Control device

Abstract

Control device (20) configured to control the operation of a fuel injector (10), wherein the fuel injector (10) comprises a housing (100) provided with a nozzle hole (511) for injecting fuel, a needle (200) configured to switch between opening and closing the nozzle hole (511) by moving inside the housing (100), and a coil (600) configured to generate an electromagnetic force for actuating the needle (200), wherein the control device (20) comprises: a current matching unit (21) configured to match a control current supplied to the coil (600);and an operating detection unit (23) configured to detect operation of the needle (200), wherein the current adjustment unit (21) is configured to perform a control to temporarily terminate the supply of the control current to the coil (600) for a preset termination period at a time of valve opening, and the control device (20) further comprises: a time adjustment unit (22) configured to adjust a length of the termination period so that the needle (200) is not operated in a valve closing direction at the time of valve opening.

Description

Cross-Reference to Related ApplicationThe present application is based on and claims priority from Japanese Patent Application No. 2019-001528 filed on Jan. 9, 2019, and published under No. 2020-112 051 A.Technical FieldThe present disclosure relates to a control device for controlling an operation of a fuel injection valve.BackgroundAs a fuel injection valve provided in the internal combustion engine, a fuel injection valve configured to switch between opening and closing of a nozzle hole, which is a fuel outlet, by operating an internal needle by means of an electromagnetic force generated by a coil is known.For example, a fuel injection valve described in Patent Literature 1 includes a fixed core fixedly mounted in an inside of a housing, a movable core mounted in the inside of the housing in a movable state, and a coil for generating a magnetic attractive force between the fixed core and the movable core. When fuel is injected from the fuel injection valve, a current is supplied to the coil. By the electromagnetic force generated at this time, the movable core moves toward a fixed core together with the needle, bringing the nozzle hole into an open state.Prior Art LiteraturePatent LiteraturePatent Literature 1: JP 5 965 253 B2WO 2015 / 163 077 A1 discloses the following: Since the ratio of the fuel injection quantity to a specific injection duration is different in a half stroke range and a full stroke range, the purpose of the subject matter disclosed here is to approximate the flow characteristic of an intermediate stroke range to the flow characteristic of the full stroke range and to improve the controllability of small fuel injection quantities. There are provided a peak power supply period in which a valve body of a fuel injection valve generates the magnetic force required for a valve opening operation and a stroke amount adjustment period in which a current lower than the peak current is allowed to pass after the peak power supply period for a predetermined period; and a current cut-off period in which a drive current is rapidly lowered before the stroke amount adjustment period.JP 2018-84 240 A discloses the following: In a driving device for controlling an opening / closing valve of a front valve element by controlling a voltage applied to solenoids of a plurality of fuel injectors having movable elements and valve elements, when a time necessary for the electric current supplied to the solenoid to reach a prescribed current value by applying a voltage to the solenoid is Tp, and a time when negative voltage is applied to the solenoid after reaching the prescribed current value or a time when the voltage is not applied is T2, the driving device changes Tp and T2 in each fuel injector based on a valve opening delay time of the valve element of each fuel injector.JP 2014-92 089 A discloses the following: A fuel injection control device is applied to a fuel injection valve for opening and operating a valve element by electromagnetic attraction force generated by energizing a coil, and controls a fuel injection state by controlling the coil electric current. The fuel injection control device includes: increase control means for increasing the coil electric current to a first target value; holding control means for holding the coil electric current increased by the increase control means at the first target value; and changing means for changing the first target value according to an operating state of the internal combustion engine.WO 2018 190 035 A1 discloses the following: In a fuel injection valve having a two or more stage variable lift mechanism, there is a possibility that exhaust emissions will deteriorate and torque will fluctuate when fuel is injected at a stroke different from a command. A control device for a fuel injection valve having a two- or multi-stage variable lift mechanism is provided, wherein: the drive lift of the fuel injection valve is detected from a turning point of a drive current during a valve opening operation or a drive voltage during a valve closing operation; and when the detected drive lift deviates from a command drive lift, the command drive lift is limited.Summary of the InventionIn the fuel injection valve configured as described above, a member that operates inside thereof, i.e., the movable core or the needle, collides with another member at the time of valve opening. In a case where an impact of the collision is large, some of the members may be damaged or worn, which may result in a state in which normal fuel injection cannot be performed.Therefore, in order to solve the above problem, the present inventors have considered to temporarily stop supplying a driving current to the coil at the time of valve opening. When the supply of the drive current is temporarily stopped, a working speed of the needle or the movable core moving in a valve opening direction is decreased, and thereby impact energy can be reduced. The longer the period in which the supply of the drive current is completed, the lower the surge energy.However, in a case where the period in which the supply of the drive current is completed is too long, there is a possibility that the needle itself operates in a valve closing direction at the time of valve opening. In this case, since an injection amount of the fuel is smaller than a required injection amount, normal fuel injection cannot be performed.It is an object of the present disclosure to provide a control device configured to allow a fuel injection valve to perform normal fuel injection while reducing impact energy at the time of valve opening.A control device according to the present disclosure is configured to control an operation of a fuel injection valve. The fuel injection valve, which is a controlled object, includes a housing provided with a nozzle hole to inject fuel, a needle configured to switch opening and closing of the nozzle hole by moving inside the housing, and a coil configured to generate an electromagnetic force for operating the needle. The control device includes: a current adjustment unit configured to adjust a drive current supplied to the coil; and an operation detection unit configured to detect an operation of the needle.The current adjustment unit is configured to execute control to temporarily stop the supply of the drive current to the coil for a preset termination period at a time of valve opening. The control device further includes a time adjustment unit that adjusts a length of the termination period so that the needle does not operate in a valve closing direction at a time of valve opening.In such a control device, the current adjustment unit performs control to temporarily stop the supply of the drive current to the coil for a preset termination period. Therefore, the impact energy at the time of valve opening can be reduced. The length of the termination period is adjusted by the time adjusting unit so that the needle does not operate in a valve closing direction at the time of valve opening. Since the needle is prevented from operating in the valve closing direction due to the termination period being too long, it is possible to allow the fuel injection valve to perform normal fuel injection.According to the present disclosure, there is provided a control device that can enable the fuel injection valve to perform normal fuel injection while reducing the impact energy at the time of valve opening.Brief Description of the DrawingsFIG. 