WO2025258199A1 - Fuel injection control device and fuel injection control method - Google Patents

Abstract

A fuel injection control device performs control to apply an intermediate pulse to a fuel injection device including a valve body, a movable element that causes the valve body to open and close, a stator that applies magnetic attraction force to the movable element, and a stopper part that suppresses the motion of the movable element to a valve-seat side, the intermediate pulse being applied between a first drive command pulse and a subsequent second drive command pulse. The end time of the intermediate pulse is determined by the time at which the movable element collides with the stopper part in the first drive command pulse, and the start time of the intermediate pulse is determined on the basis of the fluctuation of the time at which the valve body driven by the second drive command pulse is seated on the valve seat or the fluctuation of the time at which the movable element driven by the second drive command pulse collides with the stopper part.

Description

Fuel injection control device and fuel injection control method

The present invention relates to a fuel injection control device and a fuel injection control method that control the amount of fuel injected during multi-stage injection by a fuel injection device.

In recent years, downsized engines have become known, which reduce the displacement to make them more compact and use a turbocharger to generate power. By reducing the displacement, downsized engines can reduce pumping losses, thereby achieving better fuel economy.

On the other hand, downsized engines tend to have smaller cylinder diameters, which means that injected fuel is more likely to adhere to the cylinder walls, raising concerns that this could worsen exhaust performance. Furthermore, if uneven areas between fuel and air occur in downsized engines, unburned particulate matter is emitted, worsening exhaust performance.

In downsized engines, the pressure of the fuel supplied to the engine cylinder is increased, atomizing the injected fuel and forming a uniform air-fuel mixture, thereby homogenizing the air and fuel inside the engine cylinder.

In addition, in downsized engines, the amount of fuel needed for each combustion stroke is divided and injected (multi-stage injection) to form a uniform mixture, thereby homogenizing the air and fuel inside the engine cylinder. To achieve this, fuel injection valves are required to shorten the injection interval during multi-stage injection. If the injection interval is shortened, there is a risk that the variation in the injection amount will increase due to the influence of the movement (bouncing) of the moving element that transmits force to the valve disc.

In response to this, for example, Patent Document 1 describes a fuel injection device that adds an intermediate drive signal between the drive command pulses for pre-injection and post-injection, thereby suppressing irregular injection, in which fuel is unintentionally and temporarily injected during multi-stage injection.

Japanese Patent Application Laid-Open No. 2019-027348

In the fuel injection device described in Patent Document 1, an intermediate drive signal is added at a preset timing. With this method of adding an intermediate drive signal, for example, if the characteristics (individual characteristics) of the fuel injection valve change or if changes occur in environmental factors of the fuel injection valve (e.g., fuel pressure, fuel temperature, aging, etc.), it is not possible to add the intermediate drive signal at the appropriate timing in response to the changes. This makes it difficult to provide the optimal drive command pulse to the fuel injection valve. Therefore, improving the robustness of fuel injection control in response to these changes has been an issue.

The object of the present invention is to provide a fuel injection control device and a fuel injection control method that solve the above problems.

In order to solve the above problem, one embodiment of the fuel injection control device of the present invention is a fuel injection control device that is applied to a fuel injection device that includes a valve body that moves toward and away from a valve seat to open and close a fuel passage, a moving element that performs the opening and closing operation of the valve body, a stator that has a coil that is excited when current is applied and that applies a magnetic attractive force to the moving element, and a stopper portion that suppresses movement of the moving element toward the valve seat.
The fuel injection control device includes a control unit that controls the energization of the coil by a drive command pulse. When the drive command pulse is output multiple times per combustion stroke, the control unit applies an intermediate pulse between a first drive command pulse and a subsequent second drive command pulse.
The end time of the intermediate pulse is determined by the time when the moving element collides with the stopper portion in the first drive command pulse, and the start time of the intermediate pulse is determined based on the fluctuation in the time when the valve element driven by the second drive command pulse seats on the valve seat, or the fluctuation in the time when the moving element driven by the second drive command pulse collides with the stopper portion.

According to at least one aspect of the present invention, even if the injection interval between the pre-injection and the post-injection is shortened, the intermediate pulse can be applied at an appropriate timing in accordance with fluctuations in the operation of the valve body or the moving element, thereby improving the robustness of the fuel injection control against changes in the characteristics of the fuel injection device or environmental factors of the fuel injection device.
Problems, configurations, and effects other than those described above will become apparent from the following description of the preferred embodiments of the invention.

1 is an overall configuration diagram showing an example of the basic configuration of an internal combustion engine equipped with a fuel injection control device according to an embodiment of the present invention; 1 is a cross-sectional view showing an example of the internal configuration of a fuel injection device according to an embodiment of the present invention. 2 is a diagram showing a detailed configuration example of a drive circuit and an ECU of the fuel injection control device according to the embodiment of the present invention; FIG. 3A and 3B are diagrams illustrating examples of a conventional drive command pulse (injection pulse), a drive voltage, a detection filter, a filtered signal, a drive current, and displacements of a valve body and a movable iron core for the fuel injection device shown in FIG. 2. 3 is a diagram showing the drive command pulse (injection pulse), drive voltage, detection filter, filtered signal, drive current, and displacement of the valve body and movable iron core when an intermediate pulse is added to the fuel injection device shown in FIG. 2. FIG. FIG. 10 is a diagram illustrating a method for determining valve opening stability. 10 is a flowchart showing an example of a procedure for a process for calculating a valve opening stability index. FIG. 11 is a diagram showing a processing result for evaluating the valve opening stability. 10 is a flowchart illustrating an example of a procedure for optimizing an intermediate pulse start time. 10 is a flowchart illustrating an example of a procedure for an intermediate pulse control process.

The following describes a fuel injection control device and a fuel injection control method according to one embodiment of the present invention, with reference to the accompanying drawings. Note that in this specification and the accompanying drawings, identical or similar components are given the same reference numerals, and redundant explanations may be omitted or only explanations focusing on the differences may be given. The number of each component may be singular or plural unless otherwise specified.

[Internal combustion engine system]
First, the configuration of an internal combustion engine system equipped with a fuel injection control device according to this embodiment will be described.
FIG. 1 is a diagram showing the overall configuration of an internal combustion engine system equipped with a fuel injection control device according to this embodiment.

The internal combustion engine 101 shown in Figure 1 is a four-stroke engine that repeats four strokes: intake stroke, compression stroke, combustion (expansion) stroke, and exhaust stroke, and is, for example, a multi-cylinder engine with four cylinders. The internal combustion engine 101 completes one combustion stroke (combustion cycle) through four strokes for each cylinder. Note that the number of cylinders that the internal combustion engine 101 has is not limited to four, and it may have, for example, three, six, eight or more cylinders.

