JP2002221020A - Particulate filter for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost easy-to-manufacture particulate filter for a diesel engine having an excellent-durability filter element, and reducing heat emission from the outer face of the filter. SOLUTION: In this particulate filter for the diesel engine, a nearly elliptical nonwoven fabric 2 of metallic fiber is alternately unevenly bent in plural bent parts 6 along the width direction of the elliptical shape such that each the bent shape is U shape, and the periphery of the nearly cylindrical filter element 3 formed by the bent nonwoven fabric 2 is disposed with an outer cylinder 4. The outer shape of the nonwoven fabric 2 is a step-like shape wherein the width of the nonwoven fabric 2 changes in the bent parts 6. The outer cylinder 4 comprises two cylindrical parts (7a, 7b) each having a comb tooth-like end. A support bar 9 is disposed parallel to the bent parts 6 inside the U-shaped bent parts 6 of the nonwoven fabric 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a particulate filter for a diesel engine for collecting and removing fine particles (particulates) such as carbon in exhaust gas of a diesel engine. The present invention also relates to a particulate filter capable of removing harmful gas components in exhaust gas.

[0002]

2. Description of the Related Art It is extremely important for environmental measures to remove particulates mainly composed of carbon contained in exhaust gas of a diesel engine. Various techniques have been proposed for disposing a particulate trap in an exhaust gas flow path or a gas path of a diesel engine, collecting the particulates, and removing the particulates by post-processing. As a filter for collecting particulates, a honeycomb-like porous body of cordierite ceramics and a ceramic fiber trap in which ceramic fibers are made into a candle shape are known.

Japanese Patent Application Laid-Open No. 8-243333 proposes a particulate filter for a diesel engine having a small filter structure having a large filtering surface area through which exhaust gas passes, using a metal fiber nonwoven fabric as a filter material. The first embodiment has a rectangular cross section having a structure in which a large number of flat filters made of a metal fiber non-woven fabric are arranged in parallel, and gaps between the flat filters for introducing exhaust gas are alternately stopped at an exhaust gas inlet side and an exhaust gas side. A filter element having a shape is used. In a second embodiment, a plurality of cylindrical filters having similar cross sections are arranged concentrically, and a gap between the cylindrical filters for introducing exhaust gas and one end of the minimum-diameter filter are arranged on the inlet and outlet sides of the exhaust gas. A filter element having a circular cross section having a structure of alternating dead ends is used. The use of a metal fiber non-woven fabric as a filter improves durability and reliability during reproduction, and the large surface area of the non-woven fabric reduces clogging and pressure loss. In both the first and second embodiments, the dead ends of the two filters are welded by connecting the two filters or inserting a liner into the gap. In the first embodiment, the sheet-like filter can be formed by alternately bending the filter into a U shape or a U shape in the opposite direction.

In Japanese Patent Application Laid-Open No. 9-262414, a laminated material in which an even number of two or more flat filters and two or more corrugated sheets made of metal are alternately stacked is roll-wound. Particulate filters have been proposed. A flat plate made of a metal fiber nonwoven fabric functions as a particulate filter.

In a diesel engine, a catalytic converter carrying a catalyst is disposed in an exhaust gas path for the purpose of purifying an impurity gas such as NOx in the exhaust gas. The catalyst carrier has a large number of cells through which gas passes. The wall of each cell is coated with a catalyst, so that the passing gas and the catalyst can come into contact with a wide contact area.

[0006]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 8-243 is disclosed.
In the particulate trap using a metal fiber non-woven fabric as a filter as described in Japanese Patent No. 333, the location of the particulates becomes maximum near a dead end provided between the filters on the exhaust gas outlet side. For this reason, the load applied to the nonwoven fabric at the location is large, and there is a possibility that the nonwoven fabric at the location is damaged during use, and a problem that exhaust gas containing particulates is discharged may occur.

Further, the particulate filter of the first embodiment described in the above publication has a problem in that heat release from the outer surface of the filter is large.

In the second embodiment described in the publication, it is necessary to form a filter element by using a large number of different-diameter cylindrical filters and joining their ends together. JP-A-9-
In the invention described in Japanese Patent No. 262414, it is necessary to laminate two or more flat filters and two or more corrugated sheets to form a column, and to fasten the two filters at both ends of the column. In each case, complicated processing is required,
There was a problem that the cost of the filter was high.

An object of the present invention is to provide a particulate filter for a diesel engine, which solves the above problems, has excellent filter element durability, reduces heat release from the outer surface of the filter, is easy to manufacture, and has low cost. With the goal.

