JPH06272623A - Exhaust gas purifying method for otto cycle engine - Google Patents

Abstract

PURPOSE:To prevent purifying performance of exhaust gas from reducing by incomplete combustion and reduction of combustion speed by setting a sufficient combustion temperature at all times, and carrying out operation in which thermal efficiency is not deteriorated. CONSTITUTION:In an Otto cycle engine in which a Miller cycle provided with a rotary valve 18 is used jointly, exhaust gas in an engine make reverse flow in a cylinder 2 through an exhaust valve 10 at the bottom dead point in intake stroke. Hereby, a sufficient combustion temperature is set at the top dead point in compressing stroke, and operation in which thermal efficiency is not deteriorated is carried out, so that it is possible to prevent purifying performance of exhaust gas from reducing by incomplete combustion and reduction of combustion speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification method for an Otto cycle engine that also uses a Miller cycle,
In particular, the present invention relates to an exhaust gas purification method for an Otto cycle engine, which does not cause a reduction in exhaust gas purification due to incomplete combustion or a reduction in combustion speed at a partial load.

[0002]

2. Description of the Related Art In an engine that inhales a mixture of fuel and air with an equivalence ratio, the throttle valve regulates the intake of the mixture to the engine during partial load such as light load operation or idle operation. However, at this partial load, pump loss occurs and engine efficiency decreases. On the other hand, the present inventor has provided a rotary valve (rotary valve) that rotates in synchronization with the cam shaft in the ventilation passage of the engine.
By controlling the operation, a method of performing intake air amount control with less pump loss is proposed (internal combustion engine: 20
Vol. 6, No. 7, 1981).

FIG. 2 is a P-V diagram of an Otto-cycle engine in which a normal Otto-cycle engine and a Miller cycle are used in combination. In load control in the case of a normal Otto-cycle engine, throttle is used to throttle intake air. In the intake stroke, the intake pressure drops to P0, the intake stroke starts from P0, and the compression stroke starts from P2, which is the same pressure as P0, and is compressed to P3.

At this time, the temperature at the point P2 becomes the same as the atmospheric temperature due to the throttle loss represented by P7-P0-P2-Pa, and the compression temperature at the point P3 becomes the same as in the full load state without a throttle, resulting in combustion. Although no inconvenience is caused, if the proposed Otto cycle engine equipped with a rotary valve is used for the purpose of eliminating throttling loss, in the intake stroke, the intake pressure is at point P7, that is, at the atmospheric pressure, while Pa is in the middle of the intake stroke. When the intake is performed up to and the rotary valve is closed at Pa, the piston further lowers, the mixture is adiabatically expanded and the pressure and temperature are lowered, and at P2, the intake stroke bottom dead center. The compression stroke starts from P2, the pressure and temperature of the intake state again reach Pa, and the atmospheric pressure is reached. From Pa, the substantial compression stroke begins, and the compression loss occurs without reaching the compression top dead center P3. At this time, the substantial compression stroke is shorter from Pa to P3 as compared with the normal engine, which means that the compression ratio is substantially reduced, the temperature at the point P3 does not reach the required compression temperature, and the compression top dead center is reached. It is ignited by the spark plug at P3.

However, in actuality, a sufficient compression temperature is not reached at P3, in other words, P3 to P4 in FIG. 2 is not reached, and a curve route as shown by a dotted line is passed through P12 to P5.
Leading to. Then, at P5, the expansion stroke ends, the exhaust valve opens, and the pressure in the cylinder drops to almost atmospheric pressure at P6.
Although the exhaust stroke is ended at P7 and the throttling loss is reduced, not only is the increase in thermal efficiency limited by the decrease in combustion speed, but the exhaust temperature at point P5 also decreases as the compression temperature decreases, There was a problem in detoxifying exhaust gas because the operating temperature of the exhaust gas purification catalyst was not reached.

[0006]

In the Otto cycle engine equipped with the proposed rotary valve as described above, a sufficient combustion temperature may not be reached. In this case, P3-P4-P12 in FIG. The amount of work is lost by the area surrounded by the shaded area, which not only lowers the thermal efficiency but also lowers the exhaust gas purification temperature because the exhaust temperature does not reach the operating temperature of the catalyst.

