阅读说明：本技术 一种高效率低排放的时间分层扫气小型二冲程汽油机 (High-efficiency low-emission time-stratified scavenging small two-stroke gasoline engine ) 是由 刘永根 杨慧明 刘运申 秦义明 姜雪琨 宋雄伟 于 2021-07-19 设计创作，主要内容包括：本发明公开了一种高效率低排放的时间分层扫气小型二冲程汽油机,包括相互连通的曲轴箱室、气缸,气缸内有活塞,活塞侧面有储气型腔,活塞内纯空气通道一端设于活塞侧面、另一端连通储气型腔；气缸缸壁设有混合气进气口、纯空气进气口、扫气口、排气口,还包括进气管、双腔化油器,进气管一端连接于混合气进气口、纯空气进气口所在的气缸缸壁位置,进气管另一端连接双腔化油器,气缸外壁对应扫气口位置分别设有扫气室,扫气室底部连通于气缸内部。本发明能够有效减少排放尾气污染。(The invention discloses a time-layered scavenging small two-stroke gasoline engine with high efficiency and low emission, which comprises a crankcase chamber and a cylinder which are mutually communicated, wherein a piston is arranged in the cylinder, a gas storage cavity is arranged on the side surface of the piston, one end of a pure air channel in the piston is arranged on the side surface of the piston, and the other end of the pure air channel is communicated with the gas storage cavity; the cylinder wall of the cylinder is provided with a mixed gas inlet, a pure air inlet, a scavenging port and an exhaust port, and the cylinder further comprises an air inlet pipe and a double-cavity carburetor, one end of the air inlet pipe is connected to the position of the cylinder wall where the mixed gas inlet and the pure air inlet are located, the other end of the air inlet pipe is connected with the double-cavity carburetor, the positions of the outer wall of the cylinder, which correspond to the scavenging port, are respectively provided with a scavenging chamber, and the bottom of the scavenging chamber is communicated with the inside of the cylinder. The invention can effectively reduce the pollution of the discharged tail gas.)

1. The utility model provides a time layering scavenging small-size two-stroke gasoline engine that high efficiency is low discharges, includes crankcase chamber and connects in the vertical cylinder (6) of the axial at crankcase chamber top, the inside intercommunication of crankcase chamber, cylinder (6), and the interior rotation of crankcase is installed axial horizontally bent axle (3), and coaxial slidable mounting has piston (13) in cylinder (6), bent axle (3) are connected with piston (13) through connecting rod (4), and cylinder (6) top mounting is to spark plug (15) of firing in cylinder (6), its characterized in that: the two symmetrical side surfaces of the piston (13) are respectively provided with an air storage cavity (12), a pure air channel (11) is arranged in the piston (13), an inlet port of the pure air channel (11) is arranged on the side surface of the piston (13) between the two air storage cavities (12), and an outlet port of the pure air channel (11) is communicated with the two air storage cavities (12);

a mixed gas inlet (5) and a pure air inlet are arranged on the cylinder wall of one side of the cylinder (6) corresponding to the inlet end direction of the pure air channel (11), wherein the mixed gas inlet (5) is positioned below the pure air inlet, and also comprises an air inlet pipe (7) and a double-cavity carburetor (9), the air inlet pipe (7) is internally provided with two air passages, the double-cavity carburetor (9) is internally provided with a pure air cavity and a fresh mixed gas cavity, one end of the air inlet pipe (7) is connected with the cylinder wall position of the cylinder (6) where the mixed gas inlet (5) and the pure air inlet are positioned, one end of each of two air passages in the air inlet pipe (7) is communicated with the mixed gas inlet (5) and the pure air inlet one by one, the double-cavity carburetor (9) is connected with the other end of the air inlet pipe (7), the other ends of the two air passages in the air inlet pipe (7) are respectively communicated with a pure air chamber and a fresh mixed gas chamber in the double-cavity carburetor (9) in a one-to-one correspondence manner;

the cylinder walls on two sides of the cylinder (6) corresponding to the direction of the gas storage cavity (12) are respectively provided with a scavenging port, the scavenging ports on two sides are higher than the pure air inlet, the scavenging chamber is respectively arranged on the outer wall of the cylinder (6) corresponding to each scavenging port, the scavenging ports are communicated with the inside of the cylinder and the scavenging chamber on the corresponding position, and the bottom of each scavenging chamber is respectively communicated with the inside of the cylinder (6) below the mixed gas inlet (5); an air outlet (17) is further formed in the wall of the air cylinder (6) between the two scavenging ports, the height of the upper edge of each scavenging port is lower than that of the upper edge of the air outlet (17), and the distance between the upper edge of the air outlet (17) and the top of the air cylinder (6) is 8.5-9 times that between the upper edge of each scavenging port and the upper edge of the air outlet (17).

