JP2001214787A - Fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constantly perform fuel injection in a fuel injection device. SOLUTION: An ECU 81 for switching the seating and separation of a ball 63 by the charge and discharge control of a piezo actuator 13 for pressing and driving the ball 63 to switchingly control the back pressure of a needle 61 is constituted so that the increase in the load applied to the piezo actuator 13 in its abutting on the ball 63 is detected by a voltage change detecting means 81a from the change of terminal voltage of a piezo stack 66, the time delay of operation of the ball 63 is calculated from the time of the detection of the load increase, and the operating period of the piezo actuator 13 is corrected according to the time delay. According to this, even if the gap between the piezo actuator 13 and the ball 63 is dispersed because of the individual difference of the device or the like, the fuel injection can be constantly performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to fuel injection control for a fuel injection device.

[0002]

2. Description of the Related Art In a fuel injection system for an internal combustion engine, an injector for injecting fuel is provided with an ECU as control means thereof.
Performs predetermined fuel injection under control based on various operating conditions. The injector has a nozzle portion for injecting the supplied high-pressure fuel from the injection hole, and the opening and closing of the injection hole is performed by a needle inserted in the nozzle portion.

In recent years, a piezo actuator using a piezoelectric effect such as a piezoelectric ceramic has been used for controlling a needle. As a device using a piezo actuator, a back pressure chamber is provided facing the rear end surface of the needle to generate a back pressure of the needle, and a switching valve for switching the pressure of the back pressure chamber is generally provided. The piezo actuator has a configuration in which the piezo stack expands and contracts due to charging and discharging from the ECU, and drives the valve body to press.

[0004]

By the way, if the operation responsiveness of each part of the device varies due to individual differences of the device, environmental temperature changes, etc., it affects the fuel injection timing and the fuel injection time. In particular, the operation response of the switching valve that defines the operation timing of the needle is important for achieving highly accurate fuel injection.

[0005] The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a fuel injection device capable of realizing highly accurate fuel injection control with a small variation in operation response of a switching valve.

[0006]

According to the first aspect of the present invention, there is provided a nozzle portion having a needle for opening and closing an injection hole and injecting high-pressure fuel from the injection hole, and a fuel is introduced to generate a back pressure of the needle. An injector including a back pressure chamber to be urged, a switching valve for switching the pressure of the back pressure chamber between high and low, and a piezo actuator having a piezo stack and pressing and driving a valve element disposed in the valve chamber of the switching valve; Control means for controlling charging / discharging of the piezo actuator to switch the pressure level of the back pressure chamber to open / close the needle, wherein the control means includes a terminal voltage of the piezo stack. Voltage change detecting means for monitoring and detecting a change in the terminal voltage caused by a change in load applied to a piezo actuator when the valve body is pressed and driven;
And correcting means for calculating a time delay of the operation of the valve element based on the detected voltage change and correcting the operation timing of the piezo stack based on the time delay.

At the time of driving the valve body, the load applied to the piezo actuator changes at the timing when the piezo actuator comes into contact with the valve body. Since an electromotive force is generated in the piezo actuator according to this load,
The actual operation timing of the valve element is known from the change in the terminal voltage of the piezo stack. Thus, even if the time delay of the operation of the valve element varies due to a variation in the gap between the piezo actuator and the valve element, constant fuel injection can be realized by correcting the operation timing of the valve element.

In addition, since the time delay of the operation of the valve body is known without directly detecting the operation of the valve body and the gap between the piezo actuator and the valve body, the structure is simple and the design of the injector is not changed. It is feasible.

According to a second aspect of the present invention, in the configuration of the first aspect of the present invention, the correction means detects a change in the gradient of the piezo stack terminal voltage when the piezo actuator contacts the valve body. And

In the piezo actuator, the piezo stack terminal voltage increases at a predetermined gradient until a predetermined amount of charge is stored by charging. This gradient is changed by receiving a reaction force from the valve body when the tip of the piezo actuator comes into contact with the valve body and increasing the load on the piezo actuator. Thus, by detecting the change in the gradient of the piezo stack terminal voltage, it is possible to know the point in time at which the piezo actuator starts to drive the valve body.

According to a third aspect of the present invention, in the configuration of the first aspect of the present invention, the correcting means detects a vibration of a voltage between both ends of the piezo stack when the valve body is seated on a valve seat. .

