JPH08218927A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

PURPOSE: To prevent deterioration of an inner circuit by discharging a charge which is accumulated in a condenser when it is detected that a power supply switch is tuned off. CONSTITUTION: In case where a key switch SW is turned off, current-carrying is carried out to the electromagnetic solenoids L1 to L6 of an injector in a fuel injection cylinder for the invalid injection time of the injector, and thereby, a charge which is accumulated in a condenser C is discharged through the solenoids L1 to L6, and then a main relay 18 is turned off after passing a constant time. Even if the key switch SW is turned off, the charge can be surely discharged before power supply voltage of a high voltage monitor circuit 22 is reduced. As a result, power supply voltage in the ECU 6 is reduced while accumulating the charge having a high voltage in the condenser C, and voltage which is higher than the power sully voltage is inputted in the monitor circuit 22 so as to prevent deterioration of an inner element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for an internal combustion engine, which controls an electromagnetic solenoid provided in a fuel injection valve to control the fuel injection amount and injection timing to the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as a fuel injection valve for injecting and supplying fuel to an internal combustion engine, an electromagnetic valve which is provided with an electromagnetic solenoid and which is opened by energizing the electromagnetic solenoid has been used. A drive circuit for opening such a fuel injection valve is, for example, a special circuit for opening the fuel injection valve as soon as energization of the electromagnetic solenoid is started so that fuel can be injected and supplied to the internal combustion engine. Kaihei 6-101552
As disclosed in the publication, a capacitor is charged in advance to a high voltage higher than the power supply voltage by using a booster circuit including a booster coil, and the capacitor is charged when the fuel injection valve is opened. By discharging the electric charge through the electromagnetic solenoid, a large current (valve opening current) is made to flow through the electromagnetic solenoid to quickly open the fuel injection valve, and then a constant current is applied to the electromagnetic solenoid using a constant current circuit. It is known that a (holding current) is made to flow to maintain the open state of the fuel injection valve.

Further, in this type of apparatus, the valve opening timing and valve opening time of the fuel injection valve are calculated according to the operating state of the internal combustion engine, and the electromagnetic solenoid energization timing and energization time are calculated according to the calculation results. Although controlled, in order to always stably open the fuel injection valve at the start of energization of the electromagnetic solenoid, it is necessary to charge the capacitor to a constant high voltage. Therefore, in the past, the booster circuit is operated while monitoring the charging voltage of the capacitor during the period when the electromagnetic solenoid is not energized and fuel injection is not performed, and the booster circuit operates when the charging voltage reaches a certain high voltage. Is stopped to charge the capacitor to a constant high voltage before opening the fuel injection valve.

[0004]

By the way, in such a conventional fuel injection control device, since the capacitor is charged with a high voltage during the period in which fuel injection is not performed,
The power supply to the device may be cut off when the capacitor is charged with a high voltage. In this case, since the high voltage charged in the capacitor is applied to the internal circuit of the control device, there is a problem that the internal circuit, particularly the monitor circuit that monitors the charging voltage of the capacitor malfunctions or deteriorates. there were.

That is, since the monitor circuit detects the charging voltage of the capacitor, the charging voltage is usually divided by a resistor or the like so that the charging voltage is lower than the power supply voltage of the monitoring circuit. The value is converted into a value and the divided voltage is input to the monitor circuit.However, when the power supply to the control device is cut off and the power supply voltage in the control device drops, the voltage input to the monitor circuit is reduced. The piezo voltage becomes higher than the power supply voltage of the monitor circuit, the monitor circuit malfunctions, an overcurrent flows in the internal circuit, and the circuit element may deteriorate. When the monitor circuit is composed of an IC, application of a divided voltage higher than the power supply voltage causes a parasitic thyristor formed at the input terminal of the IC to conduct, resulting in an excessive current between the power supply and ground of the IC. The so-called latch-up may occur, which may deteriorate the IC.