2. A high efficiency low emission time stratified scavenging small two-stroke gasoline engine as defined in claim 1 wherein: two groups of pure air channels (11) are arranged in the piston, outlet port openings of the two groups of pure air channels (11) are communicated with the two air storage cavities (12) in a one-to-one correspondence mode, and inlet port openings of the two groups of pure air channels (11) are respectively arranged on the side face of the piston (13) between the two air storage cavities (12).

3. A high efficiency low emission time stratified scavenging small two-stroke gasoline engine as defined in claim 1 wherein: the double-cavity carburetor (9) comprises a carburetor body, a choke valve (10) is installed at the inlet end of the carburetor body, an accelerator (8) is installed at the outlet end of the carburetor body, a partition plate is arranged between the choke valve (10) and the accelerator (8), one end of the partition plate extends into the accelerator (8) to divide the accelerator (8) into two parts, the other end of the partition plate extends into the choke valve (10) to divide the choke valve (10) into two parts, and therefore the whole partition inside the carburetor body is divided into a pure air cavity and a fresh mixed gas cavity through the partition plate.

4. A high efficiency low emission time stratified scavenging small two-stroke gasoline engine as defined in claim 1 wherein: the gas scavenging device is characterized in that the outer wall of the cylinder (6) is respectively provided with a cover plate in a position corresponding to each scavenging port, the space enclosed by the cover plate and the outer wall of the cylinder (6) is formed into the scavenging chamber, the bottom of the cylinder (6) is respectively provided with an opening in a position corresponding to each scavenging chamber, the bottom of each scavenging chamber is respectively opened and communicated with the opening in the corresponding position at the bottom of the cylinder (6), and therefore each scavenging chamber is respectively communicated with the inside of the cylinder (6) below the mixed gas inlet (5).

5. A high efficiency low emission time stratified scavenging small two-stroke gasoline engine as defined in claim 1 wherein: each scavenging port is axially inclined relative to the cylinder (6), the inclined high end of each scavenging port is positioned on the inner side of the cylinder wall of the cylinder (6), and the inclined low end of each scavenging port is positioned on the outer side of the cylinder wall of the cylinder (6).

6. A high efficiency low emission time stratified scavenging small two-stroke gasoline engine as claimed in claim 5 wherein: each scavenging port axially forms an included angle of 110-130 degrees with the cylinder (6) axially.

7. A high efficiency low emission time stratified scavenging small two-stroke gasoline engine as defined in claim 1 wherein: a silencer (18) is fixed on the outer wall of the cylinder (6) corresponding to the exhaust port (17), and the exhaust port (17) is communicated with the silencer (18).

8. A high efficiency low emission time stratified scavenging small two-stroke gasoline engine as defined in claim 1 wherein: the distance between the upper edge of the exhaust port (17) and the top of the cylinder (6) is 8.75 times of the distance between the upper edge of the scavenging port and the upper edge of the exhaust port (17).

Technical Field

The invention relates to the field of small two-stroke gasoline engines, in particular to a high-efficiency low-emission time-stratified scavenging small two-stroke gasoline engine.

Background

The small two-stroke gasoline engine has the characteristics of compact structure, light operation, high power-weight ratio, low production and maintenance cost and the like, and is widely applied to the fields of agriculture and forestry machinery, gardening and greening, model airplane engines and the like which need strong power performance and are light and convenient to carry and use. After decades of development, the annual output of the domestic general small two-stroke gasoline engine accounts for more than 40% of the total output of the similar engines in the same period of the world at present.

