Fuel injection valve

Abstract

To provide a fuel injection valve that can suppress corrosion caused by attachment of water droplets (in particular, water droplets containing acid components) generated in a combustion chamber of an internal combustion engine for a long time.SOLUTION: A fuel injection valve for injecting a fuel into a combustion chamber of an internal combustion engine includes: a cylindrical part facing, across a gap, an inner peripheral surface of an insertion hole which is in communication with the combustion chamber; and a tapered part which is tapered from the cylindrical part and in which an injection hole is formed. The outer surfaces of the tapered part and the cylindrical part are water repellent regions formed by a plurality of recesses.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a fuel injection valve, and more particularly to a fuel injection valve that injects fuel into a combustion chamber of an internal combustion engine. [Background technology]

[0002] Internal combustion engines equipped with fuel injection valves that inject fuel into combustion chambers are known. When the internal combustion engine stops operating and the temperature of the combustion chamber drops, water vapor contained in the combustion gas condenses and forms droplets that adhere to the tip of the fuel injection valve and the inner wall surface of the combustion chamber. The droplets formed by condensation generally contain acidic components, such as nitrogen oxides and sulfide oxides, that were contained in the combustion gas. In particular, in internal combustion engines equipped with an EGR device, the combustion gas discharged from the combustion chamber is returned to the combustion chamber as EGR gas, resulting in an increase in the amount of acidic components contained in the droplets.

[0003] In order to prevent corrosion of fuel injection valves caused by the adhesion of water droplets containing acidic components (acidic water droplets), fuel injection valves plated with a corrosion-resistant material (e.g., chromium) have been proposed. Specifically, a plating layer is formed on the surface of the nozzle body (i.e., base material) constituting the fuel injection valve, which is exposed to the combustion chamber (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-163759 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the plating layer does not have a water-repellent effect, there is a high possibility that acidic water droplets will remain attached to the fuel injection valve. Therefore, if the fuel injection valve is used for a long period of time, the plating layer may be corroded by acidic water droplets. In addition, if the hardness of the plating layer is lower than that of the base material, the plating layer may be damaged by fine foreign matter that enters the combustion chamber during operation of the internal combustion engine, and the corrosion-suppressing effect may be reduced.

[0006] The present invention has been made in view of the above points, and has as its object to provide a fuel injection valve that can suppress corrosion caused by acidic water droplets for a long period of time. [Means for solving the problem]

[0007] In order to solve the above problems, a fuel injection valve according to a first aspect of the present invention is a fuel injection valve that injects fuel into a combustion chamber of an internal combustion engine, and has a cylindrical portion that faces an inner peripheral surface of an insertion hole that communicates with the combustion chamber with a gap therebetween, and a tapered portion that tapers from the cylindrical portion and has an injection hole formed therein, and the tapered portion and the outer surface of the cylindrical portion form a water-repellent area formed by a plurality of recesses.

[0008] A second aspect of the present invention is the fuel injection valve according to the first aspect, wherein the plurality of recesses include a longitudinal groove extending from the cylindrical portion to the tapered portion beyond the injection hole.

[0009] A third aspect of the present invention is the fuel injection valve according to the second aspect, wherein the plurality of recesses include branch grooves that are inclined vertically downward and communicate with the longitudinal groove.

[0010] A fourth aspect of the present invention is the fuel injection valve according to the first aspect, wherein the plurality of recesses include depressions arranged in a lattice pattern. [Effects of the Invention]

[0011] In the first aspect of the present invention, the water-repellent region is physically formed by the plurality of recesses, which makes it easier than ever to form a relatively wide area, including the cylindrical portion and the tapered portion, into a water-repellent region. Furthermore, the physically formed water-repellent region makes it more likely that the water-repellent effect will be maintained for a long period of time. Therefore, the first aspect of the present invention makes it more likely that corrosion caused by acidic water droplets can be suppressed over a relatively wide area for a long period of time.

[0012] In the second aspect of the present invention, the water-repellent region includes longitudinal grooves, which allow water droplets to easily flow along the longitudinal grooves. This facilitates the water droplets to reach the lower end of the fuel injection valve and further fall. Therefore, the second aspect of the present invention can further reduce the possibility of corrosion caused by acidic water droplets.

