JPH1130147A - Injector driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve flyback energy recovering efficiency by once electrification, in an injector driving device provided with a recovering function of flyback energy to be obtained by solenoid electrification of an injector. SOLUTION: A three-way solenoid valve is in the closed state by energizing force of a spring in a state where a solenoid 47 is in the non-electrification state. Flyback energy to be generated when electrification to the solenoid 47 is finished is accumulated in capacitors 68, 69. A microcomputer 61 turns on MOS transistors 67a to 67d in starting of valve opening of the three-way solenoid valve, supplies energy accumulated in the capacitors 68, 69, and opens the three-way solenoid valve. In the valve opening holding period after valve opening of the three-way solenoid valve, the MOS transistors 67a to 67d are repeatedly turned on and off, and flyback energy is accumulated in the capacitors 68, 69.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injector driving device for recovering flyback energy generated when an injector (electromagnetic fuel injection valve) is driven and using the recovered energy for driving the injector.

[0002]

2. Description of the Related Art In a fuel injection device for an internal combustion engine, there is a need for injecting fuel by opening an injector at a high speed by driving an injector at a high voltage and a large current in order to enhance engine performance. A method has been proposed in which the charged high voltage is discharged when the injector is opened to rapidly raise the current. As a method of charging a capacitor to a high voltage, Japanese Patent Application Laid-Open No. 6-299890 uses flyback energy generated by switching a switching element a plurality of times during a valve closing period of an injector. In other words, a current that does not cause the injector to open during the valve closing period of the injector is supplied to the solenoid of the injector, and flyback energy generated there is recovered. Further, the solenoid of the injector is always energized to all cylinders during the entire period of closing the injector.

[0003]

However, flyback energy recovery efficiency by one energization is not sufficient. In addition, since the solenoid of the injector is constantly energized to all cylinders during the entire period during which the injector is closed, the solenoid (coil) is likely to generate heat. Easy to get high.

Accordingly, an object of the present invention is to make it possible to improve the flyback energy recovery efficiency by one energization in an injector driving device having a function of recovering flyback energy by energizing the solenoid of the injector. In addition, it is possible to suppress the heat generation of the solenoid and the occurrence of malfunction.

[0005]

According to the injector driving device of the first aspect, the first switching element control means turns on the switching element at the start of opening of the injector solenoid valve and turns on the charging means. The stored energy is supplied to the solenoid of the injector solenoid valve to open the injector solenoid valve. Then, the second switching element control means repeatedly turns on and off the switching elements during the valve-open holding period after the injector solenoid valve is opened, and stores flyback energy in the charging means.

As described above, a current higher than the valve closing current value is supplied to the solenoid of the injector solenoid valve during the valve holding period of the injector solenoid valve, and flyback energy generated at the end of driving of the switching element is reduced. The energy collected in the charging means (such as a capacitor) and stored in the charging means (such as a capacitor) at the next drive of the injector solenoid valve can be used.

Therefore, a relatively large current can be supplied to the solenoid of the solenoid valve for the injector during the valve holding period by applying a pulse to the solenoid, so that the flyback which occurs once when the switching element is turned on / off is generated. The energy is increased as compared with the device disclosed in JP-A-6-299890. Therefore, Japanese Patent Application Laid-Open No. 6-29989
The charging means (capacitors and the like) can be fully charged in a short period of time with a smaller number of pulses than the device disclosed in Japanese Patent Publication No. 0, and the efficiency is improved.

Further, as set forth in claim 3, the second switching element control means repeatedly turns the switching element on and off only during a valve-open holding period after the injector solenoid valve is opened. Then, the driving period of the injector solenoid valve is limited to the valve opening period.
Heat generation of the injector solenoid valve can be suppressed lower than that of the device disclosed in Japanese Patent No. 9890. further,
Since the injector solenoid valve is not driven at all times as in the device disclosed in JP-A-6-299890, the probability of malfunction of the injector solenoid valve is reduced.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, the injector drive device of the present invention is embodied as a common rail fuel injection control device (diesel engine fuel injection system). FIG. 1 shows the entire configuration of the common rail fuel injection control device. This device (system) is mounted on an automobile. That is, the present invention is applied to a vehicle-mounted diesel engine.