1 is a view illustrating a configuration of a control device according to a first embodiment and a fuel injection valve that is a control target thereof. FIG. 2 is a diagram for explaining a relationship between an operation of a needle and a drive current. FIG. 3 is a diagram for explaining a relationship between the operation of the needle and the drive current. FIG. 4 is a diagram for explaining a relationship between the operation of the needle and the drive current. FIG. 5 is a diagram for explaining a relationship between the operation of the needle and the drive current. FIG. 6 is a flowchart illustrating a processing procedure performed by a control device according to the first embodiment. FIG. 7 is a flowchart illustrating a processing flow but a control device according to a second embodiment is performed.DESCRIPTION OF THE EMBODIMENTSHereinafter, the present embodiment will be described with reference to the accompanying drawings. In order to facilitate understanding of the description, the same reference numerals are assigned to the same configuration elements in the respective drawings as well as possible, and redundant description thereof is omitted.A first embodiment will be explained. A control device 20 according to the present embodiment is configured as a device for controlling an operation of a fuel injection valve 10. Before describing the control device 20, a configuration of the control target fuel injection valve 10 will be described with reference to FIG. 1.The fuel injection valve 10 is a device that is provided in an internal combustion engine (not illustrated) and injects and supplies fuel to the internal combustion engine. In the present embodiment, a gas fuel, particularly natural gas or hydrogen gas, is used as the aforementioned fuel. The fuel injection valve 10 includes a housing 100, a needle 200, a movable core 300, a fixed core 400, and a coil 600.The housing 100 is a member formed as a whole substantially as a cylindrical container. The needle 200, the movable core 300, and the fixed core 400, which will be described later, are accommodated inside the housing 100. In FIG. 1, the housing is illustrated in a state in which a longitudinal direction thereof extends along a vertical direction. As described later, in the fuel injection valve 10, the needle 200 moves along the longitudinal direction of the housing 100, thereby switching the opening and closing of the nozzle hole 511, which is a fuel outlet.Specifically, when the needle 200 moves in an upward direction in FIG. 1, i.e., in a direction from the nozzle hole 511 toward an inlet port 134, the nozzle hole 511 is opened, initiating injection of the fuel. Therefore, this direction will be referred to as a "valve opening direction" hereinafter.When the needle 200 moves from a state in which the fuel is injected from the nozzle hole 511 in a downward direction in FIG. 1, that is, in a direction from the inlet port 143 toward the nozzle hole 511, the nozzle hole 511 is closed, and the injection of the fuel is ended. Therefore, this direction will be referred to as a "valve closing direction" hereinafter.The housing 100 includes a first cylindrical member 110, a second cylindrical member 120, a third cylindrical member 130, and a fourth cylindrical member 140. Each of these is formed as a substantially cylindrical member and is disposed in a state in which the central axes thereof coincide with each other.The first cylindrical member 110 is a member disposed at a position that is on a most downstream side along a flow direction of the fuel in the housing 100. The first cylindrical member 110 is made of ferritic stainless steel, which is a magnetic body, and is subjected to quenching treatment to increase its hardness. A space 111 is formed inside the first cylindrical member 110, and the needle 200 described later is accommodated in the space 111.The injection nozzle 500 is press-fitted and welded to an inner side of an end portion of the first cylindrical member 110 closest to the valve closing direction. The injection nozzle 500 forms part of the housing 100, and includes a cylindrical portion 520 and a closing portion 510. The cylindrical portion 520 is a portion formed in a cylindrical shape. The cylindrical portion 520 is fixed inside the first cylindrical member 110 in a state in which a central axis thereof coincides with a central axis of the first cylindrical member 110. An inner peripheral surface 521 of the cylindrical portion 520 is a surface that slides in a state in which a sliding contact portion 222 of the needle 200 abuts on the inner surface 521 thereof.The closing portion 510 is a portion configured to close the end portion of the cylindrical portion 520 on the valve closing direction side. The nozzle hole 511 is formed in the closing portion 510. The nozzle hole 511 is a through hole formed to penetrate through the closing portion 510 along the central axis of the first cylindrical member 110. The nozzle hole 511 connects the inner space 111 of the first cylindrical member 110 to the outer space. The nozzle hole 511 is formed as a fuel outlet at which the fuel is injected from the fuel injection valve 10. As described above, in the fuel injection valve 10, the nozzle hole 511 for injecting the fuel in the longitudinal direction is formed at one end of the housing 100.A valve seat 512 is formed on the inner surface of the closing portion 510 to surround a periphery of the nozzle hole 511. The valve seat 512 is a portion against which a seal portion 221 of the needle 200 abuts to close the nozzle hole 511.The injection nozzle 500 is entirely formed of martensitic stainless steel and is subjected to a quenching treatment to increase its hardness. A portion of the injection nozzle 500 against which the needle 200 abuts, i.e., the valve seat 512 and the inner circumferential surface 521 are subjected to nitriding treatment. The inner peripheral surface 521 may be further subjected to DLC coating for reducing a frictional force.A diameter of a portion of the first cylindrical member 110 on an opposite side to the injection nozzle 500, i.e., a portion on the valve opening direction side is increased, and an increased diameter cylindrical portion 112 is formed to further extend from the portion toward the valve opening direction. An inner circumferential surface of the enlarged diameter cylindrical portion 112 is a portion that slides in a state in which a part of the movable core 300 abuts, as described later. Therefore, the enlarged diameter cylindrical portion 112 is subjected to nitriding treatment. An end portion of the second cylindrical member 120 on the valve closing direction side is connected to an end portion of the enlarged diameter cylindrical portion 112 on the valve opening direction side.The second cylindrical member 120 is a cylindrical member disposed at a position on an upstream side of the first cylindrical member 110 along the flow direction of the fuel in the housing 100. An inner diameter and an outer diameter of the second cylindrical member 120 are respectively equal to an inner diameter and an outer diameter