Gas fuel injection valve

Abstract

A fuel injection valve (10) comprises: a body part (11) that has a cylindrical shape, has a fuel passage (15) therein, and also has an injection hole (17) in the leading end portion thereof; an outward-opening needle valve (20) that is provided in the body part, can reciprocate in the axial direction, and closes the injection hole from outside; a biasing member (27) that biases the needle valve in such a direction that the injection hole is closed; a fixation core (31) fixed to the body part; a movable core (32) that is attracted to the fixation core and opens the needle valve in association with the generation of a driving magnetic flux; and a push rod (40) that is provided between the needle valve and the movable core in the axial direction and that can push the needle valve toward the valve opening side during the valve opening in association with the generation of the driving magnetic flux and move separately from the needle valve during the valve closing associated with the disappearance of the driving magnetic flux.

Description

Gas fuel injection valve CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2024-147820, filed on August 29, 2024, the contents of which are incorporated herein by reference.

[0002] The disclosure herein relates to a gas fuel injector for injecting gas fuel.

[0003] Because gas fuel has a lower energy density than liquid fuel, a large flow rate of gas fuel must be injected to ensure engine output. Therefore, a gas fuel injection valve that injects gas fuel requires a large lift amount of the valve element during fuel injection. In addition, gas fuel has inferior lubricity compared to liquid fuel. For these reasons, there are concerns that gas fuel injection valves may experience wear of the valve element seat due to impact when the valve closes after fuel injection, and that driving noise may increase. For example, Patent Document 1 discloses a technology for a gas fuel injection valve that can inject gas fuels such as hydrogen.

[0004] Japanese Patent Application Laid-Open No. 2021-105350

[0005] With existing technology, in gas fuel injection valves that inject a large amount of fuel per injection, there is still an issue caused by the impact that occurs when the valve closes after fuel injection, and it is believed that there is room for improvement.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to provide a technique capable of suppressing inconveniences caused by impacts when a gas fuel injection valve is closed.

[0007] The present disclosure provides a gas fuel injection valve for injecting gas fuel, comprising: a cylindrical main body having a fuel passage therein and a nozzle hole at a tip thereof; an outward-opening needle valve provided within the main body, reciprocable in an axial direction, and closing the nozzle hole from the outside; a biasing member for biasing the needle valve in a direction to close the nozzle hole; a fixed core fixed to the main body; a movable core that is attracted to the fixed core as a driving magnetic flux is generated, thereby opening the needle valve; and a push rod that is provided between the needle valve and the movable core in the axial direction, and that pushes the needle valve toward the open side when the valve is opened as a result of the generation of the driving magnetic flux, and that is movable separately from the needle valve when the valve is closed as a result of the disappearance of the driving magnetic flux.

[0008] In the gas fuel injection valve having the above configuration, when the valve is opened, the movable core is attracted to the fixed core due to the generation of a driving magnetic flux, and the push rod moves together with the movable core, thereby opening the needle valve against the biasing force of the biasing member. The gas fuel injection valve has an outward opening valve structure, and the needle valve moves outward from the main body, opening the injection hole. This starts fuel injection.

[0009] Furthermore, when the gas fuel injection valve is closed, the magnetic flux disappears, releasing the attraction of the movable core to the fixed core, and the biasing force of the biasing member returns the needle valve to the closed position. At this time, the needle valve closes the injection hole from the outside, ending fuel injection. When the needle valve returns to the closed position, the push rod moves separately from the needle valve. This reduces the impact load when the needle valve seats on the valve body seat on the main body. As a result, problems caused by the impact when the gas fuel injection valve is closed can be suppressed.

[0010] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. 1 is a cross-sectional view showing the longitudinal cross-sectional structure of a fuel injection valve, FIG. 2 is a cross-sectional view showing the fuel injection valve in an open state, FIG. 3 is a cross-sectional view showing the state of the fuel injection valve immediately after the needle valve is closed, FIG. 4 is a cross-sectional view showing an enlarged view of a connection portion between the enlarged diameter end of the needle valve and the lower end of the push rod, FIG. 5 is a cross-sectional view showing the configuration of the push rod end and a guide portion, FIG. 6 is a cross-sectional view showing the configuration related to the push rod inside the injection valve, FIG. 7 is a cross-sectional view showing the configuration related to the push rod inside the injection valve, FIG. 8 is a cross-sectional view showing the configuration of the connection end of the needle valve, FIG. 9 is a cross-sectional view showing a modified example of the push rod, FIG. 10 is a cross-sectional view showing the longitudinal cross-sectional structure of a fuel injection valve in a second embodiment, FIG. 11 is a time chart for explaining the lift behavior of the needle valve, and FIG. 12 is an enlarged view of a connection structure portion between the needle valve and the push rod. FIG. 13 is a diagram explaining the operation of the connecting structure portion when the fuel injection valve is opened and closed, FIG. 14 is a time chart explaining the lift behavior of the needle valve when the fuel injection valve is closed, FIG. 15 is a cross-sectional view showing a modified example of the connecting structure portion of the fuel injection valve, FIG. 16 is a cross-sectional view showing a modified example of the connecting structure portion of the fuel injection valve, FIG. 17 is a cross-sectional view showing a modified example of the connecting structure portion of the fuel injection valve, FIG. 18 is a cross-sectional view showing a modified example of the connecting structure portion of the fuel injection valve, FIG. 19 is a cross-sectional view showing a modified example of the connecting structure portion of the fuel injection valve, FIG. 20 is a cross-sectional view showing a modified example of the connecting structure portion of the fuel injection valve, FIG. 21 is a cross-sectional view showing a modified example of the connecting structure portion of the fuel injection valve, FIG. 22 is a cross-sectional view showing a modified example of the connecting structure portion of the fuel injection valve, FIG. 23 is a cross-sectional view showing a modified example of the connecting structure portion of the fuel injection valve, and FIG. 24 is a cross-sectional view showing a modified example of the connecting structure portion of the fuel injection valve.

[0011] Hereinafter, a gas fuel injection valve according to an embodiment of the present disclosure will be described with reference to the drawings. The gas fuel injection valve of this embodiment is applied to a direct injection gas engine (internal combustion engine) that uses gas fuel such as hydrogen, compressed natural gas (CNG), or liquefied natural gas (LNG), and the gas fuel injection valve directly injects gas fuel into the combustion chamber of the gas engine. The gas engine may be, for example, an in-vehicle engine.

[0012] First Embodiment The configuration of a fuel injection valve 10 will be described using Figure 1. Figure 1 shows a longitudinal cross-sectional structure of the fuel injection valve 10. In the following description, the direction in which the central axis of the fuel injection valve 10 extends (i.e., the vertical direction in Figure 1) is referred to as the axial direction, the direction extending radially from the axis is referred to as the radial direction, and the direction extending circumferentially around the axis is referred to as the circumferential direction. In Figure 1, the upper side is the base end side (upstream side) of the fuel injection valve 10, and the lower side is the tip end side (downstream side). For ease of explanation, the upper side of the fuel injection valve 10 will also be referred to as the upper end side and the lower side will also be referred to as the lower end side, based on the fuel injection valve 10 in Figure 1.

[0013] The fuel injection valve 10 includes a cylindrical housing 11. The housing 11 includes an inlet 12, a body 13, and a nozzle 14. The housing 11 corresponds to a "main body." The body 13 is cylindrical and extends axially, with the inlet 12 and the nozzle 14 fixed to one axial end and the other axial end of the body 13, respectively. A fuel passage 15 is provided within the housing 11, through which gas fuel flows in the axial direction. The inlet 12 is provided with an inlet 16, and the nozzle 14 is provided with an injection hole 17. In the fuel injection valve 10, gas fuel is introduced through the inlet 16 of the inlet 12, and the fuel passage 15 is filled with the gas fuel. When hydrogen gas is used as the gas fuel, gas fuel compressed above atmospheric pressure is supplied to the fuel passage 15 from an upstream fuel supply unit.

[0014] A needle valve 20, a spring 27, an electromagnetic drive unit 30, a push rod 40, and a bellows 50 are provided within the housing 11. The needle valve 20 is inserted into the injection hole 17 of the nozzle 14. The needle valve 20 has a shaft portion 21 that extends axially and is inserted into the injection hole 17, a tip valve portion 22 provided at one axial end (lower end) of the shaft portion 21, and an expanded diameter end portion 23 provided at the other axial end (upper end) of the shaft portion 21. The shaft portion 21 has a sliding portion 24 that slides within the injection hole 17. The sliding portion 24 is provided with a communication passage 24a that communicates in the axial direction. The needle valve 20 is capable of reciprocating in the axial direction with the sliding surface of the sliding portion 24 in contact with the inner circumferential surface of the injection hole 17.

