JP2010131586A - Honeycomb filter and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a honeycomb filter for collecting and removing a substance to be collected in a fluid to be treated which has an increased limit of the amount of the substance to be collected, such as PM, while suppressing an increase in pressure loss, and has excellent heat resistance and durability, and to provide a method for manufacturing the same. <P>SOLUTION: The honeycomb filter has partition walls W<SB>IO</SB>for separating collection cells CL<SB>IN</SB>and discharge cells CL<SB>OUT</SB>from each other, wherein one (SRF<SB>IN</SB>/SRF<SB>OUT</SB>) of the collection cell CL<SB>IN</SB>and the discharge cell CL<SB>OUT</SB>is formed to have a flat surface and the other (SRF<SB>OUT</SB>/SRF<SB>IN</SB>) is formed to have a concave curved surface. The partition wall W<SB>IO</SB>is partially provided with a thick-walled portion W<SB>TK</SB>, satisfying the relationship: N<SB>A</SB>>N<SB>B</SB>, wherein the number of the collection cells CL<SB>IN</SB>per unit cross-sectional area is defined as N<SB>A</SB>(cells/inch<SP>2</SP>) and the number of the discharge cells CL<SB>OUT</SB>per unit cross-sectional area is defined as N<SB>B</SB>(cells/inch<SP>2</SP>). Therefore, the honeycomb filter maintains a desired equivalent hydraulic diameter to simultaneously improve the thermal capacity and isostatic strength thereof, while suppressing an increase in pressure loss. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a honeycomb filter for removing a trapped substance in a fluid to be treated and a method for manufacturing the same, and in particular, particulate matter (hereinafter referred to as P) contained in combustion exhaust of an internal combustion engine such as a diesel engine.
Called M. ) And the like are suitable for a diesel particulate filter (hereinafter referred to as DPF).

In recent years, as an environmental measure, reduction of soot existing in combustion exhaust discharged from an internal combustion engine such as a diesel engine and PM including unburned fuel has become a major issue. For this reason, conventionally, in the combustion, an exhaust gas purifying apparatus including a DPF that collects PM in the region is installed in the exhaust gas exhaust path.

DPF is generally excellent in heat resistance and forms a honeycomb structure made of porous ceramics with innumerable pores, and plugs the end face of either the inlet or outlet of a predetermined cell. Then, by allowing combustion exhaust gas containing PM to pass through the partition walls of the honeycomb structure,
PM is trapped in the pores present in the porous partition walls.
If PM accumulates and clogs the pores of the partition wall and the pressure loss increases, it is heated by a burner or heater, or by post injection that injects a small amount of fuel after the combustion explosion of the engine.
PM collected in the DPF by introducing high-temperature combustion exhaust into the PF and heating the DPF
It is configured to be able to regenerate by burning off.

Various proposals have been made regarding the cell shape and plugging pattern of a honeycomb filter used in such a DPF.
For example, Patent Document 1 discloses a columnar honeycomb structure including a plurality of through-holes arranged in parallel in the longitudinal direction and a wall portion that separates the plurality of through-holes and constitutes an outer peripheral surface, The through-holes of the large-capacity through-hole group in which one end is sealed so that the sum of the cross-sectional areas perpendicular to the longitudinal direction is relatively large, and the sum of the cross-sectional areas is relatively It is composed of a small volume through hole group in which the other end is sealed so as to be smaller, and the outer peripheral surface of the columnar honeycomb structure has a chamfered corner. A featured honeycomb structure is disclosed.

In Patent Document 2, a plurality of cells are formed by a porous partition wall, a predetermined cell in which one end is sealed, and a remaining cell in which the other end is plugged are both ends. The honeycomb filters are alternately arranged so that each part forms a checkered pattern, and the cross-sectional areas of the predetermined cells and the remaining cells are different in the cross section, and the cross-sectional area is large for the cells having a small cross-sectional area The ratio of the flow channel hydraulic diameter of the cell is 1.2 or more, the cross-sectional shape of the cell having at least a large cross-sectional area is a circular arc-shaped portion corresponding to at least one corner, and the thickness of the partition wall, A honeycomb ceramic filter is disclosed in which the value of the ratio of the minimum thicknesses of the portions (intersection points) where the partition walls intersect is 0.7 or more and less than 1.3.

In general, when the cross-sectional area of the cylindrical flow path is A and the inner peripheral length of the cross-section of the cylindrical flow path is L, the equivalent hydraulic diameter Dh of the cylindrical flow path is four times the cross-sectional area A as the inner peripheral length L. Minus the value, that is, Dh = 4 A /
It is known that the in-channel frictional resistance represented by L and acting on the fluid passing through the cylindrical channel is proportional to the equivalent hydraulic diameter Dh of the cylindrical channel.
In addition, when a DPF is provided to remove PM in the combustion exhaust flow path of the internal combustion engine, the pressure loss when passing through the DPF affects the combustion of the engine, and the combustion performance of the engine decreases due to the increase of the pressure loss. It is known (Patent Documents 1, 2, etc.).
Therefore, in order to reduce the frictional resistance in the pipe acting on the fluid passing through the cell in order to reduce the pressure loss when the fluid to be processed passes through the cell, the equivalent hydraulic diameter of the cell is increased as much as possible. Is desirable.

