JPH018651Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an engine exhaust purification device, and particularly to an improvement in an exhaust gas purification device that supplies secondary air to a catalytic converter provided in an exhaust system.

(Prior Art) A catalytic converter that is installed in an engine exhaust system and performs an exhaust gas purifying action is preferably installed near the engine where the exhaust gas temperature is maintained at a sufficiently high temperature to promote the reaction. Therefore, when installing this type of catalytic converter,
An exhaust manifold with a short passage length in which each branch passage converges in one place is used, and a catalytic converter is installed immediately downstream of the convergence part of each passage (for example, Utility Model Application No. 57-92051 (see official bulletin).

On the other hand, this type of catalytic converter is supplied with the secondary air necessary for the oxidation reaction, and the supply device for this is an air pump, or a simple structure is a reed valve that uses exhaust pulsation. A type of device is used. This is configured so that when the exhaust system becomes negative pressure due to exhaust pulsation, the reed valve opens and air is sucked into the exhaust system from the air cleaner, etc. through the secondary air supply passage. .

However, when a secondary air supply device using this reed valve is applied to an exhaust manifold in which each of the branch passages mentioned above converges in one place, the exhaust pulsations of each cylinder cancel each other out at the converging part of the manifold. Since the required air suction effect cannot be obtained at the same time, the secondary air supply passage must be connected to a specific branch passage in the manifold. Therefore, the exhaust pulsation for one cylinder is only 2.
The problem arises that sufficient air cannot be supplied to the catalytic converter because it cannot be used for suctioning the next air.

To solve this problem, the secondary air supply passage equipped with a reed valve can be branched off and connected to multiple branch passages in the exhaust manifold, but this would complicate the piping and worsen the ease of assembly. There are also problems such as making the surrounding space cramped.

In addition, "Engine exhaust gas purification device" related to the applicant's earlier application (see Utility Model Application No. 53-83913)
As in the invention, each branch passage in the exhaust manifold is divided into two for each non-consecutive exhaust order to provide two collective passages, and one of them is connected to a secondary air supply passage using a reed valve. If configured like this, the required amount of secondary air would be obtained by utilizing the exhaust pulsation of multiple cylinders, but according to this, the two collecting passages mentioned above would be further assembled and then the catalytic converter would be installed. Therefore, the distance from the engine to the converter becomes longer, and the exhaust gas temperature decreases during that time. In addition, in this type of exhaust gas purification device, in order to promote the oxidation reaction in the catalytic converter, it is necessary to take care to mix the secondary air and exhaust gas well.
It must be constructed to prevent leakage of exhaust gas from the joint between the exhaust manifold and the catalytic converter.

(Purpose of the invention) The present invention addresses the above-mentioned conventional situation.In an engine exhaust gas purification system that supplies secondary air to a catalytic converter using a reed valve, each branch passage is connected to one place. By providing a catalytic converter directly downstream of the collecting part in the collecting exhaust manifold, high-temperature exhaust gas is introduced into the catalytic converter to accelerate the reaction, and the catalytic converter is provided with sufficient exhaust gas without complicating piping. Supplying secondary air and
The purpose of this invention is to better mix secondary air with exhaust gas to further promote the above reaction, and to further improve sealing performance at the connection between the exhaust manifold and the catalytic converter.

(Structure of the invention) The exhaust gas purification device according to the invention is structured as follows in order to achieve the above object.

That is, the configuration includes an exhaust manifold in which the branch passages gather at one place, and a catalytic converter provided immediately downstream of the gathering part in the manifold and connected to a mounting part formed at the downstream end of the manifold. In the exhaust manifold, each of the branch passages is formed independently up to the vicinity of the attachment part, and the exhaust order of these branch passages is not consecutive, and two adjacent branch passages are separated by a partition wall. A communication port for communicating both branch passages is opened at a position separated by a predetermined distance from the gathering portion of the partition wall, and a secondary air supply passage for supplying secondary air via a reed valve is connected to the exhaust manifold. It is connected to the vicinity of the above-mentioned communication port. According to such a configuration, in the exhaust manifold, each of the branch passages is gathered in one place, thereby shortening the exhaust passage, and the catalytic converter is connected directly downstream of the manifold, so that the high temperature exhaust gas is not connected to the converter. Gas will be introduced to accelerate the oxidation reaction in the converter. Since the exhaust pulsations do not cancel each other out between the two branch passages in which the communication ports are provided in the partition wall, the exhaust pulsations in these branch passages are effectively used to supply secondary air to the catalytic converter. In this case, the communication port is provided at a predetermined distance from the collecting part of the exhaust manifold, and each branch passage is independent up to the vicinity of the mounting part of the catalytic converter. The exhaust pulsations in the two branch passages are not affected by other branch passages, and the secondary air is well mixed with the exhaust gas and supplied to the catalytic converter. Furthermore, as described above, each branch passage is independent up to the vicinity of the converter attachment part, and along with this, the partition wall is also provided up to the vicinity of the converter attachment part, so that the rigidity of the attachment part is improved.
Therefore, the sealing performance at the connection between the exhaust manifold and the catalytic converter is improved, and leakage of exhaust gas from the connection is prevented.

