FUEL INJECTOR ASSEMBLY AND COATING PROCESS FOR THE SAME

Abstract

Assembly for a fuel injector comprising the following parts: a base material (100) in which a coated surface and an uncoated surface are formed on the surface, and a coating material (200) laminated in a multi-layer structure on the coated surface, wherein the coating material (200) is a bonding layer (210) laminated onto the coating area (110) of the base material (100), a carrier layer (220) laminated to the outer surface of the bonding layer (210) and a SiO-DLC functional layer (230) laminated to the outer surface of the carrier layer (220), wherein the uncoated region (120) is supported in contact by a jig (300) and is formed separately from the coated region (110) to prevent the coated region (110) from exfoliating during laser welding.

Description

[Technical field of the invention]

[0001] The present invention relates to an assembly for a fuel injector and its coating method, specifically to an assembly for a fuel injector in which a coating material is laminated to reduce friction, increase coating hardness and increase durability, and to its coating method. [Technical background of the invention]

[0002] A vehicle's fuel injector is one of the key parts that serves to supply fuel to an engine in a timely manner according to the engine's stroke.

[0003] In this context, among the fuel injector assembly, a ball and a valve seat, especially as sliding parts, are miniaturized, but since they are subjected to even higher and repetitive loads and stresses, a phenomenon occurs in which the fatigue life is rapidly shortened due to thermal shock and abrasion.

[0004] As a method for improving the abrasion resistance of these sliding parts, there is a way to improve the abrasion resistance and heat resistance of the sliding parts by forming a bonding layer on the base material of the sliding parts and forming a support layer on the surface of the bonding layer, and forming a functional layer on the surface of the support layer.

[0005] Meanwhile, JP 1994-25826 A discloses a construction of a sliding member on which a Mo-based material is applied as a coating material.

[0006] JP 1994-25826 A discloses a physical vapor deposition of an ion plating method which, with respect to the deposition of a Mo-based material, forms a Mo film by depositing Mo ions on a base material which are evaporated using a high-energy beam.

[0007] However, only in the case of the deposition method disclosed in JP 1994-25826 A, non-uniformity of the deposited particles (ions) occurs, by a phenomenon that, in addition to Mo particles (ions) evaporated by a high-energy beam from the Mo target, non-ionic particles (ions) with a relatively large diameter are deposited together on the base material. As a result, there is a problem in that a phenomenon is very likely to occur in which a durability of the coating film is significantly reduced, by a phenomenon that the roughness of the coating film and the bonding strength on the base material are overall deteriorated. KR 10 2019 0 000 789 A discloses a ball and a valve seat for a fuel injection valve and a coating method therefor. DE 10 2013 211 049 A1 discloses a coating material for an intake / exhaust valve and a method for manufacturing the same.DE 10 2016 123 562 A1 discloses a method for treating a composite piston pin and a surface-treated composite piston pin. [Content of the invention][Object of the invention]

[0008] The present invention is made to solve the above-described problems of the prior art, and a purpose of the present invention is to provide an assembly for a fuel injector having improved friction reduction, high hardenability, impact resistance, heat resistance, and fatigue resistance by dividing a coated portion and an uncoated portion.

[0009] At the same time, another purpose of the present invention is to provide a coating method of the assembly for a fuel injector, thereby offering a precise coating on a required area of ​​a miniaturized assembly. [Technical solution]

[0010] In order to achieve the above-described purpose, the assembly for a fuel injector according to the present invention is characterized by comprising the following parts: a base material on the surface of which a coated surface and an uncoated surface are formed, and a coating material laminated in a multi-layer structure on the coated surface, the coating material thus comprising a bonding layer laminated on the coating region of the base material, a support layer laminated on the outer surface of the bonding layer, and an SiO-DLC functional layer laminated on the outer surface of the support layer, the uncoated region being supported in contact by a jig and being formed separately from the coated region to prevent the coated region from peeling off during laser welding.

[0011] In this case, the SiO-DLC functional layer can be laminated by a reactive sputtering process.

[0012] In this case, the SiO-DLC functional layer can be deposited by physical vapor deposition using solid graphite as the target material and simultaneously formed by injecting a hydrocarbon gas and a siloxane gas.

[0013] In this case, the bonding layer and the support layer can be laminated by physical vapor deposition.

[0014] Meanwhile, the carrier layer can be laminated using a reactive sputtering process.

[0015] In this case, the clamping device may comprise the following parts: a support part in which a spherical base material is contacted and supported at the end part of one side in the axial direction and is provided so as to form an uncoated area on the base material, and an attractive force generating part which is arranged on the other side in the axial direction of the support part and generates a magnetic force to set the base material aside.

[0016] In this case, the support member may include the following parts: a main body of the support member formed in a cylindrical shape with a predetermined thickness, and a cover surface formed at the end part of one side in the axial direction of the main body of the support member and concavely shaped to form an uncoated area on the base material by achieving surface contact with the base material.

[0017] Meanwhile, the support part may further comprise an extension surface formed radially extending from the cover surface to enlarge an area supporting the base material.

[0018] In this case, the attractive force generating part can be provided by inserting it at the other end part in the axial direction of the support part.

[0019] Meanwhile, the support part may have an outer diameter of more than 0.8 mm and a smaller diameter than the diameter of the base material.

