JP2002349268A - Cylinder injection two-cycle gasoline engle with supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-cycle gasoline engine superior in scavenging efficiency, superior in a fuel consumption rate, and causing little environmental pollution by preventing mixing of exhaust gas of an air-fuel mixture at scavenging time. SOLUTION: This cylinder injection two-cycle gasoline engine has an exhaust means for exhausting combustion gas in a cylinder 1, a supercharging means 4 for scavenging by feeding preload air in the cylinder 1, a fuel injection means 11 for generating the air-fuel mixture by directly atomizing and injecting gasoline in the cylinder 1, and an ignition means 9 for burning the air-fuel mixture in the cylinder 1. Because of scavenging by a large quantity of costless air, the scavenging efficiency and the fuel consumption rate are improved, and the environmental pollution is reduced to thereby provide a lightweight high output gasoline engine for reducing a part while conquering the largest defect of a two-cycle engine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement of a two-stroke gasoline engine.

[0002]

2. Description of the Related Art A conventional two-stroke gasoline engine has a structure in which a series of combustion, exhaust, scavenging, and compression operations are performed in two strokes (downstroke and upstroke) of a piston.
Among these actions, the scavenging action, which is a unique action of the two-stroke gasoline engine, is to feed a fuel-air mixture generated outside the cylinder in advance into the cylinder as fuel, and use this gas-fuel mixture to transfer combustion gas to the outside of the cylinder. I try to extrude.

[0003]

Since such a conventional two-stroke gasoline engine has a structure in which a limited amount of air-fuel mixture equal to the stroke volume of the cylinder is fed into the cylinder to scavenge it, a new mixed gasoline engine is used. The gas and the combustion gas could not be completely exchanged, resulting in poor scavenging efficiency and badly affecting the combustion state of the engine. Further, a phenomenon that a new air-fuel mixture to be kept in the cylinder blows out of the cylinder as it is occurs, so that the fuel consumption efficiency with respect to the output is poor.

Further, since unburned air-fuel mixture is mixed into exhaust gas components, it is difficult to take pollution countermeasures due to a large amount of harmful substances. In recent years, however, use as an automobile engine has been shunned and has been forgotten as a past technology. The present invention has been made in consideration of the above problems, and has an object to provide a two-cycle gasoline engine with good scavenging efficiency and good fuel consumption and low pollution.

[0005]

SUMMARY OF THE INVENTION To achieve the above object, the present invention is an internal combustion engine characterized by combining a supercharger in a two-cycle engine having a gasoline in-cylinder injection device. Specifically, exhaust means for discharging the combustion gas in the cylinder, supercharging means for supplying pressurized air into the cylinder to scavenge it, and fuel for directly injecting gasoline into the cylinder to produce an air-fuel mixture An injection unit and an ignition unit for burning the air-fuel mixture are provided.

In this in-cylinder injection two-cycle gasoline engine with a supercharging device, first, the combustion gas in the burned cylinder is discharged outside the cylinder by an exhaust means near the bottom dead center (exhaust action). Thereafter, a large amount of air exceeding the stroke volume pressurized by the supercharging means is fed into the cylinder, and the combustion gas is completely pushed out of the cylinder (scavenging action). Next, in the rising stroke, gasoline is directly atomized and injected into the cylinder by the fuel injection means to generate new air in the cylinder into an air-fuel mixture. This air-fuel mixture is compressed by a piston (compression action), ignited by ignition means, and burns (combustion action). Subsequently, the process moves to a descending stroke due to expansion.

[0007] Self-ignition type fuel found in conventional diesels is successively combined with oxygen in the air during the atomization process after in-cylinder injection and ignites, whereas gasoline has a compression ratio of about 30. In order to ignite and burn atomized gasoline immediately, it is necessary to direct the air-fuel mixture to the vicinity of the spark plug, and to establish it over the entire engine speed and load range. However, gasoline direct injection engines were not practical.

In the recently developed four-cycle gasoline direct injection engine, a vertical vortex is generated after air is introduced, the angular velocity is accelerated by raising the piston, and the atomization of fuel is promoted. Only a high-concentration air-fuel mixture is formed to facilitate ignition, and an ultra-lean combustion operation with an air-fuel ratio of about 30 is possible as a whole. In addition, it is not necessary to throttle the throttle even with a relatively light partial load, and a large amount of air can flow in, so that pumping loss is reduced, so that it can be put to practical use as an efficient gasoline engine. became.

