JP2009197600A - Fuel injection valve control device and fuel injection valve control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection valve control device capable of both reducing a variation of injection switch timing and suppressing an electric power loss and noise generation in regard to the fuel injection valve having a piezoelectric element as an actuator. <P>SOLUTION: A charging circuit is applied to a piezoelectric injector constituted so that a back pressure control valve starts a valve opening operation by the extension of the piezoelectric element when a piezoelectric voltage which rises in accordance with an electric charge for the piezoelectric element exceeds a threshold Vth. At charging the piezoelectric element, the charging circuit gradually raises the piezoelectric voltage by repeatedly increasing and lowering a drive current flowing to the piezoelectric element a plurality of times. The operation of the charging circuit is controlled so that a rising speed (voltage gradient a3) of the piezoelectric voltage accompanied by the current rise of a specific time after the second time of the plurality of times of driving current rise is higher than a rising speed (voltage gradient a2) of the piezoelectric voltage accompanied by a current rise one time prior to a specific time. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel injection valve control device and a fuel injection valve control system applied to a fuel injection valve having a piezoelectric element as an actuator.

  This type of fuel injection valve includes a valve body that opens and closes a fuel injection port, a back pressure control valve that controls the back pressure of the valve body, and a piezoelectric element that operates the back pressure control valve. When the piezo element is extended by charging, the back pressure control valve starts to open by the piezo element, the back pressure of the valve body decreases, the valve body opens, and fuel is injected from the injection port. It will be.

When charging such a piezo element, a control for increasing the voltage value of the piezo element (hereinafter referred to as a piezo voltage) stepwise by repeatedly raising and lowering the drive current flowing to the piezo element a plurality of times. It is disclosed in Patent Document 1 and the like. According to this control, after charging of the piezo element is started, the back pressure control valve starts opening when the piezo voltage exceeds the threshold value Vth.
JP 2003-319667 A

  Here, the value of the piezo voltage required for the back pressure control valve to start the valve opening operation, that is, the above-described threshold value Vth differs depending on the piezo element temperature at that time. Further, it varies depending on the secular change such as wear of the valve body and the valve seat portion of the back pressure control valve, and the pressure of the supplied fuel. Due to the variation in the threshold value Vth as described above, the timing at which the back pressure control valve starts the valve opening operation may vary. Then, the valve opening operation timing (injection start timing) of the valve body varies.

  With respect to this problem, in the control described in Patent Document 1, the charge amount related to the first rise among the multiple drive current rises is made larger than the charge amount after the second time. In other words, the piezo voltage rise speed (voltage gradient) associated with the first current rise is controlled to be faster (steep) than the piezo voltage rise speed associated with the second and subsequent current rises. According to this, the variation widths Tσ1 and Tσ2 of the valve opening operation start timing with respect to the variation amount Vσ (see FIG. 8) of the threshold value Vth can be reduced as indicated by the symbol Tσ1.

However, if the charge amount is increased in the first number of times of a plurality of current increases, the drive current flowing to the piezo element increases. In particular, when the charge amount is increased in the first charge, the drive current flowing to the piezoelectric element becomes extremely high. This is because the supply energy E to the piezo element, the drive current I, and the piezo voltage V are in the relationship of the following formula 1, so that the drive current I is high in the first charge (especially the first) when the piezo voltage is low. Because it becomes.
E = ∫ (I × V) dt (Formula 1).

When the drive current I increases in this way, the power loss (loss W = I ² R) in the resistor R1 portion in the circuit and the like is significantly increased, and the drive components such as the back pressure control valve are suddenly operated. This causes noise generation due to collision with the valve seat.

  Such power loss and noise generation problems and variations in injection start timing are not limited to the fuel injection valve having the back pressure control valve, but are directly operated by opening and closing the injection port by directly operating the valve element with a piezo element. The same applies to the fuel injection valve of the type. Further, in the fuel injection valve having a structure in which the injection is stopped by the extension of the piezo element, the injection stop timing varies.

  The present invention has been made to solve the above-described problems, and an object of the present invention relates to a fuel injection valve having a piezo element as an actuator, to reduce the variation width of injection switching timing, and to reduce power loss and noise generation. An object of the present invention is to provide a fuel injection valve control device and a fuel injection valve control system that are compatible with suppression.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described. As described above, when the rate of increase of the piezo voltage is increased in the first charge, the piezo voltage is low, so that the drive current flowing to the piezo element becomes extremely high. On the other hand, in the second and subsequent charging, since the piezo voltage is in a state that has risen to some extent, the driving current does not become extremely high. The present invention described below has been made paying attention to this point.

That is, in the invention according to claim 1,
An opening / closing mechanism that opens and closes a fuel injection port; and a piezoelectric element that operates the opening / closing mechanism. When a voltage value (piezo voltage) of the piezoelectric element that rises due to charging of the piezoelectric element exceeds a threshold value, the piezoelectric element Applied to a fuel injection valve configured to start operation of the opening and closing mechanism by extension of the element;
When charging the piezo element, a charging circuit that increases the voltage value stepwise by repeatedly raising and lowering the drive current flowing to the piezo element multiple times,
Among the plurality of current increases of the drive current, the voltage value increase rate associated with the second specific number of current increases after the second time is represented by the voltage value increase rate associated with the current increase of the previous specific number of times. The operation of the charging circuit is controlled so as to be faster.

  According to this, the increase speed of the piezo voltage due to the current increase of the specific number of times is made faster than the increase speed of the piezo voltage due to the current increase of the previous time of the specific number of times. When the piezo voltage is set to exceed the threshold value Vth, the variation widths Tσ1 and Tσ2 of the operation start timing of the opening / closing mechanism with respect to the variation amount Vσ of the threshold value Vth (see FIG. 8) can be reduced as indicated by the symbol Tσ1. Therefore, for example, when the opening / closing mechanism performs the injection operation with the extension of the piezo element, the variation in the injection start timing can be reduced. In addition, for example, when the opening / closing mechanism stops injection as the piezo element extends, variation in injection stop timing can be reduced.

  Furthermore, according to the present invention, since the specific number of times is set to the second and subsequent times, the peak value of the drive current can be suppressed lower than when the increase rate of the piezo voltage is increased at the first current increase. Therefore, it is possible to solve the problem of power loss and noise generated due to the high peak value of the drive current.

