JP2019022873A - Exhaust gas purification device - Google Patents

Abstract

To provide an exhaust gas purification device in which a thickness of a catalyst layer is relatively increased so as to reduce an opening ratio in a portion where an exhaust gas flow is concentrated, in a honeycomb carrier whose a cell number, a cell shape or a thickness of a cell wall is substantially the same.SOLUTION: An exhaust gas purification device has an exhaust gas flow channel 21 of which a diameter is enlarged provided on the downstream of an exhaust gas flow channel 20, has a honeycomb carrier 3 having a catalyst layer provided in the exhaust gas flow channel 21 of which the diameter is enlarged, overlaps a catalyst layer 11A on the upstream layer with a catalyst layer 11B on the downstream side in a region where an exhaust gas flow is concentrated of the honeycomb carrier 3, compares the overlapped portion with other portions and gives a thickness in a radial direction to the catalyst layer, and is formed with a region 11C of which an opening ratio is smaller compared to other portions.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exhaust gas purification apparatus capable of improving exhaust gas purification performance.

An exhaust gas purification device is used in an automobile engine in order to improve exhaust gas purification performance.
In the honeycomb structure described in Patent Document 1, a plurality of cells communicating in parallel between two end faces are formed by a plurality of partition walls. A central region including a central axis is formed by a first partition wall having a first thickness on a surface perpendicular to a communication direction in which the cells communicate, and an outer peripheral region outside the central region is the first region. The second partition wall has a second thickness greater than the thickness of the first partition wall. The cell pitch in at least one direction of the outer peripheral region is larger than the cell pitch of the central region, the cell in the central region is a square cell, and the cells constituting the outer peripheral region are the central region It is a honeycomb structure having an opening ratio of 1.00 to 1.10 times that of the cell constituting the cell.

Japanese Patent No. 5730431

According to the prior art of the honeycomb structure described in Patent Document 1, the central region and the peripheral region can be obtained by reducing the opening ratio of the central portion of the honeycomb carrier where the exhaust gas flow is concentrated to be smaller than the opening ratio of the peripheral portion. The exhaust gas is circulated uniformly. As a result, the purification using the entire honeycomb carrier can be performed, and the exhaust gas purification performance can be improved.
However, in the structure in which the number of cells, the cell shape, or the thickness of the cell wall in the central region and the peripheral region of the honeycomb carrier are different, the manufacturing process of the honeycomb carrier is complicated.

  In the present invention, in a honeycomb carrier having substantially the same number of cells, cell shape, or cell wall thickness, the exhaust gas purification has a relatively large catalyst layer thickness in order to reduce the opening ratio of the portion where the exhaust gas flow is concentrated. An object is to provide an apparatus.

  In order to solve the above problems, the present invention provides an exhaust gas passage having a diameter expanded downstream of the exhaust gas passage, and disposing a honeycomb carrier provided with a catalyst layer in the enlarged exhaust gas passage, and the honeycomb carrier. In the region where the exhaust gas flow is concentrated, the upstream catalyst layer and the downstream catalyst layer are overlapped, and the catalyst layer has a radial thickness compared to other parts, and the opening ratio is compared with other parts This is because a region that becomes smaller is formed.