However, in the conventional DPF, the partition walls that define the cells constituting the honeycomb structure may be slightly thick due to the R shape or chamfered shape provided at the intersection, It is formed in a flat plate shape with a constant thickness. In the DPF having such a structure, if the equivalent hydraulic diameter of the cell is increased in order to reduce the pressure loss, the number of cells per unit cross-sectional area, that is, the cell density is reduced or the thickness of the cell partition wall is reduced. I have to choose one.

However, if the cell density is reduced, the PM collection amount may be reduced, and if the cell partition wall thickness is reduced, the actual weight of the honeycomb structure may be reduced and the heat capacity may be reduced. The decrease in the heat capacity leads to an excessive temperature rise due to PM combustion during DPF regeneration, and the honeycomb structure may be easily damaged by heat. In addition, the isostatic strength may be reduced due to the thinning of the partition walls.

Accordingly, in view of such circumstances, the present invention secures a desired equivalent hydraulic diameter for each cell of the honeycomb filter to suppress an increase in pressure loss, and also secures a desired heat capacity to collect a trapped substance such as PM. An object of the present invention is to provide a honeycomb filter having a large limit collection amount and excellent heat resistance and durability.

In order to solve the above-described problem, in the first invention, a plurality of cells partitioned into a substantially cylindrical shape serving as a flow path of a fluid to be treated are provided by partition walls made of porous ceramics to form a honeycomb shape. A collection cell having an end opened on the inlet side into which the fluid to be treated is introduced and the other end closed is used, and one end of the cell is closed and the other end is discharged. The discharge cell is opened on the outlet side, the collection cell and the discharge cell are arranged at predetermined positions, and the fluid to be treated passes through the partition wall that partitions the collection cell and the discharge cell. Let me
In the honeycomb filter for collecting the collected matter in the treated fluid in the partition wall,
The partition partitioning between the collection cell and the discharge cell is a curved surface in which the side facing either the collection cell or the discharge cell is a flat surface and the side facing the other is curved concavely. as, provided with a thick portion in a part of the partition wall, the number per unit cross-sectional area of the collecting cell in section orthogonal to the longitudinal direction of the substantially cylindrical cells N _{a (number} / inch ^2),
When the number per unit cross-sectional area of the discharge cells in the vertical cross section with respect to the longitudinal direction of the substantially cylindrical cell is N _B (pieces / inch ² ), the relationship of N _A > N _B is satisfied.
).

According to 1st invention, the heat capacity of the said partition becomes high with the said thick part, Furthermore, the isostatic strength of a honeycomb structure also rises. In addition, the thick part provided by curving the discharge cell reduces the fluid resistance of the exhaust gas that permeates through the collection cell and the cell wall surrounded by the collection cell and is discharged from the discharge cell. Since it can increase, the accumulation amount of PM collected by the said cell wall is suppressed, and the effect which suppresses generation | occurrence | production of a thermal damage can be anticipated by reducing the PM combustion amount per unit filtration wall. Therefore, a honeycomb filter having excellent heat resistance and durability can be realized.
Also, the number N _A per unit sectional area of the collecting cells by setting more than the number N _B per unit cross-sectional area of the discharge cell, since the collecting cell are adjacent to each other on both sides of the cell walls P
M can be deposited, and the effect of reducing the PM deposition pressure loss due to the efficient securing of the filtration area can be obtained.
Furthermore, by setting it as such a structure, the pressure loss by the side of the said discharge cell can be made relatively smaller than the pressure loss by the side of the said collection cell, and the pressure loss of the said collection cell and the said discharge cell The difference can be increased.
Therefore, it becomes possible to increase the flow rate (permeation flow rate) of the combustion exhaust gas that passes through the partition wall that partitions between the collection cell and the discharge cell, and the pressure loss during use of the honeycomb filter is reduced, and the internal combustion engine The influence on the combustion of can be suppressed.

In the second invention, one of the shape of the cross section perpendicular to the flow channel longitudinal direction of the collection cell and the discharge cell is formed in a polygon and the other is formed in a circle (Claim 2).

According to the second invention, while maintaining the equivalent hydraulic diameter of the collection cell and the discharge cell,
It is possible to form a thick part in a part of the partition wall that partitions between the collection cell and the discharge cell, and partitions between the collection cell and the discharge cell without increasing the pressure loss. It is possible to improve the heat capacity of the partition walls and increase the isostatic strength of the honeycomb structure. Therefore, a honeycomb filter having excellent heat resistance and durability can be realized.
In addition, when both the collection cell and the discharge cell are formed in a circular shape regardless of the present invention, the thick portion becomes excessively thick, and the fluid to be treated is the collection cell and the discharge cell. There is a possibility that the diffusion resistance at the time of permeation through the partition wall partitioning between the two and the pressure increases and the pressure loss increases.
By forming the collection cell and the discharge cell in different shapes as in the present invention, it is possible to realize a honeycomb filter that achieves both a reduction in pressure loss and an improvement in heat capacity.

