JPH11210531A - Injector driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the dispersion of an injection characteristic in an injector driving device recovering to accumulate flyback energy of a solenoid valve to supply it to an injector. SOLUTION: When valve closing driving of a PCV is completed, both end voltage of a capacitor and battery voltage are detected after standing by during the time of the capacitor being charged with a flyback current flowing due to cutoff of current application to the PCV (for waiting time Tw) (S110-S130). In case of both end voltage of the capacitor not reaching full charge (118V), current flowing time Ton required to generate such a flyback current to charge the capacitor full, to the PCV is set on the basis of differential voltage, and boosting switching for applying a current to the PCV and cutting off is performed according to the current flowing time Ton (S140-S200). The boosting switching is repeatedly executed while changing the setting of current flowing time according to the differential voltage until both end voltage of the capacitor reaches full charge as a result of this boosting switching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injector driving apparatus for driving an injector with a high voltage exceeding a power supply voltage, and more particularly to flyback energy generated when a solenoid valve provided for some control is de-energized. −
The present invention relates to an injector drive device utilizing

[0002]

2. Description of the Related Art Conventionally, a capacitor connected in parallel to a drive current supply path to an injector has a power supply voltage equal to or higher than a power supply voltage in order to improve the accuracy of injection amount control of an injector that injects fuel into each cylinder of an internal combustion engine. 2. Description of the Related Art There is known an injector driving device in which an injector is made to respond at a high speed by charging the capacitor to a high voltage, discharging the capacitor when the injector is opened, and supplying a peak current to the injector.

In such an injector driving device, a dedicated step-up transformer is provided for charging the capacitor, and the capacitor is connected by the high voltage induced in the secondary winding by connecting and disconnecting the primary winding. Charging, or as disclosed in JP-A-8-210170, an injector or a PCV (pump control system).
The capacitor is charged with flyback energy generated after driving an electromagnetic valve such as a valve, and supplemental charging is performed using a boosting transformer only when the capacitor cannot be fully charged by itself.

However, in any case, there is a problem that the device is increased in size because a large-sized step-up transformer, which is a large component, must be provided exclusively for charging the capacitor. On the other hand, as disclosed in Japanese Patent Application Laid-Open No. 6-299890, if the capacitor cannot be fully charged only by flyback energy after driving the solenoid valve, the electromagnetic valve is not operated during the non-operating period of the injector or the PCV. The solenoid valve is intermittently driven with an energizing time that does not operate the valve, and the flyback energy is supplied to the capacitor to perform supplementary charging, thereby charging the capacitor without using a boosting transformer dedicated for charging. Devices are known.

[0005] In this device, during auxiliary charging, the solenoid valve is driven for a fixed energizing time, so that the energy charged in the capacitor when the energization is cut off becomes constant each time. When the cutoff is repeatedly executed and the voltage across the capacitor reaches the specified value (full charge),
By stopping the control of the supplementary charging, the energy supplied from the capacitor when the injector is opened is always substantially constant.

[0006]

However, solenoid valves such as injectors and PCVs are not designed for charging capacitors, but generally have a large inductance to generate a large driving force. I have. For this reason, when the electromagnetic valve is intermittently controlled at the time of supplementary charging, the control cycle cannot be shortened so much, and energization and cutoff can be performed only a very limited number of times. As a result, the flyback energy generated by one energization / interruption must be increased, and the amount of energy charged (the voltage between both ends) of the capacitor at the time of full charge (at the time of stopping the control of the supplementary charge) varies. However, there has been a problem that the injection characteristics of the injector vary.

The present invention has been made to solve the above problems.
It is an object of the present invention to reduce variation in injection characteristics in an injector drive device that collects and stores flyback energy of a solenoid valve and supplies it to an injector.

