Gas fuel injection valve and fuel injection system

Abstract

To protect a valve element while increasing a flow rate of gas fuel.SOLUTION: In a fuel injection valve 10, during fuel injection, a first movable core 31 is sucked to a fixation core 20 along with generation of a driving magnetic flux, and lifts a valve element 42 from a valve closing position to a first lift position. Following the lift of the valve element to the first lift position by using the first movable core 41, a second movable core 41 lifts the valve element 42 from the first lift position to a second lift position where a lift amount is larger than that at the first lift position through suction to the fixation core 20 due to the driving magnetic flux. When the fuel injection is finished, the valve element 42 is returned from the second lift position to the first lift position, and is returned to the valve closing position by using energizing force of a spring 45 after temporarily stopping at the first lift position.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] TECHNICAL FIELD The disclosure herein relates to gas fuel injectors and fuel injection systems. [Background technology]

[0002] As a gas fuel injection valve used in a direct injection gas engine, for example, a gas metering valve described in Patent Document 1 is known. Patent Document 1 discloses a configuration of a gas metering valve having a valve member that opens the inlet opening of a gas chamber and a shutoff valve provided downstream of the valve member, specifically between the valve member and the outlet opening of the gas chamber, in which the upstream valve member moves to the valve opening side by the magnetic attractive force of an electromagnet, and the downstream shutoff valve moves to the valve opening side by pressure balance after the valve member is opened. Patent Document 1 also discloses a configuration in which when the upstream valve member moves to the valve opening side by the magnetic attractive force of an electromagnet, the downstream shutoff valve moves to the valve opening side mechanically linked to the valve member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2023-513065 Summary of the Invention [Problem to be solved by the invention]

[0004] In a gas fuel injection valve, since it is desired to increase the injection rate of gas fuel having a large fuel volume, it has been considered to increase the valve element lift amount. However, in a configuration in which the valve element lift amount is increased, when the valve element is moved from the open position to the closed position, the impact when the valve element hits the seat surface becomes large, and there is a concern that the valve element may be worn. Furthermore, there is a concern that the wear of the valve element may cause leakage of the gas fuel.

[0005] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a gas fuel injection valve and a fuel injection system that can protect the valve body while increasing the flow rate of gas fuel. [Means for solving the problem]

[0006] The present disclosure relates to A gas fuel injection valve that injects gas fuel, a main body having a fuel passage through which gas fuel passes and an injection hole through which the gas fuel in the fuel passage is injected; a valve body that opens and closes the injection hole; A spring member that biases the valve body in a valve closing direction; A fixed core fixed to the main body portion; a first movable core that is attracted to the fixed core in response to generation of a driving magnetic flux during fuel injection, thereby lifting the valve body from a valve closing position to a first lift position; a second movable core that, following the first movable core lifting the valve element to the first lift position, is attracted to the fixed core by the driving magnetic flux, thereby lifting the valve element from the first lift position to a second lift position having a larger lift amount than the first lift position, At the end of fuel injection, the valve body is returned from the second lift position to the first lift position, temporarily stopped at the first lift position, and then returned to the valve closed position by the biasing force of the spring member.

[0007] In the gas fuel injection valve having the above configuration, during fuel injection, the first movable core is attracted to the fixed core as a result of the generation of a driving magnetic flux, and lifts the valve element from the valve-closed position to the first lift position. Following the first movable core lifting the valve element to the first lift position, the second movable core is attracted to the fixed core by the driving magnetic flux, and lifts the valve element from the first lift position to a second lift position having a larger lift amount than the first lift position. This results in a two-stage valve element lift, enabling a large flow rate of gas fuel.

[0008] Also, at the end of fuel injection, the valve body returns from the second lift position to the first lift position, pauses at the first lift position, and then returns to the valve-closed position by the biasing force of the spring member. In this case, the valve body does not move directly from the maximum opening (second lift position) to the valve-closed position, but pauses at an intermediate position (first lift position) and then returns to the valve-closed position. Therefore, the impact when the valve body hits the seat surface is reduced, and wear of the valve body can be suppressed. As a result, while increasing the large flow rate of the gaseous fuel, the valve body can be protected.

Brief Description of the Drawings

[0009] [Figure 1] Longitudinal sectional view of the fuel injection valve. [Diagram 2] Cross-sectional view of the fuel injection valve. [Diagram 3] Explanatory drawing showing the relationship between the fixed core and each movable core. [Figure 4] Drawing for explaining the operation of the fuel injection valve at the time of valve opening. [Diagram 5] Drawing for explaining the operation of the fuel injection valve at the time of valve closing. [Figure 6] Flowchart showing the energization control process of the solenoid coil. [Figure 7] Drawing showing the relationship between the pressure of the gaseous fuel and time TA. [Figure 8] Time chart showing the change in the lift amount of each movable core, the change in the applied current, and the change in the injection rate when the fuel injection valve opens and closes. [Figure 9] Time chart showing the valve body speed when the valve body closes. [Figure 10] Longitudinal sectional view of the fuel injection valve in the second embodiment. [Figure 11] Longitudinal sectional view showing the valve-open state of the fuel injection valve in the second embodiment. [Figure 12] Flowchart showing the energization control process of the solenoid coil in the second embodiment. [Figure 13] Longitudinal sectional view of the fuel injection valve in another example.

Embodiments for Carrying Out the Invention

[0010] (First embodiment) An embodiment of the gas fuel injection valve according to the present disclosure will be described below 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, CNG (Compressed Natural Gas), and LNG (Liquefied Natural Gas), and the gas fuel is directly injected into the combustion chamber of the gas engine by the gas fuel injection valve. The gas engine is, for example, an engine mounted on a vehicle. In this embodiment, the fuel injection system equipped with the gas fuel injection valve is a so-called low-pressure direct injection system in which gas fuel compressed to about several MPa is injected from the fuel injection valve into the combustion chamber.

[0011] The configuration of the fuel injection valve 10 will be described with reference to Figure 1. Figure 1 shows a longitudinal cross-sectional structure of the main parts 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 the axial direction, the direction extending radially from the axis is the radial direction, and the direction extending circumferentially around the axis is 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 side (downstream side).

[0012] The fuel injection valve 10 includes a cylindrical housing 11 having a fuel passage 12 therein. The housing 11 is made of a magnetic material, and a non-magnetic portion 11a made of a non-magnetic material is provided in the axial middle portion. The housing 11 has a cylindrical hollow portion, and the fuel passage 12 is formed by the hollow portion extending in the axial direction. Gas fuel is supplied to the fuel passage 12 from the axial base end side (upper side in the figure). When hydrogen gas is used as the gas fuel, gas fuel compressed to, for example, about 3 MPa is supplied to the fuel passage 12 from a fuel supply portion on the upstream side. The housing 11 corresponds to the "main body."

[0013] The housing 11 has an end plate portion 14 at its axial tip, and the end plate portion 14 is provided with an injection hole 14a for injecting gas fuel into the engine combustion chamber. The injection hole 14a is provided in the center of the end plate portion 14. The fuel injection valve 10 is mounted on the gas engine such that the end plate portion 14 is exposed inside the combustion chamber. The end plate portion 14 does not necessarily have to be flat extending in a direction perpendicular to the axial direction as shown in the figure, and may be, for example, conical with a convex tip.

[0014] A fixed core 20 made of a magnetic material is fixed in the housing 11. The fixed core 20 has a communication passage 21 that communicates the upstream side with the downstream side, and in the fuel passage 12, gas fuel can flow from the upstream side to the downstream side of the fixed core 20 via the communication passage 21. FIG. 2(a) is a cross-sectional view taken along line 2a-2a in FIG. 1. As shown in the figure, the fixed core 20 is provided with a plurality of communication passages 21 that are arc-shaped and aligned in the circumferential direction. However, the opening shape of the communication passage 21 may be arbitrary.

[0015] A first movable core 31 and a second movable core 41 are disposed in the fuel passage 12 on the upstream side of the fixed core 20, in other words, on the opposite side of the injection hole 14a in the axial direction across the fixed core 20. Each of these movable cores 31, 41 is made of a magnetic material.