In the third invention, in the honeycomb filter in which the catalyst is supported on the collection cell and the discharge cell, the minimum value of the catalyst support mass per unit surface area supported on the plane side of the cell wall is set to t _C (mg / Mm ² ), the average value of the catalyst carrying mass per unit surface area supported on the curved surface side of the cell wall t _D (mg / mm ² ), the catalyst per unit surface area supported on the plane side of the cell wall T _C ≦ t _D ≦ t, where t _E (mg / mm ² ) is the maximum supported mass
The relationship of _E is satisfied (claim 3).

According to the third invention, even in a honeycomb filter that suppresses the accumulation of PM by the catalyst and reduces the pressure loss, the PM without reducing the hydraulic diameter of the collection cell and the hydraulic diameter of the discharge cell. As a result, it is possible to secure a sufficient amount of catalyst to suppress the accumulation of the catalyst, so that a honeycomb filter with less pressure loss can be realized.

More specifically, an equivalent hydraulic diameter of a virtual unit cell made of a polygon that encloses the collection cell and the discharge cell of the collection cell after supporting the catalyst is a virtual hydraulic diameter (Dh ₀ ), When the minimum thickness of the partition wall partitioning between the collection cell and the discharge cell is the minimum thickness (t), the equivalent hydraulic diameter (Dh ₁ ) of the collection cell and the equivalent hydraulic force of the discharge cell One of the diameters (Dh ₂ ) is set equal to the virtual hydraulic diameter (Dh ₀ ), and the other equivalent hydraulic diameter is subtracted from the virtual hydraulic diameter (Dh ₀ ) by twice the minimum wall thickness (t). Value (Dh ₀ -2t)
It is desirable to form.

Further, an equivalent hydraulic diameter of the virtual unit cell consisting of a polygon which encloses the said collection cell and the discharge cell as a virtual hydraulic diameter (Dh _0), defining between said collection cell and the discharge cell partition wall when the minimum value of the wall thickness and the minimum thickness (t), and the equivalent hydraulic diameter of the collecting cells (Dh ₁₎ equivalent hydraulic diameter of the discharge cells (Dh _2), the virtual hydraulic diameter (Dh ₀ ) from may be formed on the value _(Dh 0 -t) which is obtained by subtracting the above-mentioned minimum wall thickness (t).

In the method for manufacturing a honeycomb filter described as the first to third inventions,
In this invention, the ceramic is formed by extruding a ceramic clay from a mold provided with slit grooves formed by polygonal blocks each having only a straight line and circular blocks each having a curved line. A honeycomb structure forming step is provided (claim 4).
.

According to a fourth aspect of the present invention, the surface between the collection cell and the discharge cell is partitioned by a partition wall having a flat surface on the other side and a curved surface on the other surface and having a thick portion in part. Without increasing the equivalent hydraulic diameter and cell density of the collection cell and the discharge cell, the mechanical strength is increased while increasing the heat capacity of the partition wall partitioning the collection cell and the discharge cell, and Manufacturing of a honeycomb filter having a high amount of collected material can be realized.

The outline | summary of the honey-comb filter in the 1st Embodiment of this invention is shown, (a) is a perspective view showing the whole honey-comb filter structure, (b) is a longitudinal cross-sectional view along a flow-path direction. The characteristic part of the honey-comb filter in the 1st Embodiment of this invention is shown, (a) is principal part sectional drawing perpendicular | vertical to a flow-path direction, (b) is the partition which divides a collection cell and a discharge cell FIG. The characteristic part in the modification of the honey-comb filter in the 1st Embodiment of this invention is shown, (a) is principal part sectional drawing perpendicular | vertical to a flow-path direction, (b) is a collection cell and a discharge cell. Sectional drawing of the principal part of the partition to divide. (A), (b) is principal part sectional drawing perpendicular | vertical to the flow-path direction which shows the other modification of the honey-comb filter in the 1st Embodiment of this invention. The outline | summary of the metal mold | die used for shaping | molding of the honey-comb filter in the 1st Embodiment of this invention is shown, (a) is a principal part top view, (b) is principal part sectional drawing. The block diagram which shows the example of the combustion exhaust gas purification system which used the honey-comb filter in the 1st Embodiment of this invention as DPF.

The honeycomb filter 1 according to the first embodiment of the present invention uses a combustion exhaust gas from an internal combustion engine such as a diesel engine as a fluid to be processed, and is partitioned into a substantially cylindrical shape serving as a flow path of the fluid to be processed by a partition made of porous ceramics. honeycomb and without providing a large number of cells, one of the ends of the cells and collecting the cell CL _iN that allowed closing the opening allowed other end STP _OUT on the inlet side to be introduced in the fluid to be treated, one of the cell the other end brought close the end _{STP iN} and the discharge cell _{CL OUT} which allowed open on the outlet side to be discharged in the fluid to be treated, brought arranged a collecting cell _{CL iN} and the discharge cell _{CL OUT} in place The particulate matter PM contained in the combustion exhaust is used as the material to be collected, and the material to be collected in the fluid to be treated passes through the partition walls of the honeycomb filter 1 by the fluid to be treated. It is capable of removing.
The honeycomb filter 1 of the present invention, one surface of the partition wall W _IO made of porous ceramics and straight planar, the other face as a curved surface shape, thick wall portion which is thicker plate thickness of the partition wall W _IO partially _WTK is provided to increase the heat capacity of the honeycomb structure and improve the durability while maintaining a desired amount of collected PM.