Further, by adding a supercharging device to the four-cycle gasoline in-cylinder injection engine, dividing the fuel injection into two injections, cooling the combustion chamber in the first injection, and optimizing the mixing ratio in the next injection, Techniques have been developed to prevent knocking and thus increase boost pressure from low speeds. this is,
Since a large amount of air is sucked in even at low rotation speeds, there is an advantage that the total amount of exhaust gas is large and the rotation speed of the turbine can be kept high. Becomes

By combining a recent gasoline in-cylinder direct injection technology having these features and a supercharger with a two-cycle engine, scavenging can be performed with a large amount of air.
Therefore, the compression stroke starts with only air having no residual exhaust gas, and an ideal combustion comparable to a four-cycle engine can be expected. In addition, there is no mixing of unburned mixed gas into the exhaust gas.

[0011]

1 to 4 are sectional views showing an in-cylinder injection type two-cycle gasoline engine with a supercharger according to an embodiment of the present invention. FIG. 1 shows a scavenging operation, and FIG. FIG. 3 shows a combustion action, and FIG. 4 shows an exhaust action.

The cylinder 1 shown in this figure is a uniflow scavenging type cylinder having scavenging means on the side of the cylinder and exhaust means on the cylinder head. That is, a scavenging port 3 which is opened and closed by a crankshaft interlocked with a piston 2 is formed in a side portion of the cylinder 1, and a roots-type supercharger 4 driven by a crankshaft is provided near the scavenging port 3. The scavenging port 3 of the cylinder 1 and the exhaust port 5 of the supercharger 4 are connected by a casing 6. An exhaust port 8 that is opened and closed by an exhaust valve 7 is formed in the head of the cylinder 1. Similarly, a spark plug 9 and a fuel injection valve 11 connected to a gasoline pump 10 are provided at the head of the cylinder 1. In the drawings, reference numeral 12 denotes a connecting rod, and reference numeral 13 denotes a crankshaft.

Next, the operation of the present embodiment will be described. FIG.
The scavenging action of will be described. When the piston 2 descends and reaches near the bottom dead center, the scavenging port 3 is opened. In this state,
A large amount of air pressurized by the supercharger 4 is supplied from the scavenging port 3 into the cylinder 1. The combustion gas in the cylinder 1 is
The new large amount of pressurized air is pushed out to the exhaust port 8 and scavenged. When the combustion gas and the fresh air are completely replaced, the piston 2 starts to rise.

The compression operation of FIG. 2 will be described. When the piston 2 rises, the scavenging port 3 is closed by the piston 2 and the exhaust port 8 is closed by the exhaust valve 7. In this state, gasoline is directly atomized and injected into the cylinder by the fuel injection valve 11, and new air in the cylinder is generated in the air-fuel mixture. This air-fuel mixture is compressed by the ascending piston, and is stirred while the vertical vortex rotation speed is accelerated, so that sufficient vaporization is performed.

The combustion operation of FIG. 3 will be described. When the piston 2 is near the top dead center, the scavenging port 3 is closed by the piston 2 and the exhaust port 8 is closed by the exhaust valve 7. In this state, the compressed air-fuel mixture is ignited by the ignition plug 9 and burns, and the expansion of the combustion gas pushes down the piston 2.

The exhaust operation of FIG. 4 will be described. When the piston 2 descends, the exhaust valve 7 operates near the bottom dead center to open the exhaust port 8. In this state, the combustion gas in the cylinder 1 is discharged from the exhaust port 8.

In this embodiment, the roots-type supercharger 4 driven by a crankshaft is used as a supercharging device. However, the present invention is not limited to this, and a centrifugal supercharger driven by a crankshaft as shown in FIG. The exhaust gas turbine driven supercharger 34 as shown in FIG.

Further, in this embodiment, the uniflow type cylinder 1 having the scavenging port 3 on the side and the exhaust valve 7 and the exhaust port 8 on the head is used as a cylinder, but is not limited to this. A cross-scavenging cylinder 21 having a scavenging port 23 and an exhaust port 28 on the side of the cylinder as shown in FIG. 7 may be used.

[0019]

As described above, in the in-cylinder injection type two-stroke gasoline engine with a supercharging device of the present invention, the gas used for the scavenging action is not a conventional air-fuel mixture but an inexpensive air. Moreover, since it can be used in a large amount, scavenging efficiency and fuel consumption efficiency are good, and it becomes easy to add a pollution reduction device.

Since each cylinder of a four-cycle engine has one explosion per one revolution of a crank compared to one explosion for every two revolutions of a crank, the unburned gas which is a drawback of two cycles is prevented. In the case of a four-cylinder engine, which is an advantage of two cycles, it is possible to obtain an output close to that of an eight-cylinder engine and to achieve quietness and vibration balance while overcoming the poor scavenging efficiency. Conversely, it is possible to produce a small and light gasoline engine because half the number of cylinders is the same to obtain the same output. Since unburned gas does not enter the exhaust gas, hydrocarbons, carbon monoxide, and nitrogen oxides can be reduced with a structure similar to a four-cycle catalyst device.