The internal combustion engine 101 is equipped with a piston 102, an intake valve 103, and an exhaust valve 104. The intake air into the internal combustion engine 101 passes through an air flow meter (AFM) 120, which detects the amount of air flowing in, and the flow rate is adjusted by a throttle valve 119. The air that passes through the throttle valve 119 is drawn into a collector 115, which is a branching point, and is then supplied to the combustion chamber 121 of each cylinder via the intake pipe 110 and intake valve 103 provided for each cylinder.

Meanwhile, fuel is supplied from fuel tank 123 to high-pressure fuel pump 125 by low-pressure fuel pump 124, and is increased to the pressure required for fuel injection by high-pressure fuel pump 125. That is, high-pressure fuel pump 125 uses power transmitted from the exhaust camshaft (not shown) of exhaust cam 128 to move a plunger provided within high-pressure fuel pump 125 up and down, thereby pressurizing (boosting) the fuel within high-pressure fuel pump 125.

The intake port of the high-pressure fuel pump 125 is provided with an on-off valve driven by a solenoid. The solenoid is connected to a control device (hereinafter referred to as the "fuel injection control device 127") that controls a fuel injection device 200 provided within an ECU (Engine Control Unit) 109, which is an example of an engine control device. The fuel injection device 200 is a direct injection type fuel injection device that injects fuel directly into the combustion chamber 121.

As shown in Figure 2, which will be described later, the fuel injection control device 127 has a CPU (Central Processing Unit) 501, a RAM (Random Access Memory) 261 that executes computer programs, and a ROM (Read Only Memory) 260 that stores data. The ROM 260 may be a memory whose contents can be erased and rewritten.

The CPU 501 of the fuel injection control device 127 calls up a program from RAM 261 based on a control command from the ECU 109 and controls the solenoid based on the data stored in ROM 260. This drives the on-off valve so that the pressure of the fuel discharged from the high-pressure fuel pump 125 (fuel pressure) becomes the desired pressure.

Fuel pressurized by the high-pressure fuel pump 125 is sent to the fuel injection device 200 via the high-pressure fuel pipe 129. The fuel injection device 200 injects fuel directly into the combustion chamber 121 based on commands from the fuel injection control device 127. This fuel injection device 200 operates the valve body and injects fuel when a drive current is supplied (energized) to the coil 208 (described below).

The internal combustion engine 101 is also provided with a fuel pressure sensor (fuel pressure sensor) 126 that measures the fuel pressure in the high-pressure fuel pipe 129. Based on the measurement results from the fuel pressure sensor 126, the ECU 109 sends a control command to the fuel injection control device 127 to adjust the fuel pressure in the high-pressure fuel pipe 129 to the desired pressure. In other words, the ECU 109 performs so-called feedback control to adjust the fuel pressure in the high-pressure fuel pipe 129 to the desired pressure.

Furthermore, each combustion chamber 121 of the internal combustion engine 101 is provided with an ignition plug 106, an ignition coil 107, and a water temperature sensor 108. The spark plug 106 exposes an electrode portion inside the combustion chamber 121 and ignites the mixture of intake air and fuel in the combustion chamber 121 by electrical discharge. The ignition coil 107 generates a high voltage for the spark plug 106 to discharge. The water temperature sensor 108 measures the temperature of the cooling water that cools the cylinders of the internal combustion engine 101.

ECU 109 controls the energization of ignition coil 107 and ignition by spark plug 106. The mixture of intake air and fuel in combustion chamber 121 is combusted by a spark emitted from spark plug 106, and the resulting pressure pushes piston 102 down.

The exhaust gas generated by combustion is discharged into the exhaust pipe 111 via the exhaust valve 104. The exhaust pipe 111 is provided with a three-way catalyst 112 and an oxygen sensor 113. The three-way catalyst 112 purifies harmful substances contained in the exhaust gas, such as nitrogen oxides (NOx). The oxygen sensor 113 detects the oxygen concentration contained in the exhaust gas and outputs the detection result to the ECU 109. Based on the detection result of the oxygen sensor 113, the ECU 109 performs feedback control so that the amount of fuel injected from the fuel injection device 200 matches the target air-fuel ratio.

Furthermore, a crankshaft 131 is connected to the piston 102 via a connecting rod 132. The reciprocating motion of the piston 102 is converted into rotational motion by the crankshaft 131. A crank angle sensor 116 is attached to the crankshaft 131. The crank angle sensor 116 detects the rotation and phase of the crankshaft 131 and outputs the detection results to the ECU 109. The ECU 109 detects the rotational speed of the internal combustion engine 101 based on the output of the crank angle sensor 116.

Signals from the crank angle sensor 116, air flow meter 120, oxygen sensor 113, accelerator position sensor 122, and fuel pressure sensor 126 are input to the ECU 109. The accelerator position sensor 122 is a sensor that indicates the position of the accelerator operated by the driver.

The ECU 109 calculates the required torque of the internal combustion engine 101 based on the signal supplied from the accelerator position sensor 122, and determines whether the engine is idling or not. The ECU 109 also calculates the amount of intake air required for the internal combustion engine 101 from the required torque, etc., and outputs an appropriate opening signal to the throttle valve 119.

The ECU 109 also has a rotation speed detection unit that calculates the rotation speed of the internal combustion engine 101 (hereinafter referred to as engine rotation speed) based on a signal supplied from the crank angle sensor 116. Furthermore, the ECU 109 has a warm-up determination unit (not shown) that determines whether the three-way catalyst 112 is warmed up based on the coolant temperature obtained from the water temperature sensor 108 and the elapsed time since the internal combustion engine 101 was started, etc.

The fuel injection control device 127 calculates the amount of fuel (target injection amount) according to the amount of intake air, and outputs a corresponding fuel injection signal to the fuel injection device 200. Furthermore, the fuel injection control device 127 outputs an energization signal to the ignition coil 107, and outputs an ignition signal to the spark plug 106.

[Configuration of fuel injection device]
Next, the configuration of the fuel injection device 200 shown in FIG. 1 will be described with reference to FIG.
FIG. 2 is a cross-sectional view showing an example of the internal configuration of the fuel injection device 200.

As shown in Figure 2, the fuel injection device 200 is composed of a fuel supply unit 212 that supplies fuel, a valve seat 202 that has fuel injection holes 215 through which the fuel passes, and a movable iron core (movable element) 206 that drives the valve body 201. In this embodiment, an electromagnetic fuel injection device for an internal combustion engine that uses gasoline or a mixed fuel as fuel will be described as an example.

The fuel injection device 200 has a fuel supply section 212 at the upper end in the drawing, and a fuel injection hole 215 and valve seat 202 at the lower end. The movable iron core 206, valve body 201, and sleeve 214 are arranged between the fuel supply section 212 and the valve seat 202.

