CN117989024A - Two-stroke internal combustion engine - Google Patents

Abstract

The invention discloses a two-stroke internal combustion engine, which comprises a cylinder and a carburetor, wherein a pure air inlet and a mixed gas inlet are formed in the wall of the cylinder, the pure air inlet is in fluid communication with a pure air inlet channel, and the pure air inlet channel is independent of the carburetor; the mixture inlet is in fluid communication with a mixture outlet of the carburetor. According to the invention, through the independently arranged pure air inlet channel and the mixed gas inlet channel, a universal carburetor can be used, so that the cost is greatly reduced, the content of harmful components in tail gas can be reduced, the emission is improved, the fuel consumption is effectively reduced, and the purposes of energy conservation and environmental protection are realized.

Description

Two-stroke internal combustion engine

Technical Field

The invention belongs to the field of engines, and particularly relates to a two-stroke internal combustion engine.

Background

The small two-stroke engine has the characteristics of small volume, simple structure, low cost, strong explosive force, stable power output and the like, and is widely applied to the field of portable handheld garden machine products such as brush cutters, blowers, sprayers, chain saws and the like.

Currently, two-stroke internal combustion engines are widely used, wherein fresh combustible mixture is used for scavenging and scavenging the exhaust gas after combustion in a cylinder. The cylinder is provided with an exhaust port, a scavenging port and an air inlet from top to bottom in sequence, and the opening and closing of the exhaust port, the scavenging port and the air inlet are controlled by the up-and-down reciprocating motion of the top of the piston and the bottom surface of the skirt part respectively. When the piston moves upwards, negative pressure is generated in the crankcase, fresh combustible mixture is introduced into the crankcase by using the negative pressure and is increased along with gradual rising of the piston, and the maximum value is reached when the piston reaches the top dead center; when the piston descends, the combustible mixture entering the crankcase before is compressed, and two fresh combustible mixture scavenging air flows flowing out from the scavenging port firstly strike the cylinder wall opposite to the exhaust port, are folded upwards under the guidance of the cylinder wall, strike the top of the combustion chamber in one path, are folded downwards and flow to the exhaust port. The fresh combustible mixture inevitably mixes with the combusted exhaust gases and flows out of the machine through the exhaust port with the exhaust gases without combustion. In the scavenging process, a large amount of fresh mixed gas is directly lost from exhaust gas due to short circuit loss, so that the oil consumption of the two-stroke gasoline engine is increased, and the exhaust gas contains a large amount of harmful substances such as hydrocarbon HC, carbon monoxide CO and the like, so that the exhaust gas becomes one of main pollution sources of the atmosphere. Meanwhile, in the process of mixing the mixed gas with the waste gas, a part of the mixed gas is decomposed to generate toxic and harmful substances which are discharged out of the machine under the action of oxygen deficiency and high-temperature waste gas, so that the emission pollution is further aggravated and worsened. In addition, in order to reduce ventilation loss, the design of the scavenging port of the existing two-stroke gasoline engine is much lower than that of the exhaust port, when the piston moves upwards, the scavenging port is closed firstly, then the exhaust port is closed, in this period, namely in the later period of scavenging, part of combustible mixed gas in the cylinder is discharged out of the extruder through the exhaust port, namely 'useless exhaust time', so that fuel is wasted, and pollution is aggravated.

Disclosure of Invention

The invention aims to provide an energy-saving and emission-reducing two-stroke internal combustion engine so as to solve the problems. For this purpose, the invention adopts the following technical scheme:

according to an embodiment of the invention, there is provided a two-stroke internal combustion engine, comprising a cylinder and a carburetor, wherein a pure air inlet and a mixed gas inlet are formed in a cylinder wall of the cylinder, the pure air inlet is in fluid communication with a pure air inlet channel, and the pure air inlet channel is independent of the carburetor; the mixture inlet is in fluid communication with a mixture outlet of the carburetor.

In a preferred embodiment, the two-stroke internal combustion engine further comprises a carburetor seat provided with the pure air intake passage and a mixture intake passage, one end of the mixture intake passage being connected to the mixture inlet and the other end being connected to the mixture outlet of the carburetor.

In a preferred embodiment, the carburetor seat is provided with two independent pure air inlet passages, and the two pure air inlet passages are respectively connected with the two pure air inlets.

