A two-stroke engine scavenging system and portable fire pump

Abstract

The application discloses a two-stroke engine scavenging system and a portable fire pump, and belongs to the technical field of two-stroke engines, which comprises a cylinder body with an air inlet and an air outlet, a piston in sealing sliding connection with the inner wall of the cylinder body, a connecting rod in rotary connection with the piston, a cylinder cover connected to one end of the cylinder body, a combustion chamber formed between the cylinder cover and the piston, a convex bump symmetrically and uniformly arranged on the top and bottom of the cylinder body, a scavenging passage arranged in the convex bump, at least one through hole corresponding to the scavenging passage and arranged on the top and bottom of the piston, and a flow guide plate arranged on the side of the piston close to the cylinder cover. The overall structure of the application is simplified, and the air intake efficiency, scavenging quality, compactness of the whole machine, cooling safety, starting reliability and the like are remarkably improved, and the application is particularly suitable for small two-stroke power equipment such as portable fire pumps which have strict requirements on volume, weight and reliability.

Description

Technical Field

[0001] This invention belongs to the field of two-stroke engine technology, and in particular relates to a two-stroke engine scavenging system and a portable fire pump. Background Technology

[0002] Two-stroke engines are widely used in small power machinery such as portable fire pumps, lawnmowers, and chainsaws due to their advantages of simple structure, small size, light weight, and high power density. The working cycle of a two-stroke engine includes intake, compression, combustion and expansion, and exhaust, all completed within one crankshaft rotation cycle. In a two-stroke engine, the scavenging effect directly affects the engine's power and fuel economy; higher scavenging quality results in less residual exhaust gas in the cylinder, more fresh charge, and more complete combustion.

[0003] Traditional two-stroke engine intake systems typically use reed valves to control the intake airflow. These reed valves are made of thin, elastic steel sheets and are installed at the intake port of the crankcase. Their working principle is as follows: when the piston moves to top dead center, a negative pressure is generated in the crankcase, and the reed automatically opens under the pressure difference, allowing the air-fuel mixture supplied by the carburetor to enter the crankcase; when the piston moves to bottom dead center, the pressure in the crankcase increases, and the reed closes under the pressure and its own elasticity, preventing the air-fuel mixture from flowing back. However, the reed valve strikes its seat and limit plate at a high frequency during operation, making it prone to fatigue failure. It is a vulnerable component and suffers from problems such as slow response, complex structure, and space occupation.

[0004] Furthermore, in existing two-stroke engines, during the scavenging process, the fresh air-fuel mixture entering through the scavenging port easily mixes with the exhaust gas in the combustion chamber. The two scavenging air streams collide head-on in the center of the combustion chamber, forming a chaotic vortex. This causes some of the fresh air-fuel mixture to escape directly from the exhaust port without combustion, resulting in scavenging losses and reducing fuel economy and power output. Therefore, it is necessary to propose a two-stroke engine scavenging system and a portable fire pump to solve the aforementioned problems. Summary of the Invention

[0005] In view of this, in order to solve the problems of easy damage to the valve plate, slow response, complex structure and space occupation, and low scavenging efficiency caused by the head-on collision of the upper and lower airflows during the scavenging process when using reed valve intake in existing two-stroke engines, this invention provides a two-stroke engine scavenging system and a portable fire pump.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a two-stroke engine scavenging system, comprising a cylinder block having an intake port and an exhaust port, and a piston that is slidably and sealingly connected to the inner wall of the cylinder block, a connecting rod being rotatably connected to the piston, a cylinder head being connected to one end of the cylinder block, a combustion chamber being formed between the cylinder head and the piston, the top and bottom of the cylinder block being integrally provided with symmetrical protrusions, the protrusions being provided with scavenging channels, and the top and bottom of the piston being provided with at least one through hole corresponding to and cooperating with the scavenging channels;

[0007] The piston is provided with a guide plate on the side near the cylinder head, and the side of the guide plate away from the piston is an arc-shaped convex surface, which is used to guide the air-fuel mixture entering the combustion chamber toward the cylinder head side.

[0008] The arc-shaped raised surface has multiple guide grooves on both the upper and lower sides, which correspond to the upper and lower scavenging channels respectively. Together with the raised surface, the air-fuel mixture can be guided to the cylinder head from multiple paths.

[0009] The guide plate is connected to the connecting rod via a connector, allowing the guide plate to rotate back and forth with the reciprocating motion of the piston, guiding the mixture in different directions and forming a rotating airflow.

[0010] Furthermore, the side of the guide plate closest to the piston is flat and rotates in a sealed fit with the piston.

[0011] Furthermore, the arc angles of the multiple guide grooves decrease sequentially from the middle to the outside.

[0012] Furthermore, the connecting component includes a second rotating shaft that seals and rotates through one side of the piston. One end of the second rotating shaft is fixedly connected to the center point of the plane of the guide plate. A slit is provided at the end of the second rotating shaft away from the guide plate. A U-shaped block is fixedly connected to one side wall of the slit. An actuating rod that engages with the U-shaped block is fixedly connected to one side outer wall of the connecting rod.

[0013] Furthermore, it also includes a crankcase connected to the cylinder block, which is internally connected, and a crankshaft is rotatably connected inside the crankcase, and the crankshaft transmits power to the piston through a connecting rod.