The sleeve 214 is cylindrical in shape and is fitted and connected to the outer peripheral surface of the upper side of the valve body 201. A flange is formed at the upper end of the sleeve 214. The flange has a shape that protrudes outward from the upper side of the sleeve 214.

A first spring member 210 is disposed above the sleeve 214. A second spring member 216 is disposed around the sleeve 214, between the lower surface of the flange (transmission surface 219) and the movable iron core 206. The second spring member 216 biases the movable iron core 206 and sleeve 214 in a direction that moves them away from each other. The flange (transmission surface 219) of the sleeve 214 transmits the force of the second spring member 216 to the valve body 201 and the movable iron core 206.

The end of the fuel injection device 200 opposite the fuel injection hole 215 and valve seat 202 (the fuel supply unit 212 side) is connected to a high-pressure fuel pipe 129 (see Figure 1), not shown. The end of the fuel injection device 200 opposite the fuel supply unit 212 (the fuel injection hole 215 side) is inserted into a mounting hole (insertion hole) formed in a member (cylinder block, cylinder head, etc.) that forms the combustion chamber 121 (see Figure 1).

Fuel injection device 200 receives fuel from high-pressure fuel pipe 129 (see Figure 1) through fuel supply section 212, and injects the fuel into combustion chamber 121 (see Figure 1) from the tip of valve seat 202. A fuel passage is configured inside fuel injection device 200 so that fuel flows substantially along central axis 200a of fuel injection device 200 from the base end on the fuel supply section 212 side to the tip end on the fuel injection hole 215 side.

The coil 208 is disposed between the fixed iron core (stator) 207 and the housing 209. The fixed iron core 207, coil 208, and housing 209 form an electromagnet. In the closed valve state where the coil 208 is not energized, the valve element 201 abuts against the valve seat 202 due to the biasing force of the first spring member 210, which biases the valve element 201 in the valve closing direction (towards the valve seat 202). This state is called the stable closed valve state (valve closed standby state). In the stable closed valve state, the movable iron core 206 abuts against the stopper 217 and is positioned in the closed valve position. The valve element 201 is driven via the transmission surface 219 of the sleeve 214, which transmits the load from the movable iron core 206.

The stopper 217 is roughly cylindrical in shape and is fitted and connected to the outer peripheral surface of the valve body 201 downstream of the movable iron core 206 (towards the valve seat 202). The stopper 217 prevents the movable iron core 206 from moving in the valve closing direction.

In the stable valve-closed state, the sleeve 214 is biased downstream (toward the valve seat 202, in the valve-closing direction) by the force obtained by subtracting the biasing force of the second spring member 216 from the biasing force of the first spring member 210, and the valve element 201 is in contact with the valve seat 202 and remains stationary. The movable iron core 206 is biased in the valve-closing direction (toward the valve seat 202) by the biasing force of the second spring member 216, and is in contact with the stopper 217.
A gap 250 is formed between the lower end 218 of the sleeve 214 of the valve body 201 and the upper surface (transmission surface) of the movable iron core 206 .

A flange may be formed at the lower end of the sleeve 214. In this case, the lower surface of the flange formed at the lower end of the sleeve 214 serves as the transmission surface and comes into contact with the upper surface of the movable iron core 206.

The fuel injection device 200 is connected to a fuel injection control device 127 and an ECU (engine control device) 109. The fuel injection control device 127 has a circuit that receives a drive command pulse (injection pulse) from the ECU 109 and passes a drive current (drive voltage) to the fuel injection device 200.

Note that the ECU 109 and fuel injection control device 127 may be configured as an integrated component. Furthermore, the fuel injection control device 127 is a device that generates a drive voltage for the fuel injection device 200, and may be integrated with the ECU 109 or configured as a standalone component.

ECU 109 receives signals indicating the engine's condition from various sensors and calculates the appropriate pulse width and injection timing of the drive command pulse (injection pulse) according to the operating conditions of the internal combustion engine. The pulse width of the drive command pulse output from ECU 109 is input to fuel injection control device 127 via signal line 223.

The fuel injection control device 127 controls the drive voltage applied to the coil 208 and supplies a drive current to the coil 208. The ECU 109 communicates with the fuel injection control device 127 via a communication line 222. The ECU 109 then switches the drive current generated by the fuel injection control device 127 depending on the pressure of the fuel supplied to the fuel injection device 200 and the operating conditions. The fuel injection control device 127 is able to change its control constants through communication with the ECU 109, and changes the current waveform according to the control constants.

[Configuration of fuel injection control device]
Next, the configuration of the fuel injection control device 127 will be described with reference to FIG.
FIG. 3 is a diagram showing a detailed configuration example of the drive circuit of the fuel injection control device 127 and the ECU 109.

As mentioned above, the ECU 109 (see Figure 2) has a built-in CPU 501. The CPU 501 takes in various signals indicating the state of the engine from the fuel pressure sensor 126, air flow meter 120, oxygen sensor 113, crank angle sensor 116, etc. Based on these signals, the CPU 501 calculates the pulse width and injection timing of a drive command pulse (injection pulse) to control the amount of fuel injected from the fuel injection device 200 according to the operating conditions of the internal combustion engine.

The CPU 501 also calculates the appropriate pulse width and injection timing of the drive command pulse depending on the operating conditions of the internal combustion engine, and outputs the drive command pulse to the drive IC (Integrated Circuit) 502 of the fuel injection device 200 via signal line 223.

This CPU 501 represents a specific example of a control unit according to this embodiment, and includes a current control unit 501a, a voltage detection unit 501b, a digital filter unit 501c, a valve closure detection unit 501d, and a fluctuation calculation unit 501e.

The energization control unit 501 a performs energization control processing to generate a drive command pulse and output it to the drive IC 502 .
The voltage detection unit 501b performs a voltage detection process to detect the voltage value when the coil 208 is energized.
The digital filter unit 501c, which is an example of a filter unit, performs digital filtering to detect an inflection point of the waveform of the voltage value when the coil 208 is energized.
The valve closure detection unit 501d performs processing to detect the valve closure timing of the valve body 201 based on the inflection point of the waveform of the voltage value from a predetermined detection start timing (valve closure detection start time Tss in Figures 4 and 5) to a detection end timing (valve closure detection end time Tse in Figures 4 and 5).
The variation calculation unit 501e calculates the variation in the voltage value obtained by digitally filtering the drive voltage in the digital filter unit 501c, and performs processing to determine the valve opening stability (described later) from the calculation results. The valve opening stability indicates the stability of the operation of the valve element 201 before the valve is closed, i.e., the stability of the operation of the valve element 201 in the open state.

The amount of injection by fuel injection device 200 is determined by the pulse width of the drive command pulse. Then, drive IC 502 switches switching elements 505, 506, and 507 between energized and de-energized states to supply drive current to fuel injection device 200.

