JPS6296717A - Exhaust particle filter element for diesel engine and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to diesel engine exhaust particulate traps, and more particularly to an exhaust filtration system having a monolithic ceramic filter element.

The problem of limiting the amount of particulate matter emitted with the exhaust from diesel and other internal combustion engines has recently received considerable attention. In the case of diesel engines, considerable effort has been expended in developing practical and effective devices and methods for reducing the emission of large carbon-based particles in the exhaust.

It has been recognized that one way to accomplish this is to provide a suitable filter or other type of particle trap in the engine or vehicle exhaust system. Keeping this in mind,
Efforts are currently underway to identify the most effective and practical method for collecting and treating soot-like particulate matter emitted by diesel engines before the exhaust is released into the atmosphere.

SUMMARY OF THE INVENTION The present invention is directed to a novel structure and form of integral porous wall ceramic filter element capable of effectively trapping diesel engine particles. These elements are arranged in a compact, highly efficient unit with a very large filtration area relative to its volume.

To clean these filter elements, the monolithic structure, or a portion thereof, may be heated to the ashing temperature of the trapped particles. This causes the particles to burn and disappear. Various arrangements of unitary porous wall ceramic filter element structures and methods of manufacturing the same are also encompassed by the present invention.

The present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a vehicle chassis 10, which includes a V-type diesel engine 12 having a pair of cylinder rows.
It includes a frame 11 carrying a. Each cylinder row is equipped with an exhaust manifold 14 connected to an exhaust system, and only the one on the right side is shown in the figure.

Each exhaust manifold is in exclusive contact with an exhaust particle trap 16 through an exhaust pipe 15. The trap is supported on the vehicle frame by means not shown and is adapted to collect particles in the exhaust gas directed to the trap from the cylinders of each cylinder row. The outlet of the trap 16 is connected through a Y-shaped pipe 18 to a muffler 19 which leads to the rear of the vehicle through a till pipe 20.
The exhaust gas is vented to the atmosphere.

Each particle trap 16 includes a housing, which may take any suitable configuration or form for the purpose. Disposed within the housing is a highly efficient ash-cleanable ceramic filter element. This filter element may take any form, such as element 22 shown in FIG. The filter element 22 is in the form of a unitary structure having a plurality of interdigitated thin porous inner walls 24 and an inner cylindrical outer wall 23 connected to each other. The interlocking inner walls define within them two groups of parallel passages each containing an inlet passage 26 and an outlet passage 27. Each passageway extends from one end of element 22 to the other. Entrance passage 2
6 is open at the inlet end 28 of the element and closed at the outlet end 30, while the outlet passage 27 is closed at the element inlet end 28 and open at the outlet end 30.

In the embodiment of FIG. 2, these passageways are square in cross-section, but various other configurations may be utilized, as will be explained in more detail below. Further, the entrance and exit passages are arranged in vertical and horizontal rows when viewed in cross section, and the entrance passages alternate with the exit passages to form a checkerboard pattern. Thus, each inner wall portion is located at every point of the element between the inlet and outlet passages. However, this excludes areas where the inner walls engage with each other, such as corners of passages. Thus, except for the corner retainers, the inlet passages are separated from each other with the outlet passage in between, and vice versa.

In this cellarmic monolithic structure, the inner wall 24 is porous through which exhaust air flows from the inlet passage to the outlet passage.

The porosity of the inner wall is suitably selected to block a significant portion of the particles present in diesel exhaust. at present,
Tests have shown that effective filtration can be achieved with ceramic wall structures having an average porosity of about a factor of 10, i.e., an average pore size of 2 microns to 15 microns in a pore size range of 0.5 microns to 70 microns. I understand. The monolithic structure in which this was done had an average square channel of 0.06 inch (1,524 tan) on one side, and the wall thickness between the channels was about 0.15 inch (3,81 tan). Considering the total internal wall structure between the inlet and outlet passages to be the effective filtration area, it is clear that this structure provides more than 12903.2- greater filter wall area per cubic inch of integral film structure. Therefore, a filter with a large filter area and a very low restriction can be obtained in a very small package. 10 of the first test samples
It is of course conceivable that increasing the average wall porosity by more than % would further reduce the restrictions on gas flow through the filter element, at least to the point where the area of the inlet and outlet passages becomes the limiting factor on gas flow.

In operation of an engine in which the exhaust system is equipped with one or more of the aforementioned compact, high-efficiency exhaust particle filter elements, exhaust gas flows from the engine to the particle trap 16 and passes through the open end of the inlet passage at the inlet end 28 to the filter. It will go into the element. The invading gas is distributed over the length of each inlet passage and flows through all of the porous walls forming the respective passage to the adjacent outlet passage.