[0014] Furthermore, a U-shaped mounting port is provided on the crank of the crankshaft, and two scavenging blocks are symmetrically and fixedly connected inside the U-shaped mounting port. The scavenging blocks are triangular, and the outer side of the scavenging blocks is provided with an arc surface with the same curvature as the circumferential surface of the crank and a smooth transition.

[0015] The present invention also provides a portable fire pump, comprising the aforementioned two-stroke engine scavenging system, the fire pump further comprising:

[0016] A water pump is fixedly installed on one side of the crankcase. The front end of the crankshaft rotates through one side of the crankcase and is fixedly connected to the impeller inside the water pump. The water pump is provided with an inlet and an outlet for pipe connection.

[0017] The engine block is fixedly installed on the side of the crankcase away from the water pump. The rear end shaft seal of the crankshaft rotates through the other side of the crankcase and is fixedly connected to a flywheel located inside the engine block.

[0018] A hand-operated crankshaft is fixedly installed on the side of the engine block away from the crankcase and is used to drive the flywheel to rotate.

[0019] A carburetor is connected to the air intake via an air-fuel mixing line, a control handle is provided on the air-fuel mixing line, and an air filter is provided at one end of the carburetor;

[0020] The muffler is connected to the exhaust port;

[0021] The cooling pipes are located between the water pump, cylinder block, and muffler, and can automatically cool the cylinder block and muffler by utilizing the water pump's water delivery process.

[0022] Furthermore, the cooling pipeline includes an outlet pipe, a supply pipe, and a return pipe; the water pump has a first inlet port on the side near the inlet and a first outlet port on the side near the outlet; the cylinder body has a first water-cooling cavity on the side near the cylinder head, and the cylinder body has a second inlet port and a second outlet port that are simultaneously connected to the first water-cooling cavity; the muffler has a second water-cooling cavity inside, and the muffler has a third inlet port and a third outlet port that are simultaneously connected to the second water-cooling cavity; wherein, the two ends of the outlet pipe are respectively connected to the first outlet port and the second inlet port, the two ends of the supply pipe are respectively connected to the second outlet port and the third inlet port, and the two ends of the return pipe are respectively connected to the third outlet port and the first inlet port.

[0023] Furthermore, it also includes a mounting bracket, on which the engine block, water pump, cylinder block and carburetor are all fixedly mounted, and a protective cover is fixedly connected to the top of the mounting bracket.

[0024] Furthermore, a starter motor is fixedly connected to one side of the engine body, and a gear shaft is fixedly connected to the output shaft of the starter motor. A first rotating shaft is rotatably connected inside the engine body, and a gear set is fixedly sleeved on the outer wall of the first rotating shaft. The gear set consists of a large gear and a small gear. The large gear meshes with the gear shaft, and the small gear meshes with the flywheel. A battery electrically connected to the starter motor is fixedly installed on the mounting bracket.

[0025] The embodiments of the present invention have the following beneficial effects:

[0026] 1. Through the guide plate set on the piston end face, the scavenging airflow enters the combustion chamber from the scavenging passage and flows orderly along the arc-shaped convex surface of the guide plate. The upper and lower airflows flow towards the cylinder head respectively, effectively avoiding the problem of two airflows colliding head-on and forming chaotic vortices in the traditional structure. The guide groove decomposes the airflow into multiple airflow jets with different directions, forming multiple rotating airflows in the combustion chamber, prolonging the residence time of the fresh mixture in the combustion chamber, improving exhaust gas replacement efficiency, and reducing the short-circuit loss of fresh mixture;

[0027] 2. Through the interlocking action of the lever and the U-shaped block, the guide plate can automatically rotate back and forth during the reciprocating motion of the piston. In addition, the multiple guide grooves can guide the airflow at different angles and in different directions, thereby further improving the fluidity of the mixture.

[0028] 3. By setting scavenging blocks on the crankshaft and rotating synchronously with the crankshaft, the mixture in the crankcase is swept and guided, pushing the mixture towards the inlet of the scavenging channel, forming a directional airflow in the crankcase, increasing the flow rate and velocity of the mixture entering the scavenging channel, and further improving the scavenging efficiency. At the same time, the arc-shaped surface is smoothly connected to the crankshaft surface without adding additional rotational resistance.

[0029] 4. The opening and closing of the air intake is directly controlled by the reciprocating movement of the piston in the cylinder. Compared with the traditional air intake method using a reed valve, the number of parts in the whole machine is reduced, the assembly process is simplified, the manufacturing cost is significantly reduced, and the reliability and service life of the whole machine are significantly improved.

[0030] 5. The opening and closing of the intake port are directly determined by the piston position, eliminating the inherent elastic response lag of reed valves. Regardless of whether the engine is operating at low, medium, or high speeds, the opening angle and duration of the intake port are always precisely matched to the piston stroke, maintaining good intake efficiency under all operating conditions. The air-fuel mixture enters the crankcase directly from the intake port, resulting in a shorter flow path with fewer bends, significantly reducing intake resistance and improving charging efficiency, thereby effectively improving engine power.

