Two-stroke engine scavenging system and two-stroke engine

Abstract

The invention discloses a two-stroke engine scavenging system and a two-stroke engine, and belongs to the technical field of engines. The two-stroke engine scavenging system comprises a cylinder body and a piston, the cylinder body is provided with an air inlet, an air outlet and a scavenging channel, the hole wall of a combustion chamber is provided with a pair of first scavenging ports, a pair of second scavenging ports and a pair of third scavenging ports, and the heights of the upper edges of the first scavenging ports, the second scavenging ports and the third scavenging ports are sequentially reduced. And the top surface of the piston is provided with a concave cavity which is sunken downwards. The gradient change of the upper edge height and the blowing elevation angle of the three pairs of scavenging ports is utilized, the design of the collecting groove in the top face of the piston is combined, orderly driving of combustion waste gas is achieved, effective separation of scavenging gas and the combustion waste gas is achieved in combination with the blowing elevation angle change, the collecting groove in the top face of the piston is utilized for containing combustible mixed gas, and the combustion efficiency is improved. The fuel oil utilization rate of the two-stroke engine is increased, tail gas emission is improved, and the effects of energy conservation and emission reduction are achieved.

Description

Technical Field

[0001] The present invention relates to a two-stroke engine, and more particularly to a two-stroke engine scavenging system and the two-stroke engine. Background Art

[0002] A two-stroke engine completes a working cycle in two strokes. It boasts a simple structure, lightweight design, and low production and maintenance costs. It is commonly used in applications requiring high power performance and lightweight portability, such as handheld gardening equipment, agricultural machinery, drones, and motorboats. A typical two-stroke engine has intake, exhaust, and vent holes in its cylinder block. These holes are closed by the piston at specific times. Its working cycle consists of a first stroke and a second stroke. During the first stroke, the piston moves upward from bottom dead center, closing all three vents simultaneously. The air-fuel mixture entering the cylinder is compressed. Once the intake hole is exposed, the combustible mixture flows into the crankcase. In the second stroke, when the piston is compressed to near the top dead center, the spark plug ignites the combustible mixture, and the expansion of the combustion gas pushes the piston downward to perform work. At this time, the intake port is closed, and the combustible mixture enclosed in the crankcase is compressed. When the piston approaches the bottom dead center, the exhaust port opens and the exhaust gas rushes out; then the ventilation port opens, and the pre-compressed combustible mixture rushes into the cylinder to expel the exhaust gas and complete the ventilation process.

[0003] It is not difficult to see from the above structural principle of the two-stroke engine that the exhaust gas in the combustion chamber is mainly discharged by the scavenging effect of the combustible mixture entering through the ventilation hole when the piston approaches the bottom dead center. Due to the interaction between the exhaust gas and the airflow of the combustible mixture in the combustion chamber, it is easy for part of the combustible mixture to be discharged along with the exhaust gas, resulting in low fuel utilization and serious exhaust pollution. This is also the main reason why two-stroke engines are widely plagued.

[0004] Currently, scavenging technology remains the primary means for reducing fuel consumption and improving exhaust emissions in two-stroke engines, and many feasible technical solutions have been proposed in the prior art. For example, Kawasaki Heavy Industries, Ltd. filed patent application CN102297012A on June 16, 2011, entitled "Air-Scavenged Two-Stroke Engine." This patent application features a first scavenging passageway and a second scavenging passageway between the combustion chamber and the crankcase. The first and second scavenging ports at the upper ends of the first and second scavenging passageways are positioned lower than the upper end of the exhaust port, while the upper end of the second scavenging port, closer to the exhaust port, is higher than the upper end of the first scavenging port. During the scavenging process, air is first ejected from the first and second scavenging ports, followed by the mixed gas ejected from the first scavenging port. The air is closer to the exhaust port than the mixed gas, thus preventing the mixed gas from being blown out of the exhaust port. This design requires the addition of an air intake port, associated guide valves, and air ducts to the cylinder block, resulting in a complex structure and increased manufacturing difficulty. For example, on March 18, 2011, Hitachi Koki Co., Ltd. filed a patent application with patent publication number CN102782280A, entitled "Two-Stroke Engine and Engine Tool Including Such Engine." The patent application includes first and second scavenging ports located on the inner circumferential wall of the cylinder bore, and first and second scavenging channels connecting the first and second scavenging ports to the crankcase. The first and second scavenging channels are equipped with outflow direction-changing devices for directing the outflow of the air-fuel mixture from near the top dead center of the first and second scavenging ports into the cylinder bore and the outflow of the air-fuel mixture from near the bottom dead center of the first and second scavenging ports into the cylinder bore in different directions. The blowing angle of the second scavenging port has a larger inclination toward the bottom dead center than that of the first scavenging port, thereby facilitating exhaust gas discharge through the scavenging port's blowing angle orientation. This design has only two scavenging ports, and the blowing angle of the scavenging ports lacks gradient changes. It is difficult to further achieve effective separation of the fuel gas mixture and the exhaust gas by simply setting the scavenging direction. The swirling airflow generated by the exhaust gas in the combustion chamber is still easy to carry out the combustible mixture. For example: Tsinghua University filed a patent application with patent publication number CN112196663A on September 7, 2020, and the patent name is "A two-stroke diesel engine combustion system and a diesel engine containing the system". It includes an intake duct, a cylinder and a combustion chamber. The intake duct has at least one scavenging port, and different scavenging ports are connected to the cylinder at different inclination angles to perform layered swirl scavenging in the cylinder. This swirl scavenging needs to be coordinated with the ω-shaped combustion chamber structure at the top of the cylinder, but the swirl scavenging design generates a rotating combustible mixture flow in the combustion chamber. The combustible mixture at the bottom of the combustion chamber is easily mixed with the combustion exhaust gas and discharged from the exhaust port. Its effect in reducing fuel consumption remains to be discussed. Summary of the Invention

