Fuel injector with enhanced response

Abstract

The invention relates to a fuel injector (100) for an internal combustion engine, comprising at least one nozzle (1) having one or more ends (6) arranged for injecting fuel into a combustion chamber. When the fuel injector (100) is in the closed position to stop injecting fuel, the nozzle (1) is provided with a seat (7) forming a sealing surface with the needle (2). The nozzle (1) also has a blind hole (4) which extends axially from the seat (7) towards the end (6).

Description

Technical Field

[0001] The present invention relates to a high-pressure fuel injector for an internal combustion engine. In particular, the present invention relates to a fuel injector according to the preamble of the appended independent claims. Background Art

[0002] Fuel injectors are used to supply fuels such as gasoline or diesel into the combustion chambers of internal combustion engines.

[0003] WO2012 / 016819A1 discloses a fuel injector for supplying fuel to a combustion chamber of an internal combustion engine. The fuel injector described in that document includes a fuel injector housing, and at an end facing the combustion chamber of the internal combustion engine, a recess with a blind hole is formed. The blind hole has a first cylindrical section and a bottom section forming the base of the blind hole. At least one through hole for fuel is formed in the area of the blind hole. A closing member, in particular a nozzle needle, is provided which can move up and down along the longitudinal axis of the blind hole, and in its closed position, it lies on the sealing section of the recess, forming a sealing seat, and in the lifted position, it forms a passage to at least one through hole. The bottom section has a flat bottom area.

[0004] There is a desire to develop fuel injectors that can provide better response, robustness, reliability, service life, and low production costs. Summary of the Invention

[0005] The main object of the present invention is to overcome the above-mentioned drawbacks of the prior art. Another object of the present invention is to provide a robust and reliable fuel injector with improved response in terms of the coordination and synchronization between its movable components (such as the needle and the valve).

[0006] These objectives are achieved by the fuel injector defined in the appended independent claims. The fuel injector according to the present disclosure includes at least one nozzle for injecting fuel into the combustion chamber. The nozzle includes at least one end arranged for injecting fuel into the combustion chamber. The nozzle is provided with a blind hole which includes a frustoconical section. The frustoconical section tapers towards the end along the main axis.

[0007] The frustoconical section has a blind hole angle greater than 41°. This increased value of the blind hole angle slows down the speed of the needle, thereby enhancing the synchronization between the needle and the corresponding valve assembly, especially when the valve assembly includes a ball valve.

[0008] For example, the blind hole angle is between 42° and 48°, even between 44° and 46°. For example, the blind hole angle is 45°.

[0009] In a possible embodiment, the blind hole has a blind hole diameter extending radially with respect to the main axis, the value of which is greater than 1.00 mm. Thus, the blind hole diameter is arranged at a required value related to the elastic deformation of the fuel injector under high pressure. This increased value of the blind hole diameter further slows down the speed of the needle, thereby enhancing the synchronization between the needle and the corresponding valve group, especially when the valve group includes a ball valve.

[0010] For example, the blind hole diameter is greater than 1.05 mm, especially between 1.08 mm and 1.12 mm, such as 1.10 mm. Thus, the blind hole diameter is arranged at a required value related to the elastic deformation of the fuel injector under high pressure.

[0011] In a possible embodiment, the outer surface of the end of the nozzle has a frustoconical outer section parallel to the frustoconical section of the blind hole. This embodiment enhances the mechanical stability of the nozzle against high pressure or radial force components to which the inner surface of the nozzle is exposed.

[0012] In a possible embodiment, the frustoconical outer section has an end angle greater than 41°. Related to the value of the blind hole angle disclosed above, the end angle is between 42° and 48°, even between 44° and 46°, such as 45°. For example, the value of the end angle is equal to the value of the blind hole angle, so that the frustoconical section of the blind hole is parallel to the frustoconical outer section of the end. This function enhances the mechanical stability around the seat and the end of the nozzle, preventing elastic deformation.

[0013] In a possible embodiment, the frustoconical section overlaps with the frustoconical outer section with respect to the orthogonal projection of its surface. This measure further improves the mechanical stability around the seat and the end of the nozzle.

[0014] In a possible embodiment based on design optimization, the blind hole angle is between 42° and 48°, and the blind hole diameter is greater than 1.05 mm. In a further possible embodiment based on further design optimization, the blind hole angle is between 44° and 46°, and the blind hole diameter is between 1.08 mm and 1.12 mm. In a further possible embodiment based on further design optimization, the blind hole angle is 45°, and the blind hole diameter is 1.10 mm.

[0015] In a further possible embodiment based on this design optimization, the outer surface of the end of the nozzle has a frustoconical outer section parallel to the frustoconical section of the blind hole. The end angle of the frustoconical outer section is equal to the blind hole angle.

