Fuel injector with enhanced long-term sealing performance

Abstract

The invention relates to a fuel injector (1), comprising a valve block (2) having a valve seat region (20) provided with a diffuser opening (21); wherein said valve block (2) comprises a groove (23) surrounding said diffuser opening (21), said groove (23) being substantially in the form of a spherical belt side surface and being arranged so as to be able to circumferentially cover an outer surface of a spherical seal (30) when the seal is in a sealing position; furthermore, the recess (23) is obtained by embossing, which is applied to the valve seat region (20) in an axial direction towards the diffuser opening (21). The invention also relates to a method for obtaining such a fuel injector (1).

Description

Technical Field

[0001] The present invention relates to the technical field of fuel injectors. In particular, the present invention relates to enhancing the long-term sealing performance of fuel injectors, including fuel injectors having solenoid valves. Background Art

[0002] Fuel injection systems including fuel injectors are used in common rail systems used in automotive engineering. Various types of fuel injectors include valves such as solenoid valves for regulating the hydraulic pressure of the fuel and controlling the fuel injection performance of the corresponding fuel injection system.

[0003] A fuel injector valve typically includes a spherical seal for covering and sealing a diffuser opening on one side of a pressure relief chamber of the valve block in a sealed first position to prevent fuel from flowing through the diffuser opening. In a second position, the seal is temporarily deflected from the diffuser opening, the seal is stopped, and the hydraulic distribution around the valve causes the fuel to flow through the diffuser opening to the control chamber. In the first position, the seal is pressed against the valve block under the action of a mechanical force. The mechanical force can be applied by an elastic device (e.g. a compression spring), for example, on a guide for centering the seal according to the valve axis. In the case where the fuel injector includes a solenoid valve, the second position can be reached by energizing the corresponding coil to overcome the force of the elastic device with magnetic force, thereby temporarily stopping the sealing in the first position.

[0004] As a setting parameter, the axial trajectory of the seal's reciprocating motion between the first and second positions has an initial length value that affects the injection curve and the injection performance. During long-term use, which corresponds to millions of reciprocating motions of the seal along the valve axis, the sealing surface on the valve block undergoes plastic deformation. As a result, the relative position of the seal in its first position moves along the valve axis. This phenomenon can be called "armature lift drift" and leads to deviations from the initial injection curve.

[0005] Furthermore, the plastic deformation usually occurs unevenly over the entire sealing surface around the valve axis. As a result, the microstructure and mechanical stability around the sealing surface of the valve block change unevenly. This fact may cause the trajectory to deviate from the valve axis.

[0006] In addition, when the fuel injector is used, the sealing surface on the valve block and the surface around the diffuser opening are usually cavitated. This phenomenon will weaken the sealing of the valve, cause leakage, and change the injection curve in long-term use.

[0007] Particle erosion is another problem observed in fuel injectors, especially in off-highway vehicle conditions. Although the fuel usually undergoes a filtration process before entering the fuel injector, it is inevitable that some particles remain in the fuel, which can corrode the sealing surface of the valve seat area. To overcome this problem, various solutions have been proposed, including providing an anti-corrosion coating on the surface of the valve seat area that is susceptible to particle erosion. However, providing an anti-erosion coating increases the production cost.

[0008] Therefore, improving the stability of the fuel injection curve can be considered a long-term need of the fuel injector industry. Summary of the invention

[0009] The primary object of the present invention is to provide a fuel injector with enhanced long term fuel injection profile stability. Another object of the present invention is to provide a low cost solution to the injection profile stability problem. A further object of the present invention is to minimize or eliminate armature lift drift problems, particle erosion and cavitation around the sealing surface on a valve block for a fuel injector.

[0010] The invention proposes a fuel injector, which comprises a valve block for conditionally providing fluid flow communication between a pressure relief chamber and a control chamber. The valve block comprises a valve seat area, which has a generally truncated cone-shaped form facing the safety chamber. The valve seat area is arranged to accommodate a generally spherical seal and to support the seal in a first position in which the seal is in mechanical contact with the valve block.