In a preferred embodiment, two of said pure air inlets are arranged side by side in the circumferential direction of said cylinder.

In a preferred embodiment, the cylinder is sealingly connected to the carburetor seat by a first gasket and the carburetor seat is sealingly connected to the carburetor by a second gasket.

In a preferred embodiment, the pure air intake passage has an inlet section configured to have a circular cross section and an outlet section configured to have a rectangular cross section.

In a preferred embodiment, the pure air intake passage is provided with a passage switch for opening or closing the pure air intake passage.

In a preferred embodiment, the passage switch is configured in a cylindrical shape, and opens or closes the pure air intake passage by rotating.

In a preferred embodiment, the channel switch is rotationally sealed by a sealing member, and the sealing member is embedded in the pure air inlet channel and is matched with the channel switch.

In a preferred embodiment, the mixture inlet is located below the pure air inlet.

In a preferred embodiment, the cylinder is further provided with an exhaust port and a scavenging port, wherein the upper edge of the scavenging port is lower than the upper edge of the exhaust port.

In a preferred embodiment, the exhaust port comprises a first portion above the upper edge of the scavenging port and a second portion below the upper edge of the scavenging port, the ratio of the area of the first portion to the area of the second portion being between 0.3 and 0.6.

In a preferred embodiment, the scavenging port comprises two first scavenging ports and two second scavenging ports, wherein the first scavenging port is closer to the exhaust port than the second scavenging port and the two first scavenging ports are respectively positioned at two sides of the exhaust port, the upper edges of the first scavenging port and the second scavenging port are equal in height, and the height of the first scavenging port is smaller than the height of the second scavenging port.

In a preferred embodiment, the ratio of the height of the first scavenging port to the height of the second scavenging port is 0.6-1.

In a preferred embodiment, the ratio of the area of the first scavenging port to the area of the second scavenging port is 0.55 to 0.85.

In a preferred embodiment, the lower edge of the first scavenging port is higher than the lower edge of the exhaust port, and the lower edge of the second scavenging port is lower than the lower edge of the exhaust port.

In a preferred embodiment, the ratio of the difference in height of the lower edge of the first scavenging port to the lower edge of the exhaust port to the difference in height of the lower edge of the exhaust port to the lower edge of the second scavenging port is greater than 30.

According to the invention, through the independently arranged pure air inlet channel and the mixed gas inlet channel, a universal carburetor can be used, so that the cost is greatly reduced, the content of harmful components in tail gas can be reduced, the emission is improved, the fuel consumption is effectively reduced, and the purposes of energy conservation and environmental protection are realized.

Drawings

FIG. 1 is an exploded perspective view of a two-stroke internal combustion engine of the present invention;

FIG. 2 is a partially cut-away perspective view of the two-stroke internal combustion engine shown in FIG. 1;

FIG. 3 is an exploded perspective view of a carburetor seat assembly of the two-stroke internal combustion engine of FIG. 1;

FIG. 4 is another exploded perspective view of the carburetor seat assembly of the two-stroke internal combustion engine of FIG. 1;

FIG. 5 is a front view of a carburetor seat assembly of the two-stroke internal combustion engine of FIG. 1;

FIG. 6 is a cut-away perspective view of the carburetor seat assembly taken along line X-X in FIG. 5;

FIG. 7 is a cross-sectional view of the carburetor seat assembly of FIG. 6;

FIG. 8 is a schematic illustration of a piston of the two-stroke internal combustion engine shown in FIG. 1;

FIG. 9 is a schematic illustration of a cylinder of the two-stroke internal combustion engine shown in FIG. 1;

FIG. 10 is a cross-sectional view of a cylinder of the two-stroke internal combustion engine shown in FIG. 1;

FIG. 11 is a cylinder wall expansion schematic of a cylinder of the two-stroke internal combustion engine shown in FIG. 1;

FIG. 12 is a schematic airflow diagram of the two-stroke internal combustion engine of FIG. 1 in a first state;

FIG. 13 is a schematic air flow diagram of the two-stroke internal combustion engine of FIG. 1 in a second state;

FIG. 14 is a schematic air flow diagram of the two-stroke internal combustion engine of FIG. 1 in a third state;

FIG. 15 is a schematic airflow diagram of the two-stroke internal combustion engine of FIG. 1 in a fourth state;

FIG. 16 is a schematic air flow diagram of the two-stroke internal combustion engine of FIG. 1 in a fifth state.