[0016] The fuel injector may include a valve group equipped with a ball valve. Generally, the P-type nozzle design (with a short needle) is used together with a ball valve fuel injector. However, through this invention, it makes it possible to use a nozzle module with more long needles compared to a P nozzle. Description of the Drawings

[0017] The accompanying drawings (a brief description of which is hereby provided) are only used to provide a better understanding of the present invention and thus are not used to limit the scope of protection or to interpret the scope without the specification as the background.

[0018] Figure 1 A schematic diagram shows the relationship between the injection volume and time in a single injection cycle. The abscissa is the injection time (e.g., in milliseconds), and the ordinate is the volume of the liquid fuel injected through the orifices on the fuel injector nozzle (e.g., in cubic millimeters).

[0019] Figure 2 is Figure 1 A close-up view (detail J) of the schematic diagram given in

[0020] Figure 3 is Figure 1 A close-up view (detail J) of the schematic diagram given in

[0021] Figure 4 is an axial sectional view of an exemplary fuel injector embodiment according to the present disclosure.

[0022] Figure 5 is Figure 1 A close-up view near the end of the fuel injector nozzle in Detailed Description

[0023] Referring to the above accompanying drawings, the present application proposes a fuel injector 100 for an internal combustion engine. Fuel can be supplied to the combustion chamber of the internal combustion engine by injecting fuel through one or more orifices 5 on the nozzle 1 of the fuel injector 100. The fuel injector 100 may include a nozzle body provided together with the nozzle 1. The nozzle body can be considered to include a guide hole by itself, and the needle 2 is slidably guided in the guide hole reciprocatingly along the main axis A. The fuel flows around the needle 2 through the guiding region of the annular gap between the nozzle body and the injection needle 2 to the orifice 5.

[0024] The needle 2 is biased towards the seat 7 by the biasing force of an elastic device, such as a compression spring, to reach the seat position. At the seat position, the seat edge on the needle 2 contacts the inner surface of the nozzle body circumferentially to stop the fluid flow between the upper seat region and the lower seat region where the orifice 5 is located. Compared with the lower seat region, the upper seat region is closer to the valve group 3 along the main axis A and farther from the end 6 of the nozzle 1. Therefore, when the needle 2 reaches the seat position, the fuel supplied to the combustion chamber is blocked.

[0025] To supply fuel to the combustion chamber through the injection hole 5, a fluid flow communication is formed between the upper seat portion region and the injection hole 5. This is achieved by temporarily applying a force such as the magnetic force of a solenoid, which overcomes the biasing force and thus lifts the needle 2 from the seat 7. This force inherently acts in the opposite direction to the biasing force along the main axis A. During the entire injection instance, fuel is injected through the injection hole 5 in a volume amount (injection amount, abbreviated as Qinj), which is a variable related to the injection time (abbreviated as IT), as Figure 1 shown. When the force stops, the needle 2 returns to the seat position under the action of the biasing force, thus completing the injection cycle.

[0026] At the end of each injection cycle, the needle tip 2 is pushed onto the seat 7, resulting in mechanical contact and even collision between the edge of the seat 7 and the nozzle body. Therefore, the impact surfaces of the needle 2 and the nozzle body around the edge of the seat 7 are prone to wear, which leads to deviations in the injection pattern and the amount of fuel injected during the injection cycle. When the wear is unevenly distributed around the main axis A, fuel injector drift occurs, which corresponds to the deviation of the needle 2 from the main axis A. This causes the injection pattern to shift from the corresponding original design, which is usually symmetric in the radial direction relative to the main axis A.

[0027] To ensure good performance and an acceptable level of emissions of the internal combustion engine, it is necessary to maintain the consistency of the amount of fuel injected and the injection pattern during each injection cycle throughout the entire service life of the fuel injector 100.

[0028] Figure 2 is Figure 1 a close-up view of the exemplary detail J in, where the formation of a plateau is observed at the start of injection. The plateau is mostly observed at shorter energization times (such as in pilot injection). At the plateau P, the derivative of the injection amount Qinj with respect to the injection time IT converges to zero, so the injection amount Qinj does not increase as expected by the design. At the start of injection, the formation of a plateau can be considered to be observed when there is a lack of synchronization between the valves in the valve group 3 and the needle 2 in their respective translational movements along the main axis A. The formation of a plateau has a negative impact on software functions such as ZFC (zero fuel calibration) and IQA (injection amount adjustment), and results in the inability to calibrate the corresponding system. Therefore, in the case of the formation of a plateau, the engine power cannot be evaluated through system calibration.