[0015] The tip valve portion 22 faces the axial end face of the nozzle 14 at a position axially outward of the nozzle 14. In the nozzle 14, the annular axial end face surrounding the injection hole 17 is the seat portion 14a. The injection hole 17 is closed when the seat portion 14a of the nozzle 14 and the tip valve portion 22 abut against each other. This state is the closed state of the fuel injection valve 10. Furthermore, the injection hole 17 is opened when the seat portion 14a of the nozzle 14 and the tip valve portion 22 move away from each other. This state is the open state of the fuel injection valve 10. The fuel injection valve 10 has an outer opening valve structure in which the needle valve 20 moves axially outwardly of the housing 11 to open the valve.

[0016] The expanded diameter end portion 23 is provided in the shape of a flange extending radially at the end opposite the tip valve portion 22. The expanded diameter end portion 23 serves as a spring bearing that holds a compression coil spring 27 in a state in which the needle valve 20 is biased in the valve closing direction. The compression coil spring 27 is provided between the expanded diameter end portion 23 and the inner end face of the nozzle 14, and the spring 27 biases the needle valve 20 in a direction to close the injection hole 17. The spring 27 corresponds to the "biasing member."

[0017] The electromagnetic drive unit 30 has a fixed core 31 fixed within the housing 11, a movable core 32 that opens the needle valve 20, and a solenoid 33 that generates a drive magnetic flux that attracts the movable core 32 to the fixed core 31. Both the fixed core 31 and the movable core 32 are made of a magnetic material. The fixed core 31 is fixed in a position within the housing 11 on the opposite side of the needle valve 20 in the axial direction. The fixed core 31 is provided with a guide passage 34 that guides gas fuel introduced from the inlet 16 downstream.

[0018] The fixed core 31 has a recess 35 that opens to the lower end of the fuel injection valve 10, i.e., the needle valve 20 side. A movable core 32 is disposed within the recess 35 and is movable in the axial direction. The solenoid 33 is provided integrally with the fixed core 31. The recess 35 of the fixed core 31 has a large-diameter recess 35a and a small-diameter recess 35b that is closer to the outlet than the large-diameter recess 35a. The movable core 32 has a large-diameter portion 32a and a small-diameter portion 32b that extends from the large-diameter portion 32a toward the lower end in the axial direction. The movable core 32 is movable in the axial direction with the large-diameter portion 32a housed in the large-diameter recess 35a of the fixed core 31 and the small-diameter portion 32b housed in the small-diameter recess 35b of the fixed core 31.

[0019] When a driving magnetic flux is generated by energizing the solenoid 33, the driving magnetic flux attracts the large diameter portion 32a of the movable core 32 toward the stepped portion 31a of the fixed core 31, and the movable core 32 moves axially downward until the large diameter portion 32a abuts against the stepped portion 31a of the fixed core 31.

[0020] An elongated push rod 40 is provided between the needle valve 20 and the movable core 32 in the axial direction. More specifically, the push rod 40 is provided between the enlarged diameter end portion 23 of the needle valve 20 and the small diameter portion 32b of the movable core 32. The push rod 40 is provided at a position that corresponds to the axis of the fuel injection valve 10, in a direction that extends in the axial direction, and in a state that is separately movable from the needle valve 20 and the movable core 32.

[0021] The push rod 40 has a shaft portion 41 extending in the axial direction, a lower end portion 42 provided at one axial end (lower end portion) of the shaft portion 41, and an upper end portion 43 provided at the other axial end (upper end portion) of the shaft portion 41. The lower end portion 42 corresponds to the "first end portion" of the push rod 40, and the upper end portion 43 corresponds to the "second end portion." The lower end portion 42 of the push rod 40 is guided by a guide portion 25 provided at the enlarged diameter end portion 23 of the needle valve 20, and the upper end portion 43 of the push rod 40 is guided by a cylindrical guide 36 fixed to the small diameter recess 35b of the fixed core 31.

[0022] Additionally, a cylindrical bellows 50 that is expandable and contractable in the axial direction is provided within the housing 11 between the needle valve 20 and the electromagnetic driver 30 to surround the push rod 40. The lower end of the bellows 50 is fixed to the enlarged diameter end 23 of the needle valve 20, and the upper end is fixed to a circular member 37 that is fixed to the fixed core 31 and that surrounds the cylindrical guide 36. The lower end of the bellows 50 that is fixed to the needle valve 20 is the movable end, and the bellows 50 is expandable and contractable in the axial direction in response to movement of the needle valve 20. The space within the bellows 50 that accommodates the push rod 40 is a push rod accommodating space 51. The bellows 50 serves as an isolating member that isolates the push rod accommodating space 51 from the fuel passage 15 within the housing 11.

[0023] In this embodiment, the movable end of the bellows 50 is fixed to the enlarged diameter end 23, which is the upper end of the needle valve 20 (the connecting end connected to the axial end of the push rod 40), and the push rod 40 is connected to the enlarged diameter end 23 so as to be separately movable in the axial direction. The spring 27 and the bellows 50 are arranged side by side in the axial direction within the housing 11. More specifically, the spring 27 is provided in the fuel passage 15 axially closer to the tip end than the bellows 50.

[0024] Incidentally, as another possible structure of the fuel injection valve 10, a configuration in which the spring 27 is a tension spring and is disposed within the bellows 50, between the enlarged diameter end 23 of the needle valve 20 and the annular member 37 on the electromagnetic drive unit 30 side is conceivable. Compared to this configuration, in the configuration in which the spring 27 and the bellows 50 are disposed side by side in the axial direction within the housing 11 as described above, the diameter of the bellows 50 can be made smaller, and the physical size of the bellows 50 can be reduced.

[0025] The interior of the recess 35 of the fixed core 31 is open to the atmosphere via the inlet 12 and an atmosphere vent hole 38 provided in the fixed core 31. In this case, the interior of the recess 35 of the fixed core 31 (i.e., the accommodation space for the movable core 32) and the push rod accommodation space 51 are in communication with each other, and both are at atmospheric pressure. In other words, the interior of the push rod accommodation space 51 is at atmospheric pressure. Note that it is also possible to configure the recess 35 of the fixed core 31 and the push rod accommodation space 51 to be filled with a liquid such as lubricating oil in an uncompressed state.

[0026] 2 and 3 show operating states of the fuel injection valve 10. Fig. 2 is a cross-sectional view showing the fuel injection valve 10 in an open state, and Fig. 3 is a cross-sectional view showing the fuel injection valve 10 in a state immediately after the needle valve 20 is closed.

[0027] 2, when the fuel injection valve 10 is opened, a driving magnetic flux is generated by energizing the solenoid 33, and the movable core 32 is attracted to the fixed core 31. At this time, the movable core 32 moves until the large diameter portion 32a abuts against the stepped portion 31a of the fixed core 31. Furthermore, the push rod 40 moves together with the movable core 32, pushing the needle valve 20 toward the valve opening side. As a result, the needle valve 20 lifts to the valve opening position against the biasing force of the spring 27, and gas fuel is injected from the injection hole 17.

[0028] 3, when the fuel injection valve 10 is closed, the solenoid 33 is de-energized and the driving magnetic flux disappears, releasing the attraction of the movable core 32 to the fixed core 31. The biasing force of the spring 27 returns the needle valve 20 to the valve-closed position (i.e., the position where the needle valve 20 abuts against the seat portion 14a of the nozzle 14). This closes the injection hole 17 and ends fuel injection. At this time, the needle valve 20 and the push rod 40 can move separately from each other. Therefore, after the needle valve 20 abuts against the seat portion 14a, the push rod 40 moves separately from the needle valve 20 due to inertia. Therefore, when the needle valve 20 collides with the seat portion 14a, the load acting on the seat portion 14a is essentially the needle valve 20 alone. This reduces the impact load when the valve is closed compared to a configuration in which the needle valve 20 and the push rod 40 are integrated.

[0029] 1 , when the cross-sectional area of ​​the shaft portion 21 of the needle valve 20 is S1 and the cross-sectional area of ​​the shaft portion 41 of the push rod 40 is S2, the cross-sectional areas S1 and S2 preferably have a relationship of S1<S2. Note that the cross-sectional area S2 of the shaft portion 41 of the push rod 40 is the cross-sectional area of ​​the intermediate portion between the lower end portion 42 and the upper end portion 43 of the push rod 40. This configuration further enhances the effect of reducing the collision load caused by the separate movement of the push rod 40 from the needle valve 20 when the needle valve 20 is closed.

[0030] The fuel injection valve 10 has a balanced valve structure using a bellows 50. In other words, in the fuel injection valve 10, the bellows 50 is attached to the enlarged diameter end 23 of the needle valve 20, so that fuel pressure acts in opposite directions on the tip valve portion 22 and the enlarged diameter end 23 of the needle valve 20 inside the housing 11. This maintains pressure balance on the needle valve 20. Therefore, the biasing force of the spring 27 and the electromagnetic force of the solenoid can be set independently of the fuel pressure.

