JP2006204979A - Filter for cleaning exhaust gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filter for cleaning exhaust gas, the pressure loss of which is restrained from being increased owing to the accumulation of PM (particulate matter) and which is prevented from being overheated locally when accumulated PM is burned. <P>SOLUTION: The filter for cleaning exhaust gas has an axial-direction adjacent part 3 in which a wall flow part 1 and a straight flow part 2 are made adjacent to each other in the axial direction while leaving a space between them, a radial-direction adjacent part 4 in which the wall flow part 1 and the straight flow part 2 are made adjacent to each other in the radial direction and a detour 5 through which exhaust gas can be circulated while bypassing the wall flow part 1. When PM is accumulated in the wall flow part 1 in a certain extent, exhaust gas flows through the detour 5 and then through the straight flow part 1 or wall flow part 2 adjacent to the PM-accumulated wall flow part. Since this function of the detour is repeated like a chain reaction, excessive PM can be prevented from being accumulated locally. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust gas purification filter capable of purifying exhaust gas containing particulates such as exhaust gas from a diesel engine.

  As for gasoline engines, toxic components in exhaust gas are steadily decreasing due to strict regulations on exhaust gas and technological advances that can cope with it. On the other hand, for diesel engines, harmful components are discharged as particulates (particulate matter: carbon fine particles, sulfur fine particles such as sulfate, high molecular weight hydrocarbon fine particles (SOF), etc., hereinafter referred to as PM)) The exhaust gas is more difficult to purify than gasoline engines.

  As exhaust gas purification devices for diesel engines that have been developed so far, a trap type exhaust gas purification device (wall flow) and an open type exhaust gas purification device (straight flow) are known. Among these, as a trap type exhaust gas purification device, a ceramic plug-type honeycomb body (diesel PM filter (hereinafter referred to as DPF)) is known. This DPF is formed by alternately sealing both ends of the openings of the cells of the ceramic honeycomb structure, for example, in a checkered pattern, and is adjacent to the inflow side cells and the inflow side cells clogged on the exhaust gas downstream side. It consists of an outflow side cell clogged upstream of the exhaust gas, and a cell partition partitioning the inflow side cell and the outflow side cell. Filtering exhaust gas through the pores of the cell partition and collecting PM suppresses emissions. To do.

  However, in DPF, pressure loss (hereinafter referred to as pressure loss) increases due to PM accumulation, so it is necessary to periodically remove and regenerate PM accumulated by some means. Therefore, conventionally, when pressure loss increases, DPF is regenerated by burning high-temperature exhaust gas and burning PM. However, in this case, the higher the amount of PM deposited, the higher the temperature during combustion, which may cause damage such as DPF melting or DPF breaking due to thermal stress.

  On the inflow side end face of the DPF, the opening of the inflow side cell and the plugging part of the outflow side cell are adjacent. For this reason, the opening ratio of the end face is 50% or less, and PM and ash are likely to be deposited on the clogged portion. When the temperature of the entering gas is low, or when spraying of a reducing agent such as light oil continues, the PM deposition layer grows to the opening of the inflow side cell, and the opening of the inflow side cell is deposited. As a result of being blocked by PM, there arises a problem that pressure loss increases and engine output decreases.

  In view of this, Japanese Patent Application Laid-Open No. 2004-019498 proposes an exhaust gas purification filter in which a honeycomb body having a straight flow structure is integrally disposed on the upstream side of an exhaust gas body having a wall flow structure. According to this exhaust gas purification filter, even if the PM deposit layer of the clogging portion of the outflow side cell grows, the opening of the inflow side cell is prevented from being blocked, so that an increase in pressure loss can be prevented.

  Japanese Patent Laid-Open No. 2003-278524 discloses that a filter having a straight flow structure portion is integrally arranged on the outer peripheral side of the wall flow structure portion on the upstream side, and the wall flow structure portion is integrated on the outer peripheral side of the straight flow structure portion. There has been proposed an exhaust gas purification filter in which a filter having a filter is disposed downstream thereof. According to this exhaust gas purification filter, an increase in pressure loss can be suppressed by the straight flow structure. Moreover, since PM which passed the straight flow structure part can be collected by the downstream wall flow structure part, PM collection rate does not fall.

