JPS5843563B2 - Internal combustion engine exhaust purification device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust purification device for reducing harmful exhaust gases from an internal combustion engine.

Conventionally, as a means of purifying carbon monoxide (hereinafter referred to as CO) and hydrocarbons (hereinafter referred to as HC), which are harmful components in exhaust gas, a reactor is installed in the exhaust system and the exhaust gas is heated inside the reactor in a high temperature state. There is a known method for purification by introducing oxidation into the water and continuously causing an oxidation reaction by mixing.

In this reactor system, the exhaust gas emitted from the engine is introduced into the reactor in a high-temperature state, and the reactor is directly connected to the exhaust boat, so the inertial effect of the exhaust gas flow is lost and the output decreases. However, since the exhaust pulsation is attenuated, two
When it is necessary to supply secondary air, it is not possible to naturally introduce secondary air using the exhaust pulsation effect, so special auxiliary equipment such as an air pump is required, which results in high cost and installation. It has drawbacks such as space problems and power loss.

In view of these shortcomings, in order to purify exhaust gas without installing an after-treatment device such as a reactor or auxiliary equipment such as an air pump, a predetermined section of the exhaust passage after the exhaust valve is made to have a heat-insulating structure to purify the exhaust gas. A system has been proposed in which the heat-retaining structure maintains a predetermined temperature in the exhaust passage, thereby causing continuous self-reaction of the exhaust gas in the exhaust passage to purify CO and HC.

(Hereinafter, this method will be referred to as the exhaust pipe purification method).

With this exhaust pipe purification method, there is no expansion part such as a reactor in the exhaust passage, and therefore the exhaust inertia effect can be fully utilized, thereby avoiding a drop in output.In addition, the exhaust pulsation is used to naturally introduce secondary air. This has the great advantage of eliminating the need for auxiliary equipment such as air pumps.

On the other hand, on the other hand, there is no mixing of gas in the exhaust passage, so in order to allow sufficient self-reaction of the exhaust gas in the exhaust passage, the exhaust gas temperature must be set at the lowest point at the reactor entrance where the reaction occurs in the reactor system. It is necessary to maintain the temperature above the self-reaction temperature, which is higher than the temperature (referred to as the trigger temperature), and due to this necessity, in engines that adopt this method,
It is necessary to ensure that the exhaust gas temperature when exiting from the engine exhaust port is around 1000℃, which is higher than that of a normal engine.
Therefore, the ignition timing has been set much later than the maximum output ignition timing (for example, by about 10 to 20 degrees in crank angle).

However, if the ignition timing is delayed, fuel consumption increases and output also decreases.

Therefore, based on these circumstances, an object of the present invention is to maintain the sufficient inertial effect of the exhaust gas flow, which is the advantage of the above-mentioned exhaust pipe purification method, while reducing the exhaust gas temperature by delaying the ignition timing. CO
The aim is to provide an exhaust purification device that can be improved to reduce HC emissions to the target regulation value, improve fuel efficiency, and maximize output. be.

For this purpose, the exhaust gas purification device of the present invention provides, in an internal combustion engine having at least two cylinders, two exhaust passages that respectively pass exhaust gas flows from cylinders having different phases after the exhaust valve. , the above two exhaust passages are
It has a heat insulating structure, has a shape without expansion parts that allows the exhaust gas flow to pass through in the order of exhaust, and has a length that can generate sufficient exhaust inertia. , the above 2 including one expansion part having a heat retention structure.
Each downstream end of the exhaust passage is inserted into and opened in an expansion part, and the expansion part has a heat capacity sufficient to smooth out temperature fluctuations of the exhaust gas passing through the exhaust passage depending on the engine operating conditions. and the temperature of the exhaust gas entering the expansion part is set to a temperature higher than the trigger temperature of the expansion part, and a secondary air introduction passage is communicated with the exhaust passage via a check valve. be.

Embodiments of the present invention will be specifically described below with reference to the drawings.

First, in FIG. 1, 1 indicates an engine, 2 a cylinder, and an exhaust pipe 4 connected to an exhaust port 3 of the cylinder.

The exhaust port 3 and the exhaust pipe 4 are each covered with a heat insulating material 5, which prevents the exhaust gas temperature from decreasing due to its heat insulating effect.

Also, an exhaust passage a consisting of an exhaust port 3 and an exhaust pipe 4 is provided.
, b are shaped so as to pass the exhaust gas stream in the order of exhaust;
It has a sufficient length L to generate exhaust inertia.

Located downstream of the exhaust passages a and b having such a length L, an expansion part 6 having a heat-retaining structure whose outer periphery is covered with a heat insulating material 7 is provided, and the tips of each of the exhaust passages a and b are connected to this It is inserted into the extension part 6.