of the enlarged diameter cylindrical portion 112. The second cylindrical member 120 is formed of austenitic stainless steel, which is a non-magnetic body. An end portion of the third cylindrical member 130 on the valve closing direction side is connected to an end portion of the second cylindrical member 120 on the valve opening direction side.The third cylindrical member 130 is a cylindrical member disposed at a position on an upstream side of the second cylindrical member 120 along the flow direction of the fuel in the housing 100. An inner diameter and an outer diameter of the third cylindrical member 130 are equal to the inner diameter and the outer diameter of the second cylindrical member 120, respectively. The third cylindrical member 130 is formed of ferritic stainless steel, which is a magnetic body. A portion of the fourth cylindrical member 140 on the valve closing direction side is press-fitted and welded to an inner side of a portion of the third cylindrical member 130 on the valve opening direction side.The fourth cylindrical member 140 is a substantially cylindrical member disposed at a position along the flow direction of the fuel in the housing 100 that is the most upstream side. The fourth cylindrical member 140 is formed of austenitic stainless steel. An inlet port 143 is formed at an end portion of the fourth cylindrical member 140 closest to the valve opening direction. The inlet port 143 is an opening formed as an inlet for fuel introduced from the outside.A filter 142 is provided at a position in the vicinity of the inlet port 143 in the space 141 formed inside the fourth cylindrical member 140. The filter 142 is provided for collecting foreign particles contained in the fuel introduced via the inlet port 143.The needle 200 is a rod-shaped member disposed inside the housing 100. The needle 200 is disposed in a state movable along the longitudinal direction of the housing 100 in a state in which the central axis thereof has been moved toward the central axis of the housing 100. The needle 200 is formed of martensitic stainless steel and is subjected to a quenching treatment to increase its hardness. The seal portion 221 is formed at an end portion of the needle 200 on a side of the injection nozzle 500.When the needle 200 moves toward a closest valve closing direction of a movable range as illustrated in FIG. 1, the seal portion 221 comes into contact with the valve seat 512 with the nozzle hole 511 in a closed state. Therefore, the injection of the fuel from the nozzle hole 511 is ended. When the needle 200 moves toward the valve opening direction and the seal portion 221 is separated from the valve seat 512, the nozzle hole 511 is in an open state. Therefore, the fuel is injected from the nozzle hole 511. In this way, the needle 200 is provided as a member for switching the opening and closing of the nozzle hole 511 by movement along the longitudinal direction inside the housing 100.A plurality of sliding contact portions 222 protruding outward are formed on a side surface of the needle 200 at positions slightly closer to the valve opening direction than the seal portion 221. The sliding contact portion 222 is a portion that slides in a state in which a tip thereof abuts against the inner circumferential surface 521 of the cylindrical portion 520. The plurality of sliding contact portions 222 are formed to be aligned along a circumferential direction of the needle 200. A recess portion 223 is formed between adjacent sliding contact portions 222 as a path through which fuel passes. The sealing portion 221 and the sliding contact portion 222 of the needle 200 are subjected to nitriding treatment. The sliding contact portion 222 is further subjected to DLC coating. Therefore, the frictional resistance between the sliding contact portion 222 and the inner peripheral surface 521 is reduced.The needle 200 is mounted in a state in which the movable core 300 described later is penetrated along the vertical direction in FIG. 1. The end portion of the needle 200 on the valve opening direction side is disposed further on the valve opening direction side than the end portion of the movable core 300 on the valve opening direction side. A large diameter portion 210 is formed on a side surface at a portion of the needle 200 on the valve opening direction side so as to protrude outward. A surface of the large diameter portion 210 on the movable core 300 side, i.e., on the valve closing direction side abuts against the end surface of the movable core 300 on the valve opening direction side.The needle 200 is provided with a recessed portion 201 recessed from the end portion on the valve opening direction side toward the valve closing direction. The recess portion 201 is a recessed space formed to extend from the end portion of the needle 200 on the valve opening direction side of the large diameter portion 210 to a position closer to the valve closing direction than the movable core 300. At the end portion of the needle 200 on the valve opening direction side, the recess portion 201 is open to the outside. A through hole 202 is formed in the needle 200 at a position of the recess portion 201 closer to the valve closing direction than the movable core 300. The recess portion 201 and the space 111 are connected to each other via the through hole 202.The movable core 300 is a member formed in a substantially cylindrical shape as a whole. The movable core 300 is disposed in a movable state along the longitudinal direction of the housing 100 together with the needle 200 in a state in which its central axis is moved along the central axis of the housing 100. The "valve opening direction" described above may also be referred to as a direction in which the movable core 300 and the needle 200 move away from the nozzle hole 511. The "valve closing direction" may also be referred to as a direction in which the movable core 300 and the needle 200 approach the nozzle hole 511.The movable core 300 is formed of ferritic stainless steel, which is a magnetic body. A through hole 313 is formed in the center of the movable core 300 to penetrate the movable core 300 along the central axis of the housing 100. The needle 200 described above is inserted into the through hole 313.The large diameter portion 210 of the needle 200 abuts against the end surface of the movable core 300 on the valve opening direction side. As described later, a part of the end surface of the movable core 300 on the valve opening direction side is a portion abutting on the fixed core 400 at the time of valve opening. At the end surface of the movable core 300 on the valve opening direction side, the portion of the needle 200 against which the large diameter portion 210 abuts and the portion abutting against the fixed core 400 are each subjected to nitriding treatment. The end surface of the large diameter portion 210 on the valve closing direction side is also subjected to nitriding treatment.A portion of the movable core 300 on the valve closing direction side has an enlarged diameter, and an enlarged diameter portion 311 that protrudes laterally is formed. An outer circumferential surface 312 of the enlarged diameter portion 311 abuts against the inner circumferential surface of the enlarged diameter cylindrical portion 112 of the first cylindrical member 110. When the movable core 300 moves, the outer circumferential surface 312 of the enlarged diameter portion 311 slides in a state abutting against the inner circumferential surface of the enlarged diameter cylindrical portion 112. The outer peripheral surface 312 is subjected to nitriding treatment and further subjected to DLC coating.Like the movable core 300, the fixed core 400 is a member formed in a substantially cylindrical shape as a whole. The fixed core 400 is fixed to the inside of the housing 100 in a state