Fuel injection valve and marine internal combustion engine

Abstract

To improve durability of a fuel injection valve.SOLUTION: A fuel injection valve 3 has a needle valve 34 stored in a nozzle body 30. The nozzle body 30 has first and second inner wall sections 31b and 32a which store the needle valve 34, and a first seal section 32b which is a conical tip section of the second inner wall section 32a with a diameter thereof reduced in a tapered shape. The needle valve 34 has, in the order from a base side to a tip side, a sliding section 34a brought into contact with the first inner wall section 31b, a non-sliding section 34c arranged opposite to the second inner wall section 32a with a gap in between, and a second seal section 34d which is a conical tip section of the non-sliding section 34c in the tapered shape with a diameter reduction rate smaller than that of the first seal section 32b and is brought into contact with the first seal section 32b. The non-sliding section 34c has a groove section 34e formed in a manner that cut an external surface along a circumferential direction. The groove section 34e is arranged closer to the second seal section 34d than the sliding section 34a in an axial direction of the needle valve 34.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a fuel injection valve and a marine internal combustion engine including the fuel injection valve. [Background technology]

[0002] For example, Patent Document 1 discloses a fuel injection valve having a nozzle body that houses a needle valve. Specifically, the nozzle body disclosed in Patent Document 1 has a conical first seal portion (first seal surface) at its tip, while the needle valve disclosed in the same document has a conical second seal portion (second seal surface) at its tip. According to Patent Document 1, the flow of fuel can be controlled by moving the first seal portion and the second seal portion closer to and farther from each other. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-32696 Summary of the Invention [Problem to be solved by the invention]

[0004] In a typical fuel injection valve, the outer peripheral surface of the second seal portion as described in Patent Document 1 is gently inclined compared to the inner peripheral surface of the first seal portion. When the inclination angles are different in this way, the first seal portion and the second seal portion usually have line contact (per line) rather than surface contact. In this case, a specific portion of the second seal portion comes into concentrated contact with the first seal portion.

[0005] Therefore, if the contact pressure between the first seal portion and the second seal portion (particularly the maximum value of the contact pressure) becomes excessively high, the contact area (edge) may become worn or worn, potentially causing an irreversible change from the line contact to surface contact described above. If the contact changes to surface contact, the contact area becomes larger, causing a constant decrease in contact pressure, leading to problems such as a permanent decrease in valve opening pressure and worsening fuel injection cutoff. This is inconvenient in terms of improving the durability and extending the life of the fuel injection valve.

[0006] The technology disclosed herein has been developed in consideration of these points, and its purpose is to improve the durability of a fuel injection valve when the inclination angles of the first seal portion on the nozzle body side and the second seal portion on the needle valve side are made different. [Means for solving the problem]

[0007] A first aspect of the present disclosure relates to a fuel injection valve having a nozzle body that houses a needle valve and that injects fuel from a tip thereof by opening the needle valve against a spring force. In this fuel injection valve, the nozzle body has an inner wall that defines a space for housing the needle valve and a conical first seal formed by tapering the tip of the inner wall. The needle valve has, in order from the base end to the tip end, a sliding part that contacts the inner wall part internally, a non-sliding part that extends in the axial direction of the needle valve and faces the inner wall part with a gap therebetween, and a conical second seal part that has a tip end of the non-sliding part that tapers more gradually in diameter than the first seal part and abuts against the first seal part. A groove is formed in the outer surface of the non-sliding part along the circumferential direction of the non-sliding part.

[0008] According to the first aspect, the groove is disposed closer to the second seal portion than the sliding portion in the axial direction of the needle valve.

[0009] The inventors of the present application considered providing a groove portion in the non-sliding portion to reduce the rigidity near the second seal portion and prevent the contact surface pressure between the first seal portion and the second seal portion from becoming excessively high.

[0010] However, depending on the location of the groove, there is a possibility that the rigidity in the vicinity of the second seal portion may not be reduced satisfactorily. Therefore, as in the first embodiment, instead of simply providing a groove, the groove is positioned relatively close to the second seal portion, thereby making it possible to effectively reduce the rigidity in the vicinity of the second seal portion.

[0011] Furthermore, when the groove is placed close to the second seal, the groove is positioned at the tip of the non-sliding portion that extends axially. By positioning the groove at the tip of the non-sliding portion, the groove and the area near the second seal can move flexibly in the radial direction, etc.

[0012] In this way, by effectively reducing the rigidity near the second seal portion and by configuring the area near that portion to be flexible and movable, the first seal portion and the second seal portion can be brought into uniform contact with each other in the circumferential direction, which effectively prevents the contact pressure between the first seal portion and the second seal portion from becoming excessively high, thereby improving the durability of the fuel injection valve.