The present invention has been made in view of the above problems, and a fuel injection control device for an internal combustion engine, in which a capacitor is charged with a high voltage higher than a power supply voltage and the fuel injection valve is opened at the high voltage. In order to prevent the internal circuit from being deteriorated due to the high voltage charged in the capacitor when the power supply to the device is cut off.

[0007]

The invention according to claim 1 made in order to achieve the above object is provided with an electromagnetic solenoid as shown in FIG. 1, and the valve is opened by energizing the electromagnetic solenoid. Fuel injection valve for injecting fuel into the internal combustion engine, a switching element provided in series in the current supply path of the electromagnetic solenoid, a capacitor for storing charge, and a charge for boosting the power supply voltage to charge the capacitor. And a circuit, when the switching element is turned on,
A valve opening current supply means for causing a valve opening current to flow to the electromagnetic solenoid by the electric charge accumulated in the capacitor to quickly open the fuel injection valve, and a predetermined holding in the electromagnetic solenoid when the switching element is turned on. A holding current supply means for supplying an electric current to hold the fuel injection valve in an open state and a valve opening time and a valve opening time of the fuel injection valve are calculated according to an operating state of the internal combustion engine, and the calculation is performed. Fuel injection control means for turning on the switching element according to the result to open the fuel injection valve, voltage detection means for detecting the charging voltage of the capacitor, and voltage detection means for turning off the switching element The charging circuit is driven until the charging voltage of the capacitor detected in step 2 reaches a predetermined voltage higher than the power supply voltage, and the capacitor is charged with electric charge capable of supplying the valve opening current. And a charging control means for,
In a fuel injection control device for an internal combustion engine which operates by receiving power supply from the outside when the power switch is turned on, a power interruption detection means for detecting that the power switch is turned off,
Discharging means for discharging the electric charge accumulated in the capacitor when the power cutoff detecting means detects that the power switch is turned off.

The invention described in claim 2 is the same as claim 1.
In the fuel injection control device as described in above,
The switching element is turned on for a predetermined invalid injection time during which the fuel injection valve does not open to discharge the electric charge accumulated in the capacitor.

Next, the invention according to claim 3 is the fuel injection control device according to claim 2, wherein a power supply path for directly connecting an external power source and the device is formed when the power switch is turned on. A relay switch that holds the power supply path even after the power switch is turned off, and a power supply that shuts off the power supply path by turning off the relay switch after the discharging means discharges the charges accumulated in the capacitor. And a blocking means.

On the other hand, the invention described in claim 4 is the same as claim 1.
In the fuel injection control device as described in above,
The capacitor comprises a discharging switching element that short-circuits both ends of the capacitor to discharge electric charge, and the power interruption detection means monitors the power supply voltage inside the device, and when the power supply voltage drops to a predetermined voltage, the discharge It is characterized by turning on the switching element.

[0011]

In the fuel injection control device according to the present invention configured as described above, the fuel injection control means causes the fuel injection control means to open and open the fuel injection valve in accordance with the operating state of the internal combustion engine. The valve timing is calculated, and the switching element provided in the current path of the electromagnetic solenoid of the fuel injection valve is turned on according to the calculation result. Then, in the electromagnetic solenoid,
The valve-opening current flows through the capacitor of the valve-opening current supply means due to the charge precharged, the fuel injection valve opens quickly, and then the holding current supply means supplies a predetermined holding current to the electromagnetic solenoid. Thus, the open state of the fuel injection valve is maintained. Then, when the fuel injection control means turns off the switching element, the current path of the electromagnetic solenoid is cut off and the fuel injection is closed.

Further, voltage detecting means for detecting the charging voltage is connected to the capacitor of the valve opening current supply means,
When the switching element is turned off, the charging control means drives the charging circuit until the charging voltage of the capacitor detected by the voltage detecting means reaches a predetermined voltage higher than the power supply voltage, thereby opening the valve opening current to the capacitor. The charge that can be supplied is charged. Therefore, immediately after the fuel injection control means turns on the switching element, a constant valve opening current flows through the electromagnetic solenoid, and the fuel injection valve always opens at a stable speed.

