A novel needle valve tip structure for anti-cavitation common rail injectors

Abstract

This utility model belongs to the technical field of fuel injector components and discloses a novel needle valve tip structure for an anti-cavitation common rail fuel injector. It includes a first conical surface, a second conical surface, and a compound arc head, with the second conical surface located between the first conical surface and the compound arc head. The compound arc head is composed of two or more arc-shaped curved surfaces, with smooth transitions between adjacent curved surfaces. The compound arc head in this utility model optimizes the flow field, suppresses cavitation, and weakens the throttling effect. Its combination with the first and second conical surfaces effectively reduces cavitation damage, improves the overall performance of the fuel injector, and significantly extends the service life of the fuel injector.

Description

Technical Field

[0001] This utility model relates to the technical field of fuel injector components, and in particular to a novel needle valve tip structure for an anti-cavitation common rail fuel injector. Background Technology

[0002] The high-pressure common rail fuel injector system is a key technology in modern internal combustion engine fuel injection, and its performance directly affects the engine's combustion efficiency, emission control, and overall reliability. In this system, the needle valve, as the core component controlling fuel injection, precisely regulates the timing and amount of fuel injection through its opening and closing actions. However, when the needle valve opens, fuel flows at high speed through the narrow flow channel formed between the sealing edge of the needle valve tip and the valve body wall, a process that produces a severe throttling effect.

[0003] The throttling effect causes a sudden drop in fuel pressure in this region, which in turn triggers cavitation, i.e., the formation of tiny cavitation bubbles (i.e., cavitation) in the fuel. When these cavitation bubbles flow with the fuel to the high-pressure region, they quickly collapse and generate microjet streams, causing severe erosion damage to critical components such as the needle valve head and sealing surface, shortening the lifespan of the injector, and even affecting the overall performance of the engine.

[0004] To mitigate cavitation, existing technologies have undergone numerous improvements, primarily by optimizing the geometry of oil passages to improve fuel flow and reduce pressure drops, or by using high-hardness materials to manufacture needle valves to enhance their corrosion resistance. While these improvements have some effect, they still have limitations in practical applications. For example, while optimizing oil passage geometry can improve fuel flow, limitations in machining precision make it difficult to completely eliminate cavitation under ultra-high pressure conditions; and while high-hardness materials can improve corrosion resistance, they often come at the cost of increased costs and may still cause damage under extreme conditions. Utility Model Content

[0005] The purpose of this invention is to provide a novel needle valve tip structure for a common rail injector with anti-cavitation corrosion. Its structure is simple, effectively reduces cavitation damage, significantly improves injector performance and lifespan, and is highly practical.

[0006] The technical solution adopted by this utility model to solve its technical problem is:

[0007] A novel needle valve tip structure for an anti-cavitation common rail injector includes a first conical surface, a second conical surface, and a compound arc head. The second conical surface is located between the first conical surface and the compound arc head. The compound arc head is composed of two or more arc-shaped curved surfaces, with a smooth transition between adjacent arc-shaped curved surfaces.

[0008] Furthermore, in the compound arc head, the curvature of two or more arc-shaped curved surfaces decreases sequentially along the end direction of the needle valve tip.

[0009] Furthermore, the composite arc head is composed of a first arc-shaped curved surface and a second arc-shaped curved surface, and the first arc-shaped curved surface is located between the second arc-shaped curved surface and the second conical surface; wherein, the first arc-shaped curved surface bends in the direction of the center line of the needle valve tip to form an arc-shaped groove, and smoothly transitions with the second conical surface and the second arc-shaped curved surface; the second arc-shaped curved surface bends in the direction of the outer side of the needle valve tip to form an arc-shaped edge.

[0010] Furthermore, the radius of the arc of the first curved surface, R1, is 0.4-0.6 mm, and the radius of the arc of the second curved surface, R2, is 0.12-0.18 mm.

[0011] Furthermore, the flow termination surface at the end of the composite arc head is designed as a plane.

[0012] Furthermore, a sealing annular edge is formed at the junction of the first and second conical surfaces.

[0013] The beneficial effects of this utility model are as follows: the composite arc head in this utility model can optimize the flow field, suppress cavitation and weaken the throttling effect. Its combination with the first and second conical surfaces effectively reduces cavitation damage, improves the overall performance of the injector, and significantly extends the service life under ultra-high pressure conditions. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the utility model will be further described below in conjunction with the accompanying drawings and embodiments. The drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the overall structure of this utility model.

[0016] Figure 2 This is a partially enlarged schematic diagram of this utility model.

