JPS6114568Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a catalytic exhaust gas purification device that purifies exhaust gas from a multi-cylinder internal combustion engine through the action of a catalyst.

In recent years, monolithic catalysts have been used as catalysts for purifying exhaust gas in internal combustion engines, instead of pellet-type catalysts as described in, for example, Japanese Utility Model Application No. 53-130308 or 1987-159406. ing.

When the catalyst for purifying exhaust gas is a pellet type as in the above-mentioned publication, the exhaust gas passages formed in the catalyst layer are zigzag shaped and communicate with each other. In the case where exhaust gas from each cylinder of a multi-cylinder engine is introduced into a catalyst case housed in the catalyst case, distribution is hardly a problem.

However, when the catalyst is the above-mentioned monolithic catalyst, consideration must be given to the distribution of exhaust gas from each cylinder when it is introduced into the catalyst case.

In other words, this monolithic catalyst is a cylindrical ceramic body with a large number of small holes closely spaced in its axial direction to form a so-called spiral shape, and the catalyst material is held on the inner surface of each of the small holes. Since the exhaust gas flows straight through the pores without any resistance while coming into contact with the catalyst material on the wall of each pore, this monolithic catalyst has the characteristic that the flow resistance of the exhaust gas is lower than that of the pellet-type catalyst. On the other hand, the exhaust gas that enters each small hole does not enter or exit from adjacent small holes, and only passes through one small hole, so the exhaust gas from the engine is evenly distributed to all small holes. It must be distributed so that it flows.

However, when this monolithic catalyst is applied to a multi-cylinder internal combustion engine, it is not only structurally extremely difficult to guide exhaust gas from each cylinder evenly and uniformly to the countless small holes in the monolithic catalyst. , a drift will occur due to the influence of exhaust gas interference.

Therefore, Japanese Patent Application Laid-open No. 54-47923 as a prior art proposes that when this monolithic catalyst is applied to a multi-cylinder engine, the exhaust gas from each cylinder is transferred to the numerous small holes in the monolithic catalyst in the head chamber of the monolithic catalyst case. It is proposed that guide walls or the like installed in the holes be used to separate and guide small hole groups at different locations.

However, with this method, the exhaust gas from each cylinder is released intermittently according to the ignition order, and the small holes where the exhaust gas from a certain cylinder enters are exposed to the heat of the exhaust gas itself. Due to the heat of reaction, the temperature becomes higher than the small hole group where the exhaust gas has stopped flowing, and the monolith catalyst does not reach a uniform temperature.
Because there are repeated significant temperature differences at various locations, not only will the monolith catalyst break or the catalyst deteriorate due to thermal distortion, but the temperature at the small holes where exhaust gas from each cylinder enters is low, resulting in a reduction in the purification rate. Therefore, the monolith catalyst must be made large. Moreover, in supplying secondary air to this, the exhaust gas from a certain cylinder is
Supplying secondary air only enters the small hole group where the exhaust gas to which it is supplied is led, so secondary air must be supplied for each exhaust gas in each cylinder. It's inconvenient.

The present invention aims to solve the above-mentioned problems when applying a monolith catalyst to a multi-cylinder internal combustion engine.

For this reason, the present invention provides a monolith catalyst having a large number of holes in the axial direction in a catalyst case with a head chamber so that the inlet side end face of the monolith catalyst faces into the head chamber, In an exhaust gas purification device that connects exhaust pipes from each cylinder in an in-line multi-cylinder internal combustion engine, the axis of the connection opening to the head chamber in the exhaust pipe from each cylinder of the engine is It is inclined with respect to the inlet side end face of the monolithic catalyst, and connects both outer exhaust pipes from two outer cylinders of each cylinder of the engine so as to face each other with respect to the head chamber in plan view, The connection opening of one of these two outer exhaust pipes into the head chamber is designed to guide exhaust gas to a region of the inlet side end face of the monolithic catalyst that is far from the one outer exhaust pipe. Attach the guide part to the connection opening of the other outer exhaust pipe into the head chamber.
Each guide portion is provided to guide exhaust gas to a region of the inlet side end face of the monolithic catalyst that is far from the other outer exhaust pipe; The connecting opening of the exhaust pipe to the head chamber is configured so that the exhaust gas in the inner exhaust pipe is guided to the entire area of the inlet side end face of the monolithic catalyst.