[0010]

That is, the gist of the present invention is as follows. (1) The heat-resistant nonwoven fabric 2 having a substantially elliptical shape is alternately mountain-valley-bent at a plurality of bending portions 6 along the width direction of the elliptical shape, and the bent shape is U-shaped. A particulate filter for a diesel engine, wherein an outer cylinder (4) is arranged on the outer periphery of a filter element (3) having a substantially cylindrical outer periphery. (2) The outer shape of the substantially elliptical heat-resistant nonwoven fabric 2 is as follows:
The particulate filter for a diesel engine according to the above (1), wherein the bent portion 6 has a step-like shape in which the width of the nonwoven fabric changes. (3) The outer cylinder 4 is composed of two cylindrical portions 7 each having one end in the shape of a comb tooth, and a cylindrical shape formed of the heat-resistant nonwoven fabric bent by the comb teeth of the two cylindrical portions 7. The particulate filter for a diesel engine according to the above (1) or (2), wherein the outer cylinder 4 is formed by sandwiching the outer periphery of the filter element 3. (4) The particulate filter for a diesel engine according to (3), wherein the outer circumference of the outer cylinder 4 including the two cylindrical portions 7 is further wrapped by a second outer cylinder 8. (5) The particulate filter for a diesel engine according to the above (3), wherein the outer periphery of the outer cylinder composed of the two cylindrical portions is wrapped with a heat-resistant heat insulating material. (6) The particulate filter for a diesel engine according to (5), wherein the outer periphery of the heat insulating material is wrapped in a second outer cylinder. (7) The diesel engine according to any one of (1) to (6), wherein a support rod 9 is arranged inside the U-shaped bent portion 6 of the heat-resistant nonwoven fabric in parallel with the bent portion 6. Particulate filter for engine. (8) The method according to any one of (1) to (7) above, wherein a corrugated corrugated sheet of a metal plate is sandwiched between heat-resistant nonwoven fabric surfaces facing each other in a U-shape. Particulate filter for diesel engine. (9) The particulate filter for a diesel engine according to the above (8), wherein a catalyst is supported on the surface of the sandwiched corrugated sheet 10 and / or the heat-resistant nonwoven fabric 2. (10) The thickness of the sandwiched corrugated sheet 10 is 0.03 mm
The particulate filter for a diesel engine according to the above (8) or (9), which has a thickness of about 0.5 mm. (11) The heat-resistant nonwoven fabric 2 and the sandwiched corrugated sheet 10
The particulate filter for a diesel engine according to any one of the above (8) to (10), wherein a contact portion with the filter is brazed. (12) The particulate filter for a diesel engine according to any one of the above (1) to (11), wherein the distance between the heat-resistant nonwoven fabric surfaces facing each other in a U-shape is 1 mm to 10 mm. (13) The heat-resistant nonwoven fabric 2 has a thickness of 0.1 mm to 1.
(1) to (12), wherein the distance is 5 mm.
A particulate filter for a diesel engine according to any one of the above. (14) The porosity of the heat-resistant nonwoven fabric 2 is 40% to 95%.
The particulate filter for a diesel engine according to any one of the above (1) to (13), wherein (15) As for the porosity in the thickness direction of the heat-resistant nonwoven fabric 2, the porosity is high in the portion on the exhaust gas entry side,
The particulate filter for a diesel engine according to any one of the above (1) to (14), wherein the portion on the exhaust gas outlet side has a low porosity. (16) The particulate filter for a diesel engine according to any one of (1) to (15), wherein the heat-resistant nonwoven fabric 2 is a metal fiber nonwoven fabric or a ceramic fiber nonwoven fabric.

In the conventional shape in which two filters are welded and joined at the dead end of the filter, the fibers constituting the nonwoven fabric are deteriorated due to the influence of welding heat, which is the cause of the poor durability of the dead end. . Also,
In the case where the filter is bent in a U-shape or a U-shape at the dead end portion, it has been clarified that the fiber of the nonwoven fabric is deteriorated at the corners generated by the bending process, so that poor durability occurs.

On the other hand, in the present invention, as shown in FIG. 2, a heat-resistant non-woven fabric 2 is used for a filter, and a plurality of bent portions 6 along the width direction of the non-woven fabric are alternately bent into valleys and valleys. Filter element 3 as a U-shaped bend
Is formed. Since the bending shape is a U-shaped bending, the durability of the filter is excellent also on the exhaust gas outlet side. In the conventional dead end portion of the filter, poor durability such as a shape obtained by welding and joining two filters or a shape obtained by bending a filter into a U-shape or a U-shape is solved.

Further, by arranging the support rod 9 inside the U-shaped bent portion 6 of the heat-resistant nonwoven fabric in parallel with the bent portion 6 as shown in (7) of the present invention (FIG. 7), the exhaust gas is directly U
Since there is no collision with the U-shaped bent portion 6 and the U-shaped bent portion 6 does not vibrate due to the exhaust gas flow, the durability of the filter is further improved.

