JP3148748B1 - Two-stroke internal combustion engine - Google Patents

Abstract

Abstract: [PROBLEMS] To reduce the amount of blow-through as much as possible, to improve fuel economy and output, to reduce harmful components in exhaust gas, etc., and to rationally and compactly surround the engine. A possible two-stroke internal combustion engine is provided. SOLUTION: The volume of a first scavenging passage (32A, 32A) is made larger than the volume of a second scavenging passage (32B, 32B), and during the descending stroke of the piston (20),
From the second scavenging port (31B, 31B) to the combustion working chamber (15)
The air (A) is introduced before the air-fuel mixture (M), and the air (A) is introduced into the combustion working chamber (15) from the first scavenging ports (31A, 31A). Mouth (3
1B, 31B), a large amount is introduced over a period longer than the period of introduction of the air (A).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stroke internal combustion engine used for, for example, a portable power working machine, etc.
In particular, the amount of air-fuel mixture discharged without being subjected to combustion,
The present invention relates to a device capable of reducing a so-called blow-through amount as much as possible.

[0002]

2. Description of the Related Art A general two-stroke engine conventionally used for a portable power working machine such as a brush cutter or a chain saw usually has a spark plug disposed on a cylinder head and a cylinder body. An intake port, a scavenging port, and an exhaust port which are opened and closed by a piston are formed, and there is no independent stroke only for intake and exhaust, and one cycle is completed by two strokes of the piston.

More specifically, the air-fuel mixture is sucked into the crank chamber below the piston from the intake port by the upward stroke of the piston, and the air-fuel mixture is pre-compressed by the downward stroke of the piston. The pre-compressed air-fuel mixture is blown out to a combustion working chamber above the piston (also referred to as a combustion chamber, a working chamber, a cylinder chamber, etc., but in the present specification, these are collectively referred to as a combustion working chamber), so that combustion waste gas To the exhaust port, in other words,
Since the combustion waste gas is scavenged using the gas flow of the air-fuel mixture, the unburned air-fuel mixture is apt to be mixed into the combustion waste gas (exhaust gas), and is not directly used for combustion. The amount of air-fuel mixture discharged into the engine, the so-called blow-through amount, is large, so that not only is fuel efficiency lower than in a four-cycle engine, but also harmful components such as HC (unburned fuel component) and CO (fuel Complete combustion component) etc.
Although small, there is concern about environmental pollution.

[0004] Therefore, by introducing air into the combustion working chamber prior to the air-fuel mixture, the combustion waste gas is scavenged to reduce the blow-through of the air-fuel mixture.
Conventionally, various types of cycle internal combustion engines have been proposed (for example, JP-A-9-125966 and JP-A-5-336).
No. 57, etc.), even with the conventional proposal, it cannot be said that the blow-through amount can be sufficiently reduced, and the layout and structure around the engine including the mixture passage and the air passage are sufficiently kneaded. However, the space occupied by the engine is large, and further improvement is required to mount it on a portable power working machine or the like.

[0005] Here, in a conventional general Schnüll scavenging type two-stroke internal combustion engine, a so-called two-way scavenging type in which a pair of scavenging ports are provided symmetrically with respect to a vertical cross section dividing an exhaust port into two parts is used. A part of the scavenging flow of the air-fuel mixture blown out from the pair of scavenging ports is caused to collide with a stationary cylinder inner wall (cylinder bore). A so-called four-flow scavenging type provided is also known. The inventors of the present invention
Earlier, the present inventors focused on this two-stroke scavenging type two-cycle internal combustion engine and conducted intensive studies, and proposed the following two-cycle internal combustion engine (see Japanese Patent Application No. 11-134091 and the accompanying drawings).