With this configuration, exhaust gas from both outer exhaust pipes is directed to the respective outer cylinders against the inlet side end face of the monolithic catalyst at the guide portion provided at the connection opening of both outer exhaust pipes to the head chamber. While the exhaust gas from the inner cylinder can be guided to the entire area of the inlet side end face of the monolith catalyst, the exhaust gas from the inner exhaust pipe can Therefore, it is possible to increase the catalyst temperature in the portion where exhaust gas from one of the two outer exhaust pipes enters, and it is also possible to increase the catalyst temperature in the portion where exhaust gas from the other outer exhaust pipe enters. On the other hand, the temperature of the catalyst when exhaust gas enters from the inner exhaust pipe can be raised by the exhaust gas from both outer exhaust pipes in the previous exhaust stroke, and by repeating this process, the temperature of the catalyst can be increased when the exhaust gas enters from the inner exhaust pipe. The monolithic catalyst applied to the engine can be maintained at a high temperature without temperature fluctuations.

Therefore, according to the present invention, it is possible to reduce the tearing of the monolith catalyst due to thermal distortion and the deterioration of the monolith catalyst due to repeated high and low temperatures, and it is possible to improve the durability of the monolith catalyst and the purification rate by the monolith catalyst. At the same time, it has the effect of making the monolith catalyst smaller.

Furthermore, in the present invention, the connection opening of the inner exhaust pipe into the head chamber of each exhaust pipe is configured to guide the exhaust gas from the inner exhaust pipe to the entire area of the inlet side end face of the monolithic catalyst. By simply supplying secondary air to this inner exhaust pipe, the secondary air can be distributed over the entire area of the monolith catalyst, so there is no need to supply secondary air to each exhaust pipe from each cylinder. The structure for supplying secondary air can be significantly simplified, and an increase in space and weight can be avoided when supplying secondary air.

Next, an embodiment in which an example of the present invention is applied to an in-line three-cylinder internal combustion engine will be explained with reference to a drawing. A three-cylinder internal combustion engine is shown, and the ignition is carried out in the first cylinder 11 - second cylinder 12 -
The order of the third cylinder 13, and the ignition interval is 240
They are spaced at equal intervals of °, and each cylinder has one exhaust port.
1', 12', and 13'.

20 is an exhaust pipe 21, 2 connected to each cylinder.
2 and 23; 30 is a catalyst case; 31 is a case cover attached to the top surface of the catalyst case 30; 32 is an exhaust gas atmosphere discharge pipe connected to the outlet of the catalyst case 30; A monolithic catalyst 33 is made of a cylindrical ceramic body with countless small holes 34 formed in the axial direction, and a catalyst substance held on the inner surface of each small hole 34.
However, the inlet side end face 3 of the monolithic catalyst 33
3' is provided so as to look into the head chamber 35 within the case cover 31.

Then, each exhaust pipe 21, 22, 23 in the exhaust manifold 20 is connected to the case cover 3.
The exhaust pipes 21, 22, 23 from each cylinder of the engine 10 are integrally connected to the upper surface of the case cover 31 so as to open the head chamber 35 in the engine 10.
a connection opening 21a to the case cover 31,
The axes 21b, 22b, 23b of 22a, 23a are inclined obliquely downward with respect to the inlet side end surface 33' of the monolithic catalyst 33 in side view in FIGS. 2 and 3.