  However, even in the above-described exhaust gas purification filter, when a large amount of PM accumulates on the wall flow structure, there still remains a problem that it is easily damaged by the heat generated when it is burned at a time during regeneration.

In recent years, as described in JP-A-09-094434, a continuous regeneration type DPF in which a coating layer supporting a catalyst metal is formed not only in the cell partition walls but also in the pores of the cell partition walls has been used. ing. By supporting the catalyst metal in the pores, the contact probability between the PM and the catalyst metal is increased, and the PM collected in the pores can be oxidized and burned. However, in such a continuous regeneration type DPF, the coat layer must be thinned to prevent an increase in pressure loss. Accordingly, when the conditions for depositing PM are continuous, such as at low temperatures, the PM deposition amount exceeds the PM oxidation amount by the catalyst, and the problem of damage occurs as described above.
JP2004-019498 JP2003-278524 JP 09-094434

  The present invention has been made in view of the above circumstances, and a main object thereof is to suppress an increase in pressure loss due to PM deposition and to prevent local overheating when the deposited PM burns. Another object of the present invention is to form a local heat spot when used at a low temperature, and to further promote PM combustion by the heat.

The features of the exhaust gas purification filter of the present invention that solves the above-mentioned problems are characterized in that an inflow side cell clogged on the exhaust gas downstream side, an outflow side cell adjacent to the inflow side cell and clogged on the exhaust gas upstream side, and an inflow side cell And a porous cell partition wall partitioning the outflow side cell, and a wall flow part having
An exhaust gas purification filter having a straight flow part composed of straight cells that are not clogged on both the exhaust gas upstream side and the exhaust gas downstream side, and wherein a plurality of wall flow parts and a plurality of straight flow parts are joined,
An axially adjacent portion in which the wall flow portion and the straight flow portion are adjacent to each other at an interval in the axial direction, and a radially adjacent portion in which the wall flow portion and the straight flow portion are adjacent to each other in a direction crossing the axial direction, And a detour that allows the exhaust gas to circulate around the wall flow section.

  On the exhaust gas downstream side, it is desirable that the thermal conductivity of the joint portion between the wall flow portion and the straight flow portion in the radially adjacent portion is equal to or higher than the thermal conductivity of the wall flow portion or the straight flow portion.

  Further, in the vicinity of the exhaust gas inflow side end face, it is desirable that the thermal conductivity of the joint portion between the wall flow portion and the straight flow portion in the radially adjacent portion is equal to or less than the thermal conductivity of the wall flow portion or the straight flow portion.

  It is desirable that at least a part of the cell partition walls and the straight cell has an oxidation catalyst layer in which a catalyst metal is supported on a porous oxide.

  According to the exhaust gas purifying filter of the present invention, when PM is accumulated to some extent in the wall flow part, the exhaust gas flows through the straight flow part or the wall flow part in the radial direction adjacent part or the axial direction adjacent part through the bypass. When PM accumulates to some extent on the wall flow part of the part, the exhaust gas flows through the bypass or the straight flow part or wall flow part of the adjacent radial direction adjacent part or axially adjacent part. Since this action is repeated in a chain manner, excessive PM deposition is not caused and an increase in pressure loss is suppressed, and the time until regeneration processing can be extended, so that fuel efficiency is improved. In addition, since a large amount of PM does not accumulate locally in the wall flow part, damage due to overheating during regeneration is prevented. If the oxidation catalyst layer is provided, the deposited PM can be oxidized and purified within a small amount, and damage due to overheating is further prevented.

  In addition, if the joint between the wall flow part and the straight flow part in the radially adjacent part on the exhaust gas downstream side is made to have high heat conduction, the heat near the rear end of the wall flow part where the temperature rises significantly during PM combustion is straight flow part. Therefore, local high temperature is prevented and damage due to overheating can be further prevented.

