder and sintering the high heat capacity powder to form a heat relaxation layer by welding to the base material. An exhaust gas purification filter manufacturing method characterized in that (claim 8).

As described above, the production method of the present invention performs the molding step, the drying step, the plugging step, the first firing step, the filling step, and the second firing step. Thus, the exhaust gas purification filter according to the first aspect of the present invention can be obtained, which can suppress excessive temperature rise of the exhaust gas purification filter when burning the collected PM and prevent thermal damage such as melting and cracking. Can do.
In addition, since the plug portions are not provided at both ends of the cell serving as the heat relaxation cell, but the plug portions are provided only at the downstream ends, it is possible to reduce the number of processes and reduce the manufacturing cost. it can.

Moreover, in the manufacturing method of this invention, after the said plugging process, the 1st baking (1st baking process) is performed, and the said base material and the said plugging slurry arrange | positioned at this base material are baked simultaneously. . Therefore, compared with the case where the base material and the plugging slurry are separately fired, the firing step can be omitted once, and the cost can be greatly reduced.
In addition, after firing the base material and the plugging slurry (first firing step), the high heat capacity powder is used for firing the second high heat capacity powder (second firing step) filled in the base material. The quality of the heat relaxation layer can be ensured without mixing different materials (for example, the material constituting the base material and the plug portion) during the sintering of the body.

According to a fourth aspect of the present invention, there is provided a method for producing the exhaust gas purification filter of the first aspect.
A molding step of extruding a ceramic material to produce the substrate made of a honeycomb structure; and
A drying step of drying the substrate;
A first firing step of firing the substrate;
Of the opening of the cell at the upstream end and the downstream end of the base material, a plugging step of disposing a plugging slurry in a portion forming the plug portion;
Firing the base material on which the plugging slurry is disposed, and forming a plug part; a second firing step;
Among the cells in which the plug portion is formed at the downstream end, a filling step of filling the high heat capacity powder on the upstream side of the plug portion in the cell to be the heat relaxation cell,
A third firing step in which the base material filled with the high heat capacity powder is fired, and the high heat capacity powder is sintered to be welded to the base material to form the heat relaxation layer. An exhaust gas purification filter manufacturing method characterized in that (claim 9).

As described above, the manufacturing method of the present invention performs the molding step, the drying step, the first firing step, the plugging step, the second firing step, the filling step, and the third firing step. Thus, the exhaust gas purification filter according to the first aspect of the present invention can be obtained, which can suppress excessive temperature rise of the exhaust gas purification filter when burning the collected PM and prevent thermal damage such as melting and cracking. Can do.
In addition, since the plug portions are not provided at both ends of the cell serving as the heat relaxation cell, but the plug portions are provided only at the downstream ends, it is possible to reduce the number of processes and reduce the manufacturing cost. it can.

In the manufacturing method of the present invention, the first baking (first baking step) is performed after the drying step, the second baking (second baking step) is performed after the plugging step, and the filling is performed. A third firing (third firing step) is performed after the step.
That is, the air permeability in the base material (honeycomb structure) during firing can be improved as compared with the case where the first firing of the base material is performed after the plugging slurry is disposed. Therefore, a temperature difference generated in the base material during firing can be reduced, firing cracks can be suppressed, and firing yield can be improved.
In addition, after firing the base material and the plugging slurry (first firing step, second firing step), firing the high heat capacity powder filled in the base material (third firing step) The quality of the heat relaxation layer can be ensured without mixing different materials (for example, the material constituting the base material and the plug portion) during the sintering of the high heat capacity powder.

In the first invention, the difference in thermal expansion coefficient between the thermal relaxation layer and the substrate is 2 × 10 ⁻⁶ / ° C. or less. This includes the case where the thermal relaxation layer has a larger thermal expansion coefficient than the base material and the case where the base material has a larger thermal expansion coefficient than the thermal relaxation layer.

The heat capacity of the heat relaxation layer is preferably 1.30 (J / cc · K) or more.
When the heat capacity of the thermal relaxation layer is less than 1.30 (J / cc · K), the thermal relaxation layer can sufficiently absorb the combustion heat generated when the collected PM is burned and removed. It may not be possible.

The heat capacity (J / cc · K) of the heat relaxation layer is the product of the specific heat (J / cc · K), specific gravity (g / cc) and filling rate (no unit) of the high heat capacity powder to be filled. Can be expressed as The specific heat of the heat relaxation layer can be measured by a laser flash method.
Further, the heat capacities of the inflow side cell and the discharge side cell can be obtained in the same manner as the heat relaxation layer.

