JP2012026420A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device capable of both achieving faster activation and thereby improved purification, and ensuring smooth exhaust emission and purification to ensure output, and to enable both purification during cold start and purification during high load to be achieved at a high level through use of a more optimal combination among known catalysts.SOLUTION: A carrier (28) of an upstream-side catalyst (26) has a cell density of 600 CPSI and a hexagonal unit cell (S1) shape. A carrier (31) of a downstream-side catalyst (27) has a cell density of 600 CPSI and a rectangular unit cell (S2) shape, while having a smaller diameter than the carrier (28) of the upstream-side catalyst (26).

Description

  The present invention relates to an exhaust gas purification device, and more particularly to an exhaust gas purification device in which a plurality of catalysts are arranged in a column.

Some internal combustion engines mounted on vehicles are provided with an exhaust gas purification device in which a plurality of catalysts (catalytic converters) are arranged in a column.
In general, palladium (Pd), rhodium (Rh), or platinum (platinum: Pt) is used in combination as a noble metal used for the catalyst carrier of the catalyst of the exhaust gas purifying apparatus. The trimetal contains three of these palladium (Pd), rhodium (Rh), and platinum (platinum: Pt).
The cross-sectional shape of the unit cell is a polygon such as a triangle, quadrangle, or hexagon, and the cell density (CPSI) per unit cross-sectional area (SI: square inch) in which these unit cells are arranged in a grid. : Cell per square inch) is different from 300, 400, 600, 800, etc., and it is known that there are various types of catalyst carriers only by combining them. In addition, the exhaust system as a whole has devised a combination of arrangements to ensure the performance required for improving the purification capacity.
That is, in the exhaust gas purifying apparatus, a plurality of catalysts are provided in tandem, an upstream catalyst is disposed immediately downstream of the internal combustion engine (especially the exhaust manifold), and the downstream catalyst is disposed in the middle of the exhaust pipe at a distance from the upstream catalyst. It is arranged.
In such a catalyst arrangement, harmful components of the exhaust gas immediately after the start of the internal combustion engine are activated by using the relatively high temperature exhaust gas exhausted from the internal combustion engine and activating the upstream catalyst relatively early. Can be purified from an earlier stage.
Also, the total purification performance is ensured by purifying the exhaust gas that could not be purified by the upstream catalyst, particularly when the load is high, by the downstream catalyst.
Thereby, in light of the operating state of the internal combustion engine, the state in which the catalyst is activated immediately after the start of the cold engine and the state in which the output is secured in a high load state during high speed running are completely different from each other. Both of these performances are satisfied.
In the exhaust gas control of the internal combustion engine at the time of cold start, the ignition timing is retarded, the temperature of the exhaust gas is increased, and the catalyst is activated early.

JP 2006-35070 A JP 2002-106333 A Japanese Patent No. 2800181

The catalyst device according to Patent Document 1 has a structure in which a first catalyst on the upstream side and a second catalyst on the downstream side each having a large number of cells are provided, and the cells of the catalyst carrier of the first catalyst have a quadrangular cross section. The cells of the catalyst support of the second catalyst have a hexagonal cross section, and the cell density of the catalyst support of the first catalyst is higher than the cell density of the catalyst support of the second catalyst.
The engine exhaust gas purification apparatus according to Patent Document 2 circulates most of the exhaust gas through the first part having a small degree of contact with the catalyst material in a situation where purification of the component to be purified is required, The purification of the reducing agent at the side catalyst is suppressed, and a sufficient reducing agent is supplied to the downstream catalyst.
In the internal combustion engine catalyst device according to Patent Document 3, a metal-based catalytic converter having a function of a starter catalytic converter is disposed on the upstream side, and a ceramic-based catalytic converter is disposed on the downstream side.