[0013] According to the second aspect of the present disclosure, the depth of the groove in the radial direction of the needle valve may be greater than the distance between the groove and the second seal portion in the axial direction of the needle valve.

[0014] As a result of extensive research, the inventors of the present application have discovered that setting the depth of the groove portion to be greater than the distance between the groove portion and the second seal portion, as in the second embodiment, is advantageous in effectively suppressing the contact surface pressure between the first seal portion and the second seal portion.

[0015] Furthermore, according to a third aspect of the present disclosure, the groove portion may have an arc-shaped longitudinal cross section when viewed from a direction perpendicular to the central axis of the needle valve, and the depth of the groove portion in the radial direction of the needle valve may be greater than the radius of the longitudinal cross section.

[0016] As a result of extensive research, the inventors of the present application have discovered that forming the groove portion to have an arc-shaped cross section and setting the depth of the groove portion to be greater than the radius of the arc, as in the third embodiment, is advantageous in effectively suppressing the contact surface pressure between the first seal portion and the second seal portion.

[0017] A fourth aspect of the present disclosure relates to a marine internal combustion engine including the fuel injection valve. [Effects of the Invention]

[0018] As described above, according to the present disclosure, the durability of the fuel injection valve can be improved. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram illustrating the configuration of a marine internal combustion engine. [Figure 2] FIG. 2 is a vertical cross-sectional view illustrating the structure of the fuel injection valve. [Figure 3] FIG. 3 is a diagram illustrating the structure of the needle valve. [Figure 4] FIG. 4 is an enlarged longitudinal sectional view illustrating the tip of the fuel injection valve. [Figure 5] FIG. 5 is a graph showing the performance of an embodiment of the fuel injector. [Figure 6] FIG. 6 is a view corresponding to FIG. 2 showing a conventional fuel injection valve. [Figure 7A] FIG. 7A is a vertical cross-sectional view showing an example of a groove portion. [Figure 7B] FIG. 7B is a vertical cross-sectional view showing another example of the groove. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Note that the following description is an example. Figure 1 is a schematic diagram illustrating the configuration of a marine internal combustion engine (hereinafter also simply referred to as "engine 1").

[0021] The engine 1 is an in-line multi-cylinder diesel engine equipped with multiple cylinders 16. The engine 1 is configured as a uniflow scavenging two-stroke one-cycle engine, and is installed on large ships such as tankers, container ships, and car carriers.

[0022] An engine 1 mounted on a ship is used as the main engine for propelling the ship. To this end, the output shaft of the engine 1 is connected to a propeller (not shown) of the ship via a propeller shaft (not shown). When the engine 1 operates, its output is transmitted to the propeller, propelling the ship.

[0023] In particular, the engine 1 according to the present disclosure is configured as a so-called crosshead type internal combustion engine in order to achieve a long stroke. That is, in this engine 1, a piston rod 22 that supports a piston 21 from below and a connecting rod 24 that is connected to a crankshaft 23 are connected by a crosshead 25.

[0024] (1)Main configuration The main parts of the engine 1 will be described below.

[0025] As shown in Fig. 1, engine 1 includes a bed plate 11 located below, a frame 12 provided on bed plate 11, and a cylinder jacket 13 provided on frame 12. Bed plate 11, frame 12, and cylinder jacket 13 are fastened together by a plurality of tie bolts and nuts extending in the vertical direction. Engine 1 also includes a cylinder 16 provided within cylinder jacket 13, a piston 21 provided within cylinder 16, and an output shaft (e.g., crankshaft 23) that rotates in conjunction with the reciprocating movement of piston 21.

[0026] The base plate 11 constitutes the crankcase of the engine 1 and houses a crankshaft 23 and a bearing 26 that rotatably supports the crankshaft 23. The lower end of a connecting rod 24 is connected to the crankshaft 23 via a crank 27.

[0027] The frame 12 houses a pair of guide plates 28, the connecting rod 24, and a crosshead 25. Of these, the pair of guide plates 28 are made of a pair of plate-shaped members provided along the piston axial direction, and are arranged at a distance from each other in the width direction of the engine 1 (the left-right direction on the paper surface of FIG. 1). The connecting rod 24 is arranged between the pair of guide plates 28, with its lower end connected to the crankshaft 23. The upper end of the connecting rod 24 is connected to the lower end of the piston rod 22 via the crosshead 25.