In the present invention, by using the heat-resistant nonwoven fabric 2 having a substantially elliptical shape 20 as shown in FIG. 3, the filter element 3 formed of the bent heat-resistant nonwoven fabric is formed as shown in FIG. The outer periphery has a substantially cylindrical shape 21. Since the outer cylinder 4 is arranged on the outer periphery of the substantially cylindrical filter element 3 as shown in FIG. 1, the outer shape of the particulate filter is cylindrical. JP-A-8-2
In the first form of JP-A-43333, the heat dissipation from the surface was large because the cross section of the filter element was rectangular, but in the present invention, the heat dissipation from the filter was small due to the circular cross section and the small surface area. Can be reduced.

In the present invention, the filter element 3 is formed by alternately bending a single heat-resistant non-woven fabric having a substantially elliptical shape at a plurality of bent portions 6 at the peaks and valleys. Therefore, it is not necessary to connect the ends of a large number of filters, and it is possible to produce the filters at low cost.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a heat-resistant nonwoven fabric 2
For example, a metal fiber nonwoven fabric or a ceramic fiber nonwoven fabric can be used. In particular, good results can be obtained when a metal fiber nonwoven fabric is used. In the following description, a case where a metal fiber nonwoven fabric is used will be described as an example.

The outer diameter of the filter element 3 formed by bending the metal fiber nonwoven fabric 2 of the present invention and having a substantially cylindrical shape 21 is D, the length is L, and the bending radius of the U-shaped bent portion is R.
(FIG. 3). Filter element 3 after bending
Is composed of N plate portions 5 parallel to the exhaust gas flow. The length of the flat plate portion 5 is L-2R. A relationship of approximately D = 2NR holds among N, D, and R.

In the substantially elliptical nonwoven fabric 2 made of metal fiber used in the present invention, the minor axis of the ellipse is equal to the diameter D of the filter element. The major axis of the ellipse is substantially equal to the value obtained by adding the total length (π × R × (N−1)) of the U-shaped bent portion 6 to the length ((L−2R) × N) of the N plane portions 5. Become equal.
In the metal fiber nonwoven fabric 2 having such a shape, when the major axis direction of the ellipse is divided into N equal parts, the boundary part of each equally divided surface is a bent part 6 (N-1 places) along the width direction of the elliptical shape.
Becomes At the bent portion 6, the metal fiber nonwoven fabric 2 is alternately bent in a valley and a valley, and the bent shape is a U-shaped bent having a bent portion 6 having a radius R. As a result, the outer shape of the filter element 3 formed of the metal fiber nonwoven fabric 2 has a substantially cylindrical shape 21 having a diameter D and a length L (FIG. 2).

Assuming that the minor axis of the ellipse is D 'different from the above D, the outer shape of the filter element 3 is elliptical, and the major and minor axes of the external elliptical shape are D and D'. D> D '
If so, D 'is the minor axis, and vice versa, D' is the major axis. The filter element having a substantially cylindrical outer periphery according to the present invention may have such an elliptical cross section.

When the metal fiber non-woven fabric is formed into an accurate elliptical shape 20 having the above-described major and minor diameters as shown in FIG. 3 (a), the outer shape of the filter element 3 after bending is formed into a cylindrical shape. The outer shape becomes closer to a columnar shape when the plate portions 5 which are substantially parallel to the exhaust gas flow constituting the filter element are not completely parallel to each other, but are slightly opened and adjusted at an angle.

On the other hand, in the case where the flat portions 5 constituting the filter element are arranged in parallel to the exhaust gas flow, if the edges 13 on both sides of each flat portion 5 are parallel to the major axis of the ellipse, the filter after bending is formed. It is preferable to make the outer shape of the element 3 a cylindrical shape 21. Further, since the widths of the adjacent flat plate portions 5 are different from each other, the outer shape of the filter element can be made closer to a columnar shape by changing the width at the bent portion 6 of the metal fiber nonwoven fabric. That is, as shown in FIG. 3B, the shape of the metal fiber nonwoven fabric before bending is along the elliptical shape 20, the edges 13 on both sides of each flat plate portion 5 are parallel, and each bending portion 6 At a step having a slope. Therefore, as described in the above (2) of the present invention, the outer shape of the metal fiber non-woven fabric 2 having a substantially elliptical shape has a step-like shape in which the width of the non-woven fabric changes at the bent portion 6, thereby providing the filter element 3. Can be formed into a preferable cylindrical shape 21 as shown in FIG.

A cylindrical outer cylinder 4 is arranged on the outer periphery of the filter element 3 which has been bent into a substantially cylindrical shape 21 (FIG. 1). The outer cylinder 4 is preferably made of a heat-resistant metal such as stainless steel. The metal fiber nonwoven fabric 2 of the filter element 3 is in contact with the outer cylinder 4 at the edge 13. By joining the metal fiber nonwoven fabric 2 and the outer cylinder 4 at the contact portion thereof, the exhaust gas introduced from the exhaust gas inlet side 24 of the filter passes only through the metal fiber nonwoven fabric and the exhaust gas outlet side 25. Will be led to.