  According to a second aspect of the present invention, the charging energy per unit time input to the piezo element when the current rises for the specific number of times is larger than that for the current rise one time before the specific number of times. The rate of increase of the voltage value is controlled by controlling a charging circuit. According to a third aspect of the present invention, the rate of increase in the charge charged in the piezo element when the current rises for the specific number of times is faster than when the current rises one time before the specific number of times. The rate of increase of the voltage value is controlled by controlling a charging circuit. According to the control of the second and third aspects, it is possible to easily realize the control of the rising speed of the voltage value as described in the first aspect.

  More specifically, for example, as shown in FIG. 5B, the drive current is decreased on condition that the charge Q charged in the piezo element exceeds the threshold value Qth as the drive current to the piezo element increases. In the case of switching control, it is possible to increase the charge rising speed by setting the threshold value Qth large at the specific number of times, and to increase the voltage value increasing speed at the specific number of times.

  By the way, various control methods can be cited for repeatedly raising and lowering the drive current flowing to the piezoelectric element a plurality of times. For example, control for switching to decrease on condition that the value of the rising drive current exceeds the upper limit value, control for switching to increase on condition that the value of the decreasing drive current exceeds the lower limit value, value of the decreasing drive current The control which switches to a raise on condition that became zero is mentioned. However, in these controls, since the start timing of the current rise at the specific number of times is a phenomenon, the certainty that the piezo voltage exceeds the threshold value at the time of the current rise at the specific number of times is low. If the threshold value is not exceeded at the specific number of times, the above effect of reducing the variation width of the operation start timing by increasing the speed of increase of the voltage value at the specific number of times is not exhibited.

  In view of this point, the invention according to claim 4 is characterized in that the operation of the charging circuit is controlled so that the current rise start time at the specific number of times is a preset time. Therefore, it is possible to increase the certainty that the piezo voltage exceeds the threshold when the current rises for a specific number of times, and in turn, it is possible to increase the certainty that the opening / closing mechanism is activated at the specific number of times.

According to a fifth aspect of the present invention, at least one of the pressure of the high-pressure fuel supplied to the injection port, the load received by the piezo element from the high-pressure fuel, the temperature of the piezo element, and the individual information of the fuel injection valve Is used as a parameter to control the rate of increase of the voltage value. The piezo voltage (that is, the threshold value) required for the opening / closing mechanism to start the fuel injection operation or the stop operation becomes a different value depending on the above parameters (pressure, load and temperature, and individual differences of the fuel injection valve). For example, in the case where the opening / closing mechanism is constituted by a valve body and a back pressure control valve as described in claim 8, how the threshold values are different will be exemplified below.
-The higher the high-pressure fuel pressure, the greater the load that the piezo element receives from the high-pressure fuel, and the greater the force required to operate the back pressure control valve, the higher the threshold value.
Since the capacitance of the piezo element changes depending on the temperature of the piezo element, the threshold value changes depending on the temperature even if the charging energy input to the piezo element is the same.
-For example, the pressure receiving area of the portion of the back pressure control valve that receives the high-pressure fuel pressure differs among the individual fuel injection valves. Further, various sliding resistances of the valve body and the like are different among individual fuel injection valves. Due to such individual differences in fuel injection valves, individual differences occur in the threshold value.

  As described above, according to the invention of claim 5 which controls the rate of increase of the voltage value according to these parameters, it is easy to control the charging circuit so that the piezo voltage exceeds the threshold when the current increases for a specific number of times. Can be realized. For example, in the specific example shown in FIG. 5B, the threshold value Qth may be changed according to the above parameters.

  In the invention of claim 6, the individual information is an actual measurement value acquired by a test performed in advance, and an increase rate of the voltage value when the injection start timing becomes a target injection timing or A physical quantity correlated with the ascending speed is included as information. According to this, when controlling the charging circuit so that the piezo voltage exceeds the threshold value when the current rises for a specific number of times, it can be controlled based on the actual measurement value from the test, so that the opening / closing mechanism can be started at the specific number of times. The certainty can be increased, and as a result, the certainty of starting the opening / closing mechanism at a specific number of times can be enhanced.

  The invention according to claim 7 is characterized in that the individual information includes information indicating a capacitance of the piezo element or a characteristic indicating a relationship between the capacitance and the temperature of the piezo element. To do. According to this, since the charging circuit can be controlled based on the temperature characteristics of the piezo element so that the piezo voltage exceeds the threshold when the current rises a specific number of times, the opening / closing mechanism can be started to operate at a specific number of times. The certainty can be increased, and as a result, the certainty of starting the opening / closing mechanism at a specific number of times can be enhanced.

  In addition, it is desirable to store the various individual information described above in storage means such as a QR code (registered trademark), an IC memory, and a correction resistor, and to provide the storage means in the fuel injection valve.

  According to an eighth aspect of the present invention, the opening / closing mechanism includes a valve body that opens and closes the injection port, and a back pressure control valve that operates by the driving force of the piezo element to control the back pressure of the valve body. The back pressure control valve is configured to start an operation of reducing the back pressure to open the valve body when a voltage value of the piezoelectric element exceeds a threshold value. In addition to the eighth aspect of the invention, the invention may be applied to a direct-acting fuel injection valve in which a valve element is directly operated by a piezo element to open and close an injection port. In addition to the fuel injection valve that opens the valve body when the piezo element is extended by charging, the application to a fuel injection valve that closes the valve body when the piezo element is reduced by discharge from the piezoelectric element is given as a specific example. It is done.

  The invention described in claim 9 is a fuel injection valve control system comprising a fuel injection valve and the fuel injection valve control device. According to this fuel injection valve control system, the above-mentioned various effects can be exhibited similarly.

  Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
Hereinafter, a first embodiment in which a fuel injection control device according to the present invention is applied to a fuel injection control device of a common rail type diesel engine mounted on a vehicle will be described with reference to the drawings.

  FIG. 1 shows the overall configuration of the engine system in the present embodiment.

  As shown in the figure, the fuel in the fuel tank 1 is pumped up by the fuel pump 3 through the fuel filter 2. The fuel pump 3 includes a fuel metering valve 4, and the fuel metering valve 4 is operated to determine the amount of fuel discharged to the outside. The fuel from the fuel pump 3 is pressurized and supplied to the common rail 5. The common rail 5 stores the fuel pressurized and supplied from the fuel pump 3 in a high pressure state, and the accumulated high pressure fuel passes through the high pressure fuel passage 6 and piezo injectors PI (fuel) in each cylinder (here, four cylinders are illustrated). To the injection valve). The piezo injector PI is connected to the low pressure fuel passage 7 and can return the fuel to the fuel tank 1 via the low pressure fuel passage 7.