[0005] 1. Technical problem to be solved by the invention

[0006] The purpose of the present invention is to overcome the problems of low fuel utilization and serious exhaust pollution in existing two-stroke engines, and to provide a two-stroke engine scavenging system and a two-stroke engine. The technical solution of the present invention is adopted, and the gradient change of the upper edge height and the blowing elevation angle of three pairs of scavenging ports is utilized, combined with the design of the combustible mixture collecting groove on the top surface of the piston. During the downward scavenging process of the piston, the three pairs of scavenging ports are opened in sequence from far to near relative to the exhaust port, thereby realizing orderly expulsion of the combustion exhaust gas. At the same time, combined with the change of the blowing elevation angle of the three pairs of scavenging ports, effective separation of the scavenging gas and the combustion exhaust gas is realized, and the collecting groove on the top surface of the piston is used to accommodate the combustible mixture, which effectively reduces the mixing of the combustible mixture and the combustion exhaust gas, thereby reducing the combustible mixture discharged with the exhaust gas, improving the fuel utilization of the two-stroke engine, improving the exhaust emissions, and achieving the effect of energy saving and emission reduction.

[0007] 2. Technical solution

[0008] In order to achieve the above object, the technical solution provided by the present invention is:

[0009] A scavenging system for a two-stroke engine according to the present invention comprises a cylinder body and a piston capable of reciprocating in a combustion chamber of the cylinder body, the cylinder body having an intake port and an exhaust port respectively connected to the combustion chamber, the connection between the intake port and the combustion chamber being lower than the connection between the exhaust port and the combustion chamber, and the cylinder body further having a scavenging passage connecting the combustion chamber and the engine crankcase, wherein:

[0010] The hole wall of the combustion chamber is provided with a pair of first scavenging ports, a pair of second scavenging ports, and a pair of third scavenging ports in sequence and opposite to each other with the exhaust center plane of the exhaust port as the center, the first scavenging ports, the second scavenging ports, and the third scavenging ports are all connected to the corresponding scavenging channels, and the scavenging directions of the three are inclined to the side away from the exhaust port; the first scavenging port is located away from the exhaust port, and the third scavenging port is located close to the exhaust port, and the upper edge heights of the first scavenging port, the second scavenging port, and the third scavenging port are sequentially decreased, so that the first scavenging port, the second scavenging port, and the third scavenging port are opened in sequence during the downward movement of the piston, so as to use the scavenging gas to drive the combustion exhaust gas toward the exhaust port from far to near and discharge it;

[0011] The blowing elevation angles of the first scavenging port, the second scavenging port, and the third scavenging port decrease in sequence, so that the scavenging gas generated by the scavenging port opened later exerts a gas pressure away from the exhaust port on the scavenging gas generated by the scavenging port opened earlier;

[0012] The top surface of the piston is provided with a downwardly recessed cavity for collecting the scavenging gas generated by the first scavenging port, the second scavenging port and the third scavenging port into the cavity during the scavenging process.

[0013] Furthermore, the scavenging gases of each pair of the first scavenging ports, the second scavenging ports and the third scavenging ports converge at the exhaust center plane of the exhaust port, so that the scavenging gases after the convergence move in the direction away from the exhaust port; the scavenging direction angle α1 of the two first scavenging ports is 120°~130°, the scavenging direction angle α2 of the two second scavenging ports is 120°~130°, and the scavenging direction angle α3 of the two third scavenging ports is 120°~130°.

[0014] Furthermore, a height difference h1 between the upper edges of the first scavenging air port and the second scavenging air port is 1-3 mm, and a height difference h2 between the upper edges of the second scavenging air port and the third scavenging air port is 1-3 mm.

[0015] Furthermore, the lower edges of the first scavenging air port, the second scavenging air port and the third scavenging air port have the same height.

[0016] Furthermore, the lower edge heights of the first scavenging port, the second scavenging port and the third scavenging port are consistent or basically consistent with the lower edge height of the exhaust port on the combustion chamber hole wall; the upper edge height of the exhaust port on the combustion chamber hole wall is greater than the upper edge height of the first scavenging port, so that the exhaust port opens before the first scavenging port during the downward movement of the piston.

[0017] Furthermore, the blowing elevation angle θ1 of the first scavenging air port is 40° to 50°, the blowing elevation angle θ2 of the second scavenging air port is 10° to 20°, and the blowing elevation angle θ3 of the third scavenging air port is 0° to 5°.