[0017] In the diagram: 1. First conical surface; 2. Second conical surface; 3. Compound arc head; 4. Flow termination surface; 5. Sealing annular edge; 6. Transition surface;

[0018] 301. First arc-shaped curved surface; 302. Second arc-shaped curved surface. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below. Obviously, the described embodiments are some embodiments of this utility model, but not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0020] like Figures 1 to 2 As shown, a novel needle valve tip structure for an anti-cavitation common rail injector includes a first conical surface 1, a second conical surface 2, and a composite arc head 3. The second conical surface 2 is located between the first conical surface 1 and the composite arc head 3. The composite arc head 3 is composed of two or more arc-shaped curved surfaces, the curvature of which decreases sequentially along the end direction of the needle valve tip, and there is a smooth transition between adjacent arc-shaped curved surfaces.

[0021] In this invention, the first conical surface 1 is used to withstand high-pressure fuel, and the second conical surface 2 is a pressure buffer area to prevent rapid changes in fuel pressure within a single area, thus facilitating a smooth transition of fuel pressure. A sealing annular edge 5 is formed at the junction of the first conical surface 1 and the second conical surface 2, which can directly contact the valve body wall to achieve a seal and also serves a throttling function. The sealing annular edge 5 is a narrow annular edge naturally formed during the machining of the first conical surface 1 and the second conical surface 2.

[0022] When the needle valve is closed, the sealing annular edge 5 directly contacts the valve body wall for sealing. When the needle valve receives an external opening signal, it begins to move upwards. During this process, high-pressure fuel flows past the sealing annular edge 5 and first impacts the composite arc head 3. Its multi-segment arc-shaped curved surface design simultaneously optimizes the flow field, suppresses cavitation, and weakens the throttling effect, as detailed below:

[0023] Optimized flow field: The multi-segment arc-shaped curved surface design can form a gradual pressure gradient, avoid sudden changes in fuel flow rate, make fuel flow more stable, and reduce energy loss and hydrodynamic noise caused by sudden changes in flow rate.

[0024] Suppressing cavitation: The multi-segment arc-shaped curved surface design guides the smooth diffusion of fuel and reduces the formation of local low-pressure areas, thereby effectively suppressing cavitation. This reduces the impact of microjets generated during the formation and collapse of cavitation bubbles on the metal surface and lowers the risk of cavitation damage.

[0025] Reduced throttling effect: The multi-segment arc-shaped curved surface design allows fuel to form a wall-attached flow on the surface of the compound arc head 3, reducing the generation of vortices caused by flow separation, thereby reducing the throttling effect, helping to maintain stable fuel pressure, and improving the injection accuracy and response speed of the injector.

[0026] This invention, through the aforementioned structure, effectively reduces cavitation damage and improves the overall performance of the fuel injector. Simultaneously, by reducing corrosion and wear on the metal surface, it significantly extends the service life under ultra-high pressure conditions.

[0027] In a preferred embodiment of this utility model, the composite arc head 3 is composed of two arc-shaped curved surfaces, specifically including a first arc-shaped curved surface 301 and a second arc-shaped curved surface 302, with the first arc-shaped curved surface 301 located between the second arc-shaped curved surface 302 and the second conical surface 2; wherein, the arc radius R1 of the first arc-shaped curved surface 301 is 0.4-0.6 mm, and the arc radius R2 of the second arc-shaped curved surface 302 is 0.12-0.18 mm. Preferably, the arc radius R1 of the first arc-shaped curved surface 301 is 0.5 mm, and the arc radius R2 of the second arc-shaped curved surface 302 is 0.15 mm. The first arc-shaped curved surface 301 bends towards the centerline of the needle valve tip to form an arc-shaped groove, and smoothly transitions with the second conical surface 2 and the second arc-shaped curved surface 302; the second arc-shaped curved surface 302 bends towards the outside of the needle valve tip to form an arc-shaped edge.

[0028] During fuel flow, the fuel from the second conical surface 2 to the compound arc head 3 first contacts the first arc-shaped curved surface 301. Because the first arc-shaped curved surface 301 bends towards the needle valve centerline to form an arc-shaped groove and smoothly transitions with the second conical surface 2, it guides the fuel towards the center, forming a local high-pressure zone and suppressing the initial generation of cavitation bubbles. Subsequently, the fuel flows to the second arc-shaped curved surface 302. Because the second arc-shaped curved surface 302 bends outward to form an arc-shaped edge, the fuel flow direction gradually expands outward, guiding the fuel to diffuse smoothly, forming a wall-attached flow, avoiding sudden changes in fuel flow velocity, reducing the low-pressure zone, and thus suppressing cavitation development. Simultaneously, it reduces vortices generated by flow separation, weakening the throttling effect.

[0029] In this embodiment, the combination of the first arc-shaped curved surface 301 and the second arc-shaped curved surface 302 forms a gradual pressure gradient, which makes the fuel pressure change more gradual and disperses the cavitation bubble distribution, reducing the direct impact of fuel on the metal surface and extending the service life of the needle valve.