[0020] At the same time, the support part may have a thickness of 0.2 mm or more and 1.0 mm or less.

[0021] Meanwhile, the present invention, as a coating method for laminating a multi-layer coating material onto the surface of a base material of a fuel injector, is characterized by comprising the following stages: a base material setting stage in which the base material is set on a jig to divide the base material into a coated portion and an uncoated portion; a bonding layer forming stage in which a bonding layer is laminated onto the outer peripheral surface of the base material; and a bonding layer forming stage in which the bonding layer is laminated onto the outer peripheral surface of the base material.a support layer formation phase in which a support layer is laminated on an outer surface of the bonding layer, and a functional layer formation phase in which an SiO-DLC functional layer is laminated and formed on the outer surface of the support layer by a reactive sputtering method, wherein in the base material setting phase, the base material is fixed by the magnetic force of the chuck;

[0022] In this case, in the formation phase of a functional layer, a SiO-DLC functional layer can be formed using solid graphite, a hydrocarbon gas and a siloxane gas (SilOxane gas).

[0023] At the same time, during the formation phase of a functional layer, it is possible to deposit a solid graphite as a target material in a PVD process and simultaneously inject a hydrocarbon gas and a siloxane gas as a reactive gas.

[0024] Meanwhile, in the formation phase of a bonding layer and in the formation phase of a support layer, the bonding layer and the support layer can be laminated by physical vapor deposition.

[0025] In addition, during the formation phase of a carrier layer, the carrier layer can be laminated by a reactive sputtering process.

[0026] In this case, in a state where after the setting-down phase of a base material, the base material is arranged inside the reaction chamber, the coating method may further include the following phases: a vacuum formation phase in which an inner atmosphere of the reaction chamber is maintained in a vacuum state, a plasma formation phase in which a plasma state where Ar ions are generated is formed by injecting Ar gas inside the reaction chamber and raising a temperature of the reaction chamber, and a cleaning phase in which a surface of the base material is cleaned by colliding Ar ions with the surface of the base material. [Advantageous effects of the invention]

[0027] According to the fuel injector assembly and its coating method according to the present invention, as described above, there is an effect that friction reduction, high hardenability, impact resistance, heat resistance and durability of the fuel injector assembly are improved and that required areas are precisely coated. [Brief description of the drawings]

[0028] They show: Fig. 1: a partially enlarged view of an assembly for a fuel injector according to an embodiment of the present invention. Fig. 2: a schematic view showing a cross section of an assembly for a fuel injector in which a deposited coating material according to an embodiment of the present invention is laminated. Fig.3: a scanning electron microscope (SEM) photograph of a coating material deposited according to an embodiment of the present invention. Fig. 4: A schematic view for explaining a method in which a base material is divided into a coated region and an uncoated region according to an embodiment of the present invention. Fig. 5: a schematic view of a clamping device for coating an assembly for a fuel injector according to an embodiment of the present invention. Fig. 6: a schematic view illustrating a coating process for a base material in which the base material is placed on a jig for coating an assembly for a fuel injector according to an embodiment of the present invention to be coated. Fig.7: a schematic view of a clamping device for coating an assembly for a fuel injector according to another embodiment of the present invention. Fig. 8: a schematic view of a clamping device for coating an assembly for a fuel injector according to yet another embodiment of the present invention. Fig. 9: a flowchart explaining a coating method of an assembly for a fuel injector according to an embodiment of the present invention. Fig. 10: A photograph in which a jig is applied for coating an assembly for a fuel injector according to an embodiment of the present invention. Fig. 11: a photograph of an assembly for a fuel injector to which a coating method according to an embodiment of the present invention is applied. [Embodiments of the invention]

[0029] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0030] The present invention is susceptible to various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. This is not intended to limit the present invention to specific embodiments, but should be construed to include all modifications, equivalents, and substitutes included within the spirit and scope of the present invention.

[0031] In describing the present invention, terms such as "first" and "second" may be used to describe various components, but the components may not be limited by the terms. The terms serve only to distinguish one component from other components. For example, the first component may be referred to as the second component without departing from the scope of the present invention, and similarly, the second component may be referred to as the first component.

[0032] The term “and / or” may include a combination of several related described items or one of several related described items.

[0033] When a component is described as "connected" or "joining" another component, it may be directly connected or joined to the other component, but other components may be present in the middle. On the other hand, when a component is described as "directly connected" or "joining" another component, it can be understood that no other component is present in the middle.

[0034] The terms used in this patent application are used only to describe specific embodiments and are not intended to limit the present invention. Singular terms may include plural terms unless the context clearly indicates otherwise.

[0035] In this patent application, terms such as "comprise" or "have" are intended to indicate the presence of features, numbers, steps, actions, components, parts or combinations thereof that are described in the specification with one or more other features, it being understood that the presence or addition of fields or numbers, steps, operations, components, parts or combinations thereof is not precluded.

[0036] Unless otherwise defined, all terms used herein, including technical or scientific terms, may have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention relates. Terms as defined in a commonly used dictionary may be interpreted to have meanings consistent with meanings in the context of related technologies, and they may not be interpreted as having ideal or overly formal meanings unless expressly defined in the present patent application.

