JP3207088B2 - Particulate trap for diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a particulate trap for collecting and removing fine particles (particulates) such as carbon in exhaust gas of a diesel engine. Also, the present invention relates to a particulate trap capable of removing harmful gas components in exhaust gas.

[0002]

2. Description of the Related Art Exhaust gas from automobiles is one of the major causes of air pollution, and a technique for removing harmful components contained in the exhaust gas is extremely important. Particularly in a diesel engine vehicle, removal of particulates mainly composed of NOx and carbon is an important issue.

[0003] In order to remove these harmful components, exhaust gas recirculation (EGR) has been applied, fuel injection systems have been improved, and efforts have been made on the engine side. A proposal of installing an exhaust trap in an exhaust passage, collecting particulates by the trap, and removing the particulates by post-processing (Japanese Patent Laid-Open No. 58-23535, etc.) is considered to be the most practical, and the study is continued. ing.

[0004] By the way, from the conditions used as a particulate trap for collecting particulates contained in the exhaust gas of a diesel engine, it is necessary to satisfy the following performance.

[0005] First, it is necessary to have a particulate collection efficiency that satisfies the cleanliness of exhaust gas. Although the amount of particulate emissions varies depending on the displacement and load of the diesel engine, it is said that it is necessary to be able to collect 60% or more of the average amount of emissions from the diesel engine. Recently, it has been reported that, among particulates, floating particles having a particle size of 2 μm or less easily enter the human alveoli and cause lung cancer, and it is necessary that these floating particles can be sufficiently collected.

[0006] Second, pressure loss with respect to exhaust gas is small. As the particulates are collected, the pressure loss when the engine exhaust passes through the trap increases, causing a back pressure on the engine and causing an adverse effect. For this reason, it is said that it is usually necessary to suppress the pressure loss during collection to 30 Kpa or less. Therefore, it is necessary that the particulate trap not only has a small initial pressure loss, but also that the pressure loss hardly increases even if the exhaust gas passes and the particulates are collected.

[0007] Third, regeneration can be performed with low energy.
After trapping the particulates,
It must be used repeatedly by burning and regenerating it. As a regeneration method, a regeneration method using an electric heater or a light oil burner is being studied.

[0008] Fourth, it has excellent durability. Since it is exposed to high-temperature exhaust gas, it is required to have high corrosion resistance and also to withstand repetition of heat shock generated at the time of particulate combustion regeneration.

Fifth, integration with a catalytic converter is necessary. At present, in order to remove harmful gas components in exhaust gas, a catalytic converter supporting a harmful gas removal catalyst may be installed in an engine exhaust system. At the same time, when attempting to install a particulate trap, there is a problem that there is no installation space in the engine exhaust system and an increase in cost for installing two types of post-processing devices.

Heretofore, it has been considered that a wall-flow type porous honeycomb body of cordierite ceramics is most practically used as a filter element material satisfying the above requirements. However, in this method, particulates tend to accumulate locally, and cordierite ceramics have a low thermal conductivity, so that heat spots are likely to be generated during reproduction, and the filter is melted or cracked due to thermal stress. In some cases, durability could not be secured. It is also said that it is difficult to ensure durability of ceramic fiber traps made of ceramic fibers, which have recently attracted attention, in the form of candles, since the strength is deteriorated in high-temperature exhaust gas and the fibers are destroyed.

Therefore, attention has been paid to a highly reliable metal trap which is free from cracks or the like during reproduction. However, although this metal trap provides satisfactory results with respect to the durability with the regeneration of the above requirements,
It is difficult to satisfy the requirements for the collection efficiency and pressure loss. That is, when a filter is designed with a small hole to obtain a high collection efficiency, the particulates are collected only on the filter surface and become clogged. As a result, the pressure loss rises rapidly and the filter life is shortened. .

[0012]

The wall-flow type honeycomb porous body of cordierite ceramic which has been conventionally developed as a DPF (diesel particulate filter) has the following problems. (1) Due to its low thermal conductivity, it is difficult for the filter to reach a uniform temperature during regeneration. As a result, heat spots are likely to be formed during reproduction, the filter may be melted or cracked due to thermal stress, and durability cannot be ensured. (2) Since the holes have a rectangular cross section, heat dissipation due to particulate combustion during regeneration is poor, and heat is easily concentrated at the corners, so that the filter is easily broken and durability cannot be ensured. (3) Such a honeycomb-shaped porous body has a large number of holes having a square cross section, and the end holes are alternately plugged at an exhaust gas inlet / outlet. Since this plugging becomes a flow path resistance, the initial pressure loss is large. (4) In the above structure, the opening area on the exhaust gas inlet side is small, the particulate matter adheres, the opening is closed, and the pressure loss may increase despite the small amount of trapping. (5) In order to collect floating particles having a particle size of 2 μm or less among the particulates, the pore size must be reduced, and in this case, the pressure loss increases. (6) When a catalyst is supported, the honeycomb-shaped porous body has a large heat capacity, so that the temperature rising speed is slow, and a sufficient temperature rise for the catalyst to work may not be obtained.

[0013] Therefore, a metal trap which has a high thermal conductivity, hardly generates a heat spot at the time of reproduction, and has no cracks or the like and has high reliability has been attracting attention. However, although metal traps satisfy the above requirements for durability and regeneration characteristics, if a filter is designed to obtain high collection efficiency, particulates will become clogged on the filter surface, resulting in a pressure loss. It rises sharply, shortening the filter life. That is, the above-mentioned requirements cannot be satisfied by the conventional technology.

To simultaneously satisfy the above requirements with a metal trap, it is necessary to increase the surface area (filtration area) of the filter element through which exhaust gas can flow. However, if the surface area (filtration area) of the filter element is increased by using a conventional metal trap, the particulate trap becomes very large. If the filter is precision welded to the side plate, the space between the filters can be shortened to increase the space utilization efficiency and the size can be reduced to some extent, but this method is not excellent in mass productivity and increases the cost.