[0028] Specifically, the crosshead 25 is disposed between a pair of guide plates 28 and slides up and down along each of the guide plates 28. That is, the pair of guide plates 28 are configured to guide the sliding of the crosshead 25. The crosshead 25 is connected to the piston rod 22 and the connecting rod 24 via a crosshead pin 29. The crosshead pin 29 is connected to the piston rod 22 so as to move up and down integrally therewith, and is connected to the connecting rod 24 so as to rotate the connecting rod 24 around the upper end of the connecting rod 24 as a fulcrum.

[0029] The cylinder jacket 13 supports a cylinder liner 14 as an inner cylinder. The cylinder liner 14 is formed in a cylindrical shape and is inserted into the cylinder jacket 13. The internal space of the cylinder jacket 13 is connected to the internal space of the cylinder liner 14. The piston 21 described above is disposed inside the cylinder liner 14. This piston 21 moves back and forth in the vertical direction along the inner wall of the cylinder liner 14. A cylinder cover 15 is fixed to the top of the cylinder liner 14. The cylinder cover 15, together with the cylinder liner 14, constitutes a cylinder 16.

[0030] The cylinder cover 15 is also provided with an exhaust valve 18 that is operated by a valve train (not shown). The exhaust valve 18, together with a cylinder 16 formed by the cylinder liner 14 and the cylinder cover 15 and the top surface of the piston 21, defines a combustion chamber 17. The exhaust valve 18 opens and closes the communication between the combustion chamber 17 and an exhaust pipe 19. The exhaust pipe 19 has an exhaust port that communicates with the combustion chamber 17, and the exhaust valve 18 is configured to open and close the exhaust port.

[0031] Furthermore, the cylinder cover 15 is provided with a fuel injection valve 3 for supplying fuel to the combustion chamber 17. The fuel injection valve 3 injects diesel fuel into the combustion chamber 17.

[0032] Furthermore, the engine 1 according to this embodiment is equipped with a fuel pump 39 that pressure-feeds diesel fuel to the fuel injection valve 3. As shown in Fig. 1, the fuel pump 39 is laid out near the cylinder 16 and is fluidly connected to the fuel injection valve 3 via a fuel injection pipe (not shown).

[0033] An exhaust manifold 41 is also disposed near the cylinder 16. This exhaust manifold 41 is connected to the combustion chamber 17 via the exhaust pipe 19. The exhaust manifold 41 receives exhaust gas from the combustion chamber 17 through the exhaust pipe 19, temporarily stores the received exhaust gas, and converts the dynamic pressure of the exhaust gas into static pressure.

[0034] The engine 1 further includes a turbocharger 42 that supercharges combustion gas such as air, and a scavenging trunk 43 that temporarily stores the combustion gas compressed by the turbocharger 42. The turbocharger 42 uses the pressure of exhaust gas to rotate a compressor (not shown) together with a turbine (not shown), and the compressor compresses the combustion gas. The scavenging trunk 43 is provided so as to communicate with the internal space of the cylinder jacket 13. The combustion gas compressed by the turbocharger 42 (hereinafter also referred to as "compressed gas") flows from the scavenging trunk 43 into the internal space of the cylinder jacket 13, and is supplied from that internal space to the internal space of the cylinder liner 14 (the space surrounded by the inner wall portion 14b of the cylinder liner 14) through the scavenging ports 14a.

[0035] When the engine 1 is operating, diesel fuel is supplied into the combustion chamber 17 from the fuel injection valve 3, and compressed gas is supplied from the scavenging trunk 43 through the cylinder jacket 13, etc. As a result, the diesel fuel is combusted in the combustion chamber 17 by the compressed gas.

[0036] The energy generated by the diesel fuel causes the piston 21 to reciprocate up and down along the cylinder liner 14. At this time, when the exhaust valve 18 operates and the combustion chamber 17 is opened, exhaust gas generated by combustion is pushed out into the exhaust pipe 19. Furthermore, as the piston 21 reciprocates along the cylinder liner 14, compressed gas (air) is sucked from the cylinder jacket 13 into the cylinder liner 14, and the piston 21 pushes this gas into the combustion chamber 17, introducing new compressed gas into the combustion chamber 17. By repeating this process, the combustion of diesel fuel and scavenging of air within the cylinder 16 are repeatedly carried out.

[0037] Furthermore, when the piston 21 reciprocates due to combustion, the piston rod 22 reciprocates up and down together with the piston 21. This causes the crosshead 25 connected to the piston rod 22 to reciprocate up and down. This crosshead 25 allows the connecting rod 24 to rotate, and causes the connecting rod 24 to rotate around the connection point with the crosshead 25 as a fulcrum. Then, the crank 27 connected to the lower end of the connecting rod 24 performs crank motion, and the crankshaft 23 rotates in response to this crank motion. In this way, the crankshaft 23 converts the reciprocating movement of the piston 21 into rotational motion, and rotates the ship's propeller together with the propeller shaft. This propels the ship.