Moreover, it is preferable that the thermal expansion coefficient of the thermal relaxation layer is 2.5 × 10 ⁻⁶ / ° C. or less.
When the thermal expansion coefficient of the thermal relaxation layer exceeds 2.5 × 10 ⁻⁶ / ° C., thermal stress between the thermal relaxation layer and the substrate is suppressed, and the thermal shock resistance in the exhaust gas purification filter There is a possibility that sufficient thermal reliability cannot be ensured.

In addition, the occupation ratio of the heat relaxation cell is 5 to 30% with respect to the area of the region where the distance from the center is 80% or less of the distance from the center to the outer peripheral surface in the radial cross section of the base material. (Claim 4).
When the occupation rate of the heat relaxation cell is less than 5%, there is a possibility that the heat of combustion generated when the collected PM is burned and removed cannot be sufficiently absorbed by the heat relaxation layer. On the other hand, when it exceeds 30%, there is a possibility that a problem of an increase in pressure loss may occur due to an increase in the thermal relaxation cell in which the exhaust gas is not substantially passed.

Further, the cell wall is arranged in a quadrangular lattice shape by a cell wall formed in one direction and a cell wall formed in the other direction orthogonal to the cell wall. In the radial cross section of the base material, the heat formed along the one cell wall is disposed only in a region where the distance from the center is 80% or less of the distance from the center to the outer peripheral surface. It is preferable that the relaxation cells and the thermal relaxation cells formed along the other cell wall are arranged in a quadrangular lattice shape.
In this case, while suppressing the reduction of the filtration area (the area of the cell wall through which the exhaust gas can pass from the inflow side cell to the exhaust side cell) due to the formation of the thermal relaxation cell, the exhaust gas purification filter The effect of suppressing excessive temperature rise can be obtained efficiently.

  As an example of the above configuration, as shown in FIG. 5A of Example 1 described later, the cell wall is formed in one direction and the cell is formed in the other direction orthogonal to the cell wall. If the wall is disposed in a quadrangular lattice shape, the heat is applied to the cell located between the discharge side cell and the discharge side cell along the one cell wall or the other cell wall. It is effective to arrange relaxation cells.

Moreover, the arrangement | positioning of the said thermal relaxation cell can be made into various arrangement | positioning patterns like FIG.3 (b) of Example 1 mentioned later and FIG.6 (a)-(d).
Moreover, it is preferable that the said heat relaxation cell exists uniformly and uniformly in the radial direction cross section of the said base material.

In addition, since the exhaust gas does not substantially pass through the heat relaxation cell, it is preferable to dispose the heat relaxation cell while ensuring a filtration area as large as possible in order to suppress an increase in pressure loss.
For example, the thermal relaxation cell is preferably disposed in a region where the distance from the center is 80% or less of the distance from the center to the outer peripheral surface in the radial cross section of the base material.
In this case, it is possible to efficiently obtain the effect of suppressing the excessive temperature rise of the exhaust gas purification filter while suppressing the reduction of the filtration area due to the formation of the heat relaxation cell, that is, sufficiently securing the filtration area.

The heat relaxation cell is preferably disposed at least in a region where the distance from the center is 65% or less of the distance from the center to the outer peripheral surface.
When the heat relaxation cell exists only in a region where the distance from the center is less than 65% of the distance from the center to the outer peripheral surface, the region outside the region where the heat relaxation cell exists In this case, an excessive temperature rise may occur, which may cause thermal damage to the exhaust gas purification filter.

The high heat capacity powder preferably contains one or more of aluminum titanate, silicon carbide (silicon carbide), silicon nitride, cordierite, mullite, alumina, and spinel (Claim 6).
In this case, the combustion heat generated when the collected PM is burned and removed can be sufficiently absorbed by the heat relaxation layer composed of the high heat capacity powder.

  As the material constituting the substrate, cordierite, aluminum titanate, silicon carbide (silicon carbide), mullite, alumina, or the like can be used.

In the second to fourth inventions, in the filling step, the high heat capacity powder is filled from the opening at the upstream end of the cell to be the heat relaxation cell with the upstream end of the base material facing upward. (Claim 10).
In this case, the high heat capacity powder can be easily and surely filled into the cell serving as the heat relaxation cell.

In the firing step performed after the filling step, it is preferable to fire the base material with the upstream end of the base material facing upward.
In this case, the high heat capacity powder can be sintered and welded to the substrate while the high heat capacity powder is firmly filled.

Example 1
An exhaust gas purification filter according to an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the exhaust gas purification filter 1 of this example includes an outer peripheral wall 5, a cell wall 3 disposed in a honeycomb shape in the outer peripheral wall 5, and a large number of cells partitioned in the cell wall 3. 4 is provided with a substrate 2 made of a honeycomb structure.

The base material 2 is comprised from the ceramic which has a cordierite as a main component, and is exhibiting the cylindrical shape. The base material 2 has a diameter of 160 mm and a length of 100 mm.
The cell wall 3 is formed with a large number of pores for collecting PM in the passing exhaust gas G. The cell wall 3 has a thickness of 0.3 mm.