In the above (3) of the present invention, the outer cylinder 4 comprises two cylindrical portions 7 each having one end in a comb-like shape.
The shape of the teeth of the comb of the cylindrical portion 7 is as shown in FIG. 4, and the shape is such that the portion where the filter element 3 just bent is in contact with the outer cylinder 4 becomes the outer shape of the teeth of the comb. In this case, the outer diameter of the filter element 3 having the substantially cylindrical shape 21 is slightly larger than the inner diameter of the two cylindrical portions 7. When the two cylindrical portions 7 are assembled together with the cylindrical filter element 3 (FIG. 5), and the comb teeth of the two cylindrical portions 7 are engaged with each other, the non-woven fabric edge 13 of the filter element 3 is interposed between the comb teeth. Is sandwiched. At the same time, the outer cylinder 4 is constituted by the two cylindrical parts 7 combined, and the outer cylinder 4 and the edge 13 of the nonwoven fabric are joined.
The outer cylinder 4 and the filter element 3 as shown in FIG. 1 were provided by joining the portions where the outer surfaces of the two cylindrical portions 7 and the edge 13 of the nonwoven fabric were in contact with each other by means such as brazing. The particulate filter is completed.

According to the present invention (3), welding is not performed on the metal fiber non-woven fabric 2 exposed in the exhaust gas flow portion inside the outer cylinder 4, so that the non-woven fabric is deteriorated by welding heat and is It will not be damaged. In addition, it is possible to prevent the exhaust gas from leaking from the gap between the edge portion 13 of the nonwoven fabric and the outer cylinder 4. There is no need to install a component such as a liner to prevent the leakage, so that the number of components can be reduced and the cost can be reduced.

Further, as shown in (4) of the present invention shown in FIG. 6, the outer circumference of the outer cylinder 4 comprising the two cylindrical portions 7 can be further wrapped by the second outer cylinder 8. By using a double outer cylinder, radiation of the heat of the exhaust gas to the outside can be suppressed. In addition, the first in which the two cylindrical portions 7 are joined together
The outer cylinder 4 is securely fixed by the second outer cylinder 8, and the structural strength of the particulate filter can be further improved. It is preferable that the inner diameter of the second outer cylinder 8 be larger than the outer diameter of the outer cylinder 4 including the two cylindrical portions 7 within a range of 3 mm or less. Within this range, the two cylindrical portions 7
The second outer cylinder 8 can be inserted even if the joint between the metal and the metal nonwoven fabric 2 is raised on the surface, and excessive loosening does not occur.

In order to burn the particulates collected on the nonwoven fabric, a heat source of 600 ° C. or higher is required. As described in the above (5) of the present invention, the outer circumference of the outer cylinder 4 is wrapped with a heat-resistant heat insulating material, and the particulate filter is mounted in the exhaust pipe of the engine, so that the exhaust gas transmitted to the particulate filter is reduced. The heat can be spent on burning the particulates without escaping to the outer periphery. By wrapping the outer periphery of the heat insulating material with the second outer cylinder as in (6) of the present invention, the structural strength of the particulate filter can be increased, and the durability can be improved. It is preferable to use a thermal expansion sheet as the heat-resistant heat insulating material surrounding the outer cylinder. Vermiculite or ceramic fiber can be used as the heat insulating material.

The bent portion 6 of the metal fiber non-woven fabric is a portion that is directly hit by the exhaust gas on both the entrance side and the exit side of the exhaust gas, and is a place where the non-woven fabric is likely to be damaged. In the present invention, the durability of the bent portion 6 is improved by adopting a U-shaped bent shape, instead of the conventional U-shaped, U-shaped, and non-woven fabric joining means as in the related art. I was able to. Further, in the above (7) of the present invention, FIG.
As shown in (1), by arranging the support rod 9 inside the U-shaped bent portion 6 of the metal fiber nonwoven fabric in parallel with the bent portion 6, the durability of the bent portion 6 can be further improved. On the exhaust gas inlet side 24, the bent portion 6 of the nonwoven fabric is prevented from being deformed by wind pressure by the support rod 9, and on the exhaust gas outlet side 25, the support rod 9 receives the wind pressure of the exhaust gas. There is no direct wind pressure.

FIG. 7C shows the sectional shape of the support rod 9.
, Or a semicircular shape as shown in FIG. 7D. Further, the opening angle may be a fan shape with an arbitrary angle. The diameter of the support rod 9 is equal to or smaller than the bending diameter of the U-shaped bent portion 6 of the nonwoven fabric.
The diameter should be small within a range of 5 mm or less. As the material of the support rod, heat-resistant steel such as stainless steel or heat-resistant / low-thermal-expansion ceramic can be adopted.