[0011] The valve block further comprises a diffuser opening for allowing fluid to flow between the pressure relief chamber and the control chamber through the diffuser in the second position, wherein the seal is deflected from the diffuser opening to stop the mechanical contact. The valve seat area is provided with a groove around the diffuser opening, the groove being generally in the form of a spherical belt side surface and arranged to circumferentially cover the outer surface of the seal when the seal is in the first position.

[0012] The groove corresponds to an increased extent of the contact surface area between the seal and the valve block, thus improving the sealing performance compared to the circular contact of the valve of the prior art. In addition, the extent of the mechanical pressure exerted by the seal on the sealing surface formed by the groove on the valve seat area is distributed over an increased surface area compared to the circular contact of the valve of the prior art; thus, mechanical damage to the valve seat area due to mechanical impact of the seal is minimized. As a result, the groove reduces the occurrence of cavitation around the diffuser opening on the valve seat area.

[0013] In a possible embodiment, the groove may be axially separated from the diffuser opening, so that a truncated cone-shaped spacer is provided between the diffuser opening and the groove. With this embodiment, the occurrence of damage and cavitation is further reduced.

[0014] In a possible embodiment, the diffuser opening can be in the form of a circumferential chamfer. Through such an embodiment, the occurrence of damage and cavitation is further reduced.

[0015] In an alternative possible embodiment, the grooves and / or the diffuser openings are provided with one or more anti-corrosion coatings.

[0016] The invention also proposes a method for obtaining a fuel injector as described above. The method comprises forming a groove around the diffuser opening in the valve seat region, so that the resulting groove is substantially in the form of a spherical strip of lateral surfaces, which groove is arranged so as to circumferentially cover the corresponding outer surface of the seal in the first position. Thus, the method makes possible a fuel injector according to the invention.

[0017] A possible application of the method may also include arranging the groove to be axially spaced apart from the diffuser opening so that a truncated cone-shaped spacer is provided between the diffuser opening and the groove. This version of the method enables the advantages of the corresponding embodiments described above to be achieved. Thus, the fuel injector produced thereby further reduces the occurrence of damage and cavitation.

[0018] A possible version of the method according to the invention may also comprise shaping the diffuser opening so that a circumferential chamfer is formed at the diffuser opening. With the fuel injector thus produced, the occurrence of damage and cavitation is further reduced.

[0019] In a possible version of the method according to the invention, the formation of the groove is carried out by embossing which is applied to the valve seat region in the axial direction towards the diffuser opening.

[0020] In a possible version, the method further comprises providing one or more anti-corrosion coatings on the grooves and / or the diffuser openings.

[0021] The present application also proposes a fuel injector obtained by a method comprising forming a groove by embossing, the embossing being applied to the valve seat area in an axial direction towards the diffuser opening. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, a brief description of which is hereby provided, are only used to provide a better understanding of the present invention and are therefore not intended to limit the scope of protection or to interpret the context of the scope without the description.

[0023] Figure 1 An axial cross section of an exemplary fuel injector according to the present invention is shown.

[0024] Figure 2 Shows Figure 1 Close-up view of detail "J" in the middle.

[0025] Figure 3 Shows Figure 2 Close-up view of the detail "X" in the image.

[0026] Figure 4 Shows Figure 3 A version of the diagram in which the seal and example guide are extracted and not shown in order to better visualize the geometric aspects of the groove and its surroundings.

[0027] Figure 5a is a SEM image along the valve axis towards the diffuser, showing cavitation in the valve seat area around the diffuser opening of a prior art valve block after 60 hours of experimental investigation (cavitation flow test: continuous flow of fuel through the diffuser opening).

[0028] Figure 5b is a SEM image along the valve axis in the direction towards the diffuser, showing cavitation of the valve seat area around the diffuser opening of a prior art valve block after 80 hours of experimental investigation (cavitation flow test: continuous flow of fuel through the diffuser opening).