[0006] The proposed two-cycle internal combustion engine is:
Basically, the combustion working chamber (1) above the piston (20)
5) A schneur scavenging method is symmetrically interposed across a longitudinal section (F) that divides the exhaust port (34) so that the exhaust port (34) is communicated with the crank chamber (18). A pair of first scavenging passages (32A, 32A), and a pair of second scavenging passages (32B, 32B) located on the opposite side to the exhaust port (34). An air passage (42) for guiding the air (A) to the passages (32A, 32A); and a mixture passage (41) for leading the mixture (M) from the mixture generation means (40) to the crank chamber (18). Are provided, and in the descending stroke of the piston (20), after the exhaust port (34) is opened, a first scavenging port provided at a downstream end of the first scavenging passage (32A, 32A). (31A, 31A) is opened and the first scavenging port (31A, 31A) is opened. A little later, the second scavenging ports (31B, 31B) provided at the downstream end of the second scavenging passages (32B, 32B) are opened, and the air (A) is supplied to the combustion working chamber (15). ) Is introduced prior to the mixture (M).

That is, in the proposed two-stroke internal combustion engine, the first scavenging passages (32A, 32A) are used as passages exclusively for air (A), and the second scavenging passages (32B, 32B) are air-fuel mixture. The second scavenging port (32A, 32A) is opened slightly behind the first scavenging port (31A, 31A) and used as a dedicated passage, and the second scavenging port (32A, 32A) is opened from the second scavenging port (32A, 32A). Combustion working chamber (1
A relatively rich air-fuel mixture (M) is blown toward the combustion chamber portion (15a) of 5), and the blown air-fuel mixture (M) is blown out by a layer of air (A) introduced earlier. The mixture is prevented from mixing with the combustion waste gas (E), and is swirled in the vicinity of the combustion chamber (15a).

For this reason, stratified scavenging becomes possible, and the amount of air-fuel mixture discharged without being subjected to combustion, that is, the so-called blow-through amount, can be reduced as much as possible.
Can reliably and completely ignite the fuel, improve fuel efficiency and output, and reduce harmful components in exhaust gas.

[0009]

However, even in the proposed two-stroke internal combustion engine, it has not always been possible to sufficiently reduce the amount of air blown through the air-fuel mixture. That is, in the proposed two-cycle internal combustion engine, two pairs of scavenging ports (31A, 31A, 31B, 31B)
Of the first scavenging port (3) located on the exhaust port (34) side.
1A, 31A), the scavenging air (A) is introduced into the combustion working chamber (15), so that the combustion working chamber (15) has a side opposite to the exhaust port (34). Some combustion waste gas (E) remains near the inner wall surface of the cylinder, and the residual combustion waste gas (E) and the first scavenging port (3)
1A, 31A) and the mixture (M) from the second scavenging ports (31B, 31B) are mixed,
The stratified scavenging becomes incomplete, and the amount of air-fuel mixture that is discharged without being subjected to combustion, the so-called blow-through amount, cannot be reduced sufficiently. It is necessary to sufficiently improve fuel efficiency, output, and reduce harmful components in exhaust gas. Could not be planned.

[0010] As one of measures for solving the above-mentioned problem, the horizontal scavenging angle of the first scavenging ports (31A, 31A) is reduced (toward the acute angle side), and air (A) blown out therefrom is reduced. ) May be applied to the inner wall of the cylinder opposite to the exhaust port (34) to reduce the amount of the residual combustion waste gas (E). The air (A) from the air ports (31A, 31A) and the air-fuel mixture (M) from the second scavenging ports (31B, 31B) are mixed, so that the laminar scavenging is incomplete and is provided for combustion. The amount of air-fuel mixture discharged without being discharged, the so-called blow-through volume, cannot be reduced sufficiently,
It is not possible to sufficiently improve output, reduce harmful components in exhaust gas, and the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a two-stroke internal combustion engine in which a scavenging method is a four-flow scavenging type without being subjected to combustion. The amount of air-fuel mixture that is discharged, the so-called blow-by amount, can be reduced as much as possible, improving fuel efficiency and output,
It is an object of the present invention to reduce harmful components in exhaust gas and to make the area around the engine reasonable and compact.

[0012]

In order to achieve the above object, a two-stroke internal combustion engine according to the present invention is of a four-stage scavenging type, and basically comprises a combustion working chamber and a crank chamber above a piston. In order to communicate with the exhaust port, a pair of first scavenging passages located on the exhaust port side and a pair of first scavenging passages positioned symmetrically with respect to a longitudinal section that divides the exhaust port into two sections are located on the opposite side to the exhaust port. A pair of second scavenging passages are provided, and an air passage for guiding air to both the first scavenging passage and the second scavenging passage, and a mixture from the mixture generation means to the crank chamber. And a mixture passage.

