JP2001096113A - Honeycomb filter and exhaust gas cleaning apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a honeycomb filter low in pressure loss and excellent in mechanical strength. SOLUTION: In a honeycomb filter comprising a porous ceramic sintered body, the mean void size thereof is set to 5-15 μm and the mean void content thereof is set to 30-50% and more than 20% of voids are through-voids.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a honeycomb filter and an exhaust gas purifying apparatus.

[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, research results have reported that soot (diesel particulate) in exhaust gas sometimes causes allergic disorders and a decrease in sperm count. In other words, taking measures to remove diesel particulates in exhaust gas is considered to be an urgent task 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 honeycomb filter having fine holes is disposed therein. As the material for forming the honeycomb filter, heat resistance, mechanical strength,
A porous sintered body of silicon carbide is often used as a filter forming material because of its advantages such as high collection efficiency, chemical stability, and low pressure loss.

[0004] Here, "pressure loss" refers to a value obtained by subtracting a pressure value on the downstream side from a pressure value on the upstream side of the filter. Exhaust gas undergoes resistance as it passes through the filter, which is the largest contributor to pressure loss.

[0005] A honeycomb filter has a number of cells extending along its own axial direction. As exhaust gas passes through the honeycomb filter, the diesel particulates are trapped by the cell walls. Therefore, when the temperature in the honeycomb filter reaches a predetermined value (ignition temperature), the diesel particulates collected in the honeycomb filter ignite and burn. Recently, it has been found that particulates having a small particle size have a high fixation rate to the lung and a high risk to health. Therefore, there is an increasing demand for supplementing particulates with a small particle size.

[0006]

However, if the pore diameter and the porosity are small, the honeycomb filter becomes too dense, and it becomes difficult for the exhaust gas to pass through the honeycomb filter smoothly, resulting in a large pressure loss. Therefore, there is a problem in that the driving conditions of the vehicle are hindered, fuel efficiency is deteriorated, and driving feeling is deteriorated.

On the contrary, when the pore diameter and the porosity are large, the above-mentioned problem is solved. However, since the number of voids in the honeycomb filter becomes too large, fine particles cannot be collected. Therefore, there is a problem that the trapping efficiency is reduced and the mechanical strength of the honeycomb filter is reduced.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a honeycomb filter having not only a small pressure loss but also excellent mechanical strength. Another object of the present invention is to provide an exhaust gas purifying apparatus capable of increasing the collection efficiency of particulates contained in exhaust gas.

[0009]

According to the first aspect of the present invention, there is provided a honeycomb filter comprising a porous ceramic sintered body having an average pore diameter of 5 to 15 μm and an average porosity. Is 30 to 50%, and 20% or more of the pores are through pores.

According to the second aspect of the present invention, in the honeycomb filter according to the first aspect, the average pore diameter is from 8 to 12 mm.
μm and the average porosity is 35-49%,
The gist is that about 50% are through pores.

According to the third aspect of the present invention, in the honeycomb filter according to the first or second aspect, cells whose end faces are alternately sealed by sealing bodies are provided, and the number of cells is 120 per square inch. The gist is that the number of cells is equal to or more than one and the thickness of a cell wall that partitions the cell is 0.46 mm or less.

According to the present invention, an exhaust gas provided with a honeycomb filter made of a porous ceramic sintered body for removing particulates contained in the exhaust gas is provided in a casing provided in an exhaust path of the internal combustion engine. In the purifying apparatus, the honeycomb filter has an average pore diameter of 5 to 15 μm.
The gist is that the average porosity is 30 to 40%, and that 20% or more of the pores are through pores.

According to a fifth aspect of the present invention, in the exhaust gas purifying apparatus according to the fourth aspect, the honeycomb filter has an average porosity of 8 to 12 μm and an average porosity of 35 to 4 μm.
It is 9%, and the gist is that 20 to 50% or more of the pores are through pores.

According to a sixth aspect of the present invention, in the exhaust gas purifying apparatus according to the fourth or fifth aspect, the honeycomb filter has cells whose end faces are alternately sealed by sealing bodies. The gist is that the number of the cells is 120 or more per unit square inch and the thickness of the cell wall is 0.46 mm or less.