[0013] In the third aspect of the present invention, the water droplets that flow along the branch grooves reach the vertical grooves, where they grow into large droplets, which are then more likely to flow along the vertical grooves. Therefore, the third aspect of the present invention further promotes the water droplets to fall from the fuel injection valve.

[0014] The recesses arranged in a grid pattern in the fourth aspect of the invention can be formed by, for example, shot peening, which makes it even more likely that a relatively large area can be made water-repellent than before. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram of an internal combustion engine to which a fuel injection valve according to an embodiment is attached; [Figure 2] FIG. 2 is a schematic side view of the fuel injection valve. [Figure 3] 1 is a partial cross-sectional view of an internal combustion engine and a fuel injection valve. [Figure 4] 3 is a schematic side view showing a water-repellent region (longitudinal groove) formed on the fuel injection valve. FIG. [Figure 5] FIG. 2 is a schematic bottom view showing a water-repellent area of ​​the fuel injection valve. [Figure 6] FIG. [Figure 7] FIG. 10 is a schematic side view showing the water-repellent areas (longitudinal grooves and branch grooves) of the fuel injection valve according to the first modified example. [Figure 8] FIG. 10 is a schematic bottom view showing a water-repellent region of the fuel injection valve according to the first modified example. [Figure 9] FIG. 10 is a partial enlarged view of a water-repellent region according to a first modified example. [Figure 10] FIG. 10 is a partially enlarged view showing another aspect of the water-repellent region according to the first modified example. [Figure 11] FIG. 10 is a schematic side view showing the water-repellent areas (longitudinal grooves and branch grooves) of a fuel injection valve according to a second modified example. [Figure 12] FIG. 10 is a schematic bottom view showing a water-repellent region of a fuel injection valve according to a second modified example. [Figure 13] FIG. 10 is a partial enlarged view of a water-repellent region according to a second modified example. [Figure 14] FIG. 11 is a schematic side view showing the water-repellent region (recesses arranged in a grid pattern) of a fuel injection valve according to a third modified example. [Figure 15] FIG. 11 is a partial enlarged view of a water-repellent region according to a third modified example. DETAILED DESCRIPTION OF THE INVENTION

[0016] An embodiment of the present invention will be described with reference to Figures 1 to 6. The same symbols (reference numerals) in the description refer to the same elements having the same functions, even if they are not described repeatedly. Each figure has been simplified or modified to facilitate understanding of the shape, and the dimensional ratios and shapes of each part are not necessarily drawn accurately.

[0017] A fuel injection valve 1 according to this embodiment is mounted and operated in an internal combustion engine 2 shown in Fig. 1. The internal combustion engine 2 is mounted as a driving force source in a vehicle (not shown) (also referred to as an "mounted vehicle"). The internal combustion engine 2 is a compression ignition type multi-cylinder diesel engine.

[0018] Intake air is introduced into an engine body 21 (more specifically, a combustion chamber 22 shown in FIG. 3) of the internal combustion engine 2 via an intake pipe 31 and an intake manifold 32. The fuel injection valve 1 injects fuel into the combustion chamber 22 in response to an instruction (more specifically, an electric power supply) from an ECU 23 (electronic control unit). Combustion gas generated in the combustion chamber 22 is discharged via an exhaust manifold 33 and an exhaust pipe 34.

[0019] The EGR pipe 35 connects the exhaust pipe 34 and the intake pipe 31. Therefore, a portion of the combustion gas discharged from the combustion chamber 22 passes through the EGR pipe 35 and flows back into the combustion chamber 22. That is, the EGR gas is recirculated. An EGR valve 36 disposed in the EGR pipe 35 adjusts the opening of the EGR pipe 35 in accordance with instructions from the ECU 23. That is, the ECU 23 controls the EGR valve 36, thereby adjusting the amount of recirculated EGR gas.

[0020] 2, the fuel injection valve 1 includes a nozzle body 4, an injector body 51, a flow passage forming portion 52, a nozzle needle 53, and a retaining nut 54. The nozzle body 4 has a substantially cylindrical shape. A plurality of injection holes 41 are formed near the end of the nozzle body 4 (i.e., the tip of the fuel injection valve 1) (see FIG. 3).

