Structure for improving scavenging efficiency of two-stroke gasoline engine and working method thereof

Abstract

The invention discloses a structure for improving scavenging efficiency of a two-stroke gasoline engine and a working method thereof, and belongs to the technical field of internal combustion engines, the structure comprises an air cylinder and a crankcase which are connected into a whole, and a piston capable of reciprocating is arranged in the structure; an exhaust hole and a ventilation hole are formed in the cylinder wall of the cylinder; a spark plug is arranged on a cylinder cover of the cylinder; the interior of the crankcase is divided into an upper area and a lower area which are relatively independent, the upper area is communicated with the air inlet hole and an outlet of the carburetor respectively and used for forming gas mixture, the two ends of the lower area are communicated with the air inlet hole and the ventilation hole respectively, and the upper area and the lower area are communicated through a second one-way valve; the air inlet selectively communicates with the upper area and the lower area of the crankcase through the first one-way valve. The device is simple in overall structure, easy to implement and low in improvement cost, the fresh mixed gas and the waste gas are fundamentally prevented from being directly mixed and discharged from the exhaust port in a short-circuit mode, and the purposes of improving the utilization rate of the mixed gas and reducing fuel consumption and pollutant emission are achieved.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engine technology, and in particular to a structure and its working method for improving the scavenging efficiency of a two-stroke gasoline engine. Background Technology

[0002] Two-stroke gasoline engines are widely used in small general-purpose machinery (such as chainsaws, lawnmowers, and small generator sets) and some light vehicles due to their advantages such as simple structure, light weight, high power density, and relatively low manufacturing cost. However, the inherent working principle of two-stroke gasoline engines leads to a significant technical defect: scavenging short circuit (or scavenging loss).

[0003] In the traditional two-stroke gasoline engine working cycle, the exhaust and scavenging processes overlap. As the piston moves downwards, the pre-compressed fresh combustible mixture in the crankcase enters the cylinder through the scavenging port. Its purpose is not only to introduce new working fluid for the next cycle but also to "scaveng" the exhaust gases from the previous cycle from the exhaust port. Since the exhaust port usually opens earlier than the scavenging port and both open simultaneously, a large amount of unburned fresh mixture inevitably escapes directly from the exhaust port along with the exhaust gases during scavenging, causing a "short circuit." This phenomenon directly leads to low fuel efficiency, high fuel consumption rate (specific fuel consumption), and the generation of large amounts of unburned hydrocarbons (HC) emissions. This not only contradicts the current environmental trend of energy conservation and emission reduction but also makes it difficult to meet increasingly stringent exhaust emission regulations.

[0004] To alleviate the scavenging short-circuit problem, existing technologies have proposed several improvement schemes. For example, optimizing the direction and shape of the scavenging passages, and using methods such as recirculating or cross-flow scavenging to improve airflow organization; or optimizing the fuel supply timing of the mixture by precisely controlling the carburetor's fuel supply characteristics. However, the former involves significant structural modifications to core components such as the cylinder and cylinder block, limiting its versatility; the latter involves minor adjustments to the fuel supply system and cannot fundamentally prevent direct contact between the fresh mixture and exhaust gas. Other technical solutions propose adding an auxiliary combustion chamber or a complex valve system, but this significantly increases the engine's structural complexity and manufacturing cost, making it particularly unsuitable for cost-sensitive small two-stroke gasoline engines.

[0005] Therefore, the industry urgently needs a two-stroke gasoline engine technology solution that can effectively reduce scavenging short-circuit losses and has the characteristics of simple structure, easy implementation, and low modification cost. Summary of the Invention

[0006] To address the aforementioned problems, this invention proposes a structure and its working method for improving the scavenging efficiency of a two-stroke gasoline engine. The overall structure is simple, easy to implement, and has low modification costs. It fundamentally avoids the direct mixing of fresh air and exhaust gas and their short-circuit discharge from the exhaust port, thereby achieving the goals of improving air-fuel mixture utilization, reducing fuel consumption, and reducing pollutant emissions.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a structure for improving the scavenging efficiency of a two-stroke gasoline engine, comprising a cylinder block, wherein a cylinder and a crankcase are disposed within the cylinder block, the cylinder and the crankcase are integrated, and a reciprocating piston is also disposed within the cylinder block. The cylinder wall is provided with an exhaust port and a sump port, and the cylinder head is provided with a spark plug. The crankcase is divided into relatively independent upper and lower sections. The upper section is connected to the intake port and the carburetor outlet to form a fuel-air mixture. The two ends of the lower section are connected to the intake port and the air exchange port, respectively. The upper and lower sections are connected by a second one-way valve. The air intake port is selectively connected to the upper and lower sections of the crankcase via a first one-way valve.