In this embodiment, the case of using cordierite, which is widely used as a porous ceramic material, will be described as an example, but cordierite (2MgO.3Al
Not only ₂ O ₃ · 5SiO _2, but also alumina (Al ₂ O ₃ ), mullite (3Al ₂ O ₃ · 2)
SiO ₂ ), spinel (MgO · Al ₂ O ₃ ), zirconia (ZrO ₂ ), aluminum titanate (Al ₂ TiO ₅ ), lithium aluminosilicate (Li ₂ O · Al ₂ O ₃ · S)
oxide materials such as iO ₂ ), silicon carbide (SiC), boron carbide (B ₄ N), titanium carbide (Ti
Carbide materials such as C) and silicide materials such as titanium silicide (TiSi ₂ ) can be used. Further, as a catalyst for efficiently burning PM, a metal such as platinum (Pt), ruthenium (Rh), titanium (Ti), tungsten (W) or the like may be supported on the surface of the porous ceramic.

As shown in FIG. 1 (a), (b) , the honeycomb filter 1 in the present embodiment, a circular cross-section of the flow path extending collecting cell CL _IN cylindrical having a hexagonal cross section of the flow path extending tubular and the honeycomb structured body in which a discharge cell CL _OUT are more disposed with, collecting cell CL _iN the outlet side end portion inlet end is open is closed by an outlet-side second sealing plug STP _OUT The discharge cell has an inlet side end portion closed by an inlet side plugging plug STP _IN and an outlet side end portion opened.

Combustion exhaust gas containing PM introduced into the collection cell CL _IN from the inlet side of the honeycomb filter 1 passes through the partition wall _WIO partitioning between the collection cell CL _IN and the discharge cell CL _OUT, and enters the discharge cell CL _OUT . Moving.
At this time, PM in the combustion exhaust gas is collected in countless pores in the partition wall _WIO , and only the combustion exhaust gas from which PM has been removed is discharged to the outlet side.

With reference to FIG. 2, the collection cell CL _IN constituting the honeycomb filter 1 in the present embodiment.
Further, the characteristics of the discharge cell CL _OUT will be described in detail.
As shown in FIG. 2A, the equivalent hydraulic diameter φDh ₂ of the discharge cell CL _OUT is formed to have a value equal to the virtual hydraulic diameter Dh ₀ of the virtual unit cell LTC _VR made of a hexagon, and the collection cell CL _When the minimum value of the wall thickness of the partition wall _WIO partitioning between the _IN and the discharge cell CL _OUT is t, the equivalent hydraulic diameter Dh ₁ of the collection cell CL _IN is from the virtual hydraulic diameter Dh ₀ to the minimum wall thickness t. It is formed to a value (Dh−2t) obtained by subtracting 2 times.
Further, N _{A (number} / inch 2) the number per unit cross-sectional area of the collecting cells CL _IN in section orthogonal to the longitudinal direction of the substantially cylindrical ^cells, the discharge cells in the section orthogonal to the longitudinal direction of the substantially cylindrical cells When the number of CL _OUT per unit cross-sectional area is N _B (pieces / inch ² ), it is desirable that the configuration satisfy N _A > N _B.
Specifically, in the present embodiment, there are 6 discharge cells CL _OUT around the discharge cell CL _OUT .
Lined pieces of collecting cells CL _IN, lined one three discharge cells on the periphery with respect to the collecting cell CL _IN, 2 pieces of collecting cells CL _IN each other are disposed so as to be adjacent Yes.

By adopting such a configuration, as shown in FIG. 2B, the partition wall W _IO separating the collection cell CL _IN and the discharge cell CL _OUT has a surface SRF _IN on the collection cell CL _IN side. becomes a straight plane, the surface SRF _OUT of the discharge cell CL _OUT side opposed thereto becomes a curved surface curved in a concave shape, can be a part of the partition wall W _IO forms a thick portion W _TK became thick . Thick portion W _TK is configured to increase the heat capacity of the partition walls W _IO, thereby improving the isostatic strength of the honeycomb structure.
Since the collection cell CL _IN is formed in a polygonal cross section, the surface S on the collection cell CL _IN side.
The surface area of RF _IN is increased, and the amount of PM collected can be increased. On the other hand, discharge cell C
Since L _OUT has a circular cross section, an increase in pressure loss can be suppressed.
In addition, the partition wall W _II that partitions adjacent collection cells CL _IN has a minimum thickness t
It is formed to be twice as thick as. Therefore, large heat capacity of the partition walls _{W II} is, partition walls _{W II}
Thermal damage can also be suppressed when PM deposited on both sides of the gas burns.