[0031] Next, the detailed configuration of the connecting structure at both ends of the axial direction of the push rod 40 will be described.

[0032] 4 is an enlarged cross-sectional view showing the connection between the enlarged diameter end 23 of the needle valve 20 and the lower end of the push rod 40. As shown in Fig. 4, the enlarged diameter end 23, which is the upper end of the needle valve 20, is provided with a guide portion 25 that surrounds the lower end 42 of the push rod 40. The guide portion 25 has a cylindrical shape that extends axially and surrounds the axial end of the push rod 40, and guides the axial movement of the lower end 42 of the push rod 40.

[0033] The lower end 42 of the push rod 40 is provided with a spherical portion 42a having a diameter larger than that of the shaft portion 41. The guide portion 25 of the needle valve 20 is a cylindrical portion having an inner diameter the same as or slightly larger than that of the spherical portion 42a. When the spherical portion 42a is housed in the guide portion 25, the outer circumferential surface (spherical surface) of the spherical portion 42a contacts or closely faces the inner circumferential surface of the guide portion 25.

[0034] As shown in FIG. 1 , like the lower end 42, the upper end 43 of the push rod 40 is provided with a spherical portion 43a having a diameter larger than that of the shaft portion 41. The cylindrical guide 36 fixed to the fixed core 31 is a cylindrical portion having an inner diameter the same as or slightly larger than that of the spherical portion 43a. When the spherical portion 43a is housed in the cylindrical guide 36, the outer peripheral surface (spherical surface) of the spherical portion 43a contacts or closely faces the inner peripheral surface of the cylindrical guide 36. Preferably, the lower end 42 and the upper end 43 of the push rod 40 are provided with spherical portions 42a, 43a of the same shape.

[0035] 5( a), in a configuration in which a cylindrical protruding portion is provided on the lower end 42 of the push rod 40 and this protruding portion closely faces the inner circumferential surface of the guide portion 25, there is a concern that if the push rod 40 is tilted axially, the protruding portion will come into contact with only one side of the inner circumferential surface of the guide portion 25, causing the push rod 40 to become stuck to the guide portion 25 due to biting or the like. This will cause problems when moving the push rod 40 separately from the needle valve 20.

[0036] 5(b), in a configuration in which a spherical portion 42a (spherical protrusion) is provided on the lower end 42 of the push rod 40 and the spherical portion 42a closely faces the inner circumferential surface of the guide portion 25, even if the push rod 40 is tilted axially, there is no change in the state of contact of the spherical portion 42a (protrusion) with the inner circumferential surface of the guide portion 25. In this case, adhesion of the push rod 40 to the guide portion 25 is suppressed, and the push rod 40 can be suitably moved separately from the needle valve 20.

[0037] 4 , the inside of the guide portion 25 of the needle valve 20 forms a rod end accommodating portion 26 that accommodates the lower end 42 of the push rod 40. In the rod end accommodating portion 26, the spherical portion 42a of the push rod 40 is closest to the inner circumferential surface of the guide portion 25 at a position above the bottom portion 23a, which is the axial end face of the expanded diameter end portion 23. In this case, the space in the rod end accommodating portion 26 that is closer to the tip of the push rod than the position where the spherical portion 42a of the push rod 40 is closest forms the damper chamber 26a. In other words, the spherical portion 42a of the push rod 40 divides the rod end accommodating portion 26 into a space on the push rod accommodating space 51 side within the bellows 50 and the damper chamber 26a.

[0038] In the configuration in which the damper chamber 26a is provided inside the guide portion 25, when the push rod 40 starts to move axially separately from the needle valve 20 during valve closing of the fuel injection valve 10, the damper chamber 26a slows down the moving speed of the push rod 40. This prevents the movable core 32 from bouncing off the rear end face of the fixed core 31 due to the strong momentum of the movable core 32 pushed by the push rod 40 when the push rod 40 moves separately from the needle valve 20.

[0039] Furthermore, in the fuel injection valve 10, if the push rod 40 is tilted relative to the axial direction, there is a concern that the needle valve 20 may be tilted. Therefore, it is preferable that the push rod 40 is designed to be prevented from tilting excessively. The configuration thereof will be explained using Figures 6 and 7. Note that Figures 6 and 7 show simplified configurations of the enlarged diameter end portion 23 of the needle valve 20 and the like.

[0040] 6 , in the push rod 40, the axial end face 42b of the lower end 42 has a circular flat shape and abuts against the axial end face of the enlarged diameter end 23 of the needle valve 20, while the axial end face 43b of the upper end 43 has a circular flat shape and abuts against the axial end face of the movable core 32. When the diameter of the axial end faces of the lower end 42 and the upper end 43 of the push rod 40 is D1 and the maximum value of the axial misalignment e, which is the amount of axial misalignment between the lower end 42 and the upper end 43 of the push rod 40, is em, the relationship between the diameter D1 and the maximum axial misalignment em is D1 / em>1. The axial misalignment e is the amount of misalignment between the radial center points of the axial end faces 42b, 43b of the lower end 42 and the upper end 43, or the amount of misalignment between the center points of the spherical portions 42a, 43a of the lower end 42 and the upper end 43. The maximum value em of the axial misalignment amount e is the allowable axial misalignment amount that is estimated in advance for the fuel injection valve 10 .

[0041] When the push rod 40 is tilted, the edge point E1 at the axial end face 42b of the lower end 42 abuts against the axial end face of the expanded diameter end 23, and the edge point E2 at the axial end face 43b of the upper end 43 abuts against the axial end face of the movable core 32. In this case, if an axial load is generated when the fuel injection valve 10 is opened, for example, axially inward forces F1 and F2 act on the edge points E1 and E2. If the amount of axial misalignment becomes excessively large with respect to the diameter D1 of the axial end face of the upper end 43 (i.e., the push rod 40 is tilted excessively), and the relationship D1 / em≦1 holds, the axially inward forces F1 and F2 at the edge points E1 and E2 will generate opposing forces at both axial rod ends in directions perpendicular to the axial direction, potentially exacerbating the tilt of the push rod 40.

[0042] In contrast, in the configuration (configuration shown in FIG. 6 ) where the relationship D1 / em>1 is satisfied as described above, the forces F1 and F2 acting inward in the axial direction at the edge points E1 and E2 generate forces at both axial ends of the rod that are perpendicular to the axial direction and face each other. This eliminates tilt of the push rod 40. In other words, the configuration where D1 / em>1 is satisfied suppresses tilt of the push rod 40 relative to the axial direction, making it difficult for tilt of the push rod 40 to occur relative to the needle valve 20 and the movable core 32.

[0043] Furthermore, to establish the relationship D1 / em>1 as described above, it is preferable that the fuel injection valve 10 be provided with a configuration that limits the axial misalignment amount e. Specifically, as shown in Fig. 6, it is preferable that a restricting portion 61 that restricts the amount of movement of the connecting end of the needle valve 20 in a direction perpendicular to the axial direction is provided inside the housing 11. The restricting portion 61 is provided so as to surround the expanded diameter end 23 of the needle valve 20 from the circumferential outside, and is preferably provided at three or more positions at predetermined intervals in the circumferential direction, for example.

[0044] 7 , the axial end faces 42b, 43b of the lower end 42 and the upper end 43 of the push rod 40 are spherical. The relationship between the radius R1 of the spherical surface of each axial end face 42b, 43b and the axial length L of the push rod 40 satisfies R1≧L / 2. In this case, compared to a configuration in which the relationship between the radius R1 of the spherical surface of each axial end face 42b, 43b and the axial length L of the push rod 40 satisfies R1<L / 2, rotation at the lower end 42 and the upper end 43 of the push rod 40 is less likely to occur, and tilting of the push rod 40 with respect to the axial direction is suppressed.

[0045] According to the present embodiment described above in detail, the following excellent effects can be obtained.

[0046] When the fuel injection valve 10 is opened, the needle valve 20 is opened by pushing in the push rod 40, and when the fuel injection valve 10 is closed, the push rod 40 moves separately from the needle valve 20 as the needle valve 20 returns to the closed position. This reduces the impact load when the needle valve 20 seats on the valve disc seat portion of the housing 11. As a result, it is possible to suppress problems such as wear on the valve disc seat portion and driving noise caused by the impact when the fuel injection valve 10 is closed.

[0047] In the fuel injection valve 10, the movable end of the bellows 50 is fixed to the base end (expanded diameter end 23) of the needle valve 20, and the lower end of the push rod 40 is connected to it so as to be separately movable in the axial direction. In this case, the push rod 40 is separately movable from a position near the fixed location of the bellows 50 on the needle valve 20. This can enhance the effect of reducing the collision load when the needle valve 20 is closed.