Detailed Description

The preferred embodiments of the present invention will be described in detail below with reference to the attached drawings so that the objects, features and advantages of the present invention will be more clearly understood. It should be understood that the embodiments shown in the drawings are not intended to limit the scope of the invention, but rather are merely illustrative of the true spirit of the invention.

In the following description, for the purposes of explanation of various disclosed embodiments, certain specific details are set forth in order to provide a thorough understanding of the various disclosed embodiments. One skilled in the relevant art will recognize, however, that an embodiment may be practiced without one or more of the specific details. In other instances, well-known devices, structures, and techniques associated with the present application may not be shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

In the following description, for the purposes of clarity of presentation of the structure and manner of operation of the present invention, the description will be made with the aid of directional terms, but such terms as "forward," "rearward," "left," "right," "outward," "inner," "outward," "inward," "upper," "lower," etc. are to be construed as convenience, and are not to be limiting.

As shown in fig. 1 to 10, a two-stroke internal combustion engine includes a cylinder 1, a carburetor 2, a carburetor seat assembly 3, and a crankcase 4. A piston 5 is provided in the cylinder 1, and the piston 5 is connected to a crankshaft connecting rod mechanism in the crankcase 4 so that the piston 5 reciprocates up and down in the cylinder 1. The connection structure of the crankcase 4 and the piston 5 is well known and will not be described in detail here. The crankcase 4 has a closed space for storing the mixture, and the closed space is usually formed by matching left and right crankcase bodies. Two air storage chambers 51 which are radially opposite are arranged on the side wall of the piston 5, and the two air storage chambers 51 are respectively communicated with a pure air channel. The air reservoir 51 forms a sealed space with the cylinder wall of the cylinder 1 for storing pure air. The cylinder 1 is provided with a pure air inlet 11 and a mixed gas inlet 12 on the cylinder wall, and the mixed gas inlet 12 is positioned below the pure air inlet 11, so that the mixed gas is firstly introduced during air intake, and simultaneously, the pure air is firstly introduced into the combustion chamber during scavenging. The pure air inlets 11 are two and are respectively communicated with the two air storage chambers 51 through corresponding pure air channels, so that pure air can enter the two air storage chambers 51. It should be understood that there may be only one pure air inlet 11 in communication with both air reservoirs 51, or that there may be more than 2 pure air inlets 11. The carburetor seat assembly 3 includes a carburetor seat 31, the carburetor seat 31 having a pure air intake passage 311 and a mixture intake passage 312. One end of the carburetor seat 31 is mounted on the cylinder 1, and the other end is provided with a carburetor mounting portion for mounting the carburetor 2, so that one ends of the pure air intake passage 311 and the mixture air intake passage 312 are respectively connected with the pure air inlet 11 and the mixture air inlet 12 in a sealing manner, and the other end of the mixture air intake passage 312 is communicated with the mixture air outlet 21 of the carburetor 2. By providing the carburetor seat 31, no modification of the carburetor is required, that is, an existing carburetor can be used, and the cost is greatly reduced.

It should be appreciated that in some embodiments, the carburetor 2 may also be mounted directly to the cylinder 1, i.e., without the carburetor seat assembly 3, with the mixture outlet 21 of the carburetor 2 communicating directly with the mixture inlet 12; while the pure air inlet 11 is directly connected to a pure air intake pipe (corresponding to the pure air intake passage 311).

In the present embodiment, two pure air inlets 11 are arranged side by side in the circumferential direction of the cylinder 1, so that communication of two pure air intake passages can be achieved by one carburetor seat 31.

As shown in fig. 3 to 7, the carburetor seat assembly 3 further includes a first gasket 32 and a second gasket 34, wherein the first gasket 32 is used between the carburetor seat 31 and the cylinder 1, and the second gasket 34 is used between the carburetor seat 31 and the carburetor 2 to perform a sealing function. The first gasket 32 and the second gasket 34 may be made of rubber, preferably asbestos-free oil-resistant rubber. The first and second shims 32, 34 are sized and shaped according to the shape and size of the mounting location. In the illustrated embodiment, the first spacer 32 is composed of a rectangular portion and a triangular portion; the second gasket 34 is generally oval in shape. The first gasket 32 has openings 321 and 322 corresponding to the pure air inlet 11 and the mixture inlet 12, and through holes 323 corresponding to the mounting holes 16 on the cylinder 1. Similarly, the second gasket 34 has an opening 341 corresponding to the mixture outlet 21 of the carburetor 2 and a through hole 342 located at the periphery through which the mounting screw passes.