In this embodiment, a collecting part 8 is provided at the tip of the exhaust passage ayb inserted into the expanded part 6, and this collecting part 8
A gas discharge port 8a is opened at an angle θ with respect to the passage direction of the exhaust passage ayb, and the exhaust gases flowing in the two exhaust passages a and b are collected in a collecting part 8, where mixing is performed. While raising the expansion part 6 from the gas discharge port 8a.
It is designed to be discharged into the reaction chamber 9 inside.

Note that the reaction chamber 9 communicates with a tail pipe 13 via heat-extinguishing chambers 10, 11, 12, and the exhaust gas in the expanded portion 6 is introduced to the outside through the tail pipe 13.

In the case of the embodiment shown in FIG. 1, the expansion section 6 has a plurality of chambers divided therein so as to have a noise-muffling function, but the structure of the expansion section 6 is particularly limited to that shown in FIG. It's not something you can do.

For example, as in the embodiment shown in FIG. 2, the interior of the expanded portion 6' is a simple reaction chamber 14, into which the tips of the exhaust passages a and b are inserted from one side. The exhaust pipe 16 leading to the muffler 15 from the opposite side in parallel with the expansion part 6
′ may be inserted into the structure, in short, the extension part is
It may have a heat-retaining structure as long as it has a reaction chamber of a suitable volume inside and can retain the exhaust gas introduced through the exhaust passages a and b at a predetermined temperature for a predetermined period of time.

Further, the temperature of the exhaust gas brought to the expansion part 6 via the exhaust passages a and b is higher than the temperature (trigger temperature) sufficient to cause an oxidation reaction by mixing when the exhaust gas enters the next expansion part 6. is maintained.

This trigger temperature Tr is expressed as the air-fuel ratio and the expansion section volume Vtr.
Fig. 3 shows the results obtained through experiments regarding the relationship between .

In this figure, two trigger-temperature curves are shown when the volume of the extension is 1 and 4 times the engine stroke volume, the hot side being 1 times and the cold side being 4 times, entering the expansion part 6. The exhaust gas temperature is maintained above a trigger temperature corresponding to the air-fuel ratio shown herein and the ratio of expansion volume to engine stroke volume.

In addition, in FIG. 1, reference numeral 17 indicates that one end is connected to the exhaust port 3.
The other end of this introduction passage 17 is connected to an air filter 19 via a check valve 18.
is communicated with.

Reference numeral 20 designates an exhaust gas recirculation passage whose one end communicates with the exhaust port 3, and the tip of this passage 20 communicates with the suction pipe 23 of the carburetor 22 via an exhaust gas recirculation valve 21. It is opened by a negative pressure action from a negative pressure passage opened to the suction pipe 22.

In such a configuration, exhaust gas discharged from the engine 1 is routed through the exhaust passage a according to the order of discharge.

After passing through the passages a and b, the expansion part 6
flow into the world.

At this time, the temperature of the gas entering the expansion part 6 is maintained at the trigger temperature or higher as described above, so when the exhaust gas flows into the expansion part 6, it is retained in the expansion part 6. The oxidation reaction is rapidly carried out due to the staining effect when mixed with other gases.

While the exhaust gas is retained in the expansion part 6, the oxidation reaction is sustained as the exhaust gas is sequentially mixed and diffused with the subsequent introduced gas, and as a result, the unburned part of the gas is oxidized and burned, resulting in CO2. , HC are reduced to the target emission level (for example, the 50-year regulation value).

In this case, the exhaust passages a and b after the exhaust port have a length L that provides an exhaust inertial effect, so the exhaust gas flow discharged from the engine maintains a sufficient inertial effect, and therefore outputs Deterioration can be avoided.

Furthermore, when secondary air is supplied into the exhaust gas, the required amount of secondary air is naturally sucked in by utilizing the exhaust pulsation effect.

Further, in the present invention, an extended portion 6 having a heat retaining structure is provided downstream of the exhaust passages a and b having the length L as described above, and exhaust gases are mixed and diffused within this extended portion 6 to produce a mixing effect. Therefore, the gas temperature at the inlet of the expansion part required to purify CO and HC to the target value may be the trigger temperature, and the trigger temperature is the self-reaction temperature of the exhaust pipe purification method described above. Since the gas temperature is low compared to the air temperature, there is no longer a need to significantly delay the ignition timing, which was done to purify the exhaust gas.

In the present invention, the exhaust system after the exhaust valve has two exhaust passages, and each downstream of these two exhaust passages is inserted into and opened in one expansion part, so that the exhaust from the cylinders with different phases can be removed. Since each gas flow is introduced into one expansion section alternately at a predetermined exhaust timing, the mixing effect of the exhaust gas within the expansion section is high, and the temperature of the exhaust gas guided into the expansion section is reduced due to its thermal inertia. Even if the oxidation reaction is relatively low, the oxidation reaction can be carried out satisfactorily.