[0048] The spring 27 and the bellows 50 are arranged side by side in the axial direction inside the housing 11. This allows the size of the bellows 50 to be reduced.

[0049] A cylindrical guide portion 25 that surrounds the lower end portion 42 of the push rod 40 is provided at the enlarged diameter end portion 23 on the upper end side of the needle valve 20, and the axial end portion of the push rod 40 that is guided by the guide portion 25 is formed into a spherical shape. This prevents the push rod 40 from sticking even if the push rod 40 is tilted axially, and allows the needle valve 20 and the push rod 40 to move independently in an appropriate manner.

[0050] The spherical portion 42a of the push rod 40 is accommodated in the rod end accommodating portion 26 inside the guide portion 25, and a space in the rod end accommodating portion 26 closer to the tip of the push rod than the portion closest to the spherical portion 42a of the push rod 40 functions as a damper chamber 26a. In this case, when the push rod 40 begins to move separately from the needle valve 20 upon closing of the fuel injection valve 10, the damper chamber 26a can provide a deceleration effect for the push rod 40. This can suppress bouncing of the movable core 32 on the rear end face within the fixed core 31 when the push rod 40 and movable core 32 move separately from the needle valve 20.

[0051] The axial end face 42b of the lower end 42 on the needle valve side of the push rod 40 is circularly flat and abuts against the axial end face of the valve needle 20, while the axial end face 43b of the upper end 43 on the movable core side is circularly flat and abuts against the axial end face of the movable core 32 (see FIG. 6 ). The relationship between the diameter D1 of the axial end faces 42b, 43b of the push rod 40 and the maximum axial misalignment em due to tilt of the push rod 40 is D1 / em>1. In this case, tilt of the push rod 40 in the axial direction can be suppressed, and a configuration can be realized in which tilt of the push rod 40 with respect to the valve needle 20 and the movable core 32 is unlikely to occur.

[0052] The fuel injection valve 10 is configured to have a restricting portion 61 that restricts the movement of the connecting end of the needle valve 20 in a direction perpendicular to the axial direction (see FIG. 6). This makes it possible to preferably achieve a configuration in which the diameter D1 and the maximum axial deviation em satisfy the relationship D1 / em>1, thereby suppressing excessive tilt of the push rod 40.

[0053] The axial end faces 42b, 43b of the push rod 40 are each spherical (see FIG. 7), and the radius R1 of the spherical surface and the axial length L of the push rod 40 satisfy the relationship R1≧L / 2. In this case, the push rod 40 is unlikely to tilt relative to the needle valve 20 and the movable core 32, and tilting of the push rod 40 in the axial direction can be suppressed.

[0054] The needle valve 20 has a sliding portion 24 that slides within the injection hole 17. This prevents the needle valve 20 from tilting in the axial direction relative to the housing 11, thereby preventing fuel leakage from the valve seat.

[0055] The cross-sectional area S1 of the shaft portion 21 of the needle valve 20 is smaller than the cross-sectional area S2 of the shaft portion 41 of the push rod 40. This further enhances the effect of reducing the collision load caused by the push rod 40 moving separately from the needle valve 20 when the needle valve 20 is closed.

[0056] (Modification of the First Embodiment) The connecting end of the needle valve 20 connected to the push rod 40 may be configured as shown in FIG. 8 . In FIG. 8 , the connecting end of the needle valve 20 includes an end plate 71 integral with the axially extending shaft portion 21, a guide portion 25, and an intermediate plate 72 interposed between the end plate 71 and the guide portion 25. The end plate 71 and the intermediate plate 72 correspond to the expanded diameter end portion 23. At the connecting end of the needle valve 20, the end plate 71 and the guide portion 25 are fixed to the intermediate plate 72 by welding. The guide portion 25, the end plate 71 (shaft portion 21), and the intermediate plate 72 are each made of a weldable metallic material, such as stainless steel. More specifically, the end plate 71 and the guide portion 25 are made of SUS410, a martensitic stainless steel, and the intermediate plate 72 is made of SUS430, a ferritic stainless steel. The intermediate plate 72 is preferably made of a steel material having a lower carbon content than the end plates 71 and the guide portion 25. This improves weldability.

[0057] Furthermore, the guide portion 25 preferably has a surface hardness greater than that of the intermediate plate 72. The surface hardness can be measured, for example, by a Vickers hardness test (JIS Z 2244). The guide portion 25 of the needle valve 20 is a portion that holds the spherical portion 42a of the push rod 40 in a contactable state, and there is a concern that the guide portion 25 may be worn due to contact with the push rod 40. In this regard, the surface hardness of the guide portion 25 is greater than that of the intermediate plate 72, thereby suppressing wear that may occur due to contact with the push rod 40.

[0058] Figure 9 is a cross-sectional view showing a modified example of the push rod 40. Figure 9 shows the configuration of the axial end of the push rod 40 on the movable core 32 side. Note that Figure 9 omits the illustration of the same components as in Figure 1, such as the bellows 50.

[0059] The configuration of FIG. 9 differs from the configuration of FIG. 1 in that a radially protruding stopper 45 is provided on the shaft portion 41 of the push rod 40. This stopper 45 protrudes axially from the cylindrical guide 36 fixed to the fixed core 31. When the push rod 40 moves axially toward the base end (upward in the figure), the stopper 45 abuts against the cylindrical guide 36, thereby limiting the movement of the push rod 40. In this configuration, the push rod 40 and the movable core 32 can be separated from each other when the fuel injection valve 10 is closed. In this separated state, a gap SA can be formed between the push rod 40 and the movable core 32. In other words, the push rod 40 has a separation structure that transitions from a state in which the push rod 40 and the movable core 32 move together to a state in which the movable core 32 moves independently after the needle valve 20 starts moving separately from the needle valve 20 during valve closing. The stopper 45 of the push rod 40 corresponds to the separation structure.

[0060] According to the above configuration, after the needle valve 20 is seated and the push rod 40 and the movable core 32 move together in the valve closing direction, the impact when the movable core 32 reaches the inner bottom portion of the fixed core 31 is alleviated. This makes it possible to suppress wear on the axial end face (the inner bottom portion of the fixed core 31) of the electromagnetic drive unit 30 that the movable core 32 collides with when the fuel injection valve 10 is closed.

[0061] In the above embodiment, the guide portion 25 is provided at the axial end (connection end) of the needle valve 20, and the guide portion 25 guides the axial movement of the push rod 40. However, this configuration may be modified. For example, the axial end face of the needle valve 20 and the axial end face of the push rod 40 may face each other, and these end faces may be able to abut against and separate from each other. This configuration also reduces the collision load when the needle valve 20 abuts against (seats on) the valve disc seat portion of the housing 11 when the fuel injection valve 10 is closed.

[0062] In the above embodiment, the fuel injection valve 10 has a balanced valve structure using the bellows 50, but this may be modified to have a structure that does not use the bellows 50. Even in this structure, the push rod 40 can be moved separately from the needle valve 20 when the fuel injection valve 10 is closed, thereby reducing the collision load on the needle valve 20.

[0063] Second Embodiment A fuel injection valve 100, which is a gas fuel injection valve according to a second embodiment, will be described below. FIG. 10 is a longitudinal cross-sectional view showing the fuel injection valve 100 of this embodiment. In the fuel injection valve 100 of FIG. 10, components common to those of the fuel injection valve 10 shown in FIG. 1 and other figures are assigned the same component numbers. Note that in FIG. 10, the bellows 50 surrounding the push rod 120 in the fuel injection valve 100 is not shown. However, as in FIG. 1, the bellows 50 may isolate the fuel passage 15 from the push rod accommodating space 51. The fuel injection valve 100 differs from the previously described fuel injection valve 10 in the configuration of the connection portion between the needle valve 110 and the push rod 120, and the following description will focus on this difference.

[0064] 10 , in a fuel injection valve 100, a needle valve 110 that closes an injection hole 17 and a push rod 120 that is aligned axially with the needle valve 110 are provided within a cylindrical housing 11. The needle valve 110 and the push rod 120 have their axial ends connected to each other so that they can move separately. The needle valve 110 has a shaft portion 111 that extends axially and is inserted into the injection hole 17, a tip valve portion 112 provided at one axial end (lower end) of the shaft portion 111, and a cylindrical portion 113 provided at the other axial end (upper end) of the shaft portion 111.

[0065] The push rod 120 has a shaft portion 121, the lower end of which in the figure constitutes a connecting end portion 122 that is connected to the needle valve 110. The needle valve 110 and the push rod 120 are connected to each other with the connecting end portion 122 of the push rod 120 housed in a cylindrical portion 113 of the needle valve 110. The cylindrical portion 113 opens upward in the figure. The cylindrical portion 113 is a guide portion that houses the connecting end portion 122 in the push rod 120 in a state where it can move axially.