(A) Since the number of cells, cell shape, or cell wall thickness in the region where the exhaust gas flow to the honeycomb carrier is concentrated and the region other than the region where the exhaust gas flow is concentrated are substantially the same, the honeycomb carrier can be easily manufactured It is.
(B) Since the region where the catalyst layer is thick becomes resistance to the exhaust gas flow, the resistance of the concentrated region is increased. Therefore, the exhaust gas easily flows into the non-concentrated area.
(A) As a result, the flow velocity distribution of the exhaust gas flow can be made uniform. For this reason, the contact frequency between the catalyst layer carried on the outer peripheral portion and the exhaust gas increases. Accordingly, the exhaust gas purification performance is improved.
(B) Further, the temperature of the non-concentrated region can be increased more uniformly and quickly, and the supported noble metal can be efficiently used for purification. Therefore, the amount of noble metal can be reduced.
(C) Furthermore, the heat generation of the catalyst layer in the concentrated region and the non-concentrated region can be made uniform. Therefore, it is possible to suppress a decrease in performance due to thermal deterioration of the catalyst layer.
(C) The exhaust gas flowing in from the exhaust gas inlet, which is the upstream end of the honeycomb carrier, passes through the region where the catalyst layer is thick and becomes turbulent in the region where the thickness of the catalyst layer decreases. Therefore, the contact efficiency between the exhaust gas and the catalyst layer is increased. Therefore, the purification performance is improved.
(D) Since the amount of exhaust gas is approximately proportional to the rotational speed, the higher the rotational speed, the greater the amount of exhaust gas. When the amount of exhaust gas is small (the flow rate is slow) because the rotation speed is small, the exhaust gas is affected by the resistance of the concentrated area when the amount of exhaust gas is large (the flow rate is fast) because the rotation number is large. Easy to receive. For this reason, the exhaust gas tends to flow into the non-concentrated region as the rotational speed increases. Therefore, the effects (a) to (c) can be obtained particularly when the time for the exhaust gas to pass through the honeycomb carrier is short, particularly in the high rotation range.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows an exhaust gas purification apparatus provided with a honeycomb carrier according to an embodiment of the present invention, wherein (a) is a conceptual diagram, and (b) is a radial cross-sectional view of a central portion of the honeycomb carrier in the exhaust gas flow direction. 1 is a conceptual diagram showing a honeycomb carrier according to an embodiment of the present invention. It is a distribution map which shows the flow velocity distribution of the waste gas which flows into a honeycomb support | carrier. It is sectional drawing of the exhaust gas flow direction of the honeycomb support | carrier of this invention. It is radial direction sectional drawing of the exhaust gas flow direction center part of the honeycomb support | carrier of this invention. It is radial direction sectional drawing of the honeycomb support | carrier of this invention other than the exhaust gas flow direction center part. FIG. 2 shows an exhaust gas purifying apparatus equipped with a honeycomb carrier according to another embodiment of the present invention, in which (a) is a conceptual diagram, and (b) is a radial cross-sectional view of the central portion of the honeycomb carrier in the exhaust gas flow direction. FIG. 4 shows an exhaust gas purification apparatus including a honeycomb carrier according to another embodiment of the present invention, in which (a) is a conceptual diagram, and (b) is a radial cross-sectional view of a central portion of the honeycomb carrier in the exhaust gas flow direction.

Hereinafter, an exhaust gas purification apparatus including a honeycomb carrier according to an embodiment of the present invention will be described in detail with reference to the drawings shown in FIGS.

  FIG. 1 shows an exhaust gas purification device installed in an exhaust gas passage of an internal combustion engine such as an automobile. Reference numeral 1 denotes an exhaust gas purification device installed in the middle of an exhaust pipe 2 which is an exhaust gas flow path 20. A cylindrical enlarged exhaust gas passage 21 having an enlarged diameter is provided downstream of the exhaust gas passage 20 of the exhaust pipe 2, and the exhaust gas purification device 1 is installed in the enlarged exhaust gas passage 21. ing. The introduction port 20a of the exhaust gas flow channel 20 is provided on the same axis as the central axis of the expanded exhaust gas flow channel 21, and the discharge port 20b of the exhaust gas flow channel 20 is also disposed on the same axis.

As shown in FIGS. 1B and 2, the exhaust gas purification apparatus 1 includes two types of upstream side catalysts along the exhaust gas flow direction at the center of the exhaust gas flow direction of a carrier 10 provided with a large number of cells 10 a. It is composed of a honeycomb carrier 3 on which a layer 11A and a downstream catalyst layer 11B are supported in the axial direction.

