JP2671616B2 - Exhaust filter for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust filter for collecting and removing exhaust particles such as carbon which are problematic in an internal combustion engine, particularly a diesel engine.

[0002]

2. Description of the Related Art It has been conventionally considered to collect and remove exhaust particulates such as carbon, which is a problem in diesel engines, with an exhaust filter interposed in an exhaust system, and various types of exhaust filters have already been proposed. Have been.

[0003] A typical example of this exhaust filter is a filtration and collection type represented by a so-called plug-in type filter. The plugged type filter is disclosed in, for example,
As shown in JP-A-124417, a large number of fine channels are formed in a ceramic block along the exhaust flow direction, and the ends of each channel are alternately closed with ceramics. The exhaust gas passes through the ceramic partition between the flow paths, thereby filtering and collecting the exhaust fine particles.

[0004] In this filter-collection type, although a very high collection efficiency is obtained, exhaust particulates are easily collected excessively, and the particulate collection amount easily exceeds the burnout limit of the filter. In other words, if the timing of forced regeneration using a burner or the like or regeneration by exhaust heat is slightly delayed, a large amount of exhaust particulates may rapidly burn, resulting in burnout of the filter. In addition, even Ash components (such as oxides of oil additives) that cannot be removed by incineration are collected, which may eventually lead to clogging.

[0005] Therefore, an exhaust filter of an adhesion collection type has been proposed in place of the filtration and collection type. As one example thereof, a three-dimensional porous body of ceramics, that is, a so-called ceramics foam used as a filter element, as disclosed in JP-A-62-45309, and a catalyst as disclosed in JP-A-51-23615. It is known that a plurality of thin heat-resistant fiberboards carrying the are laminated to form a filter element. In this adhering and collecting type, when exhaust gas flows through a complicated flow path generated inside the filter element, exhaust particulates are adhered and collected on the surface of the flow path.

[0006]

In the case of the above-mentioned adhesion trapping type, excessive trapping is unlikely to occur and clogging due to the Ash component is unlikely to occur. However, on the other hand, the collection density becomes high only on the surface of the exhaust gas on the inlet side, and it is difficult to distribute the exhaust gas particles widely throughout the filter element. As a result, there is a risk that the temperature will rise locally during regeneration, causing burnout.

Further, at a place where a large amount of exhaust particulates exist locally, the exhaust particulates do not directly adhere to the surface of the filter material, but the exhaust particulates further adhere to the collected particulates. However, since the adhesion strength is weak, a large amount of exhaust particulates are suddenly blown off to the outside and black smoke is emitted when the engine is rapidly accelerated.

That is, in order to fully utilize the advantage of this filter of the adhering and collecting type, a slow blow-off inside the filter is allowed, and the filter element is widely spread over the entire filter element.
Moreover, it is desirable to distribute the exhaust particulates more uniformly.

Further, as in Japanese Utility Model Laid-Open No. 51-23615, in a structure in which a large number of heat-resistant fiber boards are laminated as they are, the ventilation resistance is meaninglessly increased, and the collection efficiency of exhaust particulates is so high. There is also a drawback that it does not exist.

[0010]

An exhaust gas filter for an internal combustion engine according to the present invention comprises a flat mesh-shaped metal plate and a mesh-shaped metal plate formed in a concavo-convex shape so that a cross section has a substantially square wave shape.
To form a filter element by stacking them in a single layer, and stacking them in a cylindrical shape in a plurality of layers, and accommodating the cylindrical filter element in a casing so that exhaust gas flows in the radial direction thereof. It has a feature.

[0011]

In the above construction, since the uneven mesh-shaped metal plate is sandwiched between the flat mesh-shaped metal plates wound in a large number of cylindrical shapes, an appropriate space is secured between the flat mesh-shaped metal plates. To be done. At the place where the flat mesh-shaped metal plate and the concave or convex portion of the concave-convex mesh-shaped metal plate are in contact with each other, a plurality of mesh-shaped metal plates are directly overlapped with each other, which makes it difficult for exhaust gas to pass through. On the other hand, in a portion that does not overlap with the uneven mesh-shaped metal plate or in a bent rising portion of the uneven mesh-shaped metal plate, there is a part in which the mesh-shaped metal plate is one, and exhaust gas can easily pass through here. .