[0008]

In the injector driving apparatus according to the first aspect of the present invention, when the switching element cuts off a current supply path to the solenoid valve, the injector valve generates the solenoid valve. Flyback energy is charged to the charging means. Then, the charging amount detecting means detects the energy charging amount of the charging means, and if the energy charging amount is insufficient, the switching control means:
During the non-operating period of the solenoid valve, the switching element is intermittently controlled within a range in which energization to the solenoid valve does not exceed the allowable time, and the insufficient energy is supplementarily charged to the charging means. At this time, the energization time setting means appropriately sets the energization time of the solenoid valve in the control of the switching control means based on the detection result of the charge amount detection means.

As described above, according to the injector driving apparatus of the present invention, at the time of supplementary charging during the non-operating period of the solenoid valve, a constant flyback energy is not generated every time by energizing and shutting off the solenoid valve. Since the flyback energy corresponding to the shortage of the energy charging amount of the charging means can be generated, the energy charging amount of the charging means at the time of full charge can be accurately and constant.

As a result, when the injector is opened, the energy supplied from the charging means to the solenoid valve of the injector is always constant, that is, the injection characteristics of the injector can be kept constant. Can be. The setting of the energizing time in the energizing time setting means is, as described in claim 2, a setting map indicating the relationship between the energizing time of the solenoid valve and the amount of energy charged to the charging means when the energization is cut off. May be performed by searching the setting map using the shortage of the energy storage amount obtained from the detection result of the storage amount detection unit as a reference value.

According to this, since there is no need to perform complicated calculations when setting the energization time, for example, when the energization time setting means is realized by an arithmetic processing unit such as a microcomputer, the processing amount is greatly reduced. can do. If the contents of the setting map are experimentally determined and set, high-precision control suitable for the characteristics of each device can be performed.

When the energizing time of the solenoid valve is set using the setting map as described above, the energizing path to the solenoid valve is cut off by the control of the switching control means. A learning unit may be provided for calculating the energy charged in the charging unit by the flyback energy generated by the interruption from the detection result of the charging amount detection unit and rewriting the setting map based on the calculated value.

In this case, even if the relationship between the power-on time and the amount of stored energy changes due to aging of the device or a change in the operating environment, etc., the optimum power-on time is set appropriately in accordance with the change. Because the map for use is rewritten,
Accurate control can be performed over a long period of time.

The setting map may be rewritten every time the solenoid valve is energized or cut off during auxiliary charging, or may be performed periodically. Alternatively, an average value or the like may be written based on a plurality of detection results in the past. By the way, the flyback energy generated when the energization of the solenoid valve is cut off not only changes according to the energization time of the solenoid valve but also is affected by the power supply voltage of the solenoid valve.

According to a fourth aspect of the present invention, there is provided a voltage detecting means for detecting a power supply voltage of the solenoid valve, wherein the energization time setting means prepares a plurality of setting maps corresponding to the power supply voltage. It is desirable to select one of them according to the detection result of the detection means.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a common rail fuel injection device used for a six-cylinder vehicle diesel engine.

As shown in FIG. 1, the common rail type fuel injection system includes six injectors INJ1 to INJ6 which are provided in each cylinder and supply fuel to each cylinder, and each injector INJn (n = 1 to 6). ), A common rail 6 for supplying high-pressure fuel to each of the injectors INJn via branch pipes 4 connected thereto, and a cylinder type supply pump unit 8 for pressure-feeding the fuel to the common rail 6.
And an electronic control unit (hereinafter, referred to as an ECU) 10 for controlling the pressure feed of fuel to the common rail 6 and the driving of the injectors INJ1 to INJ6 based on detection signals from various sensors and the like. In addition, each injector INJ
1 to 6 are solenoid valves L for opening and closing the fuel supply port from the branch pipe 4 to control the fuel injection amount and the injection timing.
1 to L6 are provided.

FIG. 2 is a sectional view showing a specific configuration of the supply pump unit 8. As shown in FIG. As shown in FIG. 2, the supply pump unit 8 is provided with a drive shaft 16 which is drivingly connected to a crankshaft 14 (see FIG. 1) of the engine. The drive shaft 16 has three convex portions and concave portions. A cam 18 having a smooth outer peripheral surface formed at a time and having a substantially triangular cross section perpendicular to the axial direction of the drive shaft 16 is fixed.

