A cylinder structure of a two-stroke engine

Abstract

The application discloses a cylinder structure of a two-stroke engine, comprising: a cylinder body, which is internally provided with a combustion chamber, an air inlet and an air outlet; two main scavenging channels and two auxiliary scavenging channels are symmetrically arranged on the cylinder body about the center line L of the air outlet; the included angle formed by the extension line of the side wall of the two main scavenging channels close to the center line L is θ1, the included angle formed by the extension line of the side wall of the two main scavenging channels away from the center line L is θ2; the included angle formed by the extension line of the side wall of the two auxiliary scavenging channels close to the center line L is θ3, and the included angle formed by the extension line of the side wall of the two auxiliary scavenging channels away from the center line L is θ4; wherein the extension lines of θ1, θ2, θ3 and θ4 intersect on the center line L, and satisfy the relationship θ2-θ1≥θ4-θ3. In some embodiments, the included angle of the main scavenging channel from the top to the bottom of the side wall is θ5, 93°<θ5<98°.

Description

Technical Field

[0001] This application relates to the technical field of power devices for forestry machinery and garden tools, specifically to a cylinder structure for a two-stroke engine, particularly suitable for two-stroke gasoline engine cylinders used in handheld power tools such as chainsaws and brush cutters. Background Technology

[0002] Two-stroke engines are widely used in handheld garden tools such as chainsaws and brush cutters, which require a high power-to-weight ratio and excellent portability, due to their outstanding advantages such as simple structure, high power density, light weight, and relatively low manufacturing cost. The cylinder is the core component of a two-stroke engine, containing the combustion chamber, scavenging passage, and the core space for the air exchange process. Its performance directly determines the engine's power output, fuel economy, emissions levels, and reliability.

[0003] Existing two-stroke engines used in chainsaws have significant shortcomings in their scavenging system design. Traditional scavenging passage designs struggle to achieve ideal scavenging effects under high-speed, high-load conditions, resulting in excessive residual exhaust gas in the cylinder and substantial short-circuiting loss of the fresh air-fuel mixture. There is still room for improvement in scavenging efficiency. This not only leads to low engine combustion efficiency and reduced power but also results in excessive hydrocarbon (HC) emissions, making it difficult to meet increasingly stringent environmental regulations. Furthermore, improper scavenging flow can exacerbate localized overheating and thermal deformation in the cylinder, affecting engine reliability. In addition, traditional small road engines, without complex external modifications (such as the addition of a catalytic converter), struggle to effectively reduce pollutant emissions.

[0004] The above content is only used to help understand the technical solution of this application and does not represent an admission that the above content is the closest prior art to this application. Summary of the Invention

[0005] Based on this, this application provides a cylinder block structure for a two-stroke engine to solve the problems of low scavenging efficiency, poor fuel economy, and excessive residual exhaust gas in the prior art. Through the coordinated optimization design of the combustion chamber, scavenging passage, and intake and exhaust ports, the ultimate goal is to improve engine power, reduce fuel consumption, and meet stringent emission regulations.

[0006] The technical solution adopted by this application to solve its technical problem is: a cylinder block structure for a two-stroke engine, comprising: a cylinder body, which has a combustion chamber, an intake port, and an exhaust port inside. The combustion chamber is located at the top of the cylinder block. By optimizing the shape of the combustion chamber, it is beneficial to reduce the thermal load on the cylinder, piston, and spark plug, thereby improving reliability. From the moment of spark plug ignition, the flame propagates along the designed combustion chamber shape, following the shortest and most uniform path to the entire combustion chamber. This helps to avoid knocking and incomplete combustion.

[0007] The cylinder body is symmetrically provided with two main scavenging passages and two auxiliary scavenging passages about the center line L of the exhaust port. The angle formed by the extension lines of the two main scavenging passages near the center line L is θ1, and the angle formed by the extension lines of the two auxiliary scavenging passages away from the center line L is θ2. The angle formed by the extension lines of the two auxiliary scavenging passages near the center line L is θ3, and the angle formed by the extension lines of the two auxiliary scavenging passages away from the center line L is θ4. The extension lines of θ1, θ2, θ3, and θ4 intersect on the center line L and satisfy the relationship θ2-θ1≥θ4-θ3.