By the way, in the conventional exhaust gas purifying apparatus, the demand for improving the purification capacity of the exhaust system as a whole is further increased. The state in which the catalyst is activated immediately after the start of the cold engine of the internal combustion engine, It is necessary to achieve a higher level in each of completely different states from the state in which the output is secured in the load state.
In other words, faster activation, improved purifying performance, and smooth exhaustability that can ensure engine output and securing purifying performance are both required.
And even if it combines the catalyst from which a characteristic differs in order to aim at those compatibility, the selection is very difficult.
That is, when compared with a catalyst carrier having the same outer dimensions, the larger the cell density, the larger the surface area inside the catalyst carrier, and the maximum purification capacity per unit cross-sectional area increases. The cross-sectional area of the passage becomes smaller and the ventilation resistance tends to increase.
In addition, when compared as catalyst carriers having the same outer dimensions, even if the cell density is the same, the substantial passage length in each unit cell becomes larger as the polygon of the cross-sectional shape of the unit cell becomes closer to a circle. While the air resistance increases and the ventilation resistance decreases, the surface area inside the catalyst carrier decreases, and the maximum purification capacity per unit cross-sectional area tends to decrease.
On the other hand, it is generally known that a lattice in which the unit cell has a hexagonal shape, that is, a so-called honeycomb structure, is known to be light and highly rigid. Because of this trade-off, it is difficult to balance.
Further, in an internal combustion engine with a small displacement, the amount of heat that can be generated in one combustion is relatively small, and if the heat capacity of the catalyst carrier is large, the time until activation tends to be long. The necessity of suppressing the heat capacity of the catalyst carrier for early activation has been relatively higher for small displacements.
In addition, simply increasing the cell density of the catalyst carrier increases the maximum purification capacity during activation, but structurally increases the heat capacity of the catalyst carrier. There was inconvenience that it became difficult.

  Accordingly, an object of the present invention is to achieve both faster activation and improvement in purification performance, smooth exhaustability that can ensure engine output, and purification, and an optimal combination among known catalyst carriers. Accordingly, it is an object of the present invention to provide an exhaust gas purifying apparatus that can achieve both a cleanability at cold start and a cleanability at high load at a high level.

  The present invention relates to an exhaust gas purifying device in which a plurality of catalysts are arranged in tandem in an exhaust device of an internal combustion engine, wherein the upstream catalyst is the most upstream position of an exhaust pipe connected to the exhaust manifold of the internal combustion engine, and the downstream catalyst is In the exhaust gas purifying apparatus having a downstream position of the exhaust pipe separated from the upstream catalyst, the catalyst support of the upstream catalyst has a cell density of 600 CPSI and a unit cell shape of a hexagon, and the catalyst support of the downstream catalyst Is made smaller than the catalyst support of the upstream catalyst, the cell density is 600 CPSI, and the unit cell shape is a quadrangle.

  The exhaust gas purifying apparatus of the present invention achieves both faster activation and improvement in purifying performance, and smooth exhaustability and purifying performance that can ensure engine output, and is the most optimal combination among known catalyst carriers. This makes it possible to achieve both cleanliness at cold start and cleanliness at high load at a high level.

FIG. 1 is a side view of a vehicle equipped with an exhaust gas purification device. (Example) FIG. 2A is a cross-sectional view of the catalyst carrier of the upstream catalyst. FIG. 2B is an enlarged cross-sectional view of the hexagonal cell shape of the catalyst carrier of the upstream catalyst. (Example) FIG. 3A is a cross-sectional view of the catalyst carrier of the downstream catalyst. FIG. 3B is an enlarged cross-sectional view of a square cell shape of the catalyst carrier of the downstream catalyst. (Example)

  The present invention aims to achieve both faster activation and improvement in purification performance, smooth exhaustability that can ensure engine output, and ensuring purification performance, and a more optimal combination of known catalyst carriers at the time of cold start. The catalyst support for the upstream catalyst, the cell density of 600 CPSI and the unit cell shape as a hexagon, the catalyst support for the downstream catalyst, The cell density is 600 CPSI and the unit cell shape is realized as a quadrangle while having a smaller diameter than the catalyst carrier of the upstream catalyst.

1 to 3 show an embodiment of the present invention.
In FIG. 1, 1 is a vehicle, 2 is a floor panel, and 3 is a multi-cylinder internal combustion engine with a supercharger mounted on the front of the vehicle 1. The internal combustion engine 3 includes a cylinder block 4, a cylinder head 5, and a head cover 6, and the crankshaft direction is arranged toward the vehicle width direction (vehicle left-right direction).
The cylinder block 4 is provided with a piston 8 that can reciprocate within the cylinder 7.
An intake port 9 on the vehicle rear side and an exhaust port 10 on the vehicle front side are formed in the cylinder head 5 so as to communicate with the combustion chamber 11.
The cylinder head 5 is provided with an intake cam shaft 12 and an exhaust cam shaft 13, and is operated by an intake valve 14 and an exhaust cam shaft 13 that are operated by the intake cam shaft 12 to open and close the intake port 9. An exhaust valve 15 that opens and closes the exhaust port 10 is provided.
The internal combustion engine 3 is provided with an intake device 16 on the vehicle rear side and an exhaust device 17 on the vehicle front side.
The intake device 16 includes an intake manifold 18 that communicates with the intake port 9 and is attached to the rear portion of the cylinder head 5. A fuel injection valve 19 that injects fuel into the intake port 9 is attached to the intake manifold 18.
The exhaust device 17 includes an exhaust manifold 20 connected to the exhaust port 10 and attached to the front portion of the cylinder head 5, an exhaust pipe 21 connected to the exhaust manifold 20, and a muffler provided on the downstream end side of the exhaust pipe 21. 22.
In the exhaust manifold 20, a turbine 24 of the supercharger 23 is disposed at the downstream end.