In the current common two-stroke gasoline engine on the market, an exhaust port, a scavenging port and an air inlet are sequentially arranged on an air cylinder, a piston moves upwards to generate negative pressure in a crankcase, and combustible mixture is introduced into the crankcase by using the negative pressure; when the piston moves downwards, the combustible gas mixture in the crankcase is compressed, and the opening and closing of the exhaust port, the scavenging port and the air inlet are controlled by utilizing the up-and-down reciprocating motion of the top of the piston and the bottom surface of the skirt part respectively; it features that the scavenging channels are at both sides of exhaust port, and the two streams of fresh combustible mixed gas (the mixed gas of gasoline and air produced by carburetor) flowing out from the scavenging ports first impact the cylinder wall opposite to the exhaust port, and then bend upwards under the guide of cylinder wall, along the combustion chamber of cylinder cover, and then bend downwards to flow to exhaust port. The fresh combustible mixture inevitably mixes with the combusted exhaust gas and flows out of the machine together with the exhaust gas through the exhaust port without being combusted. During the scavenging process, short circuit loss causes a large amount of fresh mixed gas to directly flow out of exhaust gas, so that the oil consumption of the two-stroke gasoline engine is increased, and exhaust tail gas contains a large amount of harmful substances such as hydrocarbon HC, carbon monoxide CO and the like, which become one of main pollution sources of the atmosphere.

The advanced countries in Europe and America continuously implement increasingly strict emission regulations, and the United states EPA has implemented the emission regulations of the general small gasoline engine at first in the nineties of the last century, which is the third requirement at present; the european union also implemented a fifth stage emissions regulation in 2017; the standard of the second stage of non-road mechanical emission is issued and implemented in 2013 in China, and the emission regulation is currently in the third stage of layout; therefore, the tail gas emission of the common small two-stroke gasoline engine is difficult to meet the increasingly stricter regulation requirement.

Meanwhile, in order to reduce the ventilation loss of the existing common two-stroke gasoline engine, the scavenging port is designed to be much lower than the exhaust port, however, when the piston moves upwards, the scavenging port is closed firstly, and then the exhaust port is closed, and in the period, namely the scavenging later stage, a part of combustible mixed gas in the cylinder is extruded out of the engine through the exhaust port, so that fuel is wasted, and pollution is aggravated. Therefore, there is a need in the market for a small two-stroke gasoline engine that is simple in structure, durable in use, and has high power and low emissions.

Disclosure of Invention

The invention aims to provide a time-stratified scavenging small two-stroke gasoline engine with high efficiency and low emission, and the problem that the emission tail gas pollution is large due to unreasonable gas circuits of the small two-stroke gasoline engine in the prior art is solved.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a time-layered scavenging small two-stroke gasoline engine with high efficiency and low emission comprises a crankcase chamber and an axial vertical cylinder (6) connected to the top of the crankcase chamber, the crankcase chamber and the cylinder (6) are communicated, an axial horizontal crankshaft (3) is rotatably arranged in the crankcase chamber, a piston (13) is coaxially and slidably arranged in the cylinder (6), the crankshaft (3) is connected with a piston (13) through a connecting rod (4), the top of the cylinder (6) is provided with a spark plug (15) which ignites into the cylinder (6), the two symmetrical side surfaces of the piston (13) are respectively provided with an air storage cavity (12), a pure air channel (11) is arranged in the piston (13), an inlet port of the pure air channel (11) is arranged on the side surface of the piston (13) between the two air storage cavities (12), and an outlet port of the pure air channel (11) is communicated with the two air storage cavities (12);

a mixed gas inlet (5) and a pure air inlet are arranged on the cylinder wall of one side of the cylinder (6) corresponding to the inlet end direction of the pure air channel (11), wherein the mixed gas inlet (5) is positioned below the pure air inlet, and also comprises an air inlet pipe (7) and a double-cavity carburetor (9), the air inlet pipe (7) is internally provided with two air passages, the double-cavity carburetor (9) is internally provided with a pure air cavity and a fresh mixed gas cavity, one end of the air inlet pipe (7) is connected with the cylinder wall position of the cylinder (6) where the mixed gas inlet (5) and the pure air inlet are positioned, one end of each of two air passages in the air inlet pipe (7) is communicated with the mixed gas inlet (5) and the pure air inlet one by one, the double-cavity carburetor (9) is connected with the other end of the air inlet pipe (7), the other ends of the two air passages in the air inlet pipe (7) are respectively communicated with a pure air chamber and a fresh mixed gas chamber in the double-cavity carburetor (9) in a one-to-one correspondence manner;