[0037] At the same time, the following embodiments are provided to better explain to those of ordinary skill in the technical field to which the present invention belongs, and the shapes and sizes of the elements in the drawings may be exaggerated for clearer explanation.

[0038] Fig. 1 is a partially enlarged view of an assembly for a fuel injector according to (an embodiment of) the present invention.

[0039] With reference to Fig. 1, a fuel injector comprises the following parts: a housing, inside which a needle is received; a valve seat C formed at the bottom of the housing; and a ball A arranged between the valve seat C and the needle B. The valve seat (C) is provided with a valve seat surface on which the ball (A) fits snugly, and a nozzle is provided in the valve seat (C) which passes through in the fuel injection direction.

[0040] The needle (B) opens and closes the nozzle formed on the valve seat (C), while the ball (A) is moved in the vertical direction by the action of a solenoid and a return spring (not shown in drawings).

[0041] Although the ball (A) has a spherical shape in Fig. 1, the present invention is not limited thereto, and furthermore, valve bodies of various shapes are applicable without limitation, and all of them are considered to be within the scope of the present invention. For the sake of simplicity, it will be described below based on an embodiment of the ball (A) having a spherical shape.

[0042] Since fuel injectors, especially direct injection fuel injectors, inject fuel directly into the cylinder, balls (A) and valve seats (C) are exposed to high temperature and high pressure, and there is a high probability that a phenomenon such as nozzle clogging may occur due to combustion byproducts such as carbon monoxide and soot.

[0043] In this way, the ball (A) and the valve seat (C) are in a state of high temperature and high pressure, and since they are easily broken by generating frictional resistance largely due to combustion by-products, the present invention is designed so that the frictional resistance can be reduced, the fatigue strength can be increased and the heat resistance can be increased by, as in Fig. 2, a multi-layer coating material is laminated to the base material 100 of the ball (A) and the valve seat (C).

[0044] With reference to the Fig.2 to 4, an assembly for a fuel injector according to an embodiment of the present invention comprises the following parts: a base material 100 and a coating material 200, wherein the base material 100 comprises a coated region 110 and an uncoated region 120, and the coating material 200 comprises a bonding layer 210, a carrier layer 220 and a SiO-DLC functional layer 230.

[0045] At the same time, a base material 100 is divided into a coated area 110 on the surface of which a coating material 200 is laminated, and an uncoated area 120 on which the coating material is not laminated because the base material is in contact with a coating jig 300.

[0046] The structure and effect of this device 300 will be described with reference to Fig. 5 described later.

[0047] Meanwhile, in the present embodiment, although a base material 100 is formed in a spherical shape to be used for an injector ball, it is not limited thereto and includes all those formed in various shapes to be applicable to various assembly parts used for an injector valve seat and a high-pressure pump.

[0048] At the same time, in this embodiment, a coating material 200 is laminated in a multi-layer structure onto the surface of the base material 100 of a fuel injector assembly and includes the following layers: a bonding layer 210 laminated onto the surface of the coating portion 110; a support layer 220 laminated onto the outer surface of the bonding layer 210; and a SiO-DLC functional layer 230 laminated onto the outer surface of the support layer 220.

[0049] Meanwhile, although Cr is used as the material of the bonding layer 210 and CrN is used as the material of the support layer 220 in the present embodiment, it is not limited thereto, and it is possible to use Mo as the material of the bonding layer 210 and MoN as the material of the support layer 220, or to use Mo as the material of the bonding layer 210 and WC as the material of the support layer 220.

[0050] In this case, the bonding layer 210 and the carrier layer 220 are laminated by physical vapor deposition, preferably PVD (Physical Vapor Deposition), and the SiO-DLC functional layer 230 is laminated by a reactive sputtering process.

[0051] With reference to Fig. 11, detailed stages in which the bonding layer 210, the support layer 220 and the SiO-DLC functional layer 230 are laminated will be described later.

[0052] The bonding layer 210 performs the function of joining the base material 100 and the support layer 220 together, and may be formed with a thickness in the range of 0.01 to 0.5 µm, and is preferably 0.1 µm, but is not limited thereto.

[0053] When the thickness of a bonding layer 210 is less than 0.01 μm, the bonding strength is reduced and a problem may occur, resulting in deterioration of durability, and when the thickness of a bonding layer 210 exceeds 0.5 μm, a problem may occur that a coating time takes 5 hours or longer, and since a problem occurs in which the hardness balance is lost due to the thick film inside the coating material, a problem may occur that the durability is deteriorated (loss of 25% or more of the thickness).

[0054] A carrier layer 220 serves to support a bonding layer 210 and a SiO-DLC functional layer 230, and may be formed with a thickness in the range of 0.1 to 5 µm, preferably 0.5 µm, but is not limited to this.

[0055] When a thickness of the support layer 220 is less than 0.1 μm, the balance of interlayer hardness is lost due to a lack of thickness of the support layer, and there are problems that fatigue life is reduced due to a loss of the balance of interlayer hardness (loss of 20% or more in thickness), and a local thickness loss and wear trace (effect of abrasion origin) occur. Therefore, when a thickness of the support layer 220 exceeds 5 μm, the coating time increases (takes more than 5 hours), and since the SiO-DLC coating is adversely affected, resulting in a columnar structure (a crispy-brittle structure), a problem may arise that the residual stress in the layer increases.