  Further, as shown in FIG. 2, the cell 4 has the downstream end 202 closed by the plug portion 6, and the inlet side cell 41 serving as the inflow side passage through which the exhaust gas G flows and the upstream end 201 closed by the plug portion 6. The discharge side cell 42 serving as a discharge side passage for discharging the exhaust gas G that has passed through the cell wall 3 from the inflow side cell 41 and the downstream end 202 are closed by the plug portion 6, and upstream of the plug portion 6. And a thermal relaxation cell 43 provided with a thermal relaxation layer 431 on the side portion.

The heat relaxation layer 431 is formed by filling a high heat capacity powder, sintering it by firing, and welding it to the base material 2. In this example, aluminum titanate was used as the high heat capacity powder.
Similarly to the base material 2, the plug portion 6 is made of ceramics whose main component is cordierite.

Further, as shown in FIG. 3A, when the base material 2 is viewed in the axial direction from the upstream side, the cells 4 (inflow side cells 41, discharge side cells 42, and thermal relaxation cells 43) are rectangular latticed cells. The wall 3 is surrounded.
Moreover, the plug part 6 is arrange | positioned by the so-called checkered pattern every other cell 4 in the vertical and horizontal directions. Further, in the cell 4 where the plug portion 6 is not disposed, the thermal relaxation cell 43 is disposed with a certain regularity.

In this example, as shown in FIG. 5A, the cell wall 3 is formed in a quadrangular lattice shape by a cell wall 31 formed in one direction and a cell wall 32 formed in the other direction orthogonal to the cell wall 31. It is arranged.
The thermal relaxation cell 43 is arranged in the cell 4 positioned between the discharge side cell 42 and the discharge side cell 42 along one cell wall 31 or the other cell wall 32.

Further, as shown in FIG. 3B, the thermal relaxation cells 43 are regularly arranged in the vertical and horizontal directions and arranged in a quadrangular lattice like a grid. FIG. 3B shows a simplified arrangement pattern of the thermal relaxation cells 43.
Further, as shown in the figure, in the thermal relaxation cell 43, the distance (n) from the center O is 80% or less of the distance (m) from the center O to the outer peripheral surface 51 in the radial cross section of the substrate 2. It exists in the region (dotted line A in FIG. 3B). Note that n = 0.8 × m.
In addition, the occupation ratio of the thermal relaxation cell 43 is such that the distance from the center O is 80% or less of the distance from the center O to the outer peripheral surface 51 in the radial section of the substrate 2 (dotted line in FIG. 3B). 14% with respect to the area of the area inside A).

Further, in the exhaust gas purification filter 1 of this example, the heat capacity of the heat relaxation layer 431 is larger than the heat capacities of the inflow side cell 41 and the exhaust side cell 42.
In this example, the heat capacity of the heat relaxation layer 431 is 1.4 (J / cc · K). The heat capacity of the inflow side cell 41 including the cell wall 4 is 0.52 (J / cc · K), and the heat capacity of the discharge side cell 42 including the cell wall 4 is 0.52 (J / cc · K). ).

Further, the difference in thermal expansion coefficient between the thermal relaxation layer 431 and the substrate 2 is 2 × 10 ⁻⁶ / ° C. or less.
In this example, the thermal expansion coefficient of the thermal relaxation layer 431 is 2.5 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of the substrate 2 is 0.5 × 10 ⁻⁶ / ° C. The difference in thermal expansion coefficient between them is 2 × 10 ⁻⁶ / ° C.

Next, the manufacturing method of the exhaust gas purification filter 1 of this example is demonstrated.
In this example, as shown in FIG. 7A, a ceramic material is extruded to form a substrate made of a honeycomb structure, a drying step of drying the substrate, and a first baking of the substrate. In the firing step, the plugging step of disposing the plugging slurry in the portion of the cell opening at the upstream end and the downstream end of the base material where the plug portion is formed, and the cell serving as the heat relaxation cell, A filling step for filling the high heat capacity powder upstream of the plugging slurry disposed, and firing the base material filled with the high heat capacity powder by placing the plugging slurry to form the plug portion At the same time, a high heat capacity powder was sintered to be welded to the base material, and a second firing step of forming a heat relaxation layer was sequentially performed to manufacture an exhaust gas purification filter.
This will be described in detail below.

First, containing kaolin, fused silica, aluminum hydroxide, alumina, talc, pore former (carbon), and finally SiO ₂ Chemical composition in _{weight: 45~55%, Al 2 O 3} : 33~ 42%, MgO: Mixing raw material powder composed of cordierite consisting of 12-18% as a main component with water, adding an organic binder and kneading to obtain a clay-like ceramic material It was.