As the exhaust air passes through, most of the carbon-based particles contained therein become trapped and collected on the inner surface of the inlet passageway walls. The collected particles form a cake on the wall, which eventually grows until it reaches a thickness that begins to impede gas flow through the wall. The clean gas that has flowed through the wall into the outlet passage flows to the open end of the outlet passage at the outlet end of the filter element and is discharged to the atmosphere through the remainder of the exhaust system.

During operation of an engine with an exhaust filter of the above type,
Periodically, the collected particles will reach a level above which restriction to gas flow becomes excessive. At this point, or at some later point, the filter element must be cleaned or replaced to enable continued effective operation of the vehicle engine. Although the compact, highly efficient monolithic ceramic element of the present invention can be used in any desired manner, the element must be heated to a temperature at which the collected particles are incinerated by reaction with oxygen in the exhaust stream. It is believed that cleaning of the elements is best achieved by Such ashing can, of course, occur by heating the exhaust gas during engine operation to the desired ashing temperature by appropriate heating methods and control of the combustion temperature.

Alternatively, the monolithic ceramic filter element can be removed from the exhaust system, placed in the controlled environment of a furnace, heated to the ashing temperature of the particles, and cleaned and reused by burning out the particles. good.

Activation of the ceramic filter element under the aforementioned conditions;
The filter element must be made of a suitable ceramic material to withstand ashing temperatures and stresses. Although many such materials may be suitable, currently the materials described by Somers, Ber, assigned to the applicant.
U.S. Patent No. 3.954.6 to g and 5hukle
It is described in No. 72. Preferably, the ceramic element is formed by first using materials and methods developed for forming ceramic components such as catalytic converters. This U.S. patent inter alia includes column 6, lines 17 to 7.
Column line 48 describes a preferred sequence of steps in a manufacturing process for extruding open-ended ceramic monoliths for use in catalytic converters and other equipment.

Upon completion of these manufacturing steps, the open-ended monolithic structure is
As mentioned above, closing the ends of the alternate passages converts the filter element into a filter element having alternately closed passages.

This is accomplished by filling and curing a suitable cement material to form the desired end closure wall.

This cement is preferably mixed with 71.5% milled cordierite-based filler made from the same type of ceramic material that forms the monolith, ground and passed through a 100 mesh screen. It is prepared by forming a mixture of 28.5% sialic silica (30% solids in 70g water). The cement can be applied in any manner, such as with a hypodermic needle plunger, and then cured by heating in an oven at 90-104°C for 8 to 10 hours, followed by heating at 538°C for 30 minutes. Heat to harden completely. Fillers based on milled cordierite can be obtained by milling scraps from monoliths.

Colossal silica is Ludox AS Co11od
ialSilica (30% 5olids) Plowea, Wilmington, E. 1. Du
Pont de Nemoures and Comp
Available from Any's Inc., Department of Industrial Chemistry.

Although the foregoing description sets forth the best presently believed mode of carrying out the invention through the description of the preferred embodiment, many changes in structure and method of manufacture are possible without departing from the inventive concept. It is. - By way of example, another construction of a ceramic diesel exhaust filter element and its use in an exhaust system is shown in Figure 3.4.

FIG. 3 shows a part of a vehicle chassis 32 having a frame 33, on which a V-type diesel engine 34 is mounted.

This engine has multiple cylinder rows and directs exhaust gas to a pair of exhaust manifolds 35 (only the exhaust manifold for the right row cylinder is shown!). Adjacent to the right side of the engine is an exhaust particle trap 37p''-device, which has a cubic housing with front and rear inlets. These inlets are connected to the left and right exhaust manifolds by exhaust pipes 3B and 39, respectively. It is connected to.

The exhaust outlet at the bottom of the housing is connected to an outlet pipe 41 to send cleaned exhaust gas to a muffler C (not shown) and to the atmosphere.

Disposed within the housing of particle trap 37 is a compact exhaust particle filter element 44 of the form shown in FIG. This element 44 has the product name Thermaco.
It is formed by a ceramic cross-flow monolith of the type made by 3M Company under +7+b. In this type of monolithic structure, a monolithic ceramic body 45 has a plurality of alternating vertical waste passages 46 and horizontal waste passages 48, which are separated from each other by a porous inner wall 49. It is used.

In the illustrated construction, the vertical passageway 46 is used as an inlet passageway and the horizontal passageway 48 is used as an outlet passageway and is vertical when seated within the particle trap 37. As is clear from FIG. 4, there is a separator wall 49 between the layers of the vertical and horizontal passages 46 and 48, and these serve as filter walls, and the surface thereof extends from the inlet passage to the outlet passage. It is designed to collect particles flowing through it.

