JPS5844858B2 - Gasoline engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION With the rapid increase in the number of automobiles in recent years, the problem of air pollution caused by automobile exhaust gas has been taken up as a major social problem both domestically and internationally.

As is well known, exhaust gas from gasoline engines contains carbon monoxide (CO) and hydrogen carbonate (HC) due to incomplete combustion.
, and nitrogen oxides (NOx) derived from the thermal dissociation of oxygen (02) and nitrogen (N2) in the air.

When these harmful components are released into the atmosphere, they result in the formation of smog through photochemical reactions and sensitizing effects such as irritation to human eyes, and the concentration of the exhaust gas is being strictly regulated from the viewpoint of social and environmental health.

As regulatory values become stricter, various purification devices have been developed, but they can be broadly divided into (1) improvements to fuel supply devices, (2) improvements to the ignition system and combustion chamber to ensure complete engine combustion. and (3) detoxification of harmful gases through exhaust post-treatment.

Regarding (1) improvements in fuel supply systems, the exhaust gas concentration has been reduced year by year through improvements in carburetors, computer-controlled gasoline injection systems, intake air temperature control systems, dual heating intake pipes, etc.

Regarding (2), the reduction of the quench region of the combustion chamber,
Measures taken include increasing exhaust gas temperature by delaying ignition timing, increasing air mixture porosity by controlling intake valves, reducing residual gas by reducing valve overlap, lowering compression, and controlling combustion temperature by exhaust gas recirculation. .

Regarding (3), a re-combustion reactor using air injection,
Afterburners equipped with spark plugs, various oxidation and reduction catalytic converters, and cyclones that trap particulates have been developed.

In reality, it is difficult to significantly reduce the exhaust gas concentration unless various of the above measures are combined.

Here, CO and HC are reduced by increasing the combustion temperature to bring it closer to complete combustion.

That is, when the air-fuel ratio of the air-fuel mixture is made to be equal to or higher than the stoichiometric mixture ratio, oxygen becomes excessive and CO becomes 0.2% or less.

In addition, if the HC mixture is diluted beyond the stoichiometric ratio, only HC will remain in the quench area such as the wall of the combustion chamber. It can be rendered almost harmless.

The reduction of Co and HC has already been achieved to some extent by appropriately combining combustion chambers with small quench regions, increased exhaust gas temperature due to ignition timing delay, and reburning reactors using air injection.

In order to reduce CO and HC, it is possible to further improve the fuel supply system, improve the distribution of the air-fuel mixture in the engine, and improve the accurate control and dynamic characteristics of the air-fuel mixture during acceleration and deceleration by combining the above purification devices with practicality. It is relatively easy to correlate the reduction in COI and HC.

However, NOx is generated by thermal dissociation of 02 and N2, and its generation occurs when the temperature of the combustion gas is 1600°C.
This becomes noticeable from the above, and as the temperature rises, the NOx concentration increases rapidly.

In a gasoline engine, the combustion gas temperature is approximately 3000
℃, and NOx levels reach around 4,000 ppm.

In order to reduce NOx, it is necessary to lower the combustion temperature or enrich the air-fuel mixture to cause combustion in an oxygen-deficient state.

Simply, if the ignition timing is delayed and combustion is performed in the expansion stroke after top dead center, the combustion will deviate from constant volume combustion and become closer to constant pressure combustion, thereby suppressing temperature rise and reducing the generation of NOx.

However, since the cylinder capacity of an engine is limited, the more the ignition timing is delayed, the more combustion will continue until the end of the expansion stroke, and the amount of combustion energy that can be effectively used as output will decrease.

Therefore, although the NOx concentration apparently decreases, the output also decreases, so a large amount of fuel is required to maintain the same vehicle speed, and the weight of NOx released into the atmosphere does not change much.

It is also conceivable to dilute the air-fuel mixture with exhaust gas in order to lower the combustion temperature.

When the amount of fuel per unit volume in the air-fuel mixture is constant, the larger the proportion of inert gas, the less oxygen there is, and the larger the amount of fuel participating in combustion, the lower the combustion temperature.

Furthermore, when the air-fuel ratio per unit volume in the air-fuel mixture is kept constant, the larger the proportion of inert gas is, the larger the heat capacity is and the lower the combustion temperature is.

Therefore, by increasing the recirculation amount of exhaust gas, the combustion temperature can be lowered and the generation of NOx can be reduced.