Next, the clay-like ceramic material was extruded by an extruder and cut to a desired length to produce a substrate made of a honeycomb structure (molding step).
In this example, a clay ceramic material was formed into a honeycomb structure having a diameter of 168 mm, a length of 101 mm, a cell wall thickness of 0.31 mm, and a cell count of 310 mesh. This size is just an example, and other sizes can be adopted depending on the application.

  Next, after drying the substrate (drying step), the substrate was held at 1430 ° C. for 20 hours in a baking furnace, and the first baking was performed (first baking step).

  Next, as shown in FIG. 4A, plugging slurry 60 is disposed in the opening portion of the cell 4 at the upstream end 201 and the downstream end 202 of the base material 2 at the portion where the plug portion is formed (plugging). Process).

Next, as shown in FIG. 4A, a masking tape 71 is applied so as to cover the upstream end 201 of the base material 2, and a portion of the masking tape 71 corresponding to the cell 4 serving as a thermal relaxation cell is punched with a soldering hand. I opened it.
Next, as shown in FIG. 4B, a shampoo hat 72 was attached to the upstream end 201 of the base material 2, and the base material 2 was placed on the vibrator 73. At this time, the substrate 2 was placed with the upstream end 201 facing upward. Then, the powder made of aluminum titanate, which is the high heat capacity powder 430, was filled on the masking tape 71.

Then, as shown in FIG.4 (c), the vibrator 73 was vibrated and the high heat capacity powder 430 was filled in the cell 4 used as a thermal relaxation cell (filling process). As a result, the high heat capacity powder 430 was filled upstream of the plugging slurry 60 in the cell 4 serving as a heat relaxation cell.
After filling, the shampoo hat 71 was removed from the base material 2, and the high heat capacity powder 430 remaining without being filled was removed.

Next, the plugging slurry was disposed, and the base material filled with the high heat capacity powder was held at 1350 ° C. for 4 hours in a firing furnace to perform second firing (second firing step). At this time, firing was performed with the upstream end of the base material facing upward.
Thereby, the stopper part was formed. Further, the high heat capacity powder was sintered and welded to the base material to form a heat relaxation layer.
Thus, an exhaust gas purification filter was produced.

Next, the effect in the exhaust gas purification filter 1 of this example is demonstrated.
In the exhaust gas purification filter 1 of this example, the cell 4 includes an inflow side cell 41, an exhaust side cell 42, and a heat relaxation cell 43. The heat relaxation cell 43 has a heat relaxation layer 431 filled with the high heat capacity powder 430, and the heat capacity of the heat relaxation layer 431 is larger than the heat capacities of the inflow side cell 41 and the discharge side cell 42. Therefore, the heat of combustion generated when the collected PM is removed by combustion can be absorbed by the heat relaxation layer 431 of the heat relaxation cell 43. Thereby, it can suppress that the exhaust gas purification filter 1 will be in an overheated state, and can prevent the thermal damage of the base material 2, such as a melting loss and a crack.

Further, the heat relaxation layer 431 is formed by filling the high heat capacity powder 430 and sintering it by firing and welding it to the substrate 2. That is, the heat relaxation layer 431 is formed integrally with the base material 2. Therefore, even when the exhaust gas purification filter 1 is in use, the heat relaxation layer 431 is not peeled off or dropped off, and sufficient earthquake resistance can be ensured.
Also, the difference in thermal expansion coefficient between the heat relaxation layer 431 and the substrate 2, 2 × 10 ^-6 / ° C. or less and small. Therefore, the thermal stress between the thermal relaxation layer 431 and the base material 2 can be suppressed, and the thermal reliability such as the thermal shock resistance in the exhaust gas purification filter 1 can be sufficiently secured.

In this example, the heat capacity of the thermal relaxation layer 431 is 1.30 (J / cc · K) or more. Therefore, the heat of combustion generated when the collected PM is burned and removed can be more fully absorbed by the heat relaxation layer 431.
Moreover, the thermal expansion coefficient of the heat relaxation layer 431 is 2.5 × 10 ⁻⁶ / ° C. or less. Therefore, sufficient thermal reliability such as thermal shock resistance in the exhaust gas purification filter 1 can be ensured.

  Further, the occupation ratio of the thermal relaxation cell 43 is 5 to 30 with respect to the area of the region in which the distance from the center O is 80% or less of the distance from the center O to the outer peripheral surface 51 in the radial cross section of the substrate 2. %. Therefore, the effect of absorbing the combustion heat generated when the collected PM is burned and removed by the heat relaxation layer 431 and the increase in pressure loss due to the heat relaxation cell 43 through which the exhaust gas G is not substantially passed are suppressed. Both effects can be achieved.