[0029] Figure 6a is an SEM image along the valve axis in the direction toward the diffuser, showing that after 60 hours of experimental study (cavitation flow test: continuous flow of fuel through the diffuser opening), there is no cavitation or minimized cavitation in the groove seat area around the diffuser opening of the fuel injector valve block according to the present invention.

[0030] Figure 6b is a SEM image along the valve axis towards the diffuser, showing that after 80 hours of experimental study (cavitation flow test: continuous flow of fuel through the diffuser opening), there is no cavitation or minimized cavitation in the groove seat area around the diffuser opening of the fuel injector valve block according to the present invention. DETAILED DESCRIPTION

[0031] With reference to the above-mentioned figures, the present invention proposes a fuel injector 1, which includes a valve block 2 for conditionally providing fluid flow communication between a pressure relief chamber 3 and a control chamber 4. The valve block 2 includes a valve seat area 20, which has a generally truncated cone form facing the pressure relief chamber 3. The valve seat area 20 is arranged to accommodate a generally cylindrical seal 30 and to support the seal 30 in a first position in which the seal 30 is in mechanical contact with the valve block 2. The valve block 2 also includes a diffuser opening 21, which is used to allow fluid to flow between the pressure relief chamber 3 and the control chamber 4 through the diffuser 22 in a second position, in which the seal 30 deviates from the diffuser opening 21 (for example, deviates along the valve axis A) to stop the mechanical contact.

[0032] In the context of the present application, the term “first position” corresponds to a sealed position in which fluid flow through the diffuser opening 21 is blocked by the seal 30 , and the term “second position” corresponds to an open state in which fluid flow is allowed to bypass the seal 30 and flow into the diffuser opening 21 .

[0033] A general view of a fuel injector 1 according to the invention is shown in FIG. Figure 1 shown. Figure 1 An axial cross section of an exemplary fuel injector 1 according to the invention is shown. Figure 2 Shows Figure 1 Close-up view of detail "J" in the middle. Figure 3 Shows Figure 2 A close-up view of detail “X” in FIG. 1 visualizes seal 30 and the surrounding of valve seat area 20 with diffuser opening 21 .

[0034] The valve seat region 20 is provided with a groove 23, which is substantially in the form of a sphere with lateral surfaces, around the diffuser opening 21. The groove 23 is arranged to cover the outer surface of the seal 30 circumferentially, ie around the valve axis A, in the first position.

[0035] Figure 4 Shows Figure 3 , in which the seal 30 and the example guide 71 are extracted and not shown, in order to better visualize the geometrical aspects of the groove 23 and its surroundings.

[0036] The above-described geometrical features of the groove 23 extend the flow path of the fuel to overcome the sealing problem, compared to a prior art fuel injector that does not include the groove 23 described herein. In other words, the sealing on such a prior art fuel injector occurs at only a circular trajectory on the corresponding valve seat area, rather than at a trajectory having the form of a spherical band as in the present invention. The extended flow path allows a smaller axial mechanical pressure to be applied to the seal 30 for sealing, compared to the pressure required to obtain a comparable degree of sealing by the circular mechanical contact of the seal in the prior art fuel injector. Therefore, the present invention reduces future mechanical depreciation associated with fuel leakage around the sealing surface and provides a longer service life for the fuel injector 1.

[0037] The above-mentioned mechanical force can be considered as a force exerted by elastic means 72, such as a compression spring, which is exerted, for example, on a guide 71 for centering the seal 30 according to the axis A. In the case where the fuel injector 1 comprises a solenoid valve, the sealing in the first position can be temporarily stopped by energizing the corresponding coil 73 to overcome the force of the elastic means 72, so as to reach the second position.

[0038] In a possible embodiment, the groove 23 may be axially separated from the diffuser opening 21, so that a truncated cone-shaped spacer 24 is provided between the diffuser opening 21 and the groove 23. The truncated cone-shaped spacer 24 provided between the diffuser opening 21 and the groove 23 is Figure 4 The shaded area is highlighted.