[0012] Therefore, the exhaust gas that attempts to flow through the cylindrical filter element in the radial direction attempts to pass through a portion having a small passage resistance in a microscopic view, and therefore is bent many times in the radial direction and the circumferential direction. However, the flow becomes turbulent and passes through the mesh metal plate many times.

Therefore, the exhaust particulates that cannot be completely collected on the exhaust inlet side of the filter element or the exhaust particulates blown off from the exhaust inlet side during acceleration or the like pass through the mesh metal plate many times while bending. Collected in the meantime. That is, exhaust gas particles are widely distributed in the filter element due to the slow blow-off inside.

Further, since there is an appropriate space between each mesh-shaped metal plate, the substantial contact surface area with exhaust gas is increased, and the collection efficiency is increased.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 5 is a sectional view showing the overall construction of the exhaust filter according to the present invention, in which an exhaust inlet pipe 2 is integrally formed at one end of a cylindrical casing 1. A cover 3 is welded to cover the opening at the other end of the casing 1, and an exhaust outlet pipe 4 is formed at the center of the cover 3.

A cylindrical filter element 5 is housed in the casing 1. The filter element 5 has an end face on the exhaust outlet pipe 4 side closed by a disc-shaped spring seat 6, and a coil spring 7 arranged in a compressed state between the spring seat 6 and the cover 3. Is pressed against the end surface of the casing 1 on the exhaust inlet pipe 2 side. An annular cushioning material 8 is interposed between the wall surface of the casing 1 and the end surface of the filter element 5. Further, a sufficient gap serving as an exhaust flow path is provided between the outer periphery of the filter element 5 and the inner peripheral surface of the casing 1.

Therefore, as a general flow of the exhaust gas, as shown by an arrow, it flows into the central portion of the filter element 5 from the exhaust inlet pipe 2 and flows in the radial direction of the filter element 5 from the outer peripheral gap. It is designed to flow out to the exhaust outlet pipe 2.

FIG. 4 is a perspective view showing the filter element 5, and FIGS. 1 and 2 show a cross section of a main part thereof.

As shown in FIG. 3, the filter element 5 has a structure in which three mesh-shaped metal plates 11, 12 and 13 are superposed on each other to form one layer, and a large number of these are laminated in a cylindrical shape.

More specifically, these mesh metal plates 11 to 11 will be described.
13 is a thin metal plate in which a large number of slits are cut, and these slits are stretched in a direction orthogonal to the slits to form a mesh shape, and the first mesh-shaped metal plate 11 is formed flat. ing. Further, the second mesh-shaped metal plate 12 located in the middle has an uneven shape in which a large number of concave portions 12a are formed at a constant pitch P along the axial direction of the filter element 5. The recess 12a has a rectangular wave-shaped cross section with a constant height, and the width T thereof is the pitch P.
It is about 1/4 of that. In addition, the third mesh-shaped metal plate 13 has the filter element 5 with a constant pitch P ′.
It has a concavo-convex shape in which a large number of convex portions 13a are formed along the axial direction. The convex portion 13a has a rectangular wave-shaped cross section having the same height as the concave portion 12a, and its width T'is about 1/4 of the pitch P '. The pitch P ′ of the third mesh-shaped metal plate 13 may be the same as the pitch P of the second mesh-shaped metal plate 12, but since the circumference length is slightly different when wound in a cylindrical shape. It is more desirable to set the pitch P ′ of the third mesh-shaped metal plate 13 on the relatively inner peripheral side to a very small value.

The mesh-shaped metal plates 11 to 13 are
A ceramic containing a catalyst is coated individually or in an assembled state to support the catalyst.

The above three mesh-shaped metal plates 11 to 13 are
They are superposed on each other and form one layer of the filter element 5. At this time, as shown in FIG. 1 and FIG.
The recess 12a of the mesh metal plate 12 and the third mesh metal plate 13
And the convex portions 13a are overlapped with each other so that they are located at equal intervals. A large number of three-layered mesh-shaped metal plates 11 to 13 are laminated around the mesh-shaped metal inner cylinder 14 having a relatively high rigidity to form the filter element 5. In addition, a long continuous mesh metal plate 1
1 to 13 may be spirally wound or may be cut into a predetermined length and laminated one by one. The layers thus laminated are fixed by spot welding or the like.