A plunger 20 which has a roller at the lower end thereof which slides on the surface of the cam 18 and which moves up and down in accordance with the rotation of the cam 18, and a pressurizing chamber 22 for pressurizing the fuel. (See FIG. 1) together with a plunger 20. A cylinder 24 is provided above the plunger 20, and a PCV (pump) which is an electromagnetic valve for controlling the amount of fuel discharged from the pressurizing chamber 22 to the common rail 6 is provided above the cylinder 24. A control valve 26 is provided.

Also, at the end of the drive shaft 16,
Driven by the drive shaft 16, the fuel tank 28
A feed pump (low-pressure pump) 30 for sucking fuel from (see FIG. 1) and supplying the fuel to the pressurizing chamber 22 is provided. Further, the drive shaft 16 is provided with a gear 32b constituting the cylinder discrimination sensor 32 together with a proximity sensor 32a arranged near the drive shaft 16. The cylinder discriminating sensor 32 generates a pulse signal each time a tooth of the gear 32b passes through the proximity sensor 32a, thereby outputting a pulse signal train corresponding to the rotation of the drive shaft 16. Things.

Then, as shown in FIG.
The PCV 26 provided on the upper part of the valve body 34 opens and closes a fuel supply port from the fuel tank 28 to the pressurizing chamber 22, a spring 36 for urging the valve body 34 in a valve opening direction, and a valve body 34 by energization. And an electromagnetic solenoid 38 for closing the valve. This is a so-called normally open type electromagnetic valve. When the internal pressure of the pressurizing chamber 22 becomes equal to or higher than a preset valve opening pressure, the pressurizing chamber 22 is opened to supply the fuel in the pressurizing chamber 22 to the common rail 6 via the fuel supply pipe 40. A check valve 42 is mounted.

In the supply pump unit 8 thus configured, the pressurizing chamber 22 is filled with the low-pressure fuel supplied by the feed pump 30 when the PCV 26 is opened.
When the PCV 26 is closed when the plunger 20 moves up, the fuel filled in the pressurizing chamber 22 is pressurized. When this pressure becomes equal to or higher than the valve opening pressure of the check valve 42, the check valve 42 opens and the high-pressure fuel in the pressurizing chamber 22 is sent to the common rail 6 by pressure. That is, when the valve closing timing of the PCV 26 is controlled, the start timing of pressurizing and pressurizing the fuel to the common rail 6 is controlled, and, consequently, the amount of pumping of the fuel to the common rail 6 is controlled.

Next, the ECU 10 controls the injector INJ
The solenoid valves L1 to L6 for controlling the fuel injection of the fuel cells 1 to 6 and the drive circuit 44 for driving the PCV 26 for controlling the high-pressure fuel supply to the common rail 6; And a computer (hereinafter, referred to as a microcomputer) 46.

The microcomputer 46 outputs a signal corresponding to the rotation of the crankshaft 14, a crank angle sensor 48, the above-described cylinder discriminating sensor 32 which outputs a signal corresponding to the rotation of the drive shaft 16, and detects the accelerator depression amount. By driving the solenoid valve Ln based on detection signals from the accelerator opening sensor 50, the common rail pressure sensor 52 for detecting the internal pressure of the common rail 6, and the like, the pilot injection and the main injection are performed continuously, so that the engine Fuel injection control for injecting fuel at a timing and amount according to the operating state of E. Similarly, by driving the PCV 26 based on a detection signal from each sensor, the internal pressure of the common rail 6 according to the operating state of the engine E Pressure control and injector INJn to make injector INJn respond fast Executes charging control for charging the energy for supplying the peak current to the solenoid valve Ln in the capacitor C1, C2, which will be described later.

On the other hand, as shown in FIG. 3, the drive circuit 44 operates in accordance with a valve drive signal Sv from the microcomputer 46.
Transistor Q that conducts and cuts off the current path of PCV26
10, a capacitor C1 connected in parallel to the transistor Q10 via a diode D11, and a capacitor C1 similarly connected in parallel to the transistor Q10 via a diode D12.
2 is provided. The capacitor C1 stores energy for flowing a peak current during pilot injection, and the capacitor C2 stores energy for flowing a peak current during main injection.