Further, both outer exhaust pipes 2 from two outer cylinders 11 and 13 of each cylinder of the engine 10 are provided.
1 and 23 are connected to the case cover 31 so as to face each other in plan view in FIG. The connecting opening 21a is connected to the outer exhaust pipe 21 of the inlet side end face 33' of the monolithic catalyst 33.
Guide part 2 that guides the guide to an area far from the
1' and 21'' into the head chamber 35 of the other outer exhaust pipe 23, the exhaust gas is connected to the inlet side end face 33' of the monolithic catalyst 33 far from the other outer exhaust pipe 23. Guide portions 23' and 23'' are provided respectively to guide the guide portions to the respective regions.

Furthermore, the head chamber 3 of the inner exhaust pipe 22 from the inner cylinder 12 of each cylinder of the engine 10
As shown in FIG. 2, due to the presence of the inclined ceiling surface 31' and/or the enlarged chamber 31'' of the case cover 31, the exhaust gas in the inner exhaust pipe 22 is connected to the monolithic catalyst. 33 so as to lead to substantially the entire area of the inlet side end surface 33'.

In addition, 36 is a socket provided in the exhaust pipe 23 of the third cylinder or the exhaust pipe 21 of the first cylinder for extracting exhaust gas when the exhaust gas is recirculated to the intake system, and 37 is a socket provided in the exhaust pipe 22 of the second cylinder. The secondary air supply sockets are shown in each figure.

With this configuration, the exhaust gas released from the first cylinder 11 to one of the outer exhaust pipes 21 is
Due to the guiding action of the guide portions 21' and 21'' provided in the connection opening 21a of the exhaust pipe 21, a region of the inlet side end face 33' of the monolithic catalyst 33 that is farther from the outer exhaust pipe 21, that is, The harmful gas components in the exhaust gas are guided toward a region approximately directly below the connection opening 23a of the other outer exhaust pipe 23, and enter the small pores of the monolith catalyst 33 in this region, and while passing through this, harmful gas components in the exhaust gas are oxidized. While being purified by the reduction reaction, the temperature of the catalyst near the small hole group increases due to the heat of the exhaust gas and the heat of reaction.Then, the exhaust gas from the second cylinder 12 is transferred to the connection opening of the inner exhaust pipe 22. 22 to monolith catalyst 3
The harmful gas components are introduced into the entire area of the inlet side end surface 33' in the monolithic catalyst 33, and are purified by redox reaction through all the small holes 34 in the monolith catalyst 33, and are purified by the heat of the exhaust gas and the reaction heat. 1 cylinder 1
The catalyst temperature near the small hole group through which the exhaust gas from No. 2 passes is maintained high, and the catalyst temperature on the opposite side, that is, No.
The catalyst temperature in the vicinity of the small hole group at a portion substantially directly below the connection opening 21a of the exhaust pipe 21 from the cylinder 11 is increased. The exhaust gas released from the third cylinder 13 to the other outer exhaust pipe 23 is
A guide portion 23' provided in the connection opening 23a of the
23'', the inlet end face 33' of the monolithic catalyst 33 is located in a region farther from the other outer exhaust pipe 23, that is, in a region substantially directly below the connection opening 21a of one outer exhaust pipe 21. The gas enters the small pores of the monolith catalyst 33 in the region, where harmful gas components are purified and the catalyst temperature near the small pores is kept high.

In other words, the exhaust gas from the second cylinder maintains the catalyst temperature near the small hole group through which the exhaust gas from the first cylinder passes at a high temperature, and also maintains the catalyst temperature near the small hole group through which the exhaust gas from the third cylinder passes. The exhaust gas from the third cylinder enters the small hole group whose temperature has been raised by the exhaust gas from the second cylinder, raising the catalyst temperature. Exhaust gas from the first cylinder enters the small hole group whose temperature has been raised by the exhaust gas from the second cylinder and increases its temperature. Furthermore, the exhaust gas from the second cylinder enters all the small hole groups whose temperature has been raised by the exhaust gas from the first and third cylinders, and repeats the process of increasing the temperature of all the small hole groups.

