JPH1026030A - Energization control device for electric load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably open a solenoid valve even when a source voltage is lowered, in a device to open and close the solenoid valve at a high speed by means of a charge voltage to two capacitors and an output from a DC source. SOLUTION: A fuel injection control device 2 is formed such that capacitors 21 and 22 are charged to a voltage higher than a source voltage by a charge circuit 30, and during pilot injection and main injection of fuel, simultaneously with energization of the solenoid 6 of an injector through a constant current circuit 28, the charge voltages of the capacitors 21 and 22 are respectively applied and the injector is driven at a high speed. During injection of fuel at a time when a source voltage + B is remarkably reduced along with the starting of an engine, simultaneous feeding to a solenoid is effected on the solenoid 6 from the two capacitors 21 and 22. As a result, even when an output a current from the constant current circuit 28 is reduced along with reduction of a power source, the injector is opened to start an engine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric load energization control device suitable for quickly energizing / de-energizing a predetermined electric load, such as a solenoid valve which opens when energized to a solenoid.

[0002]

2. Description of the Related Art Conventionally, for example, in a fuel injection control apparatus for supplying fuel to a diesel engine by opening a fuel injection solenoid valve (hereinafter also referred to as an injector),
Prior to the main injection that supplies the fuel required for the operation of the diesel engine, the pilot injection that injects a small amount of fuel is executed to slow down the initial combustion in the cylinder and reduce noise. Have been.

[0003] Further, in such an apparatus that supplies fuel to a diesel engine by performing two fuel injections, a pilot injection and a main injection, it is necessary to open and close the injector at a high speed in synchronization with the rotation of the internal combustion engine. In addition, it is necessary to shorten the time required for opening the injector as much as possible. Therefore, conventionally, a capacitor is charged to a voltage higher than a power supply voltage from a DC power supply such as an in-vehicle battery, and when the injector is opened, the solenoid is energized by the high voltage charged in the capacitor. By doing so, a large current flows through the solenoid of the injector to quickly open the injector, and two capacitors, one for pilot injection and the other for main injection, are provided as capacitors for storing high voltage for opening the injector. By applying the charging voltage of each capacitor to the injector in order between the pilot injection and the main injection,
Two fuel injections, a pilot injection and a main injection, can be reliably executed.

Further, when the injector is opened and closed sequentially by using the charging voltage to the capacitor, it is sufficient if the injector can be opened for a time corresponding to the fuel injection amount only by the energy stored in the capacitor. In such a case, it is necessary to store an enormous amount of energy in the capacitor, which causes problems such as an increase in the size of the capacitor charging circuit and an increase in the size of the capacitor due to an increase in the capacity and withstand voltage of the capacitor. For this reason,
Conventionally, instead of opening the injector only with the energy stored in the capacitor, when the injector is opened, a current is passed from the DC power supply to the solenoid, so that at the initial stage of opening the injector, a capacitor higher than the power supply voltage is used. At this time, the injector is opened at a high speed with a charging voltage of, and thereafter, a current is supplied from a DC power supply to a solenoid to maintain the injector open state. In other words, in this case, the energy stored in the capacitor need only be the energy required to open the injector, and the energy for maintaining the valve open state can be supplied from the DC power supply, so that the capacitor and the capacitor are charged. This makes it possible to reduce the size of the charging circuit.

[0005]

However, when the solenoid is energized by using the charging voltage to the capacitor and the output voltage from the DC power supply as described above, the output voltage from the DC power supply ( In other words, if the power supply voltage decreases, the amount of current supplied from the DC power supply to the electric load after the start of energization decreases even if the capacitor can be charged to the desired voltage. The diesel engine cannot be operated in some cases.

For example, when a diesel engine is started, particularly at a low temperature, the power supply voltage is significantly reduced by driving the starter motor as compared with a normal time. However, when the power supply voltage is reduced, the injector cannot be opened satisfactorily. Diesel engine cannot be started.