  Further, in the manufacturing method of this example, in the filling process, among the cells 4 in which the plugging slurry 60 is disposed at the downstream end 202, the heat is higher on the upstream side than the plugging slurry 60 in the cell 4 serving as the heat relaxation cell 43. After filling the capacity powder 430, the plugging slurry 60 is not disposed at the upstream end 201. That is, the plug portions 6 are not provided at both ends of the cell 4 to be the heat relaxation cell 43, but are provided only at the downstream end 202.

  This is because, in the firing step (second firing step) after the filling step, the high heat capacity powder 430 is sintered and welded to the base material 2 to form the heat relaxation layer 431, and the heat relaxation layer 431. This is because the substrate 2 and the substrate 2 are integrally formed. For example, in order to prevent the high heat capacity powder 430 constituting the heat relaxation layer 43 from leaking out, it is not necessary to provide the plug portions 6 at both ends of the heat relaxation cell 43. Therefore, the process can be reduced, and the manufacturing cost can be reduced.

  Thus, according to this example, the exhaust gas purification filter capable of suppressing overheating of the exhaust gas purification filter when burning the collected PM and preventing thermal damage such as melting and cracking, and the A manufacturing method can be provided.

In this example, as shown in FIG. 5A, the thermal relaxation cell 43 is arranged along one cell wall 31 or the other cell wall 32 of the cell walls 3, but FIG. As shown in b), it can be arranged in a 45 ° direction with respect to one cell wall 31 or the other cell wall 32 of the cell walls 3.
Moreover, although the arrangement pattern of the thermal relaxation cell 43 is a pattern as shown in FIG. 3A, it can be a pattern as shown in FIGS. 6A to 6D. Other patterns can also be used.

  For example, in the exhaust gas purification filter 1 shown in FIG. 6A, the heat relaxation cell 43 is configured such that the distance from the center O is 80% of the distance from the center O to the outer peripheral surface 51 in the radial cross section of the substrate 2. It is arranged only in the following areas, and exists in that area as uniformly and uniformly as possible. Further, the thermal relaxation cells 43 are arranged in a square lattice pattern along one cell wall 31 or the other cell wall 32 of the cell walls 3 (see FIG. 5A).

(Example 2)
In this example, the manufacturing method of the exhaust gas purification filter is changed.
In this example, as shown in FIG. 7B, an exhaust gas purification filter was manufactured by sequentially performing a molding process, a drying process, a plugging process, a first firing process, a filling process, and a second firing process.
This will be described in detail below.

  In this example, a substrate made of a honeycomb structure was formed (forming step) and dried (drying step), and then plugging slurry was disposed at a desired location on the substrate (plugging step). And the base material which arrange | positioned the slurry for plugging was baked (1st baking process). Thereby, the plug part was formed simultaneously with the firing of the substrate.

Next, the high heat capacity powder was filled into a desired cell of the substrate (filling step). And the base material filled with the high heat capacity powder was fired (second firing step). Thereby, the high heat capacity powder was sintered and welded to the base material to form a heat relaxation layer.
Thus, an exhaust gas purification filter was produced.
The contents of each process are the same as those in the first embodiment.

In the manufacturing method of this example, the first baking (first baking step) is performed after the plugging step, and the base material and the plugging slurry disposed on the base material are simultaneously fired. Therefore, compared with the case where the base material and the plugging slurry are separately fired, the firing step can be omitted once, and the cost can be greatly reduced.
Further, after firing the base material and the plugging slurry (first firing step), the high heat capacity powder filled in the base material is fired (second firing step). In addition, the quality of the heat relaxation layer can be ensured without being confused with different materials (for example, materials constituting the base material and the plug portion).
The other functions and effects are the same as those of the first embodiment.

(Example 3)
In this example, the manufacturing method of the exhaust gas purification filter is changed.
In this example, as shown in FIG. 7C, in manufacturing the exhaust gas purification filter, a molding process, a drying process, a first firing process, a plugging process, a second firing process, a filling process, and a third firing process are performed. Do in order.

In this example, a substrate made of a honeycomb structure was formed (forming step), dried (drying step), and fired (first firing step).
Next, a plugging slurry was disposed at a desired location on the substrate (plugging process). And the base material which arrange | positioned the slurry for plugging was baked (2nd baking process). Thereby, the stopper part was formed.

Next, the high heat capacity powder was filled into a desired cell of the substrate (filling step). Then, the base material filled with the high heat capacity powder was fired (third firing step). Thereby, the high heat capacity powder was sintered and welded to the base material to form a heat relaxation layer.
Thus, an exhaust gas purification filter was produced.
The contents of each process are the same as those in the first embodiment.