However, each layer is formed with support walls 50, which merely separate the inlet passages from each other or the outlet passages from each other, and therefore have no filtration function. Therefore, when this form of ceramic element is used as a filtration element in the manner described above, only half of the inner wall is utilized as a filtration surface. thus,
To provide the same filtration area and the same degree of freedom for flow through the porous walls, the filter element must be made approximately twice as large as the first embodiment.

When element 44 is seated within the housing of particle trap 37, the top end of vertically extending horizontal outlet passage 48 is occluded, so that exhaust must flow into exhaust pipe 41 through the bottom open end. Exhaust flow coming through exhaust pipe 38 from the left cylinder row and exhaust pipe 39 from the right cylinder row enters the inlet passage through its open ends. Exhaust gas entering from both ends of the inlet passage passes through the separator wall 4
9, enters the outlet passage 48 and exits through its lower open end into the exhaust pipe 41. As is clear,
Other arrangements may be used to connect the filter elements within the particle trap, and other arrangements of the filter elements themselves may be used, all within the scope of the present invention.

In addition to variations in the passage arrangement of monolithic ceramic filter elements as shown in Figure 2.4, a variety of passage configurations may be utilized within the elements of any given general type. For example, FIGS. 53-5n illustrate a number of possible variations in the passageway configuration utilized in a monolithic ceramic filter of the general type shown in FIG. That is,
In these monolithic structures, alternating closed parallel passageways run end-to-end within the element, with virtually all contact areas contributing to the effective filtration area, except at points of engagement with other walls. Become.

For example, FIG. 5a is a schematic cross-sectional view of some of the elements similar to those of FIG. 2, with walls 24a arranged in a checkered pattern. The inlet passageway 26a is shaded to show that it is blocked at the outlet end, while
The outlet passage 27a is blank, indicating that it is open at the outlet end. This figure clearly shows the advantages of this arrangement. That is, all internal walls are located between the inlet and outlet passages, except where they meet other walls at the edges of the passages. thus.

Approximately 100 mm of the contact area becomes the filtration area.

Although similar results can be obtained with all of the other embodiments shown in Figures 5b-5n, it is clear that there are some differences. Figures 5b-58 are similar to Figure 5a in that the parallel adjacent inlet and outlet passages are of uniform cross-section and are formed by intersecting flat walls. The channels in Figure 5b are of rectangular cross-section, while those in Figures 5e, 5d and 5e are of various triangular shapes. Figure 5f shows a diamond-shaped passageway.

A somewhat more formal arrangement is shown in Figure 5g, in which:
The walls are not straight or flat, but corrugated to increase the filtration area.

Although this figure shows the result of installing corrugated walls to imitate a square checkerboard pattern, the same results can be obtained by changing the arrangement of Figures 5b-5f to provide corrugated walls instead of flat walls. It is clear that it can be done.

All the arrangements described so far have the following common advantages: That is, the total internal wall area forms an effective filtration area between the inlet and outlet passages, and the inlet and outlet passages have the same cross-sectional area. However, during operation, particles collect on the wall of the inlet passage and form a cake, ultimately reducing the effective flow area, so that the cross-sectional area of the inlet passage is larger than the cross-sectional area of the adjacent outlet passage. A large arrangement is advantageous. The arrangement described below has this advantage, yet all the interior walls extend between the inlet and outlet passages, except for the point of contact, and virtually all of the interior walls provide an effective filtration area.

This is first shown in Figures 5h-51s5J, where the flat inner walls are arranged to create different polygonal patterns. In FIG. 5h, the inlet passage 26h has a regular hexagonal cross section, and these regular hexagons constitute the outlet passageway which has a regular triangular cross section. In FIGS. 51 and 52, the inlet passage has a scalene hexagonal cross section and the outlet passage has a scalene triangular cross section.

Another variation is to use the polygonal arrangement of Figures 5a to 5f to suitably curve the walls to form what may be called an outwardly bulging inlet passage and an inwardly bulging outlet passage. It forms the inlet and outlet passages.

Thus, for example, in Figure 5, two of the four side walls are curved into a bulging checkerboard pattern, and the inlet passageway 26 has a slightly larger area than the outlet passageway 27.

In Figure 51, all interior walls are curved to bulge outward on all sides of the inlet passageway and bulge inward on the corresponding sides of the outlet passageway to enhance filtration. A similar effect is seen in the arrangement of Figure 5m, where the equilateral triangular passage of Figure 5c is inflated to make the area of the inlet passage 26n larger than the outlet passage 27n. Finally, this concept is taken further in FIG. 5n, where the cross-section of the inlet passage 26p is circular and the outlet passage 27p is formed in the space of the contacting chambers. This is, of course, a variation of the outwardly bulging square, but it is clear that a similar effect can be achieved by arranging the circles in a triangular pattern.