As described above, exhaust gas recirculation equipment is one of the most effective means for reducing NOx, but in order to significantly reduce NOx, it is necessary to recirculate approximately 30% of the intake air volume. When such a large amount of exhaust gas is recirculated, it becomes extremely difficult to ignite the air-fuel mixture.

To compensate for this, the ignition energy was increased and the conventional 2
It is being considered to increase the ignition level from 0 to 40 millijoules to 100 to 500 millijoules to stabilize ignition.
It is difficult to stabilize the entire combustion chamber by simply increasing the ignition energy.

Furthermore, when a large amount of exhaust gas is recirculated, it is possible to increase the stability of ignition by making the mixture too rich, but if such a rich mixture is used, Co and HC will rapidly increase. However, there is a drawback that the temperature during re-combustion greatly exceeds 1000° C., which significantly impairs the durability of the reactor or catalytic converter.

Therefore, there is a limit to the reduction of NOx by the exhaust gas recirculation device, and in conventional engines, a reduction catalyst is further required to reduce NOx.

The reduction catalyst normally reduces the oxygen of NOx using CO1HC or the like, but in order to effectively operate the reduction catalyst, it is necessary to strictly control the O2 concentration using the reducing CO, HC or the catalyst.

However, with conventional carburetors, it is extremely difficult to accurately control the air-fuel ratio during transient engine operation.
Compared to a reduction catalyst under well-controlled conditions such as in a chemical plant, the action of a reduction catalyst is extremely uncertain under conditions such as an engine where temperature, mixture ratio, displacement, etc. change from time to time. becomes.

As described above, it is difficult to significantly reduce the concentrations of Co, HC, and NOx by simply combining conventional devices, and a practical pollution-free engine has not yet been developed.

The object of the present invention is to
An object of the present invention is to provide an exhaust gas purification device for a gasoline engine that greatly reduces emissions of O, HC, and NOx.

In particular, an object of the present invention is to provide an exhaust gas purification device for an engine, which is equipped with an air-fuel mixture supply means, an ignition means, an exhaust gas recirculation means, and a re-combustion means, so that a lean air-fuel mixture can be completely combusted and sufficient output can be obtained.

The present invention is characterized by supplying a mixture with an air-fuel ratio of 20 to 28 from a fuel supply device, homogenizing this mixture by a vaporization device, and further supplying exhaust gas from an exhaust gas recirculation passage. Stable ignition is achieved by controlling the amount of gas depending on the opening of the throttle valve and the pressure upstream of the recirculation control valve, and by installing multiple spark plugs in each cylinder and igniting from multiple locations in the combustion chamber. C01H emitted from the engine aims to shorten the combustion duration, achieve complete combustion with a lean mixture, and increase output and thermal efficiency.
In addition to significantly reducing C and NOx, the small amounts of HC and CO emitted from the engine are rendered harmless in a reactor and released into the atmosphere via a muffler.

An embodiment of the present invention will be described in detail below with reference to the drawings.

In Fig. 1, 1 is an engine, 2 is a spark plug, 3 is an intake pipe, 4 is an exhaust pipe, 5 is a carburetor, 6 is a reactor, and 7
8 is an ignition device, 8 is a battery, 9 is an exhaust gas recirculation device, 10 is a muffler, and 11 is an air cleaner.

A vaporizer 12 is connected to a passage 13 of the vaporizer 5.

The reactor 6 is attached in the middle of the exhaust pipe 4, and a heating burner 14 is installed in the reactor 6.

The inlet of the vaporizer 12 is connected downstream of the filter element of the air cleaner 11.

The outlet of the carburetor 12 communicates with the carburetor 5, and the air-fuel mixture of the carburetor 12 is configured to be supplied to the engine 1 through the intake pipe 3.

Here, the heat generated in the reactor 6 is transmitted to the vaporizer 5, which heats the mixture of fuel and air supplied from the vaporizer 12, thereby making the mixture homogeneous and uniform.

The exhaust gas recirculation device 9 has a configuration shown in FIG.

A part of the exhaust gas in the exhaust pipe 4 is guided to the cyclone 16 through the exhaust recirculation pipe 15 to remove dust in the exhaust gas, and then the exhaust gas is supplied to the recirculation amount control valve 17 and passed through the exhaust recirculation pipe 18 to the vaporizer 5. A portion of the exhaust gas is supplied to the inside.