  Furthermore, in the vicinity of the exhaust gas inflow side end face, if the joint part between the wall flow part and the straight flow part in the radially adjacent part has low heat conduction, or at least the straight flow part is made of a low heat conduction material, the exhaust gas has priority over the straight flow part. Therefore, the temperature rise characteristic of the straight flow part is improved by heat storage. Therefore, when the exhaust gas having a high temperature flows from the straight flow portion into the wall flow portion, combustion of PM accumulated in the wall flow portion can be promoted, and an increase in pressure loss can be further suppressed. Further, by having the oxidation catalyst layer, the catalytic activity is expressed early even at low temperatures such as at the time of starting, and the purification performance of HC and CO is improved.

  The exhaust gas purifying filter according to the present invention includes an axially adjacent portion in which a wall flow portion and a straight flow portion are adjacent to each other at an interval in an axial direction, and a wall flow portion and a straight flow portion in a direction crossing the axial direction. It has the adjacent radial direction adjacent part and the detour which can distribute | circulate waste gas by detouring a wall flow part. That is, a plurality of wall flow portions and a plurality of straight flow portions are arranged in the axial direction (exhaust gas flow direction) and the radial direction, respectively. This arrangement state may be arranged regularly or randomly.

  The wall flow section includes an inflow side cell clogged on the exhaust gas downstream side, an outflow side cell adjacent to the inflow side cell and clogged on the exhaust gas upstream side, and a porous cell partitioning the inflow side cell and the outflow side cell. It has the same structure as a conventional DPF having a cell partition wall. There are no particular restrictions on the number of cells or the cross-sectional shape of the cells. The porosity of the cell partition wall is desirably 50 to 75%. When the porosity is in this range, PM can be efficiently collected, and an increase in pressure loss can be suppressed even when the oxidation catalyst layer is formed at 50 to 200 g / L.

  The straight flow part is composed of straight cells that are not clogged on both the exhaust gas upstream side and the exhaust gas downstream side, and has the same structure as a honeycomb body used for a conventional three-way catalyst or the like. There are no particular restrictions on the number of cells or the cross-sectional shape of the cells.

  In order to manufacture the exhaust gas purification filter of the present invention, the block constituting the wall flow part and the block constituting the straight flow part are respectively used, and the axial direction (exhaust gas flow direction) and the radial direction (direction intersecting with the exhaust gas flow direction), In general, the blocks are appropriately arranged in a direction orthogonal to each other, and the blocks are joined together with an inorganic adhesive or the like in the radial direction. At this time, the wall flow block and the straight flow block are arranged adjacent to each other in the axial direction and the radial direction. In the axial direction, the wall flow unit block and the straight flow unit block are spaced apart from each other. Thereby, an axial direction adjacent part and a radial direction adjacent part can be formed. And an exhaust gas purification filter can be manufactured by cutting out the obtained block integration body into predetermined filter shapes, such as a column shape.

  In the radial adjacent part, if the adhesive is partially applied and joined so that the part where the adhesive is not applied is continuously formed in the exhaust gas flow direction, the exhaust gas flows through the part where the adhesive is not applied. Since it becomes possible, a detour can be formed in that part. Note that if there is a gap on the exhaust gas inflow side end face, PM may accumulate in the gap and be damaged by overheating. Therefore, it is desirable to join the blocks over the entire surface. Therefore, it is desirable that the detour in the radially adjacent portion is started from the downstream side of the exhaust gas inflow end surface.

  The distance between the wall flow portion and the straight flow portion in the axially adjacent portion is not particularly limited as long as exhaust gas containing PM can flow. As a result, the exhaust gas that has passed through the detour can pass through the axially adjacent portion and flow into the downstream straight flow portion. Further, the position of the axially adjacent portion is not limited as long as it is other than the exhaust gas inflow side and the outflow side end face, but it is desirable to form the axially adjacent portion at various positions in the axial direction. This can be done easily by using blocks having different lengths.