(Effects of the invention) As described above, according to the invention, high-temperature exhaust gas is introduced into the catalytic converter, secondary air is sufficiently supplied, and the secondary air and exhaust gas are mixed well. Therefore, the oxidation reaction in the converter is promoted and good exhaust gas purification performance is obtained. Also,
According to the present invention, the piping of the secondary air supply passage does not become complicated, and the leakage of exhaust gas from the connection between the exhaust manifold and the catalytic converter is reliably prevented. .

(Example) The present invention will be described below based on an example shown in the drawings.

As shown in FIG. 1, an intake manifold 3 is attached to one side of a cylinder head 2 of an engine 1, and an exhaust manifold 4 is attached to the other side, and an air cleaner 5 and a carburetor are installed upstream of the intake manifold 3. 6 is provided.

On the other hand, a catalytic converter 7 is attached to the downstream side of the exhaust manifold 4, and the exhaust manifold 4 is connected to the cylinder head 2 as shown in FIG.
It has branch passages 9 1 to 9 4 that communicate with the plurality of cylinders 8 ₁ to 8 _{4 ,} respectively, and these branch passages _{9 1 to} 9 ₄ are independent from each other up to the vicinity of the mounting portion 4'' of the catalytic converter 7. The catalytic converter 7 is formed in a shape that is gathered at one place near the attachment portion 4'', and the catalytic converter 7 is installed immediately downstream of the gathering portion 10. Here, the exhaust order (ignition order) of each of the cylinders 8 ₁ to 8 ₄ is, for example, the first cylinder 8 ₁ , the second cylinder 8 ₂ , the fourth cylinder 8 ₄ , and the third cylinder 8 ₃ . The exhaust order of the second and third cylinders 8 ₂ and 8 ₃ located in the second and third cylinders is not consecutive.

Therefore, the branch passages 9 2 and 9 3, _which are located adjacent to the central part of the exhaust manifold 4 and communicated with the second and third cylinders _{8 2 and} 8 ₃ , respectively, whose exhaust order is not consecutive, are The passages 9 ₂ and 9 3 are connected across the partition wall 11 and, as shown in FIGS. 2 and 3, are connected to each other through the partition wall 11 at a predetermined distance from the gathering portion ₁₀ of the partition wall 11. A port 12 is provided.

A secondary air inlet 13 is provided on the outer wall of the branch passage ₉₃ in the exhaust manifold 4 near the opening position of the communication port 12.
As shown in FIG. 1, a secondary air supply passage 14 led from an air cleaner 5 is connected via a reed valve 15. Here, the reed valve 1
5 defines an upstream chamber 15b on the air cleaner 5 side and a downstream chamber 15c on the exhaust manifold 4 side by a partition wall 15a, and a through hole 15d provided in the partition wall 15a. The configuration includes a lead 15e made of a thin metal plate on the downstream chamber 15c side, and when the downstream chamber 15c side becomes negative pressure, the lead 15e opens and the downstream chamber 15c is opened from the upstream chamber 15b side.
Air is sucked into the side.

According to the above configuration, each cylinder 8 ₁ of the engine 1
Exhaust gas discharged from ~8 ₄ according to a predetermined exhaust order is passed through each branch passage 9 ₁ ~ of the exhaust manifold 4.
9 and ₄ , and are introduced into the sequential catalytic converter 7, where harmful components are removed by the action of the converter 7, and then discharged to the outside. At this time, since the exhaust manifold 4 has a shape in which the branch passages 9 ₁ to 9 ₄ gather at one place, and the catalytic converter 7 is installed directly downstream of the gathering part 10 , the exhaust manifold 4 has a shape in which the branch passages 9 1 to 9 4 gather at one place, and the catalytic converter 7 is installed directly downstream of the gathering part 10 . Gas will be introduced.