In the manufacturing method of this example, the first baking (first baking process) is performed after the drying process, the second baking (second baking process) is performed after the plugging process, and the filling process is performed. A third firing (third firing step) is performed.
That is, the air permeability in the base material (honeycomb structure) during the firing can be improved as compared with the case where the first firing of the base material is performed after disposing the plugging slurry. Therefore, the temperature difference generated in the base material during firing can be reduced, firing cracks can be suppressed, and the firing yield can be improved.
Further, after firing the base material and the plugging slurry (first firing step, second firing step), the high heat capacity powder filled in the base material is fired (third firing step). The quality of the heat relaxation layer can be ensured without mixing different materials (for example, materials constituting the base material and the plug portion) during the sintering of the body.
The other functions and effects are the same as those of the first embodiment.

Example 4
In this example, for the exhaust gas purification filter, the difference in the thermal expansion coefficient between the thermal relaxation layer and the base material was changed, and the generated stress during the overheating test was calculated by simulation.

In this example, a cordierite honeycomb structure (base material) having a diameter of 160 mm, a length of 100 mm, a cell wall thickness of 0.3 mm, and a cell density of 300 cpsi was formed of aluminum titanate, which is a high heat capacity powder. An exhaust gas purification filter in which heat relaxation cells having a heat relaxation layer are arranged in a pattern shown in FIG. The thermal expansion coefficient of the substrate was 1.65 × 10 ⁻⁶ / ° C. Moreover, the thermal expansion coefficient of the heat relaxation layer is larger than the thermal expansion coefficient of the substrate.

  In the overheating test, an oxidation catalyst having a capacity of 1.3 liters and an exhaust gas purification filter are attached to an exhaust pipe of a 2 liter common rail diesel engine, and 12 g of PM is deposited on the exhaust gas purification filter. And after raising the temperature in a base material to 650 degreeC by engine control (post injection), the engine speed was reduced to the idling state and it was set as the conditions which burn PM explosively.

  The generated stress is obtained by obtaining the displacement of each of the base material and the thermal relaxation layer when the highest temperature (maximum temperature reached) in the base material is 965 ° C. during the overheating test, from which the exhaust gas purification filter is obtained. Were calculated by performing unsteady analysis using a three-dimensional finite element method analysis model.

Next, the result of the generated stress is shown in FIG. In the figure, the vertical axis represents the generated stress (MPa), and the horizontal axis represents the difference in thermal expansion coefficient (× 10 ⁻⁶ / ° C.).
From the figure, it can be seen that the generated stress is 3.95 MPa or less, which is the stress value P1 permitted in actual use, when the difference in thermal expansion coefficient is 2 × 10 ⁻⁶ / ° C. or less. Therefore, in the exhaust gas purification filter, it can be seen that the difference in thermal expansion coefficient between the heat relaxation layer and the substrate is preferably 2 × 10 ⁻⁶ / ° C. or less.

(Example 5)
In this example, with respect to the exhaust gas purification filter, the occupancy ratio of the heat relaxation cell was changed, and the maximum temperature reached in the substrate during the overheating test was measured.
The occupation rate of the thermal relaxation cell is the ratio of the thermal relaxation cell to the area of the region where the distance from the center is 80% or less of the distance from the center to the outer peripheral surface in the radial cross section of the substrate. That is.

  In this example, a cordierite honeycomb structure (base material) having a diameter of 160 mm, a length of 100 mm, a cell wall thickness of 0.3 mm, and a cell density of 300 cpsi was used. An exhaust gas purification filter in which a thermal relaxation cell having a thermal relaxation layer formed by a light or the like is arranged in a pattern shown in FIGS. 3B and 6A to 6D is used.

In the overheating test, an oxidation catalyst having a capacity of 1.3 liters and an exhaust gas purification filter are attached to an exhaust pipe of a 2 liter common rail diesel engine, and 12 g of PM is deposited on the exhaust gas purification filter. And after raising the temperature in a base material to 650 degreeC by engine control (post injection), the engine speed was reduced to an idling state and PM was explosively burned.
And the highest temperature reached in the base material was set to the highest temperature among 30 thermocouples arranged uniformly in the base material and measured during the overheating test.

Next, the result of the highest temperature reached in the substrate is shown in FIG. In the figure, the vertical axis represents the maximum temperature reached (° C.), and the horizontal axis represents the thermal relaxation cell occupancy (%).
From the figure, it can be seen that the maximum temperature reached in the base material is 960 ° C. or lower, which is a temperature value T1 permitted in actual use, when the thermal relaxation cell occupancy is 5% or higher. Therefore, it can be seen that the occupation ratio of the thermal relaxation cell is preferably 5% or more.
In addition, when the occupation rate of the heat relaxation cell exceeds 30%, there is a possibility that a problem of an increase in pressure loss may occur due to an increase in the heat relaxation cell through which the exhaust gas is not substantially passed. Therefore, the occupation ratio of the thermal relaxation cell is preferably 30% or less.