The present system is provided with a one-cylinder type supply pump (high-pressure pump) 1. The supply pump 1 is provided with a drive shaft 2 which is drivingly connected to a crankshaft 4 of a four-cylinder diesel engine 3. Further, a triangular cam 5 is fixed to the drive shaft 2. Furthermore, a cylinder 6 is provided in the supply pump 1, and a plunger 7 that slides while contacting the cam surface of the cam 5 is arranged in the cylinder 6. The fuel in the tank 10 is sucked into the plunger chamber (pressurizing chamber) 8 in the cylinder 6 via the feed pump (low-pressure pump) 9 by the downward movement of the plunger 7 accompanying the rotation of the cam 5.

A normally open type electromagnetic discharge amount control valve (PCV) 11 is disposed above the cylinder 6.
The discharge amount control valve 11 opens and closes a fuel supply passage from the feed pump 9. That is, the discharge amount control valve 1
1 is provided with a valve body 12, a spring 13, and a solenoid (electromagnetic coil) 14. When the solenoid 14 is energized, the valve body 12 is moved and closed against the urging force of the spring 13 from the open state up to that time. . When the plunger 7 moves upward with the discharge amount control valve 11 closed, the fuel pressurizing operation (pressure feeding operation) is performed in the plunger chamber 8.
The fuel discharge amount can be adjusted by adjusting the closing timing of the discharge amount control valve 11 during this pressurizing operation.

A plunger chamber 8 of the supply pump 1 is connected to a high-pressure accumulating pipe common to each cylinder by a fuel supply pipe 15.
A so-called common rail 16 is connected. A check valve 17 is provided at the end of the fuel supply pipe 15 on the pump side. The check valve 17 allows the supply of fuel from the supply pump 1 side to the common rail 16 side, and the supply pump from the common rail 16 side. The passage of fuel to one side is regulated.

The common rail 16 is connected to injectors (fuel injection valves) 19a, 19b, 19c, and 19d of the respective cylinders of the diesel engine 3 by branch pipes 18. The normally closed type three-way solenoid valves 20a, 20b, 20c,
A high pressure fuel from the common rail 16 can be injected from the injectors 19a to 19d into each cylinder by controlling the three-way solenoid valves 20a to 20d.

FIG. 2 shows injectors 19a, 19b,
19c and 19d are sectional views. As shown in FIG. 2, a valve body sliding hole 22 is provided in a valve casing 21 of the injector.
And a fuel reservoir 23, and a nozzle hole 24 communicating with the fuel reservoir 23 is formed at the tip of the casing 21. The high pressure fuel is supplied to the fuel storage chamber 23 from the common rail 16 via the flow path 25.

The large diameter portion 27 of the nozzle needle 26 is slidably fitted in the valve body sliding hole 22. A connecting portion 28 is provided above the large diameter portion 27 of the nozzle needle 26.
However, a small diameter portion 29 and a valve body 30 are integrally formed at the lower portion, and the nozzle hole 24 is opened and closed by the valve body 30.

A flange 31, a piston pin 32, and a piston 33 are integrally connected to the upper end of the connecting portion 28 of the nozzle needle 26. A compression coil spring 35 is disposed between the flange 31 and the housing 34, and the nozzle needle 26 is normally urged in the valve closing direction (downward in the figure) by the spring force of the compression coil spring 35. ing.

The piston 33 is slidably fitted in a cylinder 36 provided in a housing 34.
A working chamber 37 is formed together with the cylinder 36. A plate body 40 having an orifice 39 is in contact with the high-pressure fuel outlet 38 provided in the upper part of the working chamber 37, and the plate body 40 is pressed by the biasing force of a spring body 41 supported on the upper end surface of the piston 33. Have been.

FIG. 3 is a sectional view showing the detailed configuration of the three-way solenoid valves 20a to 20d. As shown in FIG. 3A, a sliding hole 43 is formed in the valve body 42 of each of the three-way solenoid valves 20a to 20d, and a first valve body 44 is slidable in the sliding hole 43. It is arranged. The first valve body 44 is seated on the first valve seat 46 by the urging force of the spring 45, and slides upward in the drawing by being excited by a solenoid (electromagnetic coil) 47 to be separated from the first valve seat 46. It is configured to be. Further, the valve main body 42 communicates with the sliding hole 43, and a suction hole 48 for sucking high-pressure fuel from the common rail 16, and also communicates with the sliding hole 43 to discharge fuel to the fuel tank 49. And a first connection hole 51 that communicates with the above-mentioned outflow / inlet port 38 (see FIG. 2) via the first valve seat 46.

