JPH03100318A - Two-stroke internal combustion engine - Google Patents

Abstract

PURPOSE:To contrive the atomization of fuel by interposing a solenoid valve, which is opened almost simultaneously with fuel injection, in an air passage between an accumulator chamber, which communicates with a crank chamber through a check valve, and a fuel supplying port. CONSTITUTION:A fuel injection valve 11 is provided to appear in a fuel supplying port 10 opened and formed in a side surface of a cylinder 5. While an accumulator chamber 12, which communicates with a crank chamber 4 through a check valve 15, is provided. A solenoid valve 17, which is opened almost simultaneously with fuel injection, is interposed in an air passage 16 between the accumulator chamber 12 and the fuel supplying port 10. In this way, when a piston 6 is moved downward with a pressure in the crank chamber 4 sufficiently increased, the pressure is accumulated in the accumulator chamber 12 through the check valve 15. The piston 6 is inverted in the bottom dead center and moved upward, when the piston reaches a suitable position, the solenoid valve 17 is opened with high pressure air jetted through the fuel supplying port 10. Accordingly, fuel injected from the fuel injection valve 11 is mixed with a flow of air almost simultaneously with the above and effectively atomized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to an improvement in a two-stroke internal combustion engine in which fuel is directly injected into a cylinder by a fuel injection valve.

Conventional technology In a two-stroke internal combustion engine in which a piston opens and closes the scavenging port and exhaust port that open on the side of the cylinder, it is impossible to completely eliminate the phenomenon in which fresh air flowing in from the scavenging port blows through to the exhaust port in a short circuit. It cannot be avoided. Therefore, the 2-stroke has a configuration in which only fresh air is compressed in the crank chamber and introduced into the cylinder from the scavenging port, and fuel is separately injected into the cylinder by a fuel injection valve. Various internal combustion engines have been proposed.

In this case, if only the fuel is injected and supplied at a relatively low pressure, the atomization and atomization of the fuel will be poor, and it will be difficult to form a good mixture in the cylinder. At the same time, it is generally devised to inject fuel.

For example, in SAE paper 780767, as shown in FIG.
A configuration is disclosed in which an electromagnetic fuel injection valve 23 is provided at the fuel injection port 2, and the fuel supply port 22 and the crank chamber 24 are communicated through an air passage 25. Note that 26 is an exhaust port, 27 is a scavenging port, and 28 is a piston. That is, in this configuration, a part of the air compressed in the crank chamber 24 is guided to the fuel supply port 22 and injected into the cylinder, so that the atomization of the fuel injected from the fuel injection valve 23 is promoted. It has become.

Furthermore, in JP-A-62-93481, pressurized air pressurized by an external pump is introduced into the annular passage around the poppet valve, and fuel metered by a solenoid valve is introduced into the annular passage. A two-stroke internal combustion engine using a so-called air spray valve system is disclosed, in which air and fuel are mixed and injected into the cylinder by opening the poppet valve at a predetermined time.

Problems to be Solved by the Invention However, in the former configuration, the pressure in the crank chamber 24 increases before and after the timing when the piston 28 moves downward and the scavenging port 27 opens, while the piston 28 is at the bottom dead center. When the crankshaft moves upward, the pressure within the crank chamber 24 rapidly decreases. Therefore, if you try to inject fuel relatively late (for example, before or after the time when the exhaust port 26 closes) to prevent fuel blow-by, you will hardly be able to obtain the jet of air from the fuel supply port 22, resulting in the desired effect. I can't really expect that. In other words, it is necessary to inject fuel during the downward movement of the piston 28 when the pressure inside the crank chamber 24 is high, and as a result, the discharge term for unburned components is reduced as in the case where the premixture is introduced from the crank chamber 24. It ends up being too many.

Furthermore, the latter configuration requires a separate pump to generate sufficiently high pressure air, which tends to complicate the configuration.

Means for Solving the Problems Therefore, the present invention provides a scavenging port that communicates with the crank chamber for compressing fresh air and is open on the side of the cylinder, and an exhaust port that is also open on the side of the cylinder, and that both ports are connected to each other. In a two-stroke internal combustion engine in which the piston opens and closes,
A fuel supply port is formed on the side of the cylinder, and a fuel injection valve is installed there, and a pressure accumulation chamber is provided which communicates with the crank chamber via a check valve, and the pressure accumulation chamber and the fuel supply port are connected to each other. The air passage between the two is characterized by a solenoid valve that opens almost simultaneously with fuel injection.

In the above-mentioned structure, when the piston moves downward and the pressure in the crank chamber increases sufficiently, that pressure is stored in the pressure accumulation chamber via the check valve. At this time, the solenoid valve is of course closed.

Then, the piston reverses itself at the bottom dead center and moves upward, and when it reaches an appropriate position, the solenoid valve is opened.

This causes high pressure air to blow out through the fuel supply port. At approximately the same time, the fuel injection valve operates to perform fuel injection. Therefore, the injected fuel mixes with the air stream and is effectively atomized.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a cross-sectional view showing the main parts of a two-stroke internal combustion engine according to the present invention, in which a crankcase cover 2 is fixed with bolts to the lower part of a cylinder block 2, forming a sealed crank chamber 4. together with cylinder 5
A piston 6 is slidably housed therein, and its upper end is closed by a cylinder head (not shown). Note that the ignition plug is also omitted from the illustration.