[0039] Since the valve seat area 20 has a truncated cone-shaped geometry, the axial separation of the groove 23 from the diffuser opening 21 also corresponds to the radial separation of the groove 23 and the diffuser opening 21 from each other. Therefore, the groove 23 and the diffuser opening 21 are not adjacent / juxtaposed to each other. This measure protects the diffuser opening 21 from mechanical damage or plastic deformation when the groove 23 is formed, especially when the groove 23 is formed by embossing. This measure is particularly useful when the diffuser opening 21 includes a circumferential chamfer form discussed in this specification.

[0040] Considering the geometry of the conical and spherical side surfaces, the spherical outer surface of the seal 30 is substantially prevented from contacting the surface of the underlying truncated cone or the surface of the truncated cone spacer 24. Therefore, it can be considered that the seal 1 is prevented from mechanically contacting the diffuser opening 21 when the fuel injector 30 is in use. This measure further extends the service life of the fuel injector 1 by further preventing mechanical damage at the diffuser opening 21.

[0041] Furthermore, when the fuel injector 1 is used, the diffuser opening 21 and the groove 23 are not aligned with each other, which enhances the flow curve and fuel pressure distribution around the diffuser opening 21 and causes the cavitation bubble implosion trajectory to be further separated from the diffuser opening 21. From this aspect, the service life of the fuel injector 1 is further improved.

[0042] In a possible embodiment of the fuel injector 1 according to the invention, the diffuser opening 21 may be in the form of a circumferential chamfer. The circumferential chamfer 21 at the diffuser opening may be considered to be formed around the valve axis A. The chamfer may have the geometry of the circumferential side surface of a frustum of a cone, with a sharper top angle than the geometry of the truncated cone of the valve seat area 20. The circumferential chamfer may be considered to be a so-called "Helget chamfer". The circumferential chamfer arranges the fluid flow direction to improve the distribution of the local fuel pressure, thereby preventing the formation of cavitation bubbles around the diffuser opening 21. Therefore, such an embodiment reduces the occurrence of cavitation around the diffuser opening 21, thereby increasing the service life of the fuel injector 1.

[0043] The present invention also proposes a method for obtaining a fuel injector 1, which includes a valve block 2 for conditionally providing fluid flow communication between a pressure relief chamber 3 and a control chamber 4; wherein the valve block 2 includes a valve seat area 20, which has a substantially truncated cone-shaped surface facing the pressure relief chamber 3, and the valve seat area 20 is arranged to accommodate a substantially cylindrical seal 30, i.e., a valve ball, and to support the seal 30 in a first position where the seal 30 is in mechanical contact with the valve block 2, and the valve block 2 also includes a diffuser opening 21 for allowing fluid to flow between the pressure relief chamber 3 and the control chamber 4 through the diffuser 22 (for example, along the valve axis A) in a second position, and in this second position, the seal 30 deviates from the diffuser opening 21 (for example, deviates along the valve axis A) to stop the mechanical contact.

[0044] The method according to the present invention comprises forming a groove 23 on the valve seat area 20 around the diffuser opening 21, so that the groove 23 is substantially in the form of a spherical belt side surface and is arranged to be able to circumferentially cover the corresponding outer surface of the seal 30 in the first position. In the application of the present invention, the seal 30 is a valve ball, and the spherical belt side surface corresponds to the outer surface of the valve ball in close contact to provide sealing.

[0045] This method therefore enables the fuel injector 1 according to the invention to achieve the advantages of the groove 23 as described above.

[0046] A possible application of the method according to the invention may also include arranging the groove 23 axially spaced apart from the diffuser opening 21, so that a truncated cone-shaped spacer 24 may be provided between the diffuser opening 21 and the groove 23. This version of the method enables the production of a corresponding embodiment of the above-disclosed fuel injector 1, wherein mechanical damage is prevented at the diffuser opening 21 and wherein the cavitation bubble implosion trajectory is further away from the diffuser opening 21.

[0047] A possible version of the method according to the invention may also comprise shaping the diffuser opening 21 such that a circumferential chamfer is formed at the diffuser opening 21. This version of the method enables the production of a corresponding embodiment of a fuel injector 1 according to the invention.