In this case, as taught in Japanese Unexamined Patent Publication No. 54-47923 mentioned above, the countless small holes in the monolith catalyst are divided into three cylinder groups, and each small hole group is connected to the exhaust gas from each cylinder. When guiding gas separately,
Since the exhaust gas is introduced twice into each small hole group, the catalyst temperature drops considerably during that time, and the exhaust gas is guided to the place where the temperature is lower, which improves the purification rate of combustible harmful gas components. As the temperature decreases, severe temperature unevenness will occur in various parts of the monolithic catalyst.

On the other hand, according to the present invention described above, the first
In the small hole group where the exhaust gas from the cylinder enters, the exhaust gas from the second cylinder entered once before and is skipped once, and the group where the exhaust gas from the third cylinder enters. The exhaust gas from the second cylinder enters the small hole group immediately before and is continuous, and the exhaust gas from the second cylinder enters the first cylinder immediately before.
Because the exhaust gas from the cylinders flows into the small hole group where it entered, and the small hole group where the exhaust gas from the third cylinder entered one time earlier, the temperature drop in various parts of the monolith catalyst is small and the temperature of the catalyst is low. Since the temperature is much higher than that of the prior art, the redox reaction of harmful gases in the exhaust gas can be significantly improved, and the temperature difference in various parts of the monolithic catalyst is small, so thermal distortion in the monolithic catalyst can be significantly reduced. be.

Furthermore, since the exhaust pipe 22 from the second cylinder 12 is directed to the entire area of the monolith catalyst 33, the secondary air supply socket 3 is connected to the exhaust pipe 22 of the second cylinder.
7 and supplying secondary air thereto, it is possible to distribute the secondary air to all of the small pores of the monolithic catalyst 33.

Note that the above embodiment was for a three-cylinder engine, but in the case of an in-line four-cylinder engine, the ignition would be in the first
Since the order is cylinder - 3rd cylinder - 4th cylinder - 2nd cylinder or 1st cylinder - 2nd cylinder - 4th cylinder - 3rd cylinder, the order is cylinder - 3rd cylinder - 4th cylinder - 2nd cylinder. Both exhaust pipes are connected to the head chamber of the catalyst case facing each other, while the exhaust pipes from the second and third cylinders located inside the engine are connected to the head chamber of the catalyst case over the entire area of the monolith catalyst. Needless to say, it can be applied in the same way by connecting in a directional manner.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a plan view, FIG. 2 is a cross-sectional view taken from the side of FIG. 1, and FIG. 3 is a cross-sectional view taken from the side of FIG. 1. 10... Internal combustion engine, 11, 12, 13... Cylinder, 20... Exhaust manifold, 21, 22, 2
3... Exhaust pipe, 30... Catalyst case, 33... Monolith catalyst, 33'... Inlet side end surface, 31... Case cover, 35... Head chamber, 21', 21'',
23', 23''...Guide part.

Claims (1)

[Scope of utility model registration request] A monolithic catalyst having a large number of holes in the axial direction is provided in a catalyst case with a head chamber so that the inlet side end face of the monolith catalyst faces into the head chamber, and an in-line multi-cylinder internal combustion engine with three or more cylinders is installed in the head chamber. In an exhaust gas purification device formed by connecting exhaust pipes from each cylinder of the engine, the axis of the connection opening to the head chamber in the exhaust pipe from each cylinder of the engine is defined as the inlet end face of the monolithic catalyst when viewed from the side. The two outer exhaust pipes from the two outer cylinders of the engine are connected so as to face each other with respect to the head chamber in plan view. The connection opening of one of the outer exhaust pipes into the head chamber is provided with a guide part that guides the exhaust gas to a region of the inlet side end face of the monolithic catalyst that is far from the outer exhaust pipe. Each of the connecting openings of the outer exhaust pipes into the head chamber is provided with a guide portion that guides the exhaust gas to a region of the inlet side end face of the monolithic catalyst that is far from the other outer exhaust pipe, and The connecting opening of the inner exhaust pipe from the cylinder located on the inner side of each cylinder of the engine to the head chamber is configured so that the exhaust gas of the inner exhaust pipe is guided to the entire area of the inlet side end face of the monolith catalyst. Features: Exhaust gas purification device for internal combustion engines.