The present invention has been made in view of such a problem, and is intended to reduce the output voltage from a DC power supply such as the above-described fuel injection control device for a diesel engine and the charging voltage of a capacitor charged to a voltage higher than the voltage. Utilizing the power supply to the electric load, and switching between energizing and de-energizing the electric load at high speed, the device equipped with two capacitors ensures that the electric load is energized even if the power supply voltage drops. In order to reliably execute a desired operation by energizing an electric load.

[0008]

According to a first aspect of the present invention, there is provided a power supply control apparatus for an electric load, comprising: a charging circuit for setting a first capacitor and a second capacitor higher than a power supply voltage; Charge to a predetermined voltage. Then, when the electric load is energized, the energization control means turns on the main switching element and conducts the energization path from the DC power supply to the electric load, so that the direct current is controlled via the current control circuit provided in the energization path. The current controlled by the current control circuit flows from the power supply to the electric load.

When the power supply voltage detected by the power supply voltage detection means is equal to or higher than a predetermined determination voltage when the electric load is energized, the power supply control means includes the first switching element and the main switching element. Turn on one of the second switching elements, apply the charging voltage of the first capacitor or the second capacitor to the electric load to the electric load, and when the power supply voltage is lower than the determination voltage, together with the main switching element, The first and second switching elements are simultaneously turned on to apply the charging voltage of the first and second capacitors to the electric load.

That is, in the electric load energization control device according to the present invention, in causing the electric load to execute a predetermined operation by energization, the output voltage (power supply voltage) from the DC power supply is equal to or higher than the determination voltage, and During normal times when a desired current can be supplied to the electric load via the control circuit, a large current flows through the electric load with one of the energy stored in the first capacitor and the energy stored in the second capacitor. When the power supply voltage is lower than the determination voltage and the voltage cannot supply the desired current to the electric load via the current control circuit, the first capacitor and the With the combined energy obtained by combining the energy stored in the two capacitors, a larger current is applied to the electric load than usual, and thereafter, from the DC power supply via the current control circuit. Driving an electric load by feeding electrical current.

Therefore, according to the present invention, when the power supply voltage is normally higher than the judgment voltage, the charging voltage of the first capacitor and the second capacitor charged to the predetermined voltage by the charging circuit is alternately used, and the electric load of the electric load is changed. Since a large current can be supplied to the electric load immediately after the start of energization, it is possible to quickly switch between energizing and de-energizing an electric load requiring a large current at the time of initial driving immediately after the start of energization. Further, when the power supply voltage is lower than the determination voltage, the charging voltage of the first capacitor and the charging voltage of the second capacitor cannot be alternately used to switch the energization / non-energization of the electric load at high speed. The first capacitor and the second capacitor
Since the charging voltage of the capacitor is used, not only a large current flows through the electric load immediately after the start of energization of the electric load, but also a period of energization from the capacitor to the electric load can be lengthened. Therefore, even if the current supplied from the DC power supply to the electric load via the current control circuit becomes smaller than usual due to a decrease in the power supply voltage, the electric load can be supplied with the energy necessary for driving the electric load. In addition, it is possible to prevent the electric load from becoming unable to operate normally due to a decrease in the power supply voltage.

Here, as the electric load to which the energization control device of the present invention can be applied, the higher the energizing current, the higher the energizing current, such as the solenoid valve constituting the injector, and the higher the energizing current. And an electromagnetic actuator capable of holding the operation even if the value is low.

[0013] In particular, the energization control device of the present invention includes:
If applied to a fuel injection control device that opens and closes a solenoid valve for fuel injection at a high speed and executes fuel supply to the diesel engine in two stages, pilot injection and main injection, when the engine is started at low temperature For example, it is possible to prevent a situation in which the power supply voltage is significantly reduced and the diesel engine cannot be started.

In this case, the power supply control device is configured as described in claim 2, and the power supply control means includes:
When the fuel injection solenoid valve is opened to inject fuel into the diesel engine, the determining means first determines whether or not the power supply voltage is lower than the determining voltage. When it is determined that the voltage is equal to or higher than the determination voltage, the main switching element and the first switching element or the main switching element and the second switching element are simultaneously turned on by the normal time control means, and the pilot injection is performed from the solenoid valve. Or, execute the fuel injection for the main injection, and conversely,
If the determining means determines that the power supply voltage is lower than the determining voltage, the main switching element and the first and second switching elements are simultaneously turned on by the voltage drop control means, and the fuel is supplied from the solenoid valve. Injection may be performed.

