JP2000154712A - Engine-exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an inexpensive filter in which pressure loss is lowered and which has a high purification rate in an engine-exhaust emission control device provided with a filter for collecting exhaust particulates in exhaust gas, and enable it to heat the filter at the time of regeneration so that the temperature distribution in the filter is uniform. SOLUTION: In a filter part 20 provided in an exhaust gas passage 30, a low filling density filter 21, a medium density filter 22, and a high filling density filter 23 are arranged in series so that their density is increased from the upstream toward the downstream of exhaust gas. In relation to the respective filters 21 to 23, plural stainless steel wire meshes differed from each other in mesh number are layered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust gas purifying apparatus provided with a filter for trapping exhaust particulates in engine exhaust gas.

[0002]

2. Description of the Related Art Generally, there is a filter using steel wool as a filter of an engine exhaust gas purifying apparatus (for example, JP-A-56-56921). However, in the case of steel wool, since the packing density of general commercial products is low (for example, about 5%), the collection efficiency of exhaust particulates is low. For this reason, a filter having a high filling density is required. However, specially producing steel wool having a high filling density increases costs, and it is difficult to finely control the filling density of steel wool.

Further, if a filter having a high packing density is used,
The accumulation of exhaust particulates (especially on the upstream side) causes an increase in pressure loss. Also, when steel wool is filled, the fiber direction is random, so the ratio of fibers arranged in the direction perpendicular to the flow direction is small, and it is difficult to obtain a high purification rate because the filtration area cannot be used effectively. . on the other hand,
Japanese Unexamined Utility Model Publication No. 2-3328 has been proposed. This is because a plurality of ceramic or metal foams are arranged in an exhaust gas passage as a filter of an engine exhaust gas purification device, and the foam density on the downstream side of the exhaust gas has a higher filter density (filling density) than that on the upstream side. It is set to be large. Thereby, pressure loss on the upstream side can be reduced.

However, in the case of foams, it is not easy to obtain a foamed form having an arbitrary packing density, and manufacturing a foam having an arbitrary packing density increases costs. Also, as an engine exhaust gas purification device,
Some filters are heated by a burner (regeneration heat source) provided outside the filter to regenerate the filter in response to clogging by exhaust particulates collected by the filter. However, the temperature in the filter depends on the distance from the burner. There is a problem that the distribution becomes large and the filter material is not regenerated in a low temperature portion, and the filter material is greatly deteriorated in a high temperature portion.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides an engine exhaust gas purifying apparatus provided with a filter for trapping exhaust particulates in exhaust gas, in which an inexpensive filter having a low pressure loss and a high purification rate is provided. The first object is to obtain. Further, in addition to the first object, a second object is to make it possible to uniformly heat the temperature distribution in the filter during regeneration.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, an exhaust gas passage (3) is provided.
A plurality of mesh members (21a to 23a) having meshes are arranged along the flow direction of the exhaust gas so that the packing density of the filter portion (20) provided in the exhaust gas flow increases from the upstream side to the downstream side of the exhaust gas. It is characterized by having a laminated structure.

According to the present invention, since the packing density of the filter section (20) increases from the upstream side to the downstream side of the exhaust gas, the exhaust particles in the exhaust gas do not concentrate on the upstream side, and the entire filter section does not concentrate. , The pressure loss can be reduced. Furthermore, since the filter part (20) has a configuration in which a plurality of mesh members (21a to 23a) having a mesh are stacked, a commercially available wire mesh or the like can be used, and the configuration can be inexpensive.

Further, a plurality of net members (21a to 23a)
Are laminated along the exhaust gas flow direction,
Since the net surface of each net member (21a to 23a) is arranged in a direction substantially orthogonal to the flow of the exhaust gas, the filtration area can be effectively used, and a high purification rate can be obtained. As described above, according to the present invention, an inexpensive filter configuration having a low pressure loss and a high purification rate can be obtained.

Here, a mesh member (21a to 21a) having a mesh
In the case where 3a) is formed by arranging a plurality of wires in a mesh shape, as in the invention according to claim 2, in the plurality of laminated net members (21a to 23a), the upstream and downstream of the exhaust gas are disposed. The packing density of the filter portion (20) can be increased from the exhaust gas upstream side to the downstream side by changing the wire diameter and / or the mesh interval of the wire rod with the downstream side.