Switching element 505 is connected between a high voltage source higher than voltage source VB input to the drive circuit of fuel injection control device 127 (see Figure 2) and the high voltage side terminal of solenoid 540 (corresponding to coil 208 in Figure 2) provided in fuel injection device 200. Switching elements 505, 506, 507 are formed, for example, by transistors such as FETs (Field Effect Transistors), and can switch between energizing and de-energizing fuel injection device 200.

The boost voltage VH, which is the initial voltage value of the high voltage source, is, for example, 65 V, and is generated by boosting the battery voltage VB using the boost circuit 514. The boost circuit 514 is composed of, for example, a coil 530, a transistor 531, a diode 532, and a capacitor 533.

In the boost circuit 514, when the transistor 531 is turned on, the battery voltage VB flows to the ground potential 534. On the other hand, when the transistor 531 is turned off, the high voltage generated in the coil 530 is rectified through the diode 532, and a charge is accumulated in the capacitor 533.
Then, this transistor is repeatedly turned on and off until the voltage of the capacitor 533 reaches the boosted voltage VH, thereby increasing the voltage of the capacitor 533. The transistor 531 is connected to the driving IC 502 or the CPU 501, and the boosted voltage VH output from the boost circuit 514 is configured to be detected by the driving IC 502 or the CPU 501. The boost circuit 514 may be configured by a DC/DC converter or the like.

Switching element 507 is connected between the low-voltage power supply and the high-voltage terminal of solenoid 540. Low-voltage power supply VB is, for example, a battery voltage, and its voltage value is approximately 12 to 14 V. Switching element 506 is connected between the low-voltage terminal of fuel injection device 200 (see Figure 2) and ground potential 515.

The drive IC 502 detects the current flowing through the fuel injection device 200 using current detection resistors 508, 512, and 513, and switches the switching elements 505, 506, and 507 between energized and de-energized states based on the detected current value, generating the desired drive current. Diodes 509 and 510 apply a reverse voltage to the solenoid 540 of the fuel injection device 200, rapidly reducing the current being supplied to the solenoid 540.

CPU 501 communicates with drive IC 502 via communication line 222. CPU 501 switches the drive current generated by drive IC 502 depending on the pressure of the fuel supplied to fuel injection device 200 (see Figure 2) and operating conditions. In addition, both ends of resistors 508, 512, and 513 are connected to the A/D conversion port of drive IC 502, and the voltage across resistors 508, 512, and 513 can be detected by drive IC 502.

[Operation of conventional fuel injection device]
Next, the operation of the conventional fuel injection device 200 under the control of the fuel injection control device 127 will be described with reference to FIG.
FIG. 4 is a diagram showing an example of a conventional drive command pulse (injection pulse), drive voltage, detection filter, filtered signal, drive current, and displacement of the valve body and movable core for the fuel injection device 200 shown in FIG.

As shown in Figure 4, when a drive command pulse Ti is input at time Ts, a high voltage 304 is applied to coil 208 (see Figure 2) from a high voltage source that has been boosted to a voltage higher than battery voltage VB, and current begins to be supplied to coil 208.

After current is applied to the coil 208, a magnetomotive force is generated by the electromagnet formed by the fixed iron core 207, coil 208, and housing 209. This magnetomotive force forms a magnetic path (magnetic circuit) that surrounds the coil 208 using the fixed iron core 207, housing 209, and movable iron core 206, and magnetic flux flows around the formed magnetic path. At this time, a magnetic attraction force acts between the movable iron core 206 and the fixed iron core 207, displacing the movable iron core 206 toward the fixed iron core 207. The movable iron core 206 then displaces until its upper surface abuts the lower end 218 of the sleeve 214. Note that the valve body 201 continues to maintain abutment with the valve seat 202 until the movable iron core 206 abuts against the sleeve 214.

The movable iron core 206 is displaced by the gap 250 that exists between the valve element 201 (i.e., the lower end 218 of the sleeve 214) and the movable iron core 206, and when the valve element 201 (transmission surface 219 of the sleeve 214) collides with the movable iron core 206, the valve element 201 is pulled upstream by the kinetic energy of the movable iron core 206, and the valve element 201 moves away from the valve seat 202. This creates a gap between the valve element 201 and the valve seat 202, opening the fuel passage and allowing fuel to be injected from the fuel injection hole 215. The movable iron core 206, which now has kinetic energy, causes the valve element 201 to be rapidly displaced.

The fuel injection control device 127 applies high voltage 304 and passes drive current 308 through coil 208 from time Ts until the movable iron core 206 and valve element 201 collide and the valve element 201 separates from the valve seat 202 at timing 334, or until sufficient kinetic energy is accumulated in the movable iron core 206 to open the valve element 201. This generates a necessary and sufficient magnetic attraction force between the movable iron core 206 and the fixed iron core 207, allowing the movable iron core 206 to respond quickly, as shown by displacement 335. By allowing the movable iron core 206 to respond quickly, the valve element 201 can be driven by the movable iron core 206 even when the pressure of the supplied fuel is high.

The drive current flowing through coil 208 rises sharply as shown by drive current 308 (peak current) due to the application of high voltage 304. When drive current 308 reaches peak current value Ip, fuel injection control device 127 applies high voltage 304 in the reverse direction (applies reverse voltage). That is, fuel injection control device 127 turns off all switching elements 505, 506, and 507 (see Figure 3). As a result, diodes 509 and 510 are energized by the back electromotive force caused by the inductance of fuel injection device 200, and current is fed back to boost circuit 514. As a result, the drive current flowing through coil 208 drops sharply as shown by current 317 and is then cut off. When current 317 reaches hold current 318, switching occurs at voltage 305 (battery voltage VB), and hold current 318 is maintained.

After the movable iron core 206 and fixed iron core 207 collide, the valve body 201 displaces upstream and the movable iron core 206 displaces downstream. When the movable iron core 206 collides with the fixed iron core 207, the valve body 201 and the movable iron core 206 separate, and the movable iron core 206 displaces downstream, but eventually the movable iron core 206 comes to rest at the target lift position and stabilizes. This state is called the stable open valve state.

The movable iron core 206 and the valve body 201 are configured to be capable of relative movement. Therefore, when the movable iron core 206 collides with the sleeve 214 of the valve body 201, the valve body 201 and the movable iron core 206 separate from each other, and the valve body 201 is displaced upstream.

Next, when the drive command pulse Ti turns OFF at time Te, the fuel injection control device 127 applies a drive voltage in the opposite direction to the coil 208 (applies a reverse voltage). This cuts off the current supply to the coil 208, causing the magnetic flux generated in the magnetic circuit to disappear and the magnetic attraction force to disappear. As a result, the movable iron core 206, which has lost its magnetic attraction force, is pushed back by the load of the first spring member 210 and the force due to the fuel pressure, and the valve body 201 reaches the closed position in contact with the valve seat 202.