[0030] In practical design, to ensure a smoother pressure change, a transition surface 6 is provided between adjacent curved surfaces. Specifically, in this embodiment, a transition surface 6 is provided between the first curved surface 301 and the second curved surface 302. The transition surface 6 smoothly transitions with both the first curved surface 301 and the second curved surface 302, and the curvature of the transition surface 6 is constant, with a cross-section that is a perfectly equal circle (i.e., the area enclosed by the transition surface 6 on the needle valve is a cylindrical structure). In this embodiment, the transition surface 6 connects the first curved surface 301 and the second curved surface 302 with a constant curvature, eliminating abrupt curvature changes at the junction of the two curved surfaces, making fuel pressure changes more gradual, avoiding sudden increases or decreases in local pressure, and reducing turbulence caused by sudden changes in direction.

[0031] In this embodiment, the flow termination surface 4 at the end of the composite arc head 3 is designed as a plane. Specifically, the end of the second arc-shaped curved surface 302 is designed as a plane, and the second arc-shaped curved surface 302 and the flow termination surface 4 transition smoothly.

[0032] During fuel flow, the fuel flowing from the second conical surface 2 to the composite arc head 3 first converges through the arcuate groove of the first arcuate curved surface 301, then diffuses smoothly through the arcuate edge of the second arcuate curved surface 302, finally reaching the flow termination surface 4. Because the flow termination surface 4 is a planar design, compared to the conical end of a traditional needle valve, it avoids sudden drops in local pressure. Furthermore, the flow termination surface 4 in this embodiment can suppress the generation and collapse of cavitation bubbles while also reducing pressure fluctuations caused by the throttling effect. Specifically, on the one hand, the flow termination surface 4 in this embodiment reduces the risk of secondary cavitation caused by continuous changes in flow direction by vertically cutting off the fuel flow path, dispersing fuel collapse energy across the entire contact surface rather than concentrating it at sharp points or edges, further suppressing the generation and collapse of cavitation bubbles; on the other hand, the smooth transition between the flow termination surface 4 and the second arcuate curved surface 302, as the flow boundary, reduces abrupt changes in flow separation, avoids concentrated vortex generation, enhances the adhesion effect of fuel on the plane, improves flow stability, and weakens pressure fluctuations caused by the throttling effect.

[0033] In this embodiment, the flow termination surface 4, together with the first arc-shaped curved surface 301 and the second arc-shaped curved surface 302, forms a three-stage cavitation suppression system of "progressive compression-smooth diffusion-vertical termination", which significantly reduces the risk of cavitation.

[0034] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this utility model. It should be understood that the above description is only a specific implementation method of this utility model and is not intended to limit this utility model. Any modifications, equivalent substitutions, and improvements made within the scope of the spirit of this utility model should be included within the protection scope of this utility model.

Claims

1. A new type of needle valve tip structure of anti-erosion common rail fuel injector, characterized in that, It includes a first conical surface (1), a second conical surface (2), and a compound arc head (3). The second conical surface (2) is located between the first conical surface (1) and the compound arc head (3). The compound arc head (3) is composed of two or more arc-shaped curved surfaces, and there is a smooth transition between adjacent arc-shaped curved surfaces.

2. The needle valve tip structure of the new anti-erosion common rail fuel injector according to claim 1, characterized in that, In the composite arc head (3), the curvature of two or more arc-shaped curved surfaces decreases sequentially along the end direction of the needle valve tip.

3. The needle valve tip structure of the new anti-erosion common rail fuel injector according to claim 1 or 2, characterized in that, The composite arc head (3) is composed of a first arc-shaped curved surface (301) and a second arc-shaped curved surface (302), and the first arc-shaped curved surface (301) is located between the second arc-shaped curved surface (302) and the second conical surface (2); wherein, the first arc-shaped curved surface (301) bends towards the center line of the needle valve tip to form an arc-shaped groove, and smoothly transitions with the second conical surface (2) and the second arc-shaped curved surface (302); the second arc-shaped curved surface (302) bends towards the outside of the needle valve tip to form an arc-shaped edge.

4. The needle valve tip structure of the new anti-erosion common rail fuel injector according to claim 3, characterized in that, The radius of the arc of the first curved surface (301) is R1, which is 0.4-0.6 mm, and the radius of the arc of the second curved surface (302) is R2, which is 0.12-0.18 mm.

5. The novel anti-erosion needle valve tip structure of the common rail fuel injector according to claim 1, 2 or 4, characterized in that, The flow termination surface (4) at the end of the composite arc head (3) is a planar design.

6. The needle valve tip structure of the new anti-erosion common rail fuel injector according to claim 3, characterized in that, The flow termination surface (4) at the end of the composite arc head (3) is a planar design.

7. The novel anti-erosion needle valve tip structure of the common rail fuel injector according to claim 1, 2, 4 or 6, characterized in that, A sealing annular edge (5) is formed at the junction of the first conical surface (1) and the second conical surface (2).

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