[0056] The SiO-DLC functional layer 230 corresponds to the outermost layer of a coating material 200 according to the present invention and serves as a functional layer with low friction, abrasion resistance, and heat resistance.

[0057] A thickness of the SiO-DLC functional layer 230 is 0.1 to 10 µm, preferably 1.4 µm, but is not limited thereto.

[0058] When the thickness of the SiO-DLC functional layer 230 is less than 0.1 μm, there is a problem that the durability is reduced due to increased wear and friction coefficient due to insufficient thickness of the functional layer, and when it is more than 10 μm, there may be problems that an increase in coating time (takes more than 5 hours), an increase in cost, and an increase in residual stress in the layer.

[0059] The following is based on the Fig. 5 and Fig. 6 a clamping device 300 in the assembly for a fuel injector according to the present invention is described.

[0060] The clamping device 300 includes a support part 310, an attractive force generating part 320, and a plate 330. In addition, the support part 310 is combined with the plate 330 at a predetermined distance D, and the attractive force generating part 320 is combined with the support part 310.

[0061] The support part 310 is provided so that a base material 100 is transferred and coated in the chamber while the base material 100 is placed, and includes a main body of the support part 311 and a cover surface 312. At the same time, the main body of the support part 311 is formed in a cylindrical shape with a predetermined thickness (T), and the cover surface 312 is in contact with the base material 100 in that it is formed at an end part of one side in the axial direction of the main body of the support part 311 as the attractive force generation part 320 is combined with an end part of another side in the axial direction.

[0062] Meanwhile, in this embodiment, the support part 310 is provided with a thickness (T) of 0.2 mm or more and 1.0 mm or less, and a height (H) of 2 mm or more and 12 mm or less, and its width (W) is such that a diameter of the uncoated surface 120 is more than 0.8 mm, which is equal to or smaller than the diameter of the base material 100.

[0063] When the thickness (T) of the support part 310 is less than 0.2 mm, processing is difficult, and there is a problem that the coating material flows into the jig 300 due to excessive processing errors. When the thickness (T) is more than 1.0 mm, the flow space of the coating material is reduced, and as a result, the coating efficiency is reduced. When the height (H) of the support part 310 is less than 2 mm, the coating efficiency is reduced due to insufficient flow space of the coating material, and there is difficulty in removing the base material after coating. When the height (H) of the support part 310 is more than 12 mm, there is a problem that the fixing force on the base material 100 is reduced due to a distance from the attractive force generation part 320.When the width (W) of the support part 310 is provided so that a diameter of the uncoated region 120 is less than 0.8 mm, the uncoated region 120 is insufficient and, as a result, there is a problem that the coated region 110 is exfoliated during laser welding, and when a diameter of the uncoated region 120 exceeds the diameter of the base material 100, the uncoated region 120 is excessively widened, resulting in a problem that the fatigue strength and the heat resistance are reduced.

[0064] The cover surface 312 is formed at the end part of one side in the axial direction of the main body of the support member 311, and is concave in the radial direction to make surface contact with the base material 100. At the same time, when a concave curvature of the cover surface 312 is formed corresponding to the curvature of the base material 100, the contact area between the cover surface 312 and the base material 100 is increased, and consequently, the coating material is blocked from flowing into the jig 300.

[0065] Accordingly, in the support member 310, the base material 100 is seated in a cylindrical shape on the main body of the support member 311, and the uncoated portion 120 of the base material 100 is covered by the cover surface 312. As a result, when the base material 100 is coated by the jig 300 of the present invention while the base material 100 is set aside, the coating material is not deposited on the uncoated portion 120.

[0066] The attractive force generating part 320 is formed in a cylindrical shape and provided to be inserted into an end part of another side of the axial direction (an opposite direction of the cover surface) of the support part 310. That is, the attractive force generating part 320 is inserted into the hollow support part 310 of the cylindrical shape.

[0067] An attractive force generating part 320 acts to fix the base material 100 by generating a magnetic field. That is, the base material 100 made of a metal material is fixed to the support part 310 by the magnetic force generated by the attractive force generating part 320.

[0068] Meanwhile, as in the present embodiment, since the attractive force generating part 320 is inserted inside the support part, since the following effects may occur that the distance between the attractive force generating part 320 and the base material 100 is reduced and that the magnetic force is concentrated inside the support part 310 due to the cylindrical support part 310, it is possible to reduce the strength of the magnetic force generated by the attractive force generating part 320 to fix the base material 100. Accordingly, the attractive force generating part 320 can be miniaturized to the extent that it can be inserted into the support part 310.

[0069] With reference to the Fig. 5, Fig. 6 and Fig.10, the plate 330 is provided in a flat shape, and a plurality of support members 310 are combined with each other at a predetermined pitch (D). Furthermore, although in the present embodiment, the plurality of support members 310 are arranged at a pitch D of 5 mm or more and 15 mm or less, the present invention is not limited to this, and as long as a flow space of the coating material is sufficiently ensured, it can be changed according to the shape and size of the base material 100.