At the downstream end of the mixture passage, there is provided a communication passage communicating the crank chamber and the combustion working chamber. In the descending stroke of the piston, after the exhaust port is opened, the exhaust passage is opened. The first scavenging port provided at the downstream end of one scavenging passage and the second scavenging port provided at the downstream end of the second scavenging passage are opened, and the first scavenging port and the second scavenging port are opened. Slightly later, the air-fuel mixture supply port provided at the downstream end of the communication passage is opened, and air is introduced into the combustion working chamber prior to the air-fuel mixture. Features.

In a more preferred aspect, for example, the volume of the first scavenging passage is set to be larger than the volume of the second scavenging passage, so that the combustion from the second scavenging port during the descending stroke of the piston. Air is introduced into the working chamber prior to the air-fuel mixture, and a large amount of air is introduced from the first scavenging port into the combustion working chamber for a longer period than the second scavenging port. In this case, preferably, only air is introduced from the first scavenging port to the combustion working chamber over substantially the entire area of the scavenging period.

[0015]

In a preferred mode other than the above, in the downward stroke of the piston, after the exhaust port is opened, the first scavenging port and the second scavenging port are opened substantially simultaneously. A check valve is interposed in the air passage, and a single air outlet provided at the downstream end of the air passage straddles both the first scavenging passage and the second scavenging passage to communicate with each other, Disposing a single check valve at the air outlet, joining the pair of first scavenging passages on the crank chamber side, forming the pair of first scavenging passages on the crank chamber side end The air mixture and the air-fuel mixture passage are provided adjacent to each other, and the air-fuel mixture from the air-fuel mixture supply port of the communication passage is in the combustion working chamber. Said mixture to be blown out towards the combustion chamber It means a vaporizer provided with the air passage and the mixture passage in the carburetor, providing a throttle valve in conjunction with each other to each of the air passage and the mixture passage, and the like.

According to the second embodiment of the present invention having the above-described structure,
In a preferred embodiment of the cycle internal combustion engine, during the upward stroke of the piston, external air is sucked from the air passage into the first scavenging passage, the second scavenging passage, and the crank chamber and stored therein. The air-fuel mixture from the air-fuel mixture generating means is sucked and stored in the crank chamber.

When the air-fuel mixture in the combustion working chamber above the piston is ignited and explosively burns, the piston is pushed down by the combustion gas. In the downward stroke of the piston, air and air-fuel mixture in the crank chamber, the first scavenging passage, and the second scavenging passage are compressed by the piston, and first, the exhaust port is opened. Then, when the piston further descends, the first scavenging port and the second scavenging port at the downstream ends of the first scavenging passage and the second scavenging passage are simultaneously opened, for example. At the beginning of the scavenging period in which the first and second scavenging ports are opened, from the first scavenging port and the second scavenging port, in the first scavenging passage and in the second scavenging passage,
Only the air compressed by the piston is introduced into the combustion working chamber.

Subsequently, when the piston further descends, the air in the first scavenging passage is continuously introduced from the first scavenging port into the combustion working chamber (preferably, in the scavenging period). Is introduced over substantially the entire region), whereas the introduction of air from the second scavenging port to the combustion working chamber is completed. That is, when a certain period of time has elapsed since the second scavenging port has begun to open, all the air in the second scavenging passage is introduced from the second scavenging port into the combustion working chamber. After the air, the air-fuel mixture pre-compressed in the crank chamber is introduced into the combustion working chamber through the second scavenging passage until the scavenging period is completed.

Further, after the first scavenging port and the second scavenging port are opened, the piston further descends, in other words, slightly behind the first scavenging port and the second scavenging port ( When viewed from a crank angle, for example, about 10 ° later), the air-fuel mixture supply port is opened, and the mixture-air supply port is directed toward the combustion chamber of the combustion working chamber in the air-fuel mixture passage (and the A relatively rich mixture in the crank chamber is blown out until the scavenging period is completed, and swirls near the combustion chamber.