[0048] In a possible version of the method according to the invention, the formation of the groove 23 can be achieved by embossing which is applied to the valve seat area 20 in an axial direction towards the diffuser opening 21. In the context of the present application, the axial direction may correspond to the direction along the valve axis A towards the diffuser 22.

[0049] According to the information submitted above, the present application also proposes a fuel injector 1, which is obtained by any version of the method according to the present invention. In particular, the present application proposes a fuel injector 1 obtained by such a method, which includes forming a groove 23 by embossing, which is applied to the valve seat area 20 in the axial direction towards the diffuser opening 21. In other words, the present invention proposes a fuel injector 1, which includes a valve block 2, the valve block includes a valve seat area 20, and the valve seat area 20 is provided with a diffuser opening 21; wherein the valve block 2 includes a groove 23 around the diffuser opening 21, the groove 23 is roughly in the form of a spherical band side surface and is arranged to be able to circumferentially cover the outer surface of the spherical seal 30 when it is in the sealing position; the groove 23 is obtained by applying an embossing to the valve seat area 20 in the axial direction towards the diffuser opening 21.

[0050] Considering that the valve block 2 and the valve seat area 20 can be made of metal material, the embossing machine causes the microstructure of the valve seat area 20 to change, forming the groove 23. The microstructure change achieved by embossing can be observed by metallographic imaging. Compared with the rest of the surface of the valve seat area 20 that has not been subjected to the embossing process, this microstructure change also leads to a local enhancement of the mechanical properties at the groove 23.

[0051] By means of the present invention, a controlled and circumferentially uniform microstructural change can be achieved during the production stage of the valve block 2. The mechanical strength of the material of the valve block 2 production is uniformly increased during the formation stage of the groove 23, and the sealing surface (here the groove 23) does not undergo significant geometric changes during long-term use, especially compared to the prior art valve blocks produced without such grooves 23.

[0052] In other words: the pressure applied to the valve seat area 20 by embossing when forming the groove 23 compresses and compacts the valve body material in the corresponding area of ​​the valve block 2 and moves the sealing surface (the surface that the seal 30 is to contact in the first position) in the axial direction. As a result, the groove 23 provides a hardened and radially symmetrical sealing surface, which is essentially no longer susceptible to mechanical deformation by the impact of the seal 30 during use. The potential degree of "armature lift drift" is already achieved during the production phase of the valve block 2; therefore, the long-term valve tightness or sealing performance is stabilized and the injection curve of the fuel injector 1 remains unchanged over an extended service life. Embossing prevents radially asymmetrical mechanical deformations at the sealing surface of the valve seat area 20.

[0053] Experimental study 1:

[0054] Figure 6a and Figure 6b Respectively Figure 5a and Figure 5bComparison shows that the groove 23 provides for minimization or prevention of cavitation around the diffuser opening 21 of the fuel injector 1 according to the present invention. Figure 5a , Figure 5b , Figure 6a and Figure 6b The SEM images of four valve blocks 2 along the valve axis A towards the diffuser 22 show the surroundings of the valve seat area 20 around the respective diffuser opening 21 at the end of the respective experimental tests. The experimental tests can be regarded as cavitation flow tests, which include continuous flow of fuel through the corresponding diffuser opening 21 at the operating fuel pressure of the respective surfaces around the valve block 2.

[0055] Figure 5a The cavitation around the diffuser opening 21 of a prior art valve block 2 without the above disclosed grooves 23 is shown after such an experimental investigation lasting 60 hours. Figure 5b The cavitation around the diffuser opening of the prior art valve block 2 without the above-mentioned groove 23 is shown after such experimental study lasted for 80 hours. It is worth noting that in the corresponding valve block 2 without the groove 23, even the presence of the circumferential chamfer cannot completely eliminate the cavitation around the diffuser opening 21 (and the corresponding sealing surface).

[0056] Figure 6a and Figure 6b It was shown that no cavitation was observed around the diffuser opening 21 of the valve block 21 of the recess 23 of the fuel injector 1 according to the invention, at a duration of 60 hours and 80 hours, respectively, of such experimental investigations.