On the other hand, the first valve body 44 is formed with a sliding hole 53 for slidably fitting the second valve body 52 and a pressure chamber 54 communicating with the sliding hole 53. On the inner wall of the pressure chamber 54, a second valve seat 55 for seating the second valve body 52 is formed. Further, the first valve body 44 has a communication hole 56 that communicates the pressure chamber 54 with the suction hole 48, and the pressure chamber 54 through a gap between the second valve body 52 and the second valve seat 55.
And a second connection hole 57 that communicates with the first connection hole 51.

The operation of the three-way solenoid valves 20a to 20d will be described. As shown in FIG. 3A, when the solenoid 47 is not energized (not energized), the spring 45 is turned off.
The first valve body 44 is seated on the first valve seat 46 by the urging force, and the first connection hole 51 and the discharge hole 50 are shut off.
At this time, the pressure chamber 5 is connected through the suction hole 48 and the communication hole 56.
Since the high-pressure fuel is sucked into the pressure valve 4, the second valve body 52 is pushed upward in the drawing by the working pressure, and the second valve body 52 and the second valve seat 55 are separated from each other. Then, the valve body 52 moves until the upper end of the second valve body 52 comes into contact with the regulating portion 58. Thereby, the suction hole 48 and the first connection hole 51 are communicated through the communication hole 56, the pressure chamber 54, and the second connection hole 57, and high-pressure fuel is supplied to the working chamber 37 in FIG. In such a case, the nozzle needle 26 is pushed down, and the fuel injection is held in a stopped state.

As described above, the three-way solenoid valves 20a to 20d as the injector solenoid valves are closed by the urging force of the spring 45 when the solenoid 47 is not energized.

On the other hand, as shown in FIG.
When the solenoid 47 is excited (when energized), the solenoid 47 pulls up the first valve body 44 against the urging force of the spring 45, and the first valve body 44 and the first valve seat 46 are separated. At this time, the first valve body 44 moves, and the second valve body 52 sits on the second valve seat 55. Thereby, the suction hole 4
8 and the first connection hole 51 are shut off. Further, the first connection hole 51 and the discharge hole 50 communicate with each other, and the working chamber 37 shown in FIG.
From which fuel is discharged. As a result, the nozzle needle 26 is moved in the valve opening direction by the high-pressure fuel supplied through the flow path 25 in FIG. 2, and the fuel injection is performed. That is, when the force in the valve opening direction caused by the pressure of the fuel in the fuel chamber 23 exceeds the sum of the force in the valve closing direction caused by the pressure of the fuel in the working chamber 37 and the urging force of the spring 35 or the like, The nozzle needle 26 moves in the valve opening direction.

As described above, each of the injectors 19a to 19d in this embodiment has the three-way solenoid valves 20a to 20d, and the three-way solenoid valves 20a to 20d are opened by energizing the solenoid 47 of the three-way solenoid valves 20a to 20d. The fuel is injected by moving the nozzle needle 26 (the injectors 19a to 19d open).

In FIG. 1, an electronic control unit (hereinafter, referred to as an electronic control unit)
The ECU 60 is a microcomputer (hereinafter, referred to as an ECU).
The microcomputer 61 includes a crank angle sensor 63, a cylinder discriminating sensor 64, and an accelerator opening sensor 65, which input information on the engine speed and the accelerator opening. Here, the cylinder discrimination sensor 6
4 is a gear 6 fixed to the drive shaft 2 of the pump.
4a, and a pulse signal is generated when the drive shaft 2 passes through the gear 64a as the drive shaft 2 rotates. Then, the microcomputer 61 controls the three-way solenoid valve 20a via the drive circuit 62 so that the optimal injection timing and injection amount are determined according to the engine state determined by these signals.
To 20d.

More specifically, the microcomputer 61 opens and closes the three-way solenoid valves 20a to 20d of the injectors 19a to 19d so as to inject fuel at a timing and an amount corresponding to the operating state of the diesel engine 3 (engine speed and accelerator opening). The fuel in the common rail 16 is injected into each cylinder of the diesel engine 3 under control. Here, in this example, at the time of fuel injection in each cylinder, main injection and pilot injection preceding it are performed. That is, the pilot injection signal P and the main injection signal M are generated as the injector drive signal (injection pulse) in FIG.