  On the exhaust gas downstream side, it is desirable that the thermal conductivity of the joint portion between the wall flow portion and the straight flow portion in the radially adjacent portion is equal to or higher than the thermal conductivity of the wall flow portion or the straight flow portion. In this way, heat near the rear end of the wall flow part where the temperature rises significantly during PM combustion is efficiently released to the straight flow part, so that it is prevented from becoming locally hot and further damaged by overheating. Can be prevented. In order to achieve a thermal conductivity equal to or higher than that of the wall flow part or straight flow part, at least the rear end part of the wall flow part is formed of a high thermal conductive material having a thermal conductivity equal to or higher than that of the wall flow part or straight flow part. However, it is convenient to use an adhesive having a high thermal conductivity. An adhesive having a high thermal conductivity may be used, or a high thermal conductive material such as SiC powder or metal powder may be mixed in the inorganic adhesive.

  In the vicinity of the end face on the exhaust gas inflow side, for example, an inorganic adhesive having a thermal conductivity equal to or less than that of the wall flow part or the straight flow part is used for the joint part between the wall flow part and the straight flow part in the radially adjacent part. Alternatively, it is desirable to make the thermal conductivity equal to or less than that of the wall flow part or the straight flow part, such as by forming an air layer. Since heat spots easily form heat spot near the exhaust gas inflow side end face, PM combustion is promoted even when the exhaust gas temperature is low. Furthermore, by having an oxidation catalyst layer, catalytic activity is manifested at an early stage even at low temperatures such as at start-up, and the purification performance of HC and CO is improved. In addition, since an air layer will be formed if a detour is formed, it can be set as low heat conduction by the heat insulation effect.

  Furthermore, it is also preferable that the straight flow part has a low heat capacity in the vicinity of the end face on the exhaust gas inflow side. In this way, since the temperature can be rapidly raised until the heat spot is formed, the HC and CO low-temperature purification performance is improved by having an oxidation catalyst layer.

  It is desirable that at least a part of the cell partition walls and the straight cell has an oxidation catalyst layer in which a catalyst metal is supported on a porous oxide. As a result, the deposited PM can be oxidized and burned quickly at the same time as or after the deposition, and HC and CO can be purified. The oxidation catalyst layer may be an oxidation catalyst or a three-way catalyst.

The porous oxide functions as a catalyst metal carrier, and is a composite oxide composed of at least one of oxides such as Al ₂ O ₃ , ZrO ₂ , CeO ₂ , TiO ₂ , SiO ₂ , or a plurality of these. Can be used.

  In order to form the catalyst layer, the porous oxide powder is made into a slurry together with a binder component such as alumina sol and water, and the slurry is attached to the cell partition wall and then baked to form a coat layer. May be carried. It is also possible to prepare a slurry from a catalyst powder in which a catalyst metal is previously supported on a porous oxide powder and to use it to form a coat layer. A normal dipping method can be used to attach the slurry to the cell partition walls. However, the slurry is forcibly filled into the pores of the cell partition walls by air blowing or suction, and the excess slurry contained in the pores is filled. It is desirable to remove things.

  In this case, the formation amount of the coat layer or the catalyst layer is preferably 50 to 200 g per 1 L of the exhaust gas purification filter. If the coat layer or the catalyst layer is less than 50 g / L, a decrease in the durability of the catalyst metal is unavoidable, and if it exceeds 200 g / L, the pressure loss becomes too high to be practical.

  As the catalyst metal contained in the catalyst layer, it is preferable to use at least one selected from platinum group noble metals such as Pt, Rh and Pd. The amount of the precious metal supported is preferably in the range of 1 to 10 g per liter of the exhaust gas purification filter. If the loading amount is less than this, the activity is too low to be practical, and if the loading amount exceeds this range, the activity is saturated and the cost is increased. In order to support the noble metal, a solution in which a nitrate of noble metal is dissolved can be used and supported by an adsorption support method, an impregnation support method, or the like.