Further, in the present embodiment, the opening cross-sectional area of the collecting cell _{CL IN S IN} and the discharge cell CL
In relation to the _OUT opening cross-sectional area _{S OUT of,} satisfied S IN _{<S OUT,} the whole honeycomb filter 1, and the opening cross-sectional area _{S IN} of trapping cell _{CL IN,} and the sum [sigma] s _IN,
And the opening sectional area _{S OUT} of the discharge cell _{CL OUT,} in relation to the sum [sigma] s _OUT, sigma
S _IN > ΣS _OUT is established.
By adopting such a configuration, the pressure loss on the discharge cell CL _OUT side is reduced to the collection cell CL.
It can be made relatively smaller than the pressure loss on the _IN side, and the collection cell CL _IN and the discharge cell C
The pressure loss difference with L _OUT can be increased.
Therefore, the flow velocity (permeation flow velocity) of the combustion exhaust gas that passes through the partition wall _WIO partitioning between the collection cell CL _IN and the discharge cell CL _OUT is increased, the pressure loss during use of the honeycomb filter is reduced, and the internal combustion engine The influence on the combustion of can be suppressed.
Further, the thick portion _{W TK} provided by allowed to bend the discharge cell _{CL OUT,}
The collection cell CL _IN and the discharge cell CL _OUT are transmitted through the cell wall surrounded by the collection cell CL _IN.
Since the fluid resistance of the exhaust gas exhausted can be increased, the amount of PM accumulated on the cell wall is suppressed, and the effect of suppressing the occurrence of thermal damage by reducing the amount of PM combustion per unit filtration wall Can be expected.

In the present embodiment, when allowed to carry the catalyst into the collecting cell _{CL IN} and the discharge cell _{CL OUT,} wall _{SRF IN} of collecting cells _{CL IN} becomes the planar side of the cell wall _{W IO,} the discharge cell _{CL OUT} wall _{SRF OUT} becomes the curved surface side of the cell wall _{W IO.}
The minimum value of the catalyst supporting mass per unit surface area supported on the flat surface side is expressed as t _C (mg / mm ²
), The average value of the catalyst carrying mass per unit surface area carried on the curved surface side is t _D (mg / mm
² ) The maximum value of the catalyst carrying mass per unit surface area carried on the plane side is expressed as t _E (mg / m
In the case of m ² ), in the present embodiment, the relationship of t _C ≦ t _D ≦ t _E is satisfied.
By setting the amount of catalyst supported in this range, without reducing the hydraulic diameter of the collecting cell CL _IN, it is possible to ensure the catalyst loading required for PM deposit control, can further reduce the pressure loss.

With reference to FIG. 3, the modification 1a of the honey-comb filter in the 1st Embodiment of this invention is demonstrated. The figure, (a) shows the perpendicular cross sectional view in the flow path direction, (b) is collected cells CL _I
And _N and the discharge cell _{CL OUT} is a fragmentary cross-sectional view of the partition wall _{W IO} for partitioning.
In the present embodiment, the collection cell CL _IN has an equivalent hydraulic power equal to φ (Dh ₀ −2t) obtained by subtracting twice the minimum wall thickness t from the equivalent hydraulic diameter Dh ₀ of the virtual unit cell LTC _{VR made} of hexagon. are circular in cross section with a diameter FaiDh _1, the discharge cell _{CL OUT} is formed in hexagonal cross section having an equivalent hydraulic diameter Dh ₂ equal to the equivalent hydraulic diameter Dh ₀ of the virtual unit cell _{LTC VR.}
Also in the present embodiment, the number N _A (units / inch ² ) per unit cross-sectional area of the collection cell CL _IN and the discharge cell CL _OUT per unit cross-sectional area in a vertical cross section with respect to the longitudinal direction of the flow path of the cylindrical cell. _A relationship of N _A > N _B is established between the number N _B (pieces / inch ² ).
With such a configuration, as shown in FIG. 3B, the partition wall W _IO separating the collection cell CL _IN and the discharge cell CL _OUT has a surface SRF _IN on the collection cell CL _IN side. becomes a curved surface curved in a concave shape, the surface _{SRF OUT} of the discharge cell _{CL OUT} side becomes a straight plane, can be a part of the partition wall _{W IO} forms a thick portion _{W TK} became thick. Thick part W _T
K increases the heat capacity of the partition wall _WIO and improves the isostatic strength of the honeycomb structure.
In the first embodiment of the present invention, the collection cell CL _IN side is formed in a hexagonal cross section, the discharge cell CL _OUT side is formed in a circular cross section, and in this embodiment, the collection cell CL _IN side is Although the cross section is circular and the discharge CL _OUT side is formed in a hexagonal cross section, the equivalent hydraulic diameter is the same and the pressure loss between the collection cell CL _IN and the discharge cell CL _OUT does not increase. The same effect as the above embodiment can be expected.
In addition, since the heat capacity per unit filtration wall or the heat capacity with respect to the unit PM deposition amount is increased, higher heat resistance than that of the above embodiment can be expected while suppressing an increase in pressure loss.