In the present invention, specifically, a mesh member (21a to 23a) formed by arranging a plurality of wires in a mesh shape is
The above-mentioned commercially available wire mesh can be used, and changing the wire diameter and the opening area of the mesh changes the wire diameter (fiber diameter) and the mesh number (standardized in JIS) of the wire material of the wire mesh. This can be achieved by: According to a third aspect of the present invention, there is provided the engine exhaust gas purifying apparatus according to the first and second aspects, wherein a plurality of laminated net members (21a to 21a) are arranged.
23a), an electric heater (40) is interposed therebetween, and a configuration in which a regeneration heat source is directly provided in the filter section can be employed, so that the temperature distribution in the filter section can be uniformly heated during regeneration. Here, in order to make the temperature distribution in the filter portion more uniform, it is preferable to use a plurality of electric heaters (40).

Note that the reference numerals in parentheses above are examples showing the correspondence with specific means described in the embodiments described later.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. This embodiment is applied, for example, as an exhaust gas purifying apparatus for an engine in a stationary engine heat pump. FIG. 1 is a schematic cross-sectional view of an engine exhaust gas purifying apparatus (hereinafter, simply referred to as an apparatus) 100 according to the present embodiment.

Reference numeral 10 denotes a casing for accommodating and holding the filter unit 20, which is provided at an intermediate portion of an exhaust gas passage 30 for discharging exhaust gas of an engine (not shown). Here, the exhaust gas flows as indicated by the arrows in the figure. The filter section 20 is formed by laminating a plurality of mesh members having a mesh in series along the exhaust gas flow direction such that the packing density increases from the upstream side of the exhaust gas toward the downstream side.

In the present embodiment, the filter unit 20 uses a mesh number (mesh number: 25.4 mm (1
The packing density is changed by laminating a stainless steel mesh as the above-mentioned mesh member having different numbers of meshes between (inch) and three portions having different packing densities, that is, a small density filter 21 having a small packing density, Medium density filter 22 with medium filling density, large density filter 23 with large filling density
Is composed.

More specifically, as shown in FIG. 2, a small density filter 21 (FIG. 2C) and a medium density filter 22 (FIG.
(B)), the high-density filter 23 (FIG. 2 (a)),
The mesh of the stainless wire mesh in each filter is fine. As an example, the small-density filter 21 has a wire diameter φ.
0.25 mm, mesh No. 20 is a stack of a plurality of wire meshes 21a, and the packing density can be 16%. The medium density filter 22 has a wire diameter of 0.25 mm, mesh No. 3
And a packing density of 2
4%, and the high-density filter 23 has a wire diameter of 0.25 m.
m, mesh No. A packing density of 32% is formed by stacking a plurality of 40 wire meshes 23a.

In each of the portions 21 to 23, the packing density can be changed even if the wire diameter (fiber diameter) of the wire mesh is changed. Further, since the filter section 20 has a structure in which a plurality of stainless steel meshes 21a to 23a are stacked along the exhaust gas flow direction, the mesh surface of each wire mesh (that is, all the fibers of the wire mesh) is substantially equivalent to the flow of the exhaust gas. Since they are arranged in the orthogonal direction, the filtration area can be used effectively. .

Further, as shown in FIG. 1, a plurality of electric heaters 40 are provided integrally with the filter section 20 as a regeneration heat source for heating the filter section 20 during regeneration. In the illustrated example, two electric heaters 40 are provided in contact with the exhaust gas upstream and downstream of the filter section 20, and two electric heaters 40 are further provided with the small density filter 21 and the medium density filter 2.
2, medium density filter 22 and large density filter 23
And between.

These electric heaters 40 are shown in FIG. 3 (A in FIG. 1).
As shown in FIG. 2A, a heating unit 41 which generates heat by energization and an energizing unit 42 for energizing the heating unit 41 are provided. For example, the energizing unit 42 includes a power supply and a control circuit provided in a heat pump device. Therefore, power is supplied to the heat generating portion 41 during reproduction. As shown in FIG. 1, a heat insulating material 50 is provided on the inner wall surface of the casing 10.