Further, the drive circuit 44 conducts the transistors Q21 to Q21 to turn on and off the current paths of the solenoid valves L1 to L6, respectively, according to the injection signals Sj1 to Sj6 from the microcomputer 46.
A constant current is supplied via a diode D21 to Q26 and the solenoid valves L1, L3, L5 whose current paths have been made conductive by one of the transistors Q21, Q23, Q25, and by one of the transistors Q22, Q24, Q26. A constant current circuit 54 for supplying a constant current to the solenoid valves L2, L4, L6 with current paths conducted through a diode D22; a capacitor C1 and solenoid valves L1-L6 via diodes D31, D32.
And the current path connecting to the selection signal Sr1 from the microcomputer 46.
, The capacitor C2 and the solenoid valve L via the diodes D33 and D34.
A transistor Q32 is provided for turning on and off the current path connecting the terminals 1 to L6 in accordance with the selection signal Sr2 from the microcomputer 46.

Further, the drive circuit 44 includes resistors R11 and R12, and outputs a detection signal Sc1 obtained by dividing the voltage Vc1 across the capacitor C1, and resistors R21 and R12.
22, a voltage dividing circuit 58 for outputting a detection signal Sc2 obtained by dividing the voltage Vc2 across the capacitor C2, and a resistor R3
1 and R32, and a voltage dividing circuit 60 for outputting a detection signal Sb obtained by dividing the battery voltage Vb, and a microcomputer 46 via these voltage dividing circuits 56, 58 and 60.
Can detect the voltages Vc1 and Vc2 across the capacitors C1 and C2 and the battery voltage Vb. The detection signals Sc1, Sc2 and Sb are transmitted to the microcomputer 46.
The digital signal is converted into a digital signal by an AD converter incorporated in the microcomputer 46 and used for various processes performed by the microcomputer 46.

In this embodiment, the PCV 26 corresponds to the solenoid valve according to the present invention, and the transistor Q10 includes a switching element, capacitors C1 and C2, and diodes D11 and D11.
12 is charging means, voltage dividing circuits 56 and 58 are charged amount detecting means,
The voltage dividing circuit 60 corresponds to voltage detecting means.

In the driving circuit 44 configured as described above,
When the transistor Q10 is turned off by the valve drive signal Sv from the microcomputer 46 and the current path of the PCV 26 is switched from the conductive state to the cut-off state, the diodes D11 and D12 are generated by the flyback current generated in the PCV 26.
, The capacitors C1 and C2 are charged.

On the other hand, the injection signal Sjn from the microcomputer 46
When the transistor Q2n is turned on by (n = 1 to 6), the constant current supplied from the constant current circuit 54 flows through the solenoid valve Ln corresponding to the turned on transistor Q2n. Also, while the transistor Q2n is on,
The selection signal Sr1 (or Sr2) causes the transistor Q31
(Or Q32) turns on, the capacitor C1
(Or C2) discharge causes a peak current to flow through the solenoid valve Ln.

Next, the charging control executed by the microcomputer 46 to charge the capacitors C1 and C2 will be described with reference to the flowchart shown in FIG. As shown in FIG.
When this processing is started, first, in S110, the microcomputer 4
It is determined whether the valve closing drive of the PCV 26 by the rail pressure control separately executed in step 6 has been completed, and if the valve closing drive has not been completed, the process waits by repeatedly executing S110, while the valve closes. If it is determined that the driving has been completed, S120
Move to

In S120, the control waits until a standby time Tw set at least equal to the time required for the fall of the valve closing drive current elapses, and in S130, the voltage dividing circuit 5
By reading the detection signals Sc1, Sc2, and Sb from the first, second, third, and sixth charge signals Vc, the charge voltages Vc of the capacitors C1 and C2, respectively.
1, Vc2, and the battery voltage Vb are detected.

