An air entrainment direct injection system for a four-stroke engine

Abstract

This invention discloses a direct injection system for a four-stroke engine, belonging to the field of internal combustion engine fuel injection technology. The system includes an air injector (40), a fuel injector (30), a mixing chamber (20), a common rail chamber (10), a seal (80), a limiter (70), a first bolt (50), and a second bolt (60). The mixing chamber (20) has an oil passage and an air passage connecting the air injector mounting cavity (207) and the fuel injector mounting cavity (205). The common rail chamber (10) integrates parallel through-flow oil and air rails. The upper part of the air injector (40) is sealed and installed inside the mixing chamber (20), while the lower part is used to extend into the cylinder head mounting hole. The two ends of the fuel injector (30) are respectively installed inside the mixing chamber (20) and the common rail chamber (10). The mixing chamber (20) and the common rail chamber (10) are fixed together by a second bolt (60). A seal (80) is provided at the air passage connection. A limiter (70) abuts against the end of the fuel injector (30) and applies axial preload. The system is fixed to the engine by a first bolt (50) and axially clamps the air injector (40). This system is suitable for the compact space of a four-stroke engine and does not require modification of the original engine structure.

Description

Technical Field

[0001] This invention relates to a direct injection system for a four-stroke engine, which falls under the category of internal combustion engine fuel injection technology. Background Technology

[0002] Four-stroke engine technology is mature, but fuel economy and other aspects still need improvement. Air-assisted direct injection (AADI) technology, compared to conventional injection systems, adds an air injector and an independent air passage. Fuel is premixed with compressed air in the mixing chamber before being sprayed out at high speed by the air injector, achieving secondary atomization. This significantly improves atomization quality, effectively reduces fuel consumption, and offers strong fuel adaptability. Currently, this technology is mainly used in two-stroke engines. Because their cylinder heads lack valve mechanisms, the upper space is ample, facilitating system integration. In contrast, four-stroke engine cylinder heads integrate complex valve, camshaft, spark plug, and other valve train mechanisms, resulting in extremely compact space. Traditional AADI systems, due to their integrated design of fuel injection and pressure regulation, are large and have a high mass, making them unsuitable for the limited upper space of existing four-stroke engines.

[0003] Given the well-established structure of four-stroke engines, significant modifications to core components such as the cylinder head are not advisable. Therefore, there is an urgent need to design a novel direct injection system that can adapt to the existing compact structure of four-stroke engines. This system should introduce the advantages of low-pressure, high-efficiency atomization into the four-stroke engine field without altering the original engine layout, thereby breaking through its fuel consumption bottleneck and lowering the barrier to modification. This is precisely the technical problem that this invention aims to solve. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing air-clamp direct injection systems, which are difficult to adapt to the compact structure of four-stroke engines, and to provide an air-clamp direct injection system for four-stroke engines. This system, through decoupling and optimizing the layout of the air injector, fuel injector, and their air and fuel passages, can fully utilize the installation space reserved for the fuel injection system in a four-stroke engine. It achieves the integration of air-clamp direct injection functionality without altering the engine's structure, thereby significantly reducing the modification threshold and matching costs.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A direct injection system for a four-stroke engine, characterized in that it includes an air injector, a fuel injector, a mixing chamber, a common rail chamber, a seal, a limiter, a first bolt, and a second bolt. The mixing chamber is provided with an air injector mounting cavity, a second fuel injector mounting cavity, a third oil passage, and a third air passage. The air injector mounting cavity and the second fuel injector mounting cavity are connected through the third oil passage, and the third air passage is connected to the air injector mounting cavity. The common rail compartment is provided with a fuel injector mounting cavity 1, a first oil passage, a second oil passage, a first air passage, a second air passage, and a bolt through hole. The first oil passage is connected to the fuel injector mounting cavity 1 through the second oil passage, and the first air passage is connected to the second air passage. The air injector is installed in the air injector mounting cavity. The upper part of the air injector is sealed to the wall of the air injector mounting cavity by an O-ring. The lower part of the air injector is used to extend into the mounting hole of the engine cylinder head. The two ends of the fuel injector are respectively installed in the second fuel injector mounting cavity and the first fuel injector mounting cavity. The mixing chamber and the common rail chamber are fixedly connected by the second bolt; the second air passage and the third air passage are connected to each other and the sealing element is provided between them; the limiter is disposed in the common rail chamber and abuts against the oil receiving end of the fuel injector, and is used to apply an axial elastic preload to the fuel injector. The air-clamping direct injection system is fixed to the engine cylinder head by the first bolt passing through the bolt hole, and the first bolt axially clamps and fixes the air injector between the mixing chamber and the engine cylinder head.