Further, a solenoid 14 of the discharge amount control valve 11 is connected to the microcomputer 61 of FIG. 1 via a drive circuit 62, and the opening and closing of the discharge amount control valve 11 is controlled by turning the solenoid 14 on or off. Is available. Further, the microcomputer 61 inputs a common rail pressure detection signal from a common rail pressure sensor 66 provided on the common rail 16 and controls the discharge amount control valve 11 so that the common rail pressure becomes an optimum value according to the accelerator opening and the number of revolutions. To adjust the discharge amount of the supply pump 1.

More specifically, when the diesel engine 3 starts, the cam 5 of the supply pump 1 rotates, and with this rotation, the plunger 7 reciprocates and the fuel from the feed pump 9 is supplied to the supply pump 1. High-pressure fuel is supplied to the common rail 16 through the fuel supply pipe 15, and the fuel is accumulated in the common rail 16. here,
The microcomputer 61 controls the discharge amount of the supply pump 1 so that the common rail pressure detected by the common rail pressure sensor 66 becomes an optimum value according to the accelerator opening and the number of revolutions.

Hereinafter, the microcomputer 61 and the drive circuit 62 will be described.
The ECU 60 will be described. FIG.
0 shows a specific configuration. In brief, a microcomputer 61 for controlling fuel injection, a solenoid (electromagnetic coil) 47 of the three-way solenoid valves 20a to 20d, and MOS transistors 67a, 67b, 6 for energizing the solenoid 47
7c, 67d and transistors 67a, 67b, 6
Capacitors 68 and 69 for storing flyback energy when switching between 7c and 67d are provided. The three-way solenoid valves 20a to 20d of the injector are driven using the stored energy.

The discharge amount control valve 1 is connected to the battery terminal VB.
One solenoid 14 and the MOS transistor 70 are connected in series. The diode D1 and the solenoid 47 of the three-way solenoid valve 20a are connected to the battery terminal VB.
The S transistor (injector driving element) 67a is connected in series, and the diode D1, the solenoid 47 of the three-way solenoid valve 20c, and the MOS transistor (injector driving element) 67c are also connected in series. Similarly, a diode D is connected to the battery terminal VB.
The solenoid 47 of the two- and three-way solenoid valves 20b and the MOS transistor (injector driving element) 67b are connected in series, and the diode D2 and the three-way solenoid valve 20
A solenoid 47d and a MOS transistor (injector drive element) 67d are connected in series. Thus, the MOS transistor 67 as a switching element
a, 67b, 67c, 67d are three-way solenoid valves 20a-2
0d solenoid 47 is connected in series, and one end of this series circuit is connected to a battery terminal VB as a power supply, so that the solenoid 47 is energized when turned on.

Further, connection points a1, a2, a3, a4 between each solenoid 47 and each of the transistors 67a to 67d.
Is connected to a main injection capacitor 68 and a pilot injection capacitor 69 via diodes D3, D4, D5 and D6. Further, the main discharge capacitor 68 is connected to the main discharge MOS transistor 71.
Through the solenoid 47 of each of the three-way solenoid valves 20a to 20d
Are connected in parallel. Similarly, the solenoid 47 of each of the three-way solenoid valves 20a to 20d is connected in parallel to the pilot injection capacitor 69 through the pilot discharge MOS transistor 72.

As described above, the capacitors 68 and 69 as charging means are connected to the solenoids 47 of the three-way solenoid valves 20a to 20d, and supply flyback energy generated when the energization of the solenoids 47 is terminated to the three-way solenoid valve 20a.
-20d can be stored as a driving source.

Voltage dividing resistors 73 and 74 are connected to the main injection capacitor 68, and the connection point b has a potential corresponding to the capacitor voltage. A comparator 75 is connected to the connection point b, where the voltage is compared with a predetermined voltage by the voltage dividing resistors 76 and 77. Then, the voltage of the main injection capacitor 68 is set to a predetermined potential (11 full charge voltage).
8 volts), the output of the comparator 75 goes high. Similarly, voltage dividing resistors 78 and 79 are connected to the pilot injection capacitor 69, and the connection point c has a potential corresponding to the capacitor voltage. A comparator 80 is connected to the connection point c, and the comparator 80 compares the voltage with a predetermined voltage set by the voltage dividing resistors 76 and 77. When the voltage of pilot injection capacitor 69 becomes higher than a predetermined potential (118 volts of the full charge voltage), the output of comparator 80 becomes H level. The output terminals of the comparators 75 and 80 are connected to the microcomputer 61 through the AND gate 81. When both the voltage of the main injection capacitor 68 and the voltage of the pilot injection capacitor 69 become higher than a predetermined voltage (full charge voltage of 118 volts). An H level signal is output to the microcomputer 61. The microcomputer 61 detects whether the voltage of the capacitors 68 and 69 is higher than 118 volts based on the potential of the signal line (the output level of the AND gate 81).