According to the seventh aspect of the present invention, the fourth to sixth aspects are provided.
In the exhaust gas purifying apparatus described in any one of the above, the summary that the total volume of the honeycomb filter is 1/4 to 2 times the total displacement of the internal combustion engine.

Hereinafter, the "action" of the present invention will be described. According to the first aspect of the present invention, when the pore diameter is less than 5 μm, the pressure loss increases. On the other hand, when the pore diameter is 1
If it exceeds 5 μm, the collection efficiency will decrease. If the porosity is less than 30%, the pressure loss increases. 5
If it exceeds 0%, cracks are likely to occur due to a decrease in mechanical strength. Further, when the through pores are less than 20% of the pores, the pressure loss increases. Therefore, the average pore diameter is 5 to 15 μm, the average porosity is 30 to 50%, and the
% Or more is a honeycomb filter having through pores, so that the pressure loss can be reduced and the strength can be improved.

According to the second aspect of the present invention, a honeycomb filter having an average pore size of 8 to 12 μm, an average porosity of 35 to 49%, and 20 to 50% or more of the pores having through pores is used. Therefore, the pressure loss can be further reduced, and the strength can be reliably improved.

According to the third aspect of the present invention, a honeycomb filter is used in which the number of cells is 120 or more per unit square inch, and the thickness of a cell wall dividing the cells is 0.46 mm or less. Therefore, the purification performance of the honeycomb filter can be improved.

According to the fourth aspect of the present invention, if the pore diameter is less than 5 μm, the pressure loss increases, resulting in deterioration of fuel efficiency and driving feeling. Pore size 15
If it exceeds μm, the collection rate will decrease, and the particulate filtering function will be impaired. On the other hand, if the porosity is less than 30%, the pressure loss increases, so that the driving conditions of the vehicle are hindered, and the fuel efficiency and the driving feeling are deteriorated. If the porosity exceeds 50%, the number of voids in the honeycomb filter becomes too large, so that fine particles cannot be collected. Therefore, the trapping efficiency is reduced and the mechanical strength of the honeycomb filter is reduced.
Further, when the through pores are less than 20% of the pores, the pressure loss increases.

Therefore, since a honeycomb filter having an average pore diameter of 5 to 15 μm, an average porosity of 30 to 50%, and 20% or more of the pores having through pores is used, the pressure loss can be reduced and Strength can be improved. The collection efficiency of the particulates contained in the exhaust gas can be increased.

According to the fifth aspect of the present invention, a honeycomb filter having an average pore diameter of 8 to 12 μm, an average porosity of 35 to 49%, and 20 to 50% or more of the pores having through pores is used. Therefore, the pressure loss due to the exhaust gas can be further reduced, and the strength of the honeycomb filter can be reliably improved.

According to the invention described in claim 6, a honeycomb filter is used in which the number of cells is 120 or more per unit square inch and the thickness of a cell wall for dividing the cells is 0.46 mm or less. Therefore, the contact area with the exhaust gas can be increased, and the purification performance of the honeycomb filter can be improved.

According to the present invention, a honeycomb filter having a total volume of 1/4 to 2 times the total displacement of the internal combustion engine is used. Therefore, the amount of accumulated particulates does not become too large, so that the honeycomb filter is not clogged. Further, since the size of the honeycomb filter is not increased, a temperature difference is hardly generated between the respective portions of the honeycomb filter during the burning of the particulates. Therefore, the thermal stress acting on the honeycomb filter can be reduced. As a result, the occurrence of cracks can be reliably prevented.

[0024]

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 the drawings.

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.
It is connected to. 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 the first exhaust pipe 6
And the downstream end of the casing 8 is connected to the second end.
It is connected to the upstream end of the 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 internal regions of the first exhaust pipe 6, the casing 8, and the second exhaust pipe 7 communicate with each other, and exhaust gas flows therein.

As shown in FIG. 1, the casing 8 is formed so that its central portion is larger in 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 honeycomb filter 9 is accommodated in the casing 8.