The present invention solves the problem of a cordierite ceramic wall-flow type honeycomb-shaped porous body by using a metal as a filter material, and employs a small trap structure having a large filter element surface area to obtain a conventional metal. It also solves the problem of traps made by steel. In addition, the formation of alumina whiskers on the surface of the filter material enables trapping of buoyant particulates, and the loading of the catalyst on the metal trap also realizes the integration of the particulate trap and the catalytic converter.

[0016]

In order to solve the above-mentioned problems, in the present invention, a large number of flat filters are arranged in parallel, and a gap between the flat filters for introducing exhaust gas is formed on the inlet and outlet sides of the exhaust gas. A plurality of filter elements having a structure of alternately dead ends or cylindrical filters of different diameters similar in cross section are concentrically arranged, and the gap between each cylindrical filter for introducing exhaust gas and one end of the minimum diameter filter are connected to the exhaust gas inlet. Either one of the filter elements having dead ends alternately on the side and the outlet side is mounted in a container installed in the middle of the exhaust system to form a particulate trap for a diesel engine.

Further, as a means for solving the above problems, a particulate trap for a diesel engine employing the following filter element (1) or (2) has been invented.

(1) A non-woven fabric of a heat-resistant metal fiber is used as a filter material, and a plurality of metal tapered cylindrical filters made of the filter material are concentrically arranged in such a manner that taper directions are alternately reversed. The small-diameter end of each filter is connected to the large-diameter end of the inner cylindrical filter except for the central cylindrical filter where the small-diameter end is a dead end. A filter element with a dead end that alternates between the exhaust gas inlet and outlet.

(2) A flat band filter using a heat-resistant metal fiber non-woven fabric as a filter material is alternately bent in an inverted or U-shape to form a gap between the flat filters in an exhaust gas. A filter element with a dead end that alternates between the inlet side and the outlet side.

The cylindrical filter constituting the filter element of the above (1) may be either a circular filter having a circular cross section or a polygonal filter having a cross section.

The filter constituting the filter element of the trap preferably employs a nonwoven fabric of metal fibers having continuous pores made of a heat-resistant metal. Also,
The gap for introducing exhaust gas, which is present between the flat filters or between the cylindrical filters, has a dimension in the filter thickness direction of 10 mm in order to sufficiently reduce the size of the particulate trap.
It is desirable to make the following.

Further, the filter element having the filter of the parallel plate is formed by alternately bending the sheet-like filter in a U-shape in the opposite direction, and forming a parallel-arranged plate filter and a wall for stopping one side between the gaps of the plate filter. It is particularly desirable that the liner is formed and sealed on both sides of the gap between the plate filters by inserting liners.

In addition, the filter element can be made of a material in which at least two types of filter materials having different hole diameters are combined so that the larger the hole diameter is, the closer to the exhaust gas inflow side, the pressure loss can be further reduced. It is effective above.

In any of the above filter elements, the formation of alumina whiskers on the surface of the heat-resistant metal skeleton of the filter portion is effective for trapping airborne fine particles.

In any of the above filter elements, the particulate trap and the catalytic converter can be integrated by supporting the catalyst on the filter material. The catalyst is a method of supporting a heat-resistant metal fiber as a filter material on one or both sides of a nonwoven fabric of a heat-resistant metal fiber, or a three-dimensional network structure porous body comprising a heat-resistant metal skeleton having continuous pores on one or both sides of the nonwoven fabric. There is a method of supporting the porous body.

[0026]

In the particulate trap of the present invention, the filter elements are configured by arranging the flat filters in parallel or by arranging the cylindrical filters concentrically, so that the gap between the flat filters or between the cylindrical filters is reduced. By doing so, it is possible to increase the total number of flat filters and cylindrical filters without increasing the installation space, and it is possible to secure a large surface area of the filter element while being very small. Therefore, even if the pores are reduced so as to obtain a high trapping efficiency, the clogging is reduced due to a decrease in trapping amount per unit area due to an increase in the surface area, and the differential pressure life can be extended. The diesel particulate trap structure of the present invention has a good thermal conductivity because a nonwoven fabric of metal fiber is used as a filter material, and therefore, a uniform temperature inside the filter at the time of regeneration, so that a heat spot is formed at the time of regeneration. It is not difficult to melt the filter or crack due to thermal stress.

Above all, a filter using a filter element composed of a cylindrical filter having a circular cross section improves the uniformity of heat dissipation during regeneration and further improves the durability.

A structure in which a plurality of tapered cylindrical filters made of metal are concentrically arranged with their tapered directions being alternately reversed, or a structure in which a flat plate-shaped filter is alternately bent in an inverted C-shape. Since the filter material has a structure in which the filter material is folded at an acute angle at the end of the filter element, a large filter surface area can be secured without increasing the installation space in a direction perpendicular to the exhaust gas flow (diameter direction of the particulate trap). The opening area between the filters into which the exhaust gas flows can also be set to a size such that the opening is not blocked by the adhered particulates, whereby the initial pressure loss can be significantly reduced and a small amount of particulates can be collected. The problem that the opening is closed by the amount and the pressure loss increases rapidly can also be prevented.

In particular, in the filter element in which the hole diameter of the filter element is gradually reduced from the inflow side to the outflow side of the exhaust gas, the particulates are averagely collected in the entire area in the thickness direction of the filter, so that the pressure loss is reduced. The degree of rise is small,
The differential pressure life is further extended.

The size of the gap between the filters is 1
The reason why the diameter is preferably 0 mm or less is that the smaller the gap size is, the more the filter surface area can be secured in a limited space, and the efficiency of miniaturization of the trap increases.