[0057] These positive results were achieved without any corrosion protection coating on the valve seat area 20, as Figure 6a and Figure 6b It is conceivable that the service life of the fuel injector 1 according to the present invention can be extended to a greater extent when the diffuser opening 21 (and possibly the groove 23) is provided with an anti-corrosion coating.

[0058] In the context of the present application, the term "anti-corrosion coating" corresponds to one or more coatings, such as nitrides, known for minimizing corrosion around fuel injector valve sealing surfaces.

[0059] Experimental Study 2:

[0060] After testing as described in Experimental Study 1, the valve block 2 was axially cut to observe the cavitation results of the fuel flow surface of the diffuser 22 and the corresponding throttle valve inside the valve block 2.

[0061] It is observed that cavitation occurs inside the diffuser 22, rather than at the diffuser opening 21 and the sealing surface (here around the groove 23). Therefore, the presence of the groove 23 (and possibly the presence of the truncated cone-shaped spacer 24 disposed between the diffuser opening 21 and the groove 23) axially moves the implosion trajectory of the cavitation bubble away from the surface of the valve seat area 20, and even away from the diffuser opening 21.

[0062] Experimental study 3:

[0063] The "Dust Contaminated Fuel" test (abbreviated DCF) is used to observe erosion caused by fuel contaminated with micron-sized particles, such as might be encountered in rural conditions. This test can also be considered an "off-highway vehicle test."

[0064] The fuel injectors subjected to this test differ according to the functionality of the respective valve blocks 2 provided therein. The valve blocks 2 used in the four different fuel injectors 1 can be divided into the following categories:

[0065] a) a valve block 2 for a fuel injector 1 according to the invention without an anti-corrosion coating around the diffuser opening 21 and the groove 23;

[0066] b) A first valve block of the prior art (i.e. without the groove 23), which is not provided with any anti-corrosion coating around the corresponding diffuser opening; a fuel injector with such a valve block should be used with a high-performance particulate filter to extend the service life, otherwise the service life is short;

[0067] c) a second prior art valve block (i.e. without the groove 23) having a first anti-corrosion coating around the corresponding diffuser opening; a fuel injector with such a valve block may be used with a low performance particulate filter to extend service life;

[0068] d) A third prior art valve block (ie without the groove 23) provided with a second advanced art anti-corrosion coating around the corresponding diffuser opening.

[0069] The following are the observations:

[0070] - The highest rate and extent of particle related erosion was observed in sample b (ie the first prior art valve block).

[0071] - The lowest particle related erosion rate and extent were observed in sample d (ie the third prior art valve block).

[0072] The rate and extent of particle related erosion observed in sample c and sample a are highly similar. Thus, due to the grooves 23, the fuel injector 1 according to the invention shows acceptable resistance to particle erosion, which is comparable to prior art fuel injectors with a coated prior art second valve block.

[0073] This favorable result indicates that the presence of the groove 23 (and possibly the presence of the truncated cone-shaped spacer 24 provided between the diffuser opening 21 and the groove 23) eliminates the costs associated with providing an anti-corrosion coating and achieves an acceptable degree of particle corrosion protection. It is conceivable that even with the use of a commonly used low-cost anti-corrosion coating, such as the coating used in sample c above, the degree of particle corrosion protection in the fuel injector 1 according to the present invention can be improved to a level that can only be provided by the advanced technology high-cost anti-corrosion coating used in sample d above. Therefore, the use of the fuel injector 1 and the valve block 2 can maximize the protection against particle corrosion without the need for expensive anti-corrosion coatings. Therefore, the present invention provides protection against particle erosion at the lowest production cost.

[0074] Thus, in a possible version of the method according to the invention, it may be included to provide one or more anti-erosion coatings on the groove 23 and / or the diffuser opening 21. Thus, in a possible embodiment of the fuel injector 1 according to the invention, the groove 23 and / or the diffuser opening 21 may be provided with one or more anti-corrosion coatings. For example, the one or more anti-corrosion coatings may comprise a material having a higher hardness, toughness or mechanical strength than the main body material 2 of the valve block.