the cylinder walls on two sides of the cylinder (6) corresponding to the direction of the gas storage cavity (12) are respectively provided with a scavenging port, the scavenging ports on two sides are higher than the pure air inlet, the scavenging chamber is respectively arranged on the outer wall of the cylinder (6) corresponding to each scavenging port, the scavenging ports are communicated with the inside of the cylinder and the scavenging chamber on the corresponding position, and the bottom of each scavenging chamber is respectively communicated with the inside of the cylinder (6) below the mixed gas inlet (5); an air outlet (17) is further formed in the wall of the air cylinder (6) between the two scavenging ports, the height of the upper edge of each scavenging port is lower than that of the upper edge of the air outlet (17), and the distance between the upper edge of the air outlet (17) and the top of the air cylinder (6) is 8.5-9 times that between the upper edge of each scavenging port and the upper edge of the air outlet (17).

Furthermore, two groups of pure air channels (11) are arranged in the piston, outlet port openings of the two groups of pure air channels (11) are communicated with the two air storage cavities (12) in a one-to-one correspondence manner, and inlet port openings of the two groups of pure air channels (11) are respectively arranged on the side surface of the piston (13) between the two air storage cavities (12).

Furthermore, the double-cavity carburetor (9) comprises a carburetor body, a choke valve (10) is installed at the inlet end of the carburetor body, an accelerator (8) is installed at the outlet end of the carburetor body, a partition plate is arranged between the choke valve (10) and the accelerator (8), one end of the partition plate extends into the accelerator (8) to divide the accelerator (8) into two parts, the other end of the partition plate extends into the choke valve (10) to divide the choke valve (10) into two parts, and therefore the whole inside of the carburetor body is divided into a pure air cavity and a fresh mixed gas cavity through the partition plate.

Further, the cylinder (6) outer wall is fixed with the apron corresponding to every scavenging port position housing respectively, and the space enclosed by apron and cylinder (6) outer wall constitutes the scavenging chamber, cylinder (6) bottom is equipped with the opening corresponding to every scavenging chamber position respectively, and every scavenging chamber bottom is uncovered respectively and is linked together in the opening that cylinder (6) bottom corresponds the position, makes every scavenging chamber communicate respectively inside cylinder (6) of gas mixture air inlet (5) below from this.

Furthermore, each scavenging port is axially inclined relative to the cylinder (6), the inclined high end of each scavenging port is positioned on the inner side of the cylinder wall of the cylinder (6), and the inclined low end of each scavenging port is positioned on the outer side of the cylinder wall of the cylinder (6).

Furthermore, each scavenging port axially forms an included angle of 110-130 degrees with the cylinder (6) axially.

Furthermore, a silencer (18) is fixed on the outer wall of the cylinder (6) corresponding to the position of the exhaust port (17), and the exhaust port (17) is communicated with the silencer (18).

Furthermore, the distance between the upper edge of the exhaust port (17) and the top of the cylinder (6) is 8.75 times of the distance between the upper edge of the scavenging port and the upper edge of the exhaust port (17).

The invention uses pure air to scavenge in advance in space, and then fresh mixed gas follows scavenging in sequence. The air intake system is divided into two parts by reasonably organizing air intake and scavenging flow, one path of pure air is sucked into a gas storage cavity (12) of a piston (13) through a pure air cavity of a double-cavity carburetor (9) and an air intake pipe (7) corresponding to an air passage, and the other path of fresh mixed gas directly enters a crankcase through a fresh mixed gas cavity of the double-cavity carburetor (9) and the air intake pipe (7) corresponding to the air passage.

After the air exchange process is started, pure air in the air storage cavity (12) of the piston (13) enters the scavenging chamber, and is squeezed by the fresh mixed gas pre-compressed in the crankcase chamber to flow into the cylinder (6) to scavenge exhaust gas, and then the fresh mixed gas flows into the cylinder (6). Layered flow is formed in the cylinder in time, namely, the fresh mixed gas is separated from the waste gas by pure air, so that the fresh mixed gas is prevented from directly flowing out of the exhaust port (17), and the escape of the fresh mixed gas is greatly reduced; meanwhile, the height difference between the scavenging port and the exhaust port (17) is reduced, the exhaust port (17) is flush with or slightly higher than the scavenging port, and the effective stroke is increased under the condition that waste gas is prevented from flowing back into the crankcase chamber from the scavenging port, so that the power is improved, and the discharge of harmful substances is reduced.

