JP2000279728A - Filter and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a filter by which the filter excellent in initial pressure drop characteristics at a low cost. SOLUTION: The production method of this filter includes an extrusion molding process, a cutting process, a sintering process and an assembling process. A honeycomb sintered body F1 originated in a honeycomb molding cut piece 24 obtained at the initial period of the extruding molding process, and a honeycomb sintered body F2 originated in a honeycomb molding cut piece 24 obtained at the later period, are adequately combined to perform the assembling process. Thus, an average cell wall thickness of the whole filter 9 is adjusted to nearly the same as the cell wall thickness of the honeycomb sintered body originated in the honeycomb molding cut piece 24 obtained in the middle period of the extrusion molding process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter such as a diesel particulate filter and a method for manufacturing the same.

[0002]

2. Description of the Related Art The number of automobiles has increased exponentially since the turn of the century, and the amount of exhaust gas emitted from internal combustion engines of automobiles has been increasing rapidly.
In particular, various substances contained in exhaust gas emitted from a diesel engine cause pollution, and are now seriously affecting the world environment. Also,
Recently, studies have reported that soot (diesel particulates) in exhaust gas sometimes causes allergic disorders and reduced sperm count. In other words, taking measures to remove soot in exhaust gas is considered to be an urgent issue for humanity.

Under such circumstances, various types of exhaust gas purifying devices have been proposed. A general exhaust gas purifying apparatus has a structure in which a casing is provided on an exhaust pipe connected to an exhaust manifold of an engine, and a filter having fine holes is disposed therein. Materials for forming the filter include ceramics in addition to metals and alloys. As a typical example of a ceramic filter, a cordierite honeycomb filter is known. Recently, silicon carbide is often used as a filter forming material because of its advantages such as high heat resistance, high mechanical strength, high collection efficiency, high chemical stability, and low pressure loss.

[0004] A honeycomb filter has a number of cells extending along its own axial direction. As the exhaust gas passes through the filter, soot is trapped by the cell walls. As a result, soot is removed from the exhaust gas.

However, a honeycomb filter made of a silicon carbide sintered body is vulnerable to thermal shock. Therefore, cracks are more likely to occur in the filter as the size increases. Therefore, as a means for avoiding breakage due to cracks, a technique for manufacturing a single large filter by integrating a plurality of small honeycomb sintered body pieces has been proposed in recent years.

The general method of manufacturing the above-described filter will be briefly described. First, a columnar honeycomb formed body is formed by continuously extruding a ceramic raw material through a mold of an extruder. After the extrusion forming step, the formed honeycomb body is cut into predetermined equal lengths. After the cutting step, the cut pieces of the formed honeycomb body are heated to obtain a honeycomb sintered body. After the firing step, a plurality of honeycomb sintered bodies are used to join their outer peripheral surfaces via an adhesive. Then, through such an assembling process, a desired diesel particulate filter is completed.

[0007]

However, if soot is collected for a long period of time, the pressure loss of the filter gradually increases. For this reason, it is necessary to regenerate the filter by periodically heating the entire filter to burn and eliminate soot. In many conventional exhaust gas purification devices,
Based on the result obtained by measuring the upstream pressure (back pressure) of the filter, the timing at which regeneration is to be performed is determined. Therefore, the demand for the improvement of the initial pressure loss characteristic of the filter is very severe. That is, it is severely required to reduce the variation in the initial pressure loss of the filter.

[0008] Here, "pressure loss" means a value obtained by subtracting a pressure value on the downstream side from a pressure value on the upstream side of the filter. The greatest factor that causes pressure loss is that the exhaust gas undergoes resistance as it passes through the cell wall. Therefore, the cell wall thickness greatly affects the initial pressure loss characteristics of the filter. If so, if the assembly process is performed using only the honeycomb sintered body having the cell wall thickness within the standard range, a filter having good initial pressure loss characteristics can be manufactured.

However, when the ceramic raw material is continuously extruded through the through hole of the die of the extruder, the ceramic raw material moves while constantly sliding on the die. Then, the die is gradually worn by the polishing action of the hard silicon carbide particles contained in the raw material, and the dimensions of the through holes are changed. If this dimensional change progresses, the mold eventually becomes unusable due to wear destruction, ending its life.
Of course, in this case, it is necessary to replace the mold whose life has expired with a new mold.

The effect of the dimensional change of the through hole of the mold will be described with reference to the graph of FIG. In the graph of FIG. 9A, the horizontal axis represents the extrusion length (m) of the honeycomb formed body.
The vertical axis indicates the cell wall thickness (m) of the honeycomb sintered body derived from the cut pieces of the honeycomb formed body at each stage of the extrusion forming process.
m). In the graph, L indicates the total length of the honeycomb formed body when extruded to the end of the mold life. The solid line rising upward shows the relationship between the extrusion length and the cell wall thickness. As is clear from this linear solid line, as the mold approaches the end of its life, the dimensional change of the through hole increases,
The cell wall thickness increases.