in which the central axis thereof has been moved toward the central axis of the housing 100. The position where the fixed core 400 is provided is a position adjacent to the movable core 300 on the valve opening direction side. When the sealing portion 221 of the needle 200 abuts against the valve seat 512 as illustrated in FIG. 1, a gap is formed between the fixed core 400 and the movable core 300.The fixed core 400 is made of ferritic stainless steel, which is a magnetic body. An end surface of the fixed core 400 on the movable core 300 side is a portion abutting on the movable core 300. Therefore, the end surface is subjected to nitriding treatment.A through hole 401 is formed in the center of the fixed core 400 to penetrate the fixed core 400 along the central axis of the housing 100. The recess portion 201 of the needle 200 described above connects the space 141 of the fourth cylindrical member 140 via the through hole 401.The large diameter portion 210 of the needle 200 is inserted through a portion of the through hole 401 on the movable core 300 side. The outer circumferential surface of the large diameter portion 201 abuts against the inner circumferential surface of the through hole 401.The position at which the fixed core 400 is disposed inside the housing 100 is a position substantially facing the third cylindrical member 130. An outer side surface of the fixed core 400 is fixed to the inner circumferential surface of the third cylindrical member 130 by welding.The coil 600 generates an electromagnetic force to operate the needle 200 by receiving a drive current. The coil 600 is disposed so as to cover the entirety of the second cylindrical member 120 and a part of the third cylindrical member 130 of the housing 100 from the outside in a state where the coil 600 is wound around the bobbin 610. When the driving current is supplied to the coil 600, a magnetic circuit is formed so that a magnetic flux passes through the fixed core 400, the movable core 300, the enlarged diameter cylindrical portion 112, the third cylindrical member 130, and the like. As a result, a magnetic attractive force is generated between the fixed core 400 and the movable core 300. By the magnetic attractive force, the movable core 300 moves together with the needle 200 in the valve opening direction. When the supply of the driving current to the coil 600 is stopped, the magnetic attractive force is 0. At this time, the movable core 300 moves in the valve closing direction together with the needle 200 by the pressing force of a pressing member 820, which will be described later.Other configurations of the fuel injection valve 10 will be described. A matching line 430 is press-fitted and fixed to a portion of the through hole 401 formed in the fixed core 400 on the valve opening direction side. The adjustment line 430 is a cylindrical member, and a through hole 431 is formed inside thereof to penetrate along the longitudinal direction of the housing 100.A pressing member 820 is disposed at a position of the through hole 401 closer to the valve closing direction than the adjustment pipe 430. The pressing member 820 is an elastic member whose expansion and contraction directions extend along the longitudinal direction of the housing 100, specifically, it is a coil spring. One end of the pressing member 820 abuts against the end portion of the adjustment pipe 430 on the valve closing direction side. The other end of the pressing member 820 abuts against the end portion of the needle 200 on the valve opening direction side.The pressing member 820 has a length shorter than the free length. Therefore, the needle 200 is pushed toward the valve closing direction by the pressing member 820.A pressing member 810 is disposed on the valve closing direction side of the movable core 300. The pressing member 810 is an elastic member whose expanding and contracting directions are along the longitudinal direction of the housing 100, specifically, is a coil spring. One end of the pressing member 810 abuts against the end surface of the movable core 300 on the valve closing direction side. The other end of the pressing member 810 abuts against a step portion formed in the vicinity of the end portion of the first cylindrical member 110 on the valve opening direction side.The pressing member 810 has a length shorter than the free length. Therefore, the movable core 300 is pressed against the large diameter portion 210 of the needle 200 by a force from the pressing member 810. Accordingly, both the needle 200 and the movable core 300 are pressed toward the valve opening direction by the pressing member 810. By providing the pressing member 810 and the pressing member 820, the large-diameter portion 210 and the movable core 300 are maintained in a state of coming into contact with each other.In the present disclosure, the pressing force of the pressing member 820 is larger than the pressing force of the pressing member 810. Therefore, when the supply of the driving current to the coil 600 is stopped and the magnetic attractive force is not generated between the fixed core 400 and the movable core 300, the seal portion 221 of the needle 200 abuts against the valve seat 512, that is, the nozzle hole 511 is closed.Parts of the coil 600, the third cylindrical member 130, and the fourth cylindrical member 140 are molded with a resin 900 from the outside. A part of the resin 900 protrudes outward, and the protruding portion is formed as a connector 910. The connector 910 is a portion where a line for supplying the driving current to the coil 600 is connected. The feeding terminal 920 is a terminal provided at an end of a feeding line connected to the coil 600. The drive current is supplied to the coil 600 via the feed terminal 920.The holder 700 is disposed further outside a portion of the resin 900 in which the third cylindrical member 130 is molded. The holder 700 is a cylindrical member made of a magnetic body, and is formed to extend from a position outside the enlarged diameter cylindrical portion 112 to a position closer to the valve opening direction than the end portion of the coil 600 on the valve opening direction side. A cover 710 is disposed at a position inside the holder 700 and closer to the valve opening direction than the coil 600. The cover 710 is a substantially round and tubular member made of a magnetic body, and is disposed to surround the third cylindrical member 130 from the outside. A portion of the cover 710 in the vicinity of the connector 910 is notched to prevent interference with the connector 910. Therefore, in FIG. 1, a cross section of the cover 710 is illustrated only at a position on the right side of the third cylindrical member 130. The holder 700 and the cover 710 form part of a magnetic circuit through which the magnetic flux generated in the coil 600 passes.An operation of the fuel injection valve 10 will be described. The fourth cylindrical member 140 is supplied with fuel from the inlet port 143. When the driving current is not supplied to the coil 600, the nozzle hole 511 is closed with the needle 200 as described above. Therefore, the inside of the fuel injection valve 10 becomes a pressurized state by the fuel.When the supply of the driving current to the coil 600 is initiated, the magnetic attractive force is generated between the fixed core 400 and the movable core 300, and the movable core 300 moves in the valve opening direction. At this time, since the large diameter portion 210 of the needle 200 abuts against the end surface of the movable core 300, the needle 200 also moves in the direction of the valve opening direction together with the movable core 300. Since the seal portion 221 of the needle 200 is separated from the valve seat 512 and the nozzle hole 511 is in an open state, the injection of the fuel from the nozzle hole 511 