In the present embodiment, the pure air intake passage 311 of the carburetor seat 31 includes an intake section 3111 and an outlet section 3112. Wherein the inlet section 3111 is configured with a substantially circular cross-section and the outlet section 3112 is configured with a substantially rectangular cross-section. An obtuse angle is formed between the inlet section 3111 and the outlet section 3112. The orifice outlet section 3112 is parallel to the mixture intake passage 32. It should be understood that the pure air intake passage 311 may be entirely circular. The inlet section 3111 is for connection to a pure air intake pipe (not shown), i.e., an intake pipe mounting portion is designed at an inlet end of the inlet section 3111 to facilitate connection to the pure air intake pipe. A passage switch 35 is mounted to the inlet section 3111 adjacent to the outlet section 3112. The passage switch 35 is configured in a cylindrical shape, and is controlled by rotating to open or close the pure air passage in a manner similar to a choke valve and a throttle valve of a carburetor. Specifically, the passage switch 35 has two radial through holes 351 corresponding to the two pure air intake passages 311, respectively. The passage switch 35 is orthogonal to the pure air intake passage 311. One end of the passage switch 35 is fixedly provided with a rotating shaft 352, and the other end is mounted on the carburetor seat 31 through the end cover 36. The spindle 352 may be driven by electric or pneumatic means. It should be appreciated that the passage switch 35 may also be configured to operate as a choke valve, throttle valve, of a carburetor.

The carburetor seat assembly 3 further includes a seal 33, the seal 33 being mounted at the end of the clean air intake passage 311 of the carburetor seat 31 for ensuring air tightness when the passage switch 35 is rotated. The seal 33 may be made of an elastic material (e.g., nitrile rubber). The seal 33 is provided with a projection 333 for abutting sealing with the first gasket 32. Specifically, the seal 33 includes an embedded portion 331 embedded in the pure air intake passage 311 and a flange portion 332 located outside the pure air intake passage 311. In the present embodiment, there are two insertion portions 331 that are respectively inserted into the two pure air intake passages 311. That is, the cross-sectional shape of the embedded portion 331 is the same size as the cross-sectional shape of the pure air intake passage 311. In the present embodiment, the cross-sectional shape of the embedded portion 331 is rectangular. The end of the insertion portion 331 is arc-shaped and is closely matched with the passage switch 35 in the pure air intake passage 311 to perform a sealing function when the passage switch 35 rotates. The protrusion 333 is provided on a surface of the flange portion 332 remote from the embedded portion 331, surrounding the opening of the embedded portion 331. The height of the protrusions 333 is typically around 1 mm.

The carburetor seat 31 and the passage switch 35 may each be made of a PA6 material, preferably a PA6-GF30 material or a phenolic resin material.

As shown in fig. 2, 9 to 11, the cylinder 1 is further provided with an exhaust port 13, two first scavenging ports 14, and two second scavenging ports 15. Two first scavenging ports 14 are located on both sides of the exhaust port 13, respectively, and two second scavenging ports 15 are located between the two first scavenging ports 14. That is, the first scavenging port 14 is closer to the exhaust port 15 than the second scavenging port 15. The exhaust port 13 is a generally rectangular hole. In this embodiment, the upper edge of the exhaust port 13 is straight, the lower edge is circular arc-shaped, and the middle is lowest. That is, the height of the middle portion of the exhaust port 13 is greater than the height of both ends. The ratio of the height of the exhaust port 13 to the height of the scavenging ports (i.e., the first scavenging port 14 and the second scavenging port 15) is 1.1 to 2.7, preferably 1.2 to 1.7. A scavenging passage is formed between the cylinder 1 and the side cover. Pure air and mixture may enter the combustion chamber of the cylinder 1 via the scavenging channels and the scavenging ports (the first scavenging port 14 and the second scavenging port 15). By arranging four scavenging ports, the speed of pure air and mixed gas entering the combustion chamber can be improved, and the scavenging efficiency is improved.