[0018] Furthermore, the opening sizes of the first scavenging port, the second scavenging port and the third scavenging port are reduced in sequence, so that the scavenging gas pressures generated by the first scavenging port, the second scavenging port and the third scavenging port are increased in sequence.

[0019] Furthermore, the cavity is a curved cavity structure, and has a central plane at the bottom of the cavity for suppressing the rotation of the scavenging gas.

[0020] Furthermore, the piston is rotatably connected to one end of a connecting rod, and the other end of the connecting rod is rotatably connected to a crankshaft disposed in a crankcase of the engine, so that the reciprocating motion of the piston in the combustion chamber drives the crankshaft to rotate;

[0021] When the piston moves from the bottom dead center to the top dead center, the first scavenging port, the second scavenging port, the third scavenging port and the exhaust port are closed by the piston, and the piston passes over the intake port to open the intake port, and sucks the combustible mixture into the engine crankcase through the intake port;

[0022] When the piston moves from the top dead center to the bottom dead center, the piston closes the intake port and opens the exhaust port, the first scavenging port, the second scavenging port and the third scavenging port in sequence. The combustible mixture in the engine crankcase is purged into the combustion chamber through the first scavenging port, the second scavenging port and the third scavenging port, and the combustion exhaust gas in the combustion chamber is driven to the exhaust port and discharged.

[0023] A two-stroke engine of the present invention has the above-mentioned two-stroke engine scavenging system.

[0024] 3. Beneficial effects

[0025] Compared with the existing known technologies, the technical solution provided by the present invention has the following significant effects:

[0026] (1) A scavenging system for a two-stroke engine of the present invention comprises a cylinder body and a piston capable of reciprocating in a combustion chamber of the cylinder body, a pair of first scavenging ports, a pair of second scavenging ports and a pair of third scavenging ports are provided on the hole wall of the combustion chamber in sequence with the exhaust center plane of the exhaust port as the center, the first scavenging port, the second scavenging port and the third scavenging port are all connected to the corresponding scavenging channels, and the scavenging directions of the three are all inclined to the side away from the exhaust port, the upper edge heights of the first scavenging port, the second scavenging port and the third scavenging port are successively reduced, so that the first scavenging port, the second scavenging port and the third scavenging port are opened in sequence during the downward movement of the piston, so as to utilize the scavenging ports from far to near. The gas drives the combustion exhaust gas toward the exhaust port and discharges it; the blowing elevation angles of the first, second, and third scavenging ports decrease successively, so that the scavenging gas generated by the scavenging ports that open later exerts gas pressure away from the exhaust port on the scavenging gas generated by the scavenging ports that open earlier; a downwardly concave cavity is provided on the top surface of the piston, so that the scavenging gas generated by the first, second, and third scavenging ports during the scavenging process is collected into the cavity; compared with existing two-stroke engine scavenging systems, the present invention has at least the following four innovations, which, through the synergistic cooperation of these four innovative designs, improve the fuel utilization rate of the two-stroke engine and improve exhaust emissions:

[0027] First, the present invention adopts a three-pair scavenging port design, which not only increases the scavenging volume and scavenging coverage, but also can optimize the scavenging air flow and reduce the mixing of the combustible mixture and the combustion exhaust gas by utilizing the gradient design of the parameters of the three pairs of scavenging ports;

[0028] The height of the upper edges of the second and third pairs of scavenge ports gradually increases away from the exhaust port. During the downward movement of the piston, the first scavenge port, the second scavenge port, and the third scavenge port are opened in sequence. The scavenge gas is then used to drive the combustion exhaust gas toward the exhaust port from far to near relative to the exhaust port and discharge it. This also reduces the mixing of the combustible mixture and the combustion exhaust gas, and enables the rapid discharge of the combustion exhaust gas.

[0029] Third, the blowing angles of the three pairs of scavenge ports gradually increase in the direction away from the exhaust port. In conjunction with the sequential opening of the three pairs of scavenge ports, at the initial stage of scavenging, the scavenge airflow with a larger elevation angle is used to squeeze the exhaust gas from the upper part of the combustion chamber toward the exhaust port. Then, the scavenge airflow with a smaller elevation angle is gradually used to stabilize the combustible mixture, preventing the formation of cyclones and mixing with the exhaust gas. This can create an airflow boundary between the combustible mixture and the exhaust gas, further reducing the mixing of the combustible mixture and the exhaust gas.

[0030] Fourth, the piston top surface is provided with a downwardly concave cavity, forming a collection area for collecting scavenging gas. Combined with the design of the scavenging port with a small elevation angle near the exhaust port, the downward pressure of the scavenging air flow can use the gas pressure to gather the combustible mixture into the collection area, ensuring the stability of the combustible mixture and preventing the combustible mixture from mixing with the exhaust gas.

[0031] Through the coordinated cooperation of the above-mentioned innovative designs, the mixing of the combustible mixture and the combustion exhaust gas is effectively reduced, the combustible mixture discharged with the exhaust gas is reduced, the fuel utilization rate of the two-stroke engine is improved, the exhaust emissions are improved, and the effect of energy conservation and emission reduction is achieved.

