JP2002070532A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a durable exhaust emission control device capable of uniformizing the amount of particulates accumulated on a filter over the whole filter and preventing the generation of cracks in the filter in the regeneration treatment. SOLUTION: This exhaust emission control device has the filter for controlling the exhaust gas arranged through a filter holding sealing body in a casing to which an introducing pipe through which the exhausted gas exhausted from the internal combustion engine is passed and an exhaust pipe exhausting the exhaust gas is connected, and the streamline of the exhaust gas flowing in the casing through the introducing pipe and the axis line of the filter are set so as not to become parallel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas purifying apparatus for removing particulates and the like in exhaust gas discharged from an internal combustion engine such as a diesel engine.

[0002]

2. Description of the Related Art Recently, it has become a problem that particulates contained in exhaust gas discharged from internal combustion engines such as vehicles such as buses and trucks and construction machines cause harm to the environment and human bodies. Various ceramic filters have been proposed which purify the exhaust gas by collecting the particulates in the exhaust gas by passing the exhaust gas through a porous ceramic.

[0003] Such ceramic filters are usually
As in the honeycomb filter 20 shown in FIG. 2, a plurality of porous ceramic members 30 are bound,
A filter holding seal body 43 is wound around the outer periphery. As shown in FIG. 3, the porous ceramic member 30 has a large number of through holes 31 arranged in the longitudinal direction, and a partition wall 33 separating the through holes 31 functions as a filter.

[0004] That is, as shown in FIG. 3 (b), the through hole 31 formed in the porous ceramic member 30 is plugged with a filler 32 at either the inlet or outlet end of the exhaust gas. The exhaust gas that has flowed into one through-hole 31 always flows through the partition wall 33 separating the through-hole 31 and then flows out from the other through-hole 31. Among such porous ceramic members 30, for example, a porous silicon carbide member is used for various large-sized vehicles and the like because of extremely excellent heat resistance and easy reprocessing.

[0005] In the exhaust gas purifying apparatus, the honeycomb filter 20 having such a configuration is provided in the exhaust passage of the internal combustion engine, and the particulates in the exhaust gas discharged from the internal combustion engine pass through the honeycomb filter when passing through the honeycomb filter. 33
And the exhaust gas is purified.

FIG. 4A is a cross-sectional view schematically showing a conventional exhaust gas purifying apparatus, and FIG. 4B is a schematic view showing a state in which exhaust gas passes through an introduction pipe and flows into a casing. FIG. 2 is a partially enlarged sectional view shown in FIG. As shown in FIG. 4A, in the exhaust gas purifying apparatus 40, an introduction pipe 44 into which exhaust gas from the internal combustion engine is introduced is connected to one end of the casing 41, and the other end is provided with a honeycomb. An exhaust pipe 45 for exhausting the exhaust gas passing through the filter 20 to the outside
Is provided. Also, inside the casing 41,
The honeycomb filter 20 is provided via a filter holding seal body 43. In addition, the introduction pipe 44, the casing 41, the honeycomb filter 20, and the discharge pipe 45
Are installed such that their central axes overlap on the same line.

Further, although not shown, an electric heater for burning the particulates accumulated in the honeycomb filter 20 is provided in a portion on the exhaust gas introduction side with respect to the honeycomb filter 20, and a temperature sensor is provided. It is installed so as to be in contact with the honeycomb filter 20, and a pipe for sending in air or the like when performing combustion is connected.

Exhaust gas flows from the inlet pipe 44 into the casing 41 in a state substantially parallel to the central axis, passes through the honeycomb filter 20, traps particulates in the partition wall 33, and is discharged from the outlet pipe 45. Is done. And
When the amount of accumulated particulates increases and the pressure loss of the honeycomb filter 20 increases, a regeneration process for burning and removing the particulates is performed.

However, in the conventional exhaust gas purifying apparatus 40 having such a configuration, the exhaust gas passing through the introduction pipe 44 is in a state close to a laminar flow, and this exhaust gas has a state shown in FIG. As shown in ()), a velocity distribution was generated such that the flow velocity at the center became highest. The arrows in the figure show the difference in the flow rate of the exhaust gas, and the longer the flow rate, the faster the flow rate.

In the conventional exhaust gas purifying apparatus 40, as described above, since the exhaust gas passes through the honeycomb filter 20 in a state of having a velocity distribution, the particulates are apt to collect at a high-speed central portion. In the meantime, the amount of accumulated particulates is biased between the central portion and the peripheral portion of the honeycomb filter 20, and more particulates are accumulated near the central portion.