Further, an element having a parallel plate filter is completed by, for example, alternately bending a sheet-like filter in a U-shape in the opposite direction and then sealing both sides between the plate filters with liners. Excellent mass productivity and can be manufactured at low cost. In addition, a plurality of independent plate filters are arranged in parallel, liners are inserted alternately at one end and the other end of the gap between each plate filter, and the part is sealed, and both sides are sealed with liners. Are also excellent in mass productivity and can be manufactured at low cost.

Elements in which cylindrical filters of different diameters are arranged concentrically can be mass-produced relatively easily and inexpensively by the method described in the embodiment.

In general, when producing a filter having a small volume and a large surface area, a method of precisely welding both sides of the filter material to the side plate can be considered. However, this method of welding all filter materials having a small pitch arrangement is technically difficult. With the difficulty, the feasibility is uncertain. Also, even if feasible, the cost will be extremely high. On the other hand, the filter element used in the trap of the present invention can be manufactured at low cost because precision welding is not required.

Further, by forming alumina whiskers on the skeleton surface of the filter material made of a nonwoven fabric of heat-resistant metal fibers, the filter holes between the metal fibers can be made smaller. As a result, it becomes possible to collect floating fine particles having a particle size of 2 μm or less among the particulates.

A three-dimensional mesh-structure porous body made of a heat-resistant metal skeleton is provided on one or both sides of a filter material made of a nonwoven fabric of heat-resistant metal fibers, or on one or both sides of the filter material. By supporting the catalyst on the body, the integration of the particulate trap and the catalytic converter can be realized. Since the catalyst carrier is a metal having a low filling factor, the heat capacity is small, and as a result, the temperature of the catalyst is increased quickly by the exhaust gas, and it is easy to obtain a sufficient temperature for the catalyst to work.

The above-mentioned alumina whisker is useful for increasing the area for supporting the catalyst when the catalyst is supported after the formation of the whisker.

[0037]

FIG. 1 shows an example of a filter element used in a particulate trap according to the present invention.
In this filter element 1, different diameter tapered cylindrical filters 2, 3, 4, 5, 6, 7 made of a heat-resistant metal are concentrically arranged so that the taper directions are alternately reversed. It has been turned. The central cylindrical filter 2 has a dead end at the small diameter end side. Here, the dead end is realized by making the filter 2 conical,
A structure in which a small-diameter end side is a dead end by a disk filter may be used.

The small-diameter end of the filter 3 is connected to the large-diameter end of the filter 2 and the small-diameter end of the filter 4 is connected to the large-diameter end of the filter 3. _i, and finishing the G _o the filter element 1 filter 2-7 is integrated with the inlet and outlet sides in the dead-end in alternating exhaust gas.

The outermost filter 7 is provided with a flange 8 for attaching an element, but this may be provided as needed.

It is to be noted that, although the filter element 1 having an exemplary structure based on a cylinder is most preferable in terms of space efficiency and uniform heat dissipation during regeneration, the structure in which a tapered square tube is combined is not limited. . Even when the filter element 1 is formed of a combination of tapered rectangular cylinders, it is desirable that the gap dimension g (see FIG. 1b) between the cylindrical filters at the exhaust gas inlet / outlet is limited to 10 mm or less.

FIG. 2 shows an example of another type of filter element. This filter element 11
A series of flat band filters made of a heat-resistant metal are alternately bent in the shape of a U-shape (or a U-shape) in the opposite direction so that the gap between the flat filters 12 is formed on the inlet side and the outlet side of the exhaust gas. With dead ends alternately. A filler 13 made of a heat-resistant metal plate is provided on both sides of each flat filter 12 by welding or the like.

FIG. 3 shows a method of manufacturing a filter element of a third embodiment used in the particulate trap of the present invention.

As shown in FIG. 5A, first, the sheet-like filter 22 is folded in a zigzag manner, that is, alternately folded in a U-shape in the opposite direction to form a parallel-arranged flat filter 22a.
A wall 22b that alternately forms a dead end at one end of the gap between the filter and the flat filter is created. Next, as shown in FIG. 3B, a liner 23 is inserted into a side portion of each flat filter to fill a gap between the flat filters. Then, as shown in FIG. 2C, the flat filter 22a and the liner 23 are fastened and fixed with bolts 24. Of course, the fixing may be performed by welding. At this time, as shown in FIG.
Can also be fastened together.

The filter element 21 of the third embodiment
As shown in FIG. 4, a plurality of independent plate filters 22a are arranged in parallel as shown in FIG. 4A, and then, as shown in FIG. The liners 26 are alternately inserted into one end side and the other end side of each other and welded. Further, before or after the insertion of the liner 26, the liners 23 are inserted into both sides of the gap, and the liner 23 is fixed by welding, bolting, or the like. (After that, the reinforcing side plate 25 as shown in FIG. 3 can be attached).

FIG. 5 shows a fourth embodiment of a method of manufacturing a filter element using a cylindrical filter. The filter element 31 is made of filter materials to form cylindrical bodies 32a to 32n (n is the number of combinations) having different diameters as shown in FIG. Although the figure shows a cylindrical body, the figure may be a square cylinder as long as the cross section is similar. Next, the minimum diameter cylinder 3
2a is the second smallest cylindrical body 32 as shown in FIG.
b. Then, an end plate 33 is welded to an opening on one end side of 32a, and an annular liner 34 is sandwiched between 32a and 32b on the other end side. Thereafter, this is inserted into the third smallest cylindrical body 32c, and one end of the cylindrical body 32c is inserted.
2b is closed with an annular liner 34. By repeating this operation sequentially, the target filter element 31 is completed.

The assembling may be performed from the side of the cylinder having the largest diameter. Also, instead of inserting a liner, attach a bent flange to the end of each cylinder, connect the inner and outer cylinders via this flange, and simultaneously stop one end of the gap between the cylinders with the flange at the dead end The structure may be such that:

Filters 2 to 7, 12, 22, and 32a to
32n is formed by stacking at least two layers of the above-mentioned material, that is, a non-woven fabric of a metal fiber, and a material having a difference in the hole diameter of the material such that the larger the hole diameter, the closer to the exhaust gas inflow side. Made of combined materials.