[0016] The first movable core 31 is capable of reciprocating in the axial direction within the fuel passage 12 along the inner peripheral surface of the housing 11. The first movable core 31 has a plurality of communication passages 33 that communicate in the axial direction. FIG. 2(b) is a cross-sectional view taken along line 2b-2b in FIG. 1. As shown in the figure, the first movable core 31 is provided with a plurality of arc-shaped communication passages 33 that are aligned in the circumferential direction. The communication passages 33 are preferably provided at positions that are continuous with the communication passages 21 of the fixed core 20 in the axial direction.

[0017] The housing 11 is provided with a position restriction portion 15 that restricts the axial position of the first movable core 31. The first movable core 31 is movable in the axial direction between the position restriction portion 15 and the fixed core 20. The downstream end face of the first movable core 31 and the upstream end face of the fixed core 20 face each other and are parallel to each other.

[0018] The first movable core 31 is formed with a recess 35 that opens to the downstream side, and the second movable core 41 is provided in a state of being incorporated into the recess 35 of the first movable core 31. This allows the second movable core 41 to move integrally with the first movable core 31 to the valve opening side (the lower side in the figure). In other words, the first movable core 31 is in the form of a bottomed cylinder having a hollow portion, and the second movable core 41 is housed in the hollow portion in a movably state. Furthermore, the second movable core 41 is capable of reciprocating axially relative to the first movable core 31 within the recess 35.

[0019] The recess 35 of the first movable core 31 and the second movable core 41 are both circular in cross section, and the second movable core 41 is housed inside the annular first movable core 31. In this case, the upstream end face of the second movable core 41 faces the bottom (axial end face) of the recess 35, and when the first movable core 31 moves to the valve opening side, the first movable core 31 abuts against the second movable core 41, and these movable cores 31, 41 move together to the valve opening side.

[0020] The first movable core 31 is provided with a through hole 36 that penetrates in the axial direction and communicates with the recess 35. This allows gas fuel to flow into the back side of the second movable core 41. Here, in the first movable core 31, the through hole 36 is provided by reducing the diameter of the recess 35, and a step portion formed by the recess 35 and the through hole 36 serves as an abutment portion 37 that abuts against the second movable core 41 when the first movable core 31 moves integrally with the second movable core 41.

[0021] A sheet-like non-magnetic portion 43 made of a non-magnetic material is provided on the upstream end surface of the second movable core 41. The non-magnetic portion 43 may be provided between the bottom surface of the recess of the first movable core 31 and the second movable core 41, and may be provided on at least one of the bottom surface of the recess of the first movable core 31 and the second movable core 41.

[0022] A valve element 42 that opens and closes the injection hole 14a is integrated with the second movable core 41. The valve element 42 is needle-shaped and is provided so as to extend in the axial direction from the downstream end face of the second movable core 41. The valve element 42 is provided in a state in which it is inserted into the insertion hole 26 of the fixed core 20. The valve element 42 is an outward opening valve that opens when it moves to the outside of the housing.

[0023] The valve body 42 has a tip valve portion 44 at its axial tip. The valve body 42 is inserted into the injection hole 14a, and the tip valve portion 44 closes the injection hole 14a from the outside of the housing. In this case, the injection hole 14a is opened by the tip valve portion 44 moving away from the end plate portion 14. The valve body 42 is preferably made of a metal material, a nonmetal material, or other non-elastomer material having excellent heat resistance. The valve body 42 has an outward opening structure, which suppresses the flame and combustion pressure in the engine combustion chamber from flowing into the injection valve.

[0024] A spring 45 made of a compression coil spring is provided as a spring member between the second movable core 41 and the fixed core 20. The spring 45 urges the second movable core 41 toward a side moving away from the fixed core 20, i.e., toward a side where the tip valve portion 44 of the valve body 42 closes the injection hole 14a (valve closing side). The fixed core 20 is formed with a spring accommodating portion 23 at a position surrounding the shaft portion of the valve body 42, and the spring 45 is provided in a state of being accommodated in the spring accommodating portion 23.

[0025] Further, a recess 24 is formed in the center of the cross-section on the upstream end face of the fixed core 20. The recess 24 is provided with a size capable of accommodating the tip side of the second movable core 41 at a position axially opposed to the second movable core 41. An annular non-magnetic body portion 25 made of a non-magnetic material is provided on the inner peripheral surface of the recess 24 in the fixed core 20.

[0026] Since the second movable core 41 is biased toward the valve closing side by the spring 45, the tip valve portion 44 of the valve body 42 closes the injection hole 14a, and an air gap is formed between the second movable core 41 and the bottom surface of the recess 24 of the fixed core 20.

[0027] In addition to providing the spring 45 between the second movable core 41 and the fixed core 20, it is also possible to adopt a configuration in which a spring (compression coil spring) is provided between the first movable core 31 and the fixed core 20.

[0028] Both the first movable core 31 and the second movable core 41 face the fixed core 20 from the upstream side in the axial direction, but the separation distances (air gap dimensions) of the respective air gaps are different, and the configuration will be supplemented and explained with reference to FIG. 3. FIG. 3 is an explanatory diagram showing the relationship between the fixed core 20 and the movable cores 31 and 41. In FIG. 3, the communication passages 21 and 33 of the fixed core 20 and the first movable core 31 are not shown.

[0029] As shown in FIG. 3, an air gap G1 is formed between the downstream end face of the first movable core 31 and the upstream end face of the fixed core 20, and an air gap G2 is formed between the downstream end face of the second movable core 41 and the upstream end face of the fixed core 20 (specifically, the bottom surface of the recess 24). The separation distance D1 of the air gap G1 and the separation distance D2 of the air gap G2 satisfy D1 < D2. In this case, the first movable core 31 can move in the axial direction with the separation distance D1 as the upper limit, and the second movable core 41 can move in the axial direction with the separation distance D2 as the upper limit.

[0030] In FIGS. 1 and 3, the downstream end faces of the first movable core 31 and the second movable core 41 are flush with each other in the initial state (non-operating state), but the present invention is not limited to this configuration. For example, a configuration in which the downstream end face of the second movable core 41 is recessed into the inner side of the recess with respect to the downstream end face of the first movable core 31, or a configuration in which the downstream end face of the second movable core 41 protrudes outside the recess with respect to the downstream end face of the first movable core 31 may be employed. In any case, it is sufficient that the separation distances D1 and D2 of the air gaps G1 and G2 satisfy the relationship D1 < D2.

[0031] A solenoid coil 51 is provided at a position surrounding the first movable core 31 and the fixed core 20 in the fuel injection valve 10. The solenoid coil 51 is provided at a position overlapping the fixed core 20 and the respective movable cores 31 and 41 in the axial direction.

[0032] In addition to the fuel injection valve 10, the fuel injection system of the present embodiment includes a drive circuit 53 that energizes the solenoid coil 51 and a control device 54 that controls the fuel injection of the fuel injection valve 10. In the fuel injection system, the drive circuit 53 is connected to the solenoid coil 51 via a harness 52. The energization by the drive circuit 53 is controlled by the control device 54. The control device 54 includes a microcomputer having a CPU and various memories, and outputs an energization signal to the drive circuit 53 according to the combustion cycle of each cylinder during engine operation to cause the fuel injection valve 10 to perform fuel injection.

[0033] Further, in the fuel injection system of the present embodiment, the pressure of the gas fuel supplied to the fuel injection valve 10, that is, the injection pressure, is variably adjusted, and the control device 54 controls the pressure of the gas fuel based on the operating state of the gas engine and the like. The pressure of the gas fuel is set, for example, in the range of about 0.5 to 5 MPa.

[0034] In the fuel injection valve 10, the solenoid coil 51 is energized by the drive circuit 53 to generate magnetic energy, which attracts the first movable core 31 and the second movable core 41 to the fixed core 20. This moves the valve body 42 to the valve opening position, and gas fuel is injected from the injection hole 14a. In this embodiment, one solenoid coil 51 is configured to simultaneously drive the two movable cores 31, 41 to the valve opening side.