[0021] More specifically, the nozzle body 4 includes a reduced diameter section 42, a cylindrical section 43, and a tapered section 44. The reduced diameter section 42 has an outer diameter that decreases toward the cylindrical section 43. The tapered section 44 has an outer diameter that decreases toward the tip. The tapered section 44 includes a conical section 44a having a substantially conical shape and a spherical section 44b having a substantially hemispherical shape. Each of the injection holes 41 is disposed in the spherical section 44b. The nozzle needle 53 is housed in a flow passage (see FIG. 3) formed in the nozzle body 4 and is a valve body that opens and closes the injection holes 41.

[0022] The retaining nut 54 has a generally cylindrical shape. A locking portion 54s, which is an annular flat surface formed by reducing the diameter of the inner circumferential surface, is provided near one end of the retaining nut 54 (specifically, the end portion on the tip side of the fuel injection valve 1). A female thread (not shown) is formed on the inner circumferential surface on the other end side of the retaining nut 54.

[0023] The nozzle body 4 is provided with a locking portion 4s, which is an annular flat surface formed by increasing the diameter of the outer circumferential surface, so as to face the locking portion 54s of the retaining nut 54. A male thread (not shown) that screws into the retaining nut 54 is formed on the outer circumferential surface near one end side of the injector body 51 (specifically, the tip side of the fuel injection valve 1).

[0024] The injector body 51 is screwed onto the retaining nut 54 with the locking portion 4s of the nozzle body 4 locked to the locking portion 54s and with the flow path forming portion 52 sandwiched between the nozzle body 4 and the injector body 51. Therefore, the injector body 51, the flow path forming portion 52, and the nozzle body 4 are held in a pressed state against each other. At this time, a fuel flow path (not shown) is formed from the injector body 51 through the flow path forming portion 52 to the injection hole 41 of the nozzle body 4.

[0025] High-pressure fuel is supplied to the injector body 51 from a common rail device (not shown). In addition, the injector body 51 incorporates an electromagnetic control valve (not shown) that operates in response to power supply. Furthermore, the nozzle body 4 incorporates a needle spring (not shown) that biases the nozzle needle 53 in a direction that closes the injection holes 41. Specifically, the biasing force of the needle spring causes one end of the nozzle needle 53 to abut against the inner surface of the tapered portion 44, and therefore each injection hole 41 is closed by the nozzle needle 53.

[0026] When the electromagnetic control valve of the injector body 51 is actuated, the nozzle hole 41 is opened. Specifically, the pressure on the other end side of the nozzle needle 53 in the flow passage formed in the nozzle body 4 (i.e., back pressure) changes due to the actuation of the electromagnetic control valve, so that the nozzle needle 53 moves within the flow passage and separates from the inner surface of the tapered portion 44 (see FIG. 3). That is, the nozzle hole 41 is opened, and as a result, fuel supplied from the common rail device is injected into the combustion chamber 22 through the nozzle hole 41.

[0027] The electromagnetic control valve of the injector body 51 is controlled by the ECU 23. That is, the ECU 23 controls the electromagnetic control valve of the injector body 51 to open and close the injection hole 41. In other words, the fuel injection valve 1 injects fuel into the combustion chamber 22 in response to an instruction from the ECU 23.

[0028] As shown in FIG. 3 , the fuel injection valve 1 is fixed in a state in which it is inserted into an insertion hole 21a formed in the engine body 21 (more specifically, the cylinder head of the engine body 21). The insertion hole 21a is a through-hole formed to mount the fuel injection valve 1 to the internal combustion engine 2 and communicates with the combustion chamber 22. At this time, the injection hole 41 is positioned within the combustion chamber 22. The axis L1 of the fuel injection valve 1 fixed to the engine body 21 extends in a substantially vertical direction. A gap C1 is formed between the inner circumferential surface of the insertion hole 21a and the outer circumferential surface of the cylindrical portion 43 of the fuel injection valve 1. In addition, a gap C2 is formed between the inner circumferential surface of the retaining nut 54 and the outer circumferential surfaces of the reduced diameter portion 42 and the cylindrical portion 43.