The biasing force of the first spring member 210 acting on the valve element 201 is transmitted to the movable iron core 206 via the lower end 218 of the sleeve 214, which is connected to the valve element 201. When the required valve closing time has elapsed (at time Tc1), from time Te when the drive command pulse Ti turns OFF to time Tc1 when the valve is completely closed, the valve element 201 comes into contact with the valve seat 202.

After the valve element 201 comes into contact with the valve seat 202, the movable iron core 206 separates from the lower end 218 of the sleeve 214 of the valve element 201 and continues to move downward (in the valve closing direction). After time Tc1, when the valve is completely closed, the movable iron core 206 and the sleeve 214 of the valve element 201 become separated. At this time, a bend-like change appears in the drive voltage, as shown by inflection point 330 (an example of a first inflection point). This change makes it possible to detect the time Tc1 when the valve is completely closed.

When the fuel injection device 200 is closed, after the valve body 201 collides with the valve seat 202, only the biasing force of the second spring member 216 acts on the movable iron core 206, causing it to collide with the stopper 217 due to the biasing force of the second spring member 216 and the inertial force of the movable iron core 206. At this time, a bend-like change appears in the drive voltage, as shown by inflection point 331 (an example of a second inflection point). This change makes it possible to detect the time Td1 at which the movable iron core 206 collides with the stopper 217.

In this way, when the movement of the movable iron core 206 changes, the acceleration of the movable iron core 206 changes, and the inductance of the coil 208 changes. In other words, when the fuel injection device 200 is closed, the drive current flowing through the coil 208 is cut off and a back electromotive force is applied to the coil 208. Then, as the drive current converges, the back electromotive force also gradually decreases, and as the back electromotive force decreases, the inductance changes.

When the valve disc 201 collides with the valve seat 202 (time Tc1), a change in inductance causes an inflection point 330 to occur in the drive voltage of the coil 208. Furthermore, when the movable iron core 206 collides with the stopper 217 (time Td1), a change in inductance causes an inflection point 331 to occur in the drive voltage of the coil 208.

Inflection point 330 is the timing at which the fuel injection device 200 completes valve closing. For example, inflection point 330 appears as an extreme value (maximum or minimum value) when the time series data of the drive voltage applied to coil 208 is differentiated twice. Therefore, inflection point 330 can be identified by differentiating the time series data of the drive voltage twice and detecting the extreme value. Inflection point 331 can also be determined by differentiating the time series data of the drive voltage twice.

The filtered signal is a signal obtained by performing digital filtering on the drive voltage, and is a waveform obtained by second-order differentiation of the drive voltage. Figure 4 and Figure 5, described below, show a schematic waveform of the filtered signal (second-order differential value), and Figure 6, described below, shows an example of a detailed waveform of the filtered signal.

As described above, as the slope of the drive voltage changes, the waveform obtained by second-order differentiation of the drive voltage changes in the value of the voltage after digital filtering. In other words, when the valve element 201 closes, the acceleration of the movable iron core 206 changes, which appears as a change in the drive voltage. Therefore, by calculating the maximum value of the voltage value after digital filtering, i.e., the maximum value between the determined valve close detection start time Tss and valve close detection end time Tse, it is possible to detect the time Tc1 when the valve element 201 closes and the time Td1 when the movable iron core 206 collides with the stopper 217.

As shown in Figure 4, after the movable iron core 206 collides with the stopper 217, kinetic energy is consumed by the collision. Then, due to the biasing force of the second spring member 216 in the valve closing direction, the movement of the movable iron core 206 gradually decreases, and eventually the valve transitions to a stable closed state. Here, by shortening the time until the time Tst at which the stable closed state is reached, it becomes possible to inject fuel stably even if the interval Tdw between the drive command pulse Ti1 for the pre-injection and the drive command pulse Ti2 for the subsequent injection is set small. Hereinafter, when there is no need to distinguish between the drive command pulse Ti1 for the pre-injection and the drive command pulse Ti2 for the subsequent injection, they will be referred to as "drive command pulse Ti."

However, when the interval Tdw between the drive command pulse Ti1 for the pre-injection and the drive command pulse Ti2 for the subsequent injection is extremely small, the drive command pulse Ti2 for the subsequent injection may be applied before the time Tst at which the valve element 201 reaches a stable closed valve state. In this case, the drive command pulse Ti2 for the subsequent injection is applied during the time period when the movable iron core 206 is bouncing, which may cause the movement of the movable iron core 206 and the valve element 201 to become unstable, resulting in the risk that the amount of fuel injected from the fuel injection device 200 may deviate from the target injection amount. For this reason, it is desirable that the time from the time Tc1 at which the valve element 201 collides with the valve seat 202 to the time Tst at which the valve element reaches a stable closed valve state be short.

[Operation of the fuel injection device of this embodiment]
Next, the operation of the fuel injection device 200 under the control of the fuel injection control device 127 according to this embodiment will be described with reference to Figures 5 to 9. In particular, a method for shortening the time from when the valve body 201 comes into contact with the valve seat 202 during the valve closing operation until the valve is in a stable closed state will be described.
FIG. 5 is a diagram showing an example of the drive command pulse (injection pulse), drive voltage, detection filter, filtered signal, drive current, and displacement of the valve body and movable core when an intermediate pulse is added to the fuel injection device 200 shown in FIG.

As shown in FIG. 5, when an intermediate pulse Tbp is applied between the drive command pulse Ti1 for the pre-injection and the drive command pulse Ti2 for the subsequent injection, a high voltage 306 is applied to the coil 208, and current begins to be supplied to the coil 208. By energizing the coil 208, a magnetic attraction force can be generated in the valve opening direction until the movable iron core 206 collides with the stopper 217. This reduces the speed at which the movable iron core 206 collides with the stopper 217, and shortens the time until the movable iron core 206 stabilizes at time Tst. As a result, the fuel injection device 200 quickly transitions to a stable valve-closed state, stabilizing the amount of fuel injected from the fuel injection device 200 to the internal combustion engine 101. This homogenizes the air and fuel in the engine cylinder, improving exhaust performance.

As mentioned above, the operation of the valve body 201 varies depending on changes in the characteristics of the fuel injection device 200 and environmental factors. The characteristics of the fuel injection device 200, in other words, individual characteristics, include, for example, the characteristics of the magnetic circuit and spring. Furthermore, environmental factors of the fuel injection device 200 include, for example, fuel pressure and fuel temperature. Furthermore, the characteristics and environmental factors of individual fuel injection devices may change due to deterioration over time.