In the graph of FIG. 9B, the horizontal axis indicates the extrusion length (m) of the honeycomb formed body, and the vertical axis indicates the honeycomb sintered body derived from the cut pieces of the honeycomb formed body at each stage of the extrusion forming process. Indicates pressure loss (kPa). The solid line rising upward shows the relationship between the extrusion length and the pressure loss. As is clear from the linear solid line, the pressure loss increases as the mold approaches the end of its life. That is, as the cell wall thickness increases, the pressure loss increases in proportion thereto.

The specification range of the pressure loss required for the filter is as follows:
Assuming that the pressure is 9.5 kPa to 10.5 kPa, the cut pieces of the honeycomb formed body in the initial and late stages of the extrusion forming step are all out of the standard range. Therefore,
Those that correspond to about half of the moldable length before the end of the life of the mold become nonstandard products and are eventually discarded as unsuitable for use. The reason is that when the assembly process is performed using a plurality
This is because it is inevitable that the initial pressure loss varies between the initial, middle and late stages of the extrusion.

From the above, conventionally, it has been necessary to replace the mold and perform a new extrusion molding before the end of the original life. Therefore, there is a problem that the usable period of the mold is shortened substantially, which has increased the equipment cost. Moreover, the large loss of the ceramic raw material has increased the material cost, which has hindered the cost reduction of the filter itself.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a filter suitable for cost reduction. Another object of the present invention is to provide a method of manufacturing a filter that can obtain a filter having good initial pressure loss characteristics at low cost.

[0015]

According to the first aspect of the present invention, a honeycomb formed body is formed by continuously extruding a ceramic raw material through a mold of an extruder. Extrusion forming step, cutting step of cutting the honeycomb formed body to a predetermined length, baking step of heating the honeycomb formed body cut pieces into a honeycomb sintered body, and integrating a plurality of honeycomb sintered bodies. A method of manufacturing a filter including an assembling step, by performing the assembling step by appropriately combining the honeycomb sintered bodies derived from the honeycomb molded body cut pieces obtained at different times in a series of extrusion molding steps, the filter Adjust the average cell wall thickness of the whole to about the same as the cell wall thickness of the honeycomb sintered body derived from the honeycomb molded body cut pieces obtained at a specific time in the extrusion forming process. The manufacturing method of the filter, characterized by the spirit thereof.

According to the second aspect of the present invention, there is provided an extrusion forming step of forming a honeycomb formed body by continuously extruding a ceramic raw material through a mold of an extruder, and forming the honeycomb formed body to a predetermined length. A cutting step of cutting, a firing step of heating the honeycomb molded body cut pieces to form a honeycomb sintered body, and an assembling step of joining their outer peripheral surfaces to each other with an adhesive using a plurality of honeycomb sintered bodies. And a honeycomb sintered body derived from a honeycomb molded body cut piece obtained in the early stage of the extrusion molding step, and a honeycomb sintered body derived from the honeycomb molded body cut piece obtained in the late stage. By performing the assembling step in an appropriate combination, the average cell wall thickness of the entire filter is reduced to a honeycomb sintered body derived from a honeycomb molded body cut piece obtained in the middle stage of the extrusion forming step. The method for producing a filter and adjusting the substantially the same as the cell wall thickness as its gist.

According to the invention described in claim 3, according to claim 2,
In the assembling step, when combining a honeycomb sintered body derived from a honeycomb molded body cut piece obtained in the early stage of the extrusion molding step and a honeycomb molded body cut piece obtained in the late stage, Approximately the same number of the cell wall thicknesses deviating from the standard range were used.

According to a fourth aspect of the present invention, in the second or third aspect, the filter is a diesel particulate filter made of porous silicon carbide. According to a fifth aspect of the present invention, in any one of the second to fourth aspects, the adhesive is a ceramic heat-resistant adhesive in which ceramic fibers are dispersed.

The invention described in claim 6 is the invention according to claims 2 to 5
In any one of the above, the cross-sectional area when the honeycomb sintered body is cut perpendicular to the axial direction is 、 of the cross-sectional area when the entire filter is cut perpendicular to the axial direction.
It was assumed to be 00 to 1/15.