[0038] As will be described later, the fuel injection valve 3 according to this embodiment has a needle valve 34 housed in its nozzle body 30, and is configured to inject fuel from the tip of the fuel injection valve 3 by opening the needle valve 34 against the spring force.

[0039] As a result of extensive research, the inventors of the present invention have succeeded in realizing a longer life for the fuel injection valve 3 by devising an ingenious structure for the needle valve 34.

[0040] Among the components of the fuel injection valve 3, the components relating to the needle valve 34 will be described in detail below.

[0041] (2) Configuration of fuel injection valve Fig. 2 is a vertical cross-sectional view illustrating the structure of the fuel injection valve 3. Fig. 3 is a view illustrating the structure of the needle valve 34. Fig. 4 is a vertical cross-sectional view illustrating an enlarged example of the tip of the fuel injection valve 3. Fig. 4 shows a cross-sectional view of a second body portion 32 (described later) and a portion of the needle valve 34 showing the depth B and the radius of curvature R.

[0042] In the following description, the direction along the central axis C of the needle valve 34 illustrated in Figure 2 is defined as the "axial direction," and the direction extending radially from this central axis C is defined as the "radial direction." Furthermore, the clockwise and counterclockwise directions around this central axis C are defined as the "circumferential direction."

[0043] The axial direction can also be referred to as the “up-down direction.” In addition, the direction along the axial direction from the base end (sliding portion 34a) of the needle valve 34 to the tip end (second seal portion 34d) is sometimes referred to as the “downward direction,” and the opposite direction is sometimes referred to as the “upward direction.”

[0044] The radial direction is perpendicular to the above-mentioned up-down direction. In addition, one side in the radial direction that is closer to the central axis C may be referred to as the "inner side," and the other side that is farther away from the central axis C may be referred to as the "outer side."

[0045] Specifically, the fuel injection valve 3 according to this embodiment includes a nozzle body 30, a needle valve 34 housed in the nozzle body 30, and a biasing mechanism (not shown) that applies a spring force to the base end of the needle valve 34.

[0046] Of these, the nozzle body 30 has a first body portion 31 for accommodating the base end portion (sliding portion 34a) of the needle valve 34, a second body portion 32 for accommodating the tip end portion (connecting portion 34b, non-sliding portion 34c, groove portion 34e and second seal portion 34d) of the needle valve 34, and a third body portion 33 in which a fuel injection port 33a is formed.

[0047] The first body portion 31 is formed of a substantially cylindrical member with both upper and lower ends open. The upper end of the needle valve 34 protrudes from the upper opening of the first body portion 31, while the second body portion 32 is fitted into the lower opening.

[0048] More specifically, the first body portion 31 has an inlet passage 31a for introducing fuel from the outside, and a first inner wall portion 31b that, together with a second inner wall portion 32a in the second body portion 32, defines an accommodation space S for the needle valve 34.

[0049] 2, the inner diameter of the first inner wall portion 31b substantially matches the outer diameter of the sliding portion 34a of the needle valve 34. Therefore, this first inner wall portion 31b is in contact with the inner surface of the sliding portion 34a of the needle valve 34 and guides the sliding of the sliding portion 34a in the axial direction. The lower end of the first inner wall portion 31b communicates with the lower end of the introduction passage 31a and defines, together with the upper end of the second body portion 32, a substantially dome-shaped space. This space functions as a so-called oil reservoir.

[0050] On the other hand, the second body portion 32 is formed of a substantially cylindrical member that is open at both the top and bottom ends and has a smaller diameter than the first body portion 31. The upper side of the second body portion 32 is The lower half of the needle valve 34 is inserted into the opening on the first side, while the third body portion 33 is attached to the opening on the lower side.

[0051] In detail, the second body portion 32 is provided with a second inner wall portion 32a which, together with the aforementioned first inner wall portion 31b, defines the storage space for the needle valve 34, and a conical first seal portion 32b which abuts against the tip (second seal portion 34d) of the needle valve 34.

[0052] 2, the inner diameter of the second inner wall portion 32a is larger than the outer diameter of the non-sliding portion 34c of the needle valve 34. Therefore, the second inner wall portion 32a does not contact the inside of the non-sliding portion 34c of the needle valve 34, but faces the non-sliding portion 34c with a gap therebetween. The second inner wall portion 32a, together with the first inner wall portion 31b, constitutes the "inner wall portion of the nozzle body" in this embodiment.