[0006] Preferably, the axis of the air injector mounting cavity and the axis of the fuel injector mounting cavity 2 have an included angle α, and 25°≤α≤65°.

[0007] Preferably, the common rail compartment is elongated, and the first air passage and the first oil passage extend along the length of the common rail compartment and are parallel to each other, and penetrate the common rail compartment.

[0008] Preferably, a second mating plane is provided on the side of the mixing chamber opposite to the common rail chamber, and a first mating plane is provided on the common rail chamber. The second mating plane fits into the first mating plane, and the sealing element is provided between the two.

[0009] Preferably, the limiter is a helical spring or a disc spring.

[0010] Preferably, the sealing element is an O-ring, and a sealing groove is provided around the third air passage on the mixing chamber, with the O-ring disposed within the sealing groove.

[0011] Furthermore, the sealing element is a sealing gasket, which is sandwiched between the first mating plane and the second mating plane. Beneficial effects

[0012] This invention, stemming from an innovative design, has the following beneficial effects: This system optimizes and distributes the air injectors, fuel injectors, and their air and oil circuits to fit the space. While maintaining a highly integrated and compact design, it can perfectly match the cylinder head and surrounding narrow installation space of a four-stroke engine. Installation and adaptation can be completed without structural modifications to the original cylinder head, valve train, or other components.

[0013] Compared to traditional integrated air-fuel injection systems, this system makes full use of the installation position reserved for the fuel injection system in the four-stroke engine without sacrificing the quality of the air-fuel mixture and the atomization effect. This avoids the extended development cycle and increased manufacturing costs caused by major modifications, and significantly lowers the threshold for modification.

[0014] The system maintains a high degree of modular integration in its structure, with a reasonable layout and reliable connection of the air and oil circuits, making it easy to upgrade existing four-stroke engines without affecting the convenience of maintenance and repair of the original engines. It has good engineering practicality and prospects for promotion. Attached Figure Description

[0015] Figure 1 This is an assembly diagram of the present invention; Figure 2 This is a cross-sectional view of the assembly drawing of the present invention, taken along the plane formed by the axis of the second airway. Figure 3 This is a cross-sectional view of the assembly drawing of the present invention, taken along the plane formed by the axes of the air injector and the fuel injector. Figure 4 This is a front view of the common rail compartment of the present invention; Figure 5 This is a cross-sectional view (AA) of the common rail compartment of the present invention; Figure 6 This is a front view and AA cross-sectional view of the mixing chamber of the present invention; In the picture: 10-Common rail compartment; 20-Mix compartment; 30-Fuel injector; 40-Air injector; 50-First bolt; 60-Second bolt; 70-Limiter; 80-Seal; 90-Air chamber; 101-Fuel injector mounting cavity one; 102-Second air passage; 103-Bolt through hole; 104-Threaded hole; 105-Mating surface one; 106-First oil passage; 107-First air passage; 108-Second oil passage; 109-Limiter mounting seat; 201-Third air passage; 202-Sealing groove; 203-Fixing hole; 204-Mating surface two; 205-Fuel injector mounting cavity two; 206-Third oil passage; 207-Air injector mounting cavity (207); 301 - Fuel injector injection end; 302 - Fuel injector receiving end; 401 - Air injector fuel end; 402 - Air injector air end; 403 - Air injector injection end; 404 - Upper O-ring of air injector. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. This embodiment takes a matched inline four-cylinder four-stroke engine as an example. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit its scope of protection.

[0017] like Figure 1-3 As shown, the present invention provides an air-clamping direct injection system for a four-stroke engine, which mainly includes an air injector (40), a fuel injector (30), a mixing chamber (20), a common rail chamber (10), a seal (80), a limiter (70), a first bolt (50), and a second bolt (60).