5th ht 5 is 5jt 5, 51.5m5Sn
Each of the arrangements shown in the figures and described in which the inlet passage area is larger than the outlet passage area still retains the advantage that almost all of the inner wall area is available for filtration. This is because it has the fundamental advantage that the inlet and outlet passages are separated by their inner walls except at their points of contact. However, not all polygonal or other cross-sectional shaped passage arrangements have the advantages described above. For example, in the case of alternating inlet and outlet passages, parallel passages with hexagonal cross-sections are provided in a pattern that results in a significant portion of the non-contacting wall area separating the two inlet and outlet passages. You can also do that. This contact area would not be effective for filtration. This also applies to as many other patterns as you can think of. Nevertheless, the patterns described above are representative of those with the desired advantages;
Not all patterns fall within the scope of this invention.

Preferably, the cross-sectional area of the passageways in the filter element described above is less than an average of 12.9032 mA (C0.02 square inches). This is the meaning of the term "small" used in the claims with respect to the inlet and outlet passages. Also, the wall thickness of the channel of the element is preferably 0.762 mm.
(0.3 inches) or less.

Certain features of the present invention are described in the applicant's pending application (A.D.
H/1278).

[Brief explanation of drawings]

1 is a perspective view of a portion of the chassis of a vehicle containing a diesel engine having an exhaust system with a pair of exhaust particle traps according to the present invention; FIG. 2 is a monolithic ceramic for use in the particle trap of FIG. 1; FIG. 3 is a fragmentary perspective view of a part of the chassis of a vehicle equipped with another embodiment of the diesel particle trap according to the invention; FIG. 4 is the particle trap of FIG. 3; FIGS. 5a to 5n are fragmentary perspective views showing the structure of a ceramic filter element used in FIG. It is a diagram. DESCRIPTION OF SYMBOLS 10... Chassis, 11... Frame, 12... Diesel engine, 14... Exhaust manifold, 15... Exhaust pipe, 16... Exhaust particle trap, 19... Muffler, 20... - Tail pipe, 22... Filter element, 24... Inner wall, 26... Inlet passage, 27... Outlet passage, 28... Inlet end, 30... Outlet end.

Claims (1)

Claims: 1. An exhaust particulate filter element for a diesel engine, having a plurality of thin interlocking gas filtration porous inner walls 24 defining a plurality of parallel passageways extending to opposite ends of the filter element. A highly efficient ashed-cleanable ceramic monolithic structure 22 is provided, the plurality of passages comprising a first group and an inlet passage 26 which is open at one end 28 of the filter element and closed at the other end 30; a second group of outlet passages 27 closed at one end 28 and open at the other end 30, each non-engaging portion of all inner walls 24 of said monolithic structure being between an inlet passage 26 and an outlet passage 27; The inlet and outlet passages are arranged so as to form a filtration surface between them for the flow of gas, and the porosity of the wall allows the passage of diesel through the filter element from the inlet passage 26 to the outlet passage 27. A filter element characterized in that it is adapted to filter out a substantial part of the particles present in the exhaust air. 2. The inner wall structure 24, 49 has an average porosity of 10 percent or more, with an average pore size between 2 and 15 microns, with individual pore sizes ranging from 0.5 to 70 microns over substantially the entire area. The exhaust particulate filter for a diesel engine according to claim 1, further having a filtration area of 5.90 cm^2 or more per cubic centimeter of the integral film structure. element. 3. In a method of manufacturing a compact, highly efficient, ash-cleanable exhaust particulate filter element for a diesel engine, a plurality of parallel passages 26, 27 of a first and second group extending therethrough are provided inwardly. forming a ceramic monolith of combined porous wall elements subjected to a process, with each non-engaging portion 24 of the inner wall elements forming a part of each group of passageways and allowing gas to flow between them through the pores of said inner wall elements. All ends of the first group 26 of passages located at one end 30 of the structure and all the second group 27 of passages located at the other end 28 of the structure are made of high temperature resistant material to allow the flow of air. The gas flow through the filter element entering the first group of passages 26 must pass through the porous wall element for filtration before being discharged through the second group of passages 27. A method characterized by: 4. Compact, highly efficient and ashes-cleanable honeycomb structure with parallel longitudinally extending channels defined by gas-permeable porous ceramic thin walls, with several channels 27 of the honeycomb body; An exhaust particulate filter element for a diesel engine, characterized in that one end surface 28 of the channel 26 is sealed with a sealing material, and the other end surface 30 of the remaining channel 26 is sealed with a sealing material.