Further, as shown in FIG. 6, it is conceivable to provide a metal fiber nonwoven fabric with a large number of small holes by adding a large number of alumina whiskers 9 finer than the skeleton to the fiber skeleton FB. .

FIG. 7 is an enlarged view of the filters 2 to 7, 12, 22, and 32a to 32n. Filters 2 to 7, 1
On layers 2, 22, and 32a to 32n, in addition to a layer 301 for collecting particulates made of the above-described filter material, layers for supporting a catalyst (indicated by 302 and 303 as an example in the figure). It is also conceivable to use a material having a plurality of layers.

FIG. 8 shows an example of a particulate trap of the present invention using the filter element 1 of FIG. 1 or the filter element 11 of FIG. The particulate trap 100 is configured by mounting the above-described filter element 1 or 11 in a metal container 101 inserted in the exhaust system of a diesel engine. Although the arrows in the figure indicate the flow of the exhaust gas, it is also conceivable that the direction of attachment of the container 101 is reversed so that the exhaust gas flows in the opposite direction to the arrow in the figure.

FIG. 9 is another example (cross-sectional view) of the particulate trap of the present invention. This trap 200
Is constructed by mounting the filter element 21 shown in FIG. 3 or the filter element 31 shown in FIG. 5 manufactured by the method described above in a container 201 inserted in the exhaust system. The arrows in the figure indicate the flow of the exhaust gas.
It is also conceivable to reverse the mounting direction of 01 and pass the exhaust gas in the direction opposite to the arrow in the figure.

FIG. 10 shows an experimental device for measuring the initial pressure loss. In this apparatus, air flows into a particulate trap, and the relationship between the air flow rate and the pressure loss is examined.

FIG. 11 shows an experimental apparatus for evaluating the collection efficiency, pressure loss during particulate collection, durability, NO purification rate and SOF purification rate. This device is 3400c
c, a four-cylinder direct-injection diesel engine vehicle, chassis dynamometer, and dilution tunnel.

[0054]

EXAMPLE 1 FIG. 1 or FIG.
The particulate trap 100 using each of the filter elements 1 and 11 of FIG. 2 was incorporated. Filter elements 1 and 11 are Sample A and Sample B shown in Table 1. Each of the samples A and B has a surface area of 1.2 m ² into which exhaust gas can flow, and is housed in a case having an internal volume of 2.5 liters. These samples are shown in FIG.
(B), as shown in the cross-sectional view of FIG. 2 (b), after exhaust gas is introduced from every other gap Gi, passes through the wall of the filter, flows into the gap Go between Gi, and then becomes external. It is supposed to go to.

The metals constituting the samples A and B are Fe
Although the -Cr-Al alloy and the Ni-Cr-Al alloy have been described as examples, this is only an example.

For comparison, a particulate trap for a diesel engine having a honeycomb structure, which is said to have sufficient trapping performance (material cordierite,
An experiment was also performed on DHC-221) manufactured by NGK and used as sample Q. This trap has a capacity of 2.5 liters and has the same conditions as those of the samples A and B.

[0057]

[Table 1]

First, the collection efficiency and pressure loss were evaluated. The experimental results are shown in FIGS. As the trapping performance, changes in pressure loss and trapping efficiency with respect to the trapped PM (particulate) amount are shown. From this result, it can be seen that the samples A and B of the present invention have a low initial pressure loss and are superior to the diesel particulate trap having a honeycomb structure. In addition, the trapping performance is the same, and it can be said that it has sufficient performance.

Next, an evaluation test was conducted on the durability of the filter element by regeneration. 15 g of fine particles (particulates) discharged from the diesel engine are collected, the diesel engine is put into an eye drink state, and a gas at 600 ° C. is introduced into the diesel particulate trap by an electric heater installed on the entire surface of the diesel particulate trap. The playback was performed as follows. This regeneration was performed five times for each of the samples A, B and Q, and thereafter, the destruction state of the samples was investigated. Table 2 shows the results.

[0060]

[Table 2]

As can be seen from Table 2, the samples A and B did not break, but the sample Q cracked.

As is evident from the results of the above experiments, the samples A and B according to the present invention exhibit almost the same trapping characteristics and pressure loss characteristics as cordierite honeycombs. In addition, it shows high reliability for combustion regeneration, and is extremely excellent as a diesel particulate trap.

[0063]

Embodiment 2 A particulate trap 100 using the filter elements 1 and 11 shown in FIGS. 1 and 2 was incorporated in the experimental apparatus shown in FIG. 10 or FIG. The filter elements 1 and 11 are Sample C, Sample D and Sample E shown in Table 3. Each of the samples C, D and E has a surface area of 1.2 m ^{2 through} which exhaust gas can flow, and an internal volume of 2.5 m ^2.
It is stored in a liter case. These samples are
It is composed of three layers: a layer carrying NOx catalyst (302 in FIG. 7), a layer for trapping particulates (301 in FIG. 7), and a layer carrying NOx catalyst (303 in FIG. 7). As shown in the cross-sectional views of FIG. 1B and FIG. 2B, exhaust gas is introduced from gaps Gi generated at every other interval and passes through all layers in the filter. After flowing into the gap Go between Gi, it goes to the outside. The NOx catalyst layer is made of Ni manufactured by Sumitomo Electric Industries, Ltd.
Γ- for supporting a catalyst is attached to the skeleton of a Ni-Cr-Al-based porous body having a three-dimensional network structure (trade name: Celmet # 7)
Alumina is coated with 100 g per liter of metal non-woven fabric, and then as a catalyst, 1.0 g per liter of Cu is used.
In a uniform amount.

The metal non-woven fabrics constituting the samples C, D and E are exemplified by Fe-Cr-Al alloy and Ni-Cr-Al alloy, but this is only an example.

