JPS6018568Y2 - Exhaust gas purification device for multi-cylinder internal combustion engines - Google Patents

Description

[Detailed Description of the Invention] A. Purpose of the Invention (1) Industrial Application Field The present invention relates to an exhaust gas purification device using a catalyst in a multi-cylinder internal combustion engine.

(2) Conventional technology In general, in a multi-cylinder internal combustion engine, each independent intake system is connected to the intake port connected to each cylinder, and each independent exhaust system is connected to the exhaust port connected to each cylinder, and the output per unit weight is increased. High-output internal combustion engines that increase the It is unavoidable that the amount of air-fuel mixture supplied to each cylinder and its air-fuel ratio will become non-uniform for each cylinder due to errors in construction, assembly errors, etc.

By the way, if a catalytic converter is installed in each exhaust section to purify the exhaust gas of such an internal combustion engine, the catalytic converter for each cylinder will be Since exhaust gases having different amounts of exhaust gases and different amounts of unburned components such as CO and HC contained therein are supplied, it may be difficult to fully demonstrate the purification performance of each catalytic converter.

Therefore, a buffer is provided on the upstream side of the catalytic converter to connect multiple exhaust pipes with each other, and the exhaust gases flowing through each exhaust pipe are combined and mixed in the buffer, and unburned components such as Co and HC are delivered to each catalytic converter. It has been proposed to increase the purification efficiency of each catalytic converter by supplying equal amounts of exhaust gas having the same content to each catalytic converter (see Japanese Patent Laid-Open No. 54-64217).

(3) Problems to be solved by the invention In the conventional device, the buffer has a larger capacity than the exhaust pipes, so it has the advantage of being able to sufficiently merge and mix the exhaust gases flowing through each exhaust pipe. It has the following defects.

That is, when the buffer is still at a low temperature, such as immediately after starting the internal combustion engine, a large amount of heat from the large amount of exhaust gas passing through the buffer is consumed to heat the buffer, so the exhaust gas is not transferred to the catalytic converter. The temperature drops considerably before reaching the reaction temperature, and therefore it takes time for the catalyst in the catalytic converter to reach the reaction temperature, during which time the catalytic converter cannot fully demonstrate its exhaust gas purification performance.

In order to solve this problem, for example, a normally closed valve that opens only when the engine temperature is above a predetermined value is installed downstream of the buffer in some exhaust systems, so that the engine temperature does not reach the predetermined value. In this case, it is possible to cause the exhaust gas flowing in one part of the exhaust system to flow into the catalytic converter of the other exhaust system to rapidly heat the catalytic converter, but in that case, the above-mentioned normally closed valve or Another drawback is that the control means must be specially provided, which complicates the structure and increases costs.

The present invention has been proposed in view of the above, and it is an object of the present invention to provide an exhaust gas purification device for a multi-cylinder internal combustion engine that has a simple structure and eliminates all of the above-mentioned problems of conventional devices.

B. Structure of the invention (1) Means for solving the problem The present invention is a multi-cylinder internal combustion engine in which an independent intake system is connected to each cylinder, and each exhaust port connected to each cylinder is connected to an independent intake system. Exhaust pipes are connected, and the downstream opening end of each exhaust pipe communicates with a buffer chamber of a shock absorber, and the buffer chamber contains a plurality of silencers each having a built-in catalytic converter, each corresponding to each of the exhaust pipes. the downstream opening ends of the exhaust pipes such that the inlets communicate with each other and a portion of the exhaust gas flowing out from the downstream opening ends of each of the exhaust pipes flows straight into the inlet of the corresponding muffler without being dispersed within the buffer chamber; and the corresponding inlet of the muffler are arranged substantially on the same axis and are closely opposed to each other with a gap in the buffer chamber.

(2) Effect The exhaust gas flowing between the multiple exhaust gases is sufficiently merged and mixed in the buffer chamber of the buffer before flowing into the multiple silencers almost equally, so that each catalytic converter in these silencers The exhaust gas purification performance can be fully exhibited without variation.

Also, of the exhaust gas flowing out from the downstream opening end of each exhaust pipe,
It is possible to increase the amount of exhaust gas that flows straight into the inlet of the muffler without being dispersed into the buffer chamber.
Exhaust gas is able to reach each catalytic converter at a high temperature without a significant amount of heat being removed by the buffer, promoting heating of the catalyst, and as a result, the exhaust gas purification performance of the catalytic converter improves immediately after engine startup. Effectively demonstrated.