The present invention has been made in view of the current state of the operation of an Otto cycle engine that also uses a Miller cycle equipped with a rotary valve as described above, and an object thereof is to always achieve a sufficient combustion temperature and achieve a thermal efficiency. It is an object of the present invention to provide an exhaust gas purification method for an Otto-cycle engine, in which the exhaust gas temperature is prevented from lowering due to incomplete combustion or a decrease in combustion temperature by performing an operation without deterioration of the exhaust gas.

[0008]

SUMMARY OF THE INVENTION The above object is to provide an exhaust gas purification method for an Otto cycle engine that also uses a Miller cycle equipped with a rotary valve, in which the exhaust gas of the engine is introduced into the cylinder through the exhaust valve at the bottom dead center of the intake stroke. It is achieved by regurgitating.

[0009]

According to this means, the exhaust gas flows back into the cylinder at the bottom dead center of the intake stroke of the engine, and the gas in the cylinder has a pressure from negative pressure to near atmospheric pressure, which is shown in FIG.
Adiabatic compression is performed while increasing the pressure from 2 to P8, and the temperature rises, and further the temperature rises due to the mixed high-temperature exhaust gas. Since the compression stroke is started from this state, the temperature at the end of the compression stroke rises, a sufficient combustion temperature is always obtained, and not only the incomplete combustion and the reduction of the combustion speed but also the operation without the reduction of the thermal efficiency are performed. Also, the exhaust gas temperature does not rise and the exhaust gas purification does not decrease.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. Here, FIG. 1 is an explanatory diagram showing a configuration of a main part of an Otto cycle engine using a Miller cycle used in the exhaust gas purification method of the embodiment in a state where intake and exhaust valves are closed, and FIG. 2 is related to the embodiment. Fig. 3 is a P-V diagram, Fig. 3 is an explanatory view of the state of the air-fuel mixture in the cylinder before and after the exhaust gas reverse flow, and Fig. 4 is an exhaust valve of the Otto cycle engine used in the exhaust purification method of the embodiment. FIG. 5 is an explanatory view showing a configuration of a main part when the rotary valve is closed, FIG. 5 is an explanatory view of an operation of the embodiment, and FIG. 6 is an explanatory view of an opening / closing timing adjusting device of the rotary valve.

First, the construction of an Otto cycle engine used in combination with the Miller cycle used in the embodiment will be described.
This mirror cycle engine is basically a four-cycle engine in which a piston 2 slides in a cylinder 1 and a crankshaft (not shown) is rotated by a connecting rod 3 as shown in FIG. The spark plug 5, the intake valve 7 and the fuel injection valve 8 at the intake port 6, and the exhaust valve 10 at the exhaust port 9, respectively.
A spring bearing 1 that receives the force of a valve spring 11 at the end of the exhaust valve 10.
2 and a tappet 15 for transmitting the movement of a cam 14 having an auxiliary cam 13 are installed.

The spark plug 5 carries out an ignition operation in synchronization with the crankshaft of the engine, and also has an intake valve 7 and an exhaust valve 10.
Also, since it is opened / closed by a known valve opening / closing mechanism in synchronization with the crankshaft, the opening / closing cycle thereof is set in the same manner as in a normal engine. In the engine, the auxiliary cam 13 operates near the bottom dead center of the intake stroke to move the exhaust valve 10 from near the bottom dead center of the intake stroke to after the bottom dead center as shown in FIG. The exhaust gas is made to flow back into the cylinder 1 for a predetermined period of time. An intake manifold 17 is installed at one end of an intake branch pipe 16 communicating with the intake port 6 to form an intake passage.

A rotary valve 18 as a control valve is arranged in the intake branch pipe 16 arranged in each cylinder of such a multi-cylinder engine, and is driven by a crankshaft through a synchronous transmission mechanism. The opening / closing timing is adjusted by the opening / closing timing adjusting device shown in FIG. A catalyst 19 is arranged downstream of the exhaust manifold 20 communicating with the exhaust port 9 to purify the exhaust gas.

The rotary valve 1 used in the present invention
The opening / closing timing adjusting device 8 will be described with reference to FIG. In FIG. 6, a helical spline 22 is installed at one end 21a of the shaft 21 of the rotary valve 18, and the opposite drive shaft 2
A helical spline 24 that is twisted in the opposite direction to the spline 22 is installed at one end of 3. A gear 25 meshes with the other end of the drive shaft 23 in synchronization with a crank gear (not shown) provided at one end of the crank shaft to drive the drive shaft 23.