A heat insulating material 10 is provided between the outer peripheral surface of the honeycomb filter 9 and the inner peripheral surface of the casing 8.
The heat insulating material 10 is a mat-like material including a ceramic fiber, and has a thickness of several mm to several tens mm.
The heat insulating material 10 preferably has thermal expansion properties. The term “thermal expansion” as used herein refers to a function of releasing thermal stress due to having an elastic structure. The reason is that by preventing heat from escaping from the outermost peripheral portion of the honeycomb filter 9, energy loss during regeneration is minimized. Further, by expanding the ceramic fiber by the heat at the time of regeneration, it is possible to prevent the displacement of the honeycomb filter 9 caused by the pressure of the exhaust gas, the vibration caused by running, and the like.

Since the honeycomb filter 9 used in the present embodiment removes diesel particulates as described above, it is generally called a diesel particulate filter (DPF). As shown in FIG. 2 and the like, the honeycomb filter 9 of the present embodiment has a columnar shape.

As shown in FIGS. 2, 3, and 4, the honeycomb filter 9 of the present embodiment has a so-called honeycomb structure. The reason for adopting the honeycomb structure is that there is an advantage that the pressure loss is small even when the amount of collected fine particles increases. In the honeycomb filter 9, a plurality of ventilation holes 12 having a substantially square cross section are formed regularly along the axial direction. Each vent 12 is separated from each other by a thin cell wall 13. On the outer surface of the cell wall 13, an oxidation catalyst comprising a platinum group element (for example, Pt or the like) or another metal element and an oxide thereof is supported. The opening of each ventilation hole 12 has one of the end faces 9.
On the side of a and 9b, it is sealed by the sealing body 14. Accordingly, the end faces 9a and 9b as a whole have a checkered pattern. As a result, the honeycomb filter 9 includes:
A large number of cells having a square cross section are formed. Of the large number of cells, about half of the cells are open at the upstream end face 9a, and the remaining cells are open at the downstream end face 9b.

The cell density is 120 cells / inch ² (18
Pieces / cm ² ) or more, more specifically, 120 to 180 pieces / cm ²
Inch ² is preferable. If the density of the cells is less than 120, the contact area with the exhaust gas becomes small, so that the purification performance of the honeycomb filter 9 decreases.

The thickness of the cell wall 13 is preferably 0.46 mm or less, more specifically, in the range of 0.20 to 0.46 mm. If the thickness of the cell wall 13 exceeds 0.46 mm, the opening area of the cell becomes small, and the contact area with the exhaust gas becomes small, so that the purification performance of the honeycomb filter 9 decreases. Also, if the thickness of the cell wall 13 is made larger than 0.46 mm while securing the opening area of the cell, the whole honeycomb filter 9 will be enlarged.

The average pore diameter of the honeycomb filter 9 is 5 μm.
１５15 μm, more preferably 8 μm-12 μm. If the average pore diameter is less than 5 μm, clogging of the honeycomb filter 9 due to accumulation of particulates becomes remarkable. As a result, the pressure loss increases, which hinders the driving conditions of the vehicle, leading to deterioration of fuel efficiency and deterioration of driving feeling. On the other hand, if the average pore diameter exceeds 50 μm, fine particles cannot be collected, so that the collection efficiency is reduced and the filtering function of particulates is impaired.

The porosity of the honeycomb filter 9 is 30% to 5%.
It is preferably 0%, more preferably 35% to 49%.
If the porosity is less than 30%, the honeycomb filter 9 becomes too dense, and there is a possibility that the exhaust gas cannot be circulated inside. On the other hand, if the porosity exceeds 50%, the number of voids in the honeycomb filter 9 becomes too large, so that the strength becomes weak and the efficiency of collecting fine particles may be reduced.

At least 20% of the pores formed in the honeycomb filter 9, more specifically, 20% to 80%
%, In particular, 20% to 50% are preferably through-pores. Here, the through-hole means a gap portion formed in the cell wall 13 and communicating the adjacent vent holes 12 with each other. If the number of through-holes is less than 20% of the pores, the pressure loss increases, which hinders the driving conditions of the vehicle, leading to deterioration of fuel efficiency and deterioration of driving feeling. on the other hand,
If the number of through-holes exceeds 80% of the pores, production may be difficult in practice, and stable material supply may be difficult.