When the piezo actuator receives a large reaction force from the valve body when the valve body is seated on the valve seat, the displacement is suddenly stopped. Due to the large impact at the time of stop, a vibration component is generated in the piezo stack terminal voltage. By detecting this vibration component, it is possible to know the time when the valve element is seated.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A common rail type fuel injection device for a diesel engine to which the present invention is applied will be described with reference to FIGS. In FIG. 2 showing the entire configuration of the common rail type fuel injection device, a common common rail 74 is provided which communicates with the injector 1 of each cylinder of the diesel engine via a supply line 75. The common rail 74 is pressure-fed from a high pressure supply pump 73. The high pressure fuel accumulates. In the illustrated example, the injector 1 is 1
Although only one is shown, the same configuration is provided for each cylinder. The injector 1 is such that the ECU 81
Of the piezo stack 66 described later, and injects fuel from the injector 1 into the combustion chamber of each cylinder from the injector 1 at a necessary time at an injection pressure substantially equal to the fuel pressure of the common rail 74 (hereinafter referred to as the common rail pressure). It has become.

The common rail pressure is detected by a pressure sensor 82, and based on the detection result, the ECU 81 controls the suction metering valve 72 to adjust the amount of fuel supplied to the common rail 74, and the common rail pressure is input to another sensor. Is controlled so as to have an appropriate injection pressure according to the operating condition known by the following.

The fuel supplied from the common rail 74 to the injector 1 is used not only for injection into the combustion chamber, but also for control hydraulic pressure of the injector 1. The fuel is supplied from the injector 1 to the fuel tank via a low-pressure drain line 76. Reflux to 71.

FIG. 1 shows a sectional structure of the injector 1. The injector 1 is mounted so as to penetrate an unillustrated combustion chamber wall of the engine so that a lower end portion in the drawing projects into the combustion chamber, and a nozzle portion 11, a back pressure control valve 12, which is a switching valve, and a piezo actuator 13 are arranged in order from the lower end portion. Be composed. The injector 1 has a rod-shaped body 2,
Holes for accommodating the components constituting the components 1 to 13 and passages through which fuel flows are formed.

The nozzle portion 11 has a sack portion 42 formed at a lower end portion of the rod 2 and an injection hole 43 for fuel injection is formed through a wall where the sack portion 42 is formed. The sack portion 42 is connected to the high-pressure passage 31 communicating with the supply line 75. A vertical hole 21 is formed in the rod-shaped body 2.
A stepped nozzle needle 61 is slidably held by an upper large-diameter portion 612 of the upper portion of the nozzle needle 61. An annular oil reservoir 41 is formed on the outer periphery of the lower small-diameter portion 611 of the nozzle needle 61, The oil reservoir 41 always communicates with the high-pressure passage 31 and is supplied with high-pressure fuel from a common rail 74.

When the nozzle needle 61 is lowered, the lower end of the conical shape closes the upper end of the sack portion 42 to inhibit fuel injection from the injection hole 43. When the fuel is injected, the nozzle needle 61 rises to the upper end of the sack portion 42. Open the department.

The high-pressure fuel in the oil reservoir 41 acts upward on the stepped surface 61a of the nozzle needle 61 and the conical surface 61b at the lower end thereof to urge the nozzle needle 61 in the valve opening direction.

In a space 53 defined by the wall surface of the vertical hole 21 above the nozzle needle 61, fuel pressure as control oil pressure is introduced from the high-pressure passage 31 through the in-orifice 51, and the back pressure of the nozzle needle 61 is increased. Are generated as the back pressure chamber 53 that generates the pressure. This back pressure acts downward on the nozzle needle 61, and the spring 6 housed in the back pressure chamber 53.
2 and the nozzle needle 61 is urged in the valve closing direction.

The back pressure chamber 53 is always in communication with a valve chamber 55 via an out orifice 54. The valve room 55 has a ceiling surface 5
52 is formed in a conical shape, and is connected to the low-pressure passage 32 communicating with the drain line 76 through the small hole 22 opened at the top of the ceiling surface 552. An annular space 56 is formed in the vertical hole 22 around an outer periphery of a piston 64 described later, and communicates with the low-pressure passage 32.