In the state where a large number of three-layer mesh metal plates 11 to 13 are stacked as described above, the third mesh metal plate of the next layer is provided on the outer periphery of the flat first mesh metal plate 11. Thirteen
Are overlapped with each other, resulting in a cross sectional state as shown in FIG. 1 or 2. That is, an appropriate gap 16 is secured by the second and third mesh-shaped metal plates 12 and 13 between the flat first mesh-shaped metal plates 11 of each layer, and the gap 16 is the second and third mesh plates. The mesh-shaped metal plates 12 and 13 are divided into substantially equal intervals by the rising and falling portions. In addition, the concave portion 12a of the second mesh-shaped metal plate 12
At the position where the tip portion or the tip portion of the convex portion 13a of the third mesh-shaped metal plate 13 is in contact with the first mesh-shaped metal plate 11, 2 to 4 mesh-shaped metal plates are closely overlapped due to the overlapping condition of each layer. It is in a state of On the contrary, depending on how the layers overlap, as shown in FIG. 2, the gap 16 between the upper and lower layers is the first.
A part of the mesh-shaped metal plate 11 that is partitioned by one sheet also occurs.

Therefore, as for the exhaust gas which flows toward the entire filter element 5 in the substantially radial direction, as shown by the arrows in FIGS. 1 and 2, the exhaust gas is applied to a place where the number of mesh metal plates is small, that is, a place where the ventilation resistance is low. Microscopically, it does not flow linearly in the radial direction because it tries to flow selectively, but it flows in a very disturbed form in the radial and circumferential directions. Then, it passes through the mesh-like metal plates 11 to 13 much more times than the case of linearly flowing in the radial direction.

For this reason, even if exhaust particulate matter that adheres to the inner peripheral portion of the filter element 5 initially blows off at the time of sudden acceleration, etc., the mesh-shaped metal plates 11 to 11 on the outer peripheral side than this.
It is adhered and collected again at 13 and does not suddenly blow off to the outside.

That is, a slow internal blow-off is performed,
Exhaust particles are widely distributed throughout the filter element 5. Therefore, local overheating during regeneration is prevented.

Further, since the sufficient gap 16 is secured between the mesh-like metal plates 11 to 13 of each layer, the substantial contact area with the exhaust gas is increased, and the ventilation resistance is not significantly increased. Collection efficiency can be improved. The collection efficiency is further improved by applying a ceramic coating on the surface.

As described above, since the distribution of exhaust particulates is relatively uniform and a large number of gaps 16 are present inside, the contact efficiency with the catalyst becomes good, and the regeneration ability by catalyst action and exhaust purification. The action is improved.

Moreover, since the filter element 5 is entirely made of metal, the heat capacity can be made extremely small, and the temperature rising characteristics at the time of engine start and the like can be excellent.

In the above construction, since the collection itself is carried out in the form of adhering collection, excessive collection such as filtration collection is prevented, and clogging due to the Ash component hardly occurs.

The embodiment of the present invention has been described above.
The present invention is not limited to the above-mentioned embodiment, and may have, for example, a configuration in which one corrugated metal plate is used.

In the above embodiment, the mesh metal plate 11 is used.
Although the catalyst is supported on ~ 13, this catalyst support is not essential.

[0034]

As is clear from the above description, in the exhaust gas filter of the internal combustion engine according to the present invention, the exhaust flow is complicatedly bent in the radial direction and the circumferential direction in the filter element made of the mesh metal plate. Since it flows, the trapping efficiency can be improved without significantly increasing the ventilation resistance. Then, a slow internal blow-off can be realized, exhaust particulates can be widely distributed over the entire filter element, and abrupt blow-off to the outside during acceleration or the like can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a filter element of an exhaust filter according to the present invention.

FIG. 2 is a sectional view of an essential part of a different part of the filter element.

FIG. 3 is an explanatory view showing one layer of the filter element in a disassembled state.

FIG. 4 is a perspective view of a filter element.

FIG. 5 is a sectional view of the entire exhaust filter.

[Explanation of symbols]

 1 ... Casing 5 ... Filter element 11-13 ... Mesh metal plate 16 ... Gap

Claims (1)

(57) [Claims] 1. A flat reticulated metal plate and a reticulated metal plate formed in a concave-convex shape so that the cross section has a substantially square wave shape are stacked to form a single layer, and the multi-layered cylindrical plates are laminated. An exhaust filter for an internal combustion engine, characterized in that a cylindrical filter element is housed in a casing so that exhaust gas flows in a radial direction thereof.