In this embodiment, the inside of the expanded portion 6 provided downstream of the exhaust passages a and b has sufficient heat capacity and large thermal inertia.
For example, when the exhaust gas temperature fluctuates widely as in 10 modes, even if the gas temperature in the exhaust passage is below the trigger temperature at which no reaction occurs when it enters the expansion section, the gas expands. When the gas enters the chamber, it receives heat and its temperature rises, causing a reaction.Also, gas that enters at a temperature much higher than the trigger temperature causes a reaction, and at the same time the expansion section gives heat, causing the gas temperature inside the expansion section to increase. is smoothed.

Due to the above action, in the embodiment, by maintaining the average gas temperature in the exhaust passage at the trigger temperature rather than the minimum gas temperature, the oxidation reaction is continuously carried out during this mode, and the CO
and HC can be sufficiently purified to a predetermined value.

Experimental data regarding these points are shown in FIGS. 4 to 7.

FIGS. 4 and 5 show experimental data for the case where the extended portion 6 is not provided downstream of the exhaust square passages a and b, and FIGS. 6 and 7 show experimental data for the apparatus of the present invention provided with the extended portion 6.

This data represents the fluctuations in exhaust gas temperature during operation at a running speed of 40 for an engine with an air-fuel ratio of 17 and an engine with an air-fuel ratio of 13.5. The data was also obtained using equipment that satisfies the CO and HC emission regulation values in the ``50-year regulations'' for automobile exhaust gas.

In these data, as can be seen by comparing Figures 4 and 6, and Figures 5 and 7, the device of the present invention provided with an extension section has a higher performance than the device without an extension section. As a result, the exhaust gas temperature at the engine outlet can be lowered during all operations (see D1-D2 in the figure).

In this way, the present invention can lower the exhaust gas temperature for purifying CO and HC, so there is no need to significantly delay the ignition timing, which has been done to purify the exhaust gas, and Since the maximum output ignition timing is sufficient, combustion is improved, fuel consumption can be improved, and sufficient output can be produced.

In terms of fuel consumption, comparison data between a vehicle without an expansion portion and a vehicle of the present invention provided with an expansion portion are shown in FIGS. 8 to 10.

As is clear from these data, it is clear that the fuel consumption of the fuel tank of the present invention provided with the expanded portion is greatly improved.

Thus, according to the present invention, in particular, the exhaust passage having a length capable of generating sufficient exhaust inertia is communicated with the expanded portion while maintaining the inertia effect of the exhaust gas flow discharged into the exhaust passage. This has the excellent effect of providing an exhaust purification device that can maximize engine output, purify CO and HC well, and improve fuel consumption.

[Brief Description of the Drawings] Fig. 1 is an explanatory diagram showing one embodiment of the exhaust purification device according to the present invention, Fig. 2 is an explanatory diagram of another embodiment, and Figs.
Figures 8 to 10 show experimental data comparing exhaust gas temperature changes between a model without an expansion part and a model of the present invention with an expansion part during operation in the 10 mode and at a running speed of 40. also has no extension,
This is data comparing the fuel consumption rate with that of the present invention having an expanded portion. 1...Engine, 2...Cylinder, 3
-... Exhaust port, 4... Exhaust pipe, 5.
...Insulation material, 6,6'...Expansion part, 7.
...Insulation material, 8...Collection part, 9...
...Reaction chamber, 10, 11, 12... Sound deadening chamber, 1
3... Tail pipe, 14... Reaction chamber, 15... Muffler, 16... Exhaust pipe,
a, b...exhaust passage.

Claims (1)

[Claims] 1. In an internal combustion engine having at least two cylinders, two exhaust passages are provided after the exhaust valve to allow exhaust gas flows from the cylinders with different phases to pass through separately, and the two exhaust passages have a heat insulating structure. It has a shape without an expansion part that allows the exhaust gas flow to pass through in the order of exhaust, and has a length that can sufficiently generate exhaust inertia, and these two
An expansion part having a heat-retaining structure is provided downstream of the main exhaust passage, and each downstream of the two exhaust passages is inserted into the expansion part and opened. It has a heat capacity sufficient to smooth out temperature fluctuations in the exhaust gas passing through the passage within the expansion part, and sets the temperature of the exhaust gas entering the expansion part to be equal to or higher than the trigger temperature of the expansion part,
An exhaust purification device for an internal combustion engine, in which a secondary air introduction passage is communicated with the exhaust passage through a check valve.