Further, the exhaust device 17 is provided with an exhaust gas purification device 25 below the center tunnel portion of the floor panel 2 and between the supercharger 23 and the muffler 22.
The exhaust gas purification device 25 has a structure in which an upstream catalyst (front catalyst) 26 and a downstream catalyst (rear catalyst) 27 are arranged in a column as a plurality of catalysts (catalytic converters).
The upstream catalyst 26 is disposed at the most upstream position of the exhaust pipe 21 connected to the exhaust manifold 20 of the internal combustion engine 3, holds the upstream catalyst carrier 28 with the upstream supporter 29, and further, this upstream supporter 29 is upstream. It is configured to be stored in a storage case (container) 30.
The downstream catalyst 27 is disposed at a downstream position of the exhaust pipe 21 spaced from the upstream catalyst 26, holds the downstream catalyst carrier 31 with the downstream supporter 32, and further holds the downstream supporter 32 in the downstream storage case ( Container) 33.
The exhaust pipe 21 includes an upstream exhaust pipe 34 connected to the downstream end of the upstream storage case 30 and a downstream exhaust pipe 35 provided with a muffler 22. The downstream end of the upstream exhaust pipe 34 and the upstream end of the downstream storage case 33 are connected by an upstream connecting portion 36. The downstream end of the downstream storage case 33 and the upstream end of the downstream exhaust pipe 35 are connected by a downstream connecting portion 37.

As shown in FIGS. 1 and 2, the upstream side catalyst carrier 28 of the upstream side catalyst 26 is formed with a predetermined outer diameter D1 and a predetermined length L1, and has a cell density of 600 CPSI (CPSI). -Square inch) and the unit cell (S1) has a hexagonal shape. The cell pitch of the hexagonal unit cell (S1) is CP1, as shown in FIG. The upstream catalyst carrier 28 is, for example, an HC trap coated with a palladium (Pd) / rhodium (Rh) catalyst, a trimetal catalyst, a platinum (platinum: Pt) / rhodium (Rh) catalyst, or a zeolite as a ceramic material. It is formed using a type of catalyst or the like, and is disposed immediately after the supercharger 23, thereby improving the catalytic activity when the internal combustion engine 3 is cold-started. The upstream catalyst carrier 28 may be a zone coating catalyst in which precious metal species / amounts or coating components at the inlet and outlet are separately applied.
Further, as shown in FIGS. 1 and 3, the downstream catalyst carrier 31 of the downstream catalyst 27 has an outer diameter D2 smaller than the outer diameter D1 of the upstream catalyst carrier 28 and a predetermined length L2. However, the cell density is 600 CPSI and the shape of the unit cell (S2) is a square. The cell pitch of the rectangular unit cell (S2) is CP2 smaller than the above-mentioned CP1, as shown in FIG. Even if the downstream catalyst carrier 31 cannot purify all of the exhaust gas under engine load conditions (for example, 70 Km / h or more) such as high speed running, the downstream side catalyst carrier 31 does not exhaust the exhaust gas as a whole vehicle. It is something to purify. The downstream catalyst carrier 31 is coated with, for example, a palladium (Pd) / rhodium (Rh) catalyst, a trimetal catalyst, a platinum (platinum: Pt) / rhodium (Rh) catalyst, or zeolite as a ceramic material. It is also possible to form a zone coating catalyst that is formed using an HC trap type catalyst or the like, or in which noble metal species / amounts or coating components at the inlet and outlet are separately applied. Further, the outer diameter D2 of the downstream catalyst carrier 31 is substantially half of the outer diameter D1 of the upstream catalyst carrier 28. Further, the length L2 of the downstream catalyst carrier 31 is set to be shorter than the length L1 of the upstream catalyst carrier 28.
By such a structure of the upstream catalyst carrier 28 and the downstream catalyst carrier 31, the heat capacity of the upstream catalyst carrier 28 of the upstream catalyst 26 is lowered to enable early activation, thereby effectively purifying the exhaust gas. The time to do this can be lengthened and the total cooling performance can be improved. Further, the downstream catalyst carrier 31 of the downstream catalyst 27 is made to have a small diameter, the heat capacity is lowered to prevent thermal contraction (the temperature is difficult to decrease when warmed), and sufficient exhaust gas purification performance is ensured even with a small catalyst carrier. Can do. Furthermore, since the cell density is relatively high, even if the effective passage diameter of the exhaust gas varies depending on the unit cell shape, a high catalyst purification capacity can be secured.