[0035] Next, a detailed description will be given of the operation of the fuel injection valve 10 when it is opened and closed. Figures 4(a) to (c) are diagrams for explaining the operation of the fuel injection valve 10 when it is opened, and Figures 5(a) to (c) are diagrams for explaining the operation of the fuel injection valve 10 when it is closed.

[0036] First, the operation of the fuel injection valve 10 when it is opened will be described with reference to Figs. 4(a) to (c). Fig. 4(a) shows an initial state, in which current is applied to the solenoid coil 51. As a result, as shown in Fig. 4(b), a driving magnetic flux is generated, a magnetic circuit is formed in the first magnetic flux path indicated by the arrow C1 in the figure, and a magnetic attraction force is generated that attracts the first movable core 31 and the fixed core 20 to each other. Then, the first movable core 31 is attracted to the fixed core 20, so that the second movable core 41 moves together with the first movable core 31, and the valve body 42 is lifted from the valve-closed position to the first lift position. At this time, the first movable core 31 and the second movable core 41 have different separation distances D1 and D2 from the fixed core 20 in the initial state (see Fig. 3), and at the beginning of current application to the solenoid coil 51, a magnetic circuit is formed in a path that passes through the first movable core 31, which is closer to the first movable core 31 of the two movable cores 31 and 41. As a result, when current begins to flow, magnetic flux flows intensively through the first magnetic flux path C1 including the first movable core 31, and the responsiveness of the first movable core 31 during its attraction movement is improved.

[0037] In the fuel injection valve 10, the first movable core 31 is disposed inside the solenoid coil 51, and the second movable core 41 is disposed further inside the first movable core 31. That is, the first movable core 31 is disposed radially outside the second movable core 41, that is, closer to the solenoid coil 51 than the second movable core 41. Therefore, when the solenoid coil 51 starts to be energized, a stronger magnetic attraction force is generated in the first movable core 31 against the fixed core 20 than in the second movable core 41, and the responsiveness of the first movable core 31 during the attraction movement is improved.

[0038] Further, a non-magnetic part 43 is interposed between the opposing surfaces of the first movable core 31 and the second movable core 41 that face each other in the axial direction. The non-magnetic part 43 functions as a magnetic flux regulating part that regulates the passage of magnetic flux between the first movable core 31 and the second movable core 41 in the state shown in Figures 4(a) and (b). This prevents magnetic flux from passing through unintended paths, and causes magnetic flux to flow intensively through the first magnetic flux path C1.

[0039] In the state of Fig. 4(b), the first movable core 31 abuts (seats) on the fixed core 20, and the distance between the second movable core 41 and the fixed core 20 is narrower than that in Fig. 4(a). The second movable core 41 moves to the valve opening side together with the first movable core 31 until the first movable core 31 abuts on the fixed core 20, and moves to the valve opening side by itself due to inertia after the first movable core 31 abuts on the fixed core 20. Therefore, the distance between the second movable core 41 and the fixed core 20 is narrowed, and a magnetic circuit is formed by the second magnetic flux path indicated by the arrow C2 in addition to the first magnetic flux path indicated by the arrow C1, and a magnetic attraction force is generated that attracts the second movable core 41 and the fixed core 20 to each other.

[0040] As a result, as shown in Fig. 4(c), the second movable core 41 is attracted to the fixed core 20 and seats on the fixed core 20. In this state, both the first movable core 31 and the second movable core 41 are seated on the fixed core 20, and the valve body 42 is lifted from the first lift position shown in Fig. 4(b) to the second lift position shown in Fig. 4(c). As a result, the opening of the injection hole 14a by the valve body 42 becomes the maximum opening. The state of Fig. 4(c) is maintained by continuing the energization of the solenoid coil 51.

[0041] Here, the portion of the fixed core 20 facing the first movable core 31 is thinned in the radial direction by providing the communication passage 21, forming a magnetically restricted portion. In this case, magnetic saturation occurs in the magnetically restricted portion of the fixed core 20 (i.e., the first magnetic flux path C1 passing through the first movable core 31 and the fixed core 20), and the amount of magnetic flux in the second magnetic flux path C2 (detour path) passing through the second movable core 41 and the fixed core 20 increases. This allows the second movable core 41 to be attracted to the fixed core 20 appropriately.

[0042] 4(c), a non-magnetic part 25 is interposed between the fixed core 20 and the second movable core 41 which face each other in the radial direction. The non-magnetic part 25 functions as a magnetic flux restricting part which restricts magnetic flux from passing in the radial direction between the fixed core 20 and the second movable core 41. This allows the fixed core 20 and the second movable core 41 to appropriately generate a magnetic attraction force in the axial direction.

[0043] As shown in Fig. 4(a), when the first movable core 31 is attracted to the fixed core 20 with the generation of the driving magnetic flux, the moving amount of the first movable core 31 is A1. As shown in Fig. 4(b), after the movement of the first movable core 31, when the second movable core 41 is attracted to the fixed core 20 alone, the moving amount of the second movable core is A2. And the moving amounts A1 and A2 are in the relationship of A1 < A2. In this case, since the moving amount A1 of the first movable core 31 at the beginning of energization is relatively small, the responsiveness of the movement of the first movable core 31 at the beginning of energization is enhanced. Also, since the single moving amount A2 of the second movable core is relatively large, the maximum opening degree of the valve body 42 can be increased while taking into account that an inertial force is applied to the second movable core 41 by the movement of the first movable core 31.

[0044] Next, the operation of the fuel injection valve 10 when closing the valve will be described with reference to Figs. 5(a) to 5(c). In Fig. 5(a), when driving magnetic fluxes flow through the magnetic flux paths C1 and C2, the first movable core 31 and the second movable core 41 are attracted to the fixed core 20, and the valve body 42 is held at the second lift position which is the maximum opening degree position. And at the end of fuel injection, as shown in Fig. 5(b), when switching from the state where magnetic fluxes flow through the magnetic flux paths C1 and C2 to the state where magnetic flux flows only through the first magnetic flux path C1, the valve body 42 is returned from the second lift position to the first lift position which is the intermediate position. At this time, as the energizing current of the solenoid coil 51 is reduced, the magnetic flux in the second magnetic flux path C2, which is farther from the solenoid coil 51 among the magnetic flux paths C1 and C2, disappears, and due to the biasing force of the spring 45, the second movable core 41 and the valve body 42 return from the second lift position to the first lift position. And the valve body 42 is temporarily stopped at the first lift position.

[0045] Here, in the fuel injection valve 10, the first movable core 31 is arranged inside the solenoid coil 51, and further, the second movable core 41 is arranged inside it. Therefore, when the first movable core 31 and the second movable core 41 are attracted to the fixed core 20, when the energizing current of the solenoid coil 51 is reduced, the magnetic flux weakens in the second magnetic flux path C2 which is farther from the solenoid coil 51 among the magnetic flux paths C1 and C2, and only the second movable core 41 moves away from the fixed core 20.

[0046] In addition, the second movable core 41 has a contact portion 37 of the first movable core 31 on the opposite side of the valve body 42, and the contact portion 37 has a through hole 36. The through hole 36 is a throttle passage. In this case, when the valve body 42 is lifted to the second lift position, a back space S is formed on the back side of the second movable core 41, i.e., between the second movable core 41 and the contact portion 37 of the first movable core 31, and when the valve body 42 returns from the second lift position to the first lift position, the back space S becomes a damper chamber, and the impact when the second movable core 41 hits the contact portion 37 is mitigated. In other words, the portion (the contact portion 37, the through hole 36, etc.) that forms the back space S in the first movable core 31 serves as a buffer portion that mitigates the impact when the second movable core 41 hits the contact portion 37 when the valve body 42 returns from the second lift position to the first lift position.