A high-pressure control passage 5 communicating with the high-pressure passage 31 is provided at a position corresponding to the vertical hole 22 on the bottom surface 551 of the valve chamber 55.
2 is open.

In the valve chamber 55, a ball 63 whose lower part is cut horizontally is provided. The ball 63 is a valve body that can move up and down. When the ball 63 descends, it sits on a valve chamber bottom surface (hereinafter, referred to as a high pressure side seat) 551 as a valve seat with the cut surface to shut off the valve chamber 55 from the high pressure control passage 52. When ascending, the valve chamber 55 is seated on the ceiling surface (hereinafter, referred to as a low-pressure side seat) 552 as a valve seat to shut off the valve chamber 55 from the annular space 56. Thereby, when the ball 63 descends, the back pressure chamber 53
Communicates with the low pressure passage 32 through the out orifice 54, the valve chamber 55, and the annular space 56, so that the back pressure of the nozzle needle 61 is reduced and the nozzle needle 61 is lifted. On the other hand, when ascending, the back pressure chamber 53 is out of the orifice 54 and the valve chamber 5
5. communicating with the high-pressure passage 31 via the high-pressure control passage 52;
The back pressure of the nozzle needle 61 rises and the nozzle needle 6
One sits.

The ball 63 is pressed and driven by the piezo actuator 13. The piezo actuator 13 includes a piston 64, a disc spring 65, and a piezo stack 66 disposed coaxially with the vertical hole 23.

The piston 64 has an equal-diameter portion 643 slidably held at the lower small-diameter portion of the vertical hole 23. Below the equal-diameter portion 643 is a conical portion 642 whose diameter decreases toward the lower side. The tip of the lower piezo actuator 13 penetrates the small hole 22 and faces the ball 63.
Pressure pin 641 for pressing the pressure. Conical part 6
The annular space 56 is formed around the outer circumference of the pressure pin 42 and the pressure pin 641.

Above the piston constant diameter portion 643 is a flange portion 644
The disc spring 65 presses the lower end surface of the flange portion 644 upward. On the other hand, a piezo stack 66 is in contact with the upper end surface of the flange portion 644.

When the piezo stack 66 is contracted in the discharge state, a contact or a slight gap is formed between the pressure pin 641 and the ball 63 in a non-pressed state. The high pressure fuel in the valve chamber 55 is urged upward only by the pressure receiving surface of the ball 63 corresponding to the area of the ball 63, so that the ball 63 is seated on the low pressure side seat 552. On the other hand, when the piezo stack 66 is charged and extended, the piston 64 is depressed and the ball 63 is seated on the high pressure side seat 551.

In the fuel injection, first, the piezo stack 66 is extended by charging the piezo stack 66, the pressure pin 641 is lowered, and the ball 63 is pushed down. As a result, the ball 63 is separated from the low-pressure side seat 552 and seated on the high-pressure side seat 551 to switch the fuel pressure of the valve chamber 55 from “high” to “low” to lift the needle 61 and start fuel injection. . On the contrary, the injection of the ball 6 is stopped by reducing the piezo stack 66 by discharging the piezo stack 66 and releasing the pushing force to the ball 63.
3 is separated from the high-pressure side seat 551 and is seated again on the low-pressure side seat 552 to switch the fuel pressure of the valve chamber 55 from “low” to “high” to seat the needle 61. By setting the charge holding period of the piezo stack 66 in this way, fuel is injected from the injector 1 for a certain period corresponding to the charge holding period.

The charge and discharge of the piezo stack 66 is performed by the ECU 81
This is performed by the drive circuit 812 constituting. Drive circuit 8
Reference numeral 12 denotes a well-known configuration for driving a piezo stack mounted on the injector, such as a DC-DC circuit, an inductor for limiting a charge / discharge current to the piezo stack 66, a switch circuit for controlling movement of electric charges in the piezo stack 66, and the like. The setting of the charge holding period and the charge amount of the piezo stack 66 is performed by the ECU 8 together with the drive circuit 812.
1 can be controlled by controlling the switch circuit by a control signal from the control circuit 811 constituting the first circuit.

The ECU 81 includes a piezo stack 6.
6, a voltage monitor circuit 813 is provided as an input, and is a monitor signal of a piezo stack terminal voltage.
The output signal is input together with the voltage monitor circuit 813 to the waveform processing circuit 814 constituting the voltage change detection means 81a. The waveform processing circuit 814 has a differentiating circuit, and outputs a signal proportional to the gradient of the voltage across the piezo stack to the control circuit 811.
Output. The waveform processing circuit 81
4 may use digital means such as a DSP in addition to a general analog circuit.

