JP2561593B2 - Multi-cylinder two-cycle engine with stepped pistons - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-cycle engine having a plurality of cylinders having a two-stage cylinder fitted with a two-stage piston.

[0002]

2. Description of the Related Art In a general two-cycle engine, by feeding an air-fuel mixture sucked into a crank chamber into a working chamber,
Scavenging combustion gas in the working chamber (fuel chamber). in this case,
Since a part of the air-fuel mixture causes a blow-through phenomenon in which it flows out from the working chamber through the exhaust holes together with the combustion gas, the exhaust gas contains components such as HC.

Therefore, conventionally, two cylinders having a phase difference with each other have a small diameter portion and a large diameter portion, respectively.
There is known a two-cycle engine in which a two-stage cylinder is provided and a two-stage piston having a small diameter portion and a large diameter portion is fitted to the two-stage cylinder (see, for example, Japanese Patent Publication No. 51-44249). In this prior art, the combustion gas is scavenged with a lean air-fuel mixture from the crank chamber, while the rich air-fuel mixture is introduced into the working chamber from the auxiliary suction chamber formed between the large diameter part of the cylinder and the small diameter part of the piston. By supplying, the blow-through phenomenon is reduced.

[0004]

However, in the above prior art, the scavenging of the combustion gas in the working chamber is performed by introducing a lean air-fuel mixture into the working chamber while the exhaust hole is wide open. However, the blow-through phenomenon cannot be sufficiently prevented. The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a multi-cylinder two-cycle engine having a stepped piston that can purify exhaust gas by preventing a blow-through phenomenon.

[0005]

In order to achieve the above-mentioned object, the invention of claim 1 is, in the first aspect, a two-stroke engine including a plurality of cylinders having a phase difference from each other. Each pump chamber formed between the diameter portion and the small diameter portion of the two-stage piston is provided with an air intake hole for taking in air. In addition, it opens in the upper part of the working chamber, and the air pressure-fed from the pump chamber of the other cylinder is passed through the communication passage.
An intake hole incorporated into the working chamber, to the intake hole,
The exhaust hole is opened by the small diameter part of the two-stage piston in the descending stroke.
Open the valve immediately before or after opening the hole, and follow the above 2
The small diameter part of the multi-stage piston closes the exhaust hole at the time after closing.
An intake valve is installed. Furthermore, when the intake valve is opened
After a certain period of time from the point, the mixture is passed through the intake valve and
As it is introduced into the working chamber is provided with a fuel supply device for supplying fuel to the intake hole or communication passage at a predetermined timing. In addition, other empty spaces that take air into the crank chamber
The air intake hole and the air in the crank chamber in the same cylinder
A scavenging passage leading to the working chamber is also provided.

According to the first aspect of the present invention, the air taken into each pump chamber is compressed in each pump chamber and then sent under pressure from the intake hole to the working chamber of the other cylinder through the communication passage.
Here, the intake valve is opened and the pumped air is scavenged in the working chamber in a state where the exhaust hole is opened immediately before or is opened by the small diameter portion of the two-stage piston in the descending stroke. Promote. Thereafter, the exhaust hole by the small-diameter portion of the two-stage piston upstroke is during the compression stroke after closing hole, closed intake valve. The fuel supply device supplies the fuel to the intake hole or the communication passage after scavenging during the opening period of the intake valve. Before the supplied mixture of fuel and air reaches the exhaust hole of the working chamber, the exhaust hole is closed and scavenging is completed. Therefore, the air-fuel mixture introduced into the working chamber is unlikely to flow out from the exhaust hole. Further, since the air in the crank chamber is introduced into the working chamber, the scavenging of the combustion gas in the working chamber is promoted by the pressure feeding of this air.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention. FIG.
As shown in, the engines are 180 ° out of phase with each other.
It is a two-cylinder engine having first and second cylinders 1 and 2 which are different and have the same shape. In the two-stage cylinders 3A and 3B of the first and second cylinders 1 and 2, a small diameter portion 3a and a large diameter portion 3b are concentrically formed vertically. On the other hand, the two-stage piston 4 of each of the cylinders 1 and 2 has a small diameter portion 4a and a large diameter portion 4b, respectively.
The small diameter portion 3a and the large diameter portion 3b of A and 3B are fitted.

The two-stage cylinder 3 in each of the cylinders 1 and 2
Large diameter part 3b of A and 3B and small diameter part 4a of two-stage piston 4
The annular pump chambers 5A and 5B are formed between and. These pump chambers 5A and 5B include pump chambers 5A,
5B is provided with air intake holes 7A and 7B for taking in the air A1. The air intake holes 7A and 7B communicate with the air cleaner 14 via the first reed valve 12.
The first reed valve 12 is provided in the pump chambers 5A and 5B.
The air A1 to the pump chambers 5A and 5B to prevent the air A1 from flowing out.