By the way, the fuel injection control device of the present invention is
When the power switch is turned on, it operates by receiving power from the outside, so when the power switch is turned off and the internal power supply voltage drops, the above series of fuel injection control is terminated. When a high voltage is charged in the capacitor of, the high voltage remains applied to the internal circuit, especially to the voltage detection means for detecting the charging voltage of the capacitor, and the internal voltage detection means, etc. The circuit malfunctions and deteriorates.

Therefore, in the present invention, a power cutoff detecting means for detecting that the power switch is turned off is provided, and when the power cutoff detecting means detects that the power switch is turned off, the discharging means detects the capacitor. It is designed to discharge the electric charge accumulated in. Therefore, according to the fuel injection control device of the first aspect, when the power switch is turned off,
Even if the capacitor is charged with a high voltage, the charge can be quickly discharged to prevent the internal circuit from malfunctioning or deteriorating due to the high voltage.

Next, in the fuel injection control device according to the second aspect of the invention, the discharging means turns on the switching element for energizing the electromagnetic solenoid for a predetermined invalid injection time during which the fuel injection valve does not open. The electric charge accumulated in the capacitor is discharged through the electromagnetic solenoid.

Therefore, the fuel injection control device according to the second aspect can be realized without providing a special circuit for discharging the electric charge accumulated in the capacitor. By the way, when the electric charge accumulated in the capacitor is discharged through the electromagnetic solenoid of the fuel injection valve when the power switch is turned off in this way, the electromagnetic solenoid has a predetermined inductance, and therefore the discharge takes some time. It takes. If the time required for this discharge is longer than the time required for the power supply voltage inside the device to drop after the power switch is turned off, even if the electric charge of the capacitor is discharged by the discharging means, the internal circuit of the voltage detecting means, etc. Is applied with a high voltage higher than the power supply voltage, which may have an adverse effect such as malfunction.

Therefore, in the fuel injection control device according to claim 3, in addition to the device according to claim 2, a power supply path for directly supplying power from an external power supply to the device when the power switch is turned on. When a power switch is turned off, the power cutoff means discharges the electric charge accumulated in the capacitor, and then the relay switch is turned off to disconnect the power supply path from the external power source. I'm trying to shut it off.

Therefore, according to the fuel injection control device of the third aspect, when the electric charge accumulated in the capacitor is discharged through the electromagnetic solenoid of the fuel injection valve when the power switch is turned off, the discharge is performed. Even when it takes a certain amount of time, it is possible to reliably prevent the internal circuit from malfunctioning or deteriorating due to the charges accumulated in the capacitor.

On the other hand, in the fuel injection control device according to the fourth aspect, the discharging means is composed of a discharging switching element which short-circuits both ends of the capacitor to directly discharge the electric charge. The power supply voltage inside the device is monitored, and the discharge switching element is turned on when the power supply voltage drops to a predetermined voltage.

As a result, according to the fuel injection control device of the fourth aspect, although a dedicated switching element for discharging the electric charge accumulated in the capacitor is required, the power switch is turned off and the inside of the device is turned off. When the power supply voltage starts to drop, the electric charge accumulated in the capacitor can be quickly discharged, and malfunction of the internal circuit due to the electric charge accumulated in the capacitor can be surely prevented.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 2 is a schematic configuration diagram showing the overall configuration of the fuel injection control device of the embodiment. As shown in FIG. 2, the fuel injection control device 1 of the present embodiment includes an electromagnetic fuel injection valve (injector) 3 that supplies fuel to each cylinder of the diesel engine 2 (6 cylinders in this embodiment). , A pressure accumulating chamber (common rail) 4 for accumulating high-pressure fuel to be supplied to the injector 3, a fuel supply pump 5 for pumping high-pressure fuel to the common rail 4, and an electronic control device (EC
U) 6 and.