Variations in the operation of the valve disc 201 affect fluctuations in the time Tc1 at which the valve is completely closed. Variations in the operation of the valve disc 201 also affect the bounding behavior of the movable iron core 206 after it collides with the stopper 217. Because the optimal intermediate pulse Tbp changes depending on the operation of the valve disc 201 and the movable iron core 206, it is necessary to correct the intermediate pulse Tbp in accordance with these changes. Therefore, a method for achieving the optimal intermediate pulse Tbp will be described.

In order to properly control the intermediate pulse Tbp, it is necessary to appropriately set the start time Tbp_s and end time Tbp_e of the intermediate pulse Tbp. The method for setting the intermediate pulse is explained below.

(End time of intermediate pulse)
First, the process of determining the end time of the intermediate pulse Tbp will be described.
When the movable core 206 collides with the stopper 217, the movable core 206 bounds. If the intermediate pulse Tbp is applied while the movable core 206 is bounding in the valve-opening direction, a magnetic attractive force is generated in the valve-opening direction, which accelerates the bounding of the movable core 206. Therefore, it is desirable to eliminate the magnetic attractive force generated by the intermediate pulse Tbp before the movable core 206 collides with the stopper 217.

In other words, the time Td1 when the movable iron core 206 collides with the stopper 217 is detected, and the end time Tbp_e of the intermediate pulse Tbp is determined taking into account the drive current and the time until the magnetic attractive force disappears. The end time Tbp_e of the intermediate pulse Tbp is earlier than the time when the magnetic attractive force disappears. Using this approach, it is possible to set an optimal end time for the intermediate pulse Tbp.

As described above, in this embodiment, the end time of the intermediate pulse is determined by the time when the movable iron core 206 collides with the stopper portion (stopper 217) during the first drive command pulse (pre-injection drive command pulse Ti1).
This allows the application of the intermediate pulse to be terminated at an appropriate timing according to fluctuations in the movement of the mover, even when the injection interval between the preceding injection and the succeeding injection is shortened, thereby improving (suppressing) the effect of the mover's behavior (bouncing) on the next injection.

More specifically, the end time of the intermediate pulse is determined based on the timing of the second inflection point (inflection point 331) after the first drive command pulse (pre-injection drive command pulse Ti1).
By using the second inflection point in this manner, it is possible to reliably detect the time when the mover (movable iron core 206) collides with the stopper portion (stopper 217).

The time from the end of the intermediate pulse Tbp until the magnetic attractive force disappears may be set to a fixed value. Alternatively, a model showing the magnetic attractive force, drive current, and magnetic attractive force characteristics may be prepared in advance within ECU 109, and this model may be used to calculate the time until the magnetic attractive force disappears. For example, a model that learns the time difference between the disappearance of the magnetic attractive force and the current value of the drive current may be used as the model. Instead of a model, map data that associates the current value of the drive current with this time difference may also be used.

(Start time of intermediate pulse)
Next, the process of determining the start time of the intermediate pulse Tbp will be described with reference to FIG.
6 is a diagram showing an example of a method for determining valve opening stability, showing an example of voltage values after digital filtering (second-order differentiation) of the drive voltage, which are used by the fluctuation calculation unit 501e (see FIG. 3) to determine valve opening stability. The vertical axis in the diagram represents the voltage value after digital filtering of the drive voltage ("-" means that there is no unit). The horizontal axis represents the time elapsed from the end time of the drive command pulse Ti.

As shown in Figure 6, when the valve element 201 is stably open, the valve element 201 collides with the valve seat 202 after the drive command pulse Ti ends, and the voltage value 601 after digital filtering becomes relatively large.

On the other hand, if the operation of the valve disc 201 is unstable, the valve disc 201 may collide with the valve seat 202 before the end of the drive command pulse Ti. This is the case when the magnetic attraction force of the coil 208 is not sufficient, and the valve disc 201 is biased in the valve closing direction, preventing it from opening. In this case, the voltage value 602 after digital filtering is smaller than the voltage value 601 during stable operation, as shown in Figure 6.

Therefore, by comparing the voltage value after digital filtering with a preset threshold value Vth and using the comparison result, it is possible to determine whether the valve element 201 is stable or unstable before the valve is closed. The voltage value after digital filtering that is compared with the threshold value Vth is the voltage value between the preset valve closure detection start time Tss and valve closure detection end time Tse.

In the example of Figure 6, if the operation of the valve element 201 is stable, the voltage value 601 after digital filtering is greater than the threshold value Vth, so the difference (deviation from the stable valve opening condition) is a positive value. In this case, it can be determined that the valve is stably open. Conversely, if the operation of the valve element 201 is unstable, the voltage value 602 after digital filtering is less than the threshold value Vth, so the difference (deviation from the unstable valve opening condition) is a negative value. In this case, it can be determined that the state is unstable.

In this embodiment, based on the concept of valve opening stability described above, for example, the start time of the intermediate pulse is determined based on the fluctuation in the time when the valve disc driven by the second drive command pulse (drive command pulse Ti2 for subsequent injection) seats on the valve seat, or the fluctuation in the time when the movable element (movable iron core 206) driven by the second drive command pulse collides with the stopper portion (stopper 217).
As a result, even if the injection interval between the pre-injection and the post-injection is shortened, the application of the intermediate pulse can be started at an appropriate timing in accordance with fluctuations in the operation of the valve body or the movable element.

More specifically, the start time of the intermediate pulse is determined, for example, by the fluctuation in the voltage value of the first inflection point (inflection point 330) or the second inflection point (inflection point 331) after the second drive command pulse (drive command pulse Ti2 for subsequent injection) calculated by the fluctuation calculation unit 501e.
In this way, by using the fluctuation in the voltage value at the first inflection point or the second inflection point, the start time of the intermediate pulse can be determined, reflecting the fluctuation in the operation of the valve body or the movable element (movable iron core 206).

[Calculation of valve opening stability index]
Next, the process of calculating the valve opening stability index in the fluctuation calculation unit 501e (see FIG. 3) of the CPU 501 will be described with reference to FIG.
7 is a flowchart showing an example of the procedure for calculating the valve opening stability index. The valve opening stability index is an index used by the fluctuation calculation unit 501e when determining the stability of the valve opening. As an example, the standard deviation of the difference (deviation) between the voltage value after digital filtering and the threshold value Vth shown in FIG. 6 can be used as the valve opening stability index.

First, in step S701, the voltage detection unit 501b acquires the voltage value of the drive voltage applied to the coil 208 by the current control unit 501a in chronological order.

Next, in step S702, the digital filter unit 501c performs digital filtering (second-order differentiation) on the voltage values acquired in time series, and obtains the voltage value V_FL after digital filtering.