The total volume of the honeycomb filter 9 is 1/4 to 2 times the total displacement of the internal combustion engine,
/ 2 to 1.5 times. If the ratio is less than 1/4, the amount of accumulated particulates increases and the clogging of the honeycomb filter 9 becomes remarkable. On the other hand, when it exceeds twice, the size of the honeycomb filter 9 increases. This is because, when the size of the honeycomb filter 9 is increased, a temperature difference is likely to occur between the respective portions of the filter 9 during combustion, thereby increasing the thermal stress acting on the honeycomb filter 9 and increasing the probability of occurrence of cracks.

When a porous silicon carbide sintered body is selected, the honeycomb filter 9 has a thermal conductivity of 20 W / mK to
75 W / mK, preferably 30 W / mK
It is particularly preferable that it is ７０70 W / mK. If the thermal conductivity is too small, a temperature difference is likely to occur in the honeycomb filter 9, which leads to generation of a large thermal stress which causes cracks. Conversely, if the thermal conductivity is to be increased, manufacturing becomes difficult, and stable material supply becomes difficult.

The honeycomb filter 9 is made of a porous silicon carbide sintered body which is a kind of a ceramic sintered body. The reason for adopting the silicon carbide sintered body is that, compared to other ceramics,
In particular, there is an advantage of being excellent in strength, heat resistance and thermal conductivity.

Impurities contained in the porous silicon carbide sintered body are suppressed to 5% by weight or less. The amount of impurities is preferably 1% by weight or less, particularly preferably 0.1% by weight or less. If the content of the impurities exceeds 5% by weight, the impurities are biased at the grain boundaries of the silicon carbide crystal grains, and the strength at the grain boundaries (bonding strength between crystal grains) is remarkably reduced, so that the grain boundaries are easily broken. In addition, as impurities, Al, Fe,
O, free C and the like.

The material for forming the sealing body 14 is also made of the same porous silicon carbide sintered body as the honeycomb filter 9. Here, too, impurities contained in the porous silicon carbide sintered body are suppressed to 5% by weight or less. If the content of the impurities exceeds 5% by weight, the impurities are biased at the grain boundaries of the silicon carbide crystal grains, and the strength at the grain boundaries (bonding strength between crystal grains) is remarkably reduced, so that the grain boundaries are easily broken. Specifically, cracks may occur in the sealing body 14.

Next, a procedure for manufacturing the above honeycomb filter 9 will be described. First, a ceramic raw material slurry used in the extrusion molding step and a sealing paste used in the end face sealing step are prepared in advance.

As the ceramic raw material slurry, a mixture obtained by mixing a predetermined amount of an organic binder and water with silicon carbide powder and kneading the mixture is 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 is used.

Next, the ceramic raw material slurry is charged into an extruder and continuously extruded through a mold. Thereafter, the extruded honeycomb formed body is cut into equal lengths to obtain cut pieces of the honeycomb formed body having a columnar shape.
Further, a predetermined amount of the sealing paste is filled into one opening of each cell of the cut piece, and both end faces of each cut piece are sealed.

Then, the desired honeycomb filter 9 is completed by setting the temperature, time, and the like to predetermined conditions and performing the main firing to completely sinter the cut pieces of the formed honeycomb body and the sealing body 14. I do. In this embodiment, the firing temperature is set to 210
The temperature is set at 0 ° C. to 2300 ° C., and the firing time is set at 0.1 hour to 5 hours. The atmosphere in the furnace during firing is an inert atmosphere, and the pressure of the atmosphere at that time is normal pressure. The firing temperature is desirably set as high as possible within the above range.

Next, the action of the above-described honeycomb filter 9 for trapping fine particles will be briefly described. Exhaust gas is supplied to the honeycomb filter 9 housed in the casing 8 from the upstream end surface 9a side. Exhaust gas supplied via the first exhaust pipe 6 first flows into a cell opened at the upstream end surface 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 honeycomb filter 9 through the opening of the cell. However, the fine particles contained in the exhaust gas cannot pass through the cell wall 13 and are trapped there. As a result, the purified exhaust gas is supplied to the downstream end face 9 b of the honeycomb filter 9.
Is discharged from The purified exhaust gas further passes through the second exhaust pipe 7 and is finally released into the atmosphere. Further, the trapped fine particles are distributed to the honeycomb filter 9.
When the internal temperature reaches a predetermined temperature, it is ignited and burned by the action of the catalyst.