The scavenging route forms an included angle with the axis of the cylinder 1, the junction is between about 80 degrees and 90 degrees, and the scavenging flow can flow along the cylinder wall in a diffusion way, 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 first and second scavenging ports 14, 15 are each substantially rectangular. The height B1 of the first scavenging port 14 is smaller than the height B2 of the second scavenging port 15, i.e. B1< B2. Specifically, the ratio B1/B2 of the height B1 of the first scavenging port 14 to the height B2 of the second scavenging port is 0.6 to 1, preferably 0.75 to 0.85.

The upper edge of the scavenging port (in this embodiment, the upper edges of the first scavenging port 14 and the second scavenging port 15 are at equal height) is lower than the upper edge of the exhaust port 13, and the absolute value of the difference in height between the two is X1. Wherein the ratio X1/A of X1 to A is 0.3 to 0.5, preferably 0.35 to 0.45, and A is the maximum height of the exhaust port 13. Specifically, the exhaust port 13 includes a first portion above the upper edge of the scavenging port and a second portion below the upper edge of the scavenging port, the ratio of the area of the first portion to the area of the second portion being 0.3 to 0.6, preferably 0.4 to 0.5, more preferably 0.45 to 0.48. Thus, the exhaust port 13 opens earlier than the scavenging port during the downward movement of the piston 5. During the downward movement of the piston 5, when the scavenging port starts to open, the first part of the exhaust port 13 is now in an open state, while the second part is in a closed but yet to be opened state. When the piston descends, the exhaust port is opened firstly, the pressure of the combustion chamber is reduced, and then the scavenging port is opened, so that pure air enters the combustion chamber firstly and is discharged together with waste. If the scavenging port is opened too early, excessive pressure of the combustion chamber and countercurrent flow of waste gas enter the scavenging channel can be generated, so that scavenging efficiency is affected; if the scavenging port is opened too late, too large a pressure difference between the combustion chamber and the scavenging passage can be generated, and the flow rate of the scavenging air flow entering the combustion chamber is too fast, so that the exhaust gas discharge is affected.

The lower edge of the first scavenging port 14 is higher than the lower edge of the exhaust port 13 (the absolute value of the difference in height is X3), and the lower edge of the second scavenging port 15 is lower than the lower edge of the exhaust port 13 (the absolute value of the difference in height is X2). Wherein the ratio of X2 to X3, X2/X3>30, preferably >40, and the ratio of B2 to X2, B2/X2>5.5. Thus, during the upward movement of the piston 5, the first scavenging port 14 starts to close first, the exhaust port 13 starts to close next, and finally the second scavenging port 15 starts to close. When the scavenging ports (the first scavenging port 14 and the second scavenging port 15) are all closed, the second portion of the exhaust port 13 is in a closed state at this time, while the first portion is in an open but about to be closed state. When the piston moves upwards, the scavenging port is closed, then the exhaust port is closed, and the mixed gas is compressed. If the exhaust port is closed too early, the mixture can flow back into the scavenging passage as the combustion chamber pressure increases, resulting in insufficient fuel in the combustion chamber; if the exhaust port is closed too late, the mixture is discharged through the exhaust port, resulting in waste of fuel and excessive discharge.

The ratio of the area of the first scavenging port 14 to the area of the second scavenging port 15 is 0.55 to 0.85, preferably 0.65 to 0.75. Since the second scavenging port 15 is larger than the first scavenging port 14 and is farther from the exhaust port 13, the pure air can sufficiently rapidly discharge the exhaust gas in the combustion chamber.

The ratio of the total area of the scavenging ports (i.e., the two first scavenging ports 14 and the two second scavenging ports 15) to the total area of the intake ports (i.e., the two pure air inlets 11 and the mixture inlet 12) is 1 to 1.2, preferably 1.07 to 1.12. The area of the scavenging port is slightly larger than the total area of the air inlet, so that pure air and mixed gas can enter the combustion chamber quickly.

In the embodiment shown, the pure air inlet 11 has a height C1 at the end close to the outlet 13 which is smaller than a height C2 at the end remote from the outlet 13. Specifically, the lower edge of the pure air inlet 11 is a straight line, and the upper edge is stepped. The mixture inlet 12 is narrow at the top and wide at the bottom, and has a substantially triangular shape.