[0053] The first seal portion 32b is formed into a conical shape by tapering the tip end of the second inner wall portion 32a. The first inclination angle θ1 of the inner peripheral surface of the first seal portion 32b is steeper than the second inclination angle θ2 of the outer peripheral surface of the second seal portion 34d (described later) (θ1<θ2). Note that the first inclination angle θ1 refers to the angle formed by the hypotenuse of the cone corresponding to the first seal portion 32b and the central axis C, which opens out like a fan toward the base end, as shown in FIG. 2. As shown in FIG. 3, the second inclination angle θ2 is defined in the same way as the first inclination angle θ1.

[0054] An oil supply hole 32c extending in the vertical direction is formed at the apex of the cone corresponding to the first seal portion 32b. The oil supply hole 32c is connected to an opening on the upper end side of the third body portion 33.

[0055] The third body portion 33 is configured as a cylindrical member with a bottom, an open upper end, and a smaller diameter than the second body portion 32. The opening on the upper end side of the third body portion 33 is connected to the oil supply hole 32c of the second body portion 32. In addition, the lower end of the third body portion 33 is formed with an injection port 33a extending obliquely downward.

[0056] On the other hand, the needle valve 34 according to this embodiment has, in order from the upper end (base end) side to the lower end (tip end) side, a sliding portion 34a, a connecting portion 34b, a non-sliding portion 34c, a groove portion 34e, and a second sealing portion 34d.

[0057] Of these, the sliding portion 34a is configured to be in contact with the inner wall portion of the nozzle body 30 (specifically, the first inner wall portion 31b of the first body portion 31). Specifically, the sliding portion 34a according to this embodiment is formed in a cylindrical shape with an outer diameter substantially the same as the inner diameter of the first inner wall portion 31b, and is disposed in sliding contact with the first inner wall portion 31b.

[0058] The connecting portion 34b is configured to connect the lower end of the sliding portion 34a and the upper end of the non-sliding portion 34c. Specifically, the connecting portion 34b according to this embodiment is formed in a truncated cone shape with a diameter that gradually decreases downward. Similar to the outer circumferential surface of the non-sliding portion 34c, the outer circumferential surface of the connecting portion 34b faces the inner wall portion (second inner wall portion 32a) of the nozzle body 30 over the entire axial and circumferential directions, with a gap therebetween. The connecting portion 34b remains in a non-contact state with the inner wall portion (second inner wall portion 32a) of the nozzle body 30 even when the needle valve 34 moves up and down due to the spring force.

[0059] The non-sliding portion 34c extends in the vertical direction (axial direction of the needle valve 34) and is configured to face, with a gap, the inner wall portion of the nozzle body 30 (specifically, the second inner wall portion 32a of the second body portion 32). Specifically, the non-sliding portion 34c according to this embodiment is formed in a cylindrical shape extending in the vertical direction. The outer peripheral surface of the non-sliding portion 34c faces, with a gap, the inner wall portion (second inner wall portion 32a) of the nozzle body 30 over the entire axial and circumferential areas. The non-sliding portion 34c remains in non-contact with the inner wall portion (second inner wall portion 32a) of the nozzle body 30 even when the needle valve 34 moves up and down due to the spring force.

[0060] That is, the non-sliding portion 34c according to this embodiment is configured so that a specific portion in the axial direction does not come into contact with the inner wall portion of the nozzle body 30, and all portions are separated from the inner wall portion.

[0061] The second seal portion 34d is configured in a conical shape with the tip of the non-sliding portion 34c tapered more gradually in diameter than the first seal portion 32b, and is configured to abut against the inner surface of the first seal portion 32b.

[0062] As described above, the second inclination angle θ2 of the outer peripheral surface of the second seal portion 34d is gentler than the first inclination angle θ1 of the inner peripheral surface of the first seal portion 32b (θ1<θ2). This second inclination angle θ2 refers to the angle formed by the hypotenuse of the cone corresponding to the second seal portion 34d and the central axis C, which opens out like a fan toward the base end, as shown in FIG.

[0063] As shown in the boxed area I in Fig. 4, by making the second seal portion 34d inclined relatively gradually, the outer peripheral surface of the second seal portion 34d and the inner peripheral surface of the first seal portion 32b come into line contact rather than surface contact. In other words, the contact surface between the second seal portion 34d and the first seal portion 32b describes a ring-shaped curve around the central axis C when viewed three-dimensionally.

[0064] The groove portion 34e is provided on the outer surface of the non-sliding portion 34c. This groove portion 34e is recessed along the circumferential direction of the non-sliding portion 34c. And the groove portion 34e according to the present embodiment is arranged so as to be closer to the second seal portion 34d than the sliding portion 34a in the axial direction (vertical direction) of the needle valve 34. In other words, in the axial direction of the needle valve 34, the distance A between the groove portion 34e and the second seal portion 34d is at least narrower than the distance between the groove portion 34e and the sliding portion 34a.