That is, the reason for waiting for the waiting time Tw is P
The flyback current generated after the valve closing drive of the CV 26 is
The capacitor C flows only during the fall time of the valve closing drive current.
This is for detecting the charging after the flyback current is completely charged and the voltages Vc1 and Vc2 across the capacitors C1 and C2 are determined in order to charge the terminals C1 and C2.

The standby time Tw may be set to the fall time of the valve closing drive current required at the maximum value in the battery voltage Vb range in which the operation of the ECU 10 is guaranteed. With this setting, as the battery voltage Vb decreases, the fall time of the valve-closing drive current decreases.
No matter how the battery voltage Vb fluctuates within the above range, during charging by the flyback current, the capacitor C
This is because the voltages Vc1 and Vc2 across the terminals C1 and C2 are not detected, and the voltages Vc1 and Vc2 across the capacitors C1 and C2 can always be accurately detected.

At S140, the lower one of the voltages Vc1 and Vc2 of the capacitors C1 and C2 detected at S130 (hereinafter referred to as the detection voltage Vc) and the predetermined full charge of the capacitors C1 and C2. From the voltage (118 V in this embodiment), the difference voltage ΔV (= 118−V)
c), and in S150, the calculated difference voltage △
Based on V, it is determined whether or not the capacitors C1 and C2 are fully charged, that is, whether or not the difference voltage ΔV is equal to or less than 0 [V]. Is larger than 0 [V], it is determined that the capacitors C1 and C2 need to be supplementarily charged, and the process shifts to S160.

The auxiliary charging described below is performed by the PCV2
The PCV 26 is energized within an allowable time Tmax during which the valve 6 does not perform the valve closing operation, and the flyback current generated when the energization is cut off is performed. That is, in S160, the previously calculated difference voltage 算出
The flyback current required to charge the capacitors C1 and C2 by the difference voltage ΔV is generated by referring to the conduction time Ton setting table shown in [Table 1] using V as a reference value. An energization time Ton of the PCV 26 necessary for generating a flyback current is set.

[0037]

[Table 1]

As shown in [Table 1], the setting table shows that the difference voltage ΔV is 50V, 40V, 30V, 20V,
Energization time Ton [ms] to be set for 10V and 0V
Is stored, and the battery voltage Vb is 12
V, 16 V, 20 V, 24 V, 28 V, and 32 V are provided for six types. The content is the difference voltage.
As V is larger and battery voltage Vb is smaller,
The set value of the energization time Ton is set to be large.
Then, the setting table is selected according to the battery voltage Vb detected simultaneously with the detection of the voltages Vc1 and Vc2 across the capacitors C1 and C2, and the energizing time Ton is set from the difference voltage ΔV according to the selected setting table. .

The battery voltage Vb and the difference voltage ΔV are
When the value is other than the value stored in the setting table, for example, when the difference voltage ΔV = 32 V, the battery voltage Vb = 17 V, and the like, two-dimensional interpolation is performed from the setting value in the setting table, so that the energization time Ton Should be set.

Next, in S170, it is determined whether or not the energizing time Ton set in S160 is longer than the allowable time Tmax during which the PCV 26 does not perform the valve closing operation. If the energizing time Ton is longer than the allowable time Tmax, the process proceeds to S180. After shifting to limit the energization time Ton to the allowable time Tmax, the process shifts to S190. On the other hand, if it is determined in S170 that the energization time Ton is equal to or shorter than the allowable time Tmax, the process proceeds to S19.
Move to 0.

In step S190, a valve drive signal Sv for turning on the transistor Q10 for the set energization time Ton is output, so that the current path of the PCV 26 is set to the energization time Ton.
Performs boost switching that conducts and shuts off only during on. As a result, when the current path of the PCV 26 is cut off, a flyback current corresponding to the conduction time Ton is generated, and the capacitors C1 and C2 are charged via the diodes D11 and D12.

In S200, the fall time of the drive current of the PCV 26 due to the step-up switching, that is, the standby time set to be longer than the time required to complete the charging of the capacitors C1 and C2 by the flyback current. T
off (0.3 ms in this embodiment) and waits for S
At 210 and S220, just as at S130 and S140, the voltage across the capacitors C1 and C2 and the battery voltage Vb are detected, and the difference voltage ΔV from the fully charged state is calculated.