[0029] Incidentally, the combustion gas generated in the combustion chamber 22 during operation of the internal combustion engine 2 contains water vapor. When the temperature of the combustion gas remaining in the combustion chamber 22 drops after the operation of the internal combustion engine 2 is stopped, the water in the combustion gas condenses. The condensed water turns into water droplets and adheres to the inner wall surface of the combustion chamber 22 and the outer surface of the fuel injection valve 1 exposed to the combustion chamber 22. The adhered water droplets contain acidic components such as nitrogen oxides and sulfide oxides that were contained in the combustion gas.

[0030] If water droplets containing an acidic component (acidic water droplets) adhere to the outer surface of the fuel injector 1, corrosion of the outer peripheral surface of the fuel injector 1 will be accelerated. Therefore, fine water-repellent grooves (specifically, longitudinal grooves 61) are formed on the outer surface of the fuel injector 1 exposed to the combustion chamber 22. For convenience, the region of the fuel injector 1 where the water-repellent grooves are formed is also referred to as the "water-repellent region." Specifically, the water-repellent region is a region that extends on the outer peripheral surfaces of the reduced diameter portion 42, the cylindrical portion 43, and the tapered portion 44, and is shown as water-repellent region 4w in FIG. 3.

[0031] As shown in Figures 4 and 5, each of the longitudinal grooves 61 formed in the water-repellent region extends substantially in the direction of the axis L1 of the fuel injection valve 1. In other words, the longitudinal grooves 61 extend substantially vertically. In addition, a portion of the longitudinal grooves 61 extends beyond the injection hole 41 to the tip of the fuel injection valve 1. Note that the reference numerals of the longitudinal grooves 61 are omitted in Figure 5.

[0032] To facilitate understanding of the direction in which the longitudinal grooves 61 extend, the longitudinal grooves 61 are represented by solid lines (single lines) in Figures 4 to 5. The number of longitudinal grooves 61 formed in the actual water-repellent region is significantly greater than the number of longitudinal grooves 61 shown in Figures 4 to 5. The longitudinal grooves 61 in the fuel injector 1 (specifically, the nozzle body 4) are formed by, for example, irradiating them with a laser beam.

[0033] The longitudinal grooves 61 are arranged side by side and extend from the reduced diameter portion 42, through the cylindrical portion 43, to the tapered portion 44, beyond the injection hole 41. However, since the outer diameter of the fuel injection valve 1 decreases toward the tip of the fuel injection valve 1, the number of longitudinal grooves 61 decreases. In other words, some of the longitudinal grooves 61 end before reaching the tip of the fuel injection valve 1. In addition, the longitudinal grooves 61 may extend intermittently up to the vicinity of the tip of the fuel injection valve 1. In other words, the longitudinal grooves 61 do not have to be formed continuously.

[0034] As shown in Fig. 6, each of the longitudinal grooves 61 divides the water-repellent region into a recess 61a and a protrusion 61b. The recess 61a is the bottom surface of the longitudinal groove 61. It can be said that the water-repellent region of the fuel injection valve 1 is formed by the recess 61a extending substantially in the direction of the axis L1. The protrusion 61b is the region of the water-repellent region other than the longitudinal groove 61 (i.e., the recess 61a).

[0035] The width W1 of the vertical grooves 61 (i.e., the width of the recessed portions 61a) is, for example, in the range of 5 to 30 μm, and is, for example, 20 μm. The spacing S1 between the vertical grooves 61 (i.e., the width of the protruding portions 61b, and the length between two adjacent vertical grooves 61) is, for example, in the range of 20 to 30 μm, and is, for example, 20 μm. The depth D1 of the vertical grooves 61 is, for example, in the range of 5 to 30 μm, and is, for example, 10 μm.

[0036] In most cases, the diameter of a water droplet (i.e., an acidic water droplet) is larger than the sum of the width W1 and the spacing S1. Therefore, the water droplet adhering to the water-repellent area comes into contact with the multiple protrusions 61b. In other words, an air layer is formed between the water droplet and the recesses 61a.