On the side surface of the cylinder 5, an exhaust port 8 and a plurality of scavenging ports 9, which are opened and closed by the piston 6, are formed in a substantially rectangular shape.

The exhaust port 8 is connected to an exhaust system consisting of a catalyst and a muffler (not shown), and is opened at a position around 90° ATDC when the piston 6 moves downward, as shown in FIG. , its opening position has been determined.

Further, the scavenging port 9 communicates with the crank chamber 4 through a passage inside the cylinder block l.

As shown in FIG. 2, the open position [1] is determined so that the piston 6 opens at a position after 120° ATDC when it moves downward.

A relatively small fuel supply port 10 is further formed on the side surface of the cylinder 5, and an electromagnetic fuel injection valve 11 is provided therein. This fuel injection valve 11 measures and injects relatively low-pressure fuel according to the ON time of a drive pulse signal.
The tip nozzle hole is located slightly recessed from the opening of 0, and an appropriate space is secured around the tip to allow air to flow. Note that the opening height position of the fuel supply port IO is set in consideration of the injection timing. That is, it goes without saying that it is necessary not to be covered by the piston 6 during injection, but if it is located at an excessively high position, combustion gas may enter, which is undesirable. In the illustrated example, it is located at a height near the upper edge of the exhaust port 8.

Further, a pressure accumulating chamber 12 is formed on the side of the cylinder block 1, which is independent for each cylinder or integrated for each cylinder. This pressure accumulation chamber I2 is located at a notch 1 on the side surface of the cylinder 5.
3 and the crank chamber 4 through the air passage I4, and at one end of the air passage 14, there is a check valve 15, such as a road valve, which prevents backflow from the pressure accumulation chamber 12 to the crank chamber 4 side. is installed. The pressure accumulation chamber 12 and the fuel supply port 10 are connected through an air passage 16, and a solenoid valve 7 is interposed in the air passage.

The lower end of the air passage 16 communicates with the notch 13, that is, the crank chamber 4, via a check valve 18 to prevent fuel from stagnation therein.

Now, in the above configuration, when the piston 6 moves downward due to an explosion, fresh air, specifically, only air, is compressed within the crank chamber 4. As a result, the pressure in the crank chamber 4 increases, and high-pressure air is stored in the pressure accumulation chamber 12 via the check valve 15. Incidentally, the timing of this pressure accumulation period, etc. is shown in FIG.

Then, when the piston 6 moves down to ATDC 90°, the exhaust port 8 opens, and when the piston 6 further moves down to about 120° ATDC, the scavenging port 9 opens, and gas exchange in the cylinder 5 is performed. By opening the scavenging port 9, the pressure in the crank chamber 4 decreases rapidly, but the check valve I
5 maintains the high pressure state within the pressure accumulator chamber 12. Note that since the fuel supply port 10 is opened before the scavenging port 9 is opened, a small amount of air flows through the check valve I8 and the air passage I6, removing the air-fuel mixture and burnt gas that had accumulated in the air passage 16. Scavenge.

Next, when the piston 6 reverses at the bottom dead center and moves upward, BT
The scavenging port 9 closes at around 120° DC and BTDC
Close exhaust port 8 at around 90°.

Then, just before the exhaust port 8 closes, the solenoid valve 17
When the valve is opened, the fuel injection valve 11 injects fuel with a slight delay. Therefore, the high-pressure air stored in the pressure accumulation chamber I2 flows from the tip of the electromagnetic valve 17 through the fuel supply port IO, and fuel is injected while being mixed with this high-speed air flow. Therefore, atomization and atomization of the fuel are promoted, and good air-fuel mixture properties can be obtained.

Effects of the Invention As is clear from the above explanation, the two-stroke internal combustion engine according to the present invention is provided with a pressure accumulation chamber that stores high-pressure air compressed in the crank chamber, and this high-pressure air is transferred to the fuel supply port during fuel injection. Since the injector is injected together with the fuel, even when the fuel is injected when the pressure inside the crank chamber is approximately atmospheric or negative, the fuel can be atomized and atomized by the high-pressure air flow. Furthermore, there is no need to use an external pump, and the configuration is relatively simple.

[Brief explanation of drawings]

Fig. 1 is a sectional view of essential parts showing an embodiment of a two-stroke internal combustion engine according to the present invention, Fig. 2 is a characteristic diagram showing fuel injection timing, etc. of this embodiment, and Fig. 3 is a conventional two-stroke internal combustion engine. FIG. 2 is a cross-sectional view of the main parts of the engine. 4... Crank chamber, 8... Exhaust port, 9... Scavenging port, 10... Fuel supply port, 11... Fuel injection valve, I2... Pressure accumulation chamber, I5... Reverse IL valve, I
7... Solenoid valve. Figure 1 9-11 air port 10--1 port 11-2 port 11 attached Figure 3

Claims (1)

[Claims] (1) In a two-stroke internal combustion engine, which is equipped with a scavenging port that communicates with the crank chamber that compresses fresh air and opens on the side of the cylinder, and an exhaust port that also opens on the side of the cylinder, both ports are opened and closed by a piston. A fuel supply port is formed on the side surface, a fuel injection valve is provided therein, and a pressure accumulation chamber is provided which communicates with the crank chamber via a check valve, and between this pressure accumulation chamber and the fuel supply port. A two-stroke internal combustion engine characterized in that a solenoid valve that opens substantially simultaneously with fuel injection is installed in the air passage of the engine.