According to a seventh aspect of the present invention, there is provided a filter formed by integrating a plurality of honeycomb sintered bodies, wherein the honeycomb sintered body has a cell wall thickness smaller than a standard range. The gist of the present invention is a filter including a honeycomb sintered body that is relatively larger than the standard range, and in which the average cell wall thickness of the entire filter falls within the standard range.

Hereinafter, the "action" of the present invention will be described. According to the first and second aspects of the present invention, even the cut pieces of the honeycomb formed body that are not suitable for use and have been discarded can be used. As a result, the loss of the ceramic raw material is reduced, and the material cost is reduced. In addition, as a result that the mold can be used up to its original life, the frequency of replacing the mold is reduced, and a rise in equipment costs is prevented. From the above,
A filter with good initial pressure loss characteristics can be obtained at low cost.

According to the third aspect of the present invention, a honeycomb sintered body derived from a honeycomb molded body cut piece obtained at all of the initial, middle and late stages of the extrusion forming step is:
It can be used evenly. Therefore, the loss of the ceramic raw material is extremely reduced, and the material cost can be further reduced.

According to the invention described in claim 4, heat resistance and
It is possible to obtain a diesel particulate filter having favorable characteristics such as high mechanical strength, high collection efficiency, high chemical stability, and low pressure loss.

According to the fifth aspect of the present invention, if the ceramic heat-resistant adhesive in which the ceramic fibers are dispersed, even if the filter is subjected to thermal shock or vibration during use, the bonded state is deteriorated. Hard to do. Therefore, rattling or falling off of the honeycomb sintered body is prevented.

According to the sixth aspect of the present invention, by setting the cross-sectional area ratio within the above-mentioned preferred range, it is possible to avoid temperature non-uniformity during filter regeneration without being affected by variations in the thickness of the adhesive. can do.

If the cross-sectional area ratio is too small, the area of the adhesive occupying the entire cross-sectional area of the filter increases, and the influence of the thickness variation of the adhesive increases. That is, the initial pressure loss tends to vary due to an increase in the variation in the thickness of the adhesive. Therefore, the assembling work must be performed carefully so that the thickness of the adhesive does not vary.
The production may be troublesome. Conversely, if the cross-sectional area ratio is too large, the number of honeycomb sintered bodies constituting the filter becomes too small, and the temperature may become non-uniform during filter regeneration. Accordingly, cracks are easily generated, and the filter is easily damaged.

According to the seventh aspect of the present invention, even non-standardized products which were originally unsuitable for use and have been discarded can be used. As a result, loss of ceramic raw materials is reduced, and material costs are reduced. Therefore, the filter is suitable for cost reduction.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An exhaust gas purifying apparatus 1 for a diesel engine according to an embodiment of the present invention will now be described.
This will be described in detail with reference to FIGS.

As shown in FIG. 1, the exhaust gas purifying device 1 is a device for purifying exhaust gas discharged from a diesel engine 2 as an internal combustion engine. The diesel engine 2 includes a plurality of cylinders (not shown). Each cylinder has an exhaust manifold 3 made of metal material.
Are connected to each other. Each branch 4 is 1
It is connected to each of the manifold bodies 5. Therefore, the exhaust gas discharged from each cylinder is concentrated at one place.

A first exhaust pipe 6 and a second exhaust pipe 7 made of a metal material are disposed downstream of the exhaust manifold 3. The upstream end of the first exhaust pipe 6 is connected to the manifold body 5. Between the first exhaust pipe 6 and the second exhaust pipe 7, a cylindrical casing 8 also made of a metal material is provided. The upstream end of the casing 8 is connected to the downstream end of the first exhaust pipe 6, and the downstream end of the casing 8 is connected to the upstream end of the second exhaust pipe 7. It can also be grasped that the casing 8 is disposed on the way of the exhaust pipes 6,7. As a result, the first exhaust pipe 6, the casing 8
The internal region of the second exhaust pipe 7 communicates with each other, and the exhaust gas flows therein.

As shown in FIG. 1, the casing 8 is formed so that its central portion has a larger diameter than the exhaust pipes 6 and 7. Therefore, the internal area of the casing 8 is wider than the internal areas of the exhaust pipes 6 and 7. A filter 9 is accommodated in the casing 8. Note that a heat insulating material layer 10 is provided between the outer peripheral surface of the filter 9 and the inner peripheral surface of the casing 8. The heat insulating material layer 10 is a mat-like material including ceramic fibers, and has a thickness of several mm to several tens mm.