[0047] This reduces the impact when the second movable core 41, separated from the fixed core 20, hits the abutment portion 37 of the first movable core 31 when the fuel injection valve 10 is closed. Therefore, the first movable core 31 is prevented from unintentionally separating from the fixed core 20 due to the impact when the second movable core 41 hits the abutment portion 37 of the first movable core 31.

[0048] Then, as shown in FIG. 5(c), when the solenoid coil 51 is de-energized, the driving magnetic flux disappears and the valve body 42 returns to the valve-closed position by the biasing force of the spring 45. This stops fuel injection. In this case, the valve body 42 does not move from the maximum opening (second lift position) to the valve-closed position in one go, but returns to the valve-closed position after stopping once at an intermediate position (first lift position). This reduces the closing speed of the valve body 42, and reduces the impact when the valve body 42 hits the seat surface around the injection hole. This suppresses wear on the valve body 42.

[0049] When the fuel injection valve 10 is opened and closed, the control device 54 controls the energization of the solenoid coil 51, and this energization control will be described below. Fig. 6 is a flowchart showing a processing procedure for the energization control of the solenoid coil 51. This processing is executed by the control device 54 every time the fuel injection valve 10 injects fuel in the gas engine. In the energization control described below, the current applied from the drive circuit 53 to the solenoid coil 51 is controlled by the control device 54.

[0050] 6, in step S11, it is determined whether or not it is time to turn on the energization signal, and if it is time to turn on the energization signal, the process proceeds to step S12. In step S12, a first current I1 is applied to the solenoid coil 51. The first current I1 is a valve-opening current that lifts the valve body 42 to the second lift position. This current application generates a driving magnetic flux, and the first movable core 31 is attracted to the fixed core 20, thereby lifting the valve body 42 from the valve-closed position to the first lift position, and subsequently, the second movable core 41 is attracted to the fixed core 20, thereby lifting the valve body 42 from the first lift position to the second lift position.

[0051] Then, in step S13, it is determined whether the valve 42 has reached the maximum opening (i.e., the second lift position). At this time, it is preferable that the valve 42 has reached the maximum opening because a predetermined time has elapsed since the start of energization of the solenoid coil 51. Then, if step S13 is positive, the process proceeds to step S14. In step S14, a second current I2 is applied to the solenoid coil 51. The second current I2 is a current smaller than the first current I1 (valve-opening current) and is a current that generates a magnetic flux for holding the valve 42 at the second lift position as a driving magnetic flux. The second current I2 corresponds to a holding current that holds the valve 42 at the second lift position. Note that steps S11 to S14 correspond to the process of the "first control".

[0052] Then, in step S15, it is determined whether or not it is time to turn off the energization signal, and if it is time to turn off the energization signal, the process proceeds to step S16. In step S16, a third current I3 is applied to the solenoid coil 51. The third current I3 is smaller than the first current I1 and the second current I2, and is at a current level that separates only the second movable core 41 from the fixed core 20 from a state in which the first movable core 31 and the second movable core 41 are attracted to the fixed core 20. The third current I3 is preferably determined in advance by compatibility or the like.

[0053] Thereafter, in step S17, it is determined whether or not to close the valve 42. At this time, it is preferable that a predetermined time TA has elapsed since the start of application of the third current I3, so that it is determined that the valve 42 is to be closed. If step S17 is positive, the process proceeds to step S18. In step S18, the current supply to the solenoid coil 51 is stopped. Steps S15 to S18 correspond to the process of "second control".

[0054] However, if the pressure of the gas fuel introduced into the fuel passage 12 is high, it is considered that the movement of the valve body 42 in the open state to the valve closing side is delayed. In this case, it is considered that the time required to move only the second movable core 41 away from the fixed core 20 from a state in which the first movable core 31 and the second movable core 41 are attracted to the fixed core 20 and return the valve body 42 to the first lift position is prolonged at the end of fuel injection.

[0055] In consideration of this, in step S17, the time TA during which the third current I3 is applied after the power-off command is issued may be variably set based on the pressure of the gas fuel. Specifically, the time TA may be set based on the pressure of the gas fuel using the relationship in Fig. 7. According to Fig. 7, the higher the pressure of the gas fuel, the longer the time TA is set.

[0056] FIG. 8 is a time chart showing the change in the lift amount of each movable core 31, 41, the change in applied current, and the change in injection rate when the fuel injection valve 10 is opened and closed. The lift amount of the second movable core 41 corresponds to the lift amount of the valve body 42. The energization signal is an injection valve control signal as an energization command output from the control device 54, and when the energization signal is turned on, the solenoid coil 51 is energized, and when the energization signal is turned off, the solenoid coil 51 is de-energized. The injection rate is the amount of fuel injected per unit time. In FIG. 8, as the lift amount of each movable core 31, 41, the lift amount of the first movable core 31 is indicated by a dashed line, and the lift amount of the second movable core 41 is indicated by a solid line.

[0057] In Fig. 8, at timing t1, the energization signal is turned on to start energizing the solenoid coil 51, and a first current I1 is applied to the solenoid coil 51. As the energization starts, the first movable core 31 and the second movable core 41 start to move, and the valve body 42 lifts to the valve opening side. At the beginning of the energization, the first movable core 31 and the second movable core 41 move together, so the lift amounts of these movable cores 31, 41 are the same. As the lift amount of the valve body 42 increases, the injection rate gradually increases.

[0058] After that, at timing t2, the first movable core 31 hits the fixed core 20, and the first movable core 31 stops at the first lift position. After timing t2, the second movable core 41 lifts independently, and the lift amount of the valve body 42 further increases.

[0059] Then, at timing t3, the second movable core 41 hits the fixed core 20, causing the valve element 42 to stop at the second lift position (maximum opening). Between timings t1 and t3, the valve element 42 performs a two-stage lift operation due to the movement of each of the movable cores 31, 41, thereby making it possible to increase the maximum opening of the injection hole 14a and increase the injection rate.

[0060] After that, at timing t4, the energizing current of the solenoid coil 51 is switched from the first current I1 for moving the valve element 42 to an open state to a second current I2 for maintaining the open state of the valve element 42. Even after timing t4, the valve element 42 is maintained in the second lift position (maximum opening).

[0061] Then, at timing t5, the energization signal is turned off and the energization current of the solenoid coil 51 is switched to the third current I3. As a result, the second movable core 41 and the valve body 42 return to the first lift position, which is an intermediate position, due to the biasing force of the spring 45, and temporarily stop at the first lift position. In this case, since the energization current is reduced from the first current I1 to the second current I2 before timing t5, which is the OFF timing of the energization signal, the energization current of the solenoid coil 51 is quickly switched to a current level (third current I3) that temporarily stops the valve body 42 at the first lift position.

[0062] Here, when the second movable core 41, which has been separated from the fixed core 20, returns to the first lift position, the second movable core 41 hits the abutment portion 37 of the first movable core 31, and if the impact at that time is large, there is a concern that the first movable core 31 will move away from the fixed core 20, making it impossible to temporarily stop the second movable core 41 at the first lift position. Therefore, at timing t5, when the second movable core 41 hits the abutment portion 37 of the first movable core 31, it is preferable that current supply control of the solenoid coil 51 is performed so that the first movable core 31 does not move away from the fixed core 20.

[0063] In other words, the third current I3 for returning the second movable core 41 to the intermediate position (first lift position) may receive the kinetic energy generated when the second movable core 41 hits the contact portion 37 of the first movable core 31 due to the biasing force of the spring 45, and may generate a magnetic attraction force that does not cause separation of the first movable core 31 from the fixed core 20 due to the kinetic energy. Also, when the current passing through the solenoid coil 51 is switched from the second current I2 to the third current I3, the current command value may not be switched all at once, but may be switched so that the current command value changes gradually.

[0064] After that, at timing t6, the solenoid coil 51 is de-energized, whereby the valve body 42 is returned to the valve-closed position by the biasing force of the spring 45, and fuel injection is stopped.

[0065] Fig. 9 is a time chart showing the valve element speed when the valve element 42 is closed. In Fig. 9, the solid line shows the change in energizing current and the change in valve element speed in this embodiment, and the dashed line shows, as a comparative example, the change in energizing current and the change in valve element speed when the energizing current is suddenly cut off from the second current I2.