[0065] Specifically, a substantially cylindrical intervening portion 34f intervenes between the groove portion 34e and the second seal portion 34d according to the present embodiment. The dimension of the intervening portion 34f in the axial direction is equal to the distance A between the groove portion 34e and the second seal portion 34d described above. This distance A is shorter than the distance between the groove portion 34e and the sliding portion 34a in the present embodiment, as is clear from FIG. 3.

[0066] Also, as shown in FIG. 4, the groove portion 34e has an arcuate longitudinal cross-section when viewed from a direction perpendicular to the central axis C of the needle valve 34 (in other words, when a longitudinal cross-section extending along the central axis C and passing through the central axis C is viewed from the front). In particular, the groove portion 34e according to the present embodiment has a substantially semi-circular longitudinal cross-section.

[0067] Here, the depth B of the groove portion 34e in the radial direction of the needle valve 34 can be defined as the dimension of the groove portion 34e (particularly, the dimension in the radial direction) when viewed in the longitudinal cross-section as shown in FIG. 4. For example, when the depth B and the radius of the groove portion 34e when viewed in the longitudinal cross-section (hereinafter, this is also referred to as the "radius of curvature") R coincide (B = R), the longitudinal cross-section of the groove portion 34e is semi-circular (a sector shape with a central angle of 180°). On the other hand, when the depth B is smaller than the radius of curvature R (B < R), the longitudinal cross-section of the groove portion 34e is a sector shape having a central angle of less than 180°.

[0068] Particularly in the present embodiment, the depth B is substantially equal to the radius of curvature R, and more specifically, is slightly larger than the radius of curvature R (B > R). In this case, the longitudinal cross-section of the groove portion 34e is a sector shape having a central angle exceeding 180°.

[0069] 7A shows an example of the cross-sectional shape of the groove 34e when the depth B is sufficiently greater than the radius of curvature R. The cross-sectional shape of the groove 34e is not limited to a sector shape. As shown in FIG. 7B, it may have a U-shaped notch shape. The depth B of the groove 34e in the radial direction is greater than the distance A between the groove 34e and the second seal portion 34d in the axial direction of the needle valve 34 (B>A).

[0070] (3) Example Fuel injection valves 3 of Examples 1 to 9 and Comparative Example 1 shown below were prepared. The configurations of each are also shown in Table 1. The inventors of the present application verified the performance achieved in Examples 1 to 9 and Comparative Example 1, and calculated the maximum value of the contact surface pressure (maximum seat surface pressure) between the first seal portion 32b and the second seal portion 34d in each fuel injection valve 3.

[0071] In the following Examples 1 to 9 and Comparative Example 1, dimensions other than the distance A between the groove portion 34e and the second seal portion 34d and the radial depth B of the groove portion 34e are common, including the radius of curvature R of the groove portion 34e. For example, the size of the diameter R' of the non-sliding portion 34c is fixed to a common value in all of the following Examples 1 to 9 and Comparative Example 1.

[0072] The ratio of the radius of curvature R to the diameter R' of the non-sliding portion 34c (=R / R') is set to 0.105 in all of Examples 1 to 9 and Comparative Example 1. Similarly, in Examples 1 to 9 and Comparative Example 1, the distance A and the depth B are exemplified as values obtained by dividing the distance A and the depth B by the diameter R' of the non-sliding portion 34c.

[0073] Moreover, the following Examples 1 to 9 correspond to configuration examples in which the above-described groove portion 34e is provided, and Comparative Example 1 corresponds to a configuration example in which the groove portion 34e is not provided. Specifically, the fuel injection valve 103 shown in FIG. 6 corresponds to the fuel injection valve 3 according to Comparative Example 1.

[0074] 6, the fuel injection valve 103 according to Comparative Example 1, like the above-described embodiment, has a nozzle body 130 and a needle valve 134 housed therein. The nozzle body 130 has a first body portion 131 and a second body portion 132 configured like the above-described embodiment, and defines an accommodation space S for the needle valve 134. Meanwhile, the needle valve 134 according to Comparative Example 1 has a sliding portion 134a that is inscribed within the inner wall portion of the first body portion 131, a non-sliding portion 134c that faces the inner wall portion 132a of the second body portion 132 with a gap therebetween, and a second seal portion 134d that is provided at the tip of the non-sliding portion 134c and is sloped more gently than the first seal portion 132b provided in the second body portion 132.