Each of the pump chambers 5A and 5B is provided with an air discharge hole 15 for discharging the compressed air A1.
The air discharge hole 15 constitutes a part of a communication passage 16 shown by a chain double-dashed line, and communicates with the working chambers 6A and 6B of the mating cylinders 1 and 2 via the communication passage 16 and the intake hole 17. ing. A check valve 27 is provided in the air discharge hole 15. In the check valve 27, the air A1 is pump chambers 5A, 5
It is allowed to be discharged from B and is prevented from flowing back into the pump chambers 5A and 5B.

The intake hole 17 is open above the working chambers 6A and 6B, and an intake valve 18 is provided in the intake hole 17. The intake valve 18 is opened and closed by a crank shaft or a cam shaft. Second of FIG.
Like the cylinder 2, the small-diameter portion 4 of the two-stage piston 4 in the descending stroke
Due to a, the intake valve 18 is opened while the exhaust hole 19 of the same cylinder is being opened or is being opened immediately before the exhaust hole 19 is opened. An exhaust hole 19 during the compression stroke after closing the hole by the small diameter portion 4a of the stage piston 4, the intake valve 18 is adapted to close. Here, while the intake valve 18 is open, the two-stage cylinders 3A, 3B, the two-stage piston 4 and the two-stage cylinders 4A and 3B are controlled so that the pressure of the air A1 in the communication passage 16 becomes higher than the pressure in the working chambers 6A, 6B. The shape and dimensions of the communication passage 16 and the like are set. The intake hole 17 is provided with a fuel injection device (fuel supply device) 31 for injecting the fuel F into the intake hole 17, and the fuel injection device 31 is provided at a specific time during the opening period of the intake valve 18. The fuel F is injected into the intake hole 17 so that the injected fuel F does not flow out from the exhaust hole 19. Incidentally, 26 in FIG. 1 is an ignition plug.

An air intake hole 21 for taking in the air A2 into the crank chamber 20 is opened in each crank chamber 20.
The air intake hole 21 communicates with an air cleaner 23 via a second reed valve 22. The second reed valve 22 allows the air A2 to flow into the crank chamber 20 and prevents the air A2 from flowing out of the crank chamber 20.

The crank chamber 20 communicates with the working chambers 6A and 6B of the same cylinder via a plurality of scavenging passages 24 and scavenging holes 25 shown by broken lines. Therefore, the air A2 compressed in the crank chamber 20 is introduced into the working chambers 6A, 6B of the same cylinder through the scavenging passage 24.

Next, the operation of the above configuration will be described. As shown in FIG. 1, since the two-stage piston 4 of the first cylinder 1 is lowered, the pump chamber 5A becomes negative pressure,
Air A1 is sucked into the pump chamber 5A from the air suction hole 7A.

The air A1 sucked into the pump chamber 5A of the first cylinder is compressed as the two-stage piston 4 shown in FIG. 2 moves up like the first cylinder 1. In this state, the intake valve 18 of the second cylinder 2 is open and the exhaust hole 19 is open.
Immediately before the hole or in the open state, the air A1 is introduced into the working chamber 6B of the second cylinder 2, and the combustion gas G in the working chamber 6B flows out from the exhaust hole 19 and is scavenged. Meanwhile, the fixie
Air A2 from the crank chamber 20 of the same cylinder is also introduced into the working chamber 6B of the second cylinder 2 expanded by the lowering of the engine 4 from the side opposite to the intake valve via the scavenging passage 24 and the scavenging hole 25.
The scavenging of the combustion gas G is promoted by being pressure-fed from the lower portion of the round working chamber 6B .

Subsequently, the fuel F is injected from the fuel injection device 31 into the intake hole 17. After this injection, as shown in FIG. 3, while the two-stage piston 4 of the second cylinder 2 rises, the fuel F mixes with the air A1 in the intake hole 17 and becomes the mixture M into the working chamber 6B. be introduced. This mixture M is the second
At the time when the exhaust hole 19 of the cylinder 2 is closed by the small diameter portion 4a of the two-stage piston 4 in the ascending stroke, the upper portion (on the spark plug 26 side) of the working chamber 6B is filled. On the other hand, in the lower part of the working chamber 6B, the air A1 from the intake hole 17 and the scavenging hole 25
Is filled with air A2 is. After the exhaust hole 19 is closed, the intake valve 18 is closed and the two-stage piston 4 rises as shown in FIG. 1, so that the mixture M and the air A in the working chamber 6B are closed.
When 1 and A2 (FIG. 3) are mixed and compressed and the two-stage piston 4 moves up to near the top dead center, it is ignited by the spark plug 26. The ignited mixture M explodes and expands, causing the second-stage piston 4 to descend.