The microcomputer 61 as the first and second switching element control means is provided with the transistors 70 and 6 described above.
The microcomputer 61 is connected to 7a, 67b, 67c, 67d, 71, 72, and controls ON / OFF of each transistor. That is, by turning on the transistor 70, the solenoid 14 is energized and the discharge amount control valve 11 is closed.
Also, transistors 67a to 67a corresponding to each injector
By turning on 67d, the energy of one of the capacitors 68 and 69 is transferred to the three-way solenoid valves 20a to 20d.
Of the injector 1
Fuel can be injected from 9a to 19d. At this time, a capacitor is selected by turning on one of the transistors 71 and 72. That is, from the state where energy is stored in the main injection capacitor 68 and the pilot injection capacitor 69, the main discharge transistor 7
1 with one of the three-way solenoid valves 20a-2
The capacitor voltage is supplied to the 0d solenoid 47 to perform the main fuel injection from the injectors 19a to 19d.
Further, while the pilot discharge transistor 72 is turned on, a capacitor voltage is supplied to the solenoid 47 of any of the three-way solenoid valves 20a to 20d to supply the injector 19a
To 19d to perform pilot injection of fuel.

Here, flyback energy generated when power supply to the solenoid 47 is terminated can be stored in the capacitors 68 and 69 by controlling on / off of the transistors 67a to 67d. That is, the capacitor 68
The energy for the main injection is stored in the condenser 69, and the energy for the pilot injection is stored in the condenser 69.

The solenoid 47 of each of the three-way solenoid valves 20a to 20d is supplied with a constant current (2 amps) for holding the valve open from the battery terminal VB via diodes D1 and D2.

Next, the operation of the thus configured diesel engine fuel injection system will be described. FIG. 5 shows the cam lift of the supply pump 1, the open / closed state of the discharge amount control valve 11, the drive pulse of the discharge amount control valve 11, and the discharge amount control valve 1.
1 solenoid energizing current, each three-way solenoid valve 20a-20d
(Injector drive signal), injector current, pilot charge voltage, main charge voltage, pilot discharge transistor 72 drive signal, and main discharge transistor 71 drive signal.

In FIG. 5, in the fuel suction stroke of the supply pump 1 with the cam lift, the discharge amount control valve 11 installed in the pump 1 is opened to suck fuel from the fuel tank 10. By the subsequent cam lift, the supply pump 1 enters a fuel pressure feeding stroke. In the fuel pumping stroke, the fuel in the pump 1 is raised to a desired fuel pressure by the pumping cam 5. Then, the microcomputer 61 turns on the transistor 70 shown in FIG. 4 at the fuel intake / pumping timing specified by the engine speed or the like (period t1 to t2 in FIG. 5). As a result, the solenoid 14 of the discharge amount control valve 11 is energized, and the discharge amount control valve 11 closes during the period from t1 'to t2' in FIG. As a result, a predetermined amount of pressurized fuel is supplied to the supply pump 1
Is sent to the common rail 16 by pressure.

Further, the microcomputer 61 in FIG. 4 injects fuel from the injectors 19a to 19d in accordance with the engine operating state (engine speed, etc.) when the fuel on the common rail 16 rises to a desired pressure. , And outputs drive signals for the drive transistors 67 a to 67 d of the injector and drive signals for the discharge transistors 71 and 72. In response to this drive signal, the transistors 67a to 67d corresponding to the fuel injection target cylinders are turned on during the period from t3 to t5 and during the period from t6 to t8 in FIG.
Energize the solenoid 47 of the three-way solenoid valve 20a.
〜20d is opened. As a result, the injectors 19a to 19d of the fuel injection target cylinder open, and the pilot and main injection are performed.

The driving process of the injectors 19a to 19d will be described in detail with reference to the flowchart of FIG. This process includes a process of collecting flyback energy generated when driving the injectors 19a to 19d in the capacitors 68 and 69.