[0066] In the case of the comparative example, when the energization signal is turned off at timing t5, the energization is immediately cut off, and the valve element 42 moves in one go to the valve-closed position due to the biasing force of the spring 45. In this case, the valve element 42 moves at a high speed when it reaches the valve-closed position, and there is a concern that the valve element 42 may be worn down by the impact of the valve element 42 hitting the seat surface around the injection hole.

[0067] In contrast, in the case of this embodiment, when the energization signal is turned off at timing t5, the energization current is temporarily reduced to the third current I3, and then the energization is cut off at timing t6. In this case, the valve element 42 stops temporarily at the intermediate position (first lift position) and then moves to the valve closing position, so that the valve element speed increases, decreases, and increases again in this order, and the valve element speed when the valve element 42 reaches the valve closing position becomes relatively small. Therefore, wear of the valve element 42 due to the impact when the valve element 42 hits the seat surface around the injection hole is suppressed.

[0068] According to the present embodiment described above in detail, the following excellent effects can be obtained.

[0069] In the fuel injection valve 10, when fuel is injected, the first movable core 31 is attracted to the fixed core 20, thereby lifting the valve element 42 from the valve closed position to the first lift position, and then the second movable core 41 is attracted to the fixed core 20, thereby lifting the valve element 42 to the second lift position. This results in a two-stage valve element lift, enabling a large flow rate of gas fuel.

[0070] Furthermore, at the end of fuel injection, the valve element 42 returns from the second lift position to the first lift position, pauses at the first lift position, and then returns to the valve closed position by the biasing force of the spring 45. In this case, the valve element 42 does not move from the maximum opening (second lift position) to the valve closed position all at once, but returns to the valve closed position after stopping temporarily at an intermediate position (first lift position). This reduces the impact when the valve element 42 hits the seat surface, and suppresses wear of the valve element 42. As a result, the valve element 42 can be protected while increasing the flow rate of gas fuel.

[0071] The second movable core 41 is movably housed in the hollow portion of the first movable core 31, and the solenoid coil 51 is provided to surround the first movable core 31 and the fixed core 20. In this case, since the first movable core 31 is disposed inside the solenoid coil 51 and the second movable core 41 is disposed further inside the first movable core 31, it is easy to move only the second movable core 41 away from the fixed core 20 from a state in which the first movable core 31 and the second movable core 41 are attracted to the fixed core 20 at the end of fuel injection. This makes it possible to preferably temporarily stop the valve body 42 at the first lift position.

[0072] After the generation of driving magnetic flux by energizing the solenoid coil 51, magnetic saturation occurs in the first magnetic flux path passing through the first movable core 31 and the fixed core 20, and this magnetic saturation increases the amount of magnetic flux in the second magnetic flux path (bypass path) passing through the second movable core 41 and the fixed core 20. As a result, when the solenoid coil 51 first starts to be energized, the first movable core 31 is attracted, i.e., the first movable core 31 moves with good responsiveness, and subsequently, the second movable core 41 is attracted, i.e., the lift amount of the valve body 42 is appropriately increased.

[0073] The amount of movement (A1) of the first movable core 31 when the first movable core 31 is attracted to the fixed core 20 due to the generation of driving magnetic flux is made smaller than the amount of movement (A2) of the second movable core 41 when the second movable core 41 is attracted independently to the fixed core 20 after the first movable core 31 moves. In this case, when the solenoid coil 51 first starts to be energized, the responsiveness of the movement of the first movable core 31 is improved, and when the valve element 42 is subsequently opened, an appropriate valve opening operation can be performed by using the inertial force imparted by the operation of the first movable core 31.

[0074] In the fuel injection valve 10, a buffer portion is provided on the opposite side of the second movable core 41 from the valve body, for buffering the impact when the second movable core 41 hits the abutment portion 37 of the first movable core 31 when the valve body 42 returns from the second lift position to the first lift position. This reduces the impact when the second movable core 41, which has been separated from the fixed core 20, hits the abutment portion 37 of the first movable core 31 when the fuel injection valve 10 is closed. This prevents the first movable core 31 from unintentionally moving away from the fixed core 20 due to the impact when the second movable core 41 hits the abutment portion 37 of the first movable core 31, and allows the second movable core 41 to be properly temporarily stopped at the first lift position.

[0075] When the fuel injection valve 10 is closed, the solenoid coil 51 is controlled to move the second movable core 41 away from the fixed core 20 from a state in which the first movable core 31 and the second movable core 41 are attracted to the fixed core 20, and the valve element 42 is temporarily stopped at the first lift position. In this case, the solenoid coil 51 is not immediately de-energized in response to a power-off command, but is controlled in two stages to temporarily stop the valve element 42 at the first lift position after the power-off command. This makes it possible to appropriately adjust the valve element speed when the valve is closed.

[0076] After the solenoid coil 51 starts to be energized, a valve-opening current that lifts the valve element 42 to the second lift position is passed through the solenoid coil 51, and after the valve element 42 has been lifted to the second lift position, a holding current that is lower than the valve-opening current and holds the valve element 42 at the second lift position is passed through the solenoid coil 51. As a result, after the fuel injector 10 opens, it is sufficient that the energizing current (driving magnetic flux) of the solenoid coil 51 is the minimum current necessary to hold the valve element 42 in the open state, and thereafter, when the fuel injector 10 is closed, the current level can be quickly shifted to a current level that temporarily stops the valve element 42 at the first lift position.

[0077] When the second movable core 41, which has been separated from the fixed core 20, hits the abutment portion 37 of the first movable core 31 when the fuel injection valve 10 is closed, the first movable core 31 may be separated from the fixed core 20 due to the impact, and if the first movable core 31 separates from the fixed core 20, the second movable core 41 cannot be temporarily stopped at the first lift position. In this regard, the current supply to the solenoid coil 51 is controlled to prevent the first movable core 31 from separating from the fixed core 20. This makes it possible to appropriately adjust the speed of the valve body 42 when the valve is closed.

[0078] If the pressure of the gas fuel introduced into the fuel passage 12, i.e., the pressure on the back side of the tip valve portion 44 of the valve body 42, is large, it is considered that the movement of the valve body 42 in the open state to the valve closing side is delayed. In this case, it is considered that the time required to move only the second movable core 41 away from the fixed core 20 from a state in which the first movable core 31 and the second movable core 41 are attracted to the fixed core 20 and return the valve body 42 to the first lift position at the end of fuel injection is prolonged. In this regard, since the time for applying the third current after the power supply OFF command is variably set based on the pressure of the gas fuel, the valve body 42 can be appropriately returned to the first lift position at the end of fuel injection even if the fuel pressure changes.

[0079] Second embodiment The fuel injection valve 10 may be configured as shown in Fig. 10. Here, the differences between the configuration of the fuel injection valve 10 in Fig. 10 and that in Fig. 1 will be described.

[0080] The fuel injection valve 10 in FIG. 10 differs from the injection valve structure shown in FIG. 1 in that the housing 11 is provided with a partition wall 61 that partitions the fuel passage 12 into an upstream side and a downstream side, and a fuel chamber 62 is formed in the housing 11 between the partition wall 61 and the end plate portion 14. The partition wall 61 is provided with a communication hole 61a that connects the upstream side and the downstream side of the partition wall 61. A plurality of communication holes 61a are provided in the partition wall 61 at positions aligned in the circumferential direction. The partition wall 61 corresponds to the "partition portion." The communication hole 61a corresponds to the "upstream opening," and the injection hole 14a corresponds to the "downstream opening."

[0081] The fixed core 20, the first movable core 31, and the second movable core 41 are provided in the fuel chamber 62. A seal member 63 is fixed to the first movable core 31 as an upstream valve body that opens and closes the communication hole 61a of the partition wall 61. The seal member 63 has an annular shape and is attached to the upstream end face of the first movable core 31 at a position facing the communication hole 61a. The seal member 63 is made of any of elastic materials having elasticity, such as rubber, resin, and elastomer. More specifically, fluororubber, EPDM (ethylene propylene diene rubber), or the like, may be used as the seal material.