Under the control of the ECU 6, the fuel supply pump 5 sucks the fuel stored in the fuel tank 10 through the low pressure pump 11 and pressurizes it to a high pressure inside itself, and the pressurized high pressure fuel is supplied. Is pressure-fed to the common rail 4 via the supply pipe 12. Each injector 3 is connected to a common rail 4 that stores high-pressure fuel by a pipe 13. When the electromagnetic solenoid is energized by the ECU 6, the solenoid valve 14 opens and the common rail 4 accumulates pressure. High-pressure fuel is injected into the combustion chamber of each cylinder of the diesel engine 2.

Next, the ECU 6 as shown in FIG. 3, the electromagnetic solenoids L1, L2, ... L6 of these injectors 3 respectively.
An injector drive circuit 20 for injecting and supplying fuel from each injector 3 to each cylinder of the diesel engine 2 by energizing (subscripts 1, 2, ... 6 represent cylinders), and fuel supply for driving the fuel supply pump 5 A pump drive circuit 25,
By driving and controlling these respective drive circuits 20 and 25 according to a preset control program, the fuel injection timing, the fuel injection amount, and the fuel pressure (common rail pressure) in the common rail 4 to each cylinder of the diesel engine 2 are controlled. , A well-known microcomputer (hereinafter simply referred to as CPU) 30 including a CPU, a ROM, a RAM, and the like.

It should be noted that, as shown in FIG.
A rotation angle sensor 7 that generates a pulse signal for each predetermined rotation angle of the diesel engine 2, an accelerator opening sensor 8 that detects an accelerator pedal depression amount (accelerator opening) ACC, and a common rail pressure sensor 9 that detects a common rail pressure.
The detection signals from the same are input.

Further, the ECU 6 is the diesel engine 2
When the key switch SW is turned on, power is supplied from the battery 16 as an external power source. As shown in FIG. 3, the internal power supply line is turned on by the main relay drive circuit 34 when the key switch SW is turned on. It is connected to the battery 16 via the relay switch (main relay) 18, and even if the key switch SW is turned off,
Until the main relay drive circuit 34 turns off the main relay 18 in accordance with the off command from the CPU 30, the battery 1
Power is supplied from 6 to the power line.

Then, the battery voltage is directly supplied to the injector drive circuit 20 and the fuel supply pump drive circuit 25 from this power supply line, and the power supply voltage input through the power supply line is supplied to the CPU 30 by a predetermined constant voltage ( A constant voltage is supplied via a constant voltage power supply circuit 32 that converts the voltage to, for example, 5V.

Next, the injector drive circuit 20 has a C
The NPN type transistors T1, T2, ... Immediately after forming the current path (in other words, immediately after the transistors T1 to T6 are turned on) with respect to the electromagnetic solenoids L1 to L6 connected to the other ends of the electromagnetic solenoids L1 to L6 and having current paths formed by the transistors T1 to T6. A valve opening current larger than the holding current through the diode D1,
A valve opening current supply circuit 23 as a valve opening current supply means for promptly opening the solenoid valve 14 is connected to the other end of each solenoid solenoid L1 to L6, and each transistor T1 is connected.
~ Electromagnetic solenoid L1 whose current path is formed by T6
To L6, a holding current supply circuit 24 as a holding current supply means for supplying a predetermined constant current (holding current) to the L6 via the diode D2 to hold the open state of the solenoid valve 14.
And are provided.

The valve-opening current supply circuit 23 has one end grounded and the other end connected to the anode side of the diode D1 so that the electric charge accumulated in advance immediately after the transistors T1 to T6 are turned on is transferred to the electromagnetic solenoids L1 to T6. One end of the primary winding is provided with a charge storage capacitor C that discharges via L6, and as a charging circuit for charging the capacitor C with a predetermined high voltage higher than the power supply voltage when the transistors T1 to T6 are turned off. The other end of the primary winding of the transformer L0 is grounded at a high frequency by performing high-speed switching by the boosting transformer L0 to which the battery voltage is applied and the high-frequency drive pulse input from the CPU 30.
By outputting the high voltage generated in the secondary winding of the transformer L0 and the high voltage generated in the secondary winding of the transformer L0 to the capacitor C, the diode D0 that charges the capacitor C is generated. I have it.