is initiated. The movable core 300 that has started moving toward the valve opening direction then abuts against the fixed core 400, stopping.After the fuel flows into the space 141 via the inlet port 143, the fuel passes through the through hole 431, the through hole 401, the recess portion 201, the through hole 202, and the space 111 in this order, being injected from the nozzle hole 511 to the outside.When the supply of the driving current to the coil 600 is stopped in a state in which the nozzle hole 511 is opened, magnetic attraction force does not act between the fixed core 400 and the movable core 300. The movable core 300 and the needle 200 move toward the valve closing direction by the pressing force of the pressing member 820, and finally the seal portion 221 abuts against the valve seat 512, that is, the nozzle hole 511 is closed. Therefore, the injection of the fuel from the nozzle hole 511 is ended.Referring still to FIG. 1, the control device 20 according to the present embodiment will be described. As described above, the control device 20 is a device for controlling an operation of the fuel injection valve 10. the control device 20 is configured as a computer system including a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and the like.The control device 20 may be configured as a dedicated device for controlling the operation of the fuel injection valve 10, and may be configured as a part of another control device. For example, the control device 20 may be configured as a part of an engine ECU that controls the entire operation of the internal combustion engine.The control device 20 includes, as functional control blocks, a current adjustment unit 21, a time adjustment unit 22, and an operation detection unit 23. the current adjustment unit 21 is a portion that executes a process for adjusting the drive current supplied to the coil 600. The current adjustment unit 21 controls the opening and closing operation of the fuel injection valve 10 by appropriately adjusting the timing of supplying or stopping the drive current to the coil 600.The current adjustment unit 21 adjusts the drive current supplied to the coil 600 by transmitting a drive signal to a current circuit (not illustrated). The current circuit is a circuit for supplying the drive current from a battery (not illustrated) mounted on the vehicle to the coil 600. Such a current circuit may be provided outside the control device 20 or may be provided inside the control device 20.When the drive signal is turned ON by the current adjustment unit 21, the drive current is supplied from the current circuit to the coil 600. When the drive signal from the current adjustment unit 21 is turned OFF, the supply of the drive current to the coil 600 is stopped. Details of the specific process executed by the current adjustment unit 21 will be described later. The functionalities of the time adjustment unit 22 and the operation detection unit 23 will be described together in the description of the process described above.With reference to FIGS. 2 and 3, an overview of the process performed by the control device 20 will be described. (A) in FIG. 2 illustrates an example of temporarily changing the drive signal when fuel is injected by the fuel injection valve 10. (B) in FIG. 2 illustrates an example of temporarily changing a stroke amount of the needle 200 when the drive signal changes as illustrated in (A) in FIG. 2. The "stroke amount" refers to the position of the needle 200 along the longitudinal direction of the housing 100. In (B) in FIG. 2, a value of the lift amount increases as the needle 200 moves in the valve opening direction.In the example of FIG. 2, the drive signal is turned ON at time t 0, and the drive signal is thereafter turned OFF at time t 10. A length of a period from time t 0 to time t 10, that is, a length of a period in which the drive signal is turned ON, is set in advance according to a target injection amount, which is a target value of the fuel injection amount.In this way, in a case where the drive signal is continuously turned ON, the magnetic attractive force acting on the movable core 300 becomes relatively large. Therefore, in the example of (B) of FIG. 2, the movable core 300 impinges on the fixed core 400 at high speed, and the needle 200 continues to move toward the valve opening direction after the collision due to its momentum. Thereafter, the needle 200 moves in the valve closing direction, with the large-diameter portion 210 abutting against the movable core 300. In (B) in FIG. 2, the time at which the needle 200 has moved farthest to the valve opening direction side is illustrated as time t 1.In a case where the movable core 300 and the needle 200 are operated at the time of valve opening as described above, there is a concern that a loud noise is generated due to the collision and the movable core 300 is damaged or worn. The needle 200 moves farthest to the valve opening direction side and then moves in the valve closing direction again, with the large-diameter portion 210 colliding with the movable core 300. Therefore, there is a possibility that the movable core 300 or the like is also damaged or worn in association with the collision.Therefore, the current adjustment unit 21 of the control device 20 according to the present embodiment temporarily stops the supply of the drive current in the middle of the valve opening, thereby reducing the impact energy as described above.FIG. 3 illustrates a specific example thereof. In (A) in FIG. 3, an example of temporarily changing the drive signal in the same manner as in (A) in FIG. 2 is illustrated. In (B) in FIG. 3, an example of temporarily changing the stroke amount of the needle 200 in the same manner as in (B) in FIG. 2 is illustrated.In the example of FIG. 3, similarly to the example of FIG. 2, the drive signal is turned ON at time t 0. However, the drive signal is temporarily turned OFF after time t 0 at time t 2. At time t3, the drive signal is thereafter turned ON again, and this state is continued until time t10.In (A) in FIG. 3, a period from time t 0 to time t 2 is illustrated as a period TM 1. A period from time t 2 to time t 3 is illustrated as a period TM 2. A period from time t 3 to time t 10 is illustrated as a period TM 3. A period from time t 0 to time t 10, that is, the entire period of periods TM 1, TM 2, and TM 3 is illustrated as a period TM 0 in (A) in FIG. 3. As described above, the length of the period TM 0 is set in advance according to the target injection amount.In the present embodiment, the supply of the drive current to the coil 600 is temporarily stopped in the period TM 2 from the time t 2 to the time t 3. In this way, the current adjustment unit 21 is configured to execute the control for temporarily stopping the supply of the drive current to the coil 600 for a preset period of time TM 2 when the fuel injection valve 10 is opened. The period TM 2 corresponds to the "termination period" in the present embodiment.As described above, when the supply of the drive current to the coil 600 is temporarily stopped during the termination period, the speed of the movable core 300 and the needle 200 moving in the valve opening direction is restricted. In the example illustrated in (B) in FIG. 3, the stroke speed of the needle 200 or the like immediately before the collision is less than the stroke speed in the case of (B) in FIG. 2, therefore, there is only a small further movement of the needle 200 after the collision, and the movable core 300 and the needle 200 stop their operation at a substantially same timing.