[0082] A spring 64 made of a compression coil spring is provided between the first movable core 31 and the fixed core 20. The first movable core 31 is biased by the spring 64 toward the side where the seal member 63 closes the communication hole 61a (valve closing side). The fixed core 20 is formed with a spring accommodating portion 65 in the shape of an annular groove, and the spring 64 is provided in a state of being accommodated in the spring accommodating portion 65. As a result, the first movable core 31 is held in a state separated from the fixed core 20, i.e., in a state where an air gap is formed between the first movable core 31 and the fixed core 20.

[0083] The second movable core 41 and the valve body 42 have the same configuration as in Fig. 1. The valve body 42 corresponds to the "downstream valve body". The spring 64 corresponds to the "first spring", and the spring 45 corresponds to the "second spring".

[0084] In the fuel injection valve 10 of FIG. 10, when fuel injection starts, the solenoid coil 51 starts to be energized in response to an energization signal being turned on, and the first movable core 31 and the second movable core 41 start to move, and both the communication hole 61a and the injection hole 14a are opened. At this time, as in the above-described embodiment, the valve body 42 is lifted continuously in two stages, the first lift position and the second lift position, by the movement of the first movable core 31 and the second movable core 41 in response to the generation of the driving magnetic flux. FIG. 11 shows a state in which the fuel injection valve 10 is opened. In FIG. 11, the first movable core 31 and the second movable core 41 are attracted to the fixed core 20 by the flow of the driving magnetic flux through the magnetic flux paths C1 and C2.

[0085] Furthermore, at the end of fuel injection, as in the previously described embodiment, after the power signal is turned off, the first movable core 31 and the second movable core 41 are attracted to the fixed core 20, and then the second movable core 41 and the valve body 42 are returned from the second lift position to the first lift position, and are temporarily stopped at the first lift position, and then are returned to the closed position by the biasing force of the spring 45.

[0086] Incidentally, in the configuration in which the valve element 42 is temporarily stopped at the first lift position (intermediate position) after the energization signal is turned off at the end of fuel injection as described above, the closing speed of the valve element 42 when it seats on the seat surface is reduced, suppressing wear of the valve element 42, but there is a concern that the injection cut-off at the end of injection may become poor. On the other hand, in the fuel injector 10 of Fig. 10, it is possible to improve the injection cut-off by changing the energization mode of the solenoid coil 51 at the end of injection.

[0087] In summary, when the energization signal is turned off, the solenoid coil 51 is deenergized and the driving magnetic flux is eliminated, so that the first movable core 31 and the second movable core 41 are attracted to the fixed core 20, and the first movable core 31 is separated from the fixed core 20, and the communication hole 61a of the partition wall 61 is closed by the seal member 63. After that, the second movable core 41 is moved to the valve closing position, and the injection hole 14a is closed by the valve body 42 at a timing delayed from the closing of the communication hole 61a. In this case, the communication hole 61a is closed first among the communication hole 61a which is the upstream opening and the injection hole 14a which is the downstream opening, so that the fuel supply from the upstream side is stopped quickly after the energization of the solenoid coil 51 is stopped, and the pressure drop in the fuel chamber 62 is accelerated. This improves the injection cut-off when the energization of the fuel injection valve 10 is terminated.

[0088] Here, in the fuel injection valve 10, when the upstream opening (communication hole 61a) is in an open state, the gas fuel flows into the back space of the second movable core 41 facing the opposite side to the valve body 42. In this case, when the upstream opening (communication hole 61a) is closed with the end of fuel injection, the back space of the second movable core 41 is preferably closed by the first movable core 31 and the seal member 63 to become a closed space. As a result, after the upstream opening (communication hole 61a) is closed, the gas fuel remaining in the closed space (back space) prevents the second movable core 41 from returning to the valve closing side. Therefore, after the current supply to the solenoid coil 51 is stopped, the fuel can be discharged from the fuel chamber 62 through the injection hole 14a as soon as possible, and thus the injection cut-off at the end of injection can be improved.

[0089] In addition, in the open state of the fuel injection valve 10, the distance between the first movable core 31 and the fixed core 20 may be greater than the distance between the second movable core 41 and the fixed core 20. Specifically, a plate-shaped spacer 66 made of a non-magnetic material may be interposed between the opposing surfaces of the first movable core 31 and the fixed core 20. The spacer 66 may be provided on at least one of the opposing surfaces of the first movable core 31 and the fixed core 20. In this case, when the driving magnetic flux disappears, the first movable core 31 is more likely to move away from the fixed core 20 than the second movable core 41. Therefore, a configuration in which the communication hole 61a is closed first among the communication hole 61a and the injection hole 14a is preferably realized.

[0090] In this embodiment, as the energization control when the fuel injection valve 10 is closed, a valve closing speed reduction control for reducing the valve closing speed of the valve body 42 and an injection cut-off improvement control for improving the injection cut-off are selectively performed. The valve closing speed reduction control is a control for returning the second movable core 41 and the valve body 42 from the second lift position to the first lift position from a state in which the first movable core 31 and the second movable core 41 are attracted to the fixed core 20 after an OFF command of the energization signal is issued at the end of fuel injection, and then temporarily stopping them at the first lift position and then returning them to the valve closed position by the biasing force of the spring 45. In addition, the injection cut-off improvement control is a control in which, at the end of fuel injection, after an OFF command of the power supply signal is given, the first movable core 31 and the second movable core 41 are attracted to the fixed core 20 (the upstream opening, the communication hole 61a, and the downstream opening, the injection hole 14a, are closed), and as the power supply is stopped, the communication hole 61a is first closed by the sealing member 63, and then the injection hole 14a is closed by the valve body 42.

[0091] Fig. 12 is a flowchart showing the current supply control process for the solenoid coil 51 in this embodiment. The process in Fig. 12 is executed by the control device 54 in place of the process in Fig. 6. In Fig. 12, the same steps as those in Fig. 6 are given the same step numbers, and the description thereof will be omitted.

[0092] 12, at the start of fuel injection, the energization signal is turned on to start energizing the solenoid coil 51, and then the energizing current is switched to the first current I1 and the second current I2 in that order, and under this energized state, the valve body 42 is held at the second lift position (steps S11 to S14). Then, in step S15, when it is determined that it is time to turn off the energization signal, the process proceeds to step S21.

[0093] In step S21, it is determined whether or not to perform valve closing speed reduction control for reducing the valve closing speed of the valve body 42. This determination is for determining the condition for selecting between valve closing speed reduction control and injection cutoff improvement control. For example, it is determined whether or not the valve body 42 of the fuel injection valve 10 is in a state in which wear suppression is performed, and if it is in a state in which wear suppression is performed, the process proceeds to step S16 after a positive result in step S21. In step S21, it is preferable to determine whether or not to perform wear suppression based on the wear state of the valve body 42. Specifically, it is preferable to determine whether or not to perform wear suppression based on the number of injections, which is the usage history of the fuel injection valve 10, the number of combustions of the gas engine, the period of use of the vehicle on which the gas engine is mounted, the mileage, etc. In this case, it is preferable to determine that the valve body 42 is in a state in which deterioration may occur, based on, for example, the number of injections of the fuel injection valve 10 being a predetermined number or more, the number of combustions of the gas engine being a predetermined number or more, etc., and to determine that wear suppression is to be performed.

[0094] In addition, when comparing the valve closing speed reduction control and the injection termination improvement control, it is considered that the injection termination improvement control will improve the fuel consumption rate. Therefore, the injection termination improvement control may be performed under the condition that the operation mode is in the economy mode or the like, where improvement of fuel efficiency is prioritized in the gas engine.

[0095] In steps S16 to S18, the valve closing speed reduction control is performed. At this time, a third current I3 smaller than the first current I1 and the second current I2 is applied to the solenoid coil 51, and when a predetermined time TA has elapsed since the start of application of the third current I3, the solenoid coil 51 is de-energized to close the valve body 42.