For comparison, an experiment was conducted on the same sample Q as that used in Example 1. The volume of the trap is 2.5 liters, and the conditions are the same as those of the samples C, D and E.

[0066]

[Table 3]

Here, first, the collection efficiency and the pressure loss were evaluated. The experimental results are shown in FIGS.
As the trapping performance, changes in pressure loss and trapping efficiency with respect to the trapped PM amount are shown. From these results, Sample C of the product of the present invention,
It can be seen that D and E have low initial pressure loss and are superior to the diesel particulate trap having the honeycomb structure. Further, the trapping performance is the same, and it can be said that it has a sufficient performance.

Next, an evaluation test was performed on the durability of the filter elements of Samples C, D, E and Q by regeneration.
The test conditions and the number of reproductions were the same as in Example 1, and thereafter,
The fracture state of the sample was investigated. Table 4 shows the results.

[0069]

[Table 4]

As can be seen from Table 4, Samples C, D and E did not break, but Sample Q did crack.

For samples C, D and E, NO
Was evaluated for purification rate. C ₂ H ₄ was introduced into the exhaust gas as a reducing agent. Table 5 shows the exhaust gas conditions.

[0072]

[Table 5]

After maintaining the exhaust gas temperature at 250 ° C., the NO concentration for 2 minutes was measured. Table 6 shows the average value.
Shown in

[0074]

[Table 6]

As described above, when the samples C, D and E are used, the NO concentration is reduced by half.

As is clear from the above experimental results, Samples C, D and E according to the present invention exhibit almost the same trapping characteristics and pressure loss characteristics as cordierite honeycombs, while having a low initial pressure loss. In addition, it shows high reliability even during combustion regeneration, and is very excellent as a diesel particulate trap. In addition, NO
Therefore, there is no need to additionally provide a catalytic converter, and it is possible to realize space saving and cost reduction in the total aspect of the diesel exhaust gas aftertreatment device.

[0077]

Embodiment 3 A particulate trap 100 using the filter elements 1 and 11 of FIGS. 1 and 2 was incorporated in the experimental apparatus of FIG. 10 or FIG. The filter elements 1 and 11 are Sample F, Sample G and Sample H shown in Table 7. Each of the samples F, G and H has a surface area of 1.2 m ^{2 through} which exhaust gas can flow, and an internal volume of 2.5 m ^2.
It is stored in a liter case. These samples are
Layer for trapping particulates (301 in FIG. 7) and S
It is composed of two layers, that is, a layer (303 in FIG. 7) that supports the OF catalyst. As shown in the cross-sectional views of FIGS. 1B and 2B, every other exhaust gas is used. The resulting gap Gi
And flows through all the respective layers in the filter into the gap Go between Gis, and then goes to the outside. The SOF catalyst layer is formed of a nonwoven fabric of metal fiber or a Ni-Cr-Al skeleton of a Ni-based three-dimensional network structure porous material (Celmet # 7) manufactured by Sumitomo Electric Industries, Ltd. -Coat 150 g of alumina per liter of metal non-woven fabric, then use Pt as catalyst
Was prepared by uniformly supporting 1.5 g per liter.

Although the Fe-Cr-Al alloy and the Ni-Cr-Al alloy have been described as examples of the porous metal bodies constituting the samples E, G and H, this is only an example.

For comparison, an experiment was also conducted on the cordierite honeycomb sample Q described above. The capacity of this trap is 2.5 liters, and samples F and G
And H.

[0080]

[Table 7]

FIGS. 18 to 20 show the evaluation results of the collection efficiency and pressure loss of each sample. As in Examples 1 and 2, evaluation was made by examining changes in pressure loss and trapping efficiency with respect to the trapped PM amount. From these results, samples F, G and H of the product of the present invention were obtained.
Shows that the initial pressure loss is low and is superior to that of a diesel particulate trap having a honeycomb structure. In addition, the trapping performance is the same and has a sufficient performance.

Next, the durability of the filter element due to regeneration was evaluated. The test conditions and the number of times of reproduction were the same as in Example 1, and the state of destruction of the sample after five times of reproduction was examined. Table 8 shows the results.

[0083]

[Table 8]

As can be seen from this table, Samples F, G and H did not break, but Sample Q cracked.

For samples F, G and H, the SOF
Was evaluated for purification rate. Table 9 shows the evaluation results at the exhaust gas temperatures of 250 ° C. and 350 ° C.

[0086]

[Table 9]

As described above, in the samples F, G and H in which Pt was supported as a catalyst, the SOF concentration could be reduced by 40% or 50%.

As is evident from the results of the above experiments, Samples F, G and H according to the present invention exhibit almost the same collection characteristics and pressure loss characteristics as cordierite honeycombs.
On the other hand, the initial pressure loss is low, and it shows high reliability for combustion regeneration, and is very excellent as a diesel particulate trap. In addition, SO
Since it also has a function of reducing F, it is not necessary to separately provide a catalytic converter, and it is possible to realize space saving and cost reduction in the total aspect of the diesel exhaust gas aftertreatment device.

[0089]

Embodiment 4 FIG. 21 shows filter elements 21 and 31 manufactured by the method of FIG. 3, and FIG. 22 shows filter elements 21 and 31 manufactured by the method of FIG. Here, the element 21 in FIG. 21 is a sample J, and the element 31 in FIG. Sample I, J
In both cases, a Ni-based three-dimensional mesh porous structure (trade name: Celmet) manufactured by Sumitomo Electric Industries, Ltd. was used as a filter material.
Sample I was Ni-Cr converted, and Sample J was Ni-Cr-Al converted.

Samples I and J both have a surface area of 1.2 m ² into which exhaust gas can flow, and are stored in a container having an internal volume of 2.5 liters. As shown in the cross-sectional views of FIGS. 21 and 22, (b) of these samples, the exhaust gas is introduced from the gap Gi generated every other interval, passes through the filter wall, and the gap between the Gi. After flowing to Go, it goes to the outside. When the stop wall is made of a filter material, part of the exhaust gas is naturally filtered at the stop wall.