[0032] (2) A two-stroke engine scavenging system of the present invention, wherein the scavenging gases of each pair of the first scavenging port, the second scavenging port and the third scavenging port all converge at the exhaust center plane of the exhaust port, so that the scavenging gases after the convergence move in the direction away from the exhaust port, and the three pairs of scavenging gases collide at the intersection to form an upper airflow, quickly discharge the exhaust gas from the upper part of the combustion chamber, and prevent the airflow from rotating, thereby avoiding the generation of adverse cyclones in the combustion chamber; at the same time, the scavenging direction angles of the three pairs of scavenging ports are 120° to 130°, so that the intersection position is far away from the exhaust port, effectively preventing part of the turbulence generated when the airflows converge from being carried away by the exhaust gas at the exhaust port.

[0033] (3) In a two-stroke engine scavenging system of the present invention, the height difference h1 between the upper edges of the first scavenging port and the second scavenging port is 1 to 3 mm, and the height difference h2 between the upper edges of the second scavenging port and the third scavenging port is 1 to 3 mm. This ensures that the three pairs of scavenging ports are opened in sequence and the time interval between the opening of the three pairs of scavenging ports is very short, thereby ensuring the instantaneous scavenging pressure when the three pairs of scavenging ports are opened, ensuring the stability of the scavenging airflow, and realizing the rapid discharge of exhaust gas.

[0034] (4) A two-stroke engine scavenging system of the present invention has an exhaust port whose upper edge height on the combustion chamber hole wall is greater than the upper edge height of the first scavenging port, so that the exhaust port opens before the first scavenging port during the downward movement of the piston, and can discharge the high-pressure combustion exhaust gas in the combustion chamber in advance, which is conducive to clearing the residual exhaust gas in the combustion chamber after the scavenging port is opened.

[0035] (5) A two-stroke engine scavenging system of the present invention has a blowing elevation angle θ1 of the first scavenging port of 40° to 50°, a blowing elevation angle θ2 of the second scavenging port of 10° to 20°, and a blowing elevation angle θ3 of the third scavenging port of 0° to 5°. The gradient design effect of the blowing elevation angle is obvious. While clearing the residual exhaust gas in the combustion chamber, it can reduce the loss of the combustible mixture, make the combustion of the combustible mixture more complete, and reduce the harmful gases in the exhaust gas.

[0036] (6) A two-stroke engine scavenging system of the present invention has a first scavenging port, a second scavenging port and a third scavenging port, the opening sizes of which are successively reduced, so that the pressures of the scavenging gas generated by the first scavenging port, the second scavenging port and the third scavenging port are successively increased, and the scavenging gas generated by the scavenging port opened later can be used to restrain the combustible mixture that enters the combustion chamber first, so that the combustible mixture is concentrated to the side away from the exhaust port, further reducing the combustible mixture being discharged with the exhaust gas.

[0037] (7) A two-stroke engine scavenging system of the present invention has a concave cavity with a curved cavity structure and a central plane at the bottom of the concave cavity for suppressing the rotation of the scavenging gas. The piston concave cavity can suppress the rotation of the combustible mixture entering the concave cavity to a certain extent, and can gradually drive the exhaust gas in the concave cavity toward the exhaust port when the first scavenging port, the second scavenging port and the third scavenging port are opened in sequence, thereby preventing the combustible mixture from rotating in the concave cavity and mixing with the exhaust gas.

[0038] (8) The two-stroke engine of the present invention has the above-mentioned two-stroke engine scavenging system, which improves the fuel utilization rate and economy of the two-stroke engine, reduces the exhaust pollution during the operation of the engine, and is more energy-saving and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the three-dimensional structure of the main components of a scavenging system for a two-stroke engine according to the present invention;

[0040] Figure 2 Schematic diagram of the top view of the main components of a scavenging system for a two-stroke engine according to the present invention;

[0041] Figure 3 for Figure 2 Schematic diagram of the cross-sectional structure in the AA direction (the piston is at the top dead center position);

[0042] Figure 4 for Figure 3 A schematic cross-sectional view of the middle piston moving to the bottom dead center position;

[0043] Figure 5 A schematic cross-sectional view of a cylinder in a scavenging system of a two-stroke engine according to the present invention;

[0044] Figure 6 for Figure 5 A partial enlarged schematic diagram of the three scavenge air ports;

[0045] Figure 7 for Figure 5 Schematic diagram of the cross-sectional structure in the middle BB direction;

[0046] Figure 8 for Figure 5 Schematic diagram of the cross-sectional structure in the CC direction;

[0047] Figure 9 A schematic structural diagram of a piston in a scavenging system of a two-stroke engine according to the present invention;

[0048] FIG10( a ) is a schematic diagram of the scavenging air flow in a scavenging system of a two-stroke engine according to the present invention when the piston descends until the first scavenging port is opened;

[0049] FIG10( b ) is a schematic diagram of the scavenging air flow when the piston descends until the second scavenging port is opened in a scavenging system of a two-stroke engine according to the present invention;

[0050] FIG10( c ) is a schematic diagram of the scavenging air flow when the piston descends to open the third scavenging port in a scavenging system of a two-stroke engine according to the present invention.