As shown in FIGS. 2 and 3, the filter 9 used in the present embodiment is a relatively large honeycomb filter. Since the filter 9 removes diesel particulates as described above, it is also called a diesel particulate filter (DPF). The filter 9 used in the present embodiment is formed by combining and integrating a plurality of honeycomb sintered bodies F1 and F2. The honeycomb sintered bodies F1 and F2 located at the center of the filter are in the shape of a quadrangular prism, and their outer dimensions are 33 mm.
X 33 mm x 167 mm. Around the square columnar honeycomb sintered bodies F1 and F2, a plurality of irregular shaped honeycomb sintered bodies F1 and F2 that are not square columnar are arranged. As a result, a cylindrical filter 9 (having a diameter of about 135 mm) is configured as a whole.

These honeycomb sintered bodies F1 and F2 are made of a porous silicon carbide sintered body which is a kind of ceramic sintered body. As a sintered body other than silicon carbide, for example, silicon nitride,
A sintered body such as sialon, alumina, or cordierite can also be selected. A plurality of through-holes 12 having a substantially square cross section are regularly formed in the honeycomb sintered bodies F1 and F2 along the axial direction. Each through hole 12 is separated from each other by a cell wall 13. Each through hole 1
The opening 2 has a sealing body 1 on one end surface 9a, 9b side.
4 (here, a porous silicon carbide sintered body), and the end faces 9a and 9b as a whole have a checkered pattern. As a result, a large number of cells having a square cross section are formed in the honeycomb sintered bodies F1 and F2. The cell density is set to around 200 cells / inch. Of the large number of cells, about half are open at the upstream end face 9a, and the remaining cells are open at the downstream end face 9b.

As shown in FIG. 2 and FIG. 3, the outer peripheral surfaces of the plurality of honeycomb sintered bodies F 1 and F 2 are joined via an adhesive 15. As the adhesive 15, a ceramic heat-resistant adhesive 15 in which ceramic fibers are dispersed is used. Silicon carbide powder is preferably dispersed in adhesive 15 in addition to the ceramic fibers.

The cross-sectional area when the honeycomb sintered bodies F1 and F2 are cut perpendicular to the axial direction is 1/400 to 1/1 of the cross-sectional area when the entire filter is cut perpendicular to the axial direction.
5, preferably 1/200 to 1/50.
It is preferred that

If the cross-sectional area ratio is too small, the area of the adhesive 15 in the cross-sectional area of the entire filter increases,
The effect of the thickness variation of the adhesive 15 becomes large. That is, the initial pressure loss tends to fluctuate due to an increase in the fluctuation of the thickness of the adhesive 15. Therefore, adhesive 1
The assembling work must be carefully performed so that the thickness variation of 5 does not occur, and the production may be troublesome. Conversely, if the cross-sectional area ratio becomes too large, the number of honeycomb sintered bodies F1, F2 constituting the filter 9 becomes too small, and the temperature may become non-uniform at the time of filter regeneration. Therefore, cracks are easily generated, and the filter 9 is easily damaged.

The length of one side when the honeycomb sintered bodies F1 and F2 are cut perpendicular to the axial direction is 1/25 to 1/25 of the diameter when the whole filter is cut perpendicular to the axial direction.
It is preferably 1/4, especially 1/20 to 1/5
It is preferred that This is for the same reason as in the case of the above-mentioned cross-sectional area ratio.

Exhaust gas is supplied to the filter 9 housed in the casing 2 from the upstream end surface 9a. No.
Exhaust gas supplied through one exhaust pipe 6 first flows into a cell opened at the upstream end face 9a. Next, the exhaust gas passes through the cell wall 13 and reaches the inside of the cell adjacent thereto, that is, the cell opened at the downstream end surface 9b. Then, the exhaust gas flows out of the downstream end face 9b of the filter 9 through the opening of the cell. However, the soot contained in the exhaust gas cannot pass through the cell wall 13 and is trapped there. As a result, the purified exhaust gas is supplied to the downstream end face 9 b of the filter 9.
Is discharged from The purified exhaust gas further passes through the second exhaust pipe 7 and is finally released into the atmosphere.

As shown in FIGS. 2 and 3, this filter 9 includes a honeycomb sintered body F1 belonging to group A (groups A1 to A4) and a honeycomb sintered body belonging to group B (groups B1 to B4).
F2, that is, two types of honeycomb sintered bodies F1 and F2
It is constituted by.

As shown in the graph of FIG. 5, here, the standard range of the cell wall thickness is set to 0.40 ± 0.4 mm. The thickness (cell wall thickness T1) of the cell wall 13 of the honeycomb sintered body F1 belonging to the A1 to A4 group is relatively smaller than the standard range.