One end 29 of a lever 28 is engaged with a groove 27 of an adjusting piece 26 which meshes with the helical splines 22 and 24.

Therefore, in the load adjustment of the present invention, by moving one end 29 of the lever 28 left and right in FIG. 6, the closing timing of the rotary valve 18, that is, the point Pa in FIG. The intake air amount (length a shown in FIG. 2) at is changed.

Next, an exhaust purification method according to the embodiment using the Otto cycle engine combined with such a 4-cycle Miller cycle will be described.

In the Otto cycle engine combined with the mirror cycle according to the embodiment, the rotary valve 18 is opened and closed at the same time as the intake valve 7 is opened and closed, and the intake port 6 and the cylinder are opened in the intake stroke of the engine in which the intake valve 7 is opened. Air close to the atmospheric pressure and gasoline in an amount corresponding to the atmospheric pressure are injected from the fuel injection valve 8 into the fuel cell 1. Then, air and gasoline form a mixture and flow into the cylinder 1. At this time, the pressure of the cylinder 1 is close to the atmosphere, and the exhaust valve 10 is opened by the auxiliary cam 13 near the bottom dead center of the intake stroke of the engine. However, the pressure difference between the inside of the cylinder 1 and the exhaust port 9 is small, the amount of exhaust gas flowing back is small, and the same operation as that of a normal 4-cycle Otto cycle engine is performed.

By the way, at the time of partial load of light load operation or idle operation, the closing timing of the rotary valve 18 is advanced so as to limit the intake amount of the air-fuel mixture, and as shown in FIG. Since the intake air amount is limited by closing at point Pa, the pressure in the cylinder 1 sucks the air-fuel mixture from point P7 in the atmospheric state to point Pa, and the rotary valve 18 is closed at Pa in the middle of the intake stroke. However, the piston 2 is further lowered, the mixture is adiabatically expanded and the pressure and temperature are lowered, and at P2, the intake stroke bottom dead center is reached.
At the bottom dead center P2 of the intake stroke, the exhaust valve 10 is opened by the auxiliary cam 13, and the exhaust gas in the exhaust port 9 under atmospheric pressure flows backward into the cylinder 1 which is a negative pressure. At this time, as shown in FIG. 3B, the air-fuel mixture in the cylinder 1 has a pressure p1 below atmospheric pressure, the volume v1 is the exhaust amount of the cylinder 1, and the temperature is t1, but the exhaust gas reverse flow Causes the air-fuel mixture to be adiabatically compressed to near atmospheric pressure.
As shown in (a), the volume decreases to v2, the pressure increases to p2 near atmospheric pressure, the temperature rises to t2, and the state of the air-fuel mixture moves from P2 to P8 in FIG. By the way, the temperature of the exhaust gas that flows back is about 200 ° C. at the time of low cooling water temperature immediately after the engine is started, and the compressed air-fuel mixture mixes with this, and at point P8 in FIG. To rise. The mixed gas of this mixed gas and exhaust gas is as shown in FIG.
The point P8 is compressed to the atmospheric pressure state at the point P8a, and the amount of the exhaust gas that flows backward at this time is shown in FIG. 3 (b).

In the embodiment, the compression stroke starts at point P8 in FIG. 2, and at the compression top dead center P9, the pressure and temperature are higher than those of the conventional point P3, where it is ignited by the ignition plug 5 and burned. The pressure in the cylinder 1 rises to the point P10, expands from the point P10, and completes the expansion stroke at the point P11. Even at the point P11 after expansion, the temperature is naturally higher than in the conventional case, and the high exhaust gas temperature gives the catalyst activity. The exhaust gas in the exhaust port 9 immediately after being discharged is highly active and has an effect as a combustion promoter. By the way, it is known that a two-cycle gasoline engine burns well even if a large amount of exhaust gas is mixed in the air-fuel mixture. Even in the examples, even if a large amount of exhaust gas is mixed, combustion failure will occur. There is no.