In addition, the catalytic converter 7 has 2 necessary for the reaction.
Secondary air is supplied from the air cleaner 5 to the secondary air supply passage 14 and when the reed valve 15 on the secondary air supply passage 14 is opened by negative pressure acting from the downstream side. It is supplied via the exhaust manifold 4. In this case, since the secondary air supply passage 14 is connected to the outer wall of the branch passage 9 ₃ in the exhaust manifold 4, when negative pressure is generated in the branch passage 9 ₃ due to exhaust pulsation, During the exhaust stroke of the cylinder 8 ₃ or at a certain period following the exhaust stroke, the reed valve 15 opens and secondary air is supplied to the catalytic converter 7 .

Therefore, a communication port 12 is provided in the partition wall 11 between the branch passage 9 ₃ and the adjacent branch passage 9 ₂ , and the secondary air supply passage 14 is connected to the vicinity of the communication port 12 . Therefore, negative pressure due to exhaust pulsation generated in the branch passage 9 ₂ during the exhaust stroke of the second cylinder 8 ₂ or at a certain period following the exhaust stroke also acts on the reed valve 15 . In that case, the exhaust pulsations occurring in this branch passage 9 ₂ and the exhaust pulsations occurring in the branch passage 9 ₃ are because the exhaust orders of the corresponding second and third cylinders 8 ₂ and 8 ₃ are not consecutive. The negative pressures caused by these exhaust pulsations act on the reed valves 15 individually to open the valves 15 without canceling each other out, and each of the branch passages 9 ₁ to 9 ₄ connects to the mounting portion 4 of the catalytic converter 7. '', the exhaust pulsations in the two branch passages 9 ₂ and 9 ₃ are not affected by the other branch passages 9 ₁ and 9 _4.Thereby , the catalytic converter 7 has the second,
During the exhaust stroke of the third cylinders 8 ₂ and 8 ₃ , secondary air is efficiently supplied twice, and the amount of air supplied is doubled. In addition, the communication port 12
Since the secondary air inlet 13 is provided at a predetermined distance from the collecting portion 10 in the partition wall 11, the secondary air introduced from this position is well mixed with the exhaust gas. In this way, the oxidation reaction in the catalytic converter 7 is promoted, and good exhaust purification performance is obtained.

Furthermore, as described above, each of the branch passages 9 ₁ to 9 ₄ is provided independently up to the vicinity of the mounting portion 4'' on the catalytic converter 7 side, and in particular,
1 is provided over the entire length of the branch passages 9 ₂ and 9 ₃ , so that the engine 1 of the exhaust manifold 4 is
The rigidity of not only the side attachment part 4' but also the converter side attachment part 4'' is improved, and along with this, the sealing performance at each connection part between the manifold 4, the engine 1, and the catalytic converter 7 is improved. This will prevent exhaust gas from leaking from these connections.

Note that the secondary air inlet 13 provided near the communication port 12 is not provided on the outer wall of one branch passage 9 ₃ as in the above embodiment, but is also provided on the outer wall of the other branch passage 9 ₂ or the communication port. It may be provided directly above 12.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which Fig. 1 is a front view of the engine, Fig. 2 is a plan view of the exhaust manifold section of the engine, and Fig. 3 is the exhaust manifold cut along the line shown in Fig. 2. FIG. 4 is a schematic enlarged sectional view of the reed valve in FIG. 1. 1...Engine, 4...Exhaust manifold, 7...
...Catalytic converter, 9 ₁ to _{9 4} ... Branch passage, 10
... Gathering part, 11 ... Partition wall, 12 ... Communication port, 1
4... Secondary air supply passage, 15... Reed valve.

Claims (1)

[Scope of utility model registration request] Exhaust gas having an exhaust manifold in which each branch passage is gathered at one place, and a catalytic converter provided immediately downstream of the gathering part in the installation manifold and connected to a mounting part formed at the downstream end of the manifold. In the purification device, each branch passage in the exhaust manifold is formed independently up to the vicinity of the attachment part, and two of these branch passages are arranged in a non-continuous exhaust order and are located adjacent to each other, and two branch passages are arranged adjacent to each other in a partition wall. A communication port is provided at a predetermined distance from the collecting portion in the partition wall to allow the two branch passages to communicate with each other, and secondary air is supplied into the exhaust manifold through the reed valve. An exhaust gas purification device for an engine, characterized in that a secondary air supply passage is connected to the manifold near the communication port.