(A) in FIG. 4 is a graph illustrating an example of a temporary change in the drive current in a case where the drive signal is temporarily turned OFF as prescribed in the termination period. In the example of (A) in FIG. 4, when the drive signal is temporarily turned OFF in the termination period, the drive current rapidly decreases from the time t 4. In the subsequent period until time t 5, the drive current is substantially 0. After that, after the time t 5, the drive current gradually increases when the termination period ends and the drive signal is turned ON again. The reason why the drive current decreases at time t 8 is that the fuel injection by the fuel injection valve 10 is ended.(B) in FIG. 4 illustrates, by way of example, the temporary change in the stroke amount of the needle 200 in a case where the drive current changes as illustrated in (A) in FIG. 4. In the example illustrated in (B) in FIG. 4, similarly to the example illustrated in (B) in FIG. 3, the stroke speed of the needle 200 or the like immediately before the collision is relatively small, and the impact energy is accordingly reduced.From the viewpoint of reducing the impact energy between the movable core 300 and the fixed core 400 or the like at the time of valve opening, it is preferable that the length of the termination period, i.e., the length of the period TM 2 in (A) in FIG. 3 is as long as possible. However, if the termination period is too long, the energy for moving the needle 200 in the valve opening direction is not sufficient. Accordingly, the needle 200 itself can move in the valve closing direction at the time of valve opening. Even if the length of the set termination period is suitable at the beginning, a case may occur in which the termination period is too long when the fuel injection valve 10 changes with time.Such an example will be described with reference to FIG. 5. In (A) in FIG. 5, an example of temporarily changing the drive current in the same manner as in (A) in FIG. 4 is illustrated. In (B) in FIG. 5, an example of temporarily changing the stroke amount of the needle 200 in the same manner as in (B) in FIG. 4 is illustrated.In the example of (A) in FIG. 5, when the drive signal is temporarily turned OFF in the termination period, the drive current rapidly decreases from time t 4. In a period of time until time t 6, the drive current is subsequently substantially 0. After that, after the time t 6, the drive current gradually increases when the termination period ends and the drive signal is turned ON again.In the example of (A) in FIG. 5, the termination period is set longer than that in the example of (A) in FIG. 4. Therefore, a length of a period from time t 4 to time t 6 is longer than the length of the period from time t 4 to time t 5 in (A) in FIG. 4.In the example of FIG. 5, the energy for moving the needle 200 in the valve opening direction is not sufficient because the termination period is set too long. Therefore, as illustrated in (B) in FIG. 5, the lift amount of the needle 200 decreases temporarily in the period TM 10 during which the valve is opened. That is, the needle 200 has moved in the valve closing direction. In this case, since the injection amount of fuel from the fuel injection valve 14 is smaller than the required injection amount, normal fuel injection cannot be performed. The operation of the needle 200 in the valve closing direction may occur in the middle of the valve opening or may occur after the valve opening is once completed.Therefore, in the control device 20 according to the present embodiment, the length of the termination period is not always constant, but is appropriately set so that the needle 200 is not operated in the valve closing direction. The time adjustment unit 22 included in the control device 20 is provided as a portion for executing the process of adjusting the length of the termination period as described above. For example, in a case where it is detected that the needle 200 has been operated in the valve closing direction, the timing adjustment unit 22 executes a process of making the length of the termination period shorter than it was before. Therefore, the length of the termination period can be adjusted to an appropriate length. Accordingly, it is possible to cause the fuel injection valve 10 to perform normal fuel injection while reducing the impact energy at the time of valve opening.It is also conceivable to provide a dedicated sensor in the fuel injection valve 10 to detect that the needle 200 has been operated in the valve closing direction at the time of valve opening. However, in a case where such a sensor is provided, the cost of the fuel injection valve 10 increases. Therefore, as described above, the control device 20 according to the present embodiment detects the operation of the needle 200 based on the temporal change in the drive current without providing the sensor. The operation detection unit 23 included in the control device 20 is provided as a portion that executes the process of detecting the operation of the needle 200 in this manner.As illustrated in (A) in FIG. 5, when the needle 200 is operated in the valve closing direction at the time of valve opening, an inflection point occurs in the graph illustrating the change in the drive current at time t 7 after time t 6. The operation detection unit 23 detects the operation of the needle 200 based on the drive current flowing through the coil 600. Specifically, based on whether or not an inflection point has occurred in the temporary change of the drive current, it is detected that the needle 200 has been operated in the valve closing direction.In order to enable the above-described detection, an amount of the drive current is always measured by a current sensor provided in, for example, a current circuit, and the measurement value is input to the control device 20.A specific processing flow executed by the control device 20 will be described with reference to FIG. 6. A series of processes illustrated in FIG. 6 is repeatedly performed by the control device 20 every time fuel is injected by the fuel injection valve 14.In the first step S 01 of the processing, the processing of turning ON the drive signal by the current adjustment unit 21 is executed. The drive signal is turned ON only for a preset predetermined period. This predetermined period is the period TM 1 illustrated in (A) in FIG. 3. In the present embodiment, the length of the period TM 1 during which the drive signal ON is turned on is fixed. Instead of such operation, the length of the period TM 1 may be changed depending on a driving situation of the vehicle or the like.In step S 02 subsequent to step S 01, the current adjustment unit 21 performs the processing for turning OFF the drive signal. The drive signal is turned OFF only for a preset termination period. This termination period is the period TM 2 illustrated in (A) in FIG. 3.In step S 03 subsequent to step S 02, the current adjustment unit 21 performs the processing for turning ON the drive signal again. The drive signal is turned ON only for a preset predetermined period. The predetermined period is the period TM 3 illustrated in (A) in FIG. 3.As described above, the length of the period TM 0 illustrated in (A) in FIG. 3 is set in advance according to the target injection amount. In step S 03, the period TM 3 is set by subtracting the respective lengths of the period TM 1 and the period TM 2 from the length of the period TM 0, the driving signal being turned ON only during the period TM 3.After the processing of steps S 01 to S 03 is executed, thereafter or temporarily, the needle 200 is started to operate in the valve opening direction. The operation detection unit 23 continuously monitors the amount of the drive current supplied to the coil 600 and monitors the operation of the needle 200 based thereon. In step S 04 subsequent to step S 03, the operation detection unit 23 executes the processing of detecting the operation of the needle 200 in the valve closing direction. As described above with reference to (B) in FIG. 4, in a case