The catalyst layer preferably also contains a NO _x storage material selected from alkali metals, alkaline earth metals and rare earth elements. If including _the NO _x storage material in the catalyst layer, since the NO _x produced by the oxidation by the catalyst metal can be occluded in _the NO _x storage material, thereby improving the purification activity of NO _x. This NO _x storage material is selected from alkali metals such as K, Na, Cs and Li, alkaline earth metals such as Ba, Ca, Mg and Sr, or rare earth elements such as Sc, Y, Pr and Nd. Can be used. In particular, it is desirable to use at least one of alkali metals and alkaline earth metals that have excellent NO _x storage ability.

The amount of the NO _x storage material supported is preferably in the range of 0.15 to 0.45 mol per liter of the exhaust gas purification filter. If the loading is less than this, the activity is too low to be practical, and if the loading is more than this range, the noble metal is covered and the activity decreases. In order to support the NO _x storage material, a solution in which acetate, nitrate or the like is dissolved may be used and supported on the coat layer by an impregnation support method or the like. The advance carries advance _the NO _x storage material on the porous oxide powders, it is also possible to form the catalyst layer by using the powder.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

Example 1
1 and 2 show an exhaust gas purification filter according to an embodiment of the present invention. This exhaust gas purification filter includes an inflow side cell 10 clogged on the exhaust gas downstream side, an outflow side cell 11 adjacent to the inflow side cell 10 and clogged on the exhaust gas upstream side, an inflow side cell 10 and an outflow side cell 11. A wall flow section 1 having a porous cell partition wall 12 for partitioning;
A straight flow portion 2 composed of straight cells that are not clogged on both the exhaust gas upstream side and the exhaust gas downstream side, and the plurality of wall flow portions 1 and the plurality of straight flow portions 2 are adjacent to each other in the axial direction and the radial direction. And an adhesive layer 20 having a thickness of about 1 mm.

  The wall flow portion 1 and the straight flow portion 2 are adjacent to each other in the axial direction, and the wall flow portion 1 and the straight flow portion 2 are adjacent to each other with a space 30 therebetween. And the detour 5 that bypasses the wall flow section 1 and allows the exhaust gas to flow therethrough.

  Hereinafter, a method for manufacturing the exhaust gas purification filter will be described, and the detailed description of the configuration will be substituted.

  A rectangular parallelepiped wall flow block 1 ′ and a straight flow block 2 ′ shown in FIG. 3 were prepared. The wall flow block 1 ′ is formed of cordierite, has a rectangular parallelepiped shape of 35 mm × 35 mm × 80 mm, and has a plurality of inflow side cells 10 and outflow side cells 11 extending in the longitudinal direction. The cell density is 300 cpsi, the cell partition wall 12 has a thickness of 250 μm, a porosity of 60%, and an average pore diameter of 15 to 30 μm. The straight flow block 2 'is made of cordierite, has a rectangular parallelepiped shape of 35 mm x 35 mm x 50 mm, has a cell density of 300 cpsi, a cell partition wall thickness of 200 μm, and a porosity of 35%.

  The wall flow block 1 ′ and the straight flow block 2 ′ were alternately laminated in the radial direction with an interval of 20 mm therebetween and adjacent to each other in the radial direction. An adhesive layer 20 was formed by applying an inorganic adhesive to the joining surfaces indicated by diagonal lines in FIG. 3 and joined by heating at 90 to 150 ° C. for 2 hours. At the exhaust gas inlet side end and the exhaust gas outlet side end, the wall flow block 1 'and the straight flow block 2' are joined only on the upper, lower, left and right four sides, and in the middle, only the upper, lower, left and right corners are joined. An air layer 21 having a thickness of about 1 mm and a width of 12 mm was formed in the central portion excluding the joined corners. This air layer 21 is open at both ends to form a bypass 5. The adhesive layer 20 at the end portion on the exhaust gas inlet side uses a cordierite-based inorganic adhesive having a thermal conductivity equal to or lower than that of the wall flow block 1 ′ or the straight flow block 2 ′. For the adhesive layer 20 of the part, a high thermal conductive adhesive containing 30 to 40% by weight of SiC powder and having a thermal conductivity equal to or higher than that of the wall flow block 1 ′ or the straight flow block 2 ′ was used.

  The obtained prismatic column with a length of 150 mm was cut into a cylindrical shape with an outer diameter of 150 mm so that both end surfaces were the end surfaces of each block.