[0018] Assembly status, such as Figure 1-6 As shown: Step 1: Based on the mixing chamber (20), install the seal (80) and the fuel injector (30). In this embodiment, the seal (80) is an O-ring. Correctly install the seal (80) into the reserved sealing groove (202) on the mixing chamber (20); correctly install the fuel injector injection end (301) into the fuel injector mounting cavity two (205) of the mixing chamber (20). During the installation process, keep the axis of the fuel injector (30) aligned with the axis of the fuel injector mounting cavity two (205).

[0019] Step 2: Based on the common rail compartment (10), first correctly install the limiter (70) in the limiter mounting seat (109). In this embodiment, a helical spring is used as the limiter. Then, correctly install the mixing compartment (20) installed in the first step into the predetermined position of the common rail compartment (10), that is: the axis of the fuel injector (30) is aligned with the axis of the fuel injector mounting cavity 1 (101) on the common rail compartment (10) and inserted into the cavity; the third air passage (201) and the second air passage (102) Axis alignment; the axes of the two fixing holes (203) on the mixing chamber (20) are aligned with the corresponding threaded holes (104) reserved on the common rail chamber (10); the second bolt (60) passes through the fixing hole (203) to fasten the mixing chamber (20) to the common rail chamber (10), so that the mating plane one (105) and the mating plane two (204) fit together, and the second air passage (102) and the third air passage (201) are sealed by the sealing element (80).

[0020] Finally, the air injector (40) is installed into the air injector mounting cavity (207) in the mixing chamber (20). The O-ring (404) on the upper part of the air injector is sealed to the wall of the air injector mounting cavity (207), thus completing the installation of one injection unit. The remaining three injection units are then installed using the same method, ultimately completing the installation as described above. Figure 1 The assembly of the air-clamping direct injection system shown.

[0021] Step 3: Install the assembled air-clamped direct injection system from Step 2 onto the cylinder head of the four-stroke engine: insert the air injector's injection end (403) into the original engine's fuel injector mounting hole; finally, pass the first bolt (50) through the bolt through hole (103) on the common rail compartment (10) to secure the entire air-clamped direct injection system to the engine cylinder head. During this tightening process, the first bolt (50) presses the common rail compartment (10) and the mixing compartment (20) downwards as a whole, while the air injector (40) is axially clamped and fixed between the mixing compartment (20) and the engine cylinder head, ensuring that the air injector (40) does not move axially under any operating conditions. Afterwards, connect the corresponding oil circuit, air circuit, or pressure sensor to both ends of the common rail compartment (10). The common rail compartment (10) has internal threads (not shown) reserved at both ends to ensure the supply of oil and air to the air-clamped direct injection system, and finally complete the system installation.

[0022] like Figure 1 As shown, the assembled air-clamping direct injection system adapted to a four-cylinder engine has the same external interface characteristics as the traditional in-cylinder direct injection system: the lower part is simple and has no redundant structure, and the main structure, parts, and installation and fixing are all designed in the common rail part; at the same time, the common rail compartment (10) of this invention integrates the entire air passage part more than the common in-cylinder direct injection common rail pipe, which perfectly solves the problem of adapting the air-clamping direct injection function to a four-stroke engine.

[0023] like Figure 1-3 As shown, the system is assembled and correctly installed on the engine. With the engine started, the fuel pump and compressed air pump begin working synchronously, filling the engine's fuel line and air line with fuel and compressed air at their rated pressures, respectively.

[0024] Air path direction: Compressed air enters the first air passage (107) from one end of the common rail chamber (10), fills the first air passage (107) along the length of the common rail chamber, and then reaches the air end (402) of the air injector through the second air passage (102) and the third air passage (201) corresponding to each injection unit and enters the air injector (40) for use.

[0025] Fuel path: Fuel enters the first fuel passage (106) from one end of the common rail chamber (10), fills the first fuel passage (106) along the length of the common rail chamber, and then reaches the fuel injector receiving end (302) through the second fuel passage (108) corresponding to each injection unit and the limiter mounting seat (109), waiting for use. Excess fuel and gas can be discharged or returned from the other end of the first fuel passage (106) and the first air passage (107), respectively.

[0026] After both oil and gas reach the designated position through the above-designed pipelines, the fuel injector (30) is opened, and a certain amount of fuel at the fuel receiving end (302) of the fuel injector is sprayed out from the fuel injector injection end (301) through the inside of the fuel injector (30). The sprayed fuel reaches the air injector fuel end (401) at the top of the air injector (40) through the third oil passage (206) and enters the inside of the air injector, where it mixes with the compressed air waiting there, completing the first atomization of the fuel and forming the initial mixture. Subsequently, the air injector (40) is opened, and the initial mixture is sprayed out at high speed through the air injector injection end (403) under the action of pressure difference and enters the engine combustion chamber, completing the second atomization of the fuel and forming the final fuel-air mixture. This completes a full working cycle of fuel injection atomization process.