For those belonging to the A1 group, T1 = 0.32 mm-
The value T1 is set to about 0.33 mm, and the value T1 deviates from the lower limit (0.36 mm) of the standard range by about 0.3 mm to 0.4 mm. Those belonging to the A2 group are T1 = 0.33mm
It is set to about 0.34 mm, and the value T1 deviates from the lower limit of the standard range by about 0.2 mm to 0.3 mm. For those belonging to the A3 group, T1 is set to about 0.34 mm to 0.35 mm, and the value T1 is 0.1 mm to 0.1 mm from the lower limit of the standard range.
It is off by about 0.2mm. T1 =
The value T1 is set to about 0.35 mm to 0.36 mm, and the value T1 deviates from the lower limit of the standard range by about 0.0 mm to 0.1 mm.

On the other hand, the thickness (cell wall thickness T2) of the cell walls 13 of the honeycomb sintered body F2 belonging to the groups B1 to B4 is relatively larger than the standard range. Those belonging to the B1 group are set to T2 = 0.47 mm to about 0.48 mm, and the value T2 deviates from the upper limit of the specification range (0.44 mm) by about 0.3 mm to 0.4 mm. Those belonging to the B2 group are set so that T2 = 0.46 mm to 0.47 mm,
The value T2 is 0.2 mm to 0.3 mm from the upper limit of the standard range.
It is out of the degree. T2 = 0.45m for those belonging to B3 group
The value T2 is set to about 0.1 mm to 0.2 mm from the upper limit of the standard range. For those belonging to the B4 group, T2 is set to about 0.44 mm to 0.45 mm, and the value T2 is 0.0 mm to 0.4 mm from the upper limit of the specification range.
It is off about 0.1mm.

The filter 9 of the present embodiment includes eight honeycomb sintered bodies F1 and eight honeycomb sintered bodies F2. In other words, the filter 9 is configured using the same number of two types of honeycomb sintered bodies F1 and F2 having different cell wall thicknesses T1 and T2.

More specifically, the degree of deviation of the cell wall thicknesses T1 and T2 from the specified range, such as A1 group-B1 group, A2 group-B2 group, A3 group-B3 group, A4 group-B4 group. Are used (see FIG. 5). As a result, the average cell wall thickness Tm of the entire filter 9
Are all about 0.40 mm, and are apparently completely within the above specified range.

FIG. 1 (b) shows the honeycomb sintered bodies F1, F
2 is shown. In the figure, the honeycomb sintered bodies F1 belonging to the group A are given odd numbers, and the honeycomb sintered bodies F2 belonging to the group B are given even numbers. That is, the honeycomb sintered body F1 and the honeycomb sintered body F2 are
It is arranged every other so that it does not adjoin.

Next, a procedure for manufacturing the filter 9 will be described. [Raw Material Adjustment Step] In the present embodiment, the ceramic raw material slurry used in the extrusion molding step, the sealing paste used in the end face sealing step, and the adhesive paste used in the adhesive application step were prepared in advance.

As the ceramic raw material slurry, a mixture obtained by mixing and kneading a predetermined amount of an organic binder and water with silicon carbide powder was used. As the sealing paste, a mixture obtained by mixing and kneading an organic binder, a lubricant, a plasticizer, and water with silicon carbide powder was used. As the adhesive paste, a mixture obtained by mixing and kneading silica sol, bulk ceramic fibers, a resin binder and water with silicon carbide powder was used. [Extrusion Molding Step] The ceramic raw material slurry was filled in the hopper of the extrusion molding machine 21. In this state, the extruder 21
Is driven to apply pressure to the slurry, and the mold 22
The slurry was continuously extruded to the outside of the extruder 21 through the through holes (see FIG. 4). As a result, honeycomb formed bodies 23 having substantially the same cross-sectional shape were continuously formed. [Cutting Step] By cutting the extruded honeycomb molded body into equal lengths using a cutter (not shown),
A large number of cut pieces 24 of a honeycomb formed body having a rectangular column shape were obtained. Then, these cut pieces 24 are combined with the eight groups (A1 to A4,
B1 to B4), and various steps up to the assembling step were performed for each of these sections. [End face sealing step] The obtained honeycomb molded body cut pieces 24 were set in a dedicated sealing material filling device, and in this state, a predetermined amount of the sealing paste was filled into one opening of each cell. As a result, both end faces of the cut piece 24 were sealed. [Firing step] After drying in advance, main firing was performed at a predetermined temperature for a predetermined time to completely sinter the cut pieces 24 and the sealed body 14 of the formed honeycomb article. As a result, two types of honeycomb sintered bodies F1 and F2 were obtained. [Adhesive Coating Step] After forming a ceramic base layer on the outer peripheral surfaces of the honeycomb sintered bodies F1 and F2, a ceramic heat-resistant adhesive 15 was further applied thereon. In this case, the thickness of the adhesive 15 was set to about 1.5 mm. [Assembling Step] Then, by using eight honeycomb sintered bodies F1 belonging to the A1 group and eight honeycomb sintered bodies F2 belonging to the B1 group, their outer peripheral surfaces are bonded and integrated with each other. A large honeycomb filter 9A was manufactured. Similarly, A2 group-B2 group, A3 group-B
A large honeycomb filter 9A was manufactured for each of the three groups, the A4 group and the B4 group (FIG. 4).
reference). [Outer shape cutting step] The honeycomb filter 9A having a square cross section obtained through the assembling step was set in a grinder, and unnecessary portions on the outer peripheral surface thereof were removed by grinding. As a result, as shown in FIG. 4, a honeycomb filter 9 having a circular cross section as a finished product was obtained.