[0037] It is known that on an uneven surface (i.e., the water-repellent region in this embodiment), the water repellency increases as the contact angle θr of the water droplet obtained based on the relationship shown in the following equation (1) (the so-called Cassie-Baxter equation) increases (where f1 + f2 = 1). cos(θr)=f1×cos(θ1)+f2×cos(θ2) ……(1)

[0038] In particular, when an air layer is formed between the water droplet and the recess 61a, the contact angle θr is obtained based on the relationship shown in the following formula (2). The value f1 in formula (2) becomes smaller as the interval S1 becomes smaller compared to the width W1 (i.e., the area of ​​the water droplet that contacts the air layer becomes larger and the area of ​​the water droplet that contacts the protrusion 61b becomes smaller). The angle θ1 is the actual contact angle of the attached water droplet. In other words, the width W1 and interval S1 related to the water-repellent area are adapted so that the value f1 in formula (2) becomes sufficiently small. cos(θr)=(f1-1)+f1×cos(θ1) ……(2)

[0039] That is, the water-repellent region has high water repellency due to its physical shape (i.e., the combination of the recessed portions 61a and the protruding portions 61b). Therefore, water droplets that adhere to the water-repellent region are easily slippery in the water-repellent region, and therefore are easily moved downward along the longitudinal grooves 61. In other words, in most cases, water droplets that adhere to the water-repellent region move downward along the longitudinal grooves 61 due to the action of gravity, reach the spherical portions 44b, and then fall. That is, the water droplets drip from the fuel injector 1 without remaining on the fuel injector 1.

[0040] (First Modification) The first modified example will be described with reference to Figures 7 to 10. The water-repellent area of ​​the fuel injection valve 1 described above has a longitudinal groove 61 formed therein. In contrast, the water-repellent area of ​​the fuel injection valve 1a (more specifically, the nozzle body 4a) of the first modified example has a longitudinal groove 62 and branch grooves 72 formed therein. This difference will be mainly described below. As shown in Figure 5, the axis L2 of the fuel injection valve 1a extends in a substantially vertical direction when mounted on an internal combustion engine 2 mounted on a vehicle, similar to the fuel injection valve 1.

[0041] 7 and 8, the reduced diameter portion 42, the cylindrical portion 43, and the conical portion 44a (i.e., the area other than the spherical portion 44b in the water-repellent area, also referred to as the "upper water-repellent area") of the fuel injector 1a are formed with longitudinal grooves 62. The longitudinal grooves 62 formed in the upper water-repellent area are similar to the longitudinal grooves 61 in the fuel injector 1, and therefore a description thereof will be omitted.

[0042] Meanwhile, the spherical portion 44b of the fuel injection valve 1a is formed with vertical grooves 62 extending between adjacent injection holes 41. In addition, branch grooves 72 are formed to extend toward one of the vertical grooves 62. More specifically, each of the branch grooves 72 is formed so as to slope vertically downward as it approaches the corresponding vertical groove 62. That is, each of the branch grooves 72 leads to the vertical groove 62 while sloping vertically downward. In other words, when water droplets move downward along the branch grooves 72, they reach the vertical groove 62. In many cases, water droplets that reach the vertical groove 62 move downward along the vertical groove 62 and fall.

[0043] 7 and 8, the longitudinal grooves 62 and branch grooves 72 are shown by solid lines to help understand the extending directions of the longitudinal grooves 62 and branch grooves 72. The number of longitudinal grooves 62 and branch grooves 72 formed in an actual water-repellent region (excluding the longitudinal grooves 62 in the spherical portion 44b) is greater than the longitudinal grooves 62 and branch grooves 72 shown in FIGS. 7 and 8. In FIG. 8, the reference numerals for the longitudinal grooves 62 and branch grooves 72 are omitted.

[0044] 9 is the bottom surface of the longitudinal groove 62. The recessed portion 72a is the bottom surface of the branch groove 72. In other words, the branch groove 72 is formed by the recessed portions 72a extending toward the recessed portion 62a. The surface of the water-repellent region other than the recessed portions 62a and 72a is the protruding portion 62b.

[0045] The width W2a of the longitudinal groove 62 in the spherical portion 44b is, for example, in the range of 15 to 30 μm, and is, for example, 20 μm. The width W2b of the branch groove 72 is, for example, in the range of 5 to 15 μm, and is, for example, 15 μm. The widths W2a and W2b may be equal to each other. The spacing S2b between the branch grooves 72 is, for example, in the range of 20 to 30 μm, and is, for example, 20 μm.