Here, in the above-mentioned four-stage scavenging type two-stroke internal combustion engine in which the first scavenging port is exclusively used for air and the second scavenging port is exclusively used for air-fuel mixture, the exhaust port is defined as follows. Although the combustion waste gas remained at a portion near the opposite cylinder inner wall surface, in the two-stroke internal combustion engine of the present invention, at the beginning of the scavenging period, both the first scavenging port and the second scavenging port were used. Since only air is introduced into the combustion working chamber from this, the combustion waste gas is pushed out to the exhaust port by the air with almost no residual, including the portion near the cylinder inner wall opposite to the exhaust port. While being scavenged, between the combustion waste gas and the air-fuel mixture delayed from the air-fuel supply port and the second air-scavenging port to the combustion working chamber, the first air- Scavenging port and the The fuel precedes from the second scavenging port. Layer is formed by the introduced air to the working chamber, this air layer, the air-fuel mixture is mixed with combustion exhaust gas is effectively prevented, thereby enabling substantially complete stratified scavenging.

That is, in a preferred embodiment of the internal combustion engine of the present invention, the first scavenging passage is used as a passage substantially exclusively for air, and the second scavenging passage is used for air at the beginning of the scavenging period. Thereafter, the mixture is used as a passage for the air-fuel mixture, and the air-fuel mixture supply port is opened slightly after the first scavenging port and the second scavenging port. And a relatively rich air-fuel mixture is blown out from the air-fuel mixture supply port toward the combustion chamber portion of the combustion working chamber. So that it is swirled in the vicinity of the combustion chamber, so that almost complete stratified combustion becomes possible, and the amount of air-fuel mixture discharged without being subjected to combustion, so-called blow-through volume Can be reduced as much as possible Both can ignition of air-fuel mixture more reliably and completely, improvement in fuel consumption, can be reduced or the like of harmful components in the exhaust gas.

Further, since the air passage and the air-fuel mixture passage are provided adjacent to each other, the area around the engine can be rationally and compactly assembled, and can be easily mounted on a portable power working machine or the like. Furthermore, since air is supplied by piston pumping without using an external pump or the like, the structure is simplified and the manufacturing cost can be reduced.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a two-stroke internal combustion engine according to the present invention will be described below with reference to the drawings.
1 is a longitudinal sectional view showing one embodiment of a two-stroke internal combustion engine according to the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG.
3 is a sectional view taken along the line III-III in FIG. 1, and FIG. 4 is a sectional view taken along the line IV-IV in FIG.
It is arrow sectional drawing.

For convenience of explanation, FF in FIG.
The left side of the line is a vertical section passing through the first scavenging port side end of the second scavenging port at the bottom dead center of the piston, and the right side is the second scavenging port side of the first scavenging port at the top dead center of the piston. A longitudinal section passing through the end is shown in a combined manner.

The two-stroke internal combustion engine 1 of the illustrated embodiment
Numeral 0 denotes a small air-cooled two-stroke gasoline engine of a four-stage scavenging type used for a portable power working machine and the like.
The cylinder includes a cylinder 12 into which a piston 0 is inserted, and a crankcase 14 that supports a crankshaft 22 that reciprocates the piston 20 through a connecting rod 24.
A large number of cooling fins 16 are provided on the outer peripheral portion of the cylinder 12, and a squish dome-shaped (hemispherical) combustion chamber portion 15 a constituting a combustion working chamber 15 is provided at the head thereof. A spark plug 17 is provided at 15a.

Further, one side of the body of the cylinder 12 (FIG. 1)
An exhaust port 34 is provided on the right side when viewed from above, and the exhaust port 34 is divided into two sections so that the combustion working chamber 15 and the crank chamber 18 above the piston 20 communicate with each other. 2) A pair of first scavenging passages 32A, 32A located on the exhaust port 34 side and a pair of second scavenging paths located on the opposite side to the exhaust port 34 are symmetrically symmetrical with respect to the exhaust port 34. Two scavenging passages 32B, 32B are provided. At the upper ends (downstream ends) of the first scavenging passages 32A, 32A, first scavenging ports 31A, 31A that open to the combustion working chamber 15 are provided, and the second scavenging passages 32B, 32B are provided.
Also at the upper end (downstream end) of 32B, second scavenging ports 31B, 31B opening to the combustion working chamber 15 are provided. Here, the height positions of the first scavenging ports 31A, 31A and the second scavenging ports 31B, 31B are the same, and they are opened almost simultaneously when the piston 20 descends.