FIG. 3 shows the behavior of the piezo stack terminal voltage and the displacement of the piezo stack 66 when the piezo stack 66 is charged. Pressure pin 641 and ball 6
The piezoelectric stack terminal voltage rises with a steep gradient until 3 contacts. Since the ball 63 is pressed against the low pressure side seat 552 by the fuel pressure in the valve chamber 55, when the pressure pin 641 abuts on the ball 63, the load applied to the piezo stack 66 increases greatly, and the reverse direction due to the load increase The slope of the piezo stack terminal voltage is reduced by the amount of the electromotive force. At this time, the output signal of the waveform processing circuit 814 decreases, and the control circuit 811 knows the time when the pressure pin 641 contacts the ball 63 from the decrease of the output signal.

The control circuit 811 comprises a microcomputer or the like. FIG. 4 shows a control flow of the fuel injection in the control circuit 811. The operation of the present fuel injection device together with the setting of the control circuit 811 will be described.

In step S01, fetching of the piezo stack terminal voltage is started.

In step S02, the injection timing Ti and the injection period Tp, which are the command values of the fuel injection, are changed to the operating conditions such as the accelerator opening, the engine speed, the common rail pressure detected by the pressure sensor 82, and the like, as in the normal injection control. Set based on

The following step S03 is a procedure as a correction means, in which the injection timing Ti and the injection period Tp are set to a correction value Δ to be described later.
The injection timing Ti is advanced and the injection period Tp is lengthened by the correction value ΔT. The correction value ΔT is set to 0 in the initialization performed when the control circuit 811 is started.

In step S04, fuel injection is performed.
A control signal defining the charge holding period of the piezo stack 66 is output to the drive circuit 812 in accordance with the corrected injection timing Ti and the injection period Tp, and the piezo stack 66 is charged at a predetermined timing and a predetermined time elapses. Later, a predetermined amount of fuel is injected.

In step S05, when the piezo stack 66 is charged as described above and the pressure pin 641 descends, the timing Tc at which the pressure pin 641 contacts the ball 63 is detected from the output signal of the waveform processing circuit 814 as described above. I do.

In step S06, it is determined whether or not the contact time Tc matches the set value Tt. The set value Tt serves as a reference for the contact time Tc and is stored in advance. The injection timing Ti and the injection period Tp calculated in step S02 are calculated so that the desired injection timing and injection time are realized when the contact timing Tc matches the set value Tt.

In step S06, the contact time Tc is set to the set value T.
If they match, the process proceeds to step S07, where the correction value ΔT
Is set to 0, and this flow ends.

In step S06, the contact time Tc is set to the set value T.
If it does not coincide with t, the process proceeds to step S08, in which the time difference (Tc-Tt) between the contact time Tc, which is the time delay of the operation of the ball 63, and the set value Tt is calculated, and the correction value ΔT is updated and updated. End the flow.

FIG. 5 is a timing chart showing the operation of each part of the apparatus before and after the fuel injection. The control signal of the piezo stack 66, the displacement of the pressure pin 641, and the valve chamber 5
5 shows the pressure and the injection rate. The period during which the control signal of the piezo stack 66 is “H” is the charge holding period of the piezo stack 66. Further, the displacement of the pressure pin 641, the pressure of the valve chamber 55, and the injection rate indicate the pressure pin 64.
Two cases are shown, one with a gap and the other with no gap in the piezo stack 66 contracted state between 1 and the ball 63. The operation when there is a gap between the pressure pin 641 and the ball 63 will be described in comparison with the case where there is no gap. If there is a gap between the pressure pin 641 and the ball 63, the timing when the pressure pin 641 contacts the ball 63 seated on the low-pressure seat 552 and the ball 63 starts to descend is delayed. That is, the timing at which the ball 63 separates from the low-pressure seat 552 and seats on the high-pressure seat 551 is delayed.