[0046] The depth D2a of the longitudinal groove 62 in the spherical portion 44b is, for example, in the range of 5 to 30 μm, and is, for example, 10 μm. The depth D2b of the branch groove 72 is, for example, in the range of 5 to 30 μm, and is, for example, 10 μm. If the depths D2a and D2b are equal to each other, the recesses 62a and 72a have continuous bottom surfaces. The depths D2a and D2b may be different from each other.

[0047] 10, each of the branch grooves 72 does not have to be connected continuously to the vertical groove 62. That is, a convex portion 62b may be formed between the end of the branch groove 72 and the vertical groove 62. In other words, the branch groove 72 may be connected indirectly to the vertical groove 62.

[0048] (Second Modification) The second modified example will be described with reference to Figures 11 to 13. The water-repellent region of the fuel injection valve 1a described above has a longitudinal groove 62 and a branch groove 72 formed therein. In contrast, the water-repellent region of the fuel injection valve 1b (more specifically, the nozzle body 4b) according to the second modified example has a longitudinal groove 63 and a branch groove 73 formed therein. This difference will be mainly described below. As shown in Figure 11, the axis L3 of the fuel injection valve 1b extends in a substantially vertical direction when mounted on an internal combustion engine 2 mounted on a vehicle, similar to the fuel injection valve 1. The upper water-repellent region of the fuel injection valve 1b has a longitudinal groove 63 formed therein, but because it is similar to the longitudinal groove 61 in the upper water-repellent region of the fuel injection valve 1, a description thereof will be omitted.

[0049] 11 to 13, a plurality of longitudinal grooves 62 are formed in the spherical portion 44b of the fuel injection valve 1b (unlike the first modified example) so as to extend between adjacent injection holes 41. In addition, a plurality of branch grooves 73 are formed in the spherical portion 44b so as to communicate with the longitudinal grooves 63. As in the first modified example, the branch grooves 73 may communicate indirectly with the longitudinal grooves 63. In FIG. 12, the reference numerals for the longitudinal grooves 63 and the branch grooves 73 are omitted.

[0050] The width W3a (see FIG. 13) of the longitudinal groove 63 in the spherical portion 44b falls within a range of, for example, 15 to 30 μm, and is, for example, 20 μm. The width W3b of the branch groove 73 falls within a range of, for example, 5 to 15 μm, and is, for example, 15 μm. The width W3a and the width W3b may be equal to each other.

[0051] The spacing S3a between the longitudinal grooves 63 in the spherical portion 44b is, for example, in the range of 20 to 30 μm, and is, for example, 20 μm. The spacing S3b between the branch grooves 73 is, for example, in the range of 20 to 30 μm, and is, for example, 20 μm. The spacing S3a and the spacing S3b may be different from each other.

[0052] The depth D3a of the vertical groove 63 in the spherical portion 44b is, for example, in the range of 5 to 30 μm, and is, for example, 10 μm. The depth D3b of the branch groove 73 is, for example, in the range of 5 to 30 μm, and is, for example, 10 μm. The depths D3a and D3b may be different from each other. Water droplets on the branch groove 73 formed in the spherical portion 44b move downward along the branch groove 73 and reach the vertical groove 63. In most cases, the water droplets that reach the vertical groove 63 move downward along the vertical groove 63 and fall.

[0053] (Third Modification) The third modified example will be described with reference to Figures 14 and 15. The water-repellent area of ​​the fuel injection valve 1 described above has longitudinal grooves 61 formed therein. In contrast, the water-repellent area of ​​the fuel injection valve 1c (more specifically, the nozzle body 4c) of the third modified example has a large number of recesses 64 arranged in a lattice pattern formed therein. That is, the water-repellent properties are improved by the recesses 64 (i.e., recesses) arranged in a lattice pattern. The following description will focus on this difference. As shown in Figure 14, the axis L4 of the fuel injection valve 1c extends in a substantially vertical direction when the fuel injection valve 1c is mounted on an internal combustion engine 2 mounted on a vehicle, just like the fuel injection valve 1.