[0046]

EXAMPLES AND COMPARATIVE EXAMPLES (Example 1) Average particle size of about 10 μm
51.5% by weight of α-type silicon carbide powder and an average particle size of about 0.1%.
5 μm α-type silicon carbide powder and 22% by weight are wet-mixed,
To the resulting mixture, an organic binder (methyl cellulose) and water were added at 6.5% by weight and 20% by weight, respectively, and kneaded.

Next, a small amount of a plasticizer and a lubricant were added to the kneaded material, and the mixture was further kneaded and extruded to obtain a honeycomb-shaped formed body. Specifically, as the α-type silicon carbide powder, a powder having an average particle diameter of about 10 μm is manufactured by Yakushima Electric Works Co., Ltd. (C-1000F),
For the powder having an average particle size of 0.5 μm, a trade name: GC-15 manufactured by Yakushima Electric Works, Ltd. was used.

Next, after the formed body was dried using a microwave drier, the air holes 12 of the formed body were sealed with a sealing paste made of a porous silicon carbide sintered body. Next, the sealing paste was dried again using a dryer.
After the end face sealing step, the dried body was degreased at 400 ° C.
It was baked at 250 ° C. for about 3 hours.

As a result, the pore diameter was 10 μm and the porosity was 4
2%, the existence ratio of through-holes to the pores is 25%, the cell density is 150 cells / inch ² , and the thickness of the cell wall 13 is 0.1%
A honeycomb filter 9 of 4 mm made of a porous silicon carbide sintered body was obtained. This honeycomb filter 9 has a diameter of 100
mm, length 200 mm, total volume 2300 cm ³ . The total volume refers to a volume obtained by subtracting the volume of the ventilation holes 12 from the volume of the entire honeycomb filter 9. The thickness of the cell wall 13 is 0.46 mm or less, more specifically, 0.20 to
It is preferably in the range of 0.46 mm.

Next, a heat insulating material 10 was wound around the honeycomb filter 9 obtained as described above, and the honeycomb filter 9 was housed in the casing 8 in this state. Then, an exhaust gas having a flow rate of 7 m / sec was supplied to the exhaust gas purifying apparatus 1 using an engine having a displacement of about 3000 cc. At this time, the pressure value of the exhaust gas on the upstream side of the honeycomb filter 9 and the pressure value of the exhaust gas on the downstream side were measured. Then, the pressure loss ΔP (mmAq), which is the difference between these values, was determined. In order to investigate the amount of particulates that could not be trapped, the soot amount was measured behind the honeycomb filter 9. Further, after a certain period of time, the honeycomb filter 9 was taken out and visually inspected to examine the occurrence of cracks. Table 1 shows the results of this investigation.

[0051]

[Table 1] As shown in Table 1, in Example 1, the pressure loss ΔP was about 80 mmAq, and the value was extremely small. The amount of particulate leakage was 0.01 g / km, and the value was extremely small. The bending strength of the honeycomb filter 9 was 6.5 Mpa, and extremely high mechanical strength was provided. No crack was observed in the honeycomb filter 9. (Examples 2 and 3) In Examples 2 and 3, the honeycomb filter 9 was manufactured basically in the same manner as in Example 1. However, in Examples 2 and 3, the honeycomb filter 9 was used.
Was the same as in Example 1. Also, by changing the compounding ratio of the forming materials, the firing temperature, the firing time, etc.,
The pore diameter, the porosity, and the percentage of through-pores with respect to the pores of the honeycomb filter 9 were adjusted as follows.

That is, in Example 2, the pore diameter was 6 μm.
m, a porosity of 32%, and a honeycomb filter 9 made of a porous silicon carbide sintered body having an abundance of through-pores of 30%.
Then, when a test similar to that in Example 1 was performed, the pressure loss ΔP was about 100 mmAq, and the value was extremely small. The amount of particulate leakage is 0.0
It was 1 g / km, and the value was extremely small. The bending strength of the honeycomb filter 9 was 6.2 Mpa, and high mechanical strength was provided. Further, no crack was observed in the honeycomb filter 9.