With this configuration, even if the power supply voltage drops at the time of starting the engine at a low temperature, etc., the injector is reliably opened by the operation of the voltage drop control means.
Since fuel can be supplied to the diesel engine, it is possible to prevent the diesel engine from being unable to operate.

In the case where the energy charged in the two capacitors for pilot injection and main injection is simultaneously used during one fuel injection,
It is necessary to charge the two capacitors to a predetermined voltage before the next fuel injection. However, when the engine is running at a high speed, the time during which the capacitors can be charged is shortened. It is difficult to charge the capacitor, and it is difficult to execute the fuel injection in two steps, the pilot injection and the main injection. But,
The power supply voltage usually drops only when the starter motor for starting the diesel engine is operating, and when starting the engine, the engine is running at a very low speed and it takes time to charge the two capacitors. The required time can be sufficiently secured. Generally, at the time of engine start, it is not necessary to execute pilot injection, and only one fuel injection (main injection) is required. Therefore, when the power supply voltage drops, it is sufficiently possible to charge the two capacitors to a predetermined voltage after the fuel injection is performed and before the next fuel injection is performed. Therefore, according to the present invention, it is possible to realize an excellent fuel injection control device with improved startability without adversely affecting the operation of the diesel engine.

When the present invention is used for controlling the energization of the solenoid valve for fuel injection of a diesel engine as described above, the operation of the voltage drop control means is controlled by the energization control means. It is preferable to provide voltage drop control permission means for permitting only when the diesel engine is started, and for executing fuel supply to the diesel engine by the operation of the normal control means after the start of the diesel engine.

That is, as described above, when pilot injection is performed after the diesel engine is started, particularly at high rotations, the time during which the capacitor can be charged is shortened.
Since the energy charged in the two capacitors is used at the same time, it is impossible to recharge the two capacitors in a very short time until the main injection even though pilot injection can be realized. Important main injection becomes impossible, and the engine may be stopped.

However, if the power supply control device is configured as described in claim 3, the voltage drop control means does not operate after the diesel engine is started, so that such engine stop can be reliably avoided. Become. In general, the power supply voltage decreases after the engine is started, when the charging system of the engine has failed, such as when the alternator has failed. Therefore, it is advisable to judge that the engine is in an abnormal state and to take additional measures for the abnormal state.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a fuel injection control device 2 for a diesel engine to which the present invention is applied.

The fuel injection control device 2 operates by receiving power supply from the battery 4, and operates according to the operation state of the diesel engine. The fuel injection control device 2 is provided with a fuel (not shown) provided in each cylinder of the engine (only one cylinder is shown in the figure). The microcomputer 10 is for injecting and supplying fuel to each cylinder of the engine by opening an injection electromagnetic valve (injector). The microcomputer 10 generates a control pulse for driving the injector according to the operation state of the diesel engine. Prepare.

The fuel injection control device 2 receives inputs from various sensors for detecting the operating state of the diesel engine, such as the accelerator opening and engine speed, and inputs from various switches such as a key switch and a starter switch. To
The buffer 12 converts the battery voltage + B to a predetermined DC constant voltage Vcc (for example, 5 V) which is converted into an appropriate electric signal and transferred to the microcomputer 10, and supplies power to each unit in the apparatus including the microcomputer 10. A power supply circuit 14 for supplying the power, a battery voltage monitoring circuit 16 as power supply voltage detecting means for converting the battery voltage + B to an appropriate level and transferring it to the microcomputer 10, and an injector according to a control pulse output from the microcomputer 10. A drive circuit 20 is provided for opening the injector by energizing the solenoid 6.