On the other hand, when the gasoline engine is in an idling working condition, the pure air cavity of the double-cavity carburetor (9) is always in a closed state, and only the fresh mixed gas cavity is opened, so that the idling performance is kept stable, and the acceleration performance is good. On the basis, HC and CO emission values of the two-stroke gasoline engine are reduced, and the aims of energy conservation and emission reduction are finally achieved. Meanwhile, the whole machine has compact structure and is durable.

The upper part of a cylinder (6) positioned above a piston (13) is used as a combustion chamber, when the piston (13) moves towards a top dead center, the upper part of the cylinder (6) is used as mixed gas in the combustion chamber and begins to be pressed, the volume of a crankcase chamber closed at the lower part of the piston (13) is increased, the pressure in the crankcase chamber is rapidly reduced, when the piston moves to a certain position, pure air firstly passes through a pure air chamber of a double-chamber carburetor (9) and an air inlet pipe corresponding to an air passage and enters the cylinder (6) from a pure air inlet, and then enters an air storage cavity (12) through a pure air passage (11) of a skirt part of the piston (13); the air storage cavity (12) is communicated with the scavenging ports on the two sides of the air cylinder (6), so that pure air enters the scavenging chamber through the scavenging ports. And then the lower edge of the piston (6) is separated from the mixed gas inlet (5) to open the mixed gas inlet (5), under the action of the internal and external pressure difference, the fresh mixed gas directly enters the crankcase through a fresh mixed gas chamber of the double-chamber carburetor (9) and a corresponding air passage of the air inlet pipe, and the crankcase starts to intake the fresh mixed gas. Passing through top dead center until the symmetrical position where intake begins closes.

Near the top dead center, a spark plug (15) ignites, and the ignited and compressed fresh mixed gas starts to expand to do work; after the piston (13) moves to the edge to close the pure air inlet and the mixed gas inlet (5), the piston (13) moves downwards again to start compression, so that the pressure of the fresh mixed gas entering the crankcase chamber is increased; when the piston (13) moves downwards to a certain position, the piston is separated from the exhaust port (17) to open the exhaust port (17), the pressure of the generated waste gas is up to 0.3MPa as the fresh mixed gas in the cylinder (6) finishes the combustion work, the waste gas is discharged from the exhaust port (17) at the sound velocity, and the exhaust process starts; when the pressure of the crankcase chamber is larger than the pressure of the waste gas in the cylinder (6), pure air stored in the scavenging chamber in advance firstly enters the cylinder (6), is mixed and swept with the waste gas in the combustion chamber, then enters the silencer (18) through the exhaust port (17) and then is exhausted out of the engine, and then fresh mixed gas at the lower part in the scavenging chamber enters the cylinder (6) through the scavenging port from the crankcase chamber to drive the waste gas to be continuously exhausted. Therefore, the phenomenon that unburned mixed gas escapes along with exhaust gas can be reduced, the emission of compounds such as HC and CO in the exhaust gas is effectively reduced, the stability in a high-speed and low-speed state is realized, and the power of the small gasoline engine can be improved.

The invention has the following advantages:

(1) the double-cavity carburetor is composed of a carburetor body and a partition plate arranged at the throat part of the carburetor body, and the partition plate is connected with an accelerator and a choke valve, so that a circular air inlet channel at the throat part is divided into a pure air cavity and a fresh mixed air cavity which are not interfered with each other on the basis of ensuring enough flow cross section area, and a double-cavity carburetor structure is formed.

(2) Corresponding to the double-cavity carburetor, the air inlet pipe is also divided into two parts to form an upper cavity channel and a lower cavity channel which are independent from each other and are respectively used for passing pure air and fresh mixed gas.

(3) The piston is different from the traditional smooth cylinder type, on the basis of meeting the structural strength, two sides of the skirt part of the piston are respectively provided with a special pure air channel and a special air storage cavity, and the pure air channel is matched with a scavenging port, a double-cavity carburetor and an air inlet pipe to form the pure air channel.