In order to detect the charging voltage (potential at point A shown in FIG. 3) of the capacitor C, a series circuit composed of two resistors R1 and R2 for voltage division is connected in parallel. The divided voltage is input to the high voltage monitor circuit 22. The high voltage monitor circuit 22 monitors the charging voltage when the capacitor C is charged, and when the charging voltage reaches a predetermined voltage, notifies the CPU 30 of that fact and switches the transistor TO. (In other words, the charging of the capacitor C) is terminated, and corresponds to the voltage detecting means of the present invention.

In the fuel injection control device of the present embodiment having such a configuration, the CPU 30 determines the combustion state of the diesel engine 2 based on the detection signals from the rotation angle sensor 7 and the accelerator opening sensor 8. The target common rail pressure for realizing the optimum fuel injection pressure is obtained in accordance with the above, and the common rail pressure actually detected by the common rail pressure sensor 9 is passed through the fuel supply pump drive circuit 25 so as to become the target common rail pressure. To control the fuel supply pump 5 by performing common rail pressure control,
The fuel injection timing and the fuel injection amount are obtained for each cylinder of the diesel engine 2, and the fuel injection control is executed to control the energization of the electromagnetic solenoids L1 to L6 of the injector 3 provided in each cylinder.

Then, of the control processing executed by the CPU 30 as described above, the fuel injection control processing, which is the main processing relating to the present invention, will be described with reference to the flowchart shown in FIG. As shown in FIG. 4, when this process is started, first in S110 (S represents a step), the output of a high frequency on / off signal to the transistor To in the injector drive circuit 20 is started, and the capacitor is turned on. Start charging to C. Then, in subsequent S120, by determining whether or not the high voltage monitor circuit 22 has detected that the charging voltage of the capacitor C has reached a predetermined high voltage higher than the power supply voltage,
Waiting for the charging voltage of the capacitor C to reach a predetermined high voltage, and when reaching the predetermined high voltage, the process proceeds to S130 to stop the output of the on / off signal to the transistor To,
The charging of the capacitor C is completed.

Next, at S140, based on the detection signals from the rotation angle sensor 7, the accelerator opening sensor 8, etc., the operating state of the diesel engine 2, that is, the engine speed N.
E and accelerator opening ACC are detected. And then S1
At 50, by determining whether or not the battery voltage is applied from the key switch SW to the main relay drive circuit 34, it is determined whether or not the key switch SW is in the on state, and the key switch SW is in the on state. If there is, S1
60, and if the key switch SW is in the off state,
The process proceeds to S190.

Next, at S160, the cylinder z (any of z: 1 to 6) in which fuel should be injected next to the diesel engine 2 based on the engine speed NE, accelerator opening ACC, etc. detected at S140. Injection amount KQ for
And the basic injection start timing KT. And then S
In 170, based on the relationship between the basic injection amount KQ and the basic injection start timing KT obtained in S160 and the injector energization time TT and the actual injection amount Q shown in FIG.
Energization start time KX at which the electromagnetic solenoid should actually be energized
And energization time KY are calculated.

That is, the injector 3 starts fuel injection by moving the electromagnetic valve 14 to the open position by energizing the electromagnetic solenoid. After the energization is started, the fuel injection from the injector 3 is started. Response delay (ineffective injection time: 0.3 msec. In this embodiment)
Therefore, in S170, based on the relationship between the injector energization time TT and the actual injection amount Q, the electromagnetic solenoid for injecting the fuel from the injector 3 by the basic injection amount KQ from the calculated basic injection start timing KT is determined. The energization start timing KX and the energization time KY are calculated.

Then, in step S180, the transistor Tz connected to the electromagnetic solenoid Lz of the cylinder z to be fuel-injected is turned on to energize the electromagnetic solenoid Lz according to the calculated energization start timing KX and energization time KY. By the injector 3 provided in the fuel injection cylinder z.
Is driven, and the process proceeds to S110 again.