Further, in the present embodiment, when allowed to carry the catalyst into the collecting cell _{CL IN} and the discharge cell _{CL OUT,} wall _{SRF IN} of collecting cells _{CL IN} becomes the curved side of the cell wall _{W IO,} the discharge cell _{CL OUT} wall _{SRF OUT} becomes the plane side of the cell wall _{W IO.}
The minimum value of the catalyst supporting mass per unit surface area supported on the flat surface side is expressed as t _C (mg / mm ²
), The average value of the catalyst carrying mass per unit surface area carried on the curved surface side is t _D (mg / mm
² ) The maximum value of the catalyst carrying mass per unit surface area carried on the plane side is expressed as t _E (mg / m
In the case of m ² ), the relationship of t _C ≦ t _D ≦ t _E is also satisfied in this embodiment.
By setting the catalyst loading in this range, the catalyst loading required for suppressing PM deposition can be ensured without reducing the hydraulic diameter of the discharge cell CL _OUT , so that the pressure loss can be reduced.

Referring to FIG. 4, another modification 1b of the honeycomb filter according to the first embodiment of the present invention.
1c will be described.
In the honeycomb filter 1b, as shown in FIG. 4A, a virtual unit cell L made of a hexagon is formed.
With respect to the equivalent hydraulic diameter Dh ₀ of TC _{VR and} the minimum cell partition wall thickness t, the equivalent hydraulic diameter Dh ₁ of the collection cell CL _IN is formed into a hexagonal cross section of (Dh ₀ -t), and the discharge cell CL _OUT The equivalent hydraulic diameter φDh ₂ is formed into a circular section of φ (Dh ₀ -t). With such a configuration, by providing the thick portion W _TK in a part of the partition wall W _IO for partitioning between the collecting cell CL _IN and the discharge cell CL _OUT, while suppressing an increase in pressure loss, An increase in heat capacity and an increase in isostatic strength can be realized simultaneously. In the present embodiment, even when a catalyst is supported, the same effect as in the above embodiment can be expected.
Moreover, in the honeycomb filter 1c, as shown in FIG. 4 (b), an equivalent hydraulic diameter Dh ₀ of the virtual unit cell _{LTC VR} consisting of hexagonal, the cell partition wall thickness minimum value t, collecting cell CL _I
An equivalent hydraulic diameter φDh ₁ of _N is formed in a circular shape of a cross section of φ (Dh ₀ −t), and the discharge cell CL _OUT
It is formed to a hexagonal cross section of the equivalent hydraulic diameter _{Dh 2} (Dh 0 -t). With such a configuration, the partition wall _{W IO} for partitioning between the collecting cell _{CL IN} and the discharge cell _{CL OUT}
Part provided thick portion W _TK of, while suppressing an increase in pressure loss can be realized an increase in growth and isostatic strength of the heat capacity at the same time. In the present embodiment, even when a catalyst is supported, the same effect as in the above embodiment can be expected.

An outline of a method for manufacturing the honeycomb filter 1 according to the first embodiment of the present invention will be described.
First, the raw material which becomes a cordierite (2MgO · 3Al ₂ O ₃ · 5SiO ₂ ) composition by firing, that is, talc (3MgO · 4SiO ₂ · H ₂ O), magnesia (MgO), silica (SiO ₂ ), kaolin ( Al ₂ O ₃ · 2SiO ₂ · 2H ₂ O), alumina (Al ₂ O
₃ ), ceramic raw material powder appropriately selected from boehmite (AlOOH), aluminum hydroxide (Al (OH) ₃ ), etc., is prepared at a predetermined mixing ratio, and has a predetermined particle size distribution by pulverization, mixing, milling, etc. Adjust to raw materials.
Further, a transition metal such as yttria (Y ₂ O ₃ ), titania (TiO ₂ ), tungsten (W), or platinum (PT) may be added to support the catalyst.

Subsequently, as an auxiliary agent such as a binder, a plasticizer, a dispersant, a lubricant, a glaze, a surfactant, a pore-forming agent, methyl cellulose (MC), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), starch paste, Select appropriate materials from polyalkylene derivatives, glycerin, gelatin, wax emulsion, carbon, sawdust, etc., knead with the above raw materials to make ceramic clay, and further make the ceramic clay have predetermined flow characteristics Adjust the water content and viscosity. In the present embodiment, for example, the silica raw material is 19 by weight ratio.
%, Talc raw material 36%, alumina raw material 45%, and this is 100,
What added 21.6% of pore making agents, 13.5% of binder, and 34% of water was used.

In the ceramic honeycomb structure forming step of forming the ceramic honeycomb structure of the present invention, a mold in which a ceramic clay whose viscosity has been adjusted is provided with predetermined lattice grooves using a plunger-type extruder or a screw-type extruder The ceramic honeycomb structure in which a large number of substantially cylindrical cells having a desired cross-sectional shape are partitioned is formed.
At both end faces of the obtained ceramic honeycomb structure on the inlet side and the outlet side, a predetermined cell is filled with a sealing agent, the collection cell CL _IN is opened on the inlet side and closed on the outlet side, and the outlet side is opened and the outlet is opened. A discharge cell CL _OUT having an open side is provided.
In the present embodiment, as shown in FIGS. 5A and 5B, slit grooves SL formed by polygonal blocks BRK1 each having only a straight line and circular blocks BRK2 having curved lines are provided. The provided mold 50 was used. At the bottom of the slit groove SL, a lower hole UH through which ceramic clay is passed is provided. By increasing the number of the lower holes UH or increasing the inner diameter of the lower hole UH, the extrusion speed of the ceramic gob extruded from the slit groove SL can be made uniform.