The pair of first scavenging passages 32A, 3A
2A and the pair of second scavenging passages 32B, 32B, the combustion working chamber 15 side is closed by a cylinder inner wall,
It is a so-called walled scavenging passage. 3 and 4, in addition to FIGS. 1 and 2, the downstream side of the pair of first scavenging passages 32A, 32A is substantially parallel to the second scavenging passages 32B, 32B. Although it extends downward in the cylinder height direction, its upstream side (the crank chamber 18 side)
Are extended in an arc shape so as to surround the combustion working chamber 15 in a plane orthogonal to the downstream portion, are joined at an upstream end portion on the crank chamber 18 side, and have a longer overall length. The volumes of the first scavenging passages 32A, 32A are considerably larger than the volumes of the second scavenging passages 32B, 32B.

Further, the upstream end 32e of the first scavenging passage 31 is narrowed as much as possible to prevent the air A from flowing back into the crank chamber 18 and falling out.
On the opposite side of the cylinder 12 from the exhaust port 34 (on the left side in FIG. 1), a vaporizer 40 as an air-fuel mixture generating means is attached via a heat insulator 46 with a passage and a packing 49. An air cleaner 50 is attached upstream of the vessel 40.

The vaporizer 40 includes the first scavenging passage 3
An air passage (upstream portion) 42 for guiding the air A purified by the air cleaner 50 to 2A, 32A, and a mixture for guiding a mixture M of air and fuel generated by the carburetor 40 to the combustion working chamber 15. A passage (upstream portion) 41 is provided, and throttle valves 44 and 43 are provided in the air passage 42 and the mixture passage 41 via a link member 45, respectively.

Here, the air passage 42 and the air-fuel mixture passage 41 are provided vertically adjacent to each other, and the downstream side of the air passage 42 is bifurcated as can be clearly understood from FIGS. Branch passage portions 42A, 42A
The air outlets 36, 36 at the downstream ends of the branch passages 42A, 42A are connected to the first scavenging passage 32.
A, 32A and the second scavenging passages 32B, 32B.
Reed valves 52, 52 with stoppers as check valves for preventing the air A from escaping to the branch passage portions 42A, 42A when the piston 20 descends are disposed in the pistons 6, 36, respectively.

In this embodiment, in order to reduce the cost, the first scavenging passage 32A and the second scavenging passage 32B
, A single check valve (reed valve 52) is shared, but a check valve may be provided separately for both of the passages 32A and 32B. Further, the mixture passage 41
A reed valve 47 with a stopper as a check valve for preventing the air-fuel mixture M from flowing back to the carburetor 40 is also provided on the heat insulator 46 on the downstream side.

In addition to the above, at the downstream end of the air-fuel mixture passage 41, a communication passage 41A for communicating the crank chamber 18 with the combustion working chamber 15 is provided. The downstream end (upper end) of the communication passage 41A is A mixture gas supply port 33 opens to the combustion working chamber 15 above the piston 20, and the mixture gas supply port 33 and a second scavenging port 31B provided at a downstream end of the second scavenging passages 32B, 32B. , 31B, the air-fuel mixture M is blown out toward the combustion chamber portion 15a in the combustion working chamber 15, and further, the air-fuel mixture passage 4
The air-fuel mixture M is also introduced into the crank chamber 18 through the crank chamber inlet 37 through the communication passage 41A and the communication passage 41A.

The second embodiment of the present invention having the above configuration
In the cycle internal combustion engine 10, during the upward stroke of the piston 20, external air flows from the air passage 42 to the first scavenging passages 32A, 32A, the second scavenging passages 32B, 3B.
The air-fuel mixture from the air-fuel mixture generating means (vaporizer 40) is sucked and stored in the air-fuel mixture passage 41 and the crank chamber 18.