[0031] 6. By utilizing the pressure difference during water pump operation to drive cooling water sequentially through the cylinder block water-cooling chamber and the muffler water-cooling chamber, no additional cooling water pump or electric fan is needed, reducing energy consumption and equipment weight. The cooled muffler surface temperature is far below the ignition point of combustibles, effectively avoiding the fire hazard of igniting dry branches and leaves on the ground during field operations, while also preventing burns to operators; cylinder block cooling controls the combustion chamber wall temperature, reducing knocking tendency and improving the engine's power output stability.

[0032] 7. By setting the electric start mode, the overall operation is simple and labor-saving, suitable for most usage scenarios; the manual start mode serves as a reliable backup, and can still work normally in situations such as battery depletion, starter motor failure, or extremely cold environments, ensuring that the equipment can start and run under any circumstances, thus enhancing the environmental adaptability of the equipment.

[0033] This invention is achieved through

[0034] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art based on the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0036] Figure 1 This is a schematic diagram of the overall structure of a portable fire pump according to the present invention;

[0037] Figure 2 This is a schematic diagram of the overall structure of a portable fire pump of the present invention after removing the mounting bracket;

[0038] Figure 3 This is a schematic diagram of the water pump structure of a portable fire pump according to the present invention;

[0039] Figure 4 For the present invention Figure 2 A schematic diagram of the overall structure excluding the water pump and crankcase;

[0040] Figure 5 This is a schematic diagram of the connection structure between the crankshaft, hand-operated dial, and starter motor of a portable fire pump according to the present invention;

[0041] Figure 6 This is a schematic diagram of the silencer structure of a portable fire pump according to the present invention;

[0042] Figure 7 This is a schematic diagram of the connection structure between the piston and cylinder block of a two-stroke engine scavenging system according to the present invention.

[0043] Figure 8 This is a schematic diagram of the cylinder block structure of a two-stroke engine scavenging system according to the present invention;

[0044] Figure 9 This is a schematic diagram of the connection structure between the crankshaft and piston in a two-stroke engine scavenging system according to the present invention;

[0045] Figure 10This is a schematic diagram of the connection structure between the connecting rod and the guide vane of a two-stroke engine scavenging system according to the present invention.

[0046] Figure 11 This is a schematic diagram of the guide vane structure of a two-stroke engine scavenging system according to the present invention.

[0047] In the diagram: 1. Mounting bracket; 2. Protective cover; 3. Engine block; 4. Water pump; 41. Water inlet; 42. Water outlet; 43. First water inlet port; 44. First water outlet port; 5. Cylinder block; 51. Air inlet; 52. Protrusion; 521. Scavenging passage; 53. First water-cooling chamber; 54. Second water inlet port; 55. Second water outlet port; 56. Exhaust port; 6. Carburetor; 7. Crankcase; 8. Cylinder head; 9. Piston; 91. Through hole; 10. Mounting plate; 11. Hand lever; 12. Control box; 13. Air-fuel mixing line; 14. Flywheel; 5. Crankshaft; 151. U-shaped mounting port; 16. Piston pin; 17. Connecting rod; 18. First rotating shaft; 19. Control handle; 20. Spark plug; 21. Water outlet pipe; 22. Muffler; 221. Second water cooling chamber; 222. Third water inlet port; 223. Third water outlet port; 23. Actuator lever; 24. Gear set; 25. Guide plate; 251. Guide groove; 26. Air filter; 27. Water supply pipe; 28. Gear shaft; 29. ​​Return water pipe; 30. Scavenging block; 31. Second rotating shaft; 311. Cutout; 32. Starter motor; 33. U-shaped block. Detailed Implementation

[0048] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0049] Example 1: Please refer to Figures 4-10This embodiment provides a scavenging system for a two-stroke engine. This system is suitable for small two-stroke gasoline engines, especially for small power equipment with strict requirements on size and weight, such as portable fire pumps. The system includes a cylinder block 5 and a crankcase 7. The cylinder block 5 is a die-cast aluminum alloy cylinder block specifically designed for two-stroke engines. Its inner wall is honed to form a mirror finish for a sealing sliding fit with the piston rings of the piston 9. One end of the cylinder block 5 is bolted to a cylinder head 8, which is a cast aluminum alloy part. The space between the cylinder head 8 and the piston 9 constitutes the combustion chamber. A threaded mounting hole is provided at the center of the cylinder head 8 for mounting a spark plug 20. The electrode of the spark plug 20 extends into the combustion chamber, and its ignition timing is controlled by an external igniter.

[0050] The crankcase 7 is bolted to one side of the cylinder block 5 and sealed, with a gasket between them to prevent gas leakage. The interior of the crankcase 7 is a sealed crank chamber used to temporarily store the fresh air-fuel mixture after mixing by the carburetor 6. A crankshaft 15 is rotatably connected to the crankcase 7 via bearings. The crankshaft 15 is a composite crankshaft, press-fitted from the front axle end, rear axle end, and crank pin. A connecting rod 17 is rotatably connected to its connecting rod journal via needle roller bearings. The other end of the connecting rod 17 is rotatably connected to the piston 9 via a piston pin 16. The piston pin 16 is horizontally fixed inside the piston 9, and the connecting rod 17 is rotatably sleeved on the outer wall of the piston pin 16 via bearings.