First, the pilot injection will be described.
In step 101, the microcomputer 61 selects one of the injectors 1 for pilot injection in the fuel injection target cylinder.
It is determined whether or not it is the valve opening timing of the injectors 9a to 19d (here, the injector 19a for the sake of explanation), and if it is the valve opening timing, the one-shot signal for starting (the pilot injection on Signal) and an ON signal to the pilot discharge transistor 72. At this time, the pilot injection capacitor 69 has been sufficiently charged by the boosting process described later, and the capacitor voltage has reached the full charge voltage of 11
8 volts. Therefore, the transistor 67a and the pilot discharge transistor 72 are connected to t3 in FIG.
, The solenoid 47 of the three-way solenoid valve 20a is energized by the charging voltage of the pilot injection capacitor 69, the three-way solenoid valve 20a is opened, and pilot injection is started. That is, the previously charged capacitor voltage is applied to the solenoid 47 of the three-way solenoid valve 20a, a large current is applied to the solenoid 47, and the injector 19a of the fuel injection target cylinder opens.

Here, it is assumed that the maximum energizing current value of the solenoid 47 at the time of the valve opening start is "I1max" and the minimum energizing current value is "I1min". Note that I1max is, for example, about 8 amps. The on-time of the transistor 67a due to the one-shot signal for starting is within several milliseconds.

Further, immediately after the injector 19a shifts to the valve open state, the transistor 67a and the discharging transistor 72 are turned off (timing t4 in FIG. 5). At the moment of the off state, the first flyback energy is generated. The flyback energy at this time is supplied to the charging capacitor 6 through the diode D3 in FIG.
Collected at 8,69.

Then, the microcomputer 61 executes step 1 in FIG.
At 03, it is determined whether or not the valve opening holding period has been entered. If it is the valve opening holding period, the routine proceeds to step 104. Then, the microcomputer 61 checks in step 104 whether the capacitor voltage is higher than 118 volts. Here, if the capacitor voltage is 118 volts or more, subsequent boosting (charging) processing is not performed.

If the capacitor voltage is less than 118 volts in step 104, the microcomputer 61 proceeds to step 1
At step 05, a drive pulse for boosting is output. With this drive pulse, the transistor 67a corresponding to the fuel injection target cylinder repeatedly turns on and off, and the capacitors 68, 69
Flyback energy is stored. Here, in this on / off control for boosting, the solenoid 4
7, the maximum energizing current value is "I2max" and the minimum energizing current value is "I2min".

That is, in the valve-opening holding period from t4 to t5 in FIG. 5, the transistor 67a is pulse-controlled a plurality of times using the battery voltage VB as a current source. In this pulse control specification, in order to maintain the open state of the three-way solenoid valve 20a (the injector 19a), the minimum value I2min is set to a current value that does not close the three-way solenoid valve 20a. That is, the transition time from the maximum value I2max to the minimum value I2min is managed to determine the pulse-off time. At this time, the pulse-off time is a time corresponding to the solenoid energizing current in a range where the three-way solenoid valve 20a does not close.

Then, the microcomputer 61 executes step 1 in FIG.
At 06 and 107, the capacitor voltage is less than 118 volts, and the valve opening end timing t5 (see FIG. 5)
If not, the step-up (charging) process is continued at step 108.

In this manner, the pulse control is performed a plurality of times during the valve-opening holding period, and the flyback energy at this time is all recovered by the capacitors 68 and 69. Then, the microcomputer 61 determines in step 106 that the capacitor voltage is 11
When the voltage reaches 8 volts, the flow shifts to step 109 to end the above-described step-up (charging) processing. Thus, the output of the pulse drive signal for boosting is stopped, and the transistor 67
a is turned on until the valve opening end time. In addition, the microcomputer 61
In step 107, if it is the valve opening end timing t5, the flow shifts to step 109 to end the boosting (charging) process.

In this way, the pilot injection is performed,
Thereafter, the main injection is performed. The main injection is as follows. The microcomputer 61 determines in step 101 in FIG. 6 whether or not it is the valve opening timing of the injector 19a for the main injection, and if it is the valve opening timing shown by t6 in FIG.
And outputs a one-shot signal for starting (main injection ON signal) to the main discharge transistor 7
1 to output an ON signal. At this time, the main injection capacitor 68 has been sufficiently charged by the boosting process, and the capacitor voltage has reached the full charge voltage of 118 volts. Therefore, when the transistor 67a and the main discharge transistor 71 are turned on, the charging voltage of the main capacitor 68 causes the solenoid 4 of the three-way solenoid valve 20a to turn on.
7 is energized, the three-way solenoid valve 20a is opened, and the main injection is started. Here, it is assumed that the maximum energizing current value of the solenoid 47 at the time of the valve-opening start of the main injection is “I1max” and the minimum energizing current value is “I1min”.