(4) The inner wall of the cylinder is different from the traditional air inlet, two air inlets are specially designed, namely a double-cavity air inlet system, one air inlet is a pure air inlet, and the other air inlet is a mixed air inlet, so that the air inflow is increased, and the air exchange efficiency is improved.

(5) The height of the exhaust port is slightly higher than that of the scavenging port. When the piston moves upwards, the distance from the scavenging port to the exhaust port of the inner wall of the cylinder is reduced, the charging is forcibly discharged by the upward movement of the piston, and if the height of the exhaust port is far higher than that of the scavenging port, a large amount of fresh mixed gas in the cylinder is discharged along with the exhaust gas after the air intake is finished, so that the oil consumption is increased, and the HC emission is increased, so that the distance from the scavenging port to the exhaust port of the inner wall of the cylinder is reduced.

Drawings

FIG. 1 is a side perspective cutaway view of the present invention.

Fig. 2 is a top dead center side plan view of the present invention.

FIG. 3 is a bottom dead center side plan view of the present invention.

Fig. 4 is a front perspective sectional view of the present invention.

Fig. 5 is a front plan sectional view of the present invention.

Fig. 6 is an external structural view of the present invention.

Fig. 7 is a schematic plan view of the piston of the present invention.

Fig. 8 is a schematic view of the relative positions of the exhaust and scavenging ports of the present invention.

FIG. 9 is a schematic exhaust phase angle diagram of the present invention.

Fig. 10 is a schematic view of the scavenging phase angle of the present invention.

Reference numbers in the figures: 1 a right crankcase; 2 a left crankcase; 3, a crankshaft; 4, connecting rods; 5, a mixed gas inlet; 6 air cylinders; 7, air inlet pipes; 8, an accelerator; 9 a dual chamber carburetor; 10 choke valve; 11 a pure air channel; 12 gas storage cavity; 13 a piston; 14 a piston pin; 15 a spark plug; 16 muffler spacers; 17 an exhaust port; 18 a muffler; 19 a bearing; 20 oil seal; 21 left scavenging cover plate; 22 right scavenging cover plate; 23 left scavenging port; 24 right scavenging port.

Detailed Description

The invention is further illustrated with reference to the following figures and examples.

As shown in fig. 1-7, the invention relates to a high-efficiency low-emission time-stratified scavenging small two-stroke gasoline engine, which comprises a right crankcase 1, a left crankcase 2, a crankshaft 3, a connecting rod 4, a cylinder 6, an air inlet pipe 7, an accelerator 8, a double-cavity carburetor 9, a choke valve 10, a pure air channel 11, an air storage cavity 12, a piston 13, a piston pin 14, a spark plug 15, a silencer gasket 16, an exhaust port 17, a silencer 18, a bearing 19, an oil seal 20, a left scavenging cover plate 21, a right scavenging cover plate 22, a left scavenging port 23 and a right scavenging port 24.

Firstly, a crankcase chamber with an inner cavity is formed by splicing a right crankcase 1 and a left crankcase 2, a bearing 19 and an oil seal 20 which are horizontal left and right in the axial direction are respectively pressed in the crankcase chamber, and then a crankshaft 3 which is horizontal left and right in the axial direction is rotatably arranged on the bearing 19. The bottom of the cylinder 6 which is vertical in the axial direction is fixedly connected with the top of the crankcase chamber, the inside of the cylinder 6 is communicated with the crankcase chamber, a piston 13 is coaxially and slidably arranged in the cylinder 6, a connecting rod 4 is arranged between the piston 13 and the crankshaft 3, one end of the connecting rod 4 is connected with the crankshaft 3, and the other end of the connecting rod 4 is connected with a piston pin 14 in the piston 13.

The upper parts of the left and right cylinder walls of the cylinder 6 are respectively and correspondingly provided with a left scavenging port 23 and a right scavenging port 24, the upper parts of the outer side surfaces of the left and right cylinder walls of the cylinder 6 are respectively and correspondingly provided with a left scavenging cover plate 21 and a right scavenging cover plate 22 corresponding to the left scavenging port 23 and the right scavenging port 24, the space enclosed between the scavenging cover plate on each side and the corresponding side wall of the cylinder 6 is used as a scavenging chamber, and the bottom of the scavenging chamber is communicated with the space at the lower part in the cylinder 6.