  Next, the structure of the piezo injector PI will be described with reference to FIG.

  A columnar needle storage portion 10a is provided at the tip of the body 10 of the piezo injector PI. The needle storage portion 10a stores a nozzle needle 11 (valve element) that can be displaced in the axial direction. Further, high pressure fuel is supplied to the needle storage portion 10a through the high pressure fuel passage 6. The nozzle needle 11 is seated on the annular needle seat portion 10b formed at the front end portion of the body 10, thereby blocking the needle storage portion 10a from the high-pressure fuel passage 6 while being separated from the needle seat portion 10b. Thus, the needle storage portion 10 a is communicated with the high pressure fuel passage 6.

  The back side of the nozzle needle 11 (the side opposite to the side facing the needle seat portion 10b) faces the back pressure chamber 10c. Fuel from the high-pressure fuel passage 6 is supplied to the back pressure chamber 10c through the orifice 10d. Further, the back pressure chamber 10c is provided with a needle spring 12 that pushes the nozzle needle 11 toward the needle seat portion 10b.

  The back pressure chamber 10 c can communicate with the low pressure fuel passage 7 via a back pressure control valve 13. The back pressure control valve 13 is cut off from the low pressure fuel passage 7 and the back pressure chamber 10c by being seated on the annular upper valve seat portion 10e on the back side, and is displaced toward the front end side of the body 10 so that the low pressure fuel passage 7 And the back pressure chamber 10c are communicated. When the body 10 is further displaced toward the tip of the body and the tip of the body 10 of the back pressure control valve 13 is seated on the annular lower valve seat portion 10g, the valve chamber in which the back pressure control valve 13 is accommodated and the high pressure fuel passage 6 are connected to each other. It is shut off by the pressure control valve 13. However, the valve chamber and the back pressure chamber 10c are always in communication with each other through the orifice 10h.

  The upper valve seat 10 e side of the back pressure control valve 13 is connected to the small diameter piston 15 via the pressure pin 14. The rear side of the small diameter piston 15 faces the tip of the large diameter piston 16 having a larger diameter than the small diameter piston 15. A displacement transmission chamber 10 f is defined by the small diameter piston 15, the large diameter piston 16, and the inner peripheral surface of the body 10. The displacement transmission chamber 10f is filled with an appropriate fluid such as fuel. On the other hand, the rear side of the body 10 of the large-diameter piston 16 is connected to the piezo element PE. Incidentally, the back surface side of the piezoelectric element PE facing the large-diameter piston 16 is fixed to the body 10. The “opening / closing mechanism” described in the claims corresponds to the nozzle needle 11, the needle spring 12, the back pressure control valve 13, the pressure pin 14, the small diameter piston 15, the large diameter piston 16, and the like.

  The piezo element PE includes a laminate (piezo stack) formed by laminating a plurality of piezoelectric elements, and functions as an actuator by expanding and contracting due to a reverse piezoelectric effect. Specifically, the piezo element PE is a capacitive load, and expands when charged and shrinks when discharged. Incidentally, the piezoelectric element PE according to the present embodiment uses a piezoelectric element of a piezoelectric material such as PZT (lead zirconate titanate).

  When no current is supplied to the piezo element PE and the piezo element PE is in a contracted state, force is exerted by the high pressure fuel in the high pressure fuel passage 6, so that the back pressure control valve 13 and the small diameter piston 15 are positioned behind the body 10. Will be. At this time, the back pressure chamber 10 c and the low pressure fuel passage 7 are blocked by the back pressure control valve 13. For this reason, the nozzle needle 11 is pushed toward the distal end side of the body 10 by the pressure of the fuel in the back pressure chamber 10c (the pressure of the fuel in the common rail 5) and the elastic force of the needle spring 12, and is seated on the needle seat portion 10b. (A closed state).

  On the other hand, when a current is supplied to the piezo element PE, the back pressure control valve 13 moves to the front end side of the body 10 when the piezo element PE is in an extended state. As a result, the back pressure chamber 10 c communicates with the low pressure fuel passage 7. As a result, the pressure of the fuel in the back pressure chamber 10c decreases, and the force F1 that pushes the nozzle needle 11 to the rear of the body 10 by the high-pressure fuel in the needle housing portion 10a increases. When the fuel F1 and the needle spring 12 in the back pressure chamber 10c push the nozzle needle 11 forward of the body 10 and the force F1 pushing backward becomes greater than a predetermined value, the nozzle needle 11 is removed from the needle seat portion 10b. The separated state (valve open state) is reached, and the fuel in the high pressure fuel passage 6 is injected from the opened injection port 10i.

  The engine system shown in FIG. 1 operates a diesel engine such as a fuel pressure sensor 5a that detects the fuel pressure (rail pressure PC) in the common rail 5 and a crank angle sensor 20a that detects the rotation angle of the output shaft of the diesel engine. Various sensors for detecting the state and an accelerator sensor 20b for detecting the operation amount of the accelerator pedal are provided.

  The detection results of these various sensors are taken into the control unit 20. The control unit 20 operates various actuators of the diesel engine such as the piezo injector PI and the fuel metering valve 4 based on the detected values. In particular, the control unit 20 performs fuel injection control by operating the piezo injector PI based on the detection values of the various sensors.

  Next, the configuration and operation outline of the control unit 20 will be described with reference to FIG.

  The microcomputer 21 included in the control unit 20 satisfies the demand for the output torque of the diesel engine based on the operation amount of the accelerator pedal detected by the accelerator sensor 20b and the rotation speed of the output shaft determined from the detected value of the crank angle sensor 20a. Calculate the required injection amount. Based on the calculated required injection amount and the detected value of the fuel pressure sensor 5a, a map operation is performed on the injection command value (command injection period) for the piezo injector PI, and a drive signal IJT corresponding to the command value is output to the control IC 22. .

  The control IC 22 controls the drive circuit 23 based on the input drive signal IJT, thereby controlling the power supply state to the piezo injector PI (that is, charging / discharging to the piezo injector PI). Thus, the piezo injector PI expands and contracts so as to inject the required injection amount of fuel at a desired timing, and the injection form such as the injection amount, injection timing, and injection stage of the fuel injected from the piezo injector PI is controlled. The control IC 22 and the drive circuit 23 correspond to the charging circuit described in the claims.

  Various detection signals are input from the drive circuit 23 to the AD converter and the DSP 24, and the detection signals are input to the AD converter and the DSP 24 and then transmitted to the microcomputer 21 and the control IC 22.