The metals constituting Samples I and J have been exemplified by Ni—Cr and Ni—Cr—Al alloys, respectively, but these are only examples.

As a comparative product, the above-mentioned cordierite honeycomb sample Q (the volume was 2.5 liters, the same as that of samples I and J) was used.

Experimental results on the collection efficiency and pressure loss of these samples are shown in FIGS. As apparent from FIGS. 23 and 24, which show changes in pressure loss and trapping efficiency with respect to the amount of deposited PM, Sample I used for the trap of the present invention,
The J filter element shows almost the same performance as the cordierite honeycomb on the collecting surface.

Next, an experiment on reproduction durability was performed.
The experiment apparatus of FIG. 11 collects 10 g of the particulates of each of the sample I, the sample J, and the sample Q, raises the exhaust gas temperature, and performs the experiment of burning the particulates five times. The condition was observed. Table 10 shows the results. As can be seen from the results, Samples I and J have higher reproduction durability than cordierite.

[0095]

[Table 10]

As is clear from the above experimental results, Samples I and J according to the present invention exhibit almost the same trapping characteristics and pressure loss characteristics as cordierite honeycombs, and have high reliability for combustion regeneration. It is very good as a diesel particulate trap.

[0097]

Embodiment 5 A particulate trap 200 using the filter elements 21 and 31 shown in FIGS. 21 and 22, respectively, was incorporated in the experimental apparatus shown in FIG. 10 or FIG. The filter elements are Sample K, Sample L and Sample M shown in Table 11.

Each of the samples K, L, and M has a surface area of 1.2 m ^{2 through} which exhaust gas can flow, and is stored in a container having an internal volume of 2.5 liters. These samples are NO
It is composed of three layers: a layer carrying the x catalyst (302 in FIG. 7), a layer collecting particulates (301 in FIG. 7), and a layer carrying the NOx catalyst (303 in FIG. 7). As shown in the cross-sectional views of FIGS. 21 (b) and 22 (b), exhaust gas is introduced from gaps Gi generated every other interval, passes through the filter wall, and enters gaps Gi between Gis. After flowing, it goes to the outside. When the stop wall is made of a filter material, part of the exhaust gas is naturally filtered at the stop wall. The NOx catalyst layer is made of a metal fiber nonwoven fabric or a Ni-based three-dimensional network structure porous body (trade name: Celmet) manufactured by Sumitomo Electric Industries, Ltd., made of Ni-Cr-A.
100 g of γ-alumina for supporting a catalyst was coated on the skeleton of the litter at a rate of 100 g per liter of metal nonwoven fabric, and then 1.0 g of Cu was uniformly supported as a catalyst.

The metals constituting the samples K, L and M are exemplified by Ni-Cr-Al and Fe-Cr-Al alloys, respectively. However, these are only examples.

As the comparative product, the cordierite honeycomb sample Q described above (the volume was 2.5 liters, the same as that of the samples K, L and M) was used.

[0101]

[Table 11]

Experimental results on the collection efficiency and pressure loss of these samples are shown in FIGS. From FIGS. 25 to 27 showing changes in the pressure loss and the collection efficiency with respect to the collected PM amount, the samples K, L and M of the present invention have low initial pressure loss,
It turns out that it is superior to the diesel particulate trap of the honeycomb structure. In addition, the trapping performance is the same and has a sufficient performance.

Next, in order to evaluate the reproduction durability, FIG.
K, L, M and Q
For each of the samples, 10 g of particulates were collected, and an experiment of burning the particulates by raising the exhaust gas temperature was performed five times, and then the state of each sample was observed. Table 12 shows the results. As can be seen from the results, Samples K, L and M have higher reproduction durability than cordierite.

[0104]

[Table 12]

For samples K, L and M, NO
Was evaluated for purification rate. C ₂ H ₄ was introduced into the exhaust gas as a reducing agent. Table 13 shows the exhaust gas conditions.

[0106]

[Table 13]

After maintaining the exhaust gas temperature at 250 ° C.,
The NO concentration for 2 minutes was measured. Table 14 shows the average value.

[0108]

[Table 14]

In the samples K, L and M, the NO concentration was reduced by half by the action of the catalyst Cu.

As is evident from the results of the above experiments, the samples K, L and M according to the present invention exhibit almost the same collection characteristics and pressure loss characteristics as cordierite honeycombs.
On the other hand, the initial pressure loss is low, and it shows high reliability even during combustion regeneration, and is very excellent as a diesel particulate trap. Furthermore, in addition, N
Since it also has the function of reducing O, it is not necessary to separately provide a catalytic converter, and it is possible to realize space saving and cost reduction in the total aspect of the diesel exhaust gas aftertreatment device.

[0111]

Embodiment 6 A particulate trap 200 using the filter elements 21 and 31 shown in FIGS. 21 and 22 was incorporated in the experimental apparatus shown in FIG. 10 or FIG. The filter elements 21 and 31 are Sample N, Sample O, and Sample P shown in Table 15.

Each of the samples N, O and P has a surface area of 1.2 m ² into which exhaust gas can flow, and is contained in a container having an internal volume of 2.5 liters. These samples consist of a layer for collecting particulates (301 in FIG. 7) and a SOF.
It is composed of two layers of catalyst-supporting layers (303 in FIG. 7). As shown in the cross-sectional views of FIGS. 21 (b) and 22 (b), exhaust gas is generated every other one. Gap Gi
From the filter, passing through the wall of the filter and passing through the gap G between Gi.
After flowing to o, it goes to the outside.

When the stop wall is made of a filter material,
Naturally, some exhaust gas stops and is also filtered at the wall. The SOF catalyst layer is made of a Ni-based three-dimensional network structure porous body (trade name: Celmet) manufactured by Sumitomo Electric Industries, Ltd.
-The skeleton of the AL was coated with γ-alumina for supporting a catalyst in an amount of 100 g per liter of a porous body, and thereafter, 1.0 g of Pt was uniformly supported as a catalyst on the porous body.