(Example 6)
In this example, exhaust gas purification filters (samples E1 to E6) having various conditions are prepared, and the maximum reached temperature, heat capacity, and pressure loss in the base material are obtained, and the respective relationships are examined.

  The exhaust gas purification filters (samples E1 to E6) prepared in this example are all cordierite honeycomb structures (base materials) having a diameter of 160 mm, a length of 100 mm, a cell wall thickness of 0.3 mm, and a cell density of 300 cpsi. On the other hand, heat relaxation cells having a heat relaxation layer formed of any high heat capacity powder are arranged in an arbitrary pattern.

Table 1 shows the high heat capacity powder, the arrangement pattern of the thermal relaxation cell, the thermal capacity of the thermal relaxation layer, and the occupation ratio of the thermal relaxation cell in each of the samples E1 to E6.
In addition, the arrangement pattern of the thermal relaxation cell is a pattern shown in any one of FIG. 3B and FIGS. The occupation rate of the thermal relaxation cell is the ratio of the thermal relaxation cell to the area of the region where the distance from the center is 80% or less of the distance from the center to the outer peripheral surface in the radial cross section of the substrate. It is.

Further, the maximum temperature reached in the substrate was measured by the same method as in Example 5.
The heat capacity is the heat capacity of the entire exhaust gas purification filter (base material + heat relaxation layer), and was determined from the specific heat, specific gravity, etc. of the base material and the heat relaxation layer.
Further, the pressure loss was obtained by passing the exhaust gas through the exhaust gas purification filter at a volume flow rate of 5000 liters / minute, and calculating the pressure difference between the inflow side pressure and the exhaust side pressure as the pressure loss.

  Next, the results of the maximum attainable temperature, heat capacity and pressure loss in the substrate are shown in FIGS. FIG. 10 shows the relationship between the maximum temperature reached in the substrate and the pressure loss. In the figure, the vertical axis represents the maximum temperature reached (° C.), and the horizontal axis represents the pressure loss (kPa). FIG. 11 shows the relationship between the maximum temperature reached in the substrate and the heat capacity. In the figure, the vertical axis represents the maximum temperature reached (° C.), and the horizontal axis represents the heat capacity (J / K).

  From FIG. 10 and FIG. 11, the sample E5 in which the heat capacity of the heat relaxation layer is 1.30 (J / cc · K) or more and the occupation ratio of the heat relaxation cell is in the range of 5 to 30% is as described above. Compared to other samples E1 to E4 and E6 that do not satisfy the conditions, it can be seen that this is very excellent from the viewpoint of coexistence of suppression of excessive temperature rise and suppression of increase in pressure loss.

1 is a perspective view showing an exhaust gas purification filter in Embodiment 1. FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing an axial cross section of an exhaust gas purification filter in Example 1; (A) Explanatory drawing which shows arrangement | positioning of a cell in Example 1, (b) Explanatory drawing which shows the arrangement pattern of a thermal relaxation cell. In Example 1, (a) Explanatory drawing which shows the process of sticking a masking tape, (b) Explanatory drawing which shows a mode that high heat capacity powder is filled, (c) Explanatory drawing which shows the state filled with high heat capacity powder. Explanatory drawing which shows the arrangement pattern of (a)-(d) thermal relaxation cell in Example 1. FIG. Explanatory drawing which shows the arrangement | positioning relationship between the (a), (b) thermal relaxation cell, the inflow side cell, and the discharge side cell in Example 1. FIG. The flowchart which shows the (a)-(c) manufacturing process in Examples 1-3. The graph which shows the relationship between the generated stress and thermal expansion coefficient difference in Example 4. The graph which shows the relationship between the highest achieved temperature and a thermal relaxation cell occupation rate in Example 5. FIG. The graph which shows the relationship between the highest attained temperature and pressure loss in Example 6. FIG. The graph which shows the relationship between the highest attained temperature and heat capacity in Example 6.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification filter 2 Base material 201 Upstream end 202 Downstream end 3 Cell wall 4 Cell 41 Inflow side cell 42 Outlet side cell 43 Thermal relaxation cell 430 High heat capacity powder 431 Thermal relaxation layer 5 Outer peripheral wall 6 Plug part G Exhaust gas

Claims (11)