[0051] When the crankshaft 15 rotates, the rotational motion is converted into the reciprocating linear motion of the piston 9 within the cylinder block 5 via the connecting rod 17. During the movement of the piston 9 from top dead center (equivalent to the extreme position near the cylinder head 8) to bottom dead center (equivalent to the extreme position far from the cylinder head 8), the power stroke and intake stroke are completed; during the movement of the piston 9 from bottom dead center to top dead center, the compression stroke and scavenging stroke are completed, thus forming a two-stroke working cycle.

[0052] like Figure 7 and Figure 8 As shown, the cylinder liner wall of the cylinder block 5 has an intake port 51 and an exhaust port 56, which are staggered on the opposite side of the cylinder block 5, meaning that the intake port 51 and the exhaust port 56 are not on the same horizontal circumferential direction to avoid direct short-circuiting loss of fresh air-fuel mixture. Specifically, the exhaust port 56 is located on the cylinder wall near the cylinder head 8 and opens first when the piston 9 moves to the bottom dead center to discharge exhaust gas; the intake port 51 is located on the cylinder wall away from the cylinder head 8 and opens when the piston 9 moves to the top dead center to draw in fresh air-fuel mixture.

[0053] like Figure 7 and Figure 8As shown, the top and bottom of the cylinder block 5 are symmetrically cast with integral protrusions 52. The protrusions 52 are cavity structures that protrude outward from the outer wall of the cylinder block 5, and a scavenging channel 521 is formed inside them. The outlet end of the scavenging channel 521 is designed to be inclined towards the cylinder head 8, so that the air-fuel mixture swept into the combustion chamber has an initial velocity component pointing towards the cylinder head 8, which is beneficial for pushing the residual exhaust gas at the top of the combustion chamber towards the exhaust port 56.

[0054] Piston 9 is an aluminum alloy casting with two compression ring grooves and one oil ring groove on its outer wall for mounting the compression ring and oil ring, respectively, to achieve a seal with the inner wall of cylinder block 5. Piston 9 has at least one through hole 91 at both its top and bottom, the position of which corresponds to and engages with scavenging passage 521. When piston 9 is near bottom dead center, scavenging passage 521 can be connected to combustion chamber through through hole 91. At this time, the fresh air-fuel mixture compressed by piston 9 in crankcase 7 enters combustion chamber through scavenging passage 521 and through hole 91, achieving scavenging. When piston 9 moves to top dead center, through hole 91 deviates from the outlet end of scavenging passage 521, scavenging passage 521 is sealed by the outer wall of piston 9, and the scavenging process ends.

[0055] like Figures 9-11 As shown, a flow guiding mechanism is provided on the side of the piston 9 near the cylinder head 8 to solve the problem of the two scavenging airflows colliding head-on in the center of the combustion chamber during the scavenging process of a traditional two-stroke engine, forming a chaotic vortex that causes the fresh air-fuel mixture to be short-circuited and lost with the exhaust gas. Specifically, the flow guiding mechanism includes a guide plate 25, which is rotatably connected to the end face of the piston 9 near the cylinder head 8 via a second rotating shaft 31. The guide plate 25 is a plate-shaped component made of metal or high-temperature resistant engineering plastic. Its side near the piston 9 is a precision-machined flat surface, which is in close contact with the end face of the piston 9. The two maintain a relatively rotatable sealed fit, that is, the flat surface of the guide plate 25 is always in contact with the end face of the piston 9 during rotation, preventing the air-fuel mixture from entering the gap between the guide plate 25 and the piston 9, thereby improving the sealing performance during rotation.

[0056] The side of the deflector 25 away from the piston 9 is an arc-shaped convex surface. The design of this arc-shaped convex surface is based on the principle of fluid mechanics: when the scavenging airflow enters the combustion chamber from the scavenging passage 521 and impacts the arc-shaped convex surface of the deflector 25, the upper and lower airflows can flow further towards the cylinder head 8 along the upper and lower sides of the arc-shaped convex surface of the deflector 25, while effectively avoiding the upper and lower airflows from directly colliding head-on in the short distance.

[0057] In this embodiment, as Figure 11As shown, multiple guide grooves 251 are equidistantly spaced on both the upper and lower sides of the arc-shaped convex surface of the guide plate 25. Each guide groove 251 is an arc-shaped groove milled onto the arc-shaped convex surface, with a depth of 0.5-2 mm. The arc angles of the multiple guide grooves 251 are inconsistent; that is, the guide grooves near the center of the guide plate 25 have a larger curvature (a greater degree of curvature on the arc-shaped convex surface), while the guide grooves near the edge have a smaller curvature (a flatter arc-shaped convex surface), or vice versa. Through the guide grooves 251 with different curvatures, the scavenging airflow is decomposed into multiple air jets with different directions, flowing towards the cylinder head 8 at different angles, forming multiple rotating airflows with different paths in the combustion chamber. This rotating airflow, on the one hand, prolongs the residence time of the fresh mixture in the combustion chamber, improving the mixing and replacement efficiency with the exhaust gas; on the other hand, it effectively pushes the exhaust gas from the exhaust port 56 direction, reducing the short-circuit loss of the fresh mixture.