Next, a slurry composed of Al ₂ O ₃ powder, TiO ₂ powder, ZrO ₂ powder, CeO ₂ powder, alumina sol and ion-exchanged water was prepared and milled so that the average particle size of the solid particles was 1 μm or less. The formed cylindrical filter is immersed in this slurry, and the slurry is poured into the cell. The slurry is pulled up and sucked from the end surface opposite to the immersion side to remove excess slurry. Baked for hours. This operation was performed twice, and adjustment was performed so that the same amount of coat layer was formed in the inflow side cell 10 and the outflow side cell 11. The coating amount is 60 g per liter of filter. The coat layer is formed on the surfaces and the pores of the inflow side cell 10 and the outflow side cell 11.

  Thereafter, a predetermined amount of an aqueous solution of dinitrodiammine platinum nitrate having a predetermined concentration was impregnated, dried and fired, and Pt was supported on the coat layer to form a catalyst layer (not shown). The amount of Pt supported is 1 g per liter of the filter.

  In the obtained filter catalyst, as shown in FIG. 2A, initially, the exhaust gas preferentially flows into the straight flow portion 2 having a low resistance, and HC and CO are purified by the catalyst layer. Thereafter, the exhaust gas flows into the wall flow section 1 on the downstream side, and PM is collected and oxidized by the catalyst layer.

  As the usage time elapses, the PM deposition amount in the downstream wall flow portion 1 increases or the PM deposits on the end surface thereof, the pressure loss of the wall flow portion 1 increases. Accordingly, as shown in FIG. 2 (b), the exhaust gas emitted from the straight flow portion 2 flows from the axially adjacent portion 3 via the detour 5 and is generated in the entire filter catalyst. Increase in pressure loss is suppressed.

  Further, since the adhesive layer 20 in the middle part uses a high thermal conductive adhesive, the heat in the vicinity of the rear end of the wall flow part 1 where the temperature rises significantly during PM combustion is efficiently released to the straight flow part 2. Therefore, high temperature is prevented and damage due to overheating is prevented.

  Furthermore, since the adhesive layer 20 is formed only at the inlet side end at the exhaust gas inlet side end, most of the straight flow part 2 is adjacent to the wall flow part 1 through the air layer 21. Therefore, due to the heat insulating action of the air layer, the heat flow spot is easily formed in the straight flow part 2, and HC and CO can be purified from the low temperature range.

(Example 2)
A filter catalyst was prepared in the same manner as in Example 1 except that the wall flow block 1 ′ and the straight flow block 2 ′ made of SiC were used.

(Example 3)
A filter catalyst was prepared in the same manner as in Example 1 except that all the adhesive layers 20 were formed of cordierite-based inorganic adhesive.

Example 4
A filter catalyst was prepared in the same manner as in Example 1 except that all the adhesive layers 20 were formed from a high thermal conductive adhesive containing SiC.

(Example 5)
A filter catalyst was prepared in the same manner as in Example 1 except that the wall flow block 1 ′ made of SiC and the straight flow block 2 ′ made of cordierite were used.

(Example 6)
As shown in FIG. 4, a filter catalyst was prepared in the same manner as in Example 1 except that the intermediate adhesive layer 20 was formed so as to extend in the axial direction from the center of each side of the end face except for the corners. did. In this case, the corner of each block in the intermediate portion becomes the detour 5.

(Example 7)
As shown in FIG. 5, a filter catalyst was prepared in the same manner as in Example 1, except that the intermediate adhesive layer 20 was not formed on the XY plane but only on the YZ plane. In this case, the entire surface of the XY plane of each block in the intermediate portion is the detour 5.

(Comparative Example 1)
Cordierite honeycomb substrate (300cpsi, wall thickness 200μm, porosity 35%) with straight flow structure 150mm in diameter and 50mm length, and cordierite filter substrate (300cpsi) with wall flow structure 150mm in diameter and length 80mm After forming catalyst layers carrying Pt on each of them in the same manner as in Example 1, using a wall thickness of 250 μm, porosity of 60%, and average pore diameter of 15 to 30 μm, the straight-flow structure honeycomb catalyst was placed on the exhaust gas upstream side. Further, a filter catalyst having a wall flow structure was disposed on the downstream side thereof.