[0066] When the fuel injection valve 100 is opened, the movable core 32 is attracted to the fixed core 31 as the solenoid 33 is energized, which moves the push rod 120 and pushes the needle valve 110 toward the valve-opening side against the biasing force of the spring 27. This causes gas fuel to be injected from the injection hole 17. When the solenoid 33 is closed, the biasing force of the spring 27 returns the needle valve 110 to the valve-closed position (i.e., the position where it abuts against the seat portion 14a of the nozzle 14). This closes the injection hole 17 and ends fuel injection.

[0067] 10, the needle valve 110 and the push rod 120 can move separately from each other, so that after the needle valve 110 contacts the seat 14a, the push rod 120 moves separately from the needle valve 110 due to inertial force. This reduces the collision load when the needle valve 110 collides with the seat 14a. However, when the needle valve 110 collides with the seat 14a, it is conceivable that the needle valve 110 may bounce independently.

[0068] 11, in the fuel injection valve 100, the needle valve 110 lifts to the valve open position after the solenoid 33 is energized, and returns to the valve closed position when the solenoid 33 is de-energized. At this time, the needle valve 110 collides with the seat portion 14a at the valve closed position after the solenoid is energized, causing the needle valve 110 to bounce.

[0069] Therefore, in the fuel injection valve 100 of this embodiment, a connecting structure is provided at the connecting portion between the axial ends of the needle valve 110 and the push rod 120, which generates a force in a direction that prevents the needle valve 110 and the push rod 120 from moving away from each other when the push rod 120 displaces separately from the needle valve 110 toward the opposite side of the needle valve after the needle valve 110 reaches the closed position from the open position.

[0070] A specific configuration of the connecting structure in the fuel injection valve 100 will be described with reference to Fig. 12 . As shown in Fig. 12 , a connecting end 122 of a push rod 120 is provided with an expanded diameter portion 123 that is spherical and has a diameter larger than that of a shaft portion 121. The tubular portion 113 of the needle valve 110 is a cylindrical portion having an inner diameter that is the same as or slightly larger than the diameter of the expanded diameter portion 123. When the expanded diameter portion 123 is housed within the tubular portion 113, the outer circumferential surface (spherical surface) of the expanded diameter portion 123 contacts or closely faces the inner circumferential surface of the tubular portion 113.

[0071] A cover 130 that closes the upper opening is attached to the cylindrical portion 113 of the needle valve 110. The cover 130 may be fixed to the cylindrical portion 113 by adhesive, welding, or the like. The cover 130 has a through hole 131 extending in the axial direction. The shaft portion 121 of the push rod 120 is inserted through the through hole 131 of the cover 130. An annular recess 132 is formed on the inner circumferential surface of the cover 130 surrounding the through hole 131, and a seal member 133 made of, for example, an O-ring is housed in the recess 132. The seal member 133 forms an airtight space inside the cylindrical portion 113.

[0072] The sealed space within the cylindrical portion 113 may be filled with, for example, air. However, the fluid sealed within the sealed space within the cylindrical portion 113 may be something other than air, such as hydrocarbon, mineral, or silicone oil. In any case, the fluid sealed within the sealed space within the cylindrical portion 113 may be a substance containing a solid having viscoelasticity or stretching properties.

[0073] The cylindrical portion 113 of the needle valve 110 is divided into two axially spaced portions by the expanded diameter portion 123 of the push rod 120. That is, a first pressure chamber S11 and a second pressure chamber S12 are provided within the cylindrical portion 113, one on each axial side of the expanded diameter portion 123. The expanded diameter portion 123 of the push rod 120 is capable of reciprocating axially within the cylindrical portion 113. Displacement of the expanded diameter portion 123 within the cylindrical portion 113 increases or decreases the volume of each pressure chamber S11, S12, thereby increasing or decreasing the pressure in each pressure chamber S11, S12. In FIG. 12 , for example, when the expanded diameter portion 123 is displaced upward, the pressure in the first pressure chamber S11 increases and the pressure in the second pressure chamber S12 decreases.

[0074] In this embodiment, of the axial ends of the needle valve 110 and the push rod 120, the axial end on the needle valve 110 side corresponds to the "first end," and the axial end on the push rod 120 side (i.e., the connecting end 122) corresponds to the "second end."

[0075] The operation of the connecting structure of the needle valve 110 and the push rod 120 when the fuel injection valve 100 is opened or closed will be described below.

[0076] Fig. 13(a) shows the connecting structure of the fuel injection valve 100 in a valve-closed state. In this state, the needle valve 110 is held in the valve-closed position by a spring 27 (not shown). In Fig. 13(b), the push rod 120 moves downward in the figure when the solenoid is energized, thereby opening the needle valve 110.

[0077] 13C, immediately after the needle valve 110 hits the seat 14a (immediately after the needle valve 110 reaches the closed position), the push rod 120 is displaced upward in the figure with the needle valve 110 abutting against the seat 14a. In this case, pressure is increased in the first pressure chamber S11 and reduced in the second pressure chamber S12. As a result, forces are generated on the needle valve 110 and the push rod 120 that do not move them away from each other. This suppresses bouncing of the needle valve 110 after it closes (i.e., after it is seated).

[0078] The spherical expanded diameter portion 123 of the push rod 120 comes into contact with the inside of the cylindrical portion 113 of the needle valve 110. In this case, the inner circumferential surface of the cylindrical portion 113 of the needle valve 110 and the expanded diameter portion 123 of the push rod 120 come into contact with each other at spherical surfaces, so that sliding wear in the connecting structure between the needle valve 110 and the push rod 120 is suppressed.

[0079] Figure 14 is a time chart showing the lift behavior of the needle valve 110 when the fuel injection valve 100 is closed. In Figure 14, the solid line shows the lift behavior of the fuel injection valve 100 having the connecting structure described in Figure 12, and the dashed line shows the lift behavior of the fuel injection valve not having the connecting structure shown in Figure 12. In this case, during the period A in Figure 14, the push rod 120 moves separately from the needle valve 110 immediately after the needle valve 110 collides with the seat portion 14a, and pressure changes occur in the pressure chambers S11 and S12, preventing the needle valve 110 from lifting again. This prevents the needle valve 110 from bouncing after closing.

[0080] The connecting structure of the needle valve 110 and the push rod 120 may have the configuration shown in Fig. 15. In the connecting structure shown in Fig. 15, a communication hole 141 is provided in the connecting end 122 of the push rod 120, connecting the first pressure chamber S11 and the second pressure chamber S12 in the cylindrical portion 113. The communication hole 141 may be a throttle passage through which pressure loss occurs when fluid passes. The communication hole 141 is, for example, a communication passage formed by a series of circular openings, and is formed in a T-shape in the vertical cross section of the push rod 120.

[0081] 15 , when the fuel injection valve 100 is closed, immediately after the first pressure chamber S11 becomes relatively high pressure and the second pressure chamber S12 becomes relatively low pressure as the push rod 120 starts to move away from the needle valve 110, the fluid in the first pressure chamber S11 moves toward the second pressure chamber S12 through the communication hole 141. This causes the pressure in the first pressure chamber S11 to escape to the second pressure chamber S12, reducing the pressure difference between the pressure chambers S11 and S12. This prevents the push rod 120 from colliding again with the needle valve 110 due to the pressure difference between the pressure chambers S11 and S12 after the push rod 120 starts to move away from the needle valve 110. In other words, by providing the communication hole 141 in the connection end 122 of the push rod 120, the push rod 120 is maintained in a state of moving toward the side away from the needle valve 110, stabilizing the behavior of the push rod 120.

[0082] The communication hole 141 is formed in a T-shape in the vertical cross section of the push rod 120, which allows for good processability and ensures shape precision. However, the shape of the communication hole 141 can be changed to other shapes, and it is also possible to configure the communication hole 141 to branch into multiple holes on the first pressure chamber S11 side and the second pressure chamber S12 side, or to configure the communication hole 141 to communicate with the pressure chambers S11, S12 in a straight line oriented obliquely to the axial direction.

[0083] The connecting structure of the needle valve 110 and the push rod 120 may also be configured as shown in Figure 16. Figure 16(b) is a cross-sectional view taken along line 16b-16b in Figure 16(a). In Figure 16, at least a portion of the spherical expanded diameter portion 123 of the push rod 120 forms a flat surface 123a. As a result, a minute gap (corresponding to a communication hole) that communicates between the pressure chambers S11 and S12 is formed between the inner circumferential surface of the cylindrical portion 113 and the flat surface 123a of the expanded diameter portion 123.

[0084] 16 , when the fuel injection valve 100 is closed, immediately after the first pressure chamber S11 becomes relatively high pressure and the second pressure chamber S12 becomes relatively low pressure as the push rod 120 starts to separate from the needle valve 110, the fluid in the first pressure chamber S11 moves to the second pressure chamber S12 through the gap between the inner circumferential surface of the cylindrical portion 113 and the expanded diameter portion 123. As a result, the pressure in the first pressure chamber S11 escapes to the second pressure chamber S12, reducing the pressure difference between these pressure chambers S11 and S12.