[0008] As a further implementation, both the second check valve and the first check valve are opened by pressure control within the crankcase.

[0009] As a further implementation, the opening pressure of the second one-way valve is set to be higher than the pressure when the crankcase is driven by pure air in the lower zone and lower than the pressure of the gas-fuel mixture after it is compressed in the upper zone.

[0010] As a further implementation, the intake port is connected to the upper and lower sections of the crankcase through two independent channels, with no carburetor installed on the channel connecting to the lower section.

[0011] As a further implementation, pure air in the lower crankcase enters the cylinder through the air exchange port before the combustion mixture in the upper crankcase, pre-scavenging the exhaust gas in the cylinder.

[0012] A second aspect of the present invention provides a method for operating a structure for improving the scavenging efficiency of a two-stroke gasoline engine, based on the structure for improving the scavenging efficiency of a two-stroke gasoline engine described in the first aspect of the present invention, comprising the following steps: As the piston moves upward, it compresses the air-fuel mixture in the cylinder and simultaneously creates a negative pressure in the crankcase. The first one-way valve opens, allowing outside air to enter the upper and lower sections of the crankcase. The air entering the upper section mixes with the fuel to form a fuel-air mixture, while the air entering the lower section is pure air. As the piston moves downward, it compresses the gas in the crankcase. First, the pure air in the lower part of the crankcase enters the cylinder through the air exchange port, pre-scavenging the exhaust gas before it is discharged through the exhaust port. When the pressure inside the crankcase rises to the pressure threshold that causes the second check valve to open, the gas-fuel mixture in the upper zone enters the cylinder through the air exchange port, completing the intake.

[0013] As a further implementation, the opening pressure threshold of the second check valve is set to be higher than the pressure in the crankcase when pure air scavenging begins, so as to ensure that pure air scavenging enters the cylinder before the combustible mixture.

[0014] As a further implementation, the opening pressure of the second one-way valve is set by the valve plate stiffness or preload to achieve timing control of pure air entering the cylinder before the gas mixture.

[0015] As a further implementation, during the scavenging and intake strokes, while pure air enters the cylinder for pre-scavenging, the fuel-air mixture is temporarily sealed in the upper region of the crankcase.

[0016] As a further implementation, a first one-way valve is located at the intake port, which is connected to the upper and lower sections of the crankcase via two independent channels, with no carburetor installed on the channel connecting to the lower section.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention relates to a structure and its working method for improving the scavenging efficiency of a two-stroke gasoline engine. Through structural innovation, it achieves an "air curtain isolation" effect in the scavenging process. By utilizing the pre-introduced pure air to form an isolation barrier between the exhaust port and the fresh air-fuel mixture, most of the exhaust gas is scavenged out first. The subsequently entering fresh air-fuel mixture, due to the air barrier in front, has a significantly reduced chance of direct contact with the exhaust gas and short-circuiting its escape from the exhaust port. This method directly cuts off the short-circuit path from a physical principle, fundamentally and effectively suppressing scavenging short-circuiting, and its effect is far superior to traditional methods that only optimize airflow direction.

[0018] The present invention relates to a structure and operating method for improving the scavenging efficiency of a two-stroke gasoline engine. Due to a significant reduction in short-circuit losses of the fresh air-fuel mixture, more fuel is effectively used for combustion and power generation, resulting in a substantial increase in mixture utilization. Under the same power output, the fuel consumption rate (specific fuel consumption) decreases significantly, improving the engine's fuel economy. Simultaneously, more complete air intake also translates to higher volumetric efficiency and potential power gains.

[0019] The present invention relates to a structure and operating method for improving the scavenging efficiency of a two-stroke gasoline engine. The reduction in scavenging short-circuiting directly translates to a significant reduction in unburned hydrocarbons (HC) emitted with the exhaust gas. This results in a qualitative improvement in the emission levels of the two-stroke gasoline engine, substantially reducing pollutant emissions and making it easier to meet current and future increasingly stringent environmental regulations, thus offering significant environmental benefits.