[0070] Meanwhile, in Fig.7 shows another embodiment of a clamping device in a fuel injector assembly according to the present invention. According to the present embodiment, the coating clamping device 1300 includes a support part 1310, an attractive force generating part 1320, and a plate 1330, wherein the support part 1310 includes a main body of the support part 1311, a cover surface 1312, and an extension surface 1313.

[0071] Meanwhile, the support part 1310, the attractive force generating part 1320, the plate 1330, the main body of the support part 1311, and the cover surface 1312 of the present embodiment have a structure and an action that are the same as those of the support part 310, the attractive force generating part 320, the plate 330, the main body of the support part 311, and the cover surface 312 according to an embodiment of the present invention, so a detailed description will be omitted.

[0072] In this embodiment, the extension surface 1313 is formed to extend radially from the cover surface 1312 and bears in contact with the base material 100.

[0073] Therefore, a trumpet-shaped support is formed by the cover surface 1312 and the extension surface 1313, and has a structure in which the base material 100 sits on the support, and as a result, there is an effect of increasing a support area of ​​the base material 100. At the same time, the extension surface 1313 can block the inflow of the coating material, thereby effectively preventing the coating material from flowing into the uncoated target area 120.

[0074] Meanwhile, in Fig.8 shows yet another embodiment of a clamping device in a fuel injector assembly according to the present invention. According to the present embodiment, the coating clamping device 2300 includes a support part 2310, an attractive force generating part 2320, and a plate 2330, wherein the support part 2310 includes a main body of the support part 2311, a cover surface 2312.

[0075] Meanwhile, the support part 2310, the attractive force generating part 2320, the plate 2330, the main body of the support part 2311, and the cover surface 2312 of the present embodiment have a structure and an action that are the same as those of the support part 310, the attractive force generating part 320, the plate 330, the main body of the support part 311, and the cover surface 312 according to an embodiment of the present invention, so a detailed description will be omitted.

[0076] In the present embodiment, the attractive force generating part 2320 is formed in a flat shape and combined with an end part of another side of the axial direction of the support part 2310. In this case, there is an advantage in that it is easy to replace and assemble the attractive force generating part 2320 according to a shape of the assembly part.

[0077] Hereinafter, a coating method of an assembly for a fuel injector according to the present invention will be described step by step with reference to Fig. 9 described.

[0078] The coating process of the fuel injector assembly includes a base material deposition phase (S10), a vacuum formation phase (S20), a plasma formation phase (S30), a cleaning phase (S40), a bonding layer formation phase (S50), a carrier layer formation phase (S60), and a functional layer formation phase (S70).

[0079] First, in the base material setting phase (S10), the base material 100 is set on the clamping device 300. At this time, since the clamping device 300 is provided with a magnet 120 (see Fig. 5), an attractive force is exerted by a magnetic field on the base material 100 formed of a metal material, so that the base material 100 is fixed to the jig 300. Accordingly, the base material is divided into a coated region 110 exposed to the outside and an uncoated region that is not exposed to the outside because it is covered by the jig 300. (S20)

[0080] In the vacuum formation phase (S20), the chuck 300 on which the base material 100 is placed is arranged inside a reaction chamber, and the internal atmosphere of the reaction chamber is formed and maintained in a vacuum state. (S20)

[0081] Next, Ar gas is supplied as a process gas in the plasma formation phase (S30), and by increasing the temperature using a thermostat, a plasma state is formed in which Ar ions are formed. (S30)

[0082] Preferably, the interior of the reaction chamber is maintained at 80°C using a thermostat.

[0083] Thereafter, in the cleaning phase (S40), a bias voltage is applied to the bias electrode 200, and by accelerating Ar ions to collide on the surface of a base material, a surface of the base material is cleaned. (S40)

[0084] This is to increase the adhesion strength between the coating material and the base material by preferably performing an etching process to remove the oxide layer and impurities naturally formed on the surface of the base material 100.

[0085] In this case, the bias voltage can be maintained in the range of 200 to 400 V. This is because the following problems may arise: when the bias voltage is less than 200 V, the acceleration voltage of Ar ions drops and the hardness of the coating material is reduced; and when the bias voltage exceeds 400 V, the lattice arrangement becomes irregular and the adhesion strength is deteriorated.

[0086] After the base material is cleaned with Ar ions (S40), a bonding layer formation phase (S50) proceeds, where the bonding layer 210 is formed by laminating Cr ions on the surface of the base material by physical vapor deposition, preferably the PVD method described above.

[0087] Meanwhile, in the bonding layer formation stage (S50) of the present embodiment, the bonding layer is formed by sputtering. That is, by injecting an inert gas in a vacuum state and applying and discharging a negative voltage to Cr (target), ionized Cr forms a thin film on the surface of the base material 100. At the same time, since the base material 100 is placed on the jig 300, the Cr bonding layer 20 is formed only on the surface of an externally exposed coated portion 110.

[0088] Meanwhile, in another embodiment different from the present embodiment, it is possible to deposit Cr ions by a reactive sputtering method in the formation stage of the bonding layer (S50) or to form the bonding layer using Mo ions.

[0089] Next, a carrier layer formation phase (S60) takes place, in which the carrier layer 220 is laminated by a physical vapor deposition method, preferably a PVD method, on the outer surface of the bonding layer 210 formed in a bonding layer formation phase (S50).