[0085] According to the present embodiment described above in detail, the following effects are achieved in addition to the effects of the first embodiment.

[0086] A connecting structure is provided at the connecting portion between the axial ends of the needle valve 110 and the push rod 120. This generates a force that prevents the needle valve 110 and the push rod 120 from moving away from each other (i.e., a pulling force) when the push rod 120 is displaced toward the opposite side of the needle valve after the needle valve 110 reaches the closed position from the open position. This makes it possible to suitably suppress bounce of the needle valve 110 after the needle valve 110 is closed (i.e., after it is seated).

[0087] The connecting end 122 of the push rod 120 is housed within the cylindrical portion 113 of the needle valve 110, and movement of the push rod 120 away from the needle valve 110 causes a pressure change within the cylindrical portion 113, which generates a force that prevents the needle valve 110 and the push rod 120 from moving away from each other. In this case, the movement of the push rod 120 attracts the needle valve 110 and the push rod 120 to each other, and bounce of the needle valve 110 can be suitably suppressed.

[0088] Within the cylindrical portion 113 of the needle valve 110, movement of the push rod 120 away from the needle valve 110 generates pressure and pressure in the first pressure chamber S11 and the second pressure chamber S12 provided on both axial sides of the expanded diameter portion 123. This makes it possible to appropriately generate a force in a direction that prevents the needle valve 110 and the push rod 120 from moving away from each other when the push rod 120 moves separately from the needle valve 110.

[0089] A communication hole 141 that communicates between the first pressure chamber S11 and the second pressure chamber S12 is provided in the connecting end 122 of the push rod 120. As a result, when the fuel injection valve 100 is closed, immediately after the first pressure chamber S11 becomes high pressure and the second pressure chamber S12 becomes low pressure as the push rod 120 starts to move away from the needle valve 110, the pressure in the first pressure chamber S11 can be released to the second pressure chamber S12, and the state in which the push rod 120 moves toward the side where the needle valve 110 moves away can be stably maintained.

[0090] The connecting end 122 of the push rod 120 is provided with a spherical expanded diameter portion 123 that expands in the radial direction. In this case, the connecting end 122 of the push rod 120 comes into contact with the cylindrical portion 113 of the needle valve 110 via the spherical expanded diameter portion 123. This suppresses sliding wear in the connecting structure between the needle valve 110 and the push rod 120, and ultimately enables favorable sliding operation even when the push rod 120 is displaced or tilted laterally.

[0091] (Modification of the Second Embodiment) The fuel injection valve 100 may have a configuration shown in FIG. 17 . In FIG. 17 , a spring 151 made of a compression coil spring is provided in the recess 35 of the fixed core 31 between the axial end surface of the recess 35 and the movable core 32. The spring 151 biases the movable core 32 downward in the figure. The spring 151 is a biasing member having a biasing force smaller than that of the spring 27 (see FIG. 10 ) that biases the needle valve 110 in the valve closing direction. The spring 151 is provided as a return assisting member that assists the push rod 120 in returning to the valve closing position where it abuts against the needle valve 110 when the fuel injection valve 100 is closed after the needle valve 110 reaches the valve closing position from the valve open position and the push rod 120 starts to move separately from the needle valve 110.

[0092] According to the above configuration, after the fuel injection valve 100 finishes injecting fuel, the push rod 120 can be returned to a state (initial state) in which it abuts against the needle valve 110 before the next fuel injection starts, i.e., before the needle valve 110 starts to lift. Therefore, it is possible to suppress the occurrence of dead time at the beginning of the valve opening.

[0093] The configuration shown in Fig. 18 may be employed as the configuration of the connecting structure between the needle valve 110 and the push rod 120. In Fig. 18, a stopper 161 is provided at the connecting end 122 of the push rod 120, inside the cylindrical portion 113 of the needle valve 110, and at a position on the side opposite the valve body tip (upper side in the figure) from the enlarged diameter portion 123. The stopper 161 is provided as a protrusion that protrudes in the radial direction.

[0094] In the fuel injection valve 100, when the movable dimension of the movable core 32 is L1 (see FIG. 10 ) and the distance between the stopper 161 of the push rod 120 and the cover 130 is L2 (see FIG. 18 ), these dimensions L1 and L2 satisfy the relationship L1 > L2. As a result, when the push rod 120 is displaced within the cylindrical portion 113, the stopper 161 of the push rod 120 abuts against the cover 130 before the movable core 32 abuts against the axial end face within the recess 35 of the fixed core 31.

[0095] The stopper 161 is provided as a displacement limiting portion that limits the displacement of the push rod 120 relative to the needle valve 110 when the push rod 120 is displaced toward the opposite side of the needle valve separately from the needle valve 110. In this configuration, the stopper 161 limits the displacement of the push rod 120 after the push rod 120 starts to move separately from the needle valve 110. This makes it possible to suitably reduce the kinetic energy of the push rod 120 after the push rod 120 starts to move separately.

[0096] The configuration shown in Fig. 19 may be employed as the configuration of the connecting structure between the needle valve 110 and the push rod 120. In Fig. 19, the seal member 133 interposed between the cover 130 on the needle valve 110 side and the connecting end 122 of the push rod 120 is made of a composite material of a thermosetting elastomer 133a and a thermoplastic resin 133b. The seal member 133 is attached in the recess 132 with the thermoplastic resin 133b in contact with the connecting end 122 of the push rod 120. In this case, the thermoplastic resin 133b, which has a self-lubricating function, improves sliding properties, while the thermosetting elastomer 133a provides a lubricant seal.

[0097] The configuration shown in Fig. 20 may be employed as the configuration of the connecting structure between the needle valve 110 and the push rod 120. In Fig. 20, a through hole 131 is provided in the cover 130 on the needle valve 110 side, and the connecting end 122 of the push rod 120 is inserted into the through hole 131 with a clearance (gap) formed between the cover 130 and the connecting end 122 of the push rod 120 and the inner circumferential surface of the through hole 131. In addition, a hollow disk-shaped diaphragm or a metal leaf spring is provided between the cover 130 and the connecting end 122 of the push rod 120 as a seal member 162 that is expandable and contractible in the axial direction of the needle valve 110. This makes it possible to achieve both reduced sliding resistance and an airtight seal in the sliding portion between the cover 130 and the connecting end 122 (shaft portion 121) of the push rod 120.

[0098] The configuration shown in Fig. 21 may be employed as the configuration of the connecting structure of the needle valve 110 and the push rod 120. In Fig. 21, a gas and a liquid are sealed in an airtight chamber closed by a cover 130 within the cylindrical portion 113 of the needle valve 110. In this case, the viscosity and compression amount in the airtight chamber can be changed by adjusting the mixture ratio of gas and liquid within the cylindrical portion 113, making it easy to adjust the damping characteristics to the desired characteristics.

[0099] The configuration shown in Fig. 22 may be employed as the configuration of the connecting structure of the needle valve 110 and the push rod 120. In Fig. 22, a hollow disk-shaped diaphragm or a metal leaf spring is provided inside the cylindrical portion 113 of the needle valve 110 between the inner circumferential surface of the cylindrical portion 113 and the connecting end portion 122 of the push rod 120 as a partition member 163 that is expandable and contractible in the axial direction of the needle valve 110 and that partitions the inside of the cylindrical portion 113 into a first pressure chamber S11 and a second pressure chamber S12.

[0100] In the fuel injection valve 100 described above, the axial end of the needle valve 110 is provided with a cylindrical portion 113, and the axial end (connecting end 122) of the push rod 120 is housed within the cylindrical portion 113. However, this configuration may be modified. That is, as shown in FIG. 23 , the axial end of the push rod 120 is provided with a cylindrical portion 125, and the axial end 115 of the needle valve 110 is housed within the cylindrical portion 125. In this case, similar to FIG. 12 etc., the axial end 115 of the needle valve 110 may be provided with a spherical enlarged diameter portion 116, and the enlarged diameter portion 116 may form a first pressure chamber S11 and a second pressure chamber S12 within the cylindrical portion 125. Note that, for other configurations, the needle valve 110 side and the push rod 120 side may be interchanged.

[0101] 23 , when the fuel injection valve 100 is closed, a pressure change occurs inside the cylindrical portion 125 due to the movement of the push rod 120 away from the needle valve 110, and this pressure change can generate a force in a direction that prevents the needle valve 110 and the push rod 120 from moving away from each other. As a result, after the needle valve 110 reaches the valve closing position, the needle valve 110 and the push rod 120 are attracted to each other, and bounce of the needle valve 110 can be suitably suppressed.