[0020] The present invention relates to a structure and its working method for improving the scavenging efficiency of a two-stroke gasoline engine. The structure is simple, the modification cost is low, and the compatibility is good. The core improvement of this invention lies mainly in the zonal design of the crankcase and the use of a one-way valve. It eliminates the need for complex redesigns of core load-bearing components such as the cylinder, piston, and cylinder head, and does not rely on expensive electronic control or injection systems. The principle of this solution is clear, and it can be implemented at a low cost through modification of existing mature two-stroke gasoline engine platforms. It has good technological inheritance and engineering application feasibility, and is particularly suitable for widespread application in the cost-sensitive field of small two-stroke gasoline engines. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 This is a schematic diagram of the structure of the present invention for improving the scavenging efficiency of a two-stroke gasoline engine during the compression and pre-intake strokes. Figure 2 This is a schematic diagram of the structure of the present invention for improving the scavenging efficiency of a two-stroke gasoline engine during pure air scavenging. Figure 3 This is a schematic diagram of the structure for improving the scavenging efficiency of a two-stroke gasoline engine according to the present invention during the intake of the air-fuel mixture.

[0023] Among them, 1. Cylinder head; 2. Cylinder block; 3. Piston; 4. Connecting rod; 5. Crankshaft; 6. Carburetor; 7. Exhaust port; 8. Intake port; 9. Swivel port; 10. First one-way valve; 11. Second one-way valve; 12. Spark plug; 13. Cylinder; 14. Crankcase; 141. Upper zone; 142. Lower zone; 15. Partition. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0026] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0027] Example 1 like Figures 1 to 3 As shown, this embodiment provides a structure for improving the scavenging efficiency of a two-stroke gasoline engine, including a cylinder block 2, a cylinder 13 and a crankcase 14 are provided inside the cylinder block 2, the cylinder 13 and the crankcase 14 are connected as one unit, and a reciprocating piston 3 is also provided inside the cylinder block 2. The cylinder wall of cylinder 13 is provided with exhaust port 7 and air exchange port 9, and its cylinder head 1 is provided with spark plug 12. The crankcase 14 is divided into two relatively independent sections, an upper section 141 and a lower section 142, by a partition 15. The main body of the partition 15 is an arc shape that matches the cross-section of the crankcase 14 (fitting the inner wall of the crankcase), and it must avoid the rotation trajectory of the crankshaft 5 and the swing range of the connecting rod 4. Specifically, its positioning is as follows: Longitudinal position: Located below the intake passage where the carburetor 6 is located and above the main journal of the crankshaft 5, dividing the inner cavity of the crankcase 14 into two independent chambers in the height direction; Lateral position: Covers most of the internal cross section of crankcase 14, with only the edge reserved for the swing of connecting rod 4 to ensure that it does not interfere with the normal operation of crankshaft-connecting rod mechanism. An arc-shaped clearance notch is set in the area corresponding to the swing of connecting rod 4, and the curvature and size of the notch are based on not restricting the swing of connecting rod 4 throughout its entire stroke.

[0028] The partition 15 has a flanged edge, which is fixed to the inner wall of the crankcase 14 by bolts or welding to ensure sealing performance and prevent cross-flow of media between the upper and lower zones. The lower zone 142 is a pure air zone, which is directly connected to the ventilation port 9. Figure 2 As shown, there are no openings. The upper zone 141 is the gas combustion zone. An opening is made in the physical partition 15 to install a one-way valve 11. This opening is only connected to the air inlet end of the one-way valve plate 11, and the air outlet end of the one-way valve plate 11 then flows into the main gas passage of the ventilation hole 9.

[0029] The upper zone 141 is connected to the air inlet 8 and the outlet of the carburetor 6 respectively to form a fuel mixture. The two ends of the lower zone 142 are connected to the air inlet 8 and the air exchange port 9 respectively. The upper zone 141 and the lower zone 142 are connected through the second one-way valve 11. The air intake port 8 is selectively connected to the upper region 141 and the lower region 142 of the crankcase 14 via the first one-way valve 10.

[0030] The specific solution of the present invention is as follows: A structure for improving the scavenging efficiency of a two-stroke gasoline engine mainly includes a cylinder head 1, a cylinder block 2, a piston 3, a connecting rod 4, a crankshaft 5, a carburetor 6, an exhaust port 7, an intake port 8, a scavenging port 9, a one-way valve plate 10, a one-way valve plate 11, a spark plug 12, a cylinder 13, a crankcase 14, and a physical partition 15; wherein, the crankcase 14 is innovatively divided into an upper region 141 and a lower region 142. The upper section is equipped with a carburetor 6, which is used to mix air and fuel to form a fuel-air mixture; The lower zone is a pure air area, with only fresh air introduced.