Therefore, according to the present embodiment, the following effects can be obtained. (1) In the graph of FIG. 5A, the horizontal axis indicates the extrusion length (m) of the honeycomb formed body 23, and the vertical axis indicates the cells of the honeycomb sintered body derived from the cut pieces 24 at each stage of the extrusion forming process. Indicates the wall thickness (mm). In the graph, L is mold 2
Honeycomb molded body 2 when extruded until its life reaches 2
3 shows the sum of the lengths. The solid line rising upward shows the relationship between the extrusion length and the cell wall thickness. In the graph of FIG. 5B, the horizontal axis indicates the extrusion length (m) of the honeycomb formed body 23, and the vertical axis indicates the cut pieces 24 at each stage of the extrusion forming process.
2 shows the pressure loss (kPa) of the honeycomb sintered body derived from the above. The solid line rising upward shows the relationship between the extrusion length and the pressure loss.

The standard range of the pressure loss required for the filter 9 is 9.5 kPa to 10.5 kPa. Therefore, the cut pieces 24 in the early and late stages of the extrusion molding process are used.
Are out of the standard range. Therefore, a product corresponding to about half of the moldable length before the end of the life of the mold 22 is a nonstandard product. Therefore, conventionally,
These were eventually destined to be discarded as unfit for use.

However, according to the manufacturing method described in detail above,
Even the honeycomb molded body cut pieces 24 which were originally unsuitable for use and discarded can be used. In particular, according to the manufacturing method of this embodiment, it is possible to uniformly use the honeycomb sintered bodies derived from the cut pieces 24 obtained at all of the initial, middle, and late stages of the extrusion molding process. Therefore, the loss of the ceramic raw material is extremely reduced, and the material cost can be further reduced. In addition, as a result that the mold 22 can be used until its original life, the frequency of replacement of the mold 22 is reduced, and a rise in equipment costs can be prevented.

From the above, according to this manufacturing method,
The filter 9 having good initial pressure loss characteristics can be obtained at extremely low cost. (2) In this manufacturing method, the diesel particulate filter 9 is manufactured using porous silicon carbide as a ceramic material. Therefore, it is possible to reliably obtain a high-performance filter 9 having high heat resistance, high mechanical strength, high collection efficiency, high chemical stability, and low pressure loss.

(3) In this manufacturing method, a ceramic heat-resistant adhesive 15 in which ceramic fibers are dispersed is used as a means for joining the honeycomb sintered bodies F1 and F2. Therefore, even when the filter 9 is subjected to thermal shock or vibration during use, deterioration of the bonding state is unlikely to occur. Therefore, it is possible to prevent the honeycomb sintered bodies F1 and F2 from rattling or falling off, and to obtain the filter 9 having excellent strength.

(4) In this manufacturing method, the sectional area ratio of the honeycomb sintered bodies F1 and F2 to the filter 9 is set within the above-described preferred range. Accordingly, the temperature non-uniformity during regeneration of the filter 9 can be avoided without being affected by the thickness variation of the adhesive 15. Therefore, it is possible to obtain the filter 9 having excellent strength without difficulty in manufacturing.

(5) The filter 9 manufactured by this manufacturing method includes eight honeycomb sintered bodies F1 and eight honeycomb sintered bodies F2. Therefore, the filter 9 is manufactured by combining only the filters whose cell wall thicknesses T1 and T2 are out of the standard range. Nevertheless, the average cell wall thickness Tm of the entire filter 9 is
Apparently, it is about 0.44 mm. That is, the average cell wall thickness Tm is completely within the standard range. Also,
In this filter 9, the honeycomb sintered bodies F1 and the honeycomb sintered bodies F2 are arranged alternately so as not to be adjacent to each other. Therefore, there is a structural advantage that the temperature of the filter 9 is not made non-uniform at the time of use and damage due to cracks is unlikely.