The operation of the two-stroke internal combustion engine of the present invention will be described below with reference to fig. 12 to 16. In the figure, M represents a mixture, a represents pure air, and E represents exhaust gas. Fig. 12 shows the direction of air flow of the two-stroke internal combustion engine in a first state. In the first state, the piston 5 is at the bottom dead center, the piston 5 moves upward, and at this time, both the pure air intake passage 311 (passage switch 35) and the mixture intake passage 312 (carburetor 2) are in the closed state; the exhaust gas E and the pure air a are sequentially discharged through the exhaust port, the mixed gas M is left in the combustion chamber, during the upward movement of the piston, the scavenging port (the second scavenging port 15) is firstly partially closed, then the exhaust port 13 is started to be closed, then the scavenging port is completely closed, at the moment, most of the exhaust port is closed, finally the exhaust port is completely closed, the pressure of the combustion chamber is increased, and the pressure of the crankcase is reduced. Fig. 13 shows the direction of air flow of the two-stroke internal combustion engine in the second state. In the second state, the piston 5 continues to ascend, and the pure air intake passage 311 and the mixture intake passage 312 are opened. During the upward movement of the piston 5, the mixture inlet 12 is first opened and the mixture M continues to enter the crankcase 4. The pure air inlet 11 is opened again, and pure air a is advanced into the air reservoir 51, and when the air reservoir 51 is aligned with the scavenging port, pure air a is then advanced up into the scavenging passage (between the side cover and the cylinder 1). The piston 5 continues to move upwards closing the pure air inlet 11. Fig. 14 shows the direction of air flow of the two-stroke internal combustion engine in a third state. In the third state, the piston 5 reaches the vicinity of the top dead center, the spark plug 6 ignites the compressed fresh mixture to start expansion and work, waste gas E is generated, the piston 5 descends, and the pressure of the fresh mixture entering the crankcase 4 is increased. The passage switch 35 and the air-fuel mixture switch (carburetor 2) are closed before the piston 5 descends. Fig. 15 shows the air flow direction of the two-stroke internal combustion engine in the fourth state. In the fourth state, the piston 5 descends, the exhaust port 13 is opened first, and the pressure of the generated exhaust gas E reaches up to 0.3MPa as the fresh mixed gas in the combustion chamber has completed combustion work, the exhaust gas E is discharged from the exhaust port 13 at a high speed, and the exhaust process is started. Fig. 16 shows the air flow direction of the two-stroke internal combustion engine in the fifth state. In the fifth state, the piston 5 continues to move downward, and the scavenging port opens shortly after the exhaust port 13 opens (the interval time is determined by the positional relationship between the scavenging port and the exhaust port (i.e., the height difference X1 between the upper edge of the exhaust port and the upper edge of the scavenging port)), and the pure air a in the air storage chamber and the scavenging passage advances into the combustion chamber and is discharged from the exhaust port together with the exhaust gas E. The mixture M in the crankcase then enters the combustion chamber through the scavenging passage. The piston 5 moves down to the bottom dead center and returns to the first state.

The two-stroke internal combustion engine utilizes pure air to mix and scavenge the exhaust gas in the cylinder in the early stage of scavenging, and then the fresh mixed gas follows the scavenging, so that the loss of the fresh mixed gas in the ventilation process is reduced, and the pollution is reduced. The reasonable air inlet and sweeping flow is realized through the structural design, the air inlet system is firstly divided into two parts, when the piston ascends to generate negative pressure in the crankcase, one path of pure air is sucked into the air storage chamber 51 positioned on the piston 5 near the scavenging port through the pure air inlet channel 311 and the pure air inlet 11, and the other path of fresh mixed gas directly enters the crankcase 4 through the mixed gas inlet channel 312 and the mixed gas inlet 12; as the piston descends, after the ventilation process starts, pure air in the air storage chamber 51 positioned on the piston 5 firstly enters the cylinder to clean waste gas, then is discharged out of the engine through the exhaust port 13, and then fresh mixed gas flows into the cylinder, and layered flow is formed in the cylinder by using time sequence. The fresh mixed gas is isolated from the waste gas by using pure air, and the fresh mixed gas is prevented from directly flowing out of the exhaust port 13, so that the loss of the fresh mixed gas discharged outside the machine without burning to do work is greatly reduced; meanwhile, the pure air is pre-filled in the combustion chamber, so that the interference of residual waste gas on the fresh mixed gas is reduced, the fuel concentration in the fresh mixed gas can be reduced, and the lean combustion function is realized. In addition, the two-stroke internal combustion engine optimizes the height difference between the scavenging port and the exhaust port, increases the effective stroke under the condition of avoiding the exhaust gas from flowing back into the crankcase from the scavenging port, improves the power, reduces the emission of harmful substances and achieves the purposes of energy conservation and emission reduction. The two-stroke internal combustion engine has simple and reliable structure and durable whole engine.