FIG. 3 shows the flow velocity distribution of the exhaust gas flowing into the honeycomb carrier 3. When the aperture ratio of the honeycomb carrier 3 is uniform, the flow velocity distribution is as shown by the dotted line S ₀ , and the flow velocity distribution of the exhaust gas at the central portion of the honeycomb carrier 3 is higher than that of the outer peripheral portion. In contrast, in the exhaust gas flow direction center L = a1 as in the present invention, by reducing the aperture ratio of the center than the outer peripheral portion, the central portion becomes the flow velocity distribution as shown by the solid line S ₁ and the outer peripheral portion The difference in flow velocity distribution from

FIG. 4 shows a cross-sectional view of the honeycomb carrier 3 of the present invention in the exhaust gas flow direction. In L = a1, the upstream-side catalyst layer 11A in the center and the downstream-side catalyst layer 11B are overlapped and formed thick. The overlap portion 11C is laminated so that the upstream catalyst layer 11A is an upper layer of the downstream catalyst layer 11B. FIG. 5 shows a radial sectional view of the honeycomb carrier 3 at the center portion L = a1 in the exhaust gas flow direction. It has a cross-sectional structure in which a region B1 with a small aperture ratio is provided inside a region A1 with a large aperture ratio. FIG. 6 shows a cross section other than L = a1. Except for L = a1, the area A2 has a uniform aperture ratio. In the region A2 having a uniform aperture ratio other than L = a1, the size of the aperture may be the same as that of the region A1 having a large aperture ratio, or may be configured by apertures having different sizes.

In forming the catalyst layer of the honeycomb carrier 3 in the present invention, the catalyst slurry is impregnated from one end side of the carrier 10 to form a catalyst layer on one end side, and then the catalyst slurry is impregnated from the other end side to the catalyst slurry. Thus, it is obtained by a method of forming the catalyst layer on the other end side. In the method of forming the catalyst layer from both ends by inverting the carrier 10 as described above, the catalyst layer is overlapped at the central portion L = a1 in the exhaust gas flow direction, and the catalyst layer has a thickness compared to other portions. A region B1 having a small aperture ratio is formed. This region B1 is disposed at the center in the radial direction. The area A1 having a large aperture ratio in the outer peripheral portion is continuously formed without overlapping the catalyst layers. That is, the present invention is a structure for an exhaust gas catalyst in which B1 (small aperture ratio) is provided inside A1 (large aperture ratio) in the radially outer peripheral portion at the central portion L = a1 in the exhaust gas flow direction.

In addition, it is preferable to provide the region 11C where the upstream catalyst layer 11A and the downstream catalyst layer 11B overlap to form a thick catalyst layer in the radial direction on the upstream side from the axial center of the honeycomb carrier 3. . The region 11C where the catalyst layer is thick is provided so as to protrude in the radial direction along the axial direction for each flow path.
In the above embodiment, the exhaust gas flow channel 20 upstream of the honeycomb carrier 3 and the expanded exhaust gas flow channel 21 in which the honeycomb carrier 3 is disposed have the same central axis, and the respective cross sections are concentric circles. It is configured as follows. The catalyst layers of the upstream catalyst layer 11A and the downstream catalyst layer 11B are provided with a catalyst layer having a relatively high catalyst activity (corresponding to the upstream catalyst layer 11A) on the upstream side of the honeycomb carrier 3 so that the catalyst activity is high. A relatively low catalyst layer (corresponding to the downstream catalyst layer 11B) is provided on the downstream side of the honeycomb carrier 3, and a catalyst layer having high catalytic activity (corresponding to the upstream catalyst layer 11A) is provided to a catalyst layer having low catalytic activity ( A region 11f of (catalyst stacked portion 11C) having a thickness of the catalyst layer in the radial direction is formed so as to overlap an upper portion of the downstream catalyst layer 11B.