When the air-fuel mixture M in the combustion working chamber 15 above the piston 20 is ignited and explosively burns, the piston 20 is pushed down by the combustion gas. In the downward stroke of the piston 20, the air and the air-fuel mixture in the crank chamber 18, the first scavenging passage 32A, and the second scavenging passage 32B are compressed by the piston 20, and In addition, the exhaust port 34 is opened, and the piston 20
Descends, the first scavenging ports 31A, 31A at the downstream ends of the first scavenging passage 32A and the second scavenging passage 32B.
And the second scavenging ports 31B, 31B are simultaneously opened.
This first scavenging port 31A, 31A and the second scavenging port 31B,
At the beginning of the scavenging period in which the 31B is opened, the first scavenging ports 31A and 31A and the second scavenging ports 31B and 31A are used.
From B, only the air A compressed by the piston 20 in the first scavenging passages 32A, 32A and in the second scavenging passages 32B, 32B is introduced into the combustion working chamber 15.

Subsequently, when the piston 20 further descends, the air A in the first scavenging passages 32A, 32A is continuously introduced into the combustion working chamber 15 from the first scavenging ports 31A, 31A. (Introduced substantially over the entire scavenging period), whereas the second scavenging ports 31B, 31
The introduction of air A from B into the combustion working chamber 15 is completed. In other words, since the capacity of the first scavenging passages 32A, 32A is larger than the capacity of the second scavenging passages 32B, 32B, after a period of time when the second scavenging ports 31B, 31B have begun to open. The second scavenging passage 3
The air in 2B and 32B is all the second scavenging port 31
B and 31B are introduced into the combustion working chamber 15, and thereafter, from the second scavenging ports 31B and 31B, the air-fuel mixture M pre-compressed in the crank chamber 18 following the air A, The gas is introduced into the combustion working chamber 15 through the second scavenging passages 32B, 32B until the scavenging period is completed.

Therefore, during the downward stroke of the piston 20, the air A precedes the air-fuel mixture M (indicated by solid arrows in FIGS. 1 and 3) from the second scavenging ports 31B, 31B to the combustion working chamber 15. And introduced
From the first scavenging ports 31A, 31A, a large amount of air A (indicated by an alternate long and short dash line in FIGS. 1 and 3) is introduced into the combustion working chamber 15 over a longer period than the second scavenging ports 31B, 31B. Will be done.

After the first scavenging ports 31A, 31A and the second scavenging ports 31B, 31B are opened, the piston 20 further descends, in other words, the first scavenging ports 31A, 31A and The second scavenging ports 31B, 31
Slightly later than B (for example, 10
The air-fuel mixture supply port 33 is opened, and the mixture-air supply port 33 is opened, and the mixture-air supply port 33 is directed toward the combustion chamber portion 15a of the combustion working chamber 15 in the mixture-air passage 41 (and the crank chamber 18). , A relatively rich mixture M (FIGS. 1 and 3)
Is indicated by a solid line arrow) until the scavenging period is completed, and swirls around the combustion chamber 15a.

In the above-described conventional example, the four-stage scavenging type, in which the first scavenging port is dedicated to air and the second scavenging port is dedicated to air-fuel mixture, is used.
In the cycle internal combustion engine, the combustion waste gas remained in a portion near the inner wall surface of the cylinder opposite to the exhaust port. However, in the two-cycle internal combustion engine 10 of the present embodiment, at the beginning of the scavenging period, One scavenging port 31A, 31
A and only the air A is introduced into the combustion working chamber 15 from both the second scavenging ports 31B and 31B,
Due to the air A, the combustion exhaust gas E (indicated by a broken arrow in FIGS. 1 and 3) hardly remains, including the portion near the inner wall of the cylinder on the opposite side to the exhaust port 34. To be scavenged and then
It is discharged outside through the muffler 60.

In this case, between the combustion waste gas E and the mixture M introduced from the mixture supply port 33 and the second scavenging ports 31B, 31B into the combustion working chamber 15 with a delay, A layer is formed from the first scavenging ports 31A, 31A and the second scavenging ports 31B, 31B by the air A introduced into the combustion working chamber 15 in advance, and the air-fuel mixture is combusted by the layer of the air A. Mixing with the waste gas E is effectively prevented, and almost complete laminar scavenging becomes possible.