Note that due to this energization, the high-voltage electric charge accumulated in the capacitor C is discharged via the electromagnetic solenoid Lz of the fuel injection cylinder z immediately after the start of energization.
The injector 3 promptly opens the valve to start fuel injection, and thereafter, the holding current supply circuit 24 supplies a constant current for maintaining the valve open state to the electromagnetic solenoid Lz, so that the electromagnetic solenoid Lz is energized. , The injector 3 is kept open, fuel injection continues, and the energization time K continues.
When Y has passed and the energization of the electromagnetic solenoid Lz is cut off, the injector 3 is closed and the fuel injection ends.

On the other hand, in S190 which is executed when the key switch SW is in the off state, a preset energization start timing LX is set as the energization start timing and the energization time for the electromagnetic solenoid Lz of the cylinder z to be next fuel-injected. And energization time LY are set. It should be noted that this energization time LY is set in advance to an invalid injection time (0.3 msec.) Or less based on the relationship between the injector energization time TT and the actual injection amount Q shown in FIG. 5 so that the actual injection amount becomes 0. Has been done.

Then, in S200, the transistor Tz connected to the electromagnetic solenoid Lz of the fuel injection cylinder z is turned on based on the energization start timing LX and the energization time LX set in S190 to energize the electromagnetic solenoid Lz. As a result, the electric charge accumulated in the capacitor C is discharged via the electromagnetic solenoid Lz. Then, in S210, it is determined whether or not a predetermined time (for example, 1 second) has elapsed after detecting the off state of the key switch SW, thereby waiting for the predetermined time after the key switch SW is turned off and waiting for the predetermined time. After a lapse of time, the process proceeds to S220 to output an off command for the main relay 18 to the main relay drive circuit 34 to turn off the main relay 18, and the process ends.

As described above, in the fuel injection control device of this embodiment, when the fuel injection is executed for a certain cylinder when the key switch SW is in the ON state,
The high voltage monitor circuit 22 is configured to charge the capacitor C until it detects that the charging voltage of the capacitor C has reached a predetermined high voltage. Therefore, as shown in FIG. 6, the next fuel injection cylinder (nth cylinder, n + 1th cylinder)
When the injector 3 of a cylinder is driven, the energizing current flowing through the electromagnetic solenoid becomes a large current immediately after the energization is started, so that the injector 3 is quickly opened and fuel injection is executed.

When the key switch SW is turned off, the electromagnetic solenoid of the injector 3 of the next fuel injection cylinder (n + 2 cylinder) is energized for the invalid injection time of the injector 3. , The electric charge accumulated in the capacitor C is discharged through the electromagnetic solenoid, and after a certain time has passed, the main relay 1
I'm trying to turn off 8.

Therefore, even if the key switch SW is turned off, before the power supply voltage of the high voltage monitor circuit 22 drops,
The electric charge accumulated in the capacitor C can be surely discharged, and as in the conventional case, the power supply voltage in the ECU 6 decreases while the high voltage electric charge is accumulated in the capacitor C, and the high voltage monitor circuit 22 There is no possibility that a voltage higher than the power supply voltage is input and the internal elements are deteriorated. Therefore, according to the present embodiment, it is possible to prevent deterioration of the high voltage monitor circuit 22, extend its life, and ensure the reliability of the device.

It should be noted that the main relay 18 is turned off after a certain period of time has passed after the discharge of the capacitor C. The main relay 18 is turned off and the power supply to the ECU 6 is cut off. This is to enable the processing of (1) to be performed, and to prevent malfunction due to the high voltage charged in the capacitor C,
After discharging the capacitor C, the main relay 18 may be turned off as it is.