The operation of the apparatus 100 having such a configuration will be described. When the exhaust gas from the engine flows into the casing 10, the exhaust particulates are removed from the downstream high-density filter 2.
3 and the medium-density filter 22 and the small-density filter 21 on the upstream side with time. Each time a constant deposition amount or a constant time is reached, the electric heater 40
Is applied to heat the filter section 20 to the ignition temperature of the exhaust particulates. In this way, the exhaust particulates collected by the filter section 20 are burned and removed, and the filter section 20 is regenerated.

By the way, in the conventional filter having a constant packing density (comparative example), exhaust particulates are concentrated and deposited only on the upstream side, so that the airflow resistance on the upstream side increases with the operating time, and the pressure loss increases. The rise is remarkable. However, in the present embodiment, by adopting a structure in which the packing density of the filter unit 20 is increased from the upstream side to the downstream side, the accumulation of exhaust particulates is not concentrated only on the upstream side, and is more uniform over the entire filter unit 20. , It is possible to suppress an increase in pressure loss and to extend the regeneration cycle time.

FIG. 4 shows the difference in the rate of increase in pressure loss between the comparative example and the present embodiment. It can be seen that even if the initial pressure loss (initial pressure loss) and the collection efficiency are equal, the rate of increase of the pressure loss is lower in the present embodiment. Further, in the present embodiment, as shown in FIG.
Since the temperature distribution in the axial direction of 0 is reduced and the entire filter section 20 can be uniformly heated to the ignition temperature of the exhaust particulates,
The power of the heater can be used effectively.

In this embodiment, the filter section 20 has a structure in which stainless steel meshes are laminated. However, stainless steel meshes having various fiber diameters and mesh numbers are commercially available unless they are very special materials. Therefore, the filter unit 20 is relatively inexpensive, and the filter unit 20 itself can be configured to be inexpensive. The packing density of the filter section 20 can be freely selected by a combination of the fiber diameter of such an inexpensive stainless steel wire mesh and the mesh number. In particular, when the filter section 20 has a multilayer structure including the filters 21 to 23 as in the present embodiment, this merit is greatly utilized.

In this embodiment, since the filter section 20 has a laminated structure of a wire mesh, all the fibers are arranged in a direction perpendicular to the flow, so that the filtration area can be effectively used and a high purification rate can be obtained. Can be done. As described above, according to the present embodiment, an inexpensive filter configuration having a low pressure loss and a high purification rate can be obtained.

(Other Embodiments) If possible, the packing density may be changed by changing the laminating interval between the wire meshes even if the fiber diameter and mesh number of each wire mesh are the same.
Further, the mesh member is not limited to a wire mesh in which a plurality of wires (fibers) are arranged in a mesh shape, but may be a punching metal in which a plurality of openings are formed in a metal plate.

The present invention can be applied to a vehicle engine exhaust gas purifying apparatus and the like in addition to the stationary engine heat pump described above.

[Brief description of the drawings]

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

FIG. 2 is a detailed explanatory diagram of a filter unit in the embodiment.

FIG. 3 is a sectional view taken along line AA of FIG. 1;

FIG. 4 is a diagram showing an effect of reducing pressure loss in the embodiment.

[Explanation of symbols]

Reference numeral 20: filter portion, 21a: stainless wire mesh of a small density filter, 22a: stainless wire mesh of a medium density filter, 2
3a: a stainless steel mesh of a high-density filter, 30: an exhaust gas passage, 40: an electric heater.

Claims (3)

[Claims] 1. An engine exhaust gas purifying apparatus comprising: a filter unit (20) provided in an exhaust gas passage (30) for exhausting exhaust gas of an engine to collect exhaust particulates in the exhaust gas. ) Indicates that a plurality of mesh members (21a to 23a) having a mesh are laminated along the exhaust gas flow direction such that the packing density increases from the exhaust gas upstream side to the downstream side. Characteristic engine exhaust gas purifier. 2. The mesh member (21a to 23a) is formed by arranging a plurality of wires in a mesh shape. In the stacked plurality of mesh members (21a to 23a), an upstream side and a downstream side of an exhaust gas are provided. The packing density of the filter portion (20) increases from the upstream side to the downstream side of the exhaust gas by changing the wire diameter of the wire and / or the opening area of the mesh on the side. Item 2. An engine exhaust gas purifying apparatus according to Item 1. 3. The plurality of laminated net members (21a).
An exhaust gas purifying apparatus for an engine according to claim 1 or 2, wherein an electric heater (40) is interposed between the exhaust gas purifying apparatus (1) and (2a).