As shown in FIGS. 2B and 3B, the wall thickness (rib thickness) WT1 of the wall W1 constituting the hexagonal unit cell S1 of the upstream catalyst carrier 28 of the upstream catalyst 26 is: The wall thickness (rib thickness) WT2 of the wall W2 constituting the rectangular unit cell S2 of the downstream catalyst carrier 31 of the downstream catalyst 27 of the same cell density is formed.
As a result, not only can the temperature increase gradient be increased to enable early activation, but the effective diameter of the passage can be slightly increased, and a smooth gas flow can be ensured over the entire catalyst cross section. As a result, the pressure loss of the exhaust gas can be reduced and the engine output can be prevented from decreasing. Further, by making the downstream side catalyst carrier 31 of the downstream side catalyst 27 small in diameter and not having a thin wall, heat shrinkage can be prevented and sufficient exhaust gas purification performance can be ensured even with a small catalyst carrier.

Further, as shown in FIG. 1, the downstream storage case 30 of the downstream catalyst 26 is formed to have a length L3 that is longer than the length L2 of the downstream catalyst carrier 31. In the downstream storage case 30, the downstream catalyst carrier 31 is packed upstream so that a volume chamber 38 of a required space is formed on the downstream side of the downstream catalyst carrier 31.
As a result, the exhaust gas can be expanded after the downstream side catalyst carrier 31 (downstream side), and the downstream side catalyst carrier 31 can be brought into an active state or kept at a high temperature so as not to cause heat sink. In addition, since the exhaust gas is expanded immediately after being slightly throttled, the noise reduction efficiency can be increased.

Hereinafter, the invention according to this embodiment will be described more specifically.
The upstream side catalyst 26 is located at the most upstream position of the exhaust pipe 21 connected to the exhaust manifold 20, that is, along the exhaust gas flow, spatially, directly downstream of the exhaust manifold 20, or in the exhaust. It is provided directly downstream of the supercharger 23 attached directly to the manifold 20. In the case of the multi-cylinder internal combustion engine 3, the upstream side catalyst 26 is disposed at a position where exhaust gases from the respective cylinders gather and prioritize early activation after starting from the cold state. Has been. In the arrangement of the upstream catalyst 26, it is desirable to reduce the ventilation resistance so as to ensure a smooth flow in order to ensure the engine output.
The upstream side catalyst carrier 28 of the upstream side catalyst 26 is a ceramic 600-hexagonal cell catalyst, that is, the cell density is relatively high 600 (CPSI), and the unit cell (S1) has a hexagonal shape. It is said. Since the shape of the hexagonal unit cell (S1) is a polygon that is closer to a circle than the shape of the square unit cell (S2), the effective diameter of the passage through which the exhaust gas passes can be increased. Thereby, by reducing the total amount of wall thickness by changing the structure, the heat capacity of the upstream catalyst carrier 28 is lowered, the temperature rising gradient is increased, and early activation is enabled, thereby increasing the time for effective purification. And improve the total cooling performance.
Further, as shown in FIGS. 2B and 3B, the upstream catalyst carrier 28 immediately below the internal combustion engine 3 has a larger diameter than the downstream catalyst carrier 31, and is further formed in the unit cell (S1). The partitioning wall W1 is a thin wall (for example, a difference of about 10% of the wall W2 partitioning the unit cell (S2)). This thin wall W1 not only increases the temperature rising gradient and enables early activation, but also allows the effective diameter of the passage to be increased slightly, and the flow of exhaust gas is smooth over the entire cross section. By ensuring the above, it is possible to reduce the pressure loss of the exhaust gas and prevent the engine output from decreasing. As a result, the exhaust gas can be discharged smoothly at a high rotation and high load when a large amount (high pressure) of the exhaust gas is discharged per time.
Furthermore, reaction heat is generated due to activation, which can be used early, and pressure loss is suppressed to a low level, so that relatively high-temperature exhaust gas can be supplied to the downstream catalyst carrier while maintaining a high flow rate. 31 and can be activated early on the downstream side.