  The piezo injector PI has various individual differences such as injection characteristics, capacitance, and the like, and such unique characteristics are measured in advance during the manufacturing process before the vehicle is shipped to the market. Individual information including adjustment data adjusted so that each piezo injector PI operates in the same manner is stored in the QR code 10j (storage means), and the QR code 10j is printed on the piezo injector PI. Note that storage means other than the QR code 10j includes an IC memory and a correction resistor.

  The individual information stored in the QR code 10j is read by the QR code reader 30 in an engine manufacturing process or a service store, and written to the EEPROM 25 in the control unit 20 by the external tool 31. In calculating the injection command value as described above, the microcomputer 21 corrects the injection command value obtained by the map calculation using the individual information or the like written in the EEPROM 25.

  Next, the configuration of the drive circuit 23 and its circuit operation will be described with reference to FIG.

  In this embodiment applied to a multi-cylinder engine, a plurality of piezo injectors PI are connected in parallel, and the piezo injector PI of the cylinder to be injected is selected by a selection switch. In FIG. 4, the selection switch is not shown.

  The drive circuit 23 includes a DC / DC converter (boost circuit) that boosts the voltage (for example, “12 V”) of the battery Ba to a high voltage (for example, “200 to 300 V”) for charging the piezo element PE. . This DC / DC converter includes a boost coil L1, a boost switch SW3, a rectifier diode D3, and a buffer capacitor C1. By turning ON / OFF the boost switch SW3 by the control IC 22, the charge to be supplied to the piezo element PE is stored in the buffer capacitor C1 with the high voltage boosted by the boost coil L1. Incidentally, it is desirable that the buffer capacitor C1 has a capacity (for example, about “30 μF to several hundred μF”) in which the voltage hardly changes by one charge process to the piezo element PE.

  A shunt resistor R1 is provided on the ground side of the buffer capacitor C1, and the control IC 22 takes in the voltage at the shunt resistor R1. Thereby, the control IC 22 detects the current that flows along with the charge / discharge of the buffer capacitor C1.

  Since the piezo element PE is electrically a capacitive load, when the electric charge of the buffer capacitor C1 is supplied to the piezo element PE and charged, the piezo element PE is driven to expand and inject fuel. Further, when the electric charge stored in the piezo element PE is discharged, the piezo element PE is driven to reduce and stop fuel injection. Hereinafter, the circuit operation when the displacement amount control of the piezoelectric element PE according to the present embodiment, that is, the charging process and the discharging process is performed will be described in detail.

(Circuit operation during charge processing)
When the drive signal IJT is input from the microcomputer 21 to the control IC 22, the control IC 22 starts chopper control by turning on / off the charging switch SW1. Specifically, when the charging switch SW1 is turned on with a rising edge of a trigger signal TRGG described later as a trigger, a closed loop circuit including a buffer capacitor C1, a charging switch SW1, a charging / discharging coil L2, and a piezo element PE is formed. . Thereby, the electric charge of the buffer capacitor C1 is charged to the piezo element PE. At this time, the amount of current flowing through the piezo element PE (hereinafter referred to as “piezocurrent”) gradually increases (current amount gradually increasing operation).

  When the integral value of the current flowing through the shunt resistor R1, that is, the charge amount Qact discharged from the buffer capacitor C1 to the piezo element PE exceeds a preset threshold value Qth (see FIG. 5B), the charge switch SW1 is turned off. Therefore, the actual behavior of the charge amount Qact is not the dotted line in FIG. 5B, but the behavior shown by the solid line limited to the threshold value Qth or less. In this embodiment, the current value from the buffer capacitor C1 detected by the shunt resistor R1 is used in place of the piezo current. However, the piezo element PE is also provided with a shunt resistor to detect the actual piezo current. It may be.

  On the other hand, after the charging switch SW1 is turned on, the charging switch SW1 is turned off based on the above-described threshold value Qth, thereby forming a closed loop circuit including the charging / discharging coil L2, the piezo element PE, and the reflux diode D2. Thereby, the flywheel energy of the charge / discharge coil L2 is charged in the piezo element PE. At this time, the piezoelectric current amount gradually decreases (current amount gradually decreasing operation). Then, the charging switch SW1 is turned on again using the rising edge of the next trigger signal TRGG as a trigger.

  As described above, when the charge switch SW1 is operated in the above-described manner, the piezoelectric element PE is charged, and the potential on the terminal side (hereinafter referred to as “piezo voltage”) that becomes a high potential of the piezoelectric element PE increases. Specifically, when the charging switch SW1 is turned on / off as shown in FIG. 5C, the piezo current is repeatedly increased and decreased as shown in FIG. 5E, and the piezo current is changed as shown in FIG. 5F. The voltage increases step by step.

(Circuit operation during discharge processing)
When the drive signal IJT from the microcomputer 21 is inverted, the control IC 22 starts chopper control by turning on / off the discharge switch SW2. Specifically, when the discharge switch SW2 is turned on using the falling edge of the drive signal IJT as a trigger, a closed loop circuit is formed by the piezo element PE, the charge / discharge coil L2, and the discharge switch SW2. Thereby, the piezo element PE is discharged. At this time, the piezoelectric current amount gradually decreases (current amount gradually decreasing operation). When the piezoelectric current falls below the threshold value Ith1, the discharge switch SW2 is turned off.

  On the other hand, after the discharge switch SW2 is turned on, the discharge switch SW2 is turned off based on the aforementioned threshold value Ith1, thereby forming a closed loop circuit by the piezo element PE, the charge / discharge coil L2, the recovery diode D1, and the buffer capacitor C1. The Thereby, the flywheel energy of the charge / discharge coil L2 is recovered by the buffer capacitor C1. At this time, the discharge amount of the piezo current gradually increases (current amount gradually increasing operation). When the piezoelectric current rises above the threshold value Ith2, the discharge switch SW2 is turned on again.

  As described above, when the discharge switch SW2 is operated in the above manner, the piezo element PE is discharged and the piezo voltage drops. Specifically, when the charging switch SW2 is turned on / off as shown in FIG. 5D, the piezo current (driving current) is repeatedly raised and lowered as shown in FIG. ) The piezo voltage falls step by step. Then, when the voltage across the charge / discharge coil L2 becomes zero, the current flow ends. The clamp diode D4 prevents the piezo voltage from becoming a negative voltage.