As the plugging method, the following known methods can be appropriately used. That is, the end face of the honeycomb structure is covered with a resin film or the like, and the resin film in a portion covering the cells filled with the sealing agent is removed by heating or the like, and masking having a desired plugging formation pattern is performed.
Next, the end face of the masked honeycomb structure is immersed in a filler adjusted to a slurry, and the filler is filled in the cell from which the masking has been removed and dried.
Each of the entrance-side end face and the exit-side end face is filled with a sealant in a desired pattern to form plugging plugs STP _IN and STP _OUT , and after drying, firing is performed simultaneously with removal of the resin film. At this time, the filler is also fired together. In the case of cordierite, for example, 140
Baking at 0 ° C.
As described above, the honeycomb filter 1 including the collection cells CL _IN having a polygonal cross-sectional shape and the discharge cells CL _OUT having a circular cross-sectional shape can be formed.
As the filler, it is desirable to use a material mainly composed of the same material as the ceramic raw material forming the honeycomb structure and made into a slurry by a dispersion medium such as water. Further, it is desirable that the sealing plugs STP _IN and STP _OUT have a finer structure than the partition wall in order to prevent passage of combustion exhaust gas, and it is not necessary to add a pore forming agent to the sealing agent.

FIG. 6 illustrates an example of a combustion exhaust purification system using the honeycomb filter 1 of the present invention as a DPF.
The honeycomb filter 1 is provided in a combustion exhaust passage of an internal combustion engine 20 such as a diesel engine, for example, and collects PM in the combustion exhaust.
The internal combustion engine 20 includes each cylinder 2 that accumulates high-pressure fuel that has been boosted to a high pressure by a high-pressure pump P.
00 and a common rail R that is common to 00 and a plurality of fuel injection valves INJ that are connected to the common rail R and inject fuel into the combustion chamber of each cylinder 200. An intake manifold 210 of the internal combustion engine 20 is connected to an intake pipe 218. The intake flow rate is adjusted by an intake throttle 214 provided in the connection portion.

The exhaust manifold 220 of the internal combustion engine 20 is connected to the exhaust pipe 224 and the exhaust pipe 22.
The honeycomb filter 1 of the present invention is installed in the route 4.
Exhaust gas from the internal combustion engine 20, the inlet side enters the DPF1 from the absorption cell C ₁ which is open, PM is trapped when passing through the porous partition wall W _IO.
The partition wall W _IO surfaces within DPF1 in contact with the exhaust, it is also possible to support a catalyst for promoting the oxidation of PM. Moreover, it is good also as a structure which provided the oxidation catalyst 110 in the upstream of DPF1. Further, a urea SCR device (not shown) may be provided on the downstream side of the DPF 1 to perform a process for removing NOx in the exhaust gas from which PM has been removed by the DPF 1.

A turbine 221 of a centrifugal supercharger is provided on the upstream side 223 of the DPF 1 in the exhaust pipe 224 and is connected to the compressor 216 provided in the intake pipe 218 via a turbine shaft 222. As a result, the turbine 221 is driven using the heat energy of the exhaust, and the compressor 216 is driven via the turbine shaft 222, and the intake filter 2 is supplied from the intake pipe 218.
The intake air introduced through 17 is compressed in the compressor 216. Intake throttle 214
An intercooler 215 is provided upstream of the intake air to cool the intake air that has been compressed by the compressor 216 to a high temperature.

The exhaust manifold 220 is connected to the intake manifold 210 by an EGR passage 212, and a part of the exhaust is returned to the intake air through the EGR passage 212. An EGR valve 211 is provided at the outlet of the EGR passage 212 to the intake manifold 210, and the amount of exhaust gas recirculated to the intake air can be adjusted by adjusting the opening thereof. In the middle of the EGR passage 212, an EGR cooler 213 for cooling the refluxed EGR gas is provided.

In the exhaust pipes 223 and 224, in order to know the amount of PM collected by the DPF 1,
A differential pressure sensor 100 for detecting a differential pressure before and after 1 is provided. One end of the differential pressure sensor 100 is D
The other end side of the exhaust pipe 223 upstream of the PF1 is connected to the exhaust pipe 224 downstream of the DPF1 via a pressure introduction pipe, so that a signal corresponding to the differential pressure across the DPF1 is output.
Further, an exhaust temperature sensor T _SEN for detecting the DPF temperature T _EX is provided at the outlet of the DPF 1,
An air-fuel ratio sensor λ _SEN is installed as an oxygen concentration detection means for detecting the oxygen concentration λ downstream of the DPF 1. Signals from these sensors are all input to the ECU 30 as control means.