On the other hand, as shown in FIG. 1, the downstream catalyst 27 is a downstream position at a sufficient distance from the upstream catalyst 26, and is disposed below the center tunnel portion of the floor panel 2 of the vehicle 1.
The downstream catalyst carrier 31 of the downstream catalyst 27 is a ceramic 600-square cell catalyst having a smaller diameter than the upstream catalyst carrier 28, that is, the cell density is 600 (CPSI) and the unit cell shape is a square. The diameter is made small to ensure the purification performance in the high load region after warming up. Further, since the downstream catalyst carrier 31 has a small diameter and is not made thin, heat shrinkage is prevented (the temperature is difficult to decrease when warmed), and even a small downstream catalyst carrier 31 can ensure sufficient purification performance. Furthermore, by setting the cell density to 600 (CPSI), the surface area can be increased and high purification performance can be ensured.
The rectangular unit cell (S2) has a larger surface area and a smaller outer dimension of the downstream catalyst carrier 31 compared to the hexagonal unit cell (S1) having the same dimensions, the same cell density, and the same wall thickness. By doing so, the total area and heat capacity are reduced. Since the total number of unit cells (S2) is smaller than that of the upstream side catalyst carrier 28, the amount of exhaust gas flowing per unit cell is relatively increased, and the amount of heat received per unit cell is also increased. The effect of preventing heat shrinkage can be enhanced.

The upstream catalyst carrier 28 and the downstream catalyst carrier 31 have the following relationship.
The upstream catalyst carrier 28 has a larger diameter than the downstream catalyst carrier 31 having the same cell density, a large effective passage diameter, and a thin wall. This is because the upstream catalyst carrier 28 has a larger diameter than the downstream catalyst carrier 31 having the same cell density, so that the effective passage diameter of each unit cell is large while lowering the average exhaust gas flow rate of each unit cell. Ventilation resistance is reduced by this, pressure loss is reduced, and the temperature rise is increased by being a thin wall.
Conversely, the downstream catalyst carrier 31 has a smaller diameter than the upstream catalyst carrier 28 having the same cell density, a smaller effective passage diameter, and a thick wall W2. This is because the downstream catalyst carrier 31 has a smaller diameter than the upstream catalyst carrier 28 having the same cell density, so that the average exhaust gas flow rate of each unit cell is increased and the effective passage diameter of each unit cell is small. By ensuring the surface area, the purification performance is ensured, and the thick wall W2 enhances the anti-heat resistance. The method of suppressing the heat capacity is different between the upstream catalyst carrier 28 and the downstream catalyst carrier 31. Even if the upstream catalyst carrier 28 and the downstream catalyst carrier 31 have the same heat capacity as well as the cell density, the same applies.

Further, the downstream catalyst 27 is formed with a cylindrical downstream storage case 33 that is sufficiently long along the extending direction of the exhaust pipe 21, and the downstream catalyst carrier 31 is packed in front of the downstream storage case 33. The volume chamber 38 is formed on the downstream side of the downstream side catalyst carrier 31. The cylindrical downstream storage case 33 is formed to be sufficiently long, for example, about twice as large as the size of the downstream catalyst carrier 31, and the outer diameter of the body portion is substantially uniform. The diameter is the same as that of the exhaust pipe 21 by the portion 33A and the reduced diameter portion 33B).
The downsizing of the downstream catalyst 27 is advantageous in securing the volume of the volume chamber 38. Here, the volume chamber 38 is approximately the same as the volume of the downstream catalyst carrier 31. Further, by setting the exhaust gas expansion substantially first after the downstream side catalyst carrier 31, that is, after the series of purification actions by the multistage catalyst is completed, in particular, the downstream side catalyst carrier 31 is The downstream catalyst carrier 31 can be kept at a high temperature so that the active state is accelerated and the heat sink does not occur.
The volume chamber 38 functions as an expansion silencer (sub-chamber) and expands immediately after being slightly throttled by the small-diameter downstream side catalyst carrier 31, so that the silencing efficiency is also increased. In addition, since the back pressure of the downstream catalyst carrier 31 is reduced, even if the overall cross-sectional area is slightly reduced by reducing the diameter of the downstream catalyst carrier 31, the pressure gradient becomes large and the exhaust efficiency can be secured.