[0051] Explanation of the numbers in the schematic diagram:

[0052] 1. Cylinder block; 1-1. Combustion chamber; 2. Piston; 2-1. Concave cavity; 2-2. Center plane; 3. Connecting rod; 4. Crankshaft; 5. Intake port; 6. Exhaust port; 7. Scavenging passage; 7a. First scavenging port; 7b. Second scavenging port; 7c. Third scavenging port; 8. Exhaust gas flow; 9. First scavenging air flow; 10. Second scavenging air flow; 11. Third scavenging air flow. DETAILED DESCRIPTION

[0053] In order to further understand the content of the present invention, the present invention is described in detail with reference to the accompanying drawings and embodiments.

[0054] [Example]

[0055] Combine Figures 1 to 9 As shown, a scavenging system of a two-stroke engine of this embodiment includes a cylinder body 1 and a piston 2 capable of reciprocating in a combustion chamber 1-1 of the cylinder body 1. The cylinder body 1 has an intake port 5 and an exhaust port 6 respectively connected to the combustion chamber 1-1. The connection between the intake port 5 and the combustion chamber 1-1 is lower than the connection between the exhaust port 6 and the combustion chamber 1-1. The cylinder body 1 also has a scavenging passage 7 connecting the combustion chamber 1-1 and the engine crankcase, wherein, as shown in FIG. Figure 8As shown, a pair of first scavenging ports 7a, a pair of second scavenging ports 7b, and a pair of third scavenging ports 7c are provided on the wall of the combustion chamber 1-1 with the exhaust center plane P of the exhaust port 6 as the center. The first scavenging ports 7a, the second scavenging ports 7b, and the third scavenging ports 7c are all connected to the corresponding scavenging channels 7, and the scavenging directions S of the three are all inclined to the side away from the exhaust port 6. The lower end of the scavenging channel 7 is connected to the engine crankcase 1. During the operation of the two-stroke engine, the reciprocating movement of the piston 2 controls the opening and closing of the intake port 5, the exhaust port 6, and each scavenging port. The first scavenging port 7a is located away from the exhaust port 6, and the third scavenging port 7c is located close to the exhaust port 6, that is, Figure 4 and Figure 5 As shown, starting from the exhaust port 6, from left to right are the third scavenging port 7c, the second scavenging port 7b and the first scavenging port 7a. The upper edge heights of the three pairs of scavenging ports have a gradient design. Specifically, the upper edge heights of the first scavenging port 7a, the second scavenging port 7b and the third scavenging port 7c are successively reduced, so that the first scavenging port 7a, the second scavenging port 7b and the third scavenging port 7c are opened in sequence during the downward movement of the piston 2, so as to drive and discharge the combustion exhaust gas from far to near by using the scavenging gas; that is, during the scavenging process, scavenging is first performed from the first scavenging port 7a farthest from the exhaust port 6, and then the second scavenging port 7b and the third scavenging port 7c are opened in sequence to scavenging, so that the exhaust gas in the combustion chamber 1-1 is driven toward the exhaust port 6 step by step. At the same time, as shown in FIG. Figure 6 As shown, the three pairs of scavenging ports have different blowing elevation angles. Specifically, the blowing elevation angles of the first scavenging port 7a, the second scavenging port 7b, and the third scavenging port 7c decrease in sequence, so that the scavenging gas generated by the scavenging port opened later exerts a gas pressure away from the exhaust port 6 on the scavenging gas generated by the scavenging port opened earlier. In conjunction with the sequential opening of the three pairs of scavenging ports, in the initial stage of scavenging, the scavenging airflow with a larger elevation angle is used to squeeze the exhaust gas from the upper part of the combustion chamber 1-1 toward the exhaust port 6. Then, the scavenging airflow with a smaller elevation angle is used step by step to stabilize the combustible mixture to prevent the formation of cyclones and mixing with the exhaust gas. Figure 3 、 Figure 4 and Figure 9As shown, to further prevent the combustible mixture from mixing with the exhaust gas, a downwardly recessed cavity 2-1 is provided on the top surface of the piston 2. This cavity 2-1 is used to collect the scavenging gas generated by the first scavenging port 7a, the second scavenging port 7b, and the third scavenging port 7c during the scavenging process. In other words, a collection area for collecting scavenging gas is formed on the top surface of the piston 2. Combined with the design of the small elevation angle scavenging port near the exhaust port, the downward pressure of the scavenging air flow can use the gas pressure to gather the combustible mixture into the collection area, thereby ensuring the stability of the combustible mixture and preventing the combustible mixture from mixing with the exhaust gas. The above-mentioned two-stroke engine scavenging system organically combines the multi-scavenging port design, the scavenging port gradient opening design, the scavenging port blowing elevation gradient change design, and the piston collection area design, achieving the synergistic cooperation of the four innovative designs, improving the fuel efficiency of the two-stroke engine and improving exhaust emissions.