As shown in Fig. 3, in the present invention, the exhaust gas recirculation rate (exhaust gas recirculation amount/intake air amount) is 0 depending on the load.
It is desirable to control it like a curve.

The reason for this is that when the opening degree of the throttle valve 19 is relatively small, the load is small, so less NOx is generated, and when the opening degree of the throttle valve 19 is large, output is required. This is because NOx can be reasonably reduced by increasing the recirculation of exhaust gas in this region, since this region is operated the most.

The reflux control valve 17 may be any type such as a poppet valve as shown in FIG. 2 or a butterfly valve, and the lift of this valve can be changed in conjunction with the throttle valve 19 of the carburetor 12. .

The combination of the lever 20, rod 21, lever 22, and rod 23 of the throttle pal 7''19 allows the carburetor 12
When the throttle valve 19 opens, the lift of the recirculation amount control valve 17 increases.

The relationship between the throttle valve 19 of the carburetor 12 and the reflux control valve 17 is such that the link mechanism is determined such that the higher the load, the smaller the opening degree of the remote flow control valve 17.

That is, the opening degree of the recirculation amount control valve 17 increases while the throttle valve 19 is fully opened, and the linkage mechanism that reduces the opening degree of the recirculation amount control valve 17 when the throttle valve 19 becomes fully open is, for example, as shown in FIG. The relationship between the lever 20, rod 21 and lever 22 is as follows from the throttle valve 1.
9 is fully open, change the rod 23 to the maximum lift, and when the throttle valve 19 is fully open, the rod 23
It is sufficient to adopt a link mechanism that reduces the lift.

Such a link mechanism is well known as a crank or cam mechanism.

Therefore, if the link mechanism is configured to reduce the lift of the recirculation amount control valve 17 when the opening degree of the throttle valve 19 increases, a characteristic like the zero curve shown in FIG. 3 can be obtained.

Further, even if the lift of the recirculation control valve 17 is constant, the amount of exhaust gas recirculation also changes depending on the exhaust pressure upstream of the recirculation amount control valve 17, so this compensation device is necessary.

Therefore, in order to prevent fluctuations in the exhaust gas recirculation rate due to changes in the pressure at the inlet of the recirculation amount control valve 17, a bellows 24 is installed in the middle of the rod 23, and a flexible pipe 25 controls the exhaust pressure at the inlet of the recirculation amount control valve 110. The bellows expands as the exhaust pressure increases, and the return flow control valve 17
It is possible to reduce the lift and suppress fluctuations in the reflux rate.

This is because the amount of exhaust gas recirculation is basically determined by the opening degree of the recirculation control valve 17 and the pressure difference between the upstream and downstream sides of the recirculation amount control valve 17, but the amount of exhaust gas recirculation may fluctuate due to changes in exhaust pressure. It is.

For example, if the opening degree of the throttle valve 19 is constant and the intake pressure is constant, that is, considering the operating conditions where the amount of intake air is constant, the opening degree of the recirculation amount control valve 17 is also constant and the intake pressure is also constant, so that the exhaust gas The reflux amount is determined by the exhaust pressure, but the bellows 24
Without it, there is a problem in that when the resistance of the exhaust system increases, the exhaust pressure increases and the amount of exhaust gas recirculation increases.

Here, the resistance of the exhaust system is caused by an increase in resistance over time due to the adhesion of oil smoke to the muffler 10 provided in the exhaust system and the exhaust pipe.

Therefore, in this case, since the air flow rate is constant, there is a problem that the recirculation rate of exhaust gas increases and combustion becomes unstable.

On the other hand, in the case of the present invention, since the bellows 24 compensates for changes in exhaust pressure, the recirculation rate of exhaust gas does not increase unnecessarily and combustion becomes unstable.

Particularly when a lean mixture is used, destabilization of combustion due to fluctuations in the amount of recirculation of exhaust gas is fatal, and from this point of view, compensation of the recirculation amount control valve 17 using exhaust pressure is effective.

The rod 21 is driven by the bellows 26, and when the temperature is low, the bellows 26 contracts, and by changing the fulcrum of the lever 22, the lift of the reflux control valve 17 is reduced, and the lift of the reflux control valve 17 is reduced. The reflux rate can be set to a value as shown in the curve.

Generally, when the engine temperature is low, the generation of nitrogen oxides is small and it is problematic to reduce the reflux rate.