[0096] Also, if it is determined that the situation is not such that the valve closing speed reduction control is implemented in step S21, step S21 is negated, steps S16 and S17 are skipped, and the process proceeds to step S18. In this case, the energization of the solenoid coil 51 is immediately stopped based on the off command of the energization signal.

[0097] Also in the fuel injection valve 10 of the present embodiment, due to the two-stage lift of the valve body 42 by the first movable core 31 and the second movable core 41, it is possible to increase the large flow rate of the gaseous fuel. Further, when closing the valve body 42 at the end of fuel injection, instead of immediately returning the valve body 42 to the valve closing position, it is temporarily stopped at the first lift position which is an intermediate position and then returned to the valve closing position. As a result, the impact when the valve body 42 hits the seat surface is reduced, and the wear of the valve body 42 is suppressed. As a result, while aiming to increase the large flow rate of the gaseous fuel, it is possible to protect the valve body 42.

[0098] Also, the valve closing speed reduction control for reducing the valve closing speed of the valve body 42 and the injection cut improvement control for improving the injection cut are selectively implemented. Thereby, in the fuel injection valve 10, it is possible to appropriately perform the energization control of the solenoid coil 51 while determining which of the wear suppression of the valve body 42 and the improvement of the injection cut should be prioritized.

[0099] (Other Embodiments) The above embodiment may be modified as follows, for example.

[0100] · In each of the above embodiments, the movement amount A1 of the first movable core 31 when the first movable core 31 is attracted to the fixed core 20 with the generation of the driving magnetic flux and the movement amount A2 of the second movable core when the second movable core 41 is attracted to the fixed core 20 alone after the movement of the first movable core 31 are in the relationship of A1 < A2, but this may be changed. The movement amounts A1 and A2 may be set such that A1 = A2 or A1 > A2.

[0101] In each of the above embodiments, the first movable core 31 is in the form of a bottomed cylinder having a hollow portion, and the annular portion and the abutment portion 37 are made of a magnetic material. However, this may be modified so that an abutment plate made of a non-magnetic material is provided as the abutment portion at the axial end of the annular portion of the first movable core 31.

[0102] In the solenoid energization control process of Fig. 6, the processes of steps S13 and S14 may be omitted. In this case, after the energization signal is turned on and energization of the solenoid coil 51 is started, the energization current remains at the first current I1, and in this energized state, the valve body 42 is held at the second lift position. The same applies to the solenoid energization control process of Fig. 12.

[0103] In the first embodiment, when fuel injection ends, the second movable core 41 may be stopped at the first lift position to temporarily reduce the valve closing speed of the valve body 42 (valve closing speed reduction control), and the control may be switched between these states. Specifically, in a fuel injection system using the fuel injection valve 10 shown in FIG. 1, a solenoid energization control process shown in FIG. 12 is executed. In this case, in step S21 in FIG. 12, it is determined whether or not to perform the valve closing speed reduction control, and if the result is affirmative, the valve closing speed reduction control is performed, and if the result is negative, the valve closing speed reduction control is not performed. This allows a configuration to be realized in which the valve closing speed reduction control is performed as necessary.

[0104] In the above embodiments, the valve element 42 of the fuel injection valve 10 is a direct acting external opening valve that operates in response to energization of the solenoid coil 51, but this may be modified so that the valve element 42 is a balance valve that operates based on pressure balance. Specifically, the fuel injection valve 10 may be configured as shown in FIG.

[0105] The fuel injection valve 10 in FIG. 13 differs from FIG. 1 in that the upper part of the first movable core 31 is an atmospheric chamber 71 that is open to the atmosphere, and the tip side of the housing 11 is a fuel chamber 72 into which gas fuel is introduced. Gas fuel at a predetermined pressure is introduced into the fuel chamber 72 through an inlet passage 73. A connecting rod 74 is fixed to the lower end surface of the second movable core 41 in the figure. An externally opening valve body 42 is arranged on the tip side of the connecting rod 74 in a state continuous with the connecting rod 74 in the axial direction. A bellows 75 that is expandable and contractible and isolates the fuel chamber 72 from the atmosphere side is provided between the connecting rod 74 and the valve body 42. A brim-shaped spring receiving portion 42a is provided on the valve body 42, and a spring 45 that biases the valve body 42 to the valve closing side is provided between the spring receiving portion 42a and the end plate portion 14. The valve element 42 opens as the movable cores 31, 41 and the connecting rod 74 move in response to energization of the solenoid coil 51, and closes after energization of the solenoid coil 51 is stopped in response to the balance between the biasing force of the spring 45 and the fuel pressure and in-cylinder pressure in the fuel chamber 72. The second movable core 41 and the connecting rod 74 may be separable.

[0106] The technical ideas extracted from the above-described embodiments will be described below. [Configuration 1] A gas fuel injection valve (10) that injects gas fuel, a main body (11) having a fuel passage (12) through which gas fuel passes and an injection hole (14a) through which the gas fuel in the fuel passage is injected; a valve body (42) for opening and closing the injection hole; a spring member (45) that biases the valve body in a valve closing direction; A fixed core (20) fixed to the main body portion; a first movable core (31) that is attracted to the fixed core as a driving magnetic flux is generated during fuel injection, and lifts the valve body from a valve closing position to a first lift position; a second movable core (41) that, following the first movable core's lift of the valve element to the first lift position, is attracted to the fixed core by the driving magnetic flux, thereby lifting the valve element from the first lift position to a second lift position having a larger lift amount than the first lift position, a valve body that is adapted to return from the second lift position to the first lift position at the end of fuel injection, and then to return to the valve closed position by the biasing force of the spring member; [Configuration 2] The first movable core is cylindrical and has a hollow portion, and the second movable core is movably accommodated in the hollow portion. 2. The gas fuel injection valve according to configuration 1, wherein a solenoid coil (51) generating the driving magnetic flux is provided so as to surround the first movable core and the fixed core. [Configuration 3] 3. The gas fuel injection valve according to claim 1, wherein after the driving magnetic flux is generated, magnetic saturation is caused in a first magnetic flux path passing through the first movable core and the fixed core, and the magnetic saturation increases an amount of magnetic flux in a second magnetic flux path passing through the second movable core and the fixed core. [Configuration 4] The gas fuel injection valve according to any one of configurations 1 to 3, wherein a movement amount of the first movable core when the first movable core is attracted to the fixed core due to generation of the driving magnetic flux is smaller than a movement amount of the second movable core when the second movable core is attracted to the fixed core after the movement of the first movable core. [Configuration 5] The valve body is an outer opening valve that opens when moved outwardly of the main body, the first movable core has a contact portion (37) that contacts the second movable core when moving together with the second movable core when the valve body is opened, A gas fuel injection valve as described in any one of configurations 1 to 4, wherein a buffer portion is provided on the opposite side of the second movable core to the valve body, for absorbing an impact when the second movable core hits the abutment portion of the first movable core when the valve body returns from the second lift position to the first lift position at the end of fuel injection. [Configuration 6] A gas fuel injection valve according to any one of configurations 1 to 5, a control device (54) for controlling fuel injection of the gas fuel injection valve, The gas fuel injection valve has a solenoid coil (51) that generates the driving magnetic flux, The control device, at the end of fuel injection, performs, as a first control, control of the energization of the solenoid coil so as to move only the second moving core away from the fixed core from a state in which the first moving core and the second moving core are attracted to the fixed core, and temporarily stop the valve body at the first lift position, and, as a second control following the first control, stops the energization of the solenoid coil with the valve body stopped at the first lift position. [Configuration 7] The fuel injection system described in configuration 6, wherein the control device controls the energization of the solenoid coil so that, after energization of the solenoid coil starts, a valve-opening current is passed through the solenoid coil to attract the first movable core and the second movable core relative to the fixed core and lift the valve body to the second lift position, and after the valve body has been lifted to the second lift position, a holding current that is lower than the valve-opening current and holds the valve body at the second lift position is passed through the solenoid coil. [Configuration 8] the first movable core has a contact portion (37) that contacts the second movable core when moving together with the second movable core when the valve body is opened, The fuel injection system according to configuration 6 or 7, wherein, as the first control, the control device controls the energization of the solenoid coil so that the first movable core does not move away from the fixed core when the second movable core separated from the fixed core hits the abutment portion of the first movable core. [Configuration 9] 9. The fuel injection system according to any one of configurations 6 to 8, wherein the control device variably sets the period during which the first control is performed based on a pressure of the gas fuel. [Configuration 10] In the gas fuel injection valve, The main body has a partition (61) that partitions the fuel passage into an upstream side and a downstream side, and an upstream opening (61a) is provided in the partition (61), and the injection hole is provided as a downstream opening (14a), an upstream valve element (63) that opens and closes the upstream opening is integrated with the first movable core, and the first movable core is biased toward a valve closing side by a first spring (64); The second movable core is integrated with the downstream valve body (42) which is the valve body, and is biased toward the valve closing side by the second spring (45) which is the spring member. the first movable core is attracted to the fixed core in response to the generation of the driving magnetic flux, whereby both the upstream valve body and the downstream valve body move to the first lift position, and thereafter, the second movable core is attracted to the fixed core by the driving magnetic flux, whereby the downstream valve body moves to the second lift position, The control device includes: a valve closing speed reduction control for reducing a valve closing speed of the downstream valve body by temporarily stopping the second moving core at the first lift position from a state in which the first moving core and the second moving core are attracted to the fixed core and then returning the first moving core and the second moving core to a valve closing position at the end of fuel injection; at the end of fuel injection, from a state in which the first movable core and the second movable core are attracted to the fixed core, the driving magnetic flux is eliminated, the biasing force of the first spring is used to return the upstream valve body to a valve closed position, and thereafter the biasing force of the second spring is used to return the downstream valve body to the valve closed position, thereby improving injection termination improvement control, 10. The fuel injection system according to any one of configurations 6 to 9, wherein the valve closing speed reduction control and the injection cut-off improvement control are selectively performed. [Explanation of symbols]