Here, the microcomputer 10 is C
Fuel injection and supply to each cylinder of the engine based on various detection signals input through the buffer 12 and representing the operating state of the diesel engine, and is constituted by a PU, a ROM, a RAM, an A / D converter (ADC), and the like. Calculates the injection amount and fuel injection timing, and according to the calculation results, the injector opening / closing valve timing (that is, the start and end timing of fuel injection)
And the operating state of the diesel engine,
If the operating state is such that the fuel injection is to be executed in two stages, the pilot injection and the main injection, the opening / closing valve timing of the injector for the pilot injection and the main injection (based on the calculated fuel injection amount and fuel injection timing) That is, the start and end timings of the pilot injection and the start and end timings of the main injection are determined. Then, in accordance with the determined start and end timings of the fuel injection, a charge pulse CP, a solenoid energizing pulse DP, a pilot injection separation pulse PS, and a main injection separation pulse MS are generated.

On the other hand, the driving circuit 20 includes a pilot injection capacitor 21 and a main injection capacitor 22.
And the charge pulse CP from the microcomputer 10
In response, the capacitors 21 and 22 are connected to the battery voltage + B
A charging circuit 30 for charging to a predetermined voltage higher than
An energization control circuit 24 is provided on an energization path from the battery 4 to the solenoid 6 of the injector and receives the solenoid energization pulse DP from the microcomputer 10 to energize the energization path. A constant current circuit 28 for controlling the current flowing from the battery + B to the solenoid 6 to a constant current when the control circuit 24 is on;
A pilot injection disconnection circuit that is turned on by a pilot injection disconnection pulse PS from the controller, connects the pilot injection capacitor 21 and the solenoid 6, and applies the high voltage charged to the pilot injection capacitor 21 to the solenoid 6. 25 and the microcomputer 1
It is turned on by a main injection disconnection pulse MS from 0, connects the main injection capacitor 22 and the solenoid 6, and applies a high voltage charged to the main injection capacitor 22 to the solenoid 6 for main injection disconnection. And a circuit 26.

In this embodiment, the power supply control circuit 24 corresponds to the main switching element of the present invention, and the constant current circuit 28
Corresponds to the current control circuit of the present invention, the pilot injection capacitor 21 and the main injection capacitor 22 correspond to the first capacitor and the second capacitor of the present invention, respectively, and the charging circuit 30 corresponds to the charging circuit of the present invention. The pilot injection disconnection circuit 25 and the main injection disconnection circuit 26 correspond to the first switching element and the second switching element of the present invention, respectively, and the microcomputer 10 corresponds to the energization control means of the present invention. And in FIG.
Separation circuit 2 for pilot injection and main injection
Although the open / close switches 5 and 26 are described, each of these disconnection circuits 25 and 26 is actually configured by a switching element (a so-called analog switch) such as a transistor.

FIG. 2 is an electric circuit diagram showing a detailed configuration of the drive circuit 20. FIG. 3 is a diagram showing control pulses CP, DP, PS,
5 is a time chart illustrating an operation of the drive circuit 20 based on MS. Hereinafter, the driving circuit 20 will be described with reference to FIGS.
And the basic operation of the microcomputer 10 and the drive circuit 20 will be described.

As shown in FIG. 2, first, the charging circuit 30 in the driving circuit 20 includes a charging transformer 40, and the battery 40 is used as a charging power supply.
Energize the primary side coil in synchronization with the charge pulse CP.
By de-energizing, a high voltage obtained by boosting the battery voltage + B is generated in the secondary coil, and the high voltage causes the capacitors 21 and 21 for pilot injection and main injection to be generated.
2 is configured as a so-called flyback type DC-DC converter.

More specifically, the charge circuit 30 has an input terminal to which a charge pulse CP is input and an input terminal to which the solenoid energizing pulse DP is inverted and inputted.
2. The base is connected to the output terminal of the AND gate 32 via a resistor R1 and grounded via a resistor R2;
The collector is connected to the power supply line to which the power supply voltage Vcc from the power supply circuit 14 is supplied via the resistor R3, the NPN transistor 34 whose emitter is grounded, and the gate is connected to the NPN transistor 34 via the resistors R5 and R6. And the drain is connected to the charging transformer 40.
An N-channel MOSFET 38 connected to the end of the primary coil opposite to the battery 4 and having a source grounded via a resistor R7.