  Next, the procedure of the charging process and the discharging process by the control IC 22 will be described with reference to FIGS. 5, 6, and 7. In the timing chart shown in FIG. 5, (a) shows a change in on / off state of the drive signal IJT, (b) shows a change in the amount of charge Qact flowing through the shunt resistor R1, and (c) shows an on / off change in the charge switch SW1. , (D) shows on / off changes of the discharge switch, (e) shows changes in piezo current, and (f) shows changes in piezo voltage. FIG. 6 is a flowchart showing a processing procedure when the control IC 22 performs the above-described charging process. FIG. 7 is a block diagram of the control IC 22 when it functions to calculate the threshold value Qth and trigger signal TRGG used in the charging process.

(Charge processing control procedure)
First, in step S1 of FIG. 6, it is determined whether or not the drive signal IJT input from the microcomputer 21 to the control IC 22 is in an on state. When the drive signal IJT is turned on to detect the rising edge of the drive signal IJT (see symbol t1 in FIG. 5A) (S1: YES), the discharge switch SW2 is turned off in the subsequent step S2 (this processing is performed). At the same time, in step S3, the trigger signal TRGG is generated based on the data in block B9 shown in FIG.

  The trigger signal TRGG is a signal for determining the on timing of the charging switch SW1, and the charging switch SW1 is turned on at the rising edge of the trigger signal TRGG. That is, the data stored in the block B9 can be said to be data that schedules the on-timing of the charging switch SW1 in one charging period (period t1 to t5 shown in FIG. 5). The data of the block B9 of the present embodiment is scheduled so that the charging switch SW1 is turned on at regular intervals, but may be at irregular intervals. In one charge, the charge switch SW1 is turned on at least three times or more. The data of the block B9 is data transferred from the microcomputer 21 to the control IC 22 at the time of initialization, and the trigger signal TRGG is generated based on the clock signal time from the microcomputer 21.

  In subsequent step S4, it is determined whether or not the trigger signal TRGG generated in step S3 is in an ON state. When the rising edge (see FIG. 5C) of the trigger signal TRGG is detected and the trigger signal TRGG is turned on (S4: YES), the charging switch SW1 is turned on in the subsequent step S5.

  In the subsequent step S6, the aforementioned threshold value Qth (see FIG. 5B) is calculated by blocks B1 to B8 described in detail later. In subsequent step S7, it is determined whether or not the charge amount Qact obtained by integrating the current flowing through the shunt resistor R1 exceeds the charge threshold value Qth calculated in step S6. If it is determined that the charge amount Qact exceeds the threshold value Qth (S7: YES), the charging switch SW1 is turned off in the subsequent step S8.

  In the subsequent step S9, it is determined whether or not a predetermined time has elapsed from the time point t1 when the drive signal IJT is turned on (see FIG. 5A) and the time point t5 has been reached. After the charging switch SW1 is repeatedly turned on and off in steps S3 to S8, at a time point t5 is reached (S9: YES), the series of charging processes shown in FIG. 6 is terminated. However, even if t5 has not been reached, if the ON generation of the trigger signal TRGG of the block B9 has been completed, the charging process has been completed at a time t4 prior to t5. Note that the value of the charge amount Qact obtained by integrating the current flowing through the shunt resistor R1 with an integrator is reset when the integrator is reset at the rising edge time t1 of the trigger signal TRGG or at a predetermined time t5. It becomes zero.

(Discharge treatment control procedure)
When the drive signal IJT input from the microcomputer 21 to the control IC 22 is turned off, the discharge process is started from the time point t6, and when the predetermined time has elapsed from the start of the discharge process and the time point t7 is reached, the discharge process is terminated. More specifically, when the falling edge of the drive signal IJT is detected at time t6, the discharge switch SW2 is turned on (see FIG. 5D). When the piezo current (shunt resistance is not shown) decreases with the turn-on of the discharge switch SW2 and becomes lower than the current threshold Ith1 (see FIG. 5 (e)), the discharge switch SW2 is turned off.

  Thereafter, when the piezo current increases with the discharge switch SW2 being turned off and becomes higher than the current threshold value Ith2, the discharge switch SW2 is turned on again. Thus, by repeatedly turning on / off the discharge switch SW2 to discharge the electric charge of the piezo element PE, the piezo voltage gradually decreases (see FIG. 5F). When the piezo voltage drops to a certain extent, the potential difference between both ends of the charge / discharge coil L1 decreases, so that the piezo current does not drop as the threshold Ith1 is exceeded. Therefore, when the on-time of the discharge switch SW2 has passed a predetermined time, switching is enabled by forcibly turning off the discharge switch SW2.

  The remaining charge remaining in the piezo element PE at the end time t7 of the discharge process is completely discharged by keeping the discharge switch SW2 turned on at the end time t7. Therefore, when the drive signal IJT is input next time, the discharge switch SW2 is first turned off as described in step S2 of FIG.

(Calculation procedure of threshold value Qth)
By the way, the energy released from the buffer capacitor C1 is charged in the piezo element PE according to the energy conservation law. Therefore, since it can be said that the charging energy E is the same as the energy released from the buffer capacitor C1, it can be calculated by the following equation 2. It is assumed that the buffer capacitor current flowing from the buffer capacitor C1 to the piezo element PE is IC1, and the buffer capacitor voltage is VC1.
E = ∫ (VC1 × IC1) dt (Formula 2).

As described above, the capacity of the buffer capacitor C1 is set to a capacity at which the voltage hardly changes by a single charging process to the piezo element PE. Therefore, it can be said that the buffer capacitor voltage VC1 is substantially constant. . Therefore, the above equation 2 can be transformed into the following equation 3.
E = VC1 × ∫IC1dt (Equation 3).

Since dt in Equation 3 is the on-time of the charge switch SW1, it can be said that the term ∫IC1dt in Equation 3 is the amount of charge Qact flowing from the buffer capacitor C1 to the piezo element PE. That is, the above expression 3 can be transformed into the following expression 4.
E = VC1 × Qact (Formula 4).

  Since the buffer capacitor voltage VC1 in Equation 4 is substantially constant, it can be said that the charging energy E is a value uniquely determined by the charge amount Qact. Therefore, controlling the amount of charge Qact released from the buffer capacitor C1 to the piezo element PE by the threshold value Qth can be said to control the charge energy to the piezo element PE. Therefore, if the buffer capacitor current IC1 is detected by the shunt resistor R1, the charging energy E can be easily grasped without actually measuring the energy.

  In view of the above points, in this embodiment, the threshold value Qth used in the charging process is calculated as follows. That is, in the charging process of FIG. 6, the on / off operation of the charging switch SW1 is open-controlled so that the charging energy E input to the piezo element PE by the single charging at t1 to t5 becomes the target energy Etgr. . The target energy Etgr is calculated mainly based on the rail pressure PC, and further corrected based on individual information, temperature characteristics, and the like of the piezo injector PI. Then, the threshold value Qth is calculated so that one charge amount becomes the target energy Etgr.