Explaining the operation of the above-described embodiment, an exhaust gas passage 21 having an enlarged diameter is provided downstream of the exhaust gas passage 20, and the exhaust gas purification device 1 is installed in the enlarged exhaust gas passage 21. (See FIG. 1).
The exhaust gas purifying device 1 is configured by a honeycomb carrier 3 in which two types of upstream catalyst layers 11A and downstream catalyst layers 11B are supported in the axial direction along the exhaust gas flow direction at the center of the exhaust gas flow direction. . In the honeycomb carrier 3, the upstream catalyst layer 11A and the downstream catalyst layer 11B are overlapped by overlapping the upstream catalyst layer 11A and the downstream catalyst layer 11B at the center portion L = a1 in the exhaust gas flow direction at the center portion in the radial direction. A catalyst layered portion 11C is formed by laminating the catalyst layer and forming a thick catalyst layer in the radial direction (see FIG. 4). Thereby, a region B1 having a smaller aperture ratio than other portions is formed (see FIG. 5).
Thus, in the exhaust gas flow direction center portion L = a1, by configuring the center portion having an opening ratio smaller than the opening ratio of the honeycomb carrier 3 outer peripheral portion, the pressure loss of the outer peripheral portion becomes smaller than that of the central portion, The flow velocity distribution of the exhaust gas concentrated in the central part can be made uniform, and the exhaust gas easily flows to the outer peripheral part. This increases the chances of contact with the catalyst carried on the outer peripheral portion and allows the outer peripheral portion to be heated and activated earlier, leading to improved exhaust gas purification performance.

The region 11f in which the catalyst laminated portion 11C of the overlapping portion where the catalyst layer is thick is provided upstream from the center of the honeycomb carrier 3 in the axial direction. When the gas passes through a1, the exhaust gas becomes turbulent, and the contact efficiency of the exhaust gas after passing with the catalyst increases, so that the purification performance increases.

The exhaust gas channel 20 upstream of the honeycomb carrier 3 and the expanded exhaust gas channel 21 in which the honeycomb carrier 3 is disposed have the same central axis and concentric sections, so that the exhaust gas is concentrated. A non-concentrated area exists around the entire circumference of the concentrated area. Therefore, compared with the case where the non-concentrated region is biased, the exhaust gas easily flows in the non-concentrated region as a whole.
(A) As a result, the flow velocity distribution of the exhaust gas flow can be made uniform. For this reason, the contact frequency between the catalyst layer carried on the outer peripheral portion and the exhaust gas increases. Accordingly, the exhaust gas purification performance is improved.
(B) Further, the temperature of the non-concentrated region can be increased more uniformly and quickly, and the supported noble metal can be efficiently used for purification. Therefore, the amount of noble metal can be reduced.
(C) Furthermore, the heat generation of the catalyst layer in the concentrated region and the non-concentrated region can be made uniform. Therefore, it is possible to suppress a decrease in performance due to thermal deterioration of the catalyst layer.

The region 11f in which the catalyst layered portion 11C is provided and the catalyst layer is thick is provided so as to protrude in the radial direction along the axial direction for each flow path. An extremely slow flow velocity distribution can be suppressed, and an effect of being easily uniform throughout can be obtained.

In the catalyst layer, a catalyst layer 11A having a relatively high catalytic activity is provided on the upstream side of the honeycomb carrier 3, and a catalyst layer 11B having a relatively low catalyst activity is provided on the downstream side of the honeycomb carrier 3, whereby a catalyst having a high catalyst activity is provided. Since the region 11f having the thickness of the catalyst layer in the radial direction is formed so that the layer 11A overlaps the upper part of the catalyst layer 11B having low catalyst activity, contact with the catalyst layer 11A having relatively high catalyst activity Increases efficiency. Therefore, the catalytic activity is improved.

7 and 8 show another embodiment of the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals, and the description of the same parts is omitted.

Figure 7 (a) (b) is shows the exhaust gas flow path 20 _{and second} inlet 20 ₂ a exhaust pipe connected to an end of the enlarged diameter exhaust passage 21 _{2 2 2,} exhaust gas passage 20 outlet 20 ₂ b ₂ is set to the inlet port 20 ₂ a symmetrical position of the exhaust gas flow path 20 _2. Diameter exhaust passage 21 ₂ honeycomb support 3 ₂ provided in the center of the small region B1 aperture ratio as compared with other portions on the same axis as inlet 20 2 _a of the exhaust passage 20 ₂ (See FIG. 7B).
Thus, since the inlet 20 2 _a and the opening ratio on the same axis of the exhaust gas passage 20 ₂ to concentrate much the flow of the exhaust gas is arranged smaller area B1 as compared with other portions, the exhaust gas opening Since the catalyst is dispersed in a portion having a high rate, the catalyst can be efficiently touched, and the exhaust gas purification performance can be improved.