In the above (8) of the present invention, since the flat plate portion 5 has the corrugated plate 10, a rectifying effect can be obtained, whereby the adhesion of the particulate to the filter can be made uniform, and the particulate The life of the filter can be extended.

As the corrugated sheet 10 used in the present invention (8), a corrugated sheet made of a heat-resistant metal foil such as stainless steel or a metal fiber nonwoven fabric can be used. The wave shape is
A semicircle, a sine wave shape, a triangle, and the like can be adopted. The wave height of the waveform is a numerical value equal to the interval between the flat portions 5 of the filter element. When a stainless steel foil is used as the corrugated sheet 10, the thickness of the corrugated sheet 10 is preferably set to 0.03 mm to 0.5 mm as described in the above (10) of the present invention. When the corrugated sheet is too thick, if the interval between the nonwoven fabric planes is reduced, the thickness of the corrugated sheet and the contact surface with the nonwoven fabric increase, and the pressure loss increases. If it is too thin, it will lack durability. More preferably, the thickness is 0.05 mm to 0.2
mm.

By brazing the contact portion between the metal fiber nonwoven fabric 2 and the sandwiched corrugated sheet 10 as in the above (11) of the present invention, the nonwoven fabric 2 and the corrugated sheet 10 can be fixed. Therefore, lateral displacement of the corrugated sheet 10 due to the pressure of the exhaust gas can be prevented, and the structural durability of the particulate filter is dramatically improved.

In the bent filter element of the present invention, when the interval between the metal fiber nonwoven fabric surfaces (flat plate portions 5) facing each other by making a U-shape is reduced, the number of flat plate portions 5 that can be stored increases, and exhaust gas is reduced. The pressure loss when passing through the nonwoven fabric 2 is reduced, and the life of the nonwoven fabric before it is clogged with particulates is extended. On the other hand, when the interval between the flat plate portions is small, the pressure loss when the exhaust gas passes through the gap increases. In the present invention, the above (1)
As in 2), it is preferable that the distance between the metal fiber non-woven fabric surfaces facing each other in a U-shape be 1 mm to 10 mm. 1mm
If it is less than 10 mm, the pressure loss when exhaust gas passes through this gap becomes too large, and if it exceeds 10 mm, the total surface area of the filter becomes too small. More preferably, the distance between the metal fiber non-woven fabric surfaces facing each other by U-shaped bending is 1 mm to
5 mm. In addition, as is clear from FIG.
Since the bending radius R of the non-woven fabric U-shaped bent portion is の of the interval between the surfaces of the non-woven fabric, the preferable range of the bending radius R is 0.
5 mm to 5 mm, more preferably 0.5 mm to 2.
5 mm.

The metal fiber nonwoven fabric 2 used in the present invention is preferably a nonwoven fabric made of metal fibers (diameter: 4 μm to 50 μm) made of a heat-resistant metal such as stainless steel. Regarding the thickness of the nonwoven fabric 2, when the thickness is increased, the collection site of the particulates by the nonwoven fabric increases, and the particulates can be collected at each site in the thickness direction of the nonwoven fabric, that is, the collection by volume. , The collection efficiency is improved. On the other hand, if the thickness of the nonwoven fabric is too large, the pressure loss of the gas passing through the nonwoven fabric increases, and the deformability of the nonwoven fabric when attempting to bend in a U-shape decreases. Further, when the fiber diameter is reduced, the pore size distribution of the nonwoven fabric is reduced, and the trapping ability is improved. Conversely, when the thickness is increased, the pore diameter increases, and a nonwoven fabric having a large collection site can be produced. From such a viewpoint, the thickness of the two nonwoven fabrics made of metal fibers is preferably in the range of 0.1 mm to 1.5 mm as described in (13) of the present invention. More preferably, the thickness of the metal fiber nonwoven fabric 2 is 0.3 mm to 0.7 mm.
mm.

When a nonwoven fabric made of ceramic fibers is used as the heat-resistant nonwoven fabric, ceramic fibers made of SiC, cordierite, mullite, crystalline alumina, or the like can be used.

Regarding the porosity of the metal fiber nonwoven fabric 2 of the present invention, the smaller the porosity, the better the trapping of particulates. On the other hand, if the porosity is small, the pressure loss during passage of exhaust gas increases. Becomes Therefore, as described in (14) of the present invention, the porosity of the metal fiber nonwoven fabric 2 is 40%.
% To 95%. The porosity is more preferably 60% or more from the viewpoint of preventing clogging of the metal fiber nonwoven fabric, and is more preferably 85% or less from the viewpoint of ensuring the strength of the metal fiber nonwoven fabric. Assuming that w is the unit mass of the nonwoven fabric and W is the same volume mass of the same material, the porosity can be represented by 100−w / W × 100. This value greatly affects the pore size distribution of the nonwoven fabric. The pore diameter can be measured based on JIS K3832 or ASTM F316-86. In order to adjust the porosity of the metal fiber nonwoven fabric 2, first, it is possible to change the thickness and the basis weight of the nonwoven fabric 2. The porosity decreases as the thickness increases and the basis weight increases. Second
Can be adjusted by reducing the fiber diameter and increasing the basis weight.