A pure air inlet is arranged at the rear side position of the middle part of the cylinder wall of the cylinder 6, and a mixed gas inlet 5 is arranged below the pure air inlet at the rear side position of the lower part of the cylinder wall of the cylinder 6. The rear side of the cylinder wall of the cylinder 6 is connected with an air inlet pipe 7 and a double-cavity carburetor 9 in sequence. The air inlet pipe 7 is provided with an upper air passage and a lower air passage, and the front ends of the upper air passage and the lower air passage are respectively communicated with a pure air inlet and a mixed gas inlet 5 of the cylinder wall of the cylinder 6 in a one-to-one correspondence mode. The double-cavity carburetor 9 comprises a carburetor body, a choke valve 10 is installed at the inlet end of the carburetor body, an accelerator 8 is installed at the outlet end of the carburetor body, a partition plate is arranged between the choke valve 10 and the accelerator 8, one end of the partition plate extends into the accelerator 8 to divide the accelerator 8 into two parts, the other end of the partition plate extends into the choke valve 10 to divide the choke valve 10 into two parts, therefore, the whole partition inside the carburetor body is divided into a pure air cavity and a fresh mixed gas cavity through the partition plate, the other end of an upper air passage of an air inlet pipe 7 is communicated with the pure air cavity, and the other end of a lower air passage of the air inlet pipe 7 is communicated with the fresh mixed gas cavity.

An exhaust port 17 is arranged at the front side of the upper part of the cylinder wall of the cylinder 6, and the height of the exhaust port 17 is slightly higher than that of the left scavenging port 23 and the right scavenging port 24. A muffler 18 is connected and mounted on the outer side surface of the cylinder wall of the cylinder 6 at a position corresponding to the exhaust port 17 through a muffler gasket 16, and the inside of the cylinder 6 and the muffler 18 are communicated through the exhaust port 17. An ignition plug 15 is mounted on the top of the cylinder 6, and the ignition plug 15 ignites the inside of the cylinder 6.

The left side surface and the right side surface of a piston 13 in the cylinder 6 are respectively provided with an air storage cavity 12, a left pure air channel 13 and a right pure air channel 13 are arranged in the piston 13, outlet port openings of the two pure air channels 13 are communicated with the left air storage cavity 12 and the right air storage cavity 12 in a one-to-one correspondence mode, and inlet port openings of the two pure air channels 13 are respectively arranged on the rear side surface of the cylinder 6. Therefore, when the cylinder 6 moves up and down, the cylinder wall of the cylinder 6 can seal the air storage cavity 12 and the inlet end of the pure air channel 13; when the piston 6 moves to the position that the gas storage cavity 12 reaches the position of the corresponding side scavenging port, the left and right gas storage cavities 12 are communicated with the left and right scavenging ports 23 and 24 correspondingly; when the piston 6 moves to the position where the inlet port of the pure air channel 13 corresponds to the pure air inlet at the rear side of the middle part of the cylinder wall of the cylinder 6, the inlet port of the pure air channel 13 can be communicated with the pure air inlet.

The double-cavity carburetor 9 forms an upper independent cavity and a lower independent cavity which are mutually noninterference by connecting the accelerator 8 and the choke valve 9, namely a pure air cavity and a fresh mixed gas cavity. Similarly, the air inlet pipe 7 is also divided into an upper air passage and a lower air passage which are independent of each other. The two air storage cavities 12 of the piston 13 which are symmetrical left and right can be matched with the inner wall of the cylinder 6 to form a sealed space and are communicated with the left pure air channel 11 and the right pure air channel 11. When the gasoline engine works, pure air is promoted to flow into an upper air passage of the air inlet pipe 7 through a pure air chamber of the double-chamber carburetor 9 and enter the air storage cavity 12 through the pure air passage 11 by means of negative pressure generated in a crankcase chamber by the upward movement of the piston 13. On the other hand, the fresh mixed gas flows into the lower air passage of the air inlet pipe 7 through the fresh mixed gas chamber of the double-chamber carburetor 9 and enters the closed space in the crankcase chamber, and the fresh mixed gas is continuously and fully atomized and mixed by utilizing negative pressure, so that the combustion efficiency of the fresh mixed gas is improved.