Figure 8 (a) (b) is intended to inlet 20 ₃ a of the exhaust gas passage 20 ₃ is shown an exhaust pipe _{2 (3)} connected to the enlarged diameter exhaust passage 21 ₃ obliquely, the exhaust gas flow path 20 ₃ outlet 20 3 _b is installed on the same axis in the expanded exhaust gas passage 21 _3. The honeycomb support 3 ₃ provided on the enlarged diameter exhaust passage 21 _3, the center of the small region B1 aperture ratio as compared with other portions with the axis of the inlet 20 3 _a of the exhaust gas passage 20 ₃ crossover The axis line is arranged to do so. A region B1 in which the aperture ratio is smaller than that of the other portion is deviated from the center and is disposed slightly on the center side with respect to the inner peripheral surface (see FIG. 8B).
Thus, since the inlet 20 3 _a numerical aperture such that the axis line and axis crossing of the exhaust gas flow path 20 ₃ to concentrate much the flow of the exhaust gas is arranged smaller area B1 as compared with other portions Since the exhaust gas is dispersed in the portion having a large aperture ratio, the catalyst can be efficiently touched, and the exhaust gas purification performance can be improved.

As described above, in the actual engine layout, the position of the honeycomb carrier 3 is often shifted from the center of the exhaust gas inlet, so that the central axis of the region B1 having a small aperture ratio is aligned with the center of the exhaust gas inlet. The exhaust gas purification performance can be improved.

The present invention is not limited to the above-described embodiment. For example, the catalyst noble metals (Pt, Pd, Rh) contained in the upstream and downstream catalyst layers may be noble metals as in the conventional zone coat. It is also desirable that the concentration be (upstream side) ≧ (downstream side). Further, the application of the present technology is not limited to a ceramic honeycomb carrier, and the same effect can be obtained in a metal carrier. Needless to say, the present invention can be implemented with appropriate modifications within the scope not changing the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification apparatus 2 Exhaust pipe 3 Honeycomb carrier 10 Support | carrier 10a Cell 11A Upstream side catalyst layer 11B Downstream side catalyst layer 11C Catalyst lamination | stacking part 11f Area | region where catalyst layer is thick 20 Exhaust gas channel 20a Inlet 20b Exhaust port 21 Expanded exhaust gas channel A1 Area with large aperture ratio B1 Area with small aperture ratio A2 Area with uniform aperture ratio

Claims (5)

An exhaust gas passage having an enlarged diameter is provided downstream of the exhaust gas passage, and a honeycomb carrier provided with a catalyst layer is disposed in the exhaust gas passage having the enlarged diameter. The catalyst layer and the downstream catalyst layer are overlapped, the catalyst layer has a radial thickness compared to other parts, and a region where the aperture ratio is smaller than other parts is formed. Exhaust gas purification device. The exhaust gas purifying apparatus according to claim 1, wherein the region where the catalyst layer is thick is provided on the upstream side of the center in the axial direction of the honeycomb carrier. The exhaust gas flow channel upstream of the honeycomb carrier and the expanded exhaust gas flow channel in which the honeycomb carrier is arranged have the same central axis and the respective cross sections are concentric circles. 2. The exhaust gas purification apparatus according to 2. The exhaust gas purifying apparatus according to any one of claims 1 to 3, wherein the region where the catalyst layer is thick is provided so as to protrude in the radial direction along the axial direction for each flow path. The catalyst layer has a catalyst layer having a relatively high catalytic activity on the upstream side of the honeycomb carrier, a catalyst layer having a relatively low catalyst activity is provided on the downstream side of the honeycomb carrier, and a catalyst layer having a high catalyst activity is catalytically active. 5. The exhaust gas purifying apparatus according to claim 1, wherein a region having a thickness of the catalyst layer in the radial direction is formed so as to overlap with an upper part of a catalyst layer having a low level.

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