Then, the microcomputer 10 outputs a high-frequency signal whose level is inverted at a predetermined cycle as a charge pulse CP (see FIG. 3A). Therefore, in the charge circuit 30, when the solenoid energizing pulse DP output from the microcomputer 10 is at a low level (that is, when the solenoid 6 is not energized), the NPN transistors 34 and 34 are synchronized with the charge pulse CP.
Eventually, the MOSFET 38 is turned on and off, and the energization / non-energization of the primary coil of the charging transformer 40 is switched. From the secondary coil of the charging transformer 40, both the pilot injection and main injection capacitors 21 and 2 are turned on.
2 and the capacitors 21 and 22 are charged to a high voltage higher than the battery voltage + B (see FIGS. 3C and 3D).

The charge circuit 30 supplies the voltage across the capacitors 21 and 22 to resistors R8 and R9,
And resistor voltage dividing circuits 45 and 46 for dividing the voltage by resistors R10 and R11, respectively, and the voltage between both ends of each of the capacitors 21 and 22 divided by the resistor voltage dividing circuits 45 and 46 to a predetermined judgment voltage. Comparator 5 whether or not it has reached
2 and 54, a high-level signal (charge completion determination signal: FIG. 3) via the AND gate 56 when the voltage across the capacitors 21 and 22 reaches the determination voltage.
(B) refer to FIG.
An NPN transistor 36 for receiving a charge completion determination signal from the charge completion determination circuit 50 and stopping the charge of the NPN transistor 34 to ground is provided.

Therefore, the charging voltage of the pilot injection and main injection capacitors 21 and 22 reaches a predetermined judgment voltage (judgment voltage> battery voltage + B) by energizing / de-energizing the primary coil of the charging transformer 40. Then
The MOSFET 38 is turned on by the charge pulse CP.
The off state is maintained regardless of the state of the NPN transistor 34 to be turned off (see FIGS. 3A to 3D).

The NPN transistor 36 holding the MOSFET 38 in the off state has a collector connected to the collector of the NPN transistor 34 and a base connected to the resistor R.
4 and connected to the output terminal of the AND gate 56 of the charge completion determination circuit via a resistor R0, and the emitter is grounded. MOSFET3
In order to protect the MOSFET 38 from overvoltage, an overvoltage protection circuit 42 including a Zener diode ZD1 and a diode D2 is provided between the drain of the transistor 8 and the resistor R6 connected to its gate.

Next, the power supply control circuit 24 has a collector connected to one end of the solenoid 6 (an end opposite to the power supply line of the battery 4 to which the constant current circuit 28 is connected), and an emitter connected to the current detecting resistor. It comprises an NPN transistor that is grounded via Ri and receives a solenoid energizing pulse DP at its base. For this reason, the energization control circuit 24
When the solenoid energizing pulse DP is at a high level, it is turned on to form an energizing path for the solenoid 6.

The voltage at the connection point between the conduction control circuit 24 and the current detection resistor Ri is input to a constant current circuit 28. When the solenoid energizing pulse DP is at a high level (that is, when it is necessary to open the injector by energizing the solenoid 6), the constant current circuit 28 sets the input voltage from the current detecting resistor Ri to a predetermined voltage. The constant current is supplied to the solenoid 6 by controlling the output current so as to be as follows.

On the other hand, the microcomputer 10 normally uses two pulse signals (high and low) for pilot injection and main injection as the solenoid energizing pulse DP in the normal state where fuel injection is divided into two, pilot injection and main injection. ) Are sequentially output (see FIG. 3 (g)). The microcomputer 10 also includes a solenoid energizing pulse DP for pilot injection among the two pulse signals.
At the time of output, the separation pulse PS for pilot injection
When the solenoid injection pulse DP for main injection is output, the disconnection pulse MS for main injection is simultaneously output (see FIGS. 3E and 3F).

As a result, when the solenoid energizing pulse DP becomes high level and the NPN transistor in the energizing control circuit 24 is turned on, the pilot injection separating circuit 25 or the main injection separating circuit 26 is simultaneously turned on. At the initial stage of energization for pilot injection or main injection, the solenoid 6 is supplied with a peak large current (hereinafter referred to as a valve opening current) by the output voltage from the pilot injection capacitor 21 or the main injection capacitor 22.
Then, a constant current (hereinafter referred to as a holding current) IH supplied from the constant current circuit 28 flows (see FIG. 3 (h)). Therefore, when the injector is opened for pilot injection and main injection, the valve opening current IP flows through the solenoid 6 to quickly open the injector, and then the valve opening state is maintained by the holding current IH. Is done.