The particulates in the exhaust gas include those having various diameters. When the particulates having various diameters are collected by the metal fiber nonwoven fabric 2, as described in (15) of the present invention, the metal fiber nonwoven fabric 2 has a void in the exhaust gas entry side in the thickness direction of the nonwoven fabric. It is preferable to use a nonwoven fabric having a high porosity and a low porosity in the portion on the exhaust gas outlet side. Particulates having a large diameter are collected in a portion having a high porosity on the exhaust gas entry side in the thickness direction of the nonwoven fabric. On the other hand, the particulate having a small diameter passes through a portion having a high porosity on the exhaust gas inlet side, and is first collected in a portion having a low porosity on the exhaust gas outlet side in the thickness direction of the nonwoven fabric. In this way, the collection point can be changed depending on the diameter of the particulate, and by collecting at each part in the thickness direction of the nonwoven fabric,
It is possible to effectively utilize all portions in the thickness direction of the nonwoven fabric. As a result, it is possible to extend the life of the filter until the nonwoven fabric is clogged.

In a diesel engine, a catalytic converter carrying a catalyst is disposed in an exhaust gas path for purifying impurity gases such as NOx in exhaust gas. If the particulate filter and the catalytic converter are to be installed separately in the exhaust gas path, it is necessary to secure an installation space for the two devices, and especially in a portion close to the engine, installation space may not be secured. . In the particulate filter of the present invention (8), in which the corrugated corrugated metal plate 10 is sandwiched between the metal fiber nonwoven fabric surfaces facing the U-shaped bend, as described in the above (9), By supporting the catalyst on the surface of the sandwiched corrugated sheet and / or the metal fiber nonwoven fabric, the particulate filter can also have a function as a catalytic converter. As a result, exhaust gas purification by the particulate filter and the catalyst can be performed by one device, and the space required for installation can be reduced.

The particulate filter of the present invention can be installed at the place after the exhaust manifold of the engine or under the floor of the automobile as in the conventional case. Furthermore, since the particulate filter of the present invention has a cylindrical outer shape and excellent durability, it can be installed in an exhaust port of an engine unlike the conventional one. When installed in the exhaust port of the engine, the temperature of the exhaust gas is high, so that the combustibility of the particulates can be improved.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Diameter D = 58 m as filter element
The present invention was applied to a particulate filter for a diesel engine using a cylindrical filter having m and a length L = 37 mm.

As shown in FIG. 2, the filter element 3 has eight bent portions 6 on the exhaust gas inlet side 24 and nine bent portions 6 on the exhaust gas outlet side 25, and has 18 flat portions 5, It has a cylindrical shape 21 as a whole. The bending radius R of the bending portion 6 is 1.5 mm.

As the nonwoven fabric 2 made of metal fiber, a material YUS2
Using 0.5-M1 stainless steel metal fiber, thickness 0.5
A nonwoven fabric having a porosity of 70 mm and a porosity of 70% was used. The shape of the metal fiber nonwoven fabric 2 is as shown in FIG.
A step-like shape in which the width of the nonwoven fabric changes at the bent portion 6 with a substantially elliptical shape 20 is employed. The minor axis of the elliptical shape 20 is 58 mm, which is equal to D, and the major axis is 738 mm. However, as shown in FIG. 3 (b), since both ends in the longitudinal direction of the metal fiber non-woven fabric 2 having a substantially elliptical shape are cut off, the length of the non-woven fabric 2 is 692 mm.

The nonwoven fabric 2 made of metal fiber is bent alternately at the bending portion so as to have a bending shape with a bending radius R = 1.5 mm.
As shown in FIG. 2, a filter element 3 as shown in FIG. 2 was formed. Since the shape of the metal fiber non-woven fabric 2 was substantially along the elliptical shape 20, the outer shape of the filter element could be made cylindrical 21. In addition, the shape of the metal fiber nonwoven fabric 2 is such that the edge 13 in the flat plate portion 5 is parallel to the major axis direction of the ellipse and the step is formed in the bent portion 6. In the case of the present embodiment in which all the flat plate portions 5 in 3 were formed in parallel to the flow direction of the exhaust gas, the outer shape of the filter element could be maintained in a cylindrical shape 21.