[0056] like Figure 8 As shown, in this embodiment, the scavenging gases from each pair of first scavenging ports 7a, second scavenging ports 7b, and third scavenging ports 7c converge at the exhaust center plane P of the exhaust port 6. Since the scavenging directions S of each scavenging port are inclined away from the exhaust port 6, the converged scavenging gases move away from the exhaust port 6, and the convergence point is located on the side away from the exhaust port 6, thereby preventing the scavenging gases from being directly discharged from the exhaust port 6. The scavenging directions S of each pair of scavenging ports can be the same or different. In this embodiment, the scavenging direction S angle α1 of the two first scavenging ports 7a is 120° to 130°, the scavenging direction S angle α2 of the two second scavenging ports 7b is 120° to 130°, and the scavenging direction S angle α3 of the two third scavenging ports 7c is 120° to 130°. This positions the convergence point away from the exhaust port 6, effectively preventing some of the turbulence generated by the convergence of the airflows from being carried away by the exhaust gas at the exhaust port 6. Preferably, the scavenging direction S angles of the three pairs of scavenging ports are the same, and are all set to 125°.

[0057] Reference Figure 6 As shown, specifically in this embodiment, the height difference h1 between the upper edges of the first scavenging air port 7a and the second scavenging air port 7b is 1 to 3 mm, and the height difference h2 between the upper edges of the second scavenging air port 7b and the third scavenging air port 7c is 1 to 3 mm. h1 and h2 can be equal or unequal, and h1 = h2 = 2 mm is preferred. The above-mentioned height difference design not only ensures the successive opening of the three pairs of scavenging air ports, but also ensures that the opening time interval of the three pairs of scavenging air ports is very short, thereby ensuring the instantaneous scavenging pressure when the three pairs of scavenging air ports are opened, ensuring the stability of the scavenging air flow, and realizing the rapid discharge of exhaust gas. In addition, the lower edge heights of the first scavenging air port 7a, the second scavenging air port 7b and the third scavenging air port 7c can be equal. As shown Figure 5 and Figure 7As shown, in this embodiment, the lower edge heights of the first scavenge air port 7a, the second scavenge air port 7b, and the third scavenge air port 7c are aligned or substantially aligned with the lower edge height of the exhaust port 6 on the wall of the combustion chamber 1-1. The upper edge height of the exhaust port 6 on the wall of the combustion chamber 1-1 is greater than the upper edge height of the first scavenge air port 7a, enabling the exhaust port 6 to open before the first scavenge air port 7a during the downward movement of the piston 2. This allows the high-pressure combustion exhaust gas within the combustion chamber 1-1 to be discharged in advance, facilitating the removal of residual exhaust gas within the combustion chamber after the scavenge air ports are opened.

[0058] catch Figure 6 As shown, in this embodiment, the blowing elevation angle θ1 of the first scavenging air port 7a is 40° to 50°, the blowing elevation angle θ2 of the second scavenging air port 7b is 10° to 20°, and the blowing elevation angle θ3 of the third scavenging air port 7c is 0° to 5°. Preferably, the blowing elevation angle θ1 of the first scavenging air port 7a is designed to be 45°, the blowing elevation angle θ2 of the second scavenging air port 7b is designed to be 15°, and the blowing elevation angle θ3 of the third scavenging air port 7c is designed to be 0°. The gradient design effect of the above-mentioned blowing elevation angle is obvious. While clearing the residual exhaust gas in the combustion chamber 1-1, it can reduce the loss of the combustible mixture, make the combustion of the combustible mixture more complete, and reduce harmful gases in the exhaust gas. In addition, as Figure 5 and Figure 6 As shown, the opening sizes of the first scavenging port 7a, the second scavenging port 7b, and the third scavenging port 7c decrease in sequence, so that the scavenging gas pressure generated by the first scavenging port 7a, the second scavenging port 7b, and the third scavenging port 7c increase in sequence. Since the scavenging gas pressure generated by the smaller scavenging port opening size is greater, the scavenging gas generated by the scavenging port that opens later can be used to constrain the combustible mixture that enters the combustion chamber earlier, causing the combustible mixture to be concentrated toward the side away from the exhaust port 6, further reducing the combustible mixture from being discharged with the exhaust gas.

[0059] Reference Figure 9 As shown, in this embodiment, the concave cavity 2-1 of the piston 2 is a curved cavity structure, and has a central plane 2-2 at the bottom of the concave cavity 2-1 for suppressing the rotation of the scavenging gas. The lowest center position of the concave cavity 2-1 is designed to be a plane, which can suppress the rotation of the combustible mixture entering the concave cavity 2-1 to a certain extent. When the first scavenging port 7a, the second scavenging port 7b and the third scavenging port 7c are opened in sequence, the exhaust gas in the concave cavity 2-1 can be gradually driven toward the exhaust port 6, thereby preventing the combustible mixture from rotating in the concave cavity 2-1 and mixing with the exhaust gas.

[0060] Similar to the existing two-stroke engine, the piston 2 in this embodiment is rotatably connected to one end of the connecting rod 3, and the other end of the connecting rod 3 is rotatably connected to the crankshaft 4 arranged in the engine crankcase. The reciprocating motion of the piston 2 in the combustion chamber 1-1 drives the crankshaft 4 to rotate. When the piston 2 moves from the bottom dead center to the top dead center, the first scavenging port 7a, the second scavenging port 7b, the third scavenging port 7c and the exhaust port 6 are closed by the piston 2, and the piston 2 passes over the intake port 5 to open the intake port 5, and sucks the combustible mixture into the engine crankcase through the intake port 5; when the piston 2 moves from the top dead center to the bottom dead center, the piston 2 closes the intake port 5, and opens the exhaust port 6, the first scavenging port 7a, the second scavenging port 7b and the third scavenging port 7c in sequence, and the combustible mixture in the engine crankcase is purged into the combustion chamber 1-1 through the first scavenging port 7a, the second scavenging port 7b and the third scavenging port 7c, and at the same time, the combustion exhaust gas in the combustion chamber 1-1 is driven toward the exhaust port 6 and discharged.