[0008] In some embodiments, the angle between the main scavenging airway from the top to the bottom of the sidewall is θ5, where 93° < θ5 < 98°.

[0009] In some embodiments, the angle between the secondary scavenging airway from the top to the bottom of the sidewall is θ6, where 110° < θ6 < 115°.

[0010] In some embodiments, the height of the main scavenging airway is h3, the height of the secondary scavenging airway is h4, and 0.1mm≤h3-h4≤0.5mm.

[0011] In some embodiments, the cross-sectional area of ​​the main scavenging airway is S1, the cross-sectional area of ​​the secondary scavenging airway is S2, and 1.3≤S1 / S2≤1.8.

[0012] In some embodiments, the cylinder diameter ∅D of the cylinder body is 35mm-46mm.

[0013] In this design, the main scavenging passage and the auxiliary scavenging passage effectively deliver fresh mixed fuel gas into the cylinder and expel residual exhaust gas from the cylinder, creating a clean and pure mixed fuel gas environment for the next combustion, which greatly improves combustion efficiency.

[0014] The beneficial effects of this application are as follows: 1) By optimizing the size and shape of the combustion chamber, a suitable temperature can be provided for combustion in the cylinder block, which helps to extend the long-term use of the cylinder block and prolong its service life.

[0015] 2) The two sets of symmetrically arranged main and auxiliary scavenging passages, through the scientific and reasonable selection of their shape, length, cross-sectional area and proportion, and installation position, improve the effect of fully scavenging combustion exhaust gas, provide a clean and pure mixed oil-gas environment for the next combustion, significantly reduce short-circuit losses, and improve engine power, torque and fuel economy.

[0016] 3) The exhaust port effectively discharges the exhaust gas after combustion into the cylinder to the greatest extent possible, while effectively reducing the escape of fresh air and air-fuel mixture. The small shape and corresponding phase of the cylinder intake port can fully ensure the timing of fresh air-fuel mixture entering the cylinder and effectively control the back injection of mixed oil, effectively improving combustion efficiency, thereby increasing engine power and reducing the exhaust emissions of the chainsaw. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 Three views of the cylinder block of this application Figure 2 Cross-sectional view of the cylinder block Figure 3 Schematic diagram of cylinder block mold core Figure 4 A top-down view of the core of the scavenging passage for the saw cylinder block. Figure 5 Front view schematic diagram of the core angle for the scavenging passage of the saw cylinder block. Figure 6 Schematic diagram of the bottom angle of the cylinder block scavenging passage assembly mold core. Figure 7 Schematic diagram of cylinder block combustion chamber Figure 8 A schematic diagram of the exhaust port on the inner wall of the cylinder. Figure 9 Schematic diagram of the air intake port on the inner wall of the cylinder. The following are the reference numerals: 1. Cylinder block, 2. Combustion chamber, 3. Intake port, 4. Exhaust port, 5. Main scavenging passage, 6. Secondary scavenging passage, 7. Spark plug assembly port, 8. Intake mold core, 9. Exhaust mold core, 10. Main scavenging passage mold core, 11. Secondary scavenging passage mold core, 12. Combustion chamber mold core. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. In addition, the technical solutions of various embodiments can be combined with each other, but this must be based on the ability of those of ordinary skill in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection of this application.