In an exhaust gas purification filter provided with a substrate made of a honeycomb structure having an outer peripheral wall, a cell wall disposed in a honeycomb shape in the outer peripheral wall, and a large number of cells partitioned in the cell wall,
The cell has an inflow side cell which becomes an inflow side passage through which the downstream end is closed by a plug portion and into which exhaust gas flows.
A discharge side cell which becomes an exhaust side passage for closing the upstream end with the plug portion and exhausting the exhaust gas passing through the cell wall from the inflow side cell;
Thermal relaxation formed by closing the downstream end with the plug portion, filling the portion upstream of the plug portion with high heat capacity powder, sintering by firing and welding to the base material A thermal relaxation cell provided with a layer,
The heat capacity of the heat relaxation layer is larger than the heat capacity of the inflow side cell and the discharge side cell, and the difference in thermal expansion coefficient between the heat relaxation layer and the base material is 2 × 10 ⁻⁶ / ° C. or less. An exhaust gas purification filter characterized by being.   The exhaust gas purification filter according to claim 1, wherein the heat capacity of the heat relaxation layer is 1.30 (J / cc · K) or more. 3. The exhaust gas purification filter according to claim 1, wherein the thermal relaxation layer has a thermal expansion coefficient of 2.5 × 10 ⁻⁶ / ° C. or less.   The occupancy ratio of the thermal relaxation cell according to any one of claims 1 to 3 is a region in which the distance from the center is 80% or less of the distance from the center to the outer peripheral surface in the radial cross section of the base material. An exhaust gas purification filter characterized by being 5 to 30% of the area. The cell wall according to claim 4, wherein the cell walls are arranged in a quadrangular lattice shape by a cell wall formed in one direction and another cell wall formed in a direction orthogonal to the cell wall.
The thermal relaxation cell is disposed only in a region where the distance from the center is 80% or less of the distance from the center to the outer peripheral surface in the radial cross section of the base material, and the one cell wall An exhaust gas purifying filter, wherein the exhaust gas purification filter is arranged in a quadrangular lattice shape by a heat relaxation cell formed along the other cell wall and a heat relaxation cell formed along the other cell wall.   The high heat capacity powder according to any one of claims 1 to 5, wherein the high heat capacity powder includes one or more of aluminum titanate, silicon carbide (silicon carbide), silicon nitride, cordierite, mullite, alumina, and spinel. An exhaust gas purification filter containing the exhaust gas purification filter. In the method of manufacturing the exhaust gas purification filter according to any one of claims 1 to 6,
A molding step of extruding a ceramic material to produce the substrate made of a honeycomb structure; and
A drying step of drying the substrate;
A first firing step of firing the substrate;
Of the opening of the cell at the upstream end and the downstream end of the base material, a plugging step of disposing a plugging slurry in a portion forming the plug portion;
Among the cells in which the plugging slurry is disposed at the downstream end, a filling step of filling the high heat capacity powder on the upstream side of the plugging slurry in the cell to be the heat relaxation cell;
The base material filled with the high heat capacity powder is fired by firing the plugging slurry, and the plug portion is formed and the high heat capacity powder is sintered to be welded to the base material. And a second firing step for forming the heat relaxation layer. A method for producing an exhaust gas purification filter, comprising: In the method of manufacturing the exhaust gas purification filter according to any one of claims 1 to 6,
A molding step of extruding a ceramic material to produce the substrate made of a honeycomb structure; and
A drying step of drying the substrate;
Of the opening of the cell at the upstream end and the downstream end of the base material, a plugging step of disposing a plugging slurry in a portion forming the plug portion;
A first firing step of forming the plug portion simultaneously with firing the base material on which the plugging slurry is disposed;
Among the cells in which the plug portion is formed at the downstream end, a filling step of filling the high heat capacity powder on the upstream side of the plug portion in the cell to be the heat relaxation cell,
A second firing step of firing the base material filled with the high heat capacity powder and sintering the high heat capacity powder to form a heat relaxation layer by welding to the base material. An exhaust gas purification filter manufacturing method characterized by the above. In the method of manufacturing the exhaust gas purification filter according to any one of claims 1 to 6,
A molding step of extruding a ceramic material to produce the substrate made of a honeycomb structure; and
A drying step of drying the substrate;
A first firing step of firing the substrate;
Of the opening of the cell at the upstream end and the downstream end of the base material, a plugging step of disposing a plugging slurry in a portion forming the plug portion;
Firing the base material on which the plugging slurry is disposed, and forming a plug part; a second firing step;
Among the cells in which the plug portion is formed at the downstream end, a filling step of filling the high heat capacity powder on the upstream side of the plug portion in the cell to be the heat relaxation cell,
A third firing step in which the base material filled with the high heat capacity powder is fired, and the high heat capacity powder is sintered to be welded to the base material to form the heat relaxation layer. An exhaust gas purification filter manufacturing method characterized by the above.   10. The high heat capacity powder according to claim 7, wherein, in the filling step, the high heat capacity powder from an opening at the upstream end of the cell that becomes the thermal relaxation cell in a state where the upstream end of the base material is directed upward. A method for producing an exhaust gas purification filter, comprising filling a body.   11. The method for manufacturing an exhaust gas purification filter according to claim 10, wherein in the firing step performed after the filling step, the base material is fired with the upstream end of the base material facing upward.

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