[0061] For the specific scavenging process, please refer to Figure 10(a) to Figure 10(c) As shown, after the combustible mixture in the combustion chamber 1-1 explodes and expands, the piston 2 is pushed downward by the explosive gas. During the downward movement of the piston 2, the exhaust port 6 located at the highest position is opened first, and most of the high-pressure exhaust gas is discharged from the exhaust port 6; when the piston 2 continues to move downward, the first scavenging port 7a is opened first. During the downward movement of the piston 2, the combustible mixture in the engine crankcase is compressed, so that the combustible mixture is blown into the combustion chamber 1-1 through the scavenging channel 7 and the first scavenging port 7a, as shown in Figure 10(a). Since the first scavenging port 7a has the largest blowing elevation angle, the scavenging gas is scavenged along the direction of the first scavenging airflow 9 in the figure. The scavenging airflow rises and drives the exhaust gas at the top of the combustion chamber 1-1 to the exhaust port 6. The direction of the exhaust gas flow 8 is shown in Figure 10(a). At the same time, part of the scavenging gas enters the concave cavity 2-1 of the piston 2; as shown in Figure 10(b), the second scavenging port 7b is then opened. The blowing elevation angle of the second scavenging port 7b is smaller than that of the first scavenging port 7a. At this time, the scavenging gas generated by the second scavenging port 7b is scavenged along the direction of the second scavenging air flow 10 in Figure 10(b). On the one hand, the exhaust gas in the combustion chamber 1-1 is further driven toward the exhaust port 6. On the other hand, the second scavenging air flow 10 can restrict the rapid upward movement of the first scavenging air flow 9, so that more scavenging gas is gathered in the concave cavity 2-1; as shown in Figure 10(c), finally the third scavenging port 7c is also opened. The blowing elevation angle of the third scavenging port 7c is smaller than that of the second scavenging port 7b. At this time, the scavenging gas generated by the third scavenging port 7c is scavenged along the direction of the third scavenging air flow 11 in Figure 10(c). Similarly, the exhaust gas flow 8 is further driven to flow toward the exhaust port 6, and the third scavenging air flow 11 and the exhaust gas flow 8 can produce a certain stratification effect, thereby cleaning the residual exhaust gas in the combustion chamber 1-1 and reducing the discharge of combustible mixture.

[0062] This embodiment also relates to a two-stroke engine. The two-stroke engine includes the aforementioned two-stroke engine scavenging system. The use of the aforementioned two-stroke engine scavenging system improves the fuel efficiency and economy of the two-stroke engine, reduces exhaust pollution during engine operation, and is more energy-efficient and environmentally friendly.

[0063] The other structures and working principles of the two-stroke engine are similar to those in the prior art and will not be elaborated here.

[0064] The two-stroke engine scavenging system and the two-stroke engine of the present invention utilize the gradient change of the upper edge height and the blowing elevation angle of the three pairs of scavenging ports, combined with the design of the combustible mixture collecting groove on the top surface of the piston. During the downward scavenging process of the piston, the three pairs of scavenging ports are opened in sequence from far to near relative to the exhaust port, thereby realizing orderly expulsion of the combustion exhaust gas. At the same time, combined with the change of the blowing elevation angle of the three pairs of scavenging ports, effective separation of the scavenging gas and the combustion exhaust gas is realized, and the collecting groove on the top surface of the piston is used to accommodate the combustible mixture, which effectively reduces the mixing of the combustible mixture and the combustion exhaust gas, thereby reducing the combustible mixture discharged with the exhaust gas, improving the fuel utilization rate of the two-stroke engine, improving the exhaust emissions, and achieving the effect of energy conservation and emission reduction.

[0065] The above is a schematic description of the present invention and its embodiments, which is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by this and, without departing from the purpose of the present invention, designs structures and embodiments similar to this technical solution without creatively designing them, they shall fall within the scope of protection of the present invention.