[0102] In the fuel injection valve 100, the configuration shown in Fig. 24 may be employed as the configuration of the connecting structure between the needle valve 110 and the push rod 120. In Fig. 24, a tension coil spring 171 is provided between the needle valve 110 and the push rod 120 as the connecting structure. Note that Fig. 24 does not show the spring 27 that biases the needle valve 110 in the valve closing direction (upward in the figure). The tension coil spring 171 is provided as an attracting member that attracts the needle valve 110 and the push rod 120 to each other when the push rod 120 moves away from the needle valve 110.

[0103] In the fuel injection valve 100 having this configuration, when the push rod 120 displaces separately from the needle valve 110 toward the side opposite the needle valve after the needle valve 110 reaches the valve closed position from the valve open position, a force is generated in a direction that prevents the needle valve 110 and the push rod 120 from moving away from each other. In this case, the movement of the push rod 120 attracts the needle valve 110 and the push rod 120 toward each other, thereby making it possible to suitably suppress the bounce of the needle valve 110.

[0104] The technical ideas extracted from the above-described embodiments will be described below. a movable core (32) that is attracted to the fixed core in response to generation of a driving magnetic flux and opens the needle valve; and a push rod (40, 120) that is provided between the needle valve and the movable core in the axial direction, the push rod pushing the needle valve toward the open valve side when the valve is opened in response to generation of the driving magnetic flux, and movable separately from the needle valve when the valve is closed in response to loss of the driving magnetic flux. [Configuration 2] The gas fuel injection valve according to Configuration 1, further comprising: a bellows (50) fixed to the needle valve and axially expandable and contractible in response to movement of the needle valve as an isolating member surrounding the push rod and isolating an accommodation space (51) of the push rod from the fuel passage within the main body, the bellows having a cylindrical shape and being fixed to the needle valve and being axially expandable and contractible in response to movement of the needle valve; a movable end of the bellows being fixed to a connecting end of the needle valve to which an axial end of the push rod is connected, and the push rod being connected to the connecting end so as to be separately movable in the axial direction. [Configuration 3] The gas fuel injection valve according to Configuration 2, further comprising: a guide portion (25) extending in the axial direction, surrounding the axial end of the push rod, and guiding axial movement of the push rod; and a spherically shaped end of the push rod guided by the guide portion.[Configuration 5] The gas fuel injection valve according to Configuration 4, wherein the cylindrical guide portion is provided at the connecting end of the needle valve, the inside of the guide portion is a rod end accommodating portion (26) that accommodates the spherically formed axial end portion of the push rod, and a space portion in the rod end accommodating portion that is closer to the tip of the push rod than a portion that is closest to the spherical portion of the axial end of the push rod forms a damper chamber (26a). [Configuration 6] The gas fuel injection valve according to Configuration 4 or 5, wherein, of the axial ends of the push rod, a first end is on the side of the needle valve and a second end is on the side of the movable core, the axial end face of the first end has a circular flat shape and abuts against the axial end face of the needle valve, while the axial end face of the second end has a circular flat shape and abuts against the axial end face of the movable core, and wherein, when a diameter of the axial end faces of the first end and the second end of the push rod is D1 and a maximum value of an axial misalignment between the first end and the second end of the push rod is em, the relationship between the diameter D1 and the maximum value of the axial misalignment em satisfies D1 / em > 1. [Configuration 7] The gas fuel injection valve according to Configuration 6, further comprising a restricting portion (61) that restricts the amount of movement of the connecting end of the needle valve in a direction perpendicular to the axial direction so that the relationship between the diameter D1 and the maximum value of the axial misalignment em satisfies D1 / em > 1. [Configuration 8] The gas fuel injection valve according to Configuration 4 or 5, wherein the push rod has two axial ends, one of which is on the needle valve side and the other is on the movable core side, and wherein the axial end faces of the first end and the second end of the push rod are spherical surfaces, and the relationship between a radius R1 of the spherical surface and an axial length L of the push rod satisfies R1≧L / 2.[Configuration 9] The gas fuel injection valve according to any one of Configurations 4 to 8, wherein a connecting end of the needle valve connected to an axial end of the push rod has an end plate (71) formed integrally with a shaft portion (21) extending in the axial direction, the guide portion, and an intermediate plate (72) interposed between the end plate and the guide portion, the end plate and the guide portion being fixed to the intermediate plate by welding, and the intermediate plate being made of a steel material having a lower carbon content than the end plate and the guide portion. [Configuration 10] The gas fuel injection valve according to any one of Configurations 4 to 9, wherein a connecting end of the needle valve connected to an axial end of the push rod has an end plate (71) formed integrally with a shaft portion (21) extending in the axial direction, the guide portion, and an intermediate plate (72) interposed between the end plate and the guide portion, and the guide portion has a surface hardness greater than that of the intermediate plate. [Configuration 11] The gas fuel injection valve according to any one of Configurations 1 to 10, wherein the needle valve has a sliding portion (24) that slides within the injection hole. [Configuration 12] The gas fuel injection valve according to any one of Configurations 1 to 11, wherein, when a cross-sectional area of ​​a stem portion (21) extending in the axial direction of the needle valve is S1 and a cross-sectional area of ​​a stem portion (41) extending in the axial direction of the push rod is S2, the cross-sectional areas S1 and S2 satisfy the relationship S1 < S2. [Configuration 13] The gas fuel injection valve according to any one of Configurations 1 to 12, wherein the push rod has a separation structure that transitions from a state in which the push rod and the movable core operate together to a state in which the movable core operates independently after the separate movement relative to the needle valve begins during a valve-closing operation of the needle valve.[Configuration 14] The gas fuel injection valve according to any one of Configurations 1 to 3, wherein the needle valve and the push rod are connected at their axial ends in a state where they can move separately from each other, and a connecting structure is provided at the connecting portion between the axial ends of the needle valve and the push rod to generate a force in a direction that prevents the needle valve and the push rod from moving apart when the push rod displaces separately from the needle valve toward the side opposite the needle valve after the needle valve reaches a valve closed position from a valve open position. [Configuration 15] The gas fuel injection valve according to Configuration 14, wherein a cylindrical portion (113, 125) is provided at a first end, which is one of the axial ends of the needle valve and the push rod, and a second end, which is the other axial end, is housed within the cylindrical portion so as to be axially movable, and the connecting structure generates a pressure change within the cylindrical portion due to movement of the push rod away from the needle valve, and the pressure change generates a force in a direction that prevents the needle valve and the push rod from moving away from each other. [Configuration 16] The gas fuel injection valve according to Configuration 15, wherein the second end is provided with an expanded diameter section (123, 116) expanded in the radial direction, a first pressure chamber (S11) is provided within the cylindrical section on one of the axially opposite sides of the expanded diameter section on the side opposite the tip of the needle valve, and a second pressure chamber (S12) is provided on the tip side of the needle valve, and in the connecting structure, movement of the push rod away from the needle valve generates pressure in the first pressure chamber and pressure in the second pressure chamber, thereby generating a force that does not move the needle valve and the push rod away from each other. [Configuration 17] The gas fuel injection valve according to Configuration 16, wherein the connecting structure has a communication hole (141) that connects the first pressure chamber and the second pressure chamber. [Configuration 18] The gas fuel injection valve according to any one of Configurations 15 to 17, wherein the second end is provided with an expanded diameter portion (123, 116) that expands in the radial direction, and the expanded diameter portion is formed in a spherical shape.[Configuration 19] The gas fuel injection valve according to any one of Configurations 15 to 18, further comprising a return assist member (151) that assists the push rod in returning to the valve closed position in contact with the valve needle after the valve needle has reached the valve closed position from the valve open position and the push rod has started to move separately from the valve needle. [Configuration 20] The gas fuel injection valve according to any one of Configurations 15 to 19, further comprising a displacement limiting portion (161) at the second end that limits displacement of the push rod relative to the valve needle when the push rod is displaced separately from the valve needle toward the side opposite the valve needle. [Configuration 21] The gas fuel injection valve according to any one of Configurations 15 to 20, wherein a cover (130) that opens to one axial side and closes the opening is attached to the cylindrical portion provided at the first end, which is one axial end of the needle valve and the push rod, the second end, which is the other axial end, is inserted into a through hole (131) of the cover, and a seal member (133) is interposed between the cover and the second end, and the seal member is a composite material of a thermosetting elastomer and a thermoplastic resin. [Configuration 22] The gas fuel injection valve according to Configuration 15, wherein a cover (130) opening to one axial side and closing the opening is attached to the cylindrical portion provided at the first end, which is one axial end of the needle valve and the push rod, the second end, which is the other axial end, is inserted into a through-hole (131) of the cover with a gap therebetween, and a seal member (162) expandable in the axial direction of the needle valve is interposed between the cover and the second end. [Configuration 23] The gas fuel injection valve according to any of Configurations 15 to 22, wherein a cover (130) opening to one axial side and closing the opening is attached to the cylindrical portion provided at the first end, which is one axial end of the needle valve and the push rod, and a gas and a liquid are sealed in an airtight chamber closed by the cover within the cylindrical portion.[Configuration 24] The gas fuel injection valve according to Configuration 14, wherein the connecting structure includes an attracting member (171) that attracts the needle valve and the push rod to each other when the push rod moves away from the needle valve.