[0031] The cylinder 13 is provided with an exhaust port 7 and an air exchange port 9. A spark plug 12 is provided on the top of the cylinder 13. A reciprocating piston 3 is provided inside the cylinder 13. The piston 3 is connected to the crankshaft 5 in the crankcase 14 through a connecting rod 4.

[0032] The crankcase 14 has been improved to have two sections, upper and lower. The upper section 141 is connected to the intake passage with the carburetor 6 (the inlet of the intake passage is the intake port 8), and the lower section 142 is a pure air area.

[0033] The intake port 8 is connected to the upper region 141 of the crankcase 14 (which is equipped with a carburetor 6) through a channel provided with a first one-way valve plate 10. At the same time, the air from the intake port 8 can also enter the lower region 142 (pure air region) of the crankcase 14.

[0034] The ventilation port 9 is connected to the lower zone 141 (pure air zone) and upper zone 142 (mixed air side) of the crankcase 14 through a channel equipped with a second one-way valve 11. The opening of the second one-way valve 11 is controlled by the pressure inside the crankcase 14. The opening pressure of the second one-way valve 11 is calibrated by its own elastic parameters and installation preload. When the pressure inside the crankcase 14 rises to a preset threshold as the piston 3 moves downward, the second one-way valve 11 will automatically open to achieve delayed delivery of the mixed air.

[0035] This invention overcomes the defects of scavenging short circuit in existing two-stroke gasoline engines and provides a two-stroke gasoline engine structure and its working method that can deliver air and mixture in stages and avoid fresh mixture being directly discharged with exhaust gas, so as to improve mixture utilization and reduce fuel consumption and exhaust emissions.

[0036] Example 2 This embodiment provides a working method for a structure that improves the scavenging efficiency of a two-stroke gasoline engine. Based on the structure for improving the scavenging efficiency of a two-stroke gasoline engine in Embodiment 1, the method includes the following steps: As piston 3 moves upward, it compresses the air-fuel mixture in cylinder 13 and simultaneously creates a negative pressure in crankcase 14. The first one-way valve 10 opens, and external air enters the upper zone 141 and lower zone 142 of crankcase 14. The air entering the upper zone 141 mixes with fuel to form a fuel-air mixture, while the air entering the lower zone 142 is pure air. As piston 3 moves downward, it compresses the gas in crankcase 14. First, the pure air in the lower section 142 of crankcase 14 enters the cylinder through the air exchange port 9, pre-scavenging the exhaust gas and discharging it through the exhaust port. When the pressure inside the crankcase 14 rises to the pressure threshold that causes the second check valve 11 to open, the gas-fuel mixture in the upper zone 141 enters the cylinder 13 through the second check valve 11 and the air exchange port 9, thus completing the intake.

[0037] The opening pressure threshold of the second one-way valve 11 is set to be higher than the pressure in the crankcase 14 when pure air scavenging begins, so as to ensure that pure air scavenging enters the cylinder before the combustible mixture.

[0038] The opening pressure of the second one-way valve 11 is set by the valve plate stiffness or preload to achieve timing control of pure air entering the cylinder 13 before the gas mixture.

[0039] During the scavenging and intake strokes, as pure air enters cylinder 13 for pre-scavenging, the fuel-air mixture is temporarily sealed in the upper zone 141 of crankcase 14.

[0040] The first one-way valve 10 is located at the air intake port 8. The air intake port 8 is connected to the upper section 141 and the lower section 142 of the crankcase 14 through two independent channels. The carburetor 6 is not installed on the channel connecting the lower section 142.

[0041] The specific work process includes the following cyclical steps: Compression stroke: Piston 3 moves upward, and the combusted mixture in cylinder 13 is compressed; at the same time, a negative pressure is formed in crankcase 14, the first one-way valve 10 opens, and outside air enters the crankcase in two ways: one way passes through carburetor 6 to form a combustion mixture and enters the upper crankcase 141; the other way directly enters the lower crankcase 142 to form a pure air area.

[0042] Scavenging and Intake Strokes: As piston 3 descends, the scavenging process is triggered: pure air from the lower crankcase 142 enters cylinder 13 through vent hole 9, performing "pre-scavenging" on the already combusted mixture in cylinder 13 and pushing most of the exhaust gas towards exhaust port 7. As piston 3 continues to descend, the pressure in crankcase 14 gradually increases. When the pressure reaches a preset threshold, the second one-way valve 11 opens, and the combustion mixture from the upper crankcase 141 enters cylinder 13 through the second one-way valve 11 and vent hole 9, completing the intake process of fresh mixture. Simultaneously, the already combusted mixture in cylinder 13 is discharged through exhaust port 7. Subsequently, spark plug 12 ignites, the combustion mixture burns and performs work, pushing the piston upward to enter the next cycle.