(3) Examples An embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, the internal combustion engine equipped with the device of the present invention is implemented in a motorcycle, and the internal combustion engine is mounted on the body frame of the motorcycle, and the engine body 1 includes eleventh and second cylinders arranged in parallel with each other. The intake ports 21 and 2□ are connected to the independent first
, second carburetors 41 and 42 are connected, and inside each of the eleventh and second cylinders 21 and 2□, a first and a second carburetor 4 are connected.
1.4 degrees so that air-fuel mixture with an appropriately adjusted air-fuel ratio is independently supplied.

Furthermore, first and second air cleaners 5□ and 5° are connected to the open ends of the first and second vaporizers 41 and 4□ facing the atmosphere.

First and second exhaust pipes 81.8□ are connected to each exhaust port 71.7□ of the first and second cylinders 21, 2□, respectively. □ are arranged symmetrically with respect to the longitudinal center line of the engine body 1, and are curved to surround the front and bottom surfaces of the engine body 1, respectively, and then extend parallel to each other in the longitudinal direction of the engine body 1. Each of the downstream opening ends 91, 9□ opens into a cylindrical shock absorber 10 disposed across them.

In order to improve the filling efficiency of the first and second cylinders 21 and 2°, respectively, the first and second exhaust pipes 81 and 8□ It is designed so that the passage area of each part from the ports 71, 7° to the shock absorber 10 is approximately uniform and the pipe lengths are approximately equal.

As clearly shown in FIG. 3, the buffer 10 is constructed by covering the inner and outer surfaces of a cylindrical heat insulating material 11 with inner and outer plates 13 and 14, and a buffer chamber 12 is formed inside thereof. .

First and second mufflers 15 are provided at the left and right rear portions of the buffer 10.
The front parts of □, 15□ are connected, and their inlets 16. ．．
16□ communicates with the buffer chamber 12 and connects the first and second
The downstream opening end 91, 9□ of the exhaust pipe 81, 8□ and the gap C9C
They face each other in close proximity.

and the first and second silencers 15. ．． 15□ inlet 1
6. ．． 16. are the corresponding first and second exhaust pipes 81,
It is located approximately on the same axis as the downstream opening ends 91 and 92 of 8□, and is arranged symmetrically with respect to the longitudinal center line of the engine body 1.

The first and second mufflers 151.15□ have conventionally known first and second catalytic converters 61, 6° built-in at the same positions, respectively.

A secondary air supply main pipe 17 whose one end is connected to the air cleaners 5□, 5° extends along the upper part of the engine body 1, and the other end is connected to a valve surface 18 disposed at the front upper part of the engine body 1. It is connected to the entrance 19.

First and second secondary air pipes 211, 21 are connected to the outlets 20° 20 opened on the left and right sides of the valve surface 18 via check valves 22, 22.
These secondary air pipes 21. ．． 21
The other end of ゜ is communicated with the exhaust ports 71, 7□ of the first and second cylinders 21, 22.

The check valves 22, 22 are both opened by the inertia and pulsation effect of the exhaust gas flow accompanying engine operation, and
The clean secondary air from the second air cleaners 51, 5□ is passed through the secondary air supply main pipe 17, the check valves 22, 22, and the first and second secondary air pipes 211.21° to the first and second cylinders 2.
It can be introduced into each of the 1 and 2 □ exhaust ports 71 and 72.

Next, the operation of one embodiment of the present invention shown in FIGS. 1 to 3 will be explained. When the engine is operated now, the first and second cylinders 2□ and 22 alternately inhale and Compression, explosion, and exhaust strokes are repeated, and the first cylinder 2□ is filled with the first carburetor 4□ alone, and the second cylinder 2□ is filled with the second carburetor 4□ alone, each with a properly adjusted air-fuel mixture. The exhaust gas generated through the alternately inhaled compression and explosion strokes is the first
, from the second cylinder 21,2□ to the first and second exhaust ports)? ,,
7□ and is alternately introduced into the 11th and second exhaust pipes 8□ and 8□.

On the other hand, due to the inertia and pulsation effect of the exhaust gas flow flowing from the 11th second exhaust port 71.7□ to the first and second exhaust pipes 81 and 8°, the check valves 22 and 22 are opened, and the first and second exhaust Approximately equal amounts of secondary air are alternately introduced into the tubes 81 and 82.

As a result, the exhaust gas mixed with secondary air is alternately flowed into the buffer chamber 12 of the common shock absorber 10 through the eleventh second exhaust pipes 81, 8□.