[0027] In this embodiment, the included angle α between the axes of the air injector (40) and the fuel injector (30) is set to 45°. This angle is mainly set to accommodate the space available for the fuel rail system in different engines. In practical applications, designers can flexibly adjust this angle according to the space available for the engine, with a recommended range of 25° to 65°.

[0028] It should be noted that the sealing element (80) in the above embodiment is described using an O-ring as an example. However, in actual applications, the sealing element (80) can also be in the form of a gasket. The gasket is directly sandwiched between the mating plane one (105) and the mating plane two (204), which can also achieve the sealing at the junction of the second air passage (102) and the third air passage (201). This equivalent substitution method is still within the protection scope of the present invention.

[0029] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A direct injection system for a four-stroke engine, characterized in that, Includes an air injector (40), a fuel injector (30), a mixing chamber (20), a common rail chamber (10), a seal (80), a limiter (70), a first bolt (50), and a second bolt (60); The mixing chamber (20) is provided with an air injector mounting cavity (207), a second fuel injector mounting cavity (205), a third oil passage (206), and a third air passage (201). The air injector mounting cavity (207) and the second fuel injector mounting cavity (205) are connected through the third oil passage (206), and the third air passage (201) is connected to the air injector mounting cavity (207). The common rail compartment (10) is provided with a fuel injector mounting cavity (101), a first oil passage (106), a second oil passage (108), a first air passage (107), a second air passage (102), and a bolt through hole (103). The first oil passage (106) is connected to the fuel injector mounting cavity (101) through the second oil passage (108), and the first air passage (107) is connected to the second air passage (102). The air injector (40) is installed in the air injector mounting cavity (207). The upper part of the air injector (40) is sealed to the wall of the air injector mounting cavity (207) by an O-ring. The lower part of the air injector (40) is used to extend into the mounting hole of the engine cylinder head. The two ends of the fuel injector (30) are respectively installed in the second fuel injector mounting cavity (205) and the first fuel injector mounting cavity (101). The mixing chamber (20) and the common rail chamber (10) are fixedly connected by the second bolt (60); the second air passage (102) is connected to the third air passage (201) and the sealing element (80) is provided between them; the limiter (70) is provided in the common rail chamber (10) and abuts against the oil receiving end (302) of the fuel injector (30) to apply axial elastic preload to the fuel injector (30); The air-clamping direct injection system is fixed to the engine cylinder head by the first bolt (50) passing through the bolt through hole (103), and the first bolt (50) axially clamps and fixes the air injector (40) between the mixing chamber (20) and the engine cylinder head.

2. The direct injection system for a four-stroke engine according to claim 1, characterized in that... The axis of the air injector mounting cavity (207) and the axis of the fuel injector mounting cavity (205) have an included angle α, and 25°≤α≤65°.

3. A direct injection system for a four-stroke engine according to claim 1, characterized in that... The common rail compartment (10) is generally elongated. The first air passage (107) and the first oil passage (106) extend along the length of the common rail compartment (10) and are parallel to each other, and penetrate the common rail compartment (10).

4. A direct injection system for a four-stroke engine according to claim 1, characterized in that... The mixing chamber (20) has a mating plane two (204) on the side opposite to the common rail chamber (10), and the common rail chamber (10) has a mating plane one (105) correspondingly provided. The mating plane two (204) fits into the mating plane one (105), and the sealing element (80) is provided between the two.

5. A direct injection system for a four-stroke engine according to claim 1, characterized in that... The limiter (70) is a helical spring or a disc spring.

6. A direct injection system for a four-stroke engine according to claim 1, characterized in that... The sealing element (80) is an O-ring, and a sealing groove (202) is provided on the mixing chamber (20) around the third air passage (201), and the O-ring is disposed in the sealing groove (202).

7. A direct injection system for a four-stroke engine according to claim 1 or 4, characterized in that... The sealing element (80) is a sealing gasket, which is sandwiched between the first mating plane (105) and the second mating plane (204).

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