When the regeneration process is performed on the honeycomb filter 20 in which the accumulation amount of the particulates is uneven, the portion near the center of the honeycomb filter 20 becomes hotter than the surroundings due to the burning of the particulates, and this uneven temperature Due to the distribution, there is a problem that a large thermal stress is generated in the honeycomb filter 20 and cracks and the like are easily generated.

The introduction pipe 44 and the honeycomb filter 20
A method has also been proposed in which a member that disturbs the flow of exhaust gas such as a baffle plate is provided between them to make the amount of particulates accumulated in the honeycomb filter 20 uniform.
In this method, it is necessary to install a member that disturbs the flow of the exhaust gas in the introduction pipe 44 or inside the casing 41,
As a result, the structure of the exhaust gas purifying device becomes complicated, and maintenance becomes complicated, resulting in a large time and economic disadvantage.

[0013]

SUMMARY OF THE INVENTION The present invention has been made to solve these problems, and the amount of particulates accumulated in the filter can be made uniform throughout the filter. In this case, it is an object of the present invention to provide an exhaust gas purifying apparatus which is excellent in durability and is free from cracks or the like in a filter due to non-uniform temperature.

[0014]

According to the present invention, there is provided an exhaust gas purifying apparatus comprising a casing in which an inlet pipe through which exhaust gas discharged from an internal combustion engine passes and a discharge pipe for discharging the exhaust gas are connected. An exhaust gas purifying filter is an exhaust gas purifying device installed via a filter holding seal body, wherein a streamline of the exhaust gas flowing into the casing via the introduction pipe, and an axis of the filter. But,
It is characterized by being set not to be parallel.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an exhaust gas purifying apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1A is a cross-sectional view schematically showing one example of the exhaust gas purifying apparatus of the present invention, and FIG.
It is the elements on larger scale which expanded a part of exhaust gas purification device of the present invention shown in (a). As shown in FIG. 1A, in an exhaust gas purifying apparatus 10 of the present invention, an introduction pipe 14 through which exhaust gas discharged from an internal combustion engine passes and a discharge pipe 15 which discharges the exhaust gas are connected. Casing 11
Inside, a filter 12 for purifying exhaust gas is installed via a filter holding seal 13.

Further, the exhaust gas purifying apparatus 10 of the present invention comprises:
The flow line of the exhaust gas flowing into the casing 11 via the introduction pipe 14 and the axis of the filter 12 are set so as not to be parallel.

Although not shown, the filter 12
In the part on the exhaust gas introduction side, the filter 1
An electric heater for burning the particulates accumulated in the fuel cell 2 may be provided, and a temperature sensor may be provided so as to be in contact with the filter 12, and a pipe for feeding air or the like when performing combustion is connected. It may be.

Further, the above-mentioned conventional exhaust gas purifying apparatus 4
Similarly to the case of 0, in the exhaust gas purifying apparatus 10 of the present invention, the exhaust gas flowing into the inside of the casing 11 from the introduction pipe 14 passes through the filter 12, the particulates are captured by the filter 12, and the exhaust pipe 15 Is discharged from When the amount of accumulated particulates increases and the pressure loss or the like of the filter 12 increases, a regeneration process for burning and removing the particulates is performed.

The above-mentioned “exhaust gas streamline” means that the exhaust gas flows from the introduction pipe 14 into the casing 11.
The direction of the flow of the exhaust gas, which is generally parallel to the longitudinal axis of the introduction pipe 14. In addition, the above “Filter 1”
The “2 axis line” means, for example, the center line of the filter 12 when the filter 12 has a columnar shape, and usually includes the porous ceramic member 30 constituting the filter 12.
Is parallel to the length direction (through hole).

As described above, by setting the flow line of the exhaust gas and the axis of the filter 12 so as not to be parallel, the traveling direction of the exhaust gas is different between the inside of the introduction pipe 14 and the inside of the casing 11. Become. As a result, the exhaust gas that has passed through the introduction pipe 14 in a substantially laminar flow state becomes turbulent in the casing 11, and the particulates are easily dispersed around the exhaust gas. It does not pass and particulates accumulate in one part.

The angle θ between the exhaust gas streamline and the axis of the filter 12 (see FIG. 1B) is preferably 10 to 70 °. If it is less than 10 °, the exhaust gas cannot be almost turbulent in the casing 11,
The amount of particulates stored in the filter 12 is biased. On the other hand, if it exceeds 70 °, the casing 11
A large amount of particulates is likely to adhere to the inner wall of the gasket, and the structure is also distorted, and the temperature of a part of the inlet pipe 14 and the casing 11 that the exhaust gas hits is increased. Large stress concentrates on the part where the connection is made, and it is easy to break.