[0058] This invention can be used in the field of two-stroke engines, and can also be applied to other fields.

[0059] Example 2: This example is a further improvement on the previous example: as follows Figures 9-11 As shown, a lever 23 is fixedly connected to the outer wall of the connecting rod 17 near the piston pin 16. The lever 23 is a steel round or square rod, one end of which is fixedly connected to the outer wall of the small end of the connecting rod 17 by welding or interference fit, and the other end extends radially outward. The second rotating shaft 31 passes through one side of the piston 9 in a sealed rotation, and one end of which is fixedly connected to the center point of the plane of the guide plate 25. A sealing ring or oil seal is provided between the second rotating shaft 31 and the piston 9 to prevent gas in the crankcase 7 from leaking into the combustion chamber through the gap between the second rotating shaft 31 and the piston 9. A notch 311 is provided at the end of the second rotating shaft 31 away from the guide plate 25. The notch 311 is formed by cutting off half of the end of the second rotating shaft 31 along the central axis. A U-shaped block 33 is fixedly connected to one side wall of the notch 311, with its opening facing outward, for accommodating and engaging the end of the lever 23.

[0060] During the reciprocating motion of piston 9, the large end of connecting rod 17 rotates with crankshaft 15, while the small end of connecting rod 17 reciprocates linearly with piston 9. Due to the combined effect of the rotation radius of crankshaft 15 and the length of connecting rod 17, connecting rod 17 oscillates at a certain angle relative to the axis of piston 9 during its motion. This included angle changes periodically during the two-stroke cycle. Simultaneously, the actuating rod 23, fixed to the small end of connecting rod 17, oscillates synchronously with connecting rod 17. The end of actuating rod 23 passes through the opening of U-shaped block 33. The reciprocating oscillation of actuating rod 23 drives U-shaped block 33 to reciprocate around the axis of second rotating shaft 31, which in turn drives guide plate 25 to reciprocate synchronously. The back-and-forth rotation of guide plate 25 drives guide groove 251 to rotate back and forth, enabling airflow to be guided at different angles and in different directions, thereby further improving the fluidity of the mixture.

[0061] Example 3: This example is a further improvement on the previous example: as follows Figure 9 As shown, to further improve the air-fuel mixture delivery efficiency within the crankcase 7, a U-shaped mounting port 151 is provided on the crank of the crankshaft 15. Two scavenging blocks 30 are symmetrically fixedly connected within the U-shaped mounting port 151. Each scavenging block 30 is triangular, with an arc-shaped surface on its outer side that has the same curvature as the crank's circumferential surface. The scavenging blocks 30 are fixedly installed within the U-shaped mounting port 151 by screws, and their arc-shaped surfaces smoothly connect with the crank's circumferential surface.

[0062] During the rotation of crankshaft 15, scavenging block 30 rotates synchronously with the crank. The triangular shape of scavenging block 30 sweeps and guides the air-fuel mixture inside crankcase 7 during rotation. The air-facing surface of scavenging block 30 pushes the air-fuel mixture towards the inlet of scavenging channel 521, forming a directional airflow within crankcase 7. This increases the flow rate and velocity of the air-fuel mixture entering scavenging channel 521, thereby improving scavenging efficiency. Simultaneously, the arc-shaped surface of scavenging block 30 smoothly connects with the crank surface, reducing rotational resistance and preventing additional strain on the rotation of crankshaft 15.

[0063] Example 4: This example provides a portable fire pump: such as Figures 1-4As shown, this fire pump adopts the two-stroke engine scavenging system proposed in Examples 1 to 3, and integrates a water pump 4, a water cooling system, and an electric starting system to form a complete portable fire-fighting power unit. Specifically, the fire pump includes a mounting bracket 1, which is welded from steel pipes and has sufficient strength and rigidity to support and fix various components. Rubber shock-absorbing pads (not shown in the figure) are provided at the four corners of the bottom of the mounting bracket 1 to absorb the vibration of the engine during operation and reduce the impact on the ground and the operator. A protective cover plate 2 is fixedly connected to the top of the mounting bracket 1. The protective cover plate 2 is made of stamped steel plate or engineering plastic cover plate, covering the top of various components and providing rainproof, dustproof, and accidental contact protection for components such as the engine body 3, water pump 4, carburetor 6, and muffler 22.

[0064] The water pump 4 is fixedly installed on one side of the crankcase 7. Specifically, the pump body of the water pump 4 is fixedly connected to the side wall of the crankcase 7 by bolts. The front end of the crankshaft 15 rotates through one side wall of the crankcase 7 and extends into the pump body of the water pump 4, where it is fixedly connected to the impeller hub inside the water pump 4 by a key. The pump body of the water pump 4 is provided with an inlet 41 and an outlet 42. Both the inlet 41 and the outlet 42 are pipe thread interfaces used to connect fire hoses or suction pipes. When the crankshaft 15 rotates, the front end directly drives the impeller to rotate synchronously. The centrifugal force generated by the rotation of the impeller draws water in from the inlet 41 of the water pump 4, accelerates it through the impeller, and discharges it from the outlet 42, thus realizing the water delivery function. This direct drive method does not require an additional clutch or transmission mechanism, has a simple structure, high transmission efficiency, and meets the lightweight requirements of portable fire pumps.