[0075] Furthermore, of the following Examples 1 to 9, Examples 1 to 3 have a depth B (more precisely, equivalent to "B / R'" divided by the diameter R' of the non-sliding portion 34c; the same applies below) of 0.105, Examples 4 to 6 have a depth B (B / R') of 0.140, and Examples 7 to 9 have a depth B (B / R') of 0.070.

[0076] Example 1 In Example 1, the distance A between the groove portion 34e and the second seal portion 34d (more precisely, this corresponds to "A / R'" divided by the diameter R' of the non-sliding portion 34c; the same applies below) is 0.070, the radial depth B (B / R') of the groove portion 34e is 0.105, and the radius of curvature R of the groove portion 34e (more precisely, this corresponds to "R / R'" divided by the diameter R' of the non-sliding portion 34c; the same applies below) is 0.105.

[0077] Example 2 In Example 2, the distance A (A / R') between the groove portion 34e and the second seal portion 34d is 0.105, the radial depth B (B / R') of the groove portion 34e is 0.105, and the radius of curvature R (R / R') of the groove portion 34e is 0.105.

[0078] Example 3 In Example 3, the distance A (A / R') between the groove portion 34e and the second seal portion 34d is 0.140, the radial depth B (B / R') of the groove portion 34e is 0.105, and the radius of curvature R (R / R') of the groove portion 34e is 0.105.

[0079] Example 4 In Example 4, the distance A (A / R') between the groove portion 34e and the second seal portion 34d is 0.070, the radial depth B (B / R') of the groove portion 34e is 0.140, and the radius of curvature R (R / R') of the groove portion 34e is 0.105.

[0080] Example 5 In Example 5, the distance A (A / R') between the groove portion 34e and the second seal portion 34d is 0.105, the radial depth B (B / R') of the groove portion 34e is 0.140, and the radius of curvature R (R / R') of the groove portion 34e is 0.105.

[0081] Example 6 In Example 6, the distance A (A / R') between the groove portion 34e and the second seal portion 34d is 0.140, the radial depth B (B / R') of the groove portion 34e is 0.140, and the radius of curvature R (R / R') of the groove portion 34e is 0.105.

[0082] Example 7 In Example 7, the distance A (A / R') between the groove portion 34e and the second seal portion 34d is 0.070, the radial depth B (B / R') of the groove portion 34e is 0.070, and the radius of curvature R (R / R') of the groove portion 34e is 0.105.

[0083] Example 8 In Example 8, the distance A (A / R') between the groove portion 34e and the second seal portion 34d is 0.105, the radial depth B (B / R') of the groove portion 34e is 0.070, and the radius of curvature R (R / R') of the groove portion 34e is 0.105.

[0084] Example 9 In Example 9, the distance A (A / R') between the groove portion 34e and the second seal portion 34d is 0.140, the radial depth B (B / R') of the groove portion 34e is 0.070, and the radius of curvature R (R / R') of the groove portion 34e is 0.105.

[0085] -Comparative Example 1- In Comparative Example 1, the groove portion 34e is not provided. Therefore, parameters such as the interval A and the depth B are not particularly set. The size of the diameter R' of the non-sliding portion 34c is the same as in Examples 1 to 9.

[0086] [Table 1]

[0087] (Evaluation method) In each fuel injection valve 3 configured as described above, a kinetic energy of 0.03 J was applied to the needle valve 34, causing it to collide with the nozzle body 30. The maximum seat pressure in each example was expressed as a percentage, with the maximum seat pressure in the comparative example being set at 100%, and the magnitude relationship was visualized in a graph.

[0088] (Evaluation results) The evaluation results are shown in graph G in Fig. 5. In this graph G, the horizontal axis is the distance A, and the vertical axis is the maximum sheet surface pressure. Also, a straight line L0 parallel to the horizontal axis represents the maximum sheet surface pressure (=100%) in Comparative Example 1, a broken line L1 represents a line graph connecting the maximum sheet surface pressures in Examples 1 to 3 (i.e., a graph where B / R' = 0.105), a broken line L2 represents a line graph connecting the maximum sheet surface pressures in Examples 7 to 9 (i.e., a graph where B / R' = 0.070), and a broken line L3 represents a line graph connecting the maximum sheet surface pressures in Examples 4 to 6 (i.e., a graph where B / R' = 0.140).

[0089] As shown in graph G5, in all of Examples 1 to 9, the maximum surface pressure of the sheet has decreased favorably. Also, the amount of decrease in the maximum surface pressure of the sheet increases as the depth B becomes larger (deeper).