where the inflection point occurs in the change in the drive current after the increase is initiated again, the operation detection unit detects that the needle 200 has been operated in the valve closing direction.In a case where the operation of the needle 200 in the valve closing direction is not detected, the series of processes illustrated in FIG. 6 ends without adjusting the length of the period TM 2. In a case where the operation of the needle 200 in the valve closing direction is detected, the processing proceeds to step S 05.In step S 05, the processing is executed in which a preset predetermined time Δt is subtracted from the length of the period TM 2 set at a current time, and the obtained value is set as a new period TM 2, i.e., a termination period. This processing is executed by the time adjustment unit 22. The predetermined time Δt is a very small time set in advance as a change amount when the termination period is adjusted.At the time of the next fuel injection, when a series of processings illustrated in FIG. 6 is performed, in step S 02, the period TM 2 that has been changed to be shorter as described above is used as the termination period. By making the termination period shorter than the previous time, it is possible to prevent the needle 200 from being operated in the valve closing direction at the time of valve opening. In a case where even at the time of the next fuel injection, the operation of the needle 200 in the valve closing direction is detected, the termination period is further changed to be shorter in step S 05.As described above, in a case where it is detected by the operation detection unit 23 that the needle 200 has been operated in the valve closing direction at the time of valve opening, the timing adjustment unit 22 executes the processing that makes the length of the termination period shorter than before. Therefore, the occurrence of the operation of the needle 200 in the valve closing direction due to an excessively long termination period can be avoided as well as possible. Even in a case where the termination period that was originally suitable is too long, when the fuel injection valve 10 changes with time, the termination period can be changed to a suitable length according to a situation. Therefore, it is possible to cause the fuel injection valve to execute normal fuel injection.In the present embodiment, the fuel injected by the fuel injection valve 14 is gaseous fuel. In this case, the resistance to which the movable core 300 and the needle 200 are subjected at the time of operation is smaller than that in a case of liquid fuel, and the impact energy at the time of valve opening tends to become larger. Therefore, the effect of performing the control as described above is large. However, the above-described control may be performed by the control device 20 for a fuel injection valve 10 injecting liquid fuel.In the series of processes illustrated in FIG. 6, the processing of step S 04 and step S 05, that is, the processing of adjusting the length of the termination period may be executed every time the fuel injection is executed as in the present embodiment, but may be executed only once between a plurality of fuel injections.The second embodiment is described. The present embodiment differs from the first embodiment in the manner of processing performed by the control device 20. Hereinafter, the aspects different from those of the first embodiment will be mainly described, and the description of aspects same as the first embodiment will be omitted accordingly.A series of processes illustrated in FIG. 7 is performed by the control device 20 according to the present embodiment, and is performed instead of the series of processes illustrated in FIG. 6. In the series of processes illustrated in FIG. 7, the processing in steps S 01 to S 03 is the same as the processing in steps S 01 to S 03 in FIG. 6.After the processing of step S 03 is executed, the process in the present embodiment proceeds to step S 11. In step S 11, the processing for determining whether or not the execution condition is satisfied is executed. The "execution condition" is a condition set in advance as a condition necessary for the time adjustment unit 22 to perform the adjustment of the length of the termination period. That is, in the present embodiment, the length of the termination period is adjusted by the time adjustment unit 22 when the execution condition is satisfied.In the present embodiment, after the engine is started in the vehicle, the fact that the rotation speed of the engine is constant is set as the execution condition. The "rotation speed is constant" means that the rotation speed of the engine is stabilized after the start, and the change in the rotation speed is within a predetermined range. In the present embodiment, since the length of the termination period is adjusted after the rotation speed of the internal combustion engine is constant, the adjustment can be always appropriately performed.In the present embodiment, the execution condition is determined to be satisfied only once during the period in which the internal combustion engine is operated in step S 11. Therefore, the adjustment of the length of the termination period by the time adjustment unit 22 is performed only once after the internal combustion engine is started. The next adjustment is performed after the engine is once stopped and then restarted.In a case where the execution condition is satisfied in step S 11, the process proceeds to step S 12. In step S 12, similarly to step S 04 in FIG. 6, the operation detection unit 23 executes the processing for detecting the operation of the needle 200 in the valve closing direction.Since the termination period is set to an appropriate length in advance, the operation of the needle 200 in the valve closing direction is not detected in many cases. In a case where the operation of the needle 200 in the valve closing direction is not detected, the process proceeds to step S 13.In a case where the process proceeds to step S 13, it is considered that the termination period is sufficiently shortened. However, if the termination period is too short, the impact energy between the movable core 300 and the fixed core 400 or the like is too large as in the example illustrated in (B) of FIG. 2. It is preferable that the termination period is as large as possible within a range in which the operation of the needle 200 in the valve closing direction does not occur.Therefore, in step S 13, the processing is executed in which a preset predetermined time Δt is added to the length of the period TM 2 set at the current time, and the obtained value is set as the new period TM 2, that is, the termination period. This processing is executed by the time adjustment unit 22. This predetermined time Δt is the same as the predetermined time Δt used in step S 05 in FIG. 6.In step S 14 subsequent to step S 13, 1 is set as a value of an operation flag FL. The "operation flag" is a variable in which 1 is set only during a period in which the adjustment of the termination period is performed, and 0 is set in other periods.Thereafter, when the series of processes illustrated in FIG. 7 is performed again, it is determined in step S 11 that the performing condition is not satisfied, and the process proceeds to step S 15. In step S 15, it is determined whether or not the value of the operation flag FL is 1. In a case where the value of the operation flag FL is 1, the process proceeds to step S 12 again.In step S 12, in a case where the operation of the needle 200 in the valve closing direction is not detected, the process proceeds to step S 13 again, and the termination period is further extended by a predetermined time Δt. That is, each time the fuel injection is executed, the termination period is extended by a predetermined