That is, in the two-stroke internal combustion engine 10 of the present embodiment, the first scavenging passages 32A, 32A
The second scavenging passages 32B, 32B are used as air passages at the beginning of the scavenging period, and thereafter used as passages for the air-fuel mixture, and are used as the first scavenging passages. The gas mixture supply port 33 is opened slightly behind the ports 31A, 31A and the second scavenging ports 31B, 31B, and after the middle of the scavenging period, the second scavenging port 31 is opened.
A relatively rich air-fuel mixture M is blown from B, 31B and the air-fuel supply port 33 toward the combustion chamber portion 15a of the combustion working chamber 15, and the blown air-fuel mixture M is
Combustion waste gas E by the layer of air A introduced earlier
Is effectively prevented from mixing with the combustion chamber 15
a, so that almost complete stratified combustion becomes possible, and the amount of air-fuel mixture discharged without being subjected to combustion, that is, the so-called blow-through amount, can be reduced as much as possible. Can be more reliably and completely ignited, thereby improving fuel efficiency, reducing harmful components in exhaust gas, and the like.

Further, since the air passage 42 and the mixture passage 41 are provided adjacent to each other, the area around the engine can be rationally and compactly assembled, and can be easily mounted on a portable power working machine or the like. . further,
Since air is supplied by piston pumping without using an external pump or the like, the structure is simplified, and the manufacturing cost can be reduced. As described above, one embodiment of the present invention has been described in detail. However, the present invention is not limited to the above-described embodiment, and various designs may be made without departing from the spirit of the invention described in the claims. Can be changed.

For example, in the embodiment, the first scavenging ports 31A, 31A and the second scavenging ports 31B, 31B
The height positions of B are the same, and they are opened almost simultaneously when the piston 20 descends.
The first scavenging port 31A, 31A and the second scavenging port 31
The height positions of B and 31B do not necessarily need to be set to be the same, and they may be provided with a height difference. In addition to the height position, the shapes, opening areas, horizontal scavenging angles, etc. of the first scavenging ports 31A, 31A and the second scavenging ports 31B, 31B enable stratified scavenging and residual combustion. Any setting may be used as long as the scavenging effect of the waste gas E can be enhanced. Further, the first scavenging passage 32A,
The volume and the like of the second scavenging passage 32B and the second scavenging passages 32B and 32B can be appropriately set in consideration of the target air-fuel ratio of the air-fuel mixture to be subjected to combustion in the combustion working chamber 15 and the like.

[0044]

As can be understood from the above description, according to the present invention, the amount of air-fuel mixture discharged without being subjected to combustion, that is, the so-called blow-by amount, can be reduced as much as possible, and the fuel consumption and output can be reduced. It is possible to provide a four-flow scavenging two-stroke internal combustion engine that can improve the exhaust gas, reduce harmful components in exhaust gas, etc., and can rationally and compactly surround the engine.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a two-cycle internal combustion engine according to the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a sectional view taken along the line III-III in FIG. 1;

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1;

FIG. 5 is a longitudinal sectional view showing a state in which a piston is at a top dead center of the engine shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Two-cycle internal combustion engine 15 Combustion working chamber 15a Combustion chamber part 18 Crank chamber 20 Piston 31A First scavenging port 31B Second scavenging port 32A First scavenging passage 32B Second scavenging passage 32e End of first scavenging passage ( Throttle portion) 33 air-fuel supply port 34 exhaust port 40 carburetor (air-fuel mixture generating means) 41 air-fuel mixture passage 41A communication passage 42 air passages 43, 44 throttle valve 47 reed valve with stopper (return valve) 52 reed valve with stopper 52 (Check valve) F Vertical cross section of exhaust port A Air M Mixture E Combustion waste gas

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-256138 (JP, A) JP-A-5-33657 (JP, A) JP-A-58-5424 (JP, A) 25522 (JP, U) Japanese Utility Model Hei 4-21725 (JP, U) Japanese Patent Publication No. 55-46488 (JP, B2) Japanese Utility Model Utility Model 55-4518 (JP, Y2) Japanese Utility Model Hei 7-21872 (JP, Y2) (58) Field surveyed (Int. Cl. ⁷ , DB name) F02B 25/00-25/28 F02B 33/04

Claims (13)