In S230, a correction table shown in [Table 2] is searched based on the difference voltage ΔV calculated in S220 to set a correction value. In S240, the correction value is set to the set correction value. After rewriting the contents of the setting table based on the above, the process returns to S150.

[0044]

[Table 2]

As shown in Table 2, the correction table shows that the difference voltage ΔV is -6V, -4V, -2V, 0V, 2
The correction value [ms] to be set in the case of V, 4V, and 6V is stored. Like the setting table, the battery voltage Vb is set to 12V, 16V, 20V, 24V, 28V.
V and 32 V are provided for six types. The correction value is set such that the larger the absolute value of the difference voltage ΔV, that is, the larger the shortage or excess with respect to the full charge, and the smaller the battery voltage Vb, the larger the correction value of the absolute value. Is positive, ie, the capacitor C
1, when the detected voltage Vc is insufficient for full charge, the sign of the correction value is positive, and when the sign of the difference voltage ΔV is negative, that is, when the detected voltage Vc of the capacitors C1, C2 is fully charged. , The sign of the correction value is set to be negative when it exceeds.

Then, a correction value is set based on the battery voltage Vb used when setting the energization time Ton and the difference voltage ΔV calculated in S220, and the value in the setting table used when setting the energization time Ton is used. Is rewritten to a value obtained by adding the correction value. For example, the state before the boost switching is such that the battery voltage Vb = 28 V, the difference voltage ΔV = 30
V, and as a result of setting the energizing time Ton of the boost switching to 1.2 ms according to the setting table, if the state after the boost switching becomes the differential voltage ΔV = 2V,
The correction value is set to 0.12 ms from the correction table, and the value of the setting table specified by the battery voltage Vb = 28 V and the difference voltage ΔV = 30 V is changed from the original 1.2 ms to 0.12 ms. It is rewritten to 1.32 ms after the addition.

That is, by performing the step-up switching in S190, ideally full charge (Vc = 118V)
However, in actuality, due to variations in the electromagnetic solenoid 38 constituting the PCV 26 and deterioration over time, P
The relationship between the energization time Ton of the CV 26 and the flyback current generated when the energization is cut off varies, and the full charge voltage may not be achieved. For this reason, the optimal set value of the energization time Ton is constantly learned based on the actually measured value in the step-up switching.

However, when the energization time Ton is limited in S180, since it is not expected that the battery will be fully charged after the boost switching, the learning process in S230 and S240 does not need to be performed. Thereafter, the same processing is repeatedly executed in accordance with the voltage between both ends of the capacitors C1 and C2 detected in S210 and the battery voltage Vb.
When it is determined that the detection voltage Vc of the capacitors C1 and C2 has reached full charge, that is, the difference voltage ΔV <0, the present process is terminated.

In this embodiment, S150 and S190 correspond to the switching control means in the present invention.
0 to S180 are energization time setting means, S230, S240
Corresponds to learning means. Here, FIG.
3 is a time chart illustrating the operation of each unit of FIG.

That is, according to the fuel injection device of this embodiment,
As shown in FIG. 5, the rail pressure control executed separately from the charging control by the microcomputer 46 drives the PCV 26 to close the PCV 26 by the valve drive signal Sv for the energization time longer than the allowable time Tmax (time t1 to t2). ).

When the valve closing drive is completed and the power supply to the PCV 26 is cut off (S110-YES), a flyback current flows due to the inductance of the PCV 26, and the capacitors C1 and C2 are charged (time t2 to t3). ). Then, when the charging of the capacitors C1 and C2 by the flyback current at the time of the valve closing drive ends (the standby time Tw elapses) (S120; time t3), the voltages Vc1 and VC2 across the capacitors C1 and C2 and the battery voltage Vb are reduced. Perform detection.
At this time, if the voltage between both ends of the capacitors C1 and C2 does not reach the full charge (118V), the valve drive signal Sv is supplied by the flyback current of the PCV 26 for the conduction time Ton such that the capacitors C1 and C2 are fully charged. Is output to energize the PCV 26. However, the energization time Ton is P
If the time exceeds the allowable time Tmax during which the CV 26 is not opened, the energization time Ton is limited to the allowable time Tmax (S
130 to S190; time t3 to t4).