[0090] Specifically, in the support layer formation stage (S60), CrN particles are formed by reacting N ions separated from nitrogen (N2) gas injected as an active gas and Cr ions generated by the sputtering method in a state where the bonding layer 210 is laminated as in the bonding layer formation stage (S50), and a support layer 220 is formed by coating the CrN particles on the outer surface of the bonding layer 210.

[0091] Meanwhile, in another embodiment different from the present embodiment, it is possible to deposit CrN particles by reactive sputtering method in the formation stage of the support layer (S60), and it is also possible to form a support layer by depositing MoN particles by reaction of Mo ions and N.

[0092] Next, a functional layer formation phase (S70) proceeds in which the SiO-DLC functional layer 230 is laminated and formed on the outer surface of the carrier layer 220 by a reactive sputtering method.

[0093] In detail, in the formation stage of a functional layer (S70), a SiO-DLC functional layer 230 is formed under the temperature conditions of 100 degrees Celsius or more and 400 degrees Celsius or less such that, by performing a physical vapor deposition (PVD method) using solid graphite (C) as a target material, a hydrocarbon gas (C X H Y ) and a siloxane gas (SilOxane) are injected as reactive gas (process gas).

[0094] At the same time, when the processing temperature is below 100 degrees Celsius, the bonding strength of the functional layer decreases, resulting in a decrease in durability due to the lack of thickness and an increase in processing time. On the other hand, when the processing temperature exceeds 400 degrees Celsius, there is a possibility of internal stress and deformation due to the latent heat of the coating layer.

[0095] Meanwhile, in the present embodiment, methane (CH 4 ) or ethane (C 2 H 6 ) is typically used as a hydrocarbon gas, but is not limited to it, and HMDSO (HexaMethylDiSilOxane) or OMCTS (OctaMethylCycloTetraSiloxane) is typically used as a siloxane gas, but is limited to it.

[0096] A DLC layer deposits a coating film on the surface using a carbon-based gas while generating plasma in a vacuum state, forming a carbon film with a diamond-like structure on the surface.

[0097] Finally, when a clamping device 300 of the present invention, as shown in Fig.9, and a coating method for a fuel injector of the present invention is applied, it is possible that during the division into a coated area and an uncoated area, an assembly for a fuel injector (see Fig. 10) which leads to increased friction reduction, high hardenability, impact resistance, heat resistance and fatigue strength.

[0098] In a conventional fuel injector assembly, only the base material is removed to secure it and allow for coating inside the chamber. Therefore, the coating material is applied to the entire base material. In this case, when a fuel injector assembly is joined to other parts by laser welding, a peeling phenomenon occurs due to the laser in the coating area, and the overall performance of the fuel injector assembly is reduced in terms of friction reduction, high hardenability, impact resistance, heat resistance, and fatigue strength.

[0099] On the other hand, in the case of the fuel injector assembly to which a jig 300 of the present invention is applied, an uncoated portion where laser welding is to be performed is formed, no peeling phenomenon occurs even if laser welding is performed, and the friction reduction, high hardenability, impact resistance, heat resistance, and fatigue strength of a fuel injector assembly can be maintained.

[0100] Hereinafter, the working examples prepared by applying a coating method of the present invention and the comparative examples prepared according to the prior art will be described, and the results of evaluation comparison of durability and evaluation comparison of physical properties will be described. Examples of implementation

[0101] First, the spherical base material 100 is placed on the support part 310 of the chuck, and a plasma state is generated inside a reaction chamber in a vacuum state using an Ar gas. After the inside of a reaction chamber is heated to 80 °C and the surface of a base material 100 made of SUS440C stainless steel is activated, the surface of the base material is cleaned by applying a bias voltage of 300 V to cause Ar ions to collide with the surface.

[0102] Thereafter, Cr ions evaporated by PVD process are laminated on the surface of the base material as a Mo bonding layer 210 with a thickness of 0.01µm.

[0103] And by N 2 as a process gas injected into the interior of the reaction chamber to react with Cr ions evaporated from the Cr target, a carrier layer 220 of the CrN component with a thickness of 0.5µm is coated

[0104] Thereafter, a SiO-DLC functional layer 230 is formed by depositing a solid graphite as a target by a PVD method and simultaneously injecting hydrocarbon gas and HMDSO gas into the reaction chamber. Comparison example 1

[0105] Different from the embodiment according to the present invention, it is characterized in that the coating material is not formed on the base material. The base material is made of SUS440C stainless steel in the same manner as in the embodiment. Comparison example 2

[0106] Here, a jig for coating an assembly for a fuel injector according to an embodiment of the present invention is used; a coating material is formed on a SUS440C stainless base material with the same thickness as in the embodiment; a Cr bonding layer is formed on the surface of the base material by a PVD method, and a CrN support layer is formed on the outer peripheral surface of the Cr bonding layer by a PVD method, and then an SiO-DLC functional layer is formed on the surface of the CrN support layer by a PACVD method. Comparison example 3

[0107] Here, a jig for coating an assembly for a fuel injector according to an embodiment of the present invention is used; a coating material is formed on a SUS440C stainless base material with the same thickness as in the embodiment; a Cr bonding layer is formed on the surface of the base material by a PVD method, and a CrN support layer is formed on the outer peripheral surface of the Cr bonding layer by a PVD method, and then an SiO-DLC functional layer is formed on the surface of the CrN support layer by a PVD method. Comparison example 4