[0075] Reference numerals list

[0076] 1 Fuel Injector

[0077] 2 Valve block

[0078] 3 Pressure relief chamber

[0079] 4 Control Room

[0080] 20 Seat area

[0081] 21 Diffuser opening

[0082] 22 Diffuser

[0083] 23 Grooves

[0084] 24 truncated cone shaped spacer

[0085] 30 Seals

[0086] 71 Guide

[0087] 72 Elastic device

[0088] 73 Coil

Claims

1. A fuel injector (1) comprising a valve block (2) for conditionally providing fluid flow communication between a pressure relief chamber (3) and a control chamber (4), The valve block (2) comprises a valve seat region (20) having a substantially truncated cone-shaped form facing the pressure relief chamber (3). The valve seat region (20) is arranged to receive a substantially spherical seal (30) and to support the seal (30) in a first position in which the seal (30) is in mechanical contact with the valve block (2). The valve block (2) further comprises a diffuser opening (21) for allowing fluid to flow through the diffuser (22) between the pressure relief chamber (3) and the control chamber (4) in a second position where the seal (30) deviates from the diffuser opening (21) to stop the mechanical contact; It is characterized in that The valve seat area (20) is arranged with a groove (23) in the form of a substantially spherical belt side surface around the diffuser opening (21), and the groove (23) is arranged to circumferentially cover and seal the outer surface of the seal (30) when the seal (30) is in the first position.

2. The fuel injector (1) according to claim 1, wherein: The groove (23) is arranged axially spaced apart from the diffuser opening (21) such that a truncated cone-shaped spacer (24) is provided between the diffuser opening (21) and the groove (23).

3. The fuel injector (1) according to claim 1 or 2, wherein: The diffuser opening (21) is in the form of a circumferential chamfer.

4. A method for obtaining a fuel injector (1), comprising a valve block (2) for conditionally providing fluid flow communication between a pressure relief chamber (3) and a control chamber (4), The valve block (2) comprises a valve seat region (20) having a substantially truncated cone-shaped form facing the pressure relief chamber (3). The valve seat region (20) is arranged to receive a substantially cylindrical seal (30) and to support the seal (30) in a first position in which the seal (30) is in mechanical contact with the valve block (2). The valve block (2) further comprises a diffuser opening (21) for allowing fluid to flow through the diffuser (22) between the pressure relief chamber (3) and the control chamber (4) in a second position where the seal (30) deviates from the diffuser opening (21) to stop the mechanical contact; It is characterized in that The method comprises forming a groove (23) on the valve seat area (20) around the diffuser opening (21), so that the groove (23) is generally in the form of a spherical belt with a lateral surface and is arranged to circumferentially cover the corresponding outer surface of the seal (30) when the seal (30) is in the first position.

5. The method according to claim 4, wherein: The method further comprises arranging the groove (23) to be axially spaced apart from the diffuser opening (21) such that a truncated cone-shaped spacer (24) is provided between the diffuser opening (21) and the groove (23).

6. The method according to claim 4 or 5, wherein: The method further comprises shaping the diffuser opening (21) so that a circumferential chamfer is formed at the diffuser opening (21).

7. A method according to any one of claims 4 to 6, wherein The formation of the groove (23) is achieved by embossing, which is applied to the valve seat area (20) in the axial direction towards the diffuser opening (21).

8. A fuel injector (1), comprising a valve block (2), the valve block (2) having a valve seat area (20) provided with a diffuser opening (21); wherein: The valve block (2) comprises a groove (23) around the diffuser opening (21), the groove (23) being roughly in the form of a spherical band side surface and arranged to be able to circumferentially cover the outer surface of the spherical seal (30) when the spherical seal (30) is in a sealing position; and the groove (23) is obtained by embossing, which is applied to the valve seat area (20) along the axial direction towards the diffuser opening (21).

Images