Thereafter, when the set energization time Ton has elapsed and the current path of the PCV 26 has been cut off, a flyback current flows and the capacitors C1 and C2 are charged (time t4 to t5). When the charging of the capacitors C1 and C2 by the boost switching ends (the standby time Toff elapses) (S200; time t5), the capacitors C1 and C2 are again turned on.
Of the two terminals Vc1 and Vc2 and the battery voltage Vb, and if the capacitors C1 and C2 have not reached full charge, step-up switching is repeatedly performed (S150 to S2).
40; times t5 to t6). As a result, capacitors C1,
When C2 reaches full charge, the charge control is terminated (S15).
0-YES; time t6).

Thereafter, in the microcomputer 46, when the fuel injection control, which is executed separately from the charge control, executes the pilot injection (time t7), the transistor Q2n is driven by the injection signal Sjn to control the solenoid valve Ln. The current path is conducted, and the transistor Q31 is driven by the selection signal Sr1 to discharge the capacitor C1. Thereby, the solenoid valve L
n, a peak current flows immediately after the start of the pilot injection, and after the disappearance of the peak current due to the end of the discharge of the capacitor C1 until the end of the pilot injection (that is, while the transistor Q2n is driven). The constant current supplied from the circuit 54 flows.

Subsequently, when the main injection is executed (time t8), the same transistor Q2n as that during the pilot injection is driven by the injection signal Sjn to make the current path of the solenoid valve Ln conductive, and the transistor Q2n is selected by the selection signal Sr2. Driving Q32 discharges the capacitor C2. As a result, a peak current flows through the solenoid valve Ln immediately after the start of the main injection, similarly to the pilot injection, and the capacitor C2
The constant current supplied from the constant current circuit 54 flows until the main injection ends (ie, while the transistor Q2n is driven) even after the peak current disappears due to the end of the discharge.

When the internal pressure of the common rail 6 decreases due to this fuel injection control, the PCV 26
Is driven, and thereafter the same control as described above is repeatedly executed. When the battery voltage Vb decreases, even if the detected difference voltage ΔV is the same, as is clear from the setting table shown in [Table 1], the energizing time Ton during the boost switching is longer. Will be set.

As described above, in the present embodiment, the energizing time Ton to the PCV 26 during the step-up switching is
Is set according to the difference voltage ΔV between the detection voltage Vc of the capacitors C1 and C2 and the voltage at the time of full charge, that is, the shortage of the charge amount. Therefore, according to the present embodiment, the voltage Vc across the capacitors C1 and C2 when full charge is reached.
1, Vc2 can be made constant with high accuracy. As a result, at the start of the injection of the injector INJn, the energy supplied from the capacitors C1 and C2 for flowing the peak current is always constant, that is, the injection characteristics of the injector INJn can be made constant. It can be carried out.

Further, in this embodiment, the setting of the energizing time Ton during the step-up switching is performed by searching a setting map using the difference voltage ΔV as a reference value. Therefore, according to the present embodiment, the energization time Ton is
The settings can be made quickly without performing complicated calculations, and the amount of processing in the microcomputer 46 can be reduced.

Further, in this embodiment, the battery voltage Vb
In addition to switching the setting map to be used in accordance with, the learning process of rewriting the setting map is performed based on the state of charge of the capacitors C1 and C2 after the boost switching. For this reason, even if the relationship between the energization time Ton and the amount of charge to the capacitors C1 and C2 changes due to aging of the apparatus, changes in the operating environment, and the like, the optimal energization time Ton is appropriately set accordingly. Since the setting map is rewritten as described above, highly accurate charging control suitable for the characteristics of each device can be performed over a long period of time.