By the way, since the volume of the buffer chamber 12 is larger than that of the first and second exhaust pipes 81°82, the exhaust gases mixed with secondary air that flowed here from the respective exhaust pipes 81°8□ are sufficiently merged and mixed with each other. At the same time, the intermittent pulsating flow is attenuated and the flow becomes nearly uniform.

Also, in the buffer chamber 12, the first and second exhaust pipes 81, 8□
The downstream opening ends 91, 9□ of the first and second silencers 15, .
15□ inlet 16. ．． It is approximately on the same axis as 16□,
In addition, since they are close to each other and face each other, the first and second exhaust pipes 8
A part of the exhaust gas mixed with secondary air flowing through
It is possible to flow straight into the silencer 151゜15□ and reach the first and second catalytic converters 6□, 6□ in a high temperature state, promoting their reactions, especially when the internal combustion engine is started. Even if the temperature in the buffer chamber 12 has not yet risen sufficiently, the exhaust gas mixed with secondary air reaches the first and second catalytic converters 61°6° in a high temperature state and quickly heats them to the reaction temperature. 1st and 2' catalytic converters 6
□, 6° purification function can be fully demonstrated, and harmful components such as CO and HC can be reliably purified over the entire operating range of the internal combustion engine.

Effects of the C design As described above, according to the present invention, the downstream opening end of each exhaust pipe and the inlet of each muffler are communicated with each other via the buffer chamber of the common buffer, so that each independent intake Even if there are variations in the amount of air-fuel mixture and air-fuel ratio supplied to each cylinder from the system, the exhaust gas flowing through the multiple exhaust pipes connected to each cylinder will be thoroughly mixed in the large-capacity buffer chamber. It can flow into each muffler almost equally, and therefore the exhaust gas purification performance of each catalytic converter in these mufflers can be fully exhibited without variation.

Further, the downstream opening end of each exhaust pipe and the corresponding muffler are arranged so that a part of the exhaust gas flowing out from the downstream opening end of each exhaust pipe flows straight into the inlet of the corresponding muffler without being dispersed in the buffer chamber. Since they are disposed approximately on the same axis as the inlet of the container and are closely opposed to each other with a gap in the buffer chamber, the exhaust gas flowing out from the downstream opening end of the inlet does not disperse into the buffer chamber. It is possible to increase the amount of exhaust gas that flows straight into the silencer inlet, and therefore, even if the buffer is still at a low temperature immediately after engine startup, the exhaust gas can flow into each catalytic converter at a high temperature. As a result, the catalytic converter's exhaust gas purification performance can be effectively exhibited immediately after the engine is started, which is advantageous in terms of exhaust gas purification measures.

Moreover, there is no need to provide a special opening/closing means such as an engine temperature-responsive valve in a part of the exhaust system to promote heating of the catalyst, and the structure is simple and can contribute to cost reduction.

[Brief explanation of the drawing]

FIG. 1 is a side view of a motorcycle equipped with the device of the present invention. FIG. 2 is a partially cutaway plan view of the device of the present invention, and FIG. 3 is a cross-sectional view taken along the line ■--■ in FIG. 1. 21.2゜...First and second cylinders as cylinders,
61.6□・・・・・・ L as a catalytic converter
Second catalytic converter, 71, 7□...First and second exhaust ports as exhaust boat, 8□, 8□...
・・No. 11 and 2nd exhaust pipe as an exhaust pipe, 91,9□・・
...Downstream opening end, 10...Buffer, 12.
...Buffer chamber, 15□, 15□...First and second silencers as silencers, 16...Inlet.

Claims (1)

[Scope of utility model registration request] In a multi-cylinder internal combustion engine in which each cylinder is connected to an independent intake system, each exhaust port connected to each cylinder is connected to an independent exhaust pipe, and the downstream opening end of each exhaust pipe is connected to the buffer chamber of the shock absorber. The buffer chamber communicates with
The inlets of a plurality of silencers each having a built-in catalytic converter, each corresponding to each of the exhaust pipes, communicate with each other, so that a portion of the exhaust gas flowing out from the downstream opening end of each of the exhaust pipes is not dispersed within the buffer chamber. The downstream opening end of the exhaust pipe and the inlet of the corresponding muffler are arranged substantially on the same axis, and there is a gap in the buffer chamber so that the exhaust pipe flows straight into the inlet of the corresponding muffler. Exhaust gas purification devices for multi-cylinder internal combustion engines, which are arranged close to each other and face each other.