The angle θ is more preferably 20 to 40 °. Within this range, the filter 12 can be circulated while the exhaust gas flowing in the laminar flow state is changed to a turbulent flow most smoothly.

The filter 12 is a honeycomb filter for purifying exhaust gas, comprising a porous ceramic sintered body in which a large number of through holes are arranged in the longitudinal direction and partition walls separating the through holes function as filters. It is preferred that While having sufficient heat resistance, it has excellent durability and particulate collection efficiency, and in the regeneration process, the regeneration time can be relatively shortened,
This is because the reproduction rate is high. Note that the specific structure of the porous ceramic sintered body is substantially the same as that of the above-described prior art porous ceramic member 30, and a description thereof will be omitted. Examples of other filters include a columnar porous ceramic filter.

The shape of the filter 12 is not particularly limited.
A cylindrical shape or a prismatic shape may be used, but usually a cylindrical shape as shown in FIG. 2 is often used.

The material of the honeycomb filter is not particularly limited, and various ceramics can be mentioned. Among them, silicon carbide having high heat resistance, excellent mechanical properties and high thermal conductivity is used. preferable.

The filter holding seal 13 is wound around the outer periphery of the filter 12 for the purpose of heat insulation or the like.
Conventionally used materials such as ceramic fibers having a high heat insulating property can be used. When the filter 12 is installed in the casing 11,
It is prepared so that the space formed by the filter 12 and the inner wall of the casing 11 can be completely closed.

The material of the casing 11 is not particularly limited, and examples thereof include stainless steel. Also, the shape is not particularly limited, and may be cylindrical,
The cylinder may have a two-part shell shape obtained by dividing the cylinder into two parts in the axial direction. The size of the casing 11 is not particularly limited, and is appropriately adjusted so that the filter 12 can be installed via the filter holding seal 13.

The exhaust gas purifying apparatus of the present invention is configured as described above. When the exhaust gas that has passed through the introduction pipe in a substantially laminar flow state flows into the casing, the direction of travel is changed, and It becomes a flow. As a result, the exhaust gas
The filter uniformly passes through the entire filter, and does not partially pass through the filter. That is, the amount of particulates accumulated in the filter can be made uniform throughout the filter, and during the regeneration process, the temperature of the entire filter rises and no thermal stress occurs, so cracks and the like occur. An exhaust gas purifying apparatus which does not occur and has excellent durability is obtained.

Further, the exhaust gas purifying apparatus of the present invention includes a back pressure sensor for measuring the pressure loss of the filter, and it is necessary to perform a regeneration process when the back pressure rises above a predetermined value. A device or the like for displaying the fact may be provided.

When the exhaust gas purifying apparatus of the present invention is provided in a vehicle, two or more exhaust gas purifying apparatuses of the present invention may be provided in parallel. In this case, two exhaust gas purifiers are connected to the exhaust gas pipe, and one of them is used by using a switching valve or the like, and the other is regenerated during that time.

Further, N is added to the exhaust gas purifying apparatus of the present invention.
A catalyst layer for removing harmful gases such as Ox and SOx may be provided so that both harmful gases and particulates can be removed. Further, according to the present invention, at the time of regeneration, the exhaust gas can be used as a combustion assisting gas. When the regeneration process is separately performed using a pump, the regeneration process can be performed by sending air into the filter using the pump.

When assembling the exhaust gas purifying apparatus of the present invention, a honeycomb filter 20 having the structure shown in FIG. 2 is prepared, and after the filter holding seal 13 is wound around the honeycomb filter 20, it is installed in the casing 11. Then, the casing 11 having the honeycomb filter 20 may be disposed between the introduction pipe 14 and the discharge pipe 15, or may be connected to the introduction pipe 14 after the discharge pipe 15 is attached to the casing 11.

At this time, the longitudinal axis of the introduction pipe 14 is
The angle formed by the longitudinal axis of the casing 11 is 10 to
The angle between them is set so as to be 70 °.

[0035]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 An organic binder, water and the like were added to silicon carbide powder, kneaded, extruded to form a honeycomb-shaped formed body, and subsequently dried, degreased, and fired. 3, a porous ceramic member 30 made of a silicon carbide sintered body having an average pore diameter of 5 to 20 μm, 31 cells / cm ² , and a partition wall thickness of 0.3 mm was produced.

Next, this porous ceramic member 30 is
By bundling a large number using a heat-resistant adhesive containing inorganic fibers such as ceramic fibers or inorganic particles such as silicon carbide, and then cutting using a diamond cutter, the diameter as shown in FIG. A honeycomb filter 20 having a length of 165 mm and a length of 150 mm was manufactured.

Then, a layer of the filter holding seal body 43 having the same composition as the heat-resistant adhesive was formed on the outer peripheral portion. In addition, the thickness of the filter holding seal body 43 is 13
mm.