[0020] In the embodiments of this application, please refer to Figure 1-9 As shown, the cylinder block structure of this two-stroke engine mainly includes: a cylinder body 1, which has a combustion chamber 2, an intake port 3, and an exhaust port 4 inside; two main scavenging passages 5 and two auxiliary scavenging passages 6 are symmetrically arranged on the cylinder body 1 about the center line L of the exhaust port 4; the angle formed by the extension lines of the sidewalls of the two main scavenging passages 5 near the center line L is θ1, and the angle formed by the extension lines of the sidewalls away from the center line L is θ2; the angle formed by the extension lines of the sidewalls of the two auxiliary scavenging passages 6 near the center line L is θ3, and the angle formed by the extension lines of the sidewalls away from the center line L is θ4; wherein the extension lines of θ1, θ2, θ3, and θ4 intersect on the center line L and satisfy the relationship θ2-θ1≥θ4-θ3. Preferably, θ1 is 90°±5°. θ2 is preferably 40°±5°, θ3 is preferably 150°±5°, and θ4 is preferably 104°±5°.

[0021] The above-mentioned relationship between the main scavenging air passage 5 and the secondary scavenging air passage 6 enables the airflow ejected from the main scavenging air passage 5 to be more directional and concentrated, mainly undertaking the task of sweeping away residual exhaust gas near the upper part of the cylinder and forming a strong tumble flow; while the airflow of the secondary scavenging air passage 6 is more divergent, mainly responsible for cleaning the exhaust gas in the lower edge area of ​​the cylinder, and working together with the main scavenging airflow to form a stable and comprehensive scavenging vortex.

[0022] The following will continue to describe some preferred / improved embodiments based on the above embodiments. Any one of the following embodiments can be selected, or multiple embodiments can be combined.

[0023] Combustion chamber 2 is located at the top of the cylinder block. Optimizing the shape of combustion chamber 2 helps reduce the thermal load on the cylinder, piston, and spark plug, thus improving reliability. From spark plug ignition onwards, the flame propagates along the designed shape of combustion chamber 2 in the shortest and most uniform path throughout the entire combustion chamber 2, helping to avoid knocking and incomplete combustion.

[0024] Specifically, such as Figure 7As shown, specifically, when combustion chamber 2 was designed, it was first based on SR b To determine the diameter, the center point (i.e., the center of the sphere) of the sphere and the entire combustion chamber 2 extending outwards during combustion is determined. The vertical centerline of the sphere coincides with the centerline of the cylinder. Additionally, a spark plug mounting port 7 is provided on the combustion chamber 2, with θ... b The angle between the axis of the spark plug fitting port 7 and the horizontal center line of the sphere is designed to ensure that the spark plug releases combustion energy as close as possible to the center of the sphere. θ a The angle formed between the edge of combustion chamber 2 and the horizontal line creates a squeezing surface within combustion chamber 2. When the spark plug ignites the combustion gas, this surface accelerates flame propagation, resulting in faster and more complete combustion. Radius R is formed at both ends of combustion chamber 2. a The arc segment is used to smoothly connect the sphere and the included angle, and effectively "sweep away" the exhaust gas, improving the scavenging efficiency. The preferred value is: SR b = 14±1mm ， θ a =42°±3° ， R a =12mm, θ b =30°±3.

[0025] like Figure 6 As shown, the angle between the top and bottom of the main scavenging airway 5 is θ5, where 93° < θ5 < 98°, and preferably θ5 is 95°.

[0026] Furthermore, the included angle between the top and bottom of the auxiliary scavenging passage 6 and the side wall is θ6, where 110° < θ6 < 115°, and preferably θ6 is 112°.

[0027] like Figure 2 As shown, the height of the main scavenging passage 5 is h3, the height of the auxiliary scavenging passage 6 is h4, and 0.1mm≤h3-h4≤0.5mm. In addition, the cylinder depth of the cylinder body 1 is h1, and the height of the upper edge of the exhaust port 4 on the cylinder body 1 is h2.

[0028] Preferably, the unit is (mm). h1=59±0.15, h2=34±0.15, h3=31.5±0.15, h4=31.3±0.15, h5=9.5±0.15.

[0029] In some embodiments, the cross-sectional area of ​​the main scavenging air passage 5 is S1, and the cross-sectional area of ​​the secondary scavenging air passage 6 is S2, with 1.3 ≤ S1 / S2 ≤ 1.8, preferably S1 = 82 ± 1 mm. 2 S 2= 135±1mm 2 .