[0108] Here, a jig for coating an assembly for a fuel injector according to an embodiment of the present invention is not used; in a state where a base material is simply set aside, a coating material having the same thickness as in the embodiment is formed on a SUS440C stainless base material; a Cr bonding layer is formed on the surface of the base material by a PVD method, and a CrN support layer is formed on the outer peripheral surface of the Cr bonding layer by a PVD method, and then an SiO-DLC functional layer is formed on the surface of the CrN support layer by a sputtering method. Experiment to evaluate durability performance

[0109] To further evaluate the durability performance, a dry-run test was conducted. The durability test was an experiment to evaluate the durability of each coating material in a short period of time, and was conducted in the same manner under the following test conditions for Working Examples and Comparative Examples 1 to 3.

[0110] A test gas was air or nitrogen; a supply pressure was 5 bar; a test temperature was conducted at room temperature; PHID (Peak & Hold, 1.2A & 0.6A current control method) was used as a driving stage; a supply voltage was 14.0 V; a pulse interval (period) was 5.0 ms; a pulse width was 2.5 ms, and an operation time was more than 30 minutes.

[0111] As an assessment criterion, it was visually checked whether there was any damage such as peeling of the surface of the coating material and the coating thickness was evaluated.

[0112] For a coating thickness, the average value of the two points at 0° and 180° on the product and the thickness deviation of the two points on the coating material were measured. The thickness was measured using a Calo tester. [Table 1] Classification Embodiment Example for comparison 1 Example for comparison 2 Example for comparison 3 Example for comparison 3 Cr / CrN / SiO-DLC SUS440C Cr / CrN / SiO-DLC Cr / CrN / SiO-DLC Cr / CrN / SiO-DLC Thickness (µm) 2.0 - 2.0 1.0 0.9 Coating time <6h - <6h <6h <6h Coating process PVD & Reactive Sputtering - PVD & PACVD PVD & PVD PVD & Reactive Sputtering clamping device Use - Use Use Do not use of the present invention Evaluation of durability performance (dry-run test) Thickness: 7% loss Visual wear: no Wear mark: large Thickness: 25% loss Visual wear: yes Thickness: 21% loss Visual wear: yes Thickness: 32% loss Visual wear: yes

[0113] According to the above Table 1 in the test results of durability performance, it is confirmed that the fuel injector assembly according to the embodiment of the present invention lost 7% of the thickness of the coating material and no wear traces are found.

[0114] On the other hand, it is confirmed that in the case of Comparative Example 2, the thickness of a coating material loses about 25% and some wear traces are found.

[0115] At the same time, it is confirmed that in the case of Comparative Example 3, the thickness of the coating material loses about 21% and some wear traces are found.

[0116] At the same time, it is confirmed that in the case of Comparative Example 4, the thickness of the coating material loses about 32% and some wear traces are found.

[0117] As a result of testing the durability performance of the fuel injector assembly, the embodiment is confirmed to have a very low loss rate of the coating material and very excellent durability performance compared with the comparative examples. Assessment of physical properties

[0118] To evaluate the physical properties of the coating material, a physical properties evaluation was conducted.

[0119] To derive the friction coefficient, a disk-on-disk experiment was conducted using 10 N, 0.1 m / s, 2 km and SUS440C pin.

[0120] A micro-indenter (0.05 N, 0.7 µm penetration depth) was used to measure the hardness.

[0121] A scratch tester and a Rockwell C tester (HF1: high bond strength, HF5: low bond strength) were used to measure the bond strength. [Table 2] Classification Embodiments Example for comparison 1 Example for comparison 2 Example for comparison 3 Example for comparison 4 Cr / CrN / SiO-DLC SUS440C (no coating) Cr / CrN / SiO-DLC Cr / CrN / SiO-DLC Cr / CrN / SiO-DLC Hardness (HV) 2538 (24.1 GPa) 772 (7.32 GPa) 885 (8.4 GPa) 1864 (17.7 GPa) 1074 (10.2 GPa) Heat-resistant 400°C - 400°C 400°C 400°C temperature Roughness Ra (µm) 0.0332 0.2 0.0331 0.039 0.0358 Dry friction coefficient 0.10 0.45 0.12 0.13 0.11 Friction coefficient with oil 0.05 0.22 0.06 0.07 0.06 Adhesive strength HF 1 HF1-2 HF1-2 HF1-3 37 N 31 N 33 N 27 N

[0122] As shown in Table 2, the embodiment of the present invention is confirmed to have superior hardness values ​​compared to the comparative examples, and also the friction coefficient is measured to be relatively low, thereby reducing the frictional resistance.

[0123] At the same time, the adhesive strength of the coating material according to the embodiment of the present invention is 37 N, which is evaluated to be superior to the adhesive strength of other comparative examples, particularly compared to Comparative Example 3 of 33, and this is analyzed because the surface roughness of the embodiment deposited according to the reactive sputtering deposition method of the present patent can be obtained very low.

[0124] In addition, it can be evaluated that the adhesive strength of the present embodiment is very good compared with Comparative Example 4 of the adhesive strength of 27 N, and this is analyzed to increase the coating efficiency using the coating jig of the present patent.