Further, in the upstream catalyst carrier 28 and the downstream catalyst carrier 31, the hexagonal shape of the cross section of the unit cell (S1) and the quadrilateral shape of the cross section of the unit cell (S2) are 600 cells (CPSI). The unit area per cell is the same.
When considering one cell in cross section, since both are composed of only walls and spaces (passages), it is sufficient to compare only the walls geometrically. And since the wall of a cell is shared by adjacent cells, the wall is halved with respect to one cell. Since the hexagon has six sides, it can be considered as half of the three sides, and the quadrangle has four sides, which is half of the two sides. The ratio of the lengths of the hexagons and the sides of the rectangle with the same area is roughly calculated: 3 sides of the hexagon: 2 sides of the rectangle = 1.86: 2, and the hexagon has a shorter wall length. I understand that. And if it is a catalyst carrier with the same dimension, it is the same as the length of total extension.
And comparing the two, the short wall length means that if the wall thickness is the same, the heat capacity will be small. The small heat capacity causes an increase in temperature that rises for the same amount of heat received from the exhaust gas, leading to early activation during cold start.
At the same time, however, the short wall length means that the surface area of the wall is also reduced. If the surface area of the wall is narrow, it means a decrease in the maximum purification capacity, which is not preferable. For example, when the outer dimensions are changed in order to equalize the purification capacity, there is a problem that the storage case for storing the catalyst carrier is increased in size.
In the upstream side catalyst carrier 28 in which the unit cell S1 is hexagonal, the wall thickness (rib thickness) WT1 is set so that the unit cell S2 is thinner than the square wall thickness (rib thickness) WT2. . In other words, the wall thickness is made thinner than that of the square-cell catalyst carrier having the same specific surface area. As a result, the length of the wall as a connection is slightly increased as the wall thickness is reduced, and the surface area of the wall can be slightly increased.
And if the surface area of the wall is increased, it means that the purification ability is improved, and furthermore, the heat capacity becomes smaller, which can lead to early activation. At the same time, since the cross-sectional area of the passage is relatively wide and the corresponding effective diameter is also large, the ventilation resistance can be reduced and the exhaust efficiency at high loads is excellent.

Further, the volume obtained from the catalyst capacity and the outer dimensions of the upstream catalyst carrier 28 is set to be approximately the same as or slightly smaller than the total displacement of the internal combustion engine 3.
In addition, vehicles with small displacements, particularly vehicles with specific small displacements such as light vehicles, tend to have a relatively large “catalyst capacity / engine displacement”. The absolute value of the capacity is small. On the other hand, a vehicle with a small displacement has a high engine speed in comparison between the same running resistances, and requires a wide operating range of the internal combustion engine when reproducing a determined running pattern.

  The exhaust gas purifying apparatus according to the present invention can be applied to various vehicles.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Floor panel 3 Internal combustion engine 17 Exhaust device 20 Exhaust manifold 21 Exhaust pipe 22 Muffler 23 Supercharger 25 Exhaust gas purification device 26 Upstream catalyst 27 Downstream catalyst 28 Upstream catalyst carrier 30 Upstream storage case 31 Downstream catalyst Carrier 33 Downstream storage case 38 Volume chamber

Claims (3)

  An exhaust gas purifying device in which a plurality of catalysts are arranged in tandem in an exhaust device of an internal combustion engine, wherein the upstream catalyst is the most upstream position of an exhaust pipe connected to the exhaust manifold of the internal combustion engine, and the downstream catalyst is the upstream catalyst In the exhaust gas purifying apparatus at the downstream position of the exhaust pipe separated from the exhaust pipe, the upstream catalyst support is a catalyst density of 600 CPSI and the unit cell shape is a hexagon, and the downstream catalyst support is the upstream catalyst support. An exhaust gas purifying apparatus characterized by having a cell density of 600 CPSI and a unit cell shape of a square while having a smaller diameter than the catalyst support of the side catalyst.   The wall thickness constituting the hexagonal unit cell of the catalyst support of the upstream catalyst is formed thinner than the wall thickness constituting the square unit cell of the catalyst support of the downstream catalyst having the same cell density, The exhaust gas purification device according to claim 1.   A storage case for the downstream catalyst is formed longer than the catalyst carrier for the downstream catalyst, and a volume chamber is formed on the downstream side by packing the catalyst carrier for the downstream catalyst upstream in the storage case for the downstream catalyst. The exhaust gas purification device according to claim 1 or 2, wherein the exhaust gas purification device is formed.

Images