In Example 3, a honeycomb filter 9 made of a porous silicon carbide sintered body having a pore diameter of 14 μm, a porosity of 48%, and an existence rate of through-pores of 45% was obtained. The test results of this example show that the pressure loss ΔP is about 60 mmAq,
Its value was extremely small. The leakage amount of the particulate was 0.015 g / km, and the value was extremely small. The bending strength of the honeycomb filter 9 was 6.0 Mpa, and high mechanical strength was provided. No crack was observed in the honeycomb filter 9. (Comparative Examples 1 to 3) Also in Comparative Examples 1 to 3, a honeycomb filter was manufactured basically in the same manner as in Example 1. However, in Comparative Example 1, the total volume of the honeycomb filter was less than 1/4 of the displacement (3000 cc).
cm ³ . Further, the pore diameter, the porosity, and the existence ratio of the through pores with respect to the pores of the honeycomb filter were set as follows.

In Comparative Example 1, a honeycomb filter made of a porous silicon carbide sintered body having a pore diameter of 3 μm, a porosity of 10%, and an existence rate of through-pores of 10% was obtained. As a result of the test of Comparative Example 1, the pressure loss ΔP was about 300 mmAq, and the value was extremely large. The amount of particulate leakage was 0.005 g / km, and the value was extremely small. The bending strength of the honeycomb filter is 7.
2 Mpa, and high mechanical strength was provided. No crack was observed in the honeycomb filter.

In Comparative Example 2, the total volume of the honeycomb filter was larger than that in Examples 1 to 3, ie, the displacement (300
0 cc), that is, 7000 cm ³ which is twice or more. or,
A honeycomb filter made of a porous silicon carbide sintered body having a pore diameter of 20 μm, a porosity of 70%, and an abundance of through-pores of 15% was obtained. In the test results of Comparative Example 2, the pressure loss ΔP was about 40 mmAq, and the value was extremely small. The leakage amount of the particulate was 0.04 g / km, and the value was extremely large. The bending strength of the honeycomb filter was 2.5 MPa, and sufficient mechanical strength could not be obtained. Cracks were observed in the honeycomb filter.

In Comparative Example 3, different from Comparative Examples 1 and 2, a cordierite honeycomb filter was obtained by a known manufacturing method. And the total volume of this honeycomb filter was 700 cm ³ . The honeycomb filter had a pore diameter of 30 μm, a porosity of 20%, and an existing rate of through-pores of 15%. In the test results of Comparative Example 3, the pressure loss ΔP was about 120 mmAq, and the value was large. Particulate leakage is 0.015
g / km, and the value was large. The bending strength of the honeycomb filter was 3.1 Mpa, and sufficient mechanical strength could not be obtained. Cracks were observed in the honeycomb filter.

As described above, Examples 1 to 3 and Comparative Examples 1 to
Table 1 shows the results of comparative study of No. 3. (Test Results) As is clear from Table 1 above, Example 1
In Nos. 3 to 3, it was recognized that the exhaust gas smoothly passed through the honeycomb filter 9. In addition, there was almost no leakage of particulates, and the mechanical strength of the honeycomb filter 9 could be secured. On the other hand, in Comparative Example 1, the mechanical strength of the honeycomb filter could be ensured. However, it was not recognized that the exhaust gas passed through the honeycomb filter smoothly.
Further, in Comparative Example 2, it was recognized that the exhaust gas smoothly passed through the honeycomb filter. However, the mechanical strength of the honeycomb filter could not be ensured. Furthermore, in Comparative Example 3, it was not recognized that the exhaust gas smoothly passed through the honeycomb filter, and the mechanical strength of the honeycomb filter could not be secured.