[0054] Each of the recesses 64 has a hemispherical shape with a diameter R4 (see FIG. 15). The recesses 64 are formed, for example, by shot peening. The diameter R4 is, for example, in the range of 20 to 30 μm, and is, for example, 20 μm. The depth D4 of the recesses 64 is, for example, in the range of 10 to 15 μm, and is, for example, 10 μm. The spacing S4 between the recesses 64 is, for example, in the range of 10 to 30 μm, and is, for example, 15 μm.

[0055] As explained above, in the area of ​​the fuel injection valves 1 to 1c exposed to the combustion chamber 22 (i.e., the area in contact with the combustion gas), a water-repellent area is formed by a plurality of recesses (specifically, the longitudinal grooves 61 to 63, the branch grooves 72 to 73, and the depression 64), thereby improving water repellency. Therefore, even if water droplets (especially acidic water droplets) generated by condensation in the combustion chamber 22 adhere to the fuel injection valves 1 to 1c, the adhered water droplets become smaller and more slippery in the water-repellent area. In other words, the falling of the adhered water droplets is promoted.

[0056] As a result, corrosion caused by water droplets remaining on the fuel injection valves 1 to 1c is suppressed. In other words, the fuel injection valves 1 to 1c are likely to be able to suppress corrosion caused by acidic water droplets for a long period of time. In particular, in the internal combustion engine 2, the acidic components contained in the combustion gas increase due to the recirculation of EGR gas, but the fuel injection valves 1 to 1c including the water-repellent region can suitably suppress corrosion.

[0057] In addition, in the fuel injection valves 1 to 1c, the water-repellent region is physically formed by multiple recesses, which makes it more likely than ever before that a relatively wide region, including the cylindrical portion 43 and the tapered portion 44, can be made water-repellent. Furthermore, a physically realized water-repellent region is more likely to maintain its water-repellent effect over a long period of time. If a water-repellent region were to be realized by a chemical method (e.g., plating), it would be relatively difficult to uniformly process a wide region. Furthermore, if a water-repellent region were realized by a chemical method, the water-repellent properties would likely deteriorate over long-term use.

[0058] Furthermore, if reduced diameter section 42 is plated, there is a possibility that the plating will deteriorate at the point where it comes into contact with retaining nut 54 due to continuous contact with the material that constitutes retaining nut 54. Furthermore, if the physical strength of the plating is lower than that of the base material that constitutes nozzle body 4-4c, there is a possibility that the plating will be damaged by minute substances contained in the combustion gas, resulting in a decrease in water repellency.

[0059] Furthermore, in the fuel injection valves 1 to 1b, the vertical grooves 61 to 63 and the branch grooves 72 to 73 promote the vertical downward movement of water droplets on the nozzle body 4. That is, the fuel injection valves 1 to 1b more reliably reduce the time that water droplets adhere, thereby making it possible to suppress corrosion.

[0060] Additionally, in the fuel injection valves 1a-1b, there is a high possibility that water droplets that have flowed along the branch grooves 72-73 will reach the longitudinal grooves 62-63 and then flow further along the longitudinal grooves 62-63 to drip. Specifically, there is a high possibility that multiple water droplets that have flowed along the branch grooves 72-73 will become one large water droplet in the longitudinal groove 62-63 and drip quickly. Furthermore, because branch grooves 72-73 are formed near the injection hole 41 but the longitudinal grooves 62-63 are not formed, there is a low possibility that water droplets will be present near the injection hole 41. Therefore, there is a low possibility that impurities contained in the water droplets will accumulate near the injection hole 41.

[0061] On the other hand, in the fuel injection valve 1c, the water-repellent region is formed by the recesses 64, so it is highly likely that the water-repellent region can be easily expanded. Also, for example, if each of the recesses 64 is formed by shot peening, there is a possibility that corrosion resistance will be improved due to the modified coins generated on the outer surface of the nozzle body 4.

[0062] Although the embodiments of the present invention have been described above with reference to the above structures, many modifications, improvements, and variations are possible without departing from the scope of the present invention. Therefore, the present invention includes all modifications, improvements, and variations that do not depart from the spirit and scope of the appended claims. The present invention is not limited to the specific structures described above, and modifications such as those described below are possible.