Further, immediately after the injector 19a shifts to the valve opening state, the transistor 67a and the discharging transistor 71 are turned off immediately (timing t7 in FIG. 5). Flyback energy is generated at the moment of the off state. The flyback energy at this time is shown in FIG.
Capacitors 68, 69 through the diode D3 of
Will be collected.

Then, the microcomputer 61 determines in step 103 whether or not the valve opening holding period has been entered. When the valve opening holding period indicated by t7 in FIG. 5 has entered, the process proceeds to step 104, where the capacitor voltage becomes 118 volts or more. After confirming whether or not there is no driving pulse, a driving pulse for boosting is output in step 105. This drive pulse turns on the transistor 67a.
By repeating turning off, flyback energy to the capacitors 68 and 69 is accumulated. In other words, FIG.
In the valve-opening holding period shown in (1), the transistor 67a is pulse-controlled a plurality of times using the battery voltage VB as a current source. This pulse control specification maintains the open state of the three-way solenoid valve 20a (the injector 19a).
The current value is set to 2 min so that the three-way solenoid valve 20a does not close. That is, the transition time from the maximum value I2max to the minimum value I2min is managed to determine the pulse-off time. At this time, the pulse-off time is a time corresponding to the solenoid energizing current in a range where the three-way solenoid valve 20a does not close.

Then, the microcomputer 61 executes step 1 in FIG.
At 06 and 107, the capacitor voltage is less than 118 volts, and the valve opening end timing t8 (see FIG. 5)
If not, the step-up (charging) process is continued at step 108.

The microcomputer 61 determines in step 106,
If the capacitor voltage reaches 118 volts or the valve opening end timing t5 at 107, the process shifts to step 109 to end the boosting (charging) process.

Here, the flyback energy amount will be described. (I) Periods t3 to t4 and t6 to t7 in FIG. 5; the flyback energy Q1 (unit J: joule) of the injector 19a due to the discharge from the capacitor is represented by the solenoid inductance L, the solenoid energizing maximum current I1max, and the energizing minimum current I2min. Is obtained by the following equation. Q1 = 1/2 × L × (I1max−I2min) ² (ii) Period of t4 to t5 and t7 to t8 in FIG. 5; Flyback energy Q2 (unit J: joule) during the valve-opening holding period is a solenoid inductance L, the solenoid energization maximum current I2max, the energization minimum current I2min, and the drive pulse frequency f are obtained by the following equations. Q2 = 1/2 × L × (I2max−I2min) ² × f (iii) Period of t3 to t8 in FIG. 5; since the pilot injection and the main injection are performed twice, the total flyback energy per cylinder Qtotal (Unit J: joule) is as follows. However, I1min = I2min (valve-opening holding current). Qtotal = 2 × (1/2 × L × (I1max−I2min) ² +
1/2 × L × (I2max−I2min) ² × f) This total flyback energy Qtotal is the energy required for the next injector drive.

In this way, the pilot and main injection are performed on the cylinder by the injector 19a corresponding to the current fuel injection cylinder, and thereafter, the pilot and main injection on the next cylinder to be fuel injected are performed similarly. . That is, in the first cylinder, the injector 1
When the driving of the charging capacitors 68 and 6 is completed,
9 is charged with energy required for driving the injector of the second cylinder (for example, the injector 19b). The pilot drive and the main injection of the second cylinder are driven in the same manner as in the first cylinder, and the flyback energy at that time is again stored in the charging capacitors 68 and 69. The energy is used for driving the injector of the third cylinder (for example, the injector 19c).
Hereinafter, similarly, this operation is sequentially repeated for all cylinders.

As described above, the injector driving device according to the present embodiment has the following features. (A) The microcomputer 61 turns on the MOS transistors 67a to 67d at the start of opening of the three-way solenoid valves 20a to 20d in the processing of steps 101 and 102 in FIG. 20
a to 20d are supplied to the solenoids 47 to 20d.
a to 20d are opened, and then, in steps 103 to 1
In the process of step 09, during the valve-open holding period after this valve opening,
The MOS transistors 67a to 67d are repeatedly turned on and off to reduce flyback energy to the capacitors 68 and 69.
To accumulate.