Next, in step S703, the digital filter unit 501c obtains a first inflection point (corresponding to inflection point 330) and a second inflection point (corresponding to inflection point 331) based on the voltage value V_FL after digital filtering.

In this embodiment, the digital filter unit 501c performs digital filtering to detect the first and second inflection points in advance from the waveform of the drive voltage. There are two main timings for detecting the first and second inflection points.
(1) An inflection point is obtained from the filtered signal of the drive voltage in the cycle immediately preceding the target combustion stroke cycle.
(2) In the learning mode when the internal combustion engine system is idling, an inflection point is obtained from the filtered signal of the drive voltage. During idling, the actual injection amount may be small.

Next, in step S704, the variation calculation unit 501e calculates the difference D_th (deviation in Figure 6) between the voltage value of the first inflection point or the second inflection point of the filtered signal and a preset threshold value Vth.

Next, in step S705, the fluctuation calculation unit 501e calculates the standard deviation σ _toff (an example of a valve opening stability index) of the difference D_th between the voltage value at the first inflection point or the second inflection point of the filtered signal and the threshold value Vth.
The digital filter unit 501c calculates the voltage value of the first inflection point or the second inflection point of the filtered signal for multiple combustion stroke cycles and stores the calculated voltage value in memory. The fluctuation calculation unit 501e then calculates the standard deviation σ _toff of the difference D_th between the voltage value of the first inflection point or the second inflection point and the threshold Vth for multiple combustion stroke cycles. Note that the standard deviation σ _toff of the difference D_th between the voltage value of the first inflection point and the voltage value of the second inflection point and the threshold Vth may be calculated separately.

As described above, in this embodiment, the fluctuation calculation unit 501e calculates the fluctuation of the voltage value when the coil 208 is energized using the standard deviation σ _toff (an example of a valve opening stability index) of the difference D_th between the voltage value at the first inflection point or the second inflection point of the voltage value waveform and the threshold value Vth.

In this way, the standard deviation σ _toff of the difference D_th from the threshold Vth is calculated for the voltage value at the first inflection point or the second inflection point as a valve opening stability index, and the standard deviation σ _toff is compared with a predetermined threshold to determine the valve opening stability. If the standard deviation σ _toff is smaller than the predetermined threshold, it can be determined that the valve is stably open.

Alternatively, the valve opening stability of the valve element 201 can be determined based on whether the voltage value after digital filtering exceeds a threshold value Vth. For example, a threshold number of times to be used for determining valve opening stability can be determined in advance, and the valve opening stability of the valve element 201 can be determined using the results of comparing the number of times the threshold value Vth is exceeded among the determined number of injections with the threshold number of times. If the number of times the threshold value Vth is exceeded is greater than the threshold number of times, it can be determined that the valve is stably open.

As described above, by using the voltage value after digital filtering and a predetermined threshold value Vth, it is possible to determine the valve opening stability.

[Optimization process for intermediate pulse start time]
Using the fluctuation calculation unit 501e (see FIG. 3), it is possible to set the optimal start time Tbp_s of the intermediate pulse Tbp. Optimization of the start time of the intermediate pulse Tbp will be described below with reference to FIG.
8 is a flowchart showing an example of the procedure for optimizing the intermediate pulse start time in the variation calculation unit 501e. In this flowchart, the optimal start timing of the intermediate pulse Tbp is set.

First, in step S801, the fluctuation calculation unit 501e generates candidates for the time that will be the start time of the intermediate pulse Tbp. As an example, based on the first inflection point, a time near the timing when the valve disc 201 seats on the valve seat 202 (time Tc1 in Figure 4) can be determined as a candidate for the intermediate pulse start time. Multiple times near the seating timing can be set as candidates for the intermediate pulse start time.

Next, in step S802, the fluctuation calculation unit 501e calculates and acquires the valve opening stability index (standard deviation σ toff of the difference D_th) at the time of the drive command pulse Ti2 for the subsequent injection after the application of the intermediate pulse Tbp, for multiple candidates for the start time of the intermediate pulse _Tbp .

Next, in step S803, the fluctuation calculation unit 501e calculates and acquires a candidate for the start time of the intermediate pulse when the valve opening stability index (standard deviation _σtoff of the difference D_th) is minimum. The fluctuation calculation unit 501e determines that this candidate for the start time of the intermediate pulse is the start time Tbp_s of the intermediate pulse Tbp. After processing step S803, the process proceeds to step S906 shown in FIG. 9.

In this way, the variation calculation section 501e selects the time at which the standard deviation σ _toff of the calculated difference D_th is smallest from among the preset candidates for the start time of the intermediate pulse as the start time Tbp_s of the intermediate pulse.
By going through the above-described series of processing steps, the optimal start time Tbp_s of the intermediate pulse Tbp can be obtained. Then, the intermediate pulse Tbp can be determined based on the optimal start time Tbp_s and end time Tbp_e, taking into account individual variations in the operation of the valve element 201.
The information on the determined intermediate pulse Tbp is stored in the ROM 260.

[Intermediate pulse control processing]
Next, the intermediate pulse control process by the CPU 501 (see FIG. 3) will be described with reference to FIG.
FIG. 9 is a flowchart showing an example of the procedure of the intermediate pulse control process.

First, in step S901, the power supply control unit 501a determines whether the number of injections during one combustion stroke is multiple. If the number of injections is not multiple (NO in step S901), the intermediate pulse control process ends.

On the other hand, if the number of injections during one combustion stroke is multiple (YES in step S901), in step S902, the current control unit 501a acquires the second inflection point (inflection point 331 in Figure 4) that occurred in the drive voltage during the pre-injection using the digital filter unit 501c.

Next, in step S903, the energization control unit 501a determines the end time Tbp_e of the intermediate pulse Tbp based on the time Td1 (see Figure 4) when the second inflection point occurs.

Next, in step S904, the energization control unit 501a determines whether the start time of the intermediate pulse Tbp has been optimized. If the start time of the intermediate pulse Tbp has been optimized (YES in step S904), the process proceeds to step S906.

On the other hand, if the start time of the intermediate pulse Tbp has not been optimized (NO judgment in step S904), proceed to step S905. In step S905, the variation calculation unit 501e optimizes the start time of the intermediate pulse Tbp. In this step S905, the optimization process for the intermediate pulse start time is performed according to steps S801 to S803 shown in FIG. 8.

If the start time of the intermediate pulse Tbp has been optimized (YES in step S904 or after processing in step S905), in step S906, the energization control unit 501a determines the start time Tbp_s of the intermediate pulse Tbp.