The embodiment of the present invention may be modified as follows. -When manufacturing one filter 9, it is not always necessary to combine the same number of honeycomb sintered bodies F1 and F2. That is, any one of them may be used more than the other.

In manufacturing one filter 9, those having unequal cell wall thicknesses T1 and T2 out of the specified range may be used in combination. One large filter 9 may be manufactured by appropriately combining not only those outside the standard range but also those within the standard range. In this case, for example, C1 group-C8 group,
What is necessary is just to make a combination of C2-group C7, C3-group C6, C4-group C5 (see FIG. 6).

One large filter 9 may be manufactured by appropriately combining a filter outside the standard range and a filter within the standard range (see FIG. 7). Incidentally, the graph of FIG.
The combination of group-A8 group is shown.

As shown in the graph of FIG. 8, the filter 9 may be manufactured in a combination of, for example, A1 group-A4 group-B3 group. That is, the honeycomb sintered body F
1, F2 may be collected not only from two groups but also from three or more groups, and a single large filter 9 may be manufactured by combining them.

As the adhesive 15 for joining the honeycomb sintered bodies F1 and F2, a ceramic adhesive containing no ceramic fiber, a non-ceramic adhesive, or the like may be selected. In addition, the honeycomb sintered body F is formed by other methods without using the adhesive 15 itself.
It is also possible to integrate F1 and F2.

The filter 9 of the present invention may be embodied as a filter other than the diesel particulate filter 9 shown in the embodiment. Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the above-described embodiments will be enumerated below together with their effects as necessary.

(1) In any one of claims 2 to 5, the length of one side when the honeycomb sintered body is cut perpendicular to the axial direction is determined by cutting the entire filter perpendicular to the axial direction. 1/25 to 1/4 of the diameter at the time. Therefore, according to the invention described in the technical idea 1,
By setting the dimensional ratio within the above preferred range, it is possible to avoid temperature non-uniformity during filter regeneration without being affected by variations in the thickness of the adhesive.

(2) The filter according to any one of claims 1 to 6, wherein after the assembling step is performed using the plurality of honeycomb sintered bodies, an outer shape cutting step is performed to form the filter into a predetermined sectional shape. Adjust to

(3) A method according to any one of claims 1 to 6, wherein the honeycomb sintered body derived from the honeycomb molded body cut piece obtained in the early stage of the extrusion forming step and the honeycomb molded body cut piece obtained in the latter stage are formed. Originating honeycomb sintered bodies are arranged every other so as not to be adjacent to each other. Therefore, according to the invention described in the technical idea 3, the temperature of the filter is not made non-uniform at the time of use, and the filter is less likely to be damaged.

(4) After the extrusion forming step of forming the honeycomb formed body by continuously extruding the ceramic raw material through the mold of the extruder, the honeycomb formed body is cut into a predetermined length. Among the obtained cut pieces, a method using a cell wall thickness that is out of the standard range, wherein a plurality of honeycomb formed body cut pieces obtained in the early stage of the extrusion forming step, approximately the same number of pieces obtained in the later stage A method for using a cut piece of honeycomb formed body, which is used together with a cut piece of honeycomb formed body.

(5) A filter using a plurality of honeycomb sintered bodies and joining their outer peripheral surfaces to each other via an adhesive, wherein the average cell wall thickness is relatively smaller than a specified range. And a honeycomb sintered body having substantially the same number as that of the honeycomb sintered body and having an average cell wall thickness relatively larger than the standard range, and the average cell wall thickness of the entire filter falls within the standard range. Filter.

(6) A DPF in which ten or more silicon carbide honeycomb sinters are joined to each other using a ceramic heat resistant adhesive to form an outer peripheral surface of the DPF having a cell wall thickness of 0.36 mm or more. And a plurality of honeycomb sintered bodies having the same number of honeycomb sintered bodies and a cell wall thickness larger than 0.44 mm, and the average cell wall thickness of the entire filter is about 0.40 mm. DPF.

[0067]

As described in detail above, according to the first to sixth aspects of the present invention, it is possible to provide a filter manufacturing method capable of obtaining a filter having good initial pressure loss characteristics at low cost.

According to the third aspect of the invention, the loss of the ceramic raw material is extremely reduced, and the material cost can be further reduced, so that the cost can be further reduced.

According to the fourth aspect of the present invention, a high-performance diesel particulate filter having good characteristics can be obtained. According to the invention described in claim 5,
A filter having excellent strength can be obtained.

According to the sixth aspect of the present invention, a filter having excellent strength can be obtained without difficulty in manufacturing. According to the invention described in claim 7, it is possible to provide a filter suitable for cost reduction.