In the embodiment, the reverse flow of the exhaust gas is generated by the negative pressure in the cylinder 1. Therefore, at a low load with a large negative pressure and a low exhaust temperature, the amount thereof is large and the temperature rise of the exhaust gas is also large. The negative pressure in the cylinder 1 decreases as the load increases. Therefore, the reverse flow rate of the exhaust gas is also reduced, and when the throttle valve is fully opened at full load, the pressure in the cylinder 1 becomes almost atmospheric pressure, and the reverse flow of the exhaust gas hardly occurs. Air-fuel mixture can be inhaled and the same output can be obtained. Further, also in the known engine, the exhaust temperature rises as the load increases, so even if the reverse flow rate of the exhaust gas is reduced as the load increases, the activity of the catalyst 19 of the embodiment will not be hindered. Absent.

As described above, according to the embodiment, the compression top dead center P
In No. 9, since a sufficient combustion temperature is given, incomplete combustion or reduction in combustion speed does not occur, operation without deterioration of thermal efficiency is performed, and thermal efficiency does not decrease due to incomplete combustion or reduction in combustion speed.

Further, in the Otto cycle engine which also uses the Miller cycle according to the embodiment, the intake valve 7 is open even at the bottom dead center of the intake stroke as shown in FIG. Since the valve 10 also opens,
In a configuration in which only one throttle valve is provided at one end of the intake manifold as in a known engine, a part of the exhaust gas that flows backward from the exhaust port 9 flows in the cylinder 1 as shown by an arrow in FIG. It passes through the intake pipe 16 and is sucked into the cylinder during another intake stroke. Then, it was confirmed that the air-fuel mixture in the cylinder 1 was not effectively compressed and the effect of the embodiment was diminished. On the other hand, in the configuration of the embodiment, the rotary valve 18 is arranged in each of the intake pipes of the multi-cylinder engine in a part of the intake branch pipe 16 so that the exhaust gas that flows back into the intake port 6 is discharged. Overflow to the upstream side of the rotary valve 18, which is at atmospheric pressure, is prevented, and compression of the air-fuel mixture due to reverse flow of exhaust gas is ensured even in the cylinder 1.

[0024]

As described above, according to the present invention, in an Otto cycle engine which also uses a Miller cycle equipped with a rotary valve, exhaust gas of the engine is exhausted at the bottom dead center of the intake stroke during partial load. By backflowing into the cylinder through the cylinder, a sufficient combustion temperature is set at the compression top dead center, not only the exhaust gas purification is promoted, but also the operation without deterioration of the thermal efficiency is performed, resulting in incomplete combustion and reduction of the combustion speed. It is possible to provide an exhaust gas purification method that does not cause a decrease in exhaust gas.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the configuration of an Otto cycle engine used together with a Miller cycle used in an embodiment of the present invention in a state where an intake valve is closed.

FIG. 2 is a P-V diagram for explaining the operation of the embodiment.

FIG. 3 is an explanatory view of the state of the air-fuel mixture in the cylinder due to the backflow of exhaust gas of the one embodiment, FIG.
(B) is explanatory drawing before the backflow of (a).

FIG. 4 is an explanatory diagram showing a configuration of an Otto cycle engine that also uses a Miller cycle used in the one embodiment in a state where an intake valve is opened.

FIG. 5 is an explanatory diagram of an operation of the one embodiment.

6A and 6B are explanatory views of an opening / closing timing adjusting device for a rotary valve used in the present invention, FIG. 6A is an overall schematic view, and FIG.

[Explanation of symbols]

 1 Cylinder 2 Piston 3 Connecting Rod 4 Cylinder Head 5 Spark Plug 6 Intake Port 7 Intake Valve 8 Fuel Injection Valve 9 Exhaust Port 10 Exhaust Valve 11 Valve Spring 12 Spring Bearing 13 Auxiliary Cam 14 Cam 15 Tappet 16 Intake Branch Pipe 17 Intake Collecting Pipe 18 Rotary valve 19 Catalyst 20 Exhaust manifold

Claims (1)

[Claims] 1. An exhaust gas purification method for an Otto cycle engine that also uses a Miller cycle equipped with a rotary valve, wherein exhaust gas of the engine is caused to flow backward through the exhaust valve into the cylinder at the bottom dead center of the intake stroke. Exhaust purification method for Otto cycle engine.