[0065] The engine block 3 is fixedly mounted on the side of the crankcase 7 away from the water pump 4. The engine block 3 is a die-cast aluminum alloy housing, which houses the flywheel 14 and the starting transmission mechanism. The rear end shaft of the crankshaft 15 is rotatably supported on the housing of the engine block 3 by bearings, and rotates through the other side wall of the crankcase 7, extending into the interior of the engine block 3 and fixedly connected to the flywheel 14. Additionally, the outer edge of the flywheel 14 has a starting gear ring for engaging with the starting mechanism. A hand-operated pull plate 11 is fixedly mounted on the side of the engine block 3 away from the crankcase 7, which drives the flywheel 14 to rotate via a ratchet mechanism (a conventional technology, not shown in the figure, and will not be described in detail here), thereby driving the crankshaft 15 to rotate.

[0066] The carburetor 6 is connected to the air intake 51 via the air-fuel mixing line 13. Its function is to mix gasoline and air in a certain proportion to form a combustible mixture. An air filter 26 is installed at one end of the carburetor 6 to filter dust and impurities from the air entering the carburetor 6, protecting internal engine parts from wear. Additionally, a control handle 19 is installed on the air-fuel mixing line 13, connected to the throttle or choke of the carburetor 6. The operator can adjust the fuel supply and air intake of the carburetor 6 by operating the control handle 19, controlling the engine speed and power output. The combustible mixture output from the carburetor 6 is delivered to the air intake 51 via the air-fuel mixing line 13 and is drawn into the crankcase 7 for temporary storage when the piston 9 moves to top dead center and negative pressure is generated in the crankcase 7.

[0067] This invention abandons the traditional reed valve structure and adopts a piston valve intake method instead. Specifically, it directly utilizes the reciprocating movement of the piston 9 within the cylinder 5 to automatically control the opening and closing of the intake port 51, achieving automatic switching between intake and scavenging functions without the need for additional valve components. This invention, by replacing the traditional reed valve intake method with a piston valve intake method, has the following significant advantages:

[0068] 1. The number of parts in the whole machine is reduced, the assembly process is simplified, the manufacturing cost is reduced, and the reliability of the whole machine is significantly improved;

[0069] 2. The opening and closing of the air intake 51 is directly determined by the position of the piston 9. The two are rigidly connected and there is no response lag, which can maintain good intake efficiency.

[0070] 3. The air inlet 51 is directly opened on the cylinder wall of the cylinder body 5, eliminating the need for an additional external valve body. This reduces the overall width of the machine, making it more suitable for applications such as portable fire pumps where there are strict requirements for equipment width.

[0071] 4. The air-fuel mixture enters the crankcase 7 directly from the intake port 51. The flow path is short and has fewer bends, which significantly reduces intake resistance, improves charging efficiency, and enhances engine power performance.

[0072] The muffler 22 is connected to the exhaust port 56. The muffler 22 is an expansion type or impedance composite type muffler, which has an expansion cavity, a perforated tube and sound-absorbing material inside, used to reduce the high-frequency and low-frequency noise generated during engine exhaust.

[0073] Example 5: This example is a further improvement on the previous example: as follows Figure 3 As shown, the water pump 4 has a first inlet port 43 on the side near the inlet 41, which is connected to the inlet chamber of the water pump 4. The water pump 4 has a first outlet port 44 on the side near the outlet 42, which is connected to the outlet chamber (high-pressure chamber) of the water pump 4.

[0074] like Figure 7 and Figure 8 As shown, a first water-cooling chamber 53 is provided inside the cylinder block 5 on the side near the cylinder head 8. The first water-cooling chamber 53 is a water jacket structure formed during the casting process of the cylinder block 5, surrounding the combustion chamber. It has several reinforcing ribs and flow guide baffles inside to guide the cooling water to flow evenly across the combustion chamber perimeter. The cylinder block 5 is provided with a second water inlet port 54 and a second water outlet port 55 that are simultaneously connected to the first water-cooling chamber 53.

[0075] like Figure 6 As shown, the muffler 22 has a second water-cooling chamber 221 inside. The second water-cooling chamber 221 is a space between the outer shell and the inner shell of the muffler 22, surrounding the exhaust pipe of the muffler 22. The muffler 22 has a third water inlet port 222 and a third water outlet port 223 that are connected to the second water-cooling chamber 221.

[0076] like Figure 2 and Figure 4 As shown, the two ends of the water outlet pipe 21 are connected to the first water outlet port 44 and the second water inlet port 54, respectively. The two ends of the water supply pipe 27 are connected to the second water outlet port 55 and the third water inlet port 223, respectively. The two ends of the return water pipe 29 are connected to the third water outlet port 222 and the first water inlet port 43, respectively. All water pipes are made of high-temperature resistant material, and both ends are connected to the respective ports via quick couplings.