[0063] The water-repellent region in the fuel injection valves 1 to 1c extends from the tapered portion 44 to the reduced diameter portion 42. Alternatively, the water-repellent region may be changed in accordance with the outer surface of the fuel injection valves 1 to 1c that is exposed to the combustion chamber 22. For example, if the upper region of the cylindrical portion 43 is covered without any gaps by the retaining nut 54, the water-repellent region may extend from the tapered portion 44 to the remaining region of the cylindrical portion 43.

[0064] When the fuel injection valves 1 to 1c are mounted on the internal combustion engine 2, the axes L1 to L4 extend in a substantially vertical direction. Alternatively, the fuel injection valves 1 to 1c may be mounted on the internal combustion engine in an inclined state (i.e., the axes L1 to L4 do not extend in the vertical direction but point vertically downward as they approach the tip of the fuel injection valves 1 to 1c). For example, the fuel injection valves 1 to 1c may be mounted on a V-type multi-cylinder engine (i.e., an internal combustion engine with a V-type bank). In this case, due to the inclination of the fuel injection valves 1 to 1c, a phenomenon may occur in which water droplets that have moved along the longitudinal grooves 61 to 63 and the branch grooves 72 to 73 move away from the tip of the fuel injection valves 1 to 1c. Even in such a case, the longitudinal grooves 61 to 63 and the branch grooves 72 to 73 can promote the falling of the water droplets. For example, when water droplets move from the tapered portion 44 toward the cylindrical portion 43 , the water droplets may fall at the boundary between the tapered portion 44 and the cylindrical portion 43 .

[0065] In the longitudinal grooves 61-63 and branch grooves 72-73 shown in Figures 6, 9-10, and 13, the side wall surfaces connecting the recessed portions and the protruding portions (for example, the side wall surfaces formed between the recessed portion 61a and the protruding portion 61b shown in Figure 6) are substantially perpendicular to the surfaces of the protruding portions. Alternatively, the side wall surfaces connecting the recessed portions and the protruding portions may be inclined with respect to the surfaces of the protruding portions. In other words, some or all of the longitudinal grooves 61-63 and the branch grooves 72-73 may have a tapered shape (or an inverse tapered shape).

[0066] The recesses 64 formed in the fuel injector 1c have a hemispherical shape. Alternatively, some or all of the recesses 64 may have a cylindrical shape. Alternatively, some or all of the recesses 64 may have a prismatic shape. Furthermore, the recesses 64 may be formed together with any one or more of the longitudinal grooves 61-63 and branch grooves 72-73 of the fuel injectors 1-1b. [Explanation of symbols]

[0067] 1~1c...Fuel injection valve 2...internal combustion engine, 21...engine body, 21a...insertion hole, 22...combustion chamber, 23...ECU 31...intake pipe, 32...intake manifold, 33...exhaust manifold, 34...exhaust pipe 35...EGR pipe, 36...EGR valve 4~4c...Nozzle body, 4s...Latching part, 4w...Water-repellent area 41... nozzle hole, 42... reduced diameter portion, 43... cylindrical portion 44...tapered portion, 44a...conical portion, 44b...spherical portion 51... injector body, 52... flow path forming portion, 53... nozzle needle 54...Retaining nut, 54s...Latching part 61...longitudinal groove, 61a...recess, 61b...projection 62...longitudinal groove, 62a...recess, 62b...projection 63...Vertical groove, 64...Dimple 72...branch groove, 72a...recess, 73...branch groove

Claims

1. A fuel injection valve that injects fuel into a combustion chamber of an internal combustion engine, a cylindrical portion facing an inner circumferential surface of the insertion hole communicating with the combustion chamber with a gap therebetween; a tapered portion tapered from the cylindrical portion and having an injection hole formed therein, The fuel injection valve, wherein the tapered portion and the outer surface of the cylindrical portion are water-repellent areas formed by a plurality of recesses.

2. 2. The fuel injection valve according to claim 1, The plurality of recesses include a longitudinal groove extending from the cylindrical portion to the tapered portion beyond the injection hole.

3. 3. A fuel injection valve according to claim 2, The plurality of recesses include branch grooves that are inclined vertically downward and communicate with the longitudinal groove.

4. 2. The fuel injection valve according to claim 1, The plurality of recesses include depressions arranged in a grid pattern.

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