  The calculation method of the threshold value Qth will be described more specifically with reference to blocks B1 to B8 in FIG. 7. First, in block B1, based on the individual information of the rail pressure PC and the piezo injector PI, the map is used to calculate the target energy Etgr. A base value Ebas is calculated. As described above, the valve opening operation is started when the extension force of the piezo element PE exceeds the force received by the back pressure control valve 13 from the high pressure fuel. Therefore, as shown in FIG. 9, the higher the rail pressure PC, the greater the extension force required to start the valve opening operation. Therefore, in the predetermined region of the rail pressure PC, the base value Ebas is set higher as the rail pressure PC is higher. Further, the value of the base value Ebas with respect to the rail pressure PC is changed according to the individual difference of the piezo injector PI.

  The individual difference information used in the blocks B1, B5, etc. is preferably measured in advance during the manufacturing process before shipping the vehicle to the market and stored in the above-described QR code 10j. Alternatively, estimation may be performed based on various detection values.

  The extension amount of the piezo injector PI varies depending on the piezo element temperature TP 'at that time even if the charging energy E is the same. Therefore, in block B6, the correction amount ΔE is calculated using a map based on the piezo element temperature TP ′, and in block B2, the final target energy Etgr is calculated by adding the correction amount ΔE to the base value Ebas.

  The piezo element temperature TP ′ used in the block B6 is estimated using a map based on the separately calculated capacitance Cp of the piezo element PE and solid state information of the piezo injector PI in the blocks B4 and B5. Specifically, since the piezo capacitance Cp has a characteristic that changes depending on the temperature, the piezo element temperature TP can be estimated in the block B4 based on the piezo capacitance Cp. The piezo element temperature TP estimated in the block B4 is corrected by multiplying the value of the individual information of the piezo injector PI in the block B5.

  Controlling the charging energy E by controlling the threshold value Qth is as described above. Therefore, in blocks B3, B7, and B8, the target energy Etgr calculated in block B2 is converted to a threshold value Qth used in the process of step S7 in FIG. Specifically, a base value Qbas for the threshold value Qth is determined in block B7, and a gain Kgain is calculated in block B3 using a map based on the target energy Etgr. Then, the threshold value Qth is calculated by multiplying the base value Qbas by the gain Kgain in the block B8.

  Here, the timing at which the back pressure control valve 13 is separated from the upper valve seat portion 10e so that the nozzle needle 11 is separated from the needle seat portion 10b and the injection port 10i is opened (timing for starting the valve opening operation). Does not coincide with the timing at which charging of the piezo element PE is started. That is, when the charging starts, the extension force of the piezo element PE gradually increases, and when the extension force exceeds the force received by the back pressure control valve 13 from the high pressure fuel in the high pressure fuel passage 6, the upper valve seat. It will be separated from the part 10e and a valve opening operation will be started.

  Accordingly, the back pressure control valve 13 performs the valve opening operation when the piezo voltage that increases stepwise as the charging of the piezo element PE starts exceeds the threshold value Vth (see the one-dot chain line in FIG. 5F). Will start. This threshold value Vth can be said to be a voltage necessary for causing the back pressure control valve 13 to start the valve opening operation.

However, the threshold value Vth varies depending on various factors exemplified below.
-The higher the high-pressure fuel pressure, the greater the load that the piezo element PE receives from the high-pressure fuel via the back pressure control valve 13 or the like. Then, since the force required to start the valve opening operation of the back pressure control valve 13 increases, the threshold value Vth increases.
Since the capacitance of the piezo element PE varies depending on the temperature of the piezo element PE, the threshold value Vth varies depending on the temperature even if the charging energy supplied to the piezo element PE is the same.
The pressure receiving area of the portion receiving the high pressure fuel pressure in the back pressure control valve 13 differs among the individual piezo injectors PI. Further, various sliding resistances such as the nozzle needle 11 and the large-diameter piston 16 are different among the individual piezo injectors PI. Due to such individual differences in the piezo injector PI, individual differences occur in the threshold value Vth.

  Due to the variation in the threshold value Vth as described above, the timing at which the back pressure control valve 13 starts the valve opening operation may vary. Then, the valve opening operation timing (injection start timing) of the nozzle needle 11 will vary, and as a result, the fuel injection timing from the injection port 10i will vary.

  To solve this problem, the present inventors set the charge amount related to the second and subsequent specified number of times (third time in the example of FIG. 5) of the increase of the piezo current one time before the specified number of times ( In the example of FIG. 5, it was recalled that the charge amount was larger than the charge amount of the second time). In other words, if the piezo voltage increase rate (voltage gradient a3) accompanying the third current increase is made faster (steep) than the piezo voltage increase rate (voltage gradient a2) associated with the second current increase. ), The variation widths Tσ1 and Tσ2 of the valve opening operation start timing with respect to the variation amount Vσ (see FIG. 8) of the threshold value Vth can be reduced as indicated by the symbol Tσ1.

  In this embodiment, paying attention to this point, the charge threshold value Qth is variably set in the block B7, and the value of the charge threshold value Qth when the piezoelectric current rises for a specific number of times is set before the specific number of times (see FIG. 5). In the example, it is larger than the value at the time of current rise in the first and second times). According to this, as shown in FIG. 10, the amount of charge Qact (that is, the average charge rate) that flows into the piezo element PE per unit time due to energization a specific number of times (third time) is larger than the first time and the second time ( (See FIG. 10). As described above, the voltage gradient a3 (see FIG. 5F) for the specific number of times is made steeper than the voltage gradients a1 and a2 before (first and second times). Therefore, the variation width Tσ of the valve opening operation start timing of the back pressure control valve 13 can be reduced, and consequently the variation of the fuel injection timing from the injection port 10i can be reduced.

  Here, if the variation amount Vσ of the threshold value Vth can be set so as to be within the range of the voltage gradient a3 of the specific number of times, the following effect is obtained. That is, if there is a variation width Tσ across a plurality of adjacent voltage gradients a3 and a4, a period during which the piezo current falls is included. Then, since the piezo voltage hardly increases during this period, the variation width Tσ of the valve opening operation start timing increases by the period, so that the timing of fuel injection from the injection port 10i varies greatly.