[0105] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A gas fuel injection valve (10, 100) for injecting gas fuel, comprising: a cylindrical main body (11) having a fuel passage (15) therein and a nozzle hole (17) at its tip; an outward-opening needle valve (20, 110) provided within the main body, reciprocable in the axial direction, and closing the nozzle hole from the outside; a biasing member (27) for biasing the needle valve in a direction for closing the nozzle hole; a fixed core (31) fixed to the main body; a movable core (32) that is attracted to the fixed core as a driving magnetic flux is generated, and opens the needle valve; and a push rod (40, 120) provided between the needle valve and the movable core in the axial direction, for pushing the needle valve toward the valve opening side when the valve is opened as the driving magnetic flux is generated, and for being movable separately from the needle valve when the valve is closed as the driving magnetic flux is lost.

2. A gas fuel injection valve as described in claim 1, comprising a bellows (50) fixed to the needle valve and capable of expanding and contracting in the axial direction as the needle valve moves, as an isolating member that is cylindrical and surrounds the push rod and isolates the push rod accommodation space (51) from the fuel passage within the main body, and the movable end of the bellows is fixed to a connecting end of the needle valve to which the axial end of the push rod is connected, and the push rod is connected to the connecting end so as to be separately movable in the axial direction.

3. The gas fuel injection valve according to claim 2, wherein the biasing member and the bellows are arranged side by side in the axial direction within the main body.

4. A gas fuel injection valve as set forth in any one of claims 1 to 3, wherein a connecting end of the needle valve that is connected to the axial end of the push rod is provided with a guide portion (25) that extends axially, has a shape that surrounds the axial end of the push rod, and guides the axial movement of the push rod, and the axial end of the push rod that is guided by the guide portion is formed in a spherical shape.

5. A gas fuel injection valve as set forth in claim 4, wherein the cylindrical guide portion is provided at the connecting end of the needle valve, the inside of the guide portion is a rod end accommodating portion (26) in which the spherically formed axial end portion of the push rod is accommodated, and the space in the rod end accommodating portion closer to the tip of the push rod than the portion closest to the spherical portion of the axial end of the push rod forms a damper chamber (26a).

6. A gas fuel injection valve as set forth in claim 4, wherein the push rod has two axial ends, one on the needle valve side is a first end and one on the movable core side, the axial end face of the first end is circular and flat and abuts the axial end face of the needle valve, while the axial end face of the second end is circular and flat and abuts the axial end face of the movable core, and wherein, when the diameter of the axial end faces of the first end and the second end of the push rod is D1 and the maximum axial misalignment amount, which is the amount of axial misalignment between the first end and the second end of the push rod, is em, the relationship between the diameter D1 and the maximum axial misalignment amount em satisfies D1 / em>1.

7. A gas fuel injection valve as described in claim 6, having a regulating portion (61) that regulates the amount of movement of the connecting end of the needle valve in a direction perpendicular to the axial direction so that the relationship between the diameter D1 and the maximum axial deviation amount em is D1 / em>1.

8. A gas fuel injection valve as set forth in claim 4, wherein the push rod has two axial ends, one of which is on the needle valve side and the other is on the movable core side, the axial end faces of the first end and the second end of the push rod are spherical surfaces, and the relationship between the radius R1 of the spherical surface and the axial length L of the push rod satisfies R1 ≧ L / 2.

9. A gas fuel injection valve as described in claim 4, wherein the connecting end of the needle valve connected to the axial end of the push rod has an end plate (71) formed integrally with an axially extending shaft portion (21), the guide portion, and an intermediate plate (72) interposed between the end plate and the guide portion, the end plate and the guide portion being fixed to the intermediate plate by welding, and the intermediate plate being made of steel having a lower carbon content than the end plate and the guide portion.

10. A gas fuel injection valve as described in claim 4, wherein the connecting end of the needle valve connected to the axial end of the push rod has an end plate (71) formed integrally with an axially extending shaft portion (21), the guide portion, and an intermediate plate (72) interposed between the end plate and the guide portion, and the guide portion has a surface hardness greater than that of the intermediate plate.

11. A gas fuel injection valve according to any one of claims 1 to 3, wherein the needle valve has a sliding portion (24) that slides within the injection hole.

12. A gas fuel injection valve as set forth in any one of claims 1 to 3, wherein, when the cross-sectional area of ​​the axially extending shaft portion (21) of the needle valve is S1 and the cross-sectional area of ​​the axially extending shaft portion (41) of the push rod is S2, the cross-sectional areas S1 and S2 satisfy the relationship S1 < S2.

13. A gas fuel injection valve as claimed in any one of claims 1 to 3, wherein the push rod has a separation structure that transitions the push rod and the movable core from a state of integral operation to a state of independent operation of the movable core after the separate movement relative to the needle valve is initiated during the closing operation of the needle valve.

14. A gas fuel injection valve as claimed in any one of claims 1 to 3, wherein the axial ends of the needle valve and the push rod are connected together in a state in which they can move separately from each other, and the connecting portion between the axial ends of the needle valve and the push rod is provided with a connecting structure that generates a force in a direction that prevents the needle valve and the push rod from moving apart when the push rod displaces separately from the needle valve towards the side opposite the needle valve after the needle valve has reached its open position to its closed position.

15. A gas fuel injection valve as described in claim 14, wherein a cylindrical tubular portion (113, 125) is provided at one of the axial ends of the needle valve and the push rod, i.e., a first end, and the other axial end, i.e., a second end, is housed within the cylindrical portion so as to be movable in the axial direction, and the connecting structure portion generates a pressure change within the cylindrical portion due to movement of the push rod away from the needle valve, and this pressure change generates a force in a direction that prevents the needle valve and the push rod from moving away from each other.

16. A gas fuel injection valve as described in claim 15, wherein the second end is provided with an expanded diameter section (123, 116) expanded in the radial direction, a first pressure chamber (S11) is provided within the cylindrical section on both axial sides of the expanded diameter section on the side opposite the tip of the needle valve, and a second pressure chamber (S12) is provided on the tip side of the needle valve, and in the connecting structure section, movement of the push rod away from the needle valve causes pressurization in the first pressure chamber and depressurization in the second pressure chamber, thereby generating a force in a direction that prevents the needle valve and the push rod from moving away from each other.

17. A gas fuel injection valve according to claim 16, wherein the connecting structure has a communication hole (141) that communicates the first pressure chamber with the second pressure chamber.

18. A gas fuel injection valve according to claim 15, wherein the second end is provided with an expanded diameter portion (123, 116) that expands in the radial direction, and the expanded diameter portion is formed in a spherical shape.

19. A gas fuel injection valve as described in claim 15, further comprising a return assist member (151) that assists the push rod in returning to the closed position in which it abuts against the needle valve after the needle valve has reached the closed position from the open position and the push rod has begun to move separately from the needle valve.

20. A gas fuel injection valve as described in claim 15, wherein the second end has a displacement limiting portion (161) that limits the displacement of the push rod relative to the needle valve when the push rod is displaced separately from the needle valve toward the side opposite the needle valve.

21. A gas fuel injection valve as described in claim 15, wherein a cover (130) that opens to one axial side and closes the opening is attached to the cylindrical portion provided at the first end, which is one axial end of the needle valve and the push rod, the second end, which is the other axial end, is inserted into a through hole (131) of the cover, a sealing member (133) is interposed between the cover and the second end, and the sealing member is a composite material of a thermosetting elastomer and a thermoplastic resin.

22. A gas fuel injection valve as described in claim 15, wherein a cover (130) that opens to one axial side and closes the opening is attached to the cylindrical portion provided at the first end, which is one axial end of the needle valve and the push rod, and the second end, which is the other axial end, is inserted into a through hole (131) of the cover with a gap therebetween, and a sealing member (162) that is expandable and contractible in the axial direction of the needle valve is interposed between the cover and the second end.

23. A gas fuel injection valve as set forth in claim 15, wherein a cover (130) that opens to one axial side and closes said opening is attached to said cylindrical portion provided at said first end, which is one axial end of said needle valve and said push rod, and a gas and a liquid are sealed in an airtight chamber within said cylindrical portion that is closed by said cover.

24. A gas fuel injection valve as described in claim 14, wherein the connecting structure has an attracting member (171) that attracts the needle valve and the push rod to each other when the push rod moves away from the needle valve.

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