In the above-described interception, the fuel supplied from the carburetor 12 is heated by the vaporizer 5, and the air-fuel mixture at an air-fuel ratio of around 20 to 28 is homogenized within the vaporizer 5.

The reason for using an air-fuel mixture with an air-fuel ratio of around 20 to 28 is as follows.

That is, the amount of NOx generated peaks at an air-fuel ratio of 16 to 17 and decreases depending on whether the air-fuel mixture becomes rich or lean.

In terms of fuel consumption, it is advantageous to use a lean mixture.

On the other hand, even if the air-fuel mixture is lean, the amount of NOx generated is still relatively large at air-fuel ratios around 18 to 19, and NOx significantly decreases at air-fuel ratios of 20 or higher.

Therefore, if an air-fuel mixture with an air-fuel ratio of 20 or higher is stably combusted, NOx, HC, and CO can be significantly reduced compared to the conventional method.

Incidentally, if the air-fuel ratio is increased too much, there is a problem that combustion becomes unstable, and the limit thereof is about 28.

If such a mixture is used, NOx and H
Although C and CO are significantly reduced, NOx and HC
, Co, it is advantageous to recirculate the exhaust gas and reburn the exhaust gas.

Therefore, in the present invention, the amount of exhaust gas recirculation is controlled using a device as shown in FIG. 2 so as to accurately recirculate the exhaust gas.

Furthermore, since the exhaust gas is supplied according to the curve shown in FIG. 3, the amount of oxygen in the air-fuel mixture is reduced in the region where NOx is most likely to be generated, making it possible to further suppress the generation of NOx.

Next, the mixture is supplied to the engine, but the mixture is 20
The spark plug is thin, with a diameter of about 2.8 mm, and there is a problem in that even if it is ignited with a normal spark plug, sufficient output cannot be obtained.

Therefore, two spark plugs 2 are installed to increase the ignition energy for ignition, which increases the combustion speed of the air-fuel mixture and prevents a decrease in output due to a lean air-fuel mixture.

Since a lean mixture is used in this way, the amount of CO1HC generated is small, NOx is reduced by introducing inert gas through exhaust gas recirculation, and the mixture is ignited by two spark plugs. This can accelerate the combustion rate and compensate for the decrease in output.

Furthermore, since the exhaust pipe is provided with an oxidizing reactor 6, it is possible to purify the C01HC that could not be combusted by the engine.

As described above, the present invention reduces the amount of NOx, HC, and CO generated by controlling the air-fuel ratio of the air-fuel mixture supplied to the engine to 20 to 28, and further reduces the amount of exhaust gas generated in the region where NOx is likely to be generated. Creates an optimal atmosphere that can reduce HC, CO, and NOx by accurately increasing the amount of reflux and reducing the amount of oxygen in the mixture, and prevents the resulting drop in output by igniting with multiple spark plugs. death,
Furthermore, we reduced HC and Co in the reactor, so
This makes it possible to effectively reduce exhaust gas and prevent a decrease in output.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an exhaust gas purification device for a gasoline engine according to the present invention, FIG. 2 is a block diagram of an exhaust gas recirculation device, and FIG. 3 is a diagram of exhaust gas recirculation characteristics. 1... Engine, 2... Spark plug,
5... vaporizer, 6... reactor, 9
...Exhaust recirculation device, 12...Carburizer,
15... Exhaust recirculation pipe, 17... Reflux control valve, 19... Throttle valve, 24...
...Bellows

Claims (1)

[Claims] 1. A fuel supply device that supplies a mixture whose air-fuel ratio in the engine combustion chamber is around 20 to 28 under normal operating conditions; and a vaporization device that is connected to the wake of the fuel supply device and heats the intake air-fuel mixture. , an ignition device having a plurality of spark plugs installed in each engine combustion chamber; an oxidation reaction device formed in the middle of an exhaust pipe; a muffler provided in the exhaust pipe downstream of the oxidation reaction device; an exhaust gas recirculation device that communicates the exhaust pipe between the oxidation reaction device and the muffler with a downstream side of a throttle valve provided in the fuel supply device; and an opening degree of the throttle valve provided in the middle of the exhaust gas recirculation passage. a recirculation control valve that controls exhaust gas flowing through the exhaust recirculation passage depending on the flow rate of the recirculation control valve; An exhaust gas purification device for a gasoline engine comprising an exhaust pressure compensating means for compensating to reduce the opening degree.