While the preferred embodiments of the present application have been described in detail, it will be appreciated that those skilled in the art, upon reading the above teachings, may make various changes and modifications to the application. Such equivalents are also intended to fall within the scope of the application as defined by the following claims.

Claims (17)

1. A two-stroke internal combustion engine comprising a cylinder and a carburetor, wherein a pure air inlet and a mixed gas inlet are formed in the wall of the cylinder, wherein the pure air inlet is in fluid communication with a pure air inlet channel, and the pure air inlet channel is independent of the carburetor; the mixture inlet is in fluid communication with a mixture outlet of the carburetor.

2. The two-stroke internal combustion engine as recited in claim 1 further comprising a carburetor seat provided with said pure air intake passage and a mixture intake passage, said mixture intake passage being connected at one end to said mixture inlet and at the other end to said mixture outlet of said carburetor.

3. A two-stroke internal combustion engine as claimed in claim 2 wherein said carburetor seat is provided with two separate said pure air intake passages, each of said pure air intake passages being connected to two of said pure air inlets.

4. A two-stroke internal combustion engine according to claim 3, wherein two of said pure air inlets are arranged side by side in the circumferential direction of said cylinder.

5. A two-stroke internal combustion engine as recited in claim 2 wherein said cylinder is sealingly connected to said carburetor seat by a first gasket and said carburetor seat is sealingly connected to said carburetor by a second gasket.

6. The two-stroke internal combustion engine of claim 2, wherein the pure air intake passage has an inlet section and an outlet section, wherein the inlet section is configured to have a circular cross section and the outlet section is configured to have a rectangular cross section.

7. A two-stroke internal combustion engine according to claim 2, wherein said pure air intake passage is provided with a passage switch for opening or closing said pure air intake passage.

8. The two-stroke internal combustion engine according to claim 7, wherein the passage switch is configured in a cylindrical shape, and opens or closes the pure air intake passage by rotation.

9. The two-stroke internal combustion engine according to claim 8, wherein said passage switch is rotationally sealed by a seal embedded in said pure air intake passage and cooperating with said passage switch.

10. A two-stroke internal combustion engine according to claim 1, wherein said mixture inlet is located below said pure air inlet.

11. The two-stroke internal combustion engine according to claim 1, wherein the cylinder is further provided with an exhaust port and a scavenging port, wherein an upper edge of the scavenging port is lower than an upper edge of the exhaust port.

12. The two-stroke internal combustion engine according to claim 11, wherein the exhaust port includes a first portion above the upper edge of the scavenging port and a second portion below the upper edge of the scavenging port, the ratio of the area of the first portion to the area of the second portion being 0.3 to 0.6.

13. The two-stroke internal combustion engine as recited in claim 11 wherein said scavenging port comprises two first scavenging ports and two second scavenging ports, wherein said first scavenging port is closer to said exhaust port than said second scavenging port and said two first scavenging ports are located on either side of said exhaust port, and wherein the upper edges of said first scavenging port and said second scavenging port are of equal height and the height of said first scavenging port is less than the height of said second scavenging port.

14. The two-stroke internal combustion engine according to claim 13, wherein the ratio of the height of the first scavenging port to the height of the second scavenging port is 0.6 to 1.

15. The two-stroke internal combustion engine according to claim 13, wherein the ratio of the area of the first scavenging port to the area of the second scavenging port is 0.55 to 0.85.

16. The two-stroke internal combustion engine according to claim 13, wherein the lower edge of the first scavenging port is higher than the lower edge of the exhaust port, and the lower edge of the second scavenging port is lower than the lower edge of the exhaust port.

17. The two-stroke internal combustion engine according to claim 16, wherein the ratio of the difference in height of the lower edge of the first scavenging port and the lower edge of the exhaust port to the difference in height of the lower edge of the exhaust port and the lower edge of the second scavenging port is greater than 30.