As a result, the pressure in the valve chamber 55 that defines the back pressure of the needle 61 decreases with a delay, so that the needle 61 does not reach the liftable pressure (injectable pressure) and the start of fuel injection is delayed. With piezo stack 66
At the end of the charge holding period, that is, at the time of discharge, the pressure of the valve chamber 55 becomes high, and the pressure of the valve chamber 55 is restored by the discharge of the piezo stack 66, and the pressure at which the needle 61 can be seated (the injection end pressure) is quickly reached. The fuel injection end timing is advanced. That is, as the gap between the pressure pin 641 and the ball 63 is larger and the time delay of the lowering operation of the ball 63 is larger, the fuel injection timing is delayed and the injection time is shorter. The inventors have confirmed that when the gap is changed to a maximum of 10 μm, a delay of the injection timing occurs at a maximum of 100 μs, and the injection amount varies at a maximum of 50% in the range of 2 to 60 mm ³ / st.

In the present fuel injection device, there are individual differences between the devices, and deformation of members constituting the injector 1 due to a change in environmental temperature, particularly expansion and contraction of the piston 64 and the piezo stack 66 in the length direction. Therefore, even if the gap between the pressure pin 641 and the ball 63 fluctuates and the operation response of the ball 63 is not constant, the injection timing Ti,
The injection period Tp is corrected as described above, and the effect of the time delay of the operation of the ball 63 on the actual fuel injection timing and the injection period is cancelled, so that highly accurate fuel injection can be realized.

In addition, in the embodiment, the configuration is simple because it is only necessary to add a circuit for detecting the gradient of the piezo stack terminal voltage. In addition, the cost is low because the design of the injector is not changed.

Note that the time delay of the operation of the ball 63 may be detected based on the timing of the contact of the ball 63 with the high-pressure side seat 551 instead of detecting the contact point of the pressure pin 641 with the ball 63. . FIG. 3 above
As shown in FIG. 7, when the ball 63 comes into contact with the high-pressure side seat 551, a vibration occurs in the piezo stack terminal voltage due to the impact load, and this vibration is detected. The waveform processing circuit may detect the generation point of the vibration by passing the output signal of the voltage monitor circuit through only the AC component, that is, the vibration component by the differentiating circuit. For example, the vibration component can be detected by a diode or the like to obtain an envelope output of the vibration, and this can be compared with a predetermined threshold value to detect the occurrence of the vibration.

In this case, the control circuit may be set so as to execute the same control procedure as that shown in FIG. 4. During the control procedure, the contact time Tc is set to the high-pressure seating time Ts of the ball, and the set value Tt is set. The timing may be set to the reference timing of the high-pressure seating time Ts of the ball.

(Second Embodiment) FIG. 6 shows another common rail type fuel injection device to which the present invention is applied. The configuration of a part of the injector is replaced with another one. In the figure, the parts denoted by the same reference numerals as those in the first embodiment perform substantially the same operation, and therefore, the description will be focused on the differences.

Piezo actuator 1 of injector 1A
3A, a small-diameter piston 67, a disc spring 65, a large-diameter piston 68, and a piezo-tack 66 are disposed in the vertical hole 23A above the small hole 22 from below. The small piston 67 is the first
The piston has substantially the same configuration as the lower half of the piston of the embodiment, and is slidably held in the vertical hole 23A by the equal diameter portion 673, and the lower portion is a conical portion 672 whose diameter decreases toward the lower end. The lower end of the piezo actuator 13A has a pressure pin 671 for pressing the ball 63.
It has become. In the small hole 22 and the vertical hole 23A, an annular space 5 is provided around the outer periphery of the conical portion 672 and the pressure pin 671.
6 are formed.

A spring 69 is provided in the annular space 56 to urge the small-diameter piston 67 upward. The upper displacement end of the small-diameter piston 67 is positioned by a step 231 formed on the peripheral wall surface of the vertical hole 23A, and the position of the small-diameter piston 67 at this time is an initial position to be restored when the piezo stack 66 is discharged. At this time, the pressure pin 671 and the ball 63 are in contact with each other or have a minute gap.

The large-diameter piston 68 is a circular member having a larger diameter than the small-diameter piston 67 and is slidably held in the vertical hole 23A.
The spring can be biased upward from the disc spring 65 and downward from the piezo stack 66.