Here, in the above embodiment, the key switch S
When W is turned off, the electric charge accumulated in the capacitor C is discharged through the electromagnetic solenoid of the injector 3 of the cylinder to which fuel should originally be injected and supplied. However, for example, the key switch SW is An injector for a specific preset cylinder may be used as the injector for discharging the electric charge accumulated in the capacitor C when it is turned off, and the transistor T1 for all cylinders may be used.
It is also possible to turn on T6 to discharge electricity through the electromagnetic solenoids of the injectors of all cylinders.

Further, the fuel injection control device of the above embodiment is
When power is supplied to the ECU 6 via the key switch SW, the power supply voltage inside the ECU 6 (particularly in the high voltage monitor circuit 22) is set after the key switch SW is turned off and before the charge of the capacitor C is discharged. It is configured under the assumption that the power supply voltage will decrease. For example, even when power is supplied to the ECU 6 via the key switch SW, the electric charge of the capacitor C is discharged. In the case where the power supply voltage inside the ECU 6 does not decrease until the time, the power may be supplied to the inside of the ECU 6 via the key switch SW without using the main relay 18.

In the above embodiment, the electric charge of the capacitor C is discharged through the electromagnetic solenoid of the injector 3. However, for example, as shown in FIG. You may make it discharge the electric charge of. That is, FIG. 7 shows the high voltage monitor circuit 2
2 represents an internal configuration of the ECU 6 configured to operate by receiving the constant voltage Vcc generated by the constant voltage power supply circuit 32. In the case of such a device, the capacitor C
The charging side terminal (point A) receives the same constant voltage V CC as the power supply voltage of the high voltage monitor circuit 22, and the constant voltage V CC reaches a predetermined reference voltage V th (for example, 4 V from a steady state (for example, 5 V)).
Even if the discharge circuit 40 is provided to discharge the electric charge accumulated in the capacitor C by judging that the key switch SW is turned off when the voltage drops to V), the point A of the capacitor C is grounded. The same effect as the example can be obtained.

The discharge circuit 40 shown in FIG. 7 receives the divided resistors R11 and R12 for dividing the constant voltage Vcc and the divided voltage by the resistors R11 and R12 at the base, and divides the divided voltage. Is a predetermined voltage or more, and the constant voltage Vcc is the reference voltage V
If th or more, it is on, otherwise it is off,
An NPN-type transistor T11 having a grounded emitter and a base are connected to the collector of the transistor T11, and are also connected to the point A of the capacitor C through a resistor R13 having a high resistance value of 1 MΩ or more, and the collector is 20Ω. It is composed of a grounded emitter NPN type transistor T12 connected to the point A of the capacitor C via a resistor R14 having a low resistance value.

In the discharge circuit 40, as shown in FIG. 8, when the key switch SW is on and the constant voltage Vcc generated by the constant voltage power supply circuit 32 is equal to or higher than the reference voltage Vth, the transistor T11 is turned on. When the transistor T12 is turned on and the transistor T12 is turned off, the point A of the capacitor C is grounded through the transistor T11 and the resistor R13.
Since 13 has a high resistance value of 1 MΩ or more,
Almost no current flows, and charging / discharging of the capacitor C, in other words, control of energization of the injector 3 is executed as usual.

On the other hand, when the key switch SW is turned off and the constant voltage Vcc falls below the reference voltage Vth, the transistor T11 is turned off and the transistor T12 is turned on, and the point A of the capacitor C has a low resistance value with the transistor T12. Resistor R
Since it is grounded via 14, the electric charge accumulated in the capacitor C is quickly discharged (for example, the resistor R14
If Ω and the capacitance of the capacitor C are 20 μF, the discharge is performed with a time constant of 0.4 msec.).

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.
Various aspects can be taken. For example, in the above embodiment, the device for performing the fuel injection control for the 6-cylinder diesel engine has been described. It can be applied to obtain the same effect.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of the present invention.

FIG. 2 is a configuration diagram showing an overall configuration of a fuel injection control device according to an embodiment.

FIG. 3 is an electric circuit diagram showing an internal configuration of an electronic control circuit (ECU) of the embodiment.

FIG. 4 is a flowchart showing a fuel injection control process executed by the CPU of the embodiment.