The metals constituting samples N, O and P are Ni-Cr-Al and Fe-Cr-Al alloys, respectively, but these are only examples.

As a comparative product, cordierite honeycomb sample Q having the same volume (2.5 liters) as samples N, O and P was used.

[0116]

[Table 15]

Experimental results on the collection efficiency and pressure loss of each sample are shown in FIGS. From these figures showing changes in pressure loss and trapping efficiency with respect to the trapped PM amount, it can be seen that the samples N, O and P of the present invention have a low initial pressure loss and are superior to the honeycomb structured diesel particulate trap. Understand. In addition, the trapping performances are equivalent, and it can be seen that they have sufficient performance.

Next, in order to evaluate the reproduction durability, FIG.
Samples N, O, P, and Q were collected by the experimental apparatus of Example 1 to collect 10 g of the particulates, and an experiment was conducted in which the particulates were burned by raising the exhaust gas temperature five times. The condition of the sample was observed. Table 16 shows the results. As can be seen from the results, Samples N, O and P have higher reproduction durability than cordierite.

[0119]

[Table 16]

For samples N, O and P, the SOF
Was evaluated for purification rate. Table 17 shows the evaluation results at the exhaust gas temperatures of 250 ° C. and 350 ° C.

[0121]

[Table 17]

For the samples N, O and P, the SOF concentration was 40%
Or it could be reduced by 50%.

As is evident from the results of the above experiments, the samples N, O and P according to the present invention exhibit almost the same trapping characteristics and pressure loss characteristics as cordierite honeycombs.
On the other hand, the initial pressure loss is low, and it shows high reliability even during combustion regeneration, and is very excellent as a diesel particulate trap. Furthermore, in addition, S
Since it also has a function of reducing OF, there is no need to provide another catalytic converter, and it is possible to realize space saving and cost reduction in the total aspect of the diesel exhaust gas aftertreatment device.

[0124]

As described above, the particulate trap of the present invention is small in size, has a sufficient surface area of the filter to obtain a high trapping efficiency, and suppresses the rise in pressure loss to a low level. Furthermore, since the characteristics of the metal trap are sufficiently utilized for regeneration and durability, the performance of the particulate trap for a diesel engine is not lacking, and the air pollution caused by the particulates is prevented.

[0125] Further, in the case where alumina whiskers are formed on the skeleton surface of a filter material made of a metal fiber non-woven fabric, the pores of the filter become smaller, and it becomes possible to collect floating fine particles having a particle size of 2 µm or less. .

Further, in the case where a metal three-dimensional net structure porous body is provided on the filter material or on one or both surfaces of the filter material and the porous body carries a catalyst, it is not necessary to separately provide a catalytic converter. The exhaust gas post-processing device can be simplified and reduced in cost. In addition, since the heat capacity of the filter skeleton is small, the function of the catalyst is ensured, and a more excellent effect on environmental purification can be expected.

[Brief description of the drawings]

FIG. 1A is a perspective view showing an outline of an example of a filter element used in the present invention. FIG. 1B is a cross-sectional view of the filter element.

FIG. 2A is a perspective view showing an example of a filter element of another embodiment. FIG. 2B is a cross-sectional view of the filter element.

FIG. 3 is a view showing a manufacturing procedure of a filter element according to a third embodiment.

FIG. 4 is a diagram showing another manufacturing procedure of the filter element according to the third embodiment.

FIG. 5 is a view showing a manufacturing procedure of a filter element according to a fourth embodiment.

FIG. 6 is a schematic view showing a state in which alumina whiskers are generated in a filter skeleton.

FIG. 7 is an enlarged conceptual diagram of a cross section of a filter.

FIG. 8 is a sectional view showing an example of a particulate trap of the present invention.

FIG. 9 is a sectional view showing another example of the particulate trap of the present invention.

FIG. 10 is a schematic configuration diagram of an initial pressure loss evaluation device.

FIG. 11 is a schematic configuration diagram of a test apparatus for evaluating pressure loss and durability.

FIG. 12 is a chart showing initial pressure losses of samples A, B, and Q;

FIG. 13 is a table showing a change in pressure loss with respect to a collected PM amount of samples A, B, and Q;

FIG. 14 is a table showing a change in the collection efficiency of the samples A, B, and Q with respect to the amount of collected PM.

FIG. 15 is a table showing initial pressure losses of samples C, D, E, and Q;

FIG. 16 is a chart showing a change in pressure loss with respect to a trapped PM amount of samples C, D, E, and Q;

FIG. 17 is a chart showing a change in the collection efficiency of the samples C, D, E, and Q with respect to the amount of collected PM.

FIG. 18 is a chart showing initial pressure losses of samples F, G, H, and Q;

FIG. 19 is a graph showing a change in pressure loss with respect to a collected PM amount of samples F, G, H, and Q;

FIG. 20 is a table showing changes in the collection efficiency of the samples F, G, H, and Q with respect to the amount of collected PM.

21A is a perspective view of a filter element according to a third embodiment, and FIG. 21B is a cross-sectional view of the filter element.

22A is a perspective view of a filter element according to a fourth embodiment, and FIG. 22B is a cross-sectional view of the filter element.

FIG. 23 is a graph showing a change in pressure loss with respect to a collected PM amount of Samples I, J and Q.