A round support rod 9 as shown in FIG. 7C is arranged inside the U-shaped bent portion of the filter element 3. The diameter of the support rod 9 was 2 mm. Further, a corrugated plate 10 as shown in FIG. 8 was inserted into the gap between the flat plate portions 5 of the filter element 3. The material of the corrugated plate 10 is YUS2
05-M1 stainless steel, thickness 0.02 mm, wave shape is semicircular.

As the outer cylinder 4, two cylindrical portions (7a, 7b) shown in FIG. The cylindrical part is made of YUS180 stainless steel, 1.5mm thick
Was used. As shown in FIG. 5, an outer cylinder 4 is formed by sandwiching the outer periphery of the filter element 3 between two cylindrical portions, and has the shape shown in FIG. The length of the outer cylinder 4 is 43 mm. At the outer peripheral portion of the outer cylinder 4, the two cylindrical portions and the edge 13 of the filter element 3 were joined by brazing.
Since the edge 13 of the filter element 3 made of the metal fiber nonwoven fabric 2 is brazed and joined only at the outer peripheral portion of the outer cylinder 4, the metal fiber nonwoven fabric 2 has no brazing portion inside the outer cylinder 4, Deterioration of durability of the nonwoven fabric due to brazing was prevented.

On the outer periphery of the outer cylinder 4, a second outer cylinder 8
The particulate filter 1 for a diesel engine as shown in FIG. 6 was completed. The material, thickness, and length of the second outer cylinder were the same as those of the outer cylinder 4. A clearance of 1 mm was provided between the outer diameter of the outer cylinder 4 and the inner diameter of the second outer cylinder 8.

Further, a retainer 14 as shown in FIG. 9 is provided on the exhaust gas outlet side 25, and is supported by the retainer 14 so that the filter element 3 is not deformed to the exhaust gas outlet side 25 by the wind pressure of the exhaust gas. did. Stainless steel of the same material as the outer cylinder 4 was used for the retainer 14.

Using the particulate filter 1 formed as described above, particulates contained in exhaust gas of a diesel engine were collected. The installation place of the particulate filter 1 of the present invention was attached to each exhaust port of the diesel engine. Since the particulate filter of the present invention could be reduced in size, it could be attached to the exhaust port. On the other hand, since the conventional particulate filter has a large shape, it cannot be installed at the exhaust port, and is installed after the exhaust manifold. Since the exhaust gas temperature at the exhaust port is higher than that after the exhaust manifold, the particulate filter according to the present invention has the effect of improving the combustibility of the particulates.

[0048]

According to the present invention, breakage of the non-woven fabric at the bent portion is prevented by using a heat-resistant non-woven fabric for the filter and alternately bending the non-woven fabric at the bent portion 6 to form a U-shaped bent portion. Therefore, the durability of the filter is excellent. Further, by disposing the support rod 9 inside the U-shaped bent portion of the heat-resistant nonwoven fabric, the durability of the filter is further improved.

By using the heat-resistant nonwoven fabric having a substantially elliptical shape, the filter element formed of the bent heat-resistant nonwoven fabric has a substantially cylindrical shape, so that the surface area of the filter is small and the heat dissipation from the filter can be reduced. it can.

According to the present invention, a filter element is formed by alternately bending a single heat-resistant nonwoven fabric having a substantially elliptical shape at a plurality of bending portions. Therefore, it is not necessary to connect the ends of a large number of filters, and it is possible to produce the filters at low cost.

[Brief description of the drawings]

FIG. 1 is a perspective view of a particulate filter for a diesel engine according to the present invention.

FIG. 2 is a view showing a filter element of the present invention;
(A) is a perspective view, (b) is a side view, and (c) is an enlarged view of a bent portion.

3A and 3B are diagrams showing the shape of a heat-resistant nonwoven fabric used in the present invention, wherein FIG. 3A shows an elliptical shape, and FIG.

FIG. 4 is a perspective view showing two cylindrical portions having a comb tooth shape of the present invention.

FIG. 5 is a perspective view showing a situation in which two cylindrical portions and a filter element are assembled.

FIG. 6 is a perspective view showing a particulate filter of the present invention having a second outer cylinder.

FIG. 7 shows the invention with a support bar, (a)
Is a perspective view showing a filter element on which a support rod is arranged,
(B) is a side sectional view showing a filter having a support rod,
(C) (d) is a partial sectional view showing the shape of the support rod.

8A and 8B are views showing the present invention having a corrugated plate, and FIG. 8A is a perspective view showing a filter element on which the corrugated plate is arranged;
(B) is a plan view showing a filter having a corrugated plate.