[0043] The preset threshold for the opening pressure of the second one-way valve plate 11 is a specific positive pressure range that is sufficient to overcome the pre-tightening force of the valve plate and achieve delayed intake of the mixture after the crankcase 14 changes from negative pressure to positive pressure as the piston 3 moves downward and the pure air completes the pre-scavenging. Its size is adapted to the mechanical characteristics of the valve plate, the engine displacement conditions and the requirements for the pre-scavenging effect.

[0044] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0045] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A structure for improving the scavenging efficiency of a two-stroke gasoline engine, characterized in that, Includes a cylinder body, which contains a cylinder and a crankcase, the cylinder and the crankcase being integrated, and the cylinder body also contains a reciprocating piston; The cylinder wall is provided with an exhaust port and a sump port, and the cylinder head is provided with a spark plug. The crankcase is divided into a relatively independent upper and lower section. The upper section is connected to the intake port and the carburetor outlet to form a fuel-air mixture. The two ends of the lower section are connected to the intake port and the air exchange port, respectively. The upper and lower sections are connected by a second one-way valve. The air intake port is selectively connected to the upper and lower sections of the crankcase via a first one-way valve.

2. The structure for improving the scavenging efficiency of a two-stroke gasoline engine as described in claim 1, characterized in that, Both the second check valve and the first check valve are opened by pressure control within the crankcase.

3. The structure for improving the scavenging efficiency of a two-stroke gasoline engine as described in claim 1, characterized in that, The opening pressure of the second one-way valve is set to be higher than the pressure when the crankcase is driven by pure air in the lower zone and lower than the pressure of the gas-fuel mixture after compression in the upper zone.

4. The structure for improving the scavenging efficiency of a two-stroke gasoline engine as described in claim 1, characterized in that, The intake port is connected to the upper and lower sections of the crankcase via two independent channels, with no carburetor installed on the channel connecting to the lower section.

5. The structure for improving the scavenging efficiency of a two-stroke gasoline engine as described in claim 1, characterized in that, Pure air in the lower crankcase enters the cylinder through the air exchange port before the combustion mixture in the upper crankcase, pre-scavenging the exhaust gas in the cylinder.

6. A method for operating a structure to improve the scavenging efficiency of a two-stroke gasoline engine, characterized in that, Based on the structure for improving the scavenging efficiency of a two-stroke gasoline engine as described in any one of claims 1-5, the method includes the following steps: As the piston moves upward, it compresses the air-fuel mixture in the cylinder and simultaneously creates a negative pressure in the crankcase. The first one-way valve opens, allowing outside air to enter the upper and lower sections of the crankcase. The air entering the upper section mixes with the fuel to form a fuel-air mixture, while the air entering the lower section is pure air. As the piston moves downward, it compresses the gas in the crankcase. First, the pure air in the lower part of the crankcase enters the cylinder through the air exchange port, pre-scavenging the exhaust gas and then discharging it through the exhaust port. When the pressure inside the crankcase rises to the pressure threshold that causes the second check valve to open, the gas-fuel mixture in the upper zone enters the cylinder through the air exchange port, completing the intake.

7. The working method of the structure for improving the scavenging efficiency of a two-stroke gasoline engine as described in claim 6, characterized in that, The opening pressure threshold of the second check valve is set higher than the pressure in the crankcase when pure air scavenging begins, to ensure that pure air scavenging enters the cylinder before the combustible mixture.

8. The working method of the structure for improving the scavenging efficiency of a two-stroke gasoline engine as described in claim 6, characterized in that, The opening pressure of the second one-way valve is set by the valve plate stiffness or preload to achieve timing control of pure air entering the cylinder before the gas mixture.

9. The working method of the structure for improving the scavenging efficiency of a two-stroke gasoline engine as described in claim 6, characterized in that, During the scavenging and intake strokes, as pure air enters the cylinder for pre-scavenging, the fuel-air mixture is temporarily sealed in the upper section of the crankcase.

10. The working method of the structure for improving the scavenging efficiency of a two-stroke gasoline engine as described in claim 6, characterized in that, The first one-way valve is located at the intake port, which is connected to the upper and lower sections of the crankcase via two independent channels. The channel connecting to the lower section does not have a carburetor.

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