[0030] Furthermore, the cylinder diameter ∅D of the cylinder body 1 is 35mm-46mm, preferably 43mm.

[0031] like Figure 8 The diagram shows the unfolded schematic of exhaust port 4. The specific value of W1 is selected by referencing the height h2 of the upper edge of exhaust port 4 in cylinder body 1 and the height h3 of the main scavenging passage 5 in the cylinder body. This controls the timing of exhaust gas discharge from cylinder body 1 and the total exhaust gas discharge time. This maximizes the effective discharge of combusted exhaust gas from the cylinder body while effectively reducing the escape of fresh air and air-fuel mixture, achieving more complete combustion. The area of ​​complete exhaust is determined by L1 × W1. Within the limits of the overall cylinder body design, L1 tends towards the maximum allowable value. Preferred values ​​are: L1 = 24 ± 1 mm, W1 = 7 ± 1 mm.

[0032] like Figure 9 The diagram shows the unfolded shape of intake port 3. The area values ​​of L2×W2 are used to control the intake volume within a single stroke. W2 ensures the timing of fresh air-fuel mixture entering the cylinder block and the total intake time, as well as effectively controlling the back injection of the fuel mixture. The value of L2 tends towards the maximum value allowed by the design to improve the utilization rate of the air-fuel mixture in combustion. W3 and L3 ensure the airtightness of the piston rings during piston downward movement to increase engine durability. Preferred values ​​are: L2=20±1mm, W2=11.6±1mm, W3=4.3±0.3mm, L3=5.4±0.3mm.

[0033] This application improves the effectiveness of scavenging combustion exhaust by scientifically and rationally selecting and matching parameters such as the shape, length, cross-sectional area and proportion of the main scavenging passage 5, the secondary scavenging passage 6, the air intake 3 and the exhaust port 4, as well as their installation positions. This provides a clean and pure mixed oil-gas environment for combustion, significantly reduces short-circuit losses, improves engine power, torque and fuel economy, and effectively reduces pollutant emissions.

[0034] The various embodiments of this application have now been described in detail. To avoid obscuring the concept of this application, some details known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein based on the above description.

[0035] Finally, it should be noted that the above description is only a preferred embodiment of this application. The foregoing embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A cylinder block structure for a two-stroke engine, comprising: A cylinder body, which has a combustion chamber, an intake port and an exhaust port inside, is characterized in that two main scavenging passages and two auxiliary scavenging passages are symmetrically arranged on the cylinder body about the center line L of the exhaust port. The angle formed by the extension lines of the sidewalls of the two main scavenging passages near the center line L is θ1, and the angle formed by the extension lines of the sidewalls away from the center line L is θ2. The angle formed by the extension lines of the sidewalls of the two auxiliary scavenging passages near the center line L is θ3, and the angle formed by the extension lines of the sidewalls away from the center line L is θ4. The extensions of θ1, θ2, θ3, and θ4 intersect on the center line L, and satisfy the relationship θ2-θ1≥θ4-θ3.

2. The cylinder block structure of a two-stroke engine according to claim 1, characterized in that, The angle between the top of the main scavenging airway and the bottom of the side wall is θ5, where 93° < θ5 < 98°.

3. The cylinder block structure of a two-stroke engine according to claim 1, characterized in that, The angle between the top and bottom of the auxiliary scavenging passage and the side wall is θ6, where 110° < θ6 < 115°.

4. The cylinder block structure of a two-stroke engine according to claim 1, characterized by The height of the main scavenging airway is h3, and the height of the secondary scavenging airway is h4, with 0.1mm ≤ h3 - h4 ≤ 0.5mm.

5. The cylinder block structure of a two-stroke engine according to claim 1, characterized by The cross-sectional area of ​​the main scavenging airway is S1, and the cross-sectional area of ​​the secondary scavenging airway is S2, with 1.3 ≤ S1 / S2 ≤ 1.

8.

6. The cylinder block structure of a two-stroke engine according to claim 1, characterized by The cylinder body has a diameter ∅D of 35mm-46mm.

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