The space between the small-diameter piston 67 and the large-diameter piston 68 is filled with fuel to form a hydraulic expansion chamber 57 serving as a pump chamber. When the large-diameter piston 68 is pressed by the extension of the piezo stack 66, the pressing force increases the hydraulic pressure. The fuel is transmitted to the small-diameter piston 67 via the fuel in the chamber 57. Here, since the small-diameter piston 67 has a smaller diameter than the large-diameter piston 68, the extension amount of the piezo stack 66 is increased. The hydraulic pressure expansion chamber 57 communicates with the low pressure passage 32 via a check valve 321 so that the fuel is always filled. The check valve 321 is connected from the low pressure passage 32 to the hydraulic expansion chamber 5.
7 is provided as a forward direction. When the large-diameter piston 68 is pressed by the extension of the piezo stack 66, the large-diameter piston 68 is closed and the fuel is confined in the hydraulic expansion chamber 57.

In the case of such an injector, since the position of the pressure pin 671 itself when the piezo stack 66 is reduced is defined by the step 231, the piezo stack 6
6, the gap between the pressure pin 641 and the ball 63 hardly fluctuates.
The gap between 1 and ball 63 can vary. Therefore, the present invention can be suitably applied to a fuel injection device having such an injector.

In each of the above embodiments, the fuel injection timing Ti, the fuel injection period T
Any of the corrections of p can be omitted to simplify the control.

In each of the above embodiments, the ball is pushed down by charging the piezo stack and the back pressure chamber is switched to low pressure to lift the needle. However, the needle is seated by the ball pressing drive by charging the piezo stack. The configuration may be as follows. In this case, the piezo actuator presses and drives the ball at the end of fuel injection. Therefore, as the gap between the pressure pin and the ball is larger, the injection end time is delayed and the injection time is longer. Therefore, the correction may be made so as to shorten the command injection period according to the time delay of the ball operation at the end of the injection.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram of a common rail type fuel injection device to which the present invention is applied.

FIG. 2 is an overall configuration diagram of the common rail type fuel injection device.

FIG. 3 shows E constituting the common rail fuel injection device.
It is a graph which shows the control content in CU.

FIG. 4 shows E constituting the common rail fuel injection device.
It is a flowchart which shows the control content in CU.

FIG. 5 is a time chart showing the operation of each part of an injector constituting the common rail fuel injection device.

FIG. 6 is a main part configuration diagram of another common rail type fuel injection device to which the present invention is applied.

[Explanation of symbols]

 1, 1A Injector 11 Nozzle part 12 Back pressure control valve (switching valve) 13, 13A Piezo actuator 43 Injection hole 53 Back pressure chamber 55 Valve chamber 551 High pressure side seat (valve seat) 552 Low pressure side seat 61 Needle 63 Ball (valve body) 641, 671 Pressure pin (tip) 66 Piezo stack 74 Common rail 81 ECU (control means) 811 Control circuit (correction means) 81a Voltage change detection circuit 813 Voltage monitor circuit 814 Waveform processing circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G066 AA07 AC09 CC05U CC15 CC26 CC67 CC68U CD26 CE27 CE29 DA01 DA04 DC04 DC09 DC18 3G301 HA02 LC05 LC10 MA11 MA18 NA08 NE11 NE22 PB08Z PE01Z PF03Z

Claims (3)

[Claims] 1. A nozzle portion having a needle for opening and closing an injection hole and injecting high-pressure fuel from the injection hole, a back pressure chamber for introducing fuel to generate a back pressure of the needle, and a pressure in the back pressure chamber. A switching valve for switching the pressure between high and low, an injector having a piezo stack, and a piezo actuator for pressing and driving a valve element disposed in the valve chamber of the switching valve; and Control means for switching the pressure level of the pressure chamber to control the opening and closing of the needle, wherein the control means monitors a terminal voltage of the piezo stack and applies a pressure to a piezo actuator when the valve body is pressed. A voltage change detecting means for detecting a change in the terminal voltage caused by the load change; and a timer for operating the valve element based on the detected voltage change. And a correction means for calculating a time delay and correcting the operation timing of the piezo stack based on the time delay. 2. The fuel injection device according to claim 1, wherein
A fuel injection device, wherein the correction means detects a change in a gradient of a voltage between both ends of the piezo stack when the piezo actuator contacts the valve body. 3. The fuel injection device according to claim 1, wherein
A fuel injection device, wherein the correction means detects a vibration of a terminal voltage of the piezo stack when the valve body is seated on a valve seat.