  On the other hand, in the present embodiment, the average charge rate of the specific number of times is the largest in the energization after the second time (see FIG. 10), so that the piezo voltage exceeds the threshold value Vth at the specific number of times. Can improve the certainty. Therefore, since the variation width Tσ of the valve opening operation start timing can be avoided from increasing by the period, an increase in variation in the fuel injection timing can be avoided.

  Incidentally, although the charge threshold value Qth after the third time is set to a constant value and the charging energy per switching time of the charge switch SW1 is the same after the third time, the average is obtained as shown in FIG. The charge rate gradually decreases. This is because the piezo voltage gradually increases with each turn, and the piezo current gradually decreases as the voltage increases.

Contrary to the present embodiment, if the piezo voltage is set to exceed the threshold value Vth in the first charging by switching, the piezo current at the first charging will be extremely high as explained earlier using Equation 1. That's right. On the other hand, according to the present embodiment, the charge threshold value Qth is variably set in the block B7 so that the time when the piezoelectric voltage exceeds the threshold value Vth is after the second charge (during the third charge). Peak value can be reduced. Thus, a significant increase in power loss (loss W = I ² R) in various resistance portions in the drive circuit 23 can be avoided, and the back pressure control valve 13 is suddenly opened to return to the lower valve seat portion 10g. Noise generation due to collision can be suppressed.

  Furthermore, according to the present embodiment, the on-timing of the charging switch SW1 is schedule-controlled by the data stored in the block B9, and the charging switch is set so that the current rising start time at the specific number of times becomes a preset time. Controls the ON timing of SW1. Therefore, it is possible to improve the certainty that the variation width Tσ1 of the valve opening operation start timing is within the range of the voltage gradient a3 of the specific number of times, and as a result, the piezo voltage exceeds the threshold value Vth when the current increases for the specific number of times. The certainty can be improved.

(Second Embodiment)
By the way, the data of the block B9 indicates that the variation width Tσ1 of the valve opening operation start timing (hereinafter referred to as “valve opening time”) at which the back pressure control valve 13 is separated from the upper valve seat portion 10e is a specific number of times of voltage. Although it is set based on a test during the manufacturing process so as to exist within the range of the inclination a3, when the position of the variation width Tσ1 shifts due to aging deterioration of the piezo injector PI, a plurality of adjacent voltage inclinations a3, a4 There is a possibility that the variation width Tσ exists over the two. Specific examples of the aging deterioration include wear of the back pressure control valve 13, the upper valve seat portion 10e of the body 10, the lower valve seat portion 10g, the nozzle needle 11, and the like.

  In order to solve this problem, the present embodiment includes means (not shown) for detecting the actual valve opening time. Then, by correcting the base value Ebas with respect to the target energy Etgr according to the deviation between the detected valve opening time and the target time, the position where the variation width Tσ1 exists is within the range of the voltage gradient a3 of the specific number of times. Feedback control.

  As means for detecting the valve opening time, in this embodiment, a load (hereinafter referred to as “piezo load”) applied to the piezo element PE is detected as a physical quantity correlated with the valve opening time. FIG. 11 is a timing chart showing the above correlation, where (a) shows the on / off change of the drive signal IJT, (b) shows the change in the piezo current, (c) shows the change in the piezo voltage, and (d) shows the piezo element. Changes in the amount of displacement (extension) of PE, (e) shows changes in piezo load, and (f) shows changes in lift amount of the back pressure control valve 13.

  As shown in FIG. 11, the piezo load increases as the piezo voltage increases stepwise from the charging start t1. Then, at a certain point, the piezo element PE starts to expand. At the time when the back pressure control valve 13 is separated from the upper valve seat portion 10e after the start of the extension (valve opening time topen), the value of the piezo load reaches a peak. Thereafter, the value of the piezo load decreases until the back pressure control valve 13 is seated from the lower valve seat portion 10g (between topen and t3), and the piezo load increases again when seated on the lower valve seat portion 10g. To do.

  Thus, in the range (t1 to t3) in which the valve opening time is expected, the time at which the peak value of the piezo load appears and the valve opening time topen are correlated and almost coincide. Therefore, the actual valve opening time topen is detected by detecting the piezo load during the period of the valve opening time prediction range t1 to t3. Specifically, the AD converter and the DSP 24 (see FIG. 3) are used to perform processing for converting the detected value of the piezo load into the valve opening time topen. A black circle in FIG. 11E indicates a detected value of the piezo load, and the piezo load is detected at a predetermined cycle in the valve opening determination regions t1 to t3.

  As an example of the piezo load detection means, when a piezo stack (stacked body) is configured by stacking a large number of piezo elements PE, one piezo element constituting the piezo stack can be used as the load detection means. Can be mentioned.

  FIG. 12 is a block diagram of the control IC 22 according to the present embodiment. Blocks B10, B11, and B12 for executing the feedback control are added to the block diagram of FIG. 7 according to the first embodiment. Yes. First, in block B10, the deviation between the detected valve opening time topen and the target time Ttrg is calculated. In block B11, a correction amount ΔE2 is calculated using a map based on the deviation calculated in block B10. In the map of block B11, the correction amount ΔE2 is set so that the target energy Etgr is increased as the detected actual valve opening time topen is later than the target time Ttrg. If the deviation value is near zero, the correction amount ΔE2 is set to zero, and an upper limit and a lower limit are provided for the correction amount ΔE2.

  In block 2, the value obtained by integrating the correction amount ΔE2 calculated in block B11 in block B12 and the correction amount ΔE calculated in block B6 are added to the base value Ebas calculated in block B1. The final target energy Etgr is calculated.

  As described above, according to the present embodiment, feedback control is performed so that the deviation between the actual valve opening time topen and the target time Ttrg approaches zero. Therefore, even if the piezo injector PI deteriorates over time, the variation width of the valve opening time topen It is possible to easily make Tσ1 exist within the range of the voltage slope a3 of the specific number of times, and as a result, it is possible to improve the certainty that the piezo voltage exceeds the threshold value Vth when the current rises the specific number of times.

(Other embodiments)
The above embodiments may be implemented with the following modifications. Further, the present invention is not limited to the description of the above embodiment, and the characteristic structures of the embodiments may be arbitrarily combined.

  In each of the above embodiments, the specific number of times that maximizes the amount of charge (average charge rate) among the multiple increases in piezo current is set to the third time. May be. However, if the number of times is set too late, the valve opening time topen with respect to the on-rising time t1 of the drive signal IJT becomes too late, and the response of the injection timing to the injection command cannot be sufficiently secured. It is desirable to set the second to fourth times.