FIG. 24 is a chart showing a change in collection efficiency with respect to a collected PM amount of samples I, J, and Q;

FIG. 25 is a chart showing initial pressure losses of samples K, L, M, and Q;

FIG. 26 is a table showing changes in pressure loss with respect to the amount of collected PM of samples K, L, M, and Q;

FIG. 27 is a chart showing a change in collection efficiency with respect to a collected PM amount of samples K, L, M, and Q;

FIG. 28 is a chart showing initial pressure losses of samples N, O, P, and Q;

FIG. 29 is a table showing changes in pressure loss with respect to the amount of collected PM of samples N, O, P, and Q;

FIG. 30 is a chart showing a change in collection efficiency with respect to a collected PM amount of samples N, O, P, and Q;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 11, 21, 31 Filter element 2-7 Different diameter taper cylindrical filter 8 Flange 9 Alumina whisker 12 Flat filter 13 Filler 22 Sheet filter 22a Flat filter 22b Dead end wall 23, 26 Liner 24 Liner 24 Bolt 25 Side plate 32a to 32n Different Diameter Cylindrical Filter 33 End Plate 34 Annular Liner 100, 200 Particulate Trap 101, 201 Vessel Gi Gap on Exhaust Gas Inlet Side Go Gap on Exhaust Gas Outlet Side FB Filter Skeleton 301 Particulate Filter Part 302, 303 Catalyst carrier

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI B01J 23/86 ZAB B01J 35/06 C 35/04 331 F01N 3/02 301A 35/06 301E F01N 3/02 301 ZAB B01D 53 / 36 ZABB ZAB 102B 103B 103C (72) Inventor Yoichi Nagai 1-1-1 Kunyokita, Itami-shi Itami Works, Sumitomo Electric Industries, Ltd. (72) Inventor Kiyoshi Kobata 1-Toyota-cho, Toyota-shi (72) Inventor Hiromichi Yanagihara 1 Toyota Town, Toyota City Inside Toyota Motor Corporation (56) References JP-A-1-155923 (JP, A) JP-A-5-228320 (JP, A) JP-A-7-112135 (JP, A) JP-A-62-83018 (JP, A) JP-A-7-7331 (JP, A) JP-A-60-139307 JP, A) JitsuHiraku Akira 59-119319 (JP, U) JitsuHiraku Akira 61-88019 (JP, U) (58 ) investigated the field (Int.Cl. ^7, DB name) B01D 46/00 - 46/54 B01D 39/20 ZAB B01D 53/86 ZAB B01D 53/94 B01J 23/86 ZAB B01J 35/04 331 F01N 3/02 301

Claims (11)

(57) [Claims] 1. An independent flat sheet made of a metal fiber non-woven fabric.
Arrange multiple filters on the plate in parallel, and
Insert a liner into the gap between
And a dead end alternately at the exit side, and furthermore,
A particulate trap for diesel engines that is constructed by installing a filter element with a structure in which liners are also inserted and sealed on both sides in the exhaust system. 2. A plurality of cylindrical filters of similar diameter in cross section made of a non-woven fabric of metal fibers are concentrically arranged, and a gap between the cylindrical filters for introducing exhaust gas and one end of the minimum-diameter filter are connected to the exhaust gas. A particulate trap for diesel engines that is constructed by installing filter elements with dead ends alternately on the inlet and outlet sides in the exhaust system. 3. A process according to claim 1 or to one or both sides of the filter material forming the filter element is supported catalyst
3. The particulate trap for a diesel engine according to 2 . 4. A three-dimensional network porous body comprising a heat-resistant metal skeleton having continuous holes is provided on one or both sides of a filter material constituting a filter element, and a catalyst is carried on the three-dimensional network porous body. The particulate trap for a diesel engine according to claim 1 or 2 . 5. A filter element having a structure in which flat filters made of a non-woven fabric of metal fibers are arranged in parallel, and a gap between the flat filters for introducing exhaust gas is alternately stopped at an exhaust gas inlet side and an exhaust gas side. , Installed in the middle of the exhaust system ,
Heat-resistant metal skeleton with continuous pores on one or both sides
A three-dimensional net-like porous body consisting of
Particulate trap for diesel engines constructed by supporting a catalyst on a porous structure . 6. The filter element, wherein a sheet-like filter is alternately bent in a U-shape in the opposite direction to form a parallel-arranged plate filter and a wall that makes one end between the plate filter gaps a dead end. 6. The particulate trap for a diesel engine according to claim 5, wherein both sides of the gap are sealed by inserting a liner. 7. A non-woven fabric made of a heat-resistant metal fiber is used as a filter material, and a plurality of metal tapered cylindrical filters made of the filter material are concentrically arranged in such a manner that taper directions are alternately reversed. The small-diameter end of each filter is connected to the large-diameter end of the inner cylindrical filter except for the center cylindrical filter whose side end is dead end, and the gap between the cylindrical filters is exhausted. A filter element having a structure in which dead ends are alternately provided on the gas inlet side and the gas outlet side is installed in the exhaust system to constitute the filter element.
Heat resistant with continuous holes on one or both sides of the filter material
A three-dimensional network porous body consisting of a conductive metal skeleton is installed
Particulate trap for diesel engines constructed by supporting a catalyst on a porous body having a three-dimensional network structure . 8. A flat plate-shaped filter using a heat-resistant metal fiber non-woven fabric as a filter material is alternately bent in the shape of a letter in the opposite direction, and a gap between each flat filter is formed between the filter and the exhaust gas inlet side. A filter element with a dead end alternately installed at the outlet side is installed in the exhaust system,
One side of the filter material that constitutes the filter element or
3D consisting of heat-resistant metal skeleton with continuous holes on both sides
A porous body having a network structure is installed, and the porous body having a three-dimensional structure
A particulate trap for a diesel engine configured to carry a catalyst . 9. Any diesel engine particulate trap according to claim 1-8 where the gap size of the exhaust gas inlet and outlet part between the filter was 10mm or less. 10. A according to any one of claims 1 to 9, a material that combines such that the with a difference in pore size of at least two types of filter material in large ones as the exhaust gas inlet side of the pore size to constitute a said filter element Particulate trap for diesel engines. 11. diesel engine particulate trap according to any one of claims 1 to 10 skeletal surface of the filter material to produce alumina whiskers constituting the filter element.