Therefore, according to the embodiment of the present embodiment, the following effects can be obtained. (1) A casing 8 is provided on the exhaust side of the diesel engine 2.
The casing 8 is provided with a honeycomb filter 9 made of a porous silicon carbide sintered body. The honeycomb filter 9 has an average pore diameter of 5 to 15
μm, the average porosity is set to 30 to 40%, and the existence ratio of through pores to the pores is set to 20% or more. for that reason,
Since the honeycomb filter 9 does not become too dense, the exhaust gas can smoothly pass through the inside and the pressure loss can be reduced. Therefore, fuel efficiency can be improved and the driving feeling can be prevented from deteriorating.
In addition, since the amount of voids in the honeycomb filter 9 does not become too large, fine particulates can be reliably collected, and the collection efficiency can be improved. Furthermore, even if the honeycomb filter 9 is porous, sufficient mechanical strength can be ensured. Therefore, it is possible to obtain the honeycomb filter 9 that is not easily broken by vibration or thermal shock.

(2) The honeycomb filter 9 has an average pore diameter of 8 to 12 μm, an average porosity of 35 to 49%, and an existing rate of through-pores to pores of 20 to 50% or more. Therefore, the pressure loss can be further reduced, and the strength can be reliably improved.

(3) On both end faces of the honeycomb filter 9, cells sealed alternately by the sealing members 14 are formed. And the number of cells is 12 per square inch
Zero or more and the thickness of the cell wall 13 is set to 0.46 mm or less. Therefore, the contact area with the exhaust gas can be increased. Therefore, the purification performance of the honeycomb filter 9 can be improved.

(4) The total volume of the honeycomb filter 9 is １ ／ of the total displacement of the diesel engine 2.
It is set to double. For this reason, since the amount of the accumulated particulates does not become too large, it is possible to prevent the honeycomb filter 9 from being clogged. Further, since the size of the honeycomb filter 9 is not increased, it is possible to prevent a temperature difference from occurring between the respective portions of the honeycomb filter 9 during combustion. Therefore, the thermal stress acting on the honeycomb filter 9 can be reduced, and the occurrence of cracks can be reliably prevented.

The embodiment of the present invention may be modified as follows. The shape of the honeycomb filter 9 is not limited to a columnar shape as in the embodiment, and may be changed to a triangular prism, a quadrangular prism, a hexagonal prism, or the like.

As shown in FIG. 5, a single ceramic filter assembly 21 may be manufactured by combining a plurality of (here, 16) honeycomb filters 23. Prismatic honeycomb filter 2 constituting the aggregate 21
3 has an average porosity of 8 to 12 μm and an average porosity of 35.
４９49%, and 20-50% of the pores are through pores. The outer peripheral surfaces of the honeycomb filters 23 are bonded to each other via a ceramic sealing material layer 22. As a result, the respective honeycomb filters 23 are integrated in a bundled state. With such a configuration, it is possible to prevent the occurrence of cracks due to the stress caused by the temperature gradient due to heating, and to increase the resistance to thermal shock. Therefore, the size of the filter can be relatively easily increased.

The number of combinations of the honeycomb filters 23 does not have to be 16 as in the above-mentioned another example, but can be any number. In this case, it is of course possible to use honeycomb filters 23 having different sizes and shapes in appropriate combinations.

In the embodiment, the honeycomb filter (or the ceramic filter assembly) of the present invention is embodied as a filter for an exhaust gas purification device attached to the diesel engine 2. Of course, the honeycomb filter (or the ceramic filter assembly) of the present invention can be embodied as a filter other than the filter for the exhaust gas purification device. Examples thereof include a heat exchanger member, a filter for high temperature fluid and high temperature steam, and the like.
Furthermore, the porous silicon carbide sintered body of the present invention can be applied to uses other than filters.

Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the above-mentioned embodiments will be listed below together with their effects. (1) In any one of claims 1, 2, 4, and 5, the number of cells per unit square centimeter is 18 or more, and the thickness of the cell wall is 0.46 mm or less.
According to this configuration, the same effect as the third or sixth aspect can be obtained.

(2) A honeycomb filter made of a sintered body having a porous structure constituted by silicon carbide crystal particles is used as a constituent member, and the outer peripheral surfaces thereof are bonded to each other via a ceramic sealing material layer, whereby An aggregate formed by integrating each honeycomb filter, wherein the pore diameter is 8 to 12 μm, the porosity is 35 to 49%, and 20% or more of the pores are through pores. body.