[0077] Working Principle: When the engine starts, the crankshaft 15 drives the impeller of the water pump 4 to rotate, and the water pump 4 begins to draw water in. Water is drawn into the water inlet chamber of the water pump 4 from the inlet 41, accelerated by the impeller, and discharged from the outlet 42. At the outlet 42, the water flow is under high pressure. Since the first outlet port 44 is located at the high-pressure outlet chamber of the water pump 4, and the second inlet port 54 is connected to the first water-cooling chamber 53 of the cylinder block 5, a pressure difference is formed at both ends of the outlet pipe 21. While the water pump 4 is working, a portion of the high-pressure water flows from the first outlet port 44 through the outlet pipe 21 into the first water-cooling chamber 53 of the cylinder block 5, providing forced water cooling to the area of ​​the cylinder block 5 near the combustion chamber. This cooling effect keeps the operating temperature of the cylinder block 5 within a reasonable range, preventing lubricating oil deterioration and piston ring seizure caused by high temperatures, thus extending the engine's service life.

[0078] Water flowing through the first water-cooling chamber 53 of the cylinder 5 exits from the second outlet port 55 and enters the second water-cooling chamber 221 of the muffler 22 via the water supply pipe 27, cooling the muffler 22. When high-temperature exhaust gas passes through, the surface temperature of the muffler 22 can reach over 200℃; water cooling can reduce the outer surface temperature of the muffler 22 to below 60℃. Water flowing out of the second water-cooling chamber 221 of the muffler 22 flows back to the first inlet port 43 of the water pump 4 via the return water pipe 29 from the third outlet port 222, merging with the new water drawn in at the inlet port 41 before re-entering the impeller of the water pump 4, forming a cooling cycle. The return water pipe 29 returns the water that has absorbed heat to the inlet of the water pump 4, recovering the water's potential energy.

[0079] This design offers the following technical advantages:

[0080] 1. The cooling water circulation is driven by the pressure difference when the water pump 4 is working, eliminating the need for an additional cooling water pump or electric fan, thus reducing energy consumption and equipment weight;

[0081] 2. The cooling water circulation path passes through the cylinder block 5 and the muffler 22 in sequence. The heat exchange efficiency between the high-temperature components and the cooling water is high, which effectively reduces the surface temperature of the cylinder block 5 and the muffler 22.

[0082] 3. Water cooling lowers the temperature of the outer surface of the silencer 22. In forest fire prevention operations, fire pumps are usually placed directly on the ground, where there may be dead branches and leaves. The high temperature of the silencer 22 surface can easily ignite these combustibles, causing forest fires. The water-cooled silencer 22 surface temperature is much lower than the ignition point of combustibles, effectively avoiding fire hazards.

[0083] 4. It reduces the temperature of the outer surface of the silencer 22, preventing operators from being burned when handling or maintaining the fire pump, thus improving safety.

[0084] 5. The cooling of cylinder block 5 controls the temperature of the combustion chamber wall, reduces the tendency of knocking, and improves the stability of engine power output.

[0085] Example 6: This example is a further improvement on the previous example: as follows Figure 2 , Figure 4 and Figure 5As shown, a starter motor 32 is fixedly connected to one side of the engine block 3. The starter motor 32 is a DC motor, electrically connected to a battery via wires. The battery is fixedly mounted on the mounting bracket 1. The battery is a 12V maintenance-free lead-acid battery or lithium battery, which is charged by a charger before use. A gear shaft 28 is fixedly connected to the output shaft of the starter motor 32. Inside the engine block 3, a first rotating shaft 18 is rotatably connected via bearings. A gear set 24 is fixedly sleeved on the outer wall of the first rotating shaft 18. The gear set 24 consists of a large gear and a small gear arranged coaxially. The large gear meshes with the gear shaft 28, and the small gear meshes with the flywheel 14, forming a differential transmission.

[0086] When the operator presses the start button, the battery supplies power to the starter motor 32, and the rotor of the starter motor 32 drives the gear shaft 28 to rotate at high speed. The gear shaft 28 drives the large gear of the gear set 24 to rotate through gear meshing, and the large gear drives the small gear to rotate synchronously through the first rotating shaft 18. The small gear drives the starter gear ring on the outer edge of the flywheel 14 to rotate through meshing, and the flywheel 14 drives the crankshaft 15 to rotate. The crankshaft 15 drives the piston 9 to reciprocate through the connecting rod 17. During the starting process, the speed of the flywheel 14 is relatively low, while the speed of the starter motor 32 is relatively high. The combination of the large and small gears in the gear set 24 realizes the reduction and torque increase from high speed and low torque to low speed and high torque, ensuring sufficient starting torque. In addition, when the battery power is insufficient or the starter motor 32 fails, the operator can also pull the hand pull plate 11 to start the engine.

[0087] In this embodiment, as Figure 1 As shown, a mounting plate 10 is fixedly connected to the mounting bracket 1, and a control box 12 is fixedly mounted on the outer side of the mounting plate 10. The control box 12 contains electrical components such as an igniter, a starting relay, and a fuse. Its panel is equipped with a start button, a flameout switch, and a charging interface, which can centrally control the switching of various electrical components, facilitating the operation and use of the entire fire pump.