As described above, during the valve holding period of the three-way solenoid valves 20a to 20d, a current higher than the valve closing current value is supplied to the solenoid 47 of the three-way solenoid valves 20a to 20d, and the driving of the MOS transistors 67a to 67d is completed. Flyback energy generated at the time is collected in the capacitors 68 and 69, and the energy stored in the capacitors 68 and 69 at the time of driving the next three-way solenoid valves 20a to 20d can be used. Therefore, the three-way solenoid valves 20a to 20
By supplying a pulse current to the solenoid 47 of d, a relatively large current can be supplied to the solenoid 47. Therefore, the flyback energy generated at one time of ON / OFF of the solenoid 47 is described in Japanese Patent Application Laid-Open No. 6-299890. Increase compared to the device. Therefore, the capacitors 68 and 69 can be fully charged in a short period of time with a smaller number of pulses than the device disclosed in JP-A-6-299890, and an efficient device can be obtained. (B) The microcomputer 61 controls the MOS transistor 67a only during the valve-open holding period after the three-way solenoid valves 20a to 20d are opened.
To 67d are repeatedly turned on and off. As described above, since the driving period of the three-way solenoid valves 20a to 20d is limited to the valve opening period, compared to the apparatus disclosed in JP-A-6-299890,
Heat generation of the three-way solenoid valves 20a to 20d can also be suppressed low. Further, since the three-way solenoid valves 20a to 20d are not always driven as in the apparatus disclosed in Japanese Patent Laid-Open No. 6-299890, the probability of malfunction of the three-way solenoid valves 20a to 20d is reduced.

In addition to the embodiment described above, the following embodiment may be implemented. In the above description, a four-cylinder engine is assumed, but the invention may be embodied as a single-cylinder engine, a two-cylinder engine, a three-cylinder engine, or an engine having five or more cylinders.

Although the present invention has been applied to a system in which pilot injection is performed prior to the main injection, the present invention may be applied to a system in which pilot injection is not performed. In addition, although the arithmetic processing (software) is performed by the microcomputer as the drive control method of the injector, the same processing may be performed by a hardware configuration.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a common rail fuel injection control device according to an embodiment.

FIG. 2 is a sectional view showing a specific configuration of the injector.

FIG. 3 is a sectional view for explaining the operation of the three-way solenoid valve.

FIG. 4 is a specific configuration diagram of an ECU.

FIG. 5 is a timing chart for explaining operation.

FIG. 6 is a flowchart for explaining the operation.

[Explanation of symbols]

19a, 19b, 19c, 19d ... injector, 20
a, 20b, 20c, 20d: three-way solenoid valve, 45: spring, 47: solenoid, 61: microcomputer, 67a,
67b, 67c, 67d ... MOS transistors, 68 ...
Main injection capacitor, 69: pilot injection capacitor, VB: battery terminal.

Continuing from the front page (72) Inventor Mikio Kumano 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Kazutoshi Nishimura 1-1-1, Showa-cho, Kariya City, Aichi Prefecture Inside Denso Corporation

Claims (3)

[Claims] 1. A solenoid valve for an injector, which is closed by an urging force of a spring when a solenoid is not energized, and a solenoid connected to the solenoid of the solenoid valve for an injector in series, and a power supply is connected to one end of the series circuit. Is connected, and a switching element to which the solenoid is energized in the ON operation, and a flyback energy which is connected to the solenoid of the injector solenoid valve and which is generated when the energization of the solenoid is terminated is performed by the injector solenoid valve. Charging means for accumulating as a driving source; and opening of the solenoid valve for the injector when the opening of the solenoid valve for the injector is started to supply the energy stored in the charging means to the solenoid of the solenoid valve to open the solenoid valve. First switching element control means for causing the solenoid valve for injector to open after opening. In the holding period, the injector driving apparatus characterized by repeating the flyback energy on and off the switching element and a second switching element control means for storing in said charging means. 2. The injector drive according to claim 1, wherein the second switching element control means sets the off time of the switching element to a time corresponding to a solenoid energizing current in a range in which the injector solenoid valve does not close. apparatus. 3. The injector driving device according to claim 1, wherein the second switching element control means repeatedly turns the switching element on and off only during a valve-open holding period after the injector solenoid valve is opened. .