The charging path from the secondary coil of the charging transformer 40 to each of the capacitors 21 and 22, the high voltage power supply path from each of the capacitors 21 and 22 to the solenoid 6 via the disconnecting circuits 25 and 26, and the constant current Circuit 2
The energization paths from 8 to the solenoid 6 are provided with backflow prevention diodes D3 to D7, respectively.

As described above, during the pilot injection, the microcomputer 10 outputs the pilot injection disconnection pulse PS and the solenoid energizing pulse DP from the microcomputer 10, and at the time of the main injection, the microcomputer 10 outputs the main injection disconnection pulse MS and the solenoid. Either the energy stored in the pilot injection capacitor 21 or the energy stored in the main injection capacitor 22 when opening the injector and performing fuel injection such as outputting the energizing pulse DP. When the injector is opened using one of the two, when the battery voltage + B is significantly reduced, such as when the engine is started at a low temperature, the current supply capacity of the constant current circuit 28 is reduced, and the injector is opened. May not be able to be opened.

That is, assuming that the resistance value of the solenoid 6 is R and the constant current supplied to the solenoid 6 by the constant current circuit 28 is Io, if the resistance value of the current detection resistor Ri is ignored, the battery voltage + B becomes It must be equal to or greater than these multiplication values (R · Io). However, the battery voltage + B decreases,
If this condition cannot be satisfied, the constant current circuit 28 cannot supply the constant current Io, and + B <R · Io
Under the condition (1), the holding current IH decreases as the battery voltage + B decreases (see FIG. 4).

Therefore, when the injector is opened and fuel injection is executed when the battery voltage + B decreases, even if the capacitors 21 and 22 can be charged to the determination voltage, the injector 6 May not be able to supply energy for maintaining the valve open state, and may not be able to inject and supply fuel from the injector to the diesel engine.

That is, when the solenoid 6 is energized by using one of the charging voltages of the capacitors 21 and 22 during fuel injection, when the battery voltage is normal, as shown by a solid line in FIG. Even if a current is applied to the solenoid 6 to open the injector and maintain the open state, the valve of the injector can be normally opened.
When the battery voltage drops, as shown by the dotted line in FIG.
Since the holding current IH that can be supplied from the constant current circuit 28 decreases, the injector valve cannot be opened and the diesel engine cannot operate normally.

These problems are caused by the problems of the capacitors 21 and
The problem can be solved by ensuring that the injector can be opened only by the valve opening current IP caused by the discharge from the capacitor 22. For this purpose, the charge completion determination circuit 50 determines the charging voltage V of the capacitor for which the charge completion is determined. By increasing or increasing the capacitance of the capacitors 21 and 22, the energy E (E = E =
C × V ^2/2, C is capacitance, V is need to increase the charge voltage). In this case, it is necessary to charge the capacitors 21 and 22 at a higher speed, so that the size of the charge circuit 30 is increased, and the size and cost of the capacitors 21 and 22 are increased.

Therefore, in this embodiment, when the battery voltage + B drops, as shown in FIG. 6, when the microcomputer 10 outputs a control pulse to the drive circuit 20 for fuel injection, the control pulse is output together with the solenoid energizing pulse DP. By simultaneously outputting the pilot injection separation pulse PS and the main injection separation pulse MS, the injector can be reliably opened. Hereinafter, control processing executed by the microcomputer 10 for this purpose will be described.

FIG. 7 shows that the microcomputer 10 calculates the fuel injection amount and the fuel injection timing in accordance with the operation state of the diesel engine, and performs a predetermined time period separately from the control amount calculation process for determining the opening / closing valve timing of the injector. It is a flowchart showing the control pulse output process performed as an interruption process for every.

As shown in this figure, when outputting the control pulses CP, PS, MS, and DP, the microcomputer 10 first turns on the starter switch in S100 (S represents a step). In this state, by determining whether the starter motor is operating or not, it is determined whether or not the diesel engine is currently being started.