  The voltage gradient a3 at the specific number of times is not limited to the maximum among all the voltage gradients, but the voltage gradient a3 at the specific number of times is maximized among the voltage gradients a1, a2, and a3 up to the specific number of times. The voltage gradient a4 after the specific number of times may be set to be larger than the voltage gradient a3 of the specific number of times.

  In each of the above embodiments, the voltage gradient a3 of the specific number of times is made steeper than the voltage gradients a1 and a2 of all the previous (first and second times) voltage. The voltage gradient a3 is only required to be steeper than the voltage gradient a2 of the previous time, and is not limited to be steeper than the voltage gradient a1 of the previous time (first time).

  Regarding the on trigger of the charge switch SW1, in the above embodiments, the on timing of the charge switch SW1 scheduled in the block B9 is set at equal intervals, but may be set at unequal intervals. In each of the above embodiments, all of the on-triggers are scheduled in block B9. However, when the present invention is implemented, only a specific number of on-triggers are scheduled, and the charging switch SW1 is turned on for other times. Alternatively, the on-trigger may be turned on, such as when an on-trigger is made when the value of the descending piezoelectric current becomes zero.

  In the second embodiment, the piezo load is detected as a physical quantity correlated with the valve opening time topen. In addition to detecting the piezo load, the displacement of the piezo element PE and the lift of the back pressure control valve 13 are detected. Detecting the amount. That is, when the displacement amount of the piezo element PE that expands with charging reaches a predetermined threshold value αth (see FIG. 11D), it substantially coincides with the valve opening time topen. Further, when the lift amount of the back pressure control valve 13 that lifts toward the lower valve seat portion 10g due to charging reaches a predetermined threshold value βth (see FIG. 11 (f)), it almost coincides with the valve opening time topen. To do.

  In each of the above embodiments, the drive circuit 23 is configured by the buffer capacitor C1, the charge switch SW1, and the like, and the charge discharge from the buffer capacitor C1 (charge energy to the piezo element PE) is performed in one charge period (shown in FIG. 5). Control is performed by turning on / off the charging switch SW1 a plurality of times during the period from t1 to t5. The present invention is not limited to such a multi-switch type drive circuit 23. For example, by switching control of the primary current to the transformer, the energy charged to the piezo element PE by the secondary current of the transformer is controlled. It may be a drive circuit of the system. Further, a drive circuit of a method of charging the piezo element PE by a plurality of LC resonances by the LC resonance circuit may be used.

  In the second embodiment, feedback control is performed to cope with the aging deterioration of the piezo injector PI. Instead of this feedback control, for example, a correction amount ΔE2 is set based on the number of operations of the charging switch SW1 and the like. May be. According to this, it is possible to cope with the above-mentioned deterioration over time while making it unnecessary to detect the valve opening time topen.

The figure which shows the whole structure of the engine system concerning 1st Embodiment of this invention. Sectional drawing which shows the cross-sectional structure of the piezo injector concerning the embodiment. The figure which shows the structure of the control unit 20 concerning the embodiment. The figure which shows the structure of the drive circuit concerning the embodiment. The timing chart when the charge process and discharge process concerning the embodiment are performed. The flowchart which shows the procedure of the charge process concerning the embodiment. The block diagram of the control IC concerning the embodiment. The figure explaining the effect of steepening the voltage inclination at the time of charge processing. The figure explaining the relationship between the extending | stretching force required for a valve opening operation | movement start, and rail pressure PC. The figure which shows transition of the average charge speed concerning the charge process of the embodiment. The timing chart when the charge process and discharge process concerning 2nd Embodiment of this invention are performed. The block diagram of control IC concerning a 2nd embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10i ... Injection port, 11 ... Nozzle needle (valve body), 13 ... Back pressure control valve (opening-closing mechanism), 22 ... Control IC (charging circuit), 23 ... Drive circuit (charging circuit), PI ... Piezo injector (fuel injection) Valve), PE ... Piezo element.

Claims (9)

An opening / closing mechanism that opens and closes a fuel injection port; and a piezoelectric element that operates the opening / closing mechanism. When a voltage value of the piezoelectric element that rises due to charging of the piezoelectric element exceeds a threshold value, the piezoelectric element expands. Applied to a fuel injection valve configured to start the opening and closing mechanism;
When charging the piezo element, a charging circuit that increases the voltage value stepwise by repeatedly raising and lowering the drive current flowing to the piezo element multiple times,
Among the plurality of current increases of the drive current, the voltage value increase rate associated with the second specific number of current increases after the second time is represented by the voltage value increase rate associated with the current increase of the previous specific number of times. A fuel injection valve control device that controls the operation of the charging circuit so as to be faster.   By controlling the charging circuit so that the charging energy per unit time input to the piezo element at the specific number of times of current increase is greater than that at the time of current increase one time before the specific number of times, The fuel injection valve control device according to claim 1, wherein the rate of increase of the voltage value is controlled.   By controlling the charging circuit so that the rising speed of the charge charged in the piezo element when the current rises for the specific number of times is faster than when the current rises one time before the specific number of times, The fuel injection valve control device according to claim 2, wherein the rate of increase of the value is controlled.   The fuel injection valve control device according to any one of claims 1 to 3, wherein the operation of the charging circuit is controlled such that a start time of current increase at the specific number of times is a preset time. .   Using at least one of the pressure of the high-pressure fuel supplied to the injection port, the load received by the piezo element from the high-pressure fuel, the temperature of the piezo element, and the individual information of the fuel injection valve as parameters, the voltage value The fuel injection valve control device according to any one of claims 1 to 4, wherein the rising speed is controlled.   The individual information is an actual measurement value acquired by a test performed in advance, and is a physical quantity that correlates with the increasing speed of the voltage value when the injection start timing becomes the target injection timing. Is included as information, 6. The fuel injection valve control device according to claim 5, wherein   7. The individual information includes information indicating a capacitance of the piezo element or a characteristic indicating a relationship between the capacitance and the temperature of the piezo element as information. Fuel injection valve control device. The opening / closing mechanism includes a valve body that opens and closes the injection port, and a back pressure control valve that operates by a driving force of the piezo element to control a back pressure of the valve body,
The said back pressure control valve starts the operation | movement which reduces the said back pressure to open the said valve body, if the voltage value of the said piezoelectric element exceeds a threshold value, The any one of Claims 1-7 characterized by the above-mentioned. The fuel injection valve control device according to one.   A fuel injection valve control system comprising: a fuel injection valve; and the fuel injection valve control device according to any one of claims 1 to 8.

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