In the above structure, FIG. 3 (scavenging passage 24 is
The exhaust hole 19 is closed as in the second cylinder 2 ( omitted) .
At certain times, the inside of the working chamber 6B is filled with the air-fuel mixture M at the upper part and is filled with the air A1 and A2 at the lower part to form a so-called stratified air supply. Therefore, only the airs A1 and A2 flow out from the exhaust hole 19, and unlike the conventional case, the air-fuel mixture M is not discharged from the exhaust hole 19, so that the blow-through phenomenon can be prevented.

Further, in this embodiment, the first cylinder 1 shown in FIG.
As described above, since the air A2 compressed in the crank chamber 20 is pressure-fed to the working chambers 6A and 6B of the same cylinder for scavenging, the working chamber 6
As the scavenging of the combustion gas G in A and 6B is promoted,
It is also possible to promote stratified air supply.

By the way, although the fuel injection device 31 is provided in the intake hole 17 in the first embodiment, the fuel injection device 31 may be provided in the communication passage 16. In this case, the air-fuel mixture M is formed in the communication passage 16, but its operation is the same as in the first embodiment. In addition, when the air-fuel mixture M is formed in the communication passage 16, it takes a long time to move to the working chambers 6A and 6B after the air-fuel mixture M is formed, which is advantageous in improving the mixing state .

[0019] Also, in the first embodiment, the air discharge holes 1
Although the check valve 27 is provided in No. 5, it is not always necessary to provide the check valve 27. In addition, the first embodiment has been described with respect to a two-cylinder engine.
The present invention can be applied to an engine having more than a cylinder as in the case of this embodiment. Further, even in the case of an odd number of cylinders, the present invention can be applied by appropriately setting the phase difference.

[0020]

As described above, according to the present invention, from the pump chamber formed between the large diameter portion of the two-stage cylinder and the small diameter portion of the two-stage piston of the plurality of cylinders having a phase difference from each other, in two-stroke engines for pumping air to the working chamber of the mating cylinder, provided with a fuel supply device for supplying fuel to the intake hole or communication passage, since the intake valve provided in the intake hole, the air-fuel mixture reaches the exhaust hole Since it can be prevented, the blow-through phenomenon can be prevented. Further, by pressure-feeding the air in the crank chamber to the working chamber, formation of stratified charge and scavenging of combustion gas in the working chamber can be promoted.
Engine output and fuel efficiency are improved by improving scavenging efficiency.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a two-cycle engine showing a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a two-cycle engine in which the first cylinder is also at top dead center.

FIG. 3 is a second state in which the exhaust hole of the second cylinder is also closed.
It is a schematic block diagram of a cycle engine.

[Explanation of symbols]

1 ... 1st cylinder, 2 ... 2nd cylinder, 3A, 3B ... 2 stage cylinder, 3a ... small diameter part, 3b ... large diameter part, 4 ... 2 stage piston,
4a ... small diameter part, 4b ... large diameter part, 5A, 5B ... pump chamber,
6A, 6B ... Working chamber, 7A, 7B ... Air intake hole, 16 ...
Communication passage, 17 ... intake hole, 18 ... intake valve, 19 ... exhaust hole,
20 ... Crank chamber, 21 ... Air intake hole, 24 ... Scavenging passage, 31 ... Fuel supply device, A1, A2 ... Air, M ... Mixture.

Claims (1)

(57) [Claims] 1. A two-stage cylinder having a small diameter portion and a large diameter portion is provided in each of a plurality of cylinders having a phase difference from each other,
A multi-cylinder two-cycle engine having a stepped piston in which a two-stage piston having a small-diameter portion and a large-diameter portion is fitted to the two-stage cylinder, wherein the large-diameter portion of the two-stage cylinder and the small-diameter portion of the two-stage piston are provided. and entry apertures intake air introducing air into each pump chamber formed between the part, open to the top of the working chamber, the air being pumped from the pump chamber of the mating cylinder through the communicating path the working chamber The intake hole to be taken in, and the two-stage piston installed in this intake hole in the descending stroke.
The small diameter part opens the exhaust hole immediately before or after the opening.
Exhaust due to the small diameter part of the above-mentioned two-stage piston in the valve stroke and ascending stroke
The intake valve closes after the hole is closed, and the air- fuel mixture is raised after a certain period of time has elapsed since the intake valve was opened.
Prescribed so that it can be introduced into the working chamber via the intake valve.
Fuel supply device for supplying fuel to the intake hole or the communication passage at the timing of, another air intake hole for taking in air to the crank chamber, and air in the crank chamber in the same cylinder for the working chamber.
A multi-cylinder two-cycle engine having a stepped piston with a scavenging passage leading to the lower part .