[0090] Also, as shown by the comparison between the leftmost plot on the broken line L1 (the plot showing the evaluation result of Example 1) and the central plot (the plot showing the evaluation result of Example 2), when the depth B is larger than the interval A, the maximum surface pressure of the sheet decreases more than when it is smaller. The same tendency is also shown by the comparison between the rightmost plot on the broken line L3 (the plot showing the evaluation result of Example 6) and the central and leftmost plots (the plots showing the evaluation results of Examples 4 and 5). On the other hand, in the broken line L2, it can be seen that the magnitude relationship between the interval A and the depth B does not reverse, and the maximum surface pressure of the sheet does not change significantly as much as the other broken lines L1 and L3.

[0091] Also, in graph G5, the broken line L2 shows the case where the depth B is smaller than the radius of curvature R (B < R), the broken line L1 shows the case where the depth B coincides with the radius of curvature R (B = R), and the broken line L3 shows the case where the depth B is larger than the radius of curvature R (B > R). As shown by the comparison among the broken lines L1 to L3, as the depth B increases, the maximum surface pressure of the sheet gradually decreases. In particular, as shown by the comparison between the broken line L3 and the broken lines L1 and L2, when the depth B is larger than the radius of curvature R, the maximum surface pressure of the sheet decreases significantly compared to the case where it is below the radius of curvature R. Such a tendency is common for all intervals A.

[0092] (4) Regarding the durability of the fuel injection valve As described above, according to the said embodiment and its examples, as shown in FIG. 4, not only is the groove portion 34e simply provided, but by making the groove portion 34e relatively close to the second seal portion 34d, the rigidity in the vicinity of the second seal portion 34d can be favorably decreased.

[0093] Furthermore, when groove 34e is brought close to second seal portion 34d, groove 34e is positioned at the tip of non-sliding portion 34c, which extends long in the axial direction. By positioning groove 34e at the tip of non-sliding portion 34c, groove 34e and the area near second seal portion 34d can move flexibly in the radial direction, etc.

[0094] In this way, by effectively reducing the rigidity near the second seal portion 34d and by configuring the area around that portion to be flexible and movable, it becomes possible to make the first seal portion 32b and the second seal portion 34d come into uniform contact with each other in the circumferential direction. As a result, it is possible to effectively prevent the contact pressure between the first seal portion 32b and the second seal portion 34d from becoming excessively high, and ultimately to improve the durability of the fuel injection valve 3.

[0095] Furthermore, as explained using graph G in FIG. 5, setting the depth B of groove portion 34e to be larger than the distance A between groove portion 34e and second seal portion 34d is advantageous in effectively suppressing the contact surface pressure between first seal portion 32b and second seal portion 34d.

[0096] Furthermore, as explained using graph G in FIG. 5, setting the depth B of groove portion 34e to be larger than the radius of curvature R of groove portion 34e is advantageous in effectively suppressing the contact surface pressure between the first seal portion 32b and the second seal portion 34d. [Explanation of symbols]

[0097] 1. Engine (marine internal combustion engine) 3 fuel injection valve 30 Nozzle body 31 First Body Section 31b 1st inner wall part (inner wall part) 32 Second Body Section 32a 2nd inner wall part (inner wall part) 32b First seal part 34 Needle valve 34a Sliding part 34c Non-sliding part 34d Second seal part A: Distance between groove and second seal B Groove depth R Groove curvature radius C center axis S Storage space

Claims

1. A fuel injection valve having a needle valve housed in a nozzle body, the needle valve being opened against a spring force to inject fuel from a tip thereof, The nozzle body an inner wall portion that defines an accommodation space for the needle valve; a conical first seal portion formed by tapering a tip end portion of the inner wall portion, The needle valve is, in order from the base end side to the tip end side, a sliding portion in contact with the inner wall portion; a non-sliding portion extending in the axial direction of the needle valve and facing the inner wall portion with a gap therebetween; a conical second seal portion, the tip of which is formed by gradually reducing the diameter of the non-sliding portion compared to the first seal portion, and which abuts against the first seal portion; a groove is formed on an outer surface of the non-sliding portion along a circumferential direction of the non-sliding portion; the groove portion is disposed closer to the second seal portion than the sliding portion in the axial direction of the needle valve, The groove portion has an arc-shaped longitudinal cross section when viewed from a direction perpendicular to the central axis of the needle valve, Let B be the depth of the groove in the radial direction of the needle valve, A be the distance between the groove and the second seal portion in the axial direction of the needle valve, and R be the radius of curvature of the groove when viewed in the vertical cross section. The depth B is greater than the radius R, and the depth R is greater than the distance A. A fuel injection valve characterized by:

2. A fuel injection valve according to claim 1 is provided. A marine internal combustion engine characterized by:

Images