(3) In (2), the ceramic sealing material layer contains ceramic fiber and silicon carbide powder. According to this configuration, since the ceramic sealing material layer contains ceramic fibers and silicon carbide powder, it has not only excellent heat resistance but also a thermal expansion coefficient similar to that of a honeycomb filter made of a porous silicon carbide sintered body. ing. Therefore, the use of the ceramic sealing material layer contributes to prevention of breakage of the aggregate due to application of a large back pressure of the exhaust gas.

[0069]

As described in detail above, according to the first aspect of the present invention, the pressure loss can be reduced and the strength can be improved.

According to the second aspect of the present invention, the pressure loss can be further reduced, and the strength can be reliably improved. According to the third aspect of the invention, the purification performance of the honeycomb filter can be improved.

According to the fourth aspect of the present invention, the pressure loss of the honeycomb filter can be reduced, and the mechanical strength can be improved. Further, the collection efficiency of the particulates contained in the exhaust gas can be improved.

According to the fifth aspect of the present invention, the pressure loss can be further reduced, and the strength can be reliably improved. According to the invention described in claim 6, the contact area with the exhaust gas can be increased, and the exhaust gas purification performance of the honeycomb filter can be improved.

According to the seventh aspect of the present invention, since it has high strength and can be used for a long period of time, it has excellent practicality.

[Brief description of the drawings]

FIG. 1 is an overall schematic view of an exhaust gas purifying apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view of the honeycomb filter of the embodiment.

FIG. 3 is a sectional view taken along line AA of the honeycomb filter of the embodiment.

FIG. 4 is an enlarged sectional view of a main part of the exhaust gas purification device.

FIG. 5 is a perspective view of another example of a ceramic filter assembly configured by using a plurality of honeycomb filters.

[Explanation of symbols]

2 ... diesel engine (internal combustion engine), 8 ... casing, 9 ... honeycomb filter, 13 ... cell wall.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F01N 3/24 F01N 3/24 E 3/28 301 3/28 301S F-term (Reference) 3G090 AA03 BA01 3G091 AA02 AA18 AA28 AB02 AB13 BA09 BA10 BA38 BA39 CA27 FB10 GA06 GA07 GA20 GA24 GB01W GB01X GB05W GB06W GB10W GB13X GB17X GB17Z HA14 HA27 HA29 4D019 AA01 BA05 BB06 BC07 BC12 CA01 CB04 4D058 JA32 JA38 JB06 SA06 TA06

Claims (7)

[Claims] 1. A honeycomb filter made of a porous ceramic sintered body, having an average pore diameter of 5 to 15 μm and an average porosity of 30 to 50.
%, And 20% or more of the pores are through pores. 2. The honeycomb filter according to claim 1, wherein the average pore size is 8 to 12 μm, the average porosity is 35 to 49%, and 20 to 50% of the pores are through pores. 3. A cell whose end faces are alternately sealed by a sealing body is provided, and the number of cells is 12 per unit square inch.
The honeycomb filter according to claim 1, wherein the number is zero or more, and the thickness of a cell wall that partitions the cell is 0.46 mm or less. 4. 4. An exhaust gas purifying apparatus comprising: a honeycomb filter made of a porous ceramic sintered body for removing particulates contained in exhaust gas in a casing provided in an exhaust path of an internal combustion engine. An exhaust gas purifying apparatus, characterized in that the average pore diameter is 5 to 15 μm and the average porosity is 30 to 40%, and 20% or more of the pores are through pores. 5. The honeycomb filter according to claim 1, wherein said honeycomb filter has an average pore diameter of 8
The exhaust gas purifying apparatus according to claim 4, wherein the average porosity is 35 to 49%, and 20 to 50% or more of the pores are through pores. 6. The honeycomb filter has cells whose end faces are alternately sealed by a sealing body, the number of the cells is 120 or more per unit square inch, and the thickness of the cell wall is zero. The exhaust gas purifying apparatus according to claim 4, wherein the exhaust gas purifying apparatus is equal to or less than .46 mm. 7. The exhaust gas purification apparatus according to claim 4, wherein a total volume of the honeycomb filter is 1/4 to 2 times a total displacement of the internal combustion engine. apparatus.