[0029] For example, a ball valve can be used in the fuel injector 100, and the ball valve itself is slower compared to various types of needles 2. Therefore, during armature bounce, the nozzle 1 will open, resulting in the formation of a plateau. In other words, the armature bounce and the movement of the needle 2 away from the end 6 of the nozzle 1 overlap, and this phenomenon leads to the formation of a plateau. However, the valve assembly 3 with a ball valve is one of the cheapest valve assemblies among various valve types. Therefore, the fuel injector 100 according to the present invention is provided with such a valve assembly 3 to reduce the production cost, thereby obtaining the fuel injector 100. To minimize or even eliminate the formation of the plateau P, the nozzle 1 is arranged to counteract the impedance, which is achieved by increasing the blind hole angle β and increasing the blind hole diameter "D" with respect to the fuel injector 100 of the internal combustion engine in the automotive industry in the prior art or existing use. The value of the blind hole angle in the prior art can be considered to be 40° or less, which is far from the minimum value proposed in this application. On the other hand, the value of the blind hole diameter in the prior art can be considered to be 0.9 mm, which is also far from the minimum value proposed in this application. Considering that the seat 7 for the needle 2 itself has a hollow frustoconical geometry, which has a predetermined apex angle (i.e., seat angle) in the axial direction towards the end 6 of the nozzle, so as to make mechanical contact with the corresponding frustoconical side surface of the needle 2. The blind hole 4 can be defined as a hollow volume that is axially closer to the end 6 of the nozzle with respect to the seat 7. The blind hole 4 narrows towards the end 6 of the nozzle. Near the seat 7, the blind hole 4 includes an axially extending frustoconical section 41, and its blind hole angle β is smaller than the seat angle. Therefore, the blind hole 4 is arranged not to maintain mechanical contact with the needle 2 under any circumstances during the entire injection cycle. The injection hole 5 can be considered to be arranged around the blind hole 4, for example, at the frustoconical section 41.

[0030] Figure 4 is a schematic axial cross-sectional view of an exemplary embodiment of the fuel injector 100 according to the present disclosure. Figure 5 An exemplary axial cross-section around the end 6 of the nozzle is shown, highlighting the non-contact structure of the blind hole 4 through relative geometric design measures regarding the needle 2 and the seat 7. When in the closed position, the mechanical force components orthogonally applied to the seat 7 by the high-pressure fuel and / or the needle 2 are visualized using hollow bold arrows. Due to these force components, the nozzle 1 tends to undergo elastic deformation, that is, the nozzle 1 is temporarily deformed radially with respect to the main axis A. Therefore, at the regulated nozzle 1, the minimum value of the diameter of the hydraulically acting seat is reduced to the blind hole diameter D. The present disclosure proposes some measures to minimize or eliminate the following situations that may occur due to the above elastic deformation:

[0031] - A temporary increase in the seat angle, which will cause the force components to concentrate on the circumferential transition region 8 around the main axis A between the seat 7 and the blind hole 4, thereby increasing the pressure applied to the transition region 8. This will increase the wear of the seat 7 near the transition region 8.

[0032] These effects are exacerbated as the value of the seat angle increases because the greater the value of the seat angle, the greater the value of the force component. On the other hand, the present disclosure proposes to enhance the coordination and synchronization between the needle 2 and the valves in the valve group 3 by slowing down the response of the needle 2 when taking the open position. This is achieved by increasing the blind hole angle β and the blind hole diameter D. Increasing the blind hole diameter D results in an increase in the minimum value of the seat diameter of the hydraulic action, thereby delaying the opening time and reducing the plateau that occurs when the fuel injector opens. It can be considered that preferably the increase in the blind hole diameter D is kept within the smallest possible range to minimize possible wear. However, considering the geometry and dimensions of the relevant features near the end 6 of the nozzle, the range of the blind hole diameter D proposed in this specification is very different from the ranges available in the prior art or in currently used fuel injectors.

[0033] The present disclosure proposes the following method to slow down the axial retraction of the needle 2 away from the end 6 of the nozzle:

[0034] - The blind hole angle β is greater than 41°, preferably in the range of 42° to 48°, more preferably in the range of 44° to 46°, and even more preferably is 45° (on the full angle of 360 degrees); and - The blind hole diameter D is preferably greater than 1.00 mm, more preferably greater than 1.05 mm, and even more preferably in the range of 1.08 mm to 1.12 mm, and even more preferably is 1.10 mm.

[0035] To reduce the possibility of temporary radial expansion of the nozzle 1 when the fuel injector 100 is in the closed position, the present disclosure proposes a geometric design measure regarding the end 6 of the nozzle. According to this measure, the outer surface of the end 6 of the nozzle has a frustoconical outer section 61 parallel to the frustoconical section 41 of the blind hole 4, thereby enhancing the mechanical stability of the nozzle 1 near the end 6 of the nozzle. In other words, the projection of the frustoconical section 41 perpendicular to its frustoconical surface at least substantially overlaps with the frustoconical outer section 61.