Next, in step S907, the energization control unit 501a generates an intermediate pulse Tbp from the start time Tbp_s and end time Tbp_e determined in steps S903 and S906. The voltage value of the high voltage 306 (see FIG. 5) of the intermediate pulse Tbp is set in advance. For example, the voltage value of the high voltage 306 may be the same as the voltage value of the high voltage 304. Alternatively, the voltage value of the high voltage 304 may be set according to the interval Tdw between the drive command pulse Ti1 for the pre-injection and the drive command pulse Ti2 for the subsequent injection.

The current supply control unit 501a executes the intermediate pulse control process of steps S901 to S907 for each cycle of the combustion stroke, and then adds the generated intermediate pulse Tbp between the drive command pulse for the pre-injection and the drive command pulse for the post-injection.
The driving IC 502 applies a driving voltage (high voltage 306) to the solenoid 540 in FIG. 3 (coil 208 in FIG. 2) in accordance with the intermediate pulse Tbp generated by the current control unit 501a.

In this way, by using an intermediate pulse Tbp with appropriately set start and end times, it is possible to effectively suppress the bounding of the movable core 206 when it collides with the stopper 217. As a result, even if the injection interval between the pre-injection and post-injection is shortened, the intermediate pulse can be applied at the appropriate timing in accordance with fluctuations in the operation of the valve body or the movable element. Therefore, even if the characteristics of the fuel injection device or environmental factors of the fuel injection device change, the robustness of fuel injection control in response to these changes can be improved.

For example, as shown in the voltage value 601 after digital filtering in Figure 6, the operation of the valve body 201 is stabilized, shot variation by the fuel injection device 200 is reduced, and the amount of fuel injected can be stabilized. In other words, fuel can be supplied to the engine stably from the fuel injection device 200. This makes it possible to improve the combustion stability of an engine using the fuel injection device 200, and ultimately improve the exhaust emitted from the engine. This makes it possible to improve the engine's exhaust performance and reduce fuel consumption.

As mentioned above, the present invention is not limited to the above-described embodiments, and of course various other modifications and applications are possible as long as they do not deviate from the gist of the invention as set forth in the claims. For example, the above-described embodiments have been described in detail and specifically to clearly explain the invention, and are not necessarily limited to those that include all of the components described. Furthermore, it is also possible to add, replace, or delete other components from part of the configuration of an embodiment.

Furthermore, in this specification, processing steps describing chronological processing include not only processing that is performed chronologically in the order described, but also processing that is not necessarily performed chronologically but is performed in parallel or individually (for example, processing by objects).

REFERENCE SIGNS LIST 101...internal combustion engine, 109...ECU, 127...fuel injection control device, 200...fuel injection device, 201...valve body, 202...valve seat, 206...movable iron core (movable element), 207...stationary iron core (stator), 208...coil, 209...housing, 210...first spring member, 212...fuel supply unit, 214...sleeve, 215...fuel injection hole, 216...second spring member, 217...stopper, 218...lower end of sleeve, 219...transmission surface, 250...gap, 260...ROM, 261...RAM, 330...inflection point (first inflection point), 331...inflection point (second inflection point), 501...CPU (control unit), 501a...energization control unit, 501b...voltage detection unit, 501c...digital filter unit (filter unit),
501d...valve closing detection unit, 501e...variation calculation unit, 540...solenoid (corresponding to coil 208), Ti1...pre-injection drive command pulse (first drive command pulse), Tc1...time when the valve disc collides with the valve seat (time when valve closing is completed), Td1...time when the movable iron core collides with the stopper, Ti2...subsequent injection drive command pulse (second drive command pulse), Tdw...interval, Tbp...intermediate pulse, Tbp_s...start time of the intermediate pulse, Tbp_e...end time of the intermediate pulse

Claims (5)

a valve body that moves toward and away from a valve seat to open and close a fuel passage;
a movable element that opens and closes the valve body;
a stator having a coil that is excited when energized and that exerts a magnetic attraction force on the mover;
a stopper portion that suppresses movement of the movable element toward the valve seat;
A fuel injection control device applied to a fuel injection device comprising:
a control unit that controls energization of the coil by a drive command pulse,
the control unit, when outputting a plurality of drive command pulses per combustion stroke cycle, performs control to apply an intermediate pulse between a first drive command pulse and a subsequent second drive command pulse;
an end time of the intermediate pulse is determined by a time at which the movable element collides with the stopper portion in the first drive command pulse;
a start time of the intermediate pulse is determined based on a fluctuation in a time when the valve disc driven by the second drive command pulse seats on the valve seat, or a fluctuation in a time when the movable element driven by the second drive command pulse collides with the stopper portion. The control unit
an energization control unit that controls an energization time of the coil by a pulse width of a drive command pulse;
a voltage detection unit that detects a voltage value when the coil is energized;
a filter unit that detects an inflection point of the waveform of the voltage value;
a valve closing detection unit that detects a valve closing timing of the valve body based on an inflection point of the waveform of the voltage value during a time period from a predetermined detection start timing to a predetermined detection end timing;
a fluctuation calculation unit that compares a voltage value at a first inflection point corresponding to the time when the valve element sits on the valve seat and/or a voltage value at a second inflection point corresponding to the time when the movable element collides with the stopper portion with a preset threshold value, and calculates a fluctuation in the voltage value at the first inflection point or the second inflection point,
an end time of the intermediate pulse is determined based on a timing of the second inflection point after the first drive command pulse;
2. The fuel injection control device according to claim 1, wherein the start time of the intermediate pulse is determined from a fluctuation in the voltage value of the first inflection point or the second inflection point after the second drive command pulse, which is calculated by the fluctuation calculation unit. 3. The fuel injection control device according to claim 2, wherein the fluctuation calculation unit calculates the fluctuation of the voltage value when the coil is energized using a standard deviation of a difference between the voltage value at the first inflection point or the second inflection point of the waveform of the voltage value and the threshold value. The fuel injection control device according to claim 3 , wherein the variation calculation unit selects, from among preset candidates for the start time of the intermediate pulse, a time at which the standard deviation of the calculated difference is smallest as the start time of the intermediate pulse. a valve body that moves toward and away from a valve seat to open and close a fuel passage;
a movable element that opens and closes the valve body;
a stator having a coil that is excited when energized and that exerts a magnetic attraction force on the mover;
a stopper portion that suppresses movement of the movable element toward the valve seat;
A fuel injection control method applied to a fuel injection device comprising:
a control process for controlling energization of the coil by a drive command pulse;
the control process performs control to apply an intermediate pulse between a first drive command pulse and a subsequent second drive command pulse when a drive command pulse is output multiple times per combustion stroke cycle;
an end time of the intermediate pulse is determined by a time at which the movable element collides with the stopper portion in the first drive command pulse;
a start time of the intermediate pulse is determined based on a fluctuation in a time when the valve disc driven by the second drive command pulse seats on the valve seat, or a fluctuation in a time when the movable element driven by the second drive command pulse collides with the stopper portion.