(57) [Claims] 1. A combustion working chamber (1) above a piston (20).
5) A schneur scavenging method is symmetrically interposed across a longitudinal section (F) that divides the exhaust port (34) so that the exhaust port (34) is communicated with the crank chamber (18). A pair of first scavenging passages (32A, 32A) and a pair of second scavenging passages (32B, 32B) located on the opposite side to the exhaust port (34). (32A, 32A) and the second scavenging passage (32B, 3A).
2B) An air passage (42) for guiding air (A) to both sides
And an air-fuel mixture passage (41) for guiding the air-fuel mixture (M) from the air-fuel mixture generating means (40) to the crank chamber (18), and at a downstream end of the air-fuel mixture passage (41), The crank chamber (18) and the combustion working chamber (15)
Is provided at the downstream end of the first scavenging passage (32A, 32A) after the exhaust port (34) is opened during the downward stroke of the piston (20). The first scavenging port (31A, 31A) provided and the second scavenging port (31B, 31B) provided at the downstream end of the second scavenging passage (32B, 32B) are opened, and the first scavenging port is opened. Port (31A, 31A) and the second scavenging port (31
B, 31B), the air-fuel mixture supply port (33) provided at the downstream end of the communication passage (41A) is opened, and air (A) is supplied to the combustion working chamber (15). A two-stroke internal combustion engine characterized in that it is introduced prior to the mixture (M). 2. In the descending stroke of the piston (20), air (A) is introduced from the second scavenging ports (31B, 31B) into the combustion working chamber (15) prior to the air-fuel mixture (M). And the first scavenging port (31A, 31A)
2. The method according to claim 1, wherein a large amount of air (A) is introduced from A) to the combustion working chamber (15) over a longer period than the second scavenging ports (31 </ b> B, 31 </ b> B). 3. A two-stroke internal combustion engine as described. 3. The capacity of the first scavenging passage (32A, 32A) is larger than the capacity of the second scavenging passage (32B, 32B).
A two-stroke internal combustion engine according to claim 1. 4. A method wherein only air (A) is introduced from the first scavenging ports (31A, 31A) into the combustion working chamber (15) over substantially the entire scavenging period. A two-stroke internal combustion engine according to any one of the preceding claims. 5. In the descending stroke of the piston (20), after the exhaust port (34) is opened, the first scavenging port (31A, 31A) and the second scavenging port (31B, 31).
A two-stroke internal combustion engine according to any of the preceding claims, characterized in that B) and (B) are opened substantially simultaneously. 6. A check valve (5) in the air passage (42).
The method according to claim 1, wherein 2) is interposed.
A two-stroke internal combustion engine according to any one of the preceding claims. 7. An air outlet (36, 36) provided at a downstream end of the air passage (42) is connected to the first scavenging passage (32A, 32A) and the second scavenging passage (32B, 3B).
2B), and a single check valve (52, 52) is provided at the air outlet (36). A two-stroke internal combustion engine according to any one of the preceding claims. 8. The pair of first scavenging passages (32A, 32A).
A two-stroke internal combustion engine according to any one of the preceding claims, wherein A) is merged on the crankcase (18) side. 9. The pair of first scavenging passages (32A, 32A).
The two-stroke internal combustion engine according to any one of claims 1 to 8, wherein in (A), the end (32e) on the side of the crank chamber (18) is narrowed. 10. A check valve (4) is provided in said mixture passage (41).
7. The method according to claim 1, wherein the step (7) is interposed.
A two-stroke internal combustion engine according to any one of the preceding claims. 11. The two-stroke internal combustion engine according to claim 1, wherein the air passage (42) and the mixture passage (41) are provided adjacent to each other. 12. The mixture (M) from the mixture supply port (33) of the communication passage (41A) is supplied to the combustion working chamber (1).
The two-stroke internal combustion engine according to any one of claims 1 to 11, characterized in that the two-stroke internal combustion engine is blown toward a combustion chamber (15a) in the inside (5). 13. The gas mixture generating means includes a vaporizer (40).
The carburetor (40) is provided with the air passage (42) and the mixture passage (41), and the throttles are interlocked with the air passage (42) and the mixture passage (41), respectively. 13. The two-stroke internal combustion engine according to claim 1, wherein valves (44, 43) are provided.