(Comparative Example 2)
It is the same as Comparative Example 1 except that a filter substrate made of SiC is used as the filter catalyst of the wall flow structure filter catalyst.

<Test and evaluation>
The filter catalyst of each of the above examples and the tandem catalyst of each comparative example are respectively mounted on the exhaust system of a 2.0 L diesel engine, and after 10-15 mode traveling for 300 km, PM forced combustion is performed by adding fuel during 120 km / h traveling The load was dropped to idle and the maximum catalyst temperature was measured. Further, after traveling for 10 km in the 10-15 mode, the emission of HC and CO was measured under the conditions of the 10-15 mode, and the ratio to the result of the tandem catalyst in Comparative Example 1 was calculated. The results are shown in Table 1.

  From Table 1, it can be seen that the filter catalyst of each example has a lower maximum temperature during forced regeneration than the tandem catalyst of Comparative Example 1, which indicates that PM does not accumulate excessively in the filter catalyst of each example. , And also means that it was dispersed and deposited. That is, according to the filter catalyst of each Example, it is clear that accumulation of much PM is suppressed locally.

  Moreover, the filter catalyst of each Example has high purification activity of HC and CO, and is excellent in low temperature activity compared with the tandem catalyst of Comparative Examples 1-2. This is considered to be because the flow of exhaust gas in the catalyst is complicated in each embodiment, and the contact time with the catalyst metal is increased. In addition, the comparison between Examples shows that the purification activity of HC and CO is improved by making the adhesive have low thermal conductivity on the upstream straight flow base material, which is because heat spots are easily formed. it is conceivable that.

It is a perspective view of the exhaust gas purification filter of one Example of this invention. It is sectional drawing of the exhaust gas purification filter of one Example of this invention. It is a perspective view explaining the manufacturing method of the exhaust gas purification filter of one Example of this invention. It is a perspective view explaining the manufacturing method of the exhaust gas purification filter of the 6th Example of this invention. It is a perspective view explaining the manufacturing method of the exhaust gas purification filter of the 7th Example of this invention.

Explanation of symbols

1: Wall flow part 2: Straight flow part 3: Axial adjacent part 4: Radial adjacent part 5: Detour 20: Adhesive layer

Claims (4)

An inflow side cell clogged on the exhaust gas downstream side, an outflow side cell adjacent to the inflow side cell and clogged on the exhaust gas upstream side, and a porous cell partition wall that partitions the inflow side cell and the outflow side cell And a wall flow part having,
A straight flow part composed of straight cells that are not clogged on both the exhaust gas upstream side and the exhaust gas downstream side, and an exhaust gas purification filter in which a plurality of the wall flow parts and a plurality of the straight flow parts are joined,
An axially adjacent portion in which the wall flow portion and the straight flow portion are adjacently spaced apart from each other in the axial direction;
A radially adjacent portion in which the wall flow portion and the straight flow portion are adjacent to each other in a direction intersecting the axial direction;
An exhaust gas purification filter comprising: a bypass circuit that bypasses the wall flow part and allows exhaust gas to flow therethrough.   2. The heat conductivity of the joint portion between the wall flow portion and the straight flow portion in the radially adjacent portion on the downstream side of the exhaust gas is equal to or higher than the heat conductivity of the wall flow portion or the straight flow portion. Exhaust gas purification filter.   2. Near the exhaust gas inflow side end face, the thermal conductivity of the joint portion between the wall flow portion and the straight flow portion in the radially adjacent portion is equal to or less than the thermal conductivity of the wall flow portion or the straight flow portion. Or the exhaust gas purification filter of Claim 2.   The exhaust gas purification filter according to any one of claims 1 to 3, wherein at least a part of the cell partition wall and the straight cell has an oxidation catalyst layer formed by supporting a catalyst metal on a porous oxide.

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