If the engine is not currently being started, in step S110, for pilot injection or main injection, the solenoid energizing pulse DP is used together with the solenoid energizing pulse DP according to the injector opening / closing valve timing determined in the control amount calculation process. Normal control is executed to output one of the pilot injection separation pulse PS and the main injection separation pulse MS. In this normal control, the output control of the charge pulse CP for repeatedly outputting the charge pulse CP for charging the capacitors 21 and 22 at a predetermined cycle is also executed at the same time.

On the other hand, if it is determined in S100 that the engine is being started, the battery voltage + B input from the battery voltage monitoring circuit 16 is read in S120, and the read battery voltage is input in S130. It is determined whether or not + B is lower than a determination voltage (for example, 8 V) significantly lower than a normal voltage (for example, 12 V). If the battery voltage + B is equal to or higher than this determination voltage, normal control is executed in S110. On the other hand, if the battery voltage + B is lower than the determination voltage, the process proceeds to S140.

Then, in S140, according to the opening / closing valve timing of the injector determined in the control amount calculation processing,
A start-up control for simultaneously outputting the solenoid energizing pulse DP, the pilot injection disconnection pulse PS, and the main injection disconnection pulse MS is executed. In this start-up control, as in S110, output control of the charge pulse CP for repeatedly outputting the charge pulse CP for charging the capacitors 21 and 22 at a predetermined cycle is also executed.

As a result, according to the present embodiment, when the engine is started, the operation of the starter motor causes the battery voltage + B
Is significantly reduced, the energy required to open the injector can be supplied to the solenoid 6 to reliably open the injector.

That is, according to the present embodiment, when the battery voltage + B is lower than the determination voltage, the energization of the solenoid 6 is performed based on the combined value of the energy stored in the capacitors 21 and 22 and the constant current circuit 28. The conventional device always supplies electricity to the solenoid 6 with the energy charged in one of the capacitors 21 and 22 and the supply current from the constant current circuit 28 irrespective of the battery voltage + B. As described above, at the time of engine start, a sufficient current cannot flow through the solenoid 6 due to the decrease of the battery voltage + B, and the valve of the injector cannot be opened. Even so, a current necessary for valve opening can be supplied to the solenoid 6 to reliably open the valve of the injector. Than is Uninaru (see FIG. 8).

Therefore, according to the present embodiment, it is possible to improve the startability of the diesel engine without preventing the diesel engine from starting due to the decrease in the battery voltage + B when the engine is started.
As described above, for one fuel injection, the pilot injection condenser 21 and the main injection condenser 2
If the energy charged to the two capacitors 21 and 22 is used at the same time, the two capacitors 21 and 22 must be used before the next fuel injection.
Must be charged to a predetermined voltage, and when the engine is running at high speed, the charging time for the capacitor is shortened.
It is difficult to divide the fuel injection into two, the pilot injection and the main injection. However, as described above, the battery voltage usually drops only at the start of the operation of the starter motor. In this case, the engine speed is extremely low, and it takes time to charge the two capacitors. The required time can be sufficiently secured. Further, at the time of starting the engine, it is not necessary to execute the pilot injection, and only one fuel injection (main injection) is required. Therefore, after the fuel injection is performed, the capacitor 2 is not used until the next fuel injection is performed.
It is sufficiently possible to charge the batteries 1 and 22 to a predetermined voltage. According to the present embodiment, the diesel engine can be reliably started even if the battery voltage + B decreases at the time of engine startup.

In the present embodiment, of the control pulse output processing executed by the microcomputer 10 as described above, the determination processing during engine start executed in S100 is the voltage drop control permission of the present invention. Means, S
The determination process of the battery voltage + B performed in 130 corresponds to the determination unit of the present invention, the normal control performed in S110 corresponds to the normal control unit of the present invention, and the starting process performed in S140 The control corresponds to the voltage drop control means of the present invention.

Although one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment and can take various forms. For example, in the above embodiment, the case where the present invention is applied to the fuel injection control device of the diesel engine which performs the pilot injection prior to the main injection has been described. In the case of a device provided with two capacitors for supplying a large current in order to quickly switch between energizing and de-energizing a required electric load, the same method as in the above embodiment can be applied. Can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a configuration of a fuel injection control device according to an embodiment.