FIG. 5 is an explanatory diagram showing a relationship between an injector energization time and an actual injection amount of fuel from the injector.

6 is a time chart for explaining the operation of each part of the injector drive system by the combustion injection control process of FIG.

FIG. 7 is an electric circuit diagram showing an internal configuration of an electronic control unit (ECU) of an embodiment provided with a dedicated discharge circuit.

8 is a time chart explaining the operation of each part of the injector drive system in the electronic control unit (ECU) of FIG.

[Explanation of symbols]

1 ... Fuel injection control device 2 ... Diesel engine
3 ... Injector 4 ... Common rail 5 ... Fuel supply pump 7 ... Rotation angle sensor 8 ... Accelerator opening sensor 9 ... Common rail pressure sensor 10 ... Fuel tank 11 ... Low pressure pump 3 ... Injector (fuel injection valve) 14 ... Solenoid valve L1 to L6 … Electromagnetic solenoid 16
... Battery 18 ... Main relay SW ... Key switch 32 ...
Constant voltage power supply circuit 34 ... Main relay drive circuit 20 ... Injector drive circuit T1-T6 ... Transistor (for electromagnetic solenoid energization) 22 ... High voltage monitor circuit 24 ... Holding current supply circuit 25 ... Fuel supply pump drive circuit 23 ... Valve opening current Supply circuit LO ... Transformer TO ... Transistor (for capacitor charging) 40 ... Discharge circuit T12 ... Transistor (for capacitor discharging)

Claims (4)

[Claims] 1. A fuel injection valve comprising an electromagnetic solenoid, which is opened by energizing the electromagnetic solenoid to inject fuel into an internal combustion engine, and a switching element provided in series in a current supply path of the electromagnetic solenoid. And a charge storage capacitor and a charging circuit for charging the capacitor by boosting the power supply voltage, and when the switching element is turned on, a valve opening current is supplied to the electromagnetic solenoid by the charge accumulated in the capacitor. And a valve-opening current supply means for quickly opening the fuel injection valve, and a holding current for holding the fuel injection valve in an open state by supplying a predetermined holding current to the electromagnetic solenoid when the switching element is turned on. The valve opening time and the valve opening timing of the fuel injection valve are calculated according to the current supply means and the operating state of the internal combustion engine, and the switch is opened according to the calculation result. A fuel injection control means for turning on the switching element to open the fuel injection valve, a voltage detection means for detecting the charging voltage of the capacitor, and a voltage detection means when the switching element is off. Charging control means for driving the charging circuit until the charging voltage of the capacitor reaches a predetermined voltage higher than the power supply voltage, and charging the capacitor with electric charge capable of supplying the valve opening current, and externally when the power switch is turned on. In a fuel injection control device for an internal combustion engine, which operates by receiving power supply from a power source, the power source cutoff detecting unit detects that the power source switch is turned off, and the power source shutoff detecting unit detects that the power source switch is turned off. Then, a discharge means for discharging the electric charge accumulated in the capacitor, and a fuel injection control device for an internal combustion engine, characterized in that: . 2. The discharging means turns on the switching element for a predetermined invalid injection time during which the fuel injection valve does not open to discharge the electric charge accumulated in the capacitor. 1. A fuel injection control device for an internal combustion engine according to 1. 3. A relay switch that forms a power supply path that directly connects an external power source and the device when the power switch is turned on, and that holds the power supply path even after the power switch is turned off, and the discharging means is the above-mentioned. 3. The fuel injection for an internal combustion engine according to claim 2, further comprising: a power cutoff unit that cuts off the power supply path by turning off the relay switch after discharging the electric charge accumulated in the capacitor. Control device. 4. The discharging means comprises a discharging switching element that short-circuits both ends of the capacitor to discharge electric charge, and the power cutoff detecting means monitors the power supply voltage inside the device, and the power supply voltage is The fuel injection control device for an internal combustion engine according to claim 1, wherein the discharge switching element is turned on when the voltage drops to a predetermined voltage.