The left and right sides of the cylinder 6 are equipped with a left scavenging cover plate 21 and a right scavenging cover plate 22 which respectively form a left scavenging chamber and a right scavenging chamber with the outer wall of the cylinder 6, and the left scavenging chamber and the right scavenging chamber are communicated with a left scavenging port 23 and a right scavenging port 24 which are corresponding to the upper part of the cylinder wall of the cylinder 6. And a scavenging route of the scavenging port forms a certain included angle with the axis of the cylinder, and the scavenging route can enable scavenging flow to flow along the cylinder wall of the cylinder 6 at an angle of 110-130 degrees, so that the scavenging short circuit phenomenon is prevented, the short circuit loss can be reduced, and the effects of saving oil and reducing emission are achieved.

The piston 13 continues to move upwards for a small section, at the moment, the space of the left and right gas storage cavities 12 just corresponds to the positions of the left scavenging port 23 and the right scavenging port 24, pure air immediately enters the upper parts of the left and right scavenging chambers formed by the left scavenging cover plate 21 and the right scavenging cover plate 22 respectively, and fresh mixed gas continues to enter the closed space in the crankcase chamber. The piston 13 continues to move upwards to the vicinity of the top dead center, the spark plug 15 starts to ignite, the combustible mixture in the combustion chamber at the upper part of the cylinder 6 burns and does work to push the piston 13 to move downwards, at the moment, the fresh mixture in the closed space in the crankcase chamber starts to be pressurized, when the piston 13 continues to move downwards to open the exhaust port 17, the burnt waste gas flows into the muffler 18 at a high speed through the exhaust port 17 and is discharged out of the engine.

In the present invention, the distance from the closing of the left and right scavenging ports 23, 24 to the closing of the exhaust port 17 on the inner wall of the cylinder 6 is reduced as much as possible. The top surface of the piston 13 is used to open and close the exhaust port 17 and the left and right scavenging ports 23 and 24, so that the opening and closing time of the two types of ports is only related to the positions of the upper edges of the ports. The distances from the exhaust port 17, the left scavenging port 23 and the right scavenging port 24 to the top surface of the cylinder 6 are very important, and the shorter the distance is, the better the rotating speed of the engine is, under the condition of ensuring the effective compression ratio, because the time for clearing the waste gas is shortened at high speed, the time for opening the engine in advance is prolonged, and the time for exhausting and scavenging is also prolonged. In the design of the invention, the heights of the upper edges of the left scavenging port 23 and the right scavenging port 24 are lower than the height of the upper edge of the exhaust port 17, and the distance between the upper edge of the exhaust port 17 and the top of the cylinder 6 is 8.5-9 times of the distance between the upper edge of the scavenging port and the upper edge of the exhaust port 17, and the optimal value is 8.75 times. For example, if the distance between the upper edge of the exhaust port 17 and the top surface of the cylinder 6 is 21mm, the distance between the upper edges of the left scavenging port 23 and the right scavenging port 24 and the upper edge of the exhaust port 17 is 2.4mm (as shown in fig. 8), the exhaust phase angle is 127.3 ° (as shown in fig. 9), and the scavenging phase angle is 88.9 ° (as shown in fig. 10).

The escape of the fresh mixed gas is prevented when the scavenging port is opened. When the piston 13 moves to open the left scavenging port 23 and the right scavenging port 24, the pure air stored at the upper parts of the left scavenging chamber and the right scavenging chamber formed by the left scavenging cover plate 21 and the right scavenging cover plate 22 respectively is pushed into the combustion chamber of the cylinder 6 by the pre-compressed fresh air mixture for scavenging, and then the fresh air mixture enters the combustion chamber again for scavenging. Pure air scavenging is used, so that the escape of unburned fresh mixed gas can be reduced, the emission of harmful components (HC + CO) and the like in tail gas can be reduced, the oil consumption is reduced, the power is increased, and the economical efficiency is improved. Meanwhile, under the idle working condition, the pure air channel 11 is always in a closed state, and only fresh mixed gas enters the cylinder 6; the idling of the gasoline engine is stable, the acceleration performance is good, and the power of the gasoline engine can be effectively improved.

The embodiments of the present invention are described only for the preferred embodiments of the present invention, and not for the limitation of the concept and scope of the present invention, and various modifications and improvements made to the technical solution of the present invention by those skilled in the art without departing from the design concept of the present invention shall fall into the protection scope of the present invention, and the technical content of the present invention which is claimed is fully set forth in the claims.