[Brief description of the drawings]

FIG. 1A is a schematic view showing an exhaust gas purifying apparatus using a diesel particulate filter according to an embodiment of the present invention, and FIG. 1B is a schematic front view of the filter.

FIG. 2 is a front view of the filter according to the embodiment.

FIG. 3 is a partially enlarged cross-sectional view of the filter according to the embodiment.

FIG. 4 is a schematic view for explaining a manufacturing process of the filter of the embodiment.

5A is a graph showing the relationship between the extrusion length and the cell wall thickness in the embodiment, and FIG. 5B is a graph showing the relationship between the extrusion length and the pressure loss in the embodiment.

FIG. 6A is a graph showing the relationship between the extrusion length and the cell wall thickness in another example, and FIG. 6B is a graph showing the relationship between the extrusion length and the pressure loss in another example.

7A is a graph showing the relationship between the extrusion length and the cell wall thickness in another example, and FIG. 7B is a graph showing the relationship between the extrusion length and the pressure loss.

8A is a graph showing the relationship between the extrusion length and the cell wall thickness in another example, and FIG. 8B is a graph showing the relationship between the extrusion length and the pressure loss in another example.

9A is a graph showing the relationship between the extrusion length and the cell wall thickness in the conventional example, and FIG. 9B is a graph showing the relationship between the extrusion length and the pressure loss in the same manner.

[Explanation of symbols]

13: Cell wall, 15: Ceramic heat-resistant adhesive as adhesive, 21: Extruder, 22: Die, 23: Honeycomb molded body, 24: Cut piece of honeycomb molded body, F1: Obtained at the beginning of extrusion molding process F2: Honeycomb sintered body derived from the honeycomb formed body obtained at a later stage of the extrusion forming step; T1, T2: Cell wall thickness.

Claims (7)

[Claims] An extruding step of forming a honeycomb formed body by continuously extruding a ceramic raw material through a mold of an extruder; a cutting step of cutting the honeycomb formed body into a predetermined length; A method for producing a filter, comprising: a firing step of heating a cut piece of a formed body to form a honeycomb sintered body; and an assembling step of integrating a plurality of honeycomb sintered bodies, wherein different times in a series of extrusion forming steps By appropriately combining the honeycomb sintered bodies derived from the cut pieces of the honeycomb molded body obtained in the above, and performing the assembling step, the average cell wall thickness of the entire filter can be obtained at a specific time in the extrusion molding step. A method for producing a filter, characterized in that the thickness is adjusted to approximately the same as the cell wall thickness of a honeycomb sintered body derived from a cut piece. 2. An extrusion forming step of forming a honeycomb formed body by continuously extruding a ceramic raw material through a mold of an extrusion forming machine; a cutting step of cutting the honeycomb formed body into a predetermined length; A method of manufacturing a filter including a firing step of heating a cut piece of a formed body to form a honeycomb sintered body, and an assembling step of joining a plurality of honeycomb sintered bodies to each other using a plurality of honeycomb sintered bodies via an adhesive. Then, the assembling step is performed by appropriately combining the honeycomb sintered body derived from the honeycomb molded body cut piece obtained in the early stage of the extrusion molding step and the honeycomb sintered body derived from the honeycomb molded body cut piece obtained in the late stage. By doing so, the average cell wall thickness of the whole filter is adjusted to be approximately the same as the cell wall thickness of the honeycomb sintered body derived from the honeycomb molded body cut piece obtained in the middle stage of the extrusion forming process. A method for producing a filter. 3. In the assembling step, a honeycomb sintered body derived from a honeycomb molded body cut piece obtained at an early stage of an extrusion molding step and a honeycomb sintered body derived from a honeycomb molded body cut piece obtained at a later stage of the extrusion molding step are formed. 3. The method according to claim 2, wherein, when assembling, approximately the same number of cell wall thicknesses that deviate from a standard range are used in substantially the same number. 4. The method according to claim 3, wherein the filter is a diesel particulate filter made of porous silicon carbide. 5. The method according to claim 2, wherein the adhesive is a ceramic heat-resistant adhesive in which ceramic fibers are dispersed. 6. A cross-sectional area of the honeycomb sintered body cut in a direction perpendicular to the axial direction thereof is 1/400 to 1/1 of a cross-sectional area of the entire filter cut in a direction perpendicular to the axial direction.
5. The method according to claim 2, wherein the number is 5.
Item 14. The method for producing a filter according to item 5. 7. A filter in which a plurality of honeycomb sintered bodies are integrated, wherein the honeycomb sintered body has a cell wall thickness smaller than a specified range, and a cell wall thickness relatively smaller than a specified range. A filter including a large honeycomb sintered body, wherein an average cell wall thickness of the entire filter falls within a standard range.