FIG. 9 is a perspective view showing a particulate filter of the present invention in which a retainer is arranged on the exhaust gas outlet side.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Particulate filter for diesel engines 2 Heat resistant nonwoven fabric (nonwoven fabric made of metal fiber) 3 Filter element 4 Outer cylinder 5 Flat plate part 6 Bending part 7 Cylindrical part 8 Second cylinder 9 Support rod 10 Corrugated plate 11 Metal fiber 12 Catalyst support layer 13 Edge 14 Retainer 20 Oval shape 21 Cylindrical shape 24 Exhaust gas inlet side 25 Exhaust gas outlet side D Diameter of filter element L Length of filter element N Number of flat plate parts R Curvature radius of bent part

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) B01D 39/20 B01D 39/20 A D 46/52 46/52 A 53/94 F01N 3/24 E F01N 3/24 3 / 28 F 3/28 B01D 53/36 103B (72) Inventor Takeshi Shinoda 5-3 Tokai-cho, Tokai City Inside Nippon Steel Corporation Nagoya Works (72) Inventor Kazuhiko Shiratani 1-Toyota-cho, Toyota-shi, Aichi Prefecture Toyota Motor Corporation (72) Inventor Toshihisa Sugiyama 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 3G090 AA01 AA03 EA01 3G091 AA02 AA18 AB05 AB13 BA00 BA14 BA21 BA39 GA03 GA05 GA16 GB01X GB17X HA14 HA28 4D019 AA01 BA02 BA05 BB03 BC07 BD01 BD06 CA01 CA03 CB04 4D048 AA14 AB01 BA03X BA06X BA10X BA39X BA41X BA45X BB04 BB08 BB12 BB18 CA01 CC06 CC08 CC09 CC38 CC41 4D058 JA13 JA33 JB03 JB06 TA06

Claims (16)

[Claims] 1. A heat-resistant nonwoven fabric having a substantially elliptical shape is bent alternately at a plurality of bent portions along a width direction of the elliptical shape, and the bent shape is formed into a U-shape. A particulate filter for a diesel engine, wherein an outer cylinder is arranged around an outer periphery of a filter element having a substantially cylindrical shape. 2. The diesel engine patty according to claim 1, wherein the outer shape of the substantially elliptical heat-resistant non-woven fabric has a step-like shape in which the width of the non-woven fabric changes at a bent portion. Curated filter. 3. The outer cylinder includes two cylindrical portions each having a comb-like shape at one end, and a cylindrical shape formed of the heat-resistant nonwoven fabric bent by the comb teeth of the two cylindrical portions. 3. The particulate filter for a diesel engine according to claim 1, wherein an outer cylinder is formed by sandwiching an outer periphery of the filter element. 4. The particulate filter for a diesel engine according to claim 3, wherein a further outer circumference of the outer cylinder formed of the two cylindrical portions is wrapped by a second outer cylinder. 5. The particulate filter for a diesel engine according to claim 3, wherein an outer circumference of the outer cylinder formed of the two cylindrical portions is wrapped with a heat-resistant heat insulating material. 6. A particulate filter for a diesel engine according to claim 5, wherein an outer periphery of said heat insulating material is wrapped by a second outer cylinder. 7. The particulate matter for a diesel engine according to claim 1, wherein a support rod is arranged inside the U-shaped bent portion of the heat-resistant nonwoven fabric in parallel with the bent portion. filter. 8. The diesel engine according to claim 1, wherein a corrugated corrugated metal plate is sandwiched between heat-resistant nonwoven fabric surfaces that face each other in a U-shaped bend. For particulate filter. 9. The particulate filter for a diesel engine according to claim 8, wherein a catalyst is carried on the surface of the sandwiched corrugated sheet and / or the heat-resistant nonwoven fabric. 10. The sandwiched corrugated sheet having a thickness of 0.03
The particulate filter for a diesel engine according to claim 8, wherein the particle size is from 0.5 mm to 0.5 mm. 11. The particulate filter for a diesel engine according to claim 8, wherein a contact portion between the heat-resistant nonwoven fabric and the sandwiched corrugated sheet is brazed. 12. The particulate filter for a diesel engine according to claim 1, wherein an interval between the heat-resistant nonwoven fabric surfaces facing each other in a U-shape is 1 mm to 10 mm. 13. The heat-resistant nonwoven fabric has a thickness of 0.1 mm.
13. It is 1.5 mm.
A particulate filter for a diesel engine according to any one of the above. 14. The heat-resistant nonwoven fabric has a porosity of 40% to 40%.
The particulate filter for a diesel engine according to any one of claims 1 to 13, wherein the particulate filter is 95%. 15. The porosity in the thickness direction of the heat-resistant nonwoven fabric is such that the porosity is high at a portion on the exhaust gas entry side and low at the portion on the exhaust gas exit side. 15. The particulate filter for a diesel engine according to any one of 1 to 14. 16. The particulate filter for a diesel engine according to claim 1, wherein the heat-resistant non-woven fabric is a metal fiber non-woven fabric or a ceramic fiber non-woven fabric.