[0088] However, as is well known to those skilled in the art, the working principles and wiring methods of the water pump 4, carburetor 6, control box 12, spark plug 20 and starter motor 32 are commonplace and are all conventional methods or common knowledge. They will not be described in detail here. Those skilled in the art can make any selections according to their needs or convenience.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A scavenging system for a two-stroke engine, comprising a cylinder block having an intake port and an exhaust port, and a piston that is slidably and sealingly connected to the inner wall of the cylinder block, a connecting rod rotatably connected to the piston, a cylinder head connected to one end of the cylinder block, and a combustion chamber formed between the cylinder head and the piston, characterized in that, The top and bottom of the cylinder are symmetrically provided with convex bulges, and the convex bulges are provided with scavenging channels. The top and bottom of the piston are provided with at least one through hole that corresponds to and cooperates with the scavenging channels. The piston is provided with a guide plate on the side near the cylinder head, and the side of the guide plate away from the piston is an arc-shaped convex surface, which is used to guide the air-fuel mixture entering the combustion chamber toward the cylinder head side. The arc-shaped raised surface has multiple guide grooves on both the upper and lower sides, which correspond to the upper and lower scavenging channels respectively. Together with the raised surface, the air-fuel mixture can be guided to the cylinder head from multiple paths. The guide plate is connected to the connecting rod via a connector, allowing the guide plate to rotate back and forth with the reciprocating motion of the piston, guiding the mixture in different directions and forming a rotating airflow.

2. The scavenging system for a two-stroke engine as described in claim 1, characterized in that, The guide plate is flat on the side near the piston and rotates in a sealed fit with the side of the piston near the cylinder head.

3. The scavenging system for a two-stroke engine as described in claim 2, characterized in that, The arc angles of the multiple guide grooves decrease sequentially from the middle to the outside.

4. A two-stroke engine scavenging system as described in claim 1 or 3, characterized in that, The connecting component includes a second rotating shaft that seals and rotates through one side of the piston. One end of the second rotating shaft is fixedly connected to the center point of the plane of the guide plate. A slit is provided at the end of the second rotating shaft away from the guide plate. A U-shaped block is fixedly connected to one side wall of the slit. A toggle rod that engages with the U-shaped block is fixedly connected to one side outer wall of the connecting rod.

5. A two-stroke engine scavenging system as described in claim 4, characterized in that, It also includes a crankcase connected to the cylinder block, which is internally connected, and a crankshaft is rotatably connected inside the crankcase, and the crankshaft transmits power to the piston through a connecting rod.

6. A two-stroke engine scavenging system as described in claim 5, characterized in that, The crankshaft has a U-shaped mounting port, and two scavenging blocks are symmetrically fixedly connected inside the U-shaped mounting port. The scavenging blocks are triangular, and the outer side of the scavenging blocks has an arc surface with the same curvature as the circumferential surface of the crankshaft and a smooth transition.

7. A portable fire pump, characterized in that, The system includes a two-stroke engine scavenging system as described in claim 6, and further includes: A water pump is fixedly installed on one side of the crankcase. The front end of the crankshaft rotates through one side of the crankcase and is fixedly connected to the impeller inside the water pump. The water pump is provided with an inlet and an outlet for pipe connection. The engine block is fixedly installed on the side of the crankcase away from the water pump. The rear end shaft seal of the crankshaft rotates through the other side of the crankcase and is fixedly connected to a flywheel located inside the engine block. A hand-operated crankshaft is fixedly installed on the side of the engine block away from the crankcase and is used to drive the flywheel to rotate. A carburetor is connected to the air intake via an air-fuel mixing line, a control handle is provided on the air-fuel mixing line, and an air filter is provided at one end of the carburetor; The muffler is connected to the exhaust port; The cooling pipes are located between the water pump, cylinder block, and muffler, and can automatically cool the cylinder block and muffler by utilizing the water pump's water delivery process.

8. A portable fire pump as described in claim 7, characterized in that, The cooling pipeline includes an outlet pipe, a supply pipe, and a return pipe; The water pump has a first inlet port on the side near the inlet and a first outlet port on the side near the outlet. The cylinder body has a first water-cooling chamber on the side near the cylinder head, and the cylinder body has a second water inlet port and a second water outlet port that are simultaneously connected to the first water-cooling chamber. The silencer has a second water-cooling chamber inside, and the silencer has a third water inlet port and a third water outlet port that are simultaneously connected to the second water-cooling chamber. The two ends of the water outlet pipe are connected to the first water outlet port and the second water inlet port, respectively; the two ends of the water delivery pipe are connected to the second water outlet port and the third water inlet port, respectively; and the two ends of the return water pipe are connected to the third water outlet port and the first water inlet port, respectively.

9. A portable fire pump as described in claim 7 or 8, characterized in that, It also includes a mounting bracket, on which the engine block, water pump, cylinder block and carburetor are all fixedly mounted, and a protective cover is fixedly connected to the top of the mounting bracket.

10. A portable fire pump as described in claim 9, characterized in that, A starter motor is fixedly connected to one side of the engine body. A gear shaft is fixedly connected to the output shaft of the starter motor. A first rotating shaft is rotatably connected inside the engine body. A gear set is fixedly sleeved on the outer wall of the first rotating shaft. The gear set consists of a large gear and a small gear. The large gear meshes with the gear shaft, and the small gear meshes with the flywheel. A battery electrically connected to the starter motor is fixedly mounted on the mounting bracket.

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