Using the honeycomb filter 20 manufactured by the above method, an exhaust gas purifying apparatus 10 as shown in FIG.
Was prepared. At this time, the angle θ between the exhaust gas streamline shown in FIG. 1B and the axis of the filter (honeycomb filter 20) was set to 30 °.

Next, the inlet pipe 14 of the exhaust gas purifying apparatus 10 is connected to the exhaust gas outlet of the engine, and the above-mentioned engine is operated under the no-load condition at the maximum number of revolutions for 8 hours. Was done.

Thereafter, the honeycomb filter 20 was taken out, the accumulation state of the particulates was observed, and the amount of the accumulated particulates was measured. As a result, the particulates were almost uniformly accumulated in the entire honeycomb filter 20, and the amount Was 65 g. Then, a regeneration process for heating and removing the particulates by heating the honeycomb filter 20 was performed, and the state of the honeycomb filter 20 was observed. As a result, no crack or the like occurred in the honeycomb filter 20.

Comparative Example 1 A honeycomb filter was manufactured in the same manner as in Example 1.
Next, using the manufactured honeycomb filter, the exhaust gas purification was performed by setting the streamline of the exhaust gas flowing into the casing from the introduction pipe and the axis of the filter as shown in FIG. The device 40 was manufactured, and a particulate collection test was performed in the same manner as in Example 1.

As a result, the particulates were accumulated near the center of the honeycomb filter, and the amount of the accumulated particulates was 65 g. Also, in the same manner as in Example 1,
When the honeycomb filter was regenerated, cracks were observed in a part of the honeycomb filter.

From the results shown in the first embodiment, by setting the exhaust gas streamline of the exhaust gas purifier and the axis of the filter so as not to be parallel, the laminar exhaust gas can be reduced.
Example 1 is turbulent when passing through the filter.
Therefore, it is possible to uniformly collect the particulates without causing a bias in the amount of accumulated particulates in the filter according to (1). On the other hand, from the results shown in Comparative Example 1, the exhaust gas passes through the filter in a laminar state by setting the exhaust gas streamline of the exhaust gas purification device and the axis of the filter in a straight line. The amount of accumulated particulates in the filter according to Example 1 is biased toward the center.

[0045]

The exhaust gas purifying apparatus according to the present invention is as described above, and the amount of particulates accumulated in the filter can be made uniform throughout the filter. No danger occurs and the durability can be improved.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view schematically showing an example of an exhaust gas purifying apparatus of the present invention, and FIG. 1B is a partially enlarged cross-sectional view thereof.

FIG. 2 is a perspective view schematically showing one example of a honeycomb filter used for an exhaust gas purification device.

3A is a perspective view schematically showing a porous ceramic member used for the honeycomb filter shown in FIG. 2, and FIG. 3B is a longitudinal sectional view thereof.

FIG. 4A is a cross-sectional view schematically showing an example of a conventional exhaust gas purifying apparatus, and FIG. 4B is a partially enlarged cross-sectional view thereof.

[Explanation of symbols]

 10, 40 Exhaust gas purifier 11, 41 Casing 12 Filter 13, 43 Filter holding seal 14, 44 Inlet 15, 45 Outlet 20 Honeycomb filter 30 Porous ceramic member 31 Through hole 32 Filler 33 Partition wall

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G090 AA02 BA04 CA01 CA03 DA13 EA01 4D019 AA01 BA05 BB06 BC07 BC12 CA01 CB09 4D058 JA32 JB06 KA12 KA18 KC28 MA41 QA01 QA11 QA17 SA08 TA06

Claims (4)

[Claims] An exhaust gas purifying filter includes a filter holding sealer in a casing connected to an inlet pipe through which exhaust gas discharged from an internal combustion engine passes and an exhaust pipe discharging the exhaust gas. An exhaust gas purifying device installed through the inlet pipe, wherein a streamline of the exhaust gas flowing into the casing via the introduction pipe and an axis of the filter are set so as not to be parallel to each other. Exhaust gas purifier characterized. 2. The exhaust gas purifying apparatus according to claim 1, wherein an angle between a streamline of the exhaust gas and an axis of the filter is 10 to 70 °. 3. The exhaust gas purifying apparatus according to claim 1, wherein the angle between the streamline of the exhaust gas and the axis of the filter is 20 to 40 °. 4. A filter for purifying exhaust gas, comprising a porous ceramic sintered body in which a filter has a large number of through-holes arranged in a longitudinal direction and partition walls separating the through-holes function as a filter. The exhaust gas purification device according to any one of claims 1 to 3, which is a filter.