[0021] Further, in spite of two cycles, similar to a four-cycle direct injection type gasoline engine, a vertical vortex is generated at the time of air inflow, and the angular velocity of the vortex is further accelerated by a volume reduction due to the rise of the piston, thereby atomizing the fuel. And a high-concentration air-fuel mixture is formed only in the vicinity of the spark plug to facilitate ignition. As a whole, ultra-lean mixed combustion with an air-fuel ratio of about 30 can be expected. Further, since it is not necessary to reduce the amount of inflow air even at the time of low load, the pumping loss due to the suction resistance is reduced and the efficiency is improved as in the case of the 4-cycle direct injection. further,
Since a large amount of air is sucked in even at low speeds, the total amount of exhaust gas also increases, and in an exhaust turbine driven turbocharger, low-speed torque is large and excellent accelerator response is achieved by keeping the turbine rotation high from low rotation. It is the same as the 4-cycle direct injection that it is easy to set the engine to be easy to handle.

In addition, a two-cycle engine requires one combustion per rotation of the crank, so that the output, quietness, and low vibration equivalent to twice the number of cylinders can be expected as compared with four cycles.
The advantage that the torque at low rotation is large, the transmission does not need to be multistage, and the number of parts of the engine is small can be utilized as it is.

Since the exhaust gas is free from unburned gas, it is burned by giving an air-fuel mixture sometimes to reduce nitrogen oxides in an environment with a small amount of reducing substances such as hydrocarbons and carbon monoxide. Purging below the emission standards currently required for vehicles by using lean NOx catalyst technology that temporarily stores and reduces nitrogen oxides while intermittently supplying hydrocarbons and carbon monoxide into the gas Becomes possible.

In the two-cycle gasoline direct injection by supercharging, the injection time during the compression stroke is shorter than that in four cycles, and it is expected that atomization injection must be performed in a short time. It is possible to respond by adopting the technology to make it. In order to cope with high-speed rotation, it is necessary to use a large-sized injection device. However, as it is, a small spray amount at low rotation tends to vary, and idling becomes unstable. In overcoming these problems, it is also effective to increase the injection pressure during high-speed and high-load operation and reduce the pressure during idling to achieve stable engine rotation.

However, the in-cylinder injection type two-cycle gasoline engine with the supercharging device having the same displacement as the four-cycle supercharging direct injection has twice the number of explosions per revolution, and is theoretically effective for output. The acupressure diagram area per unit time is also doubled, and the same shaft output can be obtained at half the rotation speed.
It is also a characteristic that high output can be obtained without forcibly using a high-speed rotating engine.

The gasoline in-cylinder injection device that has been put into practical use in recent years is a two-stroke engine combined with a supercharging device, and can be said to be a technology that demonstrates its true value.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an internal structure of a direct injection two-stroke gasoline engine with a supercharging device and an exhaust and scavenging action according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an internal structure of a direct injection type two-stroke gasoline engine with a supercharger according to the embodiment of the present invention and a compression action while atomizing and injecting gasoline.

FIG. 3 is a cross-sectional view showing an internal structure and a combustion action of a direct injection two-cycle gasoline engine with a supercharging device according to the embodiment of the present invention.

FIG. 4 is a cross-sectional view showing an internal structure and an exhaust action of a direct injection two-stroke gasoline engine with a supercharging device according to the embodiment of the present invention.

FIG. 5 is a sectional view showing an internal structure of a direct injection two-cycle gasoline engine with a supercharging device according to another embodiment of the present invention.

FIG. 6 is a cross-sectional view showing an internal structure of a direct injection two-cycle gasoline engine with a supercharger according to another embodiment of the present invention.

FIG. 7 is a sectional view showing the internal structure of a direct injection two-cycle gasoline engine with a supercharging device according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston 3 Scavenging port (scavenging means) 4 Supercharger (supercharging means) 5 Exhaust port 6 Casing 7 Exhaust valve (exhausting means) 8 Exhaust port (exhausting means) 9 Spark plug (ignition means) 10 Gasoline pump 11 Fuel injection valve (fuel injection means) 12 Connecting rod 13 Crankshaft 21 Transverse scavenging cylinder 23 Scavenging port 24 Crankshaft driven supercharger 28 Exhaust port 34 Exhaust turbine driven supercharger

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Claims (1)

[Claims] An exhaust means for discharging combustion gas in a cylinder, a supercharging means for supplying pressurized air into a cylinder for scavenging, and a fuel for directly injecting gasoline into a cylinder to produce an air-fuel mixture. An in-cylinder injection two-cycle gasoline engine with a supercharging device, comprising an injection means and an ignition means for burning an air-fuel mixture in a cylinder.