Claims

1. A scavenging system for a two-stroke engine, comprising a cylinder (1) and a piston (2) capable of reciprocating in a combustion chamber (1-1) of the cylinder (1), the cylinder (1) having an intake port (5) and an exhaust port (6) respectively connected to the combustion chamber (1-1), the connection between the intake port (5) and the combustion chamber (1-1) being lower than the connection between the exhaust port (6) and the combustion chamber (1-1), the cylinder (1) also having a scavenging passage (7) connecting the combustion chamber (1-1) and the engine crankcase, characterized in that: A pair of first scavenging ports (7a), a pair of second scavenging ports (7b) and a pair of third scavenging ports (7c) are sequentially arranged on the hole wall of the combustion chamber (1-1) with the exhaust center plane (P) of the exhaust port (6) as the center. The first scavenging ports (7a), the second scavenging ports (7b) and the third scavenging ports (7c) are all connected to the corresponding scavenging channels (7), and the scavenging directions (S) of the three are all inclined toward the side away from the exhaust port (6); the first scavenging ports ( 7a) is located away from the exhaust port (6), the third scavenging port (7c) is located near the exhaust port (6), and the upper edge heights of the first scavenging port (7a), the second scavenging port (7b) and the third scavenging port (7c) are successively lowered, so that the first scavenging port (7a), the second scavenging port (7b) and the third scavenging port (7c) are opened in sequence during the downward movement of the piston (2), so as to drive the combustion exhaust gas toward the exhaust port (6) from far to near by using the scavenging gas and discharge it; The blowing elevation angles of the first scavenging port (7a), the second scavenging port (7b), and the third scavenging port (7c) decrease in sequence, so that the scavenging gas generated by the scavenging port opened later exerts a gas pressure away from the exhaust port (6) on the scavenging gas generated by the scavenging port opened earlier; The top surface of the piston (2) is provided with a downwardly recessed cavity (2-1) for collecting scavenging gas generated by the first scavenging port (7a), the second scavenging port (7b) and the third scavenging port (7c) into the cavity (2-1) during the scavenging process.

2. The two-stroke engine scavenging system according to claim 1, characterized in that: The scavenging gases of each pair of the first scavenging ports (7a), the second scavenging ports (7b) and the third scavenging ports (7c) all converge at the exhaust center plane (P) of the exhaust port (6), so that the converged scavenging gases move in a direction away from the exhaust port (6); the scavenging direction (S) angle α1 of the two first scavenging ports (7a) is 120° to 130°, the scavenging direction (S) angle α2 of the two second scavenging ports (7b) is 120° to 130°, and the scavenging direction (S) angle α3 of the two third scavenging ports (7c) is 120° to 130°.

3. The two-stroke engine scavenging system according to claim 1, characterized in that: The height difference h1 between the upper edges of the first scavenging port (7a) and the second scavenging port (7b) is 1 to 3 mm, and the height difference h2 between the upper edges of the second scavenging port (7b) and the third scavenging port (7c) is 1 to 3 mm.

4. The two-stroke engine scavenging system according to claim 3, characterized in that: The lower edges of the first scavenging air port (7a), the second scavenging air port (7b) and the third scavenging air port (7c) have the same height.

5. The two-stroke engine scavenging system according to claim 4, characterized in that: The lower edge heights of the first scavenging port (7a), the second scavenging port (7b), and the third scavenging port (7c) are consistent or substantially consistent with the lower edge height of the exhaust port (6) on the hole wall of the combustion chamber (1-1); the upper edge height of the exhaust port (6) on the hole wall of the combustion chamber (1-1) is greater than the upper edge height of the first scavenging port (7a), so that the exhaust port (6) opens before the first scavenging port (7a) during the downward movement of the piston (2).

6. The two-stroke engine scavenging system according to claim 1, characterized in that: The blowing elevation angle θ1 of the first scavenging air port (7a) is 40° to 50°, the blowing elevation angle θ2 of the second scavenging air port (7b) is 10° to 20°, and the blowing elevation angle θ3 of the third scavenging air port (7c) is 0° to 5°.

7. The two-stroke engine scavenging system according to claim 6, characterized in that: The opening sizes of the first scavenging port (7a), the second scavenging port (7b) and the third scavenging port (7c) are reduced in sequence, so that the scavenging gas pressures generated by the first scavenging port (7a), the second scavenging port (7b) and the third scavenging port (7c) are increased in sequence.

8. The two-stroke engine scavenging system according to claim 1, characterized in that: The concave cavity (2-1) is a curved cavity structure, and has a central plane (2-2) at the bottom of the concave cavity (2-1) for suppressing the rotation of the scavenging gas.

9. The two-stroke engine scavenging system according to any one of claims 1 to 8, characterized in that: The piston (2) is rotatably connected to one end of a connecting rod (3), and the other end of the connecting rod (3) is rotatably connected to a crankshaft (4) disposed in a crankcase of an engine. The reciprocating motion of the piston (2) in the combustion chamber (1-1) drives the crankshaft (4) to rotate. When the piston (2) moves from the bottom dead center to the top dead center, the first scavenging port (7a), the second scavenging port (7b), the third scavenging port (7c) and the exhaust port (6) are closed by the piston (2), and the piston (2) passes over the intake port (5) to open the intake port (5), and inhales the combustible mixed gas into the engine crankcase through the intake port (5); When the piston (2) moves from the top dead center to the bottom dead center, the piston (2) closes the air inlet (5) and opens the exhaust port (6), the first scavenging port (7a), the second scavenging port (7b) and the third scavenging port (7c) in sequence. The combustible mixture in the engine crankcase is purged into the combustion chamber (1-1) through the first scavenging port (7a), the second scavenging port (7b) and the third scavenging port (7c), and the combustion exhaust gas in the combustion chamber (1-1) is driven toward the exhaust port (6) and discharged.

10. A two-stroke engine, characterized in that: A two-stroke engine scavenging system according to any one of claims 1 to 9.

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