FIG. 2 is an electric circuit diagram showing details of a drive circuit according to the embodiment.

FIG. 3 is a time chart for explaining a control pulse output from a microcomputer when a pilot injection and a main injection are executed and an operation of a drive circuit.

FIG. 4 is an explanatory diagram illustrating a relationship between a battery voltage and an output current (holding current) from a constant current circuit.

FIG. 5 is an explanatory diagram illustrating a conventional problem that occurs when the battery voltage drops.

FIG. 6 is a time chart illustrating a control pulse output from the microcomputer when the battery voltage drops and the operation of the drive circuit.

FIG. 7 is a flowchart showing a control pulse output process executed by the microcomputer.

FIG. 8 is an explanatory diagram illustrating a relationship between a solenoid current at the time of a battery voltage drop and a valve state of an injector in the embodiment in comparison with the related art.

[Explanation of symbols]

2 ... fuel injection control device 4 ... battery 6 ... solenoid 10 ... microcomputer 12 ... buffer 1
DESCRIPTION OF SYMBOLS 4 ... Power supply circuit 16 ... Battery voltage monitoring circuit 20 ... Drive circuit 21 ... Pilot injection capacitor 22 ... Main injection capacitor 24 ... Energization control circuit 25 ... Pilot injection separation circuit 26 ... Main injection separation circuit 28 ... Constant current circuit 30: charge circuit CP: charge pulse DP: solenoid energizing pulse MS: disconnection pulse for main injection PS: disconnection pulse for pilot injection

Claims (3)

[Claims] A main switching element provided on an energizing path from a DC power supply to an electric load; and a current flowing from the DC power supply to the electric load when the main switching element is turned on, the main switching element being provided on the energizing path. A current control circuit that performs charging; a first capacitor and a second capacitor for charging; a charging circuit that charges the first and second capacitors to a predetermined voltage higher than a power supply voltage of the DC power supply; A first switching element and a second switching element for connecting capacitors respectively connected to the energizing paths and supplying energy stored in the capacitors to the electric load; and turning on the main switching element when the electric load is energized. And the DC power supply controlled by the current control circuit by turning on one of the first and second switching elements. And an energization control unit for energizing the electric load based on the output current and the charging voltage of the first or second capacitor. An energization control device for an electric load, comprising: detecting a power supply voltage of the DC power supply. A power supply voltage detecting unit, wherein when the detected power supply voltage is lower than a predetermined determination voltage, the main switching element and the first and second power supply units are energized when the electric load is energized. (2) a configuration in which the switching element is turned on, and the electric load is energized by the output current from the DC power supply controlled by the current control circuit and the charging voltage of the first and second capacitors. A power supply control device for an electric load, comprising: 2. The electric load is a fuel injection solenoid valve that opens when energized to a solenoid and injects fuel into a diesel engine, and wherein the first capacitor and the second capacitor are connected to the solenoid valve. Is a capacitor that accumulates energy for pilot injection and energy for main injection, respectively, in order to separately perform fuel injection of pilot injection and main injection, and the energization control unit opens the electromagnetic valve. Determining whether the power supply voltage is lower than the determination voltage when injecting and supplying fuel to the diesel engine, and determining that the power supply voltage is equal to or higher than the determination voltage by the determination means. In this case, the main switching element and the first switching element, or the main switching element and the second switching element are simultaneously turned on, and the A normal operation control means for executing the fuel injection for the pilot injection or the main injection, when the power supply voltage by said determination unit is determined to be lower than the determination voltage, the main switching element and the first
2. The power supply control device according to claim 1, further comprising: a voltage drop control unit that simultaneously turns on the second switching element and the second switching element to execute fuel injection from the solenoid valve. 3. 3. The energization control means permits the operation of the voltage drop control means only when the diesel engine starts, and after the diesel engine starts, the normal control means operates the diesel engine. 3. The power supply control device according to claim 2, further comprising a voltage drop control permitting unit for executing fuel supply to the electric load.