The ECU 30 further includes an opening OP _IN of the intake throttle 214, a valve opening OP _EGR of the EGR valve 211, an engine speed NE, a vehicle speed SP, an accelerator opening AC, a coolant temperature TW, a crank position CA, and a fuel pressure P _CYL. Signals are input from various sensors that detect the above, and the operation state of the internal combustion engine 20 is detected. The ECU 20 calculates the optimal fuel injection amount and EGR amount according to the operating state, and performs feedback control of the intake throttle 214, the fuel injection valve INJ, the EGR valve 211, and the like. The ECU 30 also detects the exhaust gas flow rate (volume flow rate) calculated from the detected values of the intake air amount sensor AR _SEN and the exhaust gas temperature sensor T _SEN that detect the intake air amount introduced into the intake pipe 218, and the differential pressure sensor 100. Based on the differential pressure across the DPF 1, the amount of PM trapped can be calculated to control the regeneration of the DPF 1. In general, the differential pressure increases as the amount of collected PM increases for a certain exhaust flow rate.
The amount collected can be calculated. Then, when the calculated amount of collected PM exceeds a predetermined value, the DPF 1 is heated to perform a regeneration process for burning and removing PM.

As a regeneration means for the DPF 1, specifically, when fuel is injected from the fuel injection valve INJ into the combustion chamber, post injection or delay of the injection timing is performed, or the intake throttle 214 is closed from the normal side, etc. The method of raising the temperature of the exhaust can be adopted. For example, when post-injection or retarding is performed, due to a delay in the ignition timing, a part of the energy is not returned to the motive power, but becomes the heat energy of the exhaust, so the exhaust temperature in the normal injection (150 to 400) In contrast, high temperature (300
˜700) is introduced into the DPF 1. Similarly, when the intake throttle 214 is closed, the intake air amount is reduced, and the heat capacity of the gas flowing into the combustion chamber of the internal combustion engine 20 is reduced, so that the exhaust temperature rises. Due to this high-temperature exhaust, PM adhering in the DPF 1 can be burned and the collection ability can be recovered. Depending on the operating state, a plurality of regeneration means can be used properly, or a heating device such as a burner or a heater can be used as the regeneration means.

1 Honeycomb filter (DPF)
CL _IN collection cell CL _OUT discharge cell Dh ₀ virtual unit cell equivalent hydraulic diameter Dh ₁ collection cell hydraulic diameter Dh ₂ discharge cell hydraulic diameter W _IO collection cell discharge cell interval wall W _II collection cell interval wall W _TK thickness meat portions _{SRF iN} inlet side wall _{SRF OUT} outlet side wall _{STP iN} inlet side sealing plug _{STP OUT} outlet sealing plug _N number per unit cross-sectional area of the number _{N B} discharge cells per unit sectional area of the _a collecting cells

International Publication No. 2004/024295 Pamphlet JP-A-2005-270969

Claims (4)

A large number of cells partitioned into a substantially cylindrical shape that serves as a flow path for the fluid to be processed are provided by partition walls made of porous ceramics to form a honeycomb shape, and one end of the cell is opened to the inlet side where the fluid to be processed is introduced. A collecting cell with the other end of the caulking closed, and a discharge cell with one end of the cell closed and the other end opened on the outlet side from which the fluid to be treated is discharged. And the discharge cell are disposed at predetermined positions, and the fluid to be treated is allowed to pass through a partition wall that partitions the collection cell and the discharge cell, and the collected material in the fluid to be treated is In the honeycomb filter collected in the partition wall,
The partition partitioning between the collection cell and the discharge cell is a curved surface in which the side facing either the collection cell or the discharge cell is a flat surface and the side facing the other is curved concavely. As providing a thick part in a part of the partition,
The number per unit cross-sectional area of the collection cell in the vertical cross section with respect to the longitudinal direction of the substantially cylindrical cell is N _A (pieces / inch ² ), and the number of the discharge cells in the vertical cross section with respect to the longitudinal direction of the substantially cylindrical cell. When the number per unit cross-sectional area is N _B (pieces / inch ² ), N _A >
The honeycomb filter being characterized in that allowed satisfy the relationship of N _B. 2. The honeycomb according to claim 1, wherein one of the shape of a cross section perpendicular to the flow channel longitudinal direction of the collection cell and the discharge cell is formed in a polygon and the other is formed in a circle. filter. In the honeycomb filter in which the catalyst is supported on the collection cell and the discharge cell, the minimum value of the catalyst supported mass per unit surface area supported on the plane side of the cell wall is t _C (mg / mg
mm ² ), t _D (mg / mm ² ), the average value of the catalyst support mass per unit surface area supported on the curved surface side of the cell wall, and the catalyst support per unit surface area supported on the plane side of the cell wall When the maximum value of mass is t _E (mg / mm ² ),
The honeycomb filter according to claim 1 or 2, wherein a relationship of t _C ≤ t _D ≤ t _E is satisfied. The method for manufacturing a honeycomb filter according to any one of claims 1 to 3, wherein a gold is provided with slit grooves formed by polygonal blocks each having only a straight line and circular blocks each having a curved line. A honeycomb filter manufacturing method including a ceramic honeycomb structure forming step of forming a ceramic honeycomb structure by extruding a ceramic clay from a mold.

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