[0107] Reference Signs List 10: fuel injection valve, 11: housing, 12: fuel passage, 14a: injection hole, 20: fixed core, 31: first movable core, 41: second movable core, 42: valve body, 45: spring.

Claims

1. A gas fuel injection valve (10) for injecting gas fuel, a main body (11) having a fuel passage (12) through which gas fuel passes and an injection hole (14a) through which the gas fuel in the fuel passage is injected; a valve body (42) for opening and closing the injection hole; a spring member (45) that biases the valve body in a valve closing direction; a fixed core (20) fixed to the main body; a first movable core (31) that is attracted to the fixed core in response to generation of a driving magnetic flux during fuel injection, thereby lifting the valve element from a valve closing position to a first lift position; a second movable core (41) that, following the valve element lift to the first lift position by the first movable core, lifts the valve element from the first lift position to a second lift position having a lift amount greater than that of the first lift position by being attracted to the fixed core by the driving magnetic flux, the first movable core is cylindrical and has a hollow portion, and the second movable core is movably accommodated in the hollow portion; a solenoid coil (51) that generates the driving magnetic flux is provided so as to surround the first movable core and the fixed core; the first movable core and the second movable core face each other in a valve element lift direction relative to the fixed core, a non-magnetic portion (25) having an annular shape and made of a non-magnetic material is provided between the fixed core and the first movable core; In a valve element lift state at the second lift position, the first movable core is attracted to the fixed core by magnetic flux of a first magnetic flux path (C1) that passes through the first movable core and the fixed core at the radially outer side of the non-magnetic material portion, and the second movable core is attracted to the fixed core by magnetic flux of a second magnetic flux path (C2) that passes through the second movable core and the fixed core at the radially inner side of the non-magnetic material portion, a gas fuel injection valve in which, when returning the valve body from the second lift position to the first lift position following the end of fuel injection, magnetic flux is caused to flow only through a first magnetic flux path out of the first magnetic flux path and the second magnetic flux path, thereby displacing the valve body to the first lift position, and after temporarily stopping the valve body at the first lift position, the valve body is returned to the valve closed position by the biasing force of the spring member.

2. 2. The gas fuel injection valve according to claim 1, wherein after the driving magnetic flux is generated, magnetic saturation is caused in the first magnetic flux path, and the amount of magnetic flux in the second magnetic flux path is increased by the magnetic saturation.

3. 2. The gas fuel injection valve according to claim 1, wherein a movement amount of the first movable core when the first movable core is attracted to the fixed core due to the generation of the driving magnetic flux is smaller than a movement amount of the second movable core when the second movable core is attracted to the fixed core after the movement of the first movable core.

4. the valve body is an outward-opening valve that opens when it moves outward from the main body, the first movable core has an abutment portion (37) that abuts against the second movable core when moving together with the second movable core when the valve body is opened, 2. The gas fuel injection valve according to claim 1, wherein a buffer portion is provided on the opposite side of the second movable core from the valve body, the buffer portion absorbing an impact when the second movable core hits the abutment portion of the first movable core when the valve body returns from the second lift position to the first lift position at the end of fuel injection.

5. a gas fuel injection valve according to any one of claims 1 to 4; a control device (54) for controlling fuel injection from the gas fuel injection valve, The control device, at the end of fuel injection, performs a first control to control the energization of the solenoid coil so that, from a state in which the first movable core and the second movable core are attracted to the fixed core, only the second movable core is separated from the fixed core to temporarily stop the valve body at the first lift position, and, as a second control following the first control, stops the energization of the solenoid coil when the valve body is stopped at the first lift position.

6. 6. The fuel injection system according to claim 5, wherein the control device controls energization so that, after energization of the solenoid coil begins, a valve-opening current is passed through the solenoid coil to attract the first movable core and the second movable core relative to the fixed core and lift the valve body to the second lift position, and after the valve body has been lifted to the second lift position, a holding current that is lower than the valve-opening current and that holds the valve body at the second lift position is passed through the solenoid coil.

7. the first movable core has an abutment portion (37) that abuts against the second movable core when moving together with the second movable core when the valve body is opened, 6. The fuel injection system according to claim 5, wherein the control device, as the first control, controls the energization of the solenoid coil so that the first movable core does not move away from the fixed core when the second movable core separated from the fixed core comes into contact with the abutment portion of the first movable core.

8. The fuel injection system according to claim 5 , wherein the control device variably sets the period during which the first control is performed based on the pressure of the gas fuel.

9. In the gas fuel injection valve, The main body has a partition (61) that partitions the fuel passage into an upstream side and a downstream side, and an upstream opening (61a) is provided in the partition (61), and the injection hole is provided as a downstream opening (14a), The first movable core is integrated with an upstream valve body (63) that opens and closes the upstream opening, and is biased toward the valve closing side by a first spring (64). The second movable core is integrated with the downstream valve body (42) which is the valve body, and is biased toward the valve closing side by the second spring (45) which is the spring member, When the driving magnetic flux is generated, the first movable core is attracted to the fixed core, and the upstream valve body and the downstream valve body both move to the first lift position. Thereafter, the driving magnetic flux attracts the second movable core to the fixed core, and the downstream valve body moves to the second lift position. The control device a valve closing speed reduction control that, at the end of fuel injection, temporarily stops the second moving core at the first lift position from a state in which the first moving core and the second moving core are attracted to the fixed core, and then returns the first moving core and the second moving core to a valve closing position, thereby reducing the valve closing speed of the downstream valve body; At the end of fuel injection, from a state in which the first movable core and the second movable core are attracted to the fixed core, the driving magnetic flux is eliminated, the biasing force of the first spring is used to return the upstream valve body to the valve closed position, and thereafter the biasing force of the second spring is used to return the downstream valve body to the valve closed position, thereby enabling injection termination improvement control to be implemented, which improves injection termination; 6. The fuel injection system according to claim 5, wherein the valve closing speed reduction control and the injection termination improvement control are selectively performed.

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