[0036] Therefore, preferably, the frustoconical outer section 61 has an end angle α greater than 41°, which is preferably in the range of 42° to 48°, more preferably in the range of 44° to 46°, and even more preferably is 45° (on the full angle of 360 degrees). Through these measures, the mechanical stability of the nozzle 1 is enhanced to minimize or eliminate the tendency of radial expansion, thereby minimizing or eliminating the wear around the transition zone 8, and thus extending the service life of the fuel injector 100.

[0037] The blind hole diameter D can be defined as the distance corresponding to the maximum value of the radial width of the blind hole 4 at the transition zone 8 without applying the mechanical force component. Such an example can be illustrated as follows:

[0038] - An example where the fuel injector 100 is disassembled, or

[0039] - The needle 2 is moved away from the end 6 of the nozzle so as to perform injection through the injection holes 5 via the open position.

[0040] This development is the solution with the least difficulty in production technology. The solution proposed by this innovation does not bring additional costs to the fuel injector 100, thus maintaining the use of low-cost fuel injectors 100. The improved response achieved by solving the platform problem provides compliance with emission regulations. The proposed geometric design measures coordinate the combined response of the valve group 3 and the needle 2 by slowing down the latter, thereby minimizing or eliminating the formation of the platform; and by providing enhanced mechanical stability to the nozzle 1, minimizing the possibility of wear of the seat 7. The minimization or even elimination of platform formation was first observed in computational fluid dynamics (CFD) simulations, and then a correlation was established between the simulation results and the actual test results. It has been observed that the platform-related behavior of the proposed fuel injector 100 is acceptably low or completely absent.

[0041] List of reference numerals

[0042] 1 Nozzle

[0043] 2 Needle

[0044] 3 Valve group

[0045] 4 Blind hole

[0046] 41 Frustoconical section

[0047] 5 Injection hole

[0048] 6 End

[0049] 61 Frustoconical outer section

[0050] 7 Seat

[0051] 8 Transition zone

[0052] 100 Fuel injector

[0053] A Main axis

[0054] α End angle

[0055] β Blind hole angle

[0056] Qinj Injection quantity

[0057] IT Injection time

[0058] D Blind hole diameter

Claims

1. A fuel injector (100) for an internal combustion engine, comprising an arrangement of at least one nozzle (1), the nozzle (1) having an end (6) for injecting fuel into a combustion chamber, the nozzle (1) being provided with a blind hole (4), the blind hole (4) comprising a frustoconical section (41) narrowing along a main axis (A) towards the end (6), It is characterized in that The frustoconical segment (41) has a blind hole angle (β) greater than 41°.

2. The fuel injector according to claim 1, wherein: The blind hole angle (β) is in the range of 42° to 48°.

3. The fuel injector according to claim 1 or 2, wherein: The blind hole (4) has a blind hole diameter (D) radial to the main axis (A), and the value of the blind hole diameter (D) is greater than 1.00 mm.

4. The fuel injector according to claim 3, wherein: The blind hole diameter (D) is greater than 1.05 mm.

5. The fuel injector according to claim 3 or 4, wherein: The blind hole diameter (D) is in the range of 1.08 mm to 1.12 mm.

6. The fuel injector according to claim 3 or 4, wherein: The blind hole diameter (D) is 1.10 mm.

7. The fuel injector according to any one of claims 1 to 6, wherein: The outer side surface of the end portion (6) of the nozzle has a frustoconical outer section (61) parallel to the frustoconical section (41) of the blind hole (4).

8. The fuel injector according to claim 7, wherein: The frustoconical outer section (61) has an end angle (α) greater than 41°.

9. The fuel injector according to claim 7 or 8, wherein: The orthogonal projection of the frustoconical section (41) relative to its surface overlaps the frustoconical outer section (61).

10. The fuel injector according to claim 3, wherein: The blind hole angle (β) is in the range of 42° to 48°, and the blind hole diameter (D) is greater than 1.05 mm.

11. The fuel injector according to claim 10, wherein: The blind hole angle (β) is in the range of 44° to 46°, and the blind hole diameter (D) is in the range of 1.08 mm to 1.12 mm.

12. The fuel injector according to claim 10 or 11, wherein: The blind hole angle (β) is 45 degrees, and the blind hole diameter (D) is 1.10 mm.

13. A fuel injector according to any one of claims 10 to 12, wherein: The outer side surface of the end portion (6) of the nozzle has a frustoconical outer section (61) parallel to the frustoconical section (41) of the blind hole (4), and the frustoconical outer section (61) has an end angle (α) equal to the blind hole angle (β).

14. The fuel injector according to any one of claims 1 to 13, wherein: The fuel injector (100) is provided with a valve group (3) having a ball valve.

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