[0125] Although the present invention will be described in detail by specific embodiments, this is for the purpose of describing the present invention in detail, to which the present invention is not limited, and it is understood that the present invention can be modified or improved by those of ordinary skill in the art within the technical spirit of the present invention. All simple modifications or variations of the present invention are within the scope of the present invention, and the specific scope of the present invention is clarified by the appended claims.

Claims

[1] Assembly for a fuel injector comprising the following parts: a base material (100) in which a coated surface and an uncoated surface are formed on the surface, and a coating material (200) laminated in a multi-layer structure on the coated surface, wherein the coating material (200) is a bonding layer (210) laminated onto the coating area (110) of the base material (100), a carrier layer (220) laminated to the outer surface of the bonding layer (210) and a SiO-DLC functional layer (230) laminated to the outer surface of the carrier layer (220), wherein the uncoated region (120) is supported in contact by a jig (300) and is formed separately from the coated region (110) to prevent the coated region (110) from exfoliating during laser welding. [2] Fuel injector assembly according to claim 1, characterized by that the SiO-DLC functional layer (230) is laminated by a reactive sputtering process. [3] Assembly for a fuel injector according to claim 2, characterized by that the SiO-DLC functional layer (230) is deposited by physical vapor deposition using solid graphite as a target material and simultaneously formed by injecting a hydrocarbon gas and a siloxane gas. [4] Fuel injector assembly according to claim 1, characterized by that the bonding layer (210) and the carrier layer (220) are laminated by physical vapor deposition. [5] Fuel injector assembly according to claim 1, characterized by that the clamping device (300) comprises the following parts: a support part (310) in which a spherical base material (100) is contacted and supported at the end part of one side in the axial direction and is provided so as to form an uncoated area (110) on the base material (100), and an attraction force generating part (320) arranged on the other side in the axial direction of the support part (310) and generating a magnetic force to set the base material (100) aside. [6] Fuel injector assembly according to claim 5, characterized by that the support part (310) comprises the following parts: a main body of the support member (310) formed in a cylindrical shape with a predetermined thickness, and a cover surface (312) formed at the end part of one side in the axial direction of the main body of the support part (310) and concavely shaped to form an uncoated area (110) on the base material (100) by achieving surface contact with the base material (100). [7] Assembly for a fuel injector according to claim 6, characterized by that the support part (310) further comprises an extension surface which is formed to extend radially from the cover surface (312) in order to enlarge an area which supports the base material (100). [8] Fuel injector assembly according to claim 5, characterized by that the attraction force generating part (320) is provided so that it is inserted into the interior of the support part (310). [9] Assembly for a fuel injector according to claim 5, characterized bythat the support part (310) has an outer diameter of more than 0.8 mm and a smaller diameter than the diameter of the base material (100). [10] Fuel injector assembly according to claim 5, characterized by that the support part (310) has a thickness of 0.2 mm or more and 1.0 mm or less. [11] A coating method for a fuel injector, comprising the steps of laminating a multilayer coating material (200) onto the surface of a base material (100) of a fuel injector assembly, the method comprising the following steps: a base material (100) setting-down phase in which the base material (100) is set down on a clamping device (300) in order to divide the base material (100) into a coated region (120) and an uncoated region (110); a bonding layer (210) forming step in which a bonding layer (210) is laminated onto the outer peripheral surface of the base material (100); a carrier layer (220) formation phase in which a carrier layer (220) is laminated on an outer surface of the bonding layer (210), and a functional layer formation phase in which a SiO-DLC functional layer (230) is laminated and formed on the outer surface of the carrier layer (220) by a reactive sputtering method, wherein in the base material (100) setting phase, the base material (100) is fixed by the magnetic force of the chuck (300). [12] Coating method for a fuel injector according to claim 11, characterized by that in the formation phase of a functional layer, the SiO-DLC functional layer (230) is laminated by a reactive sputtering process. [13] Coating method for a fuel injector according to claim 12, characterized bythat in the formation phase of a functional layer, a SiO-DLC functional layer (230) is formed using solid graphite, a hydrocarbon gas and a siloxane gas (SilOxane gas). [14] Coating method for a fuel injector according to claim 13, characterized by that in the formation phase of a functional layer it is possible to deposit a solid graphite as a target material in a PVD process and simultaneously inject a hydrocarbon gas and a siloxane gas as a reactive gas. [15] Coating method for a fuel injector according to claim 12, characterized by that in the formation phase of a bonding layer (210) and in the formation phase of a carrier layer (220), the bonding layer (210) and the carrier layer (220) are laminated by physical vapor deposition. [16] Coating method for a fuel injector according to claim 11, characterized bythat in a state where, after the set-down phase of a base material (100), the base material (100) is arranged inside the reaction chamber, it still comprises the following phases: a vacuum formation phase in which an internal atmosphere of the reaction chamber is maintained in a vacuum state, a plasma formation phase in which a plasma state where Ar ions are generated is formed by injecting Ar gas inside the reaction chamber and increasing a temperature of the reaction chamber, and a cleaning phase in which a surface of the base material (100) is cleaned by colliding Ar ions with the surface of the base material (100).

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