time Δt until the operation of the needle 200 in the valve closing direction is detected.When the operation of the needle 200 in the valve closing direction is detected in step S 12, the process proceeds to step S 16. The proceeding to step S 16 means that the termination period changed to be repeatedly extended in step S 13 has exceeded the appropriate length for the first time. Therefore, in step S 16, the processing of subtracting the predetermined time Δt from the length of the period TM 2 set at the current time and setting the obtained value as the new period TM 2, that is, the termination period, is executed. That is, the processing of resetting the length of the termination period to the length at the time of the previous injection is executed. Since the operation of the needle 200 in the valve closing direction has not been detected at the time of the previous injection, the termination period set here is the longest period within a range in which the operation of the needle 200 in the valve closing direction does not occur.In a step S 17 subsequent to the step S 16, the processing of resetting the value of the operation flag FL to 0 is executed. Therefore, at the time of the subsequent fuel injection, after proceeding from step S 11 to step S 15, the series of processes illustrated in FIG. 7 ends without adjusting the length of the termination period.As described above, the timing adjustment unit 22 according to the present embodiment increases the termination period by a predetermined time Δt every time the fuel injection is performed by the fuel injection valve 10, and in a case where the operation detection unit 23 detects that the needle 200 has been operated in the valve closing direction at the time of valve opening, the timing adjustment unit 22 shortens the termination period by the predetermined time Δt. Therefore, the length of the termination period can be set as long as possible within a range in which the operation of the needle 200 in the valve closing direction does not occur. It is possible to cause the fuel injection valve 10 to perform the normal fuel injection while reducing the impact energy at the time of valve opening.As the execution condition used for the determination in step S 11, a condition different from that of the present embodiment may be set. For example, the execution condition may be set to be satisfied in a case where the number of fuel injections by the fuel injection valve 10 reaches a predetermined number after the adjustment of the length of the termination period is last performed. In this case, the adjustment of the length of the termination period is repeatedly performed while the vehicle is moving.The adjustment of the length of the termination period in the first embodiment, that is, the processing in steps S 04 and S 05 in FIG. 6 can be executed only in a case where the same execution condition as that in the present embodiment is satisfied.The series of processes illustrated in FIG. 6 and the processing after step S 11 on the series of processes illustrated in FIG. 7 may be performed in parallel. In this case, in the period in which the value of the operation flag FL is 1, the processing of step S 04 and step S 05 in FIG. 6 may be temporarily suspended.The present embodiment has been described with reference to the specific examples. However, the present disclosure is not limited to these specific examples. These specific examples, for which those skilled in the art can make appropriate design modifications, are included within the scope of the present disclosure as long as they have features of the present disclosure. Each element included in each of the specific examples described above, as well as an arrangement, condition, shape, and the like thereof, is not limited to that illustrated, and may be appropriately changed. Any element contained in each of the specific examples described above may be combined as appropriate as long as no technical contradiction arises.The control device and the control method described in the present disclosure may be implemented by one or more dedicated computers provided by configuring a processor and a memory programmed to perform one or more functions configured as a computer program. The control device and the control method described in the present disclosure may be implemented by a dedicated computer provided by configuring a processor including one or more dedicated hardware logic circuits. The control device and the control method described in the present disclosure may be implemented by one or more dedicated computers configured by configuring a processor and a memory programmed to perform one or more functions, and a processor including one or more hardware logic circuits. The computer program may be stored on a computer readable non-transitory tangible storage medium as instructions executable by a computer. The dedicated hardware logic circuit and the hardware logic circuit may be realized by a digital circuit including a plurality of logic circuits or by analog circuits.

Claims

A control device (20) configured to control an operation of a fuel injection valve (10), the fuel injection valve (10) including a housing (100) provided with a nozzle hole (511) for injecting fuel, a needle (200) configured to switch between opening and closing of the nozzle hole (511) by moving inside the housing (100), and a coil (600) configured to generate an electromagnetic force for operating the needle (200), the control device (20) comprising: a current adjustment unit (21) configured to adjust a drive current supplied to the coil (600); An operation detection unit (23) configured to detect an operation of the needle (200), wherein the current adjustment unit (21) is configured to execute control to temporarily stop the supply of the driving current to the coil (600) for a preset termination period at a time of valve opening, and the control device (20) further comprises: a time adjustment unit (22) configured to adjust a length of the termination period so that the needle (200) is not operated in a valve closing direction at the time of valve opening.The control device (20) according to claim 1, wherein the time adjustment unit (22) is configured to shorten the length of the termination period when the operation detection unit (23) detects that the needle (200) has been operated in the valve closing direction at the time of valve opening.The control device (20) according to claim 1, wherein the time adjustment unit (22) is configured to increase the termination period by a predetermined time each time the fuel injection valve (10) injects fuel, and the time adjustment unit (22) is configured to shorten the termination period by the predetermined time when the operation detection unit (23) detects that the needle (200) has been operated in the valve closing direction at the time of valve opening.The control device (20) according to any one of claims 1 to 3, wherein the operation detection unit (23) is configured to detect the operation of the needle (200) based on the driving current flowing through the coil (600).The control device (20) according to claim 4, wherein the operation detection unit (23) is configured to detect that the needle (200) has been operated in the valve closing direction based on whether or not an inflection point has occurred in a temporal change of the drive current.The control device (20) according to any one of claims 1 to 5, wherein the time adjustment unit (22) is configured to perform the adjustment of the length of the termination period when a predetermined execution condition is satisfied.The control device (20) according to claim 6, wherein the execution condition is that a rotation speed of an engine is constant after the engine is started in a vehicle.

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