As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and can be implemented in various modes. For example, in the above embodiment, after setting the energizing time Ton for the boost switching, the energizing time Ton is compared with the allowable time Tmax, and the energizing time Ton is limited so that the PCV 26 does not perform the valve closing operation by the boost switching. However, the processing of S170 and S180 may be omitted by limiting the value of the setting table to the allowable time Tmax or less in advance.

In the above-described embodiment, when the boost switching is performed, the setting map is rewritten every time, but may be performed periodically. In addition, the setting map may be rewritten based on the average value of the correction values in a plurality of times in the past. Furthermore, in the above-described embodiment, the standby time Toff after the boost switching is set to a constant value. However, similarly to the energization time Ton, the standby time Toff may be set based on a table using the difference voltage ΔV and the battery voltage Vb as parameters. Good.

Further, in the above embodiment, the capacitor C
The PCV 26 is used to generate a flyback current for charging the C1 and C2.
Any solenoid valve may be used as long as it has a non-operation period in which boost switching can be performed, such as the solenoid valve Ln of Jn.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a common rail type fuel injection device of an embodiment.

FIG. 2 is a sectional view illustrating a configuration of a supply pump unit.

FIG. 3 is a circuit diagram illustrating a configuration of a drive circuit.

FIG. 4 is a flowchart illustrating charging control performed by a microcomputer.

FIG. 5 is a timing chart illustrating the operation of each part of the drive circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 4 ... Branch pipe 6 ... Common rail 8 ... Supply pump unit 10 ... Electronic control unit (ECU) 14 ... Crankshaft 16 ... Drive shaft 18 ... Cam 20 ... Plunger 22 ... Pressurizing chamber 24 ... Cylinder 28 ... Fuel tank 30 ... Feed pump 32 ... cylinder discrimination sensor 3
4 ... Valve element 36 ... Spring 38 ... Electromagnetic solenoid 40 ...
Fuel supply pipe 42 Check valve 44 Drive circuit 46 Microcomputer 48 Crank angle sensor 50 Accelerator opening sensor 54 Constant current circuit 56, 58, 60 Voltage dividing circuit E Engine INJ1-6 Injector L1
~ 6 ... Solenoid valves C1, C2 ... Capacitors R11, R12, R21, R22,
R31, R32: resistors D11, D12, D21, D22, D31 to D34: diodes Q10, Q21 to Q26, Q31, Q32: transistors

Claims (4)

[Claims] 1. An electromagnetic valve that operates by continuous energization for an allowable time or longer, a switching element that communicates and shuts off an energizing path to the electromagnetic valve, and when the energizing path to the electromagnetic valve is shut off by the switching element. Charging means for charging generated flyback energy; charging amount detecting means for detecting an energy charging amount of the charging means; and an energy charging amount of the charging means being insufficient.
During the non-operating period of the solenoid valve, switching control means for intermittently controlling the switching element within a range in which energization of the solenoid valve does not exceed the permissible time, comprising: In an injector driving device that supplies an electromagnetic valve of the injector when the injector is opened, an energization time setting that sets an energization time of the electromagnetic valve in control of the switching control unit based on a detection result of the charge amount detection unit. An injector driving device comprising means. 2. The energization time setting means includes a setting map representing a relationship between an energization time of the solenoid valve and an amount of energy charged to the charging means when the energization is cut off, and the accumulation amount detection means. The injector drive device according to claim 1, wherein the energization time of the solenoid valve is set by searching the setting map by using a shortage of the energy charge amount obtained from the detection result of (i) as a reference value. 3. The injector driving device according to claim 2, wherein each time an energizing path to the solenoid valve is interrupted under the control of the switching control means, the charging means is provided with flyback energy generated by the interruption. An injector drive device comprising: a learning unit that calculates charged energy from a detection result of the charge amount detection unit and rewrites the setting map based on the calculated value. 4. The injector driving device according to claim 2, further comprising a voltage detection unit that detects a power supply voltage of the solenoid valve, wherein the energization time setting unit performs a plurality of settings corresponding to the power supply voltage. An injector driving device, comprising: a setting map to be used in accordance with a detection result of the voltage detecting means.