JPH09299730A - Exhaust gas filter - Google Patents

Abstract

It is an object of the present invention to provide an exhaust gas filter having good dimensional accuracy and excellent vibration resistance and thermal shock resistance. SOLUTION: (a) First particles made of aluminum titanate, and (b) Second particles made of aluminum titanate having a particle size smaller than at least the first particles, or titania having a particle size smaller than at least the first particles. An exhaust gas filter comprising a honeycomb structure obtained by sintering a mixture containing a second particle made of alumina and (c) a SiO ₂ component, wherein the weight of the first particle in the mixture is smaller than the weight of the second particle. Often, the third particles are 2 based on the total weight of the mixture.
By containing ~ 9% by weight, dimensional accuracy is good,
It is possible to provide an exhaust gas filter having excellent vibration resistance and thermal shock resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas filter for collecting particulate matter in exhaust gas discharged from an internal combustion engine such as a diesel engine.

[0002]

2. Description of the Related Art In recent years, as the global environmental problems have become more serious, there is a need for a technology for removing particulate matter emitted from diesel engines and the like with exhaust gas filters and the like, and exhaust gas filters are being actively developed. Has been done in. The structure of a conventional exhaust gas filter is shown below in FIGS.
This will be described with reference to FIG.

FIG. 4 is a perspective view of a conventional exhaust gas filter, and FIG. 5 is a partial sectional view of the conventional exhaust gas filter.
4 and 5, 9 is an outer peripheral wall, 10 is a lattice, and 11
Is a plug, 12 is a lattice wall, and 13 is a cell. As shown in FIGS. 4 and 5, the exhaust gas filter has a grid 10
It is composed of a honeycomb structure of ceramics or the like divided into. Since the lattice wall 12 has a large number of holes, the lattice wall 1
A plug 11 is formed at one end of a cell 13 partitioned by 2, and the plug 11 is formed on the opposite end surface of the adjacent cells 13. The exhaust gas flowing into the exhaust gas filter having such a structure moves to the adjacent cell as shown by the arrow in FIG. 5 through the holes of the lattice wall 12, but is contained in the exhaust gas at that time. The particulate matter is filtered and collected by the exhaust gas filter. When the trapped amount of the particulate matter reaches a predetermined value, the exhaust gas filter that burns the particulate matter and removes it from the exhaust gas filter is regenerated. That is, the exhaust gas filter is used by repeatedly collecting the particulate matter and regenerating the exhaust gas filter. For the regeneration of the exhaust gas filter, an electric heater system is mainly used in which the particulate matter is heated and ignited by an electric heater arranged on the inflow side or the outflow side of the exhaust gas to burn. The combustion temperature at this time is controlled by the flow rate of the air supplied into the exhaust gas filter and the like, but in reality, the exhaust gas filter has a portion where particulate matter is burning and a portion where it is not burning. Therefore, an exhaust gas filter having a small coefficient of thermal expansion and excellent vibration resistance and thermal shock resistance is required so as to have sufficient durability against the stress generated by such a thermal gradient.

Exhaust gas filters using cordierite have hitherto been used in response to such demands. However, the exhaust gas filters cause abnormal combustion in which combustion is performed at a temperature much higher than a normal combustion temperature. However, there is a problem that cordierite is melted by this. Due to this abnormal combustion, it is difficult to accurately detect the amount of particulate matter trapped in the exhaust gas filter, and at present, the actual trapped amount is approximately ± 40% of the target value that is a guideline for regeneration. Is also different. That is, when a larger amount of particulate matter than the target value is collected, the combustion of the particulate matter is rapidly accelerated, resulting in abnormal combustion. Further, since the exhaust gas filter made of cordierite can maintain its shape up to about 1400 ° C., it is estimated that the exhaust gas filter reaches a temperature higher than this during abnormal combustion. If the exhaust gas filter melts or changes its shape due to such abnormal combustion, not only the particulate matter trapping ability decreases, but also the amount of trapped particles in each cell of the exhaust gas filter varies, which induces new melting loss. However, there is a possibility that the function of the exhaust gas filter will eventually deteriorate and cause an abnormality in the engine. Therefore, an exhaust gas filter using aluminum titanate has been developed as a material to replace cordierite. The melting temperature of aluminum titanate is 1700 ° C. or higher, which has better heat resistance than cordierite and excellent durability against abnormal combustion of the exhaust gas filter. On the other hand, the mechanical strength is low due to the presence of microcracks due to the anisotropy of the crystal axis,
There is also a problem that the thermal expansion becomes large by decomposing into alumina and titania at around 00 ° C. To solve this problem, aluminum titanate contains 1 to 10% by weight of SiO 2 as disclosed in JP-A-63-11585.
₂ and 1 to 10% by weight of Al ₂ O ₃ and 0.1 to 5% by weight
Fe ₂ O ₃ is added to the aluminum titanate as disclosed in JP-A-1-249657.
10 wt% MgO and 0.5-10 wt% SiO ₂
A technique has been proposed in which a sintered body is obtained by adding. When these additive components are present as a solid solution with aluminum titanate, they have the effects of improving the strength between the crystal grains of aluminum titanate and suppressing the decomposition of aluminum titanate. In particular, it works effectively when the crystal grain size of aluminum titanate is relatively small or when the sintered density of the sintered body is high.

[0005]

However, in the conventional exhaust gas filter using aluminum titanate, it is necessary to fire at a high temperature of 1450 ° C. or higher in order to reduce the coefficient of thermal expansion of the sintered body. If the crystal grain size of aluminum is small, there is a problem that the shrinkage factor during firing is large and the dimensional accuracy is deteriorated. On the other hand, when the crystal grain size of aluminum titanate is large, the dimensional accuracy of the sintered body is improved and the specific surface area of the crystal grains is small, so that the decomposition of aluminum titanate tends to be suppressed, but the mechanical strength is low. There is a problem in that the vibration resistance and the thermal shock resistance are impaired due to a remarkable decrease.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide an exhaust gas filter having good dimensional accuracy and excellent vibration resistance and thermal shock resistance.

[0007]

The present invention comprises (a) first particles of aluminum titanate and (b) at least second particles of aluminum titanate having an average particle size smaller than that of the first particles. Second particles made of alumina and titania having a smaller average particle diameter than the first particles,
(C) An exhaust gas filter comprising a honeycomb structure obtained by sintering a mixture containing a SiO ₂ component, wherein the weight of the first particles in the mixture is greater than the weight of the second particles, and S
₂ to 9% by weight of iO ₂ component based on the total weight of the mixture
It consists of the included configuration. With this configuration, it is possible to provide an exhaust gas filter having good dimensional accuracy and excellent vibration resistance and thermal shock resistance.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention comprises (a) first particles comprising aluminum titanate;
(B) at least second particles composed of aluminum titanate having an average particle size smaller than that of the first particles, and (c) S
An exhaust gas filter comprising a honeycomb structure obtained by sintering a mixture containing an iO ₂ component, wherein the weight of the first particles in the mixture is greater than the weight of the second particles, and the SiO ₂ component accounts for the total weight of the mixture. On the other hand, the content is determined to be 2 to 9% by weight, and has an effect of providing an exhaust gas filter having good dimensional accuracy and excellent vibration resistance and thermal shock resistance. When the weight ratio of the SiO ₂ component is less than 2% by weight, the decomposition reaction of aluminum titanate tends to occur, and when it exceeds 9% by weight, the shrinkage ratio during firing tends to increase. , Neither is preferable.

The invention according to claim 2 of the present invention is (a)
Sintering a mixture containing first particles made of aluminum titanate, (b) second particles made of titania and alumina having an average particle size smaller than at least the first particles, and (c) a SiO ₂ component. An exhaust gas filter comprising the honeycomb structure, wherein the weight of the first particles in the mixture is larger than that of the second particles, and the SiO ₂ component is contained in an amount of 2 to 9% by weight based on the total weight of the mixture. This has the effect of providing an exhaust gas filter having good dimensional accuracy and excellent vibration resistance and thermal shock resistance. When the weight ratio of the SiO ₂ component is less than 2% by weight, the decomposition reaction of aluminum titanate tends to occur, and when it exceeds 9% by weight, the shrinkage ratio during firing tends to increase. , Neither is preferable.

The invention according to claim 3 of the present invention is the invention according to any one of claims 1 and 2, wherein the average particle diameter of the first particles is 11 to 26 μm. Therefore, the dimensional accuracy of the exhaust gas filter is improved and the decomposition reaction of aluminum titanate is suppressed. If the average particle diameter of the first particles is smaller than 11 μm, the decomposition reaction of aluminum titanate tends to occur easily, and if it is larger than 26 μm, the mechanical strength of the exhaust gas filter tends to decrease, so both are preferable. Absent.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the average particle size of the second particles is 0.5 to 2 μm. This has the effect of improving the dimensional accuracy of the exhaust gas filter by suppressing shrinkage during sintering. If the average particle size of the second particles is smaller than 0.5 μm, the shrinkage factor during firing tends to increase, and if it is larger than 2 μm, the mechanical strength of the exhaust gas filter tends to decrease, so both are preferred. Absent.

The invention described in claim 5 of the present invention is the invention described in any one of claims 1 to 4, in which the area Sa occupied by the first particles on the wall surface of the lattice wall of the honeycomb structure and the area The ratio Sb / Sa of the area Sb occupied by the two particles is
It is set to 0.02 to 0.10, and by lowering the proportion of aluminum titanate having a small particle size, it is possible to effectively suppress the decomposition of aluminum titanate. Sb / Sa is
If it is less than 0.02, the mechanical strength of the exhaust gas filter tends to decrease, and if it is more than 0.10, the decomposition reaction of aluminum titanate is likely to occur, and the shrinkage factor during firing tends to increase. Is also not preferable.

The invention according to claim 6 of the present invention is the invention according to any one of claims 1 to 5, wherein the ratio Ta of the thickness Ta of the outer peripheral wall of the honeycomb structure to the thickness Tb of the lattice wall is Ta. / Tb is set to be 1.0 to 3.0, which has the effect of improving the mechanical strength of the outer peripheral portion of the honeycomb structure. If Ta / Tb is less than 1.0, the mechanical strength tends to decrease, and if it is greater than 3.0, the moldability of the outer peripheral portion when molding into a honeycomb structure tends to deteriorate. Neither is preferable.

According to a seventh aspect of the present invention, in the invention according to any one of the second to sixth aspects, the aluminum titanate synthesized from titania and alumina is used in the lattice wall of the honeycomb structure. Average particle size of 1-3
The thickness of the honeycomb structure is determined to be μm, and the decomposition reaction of aluminum titanate, which is the first particle, is suppressed, and the strength of the honeycomb structure is improved. If the average particle size of the synthesized aluminum titanate is smaller than 1 μm, the shrinkage ratio during firing tends to increase,
If it is larger than 3 μm, the mechanical strength of the exhaust gas filter tends to be lowered, so that both are not preferable.

Specific examples of the embodiments of the present invention will be described below. An exhaust gas filter according to an embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a perspective view of an exhaust gas filter according to an embodiment of the present invention, FIG. 2 is a partial sectional view of an exhaust gas filter according to an embodiment of the present invention, and FIG. It is an expansion schematic diagram of the lattice wall of the exhaust gas filter in an embodiment. 1-3, 1 is an outer peripheral wall,
2 is a lattice, 3 is a plug, 4 is a lattice wall, 5 is a cell, 6 is a first particle, 7 is a second particle or aluminum titanate synthesized from titania and alumina, and 8 is a hole.
As shown in FIGS. 1 to 3, the exhaust gas filter according to the present embodiment is composed of a honeycomb structure divided into lattices 2, and has a large number of pores 8 in the lattice wall 4.
A plug 3 is formed at one end of the cell 5 partitioned by the, and the plug 3 is formed on the opposite end surface of the adjacent cells. The exhaust gas flowing into the exhaust gas filter having such a structure moves to the adjacent cell as shown by the arrow in FIG. Particulate matter contained in the exhaust gas is filtered and collected by the exhaust gas filter. The exhaust gas filter in the present embodiment differs from the conventional example in that, as shown in FIG. 3, the first particles made of aluminum titanate and the second particles made of aluminum titanate having a smaller particle size than the first particles are used. This is because it contains titania having a smaller particle size than the particles or the first particles and aluminum titanate having a smaller particle size than the first particles synthesized from alumina. With this configuration, it is possible to reduce the shrinkage rate during sintering and improve the mechanical strength of the exhaust gas filter.

As described above, according to the present embodiment, it is possible to provide an exhaust gas filter having good dimensional accuracy and excellent vibration resistance and thermal shock resistance.

In this embodiment, the columnar honeycomb structure is used, but it is not particularly limited to this shape. Further, although the shape of the lattice is a quadrangle, the shape is not particularly limited to this, and may be any shape such as a triangle, a hexagon, other polygons, and a circle.

Next, the present invention will be described with reference to Examples, Experimental Examples and Comparative Examples.

[0020]

【Example】

Example A mixture of 98 parts by weight of a mixture of first particles of aluminum titanate having an average particle size of 11 μm and 2 parts by weight of SiO ₂ and 2 parts by weight of aluminum titanate having an average particle size of 0.5 μm. A ceramic mixture was obtained by mixing a mixture of 2 particles and 2 parts by weight of SiO ₂ . The average particle size in this example is an arithmetic average value of particle sizes measured by a laser particle size distribution measuring device. To 100 parts by weight of this ceramic mixture, 11 parts by weight of resin powder as a pore-forming agent for forming pores and 14 parts by weight of methyl cellulose as a binder were dry-mixed with a mixer to obtain a mixture. To this mixture, 5 parts by weight of glycerin, which is a plasticizer, and 2 parts by weight of 100 parts by weight of the ceramic mixture were added.
After adding 5 parts by weight of water, the mixture was kneaded and kneaded with a kneader and three rollers to obtain a kneaded clay mixture. This kneaded clay mixture was extruded by an extruder and had an outer diameter of 142 mm and a length of 1
A honeycomb structure having a columnar shape of 52 mm and a lattice wall thickness of about 0.4 mm and a pitch of about 3 mm was formed. After the honeycomb structure is dried and cured at 90 ° C., a slurry having the same composition as the kneaded clay-like mixture at a depth of 5 to 10 is supplied from a predetermined end of each cell formed in the honeycomb structure.
It was poured up to mm, dried and cured to form a plug. The honeycomb structure with the plugging formed was fired in an electric furnace at 1500 ° C. for 4 hours to produce an exhaust gas filter. For the exhaust gas filter of this example, the thickness Ta of the outer peripheral wall and the thickness Tb of the lattice wall were measured.
/ Tb was 1.0. Further, the lattice wall of the exhaust gas filter in this example was observed with an electron microscope. From the photograph of the wall surface taken, it is possible to distinguish between the first particle and the second particle due to the difference in particle size. The area Sa occupied by the first particle and the area occupied by the second particle can be processed by performing graphic processing on the photograph of the wall surface. As a result of calculating Sb, Sa / Sb was 0.02.

Next, the method of measuring the firing shrinkage and the mechanical strength measured for the exhaust gas filter in this example and the test method of the vibration resistance test and thermal shock resistance test performed for the exhaust gas filter in this example will be described. . The firing shrinkage is the outer diameter L1 of the exhaust gas filter before firing.
And calculated from the outer diameter L2 of the exhaust gas filter after firing by (Equation 1).

Firing shrinkage (%) = 100 (L1-L2) / L1 (Equation 1) As for mechanical strength, the compression strength in the flow passage direction of the exhaust gas flowing through the exhaust gas filter is measured using a universal testing machine. 10 times and the average value was calculated. In the vibration resistance test, after covering the outer periphery of the exhaust gas filter with an interram 3M heat insulating material having a thickness of about 5 mm and then storing it as a casing in a stainless steel container having a thickness of 1.5 mm, the temperature and humidity vibration combined acceleration tester was used to test the automobile. According to JIS-D1601, the vibration test of parts, the vibration frequency was 67 Hz and the vibration acceleration was 10 G. The vibration time was 4 hours up and down, 2 hours left and right, and 2 hours before and after. After performing the vibration resistance test, a pressure loss measuring device was used to measure the pressure difference between inflow and outflow when air was passed through the exhaust gas filter. In the evaluation of the vibration resistance test, it was judged that there was no breakage only when the pressure difference between inflow and outflow was almost zero. In the thermal shock resistance test, the exhaust gas filter is ventilated with air containing acetylene carbon, and after collecting a predetermined amount, it is heated by an electric heater installed near the outflow part of the exhaust gas filter while supplying air into the exhaust gas filter. Then, the collection / regeneration cycle of burning the collected acetylene carbon was repeated. In this collection / regeneration cycle, after the paper was exposed to the outflow part of the exhaust gas filter for several seconds at the time of collection immediately after regeneration, the light transmittance of this paper was measured with a smoke meter, and this measured value was 1%. It was judged that the exhaust gas filter had been destroyed when the above became. The set collection amount in the thermal shock resistance test is about 0.01 g / cm ³ per unit volume of the exhaust gas filter, the electric heater temperature is 600 to 700 ° C., and the supply air flow rate is 0.06 m ³ /
When no damage was observed even after being regenerated 50 times, it was judged to be excellent in thermal shock resistance, and the test was stopped. By the reference value, the measured value of the smoke meter when the exhaust gas filter was not used under the above conditions was about 40%.

The exhaust gas filter in this example had a firing shrinkage of 11% and a mechanical strength of 72 kgf / cm ² , no breakage was observed in the vibration resistance test, and it was regenerated 50 times in the thermal shock resistance test. Since destruction was repeatedly observed, it was found that the exhaust gas filter in this example had excellent vibration resistance and thermal shock resistance.

(Experimental example) By the same method as in the example,
An exhaust gas filter was produced by firing a mixture having the composition shown in (Table 1).

[0025]

[Table 1]

In Table 1, the compounding ratio of the first particles and the second particles is the mixing ratio of only the first particles and the second particles in parts by weight, and the weight ratio of SiO ₂ is 2 shows the weight ratio of SiO _{2 to} the total weight of a mixture of 1 particle, 2nd particle and SiO ₂ . When the second particles are titania and alumina, titania and alumina are mixed at a molar ratio of 1: 1 and the above mixing ratio is calculated by using the weight of the mixture having a molar ratio of 1: 1. There is. next,
The division of A group, B group, C group, and D group in (Table 1) will be described. The groups A and C have an average particle size of the second particles of aluminum titanate or titania and alumina of 0.
5 μm, the samples in which the particle size of aluminum titanate which is the first particle, the mixing ratio of the first particle and the second particle, and the weight ratio of SiO ₂ are changed are shown. Group B and group D have the average particle diameter of aluminum titanate or titania of the second particles and alumina of 2 μm, the particle diameter of aluminum titanate of the first particles, the mixing ratio of the first particles and the second particles, SiO
Samples with different weight ratios of ₂ are shown. Further, the shapes and dimensions of the honeycomb structures fired from the samples of the groups A and B are the same as those of the examples, but the honeycomb structures fired from the samples of the groups C and D have a thickness of the outer peripheral wall. The length of the group C is about 0.6 mm, and that of the group D is about 1.2 mm, and the other shapes and dimensions are the same as those of the embodiment.

(Comparative Example) For comparison, an exhaust gas filter was produced by firing a mixture having the composition shown in (Table 2) in the same manner as in the example.

[0028]

[Table 2]

In Table 2, the compounding ratio of the first particles and the second particles and the weight ratio of SiO ₂ are the same as those described in Table 1. Next, E group, F group, and G in (Table 2)
The division of groups will be described. Group E is a sample composed of a mixture of aluminum titanate and SiO ₂ having an average particle size of 1 type, and groups F and G use the first particles and the second particles of the present invention. This is a sample in which the weight ratio of ₂ is outside the scope of the present invention. Further, the honeycomb structures fired from these samples were made to have the same shape and size as those of the examples.

For each of the experimental and comparative samples shown in (Table 1) and (Table 2), the value of Sa / Sb was obtained, and the firing shrinkage and mechanical strength measured by the same method as in Examples. The measured values, the test results of the vibration resistance test conducted by the same method as in the example, and the number of times of reproduction of the thermal shock resistance test are shown in (Table 3) and (Table 4), respectively.

[0031]

[Table 3]

[0032]

[Table 4]

Further, (Table 3) and (Table 4) show that titanic acid synthesized from titania and alumina was observed from a microscope observation of the lattice wall of an exhaust gas filter obtained by firing a sample using titania and alumina as the second particles. The average particle size determined for aluminum is also shown. In addition, regarding the sample having a firing shrinkage ratio of more than 20%, the shape was significantly different from that before firing, so that the mechanical strength measurement, the vibration resistance test, and the thermal shock resistance test were not performed. Also, group C and D in (Table 1)
For the samples of the group, the mechanical strength was not measured because the thickness of the outer peripheral wall was different from the other samples, and the firing shrinkage and vibration resistance test results and the number of times of thermal shock resistance tests were regenerated. It is shown in 3).

From the comparison of the E group of (Table 3) and (Table 4),
It was found that the exhaust gas filter in the experimental example is excellent in vibration resistance and thermal shock resistance, and has a small firing shrinkage ratio, as compared with the exhaust gas filter in the comparative example using aluminum titanate having one average particle size. Also (Table 3)
From the comparison between the F group and the G group of (Table 4), the exhaust gas filter in the experimental example in which the weight ratio of SiO ₂ was 2 to 9% by weight was excellent in vibration resistance and thermal shock resistance, and at the same time, the shrinkage rate by firing was high. It turned out to be small.

The exhaust gas filters of Examples, Experimental Examples and Comparative Examples had a pore diameter of 7 to 11 μm and a porosity of 33.
Was ~ 38%.

[0036]

As described above, according to the present invention, since the dimensional accuracy of the exhaust gas filter can be improved, it is possible to provide the exhaust gas filter with good productivity and mass productivity. can get. Further, according to the present invention, since it is possible to improve the vibration resistance and thermal shock resistance of the exhaust gas filter, there is an excellent effect that it is possible to provide an exhaust gas filter excellent in durability and long-term reliability. can get.

[Brief description of drawings]

FIG. 1 is a perspective view of an exhaust gas filter according to an embodiment of the present invention.

FIG. 2 is a partial sectional view of an exhaust gas filter according to an embodiment of the present invention.

FIG. 3 is an enlarged schematic view of a lattice wall of an exhaust gas filter according to an embodiment of the present invention.

FIG. 4 is a perspective view of a conventional exhaust gas filter.

FIG. 5 is a partial sectional view of a conventional exhaust gas filter.

[Explanation of symbols]

1,9 Outer peripheral wall 2,10 Lattice 3,11 Plugging 4,12 Lattice wall 5,13 Cell 6 First particle 7 Second particle or aluminum titanate synthesized from titania and alumina 8 Voids

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukinori Ikeda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Koichi Watanabe, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (7)

[Claims] 1. (a) First particles made of aluminum titanate, and (b) Second particles made of aluminum titanate having an average particle size smaller than at least the first particles.
(C) An exhaust gas filter comprising a honeycomb structure obtained by sintering a mixture containing a SiO ₂ component, wherein the weight of the first particles in the mixture is greater than the weight of the second particles, and the SiO ₂ An exhaust gas filter, wherein the components are contained in an amount of 2 to 9% by weight based on the total weight of the mixture. 2. (a) First particles made of aluminum titanate, and (b) Second particles made of alumina and titania having an average particle size smaller than at least the first particles.
(C) An exhaust gas filter comprising a honeycomb structure obtained by sintering a mixture containing a SiO ₂ component, wherein the weight of the first particles in the mixture is greater than the weight of the second particles, and the SiO ₂ An exhaust gas filter, wherein the components are contained in an amount of 2 to 9% by weight based on the total weight of the mixture. 3. The average particle size of the first particles is 11 to 26 μm.
The exhaust gas filter according to claim 1, wherein the exhaust gas filter is m. 4. The average particle diameter of the second particles is 0.5 to 2 μm.
The exhaust gas filter according to any one of claims 1 to 3, wherein m is m. 5. The ratio Sb / Sa of the area Sa occupied by the first particles and the area Sb occupied by the second particles on the wall surface of the lattice wall of the honeycomb structure is 0.02 to 0.10. The exhaust gas filter according to any one of claims 1 to 4, which is characterized. 6. The ratio Ta / Tb of the thickness Ta of the outer peripheral wall and the thickness Tb of the lattice wall of the honeycomb structure is 1.0 to 3.0, and the ratio Ta / Tb is 1.0 to 3.0. Either one
The exhaust gas filter described in. 7. The average particle size of aluminum titanate synthesized from the titania and alumina in the lattice wall of the honeycomb